Neuroinflammation Activates Mdr1b Efflux Transport Through NFκB: Promoter Analysis in BBB Endothelia

Abstract

Background/aims: Although it is known that drug delivery across the blood-brain barrier (BBB) may be hampered by efflux transport activity of the multidrug resistance (mdr) gene product P-glycoprotein, it is not clear how inflammation regulates efflux transporters. In rat brain endothelial (RBE4) cells of BBB origin, the proinflammatory cytokine TNF mainly induced transcriptional upregulation of mdr1b, and to a lesser extent mdr1a, resulting in greater efflux of the substrates. This study further determines the mechanisms by which TNF activates mdr1b promoter activity. Methods/Results: Luciferase reporter assays and DNA binding studies show that (1) maximal basal promoter activity was conferred by a 476 bp sequence upstream to the mdr1b transcriptional initiation site; (2) TNF induced upregulation of promoter activity by NFκB nuclear translocation; and (3) the NFκB binding site of the mdr1b promoter was solely responsible for basal and TNF-activated gene transcription, whereas the p53 binding site was not involved. Binding of the p65 subunit of NFκB to nuclear DNA from RBE4 cells was shown by electrophoretic mobility shift assay and chromatin immunoprecipitation assays. Conclusion: NFκB mediates TNF-induced upregulation of mdr1b promoter activity, illustrating how inflammation activates BBB efflux transport.

Rosiglitazone Monotherapy in Mild-to-Moderate Alzheimer’s Disease: Results from a Randomized, Double-Blind, Placebo-Controlled Phase III Study

“…Another limitation may be that effective levels of RSG may not be achieved in target tissues in the brain since RSG is a substrate for the multidrug-resistant gene product permeability glycoprotein [22,58] . In addition, evidence suggests that the permeability glycoprotein efflux transporter is upregulated in the presence of inflammatory cytokines [59] , raising the possibility that neuroinflammation common in AD could limit RSG exposure and obviate its potential benefit [60] . A PPAR-␥ with high penetration of the blood-brain barrier should be investigated to further evaluate the role of this class of agents in AD.…”

Targeting Prostaglandin E2 EP1 Receptors Prevents Seizure-Associated P-glycoprotein Up-Regulation

“…Further research is necessary regarding the downstream events that mediate the effects of EP1 receptor activation on P-glycoprotein expression. The transcription factor NF-B represents a probable candidate as EP receptor signaling can result in activation of NF-B, and NF-B in turn can affect P-glycoprotein expression rates (Yu et al, 2008).…”

NFĸB is an Unexpected Major Mediator of Interleukin-15 Signaling in Cerebral Endothelia

“…Dimerization and nuclear translocation are tightly controlled by a family of inhibitory molecules (I B) that keep NF B in the cytoplasm [10]. TNF induces NF B through a signaling cascade that includes binding to the TNF receptor (TNFR), binding of TNFR associated factor (TRAF)-2, activation of I B kinase (IKK), phosphorylation and proteasomal degradation of I B, dimerization and nuclear translocation of NF B, and activation of gene expression by binding to cognate DNA binding sites [11,12].…”