Brought to you by Portland Press Ltd.
Published on behalf of the International Federation for Cell Biology
Cancer Cell death Cell cycle Cytoskeleton Exo/endocytosis Differentiation Division Organelles Signalling Stem cells Trafficking
Cell Biology International (2006) 30, 101–113 (Printed in Great Britain)
Modulation of the epithelial barrier by dexamethasone and prolactin in cultured Madin–Darby canine kidney (MDCK) cells
E.B.M.I. Peixoto and C.B. Collares‑Buzato*
Department of Histology and Embryology, Institute of Biology, State University of Campinas (UNICAMP), Campinas, CP 6109, R. Charles Darwin s/n, 13083-970 Campinas, SP, Brazil


Abstract

Glucocorticoids and prolactin (PRL) have a direct effect on the formation and maintenance of tight junctions (TJs) in cultured endothelial and mammary gland epithelial cells. In this work, we investigated the effect of a synthetic glucocorticoid dexamethasone (DEX) and PRL on the paracellular barrier function in MDCK renal epithelial cells. DEX (4μM)+PRL (2μg/ml) and DEX alone increased significantly the transepithelial electrical resistance after chronic treatment (4 days) of confluent MDCK monolayers or after 24h treatment of subconfluent monolayers. Immunoblotting and immunocytochemistry revealed no changes in the expression and distribution of TJ-associated proteins occludin, ZO-1 and claudin-1 in confluent monolayers after hormone addition. However, a marked increase in junctional content for occludin and ZO-1 with no changes in their total expression was observed in subconfluent MDCK monolayers 24h exposed to DEX or DEX+PRL. No change in cell proliferation/growth was detected at subconfluent conditions following hormone treatment. An increase in the total number of viable cells was observed only in confluent MDCK monolayers after exposure to DEX+PRL suggesting that the main effect of these hormones on already established barrier may be associated with the inhibition of cell death. In conclusion, our data suggest that these hormones (specially dexamethasone) have an effect on TJ structure and function only during the formation of MDCK epithelial barrier by probably modulating the localization, stability or assembly of TJ proteins to membrane sites of intercellular contact.


Key words: Epithelial barrier, Tight junction, Dexamethasone, Prolactin, MDCK cell line, Kidney, Junctional proteins.

*Corresponding author. Tel.: +55 19 3788 6246; fax: +55 19 3289 3124.


Received 18 August 2005; accepted 22 August 2005

doi:10.1016/j.cellbi.2005.08.004


ISSN Print: 1065-6995
ISSN Electronic: 1095-8355
Published by Portland Press Limited on behalf of the International Federation for Cell Biology (IFCB)