mitoNEET as a therapeutic target of pioglitazone following TBI

Traumatic brain injury (TBI) is a serious health care problem in the United States with an estimated 1.7 million injuries annually at an estimated yearly cost of greater than 76.5 billion dollars. However, there are currently no pharmacological treatments approved for the clinical treatment of this condition. 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 test the novel hypothesis that pioglitazone can afford neuroprotection following TBI by directly ameliorating mitochondrial dysfunction and to elucidate the mechanism(s) by which pioglitazone confers neuroprotection. To test this hypothesis we propose two 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 (PI). 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. We will then measure the degree of cortical sparing and behavior improvements that are mediated through pioglitazone treatment after TBI using the optimal dosage and therapeutic window. We will use T2 weighted and DTI MRI to longitudinally assess changes in cortical and hippocampal morphology at -3, 3, 7, and 28 days PI followed by unbiased stereology at 30 days PI. Additionally we will measure motor and serial cognitive behavioral endpoints. Specific Aim 2 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 15 days following TBI. The results of these studies will not only shed light on the fundamental processes involved in TBI neuropathology but the proposed experiments may pinpoint potential novel interventions and novel targets for the treatment of TBI and perhaps, other acute neuronal injuries.