Peripheral loss of EphA4 ameliorates TBI-induced neuroinflammation and tissue damage
Kowalski, Elizabeth A.
Fritsch, Lauren E.
Gudenschwager-Basso, Erwin K.
Pickrell, Alicia M.
Matson, John B.
Allen, Irving C.
Theus, Michelle H.
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Background The continuum of pro- and anti-inflammatory response elicited by traumatic brain injury (TBI) is suggested to play a key role in the outcome of TBI; however, the underlying mechanisms remain ill -defined. Methods Here, we demonstrate that using bone marrow chimeric mice and systemic inhibition of EphA4 receptor shifts the pro-inflammatory milieu to pro-resolving following acute TBI. Results EphA4 expression is increased in the injured cortex as early as 2 h post-TBI and on CX3CR1gfp-positive cells in the peri-lesion. Systemic inhibition or genetic deletion of EphA4 significantly reduced cortical lesion volume and shifted the inflammatory profile of peripheral-derived immune cells to pro-resolving in the damaged cortex. These findings were consistent with in vitro studies showing EphA4 inhibition or deletion altered the inflammatory state of LPS-stimulated monocyte/macrophages towards anti-inflammatory. Phosphoarray analysis revealed that EphA4 may regulate pro-inflammatory gene expression by suppressing the mTOR, Akt, and NF-κB pathways. Our human metadata analysis further demonstrates increased EPHA4 and pro-inflammatory gene expression, which correlates with reduced AKT concurrent with increased brain injury severity in patients. Conclusions Overall, these findings implicate EphA4 as a novel mediator of cortical tissue damage and neuroinflammation following TBI.
- Journal Articles, BioMed Central and SpringerOpen 
- Open Access Subvention Fund Articles 
- Scholarly Works, Department of Mechanical Engineering 
- Scholarly Works, Department of Biomedical Sciences and Pathobiology 
- Scholarly Works, Department of Chemistry 
- Scholarly Works, School of Neuroscience 
- Scholarly Works, Virginia Tech Center for Drug Discovery