Effect of short-term sterigmatocystin exposure on lipid peroxidation and glutathione redox system and expression of glutathione redox system regulatory genes in common carp liver.

Sterigmatocystin (STC) is structurally close to the mycotoxin aflatoxin B as it shares its biosynthetic pathway with aflatoxins. The purpose of the present study was to investigate the short-term (24 h) effects of STC contaminated diet at different doses (1 mg, 2 mg and 4 mg STC kg feed) in one year old common carp juveniles. Liver samples were taken in 8-h intervals. The markers of the lipid peroxidation showed moderate changes after the application of sterigmatocystin-contaminated diet, significant elevations were only observed in the lowest applied dose group of sterigmatocystin after 16 h of exposure. Reduced glutathione content showed higher levels than control group after 16 h of exposure as effect of low dose of sterigmatocystin. Glutathione peroxidase (GPX4) activity was lower than control in the group treated with 2 mg STC kg feed after 24 h of exposure. Gene expression measurements of keap1, nrf2, gpx4a, gpx4b and gss genes revealed a dual response. Down-regulation or near control values were observed 8 h after exposure which was followed by an induction 16 and 24 h after exposure. In case of gsr, gene expression values returned to control levels by the 24th hour. In summary, these results suggest that lower doses of STC caused oxidative stress earlier than higher doses, which efficiently activated the Keap1-Nrf2 pathway, while higher doses revealed long-drawn activation of this pathway.