Antagonism of RANTES Receptors Reduces Atherosclerotic Plaque Formation in Mice

Regulation of CCL5 expression in smooth muscle cells following arterial injury

Chemokines play a crucial role in inflammation and in the pathophysiology of atherosclerosis by recruiting inflammatory immune cells to the endothelium. Chemokine CCL5 has been shown to be involved in atherosclerosis progression. However, little is known about how CCL5 is regulated in vascular smooth muscle cells. In this study we report that CCL5 mRNA expression was induced and peaked in aorta at day 7 and then declined after balloon artery injury, whereas IP-10 and MCP-1 mRNA expression were induced and peaked at day 3 and then rapidly declined.

The expression of CCL5 receptors (CCR1, 3 & 5) were also rapidly induced and then declined except CCR5 which expression was still relatively high at day 14 after balloon injury. In rat smooth muscle cells (SMCs), similar as in aorta CCL5 mRNA expression was induced and kept increasing after LPS plus IFN-gamma stimulation, whereas IP-10 mRNA expression was rapidly induced and then declined. Our data further indicate that induction of CCL5 expression in SMCs was mediated by IRF-1 via binding to the IRF-1 response element in CCL5 promoter. Moreover, p38 MAPK was involved in suppression of CCL5 and IP-10 expression in SMCs through common upstream molecule MKK3. The downstream molecule MK2 was required for p38-mediated CCL5 but not IP-10 inhibition. Our findings indicate that CCL5 induction in aorta and SMCs is mediated by IRF-1 while activation of p38 MAPK signaling inhibits CCL5 and IP-10 expression. Methods targeting MK2 expression could be used to selectively regulate CCL5 but not IP-10 expression in SMCs.

RANTES/CCL5 and risk for coronary events: results from the MONICA/KORA Augsburg case-cohort, Athero-Express and CARDIoGRAM studies

BACKGROUND

The chemokine RANTES (regulated on activation, normal T-cell expressed and secreted)/CCL5 is involved in the pathogenesis of cardiovascular disease in mice, whereas less is known in humans. We hypothesised that its relevance for atherosclerosis should be reflected by associations between CCL5 gene variants, RANTES serum concentrations and protein levels in atherosclerotic plaques and risk for coronary events.

METHODS AND FINDINGS

We conducted a case-cohort study within the population-based MONICA/KORA Augsburg studies. Baseline RANTES serum levels were measured in 363 individuals with incident coronary events and 1,908 non-cases (mean follow-up: 10.2±4.8 years). Cox proportional hazard models adjusting for age, sex, body mass index, metabolic factors and lifestyle factors revealed no significant association between RANTES and incident coronary events (HR [95% CI] for increasing RANTES tertiles 1.0, 1.03 [0.75-1.42] and 1.11 [0.81-1.54]). None of six CCL5 single nucleotide polymorphisms and no common haplotype showed significant associations with coronary events. Also in the CARDIoGRAM study (>22,000 cases, >60,000 controls), none of these CCL5 SNPs was significantly associated with coronary artery disease. In the prospective Athero-Express biobank study, RANTES plaque levels were measured in 606 atherosclerotic lesions from patients who underwent carotid endarterectomy. RANTES content in atherosclerotic plaques was positively associated with macrophage infiltration and inversely associated with plaque calcification. However, there was no significant association between RANTES content in plaques and risk for coronary events (mean follow-up 2.8±0.8 years).

CONCLUSIONS

High RANTES plaque levels were associated with an unstable plaque phenotype. However, the absence of associations between (i) RANTES serum levels, (ii) CCL5 genotypes and (iii) RANTES content in carotid plaques and either coronary artery disease or incident coronary events in our cohorts suggests that RANTES may not be a novel coronary risk biomarker. However, the potential relevance of RANTES levels in platelet-poor plasma needs to be investigated in further studies.

Atherosclerosis: current pathogenesis and therapeutic options

Coronary artery disease (CAD) arising from atherosclerosis is a leading cause of death and morbidity worldwide. The underlying pathogenesis involves an imbalanced lipid metabolism and a maladaptive immune response entailing a chronic inflammation of the arterial wall. The disturbed equilibrium of lipid accumulation, immune responses and their clearance is shaped by leukocyte trafficking and homeostasis governed by chemokines and their receptors. New pro- and anti-inflammatory pathways linking lipid and inflammation biology have been discovered, and genetic profiling studies have unveiled variations involved in human CAD. The growing understanding of the inflammatory processes and mediators has uncovered an intriguing diversity of targetable mechanisms that can be exploited to complement lipid-lowering therapies. Here we aim to systematically survey recently identified molecular mechanisms, translational developments and clinical strategies for targeting lipid-related inflammation in atherosclerosis and CAD.

Clinical utility of maraviroc

Maraviroc belongs to the family of chemokine (C-C motif) receptor 5 (CCR5) antagonists that prevent the entry of human immunodeficiency virus (HIV) into host CD4+ T cells by blocking the CCR5 co-receptor R5. Maraviroc is currently the only CC5R co-receptor inhibitor that has been approved for clinical use in HIV-1-infected patients carrying the CCR5 tropism who are antiretroviral-naïve or have experienced therapeutic failure following traditional antiretroviral therapies. This article is a review of the main characteristics of maraviroc and the latest data regarding its clinical application. Maraviroc is effective and well tolerated in pre-treated and antiretroviral-naïve patients with HIV-1 infections carrying the CCR5 tropism. Data from the phase III programme of maraviroc, which includes the MOTIVATE 1 and 2 studies and the MERIT study, indicate that maraviroc significantly (p < 0.001) increases CD4+ cell counts compared with placebo in pre-treated patients and to a similar extent as efavirenz in antiretroviral-naïve patients. Even in cases where viral load is not completely suppressed, maraviroc improves immunological response compared with placebo. In addition, promising research suggests that maraviroc has favourable pharmacokinetic and safety profiles in patients with high cardiovascular risk or those co-infected with tuberculosis or hepatitis and could be considered an option for treatment of HIV-infected patients with these co-morbidities. Resistance to maraviroc is low and mainly related to the presence of chemokine (C-X-C motif) receptor 4 (CXCR4) tropism HIV-1-infections or to mutations in the V3 region of glycoprotein (gp) 120; however, the exact mechanisms by which resistance is acquired and their genotypic and phenotypic pattern have not yet been established. It is recommended that a tropism test should be performed when considering maraviroc as an alternate drug in HIV-1-infected patients. Current tropism assays have increased sensitivity to reliably detect CXCR4 HIV with rapid turn-around and at a low cost. Improved detection together with positive data on the drug's efficacy and safety profiles should help physicians to identify more accurately the appropriate candidates for commencement of treatment with maraviroc. In summary, maraviroc improves immunological response and has shown favourable pharmacokinetic and safety profiles in patients with high cardiovascular risk or in those co-infected with tuberculosis or hepatitis. Long-term studies are needed to confirm whether therapeutic expectations resulting from clinical trials with maraviroc translate into a real benefit for HIV-1-infected patients for whom traditional antiretroviral therapies have failed or are not suitable.

Chemokines: established and novel targets in atherosclerosis

In their role as small chemotactic cytokines, chemokines are crucial mediators and regulators of leukocyte trafficking during immune surveillance and inflammation. Their involvement in the development and progression of inflammatory diseases has been subject of intense investigation. Concordantly, the chemokine system has been explored in search for therapeutic targets to prevent or treat inflammatory disorders, such as atherosclerosis. Targeting the chemokine system offers various entry points for a causative treatment of this widespread and chronic illness. Although this approach has encountered some setbacks, several innovative compounds are currently in an advanced stage of development. In this review, the current standing of this dynamic field is highlighted and the potential advantages and drawbacks of particular strategies are discussed.

Aging enhances the basal production of IL-6 and CCL2 in vascular smooth muscle cells

OBJECTIVE

Increased circulating cytokine levels are a prominent feature of aging that may contribute to atherosclerosis. However, the role vascular cells play in chronic inflammation induced by aging is not clear. Here, we examined the role of aging on inflammatory responses of vascular cells.

METHODS AND RESULTS

In an ex vivo culture system, we examined the inflammatory response of aortas from young (2-4 months) and aged (16-18 months) mice under nonstimulatory conditions. We found that basal levels of interleukin-6 were increased in aged aortas. Aged aortic vascular smooth muscle cells (VSMC) exhibited a higher basal secretion of interleukin-6 than young VSMC. Gene and protein expression analysis revealed that aged VSMC exhibited upregulation of chemokines (eg, CCL2), adhesion molecules (eg, intracellular adhesion molecule 1), and innate immune receptors (eg, Toll-like receptor [TLR] 4), which all contribute to atherosclerosis. Using VSMC from aged TL4(-/-) and Myd88(-/-) mice, we demonstrate that signaling via TLR4 and its signal adaptor, MyD88, are in part responsible for the age-elevated basal interleukin-6 response.

CONCLUSIONS

Aging induces a proinflammatory phenotype in VSMC due in part to increased signaling of TLR4 and MyD88. Our results provide a potential explanation as to why aging leads to chronic inflammation and enhanced atherosclerosis.

Using a genetic, observational study as a strategy to estimate the potential cost-effectiveness of pharmacological CCR5 blockade in dialysis patients

BACKGROUND AND OBJECTIVE

Randomized clinical trials are expensive and time consuming. Therefore, strategies are needed to prioritise tracks for drug development. Genetic association studies may provide such a strategy by considering the differences between genotypes as a proxy for a natural, lifelong, randomized at conception, clinical trial. Previously an association with better survival was found in dialysis patients with systemic inflammation carrying a deletion variant of the CC-chemokine receptor 5 (CCR5). We hypothesized that in an analogous manner, pharmacological CCR5 blockade could protect against inflammation-driven mortality and estimated if such a treatment would be cost-effective.

METHODS

A genetic screen and treat strategy was modelled using a decision-analytic Markov model, in which patients were screened for the CCR5 deletion 32 polymorphism and those with the wild type and systemic inflammation were treated with pharmacological CCR5 blockers. Kidney transplantation and mortality rates were calculated using patient level data. Extensive sensitivity analyses were performed.

RESULTS

The cost-effectiveness of the genetic screen and treat strategy was &OV0556;18 557 per life year gained and &OV0556;21 896 per quality-adjusted life years gained. Concordance between the genetic association and pharmacological effectiveness was a main driver of cost-effectiveness. Sensitivity analyses showed that even a modest effectiveness of pharmacological CCR5 blockade would result in a treatment strategy that is good value for money.

CONCLUSION

Pharmacological blockade of the CCR5 receptor in inflamed dialysis patients can be incorporated in a potentially cost-effective screen and treat programme. These findings provide formal rationale for clinical studies. This study illustrates the potential of genetic association studies for drug development, as a source of Mendelian randomized evidence from an observational setting.

Platelets in atherosclerosis

Beyond obvious functions in haemostasis and thrombosis, platelets are considered to be essential in proinflammatory surroundings such as atherosclerosis, allergy, rheumatoid arthritis and even cancer. In atherosclerosis, platelets facilitate the recruitment of inflammatory cells towards the lesion sites and release a plethora of inflammatory mediators, thereby enriching and boosting the inflammatory milieu. Platelets do so by interacting with endothelial cells, circulating leukocytes (monocytes, neutrophils, dendritic cells, T-cells) and progenitor cells. This cross-talk enforces leukocyte activation, adhesion and transmigration. Furthermore, platelets are known to function in innate host defense through the release of antimicrobial peptides and the expression of pattern recognition receptors. In severe sepsis, platelets are able to trigger the formation of neutrophil extracellular traps (NETs), which bind and clear pathogens. The present antiplatelet therapies that target key pathways of platelet activation and aggregation therefore hold the potential to modulate platelet-derived immune functions by reducing cellular interactions of platelets with other immune components and by reducing the secretion of inflammatory proteins into the milieu. The objective of this review is to update and discuss the current perceptions of the platelet immune constituents and their prospect as therapeutic targets in an atherosclerotic setting.

Differential effects of dietary protein sources on postprandial low-grade inflammation after a single high fat meal in obese non-diabetic subjects

Background

Obesity is a state of chronic low-grade inflammation. Chronic low-grade inflammation is associated with the pathophysiology of both type-2 diabetes and atherosclerosis. Prevention or reduction of chronic low-grade inflammation may be advantageous in relation to obesity related co-morbidity. In this study we investigated the acute effect of dietary protein sources on postprandial low-grade inflammatory markers after a high-fat meal in obese non-diabetic subjects.

Methods

We conducted a randomized, acute clinical intervention study in a crossover design. We supplemented a fat rich mixed meal with one of four dietary proteins - cod protein, whey isolate, gluten or casein. 11 obese non-diabetic subjects (age: 40-68, BMI: 30.3-42.0 kg/m2) participated and blood samples were drawn in the 4 h postprandial period. Adiponectin was estimated by ELISA methods and cytokines were analyzed by multiplex assay.

Results

MCP-1 and CCL5/RANTES displayed significant postprandial dynamics. CCL5/RANTES initially increased after all meals, but overall CCL5/RANTES incremental area under the curve (iAUC) was significantly lower after the whey meal compared with the cod and casein meals (P = 0.0053). MCP-1 was initially suppressed after all protein meals. However, the iAUC was significantly higher after whey meal compared to the cod and gluten meals (P = 0.04).

Conclusion

We have demonstrated acute differential effects on postprandial low grade inflammation of four dietary proteins in obese non-diabetic subjects. CCL5/RANTES initially increased after all meals but the smallest overall postprandial increase was observed after the whey meal. MCP-1 was initially suppressed after all 4 protein meals and the whey meal caused the smallest overall postprandial suppression.

Trial Registration

ClinicalTrials.gov ID: NCT00863564

Pattern specification and immune response transcriptional signatures of pericardial and subcutaneous adipose tissue

Cardiovascular disease (CVD) remains the leading cause of morbidity and mortality in the United States. Recent studies suggest that pericardial adipose tissue (PCAT) secretes inflammatory factors that contribute to the development of CVD. To better characterize the role of PCAT in the pathogenesis of disease, we performed a large-scale unbiased analysis of the transcriptional differences between PCAT and subcutaneous adipose tissue, analysing 53 microarrays across 19 individuals. As it was unknown whether PCAT-secreted factors are produced by adipocytes or cells in the supporting stromal fraction, we also sought to identify differentially expressed genes in isolated pericardial adipocytes vs. isolated subcutaneous adipocytes. Using microarray analysis, we found that: 1) pericardial adipose tissue and isolated pericardial adipocytes both overexpress atherosclerosis-promoting chemokines and 2) pericardial and subcutaneous fat depots, as well as isolated pericardial adipocytes and subcutaneous adipocytes, express specific patterns of homeobox genes. In contrast, a core set of lipid processing genes showed no significant overlap with differentially expressed transcripts. These depot-specific homeobox signatures and transcriptional profiles strongly suggest different functional roles for the pericardial and subcutaneous adipose depots. Further characterization of these inter-depot differences should be a research priority.

Apheresis-inducible cytokine pattern change in severe, genetic dyslipidemias

OBJECTIVE

The effects of direct adsorption of lipids LDL-apheresis (DALILDL-a) on plasma cytokines in two Homozygous and heterozygous familial hypercholesterolemic (HozFH, HtzFH) and in four HyperLp(a)lipoproteinemic [HyperLp(a)] patients, were evaluated.

METHODS

Plasma, macrophage inflammatory proteins 1α (MIP-1α), macrophage inflammatory proteins 1β (MIP-1β), monocyte chemoattractant protein-1 (MCP-1), RANTES (Regulated upon Activation, Normal T-cell Expressed, and Secreted), granulocyte-colony stimulating factor (GCSF), granulocyte macrophage-colony stimulating factor (GM-CSF), interleukin-1α (IL-1α), interleukin-1β (IL-1β), interleukin-2 (IL-2), interleukin-6 (IL-6), interferon-γ (IFN-γ), concentrations, were measured before and after LDL-a on three consecutive sessions for each patient.

RESULTS

MIP-1α was significantly reduced (P=0.05), while MIP-1β was significantly increased (P=0.05). Plasma MCP-1 was reduced, although not significantly, while RANTES was significantly increased (P=0.05). GCSF and GM-CSF were both significantly reduced (GM-CSF: P=0.05, GCSF: P=0.05, respectively). IL-1α level was significantly reduced (P=0.001). IL-1β, IL-6, and IFN-γ levels were significantly reduced in plasma after apheresis (IL-1β: P=0.001, IL-6: T1 P=0.001; T2 P=0.05, respectively, IFN-γ: P=0.001). IL-2 level in plasma was significantly reduced at T0, and T2, (P=0.001). However, IL-2 level showed a statistically significant increase at T1 (P=0.001). A significant correlation between IL-1α and IFN-γ was found: r=0.882 (P=0.001).

CONCLUSIONS

In this study LDL-a induced profound changes in several circulating cytokines and promoted anti-inflammatory and anti-atherogenic cytokine profile in plasma of patients with severe dyslipidemia, with pre-existing angiographically demonstrated Coronary heart disease (CHD), and aortic valvular disease (#=1) (AVD).

Differential role of monocyte subsets in atherosclerosis

Endothelial dysfunction and inflammation of the arterial wall continuously drive the development of atherosclerosis. Details regarding the sequential involvement of different monocyte subsets in the pathology of this disease have recently emerged. This review concentrates on major monocyte subpopulations in mouse and men and specifically addresses their phenotype, function and recruitment during primary atherosclerosis as well as their contribution to angiogenesis and tissue regeneration secondary to plaque rupture.

CCR5Δ32 variant and cardiovascular disease in patients with rheumatoid arthritis: a cohort study

Introduction

The aim of our study was to analyze the influence of the CCR5Δ32 polymorphism in the risk of cardiovascular (CV) events and subclinical atherosclerosis among patients with rheumatoid arthritis (RA).

Methods

A total of 645 patients fulfilling the American Rheumatism Association 1987 revised classification criteria for RA were studied. Patients were genotyped for the CCR5 rs333 polymorphism using predesigned TaqMan assays. Also, HLA DRB1 genotyping was performed using molecular-based methods. Carotid intima-media thickness, flow-mediated endothelium-dependent dilatation (FMD) and endothelium-independent vasodilatation, which were used as surrogate markers of subclinical atherosclerosis, were measured in a subgroup of patients with no clinical CV disease.

Results

A lower frequency of carriers of the CCR5Δ32 allele among patients with CV events (3.4% versus 11.3%, P = 0.025, odds ratio 0.28, 95% confidence interval (95% CI) 0.06 to 0.89) was observed. However, after adjusting for gender, age at time of RA diagnosis, and the presence of shared epitope, rheumatoid factor and classic CV risk factors in the Cox regression analysis, this reduction of CV events in CCR5Δ32 allele carriers was slightly outside the range of significance (P = 0.097; hazard ratio 0.37 (95% CI 0.12 to 1.19)). Carriers of the CCR5Δ32 deletion also showed higher FMD values than the remaining patients (CCR5/CCR5Δ32 patients: 7.03% ± 6.61% versus CCR5/CCR5 patients: 5.51% ± 4.66%). This difference was statistically significant when analysis of covariance was performed (P = 0.024).

Conclusions

Our results show a potential influence of the CCR5Δ32 deletion on the risk of CV disease among patients with RA. This may be due to a protective effect of this allelic variant against the development of vascular endothelial dysfunction.

Targeting chemokine receptors in chronic inflammatory diseases: an extensive review

The traffic of the different types of immune cells is an important aspect in the immune response. Chemokines are soluble peptides that are able to attract cells by interaction with chemokine receptors on their target cells. Several different chemokines and receptors exist enabling the specific trafficking of different immune cells. In chronic inflammatory disorders there is abundance of immune cells present at the inflammatory site. This review focuses on the role of chemokine receptors in chronic inflammatory disorders of the lungs, intestine, joints, skin and nervous system and the potential of targeting these receptors as therapeutic intervention in these disorders.

Chemokine receptor CCR5: from AIDS to atherosclerosis

There is increasing recognition of an important contribution of chemokines and their receptors in the pathology of atherosclerosis and related cardiovascular disease. The chemokine receptor CCR5 was initially known for its role as a co-receptor for HIV infection of macrophages and is the target of the recently approved CCR5 antagonist maraviroc. However, evidence is now emerging supporting a role for CCR5 and its ligands CCL3 (MIP-1α), CCL4 (MIP-1β) and CCL5 (RANTES) in the initiation and progression of atherosclerosis. Specifically, the CCR5 deletion polymorphism CCR5delta32, which confers resistance to HIV infection, has been associated with a reduced risk of cardiovascular disease and both CCR5 antagonism and gene deletion reduce atherosclerosis in mouse models of the disease. Antagonism of CCL5 has also been shown to reduce atherosclerotic burden in these animal models. Crucially, CCR5 and its ligands CCL3, CCL4 and CCL5 have been identified in human and mouse vasculature and have been detected in human atherosclerotic plaque. Not unexpectedly, CC chemokines have also been linked to saphenous vein graft disease, which shares similarity to native vessel atherosclerosis. Distinct roles for chemokine-receptor systems in atherogenesis have been proposed, with CCR5 likely to be critical in recruitment of monocytes to developing plaques. With an increased burden of cardiovascular disease observed in HIV-infected individuals, the potential cardiovascular-protective effects of drugs that target the CCR5 receptor warrant greater attention. The availability of clinically validated antagonists such as maraviroc currently provides an advantage for targeting of CCR5 over other chemokine receptors.

The inflammatory preatherosclerotic remodeling induced by intermittent hypoxia is attenuated by RANTES/CCL5 inhibition

RATIONALE

The highly prevalent obstructive sleep apnea syndrome (OSA) with its main component intermittent hypoxia (IH) is a risk factor for cardiovascular mortality. The poor knowledge of its pathophysiology has limited the development of specific treatments, whereas the gold standard treatment, continuous positive airway pressure, may not fully reverse the chronic consequences of OSA and has limited acceptance in some patients.

OBJECTIVES

To examine the contribution of IH-induced inflammation to the cardiovascular complications of OSA.

METHODS

We investigated systemic and vascular inflammatory changes in C57BL6 mice exposed to IH (21-5% Fi(O(2)), 60-s cycle) or normoxia 8 hours per day up to 14 days. Vascular alterations were reassessed in mice treated with a blocking antibody of regulated upon activation, normal T-cell expressed and secreted (RANTES)/CC chemokine ligand 5 (CCL5) signaling pathway, or with the IgG isotype control throughout the IH exposure.

MEASUREMENTS AND MAIN RESULTS

IH induced systemic inflammation combining increased splenic lymphocyte proliferation and chemokine expression, with early and predominant RANTES/CCL5 alterations, and enhanced splenocyte migration toward RANTES/CCL5. IH also induced structural and inflammatory vascular alterations. Leukocyte-endothelium adhesive interactions were increased, attested by leukocyte rolling and intercellular adhesion molecule-1 expression in mesenteric vessels. Aortas had increased intima-media thickness with elastic fiber alterations, mucoid depositions, nuclear factor-κB-p50 and intercellular adhesion molecule-1 overexpression, hypertrophy of smooth-muscle cells overexpressing RANTES/CCL5, and adventitial-periadventitial T-lymphocyte infiltration. RANTES/CCL5 neutralization prevented both intima-media thickening and inflammatory alterations, independently of the IH-associated proatherogenic dyslipidemia.

CONCLUSIONS

Inflammation is a determinant mechanism for IH-induced preatherosclerotic remodeling involving RANTES/CCL5, a key chemokine in atherogenesis. Characterization of the inflammatory response could allow identifying at-risk patients for complications, and its pharmacologic manipulation may represent a potential complementary treatment of sleep apnea consequences.

Maraviroc can improve lipid profiles in dyslipidemic patients with HIV: results from the MERIT trial

PURPOSE

We investigated the effects of maraviroc, the first approved CC-chemokine receptor 5 (CCR5) antagonist, on blood lipids in a post hoc analysis of the phase 3 MERIT study in treatment-naïve patients.

METHODS

Patients received maraviroc 300 mg twice daily (n = 360) or efavirenz 600 mg once daily (n = 361), both in combination with zidovudine/lamivudine, for up to 96 weeks. Baseline and on- treatment lipid profiles were analyzed according to National Cholesterol Education Program (NCEP) thresholds.

RESULTS

Baseline characteristics and lipid profiles were comparable between groups. Among patients with total cholesterol (TC) and low-density lipoprotein cholesterol (LDL-c) below NCEP treatment thresholds at baseline, significantly more efavirenz- than maraviroc-treated patients exceeded those thresholds at 96 weeks (TC: 35% [74/209] vs 11% [20/188], P < .0001; LDL-c: 23% [47/197] vs 8% [15/183], P < .0001). Among patients exceeding NCEP thresholds at baseline, significantly more efavirenz- than maraviroc-treated patients exceeded the thresholds at 96 weeks (TC: 83% [24/29] vs 50% [17/34], P = .0084; LDL-c: 86% [19/22] vs 55% [16/29], P = .0314). Of those with baseline high- density lipoprotein cholesterol (HDL-c) < 40 mg/dL, 43% (56/130) of maravirocand 62% (86/139) of efavirenz-treated patients achieved HDL-c≥40 mg/dL at 96 weeks (P = .0020).

CONCLUSIONS

Maraviroc was not associated with elevations in TC, LDL-c, or triglycerides and showed beneficial effects on lipid profiles of dyslipidemic patients.

The RANTES gene promoter polymorphisms are associated with the risk of atherothrombotic cerebral infarction in Northern Han Chinese

BACKGROUND

Regulated upon activation, normal T-cell expressed and secreted (RANTES) plays an important role in the inflammatory process. This study is aimed at evaluating the potential association of the -403G/A (rs2107538) and -28C/G (rs2280788) polymorphisms of the RANTES gene promoter with the risk of atherothrombotic cerebral infarction (ACI) in Northern Han Chinese.

METHOD

A total of 314 patients with ACI and 389 unrelated aged-matched healthy controls were recruited. Their genotypes of the RANTES gene promoter -403G/A (rs2107538) and -28C/G (rs2280788) were analyzed by multiplex polymerase chain reaction (multiplex PCR) and multiplex SNaPshot analysis. The potential association of genotyping and allele frequencies with ACI in this population was assessed statistically.

RESULTS

The frequencies of -403AA genotype and A allele in ACI male patients were significantly higher than that in healthy controls (P=0.007, P=0.009, respectively). Female patients were not different. Multiple logistic regression analysis revealed that the -403AA genotype in males was significantly associated with an increased risk of ACI, even after adjusting for confounding factors (OR=4.344; 95% CI=1.969-9.582; P<0.001). Although there was no significant association of the -28C/G polymorphism with ACI, the A-(403)C-(28) haplotype was significantly associated with an increased risk of ACI in Han Chinese [OR=1.56, 95% CI=1.23-1.98, P<0.001].

CONCLUSIONS

Our data suggest that the -403AA genotype and A allele of the RANTES promoter were associated with increased risk for the development of ACI in male Northern Han Chinese.

[Atherosclerosis : on the trail of chemokines]

Atherosclerosis, which is more than a problem of lipid metabolism, is associated with chronic inflammation of large arteries. This is notably caused by the recruitment of circulating blood monocytes to the arterial wall. Extensive studies in humans and mice have shown that the chemokines and their receptors, responsible for leukocyte recirculation, are strongly implicated in the initial onset of atherosclerosis. Murine models have provided further proof of the role of the CCR2/CCL2, CX3CR1/CXCL16 and CCR5/CCL5 axes in the different stages of disease, as well as the preventative roles of CCR1/CCL5 and CXCR6/CXCL16. The integration at the cellular level of various signals in the chemokine network underlines the complex process of leukocyte recruitment to the lesional area. Furthermore the capacity of chemokines to modulate atherosclerosis lies not just with their chemoattractant properties but also with their influence on leukocyte homeostasis. These molecules have therefore quickly become therapeutic targets for atherosclerosis and have opened up new avenues for treating inflammatory diseases. This review principally addresses the implication of chemokines and their receptors in the initial recruitment steps of blood monocytes, and provides an overview of recent research on these molecular controllers of inflammation.

Sphingosine-1-Phosphate-Specific G Protein-Coupled Receptors as Novel Therapeutic Targets for Atherosclerosis

Atherosclerosis is a chronic inflammatory process involving complex interactions of modified lipoproteins, monocyte-derived macrophages or foam cells, lymphocytes, endothelial cells (ECs), and vascular smooth muscle cells. Sphingosine-1-phosphate (S1P), a biologically active blood-borne lipid mediator, exerts pleiotropic effects such as cell proliferation, migration and cell-cell adhesion in a variety of cell types via five members of S1P-specific high-affinity G protein-coupled receptors (S1P₁-S1P₅). Among them, S1P₁, S1P₂ and S1P₃ are major receptor subtypes which are widely expressed in various tissues. Available evidence suggest that S1P and HDL-bound S1P exert atheroprotective effects including inhibition of leukocyte adhesion and stimulation of endothelial nitric oxide synthase (eNOS) in endothelial cells (ECs) through the activation of G_i signaling pathway via S1P₃ and probably S1P₁, although there is still controversy. FTY720, the phosphorylation product of which is a high-affinity agonist for all S1P receptors except S1P₂ and act as an immunosuppressant by downregulating S1P₁ on lymphocytes, inhibits atherosclerosis in LDL receptor-null mice and apoE-null mice through the inhibition of lymphocyte and macrophage functions and probably stimulation of EC functions, without influencing plasma lipid concentrations. In contrast to S1P₁ and S1P₃, S1P₂ facilitates atherosclerosis by activating G_12/13-Rho-Rho kinase (ROCK) in apoE-null mice. S1P₂ mediates transmigration of monocytes into the arterial intima, oxidized LDL accumulation and cytokine secretion in monocyte-derived macrophages, and eNOS inhibition and cytokine secretion in ECs through Rac inhibition, NF-κB activation and 3′-specific phosphoinositide phosphatase (PTEN) stimulation downstream of G_12/13-Rho-ROCK. Systemic long-term administration of a selective S1P₂-blocker remarkably inhibits atherosclerosis without overt toxicity. Thus, multiple S1P receptors positively and negatively regulate atherosclerosis through multitudes of mechanisms. Considering the essential and multi-faceted role of S1P₂ in atherogenesis and the impact of S1P₂ inactivation on atherosclerosis, S1P₂ is a particularly promising therapeutic target for atherosclerosis.

Sphingosine-1-phosphate receptor-2 deficiency leads to inhibition of macrophage proinflammatory activities and atherosclerosis in apoE-deficient mice

Sphingosine-1-phosphate (S1P) is a biologically active sphingolipid that has pleiotropic effects in a variety of cell types including ECs, SMCs, and macrophages, all of which are central to the development of atherosclerosis. It may therefore exert stimulatory and inhibitory effects on atherosclerosis. Here, we investigated the role of the S1P receptor S1PR2 in atherosclerosis by analyzing S1pr2-/- mice with an Apoe-/- background. S1PR2 was expressed in macrophages, ECs, and SMCs in atherosclerotic aortas. In S1pr2-/-Apoe-/- mice fed a high-cholesterol diet for 4 months, the area of the atherosclerotic plaque was markedly decreased, with reduced macrophage density, increased SMC density, increased eNOS phosphorylation, and downregulation of proinflammatory cytokines compared with S1pr2+/+Apoe-/- mice. Bone marrow chimera experiments indicated a major role for macrophage S1PR2 in atherogenesis. S1pr2-/-Apoe-/- macrophages showed diminished Rho/Rho kinase/NF-κB (ROCK/NF-κB) activity. Consequently, they also displayed reduced cytokine expression, reduced oxidized LDL uptake, and stimulated cholesterol efflux associated with decreased scavenger receptor expression and increased cholesterol efflux transporter expression. S1pr2-/-Apoe-/- ECs also showed reduced ROCK and NF-κB activities, with decreased MCP-1 expression and elevated eNOS phosphorylation. Pharmacologic S1PR2 blockade in S1pr2+/+Apoe-/- mice diminished the atherosclerotic plaque area in aortas and modified LDL accumulation in macrophages. We conclude therefore that S1PR2 plays a critical role in atherogenesis and may serve as a novel therapeutic target for atherosclerosis.

Relationship between circulating levels of RANTES (regulated on activation, normal T-cell expressed, and secreted) and carotid plaque characteristics: the Atherosclerosis Risk in Communities (ARIC) Carotid MRI Study

AIMS

To assess the relationship between regulated on activation, normal T-cell expressed and secreted (RANTES) and carotid atherosclerotic plaque burden and plaque characteristics.

METHODS AND RESULTS

Gadolinium-enhanced magnetic resonance imaging (MRI) of the carotid artery was performed in 1901 participants from the Atherosclerosis Risk in Communities (ARIC) Study. Wall thickness and volume, lipid-core volume, and fibrous cap thickness (by MRI) and plasma RANTES levels (by ELISA) were measured. Regression analysis was performed to study the associations between MRI variables and RANTES. Among 1769 inclusive participants, multivariable regression analysis revealed that total wall volume [beta-coefficient (β) = 0.09, P = 0.008], maximum wall thickness (β = 0.08, P = 0.01), vessel wall area (β = 0.07, P = 0.02), mean minimum fibrous cap thickness (β = 0.11, P = 0.03), and high-sensitivity C-reactive protein (β = 0.09, P = 0.01) were positively associated with RANTES. Total lipid-core volume showed positive association in unadjusted models (β = 0.18, P = 0.02), but not in fully adjusted models (β = 0.13, P = 0.09). RANTES levels were highest in Caucasian females followed by Caucasian males, African-American females, and African-American males (P < 0.0001). Statin use attenuated the relationship between RANTES and measures of plaque burden.

CONCLUSION

Positive associations between RANTES and carotid wall thickness and lipid-core volume (in univariate analysis) suggest that higher RANTES levels may be associated with extent of carotid atherosclerosis and high-risk plaques. Associations between fibrous cap thickness and RANTES likely reflect the lower reliability estimate for fibrous cap measurements compared with wall volume or lipid-core volume measurements. Statin use may modify the association between RANTES and carotid atherosclerosis. Furthermore, RANTES levels vary by race.

CD14++CD16+ monocytes and cardiovascular outcome in patients with chronic kidney disease

AIMS

Patients with chronic kidney disease (CKD) pose a worldwide growing burden to health care systems due to accelerated atherosclerosis and subsequent high cardiovascular (CV) morbidity. Atherogenesis is prominently driven by monocytes and monocyte-derived macrophages. The expression of CD14 and CD16 characterizes three monocyte subsets: CD14(++)CD16(-), CD14(++)CD16(+), and CD14((+))CD16(+) cells; the latter two are often denoted as 'proinflammatory' CD16(+) monocytes. Despite an association between CD16(+) monocyte counts and higher CV risk in cross-sectional cohorts, the prognostic impact of elevated CD16(+) monocyte counts is poorly understood.

METHODS AND RESULTS

We assessed monocyte heterogeneity using flow cytometry in 119 patients with non-dialysis CKD, who were prospectively followed for a median of 4.9 (inter-quartile range 4.8-5.0) years for the occurrence of CV events. In addition, we assessed expression of chemokine receptors on monocyte subsets. CD14(++)CD16(+) monocyte were independently associated with CV events [hazard ratio (for an increase of 10 cells/μL) 1.26 (confidence interval: 1.04-1.52; P = 0.018)] after adjustment for variables that significantly affected CD14(++)CD16(+) cell counts at baseline. Across the spectrum of CKD, CD14(++)CD16(+) monocytes selectively expressed CCR5.

CONCLUSION

We found that CD14(++)CD16(+) monocytes were independently associated with CV events in non-dialysis CKD patients. Our results support the notion that CD16(+) monocytes rather than CD16(-) monocytes are involved in human atherosclerosis.

Chemokines as therapeutic targets for atherosclerotic plaque destabilization and rupture

Chemokines are instrumental in the initiation and progression of atherosclerosis. Recent advances in genomic technologies and the recognition of atherosclerosis as an inflammatory disease have given great impetus to studies addressing the relevance of chemokines for the clinically manifest stages of atherosclerosis and acute cardiovascular syndromes. In this paper, we will review the current status of these studies, highlighting those chemokines that have already been associated with plaque destabilization and rupture. We will recapitulate recent epidemiologic, genomic, histopathological and experimental support for the prominent role of particular chemokines in acute cardiovascular syndromes. Collectively, these data underpin the potential of chemokines as biomarkers and/or therapeutic targets, but also expose the lacunae in our understanding of the precise function of chemokines in the atherosclerosis-related disorders and in the efficacy of chemokine-targeted clinical trials.

Therapeutic implications of chemokine-mediated pathways in atherosclerosis: realistic perspectives and utopias

Current perspectives on the pathogenesis of atherosclerosis strongly support the involvement of inflammatory mediators in the establishment and progression of atherosclerostic lesions. Chemokine-mediated mechanisms are potent regulators of such processes by orchestrating the interactions of inflammatory cellular components of the peripheral blood with cellular components of the arterial wall. The increasing evidence supporting the role of chemokine pathways in atherosclerosis renders chemokine ligands and their receptors potential therapeutic targets. In the following review, we aim to highlight the special structural and functional features of chemokines and their receptors in respect to their roles in atherosclerosis, and examine to what extent available data can be applied in disease management practices.

Noninfectious HIV-related comorbidities and HAART toxicities: choosing alternative antiretroviral strategies

In the HAART era, clinicians are faced with the challenge of treating an aging HIV-infected population increasingly affected by severe comorbidities, which may compromise the tolerability of antiretroviral regimens. In this special population, it is imperative for physicians to carefully tailor antiretroviral treatment in order not to worsen patients’ underlying clinical conditions and to achieve both tolerability and immune–virologic efficacy. This article aims to explore the impact of standard HAART regimens on the different noninfectious HIV-related comorbidities: metabolic, cardiovascular, bone and renal diseases, in order to provide tools to fit the most appropriate antiretroviral combination according to individual clinical conditions. Clinical experience with alternative antiretroviral strategies, avoiding nucleoside reverse transcriptase inhibitor toxicities and involving new antiretroviral classes, will be reviewed to obtain an overview on future perspectives.

Myeloid type I interferon signaling promotes atherosclerosis by stimulating macrophage recruitment to lesions

Inflammatory cytokines are well-recognized mediators of atherosclerosis. Depending on the pathological context, type I interferons (IFNs; IFNalpha and IFNbeta) exert either pro- or anti-inflammatory immune functions, but their exact role in atherogenesis has not been clarified. Here, we demonstrate that IFNbeta enhances macrophage-endothelial cell adhesion and promotes leukocyte attraction to atherosclerosis-prone sites in mice in a chemokine-dependent manner. Moreover, IFNbeta treatment accelerates lesion formation in two different mouse models of atherosclerosis and increases macrophage accumulation in the plaques. Concomitantly, absence of endogenous type I IFN signaling in myeloid cells inhibits lesion development, protects against lesional accumulation of macrophages, and prevents necrotic core formation. Finally, we show that type I IFN signaling is upregulated in ruptured human atherosclerotic plaques. Hereby, we identify type I IFNs as proatherosclerotic cytokines that may serve as additional targets for prevention or treatment.

T-cell co-stimulators as anti-inflammatory targets for atherosclerotic disease

Currently, most pharmacological therapies for atherosclerosis rely on lowering plasma low-density lipoprotein levels. Several ongoing clinical trials are testing the possibility of reducing atherosclerosis with drugs that raise plasma high-density lipoprotein levels and/or promote high-density lipoprotein-mediated protective functions. Atherosclerosis can also be treated by targeting inflammatory cells. Recent studies have shown that atherosclerosis is primarily an inflammatory disease and that immune cells, particularly T cells, are found in atherosclerotic lesions throughout the early and late stages. Therefore, therapies that modulate T-cell co-stimulators might slow down the atherosclerosis process by inhibiting T-cell-mediated inflammation.

Suppressive effect of insulin infusion on chemokines and chemokine receptors

OBJECTIVE

In view of the previously described anti-inflammatory effects of insulin, we investigated the potential suppressive effect of insulin on plasma concentrations and expression of the chemokines, monocyte chemoattractant protein-1 (MCP-1) and regulated on activation normal T-cell expressed and secreted (RANTES) and their receptors, chemokine receptor (CCR)-2 and CCR-5, in mononuclear cells (MNCs). We also investigated the effect of insulin on other chemokines.

RESEARCH DESIGN AND METHODS

Ten obese type 2 diabetic patients were infused with insulin (2 units/h with 100 ml of 5% dextrose/h) for 4 h. Another 8 and 6 type 2 diabetic patients were infused with 100 ml of 5% dextrose/h or saline for 4 h, respectively, and served as control subjects. Blood samples were obtained at 0, 2, 4, and 6 h.

RESULTS

Insulin infusion significantly suppressed the plasma concentrations of MCP-1, eotaxin, and RANTES and the expression of RANTES, macrophage inflammatory protein (MIP)-1beta, CCR-2, and CCR-5 in MNCs at 2 and 4 h. Dextrose and saline infusions did not alter these indexes.

CONCLUSIONS

A low-dose infusion of insulin suppresses the plasma concentration of key chemokines, MCP-1, and RANTES, and the expression of their respective receptors, CCR-2 and CCR-5, in MNCs. Insulin also suppresses the expression of RANTES and MIP-1beta in MNCs. These actions probably contribute to the comprehensive anti-inflammatory effect of insulin.

Dual targeting of CCR2 and CCR5: therapeutic potential for immunologic and cardiovascular diseases

A cardinal feature of inflammation is the tissue recruitment of leukocytes, a process that is mediated predominantly by chemokines via their receptors on migrating cells. CCR2 and CCR5, two CC chemokine receptors, are important players in the trafficking of monocytes/macrophages and in the functions of other cell types relevant to disease pathogenesis. This review provides a brief overview of the biological actions of CCR2 and CCR5 and a comprehensive summary of published data that demonstrate the involvement of both receptors in the pathogenesis of immunologic diseases (RA, CD, and transplant rejection) and cardiovascular diseases (atherosclerosis and AIH). In light of the potential for functional redundancy of chemokine receptors in mediating leukocyte trafficking and the consequent concern over insufficient efficacy offered by pharmacologically inhibiting one receptor, this review presents evidence supporting dual targeting of CCR2 and CCR5 as a more efficacious strategy than targeting either receptor alone. It also examines potential safety issues associated with such dual targeting.

Inflammatory cell recruitment in cardiovascular disease: murine models and potential clinical applications

Atherosclerosis is the pathological process that underlies the development of cardiovascular disease, a leading cause of mortality. Atherosclerotic plaque formation is driven by the recruitment of inflammatory monocytes into the artery wall, their differentiation into macrophages and the subsequent transformation of macrophages into cholesterol-laden foam cells. Models of hypercholesterolaemia such as the ApoE (apolipoprotein E)-/- mouse and the application of transgenic technologies have allowed us to undertake a thorough dissection of the cellular and molecular biology of the atherosclerotic disease process. Murine models have emphasized the central role of inflammation in atherogenesis and have been instrumental in the identification of adhesion molecules that support monocyte recruitment, scavenger receptors that facilitate cholesterol uptake by macrophages and other macrophage activation receptors. The study of mice deficient in multiple members of the chemokine family, and their receptors, has shown that chemokines play a critical role in promoting atherosclerotic plaque formation. In the present review, we will discuss novel therapeutic avenues for the treatment of cardiovascular disease that derive directly from our current understanding of atherogenesis gained in experimental animal models.

Therapeutic targeting of chemokine interactions in atherosclerosis

Atherosclerosis is a chronic inflammatory disease of the arterial wall that is characterized by a disturbed equilibrium of immune responses and lipid accumulation, leading to the development of plaques. The atherogenic influx of mononuclear cells is orchestrated by chemokines and their receptors. Studies using gene-deficient mice and antagonists based on peptides and small molecules have generated insight into targeting chemokine-receptor axes for treating atherosclerosis, which might complement lipid-lowering strategies and risk factor modulation. Combined inhibition of multiple chemokine axes could interfere with the contributions of chemokines to disease progression at specific cells, stages or sites. In addition, the recently characterized heterophilic interactions of chemokines might present a novel target for the treatment and prevention of inflammatory diseases such as atherosclerosis.

[CCR5 antagonists and HIV-1 infection: Bases and consequences of this therapeutic approach]

La molécule CCR5 est un récepteur de chimiokines qui joue un rôle important en pathologie infectieuse : corécepteur des souches du VIH-1 à tropisme R5, il est également impliqué dans la défense immunitaire contre certains agents transmissibles. Les antagonistes de CCR5 constituent une nouvelle approche thérapeutique antirétrovirale. Trois inhibiteurs du CCR5 ont atteint les phases IIb et III de développement clinique : aplaviroc (GlaxoSmithKine), vicriviroc (Schering-Plough) et maraviroc (Pfizer). Le développement de l’aplaviroc a été interrompu pour toxicité hépatique. Les essais ACTG 5211 et Motivate ont démontré une amélioration de la réponse antirétrovirale par l’addition respectivement de vicriviroc (actuellement en phase III) et de maraviroc (ayant déjà obtenu l’Autorisation de Mise sur le Marché) à un traitement optimisé chez des patients en échec thérapeutique. Le rôle de cette nouvelle cible thérapeutique dans les stratégies de traitement initial, de substitution ou de sauvetage reste à préciser, de même que leur intérêt chez des patients ayant une réponse immunovirologique dissociée, en immunodépresssion sévère ou infectés par des souches à tropisme non-R5. Plusieurs points sont également à éclaircir comme la tolérance à long terme, le risque d’induire une commutation R5-X4, en particulier dans les tissus, le risque d’interférer avec les réponses immunitaires, ainsi que l’impact d’une discordance de tropisme entre le plasma et les autres compartiments de l’organisme.

Genetic association of the CCR5 region with lipid levels in at-risk cardiovascular patients

BACKGROUND

There is mounting evidence to suggest that chemokine receptor 5 (CCR5) plays an important role in the development and progression of atherosclerosis. A naturally occurring variant of the CCR5 gene CCR532, exists at allele frequencies of typically 10% in European populations and results in a nonfunctional CCR5 receptor.

METHODS AND RESULTS

The CCR5Delta32 deletion and 26 other variants within the chemokine receptor 2-CCR5-chemokine receptor-like protein 2 (CCRL2) gene cluster spanning 59 kilobases of chromosome 3 were genotyped in 5748 subjects from the Treating to New Targets atorvastatin trial to determine whether genetic associations could be identified with circulating lipid values and cardiovascular disease. Our results demonstrate an association between the CCR5Delta32 deletion and increased plasma high-density lipoprotein cholesterol and decreased plasma triglycerides, both of which are beneficial from a cardiovascular perspective. Three single-nucleotide polymorphisms (rs1154428, rs6808835, and rs6791599) in CCRL2 in linkage disequilibrium (r(2)> or =0.65) with CCR5Delta32 and located up to 45 kilobases distal to it were associated with high-density lipoprotein cholesterol. The high-density lipoprotein cholesterol and triglycerides findings were replicated in an additional set of >6000 individuals from the Incremental Decrease in Endpoints through Aggressive Lipid Lowering atorvastatin trial.

CONCLUSIONS

Our study provides evidence that a locus within the region of the genome encompassing the CCR5-CCRL2 region is associated with lipid levels and suggests that chemokine activity influences lipid levels in populations with preexisting cardiovascular disease. CLINICAL TRIAL REGISTRATION- clinicaltrials.gov. Identifier: TNT, NCT00327691; IDEAL, NCT00159835.

Epigenetics in atherosclerosis and inflammation

Atherosclerosis is a multifactorial disease with a severe burden on western society. Recent insights into the pathogenesis of atherosclerosis underscore the importance of chronic inflammation in both the initiation and progression of vascular remodelling. Expression of immunoregulatory molecules by vascular wall components within the atherosclerotic lesions is accordingly thought to contribute to the ongoing inflammatory process. Besides gene regulatory proteins (transcription factors), epigenetic mechanisms also play an essential and fundamental role in the transcriptional control of gene expression. These epigenetic mechanisms change the accessibility of chromatin by DNA methylation and histone modifications. Epigenetic modulators are thus critically involved in the regulation of vascular, immune and tissue-specific gene expression within the atherosclerotic lesion. Importantly, epigenetic processes are reversible and may provide an excellent therapeutic target. The concept of epigenetic regulation is gradually being recognized as an important factor in the pathogenesis of atherosclerosis. Recent research provides an essential link between inflammation and reprogramming of the epigenome. In this review we therefore discuss the basis of epigenetic regulation – and the contribution thereof in the regulation of inflammatory processes in general and during atherosclerosis in particular. Moreover we highlight potential therapeutic interventions based on epigenetic mechanisms.

Experimental immunotherapeutic approaches for atherosclerosis

Therapeutic options in atherosclerosis have largely been limited to the control of risk factors, such as hypercholesterolemia, hypertension, or diabetes. However, atherosclerosis is a chronic inflammatory disease in which dyslipidemia and inflammation are equally involved in disease pathogenesis. Moreover, abundant epidemiological and experimental evidence point to an important modulatory role of innate and adaptive immunity in atherogenesis, providing novel therapeutic targets for this disease. Indeed, there is now accumulating data in animal models demonstrating the potential for immunotherapeutic approaches to treat atherosclerosis. These include both general and antigen-specific ways of modulating immune functions, and they show great promise for the development of alternative and/or adjuvant therapies for atherosclerosis.

Stat3-dependent acute Rantes production in vascular smooth muscle cells modulates inflammation following arterial injury in mice

Inflammation is a key component of arterial injury, with VSMC proliferation and neointimal formation serving as the final outcomes of this process. However, the acute events transpiring immediately after arterial injury that establish the blueprint for this inflammatory program are largely unknown. We therefore studied these events in mice and found that immediately following arterial injury, medial VSMCs upregulated Rantes in an acute manner dependent on Stat3 and NF-kappaB (p65 subunit). This led to early T cell and macrophage recruitment, processes also under the regulation of the cyclin-dependent kinase inhibitor p21Cip1. Unique to VSMCs, Rantes production was initiated by Tnf-alpha, but not by Il-6/gp130. This Rantes production was dependent on the binding of a p65/Stat3 complex to NF-kappaB-binding sites within the Rantes promoter, with shRNA knockdown of either Stat3 or p65 markedly attenuating Rantes production. In vivo, acute NF-kappaB and Stat3 activation in medial VSMCs was identified, with acute Rantes production after injury substantially reduced in Tnfa-/- mice compared with controls. Finally, we generated mice with SMC-specific conditional Stat3 deficiency and confirmed the Stat3 dependence of acute Rantes production by VSMCs. Together, these observations unify inflammatory events after vascular injury, demonstrating that VSMCs orchestrate the arterial inflammatory response program via acute Rantes production and subsequent inflammatory cell recruitment.

The role of chemokines in recruitment of immune cells to the artery wall and adipose tissue

The role of the immune system is to recognize pathogens, tumor cells or dead cells and to react with a very specific and localized response. By taking advantage of a highly sophisticated system of chemokines and chemokine receptors, leukocytes such as neutrophils, macrophages, and T-lymphocytes are targeted to the precise location of inflammation. While this is a beneficial process for acute infection and inflammation, recruitment of immune cells to sites of chronic inflammation can be detrimental. It is becoming clear that these inflammatory cells play a significant role in the initiation and progression of metabolic disorders such as atherosclerosis and insulin resistance by infiltrating the artery wall and adipose tissue (AT), respectively. Data from human studies indicate that elevated plasma levels of chemokines are correlated with these metabolic diseases. Recruitment of macrophages to the artery wall is well known to be one of the first steps in early atherosclerotic lesion formation. Likewise, recruitment of macrophages to AT is thought to contribute to insulin resistance associated with obesity. Based on this knowledge, much recent work in these areas has focused on the role of chemokines in attracting immune cells (monocytes/macrophages in particular) to these 2 sites. Thus, understanding the potential for chemokines to contribute to metabolic disease can help direct studies of chemokines as therapeutic targets. In this article, we will review current literature regarding the role of chemokines in atherosclerosis and obesity-related insulin resistance. We will focus on novel work showing that chemokine secretion from endothelial cells, platelets, and adipocytes can contribute to immune cell recruitment, with a diagram showing the time course of chemokine expression and leukocyte recruitment to AT. We will also highlight a few of the less-commonly known chemokine-chemokine receptor pairs. Finally, we will discuss the potential for chemokines as therapeutic targets for treatment of atherosclerosis and insulin resistance.

Thiol oxidative stress induced by metabolic disorders amplifies macrophage chemotactic responses and accelerates atherogenesis and kidney injury in LDL receptor-deficient mice

BACKGROUND

Strengthening the macrophage glutathione redox buffer reduces macrophage content and decreases the severity of atherosclerotic lesions in LDL receptor-deficient (LDLR(-/-)) mice, but the underlying mechanisms were not clear. This study examined the effect of metabolic stress on the thiol redox state, chemotactic activity in vivo, and the recruitment of macrophages into atherosclerotic lesions and kidneys of LDL-R(-/-) mice in response to mild, moderate, and severe metabolic stress.

METHODS AND RESULTS

Reduced glutathione (GSH) and glutathione disulfide (GSSG) levels in peritoneal macrophages isolated from mildly, moderately, and severe metabolically-stressed LDL-R(-/-) mice were measured by HPLC, and the glutathione reduction potential (E(h)) was calculated. Macrophage E(h) correlated with the macrophage content in both atherosclerotic (r(2)=0.346, P=0.004) and renal lesions (r(2)=0.480, P=0.001) in these mice as well as the extent of both atherosclerosis (r(2)=0.414, P=0.001) and kidney injury (r(2)=0.480, P=0.001). Compared to LDL-R(-/-) mice exposed to mild metabolic stress, macrophage recruitment into MCP-1-loaded Matrigel plugs injected into LDL-R(-/-) mice increased 2.6-fold in moderately metabolically-stressed mice and 9.8-fold in severely metabolically-stressed mice. The macrophage E(h) was a strong predictor of macrophage chemotaxis (r(2)=0.554, P<0.001).

CONCLUSIONS

Thiol oxidative stress enhances macrophage recruitment into vascular and renal lesions by increasing the responsiveness of macrophages to chemoattractants. This novel mechanism contributes at least in part to accelerated atherosclerosis and kidney injury associated with dyslipidemia and diabetes in mice.