Mechanism of calpain 2 and its inhibitor calpastatin in the apoptosis of hepatic cells during liver fibrosis

Abstract:

Objective：To observe the changes in expressions of calpain2 and its inhibitor calpastatin cluring liver fibrosis and to explore their effects on apoptosis of hepatic cells. Methods：Forty male Wistar rats were randomly divided into four groups（4 weeks normal control group，8 weeks normal control group，4 weeks liver fibrosis group and 8 weeks liver fibrosis group），each group in－cluded 10 rats. Groups were induced by hypodermic injection of 40% CCl4 every 3 d for 4 weeks and 8 weeks respectively，the dosage of CCl4 is 0.3 ml/100 g body weight. Apoptosis of hepatic cells was detected by TUNEL. Additionally，protein expressions of calpain 2，calpastatin and activated caspase 3 were determined by immunohistochemistry and Western blot and mRNA expressions of cal－pain2 and calpastatin were determined by real-time PCR. Results：Results of immunohistochemistry and Western blot revealed that there was no difference in expressions of calpain 2 and calpastatin protein between 4 weeks fibrosis group and normal control group（P >0.05）. In 8 weeks fibrosis group，expressions of calpain2 were increased obviously and expressions of calpastatin were decreased with the increase of liver fibrosis degree. Additionally，real-time PCR results revealed that expressions of calpain2 mRNA in 4 weeks and 8 weeks fibrosis groups were elevated compared with those in normal control group（P＜0.01），while expressions of calpastatin mRNA were decreased in 8 weeks fibrosis group（P＜0.01）. Expressions of activated caspase3 protein in 4 weeks and 8 weeks fibrosis groups were increased compared with those in normal control group and the number of apoptotic cells were also elevated in fibrosis groups than in normal control group（P＜0.01）. Conclusion：Calpain2 and calpastatin may play important roles in the process of liver fibrosis. Their effects on fibrosis might be exerted through promoting the apoptosis of hepatic cells.