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PubMed1985

Influence of ligation of pancreatic and bile ducts on the interaction of vasoactive intestinal peptide with rat duodenal epithelial cells.

The specific binding of vasoactive intestinal peptide (VIP) and the stimulatory effect of the neuropeptide on cyclic AMP in duodenal epithelial cells were modified 3 days following pancreaticobiliary exclusion. The binding capacity, but not the affinity, of VIP receptors decreased (by about 50%) as a consequence of the surgical manipulation. VIP was equally potent but showed a lower efficiency (about 45%) in stimulating cyclic AMP after ligation of the pancreatic and bile ducts. These observations may be either a consequence or a cause of the adaptive response of duodenal epithelium, the last possibility suggesting a role of VIP in the mechanisms of growth and differentiation of intestinal mucosa.

Animals↗
PubMed1996

Vasoactive intestinal peptide and gastrin-releasing peptide play distinct roles in the suprachiasmatic nucleus.

Vasoactive intestinal peptide and gastrin-releasing peptide levels were measured in the punched-out suprachiasmatic nucleus tissue from rats kept under a prolonged dim light (in vivo). Vasoactive intestinal peptide content increased from 4 to 8 h, returned to the baseline level at 12 to 16 h, and then increased again until 36 h after the light was switched off (dim light). Gastrin-releasing peptide level, in contrast, showed no significant changes, but a slight decrease from 1 to 4 h was detected under the dim light. In suprachiasmatic nucleus explant-slice culture, in vitro, Arg-vasopressin release increased transiently or showed a decrease at 30 min after exposure to vasoactive intestinal peptide or gastrin-releasing peptide, respectively. Treatment with anti-vasoactive intestinal peptide and anti-gastrin-releasing peptide antibodies reversed these effects. These findings suggest reciprocal roles of vasoactive intestinal peptide and gastrin-releasing peptide in Arg-vasopressin release.

Animals↗
PubMed1980

Immunoreactive somatostatin and vasoactive intestinal peptide in the digestive tract of cats.

Somatostatin and vasoactive intestinal peptide were measured by radioimmunoassay in acetic acid extracts of tissue samples from the digestive tracts of seven adult cats. The concentration of immunoreactive somatostatin in antral mucosa (2926 +/- 978 pmol/g wet weight, mean +/- SE) was far above the concentrations in the head of the pancreas (442 +/- 94), distal duodenum (377 +/- 91), and ileum (355 +/- 48). Large amounts of immunoreactive vasoactive intestinal peptide were recovered from both mucosal and muscular layers of gastrointestinal tract; the highest values were observed in the muscular layer of the cecum (579 +/- 82 pmol/g) and the mucosa of the right colon (564 +/- 244). The mucosal/muscular layer ratio of vasoactive intestinal peptide concentrations increased caudally from 0.20 in the esophagus to over 1 in the ileum and colon. Upon gel filtration on G-50 Sephadex, somatostatin in the antrum, duodenum, and pancreas were eluted as a predominant peak in the volume of the tetradecapeptide, but somatostatin from the ileum and cecum was associated with a major faster component. Vasoactive intestinal peptide in the muscular layer of gastrointestinal tract and in mucosa of antrum and duodenum consisted essentially of a single form, which coeluted with the purified porcine peptide; a slower component was detected in the mucosa of the ileum and cecum. These reults indicate molecular heterogeneity of both immunoreactive somatostatin amd vasoactive intestinal peptide in the digestive tract of cats, and suggest that the variable ratio of the different molecular forms of each peptide along the gastrointestinal tract may reflect regional specificity of biologic effects and metabolism.

Animals↗
PubMed1986

Interaction of thymic peptide thymosin alpha 1 with vasoactive intestinal peptide (VIP) receptors.

Thymic peptide thymosin alpha 1 (10(-9) to 3 X 10(-7) M) is shown to inhibit the specific binding of [125I]VIP to rat blood mononuclear cells and liver plasma membranes. Thymosin alpha 1 was 160 and 6250 times less potent that VIP at inhibiting [125I]VIP binding to blood mononuclear cells and liver plasma membranes, respectively. Thymosin alpha 1 (10(-10) to 10(-7) M) was weak in stimulating adenylate cyclase activity. Its efficacy is about 25% and 27% that of native VIP in blood mononuclear cells and liver plasma membranes, respectively. Thymosin alpha 1 may behave as a partial VIP agonist in rat.

Adenylyl Cyclases↗
PubMed1984

Gastric inhibitory peptide (GIP), pancreatic glucagon and vasoactive intestinal peptide (VIP) are cAMP-inducing hormones in the human gastric cancer cell line HGT-1. Homologous desensitization of VIP receptor activity.

GIP (EC50 = 8 X 10(-9) M, 5-fold stimulation), pancreatic glucagon (EC50 = 10(-8)M, 13-fold) and porcine or chicken VIP (EC50 = 2.5 X 10(-9) M, 10-fold) are shown to activate the cAMP generating system in HGT -1 cells. Combinations of GIP, pancreatic glucagon and VIP indicate the occurrence of 3 separate sets of recognitions sites for these 3 peptides. Accordingly, chronic treatment of cultured HGT -1 cells by VIP (10(-8) M) during 6 days resulted in homologous desensitization of VIP receptor activity. Other peptides structurally related to the secretin-glucagon family, to neurotensin, or to gastrin are either ineffective or very weak agonist (hpGRF). GIP or pancreatic glucagon are inactive on the human colonic cell line HT-29, indicating the gastric specificity of the effect of GIP and glucagon in transformed epithelial cells originating from the human gastrointestinal tract. This implies that GIP and (pancreatic-entero) glucagon peptides may regulate gastric secretions directly, under similar mechanisms that those we evidenced in the rat.

Cell Line↗
PubMed1986

Actions of vasoactive intestinal peptide and secretin on chief cells prepared from guinea pig stomach.

Vasoactive intestinal peptide and secretin increased cellular cAMP and pepsinogen secretion in dispersed chief cells from guinea pig gastric mucosa. With each peptide there was a close correlation between the dose-response curve for changes in cellular cAMP and that for changes in pepsinogen secretion. Vasoactive intestinal peptide-(10-28) and secretin-(5-27) had no agonist activity and antagonized the actions of vasoactive intestinal peptide and secretin on cellular cAMP and pepsinogen secretion. Studies of binding of 125I-vasoactive intestinal peptide and of 125I-secretin indicated that gastric chief cells possess four classes of binding sites for vasoactive intestinal peptide and secretin and that occupation of two of these classes of binding sites correlates with the abilities of vasoactive intestinal peptide and secretin to increase cellular cAMP and pepsinogen secretion. What function, if any, is mediated by occupation by the other two classes of binding sites remains to be determined.

Animals↗
PubMed1979

Interaction of secretin5-27 and its analogues with hormone receptors on pancreatic acini.

The C-terminal tricosapeptide of secretin (S5-27) and two analogues, one with asparagine replacing aspartic acid in position 15 (15-Asn-S5--27) and one with lysine replacing aspartic acid in position 15 (15-Lys-S5-27) were tested for their abilities to interact with hormone receptors on pancreatic acinar cells. In interacting with the receptors which prefer vasoactive intestinal peptide (vasoactive intestinal peptide-preferring receptors), the apparent affinity of 15-Asn S5-27 was equal to that of 15-Lys-S5-27 and was greater than that of S5-27. In interacting with secretin-preferring receptors, the apparent affinity of 15-Asn-S5--27 was equal to that of S5-27 and was greater than that of 15-Lys-S5-27. In interacting with the secretin-preferring receptors each of the secretin fragments was approximately 2% as effective as secretin in causing an increase in cellular cyclic AMP. None of these fragments was able to cause a detectable increase in cyclic AMP mediated by the vasoactive intestinal peptide-preferring receptors. The dose vs. response curves for the action of secretin and vasoactive intestinal peptide on cellular cyclic AMP and on amylase secretion as well as the pattern of effects of secretin fragments on these actions indicated that the increase in amylase secretion caused by vasoactive intestinal peptide and secretin is mediated exclusively by the vasoactive intestinal peptide-preferring receptors. Furthermore, occupation of approximately 50% of the vasoactive intestinal peptide-preferring receptors is sufficient to cause maximal stimulation of amylase secretion.

Amylases↗
PubMed1985

Vasoactive intestinal peptide effects on GH3 pituitary tumor cells: high affinity binding, affinity labeling, and adenylate cyclase stimulation. Comparison with peptide histidine isoleucine and growth hormone-releasing factor.

The vasoactive intestinal polypeptide (VIP) receptor was characterized on the GH3 rat pituitary tumor cell line using competitive binding studies with peptides having sequence homology with VIP. Further studies investigated receptor coupling to the adenylate cyclase complex by measurement of cAMP levels. Finally, the molecular weight of the receptor was estimated by affinity labeling techniques. Studies using 125I-VIP and unlabeled competing peptides revealed a single class of high affinity binding sites with a dissociation constant (KD) of 17 +/- 2 nM (mean +/- S.E.M.) for VIP, 275 +/- 46 nM for peptide histidine isoleucine (PHI), and 1380 +/- 800 nM for human pancreatic growth hormone releasing factor (GHRF). VIP and PHI each stimulated intracellular cAMP accumulation in a dose-dependent manner; both peptides demonstrated synergism with forskolin. In contrast, GHRF neither stimulated accumulation of cAMP nor demonstrated synergism with forskolin. VIP plus PHI (1 microM each) caused no significant increase in cAMP over either VIP or PHI alone, implying that the two peptides act through the same receptor. Covalent crosslinking of 125I-VIP to its binding site using either disuccinimidyl suberate (DSS) or ethylene glycol bis(succinimidyl succinate) (EGS) was followed by SDS-PAGE and autoradiography. The result is consistent with an Mr 47 000 VIP-binding subunit comprising or being associated with the VIP receptor of GH3 pituitary tumor cells.

Adenylyl Cyclases↗
PubMed2005

Development of simplified vasoactive intestinal peptide analogs with receptor selectivity and stability for human vasoactive intestinal peptide/pituitary adenylate cyclase-activating polypeptide receptors.

Vasoactive intestinal peptide (VIP) is a widespread neurotransmitter whose physiological and pathophysiological actions are mediated by two receptor classes, VIP/pituitary adenylate cyclase-activating polypeptide (VPAC) 1 and VPAC2. VIP is a 28-amino acid peptide that is rapidly degraded and simplified; metabolically stable analogs are needed. In this study, we use information from studies of the VIP pharmacophore for VPAC1/VPAC2 to design nine simplified VIP analogs that could have high affinity and selectivity for each VPAC or that retained high affinity for both VPACs and were metabolically stable. From binding studies of their abilities to directly interact with hVPAC1 (T47D cells, hVPAC1-transfected cells) and hVPAC2 (Sup T1- and VPAC2-transfected cells) and to stimulate adenylate cyclase in each, two analogs [(Ala(2,8,9,11,19,22,24,25,27,28))VIP and (Ala(2,8,9,11,19,24-28))VIP] were found to have >2000- and >600-fold selectivity for hVPAC1. None of the nine analogs had hVPAC2 selectivity. However, two simplified analogs [(Ala(2,8,9,16,19,24))VIP and (Ala(2,8,9,16,19,24,25))VIP] retained high affinity and potency for both hVPACs. 125I-[Ala(2,8,9,16,19,24,25)]VIP was much more metabolically stable than 125I-VIP. The availability of these simplified analogs of VIP, which are metabolically stable and have either hVPAC1 selectivity or retain high affinity for both hVPACs, should be useful for exploring the role of VPAC subtypes in mediating VIPs' actions as well as being useful therapeutically and for exploring the usefulness of VIP receptor imaging of tumors and VIP receptor-mediated tumor cytotoxicity.

Amino Acid Sequence↗
PubMed1992

Changes of colonic vasoactive intestinal peptide and cholinergic activity in rats with chemical colitis.

The vasoactive intestinal peptide concentration was examined in the colonic wall and portal venous plasma of rats with chemical colitis by radioimmunoassay, and the colonic localization was determined with immunocytochemistry. Colonic acetylcholine esterase activity was also measured, and the response of vasoactive intestinal peptide to acetylcholine administration was determined. Colitis was induced by administration of dextran sulfate for three months. The chemical colitis was histologically similar to active human ulcerative colitis. We observed a significant increase of immunostained neurons and nerve fibers and a significant rise in the colonic wall vasoactive intestinal peptide content in chemical colitis rats, while plasma concentrations of the peptide did not change significantly. Colonic acetylcholine esterase activity was significantly elevated in colitis rats compared with control rats. Systemic administration of acetylcholine significantly increased the colonic and plasma vasoactive intestinal peptide concentrations in colitis rats. These findings demonstrated a positive association between colitis activity and an increase of vasoactive intestinal peptide and suggested that increased vagal tone promoted the peptide's release.

Acetylcholine↗
PubMed1996

Differential effects of gastrin-releasing peptide, neuropeptide Y, somatostatin and vasoactive intestinal peptide on interleukin-1 beta, interleukin-6 and tumor necrosis factor-alpha production by whole blood cells from healthy young and old subjects.

In the present study, we have investigated the effect in vitro of gastrin-releasing peptide (GRP, 10(-10) M), neuropeptide Y (NPY, 10(-10) M), somatostatin (10(-10) M) and vasoactive intestinal peptide (VIP, 10(-9) M) on the production of IL-1 beta, IL-6 and TNF alpha by peripheral whole blood cells from healthy young and old people. We have found that GRP, NPY, somatostatin and VIP stimulated the production of IL-1 beta in old subjects, and NPY, somatostatin and VIP in young ones. In addition, the production of IL-6 was enhanced by GRP, NPY and VIP in young and old people. The TNF alpha production was stimulated by NPY and somatostatin in young subjects, and by NPY, somatostatin and VIP in old ones, whereas GRP produced a decrease of TNF alpha in young persons. GRP in old subjects and VIP in young and old subjects stimulated in a great degree the LPS-induced IL-6 production by whole blood cells. On the contrary, GRP and VIP inhibited highly the LPS-induced TNF alpha production in young controls. Our results show that these neuropeptides, when added to whole blood cells at physiological concentrations, are able to stimulate the production of IL-1 beta, IL-6 and TNF alpha in a differential way according to the subject age.

Adult↗
PubMed1988

Autocrine control of prolactin secretion by vasoactive intestinal peptide.

The functions of vasoactive intestinal polypeptide (VIP) and the many other neuropeptides that are localized in the anterior pituitary gland remain unknown although VIP of hypothalamic origin is established to act as a PRL-releasing factor. Evidence is presented here that locally-produced VIP acts in an autocrine fashion to stimulate PRL release. VIP antibodies or a VIP antagonist profoundly but reversibly suppressed PRL secretion in primary cultures of rat pituitary cells or the GH3 cell line. This evidence was obtained with the use of a reverse hemolytic plaque assay for microscopic demonstration of PRL release from individual cells under conditions precluding cell-cell interaction. We suggest that most of the high rate of "spontaneous" PRL secretion attributed to lactotropes deprived of hypothalamic influence is due in fact to the stimulatory effects of VIP acting in an autocrine fashion.

Animals↗
PubMed2000

Identification of key residues for interaction of vasoactive intestinal peptide with human VPAC1 and VPAC2 receptors and development of a highly selective VPAC1 receptor agonist. Alanine scanning and molecular modeling of the peptide.

The widespread neuropeptide vasoactive intestinal peptide (VIP) has two receptors VPAC(1) and VPAC(2). Solid-phase syntheses of VIP analogs in which each amino acid has been changed to alanine (Ala scan) or glycine was achieved and each analog was tested for: (i) three-dimensional structure by ab initio molecular modeling; (ii) ability to inhibit (125)I-VIP binding (K(i)) and to stimulate adenylyl cyclase activity (EC(50)) in membranes from cell clones stably expressing human recombinant VPAC(1) or VPAC(2) receptor. The data show that substituting residues at 14 positions out of 28 in VIP resulted in a >10-fold increase of K(i) or EC(50) at the VPAC(1) receptor. Modeling of the three-dimensional structure of native VIP (central alpha-helice from Val(5) to Asn(24) with random coiled N and C terminus) and analogs shows that substitutions of His(1), Val(5), Arg(14), Lys(15), Lys(21), Leu(23), and Ile(26) decreased biological activity without altering the predicted structure, supporting that those residues directly interact with VPAC(1) receptor. The interaction of the analogs with human VPAC(2) receptor is similar to that observed with VPAC(1) receptor, with three remarkable exceptions: substitution of Thr(11) and Asn(28) by alanine increased K(i) for binding to VPAC(2) receptor; substitution of Tyr(22) by alanine increased EC(50) for stimulating adenylyl cyclase activity through interaction with the VPAC(2) receptor. By combining 3 mutations at positions 11, 22, and 28, we developed the [Ala(11,22,28)]VIP analog which constitutes the first highly selective (>1,000-fold) human VPAC(1) receptor agonist derived from VIP ever described.

Adenylyl Cyclases↗
PubMed2006

[Effect of vasoactive intestinal peptide and epidermal growth factor on the adhesion of eosinophils to bronchial epithelial cells].

OBJECTIVE: To investigate the effect of intrapulmonary regulatory peptides on adhesion of eosinophils (EOS) to bronchial epithelial cells (BECs). METHODS: Two regulatory peptides, namely vasoactive intestinal peptide (VIP) and epidermal growth factor (EGF) were investigated. VIP and EGF were observed on the secretion of ILs and expression of intercellular adhesion molecule-1 (ICAM-1). RESULTS: VIP and EGF could decrease ILs secretion and ICAM-1 expression. CONCLUSION: VIP and EGF inhibited the adhesion of EOS to BEC in the inflammatory process to lighten the airway inflammation.

Animals↗
PubMed2003

A lymphocyte-generated fragment of vasoactive intestinal peptide with VPAC1 agonist activity and VPAC2 antagonist effects.

Vasoactive intestinal peptide receptors 1 (VPAC1) and 2 (VPAC2) have been identified in humans. Cell lines expressing only VPAC1 (HT-29) or VPAC2 (Molt-4b) were identified using real-time reverse transcriptase polymerase chain reaction. Vasoactive intestinal peptide (VIP) and related peptides, VIP-6-28, VIP4-28, and VIP10-28, previously isolated from cultures of human leukocytes, were evaluated for their ability to bind to VPAC1 and VPAC2 and to increase the levels of cAMP in HT-29 and Molt-4b cells. VIP bound to membranes of HT-29 colon carcinoma cells and Molt-4b lymphoblasts with high affinity (KD = 1.6 +/- 0.2 and 1.7 +/- 0.9 nM, respectively). VIP4-28 also demonstrated high-affinity binding (KD = 1.7 +/- 0.2 and 1.7 +/- 0.7 nM in HT-29 and Molt-4b, respectively). VIP and VIP4-28 are potent VPAC1 agonists, inducing maximal 200- and 400-fold increases in cAMP, respectively. VIP demonstrated weak VPAC2 agonist activity, inducing a maximal 14-fold increase in cAMP. VIP4-28 had no VPAC2 agonist activity but demonstrated potent VPAC2 antagonist activity. VIP4-28 inhibited VPAC2-mediated increases in cAMP in Molt-4b cells up to 95%, but had no antagonistic effect on VPAC1. Lymphoblasts did not hydrolyze VIP4-28 to a form with VPAC1 antagonist activity. VIP4-28 thus is a lymphocyte-generated VIP fragment with potent agonist activity for VPAC1 and potent antagonist activity for VPAC2.

Cell Line↗
PubMed1999

99mTc-labeled vasoactive intestinal peptide receptor agonist: functional studies.

UNLABELLED: Vasoactive intestinal peptide (VIP) is a naturally occurring 28-amino acid peptide with a wide range of biological activities. Recent reports suggest that VIP receptors are expressed on a variety of malignant tumor cells and that the receptor density is higher than for somatostatin. Our aims were to label VIP with 99mTc--a generator-produced, inexpensive radionuclide that possesses ideal characteristics for scintigraphic imaging--and to evaluate 99mTc-VIP for bioactivity and its ability to detect experimental tumors. METHODS: VIP28 was modified at the carboxy terminus by the addition of four amino acids that provided an N4 configuration for a strong chelation of 99mTc. To eliminate steric hindrance, 4-aminobutyric acid (Aba) was used as a spacer. VIP28 was labeled with 1251, which served as a control. Biological activity of the modified VIP28 agonist (TP3654) was examined in vitro using a cell-binding assay and an opossum internal anal sphincter (IAS) smooth muscle relaxivity assay. Tissue distribution studies were performed at 4 and 24 h after injection, and receptor-blocking assays were also performed in nude mice bearing human colorectal cancer LS174T. Blood clearance was examined in normal Sprague-Dawley rats. RESULTS: The yield of 99mTc-TP3654 was quantitative, and the yields of 125I-VIP and 1251-TP3654 were >90%. All in vitro data strongly suggested that the biological activity of 99mTc-TP3654 agonist was equivalent to that of VIP28. As the time after injection increased, radioactivity in all tissues decreased, except in the receptor-enriched tumor (P = 0.84) and in the lungs (P = 0.78). The tumor uptake (0.23 percentage injected dose per gram of tissue [%ID/g]) was several-fold higher than 125I-VIP (0.06 %ID/g) at 24 h after injection in the similar system. In mice treated with unlabeled VIP or TP3654, the uptake of 99mTc-TP3654 decreased in all VIP receptor-rich tissues except the kidneys. The blood clearance was biphasic; the alpha half-time was 5 min and the beta half-time was approximately 120 min. CONCLUSION: VIP28 was modified and successfully labeled with 99mTc. The results of all in vitro examinations indicated that the biological activity of TP3654 was equivalent to that of native VIP28 and tumor binding was receptor specific.

Animals↗
PubMed2005

Sympathectomy-induced increases in calcitonin gene-related peptide (CGRP)-, substance P- and vasoactive intestinal peptide (VIP)-levels in parotid and submandibular glands of the rat.

The neuropeptide contents of rat salivary glands were increased four weeks after sympathetic postganglionic denervation (but not after preganglionic denervation): calcitonin gene-related peptide (CGRP) by 400 and 65% in the parotid and submandibular glands, respectively; substance P by 30% in the submandibular gland; and vasoactive intestinal peptide (VIP) by 30% in the parotid gland. The sensory neurotoxin capsaicin prevented the expected increases of CGRP and substance P in the submandibular glands and of VIP in the parotid glands. The CGRP-increase in the parotid gland was, however, only reduced (by 65%). Parasympathetic otic ganglionectomy reduced the peptide levels in the parotid glands (CGRP--50%, VIP--98% and substance P--99%). From these residual levels, CGRP increased almost 8-fold and substance P 3-fold in response to the sympathetic denervation, while VIP was unaffected. In the parasympathetically denervated glands, the capsaicin-sensitive contribution to the CGRP-response to sympathetic denervation was roughly estimated to be more than 25% but less than 40%, while the corresponding contribution to the substance P-response was roughly estimated to be more than 6% but less than 58%. Most likely not only CGRP/substance P-containing sensory C-fibres (submandibular and parotid glands) but also parasympathetic VIP-containing secretomotor and vasomotor fibres (parotid glands) contributed to the capsaicin-sensitive response to sympathetic denervation.

Animals↗