RANKL Mediates Muscle Atrophy and Dysfunction in a Cigarette Smoke-induced Model of Chronic Obstructive Pulmonary Disease

Am J Respir Cell Mol Biol. 2021 May;64(5):617-628. doi: 10.1165/rcmb.2020-0449OC.

Abstract

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 in vitro. 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 in vitro 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.

Keywords: COPD; RANKL; cigarette smoke; skeletal muscle dysfunction.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Antibodies, Neutralizing / pharmacology
  • Cell Line
  • Cigarette Smoking / adverse effects
  • Complex Mixtures / antagonists & inhibitors
  • Complex Mixtures / pharmacology
  • Disease Models, Animal
  • Female
  • Gene Expression Regulation
  • Hand Strength / physiology
  • Insulin-Like Growth Factor I / genetics
  • Insulin-Like Growth Factor I / metabolism
  • Mice
  • Mice, Inbred C57BL
  • Muscle Fibers, Skeletal / drug effects
  • Muscle Fibers, Skeletal / metabolism
  • Muscle Fibers, Skeletal / pathology
  • Muscle Proteins / genetics
  • Muscle Proteins / metabolism
  • Muscle Strength / drug effects
  • Muscle Strength / genetics
  • Muscle, Skeletal / drug effects
  • Muscle, Skeletal / metabolism
  • Muscle, Skeletal / pathology
  • Muscular Atrophy / genetics*
  • Muscular Atrophy / metabolism
  • Muscular Atrophy / pathology
  • Muscular Atrophy / prevention & control
  • Myogenin / genetics
  • Myogenin / metabolism
  • Myostatin / genetics
  • Myostatin / metabolism
  • NF-kappa B / genetics*
  • NF-kappa B / metabolism
  • Pulmonary Disease, Chronic Obstructive / chemically induced
  • Pulmonary Disease, Chronic Obstructive / genetics*
  • Pulmonary Disease, Chronic Obstructive / metabolism
  • Pulmonary Disease, Chronic Obstructive / prevention & control
  • RANK Ligand / antagonists & inhibitors
  • RANK Ligand / genetics*
  • RANK Ligand / metabolism
  • Receptor Activator of Nuclear Factor-kappa B / genetics*
  • Receptor Activator of Nuclear Factor-kappa B / metabolism
  • SKP Cullin F-Box Protein Ligases / genetics
  • SKP Cullin F-Box Protein Ligases / metabolism
  • Signal Transduction
  • Tripartite Motif Proteins / genetics
  • Tripartite Motif Proteins / metabolism
  • Ubiquitin-Protein Ligases / genetics
  • Ubiquitin-Protein Ligases / metabolism

Substances

  • Antibodies, Neutralizing
  • Complex Mixtures
  • Mstn protein, mouse
  • Muscle Proteins
  • Myog protein, mouse
  • Myogenin
  • Myostatin
  • NF-kappa B
  • RANK Ligand
  • Receptor Activator of Nuclear Factor-kappa B
  • Tnfrsf11a protein, mouse
  • Tnfsf11 protein, mouse
  • Tripartite Motif Proteins
  • insulin-like growth factor-1, mouse
  • Insulin-Like Growth Factor I
  • Fbxo32 protein, mouse
  • SKP Cullin F-Box Protein Ligases
  • Trim63 protein, mouse
  • Ubiquitin-Protein Ligases