Abstract

Reactive oxigen species (ROS) are produced as the consequence of the normal aerobic physiological metabolism. The electron transport chain in mitochondrial, peroxisomes, NADPH oxidases, uncoupled nitric oxide synthase (NOS) and cytochrome P450 system are the most important sources of ROS production.

The imbalance of the ROS production and antioxidants defense system in the living systems causes oxidative stress brings to cellular function disruption and damage. This imbalance occurs due to over production of ROS and reduction of the antioxidant defense mechanism. Protective actions against ROS are performed by several enzymes (superoxide dismutase, catalase and glutation peroxidase) as well as nonenzimatic compounds (vitamin E, ascorbate, glutathione, transferrin, ceruloplasmin, etc). ROS are crucial modulators of cellular functions. At low concentrations, ROS are essential participants in cell signaling, induction of mitogenic response, involvement in defense against infectious agents, whereas excess ROS can disrupt normal cellular function and promote irreversible damage to cellular lipids, nucleic acids, and proteins. ROS, especially H2O2, serve as a signal molecule through oxidative modification of signaling proteins. Thus, a balance between ROS production and their removal allows for normal celular function, whereas an imbalance causes oxidative stress with pathological consequences.

Key words: Oxidative stress; antioxidants; reactive oxygen species; redox control; free radicals