Inhibition of growth and p21ras methylation in vascular endothelial cells by homocysteine but not cysteine

SAH is a major metabolic sensor mediating worsening metabolic crosstalk in metabolic syndrome

In this study, we observed worsening metabolic crosstalk in mouse models with concomitant metabolic disorders such as hyperhomocysteinemia (HHcy), hyperlipidemia, and hyperglycemia and in human coronary artery disease by analyzing metabolic profiles. We found that HHcy worsening is most sensitive to other metabolic disorders. To identify metabolic genes and metabolites responsible for the worsening metabolic crosstalk, we examined mRNA levels of 324 metabolic genes in Hcy, glucose-related and lipid metabolic systems. We examined Hcy-metabolites (Hcy, SAH and SAM) by LS-ESI-MS/MS in 6 organs (heart, liver, brain, lung, spleen, and kidney) from C57BL/6J mice. Through linear regression analysis of Hcy-metabolites and metabolic gene mRNA levels, we discovered that SAH-responsive genes were responsible for most metabolic changes and all metabolic crosstalk mediated by Serine, Taurine, and G3P. SAH-responsive genes worsen glucose metabolism and cause upper glycolysis activation and lower glycolysis suppression, indicative of the accumulation of glucose/glycogen and G3P, Serine synthesis inhibition, and ATP depletion. Insufficient Serine due to negative correlation of PHGDH with SAH concentration may inhibit the folate cycle and transsulfurarion pathway and consequential reduced antioxidant power, including glutathione, taurine, NADPH, and NAD+. Additionally, we identified SAH-activated pathological TG loop as the consequence of increased fatty acid (FA) uptake, FA β-oxidation and Ac-CoA production along with lysosomal damage. We concluded that HHcy is most responsive to other metabolic changes in concomitant metabolic disorders and mediates worsening metabolic crosstalk mainly via SAH-responsive genes, that organ-specific Hcy metabolism determines organ-specific worsening metabolic reprogramming, and that SAH, acetyl-CoA, Serine and Taurine are critical metabolites mediating worsening metabolic crosstalk, redox disturbance, hypomethylation and hyperacetylation linking worsening metabolic reprogramming in metabolic syndrome.

Identification of methylation-regulated genes modulating microglial phagocytosis in hyperhomocysteinemia-exacerbated Alzheimer's disease

BACKGROUND

Hyperhomocysteinemia (HHcy) has been linked to development of Alzheimer's disease (AD) neuropathologically characterized by the accumulation of amyloid β (Aβ). Microglia (MG) play a crucial role in uptake of Aβ fibrils, and its dysfunction worsens AD. However, the effect of HHcy on MG Aβ phagocytosis remains unstudied.

METHODS

We isolated MG from the cerebrum of HHcy mice with genetic cystathionine-β-synthase deficiency (Cbs-/-) and performed bulk RNA-seq. We performed meta-analysis over transcriptomes of Cbs-/- mouse MG, human and mouse AD MG, MG Aβ phagocytosis model, human AD methylome, and GWAS AD genes.

RESULTS

HHcy and hypomethylation conditions were identified in Cbs-/- mice. Through Cbs-/- MG transcriptome analysis, 353 MG DEGs were identified. Phagosome formation and integrin signaling pathways were found suppressed in Cbs-/- MG. By analyzing MG transcriptomes from 4 AD patient and 7 mouse AD datasets, 409 human and 777 mouse AD MG DEGs were identified, of which 37 were found common in both species. Through further combinatory analysis with transcriptome from MG Aβ phagocytosis model, we identified 130 functional-validated Aβ phagocytic AD MG DEGs (20 in human AD, 110 in mouse AD), which reflected a compensatory activation of Aβ phagocytosis. Interestingly, we identified 14 human Aβ phagocytic AD MG DEGs which represented impaired MG Aβ phagocytosis in human AD. Finally, through a cascade of meta-analysis of transcriptome of AD MG, functional phagocytosis, HHcy MG, and human AD brain methylome dataset, we identified 5 HHcy-suppressed phagocytic AD MG DEGs (Flt1, Calponin 3, Igf1, Cacna2d4, and Celsr) which were reported to regulate MG/MΦ migration and Aβ phagocytosis.

CONCLUSIONS

We established molecular signatures for a compensatory response of Aβ phagocytosis activation in human and mouse AD MG and impaired Aβ phagocytosis in human AD MG. Our discoveries suggested that hypomethylation may modulate HHcy-suppressed MG Aβ phagocytosis in AD.

Early hyperlipidemia triggers metabolomic reprogramming with increased SAH, increased acetyl-CoA-cholesterol synthesis, and decreased glycolysis

To identify metabolomic reprogramming in early hyperlipidemia, unbiased metabolome was screened in four tissues from ApoE-/- mice fed with high fat diet (HFD) for 3 weeks. 30, 122, 67, and 97 metabolites in the aorta, heart, liver, and plasma, respectively, were upregulated. 9 upregulated metabolites were uremic toxins, and 13 metabolites, including palmitate, promoted a trained immunity with increased syntheses of acetyl-CoA and cholesterol, increased S-adenosylhomocysteine (SAH) and hypomethylation and decreased glycolysis. The cross-omics analysis found upregulation of 11 metabolite synthetases in ApoE‾/‾ aorta, which promote ROS, cholesterol biosynthesis, and inflammation. Statistical correlation of 12 upregulated metabolites with 37 gene upregulations in ApoE‾/‾ aorta indicated 9 upregulated new metabolites to be proatherogenic. Antioxidant transcription factor NRF2-/- transcriptome analysis indicated that NRF2 suppresses trained immunity-metabolomic reprogramming. Our results have provided novel insights on metabolomic reprogramming in multiple tissues in early hyperlipidemia oriented toward three co-existed new types of trained immunity.

Advances in the role of epigenetics in homocysteine-related diseases

Homocysteine has a wide range of biological effects. However, the specific molecular mechanism of its pathogenicity is still unclear. The diseases induced by hyperhomocysteinemia (HHcy) are called homocysteine-related diseases. Clinical treatment of HHcy is mainly through folic acid and B-complex vitamins, which are not effective in reducing the associated end point events. Epigenetics is the alteration of heritable genes caused by DNA methylation, histone modification, noncoding RNAs and chromatin remodeling without altering the DNA sequence. In recent years the role of epigenetics in homocysteine-associated diseases has been gradually discovered. This article summarizes the latest evidence on the role of epigenetics in HHcy, providing new directions for its prevention and treatment.

Homocysteine-Potential Novel Diagnostic Indicator of Health and Disease in Horses

Homocysteine is an endogenous, non-protein sulfuric amino acid, an intermediate metabolite formed by the methionine transmethylation reaction. Its elevated serum concentration in humans, hyperhomocysteinemia, is a sensitive indicator and a risk factor for coagulation disorders, cardiovascular diseases and dementia. However, the role of homocysteine in veterinary species has not been unequivocally established. Although some research has been conducted in dogs, cats, cattle and pigs, relatively few studies on homocysteine have been conducted in horses. So far, it has been established in this species that homocysteine has an atherogenic effect, plays a role in early embryo mortality and is responsible for the induction of oxidative stress. These preliminary findings support establishing a reference range in a normal population of horses, including horses in training and merit further investigations into the role of this amino acid in health and disease in this species.

Identification of molecular subtypes of coronary artery disease based on ferroptosis- and necroptosis-related genes

Aim: Coronary artery disease (CAD) is a heterogeneous disorder with high morbidity, mortality, and healthcare costs, representing a major burden on public health. Here, we aimed to improve our understanding of the genetic drivers of ferroptosis and necroptosis and the clustering of gene expression in CAD in order to develop novel personalized therapies to slow disease progression.

Methods: CAD datasets were obtained from the Gene Expression Omnibus. The identification of ferroptosis- and necroptosis-related differentially expressed genes (DEGs) and the consensus clustering method including the classification algorithm used km and distance used spearman were performed to differentiate individuals with CAD into two clusters (cluster A and cluster B) based expression matrix of DEGs. Next, we identified four subgroup-specific genes of significant difference between cluster A and B and again divided individuals with CAD into gene cluster A and gene cluster B with same methods. Additionally, we compared differences in clinical information between the subtypes separately. Finally, principal component analysis algorithms were constructed to calculate the cluster-specific gene score for each sample for quantification of the two clusters.

Results: In total, 25 ferroptosis- and necroptosis-related DEGs were screened. The genes in cluster A were mostly related to the neutrophil pathway, whereas those in cluster B were mostly related to the B-cell receptor signaling pathway. Moreover, the subgroup-specific gene scores and CAD indices were higher in cluster A and gene cluster A than in cluster B and gene cluster B. We also identified and validated two genes showing upregulation between clusters A and B in a validation dataset.

Conclusion: High expression of CBS and TLR4 was related to more severe disease in patients with CAD, whereas LONP1 and HSPB1 expression was associated with delayed CAD progression. The identification of genetic subgroups of patients with CAD may improve clinician knowledge of disease pathogenesis and facilitate the development of methods for disease diagnosis, classification, and prognosis.

Co-existing Hypertension and Hyperhomocysteinemia Increases the Risk of Carotid Vulnerable Plaque and Subsequent Vascular Event: An MR Vessel Wall Imaging Study

Purpose

This study sought to determine the associations of co-existing hypertension and hyperhomocysteinemia (H-Hcy) with carotid vulnerable plaque features and subsequent vascular events.

Methods

Symptomatic patients with carotid atherosclerosis were enrolled and underwent carotid magnetic resonance (MR) vessel wall imaging. The patients were divided into the following groups: co-existing hypertension and H-Hcy group; isolated hypertension group; isolated H-Hcy group; and control group. The morphological and compositional characteristics of carotid plaques were assessed on MR images and compared among different groups. Univariate and multivariate cox regressions were used to calculate the hazard ratio (HR) and corresponding 95% confidence interval (CI) of co-existing hypertension and H-Hcy in predicting subsequent vascular events after at least 1-year followed-up.

Results

In total, 217 patients (mean age, 59.4 ± 11.9 years; 154 males) were recruited. Patients in co-existing hypertension and H-Hcy group had a significantly higher prevalence of carotid lipid-rich necrotic core (LRNC) than isolated H-Hcy and control group (73.2 vs. 43.3 vs. 50%, p = 0.015). During the median follow-up time of 12.2 ± 4.3 months, 61 (39.8%) patients experienced vascular events. After adjusting for baseline confounding factors, co-existing hypertension and H-Hcy (HR, 1.82; 95% CI, 1.01–3.27; p = 0.044), presence of carotid LRNC (HR, 2.25; 95% CI, 1.09–4.65; p = 0.029), and combination of co-existing hypertension and H-Hcy and carotid LRNC (HR, 2.39; 95% CI, 1.26–4.43; p = 0.007) were significantly associated with subsequent vascular events.

Conclusions

Co-existing hypertension and H-Hcy are associated with carotid vulnerable plaque features, such as LRNC. Combining co-existing hypertension and H-Hcy with carotid vulnerable plaque features has a stronger predictive value for subsequent vascular events than each measurement alone.

Hyperlipidemia May Synergize with Hypomethylation in Establishing Trained Immunity and Promoting Inflammation in NASH and NAFLD

We performed a panoramic analysis on both human nonalcoholic steatohepatitis (NASH) microarray data and microarray/RNA-seq data from various mouse models of nonalcoholic fatty liver disease NASH/NAFLD with total 4249 genes examined and made the following findings: (i) human NASH and NAFLD mouse models upregulate both cytokines and chemokines; (ii) pathway analysis indicated that human NASH can be classified into metabolic and immune NASH; methionine- and choline-deficient (MCD)+high-fat diet (HFD), glycine N-methyltransferase deficient (GNMT-KO), methionine adenosyltransferase 1A deficient (MAT1A-KO), and HFCD (high-fat-cholesterol diet) can be classified into inflammatory, SAM accumulation, cholesterol/mevalonate, and LXR/RXR-fatty acid β-oxidation NAFLD, respectively; (iii) canonical and noncanonical inflammasomes play differential roles in the pathogenesis of NASH/NAFLD; (iv) trained immunity (TI) enzymes are significantly upregulated in NASH/NAFLD; HFCD upregulates TI enzymes more than cytokines, chemokines, and inflammasome regulators; (v) the MCD+HFD is a model with the upregulation of proinflammatory cytokines and canonical and noncanonical inflammasomes; however, the HFCD is a model with upregulation of TI enzymes and lipid peroxidation enzymes; and (vi) caspase-11 and caspase-1 act as upstream master regulators, which partially upregulate the expressions of cytokines, chemokines, canonical and noncanonical inflammasome pathway regulators, TI enzymes, and lipid peroxidation enzymes. Our findings provide novel insights on the synergies between hyperlipidemia and hypomethylation in establishing TI and promoting inflammation in NASH and NAFLD progression and novel targets for future therapeutic interventions for NASH and NAFLD, metabolic diseases, transplantation, and cancers.

Improvement of cognitive performance by a nutraceutical formulation: Underlying mechanisms revealed by laboratory studies

Cognitive decline, decrease in neuronal function and neuronal loss that accompany normal aging and dementia are the result of multiple mechanisms, many of which involve oxidative stress. Herein, we review these various mechanisms and identify pharmacological and non-pharmacological approaches, including modification of diet, that may reduce the risk and progression of cognitive decline. The optimal degree of neuronal protection is derived by combinations of, rather than individual, compounds. Compounds that provide antioxidant protection are particularly effective at delaying or improving cognitive performance in the early stages of Mild Cognitive Impairment and Alzheimer's disease. Laboratory studies confirm alleviation of oxidative damage in brain tissue. Lifestyle modifications show a degree of efficacy and may augment pharmacological approaches. Unfortunately, oxidative damage and resultant accumulation of biomarkers of neuronal damage can precede cognitive decline by years to decades. This underscores the importance of optimization of dietary enrichment, antioxidant supplementation and other lifestyle modifications during aging even for individuals who are cognitively intact.

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.

•

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.

•

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

•

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

•

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

•

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

•

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

•

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.

•

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

•

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

•

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

The Antioxidant Role of One-Carbon Metabolism on Stroke

One-carbon (1C) metabolism is a metabolic network that is centered on folate, a B vitamin; it integrates nutritional signals with biosynthesis, redox homeostasis, and epigenetics. This metabolic pathway also reduces levels of homocysteine, a non-protein amino acid. High levels of homocysteine are linked to increased risk of hypoxic events, such as stroke. Several preclinical studies have suggested that 1C metabolism can impact stroke outcome, but the clinical data are unclear. The objective of this paper was to review preclinical and clinical research to determine whether 1C metabolism has an antioxidant role on stroke. To accomplish the objective, we searched for publications using the following medical subject headings (MeSH) keywords: antioxidants, hypoxia, stroke, homocysteine, one-carbon metabolism, folate, methionine, and dietary supplementation of one-carbon metabolism. Both pre-clinical and clinical studies were retrieved and reviewed. Our review of the literature suggests that deficiencies in 1C play an important role in the onset and outcome of stroke. Dietary supplementation of 1C provides beneficial effects on stroke outcome. For stroke-affected patients or individuals at high risk for stroke, the data suggest that nutritional modifications in addition to other therapies could be incorporated into a treatment plan.

Homocysteine Serum Levels as Prognostic Marker of Hepatocellular Carcinoma with Portal Vein Thrombosis

BACKGROUND

Portal vein thrombosis (PVT) is a common complication of endstage hepatocellular carcinoma (HCC). The aim of our study was to evaluate the role of Homocysteine (Hcy) in HCC patient with PVT. Hcy is a sulphur amino-acid involved in two pathways, trans-sulphuration and remethylation, that involve vitamins B6, B12 and folates.

METHODS

We recruited 54 patients with HCC and PVT, 60 patients with HCC and without PVT and 60 control subjects. We measured serum levels of Hcy, folate, vitamins B6 and B12.

RESULTS

The comparison between HCC patients with PVT versus HCC without PVT was shown that mean values of Hcy were 6.4 nmol/L (p<0.0073) higher, LDL cholesterol were 4.8 mg/dl (p<0.0079) lower, vitamin B6 were 4.6 nmol/L(p=0.0544) lower, vitamins B 12 were 22.1 pg/ml (p=0.0001) lower.

CONCLUSION

High serum levels of Hcy are an established thrombotic risk factor in the general population. We found significantly higher levels of Hcy in HCC patients with PVT versus both HCC patients without PVT and controls.

DNA Methylation Dysfunction in Chronic Kidney Disease

Renal disease is the common denominator of a number of underlying disease conditions, whose prevalence has been dramatically increasing over the last two decades. Two aspects are particularly relevant to the subject of this review: (I) most cases are gathered under the umbrella of chronic kidney disease since they require—predictably for several lustrums—continuous clinical monitoring and treatment to slow down disease progression and prevent complications; (II) cardiovascular disease is a terrible burden in this population of patients, in that it claims many lives yearly, while only a scant minority reach the renal disease end stage. Why indeed a review on DNA methylation and renal disease? As we hope to convince you, the present evidence supports the role of the existence of various derangements of the epigenetic control of gene expression in renal disease, which hold the potential to improve our ability, in the future, to more effectively act toward disease progression, predict outcomes and offer novel therapeutic approaches.

Homocysteine-methionine cycle is a metabolic sensor system controlling methylation-regulated pathological signaling

Homocysteine-Methionine (HM) cycle produces universal methyl group donor S-adenosylmethione (SAM), methyltransferase inhibitor S-adenosylhomocysteine (SAH) and homocysteine (Hcy). Hyperhomocysteinemia (HHcy) is established as an independent risk factor for cardiovascular disease (CVD) and other degenerative disease. We selected 115 genes in the extended HM cycle (31 metabolic enzymes and 84 methyltransferases), examined their protein subcellular location/partner protein, investigated their mRNA levels and mapped their corresponding histone methylation status in 35 disease conditions via mining a set of public databases and intensive literature research. We have 6 major findings. 1) All HM metabolic enzymes are located only in the cytosol except for cystathionine-β-synthase (CBS), which was identified in both cytosol and nucleus. 2) Eight disease conditions encountered only histone hypomethylation on 8 histone residues (H3R2/K4/R8/K9/K27/K36/K79 and H4R3). Nine disease conditions had only histone hypermethylation on 8 histone residues (H3R2/K4/K9/K27/K36/K79 and H4R3/K20). 3) We classified 9 disease types with differential HM cycle expression pattern. Eleven disease conditions presented most 4 HM cycle pathway suppression. 4) Three disease conditions had all 4 HM cycle pathway suppression and only histone hypomethylation on H3R2/K4/R8/K9/K36 and H4R3. 5) Eleven HM cycle metabolic enzymes interact with 955 proteins. 6) Five paired HM cycle proteins interact with each other. We conclude that HM cycle is a key metabolic sensor system which mediates receptor-independent metabolism-associated danger signal recognition and modulates SAM/SAH-dependent methylation in disease conditions and that hypomethylation on frequently modified histone residues is a key mechanism for metabolic disorders, autoimmune disease and CVD. We propose that HM metabolism takes place in the cytosol, that nuclear methylation equilibration requires a nuclear-cytosol transfer of SAM/SAH/Hcy, and that Hcy clearance is essential for genetic protection.

The Contribution of Homocysteine Metabolism Disruption to Endothelial Dysfunction: State-of-the-Art

Homocysteine (Hcy) is a sulfur-containing non-proteinogenic amino acid formed during the metabolism of the essential amino acid methionine. Hcy is considered a risk factor for atherosclerosis and cardiovascular disease (CVD), but the molecular basis of these associations remains elusive. The impairment of endothelial function, a key initial event in the setting of atherosclerosis and CVD, is recurrently observed in hyperhomocysteinemia (HHcy). Various observations may explain the vascular toxicity associated with HHcy. For instance, Hcy interferes with the production of nitric oxide (NO), a gaseous master regulator of endothelial homeostasis. Moreover, Hcy deregulates the signaling pathways associated with another essential endothelial gasotransmitter: hydrogen sulfide. Hcy also mediates the loss of critical endothelial antioxidant systems and increases the intracellular concentration of reactive oxygen species (ROS) yielding oxidative stress. ROS disturb lipoprotein metabolism, contributing to the growth of atherosclerotic vascular lesions. Moreover, excess Hcy maybe be indirectly incorporated into proteins, a process referred to as protein N-homocysteinylation, inducing vascular damage. Lastly, cellular hypomethylation caused by build-up of S-adenosylhomocysteine (AdoHcy) also contributes to the molecular basis of Hcy-induced vascular toxicity, a mechanism that has merited our attention in particular. AdoHcy is the metabolic precursor of Hcy, which accumulates in the setting of HHcy and is a negative regulator of most cell methyltransferases. In this review, we examine the biosynthesis and catabolism of Hcy and critically revise recent findings linking disruption of this metabolism and endothelial dysfunction, emphasizing the impact of HHcy on endothelial cell methylation status.

Restoration of skeletal muscle homeostasis by hydrogen sulfide during hyperhomocysteinemia-mediated oxidative/ER stress condition 1

Elevated homocysteine (Hcy), i.e., hyperhomocysteinemia (HHcy), causes skeletal muscle myopathy. Among many cellular and metabolic alterations caused by HHcy, oxidative and endoplasmic reticulum (ER) stress are considered the major ones; however, the precise molecular mechanism(s) in this process is unclear. Nevertheless, there is no treatment option available to treat HHcy-mediated muscle injury. Hydrogen sulfide (H₂S) is increasingly recognized as a potent anti-oxidant, anti-apoptotic/necrotic/pyroptotic, and anti-inflammatory compound and also has been shown to improve angiogenesis during ischemic injury. Patients with CBS mutation produce less H₂S, making them vulnerable to Hcy-mediated cellular damage. Many studies have reported bidirectional regulation of ER stress in apoptosis through JNK activation and concomitant attenuation of cell proliferation and protein synthesis via PI3K/AKT axis. Whether H₂S mitigates these detrimental effects of HHcy on muscle remains unexplored. In this review, we discuss molecular mechanisms of HHcy-mediated oxidative/ER stress responses, apoptosis, angiogenesis, and atrophic changes in skeletal muscle and how H₂S can restore skeletal muscle homeostasis during HHcy condition. This review also highlights the molecular mechanisms on how H₂S could be developed as a clinically relevant therapeutic option for chronic conditions that are aggravated by HHcy.

Hydrogen sulfide improves postischemic neoangiogenesis in the hind limb of cystathionine-β-synthase mutant mice via PPAR-γ/VEGF axis

Neoangiogenesis is a fundamental process which helps to meet energy requirements, tissue growth, and wound healing. Although previous studies showed that Peroxisome proliferator-activated receptor (PPAR-γ) regulates neoangiogenesis via upregulation of vascular endothelial growth factor (VEGF), and both VEGF and PPAR-γ expressions were inhibited during hyperhomocysteinemic (HHcy), whether these two processes could trigger pathological effects in skeletal muscle via compromising neoangiogenesis has not been studied yet. Unfortunately, there are no treatment options available to date for ameliorating HHcy-mediated neoangiogenic defects. Hydrogen sulfide (H2 S) is a novel gasotransmitter that can induce PPAR-γ levels. However, patients with cystathionine-β-synthase (CBS) mutation(s) cannot produce a sufficient amount of H2 S. We hypothesized that exogenous supplementation of H2 S might improve HHcy-mediated poor neoangiogenesis via the PPAR-γ/VEGF axis. To examine this, we created a hind limb femoral artery ligation (FAL) in CBS+/- mouse model and treated them with GYY4137 (a long-acting H2 S donor compound) for 21 days. To evaluate neoangiogenesis, we used barium sulfate angiography and laser Doppler blood flow measurements in the ischemic hind limbs of experimental mice post-FAL to assess blood flow. Proteins and mRNAs levels were studied by Western blots and qPCR analyses. HIF1-α, VEGF, PPAR-γ and p-eNOS expressions were attenuated in skeletal muscle of CBS+/- mice after 21 days of FAL in comparison to wild-type (WT) mice, that were improved via GYY4137 treatment. We also found that the collateral vessel density and blood flow were significantly reduced in post-FAL CBS+/- mice compared to WT mice and these effects were ameliorated by GYY4137. Moreover, we found that plasma nitrite levels were decreased in post-FAL CBS+/- mice compared to WT mice, which were mitigated by GYY4137 supplementation. These results suggest that HHcy can inhibit neoangiogenesis via antagonizing the angiogenic signal pathways encompassing PPAR-γ/VEGF axis and that GYY4137 could serve as a potential therapeutic to alleviate the harmful metabolic effects of HHcy conditions.

The Impact of Uremic Toxins on Cerebrovascular and Cognitive Disorders

Individuals at all stages of chronic kidney disease (CKD) have a higher risk of developing cognitive disorders and dementia. Stroke is also highly prevalent in this population and is associated with a higher risk of neurological deterioration, in-hospital mortality, and poor functional outcomes. Evidence from in vitro studies and in vivo animal experiments suggests that accumulation of uremic toxins may contribute to the pathogenesis of stroke and amplify vascular damage, leading to cognitive disorders and dementia. This review summarizes current evidence on the mechanisms by which uremic toxins may favour the occurrence of cerebrovascular diseases and neurological complications in CKD.

Prediction of Methionine and Homocysteine levels in Zucker diabetic fatty (ZDF) rats as a T2DM animal model after consumption of a Methionine-rich diet

Background

Although alterations in the methionine metabolism cycle (MMC) have been associated with vascular complications of diabetes, there have not been consistent results about the levels of methionine and homocysteine in type 2 diabetes mellitus (T2DM). The aim of the current study was to predict changes in plasma methionine and homocysteine concentrations after simulated consumption of methionine-rich foods, following the development of a mathematical model for MMC in Zucker Diabetic Fatty (ZDF) rats, as a representative T2DM animal model.

Method

The model building and simulation were performed using NONMEM® (ver. 7.3.0) assisted by Perl-Speaks-NONMEM (PsN, ver. 4.3.0). Model parameters were derived using first-order conditional estimation method with interactions permitted among the parameters (FOCE-INTER). NCA was conducted using Phoenix (ver. 6.4.0). For all tests, we considered a P-value < 0.05 to reflect statistical significance.

Results

Our model featured seven compartments that considered all parts of the cycle by applying non-linear mixed effects model. Conversion of S-adenosyl-L-homocysteine (SAH) to homocysteine increased and the metabolism of homocysteine was reduced under diabetic conditions, and consequently homocysteine accumulated in the elimination phase.

Using our model, we performed simulations to compare the changes in plasma methionine and homocysteine concentrations between ZDF and normal rats, by multiple administrations of the methionine-rich diet of 1 mmol/kg, daily for 60 days. The levels of methionine and homocysteine were elevated approximately two- and three-fold, respectively, in ZDF rats, while there were no changes observed in the normal control rats.

Conclusion

These results can be interpreted to mean that both methionine and homocysteine will accumulate in patients with T2DM, who regularly consume high-methionine foods.

S-adenosylhomocysteine hydrolase over-expression does not alter S-adenosylmethionine or S-adenosylhomocysteine levels in CBS deficient mice

Elevated plasma total homocysteine (tHcy) is associated with a number of human diseases including coronary artery disease, stroke, osteoporosis and dementia. It is highly correlated with intracellular S-adenosylhomocysteine (SAH). Since SAH is a strong inhibitor of methyl-transfer reactions involving the methyl-donor S-adenosylmethionine (SAM), elevation in SAH could be an explanation for the wide association of tHcy and human disease. Here, we have created a transgenic mouse (Tg-hAHCY) that expresses human S-adenosylhomocysteine hydrolase (AHCY) from a zinc-inducible promoter in the liver and kidney. Protein analysis shows that human AHCY is expressed well in both liver and kidney, but elevated AHCY enzyme activity (131% increase) is only detected in the kidney due to the high levels of endogenous mouse AHCY expression in liver. Tg-hAHCY mice were crossed with mice lacking cystathionine β-synthase activity (Tg-I278T Cbs^−/−) to explore the effect to AHCY overexpression in the context of elevated serum tHcy and elevated tissue SAM and SAH. Overexpression of AHCY had no significant effect on the phenotypes of Tg-I278T Cbs^−/− mice or any effect on the steady state concentrations of methionine, total homocysteine, SAM, SAH, and SAM/SAH ratio in the liver and kidney. Furthermore, enhanced AHCY activity did not lower serum and tissue tHcy or methionine levels. Our data suggests that enhancing AHCY activity does not alter the distribution of methionine recycling metabolites, even when they are greatly elevated by Cbs mutations.

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.

Metabolism-associated danger signal-induced immune response and reverse immune checkpoint-activated CD40+ monocyte differentiation

Adaptive immunity is critical for disease progression and modulates T cell (TC) and antigen-presenting cell (APC) functions. Three signals were initially proposed for adaptive immune activation: signal 1 antigen recognition, signal 2 co-stimulation or co-inhibition, and signal 3 cytokine stimulation. In this article, we propose to term signal 2 as an immune checkpoint, which describes interactions of paired molecules leading to stimulation (stimulatory immune checkpoint) or inhibition (inhibitory immune checkpoint) of an immune response. We classify immune checkpoint into two categories: one-way immune checkpoint for forward signaling towards TC only, and two-way immune checkpoint for both forward and reverse signaling towards TC and APC, respectively. Recently, we and others provided evidence suggesting that metabolic risk factors (RF) activate innate and adaptive immunity, involving the induction of immune checkpoint molecules. We summarize these findings and suggest a novel theory, metabolism-associated danger signal (MADS) recognition, by which metabolic RF activate innate and adaptive immunity. We emphasize that MADS activates the reverse immune checkpoint which leads to APC inflammation in innate and adaptive immunity. Our recent evidence is shown that metabolic RF, such as uremic toxin or hyperhomocysteinemia, induced immune checkpoint molecule CD40 expression in monocytes (MC) and elevated serum soluble CD40 ligand (sCD40L) resulting in CD40⁺ MC differentiation. We propose that CD40⁺ MC is a novel pro-inflammatory MC subset and a reliable biomarker for chronic kidney disease severity. We summarize that CD40:CD40L immune checkpoint can induce TC and APC activation via forward stimulatory, reverse stimulatory, and TC contact-independent immune checkpoints. Finally, we modeled metabolic RF-induced two-way stimulatory immune checkpoint amplification and discussed potential signaling pathways including AP-1, NF-κB, NFAT, STAT, and DNA methylation and their contribution to systemic and tissue inflammation.

Plasma S-adenosylhomocysteine: A potential risk marker for cerebral venous thrombosis

BACKGROUND

Despite a plethora of studies suggesting that hyperhomocysteinemia is associated with an increased risk for arterial and venous thrombosis, there is paucity of data on the role of the S-adenosylhomocysteine (SAH), the metabolic precursor of homocysteine (Hcy) as a risk predictor for cerebral venous thrombosis (CVT).

METHOD

We estimated fasting plasma concentrations of total homocysteine (tHcy), SAH and S-adenosylmethionine (SAM), in 185 CVT patients and 248 healthy controls, by reverse-phase high performance liquid chromatography coupled with coulometric electrochemical detection.

RESULTS

Fasting tHcy, SAH and SAM were significantly higher in patients compared with controls. Increased tHcy and SAH concentrations were associated with 4.54-fold (95% CI, 2.74-7.53) and 35.77-fold (95% CI, 19.45-65.79) increase in risk for CVT, respectively. Receiver operating characteristic (ROC) curve analysis showed that the area under curve, sensitivity and specificity was higher for SAH compared to tHcy. Further, discriminant analysis to distinguish between tHcy and SAH showed that SAH had a significantly higher percentage classification, with lower Wilk's lambda and higher χ(2), compared to tHcy.

CONCLUSION

Increased plasma SAH may be a more sensitive risk marker for CVT than plasma tHcy.

Caspase-1 Inflammasome Activation Mediates Homocysteine-Induced Pyrop-Apoptosis in Endothelial Cells

RATIONALE

Endothelial injury is an initial mechanism mediating cardiovascular disease.

OBJECTIVE

Here, we investigated the effect of hyperhomocysteinemia on programed cell death in endothelial cells (EC).

METHODS AND RESULTS

We established a novel flow-cytometric gating method to define pyrotosis (Annexin V(-)/Propidium iodide(+)). In cultured human EC, we found that: (1) homocysteine and lipopolysaccharide individually and synergistically induced inflammatory pyroptotic and noninflammatory apoptotic cell death; (2) homocysteine/lipopolysaccharide induced caspase-1 activation before caspase-8, caspase-9, and caspase-3 activations; (3) caspase-1/caspase-3 inhibitors rescued homocysteine/lipopolysaccharide-induced pyroptosis/apoptosis, but caspase-8/caspase-9 inhibitors had differential rescue effect; (4) homocysteine/lipopolysaccharide-induced nucleotide-binding oligomerization domain, and leucine-rich repeat and pyrin domain containing protein 3 (NLRP3) protein caused NLRP3-containing inflammasome assembly, caspase-1 activation, and interleukin (IL)-1β cleavage/activation; (5) homocysteine/lipopolysaccharide elevated intracellular reactive oxygen species, (6) intracellular oxidative gradient determined cell death destiny as intermediate intracellular reactive oxygen species levels are associated with pyroptosis, whereas high reactive oxygen species corresponded to apoptosis; (7) homocysteine/lipopolysaccharide induced mitochondrial membrane potential collapse and cytochrome-c release, and increased B-cell lymphoma 2-associated X protein/B-cell lymphoma 2 ratio which were attenuated by antioxidants and caspase-1 inhibitor; and (8) antioxidants extracellular superoxide dismutase and catalase prevented homocysteine/lipopolysaccharide -induced caspase-1 activation, mitochondrial dysfunction, and pyroptosis/apoptosis. In cystathionine β-synthase-deficient (Cbs(-/-)) mice, severe hyperhomocysteinemia-induced caspase-1 activation in isolated lung EC and caspase-1 expression in aortic endothelium, and elevated aortic caspase-1, caspase-9 protein/activity and B-cell lymphoma 2-associated X protein/B-cell lymphoma 2 ratio in Cbs(-/-) aorta and human umbilical vein endothelial cells. Finally, homocysteine-induced DNA fragmentation was reversed in caspase-1(-/-) EC. Hyperhomocysteinemia-induced aortic endothelial dysfunction was rescued in caspase-1(-/-) and NLRP3(-/-) mice.

CONCLUSIONS

Hyperhomocysteinemia preferentially induces EC pyroptosis via caspase-1-dependent inflammasome activation leading to endothelial dysfunction. We termed caspase-1 responsive pyroptosis and apoptosis as pyrop-apoptosis.

Cystathionine β-synthase regulates endothelial function via protein S-sulfhydration

Deficiencies of the human cystathionine β-synthase (CBS) enzyme are characterized by a plethora of vascular disorders and hyperhomocysteinemia. However, several clinical trials demonstrated that despite reduction in homocysteine levels, disease outcome remained unaffected, thus the mechanism of endothelial dysfunction is poorly defined. Here, we show that the loss of CBS function in endothelial cells (ECs) leads to a significant down-regulation of cellular hydrogen sulfide (H2S) by 50% and of glutathione (GSH) by 40%. Silencing CBS in ECs compromised phenotypic and signaling responses to the VEGF that were potentiated by decreased transcription of VEGF receptor (VEGFR)-2 and neuropilin (NRP)-1, the primary receptors regulating endothelial function. Transcriptional down-regulation of VEGFR-2 and NRP-1 was mediated by a lack in stability of the transcription factor specificity protein 1 (Sp1), which is a sulfhydration target of H2S at residues Cys68 and Cys755. Reinstating H2S but not GSH in CBS-silenced ECs restored Sp1 levels and its binding to the VEGFR-2 promoter and VEGFR-2, NRP-1 expression, VEGF-dependent proliferation, and migration phenotypes. Thus, our study emphasizes the importance of CBS-mediated protein S-sulfhydration in maintaining vascular health and function.-Saha, S., Chakraborty, P. K., Xiong, X., Dwivedi, S. K. D., Mustafi, S. B., Leigh, N. R., Ramchandran, R., Mukherjee, P., Bhattacharya, R. Cystathionine β-synthase regulates endothelial function via protein S-sulfhydration.

S-adenosylhomocysteine induces inflammation through NFkB: A possible role for EZH2 in endothelial cell activation

S-adenosylhomocysteine (SAH) can induce endothelial dysfunction and activation, contributing to atherogenesis; however, its role in the activation of the inflammatory mediator NFkB has not been explored. Our aim was to determine the role of NFkB in SAH-induced activation of endothelial cells. Furthermore, we examined whether SAH, as a potent inhibitor of S-adenosylmethionine-dependent methyltransferases, suppresses the function of EZH2 methyltransferase to contribute to SAH-induced endothelial cell activation. We found that excess SAH increases the expression of adhesion molecules and cytokines in human coronary artery endothelial cells. Importantly, this up-regulation was suppressed in cells expressing a dominant negative form of the NFkB inhibitor, IkB. Moreover, SAH accumulation triggers the activation of both the canonical and non-canonical NFkB pathways, decreases EZH2, and reduces histone 3 lysine 27 trimethylation. EZH2 knockdown recapitulated the effects of excess SAH on endothelial activation, i.e., it induced NFkB activation and the subsequent up-regulation of adhesion molecules and cytokines. Our findings suggest that suppression of the epigenetic regulator EZH2 by excess SAH may contribute to NFkB activation and the consequent vascular inflammatory response. These studies unveil new targets of SAH regulation, demonstrating that EZH2 suppression and NFkB activation mediated by SAH accumulation may contribute to its adverse effects in the vasculature.

Homocysteine, hyperhomocysteinemia and vascular contributions to cognitive impairment and dementia (VCID)

Homocysteine is produced physiologically in all cells, and is present in plasma of healthy individuals (plasma [HCy]: 3-10μM). While rare genetic mutations (CBS, MTHFR) cause severe hyperhomocysteinemia ([HCy]: 100-200μM), mild-moderate hyperhomocysteinemia ([HCy]: 10-100μM) is common in older people, and is an independent risk factor for stroke and cognitive impairment. As B-vitamin supplementation (B6, B12 and folate) has well-validated homocysteine-lowering efficacy, this may be a readily-modifiable risk factor in vascular contributions to cognitive impairment and dementia (VCID). Here we review the biochemical and cellular actions of HCy related to VCID. Neuronal actions of HCy were at concentrations above the clinically-relevant range. Effects of HCy <100μM were primarily vascular, including myocyte proliferation, vessel wall fibrosis, impaired nitric oxide signalling, superoxide generation and pro-coagulant actions. HCy-lowering clinical trials relevant to VCID are discussed. Extensive clinical and preclinical data support HCy as a mediator for VCID. In our view further trials of combined B-vitamin supplementation are called for, incorporating lessons from previous trials and from recent experimental work. To maximise likelihood of treatment effect, a future trial should: supply a high-dose, combination supplement (B6, B12 and folate); target the at-risk age range; and target cohorts with low baseline B-vitamin status. This article is part of a Special Issue entitled: Vascular Contributions to Cognitive Impairment and Dementia edited by M. Paul Murphy, Roderick A. Corriveau and Donna M. Wilcock.

Liver transplantation for treatment of severe S-adenosylhomocysteine hydrolase deficiency

A child with severe S-adenosylhomocysteine hydrolase (AHCY) deficiency (AHCY c.428A>G, p.Tyr143Cys; c.982T>G, p.Tyr328Asp) presented at 8 months of age with growth failure, microcephaly, global developmental delay, myopathy, hepatopathy, and factor VII deficiency. Plasma methionine, S-adenosylmethionine (AdoMet), and S-adenosylhomocysteine (AdoHcy) were markedly elevated and the molar concentration ratio of AdoMet:AdoHcy, believed to regulate a myriad of methyltransferase reactions, was 15% of the control mean. Dietary therapy failed to normalize biochemical markers or alter the AdoMet to AdoHcy molar concentration ratio. At 40 months of age, the proband received a liver segment from a healthy, unrelated living donor. Mean AdoHcy decreased 96% and the AdoMet:AdoHcy concentration ratio improved from 0.52±0.19 to 1.48±0.79 mol:mol (control 4.10±2.11 mol:mol). Blood methionine and AdoMet were normal and stable during 6 months of follow-up on an unrestricted diet. Average calculated tissue methyltransferase activity increased from 43±26% to 60±22%, accompanied by signs of increased transmethylation in vivo. Factor VII activity increased from 12% to 100%. During 6 postoperative months, head growth accelerated 4-fold and the patient made promising gains in gross motor, language, and social skills.

MTHFR deficiency or reduced intake of folate or choline in pregnant mice results in impaired short-term memory and increased apoptosis in the hippocampus of wild-type offspring

Genetic or nutritional disturbances in one-carbon metabolism, with associated hyperhomocysteinemia, can result in complex disorders including pregnancy complications and neuropsychiatric diseases. In earlier work, we showed that mice with a complete deficiency of methylenetetrahydrofolate reductase (MTHFR), a critical enzyme in folate and homocysteine metabolism, had cognitive impairment with disturbances in choline metabolism. Maternal demands for folate and choline are increased during pregnancy and deficiencies of these nutrients result in several negative outcomes including increased resorption and delayed development. The goal of this study was to investigate the behavioral and neurobiological impact of a maternal genetic deficiency in MTHFR or maternal nutritional deficiency of folate or choline during pregnancy on 3-week-old Mthfr(+/+) offspring. Mthfr(+/+) and Mthfr(+/-) females were placed on control diets (CD); and Mthfr(+/+) females were placed on folate-deficient diets (FD) or choline-deficient diets (ChDD) throughout pregnancy and lactation until their offspring were 3weeks of age. Short-term memory was assessed in offspring, and hippocampal tissue was evaluated for morphological changes, apoptosis, proliferation and choline metabolism. Maternal MTHFR deficiency resulted in short-term memory impairment in offspring. These dams had elevated levels of plasma homocysteine when compared with wild-type dams. There were no differences in plasma homocysteine in offspring. Increased apoptosis and proliferation was observed in the hippocampus of offspring from Mthfr(+/-) mothers. In the maternal FD and ChDD study, offspring also showed short-term memory impairment with increased apoptosis in the hippocampus; increased neurogenesis was observed in ChDD offspring. Choline acetyltransferase protein was increased in the offspring hippocampus of both dietary groups and betaine was decreased in the hippocampus of FD offspring. Our results reveal short-term memory deficits in the offspring of dams with MTHFR deficiency or dietary deficiencies of critical methyl donors. We suggest that deficiencies in maternal one-carbon metabolism during pregnancy can contribute to hippocampal dysfunction in offspring through apoptosis or altered choline metabolism.

Hyperhomocysteinemia suppresses bone marrow CD34+/VEGF receptor 2+ cells and inhibits progenitor cell mobilization and homing to injured vasculature-a role of β1-integrin in progenitor cell migration and adhesion

Hyperhomocysteinemia (HHcy) impairs re-endothelialization and accelerates vascular remodeling. The role of CD34(+)/VEGF receptor (VEGFR) 2(+) progenitor cells (PCs) in vascular repair in HHcy is unknown. We studied the effect of HHcy on PCs and its role in vascular repair in severe HHcy (∼150 μM), which was induced in cystathionine-β synthase heterozygous mice fed a high-methionine diet for 8 weeks. Vascular injury was introduced by carotid air-dry endothelium denudation. CD34(+)/VEGFR2(+) cells were examined by flow cytometry. HHcy reduced bone marrow (BM) CD34(+)/VEGFR2(+) cells and suppressed replenishment of postinjury CD34(+)/VEGFR2(+) cells in peripheral blood (PB). Donor green fluorescent protein-positive PC homing to the injured vessel was reduced in HHcy after CD34(+) PCs from enhanced green fluorescent protein mice were adoptively transferred following carotid injury. CD34(+) PC transfusion partially reversed HHcy-suppressed re-endothelialization and HHcy-induced neointimal formation. Furthermore, homocysteine (Hcy) inhibited proliferation, adhesion, and migration and suppressed β1-integrin expression and activity in human CD34(+) endothelial colony-forming cells (ECFCs) isolated from PBs in a dose-dependent manner. A functional-activating β1-integrin antibody rescued Hcy-suppressed adhesion and migration in CD34(+) ECFCs. In conclusion, HHcy reduces BM CD34(+)/VEGFR2(+) generation and suppresses CD34(+)/VEGFR2(+) cell mobilization and homing to the injured vessel via β1-integrin inhibition, which partially contributes to impaired re-endothelialization and vascular remodeling.

Hyperhomocysteinemia and hyperglycemia induce and potentiate endothelial dysfunction via μ-calpain activation

Plasma homocysteine (Hcy) levels are positively correlated with cardiovascular mortality in diabetes. However, the joint effect of hyperhomocysteinemia (HHcy) and hyperglycemia (HG) on endothelial dysfunction (ED) and the underlying mechanisms have not been studied. Mild (22 µmol/L) and moderate (88 µmol/L) HHcy were induced in cystathionine β-synthase wild-type (Cbs(+/+)) and heterozygous-deficient (Cbs(-/+)) mice by a high-methionine (HM) diet. HG was induced by consecutive injection of streptozotocin. We found that HG worsened HHcy and elevated Hcy levels to 53 and 173 µmol/L in Cbs(+/+) and Cbs(-/+) mice fed an HM diet, respectively. Both mild and moderate HHcy aggravated HG-impaired endothelium-dependent vascular relaxation to acetylcholine, which was completely abolished by endothelial nitric oxide synthase (eNOS) inhibitor N(G)-nitro-L-arginine methyl ester. HHcy potentiated HG-induced calpain activation in aortic endothelial cells isolated from Cbs mice. Calpain inhibitors rescued HHcy- and HHcy/HG-induced ED in vivo and ex vivo. Moderate HHcy- and HG-induced μ-calpain activation was potentiated by a combination of HHcy and HG in the mouse aorta. μ-Calpain small interfering RNA (μ-calpsiRNA) prevented HHcy/HG-induced ED in the mouse aorta and calpain activation in human aortic endothelial cells (HAECs) treated with DL-Hcy (500 µmol/L) and d-glucose (25 mmol) for 48 h. In addition, HHcy accelerated HG-induced superoxide production as determined by dihydroethidium and 3-nitrotyrosin staining and urinary 8-isoprostane/creatinine assay. Antioxidants rescued HHcy/HG-induced ED in mouse aortas and calpain activation in cultured HAECs. Finally, HHcy potentiated HG-suppressed nitric oxide production and eNOS activity in HAECs, which were prevented by calpain inhibitors or μ-calpsiRNA. HHcy aggravated HG-increased phosphorylation of eNOS at threonine 497/495 (eNOS-pThr497/495) in the mouse aorta and HAECs. HHcy/HG-induced eNOS-pThr497/495 was reversed by µ-calpsiRNA and adenoviral transduced dominant negative protein kinase C (PKC)β2 in HAECs. HHcy and HG induced ED, which was potentiated by the combination of HHcy and HG via μ-calpain/PKCβ2 activation-induced eNOS-pThr497/495 and eNOS inactivation.

High homocysteine and blood pressure related to poor outcome of acute ischemia stroke in Chinese population

OBJECTIVES

To assess the association between plasma homocysteine (Hcy), blood pressure (BP) and poor outcome at hospital discharge among acute ischemic stroke patients, and if high Hcy increases the risk of poor outcome based on high BP status in a northern Chinese population.

METHODS

Between June 1, 2009 and May 31, 2013, a total of 3695 acute ischemic stroke patients were recruited from three hospitals in northern Chinese cities. Demographic characteristics, lifestyle risk factors, medical history, and other clinical characteristics were recorded for all subjects. Poor outcome was defined as a discharge modified Rankin Scale (mRS) score ≥3 or death. The association between homocysteine concentration, admission blood pressure, and risk of poor outcome following acute ischemic stroke was analyzed by using multivariate non-conditional logistic regression models.

RESULTS

Compared with those in the lowest quartile of Hcy concentration in a multivariate-adjusted model, those in the highest quartile of Hcy concentration had increased risk of poor outcome after acute ischemic stroke, (OR = 1.33, P<0.05). The dose-response relationship between Hcy concentration and risk of poor outcome was statistically significant (p-value for trend  = 0.027). High BP was significantly associated with poor outcome following acute ischemic stroke (adjusted OR = 1.44, 95%CI, 1.19-1.74). Compared with non-high BP with nhHcy, in a multivariate-adjusted model, the ORs (95% CI) of non-high BP with hHcy, high BP with nhHcy, and high BP with hHcy to poor outcome were 1.14 (0.85-1.53), 1.37 (1.03-1.84) and 1.70 (1.29-2.34), respectively.

CONCLUSION

The present study suggested that high plasma Hcy and blood pressure were independent risk factors for prognosis of acute ischemic stroke, and hHcy may further increase the risk of poor outcome among patients with high blood pressure. Additionally, the results indicate that high Hcy with high BP may cause increased susceptibility to poor outcome among acute ischemic stroke patients in a northern Chinese population.

Homocysteine serum levels in diabetic patients with non proliferative, proliferative and without retinopathy

Homocysteine has been associated with extracellular matrix changes. The diabetic retinopathy is a neurovascular complication of diabetes mellitus and it is the leading cause of vision loss among working adults worldwide. In this study, we evaluate the role of homocysteine in diabetic retinopathy analyzing the plasma levels of homocysteine in 63 diabetic type 2 patients with nonproliferative retinopathy (NPDR), 62 patients with proliferative diabetic retinopathy (PDR), 50 healthy subjects used as control group, and 75 randomly selected patients.

2,4-Dichlorophenol induces global DNA hypermethylation through the increase of S-adenosylmethionine and the upregulation of DNMTs mRNA in the liver of goldfish Carassius auratus

Altered DNA methylation is associated with changes in gene expression, signal transduction and stress response after exposure to a wide range of exogenous compounds, and abnormal methylation is a major toxic effect induced by chemicals such as benzene and phenols. 2,4-Dichlorophenol (2,4-DCP), a derivative of phenol, has been classified as a priority pollutant by the US EPA due to its toxic effects on aquatic organisms. However, the effect of 2,4-DCP on DNA methylation and its potential mechanism in fish are rarely understood. The present study aims to figure out whether 2,4-DCP could impact DNA methylation and explore its potential mechanisms by measuring the global DNA methylation levels, S-adenosylmethionine (SAM) and S-adenosylhomocysteine (SAH) contents, the mRNA expression of DNA methyltransferase1 (DNMT1) and DNA methyltransferase3 (DNMT3) in the liver of goldfish Carassius auratus. DNA methylation levels were analyzed using high performance liquid chromatography (HPLC) and MspI/HpaII ethidium bromide assay, SAM and SAH contents were determined by HPLC, the mRNA expression of DNMT1 and DNMT3 was measured by quantitative-PCR (qPCR). The results showed that 2,4-DCP caused global DNA hypermethylation, elevated the methylation levels of CpG islands, increased the SAM and SAH contents, decreased the SAM/SAH ratio, and upregulated the mRNA expression of DNMT1 and DNMT3, while depletion of SAM with Na2SeO3 and inhibition of DNMTs activity with 5-aza-2'-deoxycytidine (5AdC) impaired 2,4-DCP-induced global DNA hypermethylation, suggesting that the increase of SAM contents and upregulation of the mRNA expression of DNMT1 and DNMT3 may play important roles in 2,4-DCP-induced global DNA hypermethylation process. Our report is the first one to show that short-term 2,4-DCP exposure caused the global DNA hypermethylation via altered SAM level and DNMTs expression in fish.

Effects of DL-homocysteine thiolactone on cardiac contractility, coronary flow, and oxidative stress markers in the isolated rat heart: the role of different gasotransmitters

Considering the adverse effects of DL-homocysteine thiolactone hydrochloride (DL-Hcy TLHC) on vascular function and the possible role of oxidative stress in these mechanisms, the aim of this study was to assess the influence of DL-Hcy TLHC alone and in combination with specific inhibitors of important gasotransmitters, such as L-NAME, DL-PAG, and PPR IX, on cardiac contractility, coronary flow, and oxidative stress markers in an isolated rat heart. The hearts were retrogradely perfused according to the Langendorff technique at a 70 cm H₂O and administered 10 μM DL-Hcy TLHC alone or in combination with 30 μM L-NAME, 10 μM DL-PAG, or 10 μM PPR IX. The following parameters were measured: dp/dt max, dp/dt min, SLVP, DLVP, MBP, HR, and CF. Oxidative stress markers were measured spectrophotometrically in coronary effluent through TBARS, NO₂, O₂⁻, and H₂O₂ concentrations. The administration of DL-Hcy TLHC alone decreased dp/dt max, SLVP, and CF but did not change any oxidative stress parameters. DL-Hcy TLHC with L-NAME decreased CF, O₂⁻, H₂O₂, and TBARS. The administration of DL-Hcy TLHC with DL-PAG significantly increased dp/dt max but decreased DLVP, CF, and TBARS. Administration of DL-Hcy TLHC with PPR IX caused a decrease in dp/dt max, SLVP, HR, CF, and TBARS.

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.

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.

Homocysteine, folate, vitamin B-12, and physical function in older adults: cross-sectional findings from the Singapore Longitudinal Ageing Study

BACKGROUND

There is a paucity of studies, as well as inconsistent findings, on the associations of homocysteine, folate, and vitamin B-12 with physical function and decline in older persons.

OBJECTIVE

We investigated the independent associations of homocysteine, folate, and vitamin B-12 with gait and balance performance and Instrumental Activities of Daily Living (IADL) in community-living older persons.

DESIGN

We performed cross-sectional analyses on baseline data of 796 respondents in the Singapore Longitudinal Ageing Study who had laboratory measurements of fasting homocysteine folate and vitamin B-12 and completed Performance Oriented Mobility Assessment (POMA) of gait and balance and self-reports of IADLs.

RESULTS

In multivariate analyses in which sex, age, education, housing type, comorbidities, hospitalization, depression and global cognitive scores, BMI, creatinine, arthritis and hip fracture, serum albumin and hemoglobin, and physical activities were controlled for, we showed that homocysteine, independently of folate and vitamin B-12, showed significant negative associations with POMA balance (P = 0.02), POMA gait scores (P < 0.01), and IADL (P < 0.01). Serum folate showed a significant positive association only with POMA balance scores (P < 0.045). No significant independent associations for vitamin B-12 were observed.

CONCLUSIONS

The independent association of elevated homocysteine and low folate, but not vitamin B-12, on physical and functional decline was supported in this study. Interventional studies of the physical functional effects of folate and vitamin B-12 status in different populations are needed.

Effects of residual renal function on left ventricle and analysis of related factors in patients with hemodialysis

BACKGROUND

Left ventricular hypertrophy (LVH) and systolic dysfunction would predict the mortality of patients undergoing maintenance hemodialysis. The cause of LVH is usually related to the increase of total peripheral vascular resistance and overloading volume. The presence of residual diuresis enables greater control of the volume. This study evaluated the effects of residual renal function (RRF) on the left ventricle and analyzed the related factors involved in hemodialysis patients.

METHODS

A total of 59 hemodialysis patients were classified into two groups. The patients in the RRF (RRF+) group had a urine volume greater than 200 mL/24 h, and the patients in the non-RRF (RRF-) group had a urine volume less than 200 mL/24 h. B-type natriuretic peptide (BNP), blood total homocysteine (tHcy), and blood biochemical indexes were determined for the patients in both groups. Echocardiography and Doppler tests were performed to determine the cardiac indexes.

RESULTS

LVH and systolic dysfunction in the RRF+ group were less severe than those in the RRF- group. The concentration of tHcy and BNP in patients with RRF was decreased in comparison with those without RRF. The concentration of tHcy and BNP was positively correlated with the residual diuresis.

CONCLUSIONS

There were distinct ventricular geometric patterns and different functional performances between RRF+ and RRF- groups. The presence of residual diuresis had a beneficial effect on the left ventricular function in hemodialysis patients.

Hyperhomocysteinemia and cardiovascular disease: new mechanisms beyond atherosclerosis

The association of hyperhomocysteinemia (Hhe) with cardiovascular disease (CVD) has been explored in detail over the last four decades since initial reports in the 1960s. Although several epidemiological studies have shown an association, convincing mechanistic studies are still lacking. However, recent prospective studies demonstrate a strong association of Hhe with coronary disease. Several pathogenic mechanisms have been studied in Hhe and indicate alterations in the various components of vascular disease, namely endothelial cells, vascular smooth muscle cells, platelets, and the coagulation/fibrinolytic systems. Increased oxidative stress, hypomethylation, and protein homocysteinylation have been proposed as potential molecular mechanisms in Hhe-induced CVD. In addition, recent studies indicate a novel link between Hhe and CVD, that is, direct effects on coronary arteriolar and myocardial remodeling resulting in cardiac dysfunction.

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.

Vascular incompetence in dialysis patients--protein-bound uremic toxins and endothelial dysfunction

Patients with chronic kidney disease (CKD) have a much higher risk of cardiovascular diseases than the general population. Endothelial dysfunction, which participates in accelerated atherosclerosis, is a hallmark of CKD. Patients with CKD display impaired endothelium-dependent vasodilatation, elevated soluble biomarkers of endothelial dysfunction, and increased oxidative stress. They also present an imbalance between circulating endothelial populations reflecting endothelial injury (endothelial microparticles and circulating endothelial cells) and repair (endothelial progenitor cells). Endothelial damage induced by a uremic environment suggests an involvement of uremia-specific factors. Several uremic toxins, mostly protein-bound, have been shown to have specific endothelial toxicity: ADMA, homocysteine, AGEs, and more recently, p-cresyl sulfate and indoxyl sulfate. These toxins, all poorly removed by hemodialysis therapies, share mechanisms of endothelial toxicity: they promote pro-oxidant and pro-inflammatory response and inhibit endothelial repair. This article (i) reviews the evidence for endothelial dysfunction in CKD, (ii) specifies the involvement of protein-bound uremic toxins in this dysfunction, and (iii) discusses therapeutic strategies for lowering uremic toxin concentrations or for countering the effects of uremic toxins on the endothelium.

Vitamin B12 protects against superoxide-induced cell injury in human aortic endothelial cells

Superoxide (O(2)(•-)) is implicated in inflammatory states including arteriosclerosis and ischemia-reperfusion injury. Cobalamin (Cbl) supplementation is beneficial for treating many inflammatory diseases and also provides protection in oxidative-stress-associated pathologies. Reduced Cbl reacts with O(2)(•-) at rates approaching that of superoxide dismutase (SOD), suggesting a plausible mechanism for its anti-inflammatory properties. Elevated homocysteine (Hcy) is an independent risk factor for cardiovascular disease and endothelial dysfunction. Hcy increases O(2)(•-) levels in human aortic endothelial cells (HAEC). Here, we explore the protective effects of Cbl in HAEC exposed to various O(2)(•-) sources, including increased Hcy levels. Hcy increased O(2)(•-) levels (1.6-fold) in HAEC, concomitant with a 20% reduction in cell viability and a 1.5-fold increase in apoptotic death. Pretreatment of HAEC with physiologically relevant concentrations of cyanocobalamin (CNCbl) (10-50nM) prevented Hcy-induced increases in O(2)(•-) and cell death. CNCbl inhibited both Hcy and rotenone-induced mitochondrial O(2)(•-) production. Similarly, HAEC challenged with paraquat showed a 1.5-fold increase in O(2)(•-) levels and a 30% decrease in cell viability, both of which were prevented with CNCbl pretreatment. CNCbl also attenuated elevated O(2)(•-) levels after exposure of cells to a Cu/Zn-SOD inhibitor. Our data suggest that Cbl acts as an efficient intracellular O(2)(•-) scavenger.

Homocysteine induces oxidative-nitrative stress in heart of rats: prevention by folic acid

Hyperhomocysteinemia is a risk factor for cardiovascular disease, stroke, and thrombosis; however, the mechanisms by which homocysteine triggers these dysfunctions are not fully understood. In the present study, we investigated the effect of chronic hyperhomocysteinemia on some parameters of oxidative stress, namely thiobarbituric acid reactive substances, an index of lipid peroxidation, 2',7'-dichlorofluorescein (H(2)DCF) oxidation, activities of antioxidant enzymes named superoxide dismutase and catalase, as well as nitrite levels in heart of young rats. We also evaluated the effect of folic acid on biochemical alterations elicited by hyperhomocysteinemia. Wistar rats received daily subcutaneous injection of homocysteine (0.3-0.6 μmol/g body weight) and/or folic acid (0.011 μmol/g body weight) from their 6th to the 28th day of life. Controls and treated rats were killed 1 h and/or 12 h after the last injection. Results showed that chronic homocysteine administration increases lipid peroxidation and reactive species production and decreases enzymatic antioxidant defenses and nitrite levels in the heart of young rats killed 1 h, but not 12 h after the last injection of homocysteine. Folic acid concurrent administration prevented homocysteine effects probable by its antioxidant properties. Our data indicate that oxidative stress is elicited by chronic hyperhomocystenemia, a mechanism that may contribute, at least in part, to the cardiovascular alterations characteristic of hyperhomocysteinemic patients. If confirmed in human beings, our results could propose that the supplementation of folic acid can be used as an adjuvant therapy in cardiovascular alterations caused by homocysteine.