NNS 2015 Abstract Book

Conclusions:

fNIRS combined with hypercapnia challenge or

cognitive testing are practical, noninvasive methods to assess vascular

function after TBI and are both less expensive and more portable

than MRI-based technologies. These results support the use of both

fNIRS methods as biomarkers for clinical trials of vascular-directed

therapies.

Keywords: Near InfraRed Spectroscopy, cerebrovascular reactivity,

hypercapnia challenge, functional NIRS testing

D9-09

HEME OXYGENASE-1 AND LIPOCALIN-2 INTERACTION

DURING HEME PROCESSING AFTER TRAUMATIC BRAIN

INJURY

Nicholas Russell

, Linda Phillips

Virginia Commonwealth University, Department of Anatomy and

Neurobiology, Richmond, USA

Heme Oxygenase-1 (HO-1), the inducible form of Heme Oxygenase,

degrades heme into biliverdin, CO, and iron. It is a heat shock protein,

robustly induced by CNS vascular hemorrhage following traumatic

brain injury (TBI). Notably, HO-1 activity releases highly oxidative

iron, which can promote local pathology, as well as up-regulate

transcription to buffer acute free radical damage, and potentially af-

fect neural plasticity during postinjury recovery. HO-1 production is

partially self-regulated via induction of Nrf2 signaling; Nrf2 is a

transcription factor that activates the consensus antioxidant response

element targeting numerous antioxidant genes. We hypothesized that

time dependent HO-1/NRf2 axis activation post-TBI mediates iron

processing pathways to influence tissue recovery. Using rat central

fluid percussion TBI, post-injury HO-1 protein expression in hippo-

campus (HC) and cortex (CTX) was compared with downstream

biliverdin/bilirubin deposition and level of iron transport protein li-

pocalin-2 (LCN2). Western blot (WB) analysis demonstrated that HO-

1 protein peaks 3d post-injury and persists until 7d in HC and CTX.

CTX HO-1 is differentially distributed over post-injury time, initially

found in GFAP

astrocytes, then increasingly expressed by IBA1

cells localized at necrotic sites and around small vessels. A 3d peak in

HO-1 expression is consistent with the documented time course of

heme release/degradation after brain injury. Interestingly, HC also

exhibits a similar HO-1 protein expression profile without overt

hemorrhage. Optical analysis shows sequential evolution of biliverdin

and bilirubin deposition in the CTX through 7d. Paired Perls stain

revealed cellular iron deposition by 3d, indicating onset of significant

heme degradation. Further, WB analysis shows high LCN2 expression

immediately post-injury, peaking at 1d and declining at 3d and 7d.

Preliminary microarray gene profiling supports HO-1 transcript ele-

vation at 1d and 7d; also transient acute mRNA increase in LCN2 at

1d post-injury. Overall, our results reveal time dependent HO-1 ac-

tivation and potential interaction with LCN2 to mediate heme/iron

processing following TBI. The data also suggests that delay in post-

injury heme accumulation/breakdown, along with ongoing elevation

of heme lytic products and iron transporters, may expand the thera-

peutic window for post-injury buffering of hemorrhage-induced pa-

thology. Support: NIH-NS056247/NS057758.

Keywords: Heme Oxygenase 1, Lipocalin 2, Iron Metabolism,

Heme Metabolism

D9-10

AXONAL INJURY AND NEUROBEHAVIORAL IMPAIR-

MENT AFTER SUBARACHNOID HEMORRHAGE

Terrance Kummer

, Joong Hee Kim

, Joey Benetatos

, Eric Milner

Gregory Zipfel

, David Brody

Washington University School of Medicine, Neurology, Saint Louis,

USA

Washington University School of Medicine, Neurosurgery, Saint

Louis, USA

The great majority of acute brain injury results from trauma or from

disorders of the cerebrovasculature. Although traumatic and vascular

brain injuries are generally considered separately, brain hemorrhage

shares many physiological parallels with trauma, and both result in

debilitating chronic neurocognitive deficits. Aneurysmal subarachnoid

hemorrhage (SAH) is the most devastating variant of hemorrhagic

brain injury, carrying a 1-month mortality rate of nearly 50%. The

underlying causes of neurocognitive deficits in SAH are unknown and

invisible to clinical imaging modalities. We recently found that SAH

induces radiological and pathological axonal injury similar to that

seen after trauma. We therefore sought to develop a mouse model of

SAH-induced neurobehavioral deficits to determine whether axonal

injury is a key correlate of long-term neurobehavioral sequelae in

SAH, as it is following trauma. We developed a SAH induction and

post-SAH screening protocol that yields multi-domain neurobeha-

vioral deficits in memory and cognition (Morris Water Maze test),

depression- and anxiety-related behaviors (tail suspension and ele-

vated plus maze tests), and in social behavior (social interaction test).

These impairments parallel those reported by patients after brain

hemorrhage and trauma. We furthermore developed an advanced

diffusion MRI approach involving diffusion kurtosis and generalized

q-sampling imaging with paired histological analysis to define ra-

diological biomarkers of acute brain injury pathways following SAH,

and to correlate these biomarkers with neurobehavioral outcomes. Our

results demonstrate that post-hemorrhagic neurobehavioral outcomes

can be analyzed in a highly tractable model organism, and lay the

groundwork for mechanistic analysis of these outcomes using clinically

translatable radiological biomarkers. These findings and approaches

are likely to have application to post-traumatic neurocognitive deficits

as well.

Keywords: subarachnoid hemorrhage, MRI, diffusion tensor im-

aging, behavior

A-126