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 mu mol.L-1), on Ca2+-dependent pro-inflammatory activities, cytosolic Ca2+ fluxes and intracellular cAMP in isolated human neutrophils activated with the chemoattractants, N-formyl-L-methionyl-L-leucyl-L-phenylalanine (1 mu 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 Ca2+ fluxes by fura-2/AM-based spectrofluorimetric and radiometric (Ca-45(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 mu 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 cytosolic Ca2+ concentrations and store-operated Ca2+ influx. These montelukast-mediated alterations in Ca2+ 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. British Journal of Pharmacology ( 2009) 156, 105-115; doi: 10.1111/j.1476-5381.2008.00012.x; published online 5 December 2008