Deficiency of immunoglobulin E protects mice from experimental abdominal aortic aneurysms

Allergic asthma with high plasma IgE levels is a significant risk factor of human abdominal aortic aneurysm (AAA). This study tests a direct role of IgE in angiotensin-II (Ang-II) perfusion- and peri-aortic CaCl2 injury-induced AAA in mice. In both models, IgE-deficiency in Apoe(-/-) Ige(-/-) mice blunts AAA growth and reduces lesion accumulation of macrophages, CD4(+) and CD8(+) T cells, and lesion MHC class-II expression, CD31(+) microvessel growth, and media smooth muscle cell loss, compared with those from Apoe(-/-) control mice. Real time-PCR reveals significant reductions in expression of neutrophil chemoattractants MIP-2alpha and CXCL5 in AAA lesions or macrophages from Apoe(-/-) Ige(-/-) mice, along with reduced lesion Ly6G(+) neutrophil accumulation. Consistent with reduced lesion inflammatory cell accumulation, we find significant reductions of plasma and AAA lesion IL6 expression in Apoe(-/-) Ige(-/-) mice. Immunofluorescent staining and FACS analysis show that AAA lesion neutrophils express FcepsilonR1. Mechanistic study demonstrates that IgE induces neutrophil FcepsilonR1 expression, activates MAPK signaling, and promotes IL6 production. This study supports a direct role of IgE in AAA by promoting lesion chemokine expression, inflammatory cell accumulation, MAPK signaling, and cytokine expression. IgE inhibition may represent a novel therapeutic approach in AAA management.