Dysregulation of nuclear factor kappa B (NF-(kappa)B) and increased Ca(2+) signals have been reported in airway epithelial cells of patients with cystic fibrosis (CF). The hypothesis that Ca(2+) signaling may regulate NF-(kappa)B activation was tested in a CF bronchial epithelial cell line (IB3-1, CFTR genotype DeltaF508/W1282X) and compared to the CFTR-corrected epithelial cell line S9 using fluorescence microscopy to visualized in situ NF-(kappa)B activation at the single cell level. Upon stimulation with IL-1beta,we observed a slow but prolonged [Ca(2+)](i) increase (up to 10 min) in IB3-1 cells compared to S9 cells. The IL-1beta-induced [Ca(2+)](i) response was accompanied by an activation of NF-(kappa)B in IB3-1 but not in S9 cells. Pretreatment of IB3-1 cells with the ER Ca(2+) pump inhibitor thapsigargin inhibited the IL-1beta-induced [Ca(2+)](i) response. Treatment with either the calcium chelator BAPTA or an inhibitor of I(kappa)Balpha phosphorylation (digitoxin) led to a drastic [Ca(2+)](i) decrease accompanied by an inhibition of NF-(kappa)B activation of IL-1beta-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-1beta-induced [Ca(2+)](i) response was inhibited and no significant NF-(kappa)B activation was observed. To our knowledge, this is the first report of visualization of the Ca(2+)-mediated activation of NF-(kappa)B in individual living airway epithelial cells. Our results support the concept that [Ca(2+)](i) is a key regulator of NF-(kappa)B activation in CF airway epithelial cells.