15-Lipoxygenase-2 expression in human macrophages induces chemokine secretion and T cell migration

BACKGROUND

We determined previously that hypoxia results in increased 15-lipoxygenase type 2 (15-LOX-2) expression and CXCL8 secretion in macrophages. This study sought to determine whether 15-LOX-2 expression links directly with the secretion of inflammatory molecules in macrophages and also investigated its subsequent effects on T cell migration.

METHODS

Adenovirus-mediated gene delivery caused overexpression of 15-LOX-2 in human macrophages. We used cytometric bead array to measure chemokine secretion, and assessed T cell migration by counting cells in chemotaxis chambers. Expression of chemokine receptors was determined by FACS analysis. Using siRNA, we reduced 15-LOX-2 expression in human macrophages. We used scrambled siRNA as control.

RESULTS

Macrophages that overexpress 15-LOX-2 showed increased secretion of chemokine CXCL10 after 24h incubation. In addition, preconditioned medium from 15-LOX-2-overexpressing cells increased T cell migration and surface expression of CXCR3, the CXCL10 receptor. Knockdown of 15-LOX-2 expression decreased CXCL10 secretion from hypoxic macrophages and also reduced T cell migration.

CONCLUSION

In macrophages, overexpression of 15-LOX-2 results in increased secretion of CXCL10 and CCL2. Products released in response to increased 15-LOX-2 activation lead to increased expression of CD69, the T cell activation marker as well as increased T cell migration. Therefore, increased expression of 15-LOX-2 induced by hypoxia may participate in T cell recruitment in diseases such as atherosclerosis.

Release of protein as well as activity of MMP-9 from unstable atherosclerotic plaques during percutaneous coronary intervention

OBJECTIVES

Few studies have investigated the composition of unstable coronary plaques in vivo in humans. The aims of this study were to investigate if substances released from plaques during percutaneous coronary intervention (PCI) under distal protection could give information about plaque composition and also indicate possible biomarkers in plasma that may be used to identify patients at risk.

METHODS AND RESULTS

Twenty patients with acute coronary syndromes undergoing PCI with distal protection were included. Plasma samples were taken before, during, and after the PCI in the aortic root, locally in the culprit vessel and intravenously. Plasma was analysed for possible markers of plaque instability. During PCI, local increases were observed for matrix metalloproteinase 9 (MMP-9), protein (P < 0.001) as well as activity (P < 0.001), interleukin 6 (IL-6; P < 0.01) and oxidized low-density lipoprotein (oxLDL; P = 0.01) in the culprit coronary artery. A systemic inflammatory response was also seen with increased levels of IL-10, MMP-3, serum amyloid A and C-reactive protein, but with no increase in MMP-9.

CONCLUSIONS

Our study shows that local sampling of blood under distal protection may be used to analyse coronary plaques and to identify biomarkers for unstable plaques. Our results suggest that MMP-9 is a potential biomarker, and that IL-6, MMP9 and possibly oxLDL are released from plaques.

European guidelines on cardiovascular disease prevention in clinical practice: executive summary. Fourth Joint Task Force of the European Society of Cardiology and other societies on cardiovascular disease prevention in clinical practice (constituted by representatives of nine societies and by invited experts)

Other experts who contributed to parts of the guidelines: Edmond Walma, Schoonhoven (The Netherlands), Tony Fitzgerald, Dublin (Ireland), Marie Therese Cooney, Dublin (Ireland), Alexandra Dudina, Dublin (Ireland) European Society of Cardiology (ESC) Committee for Practice Guidelines (CPG):, Alec Vahanian (Chairperson) (France), John Camm (UK), Raffaele De Caterina (Italy), Veronica Dean (France), Kenneth Dickstein (Norway), Christian Funck-Brentano (France), Gerasimos Filippatos (Greece), Irene Hellemans (The Netherlands), Steen Dalby Kristensen (Denmark), Keith McGregor (France), Udo Sechtem (Germany), Sigmund Silber (Germany), Michal Tendera (Poland), Petr Widimsky (Czech Republic), José Luis Zamorano (Spain)

Document reviewers: Irene Hellemans (CPG Review Coordinator) (The Netherlands), Attila Altiner (Germany), Enzo Bonora (Italy), Paul N. Durrington (UK), Robert Fagard (Belgium), Simona Giampaoli(Italy), Harry Hemingway (UK), Jan Hakansson (Sweden), Sverre Erik Kjeldsen (Norway), Mogens Lytken Larsen (Denmark), Giuseppe Mancia (Italy), Athanasios J. Manolis (Greece), Kristina Orth-Gomer (Sweden), Terje Pedersen (Norway), Mike Rayner (UK), Lars Ryden (Sweden), Mario Sammut (Malta), Neil Schneiderman (USA), Anton F. Stalenhoef (The Netherlands), Lale Tokgözoglu (Turkey), Olov Wiklund (Sweden), Antonis Zampelas (Greece)

European guidelines on cardiovascular disease prevention in clinical practice: full text. Fourth Joint Task Force of the European Society of Cardiology and other societies on cardiovascular disease prevention in clinical practice (constituted by representatives of nine societies and by invited experts)

Other experts who contributed to parts of the guidelines: Edmond Walma, Tony Fitzgerald, Marie Therese Cooney, Alexandra Dudina

European Society of Cardiology (ESC) Committee for Practice Guidelines (CPG): Alec Vahanian (Chairperson), John Camm, Raffaele De Caterina, Veronica Dean, Kenneth Dickstein, Christian Funck-Brentano, Gerasimos Filippatos, Irene Hellemans, Steen Dalby Kristensen, Keith McGregor, Udo Sechtem, Sigmund Silber, Michal Tendera, Petr Widimsky, Jose Luis Zamorano

Document reviewers: Irene Hellemans (CPG Review Co-ordinator), Attila Altiner, Enzo Bonora, Paul N. Durrington, Robert Fagard, Simona Giampaoli, Harry Hemingway, Jan Hakansson, Sverre Erik Kjeldsen, Mogens Lytken Larsen, Giuseppe Mancia, Athanasios J. Manolis, Kristina Orth-Gomer, Terje Pedersen, Mike Rayner, Lars Ryden, Mario Sammut, Neil Schneiderman, Anton F. Stalenhoef, Lale Tokgözoglu, Olov Wiklund, Antonis Zampelas

C-reactive protein, interleukin-6, secretory phospholipase A2 group IIA and intercellular adhesion molecule-1 in the prediction of late outcome events after acute coronary syndromes

OBJECTIVE

We investigated whether levels of C-reactive protein (CRP), interleukin-6 (IL-6), secretory phospholipase A(2) group IIA (sPLA(2)-IIA) and intercellular adhesion molecule-1 (ICAM-I) predict late outcomes in patients with acute coronary syndromes (ACS).

DESIGN

Prospective longitudinal study. CRP (mg L(-1)), IL-6 (pg mL(-1)), sPLA(2)-IIA (ng mL(-1)) and ICAM-1 (ng mL(-1)) were measured at days 1 (n = 757) and 4 (n = 533) after hospital admission for ACS. Their relations to mortality and rehospitalization for myocardial infarction (MI) and congestive heart failure (CHF) were determined.

SETTING

Coronary Care Unit at Sahlgrenska University Hospital, Gothenburg, Sweden.

SUBJECTS

Patients with ACS alive at day 30; median follow-up 75 months.

RESULTS

Survival was related to day 1 levels of all markers. After adjustment for confounders, CRP, IL-6 and ICAM-1, but not sPLA(2)-IIA, independently predicted mortality and rehospitalization for CHF. For CRP, the hazard ratio (HR) was 1.3 for mortality (95% confidence interval (CI): 1.1-1.5, P = 0.003) and 1.4 for CHF (95% CI: 1.1-1.9, P = 0.006). For IL-6, HR was 1.3 for mortality (95% CI: 1.1-1.6, P < 0.001) and 1.4 for CHF (95% CI: 1.1-1.8, P = 0.02). For ICAM-1, HR was 1.2 for mortality (95% CI: 1.0-1.4, P = 0.04) and 1.3 for CHF (95% CI: 1.0-1.7, P = 0.03). No marker predicted MI. Marker levels on day 4 provided no additional predictive value.

CONCLUSIONS

In patients with ACS, CRP, IL-6, sPLA(2)-IIA and ICAM-1 are associated with long-term mortality and CHF, but not reinfarction. CRP, IL-6 and ICAM-1 provide prognostic information beyond that obtained by clinical variables.

Dissociation of the Inflammatory Reaction following PCI for Acute Myocardial Infarction

OBJECTIVES

Neutrophils are activated and infiltrate the myocardium after ischemia and reperfusion. The involvement of neutrophils in irreversible reperfusion injury is suggested by numerous experimental studies. The aim of this study was to investigate markers of neutrophil activation following reperfusion of acute myocardial infarction (AMI) accomplished with percutaneous coronary intervention (PCI) and their relationship to markers of lipid peroxidation, cytokines and highly-sensitive C-reactive protein (hsCRP).

DESIGN

Non-consecutive patients with their first myocardial infarction were evaluated. Setting. University hospital as primary referral center, single center.

PATIENTS AND METHODS

Forty-nine patients with AMI were evaluated. All were treated with primary PCI and infusion of abciximab. Reperfusion was verified by angiography. Blood samples for analyses of myeloperoxidase (MPO), neutrophil gelatinase-associated lipocalin (NGAL), matrix metalloproteinase-9 (MMP-9), malondialdehyde (MDA), 8-isoprostane-prostaglandin F2alpha (Iso-P), interleukin 6 (IL-6), interleukin 8 (IL-8), tumor necrosis factoralpha (TNFalpha), hsCRP, creatine kinase-monobasic fraction (CK-MB) and troponin-T (TnT) were obtained at baseline with the occluded coronary vessel, and subsequently after verified reperfusion at 1.5, 3 and 24 hours.

RESULTS

Significant increases in MMP-9, IL-6, IL-8, TNFalpha and hsCRP were observed, and a significant decrease in MPO and MDA was also observed over the same period. No significant changes in Iso-P and NGAL were found.

CONCLUSION

We found a dissociation of the inflammatory reaction after PCI for AMI: a decrease of markers of neutrophil activation and MDA, but an increase in cytokines and hsCRP. An antineutrophil effect of the PCI procedure including treatment with abciximab, an antiplatelet drug and a modulator of inflammation, is conceivable.

Apolipoproteins A-I and B: biosynthesis, role in the development of atherosclerosis and targets for intervention against cardiovascular disease

Apolipoprotein (apo) AI and apoB are the major apolipoproteins of high-density lipoprotein (HDL) and low-density lipoprotein (LDL), respectively. ApoB assembles the precursor of LDL, very-low-density lipoprotein (VLDL), in the liver. The assembly starts with the formation of a primordial particle, which is converted to VLDL2. The VLDL2 particle is then transferred to the Golgi apparatus and can either be secreted or converted to triglyceride-rich VLDL1. We have reviewed this assembly process, the process involved in the storage of triglycerides in cytosolic lipid droplets, and the relationship between these two processes. We also briefly discuss the formation ofHDL. ApoB mediates the interaction between LDL and the arterial wall. Two regions in apoB are involved in this binding. This interaction and its role in the development of atherosclerosis are reviewed. ApoB can be used to measure the number of LDL or VLDL particles present in plasma, as there is one molecule of apoB on each particle. By contrast, the amount of cholesterol and other lipids on each particle varies under different conditions. We address the possibility of using apoAl and apoB levels to estimate the risk of development of cardiovascular diseases and to monitor intervention to treat these diseases.

How can we prevent cardiovascular disease in diabetes

Evidence based goals for the treatment and prevention of atherosclerosis in diabetes are given in international and national guidelines. The importance of optimal control of lipids and blood pressure has been shown in several studies. With available drugs and behavioural modifications the treatment goals can be reached in most cases. However, only a few patients with diabetes are treated optimally today. A major possibility to reduce cardiovascular disease in diabetes is to treat patients according to guidelines. New treatment targets may include specific treatment of the dyslipidaemia, manifested in high levels of small dense LDL and low HDL, active anti-inflammatory treatments, specific reduction of inflammatory activity in adipose tissue, reduced volume of adipose tissue, antioxidants and reduction of advanced glycosylation endproducts production. Possible strategies for these treatments are available, and should be evaluated in clinical trials.

Tagging SNP haplotype analysis of the secretory PLA2-V gene, PLA2G5 , shows strong association with LDL and oxLDL levels, suggesting functional distinction from sPLA2-IIA: results from the UDACS study

Animal and human studies suggest that both secretory PLA2 (sPLA2)-V and sPLA2-IIA (encoded, respectively, by the neighbouring PLA2G5 and PLA2G2A genes) contribute to atherogenesis. Elevated plasma sPLA2-IIA predicts coronary heart disease (CHD) risk, but no mass assay for sPLA2-V is available. We previously reported that tagging single nucleotide polymorphism (tSNP) haplotypes of PLA2G2A are strongly associated with sPLA2-IIA mass, but not lipid levels. Here, we use tSNPs of the sPLA2-V gene to investigate the association of PLA2G5 with CHD risk markers. Seven PLA2G5 tSNPs genotypes, explaining >92% of the locus genetic variability, were determined in 519 patients with Type II diabetes (in whom PLA2G2A tSNP data was available), and defined seven common haplotypes (frequencies >5%). PLA2G5 and PLA2G2A tSNPs showed linkage disequilibrium (LD). Compared to the common PLA2G5 haplotype, H1 (frequency 34.9%), haplotypes H2-7 were associated with overall higher plasma LDL (P < 0.00004) and total cholesterol (P < 0.00003) levels yet lower oxLDL/LDL (P = 0.006) and sPLA2-IIA mass (P = 0.04), probably reflecting LD with PLA2G2A. Intronic tSNP (rs11573248), unlikely itself to be functional, distinguished H1 from LDL-raising haplotypes and may mark a functional site. In conclusion, PLA2G5 tSNP haplotypes demonstrate an association with total and LDL cholesterol and oxLDL/LDL, not seen with PLA2G2A, thus confirming distinct functional roles for these two sPLA2s.

Pathogenesis and treatment of diabetic vascular disease - illustrated by two cases

This publication is a summary of the presentations given at the First JIM Grand Round held at the Sahlgrenska University Hospital on 15 March 2006. The Grand Round was based on two case reports; a patient with type 2 diabetes and pronounced macrovascular disease and another patient with early microvascular disease combined with the macrovascular complications. The pathogenesis of the vascular complications and the current treatment regimens were discussed in relation to the history and examinations performed in these patients.

Hypoxia converts human macrophages into triglyceride-loaded foam cells

OBJECTIVE

Atherosclerotic lesions have regions that are hypoxic. Because the lesion contains macrophages that are loaded with lipid, we investigated whether hypoxia can influence the accumulation of lipids in these cells.

METHODS AND RESULTS

Exposure of human macrophages to hypoxia for 24 hours resulted in an increased formation of cytosolic lipid droplets and an increased accumulation of triglycerides. Exposure of the macrophages to oxidized low-density lipoprotein (oxLDL) increased the accumulation of cytosolic lipid droplets because of an increase in cellular cholesterol esters. The accumulation of lipid droplets in oxLDL-treated cells was further increased after hypoxia, caused by an increased level of triglycerides. Expression analyses combined with immunoblot or RT-PCR demonstrated that hypoxia increased the expression of several genes that could promote the accumulation of lipid droplets. Hypoxia increased the mRNA and protein levels of adipocyte differentiation-related protein (ADRP). It is well known that an increased expression of ADRP increases the formation of lipid droplets. Hypoxia decreased the expression of enzymes involved in beta-oxidation (acyl-coenzyme A synthetase and acyl-coenzyme A dehydrogenase) and increased the expression of stearoyl-coenzyme A desaturase, an important enzyme in the fatty acid biosynthesis. Moreover, exposure to hypoxia decreased the rate of beta-oxidation, whereas the accumulation of triglycerides increased.

CONCLUSIONS

The results demonstrate that exposure of human macrophages to hypoxia causes an accumulation of triglyceride-containing cytosolic lipid droplets. This indicates that the hypoxia present in atherosclerotic lesions can contribute to the formation of the lipid-loaded macrophages that characterize the lesion and to the accumulation of triglycerides in such lesions.

Augmented levels of CD44 in macrophages from atherosclerotic subjects: a possible IL-6-CD44 feedback loop?

The cell-adhesion molecule CD44 likely participates in atherosclerosis development. We have shown previously that pro-inflammatory cytokines affect CD44 expression. Therefore, this work examined the role of elevated CD44 levels in human macrophages. Macrophages from human atherosclerotic subjects (n=15) showed elevated levels of CD44 transcript and protein (1.5-fold) compared to matched controls (n=15) (P=0.050 and 0.044, respectively). To test whether genetic factors influence CD44 expression, two single nucleotide polymorphisms in the CD44 gene were analyzed but these were not associated with coronary artery disease. We also examined the potential connection between plasma cytokine levels and CD44 expression. In atherosclerotic subjects, elevated CD44 expression correlates (P=0.012) with enhanced macrophage IL-6 secretion (3.13+/-2.5 pg/mL versus 0.32+/-0.16 pg/mL in controls, P=0.021). Additionally, CD44-deficient mice exhibit less circulating IL-6 than wild-type controls (9.8+/-0.7 pg/mL versus 14.3+/-0.7 pg/mL; P=0.032). Furthermore, IL-6 augments CD44 expression in primary human macrophages after 24 h (P=0.038) and 48 h (P=0.015). Taken together, our data show an IL-6-CD44 feedback loop in macrophages. Such a positive feedback loop may aggravate atherosclerosis development.

Oxidized LDL induces a coordinated up-regulation of the glutathione and thioredoxin systems in human macrophages

Using DNA microarray analysis, we found that human macrophages respond to oxidized low-density lipoprotein (oxLDL) by activating the antioxidative glutathione and thioredoxin systems. Several genes of the glutathione and thioredoxin systems were expressed at high levels in macrophages when compared to 80 other human tissues and cell types, indicating that these systems may be of particular importance in macrophages. The up-regulation of three genes in these systems, thioredoxin (P < 0.005), thioredoxin reductase 1 (P < 0.001) and glutathione reductase (P < 0.001) was verified with real-time RT-PCR, using human macrophages from 10 healthy donors. To investigate the possible role of these antioxidative systems in the development of atherosclerosis, expression levels in macrophages from 15 subjects with atherosclerosis (12 men, 3 women) and 15 matched controls (12 men, 3 women) were analyzed using DNA microarrays. Two genes in the glutathione system Mn superoxide dismutase (P < 0.05) and catalase (P < 0.05) differed in expression between the groups. We conclude that macrophage uptake of oxidized LDL induces a coordinated up-regulation of genes of the glutathione and thioredoxin systems, suggesting that these systems may participate in the cellular defense against oxidized LDL and possibly modulate the development of atherosclerosis.

Composition of coronary plaques obtained by directional atherectomy in stable angina: its relation to serum lipids and statin treatment

OBJECTIVES

The stability and inflammatory activity in atherosclerotic plaques may be modulated by lipids and lipoproteins as well as the pleiotropic effects of statins. The aim of this study was to analyse the effect of statin treatment as well as the relation of plasma lipids and lipoproteins to tissue composition in atherosclerotic plaques.

DESIGN

Patients with stable angina and coronary plaques suitable for directional coronary atherectomy (DCA) were randomized to atorvastatin (80 mg once daily) or placebo (29 randomized, 22 underwent DCA, 11/group). After an average treatment of 10 weeks, patients underwent DCA, tissue specimens were obtained, and the tissue composition was determined by immunohistochemistry.

RESULTS

Atorvastatin reduced the T-cell content, but did not change lipid, collagen, smooth muscle cell, or macrophage content. Plasma levels of apolipoprotein AI (apoAI) correlated positively with tissue collagen and inversely with metalloproteinase-9 and macrophage content. About half the specimens contained neutrophil granulocytes.

CONCLUSIONS

Short-term atorvastatin treatment tended to reduce the T-cell content of atherosclerotic plaques, indicating modulation of cell-mediated immunity. High plasma levels of apoAI correlated with increased collagen content and reduced inflammation, supporting the notion that plasma apoAI stabilizes atherosclerotic plaques. The significance of neutrophils in the lesions merits further study.

ATP depletion in macrophages in the core of advanced rabbit atherosclerotic plaques in vivo

The cores of rabbit plaques in vivo are hypoxic, suggesting that ATP depletion due to an insufficient supply of oxygen and nutrients could contribute to macrophage death in atherosclerotic plaques. During hypoxia, however, macrophages maintain ATP levels by anaerobic glycolysis. To directly assess ATP and glucose metabolites in plaques in vivo, we used bioluminescence imaging to map the concentrations of ATP, glucose, glycogen, and lactate in normal and atherosclerotic rabbit aortas in vivo. Hypoxia was assessed with NITP (7-(4'-(2-nitroimidazol-1-yl)-butyl)-theophylline). Normal aortas and plaques <500 microm thick were not hypoxic and had homogenous concentrations of energy metabolites. In plaques >500 microm thick, however, the cores were characterized by ATP depletion, low concentrations of glucose and glycogen, and a high concentration of lactate. A majority of ATP-depleted macrophages within the core were viable but severely hypoxic and glucose depleted. Hyperoxia in vitro reversed the ATP depletion in macrophages in viable areas of the core. Our findings suggest that ATP depletion contributes to the death of macrophages in atherosclerotic lesions and to the formation of a necrotic core.

Tagging-SNP haplotype analysis of the secretory PLA2IIa gene PLA2G2A shows strong association with serum levels of sPLA2IIa: results from the UDACS study

Recent prospective analysis identified secretory phospholipase A(2)-IIa (sPLA(2)IIa) as a coronary artery disease (CAD) risk predictor. This study aimed to examine the relationship between serum levels of sPLA(2)IIa and variation in the sPLA(2)IIa gene (PLA2G2A) in a cohort of patients with Type II diabetes (T2D) mellitus. Six tagging single nucleotide polymorphisms (tSNPs) accounting for > 92% of the genetic variability in PLA2G2A were identified and distinguished six common haplotypes (frequencies > 5%). In the 523 Caucasian T2D patients, levels of sPLA(2)IIa, independent of CRP, were negatively correlated with total antioxidant status (P = 0.003) and high-density lipoprotein cholesterol (P = 0.006) in men and correlated with CAD status in women (P = 0.002) (Odds ratio of top two tertiles versus bottom = 2.50) [95% CI (1.13-5.53) P = 0.024]. Overall, tSNP haplotypes showed a highly significant association with sPLA(2)IIa levels (P < 0.0001), explaining 6.3% of the variance. The most common haplotype (frequency 14.2%) was associated with 53% higher sPLA(2)IIa levels [3.25 ng/ml (+/- 0.14)] compared with the combined other haplotypes [2.13 ng/ml (+/- 0.09), P < 0.00001]. Five of the six tSNPs were associated with significant effects on sPLA(2)IIa levels but the raising haplotype could not be distinguished by a single tSNP and none are likely to be functional. These data confirm the relationship between elevated sPLA(2)IIa levels and CAD risk reported in both cases: control and prospective analyses. The strong impact of PLA2G2A haplotypic variation on sPLA(2)IIa levels will help clarify the causality of this association.

Regulation and splicing of scavenger receptor class B type I in human macrophages and atherosclerotic plaques

BACKGROUND

The protective role of high-density lipoprotein (HDL) in the cardiovascular system is related to its role in the reverse transport of cholesterol from the arterial wall to the liver for subsequent excretion via the bile. Scavenger receptor class B type I (SR-BI) binds HDL and mediates selective uptake of cholesterol ester and cellular efflux of cholesterol to HDL. The role of SR-BI in atherosclerosis has been well established in murine models but it remains unclear whether SR-BI plays an equally important role in atherosclerosis in humans. The aim of this study was to investigate the expression of SR-BI and its isoforms in human macrophages and atherosclerotic plaques.

METHODS

The effect of hypoxia and minimally modified low-density lipoprotein (mmLDL), two proatherogenic stimuli, on SR-BI expression was studied in human monocyte-derived macrophages from healthy subjects using real-time PCR. In addition, SR-BI expression was determined in macrophages obtained from subjects with atherosclerosis (n = 15) and healthy controls (n = 15). Expression of SR-BI isoforms was characterized in human atherosclerotic plaques and macrophages using RT-PCR and DNA sequencing.

RESULTS

SR-BI expression was decreased in macrophages after hypoxia (p < 0.005). In contrast, SR-BI expression was increased by exposure to mmLDL (p < 0.05). There was no difference in SR-BI expression in macrophages from patients with atherosclerosis compared to controls. In both groups, SR-BI expression was increased by exposure to mmLDL (p < 0.05). Transcripts corresponding to SR-BI and SR-BII were detected in macrophages. In addition, a third isoform, referred to as SR-BIII, was discovered. All three isoforms were also expressed in human atherosclerotic plaque. Compared to the other isoforms, the novel SR-BIII isoform was predicted to have a unique intracellular C-terminal domain containing 53 amino acids.

CONCLUSION

We conclude that SR-BI is regulated by proatherogenic stimuli in humans. However, we found no differences between subjects with atherosclerosis and healthy controls. This indicates that altered SR-BI expression is not a common cause of atherosclerosis. In addition, we identified SR-BIII as a novel isoform expressed in human macrophages and in human atherosclerotic plaques.