TNF activates P-glycoprotein in cerebral microvascular endothelial cells

Multidrug resistance proteins (MDRs, including P-glycoproteins) are efflux pumps that serve important biological functions but hinder successful drug delivery to the CNS. Many chemotherapeutic agents, anti-epileptics, anti-HIV drugs, and opiates are substrates for MDRs. Therefore, understanding the regulation of MDRs in the endothelial cells composing the blood-brain barrier has therapeutic implications.

We used microarray, real time RT-PCR, Western blotting, and uptake of vinblastine by RBE4 cerebral endothelial cells to test the effects of tumor necrosis factor alpha (TNF) on the expression and functions of P-glycoprotein (MDR1).

The proinflammatory cytokine TNF specifically induced the expression and enhanced the function of MDR1 in RBE4 cells. The persistent upregulation of MDR1 mRNA was shown by cDNA microarray at 6, 12, and 24 h after TNF treatment. This was confirmed by real-time RT-PCR between 2 and 24 h. MDR1 protein expression was increased 6 to 24 h after TNF treatment and resulted in a significant reduction in the cellular uptake of (3)H-vinblastine.

The drug efflux transporter in cerebral endothelial cells can be upregulated by TNF. This suggests that adjunctive anti-TNF treatment has novel therapeutic potential in conditions such as brain cancer, epilepsy, neuroAIDS, and chronic pain.