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1.  Obesity and Asthma 
Rationale: Obesity is a major risk factor for asthma; the reasons for this are poorly understood, although it is thought that inflammatory changes in adipose tissue in obesity could contribute to airway inflammation and airway reactivity in individuals who are obese.
Objectives: To determine if inflammation in adipose tissue in obesity is related to late-onset asthma, and associated with increased markers of airway inflammation and reactivity.
Methods: We recruited a cohort of obese women with asthma and obese control women. We followed subjects with asthma for 12 months after bariatric surgery. We compared markers in adipose tissue and the airway from subjects with asthma and control subjects, and changes in subjects with asthma over time.
Measurements and Main Results: Subjects with asthma had increased macrophage infiltration of visceral adipose tissue (P < 0.01), with increased expression of leptin (P < 0.01) and decreased adiponectin (p < 0.001) when controlled for body mass index. Similar trends were observed in subcutaneous adipose tissue. Airway epithelial cells expressed receptors for leptin and adiponectin, and airway reactivity was significantly related to visceral fat leptin expression (rho = −0.8; P < 0.01). Bronchoalveolar lavage cytokines and cytokine production from alveolar macrophages were similar in subjects with asthma and control subjects at baseline, and tended to increase 12 months after surgery.
Conclusions: Obesity is associated with increased markers of inflammation in serum and adipose tissue, and yet decreased airway inflammation in obese people with asthma; these patterns reverse with bariatric surgery. Leptin and other adipokines may be important mediators of airway disease in obesity through direct effects on the airway rather than by enhancing airway inflammation.
doi:10.1164/rccm.201203-0573OC
PMCID: PMC3480522  PMID: 22837379
asthma; obesity; adipokine; airway hyperreactivity
2.  Regulatory Haplotypes in ARG1 Are Associated with Altered Bronchodilator Response 
Rationale: β2-agonists, the most common treatment for asthma, have a wide interindividual variability in response, which is partially attributed to genetic factors. We previously identified single nucleotide polymorphisms in the arginase 1 (ARG1) gene, which are associated with β2-agonist bronchodilator response (BDR).
Objectives: To identify cis-acting haplotypes in the ARG1 locus that are associated with BDR in patients with asthma and regulate gene expression in vitro.
Methods: We resequenced ARG1 in 96 individuals and identified three common, 5′ haplotypes (denoted 1, 2, and 3). A haplotype-based association analysis of BDR was performed in three independent, adult asthma drug trial populations. Next, each haplotype was cloned into vectors containing a luciferase reporter gene and transfected into human airway epithelial cells (BEAS-2B) to ascertain its effect on gene expression.
Measurements and Main Results: BDR varied by haplotype in each of the three populations with asthma. Individuals with haplotype 1 were more likely to have higher BDR, compared to those with haplotypes 2 and 3, which is supported by odds ratios of 1.25 (95% confidence interval, 1.03–1.71) and 2.18 (95% confidence interval, 1.34–2.52), respectively. Luciferase expression was 50% greater in cells transfected with haplotype 1 compared to haplotypes 2 and 3.
Conclusions: The identified ARG1 haplotypes seem to alter BDR and differentially regulate gene expression with a concordance of decreased BDR and reporter activity from haplotypes 2 and 3. These findings may facilitate pharmacogenetic tests to predict individuals who may benefit from other therapeutic agents in addition to β2-agonists for optimal asthma management.
Clinical trial registered with www.clinicaltrials.gov (NCT00156819, NCT00046644, and NCT00073840).
doi:10.1164/rccm.201005-0758OC
PMCID: PMC3056223  PMID: 20851928
pharmacogenetics; asthma; β2-agonist
3.  ARG1 Is a Novel Bronchodilator Response Gene 
Rationale: Inhaled β-agonists are one of the most widely used classes of drugs for the treatment of asthma. However, a substantial proportion of patients with asthma do not have a favorable response to these drugs, and identifying genetic determinants of drug response may aid in tailoring treatment for individual patients.
Objectives: To screen variants in candidate genes in the steroid and β-adrenergic pathways for association with response to inhaled β-agonists.
Methods: We genotyped 844 single nucleotide polymorphisms (SNPs) in 111 candidate genes in 209 children and their parents participating in the Childhood Asthma Management Program. We screened the association of these SNPs with acute response to inhaled β-agonists (bronchodilator response [BDR]) using a novel algorithm implemented in a family-based association test that ranked SNPs in order of statistical power. Genes that had SNPs with median power in the highest quartile were then taken for replication analyses in three other asthma cohorts.
Measurements and Main Results: We identified 17 genes from the screening algorithm and genotyped 99 SNPs from these genes in a second population of patients with asthma. We then genotyped 63 SNPs from four genes with significant associations with BDR, for replication in a third and fourth population of patients with asthma. Evidence for association from the four asthma cohorts was combined, and SNPs from ARG1 were significantly associated with BDR. SNP rs2781659 survived Bonferroni correction for multiple testing (combined P value = 0.00048, adjusted P value = 0.047).
Conclusions: These findings identify ARG1 as a novel gene for acute BDR in both children and adults with asthma.
doi:10.1164/rccm.200709-1363OC
PMCID: PMC2556451  PMID: 18617639
pharmacogenetics; asthma; bronchodilator agents
4.  Nuclear Factor-κB Activation in Airway Epithelium Induces Inflammation and Hyperresponsiveness 
Rationale: Nuclear factor (NF)-κB is a prominent proinflammatory transcription factor that plays a critical role in allergic airway disease. Previous studies demonstrated that inhibition of NF-κB in airway epithelium causes attenuation of allergic inflammation.
Objectives: We sought to determine if selective activation of NF-κB within the airway epithelium in the absence of other agonists is sufficient to cause allergic airway disease.
Methods: A transgenic mouse expressing a doxycycline (Dox)-inducible, constitutively active (CA) version of inhibitor of κB (IκB) kinase-β (IKKβ) under transcriptional control of the rat CC10 promoter, was generated.
Measurements and Main Results: After administration of Dox, expression of the CA-IKKβ transgene induced the nuclear translocation of RelA in airway epithelium. IKKβ-triggered activation of NF-κB led to an increased content of neutrophils and lymphocytes, and concomitant production of proinflammatory mediators, responses that were not observed in transgenic mice not receiving Dox, or in transgene-negative littermate control animals fed Dox. Unexpectedly, expression of the IKKβ transgene in airway epithelium was sufficient to cause airway hyperresponsiveness and smooth muscle thickening in absence of an antigen sensitization and challenge regimen, the presence of eosinophils, or the induction of mucus metaplasia.
Conclusions: These findings demonstrate that selective activation NF-κB in airway epithelium is sufficient to induce airway hyperresponsiveness and smooth muscle thickening, which are both critical features of allergic airway disease.
doi:10.1164/rccm.200707-1096OC
PMCID: PMC2361423  PMID: 18263801
airway epithelium; nuclear factor-κB; inhibitory κB kinase-β; airway hyperresponsiveness; smooth muscle cell
5.  The Synergistic Interactions of Allergic Lung Inflammation and Intratracheal Cationic Protein 
Rationale: Airways hyperresponsiveness (AHR) is a hallmark feature of asthma, and can be caused by various disparate mechanisms. Mouse models of AHR have been useful for studying these mechanisms in isolation, but such models still typically do not exhibit the same degree of AHR as seen in severe human asthma. We hypothesized that more severe AHR in mice could be achieved by imbuing them with more than one mechanism of AHR.
Objectives: We sought to determine if the airway wall thickening accompanying allergic inflammation and the exaggerated smooth muscle shortening induced by intratracheal cationic protein could act together to produce a severe form of AHR.
Methods: We used the forced oscillation technique to measure methacholine responsiveness in BALB/c mice that had been sensitized and challenged with ovalbumin followed by an intratracheal instillation of poly-l-lysine.
Measurements and Main Results: We found that both ovalbumin and poly-l-lysine treatment alone caused moderate levels of AHR. When the two treatments were combined, however, they synergized in terms of their effect on lung stiffness to an extent that could even be fatal, reflecting a significantly enhanced level of airway closure.
Conclusions: Our results suggest that mechanistic synergy between airway wall thickening and exaggerated smooth muscle shortening produces a more germane mouse model of asthma that may have particular relevance to the pathophysiology of the acute severe asthma exacerbation.
doi:10.1164/rccm.200706-832OC
PMCID: PMC2218848  PMID: 17962637
airway hyperresponsiveness; methacholine; mouse model; asthma exacerbation
6.  Transforming Growth Factor-β1 Suppresses Airway Hyperresponsiveness in Allergic Airway Disease 
Rationale: Asthma is characterized by increases in airway resistance, pulmonary remodeling, and lung inflammation. The cytokine transforming growth factor (TGF)-β has been shown to have a central role in asthma pathogenesis and in mouse models of allergic airway disease.
Objectives: To determine the contribution of TGF-β to airway hyperresponsiveness (AHR), we examined the time course, source, and isoform specificity of TGF-β production in an in vivo mouse asthma model. To then elucidate the function of TGF-β in AHR, inflammation, and pulmonary fibrosis, we examined the effects of blocking TGF-β signaling with neutralizing antibody.
Methods: Mice were sensitized and challenged with ovalbumin (OVA) to establish allergic airway disease. TGF-β activity was neutralized by intranasal administration of monoclonal antibody.
Measurements and Main Results: TGF-β1 protein levels were increased in OVA-challenged lungs versus naive controls, and airway epithelial cells were shown to be a likely source of TGF-β1. In addition, TGF-β1 levels were elevated in OVA-exposed IL-5–null mice, which fail to recruit eosinophils into the airways. Neutralization of TGF-β1 with specific antibody had no significant effect on airway inflammation and eosinophilia, although anti–TGF-β1 antibody enhanced OVA-induced AHR and suppressed pulmonary fibrosis.
Conclusions: These data show that TGF-β1 is the main TGF-β isoform produced after OVA challenge, with a likely cellular source being the airway epithelium. The effects of blocking TGF-β1 signaling had differential effects on AHR, fibrosis, and inflammation. While TGF-β neutralization may be beneficial to abrogating airway remodeling, it may be detrimental to lung function by increasing AHR.
doi:10.1164/rccm.200702-334OC
PMCID: PMC2078678  PMID: 17761617
lung; mice; hypersensitivity; cytokines
7.  Airway Hyperresponsiveness in Allergically Inflamed Mice 
Rationale: Allergically inflamed mice exhibit airway hyperresponsiveness to inhaled methacholine, which computer simulations of lung impedance suggest is due to enhanced lung derecruitment and which we sought to verify in the present study.
Methods: BALB/c mice were sensitized and challenged with ovalbumin to induce allergic inflammation; the control mice were sensitized but received no challenge. The mice were then challenged with inhaled methacholine and respiratory system impedance tracked for the following 10 minutes. Respiratory elastance (H) was estimated from each impedance measurement. One group of mice was ventilated with 100% O2 during this procedure and another group was ventilated with air. After the procedure, the mice were killed and ventilated with pure N2, after which the trachea was tied off and the lungs were imaged with micro-computed tomography (micro-CT).
Results: H was significantly higher in allergic mice than in control animals after methacholine challenge. The ratio of H at the end of the measurement period between allergic and nonallergic mice ventilated with O2 was 1.36, indicating substantial derecruitment in the allergic animals. The ratio between lung volumes determined by micro-CT in the control and the allergic mice was also 1.36, indicative of a corresponding volume loss due to absorption atelectasis. Micro-CT images and histograms of Hounsfield units from the lungs also showed increased volume loss in the allergic mice compared with control animals after methacholine challenge.
Conclusions: These results support the conclusion that airway closure is a major component of hyperresponsiveness in allergically inflamed mice.
doi:10.1164/rccm.200610-1410OC
PMCID: PMC1899295  PMID: 17255559
asthma; micro-computed tomography; input impedance; lung derecruitment; lung volume
8.  Tumor Necrosis Factor–α Overexpression in Lung Disease 
Rationale: Tumor necrosis factor α (TNF-α) has been implicated as a key cytokine in many inflammatory lung diseases. These effects are currently unclear, because a transgenic mouse overexpressing TNF-α in the lung has been shown in separate studies to produce elements of both emphysema and pulmonary fibrosis. Objectives: We sought to elucidate the phenotypic effects of TNF-α overexpression in a mouse model. Measurements: We established the phenotype by measuring lung impedance and thoracic gas volume, and using micro–computed tomography and histology. Main Results: We found that airways resistance in this mouse was not different to control mice, but that lung tissue dampening, elastance, and hysteresivity were significantly elevated. Major heterogeneous abnormalities of the parenchyma were also apparent in histologic sections and in micro–computed tomography images of the lung. These changes included airspace enlargement, loss of small airspaces, increased collagen, and thickened pleural septa. We also found significant increases in lung and chest cavity volumes in the TNF-α–overexpressing mice. Conclusions: We conclude that TNF-α overexpression causes pathologic changes consistent with both emphysema and pulmonary fibrosis combined with a general lung inflammation, and consequently does not model any single human disease. Our study thus confirms the pleiotropic effects of TNF-α, which has been implicated in multiple inflammatory disorders, and underscores the necessity of using a wide range of investigative techniques to link gene expression and phenotype in animal models of disease.
doi:10.1164/rccm.200410-1349OC
PMCID: PMC2718479  PMID: 15805183
emphysema; micro–computed tomography; plethysmography; pulmonary fibrosis

Results 1-8 (8)