Endothelial Aromatase in Sex-Specific Cerebrovascular Dysfunction After Ischemia

描述(由申请人提供)：与年龄匹配的男性相比，女性中风风险和死亡率较低。虽然这种保护部分似乎是通过卵巢雌激素介导的，但卵巢激素并不能解释女性的所有保护作用，因为即使在绝经后卵巢雌激素丢失的情况下，女性的保护仍然存在。在绝经后的女性中，雌激素的主要来源是通过芳香酶局部(性腺外)合成雌二醇。芳香酶在多种细胞类型中表达，包括血管内皮细胞(EC)。在雌性小鼠中，芳香酶基因缺失和药物抑制都会导致脑缺血后的不良结局，提示芳香酶具有保护作用。因此，需要检验的假设是，与男性相比，女性在脑缺血后免受脑血管功能障碍的保护，这是因为血管内皮细胞特异性芳香酶的表达和活性更高。为了确定是否有 为了研究小鼠脑缺血后脑血管内皮功能障碍的性别差异，我们将使用活体颅窗准备和光学微血管成像技术，比较雄性和雌性小鼠在大脑中动脉短暂性闭塞(tMCAO，1h)或假手术前后对内皮依赖性血管扩张剂乙酰胆碱(ACh)的反应。为了确定tMCAO后内皮依赖性扩张的性别差异是否由芳香酶介导，将比较野生型和芳香酶基因敲除小鼠在tMCAO或假手术前后的ACh反应。最后，为了确定EC特异性芳香酶的表达和脑血管芳香酶活性是否存在性别差异，我们将比较基线和tMCAO或假手术后雄性和雌性小鼠脑血管EC特异性芳香酶mRNA和蛋白的表达和脑血管芳香酶活性。了解EC对芳香酶的特异性调控可能会导致旨在提高局部雌激素产生的治疗策略，特别是在内皮细胞内，从而避免与全局雌激素注射相关的负面副作用，同时保持雌激素对血管系统的保护作用。 公共卫生相关性：芳香酶抑制剂临床上用于治疗荷尔蒙阳性乳腺癌，与心血管不良反应有关。这项拟议的研究将使用中风的啮齿动物模型-大脑中动脉闭塞-来确定芳香酶(产生雌二醇的酶)对脑缺血后内皮功能障碍的保护作用，特别是在雌性。了解内皮细胞对芳香化酶的特异性调节可能会导致针对卒中的治疗策略，旨在增加局部雌激素的产生，特别是在内皮细胞内 因此，避免了与全球雌激素注射相关的负面副作用，但保持了雌激素对血管系统的保护作用。

DESCRIPTION (provided by applicant): Women have lower stroke risk and mortality compared to age-matched men. While some of this protection appears to be mediated via ovarian estrogen, ovarian hormones do not account for all of the protective effects seen in females since female protection persists even after menopause when ovarian estrogen is lost. In post- menopausal women, the major source of estrogen becomes local (extra-gonadal) synthesis of estradiol by the enzyme aromatase. Aromatase is expressed in numerous cell types, including vascular endothelial cells (EC). In female mice, both aromatase gene deletion and pharmacological inhibition lead to worse outcome following cerebral ischemia, suggesting that aromatase plays a protective role. Therefore, the hypothesis to be tested is that females are protected from cerebrovascular dysfunction following cerebral ischemia compared to males due to higher expression and activity of endothelial-specific aromatase. In order to determine if there are sex differences in cerebrovascular endothelial dysfunction following cerebral ischemia in mice, responses to the endothelium-dependent vasodilator acetylcholine (ACh) will be compared in male and female mice before and after transient middle cerebral artery occlusion (tMCAO, 1h) or sham surgery using an in vivo cranial window preparation and optical microangiography imaging. To determine if sex differences in endothelium-dependent dilation after tMCAO are mediated by aromatase, ACh responses before and after tMCAO or sham surgery will be compared between wild-type and aromatase knockout mice of both sexes. Finally, to determine if there are sex differences in EC-specific aromatase expression and cerebrovascular aromatase activity, EC-specific aromatase mRNA and protein expression and cerebrovascular aromatase activity will be compared in cerebral vessels isolated from male and female mice at baseline or after tMCAO or sham surgery. Understanding EC specific regulation of aromatase may lead to therapeutic strategies aimed at enhancing local estradiol production specifically within endothelial cells, thus avoiding the negative side effects associated with global estrogen administration, but maintaining the protective effects of estrogen on the vasculature. PUBLIC HEALTH RELEVANCE: Aromatase inhibitors, which are in use clinically for the treatment of hormone positive breast cancer, have been linked to adverse cardiovascular effects. The proposed research will use a rodent model of stroke, the middle cerebral artery occlusion, to determine the protective effect of aromatase (the enzyme that produces estradiol) against endothelial dysfunction following cerebral ischemia, especially in females. Understanding endothelial cell specific regulation of aromatase may lead to therapeutic strategies for stroke aimed at enhancing local estradiol production specifically within endothelial cells, thus avoiding the negative side effects associated with global estrogen administration, but maintaining the protective effects of estrogen on the vasculature.