Vitamin D Receptor Activation Reduces Angiotensin-II-Induced Dissecting Abdominal Aortic Aneurysm in Apolipoprotein E-Knockout Mice

Abstract

Objective - Abdominal aortic aneurysm (AAA) is a vascular disorder characterized by chronic inflammation of the aortic wall. Low concentrations of vitamin D 3 are associated with AAA development; however, the potential direct effect of vitamin D 3 on AAA remains unknown. This study evaluates the effect of oral treatment with the vitamin D 3 receptor (VDR) ligand, calcitriol, on dissecting AAA induced by angiotensin-II (Ang-II) infusion in apoE -/- mice. Approach and Results - Oral treatment with calcitriol reduced Ang-II-induced dissecting AAA formation in apoE -/- mice, which was unrelated to systolic blood pressure or plasma cholesterol concentrations. Immunohistochemistry and reverse-transcription polymerase chain reaction analysis demonstrated a significant increase in macrophage infiltration, neovessel formation, matrix metalloproteinase-2 and matrix metalloproteinase-9, chemokine (CCL2 [(C-C motif) ligand 2], CCL5 [(C-C motif) ligand 5], and CXCL1 [(C-X-C motif) ligand 1]) and vascular endothelial growth factor expression in suprarenal aortic walls of apoE -/- mice infused with Ang-II, and all were significantly reduced by cotreatment with calcitriol. Phosphorylation of extracellular signal-regulated kinases 1/2, p38 mitogen-activated protein kinase, and nuclear factor-κB was also decreased in the suprarenal aortas of apoE -/- mice cotreated with calcitriol. These effects were accompanied by a marked increase in VDR-retinoid X receptor (RXR) interaction in the aortas of calcitriol-treated mice. In vitro, VDR activation by calcitriol in human endothelial cells inhibited Ang-II-induced leukocyte-endothelial cell interactions, morphogenesis, and production of endothelial proinflammatory and angiogenic chemokines through VDR-RXR interactions, and knockdown of VDR or RXR abolished the inhibitory effects of calcitriol. Conclusions - VDR activation reduces dissecting AAA formation induced by Ang-II in apoE -/- mice and may constitute a novel therapeutic strategy to prevent AAA progression.