Huntington's disease (HD) is a dominantly inherited, incurable neurodegenerative disease affecting primarily the striatum and corticostriatal pathway. Sex differences in mice and humans with HD suggest that gonadal steroid hormones may play a role in the onset and progression of HD. Neuroprotective effects of 17--3-estradiol (E2) suggest that it may contribute to these sex differences. The goal of the proposed research is to characterize the effects of E2 on neural pathophysiology and the behavioral phenotype of HD in female mice. Because HD results in damage and altered neural activity of the corticostriatal pathway, it is likely that cortical dysfunction contributes to excessive neuronal activity and a deficit of the antioxidant vitamin, ascorbate (vitamin C; AA) in the striatum. E2 effects on glutamate (GLU) transmission may normalize cortical neuronal activity in female HD mice preventing striatal AA loss and resulting in later onset and/or slower progression of HD in females. Electrophysiology and voltammetry will be used to record neural activity in the prefrontal cortex (PFC) and monitor AA release in the striatum of behaving HD mice and wild-type controls (WT) receiving either ovariectomy (OVX) + .placebo, OVX + E2, or sham surgery + placebo. During cortical recordings, mice will be engaged in a reversal learning task as this is a cortico- striatal dependent task involving PFC. One mechanism of E2 neuroprotection may be via upregulation of glial GLU transporters such as GLT1. This may prevent the GLU excitotoxicity believed to occur in HD and increase GLU clearance in female HD mice. Immunohistochemistry and behavioral assessments will be used to determine whether E2 upregulates GLT1 in the cortex and striatum, improving the behavioral phenotype of HD in female mice. Results of this study will indicate whether E2 may protect female HD mice from striatal AA loss, normalize cortical neuronal activity and improve the behavioral phenotype associated with HD. Furthermore, results will suggest whether E2 effects on GLU transmission contribute to sex differences observed in HD mice. HD affects -30,000 people in the United States and -150,000 more are at risk for inheriting the gene. If E2 is neuroprotective in HD models, it may be a suitable therapy, particularly for women with HD. Furthermore, evaluation of the role of E2 in regulating motor circuits in the brain will provide a better understanding of how this hormone regulates normal and pathological motor control. This is particularly important because more than 40 million U.S. citizens are affected by movement disorders. E2 likely plays a critical role in motor function and neuroprotection and may represent a therapy for movement disorders and neurodegenerative conditions that is currently not well investigated. ? ? ? ?
| Miller, Benjamin R; Dorner, Jenelle L; Bunner, Kendra D et al. (2012) Up-regulation of GLT1 reverses the deficit in cortically evoked striatal ascorbate efflux in the R6/2 mouse model of Huntington's disease. J Neurochem 121:629-38 |
