Eugenia Morselli

Multiple cellular stressors, including activation of the tumour suppressor p53, can stimulate autophagy. Here we show that deletion, depletion or inhibition of p53 can induce autophagy in human, mouse and nematode cells subjected to knockout, knockdown or pharmacological inhibition of p53. Enhanced autophagy improved the survival of p53-deficient cancer cells under conditions of hypoxia and nutrient depletion, allowing them to maintain high ATP levels. Inhibition of p53 led to autophagy in enucleated cells, and cytoplasmic, not nuclear, p53 was able to repress the enhanced autophagy of p53(-/-) cells. Many different inducers of autophagy (for example, starvation, rapamycin and toxins affecting the endoplasmic reticulum) stimulated proteasome-mediated degradation of p53 through a pathway relying on the E3 ubiquitin ligase HDM2. Inhibition of p53 degradation prevented the activation of autophagy in several cell lines, in response to several distinct stimuli. These results provide evidence of a key signalling pathway that links autophagy to the cancer-associated dysregulation of p53.

Cell death is essential for a plethora of physiological processes, and its deregulation characterizes numerous human diseases. Thus, the in-depth investigation of cell death and its mechanisms constitutes a formidable challenge for fundamental and applied biomedical research, and has tremendous implications for the development of novel therapeutic strategies. It is, therefore, of utmost importance to standardize the experimental procedures that identify dying and dead cells in cell cultures and/or in tissues, from model organisms and/or humans, in healthy and/or pathological scenarios. Thus far, dozens of methods have been proposed to quantify cell death-related parameters. However, no guidelines exist regarding their use and interpretation, and nobody has thoroughly annotated the experimental settings for which each of these techniques is most appropriate. Here, we provide a nonexhaustive comparison of methods to detect cell death with apoptotic or nonapoptotic morphologies, their advantages and pitfalls. These guidelines are intended for investigators who study cell death, as well as for reviewers who need to constructively critique scientific reports that deal with cellular demise. Given the difficulties in determining the exact number of cells that have passed the point-of-no-return of the signaling cascades leading to cell death, we emphasize the importance of performing multiple, methodologically unrelated assays to quantify dying and dead cells.

Caloric restriction and autophagy-inducing pharmacological agents can prolong lifespan in model organisms including mice, flies, and nematodes. In this study, we show that transgenic expression of Sirtuin-1 induces autophagy in human cells in vitro and in Caenorhabditis elegans in vivo. The knockdown or knockout of Sirtuin-1 prevented the induction of autophagy by resveratrol and by nutrient deprivation in human cells as well as by dietary restriction in C. elegans. Conversely, Sirtuin-1 was not required for the induction of autophagy by rapamycin or p53 inhibition, neither in human cells nor in C. elegans. The knockdown or pharmacological inhibition of Sirtuin-1 enhanced the vulnerability of human cells to metabolic stress, unless they were stimulated to undergo autophagy by treatment with rapamycin or p53 inhibition. Along similar lines, resveratrol and dietary restriction only prolonged the lifespan of autophagy-proficient nematodes, whereas these beneficial effects on longevity were abolished by the knockdown of the essential autophagic modulator Beclin-1. We conclude that autophagy is universally required for the lifespan-prolonging effects of caloric restriction and pharmacological Sirtuin-1 activators.

Autophagy is an evolutionarily conserved catabolic pathway that is involved in numerous physiological processes and in multiple pathological conditions including cancer. Autophagy is regulated by an intricate network of signaling cascades that have not yet been entirely disentangled. Accumulating evidence indicates that p53, the best-characterized human tumor suppressor protein, can modulate autophagy in a dual fashion, depending on its subcellular localization. On the one hand, p53 functions as a nuclear transcription factor and transactivates proapoptotic, cell cycle-arresting and proautophagic genes. On the other hand, cytoplasmic p53 can operate at mitochondria to promote cell death and can repress autophagy via poorly characterized mechanisms. This review focuses on the recently discovered function of p53 as a master regulator of autophagy.

Autophagy protects organelles, cells, and organisms against several stress conditions. Induction of autophagy by resveratrol requires the nicotinamide adenine dinucleotide-dependent deacetylase sirtuin 1 (SIRT1). In this paper, we show that the acetylase inhibitor spermidine stimulates autophagy independent of SIRT1 in human and yeast cells as well as in nematodes. Although resveratrol and spermidine ignite autophagy through distinct mechanisms, these compounds stimulate convergent pathways that culminate in concordant modifications of the acetylproteome. Both agents favor convergent deacetylation and acetylation reactions in the cytosol and in the nucleus, respectively. Both resveratrol and spermidine were able to induce autophagy in cytoplasts (enucleated cells). Moreover, a cytoplasm-restricted mutant of SIRT1 could stimulate autophagy, suggesting that cytoplasmic deacetylation reactions dictate the autophagic cascade. At doses at which neither resveratrol nor spermidine stimulated autophagy alone, these agents synergistically induced autophagy. Altogether, these data underscore the importance of an autophagy regulatory network of antagonistic deacetylases and acetylases that can be pharmacologically manipulated.

Acetyl-coenzyme A (AcCoA) is a major integrator of the nutritional status at the crossroads of fat, sugar, and protein catabolism. Here we show that nutrient starvation causes rapid depletion of AcCoA. AcCoA depletion entailed the commensurate reduction in the overall acetylation of cytoplasmic proteins, as well as the induction of autophagy, a homeostatic process of self-digestion. Multiple distinct manipulations designed to increase or reduce cytosolic AcCoA led to the suppression or induction of autophagy, respectively, both in cultured human cells and in mice. Moreover, maintenance of high AcCoA levels inhibited maladaptive autophagy in a model of cardiac pressure overload. Depletion of AcCoA reduced the activity of the acetyltransferase EP300, and EP300 was required for the suppression of autophagy by high AcCoA levels. Altogether, our results indicate that cytosolic AcCoA functions as a central metabolic regulator of autophagy, thus delineating AcCoA-centered pharmacological strategies that allow for the therapeutic manipulation of autophagy.

Throughout the process of pathogen-host co-evolution, viruses have developed a battery of distinct strategies to overcome biochemical and immunological defenses of the host. Thus, viruses have acquired the capacity to subvert host cell apoptosis, control inflammatory responses, and evade immune reactions. Since the elimination of infected cells via programmed cell death is one of the most ancestral defense mechanisms against infection, disabling host cell apoptosis might represent an almost obligate step in the viral life cycle. Conversely, viruses may take advantage of stimulating apoptosis, either to kill uninfected cells from the immune system, or to induce the breakdown of infected cells, thereby favoring viral dissemination. Several viral polypeptides are homologs of host-derived apoptosis-regulatory proteins, such as members of the Bcl-2 family. Moreover, viral factors with no homology to host proteins specifically target key components of the apoptotic machinery. Here, we summarize the current knowledge on the viral modulation of mitochondrial apoptosis, by focusing in particular on the mechanisms by which viral proteins control the host cell death apparatus.

Multiple oncogenes (in particular phosphatidylinositol 3-kinase, PI3K; activated Akt1; antiapoptotic proteins from the Bcl-2 family) inhibit autophagy. Similarly, several tumor suppressor proteins (such as BH3-only proteins; death-associated protein kinase-1, DAPK1; the phosphatase that antagonizes PI3K, PTEN; tuberous sclerosic complex 1 and 2, TSC1 and TSC2; as well as LKB1/STK11) induce autophagy, meaning that their loss reduces autophagy. Beclin-1, which is required for autophagy induction acts as a haploinsufficient tumor suppressor protein, and other essential autophagy mediators (such as Atg4c, UVRAG and Bif-1) are bona fide oncosuppressors. One of the central tumor suppressor proteins, p53 exerts an ambiguous function in the regulation of autophagy. Within the nucleus, p53 can act as an autophagy-inducing transcription factor. Within the cytoplasm, p53 exerts a tonic autophagy-inhibitory function, and its degradation is actually required for the induction of autophagy. The role of autophagy in oncogenesis and anticancer therapy is contradictory. Chronic suppression of autophagy may stimulate oncogenesis. However, once a tumor is formed, autophagy inhibition may be a therapeutic goal for radiosensitization and chemosensitization. Altogether, the current state-of-the art suggests a complex relationship between cancer and deregulated autophagy that must be disentangled by further in-depth investigation.

Autophagy constitutes one of the major responses to stress in eukaryotic cells, and is regulated by a complex network of signaling cascades. Not surprisingly, autophagy is implicated in multiple pathological processes, including infection by pathogens, inflammatory bowel disease, neurodegeneration and cancer. Both oncogenesis and tumor survival are influenced by perturbations of the molecular machinery that controls autophagy. Numerous oncoproteins, including phosphatidylinositol 3-kinase, Akt1 and anti-apoptotic members of the Bcl-2 family suppress autophagy. Conversely, several tumor suppressor proteins (e.g., Atg4c; beclin 1; Bif-1; BH3-only proteins; death-associated protein kinase 1; LKB1/STK11; PTEN; UVRAG) promote the autophagic pathway. This does not entirely apply to p53, one of the most important tumor suppressor proteins, which regulates autophagy in an ambiguous fashion, depending on its subcellular localization. Irrespective of the controversial role of p53, basal levels of autophagy appear to inhibit tumor development. On the contrary, chemotherapy- and metabolic stress-induced activation of the autophagic pathway reportedly contribute to the survival of formed tumors, thereby favoring resistance. In this context, autophagy inhibition would represent a major therapeutic target for chemosensitization. Here, we will review the current knowledge on the dual role of autophagy as an anti- and pro-tumor mechanism.

Genotoxic stress can induce autophagy in a p53-dependent fashion and p53 can transactivate autophagy-inducing genes. We have observed recently that inactivation of p53 by deletion, depletion or inhibition can trigger autophagy. Thus, human and mouse cells subjected to knockout, knockdown or pharmacological inhibition of p53 manifest signs of autophagy such as depletion of p62/SQSTM1, LC3 lipidation, redistribution of GFP-LC3 in cytoplasmic puncta, and accumulation of autophagosomes and autolysosomes, both in vitro and in vivo. Inhibition of p53 causes autophagy in enucleated cells, indicating that the cytoplasmic, non-nuclear pool of p53 can regulate autophagy. Accordingly, retransfection of p53-/- cells with wild-type p53 as well as a p53 mutant that is excluded from the nucleus (due to the deletion of the nuclear localization sequence) can inhibit autophagy, whereas retransfection with a nucleus-restricted p53 mutant (in which the nuclear localization sequence has been deleted) does not inhibit autophagy. Several distinct autophagy inducers (e.g. starvation, rapamycin, lithium, tunicamycin and thapsigargin) stimulate the rapid degradation of p53. In these conditions, inhibition of the p53-specific E3 ubiquitin ligase HDM2 can avoid p53 depletion and simultaneously prevent the activation of autophagy. Moreover, a p53 mutant that lacks the HDM2 ubiquitinylation site and hence is more stable than wild-type p53 is particularly efficient in suppressing autophagy. In conclusion, p53 plays a dual role in the control of autophagy. On one hand, nuclear p53 can induce autophagy through transcriptional effects. On the other hand, cytoplasmic p53 may act as a master repressor of autophagy. Addendum to: Tasdemir E, Maiuri MC, Galluzzi L, Vitale I, Djavaheri-Mergny M, D'Amelio M, Criollo A, Morselli E, Zhu C, Harper F, Nannmark U, Samara C, Pinton P, Vicencio JM, Carnuccio R, Moll UM, Madeo F, Paterlini-Brechot P, Rizzuto R, Szabadkai G, Pierron G, Blomgren K, Tavernarakis N, Codogno P, Cecconi F, Kroemer G. Regulation of autophagy by cytoplasmic p53. Nat Cell Biol 2008; 10:676-87.

In response to stress, cells start transcriptional and transcription‐independent programs that can lead to adaptation or death. Here, we show that multiple inducers of autophagy, including nutrient depletion, trigger the activation of the IKK (IκB kinase) complex that is best known for its essential role in the activation of the transcription factor NF‐κB by stress. Constitutively active IKK subunits stimulated autophagy and transduced multiple signals that operate in starvation‐induced autophagy, including the phosphorylation of AMPK and JNK1. Genetic inhibition of the nuclear translocation of NF‐κB or ablation of the p65/RelA NF‐κB subunit failed to suppress IKK‐induced autophagy, indicating that IKK can promote the autophagic pathway in an NF‐κB‐independent manner. In murine and human cells, knockout and/or knockdown of IKK subunits (but not that of p65) prevented the induction of autophagy in response to multiple stimuli. Moreover, the knockout of IKK‐β suppressed the activation of autophagy by food deprivation or rapamycin injections in vivo, in mice. Altogether, these results indicate that IKK has a cardinal role in the stimulation of autophagy by physiological and pharmacological stimuli.

MicroRNAs (miRNA) are noncoding RNAs that regulate multiple cellular processes, including proliferation and apoptosis. We used microarray technology to identify miRNAs that were upregulated by non-small cell lung cancer (NSCLC) A549 cells in response to cisplatin (CDDP). The corresponding synthetic miRNA precursors (pre-miRNAs) per se were not lethal when transfected into A549 cells yet affected cell death induction by CDDP, C2-ceramide, cadmium, etoposide, and mitoxantrone in an inducer-specific fashion. Whereas synthetic miRNA inhibitors (anti-miRNAs) targeting miR-181a and miR-630 failed to modulate the response of A549 to CDDP, pre-miR-181a and pre-miR-630 enhanced and reduced CDDP-triggered cell death, respectively. Pre-miR-181a and pre-miR-630 consistently modulated mitochondrial/postmitochondrial steps of the intrinsic pathway of apoptosis, including Bax oligomerization, mitochondrial transmembrane potential dissipation, and the proteolytic maturation of caspase-9 and caspase-3. In addition, pre-miR-630 blocked early manifestations of the DNA damage response, including the phosphorylation of the ataxia-telangiectasia mutated (ATM) kinase and of two ATM substrates, histone H2AX and p53. Pharmacologic and genetic inhibition of p53 corroborated the hypothesis that pre-miR-630 (but not pre-miR-181a) blocks the upstream signaling pathways that are ignited by DNA damage and converge on p53 activation. Pre-miR-630 arrested A549 cells in the G0-G1 phase of the cell cycle, correlating with increased levels of the cell cycle inhibitor p27(Kip1) as well as with reduced proliferation rates and resulting in greatly diminished sensitivity of A549 cells to the late S-G2-M cell cycle arrest mediated by CDDP. Altogether, these results identify miR-181a and miR-630 as novel modulators of the CDDP response in NSCLC.

The inositol 1,4,5-trisphosphate receptor (IP3R) is a major regulator of apoptotic signaling. Through interactions with members of the Bcl-2 family of proteins, it drives calcium (Ca2+) transients from the endoplasmic reticulum (ER) to mitochondria, thereby establishing a functional and physical link between these organelles. Importantly, the IP3R also regulates autophagy, and in particular, its inhibition/depletion strongly induces macroautophagy. Here, we show that the IP3R antagonist xestospongin B induces autophagy by disrupting a molecular complex formed by the IP3R and Beclin 1, an interaction that is increased or inhibited by overexpression or knockdown of Bcl-2, respectively. An effect of Beclin 1 on Ca2+ homeostasis was discarded as siRNA-mediated knockdown of Beclin 1 did not affect cytosolic or luminal ER Ca2+ levels. Xestospongin B- or starvation-induced autophagy was inhibited by overexpression of the IP3R ligand-binding domain, which coimmunoprecipitated with Beclin 1. These results identify IP3R as a new regulator of the Beclin 1 complex that may bridge signals converging on the ER and initial phagophore formation.

The oncosuppressor protein p53 regulates autophagy in a dual fashion. The pool of cytoplasmic p53 protein represses autophagy in a transcription-independent fashion, while the pool of nuclear p53 stimulates autophagy through the transactivation of specific genes. Here we report the discovery that Sestrin2, a novel p53 target gene, is involved in the induction of autophagy. Depletion of Sestrin2 by RNA interference reduced the level of autophagy in a panel of p53-sufficient human cancer cell lines responding to distinct autophagy inducers. In quantitative terms, Sestrin2 depletion was as efficient in preventing autophagy induction as was the depletion of Dram, another p53 target gene. Knockout of either Sestrin2 or Dram reduced autophagy elicited by nutrient depletion, rapamycin, lithium or thapsigargin. Moreover, autophagy induction by nutrient depletion or pharmacological stimuli led to an increase in Sestrin2 expression levels in p53-proficient cells. In strict contrast, the depletion of Sestrin2 or Dram failed to affect autophagy in p53-deficient cells and did not modulate the inhibition of baseline autophagy by a cytoplasmic p53 mutant that was reintroduced into p53-deficient cells. We conclude that Sestrin2 acts as a positive regulator of autophagy in p53-proficient cells.

Mitochondria are required for cellular survival, yet can also orchestrate cell death. The peculiar biochemical properties of these organelles, which are intimately linked to their compartmentalized ultrastructure, provide an optimal microenvironment for multiple biosynthetic and bioenergetic pathways. Most intracellular ATP is generated by mitochondrial respiration, which also represents the most relevant source of intracellular reactive oxygen species. Mitochondria participate in a plethora of anabolic pathways, including cholesterol, cardiolipin, heme and nucleotide biosynthesis. Moreover, mitochondria integrate numerous pro-survival and pro-death signals, thereby exerting a decisive control over several biochemical cascades leading to cell death, in particular the intrinsic pathway of apoptosis. Therefore, it is not surprising that cancer cells often manifest the deregulation of one or several mitochondrial functions. The six classical hallmarks of cancer (i.e., limitless replication, self-provision of proliferative stimuli, insensitivity to antiproliferative signals, disabled apoptosis, sustained angiogenesis, invasiveness/metastatic potential), as well as other common features of tumors (i.e., avoidance of the immune response, enhanced anabolic metabolism, disabled autophagy) may directly or indirectly implicate deregulated mitochondria. In this review, we discuss several mechanisms by which mitochondria can contribute to malignant transformation and tumor progression.

The knockout, knockdown or chemical inhibition of p53 stimulates autophagy. Moreover, autophagy-inducing stimuli such as nutrient depletion, rapamycin or lithium cause the depletion of cytoplasmic p53, which in turn is required for the induction of autophagy. Here, we show that retransfection of p53(-/-) HCT 116 colon carcinoma cells with wild type p53 decreases autophagy down to baseline levels. Surprisingly, one third among a panel of 22 cancer-associated p53 single amino acid mutants also inhibited autophagy when transfected into p53(-/-) cells. Those variants of p53 that preferentially localize to the cytoplasm effectively repressed autophagy, whereas p53 mutants that display a prominently nuclear distribution failed to inhibit autophagy. The investigation of a series of deletion mutants revealed that removal of the DNA-binding domain from p53 fails to interfere with its role in the regulation of autophagy. Altogether, these results identify the cytoplasmic localization of p53 as the most important feature for p53-mediated autophagy inhibition. Moreover, the structural requirements for the two biological activities of extranuclear p53, namely induction of apoptosis and inhibition of autophagy, are manifestly different.

Many features of aging result from the incapacity of cells to adapt to stress conditions. When damage accumulates irreversibly, mitotic cells from renewable tissues rely on either of two mechanisms to avoid replication. They can permanently arrest the cell cycle (cellular senescence) or trigger cell death programs. Apoptosis (self-killing) is the best-described form of programmed cell death, but autophagy (self-eating), which is a lysosomal degradation pathway essential for homeostasis, reportedly contributes to cell death as well. Unlike mitotic cells, postmitotic cells like neurons or cardiomyocytes cannot become senescent since they are already terminally differentiated. The fate of these cells entirely depends on their ability to cope with stress. Autophagy then operates as a major homeostatic mechanism to eliminate damaged organelles, long-lived or aberrant proteins and superfluous portions of the cytoplasm. In this mini-review, we briefly summarize the molecular networks that allow damaged cells either to adapt to stress or to engage in programmed-cell-death pathways.

Although autophagy has widely been conceived as a self-destructive mechanism that causes cell death, accumulating evidence suggests that autophagy usually mediates cytoprotection, thereby avoiding the apoptotic or necrotic demise of stressed cells. Recent evidence produced by our groups demonstrates that autophagy is also involved in pharmacological manipulations that increase longevity. Exogenous supply of the polyamine spermidine can prolong the lifespan of (while inducing autophagy in) yeast, nematodes and flies. Similarly, resveratrol can trigger autophagy in cells from different organisms, extend lifespan in nematodes, and ameliorate the fitness of human cells undergoing metabolic stress. These beneficial effects are lost when essential autophagy modulators are genetically or pharmacologically inactivated, indicating that autophagy is required for the cytoprotective and/or anti-aging effects of spermidine and resveratrol. Genetic and functional studies indicate that spermidine inhibits histone acetylases, while resveratrol activates the histone deacetylase Sirtuin 1 to confer cytoprotection/longevity. Although it remains elusive whether the same histones (or perhaps other nuclear or cytoplasmic proteins) act as the downstream targets of spermidine and resveratrol, these results point to an essential role of protein hypoacetylation in autophagy control and in the regulation of longevity.

Following the screening of a battery of distinct small-interfering RNAs that target various components of the apoptotic machinery, we found that knockdown of the voltage-dependent anion channel 1 (VDAC1) was particularly efficient in preventing cell death induced by cisplatin (CDDP) in non-small cell lung cancer cells. Both the downregulation of VDAC1 and its chemical inhibition with 4,4'-diisothiocyanatostilbene-2,2'-disulfonic acid reduced the apoptosis-associated modifications induced by CDDP, including mitochondrial transmembrane potential dissipation and plasma membrane permeabilization. VDAC1 inhibition strongly reduced the CDDP-induced conformational activation of Bax, yet had no discernible effect on the activation of Bak, suggesting that VDAC1 acts downstream of Bak and upstream of Bax. Accordingly, knockdown of Bak abolished the activation of Bax, whereas Bax downregulation had no effect on Bak activation. In VDAC1-depleted cells, the failure of CDDP to activate Bax could be reversed by means of the Bcl-2/Bcl-X(L) antagonist ABT-737, which concomitantly restored CDDP cytotoxicity. Altogether, these results delineate a novel pathway for the induction of mitochondrial membrane permeabilization (MMP) in the course of CDDP-induced cell death that involves a hierarchical contribution of Bak, VDAC1 and Bax. Moreover, our data suggest that VDAC1 may act as a facultative regulator/effector of MMP, depending on the initial cytotoxic event.

High-fat diets (HFDs) lead to obesity and inflammation in the central nervous system (CNS). Estrogens and estrogen receptor α (ERα) protect premenopausal females from the metabolic complications of inflammation and obesity-related disease. Here, we demonstrate that hypothalamic PGC-1α regulates ERα and inflammation in vivo. HFD significantly increased palmitic acid (PA) and sphingolipids in the CNS of male mice when compared to female mice. PA, in vitro, and HFD, in vivo, reduced PGC-1α and ERα in hypothalamic neurons and astrocytes of male mice and promoted inflammation. PGC-1α depletion with ERα overexpression significantly inhibited PA-induced inflammation, confirming that ERα is a critical determinant of the anti-inflammatory response. Physiologic relevance of ERα-regulated inflammation was demonstrated by reduced myocardial function in male, but not female, mice following chronic HFD exposure. Our findings show that HFD/PA reduces PGC-1α and ERα, promoting inflammation and decrements in myocardial function in a sex-specific way.

The life span of various model organisms can be extended by caloric restriction as well as by autophagy-inducing pharmacological agents. Life span-prolonging effects have also been observed in yeast cells, nematodes and flies upon the overexpression of the deacetylase Sirtuin-1. Intrigued by these observations and by the established link between caloric restriction and Sirtuin-1 activation, we decided to investigate the putative implication of Sirtuin-1 in the response of human cancer cells and Caenorhabditis elegans to multiple triggers of autophagy. Our data indicate that the activation of Sirtuin-1 (by the pharmacological agent resveratrol and/or genetic means) per se ignites autophagy, and that Sirtuin-1 is required for the autophagic response to nutrient deprivation, in both human and nematode cells, but not for autophagy triggered by downstream signals such as the inhibition of mTOR or p53. Since the life spanextending effects of Sirtuin-1 activators are lost in autophagy-deficient C. elegans, our results suggest that caloric restriction and resveratrol extend longevity, at least in experimental settings, by activating autophagy.

The tumor suppressor protein p53 tonically suppresses autophagy when it is present in the cytoplasm. This effect is phylogenetically conserved from mammals to nematodes, and human p53 can inhibit autophagy in yeast, as we show here. Bioinformatic investigations of the p53 interactome in relationship to the autophagy-relevant protein network underscored the possible relevance of a direct molecular interaction between p53 and the mammalian ortholog of the essential yeast autophagy protein Atg17, namely RB1-inducible coiled-coil protein 1 (RB1CC1), also called FAK family kinase-interacting protein of 200 KDa (FIP200). Mutational analyses revealed that a single point mutation in p53 (K382R) abolished its capacity to inhibit autophagy upon transfection into p53-deficient human colon cancer or yeast cells. In conditions in which wild-type p53 co-immunoprecipitated with RB1CC1/FIP200, p53 (K382R) failed to do so, underscoring the importance of the physical interaction between these proteins for the control of autophagy. In conclusion, p53 regulates autophagy through a direct molecular interaction with RB1CC1/FIP200, a protein that is essential for the very apical step of autophagy initiation.

Patients with non-small cell lung cancer (NSCLC) are routinely treated with cytotoxic agents such as cisplatin. Through a genome-wide siRNA-based screen, we identified vitamin B6 metabolism as a central regulator of cisplatin responses in vitro and in vivo. By aggravating a bioenergetic catastrophe that involves the depletion of intracellular glutathione, vitamin B6 exacerbates cisplatin-mediated DNA damage, thus sensitizing a large panel of cancer cell lines to apoptosis. Moreover, vitamin B6 sensitizes cancer cells to apoptosis induction by distinct types of physical and chemical stress, including multiple chemotherapeutics. This effect requires pyridoxal kinase (PDXK), the enzyme that generates the bioactive form of vitamin B6. In line with a general role of vitamin B6 in stress responses, low PDXK expression levels were found to be associated with poor disease outcome in two independent cohorts of patients with NSCLC. These results indicate that PDXK expression levels constitute a biomarker for risk stratification among patients with NSCLC.

The BH3 mimetic ABT737 induces autophagy by competitively disrupting the inhibitory interaction between the BH3 domain of Beclin 1 and the anti-apoptotic proteins Bcl-2 and Bcl-XL, thereby stimulating the Beclin 1-dependent allosteric activation of the pro-autophagic lipid kinase VPS34. Here, we examined whether ABT737 stimulates other pro-autophagic signal-transduction pathways. ABT737 caused the activating phosphorylation of AMP-dependent kinase (AMPK) and of the AMPK substrate acetyl CoA carboxylase, the activating phosphorylation of several subunits of the inhibitor of NF-κB (IκB) kinase (IKK) and the hyperphosphorylation of the IKK substrate IκB, inhibition of the activity of mammalian target of rapamycin (mTOR) and consequent dephosphorylation of the mTOR substrate S6 kinase. In addition, ABT737 treatment dephosphorylates (and hence likewise inhibits) p53, glycogen synthase kinase-3 and Akt. All these effects were shared by ABT737 and another structurally unrelated BH3 mimetic, HA14-1. Functional experiments revealed that pharmacological or genetic inhibition of IKK, Sirtuin and the p53-depleting ubiquitin ligase MDM2 prevented ABT737-induced autophagy. These results point to unexpected and pleiotropic pro-autophagic effects of BH3 mimetics involving the modulation of multiple signalling pathways.

Background: The primary cilium is a singular cellular structure that extends from the surface of many cell types and plays crucial roles in vertebrate development, including that of the heart. Whereas ciliated cells have been described in developing heart, a role for primary cilia in adult heart has not been reported. This, coupled with the fact that mutations in genes coding for multiple ciliary proteins underlie polycystic kidney disease, a disorder with numerous cardiovascular manifestations, prompted us to identify cells in adult heart harboring a primary cilium and to determine whether primary cilia play a role in disease-related remodeling. Methods: Histological analysis of cardiac tissues from C57BL/6 mouse embryos, neonatal mice, and adult mice was performed to evaluate for primary cilia. Three injury models (apical resection, ischemia/reperfusion, and myocardial infarction) were used to identify the location and cell type of ciliated cells with the use of antibodies specific for cilia (acetylated tubulin, γ-tubulin, polycystin [PC] 1, PC2, and KIF3A), fibroblasts (vimentin, α-smooth muscle actin, and fibroblast-specific protein-1), and cardiomyocytes (α-actinin and troponin I). A similar approach was used to assess for primary cilia in infarcted human myocardial tissue. We studied mice silenced exclusively in myofibroblasts for PC1 and evaluated the role of PC1 in fibrogenesis in adult rat fibroblasts and myofibroblasts. Results: We identified primary cilia in mouse, rat, and human heart, specifically and exclusively in cardiac fibroblasts. Ciliated fibroblasts are enriched in areas of myocardial injury. Transforming growth factor β-1 signaling and SMAD3 activation were impaired in fibroblasts depleted of the primary cilium. Extracellular matrix protein levels and contractile function were also impaired. In vivo, depletion of PC1 in activated fibroblasts after myocardial infarction impaired the remodeling response. Conclusions: Fibroblasts in the neonatal and adult heart harbor a primary cilium. This organelle and its requisite signaling protein, PC1, are required for critical elements of fibrogenesis, including transforming growth factor β-1–SMAD3 activation, production of extracellular matrix proteins, and cell contractility. Together, these findings point to a pivotal role of this organelle, and PC1, in disease-related pathological cardiac remodeling and suggest that some of the cardiovascular manifestations of autosomal dominant polycystic kidney disease derive directly from myocardium-autonomous abnormalities.

With increased life expectancy, women will spend over three decades of life postmenopause. The menopausal transition increases susceptibility to metabolic diseases such as obesity, diabetes, cardiovascular disease, and cancer. Thus, it is more important than ever to develop effective hormonal treatment strategies to protect aging women. Understanding the role of estrogens, and their biological actions mediated by estrogen receptors (ERs), in the regulation of cardiometabolic health is of paramount importance to discover novel targeted therapeutics. In this brief review, we provide a detailed overview of the literature, from basic science findings to human clinical trial evidence, supporting a protective role of estrogens and their receptors, specifically ERα, in maintenance of cardiometabolic health. In so doing, we provide a concise mechanistic discussion of some of the major tissue-specific roles of estrogens signaling through ERα. Taken together, evidence suggests that targeted, perhaps receptor-specific, hormonal therapies can and should be used to optimize the health of women as they transition through menopause, while reducing the undesired complications that have limited the efficacy and use of traditional hormone replacement interventions.

Macroautophagy, often referred to as autophagy, designates the process by which portions of the cytoplasm, intracellular organelles and long-lived proteins are engulfed in double-membraned vacuoles (autophagosomes) and sent for lysosomal degradation. Basal levels of autophagy contribute to the maintenance of intracellular homoeostasis by ensuring the turnover of supernumerary, aged and/or damaged components. Under conditions of starvation, the autophagic pathway operates to supply cells with metabolic substrates, and hence represents an important pro-survival mechanism. Moreover, autophagy is required for normal development and for the protective response to intracellular pathogens. Conversely, uncontrolled autophagy is associated with a particular type of cell death (termed autophagic, or type II) that is characterized by the massive accumulation of autophagosomes. Regulators of apoptosis (e.g. Bcl-2 family members) also modulate autophagy, suggesting an intimate cross-talk between these two degradative pathways. It is still unclear whether autophagic vacuolization has a causative role in cell death or whether it represents the ultimate attempt of cells to cope with lethal stress. For a multicellular organism, autophagic cell death might well represent a pro-survival mechanism, by providing metabolic supplies during whole-body nutrient deprivation. Alternatively, type II cell death might contribute to the disposal of cell corpses when heterophagy is deficient. Here, we briefly review the roles of autophagy in cell death and its avoidance.

Mitochondrial membrane permeabilization (MMP) is commonly regarded as the "point-of-no-return" in the cascade of events that delineate the intrinsic pathway of apoptosis. MMP leads to the functional impairment of mitochondria and to the release into the cytosol of toxic proteins that are normally confined within the mitochondrial intermembrane space. These include direct activators of caspases and caspase-independent effectors of the cell death program. MMP has been implicated in a plethora of pathophysiological settings. In particular, MMP contributes to both the immediate and delayed phases of cell loss that follow acute neuronal injury by ischemia/reperfusion or trauma. Although preventing MMP a priori would be the most desirable therapeutic choice, prophylactic interventions are rarely (if ever) achievable in the treatment of stroke and trauma patients. Conversely, interventions that block the post-mitochondrial phase of apoptosis (if administered within the first few hours after the accident) hold great promises for the development of novel neuroprotective strategies. In animal models of acute neuronal injury, the inhibition of caspases, apoptosis-inducing factor (AIF) and other apoptotic effectors can confer significant neuroprotection. Our review recapitulates the results of these studies and proposes novel strategies of inhibiting post-mitochondrial apoptosis in neurons.

Although the tumor suppressor protein p53 is a major senescence- and cell death-inducing transcription factor, recent work has clearly demonstrated that p53 has additional, extranuclear effects that contribute to its cell cycle-arresting and proapoptotic functions. Mitochondrial outer membrane permeabilization (MOMP) is (one of) the most prominent apoptotic checkpoint(s), and cytoplasmic p53 can induce MOMP by direct interactions with multidomain proteins from the Bcl-2 family present at the mitochondrial outer membrane (OM). Since MOMP is commonly disabled in cancer cells, its pharmacological induction constitutes a therapeutic goal, and this has stimulated the design of mitochondriotropic inducers of apoptosis, both inhibitors of antiapoptotic Bcl-2 family proteins (e.g., Bcl-2, Bcl-XL) or activators of their proapoptotic counterparts (e.g., Bak, Bax). Moreover, novel approaches of gene therapy have been designed in which p53 is specifically targeted to mitochondria and have been demonstrated to inhibit the growth of human cancer xenografts in immunodeficient mice. Thus, a number of distinct strategies can be employed to achieve the therapeutic induction of MOMP in cancer cells.

Macroautophagy (herein referred to as autophagy) constitutes a phylogenetically old mechanism leading to the lysosomal degradation of cytoplasmic structures. At baseline levels, autophagy exerts homeostatic functions by ensuring the turnover of potentially harmful organelles and long-lived aggregate-prone proteins. Moreover, the autophagic flow can be dramatically upregulated in response to a plethora of stressful conditions, including glucose, amino acid, oxygen, or growth factor deprivation, accumulation of unfolded proteins in the endoplasmic reticulum, and invasion by intracellular pathogens. In some experimental settings, stress-induced autophagy has been shown to contribute to programmed cell death. Nevertheless, autophagy most often confers cytoprotection by providing cells with new metabolic substrates or by ridding them of noxious intracellular entities including protein aggregates and invading organisms. Thus, autophagy has been implicated in an ever-increasing number of human diseases including cancer. Autophagy inhibition accelerates the demise of tumor cells that are subjected to chemo- or radiotherapy, thereby constituting an interesting target for the development of anticancer strategies. However, several oncosuppressor proteins and oncoproteins have been recently shown to stimulate and inhibit the autophagic flow, respectively, suggesting that autophagy exerts bona fide tumor-suppressive functions. In this review, we will discuss the mechanisms by which autophagy may prevent oncogenesis. Antioxid. Redox Signal. 14, 2251–2269.

Autophagy is one of the principal mechanisms of cellular defense against nutrient depletion and damage to cytoplasmic organelles. When p53 is inhibited by a pharmacological antagonist (cyclic pifithrin-alpha), depleted by a specific small interfering RNA (siRNA) or deleted by homologous recombination, multiple signs of autophagy are induced. Here, we show by epistatic analysis that p53 inhibition results in a maximum level of autophagy that cannot be further enhanced by a variety of different autophagy inducers including lithium, tunicamycin-induced stress of the endoplasmic reticulum (ER) or inhibition of Bcl-2 and Bcl-X(L) with the BH3 mimetic ABT737. Chemical inducers of autophagy (including rapamycin, lithium, tunicamycin and ABT737) induced rapid depletion of the p53 protein. The absence or the inhibition of p53 caused autophagy mostly in the G(1) phase, less so in the S phase and spares the G(2)/M phase of the cell cycle. The possible pathophysiological implications of these findings are discussed.

Autophagic responses are coupled to the activation of the inhibitor of NF-κB kinase (IKK). Here, we report that the essential autophagy mediator Beclin 1 and TGFβ-activated kinase 1 (TAK1)-binding proteins 2 and 3 (TAB2 and TAB3), two upstream activators of the TAK1-IKK signalling axis, constitutively interact with each other via their coiled-coil domains (CCDs). Upon autophagy induction, TAB2 and TAB3 dissociate from Beclin 1 and bind TAK1. Moreover, overexpression of TAB2 and TAB3 suppresses, while their depletion triggers, autophagy. The expression of the C-terminal domain of TAB2 or TAB3 or that of the CCD of Beclin 1 competitively disrupts the interaction between endogenous Beclin 1, TAB2 and TAB3, hence stimulating autophagy through a pathway that requires endogenous Beclin 1, TAK1 and IKK to be optimally efficient. These results point to the existence of an autophagy-stimulatory 'switch' whereby TAB2 and TAB3 abandon inhibitory interactions with Beclin 1 to engage in a stimulatory liaison with TAK1.

Non-communicable diseases (NCDs), also known as chronic diseases, are long-lasting conditions that affect millions of people around the world. Different factors contribute to their genesis and progression; however they share common features, which are critical for the development of novel therapeutic strategies. A persistently altered inflammatory response is typically observed in many NCDs together with redox imbalance. Additionally, dysregulated proteostasis, mainly derived as a consequence of compromised autophagy, is a common feature of several chronic diseases. In this review, we discuss the crosstalk among inflammation, autophagy and oxidative stress, and how they participate in the progression of chronic diseases such as cancer, cardiovascular diseases, obesity and type II diabetes mellitus.

Autophagy is a catabolic mechanism where intracellular material is degraded by vesicular structures called autophagolysosomes. Autophagy is necessary to maintain the normal function of the central nervous system (CNS), avoiding the accumulation of misfolded and aggregated proteins. Consistently, impaired autophagy has been associated with the pathogenesis of various neurodegenerative diseases. The proteins TAR DNA-binding protein-43 (TDP-43), which regulates RNA processing at different levels, and chromosome 9 open reading frame 72 (C9orf72), probably involved in membrane trafficking, are crucial in the development of neurodegenerative diseases such as Amyotrophic lateral sclerosis (ALS) and Frontotemporal Lobar Degeneration (FTLD). Additionally, recent studies have identified a role for these proteins in the control of autophagy. In this manuscript, we review what is known regarding the autophagic mechanism and discuss the involvement of TDP-43 and C9orf72 in autophagy and their impact on neurodegenerative diseases.

Obesity, and its associated comorbidities such as type 2 diabetes, cardiovascular diseases, and certain cancers, represent major health challenges. Importantly, there is a sexual dimorphism with respect to the prevalence of obesity and its associated metabolic diseases, implicating a role for gonadal hormones. Specifically, estrogens have been demonstrated to regulate metabolism perhaps by acting as a leptin mimetic in the central nervous system (CNS). CNS estrogen receptors (ERs) include ER alpha (ERα) and ER beta (ERβ), which are found in nuclear, cytoplasmic and membrane sites throughout the brain. Additionally, estrogens can bind to and activate a G protein-coupled estrogen receptor (GPER), which is a membrane-associated ER. ERs are expressed on neurons as well as glia, which are known to play a major role in providing nutrient supply for neurons and have recently received increasing attention for their potentially important involvement in the CNS regulation of systemic metabolism and energy balance. This brief overview summarizes data focusing on the potential role of astrocytic estrogen action as a key component of estrogenic modulation responsible for mediating the sexual dimorphism in body weight regulation and obesity.

In this review, we discuss the observations that, following chronic high-fat diet (HFD) exposure, male mice have higher levels of saturated fatty acids (FAs) and total sphingolipids, whereas lower amounts of polyunsaturated FAs in the central nervous system (CNS) than females. Furthermore, males, when compared with female mice, have higher levels of inflammatory markers in the hypothalamus following exposure to HFD. The increase in markers of inflammation in male mice is possibly due to the reductions in proliferator-activated receptor gamma coactivator 1 alpha (PGC-1α) and estrogen receptor alpha (ERα), which is not recapitulated in female mice. Consistently, hypothalamic inflammation is induced both in male and female ERα total-body knockout mice when exposed to a HFD, thus confirming the key role of ERα in the regulation of HFD-induced hypothalamic inflammation. Finally, the HFD-induced depletion of hypothalamic ERα is associated with dysregulation in metabolic homeostasis, as evidenced by reductions in glucose tolerance and decrements in myocardial function.

Chronic consumption of high fat diets (HFDs), rich in saturated fatty acids (SatFAs) like palmitic acid (PA), is associated with the development of obesity and obesity-related metabolic diseases such as type II diabetes mellitus (T2DM). Previous studies indicate that PA accumulates in the hypothalamus following consumption of HFDs; in addition, HFDs consumption inhibits autophagy and reduces insulin sensitivity. Whether malfunction of autophagy specifically in hypothalamic neurons decreases insulin sensitivity remains unknown. PA does activate the Free Fatty Acid Receptor 1 (FFAR1), also known as G protein-coupled receptor 40 (GPR40); however, whether FFAR1 mediates the effects of PA on hypothalamic autophagy and insulin sensitivity has not been shown. Here, we demonstrate that exposure to PA inhibits the autophagic flux and reduces insulin sensitivity in a cellular model of hypothalamic neurons (N43/5 cells). Furthermore, we show that inhibition of autophagy and the autophagic flux reduces insulin sensitivity in hypothalamic neuronal cells. Interestingly, the inhibition of the autophagic flux, and the reduction in insulin sensitivity are prevented by pharmacological inhibition of FFAR1. Our findings show that dysregulation of autophagy reduces insulin sensitivity in hypothalamic neuronal cells. In addition, our data suggest FFAR1 mediates the ability of PA to inhibit autophagic flux and reduce insulin sensitivity in hypothalamic neuronal cells. These results reveal a novel cellular mechanism linking PA-rich diets to decreased insulin sensitivity in the hypothalamus and suggest that hypothalamic autophagy might represent a target for future T2DM therapies.

Proper execution of cellular function, maintenance of cellular homeostasis and cell survival depend on functional integration of cellular processes and correct orchestration of cellular responses to stresses. Cancer transformation is a common negative consequence of mismanagement of coordinated response by the cell. In this scenario, by maintaining the balance among synthesis, degradation, and recycling of cytosolic components including proteins, lipids, and organelles the process of autophagy plays a central role. Several environmental stresses activate autophagy, among those hypoxia, DNA damage, inflammation, and metabolic challenges such as starvation. In addition to these chemical challenges, there is a requirement for cells to cope with mechanical stresses stemming from their microenvironment. Cells accomplish this task by activating an intrinsic mechanical response mediated by cytoskeleton active processes and through mechanosensitive protein complexes which interface the cells with their mechano-environment. Despite autophagy and cell mechanics being known to play crucial transforming roles during oncogenesis and malignant progression their interplay is largely overlooked. In this review, we highlight the role of physical forces in autophagy regulation and their potential implications in both physiological as well as pathological conditions. By taking a mechanical perspective, we wish to stimulate novel questions to further the investigation of the mechanical requirements of autophagy and appreciate the extent to which mechanical signals affect this process.

PSMD14/POH1/Rpn11 plays a crucial role in cellular homeostasis. PSMD14 is a structural subunit of the lid subcomplex of the proteasome 19S regulatory particle with constitutive deubiquitinase activity. Canonically, PSMD14 removes the full ubiquitin chains with K48-linkages by hydrolyzing the isopeptide bond between the substrate and the C-terminus of the first ubiquitin, a crucial step for the entry of substrates into the catalytic barrel of the 20S proteasome and their subsequent degradation, all in context of the 26S proteasome. However, more recent discoveries indicate PSMD14 DUB activity is not only coupled to the translocation of substrates into the core of 20S proteasome. During the assembly of the lid, activity of PSMD14 has been detected in the context of the heterodimer with PSMD7. Additionally, assembly of the lid subcomplex occurs as an independent event of the base subcomplex and 20S proteasome. This feature opens the possibility that the regulatory particle, free lid subcomplex or the heterodimer PSMD14-PSMD7 might play other physiological roles including a positive function on protein stability through deubiquitination. Here we discuss scenarios that could enhance this PSMD14 non-canonical pathway, the potential impact in preventing degradation of substrates by autophagy highlighting the main findings that support this hypothesis. Finally, we discuss why this information should be investigated in biomedicine specifically with focus on cancer progression to design new therapeutic strategies against the lid subcomplex and the heterodimer PSMD14-PSMD7, highlighting PSMD14 as a druggable target for cancer therapy.

Mitochondria play a central role in cell survival and cell death. While producing the bulk of intracellular ATP, mitochondrial respiration represents the most prominent source of harmful reactive oxygen species. Mitochondria participate in many anabolic pathways, including cholesterol and nucleotide biosynthesis, yet also control multiple biochemical cascades that contribute to the programmed demise of cells. The tumor suppressor protein p53 is best known for its ability to orchestrate a transcriptional response to stress that can have multiple outcomes, including cell cycle arrest and cell death. p53-mediated tumor suppression, however, also involves transcription-independent mechanisms. Cytoplasmic p53 can physically interact with members of the BCL-2 protein family, thereby promoting mitochondrial membrane permeabilization. Moreover, extranuclear p53 can suppress autophagy, a major prosurvival mechanism that is activated in response to multiple stress conditions. Thirty years have passed since its discovery, and p53 has been ascribed with an ever-increasing number of functions. For instance, p53 has turned out to influence the cell's redox status, by transactivating either anti- or pro-oxidant factors, and to regulate the metabolic switch between glycolysis and aerobic respiration. In this review, we will analyze the mechanisms by which p53 affects the balance between the vital and lethal functions of mitochondria.

Viral strategies for the evasion of immunogenic cell death (Symposium). J Intern Med 2010; 267: 526-542. Driven by co-evolutionary forces, viruses have refined a wide arsenal of strategies to interfere with the host defences. On one hand, viruses can block/retard programmed cell death in infected cells, thereby suppressing one of the most ancient mechanisms against viral dissemination. On the other hand, multiple viral factors can efficiently trigger the death of infected cells and uninfected cells from the immune system, which favours viral spreading and prevents/limits an active antiviral response, respectively. Moreover, several viruses are able to inhibit the molecular machinery that drives the translocation of calreticulin to the surface of dying cells. Thereby, viruses block the exposure of an engulfment signal that is required for the efficient uptake of dying cells by dendritic cells and for the induction of the immune response. In this review, we discuss a variety of mechanisms by which viruses interfere with the cell death machinery and, in particular, by which they subvert immunogenic cell death.

In this study, we analyzed the fatty acid profile of brains and plasma from male and female mice fed chow or a western-style high fat diet (WD) for 16 weeks to determine if males and females process fatty acids differently. Based on the differences in fatty acids observed in vivo, we performed in vitro experiments on N43 hypothalamic neuronal cells to begin to elucidate how the fatty acid milieu may impact brain inflammation. Using a comprehensive mass spectrometry fatty acid analysis, which includes a profile for 52 different fatty acid isomers, we assayed the plasma and brain fatty acid composition of age-matched male and female mice maintained on chow or a WD. Additionally, using the same techniques, we determined the fatty acid composition of N43 hypothalamic cells following exposure to palmitic and linoleic acid, alone or in combination. Our data demonstrate there is a sexual dimorphism in brain fatty acid content both following the consumption of the chow diet, as well as the WD, with males having an increased percentage of saturated fatty acids and reductions in ω6-polyunsaturated fatty acids when compared to females. Interestingly, we did not observe a sexual dimorphism in fatty acid content in the plasma of the same mice. Furthermore, exposure of N43 cells to the ω6-PUFA linoleic acid, which is higher in female brains when compared to males, reduces palmitic acid-induced inflammation. Our data suggest male and female brains, and not plasma, differ in their fatty acid profile. This is the first time, to our knowledge, lipidomic analyses has been used to directly test the hypothesis there is a sexual dimorphism in brain and plasma fatty acid composition following consumption of the chow diet, as well as following exposure to the WD.

Maternal nutrition has a profound long-term impact on infant health. Poor maternal nutrition influences placental development and fetal growth, resulting in low birth weight, which is strongly associated with the risk of developing chronic diseases, including heart disease, hypertension, asthma, and type 2 diabetes, later in life. Few studies have delineated the mechanisms by which maternal nutrition affects fetal lung development. Here, we report that maternal exposure to a diet high in fat (HFD) causes placental inflammation, resulting in placental insufficiency, fetal growth restriction (FGR), and inhibition of fetal lung development. Notably, pre- and postnatal exposure to maternal HFD also results in persistent alveolar simplification in the postnatal period. Our novel findings provide a strong association between maternal diet and fetal lung development.

Hypoxia Inducible Factor 1 (HIF-1) promotes fibrosis and inflammation in adipose tissues, while estrogens and Estrogen Receptor α (ERα) have the opposite effect. Here we identify an Estrogen Response Element (ERE) in the promoter of Phd3, which is a negative regulatory enzyme of HIF-1, and we demonstrate HIF-1α is ubiquitinated following 17-β estradiol (E2)/ERα mediated Phd3 transcription. Manipulating ERα in vivo increases Phd3 transcription and reduces HIF-1 activity, while addition of PHD3 ameliorates adipose tissue fibrosis and inflammation. Our findings outline a novel regulatory relationship between E2/ERα, PHD3 and HIF-1 in adipose tissues, providing a mechanistic explanation for the protective effect of E2/ERα in adipose tissue.

In this Essay, we discuss the critical need to incorporate sex and gender in pre-clinical and clinical research to enhance our understanding of the mechanisms by which metabolic processes differ by sex and gender. This knowledge will allow for development of personalized medicine which will optimize therapies specific for individuals. In this Essay, we discuss the critical need to incorporate sex and gender in pre-clinical and clinical research to enhance our understanding of the mechanisms by which metabolic processes differ by sex and gender. This knowledge will allow for development of personalized medicine which will optimize therapies specific for individuals. Most pre-clinical and clinical medical research, both animal and human, has been biased with respect to sex. There has been a tendency to treat the sexes as equivalent and not consider how fluctuations of sex hormones in experimental settings impact outcomes, thereby limiting our understanding of the molecular mechanisms that drive sexual dimorphisms. The National Institutes of Health (NIH) has recently recognized this gap in scientific knowledge and now mandates that studies be conducted in both sexes. With few exceptions, basic science—pre-clinical (Beery and Zucker, 2011Beery A.K. Zucker I. Sex bias in neuroscience and biomedical research.Neurosci. Biobehav. Rev. 2011; 35: 565-572Crossref PubMed Scopus (912) Google Scholar, Woodruff et al., 2014Woodruff T.K. Kibbe M.R. Paller A.S. Turek F.W. Woolley C.S. Commentary: "Leaning in" to support sex differences in basic science and clinical research.Endocrinology. 2014; 155: 1181-1183Crossref PubMed Scopus (26) Google Scholar) and clinical (Institute of Medicine Board on Population and Public Health, 2012Institute of Medicine Board on Population and Public HealthThe National Academies Collection: reports funded by National Institutes of Health.in: Sex-Specific Reporting of Scientific Research: A Workshop Summary. National Academies Press National Academy of Sciences, Washington, D.C.2012Google Scholar, Institute of Medicine Forum on Neuroscience and Nervous System Disorders, 2011Institute of Medicine Forum on Neuroscience and Nervous System DisordersThe National Academies Collection: reports funded by National Institutes of Health.in: Sex Differences and Implications for Translational Neuroscience Research: Workshop Summary. National Academies Press, Washington, D.C.2011Google Scholar)—research has predominately used male subjects, consequently ignoring the contribution of sex in outcome measurements. Failure to include both sexes in experiments, and/or insufficient analysis of data by sex, in fact generates data not biologically relevant to either sex. The Congressional Caucus for Women's Issues, women's health advocacy groups, and the NIH collectively realized that excluding women from clinical research was bad for women and bad for science. As a result, in 1993 the NIH Revitalization Act was passed to begin to address these inequities by requiring the inclusion of both sexes in NIH-funded clinical research. This issue has become sufficiently important that the NIH more recently established the Office of Research on Women's Health (ORWH); nonetheless, despite these efforts, many publications continue to neglect sex-based considerations, contributions, and analyses in pre-clinical and clinical studies. The NIH is now implementing policies that require grant applicants to explicitly detail plans for the use and inclusion of male and female cells and animals in pre-clinical studies, unless sex-specific exclusion is warranted based on rigorously defined exceptions. Furthermore, several relevant organizations have taken steps to increase awareness of, and address unconscious bias about, the importance and difference between sex and gender in biomedical research, and several journals now require authors to specify sex- and gender-related information. With the growing emphasis on inclusion of both sexes in research, it is critical to define and use the terms "sex" and "gender" appropriately. Sex and gender are different constructs. Sex, according to the Canadian Institutes for Health Research Panel on Sex and Gender (Canadian Institutes of Health Research, 2015Canadian Institutes of Health Research (2015). Sex, Gender and Health Research Guide: A Tool for CIHR Applicants. http://www.cihr-irsc.gc.ca/e/32019.html.Google Scholar), "refers to a set of biological attributes in humans and animals. It is primarily associated with physical and physiological features including chromosomes, gene expression, hormone levels, and reproductive/sexual anatomy." In contrast, gender refers to how people perceive themselves and others, as well as how they act and interact. Gender additionally refers to social behaviors, expectations, expressions, and identities of girls, women, boys, men, and gender-diverse people. Assessments of health and disease risk need to take both sex and gender into account (Phillips, 2005Phillips S.P. Defining and measuring gender: a social determinant of health whose time has come.Int. J. Equity Health. 2005; 4: 11Crossref PubMed Scopus (164) Google Scholar). Below are considerations pertaining to how sex and gender should be applied to pre-clinical and clinical research. Cultural norms pertaining to gender roles and sex-related behaviors fluctuate and change over time, as well as across cultures. The berdache (a French term used by Native Americans to refer to younger partners in male homosexual relationships), the fa'afafine (Samoan for "the way of a woman") in the Pacific, and the kathoey in Thailand are all examples of cultures that differ from the traditional Western classification of people into "males" and "females," demonstrating that sex and gender are not always neatly or in fact easily divided along binary lines. As an example, among some native North American communities, gender is considered a continuum, enabling acknowledgment of individuals who have both masculine and feminine qualities and characteristics. Gender impacts disease risk, diagnosis, and treatment. As one example, men are often thought to be at an increased risk for cardiovascular disease (CVD), in part due to their gender-based propensity to engage in risk-taking behaviors such as smoking or alcohol consumption. Importantly, women who have taken on societal roles associated with the male gender have an increased disease prevalence linked with the pressures associated with these gender-defined roles (Bekhouche et al., 2015Bekhouche Y.H.R. Tyson L.D. Zahidi S. The Global Gender Gap Report, 2015. World Economic Forum, 2015Google Scholar, Hausmann et al., 2012Hausmann R. Tyson Laura D. Zahidi S. The Global Gender Gap Report, 2012. World Economic Forum, 2012Google Scholar, Izadnegahdar et al., 2014Izadnegahdar M. Singer J. Lee M.K. Gao M. Thompson C.R. Kopec J. Humphries K.H. Do younger women fare worse? Sex differences in acute myocardial infarction hospitalization and early mortality rates over ten years.J. Womens Health. 2014; 23: 10-17Crossref PubMed Scopus (93) Google Scholar, Kawase et al., 2013Kawase K. Kwong A. Yorozuya K. Tomizawa Y. Numann P.J. Sanfey H. The attitude and perceptions of work-life balance: a comparison among women surgeons in Japan, USA, and Hong Kong China.World J. Surg. 2013; 37: 2-11Crossref PubMed Scopus (21) Google Scholar, Sozzi et al., 2007Sozzi F.B. Danzi G.B. Foco L. Ferlini M. Tubaro M. Galli M. Celli P. Mannucci P.M. Myocardial infarction in the young: a sex-based comparison.Coron. Artery Dis. 2007; 18: 429-431Crossref PubMed Scopus (26) Google Scholar). Lastly, using the term "gender" when referring to in vitro assays or animal studies in basic science research is incorrect, and instead the term "sex" should be used. As indicated above, the role of sex in scientific discovery, disease detection, diagnosis, and treatment is often under-appreciated. For while the sex of the subject in clinical studies is obviously important, so too is the sex of the cell, or the hormonal context in which in vitro studies incorporate sex in the model. For while many intrinsic properties of cells can appear hormone independent, cells may also exhibit differential variations upon exposure to sex hormones. Female and male cells respond differently to chemical and microbial stressors, and yet the sex of cell lines studied in vitro is mostly ignored and rarely reported. When sex is factored into disease risk, it is well established that premenopausal women are relatively protected from diseases associated with the metabolic syndrome, including cardiovascular disease (CVD), when compared to age-matched men (Collins et al., 2002Collins P. Stevenson J.C. Mosca L. Spotlight on gender.Cardiovasc. Res. 2002; 53: 535-537Crossref PubMed Scopus (24) Google Scholar, Ren and Kelley, 2009Ren J. Kelley R.O. Cardiac health in women with metabolic syndrome: clinical aspects and pathophysiology.Obesity (Silver Spring). 2009; 17: 1114-1123PubMed Google Scholar, Skafar et al., 1997Skafar D.F. Xu R. Morales J. Ram J. Sowers J.R. Clinical review 91: Female sex hormones and cardiovascular disease in women.J. Clin. Endocrinol. Metab. 1997; 82: 3913-3918Crossref PubMed Scopus (131) Google Scholar, Yanes and Reckelhoff, 2011Yanes L.L. Reckelhoff J.F. Postmenopausal hypertension.Am. J. Hypertens. 2011; 24: 740-749Crossref PubMed Scopus (132) Google Scholar). This "sex advantage" disappears after menopause, leading to the generally accepted conclusion that sex hormones, and in particular estrogens, protect against the metabolic syndrome. Compelling data suggest the protective effect of estrogens are a continuum such that low levels of estrogens are associated with increased CVD risk, with several lines of evidence linking hypoestrogenemia (HypoE) in young women to increased CVD. Additionally, early menopause, (≤45 years) is associated with accelerated atherosclerosis and a 2.6-fold increase in the risk of CVD (95% CI 2.05–3.35) (Kannel and Wilson, 1995Kannel W.B. Wilson P.W. Risk factors that attenuate the female coronary disease advantage.Arch. Intern. Med. 1995; 155: 57-61Crossref PubMed Scopus (308) Google Scholar), as well as increased CVD mortality (Cooper and Sandler, 1998Cooper G.S. Sandler D.P. Age at natural menopause and mortality.Ann. Epidemiol. 1998; 8: 229-235Abstract Full Text Full Text PDF PubMed Scopus (219) Google Scholar, Jacobsen et al., 1997Jacobsen B.K. Nilssen S. Heuch I. Kvåle G. Does age at natural menopause affect mortality from ischemic heart disease?.J. Clin. Epidemiol. 1997; 50: 475-479Abstract Full Text PDF PubMed Scopus (108) Google Scholar) compared to women experiencing later menopause. Conditions resulting in severe HypoE, including Turner's syndrome (TS) and primary ovarian insufficiency (POI), are also associated with elevated rates of CVD in young women (Swerdlow et al., 2001Swerdlow A.J. Hermon C. Jacobs P.A. Alberman E. Beral V. Daker M. Fordyce A. Youings S. Mortality and cancer incidence in persons with numerical sex chromosome abnormalities: a cohort study.Ann. Hum. Genet. 2001; 65: 177-188Crossref PubMed Google Scholar). There is a large amount of data published with a variety of findings focusing on the role of female hormones in CVD. Here, we briefly summarize the literature with respect to the protective role for estrogens in CVD. Initial observations suggested that postmenopausal women receiving hormone replacement therapy (HRT) are relatively protected from the metabolic syndrome compared to women not receiving HRT. However, these early observations have since been challenged by two randomized prospective primary and secondary prevention trials, both of which found a significantly increased CVD risk in postmenopausal women on HRT. Data on the benefits or determinants of estrogen replacement therapy in postmenopausal women have more recently given rise to the "timing hypothesis," which suggests that hormonal replacement prior to menopause is associated with reduced cardiometabolic risk, whereas hormone replacement following menopause is associated with increased cardiometabolic risk. A recent article in the New England Journal of Medicine supports the "timing hypothesis" reporting that estradiol replacement therapy in early menopause is associated with vascular benefit, whereas estradiol replacement therapy late in menopause is less advantageous or even contraindicated (Hodis et al., 2016Hodis H.N. Mack W.J. Henderson V.W. Shoupe D. Budoff M.J. Hwang-Levine J. Li Y. Feng M. Dustin L. Kono N. et al.ELITE Research GroupVascular effects of early versus late postmenopausal treatment with estradiol.N. Engl. J. Med. 2016; 374: 1221-1231Crossref PubMed Scopus (430) Google Scholar). When, at what level, and at what age are estrogens protective in females? In men, testosterone (T) can be aromatized to estrogens (E), with more than 80% of circulating E in men being derived from aromatization of T (Carani et al., 1997Carani C. Qin K. Simoni M. Faustini-Fustini M. Serpente S. Boyd J. Korach K.S. Simpson E.R. Effect of testosterone and estradiol in a man with aromatase deficiency.N. Engl. J. Med. 1997; 337: 91-95Crossref PubMed Scopus (966) Google Scholar). Finkelstein et al. found that blocking the aromatization of T results in increased adiposity and reduced sexual function in men (Finkelstein et al., 2013Finkelstein J.S. Lee H. Burnett-Bowie S.A. Pallais J.C. Yu E.W. Borges L.F. Jones B.F. Barry C.V. Wulczyn K.E. Thomas B.J. Leder B.Z. Gonadal steroids and body composition, strength, and sexual function in men.N. Engl. J. Med. 2013; 369: 1011-1022Crossref PubMed Scopus (456) Google Scholar), further supporting the concept that E deficiency is largely responsible for some of the key consequences of male hypogonadism. As serum levels of T decline with aging, there is a concomitant decline in serum levels of E. In a related report, Jankowska et al. demonstrated that men with the lowest quintile of estradiol (E2) (lowest 20%, <12.90 pg/mL) were found to have the highest death rates from congestive heart failure over a 3-year period, while men with E2 in the range of 20–30 pg/mL had the lowest rates (Jankowska et al., 2009Jankowska E.A. Rozentryt P. Ponikowska B. Hartmann O. Kustrzycka-Kratochwil D. Reczuch K. Nowak J. Borodulin-Nadzieja L. Polonski L. Banasiak W. et al.Circulating estradiol and mortality in men with systolic chronic heart failure.JAMA. 2009; 301: 1892-1901Crossref PubMed Scopus (75) Google Scholar). However, men with the highest E2 levels (≥37.40 pg/mL) also had a greater incidence of atherosclerosis (heart disease), diabetes, obesity, stroke, enlarged prostate, breast tissue growth, breast cancer, and other problems. Is there an optimal level of estrogens for men that provides disease protection, and how does this relate to age? Testosterone (T) has also been investigated with respect to modulating disease risk, and the results are conflicting. Lower T levels in middle-aged and older men are associated with insulin resistance, the metabolic syndrome, and diabetes. Furthermore, lower T in older men predicts cardiovascular events, including stroke and transient ischemic attack, and is associated with higher CVD and overall mortality (Schwarcz and Frishman, 2010Schwarcz M.D. Frishman W.H. Testosterone and coronary artery disease.Cardiol. Rev. 2010; 18: 251-257Crossref PubMed Scopus (16) Google Scholar). One interventional study using T therapy in men with CVD found beneficial effects on exercise-induced myocardial ischemia (Bhasin et al., 2006Bhasin S. Cunningham G.R. Hayes F.J. Matsumoto A.M. Snyder P.J. Swerdloff R.S. Montori V.M. Testosterone therapy in adult men with androgen deficiency syndromes: an endocrine society clinical practice guideline.J. Clin. Endocrinol. Metab. 2006; 91: 1995-2010Crossref PubMed Scopus (779) Google Scholar). However, in another trial of older men who were randomized to receive a substantial dose of T, the authors reported cardiovascular adverse effects (Snyder et al., 2016Snyder P.J. Bhasin S. Cunningham G.R. Matsumoto A.M. Stephens-Shields A.J. Cauley J.A. Gill T.M. Barrett-Connor E. Swerdloff R.S. Wang C. et al.Testosterone Trials InvestigatorsEffects of testosterone treatment in older men.N. Engl. J. Med. 2016; 374: 611-624Crossref PubMed Scopus (530) Google Scholar). Importantly, these effects were not observed in a comparable trial where men received a more conservative dose of T, suggesting that optimal dosing of T in older men with existing CVD is critical. In the Cardiovascular Risk in Young Finns Study, higher levels of T in younger men (24–45 years old) were associated with favorable cardiovascular risk profiles characterized by lower levels of triglycerides, insulin, and systolic blood pressure, and higher levels of high-density lipoprotein cholesterol (HDL-c) (Firtser et al., 2012Firtser S. Juonala M. Magnussen C.G. Jula A. Loo B.M. Marniemi J. Viikari J.S. Toppari J. Perheentupa A. Hutri-Kähönen N. Raitakari O.T. Relation of total and free testosterone and sex hormone-binding globulin with cardiovascular risk factors in men aged 24-45 years. The Cardiovascular Risk in Young Finns Study.Atherosclerosis. 2012; 222: 257-262Abstract Full Text Full Text PDF PubMed Scopus (43) Google Scholar). For women, elevations in T production, as seen with polycystic ovarian syndrome (PCOS), are associated with insulin resistance and CVD risk (Dokras, 2013Dokras A. Cardiovascular disease risk in women with PCOS.Steroids. 2013; 78: 773-776Crossref PubMed Scopus (90) Google Scholar). However, Barrett-Connor et al. followed Caucasian men (40–79 years old) for 12 years and found that none of the sex hormones measured (testosterone, androstenedione, estrone, or estradiol) was significantly associated with CVD risk at baseline or with subsequent cardiovascular mortality or ischemic heart disease morbidity or mortality (Barrett-Connor and Khaw, 1988Barrett-Connor E. Khaw K.T. Endogenous sex hormones and cardiovascular disease in men. A prospective population-based study.Circulation. 1988; 78: 539-545Crossref PubMed Scopus (317) Google Scholar). These conflicting findings suggest that adequately powered randomized control trials (RCTs) of T in middle-aged and older men are needed to clarify whether or not T intervention would reduce the incidence of disease susceptibility, and if this differs by age. As discussed above, T and E reportedly have beneficial, neutral, or harmful effects on disease risks, implying that the relative ratio of testosterone to estradiol (T/E) might be a critical variable, more so than the level of either hormone per se. Gong et al. concluded that the T/E ratio is key in the relationship between sex hormones and the risk of cerebrovascular disease (Gong et al., 2013Gong Y. Xiao H. Li C. Bai J. Cheng X. Jin M. Sun B. Lu Y. Shao Y. Tian H. Elevated t/e2 ratio is associated with an increased risk of cerebrovascular disease in elderly men.PLoS ONE. 2013; 8: e61598Crossref PubMed Scopus (22) Google Scholar). An additional study focusing on the T/E ratio in postmenopausal women with coronary heart disease (CHD) reported that the T/E ratio was negatively associated with total cholesterol, low-density lipoprotein cholesterol (LDL-c), and the atherogenic index of plasma but positively associated with HDL-c and HDL-c/LDL-c (for all, p < 0.0001). Furthermore, the authors concluded that an imbalanced T/E ratio had a strong association with cardiovascular risk factors in postmenopausal women with CHD (Dai et al., 2012Dai W. Li Y. Zheng H. Estradiol/Testosterone imbalance: impact on coronary heart disease risk factors in postmenopausal women.Cardiology. 2012; 121: 249-254Crossref PubMed Scopus (26) Google Scholar). Another study compared the effects of low T and/or low E in 3,000 aging men ages 69–80 for 4.5 years (Tivesten et al., 2009Tivesten A. Vandenput L. Labrie F. Karlsson M.K. Ljunggren O. Mellström D. Ohlsson C. Low serum testosterone and estradiol predict mortality in elderly men.J. Clin. Endocrinol. Metab. 2009; 94: 2482-2488Crossref PubMed Scopus (167) Google Scholar). Those men with low T had 65% greater all-cause mortality, but those men with low E2 also had 55% more deaths. Men who had both low E2 and low T had almost twice the risk of dying compared to men with E2 and T in the optimal range. While these data suggest that low levels of E and/or T per se increase disease risk, they further strongly suggest that focusing on either hormone in isolation may not adequately provide information as to their impact. Is there an optimal ratio of T/E that is unique for men that differs from women, and is this influenced by age? Is the optimal ratio defined by chromosomes and/or the timing of the hormonal replacement? Is there a population of individuals which can assist in defining the optimal hormonal ratio? Sex chromosomes, independent of sex hormones, are also linked to sex differences in disease risk (Wijchers et al., 2010Wijchers P.J. Yandim C. Panousopoulou E. Ahmad M. Harker N. Saveliev A. Burgoyne P.S. Festenstein R. Sexual dimorphism in mammalian autosomal gene regulation is determined not only by Sry but by sex chromosome complement as well.Dev. Cell. 2010; 19: 477-484Abstract Full Text Full Text PDF PubMed Scopus (94) Google Scholar). The X and Y chromosomes evolved over the past 160 million years from a pair of autosomes. Although they were both initially about the same size, the Y chromosome gradually lost the ability to recombine—or exchange—genetic information with the X chromosome, and therefore began to evolve independently. Subsequently, the Y chromosome contains only 3% of the genes that it once shared with the X chromosome. The Y chromosome is present exclusively in men and contains the sex-determining region (Sry), the primary determinant of testicular development, spermatogenesis, and masculinization. It was recently discovered that the genes conserved on the Y chromosome are expressed in cells and tissues throughout the body and are involved in decoding and interpreting the entirety of the genome (Bellott et al., 2014Bellott D.W. Hughes J.F. Skaletsky H. Brown L.G. Pyntikova T. Cho T.J. Koutseva N. Zaghlul S. Graves T. Rock S. et al.Mammalian Y chromosomes retain widely expressed dosage-sensitive regulators.Nature. 2014; 508: 494-499Crossref PubMed Scopus (395) Google Scholar). Despite this, the Y chromosome has mostly been excluded from the larger genome-wide association studies (GWAS), due to the belief that the Y chromosome is a "genetic wasteland" (Marshall Graves, 2002Marshall Graves J.A. The rise and fall of SRY.Trends Genet. 2002; 18: 259-264Abstract Full Text Full Text PDF PubMed Scopus (122) Google Scholar). This concept has been challenged recently as many Y chromosomal genes were found to be haploinsufficient regulatory genes (Bellott et al., 2014Bellott D.W. Hughes J.F. Skaletsky H. Brown L.G. Pyntikova T. Cho T.J. Koutseva N. Zaghlul S. Graves T. Rock S. et al.Mammalian Y chromosomes retain widely expressed dosage-sensitive regulators.Nature. 2014; 508: 494-499Crossref PubMed Scopus (395) Google Scholar). Additionally, certain single-nucleotide polymorphisms (SNPs) on the Y chromosome (Charchar et al., 2012Charchar F.J. Bloomer L.D. Barnes T.A. Cowley M.J. Nelson C.P. Wang Y. Denniff M. Debiec R. Christofidou P. Nankervis S. et al.Inheritance of coronary artery disease in men: an analysis of the role of the Y chromosome.Lancet. 2012; 379: 915-922Abstract Full Text Full Text PDF PubMed Scopus (158) Google Scholar) are correlated with risk factors associated with CVD, and this is independent of sex hormones. Females have two X chromosomes and therefore two copies of every X-linked gene. To compensate for the fact that men have only one X chromosome, one copy of the female X chromosome is randomly inactivated, or turned off. Inactivation of the X chromosome allows for adjustments in gene expression between sexes, individuals, and tissues (Deng et al., 2014Deng X. Berletch J.B. Nguyen D.K. Disteche C.M. X chromosome regulation: diverse patterns in development, tissues and disease.Nat. Rev. Genet. 2014; 15: 367-378Crossref PubMed Scopus (196) Google Scholar). When X-inactivation occurs, it utilizes cellular properties that are found only in females, making females more vulnerable than males to genetic or environmental perturbations during embryonic development (Chen et al., 2008Chen X. Watkins R. Delot E. Reliene R. Schiestl R.H. Burgoyne P.S. Arnold A.P. Sex difference in neural tube defects in p53-null mice is caused by differences in the complement of X not Y genes.Dev. Neurobiol. 2008; 68: 265-273Crossref PubMed Scopus (67) Google Scholar). To elucidate this point, a recent discovery was made using a novel mouse model where the mice were genetically engineered to visualize, at cellular resolution, X-inactivation in defined cell types. The authors found that cells silence X chromosomes in different patterns, providing a mechanism by which individual differences may be derived (Wu et al., 2014Wu H. Luo J. Yu H. Rattner A. Mo A. Wang Y. Smallwood P.M. Erlanger B. Wheelan S.J. Nathans J. Cellular resolution maps of X chromosome inactivation: implications for neural development, function, and disease.Neuron. 2014; 81: 103-119Abstract Full Text Full Text PDF PubMed Scopus (141) Google Scholar). Despite this, the X chromosome has also been basically "ignored" in the analysis of GWAS data, with only 33% of the reported studies from 2010 to 2011 factoring in the X chromosome (Wise et al., 2013Wise A.L. Gyi L. Manolio T.A. eXclusion: toward integrating the X chromosome in genome-wide association analyses.Am. J. Hum. Genet. 2013; 92: 643-647Abstract Full Text Full Text PDF PubMed Scopus (140) Google Scholar). Divergence from the normal number of X and Y chromosomes, called sex chromosome aneuploidy (SCA), accounts for approximately half of all chromosomal anomalies in humans, with a total frequency of 1:400 (Passarge, 1995Passarge E. Colour Atlas of Genetics. Thieme Medical Publishers, New York1995Google Scholar). Aneuploidy occurs in at least 5% of all pregnancies, which is a relatively high frequency, and is the most commonly recognized chromosome abnormality in humans (Hassold and Hunt, 2001Hassold T. Hunt P. To err (meiotically) is human: the genesis of human aneuploidy.Nat. Rev. Genet. 2001; 2: 280-291Crossref PubMed Scopus (1769) Google Scholar). Below are some examples: Turner Syndrome: This disorder, also referred to as monosomy X (45X), occurs only in girls and women when the X chromosome is totally or partially missing. Although 45X is a frequent chromosomal anomaly, Turner syndrome is rare, with a live-birth frequency of 1:3,000 (Hook and Warburton, 1983Hook E.B. Warburton D. The distribution of chromosomal genotypes associated with Turner's syndrome: livebirth prevalence rates and evidence for diminished fetal mortality and severity in genotypes associated with structural X abnormalities or mosaicism.Hum. Genet. 1983; 64: 24-27Crossref PubMed Scopus (335) Google Scholar). Affected individuals experience abnormal growth patterns, heart defects, and certain learning disabilities; they are short in stature; generally lack prominent female secondary sexual characteristics; and are sterile—features that in some individuals lead to social adjustment problems (The Mayo Clinic, 2016cThe Mayo Clinic (2016c). Turner Syndrome. http://www.mayoclinic.org/diseases-conditions/turner-syndrome/basics/definition/con-20032572.Google Scholar). XXX Females: Women with three X chromosomes (47XXX), referred to as Triple X syndrome, or trisomy X, experience normal development of sexual traits and are fertile. Affected individuals are usually taller than average and have slender builds and no severe phenotype, but may have a slight learning disorder (The Mayo Clinic, 2016bThe Mayo Clinic (2016b). Triple X Syndrome. http://www.mayoclinic.org/diseases-conditions/triple-x-syndrome/home/ovc-20164620?p=1.Google Scholar, U.S. National Library of Medicine, 2016U.S. National Library of Medicine (2016). Your Guide to Understanding Genetic Conditions. https://ghr.nlm.nih.gov/condition/triple-x-syndrome.Google Scholar). The frequency of women obtaining an extra X chromosome is approximately 1:1,000. Klinefelter Syndrome: Klinefelter syndrome (47XXY or XY/XXY mosaic) is the most pervasive sex chromosomal anomaly (Klinefelter et al., 1942Klinefelter H. Reifenstein E. Albright F. Syndrome characterized by gynecomastia, aspermatogenesis without A-leydigism, and increased excretion of follicle-stimulating hormone.J. Clin. Endocrinol. Metab. 1942; 2: 615-627Crossref Scopus (624) Google Scholar), affecting approximately 1 in 600 males (Nielsen and Wohlert, 1990Nielsen J. Wohlert M. Sex chromosome abnormalities found among 34,910 newborn children: results from a 13-year incidence study in Arhus, Denmark.Birth Defects Orig. Artic. Ser. 1990; 26: 209-223Crossref PubMed Scopus (764) Google Scholar). Males with Klinefelter syndrome carry two or more X chromosomes resulting in abnormal development of the testis, leading to hypogonadism and infertility (Bojesen et al., 2004Bojesen A. Juul S. Birkebaek N. Gravholt C.H. Increased mortality in Klinefelter syndrome.J. Clin. Endocrinol. Metab. 2004; 89: 3830-3834Crossref PubMed Scopus (145) Google Scholar). Affected males have incompletely developed secondary male sex characteristics, are often tall, have reductions in muscle mass, and produce relatively small amounts of T (The Mayo Clinic, 2016aThe Mayo Clinic (2016a). Klinefelter Syndrome. http://www.mayoclinic.org/diseases-conditions/klinefelter-syndrome/basics/definition/con-20033637.Google Scholar). XYY Males: Men inheriting an additional Y chromosome have higher than average levels of T and are usually taller than average and are prone to acne. Affected males are typically fertile, and many are unaware that they have a chromosomal abnorma

Various intracellular mechanisms are activated in response to stress, leading to adaptation or death. Autophagy, an intracellular process that promotes lysosomal degradation of proteins, is an adaptive response to several types of stress. Osmotic stress occurs under both physiological and pathological conditions, provoking mechanical stress and activating various osmoadaptive mechanisms. Polycystin-2 (PC2), a membrane protein of the polycystin family, is a mechanical sensor capable of activating the cell signaling pathways required for cell adaptation and survival. Here we show that hyperosmotic stress provoked by treatment with hyperosmolar concentrations of sorbitol or mannitol induces autophagy in HeLa and HCT116 cell lines. In addition, we show that mTOR and AMPK, two stress sensor proteins involved modulating autophagy, are downregulated and upregulated, respectively, when cells are subjected to hyperosmotic stress. Finally, our findings show that PC2 is required to promote hyperosmotic stress-induced autophagy. Downregulation of PC2 prevents inhibition of hyperosmotic stress-induced mTOR pathway activation. In conclusion, our data provide new insight into the role of PC2 as a mechanosensor that modulates autophagy under hyperosmotic stress conditions.

Considerable evidence points to critical roles of intracellular Ca2+ homeostasis in the modulation and control of autophagic activity. Yet, underlying molecular mechanisms remain unknown. Mutations in the gene (pkd2) encoding polycystin-2 (PC2) are associated with autosomal dominant polycystic kidney disease (ADPKD), the most common inherited nephropathy. PC2 has been associated with impaired Ca2+ handling in cardiomyocytes and indirect evidence suggests that this protein may be involved in autophagic control. Here, we investigated the role for PC2 as an essential regulator of Ca2+ homeostasis and autophagy.Activation of autophagic flux triggered by mTOR inhibition either pharmacologically (rapamycin) or by means of nutrient depletion was suppressed in cells depleted of PC2. Moreover, cardiomyocyte-specific PC2 knockout mice (αMhc-cre;Pkd2F/F mice) manifested impaired autophagic flux in the setting of nutrient deprivation. Stress-induced autophagy was blunted by intracellular Ca2+ chelation using BAPTA-AM, whereas removal of extracellular Ca2+ had no effect, pointing to a role of intracellular Ca2+ homeostasis in stress-induced cardiomyocyte autophagy. To determine the link between stress-induced autophagy and PC2-induced Ca2+ mobilization, we over-expressed either wild-type PC2 (WT) or a Ca2+-channel deficient PC2 mutant (PC2-D509V). PC2 over-expression increased autophagic flux, whereas PC2-D509V expression did not. Importantly, autophagy induction triggered by PC2 over-expression was attenuated by BAPTA-AM, supporting a model of PC2-dependent control of autophagy through intracellular Ca2+. Furthermore, PC2 ablation was associated with impaired Ca2+ handling in cardiomyocytes marked by partial depletion of sarcoplasmic reticulum Ca2+ stores. Finally, we provide evidence that Ca2+-mediated autophagy elicited by PC2 is a mechanism conserved across multiple cell types.Together, this study unveils PC2 as a novel regulator of autophagy acting through control of intracellular Ca2+ homeostasis.

Formulae display:?Mathematical formulae have been encoded as MathML and are displayed in this HTML version using MathJax in order to improve their display. Uncheck the box to turn MathJax off. This feature requires Javascript. Click on a formula to zoom.

Palmitic acid (PA) is significantly increased in the hypothalamus of mice, when fed chronically with a high-fat diet (HFD). PA impairs insulin signaling in hypothalamic neurons, by a mechanism dependent on autophagy, a process of lysosomal-mediated degradation of cytoplasmic material. In addition, previous work shows a crosstalk between autophagy and the primary cilium (hereafter cilium), an antenna-like structure on the cell surface that acts as a signaling platform for the cell. Ciliopathies, human diseases characterized by cilia dysfunction, manifest, type 2 diabetes, among other features, suggesting a role of the cilium in insulin signaling. Cilium depletion in hypothalamic pro-opiomelanocortin (POMC) neurons triggers obesity and insulin resistance in mice, the same phenotype as mice deficient in autophagy in POMC neurons. Here we investigated the effect of chronic consumption of HFD on cilia; and our results indicate that chronic feeding with HFD reduces the percentage of cilia in hypothalamic POMC neurons. This effect may be due to an increased amount of PA, as treatment with this saturated fatty acid in vitro reduces the percentage of ciliated cells and cilia length in hypothalamic neurons. Importantly, the same effect of cilia depletion was obtained following chemical and genetic inhibition of autophagy, indicating autophagy is required for ciliogenesis. We further demonstrate a role for the cilium in insulin sensitivity, as cilium loss in hypothalamic neuronal cells disrupts insulin signaling and insulin-dependent glucose uptake, an effect that correlates with the ciliary localization of the insulin receptor (IR). Consistently, increased percentage of ciliated hypothalamic neuronal cells promotes insulin signaling, even when cells are exposed to PA. Altogether, our results indicate that, in hypothalamic neurons, impairment of autophagy, either by PA exposure, chemical or genetic manipulation, cause cilia loss that impairs insulin sensitivity.

Cells respond to stress by activating cytoplasmic mechanisms as well as transcriptional programs that can lead to adaptation or death. Autophagy represents an important cytoprotective response that is regulated by both transcriptional and transcription-independent pathways. NFkappaB is perhaps the transcription factor most frequently activated by stress and has been ascribed with either pro- or anti-autophagic functions, depending on the cellular context. Our results demonstrate that activation of the IKK (IkappaB kinase) complex, which is critical for the stress-elicited activation of NFkappaB, is sufficient to promote autophagy independent of NFkappaB, and that IKK is required for the optimal induction of autophagy by both physiological and pharmacological autophagic triggers.

Macroautophagy is a self-cannibalistic process that enables cells to adapt to various stresses and maintain energy homeostasis. Additionally, autophagy is an important route for turnover of misfolded proteins and damaged organelles, with important implications in cancer, neurodegenerative diseases and aging. Resveratrol and spermidine are able to induce autophagy by affecting deacetylases and acetylases, respectively, and have been found to extend the life-span of model organisms. With the aim to reveal the signaling networks involved in this drug-induced autophagic response, we quantified resveratrol and spermidine-induced changes in the phosphoproteome using SILAC and mass spectrometry. The data were subsequently analyzed using the NetworKIN algorithm to extract key features of the autophagy-responsive kinase-substrate network. We found that two distinct sequence motifs were highly responsive to resveratrol and spermidine and that key proteins modulating the acetylation, phosphorylation, methylation and ubiquitination status were affected by changes in phosphorylation during the autophagic response. Essential parts of the apoptotic signaling network were subjected to post-translational modifications during the drug-induced autophagy response, suggesting potential crosstalk and balancing between autophagy and apoptosis. Additionally, we predicted cellular signaling networks affected by resveratrol and spermidine using a computational framework. Altogether, these results point to a profound crosstalk between distinct networks of post-translational modifications and provide a resource for future analysis of autophagy and cell death.

We show that chronic high fat diet (HFD) feeding affects the hypothalamus of male but not female mice. In our study we demonstrate that palmitic acid and sphingolipids accumulate in the central nervous system of HFD-fed males. Additionally, we show that HFD-feeding reduces proliferator-activated receptor gamma coactivator-1 alpha (PGC-1α) thus reducing estrogen receptor α (ERα) and driving hypothalamic inflammation in male but not female mice. Hypothalamic inflammation correlates with markers of metabolic dysregulation as indicated by dysregulation in glucose intolerance and myocardial function. Lastly, we demonstrate that there are blockages in mitophagy and lipophagy in hypothalamic tissues in males. Our data suggest there is a sexually dimorphic response to chronic HDF exposure, females; despite gaining the same amount of body weight following HFD-feeding, appear to be protected from the adverse metabolic effects of the HFD.

Estrogens and their receptors play key roles in regulating body weight, energy expenditure, and metabolic homeostasis. It is known that lack of estrogens promotes increased food intake and induces the expansion of adipose tissues, for which much is known. An area of estrogenic research that has received less attention is the role of estrogens and their receptors in influencing intermediary lipid metabolism in organs such as the brain. In this review, we highlight the actions of estrogens and their receptors in regulating their impact on modulating fatty acid content, utilization, and oxidation through their direct impact on intracellular signaling cascades within the central nervous system.

High-fat diet (HFD)-induced obesity is associated with increased cancer risk. Long-term feeding with HFD increases the concentration of the saturated fatty acid palmitic acid (PA) in the hypothalamus. We previously showed that, in hypothalamic neuronal cells, exposure to PA inhibits the autophagic flux, which is the whole autophagic process from the synthesis of the autophagosomes, up to their lysosomal fusion and degradation. However, the mechanism by which PA impairs autophagy in hypothalamic neurons remains unknown. Here, we show that PA-mediated reduction of the autophagic flux is not caused by lysosomal dysfunction, as PA treatment does not impair lysosomal pH or the activity of cathepsin B.Instead, PA dysregulates autophagy by reducing autophagosome-lysosome fusion, which correlates with the swelling of endolysosomal compartments that show areduction in their dynamics. Finally, because lysosomes undergo constant dynamic regulation by the small Rab7 GTPase, we investigated the effect of PA treatment on its activity. Interestingly, we found PA treatment altered the activity of Rab7. Altogether, these results unveil the cellular process by which PA exposure impairs the autophagic flux. As impaired autophagy in hypothalamic neurons promotes obesity, and balanced autophagy is required to inhibit malignant transformation, this could affect tumor initiation, progression, and/or response to therapy of obesity-related cancers.

Oral squamous cell carcinoma, the most common type of oral cancer, affects more than 275,000 people per year worldwide. Oral squamous cell carcinoma is very aggressive, as most patients die after 3 to 5 years post-diagnosis. The initiation and progression of oral squamous cell carcinoma are multifactorial: smoking, alcohol consumption, and human papilloma virus infection are among the causes that promote its development. Although oral squamous cell carcinoma involves abnormal growth and migration of oral epithelial cells, other cell types such as fibroblasts and immune cells form the carcinoma niche. An underlying inflammatory state within the oral tissue promotes differential stress-related responses that favor oral squamous cell carcinoma. Autophagy is an intracellular degradation process that allows cancer cells to survive under stress conditions. Autophagy degrades cellular components by sequestering them in vesicles called autophagosomes, which ultimately fuse with lysosomes. Although several autophagy markers have been associated with oral squamous cell carcinoma, it remains unclear whether up- or down-regulation of autophagy favors its progression. Autophagy levels during oral squamous cell carcinoma are both timing- and cell-specific. Here we discuss how autophagy is required to establish a new cellular microenvironment in oral squamous cell carcinoma and how autophagy drives the phenotypic change of oral squamous cell carcinoma cells by promoting crosstalk between carcinoma cells, fibroblasts, and immune cells.

Autophagy is a finely regulated, lysosomal catabolic pathway that contributes to the turnover of long-lived proteins and to the elimination of old/damaged organelles. Autophagy exerts bona fide oncosuppressive functions by: (1) limiting chromosomal instability; (2) reducing potentially mutagenic oxidative stress; and (3) restraining intratumoral necrosis and local inflammation. Defective autophagy constitutes a hallmark of cancer cells together with: (1) provision of autonomous growth signals, (2) insensitivity to antiproliferative stimuli, (3) disabled apoptosis, (4) limitless replication, (5) production of angiogenic factors, (6) tissue invasion with metastasis, (7) avoidance of the immune response, and (8) enhanced anabolism. p53 is the best-known human oncosuppressor protein, and its genetic/epigenetic inactivation has been observed in more than 50% of all human cancers. p53 mostly mediates tumor suppression by transactivating pro-apoptotic and cell cycle arresting genes, but also by favoring mitochondrial apoptosis in a transcription-independent fashion, by modulating metabolic circuitries and by regulating autophagy. p53 mutations (or epigenetic changes) that simultaneously abolish its pro-apoptotic and autophagy-inhibitory functions behave as "multi-hit" events, as opposed to "single-hit" mutations that only affect the classical (pro-apoptotic and/or cell cycle-arresting) functions of the p53 system. We speculate that, in this latter case, additional genetic/epigenetic events resulting in disabled autophagy are likely to contribute to accelerated oncogenesis.

The acetylase inhibitor, spermidine and the deacetylase activator, resveratrol, both induce autophagy and prolong life span of the model organism Caenorhabditis elegans in an autophagydependent fashion. Based on these premises, we investigated the differences and similarities in spermidine and resveratrol-induced autophagy. The deacetylase sirtuin 1 (SIRT1) and its orthologs are required for the autophagy induction by resveratrol but dispensable for autophagy stimulation by spermidine in human cells, Saccharomyces cerevisiae and C. elegans. SIRT1 is also dispensable for life-span extension by spermidine. Mass spectrometry analysis of the human acetylproteome revealed that resveratrol and/or spermidine induce changes in the acetylation of 560 peptides corresponding to 375 different proteins. Among these, 170 proteins are part of the recently elucidated human autophagy protein network. Importantly, spermidine and resveratrol frequently affect the acetylation pattern in a similar fashion. In the cytoplasm, spermidine and resveratrol induce convergent protein de-acetylation more frequently than convergent acetylation, while in the nucleus, acetylation is dominantly triggered by both agents. We surmise that subtle and concerted alterations in the acetylproteome regulate autophagy at multiple levels.

HAART can provoke metabolic changes and body fat redistribution, resulting in lipodystrophy, a side effect significantly involving mitochondrial function. Mitochondrial DNA (mtDNA) depletion caused by nucleosidic reverse transcription inhibitors is supposed to be a crucial mechanism in the pathogenesis of mitochondrial damages.In adipose tissue from 22 HIV-positive patients with lipodystrophy and 20 healthy controls, we analyzed gene expression by microarray analysis and real-time PCR. The most upregulated gene was further studied in the human adipocytic cell line SW872 by real-time PCR, western blot, transient transfection assays and flow cytometry.We identified 18 genes differently expressed between lipodystrophy patients and controls, and focused our attention on the nuclear-encoded mitochondrial protease LON, essential in mtDNA maintenance. In SW872 cells, treatment with stavudine (d4T) doubled LON levels, in parallel with mtDNA depletion. As d4T increased reactive oxygen species (ROS) intracellular content, we measured LON in presence of deoxyribose, which causes oxidative stress but not mtDNA depletion, and observed LON upregulation. Ethidium bromide, which markedly depletes mtDNA, did not alter LON levels. The antioxidant glutathione inhibited the increase of intracellular ROS and the increase in LON caused by d4T or deoxyribose.LON upregulation was due to d4T-induced ROS production, rather than due to mtDNA depletion, and represents a response to an oxidative stress. Other mechanisms than mtDNA depletion thus exist that explain nucleosidic reverse transcription inhibitors toxicity. This observation provides a rationale for possible therapeutic interventions aimed at reducing intracellular ROS content in patients assuming HAART.

Early human placental development begins with blastocyst implantation, then the trophoblast differentiates and originates the cells required for a proper fetal nutrition and placental implantation. Among them, extravillous trophoblast corresponds to a non-proliferating trophoblast highly invasive that allows the vascular remodeling which is essential for appropriate placental perfusion and to maintain the adequate fetal growth. This process involves different placental cell types as well as molecules that allow cell growth, cellular adhesion, tissular remodeling, and immune tolerance. Remarkably, some of the cellular processes required for proper placentation are common between placental and cancer cells to finally support tumor growth. Indeed, as in placentation trophoblasts invade and migrate, cancer cells invade and migrate to promote tumor metastasis. However, while these processes respond to a controlled program in trophoblasts, in cancer cells this regulation is lost. Interestingly, it has been shown that autophagy, a process responsible for the degradation of damaged proteins and organelles to maintain cellular homeostasis, is required for invasion of trophoblast cells and for vascular remodeling during placentation. In cancer cells, autophagy has a dual role, as it has been shown both as tumor promoter and inhibitor, depending on the stage and tumor considered. In this review, we summarized the similarities and differences between trophoblast cell invasion and cancer cell metastasis specifically evaluating the role of autophagy in both processes.

The primary cilium is a nonmotile organelle that emanates from the surface of multiple cell types and receives signals from the environment to regulate intracellular signaling pathways. The presence of cilia, as well as their length, is important for proper cell function; shortened, elongated, or absent cilia are associated with pathological conditions. Interestingly, it has recently been shown that the molecular machinery involved in autophagy, the process of recycling of intracellular material to maintain cellular and tissue homeostasis, participates in ciliogenesis. Cilium-dependent signaling is necessary for autophagosome formation and, conversely, autophagy regulates both ciliogenesis and cilium length by degrading specific ciliary proteins. Here, we will discuss the relationship that exists between the two processes at the cellular and molecular level, highlighting what is known about the effects of ciliary dysfunction in the control of energy homeostasis in some ciliopathies.

Mutations in 1-acylglycerol-3-phosphate O-acyltransferase 2 (AGPAT2) result in lipodystrophy, insulin resistance and diabetes. Autophagy is required for normal adipogenesis and adipose tissue development. The aim of this study was to determine whether impaired autophagy or excessive cell death underlie the adipogenic inability of Agpat2−/− mice preadipocytes. Preadipocytes were isolated from interscapular brown adipose tissue (BAT) of Agpat2−/− and Agpat2+/+ newborn mice and cultured/differentiated in vitro. Intracellular lipids were quantified by oil red O staining. Cell death was assessed by lactate dehydrogenase (LDH) activity. Apoptosis and autophagy regulatory factors were determined at the mRNA and protein level with Real-time PCR, immunoblot and immunofluorescence. Adipogenically induced Agpat2−/− preadipocytes had fewer lipid-loaded cells and lower levels of adipocyte markers than wild type preadipocytes. Before adipogenic differentiation, autophagy-related proteins (ATGs) ATG3, ATG5–ATG12 complex, ATG7 and LC3II were increased but autophagic flux was reduced, as suggested by increased p62 levels, in Agpat2−/− preadipocytes. Adipogenic induction increased LDH levels in the culture media in Agpat2−/− preadipocytes but no differences were observed in the activation of Caspase 3 or in markers of autophagic flux. AGPAT2 is required for in vitro adipogenesis of mouse preadipocytes. Autophagy defects or apoptosis are not involved in the adipogenic failure of Agpat2−/− preadipocytes.

Cells are exposed and respond to various mechanical forces and physical cues stemming from their environment. This interaction has been seen to differentially regulate various cellular processes for maintenance of homeostasis, of which autophagy represents one of the major players. In addition, autophagy has been suggested to regulate mechanical functions of the cells including their interaction with the environment. In this minireview, we summarize the state of the art of the fascinating interplay between autophagy and the mechanotransduction machinery associated with cell adhesions, that we name ¨Mechanoautophagy¨.

The endocannabinoid system (ECS) regulates energy metabolism, has been implicated in the pathogenesis of metabolic diseases and exerts its actions mainly through the type 1 cannabinoid receptor (CB1). Likewise, autophagy is involved in several cellular processes. It is required for the normal development of muscle mass and metabolism, and its deregulation is associated with diseases. It is known that the CB1 regulates signaling pathways that control autophagy, however, it is currently unknown whether the ECS could regulate autophagy in the skeletal muscle of obese mice. This study aimed to investigate the role of the CB1 in regulating autophagy in skeletal muscle. We found concomitant deregulation in the ECS and autophagy markers in high-fat diet-induced obesity. In obese CB1-KO mice, the autophagy-associated protein LC3 II does not accumulate when mTOR and AMPK phosphorylation levels do not change. Acute inhibition of the CB1 with JD-5037 decreased LC3 II protein accumulation and autophagic flux. Our results suggest that the CB1 regulates autophagy in the tibialis anterior skeletal muscle in both lean and obese mice.

Introduction The modern food environment facilitates excessive calorie intake, a major driver of obesity. Glucagon-like peptide 1 (GLP1) is a neuroendocrine peptide that has been the basis for developing new pharmacotherapies against obesity. The GLP1 receptor (GLP1R) is expressed in central and peripheral tissues, and activation of GLP1R reduces food intake, increases the expression of thermogenic proteins in brown adipose tissue (BAT), and enhances lipolysis in white adipose tissue (WAT). Obesity decreases the efficiency of GLP1R agonists in reducing food intake and body weight. Still, whether palatable food intake before or during the early development of obesity reduces the effects of GLP1R agonists on food intake and adipose tissue metabolism remains undetermined. Further, whether GLP1R expressed in WAT contributes to these effects is unclear. Methods Food intake, expression of thermogenic BAT proteins, and WAT lipolysis were measured after central or peripheral administration of Exendin-4 (EX4), a GLP1R agonist, to mice under intermittent-short exposure to CAF diet (3 h/d for 8 days) or a longer-continuous exposure to CAF diet (24 h/d for 15 days). Ex-vivo lipolysis was measured after EX4 exposure to WAT samples from mice fed CAF or control diet for 12 weeks. . Results During intermittent-short exposure to CAF diet (3 h/d for 8 days), third ventricle injection (ICV) and intra-peritoneal administration of EX4 reduced palatable food intake. Yet, during a longer-continuous exposure to CAF diet (24 h/d for 15 days), only ICV EX4 administration reduced food intake and body weight. However, this exposure to CAF diet blocked the increase in uncoupling protein 1 (UCP1) caused by ICV EX4 administration in mice fed control diet. Finally, GLP1R expression in WAT was minimal, and EX4 failed to increase lipolysis ex-vivo in WAT tissue samples from mice fed CAF or control diet for 12 weeks. . Discussion Exposure to a CAF diet during the early stages of obesity reduces the effects of peripheral and central GLP1R agonists, and WAT does not express a functional GLP1 receptor. These data support that exposure to the obesogenic food environment, without the development or manifestation of obesity, can alter the response to GLP1R agonists. .

The primary cilium, hereafter cilium, is an antenna-like organelle that modulates intracellular responses, including autophagy, a lysosomal degradation process essential for cell homeostasis. Dysfunction of the cilium is associated with impairment of autophagy and diseases known as "ciliopathies". The discovery of autophagy-related proteins at the base of the cilium suggests its potential role in coordinating autophagy initiation in response to physiopathological stimuli. One of these proteins, beclin-1 (BECN1), it which is necessary for autophagosome biogenesis. Additionally, polycystin-2 (PKD2), a calcium channel enriched at the cilium, is required and sufficient to induce autophagy in renal and cancer cells. We previously demonstrated that PKD2 and BECN1 form a protein complex at the endoplasmic reticulum in non-ciliated cells, where it initiates autophagy, but whether this protein complex is present at the cilium remains unknown. Anorexigenic pro-opiomelanocortin (POMC) neurons are ciliated cells that require autophagy to maintain intracellular homeostasis. POMC neurons are sensitive to metabolic changes, modulating signaling pathways crucial for controlling food intake. Exposure to the saturated fatty acid palmitic acid (PA) reduces ciliogenesis and inhibits autophagy in these cells. Here, we show that PKD2 and BECN1 form a protein complex in N43/5 cells, an in vitro model of POMC neurons, and that both PKD2 and BECN1 locate at the cilium. In addition, our data show that the cilium is required for PKD2-BECN1 protein complex formation and that PA disrupts the PKD2-BECN1 complex, suppressing autophagy. Our findings provide new insights into the mechanisms by which the cilium controls autophagy in hypothalamic neuronal cells.

Purpose of review To summarize recent findings about the neurobiological control of food reward and discuss their relevance for hedonic food intake and obesity in our current obesogenic environment. Recent findings Recent data show new roles for circuits involving neuronal subpopulations within the central amyglada (CeA) and lateral hypothalamus in the regulation of feeding and reward in rodents under free and operant conditions and also in restrain from reward consumption. Recent work also shows that the orbitofrontal cortex (OFC) codes for subjective perception of food features during reward assessment of individual foods and that activity in the nucleus accumbens (NAc) codes for anticipation for reward, which can be blocked by time-locked neurostimulation of NAc. Summary New data illustrates that different aspects of hedonic intake and food reward are coded in a distributed brain network. In particular, as our obesogenic environment facilitates access to palatable food and promotes cue-induced feeding, neuronal circuits related to control of impulsivity, food valuation and duration of hedonic intake episodes might have a significant role in our ability to control food intake and development of obesity by excess intake.

The orexin peptides promote hedonic intake and other reward behaviors through different brain sites. The opioid dynorphin peptides are co-released with orexin peptides but block their effects on reward in the ventral tegmental area (VTA). We previously showed that in the paraventricular hypothalamic nucleus (PVN), dynorphin and not orexin peptides enhance hedonic intake, suggesting they have brain-site-specific effects. Obesity alters the expression of orexin and dynorphin receptors, but whether their expression across different brain sites is important to hedonic intake is unclear. We hypothesized that hedonic intake is regulated by orexin and dynorphin peptides in PVN and that hedonic intake in obesity correlates with expression of their receptors. Here we show that in mice, injection of DYN-A1–13 (an opioid dynorphin peptide) in the PVN enhanced hedonic intake, whereas in the VTA, injection of OXA (orexin-A, an orexin peptide) enhanced hedonic intake. In PVN, OXA blunted the increase in hedonic intake caused by DYN-A1–13. In PVN, injection of norBNI (opioid receptor antagonist) reduced hedonic intake but a subsequent OXA injection failed to increase hedonic intake, suggesting that OXA activity in PVN is not influenced by endogenous opioid activity. In the PVN, DYN-A1–13 increased the intake of the less-preferred food in a two-food choice task. In obese mice fed a cafeteria diet, orexin 1 receptor mRNA across brain sites involved in hedonic intake correlated with fat preference but not caloric intake. Together, these data support that orexin and dynorphin peptides regulate hedonic intake in an opposing manner with brain-site-specific effects.

Mammalian target of rapamycin (mTOR) is an evolutionarily conserved kinase that integrates signals from nutrients and growth factors for the coordinate regulation of many cellular processes, including proliferation and cell death. Constitutive mTOR signaling characterizes multiple human malignancies, and pharmacological inhibitors of mTOR such as the immunosuppressant rapamycin and some of its nonimmunosuppressive derivatives not only have been ascribed with promising anticancer properties in vitro and in vivo but are also being extensively evaluated in clinical trials. mTOR inhibition rapidly leads to the activation of autophagy, which most often exerts prosurvival effects, although in some cases it accompanies cell death. Thus, depending on the specific experimental setting (cell type, concentration, stimulation time, and presence of concurrent stimuli), rapamycin can activate/favor a wide spectrum of cellular responses/phenotypes, ranging from adaptation to stress and survival to cell death. The (at least partial) overlap among the biochemical and morphological responses triggered by rapamycin considerably complicates the study of cell death-associated variables. Moreover, rapamycin presumably triggers acute cell death mainly via off-target mechanisms. Here, we describe a set of assays that can be employed for the routine quantification of rapamycin-induced cell death in vitro, as well as a set of guidelines that should be applied for their correct interpretation.

Calcium signaling plays a crucial role in a multitude of events within the cardiomyocyte, including cell cycle control, growth, apoptosis, and autophagy. With respect to calcium-dependent regulation of autophagy, ion channels and exchangers, receptors, and intracellular mediators play fundamental roles. In this review, we discuss calcium-dependent regulation of cardiomyocyte autophagy, a lysosomal mechanism that is often cytoprotective, serving to defend against disease-related stress and nutrient insufficiency. We also highlight the importance of the subcellular distribution of calcium and related proteins, interorganelle communication, and other key signaling events that govern cardiomyocyte autophagy.

The brain is, after the adipose tissue, the organ with the greatest amount of lipids and diversity in their composition in the human body. In neurons, lipids are involved in signaling pathways controlling autophagy, a lysosome-dependent catabolic process essential for the maintenance of neuronal homeostasis and the function of the primary cilium, a cellular antenna that acts as a communication hub that transfers extracellular signals into intracellular responses required for neurogenesis and brain development. A crosstalk between primary cilia and autophagy has been established; however, its role in the control of neuronal activity and homeostasis is barely known. In this review, we briefly discuss the current knowledge regarding the role of autophagy and the primary cilium in neurons. Then we review the recent literature about specific lipid subclasses in the regulation of autophagy, in the control of primary cilium structure and its dependent cellular signaling in physiological and pathological conditions, specifically focusing on neurons, an area of research that could have major implications in neurodevelopment, energy homeostasis, and neurodegeneration.

Excess dietary sucrose is associated with obesity and metabolic diseases. This relationship is driven by the malfunction of several cell types and tissues critical for the regulation of energy balance, including hypothalamic neurons and white adipose tissue (WAT). However, the mechanisms behind these effects of dietary sucrose are still unclear and might be independent of increased adiposity. Accumulating evidence has indicated that dysregulation of autophagy, a fundamental process for maintenance of cellular homeostasis, alters energy metabolism in hypothalamic neurons and WAT, but whether autophagy could mediate the detrimental effects of dietary sucrose on hypothalamic neurons and WAT that contribute to weight gain is a matter of debate. In this review, we examine the hypothesis that dysregulated autophagy in hypothalamic neurons and WAT is an adiposity-independent effect of sucrose that contributes to increased body weight gain. We propose that excess dietary sucrose leads to autophagy unbalance in hypothalamic neurons and WAT, which increases caloric intake and body weight, favoring the emergence of obesity and metabolic diseases.

Abstract Objective Mitochondrial dynamics and quality control in skeletal muscle are central to healthy metabolism. Resistance exercise is a recognized tool for improving skeletal muscle function; however, its effect on mitochondria is still not fully understood. We investigated the impact of resistance exercise on mitochondrial morphology and mitophagy in human skeletal muscle. Methods Eight healthy men performed resistance exercise on one leg, and muscle biopsies were subsequently obtained from the resting leg (Rest) and the exercised leg (Ex) to measure protein abundance and mitochondrial morphology. Additionally, muscle biopsies were obtained from twelve healthy men, and the abundance of BNIP3L protein was correlated with muscle cell and whole body health markers. Results Ex increased p-Drp1 and decreased MFN2, Parkin, and BNIP3L protein levels. Electron microscopy indicated an increase in mitochondrial circularity, cristae abnormality, and mitophagosome structures in Ex, with a marked increase in subsarcolemmal mitophagosomes. We also identified mitophagosomes outside the muscle. Experiments in human myotubes showed a severe decrease in BNIP3L protein in response to CCCP-induced mitochondrial damage with and without bafilomycin. A positive correlation was found between BNIP3L and exercise RQ, HOMA index, while a negative correlation was found with mitophagosomes abundance and VO 2 max. Conclusion Our study describes the effect of resistance exercise on mitochondrial dynamics and mitophagy in skeletal muscle, demonstrating induction of mitochondrial fission and mitophagy in the exercised leg. Moreover, we propose BNIP3L as a potential regulator and marker of mitophagy flux.

Polycystin-2 (PC2) is a calcium channel that can be found in the endoplasmic reticulum, the plasmatic membrane, and the primary cilium. The structure of PC2 is characterized by a highly ordered C-terminal tail with an EF-motif (calcium-binding domain) and a canonical coiled-coil domain (CCD; interaction domain), and its activity is regulated by interacting partners and post-translational modifications. Calcium mobilization into the cytosol by PC2 has been mainly associated with cell growth and differentiation, and therefore mutations or dysfunction of PC2 lead to renal and cardiac consequences. Interestingly, PC2-related pathologies are usually treated with rapamycin, an autophagy stimulator. Autophagy is an intracellular degradation process where recycling material is sequestered into autophagosomes and then hydrolyzed by fusion with a lysosome. Interestingly, several studies have provided evidence that PC2 may be required for autophagy, suggesting that PC2 maintains a physiologic catabolic state.

An important virulence trait of Salmonella enterica serovar Typhimurium (S. Typhimurium) is the ability to avoid the host immune response, generating systemic and persistent infections. Host cells play a crucial role in bacterial clearance by expressing the enzyme heme oxygenase 1 (Hmox1), which catalyzes the degradation of heme groups into Fe2+, biliverdin, and carbon monoxide (CO). The role of Hmox1 activity during S. Typhimurium infection is not clear and previous studies have shown contradictory results. We evaluated the effect of pharmacologic modulation of Hmox1 in a mouse model of acute and persistent S. Typhimurium infection by administering the Hmox1 activity inductor cobalt protoporphyrin-IX (CoPP) or inhibitor tin protoporphyrin-IX (SnPP) before infection. To evaluate the molecular mechanism involved, we measured the colocalization of S. Typhimurium and autophagosome and lysosomal markers in macrophages. Administering CoPP reduced the bacterial burden in organs of mice 5 days post-infection, while SnPP-treated mice showed bacterial loads similar to vehicle-treated mice. Furthermore, CoPP reduced bacterial loads when administered after infection in macrophages in vitro and in a persistent infection model of S. Typhimurium in vivo, while tin protoporphyrin-IX (SnPP) treatment resulted in a bacterial burden similar to vehicle-treated controls. However, we did not observe significant differences in co-localization of green fluorescent protein (GFP)-labeled S. Typhimurium with the autophagic vesicles marker microtubule-associated protein 1A/1B-light chain 3 (LC3) and the lysosomal marker lysosomal-associated membrane protein 1 (LAMP-1) in macrophages treated with CoPP. Our results suggest that CoPP can enhance antimicrobial activity in response to Salmonella infection, reducing bacterial dissemination and persistence in mice, in a CO and autophagy- independent manner.

Autophagy is an intracellular degradation mechanism that allows recycling of organelles and macromolecules. Autophagic function increases metabolite availability modulating metabolic pathways, differentiation and cell survival. The oral environment is composed of several structures, including mineralized and soft tissues, which are formed by complex interactions between epithelial and mesenchymal cells. With aging, increased prevalence of oral diseases such as periodontitis, oral cancer and periapical lesions are observed in humans. These aging-related oral diseases are chronic conditions that alter the epithelial-mesenchymal homeostasis, disrupting the oral tissue architecture affecting the quality of life of the patients. Given that autophagy levels are reduced with age, the purpose of this review is to discuss the link between autophagy and age-related oral diseases.

(Cell Metabolism 24, 203–209; August 9, 2016) As a result of an author oversight in the originally published version of this article, there were mathematical errors in the estimated number of persons in which gender identity does not match biological sex at birth. The original article stated that the number of estimated individuals for whom this applies was approximately 8 million people in the United States; this should have been stated as 800,000 people in the United States, or about 0.2%–0.3% of the population. The original article also stated that the prevalence could actually exceed 0.5% of the population, or ∼16 million people; the latter number should have been ∼1.6 million. Finally, the original article originally stated that, within the Veterans Health Administration, the incidence of transgender-related diagnoses increased by 76% from 2009 to 2013; this should have more accurately said that the incidence increased from 936 diagnoses in 2009 to 2,567 diagnoses in 2013. These errors have now been corrected in the article online. The authors apologize for these errors and any inconvenience this may have caused. Sex and Gender: Critical Variables in Pre-Clinical and Clinical Medical ResearchMorselli et al.Cell MetabolismAugust 09, 2016In BriefSex and gender differences and how they influence normal physiology and disease risk have been neglected in biomedical research. In this Essay, Clegg et al. (2016) discuss the influence of sex hormones and chromosomes on cell physiology and pathophysiology of disease states, a key step for the development of personalized medicine. Full-Text PDF Open Archive

Muscle atrophy involves a massive catabolism of intracellular components leading to a significant reduction in cellular and tissue volume. In this regard, autophagy, an intracellular mechanism that degrades proteins and organelles, has been implicated with muscle breakdown. Recently, it has shown that polycystin-2 (PC2), a membrane protein that belongs to the transient receptor potential (TRP) family, is required for the maintenance of cellular proteostasis, by regulating autophagy in several cell types. The role of PC2 in the control of atrophy and autophagy in skeletal muscle remains unknown. Here, we show that PC2 is required for the induction of atrophy in C2C12 myotubes caused by nutrient deprivation or rapamycin exposure. Consistently, overexpression of PC2 induces atrophy in C2C12 myotubes as indicated by decreasing of the myogenic proteins myogenin and caveolin-3. In addition, we show that inhibition of mTORC1, by starvation or rapamycin is inhibited in cells when PC2 is silenced. Importantly, even if PC2 regulates mTORC1, our results show that the regulation of atrophy by PC2 is independent of autophagy. This study provides novel evidence regarding the role of PC2 in skeletal muscle cell atrophy.

The intake of food with high levels of saturated fatty acids (SatFAs) is associated with the development of obesity and insulin resistance. SatFAs, such as palmitic (PA) and stearic (SA) acids, have been shown to accumulate in the hypothalamus, causing several pathological consequences. Autophagy is a lysosomal-degrading pathway that can be divided into macroautophagy, microautophagy, and chaperone-mediated autophagy (CMA). Previous studies showed that PA impairs macroautophagy function and insulin response in hypothalamic proopiomelanocortin (POMC) neurons. Here, we show in vitro that the exposure of POMC neurons to PA or SA also inhibits CMA, possibly by decreasing the total and lysosomal LAMP2A protein levels. Proteomics of lysosomes from PA- and SA-treated cells showed that the inhibition of CMA could impact vesicle formation and trafficking, mitochondrial components, and insulin response, among others. Finally, we show that CMA activity is important for regulating the insulin response in POMC hypothalamic neurons. These in vitro results demonstrate that CMA is inhibited by PA and SA in POMC-like neurons, giving an overview of the CMA-dependent cellular pathways that could be affected by such inhibition and opening a door for in vivo studies of CMA in the context of the hypothalamus and obesity.

In light of the increasing prevalence of obesity, which has become a major public health concern worldwide, there is great incentive to better understand the cellular processes and molecular mechanisms underlying the regulation of body weight. Autophagy is an intracellular catabolic process that contributes to cell and tissue homeostasis through the turnover of cytoplasmic material. Importantly, defects in autophagy in the hypothalamus, a brain region critical to body weight regulation, have been linked to obesity and obesity-related comorbidities, including diabetes. In this chapter, we discuss the effects of dysfunctional hypothalamic autophagy on body weight and on the development of obesity-associated metabolic complications.

Cardiovascular diseases are the leading cause of death and disability worldwide. After heart injury triggered by myocardial ischemia or myocardial infarction, extensive zones of tissue are damaged and some of the tissue dies by necrosis and/or apoptosis. The loss of contractile mass activates a series of biochemical mechanisms that allow, through cardiac remodeling, the replacement of the dysfunctional heart tissue by fibrotic material. Our previous studies have shown that primary cilia, non-motile antenna-like structures at the cell surface required for the activation of specific signaling pathways, are present in cardiac fibroblasts and required for cardiac fibrosis induced by ischemia/reperfusion (I/R) in mice. I/R-induced myocardial fibrosis promotes the enrichment of ciliated cardiac fibroblasts where the myocardial injury occurs. Given discussions about the existence of cilia in specific cardiac cell types, as well as the functional relevance of studying cilia-dependent signaling in cardiac fibrosis after I/R, here we describe our methods to evaluate the presence and roles of primary cilia in cardiac fibrosis after I/R in mice.

Supplementary Movie 1 from miR-181a and miR-630 Regulate Cisplatin-Induced Cancer Cell Death

Supplementary Tables 1-4 from miR-181a and miR-630 Regulate Cisplatin-Induced Cancer Cell Death

Supplementary Figure, Table and Movie Legends from miR-181a and miR-630 Regulate Cisplatin-Induced Cancer Cell Death

Supplementary Figures 1-6 from miR-181a and miR-630 Regulate Cisplatin-Induced Cancer Cell Death

Supplementary Tables 1-4 from miR-181a and miR-630 Regulate Cisplatin-Induced Cancer Cell Death

Supplementary Movie 1 from miR-181a and miR-630 Regulate Cisplatin-Induced Cancer Cell Death

Supplementary Figures 1-6 from miR-181a and miR-630 Regulate Cisplatin-Induced Cancer Cell Death

Supplementary Figure, Table and Movie Legends from miR-181a and miR-630 Regulate Cisplatin-Induced Cancer Cell Death

[This corrects the article DOI: 10.3389/fendo.2023.1164047.].

&lt;div&gt;Abstract&lt;p&gt;MicroRNAs (miRNA) are noncoding RNAs that regulate multiple cellular processes, including proliferation and apoptosis. We used microarray technology to identify miRNAs that were upregulated by non–small cell lung cancer (NSCLC) A549 cells in response to cisplatin (CDDP). The corresponding synthetic miRNA precursors (pre-miRNAs) per se were not lethal when transfected into A549 cells yet affected cell death induction by CDDP, C&lt;sub&gt;2&lt;/sub&gt;-ceramide, cadmium, etoposide, and mitoxantrone in an inducer-specific fashion. Whereas synthetic miRNA inhibitors (anti-miRNAs) targeting miR-181a and miR-630 failed to modulate the response of A549 to CDDP, pre-miR-181a and pre-miR-630 enhanced and reduced CDDP-triggered cell death, respectively. Pre-miR-181a and pre-miR-630 consistently modulated mitochondrial/postmitochondrial steps of the intrinsic pathway of apoptosis, including Bax oligomerization, mitochondrial transmembrane potential dissipation, and the proteolytic maturation of caspase-9 and caspase-3. In addition, pre-miR-630 blocked early manifestations of the DNA damage response, including the phosphorylation of the ataxia-telangiectasia mutated (ATM) kinase and of two ATM substrates, histone H2AX and p53. Pharmacologic and genetic inhibition of p53 corroborated the hypothesis that pre-miR-630 (but not pre-miR-181a) blocks the upstream signaling pathways that are ignited by DNA damage and converge on p53 activation. Pre-miR-630 arrested A549 cells in the G&lt;sub&gt;0&lt;/sub&gt;-G&lt;sub&gt;1&lt;/sub&gt; phase of the cell cycle, correlating with increased levels of the cell cycle inhibitor p27&lt;sup&gt;Kip1&lt;/sup&gt; as well as with reduced proliferation rates and resulting in greatly diminished sensitivity of A549 cells to the late S-G&lt;sub&gt;2&lt;/sub&gt;-M cell cycle arrest mediated by CDDP. Altogether, these results identify miR-181a and miR-630 as novel modulators of the CDDP response in NSCLC. Cancer Res; 70(5); 1793–803&lt;/p&gt;&lt;/div&gt;

&lt;div&gt;Abstract&lt;p&gt;MicroRNAs (miRNA) are noncoding RNAs that regulate multiple cellular processes, including proliferation and apoptosis. We used microarray technology to identify miRNAs that were upregulated by non–small cell lung cancer (NSCLC) A549 cells in response to cisplatin (CDDP). The corresponding synthetic miRNA precursors (pre-miRNAs) per se were not lethal when transfected into A549 cells yet affected cell death induction by CDDP, C&lt;sub&gt;2&lt;/sub&gt;-ceramide, cadmium, etoposide, and mitoxantrone in an inducer-specific fashion. Whereas synthetic miRNA inhibitors (anti-miRNAs) targeting miR-181a and miR-630 failed to modulate the response of A549 to CDDP, pre-miR-181a and pre-miR-630 enhanced and reduced CDDP-triggered cell death, respectively. Pre-miR-181a and pre-miR-630 consistently modulated mitochondrial/postmitochondrial steps of the intrinsic pathway of apoptosis, including Bax oligomerization, mitochondrial transmembrane potential dissipation, and the proteolytic maturation of caspase-9 and caspase-3. In addition, pre-miR-630 blocked early manifestations of the DNA damage response, including the phosphorylation of the ataxia-telangiectasia mutated (ATM) kinase and of two ATM substrates, histone H2AX and p53. Pharmacologic and genetic inhibition of p53 corroborated the hypothesis that pre-miR-630 (but not pre-miR-181a) blocks the upstream signaling pathways that are ignited by DNA damage and converge on p53 activation. Pre-miR-630 arrested A549 cells in the G&lt;sub&gt;0&lt;/sub&gt;-G&lt;sub&gt;1&lt;/sub&gt; phase of the cell cycle, correlating with increased levels of the cell cycle inhibitor p27&lt;sup&gt;Kip1&lt;/sup&gt; as well as with reduced proliferation rates and resulting in greatly diminished sensitivity of A549 cells to the late S-G&lt;sub&gt;2&lt;/sub&gt;-M cell cycle arrest mediated by CDDP. Altogether, these results identify miR-181a and miR-630 as novel modulators of the CDDP response in NSCLC. Cancer Res; 70(5); 1793–803&lt;/p&gt;&lt;/div&gt;

Lisch corneal dystrophy is a rare corneal disease characterized by the distinctive feature of highly vacuolated cells. Although this feature is important, the nature of these vacuoles within corneal cells remains unknown. Here, we sought to analyze corneal cells from a patient diagnosed with Lisch dystrophy to characterize the vacuoles within these cells. Analyses using histopathology examination, confocal microscopy, and transmission electron microscopy were all consistent with previous descriptions of Lisch cells. Importantly, the vacuoles within these cells appeared to be autophagosomes and autolysosomes, and could be stained with an anti-microtubule-associated protein 1A/1B-light chain 3 (LC3) antibody. Taken together, these findings indicate that the vacuoles we observed within superficial corneal cells of a patient with Lisch corneal dystrophy constituted autophagosomes and autolysosomes; this finding has not been previously reported and suggests a need for further analyses to define the role of autophagy in this ocular disease.

The tumor suppressor protein p53 is a transcriptor factor highly mutated in cancer. In the last decades, research has demonstrated that, in addition to its role in the nucleus, p53 has extranuclear functions in the regulation of cellular metabolism, oxidative stress, and drug response. Specifically, p53 has been shown to have a dual role in the regulation of autophagy, a cellular mechanism that allows the turnover of old and damaged proteins and organelles, as well as a key role in cancer development. Nuclear p53 increases autophagy; however, current research indicates that cytosolic p53, either in wild-type or mutated form, regulates the autophagic pathway independently and in a manner opposite from nuclear p53. In this chapter, we discuss what is known about the nuclear and cytosolic pathways induced by wild-type and p53 mutants in the regulation of autophagy and their impact on tumorigenesis. Knowledge of the signaling pathways involved in the cytosolic-nuclear interplay will help in the identification of cellular targets that might be used for the development of new cancer therapies.