Reactive oxygen species in health and disease.

With the advent of the use of oxygen as the terminal electron acceptor in aerobic respiration, came the curse in the form of reactive oxygen species (ROS). However, the evolving organism had developed elaborate defence machinery to escape from these reactive byproducts of its own metabolism, and also developed a mechanism for the utilization of these species in physiological processes to gain a survival advantage. ROS have been increasingly implicated in the ageing process and in different diseases such as cancer, Alzheimer's disease, Parkinson's disease, reperfusion injury, etc. They are also important in cellular phenomenon such as signal transduction pathways. We review the mechanisms of production of ROS in the cell, their interaction with cellular macromolecules, pathways of ROS-induced cell death, the mechanisms for protection from ROS-induced damage as well as the key biological and disease processes where ROS play an important role.