Influence of sample preparation on cellular glutathione recovery from adherent cells in culture

Development of a fluorescence-based microtiter plate method for the measurement of glutathione in yeast

The present work was aimed to the development of a fluorescence assay using the universal 96-well microplate format, for the measurement of reduced glutathione (GSH) in yeast cells. The method relies upon the reaction between GSH and a highly selective fluorogenic probe, i.e. naphthalene-2,3-dicarboxaldehyde (NDA). The optimization of the method included the extraction step of GSH from cultured yeast cells in a cold perchloric acid solution, derivatization conditions (10-min reaction at pH 8.6 and at 20+/-2 degrees C in darkness) and stability studies of the resulting fluorescent adduct. Full selectivity was observed versus other endogenous thiols (except for gamma-glutamylcysteine), glutathione disulfide (GSSG) and enzymatic reducing reagents of GSSG. Linearity was verified in the range 0.3-6.5muM (R(2)>0.98) and limits of quantification and detection were 0.3 and 0.05muM, respectively. Relative standard deviation corresponding to repeatability (n=3) and inter-day precision (n=5) were 2.8 and 6.1%, respectively. Mean GSH recovery from cell extracts was 95%. The method appeared highly correlated (R(2)=0.96) with a previously reported HPLC method. The method was then applied to the monitoring of GSH in the yeast strain Kluyveromyces lactis during its growth period and in the presence of an inhibitor of GSH biosynthesis. The method presents the main advantage of a high throughput for the measurement of biological samples. The extent of the method to the study of the redox couple GSSG/GSH by including an enzymatic reduction step and the enhancement of the fluorescence signal using cyclodextrins were discussed.

Human neuroblastoma (SH-SY5Y) cells are highly sensitive to the lysosomotropic aldehyde 3-aminopropanal

3-Aminopropanal (3-AP), a degradation product of polyamines such as spermine, spermidine and putrescine, is a lysosomotropic small aldehyde that causes apoptosis or necrosis of most cells in culture, apparently by inducing moderate or extensive lysosomal rupture, respectively, and secondary mitochondrial changes. Here, using the human neuroblastoma SH-SY5Y cell line, we found simultaneous occurrence of apoptotic and necrotic cell death when cultures were exposed to 3-AP in concentrations that usually are either nontoxic, or only cause apoptosis. At 30 mM, but not at 10 mM, the lysosomotropic base and proton acceptor NH3 completely blocked the toxic effect of 3-AP, proving that 3-AP is lysosomotropic and suggesting that the lysosomal membrane proton pump of neuroblastoma cells is highly effective, creating a lower than normal lysosomal pH and, thus, extensive intralysosomal accumulation of lysosomotropic drugs. A wave of internal oxidative stress, secondary to changes in mitochondrial membrane potential, followed and gave rise to further lysosomal rupture. The preincubation of cells for 24 h with a chain-breaking free radical-scavenger, alpha-tocopherol, before exposure to 3-AP, significantly delayed both the wave of oxidative stress and the secondary lysosomal rupture, while it did not interfere with the early 3-AP-mediated phase of lysosomal break. Obviously, the reported oxidative stress and apoptosis/necrosis are consequences of lysosomal rupture with ensuing release of lysosomal enzymes resulting in direct/indirect effects on mitochondrial permeability, membrane potential, and electron transport. The induced oxidative stress seems to act as an amplifying loop causing further lysosomal break that can be partially prevented by alpha-tocopherol. Perhaps secondary brain damage during a critical post injury period can be prevented by the use of drugs that temporarily raise lysosomal pH, inactivate intralysosomal 3-AP, or stabilize lysosomal membranes against oxidative stress.

Measurement of glutathione in activated sludges

Thermal, electric, mechanical or oxidative stress seem a promising way to reduce the production of excess activated sludge during biological wastewater treatment. However, the adaptation and the resistance of the sludge microbial ecosystem to stress conditions is a major question as it may definitively limit the effect of some treatments. Defence mechanisms developed by aerobic organisms, in particular, in response to oxidative stress involve various antioxidant activities and compounds such as glutathione. An HPLC method was developed for measuring reduced and total glutathione (GSH and GSHt) in perchloric acid sludge extracts. The method was sensitive, highly specific and validated for linearity, precision and recovery. Considering the extraction yield and the oxidation of GSH during extract storage, the measured GSH concentration was estimated to represent 60% of the GSH content from activated sludges. GSHt ranged from 0.32 to 3.34micromolg(-1) volatile solids and the GSH/GSHt ratio ranged from 32% to 91%. Measurements performed on sludges stressed in precise conditions selected to reach a reduction of sludge production showed a decrease of GSH and GSHt concentrations with thermal, mechanical, electric and ozone stress.

3-Aminopropanal, formed during cerebral ischaemia, is a potent lysosomotropic neurotoxin

Cytotoxic polyamine-derived amino aldehydes, formed during cerebral ischaemia, damage adjacent tissue (the so-called 'penumbra') not subject to the initial ischaemic insult. One such product is 3-aminopropanal (3-AP), a potent cytotoxin that accumulates in ischaemic brain, although the precise mechanisms responsible for its formation are still unclear. More relevant to the present investigations, the mechanisms by which such a small aldehydic compound might be cytotoxic are also not known, but we hypothesized that 3-AP, having the structure of a weak lysosomotropic base, might concentrate within lysosomes, making these organelles a probable focus of initial toxicity. Indeed, 3-AP leads to lysosomal rupture of D384 glioma cells, a process which clearly precedes caspase activation and apoptotic cell death. Immunohistochemistry reveals that 3-AP concentrates in the lysosomal compartment and prevention of this accumulation by the lysosomotropic base ammonia, NH(3), protects against 3-AP cytotoxicity by increasing lysosomal pH. A thiol compound, N-(2-mercaptopropionyl)glycine, reacts with and neutralizes 3-AP and significantly inhibits cytoxocity. Both amino and aldehyde functions of 3-AP are necessary for toxicity: the amino group confers lysosomotropism and the aldehyde is important for additional, presently unknown, reactions. We conclude that 3-AP exerts its toxic effects by accumulating intralysosomally, causing rupture of these organelles and releasing lysosomal enzymes which initiate caspase activation and apoptosis (or necrosis if the lysosomal rupture is extensive). These results may have implications for the development of new therapeutics designed to lessen secondary damage arising from focal cerebral ischaemia.

A sensitive and specific assay for glutathione with potential application to glutathione disulphide, using high-performance liquid chromatography-tandem mass spectrometry

We have utilised the combination of sensitivity and specificity afforded by coupling high-performance liquid chromatography (HPLC) to a tandem mass spectrometer (MS-MS) to produce an assay which is suitable for assaying glutathione (GSH) concentrations in liver tissue. The sensitivity suggests it may also be suitable for extrahepatic tissues. The method has been validated for GSH using mouse liver samples and also allows the assay of GSSG. The stability of GSH under conditions relevant to the assay has been determined. A 20-microl amount of a diluted methanol extract of tissue is injected with detection limits of 0.2 pmol for GSH and 2 pmol for GSSG. The HPLC uses an Altima C18 (150 x 4.6 mm, 5 microm) column at 35 degrees C. Chromatography utilises a linear gradient from 0 to 10% methanol in 0.1% formic acid over 5 min, with a final isocratic stage holding at 10% methanol for 5 min. Total flow rate is 0.8 ml/min. The transition from the M+H ion (308.1 m/z for GSH, and 613.3 m/z for GSSG) to the 162.0 m/z (GSH) and 355.3 m/z (GSSG) fragments are monitored.

Measurement of glutathione and glutathione disulfide

Measurements of glutathione should include quantification of both the reduced and oxidized forms. HPLC-based assays for glutathione and other cellular thiols and disulfides utilize a variety of detection methods, including ultraviolet, fluorescence, and electrochemical methods. This unit provides rapid, sensitive, highly versatile and reproducible HPLC methods for separating and quantifying sulfur-containing amino acids and related derivatives from a variety of biological samples.

Function of glutathione peroxidase in endothelial cell vitality

The two human umbilical vein endothelial cell-derived lines, ECRF24 and ECV304, differ in responsiveness to oxidative stress. In confluent monolayers of ECRF24, but not in ECV304, peroxides induce stress responses such as plasma membrane blebbing and nuclear condensation. The peroxide effect on ECRF24 was preceded by oxidation of reduced glutathione (GSH) and of NAD(P)H, and by oxidation of the redox-sensitive probe, chloromethyl 2',7'-dichlorofluorescin (DCFH). In monolayers of ECV304, peroxides induced only minimal oxidation of GSH, NAD(P)H and DCFH, which was associated with a greatly reduced GSH peroxidase activity in these cells. However, in spite of the absence of a blebbing response, ECV304 were more susceptible than ECRF24 to membrane lipid peroxidation and peroxide-induced necrosis. Only for ECV304, the culturing with high levels of polyunsaturated fatty acids increased lipid peroxidation and cellular death. Treatment of these cells with the GSH peroxidase mimic ebselen effectively reversed their decreased vitality. We conclude that, in peroxide-treated endothelial cells, cell death (necrosis) can result from lipid peroxidation by peroxide that has not been removed by GSH peroxidases, whereas extensive peroxidase activity may cause a stress response (blebbing). The data further identify ECV304 as a stress-sensitive cell line, where peroxides exert their effects independently of GSH oxidation.

The glutathione-related detoxification pathway in the human breast: a highly coordinated system disrupted in the tumour tissues

Glutathione and the associated enzymes, glutathione S-transferases, peroxidases, and reductase, have been implicated in cancer chemoresistance. This pathway was investigated in paired cancerous and peritumoral breast samples from 41 women. The tumours exhibited a higher redox status as deduced from increased transferase, peroxidase, and reductase activities and from higher total and reduced glutathione contents. Several components were strongly correlated in peritumoral tissues, suggesting a highly co-ordinated glutathione pathway that appeared disrupted in breast tumours with only a few correlations left. Therefore, resistance could spontaneously result from deregulated variations in the glutathione pathway, which might be relevant to the malignant disease progression.

Simultaneous measurement of reactive oxygen species and reduced glutathione using capillary electrophoresis and laser-induced fluorescence detection in cultured cell lines

A capillary zone electrophoretic (CZE) method coupled with laser-induced fluorescence (LIF) was developed for the simultaneous determination of two important intracellular parameters related to oxidative stress (i.e. reactive oxygen species, ROS, and reduced glutathione, GSH). This rapid and sensitive method was applied to the study of oxidative stress in cultured V79 fibroblast cells. The fluorogenic reagents selected were: (i) dihydrorhodamine-123 (DHR-123) which is converted intracellularly by ROS to the fluorescent rhodamine-123 dye (Rh-123), and (ii) naphthalene-2,3-dicarboxaldehyde (NDA), which reacts quickly with GSH in cell extracts to produce a fluorescent adduct. Separation of Rh-123, GSH-NDA and gamma-glutamylcysteine-NDA adducts was performed using an uncoated fused-silica capillary and a 100 mM borate buffer, pH 9.2, at 20 degrees C and at an applied voltage of 25 kV; LIF detection was operated using an argon laser. The cell line was also tested for its ability to alleviate oxidative stress induced by tert-butylhydroperoxide (t-BuOOH). Exposure to t-BuOOH (up to 3 mm for 2 h) did not affect the intracellular ROS and GSH concentrations. At higher (4-10 mM) t-BuOOH concentrations, an inverse relationship between the concentrations of ROS and GSH was obtained, showing that the present method can readily evaluate the gradual consumption of the primary cellular scavenger of ROS which occurs simultaneously with the increase of oxidative insult.

Determination of cellular thiols and glutathione-related enzyme activities: versatility of high-performance liquid chromatography-spectrofluorimetric detection

A high-performance liquid chromatography (HPLC) method to determine the most important cellular thiols [reduced glutathione (GSH), cysteine, gamma-glutamylcysteine and cysteinylglycine] is described. Separation relies upon isocratic ion-pairing reversed-phase chromatography and detection is operated by spectrofluorimetry coupled with post-column derivatization reactions using either N-(1-pyrenyl)maleimide (NPM) or ortho-phthalaldehyde (OPA). When OPA is used without co-reagent, only GSH and gamma-glutamylcysteine are detected (heterobifunctional reaction). However, either the OPA reaction in the presence of glycine in the mobile phase (thiol-selective reaction) or NPM allows the detection of all the cited thiols. The HPLC system has been validated as concerning linearity, accuracy and precision. The low detection limits reached (in the pmol range for each thiol injected) allow the screening and the quantification of thiols (as NPM derivatives) in V79cl and V79HGGT cells as well as the measurement of two cytosolic enzymes related to the glutathione synthesis, using the heterobifunctional OPA reaction.

The mutagenicity of the tyrosine metabolite, fumarylacetoacetate, is enhanced by glutathione depletion

The toxicity of tyrosine metabolites has been suggested, but not proven, to play a role in the ethiopathogenesis of hepatic alterations observed in hereditary tyrosinemia type I (HT I), a metabolic disease caused by a deficiency of the last enzyme in the tyrosine catabolic pathway, fumarylacetoacetate hydrolase. One of these metabolites, fumarylacetoacetate (FAA), is mutagenic in Chinese hamster V79 cells. We report here that FAA is a powerful glutathione depletor in this cell system. Moreover, the mutagenicity of FAA (100 microM) is potentiated by depletion of cellular glutathione (12% of control levels) by pretreatment with L-buthionine-(S,R)-sulphoximine. In this case, the mutation frequency induced by FAA is 10 times higher than in untreated, control cells. This enhancement is abolished by a partial replenishment of intracellular glutathione (32% of control levels) prior to FAA treatment. Reactive oxygen species are not generated during FAA treatment of glutathione-depleted or undepleted cells. Although the mechanism(s) underlying the mutagenic activity of FAA remains to be identified, these results show that the glutathione depletion activity of FAA may play an important role in the manifestation of its mutagenicity which likely contributes to the HT I-associated liver pathologies.