title: Sensitivity to environmental irritants and capsaicin cough reaction in patients with a positive methacholine provocation test before and after treatment with inhaled corticosteroids.
abstract: BACKGROUND
  Increasing evidence points to a potential role for members of the transient receptor potential family of cation channels on several features of asthmatic disease. The cough sensitivity to inhaled capsaicin is known to reflect the reactivity of these airway sensory nerves.
  
  
  OBJECTIVE
  The aim was to study, among patients having a positive methacholine provocation and diagnosed with asthma, capsaicin cough sensitivity, sensitivity to methacholine, and levels of exhaled nitric oxide before and after treatment with inhaled steroids, and further, to measure the self-reported impact from environmental irritants.
  
  
  METHODS
  Eighteen steroid-naïve patients with a positive methacholine test underwent capsaicin inhalation provocation on two occasions, before and after regular use of inhaled steroids over at least 3 months. Comparisons were made to 21 healthy controls. Sensitivity to methacholine and levels of exhaled nitric oxide were measured before and after the treatment. The participants also answered a validated questionnaire regarding environmental irritants.
  
  
  RESULTS
  The patients displayed higher capsaicin cough sensitivity than the controls before the treatment period, but not afterward. Before treatment, capsaicin cough answer correlated significantly with levels of exhaled nitric oxide, but not with methacholine sensitivity. After treatment with inhaled corticosteroids, the capsaicin cough sensitivity and the inflammatory parameters were normalized. In comparison to the control group, the patients reported more affective reactions to and behavioral disruptions induced by environmental irritants.
  
  
  CONCLUSIONS
  In steroid-naïve patients with a positive methacholine test, there is a link between that part of the airway inflammation that is reflected by exhaled nitric oxide and that followed by an augmented reactivity of capsaicin-sensitive sensory nerves. This association disappears after steroid treatment.
authors.affiliation: Department of Internal Medicine/Respiratory Medicine and Allergology, Sahlgrenska University Hospital, University of Gothenburg, Gothenburg, Sweden.
authors.forename: Ylva
authors.initials: Y
authors.lastname: Ekstrand
authors.forename: Ewa
authors.initials: E
authors.lastname: Ternesten-Hasséus
authors.forename: Monica
authors.initials: M
authors.lastname: Arvidsson
authors.forename: Kerstin
authors.initials: K
authors.lastname: Löfdahl
authors.forename: Mona
authors.initials: M
authors.lastname: Palmqvist
authors.forename: Eva
authors.initials: E
authors.lastname: Millqvist
mesh_terms: D000280:Administration, Inhalation; D000293:Adolescent; D000305:Adrenal Cortex Hormones / Q000008:administration & dosage*; D000328:Adult; D001249:Asthma / Q000175:diagnosis* / Q000188:drug therapy* / Q000276:immunology; D016535:Bronchial Hyperreactivity / Q000209:etiology / Q000503:physiopathology; D001985:Bronchial Provocation Tests; D002211:Capsaicin; D016022:Case-Control Studies; D016001:Confidence Intervals; D004785:Environmental Pollutants / Q000009:adverse effects; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007509:Irritants / Q000009:adverse effects*; D016014:Linear Models; D008297:Male; D016210:Methacholine Chloride; D008875:Middle Aged; D011446:Prospective Studies; D018570:Risk Assessment; D012720:Severity of Illness Index; D013147:Spirometry / Q000379:methods; D018709:Statistics, Nonparametric; D016896:Treatment Outcome; D055815:Young Adult
chemical_list: D000305:Adrenal Cortex Hormones; D004785:Environmental Pollutants; D007509:Irritants; D016210:Methacholine Chloride; D002211:Capsaicin