title: Montelukast inhibits neutrophil pro-inflammatory activity by a cyclic AMP-dependent mechanism.
abstract: OBJECTIVE
  The objective of this study was to characterize the effects of the cysteinyl leukotriene receptor antagonist, montelukast (0.1-2 micromol x L(-1)), on Ca(2+)-dependent pro-inflammatory activities, cytosolic Ca(2+) fluxes and intracellular cAMP in isolated human neutrophils activated with the chemoattractants, N-formyl-L-methionyl-L-leucyl-L-phenylalanine (1 micromol x L(-1)) and platelet-activating factor (200 nmol x L(-1)).
  
  
  METHODS
  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 ((45)Ca(2+)) procedures.
  
  
  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 micromol x 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 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
  Montelukast, primarily a cysteinyl leukotriene (CysLT(1)) receptor antagonist, exhibited previously undocumented, secondary, neutrophil-directed anti-inflammatory properties, which appeared to be cAMP-dependent.
authors.affiliation: Medical Research Council Unit for Inflammation and Immunity, Department of Immunology, Faculty of Health Sciences, University of Pretoria, Pretoria, South Africa. ronald.anderson@up.ac.za
authors.forename: Ronald
authors.initials: R
authors.lastname: Anderson
authors.forename: Annette J
authors.initials: AJ
authors.lastname: Theron
authors.forename: Cornelia M
authors.initials: CM
authors.lastname: Gravett
authors.forename: Helen C
authors.initials: HC
authors.lastname: Steel
authors.forename: Gregory R
authors.initials: GR
authors.lastname: Tintinger
authors.forename: Charles
authors.initials: C
authors.lastname: Feldman
mesh_terms: D015105:3',5'-Cyclic-AMP Phosphodiesterases / Q000037:antagonists & inhibitors; D000085:Acetates / Q000494:pharmacology*; D002118:Calcium / Q000378:metabolism; D002630:Chemotactic Factors / Q000494:pharmacology; D000242:Cyclic AMP / Q000378:metabolism*; D003521:Cyclopropanes; D004305:Dose-Response Relationship, Drug; D005456:Fluorescent Dyes; D016257:Fura-2; D006801:Humans; D066298:In Vitro Techniques; D020024:Leukotriene Antagonists / Q000494:pharmacology*; D007975:Leukotriene B4 / Q000378:metabolism; D009240:N-Formylmethionine Leucyl-Phenylalanine / Q000494:pharmacology; D018375:Neutrophil Activation; D009504:Neutrophils / Q000187:drug effects* / Q000378:metabolism; D010196:Pancreatic Elastase / Q000378:metabolism; D011804:Quinolines / Q000494:pharmacology*; D017382:Reactive Oxygen Species / Q000378:metabolism; D018077:Receptors, Leukotriene / Q000502:physiology*; D013440:Sulfides
chemical_list: D000085:Acetates; D002630:Chemotactic Factors; D003521:Cyclopropanes; D005456:Fluorescent Dyes; D020024:Leukotriene Antagonists; D011804:Quinolines; D017382:Reactive Oxygen Species; D018077:Receptors, Leukotriene; D013440:Sulfides; D007975:Leukotriene B4; D009240:N-Formylmethionine Leucyl-Phenylalanine; D000242:Cyclic AMP; D015105:3',5'-Cyclic-AMP Phosphodiesterases; D010196:Pancreatic Elastase; C083169:leukotriene D4 receptor; C093875:montelukast; D002118:Calcium; D016257:Fura-2