Cystic fibrosis (CF) is a genetic multiorgan disease caused by mutation of the transmembrane conductance regulator (CFTR) gene. Obstructive lung disease is the predominant cause of morbidity and mortality. Lung inflammation and lung infection (primarily by S. aureus and Pseudomonas aeruginosa) are early events occurring in the course of the disease. We studied neutrophils (PMN) derived either from sputum or from blood of young patients with cystic fibrosis (CF). In contrast to what was observed in blood neutrophils, CF sputum PMN displayed a high ex vivo spontaneous IL-8 production which was neither up-regulated by the addition of LPS nor down-regulated by synthetic glucocorticoid such as dexamethasone (Corvol et al. Am. J. Physiol. 2003, 284, L997). Also, IL-10, which inhibits IL-8 production by blood PMN activated by LPS (or peptidoglycan), had no effect on sputum PMN. In CF patients, TLR2 expression was significantly reduced on blood PMN and TLR4 expression was significantly enhanced on sputum PMN as compared to blood PMN from healthy donors. The expression of CD64 (Fcgamma receptor type I), a marker of cell activation, was increased on blood PMN of CF patients (Petit-Bertron et al. Cytokine 2008, 41, 54).
Macroarray analysis of 1050 genes revealed that the expression of 25 genes in CF blood PMNs and 16 genes in CF airway PMNs was reduced as compared to healthy blood PMNs. By contrast, the expression of 42 genes in blood PMNs of CF patients and 56 genes in CF airway PMNs was enhanced as compared to healthy blood PMNs. When comparison was performed between blood and airway PMNs of CF patients, there was, unexpectedly, a very limited difference in terms of gene expression. Only the mRNA expression of amphiregulin and of tumor necrosis factor receptor was significantly higher in airway PMNs. The presence of amphiregulin was confirmed by ELISA in the sputum of CF patients. Altogether, this study clearly demonstrates that PMNs from CF patients display a profound modification of their gene expression profile associated with the disease, with a very limited difference between blood and airway PMNs (Adib-Conquy et al. Mol. Med. 2008, 14, 36-44).
The persistent presence of PMN in airways is the hallmark of cystic fibrosis disease. We assessed whether there is a CF-related anomaly of PMN adherence, rate of apoptosis and production of inflammatory mediators (IL-6, IL-8 and lipoxin A4) when PMN are in contact with airway epithelial cells. We examined co-cultures of PMN isolated from airways and peripheral blood of CF patients and non-CF subjects with human bronchial epithelial cells bearing mutated CFTR, compared to CFTR-corrected and normal epithelial bronchial cells. Our data provided causal evidence that CFTR-deficient bronchial epithelial cells markedly increased sputum PMN adherence, prolonged their survival and induced altered inflammatory response in CF airways. We speculate that the prolonged lifespan of an elevated number of PMN adhering to CF airway epithelium may contribute to the exaggerated inflammatory response in lungs of CF patients (Tabary et al. Am J Physiol. Lung Cell Mol. Physiol, 2006; 290: L588-96)
These works were performed in collaboration with Drs H. Corvol, A. Clément J. Jacquot, and O. Tabary, (Hôp. Trousseau, Paris) and were funded by the Association Vaincre la Mucoviscidose.