title: Differential inhibitory effects of CysLT(1) receptor antagonists on P2Y(6) receptor-mediated signaling and ion transport in human bronchial epithelia.
abstract: BACKGROUND
  Cysteinyl leukotriene (CysLT) is one of the proinflammatory mediators released by the bronchi during inflammation. CysLTs exert their biological effects via specific G-protein-coupled receptors. CysLT(1) receptor antagonists are available for clinical use for the treatment of asthma. Recently, crosstalk between CysLT(1) and P2Y(6) receptors has been delineated. P2Y receptors are expressed in apical and/or basolateral membranes of virtually all polarized epithelia to control the transport of fluid and electrolytes. Previous research suggests that CysLT(1) receptor antagonists inhibit the effects of nucleotides acting at P2Y receptors. However, the detailed molecular mechanism underlying the inhibition remains unresolved.
  
  
  RESULTS
  In this study, western blot analysis confirmed that both CysLT(1) and P2Y(6) receptors were expressed in the human bronchial epithelial cell line 16HBE14o-. All three CysLT(1) antagonists inhibited the uridine diphosphate (UDP)-evoked I(SC), but only montelukast inhibited the UDP-evoked [Ca(2+)](i) increase. In the presence of forskolin or 8-bromoadenosine 3'5' cyclic monophosphate (8-Br-cAMP), the UDP-induced I(SC) was potentiated but was reduced by pranlukast and zafirlukast but not montelukast. Pranlukast inhibited the UDP-evoked I(SC) potentiated by an Epac activator, 8-(4-Chlorophenylthio)-2'-O-methyladenosine-3',5'-cyclic monophosphate (8-CPT-2'-O-Me-cAMP), while montelukast and zafirlukast had no such effect. Pranlukast inhibited the real-time increase in cAMP changes activated by 8-CPT-2'-O-Me-cAMP as monitored by fluorescence resonance energy transfer imaging. Zafirlukast inhibited the UDP-induced I(SC) potentiated by N(6)-Phenyladenosine-3',5'-cyclic monophosphorothioate, Sp-isomer (Sp-6-Phe-cAMP; a PKA activator) and UDP-activated PKA activity.
  
  
  CONCLUSIONS
  In summary, our data strongly suggest for the first time that in human airway epithelia, the three specific CysLT(1) receptor antagonists exert differential inhibitory effects on P2Y(6) receptor-coupled Ca(2+) signaling pathways and the potentiating effect on I(SC) mediated by cAMP and Epac, leading to the modulation of ion transport activities across the epithelia.
authors.affiliation: School of Biomedical Sciences, The Chinese University of Hong Kong, Hong Kong, China.
authors.forename: Wendy Ka-hoi
authors.initials: WK
authors.lastname: Lau
authors.forename: Alison Wai-ming
authors.initials: AW
authors.lastname: Chow
authors.forename: Simon Chak-leung
authors.initials: SC
authors.lastname: Au
authors.forename: Wing-hung
authors.initials: WH
authors.lastname: Ko
mesh_terms: D000085:Acetates / Q000494:pharmacology; D001980:Bronchi / Q000166:cytology*; D002118:Calcium / Q000378:metabolism; D002460:Cell Line; D002712:Chlorides / Q000378:metabolism; D000242:Cyclic AMP / Q000378:metabolism; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D003521:Cyclopropanes; D004553:Electric Conductivity; D004789:Enzyme Activation / Q000187:drug effects; D005786:Gene Expression Regulation / Q000187:drug effects; D020662:Guanine Nucleotide Exchange Factors / Q000378:metabolism; D006801:Humans; D017136:Ion Transport / Q000187:drug effects; D020024:Leukotriene Antagonists / Q000494:pharmacology*; D011804:Quinolines / Q000494:pharmacology; D018077:Receptors, Leukotriene / Q000378:metabolism*; D018048:Receptors, Purinergic P2 / Q000378:metabolism*; D020545:Respiratory Mucosa / Q000166:cytology* / Q000187:drug effects / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects*; D013440:Sulfides; D014530:Uridine Diphosphate / Q000494:pharmacology
chemical_list: D000085:Acetates; D002712:Chlorides; D003521:Cyclopropanes; D020662:Guanine Nucleotide Exchange Factors; D020024:Leukotriene Antagonists; D011804:Quinolines; C116122:RAPGEF3 protein, human; D018077:Receptors, Leukotriene; D018048:Receptors, Purinergic P2; D013440:Sulfides; C099845:purinoceptor P2Y6; D014530:Uridine Diphosphate; D000242:Cyclic AMP; D017868:Cyclic AMP-Dependent Protein Kinases; C083169:leukotriene D4 receptor; C093875:montelukast; D002118:Calcium