title: Areca nut extracts-activated secretion of leukotriene B4, and phosphorylation of p38 mitogen-activated protein kinase and elevated intracellular calcium concentrations in human polymorphonuclear leukocytes.
abstract: OBJECTIVE
  Polymorphonuclear leukocytes are the major source of leukotriene B4, which is synthesized via the 5-lipoxygenase pathway. Activation of the 5-lipoxygenase pathway is regulated by intracellular calcium and the phosphorylation of p38 mitogen-activated protein kinase (MAPK). The impact of areca nut extracts on the biosynthesis of leukotriene B4 by human polymorphonuclear leukocytes was evaluated, and some of the possible mechanisms underlying the responses were examined.
  
  
  METHODS
  Polymorphonuclear leukocytes were treated with various concentrations of areca nut extracts. The concentrations of leukotriene B4 released into the supernatants were evaluated using enzyme immunoassay. The phosphorylation of p38 MAPK was monitored using immunoblotting, and the cytosolic calcium kinetics were assessed fluorometrically using Fura-2.
  
  
  RESULTS
  Exposure of polymorphonuclear leukocytes to areca nut extracts led to a dose-dependent increase in the production of leukotriene B4, with levels peaking at 30 min and decreasing thereafter. Areca nut extracts enhanced the phosphorylation of p38 MAPK, an enzyme known to activate 5-lipoxygenase. Incubation with areca nut extracts also resulted in a rapid elevation of intracellular calcium concentrations in polymorphonuclear leukocytes. The induction of leukotriene B4 by areca nut extracts was suppressed with the p38 MAPK inhibitor, SB203580, or with the intracellular calcium chelator, BAPTA-AM.
  
  
  CONCLUSIONS
  The interaction of areca nut extracts with polymorphonuclear leukocytes activated the arachidonic acid metabolic cascade. Incubation of polymorphonuclear leukocytes with areca nut extracts resulted in the activation of intracellular events, such as phosphorylation of p38 MAPK and Ca2+ mobilization, involved in the release of pro-inflammatory lipid mediators. The results of this study emphasize the potential importance of polymorphonuclear leukocytes as a source of leukotriene B4, which may modulate the inflammatory response in areca chewers.
authors.affiliation: Institute of Oral Biology, and Faculty of Dentistry, National Yang-Ming University, and Department of Medical Research, Taipei Veterans General Hospital, Taipei, Taiwan.
authors.forename: S-L
authors.initials: SL
authors.lastname: Hung
authors.forename: Y-J
authors.initials: YJ
authors.lastname: Lin
authors.forename: E J
authors.initials: EJ
authors.lastname: Chien
authors.forename: W-G
authors.initials: WG
authors.lastname: Liu
authors.forename: H-W
authors.initials: HW
authors.lastname: Chang
authors.forename: T-Y
authors.initials: TY
authors.lastname: Liu
authors.forename: Y-T
authors.initials: YT
authors.lastname: Chen
mesh_terms: D001114:Areca; D020013:Calcium Signaling / Q000187:drug effects*; D002614:Chelating Agents / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004533:Egtazic Acid / Q000031:analogs & derivatives / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005470:Fluorometry; D006801:Humans; D007093:Imidazoles / Q000494:pharmacology; D015151:Immunoblotting; D007124:Immunoenzyme Techniques; D018836:Inflammation Mediators / Q000494:pharmacology; D007975:Leukotriene B4 / Q000037:antagonists & inhibitors / Q000378:metabolism*; D009504:Neutrophils / Q000187:drug effects* / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects; D010936:Plant Extracts / Q000494:pharmacology*; D011725:Pyridines / Q000494:pharmacology; D013997:Time Factors; D048051:p38 Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000187:drug effects* / Q000378:metabolism
chemical_list: D002614:Chelating Agents; D004791:Enzyme Inhibitors; D007093:Imidazoles; D018836:Inflammation Mediators; D010936:Plant Extracts; D011725:Pyridines; C070379:1,2-bis(2-aminophenoxy)ethane N,N,N',N'-tetraacetic acid acetoxymethyl ester; D007975:Leukotriene B4; D004533:Egtazic Acid; D048051:p38 Mitogen-Activated Protein Kinases; C093642:SB 203580