Chronic cough resembles asthma with IL-5 and granulocyte-macrophage colony-stimulating factor gene expression in bronchoalveolar cells.
BACKGROUND
Chronic cough is a multifactorial condition, which, like asthma, can be associated with eosinophilic airway inflammation. In asthma, airway eosinophilia is believed to be mediated by cytokines such as interleukin-5 and granulocyte-macrophage colony stimulating factor (GM-CSF). The role of these cytokines in chronic cough is unclear.


OBJECTIVE
The aim of this study was to examine gene expression for IL-5 and GM-CSF in chronic cough and compare the results with those found in asthma.


METHODS
We studied adults with asthma (n = 12), chronic cough responsive to inhaled corticosteroid (ICS-responsive cough) (n = 9), and chronic cough not responsive to inhaled corticosteroid (non-ICS-responsive cough) (n = 4). Bronchoalveolar lavage (BAL) was performed, and cytokine gene expression was assessed by using a semiquantitative reverse transcriptase polymerase chain reaction.


RESULTS
IL-5 mRNA was expressed by BAL cells from nine of 12 asthmatic subjects and six of nine subjects with ICS-responsive chronic cough. IL-5 mRNA was not detected in subjects with non-ICS-responsive chronic cough (zero of four subjects, p < 0.05). GM-CSF mRNA was expressed in BAL cells from seven of 12 asthmatic subjects and six of nine subjects with ICS-responsive cough. GM-CSF mRNA was not detected in non-ICS responsive cough subjects (zero of four subjects, p < 0.05). GM-CSF gene expression was related to the degree of methacholine airway responsiveness in asthmatic subjects (r = -0.59).


CONCLUSIONS
We conclude that chronic cough, like asthma, is associated with airway inflammation and gene expression for IL-5 and GM-CSF. Ongoing expression of these cytokines is likely to be related to the persistence of airway inflammation and chronic cough.
Gibson
P G
PG
Respiratory Medicine Unit, John Hunter Hospital, Newcastle, Australia.
Zlatic
K
K
Scott
J
J
Sewell
W
W
Woolley
K
K
Saltos
N
N
D000280:Administration, Inhalation; D000305:Adrenal Cortex Hormones / Q000008:administration & dosage / Q000627:therapeutic use; D000328:Adult; D001249:Asthma / Q000235:genetics / Q000276:immunology*; D001980:Bronchi / Q000276:immunology; D016535:Bronchial Hyperreactivity / Q000235:genetics / Q000276:immunology; D001985:Bronchial Provocation Tests; D001992:Bronchoalveolar Lavage Fluid / Q000166:cytology; D002908:Chronic Disease; D003371:Cough / Q000188:drug therapy / Q000235:genetics / Q000276:immunology*; D017931:DNA Primers / Q000235:genetics; D018076:DNA, Complementary / Q000235:genetics; D005260:Female; D015870:Gene Expression; D016178:Granulocyte-Macrophage Colony-Stimulating Factor / Q000235:genetics* / Q000276:immunology / Q000378:metabolism*; D006801:Humans; D007249:Inflammation / Q000276:immunology; D015848:Interleukin-5 / Q000235:genetics* / Q000276:immunology / Q000378:metabolism*; D008297:Male; D016210:Methacholine Chloride / Q000494:pharmacology; D008875:Middle Aged; D016133:Polymerase Chain Reaction; D012333:RNA, Messenger / Q000032:analysis / Q000378:metabolism; D012882:Skin Tests; D013147:Spirometry
D000305:Adrenal Cortex Hormones; D017931:DNA Primers; D018076:DNA, Complementary; D015848:Interleukin-5; D012333:RNA, Messenger; D016210:Methacholine Chloride; D016178:Granulocyte-Macrophage Colony-Stimulating Factor