Proinflammatory cytokines in irritable bowel syndrome: a comparison with inflammatory bowel disease

Background/Aims: Irritable bowel syndrome (IBS) is a common disease often considered as a functional intestinal disorder. Inflammation in IBS is a quite intriguing theory. The aim of this study was to investigate tumor necrosis factor (TNF)-alpha, interleukin (IL)-1 beta and IL-6 expression in inflammatory bowel disease (IBD) patients, IBS patients and normal controls. Methods: IBS and IBD patients along with normal controls were recruited in the study. In all groups, 2 pinch biopsies were taken at each of 3 anatomical sites (terminal ileum, cecum, and rectum). IBS patients were also subcategorized according to the syndrome clinical manifestations. Two monoclonal antibodies (mAb), TNF-alpha mAb and IL-6 mAb, and one polyclonal antibody IL-1 beta mAb were applied for immunohistochemical analysis. Results: In IBD patients intensity of TNF-alpha and IL-1 beta were lower than in IBS patients or controls, while IL-6 was significantly increased comparing to the aforementioned groups. In IBS patients TNF-alpha was increased comparing to IBD patients or controls, while IL-6 and IL-1 beta were similar to controls. In IBS subgroups, TNF-alpha was lower in diarrhea predominant IBS patients and higher constipation predominant IBS patients. Differences among IBS subgroups regarding IL-6 and IL-1 beta were nonsignificant. Conclusions: IL-6 seems to be the most important proinflammatory cytokine in IBD patients, while TNF-alpha could play a more significant role in IBS pathogenesis.