Hydrogen-rich saline alleviates inflammation and apoptosis in myocardial I/R injury via PINK-mediated autophagy

MicroRNA‑494 suppresses hypoxia/reoxygenation‑induced cardiomyocyte apoptosis and autophagy via the PI3K/AKT/mTOR signaling pathway by targeting SIRT1

Acute myocardial infarction can be caused by ischemia/reperfusion (I/R) injury; however, the mechanism underlying I/R is not completely understood. The present study investigated the functions and mechanisms underlying microRNA (miR)-494 in I/R-induced cardiomyocyte apoptosis and autophagy. Hypoxia/reoxygenation (H/R)-treated H9c2 rat myocardial cells were used as an in vitro I/R injury model. Apoptosis and autophagy were analyzed by Cell Counting Kit-8 assay, Lactic dehydrogenase and superoxide dismutase assay, flow cytometry, TUNEL staining and western blotting. Reverse transcription-quantitative PCR demonstrated that, H9c2 cells treated with 12 h hypoxia and 3 h reoxygenation displayed significantly downregulated miR-494 expression levels compared with control cells. Compared with the corresponding negative control (NC) groups, miR-494 mimic reduced H/R-induced cell apoptosis and autophagy, whereas miR-494 inhibitor displayed the opposite effects. Silent information regulator 1 (SIRT1) was identified as a target gene of miR-494. Furthermore, miR-494 inhibitor-mediated effects on H/R-induced cardiomyocyte apoptosis and autophagy were partially reversed by SIRT1 knockdown. Moreover, compared with si-NC, SIRT1 knockdown significantly increased the phosphorylation levels of PI3K, AKT and mTOR in H/R-treated and miR-494 inhibitor-transfected H9c2 cells. Collectively, the results indicated that miR-494 served a protective role against H/R-induced cardiomyocyte apoptosis and autophagy by directly targeting SIRT1, suggesting that miR-494 may serve as a novel therapeutic target for myocardial I/R injury.

Prolylcarboxypeptidase Mitigates Myocardial Ischemia/Reperfusion Injury by Stabilizing Mitophagy

The role of prolylcarboxypeptidase (PRCP) in myocardial ischemia/reperfusion (I/R) injury is unclear. Herein, we aimed to evaluate the protective effect of the PRCP-angiotensin-(1-7) [Ang-(1-7)]/bradykinin-(1-9) [BK-(1-9)] axis on myocardial I/R injury and identify the mechanisms involved. Plasma PRCP level and activity, as well as Ang-(1-7) and BK-(1-9) levels, were compared in healthy subjects, patients with unstable angina, and those with ST-segment-elevated acute myocardial infarction (AMI). Thereafter, the effects of PRCP overexpression and knockdown on left ventricular function, mitophagy, and levels of Ang-(1-7) and BK-(1-9) were examined in rats during myocardial I/R. Finally, the effects of Ang-(1-7) and BK-(1-9) on I/R-induced mitophagy and the signaling pathways involved were investigated in vitro in rat cardiomyocytes. AMI patients showed increased plasma level and activity of PRCP and levels of Ang-(1-7) and BK-(1-9) as compared with healthy subjects and those with unstable angina. PRCP protected against myocardial I/R injury in rats by paradoxical regulation of cardiomyocyte mitophagy during the ischemia and reperfusion phases, which was mediated by downstream Ang-(1-7) and BK-(1-9). We further depicted a possible role of activation of AMPK in mitophagy induction during ischemia and activation of Akt in mitophagy inhibition during reperfusion in the beneficial effects of Ang-(1-7) and BK-(1-9). Thus, the PRCP-Ang-(1-7)/BK-(1-9) axis may protect against myocardial I/R injury by paradoxical regulation of cardiomyocyte mitophagy during ischemia and reperfusion phases.

Mitochondrial quality control mechanisms as molecular targets in cardiac ischemiareperfusion injury

Mitochondrial damage is a critical contributor to cardiac ischemia/reperfusion (I/R) injury. Mitochondrial quality control (MQC) mechanisms, a series of adaptive responses that preserve mitochondrial structure and function, ensure cardiomyocyte survival and cardiac function after I/R injury. MQC includes mitochondrial fission, mitochondrial fusion, mitophagy and mitochondria-dependent cell death. The interplay among these responses is linked to pathological changes such as redox imbalance, calcium overload, energy metabolism disorder, signal transduction arrest, the mitochondrial unfolded protein response and endoplasmic reticulum stress. Excessive mitochondrial fission is an early marker of mitochondrial damage and cardiomyocyte death. Reduced mitochondrial fusion has been observed in stressed cardiomyocytes and correlates with mitochondrial dysfunction and cardiac depression. Mitophagy allows autophagosomes to selectively degrade poorly structured mitochondria, thus maintaining mitochondrial network fitness. Nevertheless, abnormal mitophagy is maladaptive and has been linked to cell death. Although mitochondria serve as the fuel source of the heart by continuously producing adenosine triphosphate, they also stimulate cardiomyocyte death by inducing apoptosis or necroptosis in the reperfused myocardium. Therefore, defects in MQC may determine the fate of cardiomyocytes. In this review, we summarize the regulatory mechanisms and pathological effects of MQC in myocardial I/R injury, highlighting potential targets for the clinical management of reperfusion.

Downregulation of DEC1 by RNA interference attenuates ischemia/reperfusion-induced myocardial inflammation by inhibiting the TLR4/NF-κB signaling pathway

Inflammation has been implicated in the pathogenesis of myocardial ischemia/reperfusion (I/R) injury (MIRI). Previous studies have confirmed that deleted in esophageal cancer 1 (DEC1) is an important transcription factor in inflammation. However, the role of DEC1 in MIRI remains unclear. The present study aimed to determine whether the downregulation of DEC1 by RNA interference alleviated inflammation to protect against MIRI. Adult Sprague-Dawley rats (n=48) were randomly divided into four groups: Sham; I/R; adenovirus expressing green fluorescent protein control (Ad-G-Control); and DEC1-targeting RNA interference (Ad-G-DEC1) groups. Following gene delivery 4 days later, the rat myocardial I/R model was established and myocardial enzymes [creatine kinase (CK) and lactate dehydrogenase (LDH)] were detected. Hematoxylin and eosin (H&E) staining was performed to evaluate the myocardial damage and the infarct area was assessed using Evans Blue/triphenyltetrazolium chloride staining. The inflammatory mediators interleukin (IL)-β and tumor necrosis factor (TNF)-α were also detected using ELISA kits to assess the inflammatory response. Finally, western blotting and reverse transcription-quantitative PCR were used to analyze the expression levels of associated proteins and mRNAs. Ad-G-DEC1 RNA interference markedly decreased DEC1 expression levels. In addition, following the downregulation of DEC1 expression, the infarct size, CK, LDH, Toll-like receptor (TLR)4, NF-κB, IL-β and TNF-α levels were all significantly decreased. In conclusion, the results of the present study suggested that the downregulation of DEC1 may decrease the inflammation by suppressing the TLR4/NF-κB signaling pathway, which may represent a therapeutic target for MIRI.

Ube2s-stabilized β-catenin protects against myocardial ischemia/reperfusion injury by activating HIF-1α signaling

The activation of hypoxia-inducible factor (HIF) is an important event for mediating the adaptive response to myocardial ischemia/reperfusion (MI/R) injury. The ubiquitin-conjugating enzyme E2S (Ube2s) catalyzes ubiquitin conjugation to target proteins. Here, we report the positive regulation of HIF-1α signaling by Ube2s via stabilizing β-catenin, by which Ube2s acts to protect against MI/R injury. We show that Ube2s expression is upregulated in the hearts of mice subjected to MI/R injury. Functionally, Ube2s depletion exacerbates and its overexpression ameliorates MI/R injury. In addition, Ube2s augments the activation of HIF-1α and reduces myocardial apoptosis. Moreover, Ube2s induces the accumulation of β-Catenin through increasing its stabilization. Importantly, β-Catenin knockdown abrogates Ube2s-augmented HIF-1α activation, and meanwhile, diminishes the protective effect of Ube2s on MI/R injury, thus establishing a causal link between Ube2s-stabilized β-catenin and HIF-1α-mediated myocardial protection. Altogether, this study identifies the Ube2s/β-catenin/HIF-1α axis as a novel protective regulator involved in MI/R injury, and also implies that it might represent a potential therapeutic target for ameliorating MI/R injury.

Pathological Roles of Mitochondrial Oxidative Stress and Mitochondrial Dynamics in Cardiac Microvascular Ischemia/Reperfusion Injury

Mitochondria are key regulators of cell fate through controlling ATP generation and releasing pro-apoptotic factors. Cardiac ischemia/reperfusion (I/R) injury to the coronary microcirculation has manifestations ranging in severity from reversible edema to interstitial hemorrhage. A number of mechanisms have been proposed to explain the cardiac microvascular I/R injury including edema, impaired vasomotion, coronary microembolization, and capillary destruction. In contrast to their role in cell types with higher energy demands, mitochondria in endothelial cells primarily function in signaling cellular responses to environmental cues. It is clear that abnormal mitochondrial signatures, including mitochondrial oxidative stress, mitochondrial fission, mitochondrial fusion, and mitophagy, play a substantial role in endothelial cell function. While the pathogenic role of each of these mitochondrial alterations in the endothelial cells I/R injury remains complex, profiling of mitochondrial oxidative stress and mitochondrial dynamics in endothelial cell dysfunction may offer promising potential targets in the search for novel diagnostics and therapeutics in cardiac microvascular I/R injury. The objective of this review is to discuss the role of mitochondrial oxidative stress on cardiac microvascular endothelial cells dysfunction. Mitochondrial dynamics, including mitochondrial fission and fusion, are critically discussed to understand their roles in endothelial cell survival. Finally, mitophagy, as a degradative mechanism for damaged mitochondria, is summarized to figure out its contribution to the progression of microvascular I/R injury.