Involvement of enhanced neurokinin NK3 receptor expression in the severe asthma guinea pig model

Back to the future: re-establishing guinea pig in vivo asthma models

Research using animal models of asthma is currently dominated by mouse models. This has been driven by the comprehensive knowledge on inflammatory and immune reactions in mice, as well as tools to produce genetically modified mice. Many of the identified therapeutic targets influencing airway hyper-responsiveness and inflammation in mouse models, have however been disappointing when tested clinically in asthma. It is therefore a great need for new animal models that more closely resemble human asthma. The guinea pig has for decades been used in asthma research and a comprehensive table of different protocols for asthma models is presented. The studies have primarily been focused on the pharmacological aspects of the disease, where the guinea pig undoubtedly is superior to mice. Further reasons are the anatomical and physiological similarities between human and guinea pig airways compared with that of the mouse, especially with respect to airway branching, neurophysiology, pulmonary circulation and smooth muscle distribution, as well as mast cell localization and mediator secretion. Lack of reagents and specific molecular tools to study inflammatory and immunological reactions in the guinea pig has however greatly diminished its use in asthma research. The aim in this position paper is to review and summarize what we know about different aspects of the use of guinea pig in vivo models for asthma research. The associated aim is to highlight the unmet needs that have to be addressed in the future.

Neuromodulation mediated by the tachykinin NK3-receptor agonist [MePhe7]-neurokinin B in the isolated perfused lung of nonsensitized nonchallenged and ovalbumin-sensitized and -challenged guinea pig

The neuromodulatory action of the tachykinin NK(3)-receptor agonist [MePhe(7)]-neurokinin B ([MePhe(7)]-NKB) was evaluated on vagal stimulation-induced bronchoconstriction in nonsensitized nonchallenged and ovalbumin (OVA)-sensitized and -challenged guinea pig using the isolated perfused lung preparation. Lungs were placed inside a warmed (37°C) glass chamber and suspended from a force displacement transducer (Grass FT-03) with both vagi connected to a stimulating electrode. Isolated lungs were stimulated at a constant voltage (20 V) and pulse duration (5 ms) with electrical stimulation frequencies ranging from 1 to 128 Hz. The authors demonstrated that vagal stimulation produced frequency-dependent bronchoconstriction and [MePhe(7)]-NKB, at a dose (0.1 μM) that does not produce bronchoconstriction by itself, potentiated the vagally induced bronchoconstriction at all frequencies in nonsensitized nonchallenged animals and to a greater extent in OVA-sensitized and -challenged guinea pigs; the potentiations were totally inhibited by the tachykinin NK(3)-receptor antagonist SR 142801 (1 μM). In a second set of experiments, [MePhe(7)]-NKB produced bronchoconstriction in a dose-dependent (1 to 300 μg/mL) manner with similar potencies and maximum responses in nonsensitized nonchallenged (EC(50) = 8.6 ± 1.1 μM; E(Max) = 61.1 ± 3.5 mm Hg) and OVA-sensitized and -challenged (EC(50) = 8.5 ± 1.3 μM; E(Max) = 63.5 ± 3.7 mm Hg) animals. In conclusion, these results demonstrated that [MePhe(7)]-NKB potentiated vagal stimulation-induced bronchoconstriction via the tachykinin NK(3)-receptors and OVA sensitization caused development of airway hyperresponsiveness in these potentiations. However, OVA sensitization had no effect on airway responsiveness of vagal stimulation-and [MePhe(7)]-NKB-induced bronchoconstrictions.

Immunohistochemical demonstration of airway epithelial cell markers of guinea pig

The guinea pig (Cavea porcellus) is a mammalian non-rodent species in the Caviidae family. The sensitivity of the respiratory system and the susceptibility to infectious diseases allows the guinea pig to be a useful model for both infectious and non-infectious lung diseases such as asthma and tuberculosis. In this report, we demonstrated for the first time, the major cell types and composition in the guinea pig airway epithelium, using cell type-specific markers by immunohistochemical staining using the commercial available immunological reagents that cross-react with guinea pig. Our results revealed the availability of antibodies cross-reacting with airway epithelial cell types of basal, non-ciliated columnar, ciliated, Clara, goblet and alveolar type II cells, as well as those cells expressing Mucin 5AC, Mucin 2, Aquaporin 4 and Calcitonin Gene Related Peptide. The distribution of these various cell types were quantified in the guinea pig airway by immunohistochemical staining and were comparable with morphometric studies using an electron microscopy assay. Moreover, this study also demonstrated that goblet cells are the main secretory cell type in the guinea pig's airway, distinguishing this species from rats and mice. These results provide useful information for the understanding of airway epithelial cell biology and mechanisms of epithelial-immune integration in guinea pig models.

RS-1748, a novel CC chemokine receptor 4 antagonist, inhibits ovalbumin-induced airway inflammation in guinea pigs

CC chemokine receptor 4 (CCR4) is generally recognized as a preferential marker for T helper 2 cells, and we have previously reported morpholine-derivative CCR4 antagonists, RS-1154 and RS-1269. Here, we investigate the pharmacological profiles of a novel pyrimidine-derivative CCR4 antagonist, 2-{4-[2-(diethylamino)ethoxy]phenyl}-N-(2,4-difluorobenzyl)-5-fluoropyrimidin-4-amine (RS-1748), which showed potency to inhibit the bindings of [(125)I]CCL17 and [(35)S]GTPgammaS to human CCR4-expressing Chinese hamster ovary (CHO) cells with IC(50) values of 59.9 nM and 18.4 nM, respectively. Furthermore, RS-1748 inhibited ovalbumin-induced airway inflammation in guinea pigs at a dose of 10 mg/kg. These results indicate that RS-1748 would be a promising lead compound for developing a therapeutic agent against asthma.

The absence of VPAC2 leads to aberrant antibody production in Aspergillus fumigatus sensitized and challenged mice

Vasoactive intestinal peptide (VIP) facilitates a "pro-allergy" phenotype when signaling through its G protein-coupled receptor, VPAC(2). We have shown that VPAC(2) knock-out (KO) mice developed an allergic phenotype marked by eosinophilia and elevated serum IgE. Therefore, we hypothesized that the humoral response to allergen challenge in these mice was T(H)2 dominant similar to wild-type (WT) C57BL/6 mice. Antibody responses in WT and KO mice were measured after Aspergillus fumigatus conidia inhalation. In contrast to previous reports, basal levels of serum IgG(2a) and IgA were significantly higher in naïve VPAC(2) KO animals. Antibody availability in the serum as well as the bronchoalveolar lavage fluid after fungal challenge was dominated by the pro-inflammatory isotype IgG(2a) and the mucosal isotype, IgA. IgA localizing cells dominated in the peribronchovascular areas of allergic KO mice while IgE immune complexes were found in WT allergic lungs. This research shows for the first time that VPAC(2) has a significant effect on antibody regulation, in the context of allergy.

Propofol preferentially relaxes neurokinin receptor-2-induced airway smooth muscle contraction in guinea pig trachea

BACKGROUND

Propofol is the anesthetic of choice for patients with reactive airway disease and is thought to reduce intubation- or irritant-induced bronchoconstriction by decreasing the cholinergic component of vagal nerve activation. However, additional neurotransmitters, including neurokinins, play a role in irritant-induced bronchoconstriction. We questioned the mechanistic assumption that the clinically recognized protective effect of propofol against irritant-induced bronchoconstriction during intubation was due to attenuation of airway cholinergic reflexes.

METHODS

Muscle force was continuously recorded from isolated guinea pig tracheal rings in organ baths. Rings were subjected to exogenous contractile agonists (acetylcholine, histamine, endothelin-1, substance P, acetyl-substance P, and neurokinin A) or to electrical field stimulation (EFS) to differentiate cholinergic or nonadrenergic, noncholinergic nerve-mediated contraction with or without cumulatively increasing concentrations of propofol, thiopental, etomidate, or ketamine.

RESULTS

Propofol did not attenuate the cholinergic component of EFS-induced contraction at clinically relevant concentrations. In contrast, propofol relaxed nonadrenergic, noncholinergic-mediated EFS contraction at concentrations within the clinical range (20-100 mum, n = 9; P < 0.05), and propofol was more potent against an exogenous selective neurokinin-2 receptor versus neurokinin-1 receptor agonist contraction (n = 6, P < 0.001).

CONCLUSIONS

Propofol, at clinically relevant concentrations, relaxes airway smooth muscle contracted by nonadrenergic, noncholinergic-mediated EFS and exogenous neurokinins but not contractions elicited by the cholinergic component of EFS. These findings suggest that the mechanism of protective effects of propofol against irritant-induced bronchoconstriction involves attenuation of tachykinins released from nonadrenergic, noncholinergic nerves acting at neurokinin-2 receptors on airway smooth muscle.

The role of neuro-immune cross-talk in the regulation of inflammation and remodelling in asthma

Despite recent advances in the development of anti-asthmatic medication, asthma continues to be a major health problem worldwide. The symptoms of asthmatic patients include wheezing, chest tightness, cough and shortness of breath, which, together with airway hyperresponiveness, previously have been attributed to a dysfunction of airway nerves. However, research in the last two decades identified Th2-sensitization and the subsequent allergic reaction to innocuous environmental antigens as a basic immunological mechanism leading to chronic airway inflammation. Recent evidence suggests that the development of allergic asthma is influenced by events and circumstances in early childhood and even in utero. Allergen, ozone or stress exposure, as well as RSV infection in early life could be able to induce irreversible changes in the developing epithelial-mesenchymal trophic unit of the airways. The co-existence of chronic inflammation and neural dysfunction have recently drawn attention to the involvement of interaction pathways between the nervous and the immune system in the airways. Intensive basic research has accumulated morphological as well as functional evidence for the interaction between nerves and immune cells. Neuropeptides and neurotrophins have come into focus of attention as the key mediators of neuro-immune interactions, which lead to the development of several pharmacological compounds specifically targeting these molecules. This review will integrate our current knowledge on the involvement of neuro-immune pathways in asthma on the cellular and molecular level. It will summarize the results of pharmacological studies addressing the potential of neuropeptides and neurotrophins as novel therapeutic targets in asthma.

Expression and coupling of neurokinin receptor subtypes to inositol phosphate and calcium signaling pathways in human airway smooth muscle cells

Neuropeptide tachykinins (substance P, neurokinin A, and neurokinin B) are present in peripheral terminals of sensory nerve fibers within the respiratory tract and cause airway contractile responses and hyperresponsiveness in humans and most mammalian species. Three subtypes of neurokinin receptors (NK1R, NK2R, and NK3R) classically couple to Gq protein-mediated inositol 1,4,5-trisphosphate (IP3) synthesis and liberation of intracellular Ca2+, which initiates contraction, but their expression and calcium signaling mechanisms are incompletely understood in airway smooth muscle. All three subtypes were identified in native and cultured human airway smooth muscle (HASM) and were subsequently overexpressed in HASM cells using a human immunodeficiency virus-1-based lentivirus transduction system. Specific NKR agonists {NK1R, [Sar9,Met(O2)11]-substance P; NK2R, [beta-Ala8]-neurokinin A(4-10); NK3R, senktide} stimulated inositol phosphate synthesis and increased intracellular Ca2+ concentration ([Ca2+]i) in native HASM cells and in HASM cells transfected with each NKR subtype. These effects were blocked by NKR-selective antagonists (NK1R, L-732138; NK2R, GR-159897; NK3R, SB-222200). The initial transient and sustained phases of increased [Ca2+]i were predominantly inhibited by the IP3 receptor antagonist 2-aminoethoxydiphenyl borate (2-APB) or the store-operated Ca2+ channel antagonist SKF-96365, respectively. These results show that all three subtypes of NKRs are expressed in native HASM cells and that IP3 levels are the primary mediators of NKR-stimulated initial [Ca2+]i increases, whereas store-operated Ca2+ channels mediate the sustained phase of the [Ca2+]i increase.

Impact of lung remodelling on respiratory mechanics in a model of severe allergic inflammation

We developed a model of severe allergic inflammation and investigated the impact of airway and lung parenchyma remodelling on in vivo and in vitro respiratory mechanics. BALB/c mice were sensitized and challenged with ovalbumin in severe allergic inflammation (SA) group. The control group (C) received saline using the same protocol. Light and electron microscopy showed eosinophil and neutrophil infiltration and fibrosis in airway and lung parenchyma, mucus gland hyperplasia, and airway smooth muscle hypertrophy and hyperplasia in SA group. These morphological changes led to in vivo (resistive and viscoelastic pressures, and static elastance) and in vitro (tissue elastance and resistance) lung mechanical alterations. Airway responsiveness to methacholine was markedly enhanced in SA as compared with C group. Additionally, IL-4, IL-5, and IL-13 levels in the bronchoalveolar lavage fluid were higher in SA group. In conclusion, this model of severe allergic lung inflammation enabled us to directly assess the role of airway and lung parenchyma inflammation and remodelling on respiratory mechanics.

Role of tachykinin NK3 receptors in the release and effects of nerve growth factor in human isolated bronchi

The nerve growth factor (NGF) is a neurotrophic factor essential for the development and survival of neurons. It has also been identified as a mediator of inflammation and can cause airway hyperresponsiveness [Frossard et al., Eur. J. Pharmacol. 500, 453 (2004)]. Evidence in rodents suggests a link between tachykinins, the sensory nerves, and NGF. Recent evidence shows that NGF is released by the proinflammatory cytokine interleukin-1beta and induces hyperresponsiveness to the tachykinin NK1 receptor agonist [Sar(9),Met(O(2))(11)]SP in isolated human bronchi. The aim of this study was to determine the role of sensory nerves through the effect of the tachykinin NK3 receptor antagonist SR142801 in the interleukin-1beta effects and/or the NGF-induced airway hyperresponsiveness. SR142801 (0.1 microM) abolished the interleukin-1beta (10 ng/ml, 21 degrees C, 15 h)-induced increased NGF release from isolated human bronchi in vitro (P<0.05). In organ bath studies, SR142801 also abolished the interleukin-1beta-induced airway hyperresponsiveness to [Sar(9),Met(O(2))(11)]SP (0.1 microM) (P<0.05). SR142801 also inhibited the NGF-induced airway hyperresponsiveness (P<0.01). This study suggests tachykininergic sensory nerves to be involved in the interleukin-1beta-induced NGF release and airway hyperresponsiveness.

Neurokinin3 receptor regulation of the airways

Neurokinin(3) (NK(3)) receptors may regulate the airways primarily through actions on the nerves. In the periphery, airway parasympathetic ganglia neurons are depolarized following NK(3) receptor activation resulting subsequently in the facilitation of synaptic transmission. Such an effect may account for the excessive parasympathetic reflex effects (e.g. airway smooth muscle contraction, vascular engorgement, mucus secretion) associated with asthma and chronic obstructive pulmonary disease (COPD). In the central nervous system (CNS), NK(3) receptor activation may regulate airway vagal afferent relay neurons, rendering them hyperresponsive to parallel inputs from glutamate containing afferent nerves. This process is analogous to the process of central sensitization regulating hyperalgesia and pain in somatic tissues. In both the CNS and in the airways, NK(3) receptors are likely activated by either substance P and/or neurokinin A (NKA), both of which are full agonists at NK(3) receptors, as there is little evidence that airway nerves express neurokinin B (NKB). Evidence for other potential sites of regulation by NK(3) receptors in the airways (e.g. vasculature, airway smooth muscle, epithelium, mucus glands) is either inconclusive or conflicting.