Impact of interleukin-6 on plaque development and morphology in experimental atherosclerosis

Increased calcification in osteoprotegerin-deficient smooth muscle cells: Dependence on receptor activator of NF-κB ligand and interleukin 6

OBJECTIVE

Vascular calcification is highly correlated with cardiovascular disease morbidity and mortality. Osteoprotegerin (OPG) is a secreted decoy receptor for receptor activator of NF-κB ligand (RANKL). Inactivation of OPG in apolipoprotein E-deficient (ApoE-/-) mice increases lesion size and calcification. The mechanism(s) by which OPG is atheroprotective and anticalcific have not been entirely determined. We investigated whether OPG-deficient vascular smooth muscle cells (VSMCs) are more susceptible to mineralization and whether RANKL mediates this process.

RESULTS

Lesion-free aortas from 12-week-old ApoE-/-OPG-/- mice had spotty calcification, an appearance of osteochondrogenic factors and a decrease of smooth muscle markers when compared to ApoE-/-OPG+/+ aortas. In osteogenic conditions, VSMCs isolated from ApoE-/-OPG-/- (KO-VSMC) mice deposited more calcium than VSMCs isolated from ApoE-/-OPG+/+ (WT-VSMC) mice. Gene expression and biochemical analysis indicated accelerated osteochondrogenic differentiation. Ablation of RANKL signaling in KO-VSMCs rescued the accelerated calcification. While WT-VSMCs did not respond to RANKL treatment, KO-VSMCs responded with enhanced calcification and the upregulation of osteochondrogenic genes. RANKL strongly induced interleukin 6 (IL-6), which partially mediated RANKL-dependent calcification and gene expression in KO-VSMCs.

CONCLUSIONS

OPG inhibits vascular calcification by regulating the procalcific effects of RANKL on VSMCs and is thus a possible target for therapeutic intervention.

Interleukin-6 signal transduction and its role in hepatic lipid metabolic disorders

Hepatic lipid dysregulation can lead to spectrum of metabolic disease conditions including metabolic syndrome (MS), fatty liver and diabetes. Liver lipids are regulated by a complex set of extra-hepatic and intra-hepatic factors including cellular cross-talk with variety of cells, inducing various cytokines. Interleukin 6(IL-6) is a pleiotropic cytokine that exerts both pro-inflammatory and anti-inflammatory effects on hepatic system through either JNK/STAT or ERK/MAPK signaling. Although, IL-6 has shown to protect the liver from fat storage in both rodent and human models and various IL-6(-/-) studies have supported this notion yet a question remains over its deleterious pro-inflammatory effects on hepatocytes. IL-6 ability to produce reactive oxygen species (ROS) and subsequently disturb the hepatic lipid balance has created a conundrum. Furthermore, IL-6 has shown to behave differently under different disease states within hepatocytes and hence, modulating the hepatic lipids accordingly. This review deals with the role of IL-6 on hepatic lipid metabolism and analyzes various data presented on this topic.

Diurnal triglyceridemia in relation to alcohol intake in men

Fasting and postprandial triglyceride concentrations largely depend on dietary and lifestyle factors. Alcohol intake is associated with triglycerides, but the effect of alcohol on diurnal triglyceridemia in a free living situation is unknown. During three days, 139 men (range: 18–80 years) measured their own capillary triglyceride (cTG) concentrations daily on six fixed time-points before and after meals, and the total daily alcohol intake was recorded. The impact of daily alcohol intake (none; low, <10 g/day; moderate, 10–30 g/day; high, >30 g/day) on diurnal triglyceridemia was analyzed by the incremental area under the cTG curve (∆cTG-AUC) reflecting the mean of the six different time-points. Fasting cTG were similar between the alcohol groups, but a trend of increased cTG was observed in men with moderate and high alcohol intake after dinner and at bedtime (p for trend <0.001) which persisted after adjustment for age, smoking and body mass index. The ∆cTG-AUC was significantly lower in males with low alcohol intake (3.0 ± 1.9 mmol·h/L) (n = 27) compared to males with no (7.0 ± 1.8 mmol·h/L) (n = 34), moderate (6.5 ± 1.8 mmol·h/L) (n = 54) or high alcohol intake (7.2 ± 2.2 mmol·h/L) (n = 24), when adjusted for age, smoking and body mass index (adjusted p value < 0.05). In males, low alcohol intake was associated with decreased diurnal triglyceridemia, whereas moderate and high alcohol intake was associated with increased triglycerides after dinner and at bed time.

Overexpression of NF-κB p65 in macrophages ameliorates atherosclerosis in apoE-knockout mice

The transcription factor NF-κB p65 is a key regulator in the regulation of an inflammatory response and in the pathology of atherosclerosis. However, there is no direct evidence for the role of NF-κB in macrophages in the development of atherosclerosis. We investigated whether macrophage overexpression of p65 in apoE-knockout mice could improve atherosclerosis. Transgenic (Tg) mice overexpressing p65 in macrophages were generated by crossing fatty acid-binding protein 4 (aP2) promoter-controlled p65 mice with apoE-knockout (KO) mice. Tg mice exhibited functional activation of NF-κB signaling in macrophages and fat tissues. We observed that the atherosclerotic lesion was 40% less in the Tg mice compared with the apoE-KO controls fed a standard atherogenic diet for 16 wk (n = 12). The Tg mice were leaner from reduced fat mass by increased energy expenditure. Moreover, the overexpression of p65 in macrophages suppressed foam cell formation. Our results show that there is 1) an increased fatty acid oxidation in macrophages, 2) a reduced scavenger receptor CD36 expression and lipid accumulation in microphages, 3) reduced-inflammation cytokines in serum, and 4) enhanced energy expenditure in Tg mice. Our data suggest that activation of NF-κB in macrophages has atheroprotective effects in mice by enhancing lipid metabolism and energy expenditure.

Flavanoids induce expression of the suppressor of cytokine signalling 3 (SOCS3) gene and suppress IL-6-activated signal transducer and activator of transcription 3 (STAT3) activation in vascular endothelial cells

The atherogenic cytokine IL-6 (interleukin-6) induces pro-inflammatory gene expression in VECs (vascular endothelial cells) by activating the JAK (Janus kinase)/STAT3 (signal transducer and activator of transcription 3) signalling pathway, which is normally down-regulated by the STAT3-dependent induction of the E3 ubiquitin ligase component SOCS3 (suppressor of cytokine signalling 3). Novel treatments based on the regulation of SOCS3 protein levels could therefore have value in the treatment of diseases with an inflammatory component, such as atherosclerosis. To this end we carried out a screen of 1031 existing medicinal compounds to identify inducers of SOCS3 gene expression and identified the flavanoids naringenin and flavone as effective inducers of SOCS3 protein, mRNA and promoter activity. This was in contrast with the action of traditional JAK/STAT3 inhibitors and the polyphenol resveratrol, which effectively suppress SOCS3 gene expression. Both naringenin and flavone also effectively suppressed IL-6-stimulated phosphorylation of STAT3 (Tyr⁷⁰⁵) which led to suppression of IL-6-induction of the atherogenic STAT3 target gene MCP1 (monocyte chemotactic protein-1), suggesting that their ability to induce SOCS3 gene expression is STAT3-independent. Supporting this idea was the observation that the general kinase inhibitor compound C inhibits flavone- and cAMP-dependent, but not JAK-dependent, SOCS3 induction in VECs. Indeed, the ability of flavanoids to induce SOCS3 expression requires activation of the ERK (extracellular-signal-regulated kinase)-dependent transcription factor SP3, and not STAT3. In the present paper we therefore describe novel molecular actions of flavanoids, which control SOCS3 gene induction and suppression of STAT3 signalling in VECs. These mechanisms could potentially be exploited to develop novel anti-atherogenic therapies.

Inflammation and immune system interactions in atherosclerosis

Cardiovascular disease (CVD) is the leading cause of mortality worldwide, accounting for 16.7 million deaths each year. The underlying cause of the majority of CVD is atherosclerosis. In the past, atherosclerosis was considered to be the result of passive lipid accumulation in the vessel wall. Today's picture is far more complex. Atherosclerosis is considered a chronic inflammatory disease that results in the formation of plaques in large and mid-sized arteries. Both cells of the innate and the adaptive immune system play a crucial role in its pathogenesis. By transforming immune cells into pro- and anti-inflammatory chemokine- and cytokine-producing units, and by guiding the interactions between the different immune cells, the immune system decisively influences the propensity of a given plaque to rupture and cause clinical symptoms like myocardial infarction and stroke. In this review, we give an overview on the newest insights in the role of different immune cells and subtypes in atherosclerosis.

Systemic treatment with neuropeptide Y receptor Y1-antagonist enhances atherosclerosis and stimulates IL-12 expression in ApoE deficient mice

AIMS

Neuropeptide Y (NPY) and Y1 receptors are involved in the mechanisms related to the development of atherosclerosis. We investigated the effects of systemically given NPY and its receptor Y1-antagonist on the development of atherosclerosis and associated inflammatory molecules in ApoE(-/-) mice during high-fat diet.

METHODS

Five weeks old ApoE(-/-) were fed atherogenic high cholesterol diet for 8weeks. The mice were injected with two doses of NPY (50 or 100μg/kg) or Y1 receptor antagonist BIBP3226 (100μg/kg) or vehicle intraperitoneally for 8weeks. Atherosclerosis lesion areas in aortic arch and descending aortas were determined, inflammatory molecules and NPY were determined in aortic wall, spleen, liver or in serum.

RESULTS

Neuropeptide Y1 receptor antagonist, BIBP3226 (100μg/kg) increased atherosclerotic lesion areas compared to vehicle in descending aortas in ApoE(-/-) mice (p=0.021). The expression levels of macrophage-derived cytokine, interleukin-12 (IL-12) in spleens and livers were 8-fold increased with BIBP3226 (p=0.006 and p=0.003, respectively) as determined by RT-qPCR. Cholesterol levels in serum correlated positively with VCAM-1 expression (p=0.003) and negatively with NPY expression (p=0.044) in aortic wall in mice treated with BIBP 3226.

CONCLUSIONS

The results indicate that systemic treatment with Y1-antagonist enhances atherosclerosis development in ApoE deficient mice by triggering an overwhelming IL-12 production. The findings are highly valuable for evaluation of the development potential of Y1 ligands for therapeutics to treat or prevent atherosclerosis.

Mechanical stretch changes coronary artery fibroblasts function by upregulating HSF1 protein expression

The study is designed to investigate effect of mechanical stretch on the function of fibroblast cells. Human coronary artery fibroblasts were cultured. They were divided into two groups: stretch group (stretch for 24h) and no-stretch group (did not stretch). ELISA analysis was used for detection of collagen secretion. CCK-8 method was used for detection of cells proliferation. RT-PCR method was used for detection of MMP, TIMP, IL-6, alpha-SMA, HSF1 and HSP70 mRNA expression. Western-blotting method was used for detection of HSF1 protein expression. Results showed that cells proliferation in stretch group was stronger than that in no-stretch group. Hydroxyproline secretion in stretch group was more than that in no-stretch group. MMP-9/TIMP, alpha-SMA, IL-6, HSF1 and HSP70 in stretch group was higher than those in no-stretch group. Western-blotting analysis showed that HSF1 protein expression was upregulated in stretch group. It can be concluded that mechanical stretch changed human coronary artery fibroblasts cells proliferation, collagen formation, the secretion of inflammatory factor possibly by upregulating HSF1 protein expression.

Role of suppressor of cytokine signaling-1 in murine atherosclerosis

Background

While the impact of inflammation as the substantial driving force of atherosclerosis has been investigated in detail throughout the years, the influence of negative regulators of pro-atherogenic pathways on plaque development has remained largely unknown. Suppressor of cytokine signaling (SOCS)-1 potently restricts transduction of various inflammatory signals and, thereby modulates T-cell development, macrophage activation and dendritic cell maturation. Its role in atherogenesis, however has not been elucidated so far.

Methods and Results

Loss of SOCS-1 in the low-density lipoprotein receptor deficient murine model of atherosclerosis resulted in a complex, systemic and ultimately lethal inflammation with increased generation of Ly-6C^hi monocytes and activated macrophages. Even short-term exposure of these mice to high-cholesterol dieting caused enhanced atherosclerotic plaque development with accumulation of M1 macrophages, Ly-6C positive cells and neutrophils.

Conclusion

Our data not only imply that SOCS-1 is athero-protective but also emphasize the fundamental, regulatory importance of SOCS-1 in inflammation-prone organisms.

Growth differentiation factor-15 deficiency inhibits atherosclerosis progression by regulating interleukin-6-dependent inflammatory response to vascular injury

BACKGROUND

Growth differentiation factor (GDF)-15 is a distant and divergent member of the transforming growth factor-β superfamily (TGF-β) . There is growing evidence indicating the involvement of GDF-15 in various pathologies. Expression of GDF-15 is induced under conditions of inflammation and increased GDF-15 serum levels are suggested as a risk factor for cardiovascular diseases.

METHODS AND RESULTS

We show here that GDF-15 and proinflammatory cytokine interleukin (IL)-6 levels are highly increased (5-fold) in cultured oxidized low-density lipoproteins-stimulated peritoneal macrophages derived from GDF-15(+/+)/apolipoprotein (apo) E(-/-), mice. Notably, IL-6 induction on oxidized low-density lipoproteins stimulation is completely abolished in the absence of GDF-15. Consistent with our in vitro data GDF-15 mRNA expression and protein levels are upregulated (2.5- to 6-fold) in the atherosclerotic vessel wall of GDF-15(+/+)/apoE(-/-) mice after a cholesterol-enriched diet. GDF-15 deficiency inhibits lumen stenosis (52%) and (18)FDG uptake (34%) in the aortic arch despite increased serum triglyceride/cholesterol levels and elevated body weight. Immunohistomorphometric investigations of atherosclerotic lesions reveal a decreased percentage of inflammatory CD11b(+) (57%) or IL-6(+), leukocytes, and apoptotic cells (74%) after 20 weeks. However, the total number of macrophages and cell density in atherosclerotic lesions of the innominate artery are increased in GDF-15(-/-)/apoE(-/-) mice.

CONCLUSIONS

Our data suggest that GDF-15 is involved in orchestrating atherosclerotic lesion progression by regulating apoptotic cell death and IL-6-dependent inflammatory responses to vascular injury.

Relationship between biomarkers and subsequent clinical and angiographic restenosis after paclitaxel-eluting stents for treatment of STEMI: a HORIZONS-AMI substudy

Drug-eluting stents (DES) reduce the incidence of in-stent restenosis (ISR) after primary percutaneous coronary intervention (PCI) for ST-elevation myocardial infarction (STEMI). Whether the use of biomarkers might be of utility to identify patients who remain at risk for DES ISR after primary PCI has never been examined. A total of 26 biomarkers were measured at enrollment and 30 days and analyzed at a central core laboratory in 501 STEMI patients from the HORIZONS-AMI trial. All patients underwent primary PCI with the TAXUS paclitaxel-eluting stent (PES), were scheduled for routine angiographic follow-up at 13 months, and were followed for 3 years. Mean in-stent late-loss was 0.28 ± 0.57 mm, and target lesion revascularization (TLR) at 3 years occurred in 9.1 % of patients. Low levels of interleukin-6 (IL-6) and placental growth factor (PLGF) at admission were associated with both higher in-stent late loss and ischemia-driven TLR. Additionally, low admission levels of cardiotrophin-1 (CT-1) were associated with higher rates of ischemia-driven TLR. At 30-day follow-up lower values of IL-1ra (IL-1ra), matrix metalloproteinase 9 (MMP9), and myeloperoxidase (MPO), and a decline relative to admission in IL-1ra, monocyte chemotactic protein-1 (MCP-1), and MMP9 were associated with higher in-stent late loss. Low values of IL-6 at 30 days were also associated with ischemia-driven TLR. After multivariate adjustment, only MPO at 30 days and a decline of MCP-1 between admission and 30 days were associated with in-stent late loss, and only CT-1 was associated with TLR. MPO at 30 days and a decline of MCP-1 between admission and 30 days were independently associated with in-stent late loss, and CT-1 was associated with TLR. Additional studies to confirm and validate the utility of these biomarkers are warranted.

Pro- and Anti-Inflammatory Cytokine Networks in Atherosclerosis

Despite advances in prevention and treatment, atherosclerotic vascular disease continues to account for significant morbidity, mortality, and economic burden in the western world. Our current understanding of this disease presents atherosclerosis as a chronic inflammatory process involving multiple cell types in various stages of activation, apoptosis, and necrosis. These cells include monocyte/macrophage, dendritic cells, lymphocytes, endothelial cells, and vascular smooth muscle cells. Activation of these cells and their processes is initiated and sustained by a complex network of soluble factors termed cytokines. Cytokines are produced and recognized by both inflammatory and resident vascular cells, allowing crosstalk between these two systems. Cytokines also regulate the phenotype of many of these cell types. Recognizing functions of these cytokines and their effects on cells which populate atherosclerotic plaque is key to uncovering targets of therapeutic intervention. This paper will present recent studies which describe the cellular protagonists of atherosclerosis and the role they play in formation of atherosclerotic plaque. It will also describe the cytokines which have been identified as produced by and directly affecting dysfunction of these cells. Because atherosclerosis is considered an inflammatory condition, emphasis will be placed on inflammatory cytokines and their effects on atherogenesis. We will conclude with new directions in therapeutic strategies and points of emphasis for future research.

The role of cytokines in cardiovascular disease in menopause

Various studies suggest that increased levels of pro-inflammatory cytokines play a key role in the declining ovarian function and the resulting complications associated with menopause. In this review article, the authors outline the role of pro- and anti-inflammatory cytokines in cardiovascular disease during menopause.

Genetic basis of atherosclerosis: insights from mice and humans

Atherosclerosis is a complex and heritable disease involving multiple cell types and the interactions of many different molecular pathways. The genetic and molecular mechanisms of atherosclerosis have, in part, been elucidated by mouse models; at least 100 different genes have been shown to influence atherosclerosis in mice. Importantly, unbiased genome-wide association studies have recently identified a number of novel loci robustly associated with atherosclerotic coronary artery disease. Here, we review the genetic data elucidated from mouse models of atherosclerosis, as well as significant associations for human coronary artery disease. Furthermore, we discuss in greater detail some of these novel human coronary artery disease loci. The combination of mouse and human genetics has the potential to identify and validate novel genes that influence atherosclerosis, some of which may be candidates for new therapeutic approaches.

Circulating levels of resistin, IL-6 and lipid profile in elderly patients with ischemic heart disease with and without diabetes

Background: The cytokines that act as inflammatory hormones show a role in coronary atherosclerotic disease. Aims: This study aimed to measure serum resistin, IL-6 levels and lipid profile in nondiabetic controls, diabetics, and ischemic heart disease subjects with and without diabetes. Association between resistin and IL-6 was also determined. Materials & methods: In this comparative cross-sectional study, 147 subjects were selected, aged between 40 and 70 years. Subjects were divided into four groups as mentioned above. Plasma glucose was measured using the gluco-oxidase method. Lipid profile levels were measured using standard enzymatic methods. Levels of resistin and IL-6 were determined by ELISA. Results: Out of 147 patients, 36 were controls and 111 were cases. Serum resistin and IL-6 levels increased significantly in diabetics (23.4 ± 0.74 ng/ml and 73.1 ± 2.57 ng/ml, respectively) and nondiabetics with ischemic heart disease (14.1 ± 0.51 ng/ml and 66.2 ± 2.08 ng/ml, respectively) compared with diabetics and nondiabetic controls. Positive correlations were found between IL-6 and resistin, and a significant positive correlation was shown in ischemic heart disease groups (r = 0.659; p = 0.001). Conclusion: This study shows that the plasma resistin and IL-6 concentrations increased significantly in patients with ischemic heart disease with and without diabetes. This shows that there is a possible role of resistin and IL-6 in inflammatory processes, especially in atherosclerosis.

Association of interleukin-6 circulating levels with coronary artery disease: a meta-analysis implementing mendelian randomization approach

BACKGROUND

We aim to investigate whether the association between circulating interleukin 6 (IL-6) levels and the risk for coronary artery disease (CAD) is robust and perhaps even causal by a meta-analysis implementing mendelian randomization approach with IL-6 gene G-174C polymorphism as an instrument.

METHODS

Data were available from 19 articles encompassing 9417 CAD patients and 15982 controls. A random effects model was applied irrespectively of between-study heterogeneity, and publication bias was examined using a funnel plot and the corresponding statistics.

RESULTS

Overall, comparison of IL-6 gene alleles -174C with -174G had 4% increased risk for CAD (95% confidence interval [95% CI]: 0.97-1.10; P=0.285), accompanying marginal heterogeneity (I(2)=38.3%; P=0.033). This association was potentiated in dominant model as odds ratio (OR) reached 1.08 (95% CI: 0.96-1.22; P=0.204) and heterogeneity was significant (I(2)=58.4%; P<0.0005). Subgroup analysis by ethnicity indicated that carriers of -174C allele were associated with a 12% increased risk for CAD in prospective studies involving White populations (OR=1.12; 95% CI: 0.95-1.33; P=0.184), whereas the association in East Asians was remarkably reversed with 37-46% reduced risk. Relative to -174GG homozygotes, carriers of -174C allele had an overall 0.24 pg/ml high circulating IL-6 levels (P=0.047). The predicted OR for 1 pg/ml elevation in IL-6 levels was 1.60 (95% CI: 1.44-1.72; P<0.01) in prospective studies involving White populations. Publication biases were absent for all comparisons (P>0.1).

CONCLUSION

Our findings provided strong evidence on the causal association of circulating IL-6 levels with the development of CAD in White populations.

Social disruption stress increases IL-6 levels and accelerates atherosclerosis in ApoE-/- mice

INTRODUCTION

We have previously shown that different forms of stress have distinctive effects on atherogenesis in mice. We showed that social stress increase atherosclerosis in ApoE(-/-) mice, while more physical forms of stress do not. Here we evaluated the effect of social disruption (SDR) stress on atherogenesis and evaluated cytokine release after SDR-stress and five more physical stressors.

METHODS

Male ApoE(-/-) mice were exposed to SDR-stress during 12 weeks, and atherosclerotic plaque area was assessed in aorta, aortic root and innominate artery. Further, male C57BL/6 mice were exposed to SDR-stress or five physical stressors, and cytokine and corticosterone levels were analyzed in plasma/serum samples immediately after stress.

RESULTS

We found a correlation between the level of SDR-stress and atherosclerotic plaque area in aorta and a numerical increased plaque area in aortic root. SDR stress did not affect histological features of plaque composition. However, SDR-stress increased levels of corticosterone, IL-6 and CXCL1. Plasma corticosterone increased for all five physical stressors, but IL-6 and CXCL1 only increased in the group exposed to restraint combined with rat odor.

CONCLUSIONS

These findings suggest that SDR-stress is indeed atherogenic, in contrast to our previous results using the physical stressors. A possible explanation to this difference is that SDR-stress, but not physical stressors, leads to release of the pro-inflammatory cytokines IL-6 and CXCL1.

Bone marrow-specific deficiency of nuclear receptor Nur77 enhances atherosclerosis

RATIONALE

Nuclear receptor Nur77, also known as NR4A1, TR3, or NGFI-B, is expressed in human atherosclerotic lesions in macrophages, endothelial cells, T cells and smooth muscle cells. Macrophages play a critical role in atherosclerosis and the function of Nur77 in lesion macrophages has not yet been investigated.

OBJECTIVE

This study aims to delineate the function of Nur77 in macrophages and to assess the effect of bone marrow-specific deficiency of Nur77 on atherosclerosis.

METHODS AND RESULTS

We investigated Nur77 in macrophage polarization using bone marrow-derived macrophages (BMM) from wild-type and Nur77-knockout (Nur77(-/-)) mice. Nur77(-/-) BMM exhibit changed expression of M2-specific markers and an inflammatory M1-phenotype with enhanced expression of interleukin-12, IFNγ, and SDF-1α and increased NO synthesis in (non)-stimulated Nur77(-/-) BMM cells. SDF-1α expression in nonstimulated Nur77(-/-) BMM is repressed by Nur77 and the chemoattractive activity of Nur77(-/-) BMM is abolished by SDF-1α inhibiting antibodies. Furthermore, Nur77(-/-) mice show enhanced thioglycollate-elicited migration of macrophages and B cells. The effect of bone marrow-specific deficiency of Nur77 on atherosclerosis was studied in low density lipoprotein receptor-deficient (Ldlr(-/-)) mice. Ldlr(-/-) mice with a Nur77(-/-)-deficient bone marrow transplant developed 2.1-fold larger atherosclerotic lesions than wild-type bone marrow-transplanted mice. These lesions contain more macrophages, T cells, smooth muscle cells and larger necrotic cores. SDF-1α expression is higher in lesions of Nur77(-/-)-transplanted mice, which may explain the observed aggravation of lesion formation.

CONCLUSIONS

In conclusion, in bone marrow-derived cells the nuclear receptor Nur77 has an anti-inflammatory function, represses SDF-1α expression and inhibits atherosclerosis.

Transsignaling of interleukin-6 crucially contributes to atherosclerosis in mice

OBJECTIVE

Transsignaling of interleukin (IL)-6 is a central pathway in the pathogenesis of disorders associated with chronic inflammation, such as Crohn disease, rheumatoid arthritis, and inflammatory colon cancer. Notably, IL-6 also represents an independent risk factor for coronary artery disease (CAD) in humans and is crucially involved in vascular inflammatory processes.

METHODS AND RESULTS

In the present study, we showed that treatment with a fusion protein of the natural IL-6 transsignaling inhibitor soluble glycoprotein 130 (sgp130) and IgG1-Fc (sgp130Fc) dramatically reduced atherosclerosis in hypercholesterolemic Ldlr(-/-) mice without affecting weight gain and serum lipid levels. Moreover, sgp130Fc treatment even led to a significant regression of advanced atherosclerosis. Mechanistically, endothelial activation and intimal smooth muscle cell infiltration were decreased in sgp130Fc-treated mice, resulting in a marked reduction of monocyte recruitment and subsequent atherosclerotic plaque progression. Of note, patients with CAD exhibited significantly lower plasma levels of endogenous sgp130, suggesting that a compromised counterbalancing of IL-6 transsignaling may contribute to atherogenesis in humans.

CONCLUSIONS

These data clarify, for the first time, the critical involvement of, in particular, the transsignaling of IL-6 in CAD and warrant further investigation of sgp130Fc as a novel therapeutic for the treatment of CAD and related diseases.

Identification of a danger-associated peptide from apolipoprotein B100 (ApoBDS-1) that triggers innate proatherogenic responses

BACKGROUND

Subendothelial deposited low-density lipoprotein particles are a known inflammatory factor in atherosclerosis. However, the causal components derived from low-density lipoprotein are still poorly defined. Apolipoprotein B100 (ApoB100) is the unexchangeable protein component of low-density lipoprotein, and the progression of atherosclerosis is associated with immune responses to ApoB100-derived peptides. In this study, we analyzed the proinflammatory activity of ApoB100 peptides in atherosclerosis.

METHODS AND RESULTS

By screening a peptide library of ApoB100, we identified a distinct native peptide referred to as ApoB100 danger-associated signal 1 (ApoBDS-1), which shows sequence-specific bioactivity in stimulation of interleukin-8, CCL2, and interleukin-6. ApoBDS-1 activates mitogen-activated protein kinase and calcium signaling, thereby effecting the expression of interleukin-8 in innate immune cells. Ex vivo stimulation of carotid plaques with ApoBDS-1 enhances interleukin-8 and prostaglandin E₂ release. Furthermore, we demonstrated that ApoBDS-1-positive peptide fragments are present in atherosclerotic lesions using immunoassays and that low-molecular-weight fractions isolated from plaque show ApoBDS-1 activity inducing interleukin-8 production.

CONCLUSIONS

Our data show that ApoBDS-1 is a previously unrecognized peptide with robust proinflammatory activity, contributing to the disease-promoting effects of low-density lipoprotein in the pathogenesis of atherosclerosis.

The problem of accelerated atherosclerosis in systemic lupus erythematosus: insights into a complex co-morbidity

Rheumatic autoimmune diseases, such as rheumatoid arthritis and systemic lupus erythematosus (SLE), are associated with antibodies to "self" antigens. Persons with autoimmune diseases, most notably SLE, are at increased risk for developing accelerated cardiovascular disease. The link between immune and inflammatory responses in the pathogenesis of cardiovascular disease has been firmly established; yet, despite our increasing knowledge, accelerated atherosclerosis continues to be a significant co-morbidity and cause of mortality in SLE. Recent animal models have been generated in order to identify mechanism(s) behind SLE-accelerated atherosclerosis. In addition, clinical studies have been designed to examine potential treatments options. This review will highlight data from recent studies of immunity in SLE and atherosclerosis and discuss the potential implications of these investigations.

Statins potently reduce the cytokine-mediated IL-6 release in SMC/MNC cocultures

Inflammatory pathways are involved in the development of atherosclerosis. Interaction of vessel wall cells and invading monocytes by cytokines may trigger local inflammatory processes. 3-Hydroxy-3-methylglutaryl coenzyme A reductase inhibitors (statins) are standard medications used in cardiovascular diseases. They are thought to have anti-inflammatory capacities, in addition to their lipid-lowering effects. We investigated the anti-inflammatory effect of statins in the cytokine-mediated-interaction-model of human vascular smooth muscle cells (SMC) and human mononuclear cells (MNC). In this atherosclerosis-related inflammatory model LPS (lipopolysaccharide, endotoxin), as well as high mobility group box 1 stimulation resulted in synergistic (i.e. over-additive) IL-6 (interleukin-6) production as measured in ELISA. Recombinant IL-1, tumour necrosis factor-α and IL-6 mediated the synergistic IL-6 production. The standard anti-inflammatory drugs aspirin and indomethacin (Indo) reduced the synergistic IL-6 production by 60%. Simvastatin, atorvastatin, fluvastatin or pravastatin reduced the IL-6 production by 53%, 50%, 64% and 60%, respectively. The inhibition by the statins was dose dependent. Combination of statins with aspirin and/or Indo resulted in complete inhibition of the synergistic IL-6 production. The same inhibitors blocked STAT3 phosphorylation, providing evidence for an autocrine role of IL-6 in the synergism. MNC from volunteers after 5 day aspirin or simvastatin administration showed no decreased IL-6 production, probably due to drug removal during MNC isolation. Taken together, the data show that anti-inflammatory functions (here shown for statins) can be sensitively and reproducibly determined in this novel SMC/MNC coculture model. These data implicate that statins have the capacity to affect atherosclerosis by regulating cytokine-mediated innate inflammatory pathways in the vessel wall.

Increased expression of endothelial lipase in symptomatic and unstable carotid plaques

The aim of this study was to evaluate endothelial lipase (EL) protein expression in advanced human carotid artery plaques (HCAP) with regard to plaque (in)stability and the incidence of symptoms. HCAP were collected from 66 patients undergoing carotid endarterectomy (CEA). The degree of plaque (in)stability was estimated by ultrasound and histology. In HCAP sections, EL expression was determined by immunostaining and the intensity was assessed on a semi-quantitative scale (low: <25%, high: >25% positive cells). Monocytes and macrophages in adjacent HCAP sections were stained with a CD163 specific antibody. High EL staining was more prevalent in histologically unstable plaques (in 33.3% of fibrous plaques, 50% of ulcerated non-complicated plaques and 79.2% of ulcerated complicated plaques; χ² test, p = 0.004) and in the symptomatic group (70.8 vs. 42.9% in the asymptomatic group; χ² test, p = 0.028). The majority of EL immunostaining was found in those HCAP regions exhibiting a strong CD163 immunostaining. EL in HCAP might be a marker and/or promoter of plaque instability and HCAP-related symptomatology.

How dendritic cells shape atherosclerosis

Atherosclerosis is an inflammatory disease of the arteries, which results in major morbidity and mortality. Immune cells initiate and sustain local inflammation. Here, we focus on how dendritic cell (DC)-mediated processes might be relevant to atherosclerosis. Although only small numbers of DCs are detected in healthy arteries, these numbers dramatically increase during atherosclerosis development. In the earliest fatty streaks, DCs are found next to the vascular endothelium. During plaque growth, new DCs are actively recruited, and their egress from the vessel wall is dampened. In the adventitia next to mature atherosclerotic lesions, tertiary lymphoid organs develop, which also contain DCs. Thus, DCs probably participate in all stages of atherosclerosis from fatty streaks to mature lesions.

STAT1 as a novel therapeutical target in pro-atherogenic signal integration of IFNγ, TLR4 and IL-6 in vascular disease

Inflammation participates importantly in host defenses against infectious agents and injury, but it also contributes to the pathophysiology of atherosclerosis. Recruitment of blood leukocytes to the injured vascular endothelium characterizes the initiation and progression of atherosclerosis and involves many inflammatory mediators, modulated by cells of both innate and adaptive immunity. The pro-inflammatory cytokine, interferon (IFN)-γ derived from T cells, is vital for both innate and adaptive immunity and is also expressed at high levels in atherosclerotic lesions. As such IFN-γ plays a crucial role in the pathology of atherosclerosis through activation of signal transducer and activator of transcription (STAT) 1. Toll-like receptors (TLRs) are innate immune pattern recognition receptors (PRRs) expressed on a variety of cells, and thus initiate and sustain the inflammatory response in atherosclerosis. More recent studies have revealed that STAT1 is involved in the signaling events mediated by TLR4, leading to increased expression of several pro-inflammatory and pro-atherogenic mediators. By upregulating members of the Suppressors Of Cytokine Signaling (SOCS) family that regulate cellular responsiveness to immune signals, IFNγ and TLR4-activated pathways have also shown to inhibit IL-6 STAT3-dependent anti-inflammatory signaling and potentially shift IL-6 to a STAT1 activating pro-inflammatory cytokine. Consequently, STAT1 has been identified as a point of convergence for the cross-talk between the pro-atherogenic IFN-γ, TLR4 and IL-6 activated pathways in immune as well as vascular cells, as such amplifying pro-inflammatory signals. This results in augmented smooth muscle cell (SMC) and leukocyte migration, leukocyte to endothelial cell (EC) adhesion and foam cell formation, and could encompass a novel mechanism involved in the initiation and progression of atherosclerosis. Therefore, application of small inhibitory compounds that specifically interact with the SH2-phosphotyrosine pocket of STAT1, proposed here as a novel working mechanism for the known STAT1 inhibitor fludarabine, could be a promising tool in the development of a therapeutical strategy for atherosclerosis.

Interleukin-6 protects human macrophages from cellular cholesterol accumulation and attenuates the proinflammatory response

Cholesterol-laden monocyte-derived macrophages are phagocytic cells characteristic of early and advanced atherosclerotic lesions. Interleukin-6 (IL-6) is a macrophage secretory product that is abundantly expressed in atherosclerotic plaques but whose precise role in atherogenesis is unclear. The capacity of macrophages to clear apoptotic cells, through the efferocytosis mechanism, as well as to reduce cellular cholesterol accumulation contributes to prevent plaque progression and instability. By virtue of its capacity to promote cellular cholesterol efflux from phagocyte-macrophages, ABCA1 was reported to reduce atherosclerosis. We demonstrated that lipid loading in human macrophages was accompanied by a strong increase of IL-6 secretion. Interestingly, IL-6 markedly induced ABCA1 expression and enhanced ABCA1-mediated cholesterol efflux from human macrophages to apoAI. Stimulation of ABCA1-mediated cholesterol efflux by IL-6 was, however, abolished by selective inhibition of the Jak-2/Stat3 signaling pathway. In addition, we observed that the expression of molecules described to promote efferocytosis, i.e. c-mer proto-oncogene-tyrosine kinase, thrombospondin-1, and transglutaminase 2, was significantly induced in human macrophages upon treatment with IL-6. Consistent with these findings, IL-6 enhanced the capacity of human macrophages to phagocytose apoptotic cells; moreover, we observed that IL-6 stimulates the ABCA1-mediated efflux of cholesterol derived from the ingestion of free cholesterol-loaded apoptotic macrophages. Finally, the treatment of human macrophages with IL-6 led to the establishment of an anti-inflammatory cytokine profile, characterized by an increased secretion of IL-4 and IL-10 together with a decrease of that of IL-1β. Taken together, our results indicate that IL-6 favors the elimination of excess cholesterol in human macrophages and phagocytes by stimulation of ABCA1-mediated cellular free cholesterol efflux and attenuates the macrophage proinflammatory phenotype. Thus, high amounts of IL-6 secreted by lipid laden human macrophages may constitute a protective response from macrophages to prevent accumulation of cytotoxic-free cholesterol. Such a cellular recycling of free cholesterol may contribute to reduce both foam cell formation and the accumulation of apoptotic bodies as well as intraplaque inflammation in atherosclerotic lesions.

Recent advances on the role of cytokines in atherosclerosis

Atherosclerosis is a chronic inflammatory disease of the arterial wall driven by innate and adaptive immune responses. Inflammation controls the development and the destabilization of arterial plaque. 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 have provided evidence for a dual role of cytokines: proinflammatory and T helper-1-related cytokines promote the development and progression of the disease, whereas antiinflammatory and regulatory T cell-related cytokines exert clear antiatherogenic activities. This review focuses on recent advances regarding the role of cytokines, with the exception of chemokines, in the development, progression, and complications of atherosclerosis.

Hematopoietic Fas deficiency does not affect experimental atherosclerotic lesion formation despite inducing a proatherogenic state

The Fas death receptor (CD95) is expressed on macrophages, smooth muscle cells, and T cells within atherosclerotic lesions. Given the dual roles of Fas in both apoptotic and nonapoptotic signaling, the aim of the present study was to test the effect of hematopoietic Fas deficiency on experimental atherosclerosis in low-density lipoprotein receptor-null mice (Ldlr(-/-)). Bone marrow from Fas(-/-) mice was used to reconstitute irradiated Ldlr(-/-) mice as a model for atherosclerosis. After 16 weeks on an 0.5% cholesterol diet, no differences were noted in brachiocephalic artery lesion size, cellularity, or vessel wall apoptosis. However, Ldlr(-/-) mice reconstituted with Fas(-/-) hematopoietic cells had elevated hyperlipidemia [80% increase, relative to wild-type (WT) controls; P < 0.001] and showed marked elevation of plasma levels of CXCL1/KC, CCL2/MCP-1, IL-6, IL-10, IL-12 subunit p70, and soluble Fas ligand (P < 0.01), as well as systemic microvascular inflammation. It was not possible to assess later stages of atherosclerosis because of increased mortality in Fas(-/-) bone marrow recipients. Our data indicate that hematopoietic Fas deficiency does not affect early atherosclerotic lesion development in Ldlr(-/-) mice.

The metabolic syndrome: the crossroads between rheumatoid arthritis and cardiovascular risk

Rheumatoid arthritis (RA) patients have an incidence of cardiovascular (CV) diseases at least two times higher than the general population. Atherosclerosis, the main determinant of CV morbidity and mortality, and carotid intima-media thickness, an early preclinical marker of atherosclerosis, also occur early on in RA. Traditional CV risk factors seem to have the same prevalence in RA and non-RA patients, and thus do not fully explain the increased CV burden, suggesting that RA inflammation and therapies play a role in increasing CV risk in these patients. The metabolic syndrome and fat tissue are likely to be the major players in this complex network. The metabolic syndrome (MetS) represents a cluster of cardiovascular risk factors that have in common insulin resistance and increased visceral adiposity. This entity has received great attention in the last few years due to its contribution to the burden of cardiovascular morbidity and mortality. Moreover, recently the adipose tissue has emerged as a dynamic organ that releases several inflammatory and immune mediators (adipokines). The association of MetS and atherosclerosis is thought to be partly mediated by altered secretion of adipokines by the adipose tissue and, on the other hand, there are evidence that adipokines may play some role in inflammatory arthritides. Obesity is now regarded as a systemic, low-grade inflammatory state, and inflammation as a link between obesity, metabolic syndrome, and cardiovascular diseases. To obtain a full control of the CV risk, data suggest that it is therefore mandatory a "tight control" of both RA and MetS inflammations.

Diet-induced aortic valve disease in mice haploinsufficient for the Notch pathway effector RBPJK/CSL

OBJECTIVE

Calcific aortic valve disease is similar to atherosclerosis in that both diseases result from chronic inflammation and endothelial dysfunction. Heterozygous NOTCH1 mutations have been associated to calcific aortic disease and a bicuspid aortic valve. We investigated whether mice with genetic inactivation of the Notch signaling pathway are prone to develop valve disease when exposed to a predisposing diet.

METHODS AND RESULTS

Using Doppler echocardiography, histology, immunohistochemistry, quantitative gene expression analysis, and cell culture assays, we examined the effect of a hypercholesterolemic diet supplemented with vitamin D on mice heterozygous for null mutations in the Notch1 receptor or the effector transcription factor gene RBPJk. After 16 weeks on the hyperlipidemic diet, calcific aortic disease was detected in heterozygous RBPJk mice. Analysis of valve leaflets revealed macrophage infiltration, enhanced collagen deposition, proosteogenic protein expression, and calcification. Heterozygous null Notch1 mice displayed milder histopathologic changes and did not develop any significant hemodynamic disturbance. Valvular disease correlated with reduced expression of the Notch target gene Hey1 in valves of RBPJk heterozygous mice fed the hyperlipidemic diet. Consistent with the in vivo data, Notch signaling inhibition in porcine valve interstitial cells led to downregulation of HEY1 transcription, activation of osteogenic markers, and increased calcified nodule formation.

CONCLUSIONS

We show that Notch signaling disruption via RBPJk heterozygous inactivation results in aortic valve disease. Notch1 heterozygous mice do not show functional impairment, suggesting that additional Notch receptors may be involved in aortic valve homeostasis and disease. Our data establish a genetic mouse model of calcific aortic valve disease and may help to identify a patient population with reduced valvular NOTCH signaling at risk for developing this disease.

Contribution of vascular cell-derived cytokines to innate and inflammatory pathways in atherogenesis

Inflammation is a central element of atherogenesis. Innate pathways contribute to vascular inflammation. However, the initial molecular process(es) starting atherogenesis remain elusive. The various risk factors, represented by particular compounds (activators), may cause altered cellular functions in the endothelium (e.g. vascular endothelial cell activation or -dysfunction), in invading cells (e.g. inflammatory mediator production) or in local vessel wall cells (e.g. inflammatory mediators, migration), thereby triggering the innate inflammatory process. The cellular components of innate immunology include granulocytes, natural killer cells and monocytes. Among the molecular innate constituents are innate molecules, such as the toll-like receptors or innate cytokines. Interleukin-1 (IL-1) and IL-6 are among the innate cytokines. Cytokines are potent activators of a great number of cellular functions relevant to maintain or commove homeostasis of the vessel wall. Within the vessel wall, vascular smooth muscle cells (SMCs) can significantly contribute to the cytokine-dependent inflammatory network by: (i) production of cytokines, (ii) response to cytokines and (iii) cytokine-mediated interaction with invading leucocytes. The cytokines IL-1 and IL-6 are involved in SMC-leucocyte interaction. The IL-6 effects are proposed to be mediated by trans-signalling. Dysregulated cellular functions resulting from dysregulated cytokine production may be the cause of cell accumulation, subsequent low-density lipoprotein accumulation and deposition of extracellular matrix (ECM). The deposition of ECM, increased accumulation of leucocytes and altered levels of inflammatory mediators may constitute an 'innate-immunovascular-memory' resulting in an ever-growing response to anew invasion. Thus, SMC-fostered inflammation, promoted by invading innate cells, may be a potent component for development and acceleration of atherosclerosis.

Inhibition of collar-induced carotid atherosclerosis by recombinant apoA-I cysteine mutants in apoE-deficient mice

The previous studies in our laboratory revealed that seven cysteine mutants of apolipoprotein A-I (apoA-I) have different structural features and biological activities in vitro and in vivo. To investigate the potential cardioprotective effects of apolipoprotein A-I(N74C) [apoA-I(N74C)], we examined the anti-inflammatory, antioxidant, and antiatherosclerotic effects of this cysteine mutant in a rapid atherosclerosis model induced by perivascular carotid collar placement in apoE⁻/⁻ mice. Lipid-free apoA-I(N74C) showed a significant increased antioxidant potency in low density lipoprotein (LDL) oxidation in vitro and reduced intracellular lipid accumulation in THP-1-derived macrophages, relative to wild-type apoA-I (apoA-Iwt). Mice injected with recombinant HDL (rHDL) reconstituted with apoA-I(N74C) (named rHDL74) through tail veins (40 mg/kg of body weight, three injections) had a significant lower level of serum interleukin-6 (IL-6) and enhanced serum antioxidation compared with mice receiving rHDL reconstituted with apoA-Iwt (named rHDLwt). Moreover, compared with rHDLwt, the rHDL74 in vivo injection resulted in a significant decrease in plaque size, ratio of aorta intima to media, arterial remodeling, and macrophage content in lesions. In summary, intravenous injection with rHDL74 reconstituted with apoA-I cysteine mutant apoA-I (N74C) dramatically delays the development of atherosclerosis induced by perivascular carotid collar placement and reduces vascular remodeling in the carotid artery in apoE⁻/⁻ mice.

IFNγ-dependent SOCS3 expression inhibits IL-6-induced STAT3 phosphorylation and differentially affects IL-6 mediated transcriptional responses in endothelial cells

IL-6 has pro- and anti-inflammatory effects and is involved in endothelial cell (EC) dysfunction. The anti-inflammatory effects of IL-6 are mediated by signal transducer and activator of transcription-3 (STAT3), which is importantly controlled by suppressor of cytokine signaling 3 (SOCS3). Therefore, cytokines that modulate SOCS3 expression might inhibit the anti-inflammatory effects of IL-6. We hypothesized that in EC, interferon-γ (IFNγ)-induced SOCS3 expression leads to inhibition of IL-6-induced STAT3 activation and IL-6-dependent expression of anti-, but not pro-inflammatory, target genes. IFNγ activated STAT1 and STAT3 and increased SOCS3 expression in EC. IL-6 only activated STAT3 and induced SOCS3 expression. IFNγ pretreatment of EC inhibited IL-6-induced STAT3 activation accompanied by increased SOCS3 protein. Inhibition of SOCS3 expression, using costimulation, Act-D, and small interfering RNA (siRNA), subsequently implicated the importance of IFNγ-induced SOCS3 in this phenomenon. Pretreatment of EC with IFNγ also affected the transcriptional program induced by IL-6. We identified 1) IL-6 anti-inflammatory target genes that were inhibited by IFNγ, 2) IFNγ-target genes of pro-inflammatory nature that were increased in response to IL-6 in the presence of IFNγ, and 3) a set of target genes that were increased upon IL-6 or IFNγ alone, or combined IFNγ and IL-6. In summary, by increasing SOCS3 expression in EC, IFNγ can selectively inhibit STAT3-dependent IL-6 signaling. This in turn leads to decreased expression of some EC protective genes. In contrast, other genes of pro-inflammatory nature are not inhibited or even increased. This IFNγ-induced shift in IL-6 signaling to a pro-inflammatory phenotype could represent a novel mechanism involved in EC dysfunction.

Heparin cofactor II attenuates vascular remodeling in humans and mice

Heparin cofactor II (HCII), a serine protease inhibitor (serpin), inactivates thrombin action in the subendothelial layer of the vascular wall. Because a congenitally HCII-deficient patient has been shown to have multiple atherosclerotic lesions, it is hypothesized that HCII plays a pivotal role in the development of vascular remodeling, including atherosclerosis. To clarify this issue, 3 clinical studies concerning plasma HCII activity and atherosclerosis were carried out, and results demonstrated that a higher incidence of in-stent restenosis after percutaneous coronary intervention, maximum carotid arterial plaque thickness, and prevalence of peripheral arterial disease occurred in subjects with low plasma HCII activity. Furthermore, HCII-deficient mice were generated by a gene targeting method to determine the mechanism of the vascular protective action of HCII. Because HCII(-/-) mice were embryonically lethal, we used HCII(+/-) mice and found that they manifested augmentation of intimal hyperplasia and increased thrombosis after cuff or wire injury to the femoral arteries. HCII(+/-) mice with vascular injury showed augmentation of inflammatory cytokines and chemokines and oxidative stress. These abnormal phenotypes of vascular remodeling observed in HCII(+/-) mice were almost restored by human HCII protein supplementation. HCII protects against vascular remodeling, including atherosclerosis, in both humans and mice, and plasma HCII activity might be a predictive biomarker and novel therapeutic target for the prevention of cardiovascular diseases.

Gax gene transfer inhibits vascular remodeling induced by adventitial inflammation in rabbits

AIMS

Adventitial fibroblasts (AFs) and inflammation play an important role in neointimal formation and vascular remodeling. The present study was aimed to investigate the therapeutic effects and underlying mechanisms of transcriptional regulator Gax gene transfection in aortic remodeling induced by adventitial inflammation.

METHODS AND RESULTS

Fifty rabbits fed a chow diet were randomly divided into a normal control group (n=10) and experimental group (n=40). All rabbits in the experimental group underwent collar placement around the abdominal aorta and intra-collar injection of lipopolysaccharide (LPS) to induce adventitial inflammation and they were further divided into model control group, saline-treated group, green fluorescence protein (Ad-GFP)-treated group and Gax gene (Ad-Gax)-treated group, respectively. Four weeks after treatment, the model control group, saline-treated group and Ad-GFP-treated group showed thickened neointima and adventitia, reduced lumen size and increased eccentricity and remodeling index of the abdominal aorta in comparison with the normal control group, whereas Ad-Gax-treated group exhibited attenuated neointimal formation and vascular remodeling (P<0.01-0.05) .The vascular expression levels of interleukin (IL)-1β, IL-6, IL-8, monocyte chemoattractant protein (MCP)-1, matrix metalloproteinase (MMP)-1, MMP-2, MMP-9, vascular cell adhesion molecule (VCAM)-1 and intercellular adhesion molecule (ICAM)-1, Smads, mitogen-activated protein kinases (MAPKs), integrins and nuclear factor kappa B (NF-kB) were significantly higher in the model control group, saline-treated group and Ad-GFP-treated group than those in the normal control group (P<0.01-0.05). In contrast, the local expression levels of these cytokines were substantially reduced by Ad-Gax gene transfer (P<0.01-0.05). Similarly, the serum levels of inflammatory cytokines including C-reactive protein (CRP), transforming growth factor (TGF)-β1, IL-1, IL-6, IL-8, tumor necrosis factor (TNF)-α, MCP-1, VCAM-1 and ICAM-1 were significantly higher in the model control group, saline-treated group and Ad-GFP-treated group than those of the Ad-Gax-treated group (P<0.01-0.05). In vitro studies showed that Gax overexpression diminished inflammatory cytokine expression in LPS-stimulated arterial fibroblasts.

CONCLUSIONS

Adventitial inflammation induces vascular remodeling via the interactions of multiple inflammatory cytokines and local Gax gene transfer in vivo can significantly inhibit these interactions and thereby attenuate local inflammation and vascular remodeling.

Associations of toenail selenium levels with inflammatory biomarkers of fibrinogen, high-sensitivity c-reactive protein, and interleukin-6: The CARDIA Trace Element Study

The authors examined the associations of toenail selenium levels with blood concentrations of fibrinogen, high-sensitivity C-reactive protein (hs-CRP), and interleukin-6 (IL-6) in an 18-year follow-up study comprising 4,032 Americans aged 20-32 years at baseline (1987) from the Coronary Artery Risk Development in Young Adults (CARDIA) Trace Element Study. Toenail samples were collected in 1987, and selenium concentrations were measured by means of instrumental neutron-activation analysis. Fibrinogen level was analyzed in 1990, 1992, and 2005; hs-CRP was assessed in 1992, 2000, and 2005; and IL-6 was measured in 2005. After adjustment for potential confounders, no statistically significant associations between toenail selenium levels and any of the 3 inflammatory biomarkers were documented. Comparing the highest quintile of toenail selenium level with the lowest, odds ratios for elevated levels of fibrinogen (>460 mg/mL), hs-CRP (>3 microg/mL), and IL-6 (>3.395 pg/mL, 80th percentile) were 1.03 (95% confidence interval (CI): 0.77, 1.38; P for trend = 0.76), 1.02 (95% CI: 0.83, 1.27; P for trend = 0.92), and 0.98 (95% CI: 0.71, 1.36; P for trend = 0.82), respectively. Gender, race/ethnicity, smoking status, and selenium supplementation did not appreciably modify these results. This study found no associations between toenail selenium and inflammation as measured by fibrinogen, hs-CRP, and IL-6.

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.

Percutaneous coronary interventions affect concentrations of interleukin 6 and its soluble receptors in coronary sinus blood in patients with stable angina

Coronary stenting may create local inflammatory reaction. Interleukin 6 effects depend on the presence of soluble receptors (sIL-6R and sgp130) that facilitate or impede interleukin 6 signal transduction. Concentrations of interleukin 6 and its soluble receptors were assessed in aorta and coronary sinus after stenting in optimally treated stable angina patients scheduled for elective stenting. Baseline levels of interleukin 6 and its soluble receptors in patients did not differ from healthy controls. Initial levels of sIL-6R in aorta were significantly higher than in coronary sinus but this difference disappeared after intervention. Stenting caused interleukin 6 concentration increase to a similar extent both in coronary sinus and in aorta. Moreover, there was significantly higher sgp130 concentration in coronary sinus than in aorta. Coronary intervention increases concentration of interleukin 6 in patients with stable angina. It affects the cardiac level of interleukin 6 soluble receptors what may influence the local inflammatory reaction.

Immune and inflammatory mechanisms of atherosclerosis (*)

Atherosclerosis is an inflammatory disease of the wall of large- and medium-sized arteries that is precipitated by elevated levels of low-density lipoprotein (LDL) cholesterol in the blood. Although dendritic cells (DCs) and lymphocytes are found in the adventitia of normal arteries, their number is greatly expanded and their distribution changed in human and mouse atherosclerotic arteries. Macrophages, DCs, foam cells, lymphocytes, and other inflammatory cells are found in the intimal atherosclerotic lesions. Beneath these lesions, adventitial leukocytes organize in clusters that resemble tertiary lymphoid tissues. Experimental interventions can reduce the number of available blood monocytes, from which macrophages and most DCs and foam cells are derived, and reduce atherosclerotic lesion burden without altering blood lipids. Under proatherogenic conditions, nitric oxide production from endothelial cells is reduced and the burden of reactive oxygen species (ROS) and advanced glycation end products (AGE) is increased. Incapacitating ROS-generating NADPH oxidase or the receptor for AGE (RAGE) has beneficial effects. Targeting inflammatory adhesion molecules also reduces atherosclerosis. Conversely, removing or blocking IL-10 or TGF-beta accelerates atherosclerosis. Regulatory T cells and B1 cells secreting natural antibodies are atheroprotective. This review summarizes our current understanding of inflammatory and immune mechanisms in atherosclerosis.

Resveratrol attenuates angiotensin II-induced interleukin-6 expression and perivascular fibrosis

Recent studies have shown that resveratrol (3,5,4'-trihydroxystilbene), a polyphenolic compound found in grapes and red wine, has various beneficial effects on cardiovascular diseases and prolongs the life span of mice fed a high-fat diet. We hypothesized that resveratrol may attenuate vascular inflammatory response induced by angiotensin (Ang) II. We examined the effect of resveratrol on Ang II-induced interleukin (IL)-6 expression in vascular smooth muscle cells (VSMCs). Resveratrol significantly attenuated Ang II-induced IL-6 mRNA expression and IL-6 protein in the supernatant of VSMC in a dose-dependent manner. Resveratrol suppressed the IL-6 gene promoter activity. Resveratrol inhibited the Ang II-induced cAMP-response element-binding protein and nuclear factor-kappa B activity, which are critical for Ang II-induced IL-6 gene activation. An increase in the serum concentration of IL-6 induced by Ang II infusion was attenuated by an oral administration of resveratrol. Resveratrol also inhibited Ang II-induced hypertension and perivascular fibrosis of the heart. Although hydralazine reduced blood pressure level equal to resveratrol, it did not reduce the Ang II-induced IL-6 production and perivascular fibrosis. These data suggest that the inhibition of Ang II-induced vascular inflammation and high blood pressure by resveratrol may contribute, at least in part, to the anti-atherogenic effects of resveratrol.

Coronary sinus concentrations of interleukin 6 and its soluble receptors are affected by reperfusion and may portend complications in patients with myocardial infarction

Interleukin 6 (IL-6) is a pleiotropic cytokine involved in both inflammatory reaction and myocardial response to stress. Its effects largely depend on the concentration of the soluble receptors (sIL-6R and sgp130). We investigated the production of IL-6, sIL-6R and sgp130 by the heart during ischemia and reperfusion.

METHODS

The levels of IL-6 were determined in blood of 34 patients with first myocardial infarction (STEMI), left anterior descending (LAD) artery occlusion, otherwise normal coronaries, without significant co-morbidities and 16 comparable subjects with stable ischemic heart disease and lesion in LAD. Blood samples from coronary sinus (CS) and aorta (Ao) were drawn before percutaneous intervention (PCI), immediately after and at the end of the procedure. Venous blood from 30 healthy volunteers served as control.

RESULTS

STEMI patients presented high IL-6 concentrations that increased further after reperfusion when its levels in CS became significantly higher than in Ao. In both groups prior to the PCI there were significantly higher concentrations of sIL-6R in Ao than in CS. This difference disappeared immediately after reperfusion. STEMI patients who experienced cardiovascular complications had higher IL-6 concentration and higher transcardiac sIL-6R gradient than patients with event-free hospitalisation. This association was confirmed in multivariate logistic regression analysis. Myocardial infarction increases concentration of IL-6 that is further elevated by reperfusion. A transcardiac gradient of sIL-6R during ischemia may indicate that large amounts of soluble IL-6 receptors are bound to the infarcted heart and thus affect signal transduction. IL-6 and initial sIL-6R gradient may portend complications in STEMI patients.

Interaction of adipocyte fatty acid-binding protein (AFABP) and JAK2: AFABP/aP2 as a regulator of JAK2 signaling

Adipocyte fatty acid-binding protein (AFABP/aP2) facilitates the intracellular solubilization and trafficking of lipids within the aqueous environment of the cell. Studies in the AFABP/aP2 knock-out mouse suggest that the protein may have roles in cellular processes broader than lipid transport. We present herein the finding that AFABP/aP2 interacts with JAK2 in a fatty acid-dependent manner. This interaction was established using yeast two-hybrid analysis, co-immunoprecipitation from adipose tissue, and 3T3-L1 adipocytes as well as in 293 cells overexpressing JAK2 and AFABP/aP2. Mutational analysis of AFABP/aP2 (R126L/Y128F) revealed that fatty acid binding activity is necessary for the interaction and that Asp(18) of the helix-turn-helix motif forms a component of the interaction domain. Mutational analysis of JAK2 (Y1007F/Y1008F) revealed that AFABP/aP2 associates with the basal unphosphorylated form of the protein. Interleukin-6, but not interleukin-10, stimulated phosphorylation of STAT3, and induction of SOCS3 mRNA expression were potentiated in a time- and dose-dependent manner in macrophage cell lines derived from AFABP/aP2-EFABP/mal1 double knock-out mice relative to cells from wild type animals. These results suggest that ligand-bound AFABP/aP2 binds to and attenuates JAK2 signaling and establishes a new role for AFABP/aP2 as a fatty acid sensor affecting cellular metabolism via protein-protein interactions.

EPAC proteins transduce diverse cellular actions of cAMP

It has now been over 10 years since efforts to completely understand the signalling actions of cAMP (3'-5'-cyclic adenosine monophosphate) led to the discovery of exchange protein directly activated by cAMP (EPAC) proteins. In the current review we will highlight important advances in the understanding of EPAC structure and function and demonstrate that EPAC proteins mediate multiple actions of cAMP in cells, revealing future targets for pharmaceutical intervention. It has been known for some time that drugs that elevate intracellular cAMP levels have proven therapeutic benefit for diseases ranging from depression to inflammation. The challenge now is to determine which of these positive actions of cAMP involve activation of EPAC-regulated signal transduction pathways. EPACs are specific guanine nucleotide exchange factors for the Ras GTPase homologues, Rap1 and Rap2, which they activate independently of the classical routes for cAMP signalling, cyclic nucleotide-gated ion channels and protein kinase A. Rather, EPAC activation is triggered by internal conformational changes induced by direct interaction with cAMP. Leading from this has been the development of EPAC-specific agonists, which has helped to delineate numerous cellular actions of cAMP that rely on subsequent activation of EPAC. These include regulation of exocytosis and the control of cell adhesion, growth, division and differentiation. Recent work also implicates EPAC in the regulation of anti-inflammatory signalling in the vascular endothelium, namely negative regulation of pro-inflammatory cytokine signalling and positive support of barrier function. Further elucidation of these important signalling mechanisms will no doubt support the development of the next generation of anti-inflammatory drugs.