Role of the lncRNA MALAT1/miR-1 Pathway in Mouse Myocardial Ischemia-Reperfusion Injury.

Myocardial ischemia-reperfusion (I/R) injury is leading cause of death worldwide. miR-34a-5p was up-regulated in myocardial ischemia-reperfusion injury rats. We aim to explore how miR-34a-5p inhibition protected myocardium against I/R injury in both cell and animal models. In vivo rat and in vitro cell model were firstly constructed. quantitative real-time polymerase chain reaction was employed to investigate expression of miR-34a-5p and its target genes. Functional assays were conducted to detect the impact of miR-34a-5p on myocardial I/R injury. Enzyme-linked immunosorbent assay was performed to validate the expression levels of marker proteins of ischemia-reperfusion I/R-induced myocardial injury. MTT was performed to assess the cell viability and flow cytometry was utilized to detect cell apoptosis and reactive oxygen species accumulation. The interaction between miR-34a-5p and Notch Receptor 1 were also examined through luciferase reporter assay. miR-34a-5p was up-regulated post-reperfusion at rat myocardium. miR-34a-5p inhibitor attenuated myocardial ischemia-reperfusion injury, as shown by decreasing apoptosis rate, reducing infarct size and reactive oxygen species accumulation. In in vitro cell model, miR-34a-5p inhibitor also promoted cell proliferation, inhibited cell apoptosis and reactive oxygen species accumulation through targeting Notch Receptor 1 signaling. Our results revealed that miR-34a-5p knocking down attenuated myocardial I/R injury by promoting Notch Receptor 1 signaling-mediated inhibition of reactive oxygen species accumulation and cell apoptosis. Hence, miR-34a-5p might be a potential target for treatment of myocardial ischemia-reperfusion injury.

MicroRNAs are well-known RNA regulators modulating biological functions in complex signaling networks. This work aims to explore the impact of microRNA-92b-3p (miR-92b-3p) on myocardial ischemia-reperfusion (I/R) injury.The I/R model was established by left anterior descending coronary artery ligation in mice. The hemodynamic parameters were detected through a multichannel physiological recorder. Myocardial injury markers: serum cardiac troponin I, myocardial kinase isoenzyme (creatine kinase-MB), and serum inflammatory factors (tumor necrosis factor-α, interleukin [IL]-1β, and IL-6) were evaluated by enzyme-linked immunosorbent assay. Cardiac tissue oxidative stress-related factors (malondialdehyde, glutathione peroxidase, total antioxidation capability, and superoxide dismutase) were assessed by colorimetry, myocardial pathology was observed by hematoxylin-eosin staining, and cardiomyocyte apoptosis was measured by triphosphate nick end-labeling staining, as well as the expression of miR-92b-3p and mitogen-activated protein kinase kinase kinase 2 (MAP3K2) in cardiac tissues were determined by reverse transcription quantitative polymerase chain reaction or western blot assay. The targeting relationship between miR-92b-3p and MAP3K2 was verified by bioinformatics, RNA immunoprecipitation, and luciferase reporter assays.miR-92b-3p was lowly expressed and MAP3K2 was highly expressed in myocardial I/R injury mice. Upregulation of miR-92b-3p improved hemodynamic indices, decreased serum levels of myocardial injury biomarkers, inhibited serum inflammatory response, alleviated cardiac tissue oxidative stress, relieved myocardial pathology, and reduced cardiomyocyte apoptosis during the myocardial I/R injury in mice. MAP3K2 was a direct target gene of miR-92b-3p.This research suggests that miR-92b-3p protects against myocardial I/R injury by inhibiting MAP3K2, which may provide novel candidates for treatment of myocardial I/R injury.

Myocardial ischemia-reperfusion (IR) injury is a common cardiovascular problem, which remains a major cause of death in the world. Emerging evidence has suggested that long noncoding RNAs are crucial players in myocardial injury. However, the functional involvement of nuclear enriched abundant transcript 1 (NEAT1) in myocardial IR injury remains poorly investigated. Our study focused on the mechanism of NEAT1 in myocardial IR injury. Here, we reported a crucial role for NEAT1 in exacerbating cardiac IR injury. NEAT1 was greatly increased in myocardial IR injury mice models. As exhibited knockdown of NEAT1 resulted in attenuated myocardial IR injury in vivo. In addition, we found that NEAT1 was dramatically induced by hypoxia/reoxygenation in H9c2 cells. Lactate dehydrogenase (LDH), malondialdehyde, reactive oxygen species levels, and endoplasmic reticulum stress-regulated cardiomyocyte apoptosis were inhibited by the downregulation of NEAT1. Here, it was shown that knockdown of NEAT1 was able to repress tumor necrosis factor-α, interleukin-1β, and IL-6 expression. The silence of NEAT1 protected against IR injury via decreasing troponin levels, cardiocytes apoptosis, creatine kinase, and lactate LDH release in vivo. Meanwhile, the mitogen-activated protein kinase (MAPK) signaling was involved in NEAT1-mediated myocardial IR injury. In summary, our data indicated that NEAT1 contributed to myocardial IR injury via activating the MAPK pathway.

Objective To observe the effect of nuclear factor-erythroid 2-related factor 2 (Nrf2) in diabetic rats preconditioning with resveratrol (Res) against myocardial ischemia/reperfusion injury (MI/RI). Methods Healthy adult male SD rats weighing 200- 220 g and aged from 4 to 5 months were fed with high-fat diet for 4 weeks and then intraperitoneally injected with streptozotocin (STZ) 30 mg/kg to establish a diabetic rat model. Thirty successfully modeled rats were divided into three groups according to a random number table (n=10): a sham operation group (a Sham group), a myocardial ischemia/reperfusion group (an MI/R group) and a myocardial ischemia/reperfusion+resveratrol group (an MI/R+Res group). A rat model of MI/RI was established by ligation of the left anterior descending coronary artery for 30 min before reperfusion for 120 min. In the MI/R+Res group, 15 mg/kg Res was intraperitoneally injected 7 d before establishment of the MI/RI model, once a day for 7 consecutive days. The Sham and MI/R groups were intraperitoneally injected with an equal volume of dimethyl sulfoxide (DMSO) and PBS mixture. Left ventricular ejection fraction (LVEF) and left ventricular short axis shortening (FS) were measured by B-mode ultrasonography. Five rats were sacrificed 120 min after reperfusion. Myocardial infarction size was measured by 2, 3, 5-triphenyl-2H-tetrazolium chloride (TTC) staining. Another five rats were sacrificed to collect blood samples from the abdominal aorta for measurement of lactate dehydrogenase (LDH), a marker of myocardial injury, and creatine kinase isoenzyme (CK-MB). Their myocardial tissues were collected to determine the levels of superoxide dismutase(SOD), malondialdehyde (MDA) and reactive oxygen species (ROS) by enzyme-linked immunosorbent assay (ELISA). The contents of Nrf2 were observed by immunohistochemistry. The expression of Nrf2, n-Nrf2 and heme oxygenase-1 (HO-1) were determined by Western blot. Results Compared with those in the Sham group, LDH, CK-MB concentration, ROS and MDA content in the MI/R and MI/R+ Res groups significantly increased while LVEF, FS, and SOD activity in the MI/R and MI/R+Res groups significantly decreased. Mean-while, the myocardial infarction sizes in the MI/R and MI/R+Res groups were increased, and the expression of Nrf2, n-Nrf2 and HO-1 protein was down-regulated (all P<0.05). Compared with those in the MI/R group, LDH, CK-MB concentration, ROS and MDA content significantly decreased in the MI/R+Res group, while LVEF, FS and SOD activity significantly increased in the MI/R+Res group. Also, in the MI/R+Res group, the myocardial infarction size decreased while the expression of Nrf2, n-Nrf2 and HO-1 protein increased (all P< 0.05). Conclusions Resveratrol preconditioning relieves myocardial injury in diabetic rats with ischemia/reperfusion, which may attribute to activation of Nrf2. Key words: Resveratrol; Transcription factor-related factor 2; Heme oxygenase-1; Diabetes; Myocardial ischemia/reperfusion

Evidence suggests that miR-146a is implicated in the pathogenesis of cardiovascular diseases; however, the role of miR-146a in myocardial ischaemia reperfusion (I/R) injury is unclear. The aim of this study was to explore the functional role of miR-146a in myocardial ischaemia reperfusion injury and the underlying mechanism. C57BL/6J mice were subjected to 45 min of ischaemia and 1 week of reperfusion to establish a myocardial I/R injury model. A miR-146a mimic (0.5 mg/kg) was administered intravenously at the beginning of the ischaemia process. Neonatal rat cardiomyocytes were also subjected to hypoxia/reperfusion (H/R). Cells were treated with the miR-146a mimic or antagonist. As a result, the miR-146a mimic attenuated H/R-induced cardiomyocyte injury, as evidenced by increased cell viability and reduced lactate dehydrogenase (LDH) levels. In addition, the miR-146a mimic inhibited oxidative stress in cells suffering from H/R injury. Moreover, the miR-146a antagonist exerted adverse effects in vitro. In mice with myocardial I/R injury, the miR-146a mimic preserved cardiac function and reduced the infarction area and fibrosis. Moreover, the miR-146a mimic decreased the inflammatory response and reactive oxygen species (ROS) accumulation in mouse hearts. Mechanistically, we found that miR-146a directly regulated the transcription of NOX4, which subsequently affected P38 signalling in cardiomyocytes. When we knocked down NOX4, the effects of the miR-146a antagonist in worsening the cell condition were counteracted in in vitro experiments. Taken together, the results suggest that miR-146a protects against myocardial ischaemia reperfusion injury by inhibiting NOX4 signalling. The miR-146a mimic may become a potential therapeutic approach for patients with myocardial ischaemia reperfusion.

Hederagenin (HDG), a medical herb, is known for its beneficial activities against diverse diseases. The cardioprotective effect of HDG has been preliminarily disclosed, but the efficacy and underlying mechanism by which HDG protects against myocardial ischemia-reperfusion (MI/R) injury have not been elucidated yet. To simulate MI/R injury, the left anterior descending artery was occluded for 30min and then reperfusion for 120min in a rat model, and the cellular model of hypoxia-reoxygenation (H/R) injury was constructed in H9c2 cardiomyocytes. Hematoxylin-eosin, Prussian blue, and 2,3,5-triphenyl-2H-tetrazolium chloride (TTC) staining were conducted to assess the histological injury, iron deposition, and myocardial infarction. Myocardial enzymes and oxidative stress-related factors were detected using their commercial kits. Lipid peroxidation was measured using BODIPY581/591 probe, and iron content was detected. Cell counting kit (CCK)-8, terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL), and flow cytometry assays were performed to assess cell viability and apoptosis. Protein levels were investigated by western blot. The interaction between HDG and 5-lipoxygenase (ALOX5) was verified using molecular docking. Our findings indicated that HDG significantly attenuated myocardial dysfunction by reducing infarction and myocardial injury. HDG significantly attenuated myocardial apoptosis in vitro and in vivo, as well as alleviating oxidative stress via reducing reactive oxygen species (ROS) and maintaining the balance between antioxidant and oxidant enzymes. Meanwhile, HDG inhibited I/R-induced ferroptosis in myocardium and cardiomyocytes, including reducing lipid peroxidation and iron level. Moreover, the binding relationship between HDG and ALOX5 was verified, and HDG could concentration dependently downregulate ALOX5. Furthermore, ALOX5 overexpression eliminated the inhibition of HDG on H/R-induced apoptosis, oxidative stress, and ferroptosis in H9c2 cardiomyocytes. HDG ameliorated myocardial dysfunction and cardiomyocyte injury by reducing apoptosis, oxidative stress, and ferroptosis through inhibiting ALOX5, providing a new perspective on the prevention and treatment of MI/R injury.

Restoring the blood perfusion of ischemic heart tissues is the main treatment for myocardial ischemia. However, the accompanying myocardial ischemia reperfusion injury (IRI) would aggravate myocardial damage. Previous studies have confirmed that aryl hydrocarbon receptor (AhR) is closely correlated to kidney and intestinal IRI. The present study aimed to explore the relationship between AhR and myocardial IRI. An oxygen glucose deprivation/reoxygenation (OGD/R) model of H9c2 cells and an ischemia/reperfusion (I/R) model of Sprague-Dawley rat myocardium were established. OGD/R cells and myocardial IRI rats were treated with different concentrations of the AhR antagonist CH-223191 or agonist 6-formylindolo[3,2-b] carbazole (FICZ). Under the conditions of normoxia and hypoxia/reoxygenation, the activity of cardiomyocytes, lactate dehydrogenase (LDH) and cell reactive oxygen species (ROS) were detected. In rats, myocardial pathological damage and markers of myocardial injury were detected. According to the results of the cell viability, LDH and ROS tests in vitro, both CH-223191 and FICZ showed no myocardial protection under OGD/R conditions. However, the histological staining and analysis of myocardial injury marker LDH in vitro revealed that CH-223191 could significantly reduce the myocardial IRI. AhR exhibited a different effect on myocardial IRI in vitro and in vivo. In vivo, CH-223191 could significantly alleviate the myocardial IRI, suggesting that inhibition of AhR may play a role in myocardial protection, and AhR may serve as a potential treatment target for myocardial IRI.

Acute myocardial infarction results in significant mortality and chronic heart failure, with reperfusion frequently inducing myocardial ischaemia-reperfusion (IR) injury mediated by infiltrating monocytes and monocyte-derived macrophages (iMacs). The olfactory receptor 2 (Olfr2) is hypothesized to serve as a pivotal inflammatory mediator in this context. This study aimed to elucidate the regulatory role of Olfr2 in mitochondrial homeostasis and inflammation in iMacs during myocardial IR injury. The surface expression of OR6A2 (human ortholog of Olfr2) on monocyte subsets was assessed to determine its association with major adverse cardiovascular events (MACEs) in IR-injured patients. The mechanistic role of Olfr2 in modulating iMacs during myocardial IR injury was investigated using both in vivo and in vitro interventions targeting Olfr2. Elevated OR6A2 levels on human monocytes and octanal, an OR6A2 agonist, were significantly associated with an increased risk of MACEs and correlated with increased oxidative stress and pro-inflammatory responses in patients with IR injury. The genetic ablation of Olfr2 in mice demonstrated significant attenuation of mitochondrial reactive oxygen species (mtROS) and pro-inflammatory cytokine in iMacs, accompanied by diminished immune cell infiltration and reduced cardiomyocyte apoptosis, ultimately ameliorating myocardial IR injury. Mechanistically, Olfr2 activated nuclear receptor subfamily 4 group A member 1 (NR4A1) via cAMP/PKA signalling, promoting dynamin-related protein 1 (Drp1)-mediated mitochondrial fission, which led to mitochondrial mtROS overproduction, mitochondrial membrane potential disruption, mitochondrial apoptosis, and the subsequent release of pro-inflammatory factors through NLRP3 inflammasome activation. Notably, monocyte/macrophage-specific NR4A1 overexpression in Olfr2 knockout mice negated the cardiovascular protection observed during IR injury. Elevated OR6A2 expression and octanal levels were significantly associated with an increased risk of MACEs. Our findings identified the Olfr2/cAMP/PKA/NR4A1 axis as a novel signalling pathway contributing to cardiac IR injury by promoting Drp1-mediated mitochondrial fission and subsequent production of pro-inflammatory cytokines.

Excessive reactive oxygen species (ROS) induced by myocardial ischemia reperfusion (IR) injury exert detrimental effects on cardiomyocytes. Antioxidant peptides can scavenge free radicals such as 2,2′-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS+), 2,2-diphenyl-1-picrylhydrazyl (DPPH) and nitic oxide (NO) in vitro, but little is known about their functions in vivo. Here, we evaluated the effects of an antioxidant peptide (antioxidant-RL) used at the beginning of reperfusion on myocardial IR injury. We performed 2, 3, 5-triphenyltetrazolium chloride staining (TTC) to determine myocardial infarct size. Creatine kinase isoenzyme-MB (CK-MB), cardiac troponin-T (CTnT), tumor necrosis factor-alpha (TNF-α), and interleukin-6 (IL-6) levels were determined with enzyme-linked immunosorbent assays (ELISAs). The levels of ROS were measured with a fluorometric Intracellular ROS kit. The expression levels of apoptosis-related proteins in cardiomyocytes were detected by western blotting. Antioxidant-RL (10 mg/kg) reduced the infarct size and levels of CK-MB and CTnT in rats. The levels of TNF-α and IL-6 also decreased. Furthermore, ROS levels were ameliorated and the expression of apoptosis-related proteins in myocytes was down-regulated by antioxidant-RL (100 µg/mL). Antioxidant-RL exerted protective effects on myocardial IR injury by scavenging excessive ROS, suppressing inflammatory factors, and inhibiting cardiomyocytes apoptosis. Thus, antioxidant-RL may serve as a potent candidate for the treatment of IR injury.

Long non-coding RNA MALAT1 modulates myocardial ischemia-reperfusion injury through the PI3K/Akt/eNOS pathway by sponging miRNA-133a-3p to target IGF1R expression

Nobiletin alleviates myocardial ischemia-reperfusion injury via ferroptosis in rats with type-2 diabetes mellitus

Aerobic exercise training attenuates ischemia-reperfusion injury in mice by decreasing the methylation level of METTL3-associated m6A RNA in cardiomyocytes.

Myocardial ischemia-reperfusion injury (MIRI) is a major cause of heart failure in patients with coronary heart disease. The excessive accumulation of reactive oxygen species (ROS) during MIRI induces the overactivation of an autophagic response, which aggravates myocardial cell damage. Asiatic acid (AA) is a triterpenoid compound, which is extracted from Centella asiatica and exhibits a variety of pharmacological effects such as hepatoprotective, neuroprotective and antioxidant. However, the association of AA with autophagy in MIRI is not fully understood. In the present study, the positive effects of AA in MIRI injury were determined via establishing a MIRI mouse model. Pre-treatment with AA was indicated to improve cardiac function and decrease cardiomyocyte autophagy in mice subjected to MIRI. To examine the protective effects of AA and the underlying mechanisms in MIRI, a cardiomyocyte glucose deprivation/reperfusion (OGD) model was established. The administration of AA decreased the levels of ROS and malondialdehyde and increased the levels of superoxide dismutase activity in OGD-treated cells. Using western blotting, it was demonstrated that treatment with AA decreased the phosphorylation of p38 and increased the expression of Bcl-2 in OGD-treated cells. Additionally, the expression of autophagy markers, including beclin-1 and the microtubule-associated proteins 1A/1B light chain 3B II/I ratio, were also decreased in AA treated cells compared with OGD-treated cells. These results demonstrated that AA pretreatment protected cardiomyocytes from ROS-mediated autophagy via a p38 mitogen-activated protein kinase/Bcl-2/beclin-1 signaling pathway in MIRI.

Myocardial ischemia-reperfusion (I/R) injury is experienced by individuals suffering from cardiovascular diseases such as coronary heart diseases and subsequently undergoing reperfusion treatments in order to manage the conditions. The occlusion of blood flow to the tissue, termed ischemia, can be especially detrimental to the heart due to its high energy demand. Several cellular alterations have been observed upon the onset of ischemia. The danger created by cardiac ischemia is somewhat paradoxical in that a return of blood to the tissue can result in further damage. Reactive oxygen species (ROS) have been studied intensively to reveal their role in myocardial I/R injury. Under normal conditions, ROS function as a mediator in many cell signaling pathways. However, stressful environments significantly induce the generation of ROS which causes the level to exceed body's antioxidant defense system. Such altered redox homeostasis is implicated in myocardial I/R injury. Despite the detrimental effects from ROS, low levels of ROS have been shown to exert a protective effect in the ischemic preconditioning. In this review, we will summarize the detrimental role of ROS in myocardial I/R injury, the protective mechanism induced by ROS, and potential treatments for ROS-related myocardial injury.

Ischemia–reperfusion injury is still a big hurdle to overcome for treatment of acute myocardial infarction