Activation of β-catenin signalling by GSK-3 inhibition increases p-glycoprotein expression in brain endothelial cells

Lim, Joseph C., Kania, Katarzyna D., Wijesuriya, Hasini, Chawla, Sangeeta, Sethi, Jaswinder K., Pulaski, Lukasz, Romero, Ignacio A., Couraud, Pierre O., Weksler, Babette B., Hladky, Stephen B. and Barrand, Margery A. (2008) Activation of β-catenin signalling by GSK-3 inhibition increases p-glycoprotein expression in brain endothelial cells. Journal of Neurochemistry, 106 (4), 1855-1865. (doi:10.1111/j.1471-4159.2008.05537.x).

Abstract

This study investigates involvement of β-catenin signalling in regulation of p-glycoprotein (p-gp) expression in endothelial cells derived from brain vasculature. Pharmacological interventions that enhance or that block β-catenin signalling were applied to primary rat brain endothelial cells and to immortalized human brain endothelial cells, hCMEC/D3, nuclear translocation of β-catenin being determined by immunocytochemistry and by western blot analysis to confirm effectiveness of the manipulations. Using the specific glycogen synthase kinase-3 (GSK-3) inhibitor 6-bromoindirubin-3′- oxime enhanced β-catenin and increased p-gp expression including activating the MDR1 promoter. These increases were accompanied by increases in p-gp-mediated efflux capability as observed from alterations in intracellular fluorescent calcein accumulation detected by flow cytometry. Similar increases in p-gp expression were noted with other GSK-3 inhibitors, i.e. 1-azakenpaullone or LiCl. Application of Wnt agonist [2-amino-4-(3,4-(methylenedioxy) benzylamino)-6-(3-methoxyphenyl)pyrimidine] also enhanced β-catenin and increased transcript and protein levels of p-gp. By contrast, down-regulating the pathway using Dickkopf-1 or quercetin decreased p-gp expression. Similar changes were observed with multidrug resistance protein 4 and breast cancer resistance protein, both known to be present at the blood-brain barrier. These results suggest that regulation of p-gp and other multidrug efflux transporters in brain vasculature can be influenced by β-catenin signalling.

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Contributors

Author: Jaswinder K. Sethi

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