The Cross-Talk between Canonical and Non-Canonical Wnt-Dependent Pathways Regulates P-Glycoprotein Expression in Human Blood–Brain Barrier Cells

Abstract

In this work, we investigate if and how transducers of the 'canonical' Wnt pathway, i.e., Wnt/glycogen synthase kinase 3 (GSK3)/bcatenin, and transducers of the 'non-canonical' Wnt pathway, i.e., Wnt/RhoA/RhoA kinase (RhoAK), cooperate to control the expression of P-glycoprotein (Pgp) in blood-brain barrier (BBB) cells. By analyzing human primary brain microvascular endothelial cells constitutively activated for RhoA, silenced for RhoA or treated with the RhoAK inhibitor Y27632, we found that RhoAK phosphorylated and activated the protein tyrosine phosphatase 1B (PTP1B), which dephosphorylated tyrosine 216 of GSK3, decreasing the GSK3-mediated inhibition of b-catenin. By contrast, the inhibition of RhoA/RhoAK axis prevented the activation of PTP1B, enhanced the GSK3-induced phosphorylation and ubiquitination of b-catenin, and reduced the b-catenin-driven transcription of Pgp. The RhoAK inhibition increased the delivery of Pgp substrates like doxorubicin across the BBB and improved the doxorubicin efficacy against glioblastoma cells co-cultured under a BBB monolayer. Our data demonstrate that in human BBB cells the expression of Pgp is controlled by a cross-talk between canonical and non-canonical Wnt pathways. The disruption of this cross-talk, e.g., by inhibiting RhoAK, downregulates Pgp and increases the delivery of Pgp substrates across the BBB.

Regulation of ABC Transporters Blood–Brain Barrier

“…One wonders how ABC transporter function is modulated through interactions with other neurovascular unit elements. Certainly, recent studies implicate both canonical and noncanonical Wnt signaling in the regulation of P-glycoprotein expression (Pinzon-Daza et al, 2014). Such signaling is one component of the neurovascular unit's conversations.…”

Therapeutic strategies to improve drug delivery across the blood-brain barrier

“…88 The authors found that downregulation of β-catenin led to a decrease in P-gp expression. It was also shown in vitro that the inhibition of β-catenin enhanced delivery of doxorubicin, a P-gp substrate, across a BBB epithelial monolayer against glioblastoma cells.…”

Regulation of ABC efflux transporters at blood-brain barrier in health and neurological disorders

“…Consistent with this finding, recent study demonstrated that the expression of P-gp in human BBB cells is controlled by a cross-talk between the Wnt/GSK3 canonical pathway and the Wnt/RhoA/RhoAK non-canonical pathway. Increased activity of Wnt/GSK3 canonical pathway reduced GSK3-mediated phosphorylation and ubiquitination of β-catenin, decreasing its proteasomal degradation, enhances its nuclear translocation, and increases P-gp expression (Pinzon-Daza et al, 2014). Similarly, RhoA activation through non-canonical Wnt3/RhoA/RhoAK pathway reduced the activity of GSK3.…”