Hyperoxia elevates adrenic acid peroxidation in marine fish and is associated with reproductive pheromone mediators.

The development of oxidative stress in the marine ecosystem is a concurring concern in fish reproductive behavior. Marine fish being rich in polyunsaturated fatty acids (PUFA) are precursors of prostaglandin pheromone mediators but also vulnerable to lipid peroxidation. It is yet to be determined if hypoxia or hyperoxia environment, a cumulative effect in the marine ecosystem affect pheromone mediators in fish, and to understand if this is associated with the generation of oxidized lipid products of PUFA. Novel oxidized lipid metabolites, isoprostanoids (15-F2t-isoprostane, 7(RS)-7-F2t-dihomo-isoprostane, 17(RS)-17-F2t-dihomo-isoprostane, 8-F3t-isoprostane, 4(RS)-4-F4t-neuroprostane, 10-F4t-neuroprostane), isofuranoids (isofurans, 10-epi-17(RS)-SC-Δ15-11-dihomo-isofuran and neurofurans), hydroxyeicosatetraenoic acids and resolvins, PUFA (arachidonic, adrenic, eicosapentaenoic and docosahexaenoic acids) and prostaglandin pheromone mediators in fish muscle were determined in marine male and female fish muscles before and after interaction in a hypoxia or hyperoxia environment. Reproductive behaviors were also assessed. Our study showed oxidized lipid metabolites of arachidonic, eicosapentaenoic, and docosahexaenoic acids were not influenced by hypoxia and hyperoxia exposure in the fishes and no gender differences were found. However, adrenic acid and its oxidized products, 17(RS)-17-F2t-dihomo-isoprostane and 10-epi-17(RS)-SC-Δ15-11-dihomo-isofuran showed strong correspondence with male fish pheromone mediators and reproductive behavior when under oxidative stress especially, hyperoxia. The occurrence of hypoxia and hyperoxia in the marine ecosystem may not be detrimental to marine fish and instead presents as being beneficial in reproductive behavior.

Profiling of oxidized lipid products of marine fish under acute oxidative stress.

Free radical products including reactive oxygen species are potent to oxidize lipids and reliable measurements have been established mostly in human and rodent. To date, robust biomarkers were not used to assess the peroxidation in marine fish. The changes of oxidized lipid products from polyunsaturated fatty acids and cholesterol were assessed after exposure of H(2)O(2) to fish (medaka). Oxidized lipid products released by free radical reaction (F(2)-isoprostanes and metabolites, F(3)-isoprostanes, neuroprostanes, 7-ketocholesterol, 7ß-hydroxycholesterol), by lipoxygenase enzymes (5(S)-, 8(S)-, 12(S)- and 15(S)-HETE, and resolvin D1) and by cytochrome P450 (9(S)-, 11(S)- and 20-HETE, and 27-hydroxycholestrol) were measured in fish muscle using LC/MS/MS. Arachidonate, docosahexaenoate, eicosapentaenoate and cholesterol levels, and antioxidant enzymes activity (catalase, SOD and gluthathione reductase) measurement were also determined. Activity of antioxidant enzymes especially catalase were elevated in presence of H(2)O(2) however longer exposure time suppressed the antioxidant activities. Arachidonate, docosahexaenoate, eicosapentaenoate and cholesterol levels were reduced in presence of H(2)O(2) and oxidized lipid products (isoprostanes, neuroprostanes 5(S)-HETE, 20-HETE, 7-ketocholesterol, 27-hydroxycholesterol and resolvin D1) were rapidly released in the fish muscle. This study validates oxidized lipid products, noticeably isoprostanes are measurable in marine fish muscle and should be considered when assessing oxidative stress especially due to exogenous factors.