Hypothermia enhances bcl-2 expression and protects against oxidative stress-induced cell death in chinese hamster ovary cells

Oxidative stress is one of the major causes of cellular injury. Various reactive oxygen (ROS) and nitrogen (RNS) species such as superoxide, hydroxyl radical, peroxynitrite, and nitric oxide are involved in the manifestations of different types of organ toxicity and the resultant syndromes, symptoms, or diseases. Hypothermic conditions have been reported to reduce the oxidative stress in various in vitro and in vivo studies. In the present study, we sought to determine the effect of lowered temperatures on oxidative stress-induced cell death in Chinese hamster ovary (CHO) cells. We also investigated the oxidative stress-induced alterations in the expression of anti-apoptotic protein, bcl-2, in CHO cells at lowered temperatures. CHO cells were incubated at four different temperatures of 30, 32, 35, and 37°C (control temperature) from 1 to 4 d. In another set, the cells were incubated with 100 μM hydrogen peroxide (H2O2) for 30 min before harvesting at different time points. The cells were harvested at 1, 2, 3, and 4 d. Cell survival was significantly higher at 30°C as compared to 37°C over 4 d of incubation. In cells incubated with H2O2, significantly higher cell viability was observed at lower temperatures as compared to the cells incubated at 37°C. The activity of glutathione peroxidase (GSH-Px) also increased significantly at lower temperatures. Lowered temperature also provided a significant increase in the expression of anti-apoptotic protein, bcl-2 after 4 d of incubation. These data suggest that hypothermic conditions lowers the risk of oxidative stress-induced cellular damage and programmed cell death by increasing the activity of GSH-Px and by the induction in the expression of the anti-apoptotic protein, bcl-2.