Evidence indicates that environmental pollutants
(including pesticides, transition metals, toxic chemical wastes, cigarette smoke, radiation gasoline and its additives) help in the deterioration
of biological macromolecules. This may result in gastrointestinal tract injury, brain and central nervous
system damage, liver and kidney damage. Differences in the toxic manifestations of these pollutants may be related to differences in solubility, absorbability, transport,
chemical reactivity and the complexes that are formed within the body.
Recent studies have demonstrated that these
environmental pollutants produce oxygen free-radicals, resulting in deterioration of lipids, proteins and DNA,
activation of procarcinogens, inhibition of cellular
and antioxidant defense systems, depletion of sulflydryls, altered calcium homeostasis, and induction of abnormal
proteins and altered gene expression.
Free radicals have been implicated in over 100 diseases, including arthritis, hemorrhagic shock, atherosclerosis, aging, ischemia and reperfusion injury
of many tissues, central nervous system injury, gastritis, tumor promotion and carcinogenesis and AIDS. This
wide range of diseases implies that increased free radical formation accompanies tissue and cellular injury in most,
if not all, human diseases.
In most cases, free radicals are believed to significantly contribute to the disease
pathophysiology. Oxygen-derived free radicals (and their metabolites) contribute to tissue injury leading to multistage
carcinogenesis, which ultimately leads to cancer. Free radical production increases with stress and exposure
to carcinogens. Antioxidants inhibit tumor promotion carcinogenesis at both initiation and transformation stages, and protect cells against oxidative damage. Natural antibiotic-producing microflora such as
Lactobacillus acidophilus and Bifidobacterium bifdwn can provide protection in the gastrointestinal tract.
FREE RADICALS
Free radicals have an unpaired electron. Because of the natural tendency of electrons to form stable pans, the
presence of unpaired electrons in free radicals makes
them short-lived and extremely reactive. Free radicals and other reactive oxygen species
are continuously produced in the human body through a variety of physiologic and pathologic processes.
Examples of free radicals and reactive oxygen species
include: superoxide anion radical, hydroxyl radical,
thiyl radical, trichloromethyl radical, hypochlorite radical
plus hypochlorous acid, and also some potentially dangerous nonradicals such as hydrogen peroxide, singlet oxygen, hypochlorous acid, and the urban air pollutant ozone. Hydroxyl radical is a highly reactive species that can
drastically attack all biological molecules including lipoproteins and DNA, usually setting off free-radical
chain reactions.
FREE RADICALS AS MEDIATORS OF DISEASES
