Cysteine Leukotriene Receptor Antagonist-Montelukast-Treatment Improves Experimental Abdominal Aortic Aneurysms in Mice

Abstract

Background: Cysteinyl leukotrienes (LTs) and their receptors are involved in the pathogenesis of abdominal aortic aneurysms (AAAs). However, whether CysLT1 receptor antagonists such as montelukast can influence experimental nondissecting AAA remains unclear. Methods: Nondissecting AAAs were induced in C57BL/6J mice by transient aortic luminal infusion of porcine pancreatic elastase (PPE). All animals were administrated montelukast (1 or 10 mg/kg, daily) or vehicle by gavage beginning 1 day before PPE infusion for 14 days. On day 0 (baseline) and day 14 after PPE infusion, abdominal aortic diameters were directly measured. Aortic aneurysmal segment samples were collected, and histopathological analysis was performed. Results: Compared to vehicle treatment, montelukast significantly decreased PPE infusion-induced aortic expansion in a dose-dependent manner (0.09-mm reduction at a low dose and 0.19-mm reduction at a high dose). Histopathological analysis also revealed that compared with vehicle treatment, montelukast treatment, especially in the high-dose group, significantly improved PPE-induced aortic elastin degradation and medial smooth muscle cell depletion. Both doses of montelukast also markedly decreased the number of local leucocytes, including macrophages, CD4⁺ T cells, CD8⁺ T cells, and B cells, infiltration and accumulation in aortic aneurysmal lesions. Montelukast treatment also downregulated matrix metalloproteinase 2 (MMP2) and MMP9 expression and inhibited mural angiogenesis in aneurysmal aortas. Conclusion: Montelukast treatment improves experimental nondissected AAAs in mice partly by improving aortic inflammation.

Keywords: abdominal aortic aneurysm; elastin; inflammation; montelukast; smooth muscle cells.

Figure 1

Montelukast inhibits the increase in aortic diameter in mice with experimental AAAs. (a) Experimental design: all mice received PPE infusion to model AAAs. Two doses of montelukast (1 or 10 mg/kg, daily) or vehicle were given by gavage (n = 10 each group). (b) Aortic diameters on Day 0 (baseline) and Day 14 (sample collection timepoint) after PPE infusion. Two-way ANOVA with multigroup comparisons was performed; ⁣^∗∗p < 0.01. (c) Representative images of abdominal aortas on Day 0 and Day 14 after surgery. (d) Increase in aortic diameter over baseline (%). One-way ANOVA with comparisons between two groups was carried out (⁣^∗∗p < 0.01).

Figure 2

Montelukast inhibits PPE infusion–induced aortic medial elastin destruction and SMC depletion. (a) Representative images of histopathological staining of aneurysmal aortic segments in frozen sections. (b) Histological grading and semiquantification of aortic medial elastin (n = 10/group). (c) Histological grading and semiquantification of aortic medial SMC depletion (n = 10/group). One-way ANOVA with a multigroup nonparametric Kruskal–Wallis test was performed (⁣^∗p < 0.05 and ⁣^∗∗p < 0.01). NS, not significant.

Figure 3

Montelukast decreases aortic leukocyte accumulation. (a) Representative images of aortic infiltrated leukocytes, macrophages, T cells, and B cells. (b–e) Quantification or semiquantification of leukocyte subsets per ACS (n = 10/group). For normally distributed data, one-way ANOVA was used (for T cells and B cells), and the nonparametric Kruskal–Wallis test was used for semiquantification of the macrophage score. ⁣^∗p < 0.05 and ⁣^∗∗p < 0.01.

Figure 4

Montelukast downregulated MMP2 and MMP9 expression. (a) Representative IHC images of aortic MMP2 and MMP9. (b, c) Quantification of MMP2- and MMP9-positive areas in the aneurysmal aorta. One-way ANOVA was used (n = 10/group). ⁣^∗∗p < 0.01.

Figure 5

Montelukast treatment reduces mural neovessel numbers. Mural neovessels were marked by CD31 IHC staining, and angiogenesis was evaluated by counting the number of neovessels per ACS. One-way ANOVA was performed for statistical analysis (n = 10/group). ⁣^∗∗p < 0.01.