Institute of Ageing and Chronic Disease, University of Liverpool, Liverpool, UK.
Aging Cell. 2011 Oct;10(5):749-60. doi: 10.1111/j.1474-9726.2011.00709.x. Epub 2011 May 6.
Mice lacking Cu,Zn superoxide dismutase (SOD1) show accelerated, age-related loss of muscle mass. Lack of SOD1 may lead to increased superoxide, reduced nitric oxide (NO), and increased peroxynitrite, each of which could initiate muscle fiber loss. Single muscle fibers from flexor digitorum brevis of wild-type (WT) and Sod1(-/-) mice were loaded with NO-sensitive (4-amino-5-methylamino-2',7'-difluorofluorescein diacetate, DAF-FM) and superoxide-sensitive (dihydroethidium, DHE) probes. Gastrocnemius muscles were analyzed for SOD enzymes, nitric oxide synthases (NOS), and 3-nitrotyrosine (3-NT) content. A lack of SOD1 did not increase superoxide availability at rest because no increase in ethidium or 2-hydroxyethidium (2-HE) formation from DHE was seen in fibers from Sod1(-/-) mice compared with those from WT mice. Fibers from Sod1(-/-) mice had decreased NO availability (decreased DAF-FM fluorescence), increased 3-NT in muscle proteins indicating increased peroxynitrite formation and increased content of peroxiredoxin V (a peroxynitrite reductase), compared with WT mice. Muscle fibers from Sod1(-/-) mice showed substantially reduced generation of superoxide in response to contractions compared with fibers from WT mice. Inhibition of NOS did not affect DHE oxidation in fibers from WT or Sod1(-/-) mice at rest or during contractions, but transgenic mice overexpressing nNOS showed increased DAF-FM fluorescence and reduced DHE oxidation in resting muscle fibers. It is concluded that formation of peroxynitrite in muscle fibers is a major effect of lack of SOD1 in Sod1(-/-) mice and may contribute to fiber loss in this model, and that NO regulates superoxide availability and peroxynitrite formation in muscle.
缺乏铜锌超氧化物歧化酶（SOD1）的小鼠表现出加速的、与年龄相关的肌肉质量损失。SOD1 的缺乏可能导致超氧化物增加、一氧化氮（NO）减少和过氧亚硝酸盐增加，每一种都可能引发肌肉纤维损失。从野生型（WT）和 Sod1（-/-）小鼠的屈趾短肌中加载 NO 敏感（4-氨基-5-甲基氨基-2'，7'-二氟荧光素二乙酸酯，DAF-FM）和超氧化物敏感（二氢乙啶，DHE）探针。分析比目鱼肌中的 SOD 酶、一氧化氮合酶（NOS）和 3-硝基酪氨酸（3-NT）含量。由于从 DHE 形成的乙啶或 2-羟乙基（2-HE）没有增加，SOD1 的缺乏在休息时并没有增加超氧化物的可用性，与 WT 小鼠相比，来自 Sod1（-/-）小鼠的纤维。Sod1（-/-）小鼠的纤维中 NO 可用性降低（DAF-FM 荧光降低），肌肉蛋白中 3-NT 增加，表明过氧亚硝酸盐形成增加，过氧亚硝酸盐还原酶过氧化物酶 V（peroxiredoxin V）含量增加，与 WT 小鼠相比。与 WT 小鼠的纤维相比，Sod1（-/-）小鼠的纤维在收缩时产生的超氧化物明显减少。在休息或收缩时，NOS 的抑制都不会影响 WT 或 Sod1（-/-）小鼠纤维中的 DHE 氧化，但过表达 nNOS 的转基因小鼠显示休息肌肉纤维中的 DAF-FM 荧光增加和 DHE 氧化减少。结论是，过氧亚硝酸盐在肌肉纤维中的形成是 Sod1（-/-）小鼠中 SOD1 缺乏的主要影响，并可能导致该模型中的纤维损失，并且 NO 调节肌肉中超氧化物的可用性和过氧亚硝酸盐的形成。
