Activating retinoid X receptor protected rat cardiomyocytes H9c2 from hypoxia/reoxygenation injury

Abstract

Objective To determine the protective effects and potential mechanism of activating retinoid X receptor (RXR) on rat cardiomyocytes H9c2 against hypoxia/reoxygenation (H/R) induced oxidative injury.Methods The model of H-/R injury was established with hypoxia for 2 hours and reoxygenation for 4 hours in cardiomyocytes of H9c2,and 9-cis-retinoic acid (c-RA) was obtained as RXR agonist,and HX531 as RXR antagonist.Cultured cardiomyocytes were randomly (random number) divided into four groups:sham group,H/R group,H/R + c-RA-pretreated group (100 nmol/L c-RA) and H/R +c-RA + HX531-pretreated group (2.5 μmol/L HX531).We measured the cell viability by MTT (methyl thiazolyl tetrazolium),apoptosis rate of cardiomyocytes by using flow cytometry,and mitochondrial membrane potential by JC-1 fluorescent probe,protein levels of Bcl-2,Bax and cleaved Caspase-9 with Western blot.All measurement data were expressed as (-x ± s),and statistically analyzed using One-way ANOVA and Dunnett-t test.Differences were considered significant when P ＜ 0.05.Results Pretreatment with RXR agonist enhanced cell viability,reduced apoptosis ratio,stabilized mitochondrial membrane potential.Dot blotting experiments demonstrated that under H/R stress conditions,Bcl-2 protein level decreased,while Bax and cleaved Caspase-9 increased.The c-RA administration prior to H/R stress prevented these effects,however,overall protective effects of activating RXR on rat cardiomyocytes against H/R induced oxidative injury were abolished when pretreated with RXR pan-antagonist HX531.Conclusions Activating RXR has the protective effects against H/R injury in rat cardiomyocytes H9c2 through attenuation of mitochondria apoptosis signaling pathway. Key words: Retinoid X receptor; Cardiomyocytes; Apoptosis; Mitochondria; Hypoxiaq/reoxygenation