TFF3-peptide increases transepithelial resistance in epithelial cells by modulating claudin-1 and -2 expression Dirk Meyer zum Bu ¨ schenfelde, Rudolf Tauber, Otmar Huber * Department of Laboratory Medicine and Pathobiochemistry, Charite ´ —Campus Benjamin Franklin, Hindenburgdamm 30, 12200 Berlin, Germany peptides 27 (2006) 3383–3390 article info Article history: Received 6 March 2006 Received in revised form 29 August 2006 Accepted 29 August 2006 Published on line 2 October 2006 Keywords: Claudin Occludin TFF3 Tight junction Epithelial barrier Abbreviations: AOX1, alcohol oxidase 1 BCA, bicinchoninic acid CIP, calf intestinal phosphatase CLDN-1, claudin-1 CLDN-2, claudin-2 ERK, extracellular signal-regulated kinase JAM, junctional adhesion molecule OCLN, occludin PBS, phosphate-buffered saline PDZ, PSD95/Dlg/ZO-1 PVDF, polyvinylidene-difluoride RT-PCR, reverse transcription- polymerase chain reaction TER, transepithelial resistance TFF, trefoil factor family ZO-1, zonula occludens protein 1 ZO-2, zonula occludens protein 2 abstract TFF3 plays an important role in the protection and repair of the gastrointestinal mucosa. The molecular mechanisms of TFF function, however, are still largely unknown. Increasing evidence indicates that apart from stabilizing mucosal mucins TFF3 induces cellular signals that modulate cell–cell junctions of epithelia. In transfected HT29/B6 and MDCK cells stably expressing FLAG-tagged human TFF3 we have recently shown that TFF3 down-regulates E- cadherin, impairs the function of adherens junctions and thus facilitates cell migration in wounded epithelial cell layers. Here we investigate TFF3-induced effects on the composition and function of tight junctions in these cells. TFF3 increased the cellular level of tightening claudin-1 and decreased the amount of claudin-2 known to form cation-selective channels. Expression of ZO-1, ZO-2 and occludin was not altered. The change in claudin-1 and -2 expression in TFF3-expressing HT29/B6 cells was accompanied by an increase in the transepithelial resistance in confluent monolayers of these cells. These data suggest that TFF3 plays a role in the regulation of intestinal barrier function by altering the claudin composition within tight junctions thus decreasing paracellular permeability of the intest- inal mucosa. # 2006 Elsevier Inc. All rights reserved. * Corresponding author at: Zentralinstitut fu ¨ r Laboratoriumsmedizin und Pathobiochemie, Charite ´ —Campus Benjamin Franklin, Hindenburgdamm 30, 12200 Berlin, Germany. Tel.: +49 30 8445 2525; fax: +49 30 8445 4152. E-mail address: otmar.huber@charite.de (O. Huber). available at www.sciencedirect.com journal homepage: www.elsevier.com/locate/peptides 0196-9781/$ – see front matter # 2006 Elsevier Inc. All rights reserved. doi:10.1016/j.peptides.2006.08.020