Sodium valproate blocks the transforming growth factor (TGF)-β1 autocrine loop and attenuates the TGF-β1-induced collagen synthesis in a human hepatic stellate cell line

Histone acetylation and deacetylation have been thought to be related to gene expression, and there are many reports indicating that histone deacetylase inhibitors (HDACis) exert antifibrogenic effects in several organs. In injured livers, hepatic stellate cells (HSCs) are activated in response to profibrogenic mediators and produce large amounts of extracellular matrix. In particular, transforming growth factor-β1 (TGF-β1) is considered as a key factor in accelerating hepatic fibrosis because it is released from activated HSCs and further stimulates them. The present study aimed to clarify whether sodium valproate (VPA) has suppressive effects on cultured human HSCs (LI90). We showed that treatment with VPA had no significantly suppressive effect on cell proliferation at a concentration of 1 mM, which corresponded approximately to the serum concentration obtained by the administration of a clinical dose. However, VPA prevented the morphological changes characteristic for activation and inhibited the expression of collagen type 1 α1 (COL1A1) and TGF-β1 in activated LI90 cells at the mRNA and protein levels. Our results support the hypothesis that VPA exerts antifibrogenic activity with little cytotoxicity at 1 mM, and HDACis are expected to be used in clinical practice for the treatment of fibrotic diseases.