Oxidation Of Homocysteine Research Articles

Thermal treatment under oxidative conditions increases the antioxidant and antiglycation activity of Chilean Tórtola beans (Phaseolus vulgaris)

The influence of oxygen on the thermal treatment (TT) of secondary metabolite-enriched extracts (SMEEs) from Tórtola beans and procyanidin C1 (PC1) on the inhibition of advanced glycation end products (AGEs) generation in proteins was investigated. SMEE was incubated at 4 °C (control) or thermally treated at 60 °C for 2 h, at either 0 % O2 (I) or 20 % O2 (II). Treatments I and II increased the content of procyanidin dimers B2. Treatment II was more effective than the control or treatment I in preventing homocysteine oxidation and AGEs generation. TT of PC1 at 0 % or 20 % O2 generated procyanidin dimers and tetramers. PC1 TT at 20 % O2 exhibited higher oxidation potentials and lower IC50 values of fluorescent AGEs than those of controls or TT at 0 % O2. These findings indicate that SMEE from Tórtola beans after treatment II changes the degree of polymerization and oxidation procyanidins, thereby increasing their antiglycation activity.

An Amperometric Biomedical Sensor for the Determination of Homocysteine Using Gold Nanoparticles and Acetylene Black-Dihexadecyl Phosphate-Modified Glassy Carbon Electrode.

A novel nanocomposite film composed of gold nanoparticles and acetylene black-dihexadecyl phosphate was fabricated and modified on the surface of a glassy carbon electrode through a simple and controllable dropping and electropolymerization method. The nanocomposite film electrode showed a good electrocatalytic response to the oxidation of homocysteine and can work as an amperometric biomedical sensor for homocysteine. With the aid of scanning electron microscopy, energy dispersive X-ray technology and electrochemical impedance spectroscopy, the sensing interface was characterized, and the sensing mechanism was discussed. Under optimal conditions, the oxidation peak current of homocysteine was linearly increased with its concentration in the range of 3.0 µmol/L~1.0 mmol/L, and a sensitivity of 18 nA/(μmol/L) was obtained. Furthermore, the detection limit was determined as 0.6 µmol/L, and the response time was detected as 3 s. Applying the nanocomposite film electrode for monitoring the homocysteine in human blood serum, the results were satisfactory.

Electrochemical Determination of Homocysteine Using Self-Assembled 6-Ferrocenylhexanethiol on a Molybdenum Disulfide Nanoparticle Modified Glassy Carbon Electrode (GCE)

The determination of homocysteine (Hcy) is important because high levels are associated with a greater risk of developing heart disease or stroke. Herein, an electrochemical sensor of homocysteine was constructed based upon the self-assembly of 6-ferrocenylhexanethiol (FcC6SH) on a MoS2 nanoparticles-modified electrode with a Nafion coating. The sensor showed a favorable electrocatalytic activity for oxidation of homocysteine since 6-ferrocenylhexanethiol acted as a good electron transfer mediator. Moreover, the MoS2 nanoparticles served as modifiers to covalently immobilize FcC6SH and enhance the electrochemical active surface area. Highly sensitive determination of homocysteine was achieved with a linear range from 2.0 to 100 µmol L−1 and a minimum detectable concentration of 0.30 µmol L−1 by chronoamperometry. The constructed sensor was applied to the analysis of immunoglobulin G (IgG) samples with satisfactory results.

Melatonin as a Reducer of Neuro- and Vasculotoxic Oxidative Stress Induced by Homocysteine.

The antioxidant properties of melatonin can be successfully used to reduce the effects of oxidative stress caused by homocysteine. The beneficial actions of melatonin are mainly due to its ability to inhibit the generation of the hydroxyl radical during the oxidation of homocysteine. Melatonin protects endothelial cells, neurons, and glia against the action of oxygen radicals generated by homocysteine and prevents the structural changes in cells that lead to impaired contractility of blood vessels and neuronal degeneration. It can be, therefore, assumed that the results obtained in experiments performed mainly in the in vitro models and occasionally in animal models may clear the way to clinical applications of melatonin in patients with hyperhomocysteinemia, who exhibit a higher risk of developing neurodegenerative diseases (e.g., Parkinson’s disease or Alzheimer’s disease) and cardiovascular diseases of atherothrombotic etiology. However, the results that have been obtained so far are scarce and have seldom been performed on advanced in vivo models. All findings predominately originate from the use of in vitro models and the scarcity of clinical evidence is huge. Thus, this mini-review should be considered as a summary of the outcomes of the initial research in the field concerning the use of melatonin as a possibly efficient attenuator of oxidative stress induced by homocysteine.

Plasma Homocysteine and Glutathione Are Independently Associated With Estimated Glomerular Filtration Rates in Patients With Renal Transplants

BackgroundElevated levels of plasma homocysteine could, through homocysteine oxidation, induce the overproduction of reactive oxygen species, leading to a reduction in glutathione-related antioxidants, and may impair graft functions in patients with renal transplants. The purpose of this study was to determine whether plasma homocysteine, glutathione, or its related antioxidants were related to graft functions in patients with renal transplants. Patients and MethodsWe recruited 66 patients (mean age 48.4 years) with renal transplants (mean transplant duration 8.3 years). Patients were divided into 2 groups, based on their estimated glomerular filtration rate (eGFR): the moderate graft function group (eGFR ≥ 60 mL/min/1.73 m2, n = 37) and low graft function group (eGFR < 60 mL/min/1.73 m2, n = 29). We then determined their fasting levels of the following: malondialdehyde (MDA), homocysteine, cysteine, pyridoxal 5′-phosphate (PLP), glutathione (GSH), oxidized glutathione (GSSG), GSH/GSH ratio, glutathione peroxidase (GSH-Px) activity. ResultsWe found in the low graft function group significantly higher levels of plasma homocysteine, cysteine, GSH, and GSH/GSSG ratios. But an intergroup difference was not found regarding levels of MDA, PLP, GSSG, and GSH-Px activity. After adjusting for potential confounders, the increased plasma homocysteine and GSH levels were independently associated with lower eGFR. No interaction existed between homocysteine and GSH levels in association with eGFR. ConclusionIncreased plasma homocysteine and GSH levels appeared to be independent indicators of decreased graft functions in patients with renal transplants.

Effect of surfactants and halide ions on the adsorption and oxidation of homocysteine at the gold electrode

This study demonstrates how adsorptive species including a series of surfactants and halide ions affect the adsorption of Hcy on the electrode surface, as well as how the change of Hcy adsorption affects the oxidation of Hcy.

Electrografting of 4‐tert‐Butylcatechol on GC Electrode. Selective Electrochemical Determination of Homocysteine

AbstractA new sensor based on the grafting of 4‐tert‐butylcatechol on the surface of a glassy carbon electrode (GC) was developed for the catalytic oxidation of homocysteine (Hcy). The GC‐modified electrode exhibited a reversible redox response at neutral pH. Under the optimum conditions cyclic voltammetric results indicated the excellent electrocatalytic activity of modified electrode toward the oxidation of Hcy at reduced over‐potential about 350 mV. A linear dynamic range of 0.01–3.0 mM and a detection limit of 1.0 µM were obtained for Hcy. The modified electrode was used as an electrochemical sensor for selective determination of Hcy in human blood.

Postnatal injection of homocysteic acid leads to the development of behaviors consistent with major‐depressive disorder in female, but not male, Sprague Dawley rats (803.11)

Recent evidence suggests that hyperfunction of N‐methyl‐D‐aspartate receptors (NMDA) may be an important factor in the pathophysiology of major depressive disorder (MDD). The NMDA receptor agonist, homocysteic acid (HCA), is an endogenous compound that is formed from the oxidation of homocysteine. Since hyperhomocysteinemia is a risk factor for several disorders, including MDD, we sought to test the hypothesis that elevated HCA levels in developing rats may lead to changes in NMDA receptor expression and the development of behaviors associated MDD. To test this hypothesis, we performed daily intraperitoneal injections of either HCA or saline in postnatal male and female rats for 14 days beginning at day P2. Six weeks later, we observed that female, HCA‐treated rats displayed increased risk‐taking behavior, anhedonia, deficits in pre‐pulse inhibition, and increased sensitivity to pain compared to control and male‐HCA treated rats, but no difference in motor performance or weight gain over the course of the experiment. Consistent with these findings, we observed that HCA exposure led to an increase in the expression of the NMDA E2 subunit and GAD‐67 in the cortex of female, but not male, rats. Given that MDD is sexually dimporphic and observed more often in females compared to males, these data suggest that early postnatal exposure to HCA may serve as an excellent animal model for MDD. This research was supported by the Hope College Neuroscience Program, Biology Department and Chemistry Department, and NSF‐REU # 0851194.Grant Funding Source: NSF‐REU # 0851194

Electrochemical determination of homocysteine using carbon nanotubes modified paste electrode and isoprenaline as a mediator

Homocysteine (HCy) is an important amino acid containing thiol group and is known as a risk factor in relation to ischemic heart disease and stroke. In this study the electrochemical determination of homocysteine (HCy) has been described using isoprenaline hydrochloride (ISP) as a mediator on multiwall carbon nanotubes modified paste electrode (MWCNTPE). Electrochemical behavior of homocysteine was investigated by cyclic voltarrtmetry and chronoamperometry. The cyclic voltammograms showed that the electrocatalytic oxidation of homocysteine occurs in the presence of ISP on the surface of MWCNTPE at a potential about 640 mV. Also, results showed that the oxidatation peak current of HCy at the modified carbon nanotubes electrode was more than unmodified electrode. The diffusion coefficient and the kinetic parameters including electron transfer coefficient and rate constant of electrocatalytic reaction were determined using electrochemical approaches. Linear sweep voltammetry results showed that electrocatalytic oxidation peak current of HCy had linear dynamic range in the range of 5.0 to 800 μmol L−1 with a detection limit of 3.3 μmol L−1 in pH 3.5 (universal buffer).

Nanostructured base electrochemical sensor for voltammetric determination of homocysteine using a modified single-walled carbon nanotubes paste electrode

A carbon paste electrode modified with benzoylferrocene (BF) and carbon nanotubes (CNTs) have been applied to the electrocatalytic oxidation of homocysteine which reduced the overpotential by about 165 mV with an obvious increase in the current response. The transfer coefficient (α) for the electrocatalytic oxidation of homocysteine and diffusion coefficient of this substance under the experimental conditions were also investigated. In a phosphate buffer solution (PBS) of pH 7.0, the oxidation current increased linearly with two concentration intervals of homocysteine; one is 0.1 to 10.0 μM, and the other is 10.0 to 80.0 μM. The detection limit (3σ) obtained by square wave voltammetry (SWV) was 50.0 nM. The proposed method was successfully applied to the determination of homocysteine in real samples.

Selective electrochemical determination of homocysteine in the presence of cysteine and glutathione

The electrochemical oxidation of 3,5-di-tert-buthylcatechol in the presence of homocysteine was used for the selective electrochemical determination of homocysteine in the presence of cysteine and glutathione at a glassy carbon and a glassy carbon electrode modified with carbon nanotube. The results revealed that the electrochemically generated 3,5-di-tert-butylcyclohexa-3,5-diene-1,2-dione exhibits high catalytic activity toward homocysteine oxidation at reduced over-potential and low catalytic activity for oxidation of cysteine. The catalytic activity 3,5-di-tert-butylcyclohexa-3,5-diene-1,2-dione toward cysteine was suppressed in the presence of 4-N,N-dimethylaminocinnamaldehyde. Contrary to homocysteine and cysteine, the reaction of glutathione with 3,5-di-tert-butylcyclohexa-3,5-diene-1,2-dione is a substituation reaction. This method exhibits three dynamic linear ranges of 2.5 to 10μmolL−1, 10 to 100μmolL−1 and 100 to 1000μmolL−1, and a lower detection limit (3σ) of 0.89±3.53% μmol L−1 for homocysteine.

Nitrogen doped graphene nanosheet supported platinum nanoparticles as high performance electrochemical homocysteine biosensors.

Functional carbon nanomaterials are significantly important for the development of high performance sensitive and selective electrochemical biosensors. In this study, graphene supported platinum nanoparticles (GN-PtNPs) and nitrogen doped graphene supported platinum nanoparticles (N-GN-PtNPs) were synthesized by a simple chemical reduction method and explored as high performance nanocatalyst supports, as well as doped nanocatalyst supports, toward electrochemical oxidation of homocysteine (HCY) for the first the time. Our studies demonstrate that N-doped graphene supported PtNPs show higher electrocatalytic activity for HCY with an experimental detection limit of 200 pM. Moreover, N-doped graphene supported Pt was demonstrated to have excellent selectivity in the electrochemical oxidation of HCY i.e., the detection of HCY is successful in the presence of a 20-fold excess of ascorbic acid (AA). The practical application of N-doped graphene supported PtNP materials is effectively shown for the determination of HCY in both human blood serum and urine samples, by differential pulse voltammetry under optimized conditions. Our findings conclude that N-doped graphene supported PtNPs can be developed as a high performance and versatile nano-electrocatalyst for electrochemical biosensor applications.

Development of Flow Injection Spectrofluorimetric Detection System for the Determination of Homocysteine

In this work, a new simple and sensitive flow injection method is developed for the determination of homocysteine with spectrofluorimetric detection technique. This method is based on the oxidation of homocysteine with Tl (III) in acidic media, producing fluorescence reagent, TlCl(3)(2-) (λ(ex) = 237 nm, λ(em) = 419 nm). The effects of chemical parameters (including pH of the solutions, the buffer, Tl (III) and potassium chloride concentrations), instrumental parameters (such as flow rate of the solutions, reaction coil length, and sample loop volume) and temperature on the fluorescence intensity as an analytical signal are studied and optimized. In the optimum conditions of the above variables, homocysteine can be determined in the range 4.0 × 10(-7)-40.0 × 10(-6) M with the LDR from 4.0 × 10(-7) to 25.0 × 10(-6) M. The detection limit (with S/N = 3) is 6.0 × 10(-8) M of homocysteine and precision for the injection of 5.0, 10.0 and 15.0 μM of homocysteine are 0.8%, 1.5% and 2.5% (n = 10) respectively. The rate of analysis is 90 samples per hour. The influence of potential interfering substances, including amino acids and carbohydrates is also studied. The proposed method has been successfully used for the determination of homocysteine in the real sample (blood serum and tap water) matrix.

Free radical reactions in atherosclerosis; An EPR spectrometry study

The copper catalysed oxidation of homocysteine has been studied by electron paramagnetic resonance (EPR) spectroscopy and spin trapping techniques to determine the nature of free radical species formed under varying experimental conditions. Three radicals; thiyl, alkyl and hydroxyl were detected with hydroxyl being predominant. A reaction mechanism is proposed involving Fenton chemistry. Inclusion of catalase to test for intermediate generation of hydrogen peroxide showed a marked reduction in amount of hydroxyl radical generated. In contrast, the addition of superoxide dismutase showed no significant effect on the level of hydroxyl radical formed. Enhanced radical formation was observed at higher levels of oxygen, an effect which has consequences for differential oxygen levels in arterial and venous systems. Implications are drawn for a higher incidence of atherosclerotic plaque formation in arteries versus veins.

Detection of homocysteine at carbon nanotube paste electrodes

The use of a carbon-nanotube paste (CNTP) electrode provides an effective means for the determination of homocysteine. A decrease of ca. 120mV in the overpotential for the oxidation of homocysteine compared to a traditional carbon paste electrode, is reported along with greatly enhanced signal-to-noise characteristics. The analytical parameters have been assessed with a linear range from 5 to 200μM and a detection limit of 4.6μM. Furthermore, the generic nature of this increased reactivity of the CNTP surface towards thiol moieties has been demonstrated with cysteine, glutathione and n-acetylcysteine, providing a greatly enhanced electrochemical response compared to the carbon paste electrode.

Influence of hyperhomocysteinemia on the cellular redox state--impact on homocysteine-induced endothelial dysfunction.

Hyperhomocysteinemia is an independent risk factor for the development of atherosclerosis. An increasing body of evidence has implicated oxidative stress as being contributory to homocysteine's deleterious effects on the vasculature. Elevated levels of homocysteine may lead to increased generation of superoxide by a biochemical mechanism involving nitric oxide synthase, and, to a lesser extent, by an increase in the chemical oxidation of homocysteine and other aminothiols in the circulation. The resultant increase in superoxide levels is further amplified by homocysteine-dependent alterations in the function of cellular antioxidant enzymes such as cellular glutathione peroxidase or extracellular superoxide dismutase. One direct clinical consequence of elevated vascular superoxide levels is the inactivation of the vasorelaxant messenger nitric oxide, leading to endothelial dysfunction. Scavenging of superoxide anion by either superoxide dismutase or 4,5-dihydroxybenzene 1,3-disulfonate (Tiron) reverses endothelial dysfunction in hyperhomocysteinemic animal models and in isolated aortic rings incubated with homocysteine. Similarly, homocysteine-induced endothelial dysfunction is also reversed by increasing the concentration of the endogenous antioxidant glutathione or overexpressing cellular glutathione peroxidase in animal models of mild hyperhomocysteinemia. Taken together, these findings strongly suggest that the adverse vascular effects of homocysteine are at least partly mediated by oxidative inactivation of nitric oxide.

Homocysteine oxidation and apoptosis: a potential cause of cleft palate

Homocysteine oxidation and apoptosis: a potential cause of cleft palate

The electrochemical oxidation of homocysteine at boron-doped diamond electrodes with application to HPLC amperometric detection.

The electrochemical oxidation of homocysteine was studied at as-deposited and anodized (oxidized) boron-doped diamond (BDD) thin film electrodes with cyclic voltammetry, flow injection analysis and high-pressure liquid chromatography with amperometric detection. At anodized boron-doped diamond electrodes, highly reproducible, well-defined cyclic voltammograms for homocysteine oxidation were obtained in acidic media, while as-deposited diamond did not provide a detectable signal. In alkaline media, however, the oxidation response was obtained both at as-deposited and anodized diamond electrodes. The potential sweep rate dependence of homocysteine oxidation (peak currents for 1 mM homocysteine linearly proportional to v(1/2), within the range of 0.01 to 0.3 V s(-1)) indicates that the oxidation involves a diffusing species, with negligible adsorption on the BDD surface at this concentration. In the flow system, BDD exhibited a highly reproducible amperometric response, with a peak variation less than 2%. An extremely low detection limit (1 nM) was obtained at 1.6 V vs. Ag/AgCl. In addition, the determination of homocysteine in a standard mixture with aminothiols and disulfide compounds by means of isocratic reverse-phase HPLC with amperometric detection at diamond electrodes has been investigated. The results showed excellent separation, with a detection limit of 1 pmol and a linear range of three orders of magnitude.

Thrombin formation in platelet-rich plasma after oral methionine loading: Preliminary report

Homocysteine, an intermediate of methionine metabolism, has been found to be an independent risk factor for thromboembolism [1]. Various mechanisms have been proposed to explain possible homocysteine-induced thrombogenicity, including endothelial damage, enhanced lipid peroxidation, impaired activity of the anticoagulant protein C system and increased expression of tissue factor [1–5]. Relevance of these findings in vivo remains controversial. Much less is known on the effects of homocysteine on platelet function [6]. In patients with homocystinuria, homocysteine might increase thromboxane A2 production [7] and stimulate platelet aggregation [8], though the effect of homocysteine on platelet survival is less evident [6]. Oxidative stress might lead to homocysteine oxidation, enhanced platelet activation and increased prothrombotic potential in hyperhomocysteinemia [9]. Methionine loading test is recognized as a method to induce a transient acute hyperhomocysteinemia and helps to identify individuals with abnormal methionine metabolism [10,11]. It remains to be determined whether in mild hyperhomocysteinemia platelet-mediated prothrombotic effects might be of importance. The aim of the study was to evaluate potential alterations in thrombin formation in platelet-rich plasma after oral methionine loading in healthy subjects. 2. Materials and methods

Relative Roles of Albumin and Ceruloplasmin in the Formation of Homocystine, Homocysteine-Cysteine-mixed Disulfide, and Cystine in Circulation

Disulfide forms of homocysteine account for >98% of total homocysteine in plasma from healthy individuals. We recently reported that homocysteine reacts with albumin-Cys(34)-S-S-cysteine to form homocysteine-cysteine mixed disulfide and albumin-Cys(34) thiolate anion. The latter then reacts with homocystine or homocysteine-cysteine mixed disulfide to form albumin-bound homocysteine (Sengupta, S., Chen, H., Togawa, T., DiBello, P. M., Majors, A. K., Büdy, B., Ketterer, M. E., and Jacobsen, D. W. (2001) J. Biol. Chem. 276, 30111-30117). We now extend these studies to show that human albumin, but not ceruloplasmin, mediates the conversion of homocysteine to its low molecular weight disulfide forms (homocystine and homocysteine-cysteine mixed disulfide) by thiol/disulfide exchange reactions. Only a small fraction of homocystine is formed by an oxidative process in which copper bound to albumin, but not ceruloplasmin, mediates the reaction. When copper is removed from albumin by chelation, the overall conversion of homocysteine to its disulfide forms is reduced by only 20%. Ceruloplasmin was an ineffective catalyst of homocysteine oxidation, and immunoprecipitation of ceruloplasmin from human plasma did not inhibit the capacity of plasma to mediate the conversion of homocysteine to its disulfide forms. In contrast, ceruloplasmin was a highly efficient catalyst for the oxidation of cysteine and cysteinylglycine to cystine and bis(-S-cysteinylglycine), respectively. However, when thiols (cysteine and homocysteine) that are disulfide-bonded to albumin-Cys(34) are removed by treatment with dithiothreitol to form albumin-Cys(34)-SH (mercaptalbumin), the conversion of homocysteine to its disulfide forms is completely blocked. In conclusion, albumin mediates the formation of disulfide forms of homocysteine by thiol/disulfide exchange, whereas ceruloplasmin converts cysteine to cystine by copper-dependent autooxidation.