| [ Summary ] |
Reactive oxygen species (ROS), whether produced endegeneously as a consequence of normal cell function or derived from external sources, pose a constant threat to cells, because ROS induce severe damage to DNA, proteins and lipids. In this regard, cells contain a variety of antioxidant defense mechanisms to minimize damage caused by ROS. However, ROS production often exceeds antioxidant capacity, resulting in a condition termed as oxidative stress. Oxidative stress elicits a wide spectrum of cellular responses ; typically, low levels of oxidative stress are mitogenic and promote cell growth, whereas intermediate levels result in growth arrest. Furthermore, severe oxidative stress induces cell death via apoptosis or necrosis. A large number of signaling pathways, which regulate cellular responses to oxidative stress, have been revealed. Regulating the signaling pathway may serve as new therapeutic interventions, aimed at treatment of diseases or conditions such as normal aging. |