Role of nerve growth factor on p38 MAPK signal pathway in experimental liver damage induced by copper sulphate

The effect of exogenous Nerve Growth Factor (NGF) application on the liver tissue damage model induced by CuSO4 in mice was investigated by histopathological, immunohistochemical, biochemical and molecular means by the emphesis on p38 MAPK signal pathway. In the study, 64 adult male BALB/c mice were randomly divided into 8 groups and all applications were performed intraperitoneally 3 times at 24 hour intervals at the doses listed below. Control group: physiological saline, NGF group: 10 µg/kg NGF, p38MAPKi group: 20 mg/kg p38 MAPK inhibitor (SB203580), NGF+p38MAPKi group: 10 µg/kg NGF and 20 mg/kg SB203580, Copper group: 20 mg/kg CuSO4, Copper+NGF group: 20 mg/kg CuSO4 and 10 µg/kg dose NGF, Copper+p38MAPK group: 20 mg/kg dose CuSO4 and 20 mg/kg SB203580, Copper+NGF+p38MAPKi group: 20 mg /kg CuSO4, 10 µg/kg NGF and 20 mg/kg SB203580. At the end of the applications, the mice were decapitated and their blood and liver tissues were collected. ALT, AST and GGT levels in blood serum and MDA, GSH, TAS and TOS levels in liver tissues were determined by biochemical methods. Histopathological and immunohistochemical (NGF, iNOS, nitrotyrosine, caspase 8, caspase 3, IL-1, IL-6 and TNF-α) examinations were performed in liver tissues. The level of p38 MAPK mRNA expression in liver tissues was determined by molecular methods. Compared to the control group, increases in ALT, AST, MDA, TOS, iNOS and nitrotyrosine levels and decreases in GSH and TAS levels were observed in Copper group. It was determined that the levels of these markers changed significantly (p<0.05) in favor of the cell homeostasis in the subjects that were given NGF together with copper. Exogenous administration of NGF with copper caused a significant (p<0.05) decrease in the acute inflammatory response (IL-1, IL-6 and TNF-α) induced by copper in hepatocytes. When SB203580, a p38 MAPK inhibitor, was applied together with copper and NGF, it was determined that the healing effect of NGF disappeared. These findings showed that NGF exerts its protective effect against copper-induced oxidative and nitrosative damage via the p38 MAPK signaling pathway. It was determined that copper caused hydropic degeneration, focal necrosis and apoptosis in liver tissue. It was observed that the severity and levels of these histopathological changes caused by copper in the livers of the subjects in the group administered NGF together with copper decreased significantly (p<0.05). The severity of hydropic degeneration and focal necrosis was significantly (p<0.05) lower in Copper+NGF group as compared to Copper+NGF+p38MAPKi group, and the decrease in the level of apoptotic cell death (caspase 8 and caspase 3) was statistically significant (p<0.05). These findings indicated that NGF exerts its protective effect on hepatocytes from apoptosis through the p38 MAPK signaling pathway in copper-induced damage.