tiRNA-HAR contributes to ischemic myocardial injury via facilitating HuR-mediated stability of P53

Cardiomyocyte death due to heart occlusion of coronary artery is the main driver to myocardial infarction (MI) and subsequent heart failure progression. tsRNA, a small RNA fragment from tRNA, have been shown to be implicated in many physiological and pathological processes by exerting different biological functions, but the roles of tsRNA in ischemic cardiac injury remained to be determined. The present study identified a hypoxia responsive-tiRNA (tiRNA-HAR) was markedly upregulated in ischemic mouse myocardium and hypoxic cardiomyocytes, respectively. Enforced expression of tiRNA-HAR by transfecting its mimic caused and aggravated, while knockdown of tiRNA-HAR mitigated cardiomyocyte apoptosis upon hypoxia. Cardiac specific knockdown of tiRNA-HAR mediated by AAV9 (adeno-associated virus 9) harboring an antisense oligonucleotide reduced cardiomyocytes apoptosis and improved cardiac function after MI. Mechanistically, tiRNA-HAR directly bound to HuR and enhanced the binding capacity of HuR and P53, thereby increasing the stability of P53. Silencing of HuR partially reversed the aggravative effects of tiRNA-HAR overexpression on cardiomyocyte apoptosis in the context of hypoxia. Collectively, our study reveals tiRNA-HAR play a critical role in regulating cardiomyocytes apoptosis and cardiac injury via targeting HuR/P53 signaling axis after MI, and tiRNA-HAR might be a novel therapeutic target for treatment of ischemic heart disease.