Salvianolic Acid B Inhibits ERK and p38 MAPK Signaling in TGF-β1-Stimulated Human Hepatic Stellate Cell Line (LX-2) via Distinct Pathways

Salvianolic acid B (SA-B) is water-soluble component of Radix Salvia miltiorrhiza. The previous work indicated that SA-B can inhibit MAPK and Smad signaling in activated hepatic stellate cells (HSCs) to performanti-fibrotic activity Lv et al. 2010. However, some studies have shown that there is cross-talk between MAPK and Smad in certain cell types. Thus, the anti-fibrotic action of SA-B may be through the cross-talk. In order to clarify the mechanism of SA-B further, we knocked down Smad in LX-2 cells (SRV4) via RNAi, and then added TGF-beta 1, and PD98059 or SB203580 and SA-B. The levels of p-MEK and p-p38 were inhibited by SA-B in SRV4 independent of TGF-beta 1. The expression of Col I and alpha-SMA in SRV4 could be reduced by SA-B independent TGF-beta 1. SB203580 had not significant effect on p-MEK in SRV4 stimulated by TGF-beta 1. The levels of p-MEK in SRV4 were not increased significantly after TGF-beta 1 stimulation. PD98059 had no effect on the levels of p-p38 in SRV4 irrespective of TGF-beta 1. In conclusion, SA-B inhibits the synthesis of Col I in LX-2 cells independent of TGF-beta 1 stimulation, and the anti-fibrotic effect of SA-B is due to direct inhibition of p38 signaling and inhibition the cross-talk of Smad to ERK signaling.