Sputum RNA signature in allergic asthmatics following allergen bronchoprovocation test.

BACKGROUND: Inhaled allergen challenge is a validated disease model of allergic asthma offering useful pharmacodynamic assessment of pharmacotherapeutic effects in a limited number of subjects. OBJECTIVES: To evaluate whether an RNA signature can be identified from induced sputum following an inhaled allergen challenge, whether a RNA signature could be modulated by limited doses of inhaled fluticasone, and whether these gene expression profiles would correlate with the clinical endpoints measured in this study. METHODS: Thirteen non-smoking, allergic subjects with mild-to-moderate asthma participated in a randomised, placebo-controlled, 2-period cross-over study following a single-blind placebo run-in period. Each period consisted of three consecutive days, separated by a wash-out period of at least 3 weeks. Subjects randomly received inhaled fluticasone ((FP) MDI; 500 mcg BID×5 doses in total) or placebo. On day 2, house dust mite extract was inhaled and airway response was measured by FEV1 at predefined time points until 7 h post-allergen. Sputum was induced by NaCl 4.5%, processed and analysed at 24 h pre-allergen and 7 and 24 h post-allergen. RNA was isolated from eligible sputum cell pellets (<80% squamous of 500 cells), amplified according to NuGEN technology, and profiled on Affymetrix arrays. Gene expression changes from baseline and fluticasone treatment effects were evaluated using a mixed effects ANCOVA model at 7 and at 24 h post-allergen challenge. RESULTS: Inhaled allergen-induced statistically significant gene expression changes in sputum, which were effectively blunted by fluticasone (adjusted p<0.025). Forty-seven RNA signatures were selected from these responses for correlation analyses and further validation. This included Th2 mRNA levels for cytokines, chemokines, high-affinity IgE receptor FCER1A, histamine receptor HRH4, and enzymes and receptors in the arachidonic pathway. Individual messengers from the 47 RNA signatures correlated significantly with lung function and sputum eosinophil counts. CONCLUSION: Our RNA extraction and profiling protocols allowed reproducible assessments of inflammatory signatures in sputum including quantification of drug effects on this response in allergic asthmatics. This approach offers novel possibilities for the development of pharmacodynamic (PD) biomarkers in asthma.

Kinetics of TH2 biomarkers in sputum of asthmatics following inhaled allergen.

BACKGROUND: Allergen-induced late airway response offers important pharmacodynamic targets, including T helper 2 (TH2) biomarkers. However, detection of inflammatory markers has been limited in dithiothreitol-processed sputum. OBJECTIVES: To test whether allergen-induced TH2 inflammatory markers can be reproducibly quantified by sensitive detection techniques in ultracentrifuged sputum and the effect of fluticasone (FP) on these endpoints. METHODS: Thirteen allergic asthmatics with dual allergen-induced airway responses, documented during a single-blind placebo run-in period, participated in a double-blind, two-period crossover study. Each period consisted of three consecutive days, separated by ≥3 weeks. Following randomization, subjects inhaled FP (500 µg bid, five doses total) or placebo. On Day 2 in each study period, allergen challenge was performed and airway response measured by forced expiratory volume in 1 sec (FEV1) until 7 h post-challenge. Sputum was induced 24 h pre-allergen and 7 and 24 h post-allergen. Sputum samples were split into two portions: TH2 biomarkers were quantified by Meso Scale multiplex platform following ultracentrifugation, and cell differentials were counted on Giemsa-May-Grünwald-stained cytospins. Allergen-induced changes in inflammatory endpoints were compared between FP and placebo using a mixed model ANCOVA. RESULTS: Inhaled allergen induced dual airway responses in all subjects during both placebo periods with reproducible late asthmatic response (LAR) and increased sputum inflammatory biomarkers (IL-2, IL-4, IL-13, and eotaxin-1) and eosinophil counts. FP effectively blunted both the LAR and the inflammatory biomarkers. CONCLUSIONS: Combining novel, sensitive quantification methods with ultracentrifugation allows reproducible quantification of sputum biomarkers following allergen challenge, reversed by FP. This approach allows non-invasive identification of pharmacodynamic targets for anti-asthma therapies.

Reproducibility of biomarkers in induced sputum and in serum from chronic smokers.

RATIONALE: Soluble inflammatory markers obtained from non-invasive airway sampling such as induced sputum may be useful biomarkers for targeted pharmaceutical interventions. However, before these soluble markers can be used as potential targets, their variability and reproducibility need to be established in distinct study populations. OBJECTIVE: This study aimed to assess the reproducibility of biomarkers obtained from induced sputum and serum in chronic smokers and non-smokers. METHOD: Sputum and serum samples were obtained from 16 healthy non-smokers and 16 asymptomatic chronic smokers (for both groups: 8M/8F, 30-52 years, FEV1 ≥80% pred.; ≥10 pack years for the smokers) on 2 separate visits 4-10 days apart. Soluble markers in serum and sputum were analysed by ELISA. The differences between smokers vs non-smokers were analysed with a t-test and variability was assessed on log-transformed data by a mixed model ANOVA. RESULTS: Analysable sputum samples could be obtained from all 32 subjects. In both study populations neutrophils and macrophages were the predominant cell types. Serum Pulmonary Surfactant Associated Protein D had favourable reproducibility criteria for reliability ratio (0.99), intra-subject coefficient of variation (11.2%) and the Bland Altman limits of agreement. Furthermore, chronic smokers, compared to non-smokers, had significantly higher sputum concentrations of IL-8 (1094.6 pg/mL vs 460.8 pg/mL, p = 0.006)), and higher serum concentrations of Pulmonary Surfactant Associated Protein D (110.9 pg/mL vs 64.7 pg/mL, p = 0.019), and lower concentrations of Serum Amyloid A (1352.4 pg/mL vs 2297.5 pg/mL, p = 0.022). CONCLUSION: Serum Pulmonary Surfactant Associated Protein D proved to be a biomarker that fulfilled the criteria for reproducibility in both study groups.

Summing up 100 years of asthma.

In this review, we aim to lead the readers through the historical highlights of pathophysiological concepts and treatment of asthma. Understanding the nature and links of asthma has modeled our diagnostic, pathophysiological and therapeutic thinking and acting. The recognition of its heterogeneous nature in combination with several refined and sophisticated technologies will mark a new era of phenotype-specific approach and treatment of asthma.