CROMOLYN INHIBITS ASSEMBLY OF THE NADPH OXIDASE AND SUPEROXIDE ANION GENERATION BY HUMAN NEUTROPHILS

Early and late phase reactions have been observed in asthma; the late phase reaction is characterized by accumulation of inflammatory cells such as neutrophils. Activated neutrophils degranulate and assemble an active NADPH oxidase, which generates superoxide anion (O-2(-)), reac tions that have been implicated in lung tissue damage. Preincubation o f neutrophils with the asthma drug cromolyn sodium selectively inhibit ed FMLP (10(-7) M) and PMA (0.1 mu g/ml) elicited O-2(-) generation bu t not degranulation. To further characterize the mechanism of this inh ibition we examined the effect of cromolyn on the NADPH oxidase comple x and the signaling pathways for its assembly. Ca2+ mobilization and a ctivation of protein kinase C have been implicated as signals for acti vation of the NADPH oxidase. Ca2+ mobilization triggered by FMLP was s ignificantly decreased by 21.2% in cromolyn-treated cells. In contrast , cromolyn did not interfere with translocation or activity of protein kinase C. Membranes prepared from neutrophils stimulated with 0.5 mu g/ml PMA generated O-2(-), indicating assembly of an active NADPH oxid ase; cromolyn did not inhibit this membrane-associated, preassembled o xidase. In contrast, preincubation of neutrophils with 100 mu M cromol yn before addition of PMA decreased the capacity of the membranes to g enerate O-2(-) by 57.3%. These results indicate that cromolyn inhibite d the assembly of an active NADPH oxidase. The efficacy of cromolyn ma y be associated with inhibition of assembly of an active NADPH oxidase in the neutrophil and prevention of oxygen radical-induced tissue dam age.