Lipid Mediators Up-regulate CD11b and Prime for Concordant Superoxide and Elastase Release in Human Neutrophils

Abstract

The pathogenesis of multiple organ failure after injury is believed to involve priming and activation of the inflammatory cascade, and the polymorphonuclear neutrophil (PMN) appears to be an integral effector. Characterization of the primed PMN is evolving. Because much research has focused on the respiratory burst, the synergistic role of cytotoxic proteases, especially elastase, has been largely ignored. In addition, CD11b has been identified as pivotal in PMN-mediated tissue injury. Our hypothesis is that the well-recognized postinjury mediators platelet-activating factor (PAF) and leukotriene B4 (LTB4) prime PMNs for the concordant release of elastase and superoxide (O2 sup -) as well as for CD11b up-regulation. Human PMNs were isolated and then incubated with PAF or LTB4 before N-formyl-methionyl-leucyl-phenylalanine activation. O2 sup - generation was measured by reduction of cytochrome c. Elastase was measured by cleavage of Ala-Ala-Pro-Val p-nitroanilide. CD11b expression was quantified by incubation with R-phycoerythrin-labeled monoclonal antibodies followed by flow cytometry. PAF and LTB4 primed PMNs maximally within 5 minutes for the production of O2 sup -, elastase release, and simultaneous up-regulation of CD11b expression on the PMN surface. PAF and LTB4 prime human PMNs for the concordant release of elastase, generation of O2 sup -, and CD11b up-regulation. Understanding the physiologic characteristics of PMN priming may offer new therapeutic targets to avoid the development of multiple organ failure after injury.