Angiotensin II-induced Abdominal Aortic Aneurysm Research Articles

JMJD3 Influences Macrophage-Mediated Inflammation in Abdominal Aortic Aneurysms

Abdominal aortic aneurysms (AAAs) are characterized by inflammatory macrophage (Mφ) infiltration and pathologic vascular remodeling. The mechanisms regulating Mφ polarization during AAA development remain unknown. There is increasing evidence that epigenetic enzymes, specifically the histone demethylase JMJD3, direct Mφ polarization. The purpose of this study was to investigate whether JMJD3-mediated epigenetic modifications regulate Mφ inflammation and drive AAA formation. Single-cell RNA sequencing was conducted on human AAA and age-matched atherosclerotic control tissue samples. In addition, the angiotensin (Ang) II-induced AAA model was used to gain mechanistic insight. Briefly, after 4 weeks of high-fat diet, mice were infused with AngII or saline to induce AAAs. AAA maximum diameters were quantified and Mφs were sorted. Messenger RNA abundance of inflammatory cytokines and Jmjd3 were determined by quantitative polymerase chain reaction; levels of histone 3 lysine 27 trimethylation (H3K27me3) on gene promoters were determined by chromatin immunoprecipitation. Statistical significance was determined using Student t-test or analysis of variance. Single-cell RNA sequencing analysis of human AAAs and age-matched atherosclerotic controls demonstrated a significant upregulation of Jmjd3 and inflammatory cytokine expression in monocyte and Mφ subsets within AAA tissue. Congruently, AAA tissue- and bone marrow-derived Mφs from AngII-induced AAAs displayed marked upregulation of Jmjd3 and increased messenger RNA abundance of inflammatory genes (interleukins 1β, 12, and 23) during AAA development (P < .05). To determine the mechanistic impact of JMJD3 on Mφ polarization, histone methylation was evaluated on monocyte-macrophages and demonstrated decreased levels of the repressive histone methylation mark H3K27me3 on inflammatory gene promoters in AngII-induced AAAs compared with controls. In vitro inhibition of JMJD3 using short interfering RNA significantly reduced Mφ inflammatory cytokine expression (P < .05). These Results suggest an important role for JMJD3 in regulating macrophage-mediated inflammation and identify a potential target for the treatment of chronic inflammation in human AAAs.

The Role of a Selective P2Y6 Receptor Antagonist, MRS2578, on the Formation of Angiotensin II-Induced Abdominal Aortic Aneurysms.

Objective The P2Y6 receptor has been shown to be involved in many cardiovascular diseases, including hypertension and atherosclerosis. The study is aimed at exploring the role of the P2Y6 receptor in Ang II-induced abdominal aortic aneurysm (AAA) formation in apolipoprotein E-deficient (apoE−/−) mice by using its selective antagonist. Methods Male apoE−/− mice were fed with high-fat diet and infused with angiotensin (Ang) II (1000 ng/kg/min) for 4 weeks to induce AAA or saline as controls. Mice were divided into four groups: normal saline (NS, placebo control) group (n = 8), Ang II+vehicle (Ang II) group (n = 14), Ang II-low dose MRS2578 (Ang II+MRS-16 mg) group (n = 14), and Ang II-high dose MRS2578 (Ang II+MRS-32 mg) group (n = 14). Daily intraperitoneal injection with vehicle or MRS2578 was pretreated one week before Ang II infusion. On postoperative day 10, aorta imaging of each group was taken by ultrasonography. After 4 weeks of Ang II infusion, the excised aortas were processed for diameter measurement and quantification of aneurysm severity and tissue characteristics; the blood samples were collected for measurement of the lipid profile and levels of cytokines. Verhoeff's Van Gieson (EVG) staining and immunochemistry staining were performed to evaluate disruption of the extracellular matrix (ECM) and infiltration of macrophages. Expression and activity of matrix metalloproteinases (MMPs) was measured by gelatin zymography. Results Treatment with MRS2578 made no significant difference in AAA formation, and maximal aortic diameter yet caused higher AAA rupture-induced mortality from 7% (Ang II) to 21.4% (Ang II+MRS-16 mg) or 42.9% (Ang II+MRS-32 mg), respectively (p < 0.05). Consistently, the severity of aneurysm tended to be more deteriorated in MRS2578-treated groups, especially the high-dosage group. The ratios of type III and IV aneurysm were much higher in the MRS2578-coadministered groups (p < 0.05). Furthermore, histological analyses showed that administration of MRS2578 significantly increased infiltration of macrophages, expression of monocyte chemotactic protein 1 (MCP-1) and vascular cell adhesion molecule-1 (VCAM-1), and activities of MMP-2 and MMP-9 followed by aggravating degradation elastin in vivo (p < 0.05). However, the multiple effects of MRS2578 on the development of AAA are independent of changes in systolic blood pressure and lipid profiles. Conclusions The present study demonstrated that administration of MRS2578 exacerbated the progression and rupture of experimental AAA through promoting proinflammatory response and MMP expression and activity, which indicated a crucial role of the P2Y6 receptor in AAA development. Clinical Relevance. Purinergic P2Y receptors have attracted much attention since the P2Y12 receptor antagonist had been successfully applied in clinical practice. Elucidating the underlying mechanisms of AAA and exploring potential therapeutic strategies are essential to prevent its progression and reduce the mortality rate.

Meprin‐α (Mep1A) enhances TNF‐α secretion by mast cells and aggravates abdominal aortic aneurysms

Abdominal aorticaneurysm (AAA) rupture is mainly due to elastic lamina degradation. As a metalloendopeptidase, meprin-α (Mep1A) critically modulates the activity of proteins and inflammatory cytokines in various diseases. Here, we sought to investigate the functional role of Mep1A in AAA formation and rupture. AAA tissues were detected by using real-time PCR (RT-PCR), western blotting (WB), and immunohistochemistry. Further mechanistic studies used RT-PCR, WB, and enzyme-linked immunosorbent assays. Mep1A mediated AAA formation by regulating the mast cell (MC) secretion of TNF-α, which promoted matrix metalloproteinase (MMP) expression and apoptosis in smooth muscle cells (SMCs). Importantly, increased Mep1A expression was found in human AAA tissues and in angiotensin II-induced mouse AAA tissues. Mep1A deficiency reduced AAA formation and increased the survival rate of AAA mice. Pathological analysis showed that Mep1A deletion decreased elastic lamina degradation and SMC apoptosis in AAA tissues. Furthermore, Mep1A was expressed mainly in MCs, wherein it mediated TNF-α expression. Mep1A inhibitor actinonin significantly inhibited TNF-α secretion in MCs. TNF-α secreted by MCs enhanced MMP2 expression in SMCs and promoted SMC apoptosis. Taken together, these data suggest that Mep1A may be vital in AAA pathophysiology by regulating TNF-α production by MCs. Knocking out Mep1A significantly decreased AAA diameter and improved AAA stability in mice. Therefore, Mep1A is a potential new therapeutic target in the development of AAA.

AVE0991, a nonpeptide angiotensin-(1-7) mimic, inhibits angiotensin II-induced abdominal aortic aneurysm formation in apolipoprotein E knockout mice.

AVE0991, a nonpeptide angiotensin-(1-7) mimic, has similar protective effects for cardiovascular system to Ang-(1-7). In this article, we aimed to explore the effects of AVE0991 and Ang-(1-7) on abdominal aortic aneurysm (AAA) induced by Ang II in apolipoprotein E knockout mice. The mice AAA model was established by Ang II infusion, and then mice received different treatment with saline, Ang II (1.44mg/kg/day), different dose AVE0991 (0.58 or 1.16μmol/kg/day), or Ang-(1-7) (400ng/kg/min). The incidence of AAA was 76%, 48%, 28%, and 24% in the vehicle, the low-dose AVE0991, high-dose AVE0991, and the Ang-(1-7) group, respectively. In comparison with control group, AVE0991 and Ang-(1-7) treatment significantly increased smooth muscle cells and decreased macrophage accumulation, the expression levels of monocyte chemoattractant protein-1 (MCP-1) and tumor necrosis factor α (TNF-α), and the expression and activity of metalloproteinases 2 and 9 in mice AAA model or in human smooth muscle cells (hVSMCs). The therapeutic effects may be contributed to reduction of oxidative stress and downregulation of P38 and ERK1/2 signal pathways via Mas receptor activation, whereas the positive impacts were reversed by co-administration with the Mas antagonist A779 (400ng/kg/min) and AVE0991 in Ang II-infused mice or in hVSMCs. Therefore, AVE0991 and Ang-(1-7) might be novel and promising interventions in the prevention and treatment of AAA. KEY MESSAGES: • AVE0991 dose-dependently inhibited Ang II-induced AAA formation in Apoe-/- mice. • Ang-(1-7) played the same protective role as high-dose AVE0991. • Inhibition of Mas receptor with A779 could reverse the protective effect of AVE0991. • The therapeutic effects may be contributed to reduction of oxidative stress and downregulation of P38 and ERK1/2 signal pathways via Mas receptor activation.

A novel STAT3 inhibitor attenuates angiotensin II-induced abdominal aortic aneurysm progression in mice through modulating vascular inflammation and autophagy

Abdominal Aortic aneurysm (AAA) is associated with chronic inflammation, cells apoptosis, and impairment of autophagy. BP-1-102, a novel potent STAT3 inhibitor, has been recently reported to significantly block inflammation-related signaling pathways of JAK2/STAT3 and NF-κB, as well as regulate autophagy. However, its role in vascular inflammation and AAA progression remains to be elucidated. In the present study, the effect and potential mechanisms of BP-1-102 on angiotensin II (AngII) induced AAA in ApoE−/− mice were investigated. AAA was induced in ApoE−/− mice with infusion of AngII for 28 days. BP-1-102 was administrated orally to mice every other day. Mice were sacrificed on day 7, day 14, and day 28 to evaluate the treatment effects. BP-1-102 markedly decreased AAA incidence and aortic diameter, maintained elastin structure and volume, reduced the expression of pro-inflammatory cytokines and MMPs, and inhibited inflammatory cells infiltration. Moreover, BP-1-102 dramatically reduced the expression of JAK2, p-STAT3, p-NF-κB, and Bcl-xL but maintained the expression of LC3B and Beclin in AAA tissues. In vitro, vascular smooth muscle cells (VSMCs) were treated with AngII and/or BP-1-102 at indicated time and concentration. BP-1-102 inhibited AngII-induced JAK2/STAT3 and NF-κB signaling activation and maintained autophagy-related proteins expression in VSMCs. Taken together, our findings suggest that BP-1-102 inhibits vascular inflammation and AAA progression through decreasing JAK2/STAT3 and NF-κB activation and maintaining autophagy.

IKK Epsilon Deficiency Attenuates Angiotensin II-Induced Abdominal Aortic Aneurysm Formation in Mice by Inhibiting Inflammation, Oxidative Stress, and Apoptosis.

Abdominal aortic aneurysm (AAA) is a vascular disorder that is considered a chronic inflammatory disease. However, the precise molecular mechanisms involved in AAA have not been fully elucidated. Recently, significant progress has been made in understanding the function and mechanism of action of inhibitor of kappa B kinase epsilon (IKKε) in inflammatory and metabolic diseases. The angiotensin II- (Ang II-) induced or pharmacological inhibitors were established to test the effects of IKKε on AAA in vivo. After mice were continuously stimulated with Ang II for 28 days, morphologically, we found that knockout of IKKε reduced AAA formation and drastically reduced maximal diameter and severity. We also observed a decrease in elastin degradation and medial destruction, which were independent of systolic blood pressure or plasma cholesterol concentrations. Western blot analyses and immunohistochemical staining were carried out to measure IKKε expression in AAA tissues and cell lines. AAA phenotype of mice was measured by ultrasound and biochemical indexes. In zymography, immunohistology staining, immunofluorescence staining, and reactive oxygen species (ROS) analysis, TUNEL assay was used to examine the effects of IKKε on AAA progression in AAA mice. IKKε deficiency significantly inhibited inflammatory macrophage infiltration, matrix metalloproteinase (MMP) activity, ROS production, and vascular smooth muscle cell (VSMC) apoptosis. We used primary mouse aortic VSMC isolated from apolipoprotein E (Apoe) −/− and Apoe−/−IKKε−/− mice. Mechanistically, IKKε deficiency blunted the activation of the ERK1/2 pathway. The IKKε inhibitor, amlexanox, has the same impact in AAA. Our results demonstrate a critical role of IKKε in AAA formation induced by Ang II in Apoe−/− mice. Targeting IKKε may constitute a novel therapeutic strategy to prevent AAA progression.

Puerarin inhibits angiotensin II-induced abdominal aortic aneurysm formation by promoting proliferation of vascular smooth muscle cells via NF-kB pathway.

Puerarin inhibits angiotensin II-induced abdominal aortic aneurysm formation by promoting proliferation of vascular smooth muscle cells via NF-kB pathway.

Metformin Does Not Attenuate Angiotensin II-Induced Abdominal Aortic Aneurysms in Low-Density Lipoprotein Receptor-Deficient Mice

Despite significant efforts to identify medical therapy for aneurysm growth, no effective substance has been approved for treating patients. Recent retrospective Veterans Affairs database studies have shown decreased abdominal aortic aneurysm (AAA) formation and growth in diabetic patients who are treated with metformin. In addition, there is some preclinical evidence showing that hyperglycemia and metformin decrease elastase-induced AAA formation in mice. In this study, we evaluated the effects of metformin on angiotensin II-induced AAA formation in mice.

Depletion of CD11c+ dendritic cells in apolipoprotein E-deficient mice limits angiotensin II-induced abdominal aortic aneurysm formation and growth.

The role of chronic inflammation in abdominal aortic aneurysm (AAA) is controversial. CD11c+ antigen-presenting cells (APCs) (dendritic cells (DCs)) have been reported in human AAA samples but their role is unclear. The effect of conditional depletion of CD11c+ cells on experimental AAA was investigated in the angiotensin II (AngII)-infused apolipoprotein E-deficient (ApoE-/-) mouse model. CD11c-diphtheria toxin (DT or D.tox) receptor (DTR), ovalbumin (OVA) fragment aa 140-386, and enhanced green fluorescent protein (eGFP)-ApoE-/- (CD11c.DOG.ApoE-/-) mice were generated and CD11c+ cell depletion achieved with D.tox injections (8 ng/g body weight, i.p., every-other-day). AAA formation and growth were assessed by measurement of supra-renal aortic (SRA) diameter in vivo by serial ultrasound and by morphometry assessment of harvested aortas at the end of the study. Depletion of CD11c+ cells by administration of D.tox on alternative days was shown to reduce the maximum diameter of AAAs induced by 28 days AngII infusion compared with controls (D.tox, 1.58 ± 0.03 mm vs Vehicle control, 1.81 ± 0.06 mm, P<0.001). CD11c+ depletion commencing after AAA establishment by 14 days of AngII infusion, was also shown to lead to smaller AAAs than controls after a further 14 days (D.tox, 1.54 ± 0.04 mm vs Vehicle control, 1.80 ± 0.03 mm, P<0.001). Flow cytometry revealed significantly lower numbers of circulating CD44hi CD62Llo effector CD4 T cells, CD44hi CD62Llo effector CD8 T cells and B220+ B cells in CD11c+ cell-depleted mice versus controls. CD11c+ depletion attenuated SRA matrix degradation indicated by decreased neutrophil elastase activity (P=0.014), lower elastin degradation score (P=0.012) and higher collagen content (P=0.002). CD11c+ cell-depletion inhibited experimental AAA development and growth associated with down-regulation of circulating effector T cells and attenuated matrix degradation. The findings suggest involvement of autoreactive immune cells in AAA pathogenesis.

1436Overexpression of Cytotoxic T-Lymphocyte Associated Antigen-4 suppresses aortic immunoinflammatory responses and prevents angiotensin II-induced abdominal aortic aneurysm formation in mice

Abstract Aims Vascular inflammation via T-cell-mediated immune responses has been shown to be critically involved in the pathogenesis of abdominal aortic aneurysm (AAA). T-cell coinhibitory molecule cytotoxic T-lymphocyte–associated antigen-4 (CTLA-4) is known to act as a potent negative regulator of immune responses. However, the role of this molecule in the development of AAA remains completely unknown. In the present study, we determined the effects of CTLA-4 overexpression on experimental AAA. Methods and results We continuously infused 12-week-old CTLA-4 transgenic (CTLA-4-Tg)/apolipoprotein E–deficient (Apoe−/−) mice (n=35) or control Apoe−/− mice (n=40) fed a high-cholesterol diet with angiotensin II by implanting osmotic mini-pumps and evaluated the development of AAA. Ninety percent of angiotensin II-infused mice developed AAA, with 50% mortality because of aneurysm rupture. Overexpression of CTLA-4 significantly reduced the incidence (66%), mortality (26%), and diameter (18%) of AAA (incidence: P=0.0104; mortality: P=0.031; diameter: P=0.011). These protective effects were associated with a decreased number of effector CD4+ T cells and the downregulated expression of costimulatory molecules CD80 and CD86, ligands for CTLA-4, on CD11c+ dendritic cells in lymphoid tissues. In addition, by performing in situ zymography of the abdominal aortic aneurysm lesions, we observed a trend toward a decrease in MMP activity in the aneurysmal lesion following overexpression of CTLA-4. Finally, CTLA-4-Tg/Apoe−/− mice had reduced macrophage and CD4+ T cell accumulation and MMP activity in the aneurysmal lesion, leading to attenuated aortic inflammation, preserved vessel integrity, and decreased susceptibility to AAA and aortic rupture. Conclusion Our findings suggest that CTLA-4 protects against AAA by suppressing immunoinflammatory responses and could be an attractive therapeutic target for AAA.

CTLA-4 Protects against Angiotensin II-Induced Abdominal Aortic Aneurysm Formation in Mice

Vascular inflammation via T-cell-mediated immune responses has been shown to be critically involved in the pathogenesis of abdominal aortic aneurysm (AAA). T-cell coinhibitory molecule cytotoxic T-lymphocyte–associated antigen-4 (CTLA-4) is known to act as a potent negative regulator of immune responses. However, the role of this molecule in the development of AAA remains completely unknown. We determined the effects of CTLA-4 overexpression on experimental AAA. We continuously infused CTLA-4 transgenic (CTLA-4-Tg)/apolipoprotein E–deficient (Apoe−/−) mice or control Apoe−/− mice fed a high-cholesterol diet with angiotensin II by implanting osmotic mini-pumps and evaluated the development of AAA. Ninety percent of angiotensin II-infused mice developed AAA, with 50% mortality because of aneurysm rupture. Overexpression of CTLA-4 significantly reduced the incidence (66%), mortality (26%), and diameter of AAA. These protective effects were associated with a decreased number of effector CD4+ T cells and the downregulated expression of costimulatory molecules CD80 and CD86, ligands for CTLA-4, on CD11c+ dendritic cells in lymphoid tissues. CTLA-4-Tg/Apoe−/− mice had reduced accumulation of macrophages and CD4+ T cells, leading to attenuated aortic inflammation, preserved vessel integrity, and decreased susceptibility to AAA and aortic rupture. Our findings suggest T-cell coinhibitory molecule CTLA-4 as a novel therapeutic target for AAA.

ASB17061, a novel chymase inhibitor, prevented the development of angiotensin II-induced abdominal aortic aneurysm in apolipoprotein E-deficient mice

Our aim was to examine the effects of ASB17061, an orally active novel chymase inhibitor, on angiotensin II–induced abdominal aortic aneurysm (AAA) in apolipoprotein E–deficient mice. Oral administration of ASB17061 (10 mg/kg) significantly suppressed angiotensin II–induced AAA formation in these mice. The pro-matrix metalloproteinase-9 (pro-MMP-9) level in AAA lesions was significantly suppressed by ASB17061 treatment, indicating that ASB17061 inhibited the accumulation of pro-MMP-9–producing cells in AAA lesions. Mouse mast cell protease 4 (mMCP-4, human chymase ortholog) was injected into BALB/c mice intraperitoneally to examine the ability of mMCP-4 to induce the accumulation of pro-MMP-9–producing cells. An intraperitoneal injection of mMCP-4 induced the accumulation of pro-MMP-9–producing cells including CD11b + Gr-1 + cells. Taken together, these data indicate that ASB17061 is a promising novel oral therapeutic agent for human AAA.

Smooth muscle-specific Gsα deletion exaggerates angiotensin II-induced abdominal aortic aneurysm formation in mice in vivo

ObjectiveAbdominal aortic aneurysm (AAA) is a life-threatening vascular disease without an effective pharmaceutical treatment. Genetic studies have proved the involvement of smooth muscle phenotype switch in the development of AAA. The alpha subunit of the heterotrimeric G stimulatory protein (Gsα) mediates receptor-stimulated production of cyclic adenosine monophosphate (cAMP). However, the role of smooth muscle Gsα in AAA formation remains unknown. Approach and resultsIn this study, mice with knockout of smooth muscle-specific Gsα (GsαSMKO) were generated by cross-breeding Gsαflox/flox mice with SM22-CreERT2 transgenic mice, induced in adult mice by tamoxifen treatment. Gsα deficiency induced a smooth muscle phenotype switch from a contractile to a synthetic state. Mechanically, Gsα deletion reduced cAMP level and increased the level of human antigen R (HuR), which binds with the adenylate uridylate–rich elements of the 3′ untranslated region of Krüppel-like factor 4 (KLF4) mRNA, thereby increasing the stability of KLF4. Moreover, genetic knockdown of HuR or KLF4 rescued the phenotype switch in Gsα-deficient smooth muscle cells. Furthermore, with acute infusion of angiotensin II, the incidence of AAA was markedly higher in ApoE−/−/GsαSMKO than ApoE−/−/Gsαflox/flox mice and induced increased elastic lamina degradation and aortic expansion. Finally, the levels of Gsα and SM α-actin were significantly lower while those of HuR and KLF4 were higher in human AAA samples than adjacent nonaneurysmal aortic sections. ConclusionsGsα may play a protective role in AAA formation by regulating the smooth muscle phenotype switch and could be a potential therapeutic target for AAA disease.

Smooth muscle-specific LKB1 deletion exaggerates angiotensin II-induced abdominal aortic aneurysm in mice

Abdominal aortic aneurysm (AAA) is a life-threatening vascular disease without an effective pharmaceutical treatment. Liver kinase B1 (LKB1), a tumor suppressor, is a central regulator of cell polarity and energy homeostasis. However, the role of LKB1 in the development of AAA has not been explored. In this study, mice with knockout of smooth muscle-specific LKB1 (LKB1SMKO) were generated by cross-breeding LKB1flox/flox mice with SM22-CreERT2 transgenic mice and induced in adult mice by tamoxifen treatment. LKB1 deficiency increased the expression of matrix metalloproteinase 2 (MMP-2), which was inhibited by LKB1 overexpression. Mechanistically, LKB1 could bind to the MMP-2 transcription factor, specificity protein 1 (Sp1), thereby reducing the binding of Sp1 to the MMP-2 promoter to inhibit MMP-2 expression. LKB1 expression was significantly reduced in abdominal aortas of the mouse AAA model. Moreover, smooth muscle-specific LKB1 deletion exaggerated angiotensin II-induced AAA formation accompanied by increased AAA incidence and aortic expansion. Finally, LKB1 level was significantly lower and MMP-2 level higher in human AAA samples than adjacent nonaneurysmal aortic sections. Thus, these results suggest that LKB1 may play a protective role in AAA formation by inhibiting MMP-2 expression and could be a potential therapeutic target for AAA disease.

Chemokine (C-X-C motif) receptor 2 blockade by SB265610 inhibited angiotensin II-induced abdominal aortic aneurysm in Apo E-/- mice.

Inflammation plays a critical role in the development of abdominal aortic aneurysm (AAA). Chemokine receptor CXCR2 mediates inflammatory cell chemotaxis in several diseases. However, the role of CXCR2 in AAA and the underlying mechanisms remain unknown. In this study, we found that the CXCR2 expressions in AAA tissues from human and angiotensin II (Ang II)-infused apolipoprotein E knockout (Apo E-/-) mice were significantly increased. The pharmacological inhibition of CXCR2 (SB265610) markedly reduced Ang II-induced AAA formation. Furthermore, SB265610 treatment significantly reduced collagen deposition, elastin degradation, the metal matrix metalloprotease expression and accumulation of macrophage cells. In conclusion, these results showed CXCR2 plays a pathogenic role in AAA formation. Inhibition of CXCR2 pathway may represent a novel therapeutic approach to treat AAA.

Invited commentary

Abdominal aortic aneurysm (AAA) accounts for >20 million deaths worldwide.1Golledge J. Norman P.E. Murphy M.P. Dalman R.L. Challenges and opportunities in limiting abdominal aortic aneurysm growth.J Vasc Surg. 2017; 65: 225-233Abstract Full Text Full Text PDF PubMed Scopus (87) Google Scholar Extrapolating from the National Inpatient Sample data set capturing 20% of inpatients in the United States, approximately 500,000 operations for AAA were performed from 2000 to 2010.2Dua A. Ali F. Traudt E. Desai S.S. Utilization of the National Inpatient Sample for abdominal aortic aneurysm research.Surgery. 2017; 162: 699-706Abstract Full Text Full Text PDF PubMed Scopus (7) Google Scholar The number of aneurysms fixed by endovascular aneurysm repair increased from 5% to approximately 75% during that period, with concomitant improvements in mortality and morbidity within 2 to 3 years of surgery.2Dua A. Ali F. Traudt E. Desai S.S. Utilization of the National Inpatient Sample for abdominal aortic aneurysm research.Surgery. 2017; 162: 699-706Abstract Full Text Full Text PDF PubMed Scopus (7) Google Scholar, 3Weinkauf C. George E. Zhou W. Open versus endovascular aneurysm repair trial review.Surgery. 2017; 162: 974-978Abstract Full Text Full Text PDF PubMed Scopus (13) Google Scholar Similar to the advancements offered by endovascular aneurysm repair, medical treatments that could reduce the growth rate of AAA even modestly would save lives and radically alter clinical practice. Perhaps research in this area truly represents an opportunity to “work ourselves out of a job” toward the benefit of patients' well-being. Thus, we continue to strive for a medical treatment that reduces AAA growth rate in the face of disappointing results associated with promising agents like doxycycline.4Meijer C. Stijnen T. Wasser M.M. Hamming J.F. van Bockel J.H. Lindeman J.H. Pharmaceutical Aneurysm Stabilisation Trial Study GroupDoxycycline for stabilization of abdominal aortic aneurysms: a randomized trial.Ann Intern Med. 2013; 159: 815-823Crossref PubMed Scopus (146) Google Scholar The report by Tsai et al evaluates benefits of fucoidan, an extract from brown seaweed, in reducing experimentally induced AAA in mice. The authors report a premise to study fucoidan in cardiovascular disease because of its anti-inflammatory, anticoagulant, and antihypertensive effects. The investigators demonstrate that in a murine model of AAA induced by infusing angiotensin II through a subcutaneous pump, aortic diameter was reduced by intraperitoneal administration of fucoidan. Treatment also mitigated degradation of aortic elastin, diminished inflammatory cell recruitment, and reduced the activities of matrix metalloproteinases (MMPs) thought to degrade extracellular matrix. In human umbilical vein endothelial cells, fucoidan also reduced MMP activity as well as reactive oxygen species expression. The authors conclude that whereas more research needs to be done, fucoidan may be a promising supplement for patients with small aneurysms. There are a few questions that emerge from the report that are worth investigating. It is not clear from the study what role inflammatory cells play in the protective process. Does the fucoidan limit elastin degradation because of a direct effect on elastin or because of an effect on inflammatory cells? Is it relevant to evaluate MMP activity and reactive oxygen species in human umbilical vein endothelial cells when the model is a murine model of aortic disease? Do angiotensin II infusion models of AAA adequately reflect the human condition that typically takes years to develop and is multifactorial? Finally, how would fucoidan be given to a patient? Could it be an oral supplement, or would it need to be administered parenterally, and if so, how often? The authors have alluded to these limitations and have committed to pursuing some of the answers in future studies. While research into aneurysm growth retardants continues, we can only offer surveillance until the aortic diameter thresholds warrant repair. The opinions or views expressed in this commentary are those of the authors and do not necessarily reflect the opinions or recommendations of the Journal of Vascular Surgery or the Society for Vascular Surgery. Fucoidan attenuates angiotensin II-induced abdominal aortic aneurysms through the inhibition of c-Jun N-terminal kinase and nuclear factor κB activationJournal of Vascular SurgeryVol. 68Issue 6PreviewRupture of abdominal aortic aneurysm (AAA) is one of the leading causes of sudden death among the elderly. Most incidental AAAs are below the threshold for intervention at the time of detection; however, there is no evidence that commonly used cardiovascular drugs have clinical beneficial effects on AAA progression. Therefore, in addition to current cardiovascular risk-reducing treatments, an adjunctive medical therapy targeting the regulation of extracellular matrix metabolism is still required in the clinical setting. Full-Text PDF Open Archive

Von Willebrand factor deficiency does not influence angiotensin II-induced abdominal aortic aneurysm formation in mice

Abdominal aortic aneurysm (AAA) refers to a localized dilation of the abdominal aorta that exceeds the normal diameter by 50%. AAA pathophysiology is characterized by progressive inflammation, vessel wall destabilization and thrombus formation. Our aim was to investigate the potential involvement of von Willebrand factor (VWF), a thrombo-inflammatory plasma protein, in AAA pathophysiology using a dissection-based and angiotensin II infusion-induced AAA mouse model. AAA formation was induced in both wild-type and VWF-deficient mice by subcutaneous implantation of an osmotic pump, continuously releasing 1000 ng/kg/min angiotensin II. Survival was monitored, but no significant difference was observed between both groups. After 28 days, the suprarenal aortic segment of the surviving mice was harvested. Both AAA incidence and severity were similar in wild-type and VWF-deficient mice, indicating that AAA formation was not significantly influenced by the absence of VWF. Although VWF plasma levels increased after the infusion period, these increases were not correlated with AAA progression. Also detailed histological analyses of important AAA hallmarks, including elastic degradation, intramural thrombus formation and leukocyte infiltration, did not reveal differences between both groups. These data suggest that, at least in the angiotensin II infusion-induced AAA mouse model, the role of VWF in AAA pathophysiology is limited.

Invited commentary

Invited commentary

Abstract 108: Lipopolysaccharide Fails to Augment Development of Angiotensin II-induced Abdominal Aortic Aneurysms in Mice

Background and objective: Our previous study demonstrated that deficiency of toll-like receptor 4 (TLR4) reduced angiotensin II (AngII)-induced abdominal aortic aneurysms (AAAs) in hypercholesterolemic mice. Lipopolysaccharide (LPS) is a well-known agonist of TLR4. Interaction of LPS and TLR4 promotes inflammation and augments hypercholesterolemia-induced atherosclerosis. The purpose of this study was to determine whether LPS augments AngII-induced AAAs. Methods and Results: Low-density lipoprotein (LDL) receptor -/- mice fed a Western diet develop hypercholesterolemia and have augmentation of AngII-induced AAAs. We found that LDL receptor -/- mice fed Western diet had increased LPS concentrations, as quantified by a Limulus Amebocyte lysate chromogenic endotoxin quantitation kit, compared to the same mice prior to Western diet feeding. To determine whether LPS plays a role on AngII-induced AAAs, 4 groups of male C57BL/6J mice, 10-week-old, were infused subcutaneously with: (1) Vehicle (N=5), (2) LPS (250 μ g/kg/day; N=10), (3) AngII (1,000 ng/kg/min; N=10), or (4) both AngII and LPS (N=10) through Alzet mini osmotic pumps for 28 days. Abdominal aortic expansion was monitored serially at 2 and 4 weeks of infusion using high frequency ultrasonography (Vevo 3100 system; FUJIFILM). Continuous luminal expansion was detected in both AngII-infused mice and mice co-infused with both AngII and LPS. These results were confirmed by ex vivo measurements of maximal outer diameters of suprarenal aortas after termination showing AngII infusion led to significant increase of abdominal aortic dilation, compared to vehicle or LPS infused mice. However, co-infusion of LPS with AngII did not augment AngII-induced AAAs. Conclusion: LPS has no effects on AngII-induced AAAs in normolipidemic mice.

Abstract 057: Adenosine Kinase Epigenetically Regulates Abdominal Aortic Aneurysm Formation

Objectives: Abdominal aortic aneurysm (AAA) is a major cause of morbidity and mortality worldwide; however, the molecular mechanisms involved in AAA formation are not well understood. The nucleoside adenosine plays important roles in modulating vascular homeostasis. In this study, we sought to determine whether adenosine kinase (ADK), the adenosine-metabolizing enzyme, modulates AAA formation via control of intracellular adenosine level and investigate the involvement of ADK-mediated epigenetic mechanism in this aortic disease. Methods and results: ADK expression and activity were increased in murine AAA models, including calcium chloride-stimulated AAA and angiotensin II-induced AAA. Using a loss-of-function genetic mouse model, we demonstrated that genetic ADK knockout mice led to increased Intracellular adenosine level in macrophages and vascular cells and developed significantly smaller aortic expansion when subjected to AAA inductions. Notably, knockout of ADK alleviated arterial inflammation and diminished infiltration of macrophages, as well as suppressed arterial extracellular matrix degradation, which was associated with down-regulation of CXCL12, MMP2/9 and adhesion molecule expression. Mechanistically, elevation of intracellular adenosine by genetic inactivation of ADK or exogenous adenosine reduces activation of the transmethylation pathway via inactivation of SAH hydrolase (SAHH) and histone H3K4 methyltransferase (HMT), thus down-regulating expression and signaling of mitogen-activated protein kinases in activated macrophages and vascular cells with pro-inflammatory stimuli. Blocking of the H3K4 transmethylation pathway by knockdown of WDR5, a core subunit of HMT complex, abrogated the beneficial effects of ADK inactivation. Conclusions: Our findings reveal a previously unrecognized role of ADK mediated epigenetic pathways in the pathogenesis of AAA and provides a therapeutic target for the prevention of AAA.