Inhibition of transforming growth factor-beta signaling accelerates atherosclerosis and induces an unstable plaque phenotype in mice

ACE and TGFBR1 genes interact in influencing the susceptibility to abdominal aortic aneurysm

A role of ACE I/D polymorphism in the pathogenesis of abdominal aortic aneurysm (AAA) has been demonstrated, possibly due to the effect of angiotensin II on vascular tissue remodelling. Angiotensin II exerts profibrogenic effects through the local induction of TGF-beta. Dysregulated TGF-beta signalling may result from mutations in TGFBR1 and TGFBR2 genes, thus resulting in degenerative changes in the vessel wall. We performed a case-control study in order to investigate the role of TGFBR1 9A6A polymorphism as predisposing factor to AAA per se, and in the presence of ACE DD and AT1R 1166 CC genotypes in 201 AAA patients (mean age+/-S.D., 71.5+/-6.9) referred to the Unit of Vascular Surgery of the University of Florence, compared with 252 healthy controls (mean age+/-S.D., 70.6+/-8.6). A significant difference in genotype distribution and allele frequency between patients and controls was found for ACE, but not for AT1R and TGFBR1 polymorphisms. At univariate analysis a significant association between ACE DD, but not AT1R CC and TGFBR1 6A allele, and the susceptibility to the disease was found [ACE DD OR=1.86 (95% CI 1.26-2.76), p=0.002]. After adjustment for age, gender, traditional cardiovascular risk factors, and CAD, PAD and CVD, ACE DD genotype still affected the susceptibility to AAA [OR=2.13 (95% CI 1.06-4.28), p=0.03], and the contemporary presence of ACE DD genotype and TGFBR1 6A allele, increased the predisposition to the disease [OR=5.09 (95% CI 1.44-18.02), p=0.01]. This study, which demonstrates an interaction between ACE and TGFBR1 genes in predisposing to AAA, may provide further information on the mechanisms contributing to AAA susceptibility, and offer a topic for future larger studies.

An overview of cytokine interactions in atherosclerosis and implications for peripheral arterial disease

Over the last three decades, a surge in research into the inflammatory pathophysiology of atherosclerosis has highlighted an array of cytokines and other inflammatory mediators associated with underlying inflammatory burden. The ability to identify and simultaneously measure multiple cytokines in peripheral blood highlights their potential as biomarkers of atherosclerosis. This has prompted much research in vascular medicine to identify the ;at-risk' groups for atherostenotic or atheroaneurysmal disease. This review is compiled with similar intentions and aims to discern the relevant evidence for cytokine profiling in peripheral arterial disease (PAD), where such information is lacking, while providing a holistic overview of cytokine interactions in atherosclerosis. This is pertinent given that cytokine profiles from coronary artery disease and aortic aneurysm studies cannot be directly extrapolated to PAD due to differences in inflammatory environments that exist in these conditions. Whilst plaque morphology and blood rheology play an important role in the cardiac manifestations of atherosclerosis, tissue thrombogenecity is very important in PAD. Further, cytokines act in concert rather than in isolation in a disease process, and no single cytokine in a cross-sectional model is able to serve as an absolute screening marker. Thus, it is essential to understand the regulation of cytokine production in atherosclerosis prior to evaluating the viability and merits of a multimarker approach for clinical risk stratification in PAD.

Genetic variation and atherosclerosis

A family history of atherosclerosis is independently associated with an increased incidence of cardiovascular events. The genetic factors underlying the importance of inheritance in atherosclerosis are starting to be understood. Genetic variation, such as mutations or common polymorphisms has been shown to be involved in modulation of a range of risk factors, such as plasma lipoprotein levels, inflammation and vascular calcification. This review presents examples of present studies of the role of genetic polymorphism in atherosclerosis.

Cholesterol modulates cellular TGF-beta responsiveness by altering TGF-beta binding to TGF-beta receptors

Transforming growth factor-beta (TGF-beta) responsiveness in cultured cells can be modulated by TGF-beta partitioning between lipid raft/caveolae- and clathrin-mediated endocytosis pathways. The TbetaR-II/TbetaR-I binding ratio of TGF-beta on the cell surface has recently been found to be a signal that controls TGF-beta partitioning between these pathways. Since cholesterol is a structural component in lipid rafts/caveolae, we have studied the effects of cholesterol on TGF-beta binding to TGF-beta receptors and TGF-beta responsiveness in cultured cells and in animals. Here we demonstrate that treatment with cholesterol, alone or complexed in lipoproteins, decreases the TbetaR-II/TbetaR-I binding ratio of TGF-beta while treatment with cholesterol-lowering or cholesterol-depleting agents increases the TbetaR-II/TbetaR-I binding ratio of TGF-beta in all cell types studied. Among cholesterol derivatives and analogs examined, cholesterol is the most potent agent for decreasing the TbetaR-II/TbetaR-I binding ratio of TGF-beta. Cholesterol treatment increases accumulation of the TGF-beta receptors in lipid rafts/caveolae as determined by sucrose density gradient ultracentrifugation analysis of cell lysates. Cholesterol/LDL suppresses TGF-beta responsiveness and statins/beta-CD enhances it, as measured by the levels of P-Smad2 and PAI-1 expression in cells stimulated with TGF-beta. Furthermore, the cholesterol effects observed in cultured cells are also found in the aortic endothelium of atherosclerotic ApoE-null mice fed a high cholesterol diet. These results indicate that high plasma cholesterol levels may contribute to the pathogenesis of certain diseases (e.g., atherosclerosis) by suppressing TGF-beta responsiveness.

Role of transforming growth factor-beta superfamily signaling pathways in human disease

Transforming growth factor beta (TGF-beta) superfamily signaling pathways are ubiquitous and essential regulators of cellular processes including proliferation, differentiation, migration, and survival, as well as physiological processes, including embryonic development, angiogenesis, and wound healing. Alterations in these pathways, including either germ-line or somatic mutations or alterations in the expression of members of these signaling pathways often result in human disease. Appropriate regulation of these pathways is required at all levels, particularly at the ligand level, with either a deficiency or an excess of specific TGF-beta superfamily ligands resulting in human disease. TGF-beta superfamily ligands and members of these TGF-beta superfamily signaling pathways also have emerging roles as diagnostic, prognostic or predictive markers for human disease. Ongoing studies will enable targeting of TGF-beta superfamily signaling pathways for the chemoprevention and treatment of human disease.

VASCULAR INFLAMMATION AND ATHEROGENESIS ARE ACTIVATED VIA RECEPTORS FOR PAMPs AND SUPPRESSED BY REGULATORY T CELLS

Despite significant advances in identifying the risk factors and elucidating atherosclerotic pathology, atherosclerosis remains the leading cause of morbidity and mortality in industrialized society. These risk factors independently or synergistically lead to chronic vascular inflammation, which is an essential requirement for the progression of atherosclerosis in patients. However, the mechanisms underlying the pathogenic link between the risk factors and atherosclerotic inflammation remain poorly defined. Significant progress has been made in two major areas, which are determination of the roles of the receptors for pathogen-associated molecular patterns (PAMPs) in initiation of vascular inflammation and atherosclerosis, and characterization of the roles of regulatory T cells in suppression of vascular inflammation and atherosclerosis. In this review, we focus on three related issues: (1) examining the recent progress in endothelial cell pathology, inflammation and their roles in atherosclerosis; (2) analyzing the roles of the receptors for pathogen-associated molecular patterns (PAMPs) in initiation of vascular inflammation and atherosclerosis; and (3) analyzing the advances in our understanding of suppression of vascular inflammation and atherosclerosis by regulatory T cells. Continuous improvement of our understanding of the risk factors involved in initiation and promotion of artherogenesis, will lead to the development of novel therapeutics for ischemic stroke and cardiovascular diseases.

Inflammation and atherosclerosis

Atherosclerosis, the cause of myocardial infarction, stroke, and ischemic gangrene, is an inflammatory disease. The atherosclerotic process is initiated when cholesterol-containing low-density lipoproteins accumulate in the intima and activate the endothelium. Leukocyte adhesion molecules and chemokines promote recruitment of monocytes and T cells. Monocytes differentiate into macrophages and upregulate pattern recognition receptors, including scavenger receptors and toll-like receptors. Scavenger receptors mediate lipoprotein internalization, which leads to foam-cell formation. Toll-like receptors transmit activating signals that lead to the release of cytokines, proteases, and vasoactive molecules. T cells in lesions recognize local antigens and mount T helper-1 responses with secretion of pro-inflammatory cytokines that contribute to local inflammation and growth of the plaque. Intensified inflammatory activation may lead to local proteolysis, plaque rupture, and thrombus formation, which causes ischemia and infarction. Inflammatory markers are already used to monitor the disease process and anti-inflammatory therapy may be useful to control disease activity.

Cholesterol suppresses cellular TGF-beta responsiveness: implications in atherogenesis

Hypercholesterolemia is a major causative factor for atherosclerotic cardiovascular disease. The molecular mechanisms by which cholesterol initiates and facilitates the process of atherosclerosis are not well understood. Here, we demonstrate that cholesterol treatment suppresses or attenuates TGF-beta responsiveness in all cell types studied as determined by measuring TGF-beta-induced Smad2 phosphorylation and nuclear translocation, TGF-beta-induced PAI-1 expression, TGF-beta-induced luciferase reporter gene expression and TGF-beta-induced growth inhibition. Cholesterol, alone or complexed in lipoproteins (LDL, VLDL), suppresses TGF-beta responsiveness by increasing lipid raft and/or caveolae accumulation of TGF-beta receptors and facilitating rapid degradation of TGF-beta and thus suppressing TGF-beta-induced signaling. Conversely, cholesterol-lowering agents (fluvastatin and lovastatin) and cholesterol-depleting agents (beta-cyclodextrin and nystatin) enhance TGF-beta responsiveness by increasing non-lipid raft microdomain accumulation of TGF-beta receptors and facilitating TGF-beta-induced signaling. Furthermore, the effects of cholesterol on the cultured cells are also found in the aortic endothelium of ApoE-null mice fed a high-cholesterol diet. These results suggest that high cholesterol contributes to atherogenesis, at least in part, by suppressing TGF-beta responsiveness in vascular cells.

'Correction:' Serum transforming growth factor beta-1 (TGF-beta-1) levels in diabetic patients are not associated with pre-existent coronary artery disease

Background

The association between TGF-β1 levels and long-term major adverse cardiovascular events (MACE) in patients with coronary artery disease (CAD) is controversial. No study specifically addressed patients with CAD and diabetes mellitus (DM). The association between TGF-β1 levels and long-term major adverse cardiovascular events (MACE) in patients with coronary artery disease (CAD) is controversial. No study specifically addressed patients with CAD and diabetes mellitus (DM).

Methods

Patients (n = 135, 30–80 years) referred for coronary angiography were submitted to clinical and laboratory evaluation, and the coronary angiograms were evaluated by two operators blinded to clinical characteristics. CAD was defined as the presence of a 70% stenosis in one major coronary artery, and DM was characterized as a fasting glycemia > 126 mg/dl or known diabetics (personal history of diabetes or previous use of anti-hyperglycemic drugs or insulin). Based on these criteria, study patients were classified into four groups: no DM and no CAD (controls, C n = 61), DM without CAD (D n = 23), CAD without DM (C-CAD n = 28), and CAD with DM (D-CAD n = 23). Baseline differences between the 4 groups were evaluated by the χ² test for trend (categorical variables) and by ANOVA (continuous variables, post-hoc Tukey). Patients were then followed-up during two years for the occurrence of MACE (cardiac death, stroke, myocardial infarction or myocardial revascularization). The association of candidate variables with the occurrence of 2-year MACE was assessed by univariate analysis.

Results

The mean age was 58.2 ± 0.9 years, and 51% were men. Patients with CAD had a higher mean age (p = 0.011) and a higher percentage were male (p = 0.040). There were no significant baseline differences between the 4 groups regarding hypertension, smoking status, blood pressure levels, lipid levels or inflammatory markers. TGF-β1 was similar between patients with or without CAD or DM (35.1 ×/÷ 1.3, 33.6 ×/÷ 1.6, 33.9 ×/÷ 1.4 and 31.8 ×/÷ 1.4 ng/ml in C, D, C-CAD and D-CAD, respectively, p = 0.547). In the 2-year follow-ip, independent predictors of 2-year MACE were age (p = 0.007), C-reactive protein (p = 0.048) and systolic blood pressure (p = 0.008), but not TGF-β1.

Conclusion

Serum TGF-β1 was not associated with CAD or MACE occurrence in patients with or without DM.

Angiotensin Inhibition Decreases Progression of Advanced Atherosclerosis and Stabilizes Established Atherosclerotic Plaques

Although increased extracellular matrix (ECM) is pathogenic in a variety of chronic tissue injuries, reduced and/or disrupted ECM may be detrimental in atherosclerosis and rather destabilize existing atherosclerotic lesions. This study therefore assessed the effects of angiotensin II (AngII) antagonism on ECM components of advanced atherosclerosis. Twenty-four-week-old apolipoprotein E-deficient mice were treated with the AngII antagonist losartan for 12 wk. Controls received water or hydralazine. AngII antagonism significantly reduced progression of established atherosclerosis, whereas hydralazine showed no benefit despite similar decrease in BP. Although there was no difference in the macrophage component, AngII antagonism increased the relative collagen portion of the lesions; lessened elastin fragmentation, increased the total elastin content of the aorta; and reduced the mRNA and activity/protein of the elastolytic proteases, cathepsin S, and metalloproteinase-9. Extracellular elastin degradation by cultured smooth muscle cells (SMC) was reduced by losartan, as was SMC invasion through an elastin gel barrier. Thus, AngII antagonism lessens progression of atherosclerosis, increases collagen, and preserves elastin components of ECM within the vascular lesions, which, at least in part, is modulated by effects on SMC. These effects not only decrease further expansion of advanced lesions but also stabilize the established atherosclerotic plaques and may underlie the decreased incidence of acute cardiovascular events that are observed in patients in whom AngII antagonism is begun after atherosclerosis is already established.

Increased plasma levels of cystatin C and transforming growth factor-beta1 in patients with coronary artery ectasia: can there be a potential interaction between cystatin C and transforming growth factor-beta1

Cystatin C, known as an inhibitor of the cathepsin family of cysteine proteases, has been evaluated in several cardiovascular disorders such as atherosclerosis and acute myocardial infarction. The potential interaction between transforming growth factor-beta1 and cystatin C has also been demonstrated in some cell types. Accordingly, we aimed to compare the plasma levels of cystatin C and transforming growth factor-beta1 in patients with coronary artery ectasia coexisting with coronary artery disease and those with coronary artery disease alone. Thirty-nine patients with coronary artery ectasia and coronary artery disease and 35 age and sex-matched patients with coronary artery disease alone were prospectively enrolled in the study. Blood samples of all patients and control participants for measuring plasma cystatin C and transforming growth factor-beta1 levels were drawn>or=24 h after the coronary angiography. Cystatin C concentrations in plasma were measured by latex-enhanced reagent on a Behring Nephelometer II. Plasma levels of transforming growth factor-beta1 were measured by using transforming growth factor-beta1 enzyme-linked immunosorbent assay kit (BioSource International, Inc., Camarillo, California, USA). Plasma level of cystatin C was significantly higher in patients with coronary artery ectasia+coronary artery disease than in patients with coronary artery disease alone (1.05+/-0.30 mg/dl vs. 0.92+/-0.18 mg/mdl, P=0.025, respectively). Transforming growth factor-beta1 was also found to be significantly higher in patients with coronary artery ectasia+coronary artery disease compared with those with coronary artery disease (2.47+/-0.43 vs. 2.22+/-0.43 pg/ml, P=0.02, respectively). The plasma level of cystatin C was significantly but weakly correlated with that of transforming growth factor-beta1 (r=0.217 P=0.02). We conclude that plasma levels of cystatin C and transforming growth factor-beta1 are significantly higher in patients with combined coronary artery ectasia and coronary artery disease than in those with coronary artery disease. Correlation between transforming growth factor-beta1 and cystatin C may also suggest that pathogenesis of coronary artery ectasia might have some different pathways from atherosclerosis with respect to the regulation of extracellular matrix remodeling. Therefore, the role of cystatin in the pathogenesis of coronary artery ectasia and its potential interaction with transforming growth factor-beta1 should be evaluated in further studies.

The role of Smad3-dependent TGF-beta signal in vascular response to injury

Transforming growth factor (TGF)-beta is a multifunctional cytokine involved in the regulation of proliferation, differentiation, migration, and survival of many different cell types. The role of TGF-beta in atherosclerosis has been intensively studied, but the precise function of the downstream signals in this disease entity remains unclear. We recently discovered that mice lacking Smad3, a major downstream mediator of TGF-beta, show enhanced neointimal hyperplasia with decreased matrix deposition in response to vascular injury. This review summarizes the current view on involvement of TGF-beta in atherosclerotic vascular disease and discusses the role of Smad3-dependent TGF-beta signal in vascular response to injury.

TGF-β1: a novel target for cardiovascular pharmacology

Transforming growth factor beta-1 (TGF-beta1) plays a key role in cardiovascular disease by a process which allows the loss of its protective properties. The first therapeutic attempt to restore its function by selectively designed novel drugs are being made. In addition, it has been recognized that the TGF-beta1 pathway is involved in the vascular mechanism of action of some current clinical drugs, such as acetylsalicylic acid, thiazolidinediones and statins. The aim of this paper is to review the possible value of TGF-beta1 as both a disease marker and a therapeutical target for cardiovascular disease.

Elevated serum soluble endoglin (sCD105) decreased during extracorporeal elimination therapy for familial hypercholesterolemia

Extracorporeal elimination is a method of LDL-lowering therapy that is used in severe familial hypercholesterolemia (FH) after other therapeutic approaches have failed. There are currently no universally accepted biomarkers that would allow determining necessary intensity of therapy and frequency of future therapeutic interventions. An ideal tool for immediate evaluation would be a readily measurable serum marker. We hypothesized that soluble endoglin (sCD105), a recently described indicator of endothelial dysfunction, may represent such a tool. Eleven patients with FH (three homozygous, eight heterozygous; Fredrickson type IIa, IIb) that have been monitored for 4.5+/-2.8 years were treated; eight by LDL-apheresis and three by hemorheopheresis. 40 sCD105 measurements were done, before and after two consecutive elimination procedures. Baseline serum sCD105 levels were significantly higher in the patients (5.74+/-1.47 microg/l in series I, 6.85+/-1.85 microg/l in series II) than in the control group (3.85+/-1.25 microg/l). They decreased to normal after LDL-elimination (p=0.0003) in all except for one patient. This return to normal was not due to a non-specific capture of endoglin in adsorption or filtration columns as demonstrated by measurement of sCD105 before and after passage through the elimination media. We conclude that the soluble endoglin levels in patients with severe FH remain elevated despite long-term intensive therapy and that they decrease after extracorporeal elimination. Endoglin can therefore serve as a marker for evaluation of the treatment efficacy and of the decreased atherosclerotic activity in patients with FH treated by extracorporeal LDL-cholesterol elimination.

Transforming growth factor-beta-regulated expression of genes in macrophages implicated in the control of cholesterol homoeostasis

The regulation of macrophage cholesterol homoeostasis is of crucial importance in the pathogenesis of atherosclerosis, an underlying cause of heart attack and stroke. Several recent studies have revealed a critical role for the cytokine TGF-beta (transforming growth factor-beta), a key regulator of the immune and inflammatory responses, in atherogenesis. We discuss here the TGF-beta signalling pathway and its role in this disease along with the outcome of our recent studies on the action of the cytokine on the expression of key genes implicated in the uptake or efflux of cholesterol by macrophages and the molecular mechanisms underlying such regulation.

Long-term treatment with TGFbeta1 impairs mechanotransduction in bovine aortic endothelial cells

BACKGROUND AND PURPOSE

Vascular endothelial cells play a role in the physiological response to mechanical stress. Transforming growth factor beta1 (TGFbeta1) induces morphological changes in endothelial cells, and this may alter their mechanosensitive responses. The aim of this study was to examine the effects of TGFbeta1 on hypotonic stress (HTS)-induced responses in bovine aortic endothelial cells (BAECs).

EXPERIMENTAL APPROACH

Cultured BAECs were treated with 3 ng ml(-1) TGFbeta1 for 24 h (24h-TGFbeta1) or 7 days (7d-TGFbeta1). Cytosolic actin fibres were stained with rhodamine-phalloidin. Intracellular Ca2+ concentration was measured using fura2. Tyrosine phosphorylation and RhoA expression were assessed by Western blotting. Expression of RhoA mRNA was assessed by real-time PCR.

KEY RESULTS

BAECs developed pseudopod-like processes within 24 h and showed a fibroblast-like appearance after 7 days. HTS induced Ca2+ transients via endogenous ATP release in both control and 24h-TGFbeta1 BAECs but not in 7d-TGFbeta1 BAECs. We have previously shown that HTS-induced ATP release is mediated by sequential activation of RhoA and tyrosine kinases. The basal amount of membrane-bound RhoA was significantly lower in 7d-TGFbeta1 than in 24h-TGFbeta1 or control BAECs. HTS increased the membrane-bound RhoA to the same fractional level in 24h-TGFbeta1 and control BAECs, but its net maximal amount was significantly lower in 7d-TGFbeta1. HTS-induced downstream signals of RhoA activation, i.e. the tyrosine phosphorylation of FAK and paxillin, were markedly suppressed in 7d-TGFbeta1 BAECs.

CONCLUSIONS AND IMPLICATIONS

These results indicate that long-term treatment with TGFbeta1 does not impair mechanoreception in BAECs but impairs mechanotransduction by affecting RhoA membrane translocation.

A comparative study of neovascularisation in atherosclerotic plaques using CD31, CD105 and TGF beta 1

OBJECTIVES

This study aims to identify plaque neovascularisation using antibodies to CD31, CD105 and TGFbeta1, and to compare their patterns of expression.

METHODS

Tissue expression of CD31, CD105 and TGFbeta1 was examined immunohistologically in atherosclerotic plaques from 53 patients who had undergone carotid endarterectomy and in 10 controls.

RESULTS

CD31 was observed in a proportion of the microvessels within atheroma. The expression of CD105 was barely visible in normal arteries, but was markedly enhanced in atherosclerotic plaques. The vast majority of the microvessels in atheroma were positive for CD105 with pronounced expression around the periphery of the lipid core. In consecutive sections, microvessels showing negative staining for CD31 were positive for CD105. Although TGFbeta1 was seen in the thickened intima, it was more strongly expressed in well-formed fibrous plaques. Consecutive sections showed that some microvessels were stained by both CD105 and TGFbeta1, but in certain areas microvessels were exclusively CD105 positive.

CONCLUSIONS

These observations highlight the distinctive expression patterns of CD31, CD105 and TGFbeta1, suggesting their specific roles in the development of atherosclerotic plaques. CD105 is almost universally expressed in microvessels within the atheroma and is therefore a better vascular marker than CD31 and TGFbeta1for assessing neovascularisation in atherosclerotic plaques.

The immune response is involved in atherosclerotic plaque calcification: could the RANKL/RANK/OPG system be a marker of plaque instability?

Atherogenesis is characterized by an intense inflammatory process, involving immune and vascular cells. These cells play a crucial role in all phases of atherosclerotic plaque formation and complication through cytokine, protease, and prothrombotic factor secretion. The accumulation of inflammatory cells and thus high amounts of soluble mediators are responsible for the evolution of some plaques to instable phenotype which may lead to rupture. One condition strongly associated with plaque rupture is calcification, a physiopathological process orchestrated by several soluble factors, including the receptor activator of nuclear factor (NF)kappaB ligand (RANKL)/receptor activator of nuclear factor (NF)kappaB (RANK)/osteoprotegerin (OPG) system. Although some studies showed some interesting correlations with acute ischemic events, at present, more evidences are needed to evaluate the predictive and diagnostic value of serum sRANKL and OPG levels for clinical use. The major limitation is probably the poor specificity of these factors for cardiovascular disease. The identification of tissue-specific isoforms could increase the importance of sRANKL and OPG in predicting calcified plaque rupture and the dramatic ischemic consequences in the brain and the heart.

Gene profiling of cathepsin K deficiency in atherogenesis: profibrotic but lipogenic

Recently, we showed that cathepsin K deficiency reduces atherosclerotic plaque progression, induces plaque fibrosis, but aggravates macrophage foam cell formation in the ApoE -/- mouse. To obtain more insight into the molecular mechanisms by which cathepsin K disruption evokes the observed phenotypic changes, we used microarray analysis for gene expression profiling of aortic arches of CatK -/-/ApoE -/- and ApoE -/- mice on a mouse oligo microarray. Out of 20 280 reporters, 444 were significantly differentially expressed (p-value of < 0.05, fold change of > or = 1.4 or < or = - 1.4, and intensity value of > 2.5 times background in at least one channel). Ingenuity Pathway Analysis and GenMAPP revealed upregulation of genes involved in lipid uptake, trafficking, and intracellular storage, including caveolin - 1, - 2, - 3 and CD36, and profibrotic genes involved in transforming growth factor beta (TGFbeta) signalling, including TGFbeta2, latent TGFbeta binding protein-1 (LTBP1), and secreted protein, acidic and rich in cysteine (SPARC), in CatK -/-/ApoE -/- mice. Differential gene expression was confirmed at the mRNA and protein levels. In vitro modified low density lipoprotein (LDL) uptake assays, using bone marrow derived macrophages preincubated with caveolae and scavenger receptor inhibitors, confirmed the importance of caveolins and CD36 in increasing modified LDL uptake in the absence of cathepsin K. In conclusion, we suggest that cathepsin K deficiency alters plaque phenotype not only by decreasing proteolytic activity, but also by stimulating TGFbeta signalling. Besides this profibrotic effect, cathepsin K deficiency has a lipogenic effect owing to increased lipid uptake mediated by CD36 and caveolins.

Transforming Growth Factor-βInhibits Coxsackievirus-Mediated Autoimmune Myocarditis

Clinical myocarditis is a precursor to dilated cardiomyopathy and a principal cause of heart failure. Nearly 30% of all recently diagnosed cases of myocarditis are attributable to infection with coxsackie B virus (CBV), the most frequently associated pathogen. CBV initially replicates in the pancreas and quickly spreads to the heart, inducing chronic autoimmunity. To determine whether immunosuppressive cytokines could act to limit the extent of autoimmunity to the heart, we infected transgenic mice that express immunosuppressive cytokines in the pancreas. Herein, we demonstrate that transgenic expression of transforming growth factor-beta (1) (TGF-beta) within the pancreatic beta cells prevented mice from developing autoimmune myocarditis after CBV infection. In contrast, transgenic expression of interleukin-4 did not inhibit virus-mediated heart disease. Furthermore, we show that TGF-beta expression reduced viral replication while promoting the recruitment of macrophages into the pancreas. These results illustrate the benefit of TGF-beta in controlling not only viral replication, but also CBV-mediated autoimmunity.

Role of platelet-derived growth factor and transforming growth factor beta1 the in the regulation of metalloproteinase expressions

BACKGROUND

We investigated the role and influence of platelet derived growth factor (PDGF) and transforming growth factor beta1 (TGF) in the pathologic mechanism at the basis of plaque instability regulating the expression of matrix metalloproteinases (MMPs).

METHODS

Plaques obtained from 70 patients who underwent carotid endarterectomy were classified histologically as stable or unstable. Serum levels of PDGF and TGF were measured pre- and postoperatively. The serum activities of MMP-2 and MMP-9 were also analyzed. Human umbilical artery smooth muscle cells (HUASMCs) were stimulated in vitro with PDGF at various concentrations (20 and 50 ng/mL) and TGF (2 and 5 ng/mL) in a serum-free medium. The release of MMPs in the conditioned medium was assessed by enzyme-linked immunosorbent assay. Release of the MMPs was confirmed by Western blot analysis; their activity and expression were determined by zymography and reverse transcription-polymerase chain reaction. Specific inhibition tests were performed on HUASMCs to evaluate the role of these growth factors.

RESULTS

Forty-two (60%) patients had an unstable carotid plaque and 28 (40%) a stable plaque. Preoperatively, patients affected with unstable carotid plaques had higher PDGF and lower TGF plasma levels than patients with stable carotid plaques (P < .001); the levels returned to normal at 1 and 30 days postoperatively, compared with 20 non-operated healthy volunteers. Release, activity, protein level, and expression of MMPs in PDGF-stimulated HUASMCs were greater than in the controls (P < .001), whereas these values in the TGF-stimulated HUASMCs were lower (P < .001). The addition of monoclonal anti-PDGF antibodies decreased the release, activity, protein level, and expression of MMPs, whereas the addition of monoclonal anti-TGF antibodies increased the release, activity, protein level and expression of MMPs (P < .001).

CONCLUSIONS

TGF seems to be an important stabilizing factor and prevents plaque rupture through the decrease of MMPs.

Sustained contraction and loss of NO production in TGFbeta1-treated endothelial cells

BACKGROUND AND PURPOSE

Transforming growth factor beta1 (TGFbeta1) is generated in atherosclerotic and injured vessel walls. We examined whether the endothelial-to-mesenchymal transdifferentiation induced by TGFbeta1 affects endothelial functions.

EXPERIMENTAL APPROACH

Bovine aortic endothelial cells (BAECs) were treated with 3 ng ml(-1) TGFbeta1 for 7 days. Contraction of TGFbeta1-treated BAECs was assessed by collagen gel contraction assay. Protein expression and phosphorylation were assessed by Western blotting. Intracellular Ca2+ concentration and NO production were measured using fura2 and DAF-2, respectively.

KEY RESULTS

TGFbeta1-treated BAECs showed dense actin fibers and expressed smooth muscle marker proteins; they also changed into smooth muscle-like, spindle-shaped cells in collagen gel cultures. ATP (10 microM) induced a gradual contraction of collagen gels containing TGFbeta1-treated BAECs but not of gels containing control BAECs. ATP-induced contraction of TGFbeta1-treated BAECs was not reversed by the removal of ATP but was partially suppressed by a high concentration of sodium nitroprusside (1 microM). TGFbeta1-treated BAECs showed sustained phosphorylation of myosin light chain in response to ATP and low levels of basal MYPT1 expression. ATP-induced Ca2+ transients as well as eNOS protein expression were not affected by TGFbeta1 in BAECs. However, ATP-induced NO production was significantly reduced in TGFbeta1-treated BAECs. Anti-TGFbeta1 antibody abolished all of these TGFbeta1-induced changes in BAECs.

CONCLUSIONS AND IMPLICATIONS

Mesenchymal transdifferentiation induced by TGFbeta1 leads to sustained contraction and reduced NO production in endothelial cells. Such effects, therefore, would not be beneficial for vascular integrity.

Chemokine receptor CX3CR1 regulates renal interstitial fibrosis after ischemia-reperfusion injury

Transient renal ischemia induces both inflammatory and fibrotic processes and is a major cause of acute and chronic renal insufficiency. Study of ischemia-reperfusion injury in gene-targeted mice has identified multiple factors responsible for inflammation, whereas mechanisms underlying fibrosis remain poorly defined. Here we demonstrate by both gene inactivation and target protein blockade that a single chemokine receptor subtype, the fractalkine receptor CX3CR1, is able to reduce both inflammation and fibrosis after ischemia-reperfusion injury in the mouse, leading to partially preserved renal function after injury. The mechanism involves selective effects in the outer medulla, including reduced accumulation of macrophages and reduced expression of the macrophage and platelet-derived fibrogenic protein platelet-derived growth factor-B. CX3CR1 is the first chemokine receptor shown to contribute to fibrogenesis in renal ischemia-reperfusion injury.

DeltaEF1 mediates TGF-beta signaling in vascular smooth muscle cell differentiation

Alteration in the differentiated state of smooth muscle cells (SMCs) is known to be integral to vascular development and the pathogenesis of vascular disease. However, it is still largely unknown how environmental cues translate into transcriptional control of SMC genes. We found that deltaEF1 is upregulated during SMC differentiation and selectively transactivates the promoters of SMC differentiation marker genes, SM alpha-actin and SM myosin heavy chain (SM-MHC). DeltaEF1 physically interacts with SRF and Smad3, resulting in a synergistic activation of SM alpha-actin promoter. Chromatin immunoprecipitation assays and knockdown experiments showed that deltaEF1 is involved in the control of the SMC differentiation programs induced by TGF-beta signaling. Overexpression of deltaEF1 inhibited neointima formation and promoted SMC differentiation, whereas heterozygous deltaEF1 knockout mice exhibited exaggerated neointima formation. It thus appears deltaEF1 mediates SMC differentiation via interaction with SRF and Smad3 during development and in vascular disease.

Inflammation in coronary artery disease: potential role for immunomodulatory therapy

Understanding of the mechanisms underlying atherosclerotic disorders has evolved beyond the view of a progressive collection of lipids and cellular debris in the vascular wall. Current evidence has implicated inflammatory pathways as an important pathogenic mechanism in atherogenesis and plaque destabilization. Although not necessarily the primary event, inflammation and cytokine activation during plaque formation and destabilization may represent a common final pathway to various stimuli. Thus, it seems that not only 'new' risk factors, such as infections with various microorganisms, but also classic risk factors for cardiovascular disease, such as hyperlipidemia, hypertension and diabetes, may promote their atherogenic effects through inflammatory responses. Indeed, recent reports have suggested that traditional cardiovascular medications may attenuate atherogenesis and enhance plaque stability, at least partly through anti-inflammatory mechanisms. However, uncovering the inflammatory pathways in atherosclerosis has raised the possibility that newer treatment modalities should be more directly targeted against inflammatory mediators. Recently, a series of experimental studies have reported reduction of atherosclerosis by immunomodulatory therapy, such as chemokine blockade, interleukin-10 and immunization/vaccination against oxidized low-density lipoprotein and heat-shock protein. It is conceivable that some of these approaches will be tested clinically and, if successful, they could provide novel treatment strategies in coronary artery disease in humans.

Frequency of polymorphisms of signal peptide of TGF-beta1 and -1082G/A SNP at the promoter region of Il-10 gene in patients with carotid stenosis

The role of inflammation in atherosclerosis is well recognized. We have evaluated the allele frequencies of the +869T/C and +915G/C polymorphisms (SNPs) at the TGF-beta1 gene and -1082G/A SNP at IL-10 promoter sequence, two well-known immunosuppressive and anti-inflammatory cytokines, in patients with carotid stenosis. Our data suggest a lack of association between these SNPs and the susceptibility to atherosclerosis although other reports have demonstrated this association. These results may be due to the pleiotropic effects of the cytokines and/or differences in haplotype combination that should be investigated to elucidate the role of TGF-beta1 and IL-10 polymorphisms in atherosclerosis.

TGF-beta1 generates a specific multicomponent extracellular matrix in human coronary SMC

BACKGROUND

Transforming growth factor (TGF-beta(1)) is postulated to play an important role in maintaining the structure and function of arterial tissue and protection against development of arteriosclerosis. The TGF-beta(1)-induced production of a stable extra-cellular matrix-rich plaque phenotype is suggested to be part of the protection against a switch to an unstable rupture-prone arteriosclerotic plaque.

MATERIALS AND METHODS

This study addresses the question of whether the expression profile and the type of extra-cellular matrix (ECM) generated by TGF-beta(1) stimulation have the structural feature of a fibril-rich stable matrix. Seventeen genes codings for ECM components of human coronary smooth muscle cells (SMCs) after a 24-h stimulation by TGF-beta(1) have been analyzed.

RESULTS

Real-time RT-PCR was used to quantify the mRNA of genes under investigation. It was found that after TGF-beta(1) stimulation (a) the up-regulation of COL1A1-specific mRNA was associated with increased [(3)H]proline incorporation into the alpha-1 and -2 chains of collagen type I, (b) the up-regulation of biglycan- and syndecan-1-specific mRNA corresponded to an increased [(35)S]sulphate and [4,5-(3)H]leucine incorporation into the biglycan molecule and to an increase of syndecan-1 protein, (c) the up-regulated FGF-2 gene accounted predominantly for the ECM-bound subfraction of FGF-2-protein and (d) fibronectin and thrombospondin exhibited a significantly higher mRNA level. In contrast collagen XIV, a minor collagen type, and the proteoglycan decorin were down-regulated. The down-regulated decorin changed its structure by elongation and reduced GlcA to IdoA epimerization of the dermatan sulphate side-chain as judged by [(35)S]sulphate metabolic labelling experiments. No significant changes in response to TGF-beta(1) were observed for the collagen types III, VI and XVI, for versican, perlecan and the syndecans-2 and -4.

CONCLUSIONS

It was concluded from the data that the TGF-beta(1)-induced formation of a highly specific multicomponent extra-cellular matrix on coronary arterial SMCs could provide in vivo mechanical strength to the neointima in arteriosclerotic lesions and to the fibrous cap overlying the lipid core.

Decorin overexpression reduces atherosclerosis development in apolipoprotein E-deficient mice

Atherosclerosis results from accumulation of macrophages and extracellular matrix in the arterial wall. Decorin, a small matrix proteoglycan, is able to regulate cell proliferation, migration and growth factors' activity. We investigated the effect of decorin overexpression on atherosclerosis progression in apolipoprotein E-deficient (ApoE(-/-)) mice. Female ApoE(-/-) mice, 10 weeks old (early treatment, n = 20) and 20 weeks old (delayed treatment, n = 20) were administered intravenously with either an adenovirus (2.5 x 10(9) plaque-forming units/mouse) containing human decorin gene (Ad-Dcn) or beta-galactosidase (LacZ), or PBS. Transgenic decorin was mainly expressed in the liver, and was secreted in the plasma up to 4 weeks. Six weeks after treatment, no significant difference in aortic root lesion size was observed between LacZ- and PBS-control groups. In contrast, Ad-Dcn-treated mice showed significantly reduced atherosclerotic lesions as compared to controls in both early and delayed treatment groups (2.9 +/- 1.1% versus 5.5 +/- 0.4%; p = 0.004 and 13.4 +/- 1.3% versus 19.9 +/- 1.41%; p = 0.009, respectively). In parallel, macrophage, gelatinase activity and collagen plaque content were also reduced. Interestingly, plasma triglycerides were reduced and decorin formed complexes with transforming growth factor-beta1 (TGF-beta1) that resulted in reduced circulating free-TGF-beta1. In conclusion, systemic overexpression of decorin reduces inflammation, triglycerides and fibrosis in atherosclerotic plaques of ApoE(-/-) mice resulting in slowing down of disease progression.

Transforming growth factor-beta regulation of immune responses

Transforming growth factor-beta (TGF-beta) is a potent regulatory cytokine with diverse effects on hemopoietic cells. The pivotal function of TGF-beta in the immune system is to maintain tolerance via the regulation of lymphocyte proliferation, differentiation, and survival. In addition, TGF-beta controls the initiation and resolution of inflammatory responses through the regulation of chemotaxis, activation, and survival of lymphocytes, natural killer cells, dendritic cells, macrophages, mast cells, and granulocytes. The regulatory activity of TGF-beta is modulated by the cell differentiation state and by the presence of inflammatory cytokines and costimulatory molecules. Collectively, TGF-beta inhibits the development of immunopathology to self or nonharmful antigens without compromising immune responses to pathogens. This review highlights the findings that have advanced our understanding of TGF-beta in the immune system and in disease.

The immune response in atherosclerosis: a double-edged sword

Immune responses participate in every phase of atherosclerosis. There is increasing evidence that both adaptive and innate immunity tightly regulate atherogenesis. Although improved treatment of hyperlipidaemia reduces the risk for cardiac and cerebral complications of atherosclerosis, these remain among the most prevalent of diseases and will probably become the most common cause of death globally within 15 years. This Review focuses on the role of immune mechanisms in the formation and activation of atherosclerotic plaques, and also includes a discussion of the use of inflammatory markers for predicting cardiovascular events. We also outline possible future targets for prevention, diagnosis and treatment of atherosclerosis.

Suppression of atherogenesis by delivery of TGFbeta1ACT using adeno-associated virus type 2 in LDLR knockout mice

TGFbeta(1) deficiency has been attributed to the development of atherosclerosis. There is, however, little direct evidence for this concept. To examine this hypothesis, low-density lipoprotein receptor knockout (LDLR(-/-)) mice were injected via tail vein with recombinant adeno-associated virus type 2 (rAAV) carrying a bioactive TGFbeta(1) mutant (AAV/TGFbeta1ACT, n=10) or granulocyte-macrophage-colony stimulating factor (AAV/GM-CSF, n=10, a negative control) or saline (n=9, control), and then put on a high cholesterol diet. At 18 weeks, blood lipids were found to be similarly elevated in all LDLR(-/-) mice. TGFbeta1ACT and GM-CSF (DNA, mRNA, and protein) were highly expressed in the tissues of mice given TGFbeta1ACT or AAV/GM-CSF, respectively, showing sustained transfection following gene delivery by the systemic route. Saline-treated and AAV/GM-CSF-treated LDLR(-/-) mice showed extensive areas of atherosclerotic lesion formation. There was evidence of intense oxidative stress (nitrotyrosine staining), inflammation (CD68 staining), and expression of adhesion molecules and the ox-LDL receptor LOX-1 (gene array analysis) in the atherosclerotic tissues. Importantly, atherosclerotic lesion formation was markedly inhibited in the LDLR(-/-) mice given AAV/TGFbeta1ACT. Expression of adhesion molecules and LOX-1, oxidative stress, and inflammatory response all were inhibited in the mice given AAV/TGFbeta1ACT (P<0.05 vs. saline-treated or GM-CSF-treated LDLR(-/-) mice). These data for the first time demonstrate that systemic delivery of TGFbeta1ACT gene via AAV can inhibit formation of atherosclerotic lesions, possibly via anti-inflammatory and anti-oxidant mechanisms. These findings suggest a novel view of TGFbeta(1) in atherogenesis and a potential new gene therapy for treatment of atherosclerosis.

Cytokines in Atherosclerosis: Pathogenic and Regulatory Pathways

Atherosclerosis is a chronic disease of the arterial wall where both innate and adaptive immunoinflammatory mechanisms are involved. Inflammation is central at all stages of atherosclerosis. It is implicated in the formation of early fatty streaks, when the endothelium is activated and expresses chemokines and adhesion molecules leading to monocyte/lymphocyte recruitment and infiltration into the subendothelium. It also acts at the onset of adverse clinical vascular events, when activated cells within the plaque secrete matrix proteases that degrade extracellular matrix proteins and weaken the fibrous cap, leading to rupture and thrombus formation. Cells involved in the atherosclerotic process secrete and are activated by soluble factors, known as cytokines. Important recent advances in the comprehension of the mechanisms of atherosclerosis provided evidence that the immunoinflammatory response in atherosclerosis is modulated by regulatory pathways, in which the two anti-inflammatory cytokines interleukin-10 and transforming growth factor-β play a critical role. The purpose of this review is to bring together the current information concerning the role of cytokines in the development, progression, and complications of atherosclerosis. Specific emphasis is placed on the contribution of pro- and anti-inflammatory cytokines to pathogenic (innate and adaptive) and regulatory immunity in the context of atherosclerosis. Based on our current knowledge of the role of cytokines in atherosclerosis, we propose some novel therapeutic strategies to combat this disease. In addition, we discuss the potential of circulating cytokine levels as biomarkers of coronary artery disease.

Cholesterol-induced Apoptotic Macrophages Elicit an Inflammatory Response in Phagocytes, Which Is Partially Attenuated by the Mer Receptor

Macrophage apoptosis and the ability of phagocytes to clear these apoptotic cells are important processes in advanced atherosclerosis. Phagocytic clearance not only disposes of dead cells but usually elicits an anti-inflammatory response. To study this process in a model of advanced lesional macrophage death, macrophages rendered apoptotic by free cholesterol loading (FC-AMs) were incubated briefly with fresh macrophages ("phagocytes"). FC-AMs were promptly ingested by the phagocytes, which was dependent upon actin polymerization and the phagocyte Mer receptor. Surprisingly, this brief exposure to FC-AMs triggered a modest proinflammatory response in the phagocytes: tumor necrosis factor-alpha (TNF-alpha) and interleukin (IL)-1beta were induced, whereas the levels of transforming growth factor-beta and IL-10 were not increased. This response required cell contact between the FC-AMs and phagocytes but not FC-AM ingestion. TNF-alpha and IL-1beta induction required one or more proteins on the FC-AM surface and was dependent on signaling through extracellular signal-regulated kinase-1/2 mitogen-activated protein kinase and nuclear factor-kappaB in the phagocytes. TNF-alpha production was markedly greater when Mer-defective phagocytes were used, indicating that Mer attenuated the inflammatory response. Interestingly, a more typical anti-inflammatory response was elicited when phagocytes were exposed to macrophages rendered apoptotic by oxidized low density lipoprotein or UV radiation. Thus, the proinflammatory milieu of advanced atherosclerotic lesions may be promoted, or at least not dampened, by contact between FC-induced apoptotic macrophages and neighboring phagocytes prior to apoptotic cell ingestion.

Different effects of simvastatin and losartan on cytokine levels in coronary artery disease

BACKGROUND AND OBJECTIVE

Use of HMG-CoA reductase inhibitors (statins) and angiotensin II type 1 (AT(1)) receptor antagonists reduces the incidence of cardiovascular events. The cytokines macrophage colony-stimulating factor (M-CSF) and transforming growth factor (TGF)-beta may exert proatherogenic and antiatherogenic effects, respectively. In this study, we examined whether treatment with a statin or an AT(1) receptor antagonist alters M-CSF and TGF-beta levels in patients with coronary artery disease.

METHODS

Twenty-seven consecutive patients with coronary artery disease were randomly assigned to the following three treatment groups for 8 weeks: simvastatin 5 mg/day (n = 10); losartan 50 mg/day (n = 9); or control (usual treatment; n = 8). Blood samples were collected before and after treatment.

RESULTS

Clinical characteristics and baseline cytokine levels were comparable among the three groups. Serum levels of M-CSF were significantly decreased only in the simvastatin group (from 403 +/- 71 to 303 +/- 116 pg/mL; p = 0.009). Plasma levels of TGF-beta were significantly increased only in the losartan group (from 5.01 +/- 1.13 to 7.50 +/- 3.83 ng/mL; p = 0.021). Simvastatin decreased serum M-CSF levels independently of changes in total cholesterol or low-density lipoprotein-cholesterol.

CONCLUSIONS

The results of this study indicate that simvastatin decreases serum levels of M-CSF while losartan increases plasma levels of TGF-beta, suggesting that the two drugs may have different anti-atherosclerotic properties.

Defects in regulation of local immune responses resulting in atherosclerosis

Atherosclerosis is nowadays generally accepted as an inflammatory disease but the mechanism of its origin and development have not yet been fully clarified. The present review focuses on the role of the local immune system as one of the key players in the pathogenesis of the complex process. Its part represented by vascular-associated lymphoid tissue (VALT) within the arterial wall participates directly in the vascular wall's homeostatis. Its inordinate activation during ontogenic development of an individual, this formerly defensive and physiologic mechanism transform into a pathological process resulting in an impairing inflammation. Hsp60, CRP and oxidized or otherwise modified LDL are serious candidates for triggering these pathological changes. The principal role is played by anti-Hsp60 antibodies and by shear stress originating on the surface of endothelium due to blood flow. The experimental and clinical data supporting this immunological hypothesis of atherosclerosis are discussed.

Transforming growth factor-beta-dependent growth inhibition in primary vascular smooth muscle cells is p38-dependent

Vascular smooth muscle cells (VSMCs) constitute the major cellular component of the vessel tunica media. VSMC proliferation is a key feature in developing vessels and pathological states such as atherosclerosis and restenosis. Transforming growth factor (TGF)-beta is a key regulator of VSMCs, but its effect on VSMC proliferation and apoptosis are controversial. Here, we characterized TGF-beta effects on basal-, serum-, and platelet-derived growth factor-BB-induced primary mouse VSMC proliferation. TGF-beta led to potent growth inhibition of VSMCs isolated from normal mouse aortae without inducing apoptosis. Growth inhibition by TGF-beta was due to G0/G1 arrest. Next, we explored distinct signaling pathways activated by TGF-beta and the effects of pharmacological inhibition of these. TGF-beta led to activation of Smad2/3, p38, p42/44, and c-Jun NH2-terminal kinase (JNK) pathways, assessed by phosphorylation, immunofluorescence, and reporter gene analysis. TGF-beta-dependent growth inhibition was specifically attenuated by pharmacological blockade of the TGF-beta type I receptor (TbetaRI) kinase or p38 mitogen-activated protein kinase pathways, whereas blockade of p42/44 or JNK kinases did not influence the effect of TGF-beta. TbetaRI kinase inhibition blocked all downstream pathways including Smad and p38 phosphorylation. In contrast, p38 inhibition did not alter Smad function, as assessed by translocation or reporter gene expression, but selectively inhibited p38 activity. These results demonstrate that TGF-beta acts as a potent antiproliferative mediator in VSMCs, irrespective of the proliferative stimulus, without inducing apoptotic effects. The anti-proliferative effect of TGF-beta is due to G0/G1 arrest and mediated primarily by the p38 pathway, suggesting that p38 kinase is central to TGF-beta-mediated growth inhibition in primary mouse VSMCs.

Transcriptional activity of genes encoding Transforming Growth Factor beta and its receptors in peripheral blood mononuclear cells from patients with acute coronary syndromes

BACKGROUND

Recent data report altered gene expression of numerous pro- and anti-inflammatory factors involved in pathology of acute coronary syndromes (ACS). Transforming growth factor beta (TGFbeta) signaling is engaged in a wide range of processes. Its effect on vessels seems to be protective due to its anti-inflammatory and anti-atherogenic action. However, it also seems to be engaged in such negative effects as neointima formation and fibrosis. The aim of the study was to assess the expression of the genes encoding TGFbeta and its receptors (type I, II, and III) in patients with ACS.

METHODS

The study was carried out on 24 patients with acute coronary syndrome (7 with unstable angina [UA] and 17 with myocardial infarction [MI]) and 10 age-matched healthy subjects (control). To evaluate gene expression of TGFbeta and its receptors total mRNA was extracted from peripheral blood mononuclear cells (PBMC) and the number of mRNA copies were assessed by quantitative reverse transcriptase polymerase chain reaction (QRT-PCR).

RESULTS

MI and UA patients demonstrated significantly lower TGFbeta gene expression compared to control (2789+/-418 c/microg vs. 20262+/-2548 c/microg; p<0.001, and 3390+/-518 c/microg vs. 20262+/-2548 c/microg; p<0.001, respectively), as well as noticeably lower transcriptional activity of genes encoding its type I (3295+/-447 c/microg vs. 12859+/-1929 c/microg; p<0.001, and 3258+/-721 c/microg vs. 12859+/-1929 c/microg; p<0.01, respectively) and type II receptors (2364+/-346 c/microg vs. 19003+/-2357 c/microg; p<0.001, and 2680+/-522 c/microg vs. 19003+/-2357 c/microg; p<0.01, respectively). Also, gene expression of the type III receptor was inferior in the studied group compared to the control, although the difference was significant only for the UA group vs. control. Expressions of the studied genes did not differ between patients with MI and those with UA.

CONCLUSION

Our report shows that the decreased activity of TGFbeta in patients with ACS is at least partly due altered transcriptional activity of genes encoding both TGFbeta and its receptors, what may be responsible for the evolution of atherosclerotic lesions.

Regulatory T cell responses: potential role in the control of atherosclerosis

PURPOSE OF REVIEW

Atherosclerosis is an inflammatory disease of the arterial wall where both innate and adaptive Th1-driven immunoinflammatory responses contribute to disease development. Th2-related responses have been shown to be either protective or pathogenic. Thus, it is unclear whether immunoregulatory activity can modulate disease development.

RECENT FINDINGS

Novel subtypes of T cells, called the regulatory T cells, have been shown recently to play a critical role in the maintenance of immunological tolerance against self and non-self antigens and prevent the development of various immunoinflammatory diseases. Preliminary studies suggest a potential role for this type of regulatory T cell response in atherosclerosis.

SUMMARY

Here we present a novel view of the immunoinflammatory response in atherosclerosis where natural and/or adaptive regulatory T cell responses modulate both Th1 and Th2 pathogenic responses and play a central role in counteracting disease initiation and progression.

Kruppel-like factor 4 is a mediator of proinflammatory signaling in macrophages

Activation of macrophages is important in chronic inflammatory disease states such as atherosclerosis. Proinflammatory cytokines such as interferon-gamma (IFN-gamma), lipopolysaccharide (LPS), or tumor necrosis factor-alpha can promote macrophage activation. Conversely, anti-inflammatory factors such as transforming growth factor-beta1 (TGF-beta1) can decrease proinflammatory activation. The molecular mediators regulating the balance of these opposing effectors remain incompletely understood. Herein, we identify Kruppel-like factor 4 (KLF4) as being markedly induced in response to IFN-gamma, LPS, or tumor necrosis factor-alpha and decreased by TGF-beta1 in macrophages. Overexpression of KLF4 in J774a macrophages induced the macrophage activation marker inducible nitric-oxide synthase and inhibited the TGF-beta1 and Smad3 target gene plasminogen activator inhibitor-1 (PAI-1). Conversely, KLF4 knockdown markedly attenuated the ability of IFN-gamma, LPS, or IFN-gamma plus LPS to induce the iNOS promoter, whereas it augmented macrophage responsiveness to TGF-beta1 and Smad3 signaling. The KLF4 induction of the iNOS promoter is mediated by two KLF DNA-binding sites at -95 and -212 bp, and mutation of these sites diminished induction by IFN-gamma and LPS. We further provide evidence that KLF4 interacts with the NF-kappaB family member p65 (RelA) to cooperatively induce the iNOS promoter. In contrast, KLF4 inhibited the TGF-beta1/Smad3 induction of the PAI-1 promoter independent of KLF4 DNA binding through a novel antagonistic competition with Smad3 for the C terminus of the coactivator p300/CBP. These findings support an important role for KLF4 as a regulator of key signaling pathways that control macrophage activation.

The role of inflammation in atherothrombosis: implications for clinical practice

Inflammation plays a key role in atherothrombosis: in the development of plaques, plaque rupture and thrombus formation. Various biochemical substances have been shown to be involved in the inflammatory process, some with pro-inflammatory activity and others with anti-inflammatory activity. Increased expression of many inflammatory mediators (e.g. C-reactive protein, CD40 ligand, P-selectin and IL-6) has been shown to correlate with increased risk of atherothrombotic events. One possible strategy for primary and secondary prevention is likely to focus on minimizing the inflammatory response and tipping the balance in favour of anti-inflammatory mediators and, therefore, plaque stability.

Nicotine modulates cytokine production by Chlamydia pneumoniae infected human peripheral blood cells

Nicotine, the addictive component of cigarette smoke, has been shown to have immunomodulatory effects. This drug alters proinflammatory cytokine production by immune cells, including lymphocytes, monocytes, and macrophages. The present study focuses on the effects of nicotine on infection by Chlamydia pneumoniae (Cpn), a ubiquitous intracellular pathogen which causes acute and chronic inflammatory diseases such as pulmonary infections, and may be associated with arthritis and atherosclerosis. Previous studies in our laboratory showed that lymphocytes and macrophages are susceptible to Cpn infection. The present study aimed at investigating the effect of nicotine on TGF-beta1, IL-10, IL-12, and TNF-alpha production in Cpn-infected human peripheral blood mononuclear cells (PBMCs). Cytokine levels in the supernatant were assessed by ELISA. The results showed that Cpn infection alters the expression levels of IL-10, IL-12, and TNF-alpha in a time-dependent fashion. Nicotine treatment of the Cpn-infected cells up-regulated IL-10, but not TNF-alpha and IL-12, and also resulted in significant down-regulation of TGF-beta1 production which was marked in the Cpn-infected control cells. The combined action of nicotine and Cpn on cytokine production may have an impact in chronic inflammatory diseases.

Polycyclic aromatic hydrocarbons induce an inflammatory atherosclerotic plaque phenotype irrespective of their DNA binding properties

Although it has been demonstrated that carcinogenic environmental polycyclic aromatic hydrocarbons (PAHs) cause progression of atherosclerosis, the underlying mechanism remains unclear. In the present study, we aimed to investigate whether DNA binding events are critically involved in the progression of PAH-mediated atherogenesis. Apolipoprotein E knockout mice were orally (24 wk, once/wk) exposed to 5 mg/kg benzo[a]pyrene (B[a]P), or its nonmutagenic, noncarcinogenic structural isoform benzo[e]pyrene (B[e]P). 32P-postlabeling of lung tissue confirmed the presence of promutagenic PAH-DNA adducts in B[a]P-exposed animals, whereas in B[e]P-exposed and vehicle control animals, these adducts were undetectable. Morphometrical analysis showed that both B[a]P and B[e]P caused an increase in plaque size, whereas location or number of plaques was unaffected. Immunohistochemistry revealed no differences in oxidative DNA damage (8-OHdG) or apoptosis in the plaques. Also plasma lipoprotein levels remained unchanged after PAH-exposure. However, T lymphocytes were increased > or =2-fold in the plaques of B[a]P- and B[e]P-exposed animals. Additionally, B[a]P and to a lesser extent B[e]P exposure resulted in increased TGFbeta protein levels in the plaques, that was mainly localized in the plaque macrophages. In vitro studies using the murine macrophage like RAW264.7 cells showed that inhibition of TGFbeta resulted in decreased tumor necrosis factor (TNF) alpha release, suggesting that enhanced TGFbeta expression in the plaque macrophages contributes to the proinflammatory effects in the vessel wall. In general, this inflammatory reaction in the plaques appeared to be a local response since peripheral blood cell composition (T cells, B cells, granulocytes, and macrophages) was not changed upon PAH exposure. In conclusion, we showed that both B[a]P and B[e]P cause progression of atherosclerosis, irrespective of their DNA binding properties. Moreover, our data revealed a possible novel mechanism of PAH-mediated atherogenesis, which likely involves a TGFbeta-mediated local inflammatory reaction in the vessel wall.

Thematic review series: The immune system and atherogenesis. Cytokines affecting endothelial and smooth muscle cells in vascular disease

The cellular and extracellular matrix accumulations that comprise the lesions of atherosclerosis are driven by local release of cytokines at sites of predilection for lesion formation, and by the specific attraction and activation of cells expressing receptors for these cytokines. Although cytokines were originally characterized for their potent effects on immune and inflammatory cells, they also promote endothelial cell dysfunction and alter smooth muscle cell (SMC) phenotype and function, which can contribute to or retard vascular pathologies. This review summarizes in vivo studies that have characterized endothelial- and smooth muscle-specific effects of altering cytokine signaling in vascular disease. Although multiple reports have identified cytokines as pivotal players in endothelial and SMC responses in vascular disease, they also have highlighted the need to delineate the critical genes and specific cellular functions regulated by individual cytokine signaling pathways.

Immunomodulation to combat atherosclerosis: the potential role of immune regulatory cells

Atherosclerosis is an inflammatory disease of the arterial wall that carries an important socio-economic burden. The available data strongly suggest that both innate and adaptive immuno-inflammatory mechanisms are the major determinants of plaque complications (called instability). Therefore, most of the important advances in the comprehension of the mechanisms of atherosclerosis came from studies that aimed at the elucidation of the critical components involved in the modulation of the immuno-inflammatory response in experimental models of atherosclerosis. As the T helper (Th)1-driven immune response has been consistently shown to promote atherosclerosis, the general belief is that immunomodulation through Th2 may be suitable to halt the disease process. Here, a novel view of the immuno-inflammatory response in atherosclerosis is presented, in which the natural and/or adaptive regulatory responses modulate both Th1 and Th2 responses, and play a central role in counteracting disease initiation and progression.

A critical role for the Sp1-binding sites in the transforming growth factor-beta-mediated inhibition of lipoprotein lipase gene expression in macrophages

Increasing evidence suggests that the cytokine transforming growth factor-β (TGF-β) inhibits the development of atherosclerosis. The lipoprotein lipase (LPL) enzyme expressed by macrophages has been implicated in the pathogenesis of atherosclerosis by stimulating the uptake of lipoprotein particles. Unfortunately, the action of TGF-β on the expression of LPL in macrophages remains largely unclear. We show that TGF-β inhibits LPL gene expression at the transcriptional level. Transient transfection assays reveal that the −31/+187 sequence contains the minimal TGF-β-responsive elements. Electrophoretic mobility shift assays show that Sp1 and Sp3 interact with two regions in the −31/+187 sequence. Mutations of these Sp1/Sp3 sites abolish the TGF-β-mediated suppression whereas multimers of the sequence impart the response to a heterologous promoter. TGF-β has no effect on the binding or steady-state polypeptide levels of Sp1 and Sp3. These results, therefore, suggest a novel mechanism for the TGF-β-mediated repression of LPL gene transcription that involves regulation of the action of Sp1 and Sp3.

Inhibitory control of TGF-beta1 on the activation of Rap1, CD11b, and transendothelial migration of leukocytes

Beta2-integrins are a family of dimeric adhesion molecules expressed on leukocytes. Their capacity to bind ligand is regulated by their state of activation. CD11b, an alphaMbeta2 integrin, is implicated in a number of physiological and pathological events such as inflammation, thrombosis, or atherosclerosis. The GTPase Rap1 is essential for its activation and could therefore play a strategic role in the regulation of leukocyte functioning. Because low levels of circulating TGF-beta have been linked with severe atherosclerosis, we have assessed the role of this cytokine in the regulation of Rap1 and CD11b activation in differentiated U937 cells and in human peripheral blood monocytes. TGF-beta1 caused a significant reduction in the expression of CD11b but not in the expression of other integrins tested. More importantly, TGF-beta1 greatly reduced the capacity of PMA or chemokines to activate CD11b and Rap1, a phenomenon paralleled by a loss of the Epac transcript and a reduction in 8-pCPT-2'-O-Me-cAMP-mediated activation of Rap1. This inhibition diminished the capacity of monocytes to migrate across a monolayer of endothelial cells. The inhibitory effect of TGF-beta1 on Rap1 activity may exert a general protective influence against aberrant transendothelial migration, thereby holding inflammatory responses in check.