LncRNA NORAD promotes the progression of myocardial infarction by targeting the miR-22-3p/PTEN axis.

NORAD is a newly identified long non-coding RNA (lncRNA) that plays an important role in cancers. NORAD has been found to be highly expressed in the mouse model of acute myocardial infarction (AMI). However, the role of NORAD in the regulation of AMI remains unknown. In the present study, we aimed to investigate the function of NORAD in AMI and explore the potential regulatory mechanisms. A mouse model of AMI was established and NORAD was knocked-down. The infarcted size of heart tissues and the cardiac function were evaluated. In addition, two cardiomyocyte cell lines were treated with hypoxia/re-oxygenation (H/R) to mimic AMI . Luciferase reporter assay, RNA pull-down assay, fluorescence hybridization, qRT-PCR, and western blot analysis were performed. Apoptotic cells and the levels of L-lactate dehydrogenase (LDH) and malondialdehyde (MDA) were detected. Our results show that downregulation of NORAD efficiently attenuates heart damage in the AMI mouse model. NORAD interacts with miR-22-3p. Knock-down of NORAD inhibits H/R-induced cell apoptosis and reduces LDH and MDA levels, while its effects are abolished by miR-22-3p inhibitor. MiR-22-3p interacts with PTEN and inhibits its expression. Overexpression of miR-22-3p inhibits H/R-induced cell apoptosis and reduces LDH and MDA levels, while its effects are abolished by overexpression of PTEN. Finally, overexpression of NORAD inhibits the AKT/mTOR signaling pathway, and its effects are attenuated by overexpression of miR-22-3p. Taken together, our study reveals that NORAD promotes the progression of AMI by regulating the miR-22-3p/PTEN axis, and the AKT/mTOR signaling may also be involved in the regulatory processes.