Glutamate up-regulates P-glycoprotein expression in rat brain microvessel endothelial cells by an NMDA receptor-mediated mechanism.
The accumulation of glutamate in the extracellular space in the central nervous system (CNS) plays a major part in ischemic and anoxic damage. In this study, we examined the effect of glutamate on the expression and activity of P-glycoprotein (P-gp) in rat brain microvessel endothelial cells (RBMECs) making up the blood-brain barrier (BBB). The level of P-gp expression significantly increased in RBMECs after the treatment of 100 microM glutamate. At this concentration, glutamate also enhanced rat mdr1a and mdr1b mRNA levels determined by RT-PCR analysis. Flow cytometry was used to study P-gp activity by analysis of intracellular rhodamine123 (Rh123) accumulation. Overexpression of P-gp resulted in a decreased intracellular accumulation of Rh123 in RBMECs. Glutamate-induced increase of intracellular reactive oxygen species (ROS) was observed by using the 2',7'-dichlorofluorescein (2',7'-DCF) assay. MK-801, a non-competitive N-methyl-D-aspartate (NMDA) receptor antagonist, and ROS scavenger N-acetylcysteine obviously blocked ROS generation and attenuated the changes of both expression and activity of P-gp induced by glutamate in RBMECs. These data suggested that glutamate up-regulated P-gp expression in RBMECs by an NMDA receptor-mediated mechanism and that glutamate-induced generation of ROS was linked to the regulation of P-gp expression. Therefore, transport of P-gp substrates in BBB appears to be affected during ischemic and anoxic injury.
Zhu
Hao-Jie
HJ
Department of Pharmacology, China Pharmaceutical University, Nanjing, Jiangsu 210009, PR China. haojie@vip.163.com
Liu
Guo-Qing
GQ
D018435:ATP Binding Cassette Transporter, Subfamily B / Q000235:genetics / Q000378:metabolism; D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000235:genetics / Q000378:metabolism*; D018528:ATP-Binding Cassette Transporters / Q000235:genetics / Q000378:metabolism; D000818:Animals; D001812:Blood-Brain Barrier / Q000187:drug effects* / Q000378:metabolism; D002470:Cell Survival / Q000187:drug effects; D002478:Cells, Cultured; D002540:Cerebral Cortex / Q000098:blood supply; D016291:Dizocilpine Maleate / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004730:Endothelium, Vascular / Q000187:drug effects* / Q000378:metabolism; D018698:Glutamic Acid / Q000494:pharmacology*; D008833:Microcirculation / Q000187:drug effects / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D051381:Rats; D017382:Reactive Oxygen Species / Q000037:antagonists & inhibitors / Q000378:metabolism; D016194:Receptors, N-Methyl-D-Aspartate / Q000037:antagonists & inhibitors / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015854:Up-Regulation; D000097202:ATP-Binding Cassette Sub-Family B Member 4
D018435:ATP Binding Cassette Transporter, Subfamily B; D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D018528:ATP-Binding Cassette Transporters; D016291:Dizocilpine Maleate; D018698:Glutamic Acid; D012333:RNA, Messenger; D017382:Reactive Oxygen Species; D016194:Receptors, N-Methyl-D-Aspartate; D000097202:ATP-Binding Cassette Sub-Family B Member 4; C095122:multidrug resistance protein 3