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response compared to WBI or CCI alone. Sustained increases in IP-10
and Rantes might facilitate recruitment of macrophages/microglia in
striatum after combined injury. Defining the mechanisms underlying
damage from secondary insults could be vital to development of ra-
diation mitigators.
Support: U19-AI068021, NS061817, NS076511.
Keywords: Multiplex
C7-13
NOCICEPTIVE STIMULATION INDUCES CASPASE 1 AC-
TIVATION FOLLOWING SPINAL CORD INJURY
Joel Turtle
1
, Misty Strain
1
, Joshua Reynolds
1
, Yung-Jen Huang
1
,
Sandra Garraway
2
, James Grau
1
1
Texas A&M University, Institute for Neuroscience, Bryan, USA
2
Emory University School of Medicine, Department of Physiology,
Atlanta, GA
Processes that unfold within the first 48 hours of spinal cord injury
(SCI) modulate cell death and determine, to a large extent, long-term
prognosis. We have shown that nociceptive signals can influence these
processes and the development of secondary damage. Based on
studies from a transection model, we hypothesize that nociceptive
input after injury undermines cell survival, impairs recovery of lo-
comotor function, and promotes neuropathic pain. However, the
mechanism of impaired recovery following nociceptive input is rel-
atively unknown. Here, we used two different models of nociceptive
stimulation (uncontrollable electrical stimulation to the tail or intra-
dermal capsaicin injection to a hind paw) to explore the mechanism of
impaired recovery following spinal cord injury. We examined loco-
motor recovery following injury as well as the underlying cellular
mechanisms using immunoblotting of the lesion site. Either intra-
dermal capsaicin injection or uncontrollable tail shock significantly
impaired locomotor recovery for at least 28 days when given 24 hours
after injury. In addition, nociceptive input increased protein expression
of active caspase 1 compared to control subjects. Further, subjects re-
ceiving capsaicin or shock treatment showed increased processing of
the pro-inflammatory cytokines IL-1beta and IL-18. These data suggest
that after spinal cord injury, nociceptive stimulation promotes the ac-
tivation of an inflammasome and leads to caspase 1 activation, in-
flammatory cytokine processing, and potentially pyroptotic cell death.
Future work is examining the cell types responsible for inflammasome
activation, other mechanisms of cell death, and potential pharmaco-
logic targets that may reverse this effect. [Supported by Neilson
Foundation and Mission Connect grants to JG]
Keywords: pyroptosis, pain, spinal cord injury, inflammation
C7-14
TIBIAL FRACTURE EXACERBATES TRAUMATIC BRAIN
INJURY OUTCOMES AND INFLAMMATION IN A MOUSE
MODEL OF MULTI-TRAUMA
Sandy Shultz
1
, Mujun Sun
1
, David Wright
1
, Rhys Brady
2
, Shijie Liu
1
,
Sinead Beynon
1
, Shannon Schmidt
2
, Terence O’Brien
1
, Stuart
McDonald
2
1
The University of Melbourne, Medicine, Parkville, Australia
2
La Trobe University, Human Biosciences, Melbourne, Australia
Multi-trauma is a common medical problem worldwide, and often
involves concurrent traumatic brain injury (TBI) and bone fracture.
Despite the high incidence of combined TBI and fracture, pre-clinical
TBI research commonly employs independent injury models that fail
to incorporate the pathophysiological interactions occurring in multi-
trauma. Here we developed a novel mouse model of multi-trauma, and
investigated whether bone fracture worsened TBI outcomes. Male
mice were assigned into four groups: sham-TBI
+
sham-fracture
(SHAM); sham-TBI
+
fracture (FX); TBI
+
sham-fracture (TBI); and
TBI
+
fracture (MULTI). The injury methods included a closed-skull
weight-drop TBI model and a closed tibial fracture. After a 35-day
recovery, mice underwent behavioral testing and MRI. MULTI mice
displayed abnormal behaviors in the open-field compared to all other
groups. On MRI MULTI mice had enlarged ventricles and diffusion
abnormalities compared to all other groups. These changes occurred
in the presence of heightened neuroinflammation in MULTI mice
at 24 h and 35 days post-injury, and elevated edema and blood-
brain-barrier disruption at 24 h post-injury. Together these findings
indicate that tibial fracture worsens TBI outcomes, and that exacer-
bated neuroinflammation may be an important factor that contributes
to these effects, which warrants further investigation.
Keywords: Multi-trauma, Polytrauma, Animal model, Inflamma-
tion, MRI, DTI
C7-15
NADPH OXIDASE 4 INHIBITION REVERSES IRON IN-
DUCED PERTURBATIONS OF REACTIVE OXYGEN SPE-
CIES WITHIN ACTIVATED MICROGLIA
Young Yauger
1
, Sara Bermudez
2
, Kimberly Byrnes
1,2
1
Uniformed Services University, Neuroscience Program, Bethesda,
USA
2
Uniformed Services University, Department of Anatomy, Physiology
and Genetics, Bethesda, USA
Iron is an essential element for cellular homeostasis. It facilitates
molecular rearrangement that aids in ATP creation, myelin synthesis,
and a myriad of enzymatic reactions. Recently, iron accumulations
within the brain have been associated with pro-inflammatory disease
states, such as Parkinson’s or Alzheimer’s. There are similarities be-
tween the inflammatory cascade of these diseases and traumatic brain
injury (TBI). Since microglia are the primary mediators of inflam-
mation within the brain parenchyma, we hypothesized that excessive
iron can exacerbate the microglia inflammatory response by accen-
tuating activity of NADPH oxidase 4 (NOX4), a known reactive ox-
ygen species (ROS) synthesizer. Utilizing the BV2 microglial cell
line, we evaluated the effect of iron sulfate (FeSO
4
) on microglial
related inflammation and NOX4. BV2 cells were cultured with lipo-
polysaccharide (LPS) prior to addition of FeSO
4
for 24 hours prior to
evaluation of ROS, cell death, and nitric oxide (NO) release. Iron
alone had no effect on any outcome measure in microglia. However,
ROS production was significantly elevated by FeSO
4
in a dose-
dependent manner when cells were pre-stimulated with LPS. Neither
FeSO
4
nor LPS induced significant changes in cell death. Finally,
assessment of NO showed a robust response of the BV2s with LPS
treatment (p
<
0.001), however no difference existed between the LPS
exposed group and those groups with FeSO
4
and LPS. In order to
determine the mechanism of FeSO
4
perturbations, we used the NOX4
specific inhibitor, GKT137831. GKT137831 reduced the production
of ROS in both LPS and LPS
+
FeSO
4
treated microglia to control
levels. These results now show that FeSO
4
increases ROS expression
in activated microglia, and suggest that iron induced ROS expression
in microglia may depend on NOX4 activation. Elevated ROS can play
a role in inducing inflammation and neuronal apoptosis; our data now
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