Mitochondrial network disruption as a final common pathway in the age-related decline of multiple tissues

越来越多的证据表明，与衰老相关的多个组织的衰退与线粒体功能的下降有关。据报道，这种情况发生在多种组织中，如肌肉（骨骼和心脏）、神经元和视觉细胞（包括RPE）。与年龄相关的线粒体功能下降包括能量生成能力下降、细胞钙处理异常、活性氧生成增加和凋亡信号传导增加。这些变化的原因尚不清楚，但越来越多的证据表明，细胞内线粒体形成了一个复杂的网络（或网状）。这在有丝分裂后的多核组织中尤其明显，如骨骼肌。线粒体的结构和分布是高度动态的，并受线粒体裂变、融合和线粒体自噬的调节。在生理条件下，线粒体裂变和融合事件以平衡的频率发生，不仅维持线粒体网络的大小和形状，而且维持线粒体网络的总体分布。融合导致线粒体延伸成相互连接的管状网络，使其内容物（即代谢物、蛋白质和mtDNA）混合并重新分配能量。此外，一个融合的网络被认为可以防止功能失调线粒体的局部积累。相比之下，线粒体裂变是一个将网络分裂成更小、离散的细胞器的过程。分裂似乎分离了可能被破坏或功能失调的网络组件，以便通过有丝分裂去除。与线粒体生物发生一起，这些过程确保了网状结构的重组，以响应刺激，包括营养可用性、细胞应激和其他分子信号。线粒体活性氧增加、呼吸速率降低、钙处理异常和细胞凋亡增加是线粒体网状结构通过增加裂变和减少融合进行重组的结果。该项目将利用新开发的电子显微镜技术和三维图像渲染来检查线粒体分布的变化，这些变化发生在衰老细胞培养模型和体内研究的组织中。这些将与裂变、融合和线粒体自噬的标记物进行比较，总体目标是确定细胞线粒体网络的破坏是否是退行性线粒体信号变化（线粒体ROS增加、呼吸速率降低和细胞凋亡增加）的先决条件，这些变化导致衰老过程中组织退化，因此可能为潜在的抗衰老干预提供目标。学生将学习许多不同的成像技术（EM和共聚焦），生化方法（ROS生成的测量，线粒体生物能量学和凋亡信号，细胞培养和分子技术）。该项目将在威廉·亨利·邓肯大楼的肌肉病理生理学实验室进行，该实验室目前由MRC、BBSRC、英国航天局和美国国立卫生研究院（NIH）的外部项目资助，研究骨骼肌老化和活性氧。

There is increasing evidence that ageing-related decline of multiple tissues is associated with a decline in mitochondrial function. This has been reported to occur in multiple tissues, such as muscle (skeletal and cardiac), neurons and in vision cells including RPE. The age-related declines in mitochondrial function include reduced capacity for energy generation, abnormal cell calcium handling, increased reactive oxygen species generation and increased apoptotic signalling. The causes of these changes are unknown, but there is increasing evidence that within cells mitochondrial form a complex network (or reticulum). This is particularly apparent in post-mitotic multi-nucleate tissues such as skeletal muscle The structure and distribution of mitochondria are highly dynamic and regulated by mitochondrial fission, fusion, and mitophagy. Under physiological conditions, mitochondrial fission and fusion events occur in a balanced frequency to maintain not only the size and shape of the mitochondrial network, but also its gross distribution. Fusion results in the elongation of mitochondria into interconnected, tubular networks enabling the mixing of their contents (i.e. metabolites, proteins and mtDNA) and redistribution of energy. Furthermore, a fused network is thought to prevent the local accumulation of dysfunctional mitochondria. In contrast, mitochondrial fission is a process that acts to fragment the network into smaller, discrete organelles. Fission appears to segregate network components, which may be damaged or dysfunctional, for removal by mitophagy. Together with mitochondrial biogenesis, these processes ensure restructuring of the reticulum in response to stimuli including nutrient availability, cellular stress, and other molecular signals. Increased mitochondrial ROS, low respiration rates, aberrant calcium handling and increased apoptosis are known to be consequences of the reorganisation of the mitochondrial reticulum via increased fission and reduced fusion.This project will utilise newly developed electron microscopy techniques with 3-D rendering of images to examine the changes in mitochondrial distribution that occur in ageing cell culture models and tissues from in vivo studies. These will be compared with markers of fission, fusion and mitophagy with the overall objective of determining whether disruption of the cellular mitochondrial network is a prerequisite for the changes in degenerative mitochondrial signalling (Increased mitochondrial ROS, low respiration rates and increased apoptosis) that lead to tissue degeneration in ageing and hence may provide a target for potential ant-ageing interventions. The student will learn a number of different imaging techniques (EM and confocal), biochemical approaches (measurements of ROS generation, mitochondrial bioenergetics and apoptotic signalling, cell culture and molecular techniques). The project will be hosted in the Muscle pathophysiology laboratories in the William Henry Duncan Building which is currently supported by external project grants examining skeletal muscle ageing and reactive oxygen species from the MRC, BBSRC, UK Space Agency and US National Institutes of Health (NIH).