Chin Eva R, Chen Dapeng, Bobyk Kostyantyn D, Mázala Davi A G
School of Public Health, University of Maryland, College Park, Maryland
School of Public Health, University of Maryland, College Park, Maryland.
Am J Physiol Cell Physiol. 2014 Dec 1;307(11):C1031-8. doi: 10.1152/ajpcell.00237.2013. Epub 2014 Sep 24.
Amyotrophic lateral sclerosis (ALS) is a progressive neurodegenerative disease characterized by skeletal muscle atrophy and weakness, ultimately leading to respiratory failure. The purpose of this study was to assess changes in skeletal muscle excitation-contraction (E-C) coupling and intracellular Ca(2+) handling during disease progression in the G93A*SOD1 ALS transgenic (ALS Tg) mouse model. To assess E-C coupling, single muscle fibers were electrically stimulated (10-150 Hz), and intracellular free Ca(2+) concentration was assessed using fura-2. There were no differences in peak fura-2 ratio at any stimulation frequency at 70 days (early presymptomatic). However, at 90 days (late presymptomatic) and 120-140 days (symptomatic), fura-2 ratio was increased at 10 Hz in ALS Tg compared with wild-type (WT) fibers (0.670 ± 0.02 vs. 0.585 ± 0.02 for 120-140 days; P < 0.05). There was also a significant increase in resting fura-2 ratio at 90 days (0.351 ± 0.008 vs. 0.390 ± 0.009 in WT vs. ALS Tg; P < 0.05) and 120-140 days (0.374 ± 0.001 vs. 0.415 ± 0.003 in WT vs. ALS Tg; P < 0.05). These increases in intracellular Ca(2+) in ALS Tg muscle were associated with reductions in the sarcoplasmic/endoplasmic reticulum Ca(2+) ATPase proteins SERCA1 (to 54% and 19% of WT) and SERCA2 (to 56% and 11% of WT) and parvalbumin (to 80 and 62% of WT) in gastrocnemius muscle at 90 and 120-140 days, respectively. There was no change in dihydropyridine receptor/l-type Ca(2+) channel at any age. Overall, these data demonstrate minimal changes in electrically evoked Ca(2+) transients but elevations in intracellular Ca(2+) attributable to decreased Ca(2+)-clearance proteins. These data suggest that elevations in cellular Ca(2+) could contribute to muscle weakness during disease progression in ALS mice.
肌萎缩侧索硬化症（ALS）是一种进行性神经退行性疾病，其特征为骨骼肌萎缩和无力，最终导致呼吸衰竭。本研究的目的是评估在G93A*SOD1 ALS转基因（ALS Tg）小鼠模型疾病进展过程中骨骼肌兴奋-收缩（E-C）偶联和细胞内Ca(2+)处理的变化。为了评估E-C偶联，对单根肌纤维进行电刺激（10 - 150 Hz），并使用fura-2评估细胞内游离Ca(2+)浓度。在70天（症状前期早期）时，任何刺激频率下的fura-2峰值比率均无差异。然而，在90天（症状前期晚期）和120 - 140天（有症状期）时，与野生型（WT）纤维相比，ALS Tg小鼠在10 Hz刺激下的fura-2比率增加（120 - 140天时为0.670 ± 0.02 vs. 0.585 ± 0.02；P < 0.05）。在90天（WT为0.351 ± 0.008 vs. ALS Tg为0.390 ± 0.009；P < 0.05）和120 - 140天（WT为0.374 ± 0.001 vs. ALS Tg为0.415 ± 0.003；P < 0.05）时，静息fura-2比率也显著增加。ALS Tg小鼠肌肉中细胞内Ca(2+)的这些增加与腓肠肌中肌浆网/内质网Ca(2+) ATP酶蛋白SERCA1（分别降至WT的54%和19%）、SERCA2（分别降至WT的56%和11%）和小清蛋白（分别降至WT的80%和62%）的减少有关，分别在90天和120 - 140天时出现。在任何年龄，二氢吡啶受体/L型Ca(2+)通道均无变化。总体而言，这些数据表明电诱发的Ca(2+)瞬变变化最小，但由于Ca(2+)清除蛋白减少导致细胞内Ca(2+)升高。这些数据表明，细胞内Ca(2+)升高可能在ALS小鼠疾病进展过程中导致肌肉无力。
