lncRNA CCAT2 Protects Against Cardiomyocyte Injury After Myocardial Ischemia/Reperfusion by Regulating BMI1 Expression.

Myocardial ischemia/reperfusion (I/R) decreases cardiac function and efficiency. Accumulating evidence suggests that long noncoding RNAs (lncRNAs) have been linked to the cellular processes of myocardial I/R injury. The present investigation elucidated the function of lncRNA colon cancer-associated transcript 2 (CCAT2) in myocardial I/R injury and the related mechanisms.AC16 cardiomyocytes were exposed to hypoxia (16 hours) /reoxygenation (6 hours) (H/R) to mimic myocardial I/R models in vitro. CCAT2 and microRNA (miR) -539-3p expressions in AC16 cardiomyocytes were measured using real-time quantitative polymerase chain reaction. B-cell-specific Moloney murine leukemia virus insertion region 1 (BMI1) protein levels in AC16 cardiomyocytes were determined by western blotting. Cell viability, lactate dehydrogenase (LDH) leakage, reactive oxygen species (ROS) levels, mitochondrial membrane potential, and apoptosis were detected using Counting Kit-8, LDH Assay Kit, dihydroethidium assay, 5,5',6,6'-tetrachloro1,1',3,3'-tetramethylbenzimidazolylcarbocyanine iodide staining, flow cytometry, and western blotting, respectively. The interactions between the molecules were confirmed using the dual-luciferase gene reporter. The wingless/integrated/beta-catenin (Wnt/ß-catenin) pathway under the H/R condition was detected by western blotting.CCAT2 and BMI1 mRNA expressions were reduced in H/R-exposed AC16 cardiomyocytes. CCAT2 overexpression exerted protective effects against H/R-induced cardiomyocyte injury, as demonstrated by increased cell viability and mitochondrial membrane potential and decreased LDH leakage, ROS levels, and apoptosis. In addition, CCAT2 positively regulated BMI1 expression by binding to miR-539-3p. CCAT2 knockdown or miR-539-3p overexpression restrained the protective effects of BMI1 against H/R-induced cardiomyocyte injury. In addition, miR-539-3p overexpression reversed the protective effects of CCAT2. Furthermore, CCAT2 activated the Wnt/ß-catenin pathway under the H/R condition via the miR-539-3p/BMI1 axis.Overall, this investigation showed the protective effects of the CCAT2/miR-539-3p/BMI1/Wnt/ß-catenin regulatory axis against cardiomyocyte injury induced by H/R.

p53 Acetylation Exerts Critical Roles in Pressure Overload-Induced Coronary Microvascular Dysfunction and Heart Failure in Mice.

BACKGROUND: Coronary microvascular dysfunction (CMD) has been shown to contribute to cardiac hypertrophy and heart failure (HF) with preserved ejection fraction. At this point, there are no proven treatments for CMD. METHODS: We have shown that histone acetylation may play a critical role in the regulation of CMD. By using a mouse model that replaces lysine with arginine at residues K98, K117, K161, and K162R of p53 (p534KR), preventing acetylation at these sites, we test the hypothesis that acetylation-deficient p534KR could improve CMD and prevent the progression of hypertensive cardiac hypertrophy and HF. Wild-type and p534KR mice were subjected to pressure overload by transverse aortic constriction to induce cardiac hypertrophy and HF. RESULTS: Echocardiography measurements revealed improved cardiac function together with a reduction of apoptosis and fibrosis in p534KR mice. Importantly, myocardial capillary density and coronary flow reserve were significantly improved in p534KR mice. Moreover, p534KR upregulated the expression of cardiac glycolytic enzymes and Gluts (glucose transporters), as well as the level of fructose-2,6-biphosphate; increased PFK-1 (phosphofructokinase 1) activity; and attenuated cardiac hypertrophy. These changes were accompanied by increased expression of HIF-1α (hypoxia-inducible factor-1α) and proangiogenic growth factors. Additionally, the levels of SERCA-2 were significantly upregulated in sham p534KR mice, as well as in p534KR mice after transverse aortic constriction. In vitro, p534KR significantly improved endothelial cell glycolytic function and mitochondrial respiration and enhanced endothelial cell proliferation and angiogenesis. Similarly, acetylation-deficient p534KR significantly improved coronary flow reserve and rescued cardiac dysfunction in SIRT3 (sirtuin 3) knockout mice. CONCLUSIONS: Our data reveal the importance of p53 acetylation in coronary microvascular function, cardiac function, and remodeling and may provide a promising approach to improve hypertension-induced CMD and to prevent the transition of cardiac hypertrophy to HF.

Neutrophils are indispensable for adverse cardiac remodeling in heart failure.

Persistent immune activation contributes significantly to left ventricular (LV) dysfunction and adverse remodeling in heart failure (HF). In contrast to their well-known essential role in acute myocardial infarction (MI) as first responders that clear dead cells and facilitate subsequent reparative macrophage polarization, the role of neutrophils in the pathobiology of chronic ischemic HF is poorly defined. To determine the importance of neutrophils in the progression of ischemic cardiomyopathy, we measured their production, levels, and activation in a mouse model of chronic HF 8 weeks after permanent coronary artery ligation and large MI. In HF mice, neutrophils were more abundant both locally in failing myocardium (more in the border zone) and systemically in the blood, spleen, and bone marrow, together with increased BM granulopoiesis. There were heightened stimuli for neutrophil recruitment and trafficking in HF, with increased myocardial expression of the neutrophil chemoattract chemokines CXCL1 and CXCL5, and increased neutrophil chemotactic factors in the circulation. HF neutrophil NETotic activity was increased in vitro with coordinate increases in circulating neutrophil extracellular traps (NETs) in vivo. Neutrophil depletion with either antibody-based or genetic approaches abrogated the progression of LV remodeling and fibrosis at both intermediate and late stages of HF. Moreover, analogous to murine HF, the plasma milieu in human acute decompensated HF strongly promoted neutrophil trafficking. Collectively, these results support a key tissue-injurious role for neutrophils and their associated cytotoxic products in ischemic cardiomyopathy and suggest that neutrophils are potential targets for therapeutic immunomodulation in this disease.

Suxiao Jiuxin Pill alleviates myocardial ischemia/reperfusion-induced autophagy via miR-193a-3p/ALKBH5 pathway.

BACKGROUND: Myocardial ischemia/reperfusion injury (MIRI) poses a formidable challenge to cardiac reperfusion therapy due to the absence of effective clinical interventions. Methylation of N6-methyladenosine (m6A), which is the most common post-transcriptional modifications occurring within mammalian mRNA, is believed to be involved in MIRI by modulating autophagy. MicroRNAs (miRNAs) play a crucial role in regulating gene expression at the post-transcriptional level and have been implicated in the regulation of m6A methylation. Suxiao Jiuxin Pill (SJP) is extensively used in China for the clinical treatment of angina pectoris and confers benefits to patients with acute coronary syndrome who have received percutaneous coronary intervention. However, the precise mechanisms underlying SJP intervention in MIRI remain unclear. PURPOSE: This study aimed to demonstrate, both in vivo and in vitro, that SJP could alleviate autophagy in MIRI by regulating miR-193a-3p to target and upregulate the demethylase ALKBH5. METHODS: An in vitro hypoxia/reoxygenation model was established using H9c2 cells, while an in vivo MIRI model was established using Wistar rats. A lentivirus harboring the precursor sequence of miR-193a-3p was employed for its overexpression. Adeno-associated viruses were used to silence both miR-193a-3p and ALKBH5 expressions. Cardiac function, infarct size, and tissue structure in rats were assessed using echocardiography, triphenyl tetrazolium chloride (TTC) staining, and HE staining, respectively. Terminal deoxynucleotidyl transferase dUTP nick-end labeling (TUNEL) was employed to detect the levels of apoptosis in rat cardiac tissue. m6A methylation levels were assessed using colorimetry. GFP-RFP-LC3B was used to monitor autophagic flux and transmission electron microscopy was used to evaluate the development of autophagosomes. Western Blot and qRT-PCR were respectively employed to assess the levels of autophagy-related proteins and miR-193a-3p. RESULTS: SJP alleviated autophagy, preserved cardiac function, and minimized myocardial damage in the hearts of MIRI rats. SJP attenuated autophagy in H/R H9C2 cells. Elevated levels of miR-193a-3p were observed in the cardiac tissues of MIRI rats and H/R H9C2 cells, whereas SJP downregulated miR-193a-3p levels in these models. ALKBH5, a target gene of miR-193, is negatively regulated by miR-193a-3p. Upon overexpression of miR-193a-3p or silencing of ALKBH5, m6A methylation decreased, and the autophagy-attenuating effects of SJP and its components, senkyunolide A and l-borneol, were lost in H/R H9C2 cells, whereas in MIRI rats, these effects were not abolished but merely weakened. Further investigation indicated that the METTL3 inhibitor STM2475, combined with the silencing of miR-193a-3p, similarly attenuated autophagy in the hearts of MIRI rats. This suggests that a reduction in m6A methylation is involved in autophagy alleviation. CONCLUSION: We demonstrated that SJP mitigates autophagy in MIRI by downregulating miR-193a-3p, enhancing ALKBH5 expression, and reducing m6A methylation, a mechanism potentially attributed to its constituents, senkyunolide A and l-borneol.

HSPA12A maintains aerobic glycolytic homeostasis and Histone3 lactylation in cardiomyocytes to attenuate myocardial ischemia/reperfusion injury.

Myocardial ischemia/reperfusion (MI/R) injury is a major cause of adverse outcomes of revascularization following myocardial infarction. Anaerobic glycolysis during myocardial ischemia is well studied, but the role of aerobic glycolysis during the early phase of reperfusion is incompletely understood. Lactylation of Histone H3 (H3) is an epigenetic indicator of the glycolytic switch. Heat shock protein A12A (HSPA12A) is an atypic member of the HSP70 family. In the present study, we report that, during reperfusion following myocardial ischemia, HSPA12A was downregulated and aerobic glycolytic flux was decreased in cardiomyocytes. Notably, HSPA12A KO in mice exacerbated MI/R-induced aerobic glycolysis decrease, cardiomyocyte death, and cardiac dysfunction. Gain- and loss-of-function studies demonstrated that HSPA12A was required to support cardiomyocyte survival upon hypoxia/reoxygenation (H/R) challenge and that its protective effects were mediated by maintaining aerobic glycolytic homeostasis for H3 lactylation. Further analyses revealed that HSPA12A increased Smurf1-mediated Hif1α protein stability, thus increasing glycolytic gene expression to maintain appropriate aerobic glycolytic activity to sustain H3 lactylation during reperfusion and, ultimately, improving cardiomyocyte survival to attenuate MI/R injury.

Engineered bone marrow mesenchymal stem cell-derived exosomes loaded with miR302 through the cardiomyocyte specific peptide can reduce myocardial ischemia and reperfusion (I/R) injury.

BACKGROUND: MicroRNA (miRNA)-based therapies have shown great potential in myocardial repair following myocardial infarction (MI). MicroRNA-302 (miR302) has been reported to exert a protective effect on MI. However, miRNAs are easily degraded and ineffective in penetrating cells, which limit their clinical applications. Exosomes, which are small bioactive molecules, have been considered as an ideal vehicle for miRNAs delivery due to their cell penetration, low immunogenicity and excellent stability potential. Herein, we explored cardiomyocyte-targeting exosomes as vehicles for delivery of miR302 into cardiomyocyte to potentially treat MI. METHODS: To generate an efficient exosomal delivery system that can target cardiomyocytes, we engineered exosomes with cardiomyocyte specific peptide (CMP, WLSEAGPVVTVRALRGTGSW). Afterwards, the engineered exosomes were characterized and identified using transmission electron microscope (TEM) and Nanoparticle Tracking Analysis (NTA). Later on, the miR302 mimics were loaded into the engineered exosomes via electroporation technique. Subsequently, the effect of the engineered exosomes on myocardial ischemia and reperfusion (I/R) injury was evaluated in vitro and in vivo, including MTT, ELISA, real-time quantitative polymerase chain reaction (PCR), western blot, TUNNEL staining, echocardiogram and hematoxylin and eosin (HE) staining. RESULTS: Results of in vitro experimentation showed that DSPE-PEG-CMP-EXO could be more efficiently internalized by H9C2 cells than unmodified exosomes (blank-exosomes). Importantly, compared with the DSPE-PEG-CMP-EXO group, DSPE-PEG-CMP-miR302-EXO significantly upregulated the expression of miR302, while exosomes loaded with miR302 could enhance proliferation of H9C2 cells. Western blot results showed that the DSPE-PEG-CMP-miR302-EXO significantly increased the protein level of Ki67 and Yap, which suggests that DSPE-PEG-CMP-miR302-EXO enhanced the activity of Yap, the principal downstream effector of Hippo pathway. In vivo, DSPE-PEG-CMP-miR302-EXO improved cardiac function, attenuated myocardial apoptosis and inflammatory response, as well as reduced infarct size significantly. CONCLUSION: In conclusion, our findings suggest that CMP-engineered exosomes loaded with miR302 was internalized by H9C2 cells, an in vitro model for cardiomyocytes coupled with potential enhancement of the therapeutic effects on myocardial I/R injury.

Forensic significance of intracardiac expressions of Nrf2 in acute myocardial ischemia.

When exposed to oxidative and electrophilic stress, a protective antioxidant response is initiated by nuclear factor erythroid 2-related factor 2 (Nrf2). However, the extent of its importance in the forensic diagnosis of acute ischemic heart diseases (AIHD), such as myocardial infarction (MI), remains uncertain. On the other hand, immunohistochemical analyses of fibronectin (FN) and the terminal complement complex (C5b-9) prove valuable in identifying myocardial ischemia that precedes necrosis during the postmortem diagnosis of sudden cardiac death (SCD). In this study, we investigated the immunohistochemical levels of Nrf2, FN, and C5b-9 in human cardiac samples to explore their forensic relevance for the identification of acute cardiac ischemia. Heart samples were obtained from 25 AIHD cases and 39 non-AIHD cases as controls. Nrf2 was localized in the nuclei of cardiomyocytes, while FN and C5b-9 were detected in the myocardial cytoplasm. The number of intranuclear Nrf2 positive signals in cardiomyocytes increased in AIHD cases compared to control cases. Additionally, the grading of positive portions of cardiac FN and C5b-9 in the myocardium was also significantly enhanced in AIHD, compared to controls. Collectively, these results indicate that the immunohistochemical investigation of Nrf2 combined with FN, and/or C5b-9 holds the potential for identifying early-stage myocardial ischemic lesions in cases of SCD.

Co-treatment with bone marrow-derived mesenchymal stem cells and curcumin improved angiogenesis in myocardium in a rat model of MI.

BACKGROUND: The cardioprotective properties of mesenchymal stem cells and the therapeutic potential of curcumin (CUR) have been explored. Combining these approaches may enhance stem cell effectiveness and expedite healing. This study aimed to investigate the synergistic effects of co-treating bone marrow mesenchymal stem cells (BMSCs) with curcumin on vascular endothelial growth factor (VEGF) levels, in a rat model of myocardial ischemia (MI). METHODS AND RESULTS: Sixty-five male rats were divided into four groups: G1 (healthy control), G2 (MI induced by isoproterenol hydrochloride), G3 (treated with BMSCs), and G4 (co-treated with curcumin and BMSCs). Blood and tissue samples were collected at specific time points (day 1, 7, 15 and 21) after MI induction. Serum levels of lactate dehydrogenase (LDH), creatine kinase (CK), cardiac troponin I (cTnI), aspartate aminotransferase (AST), CK-MB and VEGF were measured. VEGF mRNA and protein expression were evaluated using RT-qPCR and Western blot techniques. Histopathological assessments were performed using H&E staining and CD31 immunofluorescence staining. VEGF expression significantly increased on days 7 and 15 in the CUR-BMSCs group, peaking on day 7. Western blot analysis confirmed elevated VEGF protein expression on days 7 and 15 post-MI. ELISA results demonstrated increased serum VEGF levels on days 7 and 15, reaching the highest level on day 7 in CUR-BMSCs-treated animals. Treated groups showed lower levels of LDH, AST, CK, CK-MB and cTnI compared to the untreated MI group. H&E staining revealed improved myocardial structure, increased formation of new capillaries, in both treatment groups compared to the MI group. CONCLUSION: Combining curcumin with BMSCs promotes angiogenesis in the infarcted myocardium after 15 days of MI induction. These findings suggest the potential of this combined therapy approach for enhancing cardiac healing and recovery.

GCN5L1-mediated acetylation prevents Rictor degradation in cardiac cells after hypoxic stress.

Cardiomyocyte apoptosis and cardiac fibrosis are the leading causes of mortality in patients with ischemic heart disease. As such, these processes represent potential therapeutic targets to treat heart failure resulting from ischemic insult. We previously demonstrated that the mitochondrial acetyltransferase protein GCN5L1 regulates cardiomyocyte cytoprotective signaling in ischemia-reperfusion injury in vivo and hypoxia-reoxygenation injury in vitro. The current study investigated the mechanism underlying GCN5L1-mediated regulation of the Akt/mTORC2 cardioprotective signaling pathway. Rictor protein levels in cardiac tissues from human ischemic heart disease patients were significantly decreased relative to non-ischemic controls. Rictor protein levels were similarly decreased in cardiac AC16 cells following hypoxic stress, while mRNA levels remained unchanged. The reduction in Rictor protein levels after hypoxia was enhanced by the knockdown of GCN5L1, and was blocked by GCN5L1 overexpression. These findings correlated with changes in Rictor lysine acetylation, which were mediated by GCN5L1 acetyltransferase activity. Rictor degradation was regulated by proteasomal activity, which was antagonized by increased Rictor acetylation. Finally, we found that GCN5L1 knockdown restricted cytoprotective Akt signaling, in conjunction with decreased mTOR abundance and activity. In summary, these studies suggest that GCN5L1 promotes cardioprotective Akt/mTORC2 signaling by maintaining Rictor protein levels through enhanced lysine acetylation.

A multifactorial study of in situ antioxidant activity of modified GrO in myocardial reperfusion injury using the Langerdorff model.

Carbon nanomaterials possess antioxidant properties that can be applied in biomedicine and clinics for the development of new highly effective treatments against oxidative stress-induced diseases like ischemic heart disease. We previously reported the usage of graphene oxide (GrO) as a precursor for the elaboration of such prototypes. The promising findings led to the development of two new modifications of GrO: nitrogen-doped (N-GrO) and l-cysteine functionalized (S-GrO) derivatives as possible antioxidant agents in ischemia-reperfusion (I/R) conditions. In this study, the cardioprotective and antioxidant potential of modified GrO as a pre-treatment in rats was evaluated for the first time. In Langendorff isolated rat heart I/R model, the left ventricle developed pressure (LVDP), the end-diastolic pressure (EDP), the maximal (dP/dtmax) and minimal (dP/dtmin) value of the first derivative of LVDP, and heart rate (HR) were measured. The oxidative-nitrosative markers, in particular, the rate of O2*- and H2O2 generation, the content of malonic dialdehyde, diene conjugates, and leukotriene as well as cNOS and iNOS activity were estimated. Obtained results show a significant restoration of cadiodynamic parameters at the reperfusion period. Simultaneously, all samples significantly reduced the rate of reactive oxygen species (ROS) and lipid peroxidation markers in cardiac homogenates and preserved cNOS activity at the preischemic level. This evidence makes GrO derivatives promising candidates for the correction of reperfusion disorders affecting myocardial function.

Myocardial energy balance and metabolism as causes of myocardial ischemia.

The current approach to myocardial ischemia has been influenced by the misconception of a close link between ischemia and coronary atherosclerotic obstructions. Recent guidelines have, however, acknowledged the multifactorial nature of this condition, with an identifiable cause present in less than half of angina patients, and a large fraction with angina of unknown origin. Because of this background, focusing on cardiac energy metabolim offers new opportunities to manage myocardial ischemia even when its cause is unknown.

SIRT1 is a regulator of autophagy: Implications for the progression and treatment of myocardial ischemia-reperfusion.

SIRT1 is a highly conserved nicotinamide adenine dinucleotide (NAD+)-dependent histone deacetylase. It is involved in the regulation of various pathophysiological processes, including cell proliferation, survival, differentiation, autophagy, and oxidative stress. Therapeutic activation of SIRT1 protects the heart and cardiomyocytes from pathology-related stress, particularly myocardial ischemia/reperfusion (I/R). Autophagy is an important metabolic pathway for cell survival during energy or nutrient deficiency, hypoxia, or oxidative stress. Autophagy is a double-edged sword in myocardial I/R injury. The activation of autophagy during the ischemic phase removes excess metabolic waste and helps ensure cardiomyocyte survival, whereas excessive autophagy during reperfusion depletes the cellular components and leads to autophagic cell death. Increasing research on I/R injury has indicated that SIRT1 is involved in the process of autophagy and regulates myocardial I/R. SIRT1 regulates autophagy through various pathways, such as the deacetylation of FOXOs, ATGs, and LC3. Recent studies have confirmed that SIRT1-mediated autophagy plays different roles at different stages of myocardial I/R injury. By targeting the mechanism of SIRT1-mediated autophagy at different stages of I/R injury, new small-molecule drugs, miRNA activators, or blockers can be developed. For example, resveratrol, sevoflurane, quercetin, and melatonin in the ischemic stage, coptisine, curcumin, berberine, and some miRNAs during reperfusion, were involved in regulating the SIRT1-autophagy axis, exerting a cardioprotective effect. Here, we summarize the possible mechanisms of autophagy regulation by SIRT1 in myocardial I/R injury and the related molecular drug applications to identify strategies for treating myocardial I/R injury.

Sodium-glucose co-transporter 2 inhibitor canagliflozin modulates myocardial metabolism and inflammation in a swine model for chronic myocardial ischemia.

BACKGROUND: Inflammation and disruption of cardiac metabolism are prevalent in the setting of myocardial ischemia. Canagliflozin, a sodium-glucose costransporter-2 inhibitor, has beneficial effects on the heart, though the precise mechanisms are unknown. This study investigated the effects of canagliflozin therapy on metabolic pathways and inflammation in ischemic myocardial tissue using a swine model of chronic myocardial ischemia. METHODS: Sixteen Yorkshire swine underwent placement of an ameroid constrictor to the left circumflex artery to induce chronic ischemia. Two weeks later, pigs received either no drug (n = 8) or 300 mg canagliflozin (n = 8) daily. Five weeks later, pigs underwent terminal harvest and tissue collection. RESULTS: Canagliflozin treatment was associated with a trend toward decreased expression of fatty acid oxidation inhibitor acetyl-CoA carboxylase and decreased phosphorylated/inactivated acetyl-CoA carboxylase, a promotor of fatty acid oxidation, compared with control ischemic myocardium (P = .08, P = .03). There was also a significant modulation in insulin resistance markers p-IRS1, p-PKCα, and phosphoinositide 3-kinase in ischemic myocardium of the canagliflozin group compared with the control group (all P < .05). Canagliflozin treatment was associated with a significant increase in inflammatory markers interleukin 6, interleukin 17, interferon-gamma, and inducible nitric oxide synthase (all P < .05). There was a trend toward decreased expression of the anti-inflammatory cytokines interleukin 10 (P = .16) and interleukin 4 (P = .31) with canagliflozin treatment. CONCLUSION: The beneficial effects of canagliflozin therapy appear to be associated with inhibition of fatty acid oxidation and enhancement of insulin signaling in ischemic myocardium. Interestingly, canagliflozin appears to increase the levels of several inflammatory markers, but further studies are required to better understand how canagliflozin modulates inflammatory signaling pathways.

Investigation of the active ingredients of Shuangshen Ningxin Fomula and the mechanism underlying their protective effects against myocardial ischemia-reperfusion injury by mass spectrometric imaging.

BACKGROUND: Traditional Chinese medicine, particularly Shuangshen Ningxin Capsule (SSNX), has been studied intensely. SSNX includes total ginseng saponins (from Panax ginseng Meyer), total phenolic acids from Salvia miltiorrhiza Bunge, and total alkaloids from Corydalis yanhusuo W. T. Wang. It has been suggested to protect against myocardial ischemia by a mechanism that has not been fully elucidated. METHODS: The composition and content of SSNX were determined by UHPLC-Q-TOFQ-TOF / MS. Then, a rat model of myocardial ischemia-reperfusion injury was established, and the protective effect of SSNX was measured. The protective mechanism was investigated using spatial metabolomics. RESULTS: We found that SSNX significantly improved left ventricular function and ameliorated pathological damages in rats with myocardial ischemia-reperfusion injury. Using matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS), the protective mechanism of SSNX was examined by comparing the monomer components of drugs targeted in myocardial tissue with the distribution of myocardial energy metabolism-related molecules and phospholipids. Interestingly, some lipids display inconsistent content distribution in the myocardial ischemia risk and non-risk zones. These discrepancies reflect the degree of myocardial injury in different regions. CONCLUSION: These findings suggest that SSNX protects against myocardial ischemia-reperfusion injury by correcting abnormal myocardial energy metabolism, changing the levels and distribution patterns of phospholipids, and stabilizing the structure of the myocardial cell membrane. MALDI-TOF MS can detect the spatial distribution of small molecule metabolites in the myocardium and can be used in pharmacological research.

mROS­calcium feedback loop promotes lethal ventricular arrhythmias and sudden cardiac death in early myocardial ischemia.

Lethal ventricular arrhythmia­sudden cardiac death (LVA­SCD) occurs frequently during the early stage of myocardial ischemia (MI). However, the mechanism underlying higher LVA­SCD incidence is still poorly understood. The present study aimed to explore the role of mitochondrial reactive oxygen species (mROS) and Ca2+ crosstalk in promoting LVA­SCD in early MI. RyR2 S2814A mice and their wild­type littermates were used. MitoTEMPO was applied to scavenge mitochondrial ROS (mROS). Mice were subjected to severe MI and the occurrence of LVA­SCD was evaluated. Levels of mitochondrial ROS and calcium (mitoCa2+), cytosolic ROS (cytoROS), and calcium (cytoCa2+), RyR2 Ser­2814 phosphorylation, CaMKII Met­282 oxidation, mitochondrial membrane potential (MMP), and glutathione/oxidized glutathione (GSH/GSSG) ratio in the myocardia were detected. Dynamic changes in mROS after hypoxia were investigated using H9c2 cells. Moreover, the myocardial phosphoproteome was analyzed to explore the related mechanisms facilitating mROS­Ca2+ crosstalk and LVA­SCD. There was a high incidence (~33.9%) of LVA­SCD in early MI. Mice who underwent SCD displayed notably elevated levels of myocardial ROS and mROS, and the latter was validated in H9c2 cells. These mice also demonstrated overloads of cytoplasmic and mitochondrial Ca2+, decreased MMP and reduced GSH/GSSG ratio, upregulated RyR2­S2814 phosphorylation and CaMKII­M282 oxidation and transient hyperphosphorylation of mitochondrial proteomes in the myocardium. mROS­specific scavenging by a mitochondria­targeted antioxidant agent (MitoTEMPO) corrected these SCD­induced alterations. S2814A mice with a genetically inactivated CaMKII phosphorylation site in RyR2 exhibited decreased overloads in cytoplasmic and mitochondrial Ca2+ and demonstrated similar effects as MitoTEMPO to correct SCD­induced changes and prevent SCD post­MI. The data confirmed crosstalk between mROS and Ca2+ in promoting LVA­SCD. Therefore, we provided evidence that there is a higher incidence of LVA­SCD in early MI, which may be attributed to a positive feedback loop between mROS and Ca2+ imbalance.

Metagenomic sequencing revealed the regulative effect of Danshen and Honghua herb pair on the gut microbiota in rats with myocardial ischemia injury.

In recent years, more and more evidence has shown that the disorder of gut microbiota (GM) is closely correlated with myocardial ischemia (MI). Even though the Danshen and Honghua herb pair (DHHP) is widely used in treating cardiovascular disease in China and exhibits obvious clinical efficacy on MI, the anti-MI mechanism of DHHP remains and needs to be explored in depth. Thus, in this study, we investigated whether the amelioration effect and molecular mechanism of DHHP on MI were related to regulating GM through pharmacodynamics evaluation and metagenomic sequencing. Histopathological testing results showed that DHHP treatment could alleviate the pathological changes of myocardial tissue in the acute MI (AMI) rats induced by isoproterenol (ISO), especially structural disorder, irregular distribution, and enlargement of the myocardial space. These pathological changes were all alleviated to some extent by DHHP treatment. Biochemical analysis results suggested that compared with the control group, the serum levels of AST, CTn-I, CK-MB, and TNF-α in model group rats were notably decreased, and the CAT and SOD levels in serum were markedly increased. These abnormal trends were significantly reversed by DHHP treatment. Furthermore, metagenomic sequencing analysis results indicated that DHHP could improve disorders in the composition and function of GM in AMI rats, mainly reflected in increasing diversity and richness, and obviously enhancing the abundance of Bacteroides fluxus, B. uniformis, B. stercoris, Roseburia hominis, Schaedlerella arabinosiphila, and R. intestinalis, and reducing the abundance of Enterococcus avium and E. canintestini, which were associated with purine metabolism, tyrosine metabolism, cyanoamino acid metabolism, and glutathione metabolism. In conclusion, DHHP may attenuate ISO-induced MI by regulating the structure, composition, and function of GM, thus contributing to further our understanding of the anti-MI mechanisms of DHHP and providing new therapeutic ideas and diagnostic targets for the clinical studies of MI.

Deferasirox Targeting Ferroptosis Synergistically Ameliorates Myocardial Ischemia Reperfusion Injury in Conjunction With Cyclosporine A.

BACKGROUND: Ferroptosis, an iron-dependent form of regulated cell death, is a major cell death mode in myocardial ischemia reperfusion (I/R) injury, along with mitochondrial permeability transition-driven necrosis, which is inhibited by cyclosporine A (CsA). However, therapeutics targeting ferroptosis during myocardial I/R injury have not yet been developed. Hence, we aimed to investigate the therapeutic efficacy of deferasirox, an iron chelator, against hypoxia/reoxygenation-induced ferroptosis in cultured cardiomyocytes and myocardial I/R injury. METHODS AND RESULTS: The effects of deferasirox on hypoxia/reoxygenation-induced iron overload in the endoplasmic reticulum, lipid peroxidation, and ferroptosis were examined in cultured cardiomyocytes. In a mouse model of I/R injury, the infarct size and adverse cardiac remodeling were examined after treatment with deferasirox, CsA, or both in combination. Deferasirox suppressed hypoxia- or hypoxia/reoxygenation-induced iron overload in the endoplasmic reticulum, lipid peroxidation, and ferroptosis in cultured cardiomyocytes. Deferasirox treatment reduced iron levels in the endoplasmic reticulum and prevented increases in lipid peroxidation and ferroptosis in the I/R-injured myocardium 24 hours after I/R. Deferasirox and CsA independently reduced the infarct size after I/R injury to a similar degree, and combination therapy with deferasirox and CsA synergistically reduced the infarct size (infarct area/area at risk; control treatment: 64±2%; deferasirox treatment: 48±3%; CsA treatment: 48±4%; deferasirox+CsA treatment: 37±3%), thereby ameliorating adverse cardiac remodeling on day 14 after I/R. CONCLUSIONS: Combination therapy with deferasirox and CsA may be a clinically feasible and effective therapeutic approach for limiting I/R injury and ameliorating adverse cardiac remodeling after myocardial infarction.

Tumor Necrosis Factor-Alpha Induces Proangiogenic Profiling of Cardiosphere-Derived Cell Secretome and Increases Its Ability to Stimulate Angiogenic Properties of Endothelial Cells.

Ischemic heart disease and its complications, such as myocardial infarction and heart failure, are the leading causes of death in modern society. The adult heart innately lacks the capacity to regenerate the damaged myocardium after ischemic injury. Multiple lines of evidence indicated that stem-cell-based transplantation is one of the most promising treatments for damaged myocardial tissue. Different kinds of stem cells have their advantages for treating ischemic heart disease. One facet of their mechanism is the paracrine effect of the transplanted cells. Particularly promising are stem cells derived from cardiac tissue per se, referred to as cardiosphere-derived cells (CDCs), whose therapeutic effect is mediated by the paracrine mechanism through secretion of multiple bioactive molecules providing immunomodulatory, angiogenic, anti-fibrotic, and anti-inflammatory effects. Although secretome-based therapies are increasingly being used to treat various cardiac pathologies, many obstacles remain because of population heterogeneity, insufficient understanding of potential modulating compounds, and the principles of secretome regulation, which greatly limit the feasibility of this technology. In addition, components of the inflammatory microenvironment in ischemic myocardium may influence the secretome content of transplanted CDCs, thus altering the efficacy of cell therapy. In this work, we studied how Tumor necrosis factor alpha (TNFa), as a key component of the pro-inflammatory microenvironment in damaged myocardium from ischemic injury and heart failure, may affect the secretome content of CDCs and their angiogenic properties. We have shown for the first time that TNFa may act as a promising compound modulating the CDC secretome, which induces its profiling to enhance proangiogenic effects on endothelial cells. These results allow us to elucidate the underlying mechanisms of the impact of the inflammatory microenvironment on transplanted CDCs and may contribute to the optimization of CDC efficiency and the development of the technology for producing the CDC secretome with enhanced proangiogenic properties for cell-free therapy.

Dexmedetomidine Ameliorates Cardiac Ischemia/Reperfusion Injury by Enhancing Autophagy Through Activation of the AMPK/SIRT3 Pathway.

Objective: Myocardial ischemia-reperfusion (I/R) injury is a detrimental disease, resulting in high morbidity and mortality globally. In this study, we aimed to investigate the role of Dex in mitigating cardiac I/R injury. Methods: H9c2 cells were treated with Dex (1 µM) for 24 h followed by oxygen-glucose deprivation/re-oxygenation (OGD/R). ANP and BNP mRNA of H9c2 cells and the LDH release were measured. Apoptosis of H9c2 cells was analyzed by flow cytometry. Mitochondrial membrane potential and superoxide production were detected by JC-1 staining and MitoSOXTM Red, respectively. Cell aerobic respiration was measured using Seahorse analysis. In vivo, mice were injected with Dex (25 µg/kg, i.p., once daily) for 5 days and then subjected to heart I/R. Heart function was analyzed by echocardiography. CK-MB and LDH were measured by Elisa. Infarct size was measured using TTC-Evans blue staining. Mitochondrial ultrastructure was observed using transmission electron microscopy. DHE staining, SOD activity, the content of MDA, and the content of GSH/GSSG of heart were measured to evaluate the oxidative stress. In addition, inflammatory cytokines were measured in vivo and in vitro. Furthermore, AMPK, SIRT3, and autophagy-related protein expression in the heart were detected by Western blot. Results: Dex reduced the H9c2 cells injury exposed to OGD/R, accompanied by improved mitochondrial function and membrane potential. In vivo, Dex improved heart function, myocardial injury, and the mitochondria ultrastructure following I/R injury. Meanwhile, Dex inhibited myocardial oxidative stress and inflammation in the myocardial I/R. Furthermore, Compound C (an AMPK inhibitor) could inhibit Dex-induced autophagy in the I/R heart and the 3-MA (an autophagy inhibitor) could partially interfere with the effects of Dex on the protection of I/R heart. Conclusion: Dex suppressed oxidative stress and inflammation by promoting autophagy through activating the AMPK/SIRT3 pathway, thus protecting the heart against the I/R injury.

Leonurine pretreatment protects the heart from myocardial ischemia-reperfusion injury.

Myocardial ischemia-reperfusion (I/R), an important complication of reperfusion therapy for myocardial infarction, is characterized by hyperactive oxidative stress and inflammatory response. Leonurine (4-guanidino-n-butyl syringate, SCM-198), an alkaloid extracted from Herbaleonuri, was previously found to be highly cardioprotective both in vitro and in vivo. Our current study aimed to investigate the effect of SCM-198 preconditioning on myocardial I/R injury in vitro and in vivo, respectively, as well as to decipher the mechanism involved. Rats were pretreated with SCM-198 before subjected to 45 min of myocardial ischemia, which was followed by 24 h of reperfusion. Primary neonatal rat cardiac ventricular myocytes (NRCMs) were exposed to hypoxia (95% N2 + 5% CO2) for 12 h, and then to 12 h reoxygenation so as to mimic I/R. The enzymatic measurements demonstrated that SCM-198 reduced the release of infarction-related enzymes, and the hemodynamic and echocardiography measurements showed that SCM-198 restored cardiac functions, which suggested that SCM-198 could significantly reduce infarct size, maintaining cardiomyocyte morphology, and that SCM-198 pretreatment could significantly reduce cardiomyocytes apoptosis. Moreover, we demonstrated that SCM-198 could exert a cardioprotective effect by reducing reactive oxygen species (ROS) level and Akt phosphorylation while reducing the phosphorylation of p38 and JNK. In addition, the upregulation of p-Akt, Bcl-2/Bax induced by SCM-198 treatment were blocked by PI3K inhibitor LY294002, and the total protein level of Akt was not affected by SCM-198 pretreatment. Our experimental results indicated that SCM-198 could have a cardioprotective effect on I/R injury, which confirmed the utility of SCM-198 preconditioning as a strategy to prevent I/R injury.