CCK stimulates mob-1 expression and NF-κB activation via protein kinase C and intracellular Ca2+

Supraphysiological concentrations of cholecystokinin (CCK) induce chemokine expression in rat pancreatic acini through the activation of the transcription factor NF-kappa B. In the current study, the intracellular signals involved in these pathophysiological effects of CCK were investigated. CCK induction of mob-1 expression in isolated rat pancreatic acini was blocked by the protein kinase C (PKC) inhibitors GF-109203X and Re-32-0432 and by the intracellular Ca2+ chelator BAPTA. CCK induced NF-kappa B nuclear translocation, and DNA binding was also blocked by GF-109203X and BAPTA, Direct activation of PKC with TPA induced mob-1 chemokine expression and activated NF-kappa B DNA binding to a similar extent as did CCK. Increasing intracellular Ca2+ using ionomycin had no effect on mob-1 mRNA levels or NF-kappa B activity. Both CCK and TPA treatments decreased inhibitory kappa B-alpha (I kappa B-alpha) levels, whereas ionomycin had no effect. However, the effects of TPA on I kappa B-alpha degradation were less complete than for CCK. In combination, TPA and ionomycin degraded I kappa B-alpha to a similar extent as CCK. Therefore, activation of NF-kappa B and mob-1 expression by supraphysiological CCK is likely mediated by both PKC activation and elevated intracellular Ca2+.