title: TNF-α-induces airway hyperresponsiveness to cholinergic stimulation in guinea pig airways.
abstract: OBJECTIVE
  TNF-α is an inflammatory cytokine implicated in the pathogenesis of asthma and it causes airway inflammation, bronchoconstriction and airway hyperresponsiveness to a number of spasmogens following inhalation.
  
  
  METHODS
  We compared contractions of guinea pig isolated trachea incubated with saline or TNF-α for 1, 2 or 4 days to electrical field stimulation (EFS), 5-HT or methacholine. In addition, we compared bronchoconstriction in anaesthetized guinea pigs 6 h after intratracheal instillation of saline or TNF-α to vagal nerve stimulation, i.v. 5-HT or methacholine. Differential counts were performed on the bronchoalvelolar lavage fluid (BALF).
  
  
  RESULTS
  Maximum contractions to methacholine, 5-HT and EFS were not different between freshly prepared and saline-incubated tissues. Exposure to TNF-α concentration-dependently potentiated contractions to 5-HT and EFS, but not methacholine. All contractions were atropine-sensitive, but not hexamethonium-sensitive. 5-HT-evoked contractions were inhibited by ketanserin or epithelial denudation. Only EFS-evoked contractions were tetrodotoxin-sensitive. Vagal stimulation, i.v. 5-HT or MCh caused a significant atropine-sensitive, frequency- and dose-dependent bronchoconstriction and decreased blood pressure similarly in both saline and TNF-α pre-treated animals. TNF-α potentiated the bronchoconstriction to vagal stimulation and 5-HT, but not MCh. The BALF from saline-treated animals contained predominantly macrophages, whereas that from TNF-α-treated animals contained neutrophils.
  
  
  CONCLUSIONS
  TNF-α caused airway hyperresponsiveness to nerve stimulation in vivo and increased contractility in vitro. However, responsiveness to MCh was unchanged, suggesting a pre-synaptic action of TNF-α on parasympathetic nerves. TNF-α-induced airway hyperresponsiveness to 5-HT suggested an increased 5-HT(2A) receptor-mediated acetylcholine release from epithelial cells.
authors.affiliation: Sackler Institute of Pulmonary Pharmacology, Institute of Pharmaceutical Science, King's College London, London, UKUCB Celltech, Slough, UK.
authors.forename: R
authors.initials: R
authors.lastname: Makwana
authors.affiliation: Sackler Institute of Pulmonary Pharmacology, Institute of Pharmaceutical Science, King's College London, London, UKUCB Celltech, Slough, UK.
authors.forename: N
authors.initials: N
authors.lastname: Gozzard
authors.affiliation: Sackler Institute of Pulmonary Pharmacology, Institute of Pharmaceutical Science, King's College London, London, UKUCB Celltech, Slough, UK.
authors.forename: D
authors.initials: D
authors.lastname: Spina
authors.affiliation: Sackler Institute of Pulmonary Pharmacology, Institute of Pharmaceutical Science, King's College London, London, UKUCB Celltech, Slough, UK.
authors.forename: C
authors.initials: C
authors.lastname: Page
mesh_terms: D000818:Animals; D001794:Blood Pressure; D016535:Bronchial Hyperreactivity / Q000503:physiopathology*; D001992:Bronchoalveolar Lavage Fluid / Q000166:cytology; D002452:Cell Count; D004558:Electric Stimulation; D006168:Guinea Pigs; D006339:Heart Rate; D066298:In Vitro Techniques; D008297:Male; D016210:Methacholine Chloride / Q000494:pharmacology; D018721:Muscarinic Agonists / Q000494:pharmacology; D009119:Muscle Contraction / Q000502:physiology*; D009130:Muscle, Smooth / Q000502:physiology; D012701:Serotonin / Q000494:pharmacology; D017366:Serotonin Receptor Agonists / Q000494:pharmacology; D014132:Trachea / Q000502:physiology; D014409:Tumor Necrosis Factor-alpha / Q000502:physiology*
chemical_list: D018721:Muscarinic Agonists; D017366:Serotonin Receptor Agonists; D014409:Tumor Necrosis Factor-alpha; D016210:Methacholine Chloride; D012701:Serotonin