IPA: Targeting Mitostasis via Activation of Mitochondrial Biogenesis after TBI

Experience in contemporary military operations suggests that traumatic brain injury (TBI) is the signature injury of modern wars 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. Compelling experimental data demonstrate that mitochondrial dysfunction is a pivotal link in the neuropathological sequelae of brain injury. This premise comes from our published work (and that of others) demonstrating that loss of mitochondrial homeostasis and increased mitochondrial reactive oxygen species (ROS) production occurs following TBI. Protecting or restoring mitochondrial function by therapeutically targeting mitochondrial impairment improves neuronal function after TBI. Here, we propose a novel approach of activating mitochondrial biogenesis (MB), a necessary process in mitochondrial dynamics, after TBI using pharmacological intervention. Through MB, dysfunctional mitochondria are replaced via signaling networks involving peroxisome proliferator-activated receptor gamma coactivator 1- alpha (PGC-1α) as a master regulator. Activation of MB can be an important intervention to modulate mitochondrial dynamics and prevent metabolic disruption after TBI. Recently, two drugs formoterol and LY344864 have been screened by our collaborators and found to induce PGC-1α via activation of two independent receptors, β2-adrenoreceptor (β2AR) and 5-hydroxytryptamine1F (5-HT1F) respectively. We hypothesize that MB activation at the optimized drug dosage will improve mitochondrial function, mitigate pathology and restore cognitive function following TBI. To test this hypothesis, in Specific Aim 1, we will examine the temporal and spatial aspects of MB after TBI in the injured cortex and hippocampus by analyzing molecular markers of MB. We will also refine and establish the dose-response and therapeutic window of intervention for formoterol and LY344864 treatment to optimize MB after TBI. In this Aim, we will also test the hypothesis that treatment with MB activators promotes cognitive recovery following TBI at the optimal therapeutic regime. In Specific Aim 2, we will assess cell- and tissue-specific changes in energy homeostasis following TBI and MB activation therapy using bioenergetic and metabolomic approaches and a novel approach to isolate synaptic mitochondria. We will also examine the underlying metabolic mechanisms of TBI and MB activation using in vivo and ex vivo 13C-labeled tracing followed by advanced stable isotope-resolved metabolomic analysis. Lastly, in Specific Aim 3 we will assess the specificity of MB activators on induction of MB after TBI. Using 5- HT1F/β2AR KO mice, we hypothesize that functional benefit is dependent on the specific receptor signaling leading to activation of MB. Overall, we hypothesize that optimizing the therapeutic window and dose response of these MB activators after TBI will lead to improved bioenergetic homeostasis and neurocognitive performance after TBI.