Search

Single nucelotide polymorphisms (SNPs) at the FAM13A locus are among the most commonly reported risk alleles associated with chronic obstructive pulmonary disease (COPD) and other respiratory diseases; however, the physiological role of FAM13A is unclear. In humans, two major protein isoforms are expressed at the FAM13A locus: "long" and "short," but their functions remain unknown, partly because of a lack of isoform conservation in mice. We performed in-depth characterization of organotypic primary human airway epithelial cell subsets and show that multiciliated cells predominantly express the FAM13A long isoform containing a putative N-terminal Rho GTPase-activating protein (RhoGAP) domain. Using purified proteins, we directly demonstrate the RhoGAP activity of this domain. In Xenopus laevis, which conserve the long-isoform, Fam13a deficiency impaired cilia-dependent embryo motility. In human primary epithelial cells, long-isoform deficiency did not affect multiciliogenesis but reduced cilia coordination in mucociliary transport assays. This is the first demonstration that FAM13A isoforms are differentially expressed within the airway epithelium, with implications for the assessment and interpretation of SNP effects on FAM13A expression levels. We also show that the long FAM13A isoform coordinates cilia-driven movement, suggesting that FAM13A risk alleles may affect susceptibility to respiratory diseases through deficiencies in mucociliary clearance. [ABSTRACT FROM AUTHOR]

Objectives: Saccharin test (ST) is a convenient method to assess the efficiency of mucociliary clearance, the primary defense mechanism of the upper airways' tract. The study objectives are to: (1) substantiate its short- (3 days) and long-term (30 days) repeatability; (2) assess its tolerability; (3) conduct a systematic literature review and to compare our results with the existing evidence. Methods: Twenty-nine healthy subjects were enrolled in an observational prospective study to perform an ST on three separate visits (at baseline; at follow-up visits at day 3 and at day 30). Transit times were recorded and self-reported nasal and general symptoms noted. A systematic review of the literature was conducted to compare our results with the existing literature. Results: The mean values (±SD) of ST transit time (STTT) were 7.085 (±2.19), 7.788 (±2.11), and 7.790 (±2.06) minutes at baseline, day 3, and day 30, respectively. Significant linear regression analysis was observed between day 3 and baseline (r =.193; P =.019) and day 30 and baseline (r =.182 P =.024). Significant agreement for the intrasession repeatability was observed with an ICC =.354 (P =.001). Outcomes' comparisons between baseline vs day 3 (P =.197) and baseline vs day 30 (P =.173) were not statistically significant. ST was well tolerated. Concordance with existing literature's data and high level of STTT repeatability were confirmed by the qualitative analysis. Conclusion: STTT reproducibility was good both in the short- and long-term. ST tolerability was very good. Our study data are consistent with the existing literature, indicating ST as a sound methodology for detection of early respiratory health changes and for specific regulatory application in respiratory research. [ABSTRACT FROM AUTHOR]

Background: Recent studies show e-cigarette (EC) users have increased rates of chronic bronchitic symptoms that may be associated with depressed mucociliary clearance (MCC). Little is known about the acute or chronic effects of EC inhalation on in vivo MCC. Methods:In vivo MCC was measured in young adult vapers (n = 5 males, mean age = 21) after controlled inhalation of a radiolabeled (Tc99m sulfur colloid) aerosol. Whole-lung clearance of radiolabeled deposited particles was measured over a 90-minute period for baseline MCC and associated with controlled periodic vaping over the first 60 minutes of MCC measurements. The vaping challenge was administered from a fourth generation box mod EC containing unflavored e-liquid (65% propylene glycol/35% vegetable glycerin, 3 mg/mL freebase nicotine). The challenge was administered at the start of each 10-minute interval of MCC measurements and consisted of 1 puff every 30 seconds for 5 minutes (i.e., 10 puffs for each 10-minute period for a total of 60 puffs during the initial 60 minutes of MCC measurements). Results: Compared with baseline, peripheral lung average clearance (%) over the 90 minutes of MCC measures was enhanced, associated with EC challenge, 12 (±6) versus 24 (±6), respectively (p < 0.05 by Wilcoxon signed-rank test). Conclusions: Acute enhancement of in vivo MCC during EC challenge is contrary to recent studies showing nicotine-associated slowing of ciliary beat and mucus transport at higher nicotine levels than those used here. However, our findings are consistent with an acute increase in fluid volume and mucin secretion to the bronchial airway surface that is likely short lived. Research reported in this publication was supported by the National Institutes of Health R01HL139369 and registered with ClinicalTrials.gov (NCT03700892). [ABSTRACT FROM AUTHOR]

Background Methods Results Conclusions Elexacaftor/tezacaftor/ivacaftor (ETI), a combination cystic fibrosis transmembrane receptor (CFTR) modulator, has demonstrated improved pulmonary outcomes in individuals with cystic fibrosis (CF). However, ETI's impact on functional endoscopic sinus surgery (FESS) remains unclear.The TriNetX Analytics Research Network, consisting of 120 million global de‐identified electronic medical records, was queried from 2012 to 2023 for subjects with CF who underwent sinus surgery.1 Patients on ETI prior to FESS (n = 6,056) were propensity score matched to control individuals with CF not on CFTR modulators (n = 37,906) and those on other FDA‐approved CFTR modulators (tezacaftor/ivacaftor, lumacaftor/ivacaftor, and ivacaftor) (n = 2437) based on relevant factors. The primary outcome was the absolute risk reduction (ARR) of undergoing FESS. Secondary outcomes included ARR of CF‐related pulmonary exacerbations and hospital admission from 0 to 6, 6 to 12, and 12 to 24 months following FESS.ETI use demonstrated a significant ARR for FESS when compared to CF patients not on CFTR modulators (2.12%; 95% confidence interval [CI] 1.5–2.75; p‐value < 0.0001) and those on other CFTR modulators (4.7%; 95% CI 3.54–5.85; p‐value < 0.0001). No significant differences occurred in secondary outcomes between ETI and non‐CFTR modulator groups, except for reduced CF‐related pulmonary exacerbations from 0 to 6 months post‐FESS. Additionally, a significant reduction in pulmonary exacerbations was observed at all time points and hospital admissions within 6 months following FESS compared to those using other CFTR modulators.In a large dataset, CF patients on ETI demonstrated significantly reduced risk of FESS, pulmonary exacerbations, and hospital admission compared to patients not on CFTR modulators or those on other CFTR modulators, suggesting improved sinonasal disease and overall health status in CF. [ABSTRACT FROM AUTHOR]

Copyright of Retos: Nuevas Perspectivas de Educación Física, Deporte y Recreación is the property of Federacion Espanola de Asociaciones de Docentes de Educacion Fisica and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Background: Disorders of mucociliary clearance, such as cystic fibrosis (CF), primary ciliary dyskinesia (PCD) and bronchiectasis of unknown origin, are characterised by periods with increased respiratory symptoms, referred to as pulmonary exacerbations. These exacerbations are hard to predict and associated with lung function decline and the loss of quality of life. To optimise treatment and preserve lung function, there is a need for non-invasive and reliable methods of detection. Breath analysis might be such a method. Methods: We systematically reviewed the existing literature on breath analysis to detect pulmonary exacerbations in mucociliary clearance disorders. Extracted data included the study design, technique of measurement, definition of an exacerbation, identified compounds and diagnostic accuracy. Results: Out of 244 identified articles, 18 were included in the review. All studies included patients with CF and two also with PCD. Age and the definition of exacerbation differed between the studies. There were five that measured volatile organic compounds (VOCs) in exhaled breath using gas chromatography with mass spectrometry, two using an electronic nose and eleven measured organic compounds in exhaled breath condensate. Most studies showed a significant correlation between pulmonary exacerbations and one or multiple compounds, mainly hydrocarbons and cytokines, but the validation of these results in other studies was lacking. Conclusions: The detection of pulmonary exacerbations by the analysis of compounds in exhaled breath seems possible but is not near clinical application due to major differences in results, study design and the definition of an exacerbation. There is a need for larger studies, with a longitudinal design, international accepted definition of an exacerbation and validation of the results in independent cohorts. [ABSTRACT FROM AUTHOR]

Introduction: Cystic fibrosis (CF) airway disease is characterized by thick mucus and impaired mucociliary transport (MCT). Loss of functional cystic fibrosis transmembrane receptor (CFTR) leads to acidification and oxidation of airway surface mucus. Replacing bicarbonate (HCO3−) topically fails due to rapid reabsorption and neutralization, while the scavenging antioxidant, glutathione sulfhydryl (GSH), is also rapidly degraded. The objective of this study is to investigate GSH/NaHCO3 nanoparticles as novel strategy for CF airway disease. Methods: GSH/NaHCO3 poly (lactic‐co‐glycolic acid) nanoparticles were tested on primary CF (F508del/F508del) epithelial cultures to evaluate dose‐release curves, surface pH, toxicity, and MCT indices using micro‐optical coherence tomography. In vivo tests were performed in three rabbits to assess safety and toxicity. After 1 week of daily injections, histopathology, computed tomography (CT), and blood chemistries were performed and compared to three controls. Fluorescent nanoparticles were injected into a rabbit with maxillary sinusitis and explants visualized with confocal microscopy. Results: Sustained release of GSH and HCO3− with no cellular toxicity was observed over 2 weeks. Apical surface pH gradually increased from 6.54 ± 0.13 (baseline) to 7.07 ± 0.10 (24 h) (p < 0.001) and 6.87 ± 0.05 at 14 days (p < 0.001). MCT, ciliary beat frequency, and periciliary liquid were significantly increased. When injected into the maxillary sinuses of rabbits, there were no changes to histology, CT, or blood chemistries. Nanoparticles penetrated rabbit sinusitis mucus on confocal microscopy. Conclusion: Findings suggest that GSH/NaHCO3− nanoparticles are a promising treatment option for viscous mucus in CF and other respiratory diseases of mucus obstruction such as chronic rhinosinusitis. [ABSTRACT FROM AUTHOR]

Copyright of Innere Medizin (2731-7080) is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

• We tested the effect of stopping therapies in users of elexacaftor/tezacaftor/ivacaftor. • Withdrawal of hypertonic saline did not impact mucociliary clearance after 6 weeks. • Withdrawal of dornase alfa was associated with improved mucociliary clearance. Many people with CF (pwCF) desire a reduction in inhaled treatment burden after initiation of elexacaftor/tezacaftor/ivacaftor. The randomized, open-label SIMPLIFY study showed that discontinuing hypertonic saline (HS) or dornase alfa (DA) was non-inferior to continuation of each treatment with respect to change in lung function over a 6-week period. In this SIMPLIFY substudy, we used gamma scintigraphy to determine whether discontinuation of either HS or DA was associated with deterioration in the rate of in vivo mucociliary clearance (MCC) in participants ≥12 years of age. While no significant differences in MCC endpoints were associated with HS discontinuation, significant improvement in whole and peripheral lung MCC was observed after discontinuing DA. These results suggest that pwCF on ETI with mild lung disease do not experience a subclinical deterioration in MCC that could later impact health outcomes after discontinuing HS, and in fact may benefit from improved MCC after stopping DA treatment. [ABSTRACT FROM AUTHOR]

Objective: Cystic fibrosis (CF) affects multiple organs, the most severe consequences being observed in the lungs. Despite significant progress in developing CF transmembrane conductance regulator-specific treatments for CF lung disease, exploring alternative CFtargeted medications seems reasonable. We sought to evaluate the potential beneficial effects of oral benzbromarone as an adjuvant therapy in CF patients with reduced lung function. Methods: This was a prospective open-label pilot study of oral benzbromarone (100 mg/day) administered once daily for 90 days. Patients were followed at a tertiary referral center in southern Brazil. Safety was assessed by the number of reported adverse events. Secondary objectives included percent predicted FEV1 (FEV1 %) and pulmonary exacerbations. Results: Ten patients were enrolled. Benzbromarone was found to be safe, with no serious drug-related adverse events. Eight patients completed the study; the median relative change in FEV1 % tended to increase during the treatment, showing an 8% increase from baseline at the final visit. However, a nonparametric test showed that the change was not significant (p = 0.06). Of a total of ten patients, only one experienced at least one pulmonary exacerbation during the study. Conclusions: Oral benzbromarone appears to be safe, and improved FEV1 % has been observed in patients with CF. Further assessment in larger trials is warranted to elucidate whether oral benzbromarone can be a potential adjuvant therapy for CF. [ABSTRACT FROM AUTHOR]

BackgroundThe unique ability of the respiratory tract to protect the integrity of the airways by removing potentially harmful substances is defined as mucociliary clearance. This complex physiological mechanism protects the lower airways by ridding them of pollutants and pathogens. This study aimed to evaluate the potential influence of clinically relevant vasopressors on mucociliary clearance.Material and methodsThe particle transport velocity (PTV) of isolated murine tracheae was measured as a surrogate for mucociliary clearance under the influence of dopamine, norepinephrine, and vasopressin. Inhibitory substances were applied to elucidate relevant signal transduction cascades and the value and origin of calcium ions. Reverse-transcription polymerase chain reactions (RT-PCR) were performed to identify the expression of vasopressin receptor subtypes.ResultsDopamine, norepinephrine, and vasopressin significantly increased the PTV in a dose-dependent manner with half maximal effective concentrations of 0.58 µM, 1.21 µM, and 0.10 µM, respectively. Each substance increased the PTV via separate receptor pathways. While dopamine acted on D1-like receptors to increase the PTV, norepinephrine acted on β-adrenergic receptors, and vasopressin acted on V1a receptors. RT-PCR revealed the expression of V1a in the murine whole trachea and tracheal epithelium. PTV increased when protein kinase A was inhibited and norepinephrine or vasopressin were applied, but not when dopamine was applied. Phospholipase C inhibition decreased the PTV when vasopressin was applied. In general, maximum PTV was significantly reduced when extracellular calcium entry was inhibited. When intracellular calcium stores were depleted, no increase in PTV was observed after administering all three substances. Inositol trisphosphate receptor activation was found to be pivotal in the increase in murine PTV after applying dopamine and vasopressin.DiscussionDopamine, norepinephrine, and vasopressin accelerate the murine PTV via substance-specific receptor pathways. Further investigations should assess the value and interaction of these substances on mucociliary clearance in clinical practice.

Tuft cells are found in tissues with distinct stem cell compartments, tissue architecture, and luminal exposures but converge on a shared transcriptional program, including expression of taste transduction signaling pathways. Here, we summarize seminal and recent findings on tuft cells, focusing on major categories of function-instigation of type 2 cytokine responses, orchestration of antimicrobial responses, and emerging roles in tissue repair-and describe tuft cell-derived molecules used to affect these functional programs. We review what is known about the development of tuft cells from epithelial progenitors under homeostatic conditions and during disease. Finally, we discuss evidence that immature, or nascent, tuft cells with potential for diverse functions are driven toward dominant effector programs by tissue- or perturbation-specific contextual cues, which may result in heterogeneous mature tuft cell phenotypes both within and between tissues.

Air pollution plays an important role in the mortality and morbidity of chronic airway diseases, such as asthma and chronic obstructive pulmonary disease (COPD). Particulate matter (PM) is a significant fraction of air pollutants, and studies have demonstrated that it can cause airway inflammation and injury. The airway epithelium forms the first barrier of defense against inhaled toxicants, such as PM. Airway epithelial cells clear airways from inhaled irritants and orchestrate the inflammatory response of airways to these irritants by secreting various lipid mediators, growth factors, chemokines, and cytokines. Studies suggest that PM plays an important role in the pathogenesis of chronic airway diseases by impairing mucociliary function, deteriorating epithelial barrier integrity, and inducing the production of inflammatory mediators while modulating the proliferation and death of airway epithelial cells. Furthermore, PM can modulate epithelial plasticity and airway remodeling, which play central roles in asthma and COPD. This review focuses on the effects of PM on airway injury and epithelial plasticity, and the underlying mechanisms involving mucociliary activity, epithelial barrier function, airway inflammation, epithelial-mesenchymal transition, mesenchymal-epithelial transition, and airway remodeling. [ABSTRACT FROM AUTHOR]

For mucociliary clearance of pathogens, tracheal multiciliated epithelial cells (MCCs) organize coordinated beating of cilia, which originate from basal bodies (BBs) with basal feet (BFs) on one side. To clarify the self-organizing mechanism of coordinated intracellular BB-arrays composed of a well-ordered BB-alignment and unidirectional BB-orientation, determined by the direction of BB to BF, we generated double transgenic mice with GFP-centrin2-labeled BBs and mRuby3-Cep128-labeled BFs for long-term, high-resolution, dual-color live-cell imaging in primary-cultured tracheal MCCs. At early timepoints of MCC differentiation, BB-orientation and BB-local alignment antecedently coordinated in an apical microtubule-dependent manner. Later during MCC differentiation, fluctuations in BB-orientation were restricted, and locally aligned BB-arrays were further coordinated to align across the entire cell (BB-global alignment), mainly in an apical intermediate-sized filament-lattice-dependent manner. Thus, the high coordination of the BB-array was established for efficient mucociliary clearance as the primary defense against pathogen infection, identifying apical cytoskeletons as potential therapeutic targets. Synopsis: High-resolution live-cell imaging reveals the stepwise organization of ciliary basal body (BB) arrays in mouse tracheal multiciliated cells (MCCs), regulated by the apical cytoskeleton networks. A high-resolution, dual-color, live-cell imaging system is developed to monitor the dynamic organization of ciliary basal bodies (BBs) and basal feet (BF) in primary cultured mouse tracheal epithelial cells (MTECs). The unidirectional orientation of BB-BF and the alignment of BBs from local to global scales during the differentiation of multiciliated cells (MCCs) exhibit a stepwise organizational process. Apical microtubules (MTs) and apical intermediate filaments (IFs) provide stage-specific contributions to the organization of the basal body (BB) array. High-resolution live-cell imaging reveals the stepwise organization of ciliary basal body (BB) arrays in mouse tracheal multiciliated cells (MCCs), regulated by the apical cytoskeleton networks. [ABSTRACT FROM AUTHOR]

Cilia are biological structures essential to drive the mobility of secretions and maintain the proper function of the respiratory airways. However, this motile self-cleaning process is significantly compromised in the presence of silicone tracheal prosthesis, leading to biofilm growth and impeding effective treatment. To address this challenge and enhance the performance of these devices, we propose the fabrication of magnetic silicone cilia, with the prospect of their integration onto silicone prostheses. The present study presents a fabrication method based on magnetic self-assembly and assesses the interaction behavior of the cilia array with biological mucus. This protocol allows for the customization of cilia dimensions across a wide range of aspect ratios (from 6 to 85) and array densities (from 10 to 80 cilia/mm2) by adjusting the fabrication parameters, offering flexibility for adjustments according to their required characteristics. Furthermore, we evaluated the suitability of different cilia arrays for biomedical applications by analyzing their interaction with bullfrog mucus, simulating the airways environment. Our findings demonstrate that the fabricated cilia are mechanically resistant to the viscous fluid and still exhibit controlled movement under the influence of an external moving magnet. A correlation between cilia dimensions and mucus wettability profile suggests a potential role in facilitating mucus depuration, paving the way for further advancements aimed at enhancing the performance of silicone prostheses in clinical settings. [ABSTRACT FROM AUTHOR]

• Elexacaftor/tezacaftor/ivacaftor increases sputum hydration in cystic fibrosis. • Elexacaftor/tezacaftor/ivacaftor (E/T/I) markedly improves mucociliary clearance. • Exhaled breath condensate pH and sialic acid levels were unchanged after E/T/I. The cystic fibrosis transmembrane conductance regulator (CFTR) modulator elexacaftor/tezacaftor/ivacaftor (E/T/I) is highly effective clinically for those with at least one F508del-CFTR allele. The effects of E/T/I on mucociliary clearance (MCC) and sputum properties are unknown. We, therefore, sought to characterize the effects of E/T/I on in vivo MCC and sputum characteristics hypothesized to impact mucus transport. Forty-four participants ≥12 years of age were enrolled into this prospective, observational trial prior to initiation of E/T/I and had baseline measurement of MCC and characterization of induced sputum and exhaled breath condensate (EBC) samples. Study procedures were repeated after 1 month of E/T/I treatment. Average age was 27.7 years with baseline forced expiratory volume in 1 second (FEV 1) of 78.2 % predicted. 52 % of subjects had previously been treated with a 2-drug CFTR modulator combination. The average whole lung MCC rate measured over 60 min (WLAveClr60) significantly improved from baseline to post-E/T/I (14.8 vs. 22.8 %; p = 0.0002), as did other MCC indices. Sputum% solids also improved (modeled mean 3.4 vs. 2.2 %; p <0.0001), whereas non-significant reductions in sputum macrorheology (G', G") were observed. No meaningful changes in exhaled breath condensate endpoints (sialic acid:urea ratio, pH) were observed. E/T/I improved the hydration of respiratory secretions (% solids) and markedly accelerated MCC. These data confirm the link between CFTR function, mucus solid content, and MCC and help to define the utility of MCC and mucus-related bioassays in future efforts to restore CFTR function in all people with CF. [ABSTRACT FROM AUTHOR]

The article describes the most informative, direct and non-invasive radioaerosol method for studying the main protective mechanisms of the respiratory system, the processes of inhaled substances deposition and clearing them from the lungs due to the mucociliary system function (mucociliary clearance). The method involves inhalation of a diagnostic radioisotope-labelled drug and subsequent analysis of the dynamics of distribution and excretion of this drug. Based on the analysis results, the above-mentioned processes of inhaled substances deposition and clearing them from the lungs are judged. The accuracy of assessing these processes depends on the aerodynamic properties of the inhalant, for which albumin dispersion systems were chosen as the most physiological material. In order to optimize the measurement of parameters of the aerodynamic properties of a diagnostic aerosol, a comparative analysis of different measurement methods and different albumin dispersion systems was performed. It has been established that the most informative and economically feasible method for assessing the aerodynamic properties of an inhalant is the scanning electron microscopy method. This method was used to assess the dispersion systems, i.e. albumin macroaggregates produced by foreign manufacturers and albumin microspheres manufactured using domestic technology. It has been shown that domestic albumin microspheres have optimal aerodynamic parameters for studying the processes of inhaled substances deposition and mucociliary clearance of the lungs. However, to definitively assess the potential use of these albumin microspheres, direct assessment of their deposition in the lungs is necessary. [ABSTRACT FROM AUTHOR]

• PEEP-ZEEP was not superior to bag squeezing for removing bronchial secretions. • PEEP-ZEEP improves oxygenation when compared to bag-squeezing. • The PEEP-ZEEP maneuver maintains relative hemodynamic stability. It is important to clarify the secretion clearance and lung-related effects of the PEEP-ZEEP maneuver in adults undergoing mechanical ventilation (MV). There is no published comprehensive meta-analysis of the effects of PEEP-ZEEP in adults receiving MV. The aim of this study was to analyze published randomized controlled trials, investigating the effects of the PEEP-ZEEP maneuver in adults undergoing mechanical ventilation. We searched Embase, PubMed, Cochrane Central Register of Controlled Trials, Scopus, and Web of Science from the date of inception of the databases until 6 May 2023. Quality assessment was using the Cochrane Systematic Assessment Handbook. The GRADE system was used to grade the quality of the evidence. A total of 12 trials were included, and the results of the meta-analysis showed that PEEP-ZEEP was not superior to bag squeezing for the removal of bronchial secretions. One study showed a significant increase in the amount of secretion retrieved with the PEEP-ZEEP when compared with tracheal suctioning. Additionally, PEEP-ZEEP was more effective than bag squeezing at improving oxygen saturation. However, one trial showed that bag squeezing was better at improving dynamic compliance. No other differences were found between PEEP-ZEEP and other techniques, except for one study showing more frequent changes in diastolic blood pressure with PEEP-ZEEP compared with ventilator hyperinflation. PEEP-ZEEP was not superior to bag squeezing in removing bronchial secretions. However, it improves oxygen saturation when compared to bag squeezing, and no adverse effects on patients' respiratory systems have yet been observed. [ABSTRACT FROM AUTHOR]

ABSTRACT Objective: Cystic fibrosis (CF) affects multiple organs, the most severe consequences being observed in the lungs. Despite significant progress in developing CF transmembrane conductance regulator-specific treatments for CF lung disease, exploring alternative CF-targeted medications seems reasonable. We sought to evaluate the potential beneficial effects of oral benzbromarone as an adjuvant therapy in CF patients with reduced lung function. Methods: This was a prospective open-label pilot study of oral benzbromarone (100 mg/day) administered once daily for 90 days. Patients were followed at a tertiary referral center in southern Brazil. Safety was assessed by the number of reported adverse events. Secondary objectives included percent predicted FEV1 (FEV1%) and pulmonary exacerbations. Results: Ten patients were enrolled. Benzbromarone was found to be safe, with no serious drug-related adverse events. Eight patients completed the study; the median relative change in FEV1% tended to increase during the treatment, showing an 8% increase from baseline at the final visit. However, a nonparametric test showed that the change was not significant (p = 0.06). Of a total of ten patients, only one experienced at least one pulmonary exacerbation during the study. Conclusions: Oral benzbromarone appears to be safe, and improved FEV1% has been observed in patients with CF. Further assessment in larger trials is warranted to elucidate whether oral benzbromarone can be a potential adjuvant therapy for CF.

Abstract Chronic rhinosinusitis (CRS) is a pathological condition characterized by persistent inflammation in the upper respiratory tract and paranasal sinuses. The epithelium serves as the first line of defense against potential threats and protects the nasal mucosa. The fundamental mechanical barrier is formed by the cell-cell contact and mucociliary clearance (MCC) systems. The physical-mechanical barrier is comprised of many cellular structures, including adhesion junctions and tight junctions (TJs). To this end, different factors, such as the dysfunction of MCC, destruction of epithelial barriers, and tissue remodeling, are related to the onset and development of CRS. Recently published studies reported the critical role of different microorganisms, such as Staphylococcus aureus and Pseudomonas aeruginosa, in the induction of the mentioned factors. Bacteria could result in diminished ciliary stimulation capacity, and enhance the chance of CRS by reducing basal ciliary beat frequency. Additionally, bacterial exoproteins have been demonstrated to disrupt the epithelial barrier and induce downregulation of transmembrane proteins such as occludin, claudin, and tricellulin. Moreover, bacteria exert an influence on TJ proteins, leading to an increase in the permeability of polarized epithelial cells. Noteworthy, it is evident that the activation of TLR2 by staphylococcal enterotoxin can potentially undermine the structural integrity of TJs and the epithelial barrier through the induction of pro-inflammatory cytokines. The purpose of this article is an attempt to investigate the possible role of the most important microorganisms associated with CRS and their pathogenic mechanisms against mucosal surfaces and epithelial barriers in the paranasal sinuses. Video Abstract

The family of calcium-activated chloride channels, TMEM16, plays a significant role in contributing to the pathogenesis of airway inflammatory diseases. Targeting these ion channels and aiming to modulate them may provide an interesting new approach to the therapy of these potentially fatal diseases. We tested this hypothesis in both healthy and ovalbumin (OVA)-sensitized male Dunkin-Hartley guinea pigs. The ion channel activity was modulated by TMEM16A-nonselective (benzbromarone) and TMEM16A-selective blockers (CaCCinh-A01). In vivo airway reactivity, induced by histamine and methacholine, was expressed as specific airway resistance (sRaw) values. The number of citric acid-induced coughs was counted using a double-chambered body plethysmograph, and the frequency of ciliary beating (CBF) was assessed in vitro by brushing method. For comparison, salbutamol and codeine were tested under the same conditions. The results showed significant differences in the responses of unsensitized and sensitized airways to both TMEM16 blockers administered. CaCCinh-A01 and benzbromarone significantly reduced the number of cough efforts in the group of OVA-sensitized guinea pigs. Significant improvement in sRaw values could be observed in OVA-sensitized TMEM16 blocker–treated animals compared to salbutamol when challenged with inhalational histamine, and the outcome was similar to salbutamol when challenged with methacholine. CBF was significantly inhibited in animals sensitized to OVA treated with selective inhibition of TMEM16A. The results demonstrated that treatment with blockers of TMEM16 can reduce both cough effort and sRaw, and the difference between TMEM16A-selective and TMEM16A-nonselective blocking is only negligibly in favor of CaCCinh-A01. It is also worthwhile to note the impairment of CBF in OVA-sensitized animals treated with CaCCinh-A01. [ABSTRACT FROM AUTHOR]

Chronic Rhinosinusitis (CRS) is a common condition causing significant symptoms to those affected, cause burden to the healthcare consumption and productivity loss (Fokkens et al. in Rhinol J 58:82–111, 2020). Chronic Rhinosinusitis is diagnosed clinically on the basis of characteristic symptoms with inflammation of the mucosa of the nose and paranasal sinuses of at least 12 consecutive weeks duration (Fokkens et al. in A summary for otorhinolaryngologists Rhinology 50:1–12, 2012). Functional Endoscopic Sinus Surgery is a minimally invasive procedure recommended for chronic Rhinosinusitis. Patients are not routinely assessed specifically for functional and symptomatic improvement after surgery. Previous studies assessed either subjective or objective outcome of surgery (Elwany et al. in Eur Arch Otorhinolaryngol 255:511–514, 1998; Sino-nasal Outcome Test (SNOT-22): A predictor of post-surgical improvement in patients with chronic sinusitis – PMC, 2022. The present study assessed pre and post operative comparison of nasal mucociliary clearance, nasal patency and Sino-nasal outcome score and evaluated both subjective and objective outcomes of functional endoscopic sinus surgery simultaneously. To assess the effect of functional and symptomatic outcomes after Functional Endoscopic Sinus Surgery in patients with Chronic Rhinosinusitis visiting a tertiary care centre in South India. The present study was a hospital based cross-sectional study conducted in the Department of Otorhinolaryngology, in a tertiary care centre in South India, between February 2021 and May 2022. After obtaining informed consent all the patients fulfilling inclusion and exclusion criteria in the given time period were selected as the study population via consecutive sampling method. Detailed history, clinical examination and Diagnostic nasal endoscopy, Computed Tomography (CT) paranasal sinuses were done in all cases. Pre operative Saccharine transit time (STT), Peak nasal inspiratory flow rate (PNIFR) and Sino nasal outcome test (SNOT) 22 score were measured. All cases underwent Functional Endoscopic Sinus Surgery (FESS). Patients were followed up at 1st, 3rd and 6th month for functional and symptomatic outcomes. Data were analysed statistically using Friedman's ANOVA test. A total of 40 patients between the age of 20 and 60 with Chronic Rhinosinusitis with /without nasal polyposis were analysed. Incidence was found to be more common in middle aged group (37.5%). Among the study group 52.5% were females and 47.5% were males 55% was diagnosed as Chronic Rhinosinusitis with nasal polyp (CRSwNP) type and 45% as without nasal polyp (CRSsNP) type. On comparing the variation of Saccharine transit time, Peak nasal inspiratory flow rate and SNOT 22 score with post operative results done at, 1st, 3rd and 6th months using Friedman's ANOVA test showed statistically significant results (P value < 0.05). According to our study there is significant improvement in functional and symptomatic outcomes after Functional Endoscopic sinus surgery and restoration of mucociliary function in Chronic Rhinosinusitis patients. Thus, FESS is an excellent choice for treatment of CRS. [ABSTRACT FROM AUTHOR]

Airway mucociliary clearance (MCC) is required for host defense and is often diminished in chronic lung diseases. Effective clearance depends upon coordinated actions of the airway epithelium and a mobile mucus layer. Dysregulation of the primary secreted airway mucin proteins, MUC5B and MUC5AC, is associated with a reduction in the rate of MCC; however, how other secreted proteins impact the integrity of the mucus layer and MCC remains unclear. We previously identified the gene Bpifb1/Lplunc1 as a regulator of airway MUC5B protein levels using genetic approaches. Here, we show that BPIFB1 is required for effective MCC in vivo using Bpifb1 knockout (KO) mice. Reduced MCC in Bpifb1 KO mice occurred in the absence of defects in epithelial ion transport or reduced ciliary beat frequency. Loss of BPIFB1 in vivo and in vitro altered biophysical and biochemical properties of mucus that have been previously linked to impaired MCC. Finally, we detected colocalization of BPIFB1 and MUC5B in secretory granules in mice and the protein mesh of secreted mucus in human airway epithelia cultures. Collectively, our findings demonstrate that BPIFB1 is an important component of the mucociliary apparatus in mice and a key component of the mucus protein network. NEW & NOTEWORTHY BPIFB1, also known as LPLUNC1, was found to regulate mucociliary clearance (MCC), a key aspect of host defense in the airway. Loss of this protein was also associated with altered biophysical and biochemical properties of mucus that have been previously linked to impaired MCC. [ABSTRACT FROM AUTHOR]

Background: Airway tuft cells, formerly called brush cells have long been described only morphologically in human airways. More recent RNAseq studies described a chemosensory cell population, which includes tuft cells, by a distinct gene transcription signature. Yet, until which level in the tracheobronchial tree in native human airway epithelium tuft cells occur and if they function as regulators of innate immunity, e.g., by regulating mucociliary clearance, remained largely elusive. Methods: We performed immunohistochemistry, RT-PCR and immunoblotting analyses for various tuft cell markers to confirm the presence of this cell type in human tracheal samples. Immunohistochemistry was conducted to study the distribution of tuft cells along the intrapulmonary airways in humans. We assessed the influence of bitter substances and the taste transduction pathway on mucociliary clearance in mouse and human tracheal samples by measuring particle transport speed. Results: Tuft cells identified by the expression of their well-established marker POU class 2 homeobox 3 (POU2F3) were present from the trachea to the bronchioles. We identified choline acetyltransferase in POU2F3 expressing cells as well as the transient receptor potential melastatin 5 (TRPM5) channel in a small population of tracheal epithelial cells with morphological appearance of tuft cells. Application of bitter substances, such as denatonium, led to an increase in mucociliary clearance in human tracheal preparations. This was dependent on activation of the TRPM5 channel and involved cholinergic and nitric oxide signalling, indicating a functional role for human tuft cells in the regulation of mucociliary clearance. Conclusions: We were able to detect tuft cells in the tracheobronchial tree down to the level of the bronchioles. Moreover, taste transduction and cholinergic signalling occur in the same cells and regulate mucociliary clearance. Thus, tuft cells are potentially involved in the regulation of innate immunity in human airways. [ABSTRACT FROM AUTHOR]

• Mutation-independent therapeutic strategies are needed for all CF patients. • Korean red ginseng aqueous extract (RGAE) has TMEM16a potentiating properties. • CF rats that ingested RGAE exhibited enhanced UTP-mediated Cl− secretion. • RGAE also improved Cl− secretion, mucociliary transport (MCT), and histopathology. • RGAE could serve as a therapeutic strategy to rescue the MCT defect in CF. We previously discovered that Korean red ginseng aqueous extract (RGAE) potentiates the TMEM16A channel, improved mucociliary transport (MCT) parameters in CF nasal epithelia in vitro , and thus could serve as a therapeutic strategy to rescue the MCT defect in cystic fibrosis (CF) airways. The hypothesis of this study is that RGAE can improve epithelial Cl− secretion, MCT, and histopathology in an in-vivo CF rat model. Seventeen 4-month old CFTR–/– rats were randomly assigned to receive daily oral control (saline, n = 9) or RGAE (Ginsenosides 0.4mg/kg/daily, n = 8) for 4 weeks. Outcomes included nasal Cl− secretion measured with the nasal potential difference (NPD), functional microanatomy of the trachea using micro-optical coherence tomography, histopathology, and immunohistochemical staining for TMEM16a. RGAE-treated CF rats had greater mean NPD polarization with UTP (control = -5.48 +/- 2.87 mV, RGAE = -9.49 +/- 2.99 mV, p < 0.05), indicating, at least in part, potentiation of UTP-mediated Cl− secretion through TMEM16A. All measured tracheal MCT parameters (airway surface liquid, periciliary liquid, ciliary beat frequency, MCT) were significantly increased in RGAE-treated CF rats with MCT exhibiting a 3-fold increase (control, 0.45+/-0.31 vs. RGAE, 1.45+/-0.66 mm/min, p < 0.01). Maxillary mucosa histopathology was markedly improved in RGAE-treated cohort (reduced intracellular mucus, goblet cells with no distention, and shorter epithelial height). TMEM16A expression was similar between groups. RGAE improves TMEM16A-mediated transepithelial Cl− secretion, functional microanatomy, and histopathology in CF rats. Therapeutic strategies utilizing TMEM16A potentiators to treat CF airway disease are appropriate and provide a new avenue for mutation-independent therapies. [ABSTRACT FROM AUTHOR]

Key points: Our findings suggest that primary ciliary dyskinesia (PCD)‐related chronic rhinosinusitis (CRS) has a more significant impact on quality of life than CRS without nasal polyps and cystic fibrosis (CF).PCD and CF have similar mucociliary clearance defects, yet sinonasal symptom severity varies between the two. [ABSTRACT FROM AUTHOR]

The flow of nasal secretions into the pharynx and larynx manifests itself differently throughout the day. At night, this mucus flows into the larynx, irritates reflexogenic zones and causes coughing, and during the day these complaints are less noticeable, due to involuntary swallowing of secretions. We hypothesized that different types of nasal septum deviations may affect mucociliary clearance and, as a result, lead to postnasal drip syndrome. However, we did not find any studies in the literature that examined the effect of types of nasal septum deviation (NSD) on mucociliary clearance (MCC). Therefore, in our study, we evaluated the effect of the types of nasal septum deviations on MCC. The aim of the study. To investigate the activity of mucociliary clearance of the mucous membrane of the nasal cavity in patients with different types of NSD. Materials and methods. 100 patients were investigated. All patients underwent an endoscopic examination of the nasal cavity, a ST scan of the nasal cavity, and a saccharin test. The results. The analysis made it possible to reveal that in most patients with type 2 deviation of the nasal septum with the presence of a unilateral caudal ridge, which cuts into the middle turbinate, there is PNDS. At the same time, while the average ST time of the concave side of the nasal mucosa in patients with type 1 was almost unchanged, it was significantly longer in patients with type 2 (P=0,02). Therefore, in this study, the ST indicator in min. was longer on the concave side of the nasal cavity than on the convex side. Conclusions. Our research has shown that nasal septum deviation reduces nasal mucociliary activity, and this effect can be easily assessed using the saccharin test. According to our observations and research results, it was the 2nd and 3rd types of deviation that significantly disturbed the architecture of the nasal cavity, due to the presence of contralateral vertical deviation of the nasal septum, contralateral hyperplasia of the nasal turbinates, and contralateral conchobulosis. And, as a result, led to a decrease in mucociliary clearance. [ABSTRACT FROM AUTHOR]

Copyright of Monatsschrift Kinderheilkunde is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Chronic rhinosinusitis (CRS) is a pathological condition characterized by persistent inflammation in the upper respiratory tract and paranasal sinuses. The epithelium serves as the first line of defense against potential threats and protects the nasal mucosa. The fundamental mechanical barrier is formed by the cell-cell contact and mucociliary clearance (MCC) systems. The physical-mechanical barrier is comprised of many cellular structures, including adhesion junctions and tight junctions (TJs). To this end, different factors, such as the dysfunction of MCC, destruction of epithelial barriers, and tissue remodeling, are related to the onset and development of CRS. Recently published studies reported the critical role of different microorganisms, such as Staphylococcus aureus and Pseudomonas aeruginosa, in the induction of the mentioned factors. Bacteria could result in diminished ciliary stimulation capacity, and enhance the chance of CRS by reducing basal ciliary beat frequency. Additionally, bacterial exoproteins have been demonstrated to disrupt the epithelial barrier and induce downregulation of transmembrane proteins such as occludin, claudin, and tricellulin. Moreover, bacteria exert an influence on TJ proteins, leading to an increase in the permeability of polarized epithelial cells. Noteworthy, it is evident that the activation of TLR2 by staphylococcal enterotoxin can potentially undermine the structural integrity of TJs and the epithelial barrier through the induction of pro-inflammatory cytokines. The purpose of this article is an attempt to investigate the possible role of the most important microorganisms associated with CRS and their pathogenic mechanisms against mucosal surfaces and epithelial barriers in the paranasal sinuses. 1R2fDAjuKSs1gPk1V3KKLv Video Abstract [ABSTRACT FROM AUTHOR]

The nasal mucosa, being accessible and highly vascularized, opens up new opportunities for the systemic administration of drugs. However, there are several protective functions like the mucociliary clearance, a physiological barrier which represents is a difficult obstacle for drug candidates to overcome. For this reason, effective testing procedures are required in the preclinical phase of pharmaceutical development. Based on a recently reported immortalized porcine nasal epithelial cell line, we developed a test platform based on a tissue-compatible microfluidic chip. In this study, a biomimetic glass chip, which was equipped with a controlled bidirectional airflow to induce a physiologically relevant wall shear stress on the epithelial cell layer, was microfabricated. By developing a membrane transfer technique, the epithelial cell layer could be pre-cultivated in a static holder prior to cultivation in a microfluidic environment. The dynamic cultivation within the chip showed a homogenous distribution of the mucus film on top of the cell layer and a significant increase in cilia formation compared to the static cultivation condition. In addition, the recording of the ciliary transport mechanism by microparticle image velocimetry was successful. Using FITC-dextran 4000 as an example, it was shown that this nasal mucosa on a chip is suitable for permeation studies. The obtained permeation coefficient was in the range of values determined by means of other established in vitro and in vivo models. This novel nasal mucosa on chip could, in future, be automated and used as a substitute for animal testing. [ABSTRACT FROM AUTHOR]

Air pollution plays an important role in the mortality and morbidity of chronic airway diseases, such as asthma and chronic obstructive pulmonary disease (COPD). Particulate matter (PM) is a significant fraction of air pollutants, and studies have demonstrated that it can cause airway inflammation and injury. The airway epithelium forms the first barrier of defense against inhaled toxicants, such as PM. Airway epithelial cells clear airways from inhaled irritants and orchestrate the inflammatory response of airways to these irritants by secreting various lipid mediators, growth factors, chemokines, and cytokines. Studies suggest that PM plays an important role in the pathogenesis of chronic airway diseases by impairing mucociliary function, deteriorating epithelial barrier integrity, and inducing the production of inflammatory mediators while modulating the proliferation and death of airway epithelial cells. Furthermore, PM can modulate epithelial plasticity and airway remodeling, which play central roles in asthma and COPD. This review focuses on the effects of PM on airway injury and epithelial plasticity, and the underlying mechanisms involving mucociliary activity, epithelial barrier function, airway inflammation, epithelial-mesenchymal transition, mesenchymal-epithelial transition, and airway remodeling.

Airway epithelium, the first defense barrier of the respiratory system, facilitates mucociliary clearance against inflammatory stimuli, such as pathogens and particulates inhaled into the airway and lung. Inhaled particulate matter 2.5 (PM2.5) can penetrate the alveolar region of the lung, and it can develop and exacerbate respiratory diseases. Although the pathophysiological effects of PM2.5 in the respiratory system are well known, its impact on mucociliary clearance of airway epithelium has yet to be clearly defined. In this study, we used two different 3D in vitro airway models, namely the EpiAirway-full-thickness (FT) model and a normal human bronchial epithelial cell (NHBE)-based air-liquid interface (ALI) system, to investigate the effect of diesel exhaust particles (DEPs) belonging to PM2.5 on mucociliary clearance. RNA-sequencing (RNA-Seq) analyses of EpiAirway-FT exposed to DEPs indicated that DEP-induced differentially expressed genes (DEGs) are related to ciliary and microtubule function and inflammatory-related pathways. The exposure to DEPs significantly decreased the number of ciliated cells and shortened ciliary length. It reduced the expression of cilium-related genes such as acetylated α-tubulin, ARL13B, DNAH5, and DNAL1 in the NHBEs cultured in the ALI system. Furthermore, DEPs significantly increased the expression of MUC5AC, whereas they decreased the expression of epithelial junction proteins, namely, ZO1, Occludin, and E-cadherin. Impairment of mucociliary clearance by DEPs significantly improved the release of epithelial-derived inflammatory and fibrotic mediators such as IL-1β, IL-6, IL-8, GM-CSF, MMP-1, VEGF, and S100A9. Taken together, it can be speculated that DEPs can cause ciliary dysfunction, hyperplasia of goblet cells, and the disruption of the epithelial barrier, resulting in the hyperproduction of lung injury mediators. Our data strongly suggest that PM2.5 exposure is directly associated with ciliary and epithelial barrier dysfunction and may exacerbate lung injury.

The recent COVID-19 pandemic has propelled the field of aerosol science to the forefront, particularly the central role of virus-laden respiratory droplets and aerosols. The pandemic has also highlighted the critical need, and value for, an information bridge between epidemiological models (that inform policymakers to develop public health responses) and within-host models (that inform the public and health care providers how individuals develop respiratory infections). Here, we review existing data and models of generation of respiratory droplets and aerosols, their exhalation and inhalation, and the fate of infectious droplet transport and deposition throughout the respiratory tract. We then articulate how aerosol transport modeling can serve as a bridge between and guide calibration of within-host and epidemiological models, forming a comprehensive tool to formulate and test hypotheses about respiratory tract exposure and infection within and between individuals.

Many years of experience in the use of ambroxol is based on its ability to regulate the basic mechanisms of physiological production and transport of bronchial mucus. The main indication for ambroxol is the mucolytic therapy of acute and chronic bronchopulmonary diseases associated with hypersecretion and impaired mucus transport. Ambroxol has a number of the following properties: high secretolytic activity (promotes mucus clearance, facilitates expectoration of sputum, reduces productive cough); anti-inflammatory and antioxidant activity; local analgesic (anesthetic) effect through the blockade of sodium channels of cell membranes. The effect of anesthesia of the mucous membranes is attributed to the new pharmacological action of ambroxol, useful in the treatment of acute respiratory tract infections. The efficacy and safety of ambroxol in clinical practice has been confirmed by half a century of experience in its administration. The purpose of this publication was an up-to-date assessment of the controversial and indisputable chemical, pharmacological, clinical data on the properties of ambroxol in the concept of modern recovery mucolytic therapy that can improve the therapy and prognosis of patients with tracheobronchial secretion hypersecretion, impaired mucociliary clearance and unproductive cough.

Abstract Purpose Dental implants may become displaced into the maxillary sinus due to insufficient primary stability, changes in nasal air pressure, or surrounding bone resorption and should be removed as soon as possible. The aim of this study was to evaluate the efficacy of the modified endoscopic sinus surgery (MESS) approach for removal of displaced dental implants. Methods From September 2010 to November 2021, we studied 15 cases with displaced implants in the maxillary sinus. The patient characteristics, medical history, clinical and imaging results, and post-removal outcomes were retrospectively assessed. Results The symptoms included sinusitis (100%), pain (26.6%), postnasal drip (6.6%), nasal obstruction (26.6%), and oroantral communication (26.6%). Two cases were managed through the crestal approach (13.3%), while two cases were treated with the Caldwell–Luc procedure (13.3%). One case was addressed using functional endoscopic sinus surgery (6.7%), while 10 cases were managed with the MESS approach (66.7%). MESS allows functional rehabilitation of mucociliary clearance by the cilia in the sinus membrane. Implant displacement into the maxillary sinus can be classified as early, late, or delayed displacement. Conclusions MESS is a reliable treatment option that can identify migrated dental implants in any part of the sinus with endoscopic assistance for functional rehabilitation of the maxillary sinus without postoperative sequelae.

Background: Disorders of mucociliary clearance, such as cystic fibrosis (CF), primary ciliary dyskinesia (PCD) and bronchiectasis of unknown origin, are characterised by periods with increased respiratory symptoms, referred to as pulmonary exacerbations. These exacerbations are hard to predict and associated with lung function decline and the loss of quality of life. To optimise treatment and preserve lung function, there is a need for non-invasive and reliable methods of detection. Breath analysis might be such a method. Methods: We systematically reviewed the existing literature on breath analysis to detect pulmonary exacerbations in mucociliary clearance disorders. Extracted data included the study design, technique of measurement, definition of an exacerbation, identified compounds and diagnostic accuracy. Results: Out of 244 identified articles, 18 were included in the review. All studies included patients with CF and two also with PCD. Age and the definition of exacerbation differed between the studies. There were five that measured volatile organic compounds (VOCs) in exhaled breath using gas chromatography with mass spectrometry, two using an electronic nose and eleven measured organic compounds in exhaled breath condensate. Most studies showed a significant correlation between pulmonary exacerbations and one or multiple compounds, mainly hydrocarbons and cytokines, but the validation of these results in other studies was lacking. Conclusions: The detection of pulmonary exacerbations by the analysis of compounds in exhaled breath seems possible but is not near clinical application due to major differences in results, study design and the definition of an exacerbation. There is a need for larger studies, with a longitudinal design, international accepted definition of an exacerbation and validation of the results in independent cohorts.