A major role for VCAM-1, but not ICAM-1, in early atherosclerosis

The tea flavonoid epigallocatechin-3-gallate reduces cytokine-induced VCAM-1 expression and monocyte adhesion to endothelial cells

Attachment of leukocytes to the vascular endothelium and the subsequent migration of cells into the vessel wall are early events in atherogenesis. This process requires the expression of endothelial adhesion molecules. Since tea catechins are reputed to promote antiatherogenic activities, we investigated the effects of various tea catechins-i.e., epicatechin (EC), epicatechin gallate (ECG), epigallocatechin (EGC), and epigallocatechin-3-gallate (EGCG)-on cytokine-induced expression of intercellular adhesion molecule-1 (ICAM-1), vascular cell adhesion molecule-1 (VCAM-1), and endothelial leukocyte adhesion molecule-1 (E-selectin) in HUVECs by ELISA. EGCG and to a lesser extent ECG prevented the induction of VCAM-1 expression in a concentration-dependent manner after stimulation with TNF-alpha, whereas EC and EGC were without effect. EGCG also inhibited the IL-1beta-induced induction of VCAM-1 expression. Inhibition of cytokine-induced VCAM-1 expression was manifested already on the transcriptional level. Furthermore, EGCG reduced the TNF-alpha-induced adhesion of THP-1 cells to HUVECs. EGCG did not influence TNF-alpha-stimulated NF-kappaB activation.

Innate immune recognition of invasive bacteria accelerates atherosclerosis in apolipoprotein E-deficient mice

BACKGROUND

Infectious diseases have emerged as potential risk factors for cardiovascular disease (CVD). Epidemiological studies support a connection between periodontal disease, a chronic inflammatory disease of the supporting tissues of the teeth, and CVD.

METHODS AND RESULTS

To directly test the connection between periodontal disease and atherosclerosis, apoE-/- mice were orally challenged with the periodontal disease pathogen Porphyromonas gingivalis or an invasion-impaired P gingivalis fimbriae-deficient mutant (FimA-). Both wild-type P gingivalis and the FimA- mutant were detected in blood and aortic arch tissue of apoE-/- mice by PCR after challenge. ApoE-/- mice challenged with wild-type P gingivalis presented with increased atherosclerotic plaque and expressed the innate immune response markers Toll-like receptor (TLR)-2 and TLR-4 in aortic tissue. Despite detection of the FimA- mutant in the blood and in aortic arch tissue, apoE-/- mice challenged with the FimA- mutant did not present with periodontal disease, upregulation of TLRs, or accelerated atherosclerosis. Furthermore, we demonstrate that immunization to control P gingivalis-elicited periodontal disease concomitantly prevents P gingivalis-accelerated atherosclerosis.

CONCLUSIONS

We conclude that invasive P gingivalis accelerates atherosclerosis.

Application of stereological methods for the quantification of VCAM-1 and ICAM-1 expression in early stages of rabbit atherogenesis

Early stages of atherogenesis are characterized by the overexpression of cell adhesion molecules with the subsequent accumulation of macrophages, smooth muscle cells and proliferation of extracellular matrix in arterial intima. The quantification of atherogenic changes is necessary for the objective evaluation of the atherogenic process. The purpose of this study was to introduce stereological methods that may be used for the quantification of immunohistochemical staining, namely intercellular cell adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1). Twenty-four New Zealand White rabbits were subdivided into the three groups. Eighteen rabbits received a 0.4% cholesterol diet for 1, 2 and 3 months, respectively. Stereological principles of the systematic uniform random sampling and the point-counting method were applied for the quantification. Stereological analysis showed that VCAM-1 and ICAM-1 were upregulated during the consumption of high cholesterol diet and that VCAM-1, but not ICAM-1, has a considerable role in the formation of early atherosclerotic lesions. Stereological methods proved to be useful for the quantification of immunohistochemistry and can be used for an objective characterization of atherogenic changes in atherosclerosis.

The state of macrophage differentiation determines the TNF alpha response to nitrated lipoprotein uptake

Inflammatory cytokine synthesis by monocyte-macrophages in the developing plaque represents an important amplification point in atherosclerotic disease progression. Here we have investigated whether the state of monocyte-macrophage differentiation can influence TNF alpha synthesis in response to scavenged modified low-density lipoprotein (LDL). We show that LDL modified by nitration induces TNF alpha synthesis when added to undifferentiated human monocytes or a mouse cell line (RAW264.7) bearing an incompletely differentiated phenotype. However, significantly reduced levels of TNF alpha were released from in vitro differentiated human macrophages (P=0.006) or a mouse cell line (IC-21) bearing a well-differentiated macrophage phenotype (P<0.001). A possible scavenging insufficiency in macrophagic cell types was ruled out by lipoprotein-uptake studies and competency to synthesise TNF alpha was confirmed using lipopolysaccharide (LPS) as a stimulus. However, LPS-induced TNF alpha secretion in IC-21 cells was partially suppressed by pre-treatment with nitrated LDL (46%, P=0.0076), with no equivalent effect seen in RAW264.7 cells. Based on these data, we hypothesise that the state of differentiation of intimal monocyte-macrophages may play an important role in their inflammatory response to scavenged modified lipoproteins and that the fully differentiated macrophage end-point may be associated with a non-inflammatory and therefore, atheroprotective, phenotype.

Adhesion molecules and atherosclerosis

One early phase of atherosclerosis involves the recruitment of inflammatory cells from the circulation and their transendothelial migration. This process is predominantly mediated by cellular adhesion molecules, which are expressed on the vascular endothelium and on circulating leukocytes in response to several inflammatory stimuli. Selectins (P, E and L) and their ligands (mainly P-selectin ligand) are involved in the rolling and tethering of leukocytes on the vascular wall. Intercellular adhesion molecules (ICAMs) and vascular cell adhesion molecules (VCAM-1), as well as some of the integrins, induce firm adhesion of inflammatory cells at the vascular surface, whereas platelet endothelial cellular adhesion molecules (PECAM-1) are involved in extravasation of cells from the blood compartment into the vessel and underlying tissue. For most of the cellular adhesion molecules, except integrins, soluble forms have been identified in the circulation although their origins are not fully understood. Several lines of evidence support a crucial role of adhesion molecules in the development of atherosclerosis and plaque instability. Expression of VCAM-1, ICAM-1 and L-selectin has been consistently observed in atherosclerotic plaques. There is accumulating evidence from prospective studies for a predictive role of elevated circulating levels of sICAM-1 in initially healthy people, and of sVCAM-1 in patients at high risk or with overt CAD. A large number of common polymorphisms has been identified in the genes encoding the different adhesion molecules, but studies investigating their relationship either with soluble forms or with CAD are still sparse and often based on small samples. Further research is needed to firmly establish the potential clinical and therapeutic utilities of (soluble) adhesion molecules, but results in both fields hold the promise that in future, adhesion molecules might add information for clinical risk prediction and serve as therapeutic targets.

Gene interactions and stroke risk in children with sickle cell anemia

Stroke is a devastating complication of sickle cell anemia (SCA), affecting up to 30% of children with the disease. Despite the relative frequency of stroke in SCA, few predictors of risk exist. Because stroke in SCA is likely a multifactorial disease, analysis of the combined effect of multiple genetic variants may prove more successful than evaluation of individual candidate genes. We genotyped 230 children with SCA for 104 polymorphisms among 65 candidate vascular genes to identify risk associations with stroke. Patients were phenotyped based on magnetic resonance imaging/angiography (MRI/MRA) findings into large-vessel (LV) versus small-vessel (SV) disease stroke subgroups. Specific polymorphisms in the IL4R 503, TNF (-308), and ADRB2 27 genes were independently associated with stroke susceptibility in the LV stroke subgroup, while variants in the VCAM1 (-1594) and LDLR NcoI genes were associated with SV stroke risk. The combination of TNF (-308)GG homozygosity and the IL4R 503P variant carrier status was associated with a particularly strong predisposition to LV stroke (odds ratio [OR] = 5.5; 95% confidence interval [CI] = 2.3-13.1). We show that several candidate genes may play a role in predisposition to specific stroke subtypes in children with SCA. If confirmed, these results provide a basis for population screening and targeted intervention to prevent stroke in SCA.

Seeing Within

Molecular imaging is a rapidly evolving discipline with the goal of developing tools to display and quantify molecular and cellular targets in vivo. The heart of this field is based on the rational design and screening of targeted and activatable imaging reporter agents to sense fundamental processes of biology. Parallel advances in small animal imaging systems and in agent synthesis have allowed molecular imaging applications to extend into the in vivo arena. These advances have permitted, for example, in vivo sensing of inflammation, apoptosis, cell trafficking, and gene expression. In this review, we first review core principles of molecular imaging with an emphasis on smart, activatable agent technology. We then discuss applications of state-of-the-art molecular probes to interrogate important aspects of cardiovascular biology, with a focus on atherosclerosis, thrombosis, and heart failure. In the ensuing years, we anticipate that fundamental aspects of cardiovascular biology will be detectable in vivo, and that promising molecular imaging agents will be translated into the clinical arena to guide diagnosis and therapy of human cardiovascular illness.

Insulin enhances vascular cell adhesion molecule-1 expression in human cultured endothelial cells through a pro-atherogenic pathway mediated by p38 mitogen-activated protein-kinase

AIMS/HYPOTHESIS

Although hyperinsulinaemia in Type 2 diabetes in states of insulin resistance is a risk factor for atherosclerotic vascular disease, underlying mechanisms are poorly understood. We tested the hypothesis that insulin increases monocyte-endothelial interactions, which are implicated in atherosclerosis.

METHODS

We treated human umbilical vein endothelial cells with insulin (10(-10) to 10(-7) mol/l) for 0 to 24 h. To dissect potentially implicated signal transduction pathways, we treated endothelial cells with known pharmacological inhibitors of two distinct insulin signalling pathways: the phosphatidylinositol-3'-kinase (PI3'-kinase) inhibitor wortmannin (3 x 10(-8) to 10(-6) mol/l), involved in insulin-induced endothelial nitric oxide synthase stimulation, and the p38 mitogen-activated protein (p38MAP) kinase inhibitor SB-203580 (10(-7) to 2 x 10(-6) mol/l). We measured adhesion molecule expression by cell surface enzyme immunoassays and U937 monocytoid cell adhesion in rotational adhesion assays.

RESULTS

At pathophysiological concentrations (10(-9) to 10(-7) mol/l), insulin concentration-dependently induced vascular cell adhesion molecule (VCAM)-1 (average increase: 1.8-fold) peaking at 16 h. By contrast, the expression of intercellular adhesion molecule-1 and E-selectin were unchanged. The effect on VCAM-1 was paralleled by increased U937 cell adhesion. In the absence of cytotoxicity, wortmannin significantly potentiated the effect of insulin alone on VCAM-1 surface expression and monocytoid cell adhesion, whereas SB-203580 (10(-6) mol/l) completely abolished such effects.

CONCLUSIONS/INTERPRETATION

These observations indicate that insulin promotes VCAM-1 expression in endothelial cells through a p38MAP-kinase pathway, amplified by the PI3'-kinase blockage. This could contribute to explaining the increased atherosclerosis occurring in subjects with hyperinsulinaemia, or in states of insulin resistance, which feature a defective PI3'-kinase pathway.

KR‐31378 ameliorates atherosclerosis by blocking monocyte recruitment in hypercholestrolemic mice

The recruitment of monocytes into the artery wall is a crucial early step in atherogenesis. A novel compound, KR-31378, has been shown to be a neuroprotective agent for ischemia-reperfusion damage in rat brain via its potent antioxidant and antiapoptotic actions. Here, we report the effects of this compound on atherogenesis and possible mechanisms of action. In Ldlr knockout mice fed with a high-fat, high-cholesterol diet, treatment with KR-31378 significantly inhibited fatty streak formation and macrophage accumulation. To address the possibility that KR-31378 may influence the initial stages of atherogenesis, we examined its effect on the adhesion and migration of monocytes to endothelial cells stimulated with tumor necrosis factor-alpha. KR-31378 decreased the adhesion in a dose-dependent manner. The observed decreases in cell adhesion and migration correlated with KR-31378-mediated down-regulation of vascular cell adhesion molecule-1 (VCAM-1) and interleukin (IL)-8. Nuclear factor-kappaB (NF-kappaB) is known to regulate the expression of adhesive and chemotactic molecules including VCAM-1 and IL-8. Indeed, transient transfection experiments, electrophoretic mobility shift assay, and IkappaB degradation assay showed that KR-31378 decreased NF-kappaB activation. These results indicate that KR-31378 potently reduces fatty streak formation by inhibiting NF-kappaB-dependent cellular adhesion and chemotactic molecule expression, which are crucial to monocyte infiltration into the arterial wall during the early stages of atherogenesis.

Genetic Ablation of Caveolin-1 Confers Protection Against Atherosclerosis

Objective— The development of atherosclerosis is a process characterized by the accumulation of lipids in the form of modified lipoproteins in the subendothelial space. This initiating step is followed by the subsequent recruitment and proliferation of other cell types, including monocytes/macrophages and smooth muscle cells. Here, we evaluate the potential role of caveolae membrane domains in the pathogenesis of atherosclerosis by using apolipoprotein E-deficient (ApoE−/−) mice as a model system.

Methods and Results— Caveolin-1 (Cav-1) is a principal structural protein component of caveolae membrane domains. To directly assess the in vivo role of caveolae and Cav-1 in atherosclerosis, we interbred Cav-1−/− mice with ApoE−/− mice. Interestingly, loss of Cav-1 resulted in a dramatic >2-fold increase in non-HDL plasma cholesterol levels in the ApoE−/− background. However, despite this hypercholesterolemia, we found that loss of Cav-1 gene expression was clearly protective against the development of aortic atheromas, with up to an ≈70% reduction in atherosclerotic lesion area. Mechanistically, we demonstrated that loss of Cav-1 resulted in the dramatic downregulation of certain proatherogenic molecules, namely, CD36 and vascular cell adhesion molecule-1.

Conclusions— Taken together, our results indicate that loss of Cav-1 can counteract the detrimental effects of atherogenic lipoproteins. Thus, Cav-1 is a novel target for drug development in the pharmacologic prevention of atheroma formation. Our current data also provide the first molecular genetic evidence to support the hypothesis that caveolar transcytosis of modified lipoproteins (from the blood to the sub-endothelial space) is a critical initiating step in atherosclerosis.

Atomic force microscopy measurement of leukocyte-endothelial interaction

Leukocyte adhesion to vascular endothelium is a key initiating step in the pathogenesis of many inflammatory diseases. In this study, we present real-time force measurements of the interaction between monocytic human promyelocytic leukemia cells (HL-60) cells and a monolayer of human umbilical vein endothelial cells (HUVECs) by using atomic force microscopy (AFM). The detachment of HL-60-HUVEC conjugates involved a series of rupture events with force transitions of 40-100 pN. The integrated force of these rupture events provided a quantitative measure of the adhesion strength on a whole cell level. The AFM measurements revealed that HL-60 adhesion is heightened in the borders formed by adjacent HUVECs. The average force and mechanical work required to detach a single HL-60 from the borders of a tumor necrosis factor-alpha-activated HUVEC layer were twice as high as those of the HUVEC bodies. HL-60 adhesion to the monolayer was significantly reduced by a monoclonal antibody against beta1-integrins and partially inhibited by antibodies against selectins ICAM-1 and VCAM-1 but was not affected by anti-alphaVbeta3. Interestingly, adhesion was also inhibited in a dose-dependent manner (IC50 approximately 100 nM) by a cyclic arginine-glycine-aspartic acid (cRGD) peptide. This effect was mediated via interfering with the VLA-4-VCAM-1 binding. In parallel measurements, transmigration of HL-60 cells across a confluent HUVEC monolayer was inhibited by the cRGD peptide and by both anti-beta1 and anti-alphaVbeta3 antibodies. In conclusion, these data demonstrate the role played by beta1-integrins in leukocyte-endothelial adhesion and transmigration and the role played by alphaVbeta3 in transmigration, thus underscoring the high efficacy of cRGD peptide in blocking both the adhesion and transmigration of monocytes.

In vivo interrogation of the molecular display of atherosclerotic lesion surfaces

The endothelial surface of atherosclerotic lesions of ApoE knockout mice was interrogated by in vivo biopanning with a phage-displayed constrained peptidyl library. Through repeated biopanning, 103 peptidyl sequences were identified, many are homologous to known proteins. The sequence CAPGPSKSC contains motifs that are shared by 9.7% of selected peptides. On phage or as a synthetic peptide, this constrained peptide selectively bound to atherosclerotic lesion surfaces of ApoE knockout mice in vivo and of human atherosclerotic lesions ex vivo. A cell-surface protein of approximately 82 kd recognized by this peptide was affinity-purified and determined by mass spectrometry analysis as glucose-regulated protein 78 (Grp78), indicating the surprising presence of this endoplasmic reticulum chaperone on the endothelial cell surface of atherosclerotic lesions. Peptides that mimicked binding functions of their homologues were demonstrated with three peptides homologous to tissue inhibitor of metalloproteinase-2 (TIMP-2), ie, CNHRYMQMC, CNQRHQMSC, and CNNRSDGMC. Phage carrying CNHRYMQMC bound to atherosclerotic lesion endothelium of ApoE knockout mice in vivo. The three peptides bound to endothelial cells in a dose-dependent manner and were inhibited by TIMP-2 protein. These peptides provide a set of probes to interrogate the cell surface repertoire associated with atherogenesis and thrombotic complications.

Oscillatory shear stress stimulates endothelial production of O2- from p47phox-dependent NAD(P)H oxidases, leading to monocyte adhesion

Arterial regions exposed to oscillatory shear (OS) in branched arteries are lesion-prone sites of atherosclerosis, whereas those of laminar shear (LS) are relatively well protected. Here, we examined the hypothesis that OS and LS differentially regulate production of O2- from the endothelial NAD(P)H oxidase, which, in turn, is responsible for their opposite effects on a critical atherogenic event, monocyte adhesion. We used aortic endothelial cells obtained from C57BL/6 (MAE-C57) and p47phox-/- (MAE-p47-/-) mice, which lack a component of NAD(P)H oxidase. O2- production was determined by dihydroethidium staining and an electron spin resonance using an electron spin trap methoxycarbonyl-2,2,5,5-tetramethyl-pyrrolidine. Chronic exposure (18 h) to an arterial level of OS (+/- 5 dynes/cm2) increased O2- (2-fold) and monocyte adhesion (3-fold) in MAE-C57 cells, whereas chronic LS (15 dynes/cm2, 18 h) significantly decreased both monocyte adhesion and O2- compared with static conditions. In contrast, neither LS nor OS were able to induce O2- production and monocyte adhesion to MAE-p47-/-. Treating MAE-C57 with a cell-permeable superoxide dismutase compound, polyethylene glycol-superoxide dismutase, also inhibited OS-induced monocyte adhesion. In addition, over-expressing p47phox in MAE-p47-/- restored OS-induced O2- production and monocyte adhesion. These results suggest that chronic exposure of endothelial cells to OS stimulates O2- and/or its derivatives produced from p47phox-dependent NAD(P)H oxidase, which, in turn, leads to monocyte adhesion, an early and critical atherogenic event.

The VCAM-1 gene that encodes the vascular cell adhesion molecule is a target of the Sry-related high mobility group box gene, Sox18

VCAM-1 (vascular cell adhesion molecule-1) and Sox18 are involved in vascular development. VCAM-1 is an important adhesion molecule that is expressed on endothelial cells and has a critical role in endothelial activation, inflammation, lymphatic pathophysiology, and atherogenesis. The Sry-related high mobility group box factor Sox18 has previously been implicated in endothelial pathologies. Mutations in human and mouse Sox18 leads to hypotrichosis and lymphedema. Furthermore, both Sox18 and VCAM-1 have very similar spatio-temporal patterns of expression, which is suggestive of cross-talk. We use biochemical techniques, cell culture systems, and the ragged opossum (RaOP) mouse model with a naturally occurring mutation in Sox18 to demonstrate that VCAM-1 is an important target of Sox18. Transfection, site-specific mutagenesis, and gel shift analyses demonstrated that Sox18 directly targeted and trans-activated VCAM-1 expression. Importantly, the naturally occurring Sox18 mutant attenuates the expression and activation of VCAM-1 in vitro. Furthermore, in vivo quantitation of VCAM-1 mRNA levels in wild type and RaOP mice demonstrates that RaOP animals show a dramatic and significant reduction in VCAM-1 mRNA expression in lung, skin, and skeletal muscle. Our observation that the VCAM-1 gene is an important target of SOX18 provides the first molecular insights into the vascular abnormalities in the mouse mutant ragged and the human hypotrichosis-lymphedema-telangiectasia disorder.

Transdifferentiation of mouse aortic smooth muscle cells to a macrophage-like state after cholesterol loading

Mouse aortic smooth muscle cells (SMCs) were loaded for 72 h with cholesterol by using cholesterol:methyl-beta-cyclodextrin complexes, leading to approximately 2-fold and approximately 10-fold increases in the contents of total cholesterol and cholesteryl ester, respectively. Foam-cell formation was demonstrated by accumulation of intracellular, Oil Red O-stained lipid droplets. Immunostaining showed decreased protein levels of smooth muscle alpha-actin and alpha-tropomyosin and increased levels of macrophage markers CD68 and Mac-2 antigen. Quantitative real-time RT-PCR revealed that after cholesterol loading, the expression of SMC-related genes alpha-actin, alpha-tropomyosin, myosin heavy chain, and calponin H1 decreased (to 11.5 +/- 0.5%, 29.3 +/- 1.4%, 23.8 +/- 1.4%, and 3.8 +/- 0.5% of unloaded cells, respectively; P < 0.05 for all), whereas expression of macrophage-related genes CD68, Mac-2, and ABCA1 mRNA increased (to 709 +/- 84%, 330 +/- 11%, and 207 +/- 13% of unloaded cells, respectively; P < 0.05 for all), thereby demonstrating that the protein changes were regulated at the mRNA level. Furthermore, these changes were accompanied by a gain in macrophage-like function as assessed by phagocytotic activity. Expression of vascular cell adhesion molecule 1 and monocyte chemoattractant protein 1, known responders to inflammation, were not changed. In conclusion, cholesterol loading of SMC causes phenotypic changes regulated at the mRNA level that result in a transdifferentiation to a macrophage-like state. This finding suggests that not all foam cells in lesions may have a macrophage origin, despite what is indicated by immunostaining for macrophage-related markers. Furthermore, inflammatory changes in foam cells observed in vivo may not be simple consequences of cholesterol accumulation.

Celiprolol activates eNOS through the PI3K-Akt pathway and inhibits VCAM-1 Via NF-kappaB induced by oxidative stress

Vascular cell adhesion molecule-1 (VCAM-1) and reactive oxygen species play critical roles in early atherogenesis, and nitric oxide (NO) is an important regulator of the cardiovascular system. Although celiprolol, a specific beta1-antagonist with weak beta2-agonistic action, stimulates endothelial nitric oxide synthase (eNOS) production, the mechanisms remain to be determined. Because it was recently reported that phosphatidylinositol 3-kinase (PI3K) and its downstream effector Akt are implicated in the activation of eNOS and that regulation of VCAM-1 expression is mediated via nuclear factor-kappaB (NF-kappaB), we hypothesized that celiprolol activates phosphorylation of eNOS through the PI3K-Akt signaling pathway; that celiprolol modulates VCAM-1 expression, which is associated with inhibiting NF-kappaB phosphorylation; and that celiprolol suppresses NAD(P)H oxidase p22phox, p47phox, gp91phox, and nox1 expression in the left ventricle of deoxycorticosterone acetate (DOCA)-salt hypertensive rats. eNOS and Akt phosphorylation upregulated by celiprolol alone were suppressed by treatment with celiprolol plus wortmannin. Increased expression of VCAM-1, p22phox, p47phox, gp91phox, nox1, activated p65 NF-kappaB, c-Src, p44/p42 extracellular signal-regulated kinases, and their downstream effector p90 ribosomal S6 kinase phosphorylation in DOCA rats was inhibited by celiprolol. Celiprolol administration resulted in a significant improvement in cardiovascular remodeling and suppression of transforming growth factor-beta1 gene expression. In conclusion, celiprolol suppresses VCAM-1 expression because of inhibition of oxidative stress, NF-kappaB, and signal transduction, while increasing eNOS via stimulation of the PI3K-Akt signaling pathway and improving cardiovascular remodeling.

Mechanisms of leukotriene B4--triggered monocyte adhesion

OBJECTIVE

Leukotriene B4 (LTB4) has been implicated in the trafficking of monocytes to inflammatory pathologic conditions, such as transplant rejection and atherosclerosis. The aim of this study was to determine the mechanisms by which LTB4 contributes to monocyte capture from the circulation.

METHODS AND RESULTS

In in vitro and in vivo vascular models, the lipid chemoattractant LTB4 was an equipotent agonist of monocyte adhesion compared with the chemokine monocyte chemoattractant protein-1 (MCP-1). Adenoviral gene transfer of specific endothelial adhesion molecules and blocking monoclonal antibody studies demonstrated that LTB4 triggers both beta1- and beta2-integrin-dependent adhesion. Flow cytometry studies suggested that changes in integrin avidity or affinity, rather than alterations of integrin surface expression, were responsible for the chemoattractant-triggered arrest. Surprisingly, in contrast to the peptide chemokine MCP-1, LTB4 did not activate the phosphoinositide 3-kinase pathway, which is a functionally critical step in chemokine-triggered effector functions.

CONCLUSIONS

LTB4 is a potent trigger of monocyte adhesion under flow yet mediates its effects via pathways that appear to differ from peptide chemoattractants. A better understanding of the mechanisms of LTB4-induced monocyte trafficking might shed insight into disease pathogenesis and pinpoint critical steps for therapeutic intervention for multiple human inflammatory pathologic conditions.

Endothelin-1 stimulates arterial VCAM-1 expression via NADPH oxidase-derived superoxide in mineralocorticoid hypertension

Although hypertension is a major risk factor for atherosclerosis, its underlying mechanisms remain to be delineated. We have recently reported that both endothelin-1 (ET-1) and vascular cellular adhesion molecule-1 (VCAM-1) levels, key early markers of atherosclerosis, are significantly elevated in carotid arteries of deoxycorticosterone acetate (DOCA)-salt hypertensive rats, a model known for its suppressed plasma renin levels. This study tested the hypothesis that ET-1 augments arterial VCAM-1 expression through NADPH oxidase-derived superoxide (O2-). Carotid arteries of DOCA-salt or sham-operated rats were transduced ex vivo with extracellular superoxide dismutase (EC-SOD), dominant negative HA-tagged N17Rac1 that inhibits Rac1, the small GTPase component of NADPH oxidase, or beta-galactosidase (beta-gal) reporter gene (5x10(10) plaque formation units [pfu]/mL), and the effect of transgene expression on O2- and VCAM-1 levels was assayed 24 hours afterward. The arterial activity of NADPH oxidase but not xanthine oxidase was significantly higher in DOCA-salt than in sham rats, which was abolished by the selective ETA receptor antagonist ABT-627 (3x10(-8) mol/L), NADPH oxidase inhibitor apocynin (10(-4) mol/L), or dominant negative Rac1 gene transfer. The levels of O2- and VCAM-1 were significantly increased in arteries of DOCA-salt rats, an effect that was ameliorated after EC-SOD or dominant negative Rac1 but not beta-gal reporter gene transfer. ABT-627 and apocynin also significantly reduced elevated VCAM-1 levels in ET-1-treated arteries of normal rats and arteries of DOCA-salt rats. The results of this study indicate that ET-1 stimulates arterial VCAM-1 expression by producing O2- from an ETA receptor/NADPH oxidase pathway in low-renin mineralocorticoid hypertension.

A new En face method is useful to quantitate endothelial damage in vivo

Endothelial damage is considered to be an initial change in the atherosclerotic process. However, it has been difficult to detect this initial change in vivo. We established a modified En face immunostaining method that enabled us to obtain clear images of the entire endothelial surface, including at arterial bifurcations, and to quantitate the number of cells of interest in the endothelium. Using this method, we found that treatment with an atherogenic factor, albumin-derived advanced glycosylation end products, for only 2 weeks caused a significant increase in the number of proliferating cell nuclear antigen-positive endothelial cells and the number of macrophages adhering to the endothelium, suggesting that these changes might be relevant to the early events of endothelial dysfunction. In conclusion, the present modified En face immunostaining method may be a promising tool for understanding the pathophysiology of atherosclerosis.

Alcohol inflammation and coronary heart disease

This overview summarizes the experimental and epidemiological evidence linking alcohol consumption and the immune system. It focuses on findings supporting the notion that moderate alcohol consumption exerts anti-inflammatory effects which may explain, at least in part, the reduced risk of coronary heart disease morbidity and mortality in these subjects. Alcohol consumption has been shown consistently to be associated with all-cause mortality in a J- or U-shaped manner. This is due primarily to reduced risk of coronary heart disease (CHD)mortality among moderate consumers of alcohol compared to abstainers and heavy drinkers. Several mechanisms have been suggested by which moderate alcohol consumption could lower risk of CHD. However, changes in lipids, such as increased HDL cholesterol and apolipoprotein Al or a favourable haemostatic profile, can only partly explain the beneficial effects. Recently, anti-inflammatory effects of moderate intake of alcohol have been considered as an additional possible explanation, as inflammation has a fundamental role in the initiation, progression and the thrombotic complications of atherosclerosis.

Inflammatory reactions in the pathogenesis of atherosclerosis

Atherosclerosis and its complications constitute the most common causes of death in Western societies and Japan. Although several theories or hypotheses about atherogenesis have been proposed during the past decades, none can completely explain the whole process of the pathogenesis of atherosclerosis because this disease is associated with multiple risk factors. In spite of this, the concept that atherosclerosis is a specific form of chronic inflammatory process resulting from interactions between plasma lipoproteins, cellular components ( monocyte/macrophages, T lymphocytes, endothelial cells and smooth muscle cells ) and the extracellular matrix of the arterial wall, is now well accepted. Histologically, atherosclerotic lesions from the early-stage ( fatty streak ) to more complicated lesions possess all the features of chronic inflammation. It has been demonstrated that atherogenic lipoproteins such as oxidized low density lipoprotein ( LDL ), remnant lipoprotein (beta-VLDL) and lipoprotein [ Lp ] ( a ) play a critical role in the pro-inflammatory reaction, whereas high density lipoprotein ( HDL ), anti-atherogenic lipoproteins, exert anti-inflammatory functions. In cholesterol-fed animals, the earliest events in the arterial wall during atherogenesis are the adhesion of monocytes and lymphocytes to endothelial cells followed by the migration of these cells into the intima. It has been shown that these early events in atherosclerosis are triggered by the presence of high levels of atherogenic lipoproteins in the plasma and are mediated by inflammatory factors such as adhesion molecules and cytokines in the arterial wall. The development of genetically modified laboratory animals ( transgenic and knock-out mice and transgenic rabbits ) has provided a powerful approach for dissecting individual candidate genes and studying their cause-and-effect relationships in lesion formation and progression. The purpose of this article is to review the recent progress regarding the inflammatory processes during the development of atherosclerosis based on both human and experimental studies. In particular, we will address the mechanisms of atherogenic lipoproteins in terms of inflammatory reactions associated with hypercholesterolemia. Understanding the molecular mechanisms responsible for inflammatory reactions during atherogenesis may help us to develop novel therapeutic strategies to control, treat and prevent atherosclerosis in the future.

Bone morphogenic protein 4 produced in endothelial cells by oscillatory shear stress stimulates an inflammatory response

Atherosclerosis is now viewed as an inflammatory disease occurring preferentially in arterial regions exposed to disturbed flow conditions, including oscillatory shear stress (OS), in branched arteries. In contrast, the arterial regions exposed to laminar shear (LS) are relatively lesion-free. The mechanisms underlying the opposite effects of OS and LS on the inflammatory and atherogenic processes are not clearly understood. Here, through DNA microarrays, protein expression, and functional studies, we identify bone morphogenic protein 4 (BMP4) as a mechanosensitive and pro-inflammatory gene product. Exposing endothelial cells to OS increased BMP4 protein expression, whereas LS decreased it. In addition, we found BMP4 expression only in the selective patches of endothelial cells overlying foam cell lesions in human coronary arteries. The same endothelial patches also expressed higher levels of intercellular cell adhesion molecule-1 (ICAM-1) protein compared with those of non-diseased areas. Functionally, we show that OS and BMP4 induced ICAM-1 expression and monocyte adhesion by a NFkappaB-dependent mechanism. We suggest that BMP4 is a mechanosensitive, inflammatory factor playing a critical role in early steps of atherogenesis in the lesion-prone areas.

VCAM-1-mediated Rac signaling controls endothelial cell-cell contacts and leukocyte transmigration

Leukocyte adhesion is mediated totally and transendothelial migration partially by heterotypic interactions between the beta1- and beta2-integrins on the leukocytes and their ligands, Ig-like cell adhesion molecules (Ig-CAM), VCAM-1, and ICAM-1, on the endothelium. Both integrins and Ig-CAMs are known to have signaling capacities. In this study we analyzed the role of VCAM-1-mediated signaling in the control of endothelial cell-cell adhesion and leukocyte transendothelial migration. Antibody-mediated cross-linking of VCAM-1 on IL-1beta-activated primary human umbilical vein endothelial cells (pHUVEC) induced actin stress fiber formation, contractility, and intercellular gaps. The effects induced by VCAM-1 cross-linking were inhibited by C3 toxin, indicating that the small GTPase p21Rho is involved. In addition, the effects of VCAM-1 were accompanied by activation of Rac, which we recently showed induce intercellular gaps in pHUVEC in a Rho-dependent fashion. With the use of a cell-permeable peptide inhibitor, it was shown that Rac signaling is required for VCAM-1-mediated loss of cell-cell adhesion. Furthermore, VCAM-1-mediated signaling toward cell-cell junctions was accompanied by, and dependent on, Rac-mediated production of reactive oxygen species and activation of p38 MAPK. In addition, it was found that inhibition of Rac-mediated signaling blocks transendothelial migration of monocytic U937 cells. Together, these data indicate that VCAM-1-induced, Rac-dependent signaling plays a key role in the modulation of vascular-endothelial cadherin-mediated endothelial cell-cell adhesion and leukocyte extravasation.

Cellular adhesion molecules and cardiovascular disease. Part I. Their expression and role in atherogenesis

Atherosclerosis is now recognized to be an inflammatory disease, and several inflammatory markers have been shown to be associated with both the presence and future risk of symptomatic cardiovascular disease. Cellular adhesion molecules, particularly members of the selectin family and immunoglobulin superfamily, are intimately involved in the recruitment of leucocytes to sites of inflammation, including developing atherosclerotic lesions. Their role in the pathogenesis of atherosclerosis has been clearly demonstrated using knockout mice models. Plasma levels of adhesion molecules, which have been shed from the cell surface, have been associated with the presence of clinical atherosclerotic disease, although published studies differ in their findings. This limited consensus in the literature may be explained either by unrecognized confounding factors, or perhaps by the unpredictable relationship between cell surface expression and activity of cellular adhesion molecules and their shedding into the plasma. While cell surface activity of adhesion molecules appears critical in the development of atherosclerotic lesions, the measurement of plasma levels of soluble adhesion molecules may offer little additional benefit for individual patients in the prediction of the extent of atherosclerotic disease above the assessment of conventional cardiovascular risk factors.

Oxidized phospholipid-induced endothelial cell/monocyte interaction is mediated by a cAMP-dependent R-Ras/PI3-kinase pathway

OBJECTIVE

Previous studies have demonstrated the importance of endothelial apical expression of connecting segment-1 (CS-1) fibronectin in mediating the entry of monocytes into atherosclerotic lesions and other sites of chronic inflammation. We previously demonstrated that oxidized PAPC (OxPAPC) increases monocyte-specific binding to arterial endothelium by causing deposition of CS-1 fibronectin on apical alpha5beta1 integrin. The present studies identify important signal transduction components regulating this pathway.

METHODS AND RESULTS

Using endothelial cells in culture, we demonstrate that activation of R-Ras is responsible for CS-1-mediated monocyte binding. Although few natural activators of R-Ras have been demonstrated, OxPAPC activated endothelial R-Ras by 2.5-fold but decreased levels of activated H-Ras. The importance of R-Ras/H-Ras balance in regulating monocyte binding was shown by overexpression studies. Constitutively active R-Ras enhanced monocyte adhesion, whereas coexpression with constitutively active H-Ras was inhibitory. Elevated cAMP, mediated by OxPAPC and specific components POVPC and PEIPC, was responsible for R-Ras activation, and dibutyryl cAMP and pertussis toxin were also effective activators of R-Ras. Using inhibitor and dominant-negative constructs, we demonstrated that phosphatidylinositol 3-kinase (PI3K) was a key downstream effector of R-Ras in this pathway.

CONCLUSIONS

OxPAPC, POVPC, and PEIPC induce a cAMP/R-Ras/PI3K signaling pathway that contributes to monocyte/endothelial cell adhesion and potentially atherosclerosis.

Circulating ICAM‐1, VCAM‐1, E‐Selectin, P‐Selectin, and TNFαRII in Patients with Coronary Artery Disease

OBJECTIVE

To evaluate the relationship between the serum concentration of TNFalphaRII and some adhesion molecules (including ICAM-1, VCAM-1, P-selectin and E-selectin) and coronary artery stenosis.

DESIGN AND SETTING

Observational (cross-sectional) study in a university heart hospital in Tehran, Iran.

PATIENTS

81 patients with angiographically proven coronary artery disease were compared with 75 individuals who had undergone coronary angiography with no significant evidence of stenosis (control subjects).

METHODS

Soluble adhesion molecules and TNFalphaRII were determined by enzyme-linked immunosorbent assay technique. sICAM-1 and sP-selectin values were significantly higher in patients with coronary artery disease than in control subjects (146 +/- 38 vs. 132 +/- 48 p < 0.04 and 275 +/- 107 vs. 241 +/- 104 ng/ml p < 0.04 respectively). Multiple logistic regression analysis showed sICAM-1 as an independent discriminating risk factor for coronary artery disease (p < 0.03). Prediction models that incorporated sICAM-1 in addition to other established coronary risk factors were significantly better at predicting risk than the models based on the other risk factors alone. Multiple regression analysis indicated that sP-selectin levels were greater in patients with single-vessel disease than in the respective normal (p < 0.01).

CONCLUSIONS

Our findings suggest that sICAM-1 has an association with stable coronary artery disease and the evaluation of this marker may improve the coronary risk assessment in Iranian patients.

The P2Y2 nucleotide receptor mediates UTP-induced vascular cell adhesion molecule-1 expression in coronary artery endothelial cells

P2Y2 receptor up-regulation and activation induces intimal hyperplasia and monocyte/macrophage infiltration in the collared rabbit carotid artery model of vascular injury, suggesting a potential role for P2Y2 receptors in monocyte recruitment by vascular endothelium. In this study, we addressed the hypothesis that activation of P2Y2 receptors by extracellular nucleotides modulates the expression of adhesion molecules on vascular endothelial cells that are important for monocyte recruitment. Results indicated that the equipotent P2Y2 receptor agonists UTP or ATP (1-100 microm) stimulated the expression of vascular cell adhesion molecule-1 (VCAM-1) in human coronary artery endothelial cells (HCAEC) in a time- and dose-dependent manner. P2Y2 antisense oligonucleotides inhibited VCAM-1 expression induced by UTP but not by tumor necrosis factor-alpha. Furthermore, UTP induced VCAM-1 expression in human 1321N1 astrocytoma cell transfectants expressing the recombinant P2Y2 receptor, whereas vector-transfected control cells did not respond to UTP. The effect of UTP on VCAM-1 expression in HCAEC was prevented by depletion of intracellular calcium stores with thapsigargin or by inhibition of p38 mitogen-activated protein kinase or Rho kinase, but was not affected by inhibitors of the mitogen-activated protein/extracellular signal-regulated kinase pathway (i.e. MEK1/2). Consistent with a role for VCAM-1 in the recruitment of monocytes, UTP or ATP increased the adherence of monocytic U937 cells to HCAEC, an effect that was inhibited by anti-VCAM-1 antibodies. These findings suggest a novel role for the P2Y2 receptor in the p38- and Rho kinase-dependent expression of VCAM-1 that mediates the recruitment of monocytes by vascular endothelium associated with the development of atherosclerosis.

The effects of LDL reduction and HDL augmentation on physiologic and inflammatory markers

Cholesterol plays an important role in atherogenesis. Oxidized low-density lipoprotein cholesterol is harmful to arteries whereas high-density lipoprotein cholesterol appears to have beneficial properties on vascular function. There is increasing evidence that inflammation is also involved in the atherogenic process. Inflammation accelerates atherosclerosis and promotes thrombogenesis, and inflammatory biomarkers have been correlated with cardiovascular risk. There is now evidence that lowering low-density lipoprotein and raising high-density lipoprotein cholesterol have beneficial effects on inflammation that might contribute to the reduction in clinical cardiovascular events with currently available lipid-altering therapies. New therapeutic strategies are being designed to inhibit specific aspects of the inflammatory system that contribute to the initiation and progression of atherosclerosis.

Suppression of endothelial adhesion molecule up-regulation with cyclopentenone prostaglandins is dissociated from IkappaB-alpha kinase inhibition and cell death induction

The cyclopentenone prostaglandins (cPG) 15-deoxy-Delta12,14-prostaglandin J2 (dPGJ2) and PGA1 can inhibit multiple steps in nuclear factor (NF)-kappaB signaling and can induce cell death. Here we characterized the effects of dPGJ2 and PGA1 on the inflammatory induction of endothelial cell adhesion molecules (CAM). Pretreatment of endothelial cells with dPGJ2 or PGA1 at low concentrations dose dependently inhibited the up-regulation of CAM expression and monocyte arrest by tumor necrosis factor (TNF)-alpha but not expression of inhibitor of apoptosis proteins. Only at high concentrations, cPG enhanced TNF-alpha-induced cell death and inhibited TNF-alpha-induced IkappaB-alpha kinase (IKK) activation, IkappaB-alpha degradation, and NF-kappaB/p65 translocation, while promoting AP-1/c-jun phosphorylation. Expression of an IKK-beta mutant (C179A) resistant to interaction with cPG impaired cell death induction but not inhibition of CAM up-regulation by cPG. Gel shift and reporter gene analysis revealed that cPG at low concentrations directly impaired DNA binding of NF-kappaB and NF-kappaB-dependent transactivation. The synthetic analogs dPGA1 or dPGA2 were ineffective, indicating structural specificity of cPG. Thus, the suppression of endothelial CAM up-regulation with cPG is dissociated from cell death sensitization and IKK inhibition above threshold concentrations and related to interference with NF-kappaB binding. Our findings define distinct mechanisms for anti-inflammatory and proapoptotic effects of cPG in endothelial cells.

Different mechanisms of adhesion molecule expression in human dermal microvascular endothelial cells by xanthoma tissue-mediated and copper-mediated oxidized low density lipoproteins

BACKGROUND

Oxidation of low density lipoprotein (LDL) has been implicated in infiltration of foam cells derived from circulating monocytes. Monocyte adhesion to endothelial cells and migration into dermis are essential steps for infiltration of foam cells.

OBJECTIVE

We investigated the role of adhesion molecules contributing to the process of monocyte adhesion to human dermal microvascular endothelial cells (HDMEC). Special attention was paid to the signal transduction for adhesion molecule expression induced by two distinct types of oxidized LDL.

METHODS

HDMEC were incubated with xanthoma tissue-modified LDL (x-LDL), a model of extravasated LDL oxidized in xanthoma lesions, or Cu(2+)-treated LDL (Cu-LDL), a model of oxidized LDL. Adhesion of U937 cells, a human monocytic leukemia cell line, to HDMEC and expression of endothelial cell adhesion molecules on HDMEC were examined. Signal transduction pathways for the adhesion molecule expression were evaluated by employing specific inhibitors.

RESULTS

x-LDL induced adhesion of U937 cells to HDMEC through vascular cell adhesion molecule-1 (VCAM-1) and E-selectin by activating tyrosine kinase pathway. Cu-LDL up-regulated the adhesion through not only VCAM-1 and E-selectin but also intercellular cell adhesion molecule-1 (ICAM-1) by activating G(i) protein pathway.

CONCLUSION

Extravasated and oxidized LDL in xanthoma lesions contributes to foam cell recruitment by activating tyrosine kinase pathway and inducing adhesion of monocytes to HDMEC through VCAM-1 and E-selectin. Cu-LDL, on the other hand, activates G(i) protein pathway and induces the adhesion through ICAM-1, VCAM-1 and E-selectin.

Minireview: adiposity, inflammation, and atherogenesis

Adipose tissue is a dynamic endocrine organ that secretes a number of factors that are increasingly recognized to contribute to systemic and vascular inflammation. Several of these factors, collectively referred to as adipokines, have now been shown regulate, directly or indirectly, a number of the processes that contribute to the development of atherosclerosis, including hypertension, endothelial dysfunction, insulin resistance, and vascular remodeling. Several adipokines are preferentially expressed in visceral adipose tissue, and the secretion of proinflammatory adipokines is elevated with increasing adiposity. Not surprisingly, approaches that reduce adipose tissue depots, including surgical fat removal, exercise, and reduced caloric intake, improve proinflammatory adipokine levels and reduce the severity of their resultant pathologies. Systemic adipokine levels can also be favorably altered by treatment with several of the existing drug classes used to treat insulin resistance, hypertension, and hypercholesterolemia. Greater understanding of adipokine regulation, however, should result in the design of improved treatment strategies to control disease states associated with increase adiposity, an important outcome in view of the growing worldwide epidemic of obesity.

Aortic recruitment of blood lymphocytes is most pronounced in early stages of lesion formation in apolipoprotein-E-deficient mice

Lymphocyte accumulation in the arterial intima affects development of atherosclerotic lesions. We studied the kinetics of lymphocyte accumulation in the arterial wall by injecting lymphocytes from male LacZ transgenic mice into female apolipoprotein-E-deficient mice. Recipient mouse aortas were removed and separated into lesioned and non-lesioned parts 2, 24, 48, or 72 h later. The accumulation of donor lymphocytes was quantified with real-time PCR of donor lymphocyte-specific genes. The accumulation of lymphocytes in the lesioned parts of aorta decreased with increasing lesion severity (r=-0.74, P=0.0005, n=18). Moreover, the accumulation of lymphocytes in the lesioned part of aorta was larger (392+/-108%, P=0.016) compared with the accumulation in the non-lesioned part in mice with mild atherosclerosis, whereas it was smaller (58+/-19%, P<0.01) compared with the accumulation in the non-lesioned part in mice with severe atherosclerosis. The results suggest that aortic recruitment of blood lymphocytes is most pronounced in early stages of lesion formation.

Impaired renal function is associated with markers of endothelial dysfunction and increased inflammatory activity

BACKGROUND

Patients with end-stage renal disease (ESRD) as well as those with mild renal insufficiency are at increased risk for the development of cardiovascular disease, which cannot be attributed entirely to traditional risk factors. Endothelial dysfunction and chronic inflammatory activity, two important phenomena in atherogenesis, can be found in ESRD. At present, it is unclear whether endothelial dysfunction and chronic inflammatory activity are related to renal function in the pre-dialysis stage.

METHODS

In a cross-sectional, single-centre study, four groups of 20 subjects with renal function ranging from a normal, calculated creatinine clearance (>90 ml/min) to a pre-dialysis situation (<31 ml/min) were investigated. We measured markers of endothelial function [von Willebrand factor (vWf), soluble intercellular adhesion molecule-1 (sICAM-1), soluble vascular cell adhesion molecule-1 (sVCAM-1), tissue-type plasminogen activator (tPA), plasminogen activator inhibitor-1 (PAI-1) and E-selectin (ES)], and markers of inflammatory activity [secretory phospholipase A(2) (sPLA(2)) and C-reactive protein (CRP)]. Using these markers, composite endothelial function and inflammatory activity scores were constructed.

RESULTS

Creatinine clearance correlated with the endothelial function score (r=-0.43, P<0.001), the inflammatory activity score (r=-0.53, P<0.05), vWf (r=-0.54, P<0.001), sVCAM-1 (r=-0.50, P<0.001), sPLA(2) (r=-0.28, P<0.05), homocysteine (r=-0.61, P<0.001), age (r=-0.54, P<0.001) and blood pressure (r=-0.44, P<0.001). In multivariate analyses, creatinine clearance was an independent determinant of the endothelial function score (beta=-0.34, P=0.006), plasma vWf (beta=-0.37, P=0.022) and sICAM-1 (beta=-0.33, P=0.012). The relationship of creatinine clearance with sVCAM-1 and endothelial function score was not significant when plasma homocysteine was added to the model. Creatinine clearance was also a determinant of the inflammatory activity score (beta=-0.31, P=0.025) and sPLA(2) (beta=-0.32, P=0.024), although this was no longer significant after correction for systolic blood pressure.

CONCLUSIONS

Renal dysfunction is associated with markers of endothelial dysfunction and inflammatory activity. Plasma homocysteine may be an intermediate factor in the relationship between endothelial dysfunction and renal function, while blood pressure may modulate the association between inflammatory activity and renal function.

The effect of viable Chlamydia pneumoniae on serum cytokines and adhesion molecules in hemodialysis patients

BACKGROUND

Chlamydia pneumoniae (Cp) induces the production of cytokines and adhesion molecules in infected host eukaryotic cells. The causes for pro-inflammatory cytokine and adhesion molecule increase in hemodialysis (HD) patients have not been fully elucidated. The possibility that, in this particularly atherosclerotic population, Cp, a microorganism implicated in the infectious-based inflammatory hypothesis of atherosclerosis' is also responsible for these molecules' increase is assessed in this study.

METHODS

In 130 stable HD patients, serum interleukin-1 beta (IL-1), interleukin-6, tumor necrosis factor alpha, interleukin-10, L-selectin, E-selectin, intercellular adhesion molecule-1, and vascular cell adhesion molecule-1 (VCAM-1) levels were determined. Cp presence was identified by inoculation of the patient's peripheral blood mononuclear cells (PBMCs) in Hep-2 cell lines and subsequent polymerase chain reaction (PCR) in DNA extracted from cell cultures, as well as by determination of serum IgG antibodies against Cp (IgGCp).

RESULTS

Patients, positive or negative for IgGCp, had no statistically significant differences in all molecules measured. Patients with viable Cp in PBMCs had higher serum levels of IL-1 and soluble VCAM-1 than negative ones for IgGCp (IL-1 6.87 +/- 7.35 vs. 2.34 +/- 1.47 pg/mL; P = 0.0009 and VCAM-1 1647.16 +/- 513.64 vs. 1162.14 +/- 546.83 ng/mL; P = 0.0115, respectively). Viable Cp in PBMCs remained a significant predictor factor for IL-1 and VCAM-1 in statistical analysis, when patients' characteristics and dialysis conditions were also evaluated.

CONCLUSIONS

Our results showed that some serum cytokine and adhesion molecule increase in HD patients could be attributed to viable Cp presence in PBMCs. These findings support the Cp-based inflammatory atherogenous hypothesis and add a better understanding of these molecules' increase in HD patients.

Inhibition of plaque neovascularization reduces macrophage accumulation and progression of advanced atherosclerosis

Plaque angiogenesis promotes the growth of atheromas, but the functions of plaque capillaries are not fully determined. Neovascularization may act as a conduit for the entry of leukocytes into sites of chronic inflammation. We observe vasa vasorum density correlates highly with the extent of inflammatory cells, not the size of atheromas in apolipoprotein E-deficient mice. We show atherosclerotic aortas contain activities that promote angiogenesis. The angiogenesis inhibitor angiostatin reduces plaque angiogenesis and inhibits atherosclerosis. Macrophages in the plaque and around vasa vasorum are reduced, but we detect no direct effect of angiostatin on monocytes. After angiogenesis blockade in vivo, the angiogenic potential of atherosclerotic tissue is suppressed. Activated macrophages stimulate angiogenesis that can further recruit inflammatory cells and more angiogenesis. Our findings demonstrate that late-stage inhibition of angiogenesis can interrupt this positive feedback cycle. Inhibition of plaque angiogenesis and the secondary reduction of macrophages may have beneficial effects on plaque stability.

Apolipoprotein E (apoE) isoforms differentially induce nitric oxide production in endothelial cells

Although apolipoprotein E3 (apoE3) is atheroprotective, two common isoforms, apoE2 and apoE4, produce recessive and dominant hyperlipidaemias, respectively. Using a fluorescent assay, we report herein that apoE3 particles secreted from recombinant cells stimulate more nitric oxide release in cultured human EA.hy926 endothelial cells than apoE2 or apoE4 (141% more than controls vs. 61 or 11%). Phosphatidylinositol (PI) 3-kinase inhibitors suppressed the apoE effect, while apoE receptor 2 (apoER2) was tyrosine phosphorylated. We conclude that apoE stimulates endothelial nitric oxide release in an isoform-dependent manner, and propose that tyrosine phosphorylation of apoER2 initiates PI3-kinase signalling and activation of nitric oxide synthase.

Fluid shear stress and the vascular endothelium: for better and for worse

As blood flows, the vascular wall is constantly subjected to physical forces, which regulate important physiological blood vessel responses, as well as being implicated in the development of arterial wall pathologies. Changes in blood flow, thus generating altered hemodynamic forces are responsible for acute vessel tone regulation, the development of blood vessel structure during embryogenesis and early growth, as well as chronic remodeling and generation of adult blood vessels. The complex interaction of biomechanical forces, and more specifically shear stress, derived by the flow of blood and the vascular endothelium raise many yet to be answered questions:How are mechanical forces transduced by endothelial cells into a biological response, and is there a "shear stress receptor"?Are "mechanical receptors" and the final signaling pathways they evoke similar to other stimulus-response transduction systems?How do vascular endothelial cells differ in their response to physiological or pathological shear stresses?Can shear stress receptors or shear stress responsive genes serve as novel targets for the design of diagnostic and therapeutic modalities for cardiovascular pathologies?The current review attempts to bring together recent findings on the in vivo and in vitro responses of the vascular endothelium to shear stress and to address some of the questions raised above.

An emerging role for nitric oxide in sickle cell disease vascular homeostasis and therapy

Nitric oxide participates in the compensatory response to chronic vascular injury in patients with sickle cell disease. The authors have found reductions of basal and stimulated nitric oxide production and responses to exogenous nitric oxide in male patients with sickle cell disease. Gender differences in nitric oxide bioavailability are probably caused in part by the protective effects of ovarian estrogen on nitric oxide synthase expression and activity in women. Further, in men, and likely all patients during vaso-occlusive crisis and the acute chest syndrome, nitric oxide is destroyed by increased circulating plasma hemoglobin and superoxide. The combined effects of inhaled nitric oxide gas of improving pulmonary ventilation to perfusion matching and hemodynamics, reducing alveolar and systemic inflammation, and inhibiting circulating plasma hemoglobin (and thus restoring peripheral nitric oxide bioavailability) may modulate the course of the disease, including the frequency and severity of vaso-occlusive crises and acute chest syndrome episodes. Possible effects of chronic nitric oxide-based therapies on erythrocyte density, pulmonary artery pressures, and fetal hemoglobin induction deserve study.

Decreased atherosclerotic lesion formation in CX3CR1/apolipoprotein E double knockout mice

BACKGROUND

Fractalkine (CX3CL1), a CX3C chemokine, is expressed in the vessel wall and mediates the firm adhesion and chemotaxis of leukocytes expressing its receptor, CX3CR1. A polymorphism in the CX3CR1 gene is associated with low CX3CR1 expression and reduced risk of acute coronary disease in humans.

METHODS AND RESULTS

We generated CX3CR1-deficient mice (CX3CR1(-/-)) by targeted gene disruption and crossed them with the proatherogenic apolipoprotein E-deficient mice (apoE(-/-)). Here we show that the extent of lipid-stained lesions in the thoracic aorta was reduced by 59% in CX3CR1/apoE double knockout mice compared with their CX3CR1(+/+)/apoE(-/-) littermates. The development of atherosclerosis in the aortic sinus was also markedly altered in the double knockout mice, with 50% reduction in macrophage accumulation. Although lesions of CX3CR1(-/-) mice were smaller in size, they retained a substantial accumulation of smooth muscle cells and collagen, features consistent with a stable plaque phenotype. Finally, CX3CR1(+/-)/apoE(-/-) mice showed the same reduction in atherosclerosis as the CX3CR1(-/-)/apoE(-/-) mice.

CONCLUSIONS

The CX3CR1-CX3CL1 pathway seems to play a direct and critical role in monocyte recruitment and atherosclerotic lesion development in a mouse model of human atherosclerosis.

Lead discovery of alpha,beta-unsaturated sulfones from a combinatorial library as inhibitors of inducible VCAM-1 expression

alpha,beta-Unsaturated sulfones have been discovered from a combinatorial library as leads for a new series of inhibitors of inducible VCAM-1 expression. Although not essential, further conjugation of the sulfonyl group to another vinyl group or a phenyl group increases the potency dramatically.

Vascular biology of atherosclerosis: overview and state of the art

Our current understanding of the vascular biology of atherogenesis and its clinical manifestations suggests a pathophysiology that is much more complex than mere lipid storage. Recent advances support the current view of atherosclerosis as an inflammatory process that initiates and promotes lesion development to the point of acute thrombotic complications and clinical events. Inflammatory cells localize in early-stage atherosclerotic lesions, and recent basic research has established a causal relation between inflammatory mediators or cytokines, and the steps involved in progressing from local inflammation through plaque formation. Inhibition of the action of certain specific proinflammatory cytokines, such as CD40 ligand, interferes with atherogenesis in mice. Increased circulating levels of inflammatory markers indicate increased cardiovascular risk. Thus, the time has come to embrace inflammation as a common pathway for atherogenic risk factors and for providing new opportunities for therapeutic intervention.

Two Hsp70 family members expressed in atherosclerotic lesions

Gene expression profiling was carried out comparing Con A elicited peritoneal macrophages from C57BL6 and FVBN wild-type and apolipoprotein (apo)E knockout mice. An EST, was expressed at higher levels in C57BL6 compared with FVBN mice. mapped to an atherosclerosis susceptibility locus on chromosome 19 revealed in an intercross between atherosclerosis-susceptible C57BL6 and atherosclerosis-resistant FVBN apoE knockout mice. A combination of database search and Northern analysis confirmed that corresponded to 3'-UTR of a hitherto predicted gene, named HspA12A. Blasting the National Center for Biotechnology Information database revealed a closely related homologue, HspA12B. HspA12A and -B have very close human homologues. TaqMan analysis confirmed the increased HspA12A expression (2.6-fold) in elicited peritoneal macrophages from C57BL6 compared with FVBN mice. TaqMan analysis also revealed increased HspA12A and HspA12B expression (87- and 6-fold, respectively) in lesional versus nonlesional portions of the thoracic aorta from C57BL6 apoE knockout mice on a chow diet. In situ hybridization confirmed that both genes were expressed within lesions but not within nonlesional aortic tissue. Blasting of HspA12A and HspA12B against the National Center for Biotechnology Information database (NR) revealed a hit with the Conserved Domain database for Hsp70 (pfam00012.5, Hsp70). Both genes appear to contain an atypical Hsp70 ATPase domain. The BLAST search also revealed that both genes were more similar to primitive eukaryote and prokaryote than mammalian Hsp70s, making these two genes distant members of the mammalian Hsp70 family. In summary, we describe two genes that code for a subfamily of Hsp70 proteins that may be involved in atherosclerosis susceptibility.

Effects of the prostaglandin I2 analogue, beraprost sodium, on vascular cell adhesion molecule-1 expression in human vascular endothelial cells and circulating vascular cell adhesion molecule-1 level in patients with type 2 diabetes mellitus

Beraprost sodium is an orally active prostaglandin (PG)I(2) analogue, which has antiplatelet and vasodilating properties. In this study, we investigated the effects of beraprost on the expression of vascular cell adhesion molecule-1 (VCAM-1), one of the key molecules involved in atherosclerosis, in cultured vascular endothelial cells. In addition, we examined the effects of beraprost on circulating VCAM-1 level and atherosclerosis progression in patients with type 2 diabetes mellitus. Beraprost significantly decreased tumor necrosis factor-alpha (TNF-alpha)-induced VCAM-1 expression in human vascular endothelial cells. Beraprost also repressed human monocytoid U937 cell adhesion to the vascular endothelial cells. Twenty-five patients with type 2 diabetes mellitus who had atherosclerotic change of carotid arteries were enrolled for an open prospective study: 11 patients received beraprost for 3 years, while the other 14 did not. The 3-year changes of circulating VCAM-1 level, as well as those of carotid arterial intima-media thickness (IMT) were significantly lower in the patients receiving the beraprost treatment than that in the patients without the treatment. Thus, beraprost had an ability to repress the expression of VCAM-1 in human vascular endothelial cells. In addition, beraprost lowered circulating VCAM-1 level and prevented the increase of carotid IMT in patients with type 2 diabetes mellitus. Considering that circulating VCAM-1 and IMT are predictive of future vascular events, beraprost may have a beneficial effect on progression of atherosclerosis in diabetic patients.

Divergent nitric oxide bioavailability in men and women with sickle cell disease

BACKGROUND

Although reduced endothelial nitric oxide (NO) bioavailability has been demonstrated in arteriosclerotic vascular disease, the integrity of this system in sickle cell disease remains uncertain.

METHODS AND RESULTS

We measured forearm blood flow in 21 patients with sickle cell disease (hemoglobin SS genotype) and 18 black control subjects before and after intra-arterial infusions of acetylcholine, nitroprusside, and the NO synthase inhibitor NG-monomethyl-L-arginine (L-NMMA). Endothelium-dependent vasodilation, measured by the percent increase in flow induced by acetylcholine infusion, was significantly greater than in controls (252+/-37% for patients versus 134+/-24% for controls; P<0.0001). However, there was a large sex difference in blood flow responses between female and male patients (340+/-46% versus 173+/-41%; P=0.035). Similarly, basal NO bioactivity, as measured by the percent decrease in flow induced by L-NMMA, was depressed in male compared with female patients (-17+/-5% versus -34+/-4%; P=0.01), as was the response to nitroprusside (86+/-21% versus 171+/-22%; P=0.008). L-NMMA reduced the blood flow response to acetylcholine in women, but not in men. Sex differences in vascular cell adhesion molecule-1 were appreciated, with significant correlations between levels of soluble vascular cell adhesion molecule-1 and blood flow responses to L-NMMA and nitroprusside (r=0.53, P=0.004 and r=-0.66, P<0.001, respectively).

CONCLUSIONS

NO bioavailability and NO responsiveness are greater in women than in men with sickle cell disease and determines adhesion molecule expression. Endothelium-dependent blood flows are largely non-NO mediated in male patients. These results provide a possible mechanism for reported sex differences in sickle cell disease morbidity and mortality and provide a basis for novel pharmacological interventions.

Circulating activated platelets exacerbate atherosclerosis in mice deficient in apolipoprotein E

We studied whether circulating activated platelets and platelet-leukocyte aggregates cause the development of atherosclerotic lesions in apolipoprotein-E-deficient (Apoe(-/-)) mice. Circulating activated platelets bound to leukocytes, preferentially monocytes, to form platelet-monocyte/leukocyte aggregates. Activated platelets and platelet-leukocyte aggregates interacted with atherosclerotic lesions. The interactions of activated platelets with monocytes and atherosclerotic arteries led to delivery of the platelet-derived chemokines CCL5 (regulated on activation, normal T cell expressed and secreted, RANTES) and CXCL4 (platelet factor 4) to the monocyte surface and endothelium of atherosclerotic arteries. The presence of activated platelets promoted leukocyte binding of vascular cell adhesion molecule-1 (VCAM-1) and increased their adhesiveness to inflamed or atherosclerotic endothelium. Injection of activated wild-type, but not P-selectin-deficient, platelets increased monocyte arrest on the surface of atherosclerotic lesions and the size of atherosclerotic lesions in Apoe(-/-) mice. Our results indicate that circulating activated platelets and platelet-leukocyte/monocyte aggregates promote formation of atherosclerotic lesions. This role of activated platelets in atherosclerosis is attributed to platelet P-selectin-mediated delivery of platelet-derived proinflammatory factors to monocytes/leukocytes and the vessel wall.