Free radical view on aging starting under physiological conditions
I.B. Afanas'ev
Vitamin Research Institute, Nauchny pr.14A, Moscow 117820, Russia
Free radical theory of aging pointed out at major rogues responsible
for human aging - reactive oxygen and nitrogen species. This conclusion
was supported by many studies, but one of the most important question
is still remaining unanswered: How aging processes start in healthy
humans who do not suffer from any pathological disorders and all the
stimuli of pathological disorders are excluded? Of course it is a
purely hypothetical question, but if we can select "the physiological
component" of aging initiation, it could be of importance for the
understanding of a mechanism of aging. Contrary to former suggestions,
we are now aware that reactive free radicals are formed in living
organisms not only due to interfering of external factors or as a
consequence of pathological disorders but as the potent participants of
enzymatic reactions and signaling processes. However it is wrong to
consider free radicals as the fully tame species; being diffusion-free
molecules they are able to escape the most strictly regulated enzymatic
processes and start free radical-mediated damage, an origin of aging.
In the present work we consider the potential mechanism of aging
processes initiated by superoxide formed as a side product of the
enzymatic reactions catalyzed by lipoxygenase and cyclooxygenase under
physiological conditions. We suggest that superoxide escaped from these
enzymatic cycles initiates nonenzymatic lipid peroxidation leading to
the formation of prostanoids (isoprostanes), which toxic action is
already well documented. Another dangerous way of starting aging
processes is the already known superoxide-stimulated mitochondrial
aging. This free radical point of view suggests at importance of
applying the nontoxic antioxidant supplements capable of reacting with
superoxide without producing other much more reactive free radicals.
Correspondingly we consider the potential efficacy of major
antioxidants (vitamins E and C, flavonoids, SOD mimics, etc.) for
fighting against "physiological aging."
Key words:
Aging, Free Radicals, Physiological State
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