Recent trends in glutathione biochemistry--glutathione-protein interactions: a molecular link between oxidative stress and cell proliferation?

Winter-swimming as a building-up body resistance factor inducing adaptive changes in the oxidant/antioxidant status

The aim of our research was to examine whether winter-swimming for five consecutive months results in adaptational changes improving tolerance to stress induced by exposure to cryogenic temperatures during whole-body cryostimulation (WBC). The research involved 15 healthy men, with normal bodyweight, who had never been subjected to either WBC or cold water immersion. During the experiment, the participants were twice subjected to WBC (3 min/- 130°C), namely before the winter-swimming season and after the season. Blood was taken seven times: In the morning before each cryostimulation, 30 min after each cryostimulation and the next morning. Additionally, control blood was collected in the middle of the winter season, in February. Our analysis concerned changes in hematological parameters as well as in reduced glutathione and oxidized glutathione, total oxidant status, total antioxidant status and in components of the antioxidant system: Superoxide dismutase, catalase, glutathione peroxidase, glutathione reductase, glutathione S-transferase and 8-Isoprostanes as a sensitive indicator of oxidative stress. We found significant changes in hemoglobin concentration, the number of red blood cells, the hematocrit index and mean corpuscular volume of red blood cell and the percentage of monocytes and granulocytes after the winter swimming season. The response to cryogenic temperatures was milder after five months of winter-swimming. The obtained results may indicate positive adaptive changes in the antioxidant system of healthy winter-swimmers. These changes seem to increase the readiness of the human body to stress factors.

Overview of protein glutathionylation

Many proteins contain free thiols that can be modified by the reversible formation of mixed disulfides with glutathione. Protein glutathionylation is of significance for defense against oxidative damage and in redox signaling. Here we outline the mechanisms and possible significance of protein glutathionylation.

Polymer-coated echogenic lipid nanoparticles with dual release triggers

Although lipid nanoparticles are promising drug delivery vehicles, passive release of encapsulated contents at the target site is often slow. Herein, we report contents release from targeted, polymer-coated, echogenic lipid nanoparticles in the cell cytoplasm by redox trigger and simultaneously enhanced by diagnostic frequency ultrasound. The lipid nanoparticles were polymerized on the external leaflet using a disulfide cross-linker. In the presence of cytosolic concentrations of glutathione, the lipid nanoparticles released 76% of encapsulated contents. Plasma concentrations of glutathione failed to release the encapsulated contents. Application of 3 MHz ultrasound for 2 min simultaneously with the reducing agent enhanced the release to 96%. Folic acid conjugated, doxorubicin-loaded nanoparticles showed enhanced uptake and higher cytotoxicity in cancer cells overexpressing the folate receptor (compared to the control). With further developments, these lipid nanoparticles have the potential to be used as multimodal nanocarriers for simultaneous targeted drug delivery and ultrasound imaging.

Nuclear glutathione

Glutathione (GSH) is a linchpin of cellular defences in plants and animals with physiologically-important roles in the protection of cells from biotic and abiotic stresses. Moreover, glutathione participates in numerous metabolic and cell signalling processes including protein synthesis and amino acid transport, DNA repair and the control of cell division and cell suicide programmes. While it is has long been appreciated that cellular glutathione homeostasis is regulated by factors such as synthesis, degradation, transport, and redox turnover, relatively little attention has been paid to the influence of the intracellular partitioning on glutathione and its implications for the regulation of cell functions and signalling. We focus here on the functions of glutathione in the nucleus, particularly in relation to physiological processes such as the cell cycle and cell death. The sequestration of GSH in the nucleus of proliferating animal and plant cells suggests that common redox mechanisms exist for DNA regulation in G1 and mitosis in all eukaryotes. We propose that glutathione acts as "redox sensor" at the onset of DNA synthesis with roles in maintaining the nuclear architecture by providing the appropriate redox environment for the DNA replication and safeguarding DNA integrity. In addition, nuclear GSH may be involved in epigenetic phenomena and in the control of nuclear protein degradation by nuclear proteasome. Moreover, by increasing the nuclear GSH pool and reducing disulfide bonds on nuclear proteins at the onset of cell proliferation, an appropriate redox environment is generated for the stimulation of chromatin decompaction. This article is part of a Special Issue entitled Cellular functions of glutathione.

Protein glutathionylation in cellular compartments: a constitutive redox signal

Glutathione provides means of regulating protein function by the process of glutathionylation. Despite the role of oxidative stress biomarkers assumed recently by glutathionylated proteins in human diseases, so far no information is available on the intracellular distribution of glutathionylated proteins in human cell lines. In this study, we combined the specificity of monoclonal antibody labeling for protein-bound glutathione (GS-Pro) with the ability of confocal microscopy to localize molecules with high spatial resolution. We performed immunofluorescence analysis on dermal fibroblasts, both in steady state than in proliferative conditions, and on in situ extracted matrix samples. For the first time, we report the compartmentalization of constitutively glutathionylated proteins in different subcellular districts and we found a tight association between glutathione, nuclear lamina, and cytoskeleton. In proliferating cells, total GS-Pro fluorescence increases in the early phases of growth and significantly drops when cells reach confluence. Interestingly, a nuclear shift of GS-Pro was observed between 6 and 48 hours after plating, becoming homogeneous with the cytoplasm when growth slows. The ability to visualize a detailed intracellular distribution of this critical marker of protein oxidation may provide an additional tool to highlight pathways in turns 'redox-activated' and to identify new pathogenic pathways in human diseases.

Molecular Mechanisms Underlying Anti-Inflammatory Actions of 6-(Methylsulfinyl)hexyl Isothiocyanate Derived from Wasabi (Wasabia japonica)

6-(Methylsulfinyl)hexyl isothiocyanate (6-MSITC) is a major bioactive compound in wasabi (Wasabia japonica), which is a typical Japanese pungent spice. Recently, in vivo and in vitro studies demonstrated that 6-MSITC has several biological properties, including anti-inflammatory, antimicrobial, antiplatelet, and anticancer effects. We previously reported that 6-MSITC strongly suppresses cyclooxygenase-2 (COX-2), inducible nitric oxide synthase (iNOS), and cytokines, which are important factors that mediate inflammatory processes. Moreover, molecular analysis demonstrated that 6-MSITC blocks the expressions of these factors by suppressing multiple signal transduction pathways to attenuate the activation of transcriptional factors. Structure-activity relationships of 6-MSITC and its analogues containing an isothiocyanate group revealed that methylsulfinyl group and the length of alkyl chain of 6-MSITC might be related to high inhibitory potency. In this paper, we review the anti-inflammatory properties of 6-MSITC and discuss potential molecular mechanisms focusing on inflammatory responses by macrophages.

Age-dependent and tissue-related glutathione redox status in a mouse model of Alzheimer's disease

Glutathione plays an essential role in the intracellular antioxidant defense against oxidant radicals, especially the •OH radical. To understand the early and progressive cellular changes in the development of Alzheimer's disease (AD), we investigated reduced glutathione/oxidized glutathione (GSH/GSSG) status in a double mutated AD transgenic mouse model (B6.Cg-Tg), which carries Swedish amyloid-β protein precursor mutation (AβPPswe) and exon 9 deletion of the PSEN1 gene. In this study, we quantified and compared both GSH/GSSG and mixed-disulfide (Pr-SSG) levels in blood samples and three anatomic positions in brain (cerebrum, cerebellum, and hippocampus) at 3 age stages (1, 5, and 11 months) of AD transgenic (Tg)/wild type mice. The present study was designed to characterize and provide insight into the glutathione redox state of both brain tissues and blood samples at different disease stages of this Tg model. The level of Pr-SSG increased in all AD brain tissues and blood compared with controls regardless of age. The GSH/GSSG ratio in AD-Tg brain tissue started at a higher value at 1 month, fell at the transitional period of 5 months, right before the onset of amyloid plaques, followed by an increase in GSSG and associated decrease of GSH/GSSG at 11 months. These results suggest that formation of Pr-SSG may be an early event, preceding amyloid plaque appearance, and the data further implies that tissue thiol redox is tightly regulated. Notably, the high basal levels of mixed-disulfides in hippocampus suggest a potential for increased oxidative damage under oxidizing conditions and increased GSSG in this vulnerable region.

Alzheimer's disease: redox dysregulation as a common denominator for diverse pathogenic mechanisms

Alzheimer's disease (AD) is the most common cause of dementia and a progressive neurodegeneration that appears to result from multiple pathogenic mechanisms (including protein misfolding/aggregation, involved in both amyloid β-dependent senile plaques and tau-dependent neurofibrillary tangles), metabolic and mitochondrial dysfunction, excitoxicity, calcium handling impairment, glial cell dysfunction, neuroinflammation, and oxidative stress. Oxidative stress, which could be secondary to several of the other pathophysiological mechanisms, appears to be a major determinant of the pathogenesis and progression of AD. The identification of oxidized proteins common for mild cognitive impairment and AD suggests that key oxidation pathways are triggered early and are involved in the initial progression of the neurodegenerative process. Abundant data support that oxidative stress, also considered as a main factor for aging, the major risk factor for AD, can be a common key element capable of articulating the divergent nature of the proposed pathogenic factors. Pathogenic mechanisms influence each other at different levels. Evidence suggests that it will be difficult to define a single-target therapy resulting in the arrest of progression or the improvement of AD deterioration. Since oxidative stress is present from early stages of disease, it appears as one of the main targets to be included in a clinical trial. Exploring the articulation of AD pathogenic mechanisms by oxidative stress will provide clues for better understanding the pathogenesis and progression of this dementing disorder and for the development of effective therapies to treat this disease.

All glutathione forms are depleted in blood of obese and type 1 diabetic children

BACKGROUND

Oxidative stress plays an important role in the pathogenesis of type 1 diabetes (T1D), where an increase in reactive oxygen species may contribute to the initial destruction of β-cells. Accumulating evidence also suggests a role for oxidative stress in obesity, where it may potentiate the development of complications.

OBJECTIVE

To analyze the in vivo homeostasis of glutathione in children with T1D at onset and in children who are obese, to evaluate the systemic content of all glutathione forms (total, reduced, oxidized, and protein-bound glutathione) and the balance among them. Moreover, since glutathione bound to hemoglobin is a clinical marker of oxidative stress in human blood, we analyzed glutathionyl-hemoglobin in T1D and in obese children.

SUBJECTS

Children with T1D at onset (n = 30) or obesity (n = 30) at the first observation, and 30 healthy subjects chosen from the children who attended the outpatient clinic for minor problems.

METHODS

We assessed circulating levels of various glutathione forms by performing reverse-phase high performance liquid chromatography. Glutathionyl-hemoglobin analysis was carried out by cation-exchange chromatography.

RESULTS

In children with T1D and in obese children, we found a significant decrease of all glutathione forms including, for the first time, the content of total glutathione and glutathionylated proteins. The comparison among forms shows no significant imbalance in T1D patients, whereas in obese children it seems to suggest an attempt to rebalance the glutathione system homeostasis.

CONCLUSIONS

Our findings consistently show in vivo evidence of glutathione depletion upon early onset of T1D and in obese children, thus evidencing glutathione as an early marker in these two metabolic conditions.

Posttranslational modification of cysteine in redox signaling and oxidative stress: Focus on s-glutathionylation

Reactive oxygen species (ROS) and reactive nitrogen species (RNS) have become recognized as second messengers for initiating and/or regulating vital cellular signaling pathways, and they are known also as deleterious mediators of cellular stress and cell death. ROS and RNS, and their cross products like peroxynitrite, react primarily with cysteine residues whose oxidative modification leads to functional alterations in the proteins. In this Forum, the collection of six review articles presents a perspective on the broad biological impact of cysteine modifications in health and disease from the molecular to the cellular and organismal levels, focusing in particular on reversible protein-S-glutathionylation and its central role in transducing redox signals as well as protecting proteins from irreversible cysteine oxidation. The Forum review articles consider the role of S-glutationylation in regulation of the peroxiredoxin enzymes, the special redox environment of the mitochondria, redox regulation pertinent to the function of the cardiovascular system, mechanisms of redox-activated apoptosis in the pulmonary system, and the role of glutathionylation in the initiation, propagation, and treatment of neurodegenerative diseases. Several common themes emerge from these reviews; notably, the probability of crosstalk between signaling/regulation mechanisms involving protein-S-nitrosylation and protein-S-glutathionylation, and the need for quantitative analysis of the relationship between specific cysteine modifications and corresponding functional changes in various cellular contexts.

Mitochondrial thiols in antioxidant protection and redox signaling: distinct roles for glutathionylation and other thiol modifications

SIGNIFICANCE

The mitochondrial matrix contains much of the machinery at the heart of metabolism. This compartment is also exposed to a high and continual flux of superoxide, hydrogen peroxide, and related reactive species. To protect mitochondria from these sources of oxidative damage, there is an integrated set of thiol systems within the matrix comprising the thioredoxin/peroxiredoxin/methionine sulfoxide reductase pathways and the glutathione/glutathione peroxidase/glutathione-S-transferase/glutaredoxin pathways that in conjunction with protein thiols prevent much of this oxidative damage. In addition, the changes in the redox state of many components of these mitochondrial thiol systems may transduce and relay redox signals within and through the mitochondrial matrix to modulate the activity of biochemical processes.

RECENT ADVANCES

Here, mitochondrial thiol systems are reviewed, and areas of uncertainty are pointed out, focusing on recent developments in our understanding of their roles.

CRITICAL ISSUES

The areas of particular focus are on the multiple, overlapping roles of mitochondrial thiols and on understanding how these thiols contribute to both antioxidant defenses and redox signaling.

FUTURE DIRECTIONS

Recent technical progress in the identification and quantification of thiol modifications by redox proteomics means that many of the questions raised about the multiple roles of mitochondrial thiols can now be addressed.

Lens proteomics: analysis of rat crystallins when lenses are exposed to dexamethasone

To identify glucocorticoid induced cataract (GIC)-specific modified crystallins and related changes, we analyzed rat crystallins and related changes in lenses exposed to dexamethasone (Dex). To carry out proteomics analyses, we separated soluble lens proteins with two-dimensional electrophoresis (2-DE) and modified crystallins were analyzed with matrix assisted laser desorption/ionization time-of-flight tandem mass spectrometry (MALDI-TOF-MS/MS). Related changes in mRNA, protein levels and morphological and functional changes of modified crystallins were also determined. Measured masses (except for γD-crystallin as the larger and cross-link form), the isoelectric points (PIs; except for βB3-crystallin as the alkalinization form) and amino acid sequences of all known rat crystallins matched previously reported data. Analysis by 2-DE indicated that αA, αB, βB3 and γD increased when lenses were exposed to 5 μM Dex; βA4 increased when lenses were exposed to 1 μM Dex and the five proteins that had the highest expressional trend were identical with the results of Q-PCR. βA3/A1 crystallin (expressional trend identical with results of Q-PCR) and the serum albumin precursor gradually disappeared when exposed to 1-50 μM Dex. Results of Western blotting, immunohistochemistry or fluorescence analysis showed that αA and αB increased most when exposed to 5 μM Dex and βA1/A3 and KI-67 decreased obviously when exposed to 1-50 μM Dex. Electron microscopy showed that the condition of the lens was better when lenses were exposed to 5 μM Dex than at other levels and cracks between the fiber cells became larger when lenses were exposed to 1-50 μM Dex. A chaperone role of α-crystallin protecting heated catalase (CAT) and the activity of superoxide dismutase (SOD), glutathione (GSH), and caspase-3 were highest when exposed to 5 μM Dex. Moreover, αA-crystallins were associated with increased phosphorylation (PI decreased). In conclusion, the proteomics analysis and related changes of rat crystallins when lenses were exposed to Dex in this study will be useful for comparison with normal lens proteins and GIC. We also provided a mechanism for GIC from a proteomics aspect based on the in vitro model.

Assessing the structure-activity relationships of fluorotelomer unsaturated acids and aldehydes with glutathione. Reactivity of glutathione with fluorotelomer unsaturated acids and aldehydes

Fluorotelomer alcohols (FTOHs) have been shown to degrade via abiotic and biotic mechanisms to perfluorocarboxylates (PFCAs) which are environmentally persistent and bioaccumulate in humans and wildlife depending on their chain length. Fluorotelomer unsaturated aldehydes (FTUALs) and acids (FTUCAs) are intermediate metabolites that form from the degradation of FTOHs. Their potential for toxicity is not yet defined and may be more significant compared to PFCAs. Past studies have shown that these intermediates form adducts with glutathione (GSH). The purpose of this study was to further assess the reactivity of these intermediate compounds. In vitro experiments were carried out in an aqueous buffer system (pH 7.4) where FTUCAs and FTUALs of varying chain lengths were reacted with GSH. To quantify the reactivity of FTUCAs and FTUALs, unreacted free GSH was derivatized with 5,5'-dithiobis(2-nitrobenzoic acid), its absorbance measured at 412 nm, and the percentage of unconjugated free GSH evaluated over time. EC50 values were obtained for the reactions of GSH with acrolein and methyl methacrylate to assess the accuracy of the method, as well as for acrylic acid, FTUCAs, and FTUALs. The results of this study indicated that α,β-unsaturated aldehydes are comparatively the most reactive and reaction with GSH may be influenced by the length of the fluorinated tail. This is the first study to examine the relationship of FTUCAs and FTUALs with biological nucleophiles by quantifying their intrinsic reactivity.

The response to heat shock and oxidative stress in Saccharomyces cerevisiae

A common need for microbial cells is the ability to respond to potentially toxic environmental insults. Here we review the progress in understanding the response of the yeast Saccharomyces cerevisiae to two important environmental stresses: heat shock and oxidative stress. Both of these stresses are fundamental challenges that microbes of all types will experience. The study of these environmental stress responses in S. cerevisiae has illuminated many of the features now viewed as central to our understanding of eukaryotic cell biology. Transcriptional activation plays an important role in driving the multifaceted reaction to elevated temperature and levels of reactive oxygen species. Advances provided by the development of whole genome analyses have led to an appreciation of the global reorganization of gene expression and its integration between different stress regimens. While the precise nature of the signal eliciting the heat shock response remains elusive, recent progress in the understanding of induction of the oxidative stress response is summarized here. Although these stress conditions represent ancient challenges to S. cerevisiae and other microbes, much remains to be learned about the mechanisms dedicated to dealing with these environmental parameters.

Costunolide induces apoptosis in platinum-resistant human ovarian cancer cells by generating reactive oxygen species

OBJECTIVE

The acquired resistance to platinum-based drugs has become an obstacle in the management of ovarian cancer. We investigated the apoptosis-inducing effect of costunolide, a natural sesquiterpene lactone, in platinum-resistant human ovarian cancer cells, along with the molecular mechanism of action.

METHODS

Costunolide and cisplatin were examined in platinum-resistant human ovarian cancer cells. MTT assay for cell viability, PI staining for cell cycle profiling, and Annexin V assay for apoptosis analysis. ROS production and protein expression was assessed by H(2)DCFDA staining and Western blotting, respectively. Combination effect was determined using the Combination Index (CI) method.

RESULTS

It was found that costunolide is more potent than cisplatin in inhibiting cell growth in three platinum-resistant ovarian cancer cell lines (MPSC1(PT), A2780(PT), and SKOV3(PT)). Costunolide induced apoptosis of platinum-resistant cells in a time- and dose-dependent manner and suppressed tumor growth in SKOV3(PT)-bearing mouse model. In addition, costunolide triggered the activation of caspase-3, -8, and -9. Pretreatment with caspase inhibitors neutralized the pro-apoptotic activity of costunolide. We further demonstrated that costunolide induced a significant increase in intracellular reactive oxygen species (ROS). Additionally, the antioxidant N-acetyl-L-cysteine (NAC) significantly attenuated the costunolide-induced production of ROS, activation of caspases, down-regulation of Bcl-2, and apoptosis in platinum-resistant ovarian cancer cells. Moreover, costunolide synergized with cisplatin to induce cell death in platinum-resistant ovarian cancer cells.

CONCLUSIONS

Taken together, these data suggest that costunolide, alone or in combination with cisplatin, may be of therapeutic potential in platinum-resistant ovarian cancer.

S-Glutathionyl quantification in the attomole range using glutaredoxin-3-catalyzed cysteine derivatization and capillary gel electrophoresis with laser-induced fluorescence detection

S-glutathionylation (Pr-SSG) is a specific post-translational modification of cysteine residues by the addition of glutathione. S-Glutathionylated proteins induced by oxidative or nitrosative stress play an essential role in understanding the pathogenesis of the aging and age-related disorder, such as Alzheimer's disease (AD). The purpose of this research is to develop a novel and ultrasensitive method to accurately and rapidly quantify the Pr-SSG by using capillary gel electrophoresis with laser-induced fluorescence detection (CGE-LIF). The derivatization method is based on the specific reduction of protein-bound S-glutathionylation with glutaredoxin (Grx) and labeling with thiol-reactive fluorescent dye (Dylight 488 maleimide). The experiments were performed by coupling the derivatization method with CGE-LIF to study electrophoretic profiling in in vitro oxidative stress model-S-glutathionylated bovine serum albumin (BSA-SSG), oxidant-induced human colon adenocarcinoma (HT-29) cells, brain tissues, and whole blood samples from an AD transgenic (Tg) mouse model. The results showed almost an eightfold increase in S-glutathionyl abundance when subjecting HT-29 cells in an oxidant environment, resulting in Pr-SSG at 232 ± 10.64 (average ±SD; n=3) nmol/mg. In the AD-Tg mouse model, an initial quantitative measurement demonstrated the extent of protein S-glutathionylation in three brain regions (hippocampus, cerebellum, and cerebrum), ranging from 1 to 10 nmol/mg. Additionally, we described our developed method to potentially serve as a highly desirable diagnostic tool for monitoring S-glutathionylated protein profile in minuscule amount of whole blood. The whole blood samples for S-glutathionyl expression of 5-month-old AD-Tg mice are quantified as 16.3 μmol/L (=7.2 nmol/mg protein). Altogether, this is a fast, easy, and accurate method, reaching the lowest limit of Pr-SSG detection at 1.8 attomole (amol) level, reported to date.

Glutaredoxin 2a, a mitochondrial isoform, plays a protective role in a human cell line under serum deprivation

The roles of mitochondrial glutaredoxin (Grx2a) under serum deprivation were assessed using the human stable HepG2 cell lines overexpressing or down-regulating Grx2a. The Grx2a-overexpressing stable cells displayed enhanced proliferation, decreased reactive oxygen species (ROS) and caspase-3 activity levels, and increased total GSH level, compared to the vector control cells. These characteristics of the overexpressing stable cells were reversed by down-regulating Grx2a in the same cell line. In the limited serum conditions, the Grx2a-overexpressing stable pcDNA3.0/HA-Grx2a cells exhibited higher cellular viabilities and total GSH level, and showed much lower enhancement in ROS and caspase-3 activity levels than the vector control pcDNA3.0/HA cells. However, the Grx2a-down-regulating stable cells gave rise to diminished cellular viabilities and further decreased total GSH level, and contained significantly higher ROS and caspase-3 activity levels, under serum deprivation than the vector control cells. These results suggest that Grx2a plays proliferative and anti-apoptotic roles under serum deprivation.

Downregulation of glutathione S-transferase pi in asthma contributes to enhanced oxidative stress

BACKGROUND

Glutathione S-transferase pi (GSTPi) is the predominant redox regulator in the lung. Although evidence implicates an important role for GSTPi in asthma, the mechanism for this has remained elusive.

OBJECTIVES

We sought to determine how GSTPi is regulated in asthma and to elucidate its role in maintaining redox homeostasis.

METHODS

We elucidated the regulation of GSTPi in children with asthma and used murine models of asthma to determine the role of GSTPi in redox homeostasis.

RESULTS

Our findings demonstrate that GSTPi transcript levels are markedly downregulated in allergen- and IL-13-treated murine models of asthma through signal transducer and activator of transcription 6-dependent and independent pathways. Nuclear factor erythroid 2-related factor 2 was also downregulated in these models. The decrease in GSTPi expression was associated with decreased total glutathione S-transferase activity in the lungs of mice. Examination of cystine intermediates uncovered a functional role for GSTPi in regulating cysteine oxidation, whereby GSTPi-deficient mice exhibited increased oxidative stress (increase in percentage cystine) compared with wild-type mice after allergen challenge. GSTPi expression was similarly downregulated in children with asthma.

CONCLUSIONS

These data collectively suggest that downregulation of GSTPi after allergen challenge might contribute to the asthma phenotype because of disruption of redox homeostasis and increased oxidative stress. Furthermore, GSTPi might be an important therapeutic target for asthma, and evaluation of GSTPi expression might prove beneficial in identifying patients who would benefit from therapy targeting this pathway.

Determination of intracellular glutathione and glutathione disulfide using high performance liquid chromatography with acidic potassium permanganate chemiluminescence detection

Measurement of glutathione (GSH) and glutathione disulfide (GSSG) is a crucial tool to assess cellular redox state. Herein we report a direct approach to determine intracellular GSH based on a rapid chromatographic separation coupled with acidic potassium permanganate chemiluminescence detection, which was extended to GSSG by incorporating thiol blocking and disulfide bond reduction. Importantly, this simple procedure avoids derivatisation of GSH (thus minimising auto-oxidation) and overcomes problems encountered when deriving the concentration of GSSG from 'total GSH'. The linear range and limit of detection for both analytes were 7.5 × 10(-7) to 1 × 10(-5) M, and 5 × 10(-7) M, respectively. GSH and GSSG were determined in cultured muscle cells treated for 24 h with glucose oxidase (0, 15, 30, 100, 250 and 500 mU mL(-1)), which exposed them to a continuous source of reactive oxygen species (ROS). Both analyte concentrations were greater in myotubes treated with 100 or 250 mU mL(-1) glucose oxidase (compared to untreated controls), but were significantly lower in myotubes treated with 500 mU mL(-1) (p < 0.05), which was rationalised by considering measurements of H(2)O(2) and cell viability. However, the GSH/GSSG ratio in myotubes treated with 100, 250 and 500 mU mL(-1) glucose oxidase exhibited a dose-dependent decrease that reflected the increase in intracellular ROS.

Nitric oxide is the primary mediator of cytotoxicity induced by GSH depletion in neuronal cells

Glutathione (GSH) levels progressively decline during aging and in neurodegenerative disorders. However, the contribution of such event in mediating neuronal cell death is still uncertain. In this report, we show that, in neuroblastoma cells as well as in primary mouse cortical neurons, GSH decrease, induced by buthionine sulfoximine (BSO), causes protein nitration, S-nitrosylation and DNA strand breaks. Such alterations are also associated with inhibition of cytochrome c oxidase activity and microtubule network disassembly, which are considered hallmarks of nitric oxide (NO) toxicity. In neuroblastoma cells, BSO treatment also induces cell proliferation arrest through the ERK1/2-p53 pathway that finally results in caspase-independent apoptosis, as evident from the translocation of apoptosis-inducing factor from mitochondria towards nuclei. A deeper analysis of the signaling processes indicates that the NO-cGMP pathway is involved in cell proliferation arrest and death. In fact, these events are completely reversed by L-NAME, a specific NO synthase inhibitor, indicating that NO, rather than the depletion of GSH per se, is the primary mediator of cell damage. In addition, the guanylate cyclase (GC) inhibitor LY83583 is able to completely block activation of ERK1/2 and counteract BSO toxicity. In cortical neurons, NMDA (N-methyl-D-aspartic acid) treatment results in GSH decrease and BSO-mediated NO cytotoxicity is enhanced by either epidermal growth factor (EGF) or NMDA. These findings support the idea that GSH might represent the most important buffer of NO toxicity in neuronal cells, and indicate that the disruption of cellular redox buffering controlled by GSH makes neuronal cells susceptible to endogenous physiological flux of NO.

Limited DNA damage in human endothelial cells after hyperbaric oxygen treatment and protection from subsequent hydrogen peroxide exposure

BACKGROUND

In vitro studies on hyperbaric oxygen (HBO) therapy suggest that HBO may cause DNA damage, but this has not been evaluated using endothelial cells.

METHODS

Human umbilical cord endothelial cells (HUVECs) were exposed either to H(2)O(2) or to HBO for 90 min, with or without subsequent H(2)O(2) exposure. Measurements included the comet assay for DNA damage, and reduced and oxidised glutathione levels.

RESULTS

HUVECs showed sensitivity to H(2)O(2) (EC(50) of 0.2mM for DNA migration). A single 90 min HBO treatment at 2.2 ATA caused a statistically significant (ANOVA, P<0.05) increase of DNA migration in HUVECs to 6.8 ± 0.3% (mean ± SEM, n=8), which returned to normal levels (4.9 ± 0.1%, n=6) after 24h. Further exposure to 0.2mM H(2)O(2) after HBO treatment significantly increased the DNA migration in HBO-treated cells immediately post-treatment; but 24h later the cells showed 22% less DNA damage and higher glutathione than controls.

CONCLUSION

A single HBO exposure causes limited DNA damage to HUVECs, which repairs quickly. HBO treatment protects against H(2)O(2)-induced DNA damage and involves cellular glutathione.

SIGNIFICANCE

Endothelial cells are unlikely to be compromised during HBO therapy.

Interaction of GAG trinucleotide repeat and C-129T polymorphisms impairs expression of the glutamate-cysteine ligase catalytic subunit gene

Glutamate cysteine ligase (GCL) catalyzes the rate-limiting step in the de novo synthesis of glutathione (GSH). The catalytic subunit (GCLC) of GCL contains a GAG trinucleotide-repeat (TNR) polymorphism within the 5'-untranslated region (5'-UTR) that has been associated with various human disorders. Although several studies suggest that this variation influences GSH content, its implication for GCLC expression remains unknown. To better characterize its functional significance, we performed reporter gene assays with constructs containing the complete GCLC 5'-UTR upstream of a luciferase gene. Transfection of these vectors into various human cell lines did not reveal any significant differences between 7, 8, 9, or 10 GAG repeats, under either basal or oxidative stress conditions. To correlate these results with the previously described down-regulation induced by the C-129T GCLC promoter polymorphism, combinations of both variations were tested. Interestingly, the -129T allele down-regulates gene expression when combined with 7 GAG but not with 8, 9, or 10 GAG TNRs. This observation was confirmed in primary fibroblast cells, in which the combination of GAG TNR 7/7 and -129C/T genotypes decreased the GCLC protein level. These results provide evidence that interaction of the two variations can efficiently impair GCLC expression and thus suggest its involvement in the pathogenesis of diseases related to GSH metabolism.

Glutaredoxin-1 regulates TRAF6 activation and the IL-1 receptor/TLR4 signalling

Glutaredoxin-1 (GRX-1) is a cytoplasmic enzyme that highly contributes to the antioxidant defense system. It catalyzes the reversible reduction of glutathione-protein mixed disulfides, a process called deglutathionylation. Here, we investigated the role of GRX-1 in the pathway triggered by interleukin-1/Toll-like receptor 4 (IL-1R/TLR4) by using RNA interference (RNAi) in HEK293 and HeLa cells. TNF receptor-associated factor 6 (TRAF6) is an intermediate signalling molecule involved in the signal transduction by members of the interleukin-1/Toll-like receptor (IL-1R/TLR) family. TRAF6 has an E3 ubiquitin ligase activity which depends on the integrity of an amino-terminal really interesting new gene (RING) finger motif. Upon receptor activation, TRAF6 undergoes K63-linked auto-polyubiquitination which mediates protein-protein interactions and signal propagation. Our data showed that IL-1R and TLR4-mediated NF-κB induction was severely reduced in GRX-1 knockdown cells. We found that the RING-finger motif of TRAF6 is S-glutathionylated under normal conditions. Moreover, upon IL-1 stimulation TRAF6 undergoes deglutathionylation catalyzed by GRX-1. The deglutathionylation of TRAF6 is essential for its auto-polyubiquitination and subsequent activation. Taken together, our findings reveal another signalling molecule affected by S-glutathionylation and uncover a crucial role for GRX-1 in the TRAF6-dependent activation of NF-κB by IL-1R/TLRs.

Increased expression of glutathione by estradiol, tumor necrosis factor-alpha, and interleukin 1-beta in endometrial stromal cells

PROBLEM

The intracellular antioxidant system, based on glutathione (GSH), plays a key role in endometrial detoxification reactions and has been proposed to be involved in the pathogenesis endometriosis. This study was designed to evaluate whether estradiol (E(2)) and proinflammatory cytokines have any effects on expression of glutathione in endometrial stromal cells (ESCs).

METHOD OF STUDY

Glutathione levels were measured utilizing high-performance liquid chromatography following in vitro culture and treatment of ESCs with estradiol, tumor necrosis factor-alpha (TNF-alpha) and interleukin 1-beta (IL-1beta).

RESULTS

The GSH level in E(2) (10(-8) m) treatment group was significantly higher than in the control group at 48 h (P < 0.05). In vitro treatment of ESCs with TNF-alpha 10 ng/mL as well as E(2) (10(-8) m) plus TNF-alpha 10 ng/mL for 48 hr also led to a significant increase in GSH level (P < 0.05; P < 0.05, respectively). Both IL-1beta 10 ng/mL and E(2) (10(-8) m) plus IL-1beta 10 ng/mL for 48 hr increased GSH level significantly (P < 0.05; P < 0.05, respectively) as well.

CONCLUSIONS

These findings might suggest that increased production of estradiol and proinflammatory cytokines in the peritoneal cavity possibly leads to the establishment of endometriosis through increased level of GSH.

Improved viability of freeze-thawed embryonic stem cells after exposure to glutathione

Adding a potent antioxidant, glutathione (GSH), to a cryoprotective solution consisting of dimethyl sulfoxide and ethylene glycol and/or postthaw culture medium significantly improved the postthaw viability of mouse embryonic stem cells. This effect, which was caused by a decrease in reactive oxygen species, was only induced by exposure of embryonic stem cells during cryopreservation.

Studies on glyphosate-induced carcinogenicity in mouse skin: a proteomic approach

Glyphosate is a widely used broad spectrum herbicide, reported to induce various toxic effects in non-target species, but its carcinogenic potential is still unknown. Here we showed the carcinogenic effects of glyphosate using 2-stage mouse skin carcinogenesis model and proteomic analysis. Carcinogenicity study revealed that glyphosate has tumor promoting activity. Proteomic analysis using 2-dimensional gel electrophoresis and mass spectrometry showed that 22 spots were differentially expressed (>2 fold) on glyphosate, 7, 12-dimethylbenz[a]anthracene (DMBA) and 12-O-tetradecanoyl-phorbol-13-acetate (TPA) application over untreated control. Among them, 9 proteins (translation elongation factor eEF-1 alpha chain, carbonic anhydrase III, annexin II, calcyclin, fab fragment anti-VEGF antibody, peroxiredoxin-2, superoxide dismutase [Cu-Zn], stefin A3, and calgranulin-B) were common and showed similar expression pattern in glyphosate and TPA-treated mouse skin. These proteins are known to be involved in several key processes like apoptosis and growth-inhibition, anti-oxidant responses, etc. The up-regulation of calcyclin, calgranulin-B and down-regulation of superoxide dismutase [Cu-Zn] was further confirmed by immunoblotting, indicating that these proteins can be good candidate biomarkers for skin carcinogenesis induced by glyphosate. Altogether, these results suggested that glyphosate has tumor promoting potential in skin carcinogenesis and its mechanism seems to be similar to TPA.

Oxidative stress and glutathione in TGF-beta-mediated fibrogenesis

Transforming growth factor beta (TGF-beta) is the most potent and ubiquitous profibrogenic cytokine, and its expression is increased in almost all the fibrotic diseases and in experimental fibrosis models. TGF-beta increases reactive oxygen species production and decreases the concentration of glutathione (GSH), the most abundant intracellular free thiol and an important antioxidant, which mediates many of the fibrogenic effects of TGF-beta in various types of cells. A decreased GSH concentration is also observed in human fibrotic diseases and in experimental fibrosis models. Although the biological significance of GSH depletion in the development of fibrosis remains obscure, GSH and N-acetylcysteine, a precursor of GSH, have been used in clinics for the treatment of fibrotic diseases. This review summarizes recent findings in the field to address the potential mechanism whereby oxidative stress mediates fibrogenesis induced by TGF-beta and the potential therapeutic value of antioxidant treatment in fibrotic diseases.

Evaluation of equol function on anti- or prooxidant status in vivo

The present study was performed to investigate the effects of equol on oxidative stress and the antioxidant defense system in the livers of mice. Mice were orally administered equol at either 5 or 25 mg/kg body weight/day for 1, 3, or 7 wk. Equol administration significantly inhibited biomarkers of oxidative stress (thiobarbituric acid-reactive substances value, carbonyl content, and serum 8-OH-dG) at all doses and for all durations of administration, and this phenomenon was most pronounced at 3 wk. Moreover, catalase and total superoxide dismutase (SOD) activities and their mRNA expression were significantly increased by equol. Although equol increased the glutathione peroxidase (GSH-px) activity in mice treated with equol for 1 wk, long-term administration of equol (7 wk) caused a decrease in the ratio of reduced/oxidized glutathione (GSH/GSSG) and the activities of GSH-px and glutathione reductase (GR). Taken together, these results suggest that equol may act as an antioxidant through an inhibition of oxidative stress and stimulation of catalase and SOD, but can also cause prooxidant effects such as reduction of the GSH/GSSG ratio, depending on the treatment period.

The depletion of nuclear glutathione impairs cell proliferation in 3t3 fibroblasts

Background

Glutathione is considered essential for survival in mammalian cells and yeast but not in prokaryotic cells. The presence of a nuclear pool of glutathione has been demonstrated but its role in cellular proliferation and differentiation is still a matter of debate.

Principal Findings

We have studied proliferation of 3T3 fibroblasts for a period of 5 days. Cells were treated with two well known depleting agents, diethyl maleate (DEM) and buthionine sulfoximine (BSO), and the cellular and nuclear glutathione levels were assessed by analytical and confocal microscopic techniques, respectively. Both agents decreased total cellular glutathione although depletion by BSO was more sustained. However, the nuclear glutathione pool resisted depletion by BSO but not with DEM. Interestingly, cell proliferation was impaired by DEM, but not by BSO. Treating the cells simultaneously with DEM and with glutathione ethyl ester to restore intracellular GSH levels completely prevented the effects of DEM on cell proliferation.

Conclusions

Our results demonstrate the importance of nuclear glutathione in the control of cell proliferation in 3T3 fibroblasts and suggest that a reduced nuclear environment is necessary for cells to progress in the cell cycle.

Effect of Aminoethylcysteine Ketimine Decarboxylated Dimer, a Natural Sulfur Compound Present in Human Plasma, onTert-Butyl Hydroperoxide-induced Oxidative Stress in Human Monocytic U937 Cells

Aminoethylcysteine ketimine decarboxylated dimer (AECK-DD) is a natural sulphur compound present in human plasma and urine and in mammalian brain. Recently, it has been detected in many common dietary vegetables. The aim of the present study was to evaluate the ability of AECK-DD to affect cellular response of U937 human monocytic cells to tert-butyl hydroperoxide-induced oxidative stress. AECK-DD was incorporated into cells, as confirmed by GC-MS analyses, without any cytotoxic effect. A 24 h treatment with 50 and 250 microM AECK-DD resulted in the incorporation of 0.10 +/- 0.01 and 0.47 +/- 0.08ng AECK-DD x 10(6) cells, respectively. U937 cells pretreated with AECK-DD (in the range 4-100 microM) showed an increased resistance to tert-butyl hydroperoxide-induced necrotic death, as revealed by a higher percent of survival measured at all incubation times with respect to control cells. Moreover, the protective effect exhibited by AECK-DD is significantly stronger with respect to that obtained with other common antioxidants (N-acetyl cysteine and trolox) and comparable, although somewhat higher, to that of vitamin E. This effect seems to be due to the ability of AECK-DD to reduce glutathione depletion and to inhibit lipid peroxidation during tert-butyl hydroperoxide treatment. It can be concluded that AECK-DD protects cultured human monocytic cells against tert-butyl hydroperoxide-induced oxidative stress and subsequent cell death, likely through an antioxidant action inside the cell. Due to its presence in both human plasma and urine, AECK-DD may play a role in the modulation of oxidative processes in vivo.

Differential responses of proliferative and non-proliferative leukemia cells to oxidative stress

The response of three human leukemia cell lines, the proliferative promonocyte THP-1 and the promyeloid HL60 cells and the non-proliferative phorbol ester-treated HL60 cells (HL60/PMA), to oxidative stress induced by tert-butylhydroperoxide (t-BHP) treatment was analyzed by fluorescence microplate assay, anti-oxidant enzyme activity measurements, high performance liquid chromatography, yopro-1/PI incorporation, poly (ADP-ribose) polymerase and caspase 3 cleavages. After t-BHP treatment, the non-proliferative HL60/PMA cells exhibited a weak increase in reactive oxygen species (ROS) production, a better preservation of thiol content, a decrease of glutathione peroxidase activity and a high ability to undergo necrosis rather than apoptosis. Submitted to the same treatment, the proliferative HL60 and THP-1 cells exhibited a high increase of ROS production, a moderate thiol depletion and a high percentage of apoptosis. Under thiol depleting conditions, the oxidative treatment of the HL60/PMA cells resulted in a high ROS production that reached levels similar to those of the two other cell lines and in cell death mainly by necrosis. In conclusion, these results that show proliferative phenotype is essential for cell response towards oxidative stress, are of particular interest in chemotherapy involving an oxidative mechanism.

Damage to the cell antioxidative system in human erythrocytes incubated with idarubicin and glutaraldehyde

Encapsulation of antineoplastic drugs within erythrocytes is one of the studied strategies to diminish the toxic side effects of anthracycline antibiotics. Glutaraldehyde is often used as crosslinking agent to link the drugs, including idarubicin (IDA) to the cells. The previous studies indicated that in glutaraldehyde-treated human erythrocytes the elevated level of drug was observed but also the various changes in the organization of the red cells were noted. In this study, we continue our investigations and now we concentrate on the effect of these compounds on antioxidative system in erythrocytes. We determined reactive oxygen species (ROS) production, glutathione content and alterations in the activity of enzymes responsible for maintaining glutathione in reduced form in human erythrocytes. Measurements of both reduced and total glutathione levels and the activity of glutathione reductase and glucose-6-phosphate dehydrogenase were performed spectrophotometrically. The results show that ROS were produced in erythrocytes treated with IDA and with IDA and glutaraldehyde. IDA at a concentration of 10 microg/ml did not cause any changes in total or reduced glutathione levels. When IDA-preincubated erythrocytes were treated with glutaraldehyde, significant changes in the determined parameters were observed in a glutaraldehyde concentration dependent manner. It was correlated with decreased activity of glutathione reductase (GR) and glucose-6-phosphate dehydrogenase (G6PD). Together with the significant changes in reduced form of glutathione (GSH)/total glutathione ratio, the exposure of phosphatidylserine at the cell surface was also observed.

Effect of 100 mT homogeneous static magnetic field on [Ca2+]c response to ATP in HL-60 cells following GSH depletion

Calcium is an important molecule in a number of biological systems. Often these systems are signal transduction cascades involving molecules such as ATP. ATP activates second messengers which can interact with ion channels on the endoplasmic/sarcoplasmic reticulum resulting in the emptying of the intracellular calcium stores and an increase in cytosolic free calcium concentration ([Ca2+]c). Changes in [Ca2+]c can be influenced by external factors such as a static magnetic field (SMF). One hypothesis suggests that a SMF affects the cells through the radical pair mechanism. By reducing the number of antioxidant molecules like glutathione (GSH), the proportion of free radicals in the cells is increased and may lead to a greater probability of a biological response to a SMF. The purpose of this study was to determine if the [Ca2+]c response to ATP was affected by depletion of GSH by diethylmaleate (DEM) and the absence or presence of a 100 mT homogeneous SMF. Undifferentiated HL-60 cells were loaded with fura-2 AM. [Ca2+]c was measured in real time using a ratiometric fluorescence spectroscopy system. Various (DEM) ranging from 1 to 15 mM were added to deplete GSH. Cells were either exposed to sham or magnetic field (100 mT) for 13 min (780 s) and challenged with 1 microM ATP. The data show that [Ca2+]c was elevated following treatment with DEM with greater [Ca2+]c at higher [DEM]. The [Ca2+]c response to ATP was decreased as the DEM concentration increased. However, there was no effect of a 100 mT SMF on the average [Ca2+]c peak following ATP activation or the full width at half maximum (FWHM) of the [Ca2+]c response and recovery after ATP activation.

Is propylene oxide induced cell proliferation in rat nasal respiratory epithelium mediated by a severe depletion of water-soluble non-protein thiol?

Propylene oxide (PO) concentrations >or=300 ppm induced cell proliferation and tumors in rat nasal respiratory epithelium (NRE). Cell proliferation was suggested to result from depletion of glutathione (GSH) in NRE. In order to substantiate this hypothesis, cell proliferation - measured by bromodeoxyuridine incorporation into DNA of the epithelium lining middle septum, dorsal medial meatus, and medial and lateral surfaces of the nasoturbinate in transverse nasal sections taken immediately posterior to the upper incisor teeth - and water-soluble non-protein thiol (NPSH) in NRE were determined after exposing male Fischer 344 rats to 50 ppm, 100 ppm, 200 ppm, or 300 ppm PO (6 h/day, 3 days). Both parameters were also investigated after treating rats for 3 days with diethylmaleate (DEM; 2 x 250 mg/kg/day or 500 + 150 mg/kg/day) or buthionine sulfoximine (BSO; 500 mg/kg/day). Exposure to 50 ppm PO and treatment with 2 x2 50 mg/kg/day DEM resulted in NPSH levels approximating 50% and 80% of the level in untreated controls, respectively. Cell proliferation did not increase. After exposures to >or= 100 ppm PO or treatment with BSO or 500 + 150 mg/kg/day DEM, NPSH was depleted to <or=1/3 of the control level and cell proliferation increased 2.0-3.7-fold the control value. In conclusion, profound perturbation of the GSH status may represent a crucial step in PO induced rat nasal tumorigenicity.

Analysis of protein posttranslational modifications by mass spectrometry: With special reference to haemoglobin

Mass spectrometry provides a convenient platform for the study of different protein post translational modifications from clinical specimen. Analysis of different post translational modifications of hemoglobin like glycation and glutathionylation can provide useful information on the disease progression and the possible outcome of therapies. In the present study, we have addressed post translational modifications of hemoglobin like glutathionylation and glycation in relation to diabetes and chronic renal failure. We found that both alpha and beta chains of human hemoglobin are glycated irrespective of the extent of glycemia as evidenced by a mass increment of 162 Da. The phenomenon of glutathionylation was observed with only the beta globin chain of hemoglobin probably due to the presence of an accessible cysteine residue indicated by a mass increment of 305 Da. Also, the extent of gltuathionylation observed in the CRF patients could correlate with the severity of the oxidative stress owing to renal replacement therapies like dialysis and transplantation.

Positive and negative regulation of insulin signaling by reactive oxygen and nitrogen species

Regulated production of reactive oxygen species (ROS)/reactive nitrogen species (RNS) adequately balanced by antioxidant systems is a prerequisite for the participation of these active substances in physiological processes, including insulin action. Yet, increasing evidence implicates ROS and RNS as negative regulators of insulin signaling, rendering them putative mediators in the development of insulin resistance, a common endocrine abnormality that accompanies obesity and is a risk factor of type 2 diabetes. This review deals with this dual, seemingly contradictory, function of ROS and RNS in regulating insulin action: the major processes for ROS and RNS generation and detoxification are presented, and a critical review of the evidence that they participate in the positive and negative regulation of insulin action is provided. The cellular and molecular mechanisms by which ROS and RNS are thought to participate in normal insulin action and in the induction of insulin resistance are then described. Finally, we explore the potential usefulness and the challenges in modulating the oxidant-antioxidant balance as a potentially promising, but currently disappointing, means of improving insulin action in insulin resistance-associated conditions, leading causes of human morbidity and mortality of our era.

Molecular mechanisms and clinical implications of reversible protein S-glutathionylation

Sulfhydryl chemistry plays a vital role in normal biology and in defense of cells against oxidants, free radicals, and electrophiles. Modification of critical cysteine residues is an important mechanism of signal transduction, and perturbation of thiol-disulfide homeostasis is an important consequence of many diseases. A prevalent form of cysteine modification is reversible formation of protein mixed disulfides (protein-SSG) with glutathione (GSH). The abundance of GSH in cells and the ready conversion of sulfenic acids and S-nitroso derivatives to S-glutathione mixed disulfides suggests that reversible S-glutathionylation may be a common feature of redox signal transduction and regulation of the activities of redox sensitive thiol-proteins. The glutaredoxin enzyme has served as a focal point and important tool for evolution of this regulatory mechanism, because it is a specific and efficient catalyst of protein-SSG deglutathionylation. However, mechanisms of control of intracellular Grx activity in response to various stimuli are not well understood, and delineation of specific mechanisms and enzyme(s) involved in formation of protein-SSG intermediates requires further attention. A large number of proteins have been identified as potentially regulated by reversible S-glutathionylation, but only a few studies have documented glutathionylation-dependent changes in activity of specific proteins in a physiological context. Oxidative stress is a hallmark of many diseases which may interrupt or divert normal redox signaling and perturb protein-thiol homeostasis. Examples involving changes in S-glutathionylation of specific proteins are discussed in the context of diabetes, cardiovascular and lung diseases, cancer, and neurodegenerative diseases.

Quantitation of glutathione by liquid chromatography/positive electrospray ionization tandem mass spectrometry

Glutathione (GSH) is a tripeptide composed of glutamate, cysteine, and glycine. It is present in practically all cells and has several important roles, such as preventing the oxidation of the sulfhydryl groups of proteins within a cell. Evidence for GSH deficiency or depletion has been found in a variety of diseases and toxicity-related studies, including diabetes and induction of oxidative stress to form reactive oxygen species which cause DNA, lipid, and protein oxidations. A simple, selective, and sensitive analytical method for measuring low levels of GSH in biological fluids would therefore be desirable to conduct GSH deficiency or depletion-related mechanistic toxicity studies. Here a method for both low- and high-level quantitation of GSH from cultured cells and rat liver tissues via liquid chromatography/positive electrospray ionization tandem mass spectrometry (LC/ESI-MS/MS) has been developed. The lower limit of quantitation (LOQ) of the method was 5 ng/mL. The method is linear over a wide dynamic concentration range of 5.0 to 5000.0 ng/mL, with a correlation coefficient R2 > 0.99. The intra-day assay precision relative standard deviation (RSD) values for all quality control (QC) samples were < or =16.31%, with accuracy values ranging from 94.13 to 97.80%. The inter-day assay precision RSD values for all QC samples were < or =15.94%, with accuracy values ranging from 94.51 to 100.29%. With this method, low levels of GSH from diethyl maleate (DEM)-treated mouse lymphoma cells, and GSH in rat liver tissues, were quantified.

Protective effect of PicrosideⅡ against H2O2-induced damage in L-02 cells

AIM: To study the protective effect of Picroside Ⅱ on L-02 cell damage induced by oxidative stress.

METHODS: L-02 cells damage induced by hydrogen peroxide (H₂O₂) were chosen to establish the model of hepatocellular oxidative stress. The proliferation of L-02 cells was observed using 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide (MTT) assay. The apoptosis of L-02 cells was detected using Annexin-V/propidium iodide, propidium iodide stain flow cytometry (FCM). The mitochondrial membrane potential (△Ψm) was analyzed by rhodamine123 stain FCM and the level of reactive oxygen species (ROS) in L-02 cells was determined using dihy-drohodamine123 stain FCM.

RESULTS: 0.6 mmol/L H₂O₂ induced L-02 cell apoptosis, increased intracellular accumulation of ROS, decreased mitochondrial membrane potential. After treatment with 0.05, 0.5, 5 mmol/L Picroside Ⅱ, H₂O₂-induced apoptosis in L-02 significantly reduced (30.8% ± 9.09%, 10.2% ± 9.82%, 8.2% ± 7.10% vs 42.8% ± 8.28%, all P < 0.01). At the same time significantly reduced were H₂O₂-induced intracellular accumulation of ROS and mitochondrial membrane potential.

CONCLUSION: Picroside Ⅱ has protective effect on L-02 cell damage induced by oxidative stress and the effect might be attributed to its removal of ROS and increased △Ψm level.