The nitrite/elastin reaction: implications for in vivo degenerative effects

PCSK9 as an Atherothrombotic Risk Factor

Disturbances in lipid metabolism are among the most important risk factors for atherosclerotic cardiovascular disease. Proprotein convertase subtilisin/kexin type 9 (PCSK9) is a key protein in lipid metabolism that is also involved in the production of inflammatory cytokines, endothelial dysfunction and aherosclerotic plaque development. Studies have shown a connection between PCSK9 and various indicators of inflammation. Signalling pathways that include PCSK9 play important role in the initiation and development of atherosclerotic lesions by inducing vascular inflammation. Studies so far have suggested that PCSK9 is associated with procoagulation, enhancing the development of atherosclerosis. Experimentally, it was also found that an increased concentration of PCSK9 significantly accelerated the apoptosis of endothelial cells and reduced endothelial function, which created conditions for the development of atherosclerosis. PCSK9 inhibitors can therefore improve clinical outcomes not only in a lipid-dependent manner, but also through lipid-independent pathways. The aim of our review was to shed light on the impact of PCSK9 on these factors, which are not directly related to low-density lipoprotein (LDL) cholesterol metabolism.

The Importance of Arterial Stiffness Assessment in Patients with Familial Hypercholesterolemia

Cardiovascular diseases are still the leading cause of mortality due to increased atherosclerosis worldwide. In the background of accelerated atherosclerosis, the most important risk factors include hypertension, age, male gender, hereditary predisposition, diabetes, obesity, smoking and lipid metabolism disorder. Arterial stiffness is a firmly established, independent predictor of cardiovascular risk. Patients with familial hypercholesterolemia are at very high cardiovascular risk. Non-invasive measurement of arterial stiffness is suitable for screening vascular dysfunction at subclinical stage in this severe inherited disorder. Some former studies found stiffer arteries in patients with familial hypercholesterolemia compared to healthy controls, while statin treatment has a beneficial effect on it. If conventional drug therapy fails in patients with severe familial hypercholesterolemia, PCSK9 inhibitor therapy should be administered; if these agents are not available, performing selective LDL apheresis could be considered. The impact of recent therapeutic approaches on vascular stiffness is not widely studied yet, even though the degree of accelerated athero and arteriosclerosis correlates with cardiovascular risk. The authors provide an overview of the diagnosis of familial hypercholesterolemia and the findings of studies on arterial dysfunction in patients with familial hypercholesterolemia, in addition to presenting the latest therapeutic options and their effects on arterial elasticity parameters.

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.

Persistent augmentation of central arterial stiffness following viral clearance by direct-acting antivirals in chronic hepatitis C

Chronic hepatitis C virus (HCV) infection is associated with risk of cardiovascular diseases. Although direct-acting antivirals (DAA) result in rapid eradication of HCV, their long-term impact on arterial stiffness remains unclear. This study aimed to evaluate changes in parameters of central arterial stiffness from pretreatment, through sustained virological response, to one year after viral clearance. Patients with chronic HCV receiving DAA treatment were enrolled prospectively. Medical history and comorbidities of all patients were collected. Lipid profiles, liver stiffness by transient elastography and central blood pressures using pulse wave analysis of the brachial artery by cuff sphygmomanometry were measured before treatment, at viral clearance and at one year following viral clearance. Augmentation index (AIx), a parameter of aortic stiffness, was calculated as the ratio of augmentation pressure to central pulse pressure. After DAA treatment, all included patients with chronic HCV (n = 102) had achieved viral clearance. Cholesterol, low-density lipoprotein (LDL) and triglyceride/high-density lipoprotein (TG/HDL) increased significantly at viral clearance and persisted at one year (all P < .001). AIx was also elevated significantly at viral clearance and persisted one year later (P < .001). Changes in AIx remained significant only in patients with increased values from baseline in either LDL (P < .01) or TG/HDL (P < .001). Central arterial stiffness and lipid profiles in patients with chronic HCV worsen immediately after viral eradication by DAA treatment and persist at one year. Worsening of lipid profiles after DAA treatment contributes to central arterial stiffness in this patient population and persists long term.

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.

Nitrite ion modifies tyrosine and lysine residues of extracellular matrix proteins

Age-related macular degeneration (AMD) is a disease characterized by degenerative changes in the retinal pigment epithelium and Bruch's membrane. Inflammation is considered a major risk factor for the development and progression of AMD. Nitrite is a potent byproduct of inflammation and has been detected at elevated concentrations in AMD donor tissue. We hypothesize that nitrite chemically modifies the extracellular matrix (ECM) of Bruch's membrane as an initial step to degenerative changes observed in AMD. Non-enzymatically nitrated synthetic ECM peptides, fibronectin and laminin, were used as model systems for inflammation. Using LC/MS, we identified that nitration preferentially occurred on tyrosine and deamination of lysine under the studied conditions. At tyrosine residues, 3-nitrotyrosine was produced and shifted the total mass by the addition of 45 amu. Deamination of lysine occurred and resulted in the formation of either an alkene or alcohol group. The alkene group was observed with a loss of 17 amu. An addition of 1 amu was observed with alcohol formation. We hypothesize that these initial chemical modifications to the structure of ECM proteins may be the responsible for altering the structure and consequent function of Bruch's membrane.

Autoimmunity in the Abdominal Aortic Aneurysm and its Association with Smoking

Smoking increases the risk of abdominal aortic aneurysm (AAA) in both humans and mice, although the underlying mechanisms are not completely understood. An adventitial aortic antigen, AAAP-40, has been partially sequenced. It has motifs with similarities to all three fibrinogen chains and appears to be connected in evolution to a large family of proteins called fibrinogen-related proteins. Fibrinogen may undergo non-enzymatic nitration, which may result from exposure to nitric oxide in cigarette smoke. Nitration of proteins renders them more immunogenic. It has recently been reported that anti-fibrinogen antibody promotes AAA development in mice. Also, anti-fibrinogen antibodies are present in patients with AAA. These matters are reviewed in the overall context of autoimmunity in AAA. The evidence suggests that smoking amplifies an auto-immune reaction that is critical to the pathogenesis of AAA.

The relationship between serum endocan levels and the presence/severity of isolated coronary artery ectasia

Objective

The aim of this study was to investigate the relationship between serum endocan levels and the presence and severity of isolated coronary artery ectasia (CAE).

Patients and methods

A total of 52 patients with CAE without obstructive coronary artery disease and 33 participants with a normal coronary artery were included in this study. The severity of CAE was graded according to Markis classification. Serum endocan levels were measured by enzyme-linked immunosorbent assay method.

Results

In multivariate regression analysis, high sensitivity C-reactive protein and endocan levels were found to be significantly associated with the presence of isolated CAE. However, there was no relationship between serum endocan levels and the severity of CAE according to Markis classification.

Conclusion

Plasma endocan levels may reflect the presence of isolated CAE, suggesting that endocan may be involved in the pathogenesis of isolated CAE.

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.

Carotid and Aortic Stiffness in Patients with Heterozygous Familial Hypercholesterolemia

Background

The role of plasma cholesterol in impairing arterial function and elasticity remains unclear. We evaluated arterial stiffness, measured locally in the common carotid artery by high-resolution echo-tracking, and aortic stiffness, using carotid-femoral pulse wave velocity (PWV) (the “gold-standard” measurement of arterial stiffness), in treatment-naive patients with heterozygous familial hypercholesterolemia (FH).

Methods

The study included 66 patients with FH (10–66 years old) and 57 first-degree relatives without FH (11–61 years old). Carotid-femoral PWV was determined by SphygmoCor (AtCor, Australia). The parameters of carotid stiffness β-index, Peterson elastic modulus and local PWV were assessed with regard to the common carotid artery at a distance of 1cm from the bifurcation (AlokaProsound Alpha7, Japan).

Results

FH patients showed significantly higher β-index (6.3(4.8–8.2) vs. 5.2(4.2–6.4), p = 0.005), Ep (78(53–111) kPa vs. 62(48–79) kPa, p = 0.006), local PWV (5.4(4.5–6.4) m/c vs. 4.7(4.2–5.4) m/c, p = 0.005), but comparable values of carotid-femoral PWV (6.76(7.0–7.92) m/c vs. 6.48(6.16–7.12) m/c, p = 0.138). Carotid arteries and the aorta stiffened with age in patients with FH, but after 30 years, carotid arteries stiffened more significantly than the aorta.

Conclusions

Our study demonstrated that treatment-naive patients with FH had stiffer carotid arteries than their relatives, but showed no difference in aortic stiffness. We also found out that the rate of reduction of elasticity of the aorta and carotid arteries in FH patients varies: it is observed earlier in carotid arteries than in the aorta.

Plasma Endocan Levels in Patients With Isolated Coronary Artery Ectasia

Endocan is a soluble proteoglycan, secreted by human vascular endothelial cells. Endocan is a marker for vascular pathologies and an important mediator of angiogenesis, strongly associated with inflammation, vascular endothelial dysfunction, and atherosclerosis. The relationship between coronary artery ectasia (CAE) and endocan has not been evaluated. We aimed to investigate this association. Fifty-four patients with isolated CAE without coronary stenosis and 30 controls with normal coronary angiogram were included in this study. Endocan plasma concentrations were measured using an enzyme-linked immunosorbent assay. Patients with isolated CAE had significantly higher levels of endocan compared to the controls (18.9 ± 7.3 vs 15.6 ± 3.6 ng/mL; P = .007). There was a significant correlation between endocan levels and severity of isolated CAE according to the Markis classification ( r = -.593, P < .001). Plasma endocan levels may reflect the presence and severity of isolated CAE, suggesting that endocan may be involved in pathogenesis of isolated CAE.

Vitamin D induces increased systolic arterial pressure via vascular reactivity and mechanical properties

Background/Aims

The aim of this study was to evaluate whether supplementation of high doses of cholecalciferol for two months in normotensive rats results in increased systolic arterial pressure and which are the mechanisms involved. Specifically, this study assesses the potential effect on cardiac output as well as the changes in aortic structure and functional properties.

Methods

Male Wistar rats were divided into three groups: 1) Control group (C, n = 20), with no supplementation of vitamin D, 2) VD3 (n = 19), supplemented with 3,000 IU vitamin D/kg of chow; 3) VD10 (n = 21), supplemented with 10,000 IU vitamin D/kg of chow. After two months, echocardiographic analyses, measurements of systolic arterial pressure (SAP), vascular reactivity, reactive oxygen species (ROS) generation, mechanical properties, histological analysis and metalloproteinase-2 and -9 activity were performed.

Results

SAP was higher in VD3 and VD10 than in C rats (p = 0.001). Echocardiographic variables were not different among groups. Responses to phenylephrine in endothelium-denuded aortas was higher in VD3 compared to the C group (p = 0.041). Vascular relaxation induced by acetylcholine (p = 0.023) and sodium nitroprusside (p = 0.005) was impaired in both supplemented groups compared to the C group and apocynin treatment reversed impaired vasodilation. Collagen volume fraction (<0.001) and MMP-2 activity (p = 0.025) was higher in VD10 group compared to the VD3 group. Elastin volume fraction was lower in VD10 than in C and yield point was lower in VD3 than in C.

Conclusion

Our findings support the view that vitamin D supplementation increases arterial pressure in normotensive rats and this is associated with structural and functional vascular changes, modulated by NADPH oxidase, nitric oxide, and extracellular matrix components.

Elastin and collagen fibre microstructure of the human aorta in ageing and disease: a review

Aortic disease is a significant cause of death in developed countries. The most common forms of aortic disease are aneurysm, dissection, atherosclerotic occlusion and ageing-induced stiffening. The microstructure of the aortic tissue has been studied with great interest, because alteration of the quantity and/or architecture of the connective fibres (elastin and collagen) within the aortic wall, which directly imparts elasticity and strength, can lead to the mechanical and functional changes associated with these conditions. This review article summarizes the state of the art with respect to characterization of connective fibre microstructure in the wall of the human aorta in ageing and disease, with emphasis on the ascending thoracic aorta and abdominal aorta where the most common forms of aortic disease tend to occur.

Estrogen Receptor Activation Protects Against TNF-α-Induced Endothelial Dysfunction

Lack of estrogen is a cause of cardiovascular disease in men and postmenopausal women. We examined the effects of estrogen receptor (ERs) activation/inactivation on endothelial cells subjected to tumor necrosis factor (TNF) α, which is involved in vascular disease pathogenesis. Endothelial nitric oxide synthase (eNOS) and matrix metalloproteinases (MMP) 9 expression, as well as protein kinase B (PKB) activation were evaluated as markers of endothelial dysfunction. The TNF-α induces eNOS and MMP-9 expression and PKB activation. The ER activation by apigenin, a nonsteroidal compound with estrogen-like activity mediated through ER binding-dependent pathways, counteracts these effects. These effects are reversed by classic (ER-α and ER-β) and nonclassic (G-protein-coupled receptor) ER inhibitors (ICI182 780 and pertussis toxin, respectively). Our data suggest that ER activation counteracts endothelial dysfunction induced by TNF-α. The use of ER activators, such as apigenin, may represent a strategy to prevent vascular disease associated with endothelial dysfunction, while avoiding the feminizing effects of estrogens.

Impact of ADMA, endothelial progenitor cells and traditional cardiovascular risk factors on pulse wave velocity among prediabetic individuals

Background

Central arterial stiffness represents a well-established predictor of cardiovascular disease. Decreased circulating endothelial progenitor cells (EPCs), increased asymmetric dimethyl-arginine (ADMA) levels, traditional cardiovascular risk factors and insulin resistance have all been associated with increased arterial stiffness. The correlations of novel and traditional cardiovascular risk factors with central arterial stiffness in prediabetic individuals were investigated in the present study.

Methods

The study population consisted of 53 prediabetic individuals. Individuals were divided into groups of isolated impaired fasting glucose (IFG), isolated impaired glucose tolerance (IGT) and combined IGT-IFG. Age, sex, family history of diabetes, smoking history, body mass index (BMI), waist to hip ratio (WHR), waist circumference (WC), blood pressure, lipid profile, levels of high sensitive C-reactive protein (hsCRP), glomerular filtration rate (GFR), and history of antihypertensive or statin therapy were obtained from all participants. Insulin resistance was evaluated using the Homeostatic Model Assessment (HOMA-IR). Carotid -femoral pulse wave velocity was used as an index of arterial stiffness. Circulating EPC count and ADMA serum levels were also determined.

Results

Among studied individuals 30 (56.6%) subjects were diagnosed with isolated IFG, 9 (17%) with isolated IGT (17%) and 14 with combined IFG-IGT (26.4%). In univariate analysis age, mean blood pressure, fasting glucose, total cholesterol, LDL cholesterol, and ADMA levels positively correlated with pulse-wave velocity while exercise and GFR correlated negatively. EPC count did not correlate with PWV. In multivariate stepwise regression analysis PWV correlated independently and positively with LDL-Cholesterol (low density lipoprotein) and ADMA levels and negatively with exercise.

Conclusions

Elevated ADMA and LDL-C levels are strongly associated with increased arterial stiffness among pre-diabetic subjects. In contrast exercise inversely correlated with arterial stiffness.

Apigenin inhibits the TNFα-induced expression of eNOS and MMP-9 via modulating Akt signalling through oestrogen receptor engagement

Apigenin is a naturally occurring plant flavone with strong anti-oxidant and anti-inflammatory activity. While the anticancer properties of Apigenin have been extensively studied, little is known about its effects on endothelial dysfunction. We investigated the effects of Apigenin in EAhy926 endothelial cells exposed to TNFα by evaluating the expression of eNOS and MMP-9, two key molecules in endothelial dysfunction. MMP-9 activity was measured by gel zymography. Western blot analysis was performed to analyze eNOS expression and signal transduction. Treatment with Apigenin (50 μM) counteracted the TNFα-induced expression of eNOS and MMP-9 and the TNFα- triggered activation of Akt, p38MAPK and JNK signalling suggesting that multiple signalling pathways are involved in mediating the protective effects of Apigenin on endothelial function. To better understand the molecular mechanisms underlying the protective effects of Apigenin, we used a pharmacological approach with specific inhibitors. The use of an Akt inhibitor mimicked the inhibitory effects of Apigenin on eNOS and MMP-9 expression, suggesting that eNOS and MMP-9 induction by TNFα depends on Akt activation. The TNFα-induced expression of MMP-9 was also affected by the JNK inhibitor SP600125. No effect on eNOS and MMP-9 expression was observed in the presence of the p38MAPK inhibitor SB203580 or the ERK 1/2 inhibitor PD98059. Pretreatment with 'classic' (ERα and ERβ) or 'non classic' (GPR30) oestrogen receptor (ER) inhibitors (ICI182,780 and PTX, respectively) counteracted the ability of Apigenin to decrease the TNFα-triggered activation of the Akt pathway. Consistently, the use of both ER inhibitors reversed the inhibitory effects of Apigenin on the TNFα-induced expression of eNOS and, to a lesser extent, MMP-9. We can conclude that Apigenin exerts its inhibitory effect on the TNFα-induced expression of eNOS and MMP-9 through the Akt signalling inhibition generated by ER activation. Oestrogen signalling has been implicated in protection from cardiovascular disease. Therefore, having regard to its ability to bind to ERs, Apigenin may be considered an oestrogen-like molecule to potentially be used against the onset and progression of vascular diseases associated with endothelial dysfunction.

Sodium nitrite de-stiffening of large elastic arteries with aging: role of normalization of advanced glycation end-products

We tested the hypothesis that sodium nitrite treatment reverses large elastic artery stiffening in old mice via reductions in collagen I, increases in elastin and/or decreases in advanced glycation end products (AGEs) mediated by reduced oxidative stress. Aortic pulse wave velocity (aPWV), a measure of large elastic artery stiffness, was greater in old (26-28months) compared with young (4-6months) control animals (520±9 vs. 405±6cm/s, p<0.05), and this was reversed by 3weeks of sodium nitrite treatment (50mg/L) (435±17cm/s). Age-related increases (p<0.05) in aortic superoxide production were associated with greater total and adventitial nitrotyrosine staining, all of which were reversed by nitrite treatment. Total and adventitial transforming growth factor β and collagen I were increased, and total and medial elastin were reduced with aging (p<0.05), but were unaffected by sodium nitrite. Aorta from old mice had increased total, adventitial and medial AGEs (p<0.05 vs. young), which were normalized by sodium nitrite treatment. In aortic segments from young mice in vitro, pyrogallol (10μM), a superoxide generator, induced an "aging-like" increase in AGEs, and direct treatment with AGEs induced vascular stiffening; these effects were prevented by incubation with sodium nitrite. De-stiffening of aged large elastic arteries by short-term sodium nitrite therapy is mediated in part by normalization of AGEs secondary to amelioration of oxidative stress.

Age-related accumulation of 3-nitrotyrosine and nitro-A2E in human Bruch's membrane

Age-related macular degeneration (AMD) is a disease leading to severe visual loss and legal blindness in the elderly population. The pathophysiology of AMD is complex and may include genetic predispositions, accumulation of lipofuscin and drusen, local inflammation and neovascularization. Recently four independent research groups have identified a commonly inherited variant (Y402H) of the complement factor H gene in the genome from different groups of AMD patients. The Y402H variant of CFH significantly increases the risk of AMD and links the genetics of the disease with inflammation. During inflammation there is activation of inducible nitric oxide synthase and release of nitric oxide, which in principal could lead to non-enzymatic nitration within extracellular deposits and/or intrinsic extracellular matrix protein components of human Bruch's membrane. We have identified two biomarkers for non-enzymatic nitration in aged human Bruch's membrane, indicative of inflammation, that include 3-nitrotyrosine identified in Bruch's membrane preparations and nitrated A2E from the lipid soluble extract of the Bruch's membrane preparation. Approximately 30-40 times more A2E is observed in samples of the organic soluble extract of lipofuscin compared to the extract of Bruch's membrane. It is of interest to note that although A2E is a major constituent of RPE lipofuscin, nitrated A2E could not be detected in RPE extracts. We show here that nitro-A2E is a specific biomarker of nitrosative stress in Bruch's membrane and its concentration correlates directly with tissue age.

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.

Nitrite-Modified Extracellular Matrix Proteins Deleteriously Affect Retinal Pigment Epithelial Cell Function and Viability: A Comparison Study with Nonenzymatic Glycation Mechanisms

PURPOSE

Extracellular matrix (ECM) plays an important role in the regulation of cell function. The aging process may involve chemical modifications to ECM proteins, which may contribute to the aging of the Bruch membrane and pathogenesis of age-related macular degeneration (AMD). The purpose of this study is to investigate nitrite modification of basement membrane-like proteins on RPE cell behavior as a model for the aging of the Bruch membrane in age-related eye diseases. As a comparison, retinal pigment epithelium (RPE) cell behavior on glycolaldehyde-modified matrices (GMM) was also studied.

METHODS

Growth factor reduced Matrigel was reacted with nitrite or glycolaldehyde for 1 week or 12 hr, respectively. Calf RPE cells were plated on the modified matrices and examined in several ways. Attachment rates, proliferation rates, apoptosis, and necrosis were determined. Cell morphology and cell susceptibility to A2E-mediated damage was also monitored.

RESULTS

Nitrite-modified matrices (NMMs) inhibited cell attachment by 65% and proliferation by 33.7% compared to 69.6% and 21.7%, respectively, by GMM. Proliferation inhibition was not significant when cells were plated at high density on GMM (3.47%) but significant on NMM (20.9%). NMM induced cell apoptosis and necrosis, but GMM induced cell apoptosis only. Both modifications inhibited RPE differentiation. RPE cells on both matrices were more susceptible to blue light mediated damage by A2E, but damage was greater on NMM.

CONCLUSIONS

NMM has significant damaging effects on RPE cell function and viability that is similar to the damaging effects of GMM. These studies may have relevance to the RPE dysfunction observed during the progression of AMD.

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.

Inhibition of reactive oxygen species attenuates aneurysm formation in a murine model

Reactive oxygen species (ROS) are increased in human abdominal aortic aneurysms (AAA). NADPH oxidases are the predominant source of superoxide anion (O(2)(-)) in the vasculature. Inducible nitric oxide synthase (iNOS) produces a significant amount of nitric oxide (NO) during inflammatory processes. We hypothesized that ROS produced by NADPH oxidases and iNOS played an important role in aneurysm formation. We examined this hypothesis using selective blockade of NADPH oxidases and iNOS in a murine model of AAA. Mice, including C57BL/6, iNOS knockout (iNOS(-/-)) mice, and its background matched control (C57BL/6), underwent AAA induction by periaortic application of CaCl(2). Aortic diameter was measured at aneurysm induction and harvest. Beginning 1 week prior to aneurysm induction and continuing to aortic harvest 6 weeks later, one group of the C57BL/6 mice were treated with orally administered apocynin (NADPH oxidase inhibitor). Control mice were given water. The mean diameter and change in diameter of each group were compared with concurrent controls. Aortic levels of the NO metabolite, NO(x) (NO(2) and NO(3)), were significantly increased in CaCl(2)-treated wild type mice. INOS(-/-) mice were partly resistant to aneurysm induction. This was associated with reduced expression of matrix metalloproteinase (MMP)-2 and MMP-9 and decreased production of NO(x) in the aortic tissues. Inhibition of NADPH oxidase by apocynin also blocked aneurysm formation. In conclusion, both iNOS deficiency and NADPH oxidase inhibition suppressed aneurysm formation in association with decreased NO(x) levels. These studies suggest that both NADPH oxidase and iNOS pathways contribute to ROS production and AAA development.

Consumption of cured meats and prospective risk of chronic obstructive pulmonary disease in women

BACKGROUND

Most cured meats contain nitrites. Nitrites generate oxidative-nitrative stress and were shown in animal models to cause emphysema. Prospective epidemiologic data on cured meats and chronic obstructive pulmonary disease (COPD), however, are sparse.

OBJECTIVE

We examined the relation between cured meat consumption and the prospective risk of newly diagnosed COPD in women.

DESIGN

This was a prospective cohort study of 71 531 women from the Nurses' Health Study who completed a validated dietary questionnaire at baseline in 1984 and had no baseline COPD or a report of asthma. Participants were aged 38-63 y in 1984 and were followed for 16 y.

RESULTS

A total of 750 new cases of COPD were documented during the follow-up. Cured meat consumption was positively associated with COPD risk after adjustment for age, smoking, and multiple other potential confounders. The adjusted relative risks of COPD across categories of cured meat consumption (never or almost never, 1-3 servings/mo, 1 serving/wk, 2-3 servings/wk, and > or = 4 servings/wk) were 1.0, 1.14 (95% CI: 0.78, 1.66), 1.15 (95% CI: 0.79, 1.69), 1.40 (95% CI: 0.96, 2.05), and 1.51 (95% CI: 1.00, 2.27), respectively, (P for trend = 0.005). This positive association was present among both past (P for trend = 0.02) and current (P for trend = 0.03) smokers. No association was observed among never smokers, probably because of the small number of COPD cases in these women.

CONCLUSION

Frequent cured meat consumption was associated with an increased risk of newly diagnosed COPD among women who smoke.

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.

Cigarette smoking increases aortic dilatation without affecting matrix metalloproteinase-9 and -12 expression in a modified mouse model of aneurysm formation

OBJECTIVE

The development of abdominal aortic aneurysms (AAA) is presumed to result from multiple genetic and environmental factors, with exposure to tobacco smoke the single largest known factor predisposing to aneurysm growth. We have attempted to adapt the elastase-perfused animal model to determine whether tobacco exposure can lower the threshold of aortic injury necessary for AAA development.

METHODS

Adult C57BL/6 mice underwent transient perfusion of the infrarenal aorta with an active solution of elastase: high-dose (HDE, 0.19 U/mL, n=9), standard-dose (SDE, 0.16 U/mL, n=21) or low-dose (LDE, 0.07 U/mL, n=24). Control animals (n=24) were treated with heat inactivated elastase (HIE). Twenty LDE perfused mice were exposed to cigarette smoke (LDE-S) beginning 2 weeks before perfusion and continuing until aortic harvest. Aortic diameter (AD) was measured preperfusion, postperfusion, and at harvest on day 14. AAA was defined as %DeltaAD>or=100% between preperfusion and harvest. Aortas from each group (except HDE) were analyzed for matrix metalloproteinase-9 (MMP-9) and MMP-12 expression by real-time polymerase chain reaction normalized to glyceraldehyde-3-phosphate dehydrogenase.

RESULTS

All SDE mice developed large AAA by %DeltaAD (189.3%+/-16.9%, mean+/-standard error of the mean), but control mice had only a small dilatation (69.7%+/-3.7%, P<.01). Higher doses of elastase did not produce larger aneurysms in HDE mice. In contrast, only 63% of LDE mice showed aneurysmal dilatation, and these were significantly smaller (104.3%+/-4.2%, P<.01). When exposed to cigarette smoke, LDE animals developed significantly larger aneurysms (%DeltaAD, 134.5%+/-7.9%, P=.0021). There was no difference in normalized aortic MMP-9 and MMP-12 expression between elastase doses or between smoke-exposed and unexposed animals. Histologic analysis revealed that smoking increased the extent of aortic elastin degradation when compared with LDE-S animals.

CONCLUSION

Aneurysm development in the elastase model is dependent on the quantity of active elastase infused. Exposure of animals to tobacco smoke after a relatively minor aortic elastase injury produces increases in elastin degradation and aneurysm size without affecting MMP-9 or MMP-12 expression. To our knowledge, this is the first demonstration in an animal model that smoking can act as a synergistic factor in AAA development. Further understanding of the relationship between smoking and AAA in this model may help unveil the pathophysiologic pathways involved between cigarette smoke and AAAs.

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.

Effects of Calcium Channel Blocker Azelnidipine on Experimental Abdominal Aortic Aneurysms

PURPOSE

Azelnidipine has recently been recognized in vascular remodeling. However, the effects of azelnidipine on aneurysmal disease have not yet been studied. The aim of this study was to evaluate whether azelnidipine can inhibit a further expansion of aneurysmal disease.

METHODS

Experimental abdominal aortic aneurysms (AAAs) were created in a rat model by perfusing elastase. The rats in the first group received no treatment (n=10). In the second group (n=10) azelnidipine (2 mg/kg) was administered to the animals from 3 days before perfusion. The aortic diameter (AD) was measured at the time of initial surgery and death on postoperative day 14. The production of matrix metalloproteinases (MMP)-2 and -9 was analyzed by gelatin zymography.

RESULTS

The aortic diameter was smaller in the azelnidipine group than in the control (7.875+/-1.454 vs 10.745+/-0.551 mm, P<0.01). the active MMP-2 and MMP-9 levels decreased in the azelnidipine group. Hematoxylin-eosin and elastin staining revealed fewer changes in the inflammatory infiltrate and degradation of elastin in the azelnidipine group.

CONCLUSION

Azelnidipine reduced the expansion of experimental AAAs. Azelnidipine therefore appears to influence the inflammatory oxidative response seen in AAAs while also decreasing the MMP-2 and MMP-9 levels. In addition, azelnidipine inhibited aortic dilatation.

The candidate gene approach to susceptibility for abdominal aortic aneurysm: TIMP1, HLA-DR-15, ferritin light chain, and collagen XI-Alpha-1

There are two approaches to gene discovery for diseases when genetic susceptibility has been implicated by clinical genetic or case-control studies: (1) genome-wide screening and (2) evaluation of candidate genes. Each has specific advantages and disadvantages. The principal advantage of genome-wide screening is that it is impeccably objective in as much as it proceeds without any presuppositions regarding the importance of specific pathobiological features of the disease process. The principal disadvantage is that such a study is expensive and resource intensive. A large population of enrolled patients and multidisciplinary teams of investigators cooperating from several institutions are usually required. The alternative approach of evaluating candidate genes can be pursued by a small independent laboratory with limited funding and resources, a small collection of clinical specimens, and a small number of team players. The disadvantage is that it is by necessity highly subjective in the process of selecting specific candidates among many reasonable possibilities. There is no a priori assurance that effort will not be expended on one or more candidates that turn out in the end to be failures. This report reviews efforts in our laboratory to evaluate four genes as candidates. One of these tissue inhibitor of metalloprotease 1(TIMP1) led to the description of a polymorphism, but not a conclusive mutation. The other three (HLA-DR-15, ferritin light chain (FTL), and collagen XI-alpha-1 (COL11A1) are subjects of continuing interest.

Cured meat consumption, lung function, and chronic obstructive pulmonary disease among United States adults

RATIONALE

Cured meats are high in nitrites. Nitrites generate reactive nitrogen species that may cause nitrative and nitrosative damage to the lung resulting in emphysema.

OBJECTIVE

To test the hypothesis that frequent consumption of cured meats is associated with lower lung function and increased odds of chronic obstructive pulmonary disease (COPD).

METHODS

Cross-sectional study of 7,352 participants in the Third National Health and Nutrition Examination Survey, 45 years of age or more, who had adequate measures of cured meat, fish, fruit, and vegetable intake, and spirometry.

RESULTS

After adjustment for age, smoking, and multiple other potential confounders, frequency of cured meat consumption was inversely associated with FEV(1) and FEV(1)/FVC but not FVC. The adjusted differences in FEV(1) between individuals who did not consume cured meats and those who consumed cured meats 1 to 2, 3 to 4, 5 to 13, and 14 or more times per month were -37.6, -11.5, -42.0, and -110 ml, respectively (p for trend < 0.001). Corresponding differences for FEV(1)/FVC were -0.91, -0.54, -1.13, and -2.13% (p for trend = 0.001). These associations were not modified by smoking status. The multivariate odds ratio for COPD (FEV(1)/FVC <or= 0.7 and FEV(1) < 80% predicted) was 1.78 (95% confidence interval, 1.29-2.47) comparing the highest with the lowest category of cured meat consumption. The corresponding odds ratios for mild, moderate, and severe COPD were 1.11, 1.46, and 2.41, respectively.

CONCLUSIONS

Frequent cured meat consumption was associated independently with an obstructive pattern of lung function and increased odds of COPD. Additional studies are required to determine if cured meat consumption is a causal risk factor for COPD.

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.

Nitrite-induced cross-linking alters remodeling and mechanical properties of collagenous engineered tissues

Cumulative damage to long-lived connective tissue proteins play a key role in the development of age-related human diseases such as cardiovascular stiffening and age-related macular degeneration. The processes that result in the accumulation of increasingly insoluble, undigestible damaged collagen are only partially known. Nonenzymatic glycation (NEG) is one such process and has been linked to the development of diabetic-related complications and aging. An additional novel mechanism particularly relevant to smoking- and inflammation-related diseases involves the nonenzymatic nitrite (NEN) modification of connective tissue proteins. The present study was undertaken to examine the effects of NEN of fibrillar type I collagen on cell-mediated remodeling and mechanical properties of collagenous tissues. Using a modification of an in vitro fibroblast-populated collagen gel model system developed in our laboratory, we tested two hypotheses: NEN reduces the ability of primary adult cardiac fibroblasts to remodel type I collagen gels; NEN reduces the deformability of type I collagen gels subjected to mechanical testing. The results show that NEN impairs both cell-mediated remodeling and mechanical deformability in collagenous engineered tissues. Furthermore, these mechanical changes correlate with the degree of cross-linking as determined by SDS-PAGE. Thus, we concluded that NEN reactions may contribute to alterations in the biomechanical properties of collagen-containing tissues consistent with the age-related functional decline observed in human disease.

Decreased expression of fibulin-5 correlates with reduced elastin in thoracic aortic dissection

BACKGROUND

Thoracic aortic aneurysmal diseases are characterized by degeneration of elastin within the aortic wall. Although proteinases, such as matrix metalloproteinase, appear to contribute to elastin degradation, little is known about the role of elastic fiber assembly in such diseases. Fibulin-5 is an extracellular protein that is expressed in the vascular basement membrane and regulates elastic fiber assembly by microfibril machinery. In this study, we examined whether thoracic aortic dissection (TAD) is associated with abnormal fibulin-5 expression.

METHODS

Intraoperative aortic samples were obtained from 21 patients with proximal aortic dissection. Control aortic tissue was obtained from 11 organ donors, heart transplant recipients, and patients undergoing coronary artery bypass. An in vitro culture of vascular smooth muscle cells was obtained from 2 TAD patients and 1 control subject. To evaluate elastin expression, we stained tissue sections with Verhoeff-Van Gieson stain. Fibulin-5 messenger RNA (mRNA) expression was determined by quantitative real-time reverse-transcriptase-polymerase chain reaction.

RESULTS

Aortic fibulin-5 mRNA and elastin content were decreased in TAD patients, compared with controls (P=.001 and P=.02, respectively). Decreased fibulin-5 expression strongly correlated with decreased amounts and fragmentation of elastin in aortic samples from patients with TAD (r=0.83, P < .0001 and F=20.7, P < .0001 respectively). The fibulin-5 mRNA in aortic vascular smooth muscle cells collected from TAD demonstrated a 38% decrease in expression, compared with the control.

CONCLUSIONS

Patients with proximal aortic dissection exhibited significantly decreased expression of aortic fibulin-5. Decreased fibulin-5 may contribute to the pathogenesis of aortic dissection by impairing elastic fiber assembly.

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.

Decreased aortic smooth muscle contraction in a rat model of multibacterial sepsis

We investigated whether blockade of the smooth muscle cell (SMC) inducible nitric oxide synthase (iNOS)-soluble guanylyl cyclase (sGC) vasodilator pathway would restore the fall in vasoreactivity produced by sepsis following cecal ligation and perforation (CLP) in rats. Contraction of adjacent aortic rings paired for the presence or absence of endothelial cells (EC) was recorded following high [K(+)](e) (40 mm) or norepinephrine (NE, 10(-8) to 10(-5) m) in the presence of the nitric oxide synthase inhibitor (NOS), N(G)-nitro-l-arginine methyl ester (l-NAME, 0.3 mm) or the sGC inhibitor, 1H-[1,2,4]oxadiazolo[4,3-alpha]quinoxalin-1-one (ODQ, 5 mum). In EC-denuded rings, sepsis halved SMC contraction induced by high [K(+)](e) or NE; neither l-NAME nor ODQ produced an increase in NE E(max) or high [K(+)](e)-evoked contraction. In conclusion, SMC contractility is globally reduced in CLP; this reduction does not appear to be explained by induction of SMC NOS in this CLP model.

Matrix Metalloproteinase-9 (MMP-9), MMP-2, and Serum Elastase Activity Are Associated With Systolic Hypertension and Arterial Stiffness

Background— Arterial stiffness is an independent determinant of cardiovascular risk, and arterial stiffening is the predominant abnormality in systolic hypertension. Elastin is the main elastic component of the arterial wall and can be degraded by a number of enzymes, including matrix metalloproteinase-9 (MMP-9) and MMP-2. We hypothesized that elastase activity would be related to arterial stiffness and tested this using isolated systolic hypertension (ISH) as a model of stiffening and separately in a large cohort of healthy individuals.

Methods and Results— A total of 116 subjects with ISH and 114 matched controls, as well as 447 individuals free from cardiovascular disease were studied. Aortic and brachial pulse wave velocity (PWV) and augmentation index were determined. Blood pressure, lipids, C-reactive protein, MMP-9, MMP-2, serum elastase activity (SEA), and tissue-specific inhibitor 2 of metalloproteinases were measured. Aortic and brachial PWV, MMP-9, MMP-2, and SEA levels were increased in ISH subjects compared with controls ( P =0.001). MMP-9 levels correlated linearly and significantly with aortic ( r =0.45; P =0.001) and brachial PWV ( r =0.22; P =0.002), even after adjustments for confounding variables. In the younger, healthy subjects, MMP-9 and SEA were also independently associated with aortic PWV.

Conclusions— Aortic stiffness is related to MMP-9 levels and SEA, not only in ISH, but also in younger, apparently healthy individuals. This suggests that elastases including MMP-9 may be involved in the process of arterial stiffening and development of ISH.

Increased nitrotyrosine production in patients undergoing abdominal aortic aneurysm repair

Background

Vascular inflammation is implicated in the pathogenesis of atherosclerosis and abdominal aortic aneurysm (AAA), and is thought to involve reactive species such as the nitric oxide-derived oxidant peroxynitrite. In the present study nitrotyrosine was measured as a stable marker of peroxynitrite production in vivo.

Methods

Perioperative blood samples were obtained from patients undergoing elective open or endovascular repair of an AAA and from patients with intermittent claudication, smoking aged-matched controls, non-smoking aged-matched controls and non-smoking young healthy controls. Plasma nitrotyrosine was measured by an enzyme-linked immunosorbent assay.

Results

The median plasma nitrotyrosine concentration in patients with an AAA (0·46 nmol nitrated bovine serum albumin equivalents per mg protein) was significantly higher than that in patients with intermittent claudication (0·35 nmol; P = 0·002), smoking controls (0·36 nmol; P = 0·001), non-smoking controls (0·35 nmol; P = 0·002) and young healthy controls (0·27 nmol; P &lt; 0·001). Nitrotyrosine concentrations increased during early reperfusion in open AAA repair, but not during endovascular repair. AAA exclusion from the circulation reduced levels to control values (P = 0·001).

Conclusion

Patients with an AAA had raised levels of circulating nitrated proteins compared with patients with claudication and controls, suggesting a greater degree of ongoing inflammation that was not related to smoking.

Risk factors for continued cigarette use after subarachnoid hemorrhage

BACKGROUND AND PURPOSE

Cigarette smoking is a risk factor for the formation and rupture of intracranial aneurysms. Few studies have examined predictors of resumption of cigarette smoking after a first episode of subarachnoid hemorrhage (SAH).

METHODS

Of 620 SAH patients treated between July 1996 and November 2002, we prospectively evaluated continued cigarette use in 152 smokers alive at 3 months. Univariate and multivariate logistic regression analyses were used to identify potential demographic, social, and clinical predictors of continued cigarette use, defined as smoking > or =1 cigarette per week in the month before follow-up.

RESULTS

Thirty-seven percent (56 of 152) resumed smoking after their SAH. Patients who continued smoking were younger, were more often black, had begun smoking at an earlier age, and had a higher frequency of prior alcohol or cocaine use and self-reported depression or anxiety than those who quit (all P<0.05). Smoking at < or =16 years of age (odds ratio [OR], 5.88; 95% confidence interval [CI], 2.33 to 14.29), self-reported depression (OR, 5.29; 95% CI, 2.10 to 13.35), and prior alcohol use (OR, 4.51; 95% CI, 1.45 to 14.05) independently predicted continued cigarette use. Smokers had a functional outcome similar to that of nonsmokers at 3 months but were more likely to resume alcohol consumption (OR, 3.88; 95% CI, 1.91 to 7.88).

CONCLUSIONS

More than one third of prior smokers continue to use nicotine after SAH. Young age at smoking onset and a history of depression or alcohol use are risk factors for continued cigarette use. Targeted smoking cessation programs are needed to reduce the high rate of smoking resumption after SAH.

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.

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

Mounting evidence suggests that nitric oxide (NO) plays an important role in aneurysm pathogenesis. Nitric oxide synthase (NOS) expression, hemodynamic consequences of NO inhibition, and the effect of NO on matrix metalloproteinase (MMP) expression during aneurysm formation are unknown. In this study, a standard intraaortic elastase infusion rat model was used. Control animals received intraaortic elastase infusion and intraperitoneal saline injections. Experimental groups received intraaortic elastase infusion and intraperitoneal injections of aminoguanidine (500 mg/kg) or L-NAME (2 mg/kg or 10 mg/kg). Aortic diameter, blood pressure, and NO metabolites were measured at surgery and postoperative (POD) 7. A second series of rats were randomly infused with intraaortic elastase or saline and aortas were analyzed on POD 1, 3, and 7 with Western blotting for iNOS, eNOS, and MMP-9 expression. Infusion of elastase produced aneurysms (p > 0.0001) in all rats. Inhibition of NO with aminoguanidine or L-NAME limited aneurysm expansion in all groups (p > 0.05). Nitric oxide metabolites were increased (p < 0.003) in control rats on POD 7. Arterial hypertension was present in all treated animals (p < 0.05). Early up-regulation on POD 1 of iNOS (p < 0.003) was noted in elastas-infused animals, but there was no iNOS expression with saline infusion. MMP-9 expression was present in both groups, with a significant increase in expression for elastase-infused animals noted on POD 7. iNOS expression is up-regulated early in experimental aneurysm formation, followed by increases in MMP-9 expression. Inhibition of NO limits aneurysmal expansion despite production of arterial hypertension.

The nitrite/collagen reaction: non-enzymatic nitration as a model system for age-related damage

The effects of age seen in long-lived connective tissue proteins are thought to be the result of post-translational modifications by reactive molecules. One such molecule is the nitrite ion. Human nitrite exposure results predominately from endogenous production of nitric oxide as well as inhalation of cigarette smoke and ingestion of cured meats. Although nitrite reactions with various proteins have been studied previously with regard to carcinogenesis, the specific reaction with collagen and its role in age-related damage has never been examined. We describe the reaction of nitrite with type I collagen at neutral pH and body temperature. The incubation of collagen with nitrite results in an increase in cross-linking, the accumulation of a yellow chromophore, and a depletion of tyrosine residues. Similar changes also are found in aged human collagen. In addition, 3-nitro-tyrosine, which has recently been used as a marker for peroxynitrite mediated damage, is produced from this reaction. Thus, we propose non-enzymatic nitration as an in vitro model system for human collagen age-related damage.

Experimental abdominal aortic aneurysms in mice lacking expression of inducible nitric oxide synthase

To determine if nitric oxide synthase (NOS) contributes to the pathophysiology of abdominal aortic aneurysms (AAAs), C57BL/6J mice underwent transient aortic injury to induce a chronic inflammatory response. Wild-type mice developed a significant increase in aortic diameter within 14 days of elastase perfusion (115+/-16%, 40% incidence of AAAs), along with intense and widespread staining for nitrotyrosine, mononuclear inflammation, and delayed destruction of the elastic lamellae. Expression of both endothelial and neuronal forms of NOS was substantially decreased within AAAs, whereas inducible NOS (iNOS) mRNA was increased 360%, and the enzyme was localized to infiltrating inflammatory cells. By using mice with targeted deletion of iNOS to evaluate the functional importance of this enzyme, male iNOS(-/-) mice developed the same extent of aneurysmal dilatation as congenic controls (121+/-22%, 40% incidence of AAAs) and exhibited similar structural features except for diminished nitrotyrosine staining. Aneurysmal dilatation was actually enhanced in female iNOS(-/-) mice (141+/-16%, 80% incidence of AAAs; P<0.05), but this effect was reversed by previous oophorectomy. Although extensive protein nitration and increased expression of iNOS accompany the development of elastase-induced experimental AAAs, iNOS is not required in this process and its absence may be deleterious.

Inhibition of inducible nitric oxide synthase limits nitric oxide production and experimental aneurysm expansion

PURPOSE

Nitric oxide (NO), frequently cited for its protective role, can also generate toxic metabolites known to degrade elastin. Both abdominal aortic aneurysms (AAAs) and inducible nitric oxide synthase (iNOS) are associated with inflammatory states, yet the relationship between NO production by iNOS and AAA development is unknown. The current study examines iNOS expression, NO production, and the effects of selective inhibition of iNOS by aminoguanidine in experimental AAA.

METHODS

An intra-aortic elastase infusion model was used. Control rats received intra-aortic saline infusion and postoperative intraperitoneal saline injections (Group 1). In the remaining groups, intra-aortic elastase infusion was used to induce aneurysm formation. These rats were treated with intraperitoneal injections of saline postoperatively (Group 2), aminoguanidine postoperatively (Group 3), or aminoguanidine preoperatively and postoperatively (Group 4). Aortic diameter and plasma nitrite/nitrate levels were measured on the day of surgery and postoperative day 7. Aortas were harvested for biochemical and histologic analysis on postoperative day 7.

RESULTS

Infusion of elastase produced AAAs (P <.001) with significant production of iNOS (P <.05) and nitrite/nitrate (P <.003) compared with controls. Selective inhibition of iNOS with aminoguanidine in elastase-infused aortas significantly reduced aneurysm size (P <.01) compared with elastase infusion alone. Aminoguanidine-treated rats displayed suppression of iNOS expression and plasma nitrite/nitrate production not significantly different from the control group. Histologic evaluation revealed equivalent inflammatory infiltrates in elastase-infused groups.

CONCLUSION

Expression of iNOS is induced and plasma nitrite/nitrate levels are increased in experimental AAA. Inhibition of iNOS limits NO production and iNOS expression, resulting in smaller aneurysm size. NO production by iNOS plays an important role with detrimental effects during experimental aneurysm development.