Affinity chromatography of catalytic autoantibody to vasoactive intestinal peptide

An autoantibody in human IgG that hydrolyzes vasoactive intestinal peptide (VIP) was identified. The IgG did not hydrolyze VIP unless an unidentified inhibitor was removed by dialysis. The VIP antibody was fractionated by affinity chromatography on immobilized VIP by using IgG without VIP-hydrolytic activity as the starting material. The affinity-purified antibody catalyzed the hydrolysis of VIP (nominal kcat/Km: 1.1 X 10(6) M-1 min-1). The values of Km for the affinity-purified antibody preparation and unfractionated IgG (110 nM and 112 nM) suggested relatively tight antibody-VIP binding. A comparison of the reverse phase HPLC profiles of antibody-treated [Tyr10-125I]VIP with that of synthetic [125I]VIP(1-16) suggested that unfractionated IgG and the affinity-purified antibody cleaved the same peptide bond in VIP (Gln16-Met17).     

Molecular identification of receptors for vasoactive intestinal peptide in rat intestinal epithelium by covalent cross-linking. Evidence for two classes of binding sites with different structural and functional properties

The cleavable cross-linking reagent dithiobis (succinimidyl propionate) or DTSP was shown to link 125I-labeled vasoactive intestinal peptide (125I-VIP) covalently to its receptors in rat intestinal epithelial membranes. DTSP treatment of 125I-VIP-labeled membranes inhibited the dissociation of VIP-receptor complexes in a way which was dependent on both time and concentration (ED50 = 200 microM). Polyacrylamide gel electrophoresis of membrane proteins revealed three 125I-VIP-protein complexes of Mr 76 000, 36 000 and 17 000. The labeling of those compounds was not observed when: (a) treatment of membranes by DTSP was omitted; (b) the reagent quench, ammonium acetate, was added together with DTSP; (c) DTSP-treated membranes were incubated with 2-mercaptoethanol which reduces the disulfide bond present within DTSP. Labeling of Mr-76 000 and Mr-36 000 complexes was specific in that it could be abolished by native VIP, while the labeling of the Mr-17 000 was not. Densitometric scanning of autoradiographs indicated that: (a) labeling of the Mr-76 000 complex was abolished by low VIP concentrations (0.03--10 nM), by VIP agonists with the relative potency VIP greater than a peptide having N-terminal histidine and C-terminal isoleucine amide greater than secretin, and by GTP (10(-5)--1 mM) but was unaffected by various other peptide hormones; (b) labeling of the Mr-36 000 complex was inhibited by high VIP concentrations (1--300 nM), by VIP agonists at high concentrations but was not affected by GTP and various peptide hormones. Assuming one molecule of 125I-VIP was bound per molecule of protein, two proteins with Mr-73 000 and 33 000 were identified as VIP binding sites. The Mr-73 000 protein displays many characteristics (affinity, specificity, discriminating power toward agonists, sensitivity to GTP regulation) of the high-affinity VIP receptors mediating adenylate cyclase activation. The Mr-33 000 protein displays the characteristics (affinity, specificity) of a low-affinity VIP binding site. This study thus shows the molecular characteristics of the VIP receptor and further argues for the molecular heterogeneity of VIP binding sites.     

Molecular Characteristics and Peptide Specificity of Vasoactive Intestinal Peptide Receptors from Rat Cerebral Cortex

Vasoactive intestinal peptide (VIP) receptors have been identified in CNS by their chemical specificity and molecular size. Using synaptosomes isolated from rat cerebral cortex, it was shown that central VIP receptors discriminated among natural and synthetic VIP-related peptides, because half-maximal inhibition of [125I]VIP binding to synaptosomes was obtained for 0.6 nM VIP, 9 nM peptide histidine isoleucineamide (PHI), 50 nM VIP 2-28, 70 nM secretin, 100 nM rat growth hormone-releasing factor (GRF), and 350 nM human GRF. Other peptides of the VIP family, such as glucagon and gastric inhibitory polypeptide, did not interact with cortical VIP receptors. The molecular components of VIP receptors in rat cerebral cortex were identified after [125I]VIP cross-linking to synaptosomes using the cross-linker dithiobis(succinimidyl propionate). Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of synaptosomal proteins revealed two major [125I]VIP-protein complexes of Mr 49,000 and 18,000. The labeling of the Mr 49,000 component was specific, because it was abolished by native VIP, whereas the labeling of the Mr 18,000 component was not. Natural VIP agonists reduced the labeling of the Mr 49,000 component with the following order of potency: VIP greater than PHI greater than secretin approximately equal to rat GRF. In contrast, glucagon and octapeptide of cholecystokinin were without effect, a result indicating its peptide specificity. Densitometric scanning of autoradiographs showed that the labeling of the Mr 49,000 component was inhibited by low VIP concentrations between 10(-10) and 10(-6) M (IC50 = 0.8 nM), a result indicating the component's high affinity for VIP.(ABSTRACT TRUNCATED AT 250 WORDS)     

Isolation of a low molecular mass vasoactive intestinal peptide binding protein.

A vasoactive intestinal peptide (VIP) binding protein was purified in active form by detergent solubilization of lung membranes, gel filtration, VIP-Sepharose affinity chromatography, reverse phase high performance liquid chromatography, and anion exchange chromatography. The mass of this protein was estimated at 18 kDa by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and 17 kDa by gel filtration. The binding of VIP by this protein was inhibited by Mg2+, covalent cross-linking of [Tyr10-125I]VIP to the protein produced two radioactive bands at 22 and 26 kDa identified by electrophoresis, and the purified protein exhibited saturable and high affinity binding of VIP and the related neuropeptide, rat growth hormone releasing factor.     

Structure-activity relationship of synthetic truncated analogues of vasoactive intestinal peptide (VIP): an enhancement in the activity by a substitution with arginine

In order to develop potent shortened analogues of vasoactive intestinal peptide (VIP), the structure-activity relationship of C-terminally truncated analogues of VIP was investigated by examining the binding activity to rat lung VIP receptors and relaxation of smooth muscle in isolated mouse stomach. VIP(1-27) showed VIP receptor binding activity comparable to that of VIP but the activity of VIP(1-26) was reduced to one-third of VIP. The receptor binding activity of VIP(1-26) to VIP(1-23) was reduced in proportion to the decrease in amino acid residues. There was a significant correlation between the number of amino acid residues and VIP receptor binding activities of VIP and its C-terminally truncated analogues. VIP(1-22) and VIP(1-21) exhibited little binding activity even at high concentrations, suggesting the requisite of 23 amino acid residues as the minimal essential sequence for the conservation of VIP receptor binding activity. The chemical modification of VIP(1-23) generated a potent analogue, [Arg(15, 20, 21), Leu(17)]-VIP(1-23), that displayed a 22-fold higher receptor binding activity and 1.6-fold more potent relaxation of mouse stomach than VIP(1-23) did. In conclusion, it was shown that [Arg(15, 20, 21), Leu(17)]-VIP(1-23) could be a relatively potent and stable agonist of VIP receptors. The present study has provided further insight into the structure-activity relationship of VIP to generate novel shortened VIP analogues having a high affinity to VIP receptors and potent pharmacological activity.     

Identification of high affinity receptors for vasoactive intestinal peptide on human lymphocytes of B cell lineage

Specific, high affinity receptors for vasoactive intestinal peptide (VIP) have been identified on a human pre-B cell line, Nalm 6, and on a human plasma cell line, Dakiki. The single class of high affinity sites exhibited a KD of 12.6 +/- 2.9 nM for VIP in Nalm 6 cells and 9.1 +/- 2.7 nM in Dakiki plasma cells. The homologous peptides, peptide histidine methionine (PHM), growth hormone releasing factor (GHRF), and secretin were all less effective than VIP in competitively inhibiting binding of 125I-VIP to Nalm 6 and Dakiki plasma membranes. The putative receptor was characterized as a 47-kDa protein using covalent cross-linking techniques and VIP stimulated adenylate cyclase in pre-B cells. Human lymphocytes of B cell lineage thus appear to express functional VIP receptors homologous to the receptor identified in T lymphoblasts, brain, pituitary, and intestine.     

Secretory actions of vasoactive intestinal polypeptide, peptide histidine isoleucine and helodermin in rat small intestine: the effects of putative VIP antagonists upon VIP-induced ion secretion

Vasoactive intestinal polypeptide (VIP), peptide histidine isoleucine (PHI), and helodermin stimulate electrogenic anion secretion in preparations of rat jejunum stripped of muscularis propria. Concentration-response curves to exogenously applied peptides yielded EC50 values of 12 nM, 12 nM and 100 nM for VIP, PHI and helodermin respectively. These secretory responses were most probably mediated via the same receptor population given that cross-desensitisation was observed between all 3 analogues. Four putative VIP antagonists, namely, two growth hormone releasing factors (GRF); [AcTyr1, D-Phe2]GRF-(1-29)-NH2 and [AcTyr1]hGRF-(1-40)-OH as well as [4Cl-D-Phe6,Leu17]VIP and VIP-(10-28) were tested for their ability to inhibit VIP induced electrogenic ion secretion. None of the above exhibited any intrinsic agonist activity nor were they competitive antagonists, although some inhibition was observed with [AcTyr1]hGRF-(1-40)-OH and VIP-(10-28). Their use as selective VIP antagonists is therefore limited in rat jejunal mucosa.     

Cutting edge: vasoactive intestinal peptide (VIP) induces differentiation of Th17 cells with a distinctive cytokine profile

Immune cellular effects of vasoactive intestinal peptide (VIP) are transduced by VIP G protein-coupled receptors type 1 (VPAC1) and type 2 (VPAC2). We now show that VIP with TGFbeta stimulates the transformation of CD4 T cells to a distinctive type of Th17 cell that generates IL-17 but not IL-6 or IL-21. VIP induction of Th17 cells was higher in VPAC2 knockout mice than wild-type mice, suggesting that VPAC1 is the principal transducer. Compared with Th17 cells elicited by IL-6, those evoked by VIP were similar in the secretion of IL-17 and IL-22, but lacked IL-21 secretion. Suppression of VIP induction of Th17 cells by protein kinase A inhibitors and enhancement by pharmacologically increased cAMP supports a role for this signal. The ability of VIP-VPAC1 axis signals to evoke development of a novel type of Th17 cells demonstrates the unique specificity of neuroregulatory mechanisms in the immunological environment.     

Vasoactive Intestinal Peptide (VIP) Inhibits Substrate Adherence Capacity of Rat Peritoneal Macrophages by a Mechanism That Involves cAMP

In this study, vasoactive intestinal peptide (VIP) is shown to inhibit substrate adherence capacity of rat peritoneal macrophages. The inhibitory response occurred in the 0.1-1, 000 nM range of VIP concentrations and it was a time-dependent process. At 15 min, half maximal inhibition (ICw) was obtained at 0.37 ± 0.26 nM and maximal inhibition (53.8%) at 10^-6 M VIP. The inhibitory effect of VIP was correlated with the stimulation by this peptide of cyclic AMP (cAMP) production in rat peritoneal macrophages. Moreover, agents that inhibited VIP-stimulated cAMP production, such as the VIP-antagonist [4-Cl-D-Phe₆ Leu₁₇]-VIP and somatostatin, also decreased the inhibitory effect of VIP on substrate adherence capacity of macrophages. On the contrary, the phosphodiesterase inhibitor 3-isobutyl-1-methylxanthine (IBMX) and the lipid-soluble derivative of cAMP N⁶ 2'-O-dibutyryl cAMP (Bu-cAMP) inhibited the adherence of macrophages to substrate and potentiated the inhibitory action of VIP. These results demonstrate that VIP inhibits substrate adherence capacity of rat peritoneal macrophages by a mechanism that involves cAMP, and show, for the first time, an action of VIP on the function of peritoneal macrophages.     

Functional characterization of a receptor for vasoactive-intestinal-peptide-related peptides in cultured dermal melanophores from Xenopus laevis

A receptor for vasoactive-intestinal-peptide (VIP)-related peptides was functionally characterized in a cell line derived from Xenopus melanophores using a recently described microtiter-plate-based bioassay. Activation of the melanophore VIP receptor by VIP or the peptides pituitary-adenylate-cyclase-activating polypeptide (PACAP 38), PACAP 27, and helodermin stimulated intracellular 3'-5' cyclic adenosine monophosphate (cAMP) accumulation and pigment dispersion in the cells. Helodermin, with an EC50 (concentration of peptide inducing half-maximal melanosome dispersion) of 46.5 pM, was the most potent activator of pigment dispersion, followed by PACAP 38 > VIP > PACAP 27. A similar order of potencies was observed for the peptides to induce cAMP accumulation. The responses to VIP agonists were selectively inhibited by the VIP antagonists PACAP-(6-27) and (N-Ac-Tyr(1)-D-Phe2)-growth-hormone-releasing factor[GRF](1-29)-NH2. Taken together, the results suggest that the melanophores express a VIP receptor that shares certain characteristics of, but also differs significantly from, other previously identified VIP receptors.     

Vasoactive intestinal peptide: a novel stimulator of steroidogenesis by cultured rat granulosa cells

Vasoactive intestinal peptide (VIP) and VIPergic nerve fibers are present in the ovaries of several mammalian species, suggesting a possible ovarian action of VIP. We have investigated the direct effects of synthetic porcine VIP on rat granulosa cell steroidogenesis in vitro. The cells were obtained from immature, hypophysectomized, estrogen-primed rats, and cultured in a serum-free medium for 24 h in the absence or presence of varying amounts of VIP. Medium steroids were then determined by specific radioimmunoassay. Vasoactive intestinal peptide dose-dependently stimulated progesterone, 20 alpha-hydroxypregn-4-ene-3-one (20 alpha-OH-progesterone), and estrogen production with an approximate ED50 value of 3 X 10(-8) M. Maximum steroid production induced by VIP ranged from 15% to 28% of that seen with maximal follicle-stimulating hormone (FSH) stimulation. In contrast to the ability of FSH to induce luteinizing hormone (LH) receptor formation, treatment with VIP did not increase [125I]iodo-human chorionic gonadotropin (hCG) binding to granulosa cells. The ability of several gastrointestinal peptides, having 17-44% sequence identity to VIP, to stimulate granulosa cell steroidogenesis was also tested. The most closely related peptide, PHM-27 was less effective than VIP, and the least closely related, secretin and glucagon, were ineffective at 10(-6) M. Vasoactive intestinal peptide seems to act at least partly through cyclic 3',5'-adenosine monophosphate (cAMP)-dependent processes: addition of a phosphodiesterase inhibitor significantly potentiated the VIP stimulation of granulosa cell steroidogenesis, and VIP was capable of producing a dose- and time-dependent increase in both intracellular and medium cAMP levels. Vasoactive intestinal peptide stimulation of estrogen production seemed to be a result of increased aromatase activity. The increased progesterone production was associated with increased pregnenolone production, increased rate of conversion of pregnenolone to progesterone via 3 beta-hydroxysteroid dehydrogenase, and decreased metabolism of progesterone via 20 alpha-hydroxysteroid dehydrogenase. These results indicate that VIP exerts a specific action on granulosa cells to increase estrogen and progestin production. The observed direct effects of VIP, coupled with its identification in the ovary, suggest that VIP may be a physiologically important regulator of ovarian activity.     

Novel analogs of VIP with multiple C-terminal domains

The effect of multiplication of the N-terminal domain of vasoactive intestinal peptide (VIP) on the binding activity of the peptide was recently evaluated. A VIP analog with multiple N-terminal domains was found to be slightly more potent as compared to [Nle(17)]VIP towards VIP receptor type 1 (VPAC1)-related cAMP production. Here, the effect of multiplication of the C-terminal domain of VIP was evaluated with the aim of possibly amplifying peptide-receptor (VPAC1) binding and activation. Several VIP analogs were designed and synthesized, each carrying multiplication of the C-terminal domain that was obtained by either a simple linear tandem extension or by a unique branching methodology. Results show that despite significant alterations in the C-terminal domain of VIP that is considered essential to induce potent receptor binding, few peptides demonstrated only slight reduction in receptor binding and activation in comparison to [Nle(17)]VIP. Furthermore, a specific branched VIP analog with multiple C-terminal domains was equipotent to [Nle(17)]VIP in the cAMP production assay. Therefore, it is concluded that the association between the VIP ligand to the VIP receptor could be tolerable to size increases in the C-terminal region of the VIP ligand and multiplication of the C-terminal does not increase activity.     

Vasoactive Intestinal Peptide (VIP) Inhibits Substrate Adherence Capacity of Rat Peritoneal Macrophages by a Mechanism That Involves cAMP

In this study, vasoactive intestinal peptide (VIP) is shown to inhibit substrate adherence capacity of rat peritoneal macrophages. The inhibitory response occurred in the 0.1-1, 000 nM range of VIP concentrations and it was a time-dependent process. At 15 min, half maximal inhibition (ICw) was obtained at 0.37 ± 0.26 nM and maximal inhibition (53.8%) at 10^?6 M VIP. The inhibitory effect of VIP was correlated with the stimulation by this peptide of cyclic AMP (cAMP) production in rat peritoneal macrophages. Moreover, agents that inhibited VIP-stimulated cAMP production, such as the VIP-antagonist [4-Cl-D-Phe₆ Leu₁₇]-VIP and somatostatin, also decreased the inhibitory effect of VIP on substrate adherence capacity of macrophages. On the contrary, the phosphodiesterase inhibitor 3-isobutyl-1-methylxanthine (IBMX) and the lipid-soluble derivative of cAMP N⁶ 2′-O-dibutyryl cAMP (Bu-cAMP) inhibited the adherence of macrophages to substrate and potentiated the inhibitory action of VIP. These results demonstrate that VIP inhibits substrate adherence capacity of rat peritoneal macrophages by a mechanism that involves cAMP, and show, for the first time, an action of VIP on the function of peritoneal macrophages.     

Identity of a membrane-bound vasoactive intestinal peptide-binding protein with calmodulin.

A vasoactive intestinal peptide (VIP)-binding protein purified from guinea pig lung membranes (p18) was digested with trypsin, and the amino acid sequence of the peptide fragments was determined. The sequence of six tryptic fragments of p18 was identical with subsequences present in mammalian calmodulin. Authentic porcine brain calmodulin and p18 co-migrated on an sodium dodecyl sulfate-electrophoresis gel and displayed identical chromatographic behavior on a reverse phase high performance liquid chromatography column. The VIP-binding properties of p18 and calmodulin were indistinguishable. Both proteins displayed saturable and apparent high affinity binding of VIP, evidenced by potent inhibition of complexation with [Tyr10-125I]VIP by unlabeled VIP (IC50 = 6.0-8.1 nM). Rat growth hormone releasing factor and a C terminally extended form of VIP ([Leu17]VIP-GKR) also displayed potent inhibition of the binding (IC50 = 6.4 and 4 nM, respectively). These neuropeptides are potential modulators of calmodulin function.     

Concentration-dependent inactivation of superoxide dismutase

1. Vasoactive intestinal peptide (VIP) receptors were identified in crude rat hepatic membranes by 125I-labelled VIP binding and by the ability of VIP to stimulate adenylate cyclase activity. The specificity of these receptors was evaluated by the capacity of secretin, synthetic secretin analogues, and secretin fragments to inhibit 125I-labelled VIP binding and to stimulate adenylate cyclase. 2. The results were compatible with the existence of two classes of VIP binding sites that could be distinguished according to their affinity for VIP and their specificity. High-affinity sites were more specific for VIP as secretin was 175 times less potent than VIP for recognition of these sites while being only 33 times less potent than VIP for recognition of low-affinity sites. 3. Secretin analogues, monosubstituted in position 2, 3, 4 or 6 were less potent than secretin for adenylate cyclase stimulation as well as for the recognition of the two classes of receptors. [Val5]secretin was more potent than secretin and appeared definitely more VIP-like than secretin; [Ala4, Val5] and [D-Ala4,Val5]secretin were equipotent to secretin. 4. The fragment secretin (7-27) was unable to recognize VIP receptors and to stimulate adenylate cyclase. The substituted fragment [Gln9,Asn15]secretin (5-27) recognized these receptors with weak potency but could not activate the enzyme.     

Involvement of Pituitary Adenylate Cyclase-Activating Polypeptide II Vasoactive Intestinal Peptide 2 Receptor in Mouse Neocortical Astrocytogenesis

Abstract: At the end of neuronal migration, the neopallial germinative zone produces glial cells destined to colonize the upper layers of neocortex. High densities of binding sites for vasoactive intestinal peptide (VIP) have been found in the rodent germinative zone just after completion of neuronal migration, suggesting a possible role of VIP in neocortical astrocytogenesis. In the present study, administration of a VIP antagonist at embryonic days 17 and 18 to pregnant mice was followed by a dramatic depletion of astrocytes in the upper cortical layer of the offspring. The depletion of astrocytes was dose-dependent, with a 42% reduction in the density of astrocytes observed with 50 µg of antagonist. The antagonist effect was reversed by cotreatment with VIP or pituitary adenylate cyclase-activating polypeptide (PACAP), suggesting the involvement of a receptor common to these two neuropeptides. VIP antagonist-induced inhibition of astrocytogenesis was also blocked by Ro 25-1553, a long-acting cyclic VIP analogue selective for the PACAP II VIP2 receptor subclass. Our results demonstrate that VIP and/or PACAP play a crucial physiological role in neocortical astrocytogenesis, possibly through interaction with PACAP II VIP2 receptors.     

The rat liver vasoactive intestinal peptide binding site. Molecular characterization by covalent cross-linking and evidence for differences from the intestinal receptor.

To identify the molecular components of the vasoactive intestinal peptide (VIP) binding sites in the liver, 125I-labelled VIP was covalently linked to liver membranes by using the cleavable cross-linker dithiobis(succinimidylpropionate). Purified rat liver plasma membranes were incubated with 125I-VIP, washed and treated with 1 mM-cross-linker. Polyacrylamide-gel electrophoresis of membrane proteins followed by autoradiography revealed a major 125I-VIP-protein complex of Mr 51 000. A minor Mr 89 000 complex was also observed. An identical pattern of protein labelling was obtained using crude membranes from rat liver. Labelling of the Mr 51 000 and 89 000 species was specific in that it could be abolished by native VIP, but was unaffected by 1 microM-glucagon and cholecystokinin octapeptide. Densitometric scanning of autoradiographs indicated that the labelling of the two species was abolished by similar low VIP concentrations (0.1-100 nM). It was also reduced by two VIP agonists, peptide histidine isoleucine amide and secretin, with a potency that is 1/7 and 1/200 that of native VIP, respectively. The guanine nucleotide GTP in the concentration range between 10(-7) and 10(-3) M reduces the labelling of the major Mr 51 000 protein and that of the minor Mr 89 000 protein, but with a slightly higher potency. Assuming one molecule of 125I-VIP was bound per molecule of protein, a major Mr 48 000 protein and a minor Mr 86 000 protein were identified as components of the high-affinity VIP binding sites in liver. This contrasts markedly with the pattern of labelling of rat intestinal epithelial membranes, where a Mr 73 000 protein was identified as a high-affinity VIP receptor and a Mr 33 000 protein as a low-affinity VIP binding site [Laburthe, Bréant & Rouyer-Fessard (1984) Eur. J. Biochem. 139, 181-187], suggesting structural differences between VIP binding sites in rat liver and intestinal epithelium.