Gallic Acid Antagonizes P-Selectin–Mediated Platelet–Leukocyte Interactions

Abstract

Background— Current paradigm attributes the low incidence of cardiovascular disorders in Mediterranean countries despite a high saturated fat intake, the “French paradox,” to the antioxidant capacity of red wine polyphenols. Conceivably, other antiinflammatory pathways may contribute to at least a similar extent to the atheroprotective activity of these polyphenols. We have investigated whether gallic acid (GA), an abundant red wine polyphenol, modulates the activity of P-selectin, an adhesion molecule that is critically involved in the recruitment of inflammatory cells to the vessel wall and thus in atherosclerosis. Methods and Results— GA potently inhibited the binding of a peptide antagonist (IC 50 , 7.2 μmol/L) and biotin-PAA-Le a -SO 3 H, an established high-affinity ligand, to P-selectin (IC 50 , 85 μmol/L). Under dynamic flow conditions, GA markedly and dose dependently attenuated the rolling of monocytic HL60 cells over P-selectin-transfected Chinese hamster ovary cells (EC 50 , 14.5 μmol/L) while increasing the velocity of P-selectin-dependent rolling of human blood leukocytes over a platelet monolayer. In vivo tests established that GA administration to normolipidemic C57/Bl6 and aged atherosclerotic apolipoprotein E–deficient mice impaired the baseline rolling of conjugates between activated platelets and circulating monocytes over femoral vein endothelium, as judged by online video microscopy (ED 50 , 1.7±0.3 and 1.5±0.4 mg · kg −1 · h −1 , respectively). Conclusions— Our findings provide a solid mechanistic foundation through which GA intervenes in major inflammatory pathobiologies by binding and antagonizing P-selectin.