Accumulating clinical evidence, as well as experience in contemporary military operations, suggests that traumatic brain injury (TBI) is the signature injury of this war making our troops a high-risk population for TBI. Among the 327,388 OEF/OIF veterans using VA services in 2009, 6.7% were diagnosed with TBI of which 73% of those were diagnosed with posttraumatic stress disorder (PTSD). However, to date there is no approved treatment for TBI, in part due to an incomplete understanding of the pathobiology underlying TBI. Therefore progress in this area of research is desperately needed. Recently, we have shown that pioglitazone is neuroprotective following TBI and that its mechanism of action may be directly related to its interactions with the mitochondrial protein mitoNEET. Consistent with these ideas, our preliminary results indicate pioglitazone is not protective in mitoNEET knockout animals and that treatment with a specific mitoNEET ligand (NL1), is neuroprotective following TBI. The proposed experiments are designed to elucidate the mechanism(s) by which pioglitazone confers neuroprotection following TBI by testing the novel hypothesis that pioglitazone, via mitoNEET interaction directly ameliorates mitochondrial dysfunction. To test this hypothesis we propose three specific aims that include the use of multiple innovative tools and techniques that we have in hand, specifically the use of mitoNEET null transgenic mice, a novel mitoNEET ligand (NL-1) and antagonist (NL-3). In Specific Aim 1, we will determine the optimal dosage and therapeutic window of opportunity for pioglitazone to maintain mitochondrial homeostasis post-injury. These measurements will, for the first time, measure mitochondrial dysfunction from synaptic and nonsynaptic mitochondria in the injury core and penumbra from a single animal. In Specific Aim 2 will measure the degree of cortical sparing and behavior improvements that are mediated through pioglitazone treatment after TBI using the optimal dosage determined in Specific Aim 1. In this aim we will use T2 weighted and DTI MRI to longitudinally assess changes in cortical and hippocampal morphology at -3, 3, 7, 14, 28, and 168 days post-injury followed by unbiased stereology at 168 days post-injury. Additionally we will measure acute motor, serial cognitive functional testing and aggressive behavioral function and fear conditioning (chronic measurements of PTSD) to assess the degree of functional recovery as a result of treatment. Specific Aim 3 will determine the mechanism by which pioglitazone affords neuroprotection by testing the hypothesis that pioglitazone's therapeutic effect is mediated through interactions with mitoNEET. This aim will employ the use of transgenic mitoNEET null mice in tandem with a novel mitoNEET specific ligand (NL-1) and mitoNEET antagonist (NL-3). Mitochondrial bioenergetics will be measured at 24 hours and behavioral outcome and tissue sparing will be measured following TBI. The results of these studies will not only shed light on the fundamental processes involved in TBI neuropathology they also move forward the repurposing of an FDA compound for the treatment of TBI and the proposed experiments may pinpoint potential novel targets for the treatment of TBI and perhaps, other neuronal injuries.