Figure 3. Signal transduction pathways involved in TGF-ß1-stimulated uPA production. (A) Healthy and granulation-tissue gingival fibroblasts (80,000 cells) were cultured in the presence of specific MAPK inhibitors: 40 µM PD98059, 10 µM SB203580, or 10 µM SP600125 in serum-free DMEM. After 15 min, cell cultures were treated with 10 ng/mL TGF-ß1 for 48 hrs. Secreted uPA activity was evaluated by casein zymography. (B) Dose-response analysis of the effects of the JNK inhibitor SP600125 on TGF-ß1-stimulated uPA production determined through casein zymography in 3 independent experiments. (C) Gingival granulation-tissue fibroblasts (300,000 cells) were incubated with TGF-ß1 (10 ng/mL) in DMEM without serum for different periods of time, as indicated. The level of activated JNK (pJNK) was determined by Western blotting with specific antibodies.