Sputum tests in the diagnosis and monitoring of asthma

Proteomic and metabolomic proof of concept for unified airways in chronic rhinosinusitis and asthma

BACKGROUND

The pathogenesis of chronic rhinosinusitis with nasal polyps (CRSwNP) with comorbid asthma remains unclear.

OBJECTIVE

To assess upper and lower airway unity and identify a possible common pathogenesis in CRSwNP with asthma.

METHODS

This study analyzed the expression of proteins and metabolites in nasal lavage fluid cells (NLFCs) and induced sputum cells (ISCs). Differentially expressed proteins and their function-related metabolites in the upper and lower airways of patients having CRSwNP with or without asthma were identified; relevant signaling pathways were analyzed, and key pathway-related proteins were identified. Parallel reaction monitoring was used to verify these target proteins.

RESULTS

Protein or metabolite expression between NLFCs and ISCs was highly correlated and conservative on the basis of expression profiles and weighted gene coexpression network analysis. There were 17 differentially coexpressed proteins and their function-related 13 metabolites that were identified in the NLFCs and ISCs of CRSwNP, whereas 11 proteins and 11 metabolites were identified in CRSwNP with asthma. An asthma pathway was involved in the copathogenesis of upper and lower airways in whether CRSwNP or CRSwNP with asthma. The asthma pathway-related proteins proteoglycan 2 and eosinophil peroxidase, as the core of the protein-metabolism interaction networks between the upper and lower airways, were both highly coexpressed in NLFCs and ISCs in patients having either CRSwNP or CRSwNP with asthma by parallel reaction monitoring validation.

CONCLUSION

Proteomics and metabolomics reveal upper and lower airway unity. Asthma pathway-related proteins proteoglycan 2 and eosinophil peroxidase from the upper airway could be used to assess the potential risk of lower airway dysfunction in CRSwNP.

Decreased TLR7 expression was associated with airway eosinophilic inflammation and lung function in asthma: evidence from machine learning approaches and experimental validation

BACKGROUND

Asthma is a global public health concern. The underlying pathogenetic mechanisms of asthma were poorly understood. This study aims to explore potential biomarkers associated with asthma and analyze the pathological role of immune cell infiltration in the disease.

METHODS

The gene expression profiles of induced sputum were obtained from Gene Expression Omnibus datasets (GSE76262 and GSE137268) and were combined for analysis. Toll-like receptor 7 (TLR7) was identified as the core gene by the intersection of two different machine learning algorithms, namely, least absolute shrinkage and selector operation (LASSO) regression and support vector machine-recursive feature elimination (SVM-RFE), and the top 10 core networks based on Cytohubba. CIBERSORT algorithm was used to analyze the difference of immune cell infiltration between asthma and healthy control groups. Finally, the expression level of TLR7 was validated in induced sputum samples of patients with asthma.

RESULTS

A total of 320 differential expression genes between the asthma and healthy control groups were screened, including 184 upregulated genes and 136 downregulated genes. TLR7 was identified as the core gene after combining the results of LASSO regression, SVM-RFE algorithm, and top 10 hub genes. Significant differences were observed in the distribution of 13 out of 22 infiltrating immune cells in asthma. TLR7 was found to be closely related to the level of several infiltrating immune cells. TLR7 mRNA levels were downregulated in asthmatic patients compared with healthy controls (p = 0.0049). The area under the curve of TLR7 for the diagnosis of asthma was 0.7674 (95% CI 0.631-0.904, p = 0.006). Moreover, TLR7 mRNA levels were negatively correlated with exhaled nitric oxide fraction (r = - 0.3268, p = 0.0347) and the percentage of peripheral blood eosinophils (%) (r = - 0.3472, p = 0.041), and positively correlated with forced expiratory volume in the first second (FEV1) (% predicted) (r = 0.3960, p = 0.0071) and FEV1/forced vital capacity (r = 0.3213, p = 0.0314) in asthmatic patients.

CONCLUSIONS

Decreased TLR7 in the induced sputum of eosinophilic asthmatic patients was involved in immune cell infiltration and airway inflammation, which may serve as a new biomarker for the diagnosis of eosinophilic asthma.

Endogenous Adenosine 5'-Monophosphate, But Not Acetylcholine or Histamine, is Associated with Asthma Control, Quality of Life, and Exacerbations

OBJECTIVE

Endogenous adenosine 5'-monophosphate (AMP), acetylcholine (ACh), and histamine (HA) are known to be important in bronchial contraction, but their clinical relevance to asthma is poorly understood. We aimed to quantify endogenous AMP, ACh, and HA in induced sputum samples and explore their relationships with asthma control and exacerbations.

METHODS

20 healthy subjects and 112 asthmatics underwent clinical assessment, sputum induction, and blood sampling. The level of asthma control was determined by the asthma control test (ACT) questionnaire. Asthma exacerbation was evaluated according to the criteria of the American Thoracic Society/European Respiratory Society. Levels of AMP, ACh, and HA in sputum were measured by liquid chromatography coupled to tandem mass spectrometry. IL-β, IL-4, IL-5, IL-6, IL-8, IL-13, IL-17A, TNF-α, IFN-γ, and macrophage-derived chemokine (MDC) were also measured.

RESULTS

Compared to healthy controls, asthmatics had higher levels of HA, lower levels of ACh, and similar levels of AMP in induced sputum samples. Compared to controlled asthma (n = 54), uncontrolled asthma (n = 58) showed higher AMP levels (P = 0.002), but similar HA and ACh levels. AMP was negatively correlated with ACT scores (r = - 0.348) and asthma quality of life questionnaire scores (r = - 0.188) and positively correlated with blood monocytes percentage (r = 0.195), sputum MDC (r = 0.214), and IL-6 levels (r = 0.196). Furthermore, AMP was associated with an increased risk of exacerbations in the preceding year.

CONCLUSION

Endogenous AMP, but not ACh or HA, was associated with asthma control, quality of life, and exacerbations in the previous year, which indicates that AMP could be a clinically useful biomarker of asthma.

Assessment of synthetic glucocorticoids in asthmatic sputum

Nonadherence with anti-inflammatory treatment is a frequent cause of continued symptoms in asthmatic patients. Clinical assessments including patient-reported medication administration may provide the asthma specialist incomplete information regarding actual adherence to anti-inflammatory medications. The objective of this report was to describe the first case where adherence to inhaled asthma therapy was assessed by direct analysis of glucocorticoids in induced sputum. The patient's blood, urine, and sputum were tested for synthetic corticosteroids using mass spectrometry. To evaluate a clinical suspicion of poor adherence, sputum, urine, and blood were used to assess for current compliance to medication use. We report a case where asthma specialists attributed poorly controlled asthma to nonadherence to medical therapy. After modification of the medical regimen, adherence with oral and inhaled steroids was assessed-via examination of the urine, blood, and sputum. Direct analysis of glucocorticoids in sputum is feasible and in theory could provide a novel tool to document current medication adherence. Concomitant assessment of glucocorticoids and eosinophils in the same induced sputum specimen could provide insight into possible steroid resistance in select referral patients with difficult asthma.

Asthma: are we monitoring the correct measures?

The prevalence of asthma, a common chronic inflammatory disease of the airways, has risen sharply over the past 25-30 years, with the biggest increase found in children. Currently, more than 22 million Americans have asthma. Asthma also is associated with significant morbidity and mortality worldwide. Each year, asthma is responsible for $16 billion in direct and indirect costs due to health care utilization and loss of productivity, with over 14 million missed workdays. Asthma also accounts for almost 1.8 million emergency room visits and almost 500,000 hospitalizations annually. Therefore, assessment and monitoring of disease activity is critical to improve clinical and economic outcomes for patients with asthma. To help in this endeavor, practitioners and payers rely on evidence-based guidelines to classify disease severity, to guide treatment decisions, and to assess the degree of asthma control. In August 2007, the National Asthma Education and Prevention Program (NAEPP) updated its guidelines based on greater knowledge of disease pathophysiology and the development of newer therapeutic agents. This includes an increased emphasis on the need to establish disease severity, including the components of impairment and risk, as well as on the level of asthma control. Despite the availability of the NAEPP and other guidelines, asthma control often remains suboptimal. While numerous clinical and patient-reported measures are available, it is clear that the optimal monitoring schema for patients with asthma remains undefined. To clearly establish whether asthma control is attained, multiple measures are required and should include clinical and patient-reported assessments.

Increases in airway eosinophilia and a th1 cytokine during the chronic asymptomatic phase of asthma

BACKGROUND

Studies using allergen challenge models have suggested Th2 cytokines promote airway inflammation in asthma. We assessed mediators of airway inflammation during the chronic asymptomatic phase of asthma.

METHODS

Nine non-atopic asthma (NAA) patients, 19 atopic asthma (AA) patients, 20 atopic controls (AC), and 38 normal controls (NC) underwent sputum induction while asymptomatic. Sputum total cell counts and differentials were determined; levels of cytokines IL-4, IL-5, IL-13, GM-CSF, and IFN-gamma, and chemokines eotaxin (CCL11) and RANTES (CCL5) were measured by ELISA; and levels of eosinophil-derived neurotoxin (EDN) were measured by radioimmunoassay.

RESULTS

NAA patients showed higher % eosinophils and total eosinophils compared to AA. NAA and AA patients showed higher IFN-gamma and EDN levels compared to AC and NC, with no differences in IL-4, IL-5, or IL-13 levels among the four groups. GM-CSF levels were higher in AA patients compared to AC or NC. In NAA, AA, and AC patients, % eosinophils and EDN levels correlated positively with IFN-gamma, GM-CSF, eotaxin, and RANTES, but not with IL-5 levels.

CONCLUSIONS

Baseline airway inflammation of intrinsic and extrinsic asthma is characterized by eosinophilic inflammation and the Th1 cytokine, IFN-gamma. GM-CSF, instead of IL-5, and chemokines may coordinate airway eosinophilia during the chronic asymptomatic phase of asthma.

Rapid effect of inhaled ciclesonide in asthma: a randomized, placebo-controlled study

BACKGROUND

Ciclesonide is a novel inhaled corticosteroid for the treatment of asthma, and it is important to measure the onset of effect of this therapy on airway hyperresponsiveness (AHR), exhaled nitric oxide (NO), and levels of eosinophils in induced sputum.

METHODS

In a randomized, double-blind, crossover study, 21 patients with mild asthma inhaled ciclesonide 320 microg (ex-actuator) qd, ciclesonide 640 microg (ex-actuator) bid, and placebo for 7 days. Exhaled NO and AHR to adenosine monophosphate (AMP), measured as the provocative concentration of AMP producing a 20% reduction in FEV1 (PC20FEV1), were assessed after inhalation on days 1, 3 and 7. Eosinophil levels in induced sputum were also measured.

RESULTS

Ciclesonide 320 microg qd and 640 microg bid produced significantly greater improvements in PC20FEV1 compared with placebo on day 1 (within 2.5 h), and on days 3 and 7 (all p < 0.0001). On day 3, both ciclesonide doses significantly reduced exhaled NO levels by - 17.7 parts per billion (p < 0.0001) and - 15.4 parts per billion (p < 0.003) vs placebo, respectively. Significant reductions were maintained during the study with both ciclesonide doses (p < 0.01). A nonsignificant trend towards a decrease in eosinophil cell numbers was observed after 7 days of ciclesonide treatment, especially in patients receiving the higher dose.

CONCLUSIONS

A single dose of ciclesonide decreased AHR to AMP and exhaled NO within 3 h, while FEV, improved at 3 days and 7 days.

Shotgun proteomic analysis of human-induced sputum

Induced sputum is a readily accessible biological fluid whose composition may alter as a consequence of disease. To date, however, the proteins that routinely populate this biofluid are largely unknown, in part due to the technical difficulties in processing such mucin-rich samples. To provide a catalogue of sputum proteins, we have surveyed the proteome of human-induced sputum (sputome). A combination of 2-D gel analysis and GeLC-MS/MS allowed a total of 191 human proteins to be confidently assigned. In addition to the expected components, several hitherto unreported proteins were found to be present, including three members of the annexin family, kallikreins 1 and 11, and peroxiredoxins 1, 2 and 5. Other sets of proteins identified included four proteins previously annotated as hypothetical or conserved hypothetical. Taken together, these data represent the first extensive survey of the proteome of induced sputum and provide a platform for future identification of biomarkers of lung disease.

Evaluation of airway inflammation by quantitative Th1/Th2 cytokine mRNA measurement in sputum of asthma patients

BACKGROUND

Asthma is a chronic inflammatory disorder of the airways driven by T cell activation. Th2 cells and their cytokines are thought to play a role in the pathophysiology of allergic as well as non-allergic asthma.

METHODS

Airway cells were obtained by sputum induction from 15 healthy and 39 asthmatic individuals and the airway T cell cytokine profiles (interleukin (IL)-4, IL-5, IL-13, IL-10 and interferon (IFN)-gamma) at the mRNA level were studied by real time RT-PCR.

RESULTS

Asthma patients had increased expression of IL-5 (p = 0.001) and IL-13 (p = 0.03) mRNA in sputum compared with non-asthmatic controls. IL-4 mRNA and IFN-gamma mRNA were detectable in the sputum of 44% and 21% of patients, respectively, but not in controls. Sputum IL-10 mRNA levels did not differ significantly between patients and controls. Sputum mRNA expression levels of IL-4, IL-5, and IL-13 were significantly correlated with the percentage of eosinophils and were higher in subjects with allergic asthma than in those with non-allergic asthma (p = 0.03, p = 0.02 and p = 0.0002, respectively); they did not differ between mild asthmatic subjects and those with moderate to severe asthma. In contrast, IFN-gamma mRNA expression was higher in non-allergic than in allergic patients (p = 0.04) and higher in patients with moderate to severe asthma than in those with mild asthma (p<0.01). Sputum IL-5 mRNA levels (but not the other cytokine mRNA levels) were also correlated with exhaled nitric oxide (eNO) and with bronchial hyperreactivity expressed as the histamine concentration resulting in a 20% decrease in forced expiratory volume in 1 second.

CONCLUSION

Real time RT-PCR analysis of mRNA in induced sputum confirms a predominance of Th2 cytokines in both allergic and non-allergic asthma. IL-5 levels reflect eosinophil infiltration as well as eNO levels and hyperreactivity, and levels of the Th1 cytokine IFN-gamma indicate asthma severity. The technique is a promising tool for use in further studies of asthma severity and disease activity.