Lipid peroxidation and its relevance to pheromone production in marine fish under oxidative stress

Abstract

Pheromones are lipid metabolites from polyunsaturated fatty acids secreted outside by an individual and received by a second individual. It serves for communication within species and may affect the behavior and developmental process of a species. Acute oxidative stress by hydrogen peroxide exposure was found to alter lipid metabolism in medaka fish by our research group. However, the effect of oxidative stress induced by hyperoxia and hypoxia on lipid metabolism is not well known. Adult male and female marine medaka fish (Oryzias melastigma) were exposed to hypoxia, normoxia and hyperoxia condition for 1 hour. Concentration of pheromones (Prostaglandin-F2α, 15-keto- Prostaglandin-F2α, 13,14-dihydro-15-keto-prostaglandin-F2α and 17α,20β- Dihydroxy-4-pregnen-3-one) and oxidized lipid products of arachidonic, adrenic, docosahexaenoic and eicosapentaenoic acids were determined by liquid chromatography tandem mass spectrometry (LC-MS/MS) in the fish muscles. Concentration of the Prostaglandin-F2α and 17α,20β-Dihydroxy-4-pregnen-3-one were significantly higher in male than female medaka muscle. Hypoxia condition reduced Prostaglandin-F2α and15-keto-Prostaglandin-F2α concentrations compared to normoxia whereas hyperoxia condition reduced 13,14-dihydro-15- keto-prostaglandin-F2α concentration in both male and female medaka. Concentration of oxidized lipid products showed gender difference and was lower in female (F2-isoprostanes, F2-dihomo-isoprostanes, dihomo-isofurans and F4- neuroprostanes) than male medaka. Compared to normoxia, hyperoxia environment increased F2-isoprostanes in both male and female medaka muscle. However hyperoxia environment elevated F2-dihomo-isoprostanes and dihomoisofurans in female medaka only and suppressed in male medaka compared to normoxia. F3-isoprostane, neurofurans, RvE1 and RvD1 levels were low in both hypoxia and hyperoxia environment compared to normoxia and were also more apparent in female medaka muscle. Pheromones and F2-isoprostanes share the same precursor fatty acid (arachidonic acid). Our study indicates changes in oxygen tension suppress pheromone release and potentiate non-enzymatic lipid peroxidation of arachidonic acid as well as adrenic acid (an elongated product of arachidonic acid). Such outcome could affect reproductive system of marine fish and disrupt lipid metabolism.