Abstract 3612: Apelin Prevents Aortic Aneurysm Formation by Inhibiting Macrophage Inflammation and Infiltration

Abstract

To investigate the hypothesis that Apelin treatment would attenuate aortic injury in a murine model of elastase-induced abdominal aortic aneurysm (AAA) disease, by limiting disease-related vascular wall inflammatory. Male C57BL/6 mice were implanted with osmotic mini-pumps filled with Apelin (2 mg/kg/day) or saline (Control), and subsequently treated with intra-aortic porcine pancreatic elastase to create infrarenal AAA’s. Mice were sacrificed at day 3 for aortic PCR analysis or followed ultrasonographically until day 7 and then sacrificed for histological analysis (Elastic Masson, VCAM, ICAM-1, E-Selectin, and Mac-2 semi-quantitative analysis). The cellular expression of inflammatory cytokines and chemokines in response to Apelin was assessed by TaqMan analysis of both macrophages (J774, RAW, and harvested intraperitoneal cells) and rat aortic smooth muscle cells (A7R5) and compared to other stimuli. Apelin treatment resulted in diminished AAA formation, with a 30% reduction in in vivo aortic diameter by ultrasound (1.04 mm vs 1.48 mm, p < 0.05), and a 59% reduction in maximal aortic cross-sectional area by histology (0.59 mm2 vs 1.43 mm2, p < 0.05) relative to the saline-treated group. The macrophage infiltrate also was significantly reduced in the Apelin-treated mice compared to the Control group (68.6 cells/hpf vs 285.4 cells/hpf, p < 0.001). Apelin treatment was associated with reduced mean aortic MCP-1, MIP 1-alpha, IL-6 and TNF-alpha mRNA levels, although these did not reach statistical significance. Apelin stimulation of cultured macrophage models significantly reduced MCP-1 and TNF-alpha mRNA levels compared to basal conditions (−1.12 and −1.49 fold expression change, p < 0.05, respectively). No difference in endothelial cell adhesion molecule expression or smooth muscle cell cytokine production was found in response to Apelin. Apelin significantly reduces AAA formation in this accepted model of human AAA disease. The mechanism appears to be decreased macrophage infiltration, perhaps related to an apelin-mediated decrease in pro-inflammatory cytokine and chemokine activation. This research has received full or partial funding support from the American Heart Association, AHA Western States Affiliate (California, Nevada & Utah).