Bradykinin regulates the histamine-induced Ca 2+ mobilization via protein kinase C activation in human gingival fibroblasts

Abstract

We previously demonstrated that histamine and bradykinin evoke an increase in intracellular Ca 2+ ([Ca 2+] i) in human gingival fibroblasts by using a fluorescent Ca 2+ indicator Fura-2. In this paper, we further demonstrate the regulation of the histamine-induced Ca 2+ mobilization by bradykinin. In fibroblasts stimulated with bradykinin (1 μM), subsequent stimulation with histamine (100 μM) failed to mobilize Ca 2+, whereas bradykinin induced an increase in [Ca 2+] i in the cells pre-stimulated with histamine. The attenuation of the histamine response was dependent on the concentration of bradykinin for the first stimulation. Histamine also failed to induce the formation of inositol 1,4,5-trisphosphate in fibroblasts pretreated with bradykinin. In fibroblasts pretreated with bradykinin (1 μM) for 3 min and then washed with fresh medium, the effect of histamine on [Ca 2+] i quickly returned to the control level. The activation of protein kinase C by phorbol ester 12-O-tetradecanoyl-phorbol-13-acetate (PMA) elicited a marked decrease in histamine-induced Ca 2+ mobilization. When the protein kinase C activity was inhibited with H7, a protein kinase C inhibitor, or was down-regulated by pretreatment with PMA for 20 h, the inhibitory effect of PMA on the histamine response was relieved. In the fibroblasts pretreated with H7 or PMA for 20 h, histamine evoked Ca 2+ mobilization even after bradykinin stimulation. These results suggest that the histamine response is regulated by bradykinin receptor activation via the activation of protein kinase C in human gingival fibroblasts.