Reactive oxygen species (ROS) and aging: Do we need them — can we measure them — should we block them?

Reactive oxygen species (ROS) are derivatives of oxygen which arise during life in an oxygenated environment. Whereas there is a long discussion within the scientific community about the causes of aging, there is an impressive amount of data indicating that ROS are indeed a major cause for aging. An increase in radical production or a decrease in the defense against ROS appears to be associated with the decrease of the life span of an organism. On the other hand, in the last 15 years, it was shown that radicals are needed for cellular function. Therefore this review concentrates on the arguments for the link between ROS and aging, the hazardous nature of individual radicals, the possibility to analyze ROS and a short view on the impact of ROS on cellular functions.