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

描述（由申请人提供）：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（SERMs）的神经保护机制，并制定策略，发现合适的SERMs，这些SERMs可以用作神经保护剂，而不会对女性产生癌症风险或对男性产生女性化效应。雌二醇（E2）已被证明对各种神经退行性疾病，如阿尔茨海默病（AD）和帕金森病（PD）具有神经保护作用。包括他莫昔芬（TX）在内的一些SERMs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尚不完全清楚，但已知星形胶质细胞谷氨酸转运蛋白的损伤在各种神经退行性疾病的发病机制中起关键作用，包括AD和PD以及由慢性暴露于锰（Mn）引起的锰中毒（Mnism）。锰抑制谷氨酸摄取并降低谷氨酸转运蛋白的表达，这对调节细胞外谷氨酸水平至关重要。虽然E2似乎调控星形胶质细胞谷氨酸转运蛋白的表达，但其调控机制尚不明确。此外，由于TX和其他serm对乳房和子宫的负面影响较少或较少，因此被认为在治疗上优于E2，不幸的是，尚未研究确定它们是否对星形胶质谷氨酸转运蛋白表达或活性有潜在的有益增强，这是该领域需要解决的缺陷。为了解决我们在这一重要领域的知识空白，我们将使用锰（Mnism）作为受损谷氨酸转运体诱导的神经变性的实验模型，因为锰治疗可以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可以通过调节转运体运输和雌激素受体（ER）依赖性谷氨酸转运体的表达（通过调节生长因子，特别是转化生长因子(TGF)-a和TGF-b1）来逆转mn诱导的谷氨酸转运体活性抑制。我们的整体假设将在以下具体目标中进行检验：1) E2/TX是否通过增强转运蛋白的活性、表达和运输来逆转mn诱导的谷氨酸转运蛋白抑制，2)E2/TX对谷氨酸转运蛋白的作用是否依赖于er亚型，3)TGF- a和TGF-b1是否介导er依赖的E2/TX逆转mn诱导的谷氨酸转运蛋白抑制，4)E2/TX治疗是否通过增强谷氨酸转运蛋白在体内对mn诱导的神经毒性起到神经保护作用。我们的研究将对E2/TX在mism模型中的神经保护作用机制提供新的见解，并将为治疗一系列神经退行性疾病提供潜在的新靶点。

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.