PERK Overexpression-Mediated Nrf2/HO-1 Pathway Alleviates Hypoxia/Reoxygenation-Induced Injury in Neonatal Murine Cardiomyocytes via Improving Endoplasmic Reticulum Stress.

Jichun Wang,Sisi Chen,Jing Xie,Li Lu,Hong Jiang,Yanli Zhou,Shuai Lu

doi:10.1155/2020/6458060

Abstract

Reperfusion processes following acute myocardial infarction (AMI) have been reported to induce additional cardiomyocyte death, known as ischemia-reperfusion (I/R) injury. Endoplasmic reticulum (ER) stress is reported to be involved in the development of I/R injury. There is evidence that PERK exerts beneficial roles in alleviating ER stress. Here, we investigated whether upregulation of PERK improved cardiomyocytes injury induced by I/R. Specific siRNAs or adenovirus vectors were incubated with isolated neonatal cardiomyocytes (NCMs) to regulate expression levels of target genes including PERK, Nrf2, and HO-1. Afterwards, hypoxia and subsequent reoxygenation (H/R) administration was performed as the in vitro model of I/R injury. MTT assay showed that H/R intervention decreased the viability of cells, yet PERK overexpression increased the cellular proliferative rate. Moreover, the upregulation of Nrf2 or HO-1 elevated the growth rate of cells, while gene silencing of Nrf2 or HO-1 reduced the viability of NCMs treated with PERK-rAAV9. In addition, we observed that the apoptotic index of cells with H/R stimulation was reduced when NCMs were pretreated with PERK-rAAV9, Nrf2-rAAV9, or HO-1-rAAV9. After cells were incubated with Nrf2-siRNA or HO-1-siRNA, the upregulation of PERK had no roles in affecting the apoptosis rate of NCMs damaged by H/R. Then, our findings indicated that there was a level decrease of GRP78, CRT, CHOP, and Caspase-12 in NCMs of the PERK-rAAV9 group compared to that of the H/R group. Both Nrf2 overexpression and HO-1 upregulation reduced the expression of ER stress-related proapoptotic factors, yet the expression suppression of Nrf2 and HO-1 increased levels of GRP78, CRT, CHOP, and Caspase-12 in NCMs treated with PERK-rAAV9. Taken together, our results suggested that the effects of PERK against H/R injury might be attributed to the upregulation of Nrf2/HO-1 cascade, followed by the inhibition of ER stress-related apoptotic pathway.

Highlights

Epidemiological data has established that acute myocardial infarction (AMI) remains a major cause of death in the world
Gene silencing of nuclear factor erythroid 2related factor 2 (Nrf2) and HO1 dramatically weakened the improvement of cellular survival induced by protein kinase-like ER kinase (PERK) overexpression. en, we found that the level elevation of Nrf2 was unable to alter the apoptosis rate of neonatal cardiomyocytes (NCMs) damaged by the hypoxia and subsequent reoxygenation (H/R) process when cells were pretreated with heme oxygenase-1 (HO-1)-siRNA
The upregulation of PERK and downstream Nrf2/HO-1 pathway effectively improved cellular injury induced by H/R, the molecular mechanism for which might be attributed to the expression inhibition of Endoplasmic reticulum (ER) stress-related factors and relevant proapoptotic signal molecules

Summary

Introduction

Epidemiological data has established that acute myocardial infarction (AMI) remains a major cause of death in the world. Laboratory data has identified multiple potential mechanisms implicated in the detrimental effects of I/R damage, including inflammatory response, the excess formation of reactive oxygen species (ROS), intracellular calcium overload, and rapid normalization of pH [7, 8]. Strategies targeting these pathogenic factors for improving myocardial I/R injury are limited, and the effects of these approaches in the clinical setting have been unsatisfactory until now [9]

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Results

Conclusion