Epigenetics of the Aging Astrocyte: Implications for Stroke

描述（由申请人提供）：中风是美国残疾的主要原因，心脏病是死亡的主要原因。随着年龄的增长，中风导致功能障碍的风险增加，女性在绝经后的风险更高。奇怪的是，更年期的激素治疗会增加中风的风险。中风的动物模型证实，与年轻动物相比，老年动物的中风严重程度更差。在中年，我们最近的数据显示，与年轻的雌性大鼠相比，雌性大鼠的皮质和纹状体组织损伤程度更大。另一方面，中年男性与年轻男性在皮质梗死的程度上没有显著差异。这个年龄 皮质细胞损失的差异也被星形胶质细胞的功能变化所证实，这是一种特异性的 脑支持细胞星形胶质细胞在正常和病理条件下发挥关键作用。中风后，星形胶质细胞被迅速动员到梗死周围区域，通过谷氨酸摄取和液体流出来解毒受损的大脑，并分泌已知促进血管生成和神经元存活和神经发生的生长因子。从中年雌性大鼠的缺血皮质中挑选的星形胶质细胞显示出保护功能的严重丧失，包括螯合谷氨酸的能力降低、生长因子释放减少、趋化因子释放增加和募集白细胞的能力增加。这些变化与在老年女性中观察到的梗死体积增加一致。因此，在这个建议中，我们将确定年龄和性别特异性表观基因组的变化，从缺血性皮质星形胶质细胞，以确定关键的翻译和转录调节剂。在具体目标1中，我们将确定小的非编码RNA表达的年龄相关变化。MicroRNA是一种关键的翻译调控元件，调节大型基因网络，并已被证明在细胞衰老和损伤（中风）中发挥核心作用。在具体目标2中，我们将确定DNA和组蛋白甲基化模式中与年龄相关的变化。将靶向与基因转录的激活（H3K4me3和H3K9ac）或抑制（H3K9me3和H3K27me3）相关的特定亮氨酸的甲基化模式。这些互补的方法将使我们能够开发老化星形胶质细胞的分子指纹。最后，在特异性目标3中，将使用（1）miRNA模拟物或miRNA mimir和（2）去甲基化酶来操纵选择的分子靶标，以逆转星形胶质细胞中的年龄特异性模式。从这些研究中收集的数据预计将有助于最终确定预测疾病严重程度和促进发现治疗靶点的表观基因组变化。

DESCRIPTION (provided by applicant): Stroke is the leading cause of disability in the US and with heart disease, the leading cause of death. The risk for stroke with consequent functional disability is increased with age, and in women this risk is elevated after the menopause. Paradoxically, hormone therapy at menopause increases the risk for stroke. Animal models of stroke confirm that stroke severity is worse in aged animals as compared to younger animals. In middle age, our recent data shows that female rats sustain a greater degree of tissue damage in the cortex and striatum as compared to younger females. Middle aged males, on the other hand, do not differ significantly from younger males in the extent of cortical infarction. This age difference in cortical cell loss is also paralleled by functional changes in astrocytes, a specific brain support cell. Astrocytes play a key role in normal and pathological conditions. Following stroke, astrocytes are rapidly mobilized to the peri-infarct area, detoxify the injured brain via glutamate uptake and fluid efflux and secrete growth factors known to promote angiogenesis and neuronal survival and neurogenesis. Astrocytes culled from the ischemic cortex of middle aged female rats show profound loss of protective functions including a reduced ability to sequester glutamate, decreased growth factor release, increased release of chemokines and increased ability to recruit leukocytes. These changes are consistent with increased infarct volume observed in older females. Hence in this proposal we will determine age and sex-specific epigenomic changes in astrocytes obtained from the ischemic cortex, to determine critical translational and transcriptional modulators. In Specific Aim 1 we will determine age-related changes in the expression of small non-coding RNA. MicroRNA, a key translation regulatory element, regulates large gene networks, and have been shown to play a central role in cell senescence and injury (stroke). In Specific Aim 2 we will determine age-related changes in DNA and histone methlyation patterns. Methylation patterns of specific leucines associated with activation (H3K4me3 and H3K9ac) or repression (H3K9me3 and H3K27me3) of gene transcription will be targeted. These complementary approaches will allow us to develop a molecular fingerprint of the aging astrocyte. Finally, in Specific Aim 3, select molecular targets will be manipulated using (1) miRNA mimetics or antagomirs and (2) demethylases to reverse age-specific patterns in astrocytes. Data gathered from these studies is expected to aid in the eventual identification of epigenomic changes that predict disease severity and facilitate discovery of therapeutic targets.