Using established models of both uncompensated hemorrhagic hypotension (HH), traumatic brain injury (TBI) and a combined hemorrhage/brain injury paradigm (HH-TBI), this application proposes (1) to characterize and elucidate the role of cell death/survival genes, cytokines and alterations in DNA damage detection and repair mechanisms in mediating central nervous system (CNS) dysfunction following hemorrhage and mechanical injury and (2) evaluate novel pharmacotherapeutic strategies targeted at these pathways in the treatment of shock and trauma. The central hypothesis is that cellular death and dysfunction in the brain after shock or trauma is due to an up regulation of death-inducing genes (such as bax, capase-3, interleukins, TNF-alpha) and a downregulation of neuroprotective genes (such as Bcl-2, Bcl-xL), and that molecular changes in the brain following the single insults will differ from those observed following combined shock and brain trauma.
Specific Aim 1 will use in situ hybridization/ immunohistochemistry to evaluate how HH or TBI results in an alteration in the balance (ratio) of cell death/survival genes in the brain which contribute to apoptotic cell death following these insults. The response of transgenic animals, genetically engineered to over express the anti-apoptotic gene bcl-2, to HH or TBI and the efficacy of pharmacologic inhibition of the pro-apoptotic protein caspase-3 will be evaluated.
Specific Aim 2 evaluates gene expression of inflammatory cytokines in the rat brain following HH, TBI or HH-TBI to characterize the role of inflammatory cascades in mediating CNS dysfunction. Transgenic mice, genetically engineered to be deficient in expression of TNF-a (TNF-/- mice), will be used to validate the hypothesis; and the therapeutic efficacy of recombinant human interleukin-18 receptor antagonist to inhibit cytokine function will be evaluated.
Specific Aim 3 will evaluate the effects of HH, TBI or HH-TBI on endogenous DNA damage detection and repair mechanisms (activation of PARP). PARP knockout mice (PARP KO) will be used to validate out hypothesis that these insults alter DNA repair mechanisms which contributes to cell death and dysfunction. Pharmacologic inhibition of PARP will also be evaluated.
Specific Aim 4 use single-cell aRNA amplification techniques to obtain expression profiles of multiple genes from neurons exhibiting DNA fragmentation in rat brain following HH, TBI or HH-TBI to establish the coordinated genomic changes that may play a role in cell death and dysfunction. Taken together, these studies will significantly enhance understanding of the molecular response in the CNS to hemorrhage shock, TBI, and combined injury and will result in the development of more effective therapeutic approaches to the treatment of shock and trauma.
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