Abstract 446: Ebp50 Regulates Oxidative Stress Through Skp2 and Foxo1
Inflammation and oxidative stress play important roles in cardiovascular disease. Reactive oxygen- and nitric oxide (NO)-derived species affect proliferation and migration of endothelial and vascular smooth muscle cells (VSMC), and amplify vascular inflammation. In this work we explore the role of Ezrin-Radixin-Moesin (ERM) binding protein of 50kDa (EBP50) as a novel mediator of oxidative stress. EBP50 plays a critical role in vascular remodeling. We reported that EBP50 mediates migration and proliferation of VSMC. In addition, EBP50 potentiates inflammatory responses (including iNOS expression) in macrophages and vascular cells. EBP50 stabilizes S-phase kinase associated protein 2 (Skp2) - a substrate recruiting component of the E3 ubiquitin ligase that targets FoxO1 for degradation. FoxO1 is a transcription factor that controls the expression of two key antioxidant enzymes - manganese superoxide dismutase (MnSOD) and catalase. Therefore, we hypothesize that EBP50 regulates oxidative stress through Skp2-FoxO1 axis. Our findings show a significantly greater nuclear localization of FoxO1 in EBP50 depleted VSMC compared to WT VSMC. Moreover, EBP50 knockdown increased FoxO1 stability following cycloheximide treatment. Consistent with these observations, expression of MnSOD and catalase were higher in EBP50 knockout primary macrophages and VSMC. To begin addressing the role of EBP50 on oxidative stress in vivo we used bone marrow transplants in LDLR-/- mice. Following reconstitution, mice were place on a high cholesterol diet for 12 weeks. We observed a significant 25% reduction in plaque area in EBP50-deficient marrow recipients compared to WT marrow recipients. In these mice there was a significant reduction in 4-hydroxynonanal (a marker of oxidative stress) and of 3-nitro-tyrosine (a marker of oxygen- and NO-derived reactive species) staining in the atherosclerotic plaques. Collectively, these observations suggest that EBP50, by regulating the localization and Skp2-mediated degradation of FoxO1, increases oxidative stress and inflammation during atherosclerosis. These studies further highlight the actions of EBP50 in controlling multiple signaling pathways that play a critical role in the pathogenesis of vascular disease.
Author Disclosures: V. Procaccia: None. K.L. Leslie: None. E.Z. Malik: None. A. Bisello: None.
- © 2015 by American Heart Association, Inc.