Silibinin induces hepatic stellate cell cycle arrest via enhancing p53/p27 and inhibiting Akt downstream signaling protein expression

BACKGROUND： Proliferation of hepatic stellate cells （HSCs） plays a pivotal role in the progression of liver fibrosis conse- quent to chronic liver injury. Silibinin, a flavonoid compound, has been shown to possess anti-fibrogenic effects in animal models of liver fibrosis. This was attributed to an inhibition of cell proliferation of activated HSCs. The present study was to gain insight into the molecular pathways involved in silibinin anti-fibrogenic effect. METHODS： The study was conducted on LX-2 human stellate cells treated with three concentrations of silibinin （10, 50 and 100 μmol/L） for 24 and 96 hours. At the end of the treatment cell viability and proliferation were evaluated. Protein expression of p27, p21, p53, Akt and phosphorylated-Akt was evaluated by Western blotting analysis and Ki-67 protein expression was by immunocytochemistry. Sirtuin activity was evaluated by chemiluminescence based assay. RESULTS： Silibinin inhibits LX-2 cell proliferation in doseand time-dependent manner; we showed that silibinin upregulated the protein expressions of p27 and p53. Such regulation was correlated to an inhibition of both downstream Akt and phosphorylated-Akt protein signaling and Ki-67 protein expression. Sirtuin activity also was correlated to silibinin- inhibited proliferation of LX-2 cells. CONCLUSION： The anti-proliferative effect of silibinin on LX-2 human steUate cells is via the inhibition of the expres- sions of various cell cycle targets including p27, Akt and sir- tuin signaling.

Silibinin alleviates N-nitrosodimethylamine-induced glutathione dysregulation and hepatotoxicity in rats

The present study was designed to evaluate the hepatoprotective and antioxidant potentials of silibinin(SBN)against N-nitrosodimethylamine(DMN)-induced toxic insults in the rat liver.The liver damage was induced in Wistar albino rats by repeated administration of DMN(10 mg·kg-1 b.w.,i.p.)on 3 consecutive days per week for 3 weeks.SBN(100 mg·kg-1 b.w.,p.o.)was given daily to the DMN treated rats for two weeks.The marker enzymes of liver toxicity and second-line enzymic and non-enzymic antioxidants were evaluated in serum and liver tissues before and after SBN treatment.Histopathology of the liver was evaluated by H & E staining.The DMN treatment produced a progressive increase in all the serum marker enzymes(AST,ALT,ALP,LDH,and γ-GT),peaking on Day 21.This treatment produced highly significant decreases in all the second-line antioxidant parameters(GSH,GST,GR,GPx,and vitamins C and E).The SBN treatment significantly reversed the DMN-induced damages,towards normalcy.Histopathological studies confirmed the development of liver toxicity in DMN-treated rats,which was reversed by SBN treatment in corroboration with the aforementioned biochemical results,indicating the hepatoprotective and antioxidant properties of SBN.In conclusion,the DMN-induced degenerative changes in the liver were alleviated by SBN treatment and this protective ability may be attributed to its antioxidant,free radical scavenging,and membrane stabilizing properties.

Plant derived antioxidants and antifibrotic drugs:past,present and future

Hepatic fibrosis occurs as a wound-healing process after several forms of chronic hepatic injury.Activation and proliferation of hepatic stellate cells play pivotal role in the pathogenesis of hepatic fibrosis.Many researchers,from the therapeutic perspective,have focused their attention on searching for novel agents with inhibitory effects on hepatic stellate cells proliferation and activation to prevent hepatic fibrogenesis and a number of plant derived antioxidants have been tested as anti-fibrogenic agents,they generally suppress proliferation and collagen synthesis.Plants remain an imperative source of novel drugs,novel drug leads and new chemical entities.The plant based drug discovery resulted primarily in the development of antioxidant,anti-cancer and other anti-infectious agents and continues to contribute to the new leads in clinical trials.This review summarizes some of those most important plant derived anti-fibrotic drugs and their beneficial effects on experimentally induced hepatic fibrosis in vitro and in vivo.The plant derived antioxidant compounds described herein are curcumin,silymarin,silibinin,baicalein,resveratrol,salvianolic acids,tetrandine,quercetin and berberine.Studies from ours and as demonstrated by pervious workers much information has been accumulated over the past two decades through in vivo and in vitro.In light of those studies,it has been confirmed that plants derived antioxidants,particularly flavanoids,show a significant influence to block hepatic fibrosis regardless of any etiology.This review outlines recent progress in the use of plant derived drugs against experimentally induced liver fibrosis by in vitro and in vivo studies and summarizes the possible mechanisms anti-fibrotic effects of these compounds.