Mitophagy: At the heart of mitochondrial quality control in cardiac aging and frailty

Research progress of AMP-activated protein kinase and cardiac aging

The process of aging is marked by a gradual deterioration in the physiological functions and functional reserves of various tissues and organs, leading to an increased susceptibility to diseases and even death. Aging manifests in a tissue- and organ-specific manner, and is characterized by varying rates and direct and indirect interactions among different tissues and organs. Cardiovascular disease (CVD) is the leading cause of death globally, with older adults (aged >70 years) accounting for approximately two-thirds of CVD-related deaths. The prevalence of CVD increases exponentially with an individual's age. Aging is a critical independent risk factor for the development of CVD. AMP-activated protein kinase (AMPK) activation exerts cardioprotective effects in the heart and restores cellular metabolic functions by modulating gene expression and regulating protein levels through its interaction with multiple target proteins. Additionally, AMPK enhances mitochondrial function and cellular energy status by facilitating the utilization of energy substrates. This review focuses on the role of AMPK in the process of cardiac aging and maintaining normal metabolic levels and redox homeostasis in the heart, particularly in the presence of oxidative stress and the invasion of inflammatory factors.

Mitochondrial Dysfunction in Cardiac Diseases and Therapeutic Strategies

Mitochondria are the main site of intracellular synthesis of ATP, which provides energy for various physiological activities of the cell. Cardiomyocytes have a high density of mitochondria and mitochondrial damage is present in a variety of cardiovascular diseases. In this paper, we describe mitochondrial damage in mitochondrial cardiomyopathy, congenital heart disease, coronary heart disease, myocardial ischemia-reperfusion injury, heart failure, and drug-induced cardiotoxicity, in the context of the key roles of mitochondria in cardiac development and homeostasis. Finally, we discuss the main current therapeutic strategies aimed at alleviating mitochondrial impairment-related cardiac dysfunction, including pharmacological strategies, gene therapy, mitochondrial replacement therapy, and mitochondrial transplantation. It is hoped that this will provide new ideas for the treatment of cardiovascular diseases.

Mitochondria-derived vesicles and their potential roles in kidney stone disease

Recent evidence has shown significant roles of mitochondria-derived vesicles (MDVs) in mitochondrial quality control (MQC) system. Under mild stress condition, MDVs are formed to carry the malfunctioned mitochondrial components, such as mitochondrial DNA (mtDNA), peptides, proteins and lipids, to be eliminated to restore normal mitochondrial structure and functions. Under severe oxidative stress condition, mitochondrial dynamics (fission/fusion) and mitophagy are predominantly activated to rescue mitochondrial structure and functions. Additionally, MDVs generation can be also triggered as the major MQC machinery to cope with unhealthy mitochondria when mitophagy is unsuccessful for eliminating the damaged mitochondria or mitochondrial fission/fusion fail to recover the mitochondrial structure and functions. This review summarizes the current knowledge on MDVs and discuss their roles in physiologic and pathophysiologic conditions. In addition, the potential clinical relevance of MDVs in therapeutics and diagnostics of kidney stone disease (KSD) are emphasized.

Ginsenoside Rg1 Protects against Cardiac Remodeling in Heart Failure via SIRT1/PINK1/Parkin-Mediated Mitophagy

Adverse cardiac remodeling may lead to the development and progression of heart failure, which is lack of effective clinical treatment. Ginsenoside Rg1 (GRg1), a primary ingredient of Panax ginseng, protects against diverse cardiovascular disease, but its effects on cardiac remodeling remain unclear. Thus, we investigated the protective effect and mechanism of GRg1 on cardiac remodeling after myocardial infarction. GRg1 significantly ameliorated cardiac remodeling in mice with left anterior descending coronary artery ligation, reflected by reduced left ventricular dilation and decreased cardiac fibrosis, accompanied by improved cardiac function. Mechanistically, GRg1 considerably increased mitophagosomes formation, ameliorated cardiac mitochondria damage, and enhanced SIRT1/PINK1/Parkin-mediated mitophagy during cardiac remodeling. Consistently, GRg1 increased cell viability and attenuated apoptosis and fibrotic responses in H₂ O₂ -treated H9c2 cells by promoting the SIRT1/PINK1/Parkin axis. Furthermore, SIRT1-specific inhibitor (EX527) or the use of small interfering RNA against Parkin abolished the protective effect of GRg1 in vitro. These findings reveal a novel mechanism of GRg1 alleviating cardiac remodeling via enhancing SIRT1/PINK1/Parkin-mediated mitophagy.

Ablation of Shank3 alleviates cardiac dysfunction in aging mice by promoting CaMKII activation and Parkin-mediated mitophagy

Compromised mitophagy and mitochondrial homeostasis are major contributors for the etiology of cardiac aging, although the precise underlying mechanisms remains elusive. Shank3, a heart-enriched protein, has recently been reported to regulate aging-related neurodegenerative diseases. This study aimed to examine the role of Shank3 in the pathogenesis of cardiac senescence and the possible mechanisms involved. Cardiac-specific conditional Shank3 knockout (Shank3^CKO) mice were subjected to natural aging. Mitochondrial function and mitophagy activity were determined in vivo, in mouse hearts and in vitro, in cardiomyocytes. Here, we showed that cardiac Shank3 expression exhibited a gradual increase during the natural progression of the aging, accompanied by overtly decreased mitophagy activity and a decline in cardiac function. Ablation of Shank3 promoted mitophagy, reduced mitochondria-derived superoxide (H₂O₂ and O₂•^-) production and apoptosis, and protected against cardiac dysfunction in the aged heart. In an in vitro study, senescent cardiomyocytes treated with D-gal exhibited reduced mitophagy and significantly elevated Shank3 expression. Shank3 knock-down restored mitophagy, leading to increased mitochondrial membrane potential, decreased mitochondrial oxidative stress, and reduced apoptosis in senescent cardiomyocytes, whereas Shank3 overexpression mimicked D-gal-induced mitophagy inhibition and mitochondrial dysfunction in normally cultured cardiomyocytes. Mechanistically, the IP assay revealed that Shank3 directly binds to CaMKII, and this interaction was further increased in the aged heart. Enhanced Shank3/CaMKII binding impedes mitochondrial translocation of CaMKII, resulting in the inhibition of parkin-mediated mitophagy, which ultimately leads to mitochondrial dysfunction and cardiac damage in the aged heart. Our study identified Shank3 as a novel contributor to aging-related cardiac damage. Manipulating Shank3/CaMKII-induced mitophagy inhibition could thus be an optional strategy for therapeutic intervention in clinical aging-related cardiac dysfunctions.

Mitochondrial Quality Control in the Maintenance of Cardiovascular Homeostasis: The Roles and Interregulation of UPS, Mitochondrial Dynamics and Mitophagy

Maintenance of normal function of mitochondria is vital to the fate and health of cardiomyocytes. Mitochondrial quality control (MQC) mechanisms are essential in governing mitochondrial integrity and function. The ubiquitin-proteasome system (UPS), mitochondrial dynamics, and mitophagy are three major components of MQC. With the progress of research, our understanding of MQC mechanisms continues to deepen. Gradually, we realize that the three MQC mechanisms are not independent of each other. To the contrary, there are crosstalk among the mechanisms, which can make them interact with each other and cooperate well, forming a triangle interplay. Briefly, the UPS system can regulate the level of mitochondrial dynamic proteins and mitophagy receptors. In the process of Parkin-dependent mitophagy, the UPS is also widely activated, performing critical roles. Mitochondrial dynamics have a profound influence on mitophagy. In this review, we provide new processes of the three major MQC mechanisms in the background of cardiomyocytes and delve into the relationship between them.