EVALUATING THE PROTECTIVE ROLE OF SOME ANTIOXIDANTS AGAINST THE INDUCED FREE RADICALS RESULTING FROM DIFFERENT ENVIRONMENTAL POLLUTANTS

Abstract

Liver fibrosis is one of the leading causes of morbidity and mortality worldwide with very limited therapeutic options. Given the pivotal role of activated hepatic stellate cells (HSCs) in liver fibrosis, attention has been directed towards the signaling pathways underlying their activation and fibrogenic functions. Recently, hedgehog (Hh) pathway has been identified as a potentially important therapeutic target in liver fibrosis. In the present study, we explored the potential antifibrotic effect of the potent Hh signaling inhibitor, forskolin, in a rat model of carbon tetrachloride (CCl4)-induced liver fibrosis. The possible mechanisms underlying this effect were investigated as well. Male albino rats were treated with either CCl4 (0.5 ml/kg, twice a week) and/or forskolin (10 mg/kg, five times a week) for six weeks. CCl4 caused a significant increase in the liver index, serum transaminases, total cholesterol, triglycerides and total bilirubin while decreased serum albumin. Forskolin co-treatment protected against CCl4¬-induced hepatotoxicity and reduced all of the histopathological abnormalities. Hepatic fibrosis induced by CCl4 was evidenced by increased alpha smooth muscle actin (α-SMA) expression and collagen deposition as indicated by Masson’s trichrome staining and hydroxyproline content. Forskolin significantly reduced liver fibrosis as indicated by decreased α-SMA expression as well as collagen deposition. To elucidate the underlying molecular mechanisms, the effect of forskolin on oxidative stress markers, inflammatory markers, TGF-β1 as well as Hh signaling was assessed. The CCl4 depleted GSH levels and increased lipid peroxidation. In addition, CCl4 increased NF-κB, COX-2, TNF-α as well as TGF-β1 tissue expression. Hh pathway activation was confirmed by increased expression of PTCH-1, SMO and GLI-2 in fibrotic livers. Indeed, forskolin co-treatment significantly attenuated oxidative stress and inflammation, reduced TGF-β1 levels, PTCH-1, SMO and GLI-2 expression. In conclusion, these results indicate that forskolin has a promising antifibrotic effect which could be partially attributed to its antioxidant and anti-inflammatory effects as well as its effect on inhibiting Hh signaling.

Key words: liver fibrosis, CCl4, forskolin, NF-κB, hedgehog signaling pathway.