Role Of NF-κB In Rats Liver Fibrosis And Its Suppression By Melatonin

Objective To evaluate the role of NF-KB/nitric oxide(NO) signal pathway of liver fibrosis in rats, and investigate the time-effect relation of melatonin against tetrachloride(CCl4) induced-liver injury in rats and its mechanism. Method 99 rats were divided into normal group, model group, N-acetyl-L-cysteine (NAC) treated group and melatonin treated group. Melatonin and NAC were given by ip at the beginning of the establishment of the chronic hepatic injury in rats which were established with CCU. At the end of the 1st month, 2nd month and 3rd month, the rats were killed, the rats' body weight and liver wet weight, the level of alanine transaminase (ALT) , asparagic acid transaminase (AST) and albumin in serum was measured and the ratio of albumin against globulin was calculated, the content of NO in serum and liver homogenates was detected by high performance liquid chromatograpy and Griess method respectively. Liver samples were used for histopathology examination, the score of the index of hepatic inflammation and liver fibrosis was evaluated, the expression of NF-KB P65, NF-KB P50, iNOS and a -SMA in rats liver were also analyzed by immunohistochemistry method.Results The activities of ALT, AST in serum and the liver pathological score in model rats were higher than that in normal rats, the expression of NF-KB P65,NF-icB P50 and a -SMA in rats liver was showed similar tendency. At the end of the 1st month, NF-KB was strongly expressed in Kupffer cells(KC),but at the end of the 3rd month, NF-KB was strongly expressed in hepatic stellate cells(HSC). There was significantly positivecorrelation between the expression of a -SMA and NF-KB P50, NF-KB P65 in rats liver (r=0.884,p=0.08 ; r=0.73, p=0.062) .On the other hand, with the inactivation of NF-KB by NAC, the hepatic injury was ameliorated significantly and the expression of a -SMA in liver was also decreased.Melatonin inhibited the expression of NF-KB P65 and NF-KB P50, decreased transaminase in serum, increased the content of albumin and the ratio of albumin against globumin, inhibited the expression of a -SMA in liver significantly. Hepatic injury was also ameliorated by melatonin. At the end of the 1st month, melatonin ameliorated hepatic inflammation, at the 2nd, 3rd month, melatonin prevented the development of liver fibrosis.The expression of iNOS, the content of NO in serum or liver homogenates in model rats were stronger than that in normal rats. And correlation analysis showed positive correlation between the content of NO in liver homogenates and the expression of iNOS in liver (r=0.875, P=0.023; r=0.865, P=0.026; r=0.752, P=0.08) .After melatonin and NAC inhibited the activation of NF-KB, the expression of iNOS in liver and the content of NO in liver homogenates were decreased and hepatic inflammation was ameliorated correspondingly. But the content of NO in serum did not decrease . Conclusion (l)At the early phase of liver fibrosis, NF-KB mainly promotes hepatic inflammation by regulating KC releasing inflammatory factor. But during the middle or later phase, NF-KB mainly promotes liver fibrosis by regulating the activation of HSC. (2) During the early phase of CCl4-induced rat chronic hepatic injury, melatonin can inhibit the activation of NF-KB in KC, reduce the expression of inflammatory factor, and relieve hepatic inflammation. But during the middle or later phase, melatonin can inhibit the activation of NF- B in HSC and prevent the phenotype conversion of HSC, mainly inhibit liver fibrosis. (3)Expression of iNOS is regulated by NF- B, and NO takes part in hepatic inflammatory course. Melatonin suppresses the expression of iNOS by inactiviation of NF-icB in rats liver, and decreases the production of NO, improveshepatic inflammatory injury.