The roles of the inhibitory autophagy regulator Rubicon in the heart: A new therapeutic target to prevent cardiac cell death

Circular RNAs in coronary heart disease: From molecular mechanism to promising clinical application (Review)

Coronary heart disease (CHD) remains a leading cause of morbidity and mortality worldwide, posing a substantial public health burden. Despite advancements in treatment, the complex etiology of CHD necessitates ongoing exploration of novel diagnostic markers and therapeutic targets. Circular RNAs (circRNAs), a distinct class of non‑coding RNAs with a covalently closed loop structure, have emerged as significant regulators in various diseases, including CHD. Their high stability, tissue‑specific expression and evolutionary conservation underscore their potential as biomarkers and therapeutic agents in CHD. This review discusses the current knowledge on circRNAs in the context of CHD and explores the molecular mechanisms by which circRNAs influence the pathophysiology of CHD, including cardiomyocyte death, endothelial injury, vascular dysfunction and inflammation. It also summarizes the emerging evidence highlighting the differential expression of circRNAs in patients with CHD and their potential utilities as non‑invasive diagnostic and prognostic biomarkers and therapeutic targets for this disease.

Autosis: a new form of cell death in myocardial ischemia-reperfusion injury

Cardiomyocytes undergo a variety of cell death events during myocardial ischemia‒reperfusion injury (MIRI). Understanding the causes of cardiomyocyte mortality is critical for the prevention and treatment of MIRI. Among the various types of cell death, autosis is a recently identified type of autophagic cell death with distinct morphological and chemical characteristics. Autosis can be attenuated by autophagy inhibitors but not reversed by apoptosis or necrosis inhibitors. In recent years, it has been shown that during the late phase of reperfusion, autosis is activated, which exacerbates myocardial injury. This article describes the characteristics of autosis, autophagic cell death, and the relationship between autophagic cell death and autosis; reviews the mechanism of autosis in MIRI; and discusses its clinical significance.

Targeting Ubiquitin-Proteasome System (UPS) in Treating Osteoarthritis

Despite osteoarthritis (OA) being recognised for over a century as a debilitating disease that affects millions, there are huge gaps in our understanding of the underlying pathophysiology that drives this disease. Present day studies that focussed on ubiquitination (Ub) and ubiquitylation-like (Ubl) modification related mechanisms have brought light into the possibility of attenuating OA development by targeting these specific proteins in chondrocytes. In the present review, we discuss recent advances in studies involving Ub ligases and deubiquitinating enzymes (DUBs) which are of importance in the development of OA, and may offer potential therapeutic strategies for OA. Such targets may involve attenuating proteases such as MMP1, 8, 13, 4 and several ADAMTS that are well known for their role in cartilage breakdown. Ligases such as E2 and E3 that are involved in extracellular matrix (ECM) degradation in OA and of their pathogenesis would be discussed. In addition to catabolic and degenerative downstream effects of Ub and DUBs in OA, inflammatory mechanisms most notably involving NF-κB signalling pathways regulated through Ub and using various targeting molecules would also be highlighted. Challenges, gaps and insights from clinical trials will provide valuable guidance for future investigations on targeting UPS as a therapeutic option for OA.

WSSV induces Rubicon expression to regulate innate immune response in Penaeus vannamei

Rubicon, the RUN domain Beclin-1-interacting and cysteine-rich domain-containing protein plays an important role in facilitating viral replication. In this study, an involvement of P. vannamei Rubicon or PvRUBCN during white spot syndrome virus (WSSV) infection and its roles in regulation of apoptosis and innate immune response were investigated. The full-length coding sequence of PvRUBCN was 3708 bp encoding the protein of 1235 amino acids. PvRUBCN contained three conserved domains including the RUN, the PI3K-binding, and the Rubicon homology domains. PvRUBCN was grouped with the closely related RUBCN from the Penaeid species with more than 95 % identity. It was highly expressed in nerve followed by intestine, and gill. Its expression was induced upon WSSV challenge at 12 and 48 hpi. Suppression of PvRUBCN by dsRNA upon WSSV challenge resulted in more than 80 % reduction in PvRUBCN mRNA expression. Knockdown of PvRUBCN mRNA significantly decreased the WSSV copy number and prolonged the survival rate of WSSV-infected shrimp. In addition, the caspase3, a key regulator of the apoptosis pathway was significantly down-regulated. The interferon like genes including Vago4 was dramatically decreased at 72 hpi whereas Vago5 demonstrated slight reduction at 24 hpi and increase at 72 and 120 hpi, respectively. On the other hand, the expressions of the genes involved in the prophenoloxidase pathway including PPO1 and PPO2 were not changed. Taken together, PvRUBCN played important roles in the antiviral immunity in response to WSSV infection.

Molecular Mechanisms of Autophagy Decline during Aging

Macroautophagy (hereafter autophagy) is a cellular recycling process that degrades cytoplasmic components, such as protein aggregates and mitochondria, and is associated with longevity and health in multiple organisms. While mounting evidence supports that autophagy declines with age, the underlying molecular mechanisms remain unclear. Since autophagy is a complex, multistep process, orchestrated by more than 40 autophagy-related proteins with tissue-specific expression patterns and context-dependent regulation, it is challenging to determine how autophagy fails with age. In this review, we describe the individual steps of the autophagy process and summarize the age-dependent molecular changes reported to occur in specific steps of the pathway that could impact autophagy. Moreover, we describe how genetic manipulations of autophagy-related genes can affect lifespan and healthspan through studies in model organisms and age-related disease models. Understanding the age-related changes in each step of the autophagy process may prove useful in developing approaches to prevent autophagy decline and help combat a number of age-related diseases with dysregulated autophagy.

Therapeutic Relevance of Inducing Autophagy in β-Thalassemia

The β-thalassemias are inherited genetic disorders affecting the hematopoietic system. In β-thalassemias, more than 350 mutations of the adult β-globin gene cause the low or absent production of adult hemoglobin (HbA). A clinical parameter affecting the physiology of erythroid cells is the excess of free α-globin. Possible experimental strategies for a reduction in excess free α-globin chains in β-thalassemia are CRISPR-Cas9-based genome editing of the β-globin gene, forcing "de novo" HbA production and fetal hemoglobin (HbF) induction. In addition, a reduction in excess free α-globin chains in β-thalassemia can be achieved by induction of the autophagic process. This process is regulated by the Unc-51-like kinase 1 (Ulk1) gene. The interplay with the PI3K/Akt/TOR pathway, with the activity of the α-globin stabilizing protein (AHSP) and the involvement of microRNAs in autophagy and Ulk1 gene expression, is presented and discussed in the context of identifying novel biomarkers and potential therapeutic targets for β-thalassemia.

MicroRNA-142-3p alleviated high salt-induced cardiac fibrosis via downregulating optineurin-mediated mitophagy

High salt can induce cardiac damage. The aim of this present study was to explore the effect and the mechanism of microRNA (miR)-142-3p on the cardiac fibrosis induced by high salt. Rats received high salt diet to induce cardiac fibrosis in vivo, and neonatal rat cardiac fibroblasts (NRCF) treated with sodium chloride (NaCl) to induce fibrosis in vitro. The fibrosis and mitochondrial autophagy levels were increased the heart and NRCF treated with NaCl, which were alleviated by miR-142-3p upregulation. The fibrosis and mitochondrial autophagy levels were elevated in NRCF after treating with miR-142-3p antagomiR. Optineurin (OPTN) expression was increased in the mitochondria of NRCF induced by NaCl, which was attenuated by miR-142-3p agomiR. OPTN downregulation inhibited the increases of fibrosis and mitochondrial autophagy levels induced by NaCl in NRCF. These results miR-142-3p could alleviate high salt-induced cardiac fibrosis via downregulation of OPTN to reduce mitophagy.

The roles of intracellular proteolysis in cardiac ischemia-reperfusion injury

Ischemic heart disease remains a leading cause of human mortality worldwide. One form of ischemic heart disease is ischemia-reperfusion injury caused by the reintroduction of blood supply to ischemic cardiac muscle. The short and long-term damage that occurs due to ischemia-reperfusion injury is partly due to the proteolysis of diverse protein substrates inside and outside of cardiomyocytes. Ischemia-reperfusion activates several diverse intracellular proteases, including, but not limited to, matrix metalloproteinases, calpains, cathepsins, and caspases. This review will focus on the biological roles, intracellular localization, proteolytic targets, and inhibitors of these proteases in cardiomyocytes following ischemia-reperfusion injury. Recognition of the intracellular function of each of these proteases includes defining their activation, proteolytic targets, and their inhibitors during myocardial ischemia-reperfusion injury. This review is a step toward a better understanding of protease activation and involvement in ischemic heart disease and developing new therapeutic strategies for its treatment.

Diversity and complexity of cell death: a historical review

Death is the inevitable fate of all living organisms, whether at the individual or cellular level. For a long time, cell death was believed to be an undesirable but unavoidable final outcome of nonfunctioning cells, as inflammation was inevitably triggered in response to damage. However, experimental evidence accumulated over the past few decades has revealed different types of cell death that are genetically programmed to eliminate unnecessary or severely damaged cells that may damage surrounding tissues. Several types of cell death, including apoptosis, necrosis, autophagic cell death, and lysosomal cell death, which are classified as programmed cell death, and pyroptosis, necroptosis, and NETosis, which are classified as inflammatory cell death, have been described over the years. Recently, several novel forms of cell death, namely, mitoptosis, paraptosis, immunogenic cell death, entosis, methuosis, parthanatos, ferroptosis, autosis, alkaliptosis, oxeiptosis, cuproptosis, and erebosis, have been discovered and advanced our understanding of cell death and its complexity. In this review, we provide a historical overview of the discovery and characterization of different forms of cell death and highlight their diversity and complexity. We also briefly discuss the regulatory mechanisms underlying each type of cell death and the implications of cell death in various physiological and pathological contexts. This review provides a comprehensive understanding of different mechanisms of cell death that can be leveraged to develop novel therapeutic strategies for various diseases.

Beyond autophagy: LC3-associated phagocytosis and endocytosis

Noncanonical functions of the autophagy machinery in pathways including LC3-associated phagocytosis and LC3-associated endocytosis have garnered increasing interest in both normal physiology and pathobiology. New discoveries over the past decade of noncanonical uses of the autophagy machinery in these distinct molecular mechanisms have led to robust investigation into the roles of single-membrane LC3 lipidation. Noncanonical autophagy pathways have now been implicated in the regulation of multiple processes ranging from debris clearance, cellular signaling, and immune regulation and inflammation. Accumulating evidence is demonstrating roles in a variety of disease states including host-pathogen responses, autoimmunity, cancer, and neurological and neurodegenerative pathologies. Here, we broadly summarize the differences in the mechanistic regulation between autophagy and LAP and LANDO and highlight some of the key roles of LAP and LANDO in innate immune function, inflammation, and disease pathology.

Neutrophil extracellular traps-mediated Beclin-1 suppression aggravates atherosclerosis by inhibiting macrophage autophagy

A growing body of evidence suggests that neutrophil extracellular traps (NETs) critically contribute to the development of atherosclerosis. However, the detailed mechanism of how NETs promote atherogenesis remains unknown. In this study, we explored the role of NETs for promoting atherosclerosis by modulating the activity of autophagy in macrophages. NETs were effectively induced by a nicotine administration to the HL-60 cell-derived neutrophil-like cells. Treatment with NETs markedly suppressed both autophagosome formation and autophagosome–lysosome fusion in 7-ketocholesterol-treated macrophages, which are accompanied by the enhancement of inflammasome activity. NETs upregulate epidermal growth factor receptor (EGFR) activity, which enhances Beclin-1 phosphorylation of the tyrosine residues of Beclin-1 by EGFR, inhibits the PI3 kinase activity of the Beclin1–Vps34 complex, and suppresses autophagosome formation in macrophages. Furthermore, NET-induced activation of EGFR allows Rubicon to increase its expression, thereby suppressing autophagosome-lysosome fusion. In vivo experiments revealed that the suppression of NET formation by ablating peptidyl arginine deiminase-4 in neutrophil leukocytes resulted in the attenuation of atherosclerotic plaques in a nicotine-administered HFD-fed ApoE−/−mice. Taken together, these results suggest that NET-mediated EGFR–Beclin-1 signaling in the macrophages promotes atherogenesis by autophagy inhibition-mediated inflammasome activation.

Incomplete autophagy: Trouble is a friend

Incomplete autophagy is an impaired self-eating process of intracellular macromolecules and organelles in which accumulated autophagosomes do not fuse with lysosomes for degradation, resulting in the blockage of autophagic flux. In this review, we summarized the literature over the past decade describing incomplete autophagy, and found that different from the double-edged sword effect of general autophagy on promoting cell survival or death, incomplete autophagy plays a crucial role in disrupting cellular homeostasis, and promotes only cell death. What matters is that incomplete autophagy is closely relevant to the pathogenesis and progression of various human diseases, which, meanwhile, intimately linking to the pharmacologic and toxicologic effects of several compounds. Here, we comprehensively reviewed the latest progress of incomplete autophagy on molecular mechanisms and signaling pathways. Moreover, implications of incomplete autophagy for pharmacotherapy are also discussed, which has great relevance for our understanding of the distinctive role of incomplete autophagy in cellular physiology and disease. Consequently, targeting incomplete autophagy may contribute to the development of novel generation therapeutic agents for diverse human diseases.

The role of autophagy in death of cardiomyocytes

Autophagy mediates cellular quality control mechanisms and energy homeostasis through lysosomal degradation. Autophagy is typically viewed as an adaptive process that allows cells to survive against stress, such as nutrient deprivation and hypoxia. However, autophagy also mediates cell death during development and in response to stress. Cell death accompanied by autophagy activation and accumulation of autophagosomes has been classified as type II programmed cell death. Compared to the wealth of knowledge regarding the adaptive role of autophagy, however, the molecular mechanisms through which autophagy induces cell death and its functional significance are poorly understood. Autophagy is activated excessively under some conditions, causing uncontrolled degradation of cellular materials and cell death. An imbalance between autophagosome formation and lysosomal degradation causes a massive accumulation of autophagosomes, which subsequently causes cellular dysfunction and death. Dysregulation of autophagy induces a unique form of cell death, termed autosis, with defined morphological and biochemical features distinct from other forms of programmed cell death, such as apoptosis and necrosis. In the heart, dysregulated autophagy induces death of cardiomyocytes and actively mediates cardiac injury and dysfunction in some conditions, including reperfusion injury, doxorubicin cardiomyopathy, and lysosomal storage disorders. The goal in this review is to introduce the concept of autophagic cell death and discuss its functional significance in various cardiac conditions.

Repurposing drugs in autophagy for the treatment of cancer: From bench to bedside

Autophagy is a multistep degradation pathway involving the lysosome, which supports nutrient reuse and metabolic balance, and has been implicated as a process that regulates cancer genesis and development. Targeting tumors by regulating autophagy has become a therapeutic strategy of interest. Drugs with other indications can have antitumor activity by modulating autophagy, providing a shortcut to developing novel antitumor drugs (i.e., drug repurposing/repositioning), as successfully performed for chloroquine (CQ); an increasing number of repurposed drugs have since advanced into clinical trials. In this review, we describe the application of different drug-repurposing approaches in autophagy for the treatment of cancer and focus on repurposing drugs that target autophagy to treat malignant neoplasms.