Huntington's Disease (HD) is an autosomal dominant disorder resulting from selective loss of neurons in the striatum and cerebral cortex. Loss of neurons in HD results from pathological expansion of CAG repeats encoding glutamine. Though the precise mechanisms by which glutamine repeats lead to neuronal loss in HD are unclear, oxidative stress, apoptosis, and transcriptional dysregulation have all been implicated in disease pathogenesis. To understand better oxidative and transcriptional mechanisms that may lead to neuronal loss in HD, we have utilized an in vitro model of oxidative stress in primary cortical neurons. In preliminary studies we have shown that oxidative cell death can be fully abrogated by sequence-selective DNA binding drugs, including mithramycin A (MMA) and chromomcyin A3. These agents are members of the aureolic acid antitumor antibiotics that share a common chromophore, aglycon ring, but differ in the nature of the sugar moieties connected to either side of the aglycone ring. Both antibiotics inhibit transcription during macromoleclar biosynthesis by binding to the """"""""GC"""""""" rich transcriptional response elements. To test whether aureolic antibiotics can protect neurons in an in vivo model ofneurodegeneration that may inolve oxidative stress, we examined the effect of MMA in the R6/2 transgenic model of HD. We found that MMA prolongs survival in these mice by nearly 30%, a magnitude superior to any other single neuroprotective agent. These preliminary data are consistent with the overall hypothesis to be tested in this proposal: MMA inhibits neuronal death due to oxidative stress and/or mutant Huntington protein in vitro and in vivo by inhibiting the binding of pro-apoptotic zinc finger transcription factors such as TIEG, and enhancing the DNA binding of pro-survival transcription factors such as CREB. We will examine this hypothesis by determining whether protective concentrations of MMA inhibit TIEG binding to its GC rich DNA binding sites and whether TIEG is critical for oxidative death in cortical neurons. In the second aim, we will determine how MMA affects CREB DNA binding and whether increases in CREB DNA binding contribute to MMA's salutary effects. In the last specific aim, we will compare the mechanism of neuroprotection of MMA to those ofhistone deacetylase inhibitors, another class of transcriptional regulators. These studies will provide critical, mechanistic data on neuroprotective modulators of transcription.
Showing the most recent 10 out of 65 publications
