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1.  C-027 Inhibits IgE-mediated passive sensitization bronchoconstriction and acts as a histamine and serotonin antagonist in human airways 
Atopic asthma is poorly controlled by current therapies. Newer therapies and novel antihistamines are, therefore, required to treat patients whose atopic asthma is not controlled. For the first time, C-027 is shown to antagonize histamine, IgE-mediated and serotonin-induced contraction in human airways and vessels. Human precision-cut lung slices (PCLS, 250 µm thick), containing an airway or blood vessel, were pretreated with either C-027 (2 hours) or with vehicle alone and were contracted with histamine or serotonin. Known antihistamine was used as a comparator in antihistamine studies. Also, human airways were contracted via IgE passive sensitization in the presence or absence of C-027 or fexofenadine. Affinity of C-027 toward human G-protein coupled receptors was also determined, as well as the drug's biodistribution in murine model. C-027 was shown to have the highest affinity toward human histamine and serotonin receptors. Subsequently, C-027 was shown to antagonize histamine- and serotonin-induced airway and vascular smooth muscle contraction, respectively, and histamine-released bronchocontraction mediated by IgE passive sensitization in human small airways. C-027 also inhibited histamine-mediated single-cell calcium ion release. Low levels of C-027 were found in murine brain tissue. Collectively, these data suggest that C-027 markedly inhibits IgE-induced bronchoconstriction and antagonizes histamine and serotonin-contraction with little biodistribution in the brain. The compound may offer a future therapy for allergen-induced airway hyperresponsiveness in patients with asthma.
PMCID: PMC3968313  PMID: 22195688
Airway smooth muscle; allergy; antagonist; anti-histamine; anti-serotonic; asthma; IgE mediated; novel compound; PCLS; reverse agonist
2.  Reviewer acknowledgement 2013 
Respiratory Research  2014;15(1):7.
Contributing reviewers
The editors of Respiratory Research would like to thank all of our reviewers who have contributed to the journal in Volume 14 (2013).
PMCID: PMC3910687
3.  Raf-1, Actin Dynamics, and Abelson Tyrosine Kinase in Human Airway Smooth Muscle Cells 
Raf-1 is a serine/threonine protein kinase that has an essential role in cell proliferation. The mechanisms that regulate Raf-1 in airway smooth muscle are not well understood. In this study, treatment with platelet-derived growth factor (PDGF) induced spatial redistribution of Raf-1 from the cytoplasm to the periphery of human airway smooth muscle cells. Moreover, a pool of Raf-1 was found in F-actin of human airway smooth muscle cells. Activation with PDGF led to an increase in the association of Raf-1 with cytoskeletal actin. Treatment of cells with the actin polymerization inhibitor latrunculin A (LAT-A), but not the microtubule depolymerizer nocodazole, inhibited the interaction of Raf-1 with actin in response to PDGF activation. Because abelson tyrosine kinase (Abl) is known to specifically regulate actin dynamics in smooth muscle, the role of Abl in modulating the coupling of Raf-1 with actin was also evaluated. Abl knockdown by RNA interference attenuated the association of Raf-1 with actin, which is recovered by Abl rescue. Treatment with LAT-A, but not nocodazole, inhibited the spatial redistribution of Raf-1 during PDGF activation. However, treatment with both LAT-A and nocodazole attenuated smooth muscle cell proliferation. Finally, Abl knockdown attenuated the redistribution of Raf-1 and cell proliferation, which were restored by Abl reexpression. The results suggest a novel mechanism that the interaction of Raf-1 with cytoskeletal actin is critical for Raf-1 redistribution and airway smooth muscle cell proliferation during activation with the growth factor.
PMCID: PMC3604063  PMID: 23087049
Raf-1; actin polymerization; tyrosine kinase; smooth muscle; cell proliferation
4.  DHEA-S inhibits human neutrophil and human airway smooth muscle migration 
Biochimica et biophysica acta  2012;1822(10):1638-1642.
Airways diseases such as asthma, emphysema, and chronic bronchitis are, in part, characterized by reversible airflow obstruction and inflammation. In severe disease, marked decreases in lung function are associated with airway smooth muscle proliferation and airway neutrophilia. Inhaled glucocorticoids attenuate increased airflow obstruction and airway inflammation that occur, in part, due to increased smooth muscle migration and proliferation, as well as the airway neutrophilia. Glucocorticoids, however, have adverse side effects and, in some patients, are ineffective despite high doses. Recent research has explored the effects of non-traditional steroids on attenuation of inflammation associated with airways diseases. These non-traditional steroids have improved side effect profiles in comparison to glucocorticoid therapy. Our studies assessed effects of dehydroepiandrosterone-3-sulfate (DHEA-S) on migration of both human peripheral blood neutrophils (PMN) and human airway smooth muscle cells (HASM). DHEA-S dose-dependently inhibited chemotaxis of PMN and HASM while having no effect on the phosphorylation levels of Akt, ERK1/2, p38 MAPK or PKC, canonical positive regulators of cell migration. These studies demonstrate direct effects of DHEA-S on cell migration, thereby suggesting that DHEA-S may attenuate airway inflammation and cell migration.
PMCID: PMC3418395  PMID: 22771498
airway inflammation; DHEA-S; airway remodeling
5.  Regulation of CD38 Expression in Human Airway Smooth Muscle Cells 
The ADP-ribosyl cyclase activity of CD38 generates cyclic ADP-ribose, a Ca2+–mobilizing agent. In human airway smooth muscle (HASM) cells, TNF-α mediates CD38 expression through mitogen-activated protein kinases and NF-κB and AP-1. The phosphatidylinositol-3 kinase/Akt (PI3K/Akt) pathway is involved in TNF-α signaling and contributes to airway hyperresponsiveness and airway remodeling. We hypothesized that PI3Ks mediate CD38 expression and are involved in the differential induction of CD38 by TNF-α in asthmatic HASM cells. HASM cells were treated with pan-PI3K inhibitors (LY294002 or wortmannin) or class I–selective (GDC0941) or isoform-selective PI3K inhibitors (p110α-PIK-75 and p110β-TGX-221) with or without TNF-α. HASM cells were transfected with a catalytically active form of PI3K or phosphatase and tensin homolog (PTEN) or nontargeting or p110 isoform-targeting siRNAs before TNF-α exposure. CD38 expression and activation of Akt, NF-κB, and AP-1 were determined. LY294002 and wortmannin inhibited TNF-α–induced Akt activation, whereas only LY294002 inhibited CD38 expression. P110 expression caused Akt activation and basal and TNF-α–induced CD38 expression, whereas PTEN expression attenuated Akt activation and CD38 expression. Expression levels of p110 isoforms α, β, and δ were comparable in nonasthmatic and asthmatic HASM cells. Silencing of p110α or -δ, but not p110β, resulted in comparable attenuation of TNF-α–induced CD38 expression in asthmatic and nonasthmatic cells. NF-κB and AP-1 activation were unaltered by the PI3K inhibitors. In HASM cells, regulation of CD38 expression occurs by specific class I PI3K isoforms, independent of NF-κB or AP-1 activation, and PI3K signaling may not be involved in the differential elevation of CD38 in asthmatic HASM cells.
PMCID: PMC3488627  PMID: 22556157
smooth muscle; airway; CD38; PI3 kinase; PI3 kinase isoforms
6.  Airway Smooth Muscle in Asthma: Just a Target for Bronchodilation? 
Clinics in chest medicine  2012;33(3):543-558.
Airway smooth muscle (ASM) has long been recognized as the main cell type responsible for bronchial hyperresponsiveness. It has thus been considered as a target for bronchodilation. In asthma however, there is a complex relationship between ASM and inflammatory cells such as mast cells and T lymphocytes. Moreover, the increased ASM mass in the asthmatic airways is one of the key features of airway remodeling. This article aims to review the main concepts about the three possible roles of ASM in asthma including (i) contractile tone, (ii) inflammatory response and (iii) remodeling.
PMCID: PMC3431506  PMID: 22929101
Bronchodilators; Hyperresponsiveness; Inflammation; Remodeling; Smooth muscle
7.  The effect of multiple allergen immunotherapy on exhaled nitric oxide in adults with allergic rhinitis 
There is a lack of objective measures of the clinical efficacy of allergen immunotherapy which relies on patients’ perception about the effect of this treatment. We studied whether the fraction of exhaled nitric oxide is affected by multiple allergen immunotherapy in polysensitized adult subjects with allergic rhinitis. We also looked for associations between exhaled nitric oxide and subjects’ demographics, symptom scores, and pulmonary function tests.
Twenty adult, polysensitized subjects with seasonal and perennial allergic rhinitis who chose to undergo allergen immunotherapy were enrolled. They were evaluated at baseline, and 4, 8, 12, 24, and 52 weeks later. Exhaled nitric oxide was reported as the mean of triplicate determinations.
Our results indicate that multiple allergen immunotherapy did not affect exhaled nitric oxide levels and such levels did not correlate with subjects’ demographics and pulmonary function tests. However, exhaled nitric oxide was associated with rhinoconjuctivitis and asthma symptom scores at the end of the study.
In polysensitized adult subjects with allergic rhinitis, exhaled nitric oxide levels are unaffected by multiple allergen immunotherapy.
PMCID: PMC3751795  PMID: 23958488
Allergen immunotherapy; Nitric oxide; Allergic rhinitis
8.  Drug Development for Severe Asthma: What Are the Metrics? 
Pharmacology & therapeutics  2012;135(2):176-181.
Although reversible airway obstruction in part defines asthma, lung function as measured by spirometry alone inadequately predicts the value of new therapeutic agents in the treatment of severe asthma.
Our objectives are 1) to review whether pulmonary function and bronchodilator reversibility are endpoints for drug discovery and 2) to identify parameters that predict efficacy in drug development in severe asthma.
An English language literature search using MedLine and PubMed was conducted from 1997 to present concerning pathophysiology, diagnosis and therapy of severe asthma using the terms “severe asthma,” “irreversible asthma,” “difficult asthma,” “airway remodeling,” “fixed airway obstruction,” “reversibility” and “bronchodilator reversibility” as index terms. Eight studies were characterized that encompass 1,424 subjects with asthma.
Our review identified the limitations of using bronchodilator reversibility as a predictor in drug development for severe asthma. Neither improvement in lung function nor bronchodilator reversibility characterized the benefit of new drugs in the treatment of severe asthma. Newly approved drugs in the treatment of severe asthma show decreased asthma exacerbations and improved quality of life associated with steroid-sparing benefits without altering bronchodilator responsiveness or improving lung function.
Although changes in lung function predict asthma control in mild/moderate asthma, lung function alone is inadequate to assess improvement in asthma control in severe asthma manifested by fixed airway obstruction. Endpoints that focus on asthma control, as defined by the Expert Panel Report 3 and GINA guidelines, may predict the value of new therapeutics in the management of severe asthma.
PMCID: PMC3383351  PMID: 22627271
Airway remodeling; fixed airway obstruction; irreversible asthma; drug discovery
9.  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, [β-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.
PMCID: PMC3650481  PMID: 18203813
intracellular calcium; ryanodine; actin; myosin; lentivirus
10.  Reviewer acknowledgement 2012 
Respiratory Research  2013;14(1):12.
Contributing reviewers
The editors of Respiratory Research would like to thank all of our reviewers who have contributed to the journal in Volume 13 (2012).
PMCID: PMC3584980
11.  Trichostatin A Abrogates Airway Constriction, but Not Inflammation, in Murine and Human Asthma Models 
Histone deacetylase (HDAC) inhibitors may offer novel approaches in the treatment of asthma. We postulate that trichostatin A (TSA), a Class 1 and 2 inhibitor of HDAC, inhibits airway hyperresponsiveness in antigen-challenged mice. Mice were sensitized and challenged with Aspergillus fumigatus antigen (AF) and treated with TSA, dexamethasone, or vehicle. Lung resistance (RL) and dynamic compliance were measured, and bronchial alveolar lavage fluid (BALF) was analyzed for numbers of leukocytes and concentrations of cytokines. Human precision-cut lung slices (PCLS) were treated with TSA and their agonist-induced bronchoconstriction was measured, and TSA-treated human airway smooth muscle (ASM) cells were evaluated for the agonist-induced activation of Rho and intracellular release of Ca2+. The activity of HDAC in murine lungs was enhanced by antigen and abrogated by TSA. TSA also inhibited methacholine (Mch)-induced increases in RL and decreases in dynamic compliance in naive control mice and in AF-sensitized and -challenged mice. Total cell counts, concentrations of IL-4, and numbers of eosinophils in BALF were unchanged in mice treated with TSA or vehicle, whereas dexamethasone inhibited the numbers of eosinophils in BALF and concentrations of IL-4. TSA inhibited the carbachol-induced contraction of PCLS. Treatment with TSA inhibited the intracellular release of Ca2+ in ASM cells in response to histamine, without affecting the activation of Rho. The inhibition of HDAC abrogates airway hyperresponsiveness to Mch in both naive and antigen-challenged mice. TSA inhibits the agonist-induced contraction of PCLS and mobilization of Ca2+ in ASM cells. Thus, HDAC inhibitors demonstrate a mechanism of action distinct from that of anti-inflammatory agents such as steroids, and represent a promising therapeutic agent for airway disease.
PMCID: PMC3297166  PMID: 22298527
HDAC; asthma; allergen; mice; trichostatin A
12.  The nuclear membrane leukotriene synthetic complex is a signal integrator and transducer 
Molecular Biology of the Cell  2012;23(22):4456-4464.
Leukotrienes are bioactive signaling molecules derived from arachidonic acid that initiate and amplify innate immunity. A single structure, the leukotriene synthetic complex, on the nuclear membrane of neutrophils integrates and transduces extracellular signals to generate the chemotactic lipid LTB4.
Leukotrienes (LTs) are lipid-signaling molecules derived from arachidonic acid (AA) that initiate and amplify inflammation. To initiate LT formation, the 5-lipoxygenase (5-LO) enzyme translocates to nuclear membranes, where it associates with its scaffold protein, 5-lipoxygenase–activating protein (FLAP), to form the core of the multiprotein LT synthetic complex. FLAP is considered to function by binding free AA and facilitating its use as a substrate by 5-LO to form the initial LT, LTA4. We used a combination of fluorescence lifetime imaging microscopy, cell biology, and biochemistry to identify discrete AA-dependent and AA-independent steps that occur on nuclear membranes to control the assembly of the LT synthetic complex in polymorphonuclear leukocytes. The association of AA with FLAP changes the configuration of the scaffold protein, enhances recruitment of membrane-associated 5-LO to form complexes with FLAP, and controls the closeness of this association. Granulocyte monocyte colony–stimulating factor provides a second AA-independent signal that controls the closeness of 5-LO and FLAP within complexes but not the number of complexes that are assembled. Our results demonstrate that the LT synthetic complex is a signal integrator that transduces extracellular signals to modulate the interaction of 5-LO and FLAP.
PMCID: PMC3496618  PMID: 23015755
13.  β2-Adrenergic Receptor Agonists Modulate Human Airway Smooth Muscle Cell Migration via Vasodilator-Stimulated Phosphoprotein 
Severe asthma manifests as airway remodeling and irreversible airway obstruction, in part because of the proliferation and migration of human airway smooth muscle (HASM) cells. We previously reported that cyclic adenosine monophosphate–mobilizing agents, including β2-adrenergic receptor (β2AR) agonists, which are mainstay of asthma therapy, and prostaglandin E2 (PGE2), inhibit the migration of HASM cells, although the mechanism for this migration remains unknown. Vasodilator-stimulated phosphoprotein (VASP), an anticapping protein, modulates the formation of actin stress fibers during cell motility, and is negatively regulated by protein kinase A (PKA)–specific inhibitory phosphorylation at serine 157 (Ser157). Here, we show that treatment with β2AR agonists and PGE2 induces the PKA-dependent phosphorylation of VASP and inhibits the migration of HASM cells. The stable expression of PKA inhibitory peptide and the small interfering (si) RNA-induced depletion of VASP abolish the inhibitory effects of albuterol and PGE2 on the migration of HASM cells. Importantly, prolonged treatment with albuterol prevents the agonist-induced phosphorylation of VASP at Ser157, and reverses the inhibitory effects of albuterol and formoterol, but not PGE2, on the basal and PDGF-induced migration of HASM cells. Collectively, our data demonstrate that β2AR agonists selectively inhibit the migration of HASM cells via a β2AR/PKA/VASP signaling pathway, and that prolonged treatment with albuterol abolishes the inhibitory effect of β-agonists on the phosphorylation of VASP and migration of HASM cells because of β2AR desensitization.
PMCID: PMC3262659  PMID: 22210825
airway hyperresponsiveness; β2-adrenergic receptor desensitization; protein kinase A; albuterol; formoterol
14.  Gi-Coupled γ-Aminobutyric Acid–B Receptors Cross-Regulate Phospholipase C and Calcium in Airway Smooth Muscle 
γ-aminobutyric acid (GABA) is the major inhibitory neurotransmitter in the mammalian central nervous system, and exerts its actions via both ionotropic (GABAA) and metabotropic (GABAB) receptors. Although the functional expression of GABAB receptors coupled to the Gi protein was reported for airway smooth muscle, the role of GABAB receptors in airway responsiveness remains unclear. We investigated whether Gi-coupled GABAB receptors cross-regulate phospholipase C (PLC), an enzyme classically regulated by Gq-coupled receptors in human airway smooth muscle cells. Both the GABAB-selective agonist baclofen and the endogenous ligand GABA significantly increased the synthesis of inositol phosphate, whereas GABAA receptor agonists, muscimol, and 4,5,6,7-tetrahydroisoxazolo[5,4-c]pyridin-3-ol exerted no effect. The baclofen-induced synthesis of inositol phosphate and transient increases in [Ca2+]i were blocked by CGP35348 and CGP55845 (selective GABAB antagonists), pertussis toxin (PTX, which inactivates the Gi protein), gallein (a Gβγ signaling inhibitor), U73122 (an inhibitor of PLC-β), and xestospongin C, an inositol 1,4,5-triphosphate receptor blocker. Baclofen also potentiated the bradykinin-induced synthesis of inositol phosphate and transient increases in [Ca2+]i, which were blocked by CGP35348 or PTX. Moreover, baclofen potentiated the substance P–induced contraction of airway smooth muscle in isolated guinea pig tracheal rings. In conclusion, the stimulation of GABAB receptors in human airway smooth muscle cells rapidly mobilizes intracellular Ca2+ stores by the synthesis of inositol phosphate via the activation of PLC-β, which is stimulated by Gβγ protein liberated from Gi proteins coupled to GABAB receptors. Furthermore, crosstalk between GABAB receptors and Gq-coupled receptors potentiates the synthesis of inositol phosphate, transient increases in [Ca2+]i, and smooth muscle contraction through Gi proteins.
PMCID: PMC3262669  PMID: 21719794
Gi protein; Gβγ; inositol phosphate; phospholipase C; airway smooth muscle
15.  Regulator of G-Protein Signaling–5 Inhibits Bronchial Smooth Muscle Contraction in Severe Asthma 
Severe asthma is associated with fixed airway obstruction attributable to inflammation, copious luminal mucus, and increased airway smooth muscle (ASM) mass. Paradoxically, studies demonstrated that the hypertrophic and hyperplastic ASM characteristic of severe asthma has reduced contractile capacity. We compared the G-protein–coupled receptor (GPCR)–induced Ca2+ mobilization and expression of GPCRs and signaling proteins related to procontractile signaling in ASM derived postmortem from subjects who died of nonrespiratory causes, with cells from subjects who died of asthma. Despite the increased or comparable expression of contraction-promoting GPCRs (bradykinin B2 or histamine H1 and protease-activated receptor 1, respectively) in asthmatic ASM cells relative to cells from healthy donors, asthmatic ASM cells exhibited reduced histamine-induced Ca2+ mobilization and comparable responses to bradykinin and thrombin, suggesting a postreceptor signaling defect. Accordingly, the expression of regulator of G-protein signaling–5 (RGS5), an inhibitor of ASM contraction, was increased in cultured, asthmatic ASM cells and in bronchial smooth muscle bundles of both human subjects with asthma and allergen-challenged mice, relative to those of healthy human subjects or naive mice. The overexpression of RGS5 impaired the release of Ca2+ to thrombin, histamine, and carbachol, and reduced the contraction of precision-cut lung slices to carbachol. These results suggest that increased RGS5 expression contributes to decreased myocyte shortening in severe and fatal asthma.
PMCID: PMC3380291  PMID: 22281988
asthma; bronchial smooth muscle; signal transduction; G-protein–coupled receptors
16.  Altered CD38/Cyclic ADP-Ribose Signaling Contributes to the Asthmatic Phenotype 
Journal of Allergy  2012;2012:289468.
CD38 is a transmembrane glycoprotein expressed in airway smooth muscle cells. The enzymatic activity of CD38 generates cyclic ADP-ribose from β-NAD. Cyclic ADP-ribose mobilizes intracellular calcium during activation of airway smooth muscle cells by G-protein-coupled receptors through activation of ryanodine receptor channels in the sarcoplasmic reticulum. Inflammatory cytokines that are implicated in asthma upregulate CD38 expression and increase the calcium responses to contractile agonists in airway smooth muscle cells. The augmented intracellular calcium responses following cytokine exposure of airway smooth muscle cells are inhibited by an antagonist of cyclic ADP-ribose. Airway smooth muscle cells from CD38 knockout mice exhibit attenuated intracellular calcium responses to agonists, and these mice have reduced airway response to inhaled methacholine. CD38 also contributes to airway hyperresponsiveness as shown in mouse models of allergen or cytokine-induced inflammatory airway disease. In airway smooth muscle cells obtained from asthmatics, the cytokine-induced CD38 expression is significantly enhanced compared to expression in cells from nonasthmatics. This differential induction of CD38 expression in asthmatic airway smooth muscle cells stems from increased activation of MAP kinases and transcription through NF-κB, and altered post-transcriptional regulation through microRNAs. We propose that increased capacity for CD38 signaling in airway smooth muscle in asthma contributes to airway hyperresponsiveness.
PMCID: PMC3508580  PMID: 23213344
17.  Polycyclic Aromatic Hydrocarbons Impair Function of β2-Adrenergic Receptors in Airway Epithelial and Smooth Muscle Cells 
Incomplete combustion produces a pollutant mixture that includes polycyclic aromatic hydrocarbons (PAHs). Previous work by the Columbia Center for Children's Environmental Health (CCCEH) and others linked exposure to PAH with symptoms of asthma and other adverse health effects in young children. Inhaled β2-adrenergic agonists are mainstays in the treatment of reactive airway diseases. These exogenous catecholamines engage membrane-bound β2-adrenergic receptors (β2AR) on airway epithelial and smooth muscle cells to cause airway dilation. We hypothesized that exposure to PAH might similarly interfere with the function of β2AR in airway epithelial or smooth muscle cells, reducing the efficacy of a medication important for the treatment of asthma symptoms. A PAH mixture was devised, based on ambient levels measured prenatally among a cohort of pregnant women participating at the CCCEH. Primary airway epithelial and smooth muscle cells were exposed to varying concentrations of the PAH mixture, and expression, function, and signaling of β2AR were assessed. Murine tracheal epithelial cells and human airway smooth muscle cells, after exposure to a PAH mixture, exhibited reduced expression and function of β2AR. These findings support our hypothesis that environmentally relevant PAHs can impede β2AR-mediated airway relaxation, and suggest a new paradigm where air pollutants not only contribute to the pathogenesis of childhood asthma, but also diminish responsiveness to standard therapy.
PMCID: PMC3262692  PMID: 21617201
polycyclic aromatic hydrocarbons; β2-adrenergic receptors
18.  Targeting airway smooth muscle in airways diseases: an old concept with new twists 
Airway smooth muscle (ASM) manifests a hyper-responsive phenotype in airway disorders such as asthma. ASM also modulates immune responses by secreting mediators and expressing cell-surface molecules that promote recruitment of inflammatory cells to the lungs. The aim of the current article is to highlight therapeutics that may modulate ASM responses in airway disorders and exacerbations.
PMCID: PMC3276206  PMID: 22082163
antibody therapy; asthma; bronchial thermoplasty; exacerbation; remodeling
19.  Asthma outcomes: Biomarkers 
Measurement of biomarkers has been incorporated within clinical research studies of asthma to characterize the population and associate the disease with environmental and therapeutic effects.
National Institutes of Health institutes and federal agencies convened an expert group to propose which biomarkers should be assessed as standardized asthma outcomes in future clinical research studies.
We conducted a comprehensive search of the literature to identify studies that developed and/or tested asthma biomarkers. We identified biomarkers relevant to the underlying disease process progression and response to treatment. We classified the biomarkers as either core (required in future studies), supplemental (used according to study aims and standardized), or emerging (requiring validation and standardization). This work was discussed at an National Institutes of Health–organized workshop convened in March 2010 and finalized in September 2011.
Ten measures were identified; only 1, multiallergen screening to define atopy, is recommended as a core asthma outcome. Complete blood counts to measure total eosinophils, fractional exhaled nitric oxide (Feno), sputum eosinophils, urinary leukotrienes, and total and allergen-specific IgE are recommended as supplemental measures. Measurement of sputum polymorphonuclear leukocytes and other analytes, cortisol measures, airway imaging, breath markers, and system-wide studies (eg, genomics, proteomics) are considered as emerging outcome measures.
The working group participants propose the use of multiallergen screening in all asthma clinical trials to characterize study populations with respect to atopic status. Blood, sputum, and urine specimens should be stored in biobanks, and standard procedures should be developed to harmonize sample collection for clinical trial biorepositories.
PMCID: PMC3390196  PMID: 22386512
Multiallergen screen; fractional exhaled nitric oxide; sputum eosinophils; total eosinophils; IgE; urinary leukotriene E4
20.  Functional Expression of γ–Amino Butyric Acid Transporter 2 in Human and Guinea Pig Airway Epithelium and Smooth Muscle 
γ−Amino butyric acid (GABA) is a primary inhibitory neurotransmitter in the central nervous system, and is classically released by fusion of synaptic vesicles with the plasma membrane or by egress via GABA transporters (GATs). Recently, a GABAergic system comprised of GABAA and GABAB receptors has been identified on airway epithelial and smooth muscle cells that regulate mucus secretion and contractile tone of airway smooth muscle (ASM). In addition, the enzyme that synthesizes GABA, glutamic acid decarboxylase, has been identified in airway epithelial cells; however, the mechanism(s) by which this synthesized GABA is released from epithelial intracellular stores is unknown. We questioned whether any of the four known isoforms of GATs are functionally expressed in ASM or epithelial cells. We detected mRNA and protein expression of GAT2 and -4, and isoforms of glutamic acid decarboxylase in native and cultured human ASM and epithelial cells. In contrast, mRNA encoding vesicular GAT (VGAT), the neuronal GABA transporter, was not detected. Functional inhibition of 3H-GABA uptake was demonstrated using GAT2 and GAT4/betaine–GABA transporter 1 (BGT1) inhibitors in both human ASM and epithelial cells. These results demonstrate that two isoforms of GATs, but not VGAT, are expressed in both airway epithelial and smooth muscle cells. They also provide a mechanism by which locally synthesized GABA can be released from these cells into the airway to activate GABAA channels and GABAB receptors, with subsequent autocrine and/or paracrine signaling effects on airway epithelium and ASM.
PMCID: PMC3175560  PMID: 21057105
vesicular γ–amino butyric acid transporter; 3H–γ–amino butyric acid uptake; immunoblot; RT-PCR
21.  Genome-Wide Association Analysis in Asthma Subjects Identifies SPATS2L as a Novel Bronchodilator Response Gene 
PLoS Genetics  2012;8(7):e1002824.
Bronchodilator response (BDR) is an important asthma phenotype that measures reversibility of airway obstruction by comparing lung function (i.e. FEV1) before and after the administration of a short-acting β2-agonist, the most common rescue medications used for the treatment of asthma. BDR also serves as a test of β2-agonist efficacy. BDR is a complex trait that is partly under genetic control. A genome-wide association study (GWAS) of BDR, quantified as percent change in baseline FEV1 after administration of a β2-agonist, was performed with 1,644 non-Hispanic white asthmatic subjects from six drug clinical trials: CAMP, LOCCS, LODO, a medication trial conducted by Sepracor, CARE, and ACRN. Data for 469,884 single-nucleotide polymorphisms (SNPs) were used to measure the association of SNPs with BDR using a linear regression model, while adjusting for age, sex, and height. Replication of primary P-values was attempted in 501 white subjects from SARP and 550 white subjects from DAG. Experimental evidence supporting the top gene was obtained via siRNA knockdown and Western blotting analyses. The lowest overall combined P-value was 9.7E-07 for SNP rs295137, near the SPATS2L gene. Among subjects in the primary analysis, those with rs295137 TT genotype had a median BDR of 16.0 (IQR = [6.2, 32.4]), while those with CC or TC genotypes had a median BDR of 10.9 (IQR = [5.0, 22.2]). SPATS2L mRNA knockdown resulted in increased β2-adrenergic receptor levels. Our results suggest that SPATS2L may be an important regulator of β2-adrenergic receptor down-regulation and that there is promise in gaining a better understanding of the biological mechanisms of differential response to β2-agonists through GWAS.
Author Summary
Bronchodilator response (BDR) is an important asthma phenotype that measures reversibility of airway obstruction by comparing lung function before and after the administration of short-acting β2-agonists, common medications used for asthma treatment. We performed a genome-wide association study of BDR with 1,644 white asthmatic subjects from six drug clinical trials and attempted to replicate these findings in 1,051 white subjects from two independent cohorts. The most significant associated variant was near the SPATS2L gene. We knocked down SPATS2L mRNA in human airway smooth muscle cells and found that β2-adrenergic receptor levels increased, suggesting that SPATS2L may be a regulator of BDR. Our results highlight the promise of pursuing GWAS results that do not necessarily reach genome-wide significance and are an example of how results from pharmacogenetic GWAS can be studied functionally.
PMCID: PMC3390407  PMID: 22792082
22.  Anti-inflammatory Effects of Thiazolidinediones in Human Airway Smooth Muscle Cells 
Airway smooth muscle (ASM) cells have been reported to contribute to the inflammation of asthma. Because the thiazolidinediones (TZDs) exert anti-inflammatory effects, we examined the effects of troglitazone and rosiglitazone on the release of inflammatory moieties from cultured human ASM cells. Troglitazone dose-dependently reduced the IL-1β–induced release of IL-6 and vascular endothelial growth factor, the TNF-α–induced release of eotaxin and regulated on activation, normal T expressed and secreted (RANTES), and the IL-4–induced release of eotaxin. Rosiglitazone also inhibited the TNF-α–stimulated release of RANTES. Although TZDs are known to activate peroxisome proliferator–activated receptor-γ (PPARγ), these anti-inflammatory effects were not affected by a specific PPARγ inhibitor (GW 9662) or by the knockdown of PPARγ using short hairpin RNA. Troglitazone and rosiglitazone each caused the activation of adenosine monophosphate-activated protein kinase (AMPK), as detected by Western blotting using a phospho-AMPK antibody. The anti-inflammatory effects of TZDs were largely mimicked by the AMPK activators, 5-amino-4-imidazolecarboxamide ribose (AICAR) and metformin. However, the AMPK inhibitors, Ara A and Compound C, were not effective in preventing the anti-inflammatory effects of troglitazone or rosiglitzone, suggesting that the effects of these TZDs are likely not mediated through the activation of AMPK. These data indicate that TZDs inhibit the release of a variety of inflammatory mediators from human ASM cells, suggesting that they may be useful in the treatment of asthma, and the data also indicate that the effects of TZDs are not mediated by PPARγ or AMPK.
PMCID: PMC3145064  PMID: 20870897
shRNA; anti-inflammatory; PPARγ; IL-1β; TNF-α
23.  An RGS4-Mediated Phenotypic Switch of Bronchial Smooth Muscle Cells Promotes Fixed Airway Obstruction in Asthma 
PLoS ONE  2012;7(1):e28504.
In severe asthma, bronchodilator- and steroid-insensitive airflow obstruction develops through unknown mechanisms characterized by increased lung airway smooth muscle (ASM) mass and stiffness. We explored the role of a Regulator of G-protein Signaling protein (RGS4) in the ASM hyperplasia and reduced contractile capacity characteristic of advanced asthma. Using immunocytochemical staining, ASM expression of RGS4 was determined in endobronchial biopsies from healthy subjects and those from subjects with mild, moderate and severe asthma. Cell proliferation assays, agonist-induced calcium mobilization and bronchoconstriction were determined in cultured human ASM cells and in human precision cut lung slices. Using gain- and loss-of-function approaches, the precise role of RGS proteins was determined in stimulating human ASM proliferation and inhibiting bronchoconstriction. RGS4 expression was restricted to a subpopulation of ASM and was specifically upregulated by mitogens, which induced a hyperproliferative and hypocontractile ASM phenotype similar to that observed in recalcitrant asthma. RGS4 expression was markedly increased in bronchial smooth muscle of patients with severe asthma, and expression correlated significantly with reduced pulmonary function. Whereas RGS4 inhibited G protein-coupled receptor (GPCR)-mediated bronchoconstriction, unexpectedly RGS4 was required for PDGF-induced proliferation and sustained activation of PI3K, a mitogenic signaling molecule that regulates ASM proliferation. These studies indicate that increased RGS4 expression promotes a phenotypic switch of ASM, evoking irreversible airway obstruction in subjects with severe asthma.
PMCID: PMC3257220  PMID: 22253691
24.  Profile of aclidinium bromide in the treatment of chronic obstructive pulmonary disease 
Bronchodilators provide the mainstay of pharmacologic therapy for chronic obstructive pulmonary disease (COPD), and anticholinergic bronchodilators, in particular, appear to be the most effective. There are currently two anticholinergic agents available in the US for the treatment of COPD (ipratropium bromide and tiotropium bromide), but several others are in various stages of development. Aclidinium bromide, a novel, long-acting, anticholinergic bronchodilator, is currently in Phase III trials for the management of COPD. Available evidence suggests that aclidinium is a safe and well tolerated drug with a relatively rapid onset and a sufficient duration of action to provide once-daily dosing. This article will provide a pharmacologic profile of aclidinium bromide and review the preclinical and clinical studies evaluating its safety and efficacy in the treatment of COPD.
PMCID: PMC3186744  PMID: 22003291
aclidinium bromide; bronchodilators; pulmonary disease; chronic obstructive; muscarinic antagonists; pharmacokinetics; pharmacology
25.  Social stress and asthma: The role of corticosteroid insensitivity 
Psychosocial stress alters susceptibility to infectious and systemic illnesses and may enhance airway inflammation in asthma by modulating immune cell function through neural and hormonal pathways. Stress activates the hypothalamic-pituitary-adrenal (HPA) axis. Release of endogenous glucocorticoids, as a consequence, may play a prominent role in altering the airway immune homeostasis. Despite substantial corticosteroid and catecholamine plasma levels, chronic psychosocial stress evokes asthma exacerbations.
Animal studies suggest that social stress induces corticosteroid insensitivity that in part may be due to impaired glucocorticoid receptor (GR) expression and/or function. Such mechanisms likely promote and amplify airway inflammation in response to infections, allergen or irritant exposure. This review discusses evidence of an altered corticosteroid responsive state as a consequence of chronic psychosocial stress. Elucidation of the mechanisms of stress-induced impairment of glucocorticoid responsiveness and immune homeostasis may identify novel therapeutic targets that could improve asthma management.
PMCID: PMC2839059  PMID: 20153032
Airway inflammation; psychosocial stress; corticosteroids; innate immune system

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