Page 123 - NNS 2014 Program & Abstract Book

This experiment demonstrated for the first time an increase in en-
dogenous acrolein in brain tissue following experimental TBI and a
decrease of brain damage after hydralazine treatment.
Key words
acrolein, closed injury, oxidative stress, reactive aldehydes
C3-06
MICRORNA DYSREGULATION OCCURS AT ACUTE TIME
POINTS AFTER PENETRATING BALLISTIC-LIKE BRAIN
INJURY
Johnson, D., Casandra, C.M., Boutte¢ , A.M., Tortella, F.C., Dave,
J.R., Schmid, K.E.
Walter Reed Army Institute of Research, Silver Spring, USA
Recent studies have shown that microRNAs (miRNAs), small RNAs
that regulate cellular processes, may serve as novel markers of brain
injury. Therefore five miRNAs, previously reported to change in the
first 24 hours in other brain injury models, were examined as a proof-
of-concept study in our severe TBI model. MicroRNAs were measured
following penetrating ballistic-like brain injury (PBBI) where a tem-
porary cavity was generated in rats disrupting 10% of brain volume.
Sham animals received a craniotomy. Ipsilateral brain tissue was col-
lected 4 h, 24 h, 72 h and 7 d post injury. Total RNA was isolated,
reverse transcribed into cDNA and examined using real-time PCR with
Taqman assays. The relative quantities of miRNAs were normalized to
U6 endogenous reference gene. Similar to changes described in other
TBI models, all miRNAs tested (miR-21, Let-7i, miR-124a, miR-146a,
miR-107) were altered at 24 hours post PBBI. Let-7i demonstrated the
most acute profile with a 1.6-fold increase at 4 h and a 2.7-fold increase
at 24 h after injury. However, changes in Let-7i returned to normal by
72 h. MiR-146a demonstrated both an initial and delayed response to
injury with a 2.4-fold increase 24 h after injury which resolved by 72 h
but rebounded with a 3.9-fold increase at 7 days after injury. Most
notably, miR-21 demonstrated an acute response with a 1.8-fold in-
crease at 4 h that continued to increase over time where a 6.9-fold
increase was measured by 7 days post injury. Initial pathway analysis
indicated that these specific miRNAs are involved in regulating in-
flammation, cell migration and cell differentiation at 24 h, sterol me-
tabolism at 72 h and matrix polymerization at 7 days. This study
demonstrated that, similar to other TBI models, miRNAs are also al-
tered by PBBI and exhibit temporal signatures of injury. Of interest,
miR-21 showed sustained elevation for 7 days suggesting potential
value as a therapy biomarker, and potentially aiding in our under-
standing of the chronic pathology following severe TBI.
Key words
severe TBI
C3-07
CONNECTING ACUTE NEUROTRAUMA TO CHRONIC
TRAUMATIC ENCEPHALOPATHY: THE ROLE OF THE
ENDOPLASMIC RETICULUM STRESS RESPONSE
Lucke-Wold, B.P.1, Logsdon, A.F.2, Turner, R.C.1, Bailes, J.E.3, Lee,
J.M.3, Rosen, C.L.1
1West Virginia University, Department of Neurosurgery, Morgan-
town, USA
2West Virginia University, Department of Basic Pharmaceutical Sci-
ences, Morgantown, USA
3Department of Neurosurgery, NorthShore University HealthSystem,
University of Chicago Pritzker School of Medicine, Evanston, USA
Chronic Traumatic Encephalopathy (CTE) is a progressive neurode-
generative disease characterized by neurofibrillary tau tangles. Blast-
induced traumatic brain injury, the ‘signature injury’ of recent wars in
Iraq and Afghanistan, and sport-related concussion are known risk factors
for the development of CTE. The underlying mechanism linking acute
neurotrauma to tau-dependent neurodegeneration is currently unknown.
Endoplasmic reticulum (ER) stress has been implicated in several injury
paradigms. We propose that the ER stress response is continually acti-
vated during CTE progression, and that manipulation of the pathway will
improve behavioral outcomes and decrease tau hyperphosphorylation.
We examined the contribution of the ER stress response on neural injury
in young-adult male rats exposed to blast wave(s) as well as human CTE
specimens using western blot analysis and immunohistochemistry (IHC).
The three arms of the ER stress response were significantly elevated in
the entorhinal cortex of human CTE brains with IHC: phospho-
eukaryotic initiation factor 2 alpha (p-eIF2a) (F(2,12) = 13.08, p < 0.01),
X-box binding protein (F(2,12) = 38.55, p < 0.001), and activation tran-
scription factor 6 (F(2,12) = 9.935, p < 0.01). Additionally, inositol re-
quiring enzyme 2 alpha, a marker of ER stress, was co-localized with
hyperphosphorylated tau in both human CTE brains and repeat blast
samples from Sprague Dawley rats 3 weeks post-injury. Caspase-12, a
marker of apoptosis, was elevated at 24 h post-blast and was co-localized
with C/EBP homology protein (CHOP), a protein activated by all arms of
the ER stress pathway. The p-eIF2a phosphatase inhibitor, salubrinal,
was used to significantly decrease CHOP (F(2,15) = 9.172, p < 0.01) on
western blot, and also decrease impulsive behavior on elevated plus maze
after blast injury (F (2,12) = 4.409, p < 0.05). Understanding how the ER
stress response contributes to CTE development will improve diagnostic
accuracy, and ultimately contribute to novel therapeutic targets for
neurotrauma and neurodegenerative diseases.
Key words
blast traumatic brain injury, chronic traumatic encephalopathy, en-
doplasmic reticulum stress, tau-dependent neurodegeneration
C3-08
SPREADING DEPOLARIZATIONS MEDIATE GLUTAMATE
EXCITOTOXICITY IN DEVELOPMENT OF ACUTE COR-
TICAL LESIONS
Hinzman, J.M.1, DiNapoli, V.A.1 , Gerhardt, G.A.2, Hartings, J.A.1
1University of Cincinnati (UC), Department of Neurosurgery, Cin-
cinnati, US
2University of Kentucky, Department of Anatomy and Neurobiology,
Lexington, US
Although glutamate excitotoxicity is presumed to play a pivotal role
in secondary injury after TBI and stroke, failure of numerous clinical
trials targeting NMDA receptors (NMDARs) suggests an incomplete
understanding of the mechanisms involved in elevated glutamate after
neurological injury. We hypothesized that cortical spreading depo-
larizations (CSD) are the mediator of excitotoxicity in vivo, since CSD
exhibits significant overlap with excitotoxicity including glutamate
release, reversal of excitatory amino acid transporters (EAATs), ac-
tivation of NMDARs, and Ca2 + influx. Measuring extracellular glu-
tamate in real-time with enzyme-based microelectrodes we found that
CSDs evoked by 1M KCl in uninjured cortex (duration 37.5 – 2.5 s)
produced synchronous elevations in glutamate (39.7 – 2.4 s) (Pearson
r2 = 0.51, p < 0.05). Pharmacological inhibition of EAATs (TBOA)
prolonged the duration of the glutamate signal (106.0 – 19.9 s,
A-91