Local expression of inflammatory cytokines in human atherosclerotic plaques

CCR5 deletion protects against inflammation-associated mortality in dialysis patients

The CC-chemokine receptor 5 (CCR5) is a receptor for various proinflammatory chemokines, and a deletion variant of the CCR5 gene (CCR5 Delta 32) leads to deficiency of the receptor. We hypothesized that CCR5 Delta 32 modulates inflammation-driven mortality in patients with ESRD. We studied the interaction between CCR5 genotype and levels of high-sensitivity C-reactive protein (hsCRP) in 603 incident dialysis patients from the multicenter, prospective NEtherlands COoperative Study on the Adequacy of Dialysis (NECOSAD) cohort. CCR5 genotype and hsCRP levels were both available for 413 patients. During 5 yr of follow-up, 170 patients died; 87 from cardiovascular causes. Compared with the reference group of patients who had the wild-type CCR5 genotype and hsCRP <or= 10 mg/L (n = 225), those carrying the deletion allele with hsCRP <or= 10 mg/L (n = 55) had similar mortality, and those carrying the wild-type genotype with hsCRP > 10 mg/L (n = 108) had an increased risk for mortality (HR: 1.82; 95% CI: 1.29 to 2.58). However, those carrying the deletion allele with hsCRP > 10 mg/L (n = 25) had a mortality rate similar to the reference group; this seemingly protective effect of the CCR5 deletion was even more pronounced for cardiovascular mortality. We replicated these findings in an independent Swedish cohort of 302 ESRD patients. In conclusion, the CCR5 Delta 32 polymorphism attenuates the adverse effects of inflammation on overall and cardiovascular mortality in ESRD.

Macrophage inflammatory protein-1beta induced cell adhesion with increased intracellular reactive oxygen species

To investigate the role of macrophage inflammatory protein-1 beta (MIP-1beta) in the development of atherosclerosis, we designed an in vitro study to elucidate the mechanisms of monocyte-endothelium adhesion via intracellular reactive oxygen species (ROS). Angiotensin II (AngII) was used as a positive control. Furthermore, we examined the efficacy of MIP-1beta as a predictor of stroke and cardiovascular events in hypertensive patients. MIP-1beta or AngII stimulation significantly increased ROS production and adhesion of THP-1 cells to inflamed human umbilical vein endothelial cells. Cell adhesion and ROS production were inhibited in stimulated THP-1 cells by: inhibition of ROS signaling with N-acetylcysteine, diphenyleneiodonium, or PEG-Catalase; inhibition of PI3Kgamma with siRNA or LY294002; and by Rac1 siRNA. The MIP-1 beta or AngII stimulation did not increase surface expression of integrins, very late antigen 4 (VLA-4) and lymphocyte function-associated antigen 1 (LFA-1), but cell adhesion was reduced by using an antiVLA-4 or an antiLFA-1 antibody. Moreover, cell adhesion and ROS production stimulated with MIP-1beta or AngII were completely inhibited by fluvastatin. In our clinical study, patients with the highest quartile of MIP-1beta showed a higher risk of stroke and cardiovascular events by a Cox proportional-hazards model. In conclusion, MIP-1beta directly induced cell adhesion to endothelial cells through oxidative stress via PI3k-Rac1 cascades. Serum MIP-1beta level might be a useful predictor for cerebro-cardiovascular events in hypertensive patients.

CONDENSED ABSTRACT

We designed an in vitro investigation to examine the role of MIP-1beta on the development of atherosclerosis, including cell adhesion involving CAMs and ROS production, compared with angiotensin II. Furthermore, we investigated the prognostic impact of MIP-1beta on stroke and cardiovascular events in hypertensive patients in a small cohort study.

Lentiviral gene transfer to reduce atherosclerosis progression by long-term CC-chemokine inhibition

CC-chemokines are important mediators in the pathogenesis of atherosclerosis. Atherosclerosis progression is reduced by high-level, short-term inhibition of CC-chemokine activity, for example by adenoviral gene transfer. However, atherosclerosis is a chronic condition where short-term effects, while demonstrating proof-of-principle, are unlikely to provide maximum therapeutic benefit. Accordingly, we generated a recombinant lentivirus, lenti35K, encoding the broad-spectrum CC chemokine inhibitor, 35K, derived from the vaccinia virus. To investigate the effects of prolonged broad-spectrum chemokine inhibition on atherosclerosis, lenti35K, or lentiGFP or PBS were delivered to 6-week-old ApoE knockout (ApoE-KO) mice by hydrodynamic injection. Sustained lentiviral transduction and transgene expression were demonstrated by 35K mRNA and viral DNA in liver tissue, and recombinant 35K protein circulating in the plasma, 3 months after gene transfer. Plasma from lenti35K animals had reduced chemokine activity compared with plasma from lentiGFP or PBS-treated animals. Histologic analysis of aortic sinus sections revealed that atherosclerotic plaque area in lenti35K mice was significantly reduced compared with both lentiGFP and PBS controls. Furthermore, plaque macrophage content was substantially reduced in lenti35K mice. Lentiviral 35K gene transfer is a promising experimental strategy to reduce atherosclerosis progression, and demonstrates the potential of long-term CC-chemokine inhibition as a potential therapeutic target in atherosclerosis.

Experimental models investigating the inflammatory basis of atherosclerosis

Inflammation is considered an important aspect in the development of atherosclerosis. Genetic manipulations of animal models susceptible to atherosclerosis have unraveled the contribution of various inflammatory pathways implicated in the development of atherosclerosis. These inflammatory pathways not only lead to the recruitment and entry of inflammatory cells into the arterial wall, they also modify the morphology and composition of atherosclerotic plaques. Certain inflammatory pathways, such as P-selectin, intercellular adhesion molecule-1, and vascular cell adhesion molecule-1, appear to play an important role in lesion initiation, whereas others, such as interleukin-10 and CD40/CD40 ligand, seem to contribute to lesion progression and morphologic changes. An understanding of these pathways will allow the development of new strategies in the management of atherosclerosis. This review provides a roadmap for better utilization of these models in atherosclerosis research.

Human C-peptide antagonises high glucose-induced endothelial dysfunction through the nuclear factor-kappaB pathway

AIMS/HYPOTHESIS

Endothelial dysfunction in diabetes is predominantly caused by hyperglycaemia leading to vascular complications through overproduction of oxidative stress and activation of the transcription factor nuclear factor-kappaB (NF-kappaB). Many studies have suggested that decreased circulating levels of C-peptide may play a role in diabetic vascular dysfunction. To date, the possible effects of C-peptide on endothelial cells and intracellular signalling pathways are largely unknown. We therefore investigated the effect of C-peptide on several biochemical markers of endothelial dysfunction in vitro. To gain insights into potential intracellular signalling pathways affected by C-peptide, we tested NF-kappaB activation, since it is known that inflammation, secondary to oxidative stress, is a key component of vascular complications and NF-kappaB is a redox-dependent transcription factor.

METHODS

Human aortic endothelial cells (HAEC) were exposed to 25 mmol/l glucose in the presence of C-peptide (0.5 nmol/l) for 24 h and tested for expression of the gene encoding vascular cell adhesion molecule-1 (VCAM-1) by RT-PCR and flow cytometry. Secretion of IL-8 and monocyte chemoattractant protein-1 (MCP-1) was measured by ELISA. NF-kappaB activation was analysed by immunoblotting and ELISA.

RESULTS

Physiological concentrations of C-peptide affect high glucose-induced endothelial dysfunction by: (1) decreasing VCAM-1 expression and U-937 cell adherence to HAEC; (2) reducing secretion of IL-8 and MCP-1; and (3) suppressing NF-kappaB activation.

CONCLUSIONS/INTERPRETATION

During hyperglycaemia, C-peptide directly affects VCAM-1 expression and both MCP-1 and IL-8 HAEC secretion by reducing NF-kappaB activation. These effects suggest a physiological anti-inflammatory (and potentially anti-atherogenic) activity of C-peptide on endothelial cells.

Nox5 mediates PDGF-induced proliferation in human aortic smooth muscle cells

The proliferation of vascular smooth muscle cells is important in the pathogenesis of many vascular diseases. Reactive oxygen species (ROS) produced by NADPH oxidases in smooth muscle cells have been shown to participate in signaling cascades regulating proliferation induced by platelet-derived growth factor (PDGF), a powerful smooth muscle mitogen. We sought to determine the role of Nox5 in the regulation of PDGF-stimulated human aortic smooth muscle cell (HASMC) proliferation. Cultured HASMC were found to express four isoforms of Nox5. When HASMC stimulated with PDGF were pretreated with N-acetyl cysteine (NAC), proliferation was significantly reduced. Proliferation induced by PDGF was also heavily dependent on JAK/STAT activation, as the JAK inhibitor, AG490, was able to completely abolish PDGF-stimulated HASMC growth. Specific knockdown of Nox5 with a siRNA strategy reduced PDGF-induced HASMC ROS production and proliferation. Additionally, siRNA to Nox5 inhibited PDGF-stimulated JAK2 and STAT3 phosphorylation. ROS produced by Nox5 play an important role in PDGF-induced JAK/STAT activation and HASMC proliferation.

Glycated LDL increases monocyte CC chemokine receptor 2 expression and monocyte chemoattractant protein-1-mediated chemotaxis

BACKGROUND

Previous reports have suggested that levels of advanced glycation end product-modified LDL (AGE-LDL) increase in patients with diabetes due to elevated plasma glucose. However, understanding of the mechanisms by which AGE-LDL may accelerate atherogenesis remains incomplete.

METHODS AND RESULTS

Microarray and reverse transcription real-time PCR (RT-PCR) analyses revealed that AGE-LDL significantly increased levels of CC chemokine receptor 2 (CCR2) mRNA in human macrophages compared with LDL, an effect accompanied by increased levels of CCR2 protein. Flow cytometry also showed that AGE-LDL increases CCR2 expression on the cell surface following stimulation (48h) (P<0.05). This effect appeared to depend on the receptor for AGE (RAGE), since an anti-RAGE antibody significantly blocked increased CCR2 mRNA. Functional studies demonstrated that exposure of THP-1 monocytoid cells to AGE-LDL increases chemotaxis mediated by monocyte chemoattractant protein-1 (MCP-1) up to 3-fold compared to LDL treatment (P<0.05).

CONCLUSIONS

These data show that AGE-LDL can increase CCR2 expression in macrophages and stimulate the chemotactic response elicited by MCP-1. This novel mechanism may contribute to accelerated atherogenesis in diabetic patients.

Common CCR5-del32 frameshift mutation associated with serum levels of inflammatory markers and cardiovascular disease risk in the Bruneck population

BACKGROUND AND PURPOSE

Atherosclerosis is a progressive inflammatory disease and can develop in large arteries such as carotid and femoral arteries or medium-sized muscular arteries of the heart. Previous predominantly experimental studies suggested an important role of chemokines in the development of atherosclerosis. The main aim of this study was to examine potential effect of the CCR5-del32 mutation on systemic inflammation, intima-media thickness in carotid and femoral arteries, and on the indices of cardiovascular disease.

METHODS

In the present study, we have examined the association of a common functional 32-bp frameshift deletion mutation in a chemokine receptor (CCR5) in relation to inflammation and atherosclerosis. CCR5 is a G protein-coupled receptor involved in inflammatory response and regulation of leukocytes activation and migration. Genetic screening of this mutation was carried out on a well-known and previously described cohort of Bruneck (n=826) using polymerase chain reaction.

RESULTS

Screening was successful in 810 subjects of whom 7 were homozygous, 102 were heterozygous, and 701 were normal. The mutation was associated with significantly lower levels of C-reactive protein in a dose-dependent manner. Moreover, CCR5-del32 was associated with a significantly lower carotid intima-media thickness in the common carotid artery (del32/del32, 837+/-8 microm; wt/del32, 909+/-21 microm; wt/wt, 958+/-8 microm; P=0.007 after multivariable adjustment). Furthermore, incident cardiovascular disease (1995 to 2005) was markedly reduced in del32 homozygotes and heterozygotes subjects compared with wild-type homozygotes (del32/del32=0%, wt/del32=7.8%, wt/wt=14.8%, P=0.020). Findings equally applied to coronary artery and cerebrovascular disease.

CONCLUSIONS

The chemokine receptor CCR5-del32 frameshift mutation is associated with low levels of C-reactive protein, decreased intima-media thickness, and cardiovascular disease risk. These findings are consistent with the hypothesis that the chemokine receptor CCR5 is involved in the mediation of low-grade systemic inflammation and may play a role in human atherosclerosis and cardiovascular disease.

Tumor necrosis factor-alpha (TNF-alpha) induces integrin CD11b/CD18 (Mac-1) up-regulation and migration to the CC chemokine CCL3 (MIP-1alpha) on human neutrophils through defined signalling pathways

Strong evidence suggests that neutrophils may play an active role in acute and chronic inflammatory disorders, such as rheumatoid arthritis and atherosclerosis. Given the role of pro-inflammatory cytokine TNF-alpha in these inflammatory processes, we planned the present study to investigate the effect of short term incubation with TNF-alpha on neutrophil migration to CCL3, a chemokine produced in inflammatory sites and normally devoid of neutrophil chemotactic properties. We found that TNF-alpha primed neutrophils for migration to CCL3 via CCR5. TNF-alpha-induced migration was a consequence of the TNF-alpha-induced up-regulation of integrin CD11b/CD18 (Mac-1) on neutrophil surface. Furthermore, TNF-alpha activity was found to be strictly dependent on the activation of ERK 1/2 p44, cooperating with the intracellular pathways involving Src kinases, PI3K/Akt, p38 MAPK, well known as activated in response to classical chemoattractants (CXCL8) or priming agents (GM-CSF). On the contrary, the effect of TNF-alpha on neutrophil migration to CCL3 was not dependent on JNK 1/2. In conclusion, the present report shows that TNF-alpha unveils a previously unknown capacity of neutrophils to migrate to CCL3 through the intervention of Mac-1. TNF-alpha regulates Mac-1 up-regulation through signalling pathways, involving various kinases, but not JNK 1/2. Although highly speculative, ERK 1/2 p44 may represent a selective target for the pharmacologic manipulation of neutrophil-mediated adverse activities in TNF-alpha-mediated inflammatory states.

In vivo validation of signaling pathways regulating human monocyte chemotaxis

Identification of novel signal transduction pathways regulating monocyte chemotaxis can indicate unique targets for preventive therapies for treatment of chronic inflammatory diseases. To aid in this endeavor we report conditions for optimal transfection of primary human monocytes coupled with a new model system for assessing their chemotactic activity in vivo. This method can be used as a tool to identify the relevant signal transduction pathways regulating human monocyte chemotaxis to MCP-1 in the complex in vivo environment that were previously identified to regulate chemotaxis in vitro. MCP-1-dependent chemotaxis of monocytes is studied in an adoptive transfer model where human monocytes transfected with mutant cDNAs are transferred to mice followed by initiation of peritonitis. Harvesting peritoneal cells at 24 h diminishes the contribution of immunologic responses to the cross-species transfer. Validation of relevant regulatory molecules in vivo is critical for understanding the most relevant therapeutic targets for drug development.

Cardiovascular roles of nitric oxide: a review of insights from nitric oxide synthase gene disrupted mice

Nitric oxide (NO) is a gaseous molecule that plays many key roles in the cardiovascular system. Each of the enzymes that generate NO--neuronal, inducible and endothelial NO synthase-has been genetically disrupted in mice. This review discusses the cardiovascular phenotypes of each of the NO synthase (NOS) gene knockout mice, and the insights gained into the roles of NO in the cardiovascular system. Mice lacking the endothelial isoform are hypertensive, have endothelial dysfunction and show a more severe outcome in response to vascular injury, to stroke and cerebral ischaemia, and to diet-induced atherosclerosis. Mice lacking the neuronal isoform show a less severe outcome in response to stroke and cerebral ischaemia but have increased diet-induced atherosclerosis. Mice lacking the inducible isoform show reduced hypotension to septic shock. Together, NOS gene knockout mice have been useful tools that complement our other approaches to studying the multiple roles of NO in the cardiovascular system.

Novel uses for anti-platelet agents as anti-inflammatory drugs

An alteration in the character and function of platelets is manifested in patients with inflammatory diseases, and these alterations have been dissociated from the well-characterized involvement of platelets in thrombosis and haemostasis. Recent evidence reveals platelet activation is sometimes critical in the development of inflammation. The mechanisms by which platelets participate in inflammation are diverse, and offer numerous opportunities for future drug intervention. There is now acceptance that platelets act as innate inflammatory cells in immune responses, with roles as sentinel cells undergoing surveillance, responding to microbial invasion, orchestrating leukocyte recruitment, and migrating through tissue, causing damage and influencing repair processes in chronic disease. Some of these processes are targeted by drugs that are being developed to target platelet participation in atherosclerosis. The actions of platelets therefore influence the pathogenesis of diverse inflammatory diseases in various body compartments, encompassing parasitic and bacterial infection, allergic inflammation (especially asthma and rhinitis), and non-atopic inflammatory conditions, for example, chronic obstructive pulmonary disease (COPD), rheumatoid arthritis (RA), inflammatory bowel disease (IBD) and atherosclerosis. This review will first discuss the evidence for platelet activation in these various inflammatory diseases, and secondly discuss the mechanisms by which this pathogenesis occurs and the various anti-platelet agents which have been developed to combat platelet activation in atherosclerosis and their potential future use for the treatment of other inflammatory diseases.

The peptide analogue of MCP-1 65-76 sequence is an inhibitor of inflammation

Inflammation plays an important role in vessel wall remodeling that occurs in atherosclerosis and postangioplasty restenosis. Monocytic chemoattractant protein-1 (MCP-1) is one of the main attractors of monocytes and some lymphocyte subsets to the damaged vessel. The aims of the study were to confirm MCP-1 participation in the development of acute coronary syndromes, to produce the potential MCP-1 peptide antagonist, and to investigate its effects in vitro and in vivo in different animal models of inflammation. MCP-1 plasma concentration was measured by ELISA (enzyme-linked immunosorbent assay). Chemokine receptor expression by cells isolated from human atherosclerotic lesions was assessed by direct immunofluorescence and flow cytometry. MCP-1 sequence was analyzed with Peptide Companion software and peptides were synthesized using Fmoc strategy. The peptide resistance to degradation was checked by 1H-NMR spectroscopy. The peptide effect on MCP-1-stimulated cell migration was studied in Boyden chamber and in mouse air pouch model, and its influence on lipopolysaccharide (LPS)-induced inflammatory cell recruitment was investigated in models of subcutaneous inflammation in rats and nonhuman primates. We revealed nearly a 2-fold increase of MCP-1 plasma level in patients with unstable angina in comparison with patients with stable angina. The atherosclerotic plaque specimens obtained from patients with unstable angina contained a significant amount of chemokine receptor-expressing leukocytes. Peptide from MCP-1 C-terminal 65-76 sequence (peptide X) inhibited MCP-1-stimulated monocytic cell migration in vitro and in vivo. Peptide X labeled with 99mTc accumulated specifically at sites of inflammation in rats. Peptide X administrated i.m and i.v. suppressed monocyte and granulocyte recruitment induced by subcutaneous injection of LPS in the back of rats and non-human primates. Our data demonstrate that MCP-1-mediated chemotaxis could be responsible for atherosclerotic plaque "destabilization". Peptide X may represent a new class of anti-inflammatory drugs to be used in cardiology.

Monocyte chemoattractant protein-1 and atherosclerosis: is there room for an additional biomarker?

Atherosclerosis is an inflammatory disease in which several chemokines are implicated. The roles of these molecules extend from the recruitment of circulating inflammatory cells to the activation of inflammatory and pro-thrombotic cascades, which ultimately leads to an atherosclerosis-related event. One of the most studied chemokines is monocyte chemoattractant protein-1 (CCL2), which has been strongly linked to atherosclerosis in both animal and human studies. The higher the expression of either the CCL2 gene or its receptor CCR-2, the higher the likelihood of developing atherosclerosis in genetically-modified animals. Conversely, the deletion of either CCL2 or its receptor is followed by a significant reduction in the development of atherosclerotic plaques. Studies in humans yield controversial results. Most of these studies linked the plasma CCL2 concentration to the occurrence of atherosclerosis or related events; however, this relationship does not seem to be independent of the classical, known risk factors. Currently, there are no suitable analytical tools to reach strong conclusions with respect to the value of plasma CCL2 concentration as a biomarker of atherosclerosis, but experimental evidence suggests that the CCL2/CCR2 pathway should be further explored as a diagnostic, prognostic and therapeutic target.

CC chemokine receptor 5 influences late-stage atherosclerosis

Members of the chemokine system, play a central role in inflammatory processes that underlie the pathogenesis of atherosclerosis and possibly, aortic valve sclerosis. Here we show that genetic inactivation of CC chemokine receptor 5 (CCR5) in the atherosclerosis-prone Apoe-/- mice (Apoe-/- Ccr5-/-) fed a normal chow or a high-fat diet (HFD) are protected against advanced atherosclerosis as well as age-associated aortic valve thickening (AAAVT)--a murine correlate of aortic valve sclerosis. Notably, human sclerotic valves contained CCR5+ cells. We confirm that Apoe-/- Ccr5-/- mice does not influence early-atherosclerotic stage. Adoptive transfer studies showed that the atheroprotective effect of CCR5 inactivation resided in the bone marrow compartment, but was not dependent on T-cells. The CCR5-null state was associated with phenotypes postulated to be atheroprotective such as reduced macrophage accumulation in the plaque, and lower circulating levels of IL-6 and MCP-5. The lack of CCR5 expression in Apoe-/- mice was also associated with higher numbers of endothelial progenitor cells (EPCs)--another postulated athero-protective factor. Compared with controls, carriers of a polymorphism in the Ccr5 gene that leads to the lack of CCR5 in the cell surface had an increased mean percentage of EPCs, but this difference did not reach statistical significance. Collectively, these findings underscore a critical role of CCR5 in age-associated cardiovascular diseases, and highlight that the effects of the chemokine system can be temporally constrained to distinct stages of these disease processes.

Monocyte chemoattractant protein-1 or macrophage inflammatory protein-1alpha deficiency does not affect angiotensin II-induced intimal hyperplasia in carotid artery ligation model

BACKGROUND

Angiotensin II (Ang II) promotes atherosclerotic vascular diseases, in which proinflammatory and proliferative effects play a major pathogenic role. Ang II up-regulates chemokines, such as monocyte chemoattractant protein (MCP)-1 and macrophage inflammatory protein (MIP)-1alpha, which are important pro-inflammatory factors mediating infiltration of inflammatory cells into atherosclerotic lesion. The aim of the present study was to determine whether the presence of MCP-1 or MIP-1alpha is essential in Ang II-induced intimal hyperplasia in the carotid artery ligation model.

METHODS

Six-month-old male C57BL/6-, MCP-1-, or MIP-1alpha-deficient mice underwent ligation of the common left carotid artery and were randomly assigned to receive either vehicle or Ang II (1.4 mg kg(-1) day(-1)) via a subcutaneously implanted osmotic infusion pump (model 2004, Alzet) for 4 weeks.

RESULTS

Ang II not only increased MCP-1 and MIP-1alpha production but also enhanced neo-intimal formation, media thickness, and adventitia development in the ligated carotid arteries in C57BL/6 mice. However, MCP-1 or MIP-1alpha deficiency failed to affect intimal hyperplasia in vascular remodeling.

CONCLUSION

These results indicate that MCP-1 or MIP-1alpha may not be essential in mediating the proliferative effects of Ang II, a major pathological changes in intimal hyperplasia in the carotid artery ligation model.

Ccr5 But Not Ccr1 Deficiency Reduces Development of Diet-Induced Atherosclerosis in Mice

OBJECTIVE

Chemokines and their receptors are crucially involved in the development of atherosclerotic lesions by directing monocyte and T cell recruitment. The CC-chemokine receptors 1 (CCR1) and 5 (CCR5) expressed on these cells bind chemokines implicated in atherosclerosis, namely CCL5/RANTES. Although general blockade of CCL5 receptors reduces atherosclerosis, specific roles of CCR1 and CCR5 have not been unequivocally determined.

METHODS AND RESULTS

We provide two independent lines of investigation to dissect the effects of Ccr1 and Ccr5 deletion in apolipoprotein E-deficient (ApoE-/-) mice in a collaboration between Aachen/Germany and Geneva/Switzerland. Different strains of ApoE-/- Ccr5-/- mice, ApoE-/- Ccr1-/- mice or respective littermates, were fed a high-fat diet for 10 to 12 weeks. Plaque areas were quantified in the aortic roots and thoracoabdominal aortas. Concordantly, both laboratories found that lesion formation was reduced in ApoE-/- Ccr5-/- mice. Plaque quality and immune cells were assessed by immunohistochemistry or mRNA analysis. Whereas lesional macrophage content, aortic CD4, and Th1-related Tim3 expression were reduced, smooth muscle cell (SMC) content and expression of interleukin-10 in plaques, lesional SMCs, and splenocytes were elevated. Protection against lesion formation by Ccr5 deficiency was sustained over 22 weeks of high-fat diet or over 26 weeks of chow diet. Conversely, plaque area, T cell, and interferon-gamma content were increased in ApoE-/- Ccr1-/- mice.

CONCLUSIONS

Genetic deletion of Ccr5 but not Ccr1 in ApoE-/- mice protects from diet-induced atherosclerosis, associated with a more stable plaque phenotype, reduced mononuclear cell infiltration, Th1-type immune responses, and increased interleukin-10 expression. This corroborates CCR5 as a promising therapeutic target.

Statins reduce macrophage inflammatory protein-1alpha expression in human activated monocytes

1. 3-Hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitors (statins) exhibit a wide variety of anti-atherogenic effects that may be independent of their property to lower plasma cholesterol. 2. In order to systematically investigate these effects at a cellular level, we investigated gene expression in phorbol myristate acetate (PMA)-activated and non-activated human THP-1 monocytes in response to statins using cDNA arrays. 3. Of 588 genes tested, 26 were differentially expressed in the presence of statins. A marked reduction was found for the chemokine macrophage inflammatory protein-1alpha (MIP-1alpha). The decrease in MIP-1alpha mRNA expression after incubation with statins was confirmed by quantitative reverse transcription-polymerase chain reaction in THP-1 monocytes and human freshly isolated monocytes. Macrophage inflammatory protein-1alpha protein in THP-1 monocytes was reduced from 377 to 299 and 305 pg/mL by 0.1 micro mol/L simvastatin and 0.01 micro mol/L cerivastatin, respectively. The reduction in MIP-1alpha expression by statins was due, at least in part, to transcriptional inhibition of MIP-1alpha promoter activity. 4. The CC receptor ligand MIP-1alpha is a chemokine that has been implicated in atherosclerotic lesion formation. The present findings suggest that statin-mediated immunomodulation by inhibiting MIP-1alpha could contribute to the beneficial effects of statin therapy independent of lowering plasma cholesterol.

Roles of transglutaminases in cardiac and vascular diseases

All transglutaminases share the common enzymatic activity of transamidation, or the cross-linking of glutamine and lysine residues to form N epsilon (gamma-glutamyl) lysyl isopeptide bonds. The plasma proenzyme factor XIII is responsible for stabilizing the fibrin clot against physical and fibrinolytic disruption. Another member of the transglutaminase family, tissue transglutaminase or TG2 is abundantly expressed in cardiomyocytes, vascular cells and macrophages. The transglutaminases have a variety of functions independent of their transamidating activity. For example, TG2 binds and hydrolyzes GTP, thereby fostering signal transduction by several G protein coupled receptors. Accumulating evidence points to novel roles for factor XIII and TG2 in cardiovascular biology including: (a) modulating platelet activity, (b) regulating glucose control, (c) contributing to the development of hypertension, (d) influencing the progression of atherosclerosis, (e) regulating vascular permeability and angiogenesis (f) and contributing to myocardial signaling, contractile activity and ischemia/reperfusion injury. In this review, we summarize the cardiovascular biology of two members of the family of transglutaminases, Factor XIII and TG2.

Impaired renal function and duration of dialysis therapy are associated with oxidative stress and proatherogenic cytokine levels in patients with end-stage renal disease

OBJECTIVES

The present study was undertaken to clarify the role of the impaired renal function and the dialysis therapy on plasma levels of proatherogenic cytokines and Cu/Zn superoxide dismutase (Cu/Zn SOD)--as a marker of oxidative stress (SOX) in uraemia.

DESIGN AND METHODS

We have measured the levels of Cu/Zn SOD, monocyte chemoattractant protein-1 (MCP-1) macrophage inflammatory proteins (MIP-1alpha, MIP-1beta) and vascular endothelial growth factor (VEGF) in the plasma of predialysis (CRF) (n=42), on maintenance hemodialysis (HD) (n=25) or peritoneal dialysis (PD) (n=45) patients and in the healthy volunteers (n=20).

RESULTS

The increase in Cu/Zn SOD levels was in PD and HD patients compared to controls (215.56+/-125.18 and 356.28+/-122.57 versus 53.53+/-23.65 ng/ml, respectively). In plasma of the CRF, PD and HD subjects we have also observed the significant increase in the levels of MIP-1beta: [31.5 (2-149), 33.0 (1-203) and 76.0 (9-345), respectively]; MCP-1 (616.50+/-240.15, 943.64+/-348.99 and 968.50+/-355.85, respectively) and VEGF (387.93+/-184.63, 371.56+/-125.18 and 645.56+/-136.30, respectively) compared to healthy people. In the predialysis group, creatinine clearance correlated with Cu/Zn SOD and cytokine levels. Moreover, the cytokine levels were also associated with age. In dialysis patients, the correlations were between duration of dialysis treatment and both Cu/Zn SOD and cytokine levels. There was also a direct relationship between Cu/Zn SOD and both MIP-1beta and VEGF levels.

CONCLUSIONS

This study has shown that impaired renal function, age and duration of dialysis treatment are associated with increased oxidative stress and proatherogenic cytokine levels in uremic patients.

Simvastatin modulates chemokine and chemokine receptor expression by geranylgeranyl isoprenoid pathway in human endothelial cells and macrophages

OBJECTIVE

Atherosclerosis is a chronic immuno-inflammatory disease involving the recruitment of monocytes and T lymphocytes to the vascular wall of arteries. Chemokines and their receptors, known to induce leukocyte migration, have recently been implicated in atherogenesis. Recent in vitro and in vivo studies have suggested that statins (3-hydroxy-3-methylglutaryl coenzyme A (HMG CoA) reductase inhibitors) have anti-inflammatory properties beyond their lipid-lowering effects. Thus, the aim of the present study was to investigate whether simvastatin reduces the expression of chemokines and chemokine receptors in two major cell types implicated in atherogenesis and to test isoprenoid intermediates involved in their regulation.

METHODS AND RESULTS

We performed in vitro experiments on human vascular endothelial cells and human primary macrophages. First, we have shown by ELISA that 1 microM simvastatin significantly reduced MCP-1 in endothelial cells (ECs) and macrophages stimulated with TNF-alpha or IFN-gamma, respectively. Messenger RNA analysis revealed that expression of the chemokines MCP-1, MIP-1alpha and MIP-1beta, as well as the chemokine receptors CCR1, CCR2, CCR4 and CCR5, was decreased by simvastatin, both in ECs and macrophages. Furthermore, the statin effects were reversed by mevalonate and mimicked by the geranylgeranyl transferase inhibitor (GGTI), whereas the farnesyl transeferase inhibitor (FTI) had no effect. These results suggests that statins act via inhibition of the geranylgeranylation of proteins.

CONCLUSIONS

Our results demonstrate that statins reduce chemokine and chemokine receptor expressions in human ECs and macrophages via inhibition of the geranylgeranylpyrophosphate pathway. Thus, our data provide further evidence that statins have anti-inflammatory properties beyond their lipid-lowering effects. These findings highlight specific novel therapeutic targets for cardiovascular diseases to reduce inflammation mediated by chemokines and their receptors.

Long-term erythropoietin therapy decreases CC-chemokine levels and intima-media thickness in hemodialyzed patients

BACKGROUND

CC-chemokines are now widely accepted in the recruitment of leukocytes from the blood compartment into tissues, and their role in the progression of atherosclerosis has been documented. Recombinant human erythropoietin (EPO) has become widely used to treat anemic HD patients. However, little is known about the effect of EPO on the plasma CC-chemokine levels and intima-media thickness (IMT) in HD patients.

METHODS

Assessment of CC-chemokines: monocyte chemoattractant protein-1 (MCP-1), macrophage inflammatory proteins (MIP-1alpha, MIP-1beta), regulated upon activation, normal T cell expressed and secreted (RANTES) and IMT were performed in 26 stable HD patients and 15 healthy controls. The patients were divided into 3 groups: group I (n = 8, without EPO), group II (n = 9, EPO at a mean dose of 76 +/- 48 U/kg/week for more than 4 months), and group III (n = 9, EPO at a mean dose of 110.5 +/- 21 U/kg/week for more than 12 months), none of them on iron therapy.

RESULTS

MCP-1, MIP-1alpha, MIP-1beta and IMT values were significantly higher, whereas RANTES were significantly lower in HD patients without EPO therapy than those in healthy controls. CC-chemokine levels were found to be significantly lower in patients administered EPO when compared to subjects without EPO. In the patients treated with EPO for more than 12 months IMT values were significantly decreased compared to patients not receiving this hormone.

CONCLUSION

These results suggest that long-term EPO therapy decreased CC-chemokine and IMT values in patients undergoing regular HD in the absence of concomitant iron supplementation.

Inflammation but not oxidative stress is associated with beta-chemokine levels and prevalence of cardiovascular disease in uraemic patients

Inflammation and oxidative stress (SOX) have been reported in patients with chronic renal failure (CRF), but their influence on beta-chemokines levels and cardiovascular disease (CVD) prevalence remains unknown. We assessed beta-chemokines, SOX markers and high sensitivity C-reactive protein (hs CRP) as a marker of inflammation in 40 uraemic patients, both with as well as without CVD and 20 controls. Compared with the controls, the patients with CVD showed a significant increase in plasma concentrations of monocyte chemoattractant protein-1 (MCP-1), total peroxide (both p<0.05), macrophage inflammatory protein 1beta (MIP-1beta) and hs CRP (both p<0.01). The values of MCP-1 and hs CRP were more elevated in patients with CVD than without CVD (p<0.01 and p<0.05; respectively). Both subgroup of CRF patients were lower of regulated upon activation, normal T cell expressed and secreted (RANTES) levels than in the controls (both p<0.001). The positive relationships were between hs CRP and presence of CVD, MIP-1beta (both p<0.01) and MCP-1 levels (p<0.05). SOX markers did not show any significant correlation with beta-chemokines, hs CRP and presence of CVD. We documented that increased inflammation but not SOX were associated with significant elevation in plasma beta-chemokines levels and CVD prevalence in CRF patients not requiring dialysis.

Chemokines: inflammatory mediators of atherosclerosis

Atherosclerosis as the underlying mechanisms of myocardial infarction, stroke and peripheral artery disease remains the major cause of morbidity and mortality in developed countries. Recent developments in vascular biology have indicated that atherosclerosis can be best characterized as a chronic inflammatory disease of the vessel wall that promotes lesion development and progression. Chemokines regulate and control these processes by orchestrating adhesive interactions of circulating blood cells with the arterial wall and their subsequent extravasation. Exhibiting a high degree of specialization and cooperation, different chemokines mediate distinct steps during the atherogenic recruitment of monocytes and T cells. This diversity of chemokine expression and function might lead to the identification of selective therapeutic targets for the prevention and treatment of atherosclerosis.

Sequential patterns of chemokine- and chemokine receptor-synthesis following vessel wall injury in porcine coronary arteries

Inflammation plays a central role in vascular repair, and spreads into perivascular tissue (PVT) following angioplasty. Chemokines (CK) and chemokine receptors (CKR) are key determinants of inflammatory chemotaxis. We sought to assess the arterial and perivascular expression of the CK CCL2 and CXCL2, and the CKR CCR2, CCR5, and CXCR4 in balloon-injured porcine coronary arteries. Vascular cells that express specific CK and CKR mRNA during post-angioplasty time course were detected by in situ hybridization (ISH), and expression was quantified by real time RT-PCR in PVT. CCL2 was maximal in PVT from 2 to 24h post injury, coincident with local macrophage-activation. Expression was upregulated in media and adventitia from 24h to 3 days, and in neointima at 7 days. CXCL2 was detected in media at 2 and 4h, and also in some neointimal cells. CCR2 and CCR5 were maximal in PVT at 24h and 3 days, respectively. Expression shifted to media and adventitia at 2 and 3 days, and to neointima and adventitia at 7 days, and was low at 14 days. CXCR4 was low in PVT, but was upregulated in media and adventitia at 2 and 3 days, as well as in neointima and adventitia at 7 days. In conclusion, PVT is the primary source of inflammatory CK and CKR early post-angioplasty. Specific sequential patterns of CK- and CKR-synthesis are identified that may regulate phase-specific chemotaxis by spatio-temporally differential expression during coronary response to injury.

Angiotensin II-induced mononuclear leukocyte interactions with arteriolar and venular endothelium are mediated by the release of different CC chemokines

Angiotensin II (Ang-II) is associated with atherogenesis and arterial subendothelial mononuclear leukocyte infiltration. We have demonstrated that Ang-II causes the initial attachment of mononuclear cells to the arteriolar endothelium. We now report on the contribution of CC chemokines to this response. Intraperitoneal administration of 1 nM Ang-II induced MCP-1, RANTES, and MIP-1alpha generation, maximal at 4 h, followed by mononuclear leukocyte recruitment at 8 and 24 h. Using intravital microscopy within the rat mesenteric microcirculation 4 h after exposure to 1 nM Ang-II, arteriolar mononuclear cell adhesion was 80-90% inhibited by pretreatment with Met-RANTES, a CCR1 and CCR5 antagonist, or an anti-MCP-1 antiserum, without affecting the increased endothelial expression of P-selectin and VCAM-1. Conversely, leukocyte interactions with the venular endothelium, although inhibited by Met-RANTES, were little affected by the anti-MCP-1. Using rat whole blood in vitro, Ang-II (100 nM) induced the expression of monocyte CD11b that was inhibited by Met-RANTES but not by anti-MCP-1. Stimulation of human endothelial cells (human umbilical arterial endothelial cells and HUVECs) with 1-1000 nM Ang-II, predominantly acting at its AT(1) receptor, induced the release of MCP-1 within 1 h, RANTES within 4 h, and MCP-3 within 24 h. Eotaxin-3, a natural CCR2 antagonist, was released within 1 h and may delay mononuclear cell responses to MCP-1. Therefore, Ang-II-induced mononuclear leukocyte recruitment at arterioles and venules is mediated by the production of different CC chemokines. Thus, Ang-II may be a key molecule in the initial attachment of mononuclear cells to the arterial endothelium in cardiovascular disease states where this event is a characteristic feature.

Cytokine polymorphisms associated with carotid intima-media thickness in stroke patients

BACKGROUND AND PURPOSE

Carotid intima-media thickness (IMT) reflects generalized atherosclerosis and is predictive of future vascular events. Evidence exists that carotid IMT is heritable, and genetic studies can provide clues in the pathogenesis of atherosclerosis.

METHODS

We recruited 470 white ischemic stroke patients, measured common carotid artery (CCA) IMT, and analyzed 54 polymorphisms with suspected roles in atherosclerosis.

RESULTS

Among the polymorphisms tested, the angiotensin-converting enzyme insertion/deletion, osteopontin (OPN) T-443C, monocyte chemoattractant protein-1 (MCP-1) G-927C, and MCP-1 A-2578G polymorphisms were associated with CCA-IMT in age-gender-adjusted analysis. In multivariate analysis, the association between the OPN and MCP-1 polymorphisms remained significant. The OPN-443C allele was associated with increased IMT in the dominant model (0.053 mm for the TC and CC genotypes; P=0.001). The MCP-1-927C allele was associated with increased IMT in the additive model (0.040 mm for each C allele; P=0.001), and the MCP-1-2578 G allele was associated with decreased IMT in the recessive model (0.088 mm for the GG genotype; P=0.002).

CONCLUSIONS

The OPN and MCP-1 genes, coding for 2 cytokines with known roles in atherosclerosis, may contribute to increased carotid IMT and warrant further study.

Carotid atherosclerosis is associated with enhanced β-chemokine levels in patients on continuous ambulatory peritoneal dialysis

Increased oxidative stress (SOX) has been reported in continuous ambulatory peritoneal dialysis (CAPD) patients, but its influence on beta-chemokine levels and progression of atherosclerosis remains unknown. We determined three distinct SOX markers: Cu/Zn superoxide dismutase (Cu/Zn SOD), total peroxide and autoantibodies against oxidized LDL (OxLDL-Ab); high sensitivity C-reactive protein (hs CRP); beta-chemokines: monocyte chemoattractant protein-1 (CCL2), macrophage inflammatory proteins (CCL3 and CCL4) and regulated upon activation, normal T cell expressed and secreted (CCL5) and the intima-media thickness (IMT) values in CAPD patients both with and without cardiovascular disease (CVD) and healthy controls. CAPD patients both with and without CVD had significantly increased IMT (p<0.001 and <0.01), Cu/Zn SOD (both p<0.001) and CCL2 levels (p<0.001 and <0.01, respectively) as compared to controls. CCL4 (p<0.01) and hs CRP (p<0.05) were increased only in patients with CVD, whereas there were no differences in the total peroxide, OxLDL-Ab and CCL3 levels between patients and controls. CCL5 concentrations were significantly decreased in both patients subgroup (both p<0.001) versus controls. Multivariate analysis showed that age (p<0.001), male sex (p<0.01), CCL4 and CCL2 levels (both p<0.05) were the independent variables linked to IMT values. Our data suggest a possible role of enhanced beta-chemokine levels in the carotid atherosclerosis in patients treated with CAPD, in addition to age and male sex.

The role of lipolysis in mediating the proinflammatory effects of very low density lipoproteins in mouse peritoneal macrophages

Hypertriglyceridemia is an important risk factor for atherosclerosis, especially in obesity. Macrophages are one of the primary cell types involved in atherogenesis and are thought to contribute to lesion formation through both lipid accumulation and proinflammatory gene expression. In this study, we sought to determine the direct impact of triglyceride (TG)-rich VLDL-induced lipid accumulation on macrophage proinflammatory processes. Incubation of mouse peritoneal macrophages with 100 microg/ml VLDL for 6 h led to 2.8- and 3.7-fold increases in intracellular TGs and FFAs, respectively (P < 0.05). The inflammatory proteins tumor necrosis factor-alpha, interleukin-1beta, monocyte chemoattractant protein-1, intercellular adhesion molecule-1, matrix metalloproteinase 3 (MMP3), and macrophage inflammatory protein-1alpha (MIP-1alpha) were all upregulated by at least 2-fold (P < 0.05) in a dose-dependent manner in VLDL-treated macrophages. The increase in inflammatory gene expression coincided with the phosphorylation of the mitogen-activated protein kinase (MAPK) pathway members extracellular signal-regulated kinase (ERK) 1/2, stress-activated protein kinase/c-Jun NH2-terminal kinase, and p38 MAPK and was ameliorated by U0126, an inhibitor of ERK1/2. Inhibition of extracellular TG hydrolysis with tetrahydrolipstatin (Orlistat) resulted in the absence of intracellular TG and FFA accumulation and was accompanied by the amelioration of ERK1/2 phosphorylation and MIP-1alpha gene expression. These data indicate that VLDL hydrolysis, and the subsequent accumulation of intracellular FFAs and TGs, plays a substantive role in mediating the proinflammatory effects of VLDL. These data have important implications for the direct proatherogenic effects of VLDL on macrophage-driven 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.

Two-step cross-linking method for identification of NF-kappaB gene network by chromatin immunoprecipitation

The chromatin immunoprecipitation (ChIP) assay has recently been exploited as a powerful and versatile technique for probing protein-DNA interactions within the chromatin environment. In this method, intact cells are fixed with a reversible DNA-protein cross-linking agent (formaldehyde), and associated DNA is enriched by immunoprecipitating a target DNA binding protein. The bound DNA in the immune complexes is then used to identify that specific DNA binding protein's endogenous genomic targets. Nuclear factor kappaB (NF-kappaB) is a highly inducible transcription factor that controls genetic networks important for pathogen- or cytokine-induced inflammation, immune response, and cellular survival. In our studies of the genetic network under control of the inducible NF-kappaB transcription factor, we found that the conventional ChIP technique using a single formaldehyde cross-linking step did not reproducibly cross-link it to DNA. As a result, we have developed a novel ChIP assay using a two-step cross-linking procedure, incorporating N-hydroxysuccinimide (NHS)-ester-mediated protein-protein cross-linking prior to conventional DNA-protein cross-linking. We demonstrate that this technique is highly efficient, cross-linking virtually all NF-kappaB/Rel A into covalent complexes, resulting in quantitative and robust identification of inducible NF-kappaB family binding to a variety of validated NF-kappaB-dependent genomic targets. To demonstrate the general utility of this two-step cross-linking procedure, we performed enhanced capture of cytokine-inducible signal transducer and activator of transcription-3 (STAT3) binding to one of its known target genes. Our method represents a significant improvement in the efficiency of ChIP analysis in the study of endogenous targets for rare transcription factors.

Interleukin 12 induces T-cell recruitment into the atherosclerotic plaque

CD4 T cells, through the release of cytokines as well as direct effector functions, have been implicated in promoting inflammation of the atherosclerotic plaque. Plaque-infiltrating CD4 T cells include a specialized subset of (CD4+)CD28- T cells that express a unique profile of regulatory receptors and are responsive to novel microenvironmental cues. Here we report that (CD4+)CD28- T cells, either isolated from the plaque tissue or from the blood of patients with acute coronary syndrome (ACS), spontaneously express interleukin (IL)-12 receptors, even in the absence of antigenic stimulation. (CD4+)CD28- IL-12R+ cells responded to IL-12 stimulation with the upregulation of the chemokine receptor CCR5 and the C-type lectin receptor CD161, both implicated in regulating tissue homing of effector T cells. IL-12 treatment of (CD4+)CD28- T cells enhanced their chemotaxis and transendothelial migration toward the chemokine CCL5. In vivo relevance for the role of IL-12 in regulating the recruitment of (CD4+)CD28- T cells into the atheroma was examined in human atheroma-SCID mouse chimeras. Exposure of nonstimulated (CD4+)CD28- T cells to IL-12 was sufficient to amplify T-cell accumulation within the inflamed plaque, and coadministration of anti-CCR5 antibodies blocked T-cell recruitment into the plaque. Thus, (CD4+)CD28- T cells functionally resemble NK cells, which have proinflammatory activity even in the unprimed state and respond to any IL-12-inducing host infection with a shift in tissue trafficking and accrual in inflammatory lesions.

Chemokines in Children With Heterozygous Familiar Hypercholesterolemia

OBJECTIVE

Increasing data support the involvement of chemokines in atherogenesis. However, although several studies have shown increased chemokine levels in adult patients, the literature is virtually devoid of data on chemokines in children with hypercholesterolemia.

METHODS AND RESULTS

We examined the gene expression of chemokines in peripheral blood mononuclear cells (PBMCs) from clinically healthy children with and without heterozygous familial hypercholesterolemia (FH). Our main findings were: (1) compared with healthy controls, PBMCs from FH children showed significantly higher mRNA levels of RANTES, but not of the other examined chemokines; (2) an opposite pattern was seen in adult FH subjects, with markedly enhanced expression of macrophage inflammatory peptide-1alpha, but not of RANTES; (3) this increased gene expression of RANTES in PBMCs from FH children seemed to reflect enhanced RANTES expression in monocytes but not in T cells; (4) FH children also had raised serum levels of neopterin, additionally suggesting monocyte/macrophage activation in these children; and (5) PBMCs from both FH children and controls showed enhanced release of interleukin 8 on RANTES stimulation in vitro.

CONCLUSIONS

Our findings support a role of inflammation also in the early stages of atherogenesis possibly involving monocyte-derived RANTES as an important mediator.

Multiplexed flow cytometric analyses of pro- and anti-inflammatory cytokines in the culture media of oxysterol-treated human monocytic cells and in the sera of atherosclerotic patients

BACKGROUND

Some oxysterols are identified in atheromatous plaques and in plasma of atherosclerotic patients. We asked whether they might modulate cytokine secretion on human monocytic cells. In healthy and atherosclerotic subjects, we also investigated the relationships between circulating levels of C-reactive protein (CRP), conventional markers of hyperlipidemia, some oxysterols (7beta-hydroxycholesterol, 7-ketocholesterol, and 25-hydroxycholesterol), and various cytokines.

METHODS

Different flow cytometric bead-based assays were used to quantify some cytokines (IL-1beta, IL-2, IL-4, IL-5, IL-6, IL-7, IL-8, IL-10, IL-12, IL-13, IL-17, G-CSF, GM-CSF, IFN-gamma, MCP-1, MIP-1beta, or TNF-alpha) in the culture media of oxysterol-treated U937 and THP-1 cells, and in the sera of healthy and atherosclerotic subjects. CRP and markers of hyperlipidemia were determined with routine analytical methods. Oxysterols were quantified by gas chromatography/mass spectrometry. Flow cytometric and biochemical methods were used to measure IL-8 mRNA levels, intracellular IL-8 content, and protein phosphorylation in the mitogenic extracellular kinase/extracellular signal-regulated kinase1/2 (MEK/ERK1/2) signaling pathway.

RESULTS

All oxysterols investigated are potent in vitro inducers of MCP-1, MIP-1beta, TNF-alpha, and/or IL-8 secretion, the latter involving the MEK/ERK1/2 cell signaling pathway. In healthy and atherosclerotic subjects, no relationships were found between cytokines (IL-8, IL-1beta, IL-6, IL-10, TNF-alpha, IL-12, and MCP-1), CRP, conventional markers of hyperlipidemia, and oxysterols. However, in patients with arterial disorders of the lower limbs, small but statistically significant differences in the circulating levels of CRP, TNF-alpha, and IL-10 were observed comparatively to healthy subjects and according to the atherosclerotic stage considered.

CONCLUSIONS

Flow cytometric bead-based assays are well adapted to measure variations of cytokine secretion in the culture media of oxysterol-treated cells and in the sera of healthy and atherosclerotic subjects. They underline the in vitro proinflammatory properties of oxysterols and may permit to distinguish healthy and atherosclerotic subjects, as well as various atherosclerotic stages.

HIV Entry Inhibitor TAK-779 Attenuates Atherogenesis in Low-Density Lipoprotein Receptor–Deficient Mice

OBJECTIVE

HIV combination therapy using protease inhibitors is associated with elevated plasma levels of atherogenic lipoproteins and increased risk for atherosclerosis. We investigated whether the HIV entry inhibitor TAK-779 affects lipoprotein levels and atherogenesis in low-density lipoprotein receptor-deficient mice. TAK-779 is an antagonist for the chemokine receptors CCR5 and CXCR3, which are expressed on leukocytes, especially T-helper 1 cells, and these receptors may be involved in recruitment of these cells to atherosclerotic plaques.

METHODS AND RESULTS

TAK-779 treatment of low-density lipoprotein receptor-deficient mice did not elevate the levels of atherogenic lipoproteins, whereas it dramatically reduced atherosclerosis in the aortic root and in the carotid arteries. The number of T cells in the plaque was reduced by 95%, concurrently with a 98% reduction in the relative IFN-gamma area. TAK-779-treated animals showed a decreased percentage of CD4+ and CD8+ T cells in peripheral blood and in mediastinal lymph nodes compared with control-treated animals.

CONCLUSIONS

TAK-779 not only suppresses HIV entry via blockade of CCR5 but also attenuates atherosclerotic lesion formation by blocking the influx of T-helper 1 cells into the plaque. TAK-779 treatment may be especially beneficial for young HIV patients as they face lifelong treatment, and this drug impairs atherogenesis.

Proprotein convertases furin and PC5: targeting atherosclerosis and restenosis at multiple levels

Several growth factors, chemokines, adhesion molecules, and proteolytic enzymes important for cell-cell/cell-matrix interactions in atherosclerosis and restenosis are initially synthesized as inactive precursor proteins. Activation of proproteins to biologically active molecules is regulated by limited endoproteolytic cleavage at dibasic amino acid residues. This type of activation typically requires the presence of suitable proprotein convertases (PCs). The PC-isozymes furin and PC5 are expressed in human atherosclerotic lesions and have been found to be up-regulated, following vascular injury in animal models in vivo. In vitro, these PCs can regulate vascular smooth muscle cell and macrophage functions and signaling events, through activation of pro-alpha-integrins and/or pro-membrane-type matrix metalloproteinases. Integrins link the cytoskeleton with the extracellular matrix and mediate bidirectional signaling and mechanotransduction, whereas matrix metalloproteinases are the major matrix-degrading enzymes. Both activities are required for cell recruitment to the intima. Furthermore, cleavage of extracellular matrix molecules by matrix metalloproteinases potentially contributes to weakening of the fibrous cap, promoting plaque rupture. Based on these recent in vitro and in vivo data, furin and PC5 are potential contributors to the initiation, progression, and complications of atherosclerosis and restenosis. Targeting these PCs may provide future anti-atherosclerotic therapies.

Signalling mechanisms of SDF-induced endothelial cell proliferation and migration

The aim of our study was to investigate the effect of stromal-derived factor-1-alpha (SDF-1-alpha) on endothelial angiogenic effects. SDF-1-alpha (50 ng/ml) increased the number of cultured endothelial cells from 33,653 +/- 1183 to 55,398 +/- 2741, which significantly reduced by adding the BK(Ca)-inhibitor iberiotoxin, or the endothelial nitric oxide synthase-blocker, L-NMMA (n = 24, p < 0.05). Using the "Fences"-assay a significant increase of HUVEC migration induced by SDF-1-alpha was reported, which was blocked by the addition of iberiotoxin or L-NMMA (n = 12, p < 0.05). BK(Ca) open-state probability (NPo) was analysed using the patch-clamp technique and NPo was increased from 0.003 (control) to 0.052 (SDF-1-alpha; n = 10, p < 0.05). NO synthesis was measured using a cGMP-radioimmunoassay. A significant increase of cGMP levels from 0.952 pmol/mg protein to 2.179 pmol/mg protein was observed, that was abolished by L-NMMA and significantly reduced by iberiotoxin (n=15, p<0.05). SDF-1-alpha increases endothelial proliferation and migration involving the activation of BK(Ca) and an increased production of NO.

Chemokines and their receptors: roles in specific clinical conditions and measurement in the clinical laboratory

Considerable progress has been achieved in our knowledge of the function of the chemokine system and in understanding its role in the pathophysiology of human diseases. This complex system, presently including approximately 50 cytokines and 20 receptors, coordinates leukocyte recruitment in a variety of human diseases, ranging from infectious and inflammatory diseases to cancer. A large body of literature has been published describing various assays for the measurement of chemokines in biologic fluids and tissues. We review information available on the role of chemokines in selected human diseases and provide examples of clinical situations in which chemokine determination might be of practical value, and we describe the currently available assays for their measurement.

Thematic Review Series: The Immune System and Atherogenesis. Molecular mechanisms regulating monocyte recruitment in atherosclerosis

Cardiovascular disease, a progressive disorder characterized by the accumulation of lipids in the artery wall, is a leading cause of death in Western societies. One of the initial events in atherogenesis involves the recruitment of inflammatory cells from the circulation into the developing lesion. Studies during the past decade have underscored the role of inflammatory mediators in disease initiation and progression. Critical progress has been made in our understanding of the complex mechanisms by which monocytes, macrophages, and T-cells accumulate in atherosclerotic plaques. Experimental research has identified several candidate adhesion proteins and chemokines that are critically involved in the recruitment process, and encouraging data provide a mechanistic framework for new therapeutic targets. This review provides an overview of our current understanding of the mechanisms that direct the recruitment of monocytes to, and their retention in, atherosclerotic lesions.

Circulating β-chemokines and matrix metalloproteinase-9/tissue inhibitor of metalloproteinase-1 system in hemodialyzed patients – Role of oxidative stress

Matrix metalloproteinases (MMPs) and their tissue inhibitors (TIMPs), beta-chemokines, increased oxidative stress (SOX) and inflammation have been implicated as important factors in atherosclerosis and vascular remodeling. We hypothesized the possible roles of beta-chemokines [monocyte chemoattractant protein-1 (MCP-1), macrophage inflammatory proteins (MIP-1alpha, MIP-1beta) and regulated upon activation, normal T-cell expressed and secreted (RANTES)] as regulators of the metabolism of the vascular extracellular matrix in conditions of increased SOX in hemodialysis (HD) patients. We compared pre-dialysis levels of MMP-9/TIMP-1 system, beta-chemokines, Cu/Zn superoxide dismutase (Cu/Zn SOD) as a marker of SOX and C-reactive protein (CRP) as a marker of inflammation in HD patients with and without cardiovascular disease (CVD) to those of controls. HD patients, particularly those with CVD, showed a significant increase in values of Cu/Zn SOD, CRP, TIMP-1, TIMP-1/MMP-9 ratio, MCP-1 and MIP-1beta, whereas RANTES levels were lower than in the controls. The levels of MIP-1alpha as well as MMP-9 in all HD groups were similar to the controls. The positive correlations were observed between the MMP-9/TIMP-1 system and beta-chemokines, SOX and inflammation in whole HD group and in the subgroup with CVD. Multivariate analysis showed that the duration of dialysis followed by Cu/Zn SOD, MIP-1alpha and beta levels were the significant positive predictors of TIMP-1. In conclusion, our data show that MMP-9/TIMP-1 system and beta-chemokines could cooperate in conditions of elevated SOX, which ultimately predisposes hemodialysis patients to accelerated atherosclerosis.

Immunohistochemical localization of subtilisin/kexin-like proprotein convertases in human atherosclerosis

Integrins are heterodimeric alpha/beta receptors that link the cytoskeleton with the extracellular matrix, thereby regulating several cell functions important in atherosclerosis. In vitro, the subtilisin/kexin-like proprotein convertases (PCs), namely PC5 and furin, have been shown to be responsible for the endoproteolytic activation of the alpha(v) integrin subunit. Based on their cleavage activity, these PCs are potential targets in atherosclerosis. In the present study, we investigated the localization of furin and PC5 in different stages of human atherosclerosis. Immunohistochemical analysis of furin and PC5 revealed their presence in vascular smooth-muscle cells and endothelial cells in atherosclerotic and non-atherosclerotic lesions. However, in the more advanced lesions, furin and PC5 staining was significantly expressed in macrophages/foam cells. In vitro, THP-1 derived macrophages contained furin and PC5, and maturation of monocytes to macrophages was accompanied by enhanced alpha(v)beta3 cell-surface expression. Inhibition of furin/PC5 with the specific pharmacological furin-like PC-inhibitor dec-CMK inhibited alpha(v) endoproteolytic activation but did not abolish alpha(v)beta3 cell-surface expression. This indicates that furin/PC5 is required for alpha(v) endoproteolytic activation but not for alpha(v) routing and sorting to the cell surface. In conclusion, our study demonstrates that furin and PC5 are significantly expressed in mononuclear cells in advanced human atherosclerotic lesions, where they regulate alpha(v) endoproteolytic activation.

Fluvastatin inhibits the expression of tumor necrosis factor-alpha and activation of nuclear factor-kappaB in human endothelial cells stimulated by C-reactive protein

BACKGROUND

Inflammation plays a critic role in atherosclerosis and C-reactive protein (CRP) may directly facilitate the development of a proinflammatory and proatheroscleroitc phenotype. The nuclear factor-kappaB (NF-kappaB) signal transduction is known to play a key role in the expression of these proatherogenic entities including tumor necrosis factor-alpha (TNF-alpha). Much data suggest that statin possess a potential anti-inflammatory effect. However, the effects of statin on the expression of TNF-alpha and activation of NF-kappaB in endothelial cells stimulated by CRP are less studied. We determined the effects of CRP in inducing inflammatory response and the effect of fluvastatin on CRP-dependent inflammatory activation in human cultured endothelial cells.

METHODS

Human vascular endothelial cells were cultured and stimulated by concentrations of CRP (5-100 microg/ml) for 0, 2, 4, 8, 16, 24, and 48 h. Also 10 micromol/l of fluvastatin was pre-incubated for 2 h with cells in the presence of CRP. The activity of transcription factor NF-kappaB was evaluated by electrophoretic mobility shift assay (EMSA). Measurements of TNF-alpha were performed from supernatants of cultured medium in duplicate, using commercial assay kits.

RESULTS

CRP increased the release of TNF-alpha rapidly as a dose-and time-dependent manner. Induction of TNF-alpha was detected at 5 microg/ml and reached a maximum at 100 microg/ml of CRP. The CRP also significantly induces the activation of NF-kappaB in endothelial cells, and those effects were apparently inhibited by 10 micromol/l of fluvastatin, but not complete.

CONCLUSIONS

CRP stimulation result in induction of TNF-alpha and activation of NF-kappaB, and this effect could be significantly inhibited by fluvastatin, suggesting that CRP may play a direct role in atherogenesis by activating endothelial cells, and statins inhibit this response, which may provide an insight into the mechanisms of anti-inflammatory or anti-atherosclerotic actions of statins.

Adverse associations between CX3CR1 polymorphisms and risk of cardiovascular or cerebrovascular disease

OBJECTIVE

We investigated the role of monocyte-recruiting chemokines in cerebrovascular diseases among the subjects of the GENIC case-control study of brain infarction (BI).

METHODS AND RESULTS

Of the genotypes tested, only homozygosity for the rare CX3CR1 alleles was more frequent in cases than in controls: the I249 and M280 alleles were associated with an increased risk of BI (OR, 1.66 and OR, 2.62 with P<0.05, respectively). This effect was independent of other established risk factors and uncorrelated with disease severity. The study confirmed previous reports of a dominant protective association between CX3CR1-I249 allele and the risk of cardiovascular history. The risk of BI associated with homozygosity for the rare CX3CR1 alleles was enhanced in patients with no previous cardiovascular events. Ex vivo studies showed that the number of monocytes adhering to immobilized CX3CL1, the CX3CR1 ligand, increased proportionally to the number of CX3CR1 mutated alleles carried by the individual.

CONCLUSIONS

The rare CX3CR1 alleles were associated with an increased risk of BI and with reduced frequency of cardiovascular history. We propose that the extra adhesion of monocytes observed in individuals carrying rare alleles of CX3CR1 may favor mechanisms leading to stroke.

Inflammatory mediators in atherosclerotic vascular disease

An impressive body of work has established the current paradigm of atherosclerosis as an inflammatory process that promotes lesion development and progression. Early atheroma formation is characterized by leukocyte recruitment and expression of inflammatory mediators which is confounded in the context of hyperlipidemia. Evidence for an involvement of both innate and adaptive immunity in lesion formation has emerged, supporting a causal relation between the balance of pro- and anti-inflammatory cytokines and atherogenesis. The function of chemokines in distinct steps during mononuclear cell recruitment to vascular lesions has been studied in genetically deficient mice and other suitable models, and displays a high degree of specialization and cooperation. The contribution of platelet chemokines deposited on endothelium to monocyte arrest, differences in the presentation and involvement of chemokines between native and neointimal lesion formation, and related functions of macrophage migration inhibitory factor, a cytokine with striking structural homology to chemokines are of note. A novel role of chemokines in the recruitment of vascular progenitors during neointimal hyperplasia and in the recovery of endothelial denudation underscores their relevance for atherosclerotic vascular disease. The functional diversity of chemokines in vascular inflammation may potentially allow the selective therapeutic targeting of different atherosclerotic conditions.

What causes acute coronary syndromes? Applying Koch's postulates

The term "acute coronary syndromes" (ACS) is used to describe a heterogeneous spectrum of clinical conditions. This includes myocardial infarction, non-ST-elevation myocardial infarction, and unstable angina. These conditions are linked by a similar constellation of signs and symptoms but not necessarily by a common pathophysiology. They are syndromes. Several different hypotheses exist that have attempted to explain the pathological mechanisms that are involved in these conditions, however, it is not clear whether ACS are caused by variations of a single disease process or by several disease processes. The contribution of both vessel wall- and blood-related factors in the pathogenesis of acute coronary syndromes is herein discussed with the guidance of Koch's postulates.

Genetic risk factor characterizes abdominal aortic aneurysm from arterial occlusive disease in human beings: CCR5 Delta 32 deletion

OBJECTIVE

Inflammation is involved in the pathogenesis of atherosclerosis and abdominal aortic aneurysm (AAA), and chemokines are mediators of the inflammatory process. The homozygous Delta 32 deletion mutation of the gene of the chemokine receptor CCR5 is a cause of its lack in inflammatory cells. The purpose of this study was to investigate the relationship between CCR5 Delta 32 deletion mutation and AAA, peripheral arterial occlusive disease (PAOD), and carotid stenosis.

METHODS

The CCR5 Delta 32 polymorphism was genotyped in 380 subjects: 70 patients operated on to treat AAA (21 ruptured AAAs, 49 elective repair), 76 patients with PAOD, 62 patients with carotid stenosis, and 172 age-matched and sex-matched healthy control subjects. Risk factors for AAA were considered. Each patient was assessed according to a diagnostic procedure tailored to symptoms at presentation.

RESULTS

In patients with AAA the Delta allelic variation was significantly different compared with control subjects (P = .002; odds ratio [OR], 2.7; 95% confidence interval [CI], 1.41-5.15). The increased presence of this allele differentiates AAA from both PAOD (P = .017; OR, 2.77; 95% CI, 1.17-6.52) and carotid stenosis (P = .01; OR, 3.47; 95% CI, 1.31-9.11). The presence in the genotype of patients with AAA of at least 1 Delta 32 allele is more frequent in ruptured AAAs than in electively repaired AAAs (genotype: OR, 4.04; 95% CI, 1.34-12.1; P = .011; allelic frequency: OR, 2.75; 95% CI, 1.07-7.07; P = .035). Among the patients, multiple regression analysis showed that the Delta 32 allele is an independent risk factor for AAA vs PAOD (OR, 3.13; 95% CI, 1.33-7.33; P = .012) and for ruptured AAAs vs electively repaired AAAs (OR, 3.52; 95% CI, 1.01-11.80; P = .045).

CONCLUSIONS

CCR5 Delta 32 deletion mutation is significantly more frequent in patients with AAA than in control subjects and in both patients with PAOD and carotid stenosis, and could be a factor that differentiates AAA from PAOD, and ruptured AAAs from AAAs that can be electively repaired.

CLINICAL RELEVANCE

The major threat of abdominal aortic aneurysm (AAA) is rupture, accounting for extremely high mortality. This occurrence has been correlated to aneurysm size, but it is a common observation that small AAAs can rupture and large AAAs can remain stable for many years. This study was carried out in an attempt to search for genetic markers of aneurysm rupture. Some single nucleotide polymorphisms are implicated in acceleration of transcription for enzymes involved in the inflammatory process and in extracellular matrix remodeling. An association between single nucleotide polymorphisms and aneurysm rupture could enable better selection for surgical indications in patients with small AAs and in patients at poor risk with large AAAs.

The antiatherogenic potential of oat phenolic compounds

Avenanthramides are phenolic antioxidants, which are present in oats. Avenanthramides A, B, and C are the major constituents of the total soluble antioxidant phenolic compounds in oats. We tested the potential antiatherogenic activity of partially purified avenanthramides from oats by examining their effects on adhesion of monocytes to human aortic endothelial cell (HAEC) monolayers, expression of adhesion molecules, and production of proinflammatory cytokines and chemokines by HAEC. The oat avenanthramides mixture was prepared and partially purified by column chromatography. This avenanthramide-enriched mixture (AEM) had no toxicity to HAEC as tested up to 40 ng/ml. The pre-incubation of HAEC with 4, 20, and 40ng/ml AEM for 24h significantly decreased adhesion of U937 monocytic cells to interleukin (IL)-1beta-stimulated HAEC in a concentration-dependent manner. Pre-incubation of HAEC with AEM at 20 and 40 microg/ml, but not at 4 microg/ml, for 24h significantly suppressed IL-1beta-stimulated expressions of intracellular adhesion molecule-1 (ICAM-1), vascular cell adhesion molecule-1 (VCAM-1), and E-selectin and the secretion of proinflammatory cytokines IL-6, chemokines IL-8 and monocyte chemoattractant protein (MCP)-1. These data provide evidence for the potential anti-inflammatory and antiatherogenic effects of antioxidant avenanthramides present in oats.