Vasoactive intestinal peptide

Dose—response characteristics of feline corpus circular muscle were studiedin vitro for three neuropeptides individually and with vasoactive intestinal peptide. Bombesin, substance P, and cholecystokinin-octapeptide each elicited concentration-dependent isometric contractions that were reduced by 10^–8 M or 10^–7 M vasoactive intestinal peptide (P<0.01). The concentration of each neuropeptide producing a half-maximal response was increased more than one logfold to 10^–6 M by vasoactive intestinal peptide. Tetrodotoxin blocked responses to bombesin (P<0.001) and reduced responses to substance P (P<0.05), but had no effect on responses to cholecystokinin-octapeptide (P>0.1). These results demonstrate inhibition of neuropeptide responses of gastric smooth muscle and support vasoactive intestinal peptide as an inhibitory regulator of gastric motor function.     

Vasoactive intestinal peptide is a physiological mediator of prolactin release in the rat

To determine whether VIP functions as a physiological PRL-releasing factor, the effects of immunoneutralization of endogenous vasoactive intestinal peptide (VIP) on the PRL secretory response to suckling and ether stress were assessed. Using a porcine VIP-thyroglobulin conjugate as antigen, a peptide-specific antiserum was generated in a rabbit which bound porcine VIP with a Kd of 5.1 X 10(-11) M and a maximum binding capacity of 1830 ng/ml. In a RIA, this antiserum demonstrated immunoreactive VIP in tissue extracts of various regions of the brain and gastrointestinal tract. IR VIP in extracts of cerebral cortex and hypothalamus coeluted with synthetic porcine VIP on Bio-Gel P-30 column chromatography. Using chronically implanted right atrial catheters for blood sampling to avoid effects of stress and anesthesia, PRL blood levels in normal controls began to rise almost immediately after initiation of suckling from basal values of 3.0 +/- 0.9 ng/ml to reach a plateau of 158.1 +/- 33.5 ng/ml after 40 min. When the VIP antiserum was administered immediately before initiation of suckling, the onset of the PRL response was delayed by 40 min, but PRL levels then rose at a slower rate to reach the plateau level of normal animals approximately 80 min later. When VIP antiserum was administered to rats who had been suckling for at least 1 h, PRL levels fell from a mean basal elevated level of 152.7 +/- 16.0 ng/ml to a nadir of 50.4 +/- 9.1 ng/ml 80 min after injection and then gradually returned to basal levels. The effect of VIP antiserum was studied in rats in whom PRL secretion was increased by exposure to ether, a stimulus that acts on the release phase of PRL secretion. In rats in whom the depletion-transformation of PRL was induced by a prior brief period of suckling, subsequent exposure to ether caused a rise in serum PRL levels. The response was completely blocked in rats given VIP antiserum, whereas animals given nonimmune serum showed a significant increase in serum PRL to 38.6 +/- 17.3 ng/ml. We conclude from these studies that VIP mediates the acute PRL response to suckling and is required for maintenance of PRL levels in continuously suckling animals but is not the only factor causing PRL elevation. Complete abolition by the VIP antiserum of the PRL response to ether indicates that the effect of the anesthetic is mediated entirely by the release of VIP. These findings are consistent with the view that VIP is a physiological PRL-releasing factor in the rat.     

Vasoactive intestinal polypeptide as mediator of asthma

Vasoactive intestinal polypeptide (VIP) is one of the most abundant, biologically active peptides found in the human lung. VIP is a likely neurotransmitter or neuromodulator of the inhibitory non-adrenergic non-cholinergic airway nervous system and influences many aspects of pulmonary biology. In human airways VIP-immunoreactive nerve fibres are present in the tracheobronchial airway smooth muscle layer, the walls of pulmonary and bronchial vessels and around submucosal glands. Next to its prominent bronchodilatory effects, VIP potently relaxes pulmonary vessels. The precise role of VIP in the pathogenesis of asthma is still uncertain. Although a therapy using the strong bronchodilatory effects of VIP would offer potential benefits, the rapid inactivation of the peptide by airway peptidases has prevented effective VIP-based drugs so far and non-peptide VIP-agonists did not reach clinical use.     

Thrombin receptor expression in rheumatoid and osteoarthritic synovial tissue.

OBJECTIVE: To investigate the possibility that synovial cells might respond to thrombin in the inflamed human joint, using immunohistochemical detection of thrombin receptors. METHODS: Frozen sections of synovial membrane from 20 patients with rheumatoid arthritis, 16 with osteoarthritis, and four normal controls were stained using a monoclonal antibody to the human thrombin receptor. Sections were also double stained for both receptors and non-specific esterase. RESULTS: Receptor positive cells were present in rheumatoid synovia, with some cells also staining positively for non-specific esterase. In contrast, both osteoarthritic and normal synovia contained very few cells expressing receptors. CONCLUSIONS: Thrombin may mediate important pathological changes during chronic inflammatory joint disease.     

Avocado/soybean unsaponifiables increase aggrecan synthesis and reduce catabolic and proinflammatory mediator production by human osteoarthritic chondrocytes

OBJECTIVE: To investigate the effects of avocado (A)/soybean (S) unsaponifiables on the metabolism of human osteoarthritic (OA) chondrocytes cultured in alginate beads over 12 days. METHODS: Enzymatically isolated OA chondrocytes were cultured in alginate beads in a well defined culture medium for 12 days, in the presence or not of 10-10 M interleukin 1beta (IL-1beta). DNA content was measured using a fluorometric method. Production of aggrecan (AGG), stromelysin-1 (MMP-3), tissue inhibitor of metalloproteinases-1 (TIMP-1), macrophage inflammatory protein-1beta (MIP-1beta), IL-6, and IL-8 were assayed by specific enzyme amplified sensitivity immunoassays. Prostaglandin (PG) E2 was measured by a specific radioimmunoassay and nitrite by a spectrophotometric method based on the Griess reaction. A commercial avocado and soybean mixture of unsaponifiables (A1S2) and each component separately were tested in a range of 0.625 to 40.0 micro g/ml. RESULTS: After 12 days' incubation, A1S2 increased AGG synthesis and accumulation in alginate beads in a dose and time dependent manner. A1S2 promoted the recovery of aggrecan synthesis after 3 days of IL-1beta treatment. A1S2 was a potent inhibitor of basal and IL-1beta stimulated MMP-3 production. The procedure also weakly reversed the inhibitory effect of IL-1beta on TIMP-1 production. A1S2 inhibited basal production of MIP-1beta, IL-6, IL-8, NO*, and PGE2 by OA chondrocytes and partially counteracted the stimulating effect of IL-1 on PGE2. Compared to avocado or soybean added separately, the mixture had a superior effect on NO* and IL-8 production. CONCLUSION: A1S2 stimulated aggrecan production and restored aggrecan production after IL-1beta treatment. In parallel, A1S2 decreased MMP-3 production and stimulated TIMP-1 production. These results suggest A1S2 could have structure-modifying effects in OA by inhibiting cartilage degradation and promoting cartilage repair.     

Vasoactive intestinal peptide: cardiovascular effects

Vasoactive intestinal peptide (VIP) is present in the peripheral and the central nervous systems where it functions as a nonadrenergic, noncholinergic neurotransmitter or neuromodulator. Significant concentrations of VIP are present in the gastrointestinal tract, heart, lungs, thyroid, kidney, urinary bladder, genital organs and the brain. On a molar basis, VIP is 50-100 times more potent than acetylcholine as a vasodilator. VIP release in the body is stimulated by high frequency (10-20 Hz) nerve stimulation and by cholinergic agonists, serotonin, dopaminergic agonists, prostaglandins (PGE, PGD), and nerve growth factor. The VIP peptide combines with its receptor and dose-dependently activates adenylyl cyclase. The vasodilatory effect of VIP in different vascular tissues or species also may be due to increases in nitric oxide, cyclic GMP, and other signaling agents. In the heart, VIP immunoreactive nerve fibers are present not only in the epicardial coronary arteries and veins, but also the sinoatrial node, atrium, interatrial septum, atrioventricular node, intracardiac ganglia, and ventricles (right ventricle > left ventricle). In the coronary arterial walls, VIP may contribute to the regulation of normal coronary vasomotor tone. In research animals and in humans, VIP, administered into the coronary artery or intravenously, increases the epicardial coronary artery cross-sectional area, decreases coronary vascular resistance, and significantly increases coronary artery blood flow. High frequency parasympathetic (vagal) nerve stimulation also releases endogenous VIP in the coronary vessels and heart and significantly increases coronary artery blood flow. In addition, the release of VIP in the heart is increased during coronary artery occlusion and during reperfusion where VIP may promote local blood flow and may have a free-radical scavenging effect. VIP also has a primary positive inotropic effect on cardiac muscle that is enhanced by its ability to facilitate ventricular-vascular coupling by reducing mean arterial pressure by 10-15%. In concentrations of 10(-8)-10(-5) mol, VIP augments developed isometric force and increases atrial and ventricular contractility. The presence of VIP-immunoreactive nerve fibers in and around the sinus and the atrioventricular nodes of mammals strongly suggests that this peptide can affect the heart rate. In this regard, endogenously released or exogenous VIP can significantly increase the heart rate and has a more potent effect on heart rate than does norepinephrine. The presence and significant cardiovascular effects of VIP in the heart suggests that this peptide is important in the regulation of coronary blood flow, cardiac contraction, and heart rate. Current investigations are defining the physiological role of VIP in the regulation of cardiovascular function.     

Vasoactive intestinal peptide stimulates androgen biosynthesis by cultured neonatal testicular cells

Vasoactive intestinal peptide (VIP) was originally isolated from porcine duodenum and considered to be a gut hormone. Recent evidence indicates that it may also be involved in reproductive functions. In this study, a possible action of VIP on steroidogenesis by cultured testicular cells was investigated. Neonatal testicular cells were treated in vitro with hormones for 3 days and medium steroid or cAMP content was measured by radioimmunoassay. Treatment of cultured cells with VIP (10(-9) to 10(-6) M) increased the production of testosterone, progesterone, and pregnenolone in a dose-dependent fashion. Testosterone production in response to 10(-6) M VIP was about 5-10% of that maximally induced by LH. Addition of methyl-isobutyl-xanthine, a phosphodiesterase inhibitor, to the VIP-containing cultures significantly enhanced production of testosterone by 13-fold, of progesterone by 9-fold, and of pregnenolone by 2.5-fold as compared to treatment with VIP alone. Additional experiments also showed a dose-dependent stimulation of cAMP production by VIP. The VIP-related hormones PHM-27, secretin, and glucagon also stimulated progesterone and testosterone production with a potency order (PHM-27 greater than secretin greater than glucagon) consistent with that observed for other VIP receptor-mediated actions. A direct stimulatory effect of VIP on Leydig cells was indicated in studies on steroidogenesis by testicular cells separated on a metrizamide density gradient. In these studies, VIP stimulated androgen production in an LH-responsive subpopulation of testis cells but failed to affect steroid production in non-LH-responsive cells.(ABSTRACT TRUNCATED AT 250 WORDS)     

Vasoactive intestinal peptide and the mammalian circadian system

In mammals, the circadian oscillators that drive daily behavioral and endocrine rhythms are located in the hypothalamic suprachiasmatic nucleus (SCN). While the SCN is anatomically well-situated to receive and transmit temporal cues to the rest of the brain and periphery, there are many holes in our understanding of how this temporal regulation occurs. Unanswered questions include how cell autonomous circadian oscillations within the SCN remain synchronized to each other as well as communicate temporal information to downstream targets. In recent years, it has become clear that neuropeptides are critically involved in circadian timekeeping. One such neuropeptide, vasoactive intestinal peptide (VIP), defines a cell population within the SCN and is likely used as a signaling molecule by these neurons. Converging lines of evidence suggest that the loss of VIP or its receptor has a major influence on the ability of the SCN neurons to generate circadian oscillations as well as synchronize these cellular oscillations. VIP, acting through the VPAC(2) receptor, exerts these effects in the SCN by activating intracellular signaling pathways and, consequently, modulating synaptic transmission and intrinsic membrane currents. Anatomical evidence suggests that these VIP expressing neurons connect both directly and indirectly to endocrine and other output targets. Striking similarities exist between the role of VIP in mammals and the role of Pigment Dispersing Factor (PDF), a functionally related neuropeptide, in the Drosophila circadian system. Work in both mammals and insects suggests that further research into neuropeptide function is necessary to understand how circadian oscillators work as a coordinated system to impose a temporal structure on physiological processes within the organism.     

Vasoactive intestinal peptide increases prolactin messenger ribonucleic acid content in GH3 cells

The influence of vasoactive intestinal peptide (VIP), TRH, and dexamethasone (Dex) on PRL mRNA was investigated in PRL-producing GH3 cells using cytoplasmic dot hybridization and RNA blot analysis. Total cytoplasmic RNA was transferred to nitrocellulose filter paper and quantitated by hybridization to PRL recombinant DNA probes labeled with 32P. Incubation of GH3 cells with VIP for 25 h increased the content of cytoplasmic PRL mRNA. This increase was dose dependent, being significant at 2 X 10(-8) M and reaching a maximum at 2 X 10(-7) M. VIP at 2 X 10(-9) M had no effect on cytoplasmic PRL mRNA content. TRH (2 X 10(-7) M) also increased whereas Dex (2 X 10(-7) M) decreased the content of PRL mRNA. The inhibitory effect of Dex (2 X 10(-7) M) on cytoplasmic PRL mRNA was reversed by VIP (2 X 10(-7) M). Changes in medium PRL levels after these various hormone treatments paralleled those changes observed in PRL mRNA content. Examination of total poly(A)+ RNA demonstrated that incubation with VIP (2 X 10(-7) M) for 6 h increased the content of the mature PRL mRNA and its processing intermediates. Dex (2 X 10(-7) M) decreased the content of all species of PRL mRNA. These data suggest that VIP-stimulated PRL release is the result of an increase in the content of PRL mRNA and its precursors.     

Heparin modulates intracellular cyclic AMP in human trabecular bone cells and adherent rheumatoid synovial cells.

Cells were cultured from explants of human trabecular bone excised from eight patients and incubated usually for 20 minutes with bovine parathyroid hormone, salmon calcitonin, prostaglandin E2, or heparin. The intracellular content of cyclic AMP was measured by radioimmunoassay and was significantly increased by parathyroid hormone in four, by calcitonin in two, by prostaglandin E2 in eight, and by heparin in seven out of eight cultures. In the two cultures containing calcitonin-responsive cells heparin inhibited the cyclic AMP response induced by calcitonin. Heparin did not affect the cyclic AMP response to parathyroid hormone or prostaglandin E2. Heparin also increased the cyclic AMP content of cultured adherent rheumatoid synovial cells. It is proposed that, in certain situations of focal pathological bone resorption, although concentrations of circulating hormones may be normal, the local release of products such as heparin may modify the effect of hormones which regulate connective tissue homoeostasis. local changes in hormone responses could contribute to the enhanced bone resorption associated with inflammatory processes such as rheumatoid arthritis.     

Vasoactive intestinal peptide stimulates testosterone production by cultured fetal rat testicular cells

As a part of a series of studies on the regulation of testicular steroidogenesis in the fetal rat, we found that VIP stimulated fetal testicular cAMP production at a dose of 10⁻⁹ mol/l, while a dose as low as 10⁻¹² mol/l stimulated testosterone production. RT-PCR analysis could not reveal either VIP mRNA in fetal tissues or VIP1 receptor mRNA in the fetal or newborn testes, while VIP2 receptor mRNA was detected in fetal testes as early as E15.5. The testicular VIP content was unmeasurable by our radioimmunoassay method (<1 fmol/testis), while the circulating levels of VIP were 82.9±1.1 pmol/l at E17.5 and decreased with advanced fetal ages. In conclusion, our results suggest that VIP, from and extratesticular source, may regulate fetal testicular steroidogenesis through type 2 receptors as early as E15.5.     

胃腺癌血管活性肠肽受体mRNA表达的研究

目的研究血管活性肠肽受体mRNA在胃腺癌组织和AGS人胃腺癌细胞中的表达情况,探讨其在胃腺癌发病过程中的作用。方法采用RT-PCR方法,检测24例胃腺癌组织、24例正常胃腺组织及不同传代AGS人胃腺癌细胞中VIPR mRNA的表达。结果胃腺癌患者组VIPR1 mRNA表达率为45.00%(9/24),低于正常对照组的83.33%(20/24)(P0.05);VIPR2 mRNA表达率在胃腺癌患者组和正常对照组分别为50.00%(10/24)和66.67%(16/24),差异无统计学意义(P0.05)。与正常胃窦黏膜比较,VIPR1 mRNA的表达量下降(P0.05),但VIPR2 mRNA的表达量和正常胃窦黏膜差异无统计学意义(P0.05)。不同传代AGS人胃腺癌细胞中均有VIPR mRNA的表达,但传代细胞之间差异无统计学意义(P0.05)。结论VIPR mRNA的低表达可能与胃腺癌的发生发展有关,检测VIPR mRNA表达对胃腺癌的诊断具有一定的指导意义。     

Vasoactive intestinal peptide stimulates adrenal aldosterone and corticosterone secretion

Vasoactive intestinal peptide (VIP)-immunoreactive nerve fibers have been demonstrated in the rat adrenal cortex in close association with zona glomerulosa cells, suggesting neural regulation of adrenocortical cell function (5). The present studies were undertaken to study the possible role of VIP in the regulation of steroid hormone secretion from the outer zones of the normal rat adrenal cortex. Capsule-glomerulosa preparations, consisting of the capsule, zona glomerulosa, and a small but variable portion of the zona fasciculata, were perifused in vitro. To assess the secretory responsiveness of the capsule-glomerulosa preparation, aldosterone and corticosterone release were measured after stimulation with ACTH and angiotensin II. ACTH (10(-12)-10(-8) M) stimulated dose-dependent increases in aldosterone secretion (1.9- to 36.9-fold increases over basal values) and corticosterone secretion (1.4- to 14.0-fold increases over basal values). Angiotensin II (10(-8)-10(-5) M) stimulated dose-dependent increases in aldosterone secretion (1.6- to 8.8-fold increases over basal values). VIP (10(-6)-10(-4) M) stimulated dose-dependent increases in both aldosterone (1.7- to 41.0-fold) and corticosterone secretion (1.8- to 5.3-fold). However, glucagon and (N-Ac-Tyr1-D-Phe2)GRF-(1-29)NH2, peptides structurally related to VIP, stimulated neither aldosterone nor corticosterone secretion, indicating that VIP effects are likely to be specific for this peptide. It is noteworthy that in this preparation, the stimulation of corticosteroid secretion by VIP at 10(-5) and 10(-4) M was comparable to those by 10(-6) M angiotensin II and 10(-9) M ACTH, respectively. These results support the hypothesis that the VIP innervation of the adrenal cortex may contribute directly to the regulation of adrenal steroidogenesis.     

IgA rheumatoid factor synthesis by dissociated synovial cells. Characterization and relationship to IgM rheumatoid factor synthesis

We examined patterns of IgA rheumatoid factor (RF) and IgM-RF synthesis by dissociated synovial cells obtained from 27 patients with seropositive rheumatoid arthritis. Synthesis of IgA-RF was observed in 19 of 34 synovial cell preparations from these patients and constituted a mean of 16% of the total IgA produced. IgA-RF expression correlated only weakly with IgM-RF production (r = 0.385) and could be dissociated from production of IgA-RF (and IgM-RF) exhibited by simultaneously obtained peripheral blood plasma cells. While wide variations were observed in the ratio of IgA-RF:IgM-RF produced by synovial B cells in the patient sample studied, remarkable consistency in the relationship of IgA-RF to IgM-RF synthesis was observed over time in different joints of the same patient. IgA-RF synthesized by dissociated synovial cells was predominantly of the IgA1 subclass and existed in both monomeric and polymeric forms. Our results are compatible with the view that local production of IgA-RF and IgM-RF are regulated independently of each other.     

Vasoactive intestinal peptide induces the synthesis of the cholesterol side-chain cleavage enzyme complex in cultured rat ovarian granulosa cells.

Vasoactive intestinal peptide (VIP) has been identified in ovarian nerves and stimulates steroid secretion from immature ovaries. To gain insight into its mechanism of action, the effect of VIP on the synthesis of the cholesterol side-chain cleavage enzyme complex was studied in ovarian granulosa cells from immature estrogen-primed rats. The cells were cultured for 48 hr in serum-free medium; the proteins were labeled with [35S]methionine; and the synthesis of cytochrome P-450, iron-sulfur protein, and NADPH:iron-sulfur protein reductase was evaluated by electrophoretic analysis after immunoisolation with polyclonal antibodies directed against the bovine adrenal enzymes. VIP at concentrations ranging from 0.001 to 1 microM stimulated 3- to 5-fold the synthesis of cytochrome P-450 and iron-sulfur protein. Peptide NH2-terminal histidine, COOH-terminal isoleucine, which has greater than 50% sequence homology of VIP, stimulated the synthesis of both proteins at approximately 50% of VIP effectiveness. Secretin, another member of the glucagon-secretin family of peptides, which has only 30% sequence homology to VIP, was without effect. Similar results were observed with the NADPH:iron-sulfur protein reductase. VIP-induced synthesis of the cholesterol side-chain cleavage enzyme complex was accompanied by a dose-related increase in cAMP accumulation and progestin formation. It is concluded that VIP regulates the synthesis of the ovarian cholesterol side-chain cleavage enzyme complex, which catalyzes the rate-limiting reaction in progesterone biosynthesis, and that the VIP effect is at least partially mediated through cAMP. It is suggested that a stimulatory action of VIP on the synthesis of ovarian progesterone may contribute to regulating the functional development of the ovary.