INHIBITION BY NITRIC-OXIDE DONORS OF HUMAN POLYMORPHONUCLEAR LEUKOCYTE FUNCTIONS

1 The study was designed to test the hypothesis that nitric oxide (NO)-releasing compounds increase guanosine 3':5'-cyclic monophosphate (cyclic GMP) production in human polymorphonucicar leucocytes (PMNs) and concomitantly inhibit PMN functions, i.e. leukotriene B4 (LTB4) SyntheSiS, degranulation, chemotaxis and superoxide anion (O2-) release. The effects of two new NO-releasing compounds, GEA 3162 and GEA 5024 were compared to 3-morpholino-sydnonimine (SIN-1) and S-nitroso-N-acetyl-penicillamine (SNAP). 2 GEA 3162 and GEA 5024 (1-100 mum) inhibited Ca ionophore A23187-induced LTB4 and beta-glucuronidase release, chemotactic peptide FMLP-induced chemotaxis and opsonized zymosan-triggered chemiluminescence dose-dependently in human PMNs. SIN-1 and SNAP were weaker inhibitors. 3 Cellular cyclic GMP production was increased after exposure to NO-donors concomitantly with the inhibition of PMN functions. No alterations in the levels of adenosine 3':5'-cyclic monophosphate (cyclic AMP) were detected. 4 The results suggest that NO, possibly through increased cyclic GMP, inhibits the activation of human PMNs and may thus act as a local modulator in inflammatory processes.