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1.  Fibrocyte localization to the airway smooth muscle is a feature of asthma 
Airway smooth muscle (ASM) hyperplasia is a hallmark of asthma that is associated with disease severity and persistent airflow obstruction.
We sought to investigate whether fibrocytes, a population of peripheral blood mesenchymal progenitors, are recruited to the ASM compartment in asthma.
We assessed the number of fibrocytes in bronchial biopsy specimens and peripheral blood from subjects with mild-to-severe refractory asthma versus healthy control subjects. In vitro we investigated potential mechanisms controlling fibrocyte migration toward the ASM bundle.
Fifty-one subjects with asthma and 33 control subjects were studied. In bronchial biopsy specimens, the number of fibrocytes was increased in the lamina propria of subjects with severe refractory asthma (median [interquartile range] number, 1.9/mm2 [1.7/mm2]) versus healthy control subjects (median [interquartile range] number, 0/mm2 [0.3/mm2], P < .0001) and in the ASM bundle of subjects with asthma of all severities (subjects with severe asthma, median [interquartile range] number, 3.8/mm2 [9.4/mm2]; subjects with mild-to-moderate asthma, median [interquartile range] number, 1.1/mm2 [2.4/mm2]); healthy control subjects, (median [interquartile range] number, 0/mm2 [0/mm2]); P = .0004). In the peripheral blood the fibrocyte number was also increased in subjects with severe refractory asthma (median [interquartile range] number, 1.4 × 104/mL [2.6 × 104/mL]) versus healthy control subjects (median [interquartile range] number, 0.4 × 104/mL [1.0 × 104/mL], P = .002). We identified that in vitro ASM promotes fibrocyte chemotaxis and chemokinesis (distance of migration after 4.5 hours, 31 μm [2.9 μm] vs 17 μm [2.4 μm], P = .0001), which was in part mediated by platelet-derived growth factor (mean inhibition by neutralizing antibody, 16% [95% CI, 2% to 32%], P = .03) but not by activation of chemokine receptors.
This study provides the first evidence that fibrocytes are present in the ASM compartment in asthma and that ASM can augment fibrocyte migration. The importance of fibrocytes in the development of ASM hyperplasia and airway dysfunction in asthma remains to be determined.
PMCID: PMC3992369  PMID: 19081612
Asthma; airway smooth muscle; remodeling; mast cells
2.  Airway hyperresponsiveness is dissociated from airway wall structural remodeling 
Nonasthmatic eosinophilic bronchitis (EB) has emerged as a useful tool to study the structural and inflammatory mechanisms of airway hyperresponsiveness (AHR) in asthma. We have previously shown that vascular remodeling and reticular basement membrane (RBM) thickening are present in EB. However, it is not known whether other features of structural remodeling including increased airway smooth muscle (ASM) mass, matrix deposition, and glandular hyperplasia are also present in EB.
We sought to determine whether structural remodeling occurs in EB and is associated with AHR and airflow limitation.
Forty-two patients with asthma, 21 patients with EB, and 19 healthy volunteers were recruited. ASM area, RBM thickness, collagen 3 deposition, glandular area, mast cells, and granulocytes were assessed in bronchial biopsy samples.
Nonasthmatic eosinophilic bronchitis and asthma were associated with a significant increase in ASM mass and RBM thickness compared with healthy subjects. In contrast, we did not observe any significant differences in collagen 3 deposition in the lamina propria and ASM or the % area of glands in the lamina propria. Univariate analysis demonstrated that mast cell numbers in the ASM were the only feature of remodeling associated with AHR (β = −0.51; P = .004). Stepwise linear regression revealed that a combination of mast cell numbers in the ASM (β = −0.43) and disease duration (β = −0.25; model-adjusted R2 = 0.26; P = .027) best modeled AHR.
Mast cell localization to the ASM bundle, but not structural remodeling of the airway wall, is associated with AHR in asthma.
PMCID: PMC3992373  PMID: 18572228
Asthma; nonasthmatic eosinophilic bronchitis; airway hyperresponsiveness; mast cell; remodeling
3.  Increased Nicotinamide Adenine Dinucleotide Phosphate Oxidase 4 Expression Mediates Intrinsic Airway Smooth Muscle Hypercontractility in Asthma 
Rationale: Asthma is characterized by disordered airway physiology as a consequence of increased airway smooth muscle contractility. The underlying cause of this hypercontractility is poorly understood.
Objectives: We sought to investigate whether the burden of oxidative stress in airway smooth muscle in asthma is heightened and mediated by an intrinsic abnormality promoting hypercontractility.
Methods: We examined the oxidative stress burden of airway smooth muscle in bronchial biopsies and primary cells from subjects with asthma and healthy controls. We determined the expression of targets implicated in the control of oxidative stress in airway smooth muscle and their role in contractility.
Measurements and Main Results: We found that the oxidative stress burden in the airway smooth muscle in individuals with asthma is heightened and related to the degree of airflow obstruction and airway hyperresponsiveness. This was independent of the asthmatic environment as in vitro primary airway smooth muscle from individuals with asthma compared with healthy controls demonstrated increased oxidative stress–induced DNA damage together with an increased production of reactive oxygen species. Genome-wide microarray of primary airway smooth muscle identified increased messenger RNA expression in asthma of NADPH oxidase (NOX) subtype 4. This NOX4 overexpression in asthma was supported by quantitative polymerase chain reaction, confirmed at the protein level. Airway smooth muscle from individuals with asthma exhibited increased agonist-induced contraction. This was abrogated by NOX4 small interfering RNA knockdown and the pharmacological inhibitors diphenyleneiodonium and apocynin.
Conclusions: Our findings support a critical role for NOX4 overexpression in asthma in the promotion of oxidative stress and consequent airway smooth muscle hypercontractility. This implicates NOX4 as a potential novel target for asthma therapy.
PMCID: PMC3402550  PMID: 22108207
asthma; airway smooth muscle; airway hyperresponsiveness; NOX4; SOD2
4.  Functional KCa3.1 K+ channels are required for human fibrocyte migration 
Fibrocytes are bone marrow–derived CD34+ collagen I–positive cells present in peripheral blood that develop α-smooth muscle actin expression and contractile activity in tissue culture. They are implicated in the pathogenesis of tissue remodeling and fibrosis in both patients with asthma and those with idiopathic pulmonary fibrosis. Targeting fibrocyte migration might therefore offer a new approach for the treatment of these diseases. Ion channels play key roles in cell function, but the ion-channel repertoire of human fibrocytes is unknown.
We sought to examine whether human fibrocytes express the KCa3.1 K+ channel and to determine its role in cell differentiation, survival, and migration.
Fibrocytes were cultured from the peripheral blood of healthy subjects and patients with asthma. Whole-cell patch-clamp electrophysiology was used for the measurement of ion currents, whereas mRNA and protein were examined to confirm channel expression. Fibrocyte migration and proliferation assays were performed in the presence of KCa3.1 ion-channel blockers.
Human fibrocytes cultured from the peripheral blood of both healthy control subjects and asthmatic patients expressed robust KCa3.1 ion currents together with KCa3.1 mRNA and protein. Two specific and distinct KCa3.1 blockers (TRAM-34 and ICA-17043) markedly inhibited fibrocyte migration in transwell migration assays. Channel blockers had no effect on fibrocyte growth, apoptosis, or differentiation in cell culture.
The K+ channel KCa3.1 plays a key role in human fibrocyte migration. Currently available KCa3.1-channel blockers might therefore attenuate tissue fibrosis and remodeling in patients with diseases such as idiopathic pulmonary fibrosis and asthma through the inhibition of fibrocyte recruitment.
PMCID: PMC3526791  PMID: 21872912
Pulmonary fibrosis; asthma; fibrocyte; cell migration; ion channel; KCa3.1; patch clamp electrophysiology; 1-EBIO, 1-Ethyl-2-benzimidazolinone; αSMA, α-Smooth muscle actin; ASM, Airway smooth muscle; IPF, Idiopathic pulmonary fibrosis; Kd, Concentration producing 50% block
5.  Expression of the T Helper 17-Associated Cytokines IL-17A and IL-17F in Asthma and COPD 
Chest  2010;138(5):1140-1147.
Asthma and COPD are characterized by airway dysfunction and inflammation. Neutrophilic airway inflammation is a common feature of COPD and is recognized in asthma, particularly in severe disease. The T helper (Th) 17 cytokines IL-17A and IL-17F have been implicated in the development of neutrophilic airway inflammation, but their expression in asthma and COPD is uncertain.
We assessed IL-17A and IL-17F expression in the bronchial submucosa from 30 subjects with asthma, 10 ex-smokers with mild to moderate COPD, and 27 nonsmoking and 14 smoking control subjects. Sputum IL-17 concentration was measured in 165 subjects with asthma and 27 with COPD.
The median (interquartile range) IL-17A cells/mm2 submucosa was increased in mild to moderate asthma (2.1 [2.4]) compared with healthy control subjects (0.4 [2.8]) but not in severe asthma (P = .04). In COPD, IL-17A+ cells/mm2 submucosa were increased (0.5 [3.7]) compared with nonsmoking control subjects (0 [0]) but not compared with smoking control subjects (P = .046). IL-17F+ cells/mm2 submucosa were increased in severe asthma (2.7 [3.6]) and mild to moderate asthma (1.6 [1.0]) compared with healthy controls subjects (0.7 [1.4]) (P = .001) but was not increased in subjects with COPD. IL-17A and IL-17F were not associated with increased neutrophilic inflammation, but IL-17F was correlated with the submucosal eosinophil count (rs = 0.5, P = .005). The sputum IL-17 concentration in COPD was increased compared with asthma (2 [0-7] pg/mL vs 0 [0-2] pg/mL, P < .0001) and was correlated with post-bronchodilator FEV1% predicted (r = −0.5, P = .008) and FEV1/FVC (r = −0.4, P = .04).
Our findings support a potential role for the Th17 cytokines IL-17A and IL-17F in asthma and COPD, but do not demonstrate a relationship with neutrophilic inflammation.
PMCID: PMC2972626  PMID: 20538817
6.  Airway Wall Expression of OX40/OX40L and Interleukin-4 in Asthma 
Chest  2010;137(4):797-804.
The costimulatory molecule OX40 and its ligand, OX40L, mediate key aspects of allergic airway inflammation in animal models of asthma, including eosinophilic airway inflammation, airway hyperresponsiveness, and T helper 2 polarization. We sought to examine OX40/OX40L and interleukin (IL)-4 expression in asthma across severities.
Bronchial biopsies were obtained from 27 subjects with asthma (mild Global Initiative for Asthma [GINA] 1 [n = 10], moderate GINA 2-3 [n = 7], and severe GINA 4-5 [n = 10]) and 13 healthy controls. The number of OX40+, OX40L+, IL-4+, and IL-4 receptor α (IL-4Rα)+ cells in the lamina propria and airway smooth muscle (ASM) bundle and the intensity of IL-4Rα+ expression by the ASM were assessed.
The number of OX40+, OX40L+, and IL-4+ cells in the lamina propria and OX40+ and IL-4+ cells in the ASM bundle was significantly increased in subjects with mild asthma, but not in those with moderate or severe asthma, compared with healthy controls. In the subjects with asthma, OX40/OX40L expression was positively correlated with the number of eosinophils and IL-4+ cells in the lamina propria. The number of IL-4Rα+ cells in the lamina propria was significantly increased in moderate-to-severe disease, but not in mild asthma, compared with controls. IL-4Rα expression by the ASM bundle was not different among groups.
OX40/OX40L expression is increased in the bronchial submucosa in mild asthma, but not in moderate-to-severe disease, and is related to the degree of tissue eosinophilia and IL-4 expression. Whether these costimulatory molecules have a role as targets for asthma requires further investigation.
PMCID: PMC2851558  PMID: 20139223

Results 1-6 (6)