[Role of oxidative stress in aging]

In this article is presented a synthesis of the complex relationships between oxidative stress ageing. Free radicals are produced in a continous way but they are also quickly removed by very efficient defence systems. The studies trying to increase the antioxidants uptake in the diet or to produce transgenic animals overexpressing antioxidant enzymes did not lead to increased life span in mammals. Only transgenic drosophils for SOD and catalase lived longer than the parents wild type. At the cellular level, oxidative stresses speed up the passage of fibroblasts from young to old morphotypes. This shift increases with stress intensity but is also influenced by the quantity of energy available to the cell. Thermodynamics of open systems very well account for the experimental observations of cell response to stresses, oxidative stress being only one of the challenges faced by living cells. Oxidative stresses must be considered in relationship with the level of defence and turnover systems as affecting continuously various cellular functions with sometimes excessive production in pathological situations. In this case, a global response of the cell is observed which is the result of complex mechanisms linked to cell activation and changes in gene transcription.