Functional Aspects of the Mucosal Immune System

Up-regulation of nerve growth factor and interleukin-10 in inflamed and non-inflamed intestinal segments in rats with experimental colitis

Inflammatory bowel diseases are characterized by dysregulated immune response to the normal microflora and structural and functional changes of the enteric nervous system which occur in inflamed as well as non-inflamed areas of the bowel. This study describes the changes in the expression of nerve growth factor (NGF) and interleukin-10 (IL-10) in the colon and in various segments of the small intestine in two rat models of experimental colitis induced by iodoacetamide or 2,4,6-trinitrobenzene sulfonic acid (TNBS). Levels of NGF and IL-10 were measured by ELISA in tissue homogenate sampled from duodenum, jejunum, ileum and colon at different time intervals. NGF and IL-10 increased significantly in homogenates of strips isolated from all small intestinal segments, 3-6h after iodoacetamide or TNBS administration and remained elevated until the colonic inflammation subsided. Similar but more pronounced increase occurred in areas of the colon adjacent to the ulcer. Histologic examinations revealed inflammatory changes in the colon; however, examination of sections from the small intestines did not reveal significant differences between controls and rats with colitis. The marked up-regulation of nerve growth factor and interleukin-10 in colitis suggests that they play a role in limiting or resolving inflammation and in preventing it from becoming uncontrolled. It also suggests that experimental colitis may be associated with latent inflammation in the small bowel.