Suppression of experimental abdominal aortic aneurysms in the rat by treatment with angiotensin-converting enzyme inhibitors

Role of SARS-COV-2 and ACE2 in the pathophysiology of peripheral vascular diseases

The occurrence of a novel coronavirus known as severe acute respiratory syndrome-coronavirus-2 (SARS-CoV-2), created a serious challenge worldwide. SARS-CoV-2 has high infectivity, the ability to be transmitted even during the asymptomatic phase, and relatively low virulence, which has resulted in rapid transmission. SARS-CoV-2 can invade epithelial cells, hence, many patients infected with SARS-CoV-2 have suffered from vascular diseases (VDs) in addition to pulmonary manifestations. Accordingly, SARS-CoV-2 may can worsen the clinical condition of the patients with pre-existing VDs. Endothelial cells express angiotensin-converting enzyme 2 (ACE2). ACE2 is a biological enzyme that converts angiotensin (Ang)- 2 to Ang-(1-7). SARS-CoV-2 uses ACE2 as a cell receptor for viral entry. Thus, the SARS-CoV-2 virus promotes downregulation of ACE2, Ang-(1-7), and anti-inflammatory cytokines, as well as, an increase in Ang-2, resulting in pro-inflammatory cytokines. SARS-CoV-2 infection can cause hypertension, and endothelial damage, which can lead to intravascular thrombosis. In this review, we have concentrated on the effect of SARS-CoV-2 in peripheral vascular diseases (PVDs) and ACE2 as an enzyme in Renin-angiotensin aldosterone system (RAAS). A comprehensive search was performed on PubMed, Google Scholar, Scopus, using related keywords. Articles focusing on ("SARS-CoV-2", OR "COVID-19"), AND ("Vascular disease", OR "Peripheral vascular disease", OR interested disease name) with regard to MeSH terms, were selected. According to the studies, it is supposed that vascular diseases may increase susceptibility to severe SARS-CoV-2 infection due to increased thrombotic burden and endothelial dysfunction. Understanding SARS-CoV-2 infection mechanism and vascular system pathogenesis is crucial for effective management and treatment in pre-existing vascular diseases.

Increased plasma renin by vasodilators promotes the progression of abdominal aortic aneurysm

Background: It is well-accepted that antihypertensive therapy is the cornerstone of treatment for abdominal aortic aneurysm (AAA) patients with hypertension. Direct-acting vasodilators were used in the treatment of hypertension by directly relaxing vascular smooth muscle but may have destructive effects on the aortic wall by activating the renin-angiotensin system axis. Their roles in AAA disease remain to be elucidated. In this study, we used hydralazine and minoxidil, two classical direct-acting vasodilators, to investigate their influence and potential mechanisms on AAA disease. Methods and results: In this study, we investigated the plasma renin level and plasma renin activity in AAA patients. Simultaneously, age and gender ratio-matched patients diagnosed with peripheral artery disease and varicose veins were selected as the control group using a ratio of 1:1:1. Our regression analysis suggested both the plasma renin level and plasma renin activity are positively associated with AAA development. In view of the well-established relationship between direct-acting vasodilators and increased plasma renin concentration, we established a porcine pancreatic elastase-infused AAA mouse model, followed by oral administration of hydralazine (250 mg/L) and minoxidil (120 mg/L) to investigate effects of direct-acting vasodilators on AAA disease. Our results suggested both hydralazine and minoxidil promoted the progression of AAA with increased aortic degeneration. Mechanistically, the vasodilators aggravated aortic inflammation by increased leukocyte infiltration and inflammatory cytokine secretion. Conclusion and relevance: The plasma renin level and plasma renin activity are positively associated with AAA development. Direct vasodilators aggravated experimental AAA progression, which raised cautionary concerns about their applications in AAA disease.

Research advances in drug therapy for abdominal aortic aneurysms over the past five years: An updated narrative review

BACKGROUND

Abdominal aortic aneurysms (AAA) rupture can lead to patient death. Surgical treatment is currently the optimal treatment for AAA with large diameter (≥50 mm). For AAA with small diameter (30-50 mm), how to administer effective pharmacological treatment to reduce aneurysm expansion rate and rupture risk is the current focus in the field of vascular surgery. There is still no effective drug for the treatment of asymptomatic AAA.

METHODS

This article searches the PubMed, Web of Science, Embase, and Cochrane databases for clinical studies on the drug treatment of abdominal aortic aneurysms in the past 5 years. The latest progress in the drug treatment of AAA was reviewed, including antibiotics, antihypertensive drugs, antiplatelet drugs, hypoglycemic drugs, hypolipidemic drugs, mast cell inhibitors and corticosteroids.

RESULTS

25 studies were included in this narrative review. Among them, metformin revealed therapeutic effect in 2 prospective cohort study and 3 retrospective cohort study. The therapeutic effect of statins was controversial in 3 retrospective cohort study. However, the definite therapeutic effects of antihypertensive agents, antibiotics, mast cell inhibitors, antiplatelet agents and corticosteroids on abdominal aortic aneurysms have not been verified in prospective studies.

CONCLUSION

Metformin provided a positive effect in reducing expansion rate, rupture risk, and perioperative mortality. The therapeutic effect of statins was controversial, which warrant further validation in prospective cohorts. However, there is still a lack of effective agents for the treatment of AAA based on recent studies.

Silicate ions as soluble form of bioactive ceramics alleviate aortic aneurysm and dissection

Aortic aneurysm and dissection (AAD) are leading causes of death in the elderly. Recent studies have demonstrated that silicate ions can manipulate multiple cells, especially vascular-related cells. We demonstrated in this study that silicate ions as soluble form of bioactive ceramics effectively alleviated aortic aneurysm and dissection in both Ang II and β-BAPN induced AAD models. Different from the single targeting therapeutic drug approaches, the bioactive ceramic derived approach attributes to the effect of bioactive silicate ions on the inhibition of the AAD progression through regulating the local vascular microenvironment of aorta systematically in a multi-functional way. The in vitro experiments revealed that silicate ions did not only alleviate senescence and inflammation of the mouse aortic endothelial cells, enhance M2 polarization of mouse bone marrow-derived macrophages, and reduce apoptosis of mouse aortic smooth muscle cells, but also regulate their interactions. The in vivo studies further confirm that silicate ions could effectively alleviate senescence, inflammation, and cell apoptosis of aortas, accomplished with reduced aortic dilation, collagen deposition, and elastin laminae degradation. This bioactive ceramic derived therapy provides a potential new treatment strategy in attenuating AAD progression.

Carbon monoxide releasing molecule-2 attenuates angiotensin II-induced IL-6/Jak2/Stat3-associated inflammation by inhibiting NADPH oxidase- and mitochondria-derived ROS in human aortic smooth muscle cells

Abdominal aortic aneurysm (AAA) is a common inflammatory vascular disease. Angiotensin II (Ang II) involves in AAA progression by promoting the proliferation and migration of vascular smooth muscle cells, the degradation of extracellular matrices, and the generation of ROS to lead to vascular inflammation. Carbon monoxide releasing molecule-2 (CORM-2) is known to exert anti-inflammatory and antioxidant activities. However, it remains unclear whether CORM-2 can suppress Ang II-induced vascular inflammation to prevent AAA progression. Therefore, this study aimed to investigate the vasoprotective effects of CORM-2 against Ang II-induced inflammatory responses of human aortic smooth muscle cells (HASMCs) and the underlying mechanisms of those effects. The results showed that Ang II induced inflammatory responses of HASMCs via NADPH oxidase- and mitochondria-derived ROS/NF-κB/IL-6/Jak2/Stat3 pathway which was attenuated by the pretreatment with CORM-2. Additionally, CORM-2 further exhibited anti-inflammatory activities in Ang II-stimulated HASMCs, as indicated by the reduction of monocyte adhesion to HASMCs and migration of HASMCs via the suppression of ICAM-1 and VCAM-1 as well as MMP-2 and MMP-9 levels, respectively. Moreover, Ang II-induced COX-2-mediated PGE₂ secretion was also inhibited by the pretreatment with CORM-2. Importantly, our data demonstrated that CORM-2 reversed Ang II-induced IL-6 overexpression dependent on Nrf2 activation and HO-1 expression. Taken together, the present study indicates that CORM-2-induced Nrf2/HO-1 alleviates IL-6/Jak2/Stat3-mediated inflammatory responses to Ang II by inhibiting NADPH oxidase- and mitochondria-derived ROS, suggesting that CORM-2 is a promising pharmacologic candidate to reverse the pathological changes involved in the inflammation of vessel wall for the prevention and treatment of AAA.

Pharmacotherapy in Clinical Trials for Abdominal Aortic Aneurysms: A Systematic Review and Meta-Analysis

OBJECTIVE

There is no medical treatment proven to limit abdominal aortic aneurysm (AAA) progression. This systematic review aimed to summarise available trial evidence on the efficacy of pharmacotherapy in limiting AAA growth and AAA-related events.

METHODS

A systematic literature search was performed to examine the efficacy of pharmacotherapy in reducing AAA growth and AAA-related events. Pubmed, Embase (Excerpta Medica Database), and the Cochrane library were searched from March, 1999 to March 29, 2022. AAA growth (mm/year) in the intervention and control groups was expressed as mean and standard deviation (SD). The results of AAA growth were expressed as mean difference (MD) and its 95% confidence interval (95% CI). Odds ratios (ORs) were calculated for the AAA-related events.Heterogeneity was quantified using the I² statistic. Forest plots were created to show the pooled results of each outcome.

OUTCOMES

A total of 1373 articles were found in different databases according to the search strategy, and 10 articles were identified by hand searching. A total of 26 articles were included in our systematic review after the screening. For the studies of metformin, the meta-analysis demonstrated that metformin use was associated with a lower AAA growth rate (MD: -0.81 mm/y, 95% CI: -1.19 to -0.42, P < 0.0001, I² = 87%), Metformin use also was related to the lower rates of AAA-related events (OR: 0.53, 95% CI: 0.36 to 0.76, P = 0.0007, I² = 60%). The hypotensive drugs of the studies mainly included angiotensin-converting enzyme inhibitors (ACEI), angiotensin II type 1 receptor blockers (ARB), and propranolol. The overall meta-analysis of blood pressure-lowering drugs reported no significant effect in limiting the AAA growth (MD: 0.31mm/year, 95%CI: -0.03 to 0.65, P = 0.07, I² = 66%) and AAA-related events (OR: 1.33, 95%CI: 0.76 to 2.32, P = 0.32, I² = 98%), In the subgroup analysis of the hypotensive drugs, the ACEI/ARB and propranolol also showed no significant in reducing the AAA growth and AAA-related events. The meta-analysis of the antibiotics demonstrated that the antibiotics were not associated with a lower AAA growth rate (MD: -0.27 mm/y, 95% CI: -0.88 to 0.34, P = 0.39, I² = 77%) and AAA-related events (OR: 0.94, 95%CI: 0.65 to 1.35, P = 0.72, I² = 0%). The results of statins also showed no significant effect in limiting AAA growth (MD: -1.11mm/year, 95%CI: -2.38 to 0.16, P = 0.09, I² = 96%) and AAA-related events (OR: 0.53, 95%CI: 0.26 to 1.06, P = 0.07, I² = 92%).

CONCLUSION

In conclusion, effective pharmacotherapy for AAA was still lacking. Although the meta-analysis showed that metformin use was associated with lower AAA growth and AAA-related events, all of the included studies about metformin were cohort studies or case-control studies. More randomized controlled trials (RCTs) are needed for further verification.

Temporal and Quantitative Analysis of Aortic Immunopathologies in Elastase-Induced Mouse Abdominal Aortic Aneurysms

Objective

Elastase-induced abdominal aortic aneurysm (AAA) model is widely used for aneurysmal pathogenesis and translational research. However, temporal alternations in aneurysmal histologies remain unknown. This study is aimed at analyzing temporal immunopathologies of aneurysmal aorta following experimental AAA induction.

Methods

Male C57BL/6J mice at the age of 10-14 weeks received intra-aortic infusion of elastase to induce AAAs. Aortic diameters at the baseline and indicated days after AAA induction were measured, and aortae were collected for histopathological analysis.

Results

Aorta diameters increased from 0.52 mm at the baseline levels to 0.99 mm, 1.34 mm, and 1.41 mm at days 7, 14, and 28, respectively, corresponding 90%, 158%, and 171% increases over the baseline level. Average aortic diameters did not differ between days 14 and 28. Severe elastin degradation and smooth muscle cell depletion were found at days 14 and 28 as compared to the baseline and day 7. No difference in the scores of medial elastin and SMC destruction was noted between days 14 and 28. Consistent results were found for leukocyte accumulation, neoangiogenesis, and matrix metalloproteinase expression. Twenty-eight days after AAA induction, all aneurysmal pathologies showed an attenuated trend, although most histopathological parameters did no differ between days 14 and 28.

Conclusion

Our data suggest that almost aneurysmal immunohistopathologies reach maximal 14 days following AAA induction. Analysis of day 14 histologies is sufficient for AAA pathogenesis and translational studies in elastase-induced mouse experimental AAAs.

Angiotensin-converting enzyme 2, coronavirus disease 2019, and abdominal aortic aneurysms

OBJECTIVE

Severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) is the etiologic agent of the current, world-wide coronavirus disease 2019 (COVID-19) pandemic. Angiotensin-converting enzyme 2 (ACE2) is the SARS-CoV-2 host entry receptor for cellular inoculation and target organ injury. We reviewed ACE2 expression and the role of ACE2-angiotensin 1-7-Mas receptor axis activity in abdominal aortic aneurysm (AAA) pathogenesis to identify potential COVID-19 influences on AAA disease pathogenesis.

METHODS

A comprehensive literature search was performed on PubMed, National Library of Medicine. Key words included COVID-19, SARS-CoV-2, AAA, ACE2, ACE or angiotensin II type 1 (AT1) receptor inhibitor, angiotensin 1-7, Mas receptor, age, gender, respiratory diseases, diabetes, and autoimmune diseases. Key publications on the epidemiology and pathogenesis of COVID-19 and AAAs were identified and reviewed.

RESULTS

All vascular structural cells, including endothelial and smooth muscle cells, fibroblasts, and pericytes express ACE2. Cigarette smoking, diabetes, chronic obstructive pulmonary disease, lupus, certain types of malignancies, and viral infection promote ACE2 expression and activity, with the magnitude of response varying by sex and age. Genetic deficiency of AT1 receptor, or pharmacologic ACE or AT1 inhibition also increases ACE2 and its catalytic product angiotensin 1-7. Genetic ablation or pharmacologic inhibition of ACE2 or Mas receptor augments, whereas ACE2 activation or angiotensin 1-7 treatment attenuates, progression of experimental AAAs. The potential influences of SARS-CoV-2 on AAA pathogenesis include augmented ACE-angiotensin II-AT1 receptor activity resulting from decreased reciprocal ACE2-angiotensin 1-7-Mas activation; increased production of proaneurysmal mediators stimulated by viral spike proteins in ACE2-negative myeloid cells or by ACE2-expressing vascular structural cells; augmented local or systemic cross-talk between viral targeted nonvascular, nonleukocytic ACE2-expressing cells via ligand recognition of their cognate leukocyte receptors; and hypoxemia and increased systemic inflammatory tone experienced during severe COVID-19 illness.

CONCLUSIONS

COVID-19 may theoretically influence AAA disease through multiple SARS-CoV-2-induced mechanisms. Further investigation and clinical follow-up will be necessary to determine whether and to what extent the COVID-19 pandemic will influence the prevalence, progression, and lethality of AAA disease in the coming decade.

DRD4 (Dopamine D4 Receptor) Mitigate Abdominal Aortic Aneurysm via Decreasing P38 MAPK (mitogen-activated protein kinase)/NOX4 (NADPH Oxidase 4) Axis-Associated Oxidative Stress

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Contemporary outcomes of endovascular abdominal aortic aneurysm repair in patients deemed unfit for open surgical repair

OBJECTIVE

Endovascular abdominal aortic aneurysm repair (EVAR) has been preferred to open surgical repair (OSR) for the treatment of abdominal aortic aneurysms (AAAs) in high-risk patients. We compared the perioperative and long-term outcomes of EVAR for patients designated as unfit for OSR using a large national dataset.

METHODS

The Vascular Quality Initiative database was queried for patients who had undergone elective EVAR for AAAs >5 cm from 2013 to 2019. The patients were stratified into two cohorts according to their suitability for OSR (fit vs unfit). The primary outcomes included perioperative (in-hospital) major adverse events, perioperative mortality, and mortality at 1 and 5 years. Patient demographics and postoperative outcomes were analyzed to identify the predictors of perioperative and long-term mortality.

RESULTS

Of 16,183 EVARs, 1782 patients had been deemed unfit for OSR. The unfit cohort was more likely to be older and female, with a greater proportion of hypertension, coronary artery disease, congestive heart failure, chronic obstructive pulmonary disease, and larger aneurysm diameters. Postoperatively, the unfit cohort was more likely to have experienced cardiopulmonary complications (6.5% vs 3%; P < .001), with greater perioperative mortality (1.7% vs 0.6%; P < .001) and 1- and 5-year mortality (13% and 29% for the unfit vs 5% and 14% for the fit cohorts, respectively; P < .001). A subgroup analysis of the unfit cohort revealed that those deemed unfit because of a hostile abdomen had significantly lower 1- and 5-year mortality (6% and 20%, respectively) compared with those considered unfit because of cardiopulmonary compromise and frailty (14% and 30%, respectively; P = .451). Reintervention-free survival at 1 and 5 years was significantly greater in the fit cohort (93% and 82%, respectively) compared with that for the unfit cohort (85% and 68%, respectively; P < .001). The designation as unfit for OSR was an independent predictor of both perioperative (odds ratio, 1.59; 95% confidence interval [CI], 1.03-2.46; P = .038) and long-term mortality (hazard ratio [HR], 1.92; 95% CI, 1.69-2.17; P < .001). Advanced age (odds ratio, 2.91; 95% CI, 1.28-6.66; P = .011) was the strongest determinant of perioperative mortality, and end-stage renal disease (HR, 2.51; 95% CI, 1.78-3.55; P < .001) was the strongest predictor of long-term mortality. Statin use (HR, 0.77; 95% CI, 0.69-0.87; P < .001) and angiotensin-converting enzyme inhibitor use (HR, 0.83; 95% CI, 0.75-0.93; P < .001) were protective of long-term mortality.

CONCLUSIONS

Despite low perioperative mortality, the long-term mortality of those designated by operating surgeons as unfit for OSR was rather high for patients undergoing elective EVAR, likely owing to the competing risk of death from medical frailty. An unfit designation because of a hostile abdomen did not confer any additional risks after EVAR. Judicious estimation of the patient's life expectancy is essential when considering the treatment options for this subset of patients deemed unfit for OSR.

Angiotensin II and leukocyte trafficking: New insights for an old vascular mediator. Role of redox-signaling pathways

Inflammation and activation of the immune system are key molecular and cellular events in the pathogenesis of cardiovascular diseases, including atherosclerosis, hypertension-induced target-organ damage, and abdominal aortic aneurysm. Angiotensin II (Ang-II) is the main effector peptide hormone of the renin-angiotensin system. Beyond its role as a potent vasoconstrictor and regulator of blood pressure and fluid homeostasis, Ang-II is intimately involved in the development of vascular lesions in cardiovascular diseases through the activation of different immune cells. The migration of leukocytes from circulation to the arterial subendothelial space is a crucial immune response in lesion development that is mediated through a sequential and coordinated cascade of leukocyte-endothelial cell adhesive interactions involving an array of cell adhesion molecules present on target leukocytes and endothelial cells and the generation and release of chemoattractants that activate and guide leukocytes to sites of emigration. In this review, we outline the key events of Ang-II participation in the leukocyte recruitment cascade, the underlying mechanisms implicated, and the corresponding redox-signaling pathways. We also address the use of inhibitor drugs targeting the effects of Ang-II in the context of leukocyte infiltration in these cardiovascular pathologies, and examine the clinical data supporting the relevance of blocking Ang-II-induced vascular inflammation.

Captopril versus atenolol to prevent expansion rate of thoracic aortic aneurysms: rationale and design

Thoracic aortic aneurysms are correlated with significant mortality and morbidity. No therapy, however, is effective at limiting aneurysm expansion and preventing rupture. Angiotensin-converting enzyme inhibitors can reduce the wall shear stress and inflammation, both of which play vital roles in the expansion of the aneurysm. A total of 636 patients will be randomized into one of three parallel arms, receiving captopril, atenolol or placebo. The primary end point will be the rate of change in the absolute diameter of the aortic root and ascending aorta on MRI of the aorta after 36 months. The trial will investigate the efficacy of angiotensin-converting enzyme inhibitors versus beta-blocker therapy in reducing the growth rate of thoracic aortic aneurysms and rupture. Trial registration number: NCT04224675.

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.

Angiotensin I Infusion Reveals Differential Effects of Angiotensin-Converting Enzyme in Aortic Resident Cells on Aneurysm Formation

BACKGROUND

Angiotensin (Ang)I is cleaved by angiotensin-converting enzyme (ACE) to generate AngII. The purpose of this study was to determine the roles of ACE in endothelial and smooth muscle cells in aortic aneurysms.Methods and Results:AngI infusion led to thoracic and abdominal aortic aneurysms in low-density lipoprotein receptor-deficient mice, which were ablated by ACE inhibition. Endothelial or smooth muscle cell-specific ACE deletion resulted in reduction of AngI-induced thoracic, but not abdominal, aortic dilatation.

CONCLUSIONS

AngI infusion causes thoracic and abdominal aortic aneurysms in mice. ACE in aortic resident cells has differential effects on AngI-induced thoracic and abdominal aortic aneurysms.

Cellular Mechanisms of Aortic Aneurysm Formation

Aortic aneurysms are a common vascular disease in Western populations that can involve virtually any portion of the aorta. Abdominal aortic aneurysms are much more common than thoracic aortic aneurysms and combined they account for >25 000 deaths in the United States annually. Although thoracic and abdominal aortic aneurysms share some common characteristics, including the gross anatomic appearance, alterations in extracellular matrix, and loss of smooth muscle cells, they are distinct diseases. In recent years, advances in genetic analysis, robust molecular tools, and increased availability of animal models have greatly enhanced our knowledge of the pathophysiology of aortic aneurysms. This review examines the various proposed cellular mechanisms responsible for aortic aneurysm formation and identifies opportunities for future studies.

Comprehensive Cardiac Rehabilitation as a Therapeutic Strategy for Abdominal Aortic Aneurysm

Abdominal aortic aneurysms (AAA) are referred to as “time bombs”. The only way to prevent AAA rupture is elective repair beforehand using surgical replacement or an endovascular procedure. Non-surgical strategies to prevent AAA expansion are under intense investigation. At each AAA stage, that is, occurrence, expansion, and rupture, the mechanisms and risk factors are different, as discussed in this review. Based on the mechanism and risk factors for AAA expansion, the most effective strategy against AAA expansion need to be identified, but so far none has. Exercise is known to be essential for preventing atherosclerosis related to the coexistence of AAA and CAD, but some doctors are hesitant to prescribe exercise programs to AAA patients given that BP elevation during exercise can cause AAA expansion or rupture. In our retrospective study and prospective study on the safety and effectiveness of exercise for AAA patients, the protective role of mild-moderate exercise against expansion of small AAA was clearly shown. The stability of AAA on exercise might be related to reduced inflammatory activity in the aortic wall, stabilized elevation in BP during exercise, increased aortic blood flow, upregulation of transforming growth factor-β1, moderated BMI and/or fat, or improved endothelial function. Until a revolutionary drug emerges that can regress AAA, cardiac rehabilitation remains the best strategy for preventing AAA expansion and rupture.

A Targeting Nanotherapy for Abdominal Aortic Aneurysms

BACKGROUND

Abdominal aortic aneurysm (AAA) is a leading cause of mortality and morbidity in the elderly. Currently, there remain no effective drugs that can prevent the growth of aneurysms and delay aneurysm rupture in the clinical setting.

OBJECTIVES

The aim of this study was to develop a nanotherapy that can target aneurysms and release drug molecules in response to the inflammatory microenvironment.

METHODS

Using a reactive oxygen species (ROS)-responsive nanoparticle and a candidate drug rapamycin, in combination with a peptide ligand for integrin and biomimetic cloaking with macrophage cell membrane, a nanotherapy was developed. Its effectiveness was demonstrated by in vitro and in vivo studies.

RESULTS

Based on a facile and translational method, a rapamycin-loaded responsive nanotherapy was successfully prepared, which could release drug molecules upon triggering by the high level of ROS. In cells associated with the development of AAAs, the nanotherapy significantly inhibited calcification and attenuated ROS-mediated oxidative stress and apoptosis. By passively targeting aneurysms and releasing drug molecules in response to the inflammatory microenvironment, the intravenously injected ROS-responsive nanotherapy more effectively prevented aneurysm expansion in AAA rats than a nonresponsive control nanotherapy. After decoration with a peptide ligand cRGDfK and macrophage cell membrane, the aneurysmal targeting capability and therapeutic effects of a ROS-responsive nanotherapy with a mean diameter of 190 nm were further enhanced. Moreover, the nanotherapy showed a good safety profile in a preliminary safety test.

CONCLUSIONS

The multifunctional nanotherapy can be further studied as a promising targeted drug for treatment of aneurysms. The underlying design principles enable the development of a broad range of nanomedicines for targeted therapy of other vascular diseases.

ATRQβ-001 Vaccine Prevents Experimental Abdominal Aortic Aneurysms

Background

We have developed a peptide vaccine named ATRQβ‐001, which was proved to retard signal transduction initiated by angiotensin II (Ang II). Ang II was implicated in abdominal aortic aneurysm (AAA) progression, but whether the ATRQβ‐001 vaccine would prevent AAA is unknown.

Methods and Results

Ang II‐infused ApoE^−/− mice and calcium phosphate‐induced AAA in C57BL/6 mice were used to verify the efficiency of ATRQβ‐001 vaccine in AAA. Results demonstrated that the vaccine effectively restrained the aneurysmal dilation and vascular wall destruction of aorta in both animal models, beyond anti‐hypertensive effects. In Ang II‐induced AAA vascular sections, Immunohistochemical staining showed that the vaccine notably constrained vascular inflammation and vascular smooth muscle cell (VSMC) phenotypic transition, concurrently reduced macrophages infiltration. In cultured VSMC, the anti‐ATR‐001 antibody inhibited osteopontin secretion induced by Ang II, thereby impeded macrophage migration while co‐culture. Furthermore, metalloproteinases and other matrix proteolytic enzymes were also found to be limited by the vaccine in vivo and in vitro.

Conclusions

ATRQβ‐001 vaccine prevented AAA initiation and progression in both Ang II and calcium phosphate‐induced AAA models. And the beneficial effects were played beyond decrease of blood pressure, which provided a novel and promising method to take precautions against AAA.

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.

Angiotensin II Signal Transduction: An Update on Mechanisms of Physiology and Pathophysiology

The renin-angiotensin-aldosterone system plays crucial roles in cardiovascular physiology and pathophysiology. However, many of the signaling mechanisms have been unclear. The angiotensin II (ANG II) type 1 receptor (AT₁R) is believed to mediate most functions of ANG II in the system. AT₁R utilizes various signal transduction cascades causing hypertension, cardiovascular remodeling, and end organ damage. Moreover, functional cross-talk between AT₁R signaling pathways and other signaling pathways have been recognized. Accumulating evidence reveals the complexity of ANG II signal transduction in pathophysiology of the vasculature, heart, kidney, and brain, as well as several pathophysiological features, including inflammation, metabolic dysfunction, and aging. In this review, we provide a comprehensive update of the ANG II receptor signaling events and their functional significances for potential translation into therapeutic strategies. AT₁R remains central to the system in mediating physiological and pathophysiological functions of ANG II, and participation of specific signaling pathways becomes much clearer. There are still certain limitations and many controversies, and several noteworthy new concepts require further support. However, it is expected that rigorous translational research of the ANG II signaling pathways including those in large animals and humans will contribute to establishing effective new therapies against various diseases.

Comparison of Efficacy between Ramipril and Carvedilol on Limiting the Expansion of Abdominal Aortic Aneurysm in Mouse Model

Objective:

Abdominal aortic aneurysm (AAA) is a common condition that may be life-threatening when it is unrecognized. The aim of this study is to evaluate and compare the efficacy of ramipril and carvedilol on limiting AAA expansion in mouse model.

Methods and Results:

A total of 36 experimental AAA mouse model was induced with the continuous infusion of angiotensin II (Ang II) in 20-week-old male apolipoprotein E-deficient mice. They were randomly divided into 3 treatment groups and fed orally for 8 weeks; saline alone, ramipril (2.5 mg/30g/d), or carvedilol (3.125 mg/30g/d), respectively. Aortic diameter (AD) was measured by micro-computed tomography, and the level of biomarkers of aortic tissue such as monocyte chemoattractant protein-1 (MCP-1) and tissue inhibitor matrix metalloproteinase-1 (TIMP-1) was evaluated. After treatment, AD of both ramipril and carvedilol group was smaller than in the saline group. The percentage change of AD in both ramipril and carvedilol groups was significantly smaller than that of the saline group. Pathologic examination revealed relatively well-preserved aortic walls in the ramipril group compared to the carvedilol and saline groups. The level of MCP-1 was markedly decreased in both the ramipril and carvedilol groups compared to the saline group. The level of TIMP-1 was higher in the carvedilol group when compared to either the saline or ramipril groups.

Conclusions:

Ramipril and carvedilol treatment shows similar efficacy in limiting AAA expansion in mouse model. Future clinical research would be warranted to validate these results.

The binding of captopril to angiotensin I-converting enzyme triggers activation of signaling pathways

Hypertension is a global health problem, and angiotensin I (ANG I)-converting enzyme (ACE) inhibitors are largely used to control this pathology. Recently, it has been shown that ACE can also act as a transducer signal molecule when its inhibitors or substrates bind to it. This new role of ACE could contribute to understanding some of the effects not explained by its catalytic activity only. In this study, we investigated signaling pathway activation in Chinese hamster ovary (CHO) cells stably expressing ACE (CHO-ACE) under different conditions. We also investigated gene modulation after 4 h and 24 h of captopril treatment. Our results demonstrated that CHO-ACE cells when stimulated with ANG I, ramipril, or captopril led to JNK and ERK1/2 phosphorylation. To verify any physiological role at the endogenous level, we made use of primary cultures of mesangial cells from spontaneously hypertensive rats (SHR) and Wistar rats. Our results showed that ERK1/2 activation occurred mainly in primary cultures of mesangial cells from SHR rats upon captopril stimulation, suggesting that this signaling pathway could be differentially regulated during hypertension. Our results also showed that captopril treatment leads to a decrease of cyclooxygenase 2, interleukin-1β, and β-arrestin2 and a significant increase of AP2 gene expression levels. Our findings strengthen the fact that, in addition to the blockage of enzymatic activity, ACE inhibitors also trigger signaling pathway activation, and this may contribute to their beneficial effects in the treatment of hypertension and other pathologies.

Elevated 20-HETE in metabolic syndrome regulates arterial stiffness and systolic hypertension via MMP12 activation

Arterial stiffness plays a causal role in development of systolic hypertension. 20-hydroxyeicosatetraeonic acid (20-HETE), a cytochrome P450 (CYP450)-derived arachidonic acid metabolite, is known to be elevated in resistance arteries in hypertensive animal models and loosely associated with obesity in humans. However, the role of 20-HETE in the regulation of large artery remodeling in metabolic syndrome has not been investigated. We hypothesized that elevated 20-HETE in metabolic syndrome increases matrix metalloproteinase 12 (MMP12) activation leading to increased degradation of elastin, increased large artery stiffness and increased systolic blood pressure. 20-HETE production was increased ~7 fold in large, conduit arteries of metabolic syndrome (JCR:LA-cp, JCR) vs. normal Sprague-Dawley (SD) rats. This correlated with increased elastin degradation (~7 fold) and decreased arterial compliance (~75% JCR vs. SD). 20-HETE antagonists blocked elastin degradation in JCR rats concomitant with blocking MMP12 activation. 20-HETE antagonists normalized, and MMP12 inhibition (pharmacological and MMP12-shRNA-Lnv) significantly improved (~50% vs. untreated JCR) large artery compliance in JCR rats. 20-HETE antagonists also decreased systolic (182 ± 3 mmHg JCR, 145 ± 3 mmHg JCR + 20-HETE antagonists) but not diastolic blood pressure in JCR rats. Whereas diastolic pressure was fully angiotensin II (Ang II)-dependent, systolic pressure was only partially Ang II-dependent, and large artery stiffness was Ang II-independent. Thus, 20-HETE-dependent regulation of systolic blood pressure may be a unique feature of metabolic syndrome related to high 20-HETE production in large, conduit arteries, which results in increased large artery stiffness and systolic blood pressure. These findings may have implications for management of systolic hypertension in patients with metabolic syndrome.

The oral administration of clarithromycin prevents the progression and rupture of aortic aneurysm

OBJECTIVE

The pathogenesis of aortic aneurysm (AA) is associated with chronic inflammation in the aortic wall with increased levels of matrix metalloproteinases (MMPs). Clarithromycin (CAM) has been reported to suppresses MMP activity. In this study, we investigated whether CAM could prevent the formation and rupture of AA.

METHODS

Male apolipoprotein E-deficient mice (28-30 weeks of age) were infused with angiotensin II for 28 days. CAM (100 mg/kg/d) or saline (as a control) was administered orally to the mice every day (CAM group, n = 13; control group, n = 13). After the administration period, the aortic diameter, elastin content, macrophage infiltration, MMP levels, and levels of inflammatory cytokines, including nuclear factor κB (NF-κB), were measured.

RESULTS

The aortic diameter was significantly suppressed in the CAM group (P < .001). No rupture death was observed in the CAM group in contrast to five deaths (38%) in the control group (P < .01). CAM significantly suppressed the degradation of aortic elastin (56.3% vs 16.5%; P < .001) and decreased the infiltration of inflammatory macrophages (0.05 vs 0.16; P < .01). Compared with the controls, the enzymatic activity of MMP-2 and MMP-9 was significantly reduced in the CAM group (MMP-2, 0.15 vs 0.56 [P < .01]; MMP-9, 0.12 vs 0.60 [P < .01]), and the levels of interleukin 1β (346.6 vs 1066.0; P < .05), interleukin 6 (128.4 vs 346.2; P < .05), and phosphorylation of NF-κB were also decreased (0.3 vs 2.0; P < .01).

CONCLUSIONS

CAM suppressed the progression and rupture of AA through the suppression of inflammatory macrophage infiltration, a reduction in MMP-2 and MMP-9 activity, and the inhibition of elastin degradation associated with the suppression of NF-κB phosphorylation.

An evaluation of the effect of an angiotensin-converting enzyme inhibitor on the growth rate of small abdominal aortic aneurysms: a randomised placebo-controlled trial (AARDVARK)

BACKGROUND

Although data are inconsistent, angiotensin-converting enzyme inhibitors (ACE-Is) have been associated with a reduced incidence of abdominal aortic aneurysm (AAA) rupture in analysis of administrative databases.

OBJECTIVES

(1) To investigate whether or not the ACE-I perindopril (Coversyl arginine, Servier) reduces small AAA growth rate and (2) to evaluate blood pressure (BP)-independent effects of perindopril on small AAA growth and to compare the repeatability of measurement of internal and external aneurysm diameters.

DESIGN

A three-arm, multicentre, single-blind, randomised placebo-controlled trial.

SETTING

Fourteen hospitals in England.

PARTICIPANTS

Men or women aged ≥ 55 years with an AAA of 3.0-5.4 cm in diameter by internal or external measurement according to ultrasonography and who met the trial eligibility criteria.

INTERVENTIONS

Patients were randomised to receive 10 mg of perindopril arginine daily, 5 mg of the calcium channel blocker amlodipine daily or placebo daily.

MAIN OUTCOME MEASURES

The primary outcome was AAA diameter growth using external measurements in the longitudinal plane, which in-trial studies suggested was the preferred measure. Secondary outcome measures included AAA rupture, AAA repair, modelling of the time taken for the AAA to reach the threshold for intervention (5.5 cm) or referral for surgery, tolerance of study medication (measured by compliance, adverse events and quality of life) and a comparison of the repeatability of measures of internal and external AAA diameter. Patients were followed up every 3-6 months over 2 years.

RESULTS

In total, 227 patients were recruited and randomised into the three groups, which were generally well matched at baseline. Multilevel modelling was used to determine the maximum likelihood estimates for AAA diameter growth. No significant differences in the estimates of annual growth were apparent [1.68 (standard error 0.02) mm, 1.77 (0.02) mm and 1.81 (0.02) mm in the placebo, perindopril and amlodipine groups, respectively]. Similarly, no significant differences in the slopes of modelled growth over time were apparent between perindopril and placebo (p = 0.78) or between perindopril and amlodipine (p = 0.89). The results were essentially unaffected by adjustment for potential confounders. Compliance, measured by pill counts, was good throughout (> 80% at all visit time points). There were no significant in-trial safety concerns. Six patients withdrew because of adverse events attributed to the study medications (n = 2 perindopril, n = 4 amlodipine). No patients ruptured their AAA and 27 underwent elective surgery during the trial (n = 9 placebo, n = 10 perindopril, n = 8 amlodipine).

CONCLUSIONS

We were unable to demonstrate a significant impact of perindopril compared with placebo or amlodipine on small AAA growth over a 2-year period. Furthermore, there were no differences in the times to reach a diameter of 5.5 cm or undergo surgery among the three groups. Perindopril and amlodipine were well tolerated by this population. External AAA measurements were found to be more repeatable than internal measurements. The observed AAA growth measurement variability was greater than that expected pre trial. This, combined with slower than expected mean growth rates, resulted in our having limited power to detect small differences between growth rates and hence this adds uncertainty to the interpretation of the results. Several further analyses are planned including a multivariate analysis of determinants of AAA growth, an evaluation of the possible differential effect of perindopril on fast AAA growth and an investigation into the roles of central BP and BP variability on AAA growth.

TRIAL REGISTRATION

Current Controlled Trials ISRCTN51383267.

FUNDING

This project was funded by the National Institute for Health Research (NIHR) Health Technology Assessment programme and will be published in full in Health Technology Assessment; Vol. 20, No. 59. See the NIHR Journals Library website for further project information. The NIHR Biomedical Research Centre based at Imperial College NHS Trust supported the trial. Servier provided perindopril at no charge.

Inhibition or deletion of angiotensin II type 1 receptor suppresses elastase-induced experimental abdominal aortic aneurysms

OBJECTIVE

Angiotensin (Ang) II type 1 receptor (AT1) activation is essential for the development of exogenous Ang II-induced abdominal aortic aneurysms (AAAs) in hyperlipidemic animals. Experimental data derived from this modeling system, however, provide limited insight into the role of endogenous Ang II in aneurysm pathogenesis. Consequently, the potential translational value of AT1 inhibition in clinical AAA disease management remains incompletely understood on the basis of the existing literature.

METHODS

AAAs were created in wild-type (WT) and AT1a knockout (KO) mice by intra-aortic infusion of porcine pancreatic elastase (PPE). WT mice were treated with the AT1 receptor antagonist telmisartan, 10 mg/kg/d in chow, or the peroxisome proliferator-activated receptor γ (PPARγ) antagonist GW9662, 3 mg/kg/d through oral gavage, beginning 1 week before or 3 days after PPE infusion. Influences on aneurysm progression as well as mechanistic insights into AT1-mediated pathogenic processes were determined using noninvasive ultrasound imaging, histopathology, aortic gene expression profiling, and flow cytometric analysis.

RESULTS

After PPE infusion, aortic enlargement was almost completely abrogated in AT1a KO mice compared with WT mice. As defined by a ≥50% increase in aortic diameter, no PPE-infused, AT1a KO mouse actually developed an AAA. On histologic evaluation, medial smooth muscle cellularity and elastic lamellae were preserved in AT1a KO mice compared with WT mice, with marked attenuation of mural angiogenesis and leukocyte infiltration. In WT mice, telmisartan administration effectively suppressed aneurysm pathogenesis after PPE infusion as well, regardless of whether treatment was initiated before or after aneurysm creation or continued for a limited or extended time. Telmisartan treatment was associated with reduced messenger RNA levels for CCL5 and matrix metalloproteinases 2 and 9 in aneurysmal aortae, with no apparent effect on PPARγ-regulated gene expression. Administration of the PPARγ antagonist GW9662 failed to "rescue" the aneurysm phenotype in telmisartan-treated, PPE-infused WT mice. Neither effector T-cell differentiation nor regulatory T-cell cellularity was affected by telmisartan treatment status.

CONCLUSIONS

Telmisartan effectively suppresses the progression of elastase-induced AAAs without apparent effect on PPARγ activation or T-cell differentiation. These findings reinforce the critical importance of endogenous AT1 activation in experimental AAA pathogenesis and reinforce the translational potential of AT1 inhibition in medical aneurysm disease management.

Translational Relevance and Recent Advances of Animal Models of Abdominal Aortic Aneurysm

Human abdominal aortic aneurysm (AAA) pathophysiology is not yet completely understood. In conductance arteries, the insoluble extracellular matrix, synthesized by vascular smooth muscle cells, assumes the function of withstanding the intraluminal arterial blood pressure. Progressive loss of this function through extracellular matrix proteolysis is a main feature of AAAs. As most patients are now treated via endovascular approaches, surgical AAA specimens have become rare. Animal models provide valuable complementary insights into AAA pathophysiology. Current experimental AAA models involve induction of intraluminal dilation (nondissecting AAAs) or a contained intramural rupture (dissecting models). Although the ideal model should reproduce the histological characteristics and natural history of the human disease, none of the currently available animal models perfectly do so. Experimental models try to represent the main pathophysiological determinants of AAAs: genetic or acquired defects in extracellular matrix, loss of vascular smooth muscle cells, and innate or adaptive immune response. Nevertheless, most models are characterized by aneurysmal stabilization and healing after a few weeks because of cessation of the initial stimulus. Recent studies have focused on ways to optimize existing models to allow continuous aneurysmal growth. This review aims to discuss the relevance and recent advances of current animal AAA models.

Visual Overview—

An online visual overview is available for this article.

Prevention of abdominal aortic aneurysm progression by oral administration of green tea polyphenol in a rat model

OBJECTIVE

Inflammation-mediated elastin destruction in the aortic medial layer is related to progression of abdominal aortic aneurysm (AAA). Epigallocatechin-3-gallate (EGCG), a major component of green tea polyphenols, reportedly increases elastin synthesis in vitro and may possess anti-inflammatory effects. We used a rat model to investigate whether EGCG could prevent AAA progression.

METHODS

AAA was induced with administration of intraluminal elastase and extraluminal CaCl₂ in male rats. Rats were randomly divided into a control group (n = 30) and an EGCG group (n = 30). In the EGCG group, an EGCG solution (20 mg/d) was administered orally to each rat from 2 weeks before AAA induction and continued 4 weeks beyond induction.

RESULTS

The abdominal aortic diameter was significantly smaller in the EGCG group than in the control group on day 28 (2.9 ± 0.2 vs 2.3 ± 0.1 mm; P < .0001). The medial layer wall thickness and elastin content were significantly greater in the EGCG group than in the control group on day 28 (68.4 ± 13.6 vs 46.7 ± 13.4 μm [P < .001] and 20.3 ± 4.6 vs 9.5 ± 3.6% [P < .0001], respectively). Gene expression levels of tropoelastin and lysyl oxidase were significantly higher in the EGCG group immediately before AAA induction, indicating promoted elastoregeneration by EGCG administration (tropoelastin: 0.59 ± 0.36 control vs 1.24 ± 0.36 EGCG [P < .05], lysyl oxidase: 0.77 ± 0.45 control vs 1.34 ± 0.4 EGCG [P < .05]) (fold increase). Gene expression levels of inflammatory cytokines, including tumor necrosis factor-α and interleukin-1β, were significantly downregulated in the EGCG group (1.82 ± 0.71 vs 0.97 ± 0.59 [P < .05] and 3.91 ± 3.24 vs 0.89 ± 0.59 [P < .05], respectively). On day 7, gene expression levels and gelatinolytic activity of matrix metalloproteinase 9 were significantly lower in the EGCG group (1.41 ± 0.86 vs 0.51 ± 0.42 [P < .05] and 1.00 ± 0.17 vs 0.29 ± 0.12 [P < .0001], respectively), whereas gene expression levels of tissue inhibitors of metalloproteinase-1 were significantly higher in the EGCG group (0.96 ± 0.11 vs 1.14 ± 0.09; P < .05).

CONCLUSIONS

EGCG attenuated AAA progression in a rat model by preserving the aortic thickness and elastin content of the medial layer through regeneration of elastin, as mediated by anti-inflammatory effects, and subsequent reduction of matrix metalloproteinase activity.

An evaluation of the effect of an angiotensin-converting enzyme inhibitor on the growth rate of small abdominal aortic aneurysms: a randomized placebo-controlled trial (AARDVARK)

Aims

The AARDVARK (Aortic Aneurysmal Regression of Dilation: Value of ACE-Inhibition on RisK) trial investigated whether ACE-inhibition reduces small abdominal aortic aneurysms (AAA) growth rate, independent of blood pressure (BP) lowering.

Methods and results

A three-arm, multi-centre, single-blind, and randomized controlled trial (ISRCTN51383267) was conducted in 14 hospitals in England. Subjects aged ≥55 years with AAA diameter 3.0–5.4 cm were randomized 1:1:1 to receive perindopril arginine 10 mg, or amlodipine 5 mg, or placebo and followed 3–6 monthly over 2 years. The primary outcome was aneurysm growth rate (based on external antero-posterior ultrasound measurements in the longitudinal plane), determined by multi-level modelling to provide maximum likelihood estimates. Two hundred and twenty-four subjects were randomized (2011–2013) to placebo (n = 79), perindopril (n = 73), or amlodipine (n = 72). Mean (SD) changes in mid-trial systolic BP (12 months) were 0.5 (14.3) mmHg, P = 0.78 compared with baseline, −9.5 (13.1) mmHg (P < 0.001), and −6.7 (12.0) mmHg (P < 0.001), respectively. No significant differences in the modelled annual growth rates were apparent [1.68 mm (SE 0.2), 1.77 mm (0.2), and 1.81 mm (0.2), respectively]. The estimated difference in annual growth between the perindopril and placebo groups was 0.08 mm (CI −0.50, 0.65). Similar numbers of AAAs in each group reached 5.5 cm diameter and/or underwent elective surgery: 11 receiving placebo, 10 perindopril, and 11 amlodipine.

Conclusion

Small AAA growth rates were lower than anticipated, but there was no significant impact of perindopril compared with placebo or placebo and amlodipine, combined despite more effective BP lowering.

Association of diabetes mellitus with presence, expansion, and rupture of abdominal aortic aneurysm: "Curiouser and curiouser!" cried ALICE

Both coronary artery and peripheral artery disease are representative atherosclerotic diseases that are positively associated with presence of abdominal aortic aneurysm (AAA). Diabetes mellitus, which is one of major risk factors of coronary artery and peripheral artery diseases, however, has been curiously suggested to be negatively associated with AAA, despite the positive associations of coronary artery and peripheral artery diseases with presence of AAA. In the present article, we overviewed epidemiologic evidence (meta-analyses) regarding the associations of diabetes mellitus with presence, expansion, and rupture of AAA through a systematic literature search. Our exhaustive search identified seven meta-analyses. Main results of almost all meta-analyses (except for the two earliest ones) apparently found that diabetes mellitus is negatively associated with presence, expansion, and rupture of AAA.

Mast Cell: A Multi-Functional Master Cell

Mast cells are immune cells of the myeloid lineage and are present in connective tissues throughout the body. The activation and degranulation of mast cells significantly modulates many aspects of physiological and pathological conditions in various settings. With respect to normal physiological functions, mast cells are known to regulate vasodilation, vascular homeostasis, innate and adaptive immune responses, angiogenesis, and venom detoxification. On the other hand, mast cells have also been implicated in the pathophysiology of many diseases, including allergy, asthma, anaphylaxis, gastrointestinal disorders, many types of malignancies, and cardiovascular diseases. This review summarizes the current understanding of the role of mast cells in many pathophysiological conditions.

Abdominal aortic aneurysms and diabetes mellitus

There is accumulating evidence that risk profiles differ between coronary artery disease and abdominal aortic aneurysms (AAAs). However, diabetes mellitus (DM) appears to be negatively associated with AAA formation. The underlying mechanisms for this negative relationship are far from defined, but may include: increased arterial wall matrix formation via advanced glycation end products; suppression of plasmin and reduction of levels and activity of matrix metalloproteinases (MMP)-2 and 9; diminished aortic wall macrophage infiltration, elastolysis and neovascularization. In addition, the effect of pharmacological agents used for the treatment of patients with DM on AAA formation has been studied with rather controversial results. Statins, angiotensin converting enzyme inhibitors, angiotensin receptor blockers, fenofibrate, antibiotics and some hypoglycemic agents are beginning to be appreciated for a potential modest protection from AAAs, but further studies are needed.

An update on the etiology of abdominal aortic aneurysms: implications for future diagnostic testing

Abdominal aortic aneurysm (AAA) disease is multifactorial with both environmental and genetic risk factors. The current research in AAA revolves around genetic profiles and expression studies in both human and animal models. Variants in genes involved in extracellular matrix degradation, inflammation, the renin-angiotensin system, cell growth and proliferation and lipid metabolism have been associated with AAA using a variety of study designs. However, the results have been inconsistent and without a standard animal model for validation. Thus, despite the growing body of knowledge, the specific variants responsible for AAA development, progression and rupture have yet to be determined. This review explores some of the more significant genetic studies to provide an overview of past studies that have influenced the current understanding of AAA etiology. Expanding our understanding of disease pathogenesis will inform research into novel diagnostics and therapeutics and ultimately to improve outcomes for patients with AAA.

The Abdominal Aortic Aneurysm and Intraluminal Thrombus: Current Concepts of Development and Treatment

The pathogenesis of the abdominal aortic aneurysm (AAA) shows several hallmarks of atherosclerotic and atherothrombotic disease, but comprises an additional, predominant feature of proteolysis resulting in the degradation and destabilization of the aortic wall. This review aims to summarize the current knowledge on AAA development, involving the accumulation of neutrophils in the intraluminal thrombus and their central role in creating an oxidative and proteolytic environment. Particular focus is placed on the controversial role of heme oxygenase 1/carbon monoxide and nitric oxide synthase/peroxynitrite, which may exert both protective and damaging effects in the development of the aneurysm. Treatment indications as well as surgical and pharmacological options for AAA therapy are discussed in light of recent reports.

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.

The renin-angiotensin system and its involvement in vascular disease

The renin-angiotensin system (RAS) plays a critical role in the pathogenesis of many types of cardiovascular diseases including cardiomyopathy, valvular heart disease, aneurysms, stroke, coronary artery disease and vascular injury. Besides the classical regulatory effects on blood pressure and sodium homoeostasis, the RAS is involved in the regulation of contractility and remodelling of the vessel wall. Numerous studies have shown beneficial effect of inhibition of this system in the pathogenesis of cardiovascular diseases. However, dysregulation and overexpression of the RAS, through different molecular mechanisms, also induces, the initiation of vascular damage. The key effector peptide of the RAS, angiotensin II (Ang II) promotes cell proliferation, apoptosis, fibrosis, oxidative stress and inflammation, processes known to contribute to remodelling of the vasculature. In this review, we focus on the components that are under the influence of the RAS and contribute to the development and progression of vascular disease; extracellular matrix defects, atherosclerosis and ageing. Furthermore, the beneficial therapeutic effects of inhibition of the RAS on the vasculature are discussed, as well as the need for additive effects on top of RAS inhibition.

Angiotensin-Converting Enzyme Inhibitors and Angiotensin II Receptor Blockers in Patients With Abdominal Aortic Aneurysms

Objective—

The renin–angiotensin system is thought to play a pivotal role in the pathogenesis of abdominal aortic aneurysms (AAAs). However, effects of angiotensin-converting enzyme inhibitors (ACEIs) and angiotensin II type 1 receptor blockers (ARBs) on human AAAs remain unclear. We therefore examined whether treatment with ACEIs or ARBs influenced hard clinical end points in a nation-wide cohort of patients with AAA.

Approach and Results—

All patients diagnosed with AAA during the period 1995 to 2011 were identified from the Danish nation-wide registries. Subjects were divided according to ACEI and ARB treatment status and followed up for an average of 5 years. Study outcomes were evaluated by time-dependent Cox proportional hazard models. Of 9441 patients with AAA, 12.6% were treated with ACEIs and 5.0% received ARBs. Incidence rates of death from AAA per 100 patient-years were 3.7, 3.6, 4.0, and 4.7 for treatment with ACEIs or ARBs, ACEIs, ARBs, and no ACEI/ARB, respectively. Hazard ratios of death from AAA were 0.64 (95% confidence interval, 0.51–0.80; P <0.001) for patients receiving ACEIs and 0.65 (95% confidence interval, 0.48–0.88; P =0.006) for those receiving ARBs, respectively ( P for difference=0.944). The risk of surgery for AAA was significantly reduced in patients receiving ACEIs (hazard ratio, 0.86 [95% confidence interval, 0.74–0.99]; P =0.040) but not in patients receiving ARBs (hazard ratio, 1.02 [95% confidence interval, 0.84–1.23]; P =0.867; P for difference=0.119).

Conclusions—

In this observational study, treatment with ACEIs or ARBs was associated with a comparable reduction in mortality but not in surgery for AAA among patients with AAA. Randomized controlled trials are warranted to confirm these findings.

Heat shock protein 90 inhibition by 17-DMAG attenuates abdominal aortic aneurysm formation in mice

Abdominal aortic aneurysm (AAA) is a common degenerative vascular disease whose pathogenesis is associated with activation of multiple signaling pathways including Jun NH2-terminal kinases (JNK) and NF-κB. It is now well recognized that these pathways are chaperoned by the heat shock protein 90 (Hsp90), suggesting that inhibition of Hsp90 may be a novel strategy for inhibiting AAAs. The aim of this study is to investigate whether inhibition of Hsp90 by 17-DMAG (17-dimethyl-aminothylamino-17-demethoxy-geldanamycin) attenuates ANG II-induced AAA formation in mice, and, if so, to elucidate the mechanisms involved. Apolipoprotein E-null mice were infused with ANG II to induce AAA formation and simultaneously treated by intraperitoneal injection with either vehicle or 17-DMAG for 4 wk. ANG II infusion induced AAA formation in 80% of mice, which was accompanied by increased matrix metalloproteinase (MMP) activity, enhanced tissue inflammation, oxidative stress, and neovascularization. Importantly, these effects were inhibited by 17-DMAG treatment. Mechanistically, we showed that 17-DMAG prevented the formation and progression of AAA through its inhibitory effects on diverse biological pathways including 1) by blocking ANG II-induced phosphorylation of ERK1/2 and JNK that are critically involved in the regulation of MMPs in vascular smooth muscle cells, 2) by inhibiting IκB kinase expression and expression of MCP-1, and 3) by attenuating ANG II-stimulated angiogenic processes critical to AAA formation. Our results demonstrate that inhibition of Hsp90 by 17-DMAG effectively attenuates ANG II-induced AAA formation by simultaneously inhibiting vascular inflammation, extracellular matrix degradation, and angiogenesis, which are critical in the formation and progression of AAAs.

ACE inhibitors potently reduce vascular inflammation, results of an open proof-of-concept study in the abdominal aortic aneurysm

BACKGROUND

Independent of their blood pressure lowering effect, ACE inhibitors are thought to reduce vascular inflammation. The clinical relevance of this effect is unclear with the current knowledge. Abdominal aortic aneurysms (AAA) are characterized by a broad, non-specific inflammatory response, and thus provide a clinical platform to evaluate the anti-inflammatory potential of ACE inhibitors.

METHODS AND RESULTS

Eleven patients scheduled for open AAA repair received ramipril (5 mg/day) during 2-4 weeks preceding surgery. Aortic wall samples were collected during surgery, and compared to matched samples obtained from a biobank. An anti-inflammatory potential was evaluated in a comprehensive analysis that included immunohistochemistry, mRNA and protein analysis. A putative effect of ACE inhibitors on AAA growth was tested separately by comparing 18-month growth rate of patients on ACE inhibitors (n = 82) and those not taking ACE inhibitors (n = 204). Ramipril reduces mRNA expression of multiple pro-inflammatory cytokines such as IL-1β, IL-6, IL-8, TNF -α, Interferon-[Formula: see text], and MCP-1, as well as aortic wall IL-8 and MCP-1 (P = 0.017 and 0.008, respectively) protein content. The is followed by clear effects on cell activation that included a shift towards anti-inflammatory macrophage (M2) subtype. Evaluation of data from the PHAST cohort did not indicate an effect of ACE inhibitors on 18-month aneurysm progression (mean difference at 18 months: -0.24 mm (95% CI: -0.90-0.45, P = NS).

CONCLUSIONS

ACE inhibition quenches multiple aspects of vascular inflammation in AAA. However, this does not translate into reduced aneurysm growth.

TRIAL REGISTRATION

Nederlands Trial Register 1345.

Impaired glutathione redox system paradoxically suppresses angiotensin II-induced vascular remodeling

BACKGROUND

Angiotensin II (AII) plays a central role in vascular remodeling via oxidative stress. However, the interaction between AII and reduced glutathione (GSH) redox status in cardiovascular remodeling remains unknown.

METHODS

In vivo: The cuff-induced vascular injury model was applied to Sprague Dawley rats. Then we administered saline or a GSH inhibitor, buthionine sulfoximine (BSO, 30 mmol/L in drinking water) for a week, subsequently administered 4 more weeks by osmotic pump with saline or AII (200 ng/kg/minute) to the rats. In vitro: Incorporation of bromodeoxyuridine (BrdU) was measured to determine DNA synthesis in cultured rat vascular smooth muscle cells (VSMCs).

RESULTS

BSO reduced whole blood GSH levels. Systolic blood pressure was increased up to 215 ± 4 mmHg by AII at 4 weeks (p<0.01), which was not affected by BSO. Superoxide production in vascular wall was increased by AII and BSO alone, and was markedly enhanced by AII+BSO. The left ventricular weight to body weight ratio was significantly increased in AII and AII+BSO as compared to controls (2.52 ± 0.08, 2.50 ± 0.09 and 2.10 ± 0.07 mg/g respectively, p<0.05). Surprisingly, the co-treatment of BSO totally abolished these morphological changes. Although the vascular circumferential wall stress was well compensated in AII, significantly increased in AII+BSO. The anti-single-stranded DNA staining revealed increasing apoptotic cells in the neointima of injured arteries in BSO groups. BrdU incorporation in cultured VSMCs with AII was increased dose-dependently. Furthermore it was totally abolished by BSO and was reversed by GSH monoethyl ester.

CONCLUSIONS

We demonstrated that a vast oxidative stress in impaired GSH redox system totally abolished AII-induced vascular, not cardiac remodeling via enhancement of apoptosis in the neointima and suppression of cell growth in the media. The drastic suppression of remodeling may result in fragile vasculature intolerable to mechanical stress by AII.

Statin use and rupture of abdominal aortic aneurysm

BACKGROUND

Ruptured abdominal aortic aneurysm (rAAA) is associated with high mortality. Research suggests that statins may reduce abdominal aortic aneurysm (AAA) growth and improve rAAA outcomes. However, the clinical impact of statins remains uncertain in relation to both the risk and prognosis of rAAA.

METHODS

This nationwide, population-based, combined case-control and follow-up study included all patients (aged at least 50 years) with a first-time hospital admission for rAAA and 1:1 matched AAA controls without rupture in Denmark from 1996 to 2008. Individual-level data on preadmission drug use, co-morbidities, socioeconomic markers, healthcare contacts and death were obtained from Danish nationwide registries.

RESULTS

The study included 3584 cases and 3584 matched controls. Current statin use was registered for 418 patients with rAAA (11.7 per cent) and 539 AAA controls (15.0 per cent), corresponding to an age- and sex-matched odds ratio (OR) of 0.70 (95 per cent confidence interval (c.i.) 0.60 to 0.81) for rAAA in current statin users versus never users. The decreased risk of rAAA remained after adjustment for potential confounding factors (adjusted OR 0.73, 0.61 to 0.86). The overall 30-day mortality rate from time of hospital admission among patients with rAAA was 46.1 per cent in current statin users compared with 59.3 per cent in never users (adjusted mortality rate ratio (MRR) 0.80, 95 per cent c.i. 0.68 to 0.95). Patients who had formerly used statins did not have reduced mortality (adjusted MRR 0.98, 0.78 to 1.22).

CONCLUSION

Statin use was associated with a reduced risk of rAAA and lower case fatality following rAAA. These results support current guidelines that recommend statin therapy in patients diagnosed with AAA.

Abdominal aortic aneurysms targeted by functionalized polysaccharide microparticles: a new tool for SPECT imaging

Aneurysm diagnostic is nowadays limited by the lack of technology that enables early detection and rupture risk prediction. New non invasive tools for molecular imaging are still required. In the present study, we present an innovative SPECT diagnostic tool for abdominal aortic aneurysm (AAA) produced from injectable polysaccharide microparticles radiolabeled with technetium 99m (^99mTc) and functionalized with fucoidan, a sulfated polysaccharide with the ability to target P-Selectin. P-Selectin is a cell adhesion molecule expressed on activated endothelial cells and platelets which can be found in the thrombus of aneurysms, as well as in other vascular pathologies.

Microparticles with a maximum hydrodynamic diameter of 4 µm were obtained by crosslinking the polysaccharides dextran and pullulan. They were functionalized with fucoidan. In vitro interactions with human activated platelets were assessed by flow cytometry that demonstrated a specific affinity of fucoidan functionalized microparticles for P-Selectin expressed by activated platelets. For in vivo AAA imaging, microparticles were radiolabeled with ^99mTc and intravenously injected into healthy and AAA rats obtained by elastase perfusion through the aorta wall. Animals were scanned by SPECT imaging. A strong contrast enhancement located in the abdominal aorta of AAA rats was obtained, while no signal was obtained in healthy rats or in AAA rats after injection of non-functionalized control microparticles. Histological studies revealed that functionalized radiolabeled polysaccharide microparticles were localized in the AAA wall, in the same location where P-Selectin was expressed.

These microparticles therefore constitute a promising SPECT imaging tool for AAA and potentially for other vascular diseases characterized by P-Selectin expression. Future work will focus on validating the efficiency of the microparticles to diagnose these other pathologies and the different stages of AAA. Incorporation of a therapeutic molecule is also considered.