EFFECTS OF BRADYKININ AND THROMBIN ON PROSTAGLANDIN FORMATION, CELL-PROLIFERATION AND COLLAGEN BIOSYNTHESIS IN HUMAN DENTAL-PULP FIBROBLASTS

Bradykinin and thrombin caused a time- and dose-dependent stimulation of prostanoid biosynthesis in human dental-pulp fibroblasts, as assessed by the release of prostaglandin E(2) (PGE(2)) and 6-keto-prostaglandin F-1 alpha (the stable breakdown product of prostacyclin). The stimulatory effect of bradykinin and thrombin on PGE(2) biosynthesis was maximal within 5-10 min. The concentration of bradykinin producing half-maximal stimulation (EC(50)) of PGE(2) and prostacyclin formation was 10 nM. EC(50) for thrombin-induced formation of PGE(2) and prostacyclin were 0.05 and 0.2 U/ml, respectively. Bradykinin analogues with affinity to the bradykinin B-2 receptor, but not those with affinity to the B-1 receptor, caused a burst of PGE(2) formation. The stimulatory action of bradykinin and thrombin on PGE(2) biosynthesis was abolished by two structurally different cyclo-oxygenase inhibitors and significantly reduced by two corticosteroids. Thrombin dose-dependently enhanced the incorporation of [H-3]-thymidine into DNA in pulpal fibroblasts by a mechanism that was unrelated to the effect on prostanoid biosynthesis. Bradykinin did not affect thymidine incorporation. Thrombin, but not bradykinin, stimulated the biosynthesis of type 1 collagen in the pulpal fibroblasts. The stimulatory effect of thrombin on collagen biosynthesis was not affected by cyclo-oxygenase inhibitors. These data show that human dental-pulp fibroblasts are equipped with receptors for bradykinin and thrombin linked to enhanced prostanoid biosynthesis. Occupancy of the thrombin receptors also leads to a prostaglandin-independent stimulation of cell proliferation and collagen biosynthesis.