Mannitol and AMP do not induce bronchoconstriction in eosinophilic bronchitis: further evidence for dissociation between airway inflammation and bronchial hyperresponsiveness.
OBJECTIVE
Eosinophilic bronchitis (EB) shares many pathological features with asthma. However, patients with EB do not develop the characteristic physiological abnormalities of asthma: variable airflow obstruction and bronchial hyperresponsiveness (BHR) to a direct bronchial challenge with methacholine. Indirect bronchial challenges with AMP and mannitol are dependent on the presence of airway inflammation, and positive in 10% of asthmatic subjects who have a negative response to methacholine. We have therefore investigated whether subjects with EB are responsive to indirect airway challenge with AMP and mannitol.


METHODS
Subjects with asthma, EB and healthy controls attended on up to four occasions. After screening, subjects performed bronchial provocation tests to methacholine and then either AMP or mannitol. Each challenge was followed immediately by sputum induction for the measurement of airway inflammation and mast cell-derived histamine.


RESULTS
No subjects with EB responded to either AMP (n = 5) or mannitol (n = 7) while 4/8 and 7/10 subjects with asthma responded to the respective challenges (P = 0.057 for AMP, P = 0.004 for mannitol). There was no difference in induced sputum concentrations of histamine or eosinophil cell counts following methacholine challenge compared with AMP or mannitol.


CONCLUSIONS
The airways of patients with EB are not responsive to either direct or indirect bronchial challenge. This supports the view that it is the presence of functionally abnormal airway smooth muscle that is the key determinant of BHR in asthma, and that while this may be aggravated by the presence of mucosal airway inflammation, it is not caused by it.
Singapuri
Amisha
A
Department of Infection, Immunity and Inflammation, Institute for Lung Health, University of Leicester, Leicester, UK.
McKenna
Sue
S
Brightling
Chris E
CE
Bradding
Peter
P
D000249:Adenosine Monophosphate / Q000008:administration & dosage / Q000494:pharmacology*; D000280:Administration, Inhalation; D000328:Adult; D001249:Asthma / Q000473:pathology / Q000503:physiopathology; D016535:Bronchial Hyperreactivity / Q000473:pathology / Q000503:physiopathology*; D001985:Bronchial Provocation Tests; D001991:Bronchitis / Q000473:pathology / Q000503:physiopathology*; D016084:Bronchoconstriction / Q000187:drug effects* / Q000502:physiology; D016022:Case-Control Studies; D004802:Eosinophilia / Q000473:pathology / Q000503:physiopathology*; D004804:Eosinophils / Q000473:pathology; D005260:Female; D006632:Histamine / Q000378:metabolism; D006801:Humans; D008297:Male; D008353:Mannitol / Q000008:administration & dosage / Q000494:pharmacology*; D016210:Methacholine Chloride / Q000008:administration & dosage / Q000494:pharmacology; D008875:Middle Aged; D011014:Pneumonia / Q000473:pathology / Q000503:physiopathology*; D013183:Sputum / Q000166:cytology
D016210:Methacholine Chloride; D008353:Mannitol; D000249:Adenosine Monophosphate; D006632:Histamine