Hyperhomocysteinemia enhances vascular inflammation and accelerates atherosclerosis in a murine model

Homocysteine has anti-inflammatory properties in a hypercholesterolemic rat model in vivo

Inflammation is a hallmark in many neurodegenerative diseases like Alzheimer's disease or vascular dementia. Cholesterol and homocysteine are both vascular risk factors which have been associated with dementia, inflammation and blood–brain barrier dysfunction. In previous studies we found that hypercholesterolemia but not hyperhomocysteinemia induced inflammation in rats in vivo. The aim of the present study was to investigate the effect of a combined treatment of Sprague Dawley rats with cholesterol and homocysteine for 5 months on spatial learning and memory, blood–brain barrier integrity and inflammation. Cholesterol treated rats showed severe learning deficits, while rats treated with cholesterol and homocysteine (Mix) counteracted the cholesterol-induced inflammation and partly the cortical blood–brain barrier disruptions, although cognition was still impaired. To study the potential protective effect of homocysteine, inflammation was induced in organotypic rat brain cortex slices and primary microglial cells by treatment with different inflammatory stimuli (e.g. lipopolysaccharide or tissue plasminogen activator). Tissue plasminogen activator-induced inflammation was counteracted by homocysteine. In conclusion, our data demonstrate that homocysteine significantly ameliorates cholesterol-induced inflammation and blood–brain barrier disruption but not the memory impairment, possibly involving a tissue plasminogen activator-related mechanism.

Tackling endothelial dysfunction by modulating NOS uncoupling: new insights into its pathogenesis and therapeutic possibilities

Endothelial nitric oxide synthase (eNOS) serves as a critical enzyme in maintaining vascular pressure by producing nitric oxide (NO); hence, it has a crucial role in the regulation of endothelial function. The bioavailability of eNOS-derived NO is crucial for this function and might be affected at multiple levels. Uncoupling of eNOS, with subsequently less NO and more superoxide generation, is one of the major underlying causes of endothelial dysfunction found in atherosclerosis, diabetes, hypertension, cigarette smoking, hyperhomocysteinemia, and ischemia/reperfusion injury. Therefore, modulating eNOS uncoupling by stabilizing eNOS activity, enhancing its substrate, cofactors, and transcription, and reversing uncoupled eNOS are attractive therapeutic approaches to improve endothelial function. This review provides an extensive overview of the important role of eNOS uncoupling in the pathogenesis of endothelial dysfunction and the potential therapeutic interventions to modulate eNOS for tackling endothelial dysfunction.

The role of glucosamine-induced ER stress in diabetic atherogenesis

Cardiovascular disease (CVD) is the major cause of mortality in individuals with diabetes mellitus. However the molecular and cellular mechanisms that predispose individuals with diabetes to the development and progression of atherosclerosis, the underlying cause of most CVD, are not understood. This paper summarizes the current state of our knowledge of pathways and mechanisms that may link diabetes and hyperglycemia to atherogenesis. We highlight recent work from our lab, and others', that supports a role for ER stress in these processes. The continued investigation of existing pathways, linking hyperglycemia and diabetes mellitus to atherosclerosis, and the identification of novel mechanisms and targets will be important to the development of new and effective antiatherosclerotic therapies tailored to individuals with diabetes.

Ankaflavin and monascin regulate endothelial adhesion molecules and endothelial NO synthase (eNOS) expression induced by tumor necrosis factor-α (TNF-α) in human umbilical vein endothelial cells (HUVECs)

Previous studies have established that red mold rice can regulate blood pressure in spontaneously hypertensive rats (SHR) and that Monascus -fermented products, including monacolin K, ankaflavin (AF), and monascin (MS), can inhibit expression of adhesion factors such as E-selectin and endothelin-1 to prevent human acute monocytic leukemia cell line THP-1 monocytes from adhering to human aortic endothelial cells. However, it remains unknown whether AF and MS act directly on human umbilical endothelial cells (HUVECs) to enhance nitric oxide (NO) synthesis through the stimulation of endothelial NO synthase (eNOS) expression. To address this knowledge gap, this study investigated whether AF and MS directly regulate NO synthesis and attenuate adhesion factor expression induced by treatment with tumor necrosis factor-α (TNF-α) in HUVECs. The results revealed that both AF and MS (20 μM) treatments promoted increases in eNOS expression and decreases in vascular cell adhesion molecule-1 (VCAM-1), E-selectin, and endothelin-1 mRNA and protein expression resulting from 12 h of TNF-α treatment. These effects are attributed to the ability of AF and MS to inhibit extracellular signal-regulated protein kinase (ERK) phosphorylation and nuclear factor κB (NF-κB) translocation from the cytoplasm into the nucleus, thereby exerting antihypertensive activity.

Mitochondrial mitophagic mechanisms of myocardial matrix metabolism and remodelling

High levels of homocysteine (Hcy), known as hyperhomocysteinmia (HHcy), are correlated with an increase in extracellular matrix remodelling (ECM) via the matrix metalloproteinases (MMPs) and plasminogen/plasmin system. This results in an increase deposition of collagen that leads to endothelial-myocyte (EM) and myocyte-myocyte (MM) uncoupling; the physiological consequences are a plethora of cardiovascular pathologies. Homocysteine-induced increase in intracellular and mitochondrial Ca(2+) plays an important role in increasing reactive oxygen species (ROS) within mitochondria and instigating mitophagy within the cell. This occurs via several Hcy-mitigated processes: agonizing N-methyl-d-aspartate receptor-1 (NMDA-R1), decreasing expression of peroxisome proliferator activator receptor (PPAR) [thereby increasing oxidation], impairing Ca(2+) handling via Na(+)/Ca(2+) exchanger (NCX1) and Sarco endoplasmic reticulum Ca(2+) ATPase (SERCA-2a). The end result is an increase in ROS that directly or indirectly lead to MMP activation within mitochondria or the cytoplasm. Hcy induces a mitochondrial permeability transition that allows MMPs to be released from mitochondria thereby metabolizing matrix and impairing cardiac function. Further work remains to be elucidated concerning the specific mitochondrial mitophagic mechanisms under which matrix metabolism and remodelling occurs. Moreover, the therapeutic implications of NMDA and PPAR ligands are some promise to patient.

Combined methylmalonic acidemia and homocystinuria, cblC type. II. Complications, pathophysiology, and outcomes

Combined methylmalonic acidemia and homocystinuria, cblC type, is stated to be the most common inborn error of intracellular cobalamin metabolism. The disorder can display a wide spectrum of clinical manifestations, spanning the prenatal period through late adulthood. While increased homocysteine concentrations and impaired methyl group metabolism may contribute to disease-related complications, the characteristic macular and retinal degeneration seen in many affected patients appears to be unique to cblC disease. The early detection of cblC disease by newborn screening mandates a careful assessment of therapeutic approaches and provides a new opportunity to improve the outcome of affected patients. The following article reviews the current knowledge on the complications, pathophysiology, and outcome of cblC disease in an effort to better guide clinical practice and future therapeutic trials.

Paradoxical absence of a prothrombotic phenotype in a mouse model of severe hyperhomocysteinemia

Hyperhomocysteinemia confers a high risk for thrombotic vascular events, but homocysteine-lowering therapies have been ineffective in reducing the incidence of secondary vascular outcomes, raising questions regarding the role of homocysteine as a mediator of cardiovascular disease. Therefore, to determine the contribution of elevated homocysteine to thrombosis susceptibility, we studied Cbs(-/-) mice conditionally expressing a zinc-inducible mutated human CBS (I278T) transgene. Tg-I278T Cbs(-/-) mice exhibited severe hyperhomocysteinemia and endothelial dysfunction in cerebral arterioles. Surprisingly, however, these mice did not display increased susceptibility to arterial or venous thrombosis as measured by photochemical injury in the carotid artery, chemical injury in the carotid artery or mesenteric arterioles, or ligation of the inferior vena cava. A survey of hemostatic and hemodynamic parameters revealed no detectible differences between control and Tg-I278T Cbs(-/-) mice. Our data demonstrate that severe elevation in homocysteine leads to the development of vascular endothelial dysfunction but is not sufficient to promote thrombosis. These findings may provide insights into the failure of homocysteine-lowering trials in secondary prevention from thrombotic vascular events.

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.

Mechanisms of cardiovascular remodeling in hyperhomocysteinemia

In hypertension, an increase in arterial wall thickness and loss of elasticity over time result in an increase in pulse wave velocity, a direct measure of arterial stiffness. This change is reflected in gradual fragmentation and loss of elastin fibers and accumulation of stiffer collagen fibers in the media that occurs independently of atherosclerosis. Similar results are seen with an elevated level of homocysteine (Hcy), known as hyperhomocysteinemia (HHcy), which increases vascular thickness, elastin fragmentation, and arterial blood pressure. Studies from our laboratory have demonstrated a decrease in elasticity and an increase in pulse wave velocity in HHcy cystathionine β synthase heterozygote knockout (CBS(-/+)) mice. Nitric oxide (NO) is a potential regulator of matrix metalloproteinase (MMP) activity in MMP-NO-TIMP (tissue inhibitor of metalloproteinase) inhibitory tertiary complex. We have demonstrated the contribution of the NO synthase (NOS) isoforms, endothelial NOS and inducible NOS, in the activation of latent MMP. The differential production of NO contributes to oxidative stress and increased oxidative/nitrative activation of MMP resulting in vascular remodeling in response to HHcy. The contribution of the NOS isoforms, endothelial and inducible in the collagen/elastin switch, has been demonstrated. We have showed that an increase in inducible NOS activity is a key contributor to HHcy-mediated collagen/elastin switch and resulting decline in aortic compliance. In addition, increased levels of Hcy compete and suppress the γ-amino butyric acid-receptor, N-methyl-d-aspartate-receptor, and peroxisome proliferator-activated receptor. The HHcy causes oxidative stress by generating nitrotyrosine, activating the latent MMPs and decreasing the endothelial NO concentration. The HHcy causes elastinolysis and decrease elastic complicance of the vessel wall. The treatment with γ-amino butyric acid-receptor agonist (muscimol), N-methyl-d-aspartate-receptor antagonist (MK-801), and peroxisome proliferator-activated receptor agonists (ciprofibrate and ciglitazone) mitigates the cardiovascular dysfunction in HHcy [corrected].

Common variants of homocysteine metabolism pathway genes and risk of type 2 diabetes and related traits in Indians

Hyperhomocysteinemia, a risk factor for cardiovascular disorder, obesity, and type 2 diabetes, is prevalent among Indians who are at high risk of these metabolic disorders. We evaluated association of common variants of genes involved in homocysteine metabolism or its levels with type 2 diabetes, obesity, and related traits in North Indians. We genotyped 90 variants in initial phase (2.115 subjects) and replicated top signals in an independent sample set (2.085 subjects). The variant MTHFR-rs1801133 was the top signal for association with type 2 diabetes (OR = 0.78 (95%  CI = 0.67-0.92), P = 0.003) and was also associated with 2 h postload plasma glucose (P = 0.04), high-density lipoprotein cholesterol (P = 0.004), and total cholesterol (P = 0.01) in control subjects. These associations were neither replicated nor significant after meta-analysis. Studies involving a larger study population and different ethnic groups are required before ruling out the role of these important candidate genes in type 2 diabetes, obesity, and related traits.

Role of Oxytocin in deceleration of early atherosclerotic inflammatory processes in adult male rats

OBJECTIVE

The study aimed to examine the effect of exogenous OT administration on the inflammation and atherosclerosis in adult male rats and its possible mechanisms. Thirty adult male rats equally divided into three groups. Control group fed regular diet; group II fed control diet supplemented with L-methionine for 10 weeks. Group III received L-methionine and oxytocin treatment for 10 weeks. RT-PCR analysis showed that OT administration increased oxytocin receptor mRNA (2 fold, P, 0.05). Blood samples were evaluated for total homocysteine, interlukin-6 (IL-6), monocyte chemoatrratant protein-1 (MCP-1) and C-reactive protein (CRP) by ELIZA, lipid profile, nitric oxide (NO), malondialdehyde (MDA) and reduced glutathione (GSH) were determined. Specimens from aorta were processed for immunohistochemical staining for Aorta nuclear factor _B (NF-κB) p65 protein. Result showed that OT administration to group III decreased the plasma levels IL-6, MCP-1 and CRP levels which were elevated in group II. Moreover, there was decrease of the oxidative stress of group III in terms of increased plasma levels of NO and GSH and decreased plasma levels of MDA in blood. In addition, rats of group II showed histological abnormalities manifested by thickening and ulceration of the aortic wall. Marked increased expression of NF-κB in aorta of in group II was detected. However, OT administration restores the histological structure of the aorta and decreased the expression of NF-κB in aorta of group III similar to the control group.

CONCLUSION

OT has anti inflammatory pathway in atherosclerosis as it decelerates atherosclerosis by decreasing the proinflammatory responses through many mechanisms, mainly the up regulation of its receptors.

Potential synergistic and multitarget effect of herbal pair Chuanxiong Rhizome-Paeonia Albifora Pall on osteoarthritis disease: a computational pharmacology approach

OBJECTIVE

To study the polypharmacological mechanism of herbal pair Chuanxiong Rhizome-Paeonia Albifora Pall (HP CXR-PAP) on the treatment for osteoarthritis (OA).

METHODS

Chemical space was used to discuss the similarities and differences between the molecule sets of HP CXR-PAP and drugs. Docking protocol was used to study the interaction between HP CXR-PAP and OA target enzymes. The similarities and differences of HP CXR-PAP and drugs in target spaces were elucidated by network features.

RESULTS

The plots between the molecule sets of HP CXR-PAP and drugs in chemical space had the majority in the same region, and compounds from HP CXR-PAP covered a much larger additional region of space than drug molecules, which denoted the diverse structural properties in the molecule set of HP CXR-PAP. The molecules in HP CXR-PAP had the properties of promiscuous drugs and combination drug, and both HP CXR-PAP ligand-target interaction network and drug ligand-target interaction network were similar in the interaction profiles and network features, which revealed the effects of multicomponent and multitarget.

CONCLUSION

The clue of potential synergism was obtained in curing OA disease by Chinese medicine, which revealed the advantages of Chinese medicine for targeting osteoarthritis disease.

Inhibition of endothelial adhesion molecule expression by Monascus purpureus-fermented rice metabolites, monacolin K, ankaflavin, and monascin

BACKGROUND

Inflammation is an independent risk factor of cardiovascular diseases and is associated with endothelial dysfunction. Monascus purpureus-fermented rice, containing naturally occurring statins and various pigments, has lipid-modulating, anti-inflammatory and antioxidative effects.

RESULTS

The effects of monacolin K, ankaflavin and monascin, as metabolites from Monascus-fermented rice, on the expression of cell adhesion molecules (intercellular adhesion molecule-1 (ICAM-1), vascular cell adhesion molecular-1 (VCAM-1) and E-selectin) by tumor necrosis factor (TNF)-α-treated human aortic endothelial cells (HAECs) were investigated. Supplement of HAECs with these Monascus-fermented rice metabolites significantly suppressed cellular binding between the human monocytic cells U937 and TNF-α-stimulated HAECs. Immunoblot analysis showed that Monascus-fermented rice metabolites significantly attenuated TNF-α-induced VCAM-1 and E-selectin but not ICAM-1 protein expression. Gel shift assays showed that Monascus-fermented rice metabolites treatment reduced TNF-α-activated transcription factor nuclear factor (NF)-κB. Furthermore, Monascus-fermented rice metabolites also attenuated reactive oxygen species (ROS) generation in vitro and in TNF-α-treated HAECs. Supplement with an ROS scavenger N-acetylcysteine gave similar results as compared with Monascus-fermented rice metabolites.

CONCLUSION

Monascus-fermented rice metabolites reduced TNF-α-stimulated endothelial adhesiveness as well as downregulating intracellular ROS formation, NF-κB activation, and VCAM-1/E-selectin expression in HAECs, supporting the notion that the various metabolites from Monascus-fermented rice might have potential implications in clinical atherosclerosis disease.

Polymorphisms of methylenetetrahydrofolate reductase are not a risk factor for Kawasaki disease in the Korean population

PURPOSE

Hyperhomocysteinemia is known as a risk factor for atherosclerosis. Preclinical arteriosclerosis is noted and premature atherosclerosis is known to be accelerated in Kawasaki disease (KD) patients. Genetic polymorphisms in the 5,10-methylenetetrahydrofolate reductase (MTHFR) gene result in elevated plasma homocysteine concentrations and are known to be associated with the development of coronary artery disease. Our hypothesis is that single nucleotide polymorphisms (SNPs) of the MTHFR gene are related to the development of KD and coronary artery lesions (CALs).

METHODS

For this study, we selected 3 candidate single nucleotide polymorphisms (SNPs) (rs2274976, rs1801131, and rs1801133) of MTHFR. These SNPs are located on chromosome 1p36.3. We included 101 KD patients and 306 healthy adults as controls in this study. CALs were seen in 38 patients. Genotypes of the selected SNPs were determined by direct sequencing and analyzed with SNPAlyze.

RESULTS

The genetic distribution and allelic frequency of the 3 MTHFR SNPs (rs2274976, rs1801131, and rs1801133) were not significantly different in patients with KD compared to the control group (P=0.71, 0.17, and 0.96, respectively). There was no difference in the genetic distribution of the MTHFR SNPs between the normal control group and the CAL group (P=0.43, 0.39, 0.52 respectively).

CONCLUSION

The genetic distribution of the MTHFR SNPs (rs2274976, rs1801131, and rs1801133) was not different in the KD group compared to the control group. In addition, the genetic distribution of these SNPs was not different in the CAL group compared to the control group in the Korean population.

B-vitamin deficiency is protective against DSS-induced colitis in mice

Vitamin deficiencies are common in patients with inflammatory bowel disease (IBD). Homocysteine (Hcys) is a thrombogenic amino acid produced from methionine (Met), and its increase in patients with IBD indicates a disruption of Met metabolism; however, the role of Hcys and Met metabolism in IBD is not well understood. We hypothesized that disrupted Met metabolism from a B-vitamin-deficient diet would exacerbate experimental colitis. Mice were fed a B(6)-B(12)-deficient or control diet for 2 wk and then treated with dextran sodium sulfate (DSS) to induce colitis. We monitored disease activity during DSS treatment and collected plasma and tissue for analysis of inflammatory tissue injury and Met metabolites. We also quantified Met cycle activity by measurements of in vivo Met kinetics using [1-(13)C-methyl-(2)H(3)]methionine infusion in similarly treated mice. Unexpectedly, we found that mice given the B-vitamin-deficient diet had improved clinical outcomes, including increased survival, weight maintenance, and reduced disease scores. We also found lower histological disease activity and proinflammatory gene expression (TNF-α and inducible nitric oxide synthase) in the colon in deficient-diet mice. Metabolomic analysis showed evidence that these effects were associated with deficient B(6), as markers of B(12) function were only mildly altered. In vivo methionine kinetics corroborated these results, showing that the deficient diet suppressed transsulfuration but increased remethylation. Our findings suggest that disrupted Met metabolism attributable to B(6) deficiency reduces the inflammatory response and disease activity in DSS-challenged mice. These results warrant further human clinical studies to determine whether B(6) deficiency and elevated Hcys in patients with IBD contribute to disease pathobiology.

Matrix-embedded endothelial cells are protected from the uremic milieu

BACKGROUND

Endothelial cells (ECs) embedded in 3D matrices [matrix-embedded endothelial cells (MEECs)] of denatured collagen implanted around vascular access anastomoses preserve luminal patency. MEEC implant efficacy depends on embedded EC health. As the uremic milieu inhibits proliferation and induces apoptosis of ECs, we examined whether uremia might impact MEECs.

METHODS

ECs grown on 2D gelatin-coated polystyrene tissue culture plates (gTCPS) or in MEEC were treated with sera pooled from 20 healthy control or uremic patients with end-stage renal disease. EC viability was examined using 3-(4,5-dimethylthiazole-2-yl)-2,5-diphenyl tetrazolium bromide assay, cell counting and Trypan blue exclusion. Media conditioned (CM) with 2 and 3D-supported ECs were examined for its potential to inhibit vascular smooth muscle cell (vSMC) proliferation using (3)[H] thymidine incorporation and cyclin D1 expression. ECs grown on gTCPS were treated with uremic serum filtered through matrices to examine if matrices retain uremic toxins or whether EC effects were cell mediated.

RESULTS

Uremic serum significantly reduced viability and number of live, and increased dead ECs when grown on gTCPS, but not in MEECs. EC survival correlated with vSMC inhibition. While CM from ECs grown in gTCPS with uremic serum inhibited vSMC proliferation no better than uremic serum alone (22 versus 27%), MEEC CM inhibited vSMC proliferation by 47% (P = 0.0004). Cyclin D1 expression tracked with indices of vSMC proliferation. There was no significant difference in EC viability between EC treated with matrix-filtered or unfiltered uremic serum.

CONCLUSION

The viability, number and efficacy of MEECs were preserved in uremic serum compared to those of ECs on gTCPS. MEECs are protected from uremic toxicity, not from retention of uremic toxins by matrices, but likely from intrinsic changes in EC sensitivity to uremia. MEECs implanted at vascular access sites should inhibit neointimal hyperplasia in uremia. This study underscores the robustness of matrix embedding as a cell protectant, especially in hostile environments like uremia.

Therapeutical approach to plasma homocysteine and cardiovascular risk reduction

Homocysteine is a sulfur-containing aminoacid produced during metabolism of methionine. Since 1969 the relationship between altered homocysteine metabolism and both coronary and peripheral atherotrombosis is known; in recent years experimental evidences have shown that elevated plasma levels of homocysteine are associated with an increased risk of atherosclerosis and cardiovascular ischemic events. Several mechanisms by which elevated homocysteine impairs vascular function have been proposed, including impairment of endothelial function, production of reactive oxygen species (ROS) and consequent oxidation of low-density lipids. Endothelial function is altered in subjects with hyperhomocysteinemia, and endothelial dysfunction is correlated with plasma levels of homocysteine. Folic acid and B vitamins, required for remethylation of homocysteine to methionine, are the most important dietary determinants of homocysteine and daily supplementation typically lowers plasma homocysteine levels; it is still unclear whether the decreased plasma levels of homocysteine through diet or drugs may be paralleled by a reduction in cardiovascular risk.

Aged garlic extract inhibits homocysteine-induced scavenger receptor CD36 expression and oxidized low-density lipoprotein cholesterol uptake in human macrophages in vitro

AIM OF THE STUDY

Expression of CD36 scavenger receptors on macrophages is involved in oxidized low-density lipoprotein (OxLDL) uptake and foam cell formation during atherosclerotic lesion development. It has been shown previously in vitro and in vivo that the atherosclerotic risk factor homocysteine (Hcy) stimulates macrophage CD36 expression and OxLDL uptake. We now examined the effects of aged garlic extract (AGE), a garlic preparation enriched in water-soluble organic sulfur-containing compounds, on Hcy-induced CD36 expression and foam cell formation in human monocytes/macrophages.

RESULTS

Incubation with Hcy (200 μM for 72h) in THP-1-derived macrophages and primary human macrophages caused a 37.8±5.2% and 60.7±4.2% increase in CD36 expression compared to control, respectively. Coincubation with AGE (5mg/ml) significantly suppressed CD36 expression in THP-1 derived macrophages by 48.6±9.0% compared to Hcy-incubated cells only. AGE (1-5mg/ml) dose dependently inhibited Hcy-induced CD36 expression in primary human macrophages, and decreased binding of nuclear proteins to a PPARγ response element. Preincubation with AGE significantly inhibited DiI-labeled OxLDL uptake.

CONCLUSIONS

These data indicate that AGE inhibits CD36 expression and OxLDL uptake in human macrophages by modulating the PPARγ pathway, and suggest that the extract could be useful for the prevention of atherosclerotic lesions.

β-Benzene hexachloride induces apoptosis of rat Sertoli cells through generation of reactive oxygen species and activation of JNKs and FasL

β-benzene hexachloride (β-BHC), the major metabolite of benzene-hexachloride (BHC), is a weak estrogen-like chemical. It is a known persistent organic pollutant and male reproductive toxicant. However, the mechanism by which β-BHC exposure causes male reproductive toxicity remains unknown. In the present study, rat Sertoli cells were used to investigate the molecular mechanism involved in β-BHC-induced toxicity in male reproductive system. The results indicated that β-BHC exposure at over 30 μM showed the induction of apoptotic cell death. β-BHC could induce elevation in reactive oxygen species (ROS) generation, increase in the leakage rate of LDH and MDA level, and decrease in SOD activity. In addition, there was an increase in the cellular levels of phospho-JNKs and FasL in the β-BHC-induced apoptosis; and a significant reduction of procaspase-3 and -8 was observed over 30-μM β-BHC treatment. The translocation of NF-κB enhanced with the increase of concentration of β-BHC. Furthermore, NAC administration, a scavenger of ROS, reversed β-BHC-induced apoptosis effects via inhibition of JNKs activation, FasL expression, and NF-κB translocation. These results lead us to speculate that ROS generation may play a critical role in the initiation of β-BHC-induced apoptosis by activation of the JNKs, translocation of NF-κB, expression of FasL, and further activation of caspase cascade.

Evaluation of MTHFR C677T polymorphism in ischemic and hemorrhagic stroke patients. A case-control study in a Northern Indian population

OBJECTIVE

The present study was aimed to evaluate MTHFR C677T gene polymorphism in patients with ischemic stroke (IS) and intracerebral hemorrhage (ICH) and compare it with controls.

METHODS

207 patient with IS and 215 with CT/MRI proven ICH were included and compared with 188 healthy controls. The stroke risk factors, location of IS, its vascular territory and in ICH the location of hematoma were noted. MTHFR C677T polymorphism was studied by polymerase chain reaction.

RESULTS

Hypertension was present in 65.9% of ICH and 48.8% of IS. Other stroke risk factors were not significantly different. The frequency of the CC genotype in controls was 68.6%. CT in 28.7% and TT in 2.7%, whereas it was 75.3%, 20.5% and 4.2% in ICH and 66.2%, 39.4% and 2.4% respectively in IS. The frequency of these genotypes as well as allele frequency was not different in IS, ICH as compared to controls, however variant allele was more frequent in IS compared to ICH. Homocysteine level was higher in IS patients with variant genotype

INTERPRETATION

MTHFR C677T gene polymorphism was neither associated with hemorrhagic nor ischemic stroke. However raised homocysteine levels were found to be associated with MTHFRC677-TT genotype in IS patients.

Vascular remodeling and arterial calcification are directly mediated by S100A12 (EN-RAGE) in chronic kidney disease

BACKGROUND

The proinflammatory cytokine S100A12 (also known as EN-RAGE) is associated with cardiovascular morbidity and mortality in hemodialysis patients. In the current study, we tested the hypothesis that S100A12 expressed in vascular smooth muscle in nonatherosclerosis-prone C57BL/6J mice on normal rodent chow diet, but exposed to the metabolic changes of chronic kidney disease (CKD), would develop vascular disease resembling that observed in patients with CKD.

METHODS

CKD was induced in S100A12 transgenic mice and wild-type littermate mice not expressing human S100A12 by surgical ligation of the ureters. The aorta was analyzed after 7 weeks of elevated BUN (blood urea nitrogen), and cultured aortic smooth muscle cells were studied.

RESULTS

We found enhanced vascular medial calcification in S100A12tg mice subjected to CKD. Vascular calcification was mediated, at least in part, by activation of the receptor for S100A12, RAGE (receptor for advanced glycation endproducts), and by enhanced oxidative stress, since inhibition of NADPH-oxidase Nox1 and limited access of S100A12 to RAGE attenuated the calcification and gene expression of osteoblastic genes in cultured vascular smooth muscle cells.

CONCLUSION

S100A12 augments CKD-triggered osteogenesis in murine vasculature, reminiscent of features associated with enhanced vascular calcification in patients with chronic and end-stage kidney disease.

Differential effects of nutritional folic acid deficiency and moderate hyperhomocysteinemia on aortic plaque formation and genome-wide DNA methylation in vascular tissue from ApoE-/- mice

Low folate intake is associated with vascular disease. Causality has been attributed to hyperhomocysteinemia. However, human intervention trials have failed to show the benefit of homocysteine-lowering therapies. Alternatively, low folate may promote vascular disease by deregulating DNA methylation. We investigated whether folate could alter DNA methylation and atherosclerosis in ApoE null mice. Mice were fed one of six diets (n = 20 per group) for 16 weeks. Basal diets were either control (C; 4% lard) or high fat (HF; 21% lard and cholesterol, 0.15%) with different B-vitamin compositions: (1) folic acid and B-vitamin replete, (2) folic acid deficient (-F), (3) folic acid, B6 and B12 deficient (-F-B). -F diets decreased plasma (up to 85%; P < 0.05), whole blood (up to 70%; P < 0.05), and liver folate (up to 65%; P < 0.05) and hepatic SAM/SAH (up to 80%; P < 0.05). -F-B diets reduced plasma (up to 76%; P < 0.05), whole blood (up to 72%; P < 0.05), and liver B12 (up to 39%; P < 0.05) and hepatic SAM/SAH (up to 90%; P < 0.05). -F increased homocysteine 2-fold, while -F-B increased homocysteine 3.6- and 6.8-fold in the C and HF groups (P < 0.05). Plaque formation was increased 2-fold (P < 0.0001) in mice fed a HF diet. Feeding a HF-F diet increased lesion formation by 17% (P < 0.05). There was no change in 5-methyldeoxycytidine in liver or vascular tissue (aorta, periadventitial tissue and heart). These data suggest that atherogenesis is not associated with genome-wide epigenetic changes in this animal model.

Vascular complications of cystathionine β-synthase deficiency: future directions for homocysteine-to-hydrogen sulfide research

Homocysteine (Hcy), a cardiovascular and neurovascular disease risk factor, is converted to hydrogen sulfide (H(2)S) through the transsulfuration pathway. H(2)S has attracted considerable attention in recent years for many positive effects on vascular health and homeostasis. Cystathionine β-synthase (CBS) is the first, and rate-limiting, enzyme in the transsulfuration pathway. Mutations in the CBS gene decrease enzymatic activity, which increases the plasma Hcy concentration, a condition called hyperhomocysteinemia (HHcy). Animal models of CBS deficiency have provided invaluable insights into the pathological effects of transsulfuration impairment and of both mild and severe HHcy. However, studies have also highlighted the complexity of HHcy and the need to explore the specific details of Hcy metabolism in addition to Hcy levels per se. There has been a relative paucity of work addressing the dysfunctional H(2)S production in CBS deficiency that may contribute to, or even create, HHcy-associated pathologies. Experiments using CBS knockout mice, both homozygous (-/-) and heterozygous (+/-), have provided 15 years of new knowledge and are the focus of this review. These murine models present the opportunity to study a specific mechanism for HHcy that matches one of the etiologies in many human patients. Therefore, the goal of this review was to integrate and highlight the critical information gained thus far from models of CBS deficiency and draw attention to critical gaps in knowledge, with particular emphasis on the modulation of H(2)S metabolism. We include findings from human and animal studies to identify important opportunities for future investigation that should be aimed at generating new basic and clinical understanding of the role of CBS and transsulfuration in cardiovascular and neurovascular disease.

Induction of Alzheimer's-like changes in brain of mice expressing mutant APP fed excess methionine

Elevated plasma homocysteine, a risk factor for Alzheimer's disease, could result from increased production from methionine or by inefficient clearance by folate- and B-vitamin-dependent pathways. Understanding the relative contributions of these processes to pathogenesis is important for therapeutic strategies designed to lower homocysteine. To assess these alternatives, we elevated plasma homocysteine by feeding mutant amyloid precursor protein (APP)-expressing mice diets with either high methionine (HM) or deficient in B-vitamins and folate (B Def). Mutant APP mice fed HM demonstrated increased brain beta amyloid. Interestingly, this increase was not observed in mutant APP mice fed B Def diet, nor was it observed in C57Bl6 or YAC-APP mice fed HM. Furthermore, HM, but not B Def, produced a prolonged increase in brain homocysteine only in mutant APP mice but not wild-type mice. These changes were time-dependent over 10 weeks. Further, by 10 weeks HM increased brain cholesterol and phosphorylated tau in mutant APP mice. Transcriptional profiling experiments revealed robust differences in RNA expression between C57Bl6 and mutant APP mice. The HM diet in C57Bl6 mice transiently induced a transcriptional profile similar to mutant APP cortex, peaking at 2 weeks , following a time course comparable to brain homocysteine changes. Together, these data suggest a link between APP and methionine metabolism.

Epigenetic modifications and human pathologies: cancer and CVD

Epigenetic changes are inherited alterations in DNA that affect gene expression and function without altering the DNA sequence. DNA methylation is one epigenetic process implicated in human disease that is influenced by diet. DNA methylation involves addition of a 1-C moiety to cytosine groups in DNA. Methylated genes are not transcribed or are transcribed at a reduced rate. Global under-methylation (hypomethylation) and site-specific over-methylation (hypermethylation) are common features of human tumours. DNA hypomethylation, leading to increased expression of specific proto-oncogenes (e.g. genes involved in proliferation or metastasis) can increase the risk of cancer as can hypermethylation and reduced expression of tumour suppressor (TS) genes (e.g. DNA repair genes). DNA methyltransferases (DNMT), together with the methyl donor S-adenosylmethionine (SAM), facilitate DNA methylation. Abnormal DNA methylation is implicated not only in the development of human cancer but also in CVD. Polyphenols, a group of phytochemicals consumed in significant amounts in the human diet, effect risk of cancer. Flavonoids from tea, soft fruits and soya are potent inhibitors of DNMT in vitro, capable of reversing hypermethylation and reactivating TS genes. Folates, a group of water-soluble B vitamins found in high concentration in green leafy vegetables, regulate DNA methylation through their ability to generate SAM. People who habitually consume the lowest level of folate or with the lowest blood folate concentrations have a significantly increased risk of developing several cancers and CVD. This review describes how flavonoids and folates in the human diet alter DNA methylation and may modify the risk of human colon cancer and CVD.

Severe In vivo hyper-homocysteinemia is not associatedwith elevation of amyloid-beta peptides in the Tg2576 mice

Since hyper-homocysteinemia (HHcy) was recognized as a risk factor for Alzheimer's disease (AD), many studies tried to induce HHcy in animal models to investigate its effect on amyloid-beta protein precursor (AbetaPP) metabolism. Previous reports found that HHcy induced in AD transgenic mouse models, by either feedina a methionine-enriched diet or vitamin Bs deficient diet, is associated with elevation of amyloid-beta (Abeta) levels. However, there is no data available on the effect of dietary intervention which combines both excessive methionine and low levels of vitamin Bs on amyloidogenesis in any of these models. In the current study, we investigated the effect of a combination diet, which was both enriched in methionine and deficient in folate, vitamin B6 and B12, in an AD mouse model, the Tg2576. We found that 7 months treatment of this diet induced severe HHcy in these mice with plasma homocysteine level higher than 150 microM. However, no difference was detected in brain Abeta levels or deposition between the diet-treated and control group. As shown by western blot, severe HHcy did not alter the steady state levels of proteins involved in AbetaPP metabolism, either. These results demonstrate that this combination diet-induced severe HHcy does not influence amyloidogenesis in vivo.

Extracellular transsulfuration generates hydrogen sulfide from homocysteine and protects endothelium from redox stress

Homocysteine, a cardiovascular and neurocognitive disease risk factor, is converted to hydrogen sulfide, a cardiovascular and neuronal protectant, through the transsulfuration pathway. Given the damaging effects of free homocysteine in the blood and the importance of blood homocysteine concentration as a prognosticator of disease, we tested the hypotheses that the blood itself regulates homocysteine-hydrogen sulfide metabolism through transsulfuration and that transsulfuration capacity and hydrogen sulfide availability protect the endothelium from redox stress. Here we show that the transsulfuration enzymes, cystathionine β-synthase and cystathionine γ-lyase, are secreted by microvascular endothelial cells and hepatocytes, circulate as members of the plasma proteome, and actively produce hydrogen sulfide from homocysteine in human blood. We further demonstrate that extracellular transsulfuration regulates cell function when the endothelium is challenged with homocysteine and that hydrogen sulfide protects the endothelium from serum starvation and from hypoxia-reoxygenation injury. These novel findings uncover a unique set of opportunities to explore innovative clinical diagnostics and therapeutic strategies in the approach to homocysteine-related conditions such as atherosclerosis, thrombosis, and dementia.

Induction of the unfolded protein response after monocyte to macrophage differentiation augments cell survival in early atherosclerotic lesions

Endoplasmic reticulum (ER) stress causes macrophage cell death within advanced atherosclerotic lesions, thereby contributing to necrotic core formation and increasing the risk of atherothrombotic disease. However, unlike in advanced lesions, the appearance of dead/apoptotic macrophages in early lesions is less prominent. Given that activation of the unfolded protein response (UPR) is detected in early lesion-resident macrophages and can enhance cell survival against ER stress, we investigated whether UPR activation occurs after monocyte to macrophage differentiation and confers a cytoprotective advantage to the macrophage. Human peripheral blood monocytes were treated with monocyte colony-stimulating factor to induce macrophage differentiation, as assessed by changes in ultrastructure and scavenger receptor expression. UPR markers, including GRP78, GRP94, and spliced XBP-1, were induced after macrophage differentiation and occurred after a significant increase in de novo protein synthesis. UPR activation after differentiation reduced macrophage cell death by ER stress-inducing agents. Further, GRP78 overexpression in macrophages was sufficient to reduce ER stress-induced cell death. Consistent with these in vitro findings, UPR activation was observed in viable lesion-resident macrophages from human carotid arteries and from the aortas of apoE(-/-) mice. However, no evidence of apoptosis was observed in early lesion-resident macrophages from the aortas of apoE(-/-) mice. Thus, our findings that UPR activation occurs during macrophage differentiation and is cytoprotective against ER stress-inducing agents suggest an important cellular mechanism for macrophage survival within early atherosclerotic lesions.

Carbamylated LDL

Nonenzymatic modification of protein by cyanate, that is, carbamylation, has received new attention due to its apparent relevance in atherosclerosis. For example, carbamylation of low-density lipoprotein (LDL) is an important mechanism that potentially impacts high-risk atherosclerotic individuals with increased urea (renal insufficiency) or thiocyanate (tobacco smoking). Carbamylated LDL (cLDL) is increased in patients with end-stage kidney disease, especially those with atherosclerosis. In addition, cLDL exhibits distinct cytotoxic effects when tested in vitro on endothelial cells, induces the expression of adhesion molecules, and aggravates the monocyte adhesion to endothelial cells. It also facilitates the proliferation of vascular smooth-muscle cell (VSMC). Studies of potential pharmacological interruption of these processes in vivo may lead to discoveries of novel therapies for atherosclerosis.

The Herp protein pathway is not involved in the pro-amyloidogenic effect of hyperhomocysteinemia

Diet-induced high circulating levels of homocysteine, also known as hyper-homocysteinemia (HHcy), is associated with an acceleration of Alzheimer's disease-like amyloidosis. Herp is a homocysteine-responsive stress protein, which has been shown to increase the formation of amyloid-beta (Abeta) via interaction with presenilins in vitro. The aim of our paper was to investigate the functional role that Herp plays in HHcy-induced amyloidosis. Amyloidosis secondary to diet-induced HHcy in Tg2576 mice is associated with an increase of Herp protein and mRNA levels. By contrast, no other stress-related proteins are altered by the same diet regimen. Compared to wild type animals, brains from a genetically induced HHcy mouse model did not manifest any significant change in Herp levels. Cells stably over-expressing human AbetaPP Swedish mutant incubated with high levels of homocysteine had an increase in Abeta formation, but no change in Herp level. Finally, over-expression of Herp did not result in any significant modification of Abeta levels. We conclude that the Herp protein pathway is unlikely to be directly involved in the pro-amyloidotic effect of HHcy.

Evaluation of mild hyperhomocysteinemia during the development of atherosclerosis in apolipoprotein E-deficient and normal mice

We focused on the effect of mild hyperhomocysteinemia (HHcy) on the development of atherosclerosis, using apolipoprotein E-deficient (apoE(-/-)) and normal mice. Mice received diets enriched in methionine with low or high levels of folate, B(12) and B(6) (diets B and C, respectively), and diet only with low levels of folate, B(12) and B(6) (diets D), to induce mild HHcy. Normal mice fed on diets B, C and D presented mild HHcy, but they did not develop atherosclerotic lesions after 24 weeks of diet. In addition, increased endoplasmic reticulum stress was present in normal mice fed on diet B, compared to others groups. ApoE(-/-) mice fed on diet B for 20 weeks presented the greatest atherosclerotic lesion area at the aortic sinus than other groups. These results suggest that the methionine may have a toxic effect on endothelium, and the B-vitamins addition on diet may have a protective effect in the long term, despite the increase on homocysteine levels. Mild HHcy accelerated the development of atherosclerosis in apoE(-/-) mice, and supplementation with B-vitamins is important for prevention of vascular disease, principally in the long term.

Deficiencies of folate and vitamin B12 do not affect fracture healing in mice

PURPOSE

Recently, hyperhomocysteinemia has been shown to be associated with impaired fracture healing in mice. The main causes for hyperhomocysteinemia are deficiencies of folate and vitamin B12. However, there is no information on whether deficiencies of these B vitamins are affecting bone repair, too.

METHODS

We used two groups of mice to investigate the impact of folate and vitamin B12 deficiency on fracture healing: mice of the first group were fed a folate- and vitamin B12-deficient diet (n=14), while mice of the second group received an equicaloric control diet (n=13). Four weeks after stabilizing a closed femur fracture, bone repair was analyzed by histomorphometry and biomechanical testing. In addition, serum concentrations of homocysteine, folate, vitamin B12, the bone formation marker osteocalcin (OC), and the bone resorption marker collagen I C-terminal crosslaps (CTX) were measured.

RESULTS

Serum analyses revealed significantly decreased concentrations of folate and vitamin B12 in animals fed the folate- and vitamin B12-deficient diet when compared to controls. This was associated with a moderate hyperhomocysteinemia in folate- and vitamin B12-deficient mice, while no hyperhomocysteinemia was found in controls. Three-point bending tests showed no significant differences in callus stiffness between bones of folate- and vitamin B12-deficient animals and those of control animals. In accordance, the histomorphometric analysis demonstrated a comparable size and tissue composition of the callus, and also serum markers of bone turnover did not differ significantly between the two groups.

CONCLUSIONS

We conclude that folate and vitamin B12 deficiency does not affect bone repair in mice.

Diet-induced hyperhomocysteinemia increases amyloid-beta formation and deposition in a mouse model of Alzheimer's disease

Hyperhomocysteinemia (HHcy) has been recognized as a risk factor for developing Alzheimer's disease (AD). However, its underlying molecular mechanisms are still elusive. Here we show that HHcy induces an elevation of amyloid beta (Abeta) levels and deposition, as well as behavioral impairments, in a mouse model of AD-like amyloidosis, the Tg2576 mice. This elevation is not associated with significant change of the steady state levels of the Abeta precursor protein (APP), beta- or alpha-secretase pathways, nor with the Abeta catabolic pathways. By contrast, HHcy significantly reduces glycogen synthase kinase 3 (GSK3) Ser21/9 phosphorylation, but not total GSK3 protein levels. Similar results are obtained in brains homogenates from a genetic mouse model of HHcy. In vitro studies show that homocysteine increases Abeta formation, reduces phosphorylated GSK3 levels, without changes in total APP and its metabolism, and these effects are prevented by selective GSK3 inhibition. Overall, these data support a potential link between GSK3 and the pro-amyloidotic effect of HHcy in vivo and in vitro.

Animal models of ischemic stroke. Part one: modeling risk factors

Ischemic stroke is one of the leading causes of long-term disability and death in developed and developing countries. As emerging disease, stroke related mortality and morbidity is going to step up in the next decades. This is both due to the poor identification of risk factors and persistence of unhealthy habits, as well as to the aging of the population. To counteract the estimated increase in stroke incidence, it is of primary importance to identify risk factors, study their effects, to promote primary and secondary prevention, and to extend the therapeutic repertoire that is currently limited to the very first hours after stroke. While epidemiologic studies in the human population are essential to identify emerging risk factors, adequate animal models represent a fundamental tool to dissect stroke risk factors to their molecular mechanism and to find efficacious therapeutic strategies for this complex multi- factorial disorder. The present review is organized into two parts: the first part deals with the animal models that have been developed to study stroke and its related risk factors and the second part analyzes the specific stroke models. These models represent an indispensable tool to investigate the mechanisms of cerebral injury and to develop novel therapies.

Normalization of hyperhomocysteinemia improves cognitive deficits and ameliorates brain amyloidosis of a transgenic mouse model of Alzheimer's disease

Hyperhomocysteine (HHcy) is a risk factor for developing Alzheimer's disease (AD). Previously, we showed that diet-induced HHcy accelerated the AD-like phenotype of a transgenic mouse model, i.e., Tg2576. In the present work, we tested whether an HHcy-lowering strategy in this model would be beneficial. Tg2576 mice received methionine-rich or regular chow diet for 5 mo. Next, while the chow control group was kept on the same regimen, the other mice were randomized into two groups: one was kept on the methionine-rich diet (Met On), the other switched to chow (Met Off). Compared with controls, 5 mo on the methionine-rich diet resulted in HHcy (plasma Hcy level, treated: 12.7±1.2 μM vs. control: 3.1±0.4 μM) and significant behavioral impairments (% freezing, treated: 2.4±1.4% vs. control: 19.9±6.9%). At the end of the study, while the Met On group kept Hcy level elevated, the Met Off group had these values indistinguishable from the controls. The reduction in Hcy levels resulted in a significant improvement of the fear-conditioning performance, and an amelioration of the brain amyloidosis. Our results demonstrate that lowering HHcy in a transgenic AD-mouse model is beneficial since it significantly improves behavior deficits and brain amyloidosis. Our findings provide new biological insights for future clinical trials aimed at lowering this modifiable risk factor in human AD.

Effect of homocysteine-lowering B vitamin treatment on angiographic progression of coronary artery disease: a Western Norway B Vitamin Intervention Trial (WENBIT) substudy

Total plasma homocysteine (tHcy) is an independent risk factor for coronary artery disease, and tHcy is lowered by B vitamins. To assess the effect of homocysteine-lowering B-vitamin treatment on angiographic progression of coronary artery disease, this substudy of the Western Norway B Vitamin Intervention Trial (WENBIT) included patients who had undergone percutaneous coronary intervention. The patients were randomized to daily oral treatment with folic acid, vitamin B(12), and vitamin B(6) or placebo in a 2 x 2 factorial design. The coronary angiograms obtained at baseline and follow-up were evaluated. The primary angiographic end points were the changes in minimum lumen diameter and diameter stenosis. A total of 348 subjects (288 men) with a mean +/- SD age of 60 +/- 10.2 years were followed up for a median of 10.5 months (twenty-fifth, seventy-fifth percentile 9.2, 11.8). The baseline median plasma tHcy level was 10.0 mumol/L (twenty-fifth, seventy-fifth percentile 8.1, 11.0), and treatment with folic acid/vitamin B(12) lowered the tHcy levels by 22%. At follow-up, we found 309 lesions with a significant decrease from baseline in the minimum lumen diameter of a mean of -0.16 +/- 0.4 mm and an increase in the diameter stenosis of 4.4 +/- 0.7%. Treatment with folic acid/vitamin B(12) or vitamin B(6) was not associated with a change in diameter stenosis or minimum lumen diameter. In a post hoc analysis, folic acid/vitamin B(12) treatment was significantly associated with rapid progression (odds ratio 1.84, 95% confidence interval 1.07 to 3.18). In conclusion, vitamin B treatment showed no beneficial effect on the angiographic progression of coronary artery disease, and the post hoc analyses suggested that folic acid/vitamin B(12) treatment might promote more rapid progression.

Association of homocysteine and methylene tetrahydrofolate reductase (MTHFR C677T) gene polymorphism with coronary artery disease (CAD) in the population of North India

The implications of the methylene tetrahydrofolate reductase (MTHFR) gene and the level of homocysteine in the pathogenesis of coronary artery disease (CAD) have been extensively studied in various ethnic groups. Our aim was to discover the association of MTHFR (C677T) polymorphism and homocysteine level with CAD in north Indian subjects. The study group consisted of 329 angiographically proven CAD patients, and 331 age and sex matched healthy individuals as controls. MTHFR (C677T) gene polymorphism was detected based on the polymerase chain reaction and restriction digestion with HinfI. Total homocysteine plasma concentration was measured using immunoassay. T allele frequency was found to be significantly higher in patients than in the control group. We found significantly elevated levels of mean homocysteine in the patient group when compared to the control group (p = 0.00). Traditional risk factors such as diabetes, hypertension, smoking habits, a positive family history and lipid profiles (triglyceride, total cholesterol, HDL-cholesterol, LDL-cholesterol, VLDL-cholesterol), were found significantly associated through univariate analysis. Furthermore, multivariable logistics regression analysis revealed that CAD is significantly and variably associated with diabetes, hypertension, smoking, triglycerides and HDL-cholesterol. Our findings showed that MTHFR C677T polymorphism and homocysteine levels were associated with coronary artery disease in the selected population.

Hydrogen sulfide attenuates hyperhomocysteinemia-induced cardiomyocytic endoplasmic reticulum stress in rats

The mechanisms responsible for the cardioprotective effect of hydrogen sulfide (H(2)S) are unclear. The present study was designed to examine whether H(2)S could regulate hyperhomocysteinemia (HHcy)-induced cardiomyocytic endoplasmic reticulum (ER) stress. A rat model of HHcy was produced, and H9c2 cells (rat embryonic heart-derived cell line) were cultured. The plasma homocysteine was measured by using HPLC. Plasma H(2)S concentration and myocardial H(2)S production were measured with a sulfide-sensitive electrode. Confocal immunofluorescent analysis for cardiomyocytic C/EBP homologous protein (CHOP) was performed. Glucose-regulated protein 78 (GRP78), CHOP, and caspase 12 expressions by myocardial tissues and cleaved caspase 12 and p-eIF2alpha expressions by H9c2 cells were detected with Western blotting. The results showed that methionine overload induced HHcy, resulting in a marked cardiomyocytic ER stress, whereas endogenous production of H(2)S was reduced in rats with HHcy. H(2)S supplementation, however, decreased expressions of ER stress-associated proteins, including GRP78, CHOP, and caspase 12, by myocardial tissues in vivo. The inhibition of endogenous H(2)S production further enhanced cardiomyocytic ER stress, but H(2)S supplementation effectively antagonized the H9c2 cell CHOP, cleaved caspase 12 and p-eIF2alpha expressions induced by Hcy, thapsigargin, or tunicamycin in vitro. The results suggest that H(2)S can attenuate cardiomyocytic ER stress in HHcy-induced cardiomyocytic injury.

[Recurrent ischemic stroke revealing Biermer's disease]

INTRODUCTION

Biermer's disease is an autoimmune disorder characterized by vitamin B12 deficiency. Ischemic stroke is an uncommon complication of Biermer's disease, possibly though hyperhomocysteinemia.

CASE REPORT

A 58-year-old male presented with recurrent ischemic stroke. Extensive investigations were normal, except for a high plasma level of homocysteine in the context of pernicious anemia which was otherwise asymptomatic.

DISCUSSION

Hyperhomocysteinemia is a known marker, and probably a risk factor, for stroke, fostering atherosclerosis and thrombosis. It can be found among individuals suffering from homocysteinuria, but also when there is deficiency of vitamin B12 or folic acid. Vitamin B12 supplementation would reduce homocysteine concentration which in turn would reduce the risk of ischemic stroke.

Hydrogen sulfide regulates homocysteine-mediated glomerulosclerosis

BACKGROUND/AIMS

In this study we tested the hypothesis that H(2)S regulates collagen deposition, matrix metalloproteinases (MMP) and inflammatory molecules during hyperhomocysteinemia (HHcy) resulting in attenuation of glomerulosclerosis and improved renal function.

MATERIALS AND METHODS

A genetic model of HHcy, cystathionine beta-synthase heterozygous (CBS+/-) and wild-type (WT) 2-kidney (2K) mice were used in this study and supplemented with or without NaHS (30 micromol/l, H(2)S donor) in drinking water for 8 weeks. To expedite the renal damage associated with HHcy, uninephrectomized (1K) mice of similar groups were also used.

RESULTS

Results demonstrated that NAD(P)H oxidase (p47(phox)subunit) and blood pressure were upregulated in WT 1K, CBS+/- 2K and CBS+/- 1K mice with downregulation of H(2)S production and reduced glomerular filtration rate. These changes were normalized with H(2)S supplementation. Both pro- and active MMP-2 and -9 and collagen protein expressions and glomerular depositions were also upregulated in WT 1K, CBS+/- 2K and CBS+/- 1K mice. Increased expressions of inflammatory molecules, intercellular cell adhesion molecule-1 and vascular cell adhesion molecule-1, as well as increased macrophage infiltration, were detected in WT 1K, CBS+/- 2K and CBS+/- 1K mice. These changes were ameliorated with H(2)S supplementation.

CONCLUSION

Together, these results suggest that increased oxidative stress and decreased H(2)S in HHcy causes matrix remodeling and inflammation resulting in glomerulosclerosis and reduced renal function.

Metabolomic study of the LDL receptor null mouse fed a high-fat diet reveals profound perturbations in choline metabolism that are shared with ApoE null mice

Failure to express or expression of dysfunctional low-density lipoprotein receptors (LDLR) causes familial hypercholesterolemia in humans, a disease characterized by elevated blood cholesterol concentrations, xanthomas, and coronary heart disease, providing compelling evidence that high blood cholesterol concentrations cause atherosclerosis. In this study, we used (1)H nuclear magnetic resonance spectroscopy to examine the metabolic profiles of plasma and urine from the LDLR knockout mice. Consistent with previous studies, these mice developed hypercholesterolemia and atherosclerosis when fed a high-fat/cholesterol/cholate-containing diet. In addition, multivariate statistical analysis of the metabolomic data highlighted significant differences in tricarboxylic acid cycle and fatty acid metabolism, as a result of high-fat/cholesterol diet feeding. Our metabolomic study also demonstrates that the effect of high-fat/cholesterol/cholate diet, LDLR gene deficiency, and the diet-genotype interaction caused a significant perturbation in choline metabolism, notably the choline oxidation pathway. Specifically, the loss in the LDLR caused a marked reduction in the urinary excretion of betaine and dimethylglycine, especially when the mice are fed a high-fat/cholesterol/cholate diet. Furthermore, as we demonstrate that these metabolic changes are comparable with those detected in ApoE knockout mice fed the same high-fat/cholesterol/cholate diet they may be useful for monitoring the onset of atherosclerosis across animal models.

Homocysteine induces X-box-binding protein 1 splicing in the mice brain

Increasing evidence has been suggested that hyperhomocysteinemia is a risk factor of neurodegenerative diseases, although, the underlying mechanisms have not been elucidated. Here, we found peripheral application of homocysteine increases X-box-binding protein 1 (XBP1) splicing in the several areas of the mice brain, such as hippocampus, hypothalamus and cortex. Time-course experiments indicated that XBP1 splicing was observed from 2h, which was decreased thereafter. On the other hand, we did not observe GRP78 or CHOP induction in homocysteine-treated mice brain. As XBP1 is spliced in response to endoplasmic reticulum (ER) stress and ER stress has been implicated in the pathogenesis of CNS diseases such as Alzheimer's disease and Parkinson's disease, homocysteine-induced XBP1 splicing would be a key mechanism for such diseases.

p,p'-DDE induces testicular apoptosis in prepubertal rats via the Fas/FasL pathway

1,1-Dichloro-2,2 bis(p-chlorophenyl) ethylene (p,p'-DDE), the major metabolite of 2,2-bis(4-chlorophenyl)-1,1,1-trichloroethane (DDT), is a known persistent organic pollutant and male reproductive toxicant. It has antiandrogenic effect. However, the mechanism by which p,p'-DDE exposure causes male reproductive toxicity remains unknown. To elucidate the mechanism underpinning the testicular effects of p,p'-DDE, we sought to investigate Fas/FasL apoptotic pathway in the testis of prepubertal rats, including Fas, FasL, caspase-8, -3, and NF-kappaB. Animals were administered with different doses of p,p'-DDE (0, 20, 60, 100mg/kg b.wt) every other day by intraperitoneal injection for 10 days. The results indicated that p,p'-DDE exposure at over 20mg/kg b.wt showed the induction of apoptotic cell death. p,p'-DDE could induce increase in the MDA level, and decrease in SOD and GSH-Px activity. Significant elevations in the mRNA levels of Fas along with an increase in FasL, caspase-3, -8 were observed in 100mg/kg b.wt group. In protein level, p,p'-DDE could induce increase of FasL and reduction of procaspase-8. NF-kappaB p65 was activated by p,p'-DDE treatment in rat testis. In addition, the activities of caspase-3, -8 were increased in 100mg/kg b.wt group. Taken together, these results lead us to speculate that in vivo exposure to p,p'-DDE might induce testicular apoptosis in prepubertal rats through the Fas/FasL pathway.

Acceleration of brain amyloidosis in an Alzheimer's disease mouse model by a folate, vitamin B6 and B12-deficient diet

Epidemiological and clinical studies indicate that elevated circulating level of homocysteine (Hcy) is a risk factor for developing Alzheimer's disease (AD). Dietary deficiency of folate, vitamin B6 and B12 results in a significant increase of Hcy levels, a condition also known as hyperhomocysteinemia (HHcy). In the present study we tested the hypothesis that a diet deficient for these three important factors when administered to a mouse model of AD, i.e. Tg2576, will result in HHcy and in an acceleration of their amylodotic phenotype. Compared with Tg2576 mice on regular chow, the ones receiving the diet deficient for folate, B6 and B12 developed HHcy. This condition was associated with a significant increase in Abeta levels in the cortex and hippocampus, and an elevation of Abeta deposits in the same regions. No significant changes were observed for steady-state levels of total APP, BACE-1, ADAM-10, PS1 and nicastrin in the brains of mice with HHcy. No differences were observed for the main Abeta catabolic pathways, i.e. IDE and neprilysin proteins, or the Abeta chaperone apolipoprotein E. Our findings demonstrate that a dietary condition which leads to HHcy may also result in increased Abeta levels and deposition in a transgenic mouse model of AD-like amylodosis. They further support the concept that dietary factors can contribute to the development of AD neuropathology.

High plasma homocysteine levels contribute to the risk of stroke recurrence and all-cause mortality in a large prospective stroke population

Plasma homocysteine concentrations have been associated with the risk of stroke, but its relevance to secondary vascular events and mortality after stroke remains unclear because of inconsistent results from clinical trials. The aim of the present study was to investigate whether plasma homocysteine levels and the MTHFR (methylenetetrahydrofolate reductase) variant C677T contributed to the risk of stroke recurrence and all-cause mortality in a large prospective cohort of stroke patients in a Chinese population. A total of 1823 stroke patients (age, 35-74 years) were recruited during 2000-2001 and prospectively followed-up for a median of 4.5 years. During the follow-up, 347 recurrent strokes and 323 deaths from all-causes were documented. After adjustment for age, gender and other cardiovascular risk factors, a high homocysteine concentration was associated with an increased risk of 1.74-fold for stroke recurrence {RR (relative risk), 1.74 [95% CI (confidence interval), 1.3-2.3]; P<0.0001} and 1.75-fold for all-cause mortality [RR, 1.75 (95% CI, 1.3-2.4); P<0.0001] when highest and lowest categories were compared. Spline regression analyses revealed a threshold level of homocysteine for stroke recurrence. By dichotomizing homocysteine concentrations, the RRs were 1.31 (95% CI, 1.10-1.61; P=0.016) for stroke recurrence and 1.47 (95% CI, 1.15-1.88; P<0.0001) for all-cause mortality in patients with homocysteine levels > or =16 micromol/l relative to those with levels <16 micromol/l. The association of elevated plasma homocysteine concentrations with all-cause mortality was mainly due to an increased risk of cardiovascular deaths. No significant association was found between MTHFR C677T and stroke recurrence or mortality. In conclusion, our findings suggest that elevated homocysteine concentrations can predict the risk of stroke recurrence and mortality in patients with stroke.