Nitric oxide in experimental aneurysm formation: early events and consequences of nitric oxide inhibition

Effect of statins on abdominal aortic aneurysm

Abdominal aortic aneurysm (AAA) is a prevalent condition which causes progressive growth and rupture of aortic wall with a high death rate. Several studies have found that treatment with statins may decrease the progress of AAA and the risk of rupture by suppressing the inflammatory mediators, decreasing oxidative stress, and inhibiting mechanisms involved in extracellular matrix (ECM) degradation. Moreover, some studies have reported that prehospital therapy with statins can decrease mortality after surgery. The novelty of this paper is that different studies including those performed in humans and animals were reviewed and the potential mechanisms by which statins can have an effect on AAA were summarized. Overall, the evidence suggested an association between treatment with statins and improvement of AAA.

The Impact of C-Peptide and Diabetes Mellitus on Coronary Ectasia and Effect of Coronary Ectasia and C-Peptide on Long-Term Outcomes: A Retrospective Cohort Study

BACKGROUND

Coronary artery ectasia (CAE) is an entity frequently associated with atherosclerotic coronary artery disease (CAD) in clinical practice. Although it has common risk factors with atherosclerotic CAD in its development, the pathophysiology of CAE is not fully known and it is not seen in every CAD suggesting that different determinants may play a pivotal role in the development of CAD. This study aimed to reveal the impact of C-peptide and diabetes mellitus (DM) on CAE and the effect of C-peptide and coronary ectasia on long-term outcomes in patients who underwent coronary angiography.

METHODS

A total of 6611 patients who underwent coronary angiography were followed up retrospectively, and their major adverse cardiovascular event (MACE) status of an average of sixty months was recorded. According to their angiographic features, the patients were divided into two groups those with and without CAE. MACE development was accepted as the primary endpoint.

RESULTS

A total of 552 patients had CAE and MACE developed in 573 patients. Patients with CAE and higher C-peptide levels (Q4 + Q3) showed higher rates of MACE as compared to those without CAE and lower C-peptide levels (Q1 + Q2) (20.8% vs 7.6%; 70.1% vs 29.1%; p < 0.001, for both of them). In multivariate regression analysis, high C-peptide levels were determined as an independent risk factor for CAE (OR 2.417; 95% CI 2.212-2.641; p < 0.001). The Kaplan-Meier cumulative survival curves showed that the risks for MACE increased as the C-peptide levels increased. The Cox regression analysis for 5-years MACE related to the plasma C-peptide levels and presence of CAE, C-peptide, and CAE were found to be independent predictors of MACE (HR = 1.255, 95% CI: 1.164-1.336, p < 0.001 and HR = 1.012, 95% CI: 1.002-1.023, p=0.026, respectively).

CONCLUSION

Our study revealed that a high C-peptide level is an independent risk factor for CAE and that CAE and C-peptide are independent predictors for the development of MACE.

The NO signalling pathway in aortic aneurysm and dissection

Recent studies have shown that NO is a central mediator in diseases associated with thoracic aortic aneurysm, such as Marfan syndrome. The progressive dilation of the aorta in thoracic aortic aneurysm ultimately leads to aortic dissection. Unfortunately, current medical treatments have neither halt aortic enlargement nor prevented rupture, leaving surgical repair as the only effective treatment. There is therefore a pressing need for effective therapies to delay or even avoid the need for surgical repair in thoracic aortic aneurysm patients. Here, we summarize the mechanisms through which NO signalling dysregulation causes thoracic aortic aneurysm, particularly in Marfan syndrome. We discuss recent advances based on the identification of new Marfan syndrome mediators related to pathway overactivation that represent potential disease biomarkers. Likewise, we propose iNOS, sGC and PRKG1, whose pharmacological inhibition reverses aortopathy in Marfan syndrome mice, as targets for therapeutic intervention in thoracic aortic aneurysm and are candidates for clinical trials.

Plasma Metabolomics Analysis Identifies Abnormal Energy, Lipid, and Amino Acid Metabolism in Abdominal Aortic Aneurysms

Background

Abdominal aortic aneurysm (AAA) is a complicated aortic dilatation disease. Metabolomics is an emerging system biology method. This aim of this study was to identify abnormal metabolites and metabolic pathways associated with AAA and to discover potential biomarkers that could affect the size of AAAs.

Material/Methods

An untargeted metabolomic method was used to analyze the plasma metabolic profiles of 39 patients with AAAs and 30 controls. Multivariate analysis methods were used to perform differential metabolite screening and metabolic pathway analysis. Cluster analysis and univariate analysis were performed to identify potential metabolites that could affect the size of an AAA.

Results

Forty-five different metabolites were identified with an orthogonal projection to latent squares-discriminant analysis model and the differences between them in the patients with AAAs and the control group were compared. A variable importance in the projection score >1 and P<0.05 were considered statistically significant. In patients with AAAs, the pathways involving metabolism of alanine, aspartate, glutamate, D-glutamine, D-glutamic acid, arginine, and proline; tricarboxylic acid cycling; and biosynthesis of arginine are abnormal. The progression of an AAA may be related to 13 metabolites: citric acid, 2-oxoglutarate, succinic acid, coenzyme Q1, pyruvic acid, sphingosine-1-phosphate, platelet-activating factor, LysoPC (16: 00), lysophosphatidylcholine (18: 2(9Z,12Z)/0: 0), arginine, D-aspartic acid, and L- and D-glutamine.

Conclusions

An untargeted metabolomic analysis using ultraperformance liquid chromatography-tandem mass spectrometry identified metabolites that indicate disordered metabolism of energy, lipids, and amino acids in AAAs.

Alterations in phenotype and gene expression of adult human aneurysmal smooth muscle cells by exogenous nitric oxide

Abdominal aortic aneurysms (AAA) are characterized by matrix remodeling, elastin degradation, absence of nitric oxide (NO) signaling, and inflammation, influencing smooth muscle cell (SMC) phenotype and gene expression. Little is known about the biomolecular release and intrinsic biomechanics of human AAA-SMCs. NO delivery could be an attractive therapeutic strategy to restore lost functionality of AAA-SMCs by inhibiting inflammation and cell stiffening. We aim to establish the differences in phenotype and gene expression of adult human AAA-SMCs from healthy SMCs. Based on our previous study which showed benefits of optimal NO dosage delivered via S-Nitrosoglutathione (GSNO) to healthy aortic SMCs, we tested whether such benefits would occur in AAA-SMCs. The mRNA expression of three genes involved in matrix degradation (ACE, ADAMTS5 and ADAMTS8) was significantly downregulated in AAA-SMCs. Total protein and glycosaminoglycans synthesis were higher in AAA-SMCs than healthy-SMCs (p < 0.05 for AAA-vs. healthy- SMC cultures) and was enhanced by GSNO and 3D cultures (p < 0.05 for 3D vs. 2D cultures; p < 0.05 for GSNO vs. non-GSNO cases). Elastin gene expression, synthesis and deposition, desmosine crosslinker levels, and lysyl oxidase (LOX) functional activity were lower, while cell proliferation, iNOS, LOX and fibrillin-1 gene expressions were higher in AAA-SMCs (p < 0.05 between respective cases), with differential benefits from GSNO exposure. GSNO and 3D cultures reduced MMPs -2, -9, and increased TIMP-1 release in AAA-SMC cultures (p < 0.05 for GSNO vs. non-GSNO cultures). AAA-SMCs were inherently stiffer and had smoother surface than healthy SMCs (p < 0.01 in both cases), but GSNO reduced stiffness (~25%; p < 0.01) and increased roughness (p < 0.05) of both cell types. In conclusion, exogenously-delivered NO offers an attractive strategy by providing therapeutic benefits to AAA-SMCs.

Relationship of genetic factors with development of aortic dissection and aneurysm

Background

This study aims to investigate the relationship between the development of aortic dissections and aneurysms with the polymorphisms of angiotensin converting enzyme gene, methylenetetrahydrofolate reductase gene, plasminogen activator inhibitor-1 gene, and nitric oxide synthase gene.

Methods

Between April 2009 and July 2014, 38 patients with aortic dissections (28 males, 10 females; mean age 55.1±10.7 years; range, 30 to 78 years) and 67 patients with aortic aneurysms (57 males, 10 females; mean age 63.0±11.4 years; range, 31 to 82 years) were included in this cross-sectional study. The control group consisted of 60 healthy volunteers (41 males, 19 females; mean age 56.3±11.2 years; range, 30 to 82 years) without an aortic aneurysm or dissection, as assessed by thoracoabdominal computed tomography. The prespecified four genes were genotyped with competitive allelespecific polymerase chain reaction.

Results

The aortic dissection group had higher nitric oxide synthase-3 (4b/4b) expression levels, compared to the control group. The aortic aneurysm group had also higher nitric oxide synthase-3 (4b/4a) expression levels, compared to the control group. Compared to the control group, a higher rate of angiotensin converting enzyme I/D gene polymorphism was detected in the aneurysm group, while higher D/D polymorphism rates were found in the dissection group; although not statistically significant.

Conclusion

Our study results suggest that the nitric oxide synthase-3 intron 4b/4b and nitric oxide synthase-3 intron 4b/4a gene polymorphisms can be used as a predictor of aortic dissection and aneurysm development.

Molecular and cellular insights into the pathogenesis of coronary artery ectasia

Coronary artery ectasia describes a local or diffuse dilatation of the epicardial coronary arteries. This review summarizes the molecular and cellular mechanisms involved in the pathogenesis of coronary artery ectasia. Better identification of the pathophysiologic steps will shed light into the clinical significance and may have direct implications for the management strategies of this disease. Additionally, understanding the underlying etiology may help to improve treatment modalities specific to coronary artery ectasia.

Redox stress in Marfan syndrome: Dissecting the role of the NADPH oxidase NOX4 in aortic aneurysm

Marfan syndrome (MFS) is characterized by the formation of ascending aortic aneurysms resulting from altered assembly of extracellular matrix fibrillin-containing microfibrils and dysfunction of TGF-β signaling. Here we identify the molecular targets of redox stress in aortic aneurysms from MFS patients, and investigate the role of NOX4, whose expression is strongly induced by TGF-β, in aneurysm formation and progression in a murine model of MFS. Working models included aortae and cultured vascular smooth muscle cells (VSMC) from MFS patients, and a NOX4-deficient Marfan mouse model (Fbn1^C1039G/+-Nox4^-/-). Increased tyrosine nitration and reactive oxygen species levels were found in the tunica media of human aortic aneurysms and in cultured VSMC. Proteomic analysis identified nitrated and carbonylated proteins, which included smooth muscle α-actin (αSMA) and annexin A2. NOX4 immunostaining increased in the tunica media of human Marfan aorta and was transcriptionally overexpressed in VSMC. Fbn1^C1039G/+-Nox4^-/- mice aortas showed a reduction of fragmented elastic fibers, which was accompanied by an amelioration in the Marfan-associated enlargement of the aortic root. Increase in the contractile phenotype marker calponin in the tunica media of MFS mice aortas was abrogated in Fbn1^C1039G/+-Nox4^-/- mice. Endothelial dysfunction evaluated by myography in the Marfan ascending aorta was prevented by the absence of Nox4 or catalase-induced H₂O₂ decomposition. We conclude that redox stress occurs in MFS, whose targets are actin-based cytoskeleton members and regulators of extracellular matrix homeostasis. Likewise, NOX4 have an impact in the progression of the aortic dilation in MFS and in the structural organization of the aortic tunica media, the VSMC phenotypic modulation, and endothelial function.

Nitric oxide mediates aortic disease in mice deficient in the metalloprotease Adamts1 and in a mouse model of Marfan syndrome

Heritable thoracic aortic aneurysms and dissections (TAAD), including Marfan syndrome (MFS), currently lack a cure, and causative mutations have been identified for only a fraction of affected families. Here we identify the metalloproteinase ADAMTS1 and inducible nitric oxide synthase (NOS2) as therapeutic targets in individuals with TAAD. We show that Adamts1 is a major mediator of vascular homeostasis, given that genetic haploinsufficiency of Adamts1 in mice causes TAAD similar to MFS. Aortic nitric oxide and Nos2 levels were higher in Adamts1-deficient mice and in a mouse model of MFS (hereafter referred to as MFS mice), and Nos2 inactivation protected both types of mice from aortic pathology. Pharmacological inhibition of Nos2 rapidly reversed aortic dilation and medial degeneration in young Adamts1-deficient mice and in young or old MFS mice. Patients with MFS showed elevated NOS2 and decreased ADAMTS1 protein levels in the aorta. These findings uncover a possible causative role for the ADAMTS1-NOS2 axis in human TAAD and warrant evaluation of NOS2 inhibitors for therapy.

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.

Antibodies against malondialdehyde-acetaldehyde adducts can help identify patients with abdominal aortic aneurysm

OBJECTIVE

Abdominal aortic aneurysm (AAA) is a pathologic dilation of the aorta. Inflammation of the aortic wall has been shown to be involved in AAA formation. Malondialdehyde-acetaldehyde (MAA) adducts are MAA/protein hybrids with immunogenic, proinflammatory, and profibrotic properties. Levels of MAA adducts are elevated in patients with coronary artery disease; however, the role of MAA adducts in AAA is unclear. We hypothesize that levels of circulating antibodies against MAA adducts are increased in patients with AAA.

METHODS

Plasma samples were collected from mice and patients with AAA and control patients with atherosclerosis but not AAA. AAA was induced in mice by a standard CaCl2 protocol, with matching sham mice. Plasma levels of anti-MAA antibodies were quantified by enzyme-linked immunosorbent assay.

RESULTS

Patients with AAA exhibited higher levels of immunoglobulin G and immunoglobulin A anti-MAA antibody subtypes (P = .049 and .026, respectively) compared with control patients. Conversely, immunoglobulin M anti-MAA antibodies in AAA patients were lower compared with control patients (P = .018). In CaCl2-treated mice, immunoglobulin G anti-MAA antibodies were elevated after AAA formation (P = .006).

CONCLUSIONS

The pattern of anti-MAA antibodies is able to distinguish between patients with AAA and patients with atherosclerosis but no AAA. These results demonstrate that MAA adducts are associated with AAA and suggest that they may play a role in either initiating or propagating chronic inflammation in AAA.

SMAD3 deficiency promotes inflammatory aortic aneurysms in angiotensin II-infused mice via activation of iNOS

Background

Ninety percent of the patients carrying distinct SMAD3 mutations develop aortic aneurysms and dissections, called aneurysms‐osteoarthritis syndrome (AOS). However, the etiology and molecular events downstream of SMAD3 leading to the pathogenesis of aortic aneurysms in these patients still remain elusive. Therefore, we aimed to investigate the vascular phenotypes of SMAD3‐knockout mice.

Methods and Results

We have shown that angiotensin II–induced vascular inflammation, but not hypertension, leads to aortic aneurysms and dissections, ultimately causing aortic rupture and death in mice. Lipopolysaccharide‐triggered inflammation confirmed that enhanced aortic macrophage recruitment was essential for aneurysm formation in angiotensin II–infused SMAD3‐knockout mice. In contrast, phenylephrine‐triggered hypertension alone was insufficient to induce aortic aneurysms in mice. Using uniaxial tensile and contractility tests, we showed that SMAD3 deficiency resulted in defective aortic biomechanics and physiological functions, which caused weakening of the aortic wall and predisposed the mice to aortic aneurysms. Chromatin immunoprecipitation (ChIP) and re‐ChIP assays revealed that the underlying mechanism involved aberrant upregulation of inducible nitric oxide synthase (iNOS)–derived nitric oxide production and activation of elastolytic matrix metalloproteinases 2 and 9. Administration of clodronate‐liposomes and iNOS inhibitor completely abrogated these aortic conditions, thereby identifying iNOS‐mediated nitric oxide secretion from macrophages as the downstream event of SMAD3 that drives this severe pathology.

Conclusions

Macrophage depletion and iNOS antagonism represent 2 promising approaches for preventing aortic aneurysms related to SMAD3 mutations and merit further investigation as adjunctive strategies for the life‐threatening manifestations of AOS.

Agmatine promotes the migration of murine brain endothelial cells via multiple signaling pathways

AIMS

The combination of adhesion and migration of endothelial cells (ECs) is an integral process for evolution, organization, repair and vessel formation in living organisms. Agmatine, a polycationic amine existing in brain, has been investigated to exert neuroprotective effects. Up to date, there are no studies reporting that agmatine modulates murine brain endothelial (bEnd.3) cells migration. In the present study, we intend to investigate the role of agmatine in bEnd.3 cells migration and the molecular mechanism mediating this action.

MAIN METHODS

The effect of agmatine on the bEnd.3 cells migration was examined by migration assay, and the mechanism involved for this effect was investigated by western blot analysis and NO contents measurements.

KEY FINDINGS

Agmatine treatment (50, 100 and 200 μM) significantly accelerated bEnd.3 cells migration in a concentration-dependent manner. Western blotting revealed that agmatine treatment significantly induced vascular endothelial growth factor (VEGF), VEGF receptor 2 (Flk-1/KDR or VEGFR2), phosphatidylinositol 3-kinase (PI3K), Akt/protein kinase B (also known as PKB, PI3K downstream effector protein), endothelial nitric oxide synthase (eNOS) nitric oxide (NO; product by eNOS) and intercellular adhesion molecule 1 (ICAM-1) expressions during bEnd.3 cells migration. The expression of ICAM-1 and migration of bEnd.3 cells, induced by agmatine, were significantly attenuated by treatment of wortmannin, a specific PI3K inhibitor.

SIGNIFICANCE

Taken together, we provide the first evidence that activation of VEGF/VEGFR2 and the consequential PI3K/Akt/eNOS/NO/ICAM-1 signaling pathways are serial events, through which the treatment of agmatine could lead to bEnd.3 cells migration.

COMPUTATIONAL MODELING OF FORMATION OF A CEREBRAL ANEURYSM UNDER THE INFLUENCE OF SMOOTH MUSCLE CELL RELAXATION

The mechanics of cerebral aneurysm pathogenesis, evolution and rupture are not yet well understood. This paper presents a numerical analysis of the formation of a saccular cerebral aneurysm in for the first time in a 3D model of the basilar artery bifurcation under normal and hypertensive blood pressure. Due to the excessive endothelium derived nitric oxide produced in high wall shear stress, we assumed that smooth muscle cell relaxation is the origin of the aneurysm formation. Arterial wall remodeling under constant tension was considered to be the other mechanism of disease evolution. The wall was constructed from two elastic and hyperelastic isotropic regions. The flow was considered steady, laminar, Newtonian, and incompressible. The fully coupled fluid and structure models were solved with the finite elements package ADINA 8.5. The wall shear stress, effective stress and deformation distributions under normal and hypertensive blood pressure were compared to a healthy bifurcation. The model shows that although the malfunction of the endothelial cell layer and the corresponding smooth muscle cell-related loss of vascular tone is important to the inception of the disease; A saccular aneurysm may not be formed by this mechanism alone, and also requires the fiber-related arterial wall remodeling for further development.

Relationship between endothelial dependent vasodilation and size of abdominal aortic aneurysms

BACKGROUND

Flow-mediated dilation of the brachial artery (FMDB) indirectly reflects the action of nitric oxide liberated by the endothelium. In patients with abdominal aortic aneurysms (AAA), the changes in nitric oxide metabolism in close association with inflammation, appear to play a leading role in the aetiopathology of this disease, although it is still not clear. The objective was to study the correlation and behavior of FMDB relative to the aneurysm diameter (AD). To evaluate the relationship between C-reactive protein (CRP) and the FMDB in these patients. To study the correlation and behavior of FMDB relative to the aneurysm diameter (AD). To evaluate the relationship between C-reactive protein (CRP) and the FMDB in these patients.

METHODS

The FMDB value and the CRP were determined in a total of 30 patients with an AAA > or =30 mm, confirmed by computed tomography. The cardiovascular and treatment history was recorded, together with the lipid and renal profile and leucocyte count.

RESULTS

The median AD in the sample was 43 mm (25 percentile: 37 mm; 75 percentile: 60 mm). The primary variables of the study, FMDB and CRP, were the only ones that differed statistically when we stratified the sample according to AD quartiles (p < 0.001). There was a negative correlation between the FMDB and the AD (R = -0.78 [p < 0.001]) and a positive one for CRP (0.74 [p < 0.001]). The CRP/FMDB gave an R value of -0.56 (p = 0.001).

CONCLUSION

Endothelium dependent vasodilation has a linear and negative correlation with the AD. The positive correlation between the FMDB and CRP supports the hypothesis that inflammation and endothelial dysfunction are processes associated with the physiopathology of AAA and vary with their growth.

Expression of vascular endothelial growth factor receptor-1/-2 and nitric oxide in unruptured intracranial aneurysms

The biological mechanisms associated with the development and rupture of intracranial aneurysms are not fully understood. To clarify the role of VEGF and the related receptors in the pathophysiology of aneurysm, immunostaining for VEGF, VEGFR1 and VEGFR2 was performed on specimens from six unruptured aneurysms and on two specimens of normal arteries wall as a control. The results were correlated with NO concentration of CSF collected during surgery from 8 patients affected by unruptured aneurysms and in 11 control patients. The immunohistochemical data showed a different pattern of VEGF/VEGFR1/VEGFR2 in aneurysms when compared with control. The results of this preliminary study suggest an imbalance of VEGF, VEGFR1 and VEGFR2, and the interaction of VEGF and NO in the pathophysiology of unruptured aneurysms. Our data support the hypothesis of aneurysm formation associated with a loss of expression of VEGFR1, moderate expression of VEGFR2 and high concentration of nitrate.

The genetics of sporadic ruptured and unruptured intracranial aneurysms: a genetic meta-analysis of 8 genes and 13 polymorphisms in approximately 20,000 individuals

Object

Intracranial aneurysms (IAs) are thought to have a multifactorial origin. The authors undertook a comprehensive meta-analysis on all genes investigated using a case-control model in ruptured (subarachnoid hemorrhage) and unruptured aneurysms.

Methods

Electronic databases were searched until and including July 2008 for any candidate gene studied in IA or subarachnoid hemorrhage using a case-control model. The ORs and 95% CIs were determined for each gene-disease association using fixed and random effect models.

Results

Thirty studies of 8 genes and 13 polymorphisms were analyzed among 19,961 individuals (6622 cases and 13,339 controls). Two genes and 3 polymorphisms were associated with IA. The eNOS gene T786C polymorphism (OR 1.24, 95% CI 1.0–1.54; p = 0.05) and IL-6 gene G572C polymorphism (OR 7.08, 95% CI 2.85–17.57; p < 0.0001) both showed a significant association with ruptured/unruptured IA. The IL-6/G174C polymorphism exerted a significant protective effect against IA (OR 0.49, 95% CI 0.25–0.95; p = 0.04). The other candidate genes investigated (ACE, endoglin, APOE, elastin, MMP-3, and SERPINA3) showed no significant associations.

Conclusions

There is a likely genetic basis to sporadic IAs. However, the evidence base is small when compared against other complex disorders.

Nitric oxide induces the progression of abdominal aortic aneurysms through the matrix metalloproteinase inducer EMMPRIN

Nitric Oxide (NO) is involved in the development and progression of abdominal aortic aneurysms (AAA). We found that inhibition of inducible NO synthase (iNOS) protects mice in an elastase-induced AAA model, significantly inhibiting the production of matrix metalloproteinase-13 (MMP-13). The extracellular MMP inducer (EMMPRIN; CD147) was increased in human AAA biopsies and in wild-type murine AAA but not in AAA from iNOS null mice. In cells overexpressing ectopic EMMPRIN, MMP-13 secretion was stimulated, whereas silencing of EMMPRIN by RNA interference led to significant inhibition of MMP-13 expression. In addition, elastase infusion of MMP-13 null mouse aortas induced a significant increase of EMMPRIN but reduced aortic dilatation when compared with wild-type mice, suggesting that NO-mediated AAA may be mediated through EMMPRIN induction of MMP-13. These findings were further verified in elastase-infused iNOS null mice, in which daily administration of NO caused a significant aortic dilatation and the expression of EMMPRIN and MMP-13. By contrast, in iNOS wild-type mice, pharmacological inhibition of iNOS by administration of 1400 W induced a reduction of aortic diameter and inhibition of MMP-13 and EMMPRIN expression when compared with control mice. Our results suggest that NO may regulate the development of AAA in part by inducing the expression of EMMPRIN and modulating the activity of MMP-13 in murine and human aneurysms.

eNOS G894T polymorphism and abdominal aortic aneurysms

BACKGROUND

The genetic risk factors that contribute to the risk of developing abdominal aortic aneurysm (AAA) are poorly understood. We assessed the association of endothelial nitric oxide synthase (eNOS) gene polymorphism with AAA.

METHODS

eNOS gene polymorphism of 61 patients with AAA and 62 control participants were analyzed by polymerase chain reaction (PCR)-restriction technique.

RESULTS

eNOS G894 homozygote T/T genotype polymorphism and 894T allele frequency in patients with AAA were significantly higher than those of the control participants (P = .01, P = .03). Among patients with AAA, the eNOS G894 T/T polymorphism and 894T allele frequency were associated with larger AAAs.

CONCLUSION

The current study, in a small group of participants, showed a relationship between eNOS G894T polymorphism and AAA.

Pathogenetic mechanisms of coronary ectasia

Coronary ectasia is defined as local or generalized aneurysmal dilatation of the coronary arteries. The present review summarizes the molecular, cellular and vascular mechanisms which are involved in the pathobiology of coronary ectasia. Coronary ectasia likely represents an exaggerated form of expansive vascular remodeling (i.e. excessive expansive remodeling) in response to atherosclerotic plaque growth. Enzymatic degradation of the extracellular matrix of the media is the major pathophysiologic process that leads to ectasia. Atherosclerotic lesions within ectatic regions of the coronary arteries appear to be highly inflamed high-risk plaques with proclivity to rupture. Better understanding of the pathogenetic processes involved in coronary ectasia is anticipated that will provide a further insight into the clinical significance and natural history of this entity, and may also have direct clinical implications in the management and follow-up strategy of this condition.

Agmatine inhibits matrix metalloproteinase-9 via endothelial nitric oxide synthase in cerebral endothelial cells

OBJECTIVES

Matrix metalloproteinases (MMPs) are up-regulated by ischemic injury and degrade the basement membrane of brain vessels to promote cell death and tissue injury. We previously showed that agmatine has a neuroprotective effect on neurons against ischemic injury. In the present study, we investigated the effect of agmatine on the expression of MMPs and nitric oxide (NO) production in cerebral endothelial cells (CECs) after oxygen-glucose deprivation (OGD)-reperfusion injury and its potential association with endothelial nitric oxide synthase (eNOS).

METHODS

Primary cultured endothelial cells from murine brain and bEnd.3 cells were subjected to OGD-reperfusion injury. Protein and mRNA levels of both MMP-2 and MMP-9 were determined by immunocytochemical analysis, Western blot and RT-PCR. Protein levels of eNOS were evaluated by Western blot in the CECs. The production of NO was measured using the Griess reagent.

RESULTS

Agmatine attenuated the expression of MMP-2 and MMP-9 induced by ischemic injury at the protein and mRNA level, while agmatine increased the expression of eNOS directly. NO production was decreased in CECs after similar insult and was increased by agmatine treatment. In the presence of a nitric oxide synthase (NOS) inhibitor, N(omega)-nitro-L-arginine methyl ester (L-NAME), the expression levels of MMP-2 were decreased, but the expression of MMP-9 was not decreased by agmatine administration. However, NO production was suppressed by a non-specific NOS inhibitor in the agmatine treatment group.

CONCLUSION

Our study supports that the down-regulation of MMP-9 by agmatine runs parallel to the up-regulation of eNOS and the maintenance of functional NO release.

Endothelial nitric oxide synthase stimulates aneurysm growth in aged mice

BACKGROUND/AIMS

Age-associated changes in endothelial nitric oxide synthase (eNOS) expression have not been definitively linked to the pathophysiology of aortic aneurysms. We examined the role of eNOS in human patients and an age-appropriate mouse model.

METHODS

eNOS transcripts and immunodetectable protein were assessed by quantitative PCR and immunohistochemistry in human ascending thoracic aneurysms (n = 29) and referent aortae (n = 31). Carotid aneurysms were induced with CaCl2 in young adult (3 months) and aged (18 months) C57BL/6 and eNOS-knockout (eNOS-KO) mice.

RESULTS

eNOS transcripts and protein were reduced in human aneurysms compared with controls, although aortic eNOS expression also decreased with patient age. Aged wild-type mice had significantly larger aneurysm diameter than young adult mice. Aged wild-type mice had reduced eNOS transcripts and protein compared with young adult mice. Aged eNOS-KO mice had smaller aneurysms compared with aged wild-type mice but similar size aneurysms compared with young eNOS-KO and young wild-type mice.

CONCLUSION

eNOS expression is reduced in both aged human and aged mouse endothelium and eNOS expression is linked to aneurysm expansion in aged but not young adult mice. These findings support the relevance of age-associated changes in eNOS expression in clinical aneurysmal disease.

Endothelial nitric oxide synthase gene [G894T] polymorphism as a possible risk factor in aneurysmal subarachnoid haemorrhage

BACKGROUND

The exact aetiology, growth and rupture of intracranial aneurysms is unclear. In this study we investigated a possible association between intracranial aneurysm rupture and polymorphism of the endothelial nitric oxide synthase gene G894T.

METHODS

Endothelial nitric oxide synthase gene polymorphism of 53 patients with ruptured intracranial aneurysms and 60 control subjects were analysed by the polymerase chain reaction-restriction fragment length polymorphism technique. The genotype distribution and allele frequencies of endothelial nitric oxide synthase gene polymorphism in patients with ruptured intracranial aneurysm and healthy subjects were compared.

FINDINGS

The homozygous (TT) genotype frequency was significantly higher in patients with ruptured intracranial aneurysms. It was also found that the presence of eNOS 894TT genotype was significantly associated with the risk of intracranial aneurysm rupture (p < 0.05).

CONCLUSION

Polymorphism in exon 7 of the endothelial nitric oxide synthase gene G894T seems to be a possible risk factor for intracranial aneurysm rupture.

Novel insight into the pathobiology of abdominal aortic aneurysm and potential future treatment concepts

The patient with abdominal aortic aneurysm (AAA) commonly is a nondiabetic, white man with a history of smoking. Moreover, AAA represents a leading cause of death in elderly men in Western countries. The purpose of this manuscript is to review current evidence as to the pathobiology of AAA as well as potential future drug targets to prevent progression of AAA.

Novel insights into an old controversy: is coronary artery ectasia a variant of coronary atherosclerosis?

Coronary artery ectasia (CAE) is defined as a localized or diffuse non-obstructive lesion of the epicardial coronary arteries with a luminal dilation exceeding 1.5-fold the diameter of the normal adjacent arterial segment. The incidence of CAE has been reported to range between 2% and 4%, which might be an overestimation of the true frequency. The coincidence of CAE with other systemic vascular dilatations has suggested that the mechanism underlying CAE is not only localized to coronary arteries, but also to other vascular compartments such as aorta or peripheral veins. Although the pathophysiology of CAE remains largely unknown, it was supposed to represent a variant of coronary atherosclerosis. This review focuses on this controversy of whether CAE and coronary artery disease (CAD) are two manifestations of the same underlying process. There are clear differences between CAD and CAE with respect to cardiovascular risk factors such as diabetes mellitus, and pathogenic steps in disease progress such as inflammation or extracellular matrix remodeling. As this review will underscore, the current knowledge of the field is insufficient to finally clarify the causative interrelation between CAE and CAD. The clinical course and treatment of CAE mainly depends on its coexistence with CAD. When coexisting with CAD, the prognosis and treatment of CAE are the same as for CAD alone. In isolated CAE, prognosis is better and anti-platelet drugs are the mainstay of treatment. Surgical treatment can be considered in selected patients. For clarifying the mechanism underlying CAE, additional clinical, histopathological and pathophysiological investigations are required. In fact, every patient with CAE should be evaluated systematically for pathological changes in other vascular territories, both in the arterial system as well as in the venous system, which might occur in the disease process.

Role of Oxidative Stress in the Pathogenesis of Abdominal Aortic Aneurysms

The role of inflammation in the pathogenesis of abdominal aortic aneurysms (AAA) is well established. The inflammatory process leads to protease-mediated degradation of the extracellular matrix and apoptosis of smooth muscle cells (SMC), which are the predominant matrix synthesizing cells of the vascular wall. These processes act in concert to progressively weaken the aortic wall, resulting in dilatation and aneurysm formation. Oxidative stress is invariably increased in, and contributes importantly to, the pathophysiology of inflammation. Moreover, reactive oxygen species (ROS) play a key role in regulation of matrix metalloproteinases and induction of SMC apoptosis. ROS may also contribute to the pathogenesis of hypertension, a risk factor for AAA. Emerging evidence suggests that ROS and reactive nitrogen species (RNS) are associated with AAA formation in animal models and in humans. Although experimental data are limited, several studies suggest that modulation of ROS production or activity may suppress AAA formation and improve experimental outcome in rodent models. Although a number of enzymes can produce injurious ROS in the vasculature, increasing evidence points toward a role for NADPH oxidase as a source of oxidative stress in the pathogenesis of AAA.

Decreased nitrate-mediated dilatation in patients with coronary artery ectasia: an ultrasonographic evaluation of brachial artery

BACKGROUND

Coronary artery ectasia has been defined as localized or diffuse nonobstructive lesions of the epicardial coronary arteries with a luminal dilation exceeding the 1.5-fold of normal adjacent segment or vessel diameter. Although coronary artery disease is supposed to be responsible for more than 50% of coronary ectasia, the precise pathology of coronary artery ectasia is not clearly understood. The brachial artery ultrasound test for flow-mediated endothelial-dependent vasodilatory function includes administration of sublingual nitrates to examine the vasodilating effect of an exogenous source of nitric oxide. In the present study, we aimed to compare flow-mediated and nitrate-mediated responses of brachial artery in patients with coronary artery ectasia and patients with coronary artery disease.

MATERIALS AND METHODS

Thirty-six consecutive patients with coronary artery ectasia in combination with coronary artery disease and 42 age-matched and sex-matched patients with coronary artery disease alone were included in the study. Flow-mediated and nitrate-mediated dilatations were measured in all patients using a high-resolution B-mode ultrasonographic system.

RESULTS

Baseline brachial artery diameters in patients with coronary artery ectasia were not statistically different from those in patients with coronary artery disease (4.2+/-0.6 vs. 4.0+/-0.6 mm, respectively, P=0.16). Although the forearm flow-mediated dilatation of the patients with coronary artery ectasia did not differ from that of patients with coronary artery disease alone (5.5+/-3.8 vs. 4.8+/-3.6%, respectively, P=0.41), nitrate-mediated dilatation was significantly lower than that of patients with coronary artery disease alone (7.9+/-5.2 vs. 10.9+/-5.4%, respectively, P=0.02).

CONCLUSION

We have shown that patients with coronary artery ectasia have decreased nitrate-mediated response of brachial artery compared with patients with coronary artery disease alone, suggesting more severe dysfunction or, possibly, destruction of the media layer in coronary artery ectasia than in coronary artery disease.

AAA Disease: Mechanism, Stratification, and Treatment

Abdominal aortic aneurysm (AAA) is a common and frequently lethal disease of older Americans. No medical therapy has been proven effective in retarding progression of small AAAs prior to surgical repair. With the emerging ability of magnetic resonance (MR) flow imaging and MR-based computational analysis to define aortic hemodynamic conditions, and bio-imaging strategies to monitor aortic inflammation real time in vivo, the opportunity now exists to confirm the potential value of medical interventions such as supervised exercise training as first line therapy for small AAA disease.

The nitric oxide donor DETA-NONOate decreases matrix metalloproteinase-9 expression and activity in rat aortic smooth muscle and abdominal aortic explants

Our objective was to examine the role of an exogenous nitric oxide (NO) donor, DETA-NONOate (DETA), on matrix metalloproteinase (MMP)-9, MMP-2, and tissue inhibitor of matrix metalloproteinases (TIMP)-1 expression and activity in interleukin (IL)-1beta-induced rat aortic smooth muscle cells (RA-SMCs) and rat aortic explants (RAEs). RA-SMCs were incubated with IL-1beta (2 ng/ml), an inflammatory cytokine known to induce MMP-9 expression, and increasing concentrations of DETA (0, 1.0, 10, 100 microM; n = 3/group) for 48 hr. RAEs were incubated with IL-1beta (2 ng/mL) and increasing concentrations of DETA (0, 5.0, 50, 100, and 500 microM; n = 3/group) for 48 hr. Media were collected and assayed for NO(x) by the Griess reaction and MMP-9 activity by zymography. Messenger RNA (mRNA) was extracted from cells and analyzed for MMP-9, MMP-2, and TIMP-1 expression levels by quantitative real-time reverse-transcriptase polymerase chain reaction. All statistical analyses were performed by analysis of variance. In RA-SMCs and RAEs, DETA administration resulted in a dose-dependent increase in media NOx concentration (RA-SCM p < 0.01, RAE p < 0.01) and a concurrent decrease in both MMP-9 expression (RASMC p = 0.01, RAE p = 0.01) and activity (RASMC p = 0.04, RAE p = 0.006). There were no significant differences seen in MMP-2 and TIMP-1 expression or activity in response to DETA exposure. DETA decreased IL-1beta-induced MMP-9 expression and activity in both RA-SMCs and RAEs in a dose-dependent fashion. In addition, DETA administration had no effect on MMP-2 or TIMP-1 expression or activity in vitro. These data suggest that NO donors may be beneficial in decreasing MMP-9 levels and might serve to inhibit MMP-9-dependent vessel wall remodeling seen during abdominal aortic aneurysm formation.

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.

Simvastatin suppresses experimental aortic aneurysm expansion

OBJECTIVE

Abdominal aortic aneurysm (AAA) formation is a result of inflammation and extracellular matrix (ECM) remodeling mediated by matrix metalloproteinases (MMPs). Hydroxymethylglutaryl-coenzyme A inhibitors (statins), although clinically used as lipid-lowering agents, have also been demonstrated to have anti-inflammatory effects. This study was designed to determine whether the hydroxymethylglutaryl-coenzyme A inhibitor simvastatin suppresses aneurysm formation in an elastase-induced rat AAA model.

METHODS

Aneurysms were created in adult male Wistar rats by infusion of elastase into isolated infrarenal aortic segments. The rats were randomized to receive either simvastatin (n = 17) or placebo (n = 17) by gastric lavage daily starting the day before surgery. The rats were euthanized and the infrarenal aortas harvested on postoperative day 7. Aortic diameters were measured before infusion, immediately after infusion, and at the time of harvesting. Protein expression was measured by immunoblot analysis. Gene expression profiling using Affymetrix U34A rat genome chips was performed to identify changes in gene expression caused by simvastatin treatment.

RESULTS

Mean aneurysm diameter was significantly less in the simvastatin treatment group compared with controls (3.4 +/- 0.08 mm vs 4.3 +/- 0.19 mm; P = .0001). MMP-9 and nuclear factor-kappaB protein levels were decreased in the aortas of simvastatin-treated animals. Gene microarray analysis revealed 315 genes with statistically significant changes in expression (P < .05) in the simvastatin group. Genes related to inflammation, ECM remodeling, and oxidative stress function were downregulated. These included genes for interleukin 1, interleukin 4, inducible nitric oxide synthase, P-selectin, platelet-derived growth factor alpha, tumor necrosis factor, and several chemokines.

CONCLUSIONS

Simvastatin significantly suppresses experimental aneurysm expansion and reduces protein levels of MMP-9 and nuclear factor-kappaB. Gene array analysis provides evidence that several mediators of inflammation, matrix remodeling, and oxidative stress are downregulated by simvastatin treatment. This suggests that simvastatin inhibits AAA formation by blocking the expression of certain proinflammatory genes. Simvastatin may be useful as an adjuvant therapy to suppress the growth of small aneurysms.

A proposed parent vessel geometry-based categorization of saccular intracranial aneurysms: computational flow dynamics analysis of the risk factors for lesion rupture

OBJECT

The authors created a simple, broadly applicable classification of saccular intracranial aneurysms into three categories: sidewall (SW), sidewall with branching vessel (SWBV), and endwall (EW) according to the angiographically documented patterns of their parent arteries. Using computational flow dynamics analysis (CFDA) of simple models representing the three aneurysm categories, the authors analyzed geometry-related risk factors such as neck width, parent artery curvature, and angulation of the branching vessels.

METHODS

The authors performed CFDAs of 68 aneurysmal geometric formations documented on angiograms that had been obtained in patients with 45 ruptured and 23 unruptured lesions. In successfully studied CFDA cases, the wall shear stress, blood velocity, and pressure maps were examined and correlated with aneurysm rupture points. Statistical analysis of the cases involving aneurysm rupture revealed a statistically significant correlation between aneurysm depth and both neck size (p < 0.0001) and caliber of draining arteries (p < 0.0001). Wider-necked aneurysms or those with wider-caliber draining vessels were found to be high-flow lesions that tended to rupture at larger sizes. Smaller-necked aneurysms or those with smaller-caliber draining vessels were found to be low-flow lesions that tended to rupture at smaller sizes. The incidence of ruptured aneurysms with an aspect ratio (depth/neck) exceeding 1.6 was 100% in the SW and SWBV categories, whereas the incidence was only 28.75% for the EW aneurysms.

CONCLUSIONS

The application of standardized categories enables the comparison of results for various aneurysms' geometric formations, thus assisting in their management. The proposed classification system may provide a promising means of understanding the natural history of saccular intracranial aneurysms.

Expressions of inducible nitric oxide synthase and matrix metalloproteinase-9 and their effects on angiogenesis and progression of hepatocellular carcinoma

AIM: To determine the expressions of inducible nitric oxide synthase (iNOS) and matrix metalloproteinase-9 (MMP-9) in hepatocellular carcinoma (HCC) and to investigate the relationship between iNOS and MMP-9 expression and their effects on angiogenesis and progression of HCC.

METHODS: In this study, we examined iNOS, MMP-9, and CD34 expression in specimens surgically removed from 32 HCC patients and 7 normal liver tissues by immunohistochemical staining. Meanwhile, microvessel density (MVD) was determined as a marker of angiogenesis by counting CD34-positive cells.

RESULTS: The positive rates of iNOS and MMP-9 expression were 71.88% (23/32) and 78.13% (25/32) in HCC. MMP-9 expression was significantly correlated with tumor size, capsule status, TNM stage, and risk of HCC recurrence (P = 0.032, P = 0.033, P = 0.007, and P = 0.001, respectively). There was also a significant relationship between iNOS expression and capsule status and risk of HCC recurrence (P = 0.049 and P = 0.004, respectively), but no correlation between iNOS expression and tumor size and TNM stage. There was a positive association between MVD and TNM stage and risk of HCC recurrence (P = 0.037 and P = 0.000, respectively). The count of MVD was significantly different in different iNOS and MMP-9 immunoreactivity groups (F = 17.713 and 17.097, P = 0.000 and P = 0.000, respectively). The examination of Spearman’s rank correlation coefficient showed that there was a

significant positive correlation between MVD and iNOS, MMP-9 immunoreactivity (r = 0.754 and 0.751, P = 0.000 and P=0.000, respectively). There was also a significant association between MMP-9 and iNOS expression in HCC (P = 0.010).

CONCLUSION: Nitric oxide (NO) produced by iNOS could modulate MMP-9 production and therefore contribute to tumor cell angiogenesis and invasion and metastasis in HCC. The strong expression of iNOS and MMP-9 in HCC may be helpful in evaluating the recurrence of HCC, predicting poor prognosis. For patients with strong expression of MMP-9 and iNOS, the optimal treatment scheme needs to be selected.

Suppression of experimental aortic aneurysms: comparison of inducible nitric oxide synthase and cyclooxygenase inhibitors

The rat model of abdominal aortic aneurysm (AAA) is associated with inflammation, destruction of extracellular matrix, and production of both inducible nitric oxide synthase (iNOS) and matrix metalloproteinase-9 (MMP-9). Indomethacin, a nonselective cyclooxygenase inhibitor, may prevent AAA formation by inhibiting cyclooxygenase-2 (COX-2) activity. We hypothesized that indomethacin, rofecoxib (selective COX-2 inhibitor), and 1400 W (selective iNOS activity inhibitor) would decrease aneurysm formation in the rat model. Forty-six male Wistar rats underwent intraaortic elastase infusion in two parallel studies based on medication delivery route. Sixteen rats were randomized to rofecoxib or water by gastric lavage. Thirty rats were randomized to subcutaneous saline, indomethacin, or 1400 W. Heart rate, blood pressure and aortic diameters were measured. Western Blot and mRNA analysis for MMP-9 and iNOS was performed on postoperative day 7 aortic segments. Elastin degradation and inflammation were evaluated by immunohistochemistry. Elastase infusion produced AAA in all rats. 1400 W significantly limited aneurysm expansion (p = 0.01) whereas treatment with indomethacin and rofecoxib did not. Only 1400 W significantly increased blood pressure (p < 0.001). Indomethacin alone statistically decreased MMP-9 (p < 0.011). 1400 W resulted in greater conservation of aortic elastin than indomethacin (p = 0.025). All groups demonstrated statistically similar expression of iNOS. In conclusion, selective iNOS activity inhibitor, 1400 W, significantly decreased aneurysm size and preserved aortic elastin without altering MMP-9 levels. Indomethacin significantly decreased MMP-9 expression without decreasing aneurysm size. Rofecoxib did not significantly decrease MMP-9 expression or aneurysm size. Inhibition of iNOS limits aneurysmal expansion by mechanisms other than MMP-9 inhibition. MMP-9 inhibition by indomethacin is not sufficient to limit aneurysm expansion in our model.

Relationship between iNOS expression and aortic cell proliferation and apoptosis in an elastase-induced model of aorta aneurysm and the effect of 1400 W administration

BACKGROUND

In the present study, we employed an elastase infusion-dependent abdominal aortic aneurysm (AAA) model to examine inducible nitric oxide synthase (iNOS) expression in relation to cellular proliferation and apoptosis in this pathologic condition. Furthermore, we employed N-(3-(aminomethyl)benzyl)acetamidine (1400 W), a previously shown selective iNOS inhibitor, to further explore this relationship.

METHODS

Adult male Wistar rats were randomized into separate groups. Group A served as a control and received an intra-aortic saline infusion, while groups B, C, and D received an intra-aortic elastase infusion according to standard protocols. The animals in group C were administered postoperatively the highly selective iNOS inhibitor, 1400 W, while rats in group D received regularly the same compound preoperatively and postoperatively. The animals were killed at postoperative days 7 and 14. Aorta diameter and nitric oxide (NO), nitrite/nitrate, and MDA levels were measured. iNOS expression was assessed by immunohistochemistry and Western blot analysis, while Ki-67 immunohistochemistry and TUNEL assay were used to evaluate cellular proliferation and apoptosis, respectively.

RESULTS

Increased iNOS and NO levels accompanied aneurysm development in groups B, C, and D, but these levels were significantly lower in groups C and D, compared with group B. Interestingly, very low but detectable levels of iNOS were found in the control group, indicating a basal constitutive level. Cell growth parameters were augmented in group B compared with group A. In contrast, groups C and D exhibited a significant decrease of the cellular growth parameters but did not attain normal values.

CONCLUSIONS

iNOS-derived NO is associated with the cellular growth parameters of the vessel cells, predominantly smooth muscle cells. Selective iNOS blockage ameliorates the cellular remodeling in AAAs.

The presence of tandem endothelial nitric oxide synthase gene polymorphisms identifying brain aneurysms more prone to rupture

Object. It is becoming apparent that the presence of certain genetic variations (polymorphisms) may increase the individual's susceptibility to cardiovascular diseases, even in the absence of a family history. We hypothesized that brain aneurysms more prone to rupture may be identified on the basis of an individual's genotype for endothelial nitric oxide synthase (eNOS), a critical vasomodulatory protein found to be increasingly relevant to the pathobiology of aneurysms.

Methods. Patients' clinical data were recorded prospectively. Genomic DNA was isolated from blood samples obtained from individuals presenting consecutively to the Mayo Clinic with ruptured (58 patients) or unruptured (49 patients) intracranial saccular aneurysms. Using polymerase chain reaction and gene microarray technology, the following eNOS genetic polymorphisms were studied: intron-4 27—base pair variable number of tandem repeats (27 VNTR); promoter single nucleotide polymorphism (T-786C SNP); and exon-7 SNP (G894T SNP).

Both groups of patients had similar demographic and clinical characteristics. For all three polymorphisms, variant alleles (p ≤ 0.003) and their corresponding genotypes (p ≤ 0.006) were found two to four times more frequently in patients with ruptured aneurysms than in patients with unruptured aneurysms. Strikingly, the odds ratio for presenting with a ruptured brain aneurysm among individuals demonstrating the copresence of all three variant alleles was 11.4 (95% confidence interval 1.7–75.9, p = 0.004).

Conclusions. The authors have uniquely identified a set of tandem eNOS gene variations whose presence can be used to identify patients with aneurysms likely to rupture. We believe that if this finding is reproducible in a large multicenter study, in addition to known anatomical factors a rapid and cost-effective screening tool will become available to clinicians as a genetic aid to predict the risks of rupture in patients presenting with unruptured intracranial aneurysms.

Hyperglycemia reduces survival and impairs function of circulating blood-derived progenitor cells

OBJECTIVE

Function and availability of circulating progenitor cells (CPC) have been shown to be impaired in patients with diabetes mellitus (DM). Therefore, the aim of the present study was to analyze possible mechanisms leading to the reduction of CPC amount and function.

METHODS AND RESULTS

Peripheral blood mononuclear cells (MNCs) of healthy donors (n=15) were cultivated under hyperglycemia (HG) conditions (12 mmol/L D-Glucose) or in osmotic control medium (Con) (5 mmol/L D-Glucose plus 7 mmol/L L-Glucose) for 7 days. CPC amount was determined by uptake of acetylated low-density lipoprotein and lectin binding. On the functional level, cell cycle status, nitric oxide (NO) production, and migrational and integrative capacity of CPCs were assessed. HG conditions caused a significant decrease in CPC amount derived from healthy MNCs. Furthermore, HG conditions led to a functional impairment, reflected in a decreased NO production and matrix metalloproteinase (MMP)-9 activity, as well as an impairment of the migrational and integrative capacities.

CONCLUSIONS

HG, a main feature of DM, affects important functional characteristics of CPCs. These results may provide further insight into the pathomechanism of endothelial dysfunction in HG.

Update on genetic evidence for rupture-prone compared with rupture-resistant intracranial saccular aneurysms

Object

Anecdotal evidence exists for at least two subpopulations of intracranial saccular aneurysms; those that form rapidly and rupture when small and those that enlarge slowly and are particularly prone to rupture when they are 10 mm or more in diameter. The goal in this study was to determine if there was genetic evidence to support the classification of intracranial saccular aneurysms as “rupture-prone” or “rupture-resistant” lesions.

Methods

The authors prospectively obtained and analyzed clinical and genetic data in a cohort of 197 individuals composed of 58 patients with ruptured intracranial saccular aneurysms, 49 with unruptured aneurysms, and 90 healthy community volunteers. Based on recent studies supporting an increasingly relevant role for the critical vasomodulatory protein endothelial nitric oxide synthase (eNOS) in aneurysm pathobiology, the authors assayed blood from all 197 participants to determine and compare their eNOS genotypes.

TheeNOSgene intron 4 27–base pair variable-number tandem-repeat polymorphism was significantly overrepre-sented in persons with ruptured intracranial saccular aneurysms compared with community volunteers (p <0.002). When comparing eNOS genotypes among patients with ruptured or unruptured aneurysms, an approximately 10-fold increase in the odds of presenting with brain aneurysm rupture was found among individuals with multiple variant eNOS alleles (p = 0.004).

Conclusions

Uniquely, the authors have identified a set ofeNOSgene variations whose presence indicates patients with intracranial saccular aneurysms that are more prone to rupture. The authors conclude that if these findings are reproducible in the setting of a large multicenter study, then in addition to known anatomical factors, a rapid and cost-effective genetic screening tool will become available to clinicians as an aid to predicting rupture risks in patients presenting with unruptured intracranial aneurysms.

Endothelial nitric oxide synthase gene polymorphisms predict susceptibility to aneurysmal subarachnoid hemorrhage and cerebral vasospasm

Rupture of an intracranial aneurysm (subarachnoid hemorrhage) is a potentially devastating condition frequently complicated by delayed cerebral ischemia from sustained contraction of intracranial arteries (cerebral vasospasm). There is mounting evidence linking the formation of intracranial aneurysms and the pathogenesis of post-subarachnoid hemorrhage vasospasm to aberrant bioavailability and action of the vasodilator molecule nitric oxide generated by isoforms of nitric oxide synthase. In humans, the gene encoding the endothelial isoform of nitric oxide synthase (eNOS) is known to be polymorphic, with certain polymorphisms associated with increased cardiovascular disease susceptibility. In this prospective clinical study involving 141 participants, we used gene microarray technology to demonstrate that the eNOS gene intron-4 27-base pair variable number tandem repeat polymorphism (eNOS 27 VNTR) predicts susceptibility to intracranial aneurysm rupture, while the eNOS gene promoter T-786C single nucleotide polymorphism (eNOS T-786C SNP) predicts susceptibility to post-subarachnoid hemorrhage vasospasm. We believe that genetic information such as this, which can be obtained expeditiously at the time of diagnosis, may be used as a helpful adjunct to other clinical information aimed at predicting and favorably modifying the clinical course of persons with intracranial aneurysms.

Gene Therapy and Endovascular Treatment of Intracranial Aneurysms

Background— Endovascular treatment of intracranial aneurysms is safe and effective but too often is followed by recurrences. Gene therapy may improve healing after embolization, and endovascular approaches may offer future in situ delivery systems designed to prevent aneurysm rupture.

Summary of Review— Advances in coil technology have focused on coating strategies designed to modify the biological reaction to the embolic agent. Gene therapy in cardiovascular applications is limited by low efficiency and transient gene expression. Current advances include the potential use of circulating progenitor cells for ex vivo genetic manipulations followed by in vivo delivery. Direct gene transfer may also be enhanced in situ by coils carrying antibody-tethered adenovirus or through the use of cell-specific or radiation-inducible promoters. Candidate genes that may be of value in promoting healing after endovascular treatment include growth factors and metalloproteinase inhibitors. A better understanding of the biology of aneurysm is necessary to conceive strategies designed to control the development of these lesions before their rupture.

Conclusions— Many technical difficulties remain to be solved, but the combination of gene therapy and endovascular techniques offers multiple therapeutic possibilities in the future control of intracranial aneurysms.

Endothelial Nitric Oxide Synthase T-786C Single Nucleotide Polymorphism

Background and Purpose— Anecdotal evidence exists for at least 2 subpopulations of intracranial saccular aneurysms, namely, those that may form rapidly and rupture when small versus those that enlarge slowly and may rupture particularly when ≥10 mm in diameter. We sought to determine whether the endothelial nitric oxide synthase (eNOS) T-786C single nucleotide polymorphism (SNP), implicated in cardiovascular disease susceptibility, could facilitate differentiation between small (≤5 mm) versus large (≥10 mm) ruptured aneurysms.

Methods— In accordance with institutional guidelines, clinical data were recorded prospectively and genomic DNA was isolated from blood samples obtained from 52 aneurysmal subarachnoid hemorrhage (SAH) patients (cases) and 90 randomly selected controls. Samples were assayed for eNOS gene promoter T-786C SNP with the use of gene microarray technology. Statistical analyses included multiple logistic regression.

Results— Although there was no difference in genotype distributions between cases and controls, all 13 patients with large aneurysms were ( T / C ) heterozygous for the polymorphism, while 9 of 22 patients (41%) with small aneurysms were ( T / T or C / C ) homozygous ( P =0.01). The mean (±SD) ruptured aneurysm diameter among all heterozygotes (8.5±5.2 mm) was significantly greater than that for C / C (6.0±2.3 mm) or T / T (4.7±1.8 mm) homozygotes ( P =0.04). With the use of multivariate analysis, heterozygosity remained significantly associated with aneurysm size ≥10 mm ( P =0.03).

Conclusions— The eNOS T-786C SNP distinguishes genetically between small and large ruptured aneurysms. Although not predictive of SAH in the population at large, our data suggest that among persons with known intracranial aneurysms, eNOS T-786C genotype may be a factor influencing the size at which an aneurysm ruptures, a finding that should be taken into consideration along with other anatomic features of the aneurysm.

Inducible nitric oxide synthase is present in human abdominal aortic aneurysm and promotes oxidative vascular injury

OBJECTIVE

Nitric oxide (NO), catalyzed by inducible NO synthase (iNOS), may be important in the pathophysiologic characteristics of many vascular diseases. Although there is indirect evidence to support the presence of iNOS in abdominal aortic aneurysm (AAA) in human beings, no definitive study has confirm this finding. The present study was designed to assess expression of iNOS in AAA in human beings. Furthermore, the activity of iNOS and the oxidative vascular injury initiated by iNOS were assessed with detection of nitrotyrosine, which is a marker indicative of formation and activity of the NO-derived oxidant peroxynitrite.

METHODS

We studied 25 patients with AAA and 10 patients with normal abdominal aortas. In situ hybridization and immunohistochemistry were used in tissue sections to localize iNOS messenger RNA (mRNA) and protein. Double staining with a combination of in situ hybridization and immunohistochemistry was used to simultaneously demonstrate iNOS mRNA expression and its cellular localization. The presence of peroxynitrite was indirectly assessed with immunostaining with anti-nitrotyrosine antibodies.

RESULTS

In situ hybridization and immunohistochemistry confirmed the presence of iNOS in media and adventitia of AAA in all 25 patients. Specific cell markers identified iNOS mRNA-positive cells mainly as T and B lymphocytes, macrophages, and smooth muscle cells. Positive immunostaining for nitrotyrosine was present in macrophages and smooth muscle cells. Normal abdominal aorta demonstrated virtually no iNOS or nitrotyrosine expression.

CONCLUSION

Stimulated expression of iNOS is associated with degeneration of AAA in human beings, and the activity of this enzyme under such conditions preferentially promotes formation and activity of peroxynitrite and further contributes to oxidative tissue and cellular injury in AAA. This may be important in the pathogenesis of AAA.

Prospects for the medical management of abdominal aortic aneurysms

Abdominal aortic aneurysms (AAAs) are a chronic degenerative disease with life-threatening implications. While AAAs are thought to arise through a localized form of arterial wall injury superimposed on various predisposing factors, their natural history is one of progressive structural deterioration, gradual expansion, and eventual rupture. Pathologic processes contributing to the changes observed in AAAs include chronic inflammation, destructive remodeling of the extracellular matrix, and depletion of vascular smooth muscle cells. These changes result in progressive aortic dilatation accompanied by alterations in vessel geometry, redistribution of hemodynamic wall stresses, and diminished tensile strength. As outlined in this review, better understanding of the biological mechanisms underlying these changes will allow design of novel therapeutic strategies to suppress the process of aneurysmal degeneration.