Ceramide 1-Phosphate Increases P-Glycoprotein Transport Activity at the Blood-Brain Barrier via Prostaglandin E2 Signaling.

P-glycoprotein, an ATP-driven efflux pump, regulates permeability of the blood-brain barrier (BBB). Sphingolipids, endogenous to brain tissue, influence inflammatory responses and cell survival in vitro. Our laboratory has previously shown that sphingolipid signaling by sphingosine 1-phosphate decreases basal P-glycoprotein transport activity. Here, we investigated the potential for another sphingolipid, ceramide 1-phosphate (C1P), to modulate efflux pumps at the BBB. Using confocal microscopy and measuring luminal accumulation of fluorescent substrates, we assessed the transport activity of several efflux pumps in isolated rat brain capillaries. C1P treatment induced P-glycoprotein transport activity in brain capillaries rapidly and reversibly. In contrast, C1P did not affect transport activity of two other major efflux transporters, multidrug resistance protein 2 and breast cancer resistance protein. C1P induced P-glycoprotein transport activity without changing transporter protein expression. Inhibition of the key signaling components in the cyclooxygenase-2 (COX-2)/prostaglandin E2 signaling cascade (phospholipase A2, COX-2, multidrug resistance protein 4, and G-protein-coupled prostaglandin E2 receptors 1 and 2), abolished P-glycoprotein induction by C1P. We show that COX-2 and prostaglandin E2 are required for C1P-mediated increases in P-glycoprotein activity independent of transporter protein expression. This work describes how C1P activates a signaling cascade to dynamically regulate P-glycoprotein transport at the BBB and offers potential clinical targets to modulate neuroprotection and drug delivery to the CNS.

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