Abstract 15037: Novel Role of Kelch-like ECH-associated Protein 1/NF-E2-related Factor 2 System in Vascular Smooth Muscle Cell Apoptosis Following Vascular Injury
Abnormal increases in vascular smooth muscle cells (VSMCs) in the intimal region after vascular injury are a key event in the neointimal hyperplasia followed by vascular occlusive diseases. To maintain vascular functions, the number of VSMCs is tightly controlled by those proliferation and apoptosis during vascular remodeling. Kelch-like ECH-associated protein 1 (Keap1)-NF-E2-related factor 2 (Nrf2) system plays a critical role in the oxidative stress response. While Keap1 ubiquitinates Nrf2 for degradation under unstressed conditions, this Keap1 function is abrogated in response to oxidative stress, leading to Nrf2 stabilization and coordinated up-regulation of antioxidant genes. We have previously found that Nrf2 plays an important role in neointimal hyperplasia after vascular injury via regulating platelet-derived growth factor-induced reactive oxygen species-dependent VSMC migration; however, the role of Keap1-Nrf2 system in VSMC apoptosis has not been established. Here we show that TUNEL-positive cells are detected in both the layers of neointima and media, both of which observe alpha-smooth muscle actin positive and high Nrf2-expressed cells, 14 days after transluminal arterial injury in mice. Nrf2 deficient mice show decreased TUNEL-positive cells in neointimal and medial areas (60%) and enhanced neointimal formation (I/M ratio: 152%) 14 days after vascular injury compared with the wild-type mice. In VSMCs isolated from the thoracic aorta of rats, depletion of Keap1 with siRNA increases nuclear Nrf2 (685%) and induces its target genes, including NAD(P)H: quinone oxidoreductase-1 (664%) and heme oxygenase-1 (230%). Functionally, Keap1 depletion increase apoptotic morphological features such as cell shrinkage and nuclear condensation (4114%), annexin V binding (512%), and positive TUNEL staining in VSMCs, which is associated with caspase-3/7 activation (576%). Pretransfection of VSMCs with Nrf2 siRNA inhibits apotosis mediated by Keap1 siRNA. In summary, Keap1-Nrf2 system regulates VSMC apoptosis in the process of neointimal formation, thereby inhibiting VSMC hyperproliferation, which may contribute to the development of neointimal hyperplasia after vascular injury.
Author Disclosures: T. Ashino: None. M. Yamamoto: None. S. Numazawa: None.
- © 2014 by American Heart Association, Inc.