Page 126 - NNS 2014 Program & Abstract Book

C3-14
REGIONAL AND TEMPORAL HISTOPATHOLOGICAL
CHANGES FOLLOWING MILD CONCUSSIVE BRAIN IN-
JURY
Leung, L.Y., Deng-Bryant, Y., Yang, W., Winter, M., Tortella, F.C.,
Shear, D.A.
Walter Reed Army Institute of Research, Silver Spring, USA
The purpose of this study was to identify histopathological changes
across brain regions of interest in the WRAIR projectile concussive
impact (PCI) model. Rats were subjected to single PCI targeted at the
right temporoparietal region. Sham control group received anesthesia
only. All animals were then sacrificed by transcardial perfusion at 6 h,
24 h, 72 h and 7 d post-injury (n = 6/group/time point). A separate
group of rats subjected to repeated PCI (4xPCI, 1 h-interval; n = 6)
were sacrificed at 6 h following the first impact. Series of coronal
brain sections (40 lm) were immunostained for b-APP, GFAP and
Iba-1. Positive-stained areas were quantified using threshold analysis
in cortical and subcortical regions. A single PCI injury produced
significant bilateral increases in accumulation of b-APP with bulb
formation indicative of axonal injury that was primarily evident in the
corpus callosum (p < .05 vs. sham). The increase peaked at 6 h post-
injury and resolved by 72 h. Repeated PCI caused a significant in-
crease (3-fold vs. single PCI p < .05) in b-APP accumulation near the
impact location at 6 h. Hippocampal GFAP levels were slightly up-
regulated at 6 h following a single PCI and were significantly higher
than sham at 24 h in both hemispheres, suggestive of astrocyte acti-
vation. GFAP expression was still elevated at 7 days, but no longer
significantly higher than sham control. Repeated PCI significantly
increased GFAP expression at 6 h post-injury (p < .05 vs. single PCI6 h
or sham). Significant microglial activation, indicated by Iba-1, was
detected at 6 h and 72 h in the hippocampus following a single PCI
(vs. sham) and then resolved at 7 d post-injury. Iba-1 levels following
repeated PCI group were significantly (2-fold) higher than those de-
tected after a single PCI at 6 h post-injury. Overall, these findings
demonstrated that a single PCI is capable of producing quantifiable
axonal injury and glial activation in the absence of any gross pa-
thology. Further, the profiles of these neuropathological changes are
time-dependent and region-specific and are sensitive to the cumulative
effects of repeated concussive impact.
Key words
axonal injury, concussion, glial activation, histopathology
C3-15
REGION-SPECIFIC IMPAIRMENT OF CEREBRAL MITO-
CHONDRIAL BIOENERGETICS FOLLOWING PENETRA-
TING BALLISTIC-LIKE BRAIN INJURY IN RATS
Deng-Bryant, Y., Leung, L.Y., Readnower, R., Tortella, F.C., Shear,
D.A.
Walter Reed Army Institute of Research, Silver Spring, USA
Mitochondria play a pivotal role in secondary brain damage mecha-
nisms following traumatic brain injury (TBI), which have positioned
themselves as leading target for therapeutic intervention. This study
was designed to assess regional cerebral mitochondrial bioener-
getics following penetrating ballistic-like brain injury (PBBI). Spra-
gue-Dawley rats received either sham injury (craniotomy; n = 11) or
unilateral frontal PBBI (10% injury severity; n = 15). Rats were eu-
thanized at 2 hr post-injury, and brain regions of interest were dis-
sected and processed for mitochondrial Ficoll isolation. The Seahorse
Bioscience XFe24 Flux Analyzer was used to evaluate mitochondrial
bioenergetics. Outcome metrics include mitochondrial oxygen con-
sumptions during: ADP/pyruvate/malate-induced complex-I respira-
tion (State III), oligomycin-induced minimal complex-I respiration
(State IV), uncoupler (2,4-dinitrophenol)-stimulated maximal complex-I
respiration (State V-I), and succinate/rotenone-induced complex-II res-
piration (State V-II). Regional differences intrinsic to cortex, striatum
and hippocampus were compared in the uninjured brains (sham con-
trol). The results show that cortex exhibited significantly higher State
III respiration compared to striatum and hippocampus (p < 0.05).
Additionally, hippocampus showed lower State IV (p < 0.05) and State
V-I respiration (p = 0.07) compared to cortex and striatum, indicative
of a differential profile of basal mitochondrial function across normal
(sham) brain regions. Subsequently, the region-specific response to
PBBI was compared to sham controls. No between-group differences
were detected in complex-I function measured by State III and State
IV respiration across all regions tested. However, complex-I maximal
respiration measured by State V-I respiration was significantly re-
duced in cortex (34%; p < 0.05 vs. sham) and striatum (51%; p < 0.05
vs. sham), but not hippocampus, demonstrating an acute (2 hr post-
injury) onset of bioenergetic failure in cortex and striatum following
PBBI. No differences were detected in State V-II respiration, which
suggests complex-II function was not compromised at this time
point post-PBBI. Overall, the results indicate that PBBI produced
region-specific mitochondrial bioenergetic deficits that are unique
to the penetrating, temporary cavity mechanism. Furthermore, the
results demonstrate an acute onset of PBBI-induced mitochon-
drial dysfunction which underscores the importance of early ther-
apeutic intervention targeting mitochondrial bioenergetics for
neuroprotection.
Key words
mitochondrial bioenergetics, penetrating ballistic-like brain injury,
respiration
C3-16
THE INFLAMMASOME IS ACTIVATED IN THE CORTEX
OF RATS FOLLOWING PENETRATING BALLISTIC BRAIN
INJURY
Lee, S.W.1 , Gajavelli, S.1, de Rivero Vaccari, J.P.1, Brand, III, F.1,
Spurlock, M.1, Shear, D.2, Tortella, F.C.2, Bullock, M.R.1, Keane, R.W.1
1Miami Project to Cure Paralysis, Department of Neurosurgery,
University of Miami Miller School of Medicine, Miami, FL
2Walter Reed Army Institute of Research, Silver Spring, MD
Penetrating traumatic brain injury (PTBI) remains a significant cause
of death and disability in the United States. A rodent model of PTBI
known as penetrating ballistic-like brain injury (PBBI) has helped
uncover several pathophysiological mechanisms associated with
PTBI, including reduced glucose uptake followed by neurodegen-
eration. It is known that activators of innate immunity contribute to
glycolysis failure. Here, we aim to characterize proinflammatory cell
death (pyroptosis) mediated by the inflammasome (a multiprotein
complex, composed of apoptosis-associated speck-like protein con-
taining a CARD (ASC) and caspase-1) in PBBI. In this study, male
Sprague-Dawley rats (280–350 g) were subjected to PBBI. Protein
lysates from sham animals (n = 3) and animals that were injured and
sacrificed at different time points (4 h, 24 h, 48 h, 72 h, and 1 week)
(n = 3-5) were analyzed by immunoblotting using anti-IL-1b, anti-
caspase-1, anti-ASC antibodies. Our data indicate that caspase-1 and
ASC expression in the ipsilateral cortex were significantly increased
A-94