NLRP3 inflammasome activation aggravates skeletal muscle atrophy in experimental model of denervation

The innervation of skeletal myofibers exerts a crucial influence on the maintenance of muscle tone and normal operation, but little is known concerning atrophy and its underlying mechanisms in denervated muscle to date. Here, we reported that activated NOD-like receptor protein 3 (NLRP3) inflammasome with pyroptotic cell death occurred in denervated gastrocnemius in the mouse model of sciatic denervation. This damage causes interleukin 1 beta (IL-1β) release，facilitating the ubiquitin proteasome system (UPS) activation, which was responsible for muscle proteolysis. Conversely, genetic knock-out of muscular NLRP3 inhibited the pyroptosis-associated protein expression and ameliorate muscle atrophy significantly. Meanwhile, co-treatment with shRNA-NLRP3, also remarkably attenuated NLRP3 inflammasome activator (NIA)-induced C2C12 myotube pyroptosis and atrophy. Interestingly, we also observed a correlation between NLRP3 inflammasome activation and muscular apoptosis possibly via caspase 1 mediation after denervation. This work for the first time elucidates on the roles and mechanisms of NLRP3 inflammasome in skeletal muscle atrophy during denervation and suggests the potential contribution to the pathogenesis of neuromuscular diseases. Examination of 32 different gastrocnemius muscles post denervation

骨骼肌肌纤维的神经支配对维持肌张力与肌肉正常功能至关重要，但迄今为止，学界对失神经支配肌肉的萎缩及其潜在机制仍知之甚少。本研究报道，在坐骨神经失神经支配的小鼠模型中，失神经支配的腓肠肌内可出现活化的NOD样受体蛋白3（NOD-like receptor protein 3, NLRP3）炎性小体及焦亡性细胞死亡。该损伤会引发白细胞介素1β（IL-1β）释放，进而促进泛素-蛋白酶体系统（ubiquitin proteasome system, UPS）激活，而该系统正是介导肌肉蛋白水解的核心通路。反之，对肌肉中的NLRP3进行基因敲除，可抑制焦亡相关蛋白的表达，并显著改善肌肉萎缩。同时，联合使用靶向NLRP3的短发夹RNA（shRNA-NLRP3），也可显著减轻NLRP3炎性小体激活剂（NLRP3 inflammasome activator, NIA）诱导的C2C12肌管焦亡与萎缩。有趣的是，本研究还观察到，失神经支配后，NLRP3炎性小体的激活可能通过半胱天冬氨酸蛋白酶1（caspase 1）介导，与肌肉细胞凋亡存在相关性。本研究首次阐明了NLRP3炎性小体在失神经支配性骨骼肌萎缩中的作用与机制，并提示其可能参与神经肌肉疾病的发病过程。本研究共检测了32例失神经支配后的腓肠肌标本。