Protective effect of HINT2 on mitochondrial function via repressing MCU complex activation attenuates cardiac microvascular ischemia-reperfusion injury.

Current evidence indicates that coronary microcirculation is a key target for protecting against cardiac ischemia-reperfusion (I/R) injury. Mitochondrial calcium uniporter (MCU) complex activation and mitochondrial calcium ([Ca2+]m) overload are underlying mechanisms involved in cardiovascular disease. Histidine triad nucleotide-binding 2 (HINT2) has been reported to modulate [Ca2+]m via the MCU complex, and our previous work demonstrated that HINT2 improved cardiomyocyte survival and preserved heart function in mice with cardiac ischemia. This study aimed to explore the benefits of HINT2 on cardiac microcirculation in I/R injury with a focus on mitochondria, the MCU complex, and [Ca2+]m overload in endothelial cells. The present work demonstrated that HINT2 overexpression significantly reduced the no-reflow area and improved microvascular perfusion in I/R-injured mouse hearts, potentially by promoting endothelial nitric oxide synthase (eNOS) expression and phosphorylation. Microvascular barrier function was compromised by reperfusion injury, but was repaired by HINT2 overexpression via inhibiting VE-Cadherin phosphorylation at Tyr731 and enhancing the VE-Cadherin/ß-Catenin interaction. In addition, HINT2 overexpression inhibited the inflammatory response by suppressing vascular cell adhesion molecule-1 (VCAM-1) and intercellular adhesion molecule-1 (ICAM-1). Mitochondrial fission occurred in cardiac microvascular endothelial cells (CMECs) subjected to oxygen-glucose deprivation/reoxygenation (OGD/R) injury and resulted in mitochondrial dysfunction and mitochondrion-dependent apoptosis, the effects of which were largely relieved by HINT2 overexpression. Additional experiments confirmed that [Ca2+]m overload was an initiating factor for mitochondrial fission and that HINT2 suppressed [Ca2+]m overload via modulation of the MCU complex through directly interacting with MCU in CMECs. Regaining [Ca2+]m overload by spermine, an MCU agonist, abolished all the protective effects of HINT2 on OGD/R-injured CMECs and I/R-injured cardiac microcirculation. In conclusion, the present report demonstrated that HINT2 overexpression inhibited MCU complex-mitochondrial calcium overload-mitochondrial fission and apoptosis pathway, and thereby attenuated cardiac microvascular ischemia-reperfusion injury.

Overexpression of COX5A protects H9c2 cells against doxorubicin-induced cardiotoxicity.

Mitochondrial dysfunction plays a pivotal role in doxorubicin (DOX)-induced cardiomyopathy. Cytochrome c oxidase subunit 5A (COX5A) is a nuclear-encoded subunit of the terminal oxidase involved in mitochondrial electron transport. Although COX5A appears to play a key role in modulating the physiological activity of COX and involve in energy metabolism, the involvement of COX5A in DOX-induced cardiotoxicity remains unclear. In this study, we showed that COX5A was significantly downregulated by DOX treatment of H9c2 cells. Overexpression of COX5A in H9c2 cells effectively attenuated DOX-induced apoptosis. Meanwhile, DOX-induced decrease in mitochondrial membrane potential could be reserved by COX5A overexpression. Furthermore, COX5A overexpression relieved the DOX-induced suppression of mitochondrial respiration, due an increase in basal respiration, maximal respiration, ATP production, and spare respiratory capacity. These findings indicate that up-regulation of COX5A may inhibit the apoptosis and alleviate the mitochondrial dysfunction of DOX-treated H9c2 cells. Thus, COX5A may have potential for clinical use as a therapeutic target in DOX-induced cardiotoxicity.

Cell-Free circulating DNA: a new biomarker for the acute coronary syndrome.

BACKGROUND: In recent studies, concentrations of cell-free circulating DNA (cf-DNA) have been correlated with clinical characteristics and prognosis in several diseases. The relationship between cf-DNA concentrations and the acute coronary syndrome (ACS) remains unknown. Moreover, no data are available for the detection cf-DNA in ACS by a branched DNA (bDNA)-based Alu assay. The aim of the present study was to investigate cf-DNA concentrations in ACS and their relationship with clinical features. METHODS: Plasma cf-DNA concentrations of 137 ACS patients at diagnosis, of 60 healthy individuals and of 13 patients with stable angina (SA) were determined using a bDNA-based Alu assay. RESULTS: ACS patients (median 2,285.0, interquartile range 916.4-4,857.3 ng/ml), especially in ST-segment elevation myocardial infarction patients (median 5,745.4, interquartile range 4,013.5-8,643.9 ng/ml), showed a significant increase in plasma cf-DNA concentrations compared with controls (healthy controls: median 118.3, interquartile range 81.1-221.1 ng/ml; SA patients: median 202.3, interquartile range 112.7-256.1 ng/ml) using a bDNA-based Alu assay. Moreover, we found positive correlations between cf-DNA and Gensini scoring and GRACE (Global Registry of Acute Coronary Events) scoring in ACS. CONCLUSION: cf-DNA may be a valuable marker for diagnosing and predicting the severity of coronary artery lesions and risk stratification in ACS.

Biomimetic and NOS-Responsive Nanomotor Deeply Delivery a Combination of MSC-EV and Mitochondrial ROS Scavenger and Promote Heart Repair and Regeneration.

Mesenchymal stem cell-derived extracellular vesicle (MSC-EV) is shown to promote cardiac repair, however, it still falls short in initiating myocardia proliferation restart. In this regard, ROS-induced DNA damage and responses are the culprit of cellcycle arrest. Here, this work constructs a hybrid cell-derived extracellular vesicle that is composed of MSC and macrophage membranes and encompasses MitoN, a ROS scavenger, to boost the healing of the heart. The MitoN, a NAD(P)H mimic, could target the mitochondrial to eliminate the ROS resuming the arrested cell cycle. The hybrid extracellular vesicle (N@MEV) could respond to the inflammatory signals generated during myocardial injury and thus enable superior targeting and enrichment to the location of the damage. L-arginine, which could be catalyzed by NOS and ROS into NO and SO provide a driving force, is immobilized within the vesicle (NA@MEV) to further enhance the N@MEV's potential to penetrate the cardiac stroma. In combination with multiple mechanisms, NA@MEV increased heart function 1.3-fold EF% versus MSC-EV in mouse myocardial injury model. A more in-depth mechanistic study found that the NA@MEV could modulate M2 macrophage; promote angiogenesis; reduce DNA damage and response, and thereby restart cardiomyocyte proliferation. Thus, this combined therapy shows synthetic effects in heart repair and regeneration.

AKT-mTOR signaling-mediated rescue of PRKAG2 R302Q mutant-induced familial hypertrophic cardiomyopathy by treatment with ß-adrenergic receptor (ß-AR) blocker metoprolol.

Background: Protein kinase AMP-activated non-catalytic subunit gamma 2 gene (PRKAG2) cardiac syndrome, caused by mutations in PRKAG2, often shows myocardial hypertrophy and abnormal glycogen deposition in cardiomyocytes. However, it remains incurable due to a lack of a management guideline for treatment. Methods: We constructed a fluorescently labeled adenovirus carrying the wild-type or R302Q mutant of the PRKAG2 gene, infected neonatal rat cardiomyocytes (NRCMs) and H9C2 cell lines, and then analyzed changes in AMP-activated protein kinase (AMPK) activity, cell hypertrophy, glycogen storage, and cell proliferation when presence or absence of metoprolol or protein kinase A (PKA) inhibition H89, and then analyzed the changes in AKT-mTOR signal transduction activity. Results: Overexpression of PRKAG2 R302Q in primary cardiomyocytes increased the activity of AMPK, induced cellular hypertrophy and glycogen storage, and promoted the phosphorylation levels of AKT-mTOR signaling pathway. Application of either ß1-adrenergic receptor (ß1-AR) blocker metoprolol or PKA inhibitor H89 to the cardiomyocytes rescued the hypertrophic cardiomyopathy (HCM)-like phenotypes induced by PRKAG2 R302Q, including suppression of both AKT-mTOR phosphorylation and AMPK activity. Conclusions: The current study not only determined the mechanism regulating HCM induced by PRKAG2 R302Q mutant, but also demonstrated a therapeutic strategy using ß1-AR blocker to treat the patients with PRKAG2 cardiac syndrome.

Integrated Bioinformatics Algorithms and Experimental Validation to Explore Robust Biomarkers and Landscape of Immune Cell Infiltration in Dilated Cardiomyopathy.

Background: The etiology of dilated cardiomyopathy (DCM) is unclear. Bioinformatics algorithms may help to explore the underlying mechanisms. Therefore, we aimed to screen diagnostic biomarkers and identify the landscape of immune infiltration in DCM. Methods: First, the CIBERSORT algorithm was used to excavate the proportion of immune-infiltration cells in DCM and normal myocardial tissues. Meanwhile, the Pearson analysis and principal component analysis (PCA) were used to identify immune heterogeneity in different tissues. The Wilcoxon test, LASSO regression, and machine learning method were conducted to identify the hub immune cells. In addition, the differentially expressed genes (DEGs) were screened by the limma package, and DEGs were analyzed for functional enrichment. In the protein-protein interaction (PPI) network, multiple algorithms were used to calculate the score of each DEG for screening the hub genes. Subsequently, external datasets were used to further validate the expression of hub genes, and the receiver operating characteristic (ROC) curve was used to analyze the diagnostic efficacy. Finally, we examined the expression of hub biomarkers in animal models. Results: A total of 108 DEGs were screened, and these genes may be related to biological processes such as cytolysis, positive regulation of cytokine secretion, etc. Two types of hub immune cells [activated natural killer (NK) cells and eosinophils] and four hub genes (ASPN, CD163, IL10, and LUM) were identified in DCM myocardial tissues. CD163 was verified to have the capability to diagnose DCM with the most excellent specificity and sensitivity. It is worth mentioning that the combined CD163 and eosinophils may have better diagnostic efficacy. Moreover, the correlation analysis showed CD163 was negatively correlated with activated NK cells. Finally, the results of the mice model also indicated that CD163 might be involved in the occurrence of DCM. Conclusion: ASPN, CD163, IL10, and LUM may have a potential predictive ability for DCM, and especially CD163 showed the most robust efficacy. Furthermore, activated NK cells and eosinophils may relate to the occurrence of DCM.

Specific protein 1 inhibitor mithramycin A protects cardiomyocytes from myocardial infarction via interacting with PARP.

Specific protein 1 (SP1) might act as a critical transcription regulator in myocardial infarction (MI), but little evidence about its function in regulating cardiac apoptosis, a major cause of MI development, has been revealed. This study tried to investigate the role of SP1 in MI and its interaction with poly-ADP-ribose polymerase (PARP)-1 by using SP1 inhibitor, mithramycin A (mithA). Primary mouse cardiomyocytes and commercial mouse cardiomyocytes were subjected to mithA treatment under hypoxia conditions, while cell viability, Nix promoter activity, and its expression were detected correspondingly. PARP overexpression and knockdown were conducted, respectively, in mithA-treated and SP1-overexpressing cells. Co-immunoprecipitation was used to verify the interaction between PARP and SP1. For in vivo experiments, mithA administration was performed after the injections of adenovirus for PARP overexpression, and then, MI introduction was carried out. Infarct size and lactate dehydrogenase level were measured to assess MI injury. SP1 inhibitor mithA attenuated hypoxia-induced decrease of cell viability and Nix transcriptional activation, which could be inhibited by PARP overexpression. Knockdown of PARP prevented SP1-induced transcription of Nix and cell viability change, and PARP showed direct interaction with SP1. Furthermore, mithA administration reduced MI injuries, while PARP overexpression could suppress the improvement. The cardioprotective role of SP1 inhibitor mithA was demonstrated here expanding the role of SP1 in MI development involving hypoxia-induced cardiac apoptosis. Moreover, PARP acted as a transcriptional coactivator in Nix transcription involving its interaction with SP1.

Rosuvastatin protects against coronary microembolization-induced cardiac injury via inhibiting NLRP3 inflammasome activation.

Coronary microembolization (CME), a common reason for periprocedural myocardial infarction (PMI), bears very important prognostic implications. However, the molecular mechanisms related to CME remain largely elusive. Statins have been shown to prevent PMI, but the underlying mechanism has not been identified. Here, we examine whether the NLRP3 inflammasome contributes to CME-induced cardiac injury and investigate the effects of statin therapy on CME. In vivo study, mice with CME were treated with 40 mg/kg/d rosuvastatin (RVS) orally or a selective NLRP3 inflammasome inhibitor MCC950 intraperitoneally (20 mg/kg/d). Mice treated with MCC950 and RVS showed improved cardiac contractile function and morphological changes, diminished fibrosis and microinfarct size, and reduced serum lactate dehydrogenase (LDH) level. Mechanistically, RVS decreased the expression of NLRP3, caspase-1, interleukin-1ß, and Gasdermin D N-terminal domains. Proteomics analysis revealed that RVS restored the energy metabolism and oxidative phosphorylation in CME. Furthermore, reduced reactive oxygen species (ROS) level and alleviated mitochondrial damage were observed in RVS-treated mice. In vitro study, RVS inhibited the activation of NLRP3 inflammasome induced by tumor necrosis factor α plus hypoxia in H9c2 cells. Meanwhile, the pyroptosis was also suppressed by RVS, indicated by the increased cell viability, decreased LDH and propidium iodide uptake in H9c2 cells. RVS also reduced the level of mitochondrial ROS generation in vitro. Our results indicate the NLRP3 inflammasome-dependent cardiac pyroptosis plays an important role in CME-induced cardiac injury and its inhibitor exerts cardioprotective effect following CME. We also uncover the anti-pyroptosis role of RVS in CME, which is associated with regulating mitochondrial ROS.

Monocyte mimics improve mesenchymal stem cell-derived extracellular vesicle homing in a mouse MI/RI model.

Stem cell-derived extracellular vesicles (EVs) have been demonstrated to be effective in heart repair and regeneration post infarction. However, the poor homing efficiency and low yields of these therapeutics remain the major obstacles before they can be used in the clinic. To improve the delivery efficiency of EVs to ischemia-injured myocardium, we modified mesenchymal stem cell (MSC)-derived EVs with monocyte mimics through the method of membrane fusion. Monocyte mimic-bioinspired MSC-EVs (Mon-Exos) exhibited enhanced targeting efficiency to injured myocardium by mimicking the recruitment feature of monocytes after MI/RI, thus contributing to these exclusive adhesive molecules on monocyte mimics, particularly the Mac1/LFA1-ICAM-1 interaction. Through this strategy, Mon-Exos were shown to promote endothelial maturation during angiogenesis and modulate macrophage subpopulations after MI/RI, consistent with MSC-Exos biofunctions, and eventually improve therapeutic outcomes in cardiac function and pathohistology changes after treatments in a mouse MI/RI model. Ultimately, this strategy might provide us with a better way to assess the effects of stem cell EVs and offer additional techniques to help clinicians better manage regenerative therapeutics for ischemic heart diseases.

Overexpression of the histidine triad nucleotide-binding protein 2 protects cardiac function in the adult mice after acute myocardial infarction.

AIM: To explore the role of the histidine triad nucleotide-binding 2 (HINT2) protein in heart failure. METHODS: Neonatal mouse ventricle myocytes (NMVMs) and myocardial infarction-induced heart failure mice were used for in vitro or in vivo experiments. Adenovirus (ADV) and adeno-associated virus serum type 9 (AAV9) vectors were used to regulate HINT2 expression. The expression of HINT2 was determined by quantifying the mRNA and protein levels. Cell survival was analysed using the CCK-8 kit and TUNEL staining. Mitochondrial function was determined by the mitochondrial membrane potential and oxygen consumption rates. AAV9-HINT2 was injected 24 h post-myocardial infarction following which transthoracic echocardiography and histological analyses were performed after 4 weeks. Positron emission tomography tomography-computed tomography (PET/CT) and targeted metabolomics analyses were used to explore the metabolic status in vivo. NAD levels were measured using a colorimetric kit. Computer-simulated rigid body molecular docking was performed using AUTODOCK4. Molecule binding kinetics assays were performed using biolayer interferometry. RESULTS: HINT2 was down-regulated in NMVMs in hypoxia. ADV-HINT2-induced HINT2 overexpression improved NMVM survival after exposure to hypoxia. Mitochondrial function was preserved in the ADV-HINT2 group under hypoxic conditions. In vivo experiments showed that cardiac function and metabolic status was preserved by HINT2 overexpression. HINT2 overexpression restored mitochondrial NAD levels; this was dependent on nicotinamide mononucleotide (NMN). Using computer-simulated molecular docking analysis and biolayer interferometry, we observed that HINT2 potentially binds and associates with NMN. CONCLUSION: HINT2 overexpression protects cardiac function in adult mice after myocardial infarction by maintaining mitochondrial NAD homeostasis.

The characteristics of coronary-pulmonary artery fistulas and the effectivity of trans-catheter closure: a single center experience.

BACKGROUND: Due to the low prevalence, the optimal treatment strategy of coronary-pulmonary artery fistula (CPF) remains unclear, and there are no established therapeutic guidelines available. The purpose of this study is to investigate the characteristics of CPF, and evaluate the effectivity of trans-catheter closure (TCC) for CPFs. METHODS: Patients with CPFs were retrospectively reviewed and enrolled according to the inclusion criteria. The data of clinical manifestations, physical signs, electrocardiogram (ECG), echocardiography, coronary CTA, coronary angiography and intervention procedure were collected. The telephone follow-up was conducted to evaluate the prognosis. RESULTS: The most common presenting complaint was dyspnea (n=21, 48.84%), followed by chest pain (n=10, 23.36%), palpitation (n=6, 13.95%), dizziness (n=3, 6.98%), and syncope (n=3, 6.98%). Most patients were coupled with single fistula (n=17, 39.53%) or two fistulas (n=23, 53.49%). Thirty fistulas (41.67%) involved the left anterior descending (LAD) artery, 28 fistulas (38.89%) involved the right coronary, 9 fistulas (12.50%) involved the left main trunk, and 5 fistulas (6.94%) involved the circumflex branch. Most of the fistulous tracts originated within the proximal one-third of the coronary arteries, only 6 fistulous tracts (8.33%) originated from the distal segment of the coronary arteries. The size of fistulas arranged from 1 mm to 8 mm, with an average of 3.45 mm. Thirty-five patients (81.40%) with 63 fistulas (87.50%) were successfully treated by percutaneous transcatheter closure. Thirty-eight patients accepted the 6-month follow-up, 36 patients (94.74%) were asymptomatic and 2 patients (5.26%) with palpitation. In conclusion, patients with more fistulas, larger fistula diameter and more severe left-to-right shunt are always coupled with more obvious clinical manifestations. The trans-catheter coil embolization is an effective method for the closure of CPFs. CONCLUSIONS: patients with more fistulas, larger fistula diameter and more severe left-to-right shunt are always coupled with more obvious clinical manifestations. The trans-catheter coil embolization is an effective method for the closure of CPFs.

Efficacy of mesenchymal stem cell therapy in systolic heart failure: a systematic review and meta-analysis.

BACKGROUND: Heart failure (HF) is the end stage of most heart disease. Mesenchymal stem cells (MSCs), with their specific biological effects, have been applied in several clinical trials to evaluate the efficacy in HF therapy. We performed this meta-analysis to review the clinical evidence of their therapeutic effect on HF. METHODS: Three databases were searched. The outcomes of interest were death, readmission, the 6-min walk test (6MWT), New York Heart Association (NYHA) class and left ventricular ejection fraction (LVEF). The relative risk (RR) and weighted mean difference (WMD) were calculated to evaluate the effects of MSCs on HF compared to placebo. RESULTS: A total of nine studies were included, involving 612 patients who underwent MSCs or placebo treatment. The overall rate of death showed a trend of reduction of 36% (RR [CI] = 0.64 [0.35, 1.16], p = 0.143) in the MSC treatment group. The incidence of readmission was reduced by 34% (RR [CI] = 0.66 [0.51, 0.85], p = 0.001). The patients in the MSC treatment group realised an average of 40.44 m (WMD [95% CI] = 40.44 m [19.07, 61.82], p < 0.0001) improvement in 6MWT. The NYHA class was reduced obviously in the MSC group (WMD [95% CI] = - 0.42 [- 0.64, - 0.20], p < 0.0001). The changes of LVEF from baseline were significantly more than 5.25% (WMD [95% CI] = 5.25 [3.58, 6.92], p < 0.0001) in the MSCs group, unlike in the placebo group. CONCLUSIONS: Our results suggested that MSC treatment is an effective therapy for HF by improving the prognosis and exercise capacity. SCs derived from allosomes have superior therapeutic effects, and intracoronary injection is the optimum MSC delivery approach. Short-term cryopreservation is feasible in MSCs storage or transport.

Correction to: Efficacy of mesenchymal stem cell therapy in systolic heart failure: a systematic review and meta-analysis.

The original article [1] displayed a co-author, Junbo Ge who has since stated that he should not have been a co-author in the article; the article has now been amended to remove Junbo Ge accordingly. All authors agreed to this amendment.