Laboratory of Toxicology and Pharmacology, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, North Carolina 27709, USA.
J Cereb Blood Flow Metab. 2013 Mar;33(3):381-8. doi: 10.1038/jcbfm.2012.174. Epub 2012 Nov 21.
At the blood-brain and blood-spinal cord barriers, P-glycoprotein, an ATP-driven drug efflux pump, is a major obstacle to central nervous system (CNS) pharmacotherapy. Recently, we showed that signaling through tumor necrosis factor-α (TNF-α), sphingolipids, and sphingosine-1-phosphate receptor 1 (S1PR1) rapidly and reversibly reduced basal P-glycoprotein transport activity in the rat blood-brain barrier. The present study extends those findings to the mouse blood-brain and blood-spinal cord barriers and, importantly, identifies multidrug resistance-associated protein 1 (Mrp1, Abcc1) as the transporter that mediates S1P efflux from brain and spinal cord endothelial cells. In brain and spinal cord capillaries isolated from wild-type mice, TNF-α, sphingosine, S1P, the S1PR agonist fingolimod (FTY720), and its active, phosphorylated metabolite, FTY720P, reduced P-glycoprotein transport activity; these effects were abolished by a specific S1PR1 antagonist. In brain and spinal cord capillaries isolated from Mrp1-null mice, neither TNF-α nor sphingosine nor FTY720 reduced P-glycoprotein transport activity. However, S1P and FTY720P had the same S1PR1-dependent effects on transport activity as in capillaries from wild-type mice. Thus, deletion of Mrp1 alone terminated endogenous signaling to S1PR1. These results identify Mrp1 as the transporter essential for S1P efflux from the endothelial cells and thus for inside-out S1P signaling to P-glycoprotein at the blood-brain and blood-spinal cord barriers.
在血脑和血脊髓屏障中，P 糖蛋白是一种 ATP 驱动的药物外排泵，是中枢神经系统（CNS）药物治疗的主要障碍。最近，我们发现肿瘤坏死因子-α（TNF-α）、神经鞘脂和鞘氨醇-1-磷酸受体 1（S1PR1）的信号转导可迅速和可逆地降低大鼠血脑屏障中基础 P 糖蛋白转运活性。本研究将这些发现扩展到小鼠血脑和血脊髓屏障，并重要的是，确定多药耐药相关蛋白 1（Mrp1，Abcc1）为介导 S1P 从脑和脊髓内皮细胞流出的转运体。在从野生型小鼠分离的脑和脊髓毛细血管中，TNF-α、鞘氨醇、S1P、S1PR 激动剂 fingolimod（FTY720）及其活性磷酸化代谢物 FTY720P 降低 P 糖蛋白转运活性；这些作用被特定的 S1PR1 拮抗剂所阻断。在从 Mrp1 敲除小鼠分离的脑和脊髓毛细血管中，TNF-α、鞘氨醇或 FTY720 均未降低 P 糖蛋白转运活性。然而，S1P 和 FTY720P 对转运活性的作用与野生型小鼠的毛细血管相同，即依赖于 S1PR1。因此，单独缺失 Mrp1 即可终止对 S1PR1 的内源性信号转导。这些结果确定 Mrp1 为 S1P 从内皮细胞流出所必需的转运体，也是血脑和血脊髓屏障中 S1P 信号对 P 糖蛋白的外向信号的必需。
