Role of Autophagy in Proteostasis: Friend and Foe in Cardiac Diseases

Implications of endoplasmic reticulum stress and autophagy in aging and cardiovascular diseases

The average lifespan of humans has been increasing, resulting in a rapidly rising percentage of older individuals and high morbidity of aging-associated diseases, especially cardiovascular diseases (CVDs). Diverse intracellular and extracellular factors that interrupt homeostatic functions in the endoplasmic reticulum (ER) induce ER stress. Cells employ a dynamic signaling pathway of unfolded protein response (UPR) to buffer ER stress. Recent studies have demonstrated that ER stress triggers various cellular processes associated with aging and many aging-associated diseases, including CVDs. Autophagy is a conserved process involving lysosomal degradation and recycling of cytoplasmic components, proteins, organelles, and pathogens that invade the cytoplasm. Autophagy is vital for combating the adverse influence of aging on the heart. The present report summarizes recent studies on the mechanism of ER stress and autophagy and their overlap in aging and on CVD pathogenesis in the context of aging. It also discusses possible therapeutic interventions targeting ER stress and autophagy that might delay aging and prevent or treat CVDs.

Targeting autophagy in diabetic cardiomyopathy: From molecular mechanisms to pharmacotherapy

Diabetic cardiomyopathy (DCM) is a cardiac microvascular complication caused by metabolic disorders. It is characterized by myocardial remodeling and dysfunction. The pathogenesis of DCM is associated with abnormal cellular metabolism and organelle accumulation. Autophagy is thought to play a key role in the diabetic heart, and a growing body of research suggests that modulating autophagy may be a potential therapeutic strategy for DCM. Here, we have summarized the major signaling pathways involved in the regulation of autophagy in DCM, including Adenosine 5'-monophosphate-activated protein kinase (AMPK), mechanistic target of rapamycin (mTOR), Forkhead box subfamily O proteins (FOXOs), Sirtuins (SIRTs), and PTEN-inducible kinase 1 (PINK1)/Parkin. Given the significant role of autophagy in DCM, we further identified natural products and chemical drugs as regulators of autophagy in the treatment of DCM. This review may help to better understand the autophagy mechanism of drugs for DCM and promote their clinical application.

Role of autophagy and proteostasis in neurodegenerative diseases: Exploring the therapeutic interventions

Neurodegenerative disorders are devastating disorders characterized by gradual loss of neurons and cognition or mobility impairment. The common pathological features of these diseases are associated with the accumulation of misfolded or aggregation of proteins. The pivotal roles of autophagy and proteostasis in maintaining cellular health and preventing the accumulation of misfolded proteins, which are associated with neurodegenerative diseases like Huntington's disease (HD), Alzheimer's disease (AD), and Parkinson's disease (PD). This article presents an in-depth examination of the interplay between autophagy and proteostasis, highlighting how these processes cooperatively contribute to cellular homeostasis and prevent pathogenic protein aggregate accumulation. Furthermore, the review emphasises the potential therapeutic implications of targeting autophagy and proteostasis to mitigate neurodegenerative diseases. While advancements in research hold promise for developing novel treatments, the article also addresses the challenges and complexities associated with modulating these intricate cellular pathways. Ultimately, advancing understanding of the underlying mechanism of autophagy and proteostasis in neurodegenerative disorders provides valuable insights into potential therapeutic avenues and future research directions.

Cardiac proteostasis in obesity and cardiovascular disease

Cardiovascular diseases (CVD) are closely linked to protein homeostasis (proteostasis) and its failure. Beside genetic mutations that impair cardiac protein quality control, obesity is a strong risk factor for heart disease. In obesity, adipose tissue becomes dysfunctional and impacts heart function and CVD progression by releasing cytokines that contribute to systemic insulin resistance and cardiovascular dysfunction. In addition, chronic inflammation and lipotoxicity compromise endoplasmic reticulum (ER) function, eliciting stress responses that overwhelm protein quality control beyond its capacity. Impairment of proteostasis-including dysfunction of the ubiquitin-proteasome system (UPS), autophagy, and the depletion of chaperones-is intricately linked to cardiomyocyte dysfunction. Interventions targeting UPS and autophagy pathways are new potential strategies for re-establishing protein homeostasis and improving heart function. Additionally, lifestyle modifications such as dietary interventions and exercise have been shown to promote cardiac proteostasis and overall metabolic health. The pursuit of future research dedicated to proteostasis and protein quality control represents a pioneering approach for enhancing cardiac health and addressing the complexities of obesity-related cardiac dysfunction.

Targeting gut microbiota in aging-related cardiovascular dysfunction: focus on the mechanisms

The global population is aging and age-related cardiovascular disease is increasing. Even after controlling for cardiovascular risk factors, readmission and mortality rates remain high. In recent years, more and more in-depth studies have found that the composition of the gut microbiota and its metabolites, such as trimethylamine N-oxide (TMAO), bile acids (BAs), and short-chain fatty acids (SCFAs), affect the occurrence and development of age-related cardiovascular diseases through a variety of molecular pathways, providing a new target for therapy. In this review, we discuss the relationship between the gut microbiota and age-related cardiovascular diseases, and propose that the gut microbiota could be a new therapeutic target for preventing and treating cardiovascular diseases.

Targeting Autophagy in Atrial Fibrillation

Atrial fibrillation (AF) is the most common type of arrhythmia in clinical practice, and its incidence is positively correlated with risk factors that include advanced age, hypertension, diabetes, and heart failure. Although our understanding of the mechanisms that govern the occurrence and persistence of AF has been increasing rapidly, the exact mechanism of AF is still not fully understood. Autophagy is an evolutionarily highly conserved and specific physiological process in cells that has been suggested as a potential therapeutic target for several cardiovascular diseases including the pathophysiology of AF. The present article provides an updated review of the fast-progressing field of research surrounding autophagy in AF, and how regulating autophagy might be a therapeutic target to reduce the incidence of AF.

Prevention of Atrial Fibrillation: Putting Proteostasis Derailment Back on Track

Despite the many attempts to treat atrial fibrillation (AF), the most common cardiac tachyarrhythmia in the Western world, the treatment efficacy of AF is still suboptimal. A plausible reason for the suboptimal efficacy is that the current treatments are not directed at the underlying molecular mechanisms that drive AF. Recent discoveries revealed that the derailment of specific molecular proteostasis pathways drive electrical conduction disorders, contractile dysfunction and AF. The degree of this so-called 'electropathology' corresponds to the response to anti-AF treatment. Hence, to develop effective therapies to prevent AF, understanding the molecular mechanisms is of key importance. In this review, we highlight the key modulators of proteostasis derailment and describe the mechanisms that explain how they affect electrical and contractile function in atrial cardiomyocytes and AF. The key modulators of proteostasis derailment include (1) exhaustion of cardioprotective heat shock proteins (HSPs), (2) excessive endoplasmic reticulum (ER) stress and downstream autophagic protein degradation, (3) histone deacetylase 6 (HDAC6)-induced microtubule disruption, (4) activation of DNA damage-PARP1 activation and NAD⁺ axis and (5) mitochondrial dysfunction. Furthermore, we discuss druggable targets within these pathways that are involved in the prevention of proteostasis derailment, as well as the targets that aid in the recovery from AF. Finally, we will elaborate on the most favorable druggable targets for (future) testing in patients with AF, as well as drugs with potential benefits for AF recovery.

The potential therapeutic impacts of trehalose on cardiovascular diseases as the environmental-influenced disorders: An overview of contemporary findings

Cardiovascular diseases (CVDs) as environmental-influenced disorders, are a major concern and the leading cause of death worldwide. A range of therapeutic approaches has been proposed, including conventional and novel methods. Natural compounds offer a promising alternative for CVD treatment due to their ability to regulate molecular pathways with minimal adverse effects. Trehalose is natural compound and disaccharide with unique biological functions and cardio-protective properties. The cardio-protective effects of trehalose are generated through its ability to induce autophagy, which is mediated by the transcription factors TFEB and FOXO1. The stimulation of TFEB plays a significant role in regulating autophagy genes and autophagosome formation. Activation of FOXO1 through dephosphorylation of Foxo1 and blocking of p38 mitogen-activated protein kinase (p38 MAPK) also triggers autophagy dramatically. Trehalose has been shown to reduce CVD risk factors, including atherosclerosis, cardiac remodeling after a heart attack, cardiac dysfunction, high blood pressure, and stroke. It also reduces structural abnormalities of mitochondria, cytokine production, vascular inflammation, cardiomyocyte apoptosis, and pyroptosis. This review provides a molecular overview of trehalose's cardioprotective functions, including its mechanisms of autophagy and its potential to improve CVD symptoms based on clinical evidence.

Exploring the Complex Relationship between Diabetes and Cardiovascular Complications: Understanding Diabetic Cardiomyopathy and Promising Therapies

Diabetes mellitus (DM) and cardiovascular complications are two unmet medical emergencies that can occur together. The rising incidence of heart failure in diabetic populations, in addition to apparent coronary heart disease, ischemia, and hypertension-related complications, has created a more challenging situation. Diabetes, as a predominant cardio-renal metabolic syndrome, is related to severe vascular risk factors, and it underlies various complex pathophysiological pathways at the metabolic and molecular level that progress and converge toward the development of diabetic cardiomyopathy (DCM). DCM involves several downstream cascades that cause structural and functional alterations of the diabetic heart, such as diastolic dysfunction progressing into systolic dysfunction, cardiomyocyte hypertrophy, myocardial fibrosis, and subsequent heart failure over time. The effects of glucagon-like peptide-1 (GLP-1) analogues and sodium-glucose cotransporter-2 (SGLT-2) inhibitors on cardiovascular (CV) outcomes in diabetes have shown promising results, including improved contractile bioenergetics and significant cardiovascular benefits. The purpose of this article is to highlight the various pathophysiological, metabolic, and molecular pathways that contribute to the development of DCM and its significant effects on cardiac morphology and functioning. Additionally, this article will discuss the potential therapies that may be available in the future.

Protein homeostasis in aging and cancer

Aging is a major risk factor for cancer development. As dysfunction in protein homeostasis, or proteostasis, is a universal hallmark of both the aging process and cancer, a comprehensive understanding of the proteostasis system and its roles in aging and cancer will shed new light on how we can improve health and quality of life for older individuals. In this review, we summarize the regulatory mechanisms of proteostasis and discuss the relationship between proteostasis and aging and age-related diseases, including cancer. Furthermore, we highlight the clinical application value of proteostasis maintenance in delaying the aging process and promoting long-term health.

Chronic treatment with serelaxin mitigates adverse remodeling in a murine model of ischemic heart failure and modulates bioactive sphingolipid signaling

Relaxin is a pleiotropic hormone demonstrated to confer cardioprotection in animal models of myocardial infarction and ischemic heart failure by modulating inflammation, fibrosis and arrhythmogenesis. Several of these pathways in the ischemic myocardium are intricately tied with the downstream signaling of bioactive sphingolipids, which play an active role during post-infarction remodeling. In this current study, we examined the effects of relaxin on sphingosine 1-phosphate (S1P), and the potential benefits of relaxin treatment on cardiac health in a rodent model of ischemic heart failure. Acute (30 min) and sub-acute (24 h) treatment of primary cardiomyocytes with serelaxin (recombinant human relaxin-2) increased the cardiomyocyte content of S1P. In the rodent model, treatment with relaxin for 28 days following myocardial ischemia by way of permanent left coronary artery occlusion improved survival and cardiac function, reduced fibrosis and apoptosis, and mitigated the expression of several pro-inflammatory and pro-fibrotic markers. The expression of beclin-1 (autophagy marker) was also reduced. The expression of S1P was significantly higher in cardiac tissue and plasma samples extracted from serelaxin-treated mice at day 28. In conclusion, our studies show a significant protection from relaxin in ischemic heart disease, and demonstrate the association between relaxin signaling and S1P generation.

Atrial fibrillation

Atrial fibrillation (AF) is the most common cardiac arrhythmia despite substantial efforts to understand the pathophysiology of the condition and develop improved treatments. Identifying the underlying causative mechanisms of AF in individual patients is difficult and the efficacy of current therapies is suboptimal. Consequently, the incidence of AF is steadily rising and there is a pressing need for novel therapies. Research has revealed that defects in specific molecular pathways underlie AF pathogenesis, resulting in electrical conduction disorders that drive AF. The severity of this so-called electropathology correlates with the stage of AF disease progression and determines the response to AF treatment. Therefore, unravelling the molecular mechanisms underlying electropathology is expected to fuel the development of innovative personalized diagnostic tools and mechanism-based therapies. Moreover, the co-creation of AF studies with patients to implement novel diagnostic tools and therapies is a prerequisite for successful personalized AF management. Currently, various treatment modalities targeting AF-related electropathology, including lifestyle changes, pharmaceutical and nutraceutical therapy, substrate-based ablative therapy, and neuromodulation, are available to maintain sinus rhythm and might offer a novel holistic strategy to treat AF.

Role of senescence in the chronic health consequences of COVID-19

While the full impact of COVID-19 is not yet clear, early studies have indicated that upwards of 10% of patients experience COVID-19 symptoms longer than 3 weeks, known as Long-Hauler's Syndrome or PACS (postacute sequelae of SARS-CoV-2 infection). There is little known about risk factors or predictors of susceptibility for Long-Hauler's Syndrome, but older adults are at greater risk for severe outcomes and mortality from COVID-19. The pillars of aging (including cellular senescence, telomere dysfunction, impaired proteostasis, mitochondrial dysfunction, deregulated nutrient sensing, genomic instability, progenitor cell exhaustion, altered intercellular communication, and epigenetic alterations) that contribute to age-related dysfunction and chronic diseases (the "Geroscience Hypothesis") may interfere with defenses against viral infection and consequences of these infections. Heightening of the low-grade inflammation that is associated with aging may generate an exaggerated response to an acute COVID-19 infection. Innate immune system dysfunction that leads to decreased senescent cell removal and/or increased senescent cell formation could contribute to accumulation of senescent cells with both aging and viral infections. These processes may contribute to increased risk for long-term COVID-19 sequelae in older or chronically ill patients. Hence, senolytics and other geroscience interventions that may prolong healthspan and alleviate chronic diseases and multimorbidity linked to fundamental aging processes might be an option for delaying, preventing, or alleviating Long-Hauler's Syndrome.

Autophagy as a Therapeutic Target of Natural Products Enhancing Embryo Implantation

Infertility is an emerging health issue worldwide, and female infertility is intimately associated with embryo implantation failure. Embryo implantation is an essential process during the initiation of prenatal development. Recent studies have strongly suggested that autophagy in the endometrium is the most important factor for successful embryo implantation. In addition, several studies have reported the effects of various natural products on infertility improvement via the regulation of embryo implantation, embryo quality, and endometrial receptivity. However, it is unclear whether natural products can improve embryo implantation ability by regulating endometrial autophagy. Therefore, we performed a literature review of studies on endometrial autophagy, embryo implantation, natural products, and female infertility. Based on the information from these studies, this review suggests a new treatment strategy for female infertility by proposing natural products that have been proven to be safe and effective as endometrial autophagy regulators; additionally, we provide a comprehensive understanding of the relationship between the regulation of endometrial autophagy by natural products and female infertility, with an emphasis on embryo implantation.

Identification of circRNA-miRNA-mRNA Regulatory Network and Autophagy Interaction Network in Atrial Fibrillation Based on Bioinformatics Analysis

Background

Circular RNA (circRNA) has been receiving increased attention in the research of atrial fibrillation (AF). Our study aims to find potential circRNAs and identify the circRNA-miRNA-mRNA regulatory network in AF based on bioinformatics analysis.

Methods

GSE129409 was retrieved from the Gene Expression Omnibus (GEO) database, and we used R software to analyze the differentially expressed circRNAs (DECs). Subsequently, we used several bioinformatics methods to obtain the target miRNAs and the target genes. Next, we performed Gene Ontology (GO) classification and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis of the target genes. Then, we used Cytoscape 3.8.2 software to visualize and construct the circRNA-miRNA-mRNA regulatory network, the protein–protein interaction (PPI) network, and the autophagy-related genes network.

Results

We identified a total of 21 DECs, including 6 upregulated DECs and 15 downregulated DECs. After further analysis, we obtained a circRNA-miRNA-mRNA regulatory network consisting of 11 DECs, 9 target miRNAs and 410 target genes, and a PPI network. Finally, the potential novel genes of autophagy in AF were revealed by bioinformatics analysis.

Conclusion

This study could explore the potential role of circRNA, autophagy-related genes and construct the circRNA-miRNA-mRNA regulation network in AF.

Autophagy in the diabetic heart: A potential pharmacotherapeutic target in diabetic cardiomyopathy

Association of diabetes with an elevated risk of cardiac failure has been clinically evident. Diabetes potentiates diastolic and systolic cardiac failure following the myocardial infarction that produces the cardiac muscle-specific microvascular complication, clinically termed as diabetic cardiomyopathy. Elevated susceptibility of diabetic cardiomyopathy is primarily caused by the generation of free radicals in the hyperglycemic milieu, compromising the myocardial contractility and normal cardiac functions with increasing redox insult, impaired mitochondria, damaged organelles, apoptosis, and cardiomyocytes fibrosis. Autophagy is essentially involved in the recycling/clearing the damaged organelles, cytoplasmic contents, and aggregates, which are frequently produced in cardiomyocytes. Although autophagy plays a vital role in maintaining the cellular homeostasis in diligent cardiac tissues, this process is frequently impaired in the diabetic heart. Given its clinical significance, accumulating evidence largely showed the functional aspects of autophagy in diabetic cardiomyopathy, elucidating its intricate protective and pathogenic outcomes. However, etiology and molecular readouts of these contrary autophagy activities in diabetic cardiomyopathy are not yet comprehensively assessed and translated. In this review, we attempted to assess the role of autophagy and its adaptations in the diabetic heart. To delineate the molecular consequences of these events, we provided detailed insights into the autophagy regulation pieces of machinery including the mTOR/AMPK, TFEB/ZNSCAN3, FOXOs, SIRTs, PINK1/Parkin, Nrf2, miRNAs, and others in the diabetic cardiomyopathy. Given the clinical significance of autophagy in the diabetic heart, we further discussed the potential pharmacotherapeutic strategies towards targeting autophagy. Taken together, the present report meticulously assessed autophagy, its adaptations, and molecular regulations in diabetic cardiomyopathy and reviewed the current autophagy-targeting strategies.

Leucine-rich repeat kinase-2 deficiency protected against cardiac remodelling in mice via regulating autophagy formation and degradation

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LRRK2 deficiency protected cardiac remodelling induced by pressure overload

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LRRK2 deficiency preserved cardiac function by regulating both autophagosome formation and degradation.

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LRRK2 regulates autophagosome formation by regulating Bcl2 and Beclin1 interaction.

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LRRK2 regulates autophagosome fusion by interacting with Rab7.

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LRRK2 may become a target of new therapeutic methods for treating heart failure.

Introduction

Leucine-rich repetitive kinase-2 (LRRK2) is a Parkinson's disease-related gene that also participates in many inflammatory diseases. However, the functional role of LRRK2 in cardiovascular disease is not clear.

Objective

In this study, we aimed to elucidate the role of LRRK2 in cardiac remodelling under pressure overload.

Methods

Aortic banding surgery was performed to induce cardiac remodelling in a LRRK2 knockout mouse model. A cardiomyocyte remodelling model was established by phenylephrine (PE) stimulation in neonatal rat cardiomyocytes.

Results

LRRK2 was upregulated in remodelled mouse hearts and cardiomyocytes. Cardiac hypertrophy, fibrosis and dysfunction were ameliorated in LRRK2 knockout mice. LRRK2 silencing protected against the PE-induced cardiomyocyte hypertrophic response, while LRRK2 over-expression worsened the PE-induced hypertrophic response in cardiomyocytes. Decreased autophagy was observed in remodelled cardiomyocytes, whereas LRRK2 silencing increased autophagy levels and LRRK2 overexpression reduced autophagy levels. The autophagy inhibitors 3-MA, bafilomycin and chloroquine reversed the protective effects of LRRK2 deficiency. The autophagy activator rapamycin reversed the deleterious effects of LRRK2 overexpression. We found that LRRK2 inhibited Bcl-2 phosphorylation, thus decreasing the phosphorylation of Beclin1. The protective effects of LRRK2 knockout were partly counteracted by Beclin1(+/−) in vivo and Beclin1 silencing in vitro. We also observed an interaction between LRRK2 and Rab7, an autolysosome degradation-associated protein, which caused Rab7 downregulation. Rab7 knockdown almost completely reversed LRRK2 silencing-induced protection of cardiomyocytes

Conclusion

LRRK2 deficiency protected against cardiac remodelling under pressure overload by increasing Bcl-2/Beclin1 and Rab7-regulated autophagy levels in the heart.

Cell Death and Exosomes Regulation After Myocardial Infarction and Ischemia-Reperfusion

Cardiovascular disease (CVD) is the leading cause of death in the global population, accounting for about one-third of all deaths each year. Notably, with CVDs, myocardial damages result from myocardial infarction (MI) or cardiac arrhythmias caused by interrupted blood flow. Significantly, in the process of MI or myocardial ischemic-reperfusion (I/R) injury, both regulated and non-regulated cell death methods are involved. The critical factor for patients’ prognosis is the infarct area’s size, which determines the myocardial cells’ survival. Cell therapy for MI has been a research hotspot in recent years; however, exosomes secreted by cells have attracted much attention following shortcomings concerning immunogens. Exosomes are extracellular vesicles containing several biologically active substances such as lipids, nucleic acids, and proteins. New evidence suggests that exosomes play a crucial role in regulating cell death after MI as exosomes of various stem cells can participate in the cell damage process after MI. Hence, in the review herein, we focused on introducing various cell-derived exosomes to reduce cell death after MI by regulating the cell death pathway to understand myocardial repair mechanisms better and provide a reference for clinical treatment.

Shenmai injection improves doxorubicin cardiotoxicity via miR-30a/Beclin 1

BACKGROUND

Shenmai Injection (SMI) has been widely used in the treatment of cardiovascular diseases and can reduce side effects when combined with chemotherapy drugs. However, the potential protective mechanism of SMI on the cardiotoxicity caused by anthracyclines has not been clear.

METHODS

We used network pharmacology methods to collect the compound components in SMI and myocardial injury targets, constructed a 'drug-disease' target interaction network relationship diagram, and screened the core targets to predict the potential mechanism of SMI in treating cardiotoxicity of anthracyclines. In addition, the rat model of doxorubicin cardiotoxicity was induced by injecting doxorubicin through the tail vein. The rats were randomized in the model group, miR-30a agomir group, SMI low-dose group, SMI high-dose group，and the control group. The cardiac ultrasound was used to evaluate the structure and function of the rat heart. HE staining was used to observe the pathological changes of the rat myocardium. Transmission electron microscopy was used to observe myocardial autophagosomes. The expression of miR-30a and Beclin 1 mRNA in the rat myocardium was detected by RT-qPCR. Western Blot detected the expression of LC3-II/LC3-I and p62 protein.

RESULTS

The network pharmacological analysis found that SMI could act synergistically through multiple targets and multiple pathways, which might exert a myocardial protective effect through PI3K-Akt signaling pathways and cancer microRNAs. In vivo, compared with the control group, the treatment group could improve the cardiac structure and function, and reduce myocardial pathological damage and the number of autophagosomes. The expression of miR-30a in the myocardium of rats in miR-30a agomir group and SMI group increased (P < 0.01)，Beclin 1 mRNA was decreased (P < 0.01)，LC3-Ⅱ/LC3-I protein was decreased (P < 0.01 or P < 0.05)，and p62 protein was increased (P < 0.01 or P < 0.05).

CONCLUSIONS

SMI has the characteristics of multi-component, multi-target, and multi-pathway. It can inhibit myocardial excessive autophagy by regulating the expression of miR-30a/Beclin 1 and alleviate the myocardial injury induced by doxorubicin.

Protection against Doxorubicin-Induced Cardiac Dysfunction Is Not Maintained Following Prolonged Autophagy Inhibition

Doxorubicin (DOX) is a highly effective chemotherapeutic agent used in the treatment of various cancer types. Nevertheless, it is well known that DOX promotes the development of severe cardiovascular complications. Therefore, investigation into the underlying mechanisms that drive DOX-induced cardiotoxicity is necessary to develop therapeutic countermeasures. In this regard, autophagy is a complex catabolic process that is increased in the heart following DOX exposure. However, conflicting evidence exists regarding the role of autophagy dysregulation in the etiology of DOX-induced cardiac dysfunction. This study aimed to clarify the contribution of autophagy to DOX-induced cardiotoxicity by specifically inhibiting autophagosome formation using a dominant negative autophagy gene 5 (ATG5) adeno-associated virus construct (rAAV-dnATG5). Acute (2-day) and delayed (9-day) effects of DOX (20 mg/kg intraperitoneal injection (i.p.)) on the hearts of female Sprague–Dawley rats were assessed. Our data confirm established detrimental effects of DOX on left ventricular function, redox balance and mitochondrial function. Interestingly, targeted inhibition of autophagy in the heart via rAAV-dnATG5 in DOX-treated rats ameliorated the increase in mitochondrial reactive oxygen species emission and the attenuation of cardiac and mitochondrial function, but only at the acute timepoint. Deviation in the effects of autophagy inhibition at the 2- and 9-day timepoints appeared related to differences in ATG5–ATG12 conjugation, as this marker of autophagosome formation was significantly elevated 2 days following DOX exposure but returned to baseline at day 9. DOX exposure may transiently upregulate autophagy signaling in the rat heart; thus, long-term inhibition of autophagy may result in pathological consequences.

Role of Exercise on Alleviating Pressure Overload-Induced Left Ventricular Dysfunction and Remodeling via AMPK-Dependent Autophagy Activation

Cardiac hypertrophy is one of the significant risk factors that result in maladaptive cardiac remodeling and heart failure, and exercise is known to exert cardioprotection. In this research, the cardioprotective function and exercise mechanisms were explored.The rats underwent transverse aortic constriction (TAC) or a sham operation. The rats that received TAC were randomly assigned to five groups: (1) rats subjected to a sham operation as control group (SC), (2) rats that underwent TAC group (TC), (3) TAC and moderate-intensity exercise group (TE), (4) TE plus 3-MA group (TEM), and (5) TE plus Compound C group (TEC). The heart function was measured via echocardiography. Histological analysis and relative protein testing were conducted to analyze collagen deposition and apoptosis. Furthermore, western blot was employed to measure the protein expression of relevant signaling pathways. Impaired cardiac function, interstitial fibrosis, enhanced apoptosis, and ER stress were observed in the TAC-induced left ventricular hypertrophy. Exercise attenuated TAC-induced cardiac dysfunction, interstitial fibrosis, and ER stress-related apoptosis. In addition, exercise significantly improved autophagy and upregulated AMPK phosphorylation. Furthermore, AMPK inhibitor Compound C repressed the activation of AMPK, and autophagy inhibitor 3-methyladenine reversed exercise-induced autophagy. All of these abolished the protection of exercise against cardiac dysfunction and fibrosis induced by TAC.Our results indicated that 4 weeks of treadmill exercise could alleviate pressure overload-induced LV dysfunction and remodeling via an autophagy-dependent mechanism, which was induced by enhancing autophagy through the activation of AMPK.

Activated FMS-like tyrosine kinase 3 ameliorates angiotensin II-induced cardiac remodelling

AIM

FMS-like receptor tyrosine kinase 3 (Flt3) has been reported to be increased in cardiomyocytes responding to ischaemic stress. This study was to determine whether Flt3 activation could ameliorate pressure overload-induced heart hypertrophy and fibrosis, and to elucidate the mechanisms of action.

METHODS

In vivo cardiac hypertrophy and remodelling experiments were conducted by infusing angiotensin II (Ang II) chronically in male C57BL/6 mice. Flt3-specific ligand (FL) was administered intraperitoneally every two days (5 µg/mouse). In vitro experiments on hypertrophy, apoptosis and autophagy mechanism were performed in neonatal rat cardiomyocytes (NRCMs) and H9c2 cells with adenovirus vector-mediated overexpression of Flt3.

RESULTS

Our results demonstrated that following chronic Ang II infusion for 4 weeks, the mice exhibited heart hypertrophy, fibrosis, apoptosis and contractile dysfunction. Meanwhile, Ang II induced autophagic responses in mouse hearts, as evidenced by increased LC3 II and decreased P62 expression. These pathological alterations in Ang II-treated mice were significantly ameliorated by Flt3 activation with FL administration. In NRCMs and Flt3-overexpressed H9c2 cells, FL attenuated Ang II-induced pathological autophagy and inactivated AMPK/mTORC1/FoxO3a signalling, thereby efficiently mitigating cell hypertrophy and apoptosis. Conversely, the AMPK activator metformin or the mTORC1 inhibitor rapamycin reversed the effects of FL on the alterations of autophagy, hypertrophy and apoptosis in cardiomyocytes induced by Ang II.

CONCLUSION

Flt3 activation ameliorates cardiac hypertrophy, fibrosis and contractile dysfunction in the mouse model of chronic pressure overload, most likely via suppressing AMPK/mTORC1/FoxO3a-mediated autophagy. These results provide new evidence supporting Flt3 as a novel therapeutic target in maladaptive cardiac remodelling.

BW373U86 upregulates autophagy by inhibiting the PI3K/Akt pathway and regulating the mTOR pathway to protect cardiomyocytes from hypoxia-reoxygenation injury

The purpose of this study was to explore the protective effect of BW373U86 (a δ-opioid receptor (DOR) agonist) on ischemia-reperfusion (I/R) injury in rat cardiomyocytes and its underlying mechanism. Primary rat cardiomyocytes were cultured and pretreated with BW373U86 for intervention. The cardiomyocytes were cultured under the condition of 94% N₂ and 5% CO₂ for 24 h to perform hypoxia culture and conventionally cultured for 12 h to perform reoxygenation culture. The cell viability of cardiomyocytes was detected by an MTT assay (Sigma-Aldrich). The autophagy lysosome levels in cardiomyocytes were evaluated by acidic vesicular organelles with dansylcadaverine (MDC) staining (autophagy test kit, Kaiji Biology, kgatg001). The protein expression levels of LC3, p62, and factors in the PI3K/Akt/mTOR signaling pathway were detected by Western blot. Pretreatment with BW373U86 could improve the cell viability of cardiomyocytes with hypoxia-reoxygenation (H/R) injury (p < 0.05). Interestingly, after coculture of BW373U86 and PI3K inhibitor (3-methyladenine), the protein expression levels of p-Akt in cardiomyocytes were markedly increased in comparison with those in the BW373U86 group (p < 0.05). However, there were no significant differences in the protein expression levels of mTOR between the coculture group and the BW373U86 group (p > 0.05). BW373U86 upregulated autophagy to protect cardiomyocytes from H/R injury, which may be related to the PI3K/Akt/m TOR pathway.

Proteotoxic Stress and Cell Death in Cancer Cells

To maintain proteostasis, cells must integrate information and activities that supervise protein synthesis, protein folding, conformational stability, and also protein degradation. Extrinsic and intrinsic conditions can both impact normal proteostasis, causing the appearance of proteotoxic stress. Initially, proteotoxic stress elicits adaptive responses aimed at restoring proteostasis, allowing cells to survive the stress condition. However, if the proteostasis restoration fails, a permanent and sustained proteotoxic stress can be deleterious, and cell death ensues. Many cancer cells convive with high levels of proteotoxic stress, and this condition could be exploited from a therapeutic perspective. Understanding the cell death pathways engaged by proteotoxic stress is instrumental to better hijack the proliferative fate of cancer cells.

Substrate metabolism regulated by Sestrin2-mTORC1 alleviates pressure overload-induced cardiac hypertrophy in aged heart

Sestrin2 (Sesn2) is a stress sensor for the mammalian target of rapamycin complex 1 (mTORC1) pathway. Aging impairs cardiac mTORC1 activation, thereby sensitizing the heart to hypertrophy. C57BL/6 J young wild-type (young WT; 4-6 months), aged WT (24-26 months), and young Sestrin2 knockout mice (Y-Sesn2 KO; 4-6 months) underwent transverse aortic constriction (TAC) for pressure overload. Cardiac expression of Sesn2 decreased with age. At 4 weeks after TAC, aged WT and Y-Sesn2 KO exhibited larger hearts and impaired cardiac function, compared with young WT mice. Augmented phosphorylation of mTOR and downstream effectors; damaged mitochondria and elevated redox markers, as well as and impaired glucose and fatty acid oxidation were observed in aged WT and Y-Sesn2 KO hearts. A pressure overload-induced interaction between Sesn2 and GTPase-activating protein activity toward Rags 2 (GATOR2), which positively regulates mTORC1, was impaired in aged WT hearts. Adeno-associated virus 9-Sesn2 treatment rescued Sesn2 expression, attenuated mTORC1 activation, and increased pressure overload tolerance in aged WT and Y-Sesn2 KO hearts. These results indicated that cardiac Sesn2 acts as a pressure overload sensor for mTORC1. Furthermore, Sesn2 deficiency may cause increased sensitivity to hypertrophy in elderly individuals.

Inflammasomes and Proteostasis Novel Molecular Mechanisms Associated With Atrial Fibrillation

Atrial fibrillation (AF), the most common progressive and age-related cardiac arrhythmia, affects millions of people worldwide. AF is associated with common risk factors, including hypertension, diabetes mellitus, and obesity, and serious complications such as stroke and heart failure. Notably, AF is progressive in nature, and because current treatment options are mainly symptomatic, they have only a moderate effect on prevention of arrhythmia progression. Hereto, there is an urgent unmet need to develop mechanistic treatments directed at root causes of AF. Recent research findings indicate a key role for inflammasomes and derailed proteostasis as root causes of AF. Here, we elaborate on the molecular mechanisms of these 2 emerging key pathways driving the pathogenesis of AF. First the role of NLRP3 (NACHT, LRR, and PYD domains-containing protein 3) inflammasome on AF pathogenesis and cardiomyocyte remodeling is discussed. Then we highlight pathways of proteostasis derailment, including exhaustion of cardioprotective heat shock proteins, disruption of cytoskeletal proteins via histone deacetylases, and the recently discovered DNA damage-induced nicotinamide adenine dinucleotide⁺ depletion to underlie AF. Moreover, potential interactions between the inflammasomes and proteostasis pathways are discussed and possible therapeutic targets within these pathways indicated.

Role of autophagy in aneurysm and dissection of the ascending aorta

Maintenance of physiologically balanced levels of autophagy is crucial for cellular homeostasis and in the normal vessel wall, balanced autophagy can be considered a cytoprotective mechanism that preserves endothelial function and prevents cardiovascular disease. Recent studies pointed out the importance of the modulation of the autophagic flux in the pathogenesis of aortic dissection and aneurysms of the ascending aorta. Notably, shear stress (and its receptor p62), IL-6, Rab7 and Atg5/IRE1α pathways of autophagy may be considered the novel super-selective therapeutic target for the preventive and postoperative treatment of aortic aneurysm and aortic dissection. This review intends to summarize current evidences in this field trying to enlighten new avenues for future researches.

Pro-Senescence and Anti-Senescence Mechanisms of Cardiovascular Aging: Cardiac MicroRNA Regulation of Longevity Drug-Induced Autophagy

Chronological aging as well as biological aging accelerated by various pathologies such as diabetes and obesity contribute to cardiovascular aging, and structural and functional tissue damage of the heart and vasculature. Cardiovascular aging in humans is characterized by structural pathologic remodeling including cardiac and vascular fibrosis, hypertrophy, stiffness, micro- and macro-circulatory impairment, left ventricular diastolic dysfunction precipitating heart failure with either reduced or preserved ejection fraction, and cardiovascular cell death. Cellular senescence, an important hallmark of aging, is a critical factor that impairs repair and regeneration of damaged cells in cardiovascular tissues whereas autophagy, an intracellular catabolic process is an essential inherent mechanism that removes senescent cells throughout life time in all tissues. Several recent reviews have highlighted the fact that all longevity treatment paradigms to mitigate progression of aging-related pathologies converge in induction of autophagy, activation of AMP kinase (AMPK) and Sirtuin pathway, and inhibition of mechanistic target of rapamycin (mTOR). These longevity treatments include health style changes such as caloric restriction, and drug treatments using rapamycin, the first FDA-approved longevity drug, as well as other experimental longevity drugs such as metformin, rapamycin, aspirin, and resveratrol. However, in the heart tissue, autophagy induction has to be tightly regulated since evidence show excessive autophagy results in cardiomyopathy and heart failure. Here we discuss emerging evidence for microRNA-mediated tight regulation of autophagy in the heart in response to treatment with rapamycin, and novel approaches to monitor autophagy progression in a temporal manner to diagnose and regulate autophagy induction by longevity treatments.

SS31 Ameliorates Sepsis-Induced Heart Injury by Inhibiting Oxidative Stress and Inflammation

Sepsis-induced myocardial dysfunction (SIMD), lack of effective treatment, accounts for high mortality of sepsis. Mitochondrion-targeted antioxidant peptide SS31 has been revealed to be responsible for certain cardiovascular disease by ameliorating oxidative stress injury. But whether it protects a septic heart remains little known. This study sought to prove that SS31 was capable of improving sepsis-induced myocardial dysfunction dramatically. C57BL/6 mice were intraperitoneally administered lipopolysaccharide (LPS), exposed to systemic inflammation. Thirty-five C57BL/6 mice were randomly divided into four groups: sham group, LPS group (5 mg/kg), SS31 group (5 mg/kg), and SS31 + LPS group (treatment group). Heart tissues were harvested for pathological examination at the indicated time points. H9C2 cell were treated with LPS with or without the presence of SS31 (10 μM) at 37 °C to assess the effect on cardiomyocytes at the indicated time points. SS31 restored myocardial morphological damage and suppressed inflammatory response as evidenced by significantly decreasing the mRNA levels of IL-6, IL-1β, and TNF-α in vitro and in vivo. In addition, myocardial energy deficiency secondary to sepsis was remarkedly ameliorated by SS31. Furthermore, we found that SS-31 normalized the activity of malondialdehyde, glutathione peroxidase, and superoxide dismutase in vitro and in vivo, and maintained mitochondrial membrane potential (MMP) as well. And western blot was applied to measure the expressions of p-p38MAPK, p-JNK1/2, p-ERK, p62, and NF-κB p65; the results illuminated that the cardioprotective effect of SS31 was partly linked to NF-κB. In conclusion, SS31 therapy effectively protected the heart against LPS-induced cardiac damage.

Osteopontin induces atrial fibrosis by activating Akt/GSK-3β/β-catenin pathway and suppressing autophagy

AIMS

Atrial fibrosis is a common feature of atrial fibrillation (AF). Recently, it is reported that osteopontin (OPN) can induce fibrosis in lungs, livers and kidneys. However, its role in atrial fibrosis remains unclear. Here, we sought to determine the involvement of OPN in atrial fibrosis and the underlying mechanisms during this pathological remodeling process.

MATERIALS AND METHODS

Protein expressions were determined by enzyme-linked immunosorbent assay (ELISA), immunohistochemical staining and immunoblotting. mRNA expressions were detected by qRT-PCR. Cell proliferation was assessed by CCK-8. Left atrial electroanatomical voltage maps were created using PentaRay catheters and a 3-dimensional mapping system.

KEY FINDINGS

OPN was highly expressed in the circulation of AF patients and was further increased with the progression of AF. In addition, correlation analysis showed that circulating OPN positively related with low-voltage areas (LVAs, a marker of atrial fibrosis) in AF patients. Immunohistological staining and immunoblotting revealed an increased expression of OPN in AF patients who present a higher degree of atrial fibrosis. Furthermore, in vitro studies in cultured human atrial fibroblasts (hAFs) demonstrated that OPN promoted the proliferation of fibroblasts and increased production of collagen I and fibronectin. Mechanistically, the profibrotic effects of OPN on atrial fibroblasts were determined via activating Akt/GSK-3β/β-catenin signaling and suppressing autophagy.

SIGNIFICANCE

This study uncovered a previously unrecognized profibrotic role of OPN in atrial fibrosis, which was achieved through activation of Akt/GSK-3β/β-catenin signaling pathway and suppression of autophagy, implying a promising therapeutic target in atrial fibrosis and AF.

Imbalance of ER and Mitochondria Interactions: Prelude to Cardiac Ageing and Disease?

Cardiac disease is still the leading cause of morbidity and mortality worldwide, despite some exciting and innovative improvements in clinical management. In particular, atrial fibrillation (AF) and heart failure show a steep increase in incidence and healthcare costs due to the ageing population. Although research revealed novel insights in pathways driving cardiac disease, the exact underlying mechanisms have not been uncovered so far. Emerging evidence indicates that derailed proteostasis (i.e., the homeostasis of protein expression, function and clearance) is a central component driving cardiac disease. Within proteostasis derailment, key roles for endoplasmic reticulum (ER) and mitochondrial stress have been uncovered. Here, we describe the concept of ER and mitochondrial stress and the role of interactions between the ER and mitochondria, discuss how imbalance in the interactions fuels cardiac ageing and cardiac disease (including AF), and finally assess the potential of drugs directed at conserving the interaction as an innovative therapeutic target to improve cardiac function.

The Role of Autophagy in Acute Myocardial Infarction

Acute myocardial infarction refers to a sudden death of cardiomyocytes, which leads to a large mortality worldwide. To attenuate acute myocardial infarction, strategies should be made to increase cardiomyocyte survival, improve postinfarcted cardiac function, and reverse the process of cardiac remodeling. Autophagy, a pivotal cellular response, has been widely studied and is known to be involved in various kinds of diseases. In the recent few years, the role of autophagy in diseases has been drawn increasing attention to by researchers. Here in this review, we mainly focus on the discussion of the effect of autophagy on the pathogenesis and progression of acute myocardial infarction under ischemic and ischemia/reperfusion injuries. Furthermore, several popular therapeutic agents and strategies taking advantage of autophagy will be described.

Pharmacological modulation of autophagy as a novel potential target in the successful implementation of in vitro fertilization

Autophagy is an important intracellular process to maintain homeostasis and studies have shown the key role of autophagy in modulating the functions of reproductive system. Alongside with it, the activation of autophagy has also been found to regulate a number of important processes involved in in vitro fertilization including degeneration of granulosa cells and oocyte defects in obese and aging women; apoptosis of oocytes during vitrification-warming; quality and viability of embryo; developmental competence and pre-implantation development of in vitro produced blastocysts; placental vascularization and fetal growth. The different mechanisms that may contribute in autophagy-mediated increase in developmental competence and pre-implantation development include decrease in endoplasmic reticulum (ER) stress, activation of poly(ADP-ribosyl)ation (PARP) and reduction in free radical production. The present review discusses the role of autophagy activation in increasing the efficiency of in vitro fertilization by modulating different aspects related to fertilization.

Atrial fibrillation

Atrial fibrillation (AF) is the most common cardiac arrhythmia despite substantial efforts to understand the pathophysiology of the condition and develop improved treatments. Identifying the underlying causative mechanisms of AF in individual patients is difficult and the efficacy of current therapies is suboptimal. Consequently, the incidence of AF is steadily rising and there is a pressing need for novel therapies. Research has revealed that defects in specific molecular pathways underlie AF pathogenesis, resulting in electrical conduction disorders that drive AF. The severity of this so-called electropathology correlates with the stage of AF disease progression and determines the response to AF treatment. Therefore, unravelling the molecular mechanisms underlying electropathology is expected to fuel the development of innovative personalized diagnostic tools and mechanism-based therapies. Moreover, the co-creation of AF studies with patients to implement novel diagnostic tools and therapies is a prerequisite for successful personalized AF management. Currently, various treatment modalities targeting AF-related electropathology, including lifestyle changes, pharmaceutical and nutraceutical therapy, substrate-based ablative therapy, and neuromodulation, are available to maintain sinus rhythm and might offer a novel holistic strategy to treat AF.