Homocysteine thiolactone and N-homocysteinylated protein induce pro-atherogenic changes in gene expression in human vascular endothelial cells

Discovery of a novel homocysteine thiolactone hydrolase and the catalytic activity of its natural variants

Homocysteine thiolactone (HTL), a toxic metabolite of homocysteine (Hcy) in hyperhomocysteinemia (HHcy), is known to modify protein structure and function, leading to protein damage through formation of N-Hcy-protein. HTL has been highly linked to HHcy-associated cardiovascular and neurodegenerative diseases. The protective role of HTL hydrolases against HTL-associated vascular toxicity and neurotoxicity have been reported. Although several endogeneous enzymes capable of hydrolyzing HTL have been identified, the primary enzyme responsible for its metabolism remains unclear. In this study, three human carboxylesterases were screened to explore new HTL hydrolase and human carboxylesterase 1 (hCES1) demonstrates the highest catalytic activity against HTL. Given the abundance of hCES1 in the liver and the clinical significance of its single-nucleotide polymorphisms (SNPs), six common hCES1 nonsynonymous coding SNP (nsSNPs) variants were examined and characterized for their kinetic parameters. Variants E220G and G143E displayed 7.3-fold and 13.2-fold lower catalytic activities than its wild-type counterpart. In addition, the detailed catalytic mechanism of hCES1 for HTL hydrolysis was computational investigated and elucidated by Quantum mechanics/molecular mechanics (QM/MM) molecular dynamics (MD) method. The function of residues E220 and G143 in sustaining its hydrolytic activity of hCES1 was analyzed, and the calculated energy difference aligns well with experimental-derived results, supporting the validity of our computational insights. These findings provide insights into the potential protective role of hCES1 against HTL-associated toxicity, and warrant future studies on the possible association between specific genetic variants of hCES1 with impaired catalytic function and clinical susceptibility of HTL-associated cardiovascular and neurodegenerative diseases.

Homocysteine metabolites inhibit autophagy by upregulating miR-21-5p, miR-155-5p, miR-216-5p, and miR-320c-3p in human vascular endothelial cells

Nutritional and genetic deficiencies in homocysteine (Hcy) metabolism lead to hyperhomocysteinemia (HHcy) and cause endothelial dysfunction, a hallmark of atherosclerosis, which is a major cause of cardiovascular disease (CVD). Impaired autophagy causes the accumulation of damaged proteins and organelles and is associated with CVD. Biochemically, HHcy is characterized by elevated levels of Hcy and its metabolites, Hcy-thiolactone and N-Hcy-protein. However, whether these metabolites can dysregulate mTOR signaling and autophagy in endothelial cells is not known. Here, we examined the influence of Hcy-thiolactone, N-Hcy-protein, and Hcy on autophagy human umbilical vein endothelial cells. We found that treatments with Hcy-thiolactone, N-Hcy-protein, or Hcy significantly downregulated beclin 1 (BECN1), autophagy-related 5 (ATG5), autophagy-related 7 (ATG7), and microtubule-associated protein 1 light chain 3 (LC3) mRNA and protein levels. We also found that these changes were mediated by upregulation by Hcy-thiolactone, N-Hcy-protein, and Hcy of autophagy-targeting microRNA (miR): miR-21, miR-155, miR-216, and miR-320c. The effects of these metabolites on levels of miR targeting autophagy as well as on the levels of BECN1, ATG5, ATG7, and LC3 mRNA and protein were abrogated by treatments with inhibitors of miR-21, miR-155, miR-216, and mir320c. Taken together, our findings show that Hcy metabolites can upregulate miR-21, miR-155, miR-216, and mir320c, which then downregulate autophagy in human endothelial cells, important for vascular homeostasis.

Diet-induced hyperhomocysteinemia causes sex-dependent deficiencies in offspring musculature and brain function

Hyperhomocysteinemia (HHcy), characterized by elevated homocysteine (Hcy) levels, is a known risk factor for cardiovascular, renal, and neurological diseases, as well as pregnancy complications. Our study aimed to investigate whether HHcy induced by a high-methionine (high-Met) diet exacerbates cognitive and behavioral deficits in offspring and leads to other breeding problems. Dietary HHcy was induced four weeks before mating and continued throughout gestation and post-delivery. A battery of behavioral tests was conducted on offspring between postnatal days (PNDs) 5 and 30 to assess motor function/activity and cognition. The results were correlated with brain morphometric measurements and quantitative analysis of mammalian target of rapamycin (mTOR)/autophagy markers. The high-Met diet significantly increased parental and offspring urinary tHcy levels and influenced offspring behavior in a sex-dependent manner. Female offspring exhibited impaired cognition, potentially related to morphometric changes observed exclusively in HHcy females. Male HHcy pups demonstrated muscle weakness, evidenced by slower surface righting, reduced hind limb suspension (HLS) hanging time, weaker grip strength, and decreased activity in the beaker test. Western blot analyses indicated the downregulation of autophagy and the upregulation of mTOR activity in HHcy cortexes. HHcy also led to breeding impairments, including reduced breeding rate, in-utero fetal death, lower pups' body weight, and increased mortality, likely attributed to placental dysfunction associated with HHcy. In conclusion, a high-Met diet impairs memory and cognition in female juveniles and weakens muscle strength in male pups. These effects may stem from abnormal placental function affecting early neurogenesis, the dysregulation of autophagy-related pathways in the cortex, or epigenetic mechanisms of gene regulation triggered by HHcy during embryonic development.

Blood biomarkers for post-stroke cognitive impairment: A systematic review and meta-analysis

BACKGROUND AND PURPOSE

Post-stroke cognitive impairment (PSCI) is a frequent consequence of stroke, which affects the quality of life and prognosis of stroke survivors. Numerous studies have indicated that blood biomarkers may be the key determinants for predicting and diagnosing cognitive impairment, but the results remain varied. Therefore, this meta-analysis aims to summarize potential biomarkers associated with PSCI.

METHODS

PubMed, Web of Science, Embase, and Cochrane Library were comprehensively searched for studies exploring blood biomarkers associated with PSCI from inception to 15 April 2022.

RESULTS

63 studies were selected from 4,047 references, which involves 95 blood biomarkers associated with the PSCI. We meta-analyzed 20 potential blood biomarker candidates, the results shown that the homocysteine (Hcy) (SMD = 0.35; 95 %CI: 0.20-0.49; P < 0.00001), c-reactive protein (CRP) (SMD = 0.49; 95 %CI: 0.20-0.78; P = 0.0008), uric acid (UA) (SMD = 0.41; 95 %CI: 0.06-0.76; P = 0.02), interleukin 6 (IL-6) (SMD = 0.92; 95 % CI: 0.27-1.57; P = 0.005), cystatin C (Cys-C) (SMD = 0.58; 95 %CI: 0.28-0.87; P = 0.0001), creatinine (SMD = 0.39; 95 %CI: 0.23-0.55; P < 0.00001) and tumor necrosis factor alpha (TNF-α) (SMD = 0.45; 95 %CI: 0.08-0.82; P = 0.02) levels were significantly higher in patients with PSCI than in the non-PSCI group.

CONCLUSION

Based on our findings, we recommend that paramedics focus on the blood biomarkers levels of Hcy, CRP, UA, IL-6, Cys-C, creatinine and TNF-α in conjunction with neuroimaging and neuropsychological assessment to assess the risk of PSCI, which may help with early detection and timely preventive measures. At the same time, other potential blood biomarkers should be further validated in future studies.

Homocysteine metabolites inhibit autophagy, elevate amyloid beta, and induce neuropathy by impairing Phf8/H4K20me1-dependent epigenetic regulation of mTOR in cystathionine β-synthase-deficient mice

The loss of cystathionine β-synthase (CBS), an important homocysteine (Hcy)-metabolizing enzyme or the loss of PHF8, an important histone demethylase participating in epigenetic regulation, causes severe intellectual disability in humans. Similar neuropathies were also observed in Cbs-/- and Phf8-/- mice. How CBS or PHF8 depletion can cause neuropathy was unknown. To answer this question, we examined a possible interaction between PHF8 and CBS using Cbs-/- mouse and neuroblastoma cell models. We quantified gene expression by RT-qPCR and western blotting, mTOR-bound H4K20me1 by chromatin immunoprecipitation (CHIP) assay, and amyloid β (Aβ) by confocal fluorescence microscopy using anti-Aβ antibody. We found significantly reduced expression of Phf8, increased H4K20me1, increased mTOR expression and phosphorylation, and increased App, both on protein and mRNA levels in brains of Cbs-/- mice versus Cbs+/- sibling controls. Autophagy-related Becn1, Atg5, and Atg7 were downregulated while p62, Nfl, and Gfap were upregulated on protein and mRNA levels, suggesting reduced autophagy and increased neurodegeneration in Cbs-/- brains. In mouse neuroblastoma N2a or N2a-APPswe cells, treatments with Hcy-thiolactone, N-Hcy-protein or Hcy, or Cbs gene silencing by RNA interference significantly reduced Phf8 expression and increased total H4K20me1 as well as mTOR promoter-bound H4K20me1. This led to transcriptional mTOR upregulation, autophagy downregulation, and significantly increased APP and Aβ levels. The Phf8 gene silencing increased Aβ, but not APP, levels. Taken together, our findings identify Phf8 as a regulator of Aβ synthesis and suggest that neuropathy of Cbs deficiency is mediated by Hcy metabolites, which transcriptionally dysregulate the Phf8 → H4K20me1 → mTOR → autophagy pathway thereby increasing Aβ accumulation.

Advances in the role of epigenetics in homocysteine-related diseases

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

Epigenetic Mechanisms Involved in the Effects of Maternal Hyperhomocysteinemia on the Functional State of Placenta and Nervous System Plasticity in the Offspring

According to modern view, susceptibility to diseases, specifically to cognitive and neuropsychiatric disorders, can form during embryonic development. Adverse factors affecting mother during the pregnancy increase the risk of developing pathologies. Despite the association between elevated maternal blood homocysteine (Hcy) and fetal brain impairments, as well as cognitive deficits in the offspring, the role of brain plasticity in the development of these pathologies remains poorly studied. Here, we review the data on the negative impact of hyperhomocysteinemia (HHcy) on the neural plasticity, in particular, its possible influence on the offspring brain plasticity through epigenetic mechanisms, such as changes in intracellular methylation potential, activity of DNA methyltransferases, DNA methylation, histone modifications, and microRNA expression in brain cells. Since placenta plays a key role in the transport of nutrients and transmission of signals from mother to fetus, its dysfunction due to aberrant epigenetic regulation can affect the development of fetal CNS. The review also presents the data on the impact of maternal HHcy on the epigenetic regulation in the placenta. The data presented in the review are not only interesting from purely scientific point of view, but can help in understanding the role of HHcy and epigenetic mechanisms in the pathogenesis of diseases, such as pregnancy pathologies resulting in the delayed development of fetal brain, cognitive impairments in the offspring during childhood, and neuropsychiatric and neurodegenerative disorders later in life, as well as in the search for approaches for their prevention using neuroprotectors.

Hyperhomocysteinemia in Cardiovascular Diseases: Revisiting Observational Studies and Clinical Trials

Thromboembolic manifestations are relatively frequent in patients with intermediate/severe hyperhomocysteinemia (>30 µmol/L) related to inherited disorders and deficiencies in vitamin B12 and folate. In contrast, moderate hyperhomocysteinemia (15-30 µmol/L) is a modest predictor of cardiovascular risk. The recognition of homocysteine as a cardiovascular risk factor has been challenged by some but not all randomized clinical trials. We reviewed the main data of this controversy and formulated conclusions to be translated in clinical practice.Homocysteine-lowering trials have been performed in cardiovascular subjects with moderate but not intermediate/severe hyperhomocysteinemia despite the dose-effect risk association. The first meta-analyses found no benefit and led cardiology societies not recommending homocysteine in the assessment of cardiovascular risk. This guideline challenged the need to diagnose and treat the nutritional and genetic causes of intermediate/major hyperhomocysteinemia and was not revised when larger meta-analyses concluded to a reduced risk of stroke. In a recent observational study, 84% of consecutive cardiovascular patients assessed for homocysteine had intermediate or major hyperhomocysteinemia, which was properly assessed in only half of the cases and related to B12 and/or folate deficiency and Addison/Biermer disease in 55% of these cases.In conclusion, revisiting observational studies and clinical trials suggests that cardiovascular patients should be screened for hyperhomocysteinemia, when no other risk factor is found. Patients with intermediate/major hyperhomocysteinemia should be properly assessed and treated for B vitamin deficiencies and inherited disorders according to current guidelines. Further trials are needed to assess the effect of lowering homocysteine according to hyperhomocysteinemia categories at baseline.

Depletion of Paraoxonase 1 (Pon1) Dysregulates mTOR, Autophagy, and Accelerates Amyloid Beta Accumulation in Mice

Paraoxonase 1 (PON1), a homocysteine (Hcy)-thiolactone detoxifying enzyme, has been associated with Alzheimer's disease (AD), suggesting that PON1 plays an important protective role in the brain. To study the involvement of PON1 in the development of AD and to elucidate the mechanism involved, we generated a new mouse model of AD, the Pon1^-/-xFAD mouse, and examined how Pon1 depletion affects mTOR signaling, autophagy, and amyloid beta (Aβ) accumulation. To elucidate the mechanism involved, we examined these processes in N2a-APP_swe cells. We found that Pon1 depletion significantly downregulated Phf8 and upregulated H4K20me1; mTOR, phospho-mTOR, and App were upregulated while autophagy markers Bcln1, Atg5, and Atg7 were downregulated at the protein and mRNA levels in the brains of Pon1^─/─5xFAD vs. Pon1^+/+5xFAD mice. Pon1 depletion in N2a-APP_swe cells by RNA interference led to downregulation of Phf8 and upregulation of mTOR due to increased H4K20me1-mTOR promoter binding. This led to autophagy downregulation and significantly increased APP and Aβ levels. Phf8 depletion by RNA interference or treatments with Hcy-thiolactone or N-Hcy-protein metabolites similarly increased Aβ levels in N2a-APP_swe cells. Taken together, our findings define a neuroprotective mechanism by which Pon1 prevents Aβ generation.

Deletion of the Homocysteine Thiolactone Detoxifying Enzyme Bleomycin Hydrolase, in Mice, Causes Memory and Neurological Deficits and Worsens Alzheimer's Disease-Related Behavioral and Biochemical Traits in the 5xFAD Model of Alzheimer's Disease

BACKGROUND

Bleomycin hydrolase (BLMH), a homocysteine (Hcy)-thiolactone detoxifying enzyme, is attenuated in Alzheimer's disease (AD) brains. Blmh loss causes astrogliosis in mice while the loss of histone demethylase Phf8, which controls mTOR signaling, causes neuropathy in mice and humans.

OBJECTIVE

To examine how Blmh gene deletion affects the Phf8/H4K20me1/mTOR/autophagy pathway, amyloid-β (Aβ) accumulation, and cognitive/neuromotor performance in mice.

METHODS

We generated a new mouse model of AD, the Blmh-/-5xFAD mouse. Behavioral assessments were conducted by cognitive/neuromotor testing. Blmh and Phf8 genes were silenced in mouse neuroblastoma N2a-APPswe cells by RNA interference. mTOR- and autophagy-related proteins, and AβPP were quantified by western blotting and the corresponding mRNAs by RT-qPCR. Aβ was quantified by western blotting (brains) and by confocal microscopy (cells).

RESULTS

Behavioral testing showed cognitive/neuromotor deficits in Blmh-/- and Blmh-/-5xFAD mice. Phf8 was transcriptionally downregulated in Blmh-/- and Blmh-/-5xFAD brains. H4K20me1, mTOR, phospho-mTOR, and AβPP were upregulated while autophagy markers Becn1, Atg5, and Atg7 were downregulated in Blmh-/- and Blmh-/-5xFAD brains. Aβ was elevated in Blmh-/-5xFAD brains. These biochemical changes were recapitulated in Blmh-silenced N2a-APPswe cells, which also showed increased H4K20me1-mTOR promoter binding and impaired autophagy flux (Lc3-I, Lc3-II, p62). Phf8-silencing or treatments with Hcy-thiolactone or N-Hcy-protein, metabolites elevated in Blmh-/- mice, induced biochemical changes in N2a-APPswe cells like those induced by the Blmh-silencing. However, Phf8-silencing elevated Aβ without affecting AβPP.

CONCLUSIONS

Our findings show that Blmh interacts with AβPP and the Phf8/H4K20me1/mTOR/autophagy pathway, and that disruption of those interactions causes Aβ accumulation and cognitive/neuromotor deficits.

Correlation Between Cognitive Impairment and Homocysteine and S100B Protein in Patients with Progressive Ischemic Stroke

PURPOSE

This study aimed to investigate the relationship between cognitive impairment and homocysteine (Hcy) and S100B protein in patients with progressive ischemic stroke (PIS).

PATIENTS AND METHODS

A total of 158 patients with PIS hospitalized in the Department of Neurology in Taixing People's Hospital from January 2020 to March 2022 were enrolled in the study. After 90 days of follow-up, the patients were divided into two groups according to the MoCA score-99 cases with cognitive impairment group (observation group) and 59 cases with cognitive normal group (control group). Causal diagram was drawn to assess the association between risk factors and PIS with observation group. The risk factors indicators of cognitive impairment in patients with PIS were screened. The related predictive indicators were screened by multivariate logistic regression analysis, and Pearson correlation analysis. The predictive value was analyzed by Receiver Operating Characteristic (ROC) curve.

RESULTS

Multivariate logistic regression analysis showed that age, hypertension, lesion position, Hcy and S100B protein were related risk factors for cognitive impairment in patients with PIS. Pearson correlation analysis was conducted between Hcy and S100 B protein and MoCA score, and revealed that Hcy and S100 B protein were negatively correlated with MoCA score. ROC curve analysis showed that the Area Under the Curve (AUC) of S100 B protein and Hcy in identifying cognitive impairment after PIS was 0.709 and 0.673, respectively, and the combined AUC of Hcy and S100B protein in predicting cognitive impairment after PIS was 0.739.

CONCLUSION

Hcy and S100B protein are related risk factors for cognitive impairment in patients with PIS, and may be used as in a prediction model to predict cognitive impairment after PIS in the future.

HOMOCYSTEINE AND CARDIOVASCULAR DISEASE - A CURRENT REVIEW

Cardiovascular diseases remain the leading cause of death worldwide for the past 20 years. Of these, ischemic heart disease has the highest mortality rate. In over 98% of cases it is caused by atherosclerosis of the coronary arteries. Homocysteine is an amino acid, containing a sulfhydryl group, which is formed as a result of the metabolism of the amino acids methionine and cysteine, which is supplied with protein-containing foods. A small amount of it is necessary for the proper functioning of the body, however, an increased concentration in blood plasma, which hyperhomocysteinemia, negatively affects blood vessels leading to the development of atherosclerosis and thrombotic com¬plications. The adverse effect on blood vessels results from various mechanisms, such as: excessive activation of Toll-like 4 receptor, activation N-methyl-d-aspartate receptors, increased production of reactive oxygen species, and impairment of nitric oxide synthesis. Elevated levels of reactive oxygen species are associated with increased expression of proinflammatory cytokines such as IL-1β, IL-6, TNF-α (tumor necrosis tumor necrosis factor), MCP-1 and intracellular adhesion molecule-1. Another factor contributing to hyperhomocysteinemia is mutation of the MTHFR gene, which in normal conditions is responsible for maintaining homocysteine levels within the normal range. People with MTHFR mutation are more prone to develop atherosclerosis and the following complications: myocardial infarction, stroke, thrombotic episodes and coronary artery disease. The aim of this paper is to present evidence supporting the role of homocysteine in the development of many cardiovascular diseases.

Elevated homocysteine activates unfolded protein responses and causes aberrant trophoblast differentiation and mouse blastocyst development

Hyperhomocysteinemia may arise from folate/vitamin B12 deficiency, genetic polymorphisms, kidney disease, or hypothyroidism. It is associated with an increased risk of early pregnancy loss and placenta-related complications of pregnancy, including pre-eclampsia and fetal growth restriction. While the majority of studies of hyperhomocysteinemia focus on epigenetic changes secondary to metabolic disruption, the effects of homocysteine toxicity on placental development remain unexplored. Here, we investigated the influence of hyperhomocysteinemia on early blastocyst development and trophoblast differentiation. Exposure of cultured blastocysts to high homocysteine levels reduces cell number in the trophectoderm layer, most likely through increased apoptosis. Homocysteine also promotes differentiation of a trophoblast stem cell line. Both effects diminish the stem cell pool, and are mediated in an endoplasmic reticulum (ER) unfolded protein response (UPRER )-dependent manner. Targeted alleviation of UPRER may therefore provide a new therapeutic intervention to improve pregnancy outcome in women with hyperhomocysteinemia.

Homocysteinylation and Sulfhydration in Diseases

Homocysteine (Hcy) is an important intermediate in methionine metabolism and generation of one-carbon units, and its dysfunction is associated with many pathological states. Although Hcy is a non-protein amino acid, many studies have demonstrated protein-related homocysteine metabolism and possible mechanisms underlying homocysteinylation. Homocysteinylated proteins lose their original biological function and have a negative effect on the various disease phenotypes. Hydrogen sulfide (H₂S) has been recognized as an important gaseous signaling molecule with mounting physiological properties. H₂S modifies small molecules and proteins via sulfhydration, which is supposed to be essential in the regulation of biological functions and signal transduction in human health and disorders. This review briefly introduces Hcy and H₂S, further discusses pathophysiological consequences of homocysteine modification and sulfhydryl modification, and ultimately makes a prediction that H₂S might exert a protective effect on the toxicity of homocysteinylation of target protein via sulfhydration. The highlighted information here yields new insights into the role of protein modification by Hcy and H₂S in diseases.

The effect of homocysteine thiolactone on paraoxonase and aryl esterase activity of human serum purified paraoxonase 1 in vitro experiments

BACKGROUND

The important role of lipoproteins, particularly low-density lipoprotein (LDL) and high-density lipoprotein (HDL), has been highly regarded among the known causes of cardiovascular disease (CVD). A wide range of risk factors may cause structural and functional changes in lipoprotein particles, resulting in deposition and formation of atherosclerotic plaques. Homocysteine is one of the most important risk factors in heart disease, and its atherosclerotic properties appear to be related to its intermediate metabolite called homocysteine thiolactone (HCTL). The major aim of the present investigation was to study the effect of HCTL in different concentrations (10, 50, and 100 μM) on paraoxonase and aryl esterase activities of purified human serum paraoxonase 1 (PON1) antioxidant enzyme related to HDL, as an extracellular hydrolyzing enzyme of HCTL.

METHODS

In order to purify PON1 enzyme from human serum, three-step chromatographic methods including DEAE Sephadex A50, Sephadex G100, and DEAE Sephadex A50 were used. Protein concentration and paraoxonase and aryl esterase activities of each fraction were measured separately and the highest activities fractions were collected and subsequently pooled together for the next steps. Ultimately, both activities of PON1 in the presence of different concentrations of HCTL were measured in triplicate by spectrophotometry technique.

RESULTS

HCTL at concentrations of 50 and 100 μM decreased both paraoxonase and aryl esterase activities (P < 0.05) in comparison with the control group, which is directly related to the increase in HCTL concentration. However, at a concentration of 10 μM HCTL, no significant difference was observed in both paraoxonase and aryl esterase activities compared to the control group.

CONCLUSION

HCTL is a highly toxic and reactive compound that is produced in all cells. Extracellular enzyme PON1 causes its hydrolysis with high efficiency. The results obtained from the present study showed that paraoxonase and aryl esterase activities decreased in vitro in the presence of HCTL and therefore, HCTL may cause changing in the protein structure of this enzyme. Previous in vivo studies have also shown decrease of PON1 activity in patients with hyperhomocysteinemia.

Homocysteine-Thiolactone Modulates Gating of Mitochondrial Voltage-Dependent Anion Channel (VDAC) and Protects It from Induced Oxidative Stress

The gating of the Voltage-Dependent Anion Channel (VDAC) is linked to oxidative stress through increased generation of mitochondrial ROS with increasing mitochondrial membrane potential (ΔΨ_m). It has been already reported that H₂O₂ increases the single-channel conductance of VDAC on a bilayer lipid membrane. On the other hand, homocysteine (Hcy) has been reported to induce mitochondria-mediated cell death. It is argued that the thiol-form of homocysteine, HTL could be the plausible molecule responsible for the alteration in the function of proteins, such as VDAC. It is hypothesized that HTL interacts with VDAC that causes functional abnormalities. An investigation was undertaken to study the interaction of HTL with VDAC under H₂O₂ induced oxidative stress through biophysical and electrophysiological methods. Fluorescence spectroscopic studies indicate that HTL interacts with VDAC, but under induced oxidative stress the effect is prevented partially. Similarly, bilayer electrophysiology studies suggest that HTL shows a reduction in VDAC single-channel conductance, but the effects are partially prevented under an oxidative environment. Gly172 and His181 are predicted through bioinformatics tools to be the most plausible binding residues of HTL in Rat VDAC. The binding of HTL and H₂O₂ with VDAC appears to be cooperative as per our analysis of experimental data in the light of the Hill-Langmuir equation. The binding energies are estimated to be - 4.7 kcal mol^-1 and - 2.8 kcal mol^-1, respectively. The present in vitro studies suggest that when mitochondrial VDAC is under oxidative stress, the effects of amino acid metabolites like HTL are suppressed.

Unconventional metabolites in chromatin regulation

Chromatin, the complex of DNA and histone proteins, serves as a main integrator of cellular signals. Increasing evidence links cellular functional to chromatin state. Indeed, different metabolites are emerging as modulators of chromatin function and structure. Alterations in chromatin state are decisive for regulating all aspects of genome function and ultimately have the potential to produce phenotypic changes. Several metabolites such as acetyl-CoA, S-adenosylmethionine (SAM) or adenosine triphosphate (ATP) have now been well characterized as main substrates or cofactors of chromatin-modifying enzymes. However, there are other metabolites that can directly interact with chromatin influencing its state or that modulate the properties of chromatin regulatory factors. Also, there is a growing list of atypical enzymatic and nonenzymatic chromatin modifications that originate from different cellular pathways that have not been in the limelight of chromatin research. Here, we summarize different properties and functions of uncommon regulatory molecules originating from intermediate metabolism of lipids, carbohydrates and amino acids. Based on the various modes of action on chromatin and the plethora of putative, so far not described chromatin-regulating metabolites, we propose that there are more links between cellular functional state and chromatin regulation to be discovered. We hypothesize that these connections could provide interesting starting points for interfering with cellular epigenetic states at a molecular level.

A novel turn-on type AIE fluorescent probe for highly selective detection of cysteine/homocysteine and its application in living cells

Biothiols, associated with multiple physiological and pathological processes, have structural similarities. Monitoring Biothiols selectively in organisms is of great significance. Burdened by the aggregation-caused quenching (ACQ) effect, the applications of conventional biothiols fluorescent probes are extremely limited. Herein, we developed a "turn-on" type aggregation-induced emission (AIE) fluorescent probe BQM-NBD, which was composed of a BQM-OH fluorophore molecule with AIE effect and the recognition group 7-nitro-1,2,3-benzoxadiazole (NBD). Non-fluorescent BQM-NBD produces strong fluorescence after the addition of cysteine (Cys) or homocysteine (Hcy). BQM-NBD exhibited excellent linearity for selective detection of Cys (0-100 Μm) and Hcy (0-50 μM) with detection limits of 6.0 × 10^-8 M and 8.4 × 10^-8 M, respectively. Simultaneously, after treatment with glutathione (GSH), it appeared no fluorescence. The results demonstrated BQM-NBD exhibited good selectivity to Cys/Hcy. Furthermore, BQM-NBD was successfully performed in the imaging of Cys in living cells with low cytotoxicity, which provides a feasible strategy for the selective detection of Cys in the living system.

The Effect of Homocysteine on the Secretion of Il-1β, Il-6, Il-10, Il-12 and RANTES by Peripheral Blood Mononuclear Cells-An In Vitro Study

The contemporary theory of the inflammatory-immunological pathomechanism of atherosclerosis includes the participation of interleukin-1β (Il), Il-6, Il-10, Il-12, RANTES, and homocysteine in this process. The knowledge on the direct effect of hyperhomocysteinemia on inflammatory-state-related atherosclerosis is rather scarce. Our study is the first to account for the effects of homocysteine on the secretion of Il-10 and RANTES in vitro conditions. For this purpose, human mitogen-stimulated peripheral blood mononuclear cells (PBMNCs) were cultured in vitro and exposed to homocysteine at high concentrations. Subsequently, the concentrations of cytokines were assayed in the cell culture supernatant using flow cytofluorimetry. It has been shown that, in the presence of homocysteine, the secretion of IL-1, IL-6 and RANTES by PBMNCs was increased, whereas IL-10 concentration was significantly lower than that of the supernatant derived from a mitogen-stimulated cell culture without homocysteine. The secretion of Il-12 by PBMNCs exposed exclusively to mitogen, did not differ from homologous cells also treated with homocysteine. Therefore, in our opinion, high-concentration homocysteine affects the progression of atherosclerosis by increasing the secretion of proinflammatory cytokines secreted by PBMNCs, such as Il-1β, Il-6, RANTES, and by attenuating the secretion of Il-10.

Folate Reverses NF-κB p65/Rela/IL-6 Level Induced by Hyperhomocysteinemia in Spontaneously Hypertensive Rats

Hyperhomocysteinemia (HHcy) is derived from the abnormal metabolism of homocysteine (Hcy) and is related to metabolic-related diseases. In addition, HHcy combined with hypertension increases the risk of cardiovascular diseases (CVD). However, the mechanism of HHcy aggravating hypertensive arterial damage and the efficacy of folate (FA) as a beneficial supplement have not been fully elucidated. In this study, we established a rat HHcy model and a hypertension combined with HHcy model. Rat tail artery blood pressure (BP), plasma Hcy, serum superoxide dismutase (SOD), and malondialdehyde (MDA) were measured. Rat thoracic aorta was for pathological analysis after 12 weeks of the experiment. The relative expression levels of oxidative stress and immune/inflammation in rat arterial tissues were detected by quantitative real-time polymerase chain reaction (qRT-PCR) and western blotting. The results demonstrated that the relative expression levels of oxidative stress and immune/inflammation were the highest in the hypertension combined with HHcy group, followed by the hypertension group. Compared with the hypertension group, the hypertension combined with HHcy group up-regulated the expression levels of interleukin-6 (IL-6) and nuclear factor-κ-gene binding (NF-κB) p65/Rela, but not NADPH oxidase (Nox). Furthermore, folate inhibited the expression of IL-6 and NF-κB p65/Rela, reduced the levels of MDA and HHcy, but significantly increased the SOD level. In conclusion, HHcy synergistically aggravated the arterial damage factor of hypertension through immune/inflammatory response. However, folate demonstrated anti-inflammatory properties and reversed the NF-κB p65/Rela/IL-6 level induced by HHcy in hypertensive rats.

Impact of Physical Activity and Natural Bioactive Compounds on Endothelial Dysfunction in Chronic Kidney Disease

Chronic kidney disease (CKD) represents a world-wide public health problem. Inflammation, endothelial dysfunction (ED) and vascular calcifications are clinical features of CKD patients that increase cardiovascular (CV) mortality. CKD-related CV disease pathogenic mechanisms are not only associated with traditional factors such as arterial hypertension and dyslipidemia, but also with ED, oxidative stress and low-grade inflammation. The typical comorbidities of CKD contribute to reduce the performance and the levels of the physical activity in nephropathic patients compared to healthy subjects. Currently, the effective role of physical activity on ED is still debated, but the available few literature data suggest its positive contribution. Another possible adjuvant treatment of ED in CKD patients is represented by natural bioactive compounds (NBCs). Among these, minor polar compounds of extra virgin olive oil (hydroxytyrosol, tyrosol and oleocanthal), polyphenols, and vitamin D seem to exert a beneficial role on ED in CKD patients. The objective of the review is to evaluate the effectiveness of physical exercise protocols and/or NBCs on ED in CKD patients.

Age-Dependent Association Between Elevated Homocysteine and Cognitive Impairment in a Post-stroke Population: A Prospective Study

Background and Purpose: The results regarding the independent association between homocysteine (Hcy) levels and post-stroke cognitive impairment (PSCI) were inconsistent. The effect of age on this association has yet to be explored. This study aims to determine the relationship between Hcy levels, age, and cognitive impairment in a post-stroke population.

Methods: A total of 592 patients with acute ischemic stroke (AIS) completed follow-up. Serum Hcy levels were measured enzymatically by spectrophotometry within 24 h of admission. Cognitive function was evaluated by the Mini-Mental State Examination (MMSE) 1 month after stroke, and the scores ≤ 24 were considered as cognitive impairment. Our study was dichotomized into two groups by a cut-off of 65 years. Multivariate logistic regression models were used to determine the association between baseline Hcy levels and cognitive impairment.

Results: According to the MMSE score, 317 (53.5%) patients had cognitive impairment. Patients with higher levels of Hcy were more prone to have cognitive impairment 1 month after stroke than patients with lower levels of Hcy (p < 0.001). The optimal cut-off points of Hcy level (μmol/L) were (T1) ≤ 8, (T2) 8–12, and (T3) ≥ 12. After adjusting for confounding factors, the multivariate regression analysis showed that the third Hcy tertile was independently associated with cognitive impairment [odds ratio (OR) = 2.057, 95% confidence interval (CI) = 1.133–3.735, p = 0.018). A stronger association [T2 (OR = 2.266, 95% CI = 1.042–4.926, p = 0.039); T3 (OR =3.583, 95% CI = 1.456–8.818, p = 0.005)] was found in the younger group. However, the independent association was not confirmed in the older group.

Conclusions: Elevated Hcy levels in the acute phase of ischemic stroke were independently associated with cognitive impairment in a post-stroke population. Furthermore, the association was age-dependent and more meaningful in a younger population aged below 65. So, Hcy levels in patients with stroke should be well-monitored, especially in younger patients.

Metabolic Reprogramming of Colorectal Cancer Cells and the Microenvironment: Implication for Therapy

Colorectal carcinoma (CRC) is one of the most frequently diagnosed carcinomas and one of the leading causes of cancer-related death worldwide. Metabolic reprogramming, a hallmark of cancer, is closely related to the initiation and progression of carcinomas, including CRC. Accumulating evidence shows that activation of oncogenic pathways and loss of tumor suppressor genes regulate the metabolic reprogramming that is mainly involved in glycolysis, glutaminolysis, one-carbon metabolism and lipid metabolism. The abnormal metabolic program provides tumor cells with abundant energy, nutrients and redox requirements to support their malignant growth and metastasis, which is accompanied by impaired metabolic flexibility in the tumor microenvironment (TME) and dysbiosis of the gut microbiota. The metabolic crosstalk between the tumor cells, the components of the TME and the intestinal microbiota further facilitates CRC cell proliferation, invasion and metastasis and leads to therapy resistance. Hence, to target the dysregulated tumor metabolism, the TME and the gut microbiota, novel preventive and therapeutic applications are required. In this review, the dysregulation of metabolic programs, molecular pathways, the TME and the intestinal microbiota in CRC is addressed. Possible therapeutic strategies, including metabolic inhibition and immune therapy in CRC, as well as modulation of the aberrant intestinal microbiota, are discussed.

The lipid paradox in neuroprogressive disorders: Causes and consequences

Chronic systemic inflammation is associated with an increased risk of cardiovascular disease in an environment of low low-density lipoprotein (LDL) and low total cholesterol and with the pathophysiology of neuroprogressive disorders. The causes and consequences of this lipid paradox are explored. Circulating activated neutrophils can release inflammatory molecules such as myeloperoxidase and the pro-inflammatory cytokines interleukin-1 beta, interleukin-6 and tumour necrosis factor-alpha. Since activated neutrophils are associated with atherosclerosis and cardiovascular disease and with major depressive disorder, bipolar disorder and schizophrenia, it seems reasonable to hypothesise that the inflammatory molecules released by them may act as mediators of the link between systemic inflammation and the development of atherosclerosis in neuroprogressive disorders. This hypothesis is tested by considering the association at a molecular level of systemic inflammation with increased LDL oxidation; increased small dense LDL levels; increased lipoprotein (a) concentration; secretory phospholipase A₂ activation; cytosolic phospholipase A₂ activation; increased platelet activation; decreased apolipoprotein A1 levels and function; decreased paroxonase-1 activity; hyperhomocysteinaemia; and metabolic endotoxaemia. These molecular mechanisms suggest potential therapeutic targets.

The Effects of Medicinal Plants and Bioactive Natural Compounds on Homocysteine

Background: Among non-communicable diseases, cardiovascular diseases (CVDs) are the leading cause of mortality and morbidity in global communities. By 2030, CVD-related deaths are projected to reach a global rise of 25 million. Obesity, smoking, alcohol, hyperlipidemia, hypertension, and hyperhomocysteinemia are several known risk factors for CVDs. Elevated homocysteine is tightly related to CVDs through multiple mechanisms, including inflammation of the vascular endothelium. The strategies for appropriate management of CVDs are constantly evolving; medicinal plants have received remarkable attention in recent researches, since these natural products have promising effects on the prevention and treatment of various chronic diseases. The effects of nutraceuticals and herbal products on CVD/dyslipidemia have been previously studied. However, to our knowledge, the association between herbal bioactive compounds and homocysteine has not been reviewed in details. Thus, the main objective of this study is to review the efficacy of bioactive natural compounds on homocysteine levels according to clinical trials and animal studies. Results: Based on animal studies, black and green tea, cinnamon, resveratrol, curcumin, garlic extract, ginger, and soy significantly reduced the homocysteine levels. According to the clinical trials, curcumin and resveratrol showed favorable effects on serum homocysteine. In conclusion, this review highlighted the beneficial effects of medicinal plants as natural, inexpensive, and accessible agents on homocysteine levels based on animal studies. Nevertheless, the results of the clinical trials were not uniform, suggesting that more well-designed trials are warranted.

The role of high-density lipoprotein cholesterol, apolipoprotein A and paraoxonase-1 in the pathophysiology of neuroprogressive disorders

Lowered high-density lipoprotein (HDL) cholesterol has been reported in major depressive disorder, bipolar disorder, first episode of psychosis, and schizophrenia. HDL, its major apolipoprotein component, ApoA1, and the antioxidant enzyme paraoxonase (PON)1 (which is normally bound to ApoA1) all have anti-atherogenic, antioxidant, anti-inflammatory, and immunomodulatory roles, which are discussed in this paper. The paper details the pathways mediating the anti-inflammatory effects of HDL, ApoA1 and PON1 and describes the mechanisms leading to compromised HDL and PON1 levels and function in an environment of chronic inflammation. The molecular mechanisms by which changes in HDL, ApoA1 and PON1 might contribute to the pathophysiology of the neuroprogressive disorders are explained. Moreover, the anti-inflammatory actions of ApoM-mediated sphingosine 1-phosphate (S1P) signalling are reviewed as well as the deleterious effects of chronic inflammation and oxidative stress on ApoM/S1P signalling. Finally, therapeutic interventions specifically aimed at improving the levels and function of HDL and PON1 while reducing levels of inflammation and oxidative stress are considered. These include the so-called Mediterranean diet, extra virgin olive oil, polyphenols, flavonoids, isoflavones, pomegranate juice, melatonin and the Mediterranean diet combined with the ketogenic diet.

The Endothelium as a Target for Anti-Atherogenic Therapy: A Focus on the Epigenetic Enzymes EZH2 and SIRT1

Endothelial cell inflammatory activation and dysfunction are key events in the pathophysiology of atherosclerosis, and are associated with an elevated risk of cardiovascular events. Yet, therapies specifically targeting the endothelium and atherosclerosis are lacking. Here, we review how endothelial behaviour affects atherogenesis and pose that the endothelium may be an efficacious cellular target for antiatherogenic therapies. We discuss the contribution of endothelial inflammatory activation and dysfunction to atherogenesis and postulate that the dysregulation of specific epigenetic enzymes, EZH2 and SIRT1, aggravate endothelial dysfunction in a pleiotropic fashion. Moreover, we propose that commercially available drugs are available to clinically explore this postulation.

Proteomic exploration of cystathionine β-synthase deficiency: implications for the clinic

Introduction: Homocystinuria due to cystathionine β-synthase (CBS) deficiency, the most frequent inborn error of sulfur amino acid metabolism, is characterized biochemically by severely elevated homocysteine (Hcy) and related metabolites, such as Hcy-thiolactone and N-Hcy-protein. CBS deficiency reduces life span and causes pathological abnormalities affecting most organ systems in the human body, including the cardiovascular (thrombosis, stroke), skeletal/connective tissue (osteoporosis, thin/non-elastic skin, thin hair), and central nervous systems (mental retardation, seizures), as well as the liver (fatty changes), and the eye (ectopia lentis, myopia). Molecular basis of these abnormalities were largely unknown and available treatments remain ineffective. Areas covered: Proteomic and transcriptomic studies over the past decade or so, have significantly contributed to our understanding of mechanisms by which the CBS enzyme deficiency leads to clinical manifestations associated with it. Expert opinion: Recent findings, discussed in this review, highlight the involvement of dysregulated proteostasis in pathologies associated with CBS deficiency, including thromboembolism, stroke, neurologic impairment, connective tissue/collagen abnormalities, hair defects, and hepatic toxicity. To ameliorate these pathologies, pharmacological, enzyme replacement, and gene transfer therapies are being developed.

Role of Paraoxonase1 in the Regulation of High-Density Lipoprotein Functionality and in Cardiovascular Protection

Significance: Human paraoxonase (PON) is a member of the gene family that includes paraoxonase 1 (PON1), PON2, and PON3. PON is known for its capacity to hydrolyze a wide range of substrates, including organophosphorus compounds, nerve gases, and aromatic carboxylic acid esters. Recent Advances: Several studies have highlighted the involvement of PON, particularly PON1, in the modulation of the capacity of high-density lipoprotein (HDL) to protect against the atherosclerosis process and its clinical manifestations. PON1 exhibits antioxidant and anti-inflammatory activities and may be involved in the regulation of the principal antiatherogenic activity of HDL, that is, the regulation of the reverse cholesterol transport process. Critical Issues: Although epidemiological studies have shown that there is an inverse relationship between HDL levels and cardiovascular risk, several studies have emphasized the importance of HDL functionality in protecting against cardiovascular diseases (CVD). Given that PON1 is involved in several atheroprotective functions of HDL, the aim of this article is to review the existing literature on PON1 and to discuss the principal mechanisms by which PON1 may exert its different activities. Future Directions: The elucidation of the mechanisms by which PON1 modulates the functionality of HDL as well as the identification of the interventions that stimulate PON1 activity and/or increase its plasma concentration would make it possible to propose new strategies to prevent CVD. Antioxid. Redox Signal. 34, 191-200.

Sulfur-Containing Amino Acids and Lipid Metabolism

The metabolism of methionine and cysteine in the body tissues determines the concentrations of several metabolites with various biologic activities, including homocysteine, hydrogen sulfide (H2S), taurine, and glutathione. Hyperhomocysteinemia, which is correlated with lower HDL cholesterol in blood in volunteers and animal models, has been associated with an increased risk for cardiovascular diseases. In humans, the relation between methionine intake and hyperhomocysteinemia is dependent on vitamin status (vitamins B-6 and B-12 and folic acid) and on the supply of other amino acids. However, lowering homocysteinemia by itself is not sufficient for decreasing the risk of cardiovascular disease progression. Other compounds related to methionine metabolism have recently been identified as being involved in the risk of atherosclerosis and steatohepatitis. Indeed, the metabolism of sulfur amino acids has an impact on phosphatidylcholine (PC) metabolism, and anomalies in PC synthesis due to global hypomethylation have been associated with disturbances of lipid metabolism. In addition, impairment of H2S synthesis from cysteine favors atherosclerosis and steatosis in animal models. The effects of taurine on lipid metabolism appear heterogeneous depending on the populations of volunteers studied. A decrease in the concentration of intracellular glutathione, a tripeptide involved in redox homeostasis, is implicated in the etiology of cardiovascular diseases and steatosis. Last, supplementation with betaine, a compound that allows remethylation of homocysteine to methionine, decreases basal and methionine-stimulated homocysteinemia; however, it adversely increases plasma total and LDL cholesterol. The study of these metabolites may help determine the range of optimal and safe intakes of methionine and cysteine in dietary proteins and supplements. The amino acid requirement for protein synthesis in different situations and for optimal production of intracellular compounds involved in the regulation of lipid metabolism also needs to be considered for dietary attenuation of atherosclerosis and steatosis risk.

Paraoxonase 1 Phenotype and Protein N-Homocysteinylation in Patients with Rheumatoid Arthritis: Implications for Cardiovascular Disease

Paraoxonase 1 (PON1) is the high density lipoprotein-associated esterase which inhibits the development of atherosclerosis by metabolizing lipid peroxidation products as well as hydrolyzing proatherogenic metabolite of homocysteine (Hcy), Hcy thiolactone, which otherwise reacts with lysine groups of proteins, thus forming N-Hcy-protein in a process referred to as protein N-homocysteinylation. Rheumatoid arthritis (RA) is the chronic inflammatory autoimmune disease associated with increased risk of cardiovascular complications, but the underlying mechanisms are incompletely understood. We examined PON1 status and N-homocysteinylation of serum proteins in patients with RA. Blood was collected from 74 RA patients and 70 control subjects. PON1 activity was measured toward synthetic (paraoxon, phenyl acetate) and natural (Hcy thiolactone) substrates. PON1 protein concentration was measured by ELISA. Total Hcy as well as N-Hcy-protein were measured in serum as well. PON1 activity toward Hcy thiolactone was lower in RA patients than in control subjects which was accompanied by increased concentration of N-Hcy-protein despite normal total Hcy concentration. PON1 protein concentration was unchanged in the RA group, but the specific enzyme activity was reduced. When RA patients were categorized according to the DAS28-ESR score, PON1 concentration and enzymatic activity were lower whereas N-Hcy-protein was higher in those with high disease activity. PON1 activity and Hcy thiolactone were correlated with DAS28-ESR score and myeloperoxidase concentration. In conclusion, RA is associated with deficiency of PON1 activity and increased protein N-homocyseinylation which may contribute to accelerated development of cardiovascular diseases.

Vitamin D Provides Benefit Based on the Proinflammatory Effects of Homocysteine in Elderly Patients With Type 2 Diabetes Mellitus

PURPOSE

It is unclear whether vitamin D provides any benefit against the pro-inflammatory effects of homocysteine in elderly patients with type 2 diabetes mellitus (T2DM).

METHODS

We compared lymphocyte counts for CD3, CD19, CD4, and CD8 subsets between elderly (age ≥65 years) T2DM patients (n = 5098) and nondiabetes control subjects (n = 20,590) based on the serum concentrations of homocysteine and total vitamin D (calcidiol + calcifediol [total vitamin D, TVD]; <20, 20-30, and >30 ng/mL).

FINDINGS

Significant variation in CD19 (P = 0.019), CD4 (P = 0.015), and CD8 (P < 0.001) were associated with serum TVD in T2DM patients with homocysteine ≤15 μmol/L, whereas CD3 (P = 0.003) and CD8 (P = 0.019) varied in control subjects with homocysteine ≤15 μmol/L. In T2DM patients with high homocysteine (>15 μmol/L) levels, significant variation based on serum TVD occurred in CD19 only (P = 0.024), whereas CD3 (P = 0.016) and CD4 (P = 0.001) varied in control subjects with high homocysteine concentrations.

IMPLICATIONS

Serum TVD influences variation in CD3, CD19, CD4, and CD8 lymphocyte subsets based on the serum homocysteine concentration in elderly T2DM patients and nondiabetic individuals with moderate to high homocysteine concentrations. The effect of TVD is partially attenuated in individuals with high homocysteine concentrations, with greater attenuation occurring in patients with T2DM. Differences in the variation of lymphocyte subsets between nondiabetes subjects with moderate homocysteine concentrations and those with high homocysteine concentrations constitute a shift from CD8-positive cells to CD4-positive cells, suggesting a change in TH1/TH2 balance based on TVD and homocysteine concentrations that is absent in diabetes cases with high homocysteine concentrations.

Human tissue kallikrein-1 protects against the development of erectile dysfunction in a rat model of hyperhomocysteinemia

The aim of this study was to investigate the mechanism by which a diet inducing high hyperhomocysteinemia (HHcy) leads to the deterioration of erectile function in rats and whether this is inhibited by expression of the human tissue kallikrein-1 (hKLK1) gene. We established a rat model of HHcy by feeding methionine (Met)-rich diets to male Sprague-Dawley (SD) rats. Male wild-type SD rats (WTRs) and transgenic rats harboring the hKLK1 gene (TGRs) were fed a normal diet until 10 weeks of age. Then, 30 WTRs were randomly divided into three groups as follows: the control (n = 10) group, the low-dose (4% Met, n = 10) group, and the high-dose (7% Met, n = 10) group. Another 10 age-matched TGRs were fed the high-dose diet and designated as the TGR+7% Met group. After 30 days, in all four groups, erectile function was measured and penile tissues were harvested to determine oxidative stress, endothelial cell content, and penis fibrosis. Compared with the 7% Met group, the TGR+7% Met group showed diminished HHcy-induced erectile dysfunction (ED), indicating the improvement caused by hKLK1. Regarding corpus cavernosum endothelial cells, hKLK1 preserved endothelial cell-cell junctions and endothelial cell content, and activated protein kinase B/endothelial nitric oxide synthase (Akt/eNOS) signaling. Fibrosis assessment indicated that hKLK1 preserved normal penis structure by inhibiting apoptosis in the corpus cavernosum smooth muscle cells. Taken together, these findings showed that oxidative stress, impaired corpus cavernosum endothelial cells, and severe penis fibrosis were involved in the induction of ED by HHcy in rats, whereas hKLK1 preserved erectile function by inhibiting these pathophysiological changes.

Mechanisms of homocysteine-induced damage to the endothelial, medial and adventitial layers of the arterial wall

Homocysteine (Hcy) is a non-protein forming amino acid which is the direct metabolic precursor of methionine. Increased concentration of serum Hcy is considered a risk factor for cardiovascular disease and is specifically linked to various diseases of the vasculature. Serum Hcy is associated with atherosclerosis, hypertension and aneurysms of the aorta in humans, though the precise mechanisms by which Hcy contributes to these conditions remain elusive. Results from clinical trials that successfully lowered serum Hcy without reducing features of vascular disease in cardiovascular patients have cast doubt on whether or not Hcy directly impacts the vasculature. However, studies in animals and in cell culture suggest that Hcy has a vast array of toxic effects on the vasculature, with demonstrated roles in endothelial dysfunction, medial remodeling and adventitial inflammation. It is hypothesized that rather than serum Hcy, tissue-bound Hcy and the incorporation of Hcy into proteins could underlie the toxic effects of Hcy on the vasculature. In this review, we present evidence for Hcy-associated vascular disease in humans, and we critically examine the possible mechanisms by which Hcy specifically impacts the endothelial, medial and adventitial layers of the arterial wall. Deciphering the mechanisms by which Hcy interacts with proteins in the arterial wall will allow for a better understanding of the pathomechanisms of hyperhomocysteinemia and will help to define a better means of prevention at the appropriate window of life.

Homocysteine: Its Possible Emerging Role in At-Risk Population Groups

Increased plasma homocysteine is a risk factor for several pathological disorders. The present review focused on the role of homocysteine (Hcy) in different population groups, especially in risk conditions (pregnancy, infancy, old age), and on its relevance as a marker or etiological factor of the diseases in these age groups, focusing on the nutritional treatment of elevated Hcy levels. In pregnancy, Hcy levels were investigated in relation to the increased risk of adverse pregnancy outcomes such as small size for gestational age at birth, preeclampsia, recurrent abortions, low birth weight, or intrauterine growth restriction. In pediatric populations, Hcy levels are important not only for cardiovascular disease, obesity, and renal disease, but the most interesting evidence concerns study of elevated levels of Hcy in autism spectrum disorder (ASD) and attention deficit hyperactivity disorder (ADHD). Finally, a focus on the principal pathologies of the elderly (cardiovascular and neurodegenerative disease, osteoporosis and physical function) is presented. The metabolism of Hcy is influenced by B vitamins, and Hcy-lowering vitamin treatments have been proposed. However, clinical trials have not reached a consensus about the effectiveness of vitamin supplementation on the reduction of Hcy levels and improvement of pathological condition, especially in elderly patients with overt pathologies, suggesting that other dietary and non-dietary factors are involved in high Hcy levels. The importance of novel experimental designs focusing on intra-individual variability as a complement to the typical case-control experimental designs and the study of interactions between different factors it should be emphasized.

The Role of Hyperhomocysteinemia in the Development of Changes in the Lungs

BACKGROUND

In recent years, attention of the scientific community has been drawn to the study of the role of homocysteine in the pathology of diseases in general and the respiratory system in particular. Violations of the synthesis and disposal of homocysteine are the cause of its excessive accumulation in the body, which subsequently leads to damage to all organs and systems.

METHODS

We conducted this study on 64 white non-linear rats of 6-8 and 24-26 months old rats, which were divided into two control and experimental groups during the experiment. The study of ultrastructural changes in the lungs of rats was performed using an electron microscope.

RESULTS

The results of the conducted study show that all the animals of the experimental group, corresponding to 32 (50%) cases, possess conspicuous morphological changes in the structure of the lungs. The specific features of mature animals were the narrowing of the alveolar space of the part of the alveoli and the increase in the number of macrophages in them. Partial desquamation of capillary endothelial lining and a slight increase of collagen fibers in interalveolar membranes were observed compared to control animals. A characteristic feature for older animals was the growth of connective tissue, predominantly collagen fibers, which led to pneumosclerosis. The thickening of the aerogemic barrier was also detected, and the endothelial lining was intermittent or desquamated.

CONCLUSION

Mature animals of the experimental group were characterized by activation of inflammatory processes, oxidative stress, due to increased production of macrophages and, as a consequence, the launch of the humorous link of immunity, while in old rats were determined by fibrosis, disorders of the trophic and gas metabolism, as well as damage to the endothelium part of lungs.

Melatonin Treatment Ameliorates Hyperhomocysteinemia-Induced Impairment of Erectile Function in a Rat Model

BACKGROUND

Hyperhomocysteinemia (HHcy) has been reported to be strongly correlated with the occurrence of erectile dysfunction (ED), but the mechanisms are not fully understood. Moreover, whether melatonin could be a potential treatment of HHcy-induced ED needs to be elucidated.

AIM

The aim of this study was to investigate the effects of melatonin on HHcy-induced ED and the potential mechanisms via modulating oxidative stress and apoptosis.

METHODS

The Sprague-Dawley (SD) rat model of HHcy was induced by 7% methionine (Met)-rich diets. 36 male SD rats were randomly distributed into 3 groups (n = 12 per group): control group, 7% Met group, and 7% Met + melatonin (Mel; 10 mg/kg, intraperitoneal injection) treatment group. After 4 weeks, the erectile function of all rats was evaluated by electrical stimulation of the cavernous nerve. Histologic and molecular alterations of the corpus cavernosum were also analyzed by immunofluorescence, immunohistochemistry, enzyme-linked immunosorbent assay, Western blotting, and polymerase chain reaction.

OUTCOMES

HHcy-induced ED rat models were successfully established, and Mel could preserve erectile function mainly through inhibiting oxidative stress via the Erk1/2/Nrf2/HO-1 signaling pathway and suppression of apoptosis.

RESULTS

Erectile function was significantly reduced in the rats with HHcy compared with that in the control group and was ameliorated in the HHcy rats treated with Mel. Compared with the control group, the rats in the HHcy group showed the following: (1) higher levels of total plasma homocysteine; (2) fewer neuronal nitric oxide synthase-positive cells in the corpus cavernous; (3) higher levels of reactive oxygen species and malondialdehyde, higher expression levels of nicotinamide adenine dinucleotide phosphate oxidase, and lower activities of superoxide dismutase, indicating an overactivated oxidative stress; (4) lower expression levels of Erk1/2/Nrf2/HO-1 signaling pathway components; and (5) higher levels of apoptosis, as determined by the expression levels of Bax, Bcl-2, and caspase 3. Mel treatment improved the erectile response, as well as histologic and molecular alterations.

CLINICAL TRANSLATION

Our study on a rodent model of HHcy provided evidence that Mel could be a potential therapeutic method for HHcy-related ED.

CONCLUSIONS

Mel treatment improves erectile function in rats with HHcy probably by potential antioxidative stress activity. This finding provides evidence for a potential new therapy for HHcy-induced ED. Tang Z, Song J, Yu, Z, et al. Melatonin Treatment Ameliorates Hyperhomocysteinemia-Induced Impairment of Erectile Function in a Rat Model. J Sex Med 2019;16:1506-1517.

Implication of homocysteine in protein quality control processes

Homocysteine (Hcy) is a key metabolite generated during methionine metabolism. The elevated levels of Hcy in the blood are reffered to as hyperhomocystenimeia (HHcy). The HHcy is caused by impaired metabolism/deficiency of either folate or B12 or defects in Hcy metabolism. Accumulating evidence suggests that HHcy is associated with cardiovascular and brain diseases including atherosclerosis, endothelial injury, and stroke etc. Vitamin B12 (cobalamin; B12) is a water-soluble vitamin essential for two metabolic reactions. It acts as a co-factor for methionine synthase and L-methylmalonyl-CoA mutase. Besides, it is also vital for DNA synthesis and maturation of RBC. Deficiency of B12 is associated with haematological and neurological disorders. Hyperhomocysteinemia (HHcy)-induced toxicity is thought to be mediated by the accumulation of Hcy and its metabolites, homocysteinylated proteins. Cellular protein quality control (PQC) is essential for the maintenance of proteome integrity, and cell viability and its failure contributes to the development of multiple diseases. Chaperones, unfolded protein response (UPR), ubiquitin-proteasome system (UPS), and autophagy are analogous strategies of PQC that maintain cellular proteome integrity. Recently, multiple studies reported that HHcy responsible for perturbation of PQC by reducing chaperone levels, activating UPR, and impairing autophagy. Besides, HHcy also induce cytotoxicity, inflammation, protein aggregation and apoptosis. It has been shown that some of the factors including altered SIRT1-HSF1 axis and irreversible homocysteinylation of proteins are responsible for folate and/or B12 deficiency or HHcy-induced impairment of PQC. Therefore, this review highlights the current understanding of HHcy in the context of cellular PQC and their pathophysiological and clinical consequences, epigenomic changes, therapeutic implications of B12, and chemical chaperones based on cell culture and experimental animal models.

Dysregulation of Epigenetic Mechanisms of Gene Expression in the Pathologies of Hyperhomocysteinemia

Hyperhomocysteinemia (HHcy) exerts a wide range of biological effects and is associated with a number of diseases, including cardiovascular disease, dementia, neural tube defects, and cancer. Although mechanisms of HHcy toxicity are not fully uncovered, there has been a significant progress in their understanding. The picture emerging from the studies of homocysteine (Hcy) metabolism and pathophysiology is a complex one, as Hcy and its metabolites affect biomolecules and processes in a tissue- and sex-specific manner. Because of their connection to one carbon metabolism and editing mechanisms in protein biosynthesis, Hcy and its metabolites impair epigenetic control of gene expression mediated by DNA methylation, histone modifications, and non-coding RNA, which underlies the pathology of human disease. In this review we summarize the recent evidence showing that epigenetic dysregulation of gene expression, mediated by changes in DNA methylation and histone N-homocysteinylation, is a pathogenic consequence of HHcy in many human diseases. These findings provide new insights into the mechanisms of human disease induced by Hcy and its metabolites, and suggest therapeutic targets for the prevention and/or treatment.

Serum Proteome Alterations in Human Cystathionine β-Synthase Deficiency and Ischemic Stroke Subtypes

Ischemic stroke induces brain injury via thrombotic or embolic mechanisms involving large or small vessels. Cystathionine β-synthase deficiency (CBS), an inborn error of metabolism, is associated with vascular thromboembolism, the major cause of morbidity and mortality in affected patients. Because thromboembolism involves the brain vasculature in these patients, we hypothesize that CBS deficiency and ischemic stroke have similar molecular phenotypes. We used label-free mass spectrometry for quantification of changes in serum proteomes in CBS-deficient patients (n = 10) and gender/age-matched unaffected controls (n = 14), as well as in patients with cardioembolic (n = 17), large-vessel (n = 26), or lacunar (n = 25) ischemic stroke subtype. In CBS-deficient patients, 40 differentially expressed serum proteins were identified, of which 18 were associated with elevated homocysteine (Hcy) and 22 were Hcy-independent. We also identified Hcy-independent differentially expressed serum proteins in ischemic stroke patients, some of which were unique to a specific subtype: 10 of 32 for cardioembolic vs. large-vessel, six of 33 for cardioembolic vs. lacunar, and six of 23 for large-vessel vs. lacunar. There were significant overlaps between proteins affected by CBS deficiency and ischemic stroke, particularly the cardioembolic subtype, similar to protein overlaps between ischemic stroke subtypes. Top molecular pathways affected by CBS deficiency and ischemic stroke subtypes included acute phase response signaling and coagulation system. Similar molecular networks centering on NFκB were affected by CBS deficiency and stroke subtypes. These findings suggest common mechanisms involved in the pathologies of CBS deficiency and ischemic stroke subtypes.

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

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

Homocysteine Modification in Protein Structure/Function and Human Disease

Epidemiological studies established that elevated homocysteine, an important intermediate in folate, vitamin B₁₂, and one carbon metabolism, is associated with poor health, including heart and brain diseases. Earlier studies show that patients with severe hyperhomocysteinemia, first identified in the 1960s, exhibit neurological and cardiovascular abnormalities and premature death due to vascular complications. Although homocysteine is considered to be a nonprotein amino acid, studies over the past 2 decades have led to discoveries of protein-related homocysteine metabolism and mechanisms by which homocysteine can become a component of proteins. Homocysteine-containing proteins lose their biological function and acquire cytotoxic, proinflammatory, proatherothrombotic, and proneuropathic properties, which can account for the various disease phenotypes associated with hyperhomocysteinemia. This review describes mechanisms by which hyperhomocysteinemia affects cellular proteostasis, provides a comprehensive account of the biological chemistry of homocysteine-containing proteins, and discusses pathophysiological consequences and clinical implications of their formation.

Urinary excretion of homocysteine thiolactone and the risk of acute myocardial infarction in coronary artery disease patients: the WENBIT trial

OBJECTIVES

No individual homocysteine (Hcy) metabolite has been studied as a risk marker for coronary artery disease (CAD). Our objective was to examine Hcy-thiolactone, a chemically reactive metabolite generated by methionyl-tRNA synthetase and cleared by the kidney, as a risk predictor of incident acute myocardial infarction (AMI) in the Western Norway B-Vitamin Intervention Trial.

DESIGN

Single centre, prospective double-blind clinical intervention study, randomized in a 2 × 2 factorial design.

SUBJECTS AND METHODS

Patients with suspected CAD (n = 2049, 69.8% men; 61.2-year-old) were randomized to groups receiving daily (i) folic acid (0.8 mg)/vitamin B₁₂ (0.4 mg)/vitamin B₆ (40 mg); (ii) folic acid/vitamin B₁₂ ; (iii) vitamin B₆ or (iv) placebo. Urinary Hcy-thiolactone was quantified at baseline, 12 and 38 months.

RESULTS

Baseline urinary Hcy-thiolactone/creatinine was significantly associated with plasma tHcy, ApoA1, glomerular filtration rate, potassium and pyridoxal 5'-phosphate (positively) and with age, hypertension, smoking, urinary creatinine, plasma bilirubin and kynurenine (negatively). During median 4.7-years, 183 patients (8.9%) suffered an AMI. In Cox regression analysis, Hcy-thiolactone/creatinine was associated with AMI risk (hazard ratio = 1.58, 95% confidence interval = 1.10-2.26, P = 0.012 for trend; adjusted for age, gender, tHcy). This association was confined to patients with pyridoxic acid below median (adjusted HR = 2.72, 95% CI = 1.47-5.03, P = 0.0001; P_interaction = 0.020). B-vitamin/folate treatments did not affect Hcy-thiolactone/creatinine and its AMI risk association.

CONCLUSIONS

Hcy-thiolactone/creatinine ratio is a novel AMI risk predictor in patients with suspected CAD, independent of traditional risk factors and tHcy, but modified by vitamin B₆ catabolism. These findings lend a support to the hypothesis that Hcy-thiolactone is mechanistically involved in cardiovascular disease.

Identification of suitable reference genes for real-time qPCR in homocysteine-treated human umbilical vein endothelial cells

The imbalance in homocysteine (Hcy) metabolism has been implicated in the pathogenesis of human diseases, including cardiovascular and neurodegenerative disorders. When attempting to identify gene expression profiles using quantitative real-time reverse transcription polymerase chain reaction (RT-qPCR), the selection of suitable reference genes is important. Here, the expression levels of 10 commonly used reference genes were assessed for normalization of RT-qPCR in Hcy-treated human umbilical vein endothelial cells (HUVECs) and control cells. The suitability of eight selected candidate genes was comparatively analyzed across the tested samples and separately ranked by four programs, geNorm, NormFinder, BestKeeper, and the ΔCt method. Glyceraldehyde-3-phosphate dehydrogenase (GAPDH) was the most stable gene in the final ranking using the RankAggreg package. Surprisingly, the β-actin (ACTB) levels decreased significantly in Hcy-treated HUVECs compared with control HUVECs (P<0.05), and further study indicated that Hcy suppressed the expression of ACTB by upregulating the miR-145-5p level in Hcy-treated HUVECs. Our data suggest that GAPDH can be used as a reliable reference gene, while ACTB cannot; normalization of gene expression in RT-qPCR experiments in Hcy-treated HUVECs. The data, which identifies a suitable reference gene in Hcy-treated HUVECs, will contribute to the design of an effective and accurate method for quantitation of gene expression.

Mutations in Homocysteine Metabolism Genes Increase Keratin N-Homocysteinylation and Damage in Mice

Genetic or nutritional deficiencies in homocysteine (Hcy) metabolism increase Hcy-thiolactone, which causes protein damage by forming isopetide bonds with lysine residues, generating N-Hcy-protein. In the present work, we studied the prevalence and genetic determinants of keratin damage caused by homocysteinylation. We found that in mammals and birds, 35 to 98% of Hcy was bound to hair keratin via amide or isopeptide bond (Hcy-keratin), while 2 to 65% was S-Hcy-keratin. A major fraction of hair Hcy-keratin (56% to 93%), significantly higher in birds than in mammals, was sodium dodecyl sulfate-insoluble. Genetic hyperhomocysteinemia significantly increased N-Hcy-keratin levels in the mouse pelage. N-Hcy-keratin was elevated 3.5-, 6.3-, and 11.7-fold in hair from Mthfr -/-, Cse -/-, or Cbs -/- mice, respectively. The accumulation of N-Hcy in hair keratin led to a progressive reduction of N-Hcy-keratin solubility in sodium dodecyl sulfate, from 0.39 ± 0.04 in wild-type mice to 0.19 ± 0.03, 0.14 ± 0.01, and 0.07 ± 0.03 in Mthfr -/-, Cse -/-, or Cbs -/-animals, respectively. N-Hcy-keratin accelerated aggregation of unmodified keratin in Cbs -/- mouse hair. Keratin methionine, copper, and iron levels in mouse hair were not affected by hyperhomocysteinemia. These findings provide evidence that pelage keratin is N-homocysteinylated in vivo in mammals and birds, and that this process causes keratin damage, manifested by a reduced solubility.

Vitamin D3 prevents cardiovascular diseases by lowering serum total homocysteine concentrations in overweight reproductive women: A randomized, placebo-controlled clinical trial

Obesity and overweight are associated with vitamin D deficiency and hyperhomocysteinemia, all of which are contributing factors for developing cardiovascular disease (CVD). Therefore, we hypothesized that improving serum 25-hydroxyvitamin D [25(OH)D] levels may decrease the body weight and total homocysteine concentrations among overweight reproductive women. To test our hypothesis, a randomized, double-blind placebo-controlled clinical trial, registered under ClinicalTrials.gov Identifier No. NCT03310307, was conducted on 100 overweight reproductive women that were allocated into two groups, namely, the treatment group (n = 50), which received 50 000 IU vitamin D₃ per week, and the placebo group (n = 50), and followed for 2 months. Participants' 25(OH)D, homocysteine, parathyroid hormone, calcium, phosphorus, body weight and body mass index (BMI) were measured and compared before and after treatment. The results showed that there was a significant decrease in homocysteine levels after the first and second months of vitamin D₃ intervention in the treatment group, and no significant changes were seen in the placebo group throughout the period of follow up. Statistically significant (P ≤ .05) reductions in homocysteine concentration, body weight, BMI, and parathyroid hormone levels were noticed in the treatment group compared to the placebo. Meanwhile, 25(OH)D, calcium and phosphorus levels were statistically significantly (P ≤ .05) increased in the treatment group. In conclusion, vitamin D₃ intervention with a treatment dose of 50 000 IU per week for at least 2 months can help decrease BMI and homocysteine levels, which in turn will help prevent or minimize the risk of CVD among overweight women of reproductive age.

Combining Pathway Identification and Breast Cancer Survival Prediction via Screening-Network Methods

Breast cancer is one of the most common invasive tumors causing high mortality among women. It is characterized by high heterogeneity regarding its biological and clinical characteristics. Several high-throughput assays have been used to collect genome-wide information for many patients in large collaborative studies. This knowledge has improved our understanding of its biology and led to new methods of diagnosing and treating the disease. In particular, system biology has become a valid approach to obtain better insights into breast cancer biological mechanisms. A crucial component of current research lies in identifying novel biomarkers that can be predictive for breast cancer patient prognosis on the basis of the molecular signature of the tumor sample. However, the high dimension and low sample size of data greatly increase the difficulty of cancer survival analysis demanding for the development of ad-hoc statistical methods. In this work, we propose novel screening-network methods that predict patient survival outcome by screening key survival-related genes and we assess the capability of the proposed approaches using METABRIC dataset. In particular, we first identify a subset of genes by using variable screening techniques on gene expression data. Then, we perform Cox regression analysis by incorporating network information associated with the selected subset of genes. The novelty of this work consists in the improved prediction of survival responses due to the different types of screenings (i.e., a biomedical-driven, data-driven and a combination of the two) before building the network-penalized model. Indeed, the combination of the two screening approaches allows us to use the available biological knowledge on breast cancer and complement it with additional information emerging from the data used for the analysis. Moreover, we also illustrate how to extend the proposed approaches to integrate an additional omic layer, such as copy number aberrations, and we show that such strategies can further improve our prediction capabilities. In conclusion, our approaches allow to discriminate patients in high-and low-risk groups using few potential biomarkers and therefore, can help clinicians to provide more precise prognoses and to facilitate the subsequent clinical management of patients at risk of disease.

Paraoxonase 1 Q192R genotype and activity affect homocysteine thiolactone levels in humans

Genetic or nutritional deficiencies in 1 carbon and homocysteine (Hcy) metabolism elevate Hcy-thiolactone levels and are associated with cardiovascular and neurologic diseases. Hcy-thiolactone causes protein damage, cellular toxicity, and proatherogenic changes in gene expression in human cells and tissues. A polymorphic cardio-protective enzyme, paraoxonase 1 (PON1), hydrolyzes Hcy-thiolactone in vitro. However, whether Hcy-thiolactone hydrolysis is a physiologic function of the PON1 protein and whether polymorphisms in the PON1 gene affect Hcy-thiolactone levels in humans was unknown. Here we show that the PON1-192 genotype, which affects the enzymatic activity of the PON1 protein, also affected urinary Hcy-thiolactone levels, normalized to creatinine. Carriers of the PON1-192R allele had significantly lower Hcy-thiolactone/creatinine levels than individuals carrying the PON1-192Q allele. Individuals with low serum PON1 paraoxonase activity had significantly higher Hcy-thiolactone/creatinine levels compared with individuals with high paraoxonase activity. In contrast, Hcy-thiolactone/creatinine levels were unaffected by serum PON1 arylesterase activity or by PON1 protein levels. Taken together, these findings suggest that PON1 hydrolyzes Hcy-thiolactone in humans and that the interindividual variations in PON1 genotype/activity can modulate the pathology of hyperhomocysteinemia.-Perła-Kaján, J., Borowczyk, K., Głowacki, R., Nygård, O., Jakubowski, H. Paraoxonase 1 Q192r genotype and activity affect homocysteine thiolactone levels in humans.

Stachydrine protects eNOS uncoupling and ameliorates endothelial dysfunction induced by homocysteine

BACKGROUND

Hyperhomocysteinemia (HHcy) is an independent risk factor for cardiovascular diseases (CVDs). Stachydrine (STA) is an active component in Chinese motherwort Leonurus heterophyllus sweet, which has been widely used for gynecological and cardiovascular disorders. This study is aimed to examine the effects of STA on homocysteine (Hcy)-induced endothelial dysfunction.

METHODS

The effects of STA on vascular relaxation in rat thoracic aortas (TA), mesenteric arteries (MA) and renal arteries (RA) were measured by using Multi Myograph System. The levels of nitric oxide (NO), tetrahydrobiopterin (BH4) and guanosine 3', 5' cyclic monophosphate (cGMP) were determined. Endothelial nitric oxide synthase (eNOS) dimers and monomers were assayed by using Western blotting. GTP cyclohydrolase 1 (GTPCH1) and dihydrofolate reductase (DHFR) expressions were measured by using quantitative reverse transcriptase-PCR (qRT-PCR) and Western blotting.

RESULTS

STA effectively blocked Hcy-induced impairment of endothelium-dependent vasorelaxation in rat TA, MA and RA. STA-elicited arterial relaxations were reduced by NOS inhibitor NG-nitro-L-arginine methyl ester (L-NAME) or the NO-sensitive guanylyl cyclase inhibitor 1H- [1, 2, 4] Oxadiazolo[4,3-a]quinoxalin-1-one (ODQ), but not by inducible iNOS inhibitor 1400 W nor the nonselective COX inhibitor indomethacin. Hcy caused eNOS uncoupling and decreases in NO, cGMP and BH4, which were attenuated by STA. Moreover, STA prevented decreases of GTPCH1 and DHFR levels in Hcy-treated BAECs.

CONCLUSION

We demonstrated that STA effectively reversed the Hcy-induced endothelial dysfunction and prevented eNOS uncoupling by increasing the expression of GTPCH1 and DHFR. These results revealed a novel mechanism by which STA exerts its beneficial vascular effects.

Endothelial Cell Metabolism

Endothelial cells (ECs) are more than inert blood vessel lining material. Instead, they are active players in the formation of new blood vessels (angiogenesis) both in health and (life-threatening) diseases. Recently, a new concept arose by which EC metabolism drives angiogenesis in parallel to well-established angiogenic growth factors (e.g., vascular endothelial growth factor). 6-Phosphofructo-2-kinase/fructose-2,6-bisphosphatase-3-driven glycolysis generates energy to sustain competitive behavior of the ECs at the tip of a growing vessel sprout, whereas carnitine palmitoyltransferase 1a-controlled fatty acid oxidation regulates nucleotide synthesis and proliferation of ECs in the stalk of the sprout. To maintain vascular homeostasis, ECs rely on an intricate metabolic wiring characterized by intracellular compartmentalization, use metabolites for epigenetic regulation of EC subtype differentiation, crosstalk through metabolite release with other cell types, and exhibit EC subtype-specific metabolic traits. Importantly, maladaptation of EC metabolism contributes to vascular disorders, through EC dysfunction or excess angiogenesis, and presents new opportunities for anti-angiogenic strategies. Here we provide a comprehensive overview of established as well as newly uncovered aspects of EC metabolism.