NITRIC-OXIDE INHIBITS NEUTROPHIL BETA-2 INTEGRIN FUNCTION BY INHIBITING MEMBRANE-ASSOCIATED CYCLIC-GMP SYNTHESIS

The aim of this investigation was to identify the mechanism by which n itric oxide inhibits neutrophil beta(2) integrin dependent adherence. Isolated rat neutrophils from blood and peritoneal exudates were expos ed for 2 min to nitric oxide generated by diethylamine-NO at rates bet ween 1.6 and 138 nmol/min. Exposure to nitric oxide at rates less than 14 nmol/min had no effect on adherence. Exposure to 14 to 56 nmol nit ric oxide/min inhibited beta(2) integrin dependent adherence to endoth elial cells, nylon columns, and fibrinogen-coated plates, but higher c oncentrations had no significant effect on adherence. Adherence by bet a(2) integrins could be restored by incubating cells with dithioerythr itol, phorbol 12-myristate 13-acetate, or 8-bromo cyclic CMP. Elevatio ns in cellular cyclic GMP concentration were associated with adherence , but this did not occur after cells were exposed to concentrations of nitric oxide that inhibited beta(2) integrin-dependent adherence. Ele vations in cyclic GMP did occur after cells were incubated with dithio erythritol or phorbol 12-myristate 13-acetate. Concentrations of nitri c oxide that inhibited beta(2) integrin-dependent adherence also inhib ited catalytic activity of membrane associated guanylate cyclase and b inding of atrial natriuretic peptide, but were insufficient to activat e cytosolic guanylate cyclase. Nitric oxide did not inhibit neutrophil oxidative burst or degranulation, nor effect beta(2) integrin express ion or adherence that did not depend on beta(2) integrins, nor cause o xidative stress identified in terms of cellular glutathione concentrat ion or protein nitrotyrosine. The results indicate that nitric oxide i nhibited beta(2) integrins in a concentration-dependent fashion by inh ibiting cell-surface transduction of signals linked to the activity of membrane-bound guanylate cyclase. The inhibitory effect could be over come by providing cells with cyclic GMP exogenously or by stimulating cytosolic guanylate cyclase. (C) 1997 Wiley-Liss, Inc.