Thrombin activates Ras-CREB/ATF-1 signaling and stimulates c-fos, c-jun, and c-myc expression in human gingival fibroblasts

Background: Protease-activated receptors (PARs) can be stimulated by thrombin and other proteases generated by periodontal pathogens. Activation of PARs in gingival fibroblasts (GFs) can modulate wound healing and inflammatory responses in gingival tissues. Methods: The mRNA expression of PARs and early responsive genes in GFs and other oral cells was studied by reverse transcription-polymerase chain reaction. Western blotting was used to study the activation of p38 and cAMP responsive element binding protein (CREB)/activating transcription factor (ATF)-1 as well as Ras. Results: GFs, dental pulp cells, and buccal mucosal fibroblasts expressed PAR-1 and -3 receptors, whereas gingival keratinocytes expressed PAR-1 and -2 receptors. Stimulation of GFs by thrombin rapidly activated Ras signaling and the phosphorylation of CREB/ATF-1 and p38. Thrombin also stimulated the expression of c-fos in GFs within 1 hour of exposure. Stimulation of c-jun mRNA expression showed biphasic responses with two peaks after 1 and 8 hours of exposure. Elevated c-myc expression in GFs by thrombin was noted after 2 hours of exposure. Moreover, the stimulation of c-fos and c-myc mRNA expression by thrombin can be attenuated by D-Phe-Pro-ArgCH ₂Cl, a serine-proteinase inhibitor. Conclusions: PAR activation during gingival wounding or inflammation may stimulate Ras-CREB/ATF-1 signaling and c-fos, c-jun, and c-myc expression. Thismight be due to the proteinase activity of thrombin. These signaling events are important for wound healing and inflammatory responses in gingival tissues.