Vasoactive intestinal peptide (VIP) is a small molecule basic polypeptide with a straight chain structure composed of 28 amino acid residues, 20% of which is a helical structure, and 80% of which is a loose and disordered structure, pp. 10-28 The bit sequence is critical to the specificity of its action; in the pathological circulation state of the body, VIP degrades slowly. Once its content and receptor sensitivity change, it will lead to the occurrence of multi-system diseases, especially the secretion of digestive system diseases. Functional disorder. It is produced by the central nervous system and peripheral nervous system, released by parasympathetic postganglionic fibers, and coexists with acetylcholine, playing a regulatory role in local mucosal immune regulation. VIP exists in all areas of the digestive system, mainly distributed in The endocrine cells of the gastrointestinal mucosa and the submucosal nerve plexus and smooth muscle layer. The nerve fibers of the digestive system VIP belong to preganglionic cholinergic innervation, which mainly acts on target cells in a paracrine form. In some tumor cells of the digestive system , such as gastric cancer and colon cancer cells, also secrete a certain amount of VIP on their own. VIP exerts a variety of biological functions by binding to its receptors and through a series of signal transduction and different gene expression processes. Its specific receptor is PACAPⅡ It is a G protein-coupled receptor, also known as the secretin receptor family. VIP plays an inhibitory role in regulating the movement of the digestive system. VIP may be involved in the pathophysiological processes of various diseases of the digestive system.
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The role of VIP in digestive system tumors
It has been confirmed that the concentration of VIP in the plasma and tumor tissues of patients with a variety of digestive system malignant tumors increases, and VIPR is expressed. The related symptoms such as diarrhea, abdominal pain, constipation, and achlorhydria in patients are related to the increased VIP content. VIP is mainly expressed through cells Immunity promotes and/or inhibits the growth of digestive system tumors, and has a certain regulatory effect on the proliferation and differentiation of tumor cells. Experimental studies have shown that injecting a certain dose of VIP only affects the growth of tumor cells, but not normal cells. The body has no obvious effect. VIP plays an important role in the occurrence and development of digestive system tumors. Understanding its etiology and growth characteristics of tumors is expected to provide guidance for the early diagnosis and clinical treatment of VIPR-positive tumors. ideas.
The impact of VIP on liver cirrhosis
Under physiological conditions, VIP enters the liver with the portal blood flow, and most of the VIPR on the surface of hepatocytes enters the cells and is digested and degraded by lysosomes. In liver cirrhosis, liver dysfunction leads to reduced VIP inactivation, and the increase in VIP plasma concentration leads to peripheral vascular damage. Expansion. VIP may play a regulatory role in the pathology and pathophysiology of liver cirrhosis in an endocrine and/or paracrine manner. Measuring plasma VIP levels in patients with liver cirrhosis may have certain reference value in judging disease progression and prognosis.
The role of VIP in gallbladder stones
VIP is the main inhibitory hormone for gallbladder emptying. The VIP produced by the gallbladder is mainly released by the VIP-ergic nerve fibers in the gallbladder wall. When the vagus nerve is stimulated, VIP can increase the release of VIP from the nerve. VIP binds to the corresponding specific high-affinity receptor. Afterwards, it can antagonize the contraction of gallbladder muscle strips caused by cholecystokinin, relax the gallbladder and sphincter of Oddi, inhibit the interdigestive transitional motor complex phase III activity of the gallbladder, lead to biliary motility dysfunction and bile stasis, and promote the formation of gallbladder stones. . During the formation of gallbladder stones, the impact and role of VIP regulatory disorders on biliary epithelial cell function and bile component metabolism require further in-depth study.
VIP and severe pancreatitis
Although VIP has anti-inflammatory effects and can locally regulate the intestinal mucosal barrier function in severe acute pancreatitis (SAP), it is mainly an inhibitory neurotransmitter in the gastrointestinal tract and can aggravate the gastrointestinal tract of SAP and other diseases. Motility disorders. Serum VIP levels in SAP patients increase. After treatment, VIP levels decrease, suggesting that VIP plays an important role in affecting the gastrointestinal motility function of SAP. It is speculated that pain during SAP can aggravate sympathetic nervous tension, leading to visceral motility disorders Vasoconstriction and intestinal ischemia lead to the release of VIP. Studies have found that the progressive increase in plasma and intestinal tissue VIP after a transient decrease in SAP may be the body's compensatory response, which can alleviate the progression of SAP to a certain extent. Research on the role of VIP in SAP The changes in SAP and their role in SAP gastrointestinal motility disorders have certain significance for the treatment and prognosis of SAP.
Effect of VIP on achalasia
VIP can inhibit lower esophageal sphincter (LES) tension. When the VIP concentration in plasma increases, it is accompanied by a decrease in lower esophageal sphincter pressure (LESP), which may be achieved directly through VIP.
VIP and gastric mucosal related diseases
VIP can regulate gastric blood flow, reduce gastric tension, inhibit gastric acid secretion, and protect gastric mucosa. The role of changes in VIP levels in the pathophysiology of gastric mucosa-related diseases needs further research to confirm.
VIP and irritable bowel syndrome
VIP can relax gastrointestinal smooth muscle, inhibit colon and rectal tone, inhibit small intestinal motility, weaken gastrointestinal motility, participate in the relaxation of gastric reflexes caused by colon distension and pain stimulation, and interfere with the motility and secretion absorption functions of the gastrointestinal tract. Irritable bowel syndrome (IBS) has had a certain impact. It is believed that abnormal secretion of VIP or increased intestinal sensitivity to VIP may be one of the mechanisms of the pathogenesis of IBS.
The role of VIP in ulcerative colitis
VIP regulates cytokines and exerts a protective effect on the intestinal mucosal barrier, making it expected to become an effective drug for the clinical treatment of intestinal mucosal barrier dysfunction.
In conclusion
VIP is a molecule with a wide range of biological activities. At present, VIP has been widely and deeply studied in the gastrointestinal tract, and many digestive diseases have metabolic disorders of VIP. Although research in this field has made certain progress, there are still some problems with VIP. There are few studies on the further impact of metabolic disorders on digestive diseases. Although most research is still in the process of animal experiments, the broad application prospects of VIP in digestive diseases are unquestionable.