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Abstract
Purpose: Radiation-induced oral mucositis limits delivery of high-dose radiation to targeted cancers. Therefore, it is necessary to develop a treatment strategy to alleviate radiation-induced oral mucositis during radiation therapy. We previously reported that inhibiting reactive oxygen species (ROS) generation suppresses autophagy. Irradiation induces autophagy, suggesting that antioxidant treatment may be used to inhibit radiation-induced oral mucositis.

Materials and methods: We determined whether treatment with N-acetyl cysteine (NAC) could attenuate radiation-induced buccal mucosa damage in vitro and in vivo. The protective effects of NAC against oral mucositis were confirmed by transmission electron microscopy and immunocytochemistry. mRNA and protein levels of DNA damage and autophagy-related genes were measured by quantitative real-time polymerase chain reaction and western blot analysis, respectively.

Results: Rats manifesting radiation-induced oral mucositis showed decreased oral intake, loss of body weight, and low survival rate. NAC intake slightly increased oral intake, body weight, and the survival rate without statistical significance. However, histopathologic characteristics were markedly restored in NAC-treated irradiated rats. LC3B staining of rat buccal mucosa revealed that NAC treatment significantly decreased the number of radiation-induced autophagic cells. Further, NAC inhibited radiation-induced ROS generation and autophagy signaling. In vitro, NAC treatment significantly reduced the expression of NRF2, LC3B, p62, and Beclin-1 in keratinocytes compared with that after radiation treatment.

Conclusion: NAC treatment significantly inhibited radiation-induced autophagy in keratinocytes and rat buccal mucosa and may be a potentially safe and effective option for the prevention of radiation-induced buccal mucosa damage.

Affiliations

Haeng Jun Kim  1 , Sung Un Kang  2 , Yun Sang Lee  2 , Jeon Yeob Jang  2 , Hami Kang  3 , Chul-Ho Kim  2
1 Department of Molecular Science & Technology, Ajou University, Suwon, Korea.
2 Department of Otolaryngology, Ajou University School of Medicine, Suwon, Korea.
3 Program of Public Health Studies, Johns Hopkins University, Baltimore, MD, USA.