Homocysteine inhibits arterial endothelial cell growth through transcriptional downregulation of fibroblast growth factor-2 involving G protein and DNA methylation

Moderate Elevation of Homocysteine Induces Endothelial Dysfunction through Adaptive UPR Activation and Metabolic Rewiring

Elevation of the intermediate amino acid metabolite Homocysteine (Hcy) causes Hyperhomocysteinemia (HHcy), a metabolic disorder frequently associated with mutations in the methionine-cysteine metabolic cycle as well as with nutritional deficiency and aging. The previous literature suggests that HHcy is a strong risk factor for cardiovascular diseases. Severe HHcy is well-established to correlate with vascular pathologies primarily via endothelial cell death. Though moderate HHcy is more prevalent and associated with an increased risk of cardiovascular abnormalities in later part of life, its precise role in endothelial physiology is largely unknown. In this study, we report that moderate elevation of Hcy causes endothelial dysfunction through impairment of their migration and proliferation. We established that unlike severe elevation of Hcy, moderate HHcy is not associated with suppression of endothelial VEGF/VEGFR transcripts and ROS induction. We further showed that moderate HHcy induces a sub-lethal ER stress that causes defective endothelial migration through abnormal actin cytoskeletal remodeling. We also found that sub-lethal increase in Hcy causes endothelial proliferation defect by suppressing mitochondrial respiration and concomitantly increases glycolysis to compensate the consequential ATP loss and maintain overall energy homeostasis. Finally, analyzing a previously published microarray dataset, we confirmed that these hallmarks of moderate HHcy are conserved in adult endothelial cells as well. Thus, we identified adaptive UPR and metabolic rewiring as two key mechanistic signatures in moderate HHcy-associated endothelial dysfunction. As HHcy is clinically associated with enhanced vascular inflammation and hypercoagulability, identifying these mechanistic pathways may serve as future targets to regulate endothelial function and health.

miR-129-5p/FGF2 Axis is Associated with Homocysteine-induced Human Umbilical Vein Endothelial Cell Injury

PURPOSE

Homocysteine (Hcy)-induced endothelial cell injury is a key event in atherosclerosis pathogenesis. In this study, we aimed to explore the mechanisms underlying Hcy-induced endothelial injury by assessing the effects of Hcy on endothelial cell proliferation and the microRNA (miR)-129-5p/fibroblast growth factor 2 (FGF2) axis.

METHODS

Human umbilical vein endothelial cells (HUVECs) were treated with Hcy to construct an endothelial cell injury model. Expression levels of FGF2 in Hcy-induced HUVECs were determined using quantitative real-time polymerase chain reaction and western blotting. An FGF2 overexpression lentiviral vector was constructed to upregulate FGF2 expression in HUVECs via lentivirus transduction. A cell counting kit-8 assay was used to explore the effects of FGF2 overexpression on HUVEC proliferation. An upstream regulatory miRNA was predicted, and its targetbinding relationship with FGF2 was evaluated using a dual-luciferase reporter assay.

RESULTS

We found that FGF2 expression in HUVECs was inhibited by Hcy treatment. Lentivirus transduction led to the overexpression of FGF2 in HUVECs, which significantly reversed the effect of Hcy on endothelial cell proliferation. miR-129-5p was experimentally validated as an upstream regulator of FGF2, and its decreased levels in HUVECs led to increased FGF2 expression. In addition, HUVEC proliferation was enhanced by the knockdown of miR-129-5p, and this effect was reversed by Hcy treatment.

CONCLUSION

Taken together, the results of this study revealed that Hcy inhibits FGF2 expression in HUVECs, and FGF2 is regulated by upstream miR-129-5p to improve the effect of Hcy on endothelial cell proliferation.

Role of hydrogen sulphide in physiological and pathological angiogenesis

The role of hydrogen sulphide (H₂ S) in angiogenesis has been widely demonstrated. Vascular endothelial growth factor (VEGF) plays an important role in H₂ S-induced angiogenesis. H₂ S promotes angiogenesis by upregulating VEGF via pro-angiogenic signal transduction. The involved signalling pathways include the mitogen-activated protein kinase pathway, phosphoinositide-3 kinase pathway, nitric oxide (NO) synthase/NO pathway, signal transducer and activator of transcription 3 (STAT3) pathway, and adenosine triphosphate (ATP)-sensitive potassium (K_ATP ) channels. H₂ S has been shown to contribute to tumour angiogenesis, diabetic wound healing, angiogenesis in cardiac and cerebral ischaemic tissues, and physiological angiogenesis during the menstrual cycle and pregnancy. Furthermore, H₂ S can exert an anti-angiogenic effect by inactivating Wnt/β-catenin signalling or blocking the STAT3 pathway in tumours. Therefore, H₂ S plays a double-edged sword role in the process of angiogenesis. The regulation of H₂ S production is a promising therapeutic approach for angiogenesis-associated diseases. Novel H₂ S donors and/or inhibitors can be developed in the treatment of angiogenesis-dependent diseases.

Elevated Homocysteine Levels Predict Hospital-Acquired Pneumonia and Poor Functional Outcomes in Primary Intracerebral Hemorrhage

Background

Homocysteine (Hcy) has been extensively acknowledged to be correlated with inflammation. In this study, the relationship between Hcy and hospital-acquired pneumonia (HAP) in primary intracerebral hemorrhage (pICH) was explored.

Methods

We conducted a hospital-based study on screened eligible patients with primary intracerebral hemorrhage admitted within 24 h after symptom onset from January 2019 to June 2021. The associations between Hcy and HAP and poor outcomes in pICH were investigated using univariate and multivariate logistic regression analyses. The predictive accuracy of Hcy was assessed by the receiver operating characteristic curve and the optimal cutoff value of Hcy was determined by Youden Index. The patterns and magnitudes of associations between Hcy and HAP and poor outcomes were evaluated using a restricted cubic spline (RCS).

Results

A total of 579 patients with pICH were included in the study. Hcy level was significantly higher in patients with HAP and poor outcomes (p < 0.001). The univariate and multivariate logistic regression analyses demonstrated that elevated Hcy was independently associated with both HAP and poor outcomes (p < 0.001). Furthermore, receiver operating characteristic analysis indicated that Hcy exhibited a moderate predictive accuracy for both HAP and poor outcomes after pICH. The RCS model showed that there were linear relationships between Hcy and HAP and poor outcomes.

Conclusions

Higher Hcy level was independently associated with HAP and poor outcomes in patients with pICH.

Molecular processes mediating hyperhomocysteinemia-induced metabolic reprogramming, redox regulation and growth inhibition in endothelial cells

Hyperhomocysteinemia (HHcy) is an established and potent independent risk factor for degenerative diseases, including cardiovascular disease (CVD), Alzheimer disease, type II diabetes mellitus, and chronic kidney disease. HHcy has been shown to inhibit proliferation and promote inflammatory responses in endothelial cells (EC), and impair endothelial function, a hallmark for vascular injury. However, metabolic processes and molecular mechanisms mediating HHcy-induced endothelial injury remains to be elucidated. This study examined the effects of HHcy on the expression of microRNA (miRNA) and mRNA in human aortic EC treated with a pathophysiologically relevant concentration of homocysteine (Hcy 500 μM). We performed a set of extensive bioinformatics analyses to identify HHcy-altered metabolic and molecular processes. The global functional implications and molecular network were determined by Gene Set Enrichment Analysis (GSEA) followed by Cytoscape analysis. We identified 244 significantly differentially expressed (SDE) mRNA, their relevant functional pathways, and 45 SDE miRNA. HHcy-altered SDE inversely correlated miRNA-mRNA pairs (45 induced/14 reduced mRNA) were discovered and applied to network construction using an experimentally verified database. We established a hypothetical model to describe the biochemical and molecular network with these specified miRNA/mRNA axes, finding: 1) HHcy causes metabolic reprogramming by increasing glucose uptake and oxidation, by glycogen debranching and NAD⁺/CoA synthesis, and by stimulating mitochondrial reactive oxygen species production via NNT/IDH2 suppression-induced NAD⁺/NADP-NADPH/NADP⁺ metabolism disruption; 2) HHcy activates inflammatory responses by activating inflammasome-pyroptosis mainly through ↓miR193b→↑CASP-9 signaling and by inducing IL-1β and adhesion molecules through the ↓miR29c→↑NEDD9 and the ↓miR1256→↑ICAM-1 axes, as well as GPCR and interferon α/β signaling; 3) HHcy promotes cell degradation by the activation of lysosome autophagy and ubiquitin proteasome systems; 4) HHcy causes cell cycle arrest at G1/S and S/G2 transitions, suppresses spindle checkpoint complex and cytokinetic abscission, and suppresses proliferation through ↓miRNA335/↑VASH1 and other axes. These findings are in accordance with our previous studies and add a wealth of heretofore-unexplored molecular and metabolic mechanisms underlying HHcy-induced endothelial injury. This is the first study to consider the effects of HHcy on both global mRNA and miRNA expression changes for mechanism identification. Molecular axes and biochemical processes identified in this study are useful not only for the understanding of mechanisms underlying HHcy-induced endothelial injury, but also for discovering therapeutic targets for CVD in general.

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Identified multiple HHcy-altered metabolic and molecular processes potentially responsible for HHcy-induced endothelial injury via examining global mRNA/miRNA expression changes in Hcy-treated EC and performing comprehensive bioinformatic studies.

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HHcy may activate glucose uptake signaling via the ↓miR148b→↑SLC2A axis.

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HHcy may induce glucose oxidation signaling by switching pyruvate metabolism from lactate synthesis to mitochondrial oxidation via expression changes of ↑MPC1 & ↓LDHB.

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HHcy may disrupt redox homeostasis mostly by suppressing NNT/IDH2-related mt-NADPH/mt-NAD⁺ signaling.

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HHcy may increase FA β-oxidation, glutamine, TCA cycle and OXPHOS signaling.

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HHcy may activate inflammatory signaling via the ↓miR29c→↑NEDD9 and the ↓miR1256→↑ICAM-1 axes.

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HHcy may activate inflammasome/pyroptosis-related signaling by the ↓miR137→↑TLR3, the ↓miR574→↑TRAF5, and the ↓miR193b→↑CASP-9 axes, and induce IL1α/β and CASP-10/7.

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HHcy may induce inflammation signaling via GPCR activation through the ↓miRNA335→↑CXCR4/↑GNA14 axes.

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HHcy may activate molecular degradation process signaling through the ↓miRNA335→↑ASAH1/↑ABCB9 axes.

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HHcy may suppress cell cycle and proliferation through the miR491→↓HMGA2→↓CCNA2/CCNB2, the ↓miR335→↑VASH1, the ↓miR181a→↑PHLDA1, the miR6045→↓CENPH, the miR22→↓PRR11/↓BRCA2, and the miR605/miR497/miR514a→CEP55 axes

Homocysteine in Neurology: A Possible Contributing Factor to Small Vessel Disease

Homocysteine (Hcy) is a sulfur-containing amino acid generated during methionine metabolism, accumulation of which may be caused by genetic defects or the deficit of vitamin B12 and folate. A serum level greater than 15 micro-mols/L is defined as hyperhomocysteinemia (HHcy). Hcy has many roles, the most important being the active participation in the transmethylation reactions, fundamental for the brain. Many studies focused on the role of homocysteine accumulation in vascular or degenerative neurological diseases, but the results are still undefined. More is known in cardiovascular disease. HHcy is a determinant for the development and progression of inflammation, atherosclerotic plaque formation, endothelium, arteriolar damage, smooth muscle cell proliferation, and altered-oxidative stress response. Conversely, few studies focused on the relationship between HHcy and small vessel disease (SVD), despite the evidence that mice with HHcy showed a significant end-feet disruption of astrocytes with a diffuse SVD. A severe reduction of vascular aquaporin-4-water channels, lower levels of high-functioning potassium channels, and higher metalloproteinases are also observed. HHcy modulates the N-homocysteinylation process, promoting a pro-coagulative state and damage of the cellular protein integrity. This altered process could be directly involved in the altered endothelium activation, typical of SVD and protein quality, inhibiting the ubiquitin-proteasome system control. HHcy also promotes a constant enhancement of microglia activation, inducing the sustained pro-inflammatory status observed in SVD. This review article addresses the possible role of HHcy in small-vessel disease and understands its pathogenic impact.

Implication of Hyperhomocysteinemia in Blood Retinal Barrier (BRB) Dysfunction

Elevated plasma homocysteine (Hcy) level, known as hyperhomocysteinemia (HHcy) has been linked to different systemic and neurological diseases, well-known as a risk factor for systemic atherosclerosis and cardiovascular disease (CVD) and has been identified as a risk factor for several ocular disorders, such as diabetic retinopathy (DR) and age-related macular degeneration (AMD). Different mechanisms have been proposed to explain HHcy-induced visual dysfunction, including oxidative stress, upregulation of inflammatory mediators, retinal ganglion cell apoptosis, and extracellular matrix remodeling. Our previous studies using in vivo and in vitro models of HHcy have demonstrated that Hcy impairs the function of both inner and outer blood retinal barrier (BRB). Dysfunction of BRB is a hallmark of vision loss in DR and AMD. Our findings highlighted oxidative stress, ER stress, inflammation, and epigenetic modifications as possible mechanisms of HHcy-induced BRB dysfunction. In addition, we recently reported HHcy-induced brain inflammation as a mechanism of blood–brain barrier (BBB) dysfunction and pathogenesis of Alzheimer’s disease (AD). Moreover, we are currently investigating the activation of glutamate receptor N-methyl-d-aspartate receptor (NMDAR) as the molecular mechanism for HHcy-induced BRB dysfunction. This review focuses on the studied effects of HHcy on BRB and the controversial role of HHcy in the pathogenesis of aging neurological diseases such as DR, AMD, and AD. We also highlight the possible mechanisms for such deleterious effects of HHcy.

Hyperhomocysteinemia: an instigating factor for periodontal disease

Hyperhomocysteinemia (HHcy) affects bone remodeling, since a destructive process in cortical alveolar bone has been linked to it; however, the mechanism remains at large. HHcy increases proinflammatory cytokines viz. TNF-α, IL-1b, IL-6, and IL-8 that leads to a cascade that negatively impacts methionine metabolism and homocysteine cycling. Further, chronic inflammation decreases vitamins B12, B6, and folic acid that are required for methionine homocysteine homeostasis. This study aims to investigate a HHcy mouse model (cystathionine β-synthase deficient, CBS^+/-) for studying the potential pathophysiological changes, if any, in the periodontium (gingiva, periodontal ligament, cement, and alveolar bone). We compared the periodontium side-by-side in the CBS^+/- model with that of the wild-type (C57BL/6J) mice. Histology and histomorphometry of the mandibular bone along with gene expression analyses were carried out. Also, proangiogenic proteins and metalloproteinases were studied. To our knowledge, this research shows, for the first time, a direct connection between periodontal disease during CBS deficiency, thereby suggesting the existence of disease drivers during the hyperhomocysteinemic condition. Our findings offer opportunities to develop diagnostics/therapeutics for people who suffer from chronic metabolic disorders like HHcy.

B Vitamins and Fatty Acids: What Do They Share with Small Vessel Disease-Related Dementia?

Many studies have been written on vitamin supplementation, fatty acid, and dementia, but results are still under debate, and no definite conclusion has yet been drawn. Nevertheless, a significant amount of lab evidence confirms that vitamins of the B group are tightly related to gene control for endothelium protection, act as antioxidants, play a co-enzymatic role in the most critical biochemical reactions inside the brain, and cooperate with many other elements, such as choline, for the synthesis of polyunsaturated phosphatidylcholine, through S-adenosyl-methionine (SAM) methyl donation. B-vitamins have anti-inflammatory properties and act in protective roles against neurodegenerative mechanisms, for example, through modulation of the glutamate currents and a reduction of the calcium currents. In addition, they also have extraordinary antioxidant properties. However, laboratory data are far from clinical practice. Many studies have tried to apply these results in everyday clinical activity, but results have been discouraging and far from a possible resolution of the associated mysteries, like those represented by Alzheimer's disease (AD) or small vessel disease dementia. Above all, two significant problems emerge from the research: No consensus exists on general diagnostic criteria-MCI or AD? Which diagnostic criteria should be applied for small vessel disease-related dementia? In addition, no general schema exists for determining a possible correct time of implementation to have effective results. Here we present an up-to-date review of the literature on such topics, shedding some light on the possible interaction of vitamins and phosphatidylcholine, and their role in brain metabolism and catabolism. Further studies should take into account all of these questions, with well-designed and world-homogeneous trials.

Possible Role of N-Methyl-D-Aspartate Receptors in Physiology and Pathophysiology of Cardiovascular System

N-methyl-D-aspartate (NMDA) receptors belong to ionotropic glutamate receptor family, together with α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors, kainite receptors and δ-receptors. All of these receptors are tetramers composed of four subunits. NMDA receptors have several unique features in relation to other ionotropic glutamate receptors: requirement for simultaneous action of two coagonists, glutamate and glycine; dual control of receptor activation, ligand-dependent (by glutamate and glycine) and voltage-dependent (Mg2+ block) control; and influx of considerable amounts of Ca2+ following receptor activation. Increasing number of researches deals with physiological and pathophysiological roles of NMDA receptors outside of nerve tissues, especially in the cardiovascular system. NMDA receptors are found in all cell types represented in cardiovascular system, and their overstimulation in pathological conditions, such as hyperhomocysteinemia, is related to a range of cardiovascular disorders. On the other hand we demonstrated that blockade of NMDA receptors depresses heart function. There is a need for the intensive study of NMDA receptor in cardiovascular system as potential theraputical target both in prevention and treatment of cardiovascular disorders.

The Controversial Role of Homocysteine in Neurology: From Labs to Clinical Practice

Homocysteine (Hcy) is a sulfur-containing amino acid that is generated during methionine metabolism. Physiologic Hcy levels are determined primarily by dietary intake and vitamin status. Elevated plasma levels of Hcy can be caused by deficiency of either vitamin B12 or folate. Hyperhomocysteinemia (HHcy) can be responsible of different systemic and neurological disease. Actually, HHcy has been considered as a risk factor for systemic atherosclerosis and cardiovascular disease (CVD) and HHcy has been reported in many neurologic disorders including cognitive impairment and stroke, independent of long-recognized factors such as hyperlipidemia, hypertension, diabetes mellitus, and smoking. HHcy is typically defined as levels >15 micromol/L. Treatment of hyperhomocysteinemia with folic acid and B vitamins seems to be effective in the prevention of the development of atherosclerosis, CVD, and strokes. However, data from literature show controversial results regarding the significance of homocysteine as a risk factor for CVD and stroke and whether patients should be routinely screened for homocysteine. HHcy-induced oxidative stress, endothelial dysfunction, inflammation, smooth muscle cell proliferation, and endoplasmic reticulum (ER) stress have been considered to play an important role in the pathogenesis of several diseases including atherosclerosis and stroke. The aim of our research is to review the possible role of HHcy in neurodegenerative disease and stroke and to understand its pathogenesis.

Polyamine Metabolism and Gene Methylation in Conjunction with One-Carbon Metabolism

Recent investigations have revealed that changes in DNA methylation status play an important role in aging-associated pathologies and lifespan. The methylation of DNA is regulated by DNA methyltransferases (DNMT1, DNMT3a, and DNMT3b) in the presence of S-adenosylmethionine (SAM), which serves as a methyl group donor. Increased availability of SAM enhances DNMT activity, while its metabolites, S-adenosyl-l-homocysteine (SAH) and decarboxylated S-adenosylmethionine (dcSAM), act to inhibit DNMT activity. SAH, which is converted from SAM by adding a methyl group to cytosine residues in DNA, is an intermediate precursor of homocysteine. dcSAM, converted from SAM by the enzymatic activity of adenosylmethionine decarboxylase, provides an aminopropyl group to synthesize the polyamines spermine and spermidine. Increased homocysteine levels are a significant risk factor for the development of a wide range of conditions, including cardiovascular diseases. However, successful homocysteine-lowering treatment by vitamins (B6, B12, and folate) failed to improve these conditions. Long-term increased polyamine intake elevated blood spermine levels and inhibited aging-associated pathologies in mice and humans. Spermine reversed changes (increased dcSAM, decreased DNMT activity, aberrant DNA methylation, and proinflammatory status) induced by the inhibition of ornithine decarboxylase. The relation between polyamine metabolism, one-carbon metabolism, DNA methylation, and the biological mechanism of spermine-induced lifespan extension is discussed.

Lipopolysaccharide Downregulates Kruppel-Like Factor 2 (KLF2) via Inducing DNMT1-Mediated Hypermethylation in Endothelial Cells

KLF2 plays a protective role in antiinflammation and endothelial function, and can be regulated by promoter methylation alteration. Lipopolysaccharide (LPS) is a mediator of inflammatory responses, which causes epigenetic change of certain genes in host cells. We thus aimed to determine whether LPS could control the KLF2 expression by inducing methylation in promoter region. DNA methylation of 16 CpG sites within KLF2 promoter region was detected by bisulfite sequencing PCR. Results showed that methylation at 12 CpG sites were significantly increased in HUVECs after exposure to LPS among the total 16 sites, and the average level was increased by 57%. The KLF2 expressions assessed by reverse transcription quantitative real-time PCR and Western blot were significantly downregulated compared that without LPS simulation. Moreover, both messenger RNA and protein levels of KLF2 in HUVEC co-treated with LPS and DNA methyltransferase (DNMT) 1 small interfering RNA were dramatically higher than that treated with LPS only. Similar result was obtained when the cells were incubated in combination with LPS and 5-aza-2'-deoxycytidine (AZA), suggesting that the reduction of KLF2 expression induced by LPS can be reversed by DNMT1 inhibition. Finally, the presence of AZA changed the expression of genes that depends on KLF2 in LPS-stimulated HUVECs, which downregulated the E-selectin and VCAM and increased the eNOS and thrombomodulin expression. Our data demonstrated that LPS exposure resulted in hypermethylation in KLF2 promoter in HUVECs, which subsequently led to downregulation of the KLF2 expression. The study suggested that epigenetic alteration is involved in LPS-induced inflammatory response and provided a new insight into atherogenesis.

Cystathionine β-Synthase in Physiology and Cancer

Cystathionine β-synthase (CBS) regulates homocysteine metabolism and contributes to hydrogen sulfide (H₂S) biosynthesis through which it plays multifunctional roles in the regulation of cellular energetics, redox status, DNA methylation, and protein modification. Inactivating mutations in CBS contribute to the pathogenesis of the autosomal recessive disease CBS-deficient homocystinuria. Recent studies demonstrating that CBS promotes colon and ovarian cancer growth in preclinical models highlight a newly identified oncogenic role for CBS. On the contrary, tumor-suppressive effects of CBS have been reported in other cancer types, suggesting context-dependent roles of CBS in tumor growth and progression. Here, we review the physiological functions of CBS, summarize the complexities regarding CBS research in oncology, and discuss the potential of CBS and its key metabolites, including homocysteine and H₂S, as potential biomarkers for cancer diagnosis or therapeutic targets for cancer treatment.

Homocysteine is a bystander for ST-segment elevation myocardial infarction: a case-control study

Background

Homocysteine has been long considered a risk factor for atherosclerosis. However, cardiovascular events cannot be reduced through homocysteine lowering by B vitamin supplements. Although several association studies have reported an elevation of serum homocysteine levels in cardiovascular diseases, the relationship of homocysteine with ST-segment elevation myocardial infarction (STEMI) is not well established.

Methods

We prospectively enrolled STEMI patients who were consecutively admitted to an intensive care unit following coronary intervention in a single medical center in Taiwan. Control subjects were individuals who presented to the outpatient or emergency department with acute chest pain but subsequently revealed patent coronary arteries by coronary arteriography. The association between serum homocysteine levels and STEMI was investigated. A culture system using human coronary artery endothelial cells was also established to examine the toxic effects of homocysteine at the cellular level.

Results

Patients with chest pain were divided into two groups. The STEMI group included 56 patients who underwent a primary percutaneous coronary intervention. The control group included 17 subjects with patent coronary arteries. There was no difference in serum homocysteine levels (8.4 ± 2.2 vs. 7.6 ± 1.9 μmol/L, p = 0.142). When stratifying STEMI patients by the Killip classification into higher (Killip III-IV) and lower (Killip I-II) grades, CRP (3.3 ± 4.1 vs. 1.4 ± 2.3 mg/L, p = 0.032), peak creatine kinase (3796 ± 2163 vs. 2305 ± 1822 IU/L, p = 0.023), and SYNTAX scores (20.4 ± 11.1 vs. 14.8 ± 7.6, p = 0.033) were significantly higher in the higher grades, while serum homocysteine levels were similar. Homocysteine was not correlated with WBCs, CRP, or the SYNTAX score in STEMI patients. In a culture system, homocysteine at even a supraphysiological level of 100 μmol/L did not reduce the cell viability of human coronary artery endothelial cells.

Conclusions

Homocysteine was not elevated in STEMI patients regardless of Killip severity, suggesting that homocysteine is a bystander instead of a causative factor of STEMI. Our study therefore supports the current notion that homocysteine-lowering strategies are not essential in preventing cardiovascular disease.

Liver X Receptor-Binding DNA Motif Associated With Atherosclerosis-Specific DNA Methylation Profiles of Alu Elements and Neighboring CpG Islands

BACKGROUND

The signals that determine atherosclerosis-specific DNA methylation profiles are only partially known. We previously identified a 29-bp DNA motif (differential methylation motif [DMM]) proximal to CpG islands (CGIs) that undergo demethylation in advanced human atheromas. Those data hinted that the DMM docks modifiers of DNA methylation and transcription.

METHODS AND RESULTS

We sought to functionally characterize the DMM. We showed that the DMM overlaps with the RNA polymerase III-binding B box of Alu short interspersed nuclear elements and contains a DR2 nuclear receptor response element. Pointing to a possible functional role for an Alu DMM, CGIs proximal (<100 bp) to near-intact DMM-harboring Alu are significantly less methylated relative to CGIs proximal to degenerate DMM-harboring Alu or to DMM-devoid mammalian-wide interspersed repeat short interspersed nuclear elements in human arteries. As for DMM-binding factors, LXRB (liver X receptor β) binds the DMM in a DR2-dependent fashion, and LXR (liver X receptor) agonists induce significant hypermethylation of the bulk of Alu in THP-1 cells. Furthermore, we describe 3 intergenic long noncoding RNAs that harbor a DMM, are under transcriptional control by LXR agonists, and are differentially expressed between normal and atherosclerotic human aortas. Notably, CGIs adjacent to those long noncoding RNAs tend to be hypomethylated in symptomatic relative to stable human atheromas.

CONCLUSIONS

Collectively, the data suggest that a DMM is associated with 2 distinct methylation states: relatively low methylation of in cis CGIs and Alu element hypermethylation. Based on the known atheroprotective role of LXRs, we propose that LXR agonist-induced Alu hypermethylation, a landmark of atherosclerosis, is a compensatory rather than proatherogenic response.

Epigenetic modifications in hyperhomocysteinemia: potential role in diabetic retinopathy and age-related macular degeneration

To study Hyperhomocysteinemia (HHcy)-induced epigenetic modifications as potential mechanisms of blood retinal barrier (BRB) dysfunction, retinas isolated from three- week-old mice with elevated level of Homocysteine (Hcy) due to lack of the enzyme cystathionine β-synthase (cbs^-/- , cbs^+/- and cbs^+/+ ), human retinal endothelial cells (HRECs), and human retinal pigmented epithelial cells (ARPE-19) treated with or without Hcy were evaluated for (1) histone deacetylases (HDAC), (2) DNA methylation (DNMT), and (3) miRNA analysis. Differentially expressed miRNAs in mice with HHcy were further compared with miRNA analysis of diabetic mice retinas (STZ) and miRNAs within the exosomes released from Hcy-treated RPEs. Differentially expressed miRNAs were further evaluated for predicted target genes and associated pathways using Ingenuity Pathway Analysis. HHcy significantly increased HDAC and DNMT activity in HRECs, ARPE-19, and cbs mice retinas, whereas inhibition of HDAC and DNMT decreased Hcy-induced BRB dysfunction. MiRNA profiling detected 127 miRNAs in cbs^+/- and 39 miRNAs in cbs^-/- mice retinas, which were significantly differentially expressed compared to cbs^+/+ . MiRNA pathway analysis showed their involvement in HDAC and DNMT activation, endoplasmic reticulum (ER), and oxidative stresses, inflammation, hypoxia, and angiogenesis pathways. Hcy-induced epigenetic modifications may be involved in retinopathies associated with HHcy, such as age-related macular degeneration and diabetic retinopathy.

Synergistic Effects of Danshen (Salvia Miltiorrhizae Radix et Rhizoma) and Sanqi (Notoginseng Radix et Rhizoma) Combination in Angiogenesis Behavior in EAhy 926 Cells

Background: This study investigated the combination effects of the Danshen and Sanqi herb pair on angiogenesis in vitro. Methods: Nine combination ratios of Danshen-Sanqi extracts (DS-SQ) were screened for their angiogenic effects in the human vascular endothelial EAhy 926 cell line via cell proliferation, cell migration and tube formation activities against the damage to the cells exerted by DL-homocysteine (Hcy) and adenosine (Ado). The type of interaction (synergistic, antagonistic, additive) between Danshen and Sanqi was analyzed using combination index (CI) and isobologram models. The angiogenic activities of key bioactive compounds from Danshen and Sanqi were tested in the same models. Results: DS-SQ ratios of 2:8 and 3:7 (50-300 µg/mL) potentiated angiogenic synergistic effects (CI < 1) in all three assays. The observed wound healing effects of DS-SQ 2:8 was significantly attenuated by phosphatidylinositol-3 kinases (PI3K), mitogen-activated protein kinase (MEK) and extracellular signal-regulated kinases (ERK) inhibitors which inferred the potential mechanistic pathways. Out of all the tested compounds, Notoginsenoside R1 from Sanqi exhibited the most potent bioactivity in cell proliferation assay. Conclusions: This study provides scientific evidence to support the traditional use of the Danshen-Sanqi combination for vascular disease, in particular through their synergistic interactions on previously unexamined angiogenic pathways.

Homocysteine inhibits endothelial progenitor cells proliferation via DNMT1-mediated hypomethylation of Cyclin A

Endothelial progenitor cells (EPCs) contribute to neovasculogenesis and reendothelialization of damaged blood vessels to maintain the endothelium. Dysfunction of EPCs is implicated in the pathogenesis of vascular injury induced by homocysteine (Hcy). We aimed to investigate the role of Cyclin A in Hcy-induced EPCs dysfunction and explore its molecular mechanism. In this study, by treatment of EPCs with Hcy, we found that the expression of Cyclin A mRNA and protein were significantly downregulated in a dose-dependent manner. Knockdown of Cyclin A prominently reduced proliferation of EPCs, while over-expression of Cyclin A significantly promoted the cell proliferation, suggesting that Hcy inhibits EPCs proliferation through downregulation of Cyclin A expression. In addition, epigenetic study also demonstrated that Hcy induces DNA hypomethylation of the Cyclin A promoter in EPCs through downregulated expression of DNMT1. Moreover, we found that Hcy treatment of EPCs leads to increased SAM, SAH and MeCP2, while the ratio of SAM/SAH and MBD expression decrease. In summary, our results indicate that Hcy inhibits Cyclin A expression through hypomethylation of Cyclin A and thereby suppress EPCs proliferation. These findings demonstrate a novel mechanism of DNA methylation mediated by DNMT1 in prevention of Hcy associated cardiovascular disease.

Regulation of endothelial intracellular adenosine via adenosine kinase epigenetically modulates vascular inflammation

The molecular mechanisms underlying vascular inflammation and associated inflammatory vascular diseases are not well defined. Here we show that endothelial intracellular adenosine and its key regulator adenosine kinase (ADK) play important roles in vascular inflammation. Pro-inflammatory stimuli lead to endothelial inflammation by increasing endothelial ADK expression, reducing the level of intracellular adenosine in endothelial cells, and activating the transmethylation pathway through increasing the association of ADK with S-adenosylhomocysteine (SAH) hydrolase (SAHH). Increasing intracellular adenosine by genetic ADK knockdown or exogenous adenosine reduces activation of the transmethylation pathway and attenuates the endothelial inflammatory response. In addition, loss of endothelial ADK in mice leads to reduced atherosclerosis and affords protection against ischemia/reperfusion injury of the cerebral cortex. Taken together, these results demonstrate that intracellular adenosine, which is controlled by the key molecular regulator ADK, influences endothelial inflammation and vascular inflammatory diseases.

The molecular mechanisms underlying vascular inflammation are unclear. Here the authors show that pro-inflammatory stimuli lead to endothelial inflammation by increasing adenosine kinase expression, and that its knockdown in endothelial cells inhibits atherosclerosis and cerebral ischemic injury in mice.

Hyperhomocysteinaemia and vascular injury: advances in mechanisms and drug targets

Homocysteine is a sulphur-containing non-proteinogenic amino acid. Hyperhomocysteinaemia (HHcy), the pathogenic elevation of plasma homocysteine as a result of an imbalance of its metabolism, is an independent risk factor for various vascular diseases, such as atherosclerosis, hypertension, vascular calcification and aneurysm. Treatments aimed at lowering plasma homocysteine via dietary supplementation with folic acids and vitamin B are more effective in preventing vascular disease where the population has a normally low folate consumption than in areas with higher dietary folate. To date, the mechanisms of HHcy-induced vascular injury are not fully understood. HHcy increases oxidative stress and its downstream signalling pathways, resulting in vascular inflammation. HHcy also causes vascular injury via endoplasmic reticulum stress. Moreover, HHcy up-regulates pathogenic genes and down-regulates protective genes via DNA demethylation and methylation respectively. Homocysteinylation of proteins induced by homocysteine also contributes to vascular injury by modulating intracellular redox state and altering protein function. Furthermore, HHcy-induced vascular injury leads to neuronal damage and disease. Also, an HHcy-activated sympathetic system and HHcy-injured adipose tissue also cause vascular injury, thus demonstrating the interactions between the organs injured by HHcy. Here, we have summarized the recent developments in the mechanisms of HHcy-induced vascular injury, which are further considered as potential therapeutic targets in this condition.

LINKED ARTICLES

This article is part of a themed section on Spotlight on Small Molecules in Cardiovascular Diseases. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v175.8/issuetoc.

Hyperhomocysteinemia results from and promotes hepatocellular carcinoma via CYP450 metabolism by CYP2J2 DNA methylation

Hyperhomocysteinemia (HHcy) can result from liver disease or dysfunction and further alters intracellular lipid metabolism. Cytochrome P450 (CYP) arachidonic acid epoxygenases are expressed in human cancers and promote cancer metastasis. This study explored the interaction of Hcy and CYP450 metabolism in hepatocellular carcinoma (HCC). The levels of 4-epoxyeicosatrienoic acid (EET) isomers and their generative enzyme CYP2J2 level as well as intracellular Hcy level were higher in 42 cases of HCC than in paired non-tumor tissue. Elevated Hcy-decreased DNA methylation on SP1/AP1 binding motifs and enhancement on the CYP2J2 promoter via ERK1/2 signaling was essential for CYP2J2 upregulation and EET metabolism. Increased Hcy level enhanced the neoplastic cellular phenotype, which was reversed by CYP2J2 knockdown in vitro. Furthermore, tumor growth and size as well as patterns of CYP2J2 expression and DNA demethylation were increased with HHcy in mice induced orthotopically by 2% (wt/wt) L-methionine with or without folate deficiency. Moreover, the effect was attenuated by shRNA knockdown of CYP2J2. Thus, HHcy results from but can also promote hepatocarcingenesis via CYP450-EET metabolism by crosstalk of DNA demethylation of CYP2J2 and ERK1/2 signaling.

Serum homocysteine and cysteine levels and changes in the lipid profile of children and adolescents over a 12-month follow-up period

INTRODUCTION

There is evidence of associations between high serum homocysteine (Hcy) and cysteine (Cys) levels and changes in the lipid profile of adults; however, little information is available with respect to these associations in the pediatric age group.

OBJECTIVE

To identify the effect of high baseline serum Hcy and Cys levels, alone or in conjunction, on the lipid profile of children and adolescents over a 12-month follow-up period.

METHODS

A cohort study involving 540 boys and girls of 7-15 years of age was conducted over 12 months. The outcome variables were the lipid indicators and the principal exposure variable was serum Hcy and Cys levels. A generalized estimating equation (GEE) approach was used to identify the associations of interest.

RESULTS

Irrespective of age, sex, socioeconomic status, diet or anthropometric status, when serum Hcy levels were above the 5th quintile of distribution at baseline, HDL-cholesterol decreased by a mean of 2.91 mg/dl (p < 0.01), while triglyceride levels increased by a mean of 1.58 mg/dl (p < 0.01) over the 12-month follow-up period. In individuals with high baseline Cys levels, there was a reduction of 1.95 mg/dl (p < 0.01) and an increase of 1.76 mg/dl (p < 0.01) in mean serum HDL-cholesterol and triglyceride levels, respectively, over the 12-month period. When serum Hcy and Cys levels were both above the 5th quintile of distribution at baseline, there was a reduction of 3.65 mg/dl (p < 0.01) in mean HDL-cholesterol and an increase of 3.53 mg/dl (p < 0.01) in mean triglyceride levels in the 12 months of follow-up.

CONCLUSIONS

High baseline serum Hcy and Cys levels resulted in a reduction in mean HDL-cholesterol levels and an increase in mean triglycerides levels over the 12 months of follow-up in children and adolescents, with these alterations being greater when these two biochemical parameters were simultaneously high at baseline.

Epigenetic Regulation of Oxidative Stress in Ischemic Stroke

The prevalence and incidence of stroke rises with life expectancy. However, except for the use of recombinant tissue-type plasminogen activator, the translation of new therapies for acute stroke from animal models into humans has been relatively unsuccessful. Oxidative DNA and protein damage following stroke is typically associated with cell death. Cause-effect relationships between reactive oxygen species and epigenetic modifications have been established in aging, cancer, acute pancreatitis, and fatty liver disease. In addition, epigenetic regulatory mechanisms during stroke recovery have been reviewed, with focuses mainly on neural apoptosis, necrosis, and neuroplasticity. However, oxidative stress-induced epigenetic regulation in vascular neural networks following stroke has not been sufficiently explored. Improved understanding of the epigenetic regulatory network upon oxidative stress may provide effective antioxidant approaches for treating stroke. In this review, we summarize the epigenetic events, including DNA methylation, histone modification, and microRNAs, that result from oxidative stress following experimental stroke in animal and cell models, and the ways in which epigenetic changes and their crosstalk influence the redox state in neurons, glia, and vascular endothelial cells, helping us to understand the foregone and vicious epigenetic regulation of oxidative stress in the vascular neural network following stroke.

Role of DNA methylation in cardiovascular diseases

A complex interplay between genetic and environmental factors is involved in the pathogenesis of cardiovascular diseases (CVDs). Environmental factors have crucial effects on the epigenetic trait of genes, which refers to a stably heritable phenotype resulting from changes in the chromosomes without alteration of the DNA sequence, but has profound effects on the cellular repertoire. Among the epigenetic patterns, DNA methylation is of great interest. DNA methylation occurs at both global and specific gene promoter levels and relates to atherosclerosis. Aberrant DNA methylation affects the transcription and expression of critical regulatory genes and induces a proatherogenic cellular phenotype, which plays key roles in endothelia cell dysfunction, abnormal vascular smooth muscle cell proliferation, extracellular matrix formation, and inflammation in CVDs. This review focuses on the contribution of DNA methylation in the pathogenesis of CVDs.

Hydrogen Sulfide Epigenetically Attenuates Homocysteine-Induced Mitochondrial Toxicity Mediated Through NMDA Receptor in Mouse Brain Endothelial (bEnd3) Cells

Previously we have shown that homocysteine (Hcy) caused oxidative stress and altered mitochondrial function. Hydrogen sulfide (H2S) has potent anti-inflammatory, anti-oxidative, and anti-apoptotic effects. Therefore, in the present study we examined whether H2S ameliorates Hcy-induced mitochondrial toxicity which led to endothelial dysfunction in part, by epigenetic alterations in mouse brain endothelial cells (bEnd3). The bEnd3 cells were exposed to 100 μM Hcy treatment in the presence or absence of 30 μM NaHS (donor of H2S) for 24 h. Hcy-activate NMDA receptor and induced mitochondrial toxicity by increased levels of Ca(2+), NADPH-oxidase-4 (NOX-4) expression, mitochondrial dehydrogenase activity and decreased the level of nitrate, superoxide dismutase (SOD-2) expression, mitochondria membrane potentials, ATP production. To confirm the role of epigenetic, 5'-azacitidine (an epigenetic modulator) treatment was given to the cells. Pretreatment with NaHS (30 μM) attenuated the Hcy-induced increased expression of DNMT1, DNMT3a, Ca(2+), and decreased expression of DNMT3b in bEND3 cells. Furthermore, NaHS treatment also mitigated mitochondrial oxidative stress (NOX4, ROS, and NO) and restored ATP that indicates its protective effects against mitochondrial toxicity. Additional, NaHS significantly alleviated Hcy-induced LC3-I/II, CSE, Atg3/7, and low p62 expression which confirm its effect on mitophagy. Likewise, NaHS also restored level of eNOS, CD31, VE-cadherin and ET-1 and maintains endothelial function in Hcy treated cells. Molecular inhibition of NMDA receptor by using small interfering RNA showed protective effect whereas inhibition of H2S production by propargylglycine (PG) (inhibitor of enzyme CSE) showed mitotoxic effect. Taken together, results demonstrate that, administration of H2S protected the cells from HHcy-induced mitochondrial toxicity and endothelial dysfunction.

Effects of mild hyperhomocysteinemia on electron transport chain complexes, oxidative stress, and protein expression in rat cardiac mitochondria

Hyperhomocysteinemia (HHcy) is an independent risk factor of cardiovascular disease, but the mechanisms of tissue injury are poorly understood. In the present study, we investigated the effect of HHcy on rat heart function, activities electron transport chain (ETC) complexes, mitochondrial protein expression, and protein oxidative damage. HHcy was induced by subcutaneous injection of Hcy (0.45 μmol/g of body weight) twice a day for a period of 2 weeks. Performance of hearts excised after the Hcy treatment was examined according to the Langendorff method at a constant pressure. Left ventricular developed pressure, as well as maximal rates of contraction (+dP/dt) and relaxation (-dP/dt), was significantly depressed in HHcy rats. HHcy was accompanied by significant inhibition of ETC complexes II-IV, whereas activity of the complex I was unchanged. The decline in ETC activities was not associated with elevated protein oxidative damage, as indicated by unchanged protein carbonyl, thiol, and dityrosine contents. Moreover, the level of protein adducts with 4-hydroxynonenal was decreased in HHcy rats. Additionally, 2D-gel electrophoresis with matrix-assisted laser desorption/ionization time-of-flight mass spectrometry did not show alterations in contents of inhibited ETC complexes. However, mass spectrometry analyses identified 8 proteins whose expression was significantly increased by HHcy. These proteins are known to play important roles in the cellular stress response, bioenergetics, and redox balance. Altogether, the results suggest that oxidative damage and altered protein expression are not possible causes of ETC dysfunction in HHcy rats. Increased expression of the other mitochondrial proteins indicates a protective response to Hcy-induced myocardial injury.

Homocysteine Triggers Inflammatory Responses in Macrophages through Inhibiting CSE-H2S Signaling via DNA Hypermethylation of CSE Promoter

Hyperhomocysteinemia (HHcy) is an independent risk factor of atherosclerosis and other cardiovascular diseases. Unfortunately, Hcy-lowering strategies were found to have limited effects in reducing cardiovascular events. The underlying mechanisms remain unclear. Increasing evidence reveals a role of inflammation in the pathogenesis of HHcy. Homocysteine (Hcy) is a precursor of hydrogen sulfide (H₂S), which is formed via the transsulfuration pathway catalyzed by cystathionine β-synthase and cystathionine γ-lyase (CSE) and serves as a novel modulator of inflammation. In the present study, we showed that methionine supplementation induced mild HHcy in mice, associated with the elevations of TNF-α and IL-1β in the plasma and reductions of plasma H₂S level and CSE expression in the peritoneal macrophages. H₂S-releasing compound GYY4137 attenuated the increases of TNF-α and IL-1β in the plasma of HHcy mice and Hcy-treated raw264.7 cells while CSE inhibitor PAG exacerbated it. Moreover, the in vitro study showed that Hcy inhibited CSE expression and H₂S production in macrophages, accompanied by the increases of DNA methyltransferase (DNMT) expression and DNA hypermethylation in cse promoter region. DNMT inhibition or knockdown reversed the decrease of CSE transcription induced by Hcy in macrophages. In sum, our findings demonstrate that Hcy may trigger inflammation through inhibiting CSE-H₂S signaling, associated with increased promoter DNA methylation and transcriptional repression of cse in macrophages.

Glucocorticoids and fetal programming part 2: Mechanisms

The lifelong health of an individual is shaped during critical periods of development. The fetus is particularly susceptible to internal and external stimuli, many of which can alter developmental trajectories and subsequent susceptibility to disease. Glucocorticoids are critical in normal development of the fetus, as they are involved in the growth and maturation of many organ systems. The surge in fetal glucocorticoid levels that occurs in most mammalian species over the last few days of pregnancy is an important developmental switch leading to fundamental changes in gene regulation in many organs, including the brain. These changes are important for the transition to postnatal life. Exposure of the fetus to increased levels of glucocorticoids, resulting from maternal stress or treatment with synthetic glucocorticoids, can lead to long-term 'programming' of hypothalamic-pituitary-adrenal function and behaviours. Glucocorticoids act at multiple levels within the fetal brain. Growing evidence indicates that they can exert powerful effects on the epigenome, including on DNA methylation, histone acetylation and microRNA, to influence gene expression. Such influences probably represent a critical component of the 'programming' process, and might be partly responsible for the transgenerational effects of antenatal glucocorticoid exposure on neurologic, cardiovascular and metabolic function.

Maternal alcohol consumption in pregnancy enhances arterial stiffness and alters vasodilator function that varies between vascular beds in fetal sheep

While the impact of alcohol consumption by pregnant women on fetal neurodevelopment has received much attention, the effects on the cardiovascular system are not well understood. We hypothesised that repeated exposure to alcohol (ethanol) in utero would alter fetal arterial reactivity and wall stiffness, key mechanisms leading to cardiovascular disease in adulthood. Ethanol (0.75 g (kg body weight)(-1)) was infused intravenously into ewes over 1 h daily for 39 days in late pregnancy (days 95-133 of pregnancy, term ∼147 days). Maternal and fetal plasma ethanol concentrations at the end of the hour were ∼115 mg dl(-1), and then declined to apparent zero over 8 h. At necropsy (day 134), fetal body weight and fetal brain-body weight ratio were not affected by alcohol infusion. Small arteries (250-300 μm outside diameter) from coronary, renal, mesenteric, femoral (psoas) and cerebral beds were isolated. Endothelium-dependent vasodilatation sensitivity was reduced 10-fold in coronary resistance arteries, associated with a reduction in endothelial nitric oxide synthase mRNA (P = 0.008). Conversely, vasodilatation sensitivity was enhanced 10-fold in mesenteric and renal resistance arteries. Arterial stiffness was markedly increased (P = 0.0001) in all five vascular beds associated with an increase in elastic modulus and, in cerebral vessels, with an increase in collagen Iα mRNA. Thus, we show for the first time that fetal arteries undergo marked and regionally variable adaptations as a consequence of repeated alcohol exposure. These alcohol-induced vascular effects occurred in the apparent absence of fetal physical abnormalities or fetal growth restriction.

Malondialdehyde mediates oxidized LDL-induced coronary toxicity through the Akt-FGF2 pathway via DNA methylation

Background

Oxidized LDL (oxLDL) is involved in the development of atherosclerotic heart disease through a mechanism that is not fully understood. In this study, we examined the role of malondialdehyde (MDA), an important oxidative stress epitope of oxLDL, in mediating coronary endothelial cytotoxicity.

Results

Human coronary artery endothelial cells (HCAECs) were treated with oxLDL in the presence or absence of antibody against MDA (anti-MDA) or apoB100 (anti-apoB100). In HCAECs treated with oxLDL (100 μg/ml) alone, DNA synthesis, cell viability, and expression of prosurvival fibroblast growth factor 2 (FGF2) were significantly reduced (P < 0.01 vs phosphate buffered saline–treated cells). These inhibitory effects of oxLDL were significantly attenuated in HCAECs cotreated with anti-MDA (0.15 μg/ml; P < 0.05 vs oxLDL-treated cells), but not in those cotreated with anti-apoB100. When we tested the effects of a panel of signal transduction modifiers on the signal transduction pathways of MDA in oxLDL-treated HCAECs, we found that MDA-induced cytotoxicity was mediated partly through the Akt pathway. Using a reporter gene assay, we identified an oxLDL-response element in the FGF2 promoter that was responsible for the transcriptional repression of FGF2 by oxLDL. The results of bisulfite genomic DNA sequencing showed that in HCAECs treated with oxLDL, the GC-rich promoter of FGF2 was heavily methylated at cytosine residues, whereas cotreatment with anti-MDA markedly reduced oxLDL-induced FGF2 promoter methylation.

Conclusion

OxLDL disrupts the growth and survival of HCAECs through an MDA-dependent pathway involving methylation of the FGF2 promoter and repression of FGF2 transcription. This novel epigenetic mechanism of oxLDL may underlie its atherogenicity in patients with atherosclerotic cardiovascular disease.

Epigenetic programming and risk: the birthplace of cardiovascular disease?

Epigenetics, through control of gene expression circuitries, plays important roles in various physiological processes such as stem cell differentiation and self renewal. This occurs during embryonic development, in different tissues, and in response to environmental stimuli. The language of epigenetic program is based on specific covalent modifications of DNA and chromatin. Thus, in addition to the individual identity, encoded by sequence of the four bases of the DNA, there is a cell type identity characterized by its positioning in the epigenetic "landscape". Aberrant changes in epigenetic marks induced by environmental cues may contribute to the development of abnormal phenotypes associated with different human diseases such as cancer, neurological disorders and inflammation. Most of the epigenetic studies have focused on embryonic development and cancer biology, while little has been done to explore the role of epigenetic mechanisms in the pathogenesis of cardiovascular disease. This review highlights our current knowledge of epigenetic gene regulation and the evidence that chromatin remodeling and histone modifications play key roles in the pathogenesis of cardiovascular disease through (re)programming of cardiovascular (stem) cells commitment, identity and function.

Folic acid mitigates angiotensin-II-induced blood pressure and renal remodeling

Clinical data suggests an association between systolic hypertension, renal function and hyperhomocysteinemia (HHcy). HHcy is a state of elevated plasma homocysteine (Hcy) levels and is known to cause vascular complications. In this study, we tested the hypothesis whether Ang II-induced hypertension increases plasma Hcy levels and contributes to renovascular remodeling. We also tested whether folic acid (FA) treatment reduces plasma Hcy levels by enhancing Hcy remethylation and thus mitigating renal remodeling. Hypertension was induced in WT mice by infusing Ang II using Alzet mini osmotic pumps. Blood pressure, Hcy level, renal vascular density, oxidative stress, inflammation and fibrosis markers, and angiogenic- and anti-angiogenic factors were measured. Ang II hypertension increased plasma Hcy levels and reduced renal cortical blood flow and microvascular density. Elevated Hcy in Ang II hypertension was associated with decreased 4, 5-Diaminofluorescein (DAF-2DA) staining suggesting impaired endothelial function. Increased expression of Nox-2, -4 and dihydroethidium stain revealed oxidative stress. Excess collagen IV deposition in the peri-glomerular area and increased MMP-2, and -9 expression and activity indicated renal remodeling. The mRNA and protein expression of asymmetric dimethylarginine (ADMA) was increased and eNOS protein was decreased suggesting the involvement of this pathway in Hcy mediated hypertension. Decreased expressions of VEGF and increased anti-angiogenic factors, angiostatin and endostatin indicated impaired vasculogenesis. FA treatment partially reduced hypertension by mitigating HHcy in Ang II-treated animals and alleviated pro-inflammatory, pro-fibrotic and anti-angiogenic factors. These results suggest that renovascular remodeling in Ang II-induced hypertension is, in part, due to HHcy.

Plasma S-adenosylhomocysteine is associated with the risk of cardiovascular events in patients undergoing coronary angiography: a cohort study

BACKGROUND

Although cross-sectional studies have shown that plasma S-adenosylhomocysteine (SAH), the metabolic precursor of homocysteine, is associated with cardiovascular disease, the prospective relation between plasma SAH and cardiovascular disease risk is unknown.

OBJECTIVE

The aim of this study was to prospectively evaluate the association between plasma SAH and cardiovascular disease risk in coronary angiography patients.

DESIGN

Baseline plasma SAH and homocysteine concentrations were measured in 1003 patients aged between 21 and 87 y who underwent coronary angiography. Cox proportional hazards models were used to analyze the association between SAH and homocysteine and the risk of cardiovascular events, including fatal cardiovascular diseases, nonfatal myocardial infarction, and stroke.

RESULTS

During the median follow-up period of 3.0 y, 93 participants developed cardiovascular events (32.7/1000 person-years). The age- and sex-adjusted hazard ratio of cardiovascular events was 3.38 (95% CI: 2.12, 5.39) for each 1-SD increase in the natural log-transformed SAH concentration. The age- and sex-adjusted hazard ratios of cardiovascular events across quartiles of SAH concentrations were 1.0, 2.25, 2.72, and 3.40 (P-trend = 0.007). Further adjustment for other cardiovascular disease risk factors and plasma homocysteine affected the results only slightly. This positive association between SAH and cardiovascular disease risk did not change when participants were stratified by age group, sex, and other baseline covariates. The results among a subset of participants with significant coronary stenosis were similar.

CONCLUSION

Higher concentrations of plasma SAH are independently associated with an increased risk of cardiovascular events among patients undergoing coronary angiography. This trial was registered at www.chictr.org as ChiCTR-RNRC-08000270.

Apoptosis of bone marrow mesenchymal stem cells caused by homocysteine via activating JNK signal

Bone marrow mesenchymal stem cells (BMSCs) are capable of homing to and repair damaged myocardial tissues. Apoptosis of BMSCs in response to various pathological stimuli leads to the attenuation of healing ability of BMSCs. Plenty of evidence has shown that elevated homocysteine level is a novel independent risk factor of cardiovascular diseases. The present study was aimed to investigate whether homocysteine may induce apoptosis of BMSCs and its underlying mechanisms. Here we uncovered that homocysteine significantly inhibited the cellular viability of BMSCs. Furthermore, TUNEL, AO/EB, Hoechst 333342 and Live/Death staining demonstrated the apoptotic morphological appearance of BMSCs after homocysteine treatment. A distinct increase of ROS level was also observed in homocysteine-treated BMSCs. The blockage of ROS by DMTU and NAC prevented the apoptosis of BMSCs induced by homocysteine, indicating ROS was involved in the apoptosis of BMSCs. Moreover, homocysteine also caused the depolarization of mitochondrial membrane potential of BMSCs. Furthermore, apoptotic appearance and mitochondrial membrane potential depolarization in homocysteine-treated BMSCs was significantly reversed by JNK inhibitor but not p38 MAPK and ERK inhibitors. Western blot also confirmed that p-JNK was significantly activated after exposing BMSCs to homocysteine. Homocysteine treatment caused a significant reduction of BMSCs-secreted VEGF and IGF-1 in the culture medium. Collectively, elevated homocysteine induced the apoptosis of BMSCs via ROS-induced the activation of JNK signal, which provides more insight into the molecular mechanisms of hyperhomocysteinemia-related cardiovascular diseases.

Aspirin protects human coronary artery endothelial cells against atherogenic electronegative LDL via an epigenetic mechanism: a novel cytoprotective role of aspirin in acute myocardial infarction

AIMS

L5 is the most negatively charged subfraction of human low-density lipoprotein (LDL) and is the only subfraction of LDL capable of inducing apoptosis in cultured vascular endothelial cells (ECs) by inhibiting fibroblast growth factor-2 (FGF2) transcription. We examined whether plasma L5 levels are elevated in patients with ST-segment elevation myocardial infarction (STEMI) and whether aspirin provides epigenetic protection of human coronary artery ECs (HCAECs) exposed to L5.

METHODS AND RESULTS

Plasma L5 levels were compared between patients with STEMI (n = 10) and control subjects with chest pain syndrome but a normal coronary arteriogram (n = 5). L5 was isolated from the plasma of STEMI patients and control subjects, and apoptosis, FGF2 expression, and FGF2 promoter methylation were examined in HCAECs treated with L5 and aspirin. Plasma L5 levels were significantly higher in STEMI patients than in control subjects (P < 0.001). Treatment of HCAECs with L5 resulted in reduced survival and FGF2 expression and increased CpG methylation of the FGF2 promoter. Co-treatment of HCAECs with L5 and a physiologically relevant, low concentration of aspirin (0.2 mM) attenuated the adverse effects of L5 on HCAEC survival, FGF2 expression, and FGF2 promoter methylation. In contrast, high concentrations of aspirin (≥1.0 mM) accentuated the effects of L5.

CONCLUSIONS

Our results show that L5 levels are significantly increased in STEMI patients. Furthermore, L5 impairs HCAEC function through CpG methylation of the FGF2 promoter, which is suppressed in the presence of low-concentration aspirin. Our results provide evidence of a novel mechanism of aspirin in the prevention of MI.

The potential role of homocysteine mediated DNA methylation and associated epigenetic changes in abdominal aortic aneurysm formation

Previous studies have suggested that homocysteine (Hcy) has wide-ranging biological effects, including accelerating atherosclerosis, impairing post injury endothelial repair and function, deregulating lipid metabolism and inducing thrombosis. However, the biochemical basis by which hyperhomocysteinemia (HHcy) contributes to cardiovascular diseases (CVDs) remains largely unknown. Several case-control studies have reported an association between HHcy and the presence of abdominal aortic aneurysms (AAA) and there are supportive data from animal models. Genotypic data concerning the association between variants of genes involved in the methionine cycle and AAA are conflicting probably due to problems such as reverse causality and confounding. The multifactorial nature of AAA suggests the involvement of additional epigenetic factors in disease formation. Elevated Hcy levels have been previously linked to altered DNA methylation levels in various diseases. Folate or vitamin B12 based methods of lowering Hcy have had disappointingly limited effects in reducing CVD events. One possible reason for the limited efficacy of such therapy is that they have failed to reverse epigenetic changes induced by HHcy. It is possible that individuals with HHcy have an "Hcy memory effect" due to epigenetic alterations which continue to promote progression of cardiovascular complications even after Hcy levels are lowered. It is possible that deleterious effect of prior, extended exposure to elevated Hcy concentrations have long-lasting effects on target organs and genes, hence underestimating the benefit of Hcy lowering therapies in CVD patients. Therapies targeting the epigenetic machinery as well as lowering circulating Hcy concentrations may have a more efficacious effect in reducing the incidence of cardiovascular complications.

Genistein attenuates vascular endothelial impairment in ovariectomized hyperhomocysteinemic rats

Hyperhomocysteinemia (HHcy) is a well-known independent risk factor for vascular diseases in the general population. This study was to explore the effect of genistein (GST), a natural bioactive compound derived from legumes, on HHcy-induced vascular endothelial impairment in ovariectomized rats in vivo. Thirty-two adult female Wistar rats were assigned randomly into four groups (n = 8): (a) Con: control; (b) Met: 2.5% methionine diet; (c) OVX + Met: ovariectomy + 2.5% methionine diet; (d) OVX + Met + GST: ovariectomy + 2.5% methionine diet + supplementation with genistein. After 12 wk of different treatment, the rats' blood, toracic aortas and liver samples were collected for analysis. Results showed that high-methionine diet induced both elevation of plasma Hcy and endothelial dysfunction, and ovariectomy deteriorated these injuries. Significant improvement of both functional and morphological changes of vascular endothelium was observed in OVX + Met + GST group; meanwhile the plasma Hcy levels decreased remarkably. There were significant elevations of plasma ET-1 and liver MDA levels in ovariectomized HHcy rats, and supplementation with genistein could attenuate these changes. These results implied that genistein could lower the elevated Hcy levels, and prevent the development of endothelial impairment in ovariectomized HHcy rats. This finding may shed a novel light on the anti-atherogenic activities of genistein in HHcy patients.

The effects of berberine on hyperhomocysteinemia and hyperlipidemia in rats fed with a long-term high-fat diet

Background

The study was undertaken to examine the effects of berberine (BBR) on serum homocysteine, lipids and the aortic lesion in Sprague–Dawley (SD) rats fed with a long-term high-fat diet (HFD).

Methods

Healthy male SD rats weighing 190-210 g received randomly standard diet or a high-fat diet for 24 weeks. After 8 weeks of feeding, rats fed with HFD were randomized to receive berberine (200 mg · kg-1· day-1) or vehicle by gavage for 16 weeks. After overnight fasting, all rats were sacrificed and total blood samples were also collected for determinant of fasting serum homocysteine (Hcy), total cholesterol (TC) and low density lipoprotein cholesterol (LDL-c) levels. The aorta was stained with hematoxylin and eosin (HE) and Sudan Ш to evaluate aortic lesion. The livers were dissected out and snap-frozen in liquid nitrogen for hepatic TC content and molecular analysis. 3-hydroxy-3-methyl-glutaryl-CoA reductase (HMGR), Lipoprotein receptors and apolipoproteins gene expression in the liver were determined by real-time PCR.

Results

Intragastrical administration with berberine for 16 weeks lowered serum Hcy in rats fed with a high-fat diet. In parallel, it also decreased body weight and improved serum TC and LDL-c. Berberine also tended to decrease hepatic cholesterol. Consistently, berberine also upregulated LDL receptor (LDLR) mRNA level and suppressed HMGR gene expression. Meanwhile, upon berberine-treated rats, there was a significant increase in apolipoprotein E (apoE) mRNA, but no change in apoAI and scavenger receptor (SR) mRNA in the liver. Further, no atherosclerotic lesions were developed in berberine-treated rats for 16 weeks.

Conclusion

Berberine can counteract HFD-elicited hyperhomocysteinemia and hyperlipidemia partially via upregulating LDLR and apoE mRNA levels and suppressing HMGR gene expression.

Hydrogen sulfide in the mammalian cardiovascular system

For more than a century, hydrogen sulfide (H(2)S) has been regarded as a toxic gas. This review surveys the growing recognition of the role of H(2)S as an endogenous signaling molecule in mammals, with emphasis on its physiological and pathological pathways in the cardiovascular system. In biological fluids, H(2)S gas is a weak acid that exists as about 15% H(2)S, 85% HS(-), and a trace of S(2-). Here, we use "H(2)S" to refer to this mixture. H(2)S has been found to influence heart contractile functions and may serve as a cardioprotectant for treating ischemic heart diseases and heart failure. Alterations of the endogenous H(2)S level have been found in animal models with various pathological conditions such as myocardial ischemia, spontaneous hypertension, and hypoxic pulmonary hypertension. In the vascular system, H(2)S exerts biphasic regulation of a vascular tone with varying effects based on its concentration and in the presence of nitric oxide. Over the past decade, several H(2)S-releasing compounds (NaHS, Na(2)S, GYY4137, etc.) have been utilized to test the effect of exogenous H(2)S under different physiological and pathological situations in vivo and in vitro. H(2)S has been found to promote angiogenesis and to protect against atherosclerosis and hypertension, while excess H(2)S may promote inflammation in septic or hemorrhagic shock. H(2)S-releasing compounds and inhibitors of H(2)S synthesis hold promise in alleviating specific disease conditions. This comprehensive review covers in detail the effects of H(2)S on the cardiovascular system, especially in disease situations, and also the various underlying mechanisms.

The most negatively charged low-density lipoprotein L5 induces stress pathways in vascular endothelial cells

BACKGROUND/AIMS

L5, the most negatively charged species of low-density lipoprotein (LDL), has been implicated in atherogenesis by inducing apoptosis of endothelial cells (ECs) and inhibiting the differentiation of endothelial progenitor cells. In this study, we compared the effects of LDL charge on cellular stress pathways leading to atherogenesis.

METHODS

We isolated L5 and L1 (the least negatively charged LDL) from the plasma of patients with familial hypercholesterolemia and used JC-1 staining to examine the effects of L5 and L1 on the mitochondrial membrane potential (DCm) in human umbilical vein ECs (HUVECs). Additionally, we characterized the gene expression profiles of 7 proteins involved in various types of cellular stress.

RESULTS

The DCm was severely compromised in HUVECs treated with L5. Furthermore, compared with L1, L5 induced a decrease in mRNA and protein expression of the endoplasmic reticulum (ER) chaperone proteins ORP150, Grp94, and Grp58, mitochondrial proteins Prdx3 and ATP synthase, and an increase in the expression of the pro-inflammatory protein hnRNP C1/C2.

CONCLUSIONS

Our work suggests that L5, but not L1, may promote the destruction of ECs that occurs during atherogenesis by causing mitochondrial dysfunction and modulating the expression of key proteins to promote inflammation, ER dysfunction, oxidative stress, and apoptosis.

Increased endogenous H2S generation by CBS, CSE, and 3MST gene therapy improves ex vivo renovascular relaxation in hyperhomocysteinemia

Hydrogen sulfide (H(2)S) has recently been identified as a regulator of various physiological events, including vasodilation, angiogenesis, antiapoptotic, and cellular signaling. Endogenously, H(2)S is produced as a metabolite of homocysteine (Hcy) by cystathionine β-synthase (CBS), cystathionine γ-lyase (CSE), and 3-mercaptopyruvate sulfurtransferase (3MST). Although Hcy is recognized as vascular risk factor at an elevated level [hyperhomocysteinemia (HHcy)] and contributes to vascular injury leading to renovascular dysfunction, the exact mechanism is unclear. The goal of the current study was to investigate whether conversion of Hcy to H(2)S improves renovascular function. Ex vivo renal artery culture with CBS, CSE, and 3MST triple gene therapy generated more H(2)S in the presence of Hcy, and these arteries were more responsive to endothelial-dependent vasodilation compared with nontransfected arteries treated with high Hcy. Cross section of triple gene-delivered renal arteries immunostaining suggested increased expression of CD31 and VEGF and diminished expression of the antiangiogenic factor endostatin. In vitro endothelial cell culture demonstrated increased mitophagy during high levels of Hcy and was mitigated by triple gene delivery. Also, dephosphorylated Akt and phosphorylated FoxO3 in HHcy were reversed by H(2)S or triple gene delivery. Upregulated matrix metalloproteinases-13 and downregulated tissue inhibitor of metalloproteinase-1 in HHcy were normalized by overexpression of triple genes. Together, these results suggest that H(2)S plays a key role in renovasculopathy during HHcy and is mediated through Akt/FoxO3 pathways. We conclude that conversion of Hcy to H(2)S by CBS, CSE, or 3MST triple gene therapy improves renovascular function in HHcy.

MG624, an α7-nAChR antagonist, inhibits angiogenesis via the Egr-1/FGF2 pathway

Small cell lung cancer (SCLC) demonstrates a strong etiological association with smoking. Although cigarette smoke is a mixture of about 4,000 compounds, nicotine is the addictive component of cigarette smoke. Several convergent studies have shown that nicotine promotes angiogenesis in lung cancers via the α7-nicotinic acetylcholine receptor (α7-nAChR) on endothelial cells. Therefore, we conjectured that α7-nAChR antagonists may attenuate nicotine-induced angiogenesis and be useful for the treatment of human SCLC. For the first time, our study explores the anti-angiogenic activity of MG624, a small-molecule α7-nAChR antagonist, in several experimental models of angiogenesis. We observed that MG624 potently suppressed the proliferation of primary human microvascular endothelial cells of the lung (HMEC-Ls). Furthermore, MG624 displayed robust anti-angiogenic activity in the Matrigel, rat aortic ring and rat retinal explant assays. The anti-angiogenic activity of MG624 was assessed by two in vivo models, namely the chicken chorioallantoic membrane model and the nude mice model. In both of these experimental models, MG624 inhibited angiogenesis of human SCLC tumors. Most importantly, the administration of MG624 was not associated with any toxic side effects, lethargy or discomfort in the mice. The anti-angiogenic activity of MG624 was mediated via the suppression of nicotine-induced FGF2 levels in HMEC-Ls. MG624 decreased nicotine-induced early growth response gene 1 (Egr-1) levels in HMEC-Ls, and reduced the levels of Egr-1 on the FGF2 promoter. Consequently, this process decreased FGF2 levels and angiogenesis. Our findings suggest that the anti-angiogenic effects of MG624 could be useful in anti-angiogenic therapy of human SCLCs.

Homocysteine promotes human endothelial cell dysfunction via site-specific epigenetic regulation of p66shc

AIMS

Hyperhomocysteinaemia is an independent risk factor for atherosclerotic vascular disease and is associated with vascular endothelial dysfunction. Homocysteine modulates cellular methylation reactions. P66shc is a protein that promotes oxidative stress whose expression is governed by promoter methylation. We asked if homocysteine induces endothelial p66shc expression via hypomethylation of CpG dinucleotides in the p66shc promoter, and whether p66shc mediates homocysteine-stimulated endothelial cell dysfunction.

METHODS AND RESULTS

Homocysteine stimulates p66shc transcription in human endothelial cells and hypomethylates specific CpG dinucleotides in the human p66shc promoter. Knockdown of p66shc inhibits the increase in reactive oxygen species, and decrease in nitric oxide, elicited by homocysteine in endothelial cells and prevents homocysteine-induced up-regulation of endothelial intercellular adhesion molecule-1. In addition, knockdown of p66shc mitigates homocysteine-induced adhesion of monocytes to endothelial cells. Inhibition of DNA methyltransferase activity or knockdown of DNA methyltransferase 3b abrogates homocysteine-induced up-regulation of p66shc. Comparison of plasma homocysteine in humans with coronary artery disease shows a significant difference between those with highest and lowest p66shc promoter CpG methylation in peripheral blood leucocytes.

CONCLUSION

Homocysteine up-regulates human p66shc expression via hypomethylation of specific CpG dinucleotides in the p66shc promoter, and this mechanism is important in homocysteine-induced endothelial cell dysfunction.

Genetics of redox systems and their relationship with cardiovascular disease

As atherosclerosis is still one of the major causes of death in Western populations, it is important to identify those individuals who are at increased risk for the disease so that aggressive treatment may be administered as early as possible. Following the understanding that oxidative stress has a pivotal role in the development and progression of atherosclerosis, many polymorphisms in genes that are related to redox systems were examined for their association with increased risk for cardiovascular disease (CVD). Although many polymorphisms were studied, only a handful showed consistent relevance to CVD in different trials. This article focuses on six of these polymorphisms, examining their effect on the risk for CVD as well as their effect on protein expression and function. Reports regarding pharmacogenetic implications of these polymorphisms, where such exist, are discussed as well.

AMP-activated protein kinase inhibits homocysteine-induced dysfunction and apoptosis in endothelial progenitor cells

PURPOSE

Homocysteine (Hcy) has been shown to induce oxidative stress and apoptosis of endothelial progenitor cells (EPCs). AMP-activated protein kinase (AMPK) has been reported to have protective effects on endothelial function. However, effects of AMPK activation on Hcy-induced EPCs injury remain to be determined. In this study, we examined the effect of AMPK phosphorylation on Hcy-induced NO bioavailability impairment and NADPH oxidase 4 (Nox4) derived reactive oxygen species (ROS) accumulation in EPCs.

MATERIALS AND METHODS

EPCs were pre-treated with various concentrations of 5-amino-4-imidazolecarboxamide riboside-l-beta-D-ribofuranoside (AICAR), a pharmacological agonist of AMPK, and then incubated with Hcy for 24 h. Furthermore, we challenged EPCs with Hcy in the presence or absence of atorvastatin and AMPK-DN which expressed a dominant-negative mutant of AMPK. Migration, proliferation and apoptosis were assayed to evaluate EPCs function. NO production, expression of endothelial nitric oxide synthase (eNOS), intracellular ROS levels and Nox4 activation were determined to explore the potential mechanisms of Hcy-induced EPCs dysfunction.

RESULTS

We observed that AICAR attenuated the inhibition effects of Hcy on EPCs migration and proliferation. The apoptosis rates of EPCs were down-regulated by AICAR compared with the group treated with Hcy only [(0.25 mmol/L AICAR: 10.48 ± 1.6%; 0.5 mmol/L AICAR: 8.70 ± 1.0%; 1 mmol/L AICAR: 5.83 ± 1.3%) vs. (500 μmol/L Hcy only: 12.60 ± 1.9%)]. We also found that NO production and eNOS expression were up-regulated by AICAR compared with the group treated with Hcy only, while ROS accumulation and Nox4 activation were inhibited. Furthermore, atorvastatin suppressed Hcy-induced dysfunction of EPCs, increased NO production and eNOS expression, and down-regulated ROS accumulation and Nox4 activation. And these effects of atorvastatin could be blunted by AMPK-DN.

CONCLUSION

AMPK activation inhibits eNOS down-regulation and Nox4-derived ROS accumulation induced by Hcy in EPCs, and may contribute to the protective effects of atorvastatin on endothelial function.