Expression and function of NPSR1/GPRA in the lung before and after induction of asthma-like disease

In silico analysis of single nucleotide polymorphism (rs34377097) of TBXA2R gene and pollen induced bronchial asthma susceptibility in West Bengal population, India

Introduction

Prevalence of asthma is increasing steadily among general population in developing countries over past two decades. One of the causative agents of broncho-constriction in asthma is thromboxane A2 receptor (TBXA2R). However few studies of TBXA2R polymorphism were performed so far. The present study aimed to assess potential association of TBXA2R rs34377097 polymorphism causing missense substitution of Arginine to Leucine (R60L) among 482 patients diagnosed with pollen-induced asthma and 122 control participants from West Bengal, India. Also we performed in-silico analysis of mutated TBXA2R protein (R60L) using homology modeling.

Methods

Clinical parameters like Forced expiratory volume in 1 second (FEV₁), FEV₁/Forced vital capacity (FVC) and Peak expiratory flow rate (PEFR) were assessed using spirometry. Patients' sensitivity was measured by skin prick test (SPT) against 16 pollen allergens. Polymerase chain reaction-based Restriction fragment length polymorphism was done for genotyping. Structural model of wild type and homology model of polymorphic TBXA2R was generated using AlphaFold2 and MODELLER respectively. Electrostatic surface potential was calculated using APBS plugin in PyMol.

Results

Genotype frequencies differed significantly between the study groups (P=0.03). There was no significant deviation from Hardy-Weinberg equilibrium in control population (χ2=1.56). Asthmatic patients have significantly higher frequency of rs34377097TT genotype than control subjects (P=0.03). SPT of patients showed maximum sensitivity in A. indica (87.68%) followed by C. nusifera (83.29%) and C. pulcherima (74.94%). Significant difference existed for pollen sensitivity in adolescent and young adult (P=0.01) and between young and old adult (P=0.0003). Significant negative correlation was found between FEV1/FVC ratio and intensity of SPT reactions (P<0.0001). Significant association of FEV₁, FEV₁/FVC and PEFR was observed with pollen-induced asthma. Furthermore, risk allele T was found to be clinically correlated with lower FEV₁/FVC ratio (P=0.015) in patients. Our data showed R60L polymorphism, which was conserved across mammals, significantly reduced positive electrostatic charge of polymorphic protein in cytoplasmic domain thus altered downstream pathway and induced asthma response.

Discussion

The present in-silico study is the first one to report association of TBXA2R rs34377097 polymorphism in an Indian population. It may be used as prognostic marker of clinical response to asthma in West Bengal and possible target of therapeutics in future.

Neuropeptide S (NPS) and its receptor (NPSR1) in chickens: cloning, tissue expression, and functional analysis

Neuropeptide S (NPS) and its receptor neuropeptide S receptor 1 (NPSR1) have been suggested to regulate many physiological processes in the central nervous system (CNS), such as arousal, anxiety, and food intake in mammals and birds, however, the functionality and tissue expression of this NPS-NPSR1 system remain unknown in birds. Here, we cloned NPS and NPSR1 cDNAs from the chicken brain and reported their functionality and tissue expression. The cloned chicken NPS is predicted to encode a mature NPS peptide of 20 amino acids, which shows a remarkable sequence identity (∼94%) among tetrapod species examined, while NPSR1 encodes a receptor of 373 amino acids conserved across vertebrates. Using cell-based luciferase reporter systems, we demonstrated that chicken NPS could potently activate NPSR1 expressed in vitro and thus stimulates multiple signaling pathways, including calcium mobilization, cyclic adenosine monophosphate/protein kinase A (cAMP/PKA), and mitogen-activated protein kinase/extracellular signal-regulated kinase (MAPK/ERK) signaling pathways, indicating that NPS actions could be mediated by NPSR1 in birds. Quantitative real-time PCR revealed that NPS and NPSR1 are widely expressed in chicken tissues, including the hypothalamus, and NPSR1 expression is likely controlled by a promoter upstream exon 1, which shows strong promoter activities in cultured DF-1 cells. Taken together, our data provide the first proof that the avian NPS-NPSR1 system is functional and helps to explore the conserved role of NPS and NPSR1 signaling in tetrapods.

Dissociative Effects of Neuropeptide S Receptor Deficiency and Nasal Neuropeptide S Administration on T-Maze Discrimination and Reversal Learning

Cognitive flexibility refers to the ability to modify learned behavior in response to changes in the environment. In laboratory rodents, cognitive flexibility can be assessed in reversal learning, i.e., the change of contingencies, for example in T-maze discrimination learning. The present study investigated the role of the neuropeptide S (NPS) system in cognitive flexibility. In the first experiment, mice deficient of NPS receptors (NPSR) were tested in T-maze discrimination and reversal learning. In the second experiment, C57BL/6J mice were tested in the T-maze after nasal administration of NPS. Finally, the effect of nasal NPS on locomotor activity was evaluated. NPSR deficiency positively affected the acquisition of T-maze discrimination but had no effects on reversal learning. Nasal NPS administration facilitated reversal learning and supported an allocentric learning strategy without affecting acquisition of the task or locomotor activity. Taken together, the present data show that the NPS system is able to modulate both acquisition of T-maze discrimination and its reversal learning. However, NPSR deficiency only improved discrimination learning, while nasal NPS administration only improved reversal learning, i.e., cognitive flexibility. These effects, which at first glance appear to be contradictory, could be due to the different roles of the NPS system in the brain regions that are important for learning and cognitive flexibility.

Neuropeptide S-Mediated Modulation of Prepulse Inhibition Depends on Age, Gender, Stimulus-Timing, and Attention

Conflicting reports about the role of neuropeptide S (NPS) in animal models of psychotic-like behavior and inconsistent results from human genetic studies seeking potential associations with schizophrenia prompted us to reevaluate the effects of NPS in the prepulse inhibition (PPI) paradigm in mice. Careful examination of NPS receptor (NPSR1) knockout mice at different ages revealed that PPI deficits are only expressed in young male knockout animals (<12 weeks of age), that can be replicated in NPS precursor knockout mice and appear strain-independent, but are absent in female mice. PPI deficits can be aggravated by MK-801 and alleviated by clozapine. Importantly, treatment of wildtype mice with a centrally-active NPSR1 antagonist was able to mimic PPI deficits. PPI impairment in young male NPSR1 and NPS knockout mice may be caused by attentional deficits that are enhanced by increasing interstimulus intervals. Our data reveal a substantial NPS-dependent developmental influence on PPI performance and confirm a significant role of attentional processes for sensory-motor gating. Through its influence on attention and arousal, NPS appears to positively modulate PPI in young animals, whereas compensatory mechanisms may alleviate NPS-dependent deficits in older mice.

Pharmacology, Physiology and Genetics of the Neuropeptide S System

The Neuropeptide S (NPS) system is a rather ‘young’ transmitter system that was discovered and functionally described less than 20 years ago. This review highlights the progress that has been made in elucidating its pharmacology, anatomical distribution, and functional involvement in a variety of physiological effects, including behavior and immune functions. Early on, genetic variations of the human NPS receptor (NPSR1) have attracted attention and we summarize current hypotheses of genetic linkage with disease and human behaviors. Finally, we review the therapeutic potential of future drugs modulating NPS signaling. This review serves as an introduction to the broad collection of original research papers and reviews from experts in the field that are presented in this Special Issue.

Pulmonary Exposure to Magnéli Phase Titanium Suboxides Results in Significant Macrophage Abnormalities and Decreased Lung Function

Coal is one of the most abundant and economic sources for global energy production. However, the burning of coal is widely recognized as a significant contributor to atmospheric particulate matter linked to deleterious respiratory impacts. Recently, we have discovered that burning coal generates large quantities of otherwise rare Magnéli phase titanium suboxides from TiO2 minerals naturally present in coal. These nanoscale Magnéli phases are biologically active without photostimulation and toxic to airway epithelial cells in vitro and to zebrafish in vivo. Here, we sought to determine the clinical and physiological impact of pulmonary exposure to Magnéli phases using mice as mammalian model organisms. Mice were exposed to the most frequently found Magnéli phases, Ti6O11, at 100 parts per million (ppm) via intratracheal administration. Local and systemic titanium concentrations, lung pathology, and changes in airway mechanics were assessed. Additional mechanistic studies were conducted with primary bone marrow derived macrophages. Our results indicate that macrophages are the cell type most impacted by exposure to these nanoscale particles. Following phagocytosis, macrophages fail to properly eliminate Magnéli phases, resulting in increased oxidative stress, mitochondrial dysfunction, and ultimately apoptosis. In the lungs, these nanoparticles become concentrated in macrophages, resulting in a feedback loop of reactive oxygen species production, cell death, and the initiation of gene expression profiles consistent with lung injury within 6 weeks of exposure. Chronic exposure and accumulation of Magnéli phases ultimately results in significantly reduced lung function impacting airway resistance, compliance, and elastance. Together, these studies demonstrate that Magnéli phases are toxic in the mammalian airway and are likely a significant nanoscale environmental pollutant, especially in geographic regions where coal combustion is a major contributor to atmospheric particulate matter.

Memory generalization after one-trial contextual fear conditioning: Effects of sex and neuropeptide S receptor deficiency

One-trial contextual fear conditioning in laboratory mice results in a fear memory which is relatively specific to the original conditioning context shortly after conditioning but becomes more unspecific after an incubation time of one month. This process is called generalization of fear memory and is used to investigate processes which might be involved in the pathogenesis of post-traumatic stress disorder. In the present study, we investigated the effects of sex and neuropeptide S receptor (NPSR) deficiency in one-trial contextual fear conditioning. In addition to contextual fear, we also measured startle reactivity, anxiety and corticosterone plasma levels of the mice. Our data show main effects of sex and NPSR-deficiency on freezing behavior, startle magnitude, and anxiety levels. However, generalization of contextual fear memory after incubation time was not affected by sex. Notably, NPSR-deficient mice had a more specific fear memory shortly after conditioning than their wildtype littermates but after incubation time, all genotypes had a generalized fear memory. The present data further show that plasma corticosterone levels are increased after incubation time. This increase was significantly more pronounced in NPSR-deficient mice. Taken together, our study confirms the suitability of one-trial contextual fear conditioning to study the effects of incubation time on fear memory generalization but also indicates the need for control groups without incubation. We further demonstrate that the increase of plasma corticosterone levels after incubation time is exaggerated in NPSR-deficient mice. The latter finding suggests an important role of the NPS system in the regulation of corticosterone release.

Brain neuropeptide S: via GPCR activation to a powerful neuromodulator of socio-emotional behaviors

Neuropeptide S (NPS) has attracted the attention of the scientific community due to its potent anxiolytic-like and fear-attenuating effects studied in rodents. Therefore, NPS might represent a treatment option for neuropsychiatric disorders, such as anxiety disorders, even more so as single nucleotide polymorphisms in the human NPS receptor gene have been associated with increased anxiety traits that contribute to the pathogenesis of fear- and anxiety-related disorders. However, the signaling mechanisms underlying the behavioral effects of NPS and the interaction with other brain neuropeptides are still rather unknown. To illuminate how NPS modulates the expression of selected emotional and social behaviors, the present review focuses on neuroanatomical and electrophysiological studies, as well as intracellular signaling mechanisms following NPS receptor stimulation in rodents. We will also discuss interactions of the NPS system with two well-described neuropeptides, namely corticotropin-releasing factor and oxytocin, which may contribute to the fear- and anxiety-reducing effects.

Neuropeptide S precursor knockout mice display memory and arousal deficits

Activation of neuropeptide S (NPS) signaling has been found to produce arousal, wakefulness, anxiolytic-like behaviors, and enhanced memory formation. In order to further study physiological functions of the NPS system, we generated NPS precursor knockout mice by homologous recombination in embryonic stem cells. NPS^-/- mice were viable, fertile, and anatomically normal, when compared to their wild-type and heterozygous littermates. The total number of NPS neurons-although no longer synthesizing the peptide - was not affected by the knockout, as analyzed in NPS^-/- /NPS^EGFP double transgenic mice. Analysis of behavioral phenotypes revealed significant deficits in exploratory activity in NPS^-/- mice. NPS precursor knockout mice displayed attenuated arousal in the hole board test, visible as reduced total nose pokes and number of holes inspected, that was not confounded by increased repetitive or stereotypic behavior. Importantly, long-term memory was significantly impaired in NPS^-/- mice in the inhibitory avoidance paradigm. NPS precursor knockout mice displayed mildly increased anxiety-like behaviors in three different tests measuring responses to stress and novelty. Interestingly, heterozygous littermates often presented behavioral deficits similar to NPS^-/- mice or displayed intermediate phenotype. These observations may suggest limited ligand availability in critical neural circuits. Overall, phenotypical changes in NPS^-/- mice are similar to those observed in NPS receptor knockout mice and support earlier findings that suggest major functions of the NPS system in arousal, regulation of anxiety and stress, and memory formation.

TIPS pentacene loaded PEO-PDLLA core-shell nanoparticles have similar cellular uptake dynamics in M1 and M2 macrophages and in corresponding in vivo microenvironments

Nanoparticle based drug delivery platforms have the potential to transform disease treatment paradigms and therapeutic strategies, especially in the context of pulmonary medicine. Once administered, nanoparticles disperse throughout the lung and many are phagocytosed by macrophages. However, there is a paucity of knowledge regarding cellular up-take dynamics of nanoparticles due largely to macrophage heterogeneity. To address this issue, we sought to better define nanoparticle up-take using polarized M1 and M2 macrophages and novel TIPS-pentacene loaded PEO-PDLLA nanoparticles. Our data reveal that primary macrophages polarized to either M1 or M2 phenotypes have similar levels of nanoparticle phagocytosis. Similarly, M1 and M2 polarized macrophages isolated from the lungs of mice following either acute (Th1) or allergic (Th2) airway inflammation also demonstrated equivalent levels of nanoparticle up-take. Together, these studies provide critical benchmark information pertaining to cellular up-take dynamics and biodistribution of nanoparticles in the context of clinically relevant inflammatory microenvironments.

The utilization of oropharyngeal intratracheal PAMP administration and bronchoalveolar lavage to evaluate the host immune response in mice

The host immune response to pathogens is a complex biological process. The majority of in vivo studies classically employed to characterize host-pathogen interactions take advantage of intraperitoneal injections of select bacteria or pathogen associated molecular patterns (PAMPs) in mice. While these techniques have yielded tremendous data associated with infectious disease pathobiology, intraperitoneal injection models are not always appropriate for host-pathogen interaction studies in the lung. Utilizing an acute lung inflammation model in mice, it is possible to conduct a high resolution analysis of the host innate immune response utilizing lipopolysaccharide (LPS). Here, we describe the methods to administer LPS using nonsurgical oropharyngeal intratracheal administration, monitor clinical parameters associated with disease pathogenesis, and utilize bronchoalveolar lavage fluid to evaluate the host immune response. The techniques that are described are widely applicable for studying the host innate immune response to a diverse range of PAMPs and pathogens. Likewise, with minor modifications, these techniques can also be applied in studies evaluating allergic airway inflammation and in pharmacological applications.

Induction of allergic airway disease using house dust mite allergen

Mouse models of allergic airway inflammation have proven essential in understanding the mechanisms and pathophysiology underling human asthma. There is a diverse range of mouse models described in the literature that typically vary slightly by allergen, duration of exposure, and route of sensitization. In general, each of these models has proven to be acceptable surrogates for studying specific aspects of the human disease, including airway inflammation, airway hyperresponsiveness (AHR), and airway remodeling. Here, we describe a highly versatile model based on nasal sensitization with house dust mite antigen (DMA). Mice receive multiple intranasal inoculations with DMA each week for a period of 4-16 weeks, which results in increased Th2-mediated airway inflammation and AHR. However, an added feature of the long--term exposures described here is the ability to more accurately evaluate the impact of chronic inflammation on airway remodeling and lung pathophysiology in response to a clinically relevant allergen.

Enhanced expression of neuropeptide S (NPS) receptor in eosinophils from severe asthmatics and subjects with total IgE above 100IU/ml

Eosinophils are inflammatory cells of particular relevance to asthma exacerbations. Neuropeptide S (NPS) receptor was identified in a search for asthma susceptibility genes, where the risk haplotypes of the NPS receptor gene associated with total serum IgE above 100IU/ml and asthma. The aim of the present study was to investigate and compare expression of NPS receptor in human peripheral blood eosinophils derived from subjects with total serum IgE above and below 100IU/ml and patients with different phenotypes of asthma. Additionally, we aimed to study the function of NPS receptor in human eosinophils. We found higher NPS receptor protein expression in eosinophils derived from subjects with high IgE when compared to those from subjects with low IgE and the level of NPS receptor positively correlated with serum IgE. NPS receptor expression was also higher in eosinophils from patients with severe asthma than in cells from mild asthmatics or healthy controls. The receptor agonist NPS was a chemotactic agent for eosinophils. NPS also increased N-formyl-methionyl-leucyl-phenylalanine (fMLP)-stimulated CD11b integrin levels in eosinophils from subjects with high IgE. Furthermore, eosinophils from those subjects exhibited Ca(2+) mobilization but not cAMP rise in response to NPS. Altogether, NPS receptor may have a pathological role in individuals with severe asthma and/or elevated serum IgE levels as eosinophils from these patients express higher levels of NPS receptor protein and respond to NPS by enhanced migration and adhesion molecule expression.

Variants of asthma and chronic obstructive pulmonary disease genes and lung function decline in aging

BACKGROUND

A substantial proportion of the general population has low lung function, and lung function is known to decrease as we age. Low lung function is a feature of several pulmonary disorders, such as uncontrolled asthma and chronic obstructive pulmonary disease. The objective of this study is to investigate the association of polymorphisms in asthma and chronic obstructive pulmonary disease candidate genes with rates of lung function decline in a general population sample of aging men.

METHODS

We analyzed data from a cohort of 1,047 Caucasian men without known lung disease, who had a mean of 25 years of lung function data, and on whom DNA was available. The cohort was randomly divided into two groups, and we tested a total of 940 single-nucleotide polymorphisms in 44 asthma and chronic obstructive pulmonary disease candidate genes in the first group (testing cohort, n = 545) for association with change in forced expiratory volume in 1 second over time.

RESULTS

One hundred nineteen single-nucleotide polymorphisms that showed nominal associations in the testing cohort were then genotyped and tested in the second group (replication cohort, n = 502). Evidence for association from the testing and replication cohorts were combined, and after adjustment for multiple testing, seven variants of three genes (DPP10, NPSR1, and ADAM33) remained significantly associated with change in forced expiratory volume in 1 second over time.

CONCLUSIONS

Our findings that genetic variants of genes involved in asthma and chronic obstructive pulmonary disease are associated with lung function decline in normal aging participants suggest that similar genetic mechanisms may underlie lung function decline in both disease and normal aging processes.

Role of human hypoxanthine guanine phosphoribosyltransferase in activation of the antiviral agent T-705 (favipiravir)

6-Fluoro-3-hydroxy-2-pyrazinecarboxamide (T-705) is a novel antiviral compound with broad activity against influenza virus and diverse RNA viruses. Its active metabolite, T-705-ribose-5'-triphosphate (T-705-RTP), is recognized by influenza virus RNA polymerase as a substrate competing with GTP, giving inhibition of viral RNA synthesis and lethal virus mutagenesis. Which enzymes perform the activation of T-705 is unknown. We here demonstrate that human hypoxanthine guanine phosphoribosyltransferase (HGPRT) converts T-705 into its ribose-5'-monophosphate (RMP) prior to formation of T-705-RTP. The anti-influenza virus activity of T-705 and T-1105 (3-hydroxy-2-pyrazinecarboxamide; the analog lacking the 6-fluoro atom) was lost in HGPRT-deficient Madin-Darby canine kidney cells. This HGPRT dependency was confirmed in human embryonic kidney 293T cells undergoing HGPRT-specific gene knockdown followed by influenza virus ribonucleoprotein reconstitution. Knockdown for adenine phosphoribosyltransferase (APRT) or nicotinamide phosphoribosyltransferase did not change the antiviral activity of T-705 and T-1105. Enzymatic assays showed that T-705 and T-1105 are poor substrates for human HGPRT having Km(app) values of 6.4 and 4.1 mM, respectively. Formation of the RMP metabolites by APRT was negligible, and so was the formation of the ribosylated metabolites by human purine nucleoside phosphorylase. Phosphoribosylation and antiviral activity of the 2-pyrazinecarboxamide derivatives was shown to require the presence of the 3-hydroxyl but not the 6-fluoro substituent. The crystal structure of T-705-RMP in complex with human HGPRT showed how this compound binds in the active site. Since conversion of T-705 by HGPRT appears to be inefficient, T-705-RMP prodrugs may be designed to increase the antiviral potency of this new antiviral agent.

Analysis of the murine immune response to pulmonary delivery of precisely fabricated nano- and microscale particles

Nanomedicine has the potential to transform clinical care in the 21^st century. However, a precise understanding of how nanomaterial design parameters such as size, shape and composition affect the mammalian immune system is a prerequisite for the realization of nanomedicine's translational promise. Herein, we make use of the recently developed Particle Replication in Non-wetting Template (PRINT) fabrication process to precisely fabricate particles across and the nano- and micro-scale with defined shapes and compositions to address the role of particle design parameters on the murine innate immune response in both in vitro and in vivo settings. We find that particles composed of either the biodegradable polymer poly(lactic-co-glycolic acid) (PLGA) or the biocompatible polymer polyethylene glycol (PEG) do not cause release of pro-inflammatory cytokines nor inflammasome activation in bone marrow-derived macrophages. When instilled into the lungs of mice, particle composition and size can augment the number and type of innate immune cells recruited to the lungs without triggering inflammatory responses as assayed by cytokine release and histopathology. Smaller particles (80×320 nm) are more readily taken up in vivo by monocytes and macrophages than larger particles (6 µm diameter), yet particles of all tested sizes remained in the lungs for up to 7 days without clearance or triggering of host immunity. These results suggest rational design of nanoparticle physical parameters can be used for sustained and localized delivery of therapeutics to the lungs.

Characterization of NLRP12 during the in vivo host immune response to Klebsiella pneumoniae and Mycobacterium tuberculosis

The majority of nucleotide binding domain leucine rich repeats-containing (NLR) family members has yet to be functionally characterized. Of the described NLRs, most are considered to be proinflammatory and facilitate IL-1β production. However, a newly defined sub-group of NLRs that function as negative regulators of inflammation have been identified based on their abilities to attenuate NF-κB signaling. NLRP12 (Monarch-1) is a prototypical member of this sub-group that negatively regulates both canonical and noncanonical NF-κB signaling in biochemical assays and in colitis and colon cancer models. The role of NLRP12 in infectious diseases has not been extensively studied. Here, we characterized the innate immune response of Nlrp12^−/− mice following airway exposure to LPS, Klebsiella pneumoniae and Mycobacterium tuberculosis. In response to E. coli LPS, Nlrp12^−/− mice showed a slight decrease in IL-1β and increase in IL-6 production, but these levels were not statistically significant. During K. pneumoniae infection, we observed subtle differences in cytokine levels and significantly reduced numbers of monocytes and lymphocytes in Nlrp12^−/− mice. However, the physiological relevance of these findings is unclear as no overt differences in the development of lung disease were observed in the Nlrp12^−/− mice. Likewise, Nlrp12^−/− mice demonstrated pathologies similar to those observed in the wild type mice following M. tuberculosis infection. Together, these data suggest that NLRP12 does not significantly contribute to the in vivo host innate immune response to LPS stimulation, Klebsiella pneumonia infection or Mycobacterium tuberculosis.

DNA methylation in the Neuropeptide S Receptor 1 (NPSR1) promoter in relation to asthma and environmental factors

Asthma and allergy are complex disorders influenced by both inheritance and environment, a relationship that might be further clarified by epigenetics. Neuropeptide S Receptor 1 (NPSR1) has been associated with asthma and allergy and a study suggested modulation of the genetic risk by environmental factors. We aimed to study DNA methylation in the promoter region of NPSR1 in relation to asthma and environmental exposures. Electrophoretic Mobility Shift Assay (EMSA) was used to investigate potential functional roles of both genotypes and methylation status in the NPSR1 promoter. DNA methylation was analysed using EpiTYPER in blood samples from two well-characterized cohorts; the BIOAIR study of severe asthma in adults and the Swedish birth cohort BAMSE. We observed that DNA methylation and genetic variants in the promoter influenced the binding of nuclear proteins to DNA, suggesting functional relevance. Significant, although small, differences in methylation were related to both adult severe asthma (p = 0.0001) and childhood allergic asthma (p = 0.01). Furthermore, DNA methylation was associated with exposures such as current smoking in adults for two CpG sites (p = 0.005 and 0.04), parental smoking during infancy in the children (p = 0.02) and in which month the sample was taken (p = 0.01). In summary, DNA methylation levels in the promoter of NPSR1 showed small but significant associations with asthma, both in adults and in children, and to related traits such as allergy and certain environmental exposures. Both genetic variation and the methylated state of CpG sites seem to have an effect on the binding of nuclear proteins in the regulatory region of NPSR1 suggesting complex regulation of this gene in asthma and allergy.

Neuropeptide S stimulates human monocyte chemotaxis via NPS receptor activation

Neuropeptide S (NPS) produces several biological actions by activating a formerly orphan GPCR, now named NPS receptor (NPSR). It has been previously demonstrated that NPS stimulates murine leukocyte chemotaxis in vitro. In the present study we investigated the ability of NPS, in comparison with the proinflammatory peptide formyl-Met-Leu-Phe (fMLP), to stimulate human monocyte chemotaxis. At a concentration of 10(-8)M fMLP significantly stimulated chemotaxis. NPS produced a concentration dependent chemotactic action over the concentration range 10(-12) to 10(-5)M. The NPSR antagonists [D-Cys((t)Bu)(5)]NPS, [(t)Bu-D-Gly(5)]NPS and SHA 68 were used to pharmacologically characterize NPS action. Monocyte chemoattractant effect of NPS, but not fMLP, was completely blocked by either peptide antagonists or SHA with the nonpeptide molecule being more potent. None of the NPSR antagonists modified per se random cell migration. Thus, the present study demonstrated that NPS is able to stimulate human monocyte chemotaxis and that this effect is entirely due to selective NPSR activation.

Anxiolytic- and panicolytic-like effects of Neuropeptide S in the mouse elevated T-maze

Neuropeptide S (NPS) regulates various biological functions by selectively activating the NPS receptor (NPSR). Recently, epidemiological studies revealed an association between NPSR single nucleotide polymorphisms and susceptibility to panic disorders. Here we investigated the effects of NPS in mice subjected to the elevated T maze (ETM), an assay which has been proposed to model anxiety and panic. Diazepam [1 mg/kg, intraperitoneally (i.p.)] elicited clear anxiolytic effects reducing the latency to emerge from the closed to the open (CO) arm without modifying the latencies from the open to the closed (OC) arm. By contrast, chronic fluoxetine (10 mg/kg i.p., once a day for 21 days) selectively increased OC latency, suggesting a panicolytic-like effect. NPS given intracerebroventricularly at 0.001-1 nmol elicited both anxiolytic- and panicolytic-like effects. However, although the NPS anxiolytic dose-response curve displayed the classical sigmoidal shape, the dose-response curve of the putative panicolytic-like effect was bell shaped with peak effect at 0.01 nmol. The behaviour of wild-type [NPSR(+/+)] and receptor knock out [NPSR(-/-)] mice in the ETM task was superimposable. NPS at 0.01 nmol elicited anxiolytic- and panicolytic-like effects in NPSR(+/+) but not in NPSR(-/-) mice. In conclusion, this study demonstrated that NPS, via selective activation of the NPSR, promotes both anxiolytic- and panicolytic-like actions in the mouse ETM.

Prostaglandin E(2) produced by the lung augments the effector phase of allergic inflammation

Elevated PGE(2) is a hallmark of most inflammatory lesions. This lipid mediator can induce the cardinal signs of inflammation, and the beneficial actions of nonsteroidal anti-inflammatory drugs are attributed to inhibition of cyclooxygenase (COX)-1 and COX-2, enzymes essential in the biosynthesis of PGE(2) from arachidonic acid. However, both clinical studies and rodent models suggest that, in the asthmatic lung, PGE(2) acts to restrain the immune response and limit physiological change secondary to inflammation. To directly address the role of PGE(2) in the lung, we examined the development of disease in mice lacking microsomal PGE(2) synthase-1 (mPGES1), which converts COX-1/COX-2-derived PGH(2) to PGE(2). We show that mPGES1 determines PGE(2) levels in the naive lung and is required for increases in PGE(2) after OVA-induced allergy. Although loss of either COX-1 or COX-2 increases the disease severity, surprisingly, mPGES1(-/-) mice show reduced inflammation. However, an increase in serum IgE is still observed in the mPGES1(-/-) mice, suggesting that loss of PGE(2) does not impair induction of a Th2 response. Furthermore, mPGES1(-/-) mice expressing a transgenic OVA-specific TCR are also protected, indicating that PGE(2) acts primarily after challenge with inhaled Ag. PGE(2) produced by the lung plays the critical role in this response, as loss of lung mPGES1 is sufficient to protect against disease. Together, this supports a model in which mPGES1-dependent PGE(2) produced by populations of cells native to the lung contributes to the effector phase of some allergic responses.

Analysis of NLRP3 in the development of allergic airway disease in mice

The contribution of NLRP3, a member of the nucleotide-binding domain leucine-rich repeat-containing (NLR) family, to the development of allergic airway disease is currently controversial. In this study, we used multiple allergic asthma models to examine the physiologic role of NLRP3. We found no significant differences in airway eosinophilia, histopathologic condition, mucus production, and airway hyperresponsiveness between wild-type and Nlrp3(-/-) mice in either acute (alum-dependent) or chronic (alum-independent) OVA models. In addition to the OVA model, we did not detect a role for NLRP3 in the development of allergic airway disease induced by either acute or chronic house dust mite Ag exposure. Although we did not observe significant phenotypic differences in any of the models tested, we did note a significant reduction of IL-13 and IL-33 in Nlrp3(-/-) mice compared with wild-type controls in the chronic OVA model without added alum. In all of the allergic airway disease models, the NLRP3 inflammasome-associated cytokines IL-1β and IL-18 in the lung were below the level of detection. In sum, this report surveyed four different allergic asthma models and found a modest and selected role for NLRP3 in the alum-free OVA model. However, this difference did not greatly alter the clinical outcome of the disease. This finding suggests that the role of NLRP3 in allergic asthma must be re-evaluated.

Genetic and genomic approaches to asthma: new insights for the origins

PURPOSE OF REVIEW

The aim is to update current understanding of the genes identified by the recent genome-wide association studies (GWASs) of asthma and its associated traits. The review also discusses how to dissect the functional roles of novel genes in future research.

RECENT FINDINGS

More than 10 GWAS aimed at identifying the genes underlying asthma and relevant traits have been published in the past 3 years. The largest of these was from the GABRIEL consortium, which discovered that the IL18R1, IL33, SMAD3, ORMDL3, HLA-DQ and IL2RB loci were all significantly associated with asthma. Many novel asthma genes, including those previously identified by positional cloning, are expressed within the respiratory epithelium, emphasizing the importance of epithelial barriers in causing asthma . The genes controlling IgE levels have surprisingly little overlap with the genes mediating asthma susceptibility, suggesting that atopy is secondary to asthma rather than a primary driver of the disease. The next challenge will be the systematic analysis of the precise functions of these genes in the pathogenesis of asthma.

SUMMARY

GWAS have uncovered many novel genes underlying asthma and detailed functional dissection of their roles in asthma will point the way to new therapies for the disease.

Characterization of NLRP12 during the development of allergic airway disease in mice

Among the 22 members of the nucleotide binding-domain, leucine rich repeat-containing (NLR) family, less than half have been functionally characterized. Of those that have been well studied, most form caspase-1 activating inflammasomes. NLRP12 is a unique NLR that has been shown to attenuate inflammatory pathways in biochemical assays and mediate the lymph node homing of activated skin dendritic cells in contact hypersensitivity responses. Since the mechanism between these two important observations remains elusive, we further evaluated the contribution of NLRP12 to organ specific adaptive immune responses by focusing on the lung, which, like skin, is exposed to both exogenous and endogenous inflammatory agents. In models of allergic airway inflammation induced by either acute ovalbumin (OVA) exposure or chronic house dust mite (HDM) antigen exposure, Nlrp12(-/-) mice displayed subtle differences in eosinophil and monocyte infiltration into the airways. However, the overall development of allergic airway disease and airway function was not significantly altered by NLRP12 deficiency. Together, the combined data suggest that NLRP12 does not play a vital role in regulating Th2 driven airway inflammation using common model systems that are physiologically relevant to human disease. Thus, the allergic airway inflammation models described here should be appropriate for subsequent studies that seek to decipher the contribution of NLRP12 in mediating the host response to agents associated with asthma exacerbation.

Behavioural phenotypic characterization of CD-1 mice lacking the neuropeptide S receptor

Neuropeptide S (NPS) is the endogenous ligand of a previously orphan receptor now named NPSR. In the brain NPS regulates several biological functions including anxiety, arousal, locomotion, food intake, learning and memory, pain and drug abuse. Mice lacking the NPSR gene (NPSR(-/-)) represent an useful tool to investigate the neurobiology of the NPS/NPSR system. NPSR(-/-) mice have been generated in a 129S6/SvEv genetic background. In the present study we generated CD-1 congenic NPSR(+/+) and NPSR(-/-) mice and investigated their phenotype and sensitivity to NPS in various behavioural assays. The phenotype analysis revealed no locomotor differences between NPSR(+/+) and NPSR(-/-) mice. The behaviour of NPSR(+/+) and NPSR(-/-) mice in the righting reflex test was superimposable. No differences were recorded between the two genotypes in the elevated plus maze, open field and stress-induced hyperthermia tests, with the exception of rearing behaviour that was reduced in knockout animals. Moreover the behaviour of NPSR(+/+) and NPSR(-/-) mice in the forced swimming, novel object recognition and formalin assays was similar. The stimulatory effects of NPS in the locomotor activity test and its anxiolytic-like actions in the elevated plus maze and open field assays were evident in NPSR(+/+) but not NPSR(-/-) animals. In conclusion, the present study indicates that the NPS/NPSR system does not tonically control locomotion, sensitivity to diazepam, anxiety, depressive-like behaviours, memory and pain transmission in mice. Furthermore our results clearly show that the product of the NPSR gene represents the mandatory protein for all the NPS biological effects so far described.

Anatomical characterization of the neuropeptide S system in the mouse brain by in situ hybridization and immunohistochemistry

Neuropeptide S (NPS) is the endogenous ligand for GPR154, now referred to as neuropeptide S receptor (NPSR). Physiologically, NPS has been characterized as a modulator of arousal and has been shown to produce anxiolytic-like effects in rodents. Neuroanatomical analysis in the rat revealed that the NPS precursor mRNA is strongly expressed in the brainstem in only three distinct regions: the locus coeruleus area, the principal sensory trigeminal nucleus, and the lateral parabrachial nucleus. NPSR mRNA expression in the rat is widely distributed, with the strongest expression in the olfactory nuclei, amygdala, subiculum, and some cortical structures, as well as various thalamic and hypothalamic regions. Here we report a comprehensive map of NPS precursor and receptor mRNA expression in the mouse brain. NPS precursor mRNA is only expressed in two regions in the mouse brainstem: the Kölliker-Fuse nucleus and the pericoerulear area. Strong NPSR mRNA expression was found in the dorsal endopiriform nucleus, the intra-midline thalamic and hypothalamic regions, the basolateral amgydala, the subiculum, and various cortical regions. In order to elucidate projections from NPS-producing nuclei in the brainstem to NPSR-expressing structures throughout the brain, we performed immunohistochemical analysis in the mouse brain by using two polyclonal anti-NPS antisera. The distribution of NPS-immunopositive fibers overlaps well with NPSR mRNA expression in thalamic and hypothalamic regions. Mismatches between NPSR expression and NPS-immunoreactive fiber staining were observed in hippocampal, olfactory, and cortical regions. These data demonstrate that the distribution pattern of the central NPS system is only partially conserved between mice and rats.

The asthma candidate gene NPSR1 mediates isoform specific downstream signalling

Background

Neuropeptide S Receptor 1 (NPSR1, GPRA, GPR154) was first identified as an asthma candidate gene through positional cloning and has since been replicated as an asthma and allergy susceptibility gene in several independent association studies. In humans, NPSR1 encodes two G protein-coupled receptor variants, NPSR1-A and NPSR1-B, with unique intracellular C-termini. Both isoforms show distinct expression pattern in asthmatic airways. Although NPSR1-A has been extensively studied, functional differences and properties of NPSR1-B have not yet been clearly examined. Our objective was to investigate downstream signalling properties of NPSR1-B and functional differences between NPSR1-A and NPSR1-B.

Methods

HEK-293 cells transiently overexpressing NPSR1-A or NPSR1-B were stimulated with the ligand neuropeptide S (NPS) and downstream signalling effects were monitored by genome-scale affymetrix expression-arrays. The results were verified by NPS concentration-response and time series analysis using qRT-PCR, cAMP and Ca²⁺ assays, and cAMP/PKA, MAPK/JNK and MAPK/ERK pathway specific reporter assays.

Results

NPSR1-B signalled through the same pathways and regulated the same genes as NPSR1-A, but NPSR1-B yielded lower induction on effector genes than NPSR1-A, with one notable exception, CD69, a marker of regulatory T cells.

Conclusions

We conclude that NPSR1-B is regulating essentially identical set of genes as NPSR1-A, with few, but possibly important exceptions, and that NPSR1-A induces stronger signalling effects than NPSR1-B. Our findings suggest an isoform-specific link to pathogenetic processes in asthma and allergy.

The role of neuropeptide S and neuropeptide S receptor 1 in regulation of respiratory function in mice

Genome-wide screening and positional cloning have linked neuropeptide S receptor 1 (NPSR1) with asthma and airway hyperresponsiveness. However, the mechanism by which NPSR1 regulates pulmonary responses remains elusive. Because neuropeptide S and its receptor NPSR1 are expressed in brain regions that regulate respiratory rhythm, and Npsr1-deficient mice have impaired stress and anxiety responses, we aimed to investigate whether neuropeptide S and NPSR1 regulate respiratory function through a central-mediated pathway. After neuropeptide S intracerebroventricular administration, respiratory responses of wildtype and Npsr1-deficient mice were monitored by whole-body or invasive plethysmography with or without serial methacholine inhalation. Airway inflammatory and hyperresponsiveness were assessed in allergen-challenged (ovalbumin or Aspergillus fumigatus) Npsr1-deficient mice. Analysis of breathing patterns by whole-body plethysmography revealed that intracerebroventricular neuropeptide S, as compared with the artificial cerebral spinal fluid control, increased respiratory frequency and decreased tidal volume in an NPSR1-dependent manner but did not affect enhanced pause. Following serial methacholine inhalation, intracerebroventricular neuropeptide S increased respiratory frequency in wildtype mice, but not in Npsr1-deficient mice, and had no effect on tidal volume. Intracerebroventricular neuropeptide S significantly reduced airway responsiveness to methacholine as measured by whole-body plethysmography. Npsr1 deletion had no impact on airway inflammation or hyperresponsiveness in ovalbumin- or A. fumigatus-induced experimental asthma. Our results demonstrate that neuropeptide S and NPSR1 regulate respiratory function through a central nervous system-mediated pathway.

Neuropeptide S enhances memory during the consolidation phase and interacts with noradrenergic systems in the brain

Neuropeptide S (NPS) has been shown to promote arousal and anxiolytic-like effects, as well as facilitation of fear extinction. In rodents, NPS receptors (NPSR) are prominently expressed in brain structures involved in learning and memory. Here, we investigate whether exogenous or endogenous NPS signaling can modulate acquisition, consolidation, or recall of emotional, spatial, and contextual memory traces, using two common behavioral paradigms, inhibitory avoidance (IA) and novel object recognition. In the IA paradigm, immediate and delayed post-training central NPS administration dose dependently enhanced memory retention in mice, indicating that NPS may act during the consolidation phase to enhance long-term memory. In contrast, pre-training or pre-test NPS injections were ineffective, suggesting that NPS had no effect on IA memory acquisition or recall. Peripheral administration of a synthetic NPSR antagonist attenuated NPS-induced IA memory enhancement, showing pharmacological specificity. NPS also enhanced hippocampal-dependent non-aversive memory in the novel object recognition task. In contrast, NPSR knockout mice displayed deficits in IA memory, novel object recognition, and novel place or context recognition, suggesting that activity of the endogenous NPS system is required for memory formation. Blockade of adrenergic signaling by propranolol attenuated NPS-induced memory enhancement in the IA task, indicating involvement of central noradrenergic systems. These results provide evidence for a facilitatory role of NPS in long-term memory, independent of memory content, possibly by acting as a salience signal or as an arousal-promoting factor.

Neurobiology, pharmacology, and medicinal chemistry of neuropeptide S and its receptor

Neuropeptide S (NPS) is the last neuropeptide identified via reverse pharmacology techniques. NPS selectively binds and activates a previous orphan GPCR, now named NPSR, producing intracellular calcium mobilization and increases in cAMP levels. Biological functions modulated by the NPS/NPSR system include anxiety, arousal, locomotion, food intake, memory, and drug addiction. The primary sequence of NPS (in humans SFRNGVGTGMKKTSFQRAKS) is highly conserved among vertebrates especially at the N-terminus. Ala- and D-scan studies demonstrated that this part of the molecule is crucial for biological activity. Focused structure-activity studies performed on Phe(2), Arg(3), and Asn(4) confirmed this indication and revealed the chemical requirements of these positions for NPSR binding and activation. The sequence Gly(5)-Val(6)-Gly(7) seems to be important for shaping the bioactive conformation of the peptide. Structure-activity studies on Gly(5) enabled identification of the first generation of peptidergic NPSR pure antagonists including [D-Cys(tBu)(5)]NPS and [D-Val(5)]NPS whose antagonist properties were confirmed in vivo. Finally, the pharmacological features of substituted bicyclic piperazine molecules (e.g. SHA 68 (3-oxo-1,1-diphenyl-tetrahydro-oxazolo[3,4-a]pyrazine-7-carboxylic acid 4-fluoro-benzylamide) were recently published making available the first generation of nonpeptide NPSR antagonists. The use in future studies of NPSR antagonists will be of paramount importance for understanding which biological functions are controlled by the NPS/NPSR system and for defining the therapeutic potential of selective NPSR ligands.

Neuropeptide S receptor deficiency modulates spontaneous locomotor activity and the acoustic startle response

The present study investigated the phenotype of heterozygous and homozygous neuropeptide S receptor (Npsr) deficient C57BL/6 mice in NPS- and cocaine induced hyperactivity, spontaneous and reactive locomotor activity, elevated plus maze, conditioned fear, and prepulse inhibition of the acoustic startle response. In Npsr-deficient mice, a strong reduction of spontaneous locomotor activity and of the startle magnitude was observed; heterozygous mice had an intermediate phenotype. In the other experiments, Npsr deficiency leads to no or only a very modest phenotype. These results support an important role of neuropeptide S in regulating locomotor activity.

Unique populations of lung mast cells are required for antigen-mediated bronchoconstriction

BACKGROUND

Studies in both human and mouse indicate that mediators released by mast cells can lead to bronchoconstriction, and thus these are important effector cells in lifethreatening anaphylaxis. Much of our understanding of the various functions of mast cells emanates from the study of mice lacking these cells, particularly mice carrying mutations in the tyrosine kinase gene Kit. Definitive evidence for the role of mast cells in the altered immune response requires the demonstration that this response can be normalized by reconstitution of the mice with cultured bone marrow-derived mast cells (BMMCs). While many mast cell niches can be restored with BMMCs, this has not been demonstrated for mast cells present in the airways of the lung, cells poised to mediate bronchoconstriction during allergic responses.

OBJECTIVE

To determine if mast cell-deficient Kit(Wsh/Wsh) reconstituted lines are an appropriate model for the study of the role of these cells in bronchoconstriction associated with allergic responses.

METHODS

Kit(Wsh/Wsh) mice were reconstituted with either whole bone marrow (WBM) or BMMCs and responses to IgE-mediated mast cell activation were determined; including systemic hypothermia, mediator release, and bronchoconstriction in anaesthetized, mechanically ventilated animals.

RESULTS

Engraftment of Kit(Wsh/Wsh) mice with WBM and BMMCs results in reconstitution of the central airways with mast cells. While the treatment of the two groups of animals resulted in systemic changes when challenged with IgE/Ag in a model of passive anaphylaxis, bronchoconstriction was observed only in kit(Wsh/Wsh) animals, which had received a bone marrow transplant.

CONCLUSIONS

While BMMCs can populate the lung, they cannot restore IgE/Ag-mediated bronchoconstriction to mast cell-deficient animals. This suggests that the mast cell population, which mediates this function, may be unique, and to fill this niche in the lung cells must undergo a specific developmental programme, one that is no longer available to cultured mast cells.

A screening methodology based on Random Forests to improve the detection of gene-gene interactions

The search for susceptibility loci in gene-gene interactions imposes a methodological and computational challenge for statisticians because of the large dimensionality inherent to the modelling of gene-gene interactions or epistasis. In an era in which genome-wide scans have become relatively common, new powerful methods are required to handle the huge amount of feasible gene-gene interactions and to weed out false positives and negatives from these results. One solution to the dimensionality problem is to reduce data by preliminary screening of markers to select the best candidates for further analysis. Ideally, this screening step is statistically independent of the testing phase. Initially developed for small numbers of markers, the Multifactor Dimensionality Reduction (MDR) method is a nonparametric, model-free data reduction technique to associate sets of markers with optimal predictive properties to disease. In this study, we examine the power of MDR in larger data sets and compare it with other approaches that are able to identify gene-gene interactions. Under various interaction models (purely and not purely epistatic), we use a Random Forest (RF)-based prescreening method, before executing MDR, to improve its performance. We find that the power of MDR increases when noisy SNPs are first removed, by creating a collection of candidate markers with RFs. We validate our technique by extensive simulation studies and by application to asthma data from the European Committee of Respiratory Health Study II.

Further studies on the pharmacological profile of the neuropeptide S receptor antagonist SHA 68

Neuropeptide S (NPS) regulates various biological functions by selectively activating the NPS receptor (NPSR). Previous studies demonstrated that the non-peptide molecule SHA 68 acts as a selective NPSR antagonist. In the present study the pharmacological profile of SHA 68 has been further investigated in vitro and in vivo. In cells expressing the mouse NPSR SHA 68 was inactive per se up to 10microM while it antagonized NPS-stimulated calcium mobilization in a competitive manner showing a pA(2) value of 8.06. In the 10-50mg/kg range of doses, SHA 68 counteracted the stimulant effects elicited by NPS, but not those of caffeine, in mouse locomotor activity experiments. In the mouse righting reflex assay SHA 68 fully prevented the arousal-promoting action of the peptide. The anxiolytic-like effects of NPS were slightly reduced by SHA 68 in the mouse open field, fully prevented in the rat elevated plus maze and partially antagonized in the rat defensive burying paradigm. Finally, SHA 68 was found poorly active in antagonizing the NPS inhibitory effect on palatable food intake in rats. In all assays SHA 68 did not produce any effect per se. In conclusion, the present study demonstrated that SHA 68 behaves as a selective NPSR antagonist that can be used to characterize the in vivo actions of NPS. However the usefulness of this research tool is limited by its poor pharmacokinetic properties.

Non-synonymous polymorphism in the neuropeptide S precursor gene and sleep apnea

BACKGROUND

Obstructive sleep apnea syndrome (OSAS) is a complex disease with a strong genetic basis. One of the primary molecular domains affected by OSAS is sympathetic activity. Neuropeptide S (NPS) plays an important role in the regulation of the sleep-wakefulness cycle, anxiety states, and daytime sleepiness. It is important to study neuropeptides related to sympathetic activity regulation and how their function could be modified by genetic variants affecting the expression of these molecules.

OBJECTIVES

We investigated the association of the non-synonymous polymorphism rs4751440 in the NPS precursor gene with OSAS and certain variables related to OSAS (daytime sleepiness, body mass index (BMI), insulin resistance, and blood pressure). This polymorphism causes an amino acid substitution in exon 3 of the human NPS precursor gene.

PATIENTS AND METHODS

We included 253 OSAS patients and 70 healthy subjects. Genotyping was done by polymerase chain reaction using specific flanking primers and agarose gel electrophoresis. Daytime sleepiness, BMI, plasma levels of high-density lipoprotein, glucose, total cholesterol, insulin, triglycerides, and the homeostasis model assessment index were also determined.

RESULTS

A similar genotypic and allelic distribution was found in OSAS patients and controls. The risk of OSAS was not associated with the rs4751440 polymorphism. There was no significant interaction between daytime sleepiness or metabolic variables and the rs4751440 polymorphism.

CONCLUSION

Genotypic and allelic frequency distribution of the rs4751440 polymorphism was similar in OSAS patients and controls. In this population-based study, we could not show a significant association between rs4751440 polymorphism and susceptibility to OSAS or certain phenotypes related to OSAS (daytime sleepiness, BMI, systolic blood pressure, and insulin resistance) with the exception of diastolic blood pressure.

Alternative splicing of G protein-coupled receptors: physiology and pathophysiology

The G protein-coupled receptors (GPCRs) are a superfamily of transmembrane receptors that have a broad distribution and can collectively recognise a diverse array of ligands. Activation or inhibition of GPCR signalling can affect many (patho)physiological processes, and consequently they are a major target for existing and emerging drug therapies. A common observation has been that the pharmacological, signalling and regulatory properties of GPCRs can differ in a cell- and tissue-specific manner. Such "phenotypic" diversity might be attributable to post-translational modifications and/or association of GPCRs with accessory proteins, however, post-transcriptional mechanisms are also likely to contribute. Although approximately 50% of GPCR genes are intronless, those that possess introns can undergo alternative splicing, generating GPCR subtype isoforms that may differ in their pharmacological, signalling and regulatory properties. In this review we shall highlight recent research into GPCR splice variation and discuss the potential consequences this might have for GPCR function in health and disease.

Behavioral phenotyping of neuropeptide S receptor knockout mice

Central administration of neuropeptide S (NPS) in rodents induces arousal and prolonged wakefulness as well as anxiolytic-like effects. NPS has also been implicated in modulation of cognitive functions and energy homeostasis. Here we present a comprehensive phenotypical analysis of mice carrying a targeted mutation in the NPS receptor (NPSR) gene. NPSR knockout mice were found to exhibit reduced exploratory activity when challenged with a novel environment, which might indicate attenuated arousal. We also observed attenuated late peak wheel running activity in NPSR knockout mice, representing reduced activity during the subjective evening. These mice also displayed increased anxiety-like behaviors when compared to their wildtype littermates, although analysis of anxiety behaviors was limited by genetic background influences. Unexpectedly, NPSR knockout mice showed enhanced motor performance skills. No phenotypical differences were detected in the forced-swim test, startle habituation and pre-pulse inhibition paradigms. Together, these data indicate that the endogenous NPS system might be involved in setting or maintaining behavioral arousal thresholds and that the NPS system might have other yet undiscovered physiological functions.

Association of G-protein-coupled receptor 154 with asthma and total IgE in a population of the Caribbean coast of Colombia

BACKGROUND

G protein-coupled receptor 154 was described as an asthma susceptibility gene by positional cloning. It has been subsequently associated with asthma and other inflammatory diseases in several populations with different ethnic origin. Replication of associations adds reliability to these findings.

OBJECTIVE

To analyze the association of G protein-coupled receptor 154 with asthma and total and mite-specific IgE levels in a population of the Caribbean Coast of Colombia.

METHODS

We genotyped seven single nucleotide proteins (SNPs) in GPR154 in 475 asthmatics, 394 controls and 116 families from Cartagena, Colombia using either SnaPshot or TaqMan. Total and specific IgE against Blomia tropicalis and Dermatophagoides pteronyssinus were determined by ELISA. Hardy-Weinberg equilibrium was assessed and case-control and family-based analyses were performed to evaluate the association between the SNPs and their haplotypes and asthma and IgE. Association analyses in the case-control dataset were corrected by population stratification using 52 ancestry informative markers.

RESULTS

Allelic distribution was similar to that described in other populations. Two SNPs were associated with the same direction of the effect in both datasets. Allele A of Hopo546333 was protective for asthma (case-control OR: 0.42; 95% CI: 0.17-0.99, P=0.042; P=0.043; families Z score=-2,236; P=0.025). Similarly, allele C of rs740347 conferred low risk for asthma (OR: 0.44; 95% CI: 0.28-0.70, P=0.00017; Pc=0.00037) and total IgE (OR: 0.29; 95% CI: 0.09-0.88, P=0.015; Pc=0.030) in the case-control study and families (Z score=-3.207, P=0.0013; Z score=-3.182, P=0.0014, respectively). Haplotype CCAGGT was associated with total IgE (OR: 1.76; 95% CI: 1.14-2.71, P=0.006, Pc=0.007) in the case-controls group and CGCGGT with both phenotypes (P=0.044 and P=0.032, respectively) in families. Neither SNPs nor haplotypes were associated with levels of mite-specific IgE.

CONCLUSIONS

Our findings in a sample of asthmatics from Colombia suggest a relevant role of G protein-coupled receptor 154 in the pathogenesis of asthma and allergy.

Cooperation between mast cells and neurons is essential for antigen-mediated bronchoconstriction

Mast cells are important sentinels guarding the interface between the environment and the body: a breach in the integrity of this interface can lead to the release of a plethora of mediators that engage the foreign agent, recruit leukocytes, and initiate adaptive physiological changes in the organism. While these capabilities make mast cells critical players in immune defense, it also makes them important contributors to the pathogenesis of diseases such as asthma. Mast cell mediators induce dramatic changes in smooth muscle physiology, and the expression of receptors for these factors by smooth muscle suggests that they act directly to initiate constriction. Contrary to this view, we show herein that mast cell-mediated bronchoconstriction is observed only in animals with intact innervation of the lung and that serotonin release alone is required for this action. While ablation of sensory neurons does not limit bronchoconstriction, constriction after Ag challenge is absent in mice in which the cholinergic pathways are compromised. Linking mast cell function to the cholinergic system likely provides an important means of modulating the function of these resident immune cells to physiology of the lung, but may also provide a safeguard against life-threatening anaphylaxis during mast cell degranulation.

Interleukin-13-induced MUC5AC is regulated by 15-lipoxygenase 1 pathway in human bronchial epithelial cells

RATIONALE

15-Lipoxygenase-1 (15LO1) and MUC5AC are highly expressed in asthmatic epithelial cells. IL-13 is known to induce 15LO1 and MUC5AC in human airway epithelial cells in vitro. Whether 15LO1 and/or its product 15-HETE modulate MUC5AC expression is unknown.

OBJECTIVES

To determine the expression of 15LO1 in freshly harvested epithelial cells from subjects with asthma and normal control subjects and to determine whether IL-13-induced 15LO1 expression and activation regulate MUC5AC expression in human bronchial epithelial cells in vitro.

METHODS

Human airway epithelial cells from subjects with asthma and normal subjects were evaluated ex vivo for 15LO1 and MUC5AC expression. The impact of 15LO1 on MUC5AC expression in vitro was analyzed by inhibiting 15LO1 through pharmacologic (PD146176) and siRNA approaches in human bronchial epithelial cells cultured under air-liquid interface. We analyzed 15 hydroxyeicosatetraenoic acid (15-HETE) by liquid chromatography/UV/mass spectrometry. MUC5AC and 15LO1 were analyzed by real-time RT-PCR, immunofluoresence, and Western blot.

MEASUREMENTS AND MAIN RESULTS

Epithelial 15LO1 expression increased with asthma severity (P < 0.0001). 15LO1 significantly correlated with MUC5AC ex vivo and in vitro. IL-13 increased 15LO1 expression and stimulated formation of two molecular species of 15-HETE esterified to phosphotidylethanolamine (15-HETE-PE). Inhibition of 15LO1 suppressed 15-HETE-PE and decreased MUC5AC expression in the presence of IL-13 stimulation. The addition of exogenous 15-HETE partially restored MUC5AC expression.

CONCLUSIONS

Epithelial 15LO1 expression increases with increasing asthma severity. IL-13 induction of 15-HETE-PE enhances MUC5AC expression in human airway epithelial cells. High levels of 15LO1 activity could contribute to the increases of MUC5AC observed in asthma.

Neuropeptide S produces antinociceptive effects at the supraspinal level in mice

Neuropeptide S (NPS), a recently identified bioactive peptide through reverse pharmacology approach, was reported to regulate arousal, anxiety, locomotor activity, feeding behaviors and drug reward. NPS receptor (NPSR) mRNA was found in the area related to the descending control system of pain, such as the periaqueductal gray (PAG), raphe nuclei, and lateral parabrachial nucleus (PBN), suggesting a possible role of the NPS-NPSR system in the regulation of pain transmission. In the present study, we evaluated the effects of NPS in pain modulation at the supraspinal level for the first time, using the tail withdrawal test and hot-plate test in mice. NPS (mouse, 0.01-1 nmol) injected intracerebroventricularly (i.c.v.) caused a significant increase of tail withdrawal latency and paw-licking/jumping latency in the tail withdrawal test and the hot-plate test, respectively. Antinociceptive effect elicited by NPS (0.1 nmol, i.c.v.) was not affected by naloxone (i.c.v., 10 nmol co-injection or i.p., 10 mg/kg, 10 min prior to NPS) in both tail withdrawal test and hot-plate test. However, at the doses, naloxone significantly inhibited the antinociceptive effect induced by morphine (i.c.v., 3 nmol). NPS (0.1 nmol, i.c.v.)-induced antinociception was inhibited by co-injection with 10 nmol, but not 3 nmol [D-Cys(tBu)(5)]NPS, a peptidergic antagonist identified more recently, while [D-Cys(tBu)(5)]NPS (3 and 10 nmol) alone induced neither hyperalgesia nor antinociception. These results revealed that NPS could produce antinociception through NPS receptor, but not opioid receptor, and NPS-NPSR system could be a potential target for developing new analgesic drugs.

Neuropeptide S inhibits the acquisition and the expression of conditioned place preference to morphine in mice

Neuropeptide S (NPS), a recently identified bioactive peptide, was reported to regulate arousal, anxiety, motoring and feeding behaviors. NPS precursor and NPS receptor mRNA were found in the amygdala, the ventral tegmental area (VTA) and the substantia nigra, the area thought to modulate rewarding properties of drugs. In the present study, we examined the influence of NPS on the rewarding action of morphine, using the unbiased conditioned place preference (CPP) paradigm. Morphine (1, 3 and 6 nmol, i.c.v.) induced a significant place preference. For testing the effect of NPS on the acquisition of morphine CPP, mice were given the combination of NPS and morphine on the conditioning days, and without drug treatment on the followed test day. To study the effect of NPS on the expression of morphine CPP, mice received the treatment of saline/morphine on the conditioning days, and NPS on the test day, 15 min before the placement in the CPP apparatus. Our results showed that NPS (0.3-10 nmol) alone neither induced place preference nor aversion, however, NPS (1 and 3 nmol) blocked the acquisition of CPP induced by 3 nmol morphine, and acquisition of 6 nmol morphine-induced CPP was also reduced by NPS (6 and 10 nmol). Moreover, the expression of CPP induced by 6 nmol morphine was also inhibited by NPS (0.1, 1 and 10 nmol). These results revealed the involvement of NPS in rewarding activities of morphine, and demonstrated the interaction between NPS system and opioid system for the first time.

Anxiolytic-like effect of neuropeptide S in the rat defensive burying

Neuropeptide S (NPS) has been recently identified as the endogenous ligand of a previously orphan G-protein-coupled receptor now named NPSR. Both NPS and its receptor are expressed in the brain, where they modulate different functions. In particular, it has been demonstrated that intracerebroventricular (i.c.v.) injection of NPS in rodents increases wakefulness and promotes anxiolytic-like effects. In the present study we used the defensive burying (DB) test in rats to further investigate the action of human NPS (0.1-10 nmol, i.c.v.) on anxiety-related behaviors. Diazepam (1.5mg/kg, i.p.) and caffeine (20mg/kg, i.p.) were used in parallel experiments as standard anxiolytic and anxiogenic drugs, respectively. None of the tested drugs produced statistical differences in the latency to contact the probe, burying behavior latency, number of shocks received or immobility/freezing duration. Caffeine increased cumulative burying behavior and the buried bedding height in a statistically significant manner thus promoting anxiogenic like effects. Opposite results were obtained with diazepam that significantly reduced these behavioral parameters. The anxiolytic-like action of diazepam was mimicked by NPS that reduced cumulative burying behavior in a dose dependent manner. Collectively, robust anxiolytic-like effects were recorded in response to NPS in the DB test. These results are of particular interest since the outcome of this assay is marginally influenced by drug effects on locomotor activity. In conclusion, we provide further evidence that NPS evokes genuine anxiolytic-like effects in the rat; therefore NPSR selective agonists are worthy of development as innovative drugs for the treatment of anxiety disorders.

In vitro and in vivo pharmacological characterization of the neuropeptide s receptor antagonist [D-Cys(tBu)5]neuropeptide S

Neuropeptide S (NPS) was identified as the endogenous ligand of an orphan receptor now referred to as the NPS receptor (NPSR). In the frame of a structure-activity study performed on NPS Gly5, the NPSR ligand [D-Cys(tBu)(5)]NPS was identified. [D-Cys(tBu)(5)]NPS up to 100 microM did not stimulate calcium mobilization in human embryonic kidney (HEK) 293 cells stably expressing the mouse NPSR; however, in a concentration-dependent manner, the peptide inhibited the stimulatory effects elicited by 10 and 100 nM NPS (pK(B), 6.62). In Schild analysis experiments [D-Cys(tBu)(5)]NPS (0.1-100 microM) produced a concentration-dependent and parallel rightward shift of the concentration-response curve to NPS, showing a pA(2) value of 6.44. Ten micromolar [D-Cys(tBu)(5)]NPS did not affect signaling at seven NPSR unrelated G-protein-coupled receptors. In the mouse righting reflex (RR) recovery test, NPS given at 0.1 nmol i.c.v. reduced the percentage of animals losing the RR in response to 15 mg/kg diazepam and their sleeping time. [d-Cys(tBu)(5)]NPS (1-10 nmol) was inactive per se but dose-dependently antagonized the arousal-promoting action of NPS. Finally, NPSR-deficient mice were similarly sensitive to the hypnotic effects of diazepam as their wild-type littermates. However, the arousal-promoting action of 1 nmol NPS could be detected in wild-type but not in mutant mice. In conclusion, [D-Cys(tBu)(5)]NPS behaves both in vitro and in vivo as a pure and selective NPSR antagonist but with moderate potency. Moreover, using this tool together with receptor knockout mice studies, we demonstrated that the arousal-promoting action of NPS is because of the selective activation of the NPSR protein.

Neuropeptide S: anatomy, pharmacology, genetics and physiological functions

Neuropeptide S (NPS) is one of the most recent examples of a neurotransmitter identified by the orphan receptor strategy. Impressive progress has been made in the short time since its identification to determine physiological functions modulated by NPS. The anatomical distribution of NPS and its receptor, NPSR, suggests possible functions in the regulation of vigilance states and modulation of emotional behaviors. Early studies provided evidence that NPS induces behavioral arousal and promotes wakefulness by suppressing all stages of sleep. NPS was also found to produce anxiolytic-like effects in behavioral paradigms that measure fear or responses to novelty. Recent studies have demonstrated that NPS can modulate energy and endocrine homeostasis. Differential regulation of NPS and NPSR transcripts was observed after caffeine or nicotine treatment, indicating complex interactions with adenosine and cholinergic systems. NPS has been found co-localized with other excitatory transmitters such as glutamate, acetylcholine, or corticotropine-releasing factor. Activation of NPSR triggers mobilization of intracellular Ca2+ and stimulation of cAMP synthesis, therefore increasing cellular excitability. A functional polymorphism in NPSR has been identified that produces a gain-of-function phenotype by increasing agonist potency up to tenfold. Finally, a gender-specific association of this NPSR polymorphism with panic disorder was found in male patients, indicating that the NPS system might be involved in modulating anxiety responses in humans. Further studies about interactions of the NPS system with other transmitter systems might help to discover additional functions of NPS and define its role within complex neural networks.

Neuropeptide S is a stimulatory anxiolytic agent: a behavioural study in mice

BACKGROUND AND PURPOSE

Neuropeptide S (NPS) was recently identified as the endogenous ligand of an orphan receptor, now referred to as the NPS receptor. In vivo, NPS produces a unique behavioural profile by increasing wakefulness and exerting anxiolytic-like effects. In the present study, we further evaluated the effects of in vivo supraspinal NPS in mice.

EXPERIMENTAL APPROACH

Effects of NPS, injected intracerebroventricularly (i.c.v.), on locomotor activity (LA), righting reflex (RR) recovery and on anxiety states (measured with the elevated plus maze (EPM) and stress-induced hyperthermia (SIH) tests) were assessed in Swiss mice.

KEY RESULTS

NPS (0.01-1 nmol per mouse) caused a significant increase in LA in naive mice, in mice habituated to the test cages and in animals sedated with diazepam (5 mg kg(-1)). In the RR assay, NPS dose dependently reduced the proportion of animals losing the RR in response to diazepam (15 mg kg(-1)) and their sleeping time. In the EPM and SIH test, NPS dose dependently evoked anxiolytic-like effects by increasing the time spent by animals in the open arms and reducing the SIH response, respectively.

CONCLUSIONS AND IMPLICATIONS

We provide further evidence that NPS acts as a novel modulator of arousal and anxiety-related behaviours by promoting a unique pattern of effects: stimulation associated with anxiolysis. Therefore, NPS receptor ligands may represent innovative drugs for the treatment of sleep and anxiety disorders.

Lack of association between genetic variation in G-protein-coupled receptor for asthma susceptibility and childhood asthma and atopy

G-protein-coupled receptor for asthma susceptibility (GPRA or GPR154) was identified as an asthma and atopy candidate gene by positional cloning. Some subsequent studies suggest associations of GPRA single nucleotide polymorphisms (SNPs) and haplotypes with asthma or atopy susceptibility. However, the associated SNPs or haplotypes vary among studies. The role of GPRA genetic variation in asthma and atopy remains unsolved. Published data on GRPA variants and asthma come exclusively from Caucasian and Asian populations. We examined whether GPRA SNPs and haplotypes are associated with asthma and atopy in a Mexican population. We genotyped and analyzed 27 GPRA SNPs in 589 nuclear families consisting of asthmatic children aged 4-17 years of age and their parents in Mexico City. Atopy was determined by skin prick tests to 25 aeroallergens. The 27 SNPs examined provided excellent coverage of the GPRA gene. GPRA SNPs and haplotypes were not associated with childhood asthma and the degree of atopy to aeroallergens in a Mexican population. Our review of studies of GPRA variants in relation to asthma phenotypes shows considerable heterogeneity. Accordingly, our results suggest that GPRA variants are not an important contributor to childhood asthma and atopy susceptibility in a Mexican population.