S-Nitrosoglutathione (GSNO) is an endogenous bronchodilator with several beneficial pulmonary effects. Levels are decreased in the asthmatic airway, and GSNO inhalation has been proposed as an asthma therapy. 5-lipoxygenase (5-LO) is the rate-limiting enzyme in the synthetic pathway for cysteinyl leukotrienes (Cys LTs), bronchoconstricting agents that are over-produced in asthma. Here, we have studied the effect of GSNO on the expression of 5-LO in human airway A549 cell lines and in primary normal human tracheobronchial epithelial (NHBE) cells in vitro. GSNO at concentrations of 0.5 -1 µM caused a 3- to 6-fold increase in 5-LO expression. However, GSNO at > 5 µM significantly inhibited both 5-LO expression and LT production (p < 0.004). We also found that airway epithelial cells had gamma-glutamyl transpeptidase (-GT) activity. The effect of 1 µM GSNO on 5-LO expression was prevented by the -GT inhibitor, acivicin, suggesting a convergence of GSNO and Cys LT metabolic pathway that may be relevant to asthma. Our data demonstrate that GSNO levels 1 µM, likely recapitulating those in the asthmatic airway, increase 5-LO expression, an effect which may increase inflammation and bronchoconstriction. However, GSNO at concentrations > 5 µM suppress 5-LO expression. These data suggest that GSNO might inhibit 5-LO expression in the clinical setting.