5-Hydroxymethylfurfural protects against ER stress-induced apoptosis in GalN/TNF-α-injured L02 hepatocytes through regulating the PERK-eIF2α signaling pathway

5-Hydroxymethylfurfural (5-HMF), a water-soluble compound extracted from wine-processed Fructus corni, is a novel hepatic protectant for treating acute liver injury. The present study was designed to investigate the protective effect of 5-HMF in human L02 hepatocytes injured by D-galactosamine (GalN) and tumor necrosis factor- (TNF-) in vitro and to explore the underlying mechanisms of action. Our results showed that 5-HMF caused significant increase in the viability of L02 cells injured by GalN/TNF-, in accordance with a dose-dependent decrease in apoptotic cell death confirmed by morphological and flow cytometric analyses. Based on immunofluorescence and Western blot assays, we found that GalN/TNF- induced ER stress in the cells, as indicated by the disturbance of intracellular Ca2+ concentration, the activation of protein kinase RNA (PKR)-like ER kinase (PERK), phosphorylation of eukaryotic initiation factor 2 alpha (eIF2), and expression of ATF4 and CHOP proteins, which was reversed by 5-HMF pre-treatment in a dose-dependent manner. The anti-apoptotic effect of 5-HMF was further evidenced by balancing the expression of Bcl-2 family members. In addition, the knockdown of PERK suppressed the expression of phospho-PERK, phospho-eIF2, ATF4, and CHOP, resulting in a significant decrease in cell apoptosis after the treatment with GalN/TNF-. 5-HMF could enhance the effects of PERK knockdown, protecting the cells against the GalN/TNF- insult. In conclusion, these findings demonstrate that 5-HMF can effectively protect GalN/TNF--injured L02 hepatocytes against ER stress-induced apoptosis through the regulation of the PERKeIF2 signaling pathway, suggesting that it is a possible candidate for liver disease therapy.