Rapamycin antagonizes NF-κB nuclear translocation activated by TNF-α in primary vascular smooth muscle cells and enhances apoptosis

Several lines of evidence support the view that rapamycin inhibits NF-kappa B. TNF-alpha, a potent inducer of NF-kappa B, is released after artery injury (e.g., balloon angioplasty) and plays an important role in inflammation and restenosis. We investigated the effect of rapamycin on NF-kappa B activation and apoptosis in vascular smooth muscle cells (VSMCs) stimulated with TNF-alpha. Using EMSA, we found that TNF-alpha caused NF-kappa B nuclear translocation in VSMCs after 1 h of incubation. Rapamycin inhibited I kappa B alpha degradation, thereby preventing nuclear translocation. Activation of NF-kappa B was accompanied by an increase of Bcl-xL and Bfl-1/A1 proteins, detected by Western blot assay, whereas rapamycin prevented the TNF-alpha-induced enhancement of these antiapoptotic proteins. The extent of apoptosis of VSMCs exposed to TNF-alpha was significantly enhanced by rapamycin. The effect of rapamycin appeared to be independent of the phosphatidylinositol 3-kinase/Akt-protein kinase B survival pathway, because the phosphatidylinositol 3-kinase inhibitor wortmannin neither prevented I kappa B alpha degradation nor increased apoptosis of cells incubated with TNF-alpha. Finally, we demonstrate that the large immunophilin FK-506 binding protein FKBP51 is essential for TNF-alpha-induced NF-kappa B activation in VSMCs. Our findings show that rapamycin inhibits NF-kappa B activation and acts in concert with TNF-alpha in induction of VSMC apoptosis.