Regina A, Koman A, Piciotti M, El Hafny B, Center M S, Bergmann R, Couraud P O, Roux F
INSERM U26, Unité de Neuro-Pharmaco-Nutrition, Hôpital F. Widal, Paris, France.
J Neurochem. 1998 Aug;71(2):705-15. doi: 10.1046/j.1471-4159.1998.71020705.x.
Two membrane glycoproteins acting as energy-dependent efflux pumps, mdr-encoded P-glycoprotein (P-gp) and the more recently described multidrug resistance-associated protein (MRP), are known to confer cellular resistance to many cytotoxic hydrophobic drugs. In the brain, P-gp has been shown to be expressed specifically in the capillary endothelial cells forming the blood-brain barrier, but localization of MRP has not been well characterized yet. Using RT-PCR and immunoblot analysis, we have compared the expression of P-gp and Mrp1 in homogenates, isolated capillaries, primary cultured endothelial cells, and RBE4 immortalized endothelial cells from rat brain. Whereas the mdr1a P-gp-encoding mRNA was specifically detected in brain microvessels and mdr1b mRNA in brain parenchyma, mrp1 mRNA was present both in microvessels and in parenchyma. However, Mrp1 was weakly expressed in microvessels. Mrp1 expression was higher in brain parenchyma, as well as in primary cultured brain endothelial cells and in immortalized RBE4 cells. This Mrp1 overexpression in cultured brain endothelial cells was less pronounced when the cells were cocultured with astrocytes. A low Mrp activity could be demonstrated in the endothelial cell primary monocultures, because the intracellular [3H]vincristine accumulation was increased by several MRP modulators. No Mrp activity was found in the cocultures or in the RBE4 cells. We suggest that in rat brain, Mrp1, unlike P-gp, is not predominantly expressed in the blood-brain barrier endothelial cells and that Mrp1 and the mdr1b P-gp isoform may be present in other cerebral cells.
两种作为能量依赖型外排泵的膜糖蛋白，即多药耐药（mdr）编码的P-糖蛋白（P-gp）和最近发现的多药耐药相关蛋白（MRP），已知可使细胞对许多细胞毒性疏水药物产生耐药性。在大脑中，已证明P-gp特异性表达于构成血脑屏障的毛细血管内皮细胞中，但MRP的定位尚未得到很好的表征。我们使用逆转录聚合酶链反应（RT-PCR）和免疫印迹分析，比较了P-gp和Mrp1在大鼠脑匀浆、分离的毛细血管、原代培养的内皮细胞以及RBE4永生化内皮细胞中的表达。虽然mdr1a P-gp编码的mRNA在脑微血管中特异性检测到，而mdr1b mRNA在脑实质中检测到，但mrp1 mRNA在微血管和实质中均有存在。然而，Mrp1在微血管中表达较弱。Mrp1在脑实质、原代培养的脑内皮细胞和永生化的RBE4细胞中表达较高。当这些细胞与星形胶质细胞共培养时，培养的脑内皮细胞中这种Mrp1的过表达不太明显。在内皮细胞原代单培养中可证明存在低水平的Mrp活性，因为几种MRP调节剂可增加细胞内[3H]长春新碱的蓄积。在共培养物或RBE4细胞中未发现Mrp活性。我们认为，在大鼠脑中，与P-gp不同，Mrp1并非主要表达于血脑屏障内皮细胞中，且Mrp1和mdr1b P-gp亚型可能存在于其他脑细胞中。
