Abstract 15724: Intermittent Hypoxia Induces Early Pro-Atherogenic Changes in Aortic Wall Macrophages in a Murine Model of Obstructive Sleep Apnea
Background: OSA is a highly prevalent condition throughout the lifespan, and has emerged as an independent risk factor for atherosclerosis. Macrophages play a key role in the pathogenesis of atherosclerosis through shifts in the continuum between the pro-inflammatory M1 and the athero-protective M2. We hypothesized that Intermittent Hypoxia (IH) during the sleep period, a model for OSA, will induce shifts towards a pro-atherogenic state in the spectrum of macrophages within the aortic vascular wall.
Methods: 8-week old male C57BL/6J mice were exposed to IH for 12-hr/day during the light period or to room air (RA) for 6 weeks and were kept on a regular low-fat chow. Following exposure, full-length aortas were dissected and enzymatically digested. Single cell suspensions were prepared and cells were incubated with antibodies for macrophage markers previously implicated in atherogenesis and metabolic dysregulation - CD11b, F4/80, Ly6c, CD36, and CD64, and analyzed by FACS.
Results: Macrophages were defined as CD11b+/F4/80+ cells. Significant increases in the percentage of macrophages emerged in IH-exposed mice (6.4%±0.3 vs. 8%±0.3, p=0.003, n=19-20/group). Furthermore, IH induced shifts in the macrophage population toward an M1 pro-inflammatory phenotype. Specifically, IH group showed significantly higher expression of Ly6c, (MFI:522±23 vs. 699±43, p=0.004, n=12/group) and increased the percentage of Ly6c+(hi) cells (9.2% vs. 11.7%, p=0.03). Conversely, tissue-resident marker CD64 expression in the aortic macrophages was down-regulated following IH exposures (MFI:3207±453 vs. 2967±483, p=0.03, n=12/group), while scavenger receptor CD36 expression was increased in the IH-exposed group (MFI:1694±56 vs.2129±209, p=0.005).
Conclusion: Intermittent hypoxia during the sleep period leads to early expansion of the macrophage population in the aortic wall in a relatively resistant animal model for development of atherosclerosis, i.e., in the absence of a high-fat diet or of high atherogenic risk predisposing gene knockout. Furthermore IH induces changes in macrophage phenotypes, including a shift towards a pro-inflammatory phenotype, and recruitment of bone-marrow derived macrophages expressing indicators of metabolic activation.
Author Disclosures: A. Gileles-Hillel: None. I. Almendros: None. A. Khalyfa: None. S. Zhang: None. Y. Wang: None. D. Gozal: None.
- © 2014 by American Heart Association, Inc.