Reduced oxidative stress increases acute cold stress tolerance in zebrafish.

Cold stress is a major threat to fish in both nature and aquaculture, and can induce oxidative stress in various fish. While the exact role of oxidative stress in cold-caused mortality is still unknown. The purpose of the present study was to evaluate the effects of oxidative stress on cold tolerance in fish and verify whether changing oxidative status could affect cold tolerance. We firstly demonstrated that acute cold exposure induced high oxidative stress in zebrafish liver, which may lead to mortality. Then we performed in vivo and in vitro experiments to determine the effects of the altered oxidative status on cold tolerance in zebrafish and zebrafish liver cell line (ZFL), respectively. In the in vivo study, the zebrafish which were fed with α-lipoic acid or reduced glutathione had lower cold-caused oxidative stress and tissues damage, and showed higher cold tolerance. In the experiment using zebrafish cells, increasing oxidative stress by H2O2 decreased the cellular cold tolerance, and the cold tolerance was partly recovered when oxidative stress was reduced by the addition of Vitamin C (VC). Taken together, we conclude that the reduction of oxidative stress increases cold tolerance in fish.