Ageing free radicals and cellular stress
Abstract
A number of theories have attempted to account for ageing processes in various species. Following the < rate of living > theory of Pearl, Harman suggested fifty years ago that the accumulation of oxidants could explain the alteration of physical and cognitive functions with ageing. Oxygen metabolism leads to reactive species, including free radicals, which tend to oxidize surrounding molecules such as DNA, proteins and lipids. As a consequence various functions of cells and tissues can be altered, leading to DNA instability, protein denaturation and accumulation of lipid byproducts. Oxidative stress is an adaptive process which is triggered upon oxidant accumulation and which comprises the induction of protective and survival functions. Experimental evidence suggests that the ageing organism is in a state of oxidative stress, which supports the free radical theory. A number of other theories have been proposed ; some of these are actually compatible with the free radical theory. Caloric restriction is among the best models to increase life span in many species. While the relationship between caloric restriction and corrected metabolic rate is controversial, the decrease in ROS production by mitochondria appears to be experiment...Continue Reading
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