Abstract
Microcystins (MCs) are considered to be one of the most hazard groups of cyanobacteria and are known as a group of cyclic polypeptide hepatotoxins of varying potency. The study determined the variation of gene expression of GSTA, GSTR, GPX, UCP2, CYP1A1 and HSP70 genes in liver of tilapia fish (Oreochromis niloticus) under the effect of MC-LR or MC-RR toxins.
Tilapia fish adult male fishes (n = 20; 120–178 g) obtained from fish farm. Fishes injected i.p. with a single dose of 50 μg/kg MC-LR, and 20 fishes injected with 500 μg/kg MC-RR. Whereas the control group was only received the vehicle solution. Total mRNA was isolated from 50 mg of hepatic sections. The relative levels of GSTA, GSTR, GPX, UCP2, HSP70/β actin mRNA were determined by RT-real time PCR.
Significantly increased in GSTA mRNA expression was observed in the liver of fish after exposure to all exposure groups. Variable alterations in the levels of GPx, GSTR, UCP2 and CYP1A mRNA expression were observed post exposure groups. Whereas, the relative level of HSP70 mRNA was increased at 12 h after MCs exposure and was elevated gradually at 24 h until 7 days post treatment.
The presence of inducible expression of GSTA, GSTR and GPx, and no significant changes of CYP1A mRNA expression in the liver of tilapia post MCs exposure, indicates that it should be the phase II detoxification enzyme in the liver of tilapia, but not the phase I detoxification enzyme. In addition to restrain over production of ROS, increasing of UCP2 and HSP70 expression may play an important role as a molecular chaperone against oxidative stress consequently, preventing hepatic cells from apoptosis.
•Microcystins (MCs) are one of the most hazard groups of cyanobacteria.•GSTA mRNA was increased in fish liver after exposure of MC-LR and MC-RR.•Relative HSP70 mRNA was also increased after 12 h of MCs exposure.•Variable alterations were observed in mRNAs of GPx, GSTR, UCP2.•No significant changes of CYP1A mRNA expression was observed after MCs exposure.