The oxidative stress (oxidative stress) is a type of aggression constituents of cells due to reactive oxygen species (ROS, Reactive Oxygen Species in English) and the reactive oxygen species and nitrogen (RONS, N for Nitrogen in English) oxidant . These species are, by definition, free radicals. By analogy, hydrogen peroxide (H2O2) is considered as a ROS because, in the presence of iron (in the form ionic), he dismute two hydroxyl radical (OH.) (reaction Haber-Weiss).
The production of ROS and RONS is normal for all organisms living in aerobic and does not constitute either a situation of oxidative stress because the cell has a complex system of detoxification against the ROS including enzymes (superoxide dismutase, catalase, glutathione peroxidase…) and small molecules (vitamin E, vitamin C…). In physiological situation, superoxide anion (O2. -) is produced mainly by NADPH oxidases (NOX) and we know 5 isoenzymes and nitric oxide (NO.) by the family of NO synthases (3 isoforms).
The oxidative stress becomes a pathological situation when the protection system is overwhelmed by ROS and the RONS.
This may be due for example to:
-- The introduction into the cell of free radicals or reactive oxygen species (photochemical pollutants entering the body via the respiratory system, food or mucous membrane)
-- A surplus and ROS RONS induced by type process ischemia-reperfusion who are responsible for a portion of releases of transplants or the presence of certain chemical compounds prooxydants such as methyl viologène.
-- A lack of protection system, for example, a mutation inactivating an enzyme protection system or a deficiency of vitamins.
-- The introduction into the cell or in a body of highly reactive molecules, for example nanoparticles (very small and very specific surface developed). If these nanoparticles are numerous, macrophages can no longer treat and can release their oxidants in the body, causing an inflammatory reaction exacerbated.
The oxidative stress is a factor of ignition and mutagenesis, but it is also regarded as a leading cause of cancer and play a role in Alzheimer's disease, as in several more common diseases such as cardiovascular diseases, the stroke, rheumatoid arthritis or cataracts. Antioxidants well dosed decrease this damage and thus contribute to health and longevity.
In addition, macrophages produce, using the enzyme chloroperoxydase, ClO-hypochlorite ions that causes the death of pathogenic bacteria causing a situation of oxidative stress in them.
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