ATTENUATION OF OXYGEN-FREE RADICAL FORMATION AND TISSUE-INJURY DURINGEXPERIMENTAL INFLAMMATION BY P-SELECTIN BLOCKADE

Objective: Neutrophilic leukocyte rolling on postcapillary endothelium requires membrane interaction between SLe(x)-containing ligands on ne utrophils and P-selectin on endothelial cells. The current sequence of studies was performed to explore the hypothesis that the leukocyte-en dothelial rolling interaction not only precedes leukocyte migration bu t also is accompanied by oxygen free radical production and interstiti al cell death in the rat mesentery. Methods: The ratio of leukocyte ro lling velocity on the endothelium of postcapillary venules and centerl ine red cell velocity was determined after topical application of plat elet activating factor (PAF; 10(-8) mol/L). Superoxide formation was d etermined by an in situ nitroblue tetrazolium reduction to dark blue f ormazan crystals in the in situ mesentery preparation, and cell death was detected by nuclear staining with propidium iodide. Results: Leuko cyte rolling and subsequent adhesion was inhibited with a monoclonal a ntibody against P-selectin, PB1.3. Superoxide formation, as well as pa renchymal cell death, was significantly enhanced in the mesentery afte r stimulation with platelet activating factor, and both could be signi ficantly attenuated by reduction of die rolling leukocyte-endothelial interaction with PB1.3. Conclusions: These results provide direct evid ence that the interaction of leukocytes and endothelium followed by mi gration of leukocytes into the interstitium is accompanied by entrance d oxidative stress and parenchymal cell death. Early interruption of t he interaction provides significant protection even in the presence of a proinflammatory stimulus.