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1.  Pulmonary Function Measures Predict Mortality Differently in Idiopathic Pulmonary Fibrosis versus Combined Pulmonary Fibrosis and Emphysema 
The European respiratory journal  2010;38(1):176-183.
The composite physiologic index(CPI) was derived to represent the extent of fibrosis on high resolution computed tomography, adjusting for emphysema in patients with idiopathic pulmonary fibrosis(IPF). We hypothesized longitudinal change in CPI would better predict mortality than forced expiratory volume in 1 second(FEV1), forced vital capacity(FVC), or diffusing capacity for carbon monoxide(DLCO) in all patients with IPF, and especially in those with combined pulmonary fibrosis and emphysema(CPFE).
Cox proportional hazard models were performed on pulmonary function data from IPF patients at baseline (n=321), 6 months (n=211) and 12 months (n=144). Presence of CPFE was determined by high resolution computed tomography.
A 5 point increase in CPI over 12 months predicted subsequent mortality (HR 2.1, p=0.004). At 12 months, a 10% relative decline in FVC, a 15% relative decline in DLCO or an absolute increase in CPI of 5 points all discriminated median survival by 2.1 to 2.2 years versus patients with lesser change. Half our cohort had CPFE. In patients with moderate/severe emphysema, only a 10% decline in FEV1 predicted mortality (HR 3.7, p=0.046).
In IPF, a 5 point increase in CPI over 12 months predicts mortality similarly to relative declines of 10% in FVC or 15% in DLCO. For CPFE patients, change in FEV1 was the best predictor of mortality.
PMCID: PMC4084829  PMID: 21148225
Chronic Obstructive Pulmonary Disease; Idiopathic Pulmonary Fibrosis; Prognosis; Pulmonary Function; Survival
5.  Prior cardiovascular disease increases long-term mortality in COPD patients with pneumonia 
There is controversy regarding the impact of chronic obstructive pulmonary disease (COPD) in clinical outcomes in elderly patients with pneumonia. Comorbidities such as cardiovascular disease have been reported to play an important role in patients with acute exacerbations of COPD. However, limited data are available regarding the impact of cardiovascular disease in elderly COPD patients who require hospitalisation for pneumonia.
We examined a cohort of subjects with pneumonia and pre-existing COPD. Prior cardiovascular disease was defined as history of myocardial infarction, congestive heart failure, cardiac arrhythmia, unstable angina or stroke. Outcomes examined included 30-day, 90-day, 6-month and 1-year mortality.
We included 17 140 elderly COPD patients who were hospitalised for pneumonia. Prior cardiovascular disease was present in 10 240 (59.7%) patients. Prior cardiovascular disease was independently associated with 90-day mortality (21.3% versus 19.4%; hazard ratio (HR) 1.29, 95% CI 1.02–1.17), 6-month mortality (29.0% versus 26.1%; HR 1.28, 95% CI 1.07–1.50) and 12-month mortality (39.2% versus 34.5%; HR 1.33, 95% CI 1.15–1.54) when compared to no prior cardiovascular disease. The temporal differential effect between groups increases from 1.0% at 30 days to 4.7% at 1 year.
Prior cardiovascular disease is associated with increased long-term mortality in elderly COPD patients with pneumonia. Differences in mortality rates increased over time.
PMCID: PMC4066656  PMID: 23598950
6.  Pulmonary MMP-9 Activity in Mechanically Ventilated Children with RSV Disease 
The European respiratory journal  2013;43(4):1086-1096.
RSV infection is a potent stimulus for airway epithelial expression of MMP-9, and MMP-9 activity in vivo is a predictor of disease severity in children with RSV-induced respiratory failure (RSV-RF).
Human airway epithelial cells were infected with RSV A2 strain, and analyzed for MMP-9 and tissue inhibitor of metalloproteinases-1 (TIMP-1, a natural inhibitor of MMP-9) release. In addition, endotracheal samples from children with RSV-RF and controls (non-RSV pneumonia and non-lung disease controls) were analyzed for MMP-9, TIMP-1, human neutrophil elastase (HNE) and myeloperoxidase (MPO) activity.
RSV infection of airway epithelia was sufficient to rapidly induce MMP-9 transcription and protein release. Pulmonary MMP-9 activity peaked at 48 hours in infants with RSV-RF compared to controls. In the RSV group, MMP-9 activity and MMP-9:TIMP-1 ratio imbalance predicted higher oxygen requirement and worse Pediatric Risk of Mortality scores. Highest levels of HNE and MPO were measured in the RSV cohort but unlike MMP-9, these neutrophil markers failed to predict disease severity.
These results support the hypothesis that RSV is a potent stimulus for MMP-9 expression and release from human airway epithelium, and that MMP-9 is an important biomarker of disease severity in mechanically ventilated children with RSV lung infection.
PMCID: PMC4059407  PMID: 24311764
7.  APOM and High-Density Lipoprotein are associated with Lung Function and Percent Emphysema 
The European respiratory journal  2013;43(4):1003-1017.
Chronic obstructive pulmonary disease (COPD) is linked to cardiovascular disease; however, there are few studies on the associations of cardiovascular genes with COPD.
We assessed the association of lung function with 2,100 genes selected for cardiovascular diseases among 20,077 European-Americans and 6,900 African-Americans. We performed replication of significant loci in the other racial group and an independent consortium of Europeans, tested the associations of significant loci with percent emphysema, and examined gene expression in an independent sample. We then tested the association of a related lipid biomarker with FEV1/FVC and percent emphysema.
We identified one new polymorphism for FEV1/FVC (rs805301) in European-Americans (p=1.3×10−6) and a second (rs707974) in the combined European-American and African-American analysis (p=1.38×10−7). Both SNPs flank the gene for apolipoprotein M (apoM), a component of HDL. Both replicated in an independent cohort. SNPs in a second gene related to apoM and HDL, PCSK9, were associated with FEV1/FVC among African-Americans. rs707974 was associated with percent emphysema among European-Americans and African-Americans, and APOM expression was related to FEV1/FVC and percent emphysema. Higher HDL levels were associated with lower FEV1/FVC and greater percent emphysema.
These findings suggest a novel role for the APOM/HDL pathway in the pathogenesis of COPD and emphysema.
PMCID: PMC4041087  PMID: 23900982
Apolipoproteins; Cholesterol; Percent Emphysema; Polymorphism, Single Nucleotide; Pulmonary Disease, Chronic Obstructive
8.  Apoptotic cell clearance and fibrotic lung disease 
The European respiratory journal  2012;40(2):289-290.
PMCID: PMC4036233  PMID: 22855466
9.  The role of matrix metalloproteases in cystic fibrosis lung disease 
The European respiratory journal  2011;38(3):721-727.
Significant airway remodeling is a major component of the increased morbidity and mortality observed in cystic fibrosis (CF) patients. These airways feature ongoing leukocytic inflammation and unrelenting bacterial infection. In contrast to acute bacterial pneumonia, CF infection is not cleared efficiently and the ensuing inflammatory response causes tissue damage. This structural damage is mainly a result of free proteolytic activity released by infiltrated neutrophils and macrophages. Major proteases in this disease are serine and matrix metalloproteases (MMPs). While the role of serine proteases, such as elastase, has been characterized in detail, there is emerging evidence that MMPs could play a key role in the pathogenesis of CF lung disease. This review summarizes studies linking MMPs with CF lung disease and discusses the potential value of MMPs as future therapeutic targets in CF and other chronic lung diseases.
PMCID: PMC4036453  PMID: 21233269
Cystic fibrosis; lung disease; elastase; neutrophil; proteases; antiproteases
10.  Exhaled Nitric Oxide, Susceptibility and New-Onset Asthma in the Children’s Health Study 
The European respiratory journal  2010;37(3):523-531.
A substantial body of evidence suggests an etiologic role of inflammation and oxidative/nitrosative stress in asthma pathogenesis. Fractional concentration of nitric oxide in exhaled air (FeNO) may provide a non-invasive marker of oxidative/nitrosative stress and aspects of airway inflammation. We examined whether children with elevated FeNO are at increased risk for new-onset asthma.
We prospectively followed 2206 asthma-free children (age 7–10 years) who participated in the Children’s Health Study. We measured FeNO and followed these children for three years to ascertain incident asthma cases. Cox proportional hazard models were fitted to examine the association between FeNO and new-onset asthma.
We found that FeNO was associated with increased risk of new-onset asthma. Children with the highest quartile of FeNO had more than a two-fold increased risk of new-onset asthma compared to those with the lowest quartile (hazard ratio: 2.1; 95% confidence interval: 1.3–3.5). This effect did not vary by child’s history of respiratory allergic symptoms. However, the effect of elevated FeNO on new-onset asthma was most apparent among those without a parental history of asthma.
Our results indicate that children with elevated FeNO are at increased risk for new-onset asthma, especially if they have no parental history of asthma.
PMCID: PMC4020940  PMID: 20634264
Incident Asthma; Exhaled Nitric Oxide; Airway Inflammation
11.  Pathobiology of pulmonary arterial hypertension and right ventricular failure 
The European respiratory journal  2012;40(6):1555-1565.
Pulmonary arterial hypertension (PAH) is no longer an orphan disease. There are three different classes of drugs for the treatment of PAH that are currently being used and an increasing number of patients are being treated with a single drug or combination therapy. During the last 25 yrs, new insights into the pathobiology of PAH have been gained. The classical mechanical concepts of pressure, flow, shear stress, right ventricle wall stress and impedance have been complemented with the new concepts of cell injury and repair and interactions of complex multicellular systems. Integrating these concepts will become critical as we design new medical therapies in order to change the prognosis of patients with these fatal diseases. This review intends to summarise recent pathobiological concepts of PAH and right ventricle failure mainly derived from human studies, which reflect the progress made in the understanding of this complex group of pulmonary vascular diseases.
PMCID: PMC4019748  PMID: 22743666
Bone morphogenic type II receptor; genetics; growth factors; inflammation
12.  The fibroproliferative response in acute respiratory distress syndrome: mechanisms and clinical significance 
The European respiratory journal  2013;43(1):276-285.
Acute respiratory distress syndrome (ARDS) continues to be a major healthcare problem, affecting >190 000 people in the USA annually, with a mortality of 27–45%, depending on the severity of the illness and comorbidities. Despite advances in clinical care, particularly lung protective strategies of mechanical ventilation, most survivors experience impaired health-related quality of life for years after the acute illness. While most patients survive the acute illness, a subset of ARDS survivors develops a fibroproliferative response characterised by fibroblast accumulation and deposition of collagen and other extracellular matrix components in the lung.
Historically, the development of severe fibroproliferative lung disease has been associated with a poor prognosis with high mortality and/or prolonged ventilator dependence. More recent studies also support a relationship between the magnitude of the fibroproliferative response and long-term health-related quality of life. The factors that determine which patients develop fibroproliferative ARDS and the cellular mechanisms responsible for this pathological response are not well understood.
This article reviews our current understanding of the contribution of pulmonary dysfunction to mortality and to quality of life in survivors of ARDS, the mechanisms driving pathological fibroproliferation and potential therapeutic approaches to prevent or attenuate fibroproliferative lung disease.
PMCID: PMC4015132  PMID: 23520315
13.  Cardiovascular Disease Biomarkers Predict Susceptibility or Resistance to Lung Injury in World Trade Center Dust Exposed Firefighters 
Pulmonary vascular loss is an early feature of chronic obstructive pulmonary disease. Biomarkers of inflammation and of metabolic syndrome, predicts loss of lung function in World Trade Center Lung Injury (WTC-LI). We investigated if other cardiovascular disease (CVD) biomarkers also predicted WTC-LI.
This nested case-cohort study used 801 never smoker, WTC exposed firefighters with normal pre-9/11 lung function presenting for subspecialty pulmonary evaluation (SPE) before March, 2008. A representative sub-cohort of 124/801 with serum drawn within six months of 9/11 defined CVD biomarker distribution. Post-9/11/01 FEV1 at subspecialty exam defined cases: susceptible WTC-LI cases with FEV1≤77% predicted (66/801) and resistant WTC-LI cases with FEV1≥107% (68/801). All models were adjusted for WTC exposure intensity, BMI at SPE, age at 9/11, and pre-9/11 FEV1.
Susceptible WTC-LI cases had higher levels of Apo-AII, CRP, and MIP-4 with significant RRs of 3.85, 3.93, and 0.26 respectively with an area under the curve (AUC) of 0.858. Resistant WTC-LI cases had significantly higher sVCAM and lower MPO with RRs of 2.24, and 2.89 respectively; AUC 0.830.
Biomarkers of CVD in serum six-month post-9/11 predicted either susceptibility or resistance to WTC-LI. These biomarkers may define pathways producing or protecting subjects from pulmonary vascular disease and associated loss of lung function after an irritant exposure.
PMCID: PMC3642231  PMID: 22903969
Airway Inflammation; Cytokines; Pulmonary Funtion Testing
14.  High risk and rapid appearance of multidrug resistance during tuberculosis treatment in Moldova 
The European respiratory journal  2014;43(4):1132-1141.
Multidrug-resistant tuberculosis (MDR-TB) is a serious problem in the former Soviet Union and may appear during TB treatment. We aimed to estimate the prevalence of, timing of and factors associated with MDR-TB diagnosis during TB treatment in Moldova, which was part of the former Soviet Union.
We analysed data on 3 754 confirmed non-MDR-TB cases (between January 1, 2007 and December 31, 2010) in the Moldovan TB surveillance database, where patients provided sputum specimens for drug-susceptibility testing, multiple times, during treatment. We estimated the percentage of individuals with confirmed baseline non-MDR-TB that were diagnosed with MDR-TB during treatment, documented the time at which MDR-TB was diagnosed, and used a failure-time model to identify factors associated with MDR-TB diagnosis.
Between 7.2% and 9.2% of initially non-MDR-TB cases were diagnosed with MDR-TB during treatment. Half of these MDR-TB diagnoses occurred with 3 months of the initial diagnosis. An increased MDR-TB risk during treatment was associated with baseline resistance to first-line TB drugs (linear increase in risk per additional drug), previous incarceration and HIV co-infection.
MDR can appear rapidly during TB treatment. Policy considerations should emphasise management during early treatment by increasing ambulatory TB treatment to prevent nosocomial transmission, and ensuring universal rapid diagnostics access to prevent acquisition and transmission of drug resistance.
PMCID: PMC4005038  PMID: 24558181
15.  What can we learn about airway smooth muscle from the company it keeps? 
PMCID: PMC3992378  PMID: 18591333
16.  A potential role for insulin resistance in experimental pulmonary hypertension 
The European respiratory journal  2012;41(4):861-871.
Patients with pulmonary arterial hypertension have increased prevalence of insulin resistance. We aimed to determine whether metabolic defects are associated with bone morphogenic protein receptor type 2 (Bmpr2) mutations in mice, and whether these may contribute to pulmonary vascular disease development.
Metabolic phenotyping was performed on transgenic mice with inducible expression of Bmpr2 mutation, R899X. Phenotypic penetrance in Bmpr2R899X was assessed in a high-fat diet model of insulin resistance. Alterations in glucocorticoid responses were assessed in murine pulmonary microvascular endothelial cells and Bmpr2R899X mice treated with dexamethasone.
Compared to controls, Bmpr2R899X mice showed increased weight gain and demonstrated insulin resistance as assessed by the homeostatic model assessment insulin resistance (1.0±0.4 versus 2.2±1.8) and by fat accumulation in skeletal muscle and decreased oxygen consumption. Bmpr2R899X mice fed a high-fat diet had strong increases in pulmonary hypertension penetrance (seven out of 11 versus three out of 11). In cell culture and in vivo experiments, Bmpr2 mutation resulted in a combination of constitutive glucocorticoid receptor activation and insensitivity.
Insulin resistance is present as an early feature of Bmpr2 mutation in mice. Exacerbated insulin resistance through high-fat diet worsened pulmonary phenotype, implying a possible causal role in disease. Impaired glucocorticoid responses may contribute to metabolic defects.
PMCID: PMC3746982  PMID: 22936709
Dexamethasone; glucocorticoid; homeostatic model assessment of insulin resistance; insulin resistance; mouse model; pulmonary hypertension
17.  Obesity and asthma: location, location, location 
The European respiratory journal  2013;41(2):253-254.
PMCID: PMC3966106  PMID: 23370797
18.  Arsenic exposure from drinking water and dyspnoea risk in Araihazar, Bangladesh: a population-based study 
The European respiratory journal  2011;39(5):1076-1083.
Bangladesh has high well water arsenic exposure. Chronic arsenic ingestion may result in diseases that manifest as dyspnoea, although information is sparse.
Baseline values were obtained from an arsenic study. Trained physicians ascertained data on dyspnoea among 11,746 subjects. Data were collected on demographic factors, including smoking, blood pressure and arsenic exposure. Logistic regression models estimated odds ratios and confidence intervals for the association between arsenic exposure and dyspnoea.
The adjusted odds of having dyspnoea was 1.32-fold (95% CI 1.15–1.52) greater in those exposed to high well water arsenic concentrations (≥50 μg·L−1) compared with low-arsenic-exposed nonsmokers (p<0.01). A significant dose–response relationship was found for arsenic (as well as smoking) in relation to dyspnoea. In nonsmokers, the adjusted odds of having dyspnoea were 1.36, 1.96, 2.34 and 1.80-fold greater for arsenic concentrations of 7–38, 39–90, 91–178 and 179–864 μg·L−1, respectively, compared with the reference arsenic concentration of <7 μg·L−1 (p<0.01; Chi-squared test for trend).
Arsenic exposure through well water is associated with dyspnoea, independently of smoking status. This study suggests that mandated well water testing for arsenic with reduction in exposure may significantly reduce diseases that manifest as dyspnoea, usually cardiac or pulmonary.
PMCID: PMC3955754  PMID: 22088973
Arsenicosis; dyspnoea dose–response; environmental dyspnoea
19.  The resistive and elastic work of breathing during exercise in patients with chronic heart failure 
The European respiratory journal  2011;39(6):1449-1457.
Patients with heart failure (HF) display numerous derangements in ventilatory function, which together serve to increase the work of breathing (Wb) during exercise. However, the extent to which the resistive and elastic properties of the respiratory system contribute to the higher Wb in these patients is unknown.
We quantified the resistive and elastic Wb in patients with stable HF (n=9; New York Heart Association functional class I–II) and healthy control subjects (n=9) at standardised levels of minute ventilation (V′E) during graded exercise. Dynamic lung compliance was systematically lower for a given level of V′E in HF patients than controls (p<0.05). HF patients displayed slightly higher levels of inspiratory elastic Wb with greater amounts of ventilatory constraint and resistive Wb than control subjects during exercise (p<0.05).
Our data indicates that the higher Wb in HF patients is primarily due to a greater resistive, rather than elastic, load to breathing. The greater resistive Wb in these patients probably reflects an increased hysteresivity of the airways and lung tissues. The marginally higher inspiratory elastic Wb observed in HF patients appears related to a combined decrease in the compliances of the lungs and chest wall. The clinical and physiological implications of our findings are discussed.
PMCID: PMC3951372  PMID: 22034652
Heart failure; respiratory mechanics; work of breathing
20.  Association of Lung Function, Chest Radiographs and Clinical Features in Infants with Cystic Fibrosis 
The European respiratory journal  2013;42(6):10.1183/09031936.00138412.
The optimal strategy for monitoring cystic fibrosis (CF) lung disease in infancy remains unclear.
To describe longitudinal associations between infant pulmonary function tests (iPFTs), chest radiograph (CXR) scores and other characteristics.
CF patients ≤ 24 months old were enrolled in a 10-center study evaluating iPFTs 4 times over a year. CXRs ~1 year apart were scored with the Wisconsin and Brasfield systems. Associations of iPFT parameters with clinical characteristics were evaluated with mixed effects models.
The 100 participants contributed 246 acceptable flow/volume (FEV0.5, FEF75) and 303 acceptable functional residual capacity (FRC) measurements and 171 CXRs. Both Brasfield and Wisconsin CXR scores worsened significantly over the 1 year interval. Worse Wisconsin CXR scores and S. aureus were both associated with hyperinflation (significantly increased FRC) but not with diminished FEV0.5 or FEF75. Parent-reported cough was associated with significantly diminished FEF75 but not with hyperinflation.
In this infant cohort in whom we previously reported worsening in average lung function, CXR scores also worsened over a year. The significant associations detected between both Wisconsin CXR score and S. aureus and hyperinflation, as well as between cough and diminished flows, reinforce the ability of iPFTs and CXRs to detect early CF lung disease.
PMCID: PMC3795977  PMID: 23722613
cystic fibrosis; imaging; infants; lung function
21.  MEK modulates force-fluctuation-induced relengthening of canine tracheal smooth muscle 
The European respiratory journal  2010;36(3):630-637.
Tidal breathing, and especially deep breathing, is known to antagonise bronchoconstriction caused by airway smooth muscle (ASM) contraction; however, this bronchoprotective effect of breathing is impaired in asthma. Force fluctuations applied to contracted ASM in vitro cause it to relengthen, force-fluctuation-induced relengthening (FFIR). Given that breathing generates similar force fluctuations in ASM, FFIR represents a likely mechanism by which breathing antagonises bronchoconstriction. Thus it is of considerable interest to understand what modulates FFIR, and how ASM might be manipulated to exploit this phenomenon. It was demonstrated previously that p38 mitogen-activated protein kinase (MAPK) signalling regulates FFIR in ASM strips. Here, it was hypothesised that the MAPK kinase (MEK) signalling pathway also modulates FFIR.
In order to test this hypothesis, changes in FFIR were measured in ASM treated with the MEK inhibitor, U0126 (1,4-diamino-2,3-dicyano-1,4-bis[2-aminophenylthio]butadiene).
Increasing concentrations of U0126 caused greater FFIR. U0126 reduced extracellular signal-regulated kinase 1/2 phosphorylation without affecting isotonic shortening or 20-kDa myosin light chain and p38 MAPK phosphorylation. However, increasing concentrations of U0126 progressively blunted phosphorylation of high-molecular-weight caldesmon (h-caldesmon), a downstream target of MEK. Thus changes in FFIR exhibited significant negative correlation with h-caldesmon phosphorylation.
The present data demonstrate that FFIR is regulated through MEK signalling, and suggest that the role of MEK is mediated, in part, through caldesmon.
PMCID: PMC3918254  PMID: 20110395
Airway smooth muscle; asthma; bronchoconstriction; smooth muscle mechanics; tidal breathing
22.  Caveolin-1 regulation of store-operated Ca2+ influx in human airway smooth muscle 
The European respiratory journal  2012;40(2):470-478.
Caveolae, plasma membrane invaginations with constitutive caveolin proteins, harbour proteins involved in intracellular calcium ([Ca2+]i) regulation. In human airway smooth muscle (ASM), store-operated Ca2+ entry (SOCE) is a key component of [Ca2+]i regulation, and contributes to increased [Ca2+]i in inflammation. SOCE involves proteins Orai1 and stromal interaction molecule (STIM)1. We investigated the link between caveolae, SOCE and inflammation in ASM.
[Ca2+]i was measured in human ASM cells using fura-2. Small interference RNA (siRNA) or overexpression vectors were used to alter expression of caveolin-1 (Cav-1), Orai1 or STIM1. Tumour necrosis factor (TNF)-α was used as a representative pro-inflammatory cytokine.
TNF-α increased SOCE following sarcoplasmic reticulum Ca2+ depletion, and increased whole-cell and caveolar Orai1 (but only intracellular STIM1). Cav-1 siRNA decreased caveolar and whole-cell Orai1 (but not STIM1) expression, and blunted SOCE, even in the presence of TNF-α. STIM1 overexpression substantially enhanced SOCE: an effect only partially reversed by Cav-1 siRNA. In contrast, Orai1 siRNA substantially blunted SOCE even in the presence of TNF-α. Cav-1 overexpression significantly increased Orai1 expression and SOCE, especially in the presence of TNF-α.
These results demonstrate that caveolar expression and regulation of proteins such as Orai1 are important for [Ca2+]i regulation in human ASM cells and its modulation during inflammation.
PMCID: PMC3914149  PMID: 22241747
Asthma; caveolae; cytokine; inflammation; Orai1; stromal interaction molecule 1
25.  Muscarinic receptor subtypes in cilia-driven transport and airway epithelial development 
The European respiratory journal  2009;33(5):1113-1121.
Ciliary beating of airway epithelial cells drives the removal of mucus and particles from the airways. Mucociliary transport and possibly airway epithelial development are governed by muscarinic acetylcholine receptors but the precise roles of the subtypes involved are unknown.
This issue was addressed by determining cilia-driven particle transport, ciliary beat frequency, and the composition and ultrastructural morphology of the tracheal epithelium in M1–M5 muscarinic receptor gene-deficient mice.
Knockout of M3 muscarinic receptors prevented an increase in particle transport speed and ciliary beat frequency in response to muscarine. Furthermore, the ATP response after application of muscarine was blunted. Pretreatment with atropine before application of muscarine restored the response to ATP. Additional knockout of the M2 receptor in these mice partially restored the muscarine effect most likely through the M1 receptor and normalized the ATP response. M1, M4, and M5 receptor deficient mice exhibited normal responses to muscarine. None of the investigated mutant mouse strains had any impairment of epithelial cellular structure or composition.
In conclusion, M3 receptors stimulate whereas M2 receptors inhibit cilia-driven particle transport. The M1 receptor increases cilia-driven particle transport if the M3 and M2 receptor are missing. None of the receptors is necessary for epithelial development.
PMCID: PMC3895332  PMID: 19213795
cholinergic signal transduction; epithelial development; knockout mice; mucociliary clearance

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