Measurement of homocysteine concentrations and stable isotope tracer enrichments in human plasma

A novel intramolecular charge transfer-based near-infrared fluorescent probe with large Stokes shift for highly sensitive detection of cysteine in vivo

Cysteine (Cys) distribute widely in organisms as the crucial components of proteins, and play important roles in pathophysiological processes of human body. Low level of Cys might induce hepatic injury, edema and growth retardation, while superfluous level of Cys is found to be closely relevant to Alzheimer's and Parkinson's diseases. In this work, a novel near-infrared (NIR) fluorescent probe PFQ-C was developed for highly selective detection of Cys in living cells and mice by utilizing the cyclization removal reaction between acrylate group and Cys. The superior sensitivity (limit of detection, 0.036 μM), NIR emission (655 nm), large Stokes shift (135 nm) and low cytotoxicity of the probe highlight its broad potential for future clinical applications. The response mechanism of the probe towards Cys was clarified by spectroscopy, chromatography and theoretical calculation. In addition, results of fluorescence imaging of cells and mice revealed the good performance of the probe for monitoring the distributions and variations of Cys activity in vivo, which is very useful for the researches on diseases associated with Cys.

Effect of ensiled total mixed rations containing sake lees on digestion, nitrogen use, and plasma metabolite concentrations in sheep

Sake lees are a byproduct of Japanese rice wine and used as ruminant feed with high protein and ethanol contents. This study aimed to explore the effects of ensiled total mixed ration (TMR) containing sake lees on rumen fermentation, digestion, nitrogen (N) use, and plasma metabolites in sheep. Four mature wethers were assigned to a 4 × 4 Latin square design with a factorial arrangement of ensiling treatment (non-ensiled or ensiled TMR) and types of sake lees (traditional or liquefied). Although dietary ethanol consumption was higher in sheep fed ensiled TMR, ruminal and plasma concentrations of methanol and ethanol increased after feeding in all dietary treatments, which was accompanied by the increased plasma concentrations of formate. The intake and digestion of dry matter and N were lower in sheep fed ensiled TMR than in those fed non-ensiled TMR. The plasma concentrations of most amino acids decreased in sheep fed ensiled TMR. Although plasma methionine, serine, and glycine concentrations were not altered by diet, homocysteine concentration was the highest in sheep fed ensiled TMR containing traditional sake lees. The negative impacts of ensiling treatment on N digestion and amino acid utilization should be considered for formulating ensiled TMR containing sake lees.

A coumarin-based fluorescence sensor for rapid discrimination of cysteine/homocysteine and glutathione under dual excitation wavelengths

Biological thiols (Cys, Hcy and GSH) are crucial biomolecules in living cells and play indispensable roles in maintaining the redox homeostasis of organisms. But due to their similar molecular structure, the development of effective tools for distinguishing two or three of them remains a great difficulty. Herein, we constructed a sensitive sensor (CB) by connecting the bifunctional fluorescent reagent with coumarin derivatives for simultaneous recognition of these three thiols through different pathways. Free CB had no fluorescence; however, with gradual addition of thiols, the chlorine unit was replaced by sulfhydryl. Furthermore, the intramolecular rearrangement occurred between the amino and sulfhydryl groups of Cys/Hcy and yellow fluorescence was observed at 570 nm. However, GSH with a large structure could not undergo intramolecular rearrangement, and green fluorescence was excited at 505 nm. In this way, Cys/Hcy and GSH can be detected distinctively. Under dual excitation wavelengths, CB exhibited high selectivity and fast response to the three thiols. Furthermore, CB was successfully applied to imaging endogenous and exogenous thiols in living cells and zebrafish, providing us with a reliable tool for thiols recognition.

Phytol supplementation alters plasma concentrations of formate, amino acids, and lipid metabolites in sheep

The phytol moiety in chlorophyll molecules acts as an agonist of peroxisome proliferator-activated receptor-α in monogastric animals. The current study aimed to clarify the effects of dietary supplementation with phytol on the plasma concentrations of formate and amino acids related to one-carbon (1C) donors and its effects on lipid metabolism in sheep. Four mature sheep were fed with a mixed ration (metabolizable energy, 10.7 MJ/kg DM; CP, 150 g/kg DM) comprising barley, rice bran, soybean meal, and oat hay at 1.5 times maintenance metabolizable energy for three consecutive 14-day experimental periods. The first and third periods served as controls without phytol supplementation, while in the second period, phytol was added to the mixed ration at 12 g/kg of dietary DM per day. In each period, feces, urine, and jugular blood samples were collected. Dry matter intake in relation to metabolic BW was slightly lower (P < 0.01) in the first period than the second and third periods but did not differ between the latter two periods. Dry matter digestibility was slightly reduced (P = 0.05) by the phytol treatment. Nitrogen (N) intake and retention showed similar trends to DM intake, but urinary N was unchanged among the periods. Plasma cholesterol and phospholipid concentrations decreased during the phytol treatment period, while triglyceride concentration increased (P < 0.05). In the phytol treatment period, the plasma concentrations of serine and glycine (1C donors) increased, but the glutamate level decreased (P < 0.01). Plasma concentrations of formate and methionine increased (P < 0.01) from the first control period to the phytol supplementation period, but homocysteine and cysteine (intermediate and by-product of the methionine cycle) levels were unchanged among the treatment periods. In conclusion, dietary phytol affects lipid metabolism as well as amino acid metabolism and 1C donors in sheep. These effects may be associated with the activity of phytol as an agonist of the nuclear receptors, although this needs further investigation.

ICT-modulated NIR water-soluble fluorescent probe with large Stokes shift for selective detection of cysteine in living cells and zebrafish

The fluorescent probes with good water-solubility, long-wavelength emission and large Stokes shift are greatly desirable for in vivo detection. Herein, we designed a novel 1,8-naphthalimide-based near-infrared (NIR) optical and fluorescent probe (NTC) for sensing cysteine (Cys). Using acrylate as the recognition site, the probe demonstrated high selectivity and sensitivity for Cys with a low detection limit (0.093 μM) in aqueous buffer solution due to the excellent water-solubility. Upon the reaction with Cys, the recovery of intramolecular charge transfer (ICT) in the probe led to about 40-fold fluorescence enhancement. Furthermore, the reaction result was investigated by ¹H NMR, and HRMS analyses, and the sensing mechanism was validated by quantum calculations. Finally, NTC was applied to image exogenous and endogenous Cys in HeLa cells and zebrafish selectively, implying that the probe possessed great potential application in biological fluorescence sensing.

Specific detection and determination of cysteine by a luminescent samarium macrocycle-based fluorescent probe platform

A samarium macrocycle-based chemosensor bearing two imine bonds and a Sm(iii) emitter provides an indirect approach to detect and determine cysteine.

The Antioxidant Role of One-Carbon Metabolism on Stroke

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

A novel strategy for rhodamine B-based fluorescent probes with a selective glutathione response for bioimaging in living cells

The aim of this study was to overcome the reported shortcomings of the glutathione (GSH) detection of rhodamine-based fluorescent probes, such as poor selectivity to thiol groups and reversible unstable covalent binding with the thiol groups.

A bis-indole/carbazole based C5-curcuminoid fluorescent probe with large Stokes shift for selective detection of biothiols and application to live cell imaging

A series of heterocyclic C5-Curcuminoid (PJ1–PJ6) having large Stokes shift (Δλ= 104–173 nm) have been synthesized under the microwave irradiation andPJ1has been utilized for selective detection of thiols in A375 cells and apoptosis in AGS cells.

Giant single molecule chemistry events observed from a tetrachloroaurate(III) embedded Mycobacterium smegmatis porin A nanopore

Biological nanopores are capable of resolving small analytes down to a monoatomic ion. In this research, tetrachloroaurate(III), a polyatomic ion, is discovered to bind to the methionine residue (M113) of a wild-type α-hemolysin by reversible Au(III)-thioether coordination. However, the cylindrical pore geometry of α-hemolysin generates shallow ionic binding events (~5–6 pA) and may have introduced other undesired interactions. Inspired by nanopore sequencing, a Mycobacterium smegmatis porin A (MspA) nanopore, which possesses a conical pore geometry, is mutated to bind tetrachloroaurate(III). Subsequently, further amplified blockage events (up to ~55 pA) are observed, which report the largest single ion binding event from a nanopore measurement. By taking the embedded Au(III) as an atomic bridge, the MspA nanopore is enabled to discriminate between different biothiols from single molecule readouts. These phenomena suggest that MspA is advantageous for single molecule chemistry investigations and has applications as a hybrid biological nanopore with atomic adaptors.

Engineered biological nanopores enable observation of single molecule chemistry events; however a cylindrical pore geometry can have undesired effects. The authors report a conical biological pore which was embedded with tetrachloroaurate(III) to allow for discrimination between different biothiols.

A turn-on fluorescence probe for cysteine/homocysteine based on the nucleophilic-induced rearrangement of benzothiazole thioether

A fluorescent probe, 4-(benzothiazole-2-ylthio)-7-nitro-2,1,3-benzoxadiazole (TBT-NBD) was developed for cysteine (Cys) and homocysteine (Hcy). The reaction mechanism was based on the Cys/Hcy-induced nucleophilic substitution of benzothiazole thioether then Smiles rearrangement reaction to form corresponding amino-nitrobenzoxadiazole, which emitted yellow-green fluorescence and guaranteed the high selectivity for Cys/Hcy over glutathione (GSH). TBT-NBD could detect Cys/Hcy within 5 min in the presence of high concentration of GSH and other amino acids. Moreover, TBT-NBD had been exploited to identify intracellular Cys/Hcy in living cells in light of its low toxicity.

Label-free gold nanorods sensor array for colorimetric detection and discrimination of biothiols in human urine samples

Biothiols play important roles in regulating redox balance in biological systems, but their discrimination is challengeable. In this work, a colorimetric nanosensing array for biothiols was established, which was composed of gold nanorods (AuNRs) and metal ions (Hg²⁺, Pb²⁺, Cu²⁺, Ag⁺). By employing label-free AuNRs as the colorimetric probe, and the color and spectral changes of AuNRs as the output signal, principal component analysis (PCA) was applied to processing the signal and generating a clustering map. Due to the different binding affinity between biothiols and metal ions, AuNRs exhibited a unique pattern to form a fingerprint-like colorimetric array, which was able to discriminate five biothiols by the naked eyes. This strategy combines PCA and sensor array to achieve rapid and accurate discrimination and detection of biothiols. In addition, the method shows the great potential in analysis of biothiols in human urine samples.

Near-infrared turn-on fluorescent probe for discriminative detection of Cys and application in in vivo imaging

Near-infrared (NIR) fluorescent probes are widely employed in biological detection because of their lower damage to biological samples, low background interference, and high signal-to-noise ratio. Herein, a highly water-soluble NIR probe (NIRHA) based on a hemicyanine skeleton and bearing an acrylate moiety was synthesized. The probe showed high selectivity toward cysteine (Cys) over homocysteine (Hcy) and glutathione (GSH). The probe also had low cytotoxicity and was successfully applied in HeLa cells and mouse experiments. Results of bioimaging experiments indicated that the probe was effective for visualizing endogenous Cys in vitro and in vivo.

Near-infrared (NIR) fluorescent probes are widely employed in biological detection because of their lower damage to biological samples, low background interference, and high signal-to-noise ratio.

A Multi-signal Fluorescent Probe with Multiple Binding Sites for Simultaneous Sensing of Cysteine, Homocysteine, and Glutathione

A novel fluorescent probe was developed by integrating chlorinated coumarin and benzothiazolylacetonitrile and exploited for simultaneous detection of cysteine (Cys), homocysteine (Hcy), and glutathione (GSH). Featuring four binding sites and different reaction mechanisms for different biothiols, this probe exhibited rapid fluorescence turn-on for distinguishing Cys, Hcy, and GSH with 108-, 128-, 30-fold fluorescence increases at 457, 559, 529 nm, respectively, across different excitation wavelengths. Furthermore, the probe was successfully applied to the fluorescence imaging of endogenous Cys and GSH and exogenous Cys, Hcy, and GSH in living cells.

A lysosome-targetable turn-on fluorescent probe for the detection of thiols in living cells based on a 1,8-naphthalimide derivative

Biological thiols, like cysteine (Cys), homocysteine (Hcy) and glutathione (GSH), play crucial roles in biological systems and in lysosomal processes. Highly selective probes for detecting biological thiols in lysomes of living cells are rare. In this work, a lysosome-targetable turn-on fluorescent probe for the detection of thiols in living cells was designed and synthesized based on a 1,8-naphthalimide derivative. The probe has a 4-(2-aminoethyl)morpholine unit as a lysosome-targetable group and an acrylate group as the thiol recognition unit as well as a fluorescence quencher. In the absence of biothiols, the probe displayed weak fluorescence due to the photoinduced electron transfer (PET) process. Upon the addition of biothiols, the probe exhibited an enhanced fluorescence emission centered at 550nm due to cleavage of the acrylate moiety. The probe had high selectivity toward biothiols. Moreover, the probe features fast response time, excitation in the visible region and ability of working in a wide pH range. The linear response range covers a concentration range of Cys from 1.5×10^-7 to 1.0×10^-5mol·L^-1 and the detection limit is 6.9×10^-8mol·L^-1 for Cys. The probe has been successfully applied to the confocal imaging of biothiols in lysosomes of A549 cells with low cell toxicity. Furthermore, the method was successfully applied to the determination of thiols in a complex multicomponent mixture such as human serum, which suggests our proposed method has great potential for diagnostic purposes. All of such good properties prove it can be used to monitor biothiols in lysosomes of living cells and to be a good fluorescent probe for the selective detection of thiols.

Development of a two-photon turn-on fluorescent probe for cysteine and its bio-imaging applications in living cells, tissues, and zebrafish

A two-photon fluorescent probe Co-Cys for detecting cysteine has been designed to monitor cysteine in cells, tissues and zebrafish.

Nitroolefin-modified cyclometalated iridium(iii) complexes for tunable detection of biothiols with deep-red emission

Two nitroolefin-modified cyclometalated iridium(iii) complexes were employed as turn-on probes for the rapid (1 min) detection of biothiols with tunable emission.

Fluorescent Probes with Multiple Binding Sites for the Discrimination of Cys, Hcy, and GSH

Biothiols such as cysteine (Cys), homocysteine (Hcy), and glutathione (GSH) play crucial roles in maintaining redox homeostasis in biological systems. This Minireview summarizes the most significant current challenges in the field of thiol-reactive probes for biomedical research and diagnostics, emphasizing the needs and opportunities that have been under-investigated by chemists in the selective probe and sensor field. Progress on multiple binding site probes to distinguish Cys, Hcy, and GSH is highlighted as a creative new direction in the field that can enable simultaneous, accurate ratiometric monitoring. New probe design strategies and researcher priorities can better help address current challenges, including the monitoring of disease states such as autism and chronic diseases involving oxidative stress that are characterized by divergent levels of GSH, Cys, and Hcy.

Simultaneous quantification of multiple endogenous biothiols in single living cells by plasmonic Raman probes

Three endogenous biothiols in single cells were simultaneously quantified by plasmonic Raman probes and quantitative principal component analysis (qPCA).

Intracellular biothiols mediate many important physiological and pathological processes. Due to their low content and competing thiol-reactivity, it is still an unmet challenge to quantify them within a complicated intracellular environment. Herein, we demonstrated a strategy to discriminate three biothiols, i.e. cysteine (Cys), homo-cysteine (Hcy) and glutathione (GSH), and quantify their concentrations within single living cells, using one platform of Raman probe. By monitoring the reaction kinetics of biothiols with Raman probes and discriminating their products with a quantitative principal component analysis (qPCA) method, these three biothiols could be simultaneously quantified in both cell lysis and single living cells. The concentrations of Cys, Hcy and GSH in single Hela cells were 158 ± 19 μM, 546 ± 67 μM and 5.07 ± 0.62 mM, respectively, which gives the precise concentrations of these three biothiols at a single cell level for the first time. This method provides a general strategy for discriminating each component from a mixed system and has potential for quantifying any biomolecules within an in vitro or in vivo biological environment.

A highly water-soluble, sensitive, coumarin-based fluorescent probe for detecting thiols, and its application in bioimaging

In this study, a coumarin-based probe (probe 1) bearing a maleimide group was used to rapidly and selectively detect thiols.

An ultrafast turn-on thiol probe for protein labeling and bioimaging

A novel ultrafast turn-on thiol probe was developed that can be successfully applied to label protein thiols and imaging them in living cells.

Sensitive and selective determination of GSH based on the ECL quenching of Ru(II) 1,10-phenanthroline-5,6-dione complex

Electrochemiluminescence (ECL) material Ru-dpq (Ru(bpy)2dpq(2+), dpq=1,10-phenanthroline-5,6-dione; bpy=2,2'-bipyridine) is found to be produced strong and stable anodic ECL signal, which could be quenched by reduced glutathione (GSH) and exhibits high sensitivity and selectivity simultaneously. According to the mass spectra of Ru-SG (product of Ru-dpq reacted with GSH), and single crystal structure of the final oxidized product Ru-dcbpy ((Ru(bpy)2dcbpy(2+), dcbpy=3,3-dicarboxy-2,2-bipyridine), we propose a new interacted mechanism between Ru-dpq and GSH. A good linear relation is estimated to be from 0.1 pM to 50 μM in the presence of calcium ion and the detection limit is as low as 0.087 pM (with the signal-to-noise ratio of 3). The relative standard deviation is 2.3% (for three repeated measurements). Furthermore, the ECL signal of Ru-dpq under a constant potential (1.2V) is extremely stable and the intensity could be maintained over 600 s, which promotes us to determine the concentration of GSH via chronoamperometry.

A coumarin-based fluorescent turn-on probe for detection of biothiols in vitro

A novel fluorescent probe (CA-N) was designed and synthesized for detection of biothiols. CA-N displayed a strong fluorescence in the presence of biothiols with high sensitivity, and the mechanism for detection biothiols was based on the Michael addition reaction of a thiol group to α,β-unsaturated ketones. CA-N showed low detection limit for cysteine (Cys), homocysteine (Hcy), and glutathione (GSH), which were calculated as 3.16, 0.19 and 5.15 μM, respectively. At the same time, CA-N exhibited high selectivity toward biothiols compared with other biological amino acids. In vitro cell experiments proved that CA-N had no cytotoxicity, high cell permeability and could be employed in living cell imaging for biothiols.

Discriminative fluorescence sensing of biothiols in vitro and in living cells

Simultaneous discriminative sensing of biothiols in vitro and in living cells has remained challenging. Herein, we report a new sulfonamide-based self-quenched fluorescent probe 1 for this purpose with high sensitivity and good selectivity. Treatment of 1 with cysteine (Cys), homocysteine (Hcy), or glutathione (GSH) yields aminoluciferin, 2-cyano-6-aminobenzothiazole homocysteine (CBTHcy), or 2-cyano-6-aminobenzothiazole (CBT), turning "on" the fluorescence at wavelengths of 522, 517, or 490 nm, respectively. Kinetic study indicated that 1 reacts with Cys faster than with Hcy or GSH. With these unique properties of 1, we applied 1 for highly sensitive sensing of Cys, Hcy, and GSH among other 19 natural amino acids (AAs) with good selectivity. Confocal fluorescence microscopic imaging of 1-treated HepG2 cells at two channels (522 ± 8 and 490 ± 8 nm), together with quantitative analysis, indicated that the "turn-on" fluorescence was induced by intracellular Cys-dominating condensation and reduction of 1 but not by intracellular GSH-dominating reduction of 1. This suggests that 1 could be applied for discriminative sensing of intracellular Cys from the abundant GSH. Further development of 1 might bring about an efficient tool for probing cellular functions that relate to biothiols.

Voltammetric determination of homocysteine using multiwall carbon nanotube paste electrode in the presence of chlorpromazine as a mediator

We propose chlorpromazine (CHP) as a new mediator for the rapid, sensitive, and highly selective voltammetric determination of homocysteine (Hcy) using multiwall carbon nanotube paste electrode (MWCNTPE). The experimental results showed that the carbon nanotube paste electrode has a highly electrocatalytic activity for the oxidation of Hcy in the presence of CHP as a mediator. Cyclic voltammetry, double potential step chronoamperometry, and square wave voltammetry (SWV) are used to investigate the suitability of CHP at the surface of MWCNTPE as a mediator for the electrocatalytic oxidation of Hcy in aqueous solutions. The kinetic parameters of the system, including electron transfer coefficient, and catalytic rate constant were also determined using the electrochemical approaches. In addition, SWV was used for quantitative analysis. SWV showed wide linear dynamic range (0.1-210.0 μM Hcy) with a detection limit of 0.08 μM Hcy. Finally, this method was also examined as a selective, simple, and precise electrochemical sensor for the determination of Hcy in real samples.

Methods to assess amino acid requirements in humans

PURPOSE OF REVIEW

There are now different stable isotopic methods to measure minimum daily human indispensable amino acid (IAA) requirements. There has been debate on the appropriateness of statistical methods used to define the nature of change in the response.

RECENT FINDINGS

Current isotopic methods measure daily amino acid oxidation and balance of the IAA under test, or of a selected indicator amino acid, to graded intakes of the test IAA. A key concern is how response curves of oxidation/balance are analyzed to find the inflection point (breakpoint) at which the intake requirement is identified. Evaluating the pattern of the response to identify a breakpoint by a two-phase regression appears best. The indicator amino acid oxidation method has also been shortened and developed into a noninvasive protocol suitable for different populations and age groups.

SUMMARY

The indicator amino acid oxidation and balance method might be considered the best approach currently available, but it is challenging. The short-term indicator oxidation method is noninvasive and nondemanding. IAA requirements, based on these methods, have implications for the quality of protein in the dietary intake of populations. Methods that assess the IAA requirements to support optimal body function also need to be developed.

Measurement of human surfactant protein-B turnover in vivo from tracheal aspirates using targeted proteomics

We describe a method to measure protein synthesis and catabolism in humans without prior purification and use the method to measure the turnover of surfactant protein-B (SP-B). SP-B, a lung-specific, hydrophobic protein essential for fetal-neonatal respiratory transition, is present in only picomolar quantities in tracheal aspirate samples and difficult to isolate for dynamic turnover studies using traditional in vivo tracer techniques. Using infusion of [5,5,5-(2)H(3)] leucine and a targeted proteomics method, we measured both the quantity and kinetics of SP-B tryptic peptides in tracheal aspirate samples of symptomatic newborn infants. The fractional synthetic rate (FSR) of SP-B measured using the most abundant proteolytic fragment, a 10 amino acid peptide from the carboxy-terminus of proSP-B (SPTGEWLPR), from the circulating leucine pool was 0.035 +/- 0.005 h(-1), and the fractional catabolic rate was 0.044 +/- 0.003 h(-1). This technique permits high-throughput and sensitive measurement of turnover of low abundance proteins with minimal sample preparation.

Fluorescent and colorimetric probes for detection of thiols

Due to the biological importances of thiols, such as cysteine, homocysteine and glutathione, the development of optical probes for thiols has been an active research area in recent few years. This critical review focuses on the fluorescent or colorimetric sensors for thiols according to their unique mechanisms between sensors and thiols, including Michael addition, cyclization with aldehyde, cleavage of sulfonamide and sulfonate ester by thiols, cleavage of selenium-nitrogen bond by thiols, cleavage of disulfide by thiols, metal complexes-oxidation-reduction, metal complexes-displace coordination, nano-particles and others (110 references).

Association of homocysteine, asymmetric dimethylarginine, and nitric oxide with preeclampsia

PURPOSE

Endothelial dysfunction underlies the pathogenesis of preeclampsia, but its mechanism has not yet been completely understood. In this study we have aimed to measure homocysteine (Hcy), asymmetric dimethylarginine (ADMA), and nitric oxide (NO) levels as endothelial dysfunction markers in preeclamptic women.

METHODS

Control-case study with 62 preeclamptic patients and 30 controls without pregnancy complications was conducted. Plasma total Hcy, determined by capillary column gas chromatography/mass spectrometry (GC/MS), was correlated with serum ADMA (determined by liquid chromatography/tandem mass spectrometry using (13)C(6)-L: -arginine as the internal standard) and NO (analyzed by GC/MS).

RESULTS

There was a highly significant increase in the plasma concentration of homocysteine (P < 0.001) and ADMA (P < 0.001) and a highly significant decrease in the plasma concentration of nitric oxide (P < 0.001) among the preeclamptic patients. The differences were more significant between mild and severe preeclampsia, with and without eclampsia, with and without HELLP (hemolysis, elevated serum level of liver enzymes, and low platelets). In the combined patients and control groups a highly significant positive correlation was found between the plasma concentrations of homocysteine and ADMA (r = 0.853, P < 0.001). In addition, significant negative correlations were detected between the plasma concentrations of nitric oxide and the plasma concentration of homocysteine (r = -0.870, P < 0.001) and ADMA (r = -0.895, P < 0.001). These significant correlations were found to persist, even when they were restricted to the preeclamptic patients.

CONCLUSIONS

The homocysteine-ADMA-NO may be at least partly responsible for etiology in preeclampsia and could be regarded as markers for the severity of the disease. Therefore, L: -arginine may represent a novel therapy for the treatment of preeclampsia.

Determination of physiological thiols by electrochemical detection with piazselenole and its application in rat breast cancer cells 4T-1

Glutathione (GSH), the most abundant cellular thiol, has been shown to play an important role in maintaining cellular redox equilibrium that is pivotal for cell growth and function. In the present paper a novel electrochemical probe of piazselenole containing a Se-N bond was well developed for the determination of GSH. The cyclic voltammogram of piazselenole scanned at 100 mV/s displayed an irreversible reduction peak at -0.106 V (vs Ag/AgCl electrode) and a significant peak current decrease could be further provoked with the addition of GSH into piazselenole solution. On the basis of the peak current decrease of piazselenole recorded by differential pulse voltammetry with the increase of GSH concentration, a working curve was constructed for GSH determination in the range of 5.0 x 10(-10) approximately 2.2 x 10(-8) M with the linear regression equation as DeltaiP (10(-6)A) = 0.0952 + 0.4287 x CGSH (10(-8) M) and the detection limit (3sigma) as 83 pM. The proposed method was satisfactorily applied to the extracts of rat breast cancer cells 4T-1 for intracellular thiols detection.

High-throughput and simultaneous measurement of homocysteine and cysteine in human plasma and urine by liquid chromatography-electrospray tandem mass spectrometry

Total homocysteine (tHcy) and cysteine (tCys) concentrations in biological fluids are routinely used in the clinical diagnosis of genetic and metabolic diseases, and this necessitates the development of rapid and sensitive methods for quantification. Liquid chromatography-electrospray tandem mass spectrometry (LC-MS/MS) was used to measure tHcy and tCys in 23 plasma and 21 urine samples from healthy adults and 14 urine samples from healthy children. The results were compared with a standard high-performance liquid chromatography (HPLC) method. The coefficient of variation (CV) for the LC-MS/MS method ranged from 2.9% to 6.1% for the intraassay and 4.8% to 6.4% for the interassay. Mean recoveries were close to 100% for both plasma and urinary tHcy and tCys. The mean plasma tHcy and tCys concentrations in healthy adults were 8.62 and 261.40 micromol/L, respectively. The mean urinary tHcy and tCys in adults were 0.98 and 22.60 micromol/mmol creatinine, respectively. The mean urinary tHcy and tCys in children were 1.17 and 27.43 micromol/mmol creatinine, respectively. Bland-Altman difference plots of method comparison between LC-MS/MS and HPLC showed good agreement in plasma and urinary tHcy and tCys concentrations. Our method is suitable for rapid measurements, and the reported urinary values in children will help to develop a pediatric reference range for clinical use.