RESUMEN
OBJECTIVE: To investigate the effect of melatonin on the colon inflammatory injury of rats with colitis and determine whether this effect is associated with inhibition of chemoattractant molecules interleukin (IL-8) and monocyte chemoattractant protein (MCP-1). METHODS: The study was designed and implemented in JingMen No.1 People's Hospital, HuBei Province, from May 2006 to April 2007. It involved 72 animals divided into 6 groups of 12 each: normal group, model group, 5-aminosalisalicylic acid group,and melatonin group (dose of 2.5, 5.0, and 10.0mg/kg). Rat colitis model was established by 2, 4, 6-trinitrobenzene sulfonic acid (TNBS) enema. Interlukin-8 and MCP-1 proteins in colon tissue were examined by immunohistochemistry and western blot. The messenger-RNA expressions of chemokines were determined by reverse transcription polymerase chain reaction analysis. RESULTS: Trinitrobenzene sulfonic acid enema resulted in pronounced pathological changes of colonic mucosa in model rats, which were in accordance with the significantly elevated myeloperoxidase activity. Expressions of chemokines were up-regulated in colitis. Melatonin treatment reduced colonic lesions and improved colitis symptom, and decreased the protein and mRNA expressions of IL-8 and MCP-1 significantly in colon tissues of rats with colitis. CONCLUSION: Chemokines IL-8 and MCP-1 are elevated in mucosal tissues in colitis and play an important role in the perpetuation of tissue destructive inflammatory processes; melatonin reduces colonic inflammatory injury of rats colitis through down-regulating the expressions of chemokines. Melatonin can be considered as a novel therapeutic alternative for the treatment of inflammatory bowel disease.