RESUMO
Anoectochilus formosanus is used in traditional folk medicine as an hepatoprotective agent. The purpose of this study was to investigate the effects of a standardized aqueous extract of A. formosanus (SAEAF) on thioacetamide (TAA)-induced liver fibrosis. An in vitro study showed that the inhibitive effect of kinsenoside, a major component of SAEAF, on tumor necrosis factor alpha (TNF-alpha) secretion from Kupffer cells might be derived at least partly from downregulation of LPS-receptor Toll-like receptor 4 (TLR4) signaling. Hepatic fibrosis was produced by TAA (200 mg/kg, i.p.) 3 times per week for 12 weeks. Mice in the three TAA groups were treated daily with distilled water and SAEAF (1.0, 0.2 g/kg) via gastrogavage throughout the experimental period. The mice that received the SAEAF treatment had significantly reduced plasma alanine aminotransferase activity, relative liver weights, and hepatic hydroxyproline contents. A histological examination also confirmed that SAEAF reduced the degree of fibrosis caused by TAA treatment. RT-PCR analysis showed that SAEAF treatment reduced mRNA expression of collagen (alpha1)(I), lipopolysaccharide-binding protein, CD14, TLR4, and TNF receptor 1. An immunohistochemical examination also indicated that SAEAF reduced the number of CD68-positive cells (macrophages). In conclusion, oral administration of SAEAF significantly reduced TAA-induced hepatic fibrosis in mice, probably through inhibition of hepatic Kupffer cell activation.