Glaucocalyxin A Attenuates the Activation of Hepatic Stellate Cells Through the TGF-β1/Smad Signaling Pathway.

Glaucocalyxin A (GLA) is a biologically active ent-kauranoid diterpenoid isolated from Rabdosia japonica var. glaucocalyx. A large number of studies have shown that GLA possesses important pharmacological activities, such as anti-inflammatory, antitumor, antifibrosis, and antiplatelet activities. However, the role of GLA in the pathogenesis of liver fibrosis remains undefined. Therefore, the aim of this study was to investigate the effects of GLA on hepatic stellate cells (HSCs) activation/proliferation and migration in vitro and its possible mechanism in liver fibrosis. HSCs were incubated with different concentrations of GLA in the presence or absence of TGF-β1 for 24 h. Cell proliferation and migration were evaluated by the MTT assay and Transwell migration assay, respectively. Intracellular reactive oxygen species (ROS) production was measured using 2',7'-dichlorodihydrofluorescin diacetate (DCFH-DA). Western blot was used to detect the expression levels of α-smooth-muscle actin (α-SMA), collagen-I, p-Smad2, Smad2, p-Smad3, and Smad3. Our results demonstrated that GLA significantly inhibited the proliferation and migration of HSCs, and suppressed the expression of extracellular matrix in TGF-β1-stimulated HSC-T6 cells. In addition, pretreatment with GLA markedly suppressed TGF-β1-induced ROS level in HSC-T6 cells. Furthermore, GLA greatly inhibited the phosphorylation levels of Smad2 and Smad3 in TGF-β1-stimulated HSC-T6 cells. Taken together, these findings indicated that GLA inhibits the proliferation and activation of HSC-T6 cells, at least in part, through the TGF-β1/Smad signaling pathway. Therefore, GLA may be a promising potential therapeutic agent for liver fibrosis.