MUC5AC and MUC5B mucins increase in cystic fibrosis airway secretions during pulmonary exacerbation.
BACKGROUND
Cystic fibrosis (CF) is believed to be associated with mucus hypersecretion; thus, the principal airway gel-forming mucins, MUC5AC and MUC5B, are also expected to be increased relative to non-CF secretions. However, we have shown that these mucins are decreased during stable CF disease.


OBJECTIVE
In this study, we determine if these mucins increase during a pulmonary exacerbation of CF.


METHODS
Expectorated sputum was collected from 11 adults with CF during stable disease and then during a pulmonary exacerbation and from 12 healthy control subjects. MUC5AC and MUC5B proteins were measured by Western blot. DNA content was measured using microfluorimetry.


RESULTS
MUC5AC protein increased by 908% and MUC5B by 59% (p < 0.05 for both) during an exacerbation compared with periods of stable disease. During stable disease, the vol/vol quantity of MUC5AC protein was 89% less than normal mucus, and the mucin-associated sugars, measured using a lectin binding assay, were 46% less compared with normal mucus. The concentration of DNA in CF sputum did not increase during an exacerbation.


CONCLUSIONS
During a CF exacerbation, concentration of secreted mucin increased to the amount found in mucus from normal subjects, suggesting that the capacity to secrete mucin in response to an infection or inflammatory stimulus is preserved in CF airways. This might help to protect the airway from injury.
Henke
Markus O
MO
Philipps-University Marburg, Department of Pulmonary Medicine, Baldingerstrasse 1, 35043 Marburg, Germany. markus.henke@staff.uni-marburg.de.
John
Gerrit
G
Germann
Michele
M
Lindemann
Hermann
H
Rubin
Bruce K
BK
D000208:Acute Disease; D000328:Adult; D016022:Case-Control Studies; D003550:Cystic Fibrosis / Q000378:metabolism*; D005541:Forced Expiratory Volume; D006801:Humans; D055271:Mucin 5AC; D055257:Mucin-5B; D009077:Mucins / Q000378:metabolism*; D013183:Sputum / Q000737:chemistry
C524678:MUC5AC protein, human; C524578:MUC5B protein, human; D055271:Mucin 5AC; D055257:Mucin-5B; D009077:Mucins