This project investigates the role of mitochondrial integrity during the development of TBI pathology and periods of functional recovery. Treatment paradigms involving cyclosporin A (CsA) are used to test the hypothesis that a triad of injury pathology, including plasmalemmal microporation, cytoskeletal proteolysis and mitochondrial degeneration, can be mediated through direct effects on mitochondrial membrane integrity. We will investigate the effects of blocking the mitochondrial permeability transition pore complex (MPT) with CsA both prior to and following TBI. Given that our original observations show that CsA administration offers protection against axonal injury pathology in TBI, we will now test the hypotheses that somato-dendritic domains within injured neurons also exhibit the same triad of pathologies and that these domains can also be protected with CsA intervention. Our hypotheses will be tested the same triad of pathologies and that these domains can also be protected with CsA intervention. Our hypotheses will be tested in two well known models of TBI, impact acceleration and combined neuroexcitation + deafferentation lesion. Using these models we can directly compare similarities and differences in both diffuse and focal injury paradigms. We will use immunohistochemistry (IHC), electron microscopic permeability tracer methods, assays for mitochondrial oxidative enzyme function and mRNA expression, and behavioral endpoints to measure effects of CsA on TBI pathology. In addition, we will explore the pharmacokinetics of both intrathecal and intravenous administration of CsA, assaying effects of administration time and dose on the above outcome measures, as well as determining the degree of drug permeability through the blood brain barrier. Finally, we will begin to address alternative mechanisms of action for CsA in TBI, first testing its potential influence on calcineurin mediated pathways. To do this we will administer a calcineurin specific inhibitor, FK506, in treatment paradigms shown to efficacious with CsA and determine its effect on structural outcome measures. The value of our proposed studies is twofold. First, they clearly define cellular mechanisms of TBI pathology and recovery associated with metabolic function. Perhaps more importantly, these studies, combined with the related human studies in this program project proposal, will establish a solid knowledge base supporting potential CsA therapeutic efficacy in TBI patients.
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