Thrombin Promotes Matrix Metalloproteinase-13 Expression through the PKCδ/c-Src/EGFR/PI3K/Akt/AP-1 Signaling Pathway in Human Chondrocytes
Figure 6
Involvement of AP-1 in the thrombin-induced enhancement of MMP-13 production. ((a) and (b)) qPCR and ELISA analyses of MMP-13 expression in chondrocytes, which were pretreated with curcumin for 30 min or transfected with c-Jun siRNA for 24 h and then stimulated with thrombin for 24 h. ((c) and (d)) Western blotting analyses of c-Jun phosphorylation in cells incubated with thrombin for the indicated time intervals and in cells pretreated with rottlerin, PP2, AG1478, Ly294002, or the Akt inhibitor for 30 min and stimulated with thrombin. ((e) and (f)) Chromatin immunoprecipitation and luciferase activity assays of AP-1 (f). Luciferase activity assays of cells transfected with siRNAs against PAR1, PAR3, PKCδ, c-Src, EGFR, p110, or Akt for 24 h and then stimulated with thrombin for 24 h. * as compared with basal levels. # as compared with the levels in the thrombin-treated group. (g) Schematic representation of the signaling pathways involved in thrombin-induced MMP-13 expression in human chondrocytes.
