title: Platelet-mediated changes to neuronal glutamate receptor expression at sites of microthrombosis following experimental subarachnoid hemorrhage.
abstract: OBJECTIVE
  Glutamate is important in the pathogenesis of brain damage after cerebral ischemia and traumatic brain injury. Notably, brain extracellular and cerebrospinal fluid as well as blood glutamate concentrations increase after experimental and clinical trauma. While neurons are one potential source of glutamate, platelets also release glutamate as part of their recruitment and might mediate neuronal damage. This study investigates the hypothesis that platelet microthrombi release glutamate that mediates excitotoxic brain injury and neuron dysfunction after subarachnoid hemorrhage (SAH).
  
  
  METHODS
  The authors used two models, primary neuronal cultures exposed to activated platelets, as well as a whole-animal SAH preparation. Propidium iodide was used to evaluate neuronal viability, and surface glutamate receptor staining was used to evaluate the phenotype of platelet-exposed neurons.
  
  
  RESULTS
  The authors demonstrate that thrombin-activated platelet-rich plasma releases glutamate, at concentrations that can exceed 300 μM. When applied to neuronal cultures, this activated plasma is neurotoxic, and the toxicity is attenuated in part by glutamate receptor antagonists. The authors also demonstrate that exposure to thrombin-activated platelets induces marked downregulation of the surface glutamate receptor glutamate receptor 2, a marker of excitotoxicity exposure and a possible mechanism of neuronal dysfunction. Linear regression demonstrated that 7 days after SAH in rats there was a strong correlation between proximity to microthrombi and reduction of surface glutamate receptors.
  
  
  CONCLUSIONS
  The authors conclude that platelet-mediated microthrombosis contributes to neuronal glutamate receptor dysfunction and might mediate brain injury after SAH.
authors.affiliation: Faculty of Medicine and.
authors.forename: Joshua D
authors.initials: JD
authors.lastname: Bell
authors.forename: Theresa Currier
authors.initials: TC
authors.lastname: Thomas
authors.forename: Elliot
authors.initials: E
authors.lastname: Lass
authors.forename: Jinglu
authors.initials: J
authors.lastname: Ai
authors.forename: Hoyee
authors.initials: H
authors.lastname: Wan
authors.forename: Jonathan
authors.initials: J
authors.lastname: Lifshitz
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Baker
authors.forename: R Loch
authors.initials: RL
authors.lastname: Macdonald
mesh_terms: D000818:Animals; D001792:Blood Platelets / Q000166:cytology / Q000502:physiology*; D002450:Cell Communication / Q000502:physiology; D018698:Glutamic Acid / Q000502:physiology; D006490:Hemostatics / Q000494:pharmacology; D008297:Male; D008839:Microelectrodes; D009474:Neurons / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D009498:Neurotoxins / Q000378:metabolism; D009924:Organ Culture Techniques; D015539:Platelet Activation / Q000502:physiology; D053657:Platelet-Rich Plasma; D061251:Primary Cell Culture; D017207:Rats, Sprague-Dawley; D017208:Rats, Wistar; D017470:Receptors, Glutamate / Q000502:physiology*; D013345:Subarachnoid Hemorrhage / Q000378:metabolism / Q000473:pathology / Q000503:physiopathology*; D013917:Thrombin / Q000494:pharmacology; D013927:Thrombosis / Q000378:metabolism / Q000473:pathology / Q000503:physiopathology*
chemical_list: D006490:Hemostatics; D009498:Neurotoxins; D017470:Receptors, Glutamate; D018698:Glutamic Acid; D013917:Thrombin
keywords: BSA = bovine serum albumin; CNQX = 6-cyano-7-nitroquinoxaline-2,3-dione; D-AP5 = D-(-)-2-Amino-5-phosphonopentanoic acid; DAB = 3,3′-diaminobenzidine; FAST = Fast Analytical Sensing Technology; GluR2 = glutamate receptor 2; LTP = long-term potentiation; MEA = microelectrode array; PBS = phosphate-buffered saline; RFU = relative fluorescence unit; SAH = subarachnoid hemorrhage; SEM = standard error of the mean; TA-PrP = thrombin-activated plateletrich plasma; glutamate receptor expression; microthrombi; platelet; subarachnoid hemorrhage; traumatic brain injury; vascular disorders