Oxidative stress response biomarker gene expression in Piaractus brachypomus (Characiformes: Serrasalmidae)

ABSTRACT Oxidative stress may occur in the fish brain under several conditions, including tissue reoxygenation during anaesthesia, injury and toxic exposure. An imbalance in oxidative homeostasis can lead to oxidative stress, triggering several adaptive mechanisms at both the genetic and protein levels. The aim of this study was to assess the transcription levels of five oxidative stress-related genes in the Colombian native fish red-bellied pacu, Piaractus brachypomus, under anaesthesia with menthol (50 mg/L) and eugenol (40 mg/L), as well as in models of acute brain injury and organophosphate toxicity. Relative gene expression was assessed in the brain, gill and liver tissues of fish under anaesthesia and in the brain tissues of fish in the brain injury and toxicity experiments. It was found that glutathione reductase (GSR) mRNA levels in the brain were significantly higher in the eugenol group than in the menthol group, ATP synthase subunit 6 (ATP6) transcription was downregulated after brain injury, and the GSR, ATP6 and superoxide dismutase 2 (SOD2) genes were upregulated in fish exposed to the organophosphate chlorpyrifos. This is the first evaluation of the relative gene expression of oxidative response biomarkers in P. brachypomus.