Targeting blood-brain barrier sphingolipid signaling reduces basal P-glycoprotein activity and improves drug delivery to the brain

Abstract

P-glycoprotein, an ATP-driven drug efflux pump, is a major obstacle to the delivery of small-molecule drugs across the blood-brain barrier and into the CNS. Here we test a unique signaling-based strategy to overcome this obstacle. We used a confocal microscopy-based assay with isolated rat brain capillaries to map a signaling pathway that within minutes abolishes P-glycoprotein transport activity without altering transporter protein expression or tight junction permeability. This pathway encompasses elements of proinflammatory-(TNF-α) and sphingolipid-based signaling. Critical to this pathway was signaling through sphingosine-1-phosphate receptor 1 (S1PR1). In brain capillaries, S1P acted through S1PR1 to rapidly and reversibly reduce P-glycoprotein transport activity. Sphingosine reduced transport by a sphingosine kinase-dependent mechanism. Importantly, fingolimod (FTY720), a S1P analog recently approved for treatment of multiple sclerosis, also rapidly reduced P-glycoprotein activity; similar effects were found with the active, phosphorylated metabolite (FTY720P). We validated these findings in vivo using in situ brain perfusion in rats. Administration of S1P, FTY720, or FTY729P increased brain uptake of three radiolabeled P-glycoprotein substrates, C-sucrose accumulation, was not altered. Therefore, targeting signaling through S1PR1 at the blood-brain barrier with the sphingolipid-based drugs, FTY720 or FTY720P, can rapidly and reversibly reduce basal P-glycoprotein activity and thus improve delivery of small-molecule therapeutics to the brain.ABC transporters | chemotherapy | brain endothelium | ABCB1 | breast cancer related protein | multidrug resistance-associated protein

Size-selective opening of the blood–brain barrier by targeting endothelial sphingosine 1–phosphate receptor 1

“…Notably, it is reported that S1P 1 -agonism reduces P-glycoprotein (P-gp) transport activity in rodent in situ perfusion experiments (49). In that study, FTY720 was shown to increase brain accumulation of the drugs by its agonistic activity.…”

Upregulation of ABC transporters contributes to chemoresistance of sphingosine 1-phosphate lyase-deficient fibroblasts

“…Furthermore, extracellular S1P stimulated Abcb1 transport activity via S1P 1 and S1P 3 receptors, and as data not shown, it was mentioned that exogenous S1P did not modulate Abcb1 expression, suggesting differential activities of intracellular SphK1 and extracellular S1P ( 27 ). On the other hand, Cannon et al ( 33 ) and Miller ( 34 ) showed recently that exogenous S1P decreased Abcb1 activity via S1P 1 in isolated mouse brain and spinal cord capillaries, as well as in isolated killifi sh renal proximal tubules, respectively. Because this effect was rapid and reversible, it did not rely on transcriptional regulation, but either on alteration of the transporter turnover number or on traffi cking of the transport protein away from the exterior surface of the luminal plasma membrane ( 33 ).…”

“…On the other hand, Cannon et al ( 33 ) and Miller ( 34 ) showed recently that exogenous S1P decreased Abcb1 activity via S1P 1 in isolated mouse brain and spinal cord capillaries, as well as in isolated killifi sh renal proximal tubules, respectively. Because this effect was rapid and reversible, it did not rely on transcriptional regulation, but either on alteration of the transporter turnover number or on traffi cking of the transport protein away from the exterior surface of the luminal plasma membrane ( 33 ). In line with this activity, exogenous cell permeable C 2 -ceramide was able to increase cholesterol effl ux to apolipoprotein A-I by increasing the cell surface presence of Abca1 ( 35 ).…”

Sphingolipid Signaling Reduces Basal P-Glycoprotein Activity in Renal Proximal Tubule

“…For many drugs, it is a major determinant of drug pharmacokinetics, driving excretion from liver, gut, and kidney and exclusion from tumors and the CNS. We recently found that basal P-glycoprotein transport activity (but not expression) at the blood-brain and blood-spinal cord barriers could be rapidly and reversibly reduced through sphingolipid signaling (Cannon et al, 2012;Cartwright et al, 2013). Transport activity of other ABC transporters is not affected.…”