VIP (Vasoactive Intestinal Peptide)

Vasoactive Intestinal Peptide (VIP) is a 28-amino acid neuropeptide widely distributed throughout the central and peripheral nervous systems, as well as immune and gut tissues. Despite its name (derived from initial discovery of intestinal vasodilatory effects), VIP functions as a broad-spectrum regulatory peptide with effects on multiple organ systems.

VIP signals through two G protein-coupled receptors, VPAC1 and VPAC2, that activate adenylyl cyclase to increase intracellular cAMP. These receptors are expressed in the CNS, immune system, vasculature, respiratory tract, and GI tract, accounting for VIP's diverse biological activities.

As an immunomodulator, VIP has potent anti-inflammatory properties, shifting immune responses toward tolerance and suppressing pro-inflammatory cytokine production. Research has explored VIP in models of rheumatoid arthritis, inflammatory bowel disease, multiple sclerosis, and other autoimmune conditions.

VIP also functions as a neuropeptide with both neurotrophic and neuroprotective properties. It plays a role in circadian rhythm regulation through action in the suprachiasmatic nucleus and demonstrates protective effects in models of Alzheimer's and Parkinson's diseases. Its combination of immunomodulatory and neuroprotective activities makes it relevant to neuroimmune interface research.