Abstract
Reactive oxygen species (ROS) play critical roles in a wide variety of cellular functions. On the other hand, excess amounts of ROS generated within cells result in oxidative stress and are responsible for many deleterious changes, which can induce oxidative damage to DNA, proteins and lipids. Several factors can influence the susceptibility to oxidative stress by affecting the antioxidant status and ROS generation. These factors include endogenous factors (e.g., exercise and psychological stress), and exogenous factors (e.g., ionizing radiation, cigarette smoke, environmental pollutants, and UV light). ROS have been shown to participate in various biological consequences of ionizing radiation. However, the biochemical mechanisms by which ROS cause molecular damage and ultimately cellular dysfunction are not fully understood. One of the major cellular targets of ROS is proteins. ROS can oxidize both aliphatic and aromatic amino acid residues of proteins, leading to irreversible structural changes. The redox environment is controlled by a variety of redox-regulating systems that include superoxide dismutase (SOD), glutathione peroxidase (GPX), thioredoxin (Trx), thioredoxin reductase (TR), glutaredoxin (Grx) and peroxiredoxin (Prx). In this study, we examined whether and how cellular sensitivities to radiation and oxidative stress are modulated by the overexpression of SOD and Grx in cultured human cells. Specifically, we examined the change in survival, phosphorylation of H2AX, level of expression of OXR1 protein and oxidized protein after irradiation by overexpression of SOD. One of our results indicated that oxidized protein was decreased by the overexpression of SOD, which suggested that SOD and Grx play important roles in various cellular responses to radiation.
