REACTIVE OXYGEN SPECIES: STRESS AND DAMAGE IN OLD MUSCLE

在美国，每年因身体虚弱而付出的代价是巨大的，高达800亿美元，但肌肉萎缩和虚弱的原因尚不清楚。这个项目的工作假设是，老年动物骨骼肌的萎缩和衰弱是由活性氧（ROS）的产生不平衡引起的，特别是在有氧收缩的苛刻协议中，以及在抗氧化系统缺乏的情况下。该项目的目的是确定严格的等长收缩方案对8个月大（年轻/成年）和28个月大（老年）小鼠骨骼肌中ROS的产生、ROS诱导的损伤和热休克蛋白适应的影响。野生型（WT）小鼠与部分（Sod+/-和Sod1+/-）或完全（Sod2D3-/-和Sod1-/-）基因敲除导致线粒体或细胞质抗氧化系统缺陷的小鼠，或通过转基因程序（Sod2Tg+/-）或有氧调节增强的小鼠进行比较。在有氧生物中，活性氧不断产生，85%在线粒体中产生，其余来自线粒体外来源。特别是对于具有完整或增强的抗氧化系统的年轻健康动物的骨骼肌，即使需要有氧收缩方案的ROS生成增加，超氧阴离子的生成也会在热休克蛋白中产生ROS应激和适应，但不会产生ROS损伤。相反，对于年老动物或抗氧化系统受损的动物的骨骼肌，ROS应激有可能在休息或收缩时产生足够的损伤，导致萎缩、无力和丧失力量。工作假设将通过四个小组假设和特定假设进行严格的实验来验证，具体假设由项目1在年轻/成年和老年小鼠身上测试，在严格的有氧收缩协议后，ROS应激和损伤的条件下；通过项目#2研究WT和Sod2缺乏和增强小鼠肌肉的线粒体功能，通过项目#3比较不同组卫星干细胞的表达模式。这些项目将由行政、转基因动物和生物化学中心以及一个统计单位协助。

The annual cost of physical frailty in the United States is enormous, $80 billion, yet the cause of muscle atrophy and weakness is unknown. The working hypothesis of this Program Project is that the atrophy and weakness of skeletal muscles in old animals is caused by the imbalance between the generation of reactive oxygen species (ROS), particularly during demanding protocols of aerobic contractions, and in the presence of deficiencies in antioxidant systems. The purpose of the Program Project is to determine the effect of a demanding isometric contraction protocol on the generation of ROS, ROS-induced damage and adaptations of heat shock proteins in skeletal muscles of 8-month old (young/adult) and 28-month-old (old) mice. Comparisons will be made among wild type (WT) mice and mice with mitochondrial or cytosolic antioxidant systems deficiencies due to partial (Sod+/- and Sod1+/-) or complete (Sod2D3-/- and Sod1-/-) knockouts, or mice enhanced by transgenic procedures (Sod2Tg+/-) or by aerobic conditioning. In aerobic organisms, ROS are generated constantly with 85% generated in the mitochondria and the remainder from extra-mitochondrial sources. Particularly for skeletal muscles of young healthy animals with intact or enhanced antioxidant systems, even with the increased ROS generation of a demanding aerobic contraction protocol, the generation of superoxide anions produces an ROS stress and adaptations in HSPs, but no ROS damage. In contrast, for skeletal muscles of old animals, or animals with impaired antioxidant systems, ROS stress has the potential to produce sufficient damage at rest or with contract protocols to cause atrophy, weakness and loss of power. The working hypothesis will be tested rigorously through experiments on four Group Hypotheses tested collaboratively, and specific hypotheses, and specific hypotheses tested on young/adult and old mice by Project #1 on conditions of ROS stress and damage following a demanding aerobic contraction protocol; by Project #2 regarding mitochondrial function of muscles from WT and Sod2 deficient and enhanced mice, and by Project #3 comparing expression patterns of satellite stem cells from different groups. The projects will be assisted by Administrative, Transgenic Animal, and Biochemistry Cores and a Statistical Unit.