Sharlo Kristina A, Paramonova Inna I, Lvova Irina D, Mochalova Ekaterina P, Kalashnikov Vitaliy E, Vilchinskaya Natalia A, Tyganov Sergey A, Konstantinova Tatyana S, Shevchenko Tatiana F, Kalamkarov Grigoriy R, Shenkman Boris S
Myology Laboratory, Institute of Biomedical Problems RAS, 123007 Moscow, Russia.
Emanuel Institute of Biochemical Physics, RAS, 123007 Moscow, Russia.
Int J Mol Sci. 2021 Jan 29;22(3):1372. doi: 10.3390/ijms22031372.
It was observed that gravitational unloading during space missions and simulated microgravity in ground-based studies leads to both transformation of slow-twitch muscle fibers into fast-twitch fibers and to the elimination of support afferentation, leading to the "switching-off" of postural muscle motor units electrical activity. In recent years, plantar mechanical stimulation (PMS) has been found to maintain the neuromuscular activity of the hindlimb muscles. Nitric oxide (NO) was shown to be one of the mediators of muscle fiber activity, which can also promote slow-type myosin expression. We hypothesized that applying PMS during rat hindlimb unloading would lead to NO production upregulation and prevention of the unloading-induced slow-to-fast fiber-type shift in rat soleus muscles. To test this hypothesis, Wistar rats were hindlimb suspended and subjected to daily PMS, and one group of PMS-subjected animals was also treated with nitric oxide synthase inhibitor (L-NAME). We discovered that PMS led to sustained NO level in soleus muscles of the suspended animals, and NOS inhibitor administration blocked this effect, as well as the positive effects of PMS on myosin I and IIa mRNA transcription and slow-to-fast fiber-type ratio during rat hindlimb unloading. The results of the study indicate that NOS activity is necessary for the PMS-mediated prevention of slow-to-fast fiber-type shift and myosin I and IIa mRNA transcription decreases during rat hindlimb unloading.
据观察，太空任务期间的重力卸载以及地面研究中的模拟微重力会导致慢肌纤维向快肌纤维转变，同时消除支持传入神经，导致姿势肌运动单位电活动“关闭”。近年来，已发现足底机械刺激（PMS）可维持后肢肌肉的神经肌肉活动。一氧化氮（NO）被证明是肌肉纤维活动的介质之一，它也可以促进慢型肌球蛋白的表达。我们假设在大鼠后肢卸载期间应用PMS会导致NO产生上调，并防止大鼠比目鱼肌中卸载诱导的慢到快纤维类型转变。为了验证这一假设，将Wistar大鼠后肢悬吊并每日进行PMS处理，并且一组接受PMS处理的动物也用一氧化氮合酶抑制剂（L-NAME）进行处理。我们发现PMS导致悬吊动物比目鱼肌中NO水平持续升高，给予NOS抑制剂可阻断这种作用，以及PMS对大鼠后肢卸载期间肌球蛋白I和IIa mRNA转录以及慢到快纤维类型比例的积极影响。研究结果表明，NOS活性对于PMS介导的预防慢到快纤维类型转变以及大鼠后肢卸载期间肌球蛋白I和IIa mRNA转录减少是必要的。
