Oxidative stress, reactive oxygen species, antioxidants: a review

Abstract

Oxidative stress is a disturbance of the balance between the production of reactive oxygen species (ROS) and antioxidants. Oxidative stress is caused by the presence of any of a number of reactive oxygen species, which the cell is unable to counterbalance. The result is damage to one or more biomolecules including DNA, RNA, proteins and lipids. Oxidative stress has been implicated in the natural aging process as well as a variety of disease states, such as neoplastic, metabolic, neurological etc., accompanied by different complications. Risk factors of generation of oxidative stress are oxidizing species, induced by pathologies include alcohol consumption, cigarette smoking, diet, gender, geographic location specifically at high altitude and occupation. ROS are composed of superoxide, hydroxyl, peroxyl, hydroperoxyl and alkoxyl radicals, hydrogen peroxide and singlet oxygen and ozone. These compounds produced endogenous in reaction of autooxidation in respiratory chaine of bioobjects. Among exogenous sources of ROS can be listed exposure of pollutants, toxins, heavy metals, drugs with different chemical origin and effects, radiation, electromagnetic fields, alcohol, cigarette smoke, stresses, allergies, dietary factors, temperature and microscopic form of life, such as bacteria, yeasts, viruses etc. The oxidative stress in biological systems is often characterized by increase in the formation of radicals; decrease in small-molecular-weight and lipid soluble antioxidants; disturbance in cellular redox balance; oxidative damage to cellular components (biomacromolecules). The presence of oxidative stress may be tested in one of three ways: direct measurement of the ROS; measurement of the resulting damage to biomolecules; and detection of antioxidant levels. Directly measuring ROS might seem the preferred method, but many reactive oxygen species are extremely unstable and difficult to measure directly. Many markers of damage are extremely stable and therefore provide a more reliable method to measure oxidative stress. Another approach is to measure the levels of antioxidant enzymes and other redox molecules which serve to counterbalance ROS generated in the cell. At the same time, it must emphasize that oxidative stress not only has a cytotoxic effect, but also plays an important role in the modulation of messengers that regulate essential cell membrane functions, which are vital for survival. For prevention of oxidative stress cells produce or uptake antioxidants – substance significantly delays or prevents oxidation of that substrate. Antioxidants may be enzymatic and non-enzymatic in nature in which enzymatic system directly or indirectly help in defence against the ROS. Antioxidants are involved in the prevention of oxidants and ROS formation; exhibits scavenger of ROS; and repairs the oxidized molecules through sources like dietary or consecutive antioxidants. Among non-enzymatic antioxidants distinguished glutathione, α-tocopherol, ascorbic acid, beta-carotene, and uric acid; these are mostly considered to be chain-breaking antioxidants in that they interrupt the auto-catalytic spread of radical reactions. Among enzymatic antioxidants most known superoxide dismutase, catalase, glutathione-SH peroxidase. The significant correlation found between ROS, parameters of oxidative stress and pathology indicate that there is a need in finding of measures of prevention of endo- and exogenous factors provoke their generation. There is a need to continue to explore the relationship between free radicals, pathological processes and the complications of them, and to elucidate the mechanisms by which increased oxidative stress accelerates the development of complications, in an effort to expand treatment options. Improvement of complications control seems to be a beneficial factor to decrease oxidative stress. For a better investigation of oxidative stress, it would be wise to supplement the clinical research by determination of special products typical for oxidative stress that let to understand mechanism of some pathological processes more clearly.