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

Abstract

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.

Introduction

Timely reperfusion via PCI salvages myocardium and reduces mortality for patients with STEMI. However, successful restoration of epicardial coronary artery patency after prolonged occlusion does not always lead to adequate tissue reperfusion at the microvascular level (de Waha et al., 2017). Myocardial tissue hypoperfusion, termed no-flow or MVO, is a common problem and is strongly associated with mortality and hospitalization for heart failure within 1 year after primary PCI in STEMI patients(Kloner, 2017). Some options, such as various vasodilators and hypothermia, etc, have been used to address MVO. However, there is a need for larger, systematic clinical trials (Dai et al., 2017; Rezkalla et al., 2017; Schmidt et al., 2017). The pathophysiologic mechanisms underlying MVO are likely multifactorial and complicated. CME is the essential cause of MVO(Bekkers et al., 2010). Our previous animal studies showed that CME can lead to cardiomyocyte apoptosis and inhibition of this apoptosis can reduce heart damage and improve cardiac function (Liu et al., 2015; Wang et al., 2017). Recently, miRNA has been implicated in many biological processes involved in cardiovascular diseases (Chen et al., 2017; Joladarashi et al., 2015; Zhu et al., 2016). However, the effect of miRNA on cardiomyocyte apoptosis in myocardial injury induced by CME is not clear.

In the present study, we first sought to determine the differential expression of miRNAs in rat CME models through sequencing data. Then, among all the differentially expressed downregulated miRNAs, the relative abundance of miRNA-486-5p was the highest, and thus, we chose it as our research target. We next tested whether overexpression of miR-486-5p can inhibit cardiomyocyte apoptosis and investigated the possible mechanisms after CME.