Regulation of autophagy by metabolic and stress signaling pathways in the heart

Exercise preconditioning promotes myocardial GLUT4 translocation and induces autophagy to alleviate exhaustive exercise-induced myocardial injury in rats

Exercise preconditioning (EP) is a line of scientific inquiry into the short-term biochemical mediators of cardioprotection in the heart. This study examined the involvement of autophagy induced by energy metabolism in myocardial remodelling by EP and myocardial protection. A total of 120 healthy male Sprague Dawley (SD) rats were randomly divided into six groups. Plasma cTnI, HBFP staining and electrocardiographic indicators were examined in the context of myocardial ischemic/hypoxic injury and protection. Western blotting and fluorescence double labelling were used to investigate the relationship between energy metabolism and autophagy in EP-resistant myocardial injury caused by exhaustive exercise. Compared with those in the C group, the levels of myocardial ischemic/hypoxic injury were significantly increased in the EE group. Compared with those in the EE group, the levels of myocardial ischemic/hypoxic injury were significantly decreased in the EEP + EE and LEP + EE groups. Compared with that in the EE group, the level of GLUT4 in the sarcolemma was significantly increased, and the colocalization of GLUT4 with the sarcolemma was significantly increased in the EEP + EE and LEP + EE groups (P < 0.05). LC3-II and LC3-II/LC3-I levels of the EEP + EE group were significantly elevated compared with those in the EE group (P < 0.05). The levels of p62 were significantly decreased in the EEP + EE and LEP + EE groups compared with the EE group (P < 0.05). EP promotes GLUT4 translocation and induced autophagy to alleviate exhaustive exercise-induced myocardial ischemic/hypoxic injury.

Walnut-Derived Peptides Promote Autophagy via the Activation of AMPK/mTOR/ULK1 Pathway to Ameliorate Hyperglycemia in Type 2 Diabetic Mice

Autophagy flux plays a significant protective role in type 2 diabetes mellitus (T2DM). However, the mechanisms by which autophagy mediates insulin resistance (IR) to ameliorate T2DM remain unclear. This study explored the hypoglycemic effects and mechanisms of walnut-derived peptides (fraction 3-10 kDa and LP5) in streptozotocin and high-fat-diet-induced T2DM mice. Findings revealed that walnut-derived peptides reduced the levels of blood glucose and FINS and ameliorated IR and dyslipidemia. They also increased SOD and GSH-P_X activities and inhibited the secretion of TNF-α, IL-6, and IL-1β. Additionally, they increased the levels of ATP, COX, SDH, and MMP of liver mitochondria. Western blotting indicated that walnut-derived peptides up-regulated LC3-II/LC3-I and Beclin-1 expression, while they down-regulated p62 expression, which may be associated with the activation of the AMPK/mTOR/ULK1 pathway. Finally, the AMPK activator (AICAR) and inhibitor (Compound C) were used to verify that LP5 could activate autophagy through the AMPK/mTOR/ULK1 pathway in IR HepG2 cells.

The Mechanical Autophagy as a Part of Cellular Immunity; Facts and Features in Treating the Medical Disorders

Autophagy is a cellular housekeeping process that incorporates lysosomal-degradation to maintain cell survival and energy sources. In recent decades, the role of autophagy has implicated in the initiation and development of many diseases that affect humanity. Among these diseases are autoimmune diseases and neurodegenerative diseases, which connected with the lacking autophagy. Other diseases are connected with the increasing levels of autophagy such as cancers and infectious diseases. Therefore, controlling autophagy with sufficient regulators could represent an effective strategy to overcome such diseases. Interestingly, targeting autophagy can also provide a sufficient method to combat the current epidemic caused by the ongoing coronavirus. In this review, we aim to highlight the physiological function of the autophagic process to understand the circumstances surrounding its role in the cellular immunity associated with the development of human diseases.

Necroptosis mediated by impaired autophagy flux contributes to adverse ventricular remodeling after myocardial infarction

Loss of functional cardiomyocytes by cell death after myocardial infarction is most critical for the subsequent left ventricular remodeling, cardiac dysfunction and heart failure. Numerous studies have implicated that dysregulation of autophagy might contribute to cardiomyocyte death. However, the underlying mechanisms by which autophagy dysregulation-mediated cell death remains to be elusive. Herein, we showed that,in response to myocardial ischemic damage in vivo and in vitro, autophagy activity was increased quickly but followed by the process of impaired autophagic degradation as evidenced by the sustained higher level of beclin1 until 12 weeks after myocardial infarction, while, increased accumulation of LC3 and p62. The results from both tandem mRFP-GFP-LC3 adenovirus and lysosomal inhibitor chloroquine supported defective autophagy induction by ischemia injury. Importantly, we found that the impaired autophagy flux, induced not only pharmacologically by CQ but also genetically by beclin1 knockdown, upregulated the expression of RIP3 and aggravated OGD-induced necroptotic cardiomyocyte death and cardiac dysfunction. While, upregulation of autophagy by cardiac-specific beclin1 overexpression partially ameliorated cardiac dysfunction after MI. Furthermore, constitutive activation of necroptosis by forced cardiac-specific overexpression of RIP3 aggravated necrotic cardiomyocyte death, post-MI cardiac remodeling and cardiac dysfunction, but all of which could be ameliorated by inhibition of necroptosis by RIP3 knockdown. In conclusion, these results suggested that autophagy dysfunction-mediated necroptosis mechanistically contributed to loss of cardiomyocytes, adverse ventricular remodeling and progressive heart failure after myocardial Infarction. Inhibition of necroptosis might be the potential target for preventing post-infarction cardiac remodeling and heart failure.

Autophagy stimulation and intracellular sodium reduction as mediators of the cardioprotective effect of sodium-glucose cotransporter 2 inhibitors

In five large-scale trials involving >40 000 patients, sodium-glucose cotransporter 2 (SGLT2) inhibitors decreased the risk of serious heart failure events by 25-40%. This effect cannot be explained by control of hyperglycaemia, since it is not observed with antidiabetic drugs with greater glucose-lowering effects. It cannot be attributed to ketogenesis, since it is not causally linked to ketone body production, and the benefit is not enhanced in patients with diabetes. The effect cannot be ascribed to a natriuretic action, since SGLT2 inhibitors decrease natriuretic peptides only modestly, and they reduce cardiovascular death, a benefit that diuretics do not possess. Although SGLT2 inhibitors increase red blood cell mass, enhanced erythropoiesis does not favourably influence the course of heart failure. By contrast, experimental studies suggest that SGLT2 inhibitors may reduce intracellular sodium, thereby preventing oxidative stress and cardiomyocyte death. Additionally, SGLT2 inhibitors induce a transcriptional paradigm that mimics nutrient and oxygen deprivation, which includes activation of adenosine monophosphate-activated protein kinase, sirtuin-1, and/or hypoxia-inducible factors-1α/2α. The interplay of these mediators stimulates autophagy, a lysosomally-mediated degradative pathway that maintains cellular homeostasis. Autophagy-mediated clearance of damaged organelles reduces inflammasome activation, thus mitigating cardiomyocyte dysfunction and coronary microvascular injury. Interestingly, the action of hypoxia-inducible factors-1α/2α to both stimulate erythropoietin and induce autophagy may explain why erythrocytosis is strongly correlated with the reduction in heart failure events. Therefore, the benefits of SGLT2 inhibitors on heart failure may be mediated by a direct cardioprotective action related to modulation of pathways responsible for cardiomyocyte homeostasis.

Mammalian Target of Rapamycin (mTOR) and the Proteasome Attenuates IL-1β Expression in Primary Mouse Cardiac Fibroblasts

Background: IL-1β is a highly potent pro-inflammatory cytokine and its secretion is tightly regulated. Inactive pro-IL-1β is transcribed in response to innate immune receptors activating NFκB. If tissue damage occurs, danger signals released from necrotic cells, such as ATP, can activate NLRP3-inflammasomes (multiprotein complexes consisting of NLRP3, ASC, and active caspase-1) which cleaves and activates pro-IL-1β. NLRP3 activation also depends on NEK7 and mitochondrial ROS-production. Thus, IL-1β secretion may be regulated at the level of each involved component. We have previously shown that NLRP3-dependent IL-1β release can be induced in cardiac fibroblasts by pro-inflammatory stimuli. However, anti-inflammatory mechanisms targeting IL-1β release in cardiac cells have not been investigated. mTOR is a key regulator of protein metabolism, including autophagy and proteasome activity. In this study we explored whether autophagy or proteasomal degradation are regulators of NLRP3 inflammasome activation and IL-1β release from cardiac fibroblasts. Methods and Results: Serum starvation selectively reduced LPS/ATP-induced IL-1β secretion from cardiac fibroblasts. However, no other inflammasome components, nor mitochondrial mass, were affected. The mTOR inhibitor rapamycin restored pro-IL-1β protein levels as well as LPS/ATP-induced IL-1β release from serum starved cells. However, neither serum starvation nor rapamycin induced autophagy in cardiac fibroblasts. Conversely, chloroquine and bafilomycin A (inhibitors of autophagy) and betulinic acid (a proteasome activator) effectively reduced LPS-induced pro-IL-1β protein levels. Key findings were reinvestigated in human monocyte-derived macrophages. Conclusion: In cardiac fibroblasts, mTOR inhibition selectively favors pro-IL-1β synthesis while proteasomal degradation and not autophagy is the major catabolic anti-inflammatory mechanism for degradation of this cytokine.

Diet Modulation Restores Autophagic Flux in Damaged Skeletal Muscle Cells

OBJECTIVES

Autophagy is a physiological and highly regulated mechanism, crucial for cell homeostasis maintenance. Its impairment seems to be involved in the onset of several diseases, including muscular dystrophies, myopathies and sarcopenia. According to few papers, chemotherapeutic drug treatment is able to trigger side effects on skeletal muscle tissue and, among these, a defective autophagic activation, which leads to the persistence of abnormal organelles within cells and, finally, to myofiber degeneration. The aim of this work is to find a strategy, based on diet modulation, to prevent etoposide-induced damage, in a model of in vitro skeletal muscle cells.

METHODS

Glutamine supplementation and nutrient deprivation have been chosen as pre-treatments to counteract etoposide effect, a chemotherapeutic drug known to induce oxidative stress and cell death. Cell response has been evaluated by means of morpho-functional, cytofluorimetric and molecular analyses.

RESULTS

Etoposide treated cells, if compared to control, showed dysfunctional mitochondria presence, ER stress and lysosomal compartment damage, confirmed by molecular investigations.

CONCLUSIONS

Interestingly, both dietary approaches were able to rescue myofiber from etoposide-induced damage. Glutamine supplementation, in particular, seemed to be a good strategy to preserve cell ultrastructure and functionality, by preventing the autophagic impairment and partially restoring the normal lysosomal activity, thus maintaining skeletal muscle homeostasis.

Immunization with plasmids encoding M2 acetylcholine muscarinic receptor epitopes impairs cardiac function in mice and induces autophagy in the myocardium

Autoantibodies against the M2 subtype of muscarinic acetylcholine receptors with functional activities have been found in the sera of patients with dilated cardiomyopathy (DCM), and the second extracellular loop has been established as the predominant epitope. However, it has been shown that the third intracellular loop is recognized by Chagas disease patients with severe cardiac dysfunction. In this work, BALB/c mice were immunized with plasmids encoding these two epitopes, and a control group received the empty plasmid (pcDNA3 vector). Serum from these DNA-immunized animals had elevated and persistent titres of antibodies against respective antigens. Heart echocardiography indicated diminished left ventricular wall thickness and reduced ejection fraction for both epitope-immunized groups, and ergospirometry tests showed a significant decrease in the exercise time and oxygen consumption. Transfer of serum from these immunized mice into naïve recipients induced the same alterations in cardiac structure and function. Furthermore, electron microscopy analysis of donor-immunized animals revealed several ultrastructural alterations suggestive of autophagy and mitophagy, suggesting novel roles for these autoantibodies. Overall, greater functional and structural impairment was observed in the donor and recipient epitope groups, implicating the third intracellular loop epitope in the pathological effects for the first-time. Therefore, the corresponding peptides could be useful for autoimmune DCM diagnosis and targeted therapy.

Resveratrol reduces intracellular reactive oxygen species levels by inducing autophagy through the AMPK-mTOR pathway

Oxidative stress induced by free fatty acid aggravates endothelial injury, which leads to diabetic cardiovascular complications. Reduction of intracellular oxidative stress may attenuate these pathogenic processes. The dietary polyphenol resveratrol reportedly exerts potential protective effects against endothelial injury. This study determined whether resveratrol can reduce the palmitic acid (PA)-induced generation of reactive oxygen species (ROS) and further explored the underlying molecular mechanisms. We found that resveratrol significantly reduced the PA-induced endothelial ROS levels in human aortic endothelial cells. Resveratrol also induced endothelial cell autophagy, which mediated the effect of resveratrol on ROS reduction. Resveratrol stimulated autophagy via the AMP-activated protein kinase (AMPK)-mTOR pathway. Taken together, these data suggest that resveratrol prevents PA-induced intracellular ROS by autophagy regulation via the AMPK-mTOR pathway. Thus, the induction of autophagy by resveratrol may provide a novel therapeutic candidate for cardioprotection in metabolic syndrome.

The Renin-Angiotensin-Aldosterone System as a Therapeutic Target in Late Injury Caused by Ischemia-Reperfusion

Ischemia-reperfusion (I/R) injury is a well-known phenomenon that involves different pathophysiological processes. Connection in diverse systems of survival brings about cellular dysfunction or even apoptosis. One of the survival systems of the cells, to the assault caused by ischemia, is the activation of the renin-angiotensin-aldosterone system (also known as an axis), which is focused on activating diverse signaling pathways to favor adaptation to the decrease in metabolic supports caused by the hypoxia. In trying to adapt to the I/R event, great changes occur that unchain cellular dysfunction with the capacity to lead to cell death, which translates into a poor prognosis due to the progression of dysfunction of the cellular activity. The search for the understanding of the diverse therapeutic alternatives in molecular coupling could favor the prognosis and evolution of patients who are subject to the I/R process.

Characterization of phospholipid nitroxidation by LC-MS in biomimetic models and in H9c2 Myoblast using a lipidomic approach

Under nitroxidative stress conditions, lipids are prone to be modified by reaction with reactive nitrogen species (RNS) and different modifications were reported to occur in fatty acids. However, in the case of phospholipids (PL) studied under nitroxidative stress conditions, only nitroalkene derivatives of phosphatidylcholine (PC) and phosphatidylethanolamine (PE), were reported when using both in vitro biomimetic conditions and in vivo model system of type 1 diabetes mellitus. Therefore, in order to further explore other nitroxidative modifications of PL, a biomimetic model of nitroxidation combined with liquid chromatography mass spectrometry (MS) and MS/MS approaches were used to characterize the nitrated and nitroxidized derivatives of PCs and PEs. Single and multiple nitrated derivatives of phospholipids (PLs) such as nitroso and dinitroso, nitro, dinitro, and nitronitroso derivatives, together with nitroxidized derivatives were identified. Further, the specific MS/MS fragmentation pathways of these products were studied. Product ions arising from loss of HNO and HNO₂, from the combined loss of HNO (or HNO₂) and polar head groups, [NO_n-FA+O_n+H]⁺ and [NO_n-FA+O_n-H]^- (n=1-2) product ions corresponding to the modified fatty acyl chains were observed, depending on each modification. The knowledge obtained from the study of the MS/MS fragmentation pattern has allowed us to identify nitrated PCs, including NO₂-PC, (NO₂)₂-PCs, (NO₂)(NO)-PC, NO-PC; nitrated PEs, NO₂-PEs; and nitroxidized PCs, (NO₂)(2O)-PC in H9c2 cells under starvation, but not under ischemia or control conditions. The physiological relevance of this nitrated and nitroxidized PCs and PEs species observed exclusively in cardiomyoblast cells (H9c2) under starvation is still unknown but deserves to be explored.

Resveratrol attenuated hydrogen peroxide-induced myocardial apoptosis by autophagic flux

Background

Resveratrol is a Sirt-1-specific activator, which also exerts cardioprotective effects that regulate redox signalling during oxidative stress and autophagy during cardiovascular disease (CVD).

Objective

This study investigated the protective effects of resveratrol against hydrogen peroxide-induced damage in cardiomyocytes.

Design

In this article, hydrogen peroxide-induced autophagy and apoptosis in H9c2 cardiomyoblasts were studied at an increasing concentration from 0 to 100 µM.

Results

Resveratrol pretreatment with concentrations of 10, 20, and 50 µM inhibits autophagic apoptosis by increasing p-Akt and Bcl-2 protein levels in H9c2 cells. Interestingly, resveratrol treatment activates the Beclin-1, LC3, p62, and the lysosome-associated protein LAMP2a within 24 h of administration.

Conclusions

These results suggest that resveratrol-regulated autophagy may play a role in degrading damaged organelles in H9c2 cells rather than causing apoptosis, and this may be a possible mechanism by which resveratrol protects the heart during CVD.

Endolysosomal two-pore channels regulate autophagy in cardiomyocytes

KEY POINTS

Two-pore channels (TPCs) were identified as a novel family of endolysosome-targeted calcium release channels gated by nicotinic acid adenine dinucleotide phosphate, as also as intracellular Na(+) channels able to control endolysosomal fusion, a key process in autophagic flux. Autophagy, an evolutionarily ancient response to cellular stress, has been implicated in the pathogenesis of a wide range of cardiovascular pathologies, including heart failure. We report direct evidence indicating that TPCs are involved in regulating autophagy in cardiomyocytes, and that TPC knockout mice show alterations in the cardiac lysosomal system. TPC downregulation implies a decrease in the viability of cardiomyocytes under starvation conditions. In cardiac tissues from both humans and rats, TPC transcripts and protein levels were higher in females than in males, and correlated negatively with markers of autophagy. We conclude that the endolysosomal channels TPC1 and TPC2 are essential for appropriate basal and induced autophagic flux in cardiomyocytes, and also that they are differentially expressed in male and female hearts.

ABSTRACT

Autophagy participates in physiological and pathological remodelling of the heart. The endolysosomal two-pore channels (TPCs), TPC1 and TPC2, have been implicated in the regulation of autophagy. The present study aimed to investigate the role of TPC1 and TPC2 in basal and induced cardiac autophagic activity. In cultured cardiomyocytes, starvation induced a significant increase in TPC1 and TPC2 transcripts and protein levels that paralleled the increase in autophagy identified by increased LC3-II and decreased p62 levels. Small interfering RNA depletion of TPC2 alone or together with TPC1 increased both LC3II and p62 levels under basal conditions and in response to serum starvation, suggesting that, under conditions of severe energy depletion (serum plus glucose starvation), changes in the autophagic flux (as assessed by use of bafilomycin A1) occurred either when TPC1 or TPC2 were downregulated. The knockdown of TPCs diminished cardiomyocyte viability under starvation and simulated ischaemia. Electron micrographs of hearts from TPC1/2 double knockout mice showed that cardiomyocytes contained large numbers of immature lysosomes with diameters significantly smaller than those of wild-type mice. In cardiac tissues from humans and rats, TPC1 and TPC2 transcripts and protein levels were higher in females than in males. Furthermore, transcript levels of TPCs correlated negatively with p62 levels in heart tissues. TPC1 and TPC2 are essential for appropriate basal and induced autophagic flux in cardiomyocytes (i.e. there is a negative effect on cell viability under stress conditions in their absence) and they are differentially expressed in male and female human and murine hearts, where they correlate with markers of autophagy.

Interleukin-10 inhibits chronic angiotensin II-induced pathological autophagy

BACKGROUND

Although autophagy is an essential cellular salvage process to maintain cellular homeostasis, pathological autophagy can lead to cardiac abnormalities and ultimately heart failure. Therefore, a tight regulation of autophagic process would be important to treat chronic heart failure. Previously, we have shown that IL-10 strongly inhibited pressure overload-induced hypertrophy and heart failure, but role of IL-10 in regulation of pathological autophagy is unknown. Here we tested the hypothesis that IL-10 inhibits angiotensin II-induced pathological autophagy and this process, in part, leads to improve cardiac function.

METHODS AND RESULTS

Chronic Ang II strongly induced mortality, cardiac dysfunction in IL-10 Knockout mice. IL-10 deletion exaggerated pathological autophagy in response to Ang II treatment. In isolated cardiac myocytes, IL-10 attenuated Ang II-induced pathological autophagy and activated Akt/mTORC1 signaling. Pharmacological or molecular inhibition of Akt and mTORC1 signaling attenuated IL-10 effects on Ang II-induced pathological autophagy. Furthermore, lysosomal inhibition in autophagic flux experiments further confirmed that IL-10 inhibits pathological autophagy via mTORC1 signaling.

CONCLUSION

Our data demonstrate a novel role of IL-10 in regulation of pathological autophagy; thus can act as a potential therapeutic molecule for treatment of chronic heart disease.

Progression of thanatophagy in cadaver brain and heart tissues

Autophagy is an evolutionarily conserved catabolic process for maintaining cellular homeostasis during both normal and stress conditions. Metabolic reprogramming in tissues of dead bodies is inevitable due to chronic ischemia and nutrient deprivation, which are well-known features that stimulate autophagy. Currently, it is not fully elucidated whether postmortem autophagy, also known as thanatophagy, occurs in dead bodies is a function of the time of death. In this study, we tested the hypothesis that thanatophagy would increase in proportion to time elapsed since death for tissues collected from cadavers. Brain and heart tissue from corpses at different time intervals after death were analyzed by Western blot. Densitometry analysis demonstrated that thanatophagy occurred in a manner that was dependent on the time of death. The autophagy-associated proteins, LC3 II, p62, Beclin-1 and Atg7, increased in a time-dependent manner in heart tissues. A potent inducer of autophagy, BNIP3, decreased in the heart tissues as time of death increased, whereas the protein levels increased in brain tissues. However, there was no expression of BNIP3 at extended postmortem intervals in both brain and heart samples. Collectively, the present study demonstrates for the first time that thanatophagy occurs in brain and heart tissues of cadavers in a time-dependent manner. Further, our data suggest that cerebral thanatophagy may occur in a Beclin-1- independent manner. This unprecedented study provides potential insight into thanatophagy as a novel method for the estimation of the time of death in criminal investigationsAbstract: Autophagy is an evolutionarily conserved catabolic process for maintaining cellular homeostasis during both normal and stress conditions. Metabolic reprogramming in tissues of dead bodies is inevitable due to chronic ischemia and nutrient deprivation, which are well-known features that stimulate autophagy. Currently, it is not fully elucidated whether postmortem autophagy, also known as thanatophagy, occurs in dead bodies is a function of the time of death. In this study, we tested the hypothesis that thanatophagy would increase in proportion to time elapsed since death for tissues collected from cadavers. Brain and heart tissue from corpses at different time intervals after death were analyzed by Western blot. Densitometry analysis demonstrated that thanatophagy occurred in a manner that was dependent on the time of death. The autophagy-associated proteins, LC3 II, p62, Beclin-1 and Atg7, increased in a time-dependent manner in heart tissues. A potent inducer of autophagy, BNIP3, decreased in the heart tissues as time of death increased, whereas the protein levels increased in brain tissues. However, there was no expression of BNIP3 at extended postmortem intervals in both brain and heart samples. Collectively, the present study demonstrates for the first time that thanatophagy occurs in brain and heart tissues of cadavers in a time-dependent manner. Further, our data suggest that cerebral thanatophagy may occur in a Beclin-1- independent manner. This unprecedented study provides potential insight into thanatophagy as a novel method for the estimation of the time of death in criminal investigations

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Thanatophagy is a new term that means thanatos (death), auto (self), phagy (eating).

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Thanatophagy is the autophagic process that occurs when a person dies.

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Thanatophagy was increased in both heart and brain in a PMI-dependent manner.

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Cerebral thanatophagy occurs in a Beclin-1-independent manner.

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This study provides promising insights into novel tools for estimating PMI.

Ketoconazole induces apoptosis in rat cardiomyocytes through reactive oxygen species-mediated parkin overexpression

Azole antifungals such as ketoconazole are generally known to induce a variety of heart function side effects, e.g., long-QT syndrome and ventricular arrhythmias. However, a clear mechanism for the action of ketoconazole in heart cells has not been reported. In the present study, we assessed the correlation between ketoconazole-induced apoptosis and the alteration of genes in response to ketoconazole in rat cardiomyocytes. Cardiomyocyte viability was significantly inhibited by treatment with ketoconazole. Ketoconazole also stimulated H2O2 generation and TUNEL-positive apoptosis in a dose-dependent manner. DNA microarray technology revealed that 10,571 genes were differentially expressed by more than threefold in ketoconazole-exposed cardiomyocytes compared with untreated controls. Among these genes, parkin, which encodes a component of the multiprotein E3 ubiquitin ligase complex, was predominantly overexpressed among those classified as apoptosis- and reactive oxygen species (ROS)-related genes. The expression of parkin was also elevated in cardiomyocytes treated with exogenous H2O2. Moreover, cell viability and apoptosis in response to ketoconazole were inhibited in cardiomyocytes treated with ROS inhibitors and transfected with parkin siRNA. From the present findings, we concluded that ketoconazole may increase the expression of parkin via the ROS-mediated pathway, which consequently results in the apoptosis and decreased viability of cardiomyocytes.

20 years of leptin: Role of leptin in cardiomyocyte physiology and physiopathology

Since the discovery of leptin in 1994 by Zhang et al., there have been a number of reports showing its implication in the development of a wide range of cardiovascular diseases. However, there exists some controversy about how leptin can induce or preserve cardiovascular function, as different authors have found contradictory results about leptin beneficial or detrimental effects in leptin deficient/resistant murine models and in wild type tissue and cardiomyocytes. Here, we will focus on the main discoveries about the leptin functions at cardiac level within the last two decades, focusing on its role in cardiac metabolism, remodeling and contractile function.

Melatonin regulates aging and neurodegeneration through energy metabolism, epigenetics, autophagy and circadian rhythm pathways

Brain aging is linked to certain types of neurodegenerative diseases and identifying new therapeutic targets has become critical. Melatonin, a pineal hormone, associates with molecules and signaling pathways that sense and influence energy metabolism, autophagy, and circadian rhythms, including insulin-like growth factor 1 (IGF-1), Forkhead box O (FoxOs), sirtuins and mammalian target of rapamycin (mTOR) signaling pathways. This review summarizes the current understanding of how melatonin, together with molecular, cellular and systemic energy metabolisms, regulates epigenetic processes in the neurons. This information will lead to a greater understanding of molecular epigenetic aging of the brain and anti-aging mechanisms to increase lifespan under healthy conditions.

Cardiomyocyte autophagy: metabolic profit and loss

Cardiovascular disease remains the leading cause of morbidity and mortality worldwide, even despite recent scientific and technological advances and comprehensive preventive strategies. The cardiac myocyte is a voracious consumer of energy, and alterations in metabolic substrate availability and consumption are hallmark features of these disorders. Autophagy, an evolutionarily ancient response to metabolic insufficiency, has been implicated in the pathogenesis of a wide range of heart pathologies. However, the precise role of autophagy in these contexts remains obscure owing to its multifarious actions. Here, we review recently derived insights regarding the role of autophagy in cardiac hypertrophy and heart failure, highlighting its effects on metabolism.

Possible role of NF-κB in hormesis during ageing

Hormesis in ageing is probably represented by mild stress-induced stimulation of protective mechanisms in cells and organisms resulting in biologically beneficial effects. Mild stress and hormetins may act on bifurcation points in the complex network of cell signaling and transcription factors, often turning homeodynamics to health or survival. Several signaling pathways activated by diverse stimuli and by stress response converge on NF-κB activation, resulting in a regulatory system characterized by high complexity. NF-κB behaves as a chaotic oscillator and it is increasingly recognized that the number of components that impinges upon phenotypic outcomes of signal transduction pathways may be higher than those taken into consideration from canonical pathway representations. NF-κB is closely related to other important upstream signaling networks, creating chaotic oscillators with other receptor-related kinases and targeting hubs for hormesis. The great bulk of natural hormetins acts on these signaling pathways, while NF-κB appears as a key regulatory factor in this context. Due to its tight relationship with main signaling system NF-κB plays a fundamental role in stress response, apoptosis and autophagy and appears to be a possible target for hormesis in ageing.

Regulation of the proteasome by ATP: implications for ischemic myocardial injury and donor heart preservation

Several lines of evidence suggest that proteasomes are involved in multiple aspects of myocardial physiology and pathology, including myocardial ischemia-reperfusion injury. It is well established that the 26S proteasome is an ATP-dependent enzyme and that ischemic heart disease is associated with changes in the ATP content of the cardiomyocyte. A functional link between the 26S proteasome, myocardial ATP concentrations, and ischemic cardiac injury, however, has been suggested only recently. This review discusses the currently available data on the pathophysiological role of the cardiac proteasome during ischemia and reperfusion in the context of the cellular ATP content. Depletion of the myocardial ATP content during ischemia appears to activate the 26S proteasome via direct regulatory effects of ATP on 26S proteasome stability and activity. This implies pathological degradation of target proteins by the proteasome and could provide a pathophysiological basis for beneficial effects of proteasome inhibitors in various models of myocardial ischemia. In contrast to that in the ischemic heart, reduced and impaired proteasome activity is detectable in the postischemic heart. The paradoxical findings that proteasome inhibitors showed beneficial effects when administered during reperfusion in some studies could be explained by their anti-inflammatory and immune suppressive actions, leading to reduction of leukocyte-mediated myocardial reperfusion injury. The direct regulatory effects of ATP on the 26S proteasome have implications for the understanding of the contribution of the 26S proteasome to the pathophysiology of the ischemic heart and its possible role as a therapeutic target.

Carboxyl terminus of Hsp70-interacting protein (CHIP) is required to modulate cardiac hypertrophy and attenuate autophagy during exercise

The carboxyl terminus of Hsp70-interacting protein (CHIP) is a ubiquitin ligase/cochaperone critical for the maintenance of cardiac function. Mice lacking CHIP (CHIP-/-) suffer decreased survival, enhanced myocardial injury and increased arrhythmias compared with wild-type controls following challenge with cardiac ischaemia reperfusion injury. Recent evidence implicates a role for CHIP in chaperone-assisted selective autophagy, a process that is associated with exercise-induced cardioprotection. To determine whether CHIP is involved in cardiac autophagy, we challenged CHIP-/- mice with voluntary exercise. CHIP-/- mice respond to exercise with an enhanced autophagic response that is associated with an exaggerated cardiac hypertrophy phenotype. No impairment of function was identified in the CHIP-/- mice by serial echocardiography over the 5 weeks of running, indicating that the cardiac hypertrophy was physiologic not pathologic in nature. It was further determined that CHIP plays a role in inhibiting Akt signalling and autophagy determined by autophagic flux in cardiomyocytes and in the intact heart. Taken together, cardiac CHIP appears to play a role in regulating autophagy during the development of cardiac hypertrophy, possibly by its role in supporting Akt signalling, induced by voluntary running in vivo.

High content image based analysis identifies cell cycle inhibitors as regulators of Ebola virus infection

Viruses modulate a number of host biological responses including the cell cycle to favor their replication. In this study, we developed a high-content imaging (HCI) assay to measure DNA content and identify different phases of the cell cycle. We then investigated the potential effects of cell cycle arrest on Ebola virus (EBOV) infection. Cells arrested in G1 phase by serum starvation or G1/S phase using aphidicolin or G2/M phase using nocodazole showed much reduced EBOV infection compared to the untreated control. Release of cells from serum starvation or aphidicolin block resulted in a time-dependent increase in the percentage of EBOV infected cells. The effect of EBOV infection on cell cycle progression was found to be cell-type dependent. Infection of asynchronous MCF-10A cells with EBOV resulted in a reduced number of cells in G2/M phase with concomitant increase of cells in G1 phase. However, these effects were not observed in HeLa or A549 cells. Together, our studies suggest that EBOV requires actively proliferating cells for efficient replication. Furthermore, multiplexing of HCI based assays to detect viral infection, cell cycle status and other phenotypic changes in a single cell population will provide useful information during screening campaigns using siRNA and small molecule therapeutics.