Radioprotective effect of endogenous melatonin secretion associated with the circadian rhythm in irradiated rats

Abstract

Purpose: We investigated the radioprotective effect of endogenous melatonin release at different times associated with the circadian rhythm on head and neck radiotherapy.

Materials and methods: Two groups of animals were subjected daily to 8 Gy single fraction radiotherapy in the head and neck region from 5:00 to 6:00 (the morning group) or from 19:00 to 20:00 (the evening group). Corresponding untreated groups served as controls. Submandibular glands from rats sacrificed on the seventh day after irradiation were assessed biochemically and histopathologically. Melatonin, malondialdehyde and superoxide dismutase levels in blood collected immediately prior to irradiation were measured with rat-specific ELISA kits.

Results: In irradiated rats, melatonin, malondialdehyde and superoxide dismutase levels were significantly higher in the evening group than in the morning group. In nonirradiated rats, melatonin and superoxide dismutase levels were significantly higher in the evening group than in the morning group. The areas of seromucous acinar cells were similar between the irradiated and nonirradiated evening groups, but the area was higher in the evening irradiated group than in the morning irradiated group.

Conclusion: Consideration of endogenous melatonin secretion associated with the circadian rhythm may offer new therapeutic solutions for the complications of head and neck radiotherapy.

Keywords:

• Radiotherapy
• melatonin
• circadian rhythm
• radiation protection
• submandibular glands

Acknowledgements

We thank the physicists and technicians working at the Radiotherapy Department of the Teaching and Research Hospital of Rize.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was supported by Recep Tayyip Erdogan University-Scientific Research Projects Coordination Unit [grant number 2015.53001.106.03.03].

Notes on contributors

Sema Yilmaz Rakici

Sema Yilmaz Rakici, MD, is the head of the Department of Radiation Oncology, Recep Tayyip Erdogan University, Faculty of Medicine. Her research interests overlap with the areas of radiation oncology and oncology.

Levent Tumkaya

Levent Tumkaya, PhD. He is the head of the Department of Histology-Embryology, Recep Tayyip Erdogan University, Faculty of Medicine. His research interests are in the areas of histology.

Ozlem Celebi Edirvanli

Ozlem Celebi Edirvanli, MD. She is associate professor in the Department of Otorhinolaryngology, Recep Tayyip Erdogan University, Faculty of Medicine. Her research interests are in the areas of Otorhinolaryngology and neck dissection.

Ufuk Yazici

Ufuk Yazici, BTech. He is a health physicist in the Department of Radiation Oncology, Recep Tayyip Erdogan University, Faculty of Medicine. His research interests are in the areas of medical dosimetry and radiotherapy.

Engin Dursun

Engin Dursun, MD. He is the head of the Department of Otorhinolaryngology, Recep Tayyip Erdogan University, Faculty of Medicine. His research interests are in the areas of Otorhinolaryngology and Head and Neck Surgery.

Medeni Arpa

Medeni Arpa, MD. He is an assistant professor in the department of Otorhinolaryngology, Recep Tayyip Erdogan University, Faculty of Medicine. His research interests are in the areas of Medical Laboratory Technology.

Tolga Mercantepe

Tolga Mercantepe, PhD. He is assistant professor in the Department of Histology-Embryology, Recep Tayyip Erdogan University, Faculty of Medicine. His research interests are in the areas of histology and embriology.