Tyganov Sergey A, Mochalova Ekaterina P, Melnikov Ivan Y, Vikhlyantsev Ivan M, Ulanova Anna D, Sharlo Kristina A, Mirzoev Timur M, Shenkman Boris S
Myology Laboratory, Institute of Biomedical Problems, Russian Academy of Sciences, Moscow, Russia.
Institute of Theoretical and Experimental Biophysics, Russian Academy of Sciences, Pushchino, Russia.
FASEB J. 2021 Oct;35(10):e21905. doi: 10.1096/fj.202100783R.
The study was aimed at investigating the mechanisms and structures which determine mechanical properties of skeletal muscles under gravitational unloading and plantar mechanical stimulation (PMS). We hypothesized that PMS would increase NO production and prevent an unloading-induced reduction in skeletal muscle passive stiffness. Wistar rats were hindlimb suspended and subjected to a daily PMS and one group of stimulated animals was also treated with nitric oxide synthase (NOS) inhibitor (L-NAME). Animals received mechanical stimulation of the feet for 4 h a day throughout 7-day hindlimb suspension (HS) according to a scheme that mimics the normal walking of the animal. Seven-day HS led to a significant reduction in soleus muscle weight by 25%. However, PMS did not prevent the atrophic effect induced by HS. Gravitational unloading led to a significant decrease in maximum isometric force and passive stiffness by 38% and 31%, respectively. The use of PMS prevented a decrease in the maximum isometric strength of the soleus muscle. At the same time, the passive stiffness of the soleus in the PMS group significantly exceeded the control values by 40%. L-NAME (NOS inhibitor) administration attenuated the effect of PMS on passive stiffness and maximum force of the soleus muscle. The content of the studied cytoskeletal proteins (α-actinin-2, α-actinin-3, desmin, titin, nebulin) decreased after 7-day HS, but this decrease was successfully prevented by PMS in a NOS-dependent manner. We also observed significant decreases in mRNA expression levels of α-actinin-2, desmin, and titin after HS, which was prevented by PMS. The study also revealed a significant NOS-dependent effect of PMS on the content of collagen-1a, but not collagen-3a. Thus, PMS during mechanical unloading is able to maintain soleus muscle passive tension and force as well as mRNA transcription and protein contents of cytoskeletal proteins in a NOS-dependent manner.
该研究旨在探究在重力卸载和足底机械刺激（PMS）作用下决定骨骼肌力学特性的机制和结构。我们假设PMS会增加一氧化氮（NO）的产生，并防止卸载引起的骨骼肌被动僵硬度降低。将Wistar大鼠后肢悬吊，并给予每日PMS，一组受刺激的动物还接受一氧化氮合酶（NOS）抑制剂（L-NAME）治疗。在7天的后肢悬吊（HS）期间，动物每天接受4小时的足部机械刺激，刺激方案模拟动物正常行走。7天的HS导致比目鱼肌重量显著降低25%。然而，PMS并未阻止HS诱导的萎缩效应。重力卸载分别导致最大等长力和被动僵硬度显著降低38%和31%。使用PMS可防止比目鱼肌最大等长力量降低。同时，PMS组比目鱼肌的被动僵硬度显著超过对照组值40%。给予L-NAME（NOS抑制剂）减弱了PMS对比目鱼肌被动僵硬度和最大力量的影响。7天的HS后，所研究的细胞骨架蛋白（α-辅肌动蛋白-2、α-辅肌动蛋白-3、结蛋白、肌联蛋白、伴肌动蛋白）含量降低，但PMS以NOS依赖的方式成功阻止了这种降低。我们还观察到HS后α-辅肌动蛋白-2、结蛋白和肌联蛋白的mRNA表达水平显著降低，而PMS可阻止这种降低。该研究还揭示了PMS对Ⅰ型胶原蛋白（collagen-1a）含量有显著的NOS依赖效应，但对Ⅲ型胶原蛋白（collagen-3a）没有影响。因此，机械卸载期间的PMS能够以NOS依赖的方式维持比目鱼肌的被动张力和力量以及细胞骨架蛋白的mRNA转录和蛋白质含量。
