Myocardial Ischemia/reperfusion (I/R) Injury Research Articles

HMGB1-RAGE axis contributes to myocardial ischemia/reperfusion injury via regulation of cardiomyocyte autophagy and apoptosis in diabetic mice.

Patients with acute myocardial infarction complicated with diabetes are more likely to develop myocardial ischemia/reperfusion (I/R) injury (MI/RI) during reperfusion therapy. Both HMGB1 and RAGE play important roles in MI/RI. However, the specific mechanisms of HMGB1 associated with RAGE are not fully clarified in diabetic MI/RI. This study aimed to investigate whether the HMGB1-RAGE axis induces diabetic MI/RI via regulating autophagy and apoptosis. A db/db mouse model of MI/RI was established, where anti-HMGB1 antibody and RAGE inhibitor (FPS-ZM1) were respectively injected after 10 min of reperfusion. The results showed that treatment with anti-HMGB1 significantly reduced the infarct size, serum LDH, and CK-MB level. Similar situations also occurred in mice administrated with FPS-ZM1, though the HMGB1 level was unchanged. Then, we found that treatment with anti-HMGB1 or FPS-ZM1 performed the same effects in suppressing the autophagy and apoptosis, as reflected by the results of lower LAMP2 and LC3B levels, increased Bcl-2 level, reduced BAX and caspase-3 levels. Moreover, the Pink1/Parkin levels were also inhibited at the same time. Collectively, this study indicates that the HMGB1-RAGE axis aggravated diabetic MI/RI via apoptosis and Pink1/Parkin mediated autophagy pathways, and inhibition of HMGB1 or RAGE contributes to alleviating those adverse situations.

Propofol pretreatment alleviates mast cell degranulation by inhibiting SOC to protect the myocardium from ischemia-reperfusion injury.

Propofol (PPF) has a protective effect on myocardial ischemia-reperfusion (I/R) injury (MIRI). The purpose of this study was to investigate whether the myocardial protective effect of propofol is related to the inhibition of mast cell degranulation and explore the possible mechanisms involved. Our in vivo results showed that compared with the sham group, cardiac function, infarct size, histopathological damage, apoptosis, and markers of myocardial necrosis were significantly increased in the ischemia-reperfusion group, and propofol pretreatment alleviated these effects. In the coculture system, propofol-treated mast cells reduced their tryptase activity, resulting in cardiomyocyte protective effects, such as decreased apoptosis of cardiomyocytes and decreased expression of myocardial necrosis markers. Finally, experimental results in vitro revealed that thapsigargin (TG) can increase mast cell degranulation, tryptase release, calcium ion concentration, and the expression of STIM1 and Orai1 induced by H/R, but propofol pretreatment can partially reverse the above effects. These results suggested that the cardioprotective effect of propofol is achieved in part by inhibiting calcium influx through store-operated Ca2+ channels (SOCs) and thus alleviating mast cell degranulation.

Minocycline relieves myocardial ischemia-reperfusion injury in rats by inhibiting inflammation, oxidative stress and apoptosis.

Myocardial ischemia-reperfusion (I/R) injury (MIRI) is an important cause of irreversible injury to the myocardium in patients with acute myocardial infarction. The purpose of this study was to investigate the effects of minocycline (MC) on inflammation, oxidative stress and apoptosis of myocardial tissues. We used rats to establish MIRI model by ligating coronary arteries. The structure and function of rat myocardium were determined by 2, 3, 5-triphenyl tetrazolium chloride (TTC) staining, hematoxylin-eosin (HE) staining and echocardiography. In addition, we detected the expression of inflammatory factors, antioxidant enzymes and apoptosis-related molecules in rats by enzyme-linked immunosorbent assay (ELISA), immunohistochemical (IHC) staining and reverse transcription-polymerase chain reaction (RT-PCR) to determine the effect of MC on inflammation, oxidative stress and apoptosis in I/R rats. Finally, we studied the effect of MC stimulation on the viability of rat cardiomyocytes (H9c2 cells) in vitro. After I/R, the heart function of rats decreased, and the structure of myocardium was destroyed. The levels of inflammation and oxidative stress in I/R rats also increased significantly, manifested by increased inflammatory factors and decreased antioxidant enzymes in serum and myocardial tissue. After treatment of I/R rats with MC, the structure and function of rat myocardium improved significantly, and MC reduced inflammation and oxidative stress levels in rats, thus inhibiting the apoptosis of cardiomyocytes. MC also improved the viability of H9c2 cells in vitro. MC reduced inflammation and oxidative stress levels in MIRI rat model or H9c2 cells, thus inhibiting cardiomyocyte apoptosis. Therefore, MC has potential application prospects for the treatment of MIRI.

The histone demthylase KDM3A protects the myocardium from ischemia/reperfusion injury via promotion of ETS1 expression

Our prior studies have characterized the participation of histone demethylase KDM3A in diabetic vascular remodeling, while its roles in myocardial ischemia/reperfusion (I/R) injury (MIRI) remain to be illustrated. Here we show that KDM3A was significantly downregulated in rat I/R and cellular hypoxia/reoxygenation (H/R) models. Subsequently, gain- and loss-of-function experiments were performed to investigate the effects of KDM3A in the settings of MIRI. KDM3A knockout exacerbated cardiac dysfunction and cardiomyocytes injury both in vivo and in vitro. The deteriorated mitochondrial apoptosis, reactive oxygen species, and inflammation were simultaneously observed. Conversely, KDM3A overexpression developed the ameliorated alternations in MIRI. Mechanistically, the MIRI-alleviating effects of KDM3A were associated with the enhancement of ETS1 expression. ChIP-PCR affirmed that KDM3A bound to the ETS1 promoter and removed dimethylation of histone H3 lysine 9 (H3K9me2), thus promoting ETS1 transcription. Our findings suggest that KDM3A is available for alleviating multi-etiologies of MIRI through the regulation of ETS1.

MiR-190-5p Alleviates Myocardial Ischemia-Reperfusion Injury by Targeting PHLPP1.

Objective Myocardial ischemia-reperfusion (I/R) injury (MIRI) refers to the more serious myocardial injury after blood flow recovery, which seriously affects the prognosis of patients with ischemic cardiomyopathy. This study explored the new targets for MIRI treatment by investigating the effects of miR-190-5p and its downstream target on the structure and function of myocardial cells. Methods We injected agomir miR-190-5p into the tail vein of rats to increase the expression of miR-190-5p in rat myocardial cells and made an I/R rat model by coronary artery occlusion. We used 2,3,5-triphenyl tetrazolium chloride staining, lactate dehydrogenase (LDH) detection, echocardiography, and hematoxylin-eosin (HE) staining to determine the degree of myocardial injury in I/R rats. In addition, we detected the expression of inflammatory factors and apoptosis-related molecules in rat serum and myocardial tissue to determine the level of inflammation and apoptosis in rat myocardium. Finally, we determined the downstream target of miR-190-5p by Targetscan system and dual luciferase reporter assay. Results The expression of miR-190-5p in an I/R rat myocardium was significantly lower than that in normal rats. After treatment of I/R rats with agomir miR-190-5p, the ischemic area of rat myocardium and the concentration of LDH decreased. The results of echocardiography and HE staining also found that overexpression of miR-190-5p improved the structure and function of rat myocardium. miR-190-5p was also found to improve the viability of H9c2 cells in vitro and reduce the level of apoptosis of H9c2 cells. The results of Targetscan system and dual luciferase reporter assay found that miR-190-5p targeted to inhibit pleckstrin homology domain leucine-rich repeat protein phosphatase 1 (PHLPP1). In addition, inhibition of PHLPP1 was found to improve the viability of H9c2 cells. Conclusion Therefore, miR-190-5p can reduce the inflammation and apoptosis of myocardium by targeting PHLPP1, thereby alleviating MIRI.

Vitexin Mitigates Myocardial Ischemia/Reperfusion Injury in Rats by Regulating Mitochondrial Dysfunction via Epac1-Rap1 Signaling.

Revascularization is an effective therapy for rescuing myocardial tissue after ischemic events. However, the process of reperfusion can lead to more severe cardiomyocyte damage, called myocardial ischemia-reperfusion (I/R) injury (MIRI). We have previously shown that vitexin (VT) (a flavonoid compound derived from natural products) protects against MIRI; however, the exact mechanisms underpinning this effect require further elucidation. This study is aimed at elucidating the protective mechanism of VT in inhibiting ischemic myocardial mitochondrial dysfunction and reducing cardiomyocyte apoptosis by regulating Epac1-Rap1 signaling. Isolated rat hearts were subjected to MIRI in a Langendorff perfusion system, and H9c2 cells were subjected to hypoxia/reoxygenation (H/R) in vitro. Our analyses show that during I/R, Epac1 expression was upregulated, left ventricular dysfunction deteriorated, mitochondrial dynamics were disrupted, and both myocardial cells and tissues exhibited apoptosis. Furthermore, administration of 8-CPT (an Epac agonist) exacerbated cardiomyocyte injury and mitochondrial dysfunction. Interestingly, suppressing the function of Epac1 through VT or ESI-09 (an Epac inhibitor) treatment during I/R reduced the myocardial infarct size, cardiomyocyte apoptosis, and reactive oxygen species production; alleviated mitochondrial dysfunction by increasing mitochondrial membrane potential; elevated MFN2 expression; and inhibited Drp1 expression. To our knowledge, our results reveal, for the first time, the mechanisms underlying the protective effect of VT in the myocardium of rats with MIRI. Moreover, we provide a new target and theoretical basis for VT in the treatment of ischemic heart disease.

Inhibition of HMGB1 alleviates myocardial ischemia/reperfusion injury in diabetic mice via suppressing autophagy

BackgroundDiabetes aggravates myocardial ischemia/reperfusion (I/R) injury (MI/RI). The association between high mobility group box 1 protein (HMGB1) and autophagy in diabetic MI/RI remains unknown. Therefore, we investigated whether inhibiting HMGB1 can regulate autophagy in diabetic mice (DM) after I/R injury. MethodsI/R models of C57BL/KsJ mice and db/db mice were established. Histological changes, infarct size (IS), HMGB1 protein, and autophagy-related proteins were detected after 24h of reperfusion. In DM treatment groups, anti-HMGB1 antibody (H-Ig) was injected via tail vein after reperfusion for 15min, and the above-mentioned experimental methods were performed at the end of reperfusion. ResultsCompared with the I/R group, the pathological myocardial damage and IS were significantly increased in the I/R (DM) group. Additionally, the levels of HMGB1, Beclin1, and LC3II/LC3I ratio were remarkably higher in the I/R (DM) group than those in the I/R group, while p62 level was lower. In the H-Ig (DM) group, injection of H-Ig significantly reduced the IS, as well as alleviated pathological myocardial damage. Moreover, Beclin1, LC3II/LC3I ratio, and p62 levels were notably reversed after this treatment. ConclusionsI/R-induced myocardium was aggravated by diabetes, which may be related to increased release of HMGB1 and activated autophagy. Inhibition of HMGB1 alleviates diabetic MIRI which was associated with reduced autophagy.

Dexmedetomidine Preconditioning Mitigates Myocardial Ischemia/Reperfusion Injury via Inhibition of Mast Cell Degranulation

Background: The degranulation of cardiac mast cells is associated with the occurrence and development of myocardial ischemia/reperfusion (I/R) injury (MIRI). Dexmedetomidine (DEX) has a cardioprotective effect from I/R injury. The present study investigated whether DEX preconditioning-induced cardioprotection was related to suppression of the degranulation of cardiac mast cells. Methods: The ligation of the left anterior descending coronary artery for 30 min of ischemia and 120 min of reperfusion was used to establish a rat MIRI model in vivo. The MIRI Langendorff model in vitro of rat isolated heart was constructed by global ischemia for 30 min and reperfusion for 60 min. The effect of compound 48/80 (C48/80) and DEX pretreatment on MIRI was then evaluated. Hemodynamics and electrocardiogram were assessed for each rat/heart. TTC staining, hematoxylin-eosin staining, and toluidine blue staining, transmission electron microscope detection, TUNEL staining, ELISA, IHE staining, qRT-PCR, and western blot were detected. Further work was performed using a cell coculture test to verify. Findings: In vivo and in vitro experimental results revealed that hemodynamic disorder, arrhythmia, infarct size, histopathological score, and mast cell degranulation were dramatically increased in the I/R injury groups compared to the non-I/R groups. Mastocyte secretagogue compound 48/80 (C48/80) aggravated these damages, and DEX preconditioning mitigated these damages. C48/80 increased the levels of I/R injury-induced cardiac troponin-1 (cTnI) and tryptase, cardiomyocytes apoptosis, and the expression of high mobility group protein B1 (HMGB1), Toll-like receptor 4 (TLR4), and nuclear factor kappa B (NF-κB) p65 in cardiac tissues, and DEX pretreatment partially reduced these changes. C48/80 inhibited the proliferation of H9C2(2-1) and RBL-2H3, exacerbated apoptosis of H9C2(2-1), and increased the levels of cTnI and tryptase, and DEX pretreatment abolished these changes. Interpretation: Our data suggest that DEX preconditioning alleviates the MIRI-induced degranulation of mast cells and the apoptosis of cardiomyocytes, and inhibits the activation of inflammatory-related factors HMGB1, TLR4, and NF-κB p65. Funding Information: This research was supported by the National Natural Science Foundation of China (81860050 & 82060060), Yunnan Health Training Project of High Levels Talents (L-2018007), Program for Innovative Research Team of Kunming Medical University (CXTD201802), Yunnan Provincial Ten Thousand-Talent Program-Famous Doctor (YNWR-MY-2018-043), Innovative fund of Kunming Medical University (2020D013), and Yunnan Provincial Education Department (2020Y0120). Declaration of Interests: The authors declare no conflict of interest. Ethics Approval Statement: All experimental procedures were performed in accordance with the guidelines formulated by the Institutional Animal Care and Use Committee of Kunming Medical University (No. KMU20191119).

Inhibited histone deacetylase 3 ameliorates myocardial ischemia–reperfusion injury in a rat model by elevating microRNA‐19a‐3p and reducing cyclin‐dependent kinase 2

Over the years, the roles of microRNAs (miRNAs) and histone deacetylase 3 (HDAC3) in human diseases have been investigated. This study focused on the effect of miR-19a-3p and HDAC3 in myocardial ischemia-reperfusion (I/R) injury (MIRI) by targeting cyclin-dependent kinase 2 (CDK2). The I/R rat models were established by coronary artery ligation, which were then treated with RGFP966 (an inhibitor of HDAC3), miR-19a-3p agomir or antagomir, or silenced CDK2 to explore their roles in the cardiac function, pathological changes of myocardial tissues, myocardial infarction area, inflammatory factors and oxidative stress factors in rats with MIRI. The expression of miR-19a-3p, HDAC3, and CDK2 was determined by RT-qPCR and western blot assay, and the interaction among which was also verified by online prediction, luciferase activity assay and ChIP assay. The results indicated that HDAC3 and CDK2 were upregulated while miR-19a-3p was downregulated in myocardial tissues of I/R rats. The inhibited HDAC3/CDK2 or elevated miR-19a-3p could promote cardiac function, attenuate pathological changes, inflammatory reaction, oxidative stress, myocardial infarction area and apoptosis of myocardial tissues. HDAC3 mediates miR-19a-3p and CDK2 is targeted by miR-19a-3p. Inhibited HDAC3 ameliorates MIRI in a rat model by elevating miR-19a-3p and reducing CDK2, which may contribute to the treatment of MIRI.

RETRACTED: Sevoflurane up-regulates microRNA-204 to ameliorate myocardial ischemia/reperfusion injury in mice by suppressing Cotl1

The inhaled sevoflurane (sevo) is known to protect against myocardial ischemia/reperfusion (I/R) injury (MIRI), in which the functions of microRNAs (miRNAs) have been uncovered. However, the effect of sevo regulating miR-204 on this disease remains unknown. This research aims to explore the roles of sevo and miR-204 in the progression of MIRI. The MIRI mice models induced by coronary artery ligation were treated by sevo, miR-204 mimics or silenced coactosin-like protein-1 (Cotl1). The pathology of mice myocardial tissues, apoptosis and ultrastructure of cardiomyocytes were observed. The expression of miR-204, Cotl1, Bax and Bcl-2 was determined. The contents of oxidative stress-related factors and inflammatory factors in mouse myocardial tissues were assessed, and the serum levels of indicators that correlated with myocardial infarction were determined as well. The target relation between miR-204 and Cotl1 was confirmed. MiR-204 was down-regulated, and Cotl1 was up-regulated in myocardial tissues of MIRI mice, and Cotl1 was targeted by miR-204. Sevo, elevated miR-204 and inhibited Cotl1 could promote cardiac function of MIRI mice, and protect myocardial tissue against MIRI by repressing the cardiomyocyte apoptosis, oxidative stress and inflammation reaction in MIRI mice. We found that sevo could up-regulate miR-204 to ameliorate MIRI in mice by inhibiting Cotl1 expression, which may provide candidates for the MIRI treatment.

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.

SH2B1 protects cardiomyocytes from ischemia/reperfusion injury via the activation of the PI3K/AKT pathway

BackgroundApoptosis, reactive oxidative stress (ROS) and inflammation act as the pivotal pathogenesis of myocardial ischemia/reperfusion (I/R) injury (MIRI). Our prior study and other investigation have demonstrated the participations of src homology 2 (SH2) B adaptor protein 1 (SH2B1) in ischemic injury and cardiac hypertrophy; whereas, the involvements of SH2B1 in MIRI and underlying mechanisms are completely unknown. MethodIn present study, MIRI model in vivo was induced by 30 min of ligation of LAD coronary artery and 24 h of reperfusion, and primary cultured cardiomyocytes were challenged with 2 h of hypoxia followed by 4 h of reoxygenation (H/R) to mimic MIRI in vitro. Adenovirus encoding for SH2B1 or GFP were pre-transfected into myocardium prior to MIRI both in vivo and in vitro. The myocardial damage, cardiac function, apoptosis, ROS and inflammation were evaluated systematically. Immunofluorescence staining and western blotting were alternatively performed to detect protein expression. ResultsThe results exhibited that H/R or I/R significantly reduced SH2B1 in cardiomyocytes, followed by impaired cell survival and function, which were strongly reversed after the adenovirus-mediated SH2B1 up-regulation. Meanwhile, I/R- and H/R-elevated inflammation, apoptosis and ROS were also alleviated by SH2B1 up-regulation. A mechanistic study suggested that the protective contributions of SH2B1 on H/R-suffered cardiomyocytes were based on the activation of the PI3K/AKT pathway. The abolishment of the PI3K/AKT via a pharmacological inhibitor (LY294002) repressed anti-H/R capabilities of SH2B1. ConclusionTherefore, SH2B1 prevents cardiomyocytes from inflammation, apoptosis and ROS in MIRI partially through the PI3K/AKT-dependent avenues. It may provide a novel therapeutic target for the treatment of MIRI.

Formononetin ameliorates myocardial ischemia/reperfusion injury in rats by suppressing the ROS-TXNIP-NLRP3 pathway

Formononetin (FN), a methoxy isoflavone abundant in many plants and herbs, has been evidently proven to possess multiple medicinal properties. Our study aimed to clarify the impact of FN on myocardial ischemia/reperfusion (I/R) injury (MIRI) and the involved mechanism. A rat model of MIRI was produced by ligation and loosening of the left anterior descending (LAD) branch of the coronary artery. Rats received 10 and 30 mg/kg of FN when the reperfusion started. At 24 h after surgery, cardiac function, infarct size, and sera levels of the cardiac markers and inflammatory mediators were measured. To mimic the inflammasome activation in cardiomyocytes, neonatal rat cardiomyocytes (NRCMs) were cultured and treated with lipopolysaccharide (LPS) plus nigericin. Cell death and reactive oxygen species (ROS) were determined. Myocardial expression and activation of the nucleotide-binding domain and leucine-rich repeat-containing protein 3 (NLRP3) inflammasome in rats were examined by western blotting. The level of thioredoxin interacting protein (TXNIP)-NLRP3 interaction was assessed. FN notably attenuated cardiac dysfunction, infarct size, release of cardiac markers, and elevation of TNF-α, IL-1β, and IL-6. FN alleviated LPS plus nigericin-induced injury and ROS increase in NRCMs. Western blotting revealed that FN suppressed the activation of NLRP3 inflammasome and TXNIP-NLRP3 interaction in rats. These findings indicate that FN ameliorated MIRI in rats and inhibited the activation of the NLRP3 inflammasome, at least partially, attributable to suppression of the ROS-TXNIP-NLRP3 pathway.

Vitexin attenuates myocardial ischemia/reperfusion injury in rats by regulating mitochondrial dysfunction induced by mitochondrial dynamics imbalance

Vitexin (VT) is a main bioactive flavonoid compound derived from the dried leaf of hawthorn (Crataegus pinnatifida), a widely used Chinese traditional folk medicine. Recent studies have shown that vitexin presents cardioprotective effects in vivo and in vitro. Mitochondrial dysfunction is a salient feature of myocardial ischemia/reperfusion (I/R) injury (MIRI), but the potential mechanism is still unclear. This study investigated the cardioprotective effect of vitexin against MIRI and its possible mechanism. Isolated SD rat hearts were subjected to MIRI in a Langendorff perfusion system, and H9c2 cells were subjected to hypoxia/reoxygenation (H/R) in vitro. Ex vivo experiments showed improved left ventricular function and reduced infarct size in the vitexin group. Transmission electron microscopy showed that I/R caused outer mitochondrial membrane rupture, cristae disappearance and vacuolation, while vitexin reduced mitochondrial damage and ultimately reduced cardiomyocyte apoptosis. In vitro, vitexin protected H9c2 cells from H/R-induced mitochondrial dysfunction, significantly reducing ROS levels; improving mitochondrial activity, mitochondrial membrane potential and ATP content; markedly increasing MFN2 expression and reducing the recruitment of Drp1 in mitochondria. These results suggest a new protective mechanism of vitexin for ischemic heart disease treatment.

GW29-e1729 The novel protective effects of KDM3A in myocardial ischemia-reperfusion injury

Our pioneering studies have characterized the participations of histone demethylase KDM3A in diabetic vascular remodeling, though its roles in myocardial ischemia/reperfusion (I/R) injury (MIRI) remained illustrated. The aim of the present study was to explore potential contributions of KDM3A in the

PPARα activation alleviates damage to the cytoskeleton during acute myocardial ischemia/reperfusion in rats.

The cytoskeleton serves an important role in maintaining cellular morphology and function, and it is a substrate of calpain during myocardial ischemia/reperfusion (I/R) injury (MIRI). Calpain may be activated by endoplasmic reticulum (ER) stress during MIRI. The activation of peroxisome proliferator-activated receptor α (PPARα) may inhibit ischemia/reperfusion damage by regulating stress reactions. The present study aimed to determine whether the activation of PPARα protects against MIRI-induced cytoskeletal degradation, and investigated the underlying mechanism involved. Wistar rats were pretreated with or without fenofibrate and subjected to left anterior descending coronary artery ligation for 45 min, followed by 120 min of reperfusion. Calpain activity and the expression of PPARα, desmin and ER stress parameters were evaluated. Electrocardiography was performed and cardiac function was evaluated. The ultrastructure was observed under transmission electron microscopy. I/R significantly induced damage to the cytoskeleton in cardiomyocytes and cardiac dysfunction, all of which were improved by PPARα activation. In addition, I/R increased ER stress and calpain activity, which were significantly decreased in fenofibrate-pretreated rat heart tissue. The results suggested that PPARα activation may exert a protective effect against I/R in the myocardium, at least in part via ER stress inhibition. Suppression of ER stress may be an effective therapeutic target for protecting the I/R myocardium.

SOCS2 exacerbates myocardial injury induced by ischemia/reperfusion in diabetic mice and H9c2 cells through inhibiting the JAK-STAT-IGF-1 pathway

AimsThis study aimed to investigate potential candidates and molecular mechanisms of myocardial ischemia/reperfusion (I/R) injury (MIRI) in type 2 diabetes mellitus. Main methodsType 2 diabetic and myocardial I/R mouse models were established with a high fat-diet (HFD) for 24weeks and subjecting to global ischemia/reperfusion for 1h/3h, respectively. Microarray analysis was applied to screen differentially expressed genes (DEGs) in the hearts of these mice. Moreover, H9c2 cells were treated with high glucose (HG) and/or hypoxia and reoxygenation (H/R). Subsequently, the expression of suppressor of cytokine signaling 2 (SOCS2) was knocked down by siRNA followed by the above treatments. Then, the cell lipid peroxidation and apoptosis-related indicators (malondialdehyde, MDA, and lactate dehydrogenase, LDH, cleaved-caspase-3; glucose-regulated protein 78, GRP78;), Janus kinase (JAK)/signal transducers and activators of transcription (STAT) signaling pathway-related proteins (p-JAK2 and p-STAT5b) and insulin-like growth factor-1 (IGF-1) were detected. Key findingsThe mRNA levels of selected DEGs, such as Angptl4, Gadd45b, Rnf122 and SOCS2, showed a high degree of correlation with the microarray data. In addition, the levels of SOCS2, caspase-3, GRP78, LDH and MDA were increased, while the IGF-1 level was down-regulated in cells treated with HG and/or H/R compared to untreated cells (p<0.05). However, SOCS2 knockdown elevated the expression levels of IGF-1, p-JAK2 and p-STAT5b, as well as caspase-3, GRP78, LDH and MDA. SignificanceThis research suggests that overexpressed SOCS2 might exacerbates MIRI in type 2 diabetes mellitus by inhibiting the expression of IGF-1 via the JAK-STAT signaling pathway.

Radioprotective 105 kDa protein attenuates ischemia/reperfusion-induced myocardial apoptosis and autophagy by inhibiting the activation of the TLR4/NF-κB signaling pathway in rats.

Toll-like receptor 4(TLR4) serves as an important inducer of apoptotic and autophagic responses in myocardial ischemia/reperfusion(I/R) injury(MIRI). Radioprotective 105kDa protein(RP105) is a specific inhibitor of TLR4. However, the molecular mechanisms by which RP105 represses myocardial apoptosis and autophagy through TLR4‑mediated signaling during I/R have not yet been fully elucidated. Therefore, in the present study, we aimed to examine whether adenovirus-mediated RP105 overexpression repressed myocardial apoptosis and autophagy by inhibiting the TLR4-driven mechanism in MIRI. Three days after the injection of virus or saline into the myocardium, Sprague-Dawley(SD) rats were subjected to 30min of left anterior descending coronary artery occlusion and 6h of reperfusion. Myocardial specimens were prepared for analysis. We performed immunohistochemichal and histopathological analysis, the measurement of cardiac biomarkers, TUNEL assay , RT-qPCR and western blot analysis. The results indicated that the overexpression of RP105 contributed to an amelioration of myocardial histological damage, decreased leakage of creatine kinase(CK) and lactate dehydrogenase(LDH), as well as a reduction in the number of TUNEL-positive cardiomyocytes. The levels of positively associated modulators of apoptosis and autophagy were also significantly downregulated by RP105, whereas Bcl-2, which plays an opposite role in inducing apoptosis and autophagy, was inversely upregulated. Furthermore, the overexpression of RP105 led to the repression of TLR4 activity and the phosphorylation of NF-κB/p65, as well as the reduced production of the cytokines interleukin6(IL-6) and tumor necrosis factorα(TNF-α). Taken together, these data suggest that RP105 protects the myocardium against apoptosis and autophagy, and plays a cardioprotective role during I/R injury. This is most likely due to the inactivation of TLR4/NF-κB signaling pathway. Thus, RP105 may represent an innovative therapeutic target for attenuating MIRI.

Ischemic postconditioning influences electron transport chain protein turnover in Langendorff-perfused rat hearts.

Ischemia postconditioning (IPo) is a promising strategy in reducing myocardial ischemia reperfusion (I/R) injury (MIRI), but its specific molecular mechanism is incompletely understood. Langendorff-perfused isolated rat hearts were subjected to global I/R and received IPo in the absence or presence of the mitochondrial ATP-sensitive potassium channel (mitoKATP) blocker 5-hydroxydecanoate (5-HD). Myocardial mitochondria were extracted and mitochondrial comparative proteomics was analyzed. IPo significantly reduces post-ischemic myocardial infarction and improved cardiac function in I/R rat hearts, while 5-HD basically cancelled IPo’s myocardial protective effect. Joint application of two-dimensional polyacrylamide gel electrophoresis (2DE) and MALDI-TOF MS identified eight differentially expressed proteins between groups. Expression of cardiac succinate dehydrogenase (ubiquinone) flavoprotein subunit (SDHA) increased more than two-fold after I/R, while IPo led to overexpression of dihydrolipoyl dehydrogenase (DLD), NADH dehydrogenase (ubiquinone) flavoprotein 1 and isoform CRA_b (NDUFV1). When the mitoKATP was blocked, MICOS complex subunit Mic60 (IMMT) and Stress-70 protein (Grp75) were over expressed, while DLDH, ATPase subunit A (ATPA) and rCG44606 were decreased. Seven of the differential proteins belong to electron transport chain (ETC) or metabolism regulating proteins, and five of them were induced by closing mitoKATP in I/R hearts. We thus conclude that IPo’s myocardial protective effect relies on energy homeostasis regulation. DLD, SDHA, NDUFV1, Grp75, ATPA and rCG44606 may contribute to IPo’s cardial protective effect.

Sevoflurane post-conditioning reduces rat myocardial ischemia reperfusion injury through an increase in NOS and a decrease in phopshorylated NHE1 levels.

The protective effects of sevoflurane post-conditioning against myocardial ischemia/reperfusion (I/R) injury (MIRI) have been previously reported. However, the mechanisms responsible for these protective effects remain elusive. In this study, in order to investigate the molecular mechanisms responsible for the protective effects of sevoflurane post-conditioning on isolated rat hearts subjected to MIRI, Sprague-Dawley rat hearts were randomly divided into the following 6 groups: i) the sham-operated control; ii) 2.5% sevoflurane; iii) ischemia/reperfusion (I/R); iv) 2.5% sevoflurane post-conditioning plus I/R; v) 2.5% sevoflurane post-conditioning + NG-nitro-L-arginine methyl ester (L-NAME) plus I/R; and vi) L-NAME plus I/R. The infarct size was measured using 2,3,5-triphenyl tetrazolium chloride (TTC) staining. Additionally, the myocardial nitric oxide (NO), NO synthase (NOS) and nicotinamide adenine dinucleotide (NAD+) levels were determined. Autophagosomes and apoptosomes in the myocardium were detected by transmission electron microscopy. The levels of Bcl-2, cleaved caspase-3, Beclin-1, microtubule-associated protein light chain 3 (LC3)-I/II, Na+/H+ exchanger 1 (NHE1) and phosphorylated NHE1 protein were measured by western blot analysis. NHE1 mRNA levels were measured by reverse transcription-quantitative polymerase chain reaction. Compared with the I/R group, 15 min of exposure to 2.5% sevoflurane during early reperfusion significantly decreased the myocardial infarct size, the autophagic vacuole numbers, the NHE1 mRNA and protein expression of cleaved caspase-3, Beclin-1 and LC3-I/II. Post-conditioning with 2.5% sevoflurane also increased the NO and NOS levels and Bcl-2 protein expression (P<0.05 or P<0.01). Notably, the cardioprotective effects of sevoflurane were partly abolished by the NOS inhibitor, L-NAME. The findings of the present study suggest that sevoflurane post-conditioning protects the myocardium against I/R injury and reduces the myocardial infarct size. The underlying protective mechanisms are associated with the inhibition of mitochondrial permeability transition pore opening, and with the attenuation of cardiomyoctye apoptosis and excessive autophagy. These effects are mediated through an increase in NOS and a decrease in phopshorylated NHE1 levels.