MicroRNA-486-5p targeting PTEN Protects Against Coronary Microembolization-Induced Cardiomyocyte Apoptosis in Rats by activating the PI3K/AKT pathway.

Coronary microembolization (CME) is responsible for a substantial fraction of microvascular obstruction (MVO), which are strongly associated with mortality and hospitalization for heart failure within 1 year after primary percutaneous coronary intervention (PCI) in ST-segment elevation myocardial infarction (STEMI). However, the effect of miRNA on cardiomyocyte apoptosis in a CME model has been less well-studied. miRNA sequencing analysis was performed to examine differentially expressed miRNAs induced by CME in rats. Phosphatase and tensin homologue (PTEN) 3 'RACE and dual-luciferase reporter assays were performed to confirm that PTEN is a direct target gene of miR-486-5p. miRNA-486-5p overexpression was established by injecting AAV into rats via the tail vein. The CME model was established by injecting microspheres into the left ventricle of rats. 6h after surgery, cardiac function, microinfarct area, and the apoptotic index were determined. RT-PCR was used to evaluate mRNA level and Western blotting was used to evaluate protein expression. miRNA sequencing data showed that there were 5 upregulated and 8 downregulated miRNAs, and the relative expression of miRNA-486-5p was significantly downregulated. PTEN 3'RACE and dual-luciferase reporter assays confirmed that miR-486-5p directly targets the rat PTEN gene. The expression of miR-486-5p gradually declined, however, the expression of PTEN mRNA rapidly increased at early time points after CME. Overexpression of miR-486-5p reduced cardiomyocyte apoptosis and improved cardiac function through inhibition of PTEN and activation of the PI3K/Akt pathway in rat CME models. Overexpression of miR-486-5p, which targets PTEN, protects against CME-induced cardiomyocyte apoptosis and improves cardiac function in rats by activating the PI3K/Akt pathway.

Pim1 Overexpression Prevents Apoptosis in Cardiomyocytes After Exposure to Hypoxia and Oxidative Stress via Upregulating Cell Autophagy.

BACKGROUND/AIMS: Microvascular obstruction (MVO), an undesirable complication of percutaneous coronary intervention, is independently associated with adverse left ventricle remodeling and poor prognosis after acute myocardial infarction. Hypoxia and oxidative stress major roles in the pathophysiology of MVO. Pim1 serves an important protective role in the ischemic myocardium, but the underlying mechanisms remain poorly defined. Autophagy in early hypoxia or during moderate oxidative stress has been demonstrated to protect the myocardium. In this study, we investigated the association between the protective effect of Pim1 and autophagy after hypoxia and oxidative stress. METHODS: Ventricular myocytes from neonatal rat heart (NRVMs) were isolated. NRVMs were exposed to hypoxia and H2O2. Rapamycin and 3-methyladenine (3-MA) were used as an activator and inhibitor of autophagy, respectively. pHBAd-Pim1 was transfected into NRVMs. We assessed cardiomyocyte apoptosis by Annexin V-FITC/PI flow cytometry. Autophagy was evaluated by mRFP-GFP-LC3 adenovirus infection by confocal microscopy. Western blotting was used to quantify apoptosis or autophagy protein (caspase-3, LC3, P62, AMPK, mTOR, ATG5) concentrations. RESULTS: Autophagy and apoptosis in NRVMs significantly increased and peaked at 3 h and 6 h, respectively, after exposure to hypoxia and H2O2. The mTOR inhibitor rapamycin induced autophagy and decreased cardiomyocyte apoptosis, but the autophagy inhibitor 3-MA decreased autophagy and increased apoptosis at 3 h after exposure to hypoxia and H2O2. Pim1 levels in NRVMs increased at 3 h and decreased gradually after exposure to hypoxia and H2O2. Pim1 overexpression enhanced autophagy and decreased apoptosis. Pim1-induced promotion of autophagy is partly the result of activation of the AMPK/mTOR/ATG5 pathway after exposure to hypoxia and H2O2. CONCLUSION: Our results revealed that Pim1 overexpression prevented NRVMs from apoptosis via upregulating autophagy after exposure to hypoxia and oxidative stress, partly through activation of the AMPK/mTOR/ATG5 autophagy pathway.