NMDA receptor-driven calcium influx promotes ischemic human cardiomyocyte apoptosis through a p38 MAPK-mediated mechanism

N-methyl-D-aspartate receptor (NMDAR) activity plays a key role in cerebral ischemia. Although NMDAR is also expressed in cardiomyocytes, little research has been performed on NMDAR activity in myocardial ischemia. Here, using an in vitro oxygen-glucose deprivation (OGD) cardiomyocyte model, we evaluated the effects of NMDAR activity upon calcium influx, viability, apoptosis, and investigated the roles of several key mitogen-activated protein kinases (MAPKs). Primary human neonatal cardiomyocytes were cultured under OGD conditions to mimic in vivo ischemic conditions. Enhancing NMDAR activity via NMDA significantly promoted calcium influx, decreased cell viability, increased apoptosis, and enhanced p38 MAPK phosphorylation in OGD cardiomyocytes (all P < 0.05). These effects were rescued by several calcium-channel blockers (ie, MK-801, La³⁺, Gap26 peptide, 18β-glycyrrhetinic acid) but most potently rescued via the NMDAR-specific antagonist MK-801 or removal of extracellular free calcium (all P < 0.05). Knocking-down p38 MAPK activity by small-molecule inhibition or genetic methods significantly increased cell viability and reduced apoptosis (all P < 0.05). Enhancing p38 MAPK activity abolished MK-801′s apoptosis-reducing effects in a p38 MAPK-dependent manner. In conclusion, NMDAR-driven calcium influx promotes apoptosis in ischemic human cardiomyocytes, an effect which can be attributed to enhanced p38 MAPK activity.     

Inhibition of miR-181b-5p protects cardiomyocytes against ischemia/reperfusion injury by targeting AKT3 and PI3KR3

Ischemic heart disease (IHD) is the most occurring cardiovascular-associated disease, which is a primary leading cause of cardiac disability and death worldwide. Myocardial ischemia/reperfusion injury (MI/RI) has been linked to IHD-induced cardiomyocytes apoptosis and tissue damage. The clinical studies have indicated that pathophysiologic mechanisms of MI/RI are associated with reactive oxygen species generation, calcium overload, energy metabolism disorder, neutrophil infiltration, and others. However, the genetic mechanism of MI/RI remains unclear. In this study, we successfully established the reproducing abnormal heart observed in rat, of IHD-induced MI/RI post operation. By using these rats, we illustrated that expression of miR-181b-5p was increased not only in both hypoxia/reoxygenation-cultured H9C2 but also heart of myocardial ischemia/reperfusion (MI/R) rat. Suppression of the miR-181b-5p cardiomyocytes apoptosis and rescued myocardial infarction. Additionally, our data indicated that miR-181b-5p negatively regulates the expression of AKT3 and PIK3R3 through directly binding with its 3′-untranslated region. More importantly, suppression of miR-181b-5p protects the cardiomyocytes apoptosis and tissue damage from MI/R via regulation of PIK3R3 and AKT3. Hence, our study indicates that miR-181b-5p is essential for MI/RI via regulation of PI3K/Akt signaling pathway and could be a potential therapeutic target in IHD.     

Interfering with long chain noncoding RNA ANRIL expression reduces heart failure in rats with diabetes by inhibiting myocardial oxidative stress

This study is performed to elucidate whether long-chain noncoding RNA ANRIL has an effect on diabetes, and further explore the mechanism of ANRIL in diabetes. The rat model of diabetes was established via intraperitoneal injection of streptozotocin. The modeled rats were grouped into normal, diabetes, siRNA-NC, and ANRIL siRNA groups. Besides, the expression of ANRIL, cardiac function, inflammatory factor levels, cardiomyocyte apoptosis, and levels of oxidative stress index were all determined. Upregulated ANRIL was found in myocardial tissue of diabetic rats. Downregulated ANRIL improved cardiac function index and the expression of inflammatory factors, improved the pathological state of myocardial tissue and myocardial remodeling, decreased myocardial collagen deposition area and cardiomyocyte apoptosis and reduced the oxidative level of myocardial tissue in diabetic rats. This present study suggests that upregulated ANRIL is found in myocardial tissue of diabetic rats. Additionally, silencing of ANRIL reduces myocardial injury in diabetes by inhibiting myocardial oxidative stress.     

Curcumin ameliorated myocardial infarction by inhibition of cardiotoxicity in the rat model

Cardiovascular diseases are the main cause of death globally. Many attempts have been done to ameliorate the pathological changes after the occurrence of myocardial infarction. Curcumin is touted as a polyphenol phytocompound with appropriate cardioprotective properties. In this study, the therapeutic effect of curcumin was investigated on acute myocardial infarction in the model of rats. Rats were classified into four groups; control, isoproterenol hydrochloride (ISO) (100 mg/kbw), curcumin (50 mg/kbw), and curcumin plus ISO treatment groups. After 9-day administration of curcumin, levels of lactate dehydrogenase (LDH), creatine kinase (CK), and cardiac troponin I (cTnI) were determined. Superoxide dismutase (SOD) and malondialdehyde (MDA) contents were measured to investigate the oxidative status in infarct rats received curcumin. By using H & E staining, tissue inflammation was performed. Masson’s trichrome staining was conducted to show cardiac remodeling and collagen deposition. The number of apoptotic cells was determined by using the terminal deoxynucleotidyl transferase dUTP nick end labeling assay. Data showed the serum decrease of LDH, CK, and cTnI in infarct rats after curcumin intake compared to the rats given (ISO) ( P < 0.05). Curcumin was found to reduce oxidative status by reducing SOD and MDA contents ( P < 0.05). Gross and microscopic examinations revealed that the decrease of infarct area, inflammation response and collagen deposition in rats given ISO plus curcumin ( P < 0.05). We noted the superior effect of curcumin to reduce the number of apoptotic cardiomyocytes after 9 days. Data point the cardioprotective effect of curcumin to diminish the complication of infarction by the reduction of cell necrosis and apoptosis in a rat model of experimental infarction.     

Stomatin-like protein-2 relieve myocardial ischemia/reperfusion injury by adenosine 5′-monophosphate-activated protein kinase signal pathway

Previous studies have shown that stomatin-like protein-2 (SLP-2) could regulate mitochondrial biogenesis and function. The study was designed to explore the contribution of SLP-2 to the myocardial ischemia and reperfusion (I/R) injury. Anesthetized rats were treated with SLP-2 and subjected to ischemia for 30 minutes before 3 hours of reperfusion. An oxygen-glucose deprivation/reoxygenation model of I/R was established in H9C2 cells. In vivo, SLP-2 significantly improved cardiac function recovery of myocardial I/R injury rats by increasing fractional shortening and ejection fraction. SLP-2 pretreatment alleviated infarct area and myocardial apoptosis, which was paralleled by decreasing the level of cleaved caspase-3 and the ratio of Bax/Bcl-2, increasing the content of superoxide dismutase and reducing oxidative stress damage in serum. In addition, SLP-2 increased the level of ATP and stabilized mitochondrial potential (Ψm). The present in vitro study revealed that overexpression with SLP-2 reduced H9C2 cells apoptosis, accompanied by an increased level of ATP, the ratio of mitochondrial DNA/nuclear DNA, activities of complex II and V, and decreased the production of mitochondrial reactive oxygen species. Simultaneously, SLP-2 activated the adenosine 5′-monophosphate-activated protein kinase (AMPK) signaling pathway in myocardial I/R injury rats and H9C2 cells. This study revealed that SLP-2 mediates the cardioprotective effect against I/R injury by regulating AMPK signaling pathway.     

CircSAMD4A aggravates H/R‐induced cardiomyocyte apoptosis and inflammatory response by sponging miR‐138‐5p

Hypoxia/reoxygenation (H/R)‐induced myocardial cell injury is the main cause of acute myocardial infarction (AMI). Many proofs show that circular RNA plays an important role in the development of AMI. The purpose of this study was to investigate the role of circSAMD4A in H/R‐induced myocardial injury. The levels of circular SAMD4A (circSAMD4A) were detected in the heart tissues of AMI mice and H/R‐induced H9C2 cells, and the circSAMD4A was suppressed in AMI mice and H/R‐induced H9C2 cells to investigate its’ function in AMI. The levels of circSAMD4A and miR‐138‐5p were detected by real‐time quantitative PCR, and MTT assay was used to detect cell viability. TUNEL analysis and Annexin V‐FITC were used to determine apoptosis. The expression of Bcl‐2 and Bax proteins was detected by Western blot. IL‐1β, TNF‐α and IL‐6 were detected by ELISA kits. The study found that the levels of circSAMD4A were up‐regulated after H/R induction and inhibition of circSAMD4A expression would reduce the H/R‐induced apoptosis and inflammation. MiR‐138‐5p was down‐regulated in H/R‐induced H9C2 cells. circSAMD4A was a targeted regulator of miR‐138‐5p. CircSAMD4A inhibited the expression of miR‐138‐5p to promote H/R‐induced myocardial cell injury in vitro and vivo. In conclusion, CircSAMD4A can sponge miR‐138‐5p to promote H/R‐induced apoptosis and inflammatory response.     

Endothelin-1 activates p38 mitogen-activated protein kinase via endothelin-A receptor in rat myocardial cells

In myocardial cells (MCs), endothelin-1 (ET-1) exerts various effects such as hypertrophy, and causes cellular injury. Long-term treatment with an endothelin-A (ET_A) receptor antagonist improves the survival of rats with heart failure, suggesting that myocardial endothelin system contributes to the progression of heart failure. p38 mitogen-activated kinase (MAPK) is a member of the MAPK family and activated by several forms of environmental stresses. We show here the effect of ET-1 on p38 MAPK activation and the role of ET-1-activated p38 MAPK on morphological changes in MCs. ET-1-stimulated p38 MAPK phosphorylation was detectable within 2 min and maximal at 5 min and was concentration dependent. The maximum effect was obtained at 10 nM. An ET_A receptor antagonist, BQ-123, but not an endothelin-B receptor antagonist, BQ-788, inhibited these reactions. A p38 MAPK inhibitor, SB203580, failed to inhibit the morphological changes associated with ET-1-induced myocardial cell hypertrophy. These results indicate that p38 MAPK is activated by ET-1 but does not contribute to the development of ET-1-induced myocardial cell hypertrophy.