VIP

When a polypeptide of 28 amino acids was isolated from hog small intestine in 1970, what stood out first was its powerful vasodilating and blood-pressure-lowering effect. Hence the name vasoactive intestinal peptide, VIP for short. Today it is known to be made in many tissues far beyond the gut, by nerve cells as well as immune cells. It belongs to the secretin-glucagon family and is a close relative of PACAP.

Receptors and signalling: VIP acts through VPAC1 and VPAC2, two class B G-protein-coupled receptors that also bind PACAP and signal into the cell via cAMP. The 2012 IUPHAR review lists insulin secretion, circadian rhythms, immunity and inflammation among its functions.

What preclinical studies show:

• anti-inflammatory effects and vasodilation,
• influence on regulatory T-cells and on the Th1/Th2 balance, towards Th2 in autoimmune models,
• neurotrophic properties in neurodegenerative models.

A 2004 review in Pharmacological Reviews describes how the picture shifted from a vasodilating hormone to an immune modulator with the traits of a type 2 cytokine; a more recent paper from 2013 sums VIP up as neurotransmitter, immune regulator, vasodilator and secretagogue.

The practical hurdle: native VIP has a half-life of only a few minutes. Systemic experimental setups therefore often rely on stabilised analogues or on local delivery.

With us you get VIP strictly as a research compound. What you read here places the evidence in context and is not a guide to use.

VIP is described in studies as largely well tolerated. Its vascular action shapes the profile, though:

• Circulation: as a potent vasodilator it can trigger warmth, skin flushing, low blood pressure or dizziness.
• Injection site: where the needle goes in, mild redness or tenderness is the usual local finding.
• Immune modulation: shifting the Th1/Th2 balance amounts to an active hand in immune regulation.
• Very short duration: with a half-life of a few minutes, systemic delivery is hard to control.
• Evidence base: the characterisation comes mostly from preclinical models; robust long-term data in humans are missing.

This summary is no substitute for medical advice.

• Polypeptide with broad biological activity: isolation from small intestine - the first description from 1970, from hog intestine.
• The significance of vasoactive intestinal peptide in immunomodulation - 2004 review of VIP as an immune modulator with traits of a type 2 cytokine.
• Vasoactive intestinal peptide: a neuropeptide with pleiotropic immune functions - 2013 review of its many immune functions.