EGF mediates aldosterone‐induced regulatory effects of myofibroblasts on the junctional permeability of cultured colonic epithelial cells

Abstract

Aldosterone (ALDO) regulates the growth of pericryptal myofibroblasts and the permeability of the colonic epithelium in vivo. We have examined whether these effects of ALDO can be reproduced in vitro, using the myofibroblast CCD-18Co cell line to study proliferation and the colonic epithelial cell line T84 to study the expression of tight junction proteins. The possible role of the epidermal growth factor (EGF) as mediator of myofibroblasts effects on the expression of junctional proteins was also studied. Cell proliferation was quantified from bromodeoxyuridine incorporation, the expression of tight-junction proteins β-catenin and claudin IV by Western blot and EGF expression by RT-PCR. ALDO stimulated CCD-18Co proliferation by 70% (P<0.05) and increased EGF expression (P<0.05), and both effects were prevented by Spironolactone. ALDO had no direct effects on the expression of junctional proteins by the T84 cells; however, both β-catenin and claudin IV were increased when the T84 cells were incubated with medium from myofibroblasts stimulated by ALDO (conditionated medium, CM). The CM increased 40% (P<0.05) T84 proliferation and about 30% (P<0.05) the expression of β-catenin and claudin IV and these effects were prevented by anti-EGF antibodies. These results indicate that EGF is a candidate to mediate the ALDO effects on crypt epithelial permeability. Supported by BFU2006-08410, MEC, Spain.