Inhibition of VEGF (Vascular Endothelial Growth Factor)-A or its Receptor Activity Suppresses Experimental Aneurysm Progression in the Aortic Elastase Infusion Model.

OBJECTIVE: We examined the pathogenic significance of VEGF (vascular endothelial growth factor)-A in experimental abdominal aortic aneurysms (AAAs) and the translational value of pharmacological VEGF-A or its receptor inhibition in aneurysm suppression. Approaches and Results: AAAs were created in male C57BL/6J mice via intra-aortic elastase infusion. Soluble VEGFR (VEGF receptor)-2 extracellular ligand-binding domain (delivered in Ad [adenovirus]-VEGFR-2), anti-VEGF-A mAb (monoclonal antibody), and sunitinib were used to sequester VEGF-A, neutralize VEGF-A, and inhibit receptor tyrosine kinase activity, respectively. Influences on AAAs were assessed using ultrasonography and histopathology. In vitro transwell migration and quantitative reverse transcription polymerase chain reaction assays were used to assess myeloid cell chemotaxis and mRNA expression, respectively. Abundant VEGF-A mRNA and VEGF-A-positive cells were present in aneurysmal aortae. Sequestration of VEGF-A by Ad-VEGFR-2 prevented AAA formation, with attenuation of medial elastolysis and smooth muscle depletion, mural angiogenesis and monocyte/macrophage infiltration. Treatment with anti-VEGF-A mAb prevented AAA formation without affecting further progression of established AAAs. Sunitinib therapy substantially mitigated both AAA formation and further progression of established AAAs, attenuated aneurysmal aortic MMP2 (matrix metalloproteinase) and MMP9 protein expression, inhibited inflammatory monocyte and neutrophil chemotaxis to VEGF-A, and reduced MMP2, MMP9, and VEGF-A mRNA expression in macrophages and smooth muscle cells in vitro. Additionally, sunitinib treatment reduced circulating monocytes in aneurysmal mice. CONCLUSIONS: VEGF-A and its receptors contribute to experimental AAA formation by suppressing mural angiogenesis, MMP and VEGF-A production, myeloid cell chemotaxis, and circulating monocytes. Pharmacological inhibition of receptor tyrosine kinases by sunitinib or related compounds may provide novel opportunities for clinical aneurysm suppression.

Metformin treatment status and abdominal aortic aneurysm disease progression.

OBJECTIVE: In population-based studies performed on multiple continents during the past two decades, diabetes mellitus has been negatively associated with the prevalence and progression of abdominal aortic aneurysm (AAA) disease. We investigated the possibility that metformin, the primary oral hypoglycemic agent in use worldwide, may influence the progression of AAA disease. METHODS: Preoperative AAA patients with diabetes were identified from an institutional database. After tabulation of individual cardiovascular and demographic risk factors and prescription drug regimens, odds ratios for categorical influences on annual AAA enlargement were calculated through nominal logistical regression. Experimental AAA modeling experiments were subsequently performed in normoglycemic mice to validate the database-derived observations as well as to suggest potential mechanisms of metformin-mediated aneurysm suppression. RESULTS: Fifty-eight patients met criteria for study inclusion. Of 11 distinct classes of medication considered, only metformin use was negatively associated with AAA enlargement. This association remained significant after controlling for gender, age, cigarette smoking status, and obesity. The median enlargement rate in AAA patients not taking oral diabetic medication was 1.5 mm/y; by nominal logistic regression, metformin, hyperlipidemia, and age ≥70 years were associated with below-median enlargement, whereas sulfonylurea therapy, initial aortic diameter ≥40 mm, and statin use were associated with above-median enlargement. In experimental modeling, metformin dramatically suppressed the formation and progression, with medial elastin and smooth muscle preservation and reduced aortic mural macrophage, CD8 T cell, and neovessel density. CONCLUSIONS: Epidemiologic evidence of AAA suppression in diabetes may be attributable to concurrent therapy with the oral hypoglycemic agent metformin.

Peptide inhibitor of CXCL4-CCL5 heterodimer formation, MKEY, inhibits experimental aortic aneurysm initiation and progression.

OBJECTIVE: Macrophages are critical contributors to abdominal aortic aneurysm (AAA) disease. We examined the ability of MKEY, a peptide inhibitor of CXCL4-CCL5 interaction, to influence AAA progression in murine models. APPROACH AND RESULTS: AAAs were created in 10-week-old male C57BL/6J mice by transient infrarenal aortic porcine pancreatic elastase infusion. Mice were treated with MKEY via intravenous injection either (1) before porcine pancreatic elastase infusion or (2) after aneurysm initiation. Immunostaining demonstrated CCL5 and CCR5 expression on aneurysmal aortae and mural monocytes/macrophages, respectively. MKEY treatment partially inhibited migration of adaptively transferred leukocytes into aneurysmal aortae in recipient mice. Although all vehicle-pretreated mice developed AAAs, aneurysms formed in only 60% (3/5) and 14% (1/7) of mice pretreated with MKEY at 10 and 20 mg/kg, respectively. MKEY pretreatment reduced aortic diameter enlargement, preserved medial elastin fibers and smooth muscle cells, and attenuated mural macrophage infiltration, angiogenesis, and aortic metalloproteinase 2 and 9 expression after porcine pancreatic elastase infusion. MKEY initiated after porcine pancreatic elastase infusion also stabilized or reduced enlargement of existing AAAs. Finally, MKEY treatment was effective in limiting AAA formation after angiotensin II infusion in apolipoprotein E-deficient mice. CONCLUSIONS: MKEY suppresses AAA formation and progression in 2 complementary experimental models. Peptide inhibition of CXCL4-CCL5 interactions may represent a viable translational strategy to limit progression of human AAA disease.

Recombinant Interleukin-19 Suppresses the Formation and Progression of Experimental Abdominal Aortic Aneurysms.

Background Interleukin-19 is an immunosuppressive cytokine produced by immune and nonimmune cells, but its role in abdominal aortic aneurysm (AAA) pathogenesis is not known. This study aimed to investigate interleukin-19 expression in, and influences on, the formation and progression of experimental AAAs. Methods and Results Human specimens were obtained at aneurysm repair surgery or from transplant donors. Experimental AAAs were created in 10- to 12-week-old male mice via intra-aortic elastase infusion. Influence and potential mechanisms of interleukin-19 treatment on AAAs were assessed via ultrasonography, histopathology, flow cytometry, and gene expression profiling. Immunohistochemistry revealed augmented interleukin-19 expression in both human and experimental AAAs. In mice, interleukin-19 treatment before AAA initiation via elastase infusion suppressed aneurysm formation and progression, with attenuation of medial elastin degradation, smooth-muscle depletion, leukocyte infiltration, neoangiogenesis, and matrix metalloproteinase 2 and 9 expression. Initiation of interleukin-19 treatment after AAA creation limited further aneurysmal degeneration. In additional experiments, interleukin-19 treatment inhibited murine macrophage recruitment following intraperitoneal thioglycolate injection. In classically or alternatively activated macrophages in vitro, interleukin-19 downregulated mRNA expression of inducible nitric oxide synthase, chemokine C-C motif ligand 2, and metalloproteinases 2 and 9 without apparent effect on cytokine-expressing helper or cytotoxic T-cell differentiation, nor regulatory T cellularity, in the aneurysmal aorta or spleen of interleukin-19-treated mice. Interleukin-19 also suppressed AAAs created via angiotensin II infusion in hyperlipidemic mice. Conclusions Based on human evidence and experimental modeling observations, interleukin-19 may influence the development and progression of AAAs.