Cyclooxygenase-2 inhibition attenuates abdominal aortic aneurysm progression in hyperlipidemic mice

Endovascular Aneurysm Repair Versus Open Surgical Repair in Treating Abdominal Aortic Aneurysm

Abdominal aortic aneurysm (AAA) denotes an abdominal aorta dilation exceeding 3 cm, typically asymptomatic until rupture, posing severe consequences, including fatality. Therefore, continual screening is imperative, and surgical intervention is recommended upon reaching a diameter of 5.5 cm to prevent rupture. The primary surgical approaches are open surgical repair or open repair (OR) and endovascular aneurysm repair (EVAR). This review juxtaposes EVAR's short- and long-term effectiveness, safety, and perioperative complications in AAA patients versus OR, elucidating clinical benefits and avenues for further research. Following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines, an extensive literature review was conducted using the PubMed and Clinicaltrials.gov databases. The review specifically focused on clinical studies directly comparing EVAR versus OR. The comprehensive literature review revealed that EVAR confers a survival advantage for up to four years post-procedure. However, the benefit shifts to OR after four to eight years due to aneurysm-related complications, such as ruptures, underscoring the necessity of lifelong post-EVAR monitoring. Following EVAR, AAA patients necessitate significantly more frequent secondary interventions due to graft-related issues, including endoleaks, thereby escalating long-term complexity and care costs. Conversely, following OR, a notably higher proportion of patients require mechanical ventilation and blood transfusions and experience prolonged intensive-care and mid-care unit stays, consequently extending hospitalization. After EVAR, patients recover substantially faster, returning to normal activities sooner. Nonetheless, the long-term quality of life between the two procedures becomes comparable. While EVAR presents itself as a less invasive alternative to OR, especially for high surgical risk patients, the imperative of long-term surveillance and the risk of secondary interventions pose significant challenges. Advancements in EVAR technology and technique are broadening its utility. Yet, continual research is crucial to optimize patient selection, improve long-term outcomes, and ensure that EVAR's benefits outweigh the risks. Therefore, choosing EVAR over OR in treating AAA patients must factor in a patient's overall health, anatomical considerations, and the probability of long-term success.

Pharmaceutical Modulation of Intracranial Aneurysm Development and Rupture

Management of intracranial aneurysms (IAs) is determined by patient age, risk of rupture, and comorbid conditions. While endovascular and microsurgical interventions offer solutions to mitigate the risk of rupture, pharmacological management strategies may complement these approaches or serve as alternatives in appropriate cases. The pathophysiology of IAs allows for the targeting of inflammation to prevent the development and rupture of IAs. The aim of this review is to provide an updated summary of different pharmaceutical management strategies for IAs. Acetylsalicylic acid and renin-angiotensin-aldosterone system (RAAS) inhibitor antihypertensives have some evidence supporting their protective effect. Studies of selective cyclooxygenase-2 (COX-2) inhibitors, statins, ADP inhibitors, and other metabolism-affecting drugs have demonstrated inconclusive findings regarding their association with aneurysm growth or rupture. In this manuscript, we highlight the evidence supporting each drug's effectiveness.

A highly selective mPGES-1 inhibitor to block abdominal aortic aneurysm progression in the angiotensin mouse model

Abdominal aortic aneurysm (AAA) is a deadly, permanent ballooning of the aortic artery. Pharmacological and genetic studies have pointed to multiple proteins, including microsomal prostaglandin E2 synthase-1 (mPGES-1), as potentially promising targets. However, it remains unknown whether administration of an mPGES-1 inhibitor can effectively attenuate AAA progression in animal models. There are still no FDA-approved pharmacological treatments for AAA. Current research stresses the importance of both anti-inflammatory drug targets and rigor of translatability. Notably, mPGES-1 is an inducible enzyme responsible for overproduction of prostaglandin E2 (PGE2)-a well-known principal pro-inflammatory prostanoid. Here we demonstrate for the first time that a highly selective mPGES-1 inhibitor (UK4b) can completely block further growth of AAA in the ApoE-/- angiotensin (Ang)II mouse model. Our findings show promise for the use of a mPGES-1 inhibitor like UK4b as interventional treatment of AAA and its potential translation into the clinical setting.

A novel animal model of abdominal aortic aneurysm by mechanical injury

The present study established a novel and reproducible animal model to study abdominal aortic aneurysms. In total, 22 adult Lewis rats underwent a procedure to produce mechanical injuries at the infrarenal aorta which was opened temporarily. The aortas were injured 6 times and repaired. Those rats were divided into 2 groups and the aortic aneurysm tissue was harvested after 42 (6-week group) or 63 (9-week group) days and evaluated for the progression of aortic aneurysms. In the 6-week group, changes in the aneurysm were observed in 6/10 (60%) rats and the mean maximum diameter of the aorta demonstrated a 119% increase in size from the baseline measurement. In the 9-week group, changes in the aneurysm were observed in 8/11 (88%) rats and the mean maximum diameter of aorta demonstrated a 133% increase in size. Additional findings from the aortic aneurysm tissue were found microscopically, including the destruction of the tunica media and the elastic fiber. The present study demonstrated that this novel animal model for the development of abdominal aortic aneurysms (AAAs) produced by mechanical injury may have high reproducibility and similar gross and microscopic morphology to humans. This model could be helpful to investigate the treatment of AAAs.

Effect of Hydralazine on Angiotensin II-Induced Abdominal Aortic Aneurysm in Apolipoprotein E-Deficient Mice

The rupture of an abdominal aortic aneurysm (AAA) causes about 200,000 deaths worldwide each year. However, there are currently no effective drug therapies to prevent AAA formation or, when present, to decrease progression and rupture, highlighting an urgent need for more research in this field. Increased vascular inflammation and enhanced apoptosis of vascular smooth muscle cells (VSMCs) are implicated in AAA formation. Here, we investigated whether hydralazine, which has anti-inflammatory and anti-apoptotic properties, inhibited AAA formation and pathological hallmarks. In cultured VSMCs, hydralazine (100 μM) inhibited the increase in inflammatory gene expression and apoptosis induced by acrolein and hydrogen peroxide, two oxidants that may play a role in AAA pathogenesis. The anti-apoptotic effect of hydralazine was associated with a decrease in caspase 8 gene expression. In a mouse model of AAA induced by subcutaneous angiotensin II infusion (1 µg/kg body weight/min) for 28 days in apolipoprotein E-deficient mice, hydralazine treatment (24 mg/kg/day) significantly decreased AAA incidence from 80% to 20% and suprarenal aortic diameter by 32% from 2.26 mm to 1.53 mm. Hydralazine treatment also significantly increased the survival rate from 60% to 100%. In conclusion, hydralazine inhibited AAA formation and rupture in a mouse model, which was associated with its anti-inflammatory and anti-apoptotic properties.

Development of pharmacotherapies for abdominal aortic aneurysms

The cardiovascular field is still searching for a treatment for abdominal aortic aneurysms (AAA). This inflammatory disease often goes undiagnosed until a late stage and associated rupture has a high mortality rate. No pharmacological treatment options are available. Three hallmark factors of AAA pathology include inflammation, extracellular matrix remodeling, and vascular smooth muscle dysfunction. Here we discuss drugs for AAA treatment that have been studied in clinical trials by examining the drug targets and data present for each drug's ability to regulate the aforementioned three hallmark pathways in AAA progression. Historically, drugs that were examined in interventional clinical trials for treatment of AAA were repurposed therapeutics. Novel treatments (biologics, small-molecule compounds etc.) have not been able to reach the clinic, stalling out in pre-clinical studies. Here we discuss the backgrounds of previous investigational drugs in hopes of better informing future development of potential therapeutics. Overall, the highlighted themes discussed here stress the importance of both centralized anti-inflammatory drug targets and rigor of translatability. Exceedingly few murine studies have examined an intervention-based drug treatment in halting further growth of an established AAA despite interventional treatment being the therapeutic approach taken to treat AAA in a clinical setting. Additionally, data suggest that a potentially successful drug target may be a central inflammatory biomarker. Specifically, one that can effectively modulate all three hallmark factors of AAA formation, not just inflammation. It is suggested that inhibiting PGE2 formation with an mPGES-1 inhibitor is a leading drug target for AAA treatment to this end.

Acetylsalicylic Acid Is Associated With a Lower Prevalence of Ascending Aortic Aneurysm and a Decreased Aortic Expression of Cyclooxygenase 2

Background Acetylsalicylic acid (ASA) therapy has been associated with a reduced prevalence and growth rate of abdominal as well as intracranial aneurysms, but the relationship between ASA and ascending aortic aneurysm formation remains largely unknown. The aim of the present study was to investigate whether ASA therapy is associated with a lower prevalence of ascending aortic aneurysm in a surgical cohort. Methods and Results One thousand seven hundred patients undergoing open-heart surgery for ascending aortic aneurysm and/or aortic valve disease were studied in this retrospective cross-sectional study. Aortic dilatation was defined as an aortic root or ascending aortic diameter ≥45 mm. Medications were self-reported by the patients in a systematic questionnaire. Cyclooxygenase gene expression was measured in the intima-media portion of the ascending aorta (n=117). In a multivariable analysis, ASA was associated with a reduced prevalence of ascending aortic aneurysm (relative risk, 0.68 [95% CI, 0.48-0.95], P=0.026) in patients with tricuspid aortic valves, but not in patients with bicuspid aortic valves (relative risk, 0.93 [95% CI, 0.64-1.34], P=0.687). Intima-media cyclooxygenase expression was positively correlated with ascending aortic dimensions (P<0.001 for cyclooxygenase-1 and P=0.05 for cyclooxygenase-2). In dilated, but not nondilated tricuspid aortic valve aortic specimens, ASA was associated with significantly lower cyclooxygenase-2 levels (P=0.034). Conclusions Our findings are consistent with the hypothesis that ASA treatment may attenuate ascending aortic aneurysmal growth, possibly via cyclooxygenase-2 inhibition in the ascending aortic wall and subsequent anti-inflammatory actions.

Role of prostaglandin D2 receptors in the pathogenesis of abdominal aortic aneurysm formation

Prostaglandin D2 (PGD2) released from immune cells or other cell types activates its receptors, D prostanoid receptor (DP)1 and 2 (DP1 and DP2), to promote inflammatory responses in allergic and lung diseases. Prostaglandin-mediated inflammation may also contribute to vascular diseases such as abdominal aortic aneurysm (AAA). However, the role of DP receptors in the pathogenesis of AAA has not been systematically investigated. In the present study, DP1-deficient mice and pharmacological inhibitors of either DP1 or DP2 were tested in two distinct mouse models of AAA formation: angiotensin II (AngII) infusion and calcium chloride (CaCl2) application. DP1-deficient mice [both heterozygous (DP1+/-) and homozygous (DP1-/-)] were protected against CaCl2-induced AAA formation, in conjunction with decreased matrix metallopeptidase (MMP) activity and adventitial inflammatory cell infiltration. In the AngII infusion model, DP1+/- mice, but not DP1-/- mice, exhibited reduced AAA formation. Interestingly, compensatory up-regulation of the DP2 receptor was detected in DP1-/- mice in response to AngII infusion, suggesting a potential role for DP2 receptors in AAA. Treatment with selective antagonists of DP1 (laropiprant) or DP2 (fevipiprant) protected against AAA formation, in conjunction with reduced elastin degradation and aortic inflammatory responses. In conclusion, PGD2 signaling contributes to AAA formation in mice, suggesting that antagonists of DP receptors, which have been extensively tested in allergic and lung diseases, may be promising candidates to ameliorate AAA.

hsa-miR-15b-5p regulates the proliferation and apoptosis of human vascular smooth muscle cells by targeting the ACSS2/PTGS2 axis

A previous bioinformatic analysis from our group predicted that the interaction of microRNA (miRNA/miR)-15b with the acyl-CoA synthetase short chain family member 2 (ACSS2) gene was important for the development of abdominal aortic aneurysm (AAA). Apoptosis of aortic vascular smooth muscle cells (VSMCs) is a pathological feature of AAA. The present study aimed to explain the roles of miR-15b/ACSS2 in AAA by exploring their effects on the proliferation and apoptosis of aortic VSMCs. Human aortic VSMCs (T/G HA-VSMC cell line) were divided into six groups and were transfected with miR-15b-5p mimics, mimic negative control (NC), miR-15b-5p inhibitors, inhibitor NC, miR-15b-5p mimics+pcDNA3.1 and miR-15b-5p mimics+ACSS2-overexpessing vector. CCK-8 assay was used to determine cell proliferation. Annexin V-FITC/PI staining and flow cytometry assays were used to measure cell apoptosis. Dual-luciferase reporter assays were used to confirm the targeted relationship between miR-15b-5p and ACSS2. Reverse transcription-quantitative PCR and/or western blotting were used to examine the expression levels of miR-15b-5p, ACSS2 and prostaglandin-endoperoxide synthase 2 (PTGS2). Following transfection of T/G HA-VSMCs with mimics and inhibitors to respectively upregulate and downregulate miR-15b-5p, the results demonstrated that overexpression of miR-15b-5p inhibited cell proliferation and promoted cell apoptosis; silencing of miR-15b-5p obtained the opposite results. ACSS2 may be a direct target of miR-15b-5p, since the luciferase activity of a ACSS2 wild-type vector, but not that of a ACSS2 mutant reporter, was significantly inhibited by miR-15b-5p mimics compared with controls. Additionally, the expression levels of ACSS2 and its downstream gene PTGS2 were significantly reduced or increased following transfection with miR-15b-5p mimics or inhibitors, respectively. Furthermore, overexpression of ACSS2 reversed the antiproliferative and proapoptotic effects of miR-15b-5p mimics by blocking the production of PTGS2 protein. In conclusion, miR-15b-5p may promote the apoptosis and inhibit the proliferation of aortic VSMCs via targeting the ACSS2/PTGS2 axis. The present study provided preliminary evidence indicating that the miR-15b-5p/ACSS2/PTGS2 axis may be a potential target for the treatment of AAA.

Kallikrein-1 Blockade Inhibits Aortic Expansion in a Mouse Model and Reduces Prostaglandin E2 Secretion From Human Aortic Aneurysm Explants

Background Abdominal aortic aneurysm (AAA) is an important cause of mortality in older adults. The kinin B2 receptor agonist, bradykinin, has been implicated in AAA pathogenesis through promoting inflammation. Bradykinin is generated from high- and low-molecular-weight kininogen by the serine protease kallikrein-1. The aims of this study were first to examine the effect of neutralizing kallikrein-1 on AAA development in a mouse model and second to test how blocking kallikrein-1 affected cyclooxygenase-2 and prostaglandin E₂ in human AAA explants. Methods and Results Neutralization of kallikrein-1 in apolipoprotein E-deficient (ApoE^-/-) mice via administration of a blocking antibody inhibited suprarenal aorta expansion in response to angiotensin (Ang) II infusion. Kallikrein-1 neutralization decreased suprarenal aorta concentrations of bradykinin and prostaglandin E₂ and reduced cyclooxygenase-2 activity. Kallikrein-1 neutralization also decreased protein kinase B and extracellular signal-regulated kinase 1/2 phosphorylation and reduced levels of active matrix metalloproteinase 2 and matrix metalloproteinase 9. Kallikrein-1 blocking antibody reduced levels of cyclooxygenase-2 and secretion of prostaglandin E₂ and active matrix metalloproteinase 2 and matrix metalloproteinase 9 from human AAA explants and vascular smooth muscle cells exposed to activated neutrophils. Conclusions These findings suggest that kallikrein-1 neutralization could be a treatment target for AAA.

Systematic Review and Meta-Analysis of Interventions to Slow Progression of Abdominal Aortic Aneurysm in Mouse Models

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Quercetin Downregulates Cyclooxygenase-2 Expression and HIF-1α/VEGF Signaling-Related Angiogenesis in a Mouse Model of Abdominal Aortic Aneurysm

Objective

Abdominal aortic aneurysm (AAA) development has been characterized by increased expression of vascular endothelial growth factor (VEGF), which contributes to angiogenesis via cyclooxygenase-2 (COX-2). Quercetin, one of the most common and well-researched flavonoids and abundant in vegetables and fruits, has beneficial effects in inhibiting angiogenesis. This study investigated the antiangiogenic effects of quercetin on experimental aneurysms.

Methods

We utilized the in vivo AAA mouse model induced by the periaortic application of CaCl₂ to examine the effectiveness of quercetin in blocking angiogenesis. Quercetin was administered at 60 mg/kg once daily on the day of the AAA induction and then continued for 6 weeks. Celecoxib, a selective COX-2 inhibitor, was used as the positive control.

Results

Our results demonstrated that quercetin significantly attenuated aneurysm growth in AAA mice and medial neovascularization. Accordingly, quercetin decreased the expression of proangiogenic mediators, including VEGF-A, intercellular adhesion molecule-1, vascular cell adhesion molecule 1, and vascular endothelial cadherin. Quercetin treatment also inhibited the expression of COX-2 and hypoxia-inducible factor 1α (HIF-1α). It was also found that quercetin-3-glucuronide, a major quercetin metabolite, downregulated the expression of COX-2, HIF-1α, VEGF-A, and matrix metalloproteinase activities in aortic vascular smooth muscle cells isolated from AAA mice.

Conclusion

Quercetin attenuates neovascularization during AAA growth, and this effect is mediated via the inhibition of COX-2, which decreases HIF-1α/VEGF signaling-related angiogenesis.

MiR-144-5p limits experimental abdominal aortic aneurysm formation by mitigating M1 macrophage-associated inflammation: Suppression of TLR2 and OLR1

BACKGROUND

It has been noted that dysregulation of microRNAs (miRNAs) contributes to the formation of abdominal aortic aneurysm (AAA), a vascular disease associated with progressive aortic dilatation and degradation, and pathological infiltration and activation of inflammatory cells, such as macrophages. Our microarray data revealing that miR-144-5p was the top 1 downregulated miRNA in mouse AAA tissues as compared to normal aortas motivated us to explore its role in AAA development.

METHODS

We profiled miRNA and mRNA expression in Angiotensin II (Ang II)- (n = 3) and saline-infused abdominal aortas (n = 4) via Agilent microarrays, and further validated the data with real-time QPCR. In vivo, miR-144-5p or control agomirs were given to Apoe^-/- mice with Ang II infusion-induced AAA. In vitro, mouse RAW 264.7 macrophages and human THP-1 macrophage-like cells were transfected with miR-144-5p or control agomirs/antagomirs, and oxidized Low Density Lipoprotein (ox-LDL) was used to stimulate M1 macrophage polarization.

RESULTS

Based on the microarray and real-time QPCR validation data, we identified miR-144-5p as a novel downregulated miRNA in AAA tissues. Overexpression of miR-144-5p by utilizing its specific agomirs in vivo significantly attenuated Ang II-induced aortic dilatation and elastic degradation in Apoe^-/- mice and improved their survival. AAA incidence was reduced by miR-144-5p as well. MiR-144-5p polarized macrophages to M2 type in Ang II-infused aortas. Further, the expression levels of two predictive targets for miR-144-5p, Toll Like Receptor 2 (TLR2) and ox-LDL Receptor 1 (OLR1), were higher in AAA specimens, and negatively correlated to miR-144-5p (Pearson correlation coefficient r < -0.9, P < .01). These two molecules were then confirmed as novel miR-144-5p targets via dual-luciferase assay. MiR-144-5p agomirs suppressed ox-LDL-induced upregulation of M1 macrophage markers, including interleukin 1β (IL1β), tumor necrosis factor α (TNFα), prostaglandin-endoperoxide synthase 2 (PTGS2) and nitric oxide synthase 2 (NOS2), in macrophages probably by targeting TLR2. MiR-144-5p also inhibited the signaling transduction of pathways downstream to TLR2 and OLR1, including NF-κB and ERK1/2 pathways, whose abnormal activation contributed AAA formation.

CONCLUSION

Our work suggests miR-144-5p as a novel regulator for AAA pathology. Management of miR-144-5p and its targets TLR2 and OLR1 provides therapeutic potential for limiting AAA formation.

Trend and Economic Burden of Intravenous Narcotic Analgesic Utilization in Major Vascular Interventions in the United States

BACKGROUND

The use of IV narcotic analgesics (IVNA) within the context of vascular procedures is not fully described. We sought to evaluate the burden of IVNA including narcotic analgesia-related adverse drug events (NARADE), associated mortality and hospitalization cost in open and endovascular vascular procedures, and to compare it with nonnarcotic analgesia (IVNNA).

METHODS

Retrospective cross-sectional study in hospitals participating in Premier database (2009-2015). Logistic regression analysis was implemented to report the risks of NARADE and in-hospital mortality. Negative binomial regression was used to assess length of stay and generalized linear modeling was used to estimate the hospitalization cost.

RESULTS

A total of 171,473 patients were identified. NARADE occurred in 6.2% of the cohort. NARADE group was similar in gender and race but was slightly older (median age 71 vs. 70; P < 0.001). After risk-adjustment, NARADE risk was higher in patients who received IVNA-alone in carotid and lower extremity revascularization (LER) [OR (odds ratio) (95% confidence interval [CI]): 1.17 (1.02-1.34) and 1.31 (1.14-1.50)] or combined with IVNNA [OR (95% CI): 1.34 (1.13-1.59) and 1.81 (1.54-2.13)], respectively. Patients receiving aortic repair benefited from the use of IVNA + IVNNA [OR (95% CI): 0.82 (0.69-0.98)]. Occurrence of NARADE doubled the LOS, amplified mortality risk and increased cost in all domains. NARADE increased the odds of mortality by 24.3, 6.5 (4.9-8.68) and 16.6 times and added $5,368, $12,737 and $11,349 to the cost of carotid, aortic and LER interventions, respectively. In contrast, IVNNA was not associated with NARADE risk, increased LOS or cost and showed a survival benefit in patients undergoing open aortic repair [aOR (95% CI): 0.52 (0.36-0.75)].

CONCLUSIONS AND RELEVANCE

The use of opioid-based narcotics had increased the risk of NARADE, resources utilization and NARADE-related mortality. Yet the use of nonopioid-based analgesic was safe, did not increase the cost and reduced mortality in open AA repair. This entices shifting the paradigm toward exploring nonopioid-based analgesia options in order to replace or minimize opioid requirements.

Current Status and Perspectives on Pharmacologic Therapy for Abdominal Aortic Aneurysm

Background:

Abdominal aortic aneurysm (AAA), a common disease involving the segmen-tal expansion and rupture of the aorta, has a high mortality rate. Therapeutic options for AAA are cur-rently limited to surgical repair to prevent catastrophic rupture. Non-surgical approaches, particularly pharmacotherapy, are lacking for the treatment of AAA.

Objective:

We review both basic and clinical studies and discuss the current challenges to developing medical therapy that reduces AAA progression.

Results:

Studies using animal models of AAA progression and human AAA explant cultures have identified several potential targets for preventing AAA growth. However, no clinical studies have con-vincingly confirmed the efficacy of any pharmacologic treatment against the growth of AAA. Thus, there is as yet no strong recommendation regarding pharmacotherapy to reduce the risk of AAA pro-gression and rupture.

Conclusion:

This review identifies concerns that need to be addressed for the field to progress and dis-cusses the challenges that must be overcome in order to develop effective pharmacotherapy to reduce AAA progression in the future.

c‑Jun/Ap‑1 is upregulated in an Ang II‑induced abdominal aortic aneurysm formation model and mediates Chop expression in mouse aortic smooth muscle cells

Abdominal aortic aneurysm (AAA) is an asymptomatic, potentially lethal disease whose ruptures have a high mortality rate. An effective pharmacological approach to decrease expansion or prevent the rupture of AAAs in humans remains lacking. Previous studies have suggested that activator protein 1 (c-Jun/AP-1) and C/EBP homologous protein (Chop) are involved in the development of AAA. The purpose of the present study was to investigate whether c-Jun/AP-1 mediates Chop overexpression in AAA. c-Jun/AP-1 and Chop protein levels were determined in an angiotensin II (Ang II)-induced AAA model using apolipoprotein E-deficient mice. Additionally, mouse aortic smooth muscle cells (MOVAS cell line) were treated with Ang II. Apoptosis was evaluated via TUNEL assay, MOVAS cell migration ability was assessed by monolayer wound healing assay and the levels of c-Jun/AP-1 and Chop were determined by western blotting, immunofluorescence and immunocytochemical assays. Following c-Jun silencing using c-Jun-specific small interfering (si)RNA, Chop expression was evaluated. Furthermore, chromatin immunoprecipitation (ChIP) was used to investigate whether c-Jun/Ap-1 binds directly to the DNA damage-inducible transcript 3 protein (Ddit3) promoter. It was observed that c-Jun/AP-1 and Chop were synchronously overexpressed in Ang II-induced AAA and Ang II-treated cells, and that apoptosis and migration were induced by Ang II. In addition, Chop was suppressed when c-Jun was silenced by targeted siRNA. Notably, the ChIP assay demonstrated that the DNA fragments pulled down by primary antibodies against c-Jun/Ap-1 were able to be amplified by (Ddit3) promoter-specific primers. c-Jun/AP-1 may therefore mediate Chop expression in MOVAS cells via Ddit3. These results suggested that c-Jun/AP-1 may be a novel target for AAA therapy.

Pharmacologic Management of Aneurysms

Current management of aortic aneurysms relies exclusively on prophylactic operative repair of larger aneurysms. Great potential exists for successful medical therapy that halts or reduces aneurysm progression and hence alleviates or postpones the need for surgical repair. Preclinical studies in the context of abdominal aortic aneurysm identified hundreds of candidate strategies for stabilization, and data from preoperative clinical intervention studies show that interventions in the pathways of the activated inflammatory and proteolytic cascades in enlarging abdominal aortic aneurysm are feasible. Similarly, the concept of pharmaceutical aorta stabilization in Marfan syndrome is supported by a wealth of promising studies in the murine models of Marfan syndrome-related aortapathy. Although some clinical studies report successful medical stabilization of growing aortic aneurysms and aortic root stabilization in Marfan syndrome, these claims are not consistently confirmed in larger and controlled studies. Consequently, no medical therapy can be recommended for the stabilization of aortic aneurysms. The discrepancy between preclinical successes and clinical trial failures implies shortcomings in the available models of aneurysm disease and perhaps incomplete understanding of the pathological processes involved in later stages of aortic aneurysm progression. Preclinical models more reflective of human pathophysiology, identification of biomarkers to predict severity of disease progression, and improved design of clinical trials may more rapidly advance the opportunities in this important field.

Ginkgo biloba extracts prevent aortic rupture in angiotensin II-infused hypercholesterolemic mice

Abdominal aortic aneurysms (AAAs) are a chronic vascular disease characterized by pathological luminal dilation. Aortic rupture is the fatal consequence of AAAs. Ginkgo biloba extracts (GBEs), a natural herb extract widely used as food supplements, drugs, and cosmetics, has been reported to suppress development of calcium chloride-induced AAAs in mice. Calcium chloride-induced AAAs do not rupture, while angiotensin II (AngII)-induced AAAs in mice have high rate of aortic rupture, implicating potentially different mechanisms from calcium chloride-induced AAAs. This study aimed to determine whether GBE would improve aortic dilation and rupture rate of AngII-induced AAAs. Male apolipoprotein E (apoE) -/- mice were infused with AngII and administered either GBE or its major active ingredients, flavonoids and ginkgolides, individually or in combination. To determine the effects of GBE in mice with established AAAs, male apoE-/- mice were firstly infused with AngII for 28 days to develop AAAs, and then administered either GBE or vehicle in mice with established AAAs, which were continuously infused with AngII for another 56 days. GBE, but not the two major active components separately or synergistically, prevented aortic rupture, but not aortic dilation. The protection of GBE from aortic rupture was independent of systolic blood pressure, lipid, and inflammation. GBE also did not attenuate either aortic rupture or progressive aortic dilation in mice with established AAAs. GBE did not reduce the atherosclerotic lesion areas, either. In conclusion, GBE prevents aortic rupture in AngII-infused hypercholesterolemic mice, but only in the early phase of the disease development.

Chinese Herbal Medicine as a Potential Treatment of Abdominal Aortic Aneurysm

Abdominal aortic aneurysm (AAA) is an irreversible condition where the abdominal aorta is dilated leading to potentially fatal consequence of aortic rupture. Multiple mechanisms are involved in the development and progression of AAA, including chronic inflammation, oxidative stress, vascular smooth muscle (VSMC) apoptosis, immune cell infiltration and extracellular matrix (ECM) degradation. Currently surgical therapies, including minimally invasive endovascular aneurysm repair (EVAR), are the only viable interventions for AAAs. However, these treatments are not appropriate for the majority of AAAs, which measure <50 mm. Substantial effort has been invested to identify and develop pharmaceutical treatments such as statins and doxycycline for this potentially lethal condition but these interventions failed to offer a cure or to retard the progression of AAA. Chinese herbal medicine (CHM) has been used for the management of cardiovascular diseases for thousands of years in China and other Asian countries. The unique multi-component and multi-target property of CHMs makes it a potentially ideal therapy for multifactorial diseases such as AAA. In this review, we review the current scientific evidence to support the use of CHMs for the treatment of AAA. Mechanisms of action underlying the effects of CHMs on AAA are also discussed.

Rapamycin Treatment Attenuates Angiotensin II -induced Abdominal Aortic Aneurysm Formation via VSMC Phenotypic Modulation and Down-regulation of ERK1/2 Activity

The aim of the present study is to address the effect of rapamycin on abdominal aortic aneurysm (AAA) and the potential mechanisms. A clinically relevant AAA model was induced in apolipoprotein E-deficient (ApoE-/-) mice, in which miniosmotic pump was implanted subcutaneously to deliver angiotensin II (Ang II) for 14 days. Male ApoE-/- mice were randomly divided into 3 groups: saline infusion, Ang II infusion, and Ang II infusion plus intraperitoneal injection of rapamycin. The diameter of the supra-renal abdominal aorta was measured by ultrasonography at the end of the infusion. Then aortic tissue was excised and examined by Western blotting and histoimmunochemistry. Ang n with or without rapamycin treatment was applied to the cultured vascular smooth muscle cells (VSMCs) in vitro. The results revealed that rapamycin treatment significantly attenuated the incidence of Ang II induced-AAA in ApoE-/- mice. Histologic analysis showed that rapamycin treatment decreased disarray of elastin fibers and VSMCs hyperplasia in the medial layer. Immunochemistry staining and Western blotting documented the increased phospho-ERK1/2 and ERK1/2 expression in aortic walls in Ang II induced-AAA, as well as in human lesions. Whereas in the rapamycintreated group, decreased phospho-ERKl/2 expression level was detected. Moreover, rapamycin reversed Ang II -induced VSMCs phenotypic change both in vivo and in vitro. Based on those results, we confirmed that rapamycin therapy suppressed Ang II -induced AAA formation in mice, partially via VSMCs phenotypic modulation and down-regulation of ERK1/2 activity.

Defective p27 phosphorylation at serine 10 affects vascular reactivity and increases abdominal aortic aneurysm development via Cox-2 activation

Phosphorylation at serine 10 (S10) is the major posttranslational modification of the tumor suppressor p27, and is reduced in both human and mouse atherosclerosis. Moreover, a lack of p27-phospho-S10 in apolipoprotein E-null mice (apoE-/-) leads to increased high-fat diet-induced atherosclerosis associated with endothelial dysfunction and augmented leukocyte recruitment. In this study, we analyzed whether p27-phospho-S10 modulates additional endothelial functions and associated pathologies. Defective p27-phospho-S10 increases COX-2 activity in mouse aortic endothelial cells without affecting other key regulators of vascular reactivity, reduces endothelium-dependent dilation, and increases arterial contractility. Lack of p27-phospho-S10 also elevates aortic COX-2 expression and thromboxane A₂ production, increases aortic lumen diameter, and aggravates angiotensin II-induced abdominal aortic aneurysm development in apoE-/- mice. All these abnormal responses linked to defective p27-phospho-S10 are blunted by pharmacological inhibition of COX-2. These results demonstrate that defective p27-phospho-S10 modifies endothelial behavior and promotes aneurysm formation via COX-2 activation.

Animal models in the research of abdominal aortic aneurysms development

Abdominal aortic aneurysm (AAA) is a prevalent and potentially life threatening disease. Many animal models have been developed to simulate the natural history of the disease or test preclinical endovascular devices and surgical procedures. The aim of this review is to describe different methods of AAA induction in animal models and report on the effectiveness of the methods described in inducing an analogue of a human AAA. The PubMed database was searched for publications with titles containing the following terms "animal" or "animal model(s)" and keywords "research", "aneurysm(s)", "aorta", "pancreatic elastase", "Angiotensin", "AngII" "calcium chloride" or "CaCl(2)". Starting date for this search was set to 2004, since previously bibliography was already covered by the review of Daugherty and Cassis (2004). We focused on animal studies that reported a model of aneurysm development and progression. A number of different approaches of AAA induction in animal models has been developed, used and combined since the first report in the 1960's. Although specific methods are successful in AAA induction in animal models, it is necessary that these methods and their respective results are in line with the pathophysiology and the mechanisms involved in human AAA development. A researcher should know the advantages/disadvantages of each animal model and choose the appropriate model.

Microsomal Prostaglandin E Synthase-1 Expression by Aortic Smooth Muscle Cells Attenuates the Differentiated Phenotype

The development of numerous types of cardiovascular disease is associated with alteration of the vascular smooth muscle cell (SMC) phenotype. We have previously shown that abdominal aortic aneurysm progression in a mouse model of the disease is associated with reduced differentiation of SMCs within the lesion and that cyclooxygenase-2 (COX-2) is critical to initiation and progression of the aneurysms. The current studies used human aortic SMC (hASMC) cultures to better characterize mechanisms responsible for COX-2-dependent modulation of the SMC phenotype. Depending on the culture conditions, hASMCs expressed multiple characteristics of a differentiated and contractile phenotype, or a dedifferentiated and secretory phenotype. The pharmacological inhibition of COX-2 promoted the differentiated phenotype, whereas treatment with the COX-2-derived metabolite prostaglandin E2 (PGE2) increased characteristics of the dedifferentiated phenotype. Furthermore, pharmacological inhibition or siRNA-mediated knockdown of microsomal prostaglandin E synthase-1 (mPGES-1), the enzyme that functions downstream of COX-2 during the synthesis of PGE2, significantly increased expression of characteristics of the differentiated SMC phenotype. Therefore, our findings suggest that COX-2 and mPGES-1-dependent synthesis of PGE2 contributes to a dedifferentiated hASMC phenotype and that mPGES-1 may provide a novel pharmacological target for treatment of cardiovascular diseases where altered SMC differentiation has a causative role.

Oxidative stress and abdominal aortic aneurysm: potential treatment targets

Abdominal aortic aneurysm (AAA) is a significant cause of mortality in older adults. A key mechanism implicated in AAA pathogenesis is inflammation and the associated production of reactive oxygen species (ROS) and oxidative stress. These have been suggested to promote degradation of the extracellular matrix (ECM) and vascular smooth muscle apoptosis. Experimental and human association studies suggest that ROS can be favourably modified to limit AAA formation and progression. In the present review, we discuss mechanisms potentially linking ROS to AAA pathogenesis and highlight potential treatment strategies targeting ROS. Currently, none of these strategies has been shown to be effective in clinical practice.

Activation of extracellular signal-related kinase in abdominal aortic aneurysm

BACKGROUND

Extracellular matrix degeneration, caused by matrix metalloproteinase-2, facilitates smooth muscle cell migration leading to medial layer decline and, ultimately, abdominal aortic aneurysm. It remains unclear what exactly causes aneurysms to rupture, which leads to death in most patients. The extracellular signal-related kinase may be linked to the latter process. We aimed to clarify the role of extracellular signal-related kinase in aortic aneurysm development and rupture in patients.

DESIGN

Aortic fragments were harvested during open repair of nonruptured (n = 20) and ruptured (n = 8) aneurysms. As control, nondilated aortas (n = 6) were obtained during autopsy. We determined levels of phosphorylated and total extracellular signal-related kinase by Western blot, matrix metalloproteinase-2 by immunohistochemistry and medial layer thickness by conventional microscopy.

RESULTS

Nonruptured aneurysms had 1·8 times higher activation of extracellular signal-related kinase (ratio: phosphorylated/total) than controls (P = 0·011). However, the ruptured aneurysms had only 0·9 times the activation of controls (ns). Both nonruptured and ruptured aneurysms showed significantly higher matrix metalloproteinase-2 than controls (3·8 and 4·0-times, respectively; P < 0·005). Of the medial layer thickness in controls, the median was 1·5 mm, in nonruptured 1·0 mm and in ruptured aneurysms 0·7 mm. Activation of extracellular signal-related kinase correlated positively to medial layer thickness (Rs  = 0·48; P = 0·014), but not to matrix metalloproteinase-2 (Rs  = -0·36; P = 0·10).

CONCLUSIONS

In this study, nonruptured aneurysms are associated with increased extracellular signal-related kinase activation while ruptured aneurysms are not. Extracellular signal-related kinase was not related to total matrix metalloproteinase-2 expression. We therefore speculate that increased extracellular signal-related kinase, in response to medial layer decline, could be protective against aneurysm rupture.

Clonal expansion of T cells in abdominal aortic aneurysm: a role for doxycycline as drug of choice?

Most reported studies with animal models of abdominal aortic aneurysm (AAA) and several studies with patients have suggested that doxycycline favourably modifies AAA; however, a recent large long-term clinical trial found that doxycycline did not limit aneurysm growth. Thus, there is currently no convincing evidence that doxycycline reduces AAA expansion. Here, we critically review the available experimental and clinical information about the effects of doxycycline when used as a pharmacological treatment for AAA. The view that AAA can be considered an autoimmune disease and the observation that AAA tissue shows clonal expansion of T cells is placed in the light of the well-known inhibition of mitochondrial protein synthesis by doxycycline. In T cell leukaemia animal models, this inhibitory effect of the antibiotic has been shown to impede T cell proliferation, resulting in complete tumour eradication. We suggest that the available evidence of doxycycline action on AAA is erroneously ascribed to its inhibition of matrix metalloproteinases (MMPs) by competitive binding of the zinc ion co-factor. Although competitive binding may explain the inhibition of proteolytic activity, it does not explain the observed decreases of MMP mRNA levels. We propose that the observed effects of doxycycline are secondary to inhibition of mitochondrial protein synthesis. Provided that serum doxycycline levels are kept at adequate levels, the inhibition will result in a proliferation arrest, especially of clonally expanding T cells. This, in turn, leads to the decrease of proinflammatory cytokines that are normally generated by these cells. The drastic change in cell type composition may explain the changes in MMP mRNA and protein levels in the tissue samples.

Myeloid cell microsomal prostaglandin E synthase-1 fosters atherogenesis in mice

Microsomal prostaglandin E synthase-1 (mPGES-1) in myeloid and vascular cells differentially regulates the response to vascular injury, reflecting distinct effects of mPGES-1-derived PGE2 in these cell types on discrete cellular components of the vasculature. The cell selective roles of mPGES-1 in atherogenesis are unknown. Mice lacking mPGES-1 conditionally in myeloid cells (Mac-mPGES-1-KOs), vascular smooth muscle cells (VSMC-mPGES-1-KOs), or endothelial cells (EC-mPGES-1-KOs) were crossed into hyperlipidemic low-density lipoprotein receptor-deficient animals. En face aortic lesion analysis revealed markedly reduced atherogenesis in Mac-mPGES-1-KOs, which was concomitant with a reduction in oxidative stress, reflective of reduced macrophage infiltration, less lesional expression of inducible nitric oxide synthase (iNOS), and lower aortic expression of NADPH oxidases and proinflammatory cytokines. Reduced oxidative stress was reflected systemically by a decline in urinary 8,12-iso-iPF2α-VI. In contrast to exaggeration of the response to vascular injury, deletion of mPGES-1 in VSMCs, ECs, or both had no detectable phenotypic impact on atherogenesis. Macrophage foam cell formation and cholesterol efflux, together with plasma cholesterol and triglycerides, were unchanged as a function of genotype. In conclusion, myeloid cell mPGES-1 promotes atherogenesis in hyperlipidemic mice, coincident with iNOS-mediated oxidative stress. By contrast, mPGES-1 in vascular cells does not detectably influence atherogenesis in mice. This strengthens the therapeutic rationale for targeting macrophage mPGES-1 in inflammatory cardiovascular diseases.

Rapamycin limits the growth of established experimental abdominal aortic aneurysms

OBJECTIVES

Abdominal aortic aneurysm (AAA) is a chronic inflammatory disease affecting 4-8% of men older than 60 years. No pharmacologic strategies limit disease progression, aneurysm rupture, or aneurysm-related death. We examined the ability of rapamycin to limit the progression of established experimental AAAs.

METHODS

AAAs were created in 10-12-week-old male C57BL/6J mice via the porcine pancreatic elastase (PPE) infusion method. Beginning 4 days after PPE infusion, mice were treated with rapamycin (5 mg/kg/day) or an equal volume of vehicle for 10 days. AAA progression was monitored by serial ultrasound examination. Aortae were harvested for histological analyses at sacrifice.

RESULTS

Three days after PPE infusion, prior to vehicle or rapamycin treatment, aneurysms were enlarging at an equal rate between groups. In the rapamycin group, treatment reduced aortic enlargement by 38%, and 53% at 3 and 10 days, respectively. On histological analysis, medial elastin and smooth muscle cell populations were relatively preserved in the rapamycin group. Rapamycin treatment also reduced mural macrophage density and neoangiogenesis.

CONCLUSION

Rapamycin limits the progression of established experimental aneurysms, increasing the translational potential of mechanistic target of rapamycin-related AAA inhibition strategies.

Combination therapy with atorvastatin and amlodipine suppresses angiotensin II-induced aortic aneurysm formation

Background

Abdominal aortic aneurysm (AAA) is a life-threatening vascular disease. It is controversial whether statin and calcium channel blockers (CCBs) has an inhibitory effect on the expansion of AAA. Some studies reported that CCBs have an inhibitory effect on Rho-kinase activity. Rho-kinase plays an important role in the pathogenesis of various cardiovascular diseases. However, there is no study reporting of the association between Rho-kinase and human AAAs.

Methods and Results

Experimental AAA was induced in Apolipoprotein E-deficient (ApoE^-/-) mice infused with angiotensin II (AngII) for 28 days. They were randomly divided into the following 5 groups; saline infusion alone (sham), AngII infusion alone, AngII infusion plus atorvastatin (10 mg/kg/day), AngII infusion plus amlodipine (1 mg/kg/day), and AngII infusion plus combination therapy with atorvastatin (10 mg/kg/day) and amlodipine (1 mg/kg/day). The combination therapy significantly suppressed AngII-induced increase in maximal aortic diameter as compared with sham, whereas each monotherapy had no inhibitory effects. The combination therapy significantly reduced AngII-induced apoptosis and elastin degradation at the AAA lesion, whereas each monotherapy did not. Moreover, Rho-kinase activity, as evaluated by the extent of phosphorylation of myosin-binding subunit (a substrate of Rho-kinase) and matrix metalloproteinase activity were significantly increased in the AngII-induced AAA lesion as compared with sham, both of which were again significantly suppressed by the combination therapy. In human aortic samples, immunohistochemistory revealed that the activity and expression of Rho-kinase was up-regulated in AAA lesion as compared with abdominal aorta from control subjects.

Conclusions

Rho-kinase is up-regulated in the aortic wall of human AAA. The combination therapy with amlodipine and Atorvastatin, but not each monotherapy, suppresses AngII-induced AAA formation in mice in vivo, for which Rho-kinase inhibition may be involved.