Erol Gaillard

SPLUNC1 regulates airway surface liquid volume by protecting ENaC from proteolytic cleavage

Many epithelia, including the superficial epithelia of the airways, are thought to secrete “volume sensors,” which regulate the volume of the mucosal lining fluid. The epithelial Na+ channel (ENaC) is often the rate limiting factor in fluid absorption, and must be cleaved by extracellular and/or intracellular proteases before it can conduct Na+ and absorb excess mucosal liquid, a process that can be blocked by proteases inhibitors. In the airways, airway surface liquid dilution or removal activates ENaC. Therefore, we hypothesized that endogenous proteases are membrane-anchored, whereas endogenous proteolysis inhibitors are soluble and can function as airway surface liquid volume sensors to inhibit ENaC activity. Using a proteomic approach, we identified short palate, lung, and nasal epithelial clone (SPLUNC)1 as a candidate volume sensor. Recombinant SPLUNC1 inhibited ENaC activity in both human bronchial epithelial cultures and Xenopus oocytes. Knockdown of SPLUNC1 by shRNA resulted in a failure of bronchial epithelial cultures to regulate ENaC activity and airway surface liquid volume, which was restored by adding recombinant SPLUNC1 to the airway surface liquid. Despite being able to inhibit ENaC, recombinant SPLUNC1 had little effect on extracellular serine protease activity. However, SPLUNC1 specifically bound to ENaC, preventing its cleavage and activation by serine proteases. SPLUNC1 is highly expressed in the airways, as well as in colon and kidney. Thus, we propose that SPLUNC1 is secreted onto mucosal surfaces as a soluble volume sensor whose concentration and dilution can regulate ENaC activity and mucosal volumes, including that of airway surface liquid.

Classification and pharmacological treatment of preschool wheezing: changes since 2008

Since the publication of the European Respiratory Society Task Force report in 2008, significant new evidence has become available on the classification and management of preschool wheezing disorders. In this report, an international consensus group reviews this new evidence and proposes some modifications to the recommendations made in 2008. Specifically, the consensus group acknowledges that wheeze patterns in young children vary over time and with treatment, rendering the distinction between episodic viral wheeze and multiple-trigger wheeze unclear in many patients. Inhaled corticosteroids remain first-line treatment for multiple-trigger wheeze, but may also be considered in patients with episodic viral wheeze with frequent or severe episodes, or when the clinician suspects that interval symptoms are being under reported. Any controller therapy should be viewed as a treatment trial, with scheduled close follow-up to monitor treatment effect. The group recommends discontinuing treatment if there is no benefit and taking favourable natural history into account when making decisions about long-term therapy. Oral corticosteroids are not indicated in mild-to-moderate acute wheeze episodes and should be reserved for severe exacerbations in hospitalised patients. Future research should focus on better clinical and genetic markers, as well as biomarkers, of disease severity. The distinction between episodic viral and multiple-trigger wheeze is unclear in many preschool children http://ow.ly/sKYZF

Regulation of the epithelial Na+ channel and airway surface liquid volume by serine proteases

Mammalian airways are protected from infection by a thin film of airway surface liquid (ASL) which covers airway epithelial surfaces and acts as a lubricant to keep mucus from adhering to the epithelial surface. Precise regulation of ASL volume is essential for efficient mucus clearance and too great a reduction in ASL volume causes mucus dehydration and mucus stasis which contributes to chronic airway infection. The epithelial Na+ channel (ENaC) is the rate-limiting step that governs Na+ absorption in the airways. Recent in vitro and in vivo data have demonstrated that ENaC is a critical determinant of ASL volume and hence mucus clearance. ENaC must be cleaved by either intracellular furin-type proteases or extracellular serine proteases to be active and conduct Na+, and this process can be inhibited by protease inhibitors. ENaC can be regulated by multiple pathways, and once proteolytically cleaved ENaC may then be inhibited by intracellular second messengers such as cAMP and PIP2. In the airways, however, regulation of ENaC by proteases seems to be the predominant mode of regulation since knockdown of either endogenous serine proteases such as prostasin, or inhibitors of ENaC proteolysis such as SPLUNC1, has large effects on ENaC activity in airway epithelia. In this review, we shall discuss how ENaC is proteolytically cleaved, how this process can regulate ASL volume, and how its failure to operate correctly may contribute to chronic airway disease.

Pulmonary edema in meningococcal septicemia associated with reduced epithelial chloride transport.

Objectives: To test the hypothesis that meningococcal septicemia-related pulmonary edema is associated with a systemic abnormality of epithelial sodium and chloride transport and to investigate an association with hormones regulating Na+ transport. Design: Prospective observational study. Setting: The 24-bed pediatric intensive care unit and pediatric wards of Royal Liverpool Childrens Hospital. Patients: Consecutive children admitted to the pediatric intensive care unit and pediatric wards with a diagnosis of meningococcal septicemia and children (controls) with noninfectious critical illness receiving ventilatory support in the pediatric intensive care unit. Measurements and Main Results: We measured sweat and saliva electrolytes, renal electrolyte excretion, nasal potential difference, and aldosterone, thyroxine, and cortisol levels. Pulmonary edema was diagnosed by chest radiography and its severity quantified by calculation of ventilation index at admission and duration of mechanical ventilation. We recruited 17 patients with severe meningococcal septicemia (nine patients with pulmonary edema), 14 patients with mild meningococcal septicemia, and 20 controls. Sweat andsaliva Na+ and Cl− concentrations and renal Na+ excretion were significantly (p < .05) higher in patients with pulmonary edema compared with controls. Nasal potential difference and amiloride response in patients with pulmonary edema were not significantly different to controls, but response to a low Cl− solution was reduced in the nasal airway of patients with pulmonary edema (p < .05). Sweat and saliva chloride concentrations correlated significantly and better with ventilation index and duration of ventilation than sodium concentrations. Aldosterone, thyroxine, and cortisol levels were not significantly different between groups. Conclusions: We have confirmed that meningococcal septicemia-related pulmonary edema is associated with reduced systemic sodium and chloride transport. Features of reduced Cl− transport were most closely associated with markers of respiratory compromise, and this was supported by the reduced chloride channel function detected on nasal potential difference measurement.

A simple asthma prediction tool for preschool children with wheeze or cough

BACKGROUND Many preschool children have wheeze or cough, but only some have asthma later. Existing prediction tools are difficult to apply in clinical practice or exhibit methodological weaknesses. OBJECTIVE We sought to develop a simple and robust tool for predicting asthma at school age in preschool children with wheeze or cough. METHODS From a population-based cohort in Leicestershire, United Kingdom, we included 1- to 3-year-old subjects seeing a doctor for wheeze or cough and assessed the prevalence of asthma 5 years later. We considered only noninvasive predictors that are easy to assess in primary care: demographic and perinatal data, eczema, upper and lower respiratory tract symptoms, and family history of atopy. We developed a model using logistic regression, avoided overfitting with the least absolute shrinkage and selection operator penalty, and then simplified it to a practical tool. We performed internal validation and assessed its predictive performance using the scaled Brier score and the area under the receiver operating characteristic curve. RESULTS Of 1226 symptomatic children with follow-up information, 345 (28%) had asthma 5 years later. The tool consists of 10 predictors yielding a total score between 0 and 15: sex, age, wheeze without colds, wheeze frequency, activity disturbance, shortness of breath, exercise-related and aeroallergen-related wheeze/cough, eczema, and parental history of asthma/bronchitis. The scaled Brier scores for the internally validated model and tool were 0.20 and 0.16, and the areas under the receiver operating characteristic curves were 0.76 and 0.74, respectively. CONCLUSION This tool represents a simple, low-cost, and noninvasive method to predict the risk of later asthma in symptomatic preschool children, which is ready to be tested in other populations.

What is the clinical significance of filamentous fungi positive sputum cultures in patients with cystic fibrosis

In patients with cystic fibrosis (CF), the isolation of filamentous fungi, in particular Aspergillus spp. in the respiratory secretions is a common occurrence. Most of these patients do not fulfil the clinical criteria for a diagnosis of allergic bronchopulmonary aspergillosis (ABPA). The clinical relevance of filamentous fungi and whether antifungal therapy should be started in patients with persistent respiratory exacerbations who do not respond to two or more courses of appropriate oral or intravenous antibiotics and in whom no other organisms are isolated from respiratory secretions is a dilemma for the CF clinician. In this article, we review the epidemiology and clinical significance of filamentous fungi in the non-ABPA CF lung, with an emphasis on Aspergillus spp. colonisation (AC), the clinical relevance of Aspergillus spp. positive respiratory cultures and the outcome following antifungal therapy in these patients.

Improved survival and neurodevelopmental outcome after prolonged ventilation in preterm neonates who have received antenatal steroids and surfactant

AIMS To assess survival and neurodevelopmental outcome following prolonged ventilation beyond 27 or 49 days of postnatal life in neonates treated with antenatal steroids and surfactant. METHODS The medical records of 84 babies born in 1994–1996 requiring ventilation after 27 postnatal days at Liverpool Womens Hospital were reviewed to determine the duration of mechanical ventilation, survival, and neurodevelopmental outcome at 3 years of age. RESULTS Fifty six babies were mechanically ventilated after 27 postnatal days but for less than 50 days; 48 (86%) survived to 3 years. Twenty six (54%) of the survivors had normal neurodevelopment at 3 years and seven (15%) had only mild disability. Twenty eight babies were ventilated after 49 postnatal days; 14 survived to 3 years. Five of these survivors were neurodevelopmentally normal at 3 years and two had mild disability. CONCLUSIONS Survival decreases with more prolonged ventilation. When antenatal steroids and postnatal surfactant are used, there appears to be improved survival and neurodevelopmental outcome in preterm babies who require prolonged ventilation.

Carbon in airway macrophages from children with asthma

Background Airway macrophage (AM) phagocytosis is impaired in severe asthma. Prostaglandin (PG) E2 and D2 are increased in severe asthma and suppress AM phagocytic function in vitro. In this study, we sought evidence for PG-mediated impairment of phagocytosis of inhalable carbonaceous particulate matter (PM) by AM in children with severe asthma compared with mild asthmatics and healthy controls. Methods AM were obtained from children with asthma and healthy controls using induced sputum. AM carbon area (μm2) was assessed by image analysis. In a subgroup of asthmatics, urinary PGE2 and PGD2 metabolites were measured by high-performance liquid chromatography, and PM exposure at the home address was modelled. Phagocytosis of PM by human monocyte-derived macrophages and rat AM was assessed in vitro by image analysis. Results AM carbon was 51% lower in children with moderate-to-severe asthma (n=36) compared with mild asthmatics (n=12, p<0.01) and healthy controls (n=47, p<0.01). There was no association between modelled PM exposure and AM carbon in 33 asthmatics who had a urine sample, but there was an inverse association between AM carbon and urinary metabolites of PGE2 and D2 (n=33, rs=−0.40, p<0.05, and rs=−0.44, p<0.01). PGE2 10−6 M, but not PGD2 10−6 M, suppressed phagocytosis of PM10 by human macrophages in vitro (p<0.05 vs control). PGE2 10−6 M also suppressed phagocytosis of PM10 by rat AM in vitro (p<0.01 vs control). Conclusions Phagocytosis of inhaled carbonaceous PM by AMs is impaired in severe asthma. PGE2 may contribute to impaired AM phagocytic function in severe asthma.

Blood eosinophils as a marker of likely corticosteroid response in children with preschool wheeze: time for an eosinophil guided clinical trial?

Childhood wheezing is common particularly in children under the age of 6 years and in this age group is generally referred to as preschool wheezing. Particular diagnostic and treatment uncertainties exist in these young children due to the difficulty in obtaining objective evidence of reversible airways narrowing and inflammation. A diagnosis of asthma depends on the presence of relevant clinical signs and symptoms and the demonstration of reversible airways narrowing on lung function testing, which is difficult to perform in young children. Few treatments are available and inhaled corticosteroids are the recommended preventer treatment in most international asthma guidelines. There is, however, considerable controversy about its effectiveness in children with preschool wheeze and a corticosteroid responder phenotype has not been established. These diagnostic and treatment uncertainties in conjunction with the knowledge of corticosteroid side effects, in particular the reduction of growth velocity, have resulted in a variable approach to inhaled corticosteroid prescribing by medical practitioners and a reluctance in carers to regularly administer the treatment. Identifying children who are likely responders to corticosteroid therapy would be a major benefit in the management of this condition. Eosinophils have emerged as a promising biomarker of corticosteroid responsive airways disease, and evaluation of this biomarker in sputum has successfully been employed to direct management in adults with asthma. Obtaining sputum from young children is time consuming and difficult, and it is hard to justify more invasive procedures such as a bronchoscopy in young children routinely. Recently, in children, interest has shifted to assessing the value of less invasive biomarkers of likely corticosteroid response and the biomarker ‘blood eosinophils’ has emerged as an attractive candidate. The aim of this review was to summarize the evidence for blood eosinophils as a predictive biomarker for corticosteroid responsive disease with a particular focus on the difficult area of preschool wheeze.

Copy Number Variation of the Beta-Defensin Genes in Europeans: No Supporting Evidence for Association with Lung Function, Chronic Obstructive Pulmonary Disease or Asthma

Lung function measures are heritable, predict mortality and are relevant in diagnosis of chronic obstructive pulmonary disease (COPD). COPD and asthma are diseases of the airways with major public health impacts and each have a heritable component. Genome-wide association studies of SNPs have revealed novel genetic associations with both diseases but only account for a small proportion of the heritability. Complex copy number variation may account for some of the missing heritability. A well-characterised genomic region of complex copy number variation contains beta-defensin genes (DEFB103, DEFB104 and DEFB4), which have a role in the innate immune response. Previous studies have implicated these and related genes as being associated with asthma or COPD. We hypothesised that copy number variation of these genes may play a role in lung function in the general population and in COPD and asthma risk. We undertook copy number typing of this locus in 1149 adult and 689 children using a paralogue ratio test and investigated association with COPD, asthma and lung function. Replication of findings was assessed in a larger independent sample of COPD cases and smoking controls. We found evidence for an association of beta-defensin copy number with COPD in the adult cohort (OR = 1.4, 95%CI:1.02–1.92, P = 0.039) but this finding, and findings from a previous study, were not replicated in a larger follow-up sample(OR = 0.89, 95%CI:0.72–1.07, P = 0.217). No robust evidence of association with asthma in children was observed. We found no evidence for association between beta-defensin copy number and lung function in the general populations. Our findings suggest that previous reports of association of beta-defensin copy number with COPD should be viewed with caution. Suboptimal measurement of copy number can lead to spurious associations. Further beta-defensin copy number measurement in larger sample sizes of COPD cases and children with asthma are needed.