title: Blast waves from detonated military explosive reduce GluR1 and synaptophysin levels in hippocampal slice cultures.
abstract: Explosives create shockwaves that cause blast-induced neurotrauma, one of the most common types of traumatic brain injury (TBI) linked to military service. Blast-induced TBIs are often associated with reduced cognitive and behavioral functions due to a variety of factors. To study the direct effects of military explosive blasts on brain tissue, we removed systemic factors by utilizing rat hippocampal slice cultures. The long-term slice cultures were briefly sealed air-tight in serum-free medium, lowered into a 37°C water-filled tank, and small 1.7-gram assemblies of cyclotrimethylene trinitramine (RDX) were detonated 15cm outside the tank, creating a distinct shockwave recorded at the culture plate position. Compared to control mock-treated groups of slices that received equal submerge time, 1-3 blast impacts caused a dose-dependent reduction in the AMPA receptor subunit GluR1. While only a small reduction was found in hippocampal slices exposed to a single RDX blast and harvested 1-2days later, slices that received two consecutive RDX blasts 4min apart exhibited a 26-40% reduction in GluR1, and the receptor subunit was further reduced by 64-72% after three consecutive blasts. Such loss correlated with increased levels of HDAC2, a histone deacetylase implicated in stress-induced reduction of glutamatergic transmission. No evidence of synaptic marker recovery was found at 72h post-blast. The presynaptic marker synaptophysin was found to have similar susceptibility as GluR1 to the multiple explosive detonations. In contrast to the synaptic protein reductions, actin levels were unchanged, spectrin breakdown was not detected, and Fluoro-Jade B staining found no indication of degenerating neurons in slices exposed to three RDX blasts, suggesting that small, sub-lethal explosives are capable of producing selective alterations to synaptic integrity. Together, these results indicate that blast waves from military explosive cause signs of synaptic compromise without producing severe neurodegeneration, perhaps explaining the cognitive and behavioral changes in those blast-induced TBI sufferers that have no detectable neuropathology.
authors.affiliation: Biotechnology Research and Training Center, University of North Carolina-Pembroke, Pembroke, NC 28372, USA.
authors.forename: Marquitta
authors.initials: M
authors.lastname: Smith
authors.affiliation: U.S. Army Research Laboratory, Aberdeen Proving Ground, MD 21005, USA.
authors.forename: Thuvan
authors.initials: T
authors.lastname: Piehler
authors.affiliation: U.S. Army Research Laboratory, Aberdeen Proving Ground, MD 21005, USA.
authors.forename: Richard
authors.initials: R
authors.lastname: Benjamin
authors.affiliation: Biotechnology Research and Training Center, University of North Carolina-Pembroke, Pembroke, NC 28372, USA.
authors.forename: Karen L
authors.initials: KL
authors.lastname: Farizatto
authors.affiliation: Biotechnology Research and Training Center, University of North Carolina-Pembroke, Pembroke, NC 28372, USA.
authors.forename: Morgan C
authors.initials: MC
authors.lastname: Pait
authors.affiliation: Biotechnology Research and Training Center, University of North Carolina-Pembroke, Pembroke, NC 28372, USA.
authors.forename: Michael F
authors.initials: MF
authors.lastname: Almeida
authors.affiliation: Department of Cell Biology and Physiology, Neuroscience Center, University of North Carolina-Chapel Hill, Chapel Hill, NC 27599, USA.
authors.forename: Vladimir V
authors.initials: VV
authors.lastname: Ghukasyan
authors.affiliation: Biotechnology Research and Training Center, University of North Carolina-Pembroke, Pembroke, NC 28372, USA. Electronic address: Bahr@uncp.edu.
authors.forename: Ben A
authors.initials: BA
authors.lastname: Bahr
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D000831:Animals, Newborn; D001753:Blast Injuries / Q000209:etiology / Q000473:pathology*; D053834:Explosive Agents / Q000009:adverse effects; D005452:Fluoresceins / Q000493:pharmacokinetics; D006624:Hippocampus / Q000293:injuries / Q000378:metabolism*; D056464:Histone Deacetylase 2 / Q000378:metabolism; D066298:In Vitro Techniques; D020929:Mitogen-Activated Protein Kinase Kinases / Q000378:metabolism; D008962:Models, Theoretical; D009924:Organ Culture Techniques; D051381:Rats; D017207:Rats, Sprague-Dawley; D018091:Receptors, AMPA / Q000378:metabolism*; D016708:Synaptophysin / Q000378:metabolism*; D013997:Time Factors; D014227:Triazines / Q000009:adverse effects
chemical_list: D053834:Explosive Agents; D005452:Fluoresceins; D056464:Histone Deacetylase 2; D020929:Mitogen-Activated Protein Kinase Kinases; D018091:Receptors, AMPA; D016708:Synaptophysin; D014227:Triazines; C435731:fluoro jade; C533426:Hdac2 protein, rat; C009160:cyclonite
keywords: Blast-induced injury; GluR1; Military explosive; RDX; Shockwave; Synaptic decline; Synaptophysin; TBI; Traumatic brain injury