Rapid Modulation of P-Glycoprotein-Mediated Transport at the Blood-Brain Barrier by Tumor Necrosis Factor-α and Lipopolysaccharide

Abstract

At the blood-brain barrier, P-glycoprotein, an ATP-driven drug efflux pump, selectively limits drug access to the brain parenchyma, impeding pharmacotherapy of a number of central nervous system (CNS) disorders. We previously used confocal imaging to demonstrate in isolated rat brain capillaries that endothelin-1 (ET-1), acting through an ET B receptor, NO synthase, and protein kinase C, rapidly and reversibly reduces P-glycoprotein transport function. In this study, we define a link between the brain's innate immune response and functional regulation of P-glycoprotein. We show that exposing brain capillaries to the inflammatory cytokine tumor necrosis factor-␣ (TNF-␣), activated a TNF-R1 receptor, released ET-1, activated ET B receptor signaling, and essentially abolished P-glycoprotein-mediated transport. Bacterial lipopolysaccharide, a potent activator of the brain's innate immune response, reduced Pglycoprotein activity through TNF-␣ release, ET-1 release, and ET B receptor signaling. TNF-␣ and LPS effects had a rapid onset (minutes), were reversible, and did not involve changes in tight junctional permeability. These findings define a signaling pathway through which P-glycoprotein activity is acutely modulated. They show that this key component of the selective/ active blood-brain barrier is an early target of cytokine signaling during the innate immune response and suggest ways to manipulate the barrier for improved CNS pharmacotherapy.

Enhanced chemotherapy delivery by intraarterial infusion and blood‐brain barrier disruption in the treatment of cerebral metastasis

“…19 The procedure would also allow a transient decrease in the function of the Pgp pump, thereby allowing for improved delivery of chemotherapy agents that are also known substrate of this pump. 22 Even if the barrier is breached in the tumoral tissue, its integrity remains virtually intact at the periphery of the tumor. 19 Sato et al 20 elegantly demonstrated in vivo that the mannitol infusion increases the permeability of the barrier at the edge of the tumor, in the peritumoral area.…”

Activation of PKC Isoform βI at the Blood–Brain Barrier Rapidly Decreases P-Glycoprotein Activity and Enhances Drug Delivery to the Brain

“…Procedures are described in detail in the studies by Bauer et al (2007) and Hartz et al (2006). Briefly, freshly isolated brain capillaries in PBS buffer were transferred into Teflon microscope chambers with glass coverslip bottoms.…”

“…Tumor necrosis factor-a-induced loss of P-glycoprotein activity is signaled through TNF-a receptor 1, endothelin-1 (ET-1), ET B receptor, nitric oxide synthase, and protein kinase C (PKC). The effect of TNF-a or ET-1 is mimicked by treatment with 10 nmol/L PMA (phorbol-12-myristate-13-acetate), and is prevented by treatment with 10 nmol/L BIM-1 (bis-indolylmaleimide), indicating involvement of a classic PKC isoform (a/b I/II /g) (Hartz et al, 2004(Hartz et al, , 2006.…”

“…Studies from this laboratory have shown that exposing isolated rat brain capillaries to tumor necrosis factor (TNF)-a rapidly and reversibly reduces P-glycoprotein transport activity (Hartz et al, 2006). Tumor necrosis factor-a-induced loss of P-glycoprotein activity is signaled through TNF-a receptor 1, endothelin-1 (ET-1), ET B receptor, nitric oxide synthase, and protein kinase C (PKC).…”

“…We previously suggested an alternative strategy for improving delivery of P-glycoprotein substrates to the brain: targeting signaling pathways that maintain transporter activity (Hartz et al, 2004(Hartz et al, , 2006. Studies from this laboratory have shown that exposing isolated rat brain capillaries to tumor necrosis factor (TNF)-a rapidly and reversibly reduces P-glycoprotein transport activity (Hartz et al, 2006).…”