title: Roles of NMDARs in maintenance of the mouse cerebrovascular endothelial cell-constructed tight junction barrier.
abstract: Glutamate can activate NMDA receptor (NMDAR) and subsequently induces excitotoxic neuron loss. However, roles of NMDARs in the blood-brain barrier (BBB) are little known. This study used a mouse cerebrovascular endothelial cell (MCEC) model to evaluate the effects of NMDAR activation on maintenance of the BBB and its possible mechanisms. Analysis of confocal microscopy revealed expressions of NMDAR subunits, GluN1 and GLUN2B, in MCECs. An immunoblot assay further showed the existence of GluN1 in plasma membranes of MCECs. In brain tissues, a confocal microscopic analysis demonstrated co-localization of GluN1 and factor VIII, a biomarker of MCECs. In addition, GluN1 mRNA was detected in MCECs and the brain. Functional assays showed that exposure of MCECs to NMDA increased calcium influx. Separately, NMDA suppressed transendothelial electrical resistance values, levels of occludin, and occludin tight junctions. As to the mechanism, NMDA stimulated sequential phosphorylations of extracellular signal-regulated kinase (ERK)1/2 and mitogen-activated ERK (MEK)1. Interestingly, amounts of matrix metalloproteinase (MMP)2 and MMP9 in MCECs were augmented by NMDA. The NMDA-induced alterations in ERK1/2 phosphorylation and occludin levels were reversed by pretreatment with PD98059, a MEK inhibitor, and MK-801, a NMDAR antagonist, respectively. Therefore, this study shows the functional presence of NMDARs in MCECs, and NMDAR activation can disrupt the MCEC-constructed tight junction barrier via activation of the MEK1/2-ERK1/2 signaling pathway and upregulation of MMP2/9 expressions.
authors.affiliation: Graduate Institute of Clinical Medicine, College of Medicine, Taipei Medical University, Taipei, Taiwan; Department of Anesthesiology, Wan Fang Hospital, Taipei Medical University, Taipei, Taiwan.
authors.forename: Jui-Tai
authors.initials: JT
authors.lastname: Chen
authors.affiliation: Department of Anesthesiology, Wan Fang Hospital, Taipei Medical University, Taipei, Taiwan.
authors.forename: Tyng-Guey
authors.initials: TG
authors.lastname: Chen
authors.affiliation: Department of Anesthesiology, Wan Fang Hospital, Taipei Medical University, Taipei, Taiwan.
authors.forename: Yung-Chia
authors.initials: YC
authors.lastname: Chang
authors.affiliation: Graduate Institute of Clinical Medicine, College of Medicine, Taipei Medical University, Taipei, Taiwan.
authors.forename: Cheng-Yu
authors.initials: CY
authors.lastname: Chen
authors.affiliation: Comprehensive Cancer Center and Graduate Institute of Medical Sciences, College of Medicine, Taipei Medical University, Taipei, Taiwan; Brain Disease Research Center, Wan-Fang Hospital, Taipei Medical University, Taipei, Taiwan; Anesthetics Toxicology Research Center, Taipei Medical University Hospital, Taipei Medical University, Taipei 110, Taiwan. Electronic address: rmchen@tmu.edu.tw.
authors.forename: Ruei-Ming
authors.initials: RM
authors.lastname: Chen
mesh_terms: D000818:Animals; D001812:Blood-Brain Barrier / Q000187:drug effects; D001923:Brain Chemistry / Q000187:drug effects; D002560:Cerebrovascular Circulation; D016291:Dizocilpine Maleate / Q000494:pharmacology; D042783:Endothelial Cells / Q000187:drug effects*; D004730:Endothelium, Vascular / Q000166:cytology / Q000187:drug effects*; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology; D005169:Factor VIII / Q000032:analysis; D020935:MAP Kinase Signaling System / Q000187:drug effects; D008297:Male; D051379:Mice; D008813:Mice, Inbred ICR; D009419:Nerve Tissue Proteins / Q000096:biosynthesis / Q000235:genetics; D062793:Occludin / Q000096:biosynthesis; D016194:Receptors, N-Methyl-D-Aspartate / Q000096:biosynthesis / Q000187:drug effects* / Q000235:genetics; D019108:Tight Junctions / Q000187:drug effects*
chemical_list: D018691:Excitatory Amino Acid Antagonists; C121673:Gprin1 protein, mouse; C121001:NR2B NMDA receptor; D009419:Nerve Tissue Proteins; D062793:Occludin; D016194:Receptors, N-Methyl-D-Aspartate; D016291:Dizocilpine Maleate; D005169:Factor VIII
keywords: BBB; Cerebrovascular endothelial cells; MAPKs; MMPs; NMDA receptor; Occludin tight junction