The effect of ghrelin on the regulation of antioxidantenzymes and inducible nitric oxide synthase in rat liver

Abstract

In recent years, there have been prominent findings suggesting that ghrelin has antioxidant and anti-inflammatory effects. In this study we investigated the effects of ghrelin on protein expression of liver antioxidant enzymes superoxide dismutases (SODs), catalase (CAT), glutathione peroxidase (GPx), and glutathione reductase (GR) as well as protein expression of their upstream regulator, nuclear factor kappa B (NFκB). We have also studied the effects of ghrelin on liver inducible nitric oxide synthase (iNOS) protein expression. Furthermore, we aimed to investigate whether extracellular regulated protein kinase (ERK 1/2) and protein kinase B (Akt) are involved in ghrelin regulated liver antioxidant enzymes and iNOS protein expression. Male Wistar rats (200-250g) were treated with ghrelin (0,3nmol/5μl) injected into the lateral cerebral ventricle every 24 h for 5 day, 2 h after the last treatment the animals were sacrificed and liver excised. For protein expression of antioxidant enzymes, iNOS, phosphorylation of Akt at Ser, ERK1/2 and nuclear factor B (NFκB) subunits 50 and 65, Western blot method was used. Results show significantly higher protein expression of Cu/Zn SOD (p<0,05), Mn-SOD (p<0,05), CAT (p<0,01), GPx, (p<0,001), and GR (p<0,01) in the liver isolated from ghrelin treated animals compared with control animals. On the contrary, ghrelin significantly (p<0,001) reduced protein expression of iNOS. In addition, phosphorylation of NFκB subunits p65 and p50 were significantly (p<0,05) decreased by ghrelin when compared with controls. Phosphorylation of ERK1/2 and phosphorylation of Akt at Ser were significantly higher in ghrelin treated than in control animals (p<0,05 for ERK1/2; p<0,01 for Akt). In conclusion, results from this study show that activation of Akt and ERK1/2 are involved in ghrelin-mediated regulation of protein expression of antioxidant enzymes and iNOS in the rat liver. Title of doctoral dissertation: “The effect of ghrelin on the regulation of antioxidant enzymes and inducible nitric oxide synthase in rat liver”