Apoptotic cell death in atherosclerosis

ROCK inhibitor fasudil attenuated high glucose-induced MCP-1 and VCAM-1 expression and monocyte-endothelial cell adhesion

Background

Previous studies suggested that the RhoA/ROCK pathway may contribute to vascular complications in diabetes. The present study was designed to investigate whether ROCK inhibitor fasudil could prevent high glucose-induced monocyte-endothelial cells adhesion, and whether this was related to fasudil effects on vascular endothelial cell expression of chemotactic factors, vascular cell adhesion molecule-1 (VCAM-1) and monocyte chemoattractant protein-1 (MCP-1).

Methods

HUVECs were stimulated with high glucose (HG) or HG + fasudil in different concentration or different time. Monocyte-endothelial cell adhesion was determined using fluorescence-labeled monocytes. The mRNA and protein expression of VCAM-1 and MCP-1 were measured using real-time PCR and western blot. The protein levels of RhoA, ROCKI and p-MYPT were determined using western blot analysis. ELISA was employed to measure the expression of soluble VCAM-1 and MCP-1 in cell supernatants and human serum samples.

Results

Fasudil significantly suppressed HG-induced adhesion of THP-1 to HUVECs. Fasudil reduced Rho/ROCK activity (as indicated by lower p-MYPT/MYPT ratio), and prevented HG induced increases in VCAM-1 and MCP-1 mRNA and protein levels. Fasudil also decreased MCP-1 concentration in HUVEC supernatants, but increased sVCAM-1 shedding into the media. In human diabetic subjects, 2 weeks of fasudil treatment significantly decreased serum MCP-1 level from 27.9 ± 10.6 pg/ml to 13.8 ± 7.0 pg/ml (P < 0.05), while sVCAM-1 increased from 23.2 ± 7.5 ng/ml to 39.7 ± 5.6 ng/ml after fasudil treatment (P < 0.05).

Conclusions

Treatment with the Rho/ROCK pathway inhibitor fasudil attenuated HG-induced monocyte-endothelial cell adhesion, possibly by reducing endothelial expression of VCAM-1 and MCP-1. These results suggest inhibition of Rho/ROCK signaling may have therapeutic potential in preventing diabetes associated vascular inflammation and atherogenesis.

Solid-phase immunoglobulins IgG and IgM activate macrophages with solid-phase IgM acting via a novel scavenger receptor a pathway

IgG may accelerate atherosclerosis via ligation of proinflammatory Fcγ receptors; however, IgM is unable to ligate FcγR and is often considered vasculoprotective. IgM aggravates ischemia-reperfusion injury, and solid-phase deposits of pure IgM, as seen with IgM-secreting neoplasms, are well known clinically to provoke vascular inflammation. We therefore examined the molecular mechanisms by which immunoglobulins can aggravate vascular inflammation, such as in atherosclerosis. We compared the ability of fluid- and solid-phase immunoglobulins to activate macrophages. Solid-phase immunoglobulins initiated prothrombotic and proinflammatory functions in human macrophages, including NF-κB p65 activation, H(2)O(2) secretion, macrophage-induced apoptosis, and tissue factor expression. Responses to solid-phase IgG (but not to IgM) were blocked by neutralizing antibodies to CD16 (FcγRIII), consistent with its known role. Macrophages from mice deficient in macrophage scavenger receptor A (SR-A; CD204) had absent IgM binding and no activation by solid-phase IgM. RNA interference-mediated knockdown of SR-A in human macrophages suppressed activation by solid-phase IgM. IgM binding to SR-A was demonstrated by both co-immunoprecipitation studies and the binding of fluorescently labeled IgM to SR-A-transfected cells. Immunoglobulins on solid-phase particles around macrophages were found in human plaques, increased in ruptured plaques compared with stable ones. These observations indicate that solid-phase IgM and IgG can activate macrophages and destabilize vulnerable plaques. Solid-phase IgM activates macrophages via a novel SR-A pathway.

Visfatin/NAMPT: a multifaceted molecule with diverse roles in physiology and pathophysiology

Visfatin/NAMPT (nicotinamide phosphoribosyltransferase) is a protein with several suggested functions. Although the first discovery of this molecule as a pre-B-cell colony-enhancing factor suggested primarily a cytokine function, its rediscovery as the key enzyme in nicotinamide adenine dinucleotide generation has considerably widened its potential biological activities. Although originally thought to be produced in adipose tissue (i.e., adipocytes and infiltrating macrophages), its production seems to involve other cells and tissues such as skeletal muscle, liver, immune cells, cardiomyocytes, and the brain. Visfatin/NAMPT has both intracellular and extracellular effects influencing several signaling pathways. Its broad spectrum of effects is mirrored by its potential involvement in a wide range of disorders including human immunodeficiency virus infection, septicemia, myocardial failure, atherosclerosis, metabolic disorders, inflammatory diseases, malignancies, and neurodegenerative disorders and aging. Moreover, studies on visfatin/NAMPT in atherosclerotic disorders suggest a rather complex role of this molecule in pathophysiology, potentially mediating both adaptive and maladaptive responses.

Disruption of endothelial peroxisome proliferator-activated receptor γ accelerates diet-induced atherogenesis in LDL receptor-null mice

OBJECTIVE

Peroxisome proliferator-activated receptor γ (PPARγ) is widely expressed in vessel walls, and it's activation by agonists showed beneficial effects in cardiovascular diseases. However, the role of endothelial cell (EC) PPARγ in atherogenesis is not fully understood.

METHODS AND RESULTS

To assess the contribution of endothelial-specific PPARγ in atherosclerosis, EC-specific PPARγ disruption and LDL receptor (LDLR) double-knockout (PPARγ(ΔEC)/LDLR(-/-)) mice were developed. When challenged with a high-cholesterol diet for 4 weeks, PPARγ(ΔEC)/LDLR(-/-) mice exhibited severe atherosclerotic lesions compared to either their littermate controls or macrophage-specific PPARγ disruption and LDLR double knockout (PPARγ(ΔMΦ)/LDLR(-/-)) mice. Metabolic analysis showed severe dyslipidemia and significant increase in systolic blood pressure in the PPARγ(ΔEC)/LDLR(-/-) mice. Histological analysis and real-time quantitative PCR suggested an exacerbated inflammation in PPARγ(ΔEC)/LDLR(-/-) mice, as revealed by the increases of proinflammatory gene expression and macrophage infiltration in vivo and in vitro. Furthermore, in vivo endothelial permeability was also increased by endothelial PPARγ disruption. Bone-marrow transplantation studies, which reconstituted hematopoietic PPARγ, demonstrated that the accelerated atherogenesis was due to endothelial PPARγ deficiency.

CONCLUSIONS

Endothelial PPARγ plays an important protective role in atherogenesis.

Imaging the vulnerable plaque

Cardiovascular diseases are still the primary causes of mortality in the United States and in Western Europe. Arterial thrombosis is triggered by a ruptured atherosclerotic plaque and precipitates an acute vascular event, which is responsible for the high mortality rate. These rupture-prone plaques are called "vulnerable plaques." During the past decades, much effort has been put toward accurately detecting the presence of vulnerable plaques with different imaging techniques. In this review, we provide an overview of the currently available invasive and noninvasive imaging modalities used to detect vulnerable plaques. We will discuss the upcoming challenges in translating these techniques into clinical practice and in assigning them their exact place in the decision-making process.

Humanin preserves endothelial function and prevents atherosclerotic plaque progression in hypercholesterolemic ApoE deficient mice

OBJECTIVE

Humanin (HN) is a cytoprotective peptide derived from endogenous mitochondria, expressed in the endothelial layer of human vessels, but its role in atherogenesis in vivo is not known. In vitro study, however, HN reduced oxidized low-density lipoprotein induced formation of reactive oxygen species and apoptosis. The present study tested the hypothesis that long term treatment with HN will have a protective role against endothelial dysfunction and progression of atherosclerosis in vivo.

METHODS AND RESULTS

Daily intraperitonial injection of the HN analogue HNGF6A for 16 weeks prevented endothelial dysfunction and decreased atherosclerotic plaque size in the proximal aorta of ApoE-deficient mice fed on a high cholesterol diet, without showing direct vasoactive effects or cholesterol-reducing effects. HN was expressed in the endothelial layer on the aortic plaques. HNGF6A treatment reduced apoptosis and nitrotyrosine immunoreactivity in the aortic plaques without affecting the systemic cytokine profile. HNGF6A also preserved expression of endothelial nitric oxide synthase in aorta.

CONCLUSIONS

HN may have a protective effect on endothelial function and progression of atherosclerosis by modulating oxidative stress and apoptosis in the developing plaque.

IGF-1 has plaque-stabilizing effects in atherosclerosis by altering vascular smooth muscle cell phenotype

Insulin-like growth factor-1 (IGF-1) signaling is important for the maintenance of plaque stability in atherosclerosis due to its effects on vascular smooth muscle cell (vSMC) phenotype. To investigate this hypothesis, we studied the effects of the highly inflammatory milieu of the atherosclerotic plaque on IGF-1 signaling and stability-related phenotypic parameters of murine vSMCs in vitro, and the effects of IGF-1 supplementation on plaque phenotype in an atherosclerotic mouse model. M1-polarized, macrophage-conditioned medium inhibited IGF-1 signaling by ablating IGF-1 and increasing IGF-binding protein 3, increased vSMC apoptosis, and decreased proliferation. Expression of α-actin and col3a1 genes was strongly attenuated by macrophage-conditioned medium, whereas expression of matrix-degrading enzymes was increased. Importantly, all of these effects could be corrected by supplementation with IGF-1. In vivo, treatment with the stable IGF-1 analog Long R3 IGF-1 in apolipoprotein E knockout mice reduced stenosis and core size, and doubled cap/core ratio in early atherosclerosis. In advanced plaques, Long R3 IGF-1 increased the vSMC content of the plaque by more than twofold and significantly reduced the rate of intraplaque hemorrhage. We believe that IGF-1 in atherosclerotic plaques may have a role in preventing plaque instability, not only by modulating smooth muscle cell turnover, but also by altering smooth muscle cell phenotype.

Nutrition and human health from a sex-gender perspective

Nutrition exerts a life-long impact on human health, and the interaction between nutrition and health has been known for centuries. The recent literature has suggested that nutrition could differently influence the health of male and female individuals. Until the last decade of the 20th century, research on women has been neglected, and the results obtained in men have been directly translated to women in both the medicine and nutrition fields. Consequently, most modern guidelines are based on studies predominantly conducted on men. However, there are many sex-gender differences that are the result of multifactorial inputs, including gene repertoires, sex steroid hormones, and environmental factors (e.g., food components). The effects of these different inputs in male and female physiology will be different in different periods of ontogenetic development as well as during pregnancy and the ovarian cycle in females, which are also age dependent. As a result, different strategies have evolved to maintain male and female body homeostasis, which, in turn, implies that there are important differences in the bioavailability, metabolism, distribution, and elimination of foods and beverages in males and females. This article will review some of these differences underlying the impact of food components on the risk of developing diseases from a sex-gender perspective.

Proteinase inhibitor 9 is reduced in human atherosclerotic lesion development

BACKGROUND

Granzyme B, a proapoptotic serine protease, is abundant in advanced, unstable atherosclerotic plaques, and it is suggested to contribute to plaque instability by inducing vascular smooth muscle cells apoptosis and by degrading plaque extracellular matrix. Proteinase inhibitor 9, the only known endogenous inhibitor of granzyme B in humans, confers protection against granzyme-B-induced apoptosis. However, the role of proteinase inhibitor 9 in atherosclerotic lesion development has yet to be determined. We hypothesized that atherosclerotic lesions have lower proteinase inhibitor 9 expression levels that will increase their susceptibility to granzyme-B-induced apoptosis.

METHODS

Serial sections of human coronary arteries exhibiting different stages of lesion development were assessed by immunohistochemistry for proteinase inhibitor 9, α-smooth muscle cells actin, granzyme B, CD8, and active caspase-3. Frozen samples were analyzed by Western blot to evaluate total proteinase inhibitor 9 levels.

RESULTS

Vascular smooth muscle cells express less proteinase inhibitor 9 as disease severity increases, and a significant difference in proteinase inhibitor 9 expression is observed between medial and intimal smooth muscle cells. High granzyme B levels colocalize with CD8+ cells and foam cells in the shoulder region and necrotic core area of advanced lesions. In advanced lesions, increased expression of activated caspase-3 in intimal SMC was associated with reduced proteinase inhibitor 9 expression in the presence of granzyme B.

CONCLUSION

Reduced proteinase inhibitor 9 expression in human vascular smooth muscle cells is associated with atherosclerotic disease progression and is inversely related to the extent of apoptosis within the intima. Reduced proteinase inhibitor 9 expression may contribute to increased smooth muscle cell susceptibility to granzyme-B-induced apoptosis within the plaque.

Role of Bcl-2 family proteins and caspases in the regulation of apoptosis

Apoptosis, or programmed cell death, plays a pivotal role in the elimination of unwanted, damaged, or infected cells in multicellular organisms and also in diverse biological processes, including development, cell differentiation, and proliferation. Apoptosis is a highly regulated form of cell death, and dysregulation of apoptosis results in pathological conditions including cancer, autoimmune and neurodegenerative diseases. The Bcl-2 family proteins are key regulators of apoptosis, which include both anti- and pro-apoptotic proteins, and a slight change in the dynamic balance of these proteins may result either in inhibition or promotion of cell death. Execution of apoptosis by various stimuli is initiated by activating either intrinsic or extrinsic pathways which lead to a series of downstream cascade of events, releasing of various apoptotic mediators from mitochondria and activation of caspases, important for the cell fate. In view of recent research advances about underlying mechanism of apoptosis, this review highlights the basics concept of apoptosis and its regulation by Bcl-2 family of protein. Furthermore, this review discusses the interplay of various apoptotic mediators and caspases to decide the fate of the cell. We expect that this review will add to the pool of basic information necessary to understand the mechanism of apoptosis which may implicate in designing better strategy to develop biomedical therapy to control apoptosis.

Inhibitory effect of Thuja orientalis on TNF-α-induced vascular inflammation

Vascular inflammation is involved in the initiation and progression of vascular diseases including atherosclerosis. While conducting in vitro screening of 600 medicinal plant extracts, an aqueous extract of Thuja orientalis (ATO) was found to exhibit antiinflammatory activity in human umbilical vein endothelial cells (HUVEC). In the current study, the antiinflammatory activity of ATO and possible mechanisms for this were investigated in HUVEC. Preincubation with ATO (20 μg/mL) suppressed tumor necrosis factor-α (TNF-α)-induced expression of adhesion molecules including intercellular adhesion molecule-1 (ICAM-1), vascular cell adhesion molecule-1 (VCAM-1) and E-selectin at both the protein and mRNA levels. ATO also inhibited U937 monocyte adhesion to HUVEC stimulated by TNF-α. In addition, ATO attenuated TNF-α-induced p65 NF-κB translocation into the nucleus and phosphorylation of IκB-α. Furthermore, ATO significantly inhibited TNF-α-induced intracellular reactive oxygen species (ROS) production. Overall, the present data suggest that ATO can suppress TNF-α-induced vascular inflammatory processes, possibly via inhibition of ROS and NF-κB activation, in HUVEC.

Lipids-induced apoptosis is aggravated by acyl-coenzyme A: cholesterol acyltransferase inhibitor

OBJECTIVE

To investigate the role of acyl-coenzyme A: cholesterol acyltransferase inhibitor (ACATI) in apoptosis induced by lipids and whether lipids-induced apoptosis is accompanied by increase of free cholesterol in endoplasmic reticulum (ER), in order to further understand the mechanism of lipids-induced apoptosis in advanced atherosclerosis.

METHODS

Human vascular smooth muscle cells (VSMCs) and phorbol 12-myristate 13-acetate (PMA) differentiated THP-1 macrophages were used. Tritiated thymidine incorporation was applied to detect cell proliferation. Cytotoxicity was assessed by lactate dehydrogenase (LDH) release. 4',6-diamidino-2-phenylindole (DAPI) staining, caspase-3, -7 assay, and Annexin-V/propidium iodide (PI) staining were used to detect apoptosis. High performance liquid chromatography was used in intracellular free cholesterol and cholesterol ester assay. ER free cholesterol was quantified.

RESULTS

Different lipids had different effects on proliferation and cytotoxicity of VSMCs. 25-hydroxycholesterol (25OHC) had biphasic effects on the proliferation of VSMCs. At low concentration, it stimulated cell proliferation, but turned to proliferation inhibition as concentration reached 15 mug/mL. 25OHC and acetylated low density lipoprotein (AcLDL) could respectively induce apoptosis in human VSMCs and PMA differentiated THP-1 macrophages, which was aggravated by ACATI, accompanied by increase of intracellular free cholesterol content. There was also an increase of cholesterol content in ER with AcLDL-induced apoptosis in THP-1 macrophages.

CONCLUSIONS

Lipids could induce apoptosis, accompanied by increase of intracellular free cholesterol content, which could be augmented by ACATI, suggesting that insults resulting in ER free cholesterol rise might be the initiator of apoptosis.

Adipocytokines in atherothrombosis: focus on platelets and vascular smooth muscle cells

Visceral obesity is a relevant pathological condition closely associated with high risk of atherosclerotic vascular disease including myocardial infarction and stroke. The increased vascular risk is related also to peculiar dysfunction in the endocrine activity of adipose tissue responsible of vascular impairment (including endothelial dysfunction), prothrombotic tendency, and low-grade chronic inflammation. In particular, increased synthesis and release of different cytokines, including interleukins and tumor necrosis factor-α (TNF-α), and adipokines—such as leptin—have been reported as associated with future cardiovascular events. Since vascular cell dysfunction plays a major role in the atherothrombotic complications in central obesity, this paper aims at focusing, in particular, on the relationship between platelets and vascular smooth muscle cells, and the impaired secretory pattern of adipose tissue.

Regulatory role of mitochondria in oxidative stress and atherosclerosis

Mitochondrial physiology and biogenesis play a crucial role in the initiation and progression of cardiovascular disease following oxidative stress-induced damage such as atherosclerosis (AST). Dysfunctional mitochondria caused by an increase in mitochondrial reactive oxygen species (ROS) production, accumulation of mitochondrial DNA damage, and respiratory chain deficiency induces death of endothelial/smooth muscle cells and favors plaque formation/rupture via the regulation of mitochondrial biogenesis-related genes such as peroxisome proliferator-activated receptor γ coactivator (PGC-1), although more detailed mechanisms still need further study. Based on the effect of healthy mitochondria produced by mitochondrial biogenesis on decreasing ROS-mediated cell death and the recent finding that the regulation of PGC-1 involves mitochondrial fusion-related protein (mitofusin), we thus infer the regulatory role of mitochondrial fusion/fission balance in AST pathophysiology. In this review, the first section discusses the possible association between AST-inducing factors and the molecular regulatory mechanisms of mitochondrial biogenesis and dynamics, and explains the role of mitochondria-dependent regulation in cell apoptosis during AST development. Furthermore, nitric oxide has the Janus-faced effect by protecting vascular damage caused by AST while being a reactive nitrogen species (RNS) which act together with ROS to damage cells. Therefore, in the second section we discuss mitochondrial ATP-sensitive K(+) channels, which regulate mitochondrial ion transport to maintain mitochondrial physiology, involved in the regulation of ROS/RNS production and their influence on AST/cardiovascular diseases (CVD). Through this review, we can further appreciate the multi-regulatory functions of the mitochondria involved in AST development. The understanding of these related mechanisms will benefit drug development in treating AST/CVD through targeted biofunctions of mitochondria.

Activation of AMP-activated protein kinase inhibits oxidized LDL-triggered endoplasmic reticulum stress in vivo

OBJECTIVE

The oxidation of LDLs is considered a key step in the development of atherosclerosis. How LDL oxidation contributes to atherosclerosis remains poorly defined. Here we report that oxidized and glycated LDL (HOG-LDL) causes aberrant endoplasmic reticulum (ER) stress and that the AMP-activated protein kinase (AMPK) suppressed HOG-LDL-triggered ER stress in vivo.

RESEARCH DESIGN AND METHODS

ER stress markers, sarcoplasmic/endoplasmic reticulum Ca(2+) ATPase (SERCA) activity and oxidation, and AMPK activity were monitored in cultured bovine aortic endothelial cells (BAECs) exposed to HOG-LDL or in isolated aortae from mice fed an atherogenic diet.

RESULTS

Exposure of BAECs to clinically relevant concentrations of HOG-LDL induced prolonged ER stress and reduced SERCA activity but increased SERCA oxidation. Chronic administration of Tempol (a potent antioxidant) attenuated both SERCA oxidation and aberrant ER stress in mice fed a high-fat diet in vivo. Likewise, AMPK activation by pharmacological (5'-aminoimidazole-4-carboxymide-1-beta-d-ribofuranoside, metformin, and statin) or genetic means (adenoviral overexpression of constitutively active AMPK mutants) significantly mitigated ER stress and SERCA oxidation and improved the endothelium-dependent relaxation in isolated mouse aortae. Finally, Tempol administration markedly attenuated impaired endothelium-dependent vasorelaxation, SERCA oxidation, ER stress, and atherosclerosis in ApoE(-/-) and ApoE(-/-)/AMPKalpha2(-/-) fed a high-fat diet.

CONCLUSION

We conclude that HOG-LDL, via enhanced SERCA oxidation, causes aberrant ER stress, endothelial dysfunction, and atherosclerosis in vivo, all of which are inhibited by AMPK activation.

Molecular imaging of atherosclerotic plaques targeted to oxidized LDL receptor LOX-1 by SPECT/CT and magnetic resonance

BACKGROUND

The oxidized low-density lipoprotein receptor (LDLR) LOX-1 plays a crucial role in atherosclerosis. We sought to detect and assess atherosclerotic plaque in vivo by using single-photon emission computed tomography/computed tomography and magnetic resonance imaging and a molecular probe targeted at LOX-1.

METHODS AND RESULTS

Apolipoprotein E(-/-) mice fed a Western diet and LDLR(-/-) and LDLR(-/-)/LOX-1(-/-) mice fed an atherogenic diet were used. Imaging probes consisted of liposomes decorated with anti-LOX-1 antibodies or nonspecific immunoglobulin G, (111)indium or gadolinium, and 1,1'-dioctadecyl-3,3,3',3'-tetramethylindocarbocyanine fluorescence markers. In vivo imaging was performed 24 hours after intravenous injection (150 microL) of LOX-1 or nonspecific immunoglobulin G probes labeled with either (111)indium (600 muCi) or gadolinium (0.075 mmol/kg), followed by aortic excision for phosphor imaging and Sudan IV staining, or fluorescence imaging and hematoxylin/eosin staining. The LOX-1 probe also colocalized with specific cell types, apoptosis, and matrix metalloproteinase-9 expression in frozen aortic sections. Single-photon emission computed tomography/computed tomography imaging of the LOX-1 probe showed aortic arch "hot spots" in apolipoprotein E(-/-) mice (n=8), confirmed by phosphor imaging. Magnetic resonance imaging showed significant Gd enhancement in atherosclerotic plaques in LDLR(-/-) mice with the LOX-1 (n=7) but not with the nonspecific immunoglobulin G (n=5) probe. No signal enhancement was observed in LDLR(-/-)/LOX-1(-/-) mice injected with the LOX-1 probe (n=5). These results were confirmed by ex vivo fluorescence imaging. The LOX-1 probe bound preferentially to the plaque shoulder, a region with vulnerable plaque features, including extensive LOX-1 expression, macrophage accumulation, apoptosis, and matrix metalloproteinase-9 expression.

CONCLUSIONS

LOX-1 can be used as a target for molecular imaging of atherosclerotic plaque in vivo. Furthermore, the LOX-1 imaging signal is associated with markers of rupture-prone atherosclerotic plaque.

The vascular biology of atherosclerosis and imaging targets

The growing worldwide health challenge of atherosclerosis, together with advances in imaging technologies, have stimulated considerable interest in novel approaches to gauging this disease. The last several decades have witnessed a burgeoning in understanding of the molecular pathways involved in atherogenesis, lesion progression, and the mechanisms underlying the complications of human atherosclerotic plaques. The imaging of atherosclerosis is reaching beyond anatomy to encompass assessment of aspects of plaque biology related to the pathogenesis and complication of the disease. The harnessing of these biologic insights promises to provide a plethora of new targets for molecular imaging of atherosclerosis. The goals for the years to come must include translation of the experimental work to visualization of these appealing biologic targets in humans.

Absence of Akt1 reduces vascular smooth muscle cell migration and survival and induces features of plaque vulnerability and cardiac dysfunction during atherosclerosis

OBJECTIVE

Deletion of Akt1 leads to severe atherosclerosis and occlusive coronary artery disease. Vascular smooth muscle cells (VSMCs) are an important component of atherosclerotic plaques, responsible for promoting plaque stability in advanced lesions. Fibrous caps of unstable plaques contain less collagen and ECM components and fewer VSMCs than caps from stable lesions. Here, we investigated the role of Akt1 in VSMC proliferation, migration, and oxidative stress-induced apoptosis. In addition, we also characterized the atherosclerotic plaque morphology and cardiac function in an atherosclerosis-prone mouse model deficient in Akt1.

METHODS AND RESULTS

Absence of Akt1 reduces VSMC proliferation and migration. Mechanistically, the proliferation and migratory phenotype found in Akt1-null VSMCs was linked to reduced Rac-1 activity and MMP-2 secretion. Serum starvation and stress-induced apoptosis was enhanced in Akt1 null VSMCs as determined by flow cytometry using Annexin V/PI staining. Immunohistochemical analysis of atherosclerotic plaques from Akt1(-/-ApoE-/-) mice showed a dramatic increase in plaque vulnerability characteristics such as enlarged necrotic core and reduced fibrous cap and collagen content. Finally, we show evidence of myocardial infarcts and cardiac dysfunction in Akt1(-/-ApoE-/-) mice analyzed by immunohistochemistry and echocardiography, respectively.

CONCLUSIONS

Akt1 is essential for VSMC proliferation, migration, and protection against oxidative stress-induced apoptosis. Absence of Akt1 induces features of plaque vulnerability and cardiac dysfunction in a mouse model of atherosclerosis.

Protective effect of magnolol against hydrogen peroxide-induced oxidative stress in human lens epithelial cells

Oxidative stress plays a significant role in the progression of cataract. We aimed to investigate the protective effect of magnolol, a compound extracted from the Chinese herb Magnolia officinalis, against oxidative stress in human lens epithelial (HLE) cells as well as the possible molecular mechanism involved. In this study, magnolol was observed to protect against H2O2-induced cytotoxicity in HLE B-3 cells. Magnolol inhibited the generation of reactive oxygen species (ROS), loss of mitochondrial membrane potential (Delta psi m) and release of cytochrome c from mitochondria caused by H2O2 into cytosol in HLE B-3 cells. Magnolol also inhibited H2O2-induced expressions of caspase-9 and caspase-3 and reduction of Bcl-2/Bax ratio. Moreover, magnolol attenuated the deactivation of ERK/MAPK (extracellular signal-regulated kinase/mitogen activated protein kinase) and the enhanced activation of p38, JNK (c-Jun N-terminal kinase) induced by H2O2. Magnolol could be useful in protecting against oxidative stress in HLE cells, suggesting a potential protective effect against cataractogenesis effect against cataractogenesis.

Poly (ADP-Ribose) polymerase inhibition attenuates atherosclerotic plaque development in ApoE-/- mice with hyperhomocysteinemia

AIM

Hyperhomocysteinemia (Hhcy) is an important and independent risk factor for atherosclerosis. Recent studies have shown that Poly (ADP-ribose) polymerase (PARP) activation may be associated with Hhcy-induced endothelial dysfunction, which is an important mechanism for Hhcy to affect atherosclerotic progress. Thus, we investigated whether PARP inhibitors may attenuate atheroscle-rotic plaque development in an Hhcy-induced experimental animal model with atherosclerosis.

METHODS

Six-week-old homozygous apolipoprotein E-deficient (ApoE-/-) male mice fed a normal diet or high methionine diet randomly received intraperitoneal injections of 10 mg/kg 3-aminoben-zamide (3-AB, a PARP inhibitor) dissolved in phosphate-buffered saline (PBS), or physiological saline every other day for 12 weeks. Atherosclerotic lesion sizes and PARP activity were measured. Related inflammatory factors in atherogenesis were investigated by real-time quantitative PCR and Western blot analysis.

RESULTS

Our data demonstrated that ApoE-/- mice fed a high methionine diet generated Hhcy, which subsequently increased the atherosclerotic lesion size significantly, promoted oxidative stress-associated DNA damage and PARP activation, then increased the expression of proinflammatory fac-tors within atherosclerotic plaques. Although PARP inhibition by 3-AB did not markedly inhibit plaque development in ApoE-/- mice with spontaneous hyperlipidemia by feeding a normal diet, it significantly reduced the atherosclerotic lesion size by 40% in Hhcy-induced atherosclerosis without affecting plasma homocysteine levels and lipid contents, effectively suppressed PARP activation, and inhibited nuclear translocation of nuclear factor-(kappa)B (NF-(kappa)B) and subsequent production of inflam-matory factors, such as vascular cell adhesion molecule-1 (VCAM-1) and monocyte chemoattactant protein-1 (MCP-1).

CONCLUSION

Our results suggest that PARP inhibition attenuates atherosclerotic plaque development under hyperhomocysteinemic conditions, through the inhibition of PARP activation, nuclear NF-kappaB translocation and subsequent expression of inflammatory factors.

The soluble VEGF receptor sFlt1 contributes to endothelial dysfunction in CKD

Endothelial dysfunction contributes to the increased cardiovascular risk that accompanies CKD. We hypothesized that the soluble VEGF receptor 1 (sFlt-1), a VEGF antagonist, plays a role in endothelial dysfunction and decreased angiogenesis in CKD. We enrolled 130 patients with CKD stages 3 to 5 and 56 age- and gender-matched control patients. Plasma sFlt-1 levels were higher in patients with CKD and, after multivariate regression analyses, exclusively associated with renal function and levels of vWF, a marker of endothelial dysfunction. Compared with serum from control patients, both recombinant sFlt-1 and serum from patients with CKD had antiangiogenic activity in the chick chorioallantoic membrane (CAM) assay, induced endothelial cell apoptosis in vitro, and decreased nitric oxide generation in two different endothelial cell lines. Pretreating the sera with an antibody against sFlt-1 abrogated all of these effects. Furthermore, we observed increased sFlt1 levels in 5/6-nephrectomized rats compared with sham-operated animals. Finally, using real-time PCR and ELISA, we identified monocytes as a possible source of increased sFlt-1 in patients with CKD. Our findings show that excess sFlt-1 associates with endothelial dysfunction in CKD and suggest that increased sFlt-1 may predict cardiovascular risk in CKD.

Flow-Mediated Signaling Modulates Endothelial Cell Phenotype

The focal development of atherosclerosis in the vascular tree may be explained in part by the local nature of blood flow. Bifurcations and branching points, prone to early atherogenesis, experience disturbed and oscillatory flow, whereas straight vascular regions, resistant to atherosclerosis, are exposed to steady laminar flow. A large number of studies suggest that the antiatherosclerotic effects of laminar flow are in part due to the ability of flow to modulate endothelial cell phenotype. Under steady laminar flow, endothelial cells generate molecules that promote a vasoactive, anticoagulant, anti-inflammatory, and growth-inhibitory surface. In contrast, disturbed flow induces a proliferative, prothrombotic, and adhesive phenotype. Endothelial cells are able to sense the variations of flow via mechanosensitive cell surface proteins and to transduce these signals via intracellular pathways to transcription factors in the nucleus leading to phenotypic changes. This review summarizes the "outside-in" signaling events initiated by flow that modulate endothelial cell phenotype.

Humic acid induces G1 phase arrest and apoptosis in cultured vascular smooth muscle cells

Humic acid (HA) in well water used by the inhabitants for drinking is one of the possible etiological factors for Blackfoot disease (BFD). In this study, the ability of HA to inhibit cell cycle progression and induce apoptosis in cultured smooth muscle cells (SMCs; A7r5) was investigated. Treatment of the SMCs at various HA concentrations (25-200 microg/mL) resulted in sequences of events marked by apoptosis, as shown by loss of cell viability, morphology change, and internucleosomal DNA fragmentation. HA-induced apoptotic cell death that is associated with loss of mitochondrial membrane potential (Delta Psi m), cytochrome c translocation, caspase-3, -8, and -9 activation, poly ADP-ribose polymerase (PARP) degradation, dysregulation of Bcl-2 and Bax, and upregulation of p53 and phospholyrated p53 (p-p53) in SMCs. Flow cytometry analysis demonstrated that HA blocked cell cycle progress in the G1 phase in SMCs. This blockade of cell cycle was associated with reduced amounts of cyclin D1, CDK4, cyclin E, CDK2, and hyperphosphorylated retinoblastoma protein (pRb) in a time-dependent manner. Apparent DNA strand breaks (DNA damage) were also detected in a dose-dependent manner using Single-cell gel electrophoresis assay (comet assay). Furthermore, HA induced dose-dependent elevation of reactive oxygen species (ROS) level in SMCs, and antioxidant vitamin C and Trolox effectively suppressed HA-induced DNA damage and dysregulation of Bcl-2/Bax. Our findings suggest that HA-induced DNA damage, cell cycle arrest, and apoptosis in SMCs may be an underlying mechanisms for the atherosclerosis and thrombosis observed in the BFD endemic region.

Ginkgo biloba extract attenuates oxLDL-induced oxidative functional damages in endothelial cells

Atherosclerosis is a chronic inflammatory process with increased oxidative stress in vascular endothelium. Ginkgo biloba extract (GbE), extracted from Ginkgo biloba leaves, has commonly been used as a therapeutic agent for cardiovascular and neurological disorders. The aim of this study was to investigate how GbE protects vascular endothelial cells against the proatherosclerotic stressor oxidized low-density lipoprotein (oxLDL) in vitro. Human umbilical vein endothelial cells (HUVECs) were incubated with GbE (12.5–100 μg/ml) for 2 h and then incubated with oxLDL (150 μg/ml) for an additional 24 h. Subsequently, reactive oxygen species (ROS) generation, antioxidant enzyme activities, adhesion to monocytes, cell morphology, viability, and several apoptotic indexes were assessed. Our data show that ROS generation is an upstream signal in oxLDL-treated HUVECs. Cu,Zn-SOD, but not Mn-SOD, was inactivated by oxLDL. In addition, oxLDL diminished expression of endothelial NO synthase and enhanced expression of adhesion molecules (ICAM, VCAM, and E-selectin) and the adherence of monocytic THP-1 cells to HUVECs. Furthermore, oxLDL increased intracellular calcium, disturbed the balance of Bcl-2 family proteins, destabilized mitochondrial membrane potential, and triggered subsequent cytochrome c release into the cytosol and activation of caspase-3. These detrimental effects were ameliorated dose dependently by GbE ( P < 0.05). Results from this study may provide insight into a possible molecular mechanism underlying GbE suppression of the oxLDL-mediated vascular endothelial dysfunction.

Small, dense HDL 3 particles attenuate apoptosis in endothelial cells: pivotal role of apolipoprotein A-I

Plasma high-density lipoproteins (HDLs) protect endothelial cells against apoptosis induced by oxidized low-density lipoprotein (oxLDL). The specific component(s) of HDLs implicated in such cytoprotection remain(s) to be identified. Human microvascular endothelial cells (HMEC-1) were incubated with mildly oxLDL in the presence or absence of each of five physicochemically distinct HDL subpopulations fractionated from normolipidemic human plasma (n= 7) by isopycnic density gradient ultracentrifugation. All HDL subfractions protected HMEC-1 against oxLDL-induced primary apoptosis as revealed by nucleic acid staining, annexin V binding, quantitative DNA fragmentation, inhibition of caspase-3 activity and reduction of cytoplasmic release of cytochrome c and apoptosis-inducing factor. Small, dense HDL 3c displayed twofold superior intrinsic cytoprotective activity (as determined by mitochondrial dehydrogenase activity) relative to large, light HDL 2b on a per particle basis (P < 0.05). Equally, all HDL subfractions attenuated intracellular generation of reactive oxygen species (ROS); such anti-oxidative activity diminished from HDL 3c to HDL 2b. The HDL protein moiety, in which apolipoprotein A-I (apoA-I) predominated, accounted for ∼70% of HDL anti-apoptotic activity. Furthermore, HDL reconstituted with apoA-I, cholesterol and phospholipid potently protected HMEC-1 from apoptosis. By contrast, modification of the content of sphingosine-1-phosphate in HDL did not significantly alter cytoprotection. We conclude that small, dense, lipid-poor HDL 3 potently protects endothelial cells from primary apoptosis and intracellular ROS generation induced by mildly oxLDL, and that apoA-I is pivotal to such protection.

Atherosclerotic plaque stability--what determines the fate of a plaque?

Although the understanding of the underlying pathology of atherosclerosis has improved in recent years, the disease is still the main cause of death globally. Current evidence has implicated the role of inflammation in atherogenesis and plaque destabilization. Thus, inflammatory cytokines may attenuate interstitial collagen synthesis, increase matrix degradation, and promote apoptosis in several atheroma-associated cell types, and all these cellular events may enhance plaque vulnerability. Several cell types found within the lesion (ie, monocyte/macrophages, T cells, mast cells, platelets) contribute to this immune-mediated plaque destabilization, and a better understanding of these processes is a prerequisite for the development of new treatment strategies in these individuals. Such knowledge could also facilitate a better identification of high-risk individuals. In the present study, these issues will be discussed in more detail, particularly focusing on the interactions between matrix degradation, apoptotic, and inflammatory processes in plaque destabilization.

The association between plasma caspase-3, atherosclerosis, and vascular function in the Dallas Heart Study

BACKGROUND

Caspase-3, an apoptosis protease, is expressed in atherosclerotic plaques. We examined the relationship between plasma caspase-3 levels, aortic compliance, and atherosclerosis.

METHODS

Caspase-3 was measured in 3,221 subjects from the Dallas Heart Study. Electron beam computed tomography measures of coronary calcium (CAC) (n = 2,404) and magnetic resonance imaging (MRI) measures of abdominal aortic wall thickness (AWT) (n = 2,208) and aortic compliance (AC) (n = 2,328) were obtained. Multivariate analyses were performed, adjusting for age, sex, ethnicity, body mass index (BMI), traditional cardiovascular risk factors, and cardiac medications.

RESULTS

In univariable analysis, caspase-3 associated with CAC (P < 0.0001), AWT (P = 0.002), and AC (P < 0.0001). After multivariable adjustment, 4th quartile caspase-3 (compared to 1st quartile) was significantly associated with CAC (P = 0.004), AWT (P = 0.02), and AC (P < 0.0001) with similar findings for caspase-3 as a continuous variable.

CONCLUSIONS

Caspase-3 independently associates with CAC, AWT, and AC, suggesting a link between apoptosis and atherosclerosis.

Thioredoxin-1 and its natural inhibitor, vitamin D3 up-regulated protein 1, are differentially regulated by PPARalpha in human macrophages

Macrophage-derived reactive oxygen species contribute to the initiation and development of atherosclerosis. The cellular balance between oxidative and reductive states depends on the endogenous antioxidant capacity, with the thioredoxin-1 (Trx-1) system playing a major role. Peroxisome proliferator-activated receptor-alpha (PPARalpha) is expressed by human macrophages and exhibits anti-inflammatory properties. Here we show that the selective PPARalpha activator GW647 significantly increased the Trx-1 mRNA and protein expression in human macrophages as determined by quantitative polymerase chain reaction and Western immunoblotting. Consistently, the Trx-1 activity was significantly increased by PPARalpha activation. By contrast, PPARalpha activation led to the down-regulation of vitamin D(3) up-regulated protein 1 (VDUP-1), the physiological inhibitor of Trx-1. Analysis of the Trx-1 and VDUP-1 promoters with gene reporter assays, mutational analysis, gel shift assays and chromatin immunoprecipitation analyses revealed the presence of a functional response element specific for PPARalpha in the Trx-1 promoter and the presence of a functional activator protein 1 (AP-1) site in the VDUP-1 promoter. The interference of PPARalpha/retinoid X receptor alpha with the AP-1 transcription factor elements c-Jun/c-Fos resulted in the inhibition of AP-1 binding and down-regulation of the VDUP-1 gene expression. Finally, PPARalpha activation reduced the lidocaine-induced caspase-3 activity and apoptosis, which might be due to the VDUP-1-mediated regulation of the Bax/Bcl-2 ratio. Together these data indicate that stimulation of PPARalpha in human macrophages might reduce arterial inflammation through differential regulation of the Trx-1 and VDUP-1 gene expression.

Pathophysiological roles of osteoprotegerin (OPG)

Osteoprotegerin (OPG) is a secreted glycoprotein central to bone turnover via its role as a decoy receptor for the receptor activator of nuclear factor kappaB ligand (RANKL) and has traditionally been linked to a number of bone-related diseases. However, there is additional evidence that OPG can promote cell survival by inhibiting TNF-related apoptosis-inducing ligand (TRAIL)-induced apoptosis. As a result, a number of in vitro, in vivo and clinical studies have been performed assessing the role of OPG in tumourigenesis. Similar studies have been performed regarding vascular pathologies, resulting from observations of expression and regulation of OPG in the vasculature. This review aims to provide an update on this area and assess the potential protective or detrimental role of OPG in both vascular pathologies and tumourigenesis.

Heparan sulfate in perlecan promotes mouse atherosclerosis: roles in lipid permeability, lipid retention, and smooth muscle cell proliferation

Heparan sulfate (HS) has been proposed to be antiatherogenic through inhibition of lipoprotein retention, inflammation, and smooth muscle cell proliferation. Perlecan is the predominant HS proteoglycan in the artery wall. Here, we investigated the role of perlecan HS chains using apoE null (ApoE0) mice that were cross-bred with mice expressing HS-deficient perlecan (Hspg2(Delta3/Delta3)). Morphometry of cross-sections from aortic roots and en face preparations of whole aortas revealed a significant decrease in lesion formation in ApoE0/Hspg2(Delta3/Delta3) mice at both 15 and 33 weeks. In vitro, binding of labeled mouse triglyceride-rich lipoproteins and human LDL to total extracellular matrix, as well as to purified proteoglycans, prepared from ApoE0/Hspg2(Delta3/Delta3) smooth muscle cells was reduced. In vivo, at 20 minutes influx of human (125)I-LDL or mouse triglyceride-rich lipoproteins into the aortic wall was increased in ApoE0/Hspg2(Delta3/Delta3) mice compared to ApoE0 mice. However, at 72 hours accumulation of (125)I-LDL was similar in ApoE0/Hspg2(Delta3/Delta3) and ApoE0 mice. Immunohistochemistry of lesions from ApoE0/Hspg2(Delta3/Delta3) mice showed decreased staining for apoB and increased smooth muscle alpha-actin content, whereas accumulation of CD68-positive inflammatory cells was unchanged. We conclude that the perlecan HS chains are proatherogenic in mice, possibly through increased lipoprotein retention, altered vascular permeability, or other mechanisms. The ability of HS to inhibit smooth muscle cell growth may also influence development as well as instability of lesions.

Heparan Sulfate in Perlecan Promotes Mouse Atherosclerosis

Heparan sulfate (HS) has been proposed to be antiatherogenic through inhibition of lipoprotein retention, inflammation, and smooth muscle cell proliferation. Perlecan is the predominant HS proteoglycan in the artery wall. Here, we investigated the role of perlecan HS chains using apoE null (ApoE0) mice that were cross-bred with mice expressing HS-deficient perlecan ( Hspg2 Δ3/Δ3 ). Morphometry of cross-sections from aortic roots and en face preparations of whole aortas revealed a significant decrease in lesion formation in ApoE0/ Hspg2 Δ3/Δ3 mice at both 15 and 33 weeks. In vitro, binding of labeled mouse triglyceride-rich lipoproteins and human LDL to total extracellular matrix, as well as to purified proteoglycans, prepared from ApoE0/ Hspg2 Δ3/Δ3 smooth muscle cells was reduced. In vivo, at 20 minutes influx of human 125 I-LDL or mouse triglyceride-rich lipoproteins into the aortic wall was increased in ApoE0/ Hspg2 Δ3/Δ3 mice compared to ApoE0 mice. However, at 72 hours accumulation of 125 I-LDL was similar in ApoE0/ Hspg2 Δ3/Δ3 and ApoE0 mice. Immunohistochemistry of lesions from ApoE0/ Hspg2 Δ3/Δ3 mice showed decreased staining for apoB and increased smooth muscle α-actin content, whereas accumulation of CD68-positive inflammatory cells was unchanged. We conclude that the perlecan HS chains are proatherogenic in mice, possibly through increased lipoprotein retention, altered vascular permeability, or other mechanisms. The ability of HS to inhibit smooth muscle cell growth may also influence development as well as instability of lesions.

Role of microparticles in atherothrombosis

Cell activation or apoptosis leads to plasma membrane blebbing and microparticle (MP) release in the extracellular space. MPs are submicron membrane vesicles which express a panel of phospholipids and proteins specific of the cells they are derived from. Exposure of negatively charged phospholipids and tissue factor confers a procoagulant potential to MPs. MPs accumulate in the lipid core of the atherosclertotic plaque and is a major determinant of its thrombogenecity. Elevation of plasma MPs levels, particularly those of endothelial origin, reflects cellular injury and is considered now as a surrogate marker of vascular dysfunction. Thus, MPs can be seen as triggers of a vicious circle for they promote prothrombogenic and pro-inflammatory responses as well as cellular dysfunction within the vascular compartment. A better knowledge of MP composition and biological effects as well as the mechanisms leading to their clearance will probably open new therapeutic approaches in the treatment of atherothrombosis.

Effect of Buddleja officinalis on high-glucose-induced vascular inflammation in human umbilical vein endothelial cells

In this study, we aimed to investigate whether an aqueous extract of Buddleja officinalis (ABO) suppresses high-glucose-induced vascular inflammatory processes in the primary cultured human umbilical vein endothelial cells (HUVEC). The high-glucose-induced increase in expression of cell adhesion molecules (CAMs) such as intracellular adhesion molecule-1 (ICAM-1), vascular cell adhesion molecule-1 (VCAM-1), and endothelial-selectin (E-selectin) was significantly attenuated by pretreatment with ABO in a dose-dependent manner. Enhanced cell adhesion caused by high glucose in co-cultured U937 and HUVEC was also blocked by pretreatment with ABO. Pretreatment with ABO also blocked formation of high-glucose-induced reactive oxygen species (ROS). In addition, ABO suppressed the transcriptional activity of NF-kappaB and IkappaB phosphorylation under high-glucose conditions. Pretreatment with N(G)-nitro-l-arginine methyl ester (L-NAME), an endothelial nitric oxide (NO) synthase inhibitor, attenuated the protective action of ABO on high-glucose-induced CAM expression, suggesting a potential role of NO signaling. The present data suggest that ABO could suppress high-glucose-induced vascular inflammatory processes, and ABO may be closely related with the inhibition of ROS and NF-kappaB activation in HUVEC.

Increased inorganic phosphate induces human endothelial cell apoptosis in vitro

Chronic kidney disease with hyperphosphatemia is associated with accelerated atherosclerosis and endothelial dysfunction. However, the contribution of high serum phosphate levels to endothelial injury is incompletely understood. The aim of this work was to evaluate the responses of endothelial cells to elevated levels of extracellular phosphate in vitro. High phosphate in concentrations similar to those observed in uremia-associated hyperphosphatemia (>2.5 mM) induced apoptosis in two endothelial cell lines (EAhy926 cells and GM-7373 cells). This effect was enhanced when cells were incubated for 24 h in the presence of 2.8 mM calcium instead of 1.8 mM. By treating cells with 0.5 or 1.0 mM phosphonoformic acid, an inhibitor of the phosphate transporter, death was completely prevented. The process of phosphate-induced apoptosis was further characterized by increased oxidative stress, as detected by increased ROS generation and disruption of the mitochondrial membrane potential at approximately 2 h after treatment, followed by caspase activation. These findings show that hyperphosphatemia causes endothelial cell apoptosis, a process that impairs endothelial integrity. Endothelial cell injury induced by high phosphate concentrations may be an initial event leading to vascular complications in patients with chronic kidney disease.

Therapeutic potential of AIF-mediated caspase-independent programmed cell death

Resistance to anticancer drugs is often related to deficient cell death execution pathways in cancer cells. Apoptosis, which denotes a form of cell death executed by caspases, was traditionally considered as the only physiological and programmed form of cell death. However, recent evidence indicates that programmed cell death (PCD) can occur in complete absence of caspase activation. Indeed, a large number of caspase-independent models are now defined and a key protein implicated in this type of PCD, apoptosis-inducing factor (AIF), has been identified. AIF is a mitochondrial protein with two faces looking in opposite life/death directions. Recently, the identification of five different isoforms allowed a better characterization of AIFs life/mitochondrial versus death/nuclear functions, as well as definition of its pro-apoptotic region and some of its nuclear partners. Importantly, much work on caspase-independent PCD has revealed that AIF participates in more PCD systems than initially thought. A wider molecular knowledge of AIF, and of the caspase-independent PCDs in which it is involved, are key to provide new insights into the role of PCD. There is no doubt that these insights will lead to the development of more selective and efficient drugs against cancer, degenerative diseases, and other pathological disorders implicating AIF.

Loss of Akt1 leads to severe atherosclerosis and occlusive coronary artery disease

The Akt signaling pathway controls several cellular functions in the cardiovascular system; however, its role in atherogenesis is unknown. Here, we show that the genetic ablation of Akt1 on an apolipoprotein E knockout background (ApoE(-/-)Akt1(-/-)) increases aortic lesion expansion and promotes coronary atherosclerosis. Mechanistically, lesion formation is due to the enhanced expression of proinflammatory genes and endothelial cell and macrophage apoptosis. Bone marrow transfer experiments showing that macrophages from ApoE(-/-)Akt1(-/-) donors were not sufficient to worsen atherogenesis when transferred to ApoE(-/-) recipients suggest that lesion expansion in the ApoE(-/-)Akt1(-/-) strain might be of vascular origin. In the vessel wall, the loss of Akt1 increases inflammatory mediators and reduces eNOS phosphorylation, suggesting that Akt1 exerts vascular protection against atherogenesis. The presence of coronary lesions in ApoE(-/-)Akt1(-/-) mice provides a new model for studying the mechanisms of acute coronary syndrome in humans.

Lycopus lucidus inhibits high glucose-induced vascular inflammation in human umbilical vein endothelial cells

Vascular inflammatory process has been suggested to play a key role in the initiation and progression of atherosclerosis, a major complication of diabetes mellitus. Lycopus lucidus Turcz. has been used as an oriental traditional medicine including Korea and its crude drug is known to have an anti-inflammatory effect. Thus we investigated whether the aqueous extract of the leaves of L. lucidus Turcz. (ALT) suppresses vascular inflammatory process induced by high glucose in primary cultured human umbilical vein endothelial cells (HUVEC). Western blot analysis revealed that incubation of HUVEC with high glucose increased cell adhesion molecules (CAMs) expression levels. However, high glucose-induced increase of CAMs expression was significantly attenuated by pretreatment with ALT in a dose-dependent manner. The enhanced cell adhesion between monocyte and HUVEC induced by high glucose was also blocked by pretreatment with ALT. High glucose-induced hydrogen peroxide production and DCF-sensitive intracellular reactive oxygen species (ROS) formation. Pretreatment with ALT inhibited high glucose-induced ROS formation. In addition, ALT suppressed the translocation and promoter transcriptional activity of NF-kappaB increased in high glucose condition. Taken together, the present data suggested that ALT could suppress high glucose-induced vascular inflammatory process, which may be closely related with the inhibition of ROS and NF-kappaB activation in HUVEC.

Neuropilin-1 modulates p53/caspases axis to promote endothelial cell survival

Vascular permeability factor/vascular endothelial growth factor (VPF/VEGF), one of the crucial pro-angiogenic factors, functions as a potent inhibitor of endothelial cell (EC) apoptosis. Previous progress has been made towards delineating the VPF/VEGF survival signaling downstream of the activation of VEGFR-2. Here, we seek to define the function of NRP-1 in VPF/VEGF-induced survival signaling in EC and to elucidate the concomitant molecular signaling events that are pivotal for our understanding of the signaling of VPF/VEGF. Utilizing two different in vitro cell culture systems and an in vivo zebrafish model, we demonstrate that NRP-1 mediates VPF/VEGF-induced EC survival independent of VEGFR-2. Furthermore, we show here a novel mechanism for NRP-1-specific control of the anti-apoptotic pathway in EC through involvement of the NRP-1-interacting protein (NIP/GIPC) in the activation of PI-3K/Akt and subsequent inactivation of p53 pathways and FoxOs, as well as activation of p21. This study, by elucidating the mechanisms that govern VPF/VEGF-induced EC survival signaling via NRP-1, contributes to a better understanding of molecular mechanisms of cardiovascular development and disease and widens the possibilities for better therapeutic targets.

Increased endoplasmic reticulum stress in atherosclerotic plaques associated with acute coronary syndrome

BACKGROUND

The endoplasmic reticulum (ER) responds to various stresses by upregulation of ER chaperones, but prolonged ER stress eventually causes apoptosis. Although apoptosis is considered to be essential for the progression and rupture of atherosclerotic plaques, the influence of ER stress and apoptosis on rupture of unstable coronary plaques remains unclear.

METHODS AND RESULTS

Coronary artery segments were obtained at autopsy from 71 patients, and atherectomy specimens were obtained from 40 patients. Smooth muscle cells and macrophages in the fibrous caps of thin-cap atheroma and ruptured plaques, but not in the fibrous caps of thick-cap atheroma and fibrous plaques, showed a marked increase of ER chaperone expression and apoptotic cells. ER chaperones also showed higher expression in atherectomy specimens from patients with unstable angina pectoris than in specimens from those with stable angina. Expression of 7-ketocholesterol was increased in the fibrous caps of thin-cap atheroma compared with thick-cap atheroma. Treatment of cultured coronary artery smooth muscle cells or THP-1 cells with 7-ketocholesterol induced upregulation of ER chaperones and apoptosis, whereas these changes were prevented by antioxidants. We also investigated possible signaling pathways for ER-initiated apoptosis and found that the CHOP (a transcription factor induced by ER stress)-dependent pathway was activated in unstable plaques. In addition, knockdown of CHOP expression by small interfering RNA decreased ER stress-dependent death of cultured coronary artery smooth muscle cells and THP-1 cells.

CONCLUSIONS

Increased ER stress occurs in unstable plaques. Our findings suggest that ER stress-induced apoptosis of smooth muscle cells and macrophages may contribute to plaque vulnerability.

Cytotoxic phospholipid oxidation products. Cell death from mitochondrial damage and the intrinsic caspase cascade

Phospholipid oxidation products accumulate in the necrotic core of atherosclerotic lesions, in apoptotic cells, and circulate in oxidized low density lipoprotein. Phospholipid oxidation generates toxic products, but little is known about which specific products are cytotoxic, their receptors, or the mechanism(s) that induces cell death. We find the most common phospholipid oxidation product of oxidized low density lipoprotein, phosphatidylcholine with esterified sn-2-azelaic acid, induced apoptosis at low micromolar concentrations. The synthetic ether phospholipid hexadecyl azelaoyl phosphatidylcholine (HAzPC) was rapidly internalized, and overexpression of PLA2g7 (PAF acetylhydrolase) that specifically hydrolyzes such oxidized phospholipids suppressed apoptosis. Internalized HAzPC associated with mitochondria, and cytochrome c, and apoptosis-inducing factor escaped from mitochondria to the cytoplasm and nucleus, respectively, in cells exposed to HAzPC. Isolated mitochondria exposed to HAzPC rapidly swelled and released cytochrome c and apoptosis-inducing factor. Other phospholipid oxidation products induced swelling, but HAzPC was the most effective and was twice as effective as its diacyl homolog. Cytoplasmic cytochrome c completes the apoptosome, and activated caspase 9 and 3 were present in cells exposed to HAzPC. Irreversible inhibition of caspase 9 blocked downstream caspase 3 activation and prevented apoptosis. Mitochondrial damage initiated this apoptotic cascade, because overexpression of Bcl-X(L), an anti-apoptotic protein localized to mitochondria, blocked cytochrome c escape and apoptosis. Thus, exogenous phospholipid oxidation products target intracellular mitochondria to activate the intrinsic apoptotic cascade.

Poly(ADP-ribose) polymerase inhibition reduces atherosclerotic plaque size and promotes factors of plaque stability in apolipoprotein E-deficient mice: effects on macrophage recruitment, nuclear factor-kappaB nuclear translocation, and foam cell death

BACKGROUND

Poly(ADP-ribose) polymerase (PARP) was suggested to play a role in endothelial dysfunction that is associated with a number of cardiovascular diseases. We hypothesized that PARP may play an important role in atherogenesis and that its inhibition may attenuate atherosclerotic plaque development in an experimental model of atherosclerosis.

METHODS AND RESULTS

Using a mouse (apolipoprotein E [ApoE](-/-)) model of high-fat diet-induced atherosclerosis, we demonstrate an association between cell death and oxidative stress-associated DNA damage and PARP activation within atherosclerotic plaques. PARP inhibition by thieno[2,3-c]isoquinolin-5-one reduced plaque number and size and altered structural composition of plaques in these animals without affecting sera lipid contents. These results were corroborated genetically with the use of ApoE(-/-) mice that are heterozygous for PARP-1. PARP inhibition promoted an increase in collagen content, potentially through an increase in tissue inhibitor of metalloproteinase-2, and transmigration of smooth muscle cells to intima of atherosclerotic plaques as well as a decrease in monocyte chemotactic protein-1 production, all of which are markers of plaque stability. In PARP-1(-/-) macrophages, monocyte chemotactic protein-1 expression was severely inhibited because of a defective nuclear factor-kappaB nuclear translocation in response to lipopolysaccharide. Furthermore, PARP-1 gene deletion not only conferred protection to foam cells against H2O2-induced death but also switched the mode of death from necrosis to apoptosis.

CONCLUSIONS

Our results suggest that PARP inhibition interferes with plaque development and may promote plaque stability, possibly through a reduction in inflammatory factors and cellular changes related to plaque dynamics. PARP inhibition may prove beneficial for the treatment of atherosclerosis.