Dysregulation of CREB binding protein triggers thrombin-induced proliferation of vascular smooth muscle cells

Thrombin is a potent mitogen for vascular smooth muscle cells (VSMCs). CBP has been regarded as a potential therapeutic target on the basis of its ability to affect cell growth. Therefore we hypothesized that CBP mediates thrombin-induced proliferation of VSMCs. We constructed recombinant adenoviral vector that expresses four short hairpin RNA (shRNA) targeting rat CBP mRNA (CBP-shRNA/Ad). VSMCs were infected with CBP-shRNA/Ad and treated with thrombin. CBP level were analyzed by quantitative real-time PCR and Western blot. To evaluate VSMC proliferation, the cell cycle and DNA synthesis were analyzed by flow cytometry and (3)H-thymidine incorporation, respectively. CBP-shRNA/Ad infection inhibited thrombin-induced CBP expression in a dose-dependent manner concomitant with a decrease in the percentage of cells in the S phase and in DNA synthesis. These findings suggest that CBP plays a pivotal role in the S phase progression of VSMCs.