血管活性肠肽 VIP

28 肽神经内分泌递质：激动 VPAC1/VPAC2（及低亲和 PAC1）G 蛋白偶联受体升高 cAMP，产生血管舒张、支气管扩张、肠道分泌调节，并经抑制 NF-κB 通路发挥抗炎与免疫调节作用

功效：多功能调节肽；舒张血管、抗炎、调节肠道、改善肺部炎症、舒缓气道；自身免疫、肠道紊乱研究用肽

Vasoactive intestinal peptide, also known as vasoactive intestinal polypeptide or VIP, is a peptide hormone that is vasoactive in the intestine. VIP is a peptide of 28 amino acid residues that belongs to a glucagon/secretin superfamily, the ligand of class II G protein–coupled receptors.

VIP is produced in many tissues of vertebrates including the gut, pancreas, neocortex, and suprachiasmatic nuclei of the hypothalamus in the brain. VIP stimulates contractility in the heart, causes vasodilation, increases glycogenolysis, lowers arterial blood pressure and relaxes the smooth muscle of trachea, stomach and gallbladder. In humans, the vasoactive intestinal peptide is encoded by the VIP gene.

VIP has a half-life (t½) in the blood of about two minutes.

Source: English Wikipedia, "Vasoactive intestinal peptide".

VIP binds to both VPAC1 and VPAC2 receptors. When VIP binds to VPAC2 receptors, a G-alpha-mediated signaling cascade is triggered. In a number of systems, VIP binding activates adenyl cyclase activity leading to increases in cAMP concentration and PKA activity. The PKA then activates other intracellular signaling pathways like the phosphorylation of CREB and other transcriptional factors. The mPer1 and mPer2 promoters have CRE domains and thus provides the mechanism for VIP to regulate the molecular clock itself. Then it will activate gene expression pathways such as Per1 and Per2 in circadian rhythm.

In addition, GABA levels are connected to VIP in that they are co-released. Sparse GABAergic connections are thought to decrease synchronized firing. While GABA controls the amplitude of SCN neuronal rhythms, it is not critical for maintaining synchrony. However, if GABA release is dynamic, it may mask or amplify synchronizing effects of VIP inappropriately.

Circadian time is likely to affect the synapses rather than the organization of VIP circuits.

SCN and circadian rhythm Suprachiasmatic nucleus is shown in green.

The SCN coordinates daily timekeeping in the body and VIP plays a key role in communication between individual brain cells within this region. At a cellular level, the SCN expresses different electrical activity in circadian time. Higher activity is observed during the day, while during night there is lower activity. This rhythm is thought to be important feature of SCN to synchronize with each other and control rhythmicity in other regions.