Smad expression in human atherosclerotic lesions: evidence for impaired TGF-beta/Smad signaling in smooth muscle cells of fibrofatty lesions

Novel indel variation of LTBP4 gene associates with risk of sudden cardiac death in Chinese populations with coronary artery disease

The objective of this study is to investigate whether common genetic variants of the LTBP4 gene are linked to the susceptibility of sudden cardiac death in individuals who have atherosclerotic coronary artery disease (SCD-CAD) in Chinese populations. A total of 208 SCD-CAD cases and 638 controls were included in the analysis, and logistic regression was employed to assess the association between a 4-bp insertion/deletion polymorphism (rs34005443) within LTBP4 and the susceptibility to SCD-CAD among Chinese individuals. Logistic regression analysis demonstrated a notable association between the insertion allele of rs34005443 and an escalated susceptibility to SCD-CAD [odds ratio (OR) = 1.434; 95 % confidence interval:1.14-1.80; P = 1.79 × 10-3]. Genotype-phenotype correlation analysis was performed using Genotype-Tissue expression (GTEx) database and further validated by human myocardium using qPCR. Correlation analysis revealed that LTBP4 expression level was lower in samples with the insertion allele. Furthermore, the dual-luciferase activity assays indicated that rs34005443 may play a regulatory role. Additionally, we predicted 30 transcription factors that are likely to bind to rs34005443 and its highly linked genetic variants via 3DSNP database. Subsequent GO and KEGG analysis indicated that these transcription factors have a significant function in regulating gene expression. Finally, PPI network analysis suggested a tight connection between LTBP4 proteins and TGFβs, highlighting these genes as potential hub genes in the context of SCD-CAD. In summary, our study revealed that rs34005443 might contribute to SCD-CAD susceptibility by regulating LTBP4 expression. These findings revealed that this indel could be a potentially functional marker for molecular diagnosis and risk stratification of SCD-CAD.

Role of non-coding variants in cardiovascular disease

Cardiovascular diseases (CVDs) constitute one of the significant causes of death worldwide. Different pathological states are linked to CVDs, which despite interventions and treatments, still have poor prognoses. The genetic component, as a beneficial tool in the risk stratification of CVD development, plays a role in the pathogenesis of this group of diseases. The emergence of genome-wide association studies (GWAS) have led to the identification of non-coding parts associated with cardiovascular traits and disorders. Variants located in functional non-coding regions, including promoters/enhancers, introns, miRNAs and 5'/3' UTRs, account for 90% of all identified single-nucleotide polymorphisms associated with CVDs. Here, for the first time, we conducted a comprehensive review on the reported non-coding variants for different CVDs, including hypercholesterolemia, cardiomyopathies, congenital heart diseases, thoracic aortic aneurysms/dissections and coronary artery diseases. Additionally, we present the most commonly reported genes involved in each CVD. In total, 1469 non-coding variants constitute most reports on familial hypercholesterolemia, hypertrophic cardiomyopathy and dilated cardiomyopathy. The application and identification of non-coding variants are beneficial for the genetic diagnosis and better therapeutic management of CVDs.

Insights into bone morphogenetic proteins in cardiovascular diseases

Bone morphogenetic proteins (BMPs) are secretory proteins belonging to the transforming growth factor-β (TGF-β) superfamily. These proteins play important roles in embryogenesis, bone morphogenesis, blood vessel remodeling and the development of various organs. In recent years, as research has progressed, BMPs have been found to be closely related to cardiovascular diseases, especially atherosclerosis, vascular calcification, cardiac remodeling, pulmonary arterial hypertension (PAH) and hereditary hemorrhagic telangiectasia (HHT). In this review, we summarized the potential roles and related mechanisms of the BMP family in the cardiovascular system and focused on atherosclerosis and PAH.

Fibrotic Signaling in Cardiac Fibroblasts and Vascular Smooth Muscle Cells: The Dual Roles of Fibrosis in HFpEF and CAD

Patients with heart failure with preserved ejection fraction (HFpEF) and atherosclerosis-driven coronary artery disease (CAD) will have ongoing fibrotic remodeling both in the myocardium and in atherosclerotic plaques. However, the functional consequences of fibrosis differ for each location. Thus, cardiac fibrosis leads to myocardial stiffening, thereby compromising cardiac function, while fibrotic remodeling stabilizes the atherosclerotic plaque, thereby reducing the risk of plaque rupture. Although there are currently no drugs targeting cardiac fibrosis, it is a field under intense investigation, and future drugs must take these considerations into account. To explore similarities and differences of fibrotic remodeling at these two locations of the heart, we review the signaling pathways that are activated in the main extracellular matrix (ECM)-producing cells, namely human cardiac fibroblasts (CFs) and vascular smooth muscle cells (VSMCs). Although these signaling pathways are highly overlapping and context-dependent, effects on ECM remodeling mainly act through two core signaling cascades: TGF-β and Angiotensin II. We complete this by summarizing the knowledge gained from clinical trials targeting these two central fibrotic pathways.

Therapeutic Potential of Stem Cell-Derived Extracellular Vesicles on Atherosclerosis-Induced Vascular Dysfunction and Its Key Molecular Players

Atherosclerosis is a progressive, chronic inflammatory disease of the large arteries caused by the constant accumulation of cholesterol, followed by endothelial dysfunction and vascular inflammation. We hypothesized that delivery of extracellular vesicles (EVs), recognized for their potential as therapeutic targets and tools, could restore vascular function in atherosclerosis. We explored by comparison the potential beneficial effects of EVs from subcutaneous adipose tissue stem cells (EVs (ADSCs)) or bone marrow mesenchymal stem cells (EVs (MSCs)) on the consequences of atherogenic diet on vascular health. Also, the influences of siRNA-targeting Smad2/3 (Smad2/3siRNA) on endothelial dysfunction and its key molecular players were analyzed. For this study, an animal model of atherosclerosis (HH) was transplanted with EVs (ADSCs) or EVs (MSCs) transfected or not with Smad2/3siRNA. For controls, healthy or HH animals were used. The results indicated that by comparison with the HH group, the treatment with EVs(ADSCs) or EVs(MSCs) alone or in combination with Smad2/3siRNA of HH animals induced a significant decrease in the main plasma parameters and a noticeable improvement in the structure and function of the thoracic aorta and carotid artery along with a decrease in the selected molecular and cellular targets mediating their changes in atherosclerosis: 1) a decrease in expression of structural and inflammatory markers COL1A1, α-SMA, Cx43, VCAM-1, and MMP-2; 2) a slight infiltration of total/M1 macrophages and T-cells; 3) a reduced level of cytosolic ROS production; 4) a significant diminution in plasma concentrations of TGF-β1 and Ang II proteins; 5) significant structural and functional improvements (thinning of the arterial wall, increase of the inner diameter, enhanced distensibility, diminished VTI and Vel, and augmented contractile and relaxation responses); 6) a reduced protein expression profile of Smad2/3, ATF-2, and NF-kBp50/p65 and a significant decrease in the expression levels of miR-21, miR-29a, miR-192, miR-200b, miR-210, and miR-146a. We can conclude that 1) stem cell-derived EV therapies, especially the EVs (ADSCs) led to regression of structural and functional changes in the vascular wall and of key orchestrator expression in the atherosclerosis-induced endothelial dysfunction; 2) transfection of EVs with Smad2/3siRNA amplified the ability of EVs(ADSCs) or EVs(MSCs) to regress the inflammation-mediated atherosclerotic process.

The Role of ANRIL in Atherosclerosis

There is a huge number of noncoding RNA (ncRNA) transcripts in the cell with important roles in modulation of different mechanisms. ANRIL is a long ncRNA with 3.8 kb length that is transcribed in the opposite direction of the INK4/ARF locus in chromosome 9p21. It was shown that polymorphisms within this locus are associated with vascular disorders, notably coronary artery disease (CAD), which is considered as a risk factor for life-threatening events like myocardial infarction and stroke. ANRIL is subjected to a variety of splicing patterns producing multiple isoforms. Linear isoforms could be further transformed into circular ones by back-splicing. ANRIL regulates genes in atherogenic network in a positive or negative manner. This regulation is implemented both locally and remotely. While CAD is known as a proliferative disorder and cell proliferation plays a crucial role in the progression of atherosclerosis, the functions of ANRIL and CAD development are intertwined remarkably. This makes ANRIL a suitable target for diagnostic, prognostic, and even therapeutic aims. In this review, we tried to present a comprehensive appraisal on different aspects of ANRIL including its location, structure, isoforms, expression, and functions. In each step, the contribution of ANRIL to atherosclerosis is discussed.

Activin a inhibits foam cell formation and up-regulates ABCA1 and ABCG1 expression through Alk4-Smad signaling pathway in RAW 264.7 macrophages

BACKGROUND

Activin A has been reported to play important roles in the pathogenesis of atherosclerosis. The purpose of this study is to investigate the effects of activin A on oxidized low-density lipoprotein (ox-LDL)-induced foam cell formation and explore the underlying molecular mechanisms in murine macrophage-like cell line RAW 264.7.

METHODS

The effects of activin A on Dil-labeled ox-LDL uptake were examined by confocal microscopy and flow cytometry analysis. The mRNA and protein levels of cholesterol receptors were analyzed by RT-qPCR and western blot analysis, respectively. To investigate whether activin receptor-like kinase 4 (Alk4) is required for activin A-mediated cellular effects, cells were pre-treated with SB-431542. The involvement of Smad2, Smad3 and Smad4 was confirmed by transfection with specific small interfering RNAs (siRNAs).

RESULTS

Activin A inhibits ox-ldl-induced foam cell formation and class A scavenger receptors (SR-A) expression, while up-regulates ATP-binding cassette transporter A1 (ABCA1) and ABCG1 expression in RAW 264.7 macrophages. Pre-treatment with SB-431542 abolished activin A-mediated anti-atherogenic effect. Knockdown of Smad2 reversed activin A-induced inhibition of ox-LDL uptake and SR-A expression. However, knockdown of Smad3 or Smad4 did not have such effect. Meanwhile, knockdown of either Smad2, Smad3 or Smad4 reversed the activin A-induced up-regulation of ABCA1 and ABCG1.

CONCLUSIONS

Our study provides novel evidence that activin A may exert anti-atherogenic effects through Alk4-Smad signaling pathway in RAW 264.7 macrophages.

The role of bone morphogenetic protein signaling in vascular calcification

Vascular calcification is associated with atherosclerosis, chronic kidney disease, and diabetes, and results from processes resembling endochondral or intramembranous ossification, or from processes that are distinct from ossification. Bone morphogenetic proteins (BMP), as well as other ligands, receptors, and regulators of the transforming growth factor beta (TGFβ) family regulate vascular and valvular calcification by modulating the phenotypic plasticity of multipotent progenitor lineages associated with the vasculature or valves. While osteogenic ligands BMP2 and BMP4 appear to be both markers and drivers of vascular calcification, particularly in atherosclerosis, BMP7 may serve to protect against calcification in chronic kidney disease. BMP signaling regulators such as matrix Gla protein and BMP-binding endothelial regulator protein (BMPER) play protective roles in vascular calcification. The effects of BMP signaling molecules in vascular calcification are context-dependent, tissue-dependent, and cell-type specific. Here we review the current knowledge on mechanisms by which BMP signaling regulates vascular calcification and the potential therapeutic implications.

Th17/Treg Imbalance and Atherosclerosis

Atherosclerosis is nowadays recognized as a chronic inflammatory disease of large arteries. In recent years, cellular and molecular biology studies on atherosclerosis confirmed that the occurrence and development are related to inflammation and autoimmunity. A variety of immune cells, cytokines, and transcription factors are involved in this process. Current studies found that T helper cell 17, regulatory T cells, and their cytokines play an important role in the development of atherosclerosis and vulnerable plaque rupture. Here, we provide a review of the up-to-date applications of T helper cell 17, regulatory T cells, cytokines, and their balance in the prognosis and therapy of atherosclerosis.

Circulating miR-206 and Wnt-signaling are associated with cardiovascular complications and a history of preeclampsia in women

Women with a history of preeclampsia (PE) have increased risk of cardiovascular disease (CVD) later in life. However, the molecular determinants underlying this risk remain unclear. We sought to understand how circulating miRNA levels are affected by prior PE, and related to biological pathways underpinning cardiovascular disease. RNA sequencing was used to profile plasma levels of 2578 miRNAs in a retrospective study of women with a history of PE or normotensive pregnancy, in two independent cohorts with either acute coronary syndrome (ACS) (n = 17–18/group) or no ACS (n = 20/group). Differential miRNA alterations were assessed in relation to a history of PE (within each cohort) or ACS (across cohorts), and compared with miRNAs previously reported to be altered during PE. A history of PE was associated with altered levels of 30 and 20 miRNAs in the ACS and non-ACS cohorts, respectively, whereas ACS exposure was associated with alterations in 259 miRNAs. MiR-206 was identified at the intersection of all comparisons relating to past/current PE and ACS exposure, and has previously been implicated in atherogenic activities related to hepatocytes, vascular smooth muscle cells and macrophages. Integration of all differentially altered miRNAs with their predicted and experimentally validated targets in silico revealed a number of highly targeted genes with potential atherogenic functions (including NFAT5, CCND2 and SMAD2), and one significantly enriched KEGG biological pathway (Wnt signaling) that was shared between all exposure groups. The present study provides novel insights into miRNAs, target genes and biological pathways that may underlie the long-term cardiovascular sequelae of PE.

Characterization and Significance of Monocytes in Acute Stanford Type B Aortic Dissection

Acute aortic dissection (AAD) is one of the most common fatal diseases noted in vascular surgery. Human monocytes circulate in dynamic equilibrium and display a considerable heterogeneity. However, the role of monocytes in AAD remains elusive. In our recent study, we firstly obtained blood samples from 22 patients with Stanford type B AAD and 44 age-, sex-, and comorbidity-matched control subjects. And the monocyte proportions were evaluated by flow cytometry. Results showed that the percentage of total CD14⁺ monocytes in the blood samples of Stanford AAD patients was increased significantly compared with that of normal volunteers (P < 0.0005), and the absolute numbers of CD14^brightCD16⁺ and CD14^brightCD16⁻ monocytes both increased significantly regardless of the percentage of PBMC or CD14⁺ cells, while CD14^dimCD16⁺ monocytes displayed the opposite tendency. However, the percentage of CD14⁺ cells and its three subsets demonstrated no correlation with D-dimer (DD) and C-reactive protein (CRP). Then, blood mononuclear cell (PBMC) samples were collected by Ficoll density gradient centrifugation, followed with CD14⁺ magnetic bead sorting. After the purity of CD14⁺ cells was validated over 90%, AAD-related genes were concentrated in CD14⁺ monocytes. There were no significant differences observed with regard to the mRNA expression levels of MMP1 (P = 0.0946), MMP2 (P = 0.3941), MMP9 (P = 0.2919), IL-6 (P = 0.4223), and IL-10 (P = 0.3375) of the CD14⁺ monocytes in Stanford type B AAD patients compared with those of normal volunteers. The expression levels of IL-17 (P < 0.05) was higher in Stanford type B AAD patients, while the expression levels of TIMP1(P<0.05), TIMP2(P<0.01), TGF-β1 (P < 0.01), SMAD3 (P < 0.01), ACTA2 (P < 0.001), and ADAMTS-1 (P < 0.001) decreased. The data suggested that monocytes might play an important role in the development of Stanford type B AAD. Understanding of the production, differentiation, and function of monocyte subsets might dictate future therapeutic avenues for Stanford type B AAD treatment and can aid the identification of novel biomarkers or potential therapeutic targets for decreasing inflammation in AAD.

Inhibition of the ATPase Domain of Human Topoisomerase IIa on HepG2 Cells by 1, 2-benzenedicarboxylic Acid, Mono (2-ethylhexyl) Ester: Molecular Docking and Dynamics Simulations

Background:

The major attention has been received by the natural products in the prevention of diseases due to their pharmacological role.

Objective:

The major focus of the study was to search for highly potential anti-cancer compounds from marine Streptomyces sp. VITJS4 (NCIM No. 5574).

Methods:

Cytotoxic assay was examined by MTT assay on HepG2 cells. Bioassay-guided fractionation of the ethyl acetate extract from the fermented broth led to the isolation of the compound. The lead compound structure was elucidated by combined NMR and MS analysis, and the absolute configuration was assigned by extensive spectroscopic analysis.

Results:

On the basis of spectroscopic data, the compound was identified as 1, 2 benzenedicarboxylic acid, mono 2-ethylhexyl (BMEH). The compound exhibited in vitro anticancer potential against liver (HepG2) cancer cells. Based on the flow cytometric analysis, it was evident that the BMEH was also effective in arresting the cell cycle at G1 phase. Further, the Western blotting analysis confirmed the down-regulation of Bcl-2 family proteins, and activation of caspase-9 and 3. The molecular docking and dynamics simulation were performed to reveal the activity of the compound over a time period of 10ns. From the molecular dynamics studies, it was found that the stability and compactness were attained by the protein by means of the compound interaction.

Conclusion:

This study highlights our collaborative efforts to ascertain lead molecules from marine actinomycete. This is the first and foremost report to prove the mechanistic studies of the purified compound 1, 2-benzene dicarboxylic acid, mono(2-ethylhexyl) ester isolated from marine Streptomyces sp.VITJS4 against HepG2 cells.

The association between the chromosome 9p21 CDKN2B-AS1 gene variants and the lipid metabolism: A pre-diagnostic biomarker for coronary artery disease

Objective:

Recent genome-wide association studies have established that polymorphisms within CDKN2B-AS1 of chr9p21.3 locus increased susceptibility to coronary artery disease (CAD) or myocardial infarction. Common variants of CDKN2B-AS1 (including rs4977574 A>G and rs1333040 C>T) are determined to be directly associated with CADs in many populations worldwide and suggested biomarkers for the early detection of CAD. There is a lack of investigation for the association between CDKN2B-AS1 rs4977574 A>G and rs1333040 C>T genetic modifiers and CAD in a Turkish Cypriot population. The aim of the present study was to investigate the potential effects of these variants on susceptibility to developing CAD in a Turkish Cypriot population and their contribution to lipid metabolism.

Methods:

Seventy-one patients with angiography-confirmed CAD were recruited to the CAD group, whereas 153 voluntary subjects without CAD symptoms were enrolled to the control group. Genotyping for the CDKN2B-AS1 gene polymorphisms was performed by polymerase chain reaction, followed by restriction fragment length polymorphism analysis.

Results:

There is no statistical significant association observed between rs4977574 and rs1333040 single-nucleotide polymorphisms and two studied groups [odds ratio (OR): 0.763, p=0.185, 95% confidence interval (CI): 0.511–1.139 and OR: 1.060, p=0.802, 95% CI 0.672–1.671, respectively]. However, rs2977574 G and rs1333040 T alleles–the risk alleles–were found to be associated with higher level of serum total cholesterol and lower level of high-density lipoprotein-cholesterol in the CAD group (p=0.019, p=0.006 and p=0.022, p=0.031, respectively). To our knowledge, this is the first study that establishes the effect of rs1333040 on lipid metabolism.

Conclusion:

The presence of rs4977574 G and rs1333040 T alleles and interaction may exist as environmental factors associated with lipid metabolism and might be responsible for the development of CAD in a Turkish Cypriot population.

A review on coronary artery disease, its risk factors, and therapeutics

Coronary artery disease (CAD) is one of the major cardiovascular diseases affecting the global human population. This disease has been proved to be the major cause of death in both the developed and developing countries. Lifestyle, environmental factors, and genetic factors pose as risk factors for the development of cardiovascular disease. The prevalence of risk factors among healthy individuals elucidates the probable occurrence of CAD in near future. Genome-wide association studies have suggested the association of chromosome 9p21.3 in the premature onset of CAD. The risk factors of CAD include diabetes mellitus, hypertension, smoking, hyperlipidemia, obesity, homocystinuria, and psychosocial stress. The eradication and management of CAD has been established through extensive studies and trials. Antiplatelet agents, nitrates, β-blockers, calcium antagonists, and ranolazine are some of the few therapeutic agents used for the relief of symptomatic angina associated with CAD.

TGF-β Signaling in Control of Cardiovascular Function

Genetic studies in animals and humans indicate that gene mutations that functionally perturb transforming growth factor β (TGF-β) signaling are linked to specific hereditary vascular syndromes, including Osler-Rendu-Weber disease or hereditary hemorrhagic telangiectasia and Marfan syndrome. Disturbed TGF-β signaling can also cause nonhereditary disorders like atherosclerosis and cardiac fibrosis. Accordingly, cell culture studies using endothelial cells or smooth muscle cells (SMCs), cultured alone or together in two- or three-dimensional cell culture assays, on plastic or embedded in matrix, have shown that TGF-β has a pivotal effect on endothelial and SMC proliferation, differentiation, migration, tube formation, and sprouting. Moreover, TGF-β can stimulate endothelial-to-mesenchymal transition, a process shown to be of key importance in heart valve cushion formation and in various pathological vascular processes. Here, we discuss the roles of TGF-β in vasculogenesis, angiogenesis, and lymphangiogenesis and the deregulation of TGF-β signaling in cardiovascular diseases.

Bone Morphogenetic Proteins in Vascular Homeostasis and Disease

It is well established that control of vascular morphogenesis and homeostasis is regulated by vascular endothelial growth factor (VEGF), fibroblast growth factor (FGF), Delta-like 4 (Dll4), angiopoietin, and ephrin signaling. It has become clear that signaling by bone morphogenetic proteins (BMPs), which have a long history of studies in bone and early heart development, are also essential for regulating vascular function. Indeed, mutations that cause deregulated BMP signaling are linked to two human vascular diseases, hereditary hemorrhagic telangiectasia and pulmonary arterial hypertension. These observations are corroborated by data obtained with vascular cells in cell culture and in mouse models. BMPs are required for normal endothelial cell differentiation and for venous/arterial and lymphatic specification. In adult life, BMP signaling orchestrates neo-angiogenesis as well as vascular inflammation, remodeling, and calcification responses to shear and oxidative stress. This review emphasizes the pivotal role of BMPs in the vascular system, based on studies of mouse models and human vascular disorders.

Differential regulations of fibronectin and laminin in Smad2 activation in vascular endothelial cells in response to disturbed flow

BACKGROUND

Atherosclerosis occurs in arterial curvatures and branches, where the flow is disturbed with low and oscillatory shear stress (OSS). The remodeling and alterations of extracellular matrices (ECMs) and their composition is the critical step in atherogenesis. In this study, we investigated the effects of different ECM proteins on the regulation of mechanotransduction in vascular endothelial cells (ECs) in response to OSS.

METHODS

Through the experiments ranging from in vitro cell culture studies on effects of OSS on molecular signaling to in vivo examinations on clinical specimens from patients with coronary artery disease (CAD), we elucidated the roles of integrins and different ECMs, i.e., fibronectin (FN) and laminin (LM), in transforming growth factor (TGF)-β receptor (TβR)-mediated Smad2 activation and nuclear factor-κB (NF-κB) signaling in ECs in response to OSS and hence atherogenesis.

RESULTS

OSS at 0.5±12 dynes/cm² induces sustained increases in the association of types I and II TβRs with β1 and β3 integrins in ECs grown on FN, but it only transient increases in ECs grown on LM. OSS induces a sustained activation of Smad2 in ECs on FN, but only a transient activation of Smad2 in ECs on LM. OSS-activation of Smad2 in ECs on FN regulates downstream NF-κB signaling and pro-inflammatory gene expression through the activation of β1 integrin and its association with TβRs. In contrast, OSS induces transient activations of β1 and β3 integrins in ECs on LM, which associate with type I TβR to regulate Smad2 phosphorylation, resulting in transient induction of NF-κB and pro-inflammatory gene expression. In vivo investigations on diseased human coronary arteries from CAD patients revealed that Smad2 is highly activated in ECs of atherosclerotic lesions, which is accompanied by the concomitant increase of FN rather than LM in the EC layer and neointimal region of atherosclerotic lesions.

CONCLUSIONS

Our findings provide new insights into the mechanisms of how OSS regulates Smad2 signaling and pro-inflammatory genes through the complex signaling networks of integrins, TβRs, and ECMs, thus illustrating the molecular basis of regional pro-inflammatory activation within disturbed flow regions in the arterial tree.

Selenium modulates MMP2 expression through the TGFβ1/Smad signalling pathway in human umbilical vein endothelial cells and rabbits following lipid disturbance

BACKGROUND

A high-fat diet is a major risk factor for coronary heart diseases. Matrix metalloprotease (MMP) expression is changed in many cardiovascular diseases. Selenium, which is an important trace element in animals, has a close relationship with cardiovascular diseases. The TGFβ1/Smad signalling pathway is ubiquitous in diverse tissues and cells, and it is also associated with the occurrence and development of cardiovascular diseases. Therefore, in this study, we aimed to determine selenium's effect on lipid metabolism, atherosclerotic plaque formation, and MMP2 expression, as well as the underlying functional mechanism.

METHODS AND RESULTS

In vivo tests: 24 male New Zealand white rabbits were randomly divided into 4 groups: regular diet, high-fat diet, high-fat diet+selenium and regular diet+selenium groups. The high-fat diet induced the lipid disturbances of rabbits at week 12. Selenium supplementation lowered total cholesterol (TC), low-density lipoprotein cholesterol (LDL-C) and triglyceride (TG) levels (p<0.01). Selenium supplementation also suppressed MMP2 over-expression in thoracic aortas. In vitro tests: Human umbilical vein endothelial cells (HUVECs) were treated with different concentrations of selenium or ox-LDL. Ox-LDL promoted MMP2 expression by increasing TGFβ1, pSmad2, pSmad3 and Smad3 expression (p<0.01). Selenium attenuated MMP2 over-expression by regulating the TGFβ1/Smad signalling pathway.

CONCLUSIONS

Selenium suppressed high-fat diet-induced MMP2 over-expression in vivo by improving lipid metabolism. In vitro, selenium attenuated MMP2 over-expression through the TGFβ1/Smad signalling pathway.

TGF-β1-induced differentiation of SHED into functional smooth muscle cells

BACKGROUND

Adequate vascularization is crucial for supplying nutrition and discharging metabolic waste in freshly transplanted tissue-engineered constructs. Obtaining the appropriate building blocks for vascular tissue engineering (i.e. endothelial and mural cells) is a challenging task for tissue neovascularization. Hence, we investigated whether stem cells from human exfoliated deciduous teeth (SHED) could be induced to differentiate into functional vascular smooth muscle cells (vSMCs).

METHODS

We utilized two cytokines of the TGF-β family, transforming growth factor beta 1 (TGF-β1) and bone morphogenetic protein 4 (BMP4), to induce SHED differentiation into SMCs. Quantitative real-time polymerase chain reaction (RT-qPCR) was used to assess mRNA expression, and protein expression was analyzed using flow cytometry, western blot and immunostaining. Additionally, to examine whether these SHED-derived SMCs possess the same function as primary SMCs, in vitro Matrigel angiogenesis assay, fibrin gel bead assay, and functional contraction study were used here.

RESULTS

By analyzing the expression of specific markers of SMCs (α-SMA, SM22α, Calponin, and SM-MHC), we confirmed that TGF-β1, and not BMP4, could induce SHED differentiation into SMCs. The differentiation efficiency was relatively high (α-SMA+ 86.1%, SM22α+ 93.9%, Calponin+ 56.8%, and SM-MHC+ 88.2%) as assessed by flow cytometry. In vitro Matrigel angiogenesis assay showed that the vascular structures generated by SHED-derived SMCs and human umbilical vein endothelial cells (HUVECs) were comparable to primary SMCs and HUVECs in terms of vessel stability. Fibrin gel bead assay showed that SHED-derived SMCs had a stronger capacity for promoting vessel formation compared with primary SMCs. Further analyses of protein expression in fibrin gel showed that cultures containing SHED-derived SMCs exhibited higher expression levels of Fibronectin than the primary SMCs group. Additionally, it was also confirmed that SHED-derived SMCs exhibited functional contractility. When SB-431542, a specific inhibitor of ALK5 was administered, TGF-β1 stimulation could not induce SHED into SMCs, indicating that the differentiation of SHED into SMCs is somehow related to the TGF-β1-ALK5 signaling pathway.

CONCLUSIONS

SHED could be successfully induced into functional SMCs for vascular tissue engineering, and this course could be regulated through the ALK5 signaling pathway. Hence, SHED appear to be a promising candidate cell type for vascular tissue engineering.

Variants in 9p21 Predicts Severity of Coronary Artery Disease in a Chinese Han Population

Recent genome-wide association studies identified the common genetic variants in 9p21 were associated with the coronary artery disease (CAD). However, whether this locus could predict the severity of CAD in Chinese Han population is unclear. 499 CAD patients who underwent coronary angiography (CAG) have been enrolled for this study. The single-nucleotide polymorphisms rs2383207 and rs2383206 in 9p21 were genotyped in 499 CAG cases and 1519 controls in Chinese Han population. The gene dosage of 9p21 was stratified by the degree of vascular lesions and tested for association with the severity of CAD. Rs2383207 and rs2383206 demonstrated significant associations with 2-vessel and 3-vessel disease (P = 2.0×10(-3) and 1.9×10(-4) , respectively). GG genotypes of rs2383206 occurred higher proportion of left main trunk (LM) disease (P = 6.0×10(-3) ). GG genotypes of rs2383207 occurred higher proportion of left anterior descending artery disease (LAD) and right CAD (RCA) (P = 2.7×10(-6) and 1.6×10(-4) , respectively). The risk allele G of rs2383207 was associated with severity of CAD estimated by the Gensini score (P = 3.6×10(-5) ). Rs2383207 may strongly influence the development of CAD in Chinese Han population. The gene dosage in 9p21 could predict the severity of CAD.

Functional Analysis of a Novel Genome-Wide Association Study Signal in SMAD3 That Confers Protection From Coronary Artery Disease

OBJECTIVE

A recent genome-wide association study meta-analysis identified an intronic single nucleotide polymorphism in SMAD3, rs56062135C>T, the minor allele (T) which associates with protection from coronary artery disease. Relevant to atherosclerosis, SMAD3 is a key contributor to transforming growth factor-β pathway signaling. Here, we seek to identify ≥1 causal coronary artery disease-associated single nucleotide polymorphisms at the SMAD3 locus and characterize mechanisms whereby the risk allele(s) contribute to coronary artery disease risk.

APPROACH AND RESULTS

By genetic and epigenetic fine mapping, we identified a candidate causal single nucleotide polymorphism rs17293632C>T (D', 0.97; r(2), 0.94 with rs56062135) in intron 1 of SMAD3 with predicted functional effects. We show that the sequence encompassing rs17293632 acts as a strong enhancer in human arterial smooth muscle cells. The common allele (C) preserves an activator protein (AP)-1 site and enhancer function, whereas the protective (T) allele disrupts the AP-1 site and significantly reduces enhancer activity (P<0.001). Pharmacological inhibition of AP-1 activity upstream demonstrates that this allele-specific enhancer effect is AP-1 dependent (P<0.001). Chromatin immunoprecipitation experiments reveal binding of several AP-1 component proteins with preferential binding to the (C) allele. We show that rs17293632 is an expression quantitative trait locus for SMAD3 in blood and atherosclerotic plaque with reduced expression of SMAD3 in carriers of the protective allele. Finally, siRNA knockdown of SMAD3 in human arterial smooth muscle cells increases cell viability, consistent with an antiproliferative role.

CONCLUSIONS

The coronary artery disease-associated rs17293632C>T single nucleotide polymorphism represents a novel functional cis-acting element at the SMAD3 locus. The protective (T) allele of rs17293632 disrupts a consensus AP-1 binding site in a SMAD3 intron 1 enhancer, reduces enhancer activity and SMAD3 expression, altering human arterial smooth muscle cell proliferation.

Reactive Oxygen Species Can Provide Atheroprotection via NOX4-Dependent Inhibition of Inflammation and Vascular Remodeling

Objective—

Oxidative stress is considered a hallmark of atherosclerosis. In particular, the superoxide-generating type 1 NADPH oxidase (NOX1) has been shown to be induced and play a pivotal role in early phases of mouse models of atherosclerosis and in the context of diabetes mellitus. Here, we investigated the role of the most abundant type 4 isoform (NOX4) in human and mouse advanced atherosclerosis.

Approach and Results—

Plaques of patients with cardiovascular events or established diabetes mellitus showed a surprising reduction in expression of the most abundant but hydrogen peroxide (H 2 O 2 )-generating type 4 isoform (Nox4), whereas Nox1 mRNA was elevated, when compared with respective controls. As these data suggested that NOX4-derived reactive oxygen species may convey a surprisingly protective effect during plaque progression, we examined a mouse model of accelerated and advanced diabetic atherosclerosis, the streptozotocin-treated ApoE −/− mouse, with ( NOX4 −/− ) and without genetic deletion of Nox4. Similar to the human data, advanced versus early plaques of wild-type mice showed reduced Nox4 mRNA expression. Consistent with a rather protective role of NOX4-derived reactive oxygen species, NOX4 −/− mice showed increased atherosclerosis when compared with wild-type mice. Deleting NOX4 was associated with reduced H 2 O 2 forming activity and attenuation of the proinflammatory markers, monocyte chemotratic protein-1, interleukin-1β, and tumor necrosis factor-α, as well as vascular macrophage accumulation. Furthermore, there was a greater accumulation of fibrillar collagen fibres within the vascular wall and plaque in diabetic Nox4 −/− ApoE −/− mice, indicative of plaque remodeling. These data could be replicated in human aortic endothelial cells in vitro, where Nox4 overexpression increased H 2 O 2 and reduced the expression of pro-oxidants and profibrotic markers. Interestingly, Nox4 levels inversely correlated with Nox2 gene and protein levels. Although NOX2 is not constitutively active unlike NOX4 and forms rather superoxide, this opens up the possibility that at least some effects of NOX4 deletion are mediated by NOX2 activation.

Conclusions—

Thus, the appearance of reactive oxygen species in atherosclerosis is apparently not always a nondesirable oxidative stress, but can also have protective effects. Both in humans and in mouse, the H 2 O 2 -forming NOX4, unlike the superoxide-forming NOX1, can act as a negative modulator of inflammation and remodeling and convey atheroprotection. These results have implications on how to judge reactive oxygen species formation in cardiovascular disease and need to be considered in the development of NOX inhibitory drugs.

Foam Cell Formation In Vivo Converts Macrophages to a Pro-Fibrotic Phenotype

Formation of foam cell macrophages, which sequester extracellular modified lipids, is a key event in atherosclerosis. How lipid loading affects macrophage phenotype is controversial, with evidence suggesting either pro- or anti-inflammatory consequences. To investigate this further, we compared the transcriptomes of foamy and non-foamy macrophages that accumulate in the subcutaneous granulomas of fed-fat ApoE null mice and normal chow fed wild-type mice in vivo. Consistent with previous studies, LXR/RXR pathway genes were significantly over-represented among the genes up-regulated in foam cell macrophages. Unexpectedly, the hepatic fibrosis pathway, associated with platelet derived growth factor and transforming growth factor-β action, was also over-represented. Several collagen polypeptides and proteoglycan core proteins as well as connective tissue growth factor and fibrosis-related FOS and JUN transcription factors were up-regulated in foam cell macrophages. Increased expression of several of these genes was confirmed at the protein level in foam cell macrophages from subcutaneous granulomas and in atherosclerotic plaques. Moreover, phosphorylation and nuclear translocation of SMAD2, which is downstream of several transforming growth factor-β family members, was also detected in foam cell macrophages. We conclude that foam cell formation in vivo leads to a pro-fibrotic macrophage phenotype, which could contribute to plaque stability, especially in early lesions that have few vascular smooth muscle cells.

Small-nucleic-acid-based therapeutic strategy targeting the transcription factors regulating the vascular inflammation, remodeling and fibrosis in atherosclerosis

Atherosclerosis arises when injury to the arterial wall induces an inflammatory cascade that is sustained by a complex network of cytokines, together with accumulation of lipids and fibrous material. Inflammatory cascades involve leukocyte adherence and chemotaxis, which are coordinated by the local secretion of adhesion molecules, chemotactic factors, and cytokines. Transcription factors are critical to the integration of the various steps of the cascade response to mediators of vascular injury, and are induced in a stimulus-dependent and cell-type-specific manner. Several small-nucleic-acid-based therapeutic strategies have recently been developed to target transcription factors: antisense oligodeoxynucleotides, RNA interference, microRNA, and decoy oligodeoxynucleotides. The aim of this review was to provide an overview of these particular targeted therapeutic strategies, toward regulation of the vascular inflammation, remodeling and fibrosis associated with atherosclerosis.

Polymorphism of 9p21.3 locus is associated with 5-year survival in high-risk patients with myocardial infarction

Objective

The rs10757278, rs1333049 and rs4977574 are single nucleotide polymorphisms (SNPs) of chromosome 9p21 locus associated with a prevalence of acute coronary syndromes (ACS). Reports concerning their association with long-term outcome after an ACS are equivocal. The aim of our study was to investigate the association of the 9p21.3 locus with 5-year overall mortality in patients with ST-elevation myocardial infarction (STEMI).

Materials and methods

We performed a retrospective analysis of data collected prospectively in 2 independent registries of consecutive patients with STEMI (derivation and validation group). Genotyping was performed with the TaqMan method. The analyzed end-point was total mortality.

Results

The derivation group comprised 589 patients: 25.3% female (n = 149), mean age 62.4±12.0 years, total 5-year mortality 16.6% (n = 98). When all the study group was analyzed, no significant differences in mortality were found between the genotypes. However, in high-risk patients (GRACE risk score ≥155 points, n = 238), homozygotes associated with higher risk for ACS had significantly better 5-year survival compared to other genotypes. The hazard ratio associated with the high-risk genotype (a homozygote of high risk for ACS or a heterozygote) was: HR = 2.2 (1.15–4.2) for the rs10757278 polymorphism, HR = 2.7 (95% CI 1.3–5.4) for the rs4977574 one and HR = 2.3 (1.2–4.5) for the rs1333049 one (Cox proportional hazards model). Survival analysis in the validation group (n = 365) showed a clear trend towards better prognosis in GG homozygotes of the rs10757278 SNP, which confirms our initial results (p = 0.09, log-rank test).

Conclusions

The 9p21.3 locus is associated with 5-year mortality in high-risk patients with STEMI. The genotypes associated with higher risk for ACS show a protective effect in terms of further survival (instead of a deteriorating prognosis, as reported previously). This finding, due to the very high size of the effect, could potentially be applied to clinical practice, if appropriate methods are elaborated.

TGF-β/Smad signaling pathway regulates Th17/Treg balance during Echinococcus multilocularis infection

Alveolar echinococcosis (AE) is a severe parasitic disease caused by the infection of Echinococcus multilocularis (Em). Very little is known on the relationship between TGF-β/Smad signaling pathway and Treg/Th17 balance in the infected liver at different periods after Em infection. Using qRT-PCR, immunohistochemistry, flow cytometry and CBA assay, we measured the expression levels of TGF-β, Smad2/3/7, ROR-γt, Foxp3, IL-17, IL-10 and percentages of Th17 cells and Treg cells in mouse AE model, from day 2 to day 270 after infection. In the early stage of infection (day 2 to day 30), Smad7 was up-regulated and the TGF-β pathway was inactivated. In the middle stage of infection (day 30 to day 90), TGF-β and Smad2/3 were up-regulated. And levels of Treg cells, Foxp3, Th17 cells, RORγt, IL-17, IL-10 and IL-6 were significantly increased. In the late stage of infection (day 90 to day 270), Treg cells, Foxp3, TGF-β and IL-10 maintained at high levels whereas Th17 cells and IL-17 decreased significantly. TGF-β/Smad signaling pathway was activated during the chronic infection. Our data suggest that there were Treg/Th17 imbalance in the middle and especially in the late stage of Em infection and that Treg/Th17 imbalance may be regulated by TGF-β/Smad signaling pathway. Treg and Th17 subsets may be involved in regulating immune tolerance and tissue inflammation, and facilitating the long-term survival of Em in the host.

Identifying functional modules for coronary artery disease by a prior knowledge-based approach

Until recently, the underlying genetic mechanisms for coronary artery disease (CAD) have been largely unknown, with just a list of genes identified accounting for very little of the disease in the population. Hence, a systematic dissection of the sophisticated interplays between these individual disease genes and their functional involvements becomes essential. Here, we presented a novel knowledge-based approach to identify the functional modules for CAD. First, we selected 266 disease genes in CADgene database as the initial seed genes, and used PPI knowledge as a guide to expand these genes into a CAD-specific gene network. Then, we used Newman's algorithm to decompose the primary network into 14 compact modules with high modularity. By analysis of these modules, we further identified 114 hub genes, all either directly or indirectly associated with CAD. Finally, by functional analysis of these modules, we revealed several novel pathogenic mechanisms for CAD (for examples, some yet rarely concerned like peptide YY receptor activity, Fc gamma R-mediated phagocytosis and actin cytoskeleton regulation etc.).

Polymorphism of 9p21.3 locus is associated with 5-year survival in high-risk patients with myocardial infarction

OBJECTIVE

The rs1333049, rs10757278 and rs4977574 are single nucleotide polymorphisms (SNPs) of chromosome 9p21 locus that are associated with prevalence of acute coronary syndromes (ACS). The rs1333049 SNP was also associated with cardiac outcome 6 months post ACS. No data concerning their association with long term prognosis after myocardial infarction is available. The aim of our study was to investigate the association of the 9p21.3 locus with 5-year overall mortality in patients with ST-elevation myocardial infarction (STEMI) treated invasively.

MATERIALS AND METHODS

We performed a retrospective analysis of data collected prospectively in a registry of consecutive patients with STEMI treated with primary PCI. Genotyping was performed with a TaqMan method. The analyzed end-point was total 5-year mortality.

RESULTS

The study group comprised 589 patients: 25.3% of females (n = 149), mean age 62.4±11.9 years, total 5-year mortality 16.6% (n = 98). When all the study group was analyzed, no significant differences in mortality were found between the genotypes. However, in high-risk patients (Grace risk score ≥155 points, n = 238), low-risk homozygotes had significantly better 5-year survival compared to other genotypes. The hazard ratio associated with high-risk genotype (high-risk homozygote or heterozygote) was: HR = 2.9 (95%CI 1.4-6.1) for the rs4977574 polymorphism, HR = 2.6 (1.25-5.3) for the rs1333049 one and HR = 2.35 (1.2-4.6) for the rs10757278 one (Cox proportional hazards model).

CONCLUSIONS

The 9p21.3 locus is associated with 5-year mortality in high-risk patients with STEMI. This finding, due to very high effect size, could potentially be applied into clinical practice, if appropriate methods are elaborated.

Association of arterial stiffness with single nucleotide polymorphism rs1333049 and metabolic risk factors

Background

Increased arterial stiffness is a cardiovascular outcome of metabolic syndrome (MetS). The chromosome 9p21 locus has been identified as a major locus for risk of coronary artery disease (CAD). The single nucleotide polymorphism (SNP), rs1333049 on chromosome 9p21.3 has been strongly associated with CAD and myocardial infarction. Increased arterial stiffness could be the link between the 9p21 polymorphism and increased cardiovascular risk. Since the impact of a genetic polymorphism on arterial stiffness especially in Asian populations has not been well defined, we aimed to investigate the association of arterial stiffness with rs 1333049 variant on chromosome 9p21.3 in Thai subjects with and without MetS risk factors.

Methods

A total of 208 Thai subjects, aged 35–75 years, 135 with and 73 without MetS, according to IDF and NCEP-ATPIII criteria, were included in this study. Aortic-femoral pulse wave velocity (afPWV), brachial-ankle pulse wave velocity (baPWV) and aortic ankle pulse wave velocity (aaPWV) were measured and used as markers of arterial stiffness. The chromosome 9p21.3 locus, represented by the rs 1333049 variant and blood biochemistry were evaluated.

Results

Arterial stiffness was elevated in subjects with MetS when compared with nonMetS subjects. PWV, especially afPWV increased progressively with increasing number of MetS risk factors (r = 0.322, P <0.001). We also found that the frequency distribution of the rs1333049 genotypes is significantly associated with the afPWV (P <0.05). In multivariate analyses, there was an association between homozygous C allele and afPWV (Odds ratio (OR), 8.16; 95% confidence interval (CI), 1.91 to 34.90; P = 0.005), while the GC genotype was not related to afPWV (OR, 1.79; 95% CI, 0.84 to 3.77; P = 0.129) when compared with the GG genotype.

Conclusions

Our findings demonstrate for the first time that arterial stiffness is associated with genetic polymorphism in 9p21 and metabolic risk factors in a Thai population.

Assessment of the 9p21.3 locus in severity of coronary artery disease in the presence and absence of type 2 diabetes

BACKGROUND

The 9p21.3 locus is strongly associated with the risk of coronary artery disease (CAD) and with type 2 diabetes (T2D). We investigated the association of 9p21.3 variants with severity of CAD (defined by the number of vessel diseased [VD]) in the presence and absence of T2D.

METHODS

We tested 11 9p21.3-variants for association in a white Italian study (N = 2,908), and carried out replication in 2 independent white populations, a German study (N = 2,028) and a Canadian Study (N=950). SNP association and permutation analyses were conducted.

RESULTS

We identified two 9p21.3-variants, rs4977574 (P < 4×10(-4)) and rs2383207 (P < 1.5×10(-3)) that were associated with severity of CAD in subjects without T2D. Association of rs4977574 with severity of CAD was confirmed in the Canadian Study. Results from subgroup analysis among patients with T2D showed an interaction between rs10738610 and T2D with P = 4.82×10(-2). Further investigation showed that rs10738610 (P < 1.99×10(-2)) was found to be significantly associated with severity of CAD in subjects with T2D.

CONCLUSIONS

The 9p21.3 locus is significantly associated with severity of CAD. The number of associations of 9p21.3 variants with severity of CAD is variable to the presence and absence of T2D. In a CAD-susceptible region of 115 kb, there is only one variant associated with the severity of coronary vessel disease in the presence of type 2 diabetes.

The complex regulation of TGF-β in cardiovascular disease

Transforming growth factor β (TGF-β1) is a pleiotropic cytokine with many and complex effects in cell and tissue physiology. This is made possible by a very complex and interwoven signaling system, whose regulation continues to be the focus of a growing line of research. This complex regulation translates to a key role in cardiovascular physiology, hemostasis, and the blood–vessel interface. In accordance with this, the TGF-β1 pathway appears to be deregulated in related disorders, such as atherosclerotic vascular disease and myeloproliferative syndromes. It is expected that the growing amount of experimental and clinical research will yield medical advances in the applications of knowledge of the TGF-β1 pathway to diagnosis and therapeutics.

TGF-β inhibits the uptake of modified low density lipoprotein by human macrophages through a Smad-dependent pathway: a dominant role for Smad-2

The anti-atherogenic cytokine, TGF-β, plays a key role during macrophage foam cell formation by modulating the expression of key genes involved in the control of cholesterol homeostasis. Unfortunately, the molecular mechanisms underlying these actions of TGF-β remain poorly understood. In this study we examine the effect of TGF-β on macrophage cholesterol homeostasis and delineate the role of Smads-2 and ‐3 during this process. Western blot analysis showed that TGF-β induces a rapid phosphorylation-dependent activation of Smad-2 and ‐3 in THP-1 and primary human monocyte-derived macrophages. Small interfering RNA-mediated knockdown of Smad-2/3 expression showed that the TGF-β-mediated regulation of key genes implicated in the uptake of modified low density lipoproteins and the efflux of cholesterol from foam cells was Smad-dependent. Additionally, through the use of virally delivered Smad-2 and/or Smad-3 short hairpin RNA, we demonstrate that TGF-β inhibits the uptake of modified LDL by macrophages through a Smad-dependent mechanism and that the TGF-β-mediated regulation of CD36, lipoprotein lipase and scavenger receptor-A gene expression was dependent on Smad-2. These studies reveal a crucial role for Smad signaling, particularly Smad-2, in the inhibition of foam cell formation by TGF-β through the regulation of expression of key genes involved in the control of macrophage cholesterol homeostasis.

TGFβ signaling and cardiovascular diseases

Transforming growth factor β (TGFβ) family members are involved in a wide range of diverse functions and play key roles in embryogenesis, development and tissue homeostasis. Perturbation of TGFβ signaling may lead to vascular and other diseases. In vitro studies have provided evidence that TGFβ family members have a wide range of diverse effects on vascular cells, which are highly dependent on cellular context. Consistent with these observations genetic studies in mice and humans showed that TGFβ family members have ambiguous effects on the function of the cardiovascular system. In this review we discuss the recent advances on TGFβ signaling in (cardio)vascular diseases, and describe the value of TGFβ signaling as both a disease marker and therapeutic target for (cardio)vascular diseases.

Genetic mechanisms mediating atherosclerosis susceptibility at the chromosome 9p21 locus

Recent genome-wide association studies have demonstrated that common genetic variants in a region of chromosome 9p21 confer risk of coronary artery disease (CAD) and other atherosclerotic conditions. Although the absolute increase in risk is small (some 20-30% increase in risk of CAD per copy of the deleterious alleles), the common occurrence of the variants means that their effect on the population risk of disease is estimated to be substantial. Studies investigating the relationship between risk variants and both "classical" and "emerging" atherosclerotic risk factors have found no evidence of association. This suggests that the effect of the 9p21 locus on atherosclerotic risk is mediated via a hitherto unknown pathway potentially amenable to therapeutic modulation. Investigation of potential disease mechanisms at this locus is therefore a focus of intense interest. In this review, we discuss the progress that has been made in the study of mechanisms and highlight the outstanding research questions.

Mechanisms of TGF-β-induced differentiation in human vascular smooth muscle cells

BACKGROUND

Transforming growth factor-β (TGF-β) plays an important role in vascular homeostasis through effects on vascular smooth muscle cells (SMC). Fine-tuning of TGF-β signaling occurs at the level of ALK receptors or Smads, and is regulated with cell type specificity.

METHODS

Our goal was to understand TGF-β signaling in regulating SMC differentiation marker expression in human SMC. Activation of Smads was characterized, and loss- and gain-of-function reagents used to define ALK pathways. In addition, Smad-independent mechanisms were determined.

RESULTS

TGF-β type I receptors, ALK1 and ALK5, are expressed in human SMC, and TGF-β1 phosphorylates Smad1/5/8 and Smad2/3 in a time- and dosage-dependent pattern. ALK5 activity, not bone morphogenetic protein type I receptors, is required for Smad phosphorylation. Endoglin, a TGF-β type III receptor, is a TGF-β1 target in SMC, yet endoglin does not modify TGF-β1 responsiveness. ALK5, not ALK1, is required for TGF-β1-induction of SMC differentiation markers, and ALK5 signals through an ALK5/Smad3- and MAP kinase-dependent pathway.

CONCLUSION

The definition of the specific signaling downstream of TGF-β regulating SMC differentiation markers will contribute to a better understanding of vascular disorders involving changes in SMC phenotype.

The expression of a disintegrin and metalloproteinase with thrombospondin motifs 4 in human macrophages is inhibited by the anti-atherogenic cytokine transforming growth factor-β and requires Smads, p38 mitogen-activated protein kinase and c-Jun

Atherosclerosis is an inflammatory disorder of the vasculature that is orchestrated by the action of cytokines. Macrophages play a prominent role in all stages of this disease, including foam cell formation, production of reactive oxygen species, modulation of the inflammatory response and the regulation of the stability of atherosclerotic plaques. The role of the matrix metalloproteinase family in the control of plaque stability is well established. A disintegrin and metalloproteinase with thrombospondin motif (ADAMTS) family has been implicated in several diseases and the expression of ADAMTS-4 in macrophages of atherosclerotic lesions has suggested a potential role for this protease in atherosclerosis. However, the action of cytokines on the expression of ADAMTS-4 in macrophages is poorly understood. We have investigated here the effect of transforming growth factor-β (TGF-β) on ADAMTS-4 expression in macrophages along with the regulatory mechanisms underlying its actions. Consistent with the anti-atherogenic role of TGF-β, this cytokine decreased the expression of ADAMTS-4 mRNA and protein in human macrophages. Transient transfection assays showed that the −100 to +10 promoter region contained the minimal TGF-β response elements. Small-interfering RNA-mediated knockdown revealed a critical role for Smads, p38 mitogen-activated protein kinase and c-Jun in the action of TGF-β on ADAMTS-4 mRNA expression. These studies show for the first time that TGF-β inhibits the expression of ADAMTS-4 in human macrophages and identifies the signalling pathways underlying this response. The inhibition of macrophage ADAMTS-4 expression is likely to contribute to the anti-atherogenic, plaque stabilisation action of TGF-β.

Expression of linear and novel circular forms of an INK4/ARF-associated non-coding RNA correlates with atherosclerosis risk

Human genome-wide association studies have linked single nucleotide polymorphisms (SNPs) on chromosome 9p21.3 near the INK4/ARF (CDKN2a/b) locus with susceptibility to atherosclerotic vascular disease (ASVD). Although this locus encodes three well-characterized tumor suppressors, p16^INK4a, p15^INK4b, and ARF, the SNPs most strongly associated with ASVD are ∼120 kb from the nearest coding gene within a long non-coding RNA (ncRNA) known as ANRIL (CDKN2BAS). While individuals homozygous for the atherosclerotic risk allele show decreased expression of ANRIL and the coding INK4/ARF transcripts, the mechanism by which such distant genetic variants influence INK4/ARF expression is unknown. Here, using rapid amplification of cDNA ends (RACE) and analysis of next-generation RNA sequencing datasets, we determined the structure and abundance of multiple ANRIL species. Each of these species was present at very low copy numbers in primary and cultured cells; however, only the expression of ANRIL isoforms containing exons proximal to the INK4/ARF locus correlated with the ASVD risk alleles. Surprisingly, RACE also identified transcripts containing non-colinear ANRIL exonic sequences, whose expression also correlated with genotype and INK4/ARF expression. These non-polyadenylated RNAs resisted RNAse R digestion and could be PCR amplified using outward-facing primers, suggesting they represent circular RNA structures that could arise from by-products of mRNA splicing. Next-generation DNA sequencing and splice prediction algorithms identified polymorphisms within the ASVD risk interval that may regulate ANRIL splicing and circular ANRIL (cANRIL) production. These results identify novel circular RNA products emanating from the ANRIL locus and suggest causal variants at 9p21.3 regulate INK4/ARF expression and ASVD risk by modulating ANRIL expression and/or structure.

Unbiased studies of the human genome have identified strong genetic determinants of atherosclerotic vascular disease (ASVD) on chromosome 9p21.3. This region of the genome does not encode genes previously linked to ASVD, but does contain the INK4/ARF tumor suppressor locus. Products of the INK4/ARF locus regulate cell division, a process thought to be important in ASVD pathology. We and others have suggested that genetic variants in 9p21.3 influence INK4/ARF gene expression; however, the mechanisms by which these distant polymorphisms (>100,000 bp away) influence transcription of the locus is unknown. The ASVD–associated genetic variants lie within the predicted structure of a non-coding RNA (ncRNA) called ANRIL. Based upon recent work suggesting that other ncRNAs can repress nearby coding genes, we considered the possibility that ANRIL structure may regulate INK4/ARF gene expression. Coupling molecular analysis with state-of-the-art sequencing technologies in a wide variety of cell types from normal human donors and cancer cells, we found that ANRIL encodes a heterogeneous species of rare RNA transcripts. Moreover, we identified novel, circular ANRIL isoforms (cANRIL) whose expression correlated with INK4/ARF transcription and ASVD risk. These studies suggest a new model wherein ANRIL structure influences INK4/ARF expression and susceptibility to atherosclerosis.

Forearm vasodilator reactivity in homozygous carriers of the 9p21.3 rs1333049 G>C polymorphism

AIM

Recently, a novel susceptibility locus for coronary artery disease (CAD) has been identified on chromosome 9p21.3, linked to the single-nucleotide polymorphism (SNP) rs1333049 G>C. However, the physiological mechanism through which this locus confers an increased CAD-risk is still unknown. The aim of the present case-control study was to test whether this chromosome 9p21.3 locus, represented by the rs1333049 variant, is associated with altered vasodilator resistance vessel function in healthy young volunteers.

DESIGN AND RESULTS

A total of 97 healthy male volunteers were screened for homozygous carriers of either the G- or the C-allele, the minor allele in European populations. Forearm blood flow (FBF) reactivity to acetylcholine (ACh) and glycerol trinitrate (GTN) was then studied in 10 C/C-genotype carriers compared with 10 control subjects harbouring the G/G-genotype. FBF responses to ACh and GTN were reduced in subjects homozygous for the C-allele of the rs1333049 SNP (P < 0.05). FBF reactivity to the highest dose of ACh and GTN was 95% and 74% lower when compared with control subjects with the G/G-genotype.

CONCLUSION

Our study revealed a functional impairment in forearm artery vasodilator resistance in carriers of the rs1333049 C/C-genotype, thus providing evidence for a first physiological functional link underlying the genetic association of the 9p21.3 locus with an increased cardiovascular risk.

Expression of Chr9p21 genes CDKN2B (p15(INK4b)), CDKN2A (p16(INK4a), p14(ARF)) and MTAP in human atherosclerotic plaque

OBJECTIVE

The pathophysiology underlying the chromosome (Chr) 9p21 locus of atherosclerosis susceptibility is presently unknown. Here, we sought to determine whether protein coding genes in the Chr9p21 region, i.e. cyclin-dependent kinase inhibitors CDKN2B (p15(INK4b)), CDKN2A (p16(INK4a), p14(ARF)) and methylthioadenosine phosphorylase (MTAP) were expressed in human atherosclerotic lesions and whether expression was correlated with lesion composition.

METHODS AND RESULTS

Protein expression of p15(INK4b), p16(INK4a), p14(ARF) and MTAP was demonstrated by immunostaining in normal and atherosclerotic coronary arteries and co-localized with CD68 and smooth muscle alpha-actin positive cells. Quantitative RT-PCR in human endarteryectomy specimens (n = 57) revealed increased p16(INK4a) and decreased MTAP expression in macrophage-rich lesions (P<0.001 and P = 0.007, respectively). Functional studies suggest that decreased MTAP expression in macrophage-rich lesions might be mediated through down-regulation by TNF-alpha. No clear association of p15(INK4b), p16(INK4a), p14(ARF), and MTAP expression in plaque tissue with Chr9p21 haplotypes was found. The latter finding was corroborated by the lack of correlation of RNA expression of 9p21-regulated transcripts EU741058 and NR_003529 of antisense non-coding RNA in the INK4 locus (ANRIL) with mRNA expression of these genes. In contrast, ANRIL DQ485454 which is not genetically determined by the 9p21 genotype was significantly correlated with MTAP expression (P = 0.01).

CONCLUSION

CDKN2B (p15(INK4b)), CDKN2A (p16(INK4a), p14(ARF)), and MTAP are abundantly expressed in atherosclerotic lesions. While expression levels showed no clear association with Chr9p21 genotype, association of high p16(INK4a) and low MTAP expression with a less stable plaque phenotype suggests a more general role of these proteins in atherogenesis.

Genetic variants identified in a European genome-wide association study that were found to predict incident coronary heart disease in the atherosclerosis risk in communities study

In 2007, the Wellcome Trust Case Control Consortium (WTCCC) performed a genome-wide association study in 2,000 British coronary heart disease (CHD) cases and 3,000 controls after genotyping 469,557 single nucleotide polymorphisms (SNPs). Seven variants associated with CHD were initially identified, and 5 SNPs were later found in replication studies. In the current study, the authors aimed to determine whether the 12 SNPs reported by the WTCCC predicted incident CHD through 2004 in a biracial, prospective cohort study (Atherosclerosis Risk in Communities) comprising 15,792 persons aged 45-64 years who had been selected by probability sampling from 4 different US communities in 1987-1989. Cox proportional hazards models with adjustment for age and gender were used to estimate CHD hazard rate ratios (HRRs) over a 17-year period (1,362 cases in whites and 397 cases in African Americans) under an additive genetic model. The results showed that 3 SNPs in whites (rs599839, rs1333049, and rs501120; HRRs were 1.10 (P = 0.044), 1.14 (P < 0.001), and 1.14 (P = 0.030), respectively) and 1 SNP in African Americans (rs7250581; HRR = 1.60, P = 0.05) were significantly associated with incident CHD. This study demonstrates that genetic variants revealed in a case-control genome-wide association study enriched for early disease onset may play a role in the genetic etiology of CHD in the general population.

A common variant at 9p21 is associated with sudden and arrhythmic cardiac death

BACKGROUND

Although a heritable basis for sudden cardiac death (SCD) is suggested by the impact of family history on SCD risk, common genetic determinants have been difficult to identify. We hypothesized that a common variant at chromosome 9p21 related to myocardial infarction would influence SCD risk.

METHODS AND RESULTS

This was a prospective, nested, case-control analysis among individuals of European ancestry enrolled in 6 prospective cohort studies. Study subjects were followed up for development of SCD, and genotypes for rs10757274 were determined for 492 sudden and/or arrhythmic deaths and 1460 controls matched for age, sex, cohort, history of cardiovascular disease, and follow-up time. Conditional logistic regression with fixed-effects meta-analysis assuming an additive model was used to test for associations. When individual study results were combined in the meta-analysis, each increasing copy of the G allele at rs10757274 conferred a significantly elevated age-adjusted odds ratio for SCD of 1.21 (95% confidence interval, 1.04 to 1.40; P=0.01). Controlling for cardiovascular and lifestyle risk factors strengthened these relationships (odds ratio, 1.29 per G-allele copy; 95% confidence interval, 1.09 to 1.53; P=0.003). These results were not materially altered in sensitivity analyses limited to definite SCD, in models that further controlled for the development of interim cardiovascular disease, or when the highly correlated variant rs2383207 was tested.

CONCLUSIONS

The major allele of a single-nucleotide polymorphism previously associated with increased risk of coronary artery disease events is associated with increased risk of SCD in individuals of European ancestry. Study of the mechanism underlying this association may improve our understanding of lethal cardiovascular disease.