Matrix metalloproteinases: influence on smooth muscle cells and atherosclerotic plaque stability

T cell senescence and cardiovascular diseases

Age-related changes in the immune system, commonly termed "immunosenescence," contribute to deterioration of the immune response and fundamentally impact the health and survival of elderly individuals. Immunosenescence affects both the innate and adaptive immune systems; however, the most notable changes are in T cell immunity and include thymic involution, the collapse of T cell receptor (TCR) diversity, an imbalance in T cell populations, and the clonal expansion of senescent T cells. Senescent T cells have the ability to produce large quantities of proinflammatory cytokines and cytotoxic mediators; thus, they have been implicated in the pathogenesis of many chronic inflammatory diseases. Recently, an increasing body of evidence has suggested that senescent T cells also have pathogenic potential in cardiovascular diseases, such as hypertension, atherosclerosis, and myocardial infarction, underscoring the detrimental roles of these cells in various chronic inflammatory responses. Given that cardiovascular disease is the number one cause of death worldwide, there is great interest in understanding the contribution of age-related immunological changes to its pathogenesis. In this review, we discuss general features of age-related alterations in T cell immunity and the possible roles of senescent T cells in the pathogenesis of cardiovascular disease.

Circulating and adipose tissue matrix metalloproteinases in cardiometabolic risk environments: pathophysiological aspects

Matrix metalloproteinases (MMPs) play an important role during physiological tissue remodeling in embryonic development and angiogenesis, as well as in pathophysiological conditions such as obesity and development and vulnerability of atherosclerotic plaque. Moreover, MMP circulating levels have emerged as potential biomarkers of cardiovascular disease. MMP expression and activity are regulated by different factors such as insulin resistance and obesity. Expanded fat tissue has been demonstrated to be an active organ, where MMPs also exert a role in adipogenesis, angiogenesis, and proliferation of extracellular matrix (ECM). However, the lack of association between adipose tissue and plasma levels of some MMPs, specifically MMP-2 and MMP-9, suggests that this tissue is not a major contributor to circulating gelatinases. MMPs are also co-expressed or co-repressed in response to inflammatory adipocytokines, like adiponectin and leptin. Adiponectin may also play a protective role in plaque rupture through selectively increasing the tissue inhibitor of metalloproteinase (TIMP) expression. Leptin induces the expression of MMP-2 activators as well as the expression of MMP-2, MMP-9, and TIMP-1 in different human cells. Furthermore, sex hormones also participate in MMP regulation. In postmenopausal women, hormone replacement therapy produces an increase in MMP activity, leading to a breakdown in ECM homeostasis and accelerated progression of vascular pathologies. Besides, in men, an inverse relationship between testosterone levels and MMP-2 activity has been described. It is still necessary to go forward in the study of MMPs in different metabolic situations to corroborate their role as vulnerable plaque biomarkers.

Construction of biological networks from unstructured information based on a semi-automated curation workflow

Capture and representation of scientific knowledge in a structured format are essential to improve the understanding of biological mechanisms involved in complex diseases. Biological knowledge and knowledge about standardized terminologies are difficult to capture from literature in a usable form. A semi-automated knowledge extraction workflow is presented that was developed to allow users to extract causal and correlative relationships from scientific literature and to transcribe them into the computable and human readable Biological Expression Language (BEL). The workflow combines state-of-the-art linguistic tools for recognition of various entities and extraction of knowledge from literature sources. Unlike most other approaches, the workflow outputs the results to a curation interface for manual curation and converts them into BEL documents that can be compiled to form biological networks. We developed a new semi-automated knowledge extraction workflow that was designed to capture and organize scientific knowledge and reduce the required curation skills and effort for this task. The workflow was used to build a network that represents the cellular and molecular mechanisms implicated in atherosclerotic plaque destabilization in an apolipoprotein-E-deficient (ApoE(-/-)) mouse model. The network was generated using knowledge extracted from the primary literature. The resultant atherosclerotic plaque destabilization network contains 304 nodes and 743 edges supported by 33 PubMed referenced articles. A comparison between the semi-automated and conventional curation processes showed similar results, but significantly reduced curation effort for the semi-automated process. Creating structured knowledge from unstructured text is an important step for the mechanistic interpretation and reusability of knowledge. Our new semi-automated knowledge extraction workflow reduced the curation skills and effort required to capture and organize scientific knowledge. The atherosclerotic plaque destabilization network that was generated is a causal network model for vascular disease demonstrating the usefulness of the workflow for knowledge extraction and construction of mechanistically meaningful biological networks.

Plasma Levels of microRNA-145 Are Associated with Severity of Coronary Artery Disease

Background and Objective

MicroRNAs (miRNAs) have been shown to be associated with various physiological and pathological conditions, including inflammation and cardiovascular disease, but little is known about their relationship with the presence of coronary artery disease (CAD) and disease severity.

Methods

A total of 195 consecutive subjects who underwent coronary angiography for chest pain evaluation were enrolled in this study. In CAD patients severity of coronary lesions was assessed by the number of diseased vessels and the Synergy between PCI with Taxus and Cardiac surgery score (SYNTAX score). Plasma levels of miRNA-145 were quantified by real-time quantitative polymerase chain reaction test, and logarithmic transformation of miRNA-145 levels (Ln_miRNA-145) was used for analyses due to its skewed distribution.

Results

Of the 195 total subjects 167 patients were diagnosed as having CAD. Ln_miRNA-145 was significantly lower in CAD patients compared with the non-CAD group (-6.11±0.92 vs. -5.06±1.25; p <0.001). In multivariable linear regression analyses CAD was significantly associated with lower Ln_miRNA-145 (Estimate, -0.50; standard error (SE), 0.11; p <0.0001). Furthermore, among CAD patients, three-vessel disease, higher SYNTAX scores and STEMI were significantly associated with lower Ln_miRNA-145 ([Estimate, -0.40; SE, 0.07; p <0.0001]; [Estimate, -0.02, SE, 0.10; p = 0.005] and [Estimate, -0.35, SE, 0.10; p <0.001] respectively).

Conclusions

Lower plasma levels of miRNA-145 were significantly associated with the presence as well as severity of CAD. As a potential biomarker for CAD, plasma miRNA-145 may be useful in predicting CAD and its severity in patients presenting with chest pain.

Berberine inhibits Chlamydia pneumoniae infection-induced vascular smooth muscle cell migration through downregulating MMP3 and MMP9 via PI3K

The mechanisms by which Chlamydia pneumoniae infection promote vascular smooth muscle cell (VSMC) migration required in the development of atherosclerosis have not yet been fully clarified. Matrix metalloproteinases (MMPs) have important roles in VSMC migration. However, it is still unknown whether MMPs are involved in C. pneumoniae infection-induced VSMC migration. In addition, whether berberine can exert its inhibitory effects on the infection-induced VSMC migration also remains unclear. Accordingly, we investigated the effects of berberine on C. pneumoniae infection-induced VSMC migration and explored the possible mechanisms involved in this process. Herein, we found that C. pneumoniae infection could induce VSMC migration through Matrigel-coated membrane (P<0.05), which can be significantly inhibited by the broad-spectrum MMP inhibitor GM6001 (P<0.05). Our results also showed that C. pneumoniae infection upregulated both mRNA and protein expressions of MMP3 and MMP9 (P<0.05). The specific phosphoinositide 3-kinase (PI3K) inhibitor LY294002 significantly suppressed the increases in MMP3 and MMP9 protein expressions induced by C. pneumoniae infection (P<0.05). Further experiments showed that berberine significantly attenuated C. pneumoniae infection-induced VSMC migration (P<0.05). Moreover, berberine suppressed the protein expressions of MMP3 and MMP9 caused by C. pneumoniae infection in a dose-dependent manner (P<0.05). C. pneumoniae infection-induced increase in the phosphorylation level of Akt at Ser473 was inhibited by the treatment with berberine (P<0.05). Taken together, our data suggest that berberine inhibits C. pneumoniae infection-induced VSMC migration by downregulating the expressions of MMP3 and MMP9 via PI3K.

Contribution of neovascularization and intraplaque haemorrhage to atherosclerotic plaque progression and instability

Atherosclerosis is a continuous pathological process that starts early in life and progresses frequently to unstable plaques. Plaque rupture leads to deleterious consequences such as acute coronary syndrome, stroke and atherothrombosis. The vulnerable lesion has several structural and functional hallmarks that distinguish it from the stable plaque. The unstable plaque has large necrotic core (over 40% plaque volume) composed of cholesterol crystals, cholesterol esters, oxidized lipids, fibrin, erythrocytes and their remnants (haeme, iron, haemoglobin), and dying macrophages. The fibrous cap is thin, depleted of smooth muscle cells and collagen, and is infiltrated with proinflammatory cells. In unstable lesion, formation of neomicrovessels is increased. These neovessels have weak integrity and leak thereby leading to recurrent haemorrhages. Haemorrhages deliver erythrocytes to the necrotic core where they degrade promoting inflammation and oxidative stress. Inflammatory cells mostly presented by monocytes/macrophages, neutrophils and mast cells extravagate from bleeding neovessels and infiltrate adventitia where they support chronic inflammation. Plaque destabilization is an evolutionary process that could start at early atherosclerotic stages and whose progression is influenced by many factors including neovascularization, intraplaque haemorrhages, formation of cholesterol crystals, inflammation, oxidative stress and intraplaque protease activity.

Adiponectin predicts MMP-2 activity independently of obesity

BACKGROUND

Matrix metalloproteinases (MMPs), especially MMP-2 and MMP-9, have been identified in atherosclerotic plaques and have been directly associated with plaque remodelling and vulnerability. Cardiovascular disease (CVD) is related to insulin resistance (IR) and obesity, characterized by changes in plasma levels of inflammatory markers, such as adiponectin and C-reactive protein (CRP). Our aim was to evaluate the impact of both proteins on MMP-2 and MMP-9 behaviour in individuals with IR.

MATERIALS AND METHODS

Plasma MMP-2 and MMP-9 activity, adiponectin and hs-CRP concentration and lipoprotein profile were determined in 52 patients with metabolic syndrome (MS) and 27 controls.

RESULTS

Patients with MS presented significantly higher MMP-2 activity than controls: 0·95 ± 0·12 vs. 0·77 ± 0·15 relative units (RU) (P < 0·001), while MMP-9 activity was not detectable. MMP-2 activity decreased across quartiles of adiponectin, being significantly reduced in individuals with the highest levels of adiponectin in compared with the lowest levels (0·75 ± 0·17 vs. 0·93 ± 0·09 RU, P < 0·005). This difference persisted significant after adjusting by obesity markers. MMP-2 activity was significantly increased in individuals with the highest levels (G3) compared with those with the lowest levels (G1) of hs-CRP (0·94 ± 0·12 vs. 0·86 ± 0·12, P = 0·041) CONCLUSION: In this study, we observed that adiponectin levels predicted MMP-2 plasma activity independently of obesity. This finding suggests that the inflammatory process, associated with the highest CVD risk, would be involved in MMPs vascular production.

Characterization of CD8(+)CD57(+) T cells in patients with acute myocardial infarction

Although T cells are known to be involved in the pathogenesis of coronary artery disease, it is unclear which subpopulation of T cells contributes to pathogenesis in acute myocardial infarction (MI). We studied the immunological characteristics and clinical impact of CD8(+)CD57(+) T cells in acute MI patients. The frequency of CD57(+) cells among CD8(+) T cells was examined in peripheral blood sampled the morning after acute MI events. Interestingly, the frequency of CD57(+) cells in the CD8(+) T-cell population correlated with cardiovascular mortality 6 months after acute MI. The immunological characteristics of CD8(+)CD57(+) T cells were elucidated by surface immunophenotyping, intracellular cytokine staining and flow cytometry. Immunophenotyping revealed that the CD8(+)CD57(+) T cells were activated, senescent T cells with pro-inflammatory and tissue homing properties. Because a high frequency of CD8(+)CD57(+) T cells is associated with short-term cardiovascular mortality in acute MI patients, this specific subset of CD8(+) T cells might contribute to acute coronary events via their pro-inflammatory and high cytotoxic capacities. Identification of a pathogenic CD8(+) T-cell subset expressing CD57 may offer opportunities for the evaluation and management of acute MI.

Emerging regulators of vascular smooth muscle cell function in the development and progression of atherosclerosis

After a period of relative senescence in the field of vascular smooth muscle cell (VSMC) research with particular regards to atherosclerosis, the last few years has witnessed a resurgence, with extensive research re-assessing potential molecular mechanisms and pathways that modulate VSMC behaviour within the atherosclerotic-prone vessel wall and the atherosclerotic plaque itself. Attention has focussed on the pathological contribution of VSMC in plaque calcification; systemic and local mediators such as inflammatory molecules and lipoproteins; autocrine and paracrine regulators which affect cell-cell and cell to matrix contacts alongside cytoskeletal changes. In this brief focused review, recent insights that have been gained into how a myriad of recently identified factors can influence the pathological behaviour of VSMC and their subsequent contribution to atherosclerotic plaque development and progression has been discussed. An overriding theme is the mechanisms involved in the alterations of VSMC function during atherosclerosis.

MicroRNA-24 regulates macrophage behavior and retards atherosclerosis

OBJECTIVE

Our recent studies have highlighted membrane type-1 matrix metalloproteinase (MMP)-14 as a selective marker for an invasive subset of macrophages potentially related to atherosclerotic plaque progression. Moreover, colony stimulating factors (CSF) may exert divergent effects on macrophage MMP expression, possibly through microRNAs. We, therefore, aim to identify and test the pathophysiological role of microRNAs, which modulate macrophage MMP-14 expression in atherosclerotic plaque progression.

APPROACH AND RESULTS

Compared with macrophage CSF-differentiated macrophages, granulocyte/macrophage CSF-matured macrophages exhibited reduced MMP-14 mRNA levels but increased protein expression and activity, which resulted in heightened macrophage invasion. MicroRNA-24, identified to target MMP-14, was accordingly increased in macrophage CSF compared with granulocyte/macrophage CSF macrophages. Silencing microRNA-24 in macrophage CSF macrophages significantly increased MMP-14 expression and enhanced their invasive capacity, mimicking granulocyte/macrophage CSF macrophages, and suggesting that granulocyte/macrophage CSF modulates MMP-14 protein expression and subsequent macrophage invasion in a microRNA-24-dependent manner. In human coronary atherosclerotic plaques, increased MMP-14 protein expression in foam cell macrophages was associated with lesions exhibiting histological characteristics associated with an unstable phenotype. Furthermore, microRNA-24 expression in these atherosclerotic plaques was inversely related to MMP-14 protein expression. Moreover, stable plaques contained higher microRNA-24 levels than unstable plaques, and microRNA-24 colocalized with foam cell macrophages that exhibited low MMP-14 protein expression. Finally, in atherosclerotic mice (apolipoprotein E-deficient), microRNA-24 inhibition increased plaque size and macrophage MMP-14 expression.

CONCLUSIONS

Taken together, our data demonstrates that downregulation of microRNA-24 promotes an invasive macrophage subset and plays a novel regulatory role in MMP-14 proteolytic activity and, therefore, plaque stability, highlighting its therapeutic potential.

Positive association of MMP 14 gene polymorphism with vulnerable carotid plaque formation in a Han Chinese population

BACKGROUND

MMP 14 is expressed in atherosclerotic plaques and potentially plays an important role in the development of vulnerable carotid plaques. MMP 14 gene polymorphisms can influence the bioactivity or expression of MMP 14.

OBJECTIVE

The aim of this study was to investigate the association between MMP 14 position + 7096 T > C (NM_004995.2:c.855T> C, rs2236307) polymorphism and vulnerable carotid plaque formation.

METHODS

1370 patients with ischemic cerebral infarctions were enrolled and divided into three groups according to their carotid ultrasound examination: No plaque group (n = 346), stable plaque group (n = 695) and vulnerable plaque group (n = 329). The traditional atherosclerosis risk factors were recorded, and the MMP 14 polymorphism were genotyped by Applied Biosystems 7300 Real-Time PCR System using the TaqMan assay.

RESULTS

In the multiple logistic regression analysis done among the sub-groups, compared to no carotid plaque group, individuals with the MMP 14 position + 7096 TC+ CC genotype showed a significantly (p = 0.009) lower risk for vulnerable plaque (AOR = 0.675; 95% CI, 0.568-0.922) formation compared with subjects of the TT genotype; however, no relation between TC+ CC genotype and stable carotid plaque was observed (p > 0.125). Age was a risk factor for both stable plaque (p = 0.000; AOR = 3.732; 95% CI: 2.496-5.58) and vulnerable plaque formation (p = 0.001; AOR = 2.234; 95% CI: 1.387-3.597). Meanwhile, fibrinogen (> 4.0 g/L) was a risk factor for stable plaque (p = 0.004; AOR = 2.313; 95% CI: 1.308-4.091).

CONCLUSIONS

The MMP 14 position + 7096 TC+ CC genotype might lower the risk of vulnerable carotid plaque formation. Fibrinogen (> 4.0 g/L) was a risk factor for stable plaque.

Matrix metalloproteinases in coronary artery disease

Matrix metalloproteinases (MMP) are a family of zinc-containing endoproteinases that degrade extracellular matrix (ECM) components. MMP have important roles in the development, physiology and pathology of cardiovascular system. Metalloproteases also play key roles in adverse cardiovascular remodeling, atherosclerotic plaque formation and plaque instability, vascular smooth muscle cell (SMC) migration and restenosis that lead to coronary artery disease (CAD), and progressive heart failure. The study of MMP in developing animal model cardiovascular systems has been helpful in deciphering numerous pathologic conditions in humans. Increased peripheral blood MMP-2 and MMP-9 in acute coronary syndrome (ACS) may be useful as noninvasive tests for detection of plaque vulnerability. MMP function can be modulated by certain pharmacological drugs that can be exploited for treatment of ACS. CAD is a polygenic disease and hundreds of genes contribute toward its predisposition. A large number of sequence variations in MMP genes have been identified. Case-control association studies have highlighted their potential association with CAD and its clinical manifestations. Although results thus far are inconsistent, meta-analysis has demonstrated that MMP-3 Glu45Lys and MMP-9 1562C/T gene polymorphisms were associated with CAD risk.

The effect of prolonged systemic doxycycline therapy on serum tissue degrading proteinases in coronary bypass patients: a randomized, double-masked, placebo-controlled clinical trial

OBJECTIVE

Serum matrix metalloproteinases (MMP-8, MMP-7) and their regulators may be associated with the risk of incident cardiovascular disease events. Doxycycline can be used as matrix metalloproteinase (MMP) inhibitor independent of its antimicrobial activity. We aimed to investigate serum inflammatory biomarkers during 4 months of doxycycline therapy in coronary bypass patients.

MATERIALS AND METHODS

Thirty-one non-smoking men who had previous coronary bypass surgery were randomly assigned to receive placebo or 100 mg doxycycline daily for 4 months. Serum samples were collected at baseline before the treatment, and at 2, 4, and 10 months. Serum levels of MMP-7, tissue inhibitor of matrix metalloproteinase (TIMP)-1, myeloperoxidase, and neutrophil elastase were analyzed with enzyme-linked immunosorbent assay, MMP-8 by immunofluorometric assay, and C-reactive protein by rate nephelometry.

RESULTS

At baseline, no significant differences existed between the two groups. Serum levels of MMP-8, MMP-7, and MMP-8/TIMP-1 were and remained lower (p = 0.034, p = 0.041, and NS) in the doxycycline group relative to the placebo group at 4 months of follow-up.

CONCLUSIONS

Doxycycline decreases the systemic inflammatory burden in patients with myocardial infarction and especially down-regulates MMP-7, MMP-8, and MMP-8/TIMP-1. Doxycycline might prevent or reduce the risk of secondary myocardial infarctions by providing a systemic anti-proteolytic and -inflammatory shield.

Expression of matrix metalloproteinases 9 and 12 in actinic cheilitis

AIM: To investigate the role of matrix-degrading metalloproteinases 9, 12 (MMPs), as mediators of functional connective tissue damage in actinic cheilitis.

METHODS: Thirty five formalin-fixed, paraffin embedded specimens of actinic cheilitis, and twelve specimens of normal lower lip vermillion, which were obtained by the archives of the Department of Oral Medicine and Maxillofacial Pathology, were examined. From each block, 5 μm thick sections were cut and routinely stained with Hematoxylin and Eosin. Immunohistochemical studies were performed on 4-μm thick sections of formalin-fixed paraffin embedded actinic cheilitis lesions and of normal lower lip vermillion, for MMP-9 and MMP-12 in serial sections of our specimens. Appropriate positive and negative controls were performed to confirm the specificity of the staining reaction. MMP immunohistochemistry was evaluated using a semiquantitative immunoreactive score.

RESULTS: Haematoxylin and eosin staining revealed in actinic cheilitis lesions atrophic stratified squamous cell epithelium, or focally and irregularly hyperplastic of variable thickness, in some areas was observed marked keratin production. Varying degrees of epithelial dysplasia were noticed with a wide spectrum of change within the same specimen. Characteristic was the appearance of chronic inflammatory infiltration, and a band of amorphous acellular, basophilic change like solar elastosis (elastin replacement of collagen). In normal lower lip specimens weak and scanty positive expression of MMP-9 and MMP-12 was observed. Anti-MMP-9 antibody showed a weak reaction, in actinic cheilitis lesions, focal in the elastotic material, in chronic inflammatory cells and mostly in macrophages and neutrophils. Strong and in some cases diffused immunohistochemical expression of MMP-12 was detected in actinic cheilitis lesions in the areas of the fragmented, distorted and thickened elastic fibers. MMP-12 was also expressed in chronic inflammatory cells and mostly macrophages. MMP-12 was significantly higher in actinic cheilitis specimens compared with the normal lower lip specimens (P = 0.0029).

CONCLUSION: Our results suggest that especially MMP-12 may play an important role in remodeling events occurring in the connective tissue during long-term exposure to sunlight in the actinic cheilitis lesions.

PAF enhances MMP-2 production in rat aortic VSMCs via a β-arrestin2-dependent ERK signaling pathway

Platelet-activating factor (PAF), 1-O-alkyl-2-acetyl-sn-glycero-3-phosphocholine, is a potent phospholipid mediator and has been reported to be localized in atherosclerotic plaque. However, its role in the progression of atherosclerosis remains unclear. In the present study, we investigated the role of PAF in the production of matrix metalloproteinase (MMP) in primary vascular smooth muscle cells (VSMCs). When rat aortic primary VSMCs were stimulated with PAF (1 nmol/l), the expressions of MMP-2 mRNA and protein, but not of MMP-9, were significantly increased, and these upregulations were markedly attenuated by inhibiting extracellular signal-regulated kinases (ERKs) using molecular and pharmacological inhibitors, but not by using inhibitors of p38 mitogen-activated protein kinase or c-Jun N-terminal kinase. Likewise, ERK phosphorylation was markedly enhanced in PAF-stimulated VSMCs, and this was attenuated by WEB2086, but not by EGF receptor inhibitor, demonstrating the specificity of PAF receptor (PAFR) in PAF-induced ERK phosphorylation. In immunofluorescence studies, β-arrestin2 in PAF-stimulated VSMCs colocalized with PAFR and phosphorylated ERK (P-ERK). Coimmunoprecipitation results suggest that β-arrestin2-bound PAFRs existed as a complex with P-ERK. In addition, PAF-induced ERK phosphorylation and MMP-2 production were significantly attenuated by β-arrestin2 depletion. Taken together, the study shows that PAF enhances MMP-2 production in VSMCs via a β-arrestin2-dependent ERK signaling pathway.

Testosterone: a vascular hormone in health and disease

Coronary heart disease is a leading cause of premature death in men. Epidemiological studies have shown a high prevalence of low serum testosterone levels in men with cardiovascular disease (CVD). Furthermore, a low testosterone level is associated in some but not in all observational studies with an increase in cardiovascular events and mortality. Testosterone has beneficial effects on several cardiovascular risk factors, which include cholesterol, endothelial dysfunction and inflammation: key mediators of atherosclerosis. A bidirectional relationship between low endogenous testosterone levels and concurrent illness complicates attempts to validate causality in this association and potential mechanistic actions are complex. Testosterone is a vasoactive hormone that predominantly has vasodilatory actions on several vascular beds, although some studies have reported conflicting effects. In clinical studies, acute and chronic testosterone administration increases coronary artery diameter and flow, improves cardiac ischaemia and symptoms in men with chronic stable angina and reduces peripheral vascular resistance in chronic heart failure. Although the mechanism of the action of testosterone on vascular tone in vivo is not understood, laboratory research has found that testosterone is an L-calcium channel blocker and induces potassium channel activation in vascular smooth muscle cells. Animal studies have consistently demonstrated that testosterone is atheroprotective, whereas testosterone deficiency promotes the early stages of atherogenesis. The translational effects of testosterone between in vitro animal and human studies, some of which have conflicting effects, will be discussed in this review. We review the evidence for a role of testosterone in vascular health, its therapeutic potential and safety in hypogonadal men with CVD, and some of the possible underlying mechanisms.

Mechanisms of arterial remodeling: lessons from genetic diseases

Vascular disease is still the leading cause of morbidity and mortality in the Western world, and the primary cause of myocardial infarction, stroke, and ischemia. The biology of vascular disease is complex and still poorly understood in terms of causes and consequences. Vascular function is determined by structural and functional properties of the arterial vascular wall. Arterial stiffness, that is a pathological alteration of the vascular wall, ultimately results in target-organ damage and increased mortality. Arterial remodeling is accelerated under conditions that adversely affect the balance between arterial function and structure such as hypertension, atherosclerosis, diabetes mellitus, chronic kidney disease, inflammatory disease, lifestyle aspects (smoking), drugs (vitamin K antagonists), and genetic abnormalities [e.g., pseudoxanthoma elasticum (PXE), Marfan's disease]. The aim of this review is to provide an overview of the complex mechanisms and different factors that underlie arterial remodeling, learning from single gene defect diseases like PXE, and PXE-like, Marfan's disease and Keutel syndrome in vascular remodeling.

Increased expression of heparanase in symptomatic carotid atherosclerosis

OBJECTIVE

Proliferation of smooth muscle cells (SMCs) can stabilize atherosclerotic lesions but the molecular mechanisms that regulate this process in humans are largely unknown. We have previously shown that heparan sulfate proteoglycans (HSPGs), such as perlecan, regulate SMC growth in animal models by modulating heparin-binding mitogens. Since perlecan is expressed at low levels in human atherosclerosis, we speculated that the effect of heparan sulfate (HS) in human disease was rather influenced by HS degradation and investigated the expression of heparanase (HPSE) in human carotid endarterectomies.

METHODS AND RESULTS

Gene expression analysis from 127 endarterectomies in the BiKE database revealed increased expression of HPSE in carotid plaques compared with normal arteries, and a further elevation in symptomatic lesions. Increased HPSE protein expression in symptomatic plaque tissue was verified by tissue microarrays. HPSE mRNA levels correlated positively with expression of inflammatory markers IL-18, RANTES and IL-1β, and also T-cell co-stimulatory molecules, such as B7.2, CD28, LFA-1 and 4-1BB. Previously reported single nucleotide polymorphisms within HPSE were associated with differential mRNA expression in plaques. Immunohistochemistry revealed that inflammatory cells were major producers of HPSE in plaque tissue. HPSE immunoreactivity was also observed in SMCs adjacent to the necrotic core and was co-localized to deposits of fibrin.

CONCLUSIONS

This study demonstrates increased expression of HPSE in human atherosclerosis associated with inflammation, coagulation and plaque instability. Since HS can regulate SMC proliferation and influence plaque stability, the findings suggest that HPSE degradation of HS take part in the regulation of SMC function in human atherosclerosis.

Macrophage differentiation and function in atherosclerosis: opportunities for therapeutic intervention?

The macrophage is exquisitely sensitive to its microenvironment, as demonstrated primarily through in vitro study. Changes in macrophage phenotype and function within the atherosclerotic plaque have profound consequences for plaque biology, including rupture and arterial thrombosis leading to clinical events such as myocardial infarction. We review the evidence for dynamic changes in macrophage numbers and macrophage differentiation within the atherosclerotic plaque microenvironment and discuss potential approaches to target macrophage differentiation for therapeutic benefit in cardiovascular disease.

Wnt signalling in smooth muscle cells and its role in cardiovascular disorders

Vascular smooth muscle cells (SMCs) are the major cell type within blood vessels. SMCs exhibit low rates of proliferation, migration, and apoptosis in normal blood vessels. However, increased SMC proliferation, migration, and apoptosis rates radically alter the composition and structure of the blood vessel wall and contribute to cardiovascular diseases, such as atherosclerosis, and restenosis that occur after coronary artery vein grafting and stent implantation. Consequently, therapies that modulate SMC proliferation, migration, and apoptosis may be useful for treating cardiovascular diseases. The family of Wnt proteins, which were first identified in the wingless drosophila, has a well-established role in embryogenesis and development. It is now emerging that Wnt proteins also regulate SMC proliferation, migration, and survival. In this review article, we discuss recently emerging research that has revealed that Wnt proteins are important regulators of SMC behaviour via activation of β-catenin-dependent and β-catenin-independent Wnt signalling pathways.

Matrix metalloproteinase inhibitors as investigative tools in the pathogenesis and management of vascular disease

Matrix metalloproteinases (MMPs) are proteolytic enzymes that degrade various components of the extracellular matrix (ECM). MMPs could also regulate the activity of several non-ECM bioactive substrates and consequently affect different cellular functions. Members of the MMPs family include collagenases, gelatinases, stromelysins, matrilysins, membrane-type MMPs, and others. Pro-MMPs are cleaved into active MMPs, which in turn act on various substrates in the ECM and on the cell surface. MMPs play an important role in the regulation of numerous physiological processes including vascular remodeling and angiogenesis. MMPs may also be involved in vascular diseases such as hypertension, atherosclerosis, aortic aneurysm, and varicose veins. MMPs also play a role in the hemodynamic and vascular changes associated with pregnancy and preeclampsia. The role of MMPs is commonly assessed by measuring their gene expression, protein amount, and proteolytic activity using gel zymography. Because there are no specific activators of MMPs, MMP inhibitors are often used to investigate the role of MMPs in different physiologic processes and in the pathogenesis of specific diseases. MMP inhibitors include endogenous tissue inhibitors (TIMPs) and pharmacological inhibitors such as zinc chelators, doxycycline, and marimastat. MMP inhibitors have been evaluated as diagnostic and therapeutic tools in cancer, autoimmune disease, and cardiovascular disease. Although several MMP inhibitors have been synthesized and tested both experimentally and clinically, only one MMP inhibitor, i.e., doxycycline, is currently approved by the Food and Drug Administration. This is mainly due to the undesirable side effects of MMP inhibitors especially on the musculoskeletal system. While most experimental and clinical trials of MMP inhibitors have not demonstrated significant benefits, some trials still showed promising results. With the advent of new genetic and pharmacological tools, disease-specific MMP inhibitors with fewer undesirable effects are being developed and could be useful in the management of vascular disease.

A dynamic model of calcific nodule destabilization in response to monocyte- and oxidized lipid-induced matrix metalloproteinases

Vulnerable plaque remains clinically undetectable, and there is no accepted in vitro model. We characterize the calcific nodules produced by calcifying vascular cells (CVC) in ApoE-null mice, demonstrating increased destabilization of cultured nodules in the presence of oxidized low-density lipoprotein (oxLDL) and monocytes under pulsatile shear stress. CVC implanted in the subcutaneous space of hyperlipidemic mice produced nodules revealing features of calcific atherosclerotic plaque including a fibrous cap, cholesterol clefts, thin shoulder, lipids, and calcium mineral deposits. CVC nodules seeded in the pulsatile flow channel (τ(avg) = 23 dyn/cm(2), ∂τ/∂t = 71 dyn·cm(-2)·s(-1)) underwent deformation and destabilization. Computational fluid dynamics revealed distinct shear force profiles on the nodules. Presence of oxLDL or monocytic THP-1 cells significantly increased the numbers of nodules destabilized from the substrate. Both oxLDL and THP-1 increased matrix metalloproteinase (MMP) activity in CVC. The MMP inhibitor GM6001 significantly reversed oxLDL- and THP-1-induced nodule destabilization, whereas overexpression of MMP-9 increased destabilization. These findings demonstrate that CVC-derived nodules resembled calcific atherosclerotic plaque and were destabilized in the presence of active lipids and monocytes via induction of MMPs.

Increased MMP-2 in healthy postmenopausal women

Background

Matrix metalloproteases 2 (MMP-2) and 9 (MMP-9) are involved in the atherosclerosis process. The objective of the study was to evaluate MMP-2 and MMP-9 activities and other circulating inflammatory factors in healthy postmenopausal women (PMW) as a model of subclinical atherosclerosis.

Methods

Twenty-three PMW and 13 premenopausal women (PreMW) were selected following established criteria. The main measurements in plasma samples were: lipid–lipoprotein profile, high-sensitivity C-reactive protein (hs-CRP) (immunoturbidimetry), soluble vascular cellular adhesion molecules (sVCAM-1) enzyme-linked immunosorbent assay and MMP activity by zymography.

Results

The relative areas of MMP-2 were increased in PMW: 1.1 (0.1) versus 0.6 (0.05), P < 0.02. MMP-9 was only detected in three PMW and one PreMW. MMP-2 correlated with HDL-cholesterol ( r = −0.51), triglycerides ( r = 0.67), apolipoprotein B ( r = 0.47), hs-CRP ( r = 0.42), homeostasis model assessment ( r = 0.53) and waist circumference ( r = 0.40), at least P < 0.02. sVCAM-1 showed no difference between groups: 28.7 (5.5) versus 35.5 (20) ng/mL, but correlated with MMP-2 and hs-CRP ( r = 0.46 and r = 0.48 respectively, P < 0.05).

Conclusions

In postmenopause, the increase in MMP-2 reflects the systemic specific inflammatory process that accompanies atherogenesis.

Levels of Circulating MMCN-151, a Degradation Product of Mimecan, Reflect Pathological Extracellular Matrix Remodeling in Apolipoprotein E Knockout Mice

AIM

Arterial extracellular matrix (ECM) remodeling by matrix metalloproteinases (MMPs) is one of the major hallmarks of atherosclerosis. Mimecan, also known as osteoglycin has been implicated in the integrity of the ECM. This study assessed the validity of an enzyme-linked immunosorbent assay (ELISA) developed to measure a specific MMP12-derived fragment of mimecan, MMCN-151, in apolipoprotein-E knockout (ApoE-KO) mice.

METHODS AND RESULTS

A mouse monoclonal antibody raised against MMCN-151 was used to develop a competitive ELISA. The assay was validated using samples from 20 ApoE-KO and 20 wild type [C57 BL/6] male mice fed a normal or high-fat diet (HFD) for up to 20 weeks. The technical reliability of the assay was established with intra-assay variability <2% and inter-assay variability <10%. The lowest limit of quantification of MMCN-151 was 0.5 ng/ml. ApoE-KO mice fed a HFD for 20 weeks had four-fold increased circulating levels of MMCN-151 compared to baseline, whereas MMCN-151 levels in control mice on HFD increased two-fold compared with baseline. After 10 weeks of a HFD, a significant difference in MMCN-151 levels was observed between ApoE-KO and control mice (P = 0.005) and became more significant at 20 weeks (P = 0.002).

CONCLUSIONS

The newly developed assay is a reliable detector of MMCN-151 levels which ultimately may be useful indicators of arterial remodeling in patients affected by atherosclerotic disease.

Plaque oxysterols induce unbalanced up-regulation of matrix metalloproteinase-9 in macrophagic cells through redox-sensitive signaling pathways: Implications regarding the vulnerability of atherosclerotic lesions

An imbalance in the matrix metalloproteinases/tissue inhibitors of metalloproteinases (MMPs/TIMPs) contributes to atherosclerotic plaque destabilization and rupture. Here we determined whether oxysterols accumulating in advanced atherosclerotic lesions play a role in plaque destabilization. In human promonocytic U937 cells, we investigated the effects of an oxysterol mixture of composition similar to that in advanced human carotid plaques on the expression and synthesis of MMP-9 and its endogenous inhibitors TIMP-1 and TIMP-2. A marked increment of MMP-9 gene expression, but not of its inhibitors, was observed by real-time RT-PCR; MMP-9 gelatinolytic activity was also found increased by gel zymography. Consistently, a net increment of MMP-9 protein level was also observed by immunoblotting. Using antioxidants or specific inhibitors or siRNAs, we demonstrated that the oxysterol mixture induces MMP-9 expression through: (i) overproduction of reactive oxygen species, probably by NADPH-oxidase and mitochondria; (ii) up-regulation of mitogen-activated protein kinase signaling pathways via protein kinase C; and (iii) up-regulation of activator protein-1- and nuclear factor-κB-DNA binding. These results suggest, for the first time, that oxysterols accumulating in advanced atherosclerotic lesions significantly contribute to plaque vulnerability by promoting MMP-9/TIMP-1/2 imbalance in phagocytic cells.

Matrix metalloproteinase (MMP)-3 activates MMP-9 mediated vascular smooth muscle cell migration and neointima formation in mice

OBJECTIVE

Several matrix metalloproteinases (MMPs) have been implicated in extracellular matrix destruction and other actions that lead to plaque rupture and myocardial infarction. Conversely, other MMPs have been shown to promote vascular smooth muscle cell (VSMC)-driven neointima formation, which contributes to restenosis, fibrous cap formation, and plaque stability. MMP-3 knockout reduced VSMC accumulation in mouse atherosclerotic plaques, implicating MMP-3 in neointima formation. We therefore investigated the effect of MMP-3 knockout on neointima formation after carotid ligation in vivo and VSMC migration in vitro.

METHODS AND RESULTS

Twenty-eight days after left carotid ligation, MMP-3 knockout significantly reduced neointima formation (75%, P<0.01) compared with wild-type (WT) littermates, and also reduced remodeling of ligated and contralateral carotid arteries. Gelatin zymography illustrated that MMP-3 knockout abolished MMP-9 activation in ligated carotids and scratch-wounded VSMC cultures. MMP-3 knockout also attenuated VSMC migration into a scratch wound by 59% compared with WT cells. Addition of exogenous MMP-3 or activated MMP-9 restored migration of MMP-3 knockouts to that of WT VSMCs, but exogenous MMP-3 had no effect on migration in MMP-9 knockout VSMCs. MMP-9 knockout or knockdown with small interfering RNA significantly retarded VSMC migration to the same extent as MMP-3 knockout.

CONCLUSIONS

These results indicate for the first time that MMP-3 mediated activation of MMP-9 is required for efficient neointima formation after carotid ligation in vivo and for VSMC migration in vitro, whereas MMP-12 plays a redundant role. These findings add to the understanding of MMP action in plaque stability and restenosis.

Metalloproteinases in metabolic syndrome

Experimental and clinical evidence supports the concept that metalloproteinases (MMPs), beyond different physiologic functions, also play a role in the development and rupture of the atherosclerotic plaque. Interest in MMPs has been rapidly increasing during the last years, especially as they have been proposed as biomarkers of vulnerable plaques. Different components of the metabolic syndrome (MS) have been identified as possible stimulus for the synthesis and activity of MMPs, like pro-inflammatory and pro-oxidant state, hyperglycemia, hypertension and dyslipidemia. On the other hand, anti-inflammatory cytokines like adiponectin are inversely associated with MMPs. Among the several MMPs studied, collagenases (MMP-1 and MMP-8) and gelatinases (MMP-2 and MMP-9) are the most associated with MS. Our aim was to summarize and discuss the relation between different components of the MS on MMPs, as well as the effect of the cluster of the metabolic alterations itself. It also highlights the necessity of further studies, in both animals and humans, to elucidate the function of novel MMPs identified, as well as the role of the known enzymes in different steps of metabolic diseases. Understanding the mechanisms of MS impact on MMPs and vice versa is an interesting area of research that will positively enhance our understanding of the complexity of MS and atherosclerosis.

Sodium intake is associated with carotid artery structure alterations and plasma matrix metalloproteinase-9 upregulation in hypertensive adults

The mechanisms by which dietary sodium modulates cardiovascular risk are not fully understood. This study investigated whether sodium intake is related to carotid structure and hemodynamics and to plasma matrix metalloproteinase (MMP) activity in hypertensive adults. One hundred thirty-four participants were cross-sectionally evaluated by clinical history, anthropometry, carotid ultrasound, and analysis of hemodynamic, inflammatory, and metabolic variables. Daily sodium intake (DSI) was estimated by 24-h recall, discretionary sodium, and a FFQ. In 42 patients, plasma MMP-2 and MMP-9 activities were also analyzed. The mean DSI was 5.52 ± 0.29 g/d. Univariate analysis showed that DSI correlated with common carotid artery systolic and diastolic diameter (r = 0.36 and 0.34; both P < 0.001), peak and mean circumferential tension (r = 0.44 and 0.39; both P < 0.001), Young's Elastic Modulus (r = 0.40; P < 0.001), intima-media thickness (r = 0.19; P < 0.05), and internal carotid artery resistive index (r = 0.20; P < 0.05). Multivariate analyses revealed that only artery diameter, circumferential wall tension, and Young's Elastic Modulus were independently associated with DSI. Conversely, plasma MMP-9 activity was associated with DSI (r = 0.53; P < 0.001) as well as with common carotid systolic diameter (r = 0.33; P < 0.05) and Young's Elastic Modulus (r = 0.38; P < 0.01). In conclusion, sodium intake is associated with carotid alterations in hypertensive adults independently of systemic hemodynamic variables. The present findings also suggest that increased MMP-9 activity might play a role in sodium-induced vascular remodeling.

Circulating soluble lectin-like oxidized low-density lipoprotein receptor-1 levels are associated with angiographic coronary lesion complexity in patients with coronary artery disease

BACKGROUND

Angiographic coronary lesion complexity has been reported to predict plaque vulnerability. It is important to develop a noninvasive blood biomarker for accurate prognostication of angiographically complex lesions in patients with coronary artery disease (CAD).

HYPOTHESIS

Serum soluble lectin-like oxidized low-density lipoprotein receptor-1 (sLOX-1) levels may be correlated with coronary lesion complexity in patients with CAD.

METHODS

We measured serum sLOX-1 levels in 180 consecutive patients undergoing coronary angiography for the evaluation of CAD. Coronary lesions were classified as simple or complex lesions based on coronary plaque morphology.

RESULTS

Stable CAD patients with complex lesions (n=50) had significantly higher serum sLOX-1 levels than those with simple lesions (n=72), at 0.914 ng/mL (range, 0.489-1.296 ng/mL) vs 0.426 ng/mL (range, 0.195-1.075 ng/mL), respectively, P<0.01. Multivariate logistic regression analysis revealed that sLOX-1 levels were independently associated with the presence of complex lesions in patients with stable CAD (odds ratio [OR]: 1.964, 95% confidence interval [CI]: 1.149-3.356, P<0.05). Among patients with acute coronary syndrome (n=58), who had significantly higher circulating sLOX-1 levels than stable CAD patients (n=122) at 1.610 ng/mL (range, 0.941-2.264 ng/mL) vs 0.579 ng/mL (range, 0.265-1.172 ng/mL), respectively, P<0.01, sLOX-1 levels were independently associated with the presence of multiple complex coronary lesions (OR: 1.967, 95% CI: 1.075-3.600, P < 0.05).

CONCLUSIONS

Serum sLOX-1 levels were associated with complex lesions that might predict vulnerable plaques. This study suggested sLOX-1 might be a useful biomarker of coronary plaque vulnerability in patients with CAD.

Ultrastructural changes in atherosclerotic plaques following the instillation of airborne particulate matter into the lungs of rabbits

BACKGROUND

Epidemiological studies have established that cardiovascular events account for the greatest number of air pollution-related deaths. However, the underlying structural changes are still unknown.

OBJECTIVE

To investigate changes in the ultrastructure of atherosclerotic plaques in Watanabe heritable hyperlipidemic (WHHL) rabbits following the instillation of ambient particulate matter air pollution (particles smaller than 10 µm in diameter) into the lungs.

METHODS

WHHL rabbits (n=8) exposed to 5 mg of ambient particles (Environmental Health Centre - 1993 [EHC-93]; suspended in saline and instilled in the airway) twice per week for four weeks were compared with control WHHL rabbits (n=8) treated with saline alone.

RESULTS

All abdominal aortic plaques were examined using light and electron microscopy, which showed the following: increased accumulation of macrophage-derived foam cells immediately below the endothelial plaque surface (P=0.04); increased contact between these foam cells and the dense subendothelial extracellular matrix (P<0.005) with reduction (P<0.0001) and fragmentation (P<0.0001) of this matrix; and emigration of macrophage- derived foam cells from the plaques in exposed rabbits. In addition, immunohistochemistry verified the presence of type IV collagen in the thickened extracellular matrix material subtending the endothelium.

CONCLUSIONS

The ultrastructure of atherosclerotic plaques in EHC-93- instilled rabbits differed from the ultrastructure observed in rabbits that did not receive EHC-93. These ultrastructural differences are consistent with greater endothelial instability in the plaques of atherosclerosis-prone rabbits.

Adipocytokines in atherothrombosis: focus on platelets and vascular smooth muscle cells

Visceral obesity is a relevant pathological condition closely associated with high risk of atherosclerotic vascular disease including myocardial infarction and stroke. The increased vascular risk is related also to peculiar dysfunction in the endocrine activity of adipose tissue responsible of vascular impairment (including endothelial dysfunction), prothrombotic tendency, and low-grade chronic inflammation. In particular, increased synthesis and release of different cytokines, including interleukins and tumor necrosis factor-α (TNF-α), and adipokines—such as leptin—have been reported as associated with future cardiovascular events. Since vascular cell dysfunction plays a major role in the atherothrombotic complications in central obesity, this paper aims at focusing, in particular, on the relationship between platelets and vascular smooth muscle cells, and the impaired secretory pattern of adipose tissue.

Atheromas feel the pressure: biomechanical stress and atherosclerosis

Atherosclerosis, a chronic vascular disease, is the underlying cause of over half the deaths in the United States each year. Variations in local vascular hemodynamics predispose select sites in the vasculature to atherosclerosis, and the atherosclerotic lesions, in turn alter the biomechanical functioning of the local microenvironment, the consequences of which are not well understood on a molecular level. Further progress in the field of atherosclerosis will require an understanding of the relationship between biomechanics, the tissue microenvironment, and the cellular and molecular response to these factors. This review summarizes this field, particularly within the context of the vascular smooth muscle cell.

Fine ambient air particulate matter exposure induces molecular alterations associated with vascular disease progression within plaques of atherosclerotic susceptible mice

Epidemiology studies have reported associations between increased mortality and morbidity with exposure to particulate air pollution, particularly within individuals with preexisting cardiovascular disease (CVD). Clinical and toxicological studies have provided evidence that exposure to ambient air particulate matter (PM) impacts CVD by increasing plaque size. It is unclear whether PM-induced increased plaque size is associated with molecular disease progression. This study examines molecular profiles within plaques recovered from ApoE(-/-) mice exposed to concentrated ambient air particles (CAPs) to determine whether pulmonary deposition of PM contributes to molecular alterations leading to vascular disease progression. Laser capture microdissection was used to recover atherosclerotic plaques from ApoE(-/-) male mice exposed daily for 5 mo to filtered air or CAPs. Alterations in mRNA expression was assessed in microdissected plaques of CAPs-exposed and air controls using the Affymetrix microarray platform. Bioinformatic analysis indicated alterations in 611 genes: 395 genes downregulated and 216 genes upregulated. Gene ontology revealed CAPs-induced changes to inflammation, proliferation, cell cycle, hematological system, and cardiovascular pathways. Quantitative reverse-transcription polymerase chain reaction (qRT-PCR) verified microarray data also revealing gene expression alterations undetected by the microarray analysis, i.e., decreased expression of alpha-actin for smooth muscle cells, and increased expression of the macrophage marker Cd68 and of beta-actin. Comparison of CAPs-induced gene expression profiles demonstrated consistency with previously published gene expression profiles in the ApoE(-/-) mouse model and humans associated with plaque progression. These results indicate that exposure to fine PM induces molecular alterations associated with vascular disease progression and provides insight into potential biological pathways responsible for this effect.

Inflammation-induced atherosclerosis as a target for prevention of cardiovascular diseases from early life

Atherogenesis starts from the fetal life, and its natural course consists of interrelations between traditional risk factors and inflammatory, immune, and endothelial biomarkers. Even the early-stages of atherosclerotic lesions, i.e. fatty streaks present the features of chronic inflammation. Markers of inflammation are associated with insulin resistance and major atherosclerosis risk factors. Several studies have confirmed a relationship between surrogate markers of future cardiovascular disease with childhood obesity, notably abdominal obesity, as well as with the degree of obesity. Moreover, functional and structural changes are documented in arteries of children with a familial predisposition to atherosclerotic diseases; these changes are associated with clusters of inflammatory factors and markers of oxidation. In addition to the development of atheromatous plaques, inflammation also plays an essential role in the destabilization of artery plaques, and in turn in the occurrence of acute thrombo-embolic disorders. Markers of inflammation can provide predictive clinical information about outcomes of patients with acute coronary syndromes, independent of the extent of myocardial damage. Moreover, serum levels of the inflammatory markers might add prognostic information provided by traditional risk factors. Platelets have an important role in vascular inflammation and atherosclerosis and in the formation of mural thrombi. As lifestyle modification trials have been successful in decreasing endothelial dysfunction and the level of markers of inflammation among children and adolescents, it is suggested that in addition to expanding pharmacological therapies considered for secondary prevention of atherosclerotic diseases aiming to control the inflammatory process, the importance of primordial/primary prevention of atherosclerosis should be underscored.

Optical molecular imaging in atherosclerosis

Current imaging techniques focus on evaluating the anatomical structure of blood vessel wall and atherosclerotic plaque. These techniques fail to evaluate the biological processes which take place in the vessel wall and inside the plaque. Novel imaging techniques like optical imaging can evaluate the biological and cellular processes inside the plaque and provide information which can be vital for better patient risk stratification. This review highlights the various optical imaging techniques and their application in assessing biological processes in atherosclerosis.

Design, synthesis, biological evaluation, and NMR studies of a new series of arylsulfones as selective and potent matrix metalloproteinase-12 inhibitors

Overexpression of macrophage elastase (MMP-12), a member of the matrix metalloproteinases family, can be linked to tissue remodeling and degradation in some inflammatory processes, such as chronic obstructive pulmonary disease (COPD), emphysema, rheumatoid arthritis (RA), and atherosclerosis. On this basis, MMP-12 can be considered an attractive target for studying selective inhibitors that are useful in the development of new therapies for COPD and other inflammatory diseases. We report herein the design, synthesis, and in vitro evaluation of a new series of compounds, possessing an arylsulfonyl scaffold, for their potential as selective inhibitors of MMP-12. The best compound in the series showed an IC50 value of 0.2 nM, with good selectivity over MMP-1 and MMP-14. A docking study was carried out on this compound in order to investigate its binding interactions with MMP-12, and NMR studies on the complex with the MMP-12 catalytic domain were able to validate the proposed binding mode.

Reactive oxygen species-mediated effects on vascular remodeling induced by human atrial natriuretic peptide T2238C molecular variant in endothelial cells in vitro

OBJECTIVES

T2238C ANP (atrial natriuretic peptide) gene variant has been associated with increased cardiovascular risk in humans and with a significant pharmacogenomic effect on cardiovascular disease outcome in hypertensive patients. We investigated the impact of T2238C ANP gene variant on oxidative stress production, cell proliferation and migration, angiogenesis and vascular remodeling in human umbilical vein endothelial cells in vitro.

METHODS

Differentially expressed genes in human umbilical vein endothelial cells exposed to either wild-type (TT2238) or mutant (CC2238) alpha-ANP were characterized by real time-PCR-macroarray analysis using human oxidative stress, angiogenesis and matrix arrays. Reactive oxygen species (ROS) production was determined by dihydroethidium and by evaluation of dichlorofluorescein content. NADPH oxidase gp91phox subunit was investigated by western blotting. Endothelial cell proliferation, migration and tube formation were characterized both in the presence and in the absence of NADPH oxidase inhibition.

RESULTS

Compared with TT2238, CC2238 alpha-ANP altered the redox state balance of the cells in a more significant manner, favoring ROS production and reducing antioxidative stress response. Gene expression of molecules involved in atherogenesis and vascular remodeling was enhanced. In contrast to TT2238 peptide, CC2238 was unable to stimulate cell proliferation and it markedly inhibited endothelial cell tube formation. NADPH oxidase inhibition restored the cell proliferative properties under CC2238 peptide exposure.

CONCLUSION

CC2238 alpha-ANP led to ROS accumulation and increased expression of genes related to atherosclerosis and vascular remodeling in human umbilical vein endothelial cells. As a consequence of NADPH-derived ROS, blunted endothelial cell proliferation and impaired endothelial cell tube formation were observed. These in-vitro effects may link the T2238C alpha-ANP variant to enhanced susceptibility to vascular damage in vivo.

Spectroscopy to improve identification of vulnerable plaques in cardiovascular disease

Many apparent healthy persons die from cardiovascular disease, despite major advances in prevention and treatment of cardiovascular disease. Traditional cardiovascular risk factors are able to predict cardiovascular events in the long run, but fail to assess current disease activity or nearby cardiovascular events. There is a clear relation between the occurrence of cardiovascular events and the presence of so-called vulnerable plaques. These vulnerable plaques are characterized by active inflammation, a thin cap and a large lipid pool. Spectroscopy is an optical imaging technique which depicts the interaction between light and tissues, and thereby shows the biochemical composition of tissues. In recent years, impressive advances have been made in spectroscopy technology and intravascular spectroscopy is able to assess the composition of plaques of interest and thereby to identify and actually quantify plaque vulnerability. This review summarizes the current evidence for spectroscopy as a measure of plaque vulnerability and discusses the potential role of intravascular spectroscopic imaging techniques.

Stromelysin-1 and macrophage metalloelastase expression in the intestinal mucosa of Crohn's disease patients treated with infliximab

BACKGROUND AND AIMS

The mechanism by which anti-tumor necrosis factor (TNF)-alpha therapy promotes rapid closure of fistulas and mucosal wound healing in Crohn's disease (CD) remains unclear. An ex-vivo model of gut T-cell mediated injury indicated that TNF-alpha blockade prevents tissue damage concomitant with matrix metalloproteinase (MMP) inhibition. We, therefore, hypothesized that the chimeric anti-TNF-alpha antibody infliximab facilitates wound healing in CD by downregulating tissue degrading MMPs. We focused on MMP-3 (stromelysin-1) and MMP-12 (macrophage metalloelastase) as these two enzymes have been linked to connective tissue destruction in CD.

METHODS

Endoscopic biopsies were taken from 10 CD patients immediately before and after 10 weeks of treatment with infliximab. Before treatment, biopsies were taken from macroscopically inflamed areas, and after treatment were collected from the same locations as before treatment. The degree of mucosal damage was assessed by using a histological scoring system. MMP transcripts were detected by in-situ hybridization on paraffin sections. MMP proteins were determined by immunoblotting on mucosal homogenates.

RESULTS

Six out of 10 patients had a clinical response to infliximab. MMP-3 and MMP-12 transcripts and proteins, which were highly expressed in CD inflamed mucosa, decreased after treatment in those patients who responded to infliximab. MMP-3 and MMP-12 downregulation was accompanied by a concomitant improvement of the histologic score. No change in MMP expression was found in nonresponders.

CONCLUSION

The downregulation of tissue degrading MMPs in CD mucosa may explain the wound repair capacity of infliximab in healing fistulas and ulcers.

Participation of 5-lipoxygenase-derived LTB(4) in 4-hydroxynonenal-enhanced MMP-2 production in vascular smooth muscle cells

5-Lipoxygenase (5-LO) has been suggested as a modulator of atherosclerotic plaque instability, however, its role in MMP production in vascular smooth muscle cells (VSMC) is still unclear. Thus, this study investigated the role of 5-LO in HNE-enhanced MMP-2 production in VSMC, and the mechanisms by which this enzyme could be activated by HNE. VSMC stimulated with HNE (1 microM) produced MMP-2, which was markedly attenuated in 5-LO-deficient VSMC as well as in cells pretreated with a FLAP inhibitor, MK886, confirming a role for 5-LO metabolites in HNE-enhanced MMP-2 production. Related to these results, HNE increased nuclear translocation of 5-LO promoting 5-LO activity, which was attenuated not only by SB203580, a p38 MAPK inhibitor, but also by PD98059, an ERK inhibitor. In parallel, phosphorylation of p38 MAPK and ERK occurred as early as 15 min after exposure to HNE, suggesting a potential role for p38 MAPK and ERK pathways in HNE-induced activation of 5-LO. Among leukotriene (LT) receptor antagonists, U-75302, a BLT receptor antagonist, but not MK-571 and Rev-5901, cysLT receptor antagonists, showed an inhibitory effect on HNE-enhanced MMP-2 production. Moreover, MMP-2 production in VSMC was also significantly increased by LTB(4), but not by LTC(4) and LTD(4). Collectively, these data suggest that 5-LO mediates HNE-enhanced MMP-2 production via LTB(4)-BLT receptor pathways, consequently leading to atherosclerotic plaque instability.

Matrix metalloproteinase 12 silencing: a therapeutic approach to treat pathological lung tissue remodeling?

Among the large matrix metalloproteinases (MMPs) family, MMP-12, also referred to as macrophage elastase, plays a significant role in chronic pulmonary pathologies characterized by an intense tissue remodeling such as asthma and COPD. This review will summarize knowledge about MMP-12 structure, functions and mechanisms of activation and regulation, including potential MMP-12 modulation by microRNA. As MMP-12 is involved in many tissue remodeling diseases, efforts have been made to develop specific synthetic inhibitors. However, at this time, very few chemical inhibitors have proved to be efficient and specific to a particular MMP. The relevance of silencing MMP-12 by RNA interference is highlighted. The specificity of this approach using siRNA or shRNA and the strategies to deliver these molecules in the lung are discussed.

The protein synthesis inhibitor anisomycin induces macrophage apoptosis in rabbit atherosclerotic plaques through p38 mitogen-activated protein kinase

Because macrophages play a major role in atherosclerotic plaque destabilization, selective removal of macrophages represents a promising approach to stabilize plaques. We showed recently that the protein synthesis inhibitor cycloheximide, in contrast to puromycin, selectively depleted macrophages in rabbit atherosclerotic plaques without affecting smooth muscle cells (SMCs). The mechanism of action of these two translation inhibitors is dissimilar and could account for the differential effects on SMC viability. It is not known whether selective depletion of macrophages is confined to cycloheximide or whether it can also be achieved with translation inhibitors that have a similar mechanism of action. Therefore, in the present study, we investigated the effect of anisomycin, a translation inhibitor with a mechanism of action similar to cycloheximide, on macrophage and SMC viability. In vitro, anisomycin induced apoptosis of macrophages in a concentration-dependent manner, whereas SMCs were only affected at higher concentrations. In vivo, anisomycin selectively decreased the macrophage content of rabbit atherosclerotic plaques through apoptosis. The p38 mitogen-activated protein kinase (MAPK) inhibitor SB202190 [4-(4-fluorophenyl)-2-(4-hydroxyphenyl)-5-(4-pyridyl)-1H-imidazole] prevented anisomycin-induced macrophage death, without affecting SMC viability. SB202190 decreased anisomycin-induced p38 MAPK phosphorylation, did not alter c-Jun NH(2)-terminal kinase (JNK) phosphorylation, and increased extracellular signal-regulated kinase (ERK) 1/2 phosphorylation. The latter effect was abolished by the mitogen-activated protein kinase kinase 1/2 inhibitor U0126 [1,4-diamino-2,3-dicyano-1,4-bis(2-aminophynyltio)butadiene ethanolate], although the prevention of anisomycin-induced macrophage death by SB202190 remained unchanged. The JNK phosphorylation inhibitor SP600125 did not affect anisomycin-induced macrophage or SMC death. In conclusion, anisomycin selectively decreased the macrophage content in rabbit atherosclerotic plaques, indicating that this effect is not confined to cycloheximide. p38 MAPK, but not ERK1/2 or JNK, plays a major role in anisomycin-induced macrophage death.

Low-dose oral sirolimus reduces atherogenesis, vascular inflammation and modulates plaque composition in mice lacking the LDL receptor

BACKGROUND AND PURPOSE

Chronic proliferative responses of different vascular cell types have been involved in the pathogenesis of atherosclerosis. However, their functional role remains to be established. Sirolimus reduces neointimal proliferation after balloon angioplasty and chronic graft vessel disease. These studies were undertaken to investigate the effects of this anti-proliferative drug on atherogenesis.

EXPERIMENTAL APPROACH

Low-density lipoprotein receptor-deficient (LDL r-KO) mice on a cholesterol-rich diet were randomized to receive placebo or sirolimus (0.1; 0.3; or 1 mg.kg(-1)) in their diet for 8 or 16 weeks.

RESULTS

In both studies, plasma levels of the drug increased in a dose-dependent fashion, animals gained weight normally and, among groups, plasma lipids levels did not differ significantly. Compared with placebo, plasma levels of interleukin-6, monocyte chemoattractant protein-1, interferon gamma, tumour necrosis factor alpha and CD40, and their mRNA levels in aortic tissue were significantly reduced in sirolimus-treated mice. This effect resulted in a significant and dose-dependent reduction in atherosclerotic lesions, in both the root and aortic tree. Also these lesions contained less monocyte/macrophages and smooth muscle cells, but more collagen.

CONCLUSIONS AND IMPLICATIONS

The present results demonstrated that at low doses, sirolimus was an effective and safe anti-atherogenic agent in the LDL r-KO mice. It attenuated the progression of atherosclerosis and modulated the plaque phenotype by reducing the pro-inflammatory vascular responses typical of the disease.