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

M. O. Husson1,*, N. Wizla-Derambure2, D. Turck1, P. Gosset3 and B. Wallaert3

1 EA 3925, Laboratoire de Bactériologie-Hygiène, Hôpital Calmette, Boulevard du Professeur J. Leclercq, 59037 Lille, France; 2 Centre de Ressources et de Compétences pour la Mucoviscidose, Clinique de Pédiatrie, Hôpital Jeanne de Flandre, 59037 Lille, France; 3 Centre de Ressources et de Compétences pour la Mucoviscidose Adultes, Hôpital Calmette, and Inserm U416, Institut Pasteur de Lille, 59800 Lille, France


* Corresponding author. Tel: +33-320-44-49-44; Fax: +33-320-44-48-95; E-mail: mohusson{at}chru-lille.fr

Received 2 February 2005; returned 22 February 2005; revised 15 March 2005; accepted 28 April 2005


    Abstract
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 Abstract
 Introduction
 Patients and methods
 Results
 Discussion
 References
 
Objectives: The aim of this study was to evaluate the anti-inflammatory properties of intermittent inhaled tobramycin.

Methods: To establish this, we initiated a prospective study to measure the concentration of the three pro-inflammatory cytokines IL-8, IL-6 and TNF-{alpha} in the sputum from 20 cystic fibrosis (CF) patients (15 teenagers and 5 young adults) during cycles and off cycles.

Results: A significant decrease in IL-8 (P = 0.001) and a more moderate decrease in IL-6 (P = 0.046) and TNF-{alpha} (P = 0.052) levels were observed during cycles, even if no significant decrease in the number of leucocytes was observed.

Conclusions: These results associated with a decrease in the Pseudomonas aeruginosa population can contribute in part to the beneficial effect of intermittent inhaled tobramycin on pulmonary function.

Keywords: Pseudomonas aeruginosa , IL-8 , IL-6 , TNF-{alpha}


    Introduction
 Top
 Abstract
 Introduction
 Patients and methods
 Results
 Discussion
 References
 
Exacerbated inflammation is now recognized as an important component of cystic fibrosis (CF) airway disease. Significant inflammatory imbalance characterized by high local interleukin-8 (IL-8) rates associated with a marked accumulation of leucocytes is found early in the disease before any infection.1 Pulmonary inflammation is amplified and associated with an excessive production of other pro-inflammatory cytokines such as IL-6 and tumour necrosis factor-{alpha} (TNF-{alpha}) during Pseudomonas aeruginosa infections.2 Therefore, pro-inflammatory cytokines in sputum are sensitive markers of both current bacterial colonization and inflammation.

To improve lung function, intermittent inhaled administration of tobramycin has been proposed for the delivery of very high local concentrations and optimal antipseudomonal activity.3 However, very little information is available on the effect of this therapy on the inflammatory process in CF patients. Treatment consists of twice daily inhalation of 300 mg of tobramycin during a 28 day treatment period (on cycle) followed by a 28 day no-treatment period (off cycle). This study was a prospective analysis designed to measure the concentrations of three pro-inflammatory cytokines (IL-8, IL-6 and TNF-{alpha}) in the sputum of P. aeruginosa-infected CF patients treated with intermittent tobramycin aerosols.


    Patients and methods
 Top
 Abstract
 Introduction
 Patients and methods
 Results
 Discussion
 References
 
Patients

Fifteen teenagers [age (years): mean, 15.8; range, 13.5–18.8] and 5 young adults [age (years): mean, 23.1; range 21.1–25.9] followed at the Lille University Hospital Pediatric and Adult Cystic Fibrosis Centers were included. All of them were colonized with P. aeruginosa and received at least three cycles of inhaled tobramycin before the study. Treatment with oral and/or intravenous antipseudomonal antibiotics within 4 weeks preceding the study was an exclusion criterion. Written informed consent was obtained from all patients (and/or family).

Methods

Sputum samples were collected for each patient after spontaneous expectoration at the end of antibiotic aerosol cycles and at the end of off cycles, and were processed within 2 h. An aliquot of homogenized sputum in fresh 10% (v/v) dithiothreitol was used for quantitative bacterial cultures. To check the quality of samples, total cell counting was carried out in a haemocytometer, and cell viability was evaluated by means of the Trypan Blue exclusion method. A quantity of 106 cells/mL including less than 20% of squamous epithelial cells and a cell viability superior to 80% were retained as quality criteria for cytokine measurement.

TNF-{alpha}, IL-8 and IL-6 concentrations were measured using commercially available enzyme-linked immunosorbent assay kits (R&D systems, Abingdon, UK) according to the recommended protocols. They were quantified by comparison with a standard curve generated using the appropriate recombinant human cytokine. Sensitivity was as follows: IL-8, 10 ng/mL; IL-6, 0.7 pg/mL; and TNF-{alpha}, 4.4 pg/mL.

Statistical analysis

Results obtained for each patient during antibiotic cycles and off cycles were compared using the Wilcoxon test. Differences were considered significant at P < 0.05.


    Results
 Top
 Abstract
 Introduction
 Patients and methods
 Results
 Discussion
 References
 
Since variation in P. aeruginosa colonization, leucocyte counts and cytokine levels during therapy appeared identical for teenagers and adults, the results of the two populations were grouped for best analysis. The density of P. aeruginosa in sputum samples decreased during antibiotic cycles with an average reduction of 0.59 ± 0.49 log10 cfu/mL (P = 0.01). The cellular response was more variable with ranges of 3.7 to 77.2 x 106 and 3.6 to 97.6 x 106 leucocytes/mL for on and off cycles, respectively. The number of leucocytes did not show any strong modification during antibiotic cycles in about one-third of cases and the decrease in leucocytes with a mean of 8.7 ± 21 x 106 leucocytes/mL observed was not significant. The variation in cytokine levels in cycles of inhaled tobramycin is presented in Figure 1. A significant decrease in IL-8 (P = 0.001) was observed with a mean of 697 ng/mL and 1087.5 ng/mL on and off cycles, respectively. The decrease in the IL-6 and TNF-{alpha} sputum concentrations was more moderate. Their mean concentrations decreased from 2.35 pg/mL to 1.95 pg/mL for IL-6 (P = 0.046) and from 26.25 to 22.35 pg/mL (P = 0.052) for TNF-{alpha} during cycles.



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Figure 1. Sputum concentrations of IL-8 (a), IL-6 (b) and TNF-{alpha} (c) in CF patients measured on (+) and off (–) cycles of inhaled tobramycin. *P < 0.05 by Wilcoxon test.

 

    Discussion
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 Abstract
 Introduction
 Patients and methods
 Results
 Discussion
 References
 
Inhalation of tobramycin twice a day during cycles of 28 days is known to have beneficial effects by reducing the number of hospital admissions of CF patients.4 It is associated with a decrease in P. aeruginosa colonization and an improvement in pulmonary function.5 Our results confirm the beneficial effect on P. aeruginosa colonization and show that inhaled tobramycin therapy also leads to a reduction in local inflammation by reducing pro-inflammatory cytokines in sputum. Surprisingly, we did not observe a significant reduction in neutrophil number after tobramycin inhalation. One cannot exclude the possibility that inhaled tobramycin did not influence the production of other neutrophil chemotactic factors like leukotriene B4.

Reduction of pro-inflammatory cytokine secretion affects essentially IL-8 and more moderately IL-6 and TNF-{alpha}. Since the host inflammatory response is usually correlated with pulmonary infection, the significant decrease in the P. aeruginosa population may explain the beneficial effect of inhaled tobramycin on inflammation. These results are similar to those described after intravenous therapy.6,7 Along this line, it is known that CF cell lines produce significant amounts of pro-inflammatory cytokines in response to P. aeruginosa infection.8 However, one cannot exclude the possibility that inhaled tobramycin, which inhibits the production of IL-8 more than that of IL-6 and TNF-{alpha}, has a direct action on CF epithelial cells for which an up-regulation of nuclear factor-{kappa}B (NF-{kappa}B) leading especially to an activation of IL-8 production has been demonstrated.9

In conclusion, tobramycin aerosol treatment results in a marked reduction in IL-8 and IL-6 sputum levels which may contribute in part to the beneficial effect of this treatment on pulmonary function.


    Acknowledgements
 
We are indebted to Charlotte Buisine and Nathalie Blockelet, coordinating nurses of the Cystic Fibrosis Centers, for their invaluable help in making the study possible, and to L. Beguin for the statistical analysis. This work was supported by Chiron Laboratory.


    References
 Top
 Abstract
 Introduction
 Patients and methods
 Results
 Discussion
 References
 
1. Kammouni W, Figarella C, Marchand S et al. Altered cytokine production by cystic fibrosis tracheal gland serous cells. Infect Immun 1997; 65: 5176–83.[Abstract]

2. Pukhalsky AL, Kapranov NI, Kalashnikova EA et al. Inflammatory markers in cystic fibrosis patients with lung Pseudomonas aeruginosa infection. Mediators Inflamm 1999; 8: 159–67.[CrossRef][ISI][Medline]

3. Geller DE, Pitlick WH, Nardella P et al. Pharmacokinetics and bioavailability of aerosolized tobramycin in cystic fibrosis. Chest 2002; 122: 219–26.[Abstract/Free Full Text]

4. Quittner A, Buu A. Effects of tobramycin solution for inhalation on global ratings of quality of life in patients with cystic fibrosis and Pseudomonas aeruginosa infection. Pediatr Pulmonol 2002; 3: 269–76.[CrossRef]

5. Ramsey BW, Pepe MS, Quan JM et al. Intermittent administration of inhaled tobramycin in patients with cystic fibrosis. Cystic fibrosis inhaled tobramycin study group. N Engl J Med 1999; 340: 23–30.[Abstract/Free Full Text]

6. Karpati F, Hjelte FL, Wretlind B. TNF-alpha and IL-8 in consecutive sputum samples from cystic fibrosis patients during antibiotic treatment. Scand J Infect Dis 2002; 32: 75–9.

7. Cunningham S, McColm JR, Mallinson A et al. Duration of effect of intravenous antibiotics on spirometry and sputum cytokines in children with cystic fibrosis. Pediatr Pulmonol 2003; 36: 43–8.[CrossRef][ISI][Medline]

8. DiMango E, Zar HJ, Bryan R et al. Diverse Pseudomonas aeruginosa gene products stimulate respiratory epithelial cells to produce interleukin-8. J Clin Invest 1995; 96: 2204–10.[ISI][Medline]

9. DiMango E, Ratner AJ, Bryan R et al. Activation of NF-kappaB by adherent Pseudomonas aeruginosa in normal and cystic fibrosis respiratory epithelial cells. J Clin Invest 1998; 101: 2598–605.[Abstract/Free Full Text]





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