Cardioprotection requires taking out the trash. Basic Res Cardiol. 2009;104:169-180. [PMID: 19242643 DOI: 10.1007/s00395-009-0011-9]

Rhabdomyosarcoma: Current Therapy, Challenges, and Future Approaches to Treatment Strategies

Rhabdomyosarcoma is a rare cancer arising in skeletal muscle that typically impacts children and young adults. It is a worldwide challenge in child health as treatment outcomes for metastatic and recurrent disease still pose a major concern for both basic and clinical scientists. The treatment strategies for rhabdomyosarcoma include multi-agent chemotherapies after surgical resection with or without ionization radiotherapy. In this comprehensive review, we first provide a detailed clinical understanding of rhabdomyosarcoma including its classification and subtypes, diagnosis, and treatment strategies. Later, we focus on chemotherapy strategies for this childhood sarcoma and discuss the impact of three mechanisms that are involved in the chemotherapy response including apoptosis, macro-autophagy, and the unfolded protein response. Finally, we discuss in vivo mouse and zebrafish models and in vitro three-dimensional bioengineering models of rhabdomyosarcoma to screen future therapeutic approaches and promote muscle regeneration.

LncRNA LOC105378097 inhibits cardiac mitophagy in natural ageing mice

BACKGROUND

The development of heart ageing is the main cause of chronic disability, disease and death in the elderly. Ample evidence has established a pivotal role for significantly reduced mitophagy in the ageing heart. However, the underlying mechanisms of mitophagy deficiency in ageing heart are little known. The present study aimed to explore the underlying mechanisms of lncRNA LOC105378097 (Senescence-Mitophagy Associated LncRNA, lncR-SMAL) actions on mitophagy in the setting of heart ageing.

METHODS

The expression of lncR-SMAL was measured in serum from different ages of human and heart from different ages of mice through a quantitative real-time polymerase chain reaction. The effects of lncR-SMAL on heart function of mice were assessed by echocardiography and pressure-volume measurements system. Cardiac senescence was evaluated by hematoxylin-eosin staining, senescence-associated β-galactosidase staining, flow cytometry and western blot analysis of expression of ageing related markes p53 and p21. Cardiomyocyte mitophagy was assessed by western blot, mRFP-GFP-LC3 adenovirus particles transfection and mito-Keima staining. Interaction between lncR-SMAL and Parkin was validated through molecular docking, RNA immunoprecipitation (RIP) and RNA pull-down assay. Ubiquitination assay was performed to explore the molecular mechanism of Parkin inhibition. The effects of lncR-SMAL on mitochondrial function were investigated through electron microscopic examination, JC-1 staining and oxygen consumption rates analysis.

RESULTS

The heart-enriched lncR-SMAL reached the expression crest in the serum of human at an age of 60. Exogenously overexpression of lncRNA SMAL deteriorated cardiac function exactly as natural ageing and inhibited the associated cardiomyocytes mitophagy by depressing Parkin protein level. Improved heart ageing and mitophagy caused by Parkin overexpression were reversed by lncR-SMAL in mice. In contrast, the loss of lncR-SMAL in AC16 cells induced the upregulation of Parkin protein and ameliorated mitophagy and mitochondrial dysfunction, resulting in alleviated cardiac senescence. Besides, we found the interaction between lncR-SMAL and Parkin protein through computational docking analysis, pull-down and RIP assay. This would contribute to the promotive effect of lncR-SMAL on Parkin ubiquitination and decrease Parkin protein stability.

CONCLUSIONS

The present study for the first time demonstrates a heart-enriched lncRNA, SMAL, that inhibits the mitophagy of cardiomyocytes via the downregulation of Parkin protein, which further contributes to heart ageing and cardiac dysfunction in natural ageing mice.

Pentacyclic triterpene oleanolic acid protects against cardiac aging through regulation of mitophagy and mitochondrial integrity

Advanced aging exhibits altered cardiac geometry and function involving mitochondrial anomaly. Natural compounds display promises in the regulation of cardiac homeostasis via governance of mitochondrial integrity in aging. This study examined the effect of oleanolic acid (OA), a natural pentacyclic triterpenoid with free radical scavenging and P450 cyclooxygenase-regulating properties, on cardiac aging and mechanisms involved with a focus on mitophagy. Young (4-5 month-old) and old (22-24 month-old) mice were treated with OA for 6 weeks prior to assessment of cardiac function, morphology, ultrastructure, mitochondrial integrity, cell death and autophagy. Our data revealed that OA treatment alleviated aging-induced changes in myocardial remodeling (increased heart weight, chamber size, cardiomyocyte area and interstitial fibrosis), contractile function and intracellular Ca²⁺ handling, apoptosis, necroptosis, inflammation, autophagy and mitophagy (LC3B, p62, TOM20 and FUNDC1 but not BNIP3 and Parkin). OA treatment rescued aging-induced anomalies in mitochondrial ultrastructure (loss of myofilament alignment, swollen mitochondria, increased circularity), mitochondrial biogenesis and O₂^- production without any notable effect at young age. Interestingly, OA-offered benefit against cardiomyocyte aging was nullified by deletion of the mitophagy receptor FUNDC1 using FUNDC1 knockout mice, denoting an obligatory role for FUNDC1 in OA-elicited preservation of mitophagy. OA reconciled aging-induced changes in E3 ligase MARCH5 but not FBXL2, and failed to affect aging-induced rises in IP3R3. Taken together, our data indicated a beneficial role for OA in attenuating cardiac remodeling and contractile dysfunction in aging through a FUNDC1-mediated mechanism.

Exercise Preconditioning Promotes Autophagy to Cooperate for Cardioprotection by Increasing LC3 Lipidation-Associated Proteins

The cardioprotection of exercise preconditioning (EP) has been well documented. EP can be divided into two phases that are the induction of exercise preconditioning (IEP) and the protection of exercise preconditioning (PEP). PEP is characterized by biphasic protection, including early exercise preconditioning (EEP) and late exercise preconditioning (LEP). LC3 lipidation-mediated autophagy plays a pivotal role in cardioprotection. This study aimed to investigate the alterations of LC3 lipidation-associated proteins during EP-induced cardioprotection against myocardial injury induced by exhaustive exercise (EE) was used in a rat model of EP. These rats were subjected to an intermittent exercise consisting of four periods, with each period including 10 min of running at 30 m/min and 0% grade (approximately 75% VO_2max) followed by 10 min of intermittent rest. A model of EE-induced myocardial injury was developed by subjecting rats to a consecutive running (30 m/min, 0% grade) till exhaustion. Following EEP, the colocalization of LC3 with Atg7 was significantly increased, and LC3-I, LC3-II, LC3-II/LC3-I, Atg7, Atg4B, and Atg3 levels were significantly increased. Atg7, Atg4B, and Atg3 mRNAs were all significantly upregulated, and LC3 mRNAs tended to be higher. Following LEP, Atg4B, and Atg3 levels were significantly increased. Atg7, Atg4B, and Atg3 mRNAs were all significantly upregulated, and LC3 mRNAs tended to be higher. A group of rats were subjected to EEP followed by EE, and the co-localization of LC3 with Atg7 was significantly increased, while LC3-I, LC3-II, LC3-II/LC3-I, Atg7, Atg4B, and Atg3 levels were also significantly increased. Moreover, there was a significant increase in the co-localization of LC3 with Atg7, LC3-I, LC3-II, Atg7, and Atg4B levels during LEP followed by EE. The formation of autophagosome during LEP followed by EE may have been weaker than that during EEP followed by EE due to the lower lipidation of LC3. EP may promote autophagy to maintain cell homeostasis and survival, which cooperates for cardioprotection of alleviating exhaustive exercise-induced myocardial injury by increasing LC3 lipidation-associated proteins. There is a difference between EEP and LEP in terms of the mechanisms of cardioprotection afforded by these respective conditions. The positive regulation of transcription and translation level of LC3 lipidation-associated proteins may all be involved in the mechanism of EEP and LEP, while compared with LEP, the regulation of translation level of EEP is more positively to promote autophagy.

MicroRNA‑138‑5p drives the progression of heart failure via inhibiting sirtuin 1 signaling

The present study aimed to investigate the regulatory effects of microRNA-138-5p (miR-138-5p) and sirtuin 1 (SIRT1) on the progression of heart failure (HF). The binding association between miR-138-5p and SIRT1 was assessed by the dual-luciferase reporter assay. By conducting reverse transcription-quantitative polymerase chain reaction and Western blotting, relative levels of SIRT1 and p53 regulated by miR-138-5p were detected. In vitro HF models were generated by hydrogen peroxide (H₂O₂) induction in AC-16 and human cardiomyocyte (HCM) cells, followed by detection of the regulatory effects of SIRT1 on cell apoptosis and p53 expression. MiR-138-5p was negatively correlated with the SIRT1 level in cardiomyocytes. By recognizing and specifically targeting SIRT1 3′-untranslated region (3′-UTR), miR-138-5p decreased the translational level of SIRT1 and inhibited its enzyme activity, thereby decreasing the deacetylation level of p53. Through downregulating SIRT1 and activating p53 signaling, miR-138-5p induced apoptosis in H₂O₂-induced AC-16 and HCM cells. By contrast, knockdown of miR-138-5p in the in vitro HF models significantly protected the cardiomyocytes. SIRT1 contributed toward alleviate HF by inhibiting cardiomyocyte apoptosis via enhancing the deacetylation level of p53. MiR-138-5p decreases the enzyme activity of SIRT1 by specifically targeting its 3′-UTR and activates p53 signaling, followed by triggering cardiomyocyte apoptosis during the process of HF. It is considered that miR-138-5p and SIRT1 may be potential diagnostic biomarkers and therapeutic targets for HF.

Guidelines for the use and interpretation of assays for monitoring autophagy (4th edition)1

In 2008, we published the first set of guidelines for standardizing research in autophagy. Since then, this topic has received increasing attention, and many scientists have entered the field. Our knowledge base and relevant new technologies have also been expanding. Thus, it is important to formulate on a regular basis updated guidelines for monitoring autophagy in different organisms. Despite numerous reviews, there continues to be confusion regarding acceptable methods to evaluate autophagy, especially in multicellular eukaryotes. Here, we present a set of guidelines for investigators to select and interpret methods to examine autophagy and related processes, and for reviewers to provide realistic and reasonable critiques of reports that are focused on these processes. These guidelines are not meant to be a dogmatic set of rules, because the appropriateness of any assay largely depends on the question being asked and the system being used. Moreover, no individual assay is perfect for every situation, calling for the use of multiple techniques to properly monitor autophagy in each experimental setting. Finally, several core components of the autophagy machinery have been implicated in distinct autophagic processes (canonical and noncanonical autophagy), implying that genetic approaches to block autophagy should rely on targeting two or more autophagy-related genes that ideally participate in distinct steps of the pathway. Along similar lines, because multiple proteins involved in autophagy also regulate other cellular pathways including apoptosis, not all of them can be used as a specific marker for bona fide autophagic responses. Here, we critically discuss current methods of assessing autophagy and the information they can, or cannot, provide. Our ultimate goal is to encourage intellectual and technical innovation in the field.

Melatonin potentials against viral infections including COVID-19: Current evidence and new findings

Viral infections are dangerous diseases for human health worldwide, which lead to significant morbidity and mortality each year. Because of their importance and the lack of effective therapeutic approaches, further attempts should be made to discover appropriate alternative or complementary treatments. Melatonin, a multifunctional neurohormone mainly synthesized and secreted by the pineal gland, plays some roles in the treatment of viral infections. Regarding a deadly outbreak of COVID-19 across the world, we decided to discuss melatonin functions against various viral infections including COVID-19. Therefore, in this review, we summarize current evidence on melatonin therapy for viral infections with focus on possible underlying mechanisms of melatonin actions.

Bone Marrow Mesenchymal Stem Cell-Derived Exosomal miRNA-29c Decreases Cardiac Ischemia/Reperfusion Injury Through Inhibition of Excessive Autophagy via the PTEN/Akt/mTOR Signaling Pathway

BACKGROUND

Cardiac ischemia/reperfusion (I/R) injury will cause a large amount of cardiomyocyte loss and cascade reactions such as apoptosis, mitochondrial dysfunction, and excessive autophagy. Mesenchymal stem cells (MSCs) are promising therapeutic tools to replace damaged cardiomyocytes, but the underlying mechanism is still unknown.Methods and Results:Exosomes contain many microRNAs and protein, which are believed to have multiple biological functions. This study explored the role of bone marrow MSCs (BMMSCs)-derived exosomes under different oxidation levels in heart protection and miRNA-related mechanisms. Exosomes extracted from BMMSCs contained a high level of miR-29c, and its expression level changed after cells were treated under hypoxia/reoxygenation (H/R) conditions. In vivo I/R experiments also confirmed an expression change of miR-29c, and PTEN-Akt-mTOR is one of the predominant pathways that regulate autophagic change during this process.

CONCLUSIONS

This study highlighted the role of miR-29c in regulating autophagy under cardiac I/R injury, which also extended existing mechanisms of a stem cell and its derivative to explore potential therapeutic interventions in ischemic heart diseases.

CARD9 promotes autophagy in cardiomyocytes in myocardial ischemia/reperfusion injury via interacting with Rubicon directly

Autophagy in cardiomyocyte is involved in myocardial ischemia/reperfusion (M-I/R) injury. Caspase recruitment domain-containing protein 9 (CARD9) plays a critical role in cardiovascular diseases (CVDs) such as hypertension and cardiac fibrosis. However, its role in autophagy following M-I/R injury is yet to be fully elucidated. Here, we found that CARD9 expression increased in M-I/R mouse hearts, and in H9c2 or neonatal rat ventricular myocytes (NRVMs) in response to hypoxia/reoxygenation (H/R) or H₂O₂. CARD9^-/- mice exhibited a significant cardiac dysfunction following M-I/R injury (30 min of left ascending coronary (LAD) ischemia and 12 h of reperfusion) compared to wild-type (WT) mice. CARD9 deletion impaired autophagy during M-I/R in vivo and in vitro, evidenced by decrease of microtubule-associated protein 1 light chain 3 (LC3) lipidation and p62 accumulation. Conversely, CARD9 overexpression increased autophagic flux as indicated by enhanced expression of LC3 II/LC3 I and a reduction in p62. The protective effect of CARD9 on cardiomyocytes against H/R-induced oxidative stress was abolished by treatment with autophagy inhibitors, 3-methyladenine (3-MA) or Bafilomycin A1(BafA1). CARD9 interacted with RUN domain Beclin-1-interacting cysteine-rich-containing (Rubicon), a negative regulator of autophagy, and enhanced UV-irradiation-resistance-associated gene (UVRAG)-Beclin1-phosphatidylinositol 3-kinase catalytic subunit type 3 (PI3KC3) interaction and UVRAG-Vps16-mediated Rab7 activation to promote autophagosome formation, maturation, and endocytosis. Ablation of Rubicon by siRNA effectively prevented the detrimental effect of CARD9 knockdown on cardiomyocytes. These results suggest that CARD9 has protective effects on the myocardium against M-I/R injury by activating autophagy and restoring autophagic flux in vivo and in vitro.

Microvesicles derived from human Wharton's jelly mesenchymal stem cells enhance autophagy and ameliorate acute lung injury via delivery of miR-100

Objectives

Microvesicles (MVs) derived from human Wharton’s jelly mesenchymal stem cells (MSC-MVs) were demonstrated to ameliorate acute lung injury (ALI). We have previously found that MSC-MV-transferred hepatocyte growth factor was partly involved in their therapeutic effects. Since MSC-MVs also contained a substantial quantity of miR-100, which plays an important role in lung cancer and injury, we speculated that miR-100 might similarly account for a part of the therapeutic effects of MSC-MVs.

Methods

MSCs were transfected with miR-100 inhibitor to downregulate miR-100 in MSC-MVs. A rat model of ALI and cell injury in rat type II alveolar epithelial cell line (L2) was induced by bleomycin (BLM). A co-culture model of alveolar epithelial cells and MSC-MVs was utilized to examine the therapeutic role of MSC-MVs and mechanism.

Results

MSC-MV treatment attenuated BLM-induced apoptosis and inflammation in BLM-treated L2 cells and ameliorated BLM-induced lung apoptosis, inflammation, and fibrosis in BLM-induced ALI rats. The beneficial effect of MSC-MVs was partly eliminated when miR-100 was knocked down in MSCs. Moreover, MSC-MV-transferred miR-100 mediated the therapeutic effect of MSC-MVs in ALI through enhancing autophagy by targeting mTOR.

Conclusion

MSC-MVs enhance autophagy and ameliorate ALI partially via delivery of miR-100.

Astrocyte-derived exosomes transfer miR-190b to inhibit oxygen and glucose deprivation-induced autophagy and neuronal apoptosis

Our previous work has verified that astrocytes (AS)-derived exosomes (AS-Exo) inhibited autophagy and ameliorated neuronal damage in experimental ischemic stroke. However, the mechanism of AS-Exo regulation of autophagy remains unclear. The aim of this study was to investigate the regulatory mechanism of AS-Exo on neuronal autophagy. The mouse hippocampal neuronal cell line HT-22 was cultured in oxygen and glucose deprivation (OGD) condition to mimic ischemic injury. The primary astrocytes were used to isolate exosomes. Exosome labeling and uptake by HT-22 cells were observed by confocal laser microscopy. miR-190b expression was determined by qRT-PCR. HT-22 cell vitality and apoptosis were determined by CCK-8 assay and TUNEL staining, respectively. Levels of TNF-α, IL-6 and IL-1β were analyzed by ELISA. Protein levels of apoptosis-related cleaved caspase-3, Bax, Bcl-2 and autophagy-related Beclin-1, LC3-I/II, Atg7, P62 were determined by western blot. A dual-luciferase reporter assay was performed to confirm the direct interaction between miR-190b and Atg7. miR-190b expression in AS-Exo was found to be significantly higher than that in AS. AS-Exo-mediated transfer of miR-190b attenuated OGD-induced neuronal apoptosis via suppressing autophagy. Moreover, Atg7 was identified as a target of miR-190b. AS-Exo-mediated transfer of miR-190b regulated autophagy by targeting Atg7. Collectively, our data indicated that AS-Exo transferred miR-190b to inhibit OGD-induced autophagy and neuronal apoptosis.

Eupafolin ameliorates lipopolysaccharide-induced cardiomyocyte autophagy via PI3K/AKT/mTOR signaling pathway

Objective(s):

Eupafolin, a major active component of Eupatorium perfoliatum L., has anti-inflammatory and anti-oxidant properties. Lipopolysaccharide (LPS) is responsible for myocardial depression. A line of evidences revealed that LPS induces autophagy in cardiomyocytes injury. This study aims to evaluate the effects of eupafolin on LPS-induced cardiomyocyte autophagy.

Materials and Methods:

The effect of LPS on cell viability was examined by CCK-8. Autophagic protein 2 light chain 3 (LC3II), which was regulated by LPS and eupafolin, was examined using immunofluorescent staining. The expression levels of Beclin-1 and p62 were detected by western blotting. The effects of eupafolin on phosphatidylinositol-3-kinase/ protein kinase B/ mammalian target of rapamycin (PI3K/AKT/mTOR) signaling pathway were also evaluated by western blotting and immunofluorescent staining.

Results:

Eupafolin pretreatment reduced the expression of LC3II and Beclin-1, whereas p62 was significant increased. In addition, eupafolin promoted expression of PI3K/AKT/mTOR signaling pathway and mTOR inhibitor rapamycin reversed the inhibitory effects on LPS-induced cardiomyocyte autophagy.

Conclusion:

Eupafolin exerts anti-autophagy activity via activation of PI3K/AKT/mTOR signaling pathway.

Altered expression levels of autophagy-associated proteins during exercise preconditioning indicate the involvement of autophagy in cardioprotection against exercise-induced myocardial injury

Exercise has been reported to induce autophagy. We hypothesized that exercise preconditioning (EP)-related autophagy in cardiomyocytes could be attributed to intermittent ischemia-hypoxia, allowing the heart to be protected for subsequent high-intensity exercise (HE). We applied approaches, chromotrope-2R brilliant green (C-2R BG) staining and plasma cTnI levels measuring, to characterize two periods of cardioprotection after EP: early EP (EEP) and late EP (LEP). Further addressing the relationship between ischemia-hypoxia and autophagy, key proteins, Beclin1, LC3, Cathepsin D, and p62, were determined by immunohistochemical staining, western blotting, and by their adjacent slices with C-2R BG. Results indicated that exercise-induced ischemia-hypoxia is a key factor in Beclin1-dependent autophagy. High-intensity exercise was associated with the impairment of autophagy due to high levels of LC3II and unchanged levels of p62, intermittent ischemia-hypoxia by EP itself plays a key role in autophagy, which resulted in more favorable cellular effects during EEP-cardioprotection compared to LEP.

Resveratrol alleviates ischemia/reperfusion injury of diabetic myocardium via inducing autophagy

The rising incidence and complications of diabetes constitutes a major public health issue. The mortality rate of diabetes-induced myocardial ischemia/reperfusion (I/R) injury is significantly elevated. Resveratrol (RSV) is a naturally occurring polyphenol considered to be a potent cardioprotective compound. The aim of the present study was to explore the function and molecular mechanism of RSV on diabetes-induced myocardial I/R injury. Left anterior descending coronary artery ligation was performed to stimulate myocardial I/R injury in streptozotocin-induced diabetic rats. Heart electrical activity was monitored through an electrocardiogram to confirm successful models. The myocardial infarct volume was detected via 2,3,5-triphenyltetrazolium chloride staining. Western blotting was employed to examine the levels of autophagy markers. It was found that the injection of RSV mitigated the ischemia- or I/R injury-induced myocardial damage on hemodynamic function and infarct size, but the autophagy inhibitor 3-methyladenine significantly blocked the function of RSV. Furthermore, the application of RSV significantly enhanced the expression of Beclin-1 and LC-3II but inhibited the serum levels of tumor necrosis factor-α and interleukin-6. These findings revealed an alleviating effect of RSV on diabetes-induced myocardial I/R injury and provided new evidence for the successful application of RSV on the diabetic myocardium.

Clearance of damaged mitochondria via mitophagy is important to the protective effect of ischemic preconditioning in kidneys

Ischemic preconditioning (IPC) affords tissue protection in organs including kidneys; however, the underlying mechanism remains unclear. Here we demonstrate an important role of macroautophagy/autophagy (especially mitophagy) in the protective effect of IPC in kidneys. IPC induced autophagy in renal tubular cells in mice and suppressed subsequent renal ischemia-reperfusion injury (IRI). The protective effect of IPC was abolished by pharmacological inhibitors of autophagy and by the ablation of Atg7 from kidney proximal tubules. Pretreatment with BECN1/Beclin1 peptide induced autophagy and protected against IRI. These results suggest the dependence of IPC protection on renal autophagy. During IPC, the mitophagy regulator PINK1 (PTEN induced putative kinase 1) was activated. Both IPC and BECN1 peptide enhanced mitolysosome formation during renal IRI in mitophagy reporter mice, suggesting that IPC may protect kidneys by activating mitophagy. We further established an in vitro model of IPC by inducing ‘chemical ischemia’ in kidney proximal tubular cells with carbonyl cyanide 3-chlorophenylhydrazone (CCCP). Brief treatment with CCCP protected against subsequent injury in these cells and the protective effect was abrogated by autophagy inhibition. In vitro IPC increased mitophagosome formation, enhanced the delivery of mitophagosomes to lysosomes, and promoted the clearance of damaged mitochondria during subsequent CCCP treatment. IPC also suppressed mitochondrial depolarization, improved ATP production, and inhibited the generation of reactive oxygen species. Knockdown of Pink1 suppressed mitophagy and reduced the cytoprotective effect of IPC. Together, these results suggest that autophagy, especially mitophagy, plays an important role in the protective effect of IPC.

Abbreviations: ACTB: actin, beta; ATG: autophagy related; BNIP3: BCL2 interacting protein 3; BNIP3L/NIX: BCL2 interacting protein 3 like; BUN: blood urea nitrogen; CASP3: caspase 3; CCCP: carbonyl cyanide 3-chlorophenylhydrazone; COX4I1: cytochrome c oxidase subunit 4I1; COX8: cytochrome c oxidase subunit 8; DAPI: 4ʹ,6-diamidino-2-phenylindole; DNM1L: dynamin 1 like; EGFP: enhanced green fluorescent protein; EM: electron microscopy; ER: endoplasmic reticulum; FC: floxed control; FIS1: fission, mitochondrial 1; FUNDC1: FUN14 domain containing 1; H-E: hematoxylin-eosin; HIF1A: hypoxia inducible factor 1 subunit alpha; HSPD1: heat shock protein family D (Hsp60) member 1; IMMT/MIC60: inner membrane mitochondrial protein; IPC: ischemic preconditioning; I-R: ischemia-reperfusion; IRI: ischemia-reperfusion injury; JC-1: 5,5ʹ,6,6ʹ-tetrachloro-1,1ʹ,3,3ʹ-tetraethylbenzimidazolylcarbocyanine iodide; KO: knockout; MAP1LC3B/LC3B: microtubule associated protein 1 light chain 3 beta; mito-QC: mito-quality control; mRFP: monomeric red fluorescent protein; NAC: N-acetylcysteine; PINK1: PTEN induced putative kinase 1; PPIB: peptidylprolyl isomerase B; PRKN: parkin RBR E3 ubiquitin protein ligase; ROS: reactive oxygen species; RPTC: rat proximal tubular cells; SD: standard deviation; sIPC: simulated IPC; SQSTM1/p62: sequestosome 1; TOMM20: translocase of outer mitochondrial membrane 20; TUNEL: terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling

Effects of various doses of atorvastatin on vascular endothelial cell apoptosis and autophagy in vitro

Atorvastatin (Lipitor™) is a lipid‑lowering agent that is widely used in the treatment of cardiovascular diseases. Previous research has largely focused on its cholesterol‑lowering effects; however, a limited number of studies have investigated the actions of atorvastatin on vascular endothelial cells. In the present study, the effects of various doses of atorvastatin were investigated on human umbilical vein endothelial cells (HUVECs). HUVECs were treated with various concentrations of atorvastatin in serum‑free or serum‑containing medium, and alterations in HUVEC morphology were observed. Cell survival and necrosis rates were evaluated using sulforhodamine B and lactate dehydrogenase assays, respectively. In addition, the protein expression levels of cellular apoptosis and autophagy markers were detected using western blot analysis. The results revealed that HUVEC morphology was altered following treatment with various concentrations of atorvastatin. In addition, autophagy was demonstrated to be induced by atorvastatin treatment at all concentrations, whereas high concentrations appeared to induce apoptosis and suppress the survival of HUVECs. In conclusion, the results of the present study suggested that various doses of atorvastatin may exert differential effects on HUVECs, and high doses may suppress angiogenesis. Therefore, atorvastatin may present a novel potential anti‑tumor therapeutic strategy. However, further studies are required to fully elucidate the association between the dose of atorvastatin and its clinical outcome.

Autophagy and doxorubicin resistance in cancer

Doxorubicin (DOX), also known as adriamycin, is a DNA topoisomerase II inhibitor and belongs to the family of anthracycline anticancer drugs. DOX is used for the treatment of a wide variety of cancer types. However, resistance among cancer cells has emerged as a major barrier to effective treatment using DOX. Currently, the role of autophagy in cancer resistance to DOX and the mechanisms involved have become one of the areas of intense investigation. More and more preclinical data are being obtained on reversing DOX resistance through modulation of autophagy as one of the promising therapeutic strategies. This review summarizes the recent advances in autophagy-targeting therapies that overcome DOX resistance from in-vitro studies to animal models for exploration of novel delivery systems. In-depth understanding of the mechanisms of autophagy regulation in relation to DOX resistance and development of molecularly targeted autophagy-modulating agents will provide a promising therapeutic strategy for overcoming DOX resistance in cancer treatment.

Heat shock protein 70 protects cardiomyocytes through suppressing SUMOylation and nucleus translocation of phosphorylated eukaryotic elongation factor 2 during myocardial ischemia and reperfusion

Myocardial ischemia and reperfusion (MIR) results in cardiomyocyte apoptosis with severe outcomes, which blocks cardiac tissue recovering from myocardial ischemia diseases. Heat shock protein 70 (HSP70) is one of protective molecule chaperones which could regulate the nucleus translocation of other proteins. In addition, eukaryotic elongation factor 2 (eEF2), which modulates protein translation process, is vital to the recovery of heart during MIR. However, the relationship between HSP70 and eEF2 and its effects on MIR are unclear. The expression and relationship between HSP70 and eEF2 is confirmed by western blot, immunoprecipitation in vitro using cardiomyocyte cell line H9c2 and in vivo rat MIR model. The further investigation was conducted in H9c2 cells with detection for cell-cycle and apoptosis. It is revealed that eEF2 interacted and be regulated by HSP70, which kept eEF2 as dephosphorylated status and preserved the function of eEF2 during MIR. In addition, HSP70 suppressed the nucleus translocation of phosphorylated eEF2, which inhibited cardiomyocyte apoptosis during myocardial reperfusion stage. Furthermore, HSP70 also interacted with C-terminal fragment of eEF2, which could reverse the nucleus translocation and cardiomyocyte apoptosis caused by N-terminal fragment of eEF2. HSP70 draw on advantage and avoid defect of MIR through regulating phosphorylation and nucleus translocation of eEF2.

Astragalus polysaccharide restores autophagic flux and improves cardiomyocyte function in doxorubicin-induced cardiotoxicity

Doxorubicin (adriamycin), an anthracycline antibiotic, is commonly used to treat many types of solid and hematological malignancies. Unfortunately, clinical usage of doxorubicin is limited due to the associated acute and chronic cardiotoxicity. Previous studies demonstrated that Astragalus polysaccharide (APS), the extracts of Astragalus membranaceus, had strong anti-tumor activities and anti-inflammatory effects. However, whether APS could mitigate chemotherapy-induced cardiotoxicity is unclear thus far. We used a doxorubicin-induced neonatal rat cardiomyocyte injury model and a mouse heart failure model to explore the function of APS. GFP-LC3 adenovirus-mediated autophagic vesicle assays, GFP and RFP tandemly tagged LC3 (tfLC3) assays and Western blot analyses were performed to analyze the cell function and cell signaling changes following APS treatment in cardiomyocytes. First, doxorubicin treatment led to C57BL/6J mouse heart failure and increased cardiomyocyte apoptosis, with a disturbed cell autophagic flux. Second, APS restored autophagy in doxorubicin-treated primary neonatal rat ventricular myocytes and in the doxorubicin-induced heart failure mouse model. Third, APS attenuated doxorubicin-induced heart injury by regulating the AMPK/mTOR pathway. The mTOR inhibitor rapamycin significantly abrogated the protective effect of APS. These results suggest that doxorubicin could induce heart failure by disturbing cardiomyocyte autophagic flux, which may cause excessive cell apoptosis. APS could restore normal autophagic flux, ameliorating doxorubicin-induced cardiotoxicity by regulating the AMPK/mTOR pathway.

Akt2 ablation prolongs life span and improves myocardial contractile function with adaptive cardiac remodeling: role of Sirt1-mediated autophagy regulation

Aging is accompanied with unfavorable geometric and functional changes in the heart involving dysregulation of Akt and autophagy. This study examined the impact of Akt2 ablation on life span and cardiac aging as well as the mechanisms involved with a focus on autophagy and mitochondrial integrity. Cardiac geometry, contractile, and intracellular Ca2+ properties were evaluated using echocardiography, IonOptix® edge-detection and fura-2 techniques. Levels of Sirt1, mitochondrial integrity, autophagy, and mitophagy markers were evaluated using Western blot. Our results revealed that Akt2 ablation prolonged life span (by 9.1%) and alleviated aging (24 months)-induced unfavorable changes in myocardial function and intracellular Ca2+ handling (SERCA2a oxidation) albeit with more pronounced cardiac hypertrophy (58.1%, 47.8%, and 14.5% rises in heart weight, wall thickness, and cardiomyocyte cross-sectional area). Aging downregulated levels of Sirt1, increased phosphorylation of Akt, and the nuclear transcriptional factor Foxo1, as well as facilitated acetylation of Foxo1, the effects of which (except Sirt1 and Foxo1 acetylation) were significantly attenuated or negated by Akt2 ablation. Advanced aging disturbed autophagy, mitophagy, and mitochondrial integrity as evidenced by increased p62, decreased levels of beclin-1, Atg7, LC3B, BNIP3, PTEN-induced putative kinase 1 (PINK1), Parkin, UCP-2, PGC-1α, and aconitase activity, the effects of which were reversed by Akt2 ablation. Aging-induced cardiomyocyte contractile dysfunction and loss of mitophagy were improved by rapamycin and the Sirt1 activator SRT1720. Activation of Akt using insulin or Parkin deficiency prevented SRT1720-induced beneficial effects against aging. In conclusion, our data indicate that Akt2 ablation protects against cardiac aging through restored Foxo1-related autophagy and mitochondrial integrity.

Airborne particulate matter (PM2.5) triggers autophagy in human corneal epithelial cell line

PURPOSE

To investigate particulate matter (PM2.5)-induced damage to human corneal epithelial cells (HCECs) and to determine the underlying mechanisms.

METHODS

HCECs were exposed to PM2.5 at a series of concentrations for various periods. Cell viability was measured by using a 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. Cell proliferation was evaluated via 5-ethynyl-2'-deoxyuridine (EdU) analysis, while autophagy was determined by immunofluorescence and Western blot.

RESULTS

PM2.5-induced cell damage of HCECs occurred in a time- and dose-dependent manner. Decreased cell viability and proliferation as well as increased apoptosis were observed in HCECs after PM2.5 exposure for 24 h. Autophagy in HCECs was slightly inhibited in the early stage (before 4 h) of exposure but significantly activated in the late stage (after 24 h), as evidenced by a decrease in the former and increase in the latter of the expression of the autophagy-associated markers LC3B, ATG5, and BECN1. Interestingly, rapamycin, an autophagy activator, attenuated early-stage but aggravated late-stage PM2.5-induced cell damage, suggesting that the role of autophagy in HCECs may change over time during PM2.5 exposure. In addition, in the early stage, the expression of LC3B and ATG5 increased in cells co-treated with rapamycin and PM2.5 compared to rapamycin-only or PM2.5-only treated cells, suggesting that autophagy may benefit cell viability after PM2.5 exposure.

CONCLUSIONS

The results indicate the potential role of autophagy in the treatment of PM2.5-induced ocular corneal diseases and provide direct evidence for the cytotoxicity, possibly involving an autophagic process, of PM2.5 in HCECs.

Ischemic Preconditioning Confers Epigenetic Repression of Mtor and Induction of Autophagy Through G9a-Dependent H3K9 Dimethylation

Background

Ischemic preconditioning (IPC) protects the heart from prolonged ischemic insult and reperfusion injury through a poorly understood mechanism. Post‐translational modifications of histone residues can confer rapid and drastic switches in gene expression in response to various stimuli, including ischemia. The aim of this study was to investigate the effect of histone methylation in the response to cardiac ischemic preconditioning.

Methods and Results

We used cardiac biopsies from mice subjected to IPC to quantify global levels of 3 of the most well‐studied histone methylation marks (H3K9me2, H3K27me3, and H3K4me3) with Western blot and found that H3K9me2 levels were significantly increased in the area at risk compared to remote myocardium. In order to assess which genes were affected by the increase in H3K9me2 levels, we performed ChIP‐Seq and transcriptome profiling using microarray. Two hundred thirty‐seven genes were both transcriptionally repressed and enriched in H3K9me2 in the area at risk of IPC mice. Of these, Mtor (Mechanistic target of rapamycin) was chosen for mechanistic studies. Knockdown of the major H3K9 methyltransferase G9a resulted in a significant decrease in H3K9me2 levels across Mtor, increased Mtor expression, as well as decreased autophagic activity in response to rapamycin and serum starvation.

Conclusions

IPC confers an increase of H3K9me2 levels throughout the Mtor gene—a master regulator of cellular metabolism and a key player in the cardioprotective effect of IPC—leading to transcriptional repression via the methyltransferase G9a. The results of this study indicate that G9a has an important role in regulating cardiac autophagy and the cardioprotective effect of IPC.

Doxorubicin Regulates Autophagy Signals via Accumulation of Cytosolic Ca2+ in Human Cardiac Progenitor Cells

Doxorubicin (DOXO) is widely used to treat solid tumors. However, its clinical use is limited by side effects including serious cardiotoxicity due to cardiomyocyte damage. Resident cardiac progenitor cells (hCPCs) act as key regulators of homeostasis in myocardial cells. However, little is known about the function of hCPCs in DOXO-induced cardiotoxicity. In this study, we found that DOXO-mediated hCPC toxicity is closely related to calcium-related autophagy signaling and was significantly attenuated by blocking mTOR signaling in human hCPCs. DOXO induced hCPC apoptosis with reduction of SMP30 (regucalcin) and autophagosome marker LC3, as well as remarkable induction of the autophagy-related markers, Beclin-1, APG7, and P62/SQSTM1 and induction of calcium-related molecules, CaM (Calmodulin) and CaMKII (Calmodulin kinase II). The results of an LC3 puncta assay further indicated that DOXO reduced autophagosome formation via accumulation of cytosolic Ca²⁺. Additionally, DOXO significantly induced mTOR expression in hCPCs, and inhibition of mTOR signaling by rapamycin, a specific inhibitor, rescued DOXO-mediated autophagosome depletion in hCPCs with significant reduction of DOXO-mediated cytosolic Ca²⁺ accumulation in hCPCs, and restored SMP30 and mTOR expression. Thus, DOXO-mediated hCPC toxicity is linked to Ca²⁺-related autophagy signaling, and inhibition of mTOR signaling may provide a cardio-protective effect against DOXO-mediated hCPC toxicity.

Repetitive stimulation of autophagy-lysosome machinery by intermittent fasting preconditions the myocardium to ischemia-reperfusion injury

Autophagy, a lysosomal degradative pathway, is potently stimulated in the myocardium by fasting and is essential for maintaining cardiac function during prolonged starvation. We tested the hypothesis that intermittent fasting protects against myocardial ischemia-reperfusion injury via transcriptional stimulation of the autophagy-lysosome machinery. Adult C57BL/6 mice subjected to 24-h periods of fasting, every other day, for 6 wk were protected from in-vivo ischemia-reperfusion injury on a fed day, with marked reduction in infarct size in both sexes as compared with nonfasted controls. This protection was lost in mice heterozygous null for Lamp2 (coding for lysosomal-associated membrane protein 2), which demonstrate impaired autophagy in response to fasting with accumulation of autophagosomes and SQSTM1, an autophagy substrate, in the heart. In lamp2 null mice, intermittent fasting provoked progressive left ventricular dilation, systolic dysfunction and hypertrophy; worsening cardiomyocyte autophagosome accumulation and lack of protection to ischemia-reperfusion injury, suggesting that intact autophagy-lysosome machinery is essential for myocardial homeostasis during intermittent fasting and consequent ischemic cardioprotection. Fasting and refeeding cycles resulted in transcriptional induction followed by downregulation of autophagy-lysosome genes in the myocardium. This was coupled with fasting-induced nuclear translocation of TFEB (transcription factor EB), a master regulator of autophagy-lysosome machinery; followed by rapid decline in nuclear TFEB levels with refeeding. Endogenous TFEB was essential for attenuation of hypoxia-reoxygenation-induced cell death by repetitive starvation, in neonatal rat cardiomyocytes, in-vitro. Taken together, these data suggest that TFEB-mediated transcriptional priming of the autophagy-lysosome machinery mediates the beneficial effects of fasting-induced autophagy in myocardial ischemia-reperfusion injury.

Heat shock protein 70 inhibits cardiomyocyte necroptosis through repressing autophagy in myocardial ischemia/reperfusion injury

Irreversible damage of cardiac function arisen from myocardial ischemia/reperfusion injury (MIRI) leads to an emerging challenge in the treatments of cardiac ischemic diseases. Molecular chaperone heat shock protein 70 (HSP70) attenuates heat-stimulated cell autophagy, apoptosis, and damage in the heart. Under specific conditions, autophagy may, directly or indirectly, induce cell death including necroptosis. Whether HSP70 inhibits cardiomyocyte necroptosis via suppressing autophagy during MIRI is unknown. In our study, HSP70 expression was opposite to necroptosis marker RIP1 and autophagy marker LC3A/B expression after myocardial ischemia/reperfusion (MIR) in vivo. Furthermore, in vitro primary rat cardiomyocytes mimicked MIRI by hypoxia/reoxygenation (H/R) treatment. Knockdown of HSP70 expression promoted cardiomyocyte autophagy and necroptosis following H/R treatment, while the increase tendency was downregulated by autophagy inhibitor 3-MA, showing that autophagy-induced necroptosis could be suppressed by HSP70. In summary, HSP70 downregulates cardiomyocyte necroptosis through suppressing autophagy during myocardial IR, revealing the novel protective mechanism of HSP70 and supplying a novel molecular target for the treatment of heart ischemic diseases.

Macrophage Migration Inhibitory Factor (MIF) Deficiency Exacerbates Aging-Induced Cardiac Remodeling and Dysfunction Despite Improved Inflammation: Role of Autophagy Regulation

Aging leads to unfavorable geometric and functional sequelae in the heart. The proinflammatory cytokine macrophage migration inhibitory factor (MIF) plays a role in the maintenance of cardiac homeostasis under stress conditions although its impact in cardiac aging remains elusive. This study was designed to evaluate the role of MIF in aging-induced cardiac anomalies and the underlying mechanism involved. Cardiac geometry, contractile and intracellular Ca²⁺ properties were examined in young (3–4 mo) or old (24 mo) wild type and MIF knockout (MIF^−/−) mice. Our data revealed that MIF knockout exacerbated aging-induced unfavorable structural and functional changes in the heart. The detrimental effect of MIF knockout was associated with accentuated loss in cardiac autophagy with aging. Aging promoted cardiac inflammation, the effect was attenuated by MIF knockout. Intriguingly, aging-induced unfavorable responses were reversed by treatment with the autophagy inducer rapamycin, with improved myocardial ATP availability in aged WT and MIF^−/− mice. Using an in vitro model of senescence, MIF knockdown exacerbated doxorubicin-induced premature senescence in H9C2 myoblasts, the effect was ablated by MIF replenishment. Our data indicated that MIF knockout exacerbates aging-induced cardiac remodeling and functional anomalies despite improved inflammation, probably through attenuating loss of autophagy and ATP availability in the heart.

Acute hyperglycemia abolishes cardioprotection by remote ischemic perconditioning

Background

Remote ischemic perconditioning (RIPerC) has a promising therapeutic insight to improve the prognosis of acute myocardial infarction. Chronic comorbidities such as diabetes are known to interfere with conditioning interventions by modulating cardioprotective signaling pathways, such as e.g., mTOR pathway and autophagy. However, the effect of acute hyperglycemia on RIPerC has not been studied so far. Therefore, here we investigated the effect of acute hyperglycemia on cardioprotection by RIPerC.

Methods

Wistar rats were divided into normoglycemic (NG) and acute hyperglycemic (AHG) groups. Acute hyperglycemia was induced by glucose infusion to maintain a serum glucose concentration of 15–20 mM throughout the experimental protocol. NG rats received mannitol infusion of an equal osmolarity. Both groups were subdivided into an ischemic (Isch) and a RIPerC group. Each group underwent reversible occlusion of the left anterior descending coronary artery (LAD) for 40 min in the presence or absence of acute hyperglycemia. After the 10-min LAD occlusion, RIPerC was induced by 3 cycles of 5-min unilateral femoral artery and vein occlusion and 5-min reperfusion. After 120 min of reperfusion, infarct size was measured by triphenyltetrazolium chloride staining. To study underlying signaling mechanisms, hearts were harvested for immunoblotting after 35 min in both the NG and AHG groups.

Results

Infarct size was significantly reduced by RIPerC in NG, but not in the AHG group (NG + Isch: 46.27 ± 5.31 % vs. NG + RIPerC: 24.65 ± 7.45 %, p < 0.05; AHG + Isch: 54.19 ± 4.07 % vs. 52.76 ± 3.80 %). Acute hyperglycemia per se did not influence infarct size, but significantly increased the incidence and duration of arrhythmias. Acute hyperglycemia activated mechanistic target of rapamycine (mTOR) pathway, as it significantly increased the phosphorylation of mTOR and S6 proteins and the phosphorylation of AKT. In spite of a decreased LC3II/LC3I ratio, other markers of autophagy, such as ATG7, ULK1 phopsphorylation, Beclin 1 and SQSTM1/p62, were not modulated by acute hyperglycemia. Furthermore, acute hyperglycemia significantly elevated nitrative stress in the heart (0.87 ± 0.01 vs. 0.50 ± 0.04 µg 3-nitrotyrosine/mg protein, p < 0.05).

Conclusions

This is the first demonstration that acute hypreglycemia deteriorates cardioprotection by RIPerC. The mechanism of this phenomenon may involve an acute hyperglycemia-induced increase in nitrative stress and activation of the mTOR pathway.

Protein S-nitrosylation in preconditioning and postconditioning

The coronary artery disease is a leading cause of death and morbidity worldwide. This disease has a complex pathophysiology that includes multiple mechanisms. Among these is the oxidative/nitrosative stress. Paradoxically, oxidative/nitrosative signaling plays a major role in cardioprotection against ischemia/reperfusion injury. In this context, the gas transmitter nitric oxide may act through several mechanisms, such as guanylyl cyclase activation and via S-nitrosylation of proteins. The latter is a covalent modification of a protein cysteine thiol by a nitric oxide-group that generates an S-nitrosothiol. Here, we report data showing that nitric oxide and S-nitrosylation of proteins play a pivotal role not only in preconditioning but also in postconditioning cardioprotection.

Ischemic postconditioning regulates cardiomyocyte autophagic activity following ischemia/reperfusion injury

Ischemic postconditioning (IPostC) is a promising protective mechanism for combating reperfusion injury. However, the role of autophagy in the protective effects of IPostC and the associated signaling pathways have remained to be elucidated. Male Sprague Dawley rats were subjected to 30 min ischemia and 1, 2, 3, 6, 12 and 24 h of reperfusion, with or without IPostC treatment. Autophagic flux was evaluated by detecting mRNA and protein expression levels of microtubule associated protein 1 light chain 3 and p62. Phosphorylated (p)-P70S6 kinase (P70S6K), p-adenosine monophosphate-activated kinase (AMPK) and Beclin 1 protein levels were measured by western blot analysis. Myocardial infarct size was measured using staining with Evans blue dye and myocardial apoptosis was evaluated by terminal deoxynucleotidyl transferase mediated dUTP nick end labeling staining. Autophagic activity was observed to be inhibited within the first hour of reperfusion, increased during 2-6 h and reduced from 12-24 h following IPostC compared with reperfusion without IPostC. Inhibition of autophagy by chloroquine significantly reversed the effects of IPostC on myocardial infarct size and the levels of apoptosis. IPostC significantly increased Beclin 1 levels, inhibited AMPK activation and increased P70S6K activation within the first hour compared with reperfusion without IPostC. IPostC attenuated the upregulation of Beclin 1 levels, increased AMPK activation and reduced P70S6K activation between 2 and 12 h, and subsequently exerted the opposite effects on these molecules between 12 and 24 h. IPostC was demonstrated to regulate autophagic activity in a time‑dependent manner. The Beclin 1 and AMPK-mammalian target of rapamycin signaling pathways are suggested to be involved in the regulation of IPostC in autophagy.

Impact of caloric restriction on myocardial ischaemia/reperfusion injury and new therapeutic options to mimic its effects

Caloric restriction (CR) is the most reliable intervention to extend lifespan and prevent age-related disorders in various species from yeast to rodents. Short- and long-term CR confers cardio protection against ischaemia/reperfusion injury in young and even in aged rodents. A few human trials suggest that CR has the potential to mediate improvement of cardiac or vascular function and induce retardation of cardiac senescence also in humans. The underlying mechanisms are diverse and have not yet been clearly defined. Among the known mediators for the benefits of CR are NO, the AMP-activated PK, sirtuins and adiponectin. Mitochondria, which play a central role in such complex processes within the cell as apoptosis, ATP-production or oxidative stress, are centrally involved in many aspects of CR-induced protection against ischaemic injury. Here, we discuss the relevant literature regarding the protection against myocardial ischaemia/reperfusion injury conferred by CR. Furthermore, we will discuss drug targets to mimic CR and the possible role of calorie restriction in preserving cardiovascular function in humans.

SIRT1: role in cardiovascular biology

SIRT1 (silent information regulator two protein) is a type III protein deacetylase that regulates a variety of important metabolic and physiologic processes including stress resistance, metabolism, apoptosis and energy balance. It reverses cholesterol transport and reduces risk for development of atherosclerosis and cardiovascular disease. The following review highlights the potential role of SIRT1 on cardiovascular biology and function.

Cardio-protective signalling by glyceryl trinitrate and cariporide in a model of donor heart preservation

BACKGROUND

Storage of donor hearts in cardioplegic solutions supplemented with agents that mimic the ischaemic preconditioning response enhanced their post-reperfusion function. The present study examines the minimisation of cell death and activation of pro-survival signalling directed towards maintenance of mitochondrial homeostasis in hearts arrested and stored in two such agents, glyceryl-trinitrate, a nitric oxide donor and cariporide, (a sodium-hydrogen exchange inhibitor).

METHODS

After baseline functional measurement, isolated working rat hearts were arrested and stored for 6h at 4°C in either Celsior(®), Celsior(®) containing 0.1mg/ml glyceryl-trinitrate, 10μM cariporide or both agents. After reperfusion, function was remeasured. Hearts were then processed for immunoblotting or histology.

RESULTS

Necrotic and apoptotic markers present in the Celsior(®) group post-reperfusion were abolished by glyceryl-trinitrate, cariporide or both. Increased phosphorylation of ERK and Bcl2, after reperfusion in groups stored in glyceryl-trinitrate, cariporide or both along with increased phospho-STAT3 levels in the glyceryl-trinitrate/cariporide group correlated with functional recovery. Inhibition of STAT3 phosphorylation blocked recovery. No phospho-Akt increase was seen in any treatment.

CONCLUSIONS

Activation of signalling pathways that favour mitophagy activation (ERK and Bcl2 phosphorylation) and maintenance of mitochondrial transition pore closure after reperfusion (STAT3 and ERK phosphorylation) were crucial for functional recovery of the donor heart.

Loss of Sirt3 limits bone marrow cell-mediated angiogenesis and cardiac repair in post-myocardial infarction

Sirtuin-3 (Sirt3) has a critical role in the regulation of human aging and reactive oxygen species (ROS) formation. A recent study has identified Sirt3 as an essential regulator of stem cell aging. This study investigated whether Sirt3 is necessary for bone marrow cell (BMC)-mediated cardiac repair in post-myocardial infarction (MI). In vitro, BMC-derived endothelial progenitor cells (EPCs) from wild type (WT) and Sirt3KO mice were cultured. EPC angiogenesis, ROS formation and apoptosis were assessed. In vivo, WT and Sirt3 KO mice were subjected to MI and BMCs from WT and Sirt3 KO mice were injected into ischemic area immediately. The expression of VEGF and VEGFR2 was reduced in Sirt3KO-EPCs. Angiogenic capacities and colony formation were significantly impaired in Sirt3KO-EPCs compared to WT-EPCs. Loss of Sirt3 further enhanced ROS formation and apoptosis in EPCs. Overexpression of Sirt3 or treatment with NADPH oxidase inhibitor apocynin (Apo, 200 and 400 microM) rescued these abnormalities. In post-MI mice, BMC treatment increased number of Sca1⁺/c-kit⁺ cells; enhanced VEGF expression and angiogenesis whereas Sirt3KO-BMC treatment had little effects. BMC treatment also attenuated NADPH oxidase subunits p47^phox and gp91^phox expression, and significantly reduced ROS formation, apoptosis, fibrosis and hypertrophy in post-MI mice. Sirt3KO-BMC treatment did not display these beneficial effects. In contrast, Sirt3KO mice treated with BMCs from WT mice attenuated myocardial apoptosis, fibrosis and improved cardiac function. Our data demonstrate that Sirt3 is essential for BMC therapy; and loss of Sirt3 limits BMC-mediated angiogenesis and cardiac repair in post-MI.

Can short-term fasting protect against doxorubicin-induced cardiotoxicity?

Doxorubicin (Dox) is one of the most effective chemotherapeutic agents used in the treatment of several types of cancer. However the use is limited by cardiotoxicity. Despite extensive investigation into the mechanisms of toxicity and preventative strategies, Dox-induced cardiotoxicity still remains a major cause of morbidity and mortality in cancer survivors. Thus, continued research into preventative strategies is vital. Short-term fasting has proven to be cardioprotective against a variety of insults. Despite the potential, only a few studies have been conducted investigating its ability to prevent Dox-induced cardiotoxicity. However, all show proof-of-principle that short-term fasting is cardioprotective against Dox. Fasting affects a plethora of cellular processes making it difficult to discern the mechanism(s) translating fasting to cardioprotection, but may involve suppression of insulin and insulin-like growth factor-1 signaling with stimulated autophagy. It is likely that additional mechanisms also contribute. Importantly, the literature suggests that fasting may enhance the antitumor activity of Dox. Thus, fasting is a regimen that warrants further investigation as a potential strategy to prevent Dox-induced cardiotoxicity. Future research should aim to determine the optimal regimen of fasting, confirmation that this regimen does not interfere with the antitumor properties of Dox, as well as the underlying mechanisms exerting the cardioprotective effects.

Differential effects of atorvastatin on autophagy in ischemic and nonischemic myocardium in Ossabaw swine with metabolic syndrome

OBJECTIVES

The perioperative administration of pleomorphic statin drugs has been implicated in improving outcomes after cardiac surgery. Adaptive autophagy is a highly conserved cellular process that allows for the elimination of dysfunctional cell components in response to stress and survival under starving conditions. We sought to investigate the effects of the statin drug atorvastatin on autophagy in ischemic and nonischemic myocardia using a clinically relevant porcine model of metabolic syndrome.

METHODS

Male Ossabaw swine were fed a regular diet (n = 8), a high-cholesterol diet (n = 8), or a high-cholesterol diet with supplemental atorvastatin (1.5 mg/kg/d) (n = 8). After 14 weeks, all animals underwent surgical placement of an ameroid constrictor to the circumflex coronary artery to induce chronic ischemia. Nonischemic and ischemic myocardia were harvested 6 months after initiation of the diet and processed for Western blotting.

RESULTS

In the nonischemic myocardium, Western blot results demonstrate that a high cholesterol diet resulted in a statistically significant decrease in autophagy as indicated by an increase in mammalian target of rapamycin and the accumulation of several essential autophagy markers, including Beclin-1, light chain 3B-I, and light chain 3B-II. Atorvastatin supplementation prevented these changes and resulted in an increase in autophagy as indicated by a decrease in autophagy flux marker P62. In the ischemic myocardium, atorvastatin had the opposite effect, with a decrease in autophagy flux as indicated by an increase in p62 and an accumulation of light chain 3B-I, light chain B-II, and lysosome-associated membrane protein 2.

CONCLUSIONS

Atorvastatin administration has differential effects on autophagy in ischemic and nonischemic myocardia. In the setting of metabolic syndrome, atorvastatin stimulates autophagy in nonischemic myocardium while partly inhibiting autophagy in ischemic myocardium. The differential regulation on autophagy may, in part, explain the cardioprotective effect of statins in both ischemic and nonischemic myocardia, and these findings may have implications in the setting of cardiac surgery.

Estrogen protects cardiomyocytes against lipopolysaccharide by inhibiting autophagy

Autophagy has a significant role in myocardial injury induced by lipopolysaccharide (LPS). Estrogen (E2) has been demonstrated to protect cardiomyocytes against apoptosis; however, it remains to be determined whether it exhibits anti‑autophagic effects. The aim of the present study was to investigate whether estrogen-regulated autophagy attenuates cardiomyocyte injury induced by LPS. The cardiomyocytes of neonatal rats were randomized to the control (Con), LPS and estrogen + LPS groups. The LPS group was treated with 1 µg LPS for 24 h and the estrogen + LPS group was treated with 10‑8 M estrogen 30 min prior to treatment with LPS. Cardiomyocyte autophagy was quantitated by investigating the mRNA and protein level of autophagy‑related genes (Atgs). The mRNA expression of Atg5 and Beclin1 were measured by quantitative polymerase chain reaction and the microtubule‑associated protein light chain 3 (LC3) protein expression was measured by western blot analysis. To demonstrate the cardiomyocyte protection of estrogen, cell vitality and serum lactate dehydrogenase (LDH) levels were measured following LPS treatment. It was identified that LPS induced cardiomyocyte injury, together with the upregulation of Atg5, Beclin1 mRNA and LC3‑II protein. Furthermore, estrogen attenuated the effect of LPS. The present study provides evidence that estrogen has a myocardial protective role against injury induced by LPS by regulating autophagy.

Restoration of autophagic flux in myocardial tissues is required for cardioprotection of sevoflurane postconditioning in rats

AIM

Sevoflurane postconditioning (SpostC) has been shown to protect the heart from ischemia-reperfusion (I/R) injury. In this study, we examined whether SpostC affected autophagic flux in myocardial tissues that contributed to its cardioprotective effects in rats following acute I/R injury.

METHODS

SD rats underwent 30 min of left anterior descending coronary artery ligation followed by 120 min of reperfusion. The rats were subjected to inhalation of 2.4% (v/v) sevoflurane during the first 5 min of reperfusion, and chloroquine (10 mg/kg, ip) was injected 1 h before I/R. Myocardial infarct size was estimated using TTC staining. Autophagosomes in myocardial tissues were detected under TEM. Expression of LC3B-II, beclin-1, p62/SQSTM1, cathepsin B, caspase-3 and cleaved PARP was assessed using Western blot analysis. Plasma cardiac troponin I was measured using ELISA. Cardiomyocyte apoptosis was evaluated with TUNEL staining.

RESULTS

I/R procedure produced severe myocardium infarct and apoptosis accompanied by markedly increased number of autophagosomes, as well as increased levels of LC3B-II, beclin-1 and p62 in myocardial tissues. SpostC significantly reduced infarct size, attenuated myocardial apoptosis, restored intact autophagic flux and improved the lysosomal function in myocardial tissues. Administration of chloroquine that blocked autophagic flux abrogated the cardioprotective effects of SpostC.

CONCLUSION

SpostC exerts its cardioprotective effects in rats following I/R injury via restoring autophagic flux in myocardial tissues.

No evidence for activated autophagy in left ventricular myocardium at early reperfusion with protection by remote ischemic preconditioning in patients undergoing coronary artery bypass grafting

Objective

Remote ischemic preconditioning (RIPC) by repeated brief limb ischemia/reperfusion reduces myocardial injury in patients undergoing coronary artery bypass grafting (CABG). Activation of signal transducer and activator of transcription 5 (STAT5) in left ventricular (LV) myocardium at early reperfusion is associated with such protection. Autophagy, i.e., removal of dysfunctional cellular components through lysosomes, has been proposed as one mechanism of cardioprotection. Therefore, we analyzed whether or not the protection by RIPC is associated with activated autophagy.

Methods

CABG patients were randomized to undergo RIPC (3×5 min blood pressure cuff inflation/5 min deflation) or placebo (cuff deflated) before skin incision (n = 10/10). Transmural myocardial biopsies were taken from the LV before cardioplegia (baseline) and at early (5–10 min) reperfusion. RIPC-induced protection was reflected by decreased serum troponin I concentration area under the curve (194±17 versus 709±129 ng/ml × 72 h, p = 0.002). Western blotting for beclin-1-phosphorylation and protein expression of autophagy-related gene 5–12 (ATG5-12) complex, light chain 3 (LC3), parkin, and p62 was performed. STAT3-, STAT5- and extracellular signal-regulated protein kinase 1/2 (ERK1/2)-phosphorylation was used as positive control to confirm signal activation by ischemia/reperfusion.

Results

Signals of all analyzed autophagy proteins did not differ between baseline and early reperfusion and not between RIPC and placebo. STAT5-phosphorylation was greater at early reperfusion only with RIPC (2.2-fold, p = 0.02). STAT3- and ERK1/2-phosphorylation were greater at early reperfusion with placebo and RIPC (≥2.7-fold versus baseline, p≤0.05).

Conclusion

Protection through RIPC in patients undergoing CABG surgery does not appear to be associated with enhanced autophagy in LV myocardium at early reperfusion.

Resveratrol regulates autophagy signaling in chronically ischemic myocardium

OBJECTIVE

Autophagy is a cellular process by which damaged components are removed. Although autophagy can result in cell death, when optimally regulated, it might be cardioprotective. Resveratrol is a naturally occurring polyphenol also believed to be cardioprotective. Using a clinically relevant swine model of metabolic syndrome, we investigated the effects of resveratrol on autophagy in the chronically ischemic myocardium.

METHODS

Yorkshire swine were fed a regular diet (n = 7), a high cholesterol diet (n = 7), or a high cholesterol diet with supplemental resveratrol (n = 6). After 4 weeks, an ameroid constrictor was surgically placed on the left circumflex artery to induce chronic myocardial ischemia. The diets were continued another 7 weeks, and then the ischemic and nonischemic myocardium were harvested for protein analysis.

RESULTS

In the ischemic myocardium, a high cholesterol diet partly attenuated the autophagy, as determined by an increase in phosphorylated mammalian target of rapamycin (p-mTOR) and a decrease in p70 S6 kinase (P70S6K), lysosome-associated membrane protein (LAMP)-2, and autophagy-related gene 12-5 conjugate (ATG 12-5; P < .05). The addition of resveratrol blunted many of these changes, because the p-mTOR, P70S6K, and LAMP-2 levels were not significantly altered from those of the pigs fed a regular diet. Other autophagy markers were increased with a high cholesterol diet, including light chain 3A-II and beclin 1 (P < .05). In the nonischemic myocardium, beclin 1 was decreased in the high cholesterol-fed pigs (P < .05); otherwise no significant changes in protein expression were noted among the 3 groups.

CONCLUSIONS

In the chronically ischemic myocardium, resveratrol partly reversed the effects of a high cholesterol diet on autophagy. This might be a mechanism by which resveratrol exerts its cardioprotective effects.

The role of autophagy in doxorubicin-induced cardiotoxicity

Doxorubicin (Dox) is an effective chemotherapeutic agent, however, its use is limited by cardiotoxicity. The mechanisms causing cardiotoxicity have not been clearly elucidated, but known to involve, at least in part, oxidative stress, mitochondrial dysfunction and apoptosis. More recently, it has been suggested that dysregulation of autophagy may also play an important role in Dox-induced cardiotoxicity. Autophagy has dual functions. Under physiological conditions, autophagy is essential for optimal cellular function and survival by ridding the cell of damaged or unwanted proteins and organelles. Under pathological conditions, autophagy may be stimulated in order to protect the cell from stress stimuli or, alternatively, to contribute to cell death. Thus, appropriate regulation of autophagy can be a matter of life or death. The role of autophagy in Dox-induced cardiotoxicity has recently been explored, however, conflicting reports on the effects of Dox on autophagy and its role in cardiotoxicity exist. Most, but not all, of the studies conclude that Dox upregulates cardiac autophagy and contributes to the pathogenesis of Dox-induced toxicity. Dox may induce autophagy by suppressing the expression of GATA4 and/or S6K1, which may directly or indirectly regulate expression of essential autophagy genes such as Atg12, Atg5, Beclin1 and Bcl-2. Interestingly, the Dox-induced autophagic response may be species specific as Dox treatment has been shown to stimulate autophagy in rat models, but suppress autophagy in mouse models. Additional studies will elucidate this possibility.

The role of sex differences in autophagy in the heart during coxsackievirus B3-induced myocarditis

Under normal conditions, autophagy maintains cardiomyocyte health and integrity through turnover of organelles. During stress, oxygen and nutrient deprivation, or microbial infection, autophagy prolongs cardiomyocyte survival. Sex differences in induction of cell death may to some extent explain the disparity between the sexes in many human diseases. However, sex differences in gene expression, which regulate cell death and autophagy, were so far not taken in consideration to explain the sex bias of viral myocarditis. Coxsackievirus B3 (CVB3)-induced myocarditis is a sex-biased disease, with females being substantially less susceptible than males and sex hormones largely determine this bias. CVB3 was shown to induce and subvert the autophagosome for its optimal viral RNA replication. Gene expression analysis on mouse and human, healthy and CVB3-infected, cardiac samples of both sexes, suggests sex differences in autophagy-related gene expression. This review discusses the aspects of sex bias in autophagy induction in cardiomyocytes.

Doxorubicin-induced markers of myocardial autophagic signaling in sedentary and exercise trained animals

Doxorubicin (DOX) is an effective antitumor agent used in cancer treatment. However, its clinical use is limited due to cardiotoxicity. Indeed, the side effects of DOX are irreversible and include the development of cardiomyopathy and ultimately congestive heart failure. Although many studies have investigated the events leading to DOX-induced cardiotoxicity, the mechanisms responsible for DOX-induced cardiotoxicity remain unknown. In general, evidence suggests that DOX-induced cardiotoxicity is associated with an increased generation of reactive oxygen species and oxidative damage, leading to the activation of cellular proteolytic systems. In this regard, the autophagy/lysosomal proteolytic system is a constitutively active catabolic process that is responsible for the degradation of both organelles and cytosolic proteins. We tested the hypothesis that systemic DOX administration results in altered cardiac gene and protein expression of mediators of the autophagy/lysosomal system. Our results support this hypothesis, as DOX treatment increased both the mRNA and protein levels of numerous key autophagy genes. Because exercise training has been shown to be cardioprotective against DOX-induced damage, we also determined whether exercise training before DOX administration alters the expression of important components of the autophagy/lysosomal system in cardiac muscle. Our findings show that exercise training inhibits DOX-induced cardiac increases in autophagy signaling. Collectively, our results reveal that DOX administration promotes activation of the autophagy/lysosomal system pathway in the heart, and that endurance exercise training can be a cardioprotective intervention against myocardial DOX-induced toxicity.

Title efficacy of phosphodiesterase 5 inhibitor on distant burn-induced muscle autophagy, microcirculation, and survival rate

Skeletal muscle wasting is an exacerbating factor in the prognosis of critically ill patients. Using a systemic burn injury model in mice, we have established a role of autophagy in the resulting muscle wasting that is distant from the burn trauma. We provide evidence that burn injury increases the autophagy turnover in the distal skeletal muscle by conventional postmortem tissue analyses and by a novel in vivo microscopic method using an autophagy reporter gene (tandem fluorescent LC3). The effect of tadalafil, a phosphodiesterase 5 inhibitor (PDE5I), on burn-induced skeletal muscle autophagy is documented and extends our published results that PDE5Is attenuates muscle degeneration in a muscular dystrophy model. We also designed a translational experiment to examine the impact of PDE5I on whole body and demonstrated that PDE5I administration lessened muscle atrophy, mitigated microcirculatory disturbance, and improved the survival rate after burn injury.

Cardiomyocyte-specific deletion of endothelin receptor A rescues aging-associated cardiac hypertrophy and contractile dysfunction: role of autophagy

Cardiac aging is manifested as cardiac remodeling and contractile dysfunction although precise mechanisms remain elusive. This study was designed to examine the role of endothelin-1 (ET-1) in aging-associated myocardial morphological and contractile defects. Echocardiographic and cardiomyocyte contractile properties were evaluated in young (5-6 months) and old (26-28 months) C57BL/6 wild-type and cardiomyocyte-specific ET(A) receptor knockout (ETAKO) mice. Cardiac ROS production and histology were examined. Our data revealed that ETAKO mice displayed an improved survival. Aging increased plasma levels of ET-1 and Ang II, compromised cardiac function (fractional shortening, cardiomyocyte peak shortening, maximal velocity of shortening/relengthening and prolonged relengthening) and intracellular Ca(2+) handling (reduced intracellular Ca(2+) release and decay), the effects of which with the exception of ET-1 and Ang II levels was improved by ETAKO. Histological examination displayed cardiomyocyte hypertrophy and interstitial fibrosis associated with cardiac remodeling in aged C57 mice, which were alleviated in ETAKO mice. Aging promoted ROS generation, protein damage, ER stress, upregulated GATA4, ANP, NFATc3 and the autophagosome cargo protein p62, downregulated intracellular Ca(2+) regulatory proteins SERCA2a and phospholamban as well as the autophagic markers Beclin-1, Atg7, Atg5 and LC3BII, which were ablated by ETAKO. ET-1 triggered a decrease in autophagy and increased hypertrophic markers in vitro, the effect of which were reversed by the ET(A) receptor antagonist BQ123 and the autophagy inducer rapamycin. Antagonism of ET(A), but not ET(B) receptor, rescued cardiac aging, which was negated by autophagy inhibition. Taken together, our data suggest that cardiac ET(A) receptor ablation protects against aging-associated myocardial remodeling and contractile dysfunction possibly through autophagy regulation.