Melatonin reduces colon immunological injury in rats by regulating activity of macrophages

To investigate the effects of melatonin on the colon immunological injury of rats and the role of macrophages in this process.

The rats colitis was established by intrarectal injection with 2,4,6-trinitrobenzenesulfonic acid (TNBS) and ethanol. The animals were randomized into 6 groups: normal group, model group, 5-aminosalicylic acid group (100 mg/kg), and melatonin group (2.5, 5.0, and 10.0 mg/kg), treated intrarectally with saline, saline, 5-aminosalicylic acid, and melatonin, respectively (once a day, from d 7 after colitis established to d 28). At the end of the experiment, the colon mucosa damage index (CMDI), the score of histology (HS), the level of myeloperoxidase(MPO), and the sore of occult blood test (OBT) were evaluated. Meanwhile, the activity of interleukin-1 (IL-1), tumour necrosis factor-alpha (TNF-alpha, and nitric oxide (NO) were also detected.

After treated with TNBS and ethanol, the extents of CMDI, HS, OBT, and the level of MPO in model group were more higher than that in normal group. Melatonin could alleviate the colon injury, and reduce the level of MPO and the degree of OBT. The activity of IL-1, TNF-alpha, and NO which released mainly from macrophages was elevated remarkably. Melatonin could depress all this parameters.

Melatonin could reduce the colon damage in the colitis rats by regulating macrophage activity.