Hypoxia, reoxygenation and cytosolic manganese superoxide dismutase (cMnSOD) silencing in Litopenaeus vannamei: Effects on cMnSOD transcripts, superoxide dismutase activity and superoxide anion production capacity

The effects of silencing the mRNA of cytosolic manganese superoxide dismutase (cMnSOD), an enzyme involved in the antioxidant defense, were analyzed in Whiteleg shrimp, Litopenaeus vannamei adults. Shrimp were intramuscularly injected with long dsRNAs corresponding to the N-terminal portion of the cMnSOD and held under normoxic conditions for 24 h. Another group of shrimp was exposed to hypoxia for 6 h followed by reoxygenation for 1 h. Shrimp injected with long dsRNAs had lower cMnSOD transcripts in gills and hepatopancreas. In the cMnSOD silenced shrimp, superoxide dismutase (SOD) activity decreased in gills but not in hepatopancreas. Shrimp subjected to hypoxia had lower cMnSOD transcripts and SOD activity in gills and hepatopancreas; the production of superoxide anion (O2−) by hemocytes was also lower in this group. Reoxygenation reverted the effect of hypoxia increasing the levels of cMnSOD transcripts, SOD activity and the production of O2−. These results suggest that cMnSOD contributes significantly to the SOD activity in gills and hepatopancreas and indicate its importance in the redox system regulation for L. vannamei.