Estrogen-neuroprotection due to astroglial Glu transporters occurs via TGF-a/b1

描述(申请人提供)：我们研究的长期目标是阐明17b-雌二醇(E2)和选择性雌激素受体调节剂(SERM)的神经保护机制，并开发策略，发现合适的SERM，可用作神经保护剂，对女性没有癌症风险，对男性没有女性化作用。雌二醇(E_2)对阿尔茨海默病(AD)和帕金森病(PD)等多种神经退行性疾病具有神经保护作用。一些SERM，包括他莫昔芬(TX)，在AD、PD和缺血的实验模型中也具有神经保护作用。虽然神经退行性变的机制还不完全清楚，但星形胶质细胞谷氨酸转运体的损伤在多种神经退行性疾病的发病机制中起着关键作用，包括AD和PD，以及由于长期接触锰而导致的锰中毒(Mnism)。锰抑制谷氨酸的摄取，减少谷氨酸转运体的表达，这在调节细胞外谷氨酸水平中起着至关重要的作用。虽然E2似乎调节星形胶质细胞谷氨酸转运体的表达，但E2调节的机制仍然不清楚。此外，TX和其他SERM被认为具有潜在的治疗优势，因为它们对乳房和子宫没有或减少了负面副作用，不幸的是，尚未对它们进行检查，以确定它们是否对星形胶质谷氨酸转运体的表达或活性具有潜在的有益增强作用，这是该领域需要解决的一个缺陷。为了解决我们在这一重要领域的知识空白，我们将使用锰中毒(Mnism)作为谷氨酸转运体诱导的神经变性的实验模型，因为锰治疗已被证实可诱导与神经毒性相关的谷氨酸转运体损伤。我们的中心假设是，E2和TX可以通过调节转运蛋白运输和通过调节生长因子，特别是转化生长因子α和转化生长因子-β1来调节依赖雌激素受体(ER)的谷氨酸转运蛋白表达，从而逆转锰对谷氨酸转运蛋白活性的抑制。我们的总体假设将在以下特定目标进行检验：1)E2/TX是否通过促进谷氨酸转运体的活性、表达和运输而逆转锰诱导的谷氨酸转运体抑制；2)E2/TX对谷氨酸转运体的影响是否具有ER亚型依赖性；3)转化生长因子-α和转化生长因子-β1是否介导ER依赖的E2/TX逆转锰诱导的谷氨酸转运体抑制；4)E2/TX处理是否通过增强谷氨酸转运体对锰诱导的神经毒性在体内产生神经保护作用。我们的研究将为E2/TX在Mnism模型中潜在的神经保护作用机制(S)提供新的见解，并将为治疗广泛的神经退行性疾病的新靶点提供潜在的见解。 公共卫生相关性：星形胶质谷氨酸转运体受损与各种神经退行性疾病有关，包括阿尔茨海默病(AD)、帕金森病(PD)和由慢性锰暴露引起的锰中毒。鉴于他莫昔芬(TX)和172-雌二醇(E_2)在多种神经退行性疾病中具有神经保护作用，在本研究中，我们将测试E_2/SERM能否通过减轻锰对星形胶质细胞谷氨酸转运体的损伤而发挥神经保护作用。此外，我们还将测试生长因子，转化生长因子-1/2，是否介导E2/TX诱导的谷氨酸转运体的恢复。

DESCRIPTION (provided by applicant): The long-term goal of our research is to elucidate the neuroprotective mechanisms of 17b-Estradiol (E2) and selective estrogen receptor modulators (SERMs) and develop strategies for the discovery of suitable SERMs that can be used as neuroprotectants without risks of cancer for women or of feminizing effects for men. 17b- Estradiol (E2) has been shown to be neuroprotective in various neurodegenerative diseases such as Alzheimer's disease (AD) and Parkinson's disease (PD). Some SERMs, including tamoxifen (TX), also possess neuroprotective properties in the experimental models of AD, PD and ischemia. Although the mechanisms involved in neurodegeneration are incompletely understood, impairment of astroglial glutamate transporters is known to play a key role in the pathogenesis of various neurodegenerative diseases, including AD and PD as well as manganism (Mnism) caused by chronic exposure to manganese (Mn). Mn inhibits glutamate uptake and decreases glutamate transporter expression, which is vital in regulating extracellular glutamate levels. Though E2 appears to regulate astroglial glutamate transporter expression, the mechanism underlying E2 regulation remains elusive. Furthermore, TX and other SERMs, which are considered potentially therapeutically advantageous over E2 due to their lack or diminished negative side effects on the breast and uterus, unfortunately have not been examined to determine whether they exert potentially beneficial enhancement of astroglial glutamate transporter expression or activity, a deficit in the field that needs addressing. To address these gaps in our knowledge in this important area, we will use Manganism (Mnism) as an experimental model for impaired glutamate transporter-induced neurodegeneration, as Mn treatment is well established to induce impairment of glutamate transporters associated with neurotoxicity. Our central hypothesis is that E2 and TX can reverse Mn-induced inhibition of glutamate transporter activities by both modulation of transporter trafficking and by estrogen receptor (ER)-dependent expression of glutamate transporters via modulation of growth factors, in particular transforming growth factors (TGF)-a and TGF-b1. Our overall hypothesis will be tested in the following specific aims: 1) whether E2/TX reverses Mn-induced glutamate transporter inhibition by enhancing activity, expression and trafficking of the transporters, 2)whether E2/TX effects on glutamate transporters are ER-subtype dependent, 3) whether TGF- a and TGF-b1 mediate ER-dependent E2/TX-reversal of Mn-induced inhibition of glutamate transporters, 4) whether E2/TX treatment leads to neuroprotection against Mn-induced neurotoxicity in vivo by enhancing glutamate transporters. Our studies will provide novel insights into the mechanism(s) underlying the neuroprotective role of E2/TX in the model of Mnism and will offer potential insights into novel targets for treatment of a wide array of neurodegenerative disorders. PUBLIC HEALTH RELEVANCE: Impairment of astroglial glutamate transporters is associated with various neurodegenerative diseases including Alzheimer's disease (AD), Parkinson's disease (PD) and manganism, which is caused by chronic manganese (Mn) exposure. Since tamoxifen (TX) and 172-estradiol (E2) have been shown to be neuroprotective in various neurodegenerative diseases, in this proposal, we will test whether E2/SERMs can exert neuroprotective effects by attenuating Mn-induced impairment of astroglial glutamate transporters. Moreover, we will also test whether growth factors, TGF-1/2, mediate E2/TX-induced restoration of glutamate transporters.