title: Platelet-Activating Factor Receptors Mediate Excitatory Postsynaptic Hippocampal Injury in Experimental Autoimmune Encephalomyelitis.
abstract: Gray matter degeneration contributes to progressive disability in multiple sclerosis (MS) and can occur out of proportion to measures of white matter disease. Although white matter pathology, including demyelination and axon injury, can lead to secondary gray matter changes, we hypothesized that neurons can undergo direct excitatory injury within the gray matter independent of these. We tested this using a model of experimental autoimmune encephalomyelitis (EAE) with hippocampal degeneration in C57BL/6 mice, in which immunofluorescent staining showed a 28% loss of PSD95-positive excitatory postsynaptic puncta in hippocampal area CA1 compared with sham-immunized controls, despite preservation of myelin and VGLUT1-positive excitatory axon terminals. Loss of postsynaptic structures was accompanied by appearance of PSD95-positive debris that colocalized with the processes of activated microglia at 25 d after immunization, and clearance of debris was followed by persistently reduced synaptic density at 55 d. In vitro, addition of activated BV2 microglial cells to hippocampal cultures increased neuronal vulnerability to excitotoxic dendritic damage following a burst of synaptic activity in a manner dependent on platelet-activating factor receptor (PAFR) signaling. In vivo treatment with PAFR antagonist BN52021 prevented PSD95-positive synapse loss in hippocampi of mice with EAE but did not affect development of EAE or local microglial activation. These results demonstrate that postsynaptic structures can be a primary target of injury within the gray matter in autoimmune neuroinflammatory disease, and suggest that this may occur via PAFR-mediated modulation of activity-dependent synaptic physiology downstream of microglial activation.
  
  
  CONCLUSIONS
  Unraveling gray matter degeneration is critical for developing treatments for progressive disability and cognitive impairment in multiple sclerosis (MS). In a mouse model of MS, we show that neurons can undergo injury at their synaptic connections within the gray matter, independent of the white matter pathology, demyelination, and axon injury that have been the focus of most current and emerging treatments. Damage to excitatory synapses in the hippocampus occurs in association with activated microglia, which can promote excitotoxic injury via activation of receptors for platelet-activating factor, a proinflammatory signaling molecule elevated in the brain in MS. Platelet-activating factor receptor blockade protected synapses in the mouse model, identifying a potential target for neuroprotective treatments in MS.
authors.affiliation: Center for Neural Development and Disease and Department of Neurology (Neuroimmunology Division), University of Rochester Medical Center, Rochester, New York 14642, Matthew_Bellizzi@urmc.rochester.edu.
authors.forename: Matthew J
authors.identifier: http://orcid.org/0000-0001-6103-2442
authors.initials: MJ
authors.lastname: Bellizzi
authors.affiliation: Center for Neural Development and Disease, University of Rochester Medical Center, Rochester, New York 14642, and.
authors.forename: Jasmine S
authors.identifier: http://orcid.org/0000-0002-5201-7854
authors.initials: JS
authors.lastname: Geathers
authors.affiliation: Center for Neural Development and Disease, University of Rochester Medical Center, Rochester, New York 14642, and.
authors.forename: Kevin C
authors.identifier: http://orcid.org/0000-0002-4206-9781
authors.initials: KC
authors.lastname: Allan
authors.affiliation: Center for Neural Development and Disease, Departments of Neurology (Child Neurology Division), Pediatrics, and Microbiology and Immunology, University of Rochester Medical Center, Rochester, New York 14642.
authors.forename: Harris A
authors.identifier: http://orcid.org/0000-0001-5095-7976
authors.initials: HA
authors.lastname: Gelbard
mesh_terms: D000818:Animals; D002135:Calcium-Binding Proteins / Q000378:metabolism; D045744:Cell Line, Tumor; D023902:Chromosome Pairing / Q000502:physiology*; D018920:Coculture Techniques; D004195:Disease Models, Animal; D000076122:Disks Large Homolog 4 Protein; D004681:Encephalomyelitis, Autoimmune, Experimental / Q000473:pathology*; D005260:Female; D005343:Fibrinolytic Agents / Q000494:pharmacology; D046934:Ginkgolides / Q000494:pharmacology; D066128:Gray Matter / Q000378:metabolism / Q000473:pathology; D051528:Guanylate Kinases / Q000378:metabolism; D006624:Hippocampus / Q000473:pathology*; D007783:Lactones / Q000494:pharmacology; D008297:Male; D008565:Membrane Proteins / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D008840:Microfilament Proteins / Q000378:metabolism; D017628:Microglia / Q000378:metabolism / Q000473:pathology; D063308:Myelin-Oligodendrocyte Glycoprotein / Q000276:immunology; D010446:Peptide Fragments / Q000276:immunology; D010980:Platelet Membrane Glycoproteins / Q000378:metabolism*; D043562:Receptors, G-Protein-Coupled / Q000378:metabolism*; D050598:Vesicular Glutamate Transport Protein 1 / Q000378:metabolism
chemical_list: C491049:Aif1 protein, mouse; D002135:Calcium-Binding Proteins; D000076122:Disks Large Homolog 4 Protein; C501447:Dlg4 protein, mouse; D005343:Fibrinolytic Agents; D046934:Ginkgolides; D007783:Lactones; D008565:Membrane Proteins; D008840:Microfilament Proteins; D063308:Myelin-Oligodendrocyte Glycoprotein; D010446:Peptide Fragments; D010980:Platelet Membrane Glycoproteins; D043562:Receptors, G-Protein-Coupled; C493465:Slc17a7 protein, mouse; D050598:Vesicular Glutamate Transport Protein 1; C445081:myelin oligodendrocyte glycoprotein (35-55); C039351:platelet activating factor receptor; C045856:ginkgolide B; D051528:Guanylate Kinases
keywords: excitotoxicity; microglia; multiple sclerosis; neurodegeneration; neuroprotection; platelet-activating factor
references.citation: J Neurol. 2003 Jan;250(1):67-74
references.pmid: 12527995
references.citation: J Immunol. 2008 Oct 1;181(7):5008-14
references.pmid: 18802104
references.citation: Neuroreport. 2004 Feb 9;15(2):263-6
references.pmid: 15076749
references.citation: Neurology. 2004 Jul 13;63(1):89-93
references.pmid: 15249616
references.citation: J Biol Chem. 1991 Jun 15;266(17):11104-10
references.pmid: 1645725
references.citation: Neuron. 1992 Dec;9(6):1211-6
references.pmid: 1334422
references.citation: Mol Chem Neuropathol. 1995 Feb-Apr;24(2-3):95-106
references.pmid: 7632332
references.citation: J Biol Chem. 1998 Jul 10;273(28):17660-4
references.pmid: 9651362
references.citation: Lab Invest. 2010 May;90(5):774-86
references.pmid: 20157291
references.citation: J Neurol Sci. 2009 Jul 15;282(1-2):106-11
references.pmid: 19100997
references.citation: Exp Neurol. 1998 Nov;154(1):241-58
references.pmid: 9875285
references.citation: Ann Neurol. 2008 Sep;64(3):247-54
references.pmid: 18570297
references.citation: J Neurosci. 2009 Mar 18;29(11):3442-52
references.pmid: 19295150
references.citation: J Physiol. 1999 Nov 1;520 Pt 3:797-813
references.pmid: 10545145
references.citation: Neuropharmacology. 2001 Nov;41(6):693-9
references.pmid: 11640923
references.citation: Ann Neurol. 2010 Oct;68(4):477-93
references.pmid: 20976767
references.citation: Prog Neurobiol. 2011 Jan;93(1):1-12
references.pmid: 20946934
references.citation: Ann Neurol. 2011 Mar;69(3):445-54
references.pmid: 21446020
references.citation: Brain. 2011 Jul;134(Pt 7):1914-24
references.pmid: 21653539
references.citation: PLoS One. 2012;7(5):e35476
references.pmid: 22567104
references.citation: Lab Invest. 2012 Aug;92(8):1234-45
references.pmid: 22525427
references.citation: J Neurosci. 2012 Sep 5;32(36):12312-24
references.pmid: 22956822
references.citation: PLoS One. 2013;8(5):e63250
references.pmid: 23696802
references.citation: Proc Natl Acad Sci U S A. 2014 Feb 18;111(7):2806-11
references.pmid: 24550311
references.citation: Nat Rev Neurosci. 2014 Apr;15(4):209-16
references.pmid: 24646669
references.citation: Nat Commun. 2014;5:4486
references.pmid: 25047355
references.citation: J Cell Biol. 2014 Aug 4;206(3):335-45
references.pmid: 25092654
references.citation: J Neuroimmunol. 1999 Feb 1;94(1-2):212-21
references.pmid: 10376955
references.citation: J Clin Invest. 2005 Nov;115(11):3185-92
references.pmid: 16276420
references.citation: Radiology. 2006 Sep;240(3):811-20
references.pmid: 16868279
references.citation: J Neuropathol Exp Neurol. 2007 Aug;66(8):732-9
references.pmid: 17882017
references.citation: Brain Res Mol Brain Res. 2003 May 12;113(1-2):86-96
references.pmid: 12750010