Poly (ADP-ribose) polymerase inhibition protects against myocardial ischaemia/reperfusion injury via suppressing mitophagy

Cardioprotective effects of PARP Inhibitors: A meta-analysis of animal studies

Poly(adenosine diphosphate [ADP] ribose) polymerase (PARP) inhibitors are expected to provide benefits to the cardiovascular system. However, the cardioprotective effect of PARP inhibitors has not been systematically reviewed or quantitatively analyzed. This study aimed to assess the cardioprotective effects of PARP inhibitors through a meta-analysis of animal studies. Three databases PubMed, Web of Sciences, and Embase were searched until September 1, 2023. The risk of bias was assessed using SYRCLE's Risk of Bias. A total of 74 animal studies that investigated the cardiac function of PARP inhibitors compared to placebo or vehicle, were included. Outcome measures were hemodynamic indexes, cardiac contractility, and biomarkers of myocardial injury. Pooled effect size was estimated using a random-effects model with RevMan 5.4. PARP inhibitors were associated with enhanced hemodynamic indexes, including cardiac output (standardized mean difference, 0.86 [95 % CI, 0.54 to 1.17]; p < 0.00001) and stroke volume (0.42 [0.07 to 0.76]; p = 0.02). PARP inhibitors were associated with increased cardiac contractility, including ejection fraction (0.71 [0.42 to 1.01]; p < 0.00001) and fractional shortening (0.96 [0.62 to 1.31]; p < 0.00001). PARP inhibitors were associated with decreased troponin І (-1.42 [-2.16 to -0.68]; p = 0.0002), plasma B-type natriuretic peptide (-0.95 [-1.56 to -0.33]; p = 0.003), creatine kinase (-1.81 [-2.63 to -0.99]; p < 0.0001), and infarct size (-1.58 [-2.01 to -1.14]; p < 0.00001). PARP inhibitors improve cardiac functions and attenuate myocardial injury in animals, which indicate the cardioprotective effects. Further human studies are necessary.

Mitochondria and myocardial ischemia/reperfusion injury: Effects of Chinese herbal medicine and the underlying mechanisms

Ischemic heart disease (IHD) is associated with high morbidity and mortality rates. Reperfusion therapy is the best treatment option for this condition. However, reperfusion can aggravate myocardial damage through a phenomenon known as myocardial ischemia/reperfusion (I/R) injury, which has recently gained the attention of researchers. Several studies have shown that Chinese herbal medicines and their natural monomeric components exert therapeutic effects against I/R injury. This review outlines the current knowledge on the pathological mechanisms through which mitochondria participate in I/R injury, focusing on the issues related to energy metabolism, mitochondrial quality control disorders, oxidative stress, and calcium. The mechanisms by which mitochondria mediate cell death have also been discussed. To develop a resource for the prevention and management of clinical myocardial I/R damage, we compiled the most recent research on the effects of Chinese herbal remedies and their monomer components.

The PINK1/Parkin signaling pathway-mediated mitophagy: a forgotten protagonist in myocardial ischemia/reperfusion injury

Myocardial ischemia causes extensive damage, further exacerbated by reperfusion, a phenomenon called myocardial ischemia/reperfusion injury (MIRI). Nowadays, the pathological mechanisms of MIRI have received extensive attention. Oxidative stress, multiple programmed cell deaths, inflammation and others are all essential pathological mechanisms contributing to MIRI. Mitochondria are the energy supply centers of cells. Numerous studies have found that abnormal mitochondrial function is an essential "culprit" of MIRI, and mitophagy mediated by the phosphatase and tensin homolog (PTEN)-induced kinase 1 (PINK1)/Parkin signaling pathway is an integral part of maintaining mitochondrial function. Therefore, exploring the association between the PINK1/Parkin signaling pathway-mediated mitophagy and MIRI is crucial. This review will mainly summarize the crucial role of the PINK1/Parkin signaling pathway-mediated mitophagy in MIR-induced several pathological mechanisms and various potential interventions that affect the PINK1/Parkin signaling pathway-mediated mitophagy, thus ameliorating MIRI.

Mitochondrial quality control in human health and disease

Mitochondria, the most crucial energy-generating organelles in eukaryotic cells, play a pivotal role in regulating energy metabolism. However, their significance extends beyond this, as they are also indispensable in vital life processes such as cell proliferation, differentiation, immune responses, and redox balance. In response to various physiological signals or external stimuli, a sophisticated mitochondrial quality control (MQC) mechanism has evolved, encompassing key processes like mitochondrial biogenesis, mitochondrial dynamics, and mitophagy, which have garnered increasing attention from researchers to unveil their specific molecular mechanisms. In this review, we present a comprehensive summary of the primary mechanisms and functions of key regulators involved in major components of MQC. Furthermore, the critical physiological functions regulated by MQC and its diverse roles in the progression of various systemic diseases have been described in detail. We also discuss agonists or antagonists targeting MQC, aiming to explore potential therapeutic and research prospects by enhancing MQC to stabilize mitochondrial function.

ADP-ribosylation: An emerging direction for disease treatment

ADP-ribosylation (ADPr) is a dynamically reversible post-translational modification (PTM) driven primarily by ADP-ribosyltransferases (ADPRTs or ARTs), which have ADP-ribosyl transfer activity. ADPr modification is involved in signaling pathways, DNA damage repair, metabolism, immunity, and inflammation. In recent years, several studies have revealed that new targets or treatments for tumors, cardiovascular diseases, neuromuscular diseases and infectious diseases can be explored by regulating ADPr. Here, we review the recent research progress on ART-mediated ADP-ribosylation and the latest findings in the diagnosis and treatment of related diseases.

Potential relationship between autophagy and ferroptosis in myocardial ischemia/reperfusion injury

Autophagy is an evolutionarily conserved process involved in the degradation of long-lived proteins and excessive or dysfunctional organelles. As a pivotal cellular response, autophagy has been extensively studied and is known to be involved in various diseases. Ferroptosis is a recently discovered form of regulated cell death characterized by iron overload, leading to the accumulation of lethal levels of lipid hydroperoxides. Recently, an increasing number of studies have revealed a link between autophagy and ferroptosis. Myocardial ischemia/reperfusion injury (MIRI) is an urgent dilemma after myocardial infarction recanalization, which is regulated by several cell death pathways, including autophagy and ferroptosis. However, the potential relationship between autophagy and ferroptosis in MIRI remains unexplored. In this study, we briefly review the mechanisms of autophagy and ferroptosis, including their roles in MIRI. Moreover, we provide an overview of the potential crosstalk in MIRI. Clarifying the relationship between different cell death pathways may provide new ideas for the treatment of MIRI in the future.

Relationship between ferroptosis and mitophagy in cardiac ischemia reperfusion injury: a mini-review

Cardiovascular diseases (CVD), with high morbidity and mortality, seriously affect people's life and social development. Clinically, reperfusion therapy is typically used to treat ischemic cardiomyopathy, such as severe coronary heart disease and acute myocardial infarction. However, reperfusion therapy can lead to myocardial ischemia reperfusion injury (MIRI), which can affect the prognosis of patients. Studying the mechanisms of MIRI can help us improve the treatment of MIRI. The pathological process of MIRI involves many mechanisms such as ferroptosis and mitophagy. Ferroptosis can exacerbate MIRI, and regulation of mitophagy can alleviate MIRI. Both ferroptosis and mitophagy are closely related to ROS, but there is no clear understanding of the relationship between ferroptosis and mitophagy. In this review, we analyzed the relationship between ferroptosis and mitophagy according to the role of mTOR, NLPR3 and HIF. In addition, simultaneous regulation of mitophagy and ferroptosis may be superior to single therapy for MIRI. We summarized potential drugs that can regulate mitophagy and/or ferroptosis, hoping to provide reference for the development of drugs and methods for MIRI treatment.

Regulation of autophagy of the heart in ischemia and reperfusion

Ischemia/reperfusion (I/R) of the heart leads to increased autophagic flux. Preconditioning stimulates autophagic flux by AMPK and PI3-kinase activation and mTOR inhibition. The cardioprotective effect of postconditioning is associated with activation of autophagy and increased activity of NO-synthase and AMPK. Oxidative stress stimulates autophagy in the heart during I/R. Superoxide radicals generated by NADPH-oxidase acts as a trigger for autophagy, possibly due to AMPK activation. There is reason to believe that AMPK, GSK-3β, PINK1, JNK, hexokinase II, MEK, PKCα, and ERK kinases stimulate autophagy, while mTOR, PKCδ, Akt, and PI3-kinase can inhibit autophagy in the heart during I/R. However, there is evidence that PI3-kinase could stimulate autophagy in ischemic preconditioning of the heart. It was found that transcription factors FoxO1, FoxO3, NF-κB, HIF-1α, TFEB, and Nrf-2 enhance autophagy in the heart in I/R. Transcriptional factors STAT1, STAT3, and p53 inhibit autophagy in I/R. MicroRNAs could stimulate and inhibit autophagy in the heart in I/R. Long noncoding RNAs regulate the viability and autophagy of cardiomyocytes in hypoxia/reoxygenation (H/R). Nitric oxide (NO) donors and endogenous NO could activate autophagy of cardiomyocytes. Activation of heme oxygenase-1 promotes cardiomyocyte tolerance to H/R and enhances autophagy. Hydrogen sulfide increases cardiac tolerance to I/R and inhibits apoptosis and autophagy via mTOR and PI3-kinase activation.

The inhibition of PGAM5 suppresses seizures in a kainate-induced epilepsy model via mitophagy reduction

Background

Epilepsy is a common neurological disease, and excessive mitophagy is considered as one of the major triggers of epilepsy. Mitophagy is a crucial pathway affecting reactive oxygen species. Phosphoglycerate mutase 5 (PGAM5) is a protein phosphatase present in mitochondria that regulates many biological processes including mitophagy and cell death. However, the mechanism of PGAM5 in epilepsy remains unclear. The purpose of the present study was to examine whether PGAM5 affects epilepsy through PTEN-induced putative kinase 1 (PINK1)-mediated mitophagy.

Methods

After the knockdown of PGAM5 expression by the adeno-associated virus, an epilepsy model was created by kainic acid. Next, the seizure activity was recorded by local field potentials before evaluating the level of mitochondrial autophagy marker proteins. Lastly, the ultrastructure of mitochondria, neuronal damage and oxidative stress levels were further observed.

Results

A higher PGAM5 level was found in epilepsy, and its cellular localization was in neurons. The interactions between PGAM5 and PINK1 in epilepsy were further found. After the knockdown of PGAM5, the level of PINK1 and light chain 3B was decreased and the expression of the translocase of the inner mitochondrial membrane 23 and translocase of the outer mitochondrial membrane 20 were both increased. Knockdown of PGAM5 also resulted in reduced neuronal damage, decreased malondialdehyde levels, decreased reactive oxygen species production and increased superoxide dismutase activity. In addition, the duration of spontaneous seizure-like events (SLEs), the number of SLEs and the time spent in SLEs were all reduced in the epilepsy model after inhibition of PGAM5 expression.

Conclusion

Inhibition of PGAM5 expression reduces seizures via inhibiting PINK1-mediated mitophagy.

Mitochondrial quality control in cardiac ischemia/reperfusion injury: new insights into mechanisms and implications

The current effective method for the treatment of myocardial infarction is timely restoration of the blood supply to the ischemic area of the heart. Although reperfusion is essential for reestablishing oxygen and nutrient supplies, it often leads to additional myocardial damage, creating an important clinical dilemma. Reports from long-term studies have confirmed that mitochondrial damage is the critical mechanism in cardiac ischemia/reperfusion (I/R) injury. Mitochondria are dynamic and possess a quality control system that targets mitochondrial quantity and quality by modifying mitochondrial fusion, fission, mitophagy, and biogenesis and protein homeostasis to maintain a healthy mitochondrial network. The system of mitochondrial quality control involves complex molecular machinery that is highly interconnected and associated with pathological changes such as oxidative stress, calcium overload, and endoplasmic reticulum (ER) stress. Because of the critical role of the mitochondrial quality control systems, many reports have suggested that defects in this system are among the molecular mechanisms underlying myocardial reperfusion injury. In this review, we briefly summarize the important role of the mitochondrial quality control in cardiomyocyte function and focus on the current understanding of the regulatory mechanisms and molecular pathways involved in mitochondrial quality control in cardiac I/R damage.

Hydrogen therapy after resuscitation improves myocardial injury involving inhibition of autophagy in an asphyxial rat model of cardiac arrest

Hydrogen (H₂) therapy is a therapeutic strategy using molecular H₂. Due to its ability to regulate cell homeostasis, H₂ therapy has exhibited marked therapeutic effects on a number of oxidative stress-associated diseases. The present study investigated the effectiveness of H₂ therapy in protecting against myocardial injury in a rat model of asphyxial cardiac arrest and cardiopulmonary resuscitation. Rats underwent 10-min asphyxia-induced cardiac arrest (CA) and cardiopulmonary resuscitation (CPR), and were randomly divided into control and H₂ therapy groups. After resuscitation, the H₂ therapy group was administered room air mixed with 2% H₂ gas for respiration. During CA/CPR, the arterial pressure and heart rate were measured every minute. Survival rate, cardiac function, myocardial injury biomarkers creatine kinase-MB and cardiac troponin-T, and histopathological changes were evaluated to determine the protective effects of H₂ therapy in CA/CPR. Immunohistochemistry and western blot analysis were used to determine the expression levels of autophagy-associated proteins. In vitro, H9C2 cells were subjected to hypoxia/reoxygenation and H₂-rich medium was used in H₂ treatment groups. Western blotting and immunofluorescence were used to observe the expression levels of autophagy-associated proteins. Moreover, an adenovirus-monomeric red fluorescent protein-green fluorescent protein-LC3 construct was used to explore the dynamics of autophagy in the H9C2 cells. The results showed that H₂ therapy significantly improved post-resuscitation survival and cardiac function. H₂ therapy also improved mitochondrial mass and decreased autophagosome numbers in cardiomyocytes after resuscitation. The treatment inhibited autophagy activation, with lower expression levels of autophagy-associated proteins and decreased autophagosome formation in vivo and vitro. In conclusion, H₂ gas inhalation after return of spontaneous circulation improved cardiac function via the inhibition of autophagy.

Temporal Effect of Melatonin Posttreatment on Anoxia/Reoxygenation Injury in H9c2 Cells

Melatonin has been proven to reduce myocardial ischemia-reperfusion (MI/R) injury. However, in most studies, melatonin was administered prior to MI/R, thus, the results lack clinical significance in patients with acute myocardial infarction. We hypothesize that melatonin posttreatment at different times has different curative effects. Administered of Melatonin (150 μM) at different times after the onset of reoxygenation (t=-15, 0, 5, 10, 15, 30 min). Cellular apoptosis, oxidative stress and mitochondrial function were assessed. Mitophagy-related protein levels, the mitochondrial membrane potential (MMP) and mitochondrial permeability transition pore (mPTP) activity were also measured. A/R injury upregulated mitophagy, which was associated with increased cellular apoptosis, oxidative stress and mitochondrial dysfunction. Melatonin posttreatment (t= -15, 0, 5, 10, 15, 30 min) significantly inhibited excessive mitophagy after A/R injury, reduced cellular apoptosis and oxidative stress, restored mitochondrial function and MMP, and restrained mPTP opening. The therapeutic time window in which melatonin posttreatment protected H9c2 cells against A/R injury was large (from -15 to 30 min after the onset of reperfusion), but the earlier the melatonin administration was, the better its protective effect was. This mechanism is likely due to a reduction in mPTP activity and MMP collapse, which lead to the inhibition of mitophagy. This article is protected by copyright. All rights reserved.

Advances in Cardiotoxicity Induced by Altered Mitochondrial Dynamics and Mitophagy

Mitochondria are the most abundant organelles in cardiac cells, and are essential to maintain the normal cardiac function, which requires mitochondrial dynamics and mitophagy to ensure the stability of mitochondrial quantity and quality. When mitochondria are affected by continuous injury factors, the balance between mitochondrial dynamics and mitophagy is broken. Aging and damaged mitochondria cannot be completely removed in cardiac cells, resulting in energy supply disorder and accumulation of toxic substances in cardiac cells, resulting in cardiac damage and cardiotoxicity. This paper summarizes the specific underlying mechanisms by which various adverse factors interfere with mitochondrial dynamics and mitophagy to produce cardiotoxicity and emphasizes the crucial role of oxidative stress in mitophagy. This review aims to provide fresh ideas for the prevention and treatment of cardiotoxicity induced by altered mitochondrial dynamics and mitophagy.

Melatonin postconditioning ameliorates anoxia/reoxygenation injury by regulating mitophagy and mitochondrial dynamics in a SIRT3-dependent manner

Ischaemia/reperfusion (I/R) injury is accompanied by excessive mitochondrial autophagy (mitophagy) and an imbalance in mitochondrial dynamics. Melatonin has been reported to alleviate I/R injury by regulating mitophagy and mitochondrial dynamics. However, the underlying mechanism associated with this activity is not fully understood. The goal of the present study was to investigate whether and how melatonin administration at the beginning of reoxygenation exerts protective effects by regulating mitophagy and mitochondrial dynamics. H9c2 cells were transfected with sirtuin 3 (SIRT3)-targeting siRNA and then subjected to anoxia/reoxygenation (A/R) injury, with melatonin (150 μM) administered at the onset of reoxygenation. Biomarkers related to cellular apoptosis, oxidative stress, mitochondrial function, mitophagy and mitochondrial dynamics were assessed, and the expression and activity of SIRT3 was also measured. Mitochondrial fission and mitophagy were activated after A/R injury and were accompanied by cellular apoptosis, oxidative stress, and mitochondrial dysfunction. However, melatonin postconditioning inhibited excessive mitochondrial fission and mitophagy, promoted mitochondrial fusion, restored mitochondrial function and reduced cellular apoptosis, and the mitophagy inhibitor 3-methyladenine (3-MA) also attenuated A/R-induced apoptosis. Moreover, the A/R-induced decreases in SIRT3 and manganese superoxide dismutase (SOD2) activities were ameliorated by melatonin. However, SIRT3 silencing abolished the beneficial effects of melatonin, eliminated the inhibitory effects of melatonin on mitochondrial fission and mitophagy, and reversed the melatonin-induced increase in SOD2 activity. These results indicate that melatonin postconditioning protects H9c2 cells from A/R injury by inhibiting excessive mitophagy and maintaining the balance of mitochondrial fission and fusion in a SIRT3-dependent manner.

Deletion of Mitochondrial Translocator Protein (TSPO) Gene Decreases Oxidative Retinal Pigment Epithelial Cell Death via Modulation of TRPM2 Channel

Simple Summary

18 kDa mitochondrial translocator protein (TSPO) is a mitochondria protein of the cellular outer membrane in the mitochondria of several cells, including ARPE19 is TSPO. Accumulating evince indicates that the presence of TSPO participated the modulations of Ca²⁺ homeostasis and mitochondrial free reactive oxygen species (fROS) generation. The deletion of TSPO gene provides to study the action of TSPO on the levels of apoptosis, ADP-ribose (ADPR), mitochondria-fROS (Mito-fROS), and apoptosis via the stimulation of Ca²⁺ permeable channels in the models of cell culture. The stimulations of oxidative stress and ADPR induce the activation of TRPM2 in the ARPE19. For clarifying the involvement of TSPO in retinal human diseases, we used the ARPE19 human cell culture model. The current results demonstrated that the deletion of TSPO induces the regulation of TRPM2 in the TSPO gene knockout ARPE19 (ARPE19-KO) In fact, the present results show that the presence of TSPO increased the upregulations of apoptosis and mitochondria oxidative cytotoxicity values via stimulation of TRPM2 in the ARPE19. Nevertheless, the blockages of PARP-1 (PJ34 and DPQ) and TRPM2 (2APB and ACA) downregulated the values of cell death and oxidative cytotoxicity in the ARPE19. In summary, present results clearly demonstrate that the deletion of TSPO decreases mitochondrial oxidative cytotoxicity-mediated cell death via the modulation of TRPM2 in the ARPE19.

Abstract

The current results indicated the possible protective actions of 18 kDa mitochondrial translocator protein (TSPO) deletion on TRPM2 stimulation, mitochondrial free ROS (Mito-fROS) and apoptotic harmful actions in the cells of adult retinal pigment epithelial19 (ARPE19). There was a direct relationship between TSPO and the disease of age-related macular degeneration. The nature of TSPO implicates upregulation of Mito-fROS and apoptosis via the activation of Ca²⁺ channels in ARPE19, although deletion of TSPO gene downregulates the activation. The decrease of oxidative cytotoxicity and apoptosis might induce in TSPO gene deleted cells by the inhibition of Mito-fROS and PARP-1 activation-induced TRPM2 cation channel activation. The ARPE19 cells were divided into two main groups as TSPO expressing (ARPE19) and non-expressing cells (ARPE19-KO). The levels of caspase -3 (Casp -3), caspase -9 (Casp -9), apoptosis, Mito-fROS, TRPM2 current and intracellular free Ca²⁺ were upregulated in the ARPE19 by the stimulations of H₂O₂ and ADP-ribose, although their levels were downregulated in the cells by the modulators of PARP-1 (DPQ and PJ34), TRPM2 (ACA and 2APB) and glutathione. However, the H₂O₂ and ADP-ribose-mediated increases were not observed in the ARPE19-KO. The expression levels of Bax, Casp -3, Casp -9 and PARP-1 were higher in the ARPE19 group as compared to the ARPE19-KO group. In summary, current results confirmed that TRPM2-mediated cell death and oxidative cytotoxicity in the ARPE19 cells were occurred by the presence of TSPO. The deletion of TSPO may be considered as a therapeutic way to TRPM2 activation-mediated retinal oxidative injury.

Poly(ADP-Ribosyl) Code Functions

Poly(ADP-ribosyl)ation plays a key role in cellular metabolism. Covalent poly(ADP-ribosyl)ation affects the activity of the proteins engaged in DNA repair, chromatin structure regulation, gene expression, RNA processing, ribosome biogenesis, and protein translation. Non-covalent PAR-dependent interactions are involved in the various types of cellular response to stress and viral infection, such as inflammation, hormonal signaling, and the immune response. The review discusses how structurally different poly(ADP-ribose) (PAR) molecules composed of identical monomers can differentially participate in various cellular processes acting as the so-called "PAR code." The article describes the ability of PAR polymers to form functional biomolecular clusters through a phase-separation in response to various signals. This phase-separation contributes to rapid spatial segregation of biochemical processes and effective recruitment of the necessary components. The cellular PAR level is tightly controlled by a network of regulatory proteins: PAR code writers, readers, and erasers. Impaired PAR metabolism is associated with the development of pathological processes causing oncological, cardiovascular, and neurodegenerative diseases. Pharmacological correction of the PAR level may represent a new approach to the treatment of various diseases.

Melatonin and regulation of autophagy: Mechanisms and therapeutic implications

Mitochondria are essential subcellular units that generate basic energy for the cell, as well as influence Ca²⁺ flux, apoptosis, and cell signaling. Mitophagy can selectively remove impaired mitochondria to preserve mitochondrial function, which is crucial for normal cellular maintenance. Mitochondrial dysfunction and mitophagy are widely reported to be linked to various pathogeneses. In addition, there is increasing evidence regarding the beneficial role of melatonin in the regulation and intervention of mitophagy progression. In this review, we focus on specific pathological conditions, including ischemia/reperfusion injury (IRI), cancer and neurodegenerative diseases, and elucidate the essential role of melatonin in the modulation of mitophagy in each of these distinct disorders.

Dexmedetomidine inhibits pyroptosis by down-regulating miR-29b in myocardial ischemia reperfusion injury in rats

OBJECTIVE

Dexmedetomidine (DEX) was reported to protect heart against ischemic-reperfusion (IR) but the mechanism herein remains elusive. This study aims to explore the mechanism of DEX on pyroptosis induced by myocardial ischemic reperfusion (MIR).

METHODS

MIR rat models were established and injected DEX or miR-29b agomir/antagomir separately. The possible effect of DEX or miR-29b on myocardial cells was assessed according to measurement on creatine kinase-MB (CK-MB), cardiac troponin I (cTnI), interleukin-1β (IL-1β) and interleukin-18 (IL-18), myocardial infarction size, myocardial injury and apoptosis. Western blot determined the expression levels of nucleotide-binding oligomerization domain-like receptor protein 3 (NLRP3), apoptosis-associated speck-like protein containing CARD (ASC) and cleaved-caspase-1. Hypoxia/reoxygenation (H/R) cell model was established. The lactate dehydrogenase (LDH) content released by myocardial cells was examined. The relation between miR-29b and FoxO3a was confirmed by dual luciferase reporter gene assay. FoxO3a or ARC level was elevated in H/R myocardial cells to detect its effect on pyroptosis.

RESULTS

MIR rat models were successfully established, in which cell pyroptosis was triggered as evidenced by increased expression levels of NLRP3, ASC and cleaved-caspase-1. Rats with DEX precondition had attenuated cell pyroptosis and ameliorated inflammatory response. FoxO3a was a target of miR-29b. MiR-29b agomir or miR-29b antagomir could inhibit or promote the protective effect of DEX on MIR. Overexpression of FoxO3a/ARC axis could suppress myocardial pyroptosis induced by H/R.

CONCLUSION

DEX could ameliorate MIR injury (MIRI) and H/R injury in rats and inhibit H/R induced pyroptosis in myocardial cells via down-regulating miR-29b to activate FoxO3a/ARC axis.

Melatonin Attenuates Anoxia/Reoxygenation Injury by Inhibiting Excessive Mitophagy Through the MT2/SIRT3/FoxO3a Signaling Pathway in H9c2 Cells

Purpose

Autophagy caused by ischemia/reperfusion (I/R) increases the extent of cardiomyocyte damage. Melatonin (Mel) diminishes cardiac injury through regulating autophagy and mitochondrial dynamics. However, illustrating the specific role of mitophagy in the cardioprotective effects of melatonin remains a challenge. The aim of our research was to investigate the impact and underlying mechanisms of melatonin in connection with mitophagy during anoxia/reoxygenation (A/R) injury in H9c2 cells.

Methods

H9c2 cells were pretreated with melatonin with or without the melatonin membrane receptor 2 (MT2) antagonist 4-P-PDOT, the MT2 agonist IIK7 and the sirtuin 3 (SIRT3) inhibitor 3-TYP for 4 hours and then subjected to A/R injury. Cell viability, cellular apoptosis, necrosis levels and oxidative markers were assessed. The expression of SIRT3 and forkhead box O3a (FoxO3a), mitochondrial function and the levels of mitophagy-related proteins were also evaluated.

Results

A/R injury provoked enhanced mitophagy in H9c2 myocytes. In addition, increased mitophagy was correlated with decreased cellular viability, increased oxidative stress and mitochondrial dysfunction in H9c2 cells. However, melatonin pretreatment notably increased cell survival and decreased cell apoptosis and oxidative response after A/R injury, accompanied by restored mitochondrial function. The inhibition of excessive mitophagy is involved in the cardioprotective effects of melatonin, as shown by the decreased expression of the mitophagy-related molecules Parkin, Beclin1, and BCL2-interacting protein 3-like (BNIP3L, best known as NIX) and decreased light chain 3 II/light chain 3 I (LC3 II/LC3 I) ratio and upregulation of p62 expression. Moreover, the decreased expression of SIRT3 and FoxO3a in A/R-injured H9c2 cells was abrogated by melatonin, but these beneficial effects were attenuated by the MT2 antagonist 4-P-PDOT or the SIRT3 inhibitor 3-TYP and enhanced by the MT2 agonist IIK7.

Conclusion

These results indicate that melatonin protects H9c2 cells during A/R injury through suppressing excessive mitophagy by activating the MT2/SIRT3/FoxO3a pathway. Melatonin may be a useful candidate for alleviating myocardial ischemia/reperfusion (MI/R) injury in the future, and the MT2 receptor might become a therapeutic target.

New insights into the role of mitochondria in cardiac microvascular ischemia/reperfusion injury

As reperfusion therapies have become more widely used in acute myocardial infarction patients, ischemia-induced myocardial damage has been markedly reduced, but reperfusion-induced cardiac injury has become increasingly evident. The features of cardiac ischemia-reperfusion (I/R) injury include microvascular perfusion defects, platelet activation and sequential cardiomyocyte death due to additional ischemic events at the reperfusion stage. Microvascular obstruction, defined as a no-reflow phenomenon, determines the infarct zone, myocardial function and peri-operative mortality. Cardiac microvascular endothelial cell injury may occur much earlier and with much greater severity than cardiomyocyte injury. Endothelial cells contain fewer mitochondria than other cardiac cells, and several of the pathological alterations during cardiac microvascular I/R injury involve mitochondria, such as increased mitochondrial reactive oxygen species (mROS) levels and disturbed mitochondrial dynamics. Although mROS are necessary physiological second messengers, high mROS levels induce oxidative stress, endothelial senescence and apoptosis. Mitochondrial dynamics, including fission, fusion and mitophagy, determine the shape, distribution, size and function of mitochondria. These adaptive responses modify extracellular signals and orchestrate intracellular processes such as cell proliferation, migration, metabolism, angiogenesis, permeability transition, adhesive molecule expression, endothelial barrier function and anticoagulation. In this review, we discuss the involvement of mROS and mitochondrial morphofunction in cardiac microvascular I/R injury.

Mitophagy: A crucial modulator in the pathogenesis of chronic diseases

Mitophagy is an autophagic process through which damaged or dysfunctional mitochondria are specifically degraded to maintain cellular homeostasis. It is highly regulated by various signaling pathways such as the PTEN-induced putative kinase 1 (PINK1)/Parkin and NIP3-like protein X (NIX)/BNIP3 pathways. Additionally, it plays a crucial role in inducing some pathological processes. Notably, some evidence suggesting the association of mitophagy with the occurrence of chronic diseases such as Parkinson's disease (PD), cancer, diabetes, atherosclerosis (AS), and myocardial ischemia reperfusion (MIR) injury is available. Particularly, it has been reported that mitophagy could hinder the development of PD by activating the PINK1/Parkin pathway and acting as a defense mechanism against the induction of diabetes. Conversely, the induction of mitophagy plays dual roles in driving the process of cancer, AS, and MIR injury. In this review, we have explained the role and regulatory mechanisms through which mitophagy plays a role in these chronic pathologies. Importantly, the pharmacological targeting of mitophagy might prove to be a potential alternative for the treatment of these chronic diseases.

Poly (ADP-ribose) polymerase inhibition protects against myocardial ischaemia/reperfusion injury via suppressing mitophagy

Myocardial ischaemia/reperfusion (I/R) injury attenuates the beneficial effects of reperfusion therapy. Poly(ADP-ribose) polymerase (PARP) is overactivated during myocardial I/R injury. Mitophagy plays a critical role in the development of myocardial I/R injury. However, the effect of PARP activation on mitophagy in cardiomyocytes is unknown. In this study, we found that I/R induced PARP activation and mitophagy in mouse hearts. Poly(ADP-ribose) polymerase inhibition reduced the infarct size and suppressed mitophagy after myocardial I/R injury. In vitro, hypoxia/reoxygenation (H/R) activated PARP, promoted mitophagy and induced cell apoptosis in cardiomyocytes. Poly(ADP-ribose) polymerase inhibition suppressed H/R-induced mitophagy and cell apoptosis. Parkin knockdown with lentivirus vectors inhibited mitophagy and prevented cell apoptosis in H/R-treated cells. Poly(ADP-ribose) polymerase inhibition prevented the loss of the mitochondrial membrane potential (ΔΨm). Cyclosporin A maintained ΔΨm and suppressed mitophagy but FCCP reduced the effect of PARP inhibition on ΔΨm and promoted mitophagy, indicating the critical role of ΔΨm in H/R-induced mitophagy. Furthermore, reactive oxygen species (ROS) and poly(ADP-ribosylation) of CypD and TSPO might contribute to the regulation of ΔΨm by PARP. Our findings thus suggest that PARP inhibition protects against I/R-induced cell apoptosis by suppressing excessive mitophagy via the ΔΨm/Parkin pathway.