Peroxisome proliferator-activated receptor-α activation protects against endoplasmic reticulum stress-induced HepG2 cell apoptosis

Live ischemia-reperfusion injury is associated with endoplasmic reticulum (ER) stress-induced apoptosis. Activation of peroxisome proliferator-activated receptor-alpha (PPAR alpha) may inhibit hepatocyte apoptosis induced by oxidative stress and protect against liver injury. This study aimed to investigate the effects of PPAR alpha activation, through a specific agonist, on ER stress-induced apoptosis in human liver hepatocellular carcinoma (HepG2) cells. HepG2 cells were challenged with H2O2 and treated with WY14643, a selective PPAR alpha agonist, in the presence or absence of the PPAR alpha antagonist of MK886. Cell viable assay (MTT) and immunostaining were used to evaluate cell viability. The level of apoptotic cell death was quantified through Annexin V/PI staining. Alanine aminotransferase, asparatate aminotransferase, and malondialdehyde levels were measured to determine the presence of cellular injury and oxidative stress. RT-PCR and Western blot analysis were used to detect mRNA and protein expression of PPAR alpha, BiP, and CHOP. Immunofluorescence was utilized to determine the intracellular localization of CHOP. H2O2 and MK886 both reduced the viability of HepG2 cells, increased oxidative stress and apoptosis, up-regulated the BiP and CHOP expression, and induced CHOP translocation from the cytoplasm to the nucleus. Compared with cells treated with H2O2 alone, pre-administration of WY14643 increased cell viability, attenuated apoptosis, improved cell function, down-regulated BiP and CHOP expression and inhibited CHOP translocation. The effects of WY14643 were completely abolished using the MK886 antagonist. PPAR alpha activation protects against H2O2-induced HepG2 cell apoptosis. The underlying mechanisms may be associated with its activation to suppress excessive ER stress.