Hydrogen peroxide modulates antioxidant system transcription, evidencing sex-dependent responses in Caligus rogercresseyi

摘要

Hydrogen peroxide (H2O2) is a non-pharmacological antiparasitic used to control adult copepodid ectoparasites in salmonid farming worldwide. Its functional mechanism is based on forming bubbles in the haemolymph and tissues, detaching the parasite from the host. However, to date there is no information on the molecular effects of H2O2. This study evaluated the modulation of 12 genes associated with the antioxidant system in Caligus rogercresseyi exposed to three concentrations of H2O2 as an antiparasitic agent. Bioassay results showed that sea lice survival was 69, 47 and 15 for H2O2 doses of 1000, 1500 and 2000mgL(-1) respectively. The ratio of surviving males to females provided evidence that females were less sensitive to all evaluated conditions, and at a dose of 2000mgL(-1), all surviving sea lice were female. Transcriptional analysis of antioxidant genes revealed that the three H2O2 concentrations exerted differentiated effects on each sex. In females, a concentration of 1500mgL(-1) increased the gene expression of CrPRX2, CrGST1, CrGST-like and CrGST-kappa 1. For males, concentrations of 1000 and 2000mgL(-1) modulated the expression of CrPHGP1, CrCAT, CrSOD, CrSe-GPX and CrFERR. Global transcription expression evidenced that female sea lice generated a lower transcriptional response to H2O2 as compared to males, and this response was correlated with lower accumulated mortality. These results suggest that H2O2 modulates enzymes of the antioxidant system and that a sex-specific response occurs to the oxidative stress generated by this pesticide.