@article {Bauer667, author = {Bj{\"o}rn Bauer and Anika M. S. Hartz and David S. Miller}, title = {Tumor Necrosis Factor α and Endothelin-1 Increase P-Glycoprotein Expression and Transport Activity at the Blood-Brain Barrier}, volume = {71}, number = {3}, pages = {667--675}, year = {2007}, doi = {10.1124/mol.106.029512}, publisher = {American Society for Pharmacology and Experimental Therapeutics}, abstract = {The ATP-driven drug efflux pump, P-glycoprotein, is a critical and selective element of the blood-brain barrier and a primary impediment to pharmacotherapy of central nervous system (CNS) disorders. Thus, an understanding of how P-glycoprotein function is regulated has the potential to improve CNS therapy. We recently demonstrated rapid (minutes) and reversible inactivation of P-glycoprotein in rat brain capillaries signaled through tumor necrosis factor-α (TNF-α) and endothelin-1 (ET-1), components of the brain{\textquoteright}s innate immune response. In this study, we examined the longer-term consequences of continuous exposure of rat brain capillaries to low levels of TNF-α and ET-1. Exposing brain capillaries to TNF-α or ET-1 caused a rapid decrease in P-glycoprotein transport activity with no change in transporter protein expression. This was followed by a 2- to 3-h plateau at the low activity level and then by a sharp increase in both transport activity and protein expression. After 6 h, transport activity and transporter protein expression was double that of control samples. TNF-α signaled through TNF-R1, which in turn caused ET release and action through ETA and ETB receptors, nitric-oxide synthase, protein kinase C and nuclear factor-κB (NF-κB) and finally increased P-glycoprotein expression and transport activity. Assuming similar effects occur in vivo, the present results imply a tightening of the selective blood-brain barrier with chronic inflammation and thus reduced efficacy of CNS-acting drugs that are P-glycoprotein substrates. Moreover, involvement of NF-κB raises the possibility that other effectors acting through this transcription factor may have similar effects on this key blood-brain barrier transporter. The American Society for Pharmacology and Experimental Therapeutics}, issn = {0026-895X}, URL = {https://molpharm.aspetjournals.org/content/71/3/667}, eprint = {https://molpharm.aspetjournals.org/content/71/3/667.full.pdf}, journal = {Molecular Pharmacology} }