Effects of ß-sitosterol derived from Artemisia capillaris on the activated human hepatic stellate cells and dimethylnitrosamine-induced mouse liver fibrosis.

BACKGROUND: ß-sitosterol is a cholesterol-like phytosterol, which widely distributed in the plant kingdom. Here, anti-fibrotic effect of the ß-sitosterol was studied using the activated human hepatic stellate cell (HSC) model and dimethylnitrosamine (DMN)-induced mouse hepatic fibrosis model. METHOD: HSCs were activated by transforming growth factor-ß (TGF-ß) and the collagen-1 and α-smooth muscle actin (α-SMA) expressions were measured at the mRNA and protein level. We also studied the effect ß-sitosterol using DMN-induced mouse hepatic fibrosis model. We then measured the collagen-1 and α-SMA expression levels in vivo to investigate anti-hepatofibrotic effect of ß-sitosterol, at both of the mRNA and protein level. RESULTS: ß-sitosterol down regulated the mRNA and protein expression levels of collagen-1 and α-SMA in activated HSC. Oral administration of the ß-sitosterol successfully alleviated the DMN-induced mouse liver damage and prevented collagen accumulation. The mRNA and protein expression levels of collagen-1 and α-SMA were also down regulated in ß-sitosterol treated mouse group. CONCLUSIONS: This study shows the effect of ß-sitosterol on the TGF-ß -or DMN-induced hepatofibrosis. Hence, we demonstrate the ß-sitosterol as a potential therapeutic agent for the hepatofibrosis.

Purification and characterization of recombinant human endothelin receptor type A.

Human endothelin receptor type A (ET(A)) is a G-protein coupled receptor that mediates vasoconstriction of blood vessels. To determine the structural characteristics and signaling mechanism of ET(A), we have expressed recombinant ET(A) as a fusion protein with p9 envelope protein from phi6 bacteriophage. The His-tag-labeled p9-ET(A) fusion protein was highly expressed in the membrane fraction of Escherichia coli and purified to homogeneity by single affinity chromatography after solubilization with detergents. Purified p9-ET(A) appeared as an oligomer and presented mainly as an α-helical structure. The protein also showed specific binding to endothelin-1 (ET-1) and the alpha subunit of G(q) protein with apparent K(D) values of 17 and 20 nM, respectively. An antagonist of ET(A), bosentan, prevented the interaction between p9-ET(A) and ET-1 in a concentration-dependent manner. These results indicate that recombinant p9-ET(A) has a competent conformation for interactions with ET-1 and the alpha subunit of G(q) protein.