A comparative study of cisplatin-based definitive chemo-radiation in non-metastatic squamous cell carcinoma of the esophagus

The Radioprotective Effect of Combination of Melatonin and Metformin on Rat Duodenum Damage Induced by Ionizing Radiation: A Histological Study

BACKGROUND

Radiation toxicity is one of the major concerns for patients with gastrointestinal cancers that undergo radiotherapy. Duodenum is one of the most radiosensitive parts of gastrointestinal system that may be exposed to a high dose of radiation during radiotherapy for some cancers. The development or identification of appropriate radioprotectors with less toxicity is an interesting aim in radiobiology for clinical radiotherapy applications. In the present study, we aimed to evaluate the radioprotective effect of melatonin and metformin combination in rat's duodenum. In addition, we compared our results with the radioprotective effect of melatonin, when administered alone.

MATERIALS AND METHODS

Thirty male rats were divided into six groups: control, melatonin treatment, melatonin plus metformin treatment, whole-body irradiation, irradiation with melatonin treatment, and irradiation with melatonin plus metformin treatment. Irradiation was performed with 10 Gy cobalt-60 gamma rays, while 100 mg/kg of melatonin and metformin were administered 24 h before to 72 h after irradiation. After 3.5 days, their duodenum tissues were removed for histopathological evaluation.

RESULTS

Irradiation of rats led to mild-to-moderate mucositis signs, infiltration of inflammatory cells, necrosis, and damage to Brunner's glands and reduction of goblet cells. Melatonin was able to alleviate these damages, while melatonin plus metformin could reduce some radiation toxicity signs.

CONCLUSION

Administration of melatonin plus metformin could reduce mucositis in duodenum. However, the administration of melatonin is more effective for mitigation of duodenal injury compared with melatonin plus metformin.

Selenium as an adjuvant for modification of radiation response

Ionizing radiation plays a central role in several medical and industrial purposes. In spite of the beneficial effects of ionizing radiation, there are some concerns related to accidental exposure that could pose a threat to the lives of exposed people. This issue is also very critical for triage of injured people in a possible terror event or nuclear disaster. The most common side effects of ionizing radiation are experienced in cancer patients who had undergone radiotherapy. For complete eradication of tumors, there is a need for high doses of ionizing radiation. However, these high doses lead to severe toxicities in adjacent organs. Management of normal tissue toxicity may be achieved via modulation of radiation responses in both normal and malignant cells. It has been suggested that treatment of patients with some adjuvant agents may be useful for amelioration of radiation toxicity or sensitization of tumor cells. However, there are always some concerns for possible severe toxicities and protection of tumor cells, which in turn affect radiotherapy outcomes. Selenium is a trace element in the body that has shown potent antioxidant and radioprotective effects for many years. Selenium can potently stimulate antioxidant defense of cells, especially via upregulation of glutathione (GSH) level and glutathione peroxidase activity. Some studies in recent years have shown that selenium is able to mitigate radiation toxicity when administered after exposure. These studies suggest that selenium may be a useful radiomitigator for an accidental radiation event. Molecular and cellular studies have revealed that selenium protects different normal cells against radiation, while it may sensitize tumor cells. These differential effects of selenium have also been revealed in some clinical studies. In the present study, we aimed to review the radiomitigative and radioprotective effects of selenium on normal cells/tissues, as well as its radiosensitive effect on cancer cells.