Pro-inflammatory effects of Burkholderia cepacia on cystic fibrosis respiratory epithelium

Burkholderia cepacia causes pulmonary infection with high mortality in cystic fibrosis (CF) patients which is likely to involve interaction with respiratory epithelium. In this study the pro-inflammatory properties of B. cepacia were examined using a range of respiratory epithelial cell lines. B. cepacia and cell-free culture supernatants were used to stimulate cell lines with (SigmaCFTE29o- and IB3) and without (A549) the CF transmembrane conductance regulator mutation (CFTR), together with corrected cell lines (C38 and S9). Interleukin (IL)-6 and IL-8, but not GM-CSF or IL-1beta, were released from all the cell lines whereas PGE(2) (prostaglandin E(2)) was released from the A549, IB3 and S9 cell lines only. Nuclear factor (NF)-kappaB activation preceded cytokine release and suppression of NF-kappaB activity diminished cytokine release. These studies indicated that B. cepacia secretory products are potent pro-inflammatory agents for respiratory epithelium and suggest functional CFTR is not required for cytokine or prostanoid responses.     

Recombination signal sequence binding protein Jkappa is constitutively bound to the NF-kappaB site of the interleukin-6 promoter and acts as a negative regulatory factor

Analysis by electrophoretic mobility shift assays (EMSA) of the different proteins associated with the kappaB sequence of the interleukin-6 (IL-6) promoter (IL6-kappaB) allowed us to detect a specific complex formed with the recombination signal sequence binding protein Jkappa (RBP-Jkappa). Single-base exchanges within the oligonucleotide sequence defined the critical base pairs involved in the interaction between RBP-Jkappa and the IL6-kappaB motif. Binding analysis suggests that the amount of RBP-Jkappa protein present in the nucleus is severalfold higher than the total amount of inducible NF-kappaB complexes but that the latter bind DNA with a 10-fold-higher affinity. A reporter gene study was performed to determine the functional implication of this binding; we found that the constitutive occupancy of the IL6-kappaB site by the RBP-Jkappa protein was responsible for the low basal levels of IL-6 promoter activity in L929sA fibrosarcoma cells and that RBP-Jkappa partially blocked access of NF-kappaB complexes to the IL-6 promoter. We propose that such a mechanism could be involved in the constitutive repression of the IL-6 gene under normal physiological conditions.