Effect of heat stress and recovery on viability, oxidative damage, and heat shock protein expression in hepatic cells of grass carp (Ctenopharyngodon idellus)

In this study, we investigated the effects of hyperthermia and recovery on cell viability, lactate dehydrogenase (LDH) activity, superoxide dismutase (SOD) activity, malondialdehyde (MDA), total antioxidant capacity (T-AOC), and heat shock protein (HSP60, 70, and 90) mRNA expression in the hepatic cells of the grass carp, Ctenopharyngodon idellus. Triplicate groups of cultured cells were exposed to 30, 32, or 34 °C for 0.5 h and then immediately incubated at 27 °C in 5 % CO₂ for 6, 12, 24, or 48 h. Hyperthermia stress greatly reduced cell viability and increased LDH release. Cell damage declined after recovery. Hyperthermia stress increased the lipid peroxide levels and reduced the antioxidant capacity (e.g., reduced SOD and T-AOC) of the cells. However, oxidative damage declined as the recovery period increased, and the levels of MDA, SOD, and T-AOC were restored. After cells were exposed to 32 °C, the expression of HSP60 after recovery for 1, 2, and 4 h (P < 0.05), the expression of HSP70 after recovery for 0.5 and 1 h (P < 0.01), and the expression of HSP90 throughout recovery were significantly higher (P < 0.01) than the prestress levels. During the recovery period, the variations in HSP gene expression reflected the transition period from a state of cellular growth to one of the cellular repairs. In conclusion, hyperthermia depresses cell viability, induces oxidative damage, and increases HSP expression, which plays an important role during hyperthermic stress in grass carp hepatic cells.