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.

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.

The role of autophagic cell death in cardiac disease.

Cardiomyocytes undergo various forms of cell death during heart disease such as myocardial infarction and heart failure. Understanding the mechanisms of cell death in cardiomyocytes is one of the most fundamental issues in the treatment of heart failure. Among the several kinds of cell death mechanisms, this review will focus on autophagy-related cardiomyocyte cell death. Although autophagy plays an essential role in mediating cellular quality control mechanisms for cell survival, dysregulation of autophagy can cause cell death, referred to as autophagy-dependent cell death or type II programmed cell death. The recent discovery of autosis as a modality of autophagy-dependent cell death with unique morphological and biochemical features has allowed us to broaden our understanding of the mechanistic role of autophagy in cell death. Here, we discuss autophagy-dependent cardiomyocyte cell death, including autosis, in pathophysiological conditions of the heart.

The Role of Autophagy in the Heart.

Autophagy is an evolutionarily conserved mechanism by which cytoplasmic elements are degraded intracellularly. Autophagy has also emerged as a major regulator of cardiac homeostasis and function. Autophagy preserves cardiac structure and function under baseline conditions and is activated during stress, limiting damage under most conditions. It reduces injury and preserves cardiac function during ischemia. It also reduces chronic ischemic remodeling and mediates the cardiac adaptation to pressure overload by restricting misfolded protein accumulation, mitochondrial dysfunction, and oxidative stress. Impairment of autophagy is involved in the development of diabetes and aging-induced cardiac abnormalities. Autophagy defects contribute to the development of cardiac proteinopathy and doxorubicin-induced cardiomyopathy. However, massive activation of autophagy may be detrimental for the heart in certain stress conditions, such as reperfusion injury. In this review, we discuss recent evidence supporting the important role of autophagy and mitophagy in the regulation of cardiac homeostasis and adaptation to stress.

Autophagy in neurodegeneration: New insights underpinning therapy for neurological diseases.

In autophagy long-lived proteins, protein aggregates or damaged organelles are engulfed by vesicles called autophagosomes prior to lysosomal degradation. Autophagy dysfunction is a hallmark of several neurodegenerative diseases in which misfolded proteins or dysfunctional mitochondria accumulate. Excessive autophagy can also exacerbate brain injury under certain conditions. In this review, we provide specific examples to illustrate the critical role played by autophagy in pathological conditions affecting the brain and discuss potential therapeutic implications. We show how a singular type of autophagy-dependent cell death termed autosis has attracted attention as a promising target for improving outcomes in perinatal asphyxia and hypoxic-ischaemic injury to the immature brain. We provide evidence that autophagy inhibition may be protective against radiotherapy-induced damage to the young brain. We describe a specialized form of macroautophagy of therapeutic relevance for motoneuron and neuromuscular diseases, known as chaperone-assisted selective autophagy, in which heat shock protein B8 is used to deliver aberrant proteins to autophagosomes. We summarize studies pinpointing mitophagy mediated by the serine/threonine kinase PINK1 and the ubiquitin-protein ligase Parkin as a mechanism potentially relevant to Parkinson's disease, despite debate over the physiological conditions in which it is activated in organisms. Finally, with the example of the autophagy-inducing agent rilmenidine and its discrepant effects in cell culture and mouse models of motor neuron disorders, we illustrate the importance of considering aspects such a disease stage and aggressiveness, type of insult and load of damaged or toxic cellular components, when choosing the appropriate drug, timepoint and duration of treatment.

Cell death mechanisms in eukaryotes.

Like the organism they constitute, the cells also die in different ways. The death can be predetermined, programmed, and cleanly executed, as in the case of apoptosis, or it can be traumatic, inflammatory, and sudden as many types of necrosis exemplify. Nevertheless, there are a number of cell deaths-some of them bearing a resemblance to apoptosis and/or necrosis, and many, distinct from each-that serve a multitude of roles in either supporting or disrupting the homoeostasis. Apoptosis is coordinated by death ligands, caspases, b-cell lymphoma-2 (Bcl-2) family proteins, and their downstream effectors. Events that can lead to apoptosis include mitotic catastrophe and anoikis. Necrosis, although it has been considered an abrupt and uncoordinated cell death, has many molecular events associated with it. There are cell death mechanisms that share some standard features with necrosis. These include methuosis, necroptosis, NETosis, pyronecrosis, and pyroptosis. Autophagy, generally a catabolic pathway that operates to ensure cell survival, can also kill the cell through mechanisms such as autosis. Other cell-death mechanisms include entosis, ferroptosis, lysosome-dependent cell death, and parthanatos.

Multiple and complex influences of connexins and pannexins on cell death.

Cell death is a fundamental process for organogenesis, immunity and cell renewal. During the last decades a broad range of molecular tools were identified as important players for several different cell death pathways (apoptosis, pyroptosis, necrosis, autosis…). Aside from these direct regulators of cell death programs, several lines of evidence proposed connexins and pannexins as potent effectors of cell death. In the present review we discussed the potential roles played by connexins, pannexins and innexins in the different cell death programs at different scales from gap junction intercellular communication to protein-protein interactions. This article is part of a Special Issue entitled: Gap Junction Proteins edited by Jean Claude Herve.

Recent progress in research on molecular mechanisms of autophagy in the heart.

Dysregulation of autophagy, an evolutionarily conserved process for degradation of long-lived proteins and organelles, has been implicated in the pathogenesis of human disease. Recent research has uncovered pathways that control autophagy in the heart and molecular mechanisms by which alterations in this process affect cardiac structure and function. Although initially thought to be a nonselective degradation process, autophagy, as it has become increasingly clear, can exhibit specificity in the degradation of molecules and organelles, such as mitochondria. Furthermore, it has been shown that autophagy is involved in a wide variety of previously unrecognized cellular functions, such as cell death and metabolism. A growing body of evidence suggests that deviation from appropriate levels of autophagy causes cellular dysfunction and death, which in turn leads to heart disease. Here, we review recent advances in understanding the role of autophagy in heart disease, highlight unsolved issues, and discuss the therapeutic potential of modulating autophagy in heart disease.

Insulin-like growth factor-1 reduces cardiac autosis through decreasing AMPK/FOXO1 signaling and Na+/K+-ATPase-Beclin-1 interaction.

Introduction: Insulin-like growth factor-1 (IGF-1) promotes survival and inhibits cardiac autophagy disruption. Methods: Male Wistar rats were treated with IGF-1 (50 µg/kg), and 24 h after injection hearts were excised. The level of interaction between Beclin-1 and the α1 subunit of sodium/potassium-adenosine triphosphates (Na+/K+-ATPase), and phosphorylated forms of IGF-1 receptor/insulin receptor (IGF-1R/IR), forkhead box protein O1 (FOXO1) and AMP-activated protein kinase (AMPK) were measured. Results: The results indicate that IGF-1 decreased Beclin-1's association with Na+/K+-ATPase (p < 0.05), increased IGF-1R/IR and FOXO1 phosphorylation (p < 0.05), and decreased AMPK phosphorylation (p < 0.01) in rats' hearts. Conclusions: The new IGF-1 therapy may control autosis and minimize cardiomyocyte mortality.

Resveratrol-laden mesoporous silica nanoparticles regulate the autophagy and apoptosis via ROS-mediated p38-MAPK/HIF-1a /p53 signaling in hypertrophic scar fibroblasts.

Background: During the regression of hypertrophic scars, autophagy and apoptosis are the main ways of cell death. Recent investigations demonstrated effective inhibition of resveratrol on hypertrophic scar fibroblasts (HSFs). But its therapeutic value is limited by chemical instability and hydrophobicity, as well as the mechanism of its role in regulation of autophagy and apoptosis remains unknown. Aim of the study: We prepared a mesoporous silica nanoparticle laden with resveratrol (MSN@Res) which can effectively improve the solubility and stability of resveratrol. The purpose of this study was to investigate whether MSN@Res regulate autophagy and apoptosis of HSFs via inhibition of ROS/p38/HIF-1α/p53 signaling axis, as to reveal its pharmacological action and target. Materials and methods: Network pharmacology, molecular docking, and in vitro assays were carried out in this study. An in vitro model of fibroblasts cultivated in hypoxic and ischemic situations was established to simulate the scar in the proliferative phase. Results: MSN@Res surpresses HSFs by reducing physiological autophagy and inducing apoptosis, autosis may be another cell death involed in this process. According to the network pharmacological analysis and molecular docking, the mechanism by which MSN@Res alleviates hypertrophic scar may be closely related to the MAPK signaling pathway. MSN@Res significantly downregulate the expression of HIF-1α and p53 through the inhibition of ROS induced p38-MAPK phosphorylation with corresponding changes in the expression of autophagy and apoptosis related protein. Conclusion: MSN@Res is a novel drug delivery system with excellent chemical stability and drug release performance. It can inhibit protective autophagy of fibroblasts in hypoxic environment, and induce the apoptosis and autosis via the ROS -mediated p38-MAPK/HIF-1α/p53 signaling axis.

Corrigendum: Autosis as a selective type of cell death.

[This corrects the article DOI: 10.3389/fcell.2023.1164681.].

Novel cardioprotective mechanism for Empagliflozin in nondiabetic myocardial infarction with acute hyperglycemia.

Patients with AMI and hyperglycemia upon hospital admission exhibited poorer prognosis compared with those without hyperglycemia. It is unknown whether SGLT2 inhibitors can also improve nondiabetic myocardial infarction (MI) with acute hyperglycemia and the underlying mechanisms. Here we demonstrated that hyperglycemia patients were more likely to have worse cardiac function levels, such as with Killip III/IV during hospitalization. Glucose injection-induced nondiabetic MI accompanied by acute hyperglycemia in WT mice, manifested lower survival compared with control. A significant increase in both survival and LV function was observed when treated with empagliflozin (EMPA). In addition, EMPA attenuated fibrosis and autophagy of border cardiac tissue in mice with MI accompanied by acute hyperglycemia. Applying Beclin1+/- and NHE1 cKO mice, we found that Beclin1 deficiency improved survival. Mechanistically, EMPA had a more significant cardioprotective effect through inhibited its autophagy level by targeted Beclin1 rather than NHE1. In addition, EMPA rescued cardiomyocytes autosis induced by Tat-beclin1 or GD, conferring cardioprotection decreasing autophagic cell death. These findings provide new insights that SGLT2 inhibitor effectively ameliorates the myocardial injury in nondiabetic myocardial infarction with acute hyperglycemia through suppressing beclin1-dependent autosis rather than elusively targeting NHE1 in cardiomyocytes.

Induction of tumor cell autosis by myxoma virus-infected CAR-T and TCR-T cells to overcome primary and acquired resistance.

Cytotoxicity of tumor-specific T cells requires tumor cell-to-T cell contact-dependent induction of classic tumor cell apoptosis and pyroptosis. However, this may not trigger sufficient primary responses of solid tumors to adoptive cell therapy or prevent tumor antigen escape-mediated acquired resistance. Here we test myxoma virus (MYXV)-infected tumor-specific T (TMYXV) cells expressing chimeric antigen receptor (CAR) or T cell receptor (TCR), which systemically deliver MYXV into solid tumors to overcome primary resistance. In addition to T cell-induced apoptosis and pyroptosis, tumor eradication by CAR/TCR-TMYXV cells is also attributed to tumor cell autosis induction, a special type of cell death. Mechanistically, T cell-derived interferon γ (IFNγ)-protein kinase B (AKT) signaling synergizes with MYXV-induced M-T5-SKP-1-VPS34 signaling to trigger robust tumor cell autosis. CAR/TCR-TMYXV-elicited autosis functions as a type of potent bystander killing to restrain antigen escape. We uncover an unexpected synergy between T cells and MYXV to bolster solid tumor cell autosis that reinforces tumor clearance.

Tfeb-Mediated Transcriptional Regulation of Autophagy Induces Autosis during Ischemia/Reperfusion in the Heart.

Autosis is a unique form of cell death with characteristic morphological and biochemical features caused by dysregulated autophagy. Autosis is observed in the heart during the late phase of ischemia/reperfusion (I/R), when marked accumulation of autophagosomes is induced. We previously showed that the excessive accumulation of autophagosomes promotes autosis in cardiomyocytes. Although the inhibition of autophagic flux via the upregulation of Rubicon induces the accumulation of autophagosomes during I/R, it appears that additional mechanisms exacerbating autophagosome accumulation are required for the induction of autosis. Here, we show that Tfeb contributes to the induction of autosis during the late phase of I/R in the heart. During myocardial reperfusion, Tfeb is activated and translocated into the nucleus, which in turn upregulates genes involved in autophagy and lysosomal function. The overexpression of Tfeb enhanced cardiomyocyte death induced by a high dose of TAT-Beclin 1, an effect that was inhibited by the downregulation of Atg7. Conversely, the knockdown of Tfeb attenuated high-dose TAT-Beclin1-induced death in cardiomyocytes. Although the downregulation of Tfeb in the heart significantly decreased the number of autophagic vacuoles and inhibited autosis during I/R, the activation of Tfeb activity via 3,4-dimethoxychalcone, an activator of Tfeb, aggravated myocardial injury during I/R. These findings suggest that Tfeb promotes cardiomyocyte autosis during the late phase of reperfusion in the heart.

Cardioprotective mechanism of SGLT2 inhibitor against myocardial infarction is through reduction of autosis.

Sodium-glucose cotransporter 2 (SGLT2) inhibitors reduce cardiovascular mortality in patients with diabetes mellitus but the protective mechanism remains elusive. Here we demonstrated that the SGLT2 inhibitor, Empagliflozin (EMPA), suppresses cardiomyocytes autosis (autophagic cell death) to confer cardioprotective effects. Using myocardial infarction (MI) mouse models with and without diabetes mellitus, EMPA treatment significantly reduced infarct size, and myocardial fibrosis, thereby leading to improved cardiac function and survival. In the context of ischemia and nutritional glucose deprivation where autosis is already highly stimulated, EMPA directly inhibits the activity of the Na+/H+ exchanger 1 (NHE1) in the cardiomyocytes to regulate excessive autophagy. Knockdown of NHE1 significantly rescued glucose deprivation-induced autosis. In contrast, overexpression of NHE1 aggravated the cardiomyocytes death in response to starvation, which was effectively rescued by EMPA treatment. Furthermore, in vitro and in vivo analysis of NHE1 and Beclin 1 knockout mice validated that EMPA's cardioprotective effects are at least in part through downregulation of autophagic flux. These findings provide new insights for drug development, specifically targeting NHE1 and autosis for ventricular remodeling and heart failure after MI in both diabetic and non-diabetic patients.

Current strategies to induce selective killing of HIV-1-infected cells.

Although combination antiretroviral therapy (ART) has led to significant HIV-1 suppression and improvement in immune function, persistent viral reservoirs remain that are refractory to intensified ART. ART poses many challenges such as adherence to drug regimens, the emergence of resistant virus, and cumulative toxicity resulting from long-term therapy. Moreover, latent HIV-1 reservoir cells can be stochastically activated to produce viral particles despite effective ART and contribute to the rapid viral rebound that typically occurs within 2 weeks of ART interruption; thus, lifelong ART is required for continued viral suppression. Several strategies have been proposed to address the HIV-1 reservoir such as reactivation of HIV-1 transcription using latency reactivating agents with a combination of ART, host immune clearance and HIV-1-cytotoxicity to purge the infected cells-a "shock and kill" strategy. However, these approaches do not take into account the multiple transcriptional and translational blocks that contribute to HIV-1 latency or the complex heterogeneity of the HIV-1 reservoir, and clinical trials have thus far failed to produce the desired results. Here, we describe alternative strategies being pursued that are designed to kill selectively HIV-1-infected cells while sparing uninfected cells in the absence of enhanced humoral or adaptive immune responses.

Autophagic Cell Death During Development - Ancient and Mysterious.

While cell death is a normal and essential component of development and homeostasis, dysregulation of this process underlies most human diseases, including cancer, autoimmunity and neurodegeneration. The best characterized mechanism for cell death is apoptosis, although some cells die by a distinct process known as autophagy-dependent cell death (ADCD). Autophagy is mediated by the formation of double membrane vesicles that contain protein aggregates, damaged organelles like mitochondria, and bulk cytoplasm, which then fuse with lysosomes to degrade and recycle their contents. Autophagy is typically viewed as an adaptive process that allows cells to survive stresses like nutrient deprivation, although increasing evidence suggests that it may also mediate cell death during development and pathogenesis. An aggressive form of autophagy termed autosis has been described in cells following either ischemia/reperfusion injury or in response to autophagy-inducing proteins like Tat-Beclin 1. Despite an extensive literature on autophagic cell death in a variety of contexts, there are still fundamental gaps in our understanding of this process. As examples: Does autophagy directly kill cells and if so how? Is ADCD activated concurrently when cells are triggered to die via apoptosis? And is ADCD essentially a more protracted version of autosis or a distinct pathway? The goal of this mini-review is to summarize the field and to identify some of the major gaps in our knowledge. Understanding the molecular mechanisms that mediate ADCD will not only provide new insights into development, they may facilitate the creation of better tools for both the diagnostics and treatment of disease.

Cardiac Glycosides as Autophagy Modulators.

Drug repositioning is one of the leading strategies in modern therapeutic research. Instead of searching for completely novel substances and demanding studies of their biological effects, much attention has been paid to the evaluation of commonly used drugs, which could be utilized for more distinct indications than they have been approved for. Since treatment approaches for cancer, one of the most extensively studied diseases, have still been very limited, great effort has been made to find or repurpose novel anticancer therapeutics. One of these are cardiac glycosides, substances commonly used to treat congestive heart failure or various arrhythmias. Recently, the antitumor properties of cardiac glycosides have been discovered and, therefore, these compounds are being considered for anticancer therapy. Their mechanism of antitumor action seems to be rather complex and not fully uncovered yet, however, autophagy has been confirmed to play a key role in this process. In this review article, we report on the up-to-date knowledge of the anticancer activity of cardiac glycosides with special attention paid to autophagy induction, the molecular mechanisms of this process, and the potential employment of this phenomenon in clinical practice.

Induction of Autophagy to Achieve a Human Immunodeficiency Virus Type 1 Cure.

Effective antiretroviral therapy has led to significant human immunodeficiency virus type 1 (HIV-1) suppression and improvement in immune function. However, the persistence of integrated proviral DNA in latently infected reservoir cells, which drive viral rebound post-interruption of antiretroviral therapy, remains the major roadblock to a cure. Therefore, the targeted elimination or permanent silencing of this latently infected reservoir is a major focus of HIV-1 research. The most studied approach in the development of a cure is the activation of HIV-1 expression to expose latently infected cells for immune clearance while inducing HIV-1 cytotoxicity-the "kick and kill" approach. However, the complex and highly heterogeneous nature of the latent reservoir, combined with the failure of clinical trials to reduce the reservoir size casts doubt on the feasibility of this approach. This concern that total elimination of HIV-1 from the body may not be possible has led to increased emphasis on a "functional cure" where the virus remains but is unable to reactivate which presents the challenge of permanently silencing transcription of HIV-1 for prolonged drug-free remission-a "block and lock" approach. In this review, we discuss the interaction of HIV-1 and autophagy, and the exploitation of autophagy to kill selectively HIV-1 latently infected cells as part of a cure strategy. The cure strategy proposed has the advantage of significantly decreasing the size of the HIV-1 reservoir that can contribute to a functional cure and when optimised has the potential to eradicate completely HIV-1.