[Influence of reactive nitrogen and oxygen species on human organism].

Reactive nitrogen species (RNS) and oxygen (ROS) species play a very positive and important role in the process of cells communication. The maintenance of certain level of radicals in cells is necessary for the information flow between cells and inside cells. The liquidation of free radicals presence or an increase in their level may to some extent disturb the cellular communication. Even slight fluctuations in the basic level of ROS significantly affect the change in the cell's metabolism, expression of genes and posttranslational modification of proteins. When the level of free oxygen radicals exceeds the antioxidative possibilities of the cell, an oxidative stress occurs, which causes many diseases and accelerated aging of the organism. Aging is natural, complex process, but apart from the programmed aging the reactive oxygen molecules, which are external agressors, accelerate this process.