Calcium-dependent regulation of NF-κB activation in cystic fibrosis airway epithelial cells

Dysregulation of nuclear factor kappa B (NF-kappa B) and increased Ca2+ signals have been reported in airway epithelial cells of patients with cystic fibrosis (CF). The hypothesis that Ca2+ signaling may regulate NF-B-kappa activation was tested in a CF bronchial epithelial cell line (IB3-1, CFTR genotype Delta F508/W1282X) and compared to the CFTR-corrected epithelial cell line S9 using fluorescence microscopy to visualized in situ NF-B-kappa activation at the single cell level. Upon stimulation with IL-1 beta,we observed a slow but prolonged [Ca2+](i) increase (up to 10 min) in IB3-1 cells compared to S9 cells. The IL-1 beta-induced [Ca2+](i) response was accompanied by an activation of NF-B-kappa in IB3-1 but not in S9 cells. Pretreatment of IB3-1 cells with the ER Ca2+ pump inhibitor thapsigargin inhibited the IL-1 beta-induced [Ca2+](i) response. Treatment with either the calcium chelator BAPTA or an inhibitor of I kappa B alpha. phosphorylation (digitoxin) led to a drastic [Ca2+](i) decrease accompanied by an inhibition of NF-B-kappa activation of IL-1 beta-stimulated IB3-1 cells in comparison to untreated cells. In IB3-1 cells cultured at low temperature (26 degrees C) for 16 h, the IL-1 beta-induced [Ca2+] i response was inhibited and no significant NF-B-kappa activation was observed. To our knowledge, this is the first report of visualization of the Ca2+-mediated activation of NF-B-kappa in individual living airway epithelial cells. Our results support the concept that [Ca2+]i is a key regulator of NF-B-kappa activation in CF airway epithelial cells. (c) 2005 Elsevier Inc. All rights reserved.