The potential antifibrotic impact of apocynin and alpha-lipoic acid in concanavalin A-induced liver fibrosis in rats: Role of NADPH oxidases 1 and 4

Abstract

Liver fibrosis results from chronic inflammation that precipitates excessive accumulation of extracellular matrix. Oxidative stress is involved in its pathogenesis. This study aimed to elucidate the potential antifibrotic effect of the NADPH oxidase (NOX) inhibitor, apocynin against concanavalin A (ConA)-induced immunological model of liver fibrosis, and to investigate the ability of the antioxidant, alpha-lipoic acid (α-LA) to potentiate this effect. Rats were treated with apocynin and/or α-LA for six weeks. Hepatotoxicity indices, oxidative stress, insulin, NOXs, inflammatory and liver fibrosis markers were assessed. Treatment of animals with apocynin and α-LA significantly ameliorated the changes in liver functions and histopathological architecture induced by ConA. Liver fibrosis induced by ConA was evident where alpha-smooth muscle actin and transforming growth factor- beta1 were elevated, which was further confirmed by Masson's trichrome stain and increased hydroxyproline. Co-treatment with apocynin and α-LA significantly reduced their expression. Besides, apocynin and α-LA significantly ameliorated oxidative stress injury evoked by ConA, as evidenced by enhancing reduced glutathione content, antioxidant enzymes activities and decreasing lipid peroxides. ConA induced a significant elevation in serum insulin level and inflammatory markers; tumor necrosis factor-alpha, interleukin-6 and nuclear factor kappa b. Furthermore, the mRNA tissue expression of NOXs 1 and 4 was found to be elevated in the ConA group. All these elevations were significantly reduced by apocynin and α-LA co-treatment. These findings indicate that using apocynin and α-LA in combination possess marked antifibrotic effects, and that NOX enzymes are partially involved in the pathogenesis of ConA-induced liver fibrosis.