Abstract 12530: Cross-Talk of RANKL Signaling with Renin-Angiotensin II System in Vascular Calcification and Remodeling
Background: We have recently reported that RANKL (Receptor Activator of NF-κB Ligand) activation regulates vascular calcification under estrogen deficiency. Renin-angiotensin system (RAS) plays important roles in cardiovascular diseases; and high OPG serum level is considered a marker for future events. We assessed the hypothesis that RAS is the trigger of RANKL activation in vasculature, and we propose the molecular mechanism underpinning this cross-talk signaling.
Methods and Results: Angiotensin II (AngII) (10-7M) induced the expression of RANKL and RANK in VSMC, and conversely RANKL (10 ng/ml) stimulation increased AngII type 1 receptor (AT1R) and Ang II-converting enzyme (ACE) expression in VSMC via ERK phosphorylation. AngII dramatically increased calcium deposition (Alizarin Red staining) and calcification of VSMC, and induced expression of bone-related genes such as runx2 and msx2 detected by western blot. We have previously shown that ovariectomized ApoE-/- mice under high fat diet (HF) have increased RANK-RANKL expression and vascular calcification in 3 months. Infusion of a sub-pressor dose of AngII (100 ng/kg/min) in this model significantly increased the expression of RANKL system and calcification, as detected by Real Time PCR and Von Kossa staining of aorta respectively. Treatment with AngII receptor blocker (Olmesartan, 3 mg/kg/day) decreased the calcification and bone-markers expression. In addition, OPG-/- mice with unopposed RANKL activation showed a dramatic increase in vascular calcification followed by 1 month of Ang II infusion compared to wild type (WT) and OPG-/-/AT1R-/- mice. Furthermore, OPG-/- VSMC showed high basal AT1R and ACE, and pERK level; which resulted in higher proliferation and migration rate, compared to WT and OPG-/-/AT1R-/- VSMC. This phenotype of OPG-/- VSMC was evaluated in the carotid artery ligation model for vascular remodeling. OPG-/- mice showed increased neointima formation compared to WT and OPG-/-/AT1R-/- mice.
Conclusion: This study highlights a broader role of RANKL signaling in vascular physiology: RAS activates RANKL system, and conversely, unopposed RANKL stimulation activates local RAS mainly via pERK, and this vicious cycle aggravates vascular remodeling and calcification.
- © 2011 by American Heart Association, Inc.