Montelukast inhibits neutrophil pro-inflammatory activity by a cyclic AMP-dependent mechanism

Background and purpose: The objective of this study was to characterize the effects of the cysteinyl leukotriene receptor antagonist, montelukast (0.1-2 ̄mol·L -1), on Ca 2+-dependent pro-inflammatory activities, cyto/ic Ca 2+ fluxes and intracellular cAMP in i/ated human neutrophils activated with the chemoattractants, N-formyl-L-methionyl-L- leucyl-L-phenylalanine (1 ̄mol·L -1) and platelet-activating factor (200 nmol·L -1). Experimental approach: Generation of reactive oxygen species was measured by lucigenin- and luminol-enhanced chemiluminescence, elastase release by a colourimetric assay, leukotriene B 4 and cAMP by competitive binding ELISA procedures, and Ca 2+ fluxes by fura-2/AM-based spectrofluorimetric and radiometric ( 45Ca 2+) procedures. Key results: Pre-incubation of neutrophils with montelukast resulted in dose-related inhibition of the generation of reactive oxygen species and leukotriene B 4 by chemoattractant-activated neutrophils, as well as release of elastase, all of which were maximal at 2 ̄mol·L -1 (mean percentages of the control values of 30 ± 1, 12 ± 3 and 21 ± 3 respectively; P < 0.05). From a mechanistic perspective, treatment of chemoattractant- activated neutrophils with montelukast resulted in significant reductions in both post-peak cyto/ic Ca 2+ concentrations and store-operated Ca 2+ influx. These montelukast-mediated alterations in Ca 2+ handling by the cells were associated with a significant elevation in basal cAMP levels, which resulted from inhibition of cyclic nucleotide phosphodiesterases. Conclusions and implications: Montelukast, primarily a cysteinyl leukotriene (CysLT 1) receptor antagonist, exhibited previously undocumented, secondary, neutrophil-directed anti-inflammatory properties, which appeared to be cAMP-dependent. © 2008 The British Pharmacological Society.