Gliadin, zonulin and gut permeability: Effects on celiac and non-celiac intestinal mucosa and intestinal cell lines.
OBJECTIVE
Little is known about the interaction of gliadin with intestinal epithelial cells and the mechanism(s) through which gliadin crosses the intestinal epithelial barrier. We investigated whether gliadin has any immediate effect on zonulin release and signaling.


METHODS
Both ex vivo human small intestines and intestinal cell monolayers were exposed to gliadin, and zonulin release and changes in paracellular permeability were monitored in the presence and absence of zonulin antagonism. Zonulin binding, cytoskeletal rearrangement, and zonula occludens-1 (ZO-1) redistribution were evaluated by immunofluorescence microscopy. Tight junction occludin and ZO-1 gene expression was evaluated by real-time polymerase chain reaction (PCR).


RESULTS
When exposed to gliadin, zonulin receptor-positive IEC6 and Caco2 cells released zonulin in the cell medium with subsequent zonulin binding to the cell surface, rearrangement of the cell cytoskeleton, loss of occludin-ZO1 protein-protein interaction, and increased monolayer permeability. Pretreatment with the zonulin antagonist FZI/0 blocked these changes without affecting zonulin release. When exposed to luminal gliadin, intestinal biopsies from celiac patients in remission expressed a sustained luminal zonulin release and increase in intestinal permeability that was blocked by FZI/0 pretreatment. Conversely, biopsies from non-celiac patients demonstrated a limited, transient zonulin release which was paralleled by an increase in intestinal permeability that never reached the level of permeability seen in celiac disease (CD) tissues. Chronic gliadin exposure caused down-regulation of both ZO-1 and occludin gene expression.


CONCLUSIONS
Based on our results, we concluded that gliadin activates zonulin signaling irrespective of the genetic expression of autoimmunity, leading to increased intestinal permeability to macromolecules.
Drago
Sandro
S
Mucosal Biology Research Center, Center for Celiac Research and Division of Pediatric Gastroenterology and Nutrition, University of Maryland, School of Medicine, Baltimore, MD 21201, USA.
El Asmar
Ramzi
R
Di Pierro
Mariarosaria
M
Grazia Clemente
Maria
M
Tripathi
Amit
A
Sapone
Anna
A
Thakar
Manjusha
M
Iacono
Giuseppe
G
Carroccio
Antonio
A
D'Agate
Cinzia
C
Not
Tarcisio
T
Zampini
Lucia
L
Catassi
Carlo
C
Fasano
Alessio
A
D000818:Animals; D002446:Celiac Disease / Q000378:metabolism*; D002478:Cells, Cultured; D002772:Cholera Toxin / Q000037:antagonists & inhibitors / Q000378:metabolism*; D004797:Enzyme-Linked Immunosorbent Assay; D004847:Epithelial Cells / Q000187:drug effects / Q000378:metabolism; D015870:Gene Expression; D005903:Gliadin / Q000494:pharmacology*; D006242:Haptoglobins; D006801:Humans; D007413:Intestinal Mucosa / Q000187:drug effects / Q000378:metabolism*; D007421:Intestine, Small / Q000166:cytology / Q000378:metabolism*; D008565:Membrane Proteins / Q000032:analysis; D008856:Microscopy, Fluorescence; D062793:Occludin; D010539:Permeability / Q000187:drug effects; D010750:Phosphoproteins / Q000032:analysis; D011498:Protein Precursors; D051381:Rats; D019108:Tight Junctions; D062826:Zonula Occludens-1 Protein
D006242:Haptoglobins; D008565:Membrane Proteins; C568985:OCLN protein, human; D062793:Occludin; C568987:Ocln protein, rat; D010750:Phosphoproteins; D011498:Protein Precursors; C569042:TJP1 protein, human; C569044:Tjp1 protein, rat; D062826:Zonula Occludens-1 Protein; C408043:zonulin; D005903:Gliadin; D002772:Cholera Toxin