Neuropeptides and neurogenic mechanisms in oral and periodontal inflammation

It is generally accepted that the nervous system contributes to the pathophysiology of peripheral inflammation, and a neurogenic component has been implicated in many inflammatory diseases, including periodontitis. Neurogenic inflammation should be regarded as a protective mechanism, which forms the first line of defense and protects tissue integrity. However, severe or prolonged noxious stimulation may result in the inflammatory response mediating injury rather than facilitating repair. This review focuses on the accumulating evidence suggesting that neuropeptides have a pivotal role in the complex cascade of chemical activity associated with periodontal inflammation. An overview of neuropeptide synthesis and release introduces the role of neuropeptides and their interactions with other inflammatory factors, which ultimately lead to neurogenic inflammation. The biological effects of the neuropeptides substance P (SP), calcitonin gene-related peptide ( CGRP), vasoactive intestinal polypeptide ( VIP), and neuropeptide Y (NPY) are summarized, and evidence for their involvement in the localized inflammatory lesions which characterize periodontitis is presented. In this context, the role of CGRP in bone metabolism is described in more detail. Recent research highlighting the role of the nervous system in suppressing pain and inflammation is also discussed.