L. Dengqun1, Y. Tian1, Q. Lian1, J. Yuying1, H. Wang2, F. Ming3, L. Lu3, J. Lang4, and M. Feng5; 1Sichuan Cancer Hospital & Institute, Chengdu, Sichuan, China, 2The Third Peoples Hospital of Sichuan Province, chengdu, China, 3Sichuan Cancer Hospital & Institute, Sichuan Cancer Center, School of Medicine, University of Electronic Science and Technology of China, China, Chengdu, China, 4Department of Radiation Oncology, Sichuan Cancer Hospital & Institute, Sichuan Cancer Center; Cancer Hospital affiliate to University of Electronic Science and Technology of China, Chengdu, China, 5The Third Peoples Hospital of Sichuan Province, Chengdu, China
Purpose/Objective(s): Radiotherapy is an important treatment method of head and neck cancer. Patients receiving radiation suffers different degrees of xerostomia, which seriously affect the quality of life. Till now, the effect of drug therapy to alleviating xerostomia is not obvious, and the application prospect of new therapeutic methods such as gene therapy and cell therapy is broad. However, the mechanism of salivary gland regeneration and repair after radiation has not been fully clarified. Autophagy is a highly conserved catabolic process induced under various conditions of cellular stress. It is deregulated in the context of various human pathologies, including cancer. Some studies have confirmed the important role of autophagy in the repair of salivary glands after radiation. Mist1 is a serous cell-specific transcription factor and there is no studie on salivary glands in Mist1 as yet. Therefore, we aimed to explore the role of autophagy in the regeneration and repair of submandibular gland after radiation injury. Materials/
Methods: 3 methyladenine (3-MA), an inhibitor of autophagy, was administered into healthy and irradiated C57BL/6J mice by continuous i.p injection to interrupt autophagy of salivary gland. The fluorescence co-localization of autophagy lysosome with AQP5 (aquaporin 5) and NKCC1 (Na-K-Cl cotransporter) was observed, and the number of autophagy lysosome was also observed. The changes of autophagy flow before and after radiation injury with a single fraction of 15Gy were compared. The mRNA expression levels of Mist1, AQP5 and NKCC1, which were important functional proteins in submandibular gland tissue were detected. Results: The weight of submandibular gland between the autophagy inhibition group and the control group has no difference (p=0.586). However, compared with the control group, salivary secretion was significantly decreased in the autophagy inhibition group (p < 0.001), and the mRNA expression level of Mist1, AQP5, NKCC1 was significantly decreased after autophagy inhibition (p < 0.05). At 7 days after radiation, the edema of submandibular gland tissue in autophagy group was more obvious than that in the control group, and the surface area of the submandibular gland was statistically different between two groups (p < 0.0001). 3-MA significantly inhibited the protein positive intensity of Mist1, AQP5 and NKCC1 in the salivary glands of mice after radiation compared with the control group (p < 0.05). Conclusion: Autophagy is required for the maintenance of physiological morphology of salivary gland and participates in the regulation of salivary function. Inhibition of autophagy may lead to a decreased expression of Mist1 during salivary gland injury repair, and it could not induce and maintain the expression levels of AQP5 and NKCC1, which hinders the repairing process of radiation injury to a certain extent. Interaction of autophagy with Mist1 may be a new potential therapeutic target for the repairing mechanism of salivary gland injury caused by radiotherapy.
