Changes of lipid peroxidation and glutathione redox system, and expression of glutathione peroxidase regulatory genes as effect of short-term aflatoxin B1 exposure in common carp

Abstract

Lipid peroxidation, glutathione content, glutathione peroxidase activity and gene expression of transcription factors, glutathione peroxidase, glutathione synthetase and glutathione reductase was investigated in common carp liver. Short term (24 h) exposure of aflatoxin B₁ at different doses (100, 200 and 400 μg AFB₁ kg^-1 feed) was used. It was found that conjugated dienes and trienes elevated after 16 h, while thiobarbituric acid reactive substances content increased only at the lowest dose after 16 and 24 h of exposure. Glutathione content showed higher levels than control after 16 h of exposure and glutathione peroxidase (GPx4) activity was higher in all of the AFB₁ treated than the control group after 8 h of exposure. Gene expression of transcription factors showed dual response. Expression of keap1 gene down-regulated after 8 h and 16 h and nrf2 gene after16 h, but up-regulated after 24 h of exposure in the lowest, and highest dose groups. Expression of gpx4a and gpx4b genes down-regulated after 8 h and induction was found after 16 and 24 h of exposure, irrespective of the dose. The results indicated that low dose of AFB₁ provokes oxidative stress earlier than higher doses, which activated the Keap1-Nrf2 pathway. At higher doses this pathway activated later, but preformed GPx4 effectively prevented lipid peroxidation.

Keywords: Aflatoxin B(1); Antioxidant defence system; Common carp; Glutathione peroxidase.