Glutamate causes a loss in human cerebral endothelial barrier integrity through activation of NMDA receptor

1 Department of Molecular and Cellular Physiology, 2 Department of Neurosurgery, and 3 Department of Neurology, Louisiana State University Health Sciences Center, Shreveport, Louisiana 71130-3932 Submitted 4 June 2003 ; accepted in final form 28 July 2003 L -Glutamate is a major excitatory neurotransmitter that binds ionotropic and metabotropic glutamate receptors. Cerebral endothelial cells from many species have been shown to express several forms of glutamate receptors; however, human cerebral endothelial cells have not been shown to express either the N -methyl- D -aspartate (NMDA) receptor message or protein. This study provides evidence that human cerebral endothelial cells express the message and protein for NMDA receptors. Human cerebral endothelial cell monolayer electrical resistance changes in response to glutamate receptor agonists, antagonists, and second message blockers were tested. RT-PCR and Western blot analysis were used to demonstrate the presence of the NMDA receptor. Glutamate and NMDA (1 mM) caused a significant decrease in electrical resistance compared with sham control at 2 h postexposure; this response could be blocked significantly by MK-801 (an NMDA antagonist), 8-( N,N -diethylamino)- n -octyl-3,4,5-trimethyoxybenzoate (an intracellular Ca 2+ antagonist), and N -acetyl- L -cystein (an antioxidant). Trans (±)-1-amino-1,3-cyclopentanedicarboxylic acid, a metabotropic receptor agonist (1 mM), did not significantly decrease electrical resistance. Our results are consistent with a model where glutamate, at excitotoxic levels, may lead to a breakdown in the blood brain barrier via activation of NMDA receptors. N -methyl- D -aspartate; brain Address for reprint requests and other correspondence: J. S. Alexander, Dept. Molecular and Cellular Physiology, Louisiana State Univ. Health Sciences Center, 1501 Kings Hwy., Shreveport, LA 71130-3932 (E-mail: jalexa{at}lsuhsc.edu ).