Long-term dietary L-arginine supplementation increases endothelial nitric oxide synthase and vasoactive intestinal peptide immunoexpression in rat small intestine.

BACKGROUND AND AIMS: Nitric oxide (NO) and vasoactive intestinal polypeptide (VIP) are important intestinal neurotransmitters that coexist in the gut enteric nervous system and play an important role in intestinal physiology (e.g., absorption, motility, fluid secretion and smooth muscle relaxation). It is also known that cold exposure alters several aspects of gastrointestinal physiology and induces hyperphagia to meet increased metabolic demands, but there are no data regarding NO and VIP involvement in intestinal response during acclimation to cold. The objective of this study was to determine the influence of long-term L-arginine supplementation on the expression of the three isoforms of nitric oxide synthase (NOS) and VIP in small intestine of rats acclimated to room temperature or cold. METHODS: Animals (six per group) acclimated to room temperature (22 ± 1 °C) and cold (4 ± 1 °C), respectively, were treated with 2.25% L-arginine, a substrate for NOSs, or with 0.01% N(ω)-nitro-L-arginine methyl ester, an inhibitor of NOSs, for 45 days. The topographical distribution of VIP and NOSs expression in small intestine was studied by immunohistochemistry, and ImageJ software was used for semiquantitative densitometric analysis of their immunoexpression. RESULTS: Long-term dietary L-arginine supplementation increases VIP and NOSs immunoexpression at room temperature while at cold increases the endothelial NOS, inducible NOS and VIP but decrease neuronal NOS in rat small intestine. CONCLUSION: Our results demonstrate that long-term dietary L-arginine supplementation modulates NOSs and VIP immunoexpression in rat small intestine with respect to ambient temperature, pointing out the eNOS as a predominant NOS isoform with an immunoexpression pattern similar to VIP.

Dual bronchodilatory and pulmonary anti-inflammatory activity of RO5024118, a novel agonist at vasoactive intestinal peptide VPAC2 receptors.

BACKGROUND AND PURPOSE: Vasoactive intestinal peptide is expressed in the respiratory tract and induces its effects via its receptors, VPAC(1) and VPAC(2). RO5024118 is a selective VPAC(2) receptor agonist derived via chemical modification of an earlier VPAC(2) agonist, RO0251553. In the present studies, we characterized the pharmacological activity of RO5024118. EXPERIMENTAL APPROACH: Stability of RO5024118 to human neutrophil elastase was assessed. Bronchodilatory activity of RO5024118 was investigated in guinea pig and human isolated airway smooth muscle preparations and in a guinea pig bronchoconstriction model. Pulmonary anti-inflammatory activity of RO5024118 was investigated in a lipopolysaccharide mouse model and in a porcine pancreatic elastase (PPE) rat model. KEY RESULTS: RO5024118 demonstrated increased stability to neutrophil elastase compared with RO0251553. In human and guinea pig isolated airway preparations, RO5024118 induced bronchodilatory effects comparable with RO0251553 and the long-acting ß-agonist salmeterol and was significantly more potent than native vasoactive intestinal peptide and the short-acting ß-agonist salbutamol. In 5-HT-induced bronchoconstriction in guinea pigs, RO5024118 exhibited inhibitory activity with similar efficacy as, and longer duration than, RO0251553. In a lipopolysaccharide-mouse model, RO5024118 inhibited neutrophil and CD8(+) cells and myeloperoxidase levels. In rats, intratracheal instillation of PPE induced airway neutrophilia that was resistant to dexamethasone. Pretreatment with RO5024118 significantly inhibited PPE-induced neutrophil accumulation. CONCLUSIONS AND IMPLICATIONS: These results demonstrate that RO5024118 induces dual bronchodilatory and pulmonary anti-inflammatory activity and may be beneficial in treating airway obstructive and inflammatory diseases. LINKED ARTICLES: This article is part of a themed section on Analytical Receptor Pharmacology in Drug Discovery. To view the other articles in this section visit http://dx.doi.org/10.1111/bph.2010.161.issue-6.

Vasoactive intestinal peptide induces cell cycle arrest and regulatory functions in human T cells at multiple levels.

Vasoactive intestinal peptide (VIP) is a potent anti-inflammatory neuropeptide that, by inhibiting Th1-driven responses and inducing the emergence of regulatory T cells (T(reg)), has been proven successful in the induction of tolerance in various experimental models of autoimmune disorders. Here, we investigate the molecular mechanisms involved in VIP-induced tolerance. VIP treatment in the presence of T-cell receptor (TCR) signaling and CD28 costimulation induced cell cycle arrest in human T cells. VIP blocked G(1)/S transition and inhibited the synthesis of cyclins D3 and E and the activation of the cyclin-dependent kinases (CDKs) cdk2 and cdk4. This effect was accompanied by maintenance of threshold levels of the CDK inhibitor p27(kip1) and impairment of phosphatidylinositol 3-kinase (PI3K)-Akt signaling. Inhibition of interleukin 2 (IL-2) transcription and downregulation of signaling through NFAT, AP-1, and Ras-Raf paralleled the VIP-induced cell cycle arrest. Noteworthy from a functional point of view is the fact that VIP-treated T cells show a regulatory phenotype characterized by high expression of CD25, cytotoxic-T-lymphocyte-associated protein 4 (CTLA4), and Forkhead box protein 3 (FoxP3) and potent suppressive activities against effector T cells. CTLA4 appears to be critically involved in the generation and suppressive activities of VIP-induced T(reg). Finally, cyclic AMP (cAMP) and protein kinase A (PKA) activation seems to mediate the VIP-induced cell cycle arrest and T(reg) generation.

Vasoactive intestinal peptide family as a therapeutic target for Parkinson's disease.

Parkinson's disease (PD) is a common neurodegenerative disorder with no effective protective treatment, characterised by a massive degeneration of dopaminergic neurons in the substantia nigra and the subsequent loss of their projecting nerve fibres in the striatum. Because current treatments for PD are not effective, considerable research has been focused recently on a number of regulatory molecules that regulate inflammation characteristic of PD, induce neurotrophic and survival factors and reduce oxidative stress. Vasoactive intestinal peptide (VIP), a neuropeptide with a potent anti-inflammatory, antiapoptotic and neurotrophic effect, has been found to be protective in several inflammatory disorders. This review examines the putative protective effect of VIP and analogues in different models for PD. VIP emerges as a potential valuable neuroprotective agent for the treatment of pathological conditions in the CNS, such as PD, in which inflammation-induced neurodegeneration occurs.

Vasoactive intestinal polypeptide mediates circadian rhythmicity and synchrony in mammalian clock neurons.

The mammalian suprachiasmatic nucleus (SCN) is a master circadian pacemaker. It is not known which SCN neurons are autonomous pacemakers or how they synchronize their daily firing rhythms to coordinate circadian behavior. Vasoactive intestinal polypeptide (VIP) and the VIP receptor VPAC(2) (encoded by the gene Vipr2) may mediate rhythms in individual SCN neurons, synchrony between neurons, or both. We found that Vip(-/-) and Vipr2(-/-) mice showed two daily bouts of activity in a skeleton photoperiod and multiple circadian periods in constant darkness. Loss of VIP or VPAC(2) also abolished circadian firing rhythms in approximately half of all SCN neurons and disrupted synchrony between rhythmic neurons. Critically, daily application of a VPAC(2) agonist restored rhythmicity and synchrony to VIP(-/-) SCN neurons, but not to Vipr2(-/-) neurons. We conclude that VIP coordinates daily rhythms in the SCN and behavior by synchronizing a small population of pacemaking neurons and maintaining rhythmicity in a larger subset of neurons.

Comparative efficacy of VIP and analogs on activation and internalization of the recombinant VPAC2 receptor expressed in CHO cells.

Using a monoclonal antibody interacting with the extracellular amino-terminus of the human VPAC2 receptor but that did not interfere with ligand binding, we measured by flow cytometry receptor internalization and trafficking induced by full agonists, partial agonists and an antagonist in Chinese hamster ovary cells expressing the recombinant receptor. The agonists, but not the antagonist, induced a rapid, dose-dependent receptor internalization blocked by hypertonic sucrose that was more pronounced for the VIP analog N-hexanoyl-VIP (80%) than for VIP and Ro 25-1553 (50%) and the [A11]-VIP (20%). Re-expression of the receptors at the membrane was achieved within two hours after exposure to VIP and Ro 25-1553 was blocked by 25 microM monensin but not by 10 microg/ml cycloheximide. Re-expression was much slower after exposure to the acylated peptide and was blocked by preincubation with 25 microM monensin and 10 microg/ml cycloheximide.

Antagonism of VIP-stimulated cyclic AMP formation in chick brain.

Of eight peptides tested (0.01-5 microM), only two, that is, pituitary adenylate cyclase-activating polypeptide (PACAP27) and chicken vasoactive intestinal peptide (cVIP), potently stimulated cyclic AMP (cAMP) production in cerebral cortical slices of the chick. Mammalian VIP (mVIP) showed some activity only at the highest dose tested, whereas truncated forms of PACAP or VIP, that is, PACAP6-27, cVIP6-28, and mVIP6-28, or hybrid compounds, that is, neurotensin6-11-cVIP7-28 (NT-cVIP) and neurotensin6-11-mVIP7-28 (NT-mVIP), were inactive. Thirty-minute preincubation of chick cortical slices with 5 microM PACAP6-27, NT-cVIP, or NT-mVIP competitively antagonized the cAMP effects of cVIP (0.03-1 microM), with the truncated form of PACAP being the best antagonist. Preincubation of slices with 5 microM mVIP6-28 also produced a significant inhibition of the cVIP (0.1-1 microM)-induced increase in cAMP production; however its action was independent of the concentration of cVIP. In contrast to mVIP6-28, cVIP6-28 showed no antagonistic activity against the full-length peptide. In parallel experiments, 30-min pretreatment of cortical slices with 5 microM PACAP6-27 significantly antagonized the PACAP38-evoked increase in cAMP formation, whereas mVIP6-28 or the NT-mVIP hybrid was ineffective. It has been concluded that in the chick brain, PACAP and cVIP stimulate cAMP biosynthesis via PAC1 and VPAC-type receptors, respectively, and PACAP6-27 seems to be the most potent, yet PACAP/VIP receptor-nonselective antagonist. Unlike truncated PACAP, the NT-VIP hybrid peptides tested may represent VPACtype receptor-selective blocking activity.

Mechanisms of HIV type 1-induced cognitive impairment: evidence for hippocampal cholinergic involvement with overstimulation of the VIPergic system by the viral coat protein core.

HIV-1 is associated with a neuroAIDS syndrome that includes cognitive impairment. Several components of HIV-1 are capable of affecting cognition, but which of these is the major mediator is unknown. We injected into the lateral cerebral ventricle of mice HIV-1 pseudoviruses expressing the full viral genome with or without the viral coat glycoproteins, gp120/gp41. Only virus possessing gp120/gp41 induced defects in memory as assessed in an active avoidance T-maze footshock paradigm. By itself, gp120 also induced impairments that were reversed by hippocampal cholinergic stimulation. Paradoxically, low doses of gp120 could improve memory. Such low-dose, paradoxic improvement is a characteristic of substances that impair memory by overstimulating pathways that normally sustain memory. Consistent with this, a low, but not a high, dose of gp120 reversed memory impairment induced by overstimulation of the VIPergic system, a memory-sustaining pathway. Further characterization showed that two strains of gp120 (SF and MN) were equally effective at improving memory and that, unlike other actions of gp120, glycation was not required. We conclude that (1) the predominant cognitive-impairing component of HIV-1 is its viral coat glycoproteins, (2) gp120 impairs memory by overstimulating pathways that normally sustain memory, (3) the cognitive effect of gp120 is mediated by its protein core, and (4) gp120 likely impairs memory by affecting the cholinergic/VIPergic system.

Elucidation of the vasoactive intestinal peptide pharmacophore for VPAC(2) receptors in human and rat and comparison to the pharmacophore for VPAC(1) receptors.

Vasoactive intestinal peptide (VIP) functions as a neurotransmitter involved in a number of physiological and pathological conditions. The actions of VIP are mediated through VPAC(1) and VPAC(2). In contrast to VPAC(1), which has been extensively studied, little is known about the pharmacology of VPAC(2). In this study we investigated the VIP pharmacophore for VPAC(2) by using alanine and D-amino acid scanning. We found significant species differences, and the human VPAC(2) (hVPAC(2)) expressed in Chinese hamster ovary (CHO) cells, which have been used in previous studies, differed significantly from the native hVPAC(2) in Sup T(1) cells and hVPAC(2) expressed in PANC1 cells. There was a close agreement between binding affinities and potencies for VPAC(2) activation. The amino acids whose backbone or side chain orientations were most important for high affinity potency are Asp(3), Phe(6), Thr(7), Tyr(10), Arg(12), Tyr(22), and Leu(23), whereas the side chains of Ser(2), Asp(8), Asn(9), Gln(16), Val(19), Lys(20), Lys(21), Asn(24), and Ser(25) are not essential. Comparison of the VIP pharmacophore between hVPAC(1) and hVPAC(2) demonstrated that the side chains of Thr(7), Tyr(10), Thr(11), and Tyr(22) were much more critical for high affinity for the hVPAC(2) than the hVPAC(1). In contrast, the orientation of the side chain of Asn(24) was more important for high affinity for the hVPAC(1). This study shows that in assessing the pharmacophore of VIP analogs for the VPAC(2), important species differences need to be considered as well as the expression system used. These results of our study should be useful for designing VPAC subtype-selective analogs, simplified analogs, and possibly metabolically stable analogs.

The effect of the vasoactive intestinal polypeptide agonist Ro 25-1553 on induced tone in isolated human airways and pulmonary artery.

Ro 25-1553 is a metabolically stable analogue of endogenous vasoactive intestinal polypeptide (VIP). This compound is a potent bronchodilator in vitro as well as in vivo. Moreover, Ro 25-1553 has been shown to be highly selective of the VPAC2 receptor. We assessed the effect of Ro 25-1553 on isolated human bronchi and pulmonary arteries in vitro. Macroscopically normal human airways and pulmonary arteries were obtained from patients undergoing surgery for lung cancer. The relaxing capability of Ro 25-1553 on bronchial and pulmonary artery tone was measured using standard techniques. Bronchial rings were pre-contracted with 0.1 mM histamine, and tone in pulmonary artery rings was induced with 10 microM PGF2alpha. Increasing concentrations of Ro 25-1553 within a range of 1 pM to 10 microM were added and isometric tension changes were recorded. Ro 25-1553 caused a concentration-dependent relaxation of airway and pulmonary artery preparations, with an EC50 of approximately 10 nM and a maximal relaxation of 70%-75% of the induced tone. The presence of VPAC2 receptors in the two tissues, though low in density, was confirmed by in situ hybridization, immunocytochemistry and ligand binding. These findings indicate that the VIP analogue Ro 25-1553 may be useful in the treatment of asthma and/or chronic obstructive pulmonary diseases.

Vasoactive intestinal polypeptide (VIP) phase-shifts the rat suprachiasmatic nucleus clock in vitro.

In mammals, the principal circadian pacemaker is housed in the hypothalamic suprachiasmatic nuclei (SCN). The SCN exhibit high levels of vasoactive intestinal polypeptide (VIP) immunoreactivity and two of the three VIP receptors, VPAC(2) and PAC(1), are found in the rat SCN. However, the role of VIP in the SCN remains unclear. In this study, we examined the phase-resetting actions of VIP and selective VIP receptor agonists on the electrical activity rhythm of rat SCN neurons in vitro. Application of VIP during the subjective day did not shift the peak in the firing rate rhythm. However, VIP treatment during the early or late subjective night evoked a small phase delay or a large phase advance, respectively. The phase-advancing effect of VIP was reproduced by the novel VPAC(2) receptor agonist RO 25-1553, but not by pituitary adenylate cyclase-activating peptide (a potent PAC(1) receptor agonist), or by [K15,R16,L27]VIP(1-7)/GRF(8-27), a novel, selective VPAC(1) receptor agonist. These data show that VIP phase-dependently phase-resets the rodent SCN pacemaker in vitro, presumably via the VPAC(2) receptor. As the pattern of phase-shifting evoked by VIP and RO 25-1553 resembles the phase-resetting actions of light on rodent behavioural rhythms, these data support a role for VIP and the VPAC(2) receptor in photic entrainment of the rodent circadian pacemaker.

Vasoactive intestinal peptide inhibits cytokine production in T lymphocytes through cAMP-dependent and cAMP-independent mechanisms.

Previous reports indicate that VIP and the structurally related peptide PACAP, inhibit IL-2 and IL-10 production in antigen-stimulated T lymphocytes. Intracellular cAMP elevation appears to be the primary transduction pathway involved. However, in the lower concentration range, an additional, cAMP-independent transduction pathway appears to mediate the VIP inhibition of cytokine production. Here, we address this question by using VIP agonists and antagonists which act through cAMP-dependent and -independent pathways. The antagonists based on the neurotensin-VIP hybrid molecule did not affect the inhibitory effect of VIP/PACAP on IL-2 and IL-10 production, confirming that astrocytes and T lymphocytes express different receptors. A lipophilic antagonist with increased membrane permeability, partially reversed the inhibitory effect of VIP/PACAP, forskolin, prostaglandin E2, and 8-bromo-cAMP without significantly affecting cAMP levels, suggesting that it acts downstream of cAMP. Two VIP agonists inhibit IL-2 and IL-10 production. One of the agonists increases cAMP, whereas the second one does not induce cAMP/cGMP. Our results indicate that VIP inhibits cytokine production in stimulated CD4+ T cells through two separate mechanisms, which involve both cAMP-dependent and cAMP-independent transduction pathways.

Vasoactive intestinal polypeptide receptor VPAC(1) subtype is predominant in rat prostate membranes.

BACKGROUND: The 28-amino-acid neuropeptide vasoactive intestinal peptide (VIP) might play an important role in the physiology of the prostate, since it stimulates glandular secretion, inhibits muscle contraction, stimulates proliferation of epithelial cells, and increases the secretion of prostate-specific antigen (PSA). This neuropeptide may act through interaction with two types of high-affinity receptors, named VPAC(1) and VPAC(2) receptors. Recently, selective agonists and antagonists for each receptor subtype were synthesized. We used them to identify the VIP receptor subclass expressed in rat prostatic tissue. METHODS: We tested the capacity of selective labeled and unlabeled agonists and antagonists of VPAC(1) and VPAC(2) receptors to bind to rat prostatic membranes and to stimulate or prevent the stimulation of adenylate cyclase activity. RESULTS: The following selective peptides were used: VPAC(1) agonist ([K(15), R(16), L(27)] VIP (1-7)/GRF (8-27)); VPAC(1) antagonist (PG 97-269); and VPAC(2) agonist (RO 25-1553). The IC(50) values of [(125)I]-VIP binding inhibition for the different peptides in rat prostatic membranes were: VIP (1.7 nM) < VPAC(1) agonist (20 nM) < VPAC(1) antagonist (40 nM) < VPAC(2) agonist (329 nM). The EC(50) values of adenylate cyclase stimulation were similar to the IC(50) values for each peptide, and the Ki values for the VPAC(1) antagonist, inhibiting the adenylate cyclase activity stimulated by VIP and the VPAC(1) agonist, were 22 and 35 nM, respectively. Comparison of binding of [(125)I]-VIP and of [(125)I]-RO 25-1553 indicates the presence of 80% of VPAC(1) and 20% VPAC(2) receptors. CONCLUSIONS: In rat prostate membranes, VPAC(1) receptors are largely predominant. Binding studies were compatible with a ratio of 80/20 of VPAC(1)/VPAC(2) receptors, whereas functionally only VPAC(1) receptors were detected.

The long-acting vasoactive intestinal polypeptide agonist RO 25-1553 is highly selective of the VIP2 receptor subclass.

RO 25-1553 is a synthetic VIP analogue that induced a long-lasting relaxation of tracheal and bronchial smooth muscles as well as a reduction of edema and eosinophilic mobilization during pulmonary anaphylaxis. In the present study, we tested in vitro the capacity of RO 25-1553 to occupy the different VIP/PACAP receptor subclasses and to stimulate adenylate cyclase activity. The cellular models tested expressed one single receptor subtype: Chinese hamster ovary (CHO) cells transfected with the rat recombinant PACAP I, rat VIP1, and human VIP2 receptors; SUP T1 cells expressing the human VIP2 and HCT 15 and LoVo cells expressing the human VIP1 receptor. RO 25-1553 was threefold more potent than VIP on the human VIP2 receptor, 100- and 600-fold less potent than VIP on the rat and human VIP1 receptors, respectively, and 10-fold less potent than VIP and 3000-fold less potent than PACAP on the PACAP I receptor. RO 25-1553 was a full agonist on the VIP2, the PACAP I, and the rat recombinant VIP1 receptor but a partial agonist only on the human VIP1 receptor. Thus, RO 25-1553 is a highly selective agonist ligand for the VIP2 receptor subclass.

Characterization of binding sites for beta-adrenergic agonists and vasoactive intestinal peptide in the rat harderian gland.

Vasoactive intestinal peptide (VIP) receptors and beta-adrenergic receptors were investigated in rat Harderian gland membranes using 125I-VIP and 125I-cyanopindolol (125I-CYP), respectively, as ligands. The receptor bindings were rapid, reversible, saturable, specific, and dependent on time, temperature, and membrane concentration. The stoichiometric data suggested the presence of two classes of VIP receptors with Kd values of 0.36 and 65.37 nM and binding capacities of 323 and 39,537 fmol VIP/mg protein, respectively. The interaction showed a high degree of specificity, as suggested by competitive displacement experiments with several peptides structurally or not structurally related to VIP as follows: VIP > helodermin > rGRF > PHI > > secretin. Glucagon, somatostatin, insulin, and pancreastatin were ineffective at concentrations up to 1 microM. However, the stoichiometric data suggest the presence of one class of binding sites for 125I-CYP. The Kd for the single site was 290 pM with a binding capacity of 32 pmol/L. The pharmacological characterization of 125I-CYP binding to membranes showed that only isoproterenol, a beta-adrenergic agonist, and norepinephrine, an alpha beta-adrenergic agonist, was as effective as propranolol in inhibiting 125I-CYP binding to Harderian gland membranes. However, alpha 1- and alpha 2-adrenergic agonists and blockers such as methoxamine, prazosin, clonidine, and yohimbine were shown to be ineffective. These results demonstrate the presence of specific VIP and beta-adrenergic receptors in the Harderian gland and suggest a role for VIP and beta-adrenergic agonists in the physiology of this gland.

The effect of vasoactive intestinal peptide on development of form deprivation myopia in the chick: a pharmacological and immunocytochemical study.

The role of vasoactive intestinal peptide (VIP) in the development of form deprivation myopia (FDM) was examined. Daily intravitreal injection of porcine VIP reduced, but did not eliminate FDM at a maximal daily dose of 1 x 10(-5) mol/injection. A VIP analogue reported to be relatively hydrolysis-resistant in vivo, had no effect on development of FDM at any dose tested. Two VIP antagonists completely abolished FDM. The one reported to be selective for central nervous system VIP receptors was 100 times more potent than one reported to be selective for peripheral nervous system receptors (ED50 = 2 x 10(-10) and 2 x 10(-8) mol/injection respectively). By immunofluorescence using antiserum to porcine VIP, VIP-like immunoreactivity was localized to a subset of amacrine cells (AC) and in three parallel layers in the inner plexiform layer (IPL) (10%, 40% and 70% of IPL thickness from the AC layer). Immunoreactive nerve fibres were also seen in the choroid, the ciliary body and the iris. These results suggest that VIP may play a role in both normal development of the refractive properties of the eye, and in the development of FDM.

Ro 25-1553: a novel, long-acting vasoactive intestinal peptide agonist. Part II: Effect on in vitro and in vivo models of pulmonary anaphylaxis.

Studies were conducted to compare the effect of native vasoactive intestinal peptide (VIP), Ro 25-1553 (a cyclic peptide analog of VIP) and salbutamol (a beta2-adrenoceptor agonist) on antigen-induced pathophysiological effects in the guinea pig. Ro 25-1553 and salbutamol (0.01-1.0 microM) prevented antigen-induced contractions of the guinea pig trachea in vitro with IC50 values of 0.07 and 0.05 microM, respectively. VIP (0.01-1.0 microM) had no effect on antigen-induced tracheal contractions. Aerosolized Ro 25-1553 and salbutamol were equipotent in preventing antigen-induced increases in guinea pig lung resistance (IC50 value = 0.0001%), whereas aerosolized VIP (0.1%) was ineffective. Ro 25-1553 (0.1-100 micrograms), instilled intratracheally 2 min before the antigen challenge of buffer-perfused lungs from sensitized guinea pigs, produced a dose-dependent inhibition of bronchoconstrictor, vasoconstrictor and edemagenic responses, whereas intratracheal VIP (100 micrograms) had no effect. Intratracheal salbutamol (0.1-100 micrograms) inhibited antigen-induced responses in a manner comparable to Ro 25-1553. Lung inflammation was assessed as leukocyte accumulation in bronchoalveolar lavage fluid after the antigen provocation. Aerosolized antigen-induced bronchoalveolar lavage eosinophilia (13-fold increase over saline controls) at 6 hr after challenge was prevented in a concentration-dependent manner by pretreatment with nebulized Ro 25-1553 and salbutamol, but not by pretreatment with native VIP. These results indicate that Ro 25-1553 suppresses various pathophysiological features associated with pulmonary anaphylaxis and asthma, including airway reactivity, edema formation and granulocyte accumulation.(ABSTRACT TRUNCATED AT 250 WORDS)