Hepatoprotective mechanisms of Yan-gan-wan

Background and aims: A herbal prescription, Yan-gan-wan (YGW), has been known to offer hepatoprotective effects in Asian countries for years. This study investigated its mechanisms of action. Methods: The effects of YGW on CCl₄ induced liver damage were tested in mice and cultured hepatocytes. Microarray analysis screened genes affected by YGW. YGWs effects on the expression of cytochrome P450 (CYP) 2E1 and other isozymes were determined. YGWs effects on TNFα expression and NF-κB activation in Kupffer cells (KC), and TNFα promoter activity in RAW264.7 cells, were also assessed. Results: Administration of YGW reduced the plasma ALT, centrilobular necrosis, neutrophilic infiltration, and TNFα mRNA in the livers of mice acutely given CCl₄. The in vivo herb treatment reduced ALT release and necrosis of isolated hepatocytes directly exposed to CCl₄. Microarray analysis demonstrated marked reductions in CYP4A10 and 4A14 by YGW but no changes in other CYP isozymes as confirmed by immunoblot analysis. The herb treatment suppressed LPS-stimulated TNFα release in vivo and by cultured KC. Direct addition of the aqueous herb extract suppressed NF-κB activation by KC and TNFα promoter activity in RAW cells under LPS stimulation. This activity to suppress TNFα expression was largely separated into gel filtration fractions with the molecular size of 102-107 Da. YGW also attenuated liver fibrosis induced by chronic treatment of CCl₄ or porcine serum. Conclusions: The protective effects of YGW on CCl₄ hepatotoxicity are due in part to inhibition of KC NF-κB activation and TNFα expression by small water soluble molecules, and may also be related to suppressed hepatic expression of CYP4A10 and 4A14 that are considered as alternative prooxidant cytochromes.