An adventitial IL-6/MCP1 amplification loop accelerates macrophage-mediated vascular inflammation leading to aortic dissection in mice
Brian C. Tieu, Chang Lee, Hong Sun, Wanda LeJeune, Adrian Recinos 3rd, Xiaoxi Ju, Heidi Spratt, Dong-Chuan Guo, Dianna Milewicz, Ronald G. Tilton, Allan R. Brasier
Brian C. Tieu, Chang Lee, Hong Sun, Wanda LeJeune, Adrian Recinos 3rd, Xiaoxi Ju, Heidi Spratt, Dong-Chuan Guo, Dianna Milewicz, Ronald G. Tilton, Allan R. Brasier
View: Text | PDF
Research Article

An adventitial IL-6/MCP1 amplification loop accelerates macrophage-mediated vascular inflammation leading to aortic dissection in mice

Abstract

Vascular inflammation contributes to cardiovascular diseases such as aortic aneurysm and dissection. However, the precise inflammatory pathways involved have not been clearly defined. We have shown here that subcutaneous infusion of Ang II, a vasopressor known to promote vascular inflammation, into older C57BL/6J mice induced aortic production of the proinflammatory cytokine IL-6 and the monocyte chemoattractant MCP-1. Production of these factors occurred predominantly in the tunica adventitia, along with macrophage recruitment, adventitial expansion, and development of thoracic and suprarenal aortic dissections. In contrast, a reduced incidence of dissections was observed after Ang II infusion into mice lacking either IL-6 or the MCP-1 receptor CCR2. Further analysis revealed that Ang II induced CCR2+CD14hiCD11bhiF4/80– macrophage accumulation selectively in aortic dissections and not in aortas from Il6–/– mice. Adoptive transfer of Ccr2+/+ monocytes into Ccr2–/– mice resulted in selective monocyte uptake into the ascending and suprarenal aorta in regions of enhanced ROS stress, with restoration of IL-6 secretion and increased incidence of dissection. In vitro, coculture of monocytes and aortic adventitial fibroblasts produced MCP-1– and IL-6–enriched conditioned medium that promoted differentiation of monocytes into macrophages, induced CD14 and CD11b upregulation, and induced MCP-1 and MMP-9 expression. These results suggest that leukocyte-fibroblast interactions in the aortic adventitia potentiate IL-6 production, inducing local monocyte recruitment and activation, thereby promoting MCP-1 secretion, vascular inflammation, ECM remodeling, and aortic destabilization.

Authors

Brian C. Tieu, Chang Lee, Hong Sun, Wanda LeJeune, Adrian Recinos 3rd, Xiaoxi Ju, Heidi Spratt, Dong-Chuan Guo, Dianna Milewicz, Ronald G. Tilton, Allan R. Brasier

×

Figure 3

Ccr2–/– mice develop blunted responses to Ang II, but adoptive transfer of Ccr2+/+ monocytes restores cytokine secretion and dissection.

Options: View larger image (or click on image) Download as PowerPoint
Ccr2–/– mice develop blunted responses to Ang II, but adoptive transfer...
(A) Quantitation of aortic CD14+CD11b+F4/80+ macrophages in sham- and Ang II–treated Ccr2–/– mice. (B) Secreted IL-6 and MCP-1 concentrations in aortic explants culture from sham- (n = 6) or Ang II–infused (n = 7) Ccr2–/– mice. Data are mean ± SEM. *P < 0.03 versus sham treatment (Student’s t test). (C) Whole-animal imaging of DiR800-labeled Ccr2+/+ monocytes in Ccr2–/– mice with or without Ang II treatment. Monocytes (green) homed to the spleen (S), dorsal; liver (L), ventral. Nonspecific intestinal autofluorescence is shown in red. Monocyte labeling efficiency in vitro is shown (top right). (D) Aortic preparations from Ccr2–/– mice receiving Ccr2–/– or Ccr2+/+ monocytes were imaged. The suprarenal (S) and the aortic root/ascending aorta (As) regions are shown for 3 separate animals (see Supplemental Figure 7). (E) In situ DHE staining. Aortas from control or Ang II–infused mice (6 days) were separated into ascending, descending and supra- and infrarenal segments and incubated in DHE (oxidation is shown in red). Nuclei are DAPI stained (blue). Scale bar: 50 μm; original magnification, ×200. (F) Secreted IL-6 and MCP-1 concentrations were measured in aortic explant medium from sham- (n = 5) or Ang II–infused (n = 6) Ccr2–/– mice receiving Ccr2+/+ or Ccr2–/– monocytes. Data are mean ± SEM. Significant values are shown (2-way ANOVA, with P values representing Ang II effect, Ccr2 genotype effect, and interaction effect of Ang II with genotype [AngII*CCR2]). (G) Aortic cross sections after Ang II infusion in Ccr2–/– mice. Top: sham-treated; bottom: Ccr2+/+ monocyte–infused. Scale bars: 10 μm; original magnification, ×100.