Effect of intermittent inhaled tobramycin on sputum cytokine profiles in cystic fibrosis

P. aeruginosa tRNA-fMet halves secreted in outer membrane vesicles suppress lung inflammation in cystic fibrosis

Although tobramycin increases lung function in people with cystic fibrosis (pwCF), the density of Pseudomonas aeruginosa (P. aeruginosa) in the lungs is only modestly reduced by tobramycin; hence, the mechanism whereby tobramycin improves lung function is not completely understood. Here, we demonstrate that tobramycin increases 5' tRNA-fMet halves in outer membrane vesicles (OMVs) secreted by laboratory and CF clinical isolates of P. aeruginosa. The 5' tRNA-fMet halves are transferred from OMVs into primary CF human bronchial epithelial cells (CF-HBEC), decreasing OMV-induced IL-8 and IP-10 secretion. In mouse lungs, increased expression of the 5' tRNA-fMet halves in OMVs attenuated KC (murine homolog of IL-8) secretion and neutrophil recruitment. Furthermore, there was less IL-8 and neutrophils in bronchoalveolar lavage fluid isolated from pwCF during the period of exposure to tobramycin versus the period off tobramycin. In conclusion, we have shown in mice and in vitro studies on CF-HBEC that tobramycin reduces inflammation by increasing 5' tRNA-fMet halves in OMVs that are delivered to CF-HBEC and reduce IL-8 and neutrophilic airway inflammation. This effect is predicted to improve lung function in pwCF receiving tobramycin for P. aeruginosa infection.NEW & NOTEWORTHY The experiments in this report identify a novel mechanism, whereby tobramycin reduces inflammation in two models of CF. Tobramycin increased the secretion of tRNA-fMet halves in OMVs secreted by P. aeruginosa, which reduced the OMV-LPS-induced inflammatory response in primary cultures of CF-HBEC and in mouse lung, an effect predicted to reduce lung damage in pwCF.

P. aeruginosa tRNA-fMet halves secreted in outer membrane vesicles suppress lung inflammation in Cystic Fibrosis

Although tobramycin increases lung function in people with cystic fibrosis (pwCF), the density of Pseudomonas aeruginosa (P. aeruginosa) in the lungs is only modestly reduced by tobramycin; hence, the mechanism whereby tobramycin improves lung function is not completely understood. Here, we demonstrate that tobramycin increases 5' tRNA-fMet halves in outer membrane vesicles (OMVs) secreted by laboratory and CF clinical isolates of P. aeruginosa . The 5' tRNA-fMet halves are transferred from OMVs into primary CF human bronchial epithelial cells (CF-HBEC), decreasing OMV-induced IL-8 and IP-10 secretion. In mouse lung, increased expression of the 5' tRNA-fMet halves in OMVs attenuated KC secretion and neutrophil recruitment. Furthermore, there was less IL-8 and neutrophils in bronchoalveolar lavage fluid isolated from pwCF during the period of exposure to tobramycin versus the period off tobramycin. In conclusion, we have shown in mice and in vitro studies on CF-HBEC that tobramycin reduces inflammation by increasing 5' tRNA-fMet halves in OMVs that are delivered to CF-HBEC and reduce IL-8 and neutrophilic airway inflammation. This effect is predicted to improve lung function in pwCF receiving tobramycin for P. aeruginosa infection.

New and noteworthy

The experiments in this report identify a novel mechanim whereby tobramycin reduces inflammation in two models of CF. Tobramycin increased the secretion of tRNA-fMet haves in OMVs secreted by P. aeruginiosa , which reduced the OMV-LPS induced inflammatory response in primary cultures of CF-HBEC and in mouse lung, an effect predicted to reduce lung damage in pwCF.

Graphical abstract

The anti-inflammatory effect of tobramycin mediated by 5' tRNA-fMet halves secreted in P. aeruginosa OMVs. (A) P. aeruginosa colonizes the CF lungs and secrets OMVs. OMVs diffuse through the mucus layer overlying bronchial epithelial cells and induce IL-8 secretion, which recruits neutrophils that causes lung damage. ( B ) Tobramycin increases 5' tRNA-fMet halves in OMVs secreted by P. aeruginosa . 5' tRNA-fMet halves are delivered into host cells after OMVs fuse with lipid rafts in CF-HBEC and down-regulate protein expression of MAPK10, IKBKG, and EP300, which suppresses IL-8 secretion and neutrophils in the lungs. A reduction in neutrophils in CF BALF is predicted to improve lung function and decrease lung damage.

Inflammation biomarkers in sputum for clinical trials in cystic fibrosis: current understanding and gaps in knowledge

RATIONALE

Sputum biomarkers hold promise as a direct measure of inflammation within the cystic fibrosis (CF) lung, but variability in study design and sampling methodology have limited their use. A full evaluation of the reliability, validity and clinical relevance of individual biomarkers is required to optimise their use within CF clinical research.

OBJECTIVES

A biomarker Special Interest Working Group was established within the European Cystic Fibrosis Society-Clinical Trials Network Standardisation Committee, to perform a review of the evidence regarding sputum biomarkers in CF.

METHODS

From the 139 included articles, we identified 71 sputum biomarkers to undergo evaluation of their clinimetric properties, responsiveness, discriminant, concurrent and convergent validity.

RESULTS

Current evidence confirms the potential of sputum biomarkers as outcome measures in clinical trials. Inconsistency in responsiveness, concurrent and convergent validity require further research into these markers and processing standardisation before translation into wider use. Of the 71 biomarkers identified, Neutrophil Elastase (NE), IL-8, TNF-α and IL-1β, demonstrated validity and responsiveness to be currently considered for use in clinical trials. Other biomarkers show future promise, including IL-6, calprotectin, HMGB-1 and YKL-40.

CONCLUSION

A concerted international effort across the cystic fibrosis community is needed to promote high quality biomarker trial design, establish large population-based biomarker studies, and work together to create standards for collection, storage and analysis of sputum biomarkers.

Chemoattractants and cytokines in primary ciliary dyskinesia and cystic fibrosis: key players in chronic respiratory diseases

Patients with primary ciliary dyskinesia (PCD) and cystic fibrosis (CF), two inherited disorders, suffer from recurrent airway infections characterized by persistent bacterial colonization and uncontrollable inflammation. Although present in high counts, neutrophils fail to clear infection in the airways. High levels of C-X-C motif chemokine ligand 8/interleukin-8 (CXCL8/IL-8), the most potent chemokine to attract neutrophils to sites of infection, are detected in the sputum of both patient groups and might cause the high neutrophil influx in the airways. Furthermore, in CF, airway neutrophils are highly activated because of the genetic defect and the high levels of proinflammatory chemoattractants and cytokines (e.g., CXCL8/IL-8, tumor necrosis factor-α and IL-17). The overactive state of neutrophils leads to lung damage and fuels the vicious circle of infection, excessive inflammation and tissue damage. The inflammatory process in CF airways is well characterized, whereas the lung pathology in PCD is far less studied. The knowledge of CF lung pathology could be useful to guide molecular investigations of the inflammatory processes in PCD lungs. Current available therapies can not completely remedy the chronic airway infections in these diseases. This review gives an overview of the role that chemoattractants and cytokines play in these neutrophil-dominated lung pathologies. Finally, the most frequently applied treatments in CF and PCD and new experimental therapies to reduce neutrophil-dominated airway inflammation are described.

A High Level of Soluble CD40L Is Associated with P. aeruginosa Infection in Patients with Cystic Fibrosis

Objective

The aim of this study was to evaluate whether the concentration of sCD40L, a product of platelet activation, correlates with the presence of Pseudomonas aeruginosa in the airway of patients with cystic fibrosis (CF) and to determine its possible clinical association.

Methods

Sixty patients with CF, ranging in age from 2 months to 36 years, were studied. The demographics, cystic fibrosis transmembrane conductance regulator (CFTR) genotype, spirometry measurements, radiographic and tomographic scans, platelet count in peripheral blood, sCD40L, IL-6, TNF-α and ICAM1 data were collected. Infection-colonization of the airway was evaluated using sputum and throat swab cultures; the levels of anti-Pseudomonas aeruginosa antibodies (Anti-PaAb) were evaluated.

Results

Patients with CF and chronic colonization had anti-PaAb values of 11.6 ± 2.1 ELISA units (EU) and sCD40L in plasma of 1530.9 ±1162.3 pg/mL; those with intermittent infection had 5.7 ± 2.7 EU and 2243.6 ± 1475.9 pg/mL; and those who were never infected had 3.46 ± 1.8 EU (p≤0.001) and 1008.1 ± 746.8 pg/mL (p≤0.01), respectively. The cutoff value of sCD40L of 1255 pg/mL was associated with an area under the ROC (receiver operating characteristic curve) of 0.84 (95% CI, 0.71 to 0.97), reflecting P. aeruginosa infection with a sensitivity of 73% and a specificity of 89%. Lung damage was determined using the Brasfield Score, the Bhalla Score, and spirometry (FVC%, FEV1%) and found to be significantly different among the groups (p≤0.001).

Conclusion

Circulating sCD40L levels are increased in patients with cystic fibrosis and P. aeruginosa infection. Soluble CD40L appears to reflect infection and provides a tool for monitoring the evolution of lung deterioration.

High-dose tobramycin inhibits lipopolysaccharide-induced MUC5AC production in human lung epithelial cells

Tobramycin inhalation therapy is an effective therapy for cystic fibrosis as well as severe bronchiectasis that is colonized with Pseudomonas aeruginosa. The mechanism responsible for the efficacy of tobramycin in the treatment of severe chronic infectious diseases has not been elucidated. We demonstrate that high-dose tobramycin decreases MUC5AC gene expression and protein production in NCI-H292 cell stimulated with lipopolysaccharide of P. aeruginosa. MUC5AC protein of NCI-H292 cell stimulated by lipopolysaccharide was analyzed by an enzyme-linked immunosorbent assay and MUC5AC expression at the mRNA level was analyzed by RT-PCR. Western blot was performed to examine a potential role for the signaling molecules upstream of NFκB. High-dose tobramycin (500μg/ml) decreased the level of MUC5AC protein released into the supernatant of the NCI-H292 cell line at 24h after lipopolysaccharide stimulation (P<0.001). The tobramycin treatment also inhibited MUC5AC mRNA expression at 12h after lipopolysaccharide stimulation (P<0.05) and suppressed NFκB activation 60min after lipopolysaccharide stimulation (P<0.001). Tobramycin suppressed the phosphorylation of extracellular signal-regulated protein kinase, p38 MAP kinase. These results suggest that high-dose tobramycin, such as inhalation therapy, can inhibit MUC5AC gene expression and MUC5AC protein production in NCI-H292 cells, in part through the mitogen-activated protein kinase pathway. Thus, the activation of TLR4 and the subsequent immune/inflammatory responses induced by chronic infections such as P. aeruginosa might be modulated by tobramycin. Our data may reveal one of the mechanisms responsible for the clinical effect of tobramycin inhalation therapy against severe chronic respiratory diseases due to P. aeruginosa.

Inhaled versus systemic antibiotics and airway inflammation in children with cystic fibrosis and Pseudomonas

RATIONALE

Inhaled tobramycin has been shown to transiently clear Pseudomonas from lower airways in early cystic fibrosis (CF), but does not markedly reduce lung inflammation, a key factor in disease progression.

OBJECTIVE

Test the hypothesis that systemic antibiotics are more effective than inhaled antibiotics for reducing lower airways inflammation.

METHODS

Clinically stable CF children with recent Pseudomonas were randomized to receive 4 weeks of inhaled tobramycin or 2 weeks of systemic antibiotics (intravenous ceftazidime and tobramycin). Bronchoalveolar lavage fluid was obtained just before and 4-6 weeks after treatment. The primary outcome was change in % neutrophils in lavage fluid.

RESULTS

Fifteen subjects (inhaled = 6, systemic = 9) completed the protocol. Three Systemic Group subjects could not have central venous access established and were treated with oral ciprofloxacin (plus inhaled tobramycin) for 2 weeks as an alternative "systemic" regimen, per protocol. Groups were well matched in age, markers of disease severity, and initial % neutrophils. The Systemic Group showed a modest median change in percent neutrophils (-7%) which was not statistically significant compared to inhaled (+5.4%, P = 0.07). However, the Systemic Group had significantly greater reductions in total cells (-50% vs. -3%, P < 0.01) and neutrophils (-74% vs. -10%, P = 0.02) per ml lavage fluid. Both groups had reduced bacterial quantity after treatment, but there was no significant difference between groups.

CONCLUSIONS

In clinically stable children with CF, systemic antibiotics result in greater short-term reduction in lower airways inflammation than inhaled antibiotics.

Sputum trace metals are biomarkers of inflammatory and suppurative lung disease

BACKGROUND

Induced sputum cytology and protein biomarkers can be used to assess airways inflammation. Increases in sputum iron have been described in inflammatory lung disease. We hypothesized that other sputum metals may be affected by airways inflammation and investigated their potential value as biomarkers.

METHODS

Sputum was obtained from 20 healthy control subjects and from patients with inflammatory pulmonary diseases (23 with cystic fibrosis [CF], 16 with bronchiectasis, 17 with asthma, and 23 with COPD), and iron, zinc, manganese, and copper were measured. Fourteen patients with CF were also studied through an exacerbation cycle.

RESULTS

Sputum zinc and iron were elevated in CF and non-CF bronchiectasis vs controls (P < .001, zinc; P < .01 iron). Manganese was elevated in asthma (P < .01) and bronchiectasis (P < .05) vs controls. Copper was elevated in CF vs controls (P < .05). Zinc decreased (P < .01) following treatment of CF exacerbation. In subjects with CF zinc levels correlated with other biomarkers.

CONCLUSIONS

These results suggest a relationship of high concentrations of total zinc and iron with airways inflammation in CF and non-CF bronchiectasis, with longitudinal changes being observed in CF. Further work is required to elucidate potential inflammatory mechanisms related to these observations.

Tobramycin Nebulizer Solution in severe COPD patients colonized with Pseudomonas aeruginosa: effects on bronchial inflammation

INTRODUCTION

Airway colonization with Pseudomonas aeruginosa is frequent in severe chronic obstructive pulmonary disease (COPD) and may lead to progressive inflammatory damage. Inhaled Tobramycin Nebulizer Solution (TNS; a preservative-free formulation) is an effective therapy in chronic P aeruginosa infection in cystic fibrosis and bronchiectasis. In this study we aimed to investigate the effects of a TNS short course on inflammatory markers in bronchial secretions from multiresistant P aeruginosa-colonized patients with severe COPD. To the authors' knowledge, this is the first study to examine this in cases of severe COPD.

METHODS

Thirteen COPD patients (GOLD criteria 3-4; mean age 72.7+/- 8 years; mean basal forced expiratory volume in 1 second (FEV(1)) 34.8%+/-8.1%; mean FEV(1)/forced vital capacity 0.6+/-0.1) were enrolled. All patients were colonized with P aeruginosa and resistant to oral/intravenous specific antibiotics. Eosinophilic cationic protein (ECP), interleukin-1 beta (IL-1beta), interleukin-8 (IL-8), tumor necrosis factor alfa (TNF-alpha), and cell counts were measured in spontaneous secretions before and after a 2-week TNS course (300 mg twice daily).

RESULTS

The TNS course induced a significant reduction in IL-1beta (P<0.03), IL-8 (P<0.02), ECP (P<0.01) concentrations, and in eosinophil count (P<0.01). TNF-alpha levels, and neutrophil and lymphocyte counts were not significantly affected. The second week of treatment proved crucial in terms of efficacy. P aeruginosa density was lowered after 6 months; severe acute exacerbations were reduced by 42%.

CONCLUSION

TNS reduced the inflammatory impact of P aeruginosa in multiresistant, P aeruginosa-colonized patients with severe COPD. A therapeutic role for TNS can be strongly suggested in these particular conditions.

Sputum biomarkers of inflammation in cystic fibrosis lung disease

Pulmonary biomarkers are being used more frequently to monitor disease activity and evaluate response to treatment in individuals with cystic fibrosis (CF). This article summarizes the current state of knowledge of biomarkers of inflammation relevant to CF lung disease, and the tools to measure inflammation, with specific emphasis on sputum. Sputum is a rich, noninvasive source of biomarkers of inflammation and infection. Sputum induction, through the inhalation of hypertonic saline, has expanded the possibilities for monitoring airway inflammation and infection, especially in individuals who do not routinely expectorate sputum. We critically examine the existing data supporting the validity of sputum biomarkers in CF, with an eye toward their application as surrogate endpoints or outcome measures in CF clinical trials. Further validation studies are needed regarding the variability of inflammatory biomarker measurements, and to evaluate how these biomarkers relate to disease severity, and to longitudinal changes in lung function and other clinical endpoints. We highlight the need to incorporate sputum collection, by induction if necessary, and measurement of sputum biomarkers into routine CF clinical care. In the future, pulmonary biomarkers will likely be useful in predicting disease progression, indicating the onset and resolution of a pulmonary exacerbation, and assessing response to current therapies or candidate therapeutics.