Expression of c-erbB receptors and ligands in the bronchial epithelium of asthmatic subjects.
BACKGROUND
The c-erbB family of receptor tyrosine kinases act in a combinatorial fashion to regulate cell behavior. Disturbances in this system have been associated with neoplastic and inflammatory diseases.


OBJECTIVE
Although expression of the epidermal growth factor receptor (EGFR; c-erbB1) is increased in the bronchial epithelium in asthma, there is no information on expression of other members of the c-erbB receptor and ligand family that can modulate EGFR function.


METHODS
Immunohistochemistry was used to compare expression of EGFR, c-erbB2, c-erbB3, epidermal growth factor, heparin-binding epidermal growth factor-like growth factor, and transforming growth factor alpha in bronchial biopsy specimens from normal and asthmatic subjects. Scrape-wounded monolayers of 16HBE 14o(-) cells were used as an in vitro model of damage and repair. Changes in EGFR, c-erbB2, and c-erbB3 distribution were measured by means of immunocytochemistry, whereas tyrosine phosphorylation was measured by means of immunoprecipitation and Western blotting.


RESULTS
Although epithelial staining for the EGFR was significantly increased in asthmatic epithelium (P <.001), there was no difference in staining for the other receptors and ligands studied. In scrape-wounded epithelial monolayers, tyrosine phosphorylation of EGFR, c-erbB2, and c-erbB3 occurred immediately after damage; however, only EGFR showed a change in expression in response to damage.


CONCLUSIONS
Even though EGFR levels are increased in asthma, this is not linked to changes in expression of its activating ligands or other c-erbB receptors. Because bronchial epithelial cells respond to physical damage through activation of several c-erbB family members, the shift in favor of increased EGFR levels in asthma may lead to altered epithelial function by influencing the number and type of heterodimeric signaling complexes, assuming sufficient ligand availability.
Polosa
Riccardo
R
School of Medicine, Division of Respiratory Cell and Molecular Biology, Southampton General Hospital, Southampton, United Kingdom.
Puddicombe
Sarah M
SM
Krishna
M Thirumala
MT
Tuck
Angela B
AB
Howarth
Peter H
PH
Holgate
Stephen T
ST
Davies
Donna E
DE
D000328:Adult; D001249:Asthma / Q000378:metabolism*; D001980:Bronchi / Q000737:chemistry*; D004815:Epidermal Growth Factor / Q000032:analysis*; D004848:Epithelium / Q000737:chemistry; D066246:ErbB Receptors / Q000032:analysis*; D005260:Female; D066257:Heparin-binding EGF-like Growth Factor; D006801:Humans; D007150:Immunohistochemistry; D036341:Intercellular Signaling Peptides and Proteins; D008297:Male; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000032:analysis*; D020893:Receptor, ErbB-3 / Q000032:analysis*; D016211:Transforming Growth Factor alpha / Q000032:analysis*
D004815:Epidermal Growth Factor; D066246:ErbB Receptors; D066257:Heparin-binding EGF-like Growth Factor; D036341:Intercellular Signaling Peptides and Proteins; D018719:Erb-b2 Receptor Tyrosine Kinases; D020893:Receptor, ErbB-3; D016211:Transforming Growth Factor alpha; C587883:HBEGF protein, human