In vivo neuroprotective role of astrocyte mitochondrial metabolism during aging

描述（申请人提供）：星形胶质细胞在大脑的保护和维持中起着关键作用。神经元谷胱甘肽水平（GSH）在氧化应激期间迅速耗尽，其重新合成依赖于星形胶质细胞谷胱甘肽的产生。这些生理功能要求星形胶质细胞能够迅速增加其代谢活性。在衰老过程中，人们对星形胶质细胞氧化损伤的累积效应知之甚少。它们的支持和神经保护功能的退化可能会导致衰老过程。有证据表明星形胶质细胞的神经保护作用随着年龄的增长而减弱。研究还表明，星形胶质细胞对氧化应激的抵抗力和神经保护作用可以通过激活嘌呤能受体（P2Y-R）信号通路在培养的星形胶质细胞和全动物模型中得到增强。这种增强的保护途径似乎依赖于星形胶质细胞线粒体功能的增加。这项建议的长期目标是了解星形胶质细胞在维持和保护大脑老化过程中的作用。总的假设是，在衰老过程中，可以通过增加星形胶质细胞的线粒体代谢来增强神经保护。提出以下具体目标来检验这一假设。1)确定星形胶质细胞嘌呤能受体（P2Y-R）激活在衰老过程中增强活小鼠皮层神经保护作用的机制。2)确定体内衰老过程中线粒体ROS损伤对P2Y-R介导的星形细胞神经保护的影响。3)无创描述Ca2+刺激的星形胶质细胞线粒体代谢对衰老过程中体内神经保护的受体依赖性。年轻、中年和老年小鼠以及线粒体功能失调和抗氧化酶活性改变的动物模型将被用于实现这些目标。单光子和多光子显微镜将用于成像线粒体和细胞功能在体内的变化。小动物荧光成像将用于监测活鼠脑局灶性脑梗死（中风）的进展。这些研究对于理解人类衰老的潜在机制非常重要。在整个衰老过程中，大脑中可以激活的新保护途径的识别和表征也将成为解决许多神经病理过程的有吸引力的治疗靶点。星形胶质细胞氧化损伤的积累可能会降低其支持和神经保护功能，并显著促进衰老过程。从这项研究中收集的数据将有助于识别和表征星形胶质细胞中新的保护途径，这些途径可以在衰老过程中被激活以保护大脑。这些途径也应该作为一个有吸引力的治疗靶点，以解决许多神经病理过程，包括中风和痴呆。

DESCRIPTION (provided by applicant): Astrocytes play a key role in the protection and maintenance of the brain. Neuronal glutathione levels (GSH) are rapidly depleted during oxidative stress, and its re-synthesis is dependent on astrocyte GSH production. These physiological functions requires that astrocytes be capable of rapidly increasing their metabolic activity. During aging, little is known about the cumulative effects of oxidative damage on astrocytes. Degradation of their supportive and neuroprotective functions is likely to contribute to the aging process. Evidence is presented showing that astrocyte neuroprotection is diminished with age. It is also demonstrated that astrocyte resistance to oxidative stress and neuroprotection can be enhanced by activation of a purinergic receptor (P2Y-R) signaling pathway in cultured astrocytes as well as in whole animal models. This enhanced protection pathway appears to be dependent on increased mitochondrial function in astrocytes. The long-term goal of this proposal is to understand the role of astrocytes in the maintenance and protection of the brain during aging. The overall hypothesis is that neuroprotection can be enhanced by increasing mitochondrial metabolism in astrocytes at anytime during the aging process. The following Specific Aims are proposed to test this hypothesis. 1) To determine the mechanism by which purinergic receptor (P2Y-R) activation in astrocytes increases neuroprotection in the living mouse cortex throughout aging. 2) To define the impact of mitochondrial ROS damage on P2Y-R mediated astrocyte neuroprotection during the aging process in vivo. 3) To non-invasively delineate the receptor dependence of Ca2+ stimulated mitochondrial metabolism in astrocytes for in vivo neuroprotection during aging. Young, middle-aged and old mice as well from animal models with dysfunctional mitochondria and altered antioxidant enzyme activity will be used to carry out these aims. Single and mutliphoton microscopy will be used to image changes in mitochondrial and cellular function in vivo. Small animal fluorescent imaging will be used to monitor the progression of focal cerebral infarcts (strokes) in living mice brains. These studies are important to understand the underlying mechanisms of aging in humans. The identification and characterization of a novel protective pathway in the brain, which can be activated throughout the aging process, will also serve as an attractive therapeutic target to address many neuropathological processes.Accumulation of oxidative damage to astrocytes is likely to degrade their supportive and neuroprotective functions and significantly contribute to the aging process. Data collected from this research will help to identify and characterize novel protective pathways in astrocytes that can be activated to protect the brain during aging. These pathways should also serve as an attractive therapeutic targets to address many neuropathological processes, including stroke and dementias.