92 / 162
suggests that both iron and NOX4 are involved in this response and
targeting of NOX4 may have therapeutic benefits.
Keywords: Microglia, Inflammation, NOX4, Iron
C7-16
ALTERATIONS OF PROTEASOME DYNAMICS FOLLOW-
ING TRAUMATIC BRAIN INJURY
Kasey Moritz
, Barrington Burnett
Uniformed Services University of the Health Sciences, Neuroscience,
Rockville, USA
Traumatic brain injury (TBI) is a debilitating disorder that can per-
manently impair brain function leading to long term cognitive, af-
fective and motor deficits. The primary injury often leads to numerous
secondary effects including microglia activation, inflammation and
disturbances in protein homeostasis. By selectively targeting proteins
and peptides for degradation, the ubiquitin-proteasome system (UPS)
helps maintain optimal levels of cellular proteins and in so doing
mitigates some of the primary and secondary effects of brain injuries.
The 26S proteasome is a dynamic enzyme complex that responds to
cellular injury by altering the rate of protein degradation and level of
antigen presentation. However, the molecular mechanisms controlling
these processes remain unclear. We performed controlled cortical
impact injury on adult mice to assess proteasome assembly and
function. We found increased expression of the immunoproteasome
catalytic subunits and interferon gamma (IF-g) in injured mice com-
pared to sham controls indicative of a mounting immune response.
Given the role of activated microglia in the CNS immune response,
we investigated proteasome dynamics in BV2 microglia cell line
following activation with interferon gamma IF-g. Using native gel
electrophoresis we found that microglia activation resulted in in-
creased assembly of immunoproteasomes and reduced presence of the
constitutive proteasome. Furthermore, the non-catalytic proteasome
subunits were unchanged and chaperone proteins responsible for de
novo constitutive and immunoproteasome synthesis were unaltered.
Our findings suggest that the 26S proteasome is converted to the
immunoproteasome following injury by substituting the catalytic
subunits in order to facilitate the immune response to trauma.
Keywords: Proteasome, Interferon gamma, microglia
C7-17
MULTIPLE AROMATIZATION MECHANISMS INFLUENCE
MORTALITY AND CNS SECONDARY INJURY PROFILES
AFTER SEVERE TBI
Amy Wagner
1,2
, Raj Kumar
1
, Yvette Conley
3,4
, Patrick Kochanek
3,5
,
Sarah Berga
6
1
Univ Pittsburgh, PhysicalMed/Rehab, Pittsburgh, USA
2
Univ Pittsburgh, Neuroscience, Pittsburgh, USA
3
Univ Pittsburgh, Safar Center, Pittsburgh, USA
4
Univ Pittsburgh, Nursing, Pittsburgh, USA
5
Univ Pittsburgh, Critical Care, Pittsburgh, USA
6
Wake Forest Health System, Obstetrics/Gynecology, Winston-Salem,
USA
Although estradiol (E2) has several neuroprotective qualities, high
systemic E2 levels can occur early after severe TBI, despite the uni-
form occurrence of acute hypogonadotropic hypogonadism, and can
contribute to poor outcome. To better understand the production (via
aromatization) and complexity of E2 in TBI, we evaluated 1) systemic
and CNS contributors to E2 production, 2) E2 associations with
6-month mortality, and 3) CNS E2 associations with CNS s100b,
cytochrome-C, and inflammatory load. We studied 187 subjects with
severe TBI, aromatase genotypes, and available serum and cerebro-
spinal fluid (CSF) samples collected over 5d post-injury for hormone
and TBI biomarkers. After controlling for covariates, serum bio-
markers (E2, estradiol/testosterone (E2:T) ratio, TNF
a
), and ar-
omatase genetics (rs4646), relevant interactions were modeled to
assess 6-month mortality risk. There was a significant interaction
between E2:T ratio*rs4646 where CC homozygotes with higher E2:T
had reduced mortality risk versus A-carriers (p
=
0.001). Also, E2 and
the E2:T ratio*TNF
a
interaction tended to be associated with mor-
tality (p
=
0.06) suggesting unique aromatization mechanisms leading
to serum E2 production. Importantly, aromatization mechanisms that
contributed to serum E2/T and mortality risk accounted for
*
19% of
the variance observed with CSF E/T ratios. A separate CSF and ge-
netics mortality prediction model showed rs4646, rs2470152,
rs2470152*CSF E2:T ratio interaction influenced mortality, where
higher ratios, among those with the rs2470152 risk variant, were
protective (p
=
0.018). Finally, higher covariate adjusted CSF E2/T
ratios were associated with lower CSF inflammation, S100b levels,
and cytochrome-C levels. Together, these data show 1) multiple
mechanisms contribute to aromatization and E2 production after TBI
2) E2 has complex opposing effects on mortality in the periphery vs.
CNS, and 3) CNS E2 protective effects are associated with bio-
chemical evidence of a reduction in secondary injury.
Keywords: rehabilomics, aromatization, modeling, mortality, TBI,
genetics
C7-18
SERUM TUMOR NECROSIS FACTOR-
a
ASSOCIATION
WITH MORTALITY SIX MONTHS AFTER TBI: MECHAN-
ISTIC RELATIONSHIPS WITH ESTRADIOL
Amy Wagner
1,3,4
, Raj Kumar
1
, Anne Ritter
1
, Patrick Kochanek
2,3
,
Sarah Berga
5
1
Univ Pittsburgh, PhysMedicine/Rehab, Pittsburgh, USA
2
Univ Pittsburgh, Critical Care, Pittsburgh, USA
3
Univ Pittsburgh, Safar Center, Pittsburgh, USA
4
Univ Pittsburgh, Neuroscience, Pittsburgh, USA
5
Wake Forest Health System, Obstetrics Gynecology, Winston-Salem,
USA
Traumatic Brain Injury (TBI) causes
*
1/3 of injury-related deaths
yearly in the USA, and there are no approved neuroprotective
therapies, justifying continued study of acute pathophysiological
contributors to mortality. Tumor necrosis factor-
a
(TNF
a
) is a
pleiotropic, pro-inflammatory cytokine that is acutely elevated and a
primary initiator of the immunological response to TBI. TNF
a
is also
critical for aromatization and adipose tissue production of estradiol
(E2), a known mortality marker in TBI. We established how acute
serum TNF
a
measured from samples (collected over the first 5d after
TBI) influenced mortality outcomes, using time-to-event analyses in
a prospective cohort (n
=
130). After quartiling TNF
a
and E2 levels
for the cohort, we determined relationships between acute serum
TNF
a
and 1) serum E2 and 2) cerebrospinal fluid (CSF) TNF
a
, with
respect to mortality. Among a subgroup of survivors (n
=
37), mean
sub-acute (weeks 2–12) serum TNF
a
was explored for relationships
to sub-acute E2. After controlling for covariates, there was a 2-fold
increase in the hazard of death per quartile increase in acute serum
TNF
a
[HR
=
2.00, 95% CI (1.31, 3.08), p
=
0.001]. Acute serum E2
A-92