Page 116 - NNS 2014 Program & Abstract Book

stimuli, such as lipopolysaccharide and tumor necrosis factor, in-
duce expression of the PDE4B isoform, PDE4B2, in macrophages,
astrocytes and microglia. This upregulation of PDE4B2 is also
observed after SCI and TBI, and may be involved in a positive
feedback loop, potentiating the inflammatory response. However,
whether this increase in PDE4B2 expression is localized to in-
flammatory cells after TBI, and whether PDE4B inhibition im-
proves histopathological outcome after TBI is unknown. To
address these questions, adult male Sprague Dawley rats received
moderate parasagittal fluid percussion brain injury (2 – 0.2 atm) or
sham surgery. Flow cytometry was used to analyze microglia and
infiltrating leukocytes isolated from the ipsilateral parietal cortex
and hippocampus for PDE4B2 expression at 3 hrs and 24 hrs after
TBI. We found that PDE4B2 was significantly elevated in micro-
glia and infiltrating leukocytes at 24 hrs, but not 3 hrs, after TBI. To
determine how PDE4B inhibition affects pathology after TBI, an-
imals received vehicle (5% DMSO in saline) or a PDE4B inhibitor,
A33, at 0.3 mg/kg (i.p.) at 30 minutes post-TBI and once a day for 3
days. Pathology was evaluated in serial brain sections stained with
hematoxylin and eosin. We found that acute PDE4B inhibition
significantly reduced cortical contusion volume at 3 days post-
injury. These results suggest that the PDE4B subfamily may be
involved in modulating the inflammatory response after TBI.
Supported by The Miami Project to Cure Paralysis and NIH/NINDS
NS069721.
Key words
inflammation, PDE4B, phosphodiesterase, traumatic brain injury
C2-22
P75NTR MEDIATES LEUKOCYTE TRAFFICKING IN THE
BRAIN AFTER TRAUMATIC BRAIN INJURY (TBI) IN MICE
Lee, S.1, Mattingly, A.2, Sacramento, J.1, Lin, A.1, Mannent, L.3 , Castel,
M.N.3, Canolle, B.3, Delbary-Gossart, S.3, Ferzaz, B.3 , Morganti, J.M.1,
Rosi, S.1, Bresnahan, J.C.1, Beattie, M.S.1
1Dept Neurological Surgery, Brain and Spinal Injury Center, UCSF,
SF, USA
2BMS Graguate Program, UCSF, SF, USA
3Sanofi R&D, Chilly-Mazarin, France
TBI leads to progressive brain damage resulting in chronic neuro-
logical deficits, which may be partly mediated by pro-inflammatory
responses in both injured brain and the circulation. This acute in-
flammation may involve myeloid trafficking into injured brain.
Previously, we found that blocking the p75NTR-signaling pathway
by SARA, a selective p75NTR antagonist, inhibits tissue damage
and increases behavioral outcome after TBI in rats. Strikingly,
blocking p75NTR-signaling reduces microglia activation, sug-
gesting p75NTR’s involvement in local inflammatory responses
after TBI.
Since some evidence implicates p75NTR in peripheral immune
function, we examined whether p75NTR mediates leukocytes
trafficking into the injured brain. To identify peripheral leuko-
cytes, we used CCR2 RFP/ + Tg mice. We found that blocking
p75NTR-signaling with daily injections of SARA inhibited traf-
ficking of CCR2 + monocytes into injured brain as measured by
RFP positive signal. Consistently, blocking p75NTR signaling
increased surviving tissue at 7D post-injury. Using WT mice, we
confirmed that p75NTR-signaling reduced CCR2 + /CD45 + posi-
tive signals in the injured brain by immunostaining. Because
CCR2 is down-regulated in the tissue (Saederup et al., 2010), we
also examined the infiltration of F480 + and CD11c + cells in the
injured WT brain by immunostaining. Consistently, SARA treat-
ment reduced trafficking of F480 + /CD45 + cells as well as
CD11c + /CD45 + cells in injured brain. Interestingly, SARA
treatment also reduced CCR2 + monocytes in the circulation 7D
after TBI as measured by flow cytometry. These data suggest that
p75NTR inhibits leukocyte trafficking in the injured brain by at-
tenuating leukocyte activation.
Together, our findings suggest that blocking p75NTR reduces in-
flammatory monocytes in the circulation as well as in the injured
brain, and this may contribute to SARA’s therapeutic effects after
TBI.
Supported by Sanofi R&D., NS038079, UCSF/BASIC pilot funds
Key words
inflammatory response, leukocyte trafficking, p75NTR, traumatic
brain injury
C2-23
THE EFFECT OF 7, 8-DIHYDROXYFLAVONE (7,8-DHF)
FOLLOWING TRAUMATIC BRAIN INJURY
Rolfe, A., Romeika, J., Sun, D.
Virginia Commonwealth University, Department of Neurosurgery,
Richmond, USA
Following TBI, the brain undergoes series pathological changes
compromising neural survival and plasticity which contribute to
functional deficits. Treatment that has neuroprotective effect and
promotes neural plasticity is desirable. A flavone derivative, 7,8-DHF
is a recently identified small molecule TrkB agonist which binds with
high affinity and specificity to the TrkB receptor, activating its
downstream signaling cascade with functions similar to BDNF.
Compared to BDNF, 7,8-DHF has more advantages as it can pass the
blood-brain barrier and is bioactive when given intraperitoneally,
subcutaneously or orally. In this study, we assessed the optimal time
window for 7,8-DHF treatment in imporving post-TBI functional re-
covery and synaptic plasticity following a focal brain injury. In this
study, adult male Sprague-Dawley rats were used. Animals were
subjected to a moderate cortical impact injury. At 2 hr, 2 or 5 days
following injury, 7,8-DHF was administrated i.p. at the dose of 5mg/
kg. Thereafter, 4 more daily single doses were given (day 0–4; day
2–6; day 5–9). Sensorimotor functions wre tested using Beam
Walking and Rotarod tests. Cognitive functions were assessed using
Fear Conditioning tests and Morris Water Maze latency and probe
trial tests. Animals were sacrificed at 15 or 28 days post-injury. Brain
sectons were processed for histological examination to assess lesion
volume, neuronal cell survival, neurogenesis and synaptic plasticity.
We found that following TBI, 7,8-DHF given at day 0–4 but not 2–6
or 5–9 ameliorated motor deficits in both beam walking and rotarod
tests. In MWM and fear conditioning tests, injured animals with 7,8-
DHF treatment at day 0–4 or 2–6, but not 5–9 post-injury had im-
proved cognitive functional recovery compared to injured animals
which received vehicle treatment. Further studies examining lesion
volume, hippocampal neuronal cell survival, post-TBI neurogenesis
and synaptic plasticity are ongoing. Our data suggest that 7,8-DHF has
neuroprotective effects improving both motor and cognitive functional
recovery when given at early time post-injury. It also promotes neural
plasticity enhancing cognitive recovery when given at early synaptic
regeneration stage.
Key words
7, 8-DHF, cognitive function, neural plasticity, neuroprotection,
traumatic brain injury, TrkB agonist
A-84