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Induction of biologically active interleukin-8 from lung epithelial cells by Burkholderia (Pseudomonas) cepacia
R W Palfreyman1, M L Watson, C Eden
1School of Pharmacy and Pharmacology, University of Bath, United Kingdom.
Abstract:
The frequency of isolation of Burkholderia cepacia from the sputum of cystic fibrosis (CF) patients is increasing. Using the human A549 lung epithelial cell line, we have investigated the ability of B. cepacia exoproducts to stimulate interleukin-8 (IL-8) release. Cell-free supernatants from a panel of CF clinical, non-CF clinical, and nonclinical B. cepacia isolates were found to stimulate IL-8 release, with levels ranging from 11.8 +/- 2.8 to 80.0 +/- 3.5 ng/ml. A similar pattern was seen at the level of the IL-8 mRNA. The bioactivity of the IL-8 was confirmed by examining its effect on the intracellular free calcium in neutrophils and inhibition by a neutralizing anti-IL-8 antibody. B. cepacia lipopolysaccharide, which was able to stimulate IL-8 release from monocytes, did not release IL-8 from the A549 cells. Furthermore, the stimulating ability of the bacterial cell-free supernatant was not diminished by polymyxin B, was markedly reduced by boiling, and appeared unrelated to N-acylhomoserine lactones. The ability of B. cepacia to elicit IL-8 release from epithelial cells may be important in the pathology of CF.
Insights
Burkholderia cepacia in cystic fibrosis (CF) patients stimulates interleukin-8 (IL-8) release from lung epithelial cells. This bacterial exoproduct activity may contribute to CF lung inflammation and pathology.
Area of Science:
- Microbiology
- Immunology
- Cell Biology
Background:
- The prevalence of Burkholderia cepacia infections is rising in cystic fibrosis (CF) patients.
- Understanding the host-pathogen interactions in CF is crucial for managing lung disease.
Purpose of the Study:
- To investigate the capacity of Burkholderia cepacia exoproducts to stimulate interleukin-8 (IL-8) release from lung epithelial cells.
- To explore the mechanisms underlying this stimulation and its potential role in CF pathology.
Main Methods:
- Utilized the human A549 lung epithelial cell line.
- Assessed IL-8 release and mRNA levels in response to cell-free supernatants from various B. cepacia isolates.
- Confirmed IL-8 bioactivity using neutrophils and a neutralizing antibody.
- Investigated the role of lipopolysaccharide, polymyxin B, boiling, and N-acylhomoserine lactones.
Main Results:
- Cell-free supernatants from B. cepacia isolates significantly stimulated IL-8 release and mRNA expression in A549 cells.
- IL-8 bioactivity was confirmed through functional assays.
- B. cepacia lipopolysaccharide did not induce IL-8 release from A549 cells.
- Stimulation was heat-labile and not mediated by polymyxin B or N-acylhomoserine lactones.
Conclusions:
- B. cepacia exoproducts can induce IL-8 release from lung epithelial cells, independent of LPS.
- This epithelial cell response to B. cepacia may play a significant role in the inflammatory processes observed in cystic fibrosis lung disease.