Signalling pathways influencing basal and H(2)O(2)-induced P-glycoprotein expression in endothelial cells derived from the blood-brain barrier.
The drug transporter, P-glycoprotein (P-gp) on brain microvessel endothelium, influences movement of lipophilic substances in and out of the brain. Pathways regulating P-gp expression, both basal and hydrogen peroxide (H2O2)-induced, are here examined in primary cultured rat brain endothelial cells. Activation of extracellular-signal regulated kinases (ERK1/2), protein kinase C (PKC), the p46 isoform of stress-activated protein kinase (SAPK) and its downstream transcription factor, c-Jun, occurred in a time- and concentration-dependent manner following exposure of cells to H2O2 with concomitant increases in P-gp expression. Blockade of ERK activation with U0126, of PKC with Gö6976 and of SAPK with SP600125 decreased basal P-gp but did not abolish the H2O2-induced increase. Blockade of Akt with PI3-kinase inhibitor, LY294002, lowered basal P-gp and prevented the H2O2-induced increase. Inhibition of nuclear factor-kappaB (NF-kappaB), either by blocking dissociation from its inhibitory factor, IkappaB, with MG132 or its nuclear translocation with SN50 enhanced basal P-gp, obscuring the H2O2-induced increase. H2O2 itself produced no detectable activation of IkappaB, but inhibited that induced by 5 ng/mL tumour necrosis factor-alpha (TNF-alpha). P-gp expression may involve positive inputs from ERK1/2, SAPK, Akt and PKC and inhibitory influences of NF-kappaB. By depressing NF-kappaB signalling, H2O2 may still augment P-gp expression when ERK1/2, PKC or SAPK are inhibited.
Nwaozuzu
Osi M
OM
Department of Pharmacology, University of Cambridge, Tennis Court Road, Cambridge, UK. omn21@cam.ac.uk
Sellers
Lynda A
LA
Barrand
Margery A
MA
D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000096:biosynthesis*; D000818:Animals; D001812:Blood-Brain Barrier / Q000166:cytology / Q000378:metabolism*; D001921:Brain / Q000098:blood supply; D002478:Cells, Cultured; D004730:Endothelium, Vascular / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D015870:Gene Expression / Q000187:drug effects; D006861:Hydrogen Peroxide / Q000494:pharmacology*; D020928:Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D016328:NF-kappa B / Q000037:antagonists & inhibitors / Q000378:metabolism; D016877:Oxidants / Q000494:pharmacology; D010455:Peptides / Q000494:pharmacology; D000081082:Phosphoinositide-3 Kinase Inhibitors; D010766:Phosphorylation / Q000187:drug effects; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt; D016755:Proto-Oncogene Proteins c-jun / Q000378:metabolism; D051381:Rats; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology*
D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D004791:Enzyme Inhibitors; D016328:NF-kappa B; D016877:Oxidants; D010455:Peptides; D000081082:Phosphoinositide-3 Kinase Inhibitors; D011518:Proto-Oncogene Proteins; D016755:Proto-Oncogene Proteins c-jun; C118258:SN50 peptide; D006861:Hydrogen Peroxide; C494920:Akt1 protein, rat; D017346:Protein Serine-Threonine Kinases; D051057:Proto-Oncogene Proteins c-akt; D011493:Protein Kinase C; D020928:Mitogen-Activated Protein Kinases