Understanding the immune response after mild TBI: Do endothelial cells play a major role?

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PROJECT SUMMARY/ABSTRACT: The vast majority (over 90%) of traumatic brain injuries (TBI) are classified as mild TBI (mTBI). While most individuals recover from mTBI quickly, a significant minority (10-15%) of patients with mTBI experience persistent symptoms – there are no FDA approved treatments for these individuals. Chronic neuroinflammation and vascular disruption following TBI create an unfavorable environment for recovery. More broadly, neuroinflammation and vascular dysfunction are significant contributors to other CNS diseases as well, including Alzheimer’s disease. My preliminary results demonstrate that interleukin-1 (IL-1) signaling through interleukin-1 receptor 1 (IL-1R1) may be as a link between chronic neuroinflammation and vascular pathology and serve as a therapeutic avenue. IL-1, a major pro-inflammatory cytokine, is upregulated following all TBI severities. IL-1 release has been linked with downstream alterations of the vasculature, including changes to the neurovascular unit, blood flow alteration, angiogenesis, and increased release of cytokines, chemokines, and growth factors. We have found that brain endothelial cells express a high number of IL-1R1 receptors. Further, we have demonstrated that mice lacking IL-1R1 show reduced neuroinflammation following experimental mTBI. We hypothesize that following mTBI, brain endothelial cells, specifically through IL- 1R1, act as a mediator of the neuroimmune and vascular responses. To test this hypothesis, we will use a closed head injury model (CHI) to model a mTBI in mice. Further, we will manipulate IL-1R1 using an inducible endothelial cell-specific IL-1R1 knockout (eKO), a global knockout in which IL-1R1 has been restored only in the endothelial cells (eRestore), and an IL-1R1 reporter mouse in which the protein and mRNA are labeled. In aim 1, we will determine the cellular and temporal expression changes of IL-1R1 in the brain following CHI using the reporter mice. Through this aim, I will be able to determine how TBI alters IL-1R1 across time as well as IL-1R1 association with arteries, veins, and capillaries, while also honing my skills in histology techniques. In aim 2, we will delineate endothelial IL-1R1-dependent neuroinflammatory responses following CHI in wildtype, eKO, and eRestore mice. Through this aim, I will get experience in animal surgeries as well as RNA isolation and Nanostring gene expression analysis. Finally, in aim 3, we will investigate the involvement of endothelial IL-1R1 in vascular structure and blood flow changes after TBI. To do this, we will use vessel painting and speckle contrast diffusion correlated tomography (scDCT). If we find support for our hypothesis, we will provide the groundwork for the development of IL-1 therapeutics for the treatment of mTBI, as well as describe a physiological response of the CNS that can be applied to other diseases. Overall, the question outlined in this proposal not only moves the field forward but also provides significant scientific training which will position me as a strong candidate for post-doctoral work and a future career as an independent scientist.