The Role of Quinols in Estrogen Neuroprotection

喹啉在雌激素神经保护中的作用

• 批准号: 6535003
• 负责人: LASZLO PROKAI
• 金额: $ 31.23万
• 依托单位: UNIVERSITY OF FLORIDA
• 依托单位国家: 美国
• 财政年份: 2003
• 资助国家: 美国
• 起止时间: 2003-01-15 至 2006-12-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6535003
• 关键词: artery occlusion; cell line; cerebral artery; cerebral ischemia /hypoxia; drug design /synthesis /production; drug screening /evaluation; estrogen receptors; estrogens; hippocampus; hydroquinones; hydroxylation; neurons; neuroprotectants; oxidative stress; phenols; tissue /cell culture

DESCRIPTION (provided by applicant): There has been mounting evidence that estrogens express neuroprotective effects by the suppression of neurotoxic stimuli largely via their direct radical-scavenging activity. The objective of this grant application is to understand this activity by focusing on the underlying chemistry in which the molecular mechanism of the process and the chemical nature and fate of the products derived from the radical-scavenging reaction are considered the key elements. Our hypotheses center on the role of estrogen-derived quinols as specific reaction products whose involvement has been implicated by preliminary data. By systematically varying substituents in the 2- and/or 4-positions of the phenolic A-ring compounds, we should gain insight into the influence of phenoxy-radical (ArO*) stability, electron density of ArO* at the C-1i0 position and, thus, its reactivity towards hydroxyl radical (-0H). The Fenton-reaction, which leads to 0H formation, will be employed as a chemical model. We hypothesize that hydroxylation will be involved upon *0H exposure as an important process that produces non-radical products from estrogens. In the model system that will be used to study the fate of the synthetic estrogens obtained by the systematic modification of the endogenous compounds, only one type of (mono)hydroxylated species, of a quinol structure, is anticipated via a two-step hydroxyl-radical scavenging mechanism. The rate of quinol formation is expected to correlate not only with the steric and electronic elements of the steroidal compounds, but also with their neuroprotective effect. The phenol to quinol pathway may augment the estrogens' free-radical scavenging efficacy, and make a pivotal contribution to neuroprotection. A reductive quinol to phenol transformation (hence, estrogen "recycling") that prevents the depletion of the available neuroprotective estrogens in vivo will also be investigated. This reactivation (in terms of kinetics and influence by the A-ring substituents) will be studied in vitro in cell-free and cellular systems, and by in vivo microdialysis in experimental animals. Support will be sought for the hypothesis that the reduction of quinols is not accompanied by an increased formation of reactive oxygen species. By using glutamate-induced oxidative stress in HT22 cells as an experimental paradigm, we will study the neuroprotective effects of the phenolic A-ring derivatives of estrogens. In addition to structure - activity relationship studies, a correlation between the propensity of the compound to form its quinol product upon -OH exposure and its effective dose in this model system for neuroprotection will be sought. It is anticipated that the new estrogen analogs selected based on mechanistic studies and in vitro screening will show in vivo neuroprotective effects in a transient middle cerebral artery occlusion, a model for cerebral ischemia. Hence, they will serve as new lead compounds for the development of neuroprotective agents with improved efficacy.

描述（由申请人提供）：越来越多的证据表明，雌激素主要通过其直接的自由基清除活性来抑制神经毒性刺激，从而发挥神经保护作用。本次拨款申请的目的是通过关注基础化学来理解这一活动，其中过程的分子机制以及自由基清除反应产生的产物的化学性质和命运被认为是关键要素。我们的假设集中于雌激​​素衍生的对苯二酚作为特定反应产物的作用，初步数据已暗示其参与。通过系统地改变酚类 A 环化合物 2-和/或 4-位的取代基，我们应该深入了解苯氧基自由基 (ArO*) 稳定性、ArO* 在 C-1i0 位的电子密度的影响，以及它对羟基自由基 (-0H) 的反应性。导致 0H 形成的芬顿反应将被用作化学模型。我们假设*0H 暴露时将涉及羟基化，作为从雌激素产生非自由基产物的重要过程。在用于研究通过系统修饰内源性化合物获得的合成雌激素的命运的模型系统中，通过两步羟基自由基清除机制预计只有一种类型的（单）羟基化物质，即对苯二酚结构。预计对苯二酚的形成速率不仅与甾体化合物的空间和电子元素相关，而且还与它们的神经保护作用相关。苯酚到对苯二酚的途径可能会增强雌激素的自由基清除功效，并对神经保护做出关键贡献。还将研究对苯二酚还原为苯酚的转化（因此，雌激素“回收”），以防止体内可用的神经保护雌激素的消耗。这种重新激活（就动力学和 A 环取代基的影响而言）将在体外无细胞和细胞系统中以及通过实验动物的体内微透析进行研究。将寻求支持以下假设：对羟基苯酚的减少并不伴随活性氧物质形成的增加。通过使用谷氨酸诱导的HT22细胞氧化应激作为实验范例，我们将研究雌激素酚A环衍生物的神经保护作用。除了结构-活性关系研究之外，还将寻求该化合物在接触-OH时形成其对苯二酚产物的倾向与其在该神经保护模型系统中的有效剂量之间的相关性。预计根据机制研究和体外筛选选择的新雌激素类似物将在短暂的大脑中动脉闭塞（脑缺血模型）中显示出体内神经保护作用。因此，它们将作为新的先导化合物，用于开发具有改进功效的神经保护剂。