Effects of bradykinin and thrombin on prostaglandin formation, cell proliferation and collagen biosynthesis in human dental-pulp fibroblasts

Abstract

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 1α (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 [ 3H]-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.