Elsevier

Gene

Volume 675, 30 October 2018, Pages 36-43
Gene

Research paper
MiR-532-5p alleviates hypoxia-induced cardiomyocyte apoptosis by targeting PDCD4

https://doi.org/10.1016/j.gene.2018.06.087Get rights and content

Highlights

  • miR-532-5p was down-regulated in hypoxia-exposed H9c2 cells and the AMI rat myocardium.

  • miR-532-5p can alleviate hypoxia-induced H9c2 cell apoptosis.

  • PDCD4 was the direct target of miR-532-5p.

Abstract

MicroRNAs (miRNAs) are a class of endogenous non-coding RNAs involved in regulating various biological processes at the post-transcription level. Accumulating evidence suggests that hypoxia caused by acute myocardial infarction induces cardiomyocyte damage including apoptosis. Previous studies regarding the miRNAome in H9c2 cells under hypoxia have shown that hypoxia modulates miRNA expression in H9c2 cells, including miR-532-5p. We therefore investigated whether miR-532-5p has a potential function in the cardiomyocyte response to hypoxia. In the present study, we found that miR-532-5p, which was down-regulated in hypoxia-exposed H9c2 cells and the myocardium of acute myocardial infarction rats, alleviated hypoxia-induced H9c2 cell apoptosis. Additionally, we identified PDCD4 as the direct target of miR-532-5p, which partly elucidates the anti-apoptotic mechanism of miR-532-5p. In summary, this study revealed that miR-532-5p has cardioprotective effects against hypoxia-induced apoptosis in H9c2 cells.

Introduction

Acute myocardial infarction (AMI), myocardial necrosis caused by acute persistent ischemia of the coronary artery, is a major cause of death and disability worldwide (Members et al., 2016). Many clinical and experimental studies have shown that AMI is mainly characterized by interstitial fibrosis, inflammation, and cardiac hypertrophy, and can lead to heart failure (Bogomolov et al., 2013). Acute hypoxia caused by AMI triggers cardiomyocyte injury including apoptosis (Chen-Scarabelli et al., 2012; Heusch, 2015). To improve the prognosis of AMI, it is vital to prevent the loss of cardiomyocytes in the early phase of AMI. The cellular mechanisms underlying AMI are very complicated and involve numerous signaling molecules and pathway networks that may become crucial diagnostic or therapeutic targets. Among them, microRNAs (miRNAs) as ubiquitous gene expression regulators have recently received much attention in various types of heart diseases including heart failure (Thum et al., 2007), myocardial hypertrophy (Sayed et al., 2007; Wang et al., 2016), and infarction (Boon and Dimmeler, 2015).

MiRNAs are a large class of endogenous non-coding RNAs with highly conserved sequences among species, which regulate a wide range of physiological and pathological processes at the post-transcriptional level (Bartel, 2004). Functionally, an individual miRNA may regulate hundreds of target genes, and an individual mRNA may be regulated by numerous miRNAs. Thus, miRNAs are considered to be involved in almost all cellular processes such as proliferation, differentiation, and apoptosis (Chekulaeva and Filipowicz, 2009). Currently, mounting evidence indicates that miRNAs play crucial roles in AMI by regulating gene expression associated with cell survival and apoptosis. For example, miR-21 has a protective effect against AMI-induced cell apoptosis through its target, PDCD4 (Dong et al., 2009). MiR-320 exacerbates cardiomyocyte apoptosis induced by ischemia/reperfusion injury through targeting heat shock protein 20 (HSP20) (Ren et al., 2009). MiRNA-34a promotes cardiomyocyte apoptosis post-myocardial infarction via downregulating aldehyde dehydrogenase 2 (Fan et al., 2013). In our previous study, we found that miR-532-5p downregulates in H9c2 cells under acute hypoxia using small RNA sequencing (RNA-seq), while its potential functions and related molecular mechanism in the hypoxic response of cardiomyocyte remains unclear.

Here, we investigated the miR-532-5p expression pattern in hypoxia-exposed H9c2 cells and several tissues of AMI rats. We found augmentation of hypoxia-induced cardiomyocytes apoptosis in vivo and in vitro accompanied by continuous downregulation of miR-532-5p. Subsequent experiments demonstrated that miR-532-5p alleviated hypoxia-induced H9c2 cell apoptosis by suppressing its target gene, PDCD4, which may be a novel therapeutic strategy for AMI and other hypoxia-associated heart diseases.

Section snippets

Animals

Healthy male Sprague-Dawley rats (200 ± 20 g) were purchased from Dashuo Experimental Animal Co. Ltd. (Chengdu, Sichuan, China) and kept in standard conditions (21 ± 1 °C and 55%–60% humidity) with water and food ad libitum for 1 week before experiments. All animal experimental procedures were performed in accordance with the Ethics Committee of Sichuan Agricultural University.

Establishment of the rat AMI model

The rat AMI model was established as described previously (Li et al., 2014). Briefly, rats were anesthetized by

Hypoxia triggers cell apoptosis and downregulation of miR-532-5p in H9c2 cells

Our previous study indicated that acute hypoxia modulates miRNA expression in H9c2 cells as detected by small RNA-seq (Zhang et al., 2017). A similar fluctuation of some miRNAs was found in the AMI rat myocardium and hypoxia-exposed H9c2 cells by microarray and qRT-PCR, respectively (Fang et al., 2012). We found that miR-532-5p was downregulated by 2.12-fold in hypoxia-exposed H9c2 cells as detected by small RNA-seq (Table 2). Therefore, miR-532-5p might be involved in the hypoxic response of

Conclusion

In this study, we found that miR-532-5p was downregulated in hypoxia-exposed H9c2 cells and the AMI rat myocardium. It can alleviate hypoxia-induced H9c2 cell apoptosis by suppressing its target gene, PDCD4. Our results revealed that miR-532-5p has cardioprotective effects against hypoxia-induced apoptosis in H9c2 cells, which may be a novel therapeutic strategy for AMI and other hypoxia-associated heart diseases.

Competing financial interests

The authors declare no competing financial interests.

Acknowledgment

This work was supported by grants from the National Natural Science Foundation of China (31530073, 31601918 and 31522055), the Key Project of Sichuan Education Department (16ZA0025), the Program for Innovative Research Team of Sichuan Province (2015TD0012), the Science & Technology Support Program of Sichuan (2016NYZ0042), Sichuan Province & Chinese Academy of Science of Science & Technology Cooperation Project (2017JZ0025), the Science & Technology Major Projects of Sichuan (2017NZDZX0002),

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