Lesions In Human Coronary Arteries Research Articles

Desmosterol suppresses macrophage inflammasome activation and protects against vascular inflammation and atherosclerosis

Cholesterol biosynthetic intermediates, such as lanosterol and desmosterol, are emergent immune regulators of macrophages in response to inflammatory stimuli or lipid overloading, respectively. However, the participation of these sterols in regulating macrophage functions in the physiological context of atherosclerosis, an inflammatory disease driven by the accumulation of cholesterol-laden macrophages in the artery wall, has remained elusive. Here, we report that desmosterol, the most abundant cholesterol biosynthetic intermediate in human coronary artery lesions, plays an essential role during atherogenesis, serving as a key molecule integrating cholesterol homeostasis and immune responses in macrophages. Depletion of desmosterol in myeloid cells by overexpression of 3β-hydroxysterol Δ24-reductase (DHCR24), the enzyme that catalyzes conversion of desmosterol to cholesterol, promotes the progression of atherosclerosis. Single-cell transcriptomics in isolated CD45+CD11b+ cells from atherosclerotic plaques demonstrate that depletion of desmosterol increases interferon responses and attenuates the expression of antiinflammatory macrophage markers. Lipidomic and transcriptomic analysis of invivo macrophage foam cells demonstrate that desmosterol is a major endogenous liver X receptor (LXR) ligand involved in LXR/retinoid X receptor (RXR) activation and thus macrophage foam cell formation. Decreased desmosterol accumulation in mitochondria promotes macrophage mitochondrial reactive oxygen species production and NLR family pyrin domain containing 3 (NLRP3)-dependent inflammasome activation. Deficiency of NLRP3 or apoptosis-associated speck-like protein containing a CARD (ASC) rescues the increased inflammasome activity and atherogenesis observed in desmosterol-depleted macrophages. Altogether, these findings underscore the critical function of desmosterol in the atherosclerotic plaque to dampen inflammation by integrating with macrophage cholesterol metabolism and inflammatory activation and protecting from disease progression.

Accumulation of Plasma-Derived Lipids in the Lipid Core and Necrotic Core of Human Atheroma: Imaging Mass Spectrometry and Histopathological Analyses.

To clarify the pathogenesis of human atheroma, the origin of deposited lipids, the developmental mechanism of liponecrotic tissue, and the significance of the oxidation of phospholipids were investigated using mass spectrometry-aided imaging and immunohistochemistry.

Human mast cell neutral proteases generate modified LDL particles with increased proteoglycan binding

Background and aimsSubendothelial interaction of LDL with extracellular matrix drives atherogenesis. This interaction can be strengthened by proteolytic modification of LDL. Mast cells (MCs) are present in atherosclerotic lesions, and upon activation, they degranulate and release a variety of neutral proteases. Here we studied the ability of MC proteases to cleave apoB-100 of LDL and affect the binding of LDL to proteoglycans. MethodsMature human MCs were differentiated from human peripheral blood-derived CD34+ progenitors in vitro and activated with calcium ionophore to generate MC-conditioned medium. LDL was incubated in the MC-conditioned medium or with individual MC proteases, and the binding of native and modified LDL to isolated human aortic proteoglycans or to human atherosclerotic plaques ex vivo was determined. MC proteases in atherosclerotic human coronary artery lesions were detected by immunofluorescence and qPCR. ResultsActivated human MCs released the neutral proteases tryptase, chymase, carboxypeptidase A3, cathepsin G, and granzyme B. Of these, cathepsin G degraded most efficiently apoB-100, induced LDL fusion, and enhanced binding of LDL to isolated human aortic proteoglycans and human atherosclerotic lesions ex vivo. Double immunofluoresence staining of human atherosclerotic coronary arteries for tryptase and cathepsin G indicated that lesional MCs contain cathepsin G. In the lesions, expression of cathepsin G correlated with the expression of tryptase and chymase, but not with that of neutrophil proteinase 3. ConclusionsThe present study suggests that cathepsin G in human atherosclerotic lesions is largely derived from MCs and that activated MCs may contribute to atherogenesis by enhancing LDL retention.

Human Coronary Artery Lesions: 900 MHz Magnetic Resonance Micro Imaging, NMR Spectroscopy, Histopathology and Oxidative Stress Markers

Human Coronary Artery Lesions: 900 MHz Magnetic Resonance Micro Imaging, NMR Spectroscopy, Histopathology and Oxidative Stress Markers

Characterization of Proliferating Lesion-Resident Cells During All Stages of Atherosclerotic Growth.

BackgroundMonocyte recruitment leads to accumulation of macrophage foam cells and contributes to atherosclerotic lesion growth. Recent studies have reported that lesion‐resident macrophages can proliferate and represent a major cellular component during lesion development. This study was designed to assess whether the rate of macrophage proliferation changes during well‐established stages of lesion growth and to characterize other populations of proliferating cells within these lesions.Methods and ResultsUsing murine models of atherosclerosis (Apoe −/− and LDLr −/− mice) and human coronary artery lesions, in situ proliferation of lesion‐resident cells at different stages of growth was assessed by staining for Ki67 and bromodeoxyuridine (BrdU). In early lesions, close to half of all actively growing macrophages were proliferating in situ. BrdU pulse labeling allowed for accurate identification of in situ proliferating macrophages compared to those derived from monocyte recruitment. Local macrophage proliferation declined as lesions advanced. Interestingly, intimal inflammatory cell infiltrates containing proliferating T lymphocytes were identified during the active phase of lesion growth and correlated with apoptotic cell death. Inflammatory cell infiltrates were completely resolved in advanced lesions and replaced with the necrotic core.ConclusionsOur findings indicate that atherosclerotic lesions contain locally proliferating macrophages primarily during early and intermediate stages of lesion growth. Furthermore, T‐lymphocyte‐enriched inflammatory cell infiltrates represent a novel subset of proliferating cells within the atherosclerotic lesion that correlate with apoptosis and precede the necrotic core. These findings have novel implications in understanding the pathogenesis of atherosclerosis and may implicate proliferating T lymphocytes as a contributing factor to lesion progression and stability.

Abstract 141: Coronary Heart Disease-Associated Variation in TCF21 Disrupts a MicroRNA-224 Binding Site and miRNA-Mediated Regulation

Introduction: Genome-wide association studies (GWAS) have identified chromosomal loci that affect risk of coronary heart disease (CHD) independent of classical risk factors. One such association signal has been identified at 6q23.2 in both Caucasians and East Asians. The lead CHD-associated variant in this region, rs12190287, resides in the 3’ untranslated region of the basic-helix-loop-helix transcription factor, TCF21 , and is predicted to alter the seed binding site for miR-224. Allelic imbalance studies demonstrated significant imbalance of the TCF21 transcript that correlated with genotype at rs12190287. Hypothesis: We hypothesize that genetic variation at rs12190287 contributes to allele-specific TCF21 expression imbalance via miR-224 regulation, thus altering CHD risk. Methods and Results: Reporter assays in human coronary artery smooth muscle cells (HCASMC) showed that the disease-associated C allele is selectively targeted by miR-224, leading to reduced expression compared to the protective G allele. Kinetic analyses in vitro revealed faster RNA-RNA complex formation and greater binding of miR-224 with the TCF21 C allelic transcript. In addition, in vitro probing with Pb 2+ and RNase T1 revealed structural differences between the TCF21 variants in proximity of the rs12190287 variant, which are predicted to provide greater access to the C allele for miR-224 binding. miR-224 and TCF21 expression levels were anti-correlated in HCASMC, and miR-224 modulates the transcriptional response of TCF21 to transforming growth factor- and platelet derived growth factor signaling in an allele-specific manner. Lastly, miR-224 and TCF21 were localized in human coronary artery lesions and anti-correlated during atherosclerosis in vivo . Conclusions: Together, these data suggest that miR-224 interaction with the TCF21 transcript contributes to allelic imbalance of this gene, thus partly explaining the genetic risk for CHD at 6q23.2. These studies implicating rs12190287 in the miRNA-dependent regulation of TCF21 , in conjunction with previous studies showing that this variant modulates transcriptional regulation through AP-1, suggests a unique bimodal level of complexity previously unreported for disease-associated variants.

Coronary Heart Disease-Associated Variation in TCF21 Disrupts a miR-224 Binding Site and miRNA-Mediated Regulation

Genome-wide association studies (GWAS) have identified chromosomal loci that affect risk of coronary heart disease (CHD) independent of classical risk factors. One such association signal has been identified at 6q23.2 in both Caucasians and East Asians. The lead CHD-associated polymorphism in this region, rs12190287, resides in the 3′ untranslated region (3′-UTR) of TCF21, a basic-helix-loop-helix transcription factor, and is predicted to alter the seed binding sequence for miR-224. Allelic imbalance studies in circulating leukocytes and human coronary artery smooth muscle cells (HCASMC) showed significant imbalance of the TCF21 transcript that correlated with genotype at rs12190287, consistent with this variant contributing to allele-specific expression differences. 3′ UTR reporter gene transfection studies in HCASMC showed that the disease-associated C allele has reduced expression compared to the protective G allele. Kinetic analyses in vitro revealed faster RNA-RNA complex formation and greater binding of miR-224 with the TCF21 C allelic transcript. In addition, in vitro probing with Pb2+ and RNase T1 revealed structural differences between the TCF21 variants in proximity of the rs12190287 variant, which are predicted to provide greater access to the C allele for miR-224 binding. miR-224 and TCF21 expression levels were anti-correlated in HCASMC, and miR-224 modulates the transcriptional response of TCF21 to transforming growth factor-β (TGF-β) and platelet derived growth factor (PDGF) signaling in an allele-specific manner. Lastly, miR-224 and TCF21 were localized in human coronary artery lesions and anti-correlated during atherosclerosis. Together, these data suggest that miR-224 interaction with the TCF21 transcript contributes to allelic imbalance of this gene, thus partly explaining the genetic risk for coronary heart disease associated at 6q23.2. These studies implicating rs12190287 in the miRNA-dependent regulation of TCF21, in conjunction with previous studies showing that this variant modulates transcriptional regulation through activator protein 1 (AP-1), suggests a unique bimodal level of complexity previously unreported for disease-associated variants.

YIA 4 Wnt5a signalling promotes VSMC survival via WISP-1: consequences for VSMC viability in atherosclerotic plaques

Apoptosis of vascular smooth muscle cells (VSMCs) within the fibrous cap of atherosclerotic plaques causes cap thinning and thereby plaque rupture and myocardial infarction. Identification of novel mechanisms that regulate...

The influence of extracellular matrix composition on the pathogenesis of coronary atherosclerosis

The modern concept of the development of atherosclerosis implies that the underlying pathogenesis of this disease is vascular remodeling as a response of the vessel wall to hypertension associated with hyperlipidemia and subsequent inflammation. However, even though this disease has been investigated for decades, both from a basic and clinical research aspect, there are still many doubts as to what the initial phase of the disease is. In contemporary literature there are an increasing number of papers that stress the importance of the extracellular matrix (ECM) of the blood vessels connective tissue, particularly proteoglycans, in the formation of early atherosclerotic lesions of human coronary arteries.

Localization of Latent Transforming Growth Factor-.BETA. Binding Protein-1 in Human Coronary Atherosclerotic Plaques

Transforming growth factor-β (TGFβ) and its receptors have been detected by immunohistochemistry in the normal vessel wall and in atherosclerotic lesions of human coronary arteries. However, TGFβ is normally secreted as an inactive complex associated with a latent TGFβ-binding protein (LTBP). Therefore, detection of TGFβ antigen only in the arterial wall does not imply the activated form of the growth factor. In situ hybridization and immunohistochemistry demonstrated LTBP1 mRNA and protein expression throughout the media and intima of early coronary artery lesions, with the highest levels of protein at the luminal surface. In advanced lesions, LTBP1 mRNA and protein were detected mainly in regions of high cell density, such as the fibrous cap. Assays of the TGFβ signalling pathway will be required to determine the activity associated with TGFβ antigen in the vessel wall.

Mechanical Activation of Smad, A Novel Regulator for Endothelial Cell Proliferation Induced by Disturbed Flow

Atherosclerotic lesions develop at arterial branches and curvatures, where the local flow is disturbed with low and oscillatory shear stress (OSS). We investigated the role of OSS in the endothelial cell (EC) activations of Smad1/5 and their regulation in OSS‐induced EC proliferation. OSS (0.5±4 dynes/cm2) to human umbilical vein ECs induced sustained phosphorylations of Smad1/5. Smad1/5 activations were found only in the selective patches of ECs overlying foam cell lesions in human coronary arteries. These shear‐activations of Smad1/5 were not inhibited by pre‐treating ECs with Noggin, a specific antagonist of bone morphogenic proteins. Transfecting ECs with specific siRNA of BMPRII, BMPRIB, and αv and β3 integrins inhibited OSS‐induced Smad1/5 phosphorylations. OSS induced sustained increases in the association of αvβ3 integrin with BMPRIB, which was inhibited by BMPRII‐specific siRNA. OSS induced the activations of focal adhesion kinase/Shc/extracellular signal‐regulated kinase, which are required for OSS‐induced Smad1/5 phosphorylations. OSS induced increased expression of cyclin A and decreased expressions of p21CIP1 and p27KIP1 and hence proliferation in ECs. Transfecting ECs with Smad1/5‐specific siRNA inhibited these OSS‐induced responses in ECs. Our findings provide a molecular basis for the role of Smad1/5 in regulating EC proliferation in response to OSS.

Blood flow in S-shaped in-plane and out-of-plane coronary arteries

The distribution of wall shear stress (WSS) in coronary arteries is an initiating factor for coronary artery disease. The complicated three dimensional structure of coronary arteries makes it difficult to isolate the factors affecting WSS distributions. Here we present a computational fluid dynamics study of transient flow in simplified S-shaped arteries with in-plane and out-of-plane bends. For in-plane arteries there are two regions of consistently low WSS during the cardiac cycle. The WSS distribution is related to secondary velocities which appear as symmetric counter-rotating eddies and are approximately 8% of the axial velocity. For out-of-plane arteries the WSS distributions are similar, but the eddies are no longer symmetric with secondary velocities only 7% of the axial velocities. The symmetric velocity patterns produced by the in-plane model could only exist in a single bend, which limits the usefulness of this model. The results obtained give useful insights into the nature of blood flow in realistically shaped coronary arteries. References Toshihisa Asakura and Takeshi Karino. Flow patterns and spatial distribution of atherosclerotic lesions in human coronary arteries. Circ. Res., 66:1054--1066, 1990. C. G. Caro, D. J. Doorley, M. Tarnawski, K. T. Scott, Q. Long, and C. L. Dumoulin. Non-planar curvature and branching of arteries and non-planar-type flow. Proc. R. Soc. Lond. A, 452:185--197, 1996. Jie Chen and Xi-Yun Lu. Numerical investigation of the non-newtonian pulsatile blood flow in a bifurcation model with a non-planar branch. Journal of Biomechanics, 39(5):818--832, 2006. doi:10.1016/j.jbiomech.2005.02.003 M. H. Friedman, O. J. Deters, F. F. Mark, C. B. Bargeron, and G. M. Hutchins. Aterial geometry affects hemodynamics: A potential risk factor for athersclerosis. Atherosclerosis, 46:225--231, 1983. doi:10.1016/0021-9150(83)90113-2 H. W. Hoogstraten, J. G. Kootstra, B. Hillen, J. K. B. Krijger, and P. J. W. Wensing. Numerical simulation of blood flow in an artery with two successive bends. Journal of Biomechanics, 29:1075--1083, 1996. doi:10.1016/0021-9290(95)00174-3 B. M. Johnston, P. R. Johnston, S. Corney, and D. Kilpatrick. Non-{N}ewtonian blood flow in human right coronary arteries: Transient simulations. Journal of Biomechanics, 39(6):1116--1128, 2006. doi:10.1016/j.jbiomech.2005.01.034 D. Liepsch. An introduction to biofluid mechanics---basic models and applications. Journal of Biomechanics, 35:415--435, 2002. doi:10.1016/S0021-9290(01)00185-3 A. M. Malek, L. A. Seth, and S. Izumo. Hemodynamic shear stress and its role in atherosclerosis. JAMA, 282(21):2035--2042, 1999. R. M. Nerem, J. A. Rumberger, D. R. Gross, W. W. Muir, and G. L. Gelger. Hot-film coronary artery velocity measurements in horses. Cardiovasc. Res., 10:301--313, 1976. M. Ojha, R. L. Leask, J. Butany, and K. W. Johnston. Distribution of intimal and medial thickening in the human right coronary artery: a study of 17 RCAs. Atherosclerosis, 158:147--153, 2001. doi:10.1016/S0021-9150(00)00759-0 T. J. Pedley. The fluid mechanics of large blood vessels. Cambridge University Press, 1980. K. Perktold, R. M. Nerem, and R. O. Peter. A numerical calculation of flow in a curved tube model of the left main coronary artery. J. Biomechanics, 24(3--4):175--189, 1991. doi:10.1016/0021-9290(91)90176-N A. K. Qiao, X. L. Guo, S. G. Wu, Y. J. Zeng, and X. H. Xu. Numerical study of nonlinear pulsatile flow in {S}-shaped curved arteries. Medical Engineering and Physics, 26:545--552, 2004. doi:10.1016/j.medengphy.2004.04.008 D. A. Steinman, D. A. Vorp, and C. R. Ethier. Computational modeling of arterial biomechanics: {I}nsights into pathogenesis and treatment of vascular disease. Journal of Vascular Surgery, 37(5):1119--1127, 2003. doi:10.1067/mva.2003.122 J. C. Wang, S.-L. T. Normand, L Mauri, and R. E. Kuntz. Coronary artery spatial distribution of acute myocardial infarction occlusions. Circulation, 110:278--284, 2004. doi:10.1161/01.CIR.0000135468.67850.F4 C. K. Zarins, D. P. Giddens, B. K. Bharadvaj, V. S. Sottiurai, R. F. Mabon, and S. Glagov. Carotid bifurcation atherosclerosis: quantitative correlation of plaque localization with flow velocity profiles and wall shear stress. Circ. Res., 53:502--514, 1983.

Inflammatory Blues Turns Velvet Skin Into Rawhide

The directed homing of leukocytes is crucial during immune surveillance or inflammation and is accomplished by a complex cooperation of signaling and adhesion molecules.1,2 Its pathophysiologic relevance is exemplified by various inflammatory diseases such as atherosclerosis.3 At present, the course of leukocyte trafficking is well established through the classical multistep cascade of initial tethering and rolling of leukocytes over vascular endothelium, followed by firm adhesion and their subsequent spreading and transendothelial migration.1,2 Leukocyte rolling is mediated by a subgroup of C-type lectins; E-, L-, and P-selectin, through shear-resistant binding to particular cell-surface carbohydrates. E- and L-selectin are expressed on activated endothelial cells and most leukocytes, respectively, while P-selectin is stored in the secretory compartments of platelets and endothelial cells to become rapidly upregulated on cell activation. The best characterized ligand for selectins is P-selectin glycoprotein ligand-1 (PSGL-1),4 a heavily posttranslationally modified homodimeric transmembrane glycoprotein. PSGL-1 contains functionally essential sialylated and fucosylated carbohydrate moieties, known as sialyl Lewis X (sLex) groups, and is expressed on blood cells such as neutrophils, monocytes, and platelets.5 The importance of PSGL-1 for cell recruitment is highlighted by studies using transgenic mice deficient in PSGL-1, which revealed a crucial contribution to P-selectin–dependent rolling on inflamed endothelium, indicating a function of PSGL-1 in early inflammatory responses.6 Presented by endothelium-bound leukocytes, PSGL-1 supports the initial L-selectin–dependent tethering of blood-borne leukocytes to the already adherent leukocytes at the inflamed vessel wall followed by E-selectin-mediated rolling on the endothelium.7 Besides supporting leukocyte–endothelium interactions, PSGL-1 promotes the P-selectin–dependent initial tethering of platelets to monocytes8,9 followed by more stable interactions through integrins expressed on both platelets and monocytes. In addition, the interaction between PSGL-1 and P-selectin also plays an essential role in the delivery …

PPAR Activity in the Vessel Wall: Anti-Atherogenic Properties

The nuclear receptor peroxisome proliferator-activated receptor gamma (PPARgamma) is a ligand-dependent transcription factor that controls the expression of specific target genes involved in adipogenesis, inflammatory responses, and lipid metabolism. Atherosclerotic plaque progression is influenced by intraplaque inflammation and extracellular matrix deposition. Anti-inflammatory, anti-proliferative and anti-protease activity of PPARgamma may modulate the atherosclerotic process. PPARgamma is expressed in atherosclerotic lesions of human coronary arteries and has direct anti-inflammatory effects in the vascular wall. Thiazolidinediones (TZD) are ligands for PPARgamma used therapeutically to enhance insulin-mediated glucose uptake in persons with type 2 diabetes. These agents may also exert anti-atherogenic effects on cells of the vessel wall including macrophages, vascular endothelium and vascular smooth muscle. This review discusses the impact of PPARgamma and its activators in the numerous processes involved in the formation of atherosclerotic lesions. We provide an overview of in vitro and in vivo data in cell lines, animal models, and humans demonstrating the ways in which PPARgamma activation alters the biology of the arterial wall.

Characterization of Intimal Changes in Coronary Artery Specimens with MR Microscopy

To determine if magnetic resonance (MR) microscopy can yield images sufficient for discriminating early progressive atherosclerotic lesions from nonprogressive atherosclerotic lesions in human coronary arteries. Institutional review board approval and informed consent were not required. Seventeen coronary artery segments (mean diameter, 2.8 mm +/- 1.0 [standard deviation]) were collected within 36 hours after death from 11 cadavers (six men, five women; age range at death, 33-65 years). Quantitative T1, T2, intensity-weighted (IW), and magnetization transfer (MT) maps were acquired with a 9.4-T vertical-bore magnet. Coronary artery lesions were classified as adaptive intimal thickening (AIT), pathologic intimal thickening (PIT), or intimal xanthoma (IXA). Internal anatomic fiducial landmarks and stains were applied to proximal and epicardial vessel surfaces and used to register histologic sections with MR images and thus enable comparison of MR images and Movat pentachrome-stained histologic specimens. Unique 0.0012-0.0287-cm(2) regions of interest were visually identified on quantitative T1, T2, MT, and IW maps of AIT, IXA, and PIT lesions. Distributions of T1, T2, MT, and IW values were compared with Student t and Wilcoxon two-sample tests. MR microscopic images of nonprogressive AIT and IXA lesions revealed two intimal layers. The luminal intima had higher T1 and T2 values and lower MT values than did the medial intima; these findings were consistent with compositional differences observed in histologic sections. In the IXA lesion, T2 values of both intimal layers were markedly reduced when compared with T2 values of AIT lesions because of the accumulation of lipid-laden macrophages in both layers. Progressive PIT lesions had a typical multilayered appearance or foci with a short T2 relaxation time and low IW values; these features were not observed in AIT or IXA lesions. MR microscopy enabled identification of morphologic arterial wall features that enable discrimination of progressive PIT lesions from nonprogressive AIT or IXA lesions.

Edge restenosis: impact of low dose irradiation on cell proliferation and ICAM-1 expression

BackgroundLow dose irradiation (LDI) of uninjured segments is the consequence of the suggestion of many authors to extend the irradiation area in vascular brachytherapy to minimize the edge effect. Atherosclerosis is a general disease and the uninjured segment close to the intervention area is often atherosclerotic as well, consisting of neointimal smooth muscle cells (SMC) and quiescent monocytes (MC). The current study imitates this complex situation in vitro and investigates the effect of LDI on proliferation of SMC and expression of intercellular adhesion molecule-1 (ICAM-1) in MC.MethodsPlaque tissue from advanced primary stenosing lesions of human coronary arteries (9 patients, age: 61 ± 7 years) was extracted by local or extensive thrombendarterectomy. SMC were isolated and identified by positive reaction with smooth muscle α-actin. MC were isolated from buffy coat leukocytes using the MACS cell isolation kit. For identification of MC flow-cytometry analysis of FITC-conjugated CD68 and CD14 (FACScan) was applied. SMC and MC were irradiated using megavoltage photon irradiation (CLINAC2300 C/D, VARIAN, USA) of 6 mV at a focus-surface distance of 100 cm and a dose rate of 6 Gy min-1 with single doses of 1 Gy, 4 Gy, and 10 Gy. The effect on proliferation of SMC was analysed at day 10, 15, and 20. Secondly, total RNA of MC was isolated 1 h, 2 h, 3 h, and 4 h after irradiation and 5 μg of RNA was used in standard Northern blot analysis with ICAM-1 cDNA-probes.ResultsBoth inhibitory and stimulatory effects were detected after irradiation of SMC with a dose of 1 Gy. At day 10 and 15 a significant antiproliferative effect was found; at day 20 after irradiation cell proliferation was significantly stimulated. Irradiation with 4 Gy and 10 Gy caused dose dependent inhibitory effects at day 10, 15, and 20. Expression of ICAM-1 in human MC was neihter inhibited nor stimulated by LDI.ConclusionThus, the stimulatory effect of LDI on SMC proliferation at day 20 days after irradiation may be the in vitro equivalent of a beginning edge effect. Extending the irradiation area in vascular brachytherapy in vivo may therefore merely postpone and not inhibit the edge effect. The data do not indicate that expression of ICAM-1 in quiescent MC is involved in the process.

Characterization of aortic lesions in two hypercholesterolemic rabbit models and their potential application to assessing the safety of endovascular devices

The principle shortcomings of animal models routinely used for the preclinical safety assessment of endovascular systems has been the absence of vascular pathology (atherosclerosis) and thus the ability to accurately assess the healing and vascular response of diseased arteries following device implantation. The objective of this investigation was to develop and characterize a rabbit model of atherosclerosis appropriate for testing the safety and potential efficacy of endovascular devices designed for the management of complex atherosclerotic lesions in human coronary arteries. Two groups of rabbits were used for this study, with one group receiving a 2- month-pulsed, 1.0% cholesterol diet and the other group receiving a continuous 0.3% cholesterol diet. Three rabbits from each diet group were scheduled to be euthanized at 2, 4, 6, and 9 months. From each rabbit, the length of the aorta was collected and evaluated histologically at segments along its length to assess and compare the development and character of atherosclerotic-like lesions. Results of the study show that there is little difference in either the development or character of lesions between the two dietary protocols investigated. However, rabbits on the 0.3% diet could be better maintained per protocol for the duration of the study and thus were more apt to develop atherosclerotic-like lesions. Per human classification schemes for atherosclerotic lesions, lesions that develop in the aorta in hypercholesterolemic rabbits did not progress beyond “preatheromas” or Type III lesions within the time course of this study. Inferences from and the applicability of this model to assessing the preclinical safety of endovascular devices are discussed. Guidant Corporation, Vascular Intervention, Santa Clara, CA

Inflammatory Biomarkers in Acute Coronary Syndromes

The inflammatory etiology of atherosclerosis has prompted a search for biomarkers of inflammation that predict risk for coronary artery disease and its sequelae. Within the acute coronary syndromes (ACS), inflammatory biomarkers may provide independent information regarding pathophysiology, prognosis, and optimal therapeutic strategies. On the basis of the hypothesis that different pathophysiological processes provide nonoverlapping information regarding risk stratification and disease management, this review series addresses biomarkers for each step in the inflammatory process that leads to ACS. Part I reviewed cytokines; this part reviews acute-phase reactants and biomarkers of endothelial cell activation; subsequent parts will address biomarkers of oxidative stress, angiogenesis, extracellular matrix degradation, and platelet activation. In the acute-phase response, cytokines drive production of acute-phase reactants, defined by >25% change in circulating concentration during an inflammatory response. These markers may also remain elevated chronically because of continuing inflammatory stimuli (Table). View this table: Inflammatory Biomarkers in ACS ### C-Reactive Protein C-reactive protein (CRP) is a pentraxin acute-phase protein, members of which are evolutionarily conserved in most vertebrates.1 Hepatocytes and possibly smooth muscle cells and macrophages transcriptionally activate production of CRP in response to inflammatory cytokines, including interleukin-1 and interleukin-6.2 CRP is a robust clinical marker because of its stability, reproducible results, and ease of assay. Although it was originally proposed as a nonspecific marker of inflammation, several reports suggest that CRP may play a direct pathophysiological role in the development and progression of atherosclerosis. Proposed mechanisms include induction of endothelial dysfunction,3 promotion of foam cell formation,4 inhibition of endothelial progenitor cell survival and differentiation,5 and activation of complement in atherosclerotic plaque intima6 and ischemic myocardium.7 Patients with ACS have elevations in CRP in association with their presenting symptoms. There appears to be a bimodal CRP response among patients with ACS. In some patients, CRP may remain elevated for …

Endothelial Lipase Modulates Monocyte Adhesion to the Vessel Wall: A POTENTIAL ROLE IN INFLAMMATION

Endothelial lipase (EL), a new member of the lipoprotein lipase gene family, plays a central role in high density lipoprotein metabolism. Previous studies indicated that EL is expressed in endothelial cells, macrophages, and smooth muscle cells in atherosclerotic lesions in human coronary arteries. However, the functional role of EL in the local vessel wall remains obscure. In this study, we evaluated the ability of EL to modulate monocyte adhesion to the endothelial cell surface. EL mRNA and protein levels were markedly increased in tissues of the mouse model of inflammation induced by lipopolysaccharide injection. Adhesion assays in vitro revealed that overexpression of EL in COS7 or Pro5 cells enhanced monocyte bindings to the EL-expression cells. Heparin or heparinase treatment inhibited EL-mediated increases of monocyte adhesion in a dose-dependent manner. Moreover, ex vivo adhesion assays revealed that the number of adherent monocytes on aortic strips was significantly increased in EL transgenic mice and decreased in EL knock-out mice as compared with wild-type mice. These results suggest that EL on the endothelial cell surface can promote monocyte adhesion to the vascular endothelium through the interaction with heparan sulfate proteoglycans. Thus, the up-regulation of EL by inflammatory stimuli may be involved in the progression of inflammation.

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.