RXR agonists inhibit oxidative stress-induced apoptosis in H9c2 rat ventricular cells

Retinoid X receptor (RXR) plays a central role in the regulation of intracellular receptor signaling pathways. We examined its role in regulating oxidative stress-induced apoptosis in H9c2 rat ventricular cells. We showed for the first time that functional RXR protein was downregulated by hydrogen peroxide (H2O2) in H9c2 cardiomyocytes. Natural and synthetic agonists of RXR, 9-cis-RA, and LGD1069 respectively, prevented H2O2-triggered apoptosis, and this anti-apoptotic effect was inhibited by the RXR antagonist HX531. Further investigation into the protective mechanisms of RXR demonstrated that H2O2-induced loss of mitochondrial membrane potential, mitochondrial release of cytochrome c and caspase-3 activation were all significantly attenuated by pretreatment with RXR agonists. Furthermore, this protection was associated with a reduction in intracellular reactive oxygen species and an upregulation in catalase activity. Thus, these data indicate that pharmacological activation of RXR exerts protective effects against H2O2-induced apoptosis in H9c2 rat ventricular cells through antioxidant and mitochondria-protective mechanisms.