Palmitate induces H9c2 cell apoptosis by increasing reactive oxygen species generation and activation of the ERK1/2 signaling pathway

Abstract

Cardiac myocytes undergo apoptosis under conditions of high free fatty acid concentrations, including palmitate, which is implicated in lipotoxic cardiomyopathy. However, the underlying mechanisms remain unknown. The aim of the present study was to understand the role of reactive oxygen species (ROS) production and the extracellular signal-regulated kinase 1/2 (ERK1/2) signaling pathway in palmitate-induced apoptosis in H9c2 cells. H9c2 cells were exposed to palmitate for 12 h. The effect on the cell viability of H9c2 cells was evaluated using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay and cell apoptosis was determined by Hoechst 33342 staining. Levels of intracellular ROS were determined using a peroxide-sensitive fluorescent probe, 2',7'-dichlorofluorescein diacetate. Protein expression was measured by western blot analysis. Following treatment with palmitate for 12 h, H9c2 cells apoptosis was demonstrated as increased brightly condensed chromatin or unclear fragments by staining with Hoechst 33342, which was associated with increasing levels of active caspase-3 and cleaved poly (ADP-ribose) polymerase (PARP). In this model of treatment with palmitate, H9c2 cell apoptosis correlated with increased levels of p53 and Bax expression and reduced levels of Bcl-2 expression. Palmitate-induced apoptosis was observed to increase levels of intracellular ROS production and p-ERK1/2 and decrease p-Akt significantly. Consistent with these results, palmitate-induced apoptosis was attenuated by the ERK1/2 inhibitor, U0126, through partial reduction of intracellular ROS generation. Collectively, these results indicate that palmitate-induced apoptosis in H9c2 cells is mediated by activation of the ERK1/2 signaling pathway and increased ROS generation.