In Situ Ligand-Directed Growth of Gold Nanoparticles in Biological Tissues

Fundamental understandings and precise control of nanoparticle growth in the complex biological environment are crucial to broadening their potential applications in tissue imaging. Herein, we report that glutathione (GSH), a widely used capping ligand for precise control of the size of gold nanoparticle (AuNP) down to single-atom level in test tubes, can also be used to direct the selective growth of the AuNPs in the mitochondria of renal tubule cells as well as hippocampus cells in the tissues. Precise control of this growth process can lead to the formation of both ultrasmall AuNPs with near-infrared luminescence and large plasmonic AuNPs. The observed selective growth of the AuNPs is likely due to unique GSH storage function of the mitochondria. Using a different ligand, β-glucose thiol, we also found that the brush border of the intestine for glucose absorption became the major site for the growth of luminescent AuNPs. These findings suggest that selective growth of AuNPs in the biological tissues can indeed be directed with specific ligands, opening up a new avenue to tissue labeling and future development of artificial bionano hybrid systems.

Activatable Core-Shell Metallofullerene: An Efficient Nanoplatform for Bimodal Sensing of Glutathione

Metallofullerenes have attracted considerable attention as potential novel noninvasive high-relaxivity magnetic resonance contrast agents. However, the applications of metallofullerenes as stimuli-responsive biosensors to monitor biological processes are still scarce. Herein, manganese-fullerenes core-shell nanocomposites are prepared via a facile one-pot approach to achieve GSH-activatable magnetic resonance/fluorescence bimodal imaging functions. The nanocomposites initially have a FRET-induced quenched fluorescence, and water-resisting stimulated low T₁-MRI contrast. Upon exposure to GSH, collapse of the outer MnO₂ shell led to reconstruction of the nanoprobes and subsequently resulted in multicolor fluorescence recovery and longitudinal (T₁) relaxivity enhancement (r₁ value up to 29.8 mM^-1 s^-1 at 0.5 T based on Mn ion). Our work demonstrates feasibility of using fullerenes to fabricate activatable probes for molecular imaging of GSH, which may promote the development of new fullerene-based stimuli-responsive multimodal probes for the detection and regulation of particular biological processes in vivo.

One-Step Synthesis of Label-Free Ratiometric Fluorescence Carbon Dots for the Detection of Silver Ions and Glutathione and Cellular Imaging Applications

The construction of ratiometric fluorescence assay has displayed fantastic advantages in improving semi-quantitative visualization capability by presenting successive color changes. Herein, long-wavelength emission nitrogen-doped carbon dots (N-CDs) were developed for intrinsic ratiometric detection of silver ions (Ag⁺) and glutathione (GSH), accompanied by visualization fluorescence variation of orange and green. The label-free N-CDs were favorably obtained through one-step hydrothermal synthesis and displayed single long-wavelength emission at 618 nm under the excitation wavelength of 478 nm. Interestingly, a ratio rising peak emerges at 532 nm and the emission at 618 nm decreases with the introduction of Ag⁺, which exhibits ratiometric fluorescence emission characteristics ( I_618nm/ I_532nm) in the range of 0-140 μM with significant fluorescence varying from orange to green. Furthermore, the fluorescence of CDs@Ag(I) can be effectively ratiometric recovered by virtue of a specific reaction of GSH with Ag⁺, which is accompanied by the fluorescence of the solution returning from green to orange. In addition, the N-CDs hold excellent biocompatibility which can be implemented as the visualization biosensing platform for intracellular determination of Ag⁺ and GSH, demonstrating that proposed N-CDs have tremendous potential in biological systems.

A Fluorescence Inner-Filter Effect Based Sensing Platform for Turn-On Detection of Glutathione in Human Serum

A novel turn-on fluorescence assay was developed for the rapid detection of glutathione (GSH) based on the inner-filter effect (IFE) and redox reaction. Molybdenum disulfide quantum dots (MoS₂ QDs), which have stable fluorescent properties, were synthesized with hydrothermal method. Manganese dioxide nanosheets (MnO₂ NSs) were prepared by exfoliating the bulk δ-MnO₂ material in bovine serum albumin (BSA) aqueous solution. The morphology structures of the prepared nanoparticles were characterized by transmission electron microscope (TEM). Studies have shown that the fluorescence of MoS₂ QDs could be quenched in the presence of MnO₂ NSs as a result of the IFE, and is recovered after the addition of GSH to dissolve the MnO₂ NSs. The fluorescence intensity showed a good linear relationship with the GSH concentration in the range 20⁻2500 μM, the limit of detection was 1.0 μM. The detection method was applied to the analysis of GSH in human serum samples. This simple, rapid, and cost-effective method has great potential in analyzing GSH and in disease diagnosis.

Real-Time Monitoring of Glutathione in Living Cells Reveals that High Glutathione Levels Are Required to Maintain Stem Cell Function

The core functions of stem cells (SCs) are critically regulated by their cellular redox status. Glutathione is the most abundant non-protein thiol functioning as an antioxidant and a redox regulator. However, an investigation into the relationship between glutathione-mediated redox capacity and SC activities is hindered by lack of probe. Here, we demonstrate that cyanoacrylamide-based coumarin derivatives are ratiometric probes suitable for the real-time monitoring of glutathione levels in living SCs. These probes revealed that glutathione levels are heterogeneous among subcellular organelles and among individual cells and show dynamic changes and heterogeneity in repopulating SCs depending on oxidative stress or culture conditions. Importantly, a subpopulation of SCs with high glutathione levels exhibited increased stemness and migration activities in vitro and showed improved therapeutic efficiency in treating asthma. Our results indicate that high glutathione levels are required for maintaining SC functions, and monitoring glutathione dynamics and heterogeneity can advance our understanding of the cellular responses to oxidative stress.

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FreSHtracer is a reversible probe for a fast and ratiometric reaction with GSH

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FreSHtracer and its derivatives enable real-time monitoring of intracellular GSH

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FreSHtracer reports dynamic changes and heterogeneity of GSH level in stem cells

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High GSH levels are required for maintaining functional potency of stem cells

Simultaneous quantitation of oxidized and reduced glutathione via LC-MS/MS: An insight into the redox state of hematopoietic stem cells

Cellular redox balance plays a significant role in the regulation of hematopoietic stem-progenitor cell (HSC/MPP) self-renewal and differentiation. Unregulated changes in cellular redox homeostasis are associated with the onset of most hematological disorders. However, accurate measurement of the redox state in stem cells is difficult because of the scarcity of HSC/MPPs. Glutathione (GSH) constitutes the most abundant pool of cellular antioxidants. Thus, GSH metabolism may play a critical role in hematological disease onset and progression. A major limitation to studying GSH metabolism in HSC/MPPs has been the inability to measure quantitatively GSH concentrations in small numbers of HSC/MPPs. Current methods used to measure GSH levels not only rely on large numbers of cells, but also rely on the chemical/structural modification or enzymatic recycling of GSH and therefore are likely to measure only total glutathione content accurately. Here, we describe the validation of a sensitive method used for the direct and simultaneous quantitation of both oxidized and reduced GSH via liquid chromatography followed by tandem mass spectrometry (LC-MS/MS) in HSC/MPPs isolated from bone marrow. The lower limit of quantitation (LLOQ) was determined to be 5.0ng/mL for GSH and 1.0ng/mL for GSSG with lower limits of detection at 0.5ng/mL for both glutathione species. Standard addition analysis utilizing mouse bone marrow shows that this method is both sensitive and accurate with reproducible analyte recovery. This method combines a simple extraction with a platform for the high-throughput analysis, allows for efficient determination of GSH/GSSG concentrations within the HSC/MPP populations in mouse, chemotherapeutic treatment conditions within cell culture, and human normal/leukemia patient samples. The data implicate the importance of the modulation of GSH/GSSG redox couple in stem cells related diseases.

[ELEMENTS OF THE LOW MOLECULAR WEIGHT CHAIN OF ANTIOXIDANT DEFENSE IN TISSUES OF THE BLACK SEA MOLLUSC ANADARA KAGOSHIMENSIS BRUGÙIERE]

The content of reduced glutathione (GSH) and the activity of the coupled with it antioxidant enzymes - glutathione peroxidase and glutathione reductase as well the level of glucose, carbamide and amino acids were investigated in the hepatopancreas, gills and foot of the Black, Sea mollusk Anadara kagoshimensis. The highest content of GSH and the highest activity of glutathione peroxidase were found in mollusk foot, evidencing the active antioxidant role of glutathione played both within composition of this enzyme and independently. The maximal content of glucose, amino acids and carbamide was in the hepatopancreas and gills and the minimal - in the anadara's foot. The possible involvement and role of these low molecular weight antioxidants in the defense of mollusk tissues against action of free radical oxidation and in providing adaptation reactions of anadara in hypoxic habitats are considered. Key words: antioxidant complex, glutathione, glucose, carbamide, amino acids, anadara Anadara kagoshimensis, Black Sea.

4-Hydroxybenzyl-substituted glutathione derivatives from Gastrodia elata

Seven new 4-hydroxybenzyl-substituted glutathione derivatives (2-8), together with a known analogue (1), were isolated from the aqueous extract of Gastrodia elata Blume rhizomes. Their structures were determined by using spectroscopic and chemical methods. The absolute configurations of 1-8 were assigned by using Marfey's method, combined with comparing the NMR and CD spectroscopic data of sulfoxide moieties in 3-6 with those of S-(4-hydroxybenzyl)cysteine sulfoxide stereoisomers (9-12) synthesized as authentic samples. The configurations of 9-12 were confirmed by electronic CD calculations based on the quantum-mechanical time-dependent density functional theory. Furthermore, the structures of 1, 3, 5, 7, and 8 were verified by synthesis. Compound 3 was active against serum deprivation-induced PC12 cell damage and synthetic 9-14 exhibited activity against Fe(2+)-cysteine induced rat liver microsomal lipid peroxidation.

Candida utilis assimilates oligomeric sugars in rice straw hydrolysate via the Calcium-Capturing-by-Carbonation (CaCCO) process for glutathione- and cell-biomass production

Rice-straw hydrolysate (RSH) prepared via the CaCCO (Calcium Capturing by Carbonation) process contains not only monosaccharides but also significant amounts of oligosaccharides. In this study, a glutathione-producing yeast, Candida utilis NBRC 0626, was found to assimilate those oligosaccharides. The yields of reduced glutathione (GSH) and dry cell weight (DCW) per consumed sugars in a medium with RSH after 72h incubation were 10.1mg/g-sugars and 0.49g/g-sugars, respectively. The yields were comparative to those in a medium containing a model monosaccharide mix, suggesting that the assimilated oligosaccharides contribute to additional GSH and DCW production. Glycosyl linkage analysis indicated that the yeast could cleave xylose-, galactose-, and arabinose residues as well as glucose residues at the non-reducing ends. After 72h incubation, 99.1% of the total glucose residues and 84.2% of the total xylose residues in RSH were depleted. Thus the yeast could be applied for efficient utilization of lignocellulosic hydrolysates.

Mass spectrometry characterization of trypanothione and novel peptides of medical importance isolated from Acanthamoeba polyphaga

This paper presents unequivocal results about the presence of trypanothione and its precursor glutathionespermidine from the opportunistic human pathogen Acanthamoeba polyphaga. They were isolated by RP-HPLC as thiolbimane derivatives and characterized using matrix-assisted laser desorption ionization-time-of-flight (MALDI-TOF/TOF). Additionally RP-HPLC demonstrated that thiol-bimane compounds corresponding to cysteine and glutathione were also present in A. polyphaga. Besides trypanothione, we want to report four new peptides in trophozoites, a tetrapeptide, a hexapeptide, a heptapeptide and a nonapeptide. Trypanothione and two of the thiol peptides, the hexapeptide and heptapeptide, are oxidized since the reduced forms increase in amount when the normal extract is treated by DTT or by electrolytic reduction that convert the oxidized forms to reduced ones. On the other hand, they disappear when the amoeba extract is treated with NEM or when the amoeba culture is treated with various inhibitors of NADPH-dependent disulfidereducing enzymes. Comparison of the thiol peptides, including trypanothione from A. polyphaga with extracts from human lymphocytes showed that they are not present in the latter. Therefore, some of the peptides here reported could be used as antigens for rapid detection of these parasites. In regard to the presence of the enzymes that synthesize and reduce trypanothione in A. polyphaga we suggest that they can be used as drug targets.

Improved co-production of S-adenosylmethionine and glutathione using citrate as an auxiliary energy substrate

The effects of sodium citrate on the fermentative co-production of S-adenosylmethionine (SAM) and glutathione (GSH) using Candida utilis CCTCC M 209298 were investigated. Sodium citrate was beneficial for the biosynthesis of SAM and GSH and in turn improved intracellular SAM and GSH contents. Adding 2 g/L of sodium citrate at 15 h was the most efficient approach for achieving elevated co-production of SAM and GSH. Using this sodium citrate addition mode, co-production of SAM and GSH reached 663.9 mg/L, which was increased by 27.5% compared to the control. Based on analysis of the kinetic parameters, evaluation of the energy metabolism and assay of key enzymes, sodium citrate was verified to act as an auxiliary energy substrate for the overproduction of SAM and GSH.

Photoelectrochemical detection of glutathione by IrO2-hemin-TiO2 nanowire arrays

We have developed sensitive detection of glutathione using the IrO2-hemin-TiO2 nanowire arrays. Single-crystalline TiO2 nanowires are synthesized by a hydrothermal reaction, followed by surface functionalization of ~3 nm thick hemin and ~1-2 nm diameter IrO2 nanoparticles. The IrO2-hemin-TiO2 nanowire arrays offer much enhanced photocurrent with ∼100% increase compared to the pristine TiO2 nanowires and allow for label-free, real-time, sensitive photoelectrochemical detection of glutathione. The sensitivity achieved is ~10 nM in buffer, comparable to or better than most of the existing glutathione detection methods. Furthermore, cell extracts containing glutathione are robustly detected, with ~8000 cells/mL for HeLa cells and ~5000 cells/mL for human embryonic kidney 293T cells. This nanowire PEC sensor assay exhibits excellent selectivity and stability, suggesting a potential detection platform for analyzing the glutathione level in biosamples.

Electrophoretic separations in poly(dimethylsiloxane) microchips using a mixture of ionic and zwitterionic surfactants

The use of mixtures of ionic and zwitterionic surfactants in poly(dimethylsiloxane) (PDMS) microchips is reported. The effect of surfactant concentration on electroosmotic flow (EOF) was studied for a single anionic surfactant (sodium dodecyl sulfate, SDS), a single zwitterionic surfactant (N-tetradecylammonium-N,N-dimethyl-3-ammonio-1-propanesulfonate, TDAPS), and a mixed SDS/TDAPS surfactant system. SDS increased the EOF as reported previously while TDAPS showed an initial increase in EOF followed by a reduction at higher concentrations. When TDAPS was added to a solution containing SDS, the EOF decreased in a concentration-dependent manner. The EOF for all three surfactant systems followed expected pH trends, with increasing EOF at higher pH. The mixed surfactant system allowed tuning of the EOF across a range of pH and concentration conditions. After establishing the EOF behavior, the adsorption/desorption kinetics were measured and showed a slower adsorption/desorption rate for TDAPS than SDS. Finally, the separation and electrochemical detection of model catecholamines in buffer and reduced glutathione in red blood cell lysate using the mixed surfactant system were explored. The mixed surfactant system provided shorter analysis times and/or improved resolution when compared to the single surfactant systems.

Spectrofluorimetric determination of glutathione in human plasma by solid-phase extraction using graphene as adsorbent

An efficient solid phase extraction-spectrofluorimetric method using graphene as adsorbent was developed to sensitively determine glutathione (GSH) in biological samples. Fluorescent probe N-(4,4-difluoro-5,7-dimethyl-4-bora-3a,4a-diaza-s-indacene-3-yl)methyl)iodoacetamide (BODIPY Fl-C1-IA) was applied for the derivatization of GSH. The procedure was based on BODIPY Fl-C1-IA selective reaction with GSH to form highly fluorescent product BODIPY Fl-C1-IA-GSH, its extraction to the graphene-packed SPE cartridge and spectrofluorimetric determination. Some factors affecting the extraction efficiency, such as the type of the eluent and its volume, sample pH, extraction time, and sample volume were optimized. Comparative studies were also performed between graphene and other adsorbents including C18 silica, graphitic carbon, and multi-walled carbon nanotubes for the extraction of analyte. The calibration graph using the pretreatment system for GSH was linear over the range of 0.5-200 nM. The limit of detection was 0.01 nM (signal-to-noise ratio=3). Relative standard deviation for six replicate determinations of GSH at 80 nM concentration level was lower than 5.0%. The developed method was applied to the determination of GSH in human plasma with recoveries of 92-108%. This work revealed the great potentials of graphene as an excellent sorbent material in the analysis of biological samples.

Characterization and detection in cells of a novel adduct derived from the conjugation of glutathione and dehydroascorbate

Glutathione (GSH) and ascorbate (ascorbic acid, vitamin C, ASC) are two critical water-soluble antioxidants in aerobic organisms. The reaction of ascorbate with reactive oxygen species leads to dehydroascorbate. It is generally accepted that GSH reduces dehydroascorbate (DHA) to give oxidized glutathione (GSSG) and ASC (2GSH+DHA-->GSSG+ASC) as a chemical pathway of ascorbate regeneration. Here, we report the formation of a novel conjugation product between GSH and the decomposition of DHA denoted as GS-DHA*. On the basis of MS and NMR analyses, the structure of GS-DHA* consists of an intact GSH moiety attached via the thiol group to a five-carbon fragment of DHA. The conjugation product appears as a mixture of four diastereomers with very similar proton and carbon chemical shifts. The formation of GS-DHA* adducts is demonstrated in Jurkat cells upon incubation with DHA in culture followed by analysis of the whole-cell extracts by HPLC coupled to tandem mass spectrometry. This novel conjugation product may be a useful biomarker of DHA stress and model system of protein modification.

Integration of a precolumn fluorogenic reaction, separation, and detection of reduced glutathione

Reduced glutathione (GSH) has been determined by fluorescence detection after derivatization together with a variety of separations. The reactions between GSH and fluorescent reagents usually are carried out during the sample pretreatment and require minutes to hours for complete reactions. For continuous monitoring of GSH, it would be very convenient to have an integrated microdevice that could perform online precolumn derivatization, separation, and detection. Heretofore, thiol-specific fluorogenic reagents require fairly long reaction times, preventing effective online precolumn derivatization. We demonstrate here that the fluorogenic, thiol-specific reagent, ThioGlo-1, reacts rapidly enough for efficient precolumn derivatization. The second order rate constant for the reaction of GSH and reagent (pH 7.5, room temperature) is 2.1 x 10(4) M(-1)s(-1). The microchip integrates this precolumn derivatization, continuous flow gated sampling, separation, and detection on a single device. We have validated this device for monitoring GSH concentration continuously by studying the kinetics of glutathione reductase (EC 1.8.1.7), an enzyme that catalyzes the reduction of oxidized glutathione (GSSG) to GSH in the presence of beta-NADPH (beta-nicotinamide adenine dinucleotide phosphate, reduced form) as a reducing cofactor. During the experiment, GSH being generated in the enzymatic reaction was labeled with ThioGlo-1 as it passed through a mixing channel on the microfluidic chip. Derivatization reaction products were introduced into the analysis channel every 10 s using flow gated injections of 0.1 s. Baseline separation of the internal standard, ThioGlo-1, and the fluorescently labeled GSH was successfully achieved within 4.5 s in a 9 mm separation channel. Relative standard deviations of the peak area, peak height, and full width at half-maximum (fwhm) for the internal standard were 2.5%, 2.0%, and 1.0%, respectively, with migration time reproducibility for the internal standard of less than 0.1% RSD in any experiment. The GSH concentration and mass detection limit were 4.2 nM and approximately 10(-18) mol, respectively. The Michaelis constants (K(m)) for GSSG and beta-NADPH were found to be 40 +/- 11 and 4.4 +/- 0.6 muM, respectively, comparable with those obtained from UV/vis spectrophotometric measurements. These results show that this system is capable of integrating derivatization, injection, separation, and detection for continuous GSH determinations.

[Markers of chloric acid (I) in biological systems--identification and properties]

Reactive oxygen and nitrogen species are attributed to initiation and propagation of many diseases. The demonstration of elevated activity of myeloperoxidase and the level of 3-chlorotyrosine in atherosclerosis, kidney diseases and chronic inflammations brought about the interest in the biological role of another strong oxidant--hypochlorite. Concentration of this compound is extremely difficult to estimate in vivo and in vitro because of its high reactivity. The reaction of hypochlorite with biological compounds lead to formation of chlorohydrins, glutathione sulfonamides, chloramines, 3- and 3,5-dichlorotyrosines and chlorinated DNA bases (8-chloroadenine, 8-chloroguanine, 5-chlorocytosine and 5-chlorouracil). At least some of these products of hypochlorite action are believed to provide specific HOCl-biomarkers, useful especially in the analysis of clinical samples, using sensitive detection techniques.

Efficient extraction of intracellular reduced glutathione from fermentation broth of Saccharomyces cerevisiae by ethanol

Reduced glutathione (GSH) from fermentation broth of Saccharomyces cerevisiae was extracted with ethanol without disruption of the cells. The effects of ethanol concentration, extraction temperature and extraction time were assessed by using 2(3) full factorial designs (FFD). Preliminary studies showed that ethanol concentration had the most influence on GSH yield by ethanol extraction, based on the first order regression coefficients derived using MINITAB software, and an optimal ethanol concentration (25%, v/v) was obtained. However, compared to the conventional extraction technique (hot water extraction), there was no significant advantage in yield of GSH from yeast cells using ethanol extraction under these optimized conditions. But ethanol extraction has several advantages, such as lower energy consumption and lower protein concentration of extraction broth, which may reduce the complexity and cost of the purification process. Hence, ethanol extraction which does not disrupt yeast cells could be an inexpensive, simple and efficient alternative to conventional extraction techniques in the GSH industry.

Wounding of Arabidopsis leaves causes a powerful but transient protection against Botrytis infection

Physical injury inflicted on living tissue makes it vulnerable to invasion by pathogens. Wounding of Arabidopsis thaliana leaves, however, does not conform to this concept and leads to immunity to Botrytis cinerea, the causal agent of grey mould. In wounded leaves, hyphal growth was strongly inhibited compared to unwounded controls. Wound-induced resistance was not associated with salicylic acid-, jasmonic acid- or ethylene-dependent defence responses. The phytoalexin camalexin was found to be involved in this defence response as camalexin-deficient mutants were not protected after wounding and the B. cinerea strains used here were sensitive to this compound. Wounding alone did not lead to camalexin production but primed its accumulation after inoculation with B. cinerea, further supporting the role of camalexin in wound-induced resistance. In parallel with increased camalexin production, genes involved in the biosynthesis of camalexin were induced faster in wounded and infected plants in comparison with unwounded and infected plants. Glutathione was also found to be required for resistance, as mutants deficient in gamma-glutamylcysteine synthetase showed susceptibility to B. cinerea after wounding, indicating that wild-type basal levels of glutathione are required for the wound-induced resistance. Furthermore, expression of the gene encoding glutathione-S-transferase 1 was primed by wounding in leaves inoculated with B. cinerea. In addition, the priming of MAP kinase activity was observed after inoculation of wounded leaves with B. cinerea compared to unwounded inoculated controls. Our results demonstrate how abiotic stress can induce immunity to virulent strains of B. cinerea, a process that involves camalexin and glutathione.

First report of phytochelatins in a mushroom: induction of phytochelatins by metal exposure in Boletus edulis

Some species of macromycetes (mushrooms) consistently are found to contain high concentrations of toxic metals such as cadmium (Cd) and mercury (Hg), and consumption of wild-growing mushrooms is acknowledged as a significant source for Cd and Hg in humans. Yet little is known about the speciation of Cd and Hg in mushroom tissues. Here we present the first evidence of peptides of the phytochelatin family being responsible for binding a large fraction of Cd in caps of the macromycete Boletus edulis exposed to excess metals. Concentrations of Cd, Zn, Cu and Hg, as well as cytosolic Cd-binding capacity (CCBC), glutathione (GSH) and free proline (Pro) were quantified in fruiting bodies of B. edulis differentially exposed to a wide range of metals. Metal distribution among cytosolic compounds were investigated by size exclusion chromatography (SEC), followed by metal determinations with atomic absorption chromatography (AAS) and HR-ICP-MS. Cd-binding compounds in SEC elutates were investigated further by high performance liquid chromatography-mass spectrometry (HPLC-MS). CCBC was >90 times higher in the exposed group relative to the reference group (Mann-Whitney's P < 0.001), whereas concentrations of free Pro were almost identical for the two groups. For the whole study selection, CCBC correlated positively with metal exposure (Spearman's P < 0.001 for all four metals), suggesting dose-dependent induction of Cd-binding compounds by exposure to these metals, possibly as a defense mechanism. The presence of phytochelatins (PCs), a family of cystein-rich oligopeptides, was confirmed in Cd-containing SEC fractions by HPLC-MS. The appearance of more complex PCs was coupled to declining concentrations of GSH. To our knowledge this is the first report demonstrating the presence of PCs in a macromycete.

[Research development of chemistry and bioactive activity of plant peptides]

As the technologies of separation, purification and determination develop rapidly, more and more peptide compounds, which have special bioactive and medical value, have been separated from natural plants, such as oligopeptides and cyclopeptides. The chemical structures and function of these plant peptides have been researched profoundly. This paper mainly reviews the composition, structure, bioactive function and medicine value of representative plant peptides in recent years, and can give some references about research and application of plant bioactive peptides.

Simplified current decoupler for microchip capillary electrophoresis with electrochemical and pulsed amperometric detection

There is a need to develop broadly applicable, highly sensitive detection methods for microchip CE that do not require analyte derivatization. LIF is highly sensitive but typically requires analyte derivatization. Electrochemistry provides an alternative method for direct analyte detection; however, in its most common form, direct current (DC) amperometry, it is limited to a small number of easily oxidizable or reducible analytes. Pulsed amperometric detection (PAD) is an alternative waveform that can increase the number of electrochemically detectable analytes. Increasing sensitivity for electrochemical detection (EC) and PAD requires the isolation of detection current (nA) from the separation current (muA) in a process generally referred to as current decoupling. Here, we present the development of a simple integrated decoupler to improve sensitivity and its coupling with PAD. A Pd microwire is used as the cathode for decoupling and a second Au or Pt wire is used as the working electrode for either EC or PAD. The electrode system is easy to make, requiring no clean-room facilities or specialized metallization systems. Sensitive detection of a wide range of analytes is shown to be possible using this system. Using this system we were able to achieve detection limits as low as 5 nM for dopamine, 74 nM for glutathione, and 100 nM for glucose.

Separation and quantification ofN-acetyl-l-cysteine andN-acetyl-cysteine-amide by HPLC with fluorescence detection

N-acetyl-l-cysteine (NAC) is a well-known antioxidant that is capable of facilitating glutathione (GSH) biosynthesis and replenishing intracellular GSH under oxidatively challenging circumstances. N-acetyl-cysteine-amide (NACA), the amide form of NAC, is a newly designed and synthesized thiol-containing compound which is believed to be more lipophilic and permeable through cell membranes than NAC. The metabolic and antioxidant effects of these compounds in vitro and in vivo are under investigation. However, an analytical method that can separate and quantify both compounds simultaneously is not yet available, to the best of our knowledge. Because of their structural similarities, the two compounds are difficult to separate using earlier HPLC methods which were designed for NAC quantification. Therefore, the goal of this work was to develop an HPLC method with fluorescence detection for simultaneous quantification of NAC and NACA in biological blood and tissue samples. A gradient HPLC program with fluorescence detection (lambda(ex) = 330 nm, lambda(em) = 376 nm) using N-(1-pyrenyl)maleimide (NPM) as the derivatizing agent was developed. The calibration curves were linear over a concentration range of 25-5000 nm (r(2) > 0.997). The coefficients of variation for within-run precision and between-run precision ranged from 0.67 to 5.23% and for accuracy ranged from 0.98 to 10.54%; the percentage relative recovery ranged from 94.5 to 102.8%. This new method provides satisfactory separation of NAC and NACA, along with other biological thiols, in 20 min with a 5 nm limit of detection (LOD) per 5 microL injection volume.

On-column preconcentration of glutathione and glutathione disulfide using pH-mediated base stacking for the analysis of microdialysis samples by capillary electrophoresis

Capillary electrophoresis (CE) has become a useful analytical tool for the analysis of microdialysis samples. However, CE with UV detection (CE-UV) does not provide detection limits sufficient to quantify glutathione (GSH) and glutathione disulfide (GSSG) in biological samples such as liver microdialysates, because of the small optical path length in the capillary. To overcome this limitation, an on-column preconcentration technique, pH-mediated base stacking, was used in this study to improve the sensitivity of CE-UV. This stacking technique allowed large volumes of high ionic strength sample injection without deterioration of the separation efficiency and resolution. A 26-fold increase in sensitivity was achieved for both GSH and GSSG using the pH-mediated base stacking, relative to normal injection without stacking. The limit of detection for GSH and GSSG was found to be 0.75 microM (S/N=6) and 0.25 microM (S/N=6), respectively. The developed method was used to analyze GSH and GSSG in liver microdialysates of anesthetized Sprague Dawley male rats. The basal concentrations of GSH and GSSG in the liver microdialysates of male rats were found to be 4.73+/-2.08 microM (n=7) and 5.52+/-3.66 microM (n=7), respectively.

Biosynthesis of Cd-bound phytochelatins by Phaeodactylum tricornutum and their speciation by size-exclusion chromatography and ion-pair chromatography coupled to ICP–MS

Cd-bound phytochelatins (Cd-PCs) have been synthesised by incubation of Phaeodactylum tricornutum cell cultures with Cd and purified by size-exclusion chromatography-UV-Vis. These complexes, which were identified in previous work, have now been used as model substances to develop and optimise ion-pair chromatography (IPC) coupled to inductively coupled plasma-mass spectrometry (ICP-MS) for analysis of Cd-PCs. Subsequent analysis of samples taken from Silene vulgaris plants cultivated under heavy metal stress conditions revealed Cd signals but no Cd-PC signals. By use of isotopically enriched (116)Cd-PCs the sample preparation steps were verified to determine the stability of the analytes. We observed species transformation between Cd-PCs and other unidentified Cd complexes. Consequently, the kinetic and thermodynamic lability of Cd-PCs are decisive factors in their detection.

Identification of trypanothione from the human pathogen Entamoeba histolytica by mass spectrometry and chemical analysis

In this paper, we present definitive data to show, from ESI (electrospray ionization) studies, that the thiol-bimane compound isolated and purified from Entamoeba histolytica trophozoites, corresponds unequivocally to the structure of trypanothione. Trypanothione disulphide was shown to have a molecular ion of m/z 722. It was further demonstrated by MALDI-TOF (matrix-assisted laser desorption ionization-time-of-flight) MS that this thiol compound also corresponds to the characteristic monoprotonated ion of trypanothione-(bimane)(2), which has a molecular ion of m/z 1103.95. The ion pattern of the thiol-bimane compound prepared from the commercial trypanothione standard is identical with the E. histolytica thiol-bimane compound. After HPLC separation, chemical amino acid analysis by dabsylation and dansylation of the thiol bimane compound from Entamoeba showed the presence of the following trypanothione components: glutamic acid, cysteic acid, glycine and spermidine. We can conclude from these highly reliable MS experiments and chemical analyses that E. histolytica contains the thiol compound trypanothione, which was previously thought to occur only in trypanosomatids.

Capillary electrophoresis of glutathione to monitor oxidative stress and response to antioxidant treatments in an animal model

Glutathione plays a central role in metabolism and antioxidant defence. Several factors can influence the analytical efficiency and rapidity of the quantitative determination of glutathione. Procedures in sample pre-treatment have been compared in order to minimize analytical errors. Capillary electrophoresis has been chosen as a more adequate technique for obtaining a rapid and simple method for glutathione and glutathione disulfide determination in the blood and liver of the rat. The methods, once optimised, have been validated and applied for monitoring the oxidative stress in an animal model, such as the rat made diabetic by streptozotocin injection, when the animals are treated with antioxidants and compared with the corresponding controls.

[Separation and purification of proteins on monolithic anion-exchange columns]

A monolithic anion-exchange column with glycidyl methacrylate as the functional monomer and ethylene dimethacrylate as the cross linker was prepared by a free radical polymerization. The epoxide groups of the column were modified respectively by triethylamine, diethylamine and ethylenediamine that afforded anionic functionalities required for the anion-exchange chromatographic mode. The properties of the monolithic columns were investigated and the columns were successfully used as stationary phases of high performance liquid chromatography for the separation of proteins. For chromatographic analysis the effects of mobile phase composition and pH on the separation were investigated. The optimum separation for bovine serum albumin, lysozyme and glutathione was achieved with a gradient elution of mobile phase A (0.01 mol/L Tris-HCl (pH 7.0)) and mobile phase B (mobile phase A + 1.0 mol/L NaCl) with a flow rate of 1.0 mL/min at 25 degrees C. The optimum purification for cellulase enzyme was obtained with a gradient elution of mobile phase A (0.01 mol/L Tris-HCl (pH 7.1)) and mobile phase B (mobile phase A + 1.0 mol/L KBr) with the same flow rate and temperature. The columns exhibited good stability, and cellulase enzyme could be separated and purified quickly on the monolithic anion-exchange column modified by diethylamine.

Capillary zone electrophoresis for analysis of phytochelatins and other thiol peptides in complex biological samples derivatized with monobromobimane

A new method to improve the analysis of phytochelatins and their precursors (cysteine, gamma-Glu-Cys, and glutathione) derivatized with monobromobimane (mBrB) in complex biological samples by capillary zone electrophoresis is described. The effects of the background electrolyte pH, concentration, and different organic additives (acetonitrile, methanol, and trifluoroethanol) on the separation were studied to achieve optimum resolution and number of theoretical plates of the analyzed compounds in the electropherograms. Optimum separation of the thiol peptides was obtained with 150 mM phosphate buffer at pH 1.60. Separation efficiency was improved when 2.5% v/v methanol was added to the background electrolyte. The electrophoretic conditions were 13 kV and capillary dimensions with 30 cm length from the inlet to the detector (38 cm total length) and 50 microm inner diameter. The injection was by pressure at 50 mbar for 17 s. Under these conditions, the separation between desglycyl-peptides and phytochelatins was also achieved. We also describe the optimum conditions for the derivatization of biological samples with mBrB to increase electrophoretic sensitivity and number of theoretical plates. The improved method was shown to be simple, reproducible, selective, and accurate in measuring thiol peptides in complex biological samples, the detection limit being 2.5 microM glutathione at a wavelength of 390 nm.

Isolation and characterisation of renal metabolites of γ-glutamylfelinylglycine in the urine of the domestic cat (Felis catus)

The renal metabolism of the tripeptide, gamma-glutamylfelinylglycine, which our group recently identified in the blood of domestic cats (Felis catus), was investigated. To test our hypothesis that this unique tripeptide is metabolised by the kidney in a similar manner to glutathione-S-conjugates in other animal species, [(35)S]cysteine was administered intraperitoneally to an entire male cat, and urine collected at 1, 4 and 8 h post-injection. Radiolabelled fractions were isolated from the urine following reversed-phase (RP) HPLC. Four [(35)S]radiolabelled fractions were identified and characterised by amino acid analysis, mass spectrometry and comparison of retention times with synthetic compounds (felinine, N-acetyl felinine, felinylglycine, gamma-glutamylfelinylglycine). In addition to the previously described presence of free felinine, we showed the presence of several felinine-containing metabolites, including N-acetyl felinine, felinylglycine and unaltered gamma-glutamylfelinylglycine in cat urine. The results show that renal metabolism of gamma-glutamylfelinylglycine in cats, generally occurs in a similar manner to glutathione S-conjugates in other animal species, although the detection of felinylglycine indicates that subtle differences may exist. Additionally, our research indicates that previously reported estimates of felinine excretion in male cats need to be increased by as much as 54% to account for other felinine containing metabolites in the urine.

Optimization of the principal parameters for the ultrarapid electrophoretic separation of reduced and oxidized glutathione by capillary electrophoresis

Several factors can influence the analytical efficiency and rapidity of the quantitative determination of erythrocyte glutathione by capillary zone electrophoresis (CZE). We optimized the time, efficiency and resolution of the electrophoretic separation of reduced (GSH) and oxidized (GSSG) glutathione by studying the influence of the most important factors affecting the separation, i.e. the pH and ionic strength of the electrolyte solution, the capillary length and temperature. Best results in the shortest time are obtained at 25 degrees C, using an uncoated 37 cm x 75 microm i.d. capillary and a 300 mmol/l borate buffer pH 7.8. These conditions give a good reproducibility of the corrected peak areas (R.S.D. 1.41 and 1.31%) and of the migration time (R.S.D. 0.22 and 0.26%) for GSH and GSSG, respectively. The high concentration buffer, besides permitting a good resolution of standard GSH and GSSG mix, allows also N-nitrosoglutathione detection. By shortening the capillary length to 27 cm, the separation time of GSH and GSSG can be further decreased to less than 60s. This shortened method, the most rapid described in literature, can detect and quantify GSH in red blood cells despite a loss of sensitivity. To compare the new method here described with the Beutler colorimetric method, the data relative to the GSH content of red blood cells from young normal subjects were analyzed by the Passing and Bablok regression and the Bland-Altman test.

Temporal changes in muscle glutathione in ICU patients

OBJECTIVE

This study investigated the changes over time in glutathione and its constituent amino acids in skeletal muscle of ICU patients with multiple organ failure.

DESIGN AND SETTING

Prospective and descriptive pilot study in two medium-sized ICUs with ten beds.

PATIENTS

Critically ill patients ( n=10) with multiple organ failure and with an expected ICU stay longer than 6 days were included during their initial 3 days after admission to the ICU.

MEASUREMENTS AND RESULTS

Muscle biopsy and blood samples were taken on days 0, 3, and 6 after inclusion and total, reduced, and oxidized glutathione and the related amino acids were determined. During the study period both total and reduced glutathione increased and was in the normal range on day 6. The constituent amino acids normalized during the study period as well.

CONCLUSIONS

This pilot study demonstrates a recovery of muscle glutathione concentrations in critically ill patients with ongoing multiple organ failure within 1 week. Restoration of muscle glutathione seems to be a biological process of high priority in this group of patients.

N-methyl-D-glucamine improves the laser-induced fluorescence capillary electrophoresis performance in the total plasma thiols measurement

We describe an ultrarapid capillary electrophoresis with laser-induced fluorescence (CE-LIF) method for total plasma thiols measurement. Reduced thiols by 10% tri-n-butylphosphine (TBP) were derivatized in 10 min at room temperature with 5-iodoacetamidofluorescein (5-IAF) as fluorescent reagent. We show that CE-LIF allows a baseline separation of total plasma cysteinylglycine, homocysteine, cysteine, and glutathione in less than 5 min when N-methyl-D-glucamine in run buffer was added. CE was compared with high-performance liquid chromatography (HPLC) with fluorescence detection. The Bland-Altman test and Passing-Bablok regression demonstrates that the results obtained by CE-LIF and by HPLC are highly comparable. The simplified procedure of sample preparation, the short incubation and fast separation times, the high specificity, sensitivity and reproducibility, and the lower cost of analysis suggest that our proposed method can be considered valuable for the automation analysis in a routine laboratory.

Ultrarapid capillary electrophoresis method for the determination of reduced and oxidized glutathione in red blood cells

We describe a very rapid high-performance capillary electrophoresis method for the separation and quantification of reduced (GSH) and oxidized (GSSG) glutathione in red blood cells. Two procedures for sample preparation have been compared, Microcon-10 membrane filtration and acid precipitation. The separation is obtained in an uncoated capillary using a high ionic strength borate buffer at pH 7.8. The intra-assay coefficients of variation (CVs%) are 1.53 and 1.66 for GSH and GSSG, respectively. The run is shorter than 90 s and the migration time is highly reproducible both for GSH (CV% 0.22) and GSSG (CV% 0.17). When the filtration step is used only GSH is found, whereas both GSH and GSSG are detectable after acid precipitation, suggesting that GSSG revealed after acid treatment may be an artefact due to GSH oxidation. Because of its good analytical performance this method could be used for routine red blood cell glutathione measurement in healthy or pathological conditions.

Characterization of a novel hemoglobin-glutathione adduct that is elevated in diabetic patients

BACKGROUND

Typically, a diagnosis of diabetes mellitus is based on elevated circulating blood glucose levels. In an attempt to discover additional markers for the disease and predictors of prognosis, we undertook the characterization of HbA1d3 in diabetic and normal patients.

MATERIAL AND METHODS

PolyCAT A cation exchange chromatography and liquid chromatography-mass spectroscopy was utilized to separate the alpha- and beta-globin chains of HbA1d3 and characterize their presence in normal and diabetic patients.

RESULTS

We report the characterization of HbA1d3 as a glutathionylated, minor hemoglobin subfraction that occurs in higher levels in diabetic patients (2.26 +/- 0.29%) than in normal individuals (1.21 +/- 0.14%, p < 0.001). The alpha-chain spectrum displayed a molecular ion of m/z 15126 Da, which is consistent with the predicted native mass of the HbA0 alpha-globin chain. By contrast, the mass spectrum of the beta-chain showed a mass excess of 307 Da (m/z = 16173 Da) versus that of the native HbA0 beta-globin chain (m/z = 15866 Da). The native molecular weight of the modified beta-globin chain HbA0 was regenerated by treatment of HbA1d3 with dithiothreitol, consistent with a glutathionylated adduct.

CONCLUSIONS

We propose that HbA1d3 (HbSSG) forms normally in vivo, and may provide a useful marker of oxidative stress in diabetes mellitus and potentially other pathologic situations.

Methemoglobin oxidation of N-acetylbenzidine to form a sulfinamide

Aromatic amine sulfinamide adducts of hemoglobin are biomarkers of exposure and evidence for cytochrome P-450 N-hydroxylation. The possible peroxidatic formation of an N-acetylbenzidine (ABZ) sulfinamide adduct by methemoglobin was examined. Following addition of H2O2, 0.06 mM [3H]ABZ was metabolized by methemoglobin. With 0.3 mM glutathione, a new peak was observed, ABZ-SG, representing 17% of the total radioactivity. N'-Hydroxy-N-acetylbenzidine and 4'-nitro-4-acetylaminobiphenyl were not detected. Optimal ABZ-SG formation was observed with 3 uM methemoglobin, 0.1 to 0.3 mM glutathione, and pH 5.5. Higher concentrations of glutathione were inhibitory. Without glutathione, an H2O2-to-ABZ molar ratio of 1:1 resulted in complete metabolism of ABZ. This ratio increased to greater than 2:1 with 0.3 mM glutathione. Nearly complete inhibition of ABZ-SG formation by cyanide (10 mM), ascorbic acid (0.1 mM), 5,5-dimethyl-1-pyrroline N-oxide (50 mM), thiourea (1 mM), and azide (0.3 mM), and the lack of inhibition by mannitol (50 mM) and superoxide dismutase (2 microg) is consistent with a methemoglobin-mediated peroxidatic reaction, which does not involve hydroxyl radical or superoxide. ABZ-SG was identified by electrospray ionization/mass spectrometry as N'-(glutathion-S-yl)-N-acetylbenzidine S-oxide. Conjugate was hydrolyzed by 0.1 N HCl and NaOH, was relatively stable at pH 5.5 and 7.4, and was susceptible to gamma-glutamyltranspeptidase treatment. Formation of an ABZ sulfinamide conjugate with hemoglobin was demonstrated. The results demonstrate that methemoglobin can catalyze the peroxidatic formation of an ABZ sulfinamide adduct, perhaps by a diimine monocation intermediate.

Synthesis and biological evaluation of enantiopure thionitrites: the solid-phase synthesis and nitrosation of D-glutathione as a molecular probe

The D-isomer of the naturally-occurring tripeptide glutathione (gamma-L-Glu-L-Cys-Gly, L-GSH) has been synthesised using the Fmoc solid phase peptide synthesis strategy. The D-GSH obtained has been nitrosated to give the D-isomer of the bioactive thionitrite, S-nitroso-L-glutathione. The biological activity of both enantiomers of S-nitrosoglutathione has been studied and compared to the activity of the D- and L-isomers of N-acetyl-S-nitrosopenicillamine (SNAP) and S-nitrosocysteine (CysNO).

Glutathione as an essential factor for chaperon-mediated activation of lactonizing lipase (LipL) from Pseudomonas sp. 109

Pseudomonas sp. 109 produces a unique lipase (LipL) which efficiently catalyzes intramolecular transesterification of omega-hydroxyesters to form macrocyclic lactones. The production of the enzymatically active LipL requires a specific molecular chaperon (LimL protein) together with a low-M(r) lipase-activation-factor (LAF) of unknown structure. From 50 g of Pseudomonas cells, 2.15 mg of LAF was purified as a sulfobenzofurazanyl derivative after methanol extraction, derivatization, and C(18) reverse-phase HPLC. One-dimensional and two-dimensional 600 MHz (1)H-NMR and fast atom bombardment mass spectrometry (FAB-MS) revealed that LAF is glutathione. Because several SH compounds (L-cysteine and mercaptoethanol) were similarly effective to native LAF in the activation of LipL, and because only LipL contains two cysteinyl residues forming an intramolecular disulfide bond, it is concluded that the reduction of and reformation of the intramolecular disulfide bond of LipL is essential to liberate free and fully active LipL.

Low levels of glutathione in endoscopic biopsies of patients with Crohn's colitis: the role of malnutrition

BACKGROUND AND AIMS

During active Crohn's disease, generation of free radicals is increased, and nutritional depletion is frequent. We investigated the glutathione concentration of the colonic mucosa in biopsies from patients with active Crohn's colitis depending on nutritional status.

METHODS

Endoscopic biopsies were taken in 10 well-nourished control patients, and 18 patients with active Crohn's disease (11 well-nourished, seven malnourished with a recent weight loss > 10 %). Colonic biopsies were taken from healthy and inflamed mucosa and analysed for total glutathione concentration.

RESULTS

Mucosal glutathione concentration (nmol/mg wet tissue) was lower in patients with active colitis both in diseased and healthy mucosa as compared with controls (1.89 +/- 0.39, 2.08 +/- 0.4 and 6.69 +/- 4. 94, respectively, P< 0.05). Mucosal glutathione was lower in healthy mucosa from malnourished versus well-nourished patients: 1.8 +/- 0.2 vs 2.3 +/- 0.37 (P= 0.02).

CONCLUSIONS

Mucosal glutathione is markedly lower in active Crohn's colitis, even in healthy mucosa; glutathione depletion tends to be more severe in malnourished patients. Glutathione depletion may be related in part to malnutrition and contribute to a prolonged evolution of disease and could be a target for pharmacological and nutritional support.

Identification of glutathionyl-3-hydroxykynurenine glucoside as a novel fluorophore associated with aging of the human lens

A novel fluorophore was isolated from human lenses using high performance liquid chromatography (HPLC). The new fluorophore was well separated from 3-hydroxykynurenine glucoside (3-OHKG) and its deaminated isoform, 4-(2-amino-3-hydroxyphenyl)-4-oxobutanoic acid O-glucoside, which are known UV filter compounds. The new compound exhibited UV absorbance maxima at 260 and 365 nm, was fluorescent (Ex(360 nm)/Em(500 nm)), and increased in concentration with age. Further analysis of the purified compound by microbore HPLC with in-line electrospray ionization mass spectrometry revealed a molecular mass of 676 Da. This mass corresponds to that of an adduct of GSH with a deaminated form of 3-OHKG. This adduct was synthesized using 3-OHKG and GSH as starting materials. The synthetic glutathionyl-3-hydroxykynurenine glucoside (GSH-3-OHKG) adduct had the same HPLC elution time, thin-layer chromatography R(F) value, UV absorbance maxima, fluorescence characteristics, and mass spectrum as the lens-derived fluorophore. Furthermore, the (1)H and (13)C NMR spectra of the synthetic adduct were entirely consistent with the proposed structure of GSH-3-OHKG. These data indicate that GSH-3-OHKG is present as a novel fluorophore in aged human lenses. The GSH-3-OHKG adduct was found to be less reactive with beta-glucosidase compared with 3-OHKG, and this could be due to a folded conformation of the adduct that was suggested by molecular modeling.

Formation of gamma-glutamylpropargylglycylglycine from propargylglycine in human blood and erythrocytes

Gamma-Glutamylpropargylglycylglycine (gamma-Glu-PPG-Gly) was isolated as a metabolite of propargylglycine (2-amino-4-pentynoic acid, a natural and synthetic inhibitor of cystathionine gamma-lyase) from human blood incubated with D,L-propargylglycine in the presence of L-glutamate and glycine, and identified by fast-atom-bombardment mass spectrometry, indicating that human blood can metabolize propargylglycine to gamma-Glu-PPG-Gly. When whole blood was incubated with 2 mM D,L-propargylglycine in the presence of 10 mM L-glutamate and 10 mM glycine at 37 degrees C for 16h, 0.094+/-0.013 micromol of gamma-Glu-PPG-Gly was formed per ml of whole blood. When erythrocytes were incubated under the same conditions for 16h, 0.323+/-0.060 micromol of gamma-Glu-PPG-Gly was formed per ml of erythrocytes, suggesting a large contribution of erythrocytes to gamma-Glu-PPG-Gly formation in whole blood. The apparent Km value of gamma-Glu-PPG-Gly formation in human erythrocytes for D,L-propargylglycine was 0.32 mM. The observed rate of gamma-Glu-PPG-Gly formation and the Km value for D,L-propargylglycine suggest that metabolism of propargylglycine to gamma-Glu-PPG-Gly can play a definite biological role in human subjects who are loaded with propargylglycine.

S-Nitroglutathione, a product of the reaction between peroxynitrite and glutathione that generates nitric oxide

Peroxynitrite (ONOO-) has been shown in studies on vascular relaxation and guanylate cyclase activation to react with glutathione (GSH), generating an intermediate product that promotes a time-dependent production of nitric oxide (NO). In this study, reactions of ONOO- with GSH produced a new substance, which was characterized by liquid chromatography, ultraviolet spectroscopy, and electrospray tandem mass spectrometry. The mass spectrometric data provided evidence that the product of this reaction was S-nitroglutathione (GSNO2) and that S-nitrosoglutathione (GSNO) was not a detectable product of this reaction. Further evidence was obtained by comparison of the spectral and chromatographic properties with synthetic standards prepared by reaction of GSH with nitrosonium or nitronium borofluorates. Both the synthetic and ONOO-/GSH-derived GSNO2 generated a protonated ion, GSNO2H+, at m/z 353, which was unusually resistant to decomposition under collision activation, and no fragmentation was observed at collision energy of 25 eV. In contrast, an ion at m/z 337 (GSNOH+), generated from the synthetic GSNO, readily fragmented with the abundant loss of NO at 9 eV. Reactions of ONOO- with GSH resulted in the generation of NO, which was detected by the head space/NO-chemiluminescence analyzer method. The generation of NO was inhibited by the presence of glucose and/or CO2 in the buffers employed. Synthetic GSNO2 spontaneously generated NO in a manner that was not significantly altered by glucose or CO2. Thus, ONOO- reacts with GSH to form GSNO2, and GSNO2 decomposes in a manner that generates NO.

Efficient hepatic uptake and concentrative biliary excretion of a mercapturic acid

The role of the liver in the disposition of circulating mercapturic acids was examined in anesthetized rats and in the isolated perfused rat liver using S-2,4-dinitrophenyl-N-acetylcysteine (DNP-NAC) as the model compound. When DNP-NAC was infused into the jugular vein (150 or 600 nmol over 60 min) it was rapidly and nearly quantitatively excreted as DNP-NAC into bile (42-36% of the dose) and urine (48-62% of dose). Some minor metabolites were detected in bile (<4%), with the major metabolite coeluting on HPLC with the DNP conjugate of glutathione (DNP-SG). Isolated rat livers perfused single pass with 3 microM DNP-NAC removed 72 +/- 9% of this mercapturic acid from perfusate. This rapid DNP-NAC uptake was unaffected by sodium omission, or by L-cysteine, L-glutamate, L-cystine, or N-acetylated amino acids, but was decreased by inhibitors of hepatic sinusoidal organic anion transporters (oatp), indicating that DNP-NAC is a substrate for these transporters. The DNP-NAC removed from perfusate was promptly excreted into bile, eliciting a dose-dependent choleresis. DNP-NAC itself constituted approximately 75% of the total dose recovered in bile, reaching a concentration of 9 mM when livers were perfused in a recirculating mode with an initial DNP-NAC concentration of 250 microM. Other biliary metabolites included DNP-SG, DNP-cysteinylglycine, and DNP-cysteine. DNP-SG was likely formed by a spontaneous retro-Michael reaction between glutathione and DNP-NAC. Subsequent degradation of DNP-SG by biliary gamma-glutamyltranspeptidase and dipeptidase activities accounts for the cysteinylglycine and cysteine conjugates, respectively. These findings indicate the presence of efficient hepatic mechanisms for sinusoidal uptake and biliary excretion of circulating mercapturic acids in rat liver and demonstrate that the liver plays a role in their whole body elimination.

Inhibition of protein tyrosine kinase by 5-S-GAD, a novel antibacterial substance from an insect

The effect of N-beta-alanyl-5-S-glutathionyl-dopa (5-S-GAD), a compound originally isolated from Sarcophaga peregrina (a flesh fly) as an antibacterial substance, on protein phosphorylation was examined using v-src-transformed NIH3T3 cell lysates. 5-S-GAD was found to inhibit tyrosine phosphorylation of protein tyrosine kinase v-src, but not serine/threonine phosphorylation of protein kinase C. The potency of this compound was comparable to that of herbimycin A. Our results suggested that a substitution at position 5 of the catechol in 5-S-GAD with the sulfur of cysteine is essential for 5-S-GAD to inhibit protein tyrosine kinase v-src.

Properties of electrochemically active components in mammalian vitreous humor

Antioxidants are considered to have important roles in protecting the eye against radiation, oxygen toxicity and other threats. Several water-soluble electrochemically-active compounds that might function as antioxidants in vitreous humor of rabbit, rat and bovine eyes were identified and quantitated. In that the rat is a nocturnal animal species and the other two are diurnal, the results allow a tentative evaluation on the comparative physiology of light-dark behavior patterns that influence this ocular fluid. All analyses were performed by HPLC with electrochemical detection. The utility of this approach is that components of vitreous humor can be identified by their retention time and by their characteristic response when the voltages of the two sensing electrodes are progressively brought together. Four compounds regarded as functional antioxidants in the animal kingdom were identified and quantitated. Other antioxidants known to be present in several biological fluids are not present at detectable or significant levels in vitreous humor; metabolites or precursors of these might be present in trace quantities.

A new metabolite of propargylglycine, gamma-glutamylpropargylglycylglycine, in liver of D,L-propargylglycine-administered rats

A new metabolite of propargylglycine (2-amino-4-pentynoic acid, a natural and synthetic inhibitor of cystathionine gamma-lyase) was isolated from liver of rats intraperitoneally administered D,L-propargylglycine with ion-exchange chromatography, and identified as a glutathione analogue, N-[N-gamma-glutamyl(propargylglycyl)]glycine (gamma-Glu-PPG-Gly), by fast-atom-bombardment-mass spectrometry and reactions of the compound including acid hydrolysis, carboxypeptidase reaction, and gamma-glutamyltranspeptidase reaction. The content of gamma-Glu-PPG-Gly in rat liver increased dose-dependently with the increase of D,L-propargylglycine. When the dose of D,L-propargylglycine was 50 mg/kg of body weight, the increase of gamma-Glu-PPG-Gly was proportional to the time after the administration of D,L-propargylglycine, up to 8 h, and then gradually decreased to about 50% of the maximum at 24 h, where the maximum level of gamma-Glu-PPG-Gly at 8 h was 1.15 +/- 0.08 micromol/g of liver. The propargylglycine moiety of gamma-Glu-PPG-Gly in rat liver at 14 h after the administration of D,L-propargylglycine corresponded to 2-7% of the propargylglycine administered when the dose of D,L-propargylglycine was 3.125-200 mg/kg of body weight. The present results indicate that gamma-Glu-PPG-Gly is a major intermediate of propargylglycine metabolism in rat liver. The structural resemblance between glutathione and gamma-Glu-PPG-Gly suggests a possible involvement of propargylglycine and gamma-Glu-PPG-Gly as cysteine and glutathione analogues, respectively, in sulfur amino-acid metabolism.

Purification and characterization of N-beta-alanyl-5-S-glutathionyl-3,4-dihydroxyphenylalanine, a novel antibacterial substance of Sarcophaga peregrina (flesh fly)

We purified a novel antibacterial substance from immunized adult Sarcophaga and determined its molecular structure to be N-beta-alanyl-5-S-glutathionyl-3,4-dihydroxyphenylalanine (5-S-GAD). We synthesized 5-S-GAD enzymatically from N-beta-alanyl-3, 4-dihydroxyphenylalanine (beta-Ala-Dopa) and reduced glutathione (GSH). The antibacterial activity of 5-S-GAD was found to be due to its production of H2O2. This is a novel antibacterial mechanism as it differs from the mechanisms of known antibacterial peptides. Two possible roles of 5-S-GAD in insect immunity, suppression of bacterial growth and activation of a Rel family transcription factor, are proposed.

N,S-bis-fluorenylmethoxycarbonylglutathione: a new, very potent inhibitor of mammalian glyoxalase II

A very potent competitive inhibitor of mammalian glyoxalase II activity, N,S-bis-fluorenylmethoxycarbonylglutathione (DiFMOC-G) has been synthesized and characterized. The Ki value for inhibition of glyoxalase II purified from calf liver is 0.08 microM. The Ki values for glyoxalase I inhibitions range from 285 to 500 fold higher than the values obtained for glyoxalase II inhibitions, depending on the source of the enzyme. Among other enzymes involved in glutathione metabolism, such as glutathione S-transferase, glutathione reductase, and glutathione peroxidase, only glutathione S-transferase is inhibited to a small extent by DiFMOC-G. Diesters of DiFMOC-G were prepared in order to improve transport of DiFMOC-G into mammalian tumor cells (rat adrenal pheochromocytoma, PC-12) in culture. Among the diesters synthesized, diisopropyl DiFMOC-G was found to be the most inhibitory to cell viability, with a [I]0.5 value of 3 microM.