Cysteinyl leukotriene receptor 1 antagonism prevents experimental abdominal aortic aneurysm

Antonio Di Gennaro; Ana Carolina Araújo; Albert Busch; Hong Jin; Dick Wågsäter; Emina Vorkapic; Kenneth Caidahl; Per Eriksson; Bengt Samuelsson; Lars Maegdefessel; Jesper Z. Haeggström

doi:10.1073/pnas.1717906115

Contributed by Bengt Samuelsson, January 7, 2018 (sent for review October 16, 2017; reviewed by Ingrid Fleming and Charles N. Serhan)

Significance

Cysteinyl-leukotrienes (cys-LTs) are lipid mediators involved in human inflammatory diseases, in particular asthma. We have previously identified cys-LTs in tissue specimens of human abdominal aortic aneurysm (AAA) and linked these mediators to increased metalloproteinase activity. Here we show in vivo that antagonism of the CysLT1 receptor by montelukast, an established antiasthma drug, protects against aneurysm in three mouse models of AAA at doses comparable to human medical practice. Together, these data support the role of cys-LTs in AAA and indicate a new potential therapeutic approach for treatment of this clinically silent and highly lethal disease.

Abstract

Cysteinyl-leukotrienes (cys-LTs) are 5-lipoxygenase-derived lipid mediators involved in the pathogenesis and progression of inflammatory disorders, in particular asthma. We have previously found evidence linking these mediators to increased levels of proteolytic enzymes in tissue specimens of human abdominal aortic aneurysm (AAA). Here we show that antagonism of the CysLT1 receptor by montelukast, an established antiasthma drug, protects against a strong aorta dilatation (>50% increase = aneurysm) in a mouse model of CaCl₂-induced AAA at a dose comparable to human medical practice. Analysis of tissue extracts revealed that montelukast reduces the levels of matrix metalloproteinase-9 (MMP-9) and macrophage inflammatory protein-1α (MIP-1α) in the aortic wall. Furthermore, aneurysm progression was specifically mediated through CysLT1 signaling since a selective CysLT2 antagonist was without effect. A significantly reduced vessel dilatation is also observed when treatment with montelukast is started days after aneurysm induction, suggesting that the drug not only prevents but also stops and possibly reverts an already ongoing degenerative process. Moreover, montelukast reduced the incidence of aortic rupture and attenuated the AAA development in two additional independent models, i.e., angiotensin II- and porcine pancreatic elastase-induced AAA, respectively. Our results indicate that cys-LTs are involved in the pathogenesis of AAA and that antagonism of the CysLT1 receptor is a promising strategy for preventive and therapeutic treatment of this clinically silent and highly lethal disease.

Abdominal aortic aneurysm (AAA) is a clinically silent but life-threatening vascular disorder for which no medical prevention or treatment is currently available. It has a prevalence of about 5% in men and 1% in women over 60 y old and is associated with hypertension, atherosclerosis, and cigarette smoking (1). The disease process in the aortic wall is characterized by strong dilation of (thoracic and/or abdominal) aorta, infiltration of media, and adventitia layers by immune cells, such as macrophages, neutrophils, and T cells, which release inflammatory cytokines and other mediators, which in turn drive extracellular matrix degradation, eventually resulting in spontaneous aortic rupture. Several proteolytic enzymes have been described as biomarkers of degenerative AAA progression, and matrix metalloproteinases (MMPs) have been shown to play a pivotal role in the pathogenesis of AAA through direct vascular degeneration, control of inflammation, and induction of apoptosis (2 ⇓–4).

The 5-lipoxygenase (5-LO) pathway of arachidonic acid metabolism leads to biosynthesis of leukotrienes (LTs), potent lipid mediators with proinflammatory biological actions. Among the LTs, cysteinyl-leukotrienes (cys-LTs) are well-known signaling molecules in human asthma, and drugs antagonizing the CysLT1 receptor have been established and important therapeutics for clinical management of asthma for more than a decade (5). However, more recently LTs have also been implicated in cardiovascular diseases such as atherosclerosis, myocardial infarction, and stroke (6 ⇓–8). Less is known about the 5-LO pathway and leukotrienes in AAA disease. It has been proposed that leukotriene B₄ (LTB₄) plays a role in AAA as a chemotactic factor released from neutrophils within the intraluminal thrombus, and work in our laboratory identified cys-LTs as main 5-LO products in human AAA wall (9). We could also demonstrate that challenging the aneurysm wall with exogenous cys-LTs can induce the release of MMPs, and this action can be prevented by pretreatment of the tissue with the CysLT1 antagonist montelukast (9). Moreover, levels of local cys-LTs were enhanced in humans undergoing AAA surgery (10). However, the limited number of animal studies addressed to clarify the potential role of LTs in AAA has yielded different results in the angiotensin II (AngII)-induced model (11). On the other hand, targeting the LTB₄ receptor 1 (BLT1) by genetic deletion or pharmacological antagonism afforded significant protection against AngII-induced AAA (12, 13). Recently, the inhibition of 5-LO by pharmacological or genetic approaches has been described to attenuate aneurysm formation in two different AAA mouse models (14). In the present study, we used the in vivo AAA mouse model induced by periaortic application of CaCl₂ to study the antiasthma drug montelukast as possible treatment to prevent aortic aneurysm. Additionally, we used two independent and well-characterized models of AAA, i.e., infusion of AngII into apoliprotein E-deficient (ApoE^−/−) mice and the porcine pancreatic elastase (PPE) infusion model in wild-type (WT) mice.

Our results indicate a pathophysiological role for cys-LTs in experimental AAA and suggest that pharmacological abrogation of CysLT1 signaling may be a clinical approach to protect against aortic wall degeneration and AAA development.

Results

Expression of 5-LO Pathway-Related Enzymes Is Up-Regulated in CaCl₂-Induced AAA.

Infrarenal aortas were harvested 21 d after the periaortic application of CaCl₂ and NaCl. Quantitative RT-PCR (qPCR) analysis revealed increased mRNA transcript levels for all 5-LO pathway enzymes (5-LO, FLAP, LTA₄H, and LTC₄S) with 5-LO (5.39 ± 1.86, P = 0.0181) and LTC₄S (6.22 ± 2.82, P = 0.0342) folds increased in comparison with the control mice (Fig. 1A). The significant up-regulation of 5-LO and LTC₄S mRNA indicates that cys-LTs are the main products of this pathway in the mouse AAA model, in agreement with what was observed in human AAA (9). We also checked a trend to increase the FLAP and LTA₄H transcripts, indicating that other leukotriene signaling (LTA₄H) might have a (small) role in AAA development.

Fig. 1.

The effect of montelukast on aorta dilatation in CaCl₂-induced AAA. (A) 5-LO, FLAP, LTA₄H, and LTC₄S mRNA was determined by qPCR in aortic wall of C57Bl6/J mice 21 d after the treatment with CaCl₂ (n = 4) and compared with control mice (n = 4) treated with NaCl. (B) Bright field and representative immunofluorescence staining for 5-LO, FLAP, LTA₄H, and LTC₄S (Cy3, red), CD68 (FITC, green), and DNA (DAPI, blue) and merged picture. Dashed yellow lines indicate external elastic lamina. Dashed line squares represent selected area for high magnification. (Scale bars: 100 μm, inner square 10 μm.) (C) AAA was induced on mice by periaortic application of CaCl₂ (n = 25) or NaCl (n = 6). CaCl₂-induced AAA mice were divided into four groups: group 1, no treatment (n = 10); group 2, mice treated with montelukast 0.1 mg/kg/d (n = 7); group 3, mice treated with montelukast 1 mg/kg/d (n = 8); and group 4, mice treated with CysLT2 antagonist 3 mg/kg/d (HAMI3379; n = 5); AAA was also induced on Alox5^−/− mice by periaortic application of CaCl₂ (n = 7) or NaCl (n = 4) as control. After 21 d, aortas were harvested, stained, and circumferences were calculated. (D) AAA was induced by CaCl₂ application and mice were divided into three groups receiving montelukast 1 mg/kg/d for 21 (n = 8), 14 (n = 6), and 7 (n = 6) d after AAA induction. CaCl₂-treated mice without montelukast (n = 10) and NaCl-treated mice (n = 6) were used as positive and negative control, respectively. At the end of the experiment, aortas were harvested, stained, and circumferences were calculated. (E) Homogenated aortas from C57Bl6/J mice treated with NaCl (n = 8), CaCl₂ (n = 8), CaCl₂ + montelukast 0.1 mg/kg/d (n = 4), CaCl₂ + montelukast 1 mg/kg/d (n = 4), and from Alox5^−/− mice treated with NaCl (n = 4) and CaCl₂ (n = 5) were analyzed by zymography and bands were quantified. (F) Homogenated aortas from separate C57Bl6/J mice treated with NaCl (n = 3), CaCl₂ (n = 3), CaCl₂ + montelukast 0.1 mg/kg/d (n = 3), and CaCl₂ + montelukast 1 mg/kg/d (n = 3), and from Alox5^−/− mice treated with NaCl (n = 3) and CaCl₂ (n = 3) were analyzed for the presence of MIP-1α by Bio-Plex mouse cytokine assay. Data are presented as mean ± SEM. *P < 0.05, **P < 0.01, ***P < 0.001, ****P < 0.0001, L, lumen; n.s., nonsignificant.

In addition, immunohistochemistry was performed in CaCl₂-treated mice. The results showed focal accumulation in media and adventitia layers of 5-LO, FLAP, and LTC₄S positive cells that partially colocalized with positive cells for mouse macrophage marker CD68 (Fig. 1B). This result confirms previous reports, which indicated macrophages as important inflammatory cells (15, 16) and a source of LTs (11) during AAA progression.

CysLT1 Antagonism Reduces CaCl₂-Induced AAA.

The morphological analysis of sections stained by hematoxylin, 21 d after CaCl₂ challenge confirmed a significant dilatation of the vascular wall (aorta circumference: 2.34 ± 0.57 mm) compared with NaCl-treated control (aorta circumference: 1.16 ± 0.102 mm, P = 0.0001), whereas the treatment of mice with montelukast 0.1 or 1 mg/kg/d reduced the CaCl₂-induced AAA (aorta circumference: 1.76 ± 0.22 mm, P = 0.0479 and 1.62 ± 0.42 mm, P = 0.0022, respectively) (Fig. 1C). To ascertain that the protective effect of montelukast was leukotriene dependent we induced aneurysm in 5-LO–deficient mice (Alox5^−/−) that cannot produce leukotrienes. These mice were almost completely protected against CaCl₂-induced AAA (NaCl aorta circumference: 1.16 ± 0.14 mm; CaCl₂: 1.37 ± 0.12 mm), demonstrating that the effects of montelukast are not an off-target action of the drug (Fig. 1C). We also used pharmacological tools to examine the role of CysLT2 receptor signaling in this AAA model. Thus, we tested the effect of a selective CysLT2 antagonist, HAMI3379 (17), in wild-type mice. At a dose of 3 mg/kg/d, HAMI3379 had no significant protective effect (aorta circumference: 2.24 ± 0.20 mm), demonstrating that the pathophysiological effects of cys-LTs in this model are specifically signaled via CysLT1 (Fig. 1C).

Montelukast as Treatment of Ongoing AAA Development.

To test whether CysLT1 antagonism could not only prevent but also inhibit an already ongoing degenerative process in the aortic wall, we studied the effects of the drug at two time points after induction with CaCl₂. Thus, in a separate set of experiments we started treatment with 1 mg/kg/d montelukast, 7 and 14 d after CaCl₂ induction (Fig. 1D), and, interestingly, the drug significantly protected the aorta at both time points with a circumference of 1.76 ± 0.07 mm (P = 0.0075) and 1.57 ± 0.06 mm (P = 0.0017), respectively, compared to untreated mice.

Montelukast Prevents the Release of MMP-9 and MIP-1α.

Cysteinyl-leukotrienes are powerful mediators of inflammation and have been implicated in the release of proteolytic enzymes as well as proinflammatory cytokines and chemokines from immune cells (18). Therefore, to detect the MMPs activity, we examined mouse aortas by zymography. We found a sixfold increase of MMP-9 in mice undergoing AAA induction by CaCl₂ (5.84 ± 2.25, P = 0.0002 vs. NaCl) (Fig. 1E). Moreover, both doses of montelukast, 0.1 and 1 mg/kg/d, significantly attenuated this increase and maintained the protease almost at basal levels, corresponding to a twofold increase (1.84 ± 0.23, P = 0.0088 and 2.17 ± 0.26, P = 0.0040 vs. CaCl₂, respectively), indicating that cys-LTs were the major, albeit not the sole, mediator of MMP-9 induction. Additionally, Alox5^−/− mice showed no difference in MMP-9 activity between CaCl₂- and NaCl-treated mice (P = 0.5 vs. NaCl; Fig. 1E). Altogether, these results show that montelukast prevents the release of MMP-9 in a leukotriene-dependent manner.

Next we measured cytokine/chemokine levels in the aortic wall of CaCl₂-treated mice. Cytokines, i.e., interleukin (IL)-1β, IL-10, IL-13, tumor necrosis factor-α (TNFα), and chemokines, i.e., monocyte chemotactic protein-1 (MCP-1) and macrophage inflammatory protein-1α (MIP-1α) were analyzed in aorta homogenates. Out of these, only MIP-1α showed a significant increase in CaCl₂-treated mice (17.04 ± 1.12 pg/mL) compared with basal levels (1.70 ± 0.54 pg/mL, P = 0.0001 vs. change in NaCl-treated mice). Treatment with montelukast (1 mg/kg/d) maintained MIP-1α near basal level (2.79 ± 2.42 pg/mL, P = 0.0008 vs. CaCl₂) while low dose montelukast did not show any effect (Fig. 1F). We also measured levels of MIP-1α in Alox5^−/− mice and found that this chemokine was not increased during AAA induction (Fig. 1F).

Montelukast Inhibits LTD₄-Induced Expression of Cytokines and Chemokines in Human MonoMac6 Cells.

MonoMac6 (MM6) cells were treated with either 1 µM montelukast (1 h) or vehicle, followed by challenge with 100 nM LTD₄ (1 h). LTD₄ alone increased mRNA levels of the cytokines TNFα (P < 0.0001) and IL-1β (P < 0.01) as well as chemokines MIP-1α (P < 0.0001) and MCP-1 (P < 0.0001) (Fig. 2A and Fig. S1A), while no effect was observed for the transcript levels of cytokines IL-10 and TGFβ1 (Fig. S1A). In addition, increased levels of TNFα (P < 0.05) and MIP-1α (P < 0.01) were detected in the supernatants of MM6 cells challenged with LTD₄, while protein levels of the other mediators were not significantly increased (Fig. 2B and Fig. S1B). Pretreatment of cells with montelukast attenuated all LTD₄-induced increases of cytokine/chemokine mRNA and protein to levels corresponding to the untreated control (Fig. 2B and Fig. S1B).

Fig. 2.

Montelukast inhibits LTD₄-induced expression of MIP-1α and TNFα in human MonoMac6 (MM6) cells. MM6 cells were pretreated with montelukast or vehicle before challenge with LTD₄ (100 nM, 1 h). (A) qPCR analysis of MIP-1α and TNFα transcript levels in MM6 cells treated with vehicle only (control), challenged with LTD₄ only (LTD₄), or challenged with LTD₄ following pretreatment with montelukast (montelukast+LTD₄). (B) Analysis of MIP-1α and TNFα protein levels in supernatants of MM6 cells treated as in A. The graphs depict results from analysis of duplicate and triplicate samples obtained in three independent experiments. Data represent mean of experiments ±SD. *P < 0.05, **P < 0.01, ***P < 0.001, ****P < 0.0001.

Montelukast Has a Protective Effect in Aorta Rupture in AngII-Infused ApoE^−/− Mice.

In this animal model, we observed a statistically significant increase in mRNA levels of 5-LO (1.5 ± 0.18 fold; P = 0.028) and FLAP (1.4 ± 0.26 fold; P = 0.028) in the aortic wall after 28 d of challenge with AngII (Fig. 3A). Additionally, immunostaining revealed colocalization of 5-LO, FLAP, and LTC₄S in macrophages mainly localized in the adventitia (Fig. 3B). A common complication associated with the infusion of AngII in ApoE^−/− mice is the aortic rupture. We observed that the rupture rate was significantly increased in the placebo group (45%) compared with montelukast-treated mice (15%) (P = 0.03; Fig. 3C). Moreover, we observed that in the placebo group, mice died within the first week of AngII infusion, while in the group treated with montelukast, deadly ruptures were delayed until the last week of the experiment. We also examined MMP-9 expression within the suprarenal aortas of both groups and detected reduced levels of MMP-9 in the montelukast-treated group vs. placebo (P = 0.03; Fig. 3D). Altogether, we can conclude that montelukast delays aortic rupture in AngII-infused mice.

Fig. 3.

Effect of montelukast in AngII-infused ApoE^−/− mouse model. (A) 5-LO, FLAP, LTA₄H, and LTC₄S mRNA was determined by qPCR in aortic wall of AngII-infused ApoE^−/− (n = 4) and compared with ApoE^−/− mouse (n = 4). (B) Bright field and representative immunofluorescence staining for 5-LO, FLAP, LTA₄H, and LTC₄S (Cy3, red), CD68 (FITC, green), and DNA (DAPI, blue) and merged picture of suprarenal aorta in AngII-infused ApoE^−/−. Dashed yellow lines indicate external elastic lamina. Dashed line squares represent selected area for high magnification. (Scale bars: 100 μm, inner square 10 μm.) (C) Aortic rupture rate was determined in AngII-infused ApoE^−/− treated with placebo (45%, 9 of 20) vs. montelukast group (15%, 3 of 20). (D) Homogenated aortas from AngII-infused ApoE^−/− treated with placebo (n = 4) and montelukast (n = 5) were analyzed by zymography and bands were quantified. Data represent mean of experiments ±SEM. The aortic rupture was analyzed by χ² test. *P < 0.05, L, lumen; n.s., nonsignificant.

Montelukast Decreases the Aortic Dilatation in the PPE-Infusion Model of AAA.

In line with the results obtained in the previous two models, the induction of AAA by PPE infusion induced an up-regulation of transcript levels of 5-LO (3.05 ± 0.7 fold; P = 0.04), FLAP (6.95 ± 1.0 fold; P = 0.004), and LTA₄H (1.8 ± 0.2 fold; P = 0.02) in comparison with the control group (Fig. 4A). We also found a trend to increase the levels of LTC₄S transcripts in this model. In addition, immunostaining of 5-LO pathway-related proteins (5-LO, FLAP, and LTC₄S) were observed through colocalization with macrophages (Fig. 4B).

Fig. 4.

Effect of montelukast in PPE infusion model. (A) 5-LO, FLAP, LTA₄H, and LTC₄S mRNA was determined by qPCR in aortic wall of PPE (n = 3) compared with sham unoperated animals (n = 3). (B) Bright field and representative immunofluorescence staining for 5-LO, FLAP, LTA₄H, and LTC₄S (Cy3, red), CD68 (FITC, green), and DNA (DAPI, blue) and merged picture of infrarenal aorta in PPE. Dashed yellow lines indicate external elastic lamina. Dashed line squares represent selected area for high magnification. (Scale bars: 100 μm, inner square 10 μm.) (C) Representative ultrasound imaging of infrarenal aorta from mice treated with placebo and montelukast after 28 d of PPE infrarenal infusion. (D) Luminal diameter (relative dilatation from baseline) after 28 d of PPE infrarenal infusion in mice treated with placebo (n = 7) and montelukast (n = 5). (E) Homogenated infrarenal aortas from mice treated with placebo (n = 6) and montelukast (n = 5) were analyzed by zymography and bands were quantified. Data represent mean of experiments ±SEM. *P < 0.05, ***P < 0.001, L, lumen; n.s., nonsignificant.

Ultrasound imaging revealed that montelukast treatment reduced significantly the increase of abdominal aortic diameter (AAD) at day 28 (48.4% ± 3.9 vs. 81.4 ± 10.6 placebo; P = 0.03) (Fig. 4 C and D). Moreover, treatment with montelukast for 4 wk revealed a reduced activity of MMP-9 (P = 0.03 vs. placebo; Fig. 4E).

Discussion

AAA is a common, slowly developing, and highly lethal vascular disorder in elderly people. The most dangerous clinical consequence of AAA is an acute rupture, which carries a mortality of 80%. The absence of clinical signs and biomarkers able to predict this disorder brings it to late diagnosis when the aneurysm is in an advanced stage, which may, or may not, be amenable to surgical intervention. Thus, a main medical goal is to find noninvasive pharmacological therapies, which can prevent, slow down, and possibly block the progression of the vascular wall degradation at an early stage of the disease process.

The AAA pathology is characterized by chronic inflammation and increased protease activity in the vessel wall leading to extracellular matrix degradation, aneurysm growth, and finally spontaneous rupture (19).

Previous work on human aneurysm tissue has suggested that leukotrienes may be involved in AAA disease (9, 20). However, studies with the AngII model have yielded variable results (11 ⇓–13, 21). Thus, pharmacological inhibition or genetic ablation of 5-LO, the regulatory enzyme responsible for the biosynthesis of LTs, reduced vascular remodeling but did not afford significant protection against AAA (11, 22, 23), while positive results were achieved with interventions at the BLT1 receptor level (12, 13). A possible reason for this discrepancy could be that blocking 5-LO inhibits not only the formation of proinflammatory LTs, but also biosynthesis of antiinflammatory, proresolving mediators such as lipoxins and resolvins, which have been shown to attenuate murine AAA (24, 25). More recently, a study from AstraZeneca demonstrated that pretreating mice with a potent 5-LO inhibitor before the induction of AAA by either AngII infusion in LDL^−/− mice under high fat diet or PPE in WT mice reduced the aneurysm development (14). Although these results are promising, high doses of the inhibitor were required and drugs targeting 5-LO are known to be associated with side effects, limiting the translational potential of these observations. Furthering our findings on increased 5-LO pathway and cys-LTs in human AAA specimens, we tested the effects of montelukast, a well-characterized antiasthma drug, in the CaCl₂ model of murine AAA. This chemically induced model is characterized by a destruction of elastic lamellae and degradation of the aortic media that produces a strong dilatation of the lumen of the infrarenal aorta followed by influx of inflammatory cells, mainly macrophages (26).

Surprisingly, we found that already low doses of the drug (0.1–1 mg/kg) comparable to those used in the clinical management of asthma (27, 28) were sufficient to afford significant protection against aortic AAA development (Fig. 1C). However, no protective effect was observed using a selective CysLT2 antagonist (Fig. 1C), suggesting strict CysLT1 dependence of this model. We next assessed the potential of montelukast to block the progression of ongoing disease. Montelukast treatment was started at 7 and 14 d after the CaCl₂ challenge, and montelukast was able to significantly block the aortic dilation at both time points (Fig. 1D).

A large body of evidence indicates that the inflammatory microenvironment, including cytokines and chemokines, plays a pivotal role during the initiation and progression of aortic degradation (15, 16, 29). In this context, it has been shown in vitro that LTD₄ up-regulates MIP-1α gene expression from human monocyte and mouse macrophage cells lines (11), and in vivo that the 5-LO/leukotriene pathway mediates the production of this cytokine (11). MIP-1α can also in turn induce the release of proteolytic enzymes such as MMPs (30, 31). Furthermore, cys-LTs can themselves induce the release of MMPs from macrophages (32) as well as from human AAA tissue in a CysLT1-dependent manner (9). Our data indicate that this leukotriene–cytokine–protease cross-talk is involved in the in vivo AAA pathogenesis of the CaCl₂-induced AAA model since we observed increased release of MMP-9 (Fig. 1E) and MIP-1α (Fig. 1F), which could be blocked by montelukast. Moreover, human MM6 cells challenged with LTD₄ increased their expression of cytokines and chemokines, in particular MIP-1α and TNFα, confirming the potential of monocytes/macrophages to mediate proinflammatory actions of cys-LT relevant to AAA (Fig. 2). Again, these functional responses were blocked by montelukast.

To get further proof of concept, we used two additional, genetically and metabolically different, mouse models of AAA, viz. infusion of AngII in ApoE^−/− mice and PPE perfusion in WT mice, and assessed the effect of montelukast. These two models share pathological characteristics with CaCl₂-induced AAA, such as destruction of elastic lamellae and degradation of media layer, as well as the immune cell composition dominated by macrophages (26). However, the AngII model shows infiltration also of other leukocytes, i.e., B and T lymphocytes, and the aneurysm occurs in the suprarenal aorta (26).

Both models exhibited increased levels of 5-LO pathway enzymes, and at a dose of 1 mg/kg, the drug significantly reduced the rate of rupture in the AngII/ApoE^−/− model (Fig. 3C) and attenuated aortic dilatation in the PPE model (Fig. 4D), apparently due to decreased MMP-9 activity (Figs. 3D and 4E). Hence, we show in three independent in vivo AAA mouse models with specific characteristics (i.e., inflammatory homing: CaCl₂ and PPE; and aortic dissection with thrombus: AngII) (26, 33) that clinically relevant doses of montelukast act as both antiinflammatory and antiproteolytic agents, apparently by inhibiting MIP-1α and MMP-9, respectively, leading to reduced aneurysm growth and rupture.

Although we believe that montelukast acts locally in the diseased artery, we cannot rule out that actions of the drug outside the vessel wall may also play a role in our AAA models. For instance, montelukast blocks CysLT1-dependent signaling in human Th2 cells that can migrate in response to cys-LTs and are believed to contribute to airway inflammation in asthma (34). It should also be noted that studies in vitro have indicated that higher, supratherapeutic doses of montelukast can elicit off-target effects such as inhibition of 5-lipoxygenase, NF-κB activation, and eosinophil adhesion, which have been suggested to contribute to its beneficial actions in inflammatory lung diseases (35).

In the absence of noninvasive treatments for AAA (1), there is a continued strong medical need to develop preventive and therapeutic medications that can be used for patients with incipient AAA below the threshold for surgical repair. In recent years, several clinical trials have been carried out to test the protective ability of a variety of drugs such as β blockers, calcium channel blockers, mast cell inhibitors, ACE inhibitors, and the antibiotic doxycycline without any positive effect (36). Although the reasons for these failures are currently under debate, there is a general consensus to continue the search for new drug targets for evaluation in human clinical trials. Since CysLT1 antagonists target both the inflammatory and proteolytic components of AAA pathogenesis, they would represent a drug candidate with a mode of action that has not yet been clinically tested. Furthermore, CysLT1 antagonists, typified by montelukast, are effective medications against human asthma, a disease which is experimentally and epidemiologically associated with AAA and rupture (37, 38). It has also been observed that AAA and asthma share several pathophysiological similarities (39, 40) and epidemiological data have revealed a positive correlation between use of montelukast and reduced cardiovascular risk in men (41). Moreover, CysLT1 antagonists are remarkably safe, allow a once-daily dose regimen, carry few side effects, and are available as generic drugs. Hence, we firmly believe that CysLT1 antagonists hold promise as anti-AAA agents and should soon be tested in a controlled clinical trial.

Materials and Methods

Animals.

Wild-type and ApoE^−/− male mice on the background C57BL/6J were purchased from SCANBUR Sweden and Taconic, respectively. Alox5^−/− mice on the C57BL/6J background were a generous gift from Geraldine Canny (University of Lausanne, Lausanne, Switzerland). The housing and care of animals and all of the animal procedures used in this study were in accordance with national guidelines and approved by the Stockholm North Ethical Committee on Animal Experiments. Details of the mouse models of AAA are described in SI Materials and Methods.

Luminal Aortic Diameter Measurements by Ultrasound Imaging.

Ultrasound was performed in the animals before the aneurysm induction by angiotensin (Ang) II and PPE infusion and then weekly until the end of week 4 as described (42).

Isolated Cells in Vitro.

Cultivation and treatments of a monocyte/macrophage cell line followed a protocol described in ref. 11.

Immunohistochemistry and Measurements of mRNA, Protein, and Protease Activity.

Histology and immunohistochemical analysis as well as meaurements of cDNA and protein by qPCR and Bio-Plex analysis, respectively, are decribed in SI Materials and Methods. Gel zymography was used for assessment of metalloprotease activity, as described (9).

Statistical Analysis.

Data were analyzed with one-way ANOVA followed by Tukey’s post hoc test. Real-time PCR and aortic dilatation in Alox5^−/− mice data were analyzed by Student’s t test. In all cases, statistical significance was set to P < 0.05.

For further details of materials and methods, please see SI Materials and Methods.

Acknowledgments

We are grateful to Drs. Marcelo Petri as a blinded observer, Mingmei Shang for the Bio-Plex technical support, and Anders Gabrielsen for discussions and advice. This work was supported by grants from the Swedish Research Council (10350), Stockholm County Council (20150517), Linneus Grant Center of Excellence for Research on Inflammation and Cardiovascular Disease, Novo Nordisk Foundation (NNF15CC0018346 and NNF15CC0018486), the Cardiovascular Program (CVP), Swedish Heart Lung Foundation (20120615, 20130664, 20140186, and 20150423), the Ragnar Söderberg Foundation (M-14/55), the Karolinska Institutet CVP Career Development Grant, the European Research Council (Starting Grant NORVAS), and a Distinguished Professor Award from Karolinska Institutet.

Footnotes

↵¹A.D.G. and A.C.A. contributed equally to this work.
↵²To whom correspondence may be addressed. Email: bengt.samuelsson{at}ki.se or jesper.haeggstrom{at}ki.se.

Author contributions: A.D.G., A.C.A., D.W., P.E., B.S., L.M., and J.Z.H. designed research; A.D.G., A.C.A., A.B., H.J., E.V., and K.C. performed research; A.B., H.J., D.W., K.C., and L.M. contributed new reagents/analytic tools; A.D.G., A.C.A., A.B., H.J., D.W., E.V., K.C., L.M., and J.Z.H. analyzed data; and A.D.G., A.C.A., and J.Z.H. wrote the paper.
Reviewers: I.F., Goethe University, Frankfurt; and C.N.S., Brigham and Women’s Hospital and Harvard Medical School.
The authors declare no conflict of interest.
This article contains supporting information online at www.pnas.org/lookup/suppl/doi:10.1073/pnas.1717906115/-/DCSupplemental.

This open access article is distributed under Creative Commons Attribution-NonCommercial-NoDerivatives License 4.0 (CC BY-NC-ND).

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(1999) Treatment of asthma with drugs modifying the leukotriene pathway. N Engl J Med 340:197–206.
OpenUrl CrossRef PubMed
↵
1. Funk CD
(2005) Leukotriene modifiers as potential therapeutics for cardiovascular disease. Nat Rev Drug Discov 4:664–672.
OpenUrl CrossRef PubMed
↵
1. Haeggström JZ,
2. Funk CD
(2011) Lipoxygenase and leukotriene pathways: Biochemistry, biology, and roles in disease. Chem Rev 111:5866–5898.
OpenUrl CrossRef PubMed
↵
1. Hansson GK
(2005) Inflammation, atherosclerosis, and coronary artery disease. N Engl J Med 352:1685–1695.
OpenUrl CrossRef PubMed
↵
1. Di Gennaro A, et al.
(2010) Increased expression of leukotriene C4 synthase and predominant formation of cysteinyl-leukotrienes in human abdominal aortic aneurysm. Proc Natl Acad Sci USA 107:21093–21097.
OpenUrl Abstract/FREE Full Text
↵
1. Pillai PS, et al.
(2012) Chemical mediators of inflammation and resolution in post-operative abdominal aortic aneurysm patients. Inflammation 35:98–113.
OpenUrl CrossRef PubMed
↵
1. Zhao L, et al.
(2004) The 5-lipoxygenase pathway promotes pathogenesis of hyperlipidemia-dependent aortic aneurysm. Nat Med 10:966–973.
OpenUrl CrossRef PubMed
↵
1. Ahluwalia N, et al.
(2007) Inhibited aortic aneurysm formation in BLT1-deficient mice. J Immunol 179:691–697.
OpenUrl Abstract/FREE Full Text
↵
1. Kristo F, et al.
(2010) Pharmacological inhibition of BLT1 diminishes early abdominal aneurysm formation. Atherosclerosis 210:107–113.
OpenUrl CrossRef PubMed
↵
1. Bhamidipati CM, et al.
(2014) 5-Lipoxygenase pathway in experimental abdominal aortic aneurysms. Arterioscler Thromb Vasc Biol 34:2669–2678.
OpenUrl Abstract/FREE Full Text
↵
1. Hellenthal FA,
2. Buurman WA,
3. Wodzig WK,
4. Schurink GW
(2009) Biomarkers of abdominal aortic aneurysm progression. Part 2: Inflammation. Nat Rev Cardiol 6:543–552.
OpenUrl CrossRef PubMed
↵
1. Rizas KD,
2. Ippagunta N,
3. Tilson MD 3rd
(2009) Immune cells and molecular mediators in the pathogenesis of the abdominal aortic aneurysm. Cardiol Rev 17:201–210.
OpenUrl CrossRef PubMed
↵
1. Wunder F, et al.
(2010) Pharmacological characterization of the first potent and selective antagonist at the cysteinyl leukotriene 2 (CysLT(2)) receptor. Br J Pharmacol 160:399–409.
OpenUrl CrossRef PubMed
↵
1. Peters-Golden M,
2. Gleason MM,
3. Togias A
(2006) Cysteinyl leukotrienes: Multi-functional mediators in allergic rhinitis. Clin Exp Allergy 36:689–703.
OpenUrl CrossRef PubMed
↵
1. Nordon IM,
2. Hinchliffe RJ,
3. Loftus IM,
4. Thompson MM
(2011) Pathophysiology and epidemiology of abdominal aortic aneurysms. Nat Rev Cardiol 8:92–102.
OpenUrl CrossRef PubMed
↵
1. Houard X,
2. Ollivier V,
3. Louedec L,
4. Michel JB,
5. Bäck M
(2009) Differential inflammatory activity across human abdominal aortic aneurysms reveals neutrophil-derived leukotriene B4 as a major chemotactic factor released from the intraluminal thrombus. FASEB J 23:1376–1383.
OpenUrl CrossRef PubMed
↵
1. Cao RY,
2. Adams MA,
3. Habenicht AJ,
4. Funk CD
(2007) Angiotensin II-induced abdominal aortic aneurysm occurs independently of the 5-lipoxygenase pathway in apolipoprotein E-deficient mice. Prostaglandins Other Lipid Mediat 84:34–42.
OpenUrl CrossRef PubMed
↵
1. Cao RY,
2. St Amand T,
3. Gräbner R,
4. Habenicht AJ,
5. Funk CD
(2009) Genetic and pharmacological inhibition of the 5-lipoxygenase/leukotriene pathway in atherosclerotic lesion development in ApoE deficient mice. Atherosclerosis 203:395–400.
OpenUrl CrossRef PubMed
↵
1. Revermann M, et al.
(2011) A pirinixic acid derivative (LP105) inhibits murine 5-lipoxygenase activity and attenuates vascular remodelling in a murine model of aortic aneurysm. Br J Pharmacol 163:1721–1732.
OpenUrl CrossRef PubMed
↵
1. Serhan CN
(2014) Pro-resolving lipid mediators are leads for resolution physiology. Nature 510:92–101.
OpenUrl CrossRef PubMed
↵
1. Pope NH, et al.
(2016) D-series resolvins inhibit murine abdominal aortic aneurysm formation and increase M2 macrophage polarization. FASEB J 30:4192–4201.
OpenUrl CrossRef PubMed
↵
1. Daugherty A,
2. Cassis LA
(2004) Mouse models of abdominal aortic aneurysms. Arterioscler Thromb Vasc Biol 24:429–434.
OpenUrl Abstract/FREE Full Text
↵
1. Bateman ED,
2. Goehring UM,
3. Richard F,
4. Watz H
(2016) Roflumilast combined with montelukast versus montelukast alone as add-on treatment in patients with moderate-to-severe asthma. J Allergy Clin Immunol 138:142–149.e8.
OpenUrl
↵
1. Ciółkowski J,
2. Mazurek H,
3. Hydzik P,
4. Stasiowska B
(2016) Inflammatory markers as exacerbation risk factors after asthma therapy switch from inhaled steroids to montelukast. Pulm Pharmacol Ther 39:7–13.
OpenUrl
↵
1. Middleton RK, et al.
(2007) The pro-inflammatory and chemotactic cytokine microenvironment of the abdominal aortic aneurysm wall: A protein array study. J Vasc Surg 45:574–580.
OpenUrl CrossRef PubMed
↵
1. Giribaldi G,
2. Valente E,
3. Khadjavi A,
4. Polimeni M,
5. Prato M
(2011) Macrophage inflammatory protein-1alpha mediates matrix metalloproteinase-9 enhancement in human adherent monocytes fed with malarial pigment. Asian Pac J Trop Med 4:925–930.
OpenUrl PubMed
↵
1. Hoh BL, et al.
(2011) Monocyte chemotactic protein-1 promotes inflammatory vascular repair of murine carotid aneurysms via a macrophage inflammatory protein-1α and macrophage inflammatory protein-2-dependent pathway. Circulation 124:2243–2252.
OpenUrl Abstract/FREE Full Text
↵
1. Ichiyama T, et al.
(2007) Cysteinyl leukotrienes enhance tumour necrosis factor-alpha-induced matrix metalloproteinase-9 in human monocytes/macrophages. Clin Exp Allergy 37:608–614.
OpenUrl CrossRef PubMed
↵
1. Bhamidipati CM, et al.
(2012) Development of a novel murine model of aortic aneurysms using peri-adventitial elastase. Surgery 152:238–246.
OpenUrl PubMed
↵
1. Parmentier CN, et al.
(2012) Human T(H)2 cells respond to cysteinyl leukotrienes through selective expression of cysteinyl leukotriene receptor 1. J Allergy Clin Immunol 129:1136–1142.
OpenUrl CrossRef PubMed
↵
1. Tintinger GR,
2. Feldman C,
3. Theron AJ,
4. Anderson R
(2010) Montelukast: More than a cysteinyl leukotriene receptor antagonist? Sci World J 10:2403–2413.
OpenUrl
↵
1. Golledge J,
2. Norman PE,
3. Murphy MP,
4. Dalman RL
(2017) Challenges and opportunities in limiting abdominal aortic aneurysm growth. J Vasc Surg 65:225–233.
OpenUrl
↵
1. Liu CL, et al.
(2016) Asthma associates with human abdominal aortic aneurysm and rupture. Arterioscler Thromb Vasc Biol 36:570–578.
OpenUrl Abstract/FREE Full Text
↵
1. Liu CL, et al.
(2016) Allergic lung inflammation aggravates angiotensin II-induced abdominal aortic aneurysms in mice. Arterioscler Thromb Vasc Biol 36:69–77.
OpenUrl Abstract/FREE Full Text
↵
1. Sun J, et al.
(2007) Mast cells modulate the pathogenesis of elastase-induced abdominal aortic aneurysms in mice. J Clin Invest 117:3359–3368.
OpenUrl CrossRef PubMed
↵
1. Wang J, et al.
(2014) IgE actions on CD4+ T cells, mast cells, and macrophages participate in the pathogenesis of experimental abdominal aortic aneurysms. EMBO Mol Med 6:952–969.
OpenUrl Abstract/FREE Full Text
↵
1. Ingelsson E,
2. Yin L,
3. Bäck M
(2012) Nationwide cohort study of the leukotriene receptor antagonist montelukast and incident or recurrent cardiovascular disease. J Allergy Clin Immunol 129:702–707.e2.
OpenUrl CrossRef PubMed
↵
1. Azuma J, et al.
(2011) Assessment of elastase-induced murine abdominal aortic aneurysms: Comparison of ultrasound imaging with in situ video microscopy. J Biomed Biotechnol 2011:252141.
OpenUrl PubMed

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Proceedings of the National Academy of Sciences: 115 (8)

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[1] ↵
Maegdefessel L,
Dalman RL,
Tsao PS
(2014) Pathogenesis of abdominal aortic aneurysms: MicroRNAs, proteases, genetic associations. Annu Rev Med 65:49–62.
OpenUrl

[2] Maegdefessel L,

[3] Dalman RL,

[4] Tsao PS

[5] ↵
Hellenthal FA,
Buurman WA,
Wodzig WK,
Schurink GW
(2009) Biomarkers of AAA progression. Part 1: Extracellular matrix degeneration. Nat Rev Cardiol 6:464–474.
OpenUrl CrossRef PubMed

[6] Hellenthal FA,

[7] Buurman WA,

[8] Wodzig WK,

[9] Schurink GW

[10] ↵
Longo GM, et al.
(2002) Matrix metalloproteinases 2 and 9 work in concert to produce aortic aneurysms. J Clin Invest 110:625–632.
OpenUrl CrossRef PubMed

[11] Longo GM, et al.

[12] ↵
Swedenborg J,
Eriksson P
(2006) The intraluminal thrombus as a source of proteolytic activity. Ann N Y Acad Sci 1085:133–138.
OpenUrl CrossRef PubMed

[13] Swedenborg J,

[14] Eriksson P

[15] ↵
Drazen JM,
Israel E,
O’Byrne PM
(1999) Treatment of asthma with drugs modifying the leukotriene pathway. N Engl J Med 340:197–206.
OpenUrl CrossRef PubMed

[16] Drazen JM,

[17] Israel E,

[18] O’Byrne PM

[19] ↵
Funk CD
(2005) Leukotriene modifiers as potential therapeutics for cardiovascular disease. Nat Rev Drug Discov 4:664–672.
OpenUrl CrossRef PubMed

[20] Funk CD

[21] ↵
Haeggström JZ,
Funk CD
(2011) Lipoxygenase and leukotriene pathways: Biochemistry, biology, and roles in disease. Chem Rev 111:5866–5898.
OpenUrl CrossRef PubMed

[22] Haeggström JZ,

[23] Funk CD

[24] ↵
Hansson GK
(2005) Inflammation, atherosclerosis, and coronary artery disease. N Engl J Med 352:1685–1695.
OpenUrl CrossRef PubMed

[25] Hansson GK

[26] ↵
Di Gennaro A, et al.
(2010) Increased expression of leukotriene C4 synthase and predominant formation of cysteinyl-leukotrienes in human abdominal aortic aneurysm. Proc Natl Acad Sci USA 107:21093–21097.
OpenUrl Abstract/FREE Full Text

[27] Di Gennaro A, et al.

[28] ↵
Pillai PS, et al.
(2012) Chemical mediators of inflammation and resolution in post-operative abdominal aortic aneurysm patients. Inflammation 35:98–113.
OpenUrl CrossRef PubMed

[29] Pillai PS, et al.

[30] ↵
Zhao L, et al.
(2004) The 5-lipoxygenase pathway promotes pathogenesis of hyperlipidemia-dependent aortic aneurysm. Nat Med 10:966–973.
OpenUrl CrossRef PubMed

[31] Zhao L, et al.

[32] ↵
Ahluwalia N, et al.
(2007) Inhibited aortic aneurysm formation in BLT1-deficient mice. J Immunol 179:691–697.
OpenUrl Abstract/FREE Full Text

[33] Ahluwalia N, et al.

[34] ↵
Kristo F, et al.
(2010) Pharmacological inhibition of BLT1 diminishes early abdominal aneurysm formation. Atherosclerosis 210:107–113.
OpenUrl CrossRef PubMed

[35] Kristo F, et al.

[36] ↵
Bhamidipati CM, et al.
(2014) 5-Lipoxygenase pathway in experimental abdominal aortic aneurysms. Arterioscler Thromb Vasc Biol 34:2669–2678.
OpenUrl Abstract/FREE Full Text

[37] Bhamidipati CM, et al.

[38] ↵
Hellenthal FA,
Buurman WA,
Wodzig WK,
Schurink GW
(2009) Biomarkers of abdominal aortic aneurysm progression. Part 2: Inflammation. Nat Rev Cardiol 6:543–552.
OpenUrl CrossRef PubMed

[39] Hellenthal FA,

[40] Buurman WA,

[41] Wodzig WK,

[42] Schurink GW

[43] ↵
Rizas KD,
Ippagunta N,
Tilson MD 3rd
(2009) Immune cells and molecular mediators in the pathogenesis of the abdominal aortic aneurysm. Cardiol Rev 17:201–210.
OpenUrl CrossRef PubMed

[44] Rizas KD,

[45] Ippagunta N,

[46] Tilson MD 3rd

[47] ↵
Wunder F, et al.
(2010) Pharmacological characterization of the first potent and selective antagonist at the cysteinyl leukotriene 2 (CysLT(2)) receptor. Br J Pharmacol 160:399–409.
OpenUrl CrossRef PubMed

[48] Wunder F, et al.

[49] ↵
Peters-Golden M,
Gleason MM,
Togias A
(2006) Cysteinyl leukotrienes: Multi-functional mediators in allergic rhinitis. Clin Exp Allergy 36:689–703.
OpenUrl CrossRef PubMed

[50] Peters-Golden M,

[51] Gleason MM,

[52] Togias A

[53] ↵
Nordon IM,
Hinchliffe RJ,
Loftus IM,
Thompson MM
(2011) Pathophysiology and epidemiology of abdominal aortic aneurysms. Nat Rev Cardiol 8:92–102.
OpenUrl CrossRef PubMed

[54] Nordon IM,

[55] Hinchliffe RJ,

[56] Loftus IM,

[57] Thompson MM

[58] ↵
Houard X,
Ollivier V,
Louedec L,
Michel JB,
Bäck M
(2009) Differential inflammatory activity across human abdominal aortic aneurysms reveals neutrophil-derived leukotriene B4 as a major chemotactic factor released from the intraluminal thrombus. FASEB J 23:1376–1383.
OpenUrl CrossRef PubMed

[59] Houard X,

[60] Ollivier V,

[61] Louedec L,

[62] Michel JB,

[63] Bäck M

[64] ↵
Cao RY,
Adams MA,
Habenicht AJ,
Funk CD
(2007) Angiotensin II-induced abdominal aortic aneurysm occurs independently of the 5-lipoxygenase pathway in apolipoprotein E-deficient mice. Prostaglandins Other Lipid Mediat 84:34–42.
OpenUrl CrossRef PubMed

[65] Cao RY,

[66] Adams MA,

[67] Habenicht AJ,

[68] Funk CD

[69] ↵
Cao RY,
St Amand T,
Gräbner R,
Habenicht AJ,
Funk CD
(2009) Genetic and pharmacological inhibition of the 5-lipoxygenase/leukotriene pathway in atherosclerotic lesion development in ApoE deficient mice. Atherosclerosis 203:395–400.
OpenUrl CrossRef PubMed

[70] Cao RY,

[71] St Amand T,

[72] Gräbner R,

[73] Habenicht AJ,

[74] Funk CD

[75] ↵
Revermann M, et al.
(2011) A pirinixic acid derivative (LP105) inhibits murine 5-lipoxygenase activity and attenuates vascular remodelling in a murine model of aortic aneurysm. Br J Pharmacol 163:1721–1732.
OpenUrl CrossRef PubMed

[76] Revermann M, et al.

[77] ↵
Serhan CN
(2014) Pro-resolving lipid mediators are leads for resolution physiology. Nature 510:92–101.
OpenUrl CrossRef PubMed

[78] Serhan CN

[79] ↵
Pope NH, et al.
(2016) D-series resolvins inhibit murine abdominal aortic aneurysm formation and increase M2 macrophage polarization. FASEB J 30:4192–4201.
OpenUrl CrossRef PubMed

[80] Pope NH, et al.

[81] ↵
Daugherty A,
Cassis LA
(2004) Mouse models of abdominal aortic aneurysms. Arterioscler Thromb Vasc Biol 24:429–434.
OpenUrl Abstract/FREE Full Text

[82] Daugherty A,

[83] Cassis LA

[84] ↵
Bateman ED,
Goehring UM,
Richard F,
Watz H
(2016) Roflumilast combined with montelukast versus montelukast alone as add-on treatment in patients with moderate-to-severe asthma. J Allergy Clin Immunol 138:142–149.e8.
OpenUrl

[85] Bateman ED,

[86] Goehring UM,

[87] Richard F,

[88] Watz H

[89] ↵
Ciółkowski J,
Mazurek H,
Hydzik P,
Stasiowska B
(2016) Inflammatory markers as exacerbation risk factors after asthma therapy switch from inhaled steroids to montelukast. Pulm Pharmacol Ther 39:7–13.
OpenUrl

[90] Ciółkowski J,

[91] Mazurek H,

[92] Hydzik P,

[93] Stasiowska B

[94] ↵
Middleton RK, et al.
(2007) The pro-inflammatory and chemotactic cytokine microenvironment of the abdominal aortic aneurysm wall: A protein array study. J Vasc Surg 45:574–580.
OpenUrl CrossRef PubMed

[95] Middleton RK, et al.

[96] ↵
Giribaldi G,
Valente E,
Khadjavi A,
Polimeni M,
Prato M
(2011) Macrophage inflammatory protein-1alpha mediates matrix metalloproteinase-9 enhancement in human adherent monocytes fed with malarial pigment. Asian Pac J Trop Med 4:925–930.
OpenUrl PubMed

[97] Giribaldi G,

[98] Valente E,

[99] Khadjavi A,

[100] Polimeni M,

[101] Prato M

[102] ↵
Hoh BL, et al.
(2011) Monocyte chemotactic protein-1 promotes inflammatory vascular repair of murine carotid aneurysms via a macrophage inflammatory protein-1α and macrophage inflammatory protein-2-dependent pathway. Circulation 124:2243–2252.
OpenUrl Abstract/FREE Full Text

[103] Hoh BL, et al.

[104] ↵
Ichiyama T, et al.
(2007) Cysteinyl leukotrienes enhance tumour necrosis factor-alpha-induced matrix metalloproteinase-9 in human monocytes/macrophages. Clin Exp Allergy 37:608–614.
OpenUrl CrossRef PubMed

[105] Ichiyama T, et al.

[106] ↵
Bhamidipati CM, et al.
(2012) Development of a novel murine model of aortic aneurysms using peri-adventitial elastase. Surgery 152:238–246.
OpenUrl PubMed

[107] Bhamidipati CM, et al.

[108] ↵
Parmentier CN, et al.
(2012) Human T(H)2 cells respond to cysteinyl leukotrienes through selective expression of cysteinyl leukotriene receptor 1. J Allergy Clin Immunol 129:1136–1142.
OpenUrl CrossRef PubMed

[109] Parmentier CN, et al.

[110] ↵
Tintinger GR,
Feldman C,
Theron AJ,
Anderson R
(2010) Montelukast: More than a cysteinyl leukotriene receptor antagonist? Sci World J 10:2403–2413.
OpenUrl

[111] Tintinger GR,

[112] Feldman C,

[113] Theron AJ,

[114] Anderson R

[115] ↵
Golledge J,
Norman PE,
Murphy MP,
Dalman RL
(2017) Challenges and opportunities in limiting abdominal aortic aneurysm growth. J Vasc Surg 65:225–233.
OpenUrl

[116] Golledge J,

[117] Norman PE,

[118] Murphy MP,

[119] Dalman RL

[120] ↵
Liu CL, et al.
(2016) Asthma associates with human abdominal aortic aneurysm and rupture. Arterioscler Thromb Vasc Biol 36:570–578.
OpenUrl Abstract/FREE Full Text

[121] Liu CL, et al.

[122] ↵
Liu CL, et al.
(2016) Allergic lung inflammation aggravates angiotensin II-induced abdominal aortic aneurysms in mice. Arterioscler Thromb Vasc Biol 36:69–77.
OpenUrl Abstract/FREE Full Text

[123] Liu CL, et al.

[124] ↵
Sun J, et al.
(2007) Mast cells modulate the pathogenesis of elastase-induced abdominal aortic aneurysms in mice. J Clin Invest 117:3359–3368.
OpenUrl CrossRef PubMed

[125] Sun J, et al.

[126] ↵
Wang J, et al.
(2014) IgE actions on CD4+ T cells, mast cells, and macrophages participate in the pathogenesis of experimental abdominal aortic aneurysms. EMBO Mol Med 6:952–969.
OpenUrl Abstract/FREE Full Text

[127] Wang J, et al.

[128] ↵
Ingelsson E,
Yin L,
Bäck M
(2012) Nationwide cohort study of the leukotriene receptor antagonist montelukast and incident or recurrent cardiovascular disease. J Allergy Clin Immunol 129:702–707.e2.
OpenUrl CrossRef PubMed

[129] Ingelsson E,

[130] Yin L,

[131] Bäck M

[132] ↵
Azuma J, et al.
(2011) Assessment of elastase-induced murine abdominal aortic aneurysms: Comparison of ultrasound imaging with in situ video microscopy. J Biomed Biotechnol 2011:252141.
OpenUrl PubMed

[133] Azuma J, et al.

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