Regulation of smooth muscle cell growth, function and death in vitro by activated mast cells--a potential mechanism for the weakening and rupture of atherosclerotic plaques

Targeting gut microbiota and immune crosstalk: potential mechanisms of natural products in the treatment of atherosclerosis

Atherosclerosis (AS) is a chronic inflammatory reaction that primarily affects large and medium-sized arteries. It is a major cause of cardiovascular disease and peripheral arterial occlusive disease. The pathogenesis of AS involves specific structural and functional alterations in various populations of vascular cells at different stages of the disease. The immune response is involved throughout the entire developmental stage of AS, and targeting immune cells presents a promising avenue for its treatment. Over the past 2 decades, studies have shown that gut microbiota (GM) and its metabolites, such as trimethylamine-N-oxide, have a significant impact on the progression of AS. Interestingly, it has also been reported that there are complex mechanisms of action between GM and their metabolites, immune responses, and natural products that can have an impact on AS. GM and its metabolites regulate the functional expression of immune cells and have potential impacts on AS. Natural products have a wide range of health properties, and researchers are increasingly focusing on their role in AS. Now, there is compelling evidence that natural products provide an alternative approach to improving immune function in the AS microenvironment by modulating the GM. Natural product metabolites such as resveratrol, berberine, curcumin, and quercetin may improve the intestinal microenvironment by modulating the relative abundance of GM, which in turn influences the accumulation of GM metabolites. Natural products can delay the progression of AS by regulating the metabolism of GM, inhibiting the migration of monocytes and macrophages, promoting the polarization of the M2 phenotype of macrophages, down-regulating the level of inflammatory factors, regulating the balance of Treg/Th17, and inhibiting the formation of foam cells. Based on the above, we describe recent advances in the use of natural products that target GM and immune cells crosstalk to treat AS, which may bring some insights to guide the treatment of AS.

Immune system and atherosclerosis: Hostile or friendly relationship

Coronary artery disease has remained a major health challenge despite enormous progress in prevention, diagnosis, and treatment strategies. Formation of atherosclerotic plaque is a chronic process that is developmentally influenced by intrinsic and extrinsic determinants. Inflammation triggers atherosclerosis, and the fundamental element of inflammation is the immune system. The immune system involves in the atherosclerosis process by a variety of immune cells and a cocktail of mediators. It is believed that almost all main components of this system possess a profound contribution to the atherosclerosis. However, they play contradictory roles, either protective or progressive, in different stages of atherosclerosis progression. It is evident that monocytes are the first immune cells appeared in the atherosclerotic lesion. With the plaque growth, other types of the immune cells such as mast cells, and T lymphocytes are gradually involved. Each cell releases several cytokines which cause the recruitment of other immune cells to the lesion site. This is followed by affecting the expression of other cytokines as well as altering certain signaling pathways. All in all, a mix of intertwined interactions determine the final outcome in terms of mild or severe manifestations, either clinical or subclinical. Therefore, it is of utmost importance to precisely understand the kind and degree of contribution which is made by each immune component in order to stop the growing burden of cardiovascular morbidity and mortality. In this review, we present a comprehensive appraisal on the role of immune cells in the atherosclerosis initiation and development.

Oxidized LDLs as Signaling Molecules

Levels of oxidized low-density lipoproteins (oxLDLs) are usually low in vivo but can increase whenever the balance between formation and scavenging of free radicals is impaired. Under normal conditions, uptake and degradation represent the physiological cellular response to oxLDL exposure. The uptake of oxLDLs is mediated by cell surface scavenger receptors that may also act as signaling molecules. Under conditions of atherosclerosis, monocytes/macrophages and vascular smooth muscle cells highly exposed to oxLDLs tend to convert to foam cells due to the intracellular accumulation of lipids. Moreover, the atherogenic process is accelerated by the increased expression of the scavenger receptors CD36, SR-BI, LOX-1, and SRA in response to high levels of oxLDL and oxidized lipids. In some respects, the effects of oxLDLs, involving cell proliferation, inflammation, apoptosis, adhesion, migration, senescence, and gene expression, can be seen as an adaptive response to the rise of free radicals in the vascular system. Unlike highly reactive radicals, circulating oxLDLs may signal to cells at more distant sites and possibly trigger a systemic antioxidant defense, thus elevating the role of oxLDLs to that of signaling molecules with physiological relevance.

An overview of the innate and adaptive immune system in atherosclerosis

Cardiovascular disease is the leading cause of death globally. Coronary artery disease (CAD) is a chronic inflammatory disease usually caused by atherosclerosis, in which the coronary arteries become narrowed by atheromatous plaque. Plaques in atherosclerosis are formed through the accumulation of lipids and various immune cells. Both adaptive and innate immune systems are involved in the pathogenesis of atherosclerosis and facilitate plaque formation and disease progression. Almost all immune system cells, including neutrophils, B cells, T cells monocytes, macrophages, foam cells, and dendritic cells (DCs), play a vital role in atherosclerotic plaque. Atherogenesis, the normal function of the endothelium, is initially disrupted and, then, cells of the immune system are recruited to the endothelium following increased expression of cell adhesion molecules. Accumulation of immune cells and lipids leads to the formation of a necrotic nucleus. As the disease progresses, smooth muscle cells form fibrous layers, whose rupture results in exposing the necrotic nucleus and thrombosis. Accordingly, the present review was conducted to determine the role of different cells in innate and adaptive immune systems in inhibition and progression of atherosclerosis.

Mast cells as a unique hematopoietic lineage and cell system: From Paul Ehrlich's visions to precision medicine concepts

The origin and functions of mast cells (MCs) have been debated since their description by Paul Ehrlich in 1879. MCs have long been considered 'reactive bystanders' and 'amplifiers' in inflammatory processes, allergic reactions, and host responses to infectious diseases. However, knowledge about the origin, phenotypes and functions of MCs has increased substantially over the past 50 years. MCs are now known to be derived from multipotent hematopoietic progenitors, which, through a process of differentiation and maturation, form a unique hematopoietic lineage residing in multiple organs. In particular, MCs are distinguishable from basophils and other hematopoietic cells by their unique phenotype, origin(s), and spectrum of functions, both in innate and adaptive immune responses and in other settings. The concept of a unique MC lineage is further supported by the development of a distinct group of neoplasms, collectively referred to as mastocytosis, in which MC precursors expand as clonal cells. The clinical consequences of the expansion and/or activation of MCs are best established in mastocytosis and in allergic inflammation. However, MCs have also been implicated as important participants in a number of additional pathologic conditions and physiological processes. In this article, we review concepts regarding MC development, factors controlling MC expansion and activation, and some of the fundamental roles MCs may play in both health and disease. We also discuss new concepts for suppressing MC expansion and/or activation using molecularly-targeted drugs.

Dendritic Cells and T Cells, Partners in Atherogenesis and the Translating Road Ahead

Atherosclerosis is a chronic process associated with arterial inflammation, the accumulation of lipids, plaque formation in vessel walls, and thrombosis with late mortal complications such as myocardial infarction and ischemic stroke. Immune and inflammatory responses have significant effects on every phase of atherosclerosis. Increasing evidence has shown that both innate and adaptive “arms” of the immune system play important roles in regulating the progression of atherosclerosis. Accumulating evidence suggests that a unique type of innate immune cell, termed dendritic cells (DCs), play an important role as central instigators, whereas adaptive immune cells, called T lymphocytes, are crucial as active executors of the DC immunity in atherogenesis. These two important immune cell types work in pairs to establish pro-atherogenic or atheroprotective immune responses in vascular tissues. Therefore, understanding the role of DCs and T cells in atherosclerosis is extremely important. Here, in this review, we will present a complete overview, based on existing knowledge of these two cell types in the atherosclerotic microenvironment, and discuss some of the novel means of targeting DCs and T cells as therapeutic tactics for the treatment of atherosclerosis.

Extracellular Matrix Proteins and Substrate Stiffness Synergistically Regulate Vascular Smooth Muscle Cell Migration and Cortical Cytoskeleton Organization

Vascular smooth muscle cell (VSMC) migration is a critical step in the progression of cardiovascular disease and aging. Migrating VSMCs encounter a highly heterogeneous environment with the varying extracellular matrix (ECM) composition due to the differential synthesis of collagen and fibronectin (FN) in different regions and greatly changing stiffness, ranging from the soft necrotic core of plaques to hard calcifications within blood vessel walls. In this study, we demonstrate an application of a two-dimensional (2D) model consisting of an elastically tunable polyacrylamide gel of varying stiffness and ECM protein coating to study VSMC migration. This model mimics the in vivo microenvironment that VSMCs experience within a blood vessel wall, which may help identify potential therapeutic targets for the treatment of atherosclerosis. We found that substrate stiffness had differential effects on VSMC migration on type 1 collagen (COL1) and FN-coated substrates. VSMCs on COL1-coated substrates showed significantly diminished migration distance on stiffer substrates, while on FN-coated substrates VSMCs had significantly increased migration distance. In addition, cortical stress fiber orientation increased in VSMCs cultured on more rigid COL1-coated substrates, while decreasing on stiffer FN-coated substrates. On both proteins, a more disorganized cytoskeletal architecture was associated with faster migration. Overall, these results demonstrate that different ECM proteins can cause substrate stiffness to have differential effects on VSMC migration in the progression of cardiovascular diseases and aging.

Mast Cells as Potential Accelerators of Human Atherosclerosis-From Early to Late Lesions

Mast cells are present in atherosclerotic lesions throughout their development. The process of atherogenesis itself is characterized by infiltration and retention of cholesterol-containing blood-derived low-density lipoprotein (LDL) particles in the intimal layer of the arterial wall, where the particles become modified and ingested by macrophages, resulting in the formation of cholesterol-filled foam cells. Provided the blood-derived high-density lipoproteins (HDL) particles are able to efficiently carry cholesterol from the foam cells back to the circulation, the early lesions may stay stable or even disappear. However, the modified LDL particles also trigger a permanent local inflammatory reaction characterized by the presence of activated macrophages, T cells, and mast cells, which drive lesion progression. Then, the HDL particles become modified and unable to remove cholesterol from the foam cells. Ultimately, the aging foam cells die and form a necrotic lipid core. In such advanced lesions, the lipid core is separated from the circulating blood by a collagenous cap, which may become thin and fragile and susceptible to rupture, so causing an acute atherothrombotic event. Regarding the potential contribution of mast cells in the initiation and progression of atherosclerotic lesions, immunohistochemical studies in autopsied human subjects and studies in cell culture systems and in atherosclerotic mouse models have collectively provided evidence that the compounds released by activated mast cells may promote atherogenesis at various steps along the path of lesion development. This review focuses on the presence of activated mast cells in human atherosclerotic lesions. Moreover, some of the molecular mechanisms potentially governing activation and effector functions of mast cells in such lesions are presented and discussed.

Tumor necrosis factor-α regulates triggering receptor expressed on myeloid cells-1-dependent matrix metalloproteinases in the carotid plaques of symptomatic patients with carotid stenosis

OBJECTIVE

To determine the relationship between increased triggering receptor expressed on myeloid cells (TREM)-1 and plaque stability in atherosclerotic carotid stenosis.

METHODS

The mRNA transcripts and protein for TREM-1, MMP-1, MMP-9, collagen type I (COL1A1) and collagen type III (COL3A1) were analyzed by qPCR and immunofluorescence in both tissues and VSMCs isolated from atherosclerotic carotid plaques of symptomatic and asymptomatic patients with carotid stenosis.

RESULTS

The TREM-1, MMP-1 and MMP-9 mRNA transcripts were significantly increased (TREM-1, p < 0.01; MMP-1, p < 0.01 and MMP-9, p < 0.001) while COL1A1 and COL3A1 mRNA transcripts were decreased (p < 0.001) in VSMCs isolated from carotid plaques of symptomatic (S) than asymptomatic (AS) patients. Stimulation of cells with TNF-α further increased the mRNA transcripts of TREM-1, MMPs, COL1A1 and COL3A1. Modulation of TREM-1 by treatment with TREM-1 decoy receptor rTREM-1/Fc, and either TREM-1 antibodies or TREM-1 siRNA attenuated the TNF-α-induced expression of MMP-1 and MMP-9 (p < 0.01) and COL1A1 and COL3A1 (p < 0.01) in S compared to AS VSMCs isolated from carotid plaques. Inhibition of NF-kB (BAY 11-7085), JNK (SP600125) and PI3K (LY294002) signaling pathways decreased the expression of TREM-1 (p < 0.01), MMP-1 (p < 0.001) and MMP-9 (p < 0.01) in TNF-α-treated VSMCs isolated from S carotid plaques compared to AS patients.

CONCLUSION

Increased expression of TREM-1 in S compared to AS patients involving MMP-1 and MMP-9 suggest a potential role of TREM-1 in plaque destabilization. Selective blockade of TREM-1 may contribute to the development of new therapies and promising targets for stabilizing vulnerable atherosclerotic plaques.

Regulatory T cells in atherosclerosis: critical immune regulatory function and therapeutic potential

Atherosclerosis is a chronic inflammatory disease that is mediated by innate and adaptive immune responses. The disease is characterized by sub-endothelial accumulation and modification of lipids in the artery wall triggering an inflammatory reaction which promotes lesion progression and eventual plaque rupture, thrombus formation, and the respective clinical sequelae such as myocardial infarction or stroke. During the past decade, T-cell-mediated immune responses, especially control of pro-inflammatory signals by regulatory T cells (Tregs), have increasingly attracted the interest of experimental and clinical researchers. By suppression of T cell proliferation and secretion of anti-inflammatory cytokines, such as interleukin-10 (IL-10) and transforming growth factor-β, Tregs exert their atheroprotective properties. Atherosclerosis-prone, hyperlipidemic mice harbor systemically less Tregs compared to wild-type mice, suggesting an imbalance of immune cells which affects local and systemic inflammatory and potentially metabolic processes leading to atherogenesis. Restoring or increasing Treg frequency and enhancing their suppressive capacity by various modulations may pose a promising approach for treating inflammatory conditions such as cardiovascular diseases. In this review, we briefly summarize the immunological basics of atherosclerosis and introduce the role and contribution of different subsets of T cells. We then discuss experimental data and current knowledge pertaining to Tregs in atherosclerosis and perspectives on manipulating the adaptive immune system to alleviate atherosclerosis and cardiovascular disease.

Icaritin Inhibits Collagen Degradation-Related Factors and Facilitates Collagen Accumulation in Atherosclerotic Lesions: A Potential Action for Plaque Stabilization

Most acute coronary syndromes result from rupture of vulnerable atherosclerotic plaques. The collagen content of plaques may critically affect plaque stability. This study tested whether Icaritin (ICT), an intestinal metabolite of Epimedium-derived flavonoids, could alter the collagen synthesis/degradation balance in atherosclerotic lesions. Rabbits were fed with an atherogenic diet for four months. Oral administration of ICT (10 mg·kg(-1)·day(-1)) was started after two months of an atherogenic diet and lasted for two months. The collagen degradation-related parameters, including macrophages accumulation, content and activity of interstitial collagenase-1 (MMP-1), and the collagen synthesis-related parameters, including amount and distribution of smooth muscle cells (SMC) and collagen mRNA/protein levels, were evaluated in the aorta. ICT reduced plasma lipid levels, inhibited macrophage accumulation, lowered MMP-1 mRNA and protein expression, and suppressed proteolytic activity of pro-MMP-1 and MMP-1 in the aorta. ICT changed the distribution of the SMCs towards the fibrous cap of lesions without increasing the amount of SMCs. Higher collagen protein content in lesions and aorta homogenates was observed with ICT treatment compared with the atherogenic diet only, without altered collagen mRNA level. These results suggest that ICT could inhibit the collagen degradation-related factors and facilitate collagen accumulation in atherosclerotic lesions, indicating a new potential of ICT in atherosclerotic plaques.

Modulation of both activator protein-1 and nuclear factor-kappa B signal transduction of human T cells by amiodarone

Amiodarone, a common and effective antiarrhythmic drug, has been reported to have anti-inflammatory effects such as reducing the activation and movement of neutrophils. However, its effects on human T cells remain unclear. The aim of this study was to elucidate the effects and possible underlying mechanisms of amiodarone on human T cells. We isolated human primary T cells from the peripheral blood of healthy volunteers and performed enzyme-linked immunosorbent assay (ELISA), flow cytometry, electrophoretic mobility shift assay, luciferase assay, and Western blotting to evaluate the modulatory effects of amiodarone on human T cells. We found that amiodarone dose dependently inhibited the production of cytokines, including interleukin-2 (IL-2), IL-4, tumor necrosis factor-alpha, and interferon-gamma in activated human T cells. By flow cytometry, we demonstrated that amiodarone suppressed the expression of IL-2 receptor-alpha (CD25) and CD69, the cell surface markers of activated T cells. Moreover, molecular investigations revealed that amiodarone down-regulated activator protein-1 (AP-1) and nuclear factor kappa-B (NF-κB) DNA-binding activities in activated human T cells and also inhibited DNA binding and transcriptional activities of both AP-1 and NF-κB in Jurkat cells. Finally, by Western blotting, we showed that amiodarone reduced the activation of c-Jun NH(2)-terminal protein kinase and P38 mitogen-activated protein kinase, and suppressed stimuli-induced I-kappa B-alpha degradation in activated human T cells. Through regulation of AP-1 and NF-κB signaling, amiodarone inhibits cytokine production and T cell activation. These results show the pleiotropic effects of amiodarone on human T cells and suggest its therapeutic potential in inflammation-related cardiovascular disorders.

Comprehensive insight into immune regulatory mechanisms and vascular wall determinants of atherogenesis - emerging perspectives of immunomodulation

For many years atherosclerosis was believed to be the passive accumulation of cholesterol in vessel walls. Today the picture is more complex, as immune processes occur in atherogenesis. Considerable attention is focused on the particular role of adaptive immune responses orchestrated by T cell subsets. Since the role of Th1/Th2 balance and Th1 cell domination in atherogenesis is already known, the involvement of regulatory T lymphocytes and recently described Th17 cells raises new concerns. On one hand, each of these cells may specifically drive responses of vascular wall tissues and immune cells; however, they are subject to the control of a plethora of tissue- and pathogen-derived agents. Due to ineffective tissue regeneration, remodeling of the vascular wall occurs. The understanding of the immune regulatory network gives perspectives of innovative immunomodulatory therapies of atherosclerosis and the prevention of its complications, such as coronary artery disease.

Tenascin-C deficiency in apo E-/- mouse increases eotaxin levels: implications for atherosclerosis

AIM

To investigate the potential role of inflammatory cytokines in apo E-/- mouse in response to deletion of Tenascin-C (TNC) gene.

METHODS AND RESULTS

We used antibody array and ELISA to compare the profile of circulating inflammatory cytokines in apo E-/- mice and apo E-/- TNC-/- double knockout mice. In addition, tissue culture studies were performed to investigate the activity of cells from each mouse genotype in vitro. Cytokine array analysis and subsequent ELISA showed that circulating eotaxin levels were selectively and markedly increased in response to TNC gene deletion in apo E-/- mice. In addition, considerable variation was noted in the circulating level of eotaxin among the control apo E-/- mouse group. Inbreeding of apo E-/- mice with high or low levels of plasma eotaxin showed that the level of eotaxin per se determines the extent of atherosclerosis in this mouse genotype. While endothelial cells from apo E-/- mice had low level of eotaxin expression, cells derived from apo E-/- TNC-/- mice expressed a high level of eotaxin. Transient transfection of eotaxin promoter-reporter constructs revealed that eotaxin expression is regulated at the transcriptional level by TNC. Histochemical analysis of aortic sections revealed the massive accumulation of mast cells in the adventitia of double KO mice lesions whereas no such accumulation was detected in the control group. Plasma from the apo E-/- TNC-/- mice markedly stimulated mast cell migration whereas plasma from the apo E-/- mice had no such effect.

CONCLUSION

These observations support the emerging hypothesis that TNC expression controls eotaxin level in apo E-/- mice and that this chemokine plays a key role in the development of atherosclerosis.

Mast cells and vascular diseases

Mast cells are increasingly being recognized as effector cells in many cardiovascular conditions. Many mast-cell-derived products such as tryptase and chymase can, through their enzymic action, have detrimental effects on blood vessel structure while mast cell-derived mediators such as cytokines and chemokines can perpetuate vascular inflammation. Mice lacking mast cells have been developed and these are providing an insight into how mast cells are involved in cardiovascular diseases and, as knowledge increase, mast cells may become a viable therapeutic target to slow progression of cardiovascular disease.

Role of mast cell chymase and tryptase in the progression of atherosclerosis: study in 44 autopsied cases

The aim of this study was to describe the role of mast cell chymase and tryptase in the progression of atherosclerosis. Forty-four sections of aortas were obtained from autopsies. We assessed the macroscopic degree of atherosclerosis, microscopic intensity of lipid deposition in the tunica intima, percentage of collagen in the tunica intima, and density of immunostained mast cells. There was no significant difference between the density of mast cell tryptase and chymase concerning ethnicity, sex, cause of death, or degree of atherosclerosis. The density of mast cell chymase was significantly higher in the nonelderly group. The percentage of collagen was significantly higher in elderly patients. There was a positive and significant correlation between the degree of macroscopic atherosclerosis and lipidosis, the density of mast cell chymase and the percentage of collagen, the density of mast cell tryptase and the percentage of collagen, and lipidosis and the density of mast cell tryptase. The degree of macroscopic lesion of atherosclerosis increased proportionally with the increase in the density of mast cell chymase and tryptase and in the intensity of lipid deposition and with the percentage of collagen in the atherosclerotic plaques. Thus, mast cells may play a crucial role in aggravating atherosclerotic lesions.

Relevance of urocortins to cardiovascular disease

Acquired cardiovascular diseases such as coronary heart disease, peripheral artery disease and related vascular problems contribute to more than one-third of worldwide morbidity and mortality. In many instances, particularly in the under developed world, cardiovascular diseases are diagnosed at a late stage limiting the scope for improving outcomes. A range of therapies already exist for established cardiovascular disease, although there is significant interest in further understanding disease pathogenesis in order to improve diagnosis and achieve primary and secondary therapeutic goals. The urocortins are a group of recently defined peptide members of the corticotrophin-releasing factor family. Previous pre-clinical work and human association studies suggest that urocortins have potential to exert some beneficial and other detrimental effects on the heart and major blood vessels. More current evidence however favours beneficial effects of urocortins, for example these peptides have been shown to inhibit production of reactive oxygen species and vascular cell apoptosis, and thus may have potential to antagonise the progression of cardiovascular disease. This review summarises published data on the potential role of urocortins in cardiovascular disease.

Association with inflammatory cells and apolipoproteins to the progression of atherosclerosis

Purpose

Inflammatory cells are known to be associated with the progression of atherosclerosis and plaque rupture. However, the relation to inflammatory cells and apolipoproteins on the progression of atherosclerosis is unknown. This study was aimed at examining the different expressions of inflammatory cells and evaluate the effect of apolipoprotein (APO) C1 and APO E during the progression of atherosclerosis.

Methods

Ten atherosclerotic tissues were compared with five non-atherosclerotic tissues. The presence of vascular smooth muscle cells (VSMCs), macrophages, T-cells, APO C1, and APO E were identified by Western blotting and immunohistochemical analysis with antibodies. The senescence was analyzed by senescence-associated β-galactosidase.

Results

The protein expression and senescence of macrophages, APO C1 and APO E were significantly higher in the main atherosclerotic lesion than the non-atherosclerotic lesion. A high concentration of inflammatory cells and the paucity of VSMCs were present in the shoulder area. In addition, macrophage and T-cells are expressed in the early stage of atherosclerotic development and more expanded in advanced atherosclerotic plaques. APO C1 was expressed mainly within the necrotic core, and APO E existed mostly around the necrotic core and the fibrous cap in advanced atherosclerotic plaques.

Conclusion

Our study indicated that the expression and the senescence of macrophage and T-cells may be closelyrelated to induction and deposition of APO C1 and APO E. This contributes to the development and progression of atherosclerotic plaque by expanding the necrotic core.

Novel aspects of the pathogenesis of aneurysms of the abdominal aorta in humans

Aneurysm of the abdominal aorta (AAA) is a particular, specifically localized form of atherothrombosis, providing a unique human model of this disease. The pathogenesis of AAA is characterized by a breakdown of the extracellular matrix due to an excessive proteolytic activity, leading to potential arterial wall rupture. The roles of matrix metalloproteinases and plasmin generation in progression of AAA have been demonstrated both in animal models and in clinical studies. In the present review, we highlight recent studies addressing the role of the haemoglobin-rich, intraluminal thrombus and the adventitial response in the development of human AAA. The intraluminal thrombus exerts its pathogenic effect through platelet activation, fibrin formation, binding of plasminogen and its activators, and trapping of erythrocytes and neutrophils, leading to oxidative and proteolytic injury of the arterial wall. These events occur mainly at the intraluminal thrombus-circulating blood interface, and pathological mediators are conveyed outwards, where they promote matrix degradation of the arterial wall. In response, neo-angiogenesis, phagocytosis by mononuclear cells, and a shift from innate to adaptive immunity in the adventitia are observed. Abdominal aortic aneurysm thus represents an accessible spatiotemporal model of human atherothrombotic progression towards clinical events, the study of which should allow further understanding of its pathogenesis and the translation of pathogenic biological activities into diagnostic and therapeutic applications.

MMP2 genetic variation is associated with measures of fibrous cap thickness: The Atherosclerosis Risk in Communities Carotid MRI Study

OBJECTIVE

Genetic variation in matrix metalloproteinase (MMP) promoter regions alter the transcriptional activity of MMPs and has been consistently associated with CHD, presumably through plaque degradation and remodeling. We examined the association of MMP promoter variation with multiple plaque characteristics measured by gadolinium-enhanced MRI among 1700 participants in the Atherosclerosis Risk in Communities (ARIC) Carotid MRI Study.

METHODS

For the analyses presented here, 1700 participants of the biracial ARIC Carotid MRI Study ( approximately 1000 participants with thick carotid artery walls and approximately 700 randomly sampled participants) were evaluated for associations of MMP genetic variation with multiple plaque characteristics, including carotid artery wall thickness, lipid core and fibrous cap measures. MRI studies were performed on a 1.5T scanner equipped with a bilateral 4-element phased array carotid coil.

RESULTS

Fifty-one percent of the participants were female, 77% white, 23% African American, and the mean age was 70 years. MMP2 C-1306T variant genotypes (CT+TT) were significantly associated with higher cap thickness measures, but not with wall thickness or lipid core measures. Individuals with the CC genotype had approximately 0.1mm thinner cap thickness compared to those carrying a T allele (P=0.02).

CONCLUSION

Genetic variation within the MMP2 promoter region was associated with cap thickness and therefore may influence the role of MMP2 in plaque vulnerability.

Adaptive immunity and atherosclerosis

Atherosclerosis involves the formation of inflammatory arterial lesions and is one of the most common causes of death globally. It has been evident for more than 20 years that adaptive immunity and T cells in particular regulate the magnitude of the atherogenic pro-inflammatory response. T cells also influence the stability of the atherosclerotic lesion and thus the propensity for thrombus formation and the clinical outcome of disease. This review summarizes our current understanding of T cells in atherogenesis, including which antigens they recognize, the role of T cell costimulation/coinhibition, and their secretion of pro- and anti-inflammatory mediators. Furthermore, we outline future areas of research and potential clinical intervention strategies.

Relationship between neointimal coverage of sirolimus-eluting stents and lesion characteristics: a study with serial coronary angioscopy

BACKGROUND

Delayed neointimal coverage after the implantation of a drug-eluting stent (DES) is thought to be related to their potential for developing late-stent thrombosis. However, few studies have shown which factor affects the neointimal coverage after DES implantation. We hypothesized that the extent of neointimal coverage after DES implantation is affected by the underlying lesion characteristics because arterial wall components are reported to determine the transport and distribution of the drugs.

METHODS

Thirty-seven coronary artery lesions treated with a single sirolimus-eluting stent (SES) were evaluated in 37 patients with stable coronary artery disease. Angioscopy was performed before, immediately after, and 6 months after stenting to examine the existence of yellow plaque, thrombus, complex plaque, and intramural hemorrhage and the degree of neointimal coverage at 6-month follow-up. This was classified either as a noncoverage group (stent struts were predominantly exposed or visible through a thin neointima) or as a coverage group (stent struts were predominantly covered by neointimal hyperplasia and thus invisible).

RESULTS

Twenty-one lesions were classified into the noncoverage group, and 16 lesions the coverage group. The frequency of preexistent yellow plaques was significantly higher in the noncoverage group than that in the coverage group (67% vs 19%, P = .007). A multivariate logistic regression analysis showed the preexistence of yellow plaque was the only independent factor behind less neointimal coverage at 6 months after SES implantation (odds ratio 19.5, 95% confidence interval 1.58-240.50, P = .020).

CONCLUSIONS

The preexistence of yellow plaque may be associated with decreased neointimal coverage of SES.

Pharmacological treatment of abdominal aortic aneurysm

Abdominal aortic aneurysm (AAA) is a common degenerative condition with high mortality in older men. Elective surgical or endovascular repair is performed to prevent rupture of large AAAs. In contrast, despite gradual expansion, small AAAs have a low risk of rupture, and there is currently no well-defined treatment strategy for them. Therefore, a pharmacological approach for AAA is expected in the clinical setting. Indeed, several therapeutic effects of pharmacological agents have been reported in experimental models, and some agents have undergone clinical trials. Treatment with statins, angiotensin-converting enzyme-inhibitors, antibiotics, and anti-inflammatory agents appears to inhibit the growth rate of AAA in humans. However, as the sample size and follow-up period were limited in these studies, a large randomized study with long-term follow-up of small AAA should be performed to clarify the effect of these agents. Recently, the regression of AAA using molecular pharmacological approaches was reported in experimental studies. The characteristics of these strategies are the regulation of multiple molecular mediators and the signalling networks associated with AAA formation. On the basis of the results of these investigations, it may be possible to repair the injured aortic wall and obtain the remission of AAA using pharmacological therapy.

Phosphoinositide 3-kinases and their role in inflammation: potential clinical targets in atherosclerosis?

Inflammation has a central role in the pathogenesis of atherosclerosis at various stages of the disease. Therefore it appears of great interest to develop novel and innovative drugs targeting inflammatory proteins for the treatment of atherosclerosis. The PI3K (phosphoinositide 3-kinase) family, which catalyses the phosphorylation of the 3-OH position of phosphoinositides and generates phospholipids, controls a wide variety of intracellular signalling pathways. Recent studies provide evidence for a crucial role of this family not only in immune function, such as inflammatory cell recruitment, and expression and activation of inflammatory mediators, but also in antigen-dependent responses making it an interesting target to modulate inflammatory processes. The present review will focus on the regulation of inflammation within the vasculature during atherogenesis. We will concentrate on the different functions played by each isoform of PI3K in immune cells which could be involved in this pathology, raising the possibility that inhibition of one or more PI3K isoforms may represent an effective approach in the treatment of atherosclerosis.

Chymase activity is closely related with plaque vulnerability in a hamster model of atherosclerosis

OBJECTIVE

To test the hypothesis that stimulation of chymase secretion may contribute to plaque vulnerability and inhibition of chymase activity may enhance plaque stability.

METHODS AND RESULTS

Sixty eight-week-old male Syrian golden hamsters were randomly divided into normal control group, high-cholesterol (HC) treated group, HC+ovalbumin treated group and HC+tranilast treated group. The normal control group received a normal diet while the other three intervention groups received a high-cholesterol diet for 15 weeks. Hamsters in the HC+ovalbumin treated group underwent transcatheter pharmacological triggering at the end of week 15 after antigen sensitization and those in the HC+tranilast treated group were given tranilast intragastrically for 3 weeks before euthanasia. Serological, ultrasonographic, pathologic, immunohistochemical, and gene expression studies were performed in all animals. The total number of mast cells, proportion of degranulated mast cells and the number of extracellular granules in plaques, the apoptosis rate of vascular smooth cells, the local activities of chymase, the concentration of Ang II and the expression levels of inflammatory markers as well as plaque vulnerability index all increased significantly in HC+ovalbumin treated group, but remarkably decreased in HC+tranilast treated group, in comparison with the HC treated group. These results suggest that stimulation of chymase secretion contributes to plaque vulnerability while inhibition of chymase activity enhances plaque stability. We conclude that chymase activity provides a promising therapeutic target in the stabilization of atherosclerotic plaques.

Modulation of human T cells signaling transduction by lovastatin

Statins are applied clinically to treat hypercholesterolemia and proposed to have some kinds of anti-inflammatory properties for reducing the incidence of atherosclerosis-related cardiovascular events. However, it was rarely known about statins on the signal transduction on human primary T cells. To gain insight into the mechanism of statins on human T cells, we investigated the effects of both lovastatin and atorvastatin on activated human primary T cells. The human primary T cells from the blood of normal human beings were isolated. We found that lovastatin, but not atorvastatin, can dose-dependently inhibit cytokine production such as interleukin-2, interleukin-4, and interferon-gamma from activated human T cells. Neither lovastatin nor atorvastatin can regulate the TNF-alpha production on both activated human T cells and monocytes. Molecular investigation was performed that lovastatin, but not atorvastatin, could down-regulate both activator protein-1 and NF-kappaB DNA binding activities, assessed by electrophoretic mobility shift assay. Our observations may extend potential and differential therapeutic mechanisms of lovastatin with cell-mediated capacity to prevent or treat some of inflammation related diseases.

The IL-33/ST2 pathway: therapeutic target and novel biomarker

For many years, the interleukin-1 receptor family member ST2 was an orphan receptor that was studied in the context of inflammatory and autoimmune disease. However, in 2005, a new cytokine--interleukin-33 (IL-33)--was identified as a functional ligand for ST2. IL-33/ST2 signalling is involved in T-cell mediated immune responses, but more recently, an unanticipated role in cardiovascular disease has been demonstrated. IL-33/ST2 not only represents a promising cardiovascular biomarker but also a novel mechanism of intramyocardial fibroblast-cardiomyocyte communication that may prove to be a therapeutic target for the prevention of heart failure.

Second hit post burn increased proximal gut mucosa epithelial cells damage

Secondary infections after burn are common and are a major contributor to morbidity and mortality. We previously showed that burn disrupted proximal gut mucosal homeostasis through increased epithelial cell apoptosis. In the present study, we sought to determine whether proximal gut mucosal disruption is additively affected by secondary endotoxemia after a severe burn. C57BL/6 mice received 30% total body surface area full-thickness scald burns and were randomized to receive saline or LPS 1 mg/kg body weight given intraperitoneally 72 h after burn. Proximal small bowel was harvested 12 h after LPS injection. Mucosal height and epithelial cell number were assessed on hematoxylin-eosin sections, intestinal epithelial cell apoptosis was identified by terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling, and cell proliferation by immunohistochemical staining for proliferating cell nuclear antigen. Results showed that proximal gut mucosa impairment occurred 12 h after injury, including significantly decreased proximal gut wet weight, gut mucosal height, and epithelial cell number associated with increased proximal gut epithelial apoptosis (P < 0.05). This impairment diminished 72 h after burn. Second-hit endotoxemia caused additional proximal gut mucosa damage with decreased proximal gut weight, cell number, and mucosal height (P < 0.05) and significantly increased small intestinal epithelial apoptosis and mucosal atrophy, even after the first event, indicating a second detrimental effect of endotoxemia after the initial injury.

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

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

Mast cells and degradation of pericellular and extracellular matrices: potential contributions to erosion, rupture and intraplaque haemorrhage of atherosclerotic plaques

Mast cells are present in advanced human atherosclerotic plaques, where they are thought to exert multiple effects on their neighbouring cells and on the extracellular matrix of the plaque. Extensive efforts at delineating their role(s) in atherosclerotic plaques have unravelled mechanisms by which plaque mast cells may render advanced atherosclerotic plaques susceptible to erosion, rupture or intraplaque haemorrhage and so modulate their stability. In these mechanisms, the key effector molecules are mast-cell-derived neutral proteases and pro-inflammatory cytokines. These effector molecules are synthesized and stored in the cytoplasmic secretory granules of mast cells and, once the mast cells are activated to degranulate, are released into the microenvironment surrounding the activated mast cells. In the plaques, the key target cells are endothelial cells and smooth muscle cells and their pericellular matrices. In addition, the various components of the extracellular matrix of the plaques, notably collagen, are degraded when the released mast cell proteases activate matrix metalloproteinases in the plaques. By rendering the plaque susceptible to erosion, to rupture or to intraplaque haemorrhage, the mast cells may contribute to the onset of acute atherothrombotic complications of coronary atherosclerosis, such as myocardial infarction.

Vitamin E and mast cells

Mast cells play an important role in the immune system by interacting with B and T cells and by releasing several mediators involved in activating other cells. Hyperreactivity of mast cells and their uncontrolled accumulation in tissues lead to increased release of inflammatory mediators contributing to the pathogenesis of several diseases such as rheumatoid arthritis, atherosclerosis, multiple sclerosis, and allergic disorders such as asthma and allergic rhinitis. Interference with mast cell proliferation, survival, degranulation, and migration by synthetic or natural compounds may represent a preventive strategy for the management of these diseases. Natural vitamin E covers a group of eight analogues-the alpha-, beta-, gamma-, and delta-tocopherols and the alpha-, beta-, gamma-, and delta-tocotrienols, but only alpha-tocopherol is efficiently retained by the liver and distributed to peripheral tissues. Mast cells preferentially locate in the proximity of tissues that interface with the external environment (the epithelial surface of the skin, the gastrointestinal mucosa, and the respiratory system), what may render them accessible to treatments with inefficiently retained natural vitamin E analogues and synthetic derivatives. In addition to scavenging free radicals, the natural vitamin E analogues differently modulate signal transduction and gene expression in several cell lines; in mast cells, protein kinase C, protein phosphatase 2A, and protein kinase B are affected by vitamin E, leading to the modulation of proliferation, apoptosis, secretion, and migration. In this chapter, the possibility that vitamin E can prevent diseases with mast cells involvement by modulating signal transduction and gene expression is evaluated.

Cellular, molecular and clinical aspects of vitamin E on atherosclerosis prevention

Randomised clinical trials and epidemiologic studies addressing the preventive effects of vitamin E supplementation against cardiovascular disease reported both positive and negative effects, and recent meta-analyses of the clinical studies were rather disappointing. In contrast to that, many animal studies clearly show a preventive action of vitamin E in several experimental settings, which can be explained by the molecular and cellular effects of vitamin E observed in cell cultures. This review is focusing on the molecular effects of vitamin E on the cells playing a role during atherosclerosis, in particular on the endothelial cells, vascular smooth muscle cells, monocytes/macrophages, T cells, and mast cells. Vitamin E may act by normalizing aberrant signal transduction and gene expression in antioxidant and non-antioxidant manners; in particular, over-expression of scavenger receptors and consequent foam cell formation can be prevented by vitamin E. In addition to that, the cellular effects of alpha-tocopheryl phosphate and of EPC-K1, a composite molecule between alpha-tocopheryl phosphate and l-ascorbic acid, are summarized.

Mast Cell Stabilization Reduces Hemorrhage Formation and Mortality After Administration of Thrombolytics in Experimental Ischemic Stroke

Background— Thrombolysis with tissue plasminogen activator (tPA) improves stroke outcome, but hemorrhagic complications and reperfusion injury occasionally impede favorable prognosis after vessel recanalization. Perivascularly located cerebral mast cells (MCs) release on degranulation potent vasoactive, proteolytic, and fibrinolytic substances. We previously found MCs to increase ischemic and hemorrhagic brain edema and neutrophil accumulation. This study examined the role of MCs in tPA-mediated hemorrhage formation (HF) and reperfusion injury.

Methods and Results— Exposure to tPA in vitro induced strong MC degranulation. In vivo experiments in a focal cerebral ischemia/reperfusion model in rats showed 70- to 100-fold increase in HF after postischemic tPA administration ( P <0.001). Pharmacological MC stabilization with cromoglycate led to significant reduction in tPA-mediated HF at 3 (97%), 6 (76%), and 24 hours (96%) compared with controls ( P <0.01, P <0.001, and P <0.01, respectively). Furthermore, genetically modified MC-deficient rats showed similarly robust reduction of tPA-mediated HF at 6 (92%) and 24 (89%) hours compared with wild-type littermates ( P <0.01 and P <0.001, respectively). MC stabilization and MC deficiency also significantly reduced other hallmarks of reperfusion injury, such as brain swelling and neutrophil infiltration. These effects of cromoglycate and MC deficiency translated into significantly better neurological outcome ( P <0.01 and P <0.05, respectively) and lower mortality ( P <0.05 and P <0.05, respectively) after 24 hours.

Conclusions— MCs appear to play an important role in HF and reperfusion injury after tPA administration. Pharmacological stabilization of MCs could offer a novel type of therapy to improve the safety of administration of thrombolytics.

Mast cells: multipotent local effector cells in atherothrombosis

Our understanding of the relationship between the proatherogenic activities of arterial mast cells (MCs) and the development of atherosclerotic lesions is advancing. Atherosclerosis is a chronic inflammatory disease in which cholesterol and other lipids of circulating low-density lipoprotein (LDL) particles accumulate both extracellularly and intracellularly in the innermost layer of the arterial wall, the intima. One prerequisite for the proatherogenic activity of the LDL particles is their retention and proteolytic modification within the extracellular matrix of the intima. Experimental studies with activated chymase-secreting MCs have provided us fundamental insights into the molecular mechanisms of these processes. High-density lipoprotein (HDL) particles, again, remove cholesterol from the intracellular stores and carry it back to the circulation. MC chymase and tryptase actively degrade HDL and thus generate functionally defective particles that are unable to initiate cholesterol efflux from the arterial wall. In advanced atherosclerotic plaques, the accumulated lipids are separated from the circulation by a collagenous cap. By inducing apoptosis of endothelial cells (ECs), subendothelial MCs may induce detachment of ECs from the cap (plaque erosion). Moreover, MCs may weaken the cap if they disturb local collagen turnover by inducing apoptosis of the collagen-secreting smooth muscle cells or when they promote collagen degradation by activating matrix metalloproteinases. Plaques with a weak cap are vulnerable to rupture. The exposed subendothelial tissue at eroded and ruptured sites of plaques triggers local development of a platelet-rich thrombus. As regulators of the collagen-induced platelet activation and fibrin formation/fibrinolysis, the MCs may retard or accelerate the growth of the plaque-associated thrombus and ultimately participate in the wound-healing response of the injured plaque. We propose that by promoting cholesterol accumulation and plaque vulnerability and by locally regulating hemostasis, MCs in atherosclerotic lesions have the potential to contribute to the clinical outcomes of atherosclerosis, such as myocardial infarction and stroke.

Multi-cell agent-based simulation of the microvasculature to study the dynamics of circulating inflammatory cell trafficking

Leukocyte trafficking through the microcirculation and into tissues is central in angiogenesis, inflammation, and the immune response. Although the literature is rich with mechanistic detail describing molecular mediators of these processes, integration of signaling events and cell behaviors within a unified spatial and temporal framework at the multi-cell tissue-level is needed to achieve a fuller understanding. We have developed a novel computational framework that combines agent-based modeling (ABM) with a network flow analysis to study monocyte homing. A microvascular network architecture derived from mouse muscle was incorporated into the ABM. Each individual cell was represented by an individual agent in the simulation. The network flow model calculates hemodynamic parameters (blood flow rates, fluid shear stress, and hydrostatic pressures) throughout the simulated microvascular network. These are incorporated into the ABM to affect monocyte transit through the network and chemokine/cytokine concentrations. In turn, simulated monocytes respond to their local mechanical and biochemical environments and make behavioral decisions based on a rule set derived from independent literature. Simulated cell behaviors give rise to emergent leukocyte rolling, adhesion, and extravasation. Molecular knockout simulations were performed to validate the model, and predictions of monocyte adhesion, rolling, and extravasation show good agreement with the independently published corresponding mouse studies.

Construction and functional analysis of a lentiviral expression vector containing a scavenger receptor (SR-PSOX) that binds uniquely phosphatidylserine and oxidized lipoprotein

The aim of this study is to construct a lentiviral expression vector containing a scavenger receptor (SR-PSOX) that binds with uniquely phosphatidylserine and oxidized lipoprotein with six histidine tags and to investigate the function of SR-PSOX in atherosclerosis. We utilize the ViraPower lentiviral expression system which was efficient to deliver in vitro or in vivo the target gene into dividing and non-dividing mammalian cells using an enhanced biosafety replication-incompetent lentivirus. The blunt-end sequence was amplified using the reverse transcription-polymerase chain reaction and directional TOPO cloning reaction. Through a pair of the cytomegalovirus forward primer and the reverse primer of SR-PSOX, the correct clones were identified by polymerase chain reaction and sequencing. The ViraPower packaging mix and SR-PSOX-pLenti6/V5 TOPO expression plasmid were co-transfected into the 293FT cell line using Lipofectamine 2000. The expression of endogenous and exogenous SR-PSOX as well as tumor necrosis factor (TNF)-alpha protein in various foam cell models at different time points were detected by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, Western blot and indirect immunofluorescence assay. Western blot and immunofluorescence analysis confirmed that the expressions of SR-PSOX and TNF-alpha protein were upregulated in foam cell models. Our data suggested that the overexpression of recombinant human SR-PSOX protein can promote foam cell formation and upregulate the expression of the inflammatory factor TNF-alpha.

MRI visualized neo-intimal dissection and co-localization of novel apoptotic markers apolipoprotein C-1, ceramide and caspase-3 in a Watanabe hyperlipidemic rabbit model

PURPOSE

Apoptotic arterial wall vascular smooth muscle cell death is known to contribute to plaque vulnerability and rupture. Novel apoptotic markers like apolipoprotein C-I have been implicated in apoptotic human vascular smooth muscle cell death via recruiting a neutral sphingomyelinase (N-SMase)-ceramide pathway. In vivo relevance of these observations in an animal model of plaque rupture has not been shown.

METHODS AND RESULTS

Using Watanabe rabbits, we investigated three different groups (group 1, three normal Watanabe rabbits; group 2, six Watanabe rabbits fed with high cholesterol diet for 3 months; group 3, five Watanabe rabbits with similar diet but additional endothelial denudation). We followed progression of atherosclerosis to pharmacologically induced plaque rupture non-invasively using novel 3D magnetic resonance Fast-Field-Echo angiography (TR=7.2, TE=3.6 ms, matrix=512 x 512) and Fast-Spin-Echo vessel wall imaging methods (TR=3 heart beats, TE=10.5 ms, matrix=304 x 304) on 1.5 T MRI. MRI provided excellent image quality with good MRI versus histology vessel wall thickness correlation (r=0.8). In six animals of group 2/3 MRI detected neo-intimal dissection in the abdominal aorta which was accompanied by immuno-histochemical demonstration of concomitant aforementioned novel apoptotic markers, previously implicated in the apoptotic smooth muscle cell death in vitro.

CONCLUSIONS

Our studies suggest a potential role for the signal transduction pathway involving apolipoprotein C-I for in vivo apoptosis and atherosclerotic plaque rupture visualized by MRI.

Inhibition of plasma membrane Ca2+-ATPase by heparin is modulated by potassium

Heparin is related to several protein receptors that control Ca2+ homeostasis. Here, we studied the effects of heparin on the plasma membrane Ca2+-ATPase from erythrocytes. Both ATP hydrolysis and Ca2+ uptake were inhibited by heparin without modification of the steady-state level of phosphoenzyme formed by ATP. Calmodulin did neither modify the inhibition nor the binding of heparin. Inhibition by heparin was counteracted by K+ but not by Li+. This effect was extended to other sulfated polysaccharides with high number of sulfate residues. Hydrolysis of p-nitrophenylphosphate was equally inhibited by heparin. No evidence for enzyme uncoupling was observed: Ca2+ uptake and ATP hydrolysis remained tightly associated at any level of heparin, and heparin did not increase the passive Ca2+ efflux of inside-out vesicles. Vanadate blocked this efflux, indicating that the main point of Ca2+ escape from these vesicles was linked to the Ca2+ pump. It is discussed that sulfated polysaccharides may physiologically increase the steady-state level of Ca2+ in the cytosol by inhibiting the Ca2+ pumps in a K+ (and tissue) regulated way. It is suggested that heparin regulates the plasma membrane Ca2+-ATPase by binding to the E2 conformer.

T cells in atherogenesis: for better or for worse?

The idea that atherosclerosis is an inflammatory disease is no longer controversial. Instead, much of the current research is now focused on understanding what drives this inflammation and how it is regulated. Adaptive immunity, in particular T cells, is highly involved in atherogenesis. It is well known that different subsets of T cells can drive or dampen inflammatory processes, but we still have much to learn about the regulation of this balance in the context of atherosclerosis. This review summarizes our knowledge of T cells in atherogenesis, their potential antigens, their contact-dependent activities, and their secretion of inflammatory and antiinflammatory mediators, aiming to illustrate how T cells can aggravate or attenuate this disease through cross-talk with other cells within or outside the atherosclerotic plaque.

Increased expression of genes that control ionic homeostasis, second messenger signaling and metabolism in the carotid plaques from patients with symptomatic stroke

The molecular mechanisms that render a carotid atherosclerotic plaque symptomatic have not yet been identified. Using an Affymetrix Human GeneChip set, we analyzed the gene expression patterns of 44 862 mRNA transcripts in surgically removed carotid artery plaques from six patients with symptomatic stroke and four non-symptomatic patients. The age, body mass index and the degree of stenosis were similar in the two groups. Some 236 transcripts (approximately 0.5% of the total transcripts analyzed) were expressed more abundantly in the symptomatic than the asymptomatic group. Of these, 61 transcripts are those that participate in ionic homeostasis, signal transduction and metabolism. The other groups of transcripts up-regulated in the symptomatic plaques include oncogenes, growth factors, tumor markers, angiogenesis promoters, transcription factors, and RNA splicing and processing factors. This study indicates that the higher metabolic activity in some atherosclerotic plaques leads to their faster growth and precipitation of stroke symptoms. The implications of these findings are that both diagnosis and prevention of stroke symptoms may become possible at the genetic level.

[Immunological aspects of atherosclerosis]

The pathogenesis of atherosclerosis remains incompletely understood. Accumulation of oxidized lipoproteins (oxLDL) within the vascular wall drives a related immune response very early during the disease course. Such an immune response is self-amplified and eventually escapes from physiologic control mechanisms. Certain lymphocytes may become pathogenic. B cells play a protective role by producing antibodies able to neutralize oxLDL. Elucidation of the immune control mechanisms in atherosclerosis will open the way to new therapeutic perspectives.

Cytokines in Atherosclerosis: Pathogenic and Regulatory Pathways

Atherosclerosis is a chronic disease of the arterial wall where both innate and adaptive immunoinflammatory mechanisms are involved. Inflammation is central at all stages of atherosclerosis. It is implicated in the formation of early fatty streaks, when the endothelium is activated and expresses chemokines and adhesion molecules leading to monocyte/lymphocyte recruitment and infiltration into the subendothelium. It also acts at the onset of adverse clinical vascular events, when activated cells within the plaque secrete matrix proteases that degrade extracellular matrix proteins and weaken the fibrous cap, leading to rupture and thrombus formation. Cells involved in the atherosclerotic process secrete and are activated by soluble factors, known as cytokines. Important recent advances in the comprehension of the mechanisms of atherosclerosis provided evidence that the immunoinflammatory response in atherosclerosis is modulated by regulatory pathways, in which the two anti-inflammatory cytokines interleukin-10 and transforming growth factor-β play a critical role. The purpose of this review is to bring together the current information concerning the role of cytokines in the development, progression, and complications of atherosclerosis. Specific emphasis is placed on the contribution of pro- and anti-inflammatory cytokines to pathogenic (innate and adaptive) and regulatory immunity in the context of atherosclerosis. Based on our current knowledge of the role of cytokines in atherosclerosis, we propose some novel therapeutic strategies to combat this disease. In addition, we discuss the potential of circulating cytokine levels as biomarkers of coronary artery disease.

Morphological effects of myasthenia gravis patient sera on human muscle cells

Myasthenia gravis (MG) is caused primarily by autoantibodies against the nicotinic acetylcholine receptor (AChR), but autoantibodies to other muscle proteins may be present. Many of these proteins have structural or signalling functions, the disruption of which may affect muscle cell morphology or viability. In order to investigate the role of such autoantibodies in MG, we examined the effect of MG patient sera, of different autoantibody composition and obtained at different stages of disease severity, on primary human muscle cells. Sera from MG patients induced changes in cell morphology from typical elongated cells to an irregular phenotype, caused the formation of inclusion bodies and intracellular vesicles, and led to a disordered arrangement of actin microfilaments. Sera from the most severely affected patients also induced cell death, which did not occur via classic apoptosis. The effects were not complement-mediated and were dose- and time-dependent. As the effects observed in the cell culture system correlated with disease severity, a greater understanding of the individual factors responsible for these effects may improve our understanding of MG pathogenesis and be of value in the assessment of disease in individual patients.

TSC-36/FRP inhibits vascular smooth muscle cell proliferation and migration

OBJECTIVE

In-stent restenosis is a vascular proliferation/migration disorder characterized by hyperplasia of vascular smooth muscle cells (VSMCs). Because mounting evidence suggests that the therapeutic potential of anti-proliferation and anti-migration therapy, we investigated possible inhibitory effects of the matricellular protein TGF-beta-stimulated clone 36 (TSC-36) on vascular smooth muscle cell proliferation and migration in vitro and in vivo.

METHODS

Human umbilical artery smooth muscle cells (SMCs) were treated with inducting agents daidzein or estradiol. TSC-36 expression was detected by nested competitive PCR and in situ hybridization. TSC-36 was expressed in Origami (DE3) cells. The recombinant protein was used to immunize rabbits to produce polyclonal antibodies. VSMCs were treated with various concentrations of recombinant TSC-36 (rTSC-36) protein and daidzein. The MTT assay was used to analyze for cell proliferation. A transwell system was used to detect cell migration. Flow cytometry was used to detect cell phase. A rat carotid artery balloon injury model was duplicated. The rats were treated with daidzein or solvent control. Animals were sacrificed 5 weeks later, and injured arteries were taken for pathology and histology.

RESULTS

TSC-36 mRNA and protein expression was induced in SMCs. Cell proliferation and migration were inhibited by rTSC-36. rTSC-36 caused accumulation of SMCs in G2 phase. The inducting agent daidzein decreased neo-intima proliferation. TSC-36 mRNA and protein expression was induced and expressed in the neo-intima.

CONCLUSION

TSC-36 can be induced in VSMCs and inhibits VSMCs proliferation in vitro and in vivo.

Carotid atherosclerotic plaques from symptomatic stroke patients share the molecular fingerprints to develop in a neoplastic fashion: a microarray analysis study

Identification of genetic mechanisms that promote the onset of stroke and transient cerebral ischemic attack symptoms in carotid atherosclerotic patients would further our understanding of the pathophysiology of this disease and could lead to new pharmacological and molecular therapies. Using Affymetrix Human Genome 230 GeneChip set, the present study evaluated the gene expression differences in geometrically similar carotid artery plaque samples extricated from six symptomatic stroke patients and four asymptomatic patients. There was no significant difference in the degree of stenosis between the two groups. Of the 44,860 transcripts analyzed, 289 (approximately 0.6% of the total transcripts) were differentially expressed between the plaques from the symptomatic and asymptomatic groups (236 were expressed more abundantly and 53 were expressed less abundantly in the symptomatic group). Of the 236 transcripts expressed more abundantly in the symptomatic plaques, 71% (167 transcripts) indicate an active cell proliferation and neoplastic process. These include oncogenes, growth factors, tumor promoters, tumor markers, angiogenesis promoters, transcription factors, RNA splicing factors, RNA processing proteins, signal transduction mediators and those that control the metabolism. Real-time polymerase chain reaction confirmed the increased expression of 63 transcripts in the symptomatic plaques. The other groups of transcripts expressed more abundantly in the symptomatic plaques are those that control ionic homeostasis, those that participate in the progression of degenerative neurological diseases (Alzheimer's disease, amyotrophic lateral sclerosis and Huntington's disease) and epilepsy. This indicates that symptomatic plaques are molecularly and biochemically more active than the asymptomatic plaques, or active plaque growth precipitates stroke symptoms.

Thematic review series: the immune system and atherogenesis. The unusual suspects:an overview of the minor leukocyte populations in atherosclerosis

Atherosclerosis is a complex inflammatory disease process involving an array of cell types and interactions. Although macrophage foam cells and vascular smooth muscle cells constitute the bulk of the atherosclerotic lesion, other cell types have been implicated in this disease process as well. These cellular components of both innate and adaptive immunity are involved in modulating the response of macrophage foam cells and vascular smooth muscle cells to the retained and modified lipids in the vessel wall as well as in driving the chronic vascular inflammation that characterizes this disease. In this review, the involvement of a number of less prominent leukocyte populations in the pathogenesis of atherosclerosis is discussed. More specifically, the roles of natural killer cells, mast cells, neutrophils, dendritic cells, gammadelta T-cells, natural killer T-cells, regulatory T-cells, and B-cells are addressed.