Effect of tumor necrosis factor-α and interferon-γ on intestinal P-glycoprotein expression, activity, and localization in Caco-2 cells

The P-glycoprotein (Pgp), a drug efflux pump, is expressed in intestinal epithelial cells, where it constitutes a barrier against xenobiotics. In inflammatory bowel disease, a dysregulation in the production of tumor necrosis factor (TNF)alpha and interferon (IFN)gamma, and an alteration of Pgp expression and activity have been reported. The aim of this study was to investigate the effects of TNFalpha and IFNgamma on intestinal Pgp expression, activity, and localization in Caco-2 cells grown on filters. TNFalpha, induced both a strong time-dependent diminution (-56%) of MDR1 mRNA (semiquantitative reverse transcription polymerase chain reaction) and a significant decrease of unidirectional transport of rhodamine 123 after 48 h of exposure at 10 ng/mL. By confocal laser scanning microscopy, the Pgp was mainly localized to the apical plasma membrane of both control and TNFalpha-treated cells. By contrast, IFNgamma induced up-regulation of both mRNA MDR1 and Pgp protein expression without incidence on Pgp activity. Interestingly, a colocalization of Pgp with lateral F-actin was observed. Associated with TNFalpha, IFNgamma produced neither an antagonist nor synergistic effect on Pgp activity. In conclusion, our results demonstrate an inhibitory effect of TNFalpha and no effect of IFNgamma on Pgp transport activity using rhodamine 123 as a substrate. Mechanisms of action of these cytokines remain to be studied. (C) 2004 Wiley-Liss, Inc. and the American Pharmacists Association.