Besides
erythema and
sunburn reactions, UVB stress can promote erythrocyte extravasation from skin capillaries and
hemolysis, and photosensitized
hemoglobin can in turn lead to an overload of
free radicals in dermis which exacerbates photodamage. The objective of this study was to investigate in rat erythrocytes (RBC) the pattern of events leading to membrane peroxidation and
hemolysis following UVB insult (1.5-8.5 J/cm2), and the protective action of grape seed
procyanidins. UVB causes a dramatic dose-dependent decrease of intracellular
glutathione (paralleled by the formation of
pro-oxidant ferryl-
hemoglobin), of intramembrane
vitamin E and of membrane fluidity, then a rise of conjugated dienes (CD), and
thiobarbituric acid-reactive substances (
TBARS) and finally a strong hemolytic effect.
Procyanidins prevent membrane peroxidation (but not intracellular GSH depletion nor ferryl-
hemoglobin formation), with a minimal effective concentration of 0.1 microM (IC50 for
TBARS and CD after 120 min UVB exposure: 0.71 microM and 0.56 microM) and dose-dependently delay the onset of
hemolysis, by 30 min at 0.1 mciroM, by 90 and 120 min at 0.5 and 1.0 microM.
Epigallocatechin-3-O-gallate (EGCG) and
catechin, typical constituents of the fraction, were significantly less potent. This since
procyanidins (1 microM) inhibit the formation of
phospholipid hydroperoxides of the inner (
phosphatidylserine,
phosphatidylethanolamine) and outer (
phosphatidylcholine) layers of the RBC membrane (HPLC analysis), suppress the decrease in membrane fluidity due to
lipid and
protein thiol oxidation and spare
vitamin E from consumption in a dose-dependent manner (0.1-1 microM). Hence
procyanidins, preserving membrane
phospholipids, since their strong antilipoperoxidant activity, may maintain in vivo the integrity of RBC in sub-epidermal capillaries and effectively counteract in dermis the onset/exacerbation of the UVB-induced skin photodamage.