Distinct infiltration of neutrophils in lesion shoulders in ApoE-/- mice

Endothelial cells overexpressing interleukin-8 receptors reduce inflammatory and neointimal responses to arterial injury

BACKGROUND

Interleukin-8 (IL8) receptors IL8RA and IL8RB on neutrophil membranes bind to IL8 and direct neutrophil recruitment to sites of inflammation, including acutely injured arteries. This study tested whether administration of IL8RA- and/or IL8RB-transduced rat aortic endothelial cells (ECs) accelerates adhesion of ECs to the injured surface, thus suppressing inflammation and neointima formation in balloon-injured rat carotid arteries. We tested the hypothesis that targeted delivery of ECs by overexpressing IL8RA and IL8RB receptors prevents inflammatory responses and promotes structural recovery of arteries after endoluminal injury.

METHODS AND RESULTS

Young adult male rats received balloon injury of the right carotid artery and were transfused intravenously with ECs (total, 1.5×10(6) cells at 1, 3, and 5 hours after injury) transduced with adenoviral vectors carrying IL8RA, IL8RB, and IL8RA/RB (dual transduction) genes, AdNull (empty vector), or vehicle (no EC transfusion). ECs overexpressing IL8Rs inhibited proinflammatory mediators expression significantly (by 60% to 85%) and reduced infiltration of neutrophils and monocytes/macrophages into injured arteries at 1 day after injury, as well as stimulating a 2-fold increase in reendothelialization at 14 days after injury. IL8RA-EC, IL8RB-EC, and IL8RA/RB-EC treatment reduced neointima formation dramatically (by 80%, 74%, and 95%) at 28 days after injury.

CONCLUSIONS

ECs with overexpression of IL8RA and/or IL8RB mimic the behavior of neutrophils that target and adhere to injured tissues, preventing inflammation and neointima formation. Targeted delivery of ECs to arteries with endoluminal injury provides a novel strategy for the prevention and treatment of cardiovascular disease.

S100A8 and S100A9 in cardiovascular biology and disease

There is recent and widespread interest in the damage-associated molecular pattern molecules S100A8 and S100A9 in cardiovascular science. These proteins have a number of interesting features and functions. For example, S100A8 and S100A9 (S100A8/A9) have both intracellular and extracellular actions, they are abundantly expressed in inflammatory and autoimmune states, primarily by myeloid cells but also by other vascular cells, and they modulate inflammatory processes, in part through Toll-like receptor 4 and the receptor for advanced glycation end products. S100A8/A9 also have anti-inflammatory and immune regulatory actions. Furthermore, increased plasma levels of S100A8/A9 predict cardiovascular events in humans, and deletion of these proteins partly protects Apoe(-)(/)(-) mice from atherosclerosis. Understanding the roles of S100A8 and S100A9 in vascular cell types and the mechanisms whereby these proteins mediate their biological effects may offer new therapeutic strategies to prevent, treat, and predict cardiovascular diseases.

Intravital Microscopy on Atherosclerosis in Apolipoprotein E–Deficient Mice Establishes Microvessels as Major Entry Pathways for Leukocytes to Advanced Lesions

Background—

There has been considerable speculation about the role of lesion microvessels in the accumulation of leukocytes in atherosclerosis. However, direct study of microvascular recruitment of leukocytes in lesions has not been performed, and the quantitative role for this route of entry is unclear.

Methods and Results—

Here, microvascular recruitment of leukocytes was studied in advanced lesions in 12- to 24-month-old apolipoprotein E–deficient (ApoE −/− ) mice. Histology and transmission electron microscopy demonstrated the presence of mainly adventitial, but also intimal, microvessels. Interactions between leukocytes and endothelium occurred in lesion venules. Leukocyte rolling was largely P-selectin dependent; however, residual rolling was mediated by L-selectin and endothelial P-selectin glycoprotein ligand 1. Leukocyte adhesion was significant and was attenuated in mice treated with antibodies against P-selectin, CD18, or both before preparation for intravital microscopy, suggesting acute activation of these 2 molecules by surgical trauma. Nonetheless, the density of firmly arrested leukocytes was 100-fold higher in lesion venules compared with the arterial lumen even in mice pretreated with antibodies against P-selectin and CD18, indicating strong recruitment of cells from venules that is unrelated to experimental manipulation. Fluorescent myelomonocytic cells in ApoE −/− mice carrying a knock-in mutation for enhanced green fluorescent protein (EGFP) in the lysozyme M locus (ApoE −/− /lysM EGFP/EGFP mice) were distributed specifically around lesion venules, but not around arterioles or capillaries, further indicating ongoing extravasation from venules into plaque tissue.

Conclusions—

These findings provide strong data for microvascular recruitment of leukocytes in atherosclerosis and indicate roles for L-selectin and P-selectin glycoprotein ligand 1 in this process.

Atherosclerosis: current pathogenesis and therapeutic options

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

Current understanding of the role of B cell subsets and intimal and adventitial B cells in atherosclerosis

PURPOSE OF REVIEW

Inflammation, in addition to high cholesterol is a major factor contributing to atherosclerosis-associated adverse cardiovascular events. Thus, there is a pressing need for additional therapeutic strategies to reduce inflammation, by targeting immune cells and cytokines. Here we review B cell subsets and adventitial and intimal B cells in atherosclerosis development and discuss potential B cell-targeted anti-inflammatory therapies for atherosclerosis.

RECENT FINDINGS

B cell subsets can have opposing proatherogenic and atheroprotective roles in atherosclerosis. CD-20-targeted B cell depletion has been shown to decrease murine atherosclerotic lesions. The accumulation of intimal and adventitial B cells associated with atherosclerotic lesions is consistent with their participation in local inflammatory responses. As B2 B cells are proatherogenic, blocking its survival factor B cell activating factor may selectively delete this proatherogenic subset.

SUMMARY

Both intimal and adventitial B cells appear important in atherosclerosis. B2 B cells are proatherogenic and other subsets such as regulatory B cells are antiatherogenic. Future B cell-targeted therapy for atherosclerosis should be customized to selectively deplete damaging B2 B cells while sparing or expanding protective B cell subsets.

Decreased gene expression of LC3 in peripheral leucocytes of patients with coronary artery disease

BACKGROUND

Coronary artery disease (CAD) is a common and multifactorial arterial disease that is mainly caused by atherosclerosis. Macrophages, lymphocytes and neutrophils have been implicated in atherosclerotic plaque development. Autophagy, a highly conserved cellular process for the removal of long-lived protein and organelles, plays a variety of pathophysiological roles. However, the roles of autophagy in peripheral leucocytes in atherosclerosis and CAD have not been explored.

MATERIALS AND METHODS

LC3 is a marker gene for autophagy, and LC3-II, a conjugated form of LC3 protein, is a membrane marker for autophagosome and autophagolysosomes. In this study, LC3 gene expression levels and LC3-II protein levels in peripheral leucocytes were measured in patients with CAD (n = 146) and healthy controls (n = 87).

RESULTS

In patients with CAD, LC3 gene expression levels in the peripheral leucocytes were significantly decreased compared with age- and sex-matched healthy controls (P < 0·01). LC3-II protein levels were also significantly decreased in patients with CAD (P < 0·01). Multivariate logistic analyses showed that decreased LC3 gene expression levels were strongly associated with CAD. There were no differences in LC3 transcripts and LC3-II protein levels between subgroups of patients with CAD.

CONCLUSIONS

LC3 gene expression in the peripheral leucocytes was significantly decreased in patients with CAD, indicating that autophagosome formation is decreased. These data suggest that autophagy in circulating leucocytes may be involved in the pathogenesis of atherosclerosis and CAD.

Lysozyme M-positive monocytes mediate angiotensin II-induced arterial hypertension and vascular dysfunction

BACKGROUND

Angiotensin II (ATII), a potent vasoconstrictor, causes hypertension, promotes infiltration of myelomonocytic cells into the vessel wall, and stimulates both vascular and inflammatory cell NADPH oxidases. The predominant source of reactive oxygen species, eg, vascular (endothelial, smooth muscle, adventitial) versus phagocytic NADPH oxidase, and the role of myelomonocytic cells in mediating arterial hypertension have not been defined yet.

METHODS AND RESULTS

Angiotensin II (1 mg · kg(-1) · d(-1) for 7 days) increased the number of both CD11b(+)Gr-1(low)F4/80(+) macrophages and CD11b(+)Gr-1(high)F4/80(-) neutrophils in mouse aorta (verified by flow cytometry). Selective ablation of lysozyme M-positive (LysM(+)) myelomonocytic cells by low-dose diphtheria toxin in mice with inducible expression of the diphtheria toxin receptor (LysM(iDTR) mice) reduced the number of monocytes in the circulation and limited ATII-induced infiltration of these cells into the vascular wall, whereas the number of neutrophils was not reduced. Depletion of LysM(+) cells attenuated ATII-induced blood pressure increase (measured by radiotelemetry) and vascular endothelial and smooth muscle dysfunction (assessed by aortic ring relaxation studies) and reduced vascular superoxide formation (measured by chemiluminescence, cytochrome c assay, and oxidative fluorescence microtopography) and the expression of NADPH oxidase subunits gp91(phox) and p67(phox) (assessed by Western blot and mRNA reverse-transcription polymerase chain reaction). Adoptive transfer of wild-type CD11b(+)Gr-1(+) monocytes into depleted LysM(iDTR) mice reestablished ATII-induced vascular dysfunction, oxidative stress, and arterial hypertension, whereas transfer of CD11b(+)Gr-1(+) neutrophils or monocytes from gp91(phox) or ATII receptor type 1 knockout mice did not. CONCLUSIONS- Infiltrating monocytes with a proinflammatory phenotype and macrophages rather than neutrophils appear to be essential for ATII-induced vascular dysfunction and arterial hypertension.

Alterations of autophagic-lysosomal system in the peripheral leukocytes of patients with myocardial infarction

BACKGROUND

Myocardial infarction (MI) is a common and multifactorial disease. To date, causal genes and underlying mechanisms remain largely unknown. Autophagic-lysosomal system, a highly conserved degradative process in cells, has been implicated in lipid metabolism. In this study, we explored the alterations of the autophagic-lysosomal system in patients with acute MI.

METHODS

Gene expression of lysosomal associated membrane protein 2 (LAMP-2), a lysosomal marker gene, and microtubule-associated protein 1 light chain 3 (LC3), an autophagy marker gene, in the peripheral leukocytes of MI patients were examined at transcription and protein levels by RT-PCR assay and western blot analysis, respectively.

RESULTS

Compared to age- and sex-matched healthy controls (n=146), levels of LC3 gene expression and LC3-II protein, a cleaved form of LC3 protein, were significantly decreased in MI patients (n=81). LAMP-2 gene expression and protein levels were significantly increased. Decreased LC3 gene expression (OR, 2.150, 95%CI, 1.050-4.405, P=0.036) or increased LAMP-2 gene expression (OR, 3.317, 95%CI, 1.588-6.931, P<0.001) levels were associated with MI.

CONCLUSIONS

Our findings indicated that in the peripheral leukocytes of MI patients, autophagy activity is reduced and lysosomal accumulation is increased, which may contribute to the MI pathogenesis. Further genetic analyses of autophagic-lysosomal genes are warranted.

Anti-atherogenic mechanisms of high density lipoprotein: effects on myeloid cells

In some settings increasing high density lipoprotein (HDL) levels has been associated with a reduction in experimental atherosclerosis. This has been most clearly seen in apolipoprotein A-I (apoA-I) transgenic mice or in animals infused with HDL or its apolipoproteins. A major mechanism by which these treatments are thought to delay progression or cause regression of atherosclerosis is by promoting efflux of cholesterol from macrophage foam cells. In addition, HDL has been described as having anti-inflammatory and other beneficial effects. Some recent research has linked anti-inflammatory effects to cholesterol efflux pathways but likely multiple mechanisms are involved. Macrophage cholesterol efflux may have a role in facilitating emigration of macrophages from lesions during regression. While macrophages can mediate cholesterol efflux by several pathways, studies in knockout mice or cells point to the importance of active efflux mediated by ATP binding cassette transporter (ABC) A1 and G1. In addition to traditional roles in macrophages, these transporters have been implicated in the control of hematopoietic stem cell proliferation, monocytosis and neutrophilia, as well as activation of monocytes and neutrophils. Thus, HDL and cholesterol efflux pathways may have important anti-atherogenic effects at all stages of the myeloid cell/monocyte/dendritic cell/macrophage lifecycle. This article is part of a Special Issue entitled Advances in High Density Lipoprotein Formation and Metabolism: A Tribute to John F. Oram (1945-2010).

Human neutrophil peptides mediate endothelial-monocyte interaction, foam cell formation, and platelet activation

OBJECTIVE

Neutrophils are involved in the inflammatory responses during atherosclerosis. Human neutrophil peptides (HNPs) released from activated neutrophils exert immune modulating properties. We hypothesized that HNPs play an important role in neutrophil-mediated inflammatory cardiovascular responses in atherosclerosis.

METHODS AND RESULTS

We examined the role of HNPs in endothelial-leukocyte interaction, platelet activation, and foam cell formation in vitro and in vivo. We demonstrated that stimulation of human coronary artery endothelial cells with clinically relevant concentrations of HNPs resulted in monocyte adhesion and transmigration; induction of oxidative stress in human macrophages, which accelerates foam cell formation; and activation and aggregation of human platelets. The administration of superoxide dismutase or anti-CD36 antibody reduced foam cell formation and cholesterol efflux. Mice deficient in double genes of low-density lipoprotein receptor and low-density lipoprotein receptor-related protein (LRP), and mice deficient in a single gene of LRP8, the only LRP phenotype expressed in platelets, showed reduced leukocyte rolling and decreased platelet aggregation and thrombus formation in response to HNP stimulation.

CONCLUSIONS

HNPs exert proatherosclerotic properties that appear to be mediated through LRP8 signaling pathways, suggesting an important role for HNPs in the development of inflammatory cardiovascular diseases.

Deletion of L-selectin increases atherosclerosis development in ApoE-/- mice

Atherosclerosis is an inflammatory disease characterized by accumulation of leukocytes in the arterial intima. Members of the selectin family of adhesion molecules are important mediators of leukocyte extravasation. However, it is unclear whether L-selectin (L-sel) is involved in the pathogenesis of atherosclerosis. In the present study, mice deficient in L-selectin (L-sel(-/-)) animals were crossed with mice lacking Apolipoprotein E (ApoE(-/-)). The development of atherosclerosis was analyzed in double-knockout ApoE/L-sel (ApoE(-/-)L-sel(-/-)) mice and the corresponding ApoE(-/-) controls fed either a normal or a high cholesterol diet (HCD). After 6 weeks of HCD, aortic lesions were increased two-fold in ApoE(-/-)L-sel(-/-) mice as compared to ApoE(-/-) controls (2.46%±0.54% vs 1.28%±0.24% of total aortic area; p<0.05). Formation of atherosclerotic lesions was also enhanced in 6-month-old ApoE(-/-)L-sel(-/-) animals fed a normal diet (10.45%±2.58% vs 1.87%±0.37%; p<0.05). In contrast, after 12 weeks of HCD, there was no difference in atheroma formation between ApoE(-/-)L-sel(-/-) and ApoE(-/-) mice. Serum cholesterol levels remained unchanged by L-sel deletion. Atherosclerotic plaques did not exhibit any differences in cellular composition assessed by immunohistochemistry for CD68, CD3, CD4, and CD8 in ApoE(-/-)L-sel(-/-) as compared to ApoE(-/-) mice. Leukocyte rolling on lesions in the aorta was similar in ApoE(-/-)L-sel(-/-) and ApoE(-/-) animals. ApoE(-/-)L-sel(-/-) mice exhibited reduced size and cellularity of peripheral lymph nodes, increased size of spleen, and increased number of peripheral lymphocytes as compared to ApoE(-/-) controls. These data indicate that L-sel does not promote atherosclerotic lesion formation and suggest that it rather protects from early atherosclerosis.

Neutrophil activation is attenuated by high-density lipoprotein and apolipoprotein A-I in in vitro and in vivo models of inflammation

OBJECTIVE

Neutrophils play a key role in the immune response but can undesirably exacerbate inflammation. High-density lipoproteins (HDL) are antiinflammatory particles, exerting beneficial cardiovascular influences. We determined whether HDL exerts antiinflammatory effects on neutrophils and explored the mechanisms by which these occur.

METHODS AND RESULTS

CD11b on activated human neutrophils was significantly attenuated by apolipoprotein A-I (apoA-I) and HDL. The effects of apoA-I were mediated via ABCA1, whereas the effects of HDL were via scavenger receptor BI. Both were associated with a reduction in the abundance of lipid rafts, and a strong correlation between raft abundance and CD11b activation was observed. ApoA-I and HDL reduced neutrophil adhesion to a platelet monolayer under shear flow, as well as neutrophil spreading and migration. ApoA-I also inhibited leukocyte recruitment to the endothelium in an acute in vivo model of inflammation. Finally, infusion of reconstituted HDL in patients with peripheral vascular disease was demonstrated to significantly attenuate neutrophil activation.

CONCLUSION

We describe here a novel role for HDL and apoA-I in regulating neutrophil activation using in vitro, in vivo, and clinical approaches. We also show that these effects of HDL and apoA-I involve a mechanism requiring changes in membrane domain content rather than in cholesterol efflux per se.

LAMP-2 gene expression in peripheral leukocytes is increased in patients with coronary artery disease

BACKGROUND

Coronary artery disease (CAD) is a common complex disease that is caused by interaction between genetic and environmental factors. Accumulating evidence indicates that foam cells in the atherosclerotic plaques exhibit the characteristics of lysosomal storage diseases, namely lysosomal accumulation of indigested materials. In patients with lysosomal storage diseases, lysosomal accumulation of lipids and cholesterols in atherosclerotic plaque cells has been observed. However, the roles of lysosomal hydrolases and proteins in the pathogenesis of atherosclerosis and CAD remain unclear.

HYPOTHESIS

Lysosomal hydrolases and proteins may be involved in the pathogenesis of atherosclerosis and CAD by affecting lipid and cholesterol metabolism.

METHODS

Expression levels of LAMP-2, a lysosomal membrane marker gene, in the peripheral leukocytes of CAD patients (n = 134) and age- and sex-matched healthy controls (n = 80) were examined at transcription and protein levels with reverse transcriptase-polymerase chain reaction and Western blot analyses, respectively. The results were compared between CAD patients and healthy controls.

RESULTS

LAMP-2 gene expression and LAMP-2 protein levels were significantly increased in the peripheral leukocytes of CAD patients, compared with healthy controls. Furthermore, multivariate logistic regression analyses revealed that CAD is significantly associated with LAMP-2 gene expression levels (odds ratio [OR] 8.84, 95% confidence interval [CI]: 2.15-36.40, P = 0.003) or LAMP-2 protein levels (OR 2.03, 95% CI: 1.15-3.59, P = 0.015).

CONCLUSIONS

In CAD patients, LAMP-2 gene expression in the peripheral leukocytes was significantly increased than were controls, which indicates lysosomal accumulation. These data suggest that insufficient lysosomal hydrolases and proteins may lead to abnormal lipid and cholesterol metabolism, which cause initiation and progression of atherosclerosis and CAD.

S100A9 differentially modifies phenotypic states of neutrophils, macrophages, and dendritic cells: implications for atherosclerosis and adipose tissue inflammation

BACKGROUND

S100A9 is constitutively expressed in neutrophils, dendritic cells, and monocytes; is associated with acute and chronic inflammatory conditions; and is implicated in obesity and cardiovascular disease in humans. Most of the constitutively secreted S100A9 is derived from myeloid cells. A recent report demonstrated that mice deficient in S100A9 exhibit reduced atherosclerosis compared with controls and suggested that this effect was due in large part to loss of S100A9 in bone marrow-derived cells.

METHODS AND RESULTS

To directly investigate the role of bone marrow-derived S100A9 in atherosclerosis and insulin resistance in mice, low-density lipoprotein receptor-deficient, S100A9-deficient bone marrow chimeras were generated. Neither atherosclerosis nor insulin resistance was reduced in S100A9-deficient chimeras fed a diet rich in fat and carbohydrates. To investigate the reason for this lack of effect, myeloid cells were isolated from the peritoneal cavity or bone marrow. S100A9-deficient neutrophils exhibited a reduced secretion of cytokines in response to toll-like receptor-4 stimulation. In striking contrast, S100A9-deficient dendritic cells showed an exacerbated release of cytokines after toll-like receptor stimulation. Macrophages rapidly lost S100A9 expression during maturation; hence, S100A9 deficiency did not affect the inflammatory status of macrophages.

CONCLUSIONS

S100A9 differentially modifies phenotypic states of neutrophils, macrophages, and dendritic cells. The effect of S100A9 deficiency on atherosclerosis and other inflammatory diseases is therefore predicted to depend on the relative contribution of these cell types at different stages of disease progression. Furthermore, S100A9 expression in nonmyeloid cells is likely to contribute to atherosclerosis.

Regulation of endothelial cell adhesion molecule expression by mast cells, macrophages, and neutrophils

Background

Leukocyte adhesion to the vascular endothelium and subsequent transendothelial migration play essential roles in the pathogenesis of cardiovascular diseases such as atherosclerosis. The leukocyte adhesion is mediated by localized activation of the endothelium through the action of inflammatory cytokines. The exact proinflammatory factors, however, that activate the endothelium and their cellular sources remain incompletely defined.

Methods and Results

Using bone marrow-derived mast cells from wild-type, Tnf^−/−, Ifng^−/−, Il6^−/− mice, we demonstrated that all three of these pro-inflammatory cytokines from mast cells induced the expression of vascular cell adhesion molecule-1 (VCAM-1), intercellular adhesion molecule-1 (ICAM-1), P-selectin, and E-selectin in murine heart endothelial cells (MHEC) at both mRNA and protein levels. Compared with TNF-α and IL6, IFN-γ appeared weaker in the induction of the mRNA levels, but at protein levels, both IL6 and IFN-γ were weaker inducers than TNF-α. Under physiological shear flow conditions, mast cell-derived TNF-α and IL6 were more potent than IFN-γ in activating MHEC and in promoting neutrophil adhesion. Similar observations were made when neutrophils or macrophages were used. Neutrophils and macrophages produced the same sets of pro-inflammatory cytokines as did mast cells to induce MHEC adhesion molecule expression, with the exception that macrophage-derived IFN-γ showed negligible effect in inducing VCAM-1 expression in MHEC.

Conclusion

Mast cells, neutrophils, and macrophages release pro-inflammatory cytokines such as TNF-α, IFN-γ, and IL6 that induce expression of adhesion molecules in endothelium and recruit of leukocytes, which is essential to the pathogenesis of vascular inflammatory diseases.

Hyperlipidemia-Triggered Neutrophilia Promotes Early Atherosclerosis

Background—

Inflammation and activation of immune cells are key mechanisms in the development of atherosclerosis. Previous data indicate important roles for monocytes and T lymphocytes in lesion formation, whereas the contribution of neutrophils remains to be firmly established. Here, we investigate the effect of hypercholesterolemia on peripheral neutrophil counts, neutrophil recruitment to atherosclerotic lesions, and the importance of neutrophils in atherosclerotic lesion formation in Apoe −/− mice.

Methods and Results—

Hypercholesterolemia induces neutrophilia, which was attributable to enhanced granulopoiesis and enhanced mobilization from the bone marrow. The degree of hypercholesterolemia-induced neutrophilia was positively correlated with the extent of early atherosclerotic lesion formation. In turn, neutropenic mice display reduced plaque sizes at early but not late stages of atherosclerotic lesion formation. Flow cytometry of enzymatically digested aortas further shows altered cellular plaque composition in neutropenic mice with reduced numbers of inflammatory monocytes and macrophages. Aortic neutrophil infiltration peaks 4 weeks after the start of a high-fat diet and decreases afterward. The recruitment of neutrophils to large arteries was found to depend on CCR1, CCR2, CCR5, and CXCR2, which contrasts to peripheral venous recruitment, which requires CCR2 and CXCR2 only. The involvement of CCR1 and CCR5 corresponded to the endothelial deposition of the platelet-derived chemokine CCL5 in arteries but not in veins.

Conclusions—

Our data provide evidence that hypercholesterolemia-induced neutrophilia is multifactorial and that neutrophils infiltrate arteries primarily during early stages of atherosclerosis. Collectively, these data suggest an important role of neutrophils in the initiation of atherosclerosis.