REGULATION OF INTRACELLULAR POLYMORPHONUCLEAR LEUKOCYTE FC-RECEPTORS BY LIPOPOLYSACCHARIDE

Endotoxemia, in man, has been associated with an autooxidative reduction in the bioavailability of polymorphonuclear leukocyte receptors. The location and mechanisms of this phenomena have remained unclear; we investigated the effects of lipopolysaccharide (LPS) on intracellular Fc gamma receptor expression. Polymorphonuclear leukocytes (PMN) were incubated with LPS (10 ng/ml), permeabilized with saponin, followed by measurement of CD64, CD32w, and CD16 (Fc gamma RI, II, III) using I-125-monoclonal antibodies directed against these receptors. Exposure of permeabilized PMN to LPS significantly reduced intracellular Fc gamma receptor expression. PMN isolated from patients with chronic granulomatous disease or myeloperoxidase-specific deficiency did not exhibit this effect. Furthermore, specific inhibitors of components of the PMN oxidative burst (N2N3, 10 mM;L-alanine 30 mM) prevented the LPS-induced oxidative reduction in receptor expression. NADPH oxidase inhibition with diphenyleneiodonium also blocked the effect of LPS on intracellular Fc gamma receptor expression. The effects of LPS on intracellular PMN Fc gamma receptors were reproduced with monophosphoryl lipid A but required a 10 times greater concentration than LPS. Preadherence of PMN on fibronectin or arginine-glycine-aspartate-serine (RGDS), but not laminin, prevented the LPS-induced reduction in oxidative receptor expression. The effects of fibronectin/RGDS were blocked by actinomycin D and cycloheximide. Cross-linkage of intracellular Fc gamma receptors prior to exposure to LPS also prevented the LPS-induced oxidative reduction in receptor expression. These results demonstrate that an important pathophysiologic property of LPS is to induce an intracellular oxidative-derived reduction in Fcr receptor expression and that the biologically relevant proteins fibronectin and RGDS ameliorate this effect. (C) 1994 Academic Press, Inc.