Cross Talk Among Smad, MAPK, and Integrin Signaling Pathways Enhances Adventitial Fibroblast Functions Activated by Transforming Growth Factor–β1 and Inhibited by Gax

Objective— We investigated whether Smad, mitogen-activated protein kinase (MAPK), and integrin signaling pathways cross-talk to enhance adventitial fibroblast (AF) bioactivity, which was activated by transforming growth factor (TGF)-β1 and inhibited by Gax. Methods and Results— Cultured AFs were stimulated with Ad-Gax, TGF-β1, and siRNA-Gax. Assays for AFs viabilities demonstrated that TGF-β1 and siRNA-Gax enhanced AFs proliferative, migratory, and adherent abilities, whereas Gax counteracted TGF-β1–activated actions. Flow cytometry revealed that TGF-β1 and siRNA-Gax increased S phase cells; however, Gax decreased AFs in the S phase and increased those in the G0-G1 and apoptotic phases. RT-PCR, Western blotting, and immunocytochemistry showed that TGF-β1 and siRNA-Gax upregulated the expression of cytokines in Smad, MAPK, and integrin signaling pathways, and downregulated that of p15, p16, and p21. Conversely, Gax induced downregulation of these cytokines and upregulation of p15, p16, and p21. Thus, these...