Endogenous nitric oxide inhibits neutrophil adherence to lung epithelial cells to modulate interleukin-8 release

To investigate the effect of neutrophil adherence to epithelial cells on th e release of interleukin 8 (IL-8), we measured neutrophil adherence in the presence or absence of IFN-gamma +TNF-alpha +IL-1 beta (cytomix) stimulatio n on cultured A549 epithelial cells. The extent of neutrophil adherence to A549 epithelial cells was measured and the concomitant production of IL-8 a nd nitrite were assayed. The roles of adhesion molecules and nitrite in mod ulation of neutrophil adherence were examined by pretreatment with oversatu rating ICAM-1 blocking antibody and L-NAME (1mM), respectively. There was a time-dependent spontaneous and cytomix-induced release of IL-8 from epithe lial cells, as well as a time-dependent increase in the magnitude of neutro phil adherence to epithelial cells. Stimulation of epithelial cells with cy tomix induced a further increase in neutrophil adherence. Pretreatment with oversaturated ICAM-1 monoclonal antibody inhibited neutrophil adherence wi th or without cytomix stimulation. The inhibition of neutrophil adherence t o epithelial cells with ICAM-1 monoclonal antibody or a semipermeable membr ane downregulated the release of IL-8 with or without cytomix stimulation. Stimulation with cytomix decreased nitrite production. Both neutrophil adhe rence and L-NAME pretreatment significantly inhibited the production of nit rite. The inhibition of neutrophil adherence to epithelial cells with ICAM- 1 monoclonal antibody or a semipermeable membrane upregulated nitrite produ ction. Pretreatment with L-NAME failed to modify the spontaneous release of IL-8, but significantly enhanced the response to adherence and cytomix. In conclusion, endogenous nitric oxide may play a role in preventing neutroph il adherence to lung epithelial cells, thus modulating concomitant IL-8 rel ease. (C) 2001 Elsevier Science Inc. All rights reserved.