Department of Respiratory and Critical Care Medicine, Peking University Third Hospital, Beijing, China; and.
Department of Respiratory Medicine, and Medical Research Center, Beijing Chaoyang Hospital, Capital Medical University, Beijing, China.
Am J Respir Cell Mol Biol. 2021 May;64(5):617-628. doi: 10.1165/rcmb.2020-0449OC.
Skeletal muscle dysfunction is one of the important comorbidities of chronic obstructive pulmonary disease (COPD); however, the underlying mechanisms remain largely unknown. RANKL (receptor activator of nuclear factor κB ligand), a key mediator in osteoclast differentiation, was also found to play a role in skeletal muscle pathogenesis. Whether RANKL is involved in COPD-related skeletal muscle dysfunction is as-of-yet unknown. We examined the expression of RANKL/RANK in skeletal muscles from mice exposed to cigarette smoke (CS) for 24 weeks. Grip strength and exercise capacity as well as muscular morphology were evaluated in CS-exposed mice with or without anti-RANKL treatment. The expressions of protein synthesis- or muscle growth-related molecules (IGF-1, myogenin, and myostatin), muscle-specific ubiquitin E3 ligases (MuRF1 and atrogin-1), and the NF-κb inflammatory pathway were also evaluated in skeletal muscles. The effect of CS extract on RANKL/RANK expression and that of exogenous RANKL on the ubiquitin-proteasome pathway in C2C12 myotubes were investigated . Long-term CS exposure induced skeletal muscle dysfunction and atrophy together with upregulation of RANKL/RANK expression in a well-established mouse model of COPD. RANKL neutralization prevented skeletal muscle dysfunction and atrophy. RANKL inhibition decreased expressions of myostatin and MuRF1/Atrogin1 and suppressed the NF-κb pathway in skeletal muscles from CS-exposed mice. In experiments with C2C12 myotubes, CS extract induced expression of RANKL/RANK, and exogenous RANKL induced activation of the ubiquitin-proteasome pathway and NF-κb pathway via RANK. Our results revealed an important role of the RANKL/RANK pathway in muscle atrophy induced by CS exposure, suggesting that RANKL may be a potential therapeutic target in COPD-related skeletal muscle dysfunction.
骨骼肌功能障碍是慢性阻塞性肺疾病（COPD）的重要合并症之一；然而，其潜在机制在很大程度上尚不清楚。核因子 κB 配体（receptor activator of nuclear factor κB ligand，RANKL）是破骨细胞分化的关键介质，也被发现参与骨骼肌发病机制。RANKL 是否参与 COPD 相关的骨骼肌功能障碍尚不清楚。我们检查了暴露于香烟烟雾（cigarette smoke，CS）24 周的小鼠骨骼肌中 RANKL/RANK 的表达。在有或没有抗 RANKL 治疗的 CS 暴露小鼠中评估握力和运动能力以及肌肉形态。还评估了骨骼肌中蛋白质合成或肌肉生长相关分子（IGF-1、myogenin 和 myostatin）、肌肉特异性泛素 E3 连接酶（MuRF1 和 atrogin-1）以及 NF-κb 炎症通路的表达。还研究了 CS 提取物对 RANKL/RANK 表达的影响以及外源性 RANKL 对 C2C12 肌管中泛素-蛋白酶体通路的影响。
长期 CS 暴露在 COPD 的小鼠模型中诱导骨骼肌功能障碍和萎缩，同时上调 RANKL/RANK 表达。RANKL 中和可预防骨骼肌功能障碍和萎缩。RANKL 抑制降低了 CS 暴露小鼠骨骼肌中肌肉生长抑制素和 MuRF1/Atrogin1 的表达，并抑制了 NF-κb 通路。在 C2C12 肌管实验中，CS 提取物诱导了 RANKL/RANK 的表达，外源性 RANKL 通过 RANK 诱导了泛素-蛋白酶体通路和 NF-κb 通路的激活。
我们的研究结果揭示了 RANKL/RANK 通路在 CS 暴露诱导的肌肉萎缩中的重要作用，提示 RANKL 可能是 COPD 相关骨骼肌功能障碍的潜在治疗靶点。
