Increased Expression of MuRF1 Is Associated with Radiation-induced Laryngeal Muscle Atrophy

Background: Laryngeal muscles play an important role in breathing, sound production and trachea protection against food. Laryngeal dysfunctions during radiotherapy for head and neck cancers are common. In the present study, we aimed to investigate the early effect of radiation on the laryngeal muscles in vivo and possible mechanisms involved in this process. Materials and Methods: Eight-week-old female C57bl/mice received neck irradiation with a single dose of 25 Gy and bilateral thyroarytenoid (TA) muscles of mice were collected at day 3, 7 and 10 postirradiation for evaluating muscle size, myosins, myosin heavy chain (MyHC) composition and MuRF1 protein levels. Results: A significant reduction in the size of muscle fibers and myosins in the TA muscles were observed at days 3, 7, 10 after radiation (p<0.05). The loss of IIB myosin was more severe than that of IIA/X myosins at day 7 post-irradiation (75% vs. 64%). MuRF1 protein level was markedly increased at day 7 and 10 after radiation (p<0.05). Conclusion: Radiation induced an acute muscle fiber atrophy and myosin loss in the intrinsic laryngeal muscles. MuRF1 may play an important role in the radiation-induced protein degradation in the laryngeal muscles and warrants further investigation.