Abstract
OBJECTIVES: This study examined the protective effect of salubrinal and the mechanism underlying this protection against tunicamycin (TM)- and hypoxia-induced apoptosis in rat cardiomyocytes. METHODS: Neonatal rat cardiomyocytes were cultured from the ventricles of 1-day-old Wistar rats. Cells were exposed to different concentrations of salubrinal (10, 20, and 40 µmol/L) for 30 min followed by TM treatment or hypoxia for 36 h. Apoptosis was measured by a multiparameter HCS (high content screening) apoptosis assay, TUNEL assay and flow cytometry. The phosphorylation of eukaryotic translation initiation factor 2 subunit alpha (eIF2α) and the expression of cleaved caspase-12 were determined by Western blotting. C/EBP homologous protein (CHOP) was detected by immunocytochemistry. RESULTS: HCS, TUNEL assays and flow cytometry showed that salubrinal protected cardiomyocytes against apoptosis induced by TM or hypoxia. Western blotting showed that salubrinal protected cardiomyocytes against apoptosis by inducing eIF2α phosphorylation and down-regulating the expression of the endoplasmic reticulum stress-mediated apoptotic proteins, CHOP and cleaved caspase-12. CONCLUSIONS: Our study suggests that salubrinal protects rat cardiomyocytes against TM- or hypoxia-associated apoptosis via a mechanism involving the inhibition of ER stress-mediated apoptosis.