Macrophage migration inhibitory factor is associated with aneurysmal expansion

Medical treatments for abdominal aortic aneurysm: an overview of clinical trials

INTRODUCTION

Abdominal aortic aneurysm is a progressive, segmental, abdominal aortic dilation associated with a high mortality rate. Abdominal aortic aneurysms with diameters larger than 55 mm are associated with a high risk of rupture, and the most effective treatment options are surgical repair. Close observation and lifestyle adjustments are recommended for smaller abdominal aortic aneurysms with lower rupture risk. The development of medical therapies that limit or prevent the progression, expansion, and eventual rupture of abdominal aortic aneurysms remains an unmet clinical need.

AREAS COVERED

This review provides an overview of completed and ongoing clinical trials examining the efficacies of various drug classes, including antibiotics, antihypertensive drugs, hypolipidemic drugs, hypoglycemic drugs, and other potential therapies for abdominal aortic aneurysms. A search of PubMed, Web of Science, Clinical Trials, and another six clinical trial registries was conducted in January 2024.

EXPERT OPINION

None of the drugs have enough evidence to indicate that they can effectively inhibit the dilation of abdominal aortic aneurysm. More clinical trial data is required to support the efficacy of propranolol. Future research should also explore different drug delivery mechanisms, such as nanoparticles, to elevate drug concentration at the aneurysm wall.

The contribution of matrix metalloproteinases and their inhibitors to the development, progression, and rupture of abdominal aortic aneurysms

Abdominal aortic aneurysms (AAAs) account for up to 8% of deaths in men aged 65 years and over and 2.2% of women. Patients with AAAs often have atherosclerosis, and intimal atherosclerosis is generally present in AAAs. Accordingly, AAAs are considered a form of atherosclerosis and are frequently referred to as atherosclerotic aneurysms. Pathological observations advocate inflammatory cell infiltration alongside adverse extracellular matrix degradation as key contributing factors to the formation of human atherosclerotic AAAs. Therefore, macrophage production of proteolytic enzymes is deemed responsible for the damaging loss of ECM proteins, especially elastin and fibrillar collagens, which characterise AAA progression and rupture. Matrix metalloproteinases (MMPs) and their regulation by tissue inhibitors metalloproteinases (TIMPs) can orchestrate not only ECM remodelling, but also moderate the proliferation, migration, and apoptosis of resident aortic cells, alongside the recruitment and subsequent behaviour of inflammatory cells. Accordingly, MMPs are thought to play a central regulatory role in the development, progression, and eventual rupture of abdominal aortic aneurysms (AAAs). Together, clinical and animal studies have shed light on the complex and often diverse effects MMPs and TIMPs impart during the development of AAAs. This dichotomy is underlined from evidence utilising broad-spectrum MMP inhibition in animal models and clinical trials which have failed to provide consistent protection from AAA progression, although more encouraging results have been observed through deployment of selective inhibitors. This review provides a summary of the supporting evidence connecting the contribution of individual MMPs to AAA development, progression, and eventual rupture. Topics discussed include structural, functional, and cell-specific diversity of MMP members; evidence from animal models of AAA and comparisons with findings in humans; the dual role of MMPs and the requirement to selectively target individual MMPs; and the advances in identifying aberrant MMP activity. As evidenced, our developing understanding of the multifaceted roles individual MMPs perform during the progression and rupture of AAAs, should motivate clinical trials assessing the therapeutic potential of selective MMP inhibitors, which could restrict AAA-related morbidity and mortality worldwide.

Associations of aortic stiffness and intra-aortic flow parameters with epicardial adipose tissue in patients with type-2 diabetes

Background

It has been shown that increased aortic stiffness is related to type-2 diabetes (T2D) which is considered as a risk factor for cardiovascular disease. Among other risk factors is epicardial adipose tissue (EAT) which is increased in T2D and is a relevant biomarker of metabolic severity and adverse outcome.

Purpose

To assess aortic flow parameters in T2D patients as compared to healthy individuals and to evaluate their associations with EAT accumulation as an index of cardiometabolic severity in T2D patients.

Materials and methods

Thirty-six T2D patients as well as 29 healthy controls matched by age and sex were included in this study. Participants had cardiac and aortic MRI exams at 1.5 T. Imaging sequences included cine SSFP for left ventricle (LV) function and EAT assessment and aortic cine and phase-contrast imaging for strain and flow parameters quantification.

Results

In this study, we found LV phenotype to be characterized by concentric remodeling with decreased stroke volume index despite global LV mass within a normal range. EAT was increased in T2D patients compared to controls (p<0.0001). Moreover, EAT, a biomarker of metabolic severity, was negatively correlated to ascending aortic (AA) distensibility (p=0.048) and positively to the normalized backward flow volume (p=0.001). These relationships remained significant after further adjustment for age, sex and central mean blood pressure. In a multivariate model, presence/absence of T2D and AA normalized backward flow (BF) to forward flow (FF) volumes ratio are both significant and independent correlates of EAT.

Conclusion

In our study, aortic stiffness as depicted by an increased backward flow volume and decreased distensibility seems to be related to EAT volume in T2D patients. This observation should be confirmed in the future on a larger population while considering additional biomarkers specific to inflammation and using a longitudinal prospective study design.

Blood immunological profile of abdominal aortic aneurysm based on autoimmune injury

Abdominal aortic aneurysm (AAA) occupies a large part of aorta aneurysm, and if there's no timely intervention or treatment, the risks of rupture and death would rise sharply. With the depth of research in AAA, more and more evidence showed correlations between AAA and autoimmune injury. Currently, a variety of bioactive peptides and cells have been confirmed to be related with AAA progression. Despite the tremendous progress, more than half researches were sampling from lesion tissues, which would be difficult to obtain. Given that the intrusiveness and convenience, serological test take advantages in initial diagnosis. Here we review blood biomarkers associated with autoimmune injury work in AAA evolution, aiming to make a profile on blood immune substances of AAA and provide a thought for potential clinical practice.

Plasma complement component C2: a potential biomarker for predicting abdominal aortic aneurysm related complications

Blood-based adjunctive measures that can reliably predict abdominal aortic aneurysm (AAA)-related complications hold promise for mitigating the AAA disease burden. In this pilot study, we sought to evaluate the prognostic performance of complement factors in predicting AAA-related clinical outcomes. We recruited consecutive AAA patients (n = 75) and non-AAA patients (n = 75) presenting to St. Michael's Hospital. Plasma levels of complement proteins were assessed at baseline, as well as prospectively measured regularly over a period of 2 years. The primary outcome was the incidence of rapidly progressing AAA (i.e. aortic expansion), defined as change in AAA diameter by either 0.5 cm in 6 months, or 1 cm in 12 months. Secondary outcomes included incidence of major adverse aortic events (MAAE) and major adverse cardiovascular events (MACE). All study outcomes (AAA diameter, MACE and MAAE) were obtained during follow-up. Multivariable adjusted Cox regression analyses were performed to assess the prognostic value of plasma C2 levels in patients with AAA regarding rapid aortic expansion and MAAE and MACE. Event-free survival rates of both groups were also compared. Compared to non-AAA patients, patients with AAA demonstrated significantly higher plasma concentrations of C1q, C4, Factor B, Factor H and Factor D, and significantly lower plasma concentrations of C2, C3, and C4b (p = 0.001). After a median of 24 months from initial baseline measurements, C2 was determined as the strongest predictor of rapid aortic expansion (HR 0.10, p = 0.040), MAAE (HR 0.09, p = 0.001) and MACE (HR 0.14, p = 0.011). Based on the data from the survival analysis, higher levels of C2 at admission in patients with AAA predicted greater risk for rapid aortic expansion and MAAE (not MACE). Plasma C2 has the potential to be a biomarker for predicting rapid aortic expansion, MAAE, and the eventual need for an aortic intervention in AAA patients.

Bioinformatics Analysis Reveals the Potential Diagnostic Biomarkers for Abdominal Aortic Aneurysm

Objectives: Abdominal aortic aneurysms (AAAs) are associated with high mortality rates. The genes and pathways linked with AAA remain poorly understood. This study aimed to identify key differentially expressed genes (DEGs) linked to the progression of AAA using bioinformatics analysis.

Methods: Gene expression profiles of the GSE47472 and GSE57691 datasets were acquired from the Gene Expression Omnibus (GEO) database. These datasets were merged and normalized using the “sva” R package, and DEGs were identified using the limma package in R. The functions of these DEGs were assessed using Cytoscape software. We analyzed the DEGs using Gene Ontology and Kyoto Encyclopedia of Genes and Genomes pathway enrichment analysis. Protein–protein interaction networks were assembled using Cytoscape, and crucial genes were identified using the Cytoscape plugin, molecular complex detection. Data from GSE15729 and GSE24342 were also extracted to verify our findings.

Results: We found that 120 genes were differentially expressed in AAA. Genes associated with inflammatory responses and nuclear-transcribed mRNA catabolic process were clustered in two gene modules in AAA. The hub genes of the two modules were IL6, RPL21, and RPL7A. The expression levels of IL6 correlated positively with RPL7A and negatively with RPL21. The expression of RPL21 and RPL7A was downregulated, whereas that of IL6 was upregulated in AAA.

Conclusions: The expression of RPL21 or RPL7A combined with IL6 has a diagnostic value for AAA. The novel DEGs and pathways identified herein might provide new insights into the underlying molecular mechanisms of AAA.

Involvement of Myeloid Cells and Noncoding RNA in Abdominal Aortic Aneurysm Disease

Significance: Abdominal aortic aneurysm (AAA) is a potentially fatal condition, featuring the possibility of high-mortality rupture. To date, prophylactic surgery by means of open surgical repair or endovascular aortic repair at specific thresholds is considered standard therapy. Both surgical options hold different risk profiles of short- and long-term morbidity and mortality. Targeting early stages of AAA development to decelerate disease progression is desirable. Recent Advances: Understanding the pathomechanisms that initiate formation, maintain growth, and promote rupture of AAA is crucial to developing new medical therapeutic options. Inflammatory cells, in particular macrophages, have been investigated for their contribution to AAA disease for decades, whereas evidence on lymphocytes, mast cells, and neutrophils is sparse. Recently, there has been increasing interest in noncoding RNAs (ncRNAs) and their involvement in disease development, including AAA. Critical Issues: The current evidence on myeloid cells and ncRNAs in AAA largely originates from small animal models, making clinical extrapolation difficult. Although it is feasible to collect surgical human AAA samples, these tissues reflect end-stage disease, preventing examination of critical mechanisms behind early AAA formation. Future Directions: Gaining more insight into how myeloid cells and ncRNAs contribute to AAA disease, particularly in early stages, might suggest nonsurgical AAA treatment options. The utilization of large animal models might be helpful in this context to help bridge translational results to humans.

Systematic Review of Circulating, Biomechanical, and Genetic Markers for the Prediction of Abdominal Aortic Aneurysm Growth and Rupture

BACKGROUND

The natural course of abdominal aortic aneurysms (AAA) is growth and rupture if left untreated. Numerous markers have been investigated; however, none are broadly acknowledged. Our aim was to identify potential prognostic markers for AAA growth and rupture.

METHODS AND RESULTS

Potential circulating, biomechanical, and genetic markers were studied. A comprehensive search was conducted in PubMed, Embase, and Cochrane Library in February 2017, following Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Study selection, data extraction, and methodological quality assessment were conducted by 2 independent researchers. Plausibility of markers was based on the amount of publications regarding the marker (more than 3), pooled sample size (more than 100), bias risk and statistical significance of the studies. Eighty-two studies were included, which examined circulating (n=40), biomechanical (n=27), and genetic markers (n=7) and combinations of markers (n=8). Factors with an increased expansion risk included: AAA diameter (9 studies; n=1938; low bias risk), chlamydophila pneumonia (4 studies; n=311; medium bias risk), S-elastin peptides (3 studies; n=205; medium bias risk), fluorodeoxyglucose uptake (3 studies; n=104; medium bias risk), and intraluminal thrombus size (5 studies; n=758; medium bias risk). Factors with an increased rupture risk rupture included: peak wall stress (9 studies; n=579; medium bias risk) and AAA diameter (8 studies; n=354; medium bias risk). No meta-analysis was conducted because of clinical and methodological heterogeneity.

CONCLUSIONS

We identified 5 potential markers with a prognostic value for AAA growth and 2 for rupture. While interpreting these data, one must realize that conclusions are based on small sample sizes and clinical and methodological heterogeneity. Prospective and methodological consonant studies are strongly urged to further study these potential markers.

Novel biomarkers of abdominal aortic aneurysm disease: identifying gaps and dispelling misperceptions

Abdominal aortic aneurysm (AAA) is a prevalent and potentially life-threatening disease. Early detection by screening programs and subsequent surveillance has been shown to be effective at reducing the risk of mortality due to aneurysm rupture. The aim of this review is to summarize the developments in the literature concerning the latest biomarkers (from 2008 to date) and their potential screening and therapeutic values. Our search included human studies in English and found numerous novel biomarkers under research, which were categorized in 6 groups. Most of these studies are either experimental or hampered by their low numbers of patients. We concluded that currently no specific laboratory markers allow screeing for the disease and monitoring its progression or the results of treatment. Further studies and studies in larger patient groups are required in order to validate biomarkers as cost-effective tools in the AAA disease.

MIF, CD74 and other partners in kidney disease: tales of a promiscuous couple

Macrophage migration inhibitory factor (MIF) is increased in kidney and urine during kidney disease. MIF binds to and activates CD74 and chemokine receptors CXCR2 and CXCR4. CD74 is a protein trafficking regulator and a cell membrane receptor for MIF, D-dopachrome tautomerase (D-DT/MIF-2) and bacterial proteins. MIF signaling through CD74 requires CD44. CD74, CD44 and CXCR4 are upregulated in renal cells in diseased kidneys and MIF activation of CD74 in kidney cells promotes an inflammatory response. MIF or CXCR2 targeting protects from experimental kidney injury, CD44 deficiency modulates kidney injury and CXCR4 activation promotes glomerular injury. However, the contribution of MIF or MIF-2 to these actions of MIF receptors has not been explored. The safety and efficacy of strategies targeting MIF, CD74, CD44 and CXCR4 are under study in humans.

Management of small asymptomatic abdominal aortic aneurysms - a review

The approach for abdominal aortic aneurysms (AAAs) larger than 55 mm is well defined due to the risk of rupture being higher than 10% per year, and a 30-day perioperative mortality rate between 2.5% and 5%. However, the approach for small asymptomatic AAAs is less well defined.There are different definitions given to describe a small AAA. The one the authors accepted and applied is "a localized, permanent and irreversible dilation of the aorta of at least 50% in relation to the normal adjacent infrarenal or suprarenal aorta, with a maximum diameter between 30-55 mm".The investigators of the largest study on small AAAs (United Kingdom Small Aneurysm Trial [UK-SAT]) concluded, in brief, that ultrasound monitoring is the most appropriate solution because the results do not support a policy of surgical restoration for AAAs with a diameter of between 40 mm and 55 mm.The aim of the present review article is to highlight several challenges that could change the limits or create a more flexible deciding factor in the management of AAAs. There are multiple factors that influence surgical decision-making, and the limit on aneurysm diameter that indicates surgery should depend on the patient's age, life expectancy, general status, associated diseases, diameter in relation to body mass, risk factors, sex, anxiety and compliance during the follow-up period. Monitoring is an acceptable alternative for AAAs between 40 mm and 55 mm, and is probably the best solution for high-risk patients. Surgery is the most reasonable solution for patients who are at moderate risk, have a significant life expectancy, are less than 70 to 75 years of age, and/or have aortic aneurysms larger than 50 mm.

Prediction of asymptomatic abdominal aortic aneurysm expansion by means of rate of variation of C-reactive protein plasma levels

OBJECTIVE

C-reactive protein (CRP) is an independent risk factor for arteriosclerosis, but its role in abdominal aortic aneurysm (AAA) expansion remains not completely verified. There are no data about the prognostic significance of rates of variation of the CRP levels in asymptomatic AAAs. This study investigated the association between plasma CRP levels and AAA diameter and assessed the relationship between the gradient of CRP levels and rates of expansion in asymptomatic AAAs.

METHODS

Plasma levels of high-sensitive CRP (hs-CRP) were measured using a high-sensitivity technique and AAA size was determined by computed tomography in 435 patients with asymptomatic AAAs followed up in our outpatient department.

RESULTS

The median hs-CRP level was 4.23 mg/L. The aorta diameter increased in the four groups of patients determined according to hs-CRP quartiles (35 ± 2, 40 ± 3, 49 ± 4, and 58 ± 5 mm; P = .01). The median rate of CRP level variation per year was 1.4 mg/L. Patients with an elevation >1.4 mg/L had an expansion rate of 4.8 mm vs 3.9 mm in those <1.4 mg/L (P < .01). The multivariate age-adjusted logistic model confirmed initial diameter and variation of CRP level were the only factors associated with expansion, with odds ratios (95% confidence intervals) of 6.3 (3.1-7.5) and 3.4 (2.1-5.6).

CONCLUSIONS

These results confirm a statistical association between AAA diameter and hs-CRP plasma levels. This cohort study corroborates this potential causal association and contributes information about the value of the hs-CRP plasma level gradient as a marker of disease progression and rate of expansion.

Chinese red yeast rice attenuates the development of angiotensin II-induced abdominal aortic aneurysm and atherosclerosis

OBJECTIVE

Abdominal aortic aneurysm (AAA) is a chronic vascular disease characterized by medial degradation and inflammation. No medical approaches have been validated for treating AAA, and therapeutic options are limited to regular surveillance leading to surgical intervention. This study aimed to investigate whether administration of Chinese red yeast rice (Monascus purpureus; RYR) suppressed angiotensin II (AngII)-induced AAA and atherosclerosis.

METHODS AND RESULTS

Apolipoprotein E-deficient male mice fed a normal diet were administered either RYR extract (200 mg/kg/day) or vehicle by gavage for 1 week before initiating AngII infusion (1000 ng/kg/min) via subcutaneous osmotic pumps for 28 days. Red yeast rice extract administration significantly suppressed AngII-induced expansion of suprarenal diameter and area (P<.05). Furthermore, RYR extract significantly reduced atherosclerotic lesion areas in both the intima of aortic arches and cross sections of aortic roots (P<.05). These effects were associated with reductions of serum total cholesterol, intercellular adhesion molecule 1, vascular cell adhesion molecule 1, matrix metalloproteinase (MMP) 2 and increases of serum macrophage migration inhibitory factor, but no changes in serum interleukin (IL) 1α, IL-6, monocyte chemoattractant protein 1, MMP-9 and expression of MMP-2 and MMP-9 in aortic walls.

CONCLUSIONS

This study demonstrated that RYR extract administration suppressed AngII-induced AAA and atherosclerosis associated with regulating inflammation responses independent of lipid-lowering effects. Red yeast rice may have preventive potential for patients with AAA.

Diagnostic and therapeutic strategies for small abdominal aortic aneurysms

Abdominal aortic aneurysms (AAA) affect 5% of the population in developed countries and are characterized by progressive aortic dilatation with an unpredictable time course. This condition is more common in men than in women, and in smokers than in nonsmokers. If left untreated, AAA can result in aortic rupture and death. Pathologically, aortic extracellular matrix degradation, inflammation, and neovascularization are hallmarks of AAA. Diagnosis of AAA and subsequent surveillance utilize established aortic imaging methods, such as ultrasound, CT, and MRI. More-speculative diagnostic approaches include molecular and cellular imaging methods that interrogate the underlying pathological processes at work within the aneurysm. In this Review, we explore the current diagnostic and therapeutic strategies for the management of AAA. We also describe the diagnostic potential of new imaging techniques and therapeutic potential of new treatments for the management of small AAA.

Inflammation and cancer: macrophage migration inhibitory factor (MIF)--the potential missing link

Macrophage migration inhibitory factor (MIF) was the original cytokine, described almost 50 years ago and has since been revealed to be an important player in pro-inflammatory diseases. Recent work using MIF mouse models has revealed new roles for MIF. In this review, we present an increasing body of evidence implicating the key pro-inflammatory cytokine MIF in specific biological activities related directly to cancer growth or contributing towards a microenvironment favouring cancer progression.

Increased levels of thioredoxin in patients with abdominal aortic aneurysms (AAAs). A potential link of oxidative stress with AAA evolution

OBJECTIVE

Oxidative stress is a main mechanism involved in vascular pathologies. Increased thioredoxin (TRX) levels have been observed in several oxidative stress-associated cardiovascular diseases. We aim to test the potential role of TRX as a biomarker of oxidative stress in abdominal aortic aneurysm (AAA).

METHODS

TRX levels were analysed in both AAA intraluminal thrombus (ILT) tissue and in tissue-conditioned media by immunohistochemistry, Western blot and ELISA. Moreover, serum TRX levels were assessed in AAA Caucasian patients by ELISA.

RESULTS

TRX was mainly localized in the luminal part of ILT in AAA. Compared with the abluminal layer, TRX release was increased in the luminal layer of the ILT of AAA (31+/-9 ng/ml vs. 9+/-3 ng/ml, p<0.05). The interest of this approach is that we can identify proteins potentially released into the blood compartment, which could serve as biomarkers of the pathology. In a training population, serum TRX levels were significantly increased in patients with AAA relative to healthy subjects (50+/-6 ng/ml vs. 26+/-3 ng/ml, p<0.05). These results were validated in a second independent group of patients. Moreover, a positive correlation between TRX and AAA size (rho=0.5, p<0.001) was observed. Finally, in AAA samples with follow-up, TRX was positively associated to aneurismal growth rate (rho=0.25, p=0.027).

CONCLUSIONS

TRX release is increased in the luminal part of AAA and TRX serum levels are increased in AAA patients compared with healthy subjects. TRX levels correlates with AAA size and expansion, suggesting its potential role as a biomarker of AAA evolution.

Apoptotic cell death and rupture of abdominal aortic aneurysm

The abdominal aortic aneurysm (AAA) development and expansion is characterized by an extracellular matrix degradation and widespread inflammation. In contrast, the processes that characterize the AAA rupture are not completely understood. The results obtained in animal and clinical studies have shown the importance of inflammation, proteolysis, and antioxidant mechanisms in the aortic degeneration and formation of AAA. We hypothesize that the rupture of the AAA could have a similar pathway like an atherosclerotic plaque rupture, and in both the cases the apoptotic cell death of smooth muscle cells could play a significant role. If the apoptotic cell death significantly contributes to the expansion and rupture of aneurysm, the hypothesis is that aggressive medical antiapoptotic treatment with high doses of appropriate drugs could decrease the apoptotic index of smooth muscle cells, reduce the aneurysm expansion and prevent rupture.

Critical role of mast cell chymase in mouse abdominal aortic aneurysm formation

BACKGROUND

Mast cell chymase may participate in the pathogenesis of human abdominal aortic aneurysm (AAA), yet a direct contribution of this serine protease to AAA formation remains unknown.

METHODS AND RESULTS

Human AAA lesions had high numbers of chymase-immunoreactive mast cells. Serum chymase level correlated with AAA growth rate (P=0.009) in a prospective clinical study. In experimental AAA produced by aortic elastase perfusion in wild-type (WT) mice or those deficient in the chymase ortholog mouse mast cell protease-4 (mMCP-4) or deficient in mMCP-5 (Mcpt4(-/-), Mcpt5(-/-)), Mcpt4(-/-) but not Mcpt5(-/-) had reduced AAA formation 14 days after elastase perfusion. Even 8 weeks after perfusion, aortic expansion in Mcpt4(-/-) mice fell by 50% compared with that of the WT mice (P=0.0003). AAA lesions in Mcpt4(-/-) mice had fewer inflammatory cells and less apoptosis, angiogenesis, and elastin fragmentation than those of WT mice. Although Kit(W-sh/W-sh) mice had protection from AAA formation, reconstitution with mast cells from WT mice, but not those from Mcpt4(-/-) mice, partially restored the AAA phenotype. Mechanistic studies suggested that mMCP-4 regulates expression and activation of cysteine protease cathepsins, elastin degradation, angiogenesis, and vascular cell apoptosis.

CONCLUSIONS

High chymase-positive mast cell content in human AAA lesions, greatly reduced AAA formation in Mcpt4(-/-) mice, and significant correlation of serum chymase levels with human AAA expansion rate suggests participation of mast cell chymase in the progression of human and mouse AAA.

Differential regulation of aortic growth in male and female rodents is associated with AAA development

BACKGROUND

The objective was to examine effects of gonadal hormone manipulation on aortic diameter and macrophage infiltration in rodents during abdominal aortic aneurysm (AAA) formation.

METHODS

Experiment 1: 17-beta estradiol and testosterone pellets were implanted in male (ME) and female (FT) rats. No pellet was implanted in shams (MES, FTS). Experiment 2: Testes and ovaries were removed from males (MO) and females (FO), respectively. No organs were removed from shams (MOS, FOS). Experiment 3: Male and female rats were orchiectomized and oophorectomized, respectively. Four weeks post-castration, testosterone (MOT) and 17-beta estradiol (FOE) pellets were implanted. Shams underwent castration, but no pellet was implanted (MOTS, FOES). All rats underwent infrarenal aortic infusion with elastase postimplantation/postcastration. Diameters were measured on postoperative d 14. Tissue was stained for macrophages by immunohistochemistry.

RESULTS

Diameter (P = 0.046) and macrophage counts (P = 0.014) decreased in ME compared with shams, but not in females treated with testosterone (FT). Diameter (P = 0.019) and macrophage infiltration (P = 0.024) decreased in MO compared with shams, but not in FO. Diameter increased in MOT compared with MOTS (P = 0.033), but decreased in FOE compared with FOES (P = 0.002). Macrophages decreased in FOE compared with FOES (P = 0.002).

CONCLUSION

This study documents a decrease in AAA diameter in males treated with estrogen or undergoing orchiectomy, but no changes in females treated with testosterone or undergoing oophorectomy; and an increase in diameter in MOT and a decrease in FOE. These data suggest that gonadal hormones differentially regulate AAA growth in association with changes in macrophages.

Increase of macrophage migration inhibitory factor (MIF) expression in cardiomyocytes during chronic hypoxia

BACKGROUND

Macrophage migration inhibitory factor (MIF) might play an important role in the myocardium during chronic hypoxia because MIF protects the heart during myocardial ischemia by activating 5'-adenosine monophosphate activated protein kinase (AMPK).

METHODS

We investigated 35 infants with cyanotic or acyanotic cardiac defects and H9c2 embryonic rat cardiomyocytes to examine the effect of chronic hypoxia on the expression of MIF in vivo and in vitro, respectively.

RESULTS

We found out an increase of endogenous cardiac MIF expression positively correlated with degree of hypoxia. Also, AMPK activation was elevated while MIF expression was increased in cells exposed to long periods of hypoxia in vitro. There was no significant difference in the growth ratio of cells cultivated in long periods of hypoxia and normoxia.

CONCLUSIONS

The expression of MIF is significantly increased in cardiomyocytes exposed to chronic hypoxia, and the activation of AMPK was increased accordingly.

Macrophage migration inhibitory factor in cardiovascular disease

The highly conserved and archetypical yet atypical cytokine macrophage migration inhibitory factor (MIF) fulfills pleiotropic immune functions in many acute and chronic inflammatory diseases. Recent evidence has emerged from both expression and functional studies to implicate MIF in various aspects of cardiovascular disease. The present review is aimed at providing a synopsis of the involvement of MIF in the inflammatory pathogenesis of atherosclerosis and its consequences, namely unstable plaque formation, remodeling after arterial injury, aneurysm formation, myocardial infarction, or ischemia-reperfusion injury. In addition, other forms of myocardial dysfunction and inflammation and the role of MIF in angiogenesis are reviewed. The functional data are reconciled with recent progress in the identification of heptahelical (CXC chemokine) receptors for MIF, its prototypic role as their noncanonical ligand, and its signal transduction profile operative in atherogenic and inflammatory recruitment of mononuclear cells and in the oxidative damage and apoptosis of cardiomyocytes. Its unique features and functions clearly distinguish MIF from other cytokines implicated in atherogenesis and make it a prime target for achieving therapeutic regression of atherosclerosis. The potential of targeting or exploiting MIF for therapeutic strategies or as a diagnostic marker in the management of cardiovascular diseases or disorders is scrutinized.

Potential circulating biomarkers for abdominal aortic aneurysm expansion and rupture--a systematic review

BACKGROUND

The maximal diameter of abdominal aortic aneurysms (AAAs) is the dominating indication for repair. However half of the AAAs repaired would never have ruptured if left unrepaired, although small AAAs occasionally rupture. Earlier surgery may be associated with a lower mortality. More precise indicators for surgery are warranted. This systematic review identifies potential systemic biomarkers for AAA rupture or expansion.

METHODS

MEDLINE/PubMed and EMBASE (from 1985 trough May 2007) were searched with the medical subject heading abdominal aortic aneurysm and keywords "size", "progression" or "growth" or "expansion rate" or "rupture" on the basis of MESH tree and as a text search restricted to English, German, French and Italian. In addition, reference lists were studied and manual searches performed. Observational studies investigating the association of circulating biomarkers with AAA rupture, expansion or size were selected.

DATA EXTRACTION

Two reviewers (SU and GU) independently extracted the following data: year of publication, study characteristics, duration of follow-up, circulating biomarker, AAA expansion rate or size or rupture.

RESULTS

699 papers were identified. After exclusion of thoracic aneurysms and cardiac studies (n=118), surgical or medical treatment studies (n=179), case reports and animal studies (n=87), as well as reviews or letters (n=66), 249 articles were selected. Also excluded were 230 papers that did not report AAA size, expansion rate or rupture. 39 papers were included. Several potential biomarkers were identified. The strongest association with AAA was obtained with serum elastin peptides (SEP) and plasmin-antiplasmin (PAP) complexes. Matrix-degrading metalloproteinase 9 (MMP9) and interferon-gamma (IFN-gamma) could have clinical potential while many putative biomarkers showed poor association.

CONCLUSIONS

Several circulating agents in peripheral blood may predict AAA size, expansion rate or rupture. Few of them have clinical potential for future use. Confirmative studies and development of multivariate models are needed, together with continuing search for new biomarkers using the discovery based sciences within proteomics and/or genomics.

Chemokine-like functions of MIF in atherosclerosis

The cytokine macrophage migration inhibitory factor (MIF) is a unique pro-inflammatory regulator of many acute and chronic inflammatory diseases. In the pathogenesis of atherosclerosis, chronic inflammation of the arterial wall characterized by chemokine-mediated influx of leukocytes plays a central role. The contribution of MIF to atherosclerotic vascular disease has come into focus of many studies in recent years. MIF is highly expressed in macrophages and endothelial cells of different types of atherosclerotic plaques, and functional studies established the contribution of MIF to lesion progression and plaque inflammation. This proatherogenic effect may partly be explained by the finding that MIF regulates inflammatory cell recruitment to lesion areas. Similar to chemokines, MIF induces integrin-dependent arrest and transmigration of monocytes and T cells. These chemokine-like functions are mediated through interaction of MIF with the chemokine receptors CXCR2 and CXCR4 as a non-canonical ligand. In atherogenic monocyte recruitment, MIF-induced monocyte adhesion involves CD74 and CXCR2, which form a signaling receptor complex. In addition to lesion progression, MIF has been implicated in plaque destabilization, since MIF is predominantly expressed in vulnerable plaques and can induce collagen-degrading matrix metalloproteinases. The latter could be a relevant mechanism in atherosclerotic abdominal aneurysm formation, where MIF expression is correlated with aneurysmal expansion. In summary, MIF has been identified as an important regulator of atherosclerotic vascular disease with exceptional chemokine-like functions. Detailed analysis of the interaction of MIF with its receptors could provide valuable information for drug development for the anti-inflammatory treatment of established and unstable atherosclerosis.

Gene expression signature in peripheral blood detects thoracic aortic aneurysm

Background

Thoracic aortic aneurysm (TAA) is usually asymptomatic and associated with high mortality. Adverse clinical outcome of TAA is preventable by elective surgical repair; however, identifying at-risk individuals is difficult. We hypothesized that gene expression patterns in peripheral blood cells may correlate with TAA disease status. Our goal was to identify a distinct gene expression signature in peripheral blood that may identify individuals at risk for TAA.

Methods and Findings

Whole genome gene expression profiles from 94 peripheral blood samples (collected from 58 individuals with TAA and 36 controls) were analyzed. Significance Analysis of Microarray (SAM) identified potential signature genes characterizing TAA vs. normal, ascending vs. descending TAA, and sporadic vs. familial TAA. Using a training set containing 36 TAA patients and 25 controls, a 41-gene classification model was constructed for detecting TAA status and an overall accuracy of 78±6% was achieved. Testing this classifier on an independent validation set containing 22 TAA samples and 11 controls yielded an overall classification accuracy of 78%. These 41 classifier genes were further validated by TaqMan® real-time PCR assays. Classification based on the TaqMan® data replicated the microarray results and achieved 80% classification accuracy on the testing set.

Conclusions

This study identified informative gene expression signatures in peripheral blood cells that can characterize TAA status and subtypes of TAA. Moreover, a 41-gene classifier based on expression signature can identify TAA patients with high accuracy. The transcriptional programs in peripheral blood leading to the identification of these markers also provide insights into the mechanism of development of aortic aneurysms and highlight potential targets for therapeutic intervention. The classifier genes identified in this study, and validated by TaqMan® real-time PCR, define a set of promising potential diagnostic markers, setting the stage for a blood-based gene expression test to facilitate early detection of TAA.

Malondialdehyde as an indicator of oxidative stress during abdominal aortic aneurysm repair

Ischemia-reperfusion injury significantly contributes to abdominal aortic aneurysm (AAA)- related mortality and morbidity; therefore, we measured oxidative stress during open AAA repair and investigated any potential associations with intraoperative or perioperative events (aortic clamping time, blood loss, and the need to transfer to the intensive care unit). Blood samples were collected at specific time points from 53 patients undergoing open AAA repair: (1) before induction of anesthesia; (2) 15, 30, 60, and 120 minutes after aortic clamping; (3) 15 and 60 minutes after clamp removal; and (4) 24 hours postoperatively. Malondialdehyde (MDA) levels were measured by a spectrophotometric method. Baseline MDA values in patients with AAA were significantly higher than in controls (P < .0001). A positive correlation was found between preoperative MDA levels and the size of AAAs (Pearson correlation = 0.578, P < .001). No difference was observed in MDA levels between ruptured and nonruptured AAAs; however, when all symptomatic patients (ruptured and elective symptomatic AAAs, n = 18) were considered, there was a significant elevation in MDA levels (P < .001). There was also a significant increase in MDA values in patients transferred postoperatively to the intensive care unit (P < .001). Finally, a positive association was found between the duration of aortic clamping with MDA values at 15 and 60 minutes after declamping, but not after 24 hours (Pearson correlation = 0.467, P < .001). MDA levels may predict the postoperative course of elective and ruptured AAAs.

Activators of Plasminogen and the Progression of Small Abdominal Aortic Aneurysms

The aim of this study was to examine the role of activating pathways of plasminogen in the natural history of abdominal aortic aneurysms (AAA). To fulfill this objective 70 male patients with small AAA (> 3 cm) were interviewed and examined. Their blood samples were taken at diagnosis. The patients were scanned annually for a minimum period of 1 year and a maximum of 5 years (mean 2.5 years), and referred for surgery if the AAA exceeded 5 cm in diameter. Plasma levels of urokinase-like plasminogen activator (uPA), tissue-type plasminogen activator (tPA), plasminogen-activator-inhibitor-1 (PAI-1), macrophage-inhibiting factor (MIF), transforming-growth-factor-beta1 (TGF-beta1), homocysteine, and serum levels of IgA-antibodies against Chlamydia pneumoniae (IgA-CP) and cotinine (a nicotine metabolite) were measured. The annual expansion rate correlated positively with tPA, IgA-CP, and S-cotinine; rho = 0.37 (P = 0.004), 0.28 (P = 0.01), and 0.24 (P = 0.04), while PAI-1, uPA, TGF-beta1, homocysteine, and MIF did not. S-cotinine and PAI-1 also correlated positively with tPA, rho = 0.24 (P = 0.04), and 0.33 (P = 0.005). IgA-CP did not correlate with tPA. By receiver operating characteristics (ROC) curve analysis, tPA showed to be predictive of cases expanding to above 5 cm within the first 5 years with an optimal sensitivity and specificity of 0.73 and 0.71, respectively (P = 0.015). The aortic matrix degradation in AAA may be partly caused by an activation of plasminogen by tPA, but not by uPA, which usually dominates matrix degradation. Smoking seems to be an important factor for this pathway, while the pathway of IgA-CP seems different.

Abdominal aortic aneurysm: pathogenesis and implications for management

Abdominal aortic aneurysm (AAA) affects approximately 5% of elderly men and is responsible for a significant number of deaths in Western Countries. At present surgery by open or endovascular means is the only widely used therapy for this condition. In this review we examine the risk factors, serum, and genetic associations of AAA. Epidemiology studies suggest that smoking cessation and control of cholesterol and blood pressure should reduce the number of patients developing AAA. Natural history studies suggest that smoking cessation should reduce the rate of progression of AAA. Clear level 1 evidence for drug treatments of AAA are presently lacking; however, animal and human in vitro studies suggest that medication targeted at reducing inflammation and proteolysis are most likely to be beneficial, with limited data to support the use of statins, Angiotensin II inhibitors, and macrolides. Work has commenced in understanding which patients, identified by clinical, serum, and genotype, are more at risk of AAA progression and thus should be selected out for aggressive treatment. Well designed large multicenter randomized controlled trials are required to examine the medical treatment of AAA.

Pharmacological targets in the treatment of abdominal aortic aneurysms

The natural history of an abdominal aortic aneurysm (AAA) is of progressive aortic wall degeneration occurring over the course of many years, ultimately, culminating in loss of structural integrity and fatal aortic rupture. Although surgical exclusion of an aneurysm can effectively prevent aortic rupture in large aneurysms, small aneurysms are generally completely asymptomatic and are very unlikely to rupture. Further, AAA can be easily diagnosed with noninvasive testing; thus, small aneurysms present an excellent opportunity for disease-modifying pharmacological intervention. Research over the past two decades has defined many of the mechanisms which result in aortic matrix degeneration in both human tissue and particularly within animal models. This has resulted in the identification of several potential targets for pharmacological intervention. Drugs directed at inhibition of the inflammatory process and matrix degrading enzymes have been successful in multiple animal models, and early evidence now suggests that disease modification with some of these agents may be successful in slowing AAA growth in humans as well. The future of AAA therapy, however, may belong to agents which can induce aneurysm regression and to delivery methods which specifically target affected arterial tissue.

MIF: a new cytokine link between rheumatoid arthritis and atherosclerosis

Macrophage migration inhibitory factor (MIF) is well established as a key cytokine in immuno-inflammatory diseases such as rheumatoid arthritis. Inflammation is now also recognized as having a crucial role in atherosclerosis, and recent evidence indicates that MIF could also be important in this disease. Here, we review the role of MIF in rheumatoid arthritis and atherosclerosis, discuss the ways in which MIF and its relationship with glucocorticoids could link these diseases, and consider the potential of MIF as a new therapeutic target for small-molecule and antibody-based anti-cytokine drugs.

Factors Associated with Development of Large Abdominal Aortic Aneurysm in Middle-aged Men

OBJECTIVES

To investigate whether any variables in a health-screened population study were associated with later development of large abdominal aortic aneurysms (AAA).

SETTING

Malmö, Southern Sweden.

MATERIAL AND METHODS

Within the Malmö Preventive Study 22,444 men and 10,982 women were investigated between 1974 and 1991. The mean age at the health screening was 43.7 years.

RESULTS

After a median follow-up of 21 years, 126 men and six women (p<0.001) had large AAA that were symptomatic or evaluated for operation (5 cm diameter or more) or had autopsy-verified ruptured AAA. The male group (mean age 47 years) was, because of difference in age (p<0.001) also compared with an age-matched control group. The male patients with AAA showed increased diastolic blood pressure (p<0.007) at the health screening. Smoking predicted the development of AAA (p<0.0001). No difference in forced vital capacity or BMI was seen. Those who were physically inactive (e.g. not walking or cycling to work) had an increased risk of developing AAA (p<0.001). Among the laboratory markers measured, the erythrocyte sedimentation rate did not differ (7.1+/-5.9 vs. 6.4+/-5.7), but cholesterol (6.3+/-1.12 vs. 5.8+/-1.0) (p<0.0001) and triglycerides (1.9+/-0.12 vs. 1.5+/-0.07) (p<0.001) were significantly elevated in these individuals who subsequently developing AAA. The inflammatory proteins alfa-1-antitrypsin, ceruloplasmin, orosmucoid, fibrinogen, and haptoglobulin were increased (p<0.001).

CONCLUSION

Male gender, smoking, physical inactivity and cholesterol are significant factors associated with the development of AAA.

Up-regulation and coexpression of MIF and matrix metalloproteinases in human abdominal aortic aneurysms

Abdominal aortic aneurysm (AAA) is a localized dilatation of the arterial wall as a result of extensive breakdown of its structural proteins by matrix metalloproteinases (MMPs). AAA continuously expand and may eventually rupture, causing high mortality rates. The molecular processes underlying expansion and rupture of AAA are only poorly understood. In this study, evidence was sought for a direct involvement of macrophage migration inhibitory factor (MIF) in the pathogenesis of AAA through up-regulating MMPs, with particular reference to macrophages. To this end, expression and cellular localization of MIF were analyzed in human aortic wall samples of stable AAA and ruptured AAA, and compared with control aorta and atherosclerotic aorta (AS). MIF expression was up-regulated in stable AAA and further intensified in ruptured AAA. The increased aneurysmal MIF expression was paralleled by an enhanced expression of specific MMPs, viz. MMP-1, MMP-9, and MMP-12, and by a decrease of their inhibitors. Immunohistochemical analysis of AAA and AS showed MIF protein in endothelial cells, smooth muscle cells (SMCs), macrophages, and T cells. MMP-1 (in SMCs and macrophages) and MMP-9 (in macrophages) were colocalized with MIF at the cellular level in ruptured AAA. The up-regulation of aneurysmal MIF/MMP expression was associated with an increased content of cytotoxic T cells.

Heritable Disorders Predisposing to Aortic Dissection

Heritable disorders of connective tissue often predispose patients to aortic pathology and in particular aortic dissection. The Marfan syndrome, vascular Ehlers-Danlos syndrome, familial forms of thoracic aortic aneurysms or aortic dissection, and bicuspid aortic valve are all examples of heritable disorders that have associated defects affecting the integrity of the aortic wall, posing a risk of both aneurysmal dilation and dissection. The purpose of this review was to outline the phenotypes of the heritable syndromes that predispose to aortic dissection, present a guideline to their management and surveillance, and to offer insight into some of the surgical pitfalls that occur when repairing ascending aortic dissections in these types of patients.

Colocalization of oxidized low-density lipoprotein, caspase-3, cyclooxygenase-2, and macrophage migration inhibitory factor in arteriosclerotic human carotid arteries

Apoptotic and inflammatory processes occur in human arteriosclerotic lesions. We examined the hypothesis whether both processes are possibly associated by studying the colocalization of corresponding markers. In 11 human arteriosclerotic carotid arteries, proapoptotic markers (CPP32 (caspase-3), poly(ADP-ribose) polymerase, apoptosis-inducing factor, c-Jun/AP-1, and p53) and proinflammatory markers (macrophage migration inhibitory factor (MIF) and cyclooxygenase-2) were found in macrophages (MPhi) evaluated by computer-assisted immunohistomorphometry. Double-labeling studies demonstrated a colocalization of, both, proapoptotic and proinflammatory markers in these MPhi. Moreover, these MPhi also contained oxidized low-density lipoproteins (oxLDL). Exposure of cultured human MPhi to oxLDL, C6-ceramide, and tumor necrosis factor-alpha or H2O2 resulted in a significant increase of the apoptosis rate as well as of the MIF protein expression. Our study of MPhi in arteriosclerotic carotid arteries and in vitro experiments provide evidence that markers of apoptosis and inflammation are not only significantly increased but are also coexpressed. We conclude there are reciprocal modulatory interactions between apoptotic and inflammatory pathways in human plaque MPhi, which might importantly modify plaque progression or stability.

Aqueous levels of macrophage migration inhibitory factor and monocyte chemotactic protein-1 in patients with diabetic retinopathy

AIMS

To investigate the relationship of aqueous macrophage migration inhibitory factor (MIF) and monocyte chemotactic protein-1 (MCP-1) levels with the clinical stage of diabetic retinopathy.

METHODS

We assayed MIF and MCP-1 levels in aqueous humour samples obtained from 40 diabetic patients (49 eyes) and 24 non-diabetic patients (31 eyes) using enzyme-linked immunosorbent assay. According to the clinical stage of diabetic retinopathy, the diabetic patients were classified into non-diabetic retinopathy (11 eyes), non-proliferative diabetic retinopathy (14 eyes) and proliferative diabetic retinopathy (24 eyes).

RESULTS

The aqueous levels of MIF (mean +/- sd) were 6.34 +/- 4.53 ng/ml in proliferative diabetic retinopathy, 3.22 +/- 1.71 ng/ml in non proliferative diabetic retinopathy, 1.25 +/- 0.96 ng/ml in non-diabetic retinopathy and 1.07 +/- 0.94 ng/ml in non-diabetic patients. Significant differences were found among these four groups (P < 0.0001). Aqueous MCP-1 levels were 1668.6 +/- 1442.3 pg/ml in proliferative diabetic retinopathy, 1528.6 +/- 1994.6 pg/ml in non-proliferative diabetic retinopathy, 690.2 +/- 402.1 pg/ml in non-diabetic retinopathy and 622.7 +/- 245.3 pg/ml in non-diabetic patients. Significant differences were also found among these four groups (P < 0.0001). After correcting for total aqueous protein, the ratios of MIF and MCP-1 to total protein remained significantly correlated with the clinical stage of diabetic retinopathy (P < 0.0001, P = 0.0004, respectively). The ratios of MIF to total protein significantly correlated with the ratios of MCP-1 to total protein in diabetic patients (r = 0.680, P < 0.0001).

CONCLUSIONS

Aqueous MIF levels significantly correlated with aqueous MCP-1 levels and the clinical stage of diabetic retinopathy. The results suggest that MIF has a co-operative role with MCP-1 in the progression of diabetic retinopathy.

Hemodynamic forces regulate mural macrophage infiltration in experimental aortic aneurysms

Blood flow (BF) and wall shear stress (WSS) influence reactive oxygen species production and oxidative stress in abdominal aortic aneurysm (AAA) disease. To gain further insight into the mechanisms of hemodynamic influences on AAA inflammation, we examined aneurysm macrophage density, chemotaxis and survival under varying aortic flow conditions. Rat AAAs were created via porcine pancreatic elastase (PPE) infusion. In selected cohorts, AAA flow was increased via left common femoral arteriovenous fistula (AVF) creation (HF-AAA) or decreased by left common iliac ligation (LF-AAA). WSS was highest in HF-AAA (10.4 +/- 2.3 dyn/cm(2) vs. 2.4 +/- 0.4 and 0.5 +/- 0.2 for NF- and LF-AAA, respectively, P < 0.001) 7 days after PPE infusion, with reduced medial macrophage density and increased apoptosis. Adventitial macrophage density was not significantly influenced by flow. Monocyte chemoattractant protein-1 (MCP-1) and granulocyte-macrophage colony-stimulating factor (GM-CSF) gene expression correlated with observed macrophage densities in the media and adventitia. Luminal flow conditions regulate AAA inflammation in part via influences on medial macrophage density. Hemodynamic forces may modulate AAA inflammation and diameter enlargement via direct regulation of intimal macrophage adhesion, transmural migration or survival.

Evidence for a role of macrophage migration inhibitory factor in vascular disease

OBJECTIVE

Inflammation plays an essential role in atherosclerosis and restenosis. Macrophage migration inhibitory factor (MIF) is a proinflammatory cytokine that is widely expressed in vascular cells. However, there is no in vivo evidence that MIF participates directly in vascular injury and repair. Therefore, we investigated the effect of MIF blockade on the response to experimental angioplasty in atherosclerosis-susceptible mice.

METHODS AND RESULTS

Carotid artery dilation (2.5 atm) and complete endothelial denudation were performed in male C57BL/6J LDL receptor-deficient mice treated with a neutralizing anti-MIF or isotype control monoclonal antibody. After 7 days and 28 days, intimal and medial sizes were measured and intima/media area ratio (I/M) was calculated. Intimal thickening and I/M were reduced significantly by anti-MIF compared with control antibody. Vascular injury was accompanied by progressive vessel enlargement or "positive remodeling" that was comparable in both treatment groups. MIF blockade was associated with reduced inflammation and cellular proliferation and increased apoptosis after injury.

CONCLUSIONS

Neutralizing MIF bioactivity after experimental angioplasty in atherosclerosis-susceptible mice reduces vascular inflammation, cellular proliferation, and neointimal thickening. Although the molecular mechanisms responsible for these effects are not yet established, these data prompt further research directed at understanding the role of MIF in vascular disease and suggest novel therapeutic interventions for preventing atherosclerosis and restenosis.