Absence Of Airway Inflammation Research Articles

Chlorine exposure and intensive exercise induces airway hyperreactivity in a 3-week murine exercise model

RationaleExercise-induced bronchoconstriction (EIB) is defined as acute narrowing of the airways during or immediately after exercise. EIB has a high prevalence in elite swimmers probably due to the high ventilation rate and exposure to the chlorine by-products. It is still puzzling which pathophysiological mechanisms drive EIB. ObjectiveIn this study, we evaluated airway hyperreactivity, permeability, integrity and inflammation in a murine swimmers EIB model with and without chlorine exposure. MethodsMice performed a 3-week swimming protocol in a swimming pool with counter current. Three hours after the last swimming session, airway hyperreactivity to methacholine was assessed. Cytokine levels and cellular differential analysis was performed in BAL fluid. Airway permeability and tight junction expression was measured in serum and lung tissue. T-, B-, dendritic and innate lymphoid cells were determined in lung tissue via flow cytometry. ResultsA significant higher airway resistance (Rn; P < 0.0001) was observed in mice swimming in chlorinated water (mean Rn = 1.26 cmH2O.s/ml) compared to mice swimming in tap water (mean Rn = 0.76 cmH2O.s/ml) and both inhalation groups in the absence of cellular inflammation. No significant differences were found in lung immune cell populations or in lung tight junction mRNA expression. Experiments in SCID, Rag2−/−γc−/− or Cpa3cre/+ mice showed a limited involvement of the innate, adaptive immune system or the mast cells. ConclusionOur 3-week swimming murine model mimics intensive swimming in chlorinated water with the presence of airway hyperreactivity in mice swimming in chlorinated water in the absence of airway inflammation and airway epithelial damage.

Orosomucoid-like 3 (ORMDL3) upregulates airway smooth muscle proliferation, contraction, and Ca2+ oscillations in asthma

Airway hyperresponsiveness is a major feature of asthma attributed predominantly to an extrinsic immune/inflammatory response increasing airway smooth muscle (ASM) contractility. We investigated whether increased ASM expression of orosomucoid-like 3 (ORMDL3), a gene on chromosome 17q21 highly linked to asthma, induced increased ASM proliferation and contractility invitro and influenced airway contractility and calcium flux in ASM in precision-cut lung slices (PCLSs) from wild-type and hORMDL3Zp3-Cre mice (which express increased levels of human ORMDL3 [hORMDL3]). Levels of ASM proliferation and contraction were assessed in ASM cells transfected with ORMDL3 in vitro. In addition, airway contractility and calcium oscillations were quantitated in ASM cells in PCLSs derived from naive wild-type and naive hORMDL3Zp3-Cre mice, which do not have a blood supply. Increased ASM expression of ORMDL3 invitro resulted in increased ASM proliferation and contractility. PCLSs derived from naive hORMDL3Zp3-Cre mice, which do not have airway inflammation, exhibit increased airway contractility with increased calcium oscillations in ASM cells. Increased ASM ORMDL3 expression increases levels of ASM sarcoplasmic reticulum Ca2+ ATPase 2b (SERCA2b), which increases ASM proliferation and contractility. Overall, these studies provide evidence that an intrinsic increase in ORMDL3 expression in ASM can induce increased ASM proliferation and contractility, which might contribute to increased airway hyperresponsiveness in the absence of airway inflammation in asthmatic patients.

Chromosome 17q21 Genes ORMDL3 and GSDMB in Asthma and Immune Diseases.

Chromosome 17q21 contains a cluster of genes including ORMDL3 and GSDMB, which have been highly linked to asthma in genome-wide association studies. ORMDL3 is localized to the endoplasmic reticulum and regulates downstream pathways including sphingolipids, metalloproteases, remodeling genes, and chemokines. ORMDL3 inhibits serine palmitoyl-CoA transferase, the rate-limiting enzyme for sphingolipid biosynthesis. In addition, ORMDL3 activates the ATF6α branch of the unfolded protein response which regulates SERCA2b and IL-6, pathways of potential importance to asthma. The SNP-linking chromosome 17q21 to asthma is associated with increased ORMDL3 and GSDMB expression. Mice expressing either increased levels of human ORMDL3, or human GSDMB, have an asthma phenotype characterized by increased airway responsiveness and increased airway remodeling (increased smooth muscle and fibrosis) in the absence of airway inflammation. GSDMB regulates expression of 5-LO and TGF-β1 which are known pathways involved in the pathogenesis of asthma. GSDMB is one of four members of the GSDM family (GSDMA, GSDMB, GSDMC, and GSDMD). GSDMD (located on chromosome 8q24 and not linked to asthma) has emerged as a key mediator of pyroptosis. GSDMD is a key component of the NLPR3 inflammasome and is required for its activation. GSDMD undergoes proteolytic cleavage by caspase-1 to release its N-terminal fragment, which in turn mediates pyroptosis and IL-1β secretion. Chromosome 17q21 has not only been linked to asthma but also to type 1 diabetes, inflammatory bowel disease, and primary biliary cirrhosis suggesting that future insights into the biology of genes located in this region will increase our understanding of these diseases.

GSDMB induces an asthma phenotype characterized by increased airway responsiveness and remodeling without lung inflammation

Gasdermin B (GSDMB) on chromosome 17q21 demonstrates a strong genetic linkage to asthma, but its function in asthma is unknown. Here we identified that GSDMB is highly expressed in lung bronchial epithelium in human asthma. Overexpression of GSDMB in primary human bronchial epithelium increased expression of genes important to both airway remodeling [TGF-β1, 5-lipoxygenase (5-LO)] and airway-hyperresponsiveness (AHR) (5-LO). Interestingly, hGSDMBZp3-Cre mice expressing increased levels of the human GSDMB transgene showed a significant spontaneous increase in AHR and a significant spontaneous increase in airway remodeling, with increased smooth muscle mass and increased fibrosis in the absence of airway inflammation. In addition, hGSDMBZp3-Cre mice showed increases in the same remodeling and AHR mediators (TGF-β1, 5-LO) observed in vitro in GSDMB-overexpressing epithelial cells. GSDMB induces TGF-β1 expression via induction of 5-LO, because knockdown of 5-LO in epithelial cells overexpressing GSDMB inhibited TGF-β1 expression. These studies demonstrate that GSDMB, a gene highly linked to asthma but whose function in asthma is previously unknown, regulates AHR and airway remodeling without airway inflammation through a previously unrecognized pathway in which GSDMB induces 5-LO to induce TGF-β1 in bronchial epithelium.

Why is Chromosome 17q21 linked to Asthma?

Asthma is an inflammatory disorder of the airways associated with increased airway responsiveness and airway remodeling. Several genome wide association studies (GWAS) and non-GWAS studies have demonstrated a strong genetic linkage of chromosome 17q21 genes with asthma in populations of diverse ethnic backgrounds. In particular, SNPs in the 17q21 region are found within a large linkage disequilibrium (LD) block that contains not only the orosomucoid like-3 (ORMDL3) gene, but also includes other 17q21 genes i.e. gasdermin B (GSDMB), IKAROS family zinc finger 3 (IKZF3), and zona pellucida binding protein 2 (ZPBP2). Studies of mice expressing increased levels of the human ORMDL3 gene have demonstrated that these mice have spontaneous increased airway remodeling and airway responsiveness in the absence of airway inflammation. Further functional studies are needed to investigate whether some or all of these four genes could contribute to the pathogenesis of asthma.

Absence of airway inflammation in a large proportion of adolescents with asthma.

Neutrophilic inflammation has been implicated in non-eosinophilic asthma (NEA) in adults, but little is known about NEA in children/adolescents. We assessed clinical and inflammatory characteristics of NEA in adolescent asthma. Airway inflammation, sputum endotoxin, airway hyper-reactivity, atopy and lung function were assessed in 77 adolescents with asthma and 68 without asthma (12-17 years). Asthma was identified on the basis of wheeze and asthma history. The proportion of NEA (sputum eosinophils <2.5%) was 54%. In this group, atopy, sputum neutrophil, eosinophil, eosinophil cationic protein (ECP), endotoxin, neutrophil elastase and IL-8 levels were not different from those without asthma. In contrast, eosinophilic asthma (EA) was associated with atopy and sputum ECP and IL-8. The majority of NEA had no evidence of inflammation; only 14% had neutrophilia (≥61% neutrophils), compared with 11% of EA, and 15% of those without asthma. Small differences in FEV1 (NS) were found between EA and NEA, but symptom prevalence and severity was not different (63% of EA and 52% of NEA were classified moderate to severe). NEA is common in adolescent asthma and has similar clinical characteristics as EA. Neutrophils do not appear to play a role in NEA in adolescents, and underlying mechanisms may not involve airway inflammation.

Adapt or Perish.

H. G. Wells was trained as a biologist and influenced by Darwin and his concepts of evolution. He succinctly summarizes these concepts as “Adapt or perish, now as ever, is nature's inexorable imperative.” However, even in his wildest dreams of science fiction, Wells would find the environmental

Can AMP induce sputum eosinophils, even in subjects with complete asthma remission?

BackgroundThe definition of "clinical asthma remission" is based on absence of symptoms and use of medication. However, in the majority of these subjects airway inflammation is still present when measured. In the present study we investigated whether "complete asthma remission", additionally defined by the absence of bronchial hyperresponsiveness (BHR) and the presence of a normal lung function, is associated with the absence of airway inflammation.MethodsPatients with a former diagnosis of asthma and a positive histamine provocation test were re-examined to identify subjects with complete asthma remission (no asthma symptoms or medication, PC20 histamine > 32 mg/ml, FEV1 > 90% predicted). Patients with PC20 histamine ≤ 32 mg/ml were defined as current asthmatics and were divided in two groups, i.e. asthmatics with and without BHR to adenosine 5'monophoshate (AMP). Sputum induction was performed 1 week before and 1 hour after AMP provocation. Sputum induction and AMP provocation were previously shown to be sensitive markers of airway inflammation.ResultsSeven patients met criteria for complete asthma remission. Twenty-three were current asthmatics, including twelve without hyperresponsiveness to AMP. Subjects with complete asthma remission showed no AMP-induced sputum eosinophilia (median (range) 0.2 (0 - 4.6)% at baseline and 0.2 (0 - 2.6)% after AMP). After AMP, current asthmatics had a significant increase in sputum eosinophils (0.5 (0 - 26.0)% at baseline and 2.6 (0 - 32.0) % after AMP), as had the subgroup of current asthmatics without hyperresponsiveness to AMP (0.2 (0 - 1.8)% at baseline and 1.3 (0 - 6.3)% after AMP).ConclusionsSubjects with complete asthma remission, in contrast to subjects with current asthma, do not respond with eosinophilic inflammation in sputum after AMP provocations. These data lend support to the usefulness of the definition of complete asthma remission.

Airway smooth muscle dynamics: a common pathway of airway obstruction in asthma.

Excessive airway obstruction is the cause of symptoms and abnormal lung function in asthma. As airway smooth muscle (ASM) is the effecter controlling airway calibre, it is suspected that dysfunction of ASM contributes to the pathophysiology of asthma. However, the precise role of ASM in the series of events leading to asthmatic symptoms is not clear. It is not certain whether, in asthma, there is a change in the intrinsic properties of ASM, a change in the structure and mechanical properties of the noncontractile components of the airway wall, or a change in the interdependence of the airway wall with the surrounding lung parenchyma. All these potential changes could result from acute or chronic airway inflammation and associated tissue repair and remodelling. Anti-inflammatory therapy, however, does not "cure" asthma, and airway hyperresponsiveness can persist in asthmatics, even in the absence of airway inflammation. This is perhaps because the therapy does not directly address a fundamental abnormality of asthma, that of exaggerated airway narrowing due to excessive shortening of ASM. In the present study, a central role for airway smooth muscle in the pathogenesis of airway hyperresponsiveness in asthma is explored.

Low-dose carbon monoxide reduces airway hyperresponsiveness in mice.

Carbon monoxide (CO) in expired gas has been shown to be elevated with asthma; however, its function is not known, and there is some potential that it may serve a bronchoprotective role to decrease airway hyperresponsiveness (AHR). Thus the ability of CO to reverse methacholine (MCh)-induced bronchoconstriction was evaluated in C57BL/6 (C57) and A/J mice with and without airway inflammation produced by ovalbumin (OVA). Acutely administered CO (1% in air, 10 min) reduced MCh-driven increases in lung resistance in OVA-challenged C57 mice by an average of 50% (from 14.5 to 7.1 cmH2O.ml-1.s-1), whereas no effect was observed in naïve C57 mice or OVA-challenged C57 mice inhaling air alone. Acutely inhaled CO (500 ppm = 0.05%, for 10 min) reduced MCh-induced airway reactivity (AR) by 20-60% in airway hyperresponsive naïve A/J mice, whereas repeated 10-min administrations of 500 ppm CO over a 5-day period decreased AR by 50%. Repeated administration of low-dose CO [250 (0.025%) and (0.05%) 500 ppm, 1 h/day, 5 days] to A/J mice with airway inflammation likewise resulted in a drop of AR by 50%, compared with those not receiving CO. Inhibition of guanylyl cyclase/guanosine 3',5'-cyclic monophosphothioate (cGMP) using 1H-[1,2,4] oxydiazolo[4,3-a]quinoxalin-1-one or a competitive inhibitor, Rp diastereomers of 8-bromo-cGMP, resulted in inhibition of the effect of CO on AHR, suggesting that the effects of CO were mediated through this mechanism. These results indicate that low-dose CO can effectively reverse AHR in the presence and absence of airway inflammation in mice and suggest a potential role for CO in the modulation of AHR.

Late Endobronchial Wegener's Granulomatosis

CASE A 58-year-old man with a known diagnosis of Wegener's granulomatosis (WG) since 1990 was treated with prednisone and Cytoxan for 3 to 4 years until he was thought to be in remission. Despite the therapies, he continued to have shortness of breath and bilateral recurrent pneumonia. Flexible bronchoscopy revealed 20%, 90%, and 100% stenosis of the subglottic trachea, truncus intermedius (Fig. 1), and lingular bronchus respectively.FIG. 1.: Diffuse narrowing and multiple strictures involving the entire truncus intermedius in a patient with Wegener's granulomatosis.DISCUSSION WG is an idiopathic, multisystem disease characterized by necrotizing granulomatous inflammation and vasculitis that involves primarily the upper and lower respiratory tracts with associated glomerulonephritis. 1–5 Actually, WG can involve the entire respiratory tract from the nasal septum to the pleura. 6 A limited form, with a clinical finding isolated to the upper respiratory tract or the lungs, occurs in approximately one fourth of cases. 1,5,7,8 The lung is the most frequent and sometimes the only organ involved. It has been suggested that the pulmonary involvement results from enhanced exposure to inhaled substances and/or a respiratory infection combined with unique susceptibility factors found in the host. 1,9 Approximately 85% of patients develop lung involvement during the course of the disease, 6,10,11 and 45% have lung involvement at presentation. 11 Two thirds of the former group have respiratory symptoms with active disease, whereas the remaining patients are asymptomatic despite an abnormal chest radiograph. 6 In WG, pulmonary symptoms include cough, hemoptysis, and pleuritis. 1,6 The radiographic findings usually include nodules that may cavitate and are seen in half the patients, as well as alveolar and pleural opacities. 1,6 Also, lobar and segmental infiltrates or atelectasis secondary to endobronchial disease have been reported. 6,8,12 Hemoptysis is the most frequent symptom, which leads patients to undergo bronchoscopy frequently (55–59%), revealing gross endobronchial abnormalities such as isolated hemorrhage, airway inflammation, ulcerations, bronchial stenosis, and pseudotumors. 4,6,11,13 Inflammation and stenosis of the endobronchial airways has been found to occur in at least 15% of patients with lung involvement. 9,13 One of the locations where WG can cause irreversible damage is the tracheobronchial tree, which could be potentially life-threatening. 2,13 The incidence of tracheal stenosis has been reported to be 16%. 2,14 The incidence of subglottic involvement has also been reported with similar frequency. 2,5,6,14–17 Subglottic stenosis sometimes develops during the course of the disease and is a result of circumferential inflammation, edema, and fibrosis that typically extends for 3 to 4 cm below the vocal cords, 16 and results in long-term morbidity. Our patient presented with symptoms of airway obstruction and was found to have subglottic stenosis as well as stricture involving the entire truncus intermedius. Another form, called ulcerating tracheobronchitis, which is characterized by focal or diffuse airway narrowing as a result of the inflammation and edema, 6,16 can accompany WG. Also, hilar adenopathy and mediastinal masses are not uncommon with WG. 10 The diagnosis of WG relies heavily on pathologic documentation of granulomatous inflammation, necrosis, and vasculitis. 1,6,9,10,18,19 Open lung biopsy is the most sensitive method for establishing the diagnosis because it demonstrates necrotizing granulomatous vasculitis in 70% of patients. 1,3,18 Endobronchial lung biopsy has a role in the diagnostic evaluation of WG when it exhibits ulcerative, exophytic, or stenotic tracheobronchial lesions. 1,3,5,6,13,18–21 Therapeutic interventions for endobronchial WG depend on the presence or absence of airway inflammation. Airway inflammation suggests acute disease and may respond to systemic treatment. 9,15 Conversely, airway stenosis (subglottic or tracheal) may suggest a burned-out, late, irreversible aftermath of WG. Under the circumstances, interventions such as laser photoresection, dilation, and stent placement may be necessary. 9,13,15,16 Our patient underwent endobronchial photoresection using the Nd:YAG laser, balloon bronchoplasty, and mitomycin applications to the treatment areas.

Nerve Growth Factor Induces Airway Hyperresponsiveness in Mice

Background: Previous studies indicated an upregulation of nerve growth factor (NGF) production during allergic inflammation. However, the function of NGF in the lungs is currently poorly understood. It was suggested that NGF could play an important role in the pathophysiology of airway hyperresponsiveness. The regulatory network between immunological events and altered neuronal control of airway smooth muscle contractility remains to be defined. Methods: NGF was delivered into the airways of mice either by nasal instillation or by genetic engineering. Airway reactivity was then measured by electrical field stimulation. Results: Treatment of mice with NGF induced airway hyperresponsiveness to a similar extent as demonstrated in allergen-sensitized mice. NGF-transgenic mice, overexpressing NGF in Clara cells, were hyperreactive in comparison to wild-type mice. Conclusion: These data suggest that NGF by itself determines the induction of airway hyperresponsiveness in the absence of airway inflammation in mice.

Investigating paediatric airways by non‐bronchoscopic lavage: normal cellular data

Bronchoscopic bronchoalveolar lavage in children to investigate bronchial disorders such as asthma has both ethical and procedural difficulties. The aim of this study was to establish a standardized non-bronchoscopic method to perform bronchoalveolar lavage in children attending for elective surgery to obtain normal cellular data. Bronchoalveolar lavage was performed on normal children (n = 55) by infusing saline (20 mL) through an 8 FG suction catheter passed after endotracheal intubation. Oxygen saturation, heart and respiratory rate were monitored during the bronchoalveolar lavage procedure. Cellular analysis and total protein estimation of the lavage fluid were performed. Epithelial lining fluid volume was calculated (n = 15) using the urea dilution method. The procedure was well tolerated by all children. Total cell count and differential cell count for children (macrophages 70.8 +/- 2.3%, lymphocytes 3.8 +/- 0.6%, neutrophils 5.7 +/- 1.0%, eosinophils 0.14 +/- 0.03%, epithelial cells 19.6 +/- 2.1%, mast cells 0.21 +/- 0.02%) were similar to those reported for adults. Age and sex comparisons revealed no differences between groups. The mean total protein recovered in the cell free supernatant was 49.72 +/- 4.29 mg/L and epithelial lining fluid volume was 0.82 +/- 0.11% of return lavageate. This method allows bronchoalveolar lavage to be performed safely and quickly on children attending for routine elective surgery. Using this method and taking the 'window of opportunity' of elective surgery, the presence or absence of airway inflammation could be studied in children with various patterns of asthma during relatively asymptomatic periods.