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Philadelphia Biomedical Research Institute, King of Prussia, PA 19406 and * Department of Biochemistry and Biophysics, University of Pennsylvania School of Medicine, Philadelphia, PA 19104
2To whom correspondence should be addressed. E-mail: stohnishi{at}aol.com
ABSTRACT
In the circulation of sickle cell anemia patients, a certain population
of erythrocytes has an elevated density. These abnormally dense cells
are believed to be at the root of the painful crisis and anemia of the
patients. We have developed an in vitro method for the preparation of
these heavier erythrocytes by a repeated deoxy-oxy cycling of
erythrocytes from sickle cell anemia patients. By using this method, we
studied whether certain nutritional supplements would inhibit the
formation of dense cells in vitro. It was found that aged garlic
extract (AGE) as well as its components with antioxidant activity,
i.e., S-allylcysteine and
N
-(1-deoxy-D-fructos-1-yl)-L-arginine
(fructosyl arginine), inhibited the formation of dense cells in vitro.
Vitamin C, vitamin E and the spin-trapping agents,
5-diethoxyphophoryl-5-methyl-1-pyrroline-N-oxide and
-(4-pyridyl-1-oxide)-N-t-butylnitrone
were all found to inhibit the formation of dense cells in vitro. These
results suggest that, when extremely stretched sickle-shaped cells
are formed by the repeated deoxy-oxy cycling, the erythrocyte
membrane becomes susceptible to oxidative injury by reactive oxygen
species. The protection of the erythrocyte membrane from such an
oxidative injury would prevent the membranes from becoming leaky to the
calcium ion, thus inhibiting the activation of the
calcium-activated potassium efflux channel and the formation of
dense cells. We also developed a new ex vivo method of studying the
possible efficacy of antioxidants taken orally on the dense cell
formation in sickle cell patients. It involved the use of blood plasma
taken from a healthy donor (with normal hemoglobin) of AB blood type
who had consumed different types of antioxidants orally. By suspending
sickle erythrocytes in such plasma and exposing them to the
deoxy-oxy cycling, the degree of dense cell formation was
determined. The degree of inhibition in vitro by antioxidants taken
orally may be related to their efficacy in inhibiting dense cell
formation in the patients. On the basis of these in vivo and ex vivo
studies, we propose that a cocktail of antioxidants would have
beneficial effects in lessening the incidence and severity of crisis
and reducing anemia in sickle cell disease.
KEY WORDS: sickle cell anemia deoxy-oxy cycling method oxidative injury free radicals antioxidants aged garlic extract S-allylcysteine fructosyl arginine
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