[Effect of CKIP-1 on hepatocyte apoptosis in nonalcoholic fatty liver disease]

Objective: To explore the effect and underlying mechanism of casein kinase 2 interacting protein-1 (CKIP-1) on hepatocyte apoptosis in nonalcoholic fatty liver disease (NAFLD). Methods: Experimental study. An NAFLD cell model was established by inducing human hepatoma cell line, HepG₂ cells, with oleic acid (OA). Flag-CKIP-1 expression vector and shRNA-CKIP-1 were transfected into HepG₂ cells. Flow cytometry was used to detect the effect of CKIP-1 on the activity and apoptosis of NAFLD hepatocytes. The levels of apoptosis-related proteins were detected by Western blot. CKIP-1 knockout mice in C57BL/6 back-ground were fed with either standard or high-fat diet for 8 weeks. Apoptosis-related signal proteins in NAFLD hepatocytes were detected by immunohistochemistry. Results: After CKIP-1 was transfected into HepG₂ cells, the degree of OA induced cell liposis was significantly reduced (P<0.05). Annexin V-FITC/PI flow cytometry showed that CKIP-1 reduced the apoptosis of steatotic hepatocytes. Overexpression of CKIP-1 could significantly inhibit the expression of caspase-3 and caspase-9 and increase the expression of Bcl-2/Bax (P<0.05). Knockdown of CKIP-1 could increase the expression of caspase-3 and caspase-9 (P<0.05). CKIP-1 knockout could further increase the expression of caspase-3 and caspase-9 in NAFLD mice (P<0.01,P<0.05), and further decrease the expression of Bcl-2/Bax (P<0.05). Conclusion: CKIP-1 inhibited the apoptosis of steatotic hepatocytes by up-regulating the expression of apoptosis inhibitor gene, Bcl-2/Bax, and affecting the proteases, caspase-3 and caspase-9.

Expression changes of activin A in the development of hepatic fibrosis

AIM: To examine the expression of activin A, a member of the transforming growth factor (TGF-β) superfamily, recently has been reported to beoverexpressed in liver cirrhosis, in the course of carbon tetrachloride-induced rat hepatic fibrosis.

METHODS: Hepatic fibrosis was induced in rats by subcutaneous injections of 40% carbon tetrachloride oily solution for a period of 1 to 7 weeks. At the end of 1, 2, 3, 4, 5, 6 and 7 weeks after carbon tetrachloride injections, the rats were killed in group (6-10 rats each time) for study. The activin A messenger RNA expression and its protein localization were assessed by semi-quantitative reverse transcription polymerase chain reaction (RT-PCR) and immunohistochemistry.

RESULTS: The normal rat liver expressed activin A mRNA and protein, and its expression was transiently decreased and became undetectable after carbon tetrachloride injections for 2 or 3 weeks and then increased gradually. After injection of carbon tetrachloride for 6 and 7 weeks, activin A mRNA and protein expressions were significantly enchanced in rat liver. Compared with that of the normal rat liver. Activin A mRNA expression levels in rats receiving carbon tetrachloride injections for 6 and 7 weeks were 1.6 and 2.2 times that of those in normal rat liver respectively (0.456 ± 0.094 vs 0.286 ± 0.0670, P < 0.01; 0.620 ± 0.134 vs 0.286 ± 0.0670, P < 0.01). Immunohistochemistry showed that activin A expressed in hepatocytes of normal liver, and its expression was decreased in rats receiving carbon tetrachloride for 2 or 3 weeks. Compared with normal liver, activin A expression distribution mode changed in fibrotic liver, being increased significantly in hepatocytes around fibrotic areas.

CONCLUSION: Activin A expression was increased in late stage of hepatic fibrosis, and this may be involved in hepatic fibrosis formation in this period.