Oxidative Stress (OS)
is a general term used to describe the steady state level of oxidative
damage in a cell, tissue, or organ, caused by the reactive oxygen species
(ROS).
This damage can affect a specific molecule or the entire organism. Reactive
oxygen species, such as free radicals and peroxides, represent a class
of molecules that are derived from the metabolism of oxygen and exist inherently
in all aerobic organisms. There are many different sources by which the
reactive oxygen species are generated. Most reactive oxygen species come
from the endogenous sources as by-products of normal and essential metabolic
reactions, such as energy generation from mitochondria or the detoxification
reactions involving the liver cytochrome P-450 enzyme system. Exogenous
sources include exposure to cigarette smoke, environmental pollutants such
as emission from automobiles and industries, consumption of alcohol in
excess, asbestos, exposure to ionizing radiation, and bacterial,
fungal or viral infections. |