Withagulatin A inhibits hepatic stellate cell viability and procollagen I production through Akt and Smad signaling pathways

Aim: To investigate the effects of the natural product Withagulatin A on hepatic stellate cell (HSC) viability and type I procollagen production. The potential mechanism underlying the pharmacological actions was also explored.

Methods: The effect of Withagulatin A on cell viability was evaluated in HSC and LX-2 cells using a sulforhodamine B (SRB) assay. Cell cycle distribution was analyzed using flow cytometry. Type I procollagen gene expression was determined using Real-Time PCR. Regulation of signaling molecules by Withagulatin A was detected using Western blotting.

Results: Primary rat HSCs and the human hepatic stellate cell line LX-2 treated with Withagulatin A (0.625-20 micromol/L) underwent a dose-dependent decrease in cell viability, which was associated with S phase arrest and the induction of cell Apoptosis. In addition, the natural product decreased phosphorylation of the Akt/mTOR/p70S6K pathway that controls cell proliferation and survival. Furthermore, Withagulatin A (1, 2 mumol/L) inhibited transforming growth factor-beta (TGF-beta) stimulated type I procollagen gene expression, which was attributable to the suppression of TGF-beta stimulated SMAD2 and SMAD3 phosphorylation.

Conclusion: Our results demonstrated that Withagulatin A potently inhibited HSC viability and type I procollagen production, thereby implying that this natural product has potential use in the development of anti-fibrogenic reagents for the treatment of hepatic fibrosis.