Neuroinflammation activates Mdr1b efflux transport through NFkappaB: promoter analysis in BBB endothelia.
OBJECTIVE
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.


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 NFkappaB nuclear translocation; and (3) the NFkappaB 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 NFkappaB to nuclear DNA from RBE4 cells was shown by electrophoretic mobility shift assay and chromatin immunoprecipitation assays.


CONCLUSIONS
NFkappaB mediates TNF-induced upregulation of mdr1b promoter activity, illustrating how inflammation activates BBB efflux transport.
Yu
Chuanhui
C
Pennington Biomedical Research Center, Baton Rouge, LA, USA.
Argyropoulos
George
G
Zhang
Yan
Y
Kastin
Abba J
AJ
Hsuchou
Hung
H
Pan
Weihong
W
D018435:ATP Binding Cassette Transporter, Subfamily B / Q000235:genetics* / Q000378:metabolism*; D000818:Animals; D001483:Base Sequence; D001665:Binding Sites; D001812:Blood-Brain Barrier / Q000187:drug effects / Q000378:metabolism / Q000473:pathology*; D002467:Cell Nucleus / Q000187:drug effects / Q000378:metabolism; D004247:DNA / Q000378:metabolism; D004727:Endothelium / Q000187:drug effects / Q000378:metabolism / Q000473:pathology*; D005786:Gene Expression Regulation / Q000187:drug effects; D017930:Genes, Reporter; D007249:Inflammation / Q000235:genetics*; D008156:Luciferases / Q000378:metabolism; D008969:Molecular Sequence Data; D016328:NF-kappa B / Q000378:metabolism*; D017354:Point Mutation; D011401:Promoter Regions, Genetic; D011485:Protein Binding / Q000187:drug effects; D021381:Protein Transport / Q000187:drug effects; D051381:Rats; D017384:Sequence Deletion; D051996:Transcription Factor RelA / Q000378:metabolism; D014158:Transcription, Genetic / Q000187:drug effects; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism; D000097202:ATP-Binding Cassette Sub-Family B Member 4
D018435:ATP Binding Cassette Transporter, Subfamily B; D004247:DNA; D008156:Luciferases; D016328:NF-kappa B; D051996:Transcription Factor RelA; D014409:Tumor Necrosis Factor-alpha; D016159:Tumor Suppressor Protein p53; D000097202:ATP-Binding Cassette Sub-Family B Member 4