Inhibition of epithelial growth factor receptor signalling does not preserve epithelial barrier function after in vitro gliadin insult.
OBJECTIVE
In coeliac disease, small-bowel mucosal permeability is increased in response to gluten consumption. However, the signalling routes leading to such a barrier defect remain obscure. As the epidermal growth factor receptor (EGFR) pathway is up-regulated in untreated coeliac disease, and since this cascade has been related to epithelial hyperpermeability, the aim of this study was to establish whether blocking the EGFR route would restore the barrier after gliadin insult in vitro.


METHODS
Epithelial barrier function was assessed by measuring transepithelial electrical resistance (TER) in Caco-2 epithelial monolayers treated with pepsin trypsin (PT)-digested gliadin with or without monoclonal antibodies against EGFR family members or by inhibitors of the EGFR pathway signalling molecules. Furthermore, tight-junctional integrity was determined by Western blotting and immunofluorescence staining of the tight-junctional protein occludin.


RESULTS
PT-gliadin significantly reduced TER and the expression of occludin protein. Blocking of the EGFR signalling pathway could not prevent gliadin-triggered damage. In fact, a function-blocking monoclonal antibody against EGFR (ErbB1) actually potentiated the harmful effects of gliadin on TER.


CONCLUSIONS
The epithelial barrier-disrupting properties of gliadin are independent of the EGFR signalling cascade. However, our results suggest that activation of the EGFR pathway might actually be protective against gliadin-triggered hyperpermeability. Further studies are needed to elucidate the specific gliadin-triggered signalling cascades which lead to increased epithelial permeability in coeliac disease.
Paediatric Research Centre, Medical School, University of Tampere, Finland.
Kati
K
Juuti-Uusitalo
Katri
K
Lindfors
Markku
M
Mäki
Mimmi
M
Patrikainen
Jorma
J
Isola
Katri
K
Kaukinen
D015153:Blotting, Western; D018938:Caco-2 Cells; D002446:Celiac Disease / Q000378:metabolism*; D002478:Cells, Cultured; D017097:Electric Impedance; D066246:ErbB Receptors / Q000037:antagonists & inhibitors*; D005903:Gliadin / Q000494:pharmacology*; D006801:Humans; D066298:In Vitro Techniques; D007413:Intestinal Mucosa / Q000187:drug effects* / Q000378:metabolism; D018613:Microscopy, Confocal; D015398:Signal Transduction / Q000187:drug effects; D018709:Statistics, Nonparametric
D005903:Gliadin; D066246:ErbB Receptors