Autophagy: an affair of the heart

Acacetin ameliorates pressure overload-induced cardiac remodeling by targeting USP10 and inhibiting maladaptive cardiomyocyte autophagy

BACKGROUND

Numerous drugs have been developed to meet the critical demand for treatments inhibiting cardiac remodeling following cardiovascular disease. Acacetin is a flavonoid with potential therapeutic effects against various cardiovascular diseases.

PURPOSE

This study investigated the effect of acacetin on pressure overload-induced cardiac remodeling and its underlying molecular regulatory mechanisms.

METHODS

We simulated pressure overload-induced cardiac remodeling in male C57BL/6 mice by constricting the thoracic aortic arch and assessed the effect of acacetin on cardiac remodeling.

RESULTS

Acacetin significantly ameliorated cardiac remodeling by downregulating ubiquitin-specific peptidase 10 (USP10) protein expression and reducing autophagy levels in cardiomyocytes. These findings confirm that acacetin improves cardiac remodeling by suppressing cardiomyocyte autophagy and highlight the crucial role of USP10 in the Beclin 1 ubiquitination degradation-mediated inhibition of the cardiomyocyte autophagy signaling pathway.

CONCLUSION

These results suggest that acacetin is a promising candidate drug for the treatment of cardiac remodeling induced by pressure overload.

Lysosomes: guardians and healers within cells- multifaceted perspective and outlook from injury repair to disease treatment

Lysosomes, as crucial organelles within cells, carry out diverse biological functions such as waste degradation, regulation of the cellular environment, and precise control of cell signaling. This paper reviews the core functions and structural characteristics of lysosomes, and delves into the current research status of lysosomes damage repair mechanisms. Subsequently, we explore in depth the close association between lysosomes and various diseases, including but not limited to age-related chronic diseases, neuro-degenerative diseases, tumors, inflammation, and immune imbalance. Additionally, we also provide a detailed discussion of the application of lysosome-targeted substances in the field of regenerative medicine, especially the enormous potential demonstrated in key areas such as stem cell regulation and therapy, and myocardial cell repair. Though the integration of multidisciplinary research efforts, we believe that lysosomes damage repair mechanisms will demonstrate even greater application value in disease treatment and regenerative medicine.

Dysfunctional mitochondria elicit bioenergetic decline in the aged heart

Aging represents a complex biological progression affecting the entire body, marked by a gradual decline in tissue function, rendering organs more susceptible to stress and diseases. The human heart holds significant importance in this context, as its aging process poses life-threatening risks. It entails macroscopic morphological shifts and biochemical changes that collectively contribute to diminished cardiac function. Among the numerous pivotal factors in aging, mitochondria play a critical role, intersecting with various molecular pathways and housing several aging-related agents. In this comprehensive review, we provide an updated overview of the functional role of mitochondria in cardiac aging.

A review of chemotherapeutic drugs-induced arrhythmia and potential intervention with traditional Chinese medicines

Significant advances in chemotherapy drugs have reduced mortality in patients with malignant tumors. However, chemotherapy-related cardiotoxicity increases the morbidity and mortality of patients, and has become the second leading cause of death after tumor recurrence, which has received more and more attention in recent years. Arrhythmia is one of the common types of chemotherapy-induced cardiotoxicity, and has become a new risk related to chemotherapy treatment, which seriously affects the therapeutic outcome in patients. Traditional Chinese medicine has experienced thousands of years of clinical practice in China, and has accumulated a wealth of medical theories and treatment formulas, which has unique advantages in the prevention and treatment of malignant diseases. Traditional Chinese medicine may reduce the arrhythmic toxicity caused by chemotherapy without affecting the anti-cancer effect. This paper mainly discussed the types and pathogenesis of secondary chemotherapeutic drug-induced arrhythmia (CDIA), and summarized the studies on Chinese medicine compounds, Chinese medicine Combination Formula and Chinese medicine injection that may be beneficial in intervention with secondary CDIA including atrial fibrillation, ventricular arrhythmia and sinus bradycardia, in order to provide reference for clinical prevention and treatment of chemotherapy-induced arrhythmias.

Knowledge domain and emerging trends of autophagy in cardiovascular research: A bibliometric analysis

BACKGROUND

Autophagy is essential for the homeostasis and function of the cardiovascular system. Citespace is a visual analysis software developed in the context of scientometrics and data visualization. The purpose of this study is to use Citespace software to conduct bibliometric and visual analysis of the research on autophagy in cardiovascular diseases, identify the current status, hot spots and trends in this field, help researchers clarify the future research focus and direction of autophagy in cardiovascular diseases, and provide more positive and broader ideas for the treatment and drug development of cardiovascular diseases.

METHODS

In the Web of Science Core Collection database to download the data from 2004 to 2022 regarding autophagy in cardiovascular research. CitespaceV was used to collect the research status, hotspots and development trends for visual analysis.

RESULTS

The 3568 articles were published by 547 authors from 397 institutions in 75 countries. From 2004 to 2021, the annual publications increased over time. The top 3 productive nations were China, the United States, and Germany. The leading institution was China's Fudan University. The most cited paper is Guidelines for the use and interpretation of assays for monitoring autophagy (3rd edition). The research hotpots include monitoring methods for autophagy activity, changes in autophagy levels in different types of cardiovascular diseases, autophagy signal transduction mechanism in cardiovascular diseases, etc.

CONCLUSION

Bibliometric analysis provided valuable information for autophagy research in cardiovascular disease, which is full of opportunities and challenges. The research of autophagy in the field of cardiovascular diseases is still worthy of in-depth exploration. A challenge with autophagy-targeted therapies is their dichotomy in which the goal is to target maladaptive autophagy while maintaining a baseline level of cell survival to optimize a beneficial outcome. It is necessary for scientists to develop new methods to evaluate the level of autophagy from basic application to human body and reveal the signaling mechanism of autophagy in different types of cardiovascular diseases.

Myocardial ischemia/reperfusion: Translational pathophysiology of ischemic heart disease

Ischemic heart disease is the greatest health burden and most frequent cause of death worldwide. Myocardial ischemia/reperfusion is the pathophysiological substrate of ischemic heart disease. Improvements in prevention and treatment of ischemic heart disease have reduced mortality in developed countries over the last decades, but further progress is now stagnant, and morbidity and mortality from ischemic heart disease in developing countries are increasing. Significant problems remain to be resolved and require a better pathophysiological understanding. The present review attempts to briefly summarize the state of the art in myocardial ischemia/reperfusion research, with a view on both its coronary vascular and myocardial aspects, and to define the cutting edges where further mechanistic knowledge is needed to facilitate translation to clinical practice.

circRNA-miRNA-mRNA Deregulated Network in Ischemic Heart Failure Patients

Noncoding RNAs (ncRNAs), which include circular RNAs (circRNAs) and microRNAs (miRNAs), regulate the development of cardiovascular diseases (CVD). Notably, circRNAs can interact with miRNAs, influencing their specific mRNA targets' levels and shaping a competing endogenous RNAs (ceRNA) network. However, these interactions and their respective functions remain largely unexplored in ischemic heart failure (IHF). This study is aimed at identifying circRNA-centered ceRNA networks in non-end-stage IHF. Approximately 662 circRNA-miRNA-mRNA interactions were identified in the heart by combining state-of-the-art bioinformatics tools with experimental data. Importantly, KEGG terms of the enriched mRNA indicated CVD-related signaling pathways. A specific network centered on circBPTF was validated experimentally. The levels of let-7a-5p, miR-18a-3p, miR-146b-5p, and miR-196b-5p were enriched in circBPTF pull-down experiments, and circBPTF silencing inhibited the expression of HDAC9 and LRRC17, which are targets of miR-196b-5p. Furthermore, as suggested by the enriched pathway terms of the circBPTF ceRNA network, circBPTF inhibition elicited endothelial cell cycle arrest. circBPTF expression increased in endothelial cells exposed to hypoxia, and its upregulation was confirmed in cardiac samples of 36 end-stage IHF patients compared to healthy controls. In conclusion, circRNAs act as miRNA sponges, regulating the functions of multiple mRNA targets, thus providing a novel vision of HF pathogenesis and laying the theoretical foundation for further experimental studies.

The role of redox-mediated lysosomal dysfunction and therapeutic strategies

Redox homeostasis refers to the dynamic equilibrium between oxidant and reducing agent in the body which plays a crucial role in maintaining normal physiological activities of the body. The imbalance of redox homeostasis can lead to the development of various human diseases. Lysosomes regulate the degradation of cellular proteins and play an important role in influencing cell function and fate, and lysosomal dysfunction is closely associated with the development of various diseases. In addition, several studies have shown that redox homeostasis plays a direct or indirect role in regulating lysosomes. Therefore, this paper systematically reviews the role and mechanisms of redox homeostasis in the regulation of lysosomal function. Therapeutic strategies based on the regulation of redox exerted to disrupt or restore lysosomal function are further discussed. Uncovering the role of redox in the regulation of lysosomes helps to point new directions for the treatment of many human diseases.

Essential role for epithelial HIF-mediated xenophagy in control of Salmonella infection and dissemination

The intestinal mucosa exists in a state of “physiologic hypoxia,” where oxygen tensions are markedly lower than those in other tissues. Intestinal epithelial cells (IECs) have evolved to maintain homeostasis in this austere environment through oxygen-sensitive transcription factors, including hypoxia-inducible factors (HIFs). Using an unbiased chromatin immunoprecipitation (ChIP) screen for HIF-1 targets, we identify autophagy as a major pathway induced by hypoxia in IECs. One important function of autophagy is to defend against intracellular pathogens, termed “xenophagy.” Analysis reveals that HIF is a central regulator of autophagy and that in vitro infection of IECs with Salmonella Typhimurium results in induction of HIF transcriptional activity that tracks with the clearance of intracellular Salmonella. Work in vivo demonstrates that IEC-specific deletion of HIF compromises xenophagy and exacerbates bacterial dissemination. These results reveal that the interaction between hypoxia, HIF, and xenophagy is an essential innate immune component for the control of intracellular pathogens.

Dowdell et al. show that hypoxia, through stabilization of HIF-1α, activates autophagy in intestinal epithelial cells (IECs). Further, the model invasive bacterium Salmonella Typhimurium stabilizes HIF in IECs to trigger anti-bacterial autophagy (xenophagy). This mechanism demonstrates an essential mucosal innate immune response for control of invasive pathogens.

Maslinic Acid Inhibits Myocardial Ischemia-Reperfusion Injury-Induced Apoptosis and Necroptosis via Promoting Autophagic Flux

Apoptosis, necroptosis, and autophagy are the major programmed cell death in myocardial ischemia-reperfusion injury (MIRI). Maslinic acid (MA) has been found to regulate pathophysiological processes that mediate programmed cell death in MIRI, such as inflammation and oxidative stress. However, its effects on MIRI remain unclear. This study intends to explore the role of MA in MIRI. In vitro, MA had no obvious cytotoxic effects on H9C2 cells, and significantly improved the impaired cell viability caused by hypoxia reoxygenation (HR). In vivo, MA significantly alleviated ischemia reperfusion (IR)-induced left ventricular myocardial tissue injury, downregulated creatine kinase-myocardial band (CK-MB), and lactate dehydrogenase (LDH) levels in serum as well as reducing infarct size. Moreover, MA inhibited HR-induced mitochondrial apoptosis and necroptosis in vitro and in vivo. Of interest, MA interacts with lysosome-associated membrane protein 2 (LAMP2). MA protected LAMP2 from IR and promoting autophagic flux to inhibit apoptosis and necroptosis, whereas these effects were reversed by co-treatment with lysosomal inhibitor BarfA1. In conclusion, MA can inhibit MIRI-induced apoptosis and necroptosis by promoting autophagic flux. These results support that MA is a potential agent to ameliorate MIRI.

Targeting lysosomes in human disease: from basic research to clinical applications

In recent years, accumulating evidence has elucidated the role of lysosomes in dynamically regulating cellular and organismal homeostasis. Lysosomal changes and dysfunction have been correlated with the development of numerous diseases. In this review, we interpreted the key biological functions of lysosomes in four areas: cellular metabolism, cell proliferation and differentiation, immunity, and cell death. More importantly, we actively sought to determine the characteristic changes and dysfunction of lysosomes in cells affected by these diseases, the causes of these changes and dysfunction, and their significance to the development and treatment of human disease. Furthermore, we outlined currently available targeting strategies: (1) targeting lysosomal acidification; (2) targeting lysosomal cathepsins; (3) targeting lysosomal membrane permeability and integrity; (4) targeting lysosomal calcium signaling; (5) targeting mTOR signaling; and (6) emerging potential targeting strategies. Moreover, we systematically summarized the corresponding drugs and their application in clinical trials. By integrating basic research with clinical findings, we discussed the current opportunities and challenges of targeting lysosomes in human disease.

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.

Hypertrophy-Reduced Autophagy Causes Cardiac Dysfunction by Directly Impacting Cardiomyocyte Contractility

Cardiac remodeling and contractile dysfunction are leading causes in hypertrophy-associated heart failure (HF), increasing with a population's rising age. A hallmark of aged and diseased hearts is the accumulation of modified proteins caused by an impaired autophagy-lysosomal-pathway. Although, autophagy inducer rapamycin has been described to exert cardioprotective effects, it remains to be shown whether these effects can be attributed to improved cardiomyocyte autophagy and contractility. In vivo hypertrophy was induced by transverse aortic constriction (TAC), with mice receiving daily rapamycin injections beginning six weeks after surgery for four weeks. Echocardiographic analysis demonstrated TAC-induced HF and protein analyses showed abundance of modified proteins in TAC-hearts after 10 weeks, both reduced by rapamycin. In vitro, cardiomyocyte hypertrophy was mimicked by endothelin 1 (ET-1) and autophagy manipulated by silencing Atg5 in neonatal cardiomyocytes. ET-1 and siAtg5 decreased Atg5-Atg12 and LC3-II, increased natriuretic peptides, and decreased amplitude and early phase of contraction in cardiomyocytes, the latter two evaluated using ImageJ macro Myocyter recently developed by us. ET-1 further decreased cell contractility in control but not in siAtg5 cells. In conclusion, ET-1 decreased autophagy and cardiomyocyte contractility, in line with siAtg5-treated cells and the results of TAC-mice demonstrating a crucial role for autophagy in cardiomyocyte contractility and cardiac performance.

Pharmacological Pre- and Postconditioning With Levosimendan Protect H9c2 Cardiomyoblasts From Anoxia/Reoxygenation-induced Cell Death via PI3K/Akt Signaling

ABSTRACT

The calcium sensitizer levosimendan is indicated for the hemodynamic stabilization of patients with acutely decompensated heart failure and has been shown to be protective against reperfusion injury after myocardial infarction. However, affected forms of cell death and underlying signaling pathways remain controversial. Therefore, the aim of this study was to examine the influence of levosimendan preconditioning and postconditioning on anoxia/reoxygenation-induced apoptosis, necrosis, and autophagy in H9c2 myoblasts. To mimic conditions of myocardial ischemia/reperfusion, rat cardiac H9c2 myoblasts were exposed to anoxia/starvation, followed by reoxygenation/refeeding. Apoptosis, necrosis, autophagy, cell viability, survival signaling, and mitochondrial permeability transition pore (mPTP) opening were measured. Both, pharmacological preconditioning and postconditioning with levosimendan were capable to reduce apoptosis as well as necrosis in stressed H9c2 cells. However, preconditioning showed to have the stronger impact compared with postconditioning. Moreover, levosimendan preconditioning increased autophagy, suggesting enhanced repair processes initiated by the early presence of the drug. Underlying mechanisms differ between both interventions: Although both are associated with PI3/Akt activation and reduced mPTP opening, only postconditioning but not preconditioning depended on mKATP activation. This variation might indicate that a pharmacological treatment after the onset of reoxygenation at least in part directly addresses mitochondrial structures for protection. In conclusion, we demonstrate that both pharmacological preconditioning and postconditioning with levosimendan protect anoxia/reoxygenation-stressed cells but differ in the underlying mechanisms. These results are decisive to obtain more insights into the beneficial effects of levosimendan in the treatment of reperfusion-mediated damage.

Possible Susceptibility Genes for Intervention against Chemotherapy-Induced Cardiotoxicity

Recent therapeutic advances have significantly improved the short- and long-term survival rates in patients with heart disease and cancer. Survival in cancer patients may, however, be accompanied by disadvantages, namely, increased rates of cardiovascular events. Chemotherapy-related cardiac dysfunction is an important side effect of anticancer therapy. While advances in cancer treatment have increased patient survival, treatments are associated with cardiovascular complications, including heart failure (HF), arrhythmias, cardiac ischemia, valve disease, pericarditis, and fibrosis of the pericardium and myocardium. The molecular mechanisms of cardiotoxicity caused by cancer treatment have not yet been elucidated, and they may be both varied and complex. By identifying the functional genetic variations responsible for this toxicity, we may be able to improve our understanding of the potential mechanisms and pathways of treatment, paving the way for the development of new therapies to target these toxicities. Data from studies on genetic defects and pharmacological interventions have suggested that many molecules, primarily those regulating oxidative stress, inflammation, autophagy, apoptosis, and metabolism, contribute to the pathogenesis of cardiotoxicity induced by cancer treatment. Here, we review the progress of genetic research in illuminating the molecular mechanisms of cancer treatment-mediated cardiotoxicity and provide insights for the research and development of new therapies to treat or even prevent cardiotoxicity in patients undergoing cancer treatment. The current evidence is not clear about the role of pharmacogenomic screening of susceptible genes. Further studies need to done in chemotherapy-induced cardiotoxicity.

Myocardial ischaemia-reperfusion injury and cardioprotection in perspective

Despite the increasing use and success of interventional coronary reperfusion strategies, morbidity and mortality from acute myocardial infarction are still substantial. Myocardial infarct size is a major determinant of prognosis in these patients. Therefore, cardioprotective strategies aim to reduce infarct size. However, a perplexing gap exists between the many preclinical studies reporting infarct size reduction with mechanical and pharmacological interventions and the poor translation into better clinical outcomes in patients. This Review revisits the pathophysiology of myocardial ischaemia-reperfusion injury, including the role of autophagy and forms of cell death such as necrosis, apoptosis, necroptosis and pyroptosis. Other cellular compartments in addition to cardiomyocytes are addressed, notably the coronary microcirculation. Preclinical and clinical research developments in mechanical and pharmacological approaches to induce cardioprotection, and their signal transduction pathways, are discussed. Additive cardioprotective interventions are advocated. For clinical translation into treatments for patients with acute myocardial infarction, who typically are of advanced age, have comorbidities and are receiving several medications, not only infarct size reduction but also attenuation of coronary microvascular obstruction, as well as longer-term targets including infarct repair and reverse remodelling, must be considered to improve patient outcomes. Future clinical trials must focus on patients who really need adjunct cardioprotection, that is, those with severe haemodynamic alterations.

Activation of calcium‑sensing receptor‑mediated autophagy in high glucose‑induced cardiac fibrosis in vitro

Myocardial fibrosis is a major complication of diabetic cardiomyopathy (DCM) that is primarily caused by cardiac fibroblasts that are highly activated by persistent hyperglycemic stimulation, resulting in excessive collagen deposition. Calcium sensing receptor (CaSR) is a member of the G protein-coupled receptor superfamily and regulates intracellular calcium concentrations, which are associated with numerous diseases, including myocardial infarction, tumors and pulmonary hypertension. However, whether CaSR participates in the pathological process of myocardial fibrosis in DCM remains unknown. The present study aimed to investigate the mechanism via which CaSR regulates high glucose (HG)-induced cardiac fibrosis in vitro. HG treated-cardiac fibroblast (CFs) were used and western blotting, immunoprecipitation, Cell Counting Kit-8 assay, ELISA and transfection technology were performed to examine the role of CaSR. In the HG group, treatment with HG increased CaSR, α-smooth muscle actin, collagen I/III and matrix metalloproteinase 2/9 expression and enhanced autophagosome generation and CF proliferation. Furthermore, CaSR activation upregulated the expression of Smad ubiquitin regulatory factor 2 (Smurf2), which led to increased intracellular Ca²⁺ concentrations, increased ubiquitination levels of SKI like proto-oncogene and Smad7 and autophagy activation. Furthermore, the CaSR agonist (R568) or the CaSR inhibitor (Calhex231) and Smurf2-small interfering RNA promoted or inhibited HG-induced alterations, including the enhanced and weakened effects, respectively. Taken together, the results from the present study suggested that increased CaSR expression in CFs activated the Smurf2-ubiquitin proteasome and autophagy, causing excessive CF proliferation and extensive collagen deposition, which resulted in HG-induced myocardial fibrosis. These findings indicated a novel pathogenesis of DCM and may provide a novel strategy for the diagnosis and treatment of DCM.

Qi Dan Li Xin pill improves chronic heart failure by regulating mTOR/p70S6k-mediated autophagy and inhibiting apoptosis

Myocardial remodeling represents a key factor in chronic heart failure (CHF) development, and is characterized by chronic death of cardiomyocytes. Cardiac function changes may be attributed to inflammation, apoptosis and autophagy. This study assessed the effects of Qi Dan Li Xin Pill (QD) on heart function, inflammatory factors, autophagy and apoptosis in cardiac remodeling in CHF rats upon myocardial infarction (MI) induction. Male SD rats underwent a sham procedure or left anterior descending coronary artery (LADCA) ligation, causing MI. Twenty-eight days after modeling, the animals were treated daily with QD, valsartan and saline for 4 weeks. Echocardiography after 4 weeks of drug intervention revealed substantially improved left ventricular remodeling and cardiac function following QD treatment. As demonstrated by decreased IL-1β, IL-6 and TNF-α amounts, this treatment also inhibited the apoptotic process and protected the viability of the myocardium. These outcomes may be attributed to enhanced autophagy in cardiomyocytes, which further reduced pro-inflammatory and pro apoptotic effects. This process may be achieved by QD regulation of the mTOR/P70S6K signaling pathway, suggesting that the traditional Chinese medicine Qi Dan Li Xin pill is effective in heart protective treatment, and is worth further investigation.

Mitochondrial and mitochondrial-independent pathways of myocardial cell death during ischaemia and reperfusion injury

Acute myocardial infarction causes lethal injury to cardiomyocytes during both ischaemia and reperfusion (IR). It is important to define the precise mechanisms by which they die in order to develop strategies to protect the heart from IR injury. Necrosis is known to play a major role in myocardial IR injury. There is also evidence for significant myocardial death by other pathways such as apoptosis, although this has been challenged. Mitochondria play a central role in both of these pathways of cell death, as either a causal mechanism is the case of mitochondrial permeability transition leading to necrosis, or as part of the signalling pathway in mitochondrial cytochrome c release and apoptosis. Autophagy may impact this process by removing dysfunctional proteins or even entire mitochondria through a process called mitophagy. More recently, roles for other programmed mechanisms of cell death such as necroptosis and pyroptosis have been described, and inhibitors of these pathways have been shown to be cardioprotective. In this review, we discuss both mitochondrial and mitochondrial‐independent pathways of the major modes of cell death, their role in IR injury and their potential to be targeted as part of a cardioprotective strategy. This article is part of a special Issue entitled ‘Mitochondria as targets of acute cardioprotection’ and emerged as part of the discussions of the European Union (EU)‐CARDIOPROTECTION Cooperation in Science and Technology (COST) Action, CA16225.

Downregulation of miR-26b-5p, miR-204-5p, and miR-497-3p Expression Facilitates Exercise-Induced Physiological Cardiac Hypertrophy by Augmenting Autophagy in Rats

Exercise-induced autophagy is associated with physiological left ventricular hypertrophy (LVH), and a growing body of evidence suggests that microRNAs (miRNAs) can regulate autophagy-related genes. However, the precise role of miRNAs in exercise induced autophagy in physiological LVH has not been fully defined. In this study, we investigated the microRNA–autophagy axis in physiological LVH and deciphered the underlying mechanism using a rat swimming exercise model. Rats were assigned to sedentary control (CON) and swimming exercise (EX) groups; those in the latter group completed a 10-week swimming exercise without any load. For in vitro studies, H9C2 cardiomyocyte cell line was stimulated with IGF-1 for hypertrophy. We found a significant increase in autophagy activity in the hearts of rats with exercise-induced physiological hypertrophy, and miRNAs showed a high score in the pathway enriched in autophagy. Moreover, the expression levels of miR-26b-5p, miR-204-5p, and miR-497-3p showed an obvious increase in rat hearts. Adenovirus-mediated overexpression of miR-26b-5p, miR-204-5p, and miR-497-3p markedly attenuated IGF-1-induced hypertrophy in H9C2 cells by suppressing autophagy. Furthermore, miR-26b-5p, miR-204-5p, and miR-497-3p attenuated autophagy in H9C2 cells through targeting ULK1, LC3B, and Beclin 1, respectively. Taken together, our results demonstrate that swimming exercise induced physiological LVH, at least in part, by modulating the microRNA–autophagy axis, and that miR-26b-5p, miR-204-5p, and miR-497-3p may help distinguish physiological and pathological LVH.

Lysosomal Abnormalities in Cardiovascular Disease

The lysosome, a key organelle for cellular clearance, is associated with a wide variety of pathological conditions in humans. Lysosome function and its related pathways are particularly important for maintaining the health of the cardiovascular system. In this review, we highlighted studies that have improved our understanding of the connection between lysosome function and cardiovascular diseases with an emphasis on a recent breakthrough that characterized a unique autophagosome-lysosome fusion mechanism employed by cardiomyocytes through a lysosomal membrane protein LAMP-2B. This finding may impact the development of future therapeutic applications.

MicroRNA-183-3p up-regulated by vagus nerve stimulation mitigates chronic systolic heart failure via the reduction of BNIP3L-mediated autophagy

Chronic systolic heart failure (CSHF) was a complex syndrome. Recently, vagus nerve stimulation (VNS), a novel treatment method, has emerged for the treatment of CSHF. therefore the aim of this study was to explore the possible mechanism of VNS treatment alleviating CSHF in rats. Firstly, we found after VNS treatment for 72 h, the level of B-type natriuretic peptide in VNS group was lower than that in CSHF group. In addition, VNS treatment induced the elevated left ventricular ejection fraction level, reduced left ventricular end diastolic volume and left ventricular end systolic volume level in VNS group, suggesting a mitigation of CSHF by VNS. Then we found the level of miR-183-3p in CSHF group was much lower than that in VNS group by High-throughput sequencing. The further results indicated that Bcl-2 interacting protein 3 like (BNIP3L) was identified as the target gene of miR-183-3p, and the expression of BNIP3L was notably reduced in rats of VNS group compared with CSHF group. Moreover, the down-regulated expression of miR-183-3p increased BNIP3L-mediated autophagy in rats of CSHF group compared with VNS group. Further mechanism findings demonstrated that up-regulation of miR-183-3p reduced the expression of BNIP3L, while down-regulation of miR-183-3p facilitated the expression of BNIP3L in H9c2 cells. miR-183-3p could also regulate autophagy by targeting BNIP3L in vitro, which was manifested by overexpression of miR-183-3p to inhibit BNIP3L-mediated autophagy. Our data demonstrated that VNS treatment benefited CSHF via the up-regulation of miRNA-183-3p, which reduced the BNIP3L-mediated autophagy, providing a new therapeutic direction for CSHF.

Autophagy in the heart is enhanced and independent of disease progression in mus musculus dystrophinopathy models

Background

Duchenne muscular dystrophy is a muscle wasting disease caused by dystrophin gene mutations resulting in dysfunctional dystrophin protein. Autophagy, a proteolytic process, is impaired in dystrophic skeletal muscle though little is known about the effect of dystrophin deficiency on autophagy in cardiac muscle. We hypothesized that with disease progression autophagy would become increasingly dysfunctional based upon indirect autophagic markers.

Methods

Markers of autophagy were measured by western blot in 7-week-old and 17-month-old control (C57) and dystrophic (mdx) hearts.

Results

Counter to our hypothesis, markers of autophagy were similar between groups. Given these surprising results, two independent experiments were conducted using 14-month-old mdx mice or 10-month-old mdx/Utrn^± mice, a more severe model of Duchenne muscular dystrophy. Data from these animals suggest increased autophagosome degradation.

Conclusion

Together these data suggest that autophagy is not impaired in the dystrophic myocardium as it is in dystrophic skeletal muscle and that disease progression and related injury is independent of autophagic dysfunction.

Sevoflurane postconditioning alleviates hypoxia-reoxygenation injury of cardiomyocytes by promoting mitochondrial autophagy through the HIF-1/BNIP3 signaling pathway

Background

Sevoflurane postconditioning (SpostC) can alleviate hypoxia-reoxygenation injury of cardiomyocytes; however, the specific mechanism remains unclear. This study aimed to investigate whether SpostC promotes mitochondrial autophagy through the hypoxia-inducible factor-1 (HIF-1)/BCL2/adenovirus E1B 19-kDa-interacting protein 3 (BNIP3) signaling pathway to attenuate hypoxia-reoxygenation injury in cardiomyocytes.

Methods

The H9C2 cardiomyocyte hypoxia/reoxygenation model was established and treated with 2.4% sevoflurane at the beginning of reoxygenation. Cell damage was determined by measuring cell viability, lactate dehydrogenase activity, and apoptosis. Mitochondrial ultrastructural and autophagosomes were observed by transmission electron microscope. Western blotting was used to examine the expression of HIF-1, BNIP3, and Beclin-1 proteins. The effects of BNIP3 on promoting autophagy were determined using interfering RNA technology to silence BNIP3.

Results

Hypoxia-reoxygenation injury led to accumulation of autophagosomes in cardiomyocytes, and cell viability was significantly reduced, which seriously damaged cells. Sevoflurane postconditioning could upregulate HIF-1α and BNIP3 protein expression, promote autophagosome clearance, and reduce cell damage. However, these protective effects were inhibited by 2-methoxyestradiol or sinBNIP3.

Conclusion

Sevoflurane postconditioning can alleviate hypoxia-reoxygenation injury in cardiomyocytes, and this effect may be achieved by promoting mitochondrial autophagy through the HIF-1/BNIP3 signaling pathway.

The roles of oxidative stress and Beclin-1 in the autophagosome clearance impairment triggered by cardiac arrest

During cardiac arrest and return of spontaneous circulation (CA-ROSC), autophagosome clearance in the cortex is progressively impaired, but the role of reactive oxygen species (ROS) in this process and the mechanism underlying the autophagy impairment remain unknown. In this study, we investigated the impacts of ROS on the autophagy-lysosome pathway after CA-ROSC in rats. Cortices from CA-ROSC rats revealed accumulation of LC3, p62 and ubiquitin, indicating impaired autophagic flux. Furthermore, impairment of autophagic flux was related to lysosomal lesion, as indicated by decreased cathepsin D and lysosomal-associated membrane protein 2 (LAMP2) levels after CA-ROSC. In vitro, the resulting ROS generation blocked autophagosome processing and caused accumulation of LC3-II, ubiquitin, and p62, leading to mitochondrial dysfunction and cell death; this outcome was alleviated by cyclosporine A (CsA) pretreatment. Interestingly, ischemia/reperfusion injury was connected with ROS-mediated Beclin-1 upregulation and a reduction in LAMP2, which is a pivotal protein in the autophagy-lysosome pathway. Recovery of the LAMP2 levels and partial Beclin-1 silencing restored the autophagic flux and reduced cell death after CA-ROSC. Taken together, our data indicate that CA-ROSC injury impairs autophagosome clearance partially through a ROS-induced decline in LAMP2 and increase in Beclin-1, leading to increased neuronal cell death.

Aberrant regulation of autophagy in mammalian diseases

Autophagy is a major cellular metabolic pathway that facilitates degradation of a subset of long-lived proteins and cytoplasmic organelles in eukaryotic cells. This pathway plays a vital role in preserving the cellular homeostasis of the cells themselves, in addition to maintaining the normal physiological state of cell renewal. Many stressors, such as starvation, ischaemia and oxidative stress can induce autophagy. In addition to its physiological roles, autophagy also occurs in a wide variety of pathological processes, including tumour progression, metabolic disorders, and neurodegenerative and lung diseases. In recent years, a growing body of evidence has shown that autophagy also plays a key role in the development of mammalian diseases, a function that has garnered substantial attention and study. An in-depth understanding of the molecular role that autophagy plays in pathological settings is vital for both the diagnosis and treatment of mammalian diseases and will aid in the search for novel targets for therapeutic drug intervention. Here, we provide an integrated review of recent studies implicating autophagy dysfunction in the progression of mammalian disorders and summarize research suggesting that the molecular pathways involved in autophagy could serve as potential therapeutic targets.

The effect of fasting or calorie restriction on autophagy induction: A review of the literature

Autophagy is a lysosomal degradation process and protective housekeeping mechanism to eliminate damaged organelles, long-lived misfolded proteins and invading pathogens. Autophagy functions to recycle building blocks and energy for cellular renovation and homeostasis, allowing cells to adapt to stress. Modulation of autophagy is a potential therapeutic target for a diverse range of diseases, including metabolic conditions, neurodegenerative diseases, cancers and infectious diseases. Traditionally, food deprivation and calorie restriction (CR) have been considered to slow aging and increase longevity. Since autophagy inhibition attenuates the anti-aging effects of CR, it has been proposed that autophagy plays a substantive role in CR-mediated longevity. Among several stress stimuli inducers of autophagy, fasting and CR are the most potent non-genetic autophagy stimulators, and lack the undesirable side effects associated with alternative interventions. Despite the importance of autophagy, the evidence connecting fasting or CR with autophagy promotion has not previously been reviewed. Therefore, our objective was to weigh the evidence relating the effect of CR or fasting on autophagy promotion. We conclude that both fasting and CR have a role in the upregulation of autophagy, the evidence overwhelmingly suggesting that autophagy is induced in a wide variety of tissues and organs in response to food deprivation.

Adverse Effects of Fenofibrate in Mice Deficient in the Protein Quality Control Regulator, CHIP

We previously reported how the loss of CHIP expression (Carboxyl terminus of Hsc70-Interacting Protein) during pressure overload resulted in robust cardiac dysfunction, which was accompanied by a failure to maintain ATP levels in the face of increased energy demand. In this study, we analyzed the cardiac metabolome after seven days of pressure overload and found an increase in long-chain and medium-chain fatty acid metabolites in wild-type hearts. This response was attenuated in mice that lack expression of CHIP (CHIP^−/−). These findings suggest that CHIP may play an essential role in regulating oxidative metabolism pathways that are regulated, in part, by the nuclear receptor PPARα (Peroxisome Proliferator-Activated Receptor alpha). Next, we challenged CHIP^−/− mice with the PPARα agonist called fenofibrate. We found that treating CHIP^−/− mice with fenofibrate for five weeks under non-pressure overload conditions resulted in decreased skeletal muscle mass, compared to wild-type mice, and a marked increase in cardiac fibrosis accompanied by a decrease in cardiac function. Fenofibrate resulted in decreased mitochondrial cristae density in CHIP^−/− hearts as well as decreased expression of genes involved in the initiation of autophagy and mitophagy, which suggests that a metabolic challenge, in the absence of CHIP expression, impacts pathways that contribute to mitochondrial quality control. In conclusion, in the absence of functional CHIP expression, fenofibrate results in unexpected skeletal muscle and cardiac pathologies. These findings are particularly relevant to patients harboring loss-of-function mutations in CHIP and are consistent with a prominent role for CHIP in regulating cardiac metabolism.

Inhibition of ERK-Drp1 signaling and mitochondria fragmentation alleviates IGF-IIR-induced mitochondria dysfunction during heart failure

Mitochondrial dysfunction is a major contributor to myocyte loss and the development of heart failure. Myocytes have quality control mechanisms to retain functional mitochondria by removing damaged mitochondria via specialized autophagy, i.e., mitophagy. The underlying mechanisms of fission affect the survival of cardiomyocytes, and left ventricular function in the heart is poorly understood. Here, we demonstrated the direct effect and potential mechanisms of mitochondrial functional defects associated with abnormal mitochondrial dynamics in heart failure. We observed that IGF-IIR signaling produced significant changes in mitochondrial morphology and function; such changes were associated with the altered expression and distribution of dynamin-related protein (Drp1) and mitofusin (Mfn2). IGF-IIR signaled extracellular signal-regulated kinase (ERK) activation to promote Drp1 phosphorylation and translocation to mitochondria for mitochondrial fission and mitochondrial dysfunction. Moreover, IGF-IIR signaling triggered Rab9-dependent autophagosome formation by the JNK-mediated phosphorylation of Bcl-2 at serine 87 and promoted ULK1/Beclin 1-dependent autophagic membrane formation. Excessive mitochondrial fission by Drp1 enhanced the Rab9-dependent autophagosome recognition and engulfing of damaged mitochondria and eventually decreased cardiomyocyte viability. Therefore, these results demonstrated the connection between Rab9-dependent autophagosomes and mitochondrial fission in cardiac myocytes, which provides a potential therapeutic strategy for treating heart disease.

Hydrogen sulfide ameliorates rat myocardial fibrosis induced by thyroxine through PI3K/AKT signaling pathway

This study aims to investigate the role and regulatory mechanism of the Hydrogen sulfide (H₂S) in amelioration of rat myocardial fibrosis induced by thyroxine through interfering the autophagy via regulating the activity of PI3K/AKT1 signaling pathway and the expression of relative miRNA. 40 adult male SD rats were randomly divided into 4 groups (n = 10): the control group, the thyroxine model group (TH group), the model group with H₂S intervention (TH + H₂S group) and the normal group with H₂S intervention (H₂S group). Pathological changes were observed via H&E staining and Masson staining, Expressions of MMPs/TIMPs, PI3K/AKT, autophagy-related proteins in myocardial tissues were detected via Western blotting, and the expressions of miR-21, miR-34a, miR-214 and miR-221 were detected via RT-qPCR. Compared with the control group, in the TH group, myocardial fibrosis was more significant, the expressions of proteins in PI3K/AKT and autophagy-related proteins were significantly decreased, as well as the expression of miR-221; while the expressions of miR-21, miR-34a and miR-214 were significantly elevated. By contrast, all above-mentioned changes were obviously reversed with H₂S treatment, which demonstrated the positive function of H₂S in amelioration of rat myocardial fibrosis induced by thyroxine. The mechanism of such amelioration may be correlated with autophagy activated by the upregulation of expression of PI3K/AKT signaling pathway and downregulation of expressions of miR-21, miR-34a and miR-214.

Lasting pathologic complete response to chemotherapy for ovarian cancer after receiving antimalarials for dermatomyositis

Could hydroxychloroquine and quinacrine antimalarial therapy for dermatomyositis later attributed to a paraneoplasic manifestation of an ovarian cancer enhance its subsequent response to chemotherapy? Five months after being diagnosed with dermatomyositis, while somewhat improved with hydroxychloroquine, quinacrine and methotrexate, this 63-year-old woman presented with an advanced intra-abdominal epithelial ovarian cancer documented (but not resected) at laparotomy. Neoadjuvant carboplatin/paclitaxel resulted in remarkable improvement of symptoms, tumour markers and imaging findings leading to thorough cytoreductive surgery at completion of five cycles. No tumour was found in the resected omentum, gynaecologic organs, as well as hepatic and nodal sampling thus documenting a complete pathologic response; a subcutaneous port and an intraperitoneal (IP) catheter were placed for two cycles of IP cisplatin consolidation. She remains free of disease 3 years after such treatment and her dermatomyositis is in remission in the absence of any treatment. We discuss a possible role of autophagy in promoting tumour cell survival and chemoresistance that is potentially reversed by antimalarial drugs. Thus, chemotherapy following their use may subsequently lead to dramatic potentiation of anticancer treatment.

Novel targets and future strategies for acute cardioprotection: Position Paper of the European Society of Cardiology Working Group on Cellular Biology of the Heart

Ischaemic heart disease and the heart failure that often results, remain the leading causes of death and disability in Europe and worldwide. As such, in order to prevent heart failure and improve clinical outcomes in patients presenting with an acute ST-segment elevation myocardial infarction and patients undergoing coronary artery bypass graft surgery, novel therapies are required to protect the heart against the detrimental effects of acute ischaemia/reperfusion injury (IRI). During the last three decades, a wide variety of ischaemic conditioning strategies and pharmacological treatments have been tested in the clinic-however, their translation from experimental to clinical studies for improving patient outcomes has been both challenging and disappointing. Therefore, in this Position Paper of the European Society of Cardiology Working Group on Cellular Biology of the Heart, we critically analyse the current state of ischaemic conditioning in both the experimental and clinical settings, provide recommendations for improving its translation into the clinical setting, and highlight novel therapeutic targets and new treatment strategies for reducing acute myocardial IRI.

Inhibition of autophagy inhibits the conversion of cardiac fibroblasts to cardiac myofibroblasts

The incidence of heart failure with concomitant cardiac fibrosis is very high in developed countries. Fibroblast activation in heart is causal to cardiac fibrosis as they convert to hypersynthetic cardiac myofibroblasts. There is no known treatment for cardiac fibrosis. Myofibroblasts contribute to the inappropriate remodeling of the myocardial interstitium, which leads to reduced cardiac function and ultimately heart failure. Elevated levels of autophagy have been linked to stress-induced ventricular remodeling and other cardiac diseases. Previously, we had shown that TGF-β₁ treatment of human atrial fibroblasts both induced autophagy and enhanced the fibrogenic response supporting a linkage between the myofibroblast phenotype and autophagy. We now demonstrate that with in vitro culture of primary rat cardiac fibroblasts, inhibition of autophagy represses fibroblast to myofibroblast phenoconversion. Culturing unpassaged cardiac fibroblasts for 72 hours on plastic tissue culture plates is associated with elevated α-smooth muscle actin (α-SMA) expression. This activation parallels increased microtubule-associated protein 1A/1B-light chain 3 (LC-3β II) protein expression. Inhibition of autophagy with bafilomycin-A1 (Baf-A1) and chloroquine (CQ) in cardiac fibroblasts significantly reduces α-SMA and extracellular domain A fibronectin (ED-A FN) protein vs untreated controls. Myofibroblast cell migration and contractility were significantly reduced following inhibition of autophagy. These data support the possibility of a causal link between cardiac fibroblast-to-myofibroblast phenoconversion and autophagy.

Activation of calcium-sensing receptor-mediated autophagy in angiotensinII-induced cardiac fibrosis in vitro

Cardiac fibrosis is one of the primary mechanisms of ventricular remodeling, and there is no effective method for reversal. Activation of calcium sensing receptor (CaSR) has been reported to be involved in the development of myocardial fibrosis, but the molecular mechanism for CaSR activation has not yet been clarified and needs to be further explored. Here, we found that AngII induces cardiac fibroblast proliferation and phenotypic transformation in a dose-dependent manner with increased CaSR and autophagy related protein (Beclin1, LC3B) expression. CaSR activation results in intracellular calcium release, MEK1/2 pathway phosphorylation, autophagy activation and collagen formation induced by AngII in cardiac fibroblasts. However, pretreating the cells with Calhex₂₃₁, PD98059 or 3-MA partially blocked AngII-induced cardiac fibrosis. Our data indicate that the activation of CaSR-mediated MEK/ERK and autophagic pathways is involved in AngII-induced cardiac fibrosis in vitro.

Autophagy in health and disease: focus on the cardiovascular system

Autophagy is a highly conserved mechanism of lysosome-mediated protein and organelle degradation that plays a crucial role in maintaining cellular homeostasis. In the last few years, specific functions for autophagy have been identified in many tissues and organs. In the cardiovascular system, autophagy appears to be essential to heart and vessel homeostasis and function; however defective or excessive autophagy activity seems to contribute to major cardiovascular disorders including heart failure (HF) or atherosclerosis. Here, we review the current knowledge on the role of cardiovascular autophagy in physiological and pathophysiological conditions.

Hydrogen sulfide alleviates myocardial fibrosis in mice with alcoholic cardiomyopathy by downregulating autophagy

Myocardial fibrosis is one of the most important pathological features of alcoholic cardiomyopathy (ACM). Hydrogen sulfide (H2S) exerts protective effects in various types of cardiovascular disease, which has been demonstrated by many previous studies. However, there is a lack of adequate research on the effect of H2S on myocardial fibrosis in ACM. The present study aimed to investigate the etiopathogenic role of H2S in myocardial fibrosis induced by chronic alcohol intake. An ACM mouse model was induced by consumption of 4% ethanol solution in drinking water for 12 weeks. Sodium hydrosulfide (NaHS) was used as a donor to provide exogenous H2S. Twelve weeks later, mice were sacrificed to calculate the heart to body weight ratio. The degree of myocardial collagen deposition was evaluated by Masson's and Van Gieson's staining, the expression level of collagen Ⅰ was measured by immunohistochemistry and autophagosomes were observed by transmission electron microscopy. In addition, the expression levels of autophagy‑associated proteins and fibrosis-associated proteins were detected by western blotting, and the expression levels of miR-21 and miR-211 were detected by reverse transcription-quantitative polymerase chain reaction. The outcomes of the study revealed that chronic alcohol intake results in myocardial fibrosis, enhanced myocardial collagen deposition and increased expression levels of collagen I, autophagy, autophagy-associated proteins (Beclin 1, Atg3 and Atg7) and fibrosis-associated proteins (MMP8, MMP13, MMP14, MMP17 and TGF-β1), as well as miR-21 and miR-221. These results were markedly reversed following treatment with H2S. The present study confirmed that H2S relieves myocardial fibrosis in mice with ACM, and the underlying mechanism may involve the downregulation of autophagy and miR-21 and miR-211 expression levels.

Restoring diabetes-induced autophagic flux arrest in ischemic/reperfused heart by ADIPOR (adiponectin receptor) activation involves both AMPK-dependent and AMPK-independent signaling

Macroautophagy/autophagy is increasingly recognized as an important regulator of myocardial ischemia-reperfusion (MI-R) injury. However, whether and how diabetes may alter autophagy in response to MI-R remains unknown. Deficiency of ADIPOQ, a cardioprotective molecule, markedly increases MI-R injury. However, the role of diabetic hypoadiponectinemia in cardiac autophagy alteration after MI-R is unclear. Utilizing normal control (NC), high-fat-diet-induced diabetes, and Adipoq knockout (adipoq^-/-) mice, we demonstrated that autophagosome formation was modestly inhibited and autophagosome clearance was markedly impaired in the diabetic heart subjected to MI-R. adipoq^-/- largely reproduced the phenotypic alterations observed in the ischemic-reperfused diabetic heart. Treatment of diabetic and adipoq^-/- mice with AdipoRon, a novel ADIPOR (adiponectin receptor) agonist, stimulated autophagosome formation, markedly increased autophagosome clearance, reduced infarct size, and improved cardiac function (P < 0.01 vs vehicle). Mechanistically, AdipoRon caused significant phosphorylation of AMPK-BECN1 (Ser93/Thr119)-class III PtdIns3K (Ser164) and enhanced lysosome protein LAMP2 expression both in vivo and in isolated adult cardiomyocytes. Pharmacological AMPK inhibition or genetic Prkaa2 mutation abolished AdipoRon-induced BECN1 (Ser93/Thr119)-PtdIns3K (Ser164) phosphorylation and AdipoRon-stimulated autophagosome formation. However, AdipoRon-induced LAMP2 expression, AdipoRon-stimulated autophagosome clearance, and AdipoRon-suppressed superoxide generation were not affected by AMPK inhibition. Treatment with MnTMPyP (a superoxide scavenger) increased LAMP2 expression and stimulated autophagosome clearance in simulated ischemic-reperfused cardiomyocytes. However, no additive effect between AdipoRon and MnTMPyP was observed. Collectively, these results demonstrate that hypoadiponectinemia impairs autophagic flux, contributing to enhanced MI-R injury in the diabetic state. ADIPOR activation restores AMPK-mediated autophagosome formation and antioxidant-mediated autophagosome clearance, representing a novel intervention effective against MI-R injury in diabetic conditions.

Molecular mechanisms in cardiomyopathy

Cardiomyopathies represent a heterogeneous group of diseases that negatively affect heart function. Primary cardiomyopathies specifically target the myocardium, and may arise from genetic [hypertrophic cardiomyopathy (HCM), arrhythmogenic right ventricular cardiomyopathy/dysplasia (ARVC/D), mitochondrial cardiomyopathy] or genetic and acquired [dilated cardiomyopathy (DCM), restrictive cardiomyopathy (RCM)] etiology. Modern genomics has identified mutations that are common in these populations, while in vitro and in vivo experimentation with these mutations have provided invaluable insight into the molecular mechanisms native to these diseases. For example, increased myosin heavy chain (MHC) binding and ATP utilization lead to the hypercontractile sarcomere in HCM, while abnormal protein–protein interaction and impaired Ca2+ flux underlie the relaxed sarcomere of DCM. Furthermore, expanded access to genetic testing has facilitated identification of potential risk factors that appear through inheritance and manifest sometimes only in the advanced stages of the disease. In this review, we discuss the genetic and molecular abnormalities unique to and shared between these primary cardiomyopathies and discuss some of the important advances made using more traditional basic science experimentation.

The Inhibitory Effect of WenxinKeli on H9C2 Cardiomyocytes Hypertrophy Induced by Angiotensin II through Regulating Autophagy Activity

Objectives

We investigated the role of cardiomyocyte autophagy and its regulatory mechanisms by WenxinKeli (WXKL) in cells subjected to hypertrophy.

Methods

H9C2 cardiomyocytes were divided into 8 groups. Cytoskeletal proteins as well as endogenously expressed autophagy marker proteins were studied by confocal imaging. Western blotting was used to assess the levels of light chain-3 (LC3) and mechanistic target of rapamycin (mTOR). The cell viability assay was used to detect the content of ATP. Flow cytometry was used to detect apoptotic cardiomyocytes.

Results

(1) Compared with the control group, the length and width of cells in the Angiotensin II (AngII) group were significantly increased, while those in the 3-methyladenine (3-MA) and the WXKL groups were decreased. (2) Compared with AngII group, the expression of LC3 II/I protein in the 3-MA and WXKL groups was downregulated, while the expression of mTOR protein was upregulated. (3) Compared with the AngII group, the cardiomyocytes in the WXKL group showed increased ATP and decreased apoptosis rate and number of autophagosome.

Conclusions

We propose a novel role of WXKL as a likely inhibitor of cardiac hypertrophy by regulation of pathological autophagy.

Lipocalin-2 induces NLRP3 inflammasome activation via HMGB1 induced TLR4 signaling in heart tissue of mice under pressure overload challenge

Lipocalin-2 (also known as NGAL) levels are elevated in obesity and diabetes yet relatively little is known regarding effects on the heart. We induced pressure overload (PO) in mice and found that lipocalin-2 knockout (LKO) mice exhibited less PO-induced autophagy and NLRP3 inflammasome activation than Wt. PO-induced mitochondrial damage was reduced and autophagic flux greater in LKO mice, which correlated with less cardiac dysfunction. All of these observations were negated upon adenoviral-mediated restoration of normal lipocalin-2 levels in LKO. Studies in primary cardiac fibroblasts indicated that lipocalin-2 enhanced priming and activation of NLRP3-inflammasome, detected by increased IL-1β, IL-18 and Caspase-1 activation. This was attenuated in cells isolated from NLRP3-deficient mice or upon pharmacological inhibition of NLRP3. Furthermore, lipocalin-2 induced release of HMGB1 from cells and NLRP3-inflammasome activation was attenuated by TLR4 inhibition. We also found evidence of increased inflammasome activation and reduced autophagy in cardiac biopsy samples from heart failure patients. Overall, this study provides new mechanistic insight on the detrimental role of lipocalin-2 in the development of cardiac dysfunction.

DDiT4L promotes autophagy and inhibits pathological cardiac hypertrophy in response to stress

Physiological cardiac hypertrophy, in response to stimuli such as exercise, is considered adaptive and beneficial. In contrast, pathological cardiac hypertrophy that arises in response to pathological stimuli such as unrestrained high blood pressure and oxidative or metabolic stress is maladaptive and may precede heart failure. We found that the transcript encoding DNA damage-inducible transcript 4-like (DDiT4L) was expressed in murine models of pathological cardiac hypertrophy but not in those of physiological cardiac hypertrophy. In cardiomyocytes, DDiT4L localized to early endosomes and promoted stress-induced autophagy through a process involving mechanistic target of rapamycin complex 1 (mTORC1). Exposing cardiomyocytes to various types of pathological stress increased the abundance of DDiT4L, which inhibited mTORC1 but activated mTORC2 signaling. Mice with conditional cardiac-specific overexpression of DDiT4L had mild systolic dysfunction, increased baseline autophagy, reduced mTORC1 activity, and increased mTORC2 activity, all of which were reversed by suppression of transgene expression. Genetic suppression of autophagy also reversed cardiac dysfunction in these mice. Our data showed that DDiT4L may be an important transducer of pathological stress to autophagy through mTOR signaling in the heart and that DDiT4L could be therapeutically targeted in cardiovascular diseases in which autophagy and mTOR signaling play a major role.

UVRAG Deficiency Exacerbates Doxorubicin-Induced Cardiotoxicity

Doxorubicin (DOX) is an effective chemotherapeutic drug in the treatment of various types of cancers. However, its clinical application has been largely limited by potential development of cardiotoxicity. Previously we have shown that ultra-violet radiation resistance-associated gene (UVRAG), an autophagy-related protein, is essential for the maintenance of autophagic flux in the heart under physiological conditions. Here, we sought to determine the role of UVRAG-mediated autophagy in DOX-induced cardiotoxicity. Mouse models of acute or chronic DOX-induced cardiotoxicity were established. UVRAG deficiency exacerbated DOX-induced mortality and cardiotoxicity manifested by increased cytoplasmic vacuolization, enhanced collagen accumulation, elevated serum activities of lactate dehydrogenase and myocardial muscle creatine kinase, higher ROS levels, aggravated apoptosis and more depressed cardiac function. Autophagic flux was impaired in DOX-induced cardiotoxicity. UVRAG deficiency aggravated impaired autophagic flux in DOX-induced cardiotoxicity. Intermittent fasting restored autophagy and ameliorated pathological alterations of DOX-induced cardiotoxicity. Collectively, our data suggest that UVRAG deficiency exacerbates DOX-induced cardiotoxicity, at least in part, through aggravation of DOX-induced impaired autophagic flux. Intermittent fasting, which restores blunted autophagic flux and ameliorates pathology in the mouse models of DOX-induced cardiotoxicity, may be used as a potential preventive or therapeutic approach for DOX cardiotoxicity.

Mitochondria in Ischemic Heart Disease

A core feature of ischemic heart disease is injury to cardiomyocytes (CMC). Ischemic CMC manifest the molecular mechanisms to undergo the major forms of cell injury and death, namely, oncotic necrosis, necroptosis, apoptosis and unregulated autophagy. Important modulators of ischemic injury are reperfusion and conditioning. Mitochondria have a major role in mediating the injury to CMC through membrane protein complexes referred to as death channels. Apoptosis is mediated by activation of a channel regulated by the Bcl-2 protein family leading to mitochondrial outer membrane permeabilization (MOMP). Oncotic type injury is mediated by opening of the mitochondrial permeability transition pore (mPTP). Mitochondria also have a reperfusion salvage kinase pathway (RISK). With cyclosporine A serving as a prototype, ongoing research is aimed at developing pharmacological approaches to condition and preserve mitochondrial integrity in order to promote CMC survival during episodes of myocardial ischemia.

Hypoxic mitophagy regulates mitochondrial quality and platelet activation and determines severity of I/R heart injury

Mitochondrial dysfunction underlies many prevalent diseases including heart disease arising from acute ischemia/reperfusion (I/R) injury. Here, we demonstrate that mitophagy, which selectively removes damaged or unwanted mitochondria, regulated mitochondrial quality and quantity in vivo. Hypoxia induced extensive mitochondrial degradation in a FUNDC1-dependent manner in platelets, and this was blocked by in vivo administration of a cell-penetrating peptide encompassing the LIR motif of FUNDC1 only in wild-type mice. Genetic ablation of Fundc1 impaired mitochondrial quality and increased mitochondrial mass in platelets and rendered the platelets insensitive to hypoxia and the peptide. Moreover, hypoxic mitophagy in platelets protected the heart from worsening of I/R injury. This represents a new mechanism of the hypoxic preconditioning effect which reduces I/R injury. Our results demonstrate a critical role of mitophagy in mitochondrial quality control and platelet activation, and suggest that manipulation of mitophagy by hypoxia or pharmacological approaches may be a novel strategy for cardioprotection.