F. Mach

Antagonism of RANTES Receptors Reduces Atherosclerotic Plaque Formation in Mice

Abstract— Increasing evidence supports the involvement of inflammation in the early phases of atherogenesis. Recruitment of leukocytes within the vascular wall, controlled by chemokines, is an essential process in the development of this common disease. In this study, we report that blocking a chemokine pathway in vivo with the CC chemokine antagonist Met-RANTES reduces the progression of atherosclerosis in a hypercholesterolemic mouse model. The reduction of lesions was correlated with a diminution of expression of several major chemokines and chemokine receptors, a decrease in leukocyte infiltration, and an increase of collagen-rich atheroma, features associated with stable atheroma. Treatment was well tolerated and serum lipid profiles were not affected. Whereas genetically engineered mice with deletion of either a CC chemokine or its receptor have demonstrated resistance to disease, to our knowledge, this is the first demonstration that treatment with a chemokine receptor antagonist limits the progression of atherosclerosis in vivo. Thus, our findings indicate that blockade of chemokine receptor/ligand interactions might become a novel therapeutic strategy to reduce the evolution of this common disease.

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-&ggr; content were increased in ApoE−/−Ccr1−/− mice. Conclusion—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.

Thrombin Stimulates Human Endothelial Arginase Enzymatic Activity via RhoA/ROCK Pathway Implications for Atherosclerotic Endothelial Dysfunction

Background—Arginase competes with endothelial nitric oxide synthase (eNOS) for the substrate l-arginine and decreases NO production. This study investigated regulatory mechanisms of arginase activity in endothelial cells and its role in atherosclerosis. Methods and Results—In human endothelial cells isolated from umbilical veins, thrombin concentration- and time-dependently stimulated arginase enzymatic activity, reaching a 1.9-fold increase (P<0.001) at 1 U/mL for 24 hours. The effect of thrombin was prevented by C3 exoenzyme or the HMG-CoA reductase inhibitor fluvastatin, which inhibit RhoA, or by the ROCK inhibitors Y-27632 and HA-1077. Adenoviral expression of constitutively active RhoA or ROCK mutants enhanced arginase activity (≈3-fold, P<0.001), and the effect of active RhoA mutant was inhibited by the ROCK inhibitors. Neither thrombin nor the active RhoA/ROCK mutants affected arginase II protein level, the only isozyme detectable in the cells. Moreover, a significantly higher arginase II activity (1.5-fold, not the protein level) and RhoA protein level (4-fold) were observed in atherosclerotic aortas of apoE−/− compared with wild-type mice. Interestingly, l-arginine (1 mmol/L), despite a significantly higher eNOS expression in aortas of apoE−/− mice, evoked a more pronounced contraction, which was reverted to a greater vasodilation by the arginase inhibitor l-norvaline (20 mmol/L) compared with the wild-type animals (n=5, P<0.001). Conclusions—Thrombin enhances arginase activity via RhoA/ROCK in human endothelial cells. Higher arginase enzymatic activity is involved in atherosclerotic endothelial dysfunction in apoE−/− mice. Targeting vascular arginase may represent a novel therapeutic possibility for atherosclerosis.

Statins Reduce Interleukin-6–Induced C-Reactive Protein in Human Hepatocytes: New Evidence for Direct Antiinflammatory Effects of Statins

Objectives—Besides its predictive role in determining cardiovascular risk, C-reactive protein (CRP) may exert direct proatherogenic effects through proinflammatory properties. CRP is mainly produced by hepatocytes in response to interleukin-6 (IL-6) and is then released into the systemic circulation. 3-hydroxy-3-methylglutaryl (HMG)-coenzyme A (CoA) reductase inhibitors, or statins, significantly reduce cardiovascular events and mortality in patients with or without coronary artery disease and reduce plasma CRP levels in humans. However, the mechanism by which statins reduce plasma CRP levels remains unknown. Methods and Results—In this study, we report that statins limit both protein and RNA levels of IL-6-induced CRP in human hepatocytes. These effects are reversed by l-mevalonate and mimicked by an inhibitor of the geranylgeranyltransferase. IL-6–induced CRP production requires the binding of IL-6 to its cognate receptors, which results in activation and phosphorylation of the transcription factor STAT3. We provide evidence that statins reduce this IL-6–induced phosphorylation of STAT3 in hepatocytes. Conclusion—These results demonstrate that statins reduce IL-6–induced CRP production directly in hepatocytes via inhibition of protein geranylgeranylation. We further show that statins act via inhibition of STAT3 phosphorylation. These findings furnish new evidence for direct antiinflammatory properties of statins and provide new mechanistic insight into their clinical benefits.

Effects of Statin Therapy According to Plasma High-Sensitivity C-Reactive Protein Concentration in the Controlled Rosuvastatin Multinational Trial in Heart Failure (CORONA) A Retrospective Analysis

Background— We examined whether the antiinflammatory action of statins may be of benefit in heart failure, a state characterized by inflammation in which low cholesterol is associated with worse outcomes. Methods and Results— We compared 10 mg rosuvastatin daily with placebo in patients with ischemic systolic heart failure according to baseline high sensitivity-C reactive protein (hs-CRP) <2.0 mg/L (placebo, n=779; rosuvastatin, n=777) or ≥2.0 mg/L (placebo, n=1694; rosuvastatin, n=1711). The primary outcome was cardiovascular death, myocardial infarction, or stroke. Baseline low-density lipoprotein was the same, and rosuvastatin reduced low-density lipoprotein by 47% in both hs-CRP groups. Median hs-CRP was 1.10 mg/L in the lower and 5.60 mg/L in the higher hs-CRP group, with higher hs-CRP associated with worse outcomes. The change in hs-CRP with rosuvastatin from baseline to 3 months was −6% in the low hs-CRP group (27% with placebo) and −33.3% in the high hs-CRP group (−11.1% with placebo). In the high hs-CRP group, 548 placebo-treated (14.0 per 100 patient-years of follow-up) and 498 rosuvastatin-treated (12.2 per 100 patient-years of follow-up) patients had a primary end point (hazard ratio of placebo to rosuvastatin, 0.87; 95% confidence interval, 0.77 to 0.98; P=0.024). In the low hs-CRP group, 175 placebo-treated (8.9 per 100 patient-years of follow-up) and 188 rosuvastatin-treated (9.8 per 100 patient-years of follow-up) patients experienced this outcome (hazard ratio, 1.09; 95% confidence interval, 0.89 to 1.34; P>0.2; P for interaction=0.062). The numbers of deaths were as follows: 581 placebo-treated (14.1 per 100 patient-years of follow-up) and 532 rosuvastatin-treated (12.6 per 100 patient-years) patients in the high hs-CRP group (hazard ratio, 0.89; 95% confidence interval, 0.79 to 1.00; P=0.050) and 170 placebo-treated (8.3 per 100 patient-years) and 192 rosuvastatin-treated (9.7 per 100 patient-years) patients in the low hs-CRP group (hazard ratio, 1.17; 95% confidence interval, 0.95 to 1.43; P=0.14; P for interaction=0.026). Conclusion— In this retrospective hypothesis-generating study, we found a significant interaction between hs-CRP and the effect of rosuvastatin for most end points whereby rosuvastatin treatment was associated with better outcomes in patients with hs-CRP ≥2.0 mg/L. Clinical Trial Registration Information— URL: http://www.clinicaltrials.gov. Unique identifier: NCT00206310.

Differential Influence of Chemokine Receptors CCR2 and CXCR3 in Development of Atherosclerosis In Vivo

Background—Recruitment of mononuclear leukocytes within atherosclerotic lesions is a critical step in atherogenesis. Mice lacking the chemokine receptor CCR2, highly expressed on macrophages but also on T lymphocytes, show a striking reduction of atherosclerotic lesion formation. The chemokine receptor CXCR3 is a marker of activated T helper type 1 lymphocytes, the principal T lymphocyte type detected within atheroma. We investigated whether the deletion of both of these 2 important receptors expressed on the principal inflammatory cells present in atheroma would further affect atherogenesis in vivo. Methods and Results—We crossed ApoE−/− mice with either CCR2−/− or CXCR3− mice and crossed ApoE−/− CCR2−/− mice with the ApoE−/− CXCR3− mice to generate a triple knockout strain. Analysis of atherosclerosis development after 10 weeks of high-cholesterol diet revealed differential effects on early atherosclerotic lesions in the abdominal aorta and on advanced lesions in aortic roots. ApoE−/− CXCR3− mice, but not the triple knockout mice, displayed significantly reduced atherosclerotic lesion development within abdominal aortas compared with ApoE−/− CCR2−/− and ApoE−/− mice. This reduction of lesion formation correlated with an upregulation of antiinflammatory molecules such as interleukin-10, interleukin-18BP, and endothelial nitric oxide synthase and with an increased number of regulatory T lymphocytes within atherosclerotic lesions. In contrast, lesion size development within the aortic roots was more enhanced in ApoE−/− and ApoE−/− CXCR3− mice compared with ApoE−/− CCR2−/− and triple knockout mice. Conclusions—Blocking chemokine signaling in vivo through deletion of the chemokine receptors CCR2 and CXCR3 has differential effects during atherogenesis. In addition, our results point to an important role of regulatory T lymphocytes during early atherogenesis.

A Novel RANTES Antagonist Prevents Progression of Established Atherosclerotic Lesions in Mice

Background—Atherosclerosis is a chronic inflammatory disease that represents the primary cause of death through coronary disease and stroke. Chemokines are known to play a crucial role in this disease by recruiting inflammatory leukocytes to the endothelium. Recently, the chemokine variant [44AANA47]-RANTES was shown to impair inflammatory cell recruitment in vivo by interfering with heparin binding and oligomerization. Methods and Results—In this study we report that curative treatment with [44AANA47]-RANTES limits atherosclerotic plaque formation in LDLr−/− mice. This was associated with reduced infiltration of T cells and macrophages and reduced production of matrix metalloproteinase (MMP)-9. By contrast, the relative smooth muscle cell and collagen content was increased, indicating a more stable plaque phenotype. In addition, we provide evidence for direct inhibition of leukocyte recruitment into aortic root lesions, attenuated leukocyte rolling and arrest in mesenteric vessels, as well as a reduced proinflammatory response following Con A stimulation in vitro. Conclusions—Interference with chemokine oligomerization and chemokine/heparin interactions is a powerful novel approach that inhibits progression of established atherosclerosis in mice. By inhibiting leukocyte recruitment into plaques, [44AANA47]-RANTES mediates a less inflammatory plaque phenotype and thus reduced systemic inflammatory state.

Short-Term Treatment With Anti-CD3 Antibody Reduces the Development and Progression of Atherosclerosis in Mice

Background— Atherosclerosis is a chronic inflammatory disease of the large arteries that is the primary cause of heart disease and stroke. Anti-CD3–specific antibodies suppress immune responses by antigenic modulation of the CD3 antibody/T-cell receptor complex. Their unique capacity to restore self-tolerance in a mouse model of diabetes and, importantly, in patients with recent-onset type 1 diabetes involves transforming growth factor-&bgr;–dependent mechanisms via expansion and/or activation of regulatory T cells. We hypothesized that treatment with anti-CD3–specific antibodies might inhibit atherosclerosis development and progression in mice. Methods and Results— Low-density lipoprotein receptor–deficient mice were fed a high-cholesterol diet for 13 or 24 weeks. Anti-CD3 antibody was administered on 5 consecutive days beginning 1 week before or 13 weeks after the high-cholesterol diet was initiated, respectively. Control mice were injected in parallel with phosphate-buffered saline. Anti-CD3 antibody therapy reduced plaque development when administered before a high-cholesterol diet and markedly decreased lesion progression in mice with already established atherosclerosis. We found increased production of the antiinflammatory cytokine transforming growth factor-&bgr; in concanavalin A–stimulated lymph node cells and enhanced expression of the regulatory T-cell marker Foxp3 in spleens of anti-CD3 antibody–treated mice. A higher percentage of apoptotic cells within the plaques of anti-CD3 antibody–treated mice was also observed. Conclusions— Altered disease progression, combined with the emergence of this particular cytokine pattern, indicates that short-term treatment with an anti-CD3 antibody induces a regulatory T-cell phenotype that restores self-tolerance in a mouse model of atherosclerosis.

Differential Expression Patterns of Proinflammatory and Antiinflammatory Mediators During Atherogenesis in Mice

Objective—Recent advances support the current view of atherosclerosis as an inflammatory process that initiates and promotes lesion development to the point of acute thrombotic complications and clinical events. ApoE-deficient mice are a valuable model for studying the involvement of inflammatory mediators during atherogenesis. In this study, we investigated the correlation between atherosclerotic plaque development and expression of important pro- and antiinflammatory mediators during progression of atherosclerosis in ApoE−/− mice. Methods and Results—Expression of proinflammatory cytokines, chemokines, and chemokine receptors within aortic lesions increased during atherogenesis, as detected by real-time quantitative reverse-transcription polymerase chain reaction. In parallel, the number of inflammatory cells within lesions increased together with serum cholesterol and body weight. Interestingly, the majority of inflammatory mediators investigated reached their maximum expression values at 10 weeks of diet, followed by continuous decrease of their expression levels, whereas atherosclerotic plaque size further increased. We show that the expression pattern of these different inflammatory mediators mainly correlates with the amount of inflammatory cells present within the atherosclerotic lesions. Conclusion—Atherosclerosis might result from an imbalance between pro- and antiinflammatory mediators in response to endothelial injury induced by cholesterol-rich diet. These data provide important information on the expression kinetics of inflammatory mediators and point out the possible role of antiinflammatory cells during atherogenesis.

Systemic and Intraplaque Mediators of Inflammation Are Increased in Patients Symptomatic for Ischemic Stroke

Background and Purpose— The concept of “vulnerable plaque” has been extended to the more recent definition of the “cardiovascular vulnerable patient,” in which “intraplaque” and “systemic” factors contribute to the cumulative risk of acute cardiovascular events. Thus, we investigated the possible role of systemic and intraplaque inflammation in patients asymptomatic versus symptomatic for ischemic stroke. Methods— Regions upstream and downstream the blood flow were isolated from internal carotid plaques of patients asymptomatic (n=63) or symptomatic (n=18) for ischemic stroke. Specimens were analyzed for lipid, collagen, macrophage, lymphocyte, neutrophil, mast cell and smooth muscle cell content, and chemokine and cytokine mRNA expression. Chemokine receptors and adhesion molecules were assessed on circulating leukocytes by flow cytometry. Systemic inflammatory markers and biochemical parameters were measured on total blood, plasma, and serum. Results— Tumor necrosis factor-&agr; and CCL5 serum levels as well as intercellular adhesion molecule-1 expression on circulating neutrophils were increased in symptomatic as compared with asymptomatic patients. Collagen content and smooth muscle cell infiltration were decreased in symptomatic plaques. In upstream regions of symptomatic plaques, lipid content and lymphocyte infiltration were increased. In downstream regions of symptomatic plaques, macrophage, neutrophil, and mast cell infiltration were increased. Intraplaque collagen content was positively correlated with smooth muscle cell infiltration and inversely correlated with macrophages, neutrophils, or serum tumor necrosis factor-&agr;. Collagen reduction in downstream regions and serum tumor necrosis factor-&agr; were independently associated with the likelihood of being symptomatic. Conclusions— Inflammatory mediators are increased in ischemic stroke. Despite statistically significant, the correlation between tumor necrosis factor-&agr; serum level and intraplaque vulnerability was weak and probably of limited biological importance.