Honokiol Reduces Oxidative Stress, c-jun-NH₂-Termial Kinase Phosphorylation and Protects against Glycochenodeoxycholic Acid-Induced Apoptosis in Primary Cultured Rat Hepatocytes

Abstract

Hydrophobic bile acid-induced apoptosis plays an important role in cholestatic liver disease, and its prevention may be of therapeutic interest. The aim of this study was to investigate the protective effect of honokiol on glycochenodeoxycholic acid-induced apoptosis in primary cultured rat hepatocytes. Glycochenodeoxycholic acid is a hydrophobic bile salt that accumulates intrahepatically during cholestasis and induces hepatocyte apoptosis at pathophysiological concentrations. Primary rat hepatocytes were pretreated with honokiol at concentrations of 40, 20 and 10 μM 5 min before glycochenodeoxycholic acid treatment. Incubation of hepatocytes with glycochenodeoxycholic acid at a concentration of 100 μM for 4 h induced apoptosis as shown by DNA fragmentation, chromatin condensation and cleavage of poly(ADP-ribose) polymerase. Pretreatment with honokiol at concentrations of 40, 20 and 10 μM significantly inhibited the generation of intracellular reactive oxygen species and reduced activation of caspases-8, -9, and -3 and cleavage of poly-(ADP-ribose) polymerase. Glycochenodeoxycholic acid treatment up-regulated phosphorylation of stress-activated protein kinase/c-jun-NH₂-terminal kinase which was inhibited by honokiol treatment. Inhibition of stress-activated protein kinase/c-jun-NH₂-terminal kinase phosphorylation by SP600125 protected hepatocytes from apoptosis induced by glycochenodeoxycholic acid. These data indicate that honokiol protects hepatocytes from apoptosis induced by glycochenodeoxycholic acid in vitro and this protection may be due to reduced oxidative stress and inhibition of stress-activated protein kinase/c-jun-NH₂-terminal kinase phosphorylation.

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