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

Insulin and insulin-like growth factor-I receptors differentially mediate insulin-stimulated adhesion molecule production by endothelial cells

Patients with type 2 diabetes are hyperinsulinemic and insulin resistant and develop premature atherosclerosis. High concentrations of insulin stimulate the production of adhesion molecules by endothelial cells (ECs). ECs express abundant IGF-I receptors as well as insulin receptors. Whether IGF-I receptors contribute to insulin-induced endothelial production of adhesion molecules is unknown. Bovine aortic ECs (BAECs) were incubated with insulin (100 nm) for 24 h. The cellular content of vascular cell adhesion molecule-1 (VCAM-1) and intercellular adhesion molecule-1 (ICAM-1) was measured, and monocyte adhesion to ECs was quantified. Insulin increased both VCAM-1 (P < 0.001) and ICAM-1 (P < 0.0002) content, which was accompanied by an increased number of monocytes adherent to BAECs (P = 0.0001). Inhibition of either MAPK kinase-1 or p38 MAPK but not phosphatidylinositol 3-kinase abolished insulin-mediated production of adhesion molecules. Insulin receptor small interfering RNA knockdown abolished insulin-stimulated increases of ICAM-1 but not VCAM-1. Conversely, IGF-I receptor blockade with either a neutralizing antibody or specific small interfering RNA eliminated insulin-induced VCAM-1 but not ICAM-1 production. Blockade of signaling via either the insulin or IGF-I receptors decreased monocyte adherence to BAECs (P < 0.01 for each). We conclude that insulin and IGF-I receptors differentially mediate the production of adhesion molecules by ECs and monocyte adhesion onto the vascular endothelium in response to the hyperinsulinemic state. Dual-receptor activation may most effectively contribute to the pathogenesis of atherosclerotic disease in diabetes.

Adhesion of T and B lymphocytes to mouse atherosclerotic aortas: Association with lesion topology and VCAM‐1 expression

OBJECTIVE

Although T and B lymphocytes accumulate in atherosclerotic lesions and play a key role in their growth, the mechanisms involved in the adhesion and recruitment of T and B lymphocytes by the lesions have not been resolved. The aim of this study was to compare T and B lymphocyte adhesion to atherosclerotic arteries and to test the role of VCAM-1 and ICAM-1.

MATERIAL AND METHODS

T and B lymphocytes were labelled with red and green fluorescent dyes and incubated with freshly isolated aortas from apolipoprotein-E-deficient mice. In some experiments the aortas were pre-incubated with specific monoclonal antibodies. After washing, the adhering cells were detected by confocal laser scanning microscopy.

RESULTS

The number of T and B lymphocytes that adhered to the aortic intimal surface was similar in both lesioned and non-lesioned areas and in the shoulder region of the lesions. However, the adhesion of T and B lymphocytes was significantly higher in the shoulder regions compared with the lesioned (p<0.0001) and non-lesioned areas of the aorta (p<0.0001). After pre-incubation of the aortas with antibodies against VCAM-1 or ICAM-1, the lymphocyte adhesions in lesioned areas were 42 % (p = 0.04) and 55 % (p = 0.17), respectively, of those in lesioned areas that had been pre-incubated with a control antibody. However, although VCAM-1 protein expression was most pronounced in the shoulder region, the lymphocyte adhesions in the shoulder region and in non-lesioned areas were unaffected by pre-incubation with VCAM-1 antibodies.

CONCLUSIONS

The results suggest that adhesion of T and B lymphocytes to mouse aortic endothelium is similar, is affected by lesion topology and is dependent on VCAM-1 expression over the core of atherosclerotic lesions.

Biomarkers of premature atherosclerosis

C-reactive protein (CRP) is an acute phase protein and a biochemical marker with important prognostic value for cardiovascular events. Interleukins IL-1 and IL-6 are implicated in the pathogenesis of atherosclerosis and are associated with CRP. Apolipoproteins ApoA-I and ApoB are the main lipid metabolic markers implicated in the development and progression of atherosclerosis. Fibrinogen has also been proposed to be a major independent risk factor for cardiovascular events. Because premature atherosclerosis precedes the development of cardiovascular disease, identification of the associated biomarkers is of great importance. However, further studies will be needed to determine whether or not these markers are useful predictors of future cardiovascular events. Here, we review the roles of specific biomarkers that have been implicated in premature atherosclerosis.

[Serum concentration of soluble adhesive molecules in patients with different forms of coronary artery disease]

BACKGROUND/AIM

Vascular cell adhesion molecules-1 (VCAM-1) and intercellular cell adhesive molecules-1 (ICAM-1) play an important role in developing and progression of coronary atherosderosis. The aim of the paper was to compare concentrations of soluble forms of VCAM-1 and ICAM-1 in patients with different clinical presentations of coronary artery disease (CAD) and patients without CAD.

METHODS

Blood samples were taken from 25 patients with acute myocardial infarction (AMI), 25 patients with unstable angina pectoris (UAP), 25 with stable angina pectoris (SAP) and from 15 control patients without CAD, and concentrations of solubile adhesive molecules (VCAM-1, ICAM-1) were determined.

RESULTS

Obesity was more prominent in the NAP than in the SAP and the control patients (p < 0.05). There were no significant differences in gender distribution, age, duration of the CAD and body mass index between the groups. Hypertension and diabetes mellitus type 2 were more frequent in the CAD patients than in the controls (p < 0.01). Family history of the CAD was more frequent in the AMI and the UAP group than in the controls (p < 0.05). Serum concentrations of VCAM-1 was similar in the patients with AMI (955.9 +/- 117.8 ng/mL), UAP (952.4 +/- 139.1 ng/mL) and SAP (931 +/- 169.8 ng/mL), and significantly higher in these groups compared with the controls (823.4 +/- 97.6; p < 0.05, p < 0.05 and p < 0.1 respectively). Serum concentration of ICAM-1 was similar in the patients with AMI (699.2 +/- 125.6 ng/mL), UAP (727.6 +/- 171.8 ng/mL) and SAP (697.5 +/- 165.6 ng/mL), and significantly higher in these groups compared with the controls (583.4 +/- 86.6; p < 0.1, p < 0.05 and p < 0.1 respectively).

CONCLUSION

Increased concentrations of VCAM-1 and ICAM-1, as markers of inflammation, showed the importance of inflammatory processes in development of atherosclerosis and clinical expresion of CAD. Measurement of soluble ICAM-1 and VCAM-1 concentrations is a usefull indicator of atherosclerosis presence but not severity of CAD clinical presentation.

Innate and adaptive immunity in atherosclerosis

Atherosclerosis, a chronic inflammatory disorder, involves both the innate and adaptive arms of the immune response that mediate the initiation, progression, and ultimate thrombotic complications of atherosclerosis. Most fatal thromboses, which may manifest as acute myocardial infarction or ischemic stroke, result from frank rupture or superficial erosion of the fibrous cap overlying the atheroma, processes that occur in inflammatorily active, rupture-prone plaques. Appreciation of the inflammatory character of atherosclerosis has led to the application of C-reactive protein as a biomarker of cardiovascular risk and the characterization of the anti-inflammatory and immunomodulatory actions of the statin class of drugs. An improved understanding of the pathobiology of atherosclerosis and further studies of its immune mechanisms provide avenues for the development of future strategies directed toward better risk stratification of patients as well as the identification of novel anti-inflammatory therapies. This review retraces leukocyte subsets involved in innate and adaptive immunity and their contributions to atherogenesis.

Surface functionalization of single superparamagnetic iron oxide nanoparticles for targeted magnetic resonance imaging

Magnetic resonance imaging (MRI), a non-invasive, non-radiative technique, is thought to lead to cellular or even molecular resolution if optimized targeted MR contrast agents are introduced. This would allow diagnosing progressive diseases in early stages. Here, it is shown that the high binding affinity of poly(ethylene glycol)-gallol (PEG-gallol) allows freeze drying and re-dispersion of 9 +/- 2-nm iron oxide cores individually stabilized with approximately 9-nm-thick stealth coatings, yielding particle stability for at least 20 months. Particle size, stability, and magnetic properties of PEGylated particles are compared to Feridex, a commercially available untargeted negative MR contrast agent. Biotin-PEG(3400)-gallol/methoxy-PEG(550)-gallol stabilized nanoparticles are further functionalized with biotinylated human anti-VCAM-1 antibodies using the biotin-neutravidin linkage. Binding kinetics and excellent specificity of these nanoparticles are demonstrated using quartz crystal microbalance with dissipation monitoring (QCM-D). These MR contrast agents can be functionalized with any biotinylated ligand at controlled ligand surface density, rendering them a versatile research tool.

Functional role of CD11c+ monocytes in atherogenesis associated with hypercholesterolemia

BACKGROUND

Monocyte activation and migration into the arterial wall are key events in atherogenesis associated with hypercholesterolemia. CD11c/CD18, a beta2 integrin expressed on human monocytes and a subset of mouse monocytes, has been shown to play a distinct role in human monocyte adhesion on endothelial cells, but the regulation of CD11c in hypercholesterolemia and its role in atherogenesis are unknown.

METHODS AND RESULTS

Mice genetically deficient in CD11c were generated and crossbred with apolipoprotein E (apoE)-/- mice to generate CD11c-/-/apoE-/- mice. Using flow cytometry, we examined CD11c on blood leukocytes in apoE-/- hypercholesterolemic mice and found that compared with wild-type and apoE-/- mice on a normal diet, apoE-/- mice on a Western high-fat diet had increased CD11c+ monocytes. Circulating CD11c+ monocytes from apoE-/- mice fed a high-fat diet exhibited cytoplasmic lipid vacuoles and expressed higher levels of CD11b and CD29. Deficiency of CD11c decreased firm arrest of mouse monocytes on vascular cell adhesion molecule-1 and E-selectin in a shear flow assay, reduced monocyte/macrophage accumulation in atherosclerotic lesions, and decreased atherosclerosis development in apoE-/- mice on a high-fat diet.

CONCLUSIONS

CD11c, which increases on blood monocytes during hypercholesterolemia, plays an important role in monocyte recruitment and atherosclerosis development in an apoE-/- mouse model of hypercholesterolemia.

Quantum dot mediated imaging of atherosclerosis

The progression of atherosclerosis is associated with leukocyte infiltration within lesions. We describe a technique for the ex vivo imaging of cellular recruitment in atherogenesis which utilizes quantum dots (QD) to color-code different cell types within lesion areas. Spectrally distinct QD were coated with the cell-penetrating peptide maurocalcine to fluorescently-label immunomagnetically isolated monocyte/macrophages and T lymphocytes. QD-maurocalcine bioconjugates labeled both cell types with a high efficiency, preserved cell viability, and did not perturb native leukocyte function in cytokine release and endothelial adhesion assays. QD-labeled monocyte/macrophages and T lymphocytes were reinfused in an ApoE(-/-) mouse model of atherosclerosis and age-matched controls and tracked for up to four weeks to investigate the incorporation of cells within aortic lesion areas, as determined by oil red O (ORO) and immunofluorescence ex vivo staining. QD-labeled cells were visible in atherosclerotic plaques within two days of injection, and the two cell types colocalized within areas of subsequent ORO staining. Our method for tracking leukocytes in lesions enables high signal-to-noise ratio imaging of multiple cell types and biomarkers simultaneously within the same specimen. It also has great utility in studies aimed at investigating the role of distinct circulating leukocyte subsets in plaque development and progression.

Endothelial dysfunction and cardiovascular risk factors

The endothelium plays an integral role in the regulation of vascular tone, platelet activity, leukocyte adhesion, and thrombosis and is intimately involved in the development of atherosclerosis. Endothelial dysfunction has been observed in patients with established coronary artery disease or coronary risk factors, both in the coronary and peripheral vasculature. Therapeutic interventions with lipid-lowering drugs, ACE inhibitors, physical activity, and antioxidant agents have been shown to improve endothelial function in coronary and peripheral vessels. This systemic manifestation and improvement of endothelial function suggests that a common mechanism may contribute to endothelial dysfunction in the coronary and peripheral circulation.

TARGET AUDIENCE

Internist, Cardiologists, Family physicians.

LEARNING OBJECTIVES

After completion of this article, the reader should be able to define the participation of cardiovascular risk factors in the various complications associated with endothelial dysfunction.

Tumor necrosis factor-alpha deficiency retards early fatty-streak lesion by influencing the expression of inflammatory factors in apoE-null mice

Tumor necrosis factor-alpha (TNF-alpha), a key inflammatory cytokine, plays an important role in atherosclerosis. However, its precise characters in primary stage of the disease remain unclear. To assess the influence of TNF-alpha on inflammatory factors in aorta and liver in apoE and TNF-alpha double mutant (AT) mice, a comparative study on early fatty-streak lesion, the mRNA level of target gene in aorta and liver of adolescent AT and apoE-null (apoE(-/-)) mice were achieved. The characteristics of expression of inflammatory factors, and early fatty-streak lesion relevance were analyzed. The plasma cytokines in 6-week-old AT and apoE(-/-) mice were also measured. Lipid accumulation in the intima of the aorta existed as early as 3 weeks of age in apoE(-/-) mice. Fatty-streak lesion was mild in AT mice but prominent in apoE(-/-) mice, at age of 6 weeks. Furthermore, most interesting findings indicate that mRNA levels of pro-atherosclerotic factors, i.e. IL-1beta, IFN-gamma, ICAM-1, VCAM-1, MCP-1, GM-CSF and NF-kappaB (p65) were significantly downregulated in AT mice. Whereas IL-2 and IkappaB-alpha were upregulated in aorta of AT mice versus those in apoE(-/-) mice (p<0.01) and the transcript levels of pro-inflammatory cytokines, such as IL-1beta, IFN-gamma, ICAM-1, VCAM-1, MCP-1 and GM-CSF, increased with atherogenesis progression. On the other hand, the expression of these inflammatory factors in the liver displayed somewhat similar fashion to those in the aorta. Moreover, the plasma lipids profile in AT mice showed less pro-atherogenic than that of apoE(-/-) mice. Our data indicated that TNF-alpha deficiency surely, although not completely, retards fatty-streak lesion formation due to downregulated expression of the pro-atherosclerotic inflammatory factors in the present circumstance.

Inhibition of S6K1 accounts partially for the anti-inflammatory effects of the arginase inhibitor L-norvaline

Background

Pharmacological inhibition of endothelial arginase-II has been shown to improve endothelial nitric oxide synthase (eNOS) function and reduce atherogenesis in animal models. We investigated whether the endothelial arginase II is involved in inflammatory responses in endothelial cells.

Methods

Human endothelial cells were isolated from umbilical veins and stimulated with TNFα (10 ng/ml) for 4 hours. Endothelial expression of the inflammatory molecules i.e. vascular cell adhesion molecule-1 (VCAM-1), intercellular adhesion molecule-1 (ICAM-1), and E-selectin were assessed by immunoblotting.

Results

The induction of the expression of endothelial VCAM-1, ICAM-1 and E-selectin by TNFα was concentration-dependently reduced by incubation of the endothelial cells with the arginase inhibitor L-norvaline. However, inhibition of arginase by another arginase inhibitor S-(2-boronoethyl)-L-cysteine (BEC) had no effects. To confirm the role of arginase-II (the prominent isoform expressed in HUVECs) in the inflammatory responses, adenoviral mediated siRNA silencing of arginase-II knocked down the arginase II protein level, but did not inhibit the up-regulation of the adhesion molecules. Moreover, the inhibitory effect of L-norvaline was not reversed by the NOS inhibitor L-NAME and L-norvaline did not interfere with TNFα-induced activation of NF-κB, JNK, p38mapk, while it inhibited p70s6k (S6K1) activity. Silencing S6K1 prevented up-regulation of E-selectin, but not that of VCAM-1 or ICAM-1 induced by TNFα.

Conclusion

The arginase inhibitor L-norvaline exhibits anti-inflammatory effects independently of inhibition of arginase in human endothelial cells. The anti-inflammatory properties of L-norvaline are partially attributable to its ability to inhibit S6K1.

The role of the scavenger receptor CD36 in regulating mononuclear phagocyte trafficking to atherosclerotic lesions and vascular inflammation

AIMS

CD36 has been shown to associate with non-receptor Src kinases to activate mitogen-activated protein kinases and trigger cytoskeletal remodelling, important events in foam cell formation and macrophage migration. Yet, its role in regulating circulating mononuclear phagocyte trafficking to atherosclerotic lesions has not been investigated. The aim of the present study was to investigate the role of CD36 in modulating the recruitment of mononuclear phagocytes to the arterial wall and the associated vascular inflammation, using both pharmacological and genetic approaches.

METHODS AND RESULTS

Apolipoprotein E-deficient (apoE(-/-)) mice fed a high-fat, high-cholesterol diet were treated daily with a CD36 ligand, EP 80317 (300 microg/kg), or 0.9% NaCl for 6 or 12 weeks. Forty-eight hours before sacrifice, mice were injected iv with (111)Indium-labelled macrophages. A 65% (P < 0.001) reduction of labelled macrophage accumulation at aortic lesions was observed in EP 80317-treated mice, mainly at the level of the aortic arch and iliac arteries, correlating with a 43% reduction of atherosclerotic lesion areas. This was associated with reduced phosphorylation of the focal adhesion kinase Pyk2 following stimulation with oxidized phospholipid in a Src kinase- and CD36-dependent manner. At the vascular level, EP 80317 treatment reduced the expression of pro-inflammatory proteins, including NADPH oxidase, inducible nitric oxide synthase, vascular endothelial cell adhesion molecule-1, and CCL2 chemokine. Plasma IL-6 levels were also reduced by 40% (P < 0.05). In contrast, none of these proteins was modulated in EP 80317-treated apoE/CD36 double knockout (apoE(-/-)/CD36(-/-)) mice.

CONCLUSION

Our results support a role for CD36 signalling in the regulation of mononuclear phagocyte trafficking to atherosclerotic-prone sites and in the associated vascular wall inflammation.

Can O2 dysregulation induce premature aging?

Chronic intermittent or episodic hypoxia, as occurs during a number of disease states, can have devastating effects, and prolonged exposure to this hypoxia can result in cell injury or cell death. Indeed, intermittent hypoxia activates a number of signaling pathways that are involved in oxygen sensing, oxidative stress, metabolism, catecholamine biosynthesis, and immune responsiveness. The cumulative effect of these processes over time can undermine cell integrity and lead to a decline in function. Furthermore, the ability to respond adequately to various stressors is hampered, and this is traditionally defined as premature aging or senescence. This review highlights recent advances in our understanding of the cellular and molecular mechanisms that are involved in the response to intermittent hypoxia and the potential interplay among various pathways that may accelerate the aging process.

Myeloid cells in atherosclerosis: initiators and decision shapers

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

Withaferin A inhibits tumor necrosis factor-alpha-induced expression of cell adhesion molecules by inactivation of Akt and NF-kappaB in human pulmonary epithelial cells

We here investigated the functional effect of withaferin A on airway inflammation and its action mechanism. Withaferin A inhibited the expression of intercellular adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1) in human lung epithelial A549 cells stimulated with tumor necrosis factor-alpha (TNF-alpha), resulting in the suppression of leukocyte adhesion to lung epithelial A549 cells. In addition, withaferin A inhibited TNF-alpha-induced expression of adhesion molecules (ICAM-1 and VCAM-1) protein and mRNA in a dose-dependent manner. Withaferin A prevented DNA binding activity of nuclear factor-kappaB (NF-kappaB) and nuclear translocation of NF-kappaB. It also inhibited phosphorylation of Akt and extracellular signal-regulated kinase (ERK), which are upstream in the regulation of adhesion molecules by TNF-alpha. Furthermore, withaferin A inhibited U937 monocyte adhesion to A549 cells stimulated by TNF-alpha, suggesting that it may inhibit the binding of these cells by regulating the expression of critical adhesion molecules by TNF-alpha. Taken together, these results suggest that withaferin A inhibits cell adhesion through inhibition of ICAM-1 and VCAM-1 expression, at least in part, by blocking Akt and down-regulating NF-kappaB activity.

The monocyte/macrophage as a therapeutic target in atherosclerosis

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

Systemic infection, inflammation and acute ischemic stroke

Extensive evidence implicates inflammation in multiple phases of stroke etiology and pathology. In particular, there is growing awareness that inflammatory events outside the brain have an important impact on stroke susceptibility and outcome. Numerous conditions, including infection and chronic non-infectious diseases, that are established risk factors for stroke are associated with an elevated systemic inflammatory profile. Recent clinical and pre-clinical studies support the concept that the systemic inflammatory status prior to and at the time of stroke is a key determinant of acute outcome and long-term prognosis. Here, we provide an overview of the impact of systemic inflammation on stroke susceptibility and outcome. We discuss potential mechanisms underlying the impact on ischemic brain injury and highlight the implications for stroke prevention, therapy and modeling.

Immune and inflammatory mechanisms of atherosclerosis (*)

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

Vaccines in development to prevent and treat atherosclerotic disease

Coronary heart disease (CHD) remains the leading cause of death in the United States. Immune mechanisms have been recently proposed to play an important role in the development of atherosclerotic plaques in CHD. Heat shock proteins and oxidized low-density lipoprotein are proinflammatory substances that have been shown to have an important role in the pathogenesis of atherosclerosis, and are now targets for clinical vaccine development. In addition, a vaccine has been developed to inhibit cholesteryl ester transfer protein. It is now recognized that many medications used to combat plaque development and rupture have significant anti-inflammatory effects and these effects are critical for drug efficacy. The influenza vaccine is associated with an atheroprotective effect. In addition, a nicotine vaccine, an antiangiotensin vaccine, and an anti-obesity vaccine may play a therapeutic role in modifying known risk factors for the development of atherosclerosis and its complications. This article reviews these vaccines as possible additions to the armamentarium of atheroprotective treatment modalities.

Anthocyanins from purple sweet potato Ipomoea batatas cultivar Ayamurasaki suppress the development of atherosclerotic lesions and both enhancements of oxidative stress and soluble vascular cell adhesion molecule-1 in apolipoprotein E-deficient mice

We evaluated the protective potential of anthocyanins from purple sweet potato Ipomoea batatas cultivar Ayamurasaki (APSP) against low-density lipoprotein (LDL) oxidation in vitro and atherosclerotic lesion development in apolipoprotein E-deficient mice given a cholesterol- and fat-enriched diet with or without 1% APSP for 4 weeks. APSP protected LDL against oxidation more potently than other anthocyanins and l-ascorbic acid in vitro. In mice, APSP significantly lowered the atherosclerotic plaque area to about half of the control, the liver level of thiobarbituric acid-reactive substances as an oxidative stress marker, and the plasma level of soluble vascular cell adhesion molecule-1 (sVCAM-1). However, APSP showed no effects on body weight and cholesterol and lipid levels in the plasma. The results suggest that APSP can suppress the development of atherosclerotic lesions and both enhancements of oxidative stress and sVCAM-1 independently of the changes in cholesterol and lipid levels in mice.

Extravasation of leukocytes in comparison to tumor cells

The multi-step process of the emigration of cells from the blood stream through the vascular endothelium into the tissue has been termed extravasation. The extravasation of leukocytes is fairly well characterized down to the molecular level, and has been reviewed in several aspects. Comparatively little is known about the extravasation of tumor cells, which is part of the hematogenic metastasis formation. Although the steps of the process are basically the same in leukocytes and tumor cells, i.e. rolling, adhesion, transmigration (diapedesis), the molecules that are involved are different. A further important difference is that leukocyte interaction with the endothelium changes the endothelial integrity only temporarily, whereas tumor cell interaction leads to an irreversible damage of the endothelial architecture. Moreover, tumor cells utilize leukocytes for their extravasation as linkers to the endothelium. Thus, metastasis formation is indirectly susceptible to localization signals that are literally specific for the immune system. We herein compare the extravasation of leukocytes and tumor cells with regard to the involved receptors and the localization signals that direct the cells to certain organs and sites of the body.

Leukocyte adhesion molecules in animal models of inflammatory bowel disease

The dysregulated recruitment of leukocytes into the intestine is required for the initiation and maintenance of inflammatory bowel disease (IBD). Several families of molecules regulate the influx of these cells into sites of inflammation. Interference with some of these molecules has already shown efficacy in the clinics and antibodies that target the molecules involved have been approved by the FDA for use in Crohn's disease (CD), multiple sclerosis (i.e., natalizumab), and psoriasis (i.e., efalizumab). Here, we discuss basic aspects of the different families of relevant molecules and compile a large body of preclinical studies that supported the targeting of specific steps of the leukocyte adhesion cascade for therapeutic purposes in colitis and in novel models of CD-like ileitis.

Inflammation and progressive nephropathy in type 1 diabetes in the diabetes control and complications trial

OBJECTIVE

Progressive nephropathy represents a substantial source of morbidity and mortality in type 1 diabetes. Increasing albuminuria is a strong predictor of progressive renal dysfunction and heightened cardiovascular risk. Early albuminuria probably reflects vascular endothelial dysfunction, which may be mediated in part by chronic inflammation.

RESEARCH DESIGN AND METHODS

We measured baseline levels of four inflammatory biomarkers (high-sensitivity C-reactive protein, soluble intercellular adhesion molecule-1 [sICAM-1], soluble vascular cell adhesion molecule-1, and soluble tumor necrosis factor-alpha receptor-1) in stored blood samples from the 1,441 participants of the Diabetes Control and Complication Trial (DCCT). We used mixed-effects regression models to determine the average annual change in urinary albumin excretion rate (AER) by tertiles of each biomarker. We also used Cox proportional hazards models to estimate the relative risk of incident sustained microalbuminuria according to levels of each biomarker.

RESULTS

After adjustment for baseline age, sex, duration of diabetes, A1C, and randomized treatment assignment, we observed a significantly higher 5.9 microg x min(-1) x year(-1) increase in AER among those in the highest compared with the lowest tertile of baseline sICAM-1 (P = 0.04). Those in the highest tertile of sICAM-1 had an adjusted relative risk of 1.67 (95% CI 0.96-2.92) of developing incident sustained microalbuminuria (P(trend) = 0.03).

CONCLUSIONS

Higher baseline sICAM-1 levels predicted an increased risk of progressive nephropathy in type 1 diabetes and may represent an early risk marker that reflects the important role of vascular endothelial dysfunction in this long-term complication.

Delivery strategies to target therapies to inflammatory tissue

BACKGROUND

Inflammation plays a key role in many chronic disease processes as well as an acute role in injury and wound healing. Various cell types are recruited from the bloodstream to the inflamed site through adhesion molecules, cytokines, chemokines and others.

OBJECTIVES

This review examines many drug-targeting strategies that make use of these molecules or signaling pathways, and seeks to describe certain commonalities irrespective of the disease process or agent to be delivered.

METHODS

A survey of the literature, primarily within the last year, was performed. Search words included 'drug targeting' and 'inflammation' and of those, the scope was refined to include those studies that specifically sought to modify or ameliorate an aspect of the inflammatory process in the treatment of a disease.

RESULTS/CONCLUSION

Inflammation plays a key role in many diseases, and many similar targets (such as adhesion molecules) are the focus of the treatment of those diseases.

Anti-atherogenic and anti-inflammatory properties of high-density lipoprotein are affected by specific antibodies in systemic lupus erythematosus

OBJECTIVE

To determine whether antibodies against high-density lipoprotein (aHDL) and apolipoprotein A-I (aApo A-I) interfere with the anti-atherogenic functions of high-density lipoprotein (HDL) and relate to disease activity and damage in SLE.

METHODS

Seventy-seven SLE patients were compared with an age- and sex-frequency matched control group. Immunoglobulin G (IgG) aHDL, IgG aApoA-I, soluble vascular cell and intracellular cell adhesion molecules (VCAM-1 and ICAM-1, respectively) were measured by ELISA, paraoxonase (PON) activity by spectrophotometry, nitric oxide (NOx) metabolites by the Griess reaction, and total anti-oxidant capacity (TAC) by chemiluminescence.

RESULTS

Compared with controls, SLE patients showed higher titres of IgG aHDL (P < 0.0001) and IgG aApo A-I (P < 0.0001), lower PON activity (P < 0.0001), increased NOx (P < 0.0001), VCAM-1 (P < 0.0001) and ICAM-1 (P = 0.0008) and lower TAC (P = 0.0006). Titres of IgG aHDL positively correlated with IgG aApo A-I (r = 0.64, P < 0.0001), NOx (r = 0.32, P = 0.007), inversely correlated with PON activity (r = -0.34, P = 0.002) and TAC (r = -0.43, P = 0.0004) and were independently associated with ICAM-1 (t = 3.509, P = 0.001). IgG aApo A-I titres correlated positively with NO (r = 0.37, P = 0.007), inversely with PON activity (r = -0.31, P = 0.006), TAC (r = -0.47, P < 0.0001) and were independently associated with HDL (t = -2.747, P = 0.008) and VCAM-1 (t = 3.311, P = 0.002), the latter alongside NOx (T = 2.271, P = 0.02). Elevated titres of IgG aHDL and IgG aApo A-I and reduced PON activity related to increased disease score (BILAG) and damage index (SLICC/ACR DI).

CONCLUSION

In SLE, IgG aHDL and aApo A-I associate with disease activity and damage and interfere with the anti-oxidant and anti-inflammatory functions of HDL favouring atherogenesis.

Quantitative trait locus analysis of circulating adhesion molecules in hyperlipidemic apolipoprotein E-deficient mice

Circulating soluble adhesion molecules have been suggested as useful markers to predict several clinical conditions such as atherosclerosis, type 2 diabetes, obesity, and hypertension. To determine genetic factors influencing plasma levels of soluble vascular cell adhesion molecule-1 (VCAM-1) and P-selectin, quantitative trait locus (QTL) analysis was performed on an intercross between C57BL/6J (B6) and C3H/HeJ (C3H) mouse strains deficient in apolipoprotein E-deficient (apoE-/-). Female F2 mice were fed a western diet for 12 weeks. One significant QTL, named sVcam1 (71 cM, LOD 3.9), on chromosome 9 and three suggestive QTLs on chromosomes 5, 13 and 15 were identified to affect soluble VCAM-1 levels. Soluble P-selectin levels were controlled by one significant QTL, named sSelp1 (8.5 cM, LOD 3.4), on chromosome 16 and two suggestive QTLs on chromosomes 10 and 13. Both adhesion molecules showed significant or an apparent trend of correlations with body weight, total cholesterol, and LDL/VLDL cholesterol levels in the F2 population. These results indicate that plasma VCAM-1 and P-selectin levels are complex traits regulated by multiple genes, and this regulation is conferred, at least partially, by acting on body weight and lipid metabolism in hyperlipidemic apoE-/- mice.

Endothelial cell-specific NF-kappaB inhibition protects mice from atherosclerosis

Atherosclerosis is a progressive disorder of the arterial wall and the underlying cause of cardiovascular diseases such as heart attack and stroke. Today, atherosclerosis is recognized as a complex disease with a strong inflammatory component. The nuclear factor-kappaB (NF-kappaB) signaling pathway regulates inflammatory responses and has been implicated in atherosclerosis. Here, we addressed the function of NF-kappaB signaling in vascular endothelial cells in the pathogenesis of atherosclerosis in vivo. Endothelium-restricted inhibition of NF-kappaB activation, achieved by ablation of NEMO/IKKgamma or expression of dominant-negative IkappaBalpha specifically in endothelial cells, resulted in strongly reduced atherosclerotic plaque formation in ApoE(-/-) mice fed with a cholesterol-rich diet. Inhibition of NF-kappaB abrogated adhesion molecule induction in endothelial cells, impaired macrophage recruitment to atherosclerotic plaques, and reduced expression of cytokines and chemokines in the aorta. Thus, endothelial NF-kappaB signaling orchestrates proinflammatory gene expression at the arterial wall and promotes the pathogenesis of atherosclerosis.

Endothelial cell PECAM-1 promotes atherosclerotic lesions in areas of disturbed flow in ApoE-deficient mice

OBJECTIVE

Platelet endothelial cell adhesion molecule-1 (PECAM-1, CD31) has recently been shown to form an essential element of a mechanosensory complex that mediates endothelial responses to fluid shear stress. The aim of this study was to determine the in vivo role of PECAM-1 in atherosclerosis.

METHODS AND RESULTS

We crossed C57BL/6 Pecam1(-/-) mice with apolipoprotein E-deficient (Apoe(-/-)) mice. On a Western diet, Pecam1(-/-)Apoe(-/-) mice showed reduced atherosclerotic lesion size compared to Apoe(-/-) mice. Striking differences were observed in the lesser curvature of the aortic arch, an area of disturbed flow, but not in the descending thoracic or abdominal aorta. Vascular cell adhesion molecule-1 (VCAM-1) expression, macrophage infiltration, and endothelial nuclear NF-kappaB were all reduced in Pecam1(-/-)Apoe(-/-) mice. Bone marrow transplantation suggested that endothelial PECAM-1 is the main determinant of atherosclerosis in the aortic arch, but that hematopoietic PECAM-1 promotes lesions in the abdominal aorta. In vitro data show that siRNA-based knockdown of PECAM-1 attenuates endothelial NF-kappaB activity and VCAM-1 expression under conditions of atheroprone flow.

CONCLUSIONS

These results indicate that endothelial PECAM-1 contributes to atherosclerotic lesion formation in regions of disturbed flow by regulating NF-kappaB-mediated gene expression.

Inflammation and factors that may regulate inflammatory response

The concept of inflammation has a long history. Although an inflammatory response to injury or another trigger is necessary, chronic diseases, such as coronary heart disease and diabetes, may develop because of unchecked inflammatory responses that have maladapted over decades. For example, the earliest changes in atherosclerosis occur in the endothelium, leading to a cascade of inflammatory responses, such as accumulation of monocytes and T cells, migration of leukocytes into the intima, monocyte differentiation and proliferation, and lesion and fibrous cap development. Inflammatory markers, such as C-reactive protein, may allow clinical insight into these decades-long processes, adding value to predictive measures of disease outcomes. Anti-inflammatory factors, such as adiponectin, may provide further understanding of the inflammatory pathways involved. Greater understanding of the complex pathways involved in inflammation may provide alternative therapeutic strategies to combat inflammation and chronic diseases potentially arising from it.

Role of endogenous RGS proteins on endothelial ERK 1/2 activation

Endothelial cells are maintaining atherosclerotic signaling mediated by Extracellular Regulated Kinases 1 and 2 (ERK). Signaling gets activated upon stimulation of G protein-coupled receptors mediated by G(q) and G(i/o) proteins subjected to regulation by RGS proteins. The goal of the study was to delineate the specificity of RGS proteins modulating induced ERK phosphorylation. We used stimulated HUVEC, silenced specifically RGS proteins and compared assessed ERK 1/2 activation with immunohistochemical stainings on atherosclerotic plaques. Increased ERK phosphorylation was detected upon stimulation with Phenylephrine (2.6+/-0.1 times over basal), Endothelin-1 (1.8+/-0.2), Dopamine (5.1+/-0.2), TNF (9.8+/-0.7) or IL-4 (3.1+/-0.3). RGS silencing increased activation of ERK 1/2: Phen (RGS3, 5), ET-1 (RGS3, 4), Dopa (RGS3), TNF (RGS2, 3, 4) or IL-4 (RGS2, 3, 4). Immunohistochemically, increased ERK activation was detected on atherosclerotic plaques. This data supports the role of RGS proteins on ERK activation in human atherosclerosis which identifies RGS proteins as new therapeutical targets.

Increased endothelial mitogen-activated protein kinase phosphatase-1 expression suppresses proinflammatory activation at sites that are resistant to atherosclerosis

Atherosclerosis is a chronic inflammatory disease of arteries. It is triggered by proinflammatory mediators which induce adhesion molecules (eg, vascular cell adhesion molecule [VCAM]-1) in endothelial cells (ECs) by activating p38 and c-Jun N-terminal kinase (JNK) mitogen-activated protein (MAP) kinases by phosphorylation. Blood flow influences atherosclerosis by exerting shear stress (mechanical drag) on the inner surface of arteries, a force that alters endothelial physiology. Regions of the arterial tree exposed to high shear are protected from endothelial activation, inflammation, and atherosclerosis, whereas regions exposed to low or oscillatory shear are susceptible. We examined whether MAP kinase phosphatase (MKP)-1, a negative regulator of p38 and JNK, mediates the antiinflammatory effects of shear stress. We observed that expression of MKP-1 in cultured ECs was elevated by shear stress, whereas the expression of VCAM-1 was reduced. MKP-1 induction was shown to be necessary for the antiinflammatory effects of shear stress because gene silencing of MKP-1 restored VCAM-1 expression in sheared ECs. Immunostaining revealed that MKP-1 is preferentially expressed by ECs in a high-shear, protected region of the mouse aorta and is necessary for suppression of EC activation at this site, because p38 activation and VCAM-1 expression was enhanced by genetic deletion of MKP-1. We conclude that MKP-1 induction is required for the antiinflammatory effects of shear stress. Thus, our findings reveal a novel molecular mechanism contributing to the spatial distribution of vascular inflammation and atherosclerosis.

Endothelial dysfunction: from molecular mechanisms to measurement, clinical implications, and therapeutic opportunities

Endothelial dysfunction has been implicated as a key factor in the development of a wide range of cardiovascular diseases, but its definition and mechanisms vary greatly between different disease processes. This review combines evidence from cell-culture experiments, in vitro and in vivo animal models, and clinical studies to identify the variety of mechanisms involved in endothelial dysfunction in its broadest sense. Several prominent disease states, including hypertension, heart failure, and atherosclerosis, are used to illustrate the different manifestations of endothelial dysfunction and to establish its clinical implications in the context of the range of mechanisms involved in its development. The size of the literature relating to this subject precludes a comprehensive survey; this review aims to cover the key elements of endothelial dysfunction in cardiovascular disease and to highlight the importance of the process across many different conditions.

Synergistic efficacy of concurrent treatment with cilostazol and probucol on the suppression of reactive oxygen species and inflammatory markers in cultured human coronary artery endothelial cells

In the present study, we aimed to identify the synergistic effects of concurrent treatment of low concentrations of cilostazol and probucol to inhibit the oxidative stress with suppression of inflammatory markers in the cultured human coronary artery endothelial cells (HCAECs). Combination of cilostazol (0.3~3 microM) with probucol (0.03~0.3 microM) significantly suppressed TNF-alpha-stimulated NAD(P)H-dependent superoxide, lipopolysaccharide (LPS)-induced intracellular reactive oxygen species (ROS) production and TNF-alpha release in comparison with probucol or cilostazol alone. The combination of cilostazol (0.3~3 microM) with probucol (0.1~0.3 microM) inhibited the expression of vascular cell adhesion molecule-1 (VCAM-1) and monocyte chemoattractant protein-1 (MCP-1) more significantly than did the monotherapy with either probucol or cilostazol. In line with these results, combination therapy significantly suppressed monocyte adhesion to endothelial cells. Taken together, it is suggested that the synergistic effectiveness of the combination therapy with cilostazol and probucol may provide a beneficial therapeutic window in preventing atherosclerosis and protecting from cerebral ischemic injury.

Experimental models investigating the inflammatory basis of atherosclerosis

Inflammation is considered an important aspect in the development of atherosclerosis. Genetic manipulations of animal models susceptible to atherosclerosis have unraveled the contribution of various inflammatory pathways implicated in the development of atherosclerosis. These inflammatory pathways not only lead to the recruitment and entry of inflammatory cells into the arterial wall, they also modify the morphology and composition of atherosclerotic plaques. Certain inflammatory pathways, such as P-selectin, intercellular adhesion molecule-1, and vascular cell adhesion molecule-1, appear to play an important role in lesion initiation, whereas others, such as interleukin-10 and CD40/CD40 ligand, seem to contribute to lesion progression and morphologic changes. An understanding of these pathways will allow the development of new strategies in the management of atherosclerosis. This review provides a roadmap for better utilization of these models in atherosclerosis research.

Epidemiology of cytokines: the Women On the Move through Activity and Nutrition (WOMAN) Study

Using multiplex technology, the authors investigated the laboratory and biologic variation of a panel of cytokines (interleukin (IL)-1a, IL-1 receptor antagonist, IL-4, IL-6, IL-8, IL-10, interferon-inducible protein-10, monocyte chemoattractant protein-1, and tumor necrosis factor-alpha) over 18 months and their relations to cardiovascular disease risk factors, hormone therapy, and weight loss. Data were obtained from the Woman On the Move through Activity and Nutrition (WOMAN) Study, a randomized clinical trial investigating the effect of nonpharmacologic interventions on subclinical atherosclerosis among overweight, postmenopausal women in Pennsylvania. The present analysis (February 2002-August 2005) comprised 290 women aged 52-62 years (mean age = 57 years). Most of the cytokines were detectable in a majority of the samples, and the between-individual biologic variation was greater than the within-individual biologic and laboratory variation. There was little association between use of hormone therapy at baseline or change in hormone therapy by 18 months and cytokine levels. Weight loss was associated with a decrease in levels of IL-1 receptor antagonist, IL-6, and C-reactive protein. The results suggest that a wide panel of cytokines may be measured simultaneously from one sample. There is large unexplained variability in cytokine levels that is probably due to genetic-environmental associations.

Monocyte-endothelial cell interactions in the development of atherosclerosis

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

Priming effect of homocysteine on inducible vascular cell adhesion molecule-1 expression in endothelial cells

Hyperhomocysteinemia is an independent risk factor for the development of atherosclerosis, as well as for arterial and venous thrombosis. However, the mechanisms through which elevated circulating levels of homocysteine cause vascular injury and promote thrombosis remain unclear. Here, we tested the hypothesis that homocysteine (Hcy) sensitizes endothelial cells to the effect of inflammatory mediators. Human umbilical vein endothelial cells (HUVEC) were incubated with Hcy 1.0 mM for varying time points, and then treated in the absence or presence of 1.5 U/ml thrombin or 10 mg/ml lipopolysaccharide (LPS). Hcy alone had no effect on the expression of vascular cell adhesion molecule (VCAM)-1. However, Hcy enhanced thrombin- and LPS-mediated induction of VCAM-1 mRNA and protein levels. Consistent with these results, pretreatment of HUVEC with Hcy resulted in a two-fold increase in LSP-mediated induction of leukocyte adhesion. The latter effect was significantly inhibited by anti-VCAM-1 antibodies. Together, these findings suggest that Hcy sensitizes HUVEC to the effect of inflammatory mediators thrombin and LPS, at least in part through VCAM-1 expression and function.

P-selectin glycoprotein ligand-1 is highly expressed on Ly-6Chi monocytes and a major determinant for Ly-6Chi monocyte recruitment to sites of atherosclerosis in mice

BACKGROUND

Ly-6C(hi) monocytes are key contributors to atherosclerosis in mice. However, the manner in which Ly-6C(hi) monocytes selectively accumulate in atherosclerotic lesions is largely unknown. Monocyte homing to sites of atherosclerosis is primarily initiated by rolling on P- and E-selectin expressed on endothelium. We hypothesize that P-selectin glycoprotein ligand-1 (PSGL-1), the common ligand of P- and E-selectin on leukocytes, contributes to the preferential homing of Ly-6C(hi) monocytes to atherosclerotic lesions.

METHODS AND RESULTS

To test this hypothesis, we examined the expression and function of PSGL-1 on Ly-6C(hi) and Ly-6C(lo) monocytes from wild-type mice, ApoE(-/-) mice, and mice lacking both ApoE and PSGL-1 genes (ApoE(-/-)/PSGL-1(-/-)). We found that Ly-6C(hi) monocytes expressed a higher level of PSGL-1 and had enhanced binding to fluid-phase P- and E-selectin compared with Ly-6C(lo) monocytes. Under in vitro flow conditions, more Ly-6C(hi) monocytes rolled on P-, E-, and L-selectin at slower velocities than Ly-6C(lo) cells. In an ex vivo perfused carotid artery model, Ly-6C(hi) monocytes interacted preferentially with atherosclerotic endothelium compared with Ly-6C(lo) monocytes in a PSGL-1-dependent manner. In vivo, ApoE(-/-) mice lacking PSGL-1 had impaired Ly-6C(hi) monocyte recruitment to atherosclerotic lesions. Moreover, ApoE(-/-)/PSGL-1(-/-) mice exhibited significantly reduced monocyte infiltration in wire injury-induced neointima and in atherosclerotic lesions. ApoE(-/-)/PSGL-1(-/-) mice also developed smaller neointima and atherosclerotic plaques.

CONCLUSIONS

These data indicate that PSGL-1 is a new marker for Ly-6C(hi) monocytes and a major determinant for Ly-6C(hi) cell recruitment to sites of atherosclerosis in mice.

Altered gene expression in early atherosclerosis is blocked by low level apolipoprotein E

BACKGROUND

Mice deficient in apolipoprotein E (apoE(-/-)) develop atherosclerosis. The possible linkage between expression of adhesion molecules/cofactors and atherosclerosis was probed at the level of mRNA and protein expression. The hypothesis of a linkage between changes of adhesion molecules/cofactors and atherosclerosis was tested further by suppression of aortic lesion formation in apoE(-/-) mice by expression of very low levels of transgenic apolipoprotein E.

METHODOLOGY/PRINCIPAL FINDINGS

We show that at 8.5 months of age, the apoE(-/-) mice display elevated expression of mRNA for LFA-1, MAC-1, VCAM-1, ICAM-1, and for CD44, as well as MCP-1, cathepsin B, and COX-2 (but not that for eNOS) in atherosclerotic aortic arches. At earlier age, (10-13 week old) apoE(-/-) mice already display elevated expression of mRNA of CD44, LFA-1, MAC-1, VCAM-1, ICAM-1, cathepsin, and of COX-2 in lesioned aortic arches. Expressing very low levels of transgenic apolipoprotein E suppresses both aortic lesions and the expression of mRNA of LFA-1, VCAM-1, MCP-1, cathepsin B, and of ICAM-1 in ApoE(-/-) mice. We tested at the level of protein, the observations obtained for mRNA expression. CD11a (a component of LFA-1), VCAM-1 and cathepsin B expression was found to be elevated in apoE(-/-) aortas at 8-9 months; low level expression of transgenic apolipoprotein E rectifies these changes.

CONCLUSIONS/SIGNIFICANCE

Atherosclerotic lesions in apoE(-/-) mice are detected as early as 4 weeks of age. Expression of low levels of apoE is shown to be both atheroprotective and to suppress these changes in key adhesion and inflammatory molecules observed in early atherosclerotic lesions.

Enhanced expression of vascular cell adhesion molecule-1 by corticotrophin-releasing hormone contributes to progression of atherosclerosis in LDL receptor-deficient mice

Peripherally produced corticotrophin-releasing hormone (CRH) is a strong proinflammatory factor involved in many inflammatory diseases. However, to date, there is no evidence about the action of CRH on atherosclerosis, a chronic disease characterized by inflammatory reactions. In this study we observed the effect of CRH on atherosclerosis in low-density lipoprotein receptor-deficient (LDLr-/-) mice. Twelve-week-old, male LDLr-/- mice were subcutaneously injected with CRH (10microg/kg) or vehicle once a day for 8 weeks. The results indicated aortic atherosclerotic lesions were larger (P<0.01) in CRH-treated mice than those in untreated mice. CRH significantly up-regulated the expression of both protein and mRNA for vascular cell adhesion molecule-1 (VCAM-1), together with a markedly increased activation of nuclear factor kappa B (NF-kappaB) in aortas. In addition, the blood lipid levels were not influenced by CRH subcutaneous injection. The significant proatherogenic effect of CRH in LDLr-/- mice was largely attenuated by selective CRH receptor 1 (CRHR1) antagonist NBI27914 but not by specific CRH receptor 2 (CRHR2) antagonist antisauvagine-30 (anti-Svg-30). Meanwhile, both the enhanced expression of VCAM-1 and increased activation of NF-kappaB induced by CRH in aortas of LDLr-/- mice were also largely suppressed by NBI27914, whereas these inhibitory effects were not observed in anti-Svg-30 group. Taken together, these findings indicated that CRH may accelerate atherosclerosis progression in LDLr-/- mice via CRHR1. The enhanced VCAM-1 expression which probably resulted from increased activation of NF-kappaB induced by CRH, may be one of the important molecular mechanisms by which CRH accelerates atherosclerosis. This study provides a new insight into the effect of CRH on atherosclerosis and suggests a potential target for the prevention and treatment of atherosclerosis.

Insulin potentiates cytokine-induced VCAM-1 expression in human endothelial cells

Hyperinsulinemia is an independent risk factor for cardiovascular events and may contribute to cardiovascular disease. Low-grade chronic inflammation has been implicated in the pathogenesis of atherosclerosis. We aimed at determining the impact of pathophysiologically high insulin concentrations on cytokine-induced endothelial activation in human umbilical vein endothelial cells (HUVEC). HUVEC were incubated with insulin (0-24 h)+/-tumor necrosis factor (TNF)-alpha or lipopolysaccharide (LPS). At pathophysiological/pharmacological concentrations (10(-9)-10(-7) mol/L), insulin selectively induced VCAM-1 expression and potentiated the effects of TNF-alpha andLPS, effects reverted by the proteasome inhibitor lactacystin. Compared with TNF-alpha alone, insulin+TNF-alpha doubled U937 cell adhesion. Insulin markedly increased TNF-alpha-induced NF-kappaB activation and induced phosphorylated IkappaB-alpha accumulation. Therefore, hyperinsulinemia enhances cytokine-induced VCAM-1 expression in endothelial cells, thus potentially contributing to detrimental effects of other inflammatory stimuli on atherogenesis.

Increased ADAM17 mRNA expression and activity is associated with atherosclerosis resistance in LDL-receptor deficient mice

BACKGROUND

We have previously identified an atherosclerosis quantitative trait locus (QTL) on mouse chromosome (Chr) 12 in an F2-intercross of atherosclerosis-resistant FVB and atherosclerosis-susceptible C57BL/6 (B6) mice on the LDL-receptor deficient (LDL-/-) background. The aim of the present study was to identify potentially causative genes at this locus.

METHODS AND RESULTS

Expression QTL (eQTL) analysis of candidate genes in livers of F2-mice revealed that a disintegrin and metalloproteinase 17 (ADAM17) mRNA expression mapped to the physical position of ADAM17 on proximal Chr12 (21.6 Mb, LOD 3.3) and colocalized with the atherosclerosis QTL. The FVB allele was associated with significantly higher ADAM17 mRNA expression (39%) than the B6 allele. Likewise, ADAM17 mRNA levels in the parental strains were significantly elevated in FVB.LDLR-/- compared to B6.LDLR-/- mice in liver, macrophages, and aorta (68%, 58%, and 32%, respectively). Reporter gene assays revealed a genetic variant that might explain these expression differences. Moreover, FVB.LDLR-/- macrophages showed 5-fold increased PMA-induced shedding of tumor necrosis factor (TNF)-alpha and 32% increased release of TNF-receptor I compared to B6.LDLR-/-. The atherosclerosis locus and expression differences were confirmed in Chr12 interval-specific congenic mice.

CONCLUSIONS

Our data provide functional evidence for ADAM17 as a candidate gene of atherosclerosis susceptibility at the murine Chr12 QTL.

Discoidin Domain Receptor 1 ( Ddr1 ) Deletion Decreases Atherosclerosis by Accelerating Matrix Accumulation and Reducing Inflammation in Low-Density Lipoprotein Receptor–Deficient Mice

Collagens are abundant within the atherosclerotic plaque, where they contribute to lesion volume and mechanical stability and influence cell signaling. The discoidin domain receptor 1 (DDR1), a receptor tyrosine kinase that binds to collagen, is expressed in blood vessels, but evidence for a functional role during atherogenesis is incomplete. In the present study, we generated Ddr1 +/+ ; Ldlr −/− and Ddr1 −/− ; Ldlr −/− mice and fed them an atherogenic diet for 12 or 24 weeks. Targeted deletion of Ddr1 resulted in a 50% to 60% reduction in atherosclerotic lesion area in the descending aorta at both 12 and 24 weeks. Ddr1 −/− ; Ldlr −/− plaques exhibited accelerated deposition of fibrillar collagen and elastin at 12 weeks compared with Ddr1 +/+ ; Ldlr −/− plaques. Expression analysis of laser microdissected lesions in vivo, and of Ddr1 −/− smooth muscle cells in vitro, revealed increased mRNA levels for procollagen α1(I) and α1(III) and tropoelastin, suggesting an enhancement of matrix synthesis in the absence of DDR1. Furthermore, whereas plaque smooth muscle cell content was unchanged, Ddr1 −/− ; Ldlr −/− plaques had a 49% decrease in macrophage content at 12 weeks, with a concomitant reduction of in situ gelatinolytic activity. Moreover, mRNA expression of both monocyte chemoattractant protein-1 and vascular cell adhesion molecule-1 was reduced in vivo, and Ddr1 −/− ; Ldlr −/− macrophages demonstrated impaired matrix metalloproteinase expression in vitro. These data suggest novel roles for DDR1 in macrophage recruitment and invasion during atherogenesis. In conclusion, our data support a role for DDR1 in the regulation of both inflammation and fibrosis early in plaque development. Deletion of DDR1 attenuated atherogenesis and resulted in the formation of matrix-rich plaques.