NRIP1 is a downstream target of YY1 in promoting OGD/R-induced H9c2 cardiomyocyte injury and mitochondrial dysfunction.

Background and objective: From a clinical standpoint, myocardial ischemia/reperfusion injury (MIRI) has always been an enormous challenge for the treatment of acute myocardial infarction (AMI). Molecular targeting therapy may help overcome this challenge. The present work aimed to elucidate the possible involvement of Yin-Yang 1 (YY1)/nuclear receptor-interacting protein 1 (NRIP1) and discover the molecular mechanism of MIRI.

Methods: Herein, a cardiomyocyte ischemia/reperfusion (I/R) model was established via oxygen-glucose deprivation/re-oxygenation (OGD/R) damage in H9c2 cardiomyocytes. Reverse transcription-quantitative PCR and western blotting were conducted to measure the levels of YY1 and NRIP1 at the RNA and protein levels, respectively. H9c2 cell viability and apoptosis were assayed using the Cell Counting Kit-8, flow cytometry, and western blotting. In addition, superoxide dismutase, glutathione peroxidase, and malondialdehyde levels were analyzed as markers of oxidative stress. Additionally, mitochondrial membrane potential, which was measured via JC-1 staining, ATP content, Complex I activity, mitochondrial DNA copy number, and mitochondrial permeability transition pore (mPTP) opening rate were analyzed to evaluate mitochondrial activity. Moreover, luciferase reporter and chromatin immunoprecipitation assays experimentally validated the predicted affinity of YY1 with the NRIP1 promoter according to the HumanTFDB online tool.

Results: YY1/NRIP1 were both highly expressed in OGD/R-injured H9c2 cardiomyocytes. Downregulation of NRIP1 improved cell viability, whereas it inhibited cell apoptosis and oxidative stress, and suppressed mitochondrial dysfunction in OGD/R-injured H9c2 cardiomyocytes. Importantly, it was verified that YY1 could bind to the NRIP1 promoter to positively regulate NRIP1 expression. The protective effects of NRIP1 knockdown against cardiomyocyte damage and mitochondrial dysfunction in OGD/R-injured H9c2 cardiomyocytes were partly abolished through overexpression of YY1.

Conclusion: NRIP1 emerged as a downstream target of YY1 in promoting OGD/R-induced H9c2 cardiomyocyte injury and mitochondrial dysfunction, providing novel ideas for targeted treatments to alleviate MIRI.