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Background The IL-33/ST2 pathway is linked with asthma susceptibility. Inhaled allergens, pollutants, and respiratory viruses, which trigger asthma exacerbations, induce release of IL-33, an epithelial-derived “alarmin.” Astegolimab, a human IgG2 mAb, selectively inhibits the IL-33 receptor, ST2. Approved biologic therapies for severe asthma mainly benefit patients with elevated blood eosinophils (type 2-high), but limited options are available for patients with low blood eosinophils (type 2-low). Inhibiting IL-33 signaling may target pathogenic pathways in a wider spectrum of asthmatics. Objectives This study evaluated astegolimab efficacy and safety in patients with severe asthma. Methods This double-blind, placebo-controlled, dose-ranging study (ZENYATTA [A Study to Assess the Efficacy and Safety of MSTT1041A in Participants With Uncontrolled Severe Asthma]) randomized 502 adults with severe asthma to subcutaneous placebo or 70-mg, 210-mg, or 490-mg doses of astegolimab every 4 weeks. The primary endpoint was the annualized asthma exacerbation rate (AER) at week 54. Enrollment caps ensured ∼30 patients who were eosinophil-high (≥300 cells/μL) and ∼95 patients who were eosinophil-low ( Results Overall, adjusted AER reductions relative to placebo were 43% (P = .005), 22% (P = .18), and 37% (P = .01) for 490-mg, 210-mg, and 70-mg doses of astegolimab, respectively. Adjusted AER reductions for patients who were eosinophil-low were comparable to reductions in the overall population: 54% (P = .002), 14% (P = .48), and 35% (P = .05) for 490-mg, 210-mg, and 70-mg doses of astegolimab. Adverse events were similar in astegolimab- and placebo-treated groups. Conclusions Astegolimab reduced AER in a broad population of patients, including those who were eosinophil-low, with inadequately controlled, severe asthma. Astegolimab was safe and well tolerated.

Background Infection with the novel severe acute respiratory syndrome coronavirus 2 has been associated with a hypercoagulable state. Emerging data from China and Europe have consistently shown an increased incidence of venous thromboembolism (VTE). We aimed to identify the VTE incidence and early predictors of VTE at our high-volume tertiary care center. Methods We performed a retrospective cohort study of 147 patients who had been admitted to Temple University Hospital with coronavirus disease 2019 (COVID-19) from April 1, 2020 to April 27, 2020. We first identified the VTE (pulmonary embolism [PE] and deep vein thrombosis [DVT]) incidence in our cohort. The VTE and no-VTE groups were compared by univariable analysis for demographics, comorbidities, laboratory data, and treatment outcomes. Subsequently, multivariable logistic regression analysis was performed to identify the early predictors of VTE. Results The 147 patients (20.9% of all admissions) admitted to a designated COVID-19 unit at Temple University Hospital with a high clinical suspicion of acute VTE had undergone testing for VTE using computed tomography pulmonary angiography and/or extremity venous duplex ultrasonography. The overall incidence of VTE was 17% (25 of 147). Of the 25 patients, 16 had had acute PE, 14 had had acute DVT, and 5 had had both PE and DVT. The need for invasive mechanical ventilation (adjusted odds ratio, 3.19; 95% confidence interval, 1.07-9.55) and the admission D-dimer level ≥1500 ng/mL (adjusted odds ratio, 3.55; 95% confidence interval, 1.29-9.78) were independent markers associated with VTE. The all-cause mortality in the VTE group was greater than that in the non-VTE group (48% vs 22%; P = .007). Conclusions Our study represents one of the earliest reported from the United States on the incidence rate of VTE in patients with COVID-19. Patients with a high clinical suspicion and the identified risk factors (invasive mechanical ventilation, admission D-dimer level ≥1500 ng/mL) should be considered for early VTE testing. We did not screen all patients admitted for VTE; therefore, the true incidence of VTE could have been underestimated. Our findings require confirmation in future prospective studies.

Contains fulltext : 220761.pdf (Publisher’s version ) (Open Access) Rationale: The decades-long progression of chronic obstructive pulmonary disease (COPD) renders identifying different trajectories of disease progression challenging.Objectives: To identify subtypes of patients with COPD with distinct longitudinal progression patterns using a novel machine-learning tool called "Subtype and Stage Inference" (SuStaIn) and to evaluate the utility of SuStaIn for patient stratification in COPD.Methods: We applied SuStaIn to cross-sectional computed tomography imaging markers in 3,698 Global Initiative for Chronic Obstructive Lung Disease (GOLD) 1-4 patients and 3,479 controls from the COPDGene (COPD Genetic Epidemiology) study to identify subtypes of patients with COPD. We confirmed the identified subtypes and progression patterns using ECLIPSE (Evaluation of COPD Longitudinally to Identify Predictive Surrogate Endpoints) data. We assessed the utility of SuStaIn for patient stratification by comparing SuStaIn subtypes and stages at baseline with longitudinal follow-up data.Measurements and Main Results: We identified two trajectories of disease progression in COPD: a "Tissue-->Airway" subtype (n = 2,354, 70.4%), in which small airway dysfunction and emphysema precede large airway wall abnormalities, and an "Airway-->Tissue" subtype (n = 988, 29.6%), in which large airway wall abnormalities precede emphysema and small airway dysfunction. Subtypes were reproducible in ECLIPSE. Baseline stage in both subtypes correlated with future FEV1/FVC decline (r = -0.16 [P < 0.001] in the Tissue-->Airway group; r = -0.14 [P = 0.011] in the Airway-->Tissue group). SuStaIn placed 30% of smokers with normal lung function at elevated stages, suggesting imaging changes consistent with early COPD. Individuals with early changes were 2.5 times more likely to meet COPD diagnostic criteria at follow-up.Conclusions: We demonstrate two distinct patterns of disease progression in COPD using SuStaIn, likely representing different endotypes. One third of healthy smokers have detectable imaging changes, suggesting a new biomarker of "early COPD."

Background Asthma exacerbation risk increases with worsening asthma control. Prevailing numerical control tools evaluate only current symptom impairment despite the importance of also assessing risk based on exacerbation history. An easy-to-use questionnaire addressing impairment and risk domains of control is needed. Objective To validate a composite asthma control tool that includes impairment and risk assessments (Asthma Impairment and Risk Questionnaire [AIRQ]). Methods Four-hundred forty-two patients aged ≥12 years with physician-diagnosed asthma who were followed in specialty practices completed 15 impairment and risk questions with dichotomized yes/no responses. Patients spanned all Global Initiative for Asthma severities and were classified as well-controlled, not well-controlled, or very poorly controlled according to a standard of Asthma Control Test (ACT) score plus prior-year exacerbations. Logistic regression analyses identified questions with the greatest predictive validity to discriminate among patients and determine cut points for these 3 classifications. Results The final AIRQ comprises 10 equally weighted yes/no impairment and risk questions. The final 10-item models yielded receiver operating characteristic curves of 0.94 to identify well-controlled versus not well-/very poorly controlled and 0.93 to identify well-/not well-controlled versus very poorly controlled asthma, as reflected by the ACT plus prior-year exacerbations standard. Cut points of 0-1, 2-4, and 5-10 best represented well-, not well-, and very poorly controlled asthma. Conclusions AIRQ is a rigorously validated composite measure designed to identify adults and adolescents with varying degrees of asthma control. Ongoing investigations will determine test-retest reliability, responsiveness to change, and predictive ability for future exacerbations.

Pulmonary emphysema is characterized by alveolar wall destruction, and cigarette smoking is the main risk factor in this disease development. S100A8 is a member of the S100 protein family, with an oxidative stress-related and antiinflammatory role. The mechanisms of human alveolar type II (ATII) cell injury contributing to emphysema pathophysiology are not completely understood. We wanted to determine whether S100A8 can protect ATII cells against injury induced by cigarette smoke and this disease development. We used freshly isolated ATII cells from nonsmoking and smoking organ donors, as well as patients with emphysema to determine S100A8 function. S100A8 protein and mRNA levels were low in individuals with this disease and correlated with its severity as determined by using lung tissue from areas with mild and severe emphysema obtained from the same patient. Its expression negatively correlated with high oxidative stress as observed by 4-hydroxynonenal levels. We also detected decreased serine phosphorylation within S100A8 by PKAα in this disease. This correlated with increased S100A8 ubiquitination by SYVN1. Moreover, we cultured ATII cells isolated from nonsmokers followed by treatment with cigarette smoke extract. We found that this exposure upregulated S100A8 expression. We also confirmed the cytoprotective role of S100A8 against cell injury using gain- and loss-of-function approaches in vitro. S100A8 knockdown sensitized cells to apoptosis induced by cigarette smoke. In contrast, S100A8 overexpression rescued cell injury. Our results suggest that S100A8 protects ATII cells against injury and cigarette smoke-induced emphysema. Targeting S100A8 may provide a potential therapeutic strategy for this disease.

Background Identification of biomarkers of cigarette smoke –induced lung damage and early COPD is an area of intense interest. Glucose regulated protein of 78 kD (i.e., GRP78), a multi-functional protein which mediates cell responses to oxidant stress, is increased in the lungs of cigarette smokers and in the serum of subjects with COPD. We have suggested that secretion of GRP78 by lung cells may explain the increase in serum GRP78 in COPD. To assess GRP78 secretion by the lung, we assayed GRP78 in bronchoalveolar lavage fluid (BALF) in chronic smokers and non-smokers. We also directly assessed the acute effect of cigarette smoke material on GRP78 secretion in isolated human airway epithelial cells (HAEC). Methods GRP78 was measured in BALF of smokers (S; n = 13) and non-smokers (NS; n = 11) by Western blotting. GRP78 secretion by HAEC was assessed by comparing its concentration in cell culture medium and cell lysates. Cells were treated for 24 h with either the volatile phase of cigarette smoke (cigarette smoke extract (CSE) or the particulate phase (cigarette smoke condensate (CSC)). Results GRP78 was present in the BALF of both NS and S but levels were significantly greater in S (p = 0.04). GRP78 was secreted constitutively in HAEC. CSE 15% X 24 h increased GRP78 in cell-conditioned medium without affecting its intracellular concentration. In contrast, CSC X 24 h increased intracellular GRP78 expression but did not affect GRP78 secretion. Brefeldin A, an inhibitor of classical Golgi secretion pathways, did not inhibit GRP78 secretion indicating that non-classical pathways were involved. Conclusion The present study indicates that GRP78 is increased in BALF in cigarette smokers; that HAEC secrete GRP78; and that GRP78 secretion by HAEC is augmented by cigarette smoke particulates. Enhanced secretion of GRP78 by lung cells makes it a potential biomarker of cigarette smoke–induced lung injury.

Surfactant, a phospholipoprotein produced and stored by alveolar type II (ATII) cells, lowers surface tension in the alveolus and distal airways and is essential for normal lung mechanics and gas exchange.1 Decreases in surfactant production induced by prematurity or disease cause alveolar collapse, hypoxemia and reductions in lung compliance, thereby requiring greater distending pressures to inflate the lung and increases in the work of breathing.2 Prior studies dating back >30 years have shown that alveolar hypocapnia causes depletion of lamellar bodies in ATII cells and decreases surfactant production.3 However, the mechanism(s) underlying the effect(s) of hypocapnia on surfactant secretion by ATII cells are not well understood. The paper by Kiefmann et al 4 in Thorax sheds light on molecular mechanisms which may contribute to the effects of alveolar hypocapnia on surfactant production in vivo. The authors examined surfactant secretion, cytosolic and mitochondrial calcium and alveolar volume and compliance in two rodent preparations: isolated, blood-perfused rat lungs …

BACKGROUND: Asthma is a biologically heterogeneous disease and development of novel therapeutics requires understanding of pathophysiologic phenotypes. There is uncertainty regarding the stability of clinical characteristics and biomarkers in asthma over time. This report presents the longitudinal stability over 12 months of clinical characteristics and clinically accessible biomarkers from ADEPT.METHODS: Mild, moderate, and severe asthma subjects were assessed at 5 visits over 12 months. Assessments included patient questionnaires, spirometry, bronchodilator reversibility, fractional exhaled nitric oxide (FENO), and biomarkers measured in induced sputum.RESULTS: Mild (n = 52), moderate (n = 55), and severe (n = 51) asthma cohorts were enrolled from North America and Western Europe. For all clinical characteristics and biomarkers, group mean data showed no significant change from visit to visit. However, individual data showed considerable variability. FEV1/FVC ratio showed excellent reproducibility while pre-bronchodilator FEV1 and FVC were only moderately reproducible. Of note bronchodilator FEV1 reversibility showed low reproducibility, with the nonreversible phenotype much more reproducible than the reversible phenotype. The 7-item asthma control questionnaire (ACQ7) demonstrated moderate reproducibility for the combined asthma cohorts, but the uncontrolled asthma phenotype (ACQ7 > 1.5) was inconstant in mild and moderate asthma but stable in severe asthma. FENO demonstrated good reproducibility, with the FENO-low phenotype (FENO CONCLUSIONS: The ADEPT cohort showed group stability, individual stability in some parameters e.g. low FEV1/FVC ratio, and low FENO, but marked individual variability in other clinical characteristics and biomarkers e.g. type-2 biomarkers over 12 months. This variability is possibly related to seasonal variations in climate and allergen exposure, medication changes and acute exacerbations. The implications for patient selection strategies based on clinical biomarkers may be considerable.

Background Quilizumab, a humanized IgG1 monoclonal antibody, targets the M1-prime segment of membrane-expressed IgE, leading to depletion of IgE-switched and memory B cells. In patients with mild asthma, quilizumab reduced serum IgE and attenuated the early and late asthmatic reaction following whole lung allergen challenge. This study evaluated the efficacy and safety of quilizumab in adults with allergic asthma, inadequately controlled despite high-dose inhaled corticosteroids (ICS) and a second controller. Methods Five hundred seventy-eight patients were randomized to monthly or quarterly dosing regimens of subcutaneous quilizumab or placebo for 36 weeks, with a 48-week safety follow-up. Quilizumab was evaluated for effects on the rate of asthma exacerbations, lung function, patient symptoms, serum IgE, and pharmacokinetics. Exploratory analyses were conducted on biomarker subgroups (periostin, blood eosinophils, serum IgE, and exhaled nitric oxide). Results Quilizumab was well tolerated and reduced serum total and allergen-specific IgE by 30–40 %, but had no impact on asthma exacerbations, lung function, or patient-reported symptom measures. At Week 36, the 300 mg monthly quilizumab group showed a 19.6 % reduction (p = 0.38) in the asthma exacerbation rate relative to placebo, but this was neither statistically nor clinically significant. Biomarker subgroups did not reveal meaningful efficacy benefits following quilizumab treatment. Conclusions Quilizumab had an acceptable safety profile and reduced serum IgE. However, targeting the IgE pathway via depletion of IgE-switched and memory B cells was not sufficient for a clinically meaningful benefit for adults with allergic asthma uncontrolled by standard therapy. Trial registration ClinicalTrials.gov NCT01582503 Electronic supplementary material The online version of this article (doi:10.1186/s12931-016-0347-2) contains supplementary material, which is available to authorized users.

Chronic obstructive pulmonary disease (COPD) is a progressive, smoking-related, inflammatory lung disease in which tumor necrosis factor-alpha is overexpressed and has been suggested to play a pathogenic role.To determine if infliximab, an anti-TNF-alpha antibody, results in clinical benefit and has an acceptable safety profile in patients with moderate to severe COPD.In a multicenter, randomized, double-blind, placebo-controlled, parallel-group, dose-finding study, subjects with moderate to severe COPD received infliximab (3 mg/kg [n = 78] or 5 mg/kg [n = 79]) or placebo (n = 77) at Weeks 0, 2, 6, 12, 18, and 24. Efficacy, health status, and safety were assessed through Week 44.Infliximab was generally well tolerated, but showed no treatment benefit as measured by the primary endpoint, Chronic Respiratory Questionnaire total score. Similarly, there was no change in secondary measures, including prebronchodilator FEV(1), 6-min walk distance, SF-36 physical score, transition dyspnea index, or moderate-to-severe COPD exacerbations. Post hoc analysis revealed that subjects who were younger or cachectic showed improvement in the 6-min walk distance. Malignancies were diagnosed during the study in 9 of 157 infliximab-treated subjects versus 1 of 77 placebo-treated subjects. No opportunistic infections were observed, and there were no differences in the occurrence of antibiotic-requiring infections, although the incidence of pneumonia was higher in infliximab-treated subjects. No infection-related mortality was observed. Higher proportions of infliximab-treated subjects discontinued the study agent due to adverse events (20-27%) than did placebo-treated subjects (9%).Subjects with moderate to severe COPD did not benefit from treatment with infliximab. Although not statistically significant, more cases of cancer and pneumonia were observed in the infliximab-treated subjects. The impact of infliximab on malignancy risk in patients with COPD needs to be further elucidated.

Activation of the beta(2)-adrenergic receptor (beta(2)AR) system expressed by human airway epithelial cells elicits a variety of cyclic adenosine monophosphate (cAMP)-dependent processes that help determine airway caliber and the intensity of airway inflammation in asthma. Glucocorticoids, mainstays in the treatment of asthma, profoundly affect the expression and function of the beta(2)-adrenergic receptor-adenylyl cyclase (beta(2)AR-AC) system in a variety of cell types. However, the effects of glucocorticoids on the beta(2)AR-AC system expressed by human airway epithelial cells are unstudied.We examined the effects of dexamethasone (DEX) on beta(2)AR gene expression and the function of the beta(2)AR-AC system in cultured human airway epithelial cells.Studies were performed in normal airway epithelial cells and BEAS-2B cells. Beta(2)AR gene expression was assessed from measurements of beta-adrenergic receptor density, beta(2)AR mRNA, and the activity of a full-length beta(2)AR promoter-luciferase reporter construct. The function of the beta(2)AR-AC system was assessed from cAMP production in response to the beta(2)-agonist isoproterenol and the expression of the stimulatory G protein G(alpha)s.DEX had no effect on beta-adrenergic receptor density or on the beta(1)/beta(2) ratio over a wide range of concentrations and exposure times. However, DEX significantly but transiently enhanced beta(2)AR mRNA levels (approximately 1.5-fold) and beta(2)AR promoter activity (approximately 1.5-fold), indicating increased beta(2)AR gene transcription. DEX also dose-dependently enhanced cAMP responses to isoproterenol but not to forskolin, a direct activator of adenylyl cyclase. DEX-induced changes in cAMP production were associated with small (approximately 15%) increases in G(alpha)s expression.These data indicate that glucocorticoids only transiently enhance beta(2)AR gene transcription and fail to increase steady-state levels of beta(2)AR protein in human airway epithelial cells. Nonetheless, glucocorticoid-induced effects on the beta(2)AR-AC system of human airway epithelial cells contribute to the beneficial effects of corticosteroids in asthma by enhancing the functional response to beta(2)-agonists.

Protein kinase C (PKC)-activated signal transduction pathways regulate cell growth and differentiation in many cell types. We have observed that interleukin (IL)-1β upregulates β2-adrenergic receptor (β2-AR) density and β2-AR mRNA in human airway epithelial cells (e.g., BEAS-2B). We therefore tested the hypothesis that PKC-activated pathways mediate IL-1β-induced β-AR upregulation. The role of PKC was assessed from the effects of 1) the PKC activator phorbol 12-myristate 13-acetate (PMA) on β-AR density, 2) selective PKC inhibitors (calphostin C and Ro-31-8220) on β-AR density, and 3) IL-1β treatment on the cellular distribution of PKC isozymes. Recombinant human IL-1β (0.2 nM for 18 h) increased β-AR density to 213% of control values ( P < 0.001). PMA (1 μM for 18 h) increased β-AR density to 225% of control values ( P < 0.005), whereas Ro-31-8220 and calphostin C inhibited the IL-1β-induced upregulation of β-AR in dose-dependent fashion. PKC isozymes detected by Western blotting included α, βII, ε, μ, ζ, and λ/ι. IL-1β increased PKC-μ immunoreactivity in the membrane fraction and had no effect on the distribution of the other PKC isozymes identified. These data indicate that IL-1β-induced β-AR upregulation is mimicked by PKC activators and blocked by PKC inhibitors and appears to involve selective activation of the PKC-μ isozyme. We conclude that signal transduction pathways activated by PKC-μ upregulate β2-AR expression in human airway epithelial cells.

Background: Airway epithelial cells are among the first cells to come in contact with aerosolized corticosteroids. However, the relative potencies and time course of action of the several commonly used aerosolized corticosteroids on eicosanoid production by airway epithelial cells are unknown. Objectives: This study compared the effects of fluticasone, budesonide, and triamcinolone on eicosanoid output by human airway epithelial cells in vitro. We also determined the spectrum of eicosanoids affected and the mechanism for corticosteroid action. Methods: Cultured BEAS-2B airway epithelial cells (a transformed cell line) were exposed to corticosteroids (1 nmol/L to 1 μmol/L) for 2 to 48 hours and then assayed for basal- and bradykinin (BK)-stimulated eicosanoid output. The eicosanoid profile was identified by HPLC in tritiated arachidonic acid prelabelled cells, and PGE 2 , the major eicosanoid product, was quantitated by RIA. The effect of corticosteroids on the immunoreactivity of key proteins involved in eicosanoid metabolism (ie, cyclooxygenase [COX], phospholipase A2 [PLA 2 ], and Clara cell protein, a PLA 2 inhibitor) was determined by Western blotting. Results: Eicosanoid output was largely confined to prostaglandins with values of 5 ± 2 and 82 ± 35 ng PGE 2 /10 6 cells for basal- and BK stimulation, respectively (n = 8). All 3 corticosteroids inhibited basal- and BK-induced PGE 2 output in a dose- and time-dependent manner. Fluticasone and budesonide completely eliminated PGE 2 output in nanomolar concentrations in contrast to triamcinolone, which required micromolar concentration. The rank order of potency was: fluticasone=budesonide > triamcinolone. The time course of action for PGE 2 inhibition also differed, with budesonide acting more slowly than the other 2 corticosteroids ( P = .04). All 3 corticosteroids markedly reduced COX2 with little effect on COX1, cPLA 2 (Type IV), or iPLA 2 (Type VI) immunoreactivity or their relative distribution in cytosol versus membrane fractions. Clara cell protein immunoreactivity was undetectable in control and corticosteroid-treated cell lysates. Conclusion: These results show that in a human airway epithelial cell line, the 3 inhaled corticosteroids commonly used to treat asthma differ in onsets of action as inhibitors of prostaglandin synthesis and vary considerably in potency. All 3 corticosteroids act mechanistically in similar fashion by inhibiting COX2 synthesis. (J Allergy Clin Immunol 1999;103:1081-91.)

Chronic catecholamine treatment induces beta-adrenergic receptor (beta AR) downregulation, i.e., a loss of total cell receptors. In the human respiratory tract, the mechanism(s) underlying beta AR downregulation remains poorly understood. The present study, therefore, examined the effects of 24 h of exposure to isoproterenol (Iso; 10 nM or 1 microM) on beta AR density and the rate of beta AR degradation, steady-state beta 2-adrenergic receptor (beta 2 AR) mRNA levels, and the content of Gs alpha and Gi alpha proteins in cultured human bronchial epithelial cells (i.e., the BEAS-2B cell line). beta AR density assessed by binding with [125I]iodopindolol decreased in a dose-dependent fashion with 24 h of Iso exposure. With Iso (1 microM), beta AR density decreased by approximately 82%. In contrast, forskolin (100 microM) and dibutyryl adenosine 3',5'-cyclic monophosphate (1 mM), agents that also increase adenosine 3',5'-cyclic monophosphate (cAMP) levels, had no significant effect on beta AR density. Iso exposure also elicited a concomitant decrease in Iso-stimulated cAMP but had no significant effect on the content of the G proteins G alpha i2 and Gs alpha assessed by immunoblotting and toxin-catalyzed ADP ribosylation. Of note, Iso exposure (1 microM) had no effect on steady-state levels of beta 2 AR mRNA measured both by Northern analysis and by reverse transcriptase-polymerase chain reaction. However, beta AR half-life assessed in the presence of the protein synthesis inhibitor cycloheximide was reduced by approximately 60% in Iso-treated cells (i.e., from 37 h in control to 16 h in 1 microM Iso). These results suggest that, in human airway epithelial cells, beta 2 AR downregulation 1) is not primarily driven by intracellular cAMP levels, 2) is not associated with significant decreases in steady-state levels of beta 2 AR mRNA, and 3) is largely posttranslationally regulated by increases in the rate of receptor protein degradation.

To the Editor: Asthma heterogeneity has been described by the nature and intensity of granulocytic infiltration into the airways [1, 2]. Sputum, endobronchial biopsies and bronchoalveolar lavage (BAL) sample different anatomical regions of the airways. Few studies have directly compared the inflammatory cell infiltrates in these regions within a large cohort of moderate–severe asthma patients using standard techniques. In the BOBCAT (Bronchoscopic exploratory research study Of Biomarkers in Corticosteroid-refractory AsThma) study, we sampled multiple airway compartments concurrently, enabling us to evaluate relationships between granulocytic infiltrates within and between compartments in a large cohort of moderate–severe adult asthma patients. This prospective multicentre observational study was conducted in four visits over a 4–6 week period, as described previously [3]. The patients included had moderate–severe persistent asthma (forced expiratory volume in 1 s (FEV1) 40–80% predicted and Asthma Control Questionnaire (ACQ) [4] score >1.5) and, within the past 5 years, evidence of >12% post-bronchodilator reversibility or a provocative concentration of methacholine causing a 20% decline in FEV1 ≤8 mg·mL−1 despite high-dose inhaled corticosteroid (ICS) (≥1000 μg·day−1 fluticasone propionate equivalent) with or without long-acting β2-adrenergic agonist therapy. Key exclusion criteria included initiation or increase in systemic steroid use 30 days prior to screening, chronic or recent (within the past 30 days) use of immunosuppressive therapies, or other active lung disease. Patients had a prior established diagnosis of moderate–severe asthma for ≥6 months prior to screening while receiving a stable dose regimen (>6 weeks) of a high-dose ICS. Allowed concomitant medications included leukotriene receptor antagonists and oral corticosteroids. 78 patients with confirmed moderate–severe asthma were enrolled at 18 sites; 67 (86%) completed the study. All patients had persistently impaired …

To test the hypothesis that aging is associated with a reduction in the diaphragm's force-generating capacity, we compared the maximum transdiaphragmatic pressure (Pdimax) obtained during voluntary maximal inspiratory efforts in nine young (19-28 yr) and ten elderly (65-75 yr) subjects. The relationship between Pdi and lung volume was compared in the two groups by having subjects make maximal inspiratory maneuvers at specified lung volumes (i.e., 20, 40, and 80% vital capacity). Subjects underwent symptom-limited exercise tests to characterize their aerobic capacities and evaluate the relationship between aerobic capacity and Pdimax. The average Pdimax of the elderly subjects (128 +/- 9 cm H2O) was significantly lower (p < 0.003) than the average Pdimax of the younger subjects (171 +/- 8 cm H2O). In the elderly, Pdi was lower across the range of lung volumes tested (p < 0.001), and Pdimax occurred at similar relative lung volumes (elderly, at 47% total lung capacity [TLC]; young, at 50% TLC) in both groups. The elderly subjects were quite fit based on their VO2max, and there was no significant relationship between Pdimax and VO2max. This study suggests that diaphragm strength is reduced in elderly individuals. This age-related decrease in diaphragm strength may predispose elderly patients to diaphragm fatigue in the presence of conditions that impair inspiratory muscle function or increase ventilatory load.

Catecholamines acting through the beta-adrenergic receptor (beta AR) coupled-adenylylcyclase system stimulate a variety of responses by airway epithelial cells which affect airway caliber and the response to inflammatory stimuli. Although the tracheobronchial epithelium (TBE) is composed of several phenotypically differentiated cell types, surprisingly little is known about the expression of the beta AR system by the major subpopulations of TBE cells (i.e., basal and columnar). We, therefore, examined the function of the beta AR system in columnar and basal cell-enriched populations of rabbit tracheocytes. Cells were collected from 35 rabbits in 17 separate experiments and separated into basal and columnar cell-enriched fractions by centrifugal elutriation. The columnar fraction demonstrated a significantly greater (P < 0.005) adenosine 3',5'-cyclic monophosphate (cAMP) response to isoproterenol (10(-9)-10(-5) M) than the basal cell-enriched fraction (i.e., 74.7 +/- 5.1 and 49.4 +/- 2.8 pmol/10(6) cells, in columnar and basal cell-enriched fractions, respectively, P < 0.0001) as well as a higher beta AR density (i.e., 8,678 +/- 840 and 4,754 +/- 406 beta AR sites/cell, respectively, P < 0.0001). However, when corrected for differences in cell size assessed from measurements of total cell protein, cAMP production per milligram protein and beta AR density per milligram protein were similar in the two cell fractions (P > 0.50 for both comparisons). beta AR subtype assessed by beta 1AR and beta 2AR subtype selective antagonists demonstrated that the beta 2AR subtype predominated (i.e., > 90%) in both cell populations (P > 0.5).(ABSTRACT TRUNCATED AT 250 WORDS)

Background: The rabbit trachea provides a model system to test the physiological responses of the airways to various agents. Since three-dimensional organization may affect responses of an organ, an organ culture model was established in serum free medium. Methods: Tracheas were fixed in situ, at steps in the preparation of organ cultures, and after one day to three weeks in organ culture. Samples were examined by light microscopy and scanning and transmission electron microscopy for surface morphology, distribution of cell types, and characteristics of the epithelial cell layer. Results: The normal tracheal mucosa was discovered to consist of extensive circumferential folds in the cartilaginous portion, which were enhanced upon isolation of the trachea from the animal. The folds consisted principally of differences in epithelial cell height rather than folding of the lamina propria. Enhancement of folding upon removal of the trachea coincided with increased secretion by Clara and possibly mucous cells. In organ culture, epithelial cell height initially increased, producing tall folds and cell types were retained in normal proportions. After prolonged culture, cilia were lost but glandular secretion continued. Conclusions: Changes in the arrangement of basal cells and secretory activity in isolated trachea and in culture may give insight into the functional significance of the epithelial folds. © 1994 Wiley-Liss, Inc.

Although it has been recognized that limb skeletal muscles undergo changes during aging, it has been unclear to what extent age-related changes occur in respiratory muscles. This article reviews the structural organization of human skeletal muscles, including those of the respiratory system. Evidence that changes do occur in the structure and function of these muscles in elderly individuals is presented. The potential clinical significance of aging on respiratory muscle strength and endurance is discussed.

The present study examined the effects of elastase, in concentrations present in respiratory secretions, on airway smooth muscle contractile responses in vitro and the magnitude of the airway epithelial inhibition of smooth muscle tension. Experiments were performed on 126 full-thickness tracheal strips from 25 rabbits. Isometric tension responses to acetylcholine (10(-8) to 10(-4) M) and potassium chloride (10 to 110 mM) were examined before and after a 5-min exposure to either porcine pancreatic elastase (PPE) or human neutrophil elastase (HNE). PPE (5 to 40 micrograms/100 microliters) reduced the tension response to acetylcholine but had no effect on the tension response to potassium chloride. PPE and HNE (20 micrograms/100 microliters) produced similar effects. Mechanical removal of the epithelium per se significantly (P less than 0.005) decreased the ED50 response to acetylcholine but did not affect maximal tension. However, the airway epithelial inhibitory effect on the acetylcholine tension response was similar in the presence and absence of PPE (20 micrograms/100 microliters). These data suggest that the diminution of tracheal smooth muscle tension responses to receptor-mediated agonists induced by elastase is a direct effect on the muscle and is not mediated by an effect of elastase on the respiratory epithelium.

The present study investigated the effects of aging on the contractile properties of the adult diaphragm in 42 Golden Syrian hamsters. Experiments were performed on isolated diaphragm strips from three groups of animals 4.9 +/- 0.4 (SE), 12.8 +/- 0.2, and 18.8 +/- 0.3 months of age. Aging was associated with a decrease in the maximal isometric tension generated per unit cross-sectional area of muscle and slowing in the time-to-peak tension and rate of muscle relaxation. The velocity of muscle shortening at a given load was also significantly less in older than in younger animals, and the force-velocity curve became flatter with advancing age as reflected by increases in the Hill coefficient (a/P0). Changes in maximal active tension and maximal velocity of unloaded shortening with aging correlated weakly (r greater than 0.3; p less than 0.05) and were of similar magnitude (-17 to -21%), suggesting that aging affects these two indices of muscle function in similar fashion. Finally, the diaphragm fatigued more rapidly in older than in younger animals. We conclude that aging depresses the ability of the adult diaphragm to generate tension and to shorten and resist fatigue.

Several different scaling techniques, i.e., Borg category (BC) and visual analogue (VA) scales have been used to quantitate the intensity of the respiratory sensations elicited during exercise, but their relationship is unclear. Six subjects with stable chronic obstructive lung disease (FEV1 = 1.2 +/- 0.1 SE L) simultaneously rated the sense of effort to breathe with both BC and VA scales during progressive, maximal exercise tests performed three to five times on a cycle ergometer. The VA scores correlated linearly with minute ventilation in all subjects in all trials (r = 0.98 +/- 0.01), and when converted to common units (i.e., Z scores) correlated closely with simultaneous scores obtained using the Borg scale (r = 0.99 +/- 0.01). Furthermore, VA scores varied minimally over several trials. Coefficient of variation for the maximal VA scores was 6 +/- 1%, which was similar to the variation in maximal Borg score (i.e., 3 +/- 1%). We conclude that the visual analogue scale is reproducible and correlates closely with the Borg score when scaling the sense of effort to breathe during exercise in subjects with stable chronic obstructive pulmonary disease.

Background Goblet cell hyperplasia is a classic but variable pathologic finding in COPD. Current literature shows that smoking is a risk factor for chronic bronchitis but the relationship of these clinical features to the presence and magnitude of large airway goblet cell hyperplasia has not been well described. We hypothesized that current smokers and chronic bronchitics would have more goblet cells than nonsmokers or those without chronic bronchitis (CB), independent of airflow obstruction. Methods We recruited 15 subjects with moderate to severe COPD, 12 healthy smokers, and 11 healthy nonsmokers. Six endobronchial mucosal biopsies per subject were obtained by bronchoscopy and stained with periodic acid Schiff-Alcian Blue. Goblet cell density (GCD) was quantified as goblet cell number per millimeter of basement membrane. Mucin volume density (MVD) was quantified as volume of mucin per unit area of basement membrane. Results Healthy smokers had a greater GCD and MVD than nonsmokers and COPD subjects. COPD subjects had a greater GCD than nonsmokers. When current smokers (healthy smokers and COPD current smokers, n = 19) were compared with all nonsmokers (nonsmoking controls and COPD ex-smokers, n = 19), current smokers had a greater GCD and MVD. When those with CB (n = 12) were compared to those without CB (n = 26), the CB group had greater GCD. This finding was also seen in those with CB in the COPD group alone. In multivariate analysis, current smoking and CB were significant predictors of GCD using demographics, lung function, and smoking pack years as covariates. All other covariates were not significant predictors of GCD or MVD. Conclusions Current smoking is associated with a more goblet cell hyperplasia and number, and CB is associated with more goblet cells, independent of the presence of airflow obstruction. This provides clinical and pathologic correlation for smokers with and without COPD.

The in vivo effects of beta-adrenergic receptor (betaAR) agonists given chronically by metered-dose inhaler (MDI) on the molecular components of the beta-adrenoceptor system expressed by human respiratory cells are poorly understood. This study examined the effects of inhaled albuterol (180 microg four times daily for 7 days) on betaAR function of airway epithelial cells (AECs) and alveolar macrophages (AMs) freshly isolated from 10 normal subjects. Responses were related to beta2AR genotype in codons 16 and 27, regions which affect chronic responses to beta2-agonists. In AEC, betaAR density and adenosine cyclic 3',5'-phosphate (cAMP) production in response to isoproterenol (ISO) were significantly lower in the albuterol versus placebo treatment arm (p0.01 for both). Moreover, in AEC, albuterol treatment increased betaAR-kinase (betaARK) protein immunoreactivity. In contrast, in AM, albuterol tended to decrease betaAR density and cAMP production but changes did not achieve statistical significance (p0.20 for both) and had no effect on betaARK immunoreactivity. Changes in betaAR density occurred in all subjects but tended to be greater in subjects with the glycine 16 genotype. In cultured cells exposed to equal concentrations of beta-agonist in vitro, the magnitude of betaAR down-regulation (p0.05) and cAMP densensitization (p0.05) was greater in AEC than AM. These results indicate that albuterol taken by inhalation in a therapeutically relevant dose for 1 week produces betaAR down-regulation, densensitizes the cAMP response of airway epithelial cells to a beta2-adrenergic agonist, and increases betaARK immunoreactivity. Greater densensitization of AEC than AM in response to chronic albuterol inhalation likely reflects cell type-specific responses.

Transcutaneous electrophrenic twitch stimulation is a potentially powerful way to assess diaphragm contractile function in response to interventions which may alter respiratory muscle strength and endurance. At present, the variability of the transdiaphragmatic twitch pressure (Pdi(T)) over a several hour period is not well described. The present study examines the reproducibility of Pdi(T) amplitude and the twitch occlusion technique of assessing maximum transdiaphragmatic pressure (Pdi(max)) in seven normal adults stimulated intermittently every hour for a total 4-h period. In one subject, data were obtained on two occasions separated by a 2-month interval. Among all subjects, the Pdi(T) amplitude expressed as a percentage of the Pdi(max) was highly reproducible over 4 h (coefficient of variation 5.3). Peak Pdi(T) was inversely related to graded voluntary Pdi (r = -0.0996) and the relationship was virtually identical over 4 h (r = - 0.999, P = 0.96). These data show that Pdi(T) at functional residual capacity and the twitch occlusion relationship are highly reproducible.

Inflammatory cells release a variety of cytokines, including interleukin (IL)-1 beta, into the airway in asthma. This study examined the effects of human IL-1 beta on the function of the beta-adrenergic receptor (beta AR)-adenylyl cyclase (AC) system in BEAS-2B cells, a human airway epithelial cell line. IL-1 beta markedly increased beta AR density (Bmax; P < 0.001) primarily by increasing the percentage of the beta 2AR subtype (from 67 to 91%; P < 0.001). Bmax increased monotonically over time in response to 200 pM IL-1 beta and was approximately 2.5-fold greater than control cells between 36 and 42 h. In contrast, the concentration response of Bmax to IL-1 beta given for 18 h was biphasic. Bmax increased with IL-1 beta concentrations from 2 to 200 pM, but, at > 200 pM, it decreased progressively toward control values. IL-1 beta-induced increases in Bmax with IL-1 beta were associated with approximately threefold increases in beta 2 AR mRNA and were blocked by the protein synthesis inhibitor cycloheximide. Despite the marked increase in Bmax, however, IL-1 beta depressed adenosine 3',5'-cyclic monophosphate (cAMP) responses to isoproterenol and forskolin, a direct activator of AC (P < 0.001 by analysis of variance for both). The inhibitory effect of IL-1 beta on cAMP production appeared to be explained by increases in the activity of an inhibitory GTP binding protein because IL-1 beta treatment increased the activity of a pertussis toxin ADP-ribosylated Gi alpha protein by approximately 2.5-fold; and pretreatment of intact cells with pertussis toxin inhibited the effect of IL-1 beta on cAMP production. These data indicate that IL-1 beta-mediated changes in the beta AR-AC system function in airway epithelial cells are complex and involve expression of receptor protein, GTP binding protein, and possibly AC itself. Increases in IL-1 beta may contribute to abnormalities in airway function in subjects with asthma.

Beta-adrenergic agonist-mediated activation of the beta receptor coupled-adenylyl cyclase (beta AR-AC) system expressed by human airway epithelial cells alters airway function. However, little is known about the magnitude of expression, subtype, and function of the beta receptor-adenylyl cyclase (beta AR-AC) system in human airway epithelial cells from healthy, nonsmoking subjects. Therefore, we characterized beta AR number and subtype and the cAMP response to isoproterenol (iso) in acutely dissociated human tracheocytes harvested from 22 healthy, nonsmoking adults during fibroptic bronchoscopy. Moreover, because the regulation of beta AR-AC system function in response to beta-agonists or inflammatory mediators released into the airway in asthma is poorly understood, we examined the cAMP response to iso after 30 min exposure of cells to iso or the protein kinase C activator, sn-1,2-dioctanoyl glycerol (diC8). The beta AR-AC system was highly expressed and functional in human airway epithelial cells. Group mean beta AR density (i.e., Bmax), equilibrium dissociation constant (Kd), and the percentage of beta 2AR subtypes assessed by radioligand binding were approximately 8,900 receptors/cell, 45 pM, and approximately 80%, respectively. Mean maximum cAMP production was approximately 42 pmol/10(5) cells, and the mean EC50 of the response to iso was 131 nM. However, Bmax and cAMP responses to iso varied considerably across subjects. For example, Bmax varied ninefold, and the EC50 of the cAMP response varied 39-fold interindividually. The EC50 was inversely related to beta AR density (r = -0.81, p0.05), suggesting that sensitivity of the cAMP response to iso was in part dependent on beta AR density. In all experiments, cAMP responses to iso stimulation were markedly desensitized in dose-dependent fashion by 30 min pretreatment with iso or diC8. For example, pretreatment with iso 10 microM or diC8 100 microM reduced maximum cAMP production to 22 and 63% of control values, respectively. These data indicate that: (1) the beta AR-AC system is highly expressed on acutely dissociated airway epithelial cells from normal adult, but beta AR expression and its functional coupling to adenylyl cyclase vary considerably interindividually; and (2) the beta AR-AC system of normal human airway epithelial cells is rapidly desensitized by exposure to beta-adrenergic agonists or activators of PKC.

Adenosine triphosphate (ATP) acting through epithelial nucleotide receptors exerts multiple physiologic actions on airway mucociliary clearance and caliber. However, the effect of ATP on arachidonate metabolism in the airway remains unknown. In this study, the ability of ATP to regulate eicosanoid production was studied in vitro in full-thickness rabbit tracheal strips and separately in rabbit epithelial explant cultures. In the freshly isolated strips, ATP increased prostaglandin E2 (PGE2) release in a dose-dependent fashion, with an activation threshold at 10 microM ATP and a 3.5-fold increase in PGE2 output at 1 mM ATP. Epithelium removal decreased 1 mM ATP-evoked PGE2 release by 68%. Reverse-phase, high-pressure liquid chromatography (HPLC) of media from 3H-arachidonic acid-incubated epithelial explants exposed to 1 mM ATP demonstrated increased output of the cyclooxygenase products PGE2 and prostaglandin F2a (PGF2a). Other identifiable eicosanoids did not increase. The concentration-response for ATP-induced PGE2 release by explants was similar to that of tracheal strips. PGE2 release by 1 mM ATP was 27% of that elicited by ionomycin (10 microM) and was markedly inhibited by indomethacin (10 microM). Purinoceptor agonist-stimulated PGE2 release by the epithelium yielded a rank order of potency of uridine triphosphate (UTP) > or = ATP > 2-methylthio-ATP (2MeSATP) >> alpha,beta-methyleneadenosine-5'-triphosphate (AMP-CPP) > or = adenosine. These results indicate that ATP, acting primarily through an epithelial P2-purinoceptor similar to the P2a subtype, stimulates eicosanoid metabolism in rabbit airway epithelium via the cyclooxygenase pathway, producing PGE2 as the predominant species.

Despite the importance of beta 2-adrenergic receptor (beta 2AR) stimulation in mediating airway epithelial cell function, little is known regarding its regulation in airway epithelium. Perturbations of the airway environment associated with disease states, including the management of bronchomotor tone with beta-agonists, expose airways to putative regulators of beta 2AR signal transduction. In this communication, we describe the desensitization of beta 2AR signal transduction in the human airway epithelial cell line BEAS-2B. Examination of both beta-agonist- and prostaglandin E2 (PGE2)-mediated cAMP generation in BEAS-2B cells reveals both agonist-specific (homologous) and non-agonist-specific (heterologous) desensitization of these G protein-coupled receptor pathways. Short-term homologous desensitization of beta 2AR-mediated cAMP generation was characterized by an approximately 60% loss of maximal responsiveness to isoproterenol (ISO) when cells were pretreated 30 min with 10 microM ISO. A reduced sensitivity to ISO was also evidenced by an approximately 4-fold increase in the EC50 for ISO stimulation of adenylyl cyclase (AC). Short-term heterologous desensitization was characterized by an increase in EC50 (approximately 2- to 3-fold) with no change in maximal responsiveness to ISO in cells pretreated with either forskolin or PGE2. Qualitatively similar findings characterized short-term homologous and heterologous desensitization of PGE2-mediated AC activity. Short-term agonist-specific desensitization of the beta 2AR was associated with, but not dependent upon, rapid beta 2AR sequestration. Long-term pretreatment of cells with 10 nM ISO and 1 microM PGE2 eliminated AC responsiveness to subsequent ISO and PGE2 stimulation, respectively. Exposure of BEAS-2B cells to ISO for 24 h resulted in an approximately 70% loss of beta 2ARs, whereas chronic forskolin or PGE2 pretreatment had no effect on beta 2AR number. Long-term pretreatment of cells designed to elicit heterologous desensitization was associated with reductions in maximal responsiveness to ISO and PGE2 that appear to be related to a loss in inherent AC activity. These findings hold strong implications regarding the effect of beta 2AR desensitization on epithelial cell function and the role of beta-agonists in the management of airway disease.

Stimulation of adenylyl cyclase mediates the effects of beta-adrenergic agonists and prostaglandin E2 (PGE2) on tracheobronchial epithelial cell function by increasing intracellular cyclic adenosine monophosphate (cAMP). In turn, increases in cAMP affect airway function by modulating ciliary beating, chloride and water transport, mucus secretion, and release of bronchoactive substances. This study examined the function and regulation of the beta-adrenergic receptor-adenylyl cyclase system (beta AR-AC) in tracheal epithelial cells isolated from the rabbit, a frequently used animal model of airway reactivity, inflammation, and electrolyte transport. beta AR number, assessed by ligand binding using the non-subtype-specific beta-antagonist [125I]iodopindolol, averaged approximately 10,700 beta AR/cell (400 fmol/mg membrane protein). Greater than 85% of the receptors were of the beta 2 subtype as determined by competitive antagonist displacement of iodopindolol by selective beta 1- (betaxolol) and beta 2- (ICI 118,551) antagonists. cAMP synthesis was stimulated with isoproterenol, PGE2, and forskolin in a time- and concentration-dependent fashion. Preincubation of epithelial cells for 30 min with either isoproterenol (10 microM) or the peptide inflammatory mediator, bradykinin (100 microM), markedly depressed subsequent isoproterenol-stimulated cAMP synthesis. Isoproterenol-induced beta AR-AC desensitization appeared to be homologous since cAMP responses to PGE2 and forskolin, a direct activator of adenylyl cyclase, were not reduced. The effect of bradykinin on isoproterenol-stimulated cAMP response was mimicked by preincubation with either dioctanoyl glyceride or phorbol myristate acetate, activators of protein kinase C.(ABSTRACT TRUNCATED AT 250 WORDS)

The ability to obtain airway epithelial cells from the lower respiratory tract in living human donors will facilitate study of the biologic properties of these cells. We report our experience harvesting tracheobronchial epithelial cells from living human donors by brushing the mucosal surface of the trachea and mainstem bronchi. Cells were obtained on 21 occasions from 18 healthy adult subjects under direct vision with a brush-tipped catheter during fiberoptic bronchoscopy. The average number of cells harvested per subject was 14 +/- 2 x 10(6), and cell viability determined by trypan blue exclusion averaged 36 +/- 4%. Of note, cell viability was significantly enhanced when lidocaine was confined to the nares. Lidocaine was also observed to diminish cell viability in vitro in a dose-dependent fashion. Morphologic and staining properties were used to classify harvested cells into the three major cell types present in the mucosa (i.e., ciliated, secretory, and basal cells). All three subtypes were obtained. The percentage of ciliated, secretory, and basal-like cells was 24 +/- 2%, 11 +/- 1%, 29 +/- 1%, respectively, while the remaining 36% were difficult to type. In one subject in whom brushing was performed on three occasions over a 7-wk period, the percentage of each of the three subtypes was similar across procedures. Harvested cells could be successfully placed in primary culture with a plating efficiency of 50 to 60% and could be subcultured for up to seven passages. Acutely dissociated cells could be used to study the beta-adrenergic receptor adenylyl cyclase system since they produced cAMP in response to isoproterenol.(ABSTRACT TRUNCATED AT 250 WORDS)

The last decade has seen a considerable advance in our understanding of the motor control and mechanical action of the respiratory muscles and the effects of alterations in lung function, body metabolism (e.g. undernutrition) and blood chemistry (e.g. hypocalcemia) on respiratory muscle contractile function. This chapter will briefly review the determinants of respiratory muscle strength, the causes of respiratory muscle weakness and the techniques currently used to assess respiratory muscle strength in man.

This study was conducted to determine whether an amino acid solution enriched with branched-chain amino acids altered protein catabolic rates and plasma ammonia in patients with cirrhosis. Nine stable subjects were given two peripheral intravenous infusions: a standard amino acid solution (solution A) and a branched-chain-enriched solution containing 97% more leucine (solution B). Each solution was given for separate 9-day (group 1, n = 6) or 3-day (group 2, n = 3) periods. Amino acid solutions delivered 0.7 gm protein kg−1 day−1. Diets provided an additional 0.3 gm protein plus maintenance calories. Protein turnover was assessed by a primed continuous infusion of [1-14C] leucine in six patients (three patients in group 1 and three patients in group 2). Nitrogen balance and urinary 3-methyl histidine excretion were determined in group 1 patients. Compared with solution A, solution B increased leucine flux and leucine oxidation but had no significant effect on protein synthesis or catabolism based on the plasma specific activity of either leucine or α-ketoisocaproic acid. The additional leucine infused with solution B was quantitatively oxidized. Nitrogen balance did not differ with the two solutions and there was also no difference in the urinary excretion of 3-methyl histidine, suggesting that muscle protein catabolism was unchanged. Plasma ammonia concentration decreased significantly during the infusion of solution B and was associated with a slight fall in plasma glucagon concentration. The results indicated that a branched-chain-enriched amino acid solution did not alter protein synthesis or catabolism although it did lower the plasma ammonia when compared with a standard amino acid formula in stable cirrhotic patients.(HEPATOLOGY 1990;11:942-950.).

The tracheobronchial epithelium produces factor(s) that modulate the constrictor and relaxant response of airway smooth muscle. The present study sought to determine whether the tracheobronchial epithelial inhibitory effect on trachealis smooth muscle tension is under muscarinic receptor control. Studies were performed on 195 strips from 13 rabbits. In strips in which the epithelium was intact, pirenzepine (an M1 receptor antagonist) produced a dose-related (10(-8) and 10(-7)M) rightward shift (P less than 0.01 for each) and gallamine (an M2 antagonist) produced a progressive (10(-8) and 10(-7)M) leftward shift of the acetylcholine concentration responses (P less than 0.01 for each). In strips in which the epithelium was removed mechanically, neither pirenzepine nor gallamine had any effect on the acetylcholine responses. In acetylcholine precontracted (5 x 10(-6) M) muscle strips with epithelium intact, addition of pirenzepine (10(-7)M) produced a significant (P less than 0.01) reduction in steady-state tension, whereas administration of gallamine tended to increase tension, (P = NS). Neither pirenzepine nor gallamine had any effect on steady-state tension in strips in which the epithelium was removed. These results indicate that the magnitude of the tracheobronchial epithelial inhibitory effect on smooth muscle tension is under muscarinic control. Specifically, M1 receptor blockade augments and M2 receptor blockade inhibits the magnitude of the tracheobronchial epithelial effect.

The present study examined the effects of hypercapnia and positive end-expiratory pressure (PEEP) on the electromyographic (EMG) activity and tidal length changes of the expiratory muscles in 12 anesthetized, spontaneously breathing dogs. The integrated EMG activity of both abdominal (external oblique, internal oblique, rectus abdominis, and transverse abdominis) and thoracic (triangularis sterni, internal intercostal) expiratory muscles increased linearly with increasing PCO2 and PEEP. However, with both hypercapnia and PEEP, the percent increase in abdominal muscle electrical activity exceeded that of thoracic expiratory muscle activity. Both hypercapnia and PEEP increased the tidal shortening of the external oblique and rectus abdominis muscles. Changes in tidal length correlated closely with simultaneous increases in muscle electrical activity. However, during both hypercapnia and PEEP, length changes of the external oblique were significantly greater than those of the rectus abdominis. We conclude that both progressive hypercapnia and PEEP increase the electrical activity of all expiratory muscles and augment their tidal shortening but produce quantitatively different responses in the several expiratory muscles.

The adequacy of emergency room treatment of patients with acute severe asthma was assessed by analyzing the course of 127 visits to the emergency room by 102 patients. Using conventional clinical criteria as an end point (i.e., disappearance of dyspnea, elimination of labored breathing and reduction or elimination of wheezing) in 85.4 per cent of these episodes the patients responded sufficiently to emergency room treatment to allow their discharge. However, the relief of airway obstruction measured directly (1 second forced expiratory volume, FEV 1 ) was modest (mean FEV 1 on discharge was 57 per cent of the predicted normal value). Approximately one-quarter of those episodes that ended in the patient's discharge from the emergency room were followed by equally severe episodes within 10 days (relapse); 6 per cent of the patients initially discharged who returned to the emergency room required hospitalization. Subjects who had a relapse had significantly less improvement in FEV 1 during treatment and lower FEV 1 values at discharge than those who did not have a relapse (p 2 ] or oxygen [PaO 2 ] tension) was sufficiently reliable as an index of the degree of obstruction to substitute for the FEV 1 . We conclude that (1) the success of emergency room treatment depends on the degree of improvement in pulmonary function achieved; and (2) objective measures (e.g., FEV 1 ) of the degree of airway obstruction are helpful in predicting the outcome of emergency room treatment of patients with acute asthma.

Costal strips of diaphragmatic muscle obtained from animals with elastase-induced emphysema generate maximum tension at significantly shorter muscle fiber lengths than muscle strips from control animals. The present study examined the consequences of alterations in the length-tension relationship assessed in vitro on the pressure generated by the diaphragm in vivo. Transdiaphragmatic pressure (Pdi) and functional residual capacity (FRC) were measured in 22 emphysematous and 22 control hamsters 4–5 mo after intratracheal injection of pancreatic elastase or saline, respectively. In 12 emphysematous and 12 control hamsters Pdi was also measured during spontaneous contractions against an occluded airway. To allow greater control over muscle excitation, Pdi was measured during bilateral tetanic (50 Hz) electrical stimulation of the phrenic nerves in 10 emphysematous and 10 control hamsters. Mean FRC in the emphysematous hamsters was 183% of the value in control hamsters (P less than 0.01). During spontaneous inspiratory efforts against a closed airway the highest Pdi generated at FRC tended to be greater in control than emphysematous hamsters. When control hamsters were inflated to a lung volume approximating the FRC of emphysematous animals, however, peak Pdi was significantly greater in emphysematous animals (70 +/- 6 and 41 +/- 8 cmH2O; P less than 0.05). With electrophrenic stimulation, the Pdi-lung volume curve was shifted toward higher lung volumes in emphysematous hamsters. Pdi at all absolute lung volumes at and above the FRC of emphysematous hamsters was significantly greater in emphysematous compared with control animals. Moreover, Pdi continued to be generated by emphysematous hamsters at levels of lung volume where Pdi of control subjects was zero.(ABSTRACT TRUNCATED AT 250 WORDS)

During prolonged undernutrition, the mass of skeletal muscle represents the body's main store of protein and energy. Although it is known that cardiac striated muscle is relatively spared in undernutrition, and that disease-induced reductions in lean body mass do not spare respiratory muscle, the effects of undernutrition per se on the structure and function of the respiratory muscle are largely unstudied in humans. Available data are reviewed.

The purpose of these experiments was to evaluate the validity of the ‘twitch-occlusion’ method as an index of the extent of diaphragmatic activation and to assess the extent of diaphragmatic activation during inspiration. Studies were performed in situ on innervated, perfused muscle strips from the costal region of the diaphragm in ten anesthetized cats. We measured isometric tension generated by the diaphragm during inspiration and following an interpolated electrical stimulation (2Hz, 100 μsec, 3.0 × threshold) of the nerve. The extent of MU activation was assessed by comparing twitch amplitudes during electrical stimulation applied in expiration and in inspiration. Spontaneous inspiratory activity was induced by adding CO2 to the inspired oxygen. Within an animal, the relationship between diaphragmatic activation and twitch occlusion was linear (range of r values was from −0.88 to −0.94). The extent of spontaneous diaphragmatic activation was normalized by dividing tension at end inspiration by the average twitch tension caused by stimuli applied during expiration. Across animals, twitch amplitude was inversely related to diaphragmatic activation ( y = −0.36 x + 1.13, r = −0.94 ). At a respiratory drive with end-tidal PCO2 approximately 1% above apneic threshold (end-tidal PCO2 between 5 and 6%), twitch occlusion was less than 5.0%. Increasing end-tidal PCO2 to at least 5% above apneic threshold (end-tidal PCO2 between 9 and 11%), twitch occlusion was still less than 50%. These results from a preparation that allows direct measurement of isometric tension of the diaphragm show that the interpolated twitch is linearly related to the event of muscle activation through a broad range of muscle activity. In addition, these data indicate that at higher respiratory drives there exists a large reserve in the phrenic motor pool.

Microbiologic surveillance of both the patients and the ambient environment of a surgical intensive care unit allowed us to relate the incidence of nosocomial respiratory tract infection to levels of airborne bacteria. Over the study period respiratory tract nosocomial infection rates varied from 0.7% to 17.0%, and nonrespiratory infection rates varied from 1.0% to 25.0%. Airborne bacteria counts during that time varied from 1.0 ± 0.8 S.E. CFU/ft3to 96.0 ± 6.8 S.E. CFU/ft3. There was a reasonably close correlation between airborne bacteria levels and the incidence of nosocomial pneumonia (r=0.81, p

R espiratory neuromuscular output as measured by the mouth occlusion pressure increases in normal subjects when the resistance to airflow is heightened acutely. In studies conducted by Altose et al’ in patients with chronic obstructive lung disease, the compensatory response to resistive loading was found to be significantly blunted. The diminished occlusion pressure response to flow loading in patients with chronic obstructive lung disease could be due to inspiratory muscle weakness or muscle fatigue. Alternatively, abnormalities in the function of proprioceptive receptors in the muscles of the thoracic cage or in vagal mechanoreceptors in the lung or their central processing could explain the abnormal response to external flow loading. It was reasoned that defective respiratory muscle function should affect the occlusion pressure response to both types of loads equally. If impairment of sensory mechanisms accounted for the blunted P,00 response to flow loads in COPD the response to an elastic load need not be affected. To further evaluate these possibilities, we compared the effects of elastic and inspiratory flow resistive loads on ventilation and occlusion pressure in patients with COPD.

The tracheobronchial epithelium produces inhibitory substance(s) that alter the tracheal smooth muscle tension. This study examined the effect of changes in extracellular Ca2+ and temperature in vitro on the tension response of rabbit trachealis muscle to mechanical removal of the epithelium. Tension during acetylcholine- and KCl-induced contractions was examined at 0, 0.75, 1.5, 2.5, and 5 mM bath Ca2+ concentrations and at 37, 30, 23, and 41 degrees C bath temperature. At most extracellular Ca2+ concentrations (i.e., 0.75, 1.5, 2.5, and 5 mM), epithelial removal shifted the acetylcholine concentration response approximately one-half log to the left (P less than 0.001 for each condition) but had no effect on the responses to KCl (P = NS). Reductions in bath Ca2+ to 0 mM eliminated the epithelial inhibitory effect on the acetylcholine response. In contrast to the effects of reductions in Ca2+, cooling the airway to 30 and 23 degrees C progressively diminished the magnitude of the epithelial inhibitory effect. Our results indicate that the influence of the tracheal epithelium on tracheal smooth muscle responses to constrictor agonists is substance specific and can be diminished by reductions in tracheal temperature and extracellular Ca2+ concentration.