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 post-irradiation 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.

[Rationale for using helium-neon laser in medical rehabilitation of patients with atrophy]

High resolution measurements of helium-neon laser spectra have been conducted about 0.64 mm wavelength. The singlet oxygen photo-generation was demonstrated to be responsible for the bioeffects of this spectral interval. Helium-neon radiation with 0.633 mm wavelength was used for medical rehabilitation of 15 patients with muscular atrophy as a result of wearing immobilizing plaster arm-bends on lower extremity fractures. 50-day hypokinesia of a damaged extremity induced differences in functional indices between damaged and healthy extremities in the same patient. This difference was diminishing more rapidly after laser therapy than in the control group though all patients had adequate rehabilitative treatment. Due to the likelihood of hypokinesia- and weightlessness-induced atrophies, helium-neon laser may be recommended for atrophy prophylaxis and treatment in both cases.