title: Elevated exhaled nitric oxide in allergen-provoked asthma is associated with airway epithelial iNOS.
abstract: BACKGROUND
  Fractional exhaled nitric oxide is elevated in allergen-provoked asthma. The cellular and molecular source of the elevated fractional exhaled nitric oxide is, however, uncertain.
  
  
  OBJECTIVE
  To investigate whether fractional exhaled nitric oxide is associated with increased airway epithelial inducible nitric oxide synthase (iNOS) in allergen-provoked asthma.
  
  
  METHODS
  Fractional exhaled nitric oxide was measured in healthy controls (n = 14) and allergic asthmatics (n = 12), before and after bronchial provocation to birch pollen out of season. Bronchoscopy was performed before and 24 hours after allergen provocation. Bronchial biopsies and brush biopsies were processed for nitric oxide synthase activity staining with nicotinamide adenine dinucleotide phosphate diaphorase (NADPH-d), iNOS immunostaining, or gene expression analysis of iNOS by real-time PCR. NADPH-d and iNOS staining were quantified using automated morphometric analysis.
  
  
  RESULTS
  Fractional exhaled nitric oxide and expression of iNOS mRNA were significantly higher in un-provoked asthmatics, compared to healthy controls. Allergic asthmatics exhibited a significant elevation of fractional exhaled nitric oxide after allergen provocation, as well as an accumulation of airway eosinophils. Moreover, nitric oxide synthase activity and expression of iNOS was significantly increased in the bronchial epithelium of asthmatics following allergen provocation. Fractional exhaled nitric oxide correlated with eosinophils and iNOS expression.
  
  
  CONCLUSIONS
  Higher fractional exhaled nitric oxide concentration among asthmatics is associated with elevated iNOS mRNA in the bronchial epithelium. Furthermore, our data demonstrates for the first time increased expression and activity of iNOS in the bronchial epithelium after allergen provocation, and thus provide a mechanistic explanation for elevated fractional exhaled nitric oxide in allergen-provoked asthma.
authors.affiliation: Department of Medicine, Solna, Respiratory Medicine Unit, Karolinska Institutet, Stockholm, Sweden ; Department of Experimental Medical Science, Lund University, Lund, Sweden.
authors.forename: Abraham B
authors.initials: AB
authors.lastname: Roos
authors.affiliation: Department of Experimental Medical Science, Lund University, Lund, Sweden.
authors.forename: Michiko
authors.initials: M
authors.lastname: Mori
authors.affiliation: Department of Medicine, Solna, Respiratory Medicine Unit, Karolinska Institutet, Stockholm, Sweden.
authors.forename: Reidar
authors.initials: R
authors.lastname: Grönneberg
authors.affiliation: Department of Medicine, Division of Hematology, Karolinska Institutet, Stockholm, Sweden.
authors.forename: Christina
authors.initials: C
authors.lastname: Österlund
authors.affiliation: Department of Medicine, Division of Hematology, Karolinska Institutet, Stockholm, Sweden.
authors.forename: Hans-Erik
authors.initials: HE
authors.lastname: Claesson
authors.affiliation: Department of Medicine, Solna, Respiratory Medicine Unit, Karolinska Institutet, Stockholm, Sweden.
authors.forename: Jan
authors.initials: J
authors.lastname: Wahlström
authors.affiliation: Department of Medicine, Solna, Respiratory Medicine Unit, Karolinska Institutet, Stockholm, Sweden.
authors.forename: Johan
authors.initials: J
authors.lastname: Grunewald
authors.affiliation: Department of Medicine, Solna, Respiratory Medicine Unit, Karolinska Institutet, Stockholm, Sweden.
authors.forename: Anders
authors.initials: A
authors.lastname: Eklund
authors.affiliation: Department of Experimental Medical Science, Lund University, Lund, Sweden.
authors.forename: Jonas S
authors.initials: JS
authors.lastname: Erjefält
authors.affiliation: Department of Physiology and Pharmacology, Section of Pharmacological Nitric Oxide Research, Karolinska Institutet, Stockholm, Sweden.
authors.forename: Jon O
authors.initials: JO
authors.lastname: Lundberg
authors.affiliation: Department of Medicine, Solna, Respiratory Medicine Unit, Karolinska Institutet, Stockholm, Sweden ; Safety Science, Global Regulatory Affairs & Patient Safety, AstraZeneca Global Medicines Development, Mölndal, Sweden.
authors.forename: Magnus
authors.initials: M
authors.lastname: Nord
mesh_terms: D000328:Adult; D000485:Allergens; D001249:Asthma / Q000201:enzymology* / Q000473:pathology; D001980:Bronchi / Q000201:enzymology* / Q000473:pathology; D001985:Bronchial Provocation Tests; D016022:Case-Control Studies; D004847:Epithelial Cells / Q000378:metabolism / Q000473:pathology; D045853:Exhalation; D005260:Female; D015870:Gene Expression; D006801:Humans; D008297:Male; D008875:Middle Aged; D009252:NADPH Dehydrogenase / Q000235:genetics / Q000378:metabolism; D009569:Nitric Oxide / Q000096:biosynthesis*; D052247:Nitric Oxide Synthase Type II / Q000235:genetics / Q000378:metabolism*; D011058:Pollen; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism*; D020545:Respiratory Mucosa / Q000378:metabolism / Q000473:pathology
chemical_list: D000485:Allergens; D012333:RNA, Messenger; D009569:Nitric Oxide; C496319:NOS2 protein, human; D052247:Nitric Oxide Synthase Type II; D009252:NADPH Dehydrogenase