Neuropeptides in Inflammatory Bowel Disease: An Update

Extrinsic and intrinsic neurons of the gut contain multiple neuropeptides, which through complex interactions modulate mucosal defense, inflammation, and repair in response to injury. Initial changes of the neurovascular peptidergic system may represent normal protective mechanisms against tissue injury, whereas subsequent alterations of neurovascular regulation may contribute to the pathogenesis and maintenance of the inflammatory state. Multiple interactions between sensory neurons, the immune system and growth factors appear to exist, and there is also a marked plasticity of the neurovascular peptidergic system with changes in the synthesis, release, binding, and degradation of peptides during inflammatory processes. A delicate and closely regulated balance between proinflammatory (e.g., SP, VIP, NPY) and antiinflammatory neuropeptides (e.g., CGRP, somatostatin, bombesin) seems to exist in the gastrointestinal tract. Disturbances of this balance might contribute to the pathophysiology of inflammatory bowel disease. In our overview, we will describe the results of studies in animal models of experimental inflammation and focus on the potential insight they provide in understanding the pathophysiology of inflammatory conditions of the bowel such as IBD. Knowledge with respect to these regulatory systems might provide novel insights into the inflammatory process and potentially expand the available therapeutic approaches in the management of IBD.