PMNs produce direct lung injury from release of oxygen radicals, lipid peroxides, and proteases, but also serve a paracrine role by releasing proinflammatory cytokines. NFκB is an important gene transcription factor regulating cytokine expression in many cell types. PMN NFκB activity has not been evaluated. Exogenous nitric oxide (NO) inhibits PMN function (Daher et al., AJRCMB, in press, 1997). We hypothesized that PMNs express NFκB, and that exogenous NO could limit PMN function by inhibiting NFκB activation. Methods: Isolated human PMNs(2×108/sample) were incubated with or without S-nitrosoglutathione (GSNO 0.1mM-5mM; Sigma) for 2 hours. PMNs were either unstimulated or stimulated with TNFα (10 ng/ml) or n-formyl methionyl leucine phenylalanine (fMLP; 10 nM). Viability was assessed by vital dye cytotoxicity assay. After PMN nuclear extraction, protein concentration was determined by Bradford assay to provide equivalent loading. NFκB binding was determined by electrophoretic mobility shift assay. Western immunoblot technique was used to determine the effects of GSNO on degradation of IκB-α, a cytoplasmic inhibitor of NFκB nuclear translocation and activation. Results: TNFα and fMLP induced PMN nuclear NFκB activity compared to unstimulated PMNs (n=5). PMN viability was not decreased by GSNO exposure. GSNO decreased NFκB activity in a concentration-dependent fashion. GSNO alone did not affect NFκB activity in the absence of PMN stimulation. GSNO (0.5 mM) inhibited NFκB activity whether given before or during TNFα exposure. IκB-α was maximally degraded at 90 minutes of TNFα exposure. GSNO exposure (500μM) inhibited IκB-α degradation in the presence of TNFα. Conclusion: PMNs manifest NFκB activity which is increased by stimulation with TNFα and fMLP. GSNO inhibits NFκB activation, possibly by inhibiting degradation of IκB-α, a potential anti-inflammatory effect. Funded by a grant from the American Lung Association.