Memantine Protects From Exacerbation of Ischemic Stroke and Blood Brain Barrier Disruption in Mild But Not Severe Hyperhomocysteinemia.

Background Hyperhomocysteinemia is a risk factor for ischemic stroke; however, a targeted treatment strategy is lacking partly because of limited understanding of the causal role of homocysteine in cerebrovascular pathogenesis. Methods and Results In a genetic model of cystathionine beta synthase (CBS) deficiency, we tested the hypothesis that elevation in plasma total homocysteine exacerbates cerebrovascular injury and that memantine, a N-methyl-D-aspartate receptor antagonist, is protective. Mild or severe elevation in plasma total homocysteine was observed in Cbs+/- (6.1±0.3 µmol/L) or Cbs-/- (309±18 µmol/L) mice versus Cbs+/+ (3.1±0.6 µmol/L) mice. Surprisingly, Cbs-/- and Cbs+/- mice exhibited similar increases in cerebral infarct size following middle cerebral artery ischemia/reperfusion injury, despite the much higher total homocysteine levels in Cbs-/- mice. Likewise, disruption of the blood brain barrier was observed in both Cbs+/- and Cbs-/- mice. Administration of the N-methyl-D-aspartate receptor antagonist memantine protected Cbs+/- but not Cbs-/- mice from cerebral infarction and blood brain barrier disruption. Our data suggest that the differential effect of memantine in Cbs+/- versus Cbs-/- mice may be related to changes in expression of N-methyl-D-aspartate receptor subunits. Cbs-/-, but not Cbs+/- mice had increased expression of NR2B subunit, which is known to be relatively insensitive to homocysteine. Conclusions These data provide experimental evidence that even a mild increase in plasma total homocysteine can exacerbate cerebrovascular injury and suggest that N-methyl-D-aspartate receptor antagonism may represent a strategy to prevent reperfusion injury after acute ischemic stroke in patients with mild hyperhomocysteinemia.

Preeclampsia-Like Features and Partial Lactation Failure in Mice Lacking Cystathionine γ-Lyase-An Animal Model of Cystathioninuria.

Elevated plasma homocysteine levels are considered as a risk factor for cardiovascular diseases as well as preeclampsia-a pregnancy disorder characterized by hypertension and proteinuria. We previously generated mice lacking cystathionine γ-lyase (Cth) as cystathioninuria models and found them to be with cystathioninemia/homocysteinemia. We investigated whether Cth-deficient (Cth-/-) pregnant mice display any features of preeclampsia. Cth-/- females developed normally but showed mild hypertension (~10 mmHg systolic blood pressure elevation) in late pregnancy and mild proteinuria throughout development/pregnancy. Cth-/- dams had normal numbers of pups and exhibited normal maternal behavior except slightly lower breastfeeding activity. However, half of them could not raise their pups owing to defective lactation; they could produce/store the first milk in their mammary glands but not often provide milk to their pups after the first ejection. The serum oxytocin levels and oxytocin receptor expression in the mammary glands were comparable between wild-type and Cth-/- dams, but the contraction responses of mammary gland myoepithelial cells to oxytocin were significantly lower in Cth-/- dams. The contraction responses to oxytocin were lower in uteruses isolated from Cth-/- mice. Our results suggest that elevated homocysteine or other unknown factors in preeclampsia-like Cth-/- dams interfere with oxytocin that regulates milk ejection reflex.

Nox4 and soluble epoxide hydrolase synergistically mediate homocysteine-induced inflammation in vascular smooth muscle cells.

BACKGROUND: Hyperhomocysteinemia leads to a vascular smooth muscle cell (VSMC) inflammatory response. Meanwhile, Nox4 dependent reactive oxygen species (ROS) signaling and soluble epoxide hydrolase (sEH)/epoxyeicosatrienoic acids (EETs) are both involved in vascular inflammation. Herein, we hypothesized that Nox4 and soluble epoxide hydrolase cross regulated during homocysteine-induced VSMC inflammation. METHODS AND RESULTS: In cultured VSMCs, the expression of the inflammatory factors VCAM1 and ICAM1 was measured by real-time PCR and Western blotting, while supernatant MCP1 was measured by ELISA. Upon VSMC stimulation with 50 µΜ homocysteine, we observed the VCAM1 and ICAM1 mRNA levels were increased by 1.15 and 1.0 folds, respectively. The MCP1 levels in the supernatant of cultured VSMCs treated with 100 µΜ increased to 1.76 folds. As expected, homocysteine induced Nox4 expression and Nox4-dependent ROS generation. The sEH expression was also upregulated in the presence of homocysteine in a dose-dependent manner. Furthermore, we knocked down Nox4 with siRNA. Knockdown of Nox4 decreased ROS generation and homocysteine-induced sEH expression. Overexpression of Nox4 with an adenovirus stimulated sEH expression. Similarly, knockdown or chemical inhibition of sEH blunted the upregulation of Nox4 by homocysteine. In vivo, in homocysteine-fed mice, concomitant upregulation of Nox4 and sEH was associated with increased VCAM1 and ICAM1 expression in the aortic wall. CONCLUSIONS: The inflammatory response induced by homocysteine in VSMCs was accompanied by Nox4 and sEH upregulation. Nox4 and soluble epoxide hydrolase synergistically contribute to homocysteine-induced inflammation.

Salidroside attenuates endothelial cellular senescence via decreasing the expression of inflammatory cytokines and increasing the expression of SIRT3.

OBJECTIVE: Endothelial cellular senescence is an important contributor to the endothelial dysfunction and atherosclerosis. Our previous studies suggested that salidroside (SAL) can alleviate atherosclerosis and protect endothelial cells against oxidative stress induced damage. However, the effect and mechanism of SAL on endothelial cellular senescence is still unclear. Here, we investigated the underlying mechanisms of SAL on preventing endothelial cellular premature senescence. METHODS AND RESULTS: We established a hyperhomocysteinemia (HHcy)mouse model via high methionine diet (HMD) to explore the protective effect of SAL. According to our results, the HMD elevated the concentration of serum homocysteine. HHcy induced the collagen deposition and the up-regulation of senescence markers, i.e. p16INK4A and p21CIP1, in intima-medial of aorta. In addition, SAL also inhibited the expression of CD68 and intercellular adhesion molecule 1 (ICAM1) in aorta. In senescent human umbilical vein endothelial cells (HUVECs) induced by H2O2, SAL treatment alleviated the expression of p16INK4A and p21CIP1 and reduced the activity of senescence-associated (SA)-ß-gal. CONCLUSION: our data suggested that SAL decreased the expression of inflammatory cytokines and up-regulated the expression of SIRT3, which might be the underlying mechanism of SAL on preventing endothelial cells from premature senescence.

Dissecting the Role of 5-Lipoxygenase in the Homocysteine-Induced Alzheimer's Disease Pathology.

Alzheimer's disease (AD) affects over 40 million patients around the world and poses a huge economic burden on society since no effective therapy is available yet. While the cause(s) for the most common sporadic form of the disease are still obscure, lifestyle and different environmental factors have emerged as modulators of AD susceptibility. Hyperhomocysteinemia (HHCY), a condition of high circulating levels of homocysteine, is an independent but modifiable risk factor for AD. Studies in AD mouse models have linked HHCY with memory impairment, amyloidosis, tau pathology, synaptic dysfunction, and neuroinflammation. However, the exact mechanism by which HHCY affects AD pathogenesis is unclear. The 5-lipoxygenase (5LO) is a protein upregulated in postmortem AD brains and plays a functional role in AD pathogenesis. Recently, in vitro and in vivo studies showed that HHCY effects on amyloid-ß and tau pathology, synapse and memory impairments are dependent on the activation of the 5LO enzymatic pathway, since its genetic absence or pharmacological inhibition prevents them. HHCY induces 5LO gene upregulation by lowering the methylation of its promoter, which results in increased translation and transcription of its mRNA. Based on these findings, we propose that epigenetic modification of 5LO represents the missing biological link between HHCY and AD pathogenesis, and for this reason it represents a viable therapeutic target to prevent AD development in individuals bearing this risk factor.

Hyperhomocysteinemia and cardiovascular disease in animal model.

Hyperhomocysteinemia is an independent risk factor for cardiovascular disease and is associated with primary causes of mortality and morbidity throughout the world. Several studies have been carried out to evaluate the effects of a diet inducing cystathionine-ß-synthase, methyltetrafolate, folic acid, and vitamin B supplemented with methionine on the homocysteine metabolism and in lowering the plasma total homocysteine levels. A large number of molecular and biomedical studies in numerous animals, such as mice, rabbits, and pigs, have sought to elevate the plasma total homocysteine levels and to identify a disease model for human hyperhomocysteinemia. However, a specific animal model is not suitable for hyperhomocysteinemia in terms of all aspects of cardiovascular disease. In this review article, the experimental progress of animal models with plasma total homocysteine levels is examined to identify a feasible animal model of hyperhomocysteinemia for different aspects.

MTHFR A1298C and C677T Polymorphisms Are Associated with Increased Risk of Venous Thromboembolism: A Retrospective Chart Review Study.

BACKGROUND: Methylene tetrahydrofolate reductase (MTHFR) is a key enzyme in homocysteine metabolism. This study aims to determine the impact of MTHFR polymorphisms on plasma homocysteine levels and risks of venous thromboembolism (VTE). METHODS: This retrospective chart review study included a total of 188 subjects who were tested for MTHFR polymorphisms at Metrowest Coagulation Laboratory between April 2011 and April 2016. Two independent coders were trained to extract relevant clinical data for statistical analysis. RESULTS: VTE occurred in 50% of patients with compound mutation, compared with only 28.6% of subjects from the wild-type group. Patients with heterozygous or homozygous A1298C or C677T variants had an intermediate risk of VTE. The median homocysteine level in the wild-type group was slightly lower than that of heterozygous or homozygous MTHFR variants. The difference, however, was not significant (p = 0.6193). Moreover, there was no difference in plasma homocysteine level between patients with VTE versus VTE-free (p = 0.4923). CONCLUSIONS: Heterozygous or homozygous MTHFR variants, especially a compound mutation, are associated with increased risk of VTE. Hyperhomocysteinemia does not correlate with MTHFR polymorphisms or VTE risk. Hence, MTHFR genotyping provides more consistent assessment of VTE risk. This information can be incorporated into risk stratification for early intervention and prophylaxis of VTE.

CYLD Deubiquitinates Nicotinamide Adenine Dinucleotide Phosphate Oxidase 4 Contributing to Adventitial Remodeling.

OBJECTIVE: Transdifferentiation of adventitial fibroblasts (AFs) into myofibroblasts plays a critical role during the vascular remodeling that occurs during atherosclerosis, restenosis, and aortic aneurysm. The ubiquitination/deubiquitination regulatory system is essential for the quality control of proteins. The involvement of ubiquitination/deubiquitination during AF transdifferentiation remains largely unknown. In this study, we determined the role of cylindromatosis (CYLD), a deubiquitinase, in the process of AF differentiation and activation in vitro and in vivo. APPROACH AND RESULTS: Transforming growth factor-ß1 and homocysteine, 2 known inducers of AF transdifferentiation, greatly upregulated CYLD expression in a time- and dose-dependent manner. The silencing of CYLD significantly inhibited AF transdifferentiation and activation as evidenced by the expression of contractile proteins, the production of the proinflammatory cytokines MCP-1 (monocyte chemotactic protein 1) and IL-6 (interleukin-6), the deposition of extracellular matrix, and cell migration. We further asked whether CYLD mediates AF activation via the regulation of nicotinamide adenine dinucleotide phosphate oxidase 4 (Nox4) as it is an essential factor during AF transdifferentiation. Indeed, the silencing of CYLD repressed transforming growth factor-ß1-induced and homocysteine-induced Nox4 upregulation and reactive oxygen species production, whereas Nox4 overexpression greatly rescued the inhibitory effect on AF activation by CYLD silencing. Most interestingly, transforming growth factor-ß1 and homocysteine repressed Nox4 ubiquitination and prolonged the half-life of Nox4. Moreover, Nox4 was deubiquitinated via a direct interaction with the ubiquitin-specific protease domain of CYLD. In accordance, hyperhomocysteinemia significantly increased adventitial CYLD and Nox4 expression, promoted AF transdifferentiation, and aggravated CaPO4-induced abdominal aortic aneurysm in mice. These effects were abolished in CYLD-/- mice. CONCLUSIONS: CYLD contributes to the transdifferentiation of AFs via deubiquitinating Nox4 and may play a role in vascular remodeling.

The communal relation of MTHFR, MTR, ACE gene polymorphisms and hyperhomocysteinemia as conceivable risk of coronary artery disease.

Homocysteine and its modulating genes have strongly emerged as novel biomarkers for coronary artery disease (CAD). In the present study, we investigated whether polymorphisms in homocysteine pathway genes and the plasma levels of homocysteine, folate, and vitamin B12, independently or in combination, are associated with CAD risk. A total of 504 participants were recruited (cases, n = 254; controls, n = 250, respectively). Tetra primer allele refractory mutation system polymerase chain reaction (PCR) was used for resolving the genotypes of 5'10' methylenetetrahydrofolate reductase 'MTHFR' polymorphisms (rs1801133, rs1801131), 5' methyl tetrahydrofolate homocysteine methyltransferase 'MTR' polymorphism (rs1805087), paroxanse1 'PON1' polymorphism (rs662), and cystathionine beta synthase 'CBS' polymorphism (rs5742905). Conventional PCR amplification was carried out for resolving angiotensin converting enzyme 'ACE' insertion/deletion (I/D) polymorphism (rs4646994). ANOVA analysis, adjusted for the covariates, revealed that rs1801133, rs1805087 polymorphisms and homocysteine levels were associated with CAD. Logistic regression analysis (adjusted) revealed similar findings. Logistic regression analysis after applying factorial design to the studied single nucleotide polymorphisms (SNPs) revealed that homocysteine levels and heterozygous and mutant alleles at rs1801133, rs1805087, along with mutant alleles at rs1801131, rs4646994, conferred higher risk for CAD. Our results provide insight into the multifactorial nature of coronary artery disease. We highlight that SNPs in folate pathway genes and homocysteine have role in disease causation and can be used in disease prediction strategies.

Effect of Hyperhomocysteinemia on Redox Balance and Redox Defence Enzymes in Ischemia-Reperfusion Injury and/or After Ischemic Preconditioning in Rats.

Increased level of homocysteine (hHcy) in plasma is an accompanying phenomenon of many diseases, including a brain stroke. This study determines whether hyperhomocysteinemia (which is a risk factor of brain ischemia) itself or in combination with ischemic preconditioning affects the ischemia-induced neurodegenerative changes, generation of reactive oxygen species (ROS), lipoperoxidation, protein oxidation, and activity of antioxidant enzymes in the rat brain cortex. The hHcy was induced by subcutaneous administration of homocysteine (0.45 µmol/g body weight) twice a day in 8 h intervals for 14 days. Rats were preconditioned by 5 min ischemia. Two days later, 15 min of global forebrain ischemia was induced by four vessel's occlusion. The study demonstrates that in the cerebral cortex, hHcy alone induces progressive neuronal cell death and morphological changes. Neuronal damage was associated with the pro-oxidative effect of hHcy, which leads to increased ROS formation, peroxidation of lipids and oxidative alterations of cortical proteins. Ischemic reperfusion injury activates degeneration processes and de-regulates redox balance which is aggravated under hHcy conditions and leads to the augmented lipoperoxidation and protein oxidation. If combined with hHcy, ischemic preconditioning could preserve the neuronal tissue from lethal ischemic effect and initiates suppression of lipoperoxidation, protein oxidation, and alterations of redox enzymes with the most significant effect observed after prolonged reperfusion. Increased prevalence of hyperhomocysteinemia in the Western population and crucial role of elevated Hcy level in the pathogenesis of neuronal disorders makes this amino acid as an interesting target for future research. Understanding the multiple etiological mechanisms and recognition of the co-morbid risk factors that lead to the ischemic/reperfusion injury and ischemic tolerance is therefore important for developing therapeutic strategies in human brain stroke associated with the elevated level of Hcy.

Homocysteine modulates 5-lipoxygenase expression level via DNA methylation.

Elevated levels of homocysteinemia (Hcy), a risk factor for late-onset Alzheimer's disease (AD), have been associated with changes in cell methylation. Alzheimer's disease is characterized by an upregulation of the 5-lipoxygenase (5LO), whose promoter is regulated by methylation. However, whether Hcy activates 5LO enzymatic pathway by influencing the methylation status of its promoter remains unknown. Brains from mice with high Hcy were assessed for the 5LO pathway and neuronal cells exposed to Hcy implemented to study the mechanism(s) regulating 5LO expression levels and the effect on amyloid ß formation. Diet- and genetically induced high Hcy resulted in 5LO protein and mRNA upregulation, which was associated with a significant increase of the S-adenosylhomocysteine (SAH)/S-adenosylmethionine ratio, and reduced DNA methyltrasferases and hypomethylation of 5-lipoxygenase DNA. In vitro studies confirmed these results and demonstrated that the mechanism involved in the Hcy-dependent 5LO activation and amyloid ß formation is DNA hypomethylation secondary to the elevated levels of SAH. Taken together these findings represent the first demonstration that Hcy directly influences 5LO expression levels and establish a previously unknown cross talk between these two pathways, which is highly relevant for AD pathogenesis. The discovery of such a novel link not only provides new mechanistic insights in the neurobiology of Hcy, but most importantly new therapeutic opportunities for the individuals bearing this risk factor for the disease.

Hyperhomocysteinemia impairs regional blood flow: involvements of endothelial and neuronal nitric oxide.

Increasing evidence support the idea that hyperhomocysteinemia (HHcy) is responsible for pathogenesis underlying cerebral, coronary, renal, and other vascular circulatory disorders and for hypertension. Impaired synthesis of nitric oxide (NO) in the endothelium or increased production of asymmetric dimethylarginine and activated oxygen species are involved in the impairment of vasodilator effects of NO. Impaired circulation in the brain derived from reduced synthesis and actions of NO would be an important triggering factor to dementia and Alzheimer's disease. Reduced actions of NO and brain hypoperfusion trigger increased production of amyloid-ß that inhibits endothelial function, thus establishing a vicious cycle for impairing brain circulation. HHcy is involved in the genesis of anginal attack and coronary myocardial infarction. HHcy is also involved in renal circulatory diseases. The homocysteine (Hcy)-induced circulatory failure is promoted by methionine and is prevented by increased folic acid and vitamin B6/B12. Eliminating poor life styles, such as smoking and being sedentary; keeping favorable dietary habits; and early treatment maintaining constitutive NOS functions healthy, reducing oxidative stresses would be beneficial in protecting HHcy-induced circulatory failures.

Hyperhomocysteinaemia in rats is associated with erectile dysfunction by impairing endothelial nitric oxide synthase activity.

To investigate the effect of hyperhomocysteinaemia (HHCy) on penile erectile function in a rat model, a methionine-rich diet was used in which erectile function, the reproductive system, and nitric oxide synthase were characterized. The intracavernous pressure, apomorphine experiments, measurement of oxidative stress, hematoxylin and eosin staining, immunohistochemistry analysis, reverse transcription-polymerase chain reactions and measurement of endothelial nitric oxide synthase activity were utilized. Our results showed that erections in the middle-dose, high-dose, and interference (INF) groups were significantly lower than the control (P < 0.05). INF group, being fed with vitamins B and folic acid, demonstrated markedly improved penile erections compared with the middle-dose group (P < 0.05). HHCy-induced eNOS and phospho-eNOS protein expression was reduced and the antioxidant effect was markedly impaired. The data of the present data provide evidence that HHCy is a vascular risk factor for erectile dysfunction by impairing cavernosa endothelial nitric oxide synthase activity. Intake of vitamins B can alleviate this abnormality.

Methionine synthase reductase deficiency (CblE): A report of two patients and a novel mutation.

IMPORTANCE: Functional methionine synthase reductase deficiency, also known as cobalamin E disorder, is a rare autosomal recessive inherited disease that results in an impaired remethylation of homocysteine to methionine. It presents with macrocytic anemia, hyperhomocysteinemia, and hypomethioninemia, and may also be accompanied with neurological impairment. CLINICAL PRESENTATION: We describe two new cases of unrelated girls with megaloblastic anemia misclassified at first as congenital dyserythropoietic anemia with development of neurologic dysfunction in one of them. INTERVENTION: The posterior finding of biochemical features (hyperhomocysteinemia and hypomethioninemia) focused the diagnosis on the inborn errors of intracellular vitamin B12. Subsequent molecular analysis of the methionine synthase reductase (MTRR) gene revealed compound heterozygosity for a transition c.1361C > T (p.Ser454Leu) and another, not yet described in literature, c.1677-1G > A (p.Glu560fs) in one patient, and a single homozygosis mutation, c.1361C > T (p.Ser545Leu) in the other one. These mutations confirmed the diagnosis of cobalamin E deficiency. CONCLUSION: Treatment with hydroxocobalamin in combination with betaine appears to be useful for hematological improvement and prevention of brain disabilities in CblE-affected patients. Our study widens the clinical, molecular, metabolic, and cytological knowledge of deficiency MTRR enzyme.

Hyperhomocysteinemia inhibits satellite cell regenerative capacity through p38 alpha/beta MAPK signaling.

Chronic failure in maintenance and regeneration of skeletal muscles leads to lower muscle mass (sarcopenia), muscle weakness, and poor response to injury. Evidence suggests that aberrant p38 MAPK signaling undermines the repair process after injury in aged mice. Previous studies have shown that hyperhomocysteinemia (HHcy) has been associated with muscle weakness and lower than normal body weights. However, whether or not HHcy condition also compromises skeletal muscle regenerative capabilities is not clear. In the current study, we show that CBS-/+ mice, a model for HHcy condition, exhibited compromised regenerative function and cell proliferation upon injury. However, there was no significant difference in Pax7 expression levels in the satellite cells from CBS-/+ mouse skeletal muscles. Interestingly, the satellite cells from CBS-/+ mice not only exhibited diminished in vitro proliferative capabilities, but also there was heightened oxidative stress. In addition, there was enhanced p38 MAPK activation as well as p16 and p21 expression in the CBS-/+ mouse satellite cells. Moreover, the C2C12 myoblasts also exhibited higher p38 MAPK activation and p16 expression upon treatment with homocysteine in addition to enhanced ROS presence. Tissue engraftment potential and regeneration after injury were restored to some extent upon treatment with the p38-MAPK inhibitor, SB203580, in the CBS-/+ mice. These results together suggest that HHcy-induced diminished satellite cell proliferation involves excessive oxidative stress and p38 MAPK signaling. Our study further proposes that HHcy is a potential risk factor for elderly frailty, and need to be considered as a therapeutic target while designing the alleviation interventions/postinjury rehabilitation measures for adults with HHcy.

Mechanisms of hyperhomocysteinemia induced skeletal muscle myopathy after ischemia in the CBS-/+ mouse model.

Although hyperhomocysteinemia (HHcy) elicits lower than normal body weights and skeletal muscle weakness, the mechanisms remain unclear. Despite the fact that HHcy-mediated enhancement in ROS and consequent damage to regulators of different cellular processes is relatively well established in other organs, the nature of such events is unknown in skeletal muscles. Previously, we reported that HHcy attenuation of PGC-1α and HIF-1α levels enhanced the likelihood of muscle atrophy and declined function after ischemia. In the current study, we examined muscle levels of homocysteine (Hcy) metabolizing enzymes, anti-oxidant capacity and focused on protein modifications that might compromise PGC-1α function during ischemic angiogenesis. Although skeletal muscles express the key enzyme (MTHFR) that participates in re-methylation of Hcy into methionine, lack of trans-sulfuration enzymes (CBS and CSE) make skeletal muscles more susceptible to the HHcy-induced myopathy. Our study indicates that elevated Hcy levels in the CBS-/+ mouse skeletal muscles caused diminished anti-oxidant capacity and contributed to enhanced total protein as well as PGC-1α specific nitrotyrosylation after ischemia. Furthermore, in the presence of NO donor SNP, either homocysteine (Hcy) or its cyclized version, Hcy thiolactone, not only increased PGC-1α specific protein nitrotyrosylation but also reduced its association with PPARγ in C2C12 cells. Altogether these results suggest that HHcy exerts its myopathic effects via reduction of the PGC-1/PPARγ axis after ischemia.

Homocysteine accelerates senescence of endothelial cells via DNA hypomethylation of human telomerase reverse transcriptase.

OBJECTIVE: Homocysteine can accelerate the senescence of endothelial progenitor cells or endothelial cells (ECs) via telomerase inactivation and length shortening. However, the underlying mechanism is unclear. Here, we investigated whether homocysteine promotes endothelial senescence by reducing the expression and activity of human telomerase reverse transcriptase (hTERT) by DNA methylation to reduce ECs telomerase activity. APPROACH AND RESULTS: When compared with primary human umbilical vein endothelial cells grown under standard conditions, ECs with chronic homocysteine treatment showed accelerated upregulation of p16, p21, and p53, markers of cellular senescence, during 6 to 10 passages. Interestingly, homocysteine-stimulated but not angiotensin II-stimulated ECs senescence could be reversed by hypermethylation induced by folic acid or s-adenosylmethionine supplementation. Meanwhile, homocysteine promoted the shortening of telomere length specifically related to restoration of hTERT transcriptional expression and CCCTC-binding factor binding sites with hTERT promoter hypomethylation, as detected by quantitative real-time polymerase chain reaction, Western blot, methylation-specific polymerase chain reaction, and bisulfite sequencing assay. Electrophoretic mobility shift assay and chromatin immunoprecipitation results showed that homocysteine-reduced telomere activity and homocysteine-induced EC senescence might contribute to hTERT promoter demethylation by increasing CCCTC-binding factor repression and interfering in the SP1 binding to the demethylated hTERT promoter, which might relate with reduced of DNA methyltransferase 1. Furthermore, the CCCTC-binding factor-dependent mechanism of homocysteine-reduced hTERT expression via DNA demethylation was confirmed in aortic endothelia of mice with hyperhomocysteine levels. CONCLUSIONS: CCCTC-binding factor and SP1 cross talk may contribute to homocysteine-reduced hTERT DNA methylation and expression in endothelial senescence.

Predicting Hyperhomocysteinemia by Methylenetetrahydrofolate Reductase C677T Polymorphism in Chinese Patients With Hypertension.

OBJECTIVE: To evaluate the performance of methylenetetrahydrofolate reductase (MTHFR) gene C677T polymorphism in predicting hyperhomocysteinemia (HHcy) in Chinese patients with hypertension. METHODS: We measured plasma total homocysteine tHcy level and C677T genotype in 1058 Chinese patients with hypertension from 4 previous studies. We used 10, 15, and 20 µmol/L as cutoff values for the definition of mild, modest, and severe HHcy, respectively. Logistic models for HHcy were built from the study sample using the C677T genotype as well as age and gender as predictors. The receiver-operating characteristics of the models were evaluated. RESULTS: Our major findings are that (1) C677T TT genotype is consistently associated with a higher tHcy across the 4 studies, with an increase in size ranging from 38% to 68% in the 4 studies and 51% overall. The C677T polymorphism independently explained about 14% of the total variance of the normalized tHcy. (2) The TT genotype is associated with a large increase in odds ratio (OR) for HHcy. Overall, the multivariate-adjusted ORs for the TT genotype are 3.9 (95% confidence interval [CI]: 2.4-6.4), 6.5 (95% CI: 4.0-10.6), and 17.9 (95% CI: 8.4-38.1) for mild, modest, and severe HHcy, respectively. (3) Overall, the predicting performance increased with HHcy severity, with sensitivity improving from 31.0% for mild HHcy to 70.3% for severe HHcy, and with specificity slightly decreasing from 85.4% to 80.3%. Inclusion of gender and age as predictors significantly improves the sensitivity, especially for predicting mild HHcy. CONCLUSION: With an excellent sensitivity and a modest specificity, C677T could be a useful screening marker for severe HHcy.