Epigenetics of the Aging Astrocyte: Implications for Stroke

描述(申请人提供)：在美国，中风是导致残疾的主要原因，心脏病是导致死亡的主要原因。中风继而导致功能障碍的风险随着年龄的增长而增加，在女性中，这种风险在绝经后增加。矛盾的是，更年期激素治疗增加了中风的风险。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，雌性大鼠大脑皮质和纹状体的组织损伤程度更大。另一方面，中年男性在皮质梗塞的范围上与年轻男性没有显著差异。这个年龄 皮质细胞丢失的差异也与星形胶质细胞的功能变化平行，星形胶质细胞是一种特殊的 大脑支持细胞。星形胶质细胞在正常和病理条件下都起着关键作用。中风后，星形胶质细胞被迅速动员到梗死区周围，通过谷氨酸摄取和液体外流来解毒受损的大脑，并分泌已知促进血管生成、神经元存活和神经再生的生长因子。从中年雌性大鼠脑缺血皮质中挑选出的星形胶质细胞显示出严重的保护功能丧失，包括隔离谷氨酸的能力降低，生长因子释放减少，趋化因子释放增加，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塞体积增加是一致的。因此，在这项建议中，我们将确定从缺血皮质获得的星形胶质细胞的年龄和性别特异性的表观基因组变化，以确定关键的翻译和转录调节因子。在特定的目标1中，我们将确定与年龄相关的小非编码RNA的表达变化。MicroRNA是一个关键的翻译调控元件，调控着大型的基因网络，并已被证明在细胞衰老和损伤(中风)中发挥着核心作用。在特定目标2中，我们将确定与年龄相关的DNA和组蛋白甲基化模式的变化。与基因转录激活(H3K4me3和H3K9ac)或抑制(H3K9me3和H3K27me3)相关的特定亮氨酸的甲基化模式将成为目标。这些互补的方法将使我们能够开发出老化星形胶质细胞的分子指纹。最后，在特定的目标3中，将使用(1)miRNA模拟物或反配子和(2)去甲基酶来逆转星形胶质细胞中特定年龄的模式。从这些研究中收集的数据有望帮助最终识别预测疾病严重程度的表观基因组变化，并促进发现治疗靶点。 公共卫生相关性：与中风相关的风险和残疾随着年龄的增长而增加。为了开发更有效的治疗这种疾病的方法，这项应用将专注于一种名为星形胶质细胞的特定脑细胞中与年龄相关的变化。我们使用动物模型进行的研究表明，中年女性在中风后遭受的脑损伤比年轻女性更多，这与星形胶质细胞神经保护能力的功能变化有关。我们将寻求了解这种细胞类型的全球年龄相关变化，以开发疾病严重程度的标志物以及新的治疗靶点。

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. PUBLIC HEALTH RELEVANCE: The risk and disability associated with stroke increases with age. In order to develop more effective therapies for this disease, this application will focus on age-related changes in a specific brain cell called the astrocyte. Our studies using an animal model show that middle-aged females sustain more brain damage after stroke than younger females and this is associated with functional changes in the neuroprotective ability of astrocytes. We will seek to understand global age-related changes in this cell type so as to develop markers for disease severity as well as new therapeutic targets.