Apoptosis in dissociation between DNA synthesis and cellular functions of activated hepatic stellate cells--a study with carbon tetrachloride-induced rat liver injury

Role of growth factor receptor-bound 2 in CCl4-induced hepatic fibrosis

BACKGROUND

Growth Factor Receptor-bound 2 (GRB2) plays a crucial role in regulation of cellular function including proliferation and differentiation, and we previously identified GRB2 as promoting HSCs (HSCs) proliferation. However, the underlying mechanisms that are involving in the regulation of GRB2 in hepatic fibrogenesis remain unknown.

METHODS

In the present study, we tested the function of GRB2 in hepatic fibrosis. Hepatic fibrosis was induced by subcutaneous CCl₄ administration at a dose of 3mL/kg in rats. The rat HSC cell line HSC-T6 were cultured for proliferation investigation by CCK-8 and BrdU incorporation method. The levels of GRB2, HMGB1, PI3K/AKT, COL1A1 and α-SMA were analyzed by western blot or real-time PCR.

RESULTS

showed that the expression of GRB2 and HMGB1 was obviously increased in liver tissues of hepatic fibrosis rats accompanied by up-regulation of COL1A1 and α-SMA. In cultured HSCs, application of exogenous HMGB1 induced cell proliferation and cell proliferation rate concomitantly with up-regulation of GRB2 expression and PI3K/AKT phosphorylation. The effects of HMGB1-induced proliferation of HSCs and up-regulation of COL1A1 and α-SMA were abolished by GRB2 siRNA. HMGB1-induced proliferation of HSCs and up-regulation of COL1A1 and α-SMA was reversed in the presence of LY294002, an inhibitor of PI3K inhibitor.

CONCLUSIONS

These findings suggest that GRB2 plays an important role in CCl₄-induced hepatic fibrosis by regulating HSCs' function, and up-regulation of GRB2 induced by HMGB1 is mediated via the PI3K/AKT pathway.

Japanese herbal medicine Inchin-ko-to as a therapeutic drug for liver fibrosis

BACKGROUND/AIMS

Inchin-ko-to (TJ-135) is an herbal medicine used in Japan for treatment of icteric patients with cirrhosis. Its efficacy as an anti-fibrogenic drug was evaluated in relation to stellate cell activation.

METHODS/RESULTS

Liver fibrosis was induced in rats by repeated injections of carbon tetrachloride (CCl4) or pig-serum. Oral administration of TJ-135 improved the mortality of rats given CCl4 with reduced extents of liver necrosis and fibrosis. Similar improvement of liver fibrosis was found in rats given pig-serum showing no liver necrosis. DNA synthesis of stellate cells activated in vitro after isolation from normal rat liver was decreased by culture with TJ-135 in a dose-related manner, accompanied by decreased smooth muscle alpha actin expression and contractility. Such attenuation was not found in the cells cultured with geniposide, an iridoid compound of TJ-135, but genipin, an aglycone of geniposide formed in the gut by action of bacterial flora, markedly decreased stellate cell activation without affecting synthesis of proteins other than collagen.

CONCLUSIONS

TJ-135 may be useful for treatment of liver fibrosis and portal hypertension through suppression of activated hepatic stellate cell function by genipin, an absorbed form of its component.