Rosmarinic acid and baicalin epigenetically derepress peroxisomal proliferator-activated receptor γ in hepatic stellate cells for their antifibrotic effect.

UNLABELLED: Hepatic stellate cells (HSCs) undergo myofibroblastic transdifferentiation (activation) to participate in liver fibrosis and identification of molecular targets for this cell fate regulation is essential for development of efficacious therapeutic modalities for the disease. Peroxisomal proliferator-activated receptor γ (PPARγ) is required for differentiation of HSCs and its epigenetic repression underlies HSC activation. The herbal prescription Yang-Gan-Wan (YGW) prevents liver fibrosis, but its active ingredients and molecular mechanisms are unknown. Here we demonstrate YGW prevents and reverses HSC activation by way of epigenetic derepression of Pparγ involving reductions in MeCP2 expression and its recruitment to Pparγ promoter, suppressed expression of PRC2 methyltransferase EZH2, and consequent reduction of H2K27di-methylation at the 3' exon. High-performance liquid chromatography / mass spectrometry (HPLC/MS) and nuclear magnetic resonance (NMR) analyses identify polyphenolic rosmarinic acid (RA) and baicalin (BC) as active phytocompounds. RA and BC suppress the expression and signaling by canonical Wnts, which are implicated in the aforementioned Pparγ epigenetic repression. RA treatment in mice with existing cholestatic liver fibrosis inhibits HSC activation and progression of liver fibrosis. CONCLUSION: These results demonstrate a therapeutic potential of YGW and its active component RA and BC for liver fibrosis by way of Pparγ derepression mediated by suppression of canonical Wnt signaling in HSCs.

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 CCl(4) 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 TNFalpha expression and NF-kappaB activation in Kupffer cells (KC), and TNFalpha promoter activity in RAW264.7 cells, were also assessed. RESULTS: : Administration of YGW reduced the plasma ALT, centrilobular necrosis, neutrophilic infiltration, and TNFalpha mRNA in the livers of mice acutely given CCl(4). The in vivo herb treatment reduced ALT release and necrosis of isolated hepatocytes directly exposed to CCl(4). 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 TNFalpha release in vivo and by cultured KC. Direct addition of the aqueous herb extract suppressed NF-kappaB activation by KC and TNFalpha promoter activity in RAW cells under LPS stimulation. This activity to suppress TNFalpha expression was largely separated into gel filtration fractions with the molecular size of 102-107Da. YGW also attenuated liver fibrosis induced by chronic treatment of CCl(4) or porcine serum. CONCLUSIONS: : The protective effects of YGW on CCl(4) hepatotoxicity are due in part to inhibition of KC NF-kappaB activation and TNFalpha 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.