Absence of immunoreactive vasoactive intestinal polypeptide in tissue from the lungs of patients with asthma

Mast cell tryptases in allergic inflammation and immediate hypersensitivity

Dysregulated mast cell-mediated inflammation and/or activation have been linked to a number of human diseases, including asthma, anaphylaxis, chronic spontaneous urticaria, and mast cell activation syndromes. As a major mast cell granule protein, tryptase is a biomarker commonly used in clinical practice to diagnose mast cell-associated disorders and -mediated reactions, but its mechanistic roles in disease pathogenesis remains incompletely understood. Here, we summarize recent advances in the understanding of human tryptase genetics and the effects that different genetic composition may have on the quaternary structure of tetrameric mature tryptases. We also discuss how these differences may impact clinical phenotypes including allergic inflammation, immediate hypersensitivity, and others seen in patients with mast cell-associated disorders. With the increased application of next-generation sequencing, we foresee that human genetic approaches will be a major focus of understanding human tryptase functions in various human mast cell disorders and in new therapeutic development.

Mini review: Neural mechanisms underlying airway hyperresponsiveness

Neural changes underly hyperresponsiveness in asthma and other airway diseases. Afferent sensory nerves, nerves within the brainstem, and efferent parasympathetic nerves all contribute to airway hyperresponsiveness. Inflammation plays a critical role in these nerve changes. Chronic inflammation and pre-natal exposures lead to increased airway innervation and structural changes. Acute inflammation leads to shifts in neurotransmitter expression of afferent nerves and dysfunction of M₂ muscarinic receptors on efferent nerve endings. Eosinophils and macrophages drive these changes through release of inflammatory mediators. Novel tools, including optogenetics, two photon microscopy, and optical clearing and whole mount microscopy, allow for improved studies of the structure and function of airway nerves and airway hyperresponsiveness.

Airway Innervation and Plasticity in Asthma

Airway nerves represent a mechanistically and therapeutically important aspect that requires better highlighting in the context of diseases such as asthma. Altered structure and function (plasticity) of afferent and efferent airway innervation can contribute to airway diseases. We describe established anatomy, current understanding of how plasticity occurs, and contributions of plasticity to asthma, focusing on target-derived growth factors (neurotrophins). Perspectives toward novel treatment strategies and future research are provided.

Neuropeptides in asthma, chronic obstructive pulmonary disease and cystic fibrosis

The nervous system mediates key airway protective behaviors, including cough, mucus secretion, and airway smooth muscle contraction. Thus, its involvement and potential involvement in several airway diseases has become increasingly recognized. In the current review, we focus on the contribution of select neuropeptides in three distinct airway diseases: asthma, chronic obstructive pulmonary disease (COPD), and cystic fibrosis. We present data on some well-studied neuropeptides, as well as call attention to a few that have not received much consideration. Because mucus hypersecretion and mucus obstruction are common features of many airway diseases, we place special emphasis on the contribution of neuropeptides to mucus secretion. Finally, we highlight evidence implicating involvement of neuropeptides in mucus phenotypes in asthma, COPD and cystic fibrosis, as well as bring to light knowledge that is still lacking in the field.

Acute neurokinin-1 receptor antagonism fails to dampen airflow limitation or airway eosinophilia in an experimental model of feline asthma

OBJECTIVES

Feline allergic asthma is a chronic inflammatory disorder of the lower airways that may manifest with acute, life-threatening clinical signs. Tachykinins released from sensory nerves and immune cells binding neurokinin (NK)-1, NK-2 and NK-3 receptors have been implicated in asthma pathogenesis. Maropitant, an NK-1 receptor antagonist, blocks neuroimmune pathways and may be a viable treatment option for cats in asthmatic crisis. Using an experimental chronic allergic feline asthma model, we hypothesized that a single dose of maropitant given immediately after allergen challenge would blunt clinical signs, airway hyperresponsiveness (AHR) and airway eosinophilia.

METHODS

Cats (n = 7) induced to have an asthmatic phenotype using Bermuda grass allergen (BGA) were enrolled in a prospective, placebo-controlled crossover design study. Cats randomly received maropitant (2 mg/kg SC) or placebo (saline SC) immediately post-BGA challenge, followed 12 h later by pulmonary mechanics testing and measurement of airway eosinophils. After a 2 week washout, cats were crossed-over to the alternate treatment. Study endpoints included subjective clinical scoring systems post-BGA challenge, ventilator-acquired pulmonary mechanics to assess AHR after bronchoprovocation with methacholine and collection of bronchoalveolar lavage fluid to quantify airway eosinophilia. Data were analyzed using a Mann-Whitney rank sum test with P <0.05 considered significant.

RESULTS

A single injection of maropitant failed to diminish clinical composite score (P = 0.902), visual analogue scale scoring (P = 0.710), AHR (P = 0.456) or airway eosinophilia (P = 0.165) compared with placebo.

CONCLUSIONS AND RELEVANCE

A single injection of maropitant given immediately post-allergen challenge was ineffective at blunting clinical signs, AHR and airway eosinophilia, and cannot be recommended as treatment for feline status asthmaticus.

Chronic neurokinin-1 receptor antagonism fails to ameliorate clinical signs, airway hyper-responsiveness or airway eosinophilia in an experimental model of feline asthma

OBJECTIVES

Feline allergic asthma is a common chronic lower airway disease characterized by clinical signs attributed to eosinophilic inflammation, airway hyper-responsiveness (AHR) and airway remodeling. Tachykinins released from sensory nerves and immune cells bind neurokinin-1 (NK-1) receptors in the lung. The resultant neurogenic airway inflammation has been implicated in asthma pathogenesis. In mouse models and spontaneous human asthma, NK receptor antagonists reduce bronchospasm and inflammation. We hypothesized that chronic administration of maropitant, an NK-1 receptor antagonist, would decrease clinical signs of asthma, AHR and eosinophilic inflammation in experimentally asthmatic cats.

METHODS

Cats (n = 6) induced to have asthma using Bermuda grass allergen (BGA) were enrolled in a randomized, prospective, placebo-controlled crossover design study. Cats received either oral maropitant (2 mg/kg) or placebo q48h for 4 weeks; following a 2 week washout, cats were crossed-over to the alternate treatment. Study endpoints included subjective clinical scoring systems after BGA challenge, ventilator-acquired pulmonary mechanics to assess AHR after bronchoprovocation with methacholine, and collection of bronchoalveolar lavage fluid to quantify airway eosinophilia. Statistical analysis was performed using a Mann-Whitney rank sum test with P <0.05 considered significant.

RESULTS

Administration of maropitant for 1 month in experimentally asthmatic cats produced no significant difference in clinical scoring scheme (P = 0.589 and P = 1.0), AHR (P = 0.818) or airway eosinophilia (P = 0.669) compared with placebo.

CONCLUSIONS AND RELEVANCE

Chronic administration of maropitant was ineffective at blunting clinical signs, AHR and airway eosinophilia in experimental feline asthma and thus cannot be recommended as a novel treatment for this disorder.

The TRPV1 receptor agonist capsaicin is an ineffective bronchoprovocant in an experimental model of feline asthma

OBJECTIVES

Airway hyper-responsiveness (AHR), a key feature of feline asthma, can be measured using bronchoprovocation testing. Limitations of both direct and indirect bronchoprovocants evaluated to date in experimental feline asthma have led to a search for a more specific indirect bronchoprovocant (ie, one which relies on existing inflammatory cells or activated neural pathways in diseased but not healthy airways). We hypothesized that capsaicin, a transient receptor potential cation channel subfamily V member 1 agonist, would lead to dose-responsive increases in airway resistance as measured by ventilator-acquired pulmonary mechanics in experimentally asthmatic cats.

METHODS

Five cats induced to have asthma using Bermuda grass allergen (BGA) were studied. Twenty-four hours after aerosol challenge of BGA, cats were anesthetized and underwent neuromuscular blockade for ventilator-acquired pulmonary mechanics. Cats were monitored with pulse oximetry for hemoglobin desaturation. Parameters recorded on a breath-by-breath basis on the ventilator included airway resistance (Raw) and compliance. Saline at baseline and 10-fold increasing concentrations of capsaicin (0.4-4000.0 µM) were aerosolized for 30 s and data collected for 4 mins between doses. The intended endpoint of the study was a doubling in baseline airway resistance, halving of compliance or oxygen desaturation <75%.

RESULTS

All cats completed the trial, reaching the highest dose of capsaicin without reaching any of the aforementioned endpoints. No biologically significant alteration in any other pulmonary mechanics parameter was noted.

CONCLUSIONS AND RELEVANCE

Capsaicin does not appear to be an effective bronchoprovocant in a feline asthma model.

Neuronal modulation of airway and vascular tone and their influence on nonspecific airways responsiveness in asthma

The autonomic nervous system provides both cholinergic and noncholinergic neural inputs to end organs within the airways, which includes the airway and vascular smooth muscle. Heightened responsiveness of the airways to bronchoconstrictive agents is a hallmark feature of reactive airways diseases. The mechanisms underpinning airways hyperreactivity still largely remain unresolved. In this paper we summarize the substantial body of evidence that implicates dysfunction of the autonomic nerves that innervate smooth muscle in the airways and associated vasculature as a prominent cause of airways hyperresponsiveness in asthma.

Mast cell chymase reduces the toxicity of Gila monster venom, scorpion venom, and vasoactive intestinal polypeptide in mice

Mast cell degranulation is important in the pathogenesis of anaphylaxis and allergic disorders. Many animal venoms contain components that can induce mast cell degranulation, and this has been thought to contribute to the pathology and mortality caused by envenomation. However, we recently reported evidence that mast cells can enhance the resistance of mice to the venoms of certain snakes and that mouse mast cell-derived carboxypeptidase A3 (CPA3) can contribute to this effect. Here, we investigated whether mast cells can enhance resistance to the venom of the Gila monster, a toxic component of that venom (helodermin), and the structurally similar mammalian peptide, vasoactive intestinal polypeptide (VIP). Using 2 types of mast cell-deficient mice, as well as mice selectively lacking CPA3 activity or the chymase mouse mast cell protease-4 (MCPT4), we found that mast cells and MCPT4, which can degrade helodermin, can enhance host resistance to the toxicity of Gila monster venom. Mast cells and MCPT4 also can limit the toxicity associated with high concentrations of VIP and can reduce the morbidity and mortality induced by venoms from 2 species of scorpions. Our findings support the notion that mast cells can enhance innate defense by degradation of diverse animal toxins and that release of MCPT4, in addition to CPA3, can contribute to this mast cell function.

Spatio-temporal localization of vasoactive intestinal peptide and neutral endopeptidase in allergic murine lungs

Vasoactive intestinal peptide (VIP) is a neuropeptide with cytokine properties that is abundant in the lung. VIP null mice exhibit spontaneous airway inflammation and hyperresponsiveness emphasizing VIP's "anti-asthma" potential. Although VIP's impending protective role in the lung has been demonstrated, its localization in the naïve and allergic murine lungs has not. To this aim, we analyzed the availability of VIP and its protease, neutral peptidase (NEP), in naïve and Aspergillus-sensitized and challenged murine lungs after 3, 7, and 14days. Both VIP and NEP were predominantly localized to the columnar epithelia of the airways in naïve lungs. A marked decrease in VIP occurred in these cells 3days after allergen challenge. NEP localization in the columnar epithelia decreased after allergen challenge. At day 14, VIP localization in the columnar epithelia and arteriolar smooth muscle increased while NEP localization at these sites remained low. This study provides new insights into the local regulation of VIP in the columnar epithelia of the allergic lung. Its altered availability in the context of allergy provides fresh evidence for the modulation of pulmonary inflammation by VIP.

The absence of the VPAC(2) receptor does not protect mice from Aspergillus induced allergic asthma

Allergic asthma is a T(H)2-mediated disease marked by airway inflammation, increased mucus production, and elevated serum IgE in response to allergen provocation. Among its ascribed functions, the neuropeptide vasoactive intestinal peptide (VIP) is believed to promote a T(H)2 phenotype when signaling through its VPAC(2) receptor. In this study, we assessed the requirement for the VIP/VPAC(2) axis in initiating the allergic pulmonary phenotype in a murine model of fungal allergic asthma. C57BL/6 wild-type (WT) and VPAC(2) knock-out (KO) mice were sensitized with Aspergillus fumigatus antigen and challenged with an aerosol of live conidia to induce allergic airways disease. WT and KO mice exhibited similar peribronchovascular inflammation, increased number of goblet cells, and elevated serum IgE. However, the absence of VPAC(2) receptor resulted in a marked enhancement of MUC5AC mRNA with an associated increase in goblet cells and a reduction in eosinophils in the airway lumen at day 3 when VIP mRNA was undetectable in the KO lung. Sustained elevation of serum IgE was noted in KO mice at day 14, while the level in WT mice declined at this time point. These data suggest that the absence of VPAC(2) does not protect mice from developing the signs and symptoms of allergic asthma.

Neuropeptide release from airways of young and fully-grown rabbits

Nerve growth factor (NGF), a neurotrophin that regulates neuronal development, enhances production of neuropeptides that control airway caliber including substance P (SP). Little is known about the developmental interplay between neurotrophins and neuropeptides. Our goal was to assess release of NGF, SP, and vasoactive intestinal peptide (VIP) from tracheal segments of young (2-week-old) and fully-grown (13-week-old) rabbits, and ascertain location of neuropeptides in airways with mechanical denudation of epithelium and immunohistochemistry. After electrical field stimulation of nerves, bath solutions were collected and immunoassays performed to quantify NGF, SP, and VIP release. There were significant decreases in NGF, SP, and VIP release from airways in 13- versus 2-week-old rabbits. There were also significant decreases in SP and VIP release from denuded versus normal tissues at 2 weeks of age. A similar pattern for SP was seen in 13-week-old rabbits. Immunohistochemistry demonstrated increased neuropeptides in airways from younger rabbits. Although SP was seen in the epithelium and submucosal nerves in the younger group, it was localized to the latter location in fully-grown rabbits. VIP was seen in only submucosal nerves at both ages. Thus, release of NGF, SP, and VIP with neural stimulation decreases in rabbit tracheal segments with age. Decreases in SP with maturation and epithelial denudation appear related in part to decreases in epithelial SP with growth. However, decreases in VIP that occur normally and with epithelial denudation are not explained by location of VIP within the epithelium. The epithelium may be a source of factors that inhibit release of neuropeptides.

Catalytic hydrolysis of VIP in pregnant women with asthma

RATIONALE

The neuropeptide vasoactive intestinal peptide (VIP) is one of the physiologic mediators of non-adrenergic, non-cholinergic smooth muscle relaxation of the airway and an important modulator of innate and adaptive immune responses. VIP catalytic autoantibodies are increased in asthma and serum VIP level is decreased during acute exacerbation of asthma. The effect of pregnancy on asthma is variable and depends in part on the severity of pre-existing asthma, along with other physiological and pathophysiological changes. We hypothesized that hydrolysis of VIP by circulating catalytic VIP antibodies will be increased in pregnancy in patients with asthma.

STUDY OBJECTIVE

To determine the level of catalytic autoantibodies to VIP in pregnant asthmatics compared to non-pregnant asthmatics and control pregnant women without asthma.

METHODS

We prospectively enrolled eight pregnant asthmatics (age, 26.5 +/- 2.6 years; mean +/- SEM), nine pregnant women without asthma (32.0 +/- 3.0 years), seven non-pregnant women with asthma (25.0 +/-1.9 years), and seven non-pregnant women without asthma (34.4 +/- 2 years) into the study. VIP hydrolysis was performed in all subjects.

RESULTS

Immunoglobulin G (IgG) autoantibodies that catalyze the hydrolysis of vasoactive intestinal peptide (VIP) were present at greater levels in the blood of pregnant women with asthma (7.6 +/- 1.1 pM VIP/6 h) compared to pregnant women without asthma (4.0 +/- 0.5; p < 0.001), non-pregnant asthmatics (4.9 +/- 0.9; p < 0.05) or non-pregnant women without asthma (1.9 +/- 0.7; p < 0.05).

CONCLUSION

An increase in the VIP hydrolyzing activity of IgG is independently associated with asthma and pregnancy. The autoantibodies hold the potential of affecting the pathophysiology of the airways in pregnant asthmatics.

Nerve growth factor-enhanced airway responsiveness involves substance P in ferret intrinsic airway neurons

Nerve growth factor (NGF), a member of the neurotrophin family, enhances synthesis of neuropeptides in sensory and sympathetic neurons. The aim of this study was to examine the effect of NGF on airway responsiveness and determine whether these effects are mediated through synthesis and release of substance P (SP) from the intrinsic airway neurons. Ferrets were instilled intratracheally with NGF or saline. Tracheal smooth muscle contractility to methacholine and electrical field stimulation (EFS) was assessed in vitro. Contractions of isolated tracheal smooth muscle to EFS at 10 and 30 Hz were significantly increased in the NGF treatment group (10 Hz: 33.57 ± 2.44%; 30 Hz: 40.12 ± 2.78%) compared with the control group (10 Hz: 27.24 ± 2.14%; 30 Hz: 33.33 ± 2.31%). However, constrictive response to cholinergic agonist was not significantly altered between the NGF treatment group and the control group. The NGF-induced modulation of airway smooth muscle to EFS was maintained in tracheal segments cultured for 24 h, a procedure that causes a significant anatomic and functional loss of SP-containing sensory fibers while maintaining viability of intrinsic airway neurons. The number of SP-containing neurons in longitudinal trunk and superficial muscular plexus and SP nerve fiber density in tracheal smooth muscle all increased significantly in cultured trachea treated with NGF. Pretreatment with CP-99994, an antagonist of neurokinin 1 receptor, attenuated the NGF-induced increased contraction to EFS in cultured segments but had no effect in saline controls. These results show that the NGF-enhanced airway smooth muscle contractile responses to EFS are mediated by the actions of SP released from intrinsic airway neurons.

Airway remodeling from bench to bedside: current perspectives

Bronchospasm and airway inflammation can lead to a constellation of irreversible changes in airway structure termed remodeling. Remodeling theory offers insight into the permanent biomechanical and pathologic alterations of asthmatic airways. Structural changes seen in asthmatic patients can include thickening of the airway wall reticular basement membrane (RBM), the presence of an abnormal elastic fiber network, and alterations in airway cartilage structure. Although steroid therapy is helpful in symptomatic control, it does not remedy structural alterations or many aspects of the inflammatory milieu. This article discusses several studies and supports the need for further investigation.

Mice lacking the VIP gene show airway hyperresponsiveness and airway inflammation, partially reversible by VIP

The mechanisms leading to asthma, and those guarding against it, are yet to be fully defined. The neuropeptide VIP is a cotransmitter, together with nitric oxide (NO), of airway relaxation, and a modulator of immune and inflammatory responses. NO-storing molecules in the lung were recently shown to modulate airway reactivity and were proposed to have a protective role against the disease. We report here that mice with targeted deletion of the VIP gene spontaneously exhibit airway hyperresponsiveness to the cholinergic agonist methacholine as well as peribronchiolar and perivascular cellular infiltrates and increased levels of inflammatory cytokines in bronchoalveolar lavage fluid. Immunologic sensitization and challenge with ovalbumin generally enhanced the airway hyperresponsiveness and airway inflammation in all mice. Intraperitoneal administration of VIP over a 2-wk period in knockout mice virtually eliminated the airway hyperresponsiveness and reduced the airway inflammation in previously sensitized and challenged mice. The findings suggest that 1) VIP may be an important component of endogenous anti-asthma mechanisms, 2) deficiency of the VIP gene may predispose to asthma pathogenesis, and 3) treatment with VIP or a suitable agonist may offer potentially effective replacement therapy for this disease.

Reflex regulation of airway smooth muscle tone

Autonomic nerves in most mammalian species mediate both contractions and relaxations of airway smooth muscle. Cholinergic-parasympathetic nerves mediate contractions, whereas adrenergic-sympathetic and/or noncholinergic parasympathetic nerves mediate relaxations. Sympathetic-adrenergic innervation of human airway smooth muscle is sparse or nonexistent based on histological analyses and plays little or no role in regulating airway caliber. Rather, in humans and in many other species, postganglionic noncholinergic parasympathetic nerves provide the only relaxant innervation of airway smooth muscle. These noncholinergic nerves are anatomically and physiologically distinct from the postganglionic cholinergic parasympathetic nerves and differentially regulated by reflexes. Although bronchopulmonary vagal afferent nerves provide the primary afferent input regulating airway autonomic nerve activity, extrapulmonary afferent nerves, both vagal and nonvagal, can also reflexively regulate autonomic tone in airway smooth muscle. Reflexes result in either an enhanced activity in one or more of the autonomic efferent pathways, or a withdrawal of baseline cholinergic tone. These parallel excitatory and inhibitory afferent and efferent pathways add complexity to autonomic control of airway caliber. Dysfunction or dysregulation of these afferent and efferent nerves likely contributes to the pathogenesis of obstructive airways diseases and may account for the pulmonary symptoms associated with extrapulmonary disorders, including gastroesophageal reflux disease, cardiovascular disease, and rhinosinusitis.

Novel concepts of neuropeptide-based drug therapy: vasoactive intestinal polypeptide and its receptors

Chronic inflammatory airway diseases such as bronchial asthma or chronic obstructive pulmonary disease (COPD) are major contributors to the global burden of disease. Although inflammatory cells play the central role in the pathogenesis of the diseases, recent observations indicate that also resident respiratory cells represent important targets for pulmonary drug development. Especially targeting airway neuromediators offers a possible mechanism by which respiratory diseases may be treated in the future. Among numerous peptide mediators such as tachykinins, calcitonin gene-related peptide, neurotrophins or opioids, vasoactive intestinal polypeptide (VIP) is one of the most abundant molecules found in the respiratory tract. In human airways, it influences many respiratory functions via the receptors VPAC1, VPAC2 and PAC1. VIP-expressing nerve fibers are present in the tracheobronchial smooth muscle layer, submucosal glands and in the walls of pulmonary and bronchial arteries and veins. Next to its strong bronchodilator effects, VIP potently relaxes pulmonary vessels, and plays a pivotal role in the mediation of immune mechanisms. A therapy utilizing the respiratory effects of VIP would offer potential benefits in the treatment of obstructive and inflammatory diseases and long acting VIP-based synthetic non-peptide compounds may represent a novel target for drug development.

Development of dry powder inhalation system of novel vasoactive intestinal peptide (VIP) analogue for pulmonary administration

Vasoactive intestinal peptide (VIP) exerts a relaxing action on tracheal smooth muscle which is mediated through interaction with VIP receptors. The deficiency of VIP in the airways has been implicated in the pathogenesis of asthma. Thus, the administration of VIP may be useful for the therapy of pulmonary diseases. However, the therapeutic application of VIP is largely limited by its rapid degradation in addition to the systemic adverse effects due to the wide distribution of VIP receptors. To overcome these problems, we succeeded to synthesize a novel VIP derivative of VIP, [R15, 20, 21, L17]-VIP-GRR (IK312532), and to prepare its dry powder for the topical administration to the lung. The physicochemical properties of dry powder were evaluated by laser diffraction and cascade impactor. The laser diffraction analysis indicated that the carrier and fine particles had median diameter of 65.6 and 4.5 microm, respectively, and the air flow at the pressure of 0.15 MPa or higher resulted in the high dispersion and significant separation of fine particle containing peptide from the carrier molecule. The cascade impactor analysis clearly showed the high emission of dry powder from capsule and the deposition of peptide on stages 3 of the cascade impactor. The intratracheal administration of dry powder inhaler (DPI) of VIP or IK312532 brought about a significant decrease of maximal number of binding sites (Bmax) for [125I]VIP in anterior and posterior lobes of rat right lung, suggesting a significant occupancy of lung VIP receptors. This effect by IK312532-DPI compared with VIP-DPI lasted for a longer period. Thus, IK312532-DPI may be a pharmacologically useful drug delivery system for the VIP therapy of pulmonary diseases such as asthma.

Pharmacological effects and lung-binding characteristics of a novel VIP analogue, [R15, 20, 21, L17]-VIP-GRR (IK312532)

A novel VIP derivative, [R15, 20, 21, L17]-VIP-GRR (IK312532), relaxed potently the carbachol-induced contraction of guinea-pig isolated trachea with longer duration than that induced by VIP. IK312532 competed with [125I]VIP for the binding sites in the rat lung in a concentration-dependent manner. There was considerable decrease in specific [125I]VIP binding in each lobe of right and left lung 0.5 h after the intratracheal administration of IK312532 (50 microg/rat) as dry powder inhaler (DPI). Rosenthal analysis revealed that the administration of IK312532 (50 and 100 microg/rat)-DPI brought about a significant decrease of maximal number of binding sites (Bmax) for specific [125I]VIP binding in anterior and posterior lobes of rat right lung, suggesting a significant occupancy of lung VIP receptors. This effect by IK312532 in the posterior lobe of the right lung was dose-dependent and lasted until at least 2 h after the intratracheal administration. Furthermore, the antigen-evoked infiltration of granulocytes in the rat bronchiolar mucosa was markedly suppressed by the intratracheal administration of IK312532 (50 microg/rat)-DPI. In conclusion, the present study has shown that IK312532 exhibits long-lasting relaxation of tracheal smooth muscles and that the intratracheal administration of this peptide exerts a significant occupancy of lung VIP receptors as well as a suppression of the antigen-evoked infiltration of granulocytes in the bronchiolar mucosa. Thus, the formulation of IK312532 as DPI may be a pharmacologically useful drug delivery system for the therapy of pulmonary diseases such as asthma.

Liposomal Vasoactive Intestinal Peptide

Liposomes have been investigated as drug carriers since first discovered in the 1960s. However, the first-generation, so-called classic liposomes found relatively limited therapeutic utility. Nonetheless, the advent in the 1980s of the second-generation sterically stabilized liposomes (SSL) that evade uptake by the host's reticuloendothelial system greatly enhanced their utility as drug carriers because of their prolonged circulation half-life and passive targeting to injured and cancerous tissues. Over the past decade, our work focused on exploiting the bioactivity of vasoactive intestinal peptide (VIP), a ubiquitous 28-amino acid, amphipathic and pleiotropic mammalian neuropeptide, as a drug. To this end, the peptide expresses distinct and unique innate bioactivity that could be harnessed to treat several human diseases that represent unmet medical needs, such as pulmonary hypertension, stroke, Alzheimer's disease, sepsis, female sexual arousal dysfunction, acute lung injury, and arthritis. Unfortunately, the bioactive effects of VIP last only a few minutes due to its rapid degradation and inactivation by enzymes, catalytic antibodies, and spontaneous hydrolysis in biological fluids. Hence, our goal was to develop and test stable, long-acting formulations of VIP using both classic and SSL as platform technologies. We found that spontaneous association of VIP with phospholipid bilayers leads to a transition in the conformation of the peptide from random coil in an aqueous environment to alpha-helix, the preferred conformation for ligand-receptor interactions, in the presence of lipids. This process, in turn, protects VIP from degradation and inactivation and amplifies its bioactivity in vivo. Importantly, we discovered that the film rehydration and extrusion technique is the most suitable to passively load VIP onto SSL at room temperature and yields the most consistent results. Collectively, these attributes indicate that VIP on SSL represents a suitable formulation that could be tested in human disease.

The significance of vasoactive intestinal peptide in immunomodulation

First identified by Said and Mutt some 30 years ago, the vasoactive intestinal peptide (VIP) was originally isolated as a vasodilator peptide. Subsequently, its biochemistry was elucidated, and within the 1st decade, their signature features as a neuropeptide became consolidated. It did not take long for these insights to permeate the field of immunology, out of which surprising new attributes for VIP were found in the last years. VIP is rapidly transforming into something more than a mere hormone. In evolving scientifically from a hormone to a novel agent for modifying immune function and possibly a cytokine-like molecule, VIP research has engaged many physiologists, molecular biologists, biochemists, endocrinologists, and pharmacologists and it is a paradigm to explore mutual interactions between neural and neuroendocrine links in health and disease. The aim of this review is firstly to update our knowledge of the cellular and molecular events relevant to VIP function on the immune system and secondly to gather together recent data that support its role as a type 2 cytokine. Recognition of the central functions VIP plays in cellular processes is focusing our attention on this "very important peptide" as exciting new candidates for therapeutic intervention and drug development.

Transmission-ratio distortion and allele sharing in affected sib pairs: a new linkage statistic with reduced bias, with application to chromosome 6q25.3

We studied the effect of transmission-ratio distortion (TRD) on tests of linkage based on allele sharing in affected sib pairs. We developed and implemented a discrete-trait allele-sharing test statistic, Sad, analogous to the Spairs test statistic of Whittemore and Halpern, that evaluates an excess sharing of alleles at autosomal loci in pairs of affected siblings, as well as a lack of sharing in phenotypically discordant relative pairs, where available. Under the null hypothesis of no linkage, nuclear families with at least two affected siblings and one unaffected sibling have a contribution to Sad that is unbiased, with respect to the effects of TRD independent of the disease under study. If more distantly related unaffected individuals are studied, the bias of Sad is generally reduced compared with that of Spairs, but not completely. Moreover, Sad has higher power, in some circumstances, because of the availability of unaffected relatives, who are ignored in affected-only analyses. We discuss situations in which it may be an efficient use of resources to genotype unaffected relatives, which would give insights for promising study designs. The method is applied to a sample of pedigrees ascertained for asthma in a chromosomal region in which TRD has been reported. Results are consistent with the presence of transmission distortion in that region.

Postnatal remodeling of the neural components of the epithelial-mesenchymal trophic unit in the proximal airways of infant rhesus monkeys exposed to ozone and allergen

Nerves and neuroendocrine cells located within the airway epithelium are ideally situated to sample a changing airway environment, to transmit that information to the central nervous system, and to promote trophic interactions between epithelial and mesenchymal cellular and acellular components. We tested the hypothesis that the environmental stresses of ozone (O(3)) and house dust mite allergen (HDMA) in atopic infant rhesus monkeys alter the distribution of airway nerves. Midlevel bronchi and bronchioles from 6-month-old infant monkeys that inhaled filtered air (FA), house dust mite allergen HDMA, O(3), or HDMA + O(3) for 11 episodes (5 days each, 0.5 ppm O(3), 8 h/day followed by 9 days recovery) were examined using immunohistochemistry for the presence of Protein gene product 9.5 (PGP 9.5), a nonspecific neural indicator, and calcitonin gene-related peptide (CGRP). Along the axial path between the sixth and the seventh intrapulmonary airway generations, there were small significant (P < 0.05) decrements in the density of epithelial nerves in monkeys exposed to HDMA or O(3), while in monkeys exposed to HDMA + O(3) there was a greater significant (P < 0.05) reduction in epithelial innervation. In animals exposed to O(3) or HDMA + O(3) there was a significant increase in the number of PGP 9.5 positive/CGRP negative cells that were anchored to the basal lamina and emitted projections in primarily the lateral plain and often intertwined with projections and cell bodies of other similar cells. We conclude that repeated cycles of acute injury and repair associated with the episodic pattern of ozone and allergen exposure alter the normal development of neural innervation of the epithelial compartment and the appearance of a new population of undefined PGP 9.5 positive cells within the epithelium.

Neurotrophins and neurotrophin receptors in allergic asthma

The neurotrophins nerve growth factor, brain-derived neurotrophic factor, neurotrophin-3 (NT-3) and NT-4 play a pivotal role in the development of the nervous system. Despite their well-known effects on neurons, elevated neurotrophin concentrations have been observed under pathological conditions in sera of patients with inflammatory disorders. Patients with asthma feature both airway inflammation and an abnormal airway reactivity to many unspecific stimuli, referred to as airway hyperresponsiveness, which is, at least partly, neuronally controlled. Interestingly, these patients show increased levels of neurotrophins in the blood as well as locally in the lung. It has been demonstrated that neurotrophin release from immune cells is triggered by allergen contact. The presence of neurotrophins and the neurotrophin receptors p75 (p75NTR), tyrosine kinase A (TrkA), TrkB and TrkC have been described in several immune cells. There is strong evidence for an involvement of neurotrophins in regulation of hematopoiesis and, in addition, in modulation of immune cell function in mature cells circulating in blood or resting in lymphatic organs and peripheral tissues. The aim of this review is to demonstrate possible roles of neurotrophins during an allergic reaction in consideration of the temporospatial compartimentalization.

Substance P released from intrinsic airway neurons contributes to ozone-enhanced airway hyperresponsiveness in ferret trachea

Exposure to ozone (O3) induces airway hyperresponsiveness mediated partly through the release of substance P (SP) from nerve terminals in the airway wall. Although substantial evidence suggests that SP is released by sensory nerves, SP is also present in neurons of airway ganglia. The purpose of this study was to investigate the role of intrinsic airway neurons in O3-enhanced airway responsiveness in ferret trachea. To remove the effects of sensory innervation, segments of ferret trachea were maintained in culture conditions for 24 h before in vitro exposure to 2 parts/million of O3 or air for 1 h. Sensory nerve depletion was confirmed by showing that capsaicin did not affect tracheal smooth muscle responsiveness to cholinergic agonist or contractility responses to electrical field stimulation (EFS). Contractions of isolated tracheal smooth muscle to EFS were significantly increased after in vitro O3 exposure, but the constrictor response to cholinergic agonist was not altered. Pretreatment with CP-99994, an antagonist of the neurokinin 1 receptor, attenuated the increased contraction to EFS after O3 exposure but had no effect in the air exposure group. The number of SP-positive neurons in longitudinal trunk ganglia, the extent of SP innervation to superficial muscular plexus nerve cell bodies, and SP nerve fiber density in tracheal smooth muscle all increased significantly after O3 exposure. The results show that release of SP from intrinsic airway neurons contributes to O3-enhanced tracheal smooth muscle responsiveness by facilitating acetylcholine release from cholinergic nerve terminals.

Nitric oxide in respiratory diseases

The formation and modulation of nitric oxide (NO) in the lungs is reviewed. Its beneficial and deleterious roles in airways diseases, including asthma, chronic obstructive pulmonary disease, and cystic fibrosis, and in animal models is discussed. The pharmacological effects of agents that modulate NO production or act as NO donors are described. The clinical pharmacology of these agents is described and the therapeutic potential for their use in airways disease is considered.

Pharmacotherapy and airway remodelling in asthma?

Over the last few decades attention has largely focused on airway inflammation in asthma, but more recently it has been appreciated that there are important structural airway changes which have been grouped together under the term "airway remodelling". It is only now that questions have been asked about the impact of treatment on these structural changes. This review examines the nature of these structural airway changes, the mechanisms of their generation, their potential consequences, and what is known about the ability of anti-asthma treatments to modulate these changes.

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.

Helospectin, induces a potent relaxation of human airways in vitro

Helospectin is a neuropeptide of the vasoactive intestinal polypeptide/secretin/glucagon family. Several members of this family display biological activities relevant to obstructive airway disease and although the literature in this area is rapidly expanding very little is known about the effects of helospectin. The smooth muscle relaxation induced by helospectin on human bronchi and pulmonary arteries were therefore assessed in vitro, using tissue baths. Helospectin induced a potent relaxation of human bronchi and since helospectin-like immunoreactive nerve fibers along with possible target receptors previously have been reported in the human lung, helospectin might play a role in endogenous regulation of airway tone.

In vitro evaluation of VIP/PACAP receptors in healthy and diseased human tissues. Clinical implications

The evaluation of peptide receptors in man is relevant to identifying the physiological target tissues of a given peptide and to selecting diseases with a sufficient receptor overexpression for diagnostic or therapeutic intervention. VIP/PACAP receptors have been evaluated in normal and diseased human non-neuronal tissues by using in vitro receptor autoradiography with 125I-VIP or 125I-PACAP in tissue sections. As assessed by subtype-selective VIP analogs, VIP receptors of the VPAC1 subtype are found in a wide variety of tissues including liver, breast, kidney, prostate, ureter, bladder, pancreatic ducts, gastrointestinal mucosa, lung, thyroid, adipose, and lymphoid tissues. VPAC2 receptors are predominantly found in vessels and smooth muscles, whereas PAC1 receptors are present in the adrenal medulla. VIP/PACAP receptors are expressed in the majority of the most frequently occurring human tumors, including breast, prostate, pancreas, lung, colon, stomach, liver, and bladder carcinomas, as well as lymphomas and meningiomas, predominantly as VPAC1 receptors, as do their tissues of origin. Although leiomyomas predominantly express VPAC2 receptors, glial tumors, pituitary adenomas, neuroblastomas, paragangliomas, pheochromocytomas, and endometrial carcinomas preferentially express PAC1 receptors. The very wide distribution of VIP/PACAP receptors in the normal human body is indicative of the key role of these peptides in human physiology and pathophysiology. Moreover, the receptor expression in tumors is the molecular basis for clinical applications of VIP/PACAP such as in vivo scintigraphy and radiotherapy of tumors as well as VIP/PACAP analog treatment for tumor growth inhibition.

Validation of endobronchial biopsy specimens for nerve quantitation by computer-assisted image analysis

The aim of this study was to assess the validity of endoscopic bronchial biopsy specimens for the quantitation of nerves. To this end, endobronchial biopsy was simulated ex vivo on surgically resected lung specimens and nerve densities were compared in airway smooth muscle of biopsy and surrounding tissue. Specimens were stained immunohistochemically for the general neural marker protein gene product 9.5 (PGP 9.5) and for vasoactive intestinal peptide (VIP), and nerve densities were quantitated using computer-assisted image analysis. Nerve density for total (PGP 9.5-immunoreactive) nerves was slightly higher in biopsies than in corresponding lung tissue, but this difference did not reach statistical significance (p=0.08). There was also no significant difference in the density of VIP-immunoreactive nerves (p=0.60). These findings support the use of endobronchial biopsy specimens to quantitate nerves in asthma and other airway diseases.

Neural mechanisms in asthma

Advances in the understanding of neural mechanisms in asthma may provide novel therapeutic approaches in the treatment of asthma. Excessive activity of cholinergic nerves may be important in asthma. Dysfunction of M2 muscarinic receptors in asthma may lead to excessive bronchoconstriction and mucus secretion and can be induced in animal models by a range of stimuli including allergen, viral infection, ozone, eosinophil products and cytokines. Cholinergic mechanisms may be especially important in certain types of patients and anticholinergic agents provide protection against bronchospasm due to psychogenic factors or beta2-blockers. Non-adrenergic non-cholinergic (NANC) mechanisms, both inhibitory (i-NANC) and excitatory (e-NANC), may play a significant role in the pathophysiology of asthma. The putative neurotransmitters, vasoactive interstinal polypeptide (VIP) and nitric oxide (NO), mediate neural bronchodilation in human airways. There does not appear to be a defect in the i-NANC system in moderate or severe asthma. e-NANC is mediated by the sensory neuropeptides substance P (SP) and the more potent bronchoconstrictor neurokinin A (NKA). Various studies suggest that the SP content of human airways is increased in asthma. Tachykinins are not only present in sensory nerves, but also are produced by inflammatory cells such as alveolar macrophages, dendritic cells, eosinophils, lymphocytes and neutrophils. They can be released into the airways by stimuli such as allergen and ozone. Evidence suggests that in addition to smooth muscle contraction, which is mediated mainly by NK2 receptors, tachykinins also cause mucus secretion, plasma extravasation and stimulate inflammatory and immune cells. These effects are mediated by NK1 receptors. Recent studies have shown that NK2 receptor antagonists such as saredutant partially inhibit NKA-induced bronchoconstriction in asthmatics. Thus, tachykinin receptor antagonists have potential as therapies for asthma.

Consequences of long-term inflammation. Airway remodeling

Airway inflammation may not account for all the clinical manifestations of asthma. Airway remodeling, which is thought to be a result of airway chronic inflammation, may help fill this void. Remodeling is described for fatal and nonfatal asthmatics including changes in smooth muscle, collagen deposition, noncollagenous matrix, and mucus glands. This article also reviews the correlation of airway remodeling with clinical, physiologic and biologic data, experimental models of airways remodeling, and effect of therapy on airway remodeling. Throughout, it is emphasized that the concept of airway remodeling is a dynamic process that is active and potentially progressive in asthmatic patients but that may be prevented by appropriate therapy.

Biodistribution of liposomal 131I-VIP in rat using gamma camera

Vasoactive intestinal peptide (VIP), a 28 amino-acid peptide was labeled with 131I and encapsulated into liposomes. 131I-VIP or liposomal 131I-VIP was administered intravenously into the rats. The distribution was studied by a gamma camera and established by counting the radioactivity in the removed organs. The elimination half-life for the liposomal 131I-VIP in both blood and lungs was significantly longer (5.29 and 9.28 min, respectively) than that obtained after the administration of 131I-VIP (0.62 and 3.18 min, respectively). Dynamic scans using a gamma camera after the administration of liposomal 131I-VIP showed a higher uptake of the liposomal form into the lungs compared with 131I-VIP. The lack of VIP in asthmatics has been shown in previous studies. However, the clinical investigations using VIP were disappointing most probably due to the rapid degradation of the peptide in the bronchial tract. This in fact is supported by our previous study, in which we demonstrated that VIP had a half-life of 0.45 min in blood. We conclude that the encapsulation of VIP in liposomes prolongs its elimination half-life in plasma and enhances its uptake in lungs. This observation may increase the clinical use of VIP in both diagnostic and therapy.

Expression, pharmacological, and functional evidence for PACAP/VIP receptors in human lung

Pituitary adenylate cyclase-activating peptide (PACAP) type 1 (PAC(1)) and common PACAP/vasoactive intestinal peptide (VIP) type 1 and 2 (VPAC(1) and VPAC(2), respectively) receptors were detected in the human lung by RT-PCR. The proteins were identified by immunoblotting at 72, 67, and 68 kDa, respectively. One class of PACAP receptors was defined from (125)I-labeled PACAP-27 binding experiments (dissociation constant = 5.2 nM; maximum binding capacity = 5.2 pmol/mg protein) with a specificity: PACAP-27 approximately VIP > helodermin approximately peptide histidine-methionine (PHM) >> secretin. Two classes of VIP receptors were established with (125)I-VIP (dissociation constants of 5.4 and 197 nM) with a specificity: VIP approximately helodermin approximately PACAP-27 >> PHM >> secretin. PACAP-27 and VIP were equipotent on adenylyl cyclase stimulation (EC(50) = 1.6 nM), whereas other peptides showed lower potency (helodermin > PHM >> secretin). PACAP/VIP antagonists supported that PACAP-27 acts in the human lung through either specific receptors or common PACAP/VIP receptors. The present results are the first demonstration of the presence of PAC(1) receptors and extend our knowledge of common PACAP/VIP receptors in the human lung.

Role of bronchoscopy in asthma research

Over the past 15 years, much has been learned about the presence of airway inflammation in asthma through the use of investigative bronchoscopy. It has become quite clear that inflammation is present even in mild asthma. In addition to the eosinophils, T-lymphocytes and a variety of cytokines have been identified to play a prominent role in asthmatic inflammation. The concept of delayed asthmatic response after allergen exposure and its relationship to cellular inflammation and airway hyper-reactivity has become more clearly established. Our understanding of asthmatic airway inflammation, however, is incomplete. As interesting as the database has been so far, investigative FB has not defined a unique profile for patients with asthma. Specifically, lavage or endobronchial biopsy has not identified parameters that help in the diagnosis, assessment of disease severity, prognosis, or likelihood to respond to specific therapies. Also, the exact relationship between parameters in lavage compared with mucosal biopsy and how these are related to airway hyper-reactivity and the clinical syndrome of asthma remains poorly understood. In this regard, it must be confessed that currently FB with lavage and biopsy in asthmatics needs to be considered as a research tool for specimen retrieval to help characterize and express inflammation. Although these techniques have contributed immensely to our understanding of asthma pathogenesis, presently these techniques do not have any practical role or clinical usefulness.

Neuroregulation by vasoactive intestinal peptide (VIP) of mucus secretion in ferret trachea: activation of BK(Ca) channels and inhibition of neurotransmitter release

1. The aims of this study were to determine: (1) whether vasoactive intestinal peptide (VIP) regulates cholinergic and 'sensory-efferent' (tachykininergic) 35SO4 labelled mucus output in ferret trachea in vitro, using a VIP antibody, (2) the class of potassium (K+) channel involved in VIP-regulation of cholinergic neural secretion using glibenclamide (an ATP-sensitive K+ (K(ATP)) channel inhibitor), iberiotoxin (a large conductance calcium activated K+ (BK(ca)) channel blocker), and apamin (a small conductance K(ca) (SK(ca)) channel blocker), and (3) the effect of VIP on cholinergic neurotransmission using [3H]-choline overflow as a marker for acetylcholine (ACh) release. 2. Exogenous VIP (1 and 10 microM) alone increased 35SO4 output by up to 53% above baseline, but suppressed (by up to 80% at 1 microM) cholinergic and tachykininergic neural secretion without altering secretion induced by ACh or substance P (1 microM each). Endogenous VIP accounted for the minor increase in non-adrenergic, non-cholinergic (NANC), non-tachykininergic neural secretion, which was compatible with the secretory response of exogenous VIP. 3. Iberiotoxin (3 microM), but not apamin (1 microM) or glibenclamide (0.1 microM), reversed the inhibition by VIP (10 nM) of cholinergic neural secretion. 4. Both endogenous VIP (by use of the VIP antibody; 1:500 dilution) and exogenous VIP (0.1 microM), the latter by 34%, inhibited ACh release from cholinergic nerve terminals and this suppression was completely reversed by iberiotoxin (0.1 microM). 5. We conclude that, in ferret trachea in vitro, endogenous VIP has dual activity whereby its small direct stimulatory action on mucus secretion is secondary to its marked regulation of cholinergic and tachykininergic neurogenic mucus secretion. Regulation is via inhibition of neurotransmitter release, consequent upon opening of BK(Ca) channels. In the context of neurogenic mucus secretion, we propose that VIP joins NO as a neurotransmitter of i-NANC nerves in ferret trachea.

Molecular mapping of epitopes involved in ligand activation of the human receptor for the neuropeptide, VIP, based on hybrids with the human secretin receptor

Receptors for the neurotransmitter and neuroendocrine peptides, vasoactive intesinal peptide (VIP) and secretin, both belong to the Type B subfamily of G-protein-coupled receptors. This group is evolutionally as well as structurally distinct from the much larger Type A, or rhodopsin-type, subfamily. We have mapped the ligand-activating epitopes of the human VIP1 receptor by the use of hybrid receptor constructs with the human secretin receptor. Twelve chimeras were synthesized the successively replacing portions of the former receptor with corresponding portions of the latter receptor, or by interchanging the first extracellular loops. Each of the different chimeric receptor DNAs were then expressed in murine reporter cells, and their ability to activate cAMP production was investigated on stimulation with the respective natural peptide ligands. We stimulated the reporter cells with secretion or VIP following transient expression of the receptor chimeras. The experiments indicated that there are two molecular domains of importance for the recognition and activation of these peptides, namely, the inner portion of the extracellular tail and the first extracellular loop of the two receptors.

Mechanism and functional role of antibody catalysis

The light (L) chain of a model antibody (Ab) was deduced to contain a serine protease-like catalytic site capable of cleaving peptide bonds. The catalytic site is encoded by a germline VL gene. The catalytic activity can potentially be improved by somatic sequence diversification and pairing of the L chain with the appropriate heavy chain. Autoimmune disease is associated with increased synthesis of antigen (Ag)-specific Abs, but the reasons for this phenomenon are not known. Only recently has attention turned to the functional role of the catalytic function. Preliminary studies confirm that the catalytic cleavage of peptide bonds is a more potent means to achieve Ag neutralization, compared to reversible Ag binding. Administration of a monoclonal Ab to VIP in experimental animals induces an inflammatory response in the airways, suggesting that catalytic autoantibodies to this peptide found in airway disease and lupus are capable of causing airway dysfunction. The phenomenon of autoantibody catalysis can potentially be applied to isolate efficient catalysts directed against tumor or microbial Ags by exposing the autoimmune repertoire to such Ags or their analogs capable of recruiting the germline VL gene encoding the catalytic site.

Bronchial mucosal immunoreactivity of sensory neuropeptides in severe airway diseases

Neuropeptides act on most of the components of the bronchial environment. They influence bronchomotor tone and bronchial vascular caliber and permeability. To investigate the nonadrenergic, noncholinergic system within the airways in asthma and chronic bronchitis, we performed endobronchial biopsies in 16 normal human volunteers, 49 patients with asthma of varying severity, including 16 patients treated with oral corticosteroids, and 13 patients with chronic bronchitis. Frozen sections of biopsies stained with specific antibodies against the neural marker PGP 9.5, vasoactive intestinal peptide (VIP), substance P (SP), calcitonin gene-related peptide (CGRP), and neuropeptide Y (NPY) were analyzed for the presence of nerves through indirect immunofluorescence. Nerves were present in most of the biopsies and were found within and below the epithelium and adjacent to smooth muscle, glands, and blood vessels. By comparison with those in normal subjects, the numbers of VIP-immunoreactive nerves were not significantly decreased in patients with asthma and chronic bronchitis, but NPY-immunoreactive nerves were significantly decreased in the smooth muscle of these latter two groups of patients (p < 0.005). There was no correlation between disease severity and the number of nerves found in the biopsies. This study does not confirm previous findings in autopsy material of some defects in sensory and VIP-containing nerves in severe asthma.

Inflammatory cell distribution within and along asthmatic airways

Asthmatic airways are infiltrated with inflammatory cells that release mediators and cytokines into the microenvironment. In this study, we evaluated the distribution of CD45-positive leukocytes and eosinophils in lung tissue from five patients who died with severe asthma compared with five patients with cystic fibrosis. For morphometric analysis, the airway wall was partitioned into an "inner" area (between basement membrane and smooth muscle) and an "outer" area (between smooth muscle and alveolar attachments). Large airways (with a perimeter greater than 3.0 mm) from patients with asthma or cystic fibrosis had a greater density of CD45-positive cells (p < 0.05) and eosinophils (p < 0.001) in the inner airway region compared with the same airway region in small airways. Furthermore, in small airways, asthmatic lungs showed a greater density of CD45-positive cells (p < 0.01) and eosinophils (p < 0.01) in the outer compared with the inner airway wall region. These observations indicate that there are regional variations in inflammatory cell distribution within the airway wall in patients with asthma that are not observed in airways from patients with cystic fibrosis. We speculate that this inflammatory cell density in peripheral airways in severe asthma may relate to the peripheral airway obstruction characteristic of this condition.

Increased VIP-positive nerve fibers in the mucous glands of subjects with chronic bronchitis

The presence and distribution of neuropeptide-containing nerves within bronchial surgical specimens has been investigated in bronchitic (n = 12) and in nonbronchitic subjects (n = 7). Lung tissue, obtained from patients undergoing thoracotomy for limited lung lesions, was processed immediately and analyzed for nerves using the streptavidin-biotin complex peroxidase method with antisera to the neural marker protein gene product 9.5 (PGP 9.5) and the neuropeptides vasoactive intestinal peptide (VIP), substance P (SP), calcitonin-gene related peptide (CGRP). There were no significant differences between the two groups with respect to the density of PGP 9.5-, SP-, or CGRP-positive nerves in both the locations assessed (smooth muscle layer and glands). The density of VIP-positive nerves was significantly higher in the glands of bronchitic than in nonbronchitic subjects. A negative relationship was found between the presence of airway inflammation, as indexed by mononuclear cell tissue infiltration, and the density of PGP 9.5-positive nerves in both smooth muscle and glands. Likewise, a relationship was found between the smoking history (packs/yr and age of onset of smoking) and the density of VIP-positive nerves in glands. These findings support a role for VIP in the hallmark of chronic bronchitis, i.e., sputum production.

Vasoactive intestinal peptide (VIP) induces IL-6 and IL-8, but not G-CSF and GM-CSF release from a human bronchial epithelial cell line

Vasoactive intestinal polypeptide (VIP) is a 28-amino acid neuropeptide with vasodilator, bronchodilator, and anti-inflammatory effects. Little is known about pro-inflammatory effects of VIP. We investigated the effect of VIP on the secretion of IL-6, IL-8, GM-CSF, and G-CSF from a bronchial epithelial cell line (BEAS 2B). The incubation of BEAS-2B cells with VIP in concentrations of 10(-13) to 10(-7) M for 4 h, caused dose-related increases of IL-6 (98% increase above control, P < 0.001) and IL-8 (35% increase above control, P < 0.01). After 4 h of incubation, 10(-7) M PHI also increased IL-6 release by 74% (P < 0.01). After 8 h of incubation, VIP increased IL-6 release by 59% (P < 0.01), causing no effect on IL-8 release. After 24 h of incubation, VIP increased the release of IL-6 by 48% (P < 0.05) and IL-8 by 45% (P < 0.05). Ribonuclease protection assays for steady-state IL-6 mRNA revealed that increases in response to VIP stimulation occurred by 1 h and persisted through 16 h of stimulation. VIP had no significant effect on the release of G-CSF and GM-CSF. VIP did not induce cell proliferation at 24 and 48 h. These findings suggest that VIP can alter epithelial cell cytokine release and might be capable of modulating the airway inflammatory response in this manner.