Vascular adhesion molecules in atherosclerosis

Monocyte-endothelial cell interactions in the development of atherosclerosis

The activation of endothelial cells at atherosclerotic lesion-prone sites in the arterial tree results in the up-regulation of cell adhesion molecules and chemokines, which mediate the recruitment of circulating monocytes. Accumulation of monocytes and monocyte-derived phagocytes in the wall of large arteries leads to chronic inflammation and the development and progression of atherosclerosis. This review discusses the nature of these molecules and the mechanisms involved in the early steps of monocyte recruitment into atherosclerotic lesion sites within the vessel wall.

Functional differences between human Cx37 polymorphic hemichannels

A polymorphism in the human Cx37 gene (C1019T), resulting in a non-conservative amino acid change in the regulatory C-terminus of the Cx37 protein (P319S), has been proposed as a prognostic marker for atherosclerosis. We have recently demonstrated that Cx37 hemichannels control the initiation of atherosclerotic plaque development by regulating ATP-dependent monocyte adhesion in atherosclerosis-susceptible apolipoprotein E-deficient mice. In this study, we have measured the electrical properties of Cx37 hemichannels (HCs) and gap junction channels (GJCs) with voltage-clamp methods. To this end, we have transfected hCx37-P319, hCx37-S319 or empty pIRES-eGFP vector cDNA into communication-deficient HeLa cells. In clones expressing similar levels of Cx37, exposure of single cells to low-Ca(2+) solution induced a voltage-sensitive HC current. The analysis yielded a bell-shaped function g(hc)=f(V(m)) (g(hc): normalized conductance at steady state; V(m): membrane potential) with a maximum around V(m)=-30 mV. The peak g(hc) of Cx37-P319 was 3-fold larger than that of Cx37-S319 HCs. Experiments on cell pairs revealed that Cx37-P319 GJCs exhibited a 1.5-fold larger unitary conductance than Cx37-S319 GJCs. Hence, the larger peak g(hc) of the former may reflect a larger conductance of their HCs. Using the same clones, we found that Cx37-P319 cells released more ATP and were less adhesive than Cx37-S319 cells. The reduction in adhesiveness of Cx37-expressing cells was prevented by extracellular apyrase. We conclude that the differences in biophysical properties between polymorphic HCs may be responsible for inequality in ATP release between Cx37-P319 and Cx37-S319 cells, which results in differential cell adhesion.

[Effect of a high glucose load on serum adhesion markers in obese women]

BACKGROUND AND OBJECTIVE

Obesity is associated with endothelial dysfunction and increased inflammation. The expression of adhesion molecules may be influenced by a high glucose load. The aim of the present study was to evaluate serum sICAM-1, sVCAM-1 and sE-selectin concentrations in obese women, and to evaluate the role of high-glucose load on postload circulating levels of sICAM-1, sVCAM-1 and sE-selectin in obese women with normal glucose tolerance.

PATIENTS AND METHODS

A total of 21 obese women (BMI = 37,7 +/- 8,0 kg/m(2)) and 19 lean controls women (BMI = 21,6 +/- 1,9 kg/m(2)) were recruited and serum sICAM-1, sVCAM-1 and sE-selectin levels were measured in fasting state. After an overnight fast, obese (n = 6) and lean women (n = 6) underwent a 2 h - 75 g oral glucose tolerance test. Pre and postglucose load (30, 60, 120 min) sICAM-1, sVCAM-1 and sE-selectin were measured.

RESULTS

Obese women had fasting serum levels of sICAM-1 (p = .03), sVCAM-1 (p < .0001) and sE-selectin (p = .047) higher than those of control women. Serum sICAM-1 and sVCAM-1 levels were positively related to body mass index in the obese group. Serum adhesion molecules levels were no affected by a high glucose load.

CONCLUSION

Serum sICAM-1, sVCAM-1 and sE-selectin levels are increased in obese women. A high glucose load is not associated with an increase in serum adhesion molecules levels.

Surface-bound selectin-ligand binding is regulated by carrier diffusion

Two-dimensional (2D) kinetics of receptor-ligand interactions governs cell adhesion in many biological processes. While the dissociation kinetics of receptor-ligand bond is extensively investigated, the association kinetics has much less been quantified. Recently receptor-ligand interactions between two surfaces were investigated using a thermal fluctuation assay upon biomembrane force probe technique (Chen et al. in Biophys J 94:694-701, 2008). The regulating factors on association kinetics, however, are not well characterized. Here we developed an alternative thermal fluctuation assay using optical trap technique, which enables to visualize consecutive binding-unbinding transition and to quantify the impact of microbead diffusion on receptor-ligand binding. Three selectin constructs (sLs, sPs, and PLE) and their ligand P-selectin glycoprotein ligand 1 were used to conduct the measurements. It was indicated that bond formation was reduced by enhancing the diffusivity of selectin-coupled carrier, suggesting that carrier diffusion is crucial to determine receptor-ligand binding. It was also found that 2D forward rate predicted upon first-order kinetics was in the order of sPs > sLs > PLE and bond formation was history-dependent. These results further the understandings in regulating association kinetics of surface-bound receptor-ligand interactions.

New susceptibility locus for coronary artery disease on chromosome 3q22.3

We present a three-stage analysis of genome-wide SNP data in 1,222 German individuals with myocardial infarction and 1,298 controls, in silico replication in three additional genome-wide datasets of coronary artery disease (CAD) and subsequent replication in approximately 25,000 subjects. We identified one new CAD risk locus on 3q22.3 in MRAS (P = 7.44 x 10(-13); OR = 1.15, 95% CI = 1.11-1.19), and suggestive association with a locus on 12q24.31 near HNF1A-C12orf43 (P = 4.81 x 10(-7); OR = 1.08, 95% CI = 1.05-1.11).

Myeloid cells in atherosclerosis: initiators and decision shapers

Chronic inflammation is the underlying pathophysiological mechanism of atherosclerosis. Prominent suspects being involved in atherosclerosis are lymphocytes, platelets, and endothelial cells. However, recent advances suggest a potent role for myeloid leukocytes, specifically monocyte subsets, polymorphonuclear leukocytes, and mast cells. These three cell types are not just rapidly recruited or already reside in the vascular wall but also initiate and perpetuate core mechanisms in plaque formation and destabilization. Dendritic cell subsets as well as endothelial and smooth muscle progenitor cells may further emerge as important regulators of atheroprogression. To stimulate further investigations about the contribution of these myeloid cells, we highlight the current mechanistic understanding by which these cells tune atherosclerosis.

The monocyte/macrophage as a therapeutic target in atherosclerosis

It is now clear that the monocyte/macrophage has a crucial role in the development of atherosclerosis. This cell appears to be involved in all stages of atherosclerotic plaque development and is increasingly seen as a candidate for therapeutic intervention and as a potential biomarker of disease progression and response to therapy. The main mechanisms related to the activity of the monocyte/macrophage that have been targeted for therapy are those that facilitate recruitment, cholesterol metabolism, inflammatory activity and oxidative stress. There is also increasing evidence that there is heterogeneity within the monocyte/macrophage population, which may have important implications for plaque development and regression. A better insight into how specific phenotypes may influence plaque progression should facilitate the development of novel methods of imaging and more refined treatments.

IL-32-dependent effects of IL-1beta on endothelial cell functions

Increasing evidence demonstrates that interleukin (IL)-32 is a pro-inflammatory cytokine, inducing IL-1alpha, IL-1beta, IL-6, tumor necrosis factor (TNF)-alpha, and chemokines via nuclear factor (NF)-kappaB, p38 mitogen-activated protein kinase (MAPK), and activating protein (AP)-1 activation. Here we report that IL-32 is expressed and is also functional in human vascular endothelial cells (EC) of various origins. Compared with primary blood monocytes, high levels of IL-32 are constitutively produced in human umbilical vein EC (HUVEC), aortic macrovascular EC, and cardiac as well as pulmonary microvascular EC. At concentrations as low as 0.1 ng/ml, IL-1beta stimulated IL-32 up to 15-fold over constitutive levels, whereas 10 ng/ml of TNFalpha or 100 ng/ml of lipopolysaccharide (LPS) were required to induce similar quantities of IL-32. IL-1beta-induced IL-32 was reduced by inhibition of the IkappaB kinase-beta/NF-kappaB and ERK pathways. In addition to IL-1beta, pro-coagulant concentrations of thrombin or fresh platelets increased IL-32 protein up to 6-fold. IL-1beta and thrombin induced an isoform-switch in steady-state mRNA levels from IL-32alpha/gamma to beta/epsilon. Adult EC responded in a similar fashion. To prove functionality, we silenced endogenous IL-32 with siRNA, decreasing intracellular IL-32 protein levels by 86%. The knockdown of IL-32 resulted in reduction of constitutive as well as IL-1beta-induced intercellular adhesion molecule-1 (ICAM-1) (of 55% and 54%, respectively), IL-1alpha (of 62% and 43%), IL-6 (of 53% and 43%), and IL-8 (of 46% and 42%). In contrast, the anti-inflammatory/anti-coagulant CD141/thrombomodulin increased markedly when IL-32 was silenced. This study introduces IL-32 as a critical regulator of endothelial function, expanding the properties of this cytokine relevant to coagulation, endothelial inflammation, and atherosclerosis.

Angiotensin-converting enzyme inhibition and novel cardiovascular risk biomarkers: results from the Trial of Angiotensin Converting Enzyme Inhibition and Novel Cardiovascular Risk Factors (TRAIN) study

BACKGROUND

Beneficial effects of angiotensin-converting enzyme (ACE) inhibitors seem to be mediated by mechanisms that are partly independent of blood pressure lowering. The present study evaluates effects of an ACE inhibitor (ie, fosinopril) intervention on novel cardiovascular risk factors.

METHODS

Data are from the Trial of Angiotensin Converting Enzyme Inhibition and Novel Cardiovascular Risk Factors (TRAIN) study, a double-blind, crossover, randomized, placebo-controlled trial enrolling subjects > or =55 years old with high cardiovascular disease risk profile. Biomarkers of hemostasis (ie, plasminogen activator inhibitor 1, D-dimer), inflammation (ie, C-reactive protein, interleukin-6), and endothelial function (ie, endothelin 1, vascular cell adhesion molecule 1) were measured at the baseline, at the midterm, and at end of follow-up (after 1 year) clinic visits. Paired t test analyses (after Sidak's adjustment, P < .009) were performed to compare biomarkers modifications after fosinopril/placebo interventions.

RESULTS

Mean age of the sample (n = 290, women 43.4%) was 66.0 years old. No significant differences were reported for C-reactive protein, interleukin 6, plasminogen activator inhibitor 1, vascular cell adhesion molecule 1, and endothelin 1 levels in the comparisons between fosinopril and placebo interventions. D-dimer was the only biomarker showing a significant difference between fosinopril intervention (median 0.32 microg/mL, interquartile range 0.22-0.52 microg/mL) and placebo (median 0.29 microg/mL, interquartile range 0.20-0.47 microg/mL, P = .007) when analyses were restricted to participants with higher compliance to treatment and receiving the maximum ACE inhibitor dosage.

CONCLUSIONS

Angiotensin-converting enzyme inhibition does not significantly modify major biomarkers of inflammation, hemostasis, and endothelial function. Further studies should confirm the possible effect of ACE inhibitors on the fibrinolysis pathway.

Effect of Bosentan on Plasma Markers of Endothelial Cell Activity in Patients with Secondary Pulmonary Hypertension Related to Connective Tissue Diseases

Objective.

To evaluate plasma markers of endothelial cell activity in patients with pulmonary arterial hypertension (PAH) induced by connective tissue diseases (CTD) before and after 3-month administration of bosentan.

Methods.

We quantified E, L and P-selectin (sE-S, sL-S, sP-S), thrombomodulin (TM), monocyte-chemotactic protein 1 (MCP-1), human soluble CD40 ligand (sCD40L), and nitric oxide (NO) in 18 patients and 18 controls. We evaluated right ventricular systolic pressure (RVSP) and the 6-minute walk test (6-MWT).

Results.

All plasma markers but sL-S and TM at Time 0 were significantly higher in patients compared with controls. After 3 months of therapy, decreased levels were noted in NO (Time 0 24.05 ± 6.01 mmol/l, Time 1 13.92 ± 3.40 mmol/l; p < 0.001) and sCD40L (Time 0 1685.33 ± 866 pg/ml, Time 1 1055.11 ± 630.6 pg/ml; p = 0.017). In contrast, sP-S was significantly increased (Time 0 88.36 ± 47.76 ng/ml, Time 1 147.21 ± 94.43 ng/ml; p = 0.021). All patients remained stable in WHO class III, and in 9 patients we noted an improvement in 6-MWT. A correlation was found between Δ of RVSP and 6-MWT (r2= 0.5355, p < 0.001) as well as between Δ-sP-S and both Δ-6-MWT and Δ-RVSP. An increase sP-S level was found in 89% of nonresponder patients, whereas 55% of responders showed a stable or reduced sP-S level (p = 0.016 responder vs nonresponder).

Conclusion.

Treatment with bosentan for 3 months induced a beneficial effect by restoring endothelial function through a decrease in the markers of endothelial cell activity, leading to stabilization or improvement of severe PAH.

The hexosamine biosynthesis inhibitor azaserine prevents endothelial inflammation and dysfunction under hyperglycemic condition through antioxidant effects

Hexosamine biosynthetic pathway (HBP) accounts for some cardiovascular adverse effects of hyperglycemia. We investigated whether the HBP inhibitor azaserine protects against hyperglycemia-induced endothelial damage dependently of HBP. Human endothelial cells isolated from umbilical veins were exposed either to a high (30.5 mmol/l) or low concentration of glucose (5.5 mmol/l) for 4 days, followed by a stimulation with TNF-alpha (1 ng/ml, 24 h). The blockade of the rate-limiting enzyme glutamine:fructose-6-phosphate amidotransferase inhibited HBP flux and oxidative stress (generation of superoxide and peroxynitrite) under the hyperglycemic condition and prevented the synergistic stimulation of VCAM-1 and ICAM-1 expression by hyperglycemia and TNF-alpha. In the cells cultured under a low-glucose condition when no increased HBP flux occurred, azaserine enhanced the manganese-superoxide dismutase (MnSOD) protein level and also inhibited the oxidative stress and the expression of VCAM-1 and ICAM-1 in response to TNF-alpha. Moreover, the polyphenol resveratrol inhibited the oxidative stress and adhesion molecule expression and did not decrease the HBP flux under the hyperglycemia condition. In addition, in isolated rat aortas exposed to hyperglycemic buffer for 5 h when no significant HBP flux occurred, azaserine upregulated the MnSOD protein level and prevented decreased endothelium-dependent relaxations to acetylcholine. In conclusion, hyperglycemia independently increases oxidative stress and HBP flux, amplifies endothelial inflammation, and impairs endothelial function mainly through oxidative stress and not the HBP pathway. Azaserine protects against hyperglycemic endothelial damage through its antioxidant effect independently of inhibiting HBP pathway.

Plant-derived micronutrients suppress monocyte adhesion to cultured human aortic endothelial cell layer by modulating its extracellular matrix composition

Monocyte adhesion to endothelium plays an important role in atherosclerosis. We investigated the effects of micronutrients on monocyte-binding properties of extracellular matrix (ECM) produced by human aortic endothelial cells (AoEC). Confluent cultures of AoEC were exposed to ascorbic acid, quercetin, gotu kola extract (10% asiatic acid), green tea extract (40% epigallocatechin gallate), or a mixture of these micronutrients for 48 hours. AoEC-produced ECM was exposed by differential treatment. U937 monocyte adhesion was assayed by fluorescence. ECM composition was assayed immunochemically and with radiolabeled metabolic precursors. AoEC exposure to micronutrients reduced ECM capacity to bind monocytes in a dose-dependent manner. This effect was accompanied by profound changes in the ECM composition. Correlation analysis revealed that changes in monocyte adhesion to ECM had the strongest positive correlation with ECM content for laminin (CC = 0.9681, P < 0.01), followed by fibronectin, collagens type III, I, and IV, biglycan, heparan sulfate, and elastin. The strongest negative correlation was with chondroitin sulfate (CC = -0.9623, P < 0.01), followed by perlecan and versican. Individual micronutrients had diverse effects on ECM composition and binding properties, and their mixture was the most effective treatment. In conclusion, micronutrient-dependent reduction of monocyte adhesion to endothelium is partly mediated through specific modulation of ECM composition and properties.

Platelet chemokines in vascular disease

Platelets are a rich source of different chemokines and express chemokine receptors. CXCL4 is highly abundant in platelets and involved in promoting monocyte arrest from rolling and monocyte differentiation to macrophages. CXCL4 can also associate with CCL5 and amplify its effect on monocytes. The megakaryocyte CXCL7 gene product is proteolytically cleaved into the strong neutrophil chemoattractant, NAP-2, which has also been implicated in repair cell homing to vascular lesions. Platelet adhesion can induce release of CCL2 and CXCL8 from endothelial cells. Conversely, the chemokines CCL17, CCL22, and CXCL12 made by other cells amplify platelet activation. Platelet chemokines enhance recruitment of various hematopoietic cells to the vascular wall, fostering processes such as neointima formation, atherosclerosis, and thrombosis, but also vessel repair and regeneration after vascular injury.

Polymeric particles conjugated with a ligand to VCAM-1 exhibit selective, avid, and focal adhesion to sites of atherosclerosis

The increased expression of VCAM-1 on endothelial segments within plaque regions could be used as a target to deliver polymeric drug carriers selectively to sites of atherosclerosis. We probed the hypothesis that polymeric particles conjugated with a ligand for VCAM-1 exhibit selective and avid adhesion to sites of atherosclerosis. Particles made from polystyrene or the biodegradable polymer poly(sebacic acid)-block-polyethylene glycol (PSA-PEG) were conjugated with an antibody to VCAM-1 (alpha-VCAM-1) or IgG (negative control). The particles were injected into the jugular vein of ApoE(-/-) (a murine model of atherosclerosis) or wild type mice and their adhesion to the aorta determined. alpha-VCAM-1 particles exhibited significantly greater adhesion to ApoE(-/-) mouse aorta [32 +/- 5 (mean +/- SEM) particles/mm(2) for polystyrene particles and 31 +/- 7 particles/mm(2) for PSA-PEG particles] compared to the level of adhesion to wild type mouse aorta (18 +/- 1 particles/mm(2) for polystyrene particles and 6 +/- 1 particles/mm(2) for PSA-PEG particles). Within ApoE(-/-) mice, the alpha-VCAM-1 particles exhibited significantly greater adhesion to the aorta (32 +/- 5 particles/mm(2) for polystyrene particles and 31 +/- 7 particles/mm(2) for PSA-PEG particles) compared to the adhesion of IgG particles (1 +/- 1 particles/mm(2) for polystyrene particles and 2 +/- 1 particles/mm(2) for PSA-PEG particles). Detailed analysis of the adhesion revealed that alpha-VCAM-1 particles exhibited focal adhesion to plaque regions, in particular the periphery of the plaques, within the ApoE(-/-) mouse aorta. Combined the data demonstrate that polymeric particles conjugated with a ligand to VCAM-1 exhibit selective, avid and focal adhesion to sites of atherosclerosis providing strong evidence that VCAM-1 ligand bearing polymeric particles could be used for targeting drugs selectively to atherosclerotic tissue.

Involvement of native TRPC3 proteins in ATP-dependent expression of VCAM-1 and monocyte adherence in coronary artery endothelial cells

Background- Vascular cell adhesion molecule-1 (VCAM-1) is critical in monocyte recruitment to the endothelium, a key event in development of atherosclerotic lesions. Stimulation of human coronary artery endothelial cells (HCAECs) with ATP positively modulates VCAM-1 expression and function through a mechanism involving Ca(2+) signaling. We here examined the role of Ca(2+) influx and native TRPC3 channels in that mechanism.

METHODS AND RESULTS

Omission of extracellular Ca(2+) or pretreatment of cells with channel blockers markedly reduced ATP-induced VCAM-1 and monocyte adhesion. Using a siRNA strategy and real-time fluorescence, we found that native TRPC3 proteins contribute to constitutive and ATP-regulated Ca(2+) influx. ATP-dependent upregulation of VCAM-1 was accompanied by an increase in basal cation entry and TRPC3 expression. Notably, TRPC3 knock-down resulted in a dramatic reduction of ATP-induced VCAM-1 and monocyte adhesion.

CONCLUSIONS

These findings indicate that in HCAECs, native TRPC3 proteins form channels that contribute to constitutive and ATP-dependent Ca(2+) influx, and that TRPC3 expression and function are fundamental to support VCAM-1 expression and monocyte binding. This is the first evidence to date relating native TRPC3 proteins with regulated expression of cell adhesion molecules in coronary endothelium, and suggests a potential pathophysiological role of TRPC3 in coronary artery disease.

The peroxisome proliferator-activated receptor-gamma agonist pioglitazone represses inflammation in a peroxisome proliferator-activated receptor-alpha-dependent manner in vitro and in vivo in mice

OBJECTIVES

Our aim was to investigate if the peroxisome proliferator-activated receptor (PPAR)-gamma agonist pioglitazone modulates inflammation through PPARalpha mechanisms.

BACKGROUND

The thiazolidinediones (TZDs) pioglitazone and rosiglitazone are insulin-sensitizing PPARgamma agonists used to treat type 2 diabetes (T2DM). Despite evidence for TZDs limiting inflammation and atherosclerosis, questions exist regarding differential responses to TZDs. In a double-blinded, placebo-controlled 16-week trial among recently diagnosed T2DM subjects (n = 34), pioglitazone-treated subjects manifested lower triglycerides and lacked the increase in soluble vascular cell adhesion molecules (sVCAM)-1 evident in the placebo group. Previously we reported PPARalpha but not PPARgamma agonists could repress VCAM-1 expression. Since both triglyceride-lowering and VCAM-1 repression characterize PPARalpha activation, we studied pioglitazone's effects via PPARalpha.

METHODS

Pioglitazone effects on known PPARalpha responses--ligand binding domain activation and PPARalpha target gene expression--were tested in vitro and in vivo, including in wild-type and PPARalpha-deficient cells and mice, and compared with the effects of other PPARgamma (rosiglitazone) and PPARalpha (WY14643) agonists.

RESULTS

Pioglitazone repressed endothelial TNFalpha-induced VCAM-1 messenger ribonucleic acid expression and promoter activity, and induced hepatic IkappaBalpha in a manner dependent on both pioglitazone exposure and PPARalpha expression. Pioglitazone also activated the PPARalpha ligand binding domain and induced PPARalpha target gene expression, with in vitro effects that were most pronounced in endothelial cells. In vivo, pioglitazone administration modulated sVCAM-1 levels and IkappaBalpha expression in wild-type but not PPARalpha-deficient mice.

CONCLUSIONS

Pioglitazone regulates inflammatory target genes in hepatic (IkappaBalpha) and endothelial (VCAM-1) settings in a PPARalpha-dependent manner. These data offer novel mechanisms that may underlie distinct TZD responses.

Peroxiredoxin1 prevents excessive endothelial activation and early atherosclerosis

The peroxiredoxin (Prdx) family of antioxidant enzymes uses redox-active cysteines to reduce peroxides, lipid hydroperoxides, and peroxynitrites. Prdx1 is known to be important to protect red blood cells against reactive oxygen species and in tumor prevention. In this study, the role of Prdx1 in inflammation, thrombosis, and atherosclerosis was investigated. Using intravital microscopy, we showed that the number of leukocytes rolling per minute in unstimulated veins was increased by 2.5-fold in Prdx1(-/-) compared to Prdx1(+/+) mice. In Prdx1(-/-) mice, 50% of leukocytes rolled at a velocity <10 mum/sec compared with 10% in Prdx1(+/+) mice, suggesting that adhesion molecule density on the endothelium may have been increased by Prdx1 deficiency. Indeed, endothelial P-selectin, soluble P-selectin, and von Willebrand factor in plasma were increased in Prdx1(-/-) mice compared to Prdx1(+/+) mice, indicating elevated Weibel-Palade body release. In contrast to this excessive endothelial activation, Prdx1(-/-) platelets showed no sign of hyperreactivity, and their aggregation both in vitro and in vivo was normal. We also examined the role of Prdx1 in the apoE(-/-) murine spontaneous model of atherosclerosis. Prdx1(-/-)/apoE(-/-) mice fed normal chow developed larger, more macrophage-rich aortic sinus lesions than Prdx1(+/+)/apoE(-/-) mice, despite similar amounts and size distributions of cholesterol in their plasma lipoproteins. Thus, Prdx1 protects against excessive endothelial activation and atherosclerosis, and the Prdx1(-/-) mice could serve as an animal model susceptible to chronic inflammation.

Site-specific effects of PECAM-1 on atherosclerosis in LDL receptor-deficient mice

OBJECTIVE

Atherosclerosis is a vascular disease that involves lesion formation at sites of disturbed flow under the influence of genetic and environmental factors. Endothelial expression of adhesion molecules that enable infiltration of immune cells is important for lesion development. Platelet/endothelial cell adhesion molecule-1 (PECAM-1; CD31) is an adhesion and signaling receptor expressed by many cells involved in atherosclerotic lesion development. PECAM-1 transduces signals required for proinflammatory adhesion molecule expression at atherosusceptible sites; thus, it is predicted to be proatherosclerotic. PECAM-1 also inhibits inflammatory responses, on which basis it is predicted to be atheroprotective.

METHODS AND RESULTS

We evaluated herein the effect of PECAM-1 deficiency on development of atherosclerosis in LDL receptor-deficient mice. We found that PECAM-1 has both proatherosclerotic and atheroprotective effects, but that the former dominate in the inner curvature of the aortic arch whereas the latter dominate in the aortic sinus, branching arteries, and descending aorta. Endothelial cell expression of PECAM-1 was sufficient for its atheroprotective effects in the aortic sinus but not in the descending aorta, where the atheroprotective effects of PECAM-1 also required its expression on bone marrow-derived cells.

CONCLUSIONS

We conclude that PECAM-1 influences initiation and progression of atherosclerosis both positively and negatively, and that it does so in a site-specific manner.

Systemic and distal repercussions of liver-specific peroxisome proliferator-activated receptor-alpha control of the acute-phase response

The acute-phase response is characterized by the modulation of liver expression of many proteins involved in a diversity of biological functions. Among them, some are associated with the pathology of atherosclerosis. We previously found that peroxisome proliferator-activated receptor-alpha (PPARalpha) agonists attenuate the IL-6 induction of acute-phase response gene expression in vitro and in vivo. In the current work, we found a PPARalpha-dependent regulation of hepatic acute-phase response stimulated by IL-1. We also found that IL-1-stimulated expression of secondary wave cytokines such as IL-6 is prevented upon PPARalpha activation in liver. Direct involvement of hepatic PPARalpha was demonstrated using a liver-restricted expression of PPARalpha in mice. IL-1- or IL-6-mediated acute-phase response was inhibited by fenofibrate treatment in liver-specific PPARalpha-expressing mice but not in PPARalpha-deficient mice. In addition, we demonstrated that PPARalpha exerts a general control of the acute-phase response by using an inflammation/infection model of lipopolysaccharide. In such a context, liver-specific PPARalpha-expressing mice displayed lower circulating levels of TNF, IL-1, and IL-6 cytokines. We found a distal repercussion of this lowering at the vascular wall level as illustrated by a decreased expression of adhesion molecules in aorta. In conclusion, we demonstrated that through a specific liver action, PPARalpha behaves as a modulator of systemic inflammation and of the associated vascular response.

CB2 cannabinoid receptor agonist JWH-015 modulates human monocyte migration through defined intracellular signaling pathways

Recruitment of leukocytes to inflammatory sites is crucial in the pathogenesis of chronic inflammatory diseases. The aim of this study was to investigate if activation of CB2 cannabinoid receptors would modulate the chemotactic response of human monocytes. Human monocytes treated with the CB2 agonist JWH-015 for 12-18 h showed significantly reduced migration to chemokines CCL2 and CCL3, associated with reduced mRNA and surface expression of their receptors CCR2 and CCR1. The induction of ICAM-1 in response to IFN-gamma was inhibited by JWH-015. Moreover, JWH-015 cross-desensitized human monocytes for migration in response to CCL2 and CCL3 by its own chemoattractant properties. The CB2-selective antagonist SR-144528, but not the CB1 antagonist SR-147778, reversed JWH-015-induced actions, whereas the CB2 agonist JWH-133 mimicked the effects of JWH-015. The investigation of underlying pathways revealed the involvement of phosphatidylinositol 3-kinase/Akt and ERK1/2 but not p38 MAPK. In conclusion, selective activation of CB2 receptors modulates chemotaxis of human monocytes, which might have crucial effects in chronic inflammatory disorders such as atherosclerosis or rheumatoid arthritis.

Vascular versus myocardial dysfunction in acute coronary syndrome: are the adhesion molecules as powerful as NT-proBNP for long-term risk stratification?

OBJECTIVES

To determine if elevations of adhesion molecules in acute coronary syndrome (ACS) are useful for risk stratification.

DESIGN AND METHODS

A cell adhesion array (Randox Ltd.) and NT-proBNP were measured in 216 ACS patients.

RESULTS

Kaplan-Meier and Cox models indicate early elevations of NT-proBNP but not the adhesion molecules are predictive of future death/myocardial infarction.

DISCUSSION

Elevations of adhesion molecules early after pain onset in ACS are not useful for long-term risk stratification.