Scientific Reference
VIP (Vasoactive Intestinal Peptide)
Evidence profile: Predominantly preclinical
VIP, or vasoactive intestinal peptide, is a 28-residue amidated neuropeptide found in central and peripheral neurons and in the gut wall. It belongs to the secretin–glucagon family and is most closely related to pituitary adenylate cyclase-activating polypeptide (PACAP), with which it shares receptors. First isolated from intestinal tissue and named for its action on blood vessels, it is now studied as a neurotransmitter, a smooth-muscle signal and a messenger between the nervous and immune systems. Most of the literature comes from cell, tissue and animal studies. Synthetic VIP has been examined in small human studies, including in pulmonary conditions, but it is cleared from the circulation within a few minutes, which complicates that work.
Mechanism of Action
VIP binds two class B G-protein-coupled receptors, VPAC1 and VPAC2, with similar affinity, and binds the PACAP-preferring PAC1 receptor much more weakly. Both VPAC receptors couple mainly to Gs, raising cyclic AMP and activating protein kinase A, although coupling to other G proteins has been described. In immune cell cultures this signalling has been reported to alter cytokine production and T-cell differentiation. In the suprachiasmatic nucleus, mouse studies indicate that VIP acting at VPAC2 helps synchronise the neurons of the circadian clock. In smooth muscle preparations it has been examined as a relaxant signal.
Molecular Information
- Type: Neuropeptide (vasoactive intestinal peptide)
- Length: 28 amino acids
- Molecular weight: 3326.8 g/mol
- Molecular formula: C147H237N43O43S