Clinical manifestations and basic mechanisms of myocardial ischemia/reperfusion injury

Lipidomic-Based Algorithms Can Enhance Prediction of Obstructive Coronary Artery Disease

Lipidomics emerges as a promising research field with the potential to help in personalized risk stratification and improve our understanding on the functional role of individual lipid species in the metabolic perturbations occurring in coronary artery disease (CAD). This study aimed to utilize a machine learning approach to provide a lipid panel able to identify patients with obstructive CAD. In this posthoc analysis of the prospective CorLipid trial, we investigated the lipid profiles of 146 patients with suspected CAD, divided into two categories based on the existence of obstructive CAD. In total, 517 lipid species were identified, from which 288 lipid species were finally quantified, including glycerophospholipids, glycerolipids, and sphingolipids. Univariate and multivariate statistical analyses have shown significant discrimination between the serum lipidomes of patients with obstructive CAD. Finally, the XGBoost algorithm identified a panel of 17 serum biomarkers (5 sphingolipids, 7 glycerophospholipids, a triacylglycerol, galectin-3, glucose, LDL, and LDH) as totally sensitive (100% sensitivity, 62.1% specificity, 100% negative predictive value) for the prediction of obstructive CAD. Our findings shed light on dysregulated lipid metabolism's role in CAD, validating existing evidence and suggesting promise for novel therapies and improved risk stratification.

L-theanine alleviates myocardial ischemia/reperfusion injury by suppressing oxidative stress and apoptosis through activation of the JAK2/STAT3 pathway in mice

BACKGROUND

L-theanine is a unique non-protein amino acid in tea that is widely used as a safe food additive. We investigated the cardioprotective effects and mechanisms of L-theanine in myocardial ischemia-reperfusion injury (MIRI).

METHODS

The cardioprotective effects and mechanisms of L-theanine and the role of Janus Kinase 2 (JAK2)/signal transducer and activator of transcription 3 (STAT3) signaling were investigated in MIRI mice using measures of cardiac function, oxidative stress, and apoptosis.

RESULTS

Administration of L-theanine (10 mg/kg, once daily) suppressed the MIRI-induced increase in infarct size and serum creatine kinase and lactate dehydrogenase levels, as well as MIRI-induced cardiac apoptosis, as evidenced by an increase in Bcl-2 expression and a decrease in Bax/caspase-3 expression. Administration of L-theanine also decreased the levels of parameters reflecting oxidative stress, such as dihydroethidium, malondialdehyde, and nitric oxide, and increased the levels of parameters reflecting anti-oxidation, such as total antioxidant capacity (T-AOC), glutathione (GSH), and superoxide dismutase (SOD) in ischemic heart tissue. Further analysis showed that L-theanine administration suppressed the MIRI-induced decrease of phospho-JAK2 and phospho-STAT3 in ischemic heart tissue. Inhibition of JAK2 by AG490 (5 mg/kg, once daily) abolished the cardioprotective effect of L-theanine, suggesting that the JAK2/STAT3 signaling pathway may play an essential role in mediating the anti-I/R effect of L-theanine.

CONCLUSIONS

L-theanine administration suppresses cellular apoptosis and oxidative stress in part via the JAK2/STAT3 signaling pathway, thereby attenuating MIRI-induced cardiac injury. L-theanine could be developed as a potential drug to alleviate cardiac damage in MIRI.

Polymerized Human Hemoglobin-Based Oxygen Carrier Preserves Lung Allograft Function During Normothermic Ex Vivo Lung Perfusion

Normothermic ex vivo lung perfusion (EVLP) can resuscitate marginal lung allografts to increase organs available for transplantation. During normothermic perfusion, cellular metabolism is more active compared with subnormothermic perfusion, creating a need for an oxygen (O 2 ) carrier in the perfusate. As an O 2 carrier, red blood cells (RBCs) are a scarce resource and are susceptible to hemolysis in perfusion circuits, thus releasing cell-free hemoglobin (Hb), which can extravasate into the tissue space, thus promoting scavenging of nitric oxide (NO) and oxidative tissue damage. Fortunately, polymerized human Hb (PolyhHb) represents a synthetic O 2 carrier with a larger molecular diameter compared with Hb, preventing extravasation, and limiting adverse reactions. In this study, a next-generation PolyhHb-based perfusate was compared to both RBC and asanguinous perfusates in a rat EVLP model. During EVLP, the pulmonary arterial pressure and pulmonary vascular resistance were both significantly higher in lungs perfused with RBCs, which is consistent with RBC hemolysis. Lungs perfused with PolyhHb demonstrated greater oxygenation than those perfused with RBCs. Post-EVLP analysis revealed that the PolyhHb perfusate elicited less cellular damage, extravasation, iron tissue deposition, and edema than either RBCs or colloid control. These results show promise for a next-generation PolyhHb to maintain lung function throughout EVLP.

Adiponectin protects against myocardial ischemia-reperfusion injury: a systematic review and meta-analysis of preclinical animal studies

BACKGROUND

Myocardial ischemia-reperfusion injury (MIRI) is widespread in the treatment of ischemic heart disease, and its treatment options are currently limited. Adiponectin (APN) is an adipocytokine with cardioprotective properties; however, the mechanisms of APN in MIRI are unclear. Therefore, based on preclinical (animal model) evidence, the cardioprotective effects of APN and the underlying mechanisms were explored.

METHODS

The literature was searched for the protective effect of APN on MIRI in six databases until 16 November 2023, and data were extracted according to selection criteria. The outcomes were the size of the myocardial necrosis area and hemodynamics. Markers of oxidation, apoptosis, and inflammation were secondary outcome indicators. The quality evaluation was performed using the animal study evaluation scale recommended by the Systematic Review Center for Laboratory animal Experimentation statement. Stata/MP 14.0 software was used for the summary analysis.

RESULTS

In total, 20 papers with 426 animals were included in this study. The pooled analysis revealed that APN significantly reduced myocardial infarct size [weighted mean difference (WMD) = 16.67 (95% confidence interval (CI) = 13.18 to 20.16, P < 0.001)] and improved hemodynamics compared to the MIRI group [Left ventricular end-diastolic pressure: WMD = 5.96 (95% CI = 4.23 to 7.70, P < 0.001); + dP/dtmax: WMD = 1393.59 (95% CI = 972.57 to 1814.60, P < 0.001); -dP/dtmax: WMD = 850.06 (95% CI = 541.22 to 1158.90, P < 0.001); Left ventricular ejection fraction: WMD = 9.96 (95% CI = 7.29 to 12.63, P < 0.001)]. Apoptosis indicators [caspase-3: standardized mean difference (SMD) = 3.86 (95% CI = 2.97 to 4.76, P < 0.001); TUNEL-positive cells: WMD = 13.10 (95% CI = 8.15 to 18.05, P < 0.001)], inflammatory factor levels [TNF-α: SMD = 4.23 (95% CI = 2.48 to 5.98, P < 0.001)], oxidative stress indicators [Superoxide production: SMD = 4.53 (95% CI = 2.39 to 6.67, P < 0.001)], and lactate dehydrogenase levels [SMD = 2.82 (95% CI = 1.60 to 4.04, P < 0.001)] were significantly reduced. However, the superoxide dismutase content was significantly increased [SMD = 1.91 (95% CI = 1.17 to 2.65, P < 0.001)].

CONCLUSION

APN protects against MIRI via anti-inflammatory, antiapoptotic, and antioxidant effects, and this effect is achieved by activating different signaling pathways.

The protective effect of vagus nerve stimulation against myocardial ischemia/reperfusion injury: pooled review from preclinical studies

Aims: Myocardial ischemia-reperfusion (I/R) injury markedly undermines the protective benefits of revascularization, contributing to ventricular dysfunction and mortality. Due to complex mechanisms, no efficient ways exist to prevent cardiomyocyte reperfusion damage. Vagus nerve stimulation (VNS) appears as a potential therapeutic intervention to alleviate myocardial I/R injury. Hence, this meta-analysis intends to elucidate the potential cellular and molecular mechanisms underpinning the beneficial impact of VNS, along with its prospective clinical implications. Methods and Results: A literature search of MEDLINE, PubMed, Embase, and Cochrane Database yielded 10 articles that satisfied the inclusion criteria. VNS was significantly correlated with a reduced infarct size following myocardial I/R injury [Weighed mean difference (WMD): 25.24, 95% confidence interval (CI): 32.24 to 18.23, p < 0.001] when compared to the control group. Despite high heterogeneity (I2 = 95.3%, p < 0.001), sensitivity and subgroup analyses corroborated the robust efficacy of VNS in limiting infarct expansion. Moreover, meta-regression failed to identify significant influences of pre-specified covariates (i.e., stimulation type or site, VNS duration, condition, and species) on the primary estimates. Notably, VNS considerably impeded ventricular remodeling and cardiac dysfunction, as evidenced by improved left ventricular ejection fraction (LVEF) (WMD: 10.12, 95% CI: 4.28; 15.97, p = 0.001) and end-diastolic pressure (EDP) (WMD: 5.79, 95% CI: 9.84; -1.74, p = 0.005) during the reperfusion phase. Conclusion: VNS offers a protective role against myocardial I/R injury and emerges as a promising therapeutic strategy for future clinical application.

The role and mechanisms of microvascular damage in the ischemic myocardium

Following myocardial ischemic injury, the most effective clinical intervention is timely restoration of blood perfusion to ischemic but viable myocardium to reduce irreversible myocardial necrosis, limit infarct size, and prevent cardiac insufficiency. However, reperfusion itself may exacerbate cell death and myocardial injury, a process commonly referred to as ischemia/reperfusion (I/R) injury, which primarily involves cardiomyocytes and cardiac microvascular endothelial cells (CMECs) and is characterized by myocardial stunning, microvascular damage (MVD), reperfusion arrhythmia, and lethal reperfusion injury. MVD caused by I/R has been a neglected problem compared to myocardial injury. Clinically, the incidence of microvascular angina and/or no-reflow due to ineffective coronary perfusion accounts for 5-50% in patients after acute revascularization. MVD limiting drug diffusion into injured myocardium, is strongly associated with the development of heart failure. CMECs account for > 60% of the cardiac cellular components, and their role in myocardial I/R injury cannot be ignored. There are many studies on microvascular obstruction, but few studies on microvascular leakage, which may be mainly due to the lack of corresponding detection methods. In this review, we summarize the clinical manifestations, related mechanisms of MVD during myocardial I/R, laboratory and clinical examination means, as well as the research progress on potential therapies for MVD in recent years. Better understanding the characteristics and risk factors of MVD in patients after hemodynamic reconstruction is of great significance for managing MVD, preventing heart failure and improving patient prognosis.

The role of (18F)-fluoro-D-glucose positron emission tomography/computed tomography in the surveillance of abnormal myocardial energy metabolism and cardiac dysfunction in a rat model of cardiopulmonary resuscitation

PURPOSE

To investigate the feasibility and usefulness of 2-deoxy-2-(18F)-fluoro-D-glucose positron emission tomography/computed tomography [(18F)-FDG PET/CT] as a novel examination in the surveillance of abnormal myocardial energy metabolism and cardiac dysfunction after cardiopulmonary resuscitation (CPR).

METHODS

Thirteen male Sprague-Dawley rats were randomly divided into a sham group (n = 4), CPR group (n = 4), and trimetazidine (TMZ) + CPR group (n = 5). The expression levels of the myocardial injury marker cardiac troponin I (CTNI) in serum were tested at 6 hours after CPR or TMZ + CPR. The ejection fraction and fraction shortening were evaluated by echocardiography. (18F)-FDG PET/CT was used to measure the FDG uptake and the standardized uptake value (SUV) after CPR or TMZ + CPR for 6 hours. The intermediary carbohydrate metabolites of glycolysis including phosphoenolpyruvate, 3-phospho-D-glycerate, and the lactate/pyruvate ratio were detected through the multiple reaction monitoring approach. Simultaneously, the authors also tested the expression levels of the total adenosine triphosphate (ATP) and the key intermediate products of glucose ovidation as alpha ketoglutarate, citrate, and succinate in the myocardium.

RESULTS

The authors found that the aerobic oxidation of glucose was reduced, and the anaerobic glycolysis was significantly enhanced in the myocardium in the early stage of CPR. Meanwhile, the myocardial injury marker CTNI was upregulated considerably (P = 0.014, P = 0.021), and the left ventricular function of the animal heart also markedly deteriorated with the downregulation of ATP after CPR. In contrast, myocardial injury and cardiac function were greatly improved with the increase of ATP in the CPR + TMZ group. In addition, aerobic glucose oxidation metabolites were significantly increased (P < 0.05) and anaerobic glycolysis metabolites were significantly decreased (P < 0.05) after CPR in the myocardium. Surprisingly, (18F)-FDG PET/CT could track the above changes by detecting the FDG uptake value and the SUV.

CONCLUSION

Glucose metabolism is an essential factor for myocardial self-repair after CPR. (18F) FDG PET/CT, as a non-invasive technology, can monitor myocardial energy metabolism and cardiac function by tracking changes in glucose metabolism after CPR.

Protective effects of curcumin on ischemia/reperfusion injury

Ischemia/reperfusion (I/R) injury is a term used to describe phenomena connected to the dysfunction of various tissue damage due to reperfusion after ischemic injury. While I/R may result in systemic inflammatory response syndrome or multiple organ dysfunction syndrome, there is still a long way to improve therapeutic outcomes. A number of cellular metabolic and ultrastructural alterations occur by prolonged ischemia. Ischemia increases the expression of proinflammatory gene products and bioactive substances within the endothelium, such as cytokines, leukocytes, and adhesion molecules, even as suppressing the expression of other "protective" gene products and substances, such as thrombomodulin and constitutive nitric oxide synthase (e.g., prostacyclin, nitric oxide [NO]). Curcumin is the primary phenolic pigment derived from turmeric, the powdered rhizome of Curcuma longa. Numerous studies have shown that curcumin has strong antiinflammatory and antioxidant characteristics. It also prevents lipid peroxidation and scavenges free radicals like superoxide anion, singlet oxygen, NO, and hydroxyl. In our study, we highlight the mechanisms of protective effects of curcumin against I/R injury in various organs.

MicroRNA-582-5p targeting Creb1 modulates apoptosis in cardiomyocytes hypoxia/reperfusion-induced injury

BACKGROUND

Myocardial ischemia-reperfusion injury (MIRI) caused by the reperfusion therapy of myocardial ischemic diseases is a kind of major disease that threatens human health and lives severely. There are lacking of effective therapeutic measures for MIRI. MicroRNAs (miRNAs) are abundant in mammalian species and play a critical role in the initiation, promotion, and progression of MIRI. However, the biological role and molecular mechanism of miRNAs in MIRI are not entirely clear.

METHODS

We used bioinformatics analysis to uncover the significantly different miRNA by analyzing transcriptome sequencing data from myocardial tissue in the mouse MIRI model. Multiple miRNA-related databases, including miRdb, PicTar, and TargetScan were used to forecast the downstream target genes of the differentially expressed miRNA. Then, the experimental models, including male C57BL/6J mice and HL-1 cell line, were used for subsequent experiments including quantitative real-time polymerase chain reaction analysis, western blot analysis, hematoxylin and eosin staining, flow cytometry, luciferase assay, gene interference, and overexpression.

RESULTS

MiR-582-5p was found to be differentially upregulated from the transcriptome sequencing data. The elevated levels of miR-582-5p were verified in MIRI mice and hypoxia/reperfusion (H/R)-induced HL-1 cells. Functional experiments revealed that miR-582-5p promoted apoptosis of H/R-induced HL-1 cells via downregulating cAMP-response element-binding protein 1 (Creb1). The inhibiting action of miR-582-5p inhibitor on H/R-induced apoptosis was partially reversed after Creb1 interference.

CONCLUSIONS

Collectively, the research findings reported that upregulation of miR-582-5p promoted H/R-induced cardiomyocyte apoptosis by inhibiting Creb1. The potential diagnostic and therapeutic strategies targeting miR-582-5p and Creb1 could be beneficial for the MIRI treatment.

Research Progress on the Role of Pyroptosis in Myocardial Ischemia-Reperfusion Injury

Myocardial ischemia-reperfusion injury (MIRI) results in the aggravation of myocardial injury caused by rapid recanalization of the ischemic myocardium. In the past few years, there is a growing interest in investigating the complex pathophysiological mechanism of MIRI for the identification of effective targets and drugs to alleviate MIRI. Currently, pyroptosis, a type of inflammatory programmed death, has received greater attention. It is involved in the MIRI development in combination with other mechanisms of MIRI, such as oxidative stress, calcium overload, necroptosis, and apoptosis, thereby forming an intertwined association between different pathways that affect MIRI by regulating common pathway molecules. This review describes the pyroptosis mechanism in MIRI and its relationship with other mechanisms, and also highlights non-coding RNAs and non-cardiomyocytes as regulators of cardiomyocyte pyroptosis by mediating associated pathways or proteins to participate in the initiation and development of MIRI. The research progress on novel small molecule drugs, clinical drugs, traditional Chinese medicine, etc. for regulating pyroptosis can play a crucial role in effective MIRI alleviation. When compared to research on other mature mechanisms, the research studies on pyroptosis in MIRI are inadequate. Although many related protective drugs have been identified, these drugs generally lack clinical applications. It is necessary to further explore and verify these drugs to expand their applications in clinical setting. Early inhibition of MIRI by targeted regulation of pyroptosis is a key concern that needs to be addressed in future studies.

VSIG4 regulates macrophages polarization and alleviates inflammation through activating PI3K/AKT and inhibiting TLR4/NF-κB pathway in myocardial ischemia-reperfusion injury rats

Background

Myocardial infarction is the primary cause of high disability and mortality in patients with cardiovascular disease worldwide. The pathological process of myocardial ischemia/reperfusion (I/R) may trigger harmful inflammatory response and ultimately lead to serious cardiac dysfunction. The mechanism of myocardial repair post myocardial infarction has not been fully elucidated. The present study speculated that VSIG4 is related to the regulation of heart injury.

Methods

The myocardial I/R injury model was established in Sprague-Dawley (SD) rats. Before I/R operation, the viral solution containing AAV-NC or AAV-VSIG4 was intravenously injected into rats. Cardiac function indicators, mRNA expression, the apoptosis ratio of cardiomyocytes, myocardial infarct area, phenotype polarization of macrophage, and the protein expression of apoptosis or macrophage phenotype were measured.

Results

Myocardial I/R injury decreased the expression of VSIG4 and subsequently triggered myocardial apoptosis. The induction of AAV-VSIG4 produced a protective effect on general cardiac function and attenuated the I/R-induced cellular apoptosis in rats. Moreover, VSIG4 signaling might potentially modulate macrophage M1/M2-related inflammatory disorders via activation of PI3K/AKT and inhibition of TLR4/NF-κB expression.

Conclusion

In summary, the present study provided evidence that VSIG4 had cardiac protective role in myocardial I/R injury. More importantly, enhanced VSIG4 expression inhibited M1 polarization of macrophages by blocking TLR4/NF-κB activation, subsequently suppressing cardiomyocyte apoptosis. This finding provides vital insights into the role of VSIG4 in I/R injury and may provide a new target for I/R therapy.

JAK2/STAT3 pathway mediates beneficial effects of pterostilbene on cardiac contractile and electrical function in the setting of myocardial reperfusion injury

Contractile dysfunction and fatal arrhythmias are the hallmarks of myocardial ischemia/reperfusion (I/R) injury. Pterostilbene has notable cardioprotective effects, but its main mechanisms are not fully understood. Here, we investigated the effect of PTE on myocardial hemodynamics, arrhythmias, inflammatory/oxidative responses, and the causal role of the JAK2/STAT3 pathway in rats with acute myocardial I/R injury. Sixty male 7-8 months Sprague-Dawley rats (n=10/each group) experienced in vivo model of myocardial I/R injury through 40-min LAD coronary artery occlusion and subsequent 24-h reperfusion. PTE at concentrations of 5 and 25 mg/kg was intraperitoneally administered to rats five min before reperfusion. Cardiac hemodynamics, reperfusion-induced ventricular arrhythmias, infarct size, inflammatory cytokines, oxidative stress markers, the activity of the JAK2/STAT3 pathway were measured as the endpoints. Administration of PTE to I/R-injured rats recovered myocardial contractile function and reduced infarct size and ventricular arrhythmias counts and incidence in a dose-dependent manner. PTE at 25 mg/kg significantly and more potently reduced the levels of inflammatory mediators NF-κB, TNF-α, and IL-1β, suppressed intracellular ROS production, augmented the activity of glutathione, and manganese-superoxide dismutase, and upregulated the JAK2 and STAT3 phosphorylation. Importantly, pretreatment of rats with Ag490 as a JAK2 inhibitor significantly abolished the cardioprotective and signaling effects of PTE in I/R rats. PTE exerts significant protective effects on reducing arrhythmias and myocardial infarction and enhancing cardiac function by stimulating JAK2/STAT3-related suppression of inflammatory and oxidative reactions in the I/R injury setting.

Alpha-lipoic acid potentiates the anti-arrhythmic effects of ischemic postconditioning in the setting of cardiac ischemia/reperfusion injury in diabetic rats

Background

Prevention of lethal ventricular arrhythmias induced by myocardial ischemia/reperfusion (I/R) in diabetic patients is the major goal of cardioprotective strategies. Here, we aimed to examine the anti-arrhythmic effect of ischemic postconditioning (IPostC) and alpha-lipoic acid (ALA) in myocardial I/R injury of type-II diabetic rats, focusing on the involvement of connexin-43 and nitric oxide (NO) in this context.

Methods

Diabetes (duration of 12 weeks) was induced by high-fat diet and low dose of streptozotocin in thirty male Wistar rats (12 weeks old, 200-250 g). After mounting the hearts on the Langendorff apparatus, I/R was induced by the ligation of left anterior descending coronary artery for 35 min, and reperfusion for 60 min. ALA (100 mg/kg/day) was administered orally in diabetic rats for five weeks before I/R. IPostC was applied immediately at early reperfusion. The arrhythmias were evaluated according to the Lambeth convention. Connexin-43 expression and NO levels were assessed by western blotting and Griess calorimetric method, respectively.

Results

IPostC could not significantly decrease the number, duration, and incidence of premature ventricular contraction, ventricular tachycardia, and ventricular fibrillation, also the severity of arrhythmias in diabetic hearts. However, IPostC in combination with ALA-preconditioning significantly decreased the above mentioned parameters compared with untreated or monotherapies-received diabetic rats (P < 0.05 to P < 0.001). Furthermore, this combination therapy significantly increased connexin-43 expression and NO levels, compared with untreated diabetic rats (P < 0.01).

Conclusion

Preconditioning with ALA restored anti-arrhythmic effect of IPostC in diabetic hearts. Increased connexin-43 expression and NO levels may be the key players in this cardioprotection.

Therapeutic hypothermia for acute myocardial infarction: a narrative review of evidence from animal and clinical studies

Myocardial infarction (MI) is the leading cause of death from coronary heart disease and requires immediate reperfusion therapy with thrombolysis, primary percutaneous coronary intervention, or coronary artery bypass grafting. However, myocardial reperfusion therapy is often accompanied by cardiac ischemia/reperfusion (I/R) injury, which leads to myocardial injury with detrimental consequences. The causes of I/R injury are unclear, but are multifactorial, including free radicals, reactive oxygen species, calcium overload, mitochondria dysfunction, inflammation, and neutrophil-mediated vascular injury. Mild hypothermia has been introduced as one of the potential inhibitors of myocardial I/R injury. Although animal studies have demonstrated that mild hypothermia significantly reduces or delays I/R myocardium damage, human trials have not shown clinical benefits in acute MI (AMI). In addition, the practice of hypothermia treatment is increasing in various fields such as surgical anesthesia and intensive care units. Adequate sedation for anesthetic procedures and protection from body shivering has become essential during therapeutic hypothermia. Therefore, anesthesiologists should be aware of the effects of therapeutic hypothermia on the metabolism of anesthetic drugs. In this paper, we review the existing data on the use of therapeutic hypothermia for AMI in animal models and human clinical trials to better understand the discrepancy between perceived benefits in preclinical animal models and the absence thereof in clinical trials thus far.

Myocardial ischemia/reperfusion injury: Mechanisms of injury and implications for management (Review)

Myocardial infarction is one of the primary causes of mortality in patients with coronary heart disease worldwide. Early treatment of acute myocardial infarction restores blood supply of ischemic myocardium and decreases the mortality risk. However, when the interrupted myocardial blood supply is recovered within a certain period of time, it causes more serious damage to the original ischemic myocardium; this is known as myocardial ischemia/reperfusion injury (MIRI). The pathophysiological mechanisms leading to MIRI are associated with oxidative stress, intracellular calcium overload, energy metabolism disorder, apoptosis, endoplasmic reticulum stress, autophagy, pyroptosis, necroptosis and ferroptosis. These interplay with one another and directly or indirectly lead to aggravation of the effect. In the past, apoptosis and autophagy have attracted more attention but necroptosis and ferroptosis also serve key roles. However, the mechanism of MIRI has not been fully elucidated. The present study reviews the mechanisms underlying MIRI. Based on current understanding of the pathophysiological mechanisms of MIRI, the association between cell death-associated signaling pathways were elaborated, providing direction for investigation of novel targets in clinical treatment.

Integrated Bioinformatics Analysis and Verification of Gene Targets for Myocardial Ischemia-Reperfusion Injury

Background

Myocardial ischemia-reperfusion injury (MIRI) has become a thorny and unsolved clinical problem. The pathological mechanisms of MIRI are intricate and unclear, so it is of great significance to explore potential hub genes and search for some natural products that exhibit potential therapeutic efficacy on MIRI via targeting the hub genes.

Methods

First, the differential expression genes (DEGs) from GSE58486, GSE108940, and GSE115568 were screened and integrated via a robust rank aggregation algorithm. Then, the hub genes were identified and verified by the functional experiment of the MIRI mice. Finally, natural products with protective effects against MIRI were retrieved, and molecular docking simulations between hub genes and natural products were performed.

Results

230 integrated DEGs and 9 hub genes were identified. After verification, Emr1, Tyrobp, Itgb2, Fcgr2b, Cybb, and Fcer1g might be the most significant genes during MIRI. A total of 75 natural products were discovered. Most of them (especially araloside C, glycyrrhizic acid, ophiopogonin D, polyphyllin I, and punicalagin) showed good ability to bind the hub genes.

Conclusions

Emr1, Tyrobp, Itgb2, Fcgr2b, Cybb, and Fcer1g might be critical in the pathological process of MIRI, and the natural products (araloside C, glycyrrhizic acid, ophiopogonin D, polyphyllin I, and punicalagin) targeting these hub genes exhibited potential therapeutic efficacy on MIRI. Our findings provided new insights to explore the mechanism and treatments for MIRI and revealed new therapeutic targets for natural products with protective properties against MIRI.

Protective effect of resveratrol on rat cardiomyocyte H9C2 cells injured by hypoxia/reoxygenation by regulating mitochondrial autophagy PTEN-induced putative kinase protein 1/Parkinson disease protein 2 signaling pathway

OBJECTIVE

To investigate the protective effect of resveratrol on cardiomyocytes after hypoxia/ reoxygenation intervention based on PTEN-induced putative kinase protein 1/Parkinson disease protein 2 (PINK1/PARKIN) signaling pathway.

METHODS

3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenylte-trazolium bromide was used to detect the effect of resveratrol on the viability of H9C2 cells; the hypoxia/ reoxygenation (H/R) model was established in tri-gas incubator; 2', 7'-Dichlorofluorescin diacetate staining was used to measure the content of reactive oxygen species (ROS); the changes of mitochondrial membrane potential was determined by 5,5',6,6'-Tetrachloro-1,1',3,3'-tetraethyl-imidacarbocyanine iodide staining; the changes of mitochondrial respiratory chain complex activity was evaluated by enzyme activity kits; flow cytometry was used to detect the ratio of apoptotic cells; transmission electron microscope was used to observe the ultrastructure of H9C2 cells; Western blot was used to detect the protein changes of mitochondrial 20 kDa outer membrane protein (TOM20), translocase of inner mitochondrial membrane 23 (TIM23), presenilins associated rhomboid-like protein (PARL), PINK1, PARKIN and mitofusin 1 (Mfn1), mitofusin 2 (Mfn2), phosphotyrosine independent ligand for the Lck SH2 domain of 62 kDa (P62), microtubule-associated protein 1 light chain 3 beta (LC3B); the mRNA levels of PINK1 and PARKIN was detected by quantitative polymerase chain reaction; immunoprecipitation assay was used to detect the interaction between PARKIN and Ubiquitin.

RESULTS

Resveratrol could inhibit the proliferation of H9C2 cells in a time- and concentration- dependent manner; however, pretreatment with low cytotoxic resveratrol could reduce the H/R-induced increase in cellular ROS levels, alleviate the loss of mitochondrial membrane potential induced by H/R, inhibit H/R-induced apoptosis of H9C2 cells, and protect the mitochondrial structure and respiratory chain of H9C2 cells from H/R damage. Resveratrol could further increase the levels of p62, PINK1, PARKIN protein, the expression of PINK1, PARKIN mRNA and the ratio of LC3BⅡ/LC3BⅠin H/R-induced H9C2 cells, inhibit the interaction between PARKIN and Ubiquitin in H/R-induced H9C2 cells, and further reduce the expression of TOM20,TIM23, PARL, Mfn1 and Mfn2 protein in H/R-induced H9C2 cells. The effect of resveratrol is consistent with that of autophagy activator on H/R-induced H9C2 cells.

CONCLUSIONS

Resveratrol can protect H9C2 cells from H/R injury, which may be related to resveratrol promoting mitochondrial autophagy by activating PINK1/PARKIN signaling pathway.

Role of the Antioxidant Activity of Melatonin in Myocardial Ischemia-Reperfusion Injury

Ischemia-reperfusion injury is a common problem in the age of interventional cardiology; it is primarily mediated by oxidative stress and reactive agents. Melatonin has antioxidative properties that make its use promising for treating ischemia-reperfusion injury. Multiple experimental studies in murine and porcine models have been performed with good results. Clinical trials have also been conducted but given their heterogeneity, no conclusive results can be made. Melatonin pharmacokinetic properties are not ideal; therefore, many analogs have been proposed with improved characteristics, and some studies have evaluated their efficacy in animal models, but clinical trials are needed to recommend their use. In this review, we expose the results of the most impactful studies regarding melatonin use in ischemia-reperfusion injury.

Nerolidol attenuates isoproterenol-induced acute myocardial infarction in rats

Cardiovascular diseases have high morbidity and mortality rates, and their treatment is not effective in reducing the damage caused by myocardial infarction (MI). This study aimed to investigate whether nerolidol (NRD), a sesquiterpene alcohol, could attenuate MI in an isoproterenol-treated rat model. MI was induced by the administration of two doses of isoproterenol (ISO, 100 mg/kg, i.p.) with an interval of 24 h between doses.The animals were divided into four groups: control (CTR) (vehicle - NaCl 0.9% + Tween 80 0.2%), MI (ISO + vehicle), MI + NRD (50 mg/kg) and MI + NRD (100 mg/kg). An electrocardiogram was performed, and contractile parameters, cardiac enzymes, infarction size, and antioxidant parameters in the heart were measured to evaluate the effects of NRD. The ISO group showed a significant rise in ST segment, QTc, and heart rate associated with a reduction in left ventricular developed pressure (LVDP), + dP/dt, and -dP/dt. In addition, there were increases in levels of creatine kinase (CK), creatine kinase-myocardial band (CK-MB), lactate dehydrogenase (LDH), and thiobarbituric acid (TBARS); reductions in superoxide dismutase (SOD) and catalase (CAT) activities; and an increase in the infarction size. Interestingly, NRD significantly attenuated almost all the parameters of ISO-induced MI mentioned above. Our results suggest that nerolidol attenuates MI caused by ISO by a marked reduction in myocardial infarct size and suppression of oxidative stress. CK total, creatine kinase total; CK-MB, creatine kinase myocardial band; LDH, lactate dehydrogenase; SOD, superoxide dismutase; CAT, catalase. CTR (vehicle group), MI (100 mg/kg of isoproterenol), ISO + NRD 50 (50 mg/kg of nerolidol), and ISO + NRD 100 (100 mg/kg of nerolidol).

TRPV1 Contributes to Modulate the Nitric Oxide Pathway and Oxidative Stress in the Isolated and Perfused Rat Heart during Ischemia and Reperfusion

The transient vanilloid receptor potential type 1 (TRPV1) regulates neuronal and vascular functions mediated by nitric oxide (NO) and by the calcitonin gene-related peptide (CGRP). Here, we study the participation of TRPV1 in the regulation of myocardial injury caused by ischemia-reperfusion and in the control of NO, tetrahydrobiopterin (BH4), the cGMP pathway, CGRP, total antioxidant capacity (TAC), malondialdehyde (MDA) and phosphodiesterase-3 (PDE-3). Isolated hearts of Wistar rats perfused according to the Langendorff technique were used to study the effects of an agonist of TRPV1, capsaicin (CS), an antagonist, capsazepine (CZ), and their combination CZ+CS. The hearts were subjected to three conditions: (1) control, (2) ischemia and (3) ischemia-reperfusion. We determined cardiac mechanical activity and the levels of NO, cGMP, BH4, CGRP, TAC, MDA and PDE-3 in ventricular tissue after administration of CS, CZ and CZ+CS. Western blots were used to study the expressions of eNOS, iNOS and phosphorylated NOS (pNOS). Structural changes were determined by histological evaluation. CS prevented damage caused by ischemia-reperfusion by improving cardiac mechanical activity and elevating the levels of NO, cGMP, BH4, TAC and CGRP. TRPV1 and iNOS expression were increased under ischemic conditions, while eNOS and pNOS were not modified. We conclude that the activation of TRPV1 constitutes a therapeutic possibility to counteract the damage caused by ischemia and reperfusion by regulating the NO pathway through CGRP.

Role of miRNA-1 and miRNA-21 in Acute Myocardial Ischemia-Reperfusion Injury and Their Potential as Therapeutic Strategy

Coronary artery disease remains the leading cause of death. Acute myocardial infarction (MI) is characterized by decreased blood flow to the coronary arteries, resulting in cardiomyocytes death. The most effective strategy for treating an MI is early and rapid myocardial reperfusion, but restoring blood flow to the ischemic myocardium can induce further damage, known as ischemia-reperfusion (IR) injury. Novel therapeutic strategies are critical to limit myocardial IR injury and improve patient outcomes following reperfusion intervention. miRNAs are small non-coding RNA molecules that have been implicated in attenuating IR injury pathology in pre-clinical rodent models. In this review, we discuss the role of miR-1 and miR-21 in regulating myocardial apoptosis in ischemia-reperfusion injury in the whole heart as well as in different cardiac cell types with special emphasis on cardiomyocytes, fibroblasts, and immune cells. We also examine therapeutic potential of miR-1 and miR-21 in preclinical studies. More research is necessary to understand the cell-specific molecular principles of miRNAs in cardioprotection and application to acute myocardial IR injury.

miR-451-3p alleviates myocardial ischemia/reperfusion injury by inhibiting MAP1LC3B-mediated autophagy

OBJECTIVE AND DESIGN

We aim to explore the molecular mechanism of myocardial ischemia-reperfusion injury (MIRI).

METHODS

The H9C2 cells were cultured under hypoxia/reoxygenation (H/R) condition to induce myocardial injury in vitro. The expression of miR-451-3p and MAP1LC3B was detected by RT-qPCR. Dual-luciferase reporter assay and RNA pull-down assay were performed to examine the relationship between microRNA (miR)-451-3p and MAP1LC3B. CCK8 was used to test cell viability. The level of LDH and CK was evaluated via ELISA. Immunofluorescence assay and flow cytometry were applied to detect autophagy and apoptosis, respectively. Autophagy-related protein expressions were determined by western blotting. Furthermore, an in vivo rat model of MIRI was established by subjection to 30 min ischemia and subsequently 24 h reperfusion for validation of the role of miR-451-3p in regulating MIRI in vivo.

RESULTS

miR-451-3p was down-regulated in MIRI, and miR-451-3p mimics transfection alleviated autophagy and apoptosis induced by MIRI. miR-451-3p could target MAP1LC3B directly. Co-transfection miR-451-3p mimics and pcDNA 3.1 MAP1LC3B curbed the protected effects of miR-451-3p mimics on MIRI.

CONCLUSIONS

miR-451-3p played a protective role in MIRI via inhibiting MAP1LC3B-mediated autophagy, which may provide new molecular targets for the treatment of MIRI and further improves the clinical outcomes of heart diseases.

Histochrome Attenuates Myocardial Ischemia-Reperfusion Injury by Inhibiting Ferroptosis-Induced Cardiomyocyte Death

Reactive oxygen species (ROS) and intracellular iron levels are critical modulators of lipid peroxidation that trigger iron-dependent non-apoptotic ferroptosis in myocardial ischemia-reperfusion (I/R) injury. Histochrome (HC), with a potent antioxidant moiety and iron-chelating capacity, is now available in clinical practice. However, limited data are available about the protective effects of HC on ferroptotic cell death in myocardial I/R injury. In this study, we investigated whether the intravenous administration of HC (1 mg/kg) prior to reperfusion could decrease myocardial damage by reducing ferroptosis. Rats undergoing 60 min of ischemia and reperfusion were randomly divided into three groups as follows: (1) Sham, (2) I/R control, and (3) I/R + HC. Serial echocardiography up to four weeks after I/R injury showed that intravenous injection of HC significantly improved cardiac function compared to the I/R controls. In addition, the hearts of rats who received intravenous injection of HC exhibited significantly lower cardiac fibrosis and higher capillary density. HC treatment decreased intracellular and mitochondrial ROS levels by upregulating the expression of nuclear factor erythroid 2-related factor (Nrf2) and its downstream genes. HC also inhibited erastin- and RSL3-induced ferroptosis in rat neonatal cardiomyocytes by maintaining the intracellular glutathione level and through upregulated activity of glutathione peroxidase 4. These findings suggest that early intervention with HC before reperfusion rescued myocardium from I/R injury by preventing ferroptotic cell death. Therefore, HC is a promising therapeutic option to provide secondary cardioprotection in patients who undergo coronary reperfusion therapy.

Anti-apoptotic Effect of MiR-223-3p Suppressing PIK3C2A in Cardiomyocytes from Myocardial Infarction Rat Through Regulating PI3K/Akt Signaling Pathway

We aimed to explore the regulatory mechanism of the axis of miR-223-3p-PIK3C2A-PI3K/Akt on cardiomyocyte apoptosis in rats with myocardial infarction. Thirty 8-week-old healthy male SD rats were used for establishing the sham group and the model group, with HE staining, TUNEL staining, and TTC staining performed. After the identification of the targeting relationship between PIK3C2A and miR-223-3p, experimental rats were randomly divided into seven groups by plasmid transfection, including the Blank group, negative control (NC) group, miR-223-3p mimic group, miR-223-3p inhibitor group, siRNA-PIK3C2A group, oe-PIK3C2A group, and miR-223-3p inhibitor + oe-PIK3C2A group. Four weeks after transfection, the expression levels of miR-223-3p and PIK3C2A in tissues as well as PI3K, Akt, Bax, and bcl-2 mRNA in cells were detected by qRT-PCR and western blot, in combination with the detection of apoptosis rate by flow cytometry. Compared with the sham group, the model group showed typical myocardial injury and abnormal staining, higher apoptotic index, and larger myocardial infarction area (all P < 0.05). PIK3C2A was the target gene of miR-223-3p. The expression level of miR-223-3p in model group was significantly lower than that in sham group, while the mRNA and protein expression levels of PIK3C2A increased significantly (all P < 0.05). In cell tests, the expression level of miR-223-3p increased significantly in miR-223-3p mimic group (P < 0.05), which, however, showed no significant change in siRNA-PIK3C2A group (P > 0.05). MiR-223-3p inhibitor group and siRNA-PIK3C2A group had obviously increased PI3K, Akt, mTOR and Bcl-2 mRNA, and protein expression, while decreased mRNA and protein expression of PIK3C2A and Bax (all P < 0.05); miR-223-3p mimic groups had the opposite trends (all P < 0.05). siRNA-PIK3C2A + miR-223-3p mimic showed no obvious change relative to the control groups (all P > 0.05). Low expression of miR-223-3p may downregulate PIK3C2A expression, resulting in the inhibition of myocardial cell apoptosis in rats with myocardial infarction via the activation of PI3K/Akt signaling pathway.

Current Updates on Potential Role of Flavonoids in Hypoxia/Reoxygenation Cardiac Injury Model

Clinically, timely reperfusion strategies to re-establish oxygenated blood flow in ischemic heart diseases seem to salvage viable myocardium effectively. Despite the remarkable improvement in cardiac function, reperfusion therapy could paradoxically trigger hypoxic cellular injury and dysfunction. Experimental laboratory models have been developed over the years to explain better the pathophysiology of cardiac ischemia-reperfusion injury, including the in vitro hypoxia-reoxygenation cardiac injury model. Furthermore, the use of nutritional myocardial conditioning techniques have been successful. The cardioprotective potential of flavonoids have been greatly linked to its anti-oxidant, anti-apoptotic and anti-inflammatory properties. While several studies have reviewed the cardioprotective properties of flavonoids, there is a scarce evidence of their function in the hypoxia-reoxygenation injury cell culture model. Hence, the aim of this review was to lay out and summarize our current understanding of flavonoids' function in mitigating hypoxia-reoxygenation cardiac injury based on evidence from the last five years. We also discussed the possible mechanisms of flavonoids in modulating the cardioprotective effects as such information would provide invaluable insight on future therapeutic application of flavonoids.

Anti-Inflammatory Dipeptide, a Metabolite from Ambioba Secretion, Protects Cerebral Ischemia Injury by Blocking Apoptosis Via p-JNK/Bax Pathway

MQ (l-methionyl-l-glutamic acid), anti-inflammatory dipeptide, is one of the metabolites of monocyte locomotion inhibitory factor, a thermostable pentapeptide secreted by Entamoeba histolytica. Monocyte locomotion inhibitory factor injection has been approved as an investigational drug for the potential neural protection in acute ischemic stroke. This study further investigated the neuroprotective effect of MQ in ischemic brain damage. Ischemia-reperfusion injury of the brain was induced in the rat model by middle cerebral artery occlusion. 2,3,5-triphenyltetrazolium chloride staining assay was used to measure cerebral infarction areas in rats. Laser Doppler measurement instrument was used to detect blood flow changes in the rat model. Nissl staining and NeuN staining were utilized to observe the numbers and structures of neuron cells, and the pathological changes in the brain tissues were examined by hematoxylin–eosin staining. Terminal deoxynucleotidyl transferase deoxyuridine triphosphate nick end labeling (TUNEL) staining was used to assess cell apoptosis. The changes in oxidative stress indexes, superoxide dismutase and malondialdehyde (MDA), were measured in serum. Methyl thiazolyl tetrazolium was used to measure the survival rates of PC12 cells. Flow cytometry assessed the apoptosis rates and the levels of reactive oxygen species. Real-time PCR was used to evaluate the mRNA expression levels, and Western blotting was used to analyze the changes in protein levels of p-JNK, Bax, cleaved Caspase3. We revealed that MQ improved neurobehavior, decreased cerebral infarction areas, altered blood flow volume, and the morphology of the cortex and hippocampus. On the other hand, it decreased the apoptosis of cortical neurons and the levels of MDA, and increased the levels of superoxide dismutase. In vitro studies demonstrated that MQ enhanced the cell survival rates and decreased the levels of reactive oxygen species. Compared to the oxygen-glucose deprivation/reperfusion group, the protein and mRNA expressions of p-JNK, Bax, cleaved Caspase3 was decreased significantly. These findings suggested that MQ exerts a neuroprotective effect in cerebral ischemia by blocking apoptosis via the p-JNK/Bax pathway.

Long Noncoding RNAs in Myocardial Ischemia-Reperfusion Injury

Following an acute myocardial infarction, reperfusion therapy is currently the most effective way to save the ischemic myocardium; however, restoring blood flow may lead to a myocardial ischemia-reperfusion injury (MIRI). Recent studies have confirmed that long-chain noncoding RNAs (LncRNAs) play important roles in the pathophysiology of MIRIs. These LncRNA-mediated roles include cardiomyocyte apoptosis, autophagy, necrosis, oxidative stress, inflammation, mitochondrial dysfunction, and calcium overload, which are regulated through the expression of target genes. Thus, LncRNAs may be used as clinical diagnostic markers and therapeutic targets to treat or prevent MIRI. This review evaluates the research on LncRNAs involved in MIRIs and provides new ideas for preventing and treating this type of injury.

Uhrf1 regulates H3K9me2 modification of mTOR to inhibit the effect of autophagy in myocardial ischemia-reperfusion injury

The regulation of mTOR and the dimethylation of histone H3 on lysine 9 (H3K9me2) H3K9me2 by Uhrf1 and the mechanism of autophagy regulation in myocardial ischemia-reperfusion injury (MIRI) were studied in vivo and in vitro.

An in vitro I/R injury model was established using the primary mouse cardiomyocytes treated with H₂O₂. Subsequent analysis by qRT-PCR, western blot, and immunofluorescence indicated that overexpression of Uhrf1 significantly inhibited apoptosis of the H₂O₂-treated cardiomyocytes, reduced expression of apoptosis factors caspase-3 and Bax, and increased expression of apoptosis inhibitory factor Bcl-2. Furthermore, Uhrf1 was found to increase cardiomyocyte proliferation and promote the expression of mTOR, while the four expression peaks of H3K9me2 on the mTOR gene were inhibited by overexpression of Uhrf1. The expression of autophagy factors LC3, Beclin-1, and p-mTOR in Uhrf1-overexpressed cardiomyocytes was dramatically increased, and P62 expression was dramatically decreased. When an H3K9me2 inhibitor was added to the Uhrf1-knockdown cardiomyocytes, the expression of mTOR was increased, the expression of LC3, Beclin-1, and p-mTOR was decreased, and P62 expression was significantly increased.

In the present study, Uhrf1 exhibits a protective function in MIRI, reducing the apoptosis of cardiomyocytes while increasing their proliferation and viability.

Assessing the Angiogenic Efficacy of Pleiotrophin Released from Injectable Heparin-Alginate Gels

With this work, we design alginate-based hydrogels for therapeutically directing revascularization and repair processes in vivo. We immobilize pleiotrophin (PTN) in injectable hydrogel formulations as the target factor to stimulate proangiogenic responses in endothelial cells. The optimized heparin-alginate/chitosan hydrogels, produced by internal crosslinking with calcium carbonate, show good biocompatibility and injectability and allow controlling the release of immobilized proteins in the subcutaneous tissue over a period of 7 days. In vitro assays, performed with translational human induced pluripotent stem cell-derived endothelial cells, and the in vivo Matrigel plug assay are conducted to demonstrate the angiogenic effects of PTN on endothelial cells. Our results indicate that PTN stimulates endothelial cell morphogenesis in vitro and the migration of endothelial cells and macrophages as soon as 4 days after injections of the developed hydrogels, promoting the formation of structures similar to the healthy granulation tissue, which is an indicator of healing in ischemic wounds. These studies provide the rationale for further investigating this novel therapeutic for pursuing increased vascular density for efficient regeneration of ischemic tissues, by leveraging the host endothelial cell population to initiate angiogenic and reparative processes in vivo. Impact statement Localized, sustained, and controlled delivery of angiogenic factors is crucial for enabling the formation of novel vascular networks in ischemic tissues. This study describes the development of an injectable heparin-alginate/collagen hydrogel for controlling the in vivo release and bioactivity of pleiotrophin (PTN), a heparin-binding factor with significant angiogenic activity. We demonstrate that PTN promotes angiogenesis in an in vitro model of hypoxia and in preclinical subcutaneous models. These results advance our understanding of PTN function in guiding therapeutic angiogenesis and are critical to inform the development of novel translational strategies for ischemic tissue repair and regeneration.

The electrogenic sodium bicarbonate cotransporter and its roles in the myocardial ischemia-reperfusion induced cardiac diseases

Cardiac tissue ischemia/hypoxia increases glycolysis and lactic acid accumulation in cardiomyocytes, leading to intracellular metabolic acidosis. Sodium bicarbonate cotransporters (NBCs) play a vital role in modulating intracellular pH and maintaining sodium ion concentrations in cardiomyocytes. Cardiomyocytes mainly express electrogenic sodium bicarbonate cotransporter (NBCe1), which has been demonstrated to participate in myocardial ischemia/reperfusion (I/R) injury. This review outlines the structural and functional properties of NBCe1, summarizes the signaling pathways and factors that may regulate the activity of NBCe1, and reviews the roles of NBCe1 in the pathogenesis of I/R-induced cardiac diseases. Further studies revealing the regulatory mechanisms of NBCe1 activity should provide novel therapeutic targets for preventing I/R-induced cardiac diseases.

Preventive Effect of Canstatin against Ventricular Arrhythmia Induced by Ischemia/Reperfusion Injury: A Pilot Study

Ventricular arrhythmia induced by ischemia/reperfusion (I/R) injury is a clinical problem in reperfusion therapies for acute myocardial infarction. Ca2+ overload through reactive oxygen species (ROS) production is a major cause for I/R-induced arrhythmia. We previously demonstrated that canstatin, a C-terminal fragment of type IV collagen α2 chain, regulated Ca2+ handling in rat heart. In this study, we aimed to clarify the effects of canstatin on I/R-induced ventricular arrhythmia in rats. Male Wistar rats were subjected to I/R injury by ligating the left anterior descending artery followed by reperfusion. Ventricular arrhythmia (ventricular tachycardia and ventricular fibrillation) was recorded by electrocardiogram. Nicotinamide adenine dinucleotide phosphate oxidase (NOX) activity and ROS production in neonatal rat cardiomyocytes (NRCMs) stimulated with oxygen glucose deprivation/reperfusion (OGD/R) were measured by lucigenin assay and 2',7'-dichlorodihydrofluorescein diacetate staining, respectively. The H2O2-induced intracellular Ca2+ ([Ca2+]i) rise in NRCMs was measured by a fluorescent Ca2+ indicator. Canstatin (20 µg/kg) inhibited I/R-induced ventricular arrhythmia in rats. Canstatin (250 ng/mL) inhibited OGD/R-induced NOX activation and ROS production and suppressed the H2O2-induced [Ca2+]i rise in NRCMs. We for the first time demonstrated that canstatin exerts a preventive effect against I/R-induced ventricular arrhythmia, perhaps in part through the suppression of ROS production and the subsequent [Ca2+]i rise.

Schizandrin B attenuates hypoxia/reoxygenation injury in H9c2 cells by activating the AMPK/Nrf2 signaling pathway

Schizandrin B exhibits prominent antioxidant and anti-inflammatory effects, and plays an important role in ameliorating myocardial ischemia/reperfusion injury. However, the underlying protective mechanisms remain to be elucidated. The aim of the present study was to explore the cardioprotective effects of schizandrin B against hypoxia/reoxygenation (H/R)-induced H9c2 cell injury, focusing on the role of the adenosine monophosphate-activated protein kinase (AMPK)/nuclear factor erythroid 2-related factor 2 (Nrf2) pathway in this process. The results showed that schizandrin B attenuated the H/R-induced decrease in cell viability and the increase in lactate dehydrogenase release, as well as the apoptosis rate in H9c2 cells. Schizandrin B also mitigated H/R-induced oxidative stress, as illustrated by the decrease in intracellular reactive oxygen species generation, malondialdehyde content and NADPH oxidase 2 expression, and the increase in antioxidant enzyme superoxide dismutase and glutathione peroxidase activities. In addition, schizandrin B reversed the H/R-induced upregulation of pro-inflammatory cytokines [interleukin (IL)-1β (IL-1β) tumor necrosis factor-α, IL-6 and IL-8] and the downregulation of anti-inflammatory cytokines (transforming growth factor-β and IL-10) in the culture supernatant. Notably, schizandrin B increased the expression of Nrf2, NAD(P)H: Quinone oxidoreductase (NQO-1) and heme oxygenase-1 (HO-1) in H/R-treated H9c2 cells, activating the Nrf2 signaling pathway. The cardioprotection of schizandrin B against H/R injury was inhibited by Nrf2 knockdown induced byNrf-2-specific small interfering RNA (siRNA; si-Nrf2) transfection. Furthermore, schizandrin B enhanced phosphorylated (p)-AMPK expression, while AMPK knockdown induced by AMPK-specific siRNA(si-AMPK) transfection remarkably eliminated schizandrin B-induced cardioprotection and reduced Nrf2 expression in H/R-treated H9c2 cells. Taken together, these results suggested that schizandrin B exerts cardioprotection on H/R injury in H9c2 cells due to its antioxidant and anti-inflammatory activities via activation of the AMPK/Nrf2 pathway.

CircPAN3 ameliorates myocardial ischaemia/reperfusion injury by targeting miR-421/Pink1 axis-mediated autophagy suppression

Cardiovascular diseases are considered the leading cause of death worldwide. Myocardial ischaemia/reperfusion (I/R) injury is recognized as a critical risk factor for cardiovascular diseases. Although increasing advances have been made recently in understanding the mechanisms of I/R injury, they remain largely unknown. In this study, we found that the expression of circPAN3 (circular RNA PAN3) was decreased in a mouse model of myocardial I/R. Overexpression of circPAN3 significantly inhibited autophagy and alleviated cell apoptosis of cardiomyocytes, which was further verified in vivo by decreased autophagic vacuoles and reduced myocardial infarct sizes. Moreover, miR-421 (microRNA-421) was identified as a downstream target involved in circPAN3-mediated myocardial I/R injury. Additionally, miR-421 could negatively regulate Pink1 (phosphatase and tensin homologue-induced putative kinase 1) via a direct binding relationship. Furthermore, the mitigating effects of circPAN3 overexpression on myocardial I/R injury by suppressing autophagy and apoptosis were abolished by knockdown of Pink1. Our findings reveal a novel role for circPAN3 in modulating autophagy and apoptosis in myocardial I/R injury and the circPAN3-miR-421-Pink1 axis as a regulatory network, which might provide potential therapeutic targets for cardiovascular diseases.

Plantamajoside protects H9c2 cells against hypoxia/reoxygenation-induced injury through regulating the akt/Nrf2/HO-1 and NF-κB signaling pathways

Myocardial ischemia/reperfusion (I/R) injury has been found to be associated with oxidative stress. Plantamajoside (PMS) is a major compound of Plantago asiatica that was reported to possess cardioprotective and antioxidant effects. The current study was designed to investigate the effect of PMS on myocardial I/R injury. Rat cardiomyocytes H9c2 cells were exposed to hypoxia/reoxygenation (H/R) to establish in vitro model of myocardial I/R injury. MTT assay proved that H9c2 cells viability was significant reduced under H/R treatment, while the reduction was ameliorated by PMS. H/R-induced ROS production in H9c2 cells was suppressed by PMS. The decreased activities of superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GSH-Px) in the H/R group were effectively elevated by PMS. In addition, treatment with PMS attenuated H/R-stimulated production of TNF-α, IL-6 and IL-1β in H9c2 cells. Besides, PMS significantly suppressed bax expression and caspase 3 activity, as well as increased bcl-2 expression in H/R-stimulated H9c2 cells. Furthermore, we also found that PMS significantly enhanced the activation of Akt/Nrf2/HO-1 signaling pathway and suppressed the activation of NF-κB signaling pathway in H/R-stimulated H9c2 cells. These results provided substantial evidence that PMS protected against myocardial I/R injury via attenuating oxidative stress, inflammatory response and apoptosis. The protective effects of PMS were attributed to the Akt/Nrf2/HO-1 and NF-κB signaling pathways.

lncRNA-NRF is a Potential Biomarker of Heart Failure After Acute Myocardial Infarction

Long non-coding RNAs (lncRNAs) are a new focus in cardiovascular diseases. The necrosis-related factor (NRF) is a newly discovered lncRNA, which is increased in myocardial injury. We investigated the role of lncRNA-NRF in heart failure (HF) after acute myocardial infarction (AMI) to find a biomarker for early HF detection. This was a cross-sectional study of 76 AMI patients with HF and 58 AMI patients without HF. lncRNA-NRF was shown to be increased in AMI patients with HF compared with AMI patients without HF and had predictive value for diagnosis of HF. It had a high diagnostic value for HF (AUC, 0.975), while the AUC for N-terminal pro-brain natriuretic peptide was 0.720. Our findings suggest that lncRNA-NRF may represent a marker of risk for development of HF post-AMI.

The study of myocardial ischemia-reperfusion treatment through computational modelling

Reperfusion of the blood flow to ischemic myocardium is the standard treatment for patients suffering myocardial infarction. However, the reperfusion itself can also induce myocardial injury, in which the actual mechanism and its risk factors remain unclear. This work aims to study the mechanism of ischemia-reperfusion treatment using a three-dimensional (3D) oxygen diffusion model. An electrical model is then coupled to an oxygen model to identify the possible region of myocardial damage. Our findings show that the value of oxygen exceeds its optimum (>1.0) at the ischemic area during early reperfusion period. This complication was exacerbated in a longer ischemic period. While a longer reperfusion time causes a continuous excessive oxygen supply to the ischemic area throughout the reperfusion time. This work also suggests the use of less than 0.8 of initial oxygen concentration in the reperfusion treatment to prevent undesired upsurge at the early reperfusion period and further myocardial injury. We also found the region at risk for myocardial injury is confined in the ischemic vicinity revealed by its electrical conductivity impairment. Although there is a risk that reperfusion leads to myocardial injury for excessive oxygen accumulation, the reperfusion treatment is helpful in reducing the infarct size.

Elevated perfusate [Na+] increases contractile dysfunction during ischemia and reperfusion

Recent studies revealed that relatively small changes in perfusate sodium ([Na⁺]_o) composition significantly affect cardiac electrical conduction and stability in contraction arrested ex vivo Langendorff heart preparations before and during simulated ischemia. Additionally, [Na⁺]_o modulates cardiomyocyte contractility via a sodium-calcium exchanger (NCX) mediated pathway. It remains unknown, however, whether modest changes to [Na⁺]_o that promote electrophysiologic stability similarly improve mechanical function during baseline and ischemia-reperfusion conditions. The purpose of this study was to quantify cardiac mechanical function during ischemia-reperfusion with perfusates containing 145 or 155 mM Na⁺ in Langendorff perfused isolated rat heart preparations. Relative to 145 mM Na⁺, perfusion with 155 mM [Na⁺]_o decreased the amplitude of left-ventricular developed pressure (LVDP) at baseline and accelerated the onset of ischemic contracture. Inhibiting NCX with SEA0400 abolished LVDP depression caused by increasing [Na⁺]_o at baseline and reduced the time to peak ischemic contracture. Ischemia-reperfusion decreased LVDP in all hearts with return of intrinsic activity, and reperfusion with 155 mM [Na⁺]_o further depressed mechanical function. In summary, elevating [Na⁺]_o by as little as 10 mM can significantly modulate mechanical function under baseline conditions, as well as during ischemia and reperfusion. Importantly, clinical use of Normal Saline, which contains 155 mM [Na⁺]_o, with cardiac ischemia may require further investigation.

Melatonin as a therapy in cardiac ischemia-reperfusion injury: Potential mechanisms by which MT2 activation mediates cardioprotection

Introduction

Previous studies reported the beneficial effects of pretreatment with melatonin on the heart during cardiac ischemia/reperfusion (I/R) injury. However, the effects of melatonin given after cardiac ischemia, as well as its comparative temporal effects are unknown. These include pretreatment, during ischemia, and at the onset of reperfusion. Also, the association between melatonin receptors and cardiac arrhythmias, mitochondrial function and dynamics, autophagy, and mitophagy during cardiac I/R have not been investigated.

Objectives

We tested two major hypotheses in this study. Firstly, the temporal effect of melatonin administration exerts different cardioprotective efficacy during cardiac I/R. Secondly, melatonin provides cardioprotective effects via MT2 activation, leading to improvement in cardiac mitochondrial function and dynamics, reduced excessive mitophagy and autophagy, and decreased cardiac arrhythmias, resulting in improved LV function.

Methods

Male rats were subjected to cardiac I/R, and divided into 4 intervention groups: vehicle, pretreatment with melatonin, melatonin given during ischemia, and melatonin given at the onset of reperfusion. In addition, either a non-specific melatonin receptor (MT) blocker or specific MT2 blocker was given to rats.

Results

Treatment with melatonin at all time points alleviated cardiac I/R injury to a similar extent, quantified by reduction in infarct size, arrhythmia score, LV dysfunction, cardiac mitochondrial dysfunction, imbalance of mitochondrial dynamics, excessive mitophagy, and a decreased Bax/Bcl2 ratio. In H9C2 cells, melatonin increased %cell viability by reducing mitochondrial dynamic imbalance and a decrease in Bax protein expression. The cardioprotective effects of melatonin were dependent on MT2 activation.

Conclusion

Melatonin given before or after ischemia exerted equal levels of cardioprotection on the heart with I/R injury, and its beneficial effects on cardiac arrhythmias, cardiac mitochondrial function and dynamics were dependent upon the activation of MT2.

Extracellular vesicles - mediating and delivering cardioprotection in acute myocardial infarction and heart failure

New treatments are urgently needed to reduce myocardial infarct size and prevent adverse post-infarct left ventricular remodeling, in order to preserve cardiac function, and prevent the onset of heart failure in patients presenting with acute myocardial infarction (AMI). In this regard, extracellular vesicles (EVs) have emerged as key mediators of cardioprotection. Endogenously produced EVs are known to play crucial roles in maintaining normal cardiac homeostasis and function, by acting as mediators of intercellular communication between different types of cardiac cells. Endogenous EVs have also been shown to contribute to innate cardioprotective strategies such as remote ischemic conditioning. In terms of EV-based therapeutics, stem cell-derived EVs have been shown to confer cardioprotection in a large number of small and large animal AMI models, and have the therapeutic potential to be applied in the clinical setting for the benefit of AMI patients, although several challenges need to be overcome. Finally, EVs may be used as vehicles to deliver therapeutics to the infarcted heart, providing a potential synergist approach to cardioprotection. In this review article, we highlight the various roles that EVs play as mediators and deliverers of cardioprotection, and discuss their therapeutic potential for improving clinical outcomes following AMI.

Troxerutin attenuates oxygen‑glucose deprivation and reoxygenation‑induced oxidative stress and inflammation by enhancing the PI3K/AKT/HIF‑1α signaling pathway in H9C2 cardiomyocytes

Myocardial ischemia-reperfusion (MI/R) injury is a complex pathological process that occurs when tissues are reperfused following a prolonged period of ischemia. Troxerutin has been reported to have cardioprotective functions. However, the underlying mechanism by which troxerutin protects against MI/R injury has not been fully elucidated. The aim of the present study was to explore whether troxerutin-mediated protection against oxygen-glucose deprivation/reoxygenation (OGD/R)-induced H9C2 cell injury was associated with the inhibition of oxidative stress and the inflammatory response by regulating the PI3K/AKT/hypoxia-inducible factor-1α (HIF-1α) signaling pathway. The results of the present study suggested that troxerutin pretreatment prevented the OGD/R-induced reduction in cell viability, and the increase in lactate dehydrogenase activity and apoptosis. Troxerutin reversed OGD/R-induced the inhibition of the PI3K/AKT/HIF-1α signaling pathway as demonstrated by the increased expression of PI3K and HIF-1α, and the increased ratio of phosphorylated AKT/AKT. LY294002, a selective PI3K inhibitor, inhibited the PI3K/AKT/HIF-1α signaling pathway and further attenuated the protective effect of troxerutin against OGD/R-induced H9C2 cell damage. Furthermore, small interfering (si)RNA-mediated knockdown of HIF-1α reduced troxerutin-induced protection against OGD/R injury. Troxerutin pretreatment alleviated OGD/R-induced oxidative stress, as demonstrated by the reduced generation of reactive oxygen species and malonaldehyde content, and the increased activities of superoxide dismutase and glutathione peroxidase, which were reduced by HIF-1α-siRNA. Troxerutin-induced decreases in the levels of interleukin (IL)-1β, IL-6 and tumor necrosis factor-α in OGD/R conditions were also reduced by HIF-1α-siRNA. The results from the present study indicated that troxerutin aggravated OGD/R-induced H9C2 cell injury by inhibiting oxidative stress and the inflammatory response. The primary underlying protective mechanism of troxerutin was mediated by the activation of the PI3K/AKT/HIF-1α signaling pathway.

β-Sitosterol Protects against Myocardial Ischemia/Reperfusion Injury via Targeting PPARγ/NF-κB Signalling

Myocardial ischemia/reperfusion (I/R) injury is a clinically severe complication, which can cause high rates of disability and mortality particularly in patients with myocardial infarction, yet the molecular mechanisms underlying this process remain unclear. This study aimed to explore the protective effects of β-sitosterol against myocardial I/R injury and to elucidate the underlying molecular mechanisms. Our results showed that hypoxia/reoxygenation (H/R) treatment suppressed cell viability, induced cell apoptosis and reactive oxygen species production, increased caspase-3 and -9 activities, upregulated caspase-3 and -9 protein expressions, downregulated the Bcl-2 protein expression, and reduced the mitochondrial membrane potential. β-Sitosterol treatment attenuated H/R-induced cardiomyocyte injury. Moreover, β-sitosterol treatment counteracted the inhibitory effects of H/R treatment on the peroxisome proliferator-activated receptor gamma (PPARγ) expression and enhanced effects of H/R treatment on the NF-κB expression in cardiomyocytes. Furthermore, inhibition of PPARγ impaired the protective actions of β-sitosterol against H/R-induced cardiomyocyte injury. In the I/R rats, β-sitosterol treatment reduced the myocardial infarcted size and apoptosis, which was attenuated by the inhibition of PPARγ. In conclusion, our results demonstrate that β-sitosterol protected against in vitro H/R-induced cardiomyocyte injury and in vivo myocardial I/R injury. The β-sitosterol-mediated cardioprotective effects may involve the modulation of PPARγ/NF-κB signalling during myocardial I/R injury. Further studies are required to further explore the clinical application of β-sitosterol in the myocardial I/R injury.

miR-26a-5p protects against myocardial ischemia/reperfusion injury by regulating the PTEN/PI3K/AKT signaling pathway

Reperfusion strategies in acute myocardial infarction (AMI) can cause a series of additional clinical damage, defined as myocardial ischemia/reperfusion (I/R) injury, and thus there is a need for effective therapeutic methods to attenuate I/R injury. miR-26a-5p has been proven to be an essential regulator for biological processes in different cell types. Nevertheless, the role of miR-26a-5p in myocardial I/R injury has not yet been reported. We established an I/R injury model in vitro and in vivo. In vitro, we used cardiomyocytes to simulate I/R injury using hypoxia/reoxygenation (H/R) assay. In vivo, we used C57BL/6 mice to construct I/R injury model. The infarct area was examined by TTC staining. The level of miR-26a-5p and PTEN was determined by bioinformatics methods, qRT-PCR, and western blot. In addition, the viability and apoptosis of cardiomyocytes were separately detected by MTT and flow cytometry. The targeting relationship between miR-26a-5p and PTEN was analyzed by the TargetScan website and luciferase reporter assay. I/R and H/R treatment induced myocardial tissue injury and cardiomyocyte apoptosis, respectively. The results showed that miR-26a-5p was down-regulated in myocardial I/R injury. PTEN was found to be a direct target of miR-26a-5p. Furthermore, miR-26a-5p effectively improved viability and inhibited apoptosis in cardiomyocytes upon I/R injury by inhibiting PTEN expression to activate the PI3K/AKT signaling pathway. miR-26a-5p could protect cardiomyocytes against I/R injury by regulating the PTEN/PI3K/AKT pathway, which offers a potential approach for myocardial I/R injury treatment.

MicroRNA-21 mediates the protective effects of salidroside against hypoxia/reoxygenation-induced myocardial oxidative stress and inflammatory response

Myocardial ischemia-reperfusion (I/R) injury is the oxidative stress and inflammatory response that occurs when a tissue is reperfused following a prolonged period of ischemic injury. Growing evidence has demonstrated that microRNAs (miRs) are essential in the development of myocardial I/R injury. Salidroside, a phenylpropanoid glycoside isolated from a traditional Chinese medicinal plant, Rhodiola rosea, possesses multiple pharmacological functions and protects against myocardial I/R injury in vitro and in vivo. However, the role of miRs in the cardioprotective effects of salidroside against myocardial I/R injury has not been studied, to the best of our knowledge. In the present study, the role of miR21 in the underlying mechanism of salidroside-induced protection against oxidative stress and inflammatory injuries in hypoxia/reoxygenation (H/R)-treated H9c2 cardiomyocytes was determined. The cell viability was assessed with an MTT assay. Lactate dehydrogenase (LDH) release, caspase-3 activity, malondialdehyde (MDA) level, superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) activities were determined by commercial kits. Cell apoptosis was measured by flow cytometry. Intracellular reactive oxygen species (ROS) generation was monitored by DCFH-DA. The miR-21 level was quantified by reverse transcription-quantitative (RT-q)PCR. The interleukin (IL)-6, IL-1β and tumor necrosis factor (TNF)-α levels were measured by RT-qPCR and ELISA. The results showed that salidroside pretreatment significantly increased cell viability and decreased the release of LDH, accompanied by an increase in miR-21 expression in H/R-treated H9c2 cells and a miR-21 inhibitor reversed these effects. In addition, the miR-21 inhibitor also abrogated the inhibition of salidroside on H/R-induced increases in apoptosis and caspase-3 activity in H9c2 cells. Salidroside mitigated H/R-induced oxidative stress as illustrated by the downregulation of ROS generation and MDA level and increased the activities of the antioxidant enzymes, SOD and GSH-Px, all of which were abrogated in cells transfected with the miR-21 inhibitor. Salidroside induced a decrease in the expression and levels of the pro-inflammatory cytokines, IL-6, IL-1β and TNF-α, which were prevented by the miR-21 inhibitor. Together, these results provide evidence of the beneficial effects of salidroside against myocardial I/R injury by reducing myocardial oxidative stress and inflammation which are enhanced by increasing miR-21 expression.

Treatment with metformin prevents myocardial ischemia-reperfusion injury via STEAP4 signaling pathway

Objective:

The aim of the present study was to investigate the underlying mechanism of metformin in reducing myocardial apoptosis and improving mitochondrial function in rats and H9c2 cells subjected to myocardial ischemia–reperfusion (I/R) or hypoxia–reoxygenation (H/R) injuries, respectively.

Methods:

Following pretreatment with metformin, male Sprague–Dawley rats were used to establish an I/R model in vivo. Serum creatinine kinase-MB and cardiac troponin T levels were examined by enzyme-linked immunosorbent assay. Infarct size and apoptosis were measured by triphenyl tetrazolium chloride staining and terminal deoxynucleotidyl transferase dUTP nick end labeling assay. Pathological changes were evaluated by hematoxylin and eosin staining. H9c2 cells were used to establish an H/R model in vitro. Cell apoptosis and mitochondrial membrane potential (MMP) were examined by flow cytometry and Rhodamine 123. The expression levels of six-transmembrane epithelial antigen of prostate 4 (STEAP4), B-cell lymphoma 2, Bcl-2-associated X protein, and glyceraldehyde 3-phosphate dehydrogenase in both myocardial tissues and H9c2 cells were determined by western blotting.

Results:

We found that metformin decreased infarct size, increased STEAP4 expression, mitigated myocardial apoptosis, and increased MMP when the models were subjected to H/R or I/R injuries. However, STEAP4 knockdown significantly abrogated the beneficial effect of metformin.

Conclusion:

We further demonstrated the protective effect of metformin on cardiomyocytes, which might be at least partly attributable to the upregulation of STEAP4. Therefore, STEAP4 might be a new target to decrease apoptosis and rescue mitochondrial function in myocardial I/R injury.