Atherosclerosis-prone Areas Research Articles

Oscillatory shear stress promotes endothelial senescence and atherosclerosis via STING activation

Endothelial dysfunction is an initiating factor in atherosclerosis. Endothelial cells (ECs) are constantly subject to blood flow shear stress, and atherosclerotic plaques tend to occur in aortic bends or bifurcations impaired by low oscillatory shear stress (OSS). However, the mechanism that how OSS affects the initiation and progression of atherosclerosis remains to be explored. Here, we first reported that OSS can promote endothelial dysfunction and atherogenesis in vivo and in vitro by activating STING pathway. Mechanistically, at atherosclerosis-prone areas, OSS caused mitochondria damage in ECs, leading to the leakage of mitochondrial DNA (mtDNA) into the cytoplasm. The cytoplasmic mtDNA was recognized by cGAS to produce cGAMP, activating the STING pathway and leading to endothelial senescence, which resulted in endothelial dysfunction and atherosclerosis. We found that STING was activated in plaques of atherosclerotic patients and in aortic arch ECs of high-fat diet (HFD)-fed ApoeKO mice, as well as in ECs exposed to OSS. STING-specific deficiency in ECs attenuates endothelial senescence and resulted in a significant reduction in aortic arch plaque area in HFD-fed ApoeKO mice. Consistently, specific deficiency or pharmacological inhibition of STING attenuated OSS-induced senescence and endothelial dysfunction. Pharmacological depletion of mtDNA ameliorated OSS-induced senescence and endothelial dysfunction. Taken together, our study linked hemodynamics and endothelial senescence, and revealed a novel mechanism by which OSS leads to endothelial dysfunction. Our study provided new insights into the development of therapeutic strategies for endothelial senescence and atherosclerosis.

Comparison of RANS and LES turbulent flow models in a real stenosis

This study focuses on the performance of various turbulence models in predicting hemodynamic variables within a patient-specific geometry of the Brachiocephalic trunk exhibiting a severe stenosis. Numerical simulations employing Reynolds-averaged Navier-Stokes (RANS) and Large Eddy Simulation (LES) models were conducted, comparing four RANS with two LES models. Results indicated significant differences in turbulent structures between RANS and LES models, with the k-ω RANS model closely approximating LES throughout the cardiac cycle. The velocity and Turbulent Kinetic Energy (TKE) results were consistent in the stenosis region due to the proximity to the inlet and plug flow conditions. However, notable disparities were observed in bifurcation and outlet regions. Time-Averaged Wall Shear Stress (TAWSS) comparisons revealed that the k-ω-based models provided closer agreement with LES, particularly in atherosclerosis-prone areas. The study highlights the limitations and strengths of each turbulence model, emphasizing the importance of model selection in simulating complex cardiovascular conditions. While RANS models demonstrated computational efficiency, their accuracy varied across regions. The effectiveness of the k-ω model in capturing the intricacies of such a complex flow field suggests its potential as a reliable and accurate tool for simulating physiological conditions with strong curvature and advanced stenosis.

Secreted Protein Profiling of Human Aortic Smooth Muscle Cells Identifies Vascular Disease Associations.

Smooth muscle cells (SMCs), which make up the medial layer of arteries, are key cell types involved in cardiovascular disease, the leading cause of mortality and morbidity worldwide. In response to microenvironment alterations, SMCs dedifferentiate from a contractile to a synthetic phenotype characterized by an increased proliferation, migration, production of ECM (extracellular matrix) components, and decreased expression of SMC-specific contractile markers. These phenotypic changes result in vascular remodeling and contribute to the pathogenesis of cardiovascular disease, including coronary artery disease, stroke, hypertension, and aortic aneurysms. Here, we aim to identify the genetic variants that regulate ECM secretion in SMCs and predict the causal proteins associated with vascular disease-related loci identified in genome-wide association studies. Using human aortic SMCs from 123 multiancestry healthy heart transplant donors, we collected the serum-free media in which the cells were cultured for 24 hours and conducted liquid chromatography-tandem mass spectrometry-based proteomic analysis of the conditioned media. We measured the abundance of 270 ECM and related proteins. Next, we performed protein quantitative trait locus mapping and identified 20 loci associated with secreted protein abundance in SMCs. We functionally annotated these loci using a colocalization approach. This approach prioritized the genetic variant rs6739323-A at the 2p22.3 locus, which is associated with lower expression of LTBP1 (latent-transforming growth factor beta-binding protein 1) in SMCs and atherosclerosis-prone areas of the aorta, and increased risk for SMC calcification. We found that LTBP1 expression is abundant in SMCs, and its expression at mRNA and protein levels was reduced in unstable and advanced atherosclerotic plaque lesions. Our results unravel the SMC proteome signature associated with vascular disorders, which may help identify potential therapeutic targets to accelerate the pathway to translation.

Emulating Early Atherosclerosis in a Vascular Microphysiological System Using Branched Tissue-Engineered Blood Vessels.

Atherosclerosis begins with the accumulation of cholesterol-carrying lipoproteins on blood vessel walls and progresses to endothelial cell dysfunction, monocyte adhesion, and foam cell formation. Endothelialized tissue-engineered blood vessels (TEBVs) have previously been fabricated to recapitulate artery functionalities, including vasoconstriction, vasodilation, and endothelium activation. Here, the initiation of atherosclerosis is emulated by designing branched TEBVs (brTEBVs) of various geometries treated with enzyme-modified low-density-lipoprotein (eLDL) and TNF-α to induce endothelial cell dysfunction and adhesion of perfused human monocytes. Locations of monocyte adhesion under pulsatile flow are identified, and the hemodynamics in the brTEBVs are characterized using particle image velocimetry (PIV) and computational fluid dynamics (CFD). Monocyte adhesion is greater at the side outlets than at the main outlets or inlets, and is greatest at larger side outlet branching angles (60° or 80° vs 45°). In PIV experiments, the branched side outlets are identified as atherosclerosis-prone areas where fluorescent particles show a transient swirling motion following flow pulses; in CFD simulations, side outlets with larger branching angles show higher vorticity magnitude and greater flow disturbance than other areas. These results suggest that the branched TEBVs with eLDL/TNF-α treatment provide a physiologically relevant model of early atherosclerosis for preclinical studies.

SAT-049 Testosterone Therapy Reduces Inflammatory Activation of Human Monocytes in Hypogonadal Type-2 Diabetic Men as a Potential Mechanism to Improve Atherosclerosis

Testosterone deficiency is prevalent in men with type 2 diabetes (T2D) and is associated with greatly elevated risk of cardiovascular mortality. Testosterone replacement has beneficial effects on surrogate markers and risk factors of atherosclerosis including inflammation, cholesterol and insulin resistance improving survival in men with T2D. The underlying mechanisms of this action remain poorly understood. Inflammation is a central feature to both T2D and atherosclerosis and is driven by monocyte/macrophages, placing these immune cells at the crossroads of disease pathology. The recruitment of immune cells to atherosclerosis-prone areas of the vasculature is influenced by many factors including the inflammatory status of the circulating monocytes. The present study investigates the influence of testosterone replacement on monocyte inflammatory markers in a randomised double blinded placebo controlled clinical trial. 65 men with poorly controlled diabetes (HbA1c between 53 and 80 mmol/mol) and confirmed hypogonadism via early morning [0800−1200h] total testosterone ≤12 nmol/L or calculated free testosterone ≤255 pmol/L on two occasions ≥1 week apart, with at least two symptoms of hypogonadism were included in the study. Patients were randomly assigned to either placebo or treatment (depot testosterone undecanoate, 6 weekly followed by 3 monthly intramuscular injections) for 6 months. Monocytes were isolated from whole blood collected at baseline, 3 and 6 month visits followed by gene expression of key inflammatory targets IL-1β, IL-6, IL-10, TNFα, ICAM1, TLR2, TLR4, SCARB1 and MCP1 assessed via qPCR. Pro-inflammatory targets TNFα and MCP1 were significantly reduced over time in monocytes from patients treated with testosterone between 3 and 6 months (1.39±0.39 Vs 0.68±0.09, P<0.01; 15.36±7.79 Vs 1.88±0.93, P<0.01 respectively) and TNFα at 6 months compared to the start of the study (1.00±0.00 Vs 0.68±0.09, P<0.001) when normalised to baseline. TNFα expression was also significantly reduced compared to placebo treated patient monocytes at 6 months (0.68±0.09 Vs 3.45±1.50, P<0.01). Other targets were not significantly altered over time or between treatment groups. These findings importantly indicate for the first time that testosterone influences monocyte inflammatory activation in type 2 diabetic men by altering expression of the most potent atherogenic chemokine MCP1 and potent pro-inflammatory cytokine TNFα, as a potential mechanism to protect against atherosclerotic plaque development in hypogonadism.

Increased retention of LDL from type 1 diabetic patients in atherosclerosis-prone areas of the murine arterial wall

Background and aimsType 1 diabetes accelerates the development of atherosclerotic cardiovascular diseases. Retention of low-density lipoprotein (LDL) in the arterial wall is a causal step in atherogenesis, but it is unknown whether diabetes alters the propensity of LDL for retention. The present study investigated whether LDL from type 1 diabetic and healthy non-diabetic subjects differed in their ability to bind to the arterial wall in a type 1 diabetic mouse model. MethodsFluorescently-labeled LDL obtained from type 1 diabetic patients or healthy controls was injected into mice with type 1 diabetes. The amount of retained LDL in the atherosclerosis-prone inner curvature of the aortic arch was quantified by fluorescence microscopy. Healthy control LDL was in vitro glycated, analyzed for protein glycation by LC-MS/MS, and tested for retention propensity. ResultsRetention of LDL from type 1 diabetic patients was 4.35-fold higher compared to LDL from nondiabetic subjects. Nuclear magnetic resonance (NMR) spectroscopy analysis of LDL revealed no differences in the concentration of the atherogenic small dense LDL between type 1 diabetic and non-diabetic subjects. In vitro glycation of LDL from a non-diabetic subject increased retention compared to non-glycated LDL. LC-MS/MS revealed four new glycated spots in the protein sequence of ApoB of in vitro glycated LDL. ConclusionsLDL from type 1 diabetic patients showed increased retention at atherosclerosis-prone sites in the arterial wall of diabetic mice. Glycation of LDL is one modification that may increase retention, but other, yet unknown, mechanisms are also likely to contribute.

Retrospective Study of Hemodynamic Changes Before and After Carotid Stenosis Formation by Vessel Surface Repairing

Prospective observation of hemodynamic changes before and after the formation of atherosclerotic stenosis in the carotid artery is difficult. Thus, a vessel surface repairing method was used for retrospective hemodynamic study before and after atherosclerotic stenosis formation in carotid artery. The three-dimensional geometry of sixteen sinus atherosclerotic stenosis carotid arteries were repaired and restored as normal arteries. Computational fluid dynamics analysis was performed to estimate wall shear stress (WSS), velocity and vortex in atherosclerosis-free areas and sinus in stenosis-repaired carotid artery. The analysis was also performed in the stenotic segment and upstream and downstream of stenosis in stenotic carotid artery. Compared to the atherosclerosis-free areas in stenosis-repaired carotid artery, sinus presented significantly lower WSS (P < 0.05), lower velocity (P < 0.05) and apparent vortex. Compared to the sinus, the WSS in the upstream of stenosis was lower (P < 0.05), while in the downstream area was similar (P = 0.87), both upstream and downstream of stenosis demonstrated similar velocity to sinus (P = 0.76 and P = 0.36, respectively) and apparent vortex. Atherosclerosis-prone areas including normal carotid sinus and upstream and downstream of stenosis in stenotic carotid artery were subjected to lower WSS and velocity as well as apparent vortex, thereby might be associated with the formation and progress of atherosclerosis.

Type 1 diabetes increases retention of low-density lipoprotein in the atherosclerosis-prone area of the murine aorta

Background and aimsIndividuals with type 1 diabetes mellitus are at high risk of developing atherosclerotic cardiovascular disease, but the underlying mechanisms by which type 1 diabetes accelerates atherosclerosis remain unknown. Increased retention of low-density lipoprotein (LDL) in atherosclerosis-prone sites of the diabetic vascular wall has been suggested, but direct evidence is lacking. In the present study, we investigated whether retention of LDL is increased in atherosclerotic-prone areas using a murine model of type 1 diabetes. MethodsFluorescently-labeled human LDL from healthy non-diabetic individuals was injected into diabetic Ins2Akita mice and non-diabetic, wild-type littermates. The amount of retained LDL after 24 h was quantified by fluorescence microscopy of cryosections and by scans of en face preparations. Vascular gene expression in the inner curvature of the aortic arch was analyzed by microarray and quantitative polymerase chain reaction. ResultsLDL retention was readily detected in atherosclerosis-prone areas of the aortic arch being located in both intimal and medial layers. Quantitative microscopy revealed 8.1-fold more retained LDL in type 1 diabetic mice compared to wild-type mice. These findings were confirmed in independent experiments using near-infrared scanning of en face preparations of the aorta. Diabetic status did not affect arterial expression of genes known to be involved in LDL retention. ConclusionsType 1 diabetes increases the ability of the vascular wall to retain LDL in mice. These changes could contribute to the increased atherosclerotic burden seen in type 1 diabetic patients.

EPAC1 promotes adaptive responses in human arterial endothelial cells subjected to low levels of laminar fluid shear stress: Implications in flow-related endothelial dysfunction

Blood flow-associated fluid shear stress (FSS) dynamically regulates the endothelium's ability to control arterial structure and function. While arterial endothelial cells (AEC) subjected to high levels of laminar FSS express a phenotype resistant to vascular insults, those exposed to low levels of laminar FSS, or to the FSS associated with oscillatory blood flow, are less resilient. Despite numerous reports highlighting how the cAMP-signaling system controls proliferation, migration and permeability of human AECs (HAECs), its role in coordinating HAEC responses to FSS has received scant attention. Herein we show that the cAMP effector EPAC1 is required for HAECs to align and elongate in the direction of flow, and for the induction of several anti-atherogenic and anti-thrombotic genes associated with these events. Of potential therapeutic importance, EPAC1 is shown to play a dominant role the in response of HAECs to low levels of laminar FSS, such as would be found within atherosclerosis-prone areas of the vasculature. Moreover, we show that EPAC1 promotes these HAEC responses to flow by regulating Vascular Endothelial Growth Factor Receptor-2 and Akt activation, within a VE-cadherin (VECAD)/PECAM1-based mechanosensor. We submit that these findings are consistent with the novel proposition that promoting EPAC1-signaling represents a novel means through which to promote expression of an adaptive phenotype in HAECs exposed to non-adaptive FSS-encoded signals as a consequence of vascular disease.

Abstract 591: Increased Retention of LDL From Type 1 Diabetic Patients in an Atherosclerosis-prone Area of the Murine Arterial Wall

Background: Individuals with type 1 diabetes mellitus (T1DM) are at high risk of developing atherosclerotic cardiovascular disease but the exact mechanisms by which T1DM accelerates atherosclerosis remain unknown. In the present study, we investigated whether modifications of low density lipoprotein (LDL) in T1DM patients causes an increased retention of LDL in the vessel wall. Methods and Results: Fluorescently-labeled human LDL from either T1DM patients (n=10) or healthy non-diabetic subjects (control) (n=7) was injected into mice with T1DM. After 24 hours, when LDL was completely cleared from the circulation, cryosections of the inner curvature of the aortic arch (i.e. atherosclerosis prone area) was analyzed for retained LDL by fluorescence microscopy (Red in figure A). We found significantly more retained T1DM LDL (n=10) compared to LDL from non-diabetic subjects (n=7) with a fold change of 4.35 (p &lt; 0.05). Nuclear magnetic resonance (NMR) spectroscopy analysis of LDL revealed no differences in the level of the atherogenic small dense LDL between T1DM LDL (274.4±47.8 nmol/L) and non-diabetic LDL (263.8±55.3 nmol/L). Using LiCor Odyssey infrared imaging scanning of the whole aorta en face, we found that in vitro glycation of LDL from a non-diabetic subject significantly increased retention (n=8) compared to LDL prepared similarly but without glucose (n=8), with a fold change of 8.87 (p &lt; 0.001) (Figure B). Conclusion: LDL from patients with T1DM as well as ex vivo glycated LDL showed increased retention at atherosclerosis-prone sites in the arterial wall of mice. This may contribute to the accelerated development of atherosclerosis in T1DM.

Interleukin-10 protects against atherosclerosis by modulating multiple atherogenic macrophage function.

Atherosclerosis is primarily a disorder of lipid metabolism, but there is also a prominent chronic inflammatory component that drives the atherosclerotic lesion progression in the artery wall. During hyperlipidaemic conditions, there is a rapid influx of circulating monocytes into the atherosclerosis-prone areas of the arterial intima. These infiltrated monocytes differentiate into macrophages and take up the atherogenic lipoproteins in the intima of the vessel wall that have been modified within the lesion environment. Interleukin (IL)-10 is a prototypic anti-inflammatory cytokine made primarily by the macrophages and Th2 subtype T lymphocytes. In terms of atherosclerosis its major roles include inhibition of macrophage activation as well as inhibition of matrix metalloproteinase, pro-inflammatory cytokines and cyclooxygenase-2 expression in lipid-loaded and activated macrophage foam cells. Recent discoveries suggest another important role of IL-10 in atherosclerosis: its ability to alter lipid metabolism in macrophages. The current review will highlight the present knowledge on multiple ways in which IL-10 mediates atherosclerosis. As macrophages play a critical role in all stages of atherosclerosis, the review will concentrate on how IL-10 regulates the activities of macrophages that are especially important in the development of atherosclerosis.

Increased Shedding of Microvesicles from Intimal Smooth Muscle Cells in Athero-Prone Areas of the Human Aorta: Implications for Understanding of the Predisease Stage

Objective: This study evaluated whether a change in the content of matrix microvesicles might occur at the preatherosclerotic stage. Methods: Applying quantitative electron microscopic and immunohistochemical analyses, two areas of grossly normal segments of the thoracic aorta were compared: atherosclerosis-prone (AP) areas, situated at the dorsal aspect of the aorta along the rows of intercostal branch origins, and atherosclerosis-resistant (AR) areas, situated at the corresponding sites of the ventral aspect of the aorta. Results: The electron microscopic analysis showed that there were 1.4 times more microvesicles in AP areas than AR areas (p = 0.019). It was found that matrix microvesicles originated as a result of blebbing and shedding of surface membranes of smooth muscle cells. A quantitative analysis of the expression of ADP-ribosylation factor 6 (ARF6), which is known to be involved in membrane trafficking and microvesicle formation, showed that ARF6 expression was 1.3 times higher in AP areas than that in AR areas (p = 0.006). There was a positive correlation between the content of matrix microparticles and the expression of ARF6 by intimal smooth muscle cells (r = 0.61; p < 0.0001). Conclusion: The present study supports the concept that alterations of the arterial intima occur at the predisease stage.

Plasma fibronectin deficiency impedes atherosclerosis progression and fibrous cap formation

Atherosclerotic lesions are asymmetric focal thickenings of the intima of arteries that consist of lipids, various cell types and extracellular matrix (ECM). These lesions lead to vascular occlusion representing the most common cause of death in the Western world. The main cause of vascular occlusion is rupture of atheromatous lesions followed by thrombus formation. Fibronectin (FN) is one of the earliest ECM proteins deposited at atherosclerosis-prone sites and was suggested to promote atherosclerotic lesion formation. Here, we report that atherosclerosis-prone apolipoprotein E-null mice lacking hepatocyte-derived plasma FN (pFN) fed with a pro-atherogenic diet display dramatically reduced FN depositions at atherosclerosis-prone areas, which results in significantly smaller and fewer atherosclerotic plaques. However, the atherosclerotic lesions from pFN-deficient mice lacked vascular smooth muscle cells and failed to develop a fibrous cap. Thus, our results demonstrate that while FN worsens the course of atherosclerosis by increasing the atherogenic plaque area, it promotes the formation of the protective fibrous cap, which in humans prevents plaques rupture and vascular occlusion.

Leptin and EPCs in Arterial Injury

See related article, pages 536–544 Endothelial progenitor cells (EPCs) were introduced to a broad scientific readership in 1997 by Asahara et al, who demonstrated that CD34+ cells from the peripheral blood can adopt an endothelial cell-like phenotype in vitro.1 This culture-modified cell type (subsequently also termed endothelial outgrowth cells) improved ischemic neovascularization after intravenous transfusion.2 The prospect of ameliorating tissue ischemia by ex vivo–expanded autologous angioblasts resulted in extensive research activities, including the therapeutic application in patients with myocardial ischemia.3 However, the results are still conflicting, which is at least partially attributable to the fact that EPCs comprise a heterogenous pool of subpopulations originating from distinct sources and displaying diverse phenotypes.4 For instance, the common characterization of EPCs as CD34+CD133+VEGF-R2+ by flow cytometry has been recently questioned in different studies showing that only CD133−CD45− cells differentiate into endothelial cells.5,6 Early outgrowth of endothelial-like cells from mononuclear cells cultured for 5 to 7 days in the presence of endothelial growth factors represent a monocyte-like subtype with low proliferative capacity secreting high …

Beneficial effects of low doses of red wine consumption on perturbed shear stress-induced atherogenesis

Moderate wine intake is associated with a reduced risk of morbidity and mortality from cardiovascular disease. Atherosclerosis is enhanced in arterial segments exposed to disturbed flow. Perturbed shear stress increases also the endothelial expression of oxidation-sensitive responsive genes (such as ELK-1 and p-JUN). This study evaluates the effects of chronic consumption of red wine on perturbed shear stress-induced atherogenesis. Results indicated that chronic treatment with red wine significantly attenuated the activation of redox-sensitive genes (ELK-1 and p-JUN) and increased endothelial nitric oxide synthase (eNOS) expression (which was decreased by perturbed shear stress) in cultured human coronary endothelial cells (EC) and in atherosclerosis-prone areas of hypercholesterolemic mice. Oral administration of red wine to hypercholesterolemic mice reduced significantly the progression of atherosclerosis. Moreover, short-term supplementation with red wine to C57BL/6J mice significantly increased upregulation of aortic eNOS and SIRT1 expression induced by physical training. These findings establish that administration of low doses of red wine can attenuate the proatherogenic effects induced by perturbed shear stress in vitro and in vivo. This evidence may have implications for the prevention of atherosclerotic lesion progression and its clinical manifestations.

Artery regional properties and atherosclerosis susceptibility

White carneau (WC) pigeons develop spontaneous atherosclerosis in contrast to atherosclerosis-resistant show racer (SR) pigeons. In this study, cellular and extracellular components and smooth muscle cell (SMC) proliferation rates of specific aortic sites were assessed in both breeds of pigeons prior to lesion development. The atherosclerosis-susceptible site of the WC aorta was characterized by larger lumen diameter without accompanying increase in wall thickness, as well as by SMC hypocellularity, increased proteoglycan content and higher elastin content. For both breeds, cells derived from the lesion site had lower proliferation rates compared to proximal aortic control sites. WC cells had greater proliferation rates than SR cells (109% greater at the atherosclerosis-prone site and 133% greater at the control site). Fibroblast growth factor (FGF) increased the proliferation of WC lesion site cells compared to SR cells (79% vs. 35%); whereas, transforming growth factor β (TGFβ) reduced growth in SR but not in WC cells. Differences in hemodynamic properties, in cell-matrix, elastin, proteoglycan and proliferation rates of cells and responses to FGF and TGFβ in cells of the atherosclerosis-prone area have been identified as potential contributors to the enhanced atherosclerosis potential of this site in WC pigeons.

Effects of a Pomegranate Fruit Extract rich in punicalagin on oxidation-sensitive genes and eNOS activity at sites of perturbed shear stress and atherogenesis

Atherosclerosis is enhanced in arterial segments exposed to disturbed flow. Perturbed shear stress increases the expression of oxidation-sensitive responsive genes (such as ELK-1 and p-CREB). Polyphenolic antioxidants contained in the juice derived from the pomegranate contribute to the reduction of oxidative stress and atherogenesis during disturbed shear stress. To evaluate the effects of intervention with the Pomegranate Fruit Extract (PFE) rich in polyphones (punicalagin, which is a potent antioxidant) on ELK-1, p-CREB, and endothelial nitric oxide synthase (eNOS) expression induced by high shear stress in vitro and in vivo. At the doses used in the study, both the PFE and the regular pomegranate juice concentrate reduced the activation of ELK-1 and p-CREB and increased eNOS expression (which was decreased by perturbed shear stress) in cultured human endothelial cells and in atherosclerosis-prone areas of hypercholesterolemic mice. PFE and pomegranate juice increased cyclic GMP levels while there was no significant effect of both compounds on the conversion of L-arginine to L-citrulline. Administration of these compounds to hypercholesterolemic mice significantly reduced the progression of atherosclerosis and isoprostane levels and increased nitrates. This protective effect was relevant with PFE. Vasomotor reactivity was improved and EC(25) values in response to Ach and NONOate were significantly increased in treated mice in comparison to controls. This study indicates that the proatherogenic effects induced by perturbed shear stress can be also reversed by chronic administration of PFE.

Atherin: a newly identified, lesion-specific, LDL-binding protein in human atherosclerosis

Prolonged retention of LDL in focal, atherosclerosis-prone areas of arteries is a primary event in atherogenesis. To determine whether unrecognized LDL-binding proteins participate in this process, we generated a cDNA expression library from deendothelialized rabbit aorta, a model for early atherosclerosis that shows striking focal LDL retention in healing lesions. Library screening identified a previously unknown, highly conserved, 56 kDa LDL-binding protein that we call atherin. Confocal microscopy of human arteries shows that atherin is present only in atherosclerotic lesions, not in normal intima. Within lesions, atherin is found both in the extracellular compartment and within foam cells. Essentially all extracellular atherin, as well as atherin within foam cells, co-localizes with LDL across the entire spectrum of human disease, from early lesions to advanced plaques. Our results suggest that focal arterial LDL accumulation may be initiated and maintained by binding between LDL and atherin, and that atherin may play a central role in atherogenesis by immobilizing LDL in the arterial wall.

Gene expression profiling of vascular endothelial cells exposed to fluid mechanical forces: relevance for focal susceptibility to atherosclerosis.

Gene expression profiling has revealed that cultured vascular endothelial cells (EC) respond to fluid mechanical forces by modulating the mRNA level of a large number of genes. However, differences between the gene arrays and the experimental conditions employed by different researchers make comparison between data sets difficult, and limit the interpretation of the results. Despite these problems, analysis of recent data indicates that the transcriptional response of cultured EC to low-shear disturbed flow conditions similar to those at atherosclerosis-prone areas is distinct from that elicited by atheroprotective high shear laminar flow, providing a molecular basis for the focal nature of atherosclerosis. Many of the genes altered by disturbed flow are involved in key biological processes relevant to atherosclerosis such as inflammation, cell cycle control, apoptosis, thrombosis and oxidative stress. Overall, the gene expression profiling data are consistent with the hypothesis of the hemodynamic etiology of atherosclerotic predilection, viz that at predilected areas in vivo the presence of low shear, non-laminar flow is sufficient to induce a gene expression profile that pre-disposes the endothelium to the initiation and development of atherosclerotic lesions.

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.