A mechanism of perhexiline's cytotoxicity in hepatic cells involves endoplasmic reticulum stress and p38 signaling pathway

Abstract

Perhexiline is a coronary vasodilator for angina treatment that was first developed in the 1960s. Perhexiline enjoyed worldwide success before reports of severe side effects, such as hepatotoxicity and neurotoxicity, caused its withdrawal from most of the markets. The underlying mechanism of the cytotoxicity of perhexiline, however, is not yet well understood. Here we demonstrated that perhexiline induced cellular damage in primary human hepatocytes, HepaRG cells and HepG2 cells. Analysis of gene and protein expression levels of endoplasmic reticulum (ER) stress markers showed that perhexiline caused ER stress in primary human hepatocytes and HepG2 cells. The splicing of XBP1 mRNA, a hallmark of ER stress, was observed upon perhexiline treatment. Using Gluc-Fluc-HepG2 cell line, we demonstrated that protein secretion was impaired upon perhexiline treatment, suggesting functional deficits in ER. Inhibition of ER stress using ER inhibitor 4-PBA or salubrinal attenuated the cytotoxicity of perhexiline. Directly knocking down ATF4 using siRNA also partially rescued HepG2 cells upon perhexiline exposure. In addition, inhibition of ER stress using either inhibitors or siRNA transfection attenuated perhexiline-induced increase in caspase 3/7 activity, indicating that ER stress contributed to perhexiline-induced apoptosis. Moreover, perhexiline treatment resulted in activation of p38 and JNK signaling pathways, two branches of MAPK cascade. Pre-treating HepG2 cells with p38 inhibitor SB239063 attenuated perhexiline-induced apoptosis and cell death. The inhibitor also prevented the activation of CHOP and ATF4. Overall, our study demonstrated that ER stress is one important mechanism underlying the hepatotoxicity of perhexiline, and p38 signaling pathway contributes to this process. Our finding shed light on the role of both ER stress and p38 signaling pathway in drug-induced liver injury.