Zhuang W, Eby J C, Cheong M, Mohapatra P K, Bredt D S, Disatnik M H, Rando T A
Department of Neurology and Neurological Sciences, Veterans Affairs Medical Center and Stanford University School of Medicine, Room A-343, Stanford, California 94305-5235, USA.
Muscle Nerve. 2001 Apr;24(4):502-11. doi: 10.1002/mus.1033.
The free radical, nitric oxide (NO.), has been implicated in the pathogenesis of muscular dystrophies because the enzyme, nitric oxide synthase (NOS), which produces NO., binds to the dystrophin-glycoprotein complex (DGC). In various studies of tissue samples from human and animal muscular dystrophies due to DGC defects, correlations between reductions of NOS activity and disease severity have been reported. To test for any direct effect of NOS expression on muscle cell susceptibility, we examined muscle cells in vitro under conditions of experimentally altered NOS activity. There were no differences in susceptibility to oxidative stress between differentiated myotube cultures from wild-type and from neuronal NOS (nNOS)-deficient mice. Likewise, pharmacological inhibition of NOS did not alter cellular susceptibility to oxidative challenges. Overexpression of NOS neither enhanced nor diminished cellular susceptibility to oxidative stress. Finally, we assessed the effect of NOS overexpression on myotube cultures from dystrophin-deficient (mdx) mice. NOS protein was localized to both membrane and cytosolic compartments in the transduced cells. Still, no difference in susceptibility to oxidative stress was found between the NOS-overexpressing cells and control cells. These data suggest that muscle cell susceptibility to oxidative challenges is independent of the level of NOS expression. Therefore, any role NO. may play in the pathogenesis of muscular dystrophies is likely to be independent of its effect on the redox state of the cell.
自由基一氧化氮（NO.）与肌营养不良症的发病机制有关，因为产生NO.的酶一氧化氮合酶（NOS）与肌营养不良蛋白 - 糖蛋白复合物（DGC）结合。在对因DGC缺陷导致的人类和动物肌营养不良症组织样本的各种研究中，已报道了NOS活性降低与疾病严重程度之间的相关性。为了测试NOS表达对肌肉细胞易感性的任何直接影响，我们在实验性改变NOS活性的条件下体外检查了肌肉细胞。来自野生型和神经元型NOS（nNOS）缺陷小鼠的分化肌管培养物对氧化应激的易感性没有差异。同样，NOS的药理学抑制也没有改变细胞对氧化挑战的易感性。NOS的过表达既没有增强也没有降低细胞对氧化应激的易感性。最后，我们评估了NOS过表达对肌营养不良蛋白缺陷（mdx）小鼠肌管培养物的影响。NOS蛋白定位于转导细胞的膜和胞质区室。然而，在过表达NOS的细胞和对照细胞之间未发现对氧化应激的易感性差异。这些数据表明，肌肉细胞对氧化挑战 的易感性与NOS表达水平无关。因此，NO.在肌营养不良症发病机制中可能发挥的任何作用可能与其对细胞氧化还原状态的影响无关。
