FOXO3a Turns the Tumor Necrosis Factor Receptor Signaling Towards Apoptosis Through Reciprocal Regulation of c-Jun N-Terminal Kinase and NF-κB

Objective— We evaluated the full range effects of FOXO3a in endothelial cells (ECs) by microarray analysis and investigated the role of FOXO3a regulating TNF receptor signaling pathway.Methods and Results— Human umbilical vein endothelial cells (HUVECs) were transfected with adenoviral vectors expressing constitutively active FOXO3a (Ad-TM-FOXO3a). Ad-TM-FOXO3a transfection caused remarkable apoptosis, which were accompanied with upregulation of genes related with TNF receptor signaling, such as TNF-α, TANK (TRAF-associated NF-κB activator), and TTRAP (TRAF and TNF receptor-associated protein). Furthermore, κB-Ras1 (IκB-interacting Ras-like protein-1) which is known to block IκB degradation was found increased, and intranuclear translocation of NF-κB was inhibited. GADD45β and XIAP, negative regulators of c-Jun N-terminal kinase (JNK), were suppressed and JNK activity was increased. Attenuation of TNF signaling pathway either by blocking antibody for TNF receptor or by blocking JNK with DMAP (6-dimethylaminopurine) or Ad-TAM67 (dominant negative c-Jun) cotransfection, significantly reduced FOXO3a-induced apoptosis. Finally, treatment of vasculature with heat shock, an activator of endogenous FOXO3a, resulted in EC apoptosis, which was completely rescued by Ad-TAM67.Conclusion— FOXO3a promotes apoptosis of ECs, through activation of JNK and suppression of NF-κB. These data identify a novel role of FOXO3a to turn TNF receptor signaling to a proapoptotic JNK-dependent pathway.