Radioprotective effects of melatonin on colon epithelium: Role in oxidative stress and Bax/Bcl-2 regulation

This study aimed to evaluate the protective effects of melatonin on colon tissue integrity in rats exposed to low- and high-dose rate radiotherapy.

Forty rats were randomly divided into: Group1 (Control) received no treatment. Group2 was exposed to a single dose of 8 Gy radiotherapy at a low-dose rate (LDR) of 400 MU/min. Group3 (LDR+Melatonin) received of 50 mg/kg melatonin, followed by 8 Gy LDR radiotherapy (400 MU/min) to the abdominopelvic region 15 min later. Group4 was treated with 8 Gy radiotherapy at a high-dose rate (HDR) of 1400 MU/min. Group5 (HDR+Melatonin) received 50 mg/kg melatonin 15 min before 8 Gy HDR radiotherapy (1400 MU/min). Colon tissues were harvested 48 h after radiotherapy for analyses.

Radiotherapy induced damage to colon tissues, characterized by disruption of crypt architecture and depletion of goblet cells. Melatonin treatment effectively preserved these structures, exhibiting a protective effect (p < 0.001). The Bax/Bcl-2 ratio, a key marker of apoptosis, was significantly reduced in melatonin-treated groups compared to radiotherapy-only groups (p < 0.001), suggesting a reduction in apoptotic cell death. Furthermore, melatonin administration resulted in a substantial increase in total antioxidant status (T-AS) and a significant decrease in total oxidative status (T-OS) and oxidative stress index (O-SI) levels (p < 0.001).

Melatonin significantly mitigated radiation-induced oxidative stress and apoptosis in healthy colon tissue, as evidenced by the reduction in the Bax/Bcl-2 ratio. Melatonin may serve as an effective radioprotective agent, preserving the integrity of colon tissue during both low- and high-dose rate abdominopelvic radiotherapy.