Pneumologie 2011; 65 - A12
DOI: 10.1055/s-0031-1296103

Cellular Stress and Homeostatic Mechanisms Involved in Reduced Innate Immunity in Cystic Fibrosis Cell Lines

S Chillappagari 1, G Sarode 1, H Shah 1, MO Henke 1
  • 1Department of Pulmonary Medicine, Philipps-University Marburg, Marburg

Introduction: Cystic fibrosis (CF) is commonly associated with bacterial infection of the airways usually with P. aeruginosa and S. aureus. The chronic endobronchial inflammation due to persistent bacterial infection leads to progressive lung disease and is the main cause of mortality and morbidity in CF. These observations suggest a modified immune response in CF. In response, toll like receptors (TLR) act as sensors for the bacterial infections through conserved pathogen assisted molecular patterns (PAMPS), which mediate inflammation and innate immune responses of the lung via TLR signaling. We recently reported decreased TLR-4 surface expression in the bronchial epithelium of patients with CF compared with healthy control subjects and confirmed our results in a cell culture model with CFBE41o- comparing to their corrected isotypes. We investigated autophagy and anti-inflammatory intracellular pathways in response to TLR-4 to determine their involvement during reduced TLR-4 surface expression in CF.

Methods: Immunofluorscence and immunoblotting were performed using the defective CFTR (Cystic Fibrosis Transmembrane Regulator) cell line (CFBE41o-), its corrected counterpart (corr-CFBE41o-) and normal human bronchial epithelial cell line (HBE) as control to examine the expression of TLR-4, unfolded protein response (UPR), autophagy and anti-inflammatory pathways upon LPS stimulation.

Results: We observed a decreased TLR-4 surface expression in CFBE cells under unstimulated conditions and diffused TLR-4 signal upon stimulation with LPS. Immuno blotting for cellular UPR showed increased ATF4 expression in CFBE when stimulated with LPS compared to corr-CFBE. Significant differences in autophagy cargo assisting proteins LC3 II and Beclin-I were observed in CFBE when compared its corrected counterpart corr-CFBE. In contrast, decreased expression of anti-inflammatory response regulator Hemeoxygenase-I (HO-I) was observed in CFBE compared to corr-CFBE.

Conclusion: Our results hint towards a role of cellular stress mechanisms in regulating TLR-4 surface expression in cystic fibrosis. Further studies are required to understand the complex mechanisms involved.