Objective: Neutrophilic leukocyte rolling on postcapillary endothelium requires membrane interaction between SLex-containing ligands on neutrophils and P-selectin on endothelial cells. The current sequence of studies was performed to explore the hypothesis that the leukocyte-endothelial rolling interaction not only precedes leukocyte migration but also is accompanied by oxygen free radical production and interstitial cell death in the rat mesentery.
Methods: The ratio of leukocyte rolling velocity on the endothelium of postcapillary venules and centerline red cell velocity was determined after topical application of platelet activating factor (PAF; 10(-8) mol/L). Superoxide formation was determined by an in situ nitroblue tetrazolium reduction to dark blue formazan crystals in the in situ mesentery preparation, and cell death was detected by nuclear staining with propidium iodide.
Results: Leukocyte rolling and subsequent adhesion was inhibited with a monoclonal antibody against P-selectin, PB1.3. Superoxide formation, as well as parenchymal cell death, was significantly enhanced in the mesentery after stimulation with platelet activating factor, and both could be significantly attenuated by reduction of the rolling leukocyte-endothelial interaction with PB1.3.
Conclusions: These results provide direct evidence that the interaction of leukocytes and endothelium followed by migration of leukocytes into the interstitium is accompanied by enhanced oxidative stress and parenchymal cell death. Early interruption of the interaction provides significant protection even in the presence of a proinflammatory stimulus.