Persistent Pre- and Post-Synaptic Changes After Moderate Traumatic Brain Injury and Mitigation with MitoQ

创伤性脑损伤被认为是最近在阿富汗和阿富汗冲突中服役的军事人员的标志性伤害

TBI was named the signature injury among military personnel served in the recent conflicts in Afghanistan and Iraq with more than 470,000 confirmed cases of TBI from 2010- 2020. In addition, more than 82,468 Veterans who use VA for their health care have been diagnosed with at least one TBI. Chronic synapse alternations represent an underappreciated area of interest in TBI pathobiology, with only a few published studies in the literature (1),(2),(3),(4) and even less examined in in the subacute/chronic phase of TBI. Our preliminary data show that there are in face persistent pre-synaptic and post-synaptic zone structural and functional vulnerability following moderate TBI in mice. These long-term changes could hinder synaptic adaptive mechanisms of the brain (synaptoplasticity) and therefore negatively affect brain recovery following TBI. We have evidence that presynaptic and post-synaptic protein and lipid components are especially vulnerable oxidative modifications and proteolysis, then leading to their down regulation. These synaptic changes, if persisted, could hinder synaptic adaptive mechanisms of the brain (synaptoplasticity) and therefore negatively affect brain recovery following TBI. Hypothesis: (i) TBI can cause sustained down-regulation of protein complexes at the pre-synaptic terminal active zone, which are associated with diminished vesicular neurotransmitter release function. (ii) In parallel, TBI also can cause oxidative and proteolytic damage of key protein components of the post-synaptic density (PSD) - PDZ-domain scaffold proteins (PSD93, PSD95, gephyrin) and associated calmodulin-regulator neurogranin, which can lead to instability & reduction of postsynaptic membrane-bound ionotropic glutamate receptor (NR2A, NR2B GluR1, GluR2), GABA receptor-A /B and dopamine receptors (D1, D2) and thus compromising the post-synaptic neurotransmission capacity. (iii) Studying TBI–induced pre- and post-synaptic protein alternations and dysfunctions can be facilitated by the use of synaptosome preparations isolated from injured mouse brain regions following moderate controlled cortical impact (CCI) and repeated close head injury (rCHI) are ideally suited to examine pre- and postsynaptic protein complex as well as in vesicular neurotransmitter release function and post-synaptic glutamate and dopamine receptor capacity. (iv) novel therapy with an oral mitochondria-targeting BBB-crossing antioxidant Mitoquinone (MitoQ) can help reduce post-TBI presynaptic and postsynaptic alterations and improve chronic neurobehavioral functions as supported by our pilot studies. In this proposal, we first aim to (1) study chronic post- CCI and post-rCHI alterations of key pre-synaptic and post-synaptic modulatory proteins in synaptosome/synaptoneurosome preparations and by immunohistochemical (IHC) staining and Immuno-electron microscopy. We then (2) examine chronic pre- synaptic vesicular neurotransmitter release capacity and post-synaptic glutamate receptors functional integrity and capacity in synaptosome preparations. We will (3) correlate changes of pre-synaptic and post-synaptic structures and functions in hippocampus, perirhinal cortex, prefrontal cortex and amygdala with corresponding changes in neurobehavioral endpoints involving these brain regions at 3 and 12 mo. post- TBI. (4) Examine the effects of post-TBI (CCI or rCHI) oral daily MitoQ treatment for 3 and 12 mo. on reducing oxidative stress induced damage to pre-synaptic and post-synaptic structures /functions, and improved synaptic mitochondrial function in hippocampus, perirhinal cortex, prefrontal cortex and amygdala with corresponding improvement in neurobehavioral endpoints involving these brain regions. In terms of matching US VA research and Veteran care missions, this proposal is directly relevant to US Veterans with chronic TBI who might have persistent pre- and post-synaptic changes that negatively affect their recovery and neurorehabilitation process.