Markers of autophagy are downregulated in failing human heart after mechanical unloading

Sodium-Glucose Cotransporter 2 (SGLT2) Inhibitors: Guardians against Mitochondrial Dysfunction and Endoplasmic Reticulum Stress in Heart Diseases

Sodium-glucose cotransporter 2 (SGLT2) inhibitors are an innovative class of antidiabetic drugs that provide cardiovascular benefits to both diabetic and nondiabetic patients, surpassing those of other antidiabetic drugs. Although the roles of mitochondria and endoplasmic reticulum (ER) in cardiovascular research are increasingly recognized as promising therapeutic targets, the exact molecular mechanisms by which SGLT2 inhibitors influence mitochondrial and ER homeostasis in the heart remain incompletely elucidated. This review comprehensively summarizes and discusses the impacts of SGLT2 inhibitors on mitochondrial dysfunction and ER stress in heart diseases including heart failure, ischemic heart disease/myocardial infarction, and arrhythmia from preclinical and clinical studies. Based on the existing evidence, the effects of SGLT2 inhibitors may potentially involve the restoration of mitochondrial biogenesis and alleviation of ER stress. Such consequences are achieved by enhancing adenosine triphosphate (ATP) production, preserving mitochondrial membrane potential, improving the activity of electron transport chain complexes, maintaining mitochondrial dynamics, mitigating oxidative stress and apoptosis, influencing cellular calcium and sodium handling, and targeting the unfolded protein response (UPR) through three signaling pathways including inositol requiring enzyme 1α (IRE1α), protein kinase R like endoplasmic reticulum kinase (PERK), and activating transcription factor 6 (ATF6). Therefore, SGLT2 inhibitors have emerged as a promising target for treating heart diseases due to their potential to improve mitochondrial functions and ER stress.

Mitochondrial Reactive Oxygen Species Dysregulation in Heart Failure with Preserved Ejection Fraction: A Fraction of the Whole

Heart failure with preserved ejection fraction (HFpEF) is a multifarious syndrome, accounting for over half of heart failure (HF) patients receiving clinical treatment. The prevalence of HFpEF is rapidly increasing in the coming decades as the global population ages. It is becoming clearer that HFpEF has a lot of different causes, which makes it challenging to find effective treatments. Currently, there are no proven treatments for people with deteriorating HF or HFpEF. Although the pathophysiologic foundations of HFpEF are complex, excessive reactive oxygen species (ROS) generation and increased oxidative stress caused by mitochondrial dysfunction seem to play a critical role in the pathogenesis of HFpEF. Emerging evidence from animal models and human myocardial tissues from failed hearts shows that mitochondrial aberrations cause a marked increase in mitochondrial ROS (mtROS) production and oxidative stress. Furthermore, studies have reported that common HF medications like beta blockers, angiotensin receptor blockers, angiotensin-converting enzyme inhibitors, and mineralocorticoid receptor antagonists indirectly reduce the production of mtROS. Despite the harmful effects of ROS on cardiac remodeling, maintaining mitochondrial homeostasis and cardiac functions requires small amounts of ROS. In this review, we will provide an overview and discussion of the recent findings on mtROS production, its threshold for imbalance, and the subsequent dysfunction that leads to related cardiac and systemic phenotypes in the context of HFpEF. We will also focus on newly discovered cellular and molecular mechanisms underlying ROS dysregulation, current therapeutic options, and future perspectives for treating HFpEF by targeting mtROS and the associated signal molecules.

Autophagy-Dependent Secretion: Crosstalk between Autophagy and Exosome Biogenesis

The cellular secretome is pivotal in mediating intercellular communication and coordinating responses to stressors. Exosomes, initially recognized for their role in waste disposal, have now emerged as key intercellular messengers with significant therapeutic and diagnostic potential. Similarly, autophagy has transcended its traditional role as a waste removal mechanism, emerging as a regulator of intracellular communication pathways and a contributor to a unique autophagy-dependent secretome. Secretory authophagy, initiated by various stress stimuli, prompts the selective release of proteins implicated in inflammation, including leaderless proteins that bypass the conventional endoplasmic reticulum-Golgi secretory pathway. This reflects the significant impact of stress-induced autophagy on cellular secretion profiles, including the modulation of exosome release. The convergence of exosome biogenesis and autophagy is exemplified by the formation of amphisomes, vesicles that integrate autophagic and endosomal pathways, indicating their synergistic interplay. Regulatory proteins common to both pathways, particularly mTORC1, emerge as potential therapeutic targets to alter cellular secretion profiles involved in various diseases. This review explores the dynamic interplay between autophagy and exosome formation, highlighting the potential to influence the secretome composition. While the modulation of exosome secretion and cytokine preconditioning is well-established in regenerative medicine, the strategic manipulation of autophagy is still underexplored, presenting a promising but uncharted therapeutic landscape.

Genetic ablation of Lmp2 increases the susceptibility for impaired cardiac function

Proteasome degradation is an integral part of cellular growth and function. Proteasomal intervention may mitigate adverse myocardial remodeling, but is associated with the onset of heart failure. Previously, we have demonstrated that increasing abundance of cardiac Lmp2 and its incorporation into proteasome complexes is an endogenous mechanism for proteasome regulation during hypertrophic remodeling of the heart induced by chronic ß-adrenoreceptor stimulation. Here, we investigated whether Lmp2 is required for myocardial remodeling not driven by inflammation and show that Lmp2 is a tipping element for growth and function in the heart but not for proteasome insufficiency. While it has no apparent impact under unchallenged conditions, myocardial remodeling without Lmp2 exacerbates hypertrophy and restricts cardiac function. Under chronic ß-adrenoreceptor stimulation, as seen in the development of cardiovascular disease and the manifestation of heart failure, genetic ablation of Lmp2 in mice caused augmented concentric hypertrophy of the left ventricle. While the heart rate was similarly elevated as in wildtype, myocardial contractility was not maintained without Lmp2, and apparently uncoupled of the ß-adrenergic response. Normalized to the exacerbated myocardial mass, contractility was reduced by 41% of the pretreatment level, but would appear preserved at absolute level. The lack of Lmp2 interfered with elevated 26S proteasome activities during early cardiac remodeling reported previously, but did not cause bulk proteasome insufficiency, suggesting the Lmp2 containing proteasome subpopulation is required for a selected group of proteins to be degraded. In the myocardial interstitium, augmented collagen deposition suggested matrix stiffening in the absence of Lmp2. Indeed, echocardiography of left ventricular peak relaxation velocity (circumferential strain rate) was reduced in this treatment group. Overall, targeting Lmp2 in a condition mimicking chronic ß-adrenoreceptor stimulation exhibited the onset of heart failure. Anticancer therapy inhibiting proteasome activity, including Lmp2, is associated with adverse cardiac events, in particular heart failure. Sparing Lmp2 may be an avenue to reduce adverse cardiac events when chronic sympathetic nervous system activation cannot be excluded.

Association of Circulating Autophagy Proteins ATG5 and Beclin 1 with Acute Myocardial Infarction in a Case-Control Study

INTRODUCTION

Acute myocardial infarction (AMI) is a main contributor of sudden cardiac death worldwide. The discovery of new biomarkers that can improve AMI risk prediction meets a major clinical need for the identification of high-risk patients and the tailoring of medical treatment. Previously, we reported that autophagy a highly conserved catabolic mechanism for intracellular degradation of cellular components is involved in atherosclerotic plaque phenotype and cardiac pathological remodeling. The crucial role of autophagy in the normal and diseased heart has been well described, and its activation functions as a pro-survival process in response to myocardial ischemia. However, autophagy is dysregulated in ischemia/reperfusion injury, thus promoting necrotic or apoptotic cardiac cell death. Very few studies have focused on the plasma levels of autophagy markers in cardiovascular disease patients, even though they could be companion biomarkers of AMI injury. The aims of the present study were to evaluate (1) whether variations in plasma levels of two key autophagy regulators autophagy-related gene 5 (ATG5) and Beclin 1 (the mammalian yeast ortholog Atg6/Vps30) are associated with AMI and (2) their potential for predicting AMI risk.

METHODS

The case-control study population included AMI patients (n = 100) and control subjects (n = 99) at high cardiovascular risk but without known coronary disease. Plasma levels of ATG5 and Beclin 1 were measured in the whole population study by enzyme-linked immunosorbent assay.

RESULTS

Multivariate analyses adjusted on common cardiovascular factors and medical treatments, and receiver operating characteristic curves demonstrated that ATG5 and Beclin 1 levels were inversely associated with AMI and provided original biomarkers for AMI risk prediction.

CONCLUSION

Plasma levels of autophagy regulators ATG5 and Beclin 1 represent relevant candidate biomarkers associated with AMI.

Control of NAD+ homeostasis by autophagic flux modulates mitochondrial and cardiac function

Impaired autophagy is known to cause mitochondrial dysfunction and heart failure, in part due to altered mitophagy and protein quality control. However, whether additional mechanisms are involved in the development of mitochondrial dysfunction and heart failure in the setting of deficient autophagic flux remains poorly explored. Here, we show that impaired autophagic flux reduces nicotinamide adenine dinucleotide (NAD+) availability in cardiomyocytes. NAD+ deficiency upon autophagic impairment is attributable to the induction of nicotinamide N-methyltransferase (NNMT), which methylates the NAD+ precursor nicotinamide (NAM) to generate N-methyl-nicotinamide (MeNAM). The administration of nicotinamide mononucleotide (NMN) or inhibition of NNMT activity in autophagy-deficient hearts and cardiomyocytes restores NAD+ levels and ameliorates cardiac and mitochondrial dysfunction. Mechanistically, autophagic inhibition causes the accumulation of SQSTM1, which activates NF-κB signaling and promotes NNMT transcription. In summary, we describe a novel mechanism illustrating how autophagic flux maintains mitochondrial and cardiac function by mediating SQSTM1-NF-κB-NNMT signaling and controlling the cellular levels of NAD+.

The role of sphingosine-1-phosphate in autophagy and related disorders

S1P, also referred to as sphingosine-1-phosphate, is a lipid molecule with bioactive properties involved in numerous cellular processes such as cell growth, movement, programmed cell death, self-degradation, cell specialization, aging, and immune system reactions. Autophagy is a meticulously controlled mechanism in which cells repurpose their elements to maintain cellular balance. There are five stages in autophagy: initiation, nucleation, elongation and maturation, fusion, and degradation. New research has provided insight into the complex connection between S1P and autophagy, uncovering their interaction in both normal and abnormal circumstances. Gaining knowledge about the regulatory mechanism of S1P signaling on autophagy can offer a valuable understanding of its function in well-being and illness, potentially leading to innovative therapeutic concepts for diverse ailments. Hence, this review analyzes the essential stages in mammalian autophagy, with a specific emphasis on recent research exploring the control of each stage by S1P. Additionally, it sheds light on the roles of S1P-induced autophagy in various disorders.

Assessment of Autophagy Markers Suggests Increased Activity Following LVAD Therapy

Left ventricular reverse remodeling in heart failure is associated with improved clinical outcomes. However, the molecular features that drive this process are poorly defined. Left ventricular assist devices (LVADs) are the therapy associated with the greatest reverse remodeling and lead to partial myocardial recovery in most patients. In this study, we examined whether autophagy may be implicated in post-LVAD reverse remodeling. We found expression of key autophagy factors increased post-LVAD, while autophagic substrates decreased. Autolysosome numbers increased post-LVAD, further indicating increased autophagy. These findings support the conclusion that mechanical unloading activates autophagy, which may underly the reverse remodeling observed.

Ubiquitin, p62, and Microtubule-Associated Protein 1 Light Chain 3 in Cardiomyopathy

Background: The accumulation of ubiquitinated proteins has been detected in diseased hearts and has been associated with the expression of p62 and microtubule-associated protein 1 light chain 3 (LC3), which are related to autophagy. We evaluated differences in ubiquitin accumulation and p62 and LC3 expression in cardiomyopathy using endomyocardial biopsies. Methods and Results: We studied 24 patients (aged 24-70 years; mean age 55 years) diagnosed with dilated cardiomyopathy (DCM), hypertrophic cardiomyopathy (HCM), or non-cardiomyopathy (NCM) who underwent endomyocardial biopsy. Biopsied samples were evaluated by microscopy for ubiquitin accumulation and expression of p62 and LC3. Ubiquitin accumulation and p62 and LC3 expression were observed in all patients. Ubiquitin accumulation was higher in DCM than in HCM or NCM; p62 expression was higher in DCM than in HCM. There were no significant differences in LC3 expression among the groups. Ubiquitin accumulation was significantly related to serum N-terminal pro B-type natriuretic peptide concentration and the expression of p62, but not LC3. Conclusions: Ubiquitin accumulation was more prominent in DCM than in HCM and NCM, which may be due to a relative shortage of clearance, including autophagy, compared with production.

Regression of cardiac hypertrophy in health and disease: mechanisms and therapeutic potential

Left ventricular hypertrophy is a leading risk factor for cardiovascular morbidity and mortality. Although reverse ventricular remodelling was long thought to be irreversible, evidence from the past three decades indicates that this process is possible with many existing heart disease therapies. The regression of pathological hypertrophy is associated with improved cardiac function, quality of life and long-term health outcomes. However, less than 50% of patients respond favourably to most therapies, and the reversibility of remodelling is influenced by many factors, including age, sex, BMI and disease aetiology. Cardiac hypertrophy also occurs in physiological settings, including pregnancy and exercise, although in these cases, hypertrophy is associated with normal or improved ventricular function and is completely reversible postpartum or with cessation of training. Studies over the past decade have identified the molecular features of hypertrophy regression in health and disease settings, which include modulation of protein synthesis, microRNAs, metabolism and protein degradation pathways. In this Review, we summarize the evidence for hypertrophy regression in patients with current first-line pharmacological and surgical interventions. We further discuss the molecular features of reverse remodelling identified in cell and animal models, highlighting remaining knowledge gaps and the essential questions for future investigation towards the goal of designing specific therapies to promote regression of pathological hypertrophy.

Targeting the Autophagy-Lysosome Pathway in a Pathophysiologically Relevant Murine Model of Reversible Heart Failure

The key biological "drivers" that are responsible for reverse left ventricle (LV) remodeling are not well understood. To gain an understanding of the role of the autophagy-lysosome pathway in reverse LV remodeling, we used a pathophysiologically relevant murine model of reversible heart failure, wherein pressure overload by transaortic constriction superimposed on acute coronary artery (myocardial infarction) ligation leads to a heart failure phenotype that is reversible by hemodynamic unloading. Here we show transaortic constriction + myocardial infarction leads to decreased flux through the autophagy-lysosome pathway with the accumulation of damaged proteins and organelles in cardiac myocytes, whereas hemodynamic unloading is associated with restoration of autophagic flux to normal levels with incomplete removal of damaged proteins and organelles in myocytes and reverse LV remodeling, suggesting that restoration of flux is insufficient to completely restore myocardial proteostasis. Enhancing autophagic flux with adeno-associated virus 9-transcription factor EB resulted in more favorable reverse LV remodeling in mice that had undergone hemodynamic unloading, whereas overexpressing transcription factor EB in mice that have not undergone hemodynamic unloading leads to increased mortality, suggesting that the therapeutic outcomes of enhancing autophagic flux will depend on the conditions in which flux is being studied.

Dapagliflozin Inhibits Ventricular Remodeling in Heart Failure Rats by Activating Autophagy through AMPK/mTOR Pathway

Objective

Heart failure (HF) is the end stage of heart disease caused by various factors which mainly involves ventricular remodeling (VR). In HF patients with reduced ejection fraction, dapagliflozin (DAPA) reduced the risk of worsening HF or cardiovascular death. Thus, we attempted to clarify the specific role of DAPA underlying HF progression.

Methods

The HF rat model was established to mimic characteristics of HF in vivo. HE staining assessed histopathological changes in left ventricular myocardial tissue of rats in each group. ELISA measured plasma ANP and BNP levels of rats in each group. M-mode echocardiography detected cardiac function of rats in each group. TUNEL staining detected apoptosis of infarct margin cells in myocardial tissue of rats in each group. Western blot detected levels of apoptosis-related proteins, autophagy-related proteins, and AMPK/mTOR-related proteins in myocardial tissue of rats in each group. Immunohistochemical staining detected caspase-3 or LC3B level in myocardial tissue of rats in each group. The HF cellular model was established to mimic characteristics of HF in vitro. Flow cytometry detected H9C2 cell apoptosis under different conditions. Western blot detected levels of apoptosis-related proteins, autophagy-related proteins, and AMPK/mTOR-related proteins in H9C2 cells under different conditions. Immunofluorescence detected caspase-3 or LC3B level in H9C2 cells under different conditions.

Results

DAPA attenuated left VR and improved cardiac function in HF rats. DAPA attenuated cardiomyocyte apoptosis in HF rats. DAPA facilitated cardiomyocyte autophagy in HF rats via the AMPK/mTOR pathway. DAPA repressed hypoxia-induced H9C2 cell apoptosis by facilitating autophagy. DAPA repressed hypoxia-induced H9C2 cell apoptosis via the AMPK/mTOR pathway.

Conclusion

DAPA suppresses ventricular remodeling in HF through activating autophagy via AMPK/mTOR pathway, which provides a potential novel insight for seeking therapeutic plans of HF.

The role of autophagy in cardiovascular pathology

Macroautophagy/autophagy is a conserved catabolic recycling pathway in which cytoplasmic components are sequestered, degraded, and recycled to survive various stress conditions. Autophagy dysregulation has been observed and linked with the development and progression of several pathologies, including cardiovascular diseases, the leading cause of death in the developed world. In this review, we aim to provide a broad understanding of the different molecular factors that govern autophagy regulation and how these mechanisms are involved in the development of specific cardiovascular pathologies, including ischemic and reperfusion injury, myocardial infarction, cardiac hypertrophy, cardiac remodelling, and heart failure.

Impact of Autophagy on Prognosis of Patients With Dilated Cardiomyopathy

BACKGROUND

Autophagy is a cellular process that degrades a cell's own cytoplasmic components for energy provision and to maintain a proper intracellular environment. Left ventricular reverse remodeling (LVRR) promises a better prognosis for patients with dilated cardiomyopathy (DCM).

OBJECTIVES

The authors tested the hypothesis that autophagy is involved in LVRR and has prognostic value in the human failing heart.

METHODS

Using left ventricular endomyocardial biopsy specimens from 42 patients with DCM (21 LVRR-positive and 21 LVRR-negative) and 7 patients with normal cardiac function (control), the authors performed immunohistochemistry and immunofluorescent labeling of LC3 and cathepsin D and electron microscopic observation in addition to general morphometry under light microscopy.

RESULTS

The clinical characteristics of LVRR-positive patients were similar to those of the LVRR-negative patients, except for pulmonary artery pressure and left atrial dimension. Morphometry under light microscopy did not differ among specimens from DCM patients, regardless of their LVRR status. Electron microscopy revealed that autophagic vacuoles (autophagosomes and autolysosomes) and lysosomes were abundant within cardiomyocytes from DCM patients. Moreover, cardiomyocytes from LVRR-positive patients contained significantly more autophagic vacuoles with higher autolysosome ratios and cathepsin D expression levels than cardiomyocytes from LVRR-negative patients. Logistic regression analysis adjusted for age showed that increases in autophagic vacuole number and cathepsin D expression were predictive of LVRR. DCM patients who achieved LVRR experienced fewer cardiovascular events during the follow-up period.

CONCLUSIONS

The authors show that autophagy is a useful marker predictive of LVRR in DCM patients. This provides novel pathologic insight into a strategy for treating the failing DCM heart.

Accelerated Growth, Differentiation, and Ploidy with Reduced Proliferation of Right Ventricular Cardiomyocytes in Children with Congenital Heart Defect Tetralogy of Fallot

The myocardium of children with tetralogy of Fallot (TF) undergoes hemodynamic overload and hypoxemia immediately after birth. Comparative analysis of changes in the ploidy and morphology of the right ventricular cardiomyocytes in children with TF in the first years of life demonstrated their significant increase compared with the control group. In children with TF, there was a predominantly diffuse distribution of Connexin43-containing gap junctions over the cardiomyocytes sarcolemma, which redistributed into the intercalated discs as cardiomyocytes differentiation increased. The number of Ki67-positive cardiomyocytes varied greatly and amounted to 7.0–1025.5/10⁶ cardiomyocytes and also were decreased with increased myocytes differentiation. Ultrastructural signs of immaturity and proliferative activity of cardiomyocytes in children with TF were demonstrated. The proportion of interstitial tissue did not differ significantly from the control group. The myocardium of children with TF under six months of age was most sensitive to hypoxemia, it was manifested by a delay in the intercalated discs and myofibril assembly and the appearance of ultrastructural signs of dystrophic changes in the cardiomyocytes. Thus, the acceleration of ontogenetic growth and differentiation of the cardiomyocytes, but not the reactivation of their proliferation, was an adaptation of the immature myocardium of children with TF to hemodynamic overload and hypoxemia.

Oxidative distress in aging and age-related diseases: Spatiotemporal dysregulation of protein oxidation and degradation

The concept of oxidative distress had arisen from the assessment of cellular response to high concentrations of reactive species that result from an imbalance between oxidants and antioxidants and cause biomolecular damage. The intracellular distribution and flux of reactive species dramatically change in time and space contributing to the remodeling of the redox landscape and sensitivity of protein residues to oxidants. Here, we hypothesize that compromised spatiotemporal control of generation, conversions, and removal of reactive species underlies protein damage and dysfunction of protein degradation machineries. This leads to the accumulation of oxidatively damaged proteins resulted in an age-dependent decline in the organismal adaptability to oxidative stress. We highlight recent data obtained with the use of various cell cultures, animal models, and patients on irreversible and non-repairable oxidation of key redox-sensitive residues. Multiple reaction products include peptidyl hydroperoxides, alcohols, carbonyls, and carbamoyl moieties as well as Tyr-Tyr, Trp-Tyr, Trp-Trp, Tyr-Cys, His-Lys, His-Arg, and Tyr-Lys cross-links. These lead to protein fragmentation, misfolding, covalent cross-linking, oligomerization, aggregation, and ultimately, causing impaired protein function and turnover. 20S proteasome and autophagy-lysosome pathways are two major types of machinery for the degradation and elimination of oxidatively damaged proteins. Spatiotemporal dysregulation of these pathways under oxidative distress conditions is implicated in aging and age-related disorders such as neurodegenerative and cardiovascular diseases and diabetes. Future investigations in this field allow the discovery of new drugs to target components of dysregulated cell signaling and protein degradation machinery to combat aging and age-related chronic diseases.

Sphingosine-1-phosphate induces myocyte autophagy after myocardial infarction through mTOR inhibition

Sphingosine-1-phosphate (S1P)/S1P receptor 1 signaling exerts cardioprotective effects including inhibition of myocyte apoptosis. However, little is known about the effect of S1P treatment on myocyte autophagy after myocardial infarction (MI). In the present study, we tested the hypothesis that S1P induces myocyte autophagy through inhibition of the mammalian target of rapamycin (mTOR), leading to improvement of left ventricular (LV) function after MI. Sprague-Dawley rats underwent MI or sham operation. The animals were randomized to receive S1P (50 μg/kg/day, i.p.) or placebo for one week. H9C2 cardiomyocytes cultured in serum- and glucose-deficient medium were treated with or without S1P for 3 h. MI rats exhibited an increase in LV end-diastolic dimension (EDD) and decreases in LV fractional shortening (FS) and the maximal rate of LV pressure rise (+dP/dt). S1P treatment attenuated the increase in LV EDD and decreases in LV FS and +dP/dt. In the MI placebo group, the LC3 II/I ratio, a marker of autophagy, was increased, and increased further by S1P treatment. S1P also enhanced the autophagy-related proteins Atg4b and Atg5 after MI. Similarly, in cultured cardiomyocytes, autophagy was increased under glucose and serum deprivation, and increased further by S1P treatment. The effect of S1P on myocyte autophagy was associated with mTOR inhibition after MI or in cultured cardiomyocytes under glucose and serum deprivation. S1P treatment prevents LV remodeling, enhances myocyte autophagy and inhibits mTOR activity after MI. These findings suggest that S1P treatment induces myocyte autophagy through mTOR inhibition, leading to the attenuation of LV dysfunction after MI.

Enhanced oxidative stress mediates pathological autophagy and necroptosis in cardiac myocytes in pressure overload induced heart failure in rats

In cardiac myocytes in vitro, hydrogen peroxide induces autophagic cell death and necroptosis. Oxidative stress, myocyte autophagy and necroptosis coexist in heart failure (HF). In this study, we tested the hypothesis that excessive oxidative stress mediates pathological autophagy and necroptosis in myocytes in pressure overload-induced HF. HF was produced by chronic pressure overload induced by abdominal aortic constriction (AAC) in rats. Rats with AAC or sham operation were randomised to orally receive an antioxidant N-acetylcysteine (NAC) or placebo for 4 weeks. Echocardiography was performed for the assessments of left ventricular (LV) structure and function. AAC rats exhibited decreased LV fractional shortening (FS) at 4 weeks after surgery. NAC treatment attenuated decreased LV FS in AAC rats. In AAC rats, myocardial level of 8-hydroxydeoxyguanosine assessed by immunohistochemical staining, indicative of oxidative stress, was increased, LC3 II protein, a marker of autophagy, Beclin1 protein and Atg4b, Atg5, Atg7 and Atg12 mRNA expression were markedly increased, RIP1, RIP3 and MLKL expression, indicative of necroptosis, was increased, and all of the alterations in AAC rats were prevented by the NAC treatment. NAC treatment also attenuated myocyte cross-sectional area and myocardial fibrosis in AAC rats. In conclusion, NAC treatment prevented the increases in oxidative stress, myocyte autophagy and necroptosis and the decrease in LV systolic function in pressure overload-induced HF. These findings suggest that enhanced oxidative stress mediates pathological autophagy and necroptosis in myocytes, leading to LV systolic dysfunction, and antioxidants may be of value to prevent HF through the inhibition of excessive autophagy and necroptosis.

Dual Role of Mitophagy in Cardiovascular Diseases

ABSTRACT

Mitophagy is involved in the development of various cardiovascular diseases, such as atherosclerosis, heart failure, myocardial ischemia/reperfusion injury, and hypertension. Mitophagy is essential for maintaining intracellular homeostasis and physiological function in most cardiovascular origin cells, such as cardiomyocytes, endothelial cells, and vascular smooth muscle cells. Mitophagy is crucial to ensuring energy supply by selectively removing dysfunctional mitochondria, maintaining a balance in the number of mitochondria in cells, ensuring the integrity of mitochondrial structure and function, maintaining homeostasis, and promoting cell survival. Substantial research has indicated a "dual" effect of mitophagy on cardiac function, with inadequate and increased mitochondrial degradation both likely to influence the progression of cardiovascular disease. This review summarizes the main regulatory pathways of mitophagy and emphasizes that an appropriate amount of mitophagy can prevent endothelial cell injury, vascular smooth muscle cell proliferation, macrophage polarization, and cardiomyocyte apoptosis, avoiding further progression of cardiovascular diseases.

Beclin-1-Dependent Autophagy of Left Ventricular Cardiomyocytes in SHR and Wistar-Kyoto Rats with Type 1 Diabetes Mellitus

Autophagy is considered as a mechanism of progression of heart failure, but under certain conditions, it can also act as an adaptation mechanism. Beclin-1 plays the key role in autophagy. We studied the features of Beclin-1 expression in cardiomyocytes of the left ventricle in arterial hypertension, type 1 diabetes mellitus, and their combination. The experiment was performed on male 38-week-old Wistar Kyoto rats and SHR rats aged 38 and 57 weeks. Type 1 diabetes mellitus was modeled by a single parenteral administration of streptozotocin. Expression of Beclin-1 in cardiomyocytes of the left ventricle was evaluated by immunohistochemical analysis. In arterial hypertension, a decrease in the intensity of Beclin-1-dependent autophagy of cardiomyocytes was seen, while in combined pathology, we observed an opposite effect manifested as a significant increase in the expression of protein Beclin-1.

Reverse Remodeling With Left Ventricular Assist Devices

This review provides a comprehensive overview of the past 25+ years of research into the development of left ventricular assist device (LVAD) to improve clinical outcomes in patients with severe end-stage heart failure and basic insights gained into the biology of heart failure gleaned from studies of hearts and myocardium of patients undergoing LVAD support. Clinical aspects of contemporary LVAD therapy, including evolving device technology, overall mortality, and complications, are reviewed. We explain the hemodynamic effects of LVAD support and how these lead to ventricular unloading. This includes a detailed review of the structural, cellular, and molecular aspects of LVAD-associated reverse remodeling. Synergisms between LVAD support and medical therapies for heart failure related to reverse remodeling, remission, and recovery are discussed within the context of both clinical outcomes and fundamental effects on myocardial biology. The incidence, clinical implications and factors most likely to be associated with improved ventricular function and remission of the heart failure are reviewed. Finally, we discuss recognized impediments to achieving myocardial recovery in the vast majority of LVAD-supported hearts and their implications for future research aimed at improving the overall rates of recovery.

Role of Mitophagy in Cardiovascular Disease

Cardiovascular disease is the leading cause of mortality worldwide, and mitochondrial dysfunction is the primary contributor to these disorders. Recent studies have elaborated on selective autophagy-mitophagy, which eliminates damaged and dysfunctional mitochondria, stabilizes mitochondrial structure and function, and maintains cell survival and growth. Numerous recent studies have reported that mitophagy plays an important role in the pathogenesis of various cardiovascular diseases. This review summarizes the mechanisms underlying mitophagy and advancements in studies on the role of mitophagy in cardiovascular disease.

Contribution of Increased Expression of Yin Yang 2 to Development of Cardiomyopathy

Yin Yang 2 (YY2) is a member of the Yin Yang family of transcription factors. Although the bioactivity of YY2 has been previously studied, its role in cardiovascular diseases is not known. We observed the increased expression of YY2 in failing human hearts compared with control hearts, raising the question of whether YY2 is involved in the pathogenesis of cardiomyopathy. To investigate the potential contribution of YY2 to the development of cardiomyopathy, we crossed two independent transgenic (Tg) mouse lines, pCAG-YY2-Tg+and alpha-myosin heavy chain-cre (α-MHC-Cre), to generate two independent double transgenic (dTg) mouse lines in which the conditional cardiomyocyte-specific expression of YY2 driven by the α-MHC promoter was mediated by Cre recombinase, starting at embryonic day 9.0. In dTg mice, we observed partial embryonic lethality and hearts with defective cardiomyocyte proliferation. Surviving dTg mice from both lines developed cardiomyopathy and heart failure that occurred with aging, showing different degrees of severity that were associated with the level of transgene expression. The development of cardiomyopathy was accompanied by increased levels of cardiac disease markers, apoptosis, and cardiac fibrosis. Our studies further revealed that the Cre-mediated cardiomyocyte-specific increase in YY2 expression led to increased levels of Beclin 1 and LC3II, indicating that YY2 is involved in mediating autophagic activity in mouse hearts in vivo. Also, compared with control hearts, dTg mouse hearts showed increased JNK activity. Because autophagy and JNK activity are important for maintaining cardiac homeostasis, the dysregulation of these signaling pathways may contribute to YY2-induced cardiomyopathy and heart failure in vivo.

Autophagy during left ventricular redilation after ventriculoplasty: Insights from a rat model of ischemic cardiomyopathy

OBJECTIVES

Myocardial autophagy has been recognized as an important factor in heart failure. It is not known whether changes in ventricular geometry by left ventriculoplasty influence autophagy in ischemic cardiomyopathy. We hypothesized that myocardial autophagy plays an important role in left ventricular (LV) redilation after ventriculoplasty.

METHODS

Four weeks after ligation of the left anterior descending artery, ventriculoplasty or sham operation was performed. The animals were euthanized at 2 days (early) or 28 days (late) after the second operation. Ventricular autophagy was evaluated by protein expression of microtubule-associated protein light chain 3 II, an autophagosome marker. Cardiomyocyte area was assessed by histologic examination. LV function was evaluated by echocardiography. To examine the implications of autophagy, an autophagy inhibitor (3-methyladenine) was injected intraperitoneally for 3 weeks before sacrifice.

RESULTS

The LV was reduced in size early and redilated late after ventriculoplasty. LV systolic function was improved early and later worsened after ventriculoplasty. Light chain 3 II expression decreased early after ventriculoplasty and increased in the late period. Myocyte area increased from the early to late stage after ventriculoplasty. Autophagic inhibition exaggerated the increased myocyte hypertrophy and LV redilation.

CONCLUSIONS

In a rat model of myocardial infarction, autophagy decreased early after ventriculoplasty and increased again during LV redilation. These results provide new insights into the mechanism underlying the late failure of ventriculoplasty.

[Hypertrophic cardiomyopathy. Cardiomyocyte ultrastructure, the specific or stereotypic signs]

Hypertrophic cardiomyopathy (HCM) is a congenital disease caused by mutations in a number of sarcomere proteins. According to the type of mutation, clinical observations record similar clinical manifestations, myocardial pathological changes, and the timing of manifestation of the disease in HCM patients.

OBJECTIVE

To study cardiomyocyte (CMC) ultrastructural changes in the interventricular septum (IVS) of patients with HCM and evaluate their specificity for this pathology.

MATERIAL AND METHODS

IVS myocardial samples taken from 44 HCM patients aged 18-59 years at IVS myoectomy underwent an electron microscopic study. The diameter of CMCs and their nuclei was measured in semithin sections.

RESULTS

A morphometric examination of the IVS myocardium in HCM patients revealed moderate hypertrophy of CMCs and their nuclei, the diameters of which averaged 23.7±4.4 and 5.2±0.9 μm, respectively. The IVS CMCs were characterized by the ultrastructural signs of hypertrophy: the larger size and number of structures ensuring contractile and synthetic functions; the myocytes contained higher amounts of myofibrils, intermyofibrillar mitochondria, granular endoplasmic reticulum cisterns, and free ribosomes. On the contrary, some CMCs had fewer myofibrils in the perinuclear region, which is an adaptive change under hemodynamic overload conditions. In addition, a number of myocytes displayed signs of dystrophic changes: the appearance of lipofuscin granules, myelin figures, phagosomes, lipid droplets, and vacuoles, which can fill all free sarcoplasmic zones.

CONCLUSION

Ultrastructural changes characteristic of hypertrophy were found in IVS CMCs in HCM patients. In addition, there was partial myofibrillar loss and dystrophic changes in a number of myocytes, which are stereotypic compensatory-adaptive changes under hemodynamic overload conditions. All the above-mentioned changes in the CMC ultrastructure are characteristic of myocardial hypertrophy, but not specific for hypertrophic cardiomyopathy.

The immunoproteasome catalytic β5i subunit regulates cardiac hypertrophy by targeting the autophagy protein ATG5 for degradation

Pathological cardiac hypertrophy eventually leads to heart failure without adequate treatment. The immunoproteasome is an inducible form of the proteasome that is intimately involved in inflammatory diseases. Here, we found that the expression and activity of immunoproteasome catalytic subunit β5i were significantly up-regulated in angiotensin II (Ang II)-treated cardiomyocytes and in the hypertrophic hearts. Knockout of β5i in cardiomyocytes and mice markedly attenuated the hypertrophic response, and this effect was aggravated by β5i overexpression in cardiomyocytes and transgenic mice. Mechanistically, β5i interacted with and promoted ATG5 degradation thereby leading to inhibition of autophagy and cardiac hypertrophy. Further, knockdown of ATG5 or inhibition of autophagy reversed the β5i knockout-mediated reduction of cardiomyocyte hypertrophy induced by Ang II or pressure overload. Together, this study identifies a novel role for β5i in the regulation of cardiac hypertrophy. The inhibition of β5i activity may provide a new therapeutic approach for hypertrophic diseases.

Recovery of failing hearts by mechanical unloading: Pathophysiologic insights and clinical relevance

By reduction of ventricular wall-tension and improving the blood supply to vital organs, ventricular assist devices (VADs) can eliminate the major pathophysiological stimuli for cardiac remodeling and even induce reverse remodeling occasionally accompanied by clinically relevant reversal of cardiac structural and functional alterations allowing VAD explantation, even if the underlying cause for the heart failure (HF) was dilated cardiomyopathy. Accordingly, a tempting potential indication for VADs in the future might be their elective implantation as a therapeutic strategy to promote cardiac recovery in earlier stages of HF, when the reversibility of morphological and functional alterations is higher. However, the low probability of clinically relevant cardiac improvement after VAD implantation and the lack of criteria which can predict recovery already before VAD implantation do not allow so far VAD implantations primarily designed as a bridge to cardiac recovery. The few investigations regarding myocardial reverse remodeling at cellular and sub-cellular level in recovered patients who underwent VAD explantation, the differences in HF etiology and pre-implant duration of HF in recovered patients and also the differences in medical therapy used by different institutions during VAD support make it currently impossible to understand sufficiently all the biological processes and mechanisms involved in cardiac improvement which allows even VAD explantation in some patients. This article aims to provide an overview of the existing knowledge about VAD-promoted cardiac improvement focusing on the importance of bench-to-bedside research which is mandatory for attaining the future goal to use long-term VADs also as therapy-devices for reversal of chronic HF.

Molecular mechanisms of autophagy in cardiac ischemia/reperfusion injury (Review)

Autophagy is a maintenance process for recycling long-lived proteins and cytoplasmic organelles. The level of this process is enhanced during ischemia/reperfusion (I/R) injury. Autophagy can trigger survival signaling in myocardial ischemia, whereas defective autophagy during reperfusion is detrimental. Autophagy can be regulated through multiple signaling pathways in I/R, including Beclin‑1/class III phosphatidylinositol‑3 kinase (PI‑3K), adenosine monophosphate activated protein kinase/mammalian target of rapamycin (mTOR), and PI‑3K/protein kinase B/mTOR pathways, which consequently lead to different functions. Thus, autophagy has both protective and detrimental functions, which are determined by different signaling pathways and conditions. Targeting the activation of autophagy can be a promising new therapeutic strategy for treating cardiovascular disease.

Cardiac unloading by LVAD support differentially influences components of the cGMP-PKG signaling pathway in ischemic and dilated cardiomyopathy

Implantation of left ventricular assist devices (LVADs) as bridge to transplant in end-stage heart failure allows for analyzing reverse remodeling processes of the supported heart. Whether this therapy influences the cGMP-PKG signaling pathway, which is currently under thorough investigation for developing new heart failure therapeutics, is unknown. In fourteen end-stage heart failure patients (8 with dilated cardiomyopathy, DCM; 6 with ischemic cardiomyopathy, ICM) tissue specimens of left ventricles were collected at LVAD implantation and afterwards at receiver heart explantation, respectively. Then the expressions of key components of the cGMP-PKG signaling pathway were determined by polymerase chain reaction (ANP; BNP; natriuretic peptide receptor A, NPR-A; natriuretic peptide receptor C, NPR-C; neprilysin; NOS3; soluble guanylyl cyclase, sGC; PDE5; cGMP-dependent protein kinase G, PKG) and enzyme-linked immunosorbent assay (cGMP), respectively. Patients were predominantly male, 52 ± 10 years old, were receiving recommended heart failure therapy, and had their donor organ implanted after 351 ± 317 days of LVAD support. Except for more DCM patients with ICD therapy, no significant differences were detected between ICM and DCM, which also applies to the expression of cGMP-PKG pathway components at baseline. After LVAD support, ANP, NPR-C, and cGMP were significantly down-regulated and neprilysin, PDE5, and PKG I expressions were reduced with borderline significance in DCM, but not in ICM patients. Multiple significant correlations were found for expression differences (i.e., expression at LVAD implantation minus expression at heart transplantation) both in DCM and ICM, even though there was a closer connection between the NO and NP side of the cGMP-PKG pathway in DCM patients. Furthermore, duration of LVAD support negatively correlated with expression differences of PKG I, PDE5, and sGC in ICM, but not in DCM. Originating from the same activation level at LVAD implantation, cardiac unloading significantly alters key components of the cGMP-PKG pathway in DCM, but not in ICM patients. This etiology-specific regulation should be considered when analyzing therapeutic interventions with effects on this signaling pathway.

The spectrum of myocardial homeostasis mechanisms in the settings of cardiac surgery procedures (Review)

Classic cardiac surgery, determined through the function of cardiopulmonary bypass machine and myocardial cardioplegic arrest, represents the most controlled scenario for cardiomyocyte homeostatic disturbances due to systemic inflammatory response and myocardial reperfusion injury. An increasing number of studies have demonstrated that myocardial cell homeostasis in cardiac surgery procedures is a sequence of molecularly interrelated and overlapping mechanisms in the form of apoptosis, autophagy and necrosis, which are activated by a plethora of induced inflammatory mediators and gene-related signaling pathways. In this study, we outline the molecular mechanisms of the cardiomyocyte adaptive homeostatic process and the associated clinical implications, in the settings of classic cardiac surgery procedures.

TLR3 contributes to persistent autophagy and heart failure in mice after myocardial infarction

Toll-like receptors (TLRs) are essential immunoreceptors involved in host defence against invading microbes. Recent studies indicate that certain TLRs activate immunological autophagy to eliminate microbes. It remains unknown whether TLRs regulate autophagy to play a role in the heart. This study examined this question. The activation of TLR3 in cultured cardiomyocytes was observed to increase protein levels of autophagic components, including LC3-II, a specific marker for autophagy induction, and p62/SQSTM1, an autophagy receptor normally degraded in the final step of autophagy. The results of transfection with a tandem mRFP-GFP-LC3 adenovirus and use of an autophagic flux inhibitor chloroquine both suggested that TLR3 in cardiomyocytes promotes autophagy induction without affecting autophagic flux. Gene-knockdown experiments showed that the TRIF-dependent pathway mediated the autophagic effect of TLR3. In the mouse model of chronic myocardial infarction, persistent autophagy was observed, concomitant with up-regulated TLR3 expression and increased TLR3-Trif signalling. Germline knockout (KO) of TLR3 inhibited autophagy, reduced infarct size, attenuated heart failure and improved survival. These protective effects were abolished by in vivo administration of an autophagy inducer rapamycin. Similar to the results obtained in cultured cardiomyocytes, TLR3-KO did not prevent autophagic flux in mouse heart. Additionally, this study failed to detect the involvement of inflammation in TLR3-KO-derived protection, as wild-type and TLR3-KO hearts were comparable in inflammatory activity. It is concluded that up-regulated TLR3 expression and signalling contributes to persistent autophagy following MI, which promotes heart failure and lethality.

Inhibition of Mutant αB Crystallin-Induced Protein Aggregation by a Molecular Tweezer

Background

Compromised protein quality control causes the accumulation of misfolded proteins and intracellular aggregates, contributing to cardiac disease and heart failure. The development of therapeutics directed at proteotoxicity‐based pathology in heart disease is just beginning. The molecular tweezer CLR01 is a broad‐spectrum inhibitor of abnormal self‐assembly of amyloidogenic proteins, including amyloid β‐protein, tau, and α‐synuclein. This small molecule interferes with aggregation by binding selectively to lysine side chains, changing the charge distribution of aggregation‐prone proteins and thereby disrupting aggregate formation. However, the effects of CLR01 in cardiomyocytes undergoing proteotoxic stress have not been explored. Here we assess whether CLR01 can decrease cardiac protein aggregation catalyzed by cardiomyocyte‐specific expression of mutated αB‐crystallin (CryAB^R120G).

Methods and Results

A proteotoxic model of desmin‐related cardiomyopathy caused by cardiomyocyte‐specific expression of CryAB^R120G was used to test the efficacy of CLR01 therapy in the heart. Neonatal rat cardiomyocytes were infected with adenovirus expressing either wild‐type CryAB or CryAB^R120G. Subsequently, the cells were treated with different doses of CLR01 or a closely related but inactive derivative, CLR03. CLR01 decreased aggregate accumulation and attenuated cytotoxicity caused by CryAB^R120G expression in a dose‐dependent manner, whereas CLR03 had no effect. Ubiquitin‐proteasome system function was analyzed using a ubiquitin‐proteasome system reporter protein consisting of a short degron, CL1, fused to the COOH‐terminus of green fluorescent protein. CLR01 improved proteasomal function in CryAB^R120G cardiomyocytes but did not alter autophagic flux. In vivo, CLR01 administration also resulted in reduced protein aggregates in CryAB^R120G transgenic mice.

Conclusions

CLR01 can inhibit CryAB^R120G aggregate formation and decrease cytotoxicity in cardiomyocytes undergoing proteotoxic stress, presumably through clearance of the misfolded protein via increased proteasomal function. CLR01 or related compounds may be therapeutically useful in treating the pathogenic sequelae resulting from proteotoxic heart disease.

Perpetual change: autophagy, the endothelium, and response to vascular injury

Current studies of vascular health, aging, and autophagy emphasize how the endothelium adapts to stress and contributes to disease. The endothelium is far from an inert barrier to blood-borne cells, pathogens, and chemical signals; rather, it actively translates circulating mediators into tissue responses, changing rapidly in response to physiologic stressors. Macroautophagy-the cellular ingestion of effete organelles and protein aggregates to provide anabolic substrates to fuel bioenergetics in times of stress-plays an important role in endothelial cell homeostasis, vascular remodeling, and disease. These roles include regulating vascular tone, sustaining or limiting cell survival, and contributing to the development of atherosclerosis secondary to infection, inflammation, and angiogenesis. Autophagy modulates these critical functions of the endothelium in a dynamic and perpetual response to tissue and intravascular cues.

Proteostasis in cardiac health and disease

The incidence and prevalence of cardiac diseases, which are the main cause of death worldwide, are likely to increase because of population ageing. Prevailing theories about the mechanisms of ageing feature the gradual derailment of cellular protein homeostasis (proteostasis) and loss of protein quality control as central factors. In the heart, loss of protein patency, owing to flaws in genetically-determined design or because of environmentally-induced 'wear and tear', can overwhelm protein quality control, thereby triggering derailment of proteostasis and contributing to cardiac ageing. Failure of protein quality control involves impairment of chaperones, ubiquitin-proteosomal systems, autophagy, and loss of sarcomeric and cytoskeletal proteins, all of which relate to induction of cardiomyocyte senescence. Targeting protein quality control to maintain cardiac proteostasis offers a novel therapeutic strategy to promote cardiac health and combat cardiac disease. Currently marketed drugs are available to explore this concept in the clinical setting.

Metabolic Origins of Heart Failure

For more than half a century, metabolic perturbations have been explored in the failing myocardium, highlighting a reversion to a more fetal-like metabolic profile (characterized by depressed fatty acid oxidation and concomitant increased reliance on use of glucose). More recently, alterations in ketone body and amino acid/protein metabolism have been described during heart failure, as well as mitochondrial dysfunction and perturbed metabolic signaling (e.g., acetylation, O-GlcNAcylation). Although numerous mechanisms are likely involved, the current review provides recent advances regarding the metabolic origins of heart failure, and their potential contribution toward contractile dysfunction of the heart.

Sterile Inflammation and Degradation Systems in Heart Failure

In most patients with chronic heart failure (HF), levels of circulating cytokines are elevated and the elevated cytokine levels correlate with the severity of HF and prognosis. Various stresses induce subcellular component abnormalities, such as mitochondrial damage. Damaged mitochondria induce accumulation of reactive oxygen species and apoptogenic proteins, and subcellular inflammation. The vicious cycle of subcellular component abnormalities, inflammatory cell infiltration and neurohumoral activation induces cardiomyocyte injury and death, and cardiac fibrosis, resulting in cardiac dysfunction and HF. Quality control mechanisms at both the protein and organelle levels, such as elimination of apoptogenic proteins and damaged mitochondria, maintain cellular homeostasis. An imbalance between protein synthesis and degradation is likely to result in cellular dysfunction and disease. Three major protein degradation systems have been identified, namely the cysteine protease system, autophagy, and the ubiquitin proteasome system. Autophagy was initially believed to be a non-selective process. However, recent studies have described the process of selective mitochondrial autophagy, known as mitophagy. Elimination of damaged mitochondria by autophagy is important for maintenance of cellular homeostasis. DNA and RNA degradation systems also play a critical role in regulating inflammation and maintaining cellular homeostasis mediated by damaged DNA clearance and post-transcriptional regulation, respectively. This review discusses some recent advances in understanding the role of sterile inflammation and degradation systems in HF.

Regulation of autophagy by some natural products as a potential therapeutic strategy for cardiovascular disorders

Autophagy is a lysosomal degradation process through which long-lived and misfolded proteins and organelles are sequestered, degraded by lysosomes, and recycled. Autophagy is an essential part of cardiomyocyte homeostasis and increases the survival of cells following cellular stress and starvation. Recent studies made clear that dysregulation of autophagy in the cardiovascular system leads to heart hypertrophy and failure. In this manner, autophagy seems to be an attractive target in the new treatment of cardiovascular diseases. Although limited activation of autophagy is generally considered to be cardioprotective, excessive autophagy leads to cell death and cardiac atrophy. Natural products such as resveratrol, berberine, and curcumin that are present in our diet, can trigger autophagy via canonical (Beclin-1-dependent) and non-canonical (Beclin-1-independent) pathways. The autophagy-modifying capacity of these compounds should be taken into consideration for designing novel therapeutic agents. This review focuses on the role of autophagy in the cardioprotective effects of these compounds.

Autophagic vacuoles in cardiomyocytes of dilated cardiomyopathy with initially decompensated heart failure predict improved prognosis

Autophagy is a process of bulk protein degradation and organelle turnover, and is a current therapeutic target in several diseases. The present study aimed to clarify the significance of myocardial autophagy of patients with dilated cardiomyopathy (DCM). Left ventricular endomyocardial biopsy was performed in 250 consecutive patients with DCM (54.9±13.9 years; male, 79%), initially presenting with decompensated heart failure (HF). The association of these findings with HF mortality or recurrence was examined. Myofilament changes, which are apparent in the degenerated cardiomyocytes of DCM, were recognized in 164 patients (66%), and autophagic vacuoles in cardiomyocytes were identified in or near the area of myofilament changes in 86 patients (34%). Morphometrically, fibrosis (odds ratio [OR], 0.96; 95% confidence interval [CI], 0.93 to 0.99) and mitochondrial abnormality (OR, 2.24; 95% CI, 1.23 to 4.08) were independently related with autophagic vacuoles. During the follow-up period of 4.9±3.9 y, 24 patients (10%) died, including 10 (4%) who died of HF, and 67 (27%) were readmitted for HF recurrence. Multivariate analysis identified a family history of DCM (hazard ratio [HR], 2.117; 95% CI, 1.199 to 3.738), hemoglobin level (HR, 0.845; 95% CI, 0.749 to 0.953), myofilament changes (HR, 13.525; 95% CI, 5.340 to 34.255), and autophagic vacuoles (HR, 0.214; 95% CI, 0.114 to 0.400) as independent predictors of death or readmission due to HF recurrence. In conclusion, autophagic vacuoles in cardiomyocytes are associated with a better HF prognosis in patients with DCM, suggesting autophagy may play a role in the prevention of myocardial degeneration.

Autophagy-from molecular mechanisms to clinical relevance

Autophagy is a lysosomal degradation pathway of eukaryotic cells that is highly conserved from yeast to mammals. During this process, cooperating protein complexes are recruited in a hierarchic order to the phagophore assembly site (PAS) to mediate the elongation and closure of double-membrane vesicles called autophagosomes, which sequester cytosolic components and deliver their content to the endolysosomal system for degradation. As a major cytoprotective mechanism, autophagy plays a key role in the stress response against nutrient starvation, hypoxia, and infections. Although numerous studies reported that impaired function of core autophagy proteins also contributes to the development and progression of various human diseases such as neurodegenerative disorders, cardiovascular and muscle diseases, infections, and different types of cancer, the function of this process in human diseases remains unclear. Evidence often suggests a controversial role for autophagy in the pathomechanisms of these severe disorders. Here, we provide an overview of the molecular mechanisms of autophagy and summarize the recent advances on its function in human health and disease.

Rat Heterotopic Heart Transplantation Model to Investigate Unloading-Induced Myocardial Remodeling

Unloading of the failing left ventricle in order to achieve myocardial reverse remodeling and improvement of contractile function has been developed as a strategy with the increasing frequency of implantation of left ventricular assist devices in clinical practice. But, reverse remodeling remains an elusive target, with high variability and exact mechanisms still largely unclear. The small animal model of heterotopic heart transplantation (hHTX) in rodents has been widely implemented to study the effects of complete and partial unloading on cardiac failing and non-failing tissue to better understand the structural and molecular changes that underlie myocardial recovery. We herein review the current knowledge on the effects of volume unloading the left ventricle via different methods of hHTX in rats, differentiating between changes that contribute to functional recovery and adverse effects observed in unloaded myocardium. We focus on methodological aspects of heterotopic transplantation, which increase the correlation between the animal model and the setting of the failing unloaded human heart. Last, but not least, we describe the late use of sophisticated techniques to acquire data, such as small animal MRI and catheterization, as well as ways to assess unloaded hearts under "reloaded" conditions. While giving regard to certain limitations, heterotopic rat heart transplantation certainly represents the crucial model to mimic unloading-induced changes in the heart and as such the intricacies and challenges deserve highest consideration. Careful translational research will further improve our knowledge of the reverse remodeling process and how to potentiate its effect in order to achieve recovery of contractile function in more patients.

Salvianolic acid B induced upregulation of miR-30a protects cardiac myocytes from ischemia/reperfusion injury

BACKGROUND

MicroRNAs (miRNAs) are a novel class of powerful, endogenous regulators of gene expression. This study was designed to ascertain if miR-30a is involved in the cardioprotective actions of salvianolic acid B (Sal B) against myocardial ischemia-reperfusion (I-R) injury through suppression of autophagy.

METHODS

Murine myocardial cells that had undergone primary culture were induced by I-R and incubated with Sal B (25, 50, 100 μM) in the presence of a miR-30a mimic or miR-30a inhibitor. Expression of miR-30a, beclin-1, LC3-II and p-Akt protein, cell viability, and lactic acid dehydrogenase (LDH) release were assessed.

RESULTS

miR-30a expression was down-regulated remarkably in I-R cells, and this suppression could be reversed by Sal B in a dose-dependent manner. Sal B repressed autophagy in I-R myocardial cells. Sal B improved cell viability and reduced the rate of LDH leakage, which suggested that autophagy suppression was beneficial for cell survival. Knockdown of miR-30a with a miR-30a inhibitor could reverse the anti-autophagy effect of Sal B against I-R injury. Furthermore, we confirmed that Sal B has a protective role in miR-30a-mediated autophagy through the PI3K/Akt signaling pathway, which was abrogated by the PI3K inhibitor LY294002.

CONCLUSIONS

These data suggest that miR-30a is involved in Sal B-mediated cardioprotection against I-R injury through the PI3K/Akt signaling pathway.

Autophagy transduces physical constraints into biological responses

Autophagy is a fundamental cell biological process that controls the quality and quantity of the eukaryotic cytoplasm. Dysfunctional autophagy, when defective or excessive, has been linked to human pathologies ranging from neurodegenerative and infectious diseases to cancer and inflammatory diseases. Autophagy takes place at basal levels in all eukaryotic cells. The process is stimulated during metabolic, genotoxic, infectious, and hypoxic stress conditions and acts an adaptive mechanism essential for cell survival. Recent data demonstrate that changes in the mechanical cellular environment influence cell fate through the modulation of the autophagic pathway. Mechanical stimuli, such as applied forces, combine with biochemical signals to control development and physiological functions of different organs and can also contribute to the progression of various human diseases. Here we review recent findings regarding the regulation of autophagy upon three types of mechanical stress, compression, shear stress, and stretching, and discuss the potential implications of mechanical stress-induced autophagy in physiology and physiopathology.

mTOR-Independent autophagy inducer trehalose rescues against insulin resistance-induced myocardial contractile anomalies: Role of p38 MAPK and Foxo1

Insulin resistance is associated with cardiovascular diseases although the precise mechanisms remain elusive. Akt2, a critical member of the Akt family, plays an essential role in insulin signaling. This study was designed to examine the effect of trehalose, an mTOR-independent autophagy inducer, on myocardial function in an Akt2 knockout-induced insulin resistance model. Adult WT and Akt2 knockout (Akt2(-/-)) mice were administered trehalose (1mg/g/day, i.p.) for two days and were then given 2% trehalose in drinking water for two more months. Echocardiographic and myocardial mechanics, intracellular Ca(2+) properties, glucose tolerance, and autophagy were assessed. Apoptosis and ER stress were evaluated using TUNEL staining, Caspase 3 assay and Western blot. Autophagy and autophagy flux were examined with a focus on p38 mitogen activated protein kinase (MAPK), Forkhead box O (Foxo1) and Akt. Akt2 ablation impaired glucose tolerance, myocardial geometry and function accompanied with pronounced apoptosis, ER stress and dampened autophagy, the effects of which were ameliorated by trehalose treatment. Inhibition of lysosomal activity using bafilomycin A1 negated trehalose-induced induction of autophagy (LC3B-II and p62). Moreover, phosphorylation of p38 MAPK and Foxo1 were upregulated in Akt2(-/-) mice, the effect of which was attenuated by trehalose. Phosphorylation of Akt was suppressed in Akt2(-/-) mice and was unaffected by trehalose. In vitro findings revealed that the p38 MAPK activator anisomycin and the Foxo1 inhibitor (through phosphorylation) AS1842856 effectively masked trehalose-offered beneficial cardiomyocyte contractile response against Akt2 ablation. These data suggest that trehalose may rescue against insulin resistance-induced myocardial contractile defect and apoptosis, via autophagy associated with dephosphorylation of p38 MAPK and Foxo1 without affecting phosphorylation of Akt.

Dysfunction of mitochondria and deformed gap junctions in the heart of IL-18-deficient mice

Interleukin-18 (IL-18) was discovered as an interferon-γ-inducing factor and has been regarded as a proinflammatory cytokine. However, IL-18 is ubiquitously expressed both in immune/inflammatory cells and in nonimmune cells, and its biological roles have not been sufficiently elucidated. Here, we demonstrate that IL-18-deficient [IL-18 knockout (KO)] mice have heart abnormalities that may be related to impaired autophagy. In endurance running tests, IL-18KO mice ran significantly shorter distances compared with wild-type (WT) mice. Echocardiographs indicated disability in the systolic and diastolic functions of the IL-18KO mouse heart. Immunostaining of connexin 43 showed heterogeneous localization of gap junctions in the lateral membranes of the IL-18KO cardiac myocytes. Western blotting analysis revealed decreased phosphorylated connexin 43 in the IL-18KO heart. Electron microscopy revealed unusual localization of intercalated disks, swollen or damaged mitochondria, and broad, indistinct Z-lines in the IL-18KO heart. In accordance with the morphological observation, mitochondrial respiratory function, including that of complexes I and IV, was impaired, and production of reactive oxygen species was augmented in IL-18KO hearts. Notably, levels of LC3-II were markedly lower in the IL-18KO hearts than in WT hearts. In the culture of cardiac myocytes of IL-18KO neonates, exogenous IL-18 upregulated LC3-II and increased the number of intact mitochondria with high mitochondrial membrane potential. These results indicated that IL-18 has roles apart from those as a proinflammatory cytokine in cardiac myocytes and suggested that IL-18 contributes to the homeostatic maintenance of mitochondrial function and gap-junction turnover in cardiac myocytes, possibly by upregulating autophagy.