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Free Radicals and Antioxidants
Free radicals, also known as oxygen-derived free radicals, and
free-oxygen radicals, results in oxidative
injury to the blood vessels and myocardial
tissues. A free radical is a molecule with
an odd number of electrons. The unpaired
electron makes the free radical a chemically
reactive species, initiating a chain
reaction.
Free radicals are generated in a variety of tissues, including
neutrophiles, endothelial cells, and
platelets. The formation of free radicals in
neutropiles is a normal physiologic process
by which the cells defend the host against
invading microorganisms after phagocytosis.
These cells accumulate in large numbers in
the ischemic-reperfused myocardial tissues,
become activated, and release large numbers
of free radicals. They are very toxic and
travel great distances from their site of
production.
Antioxidants are naturally occurring or synthetic substances that
dismutate preformed free radicals, chelate
metal ions, or terminate the chain formation
of free radicals. Almost all living species
possess antioxidant mechanisms such as
synthesis of superoxide dismutase (SOD),
catalase and glutathione peroxidase. The
availability of these defenses in almost all
cell types maybe nature’s way of providing
the host with mechanisms to prevent damage
caused by free radicals.
The synthesis of naturally occurring antioxidants (SOD, glutathione
peroxidase) is suppressed during ischemia,
and as such, the generation of toxic free
radicals can proceed uninhibited.
Other examples of antioxidants are vitamins E and C, carotenoids,
salicylates, xanthine oxidase inhibitor
allopurinol, N-acetylcysteine, probucol, and
Ca++ channel blockers.
Nitric Oxide:
Marker of normal endothelial function
The normal endothelium synthesizes and releases nitric oxide (NO).
It has important vasodilator functions and
protects the artery from injury by
inhibiting activation and expression of
adhesion molecules, chemokines, monocyte
adhesion, platelet adhesion and aggregation,
and vascular smooth muscle cell
proliferation.
Hypercholesterolemia reduces the bioavailability of
endothelium-derived NO, thus setting the
stage for atherogenesis.
Recent clinical studies have documented endothelial dysfunction of
peripheral arteries and an impaired
flow-dependent, endothelium-mediated
dilation of conduit arteries in patients
with congestive heart failure (CHF). An
important functional consequence of
endothelial dysfunction is the inability of
a vessel to dilate in response to
endothelium derived NO after physiological
stimuli, such as increases of blood flow,
reflecting impaired flow-dependent dilation.
Clinical studies support the hypothesis that
endothelial dysfunction in CHF is due to
reduced synthesis of NO.
Over 16,000 remedies are described in
traditional Chinese medicine, most of which
are based on herbs. Ginseng is the most
famous Chinese herb of all. The Chinese
consider it a wonder drug, hence its
reputation as “Queen of medicinal herbs” or
“King of tonics.”
Prized for its remarkable therapeutic
benefits for about 7,000 years, it was so
revered that wars were fought for control of
the forests in which it thrived.
Its root was usually used with other plants,
such as liquorice or dates, which controlled
its powerful nature. It helped the old, the
weak, and people recuperating or under
stress.
An Arabian physician brought ginseng back to
Europe in the 9th century, yet its ability
to improve stamina and resistance to stress
became common knowledge in the West only
from the 18th century.
Ginseng has been researched in detail in
many countries and has been shown to
significantly improve the body’s capacity to
cope with hunger, extremes of temperature,
and mental and emotional stress. The
ginsenosides which are responsible for this
action are similar in structure to the
body’s own stress hormones. Other studies
claim that ginseng increases immune function
and resistance to infection and improves
liver function.
Over 16,000 remedies are described
in traditional Chinese medicine,
most of which are based on herbs.
Ginseng is the most famous Chinese
herb of all. The Chinese consider it
a wonder drug, hence its reputation
as “Queen of medicinal herbs” or
“King of tonics.”
Prized for its remarkable
therapeutic benefits for about 7,000
years, it was so revered that wars
were fought for control of the
forests in which it thrived.
Its root was usually used with other
plants, such as liquorice or dates,
which controlled its powerful
nature. It helped the old, the weak,
and people recuperating or under
stress.
An Arabian physician brought ginseng
back to Europe in the 9th century,
yet its ability to improve stamina
and resistance to stress became
common knowledge in the West only
from the 18th century.
Ginseng has been researched in
detail in many countries and has
been shown to significantly improve
the body’s capacity to cope with
hunger, extremes of temperature, and
mental and emotional stress. The
ginsenosides which are responsible
for this action are similar in
structure to the body’s own stress
hormones. Other studies claim that
ginseng increases immune function
and resistance to infection and
improves liver function. |
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