Listeria monocytogenes utilizes glutathione and limited inorganic sulfur compounds as sources of essential cysteine

Listeria monocytogenes (Lm) is a Gram-positive facultative intracellular pathogen that leads a biphasic lifecycle, transitioning its metabolism and selectively inducing virulence genes when it encounters mammalian hosts. Virulence gene expression is controlled by the master virulence regulator PrfA, which is allosterically activated by the host- and bacterially derived glutathione (GSH). The amino acid cysteine is the rate-limiting substrate for GSH synthesis in bacteria and is essential for bacterial growth. Unlike many bacteria, Lm is auxotrophic for cysteine and must import exogenous cysteine for growth and virulence. GSH is enriched in the host cytoplasm, and previous work suggests that Lm utilizes exogenous GSH for PrfA activation. Despite these observations, the import mechanism(s) for GSH remains elusive. Analysis of known GSH importers predicted a homologous importer in Lm comprised of the Ctp ABC transporter and the OppDF ATPases of the Opp oligopeptide importer. Here, we demonstrated that the Ctp complex is a high-affinity GSH/GSSG importer that is required for Lm growth at physiologically relevant concentrations. Furthermore, we demonstrated that OppDF is required for GSH/GSSG import in an Opp-independent manner. These data support a model where Ctp and OppDF form a unique complex for GSH/GSSG import that supports growth and pathogenesis. In addition, we show that Lm utilizes the inorganic sulfur sources thiosulfate and H2S for growth in a CysK-dependent manner in the absence of other cysteine sources. These findings suggest a pathoadaptive role for partial cysteine auxotrophy in Lm, where locally high GSH/GSSG or inorganic sulfur concentrations may signal arrival to distinct host niches.

Sleep Deprivation-Induced Oxidative Stress in Rat Models: A Scoping Systematic Review

Sleep deprivation is highly prevalent in the modern world, possibly reaching epidemic proportions. While multiple theories regarding the roles of sleep exist (inactivity, energy conservation, restoration, brain plasticity and antioxidant), multiple unknowns still remain regarding the proposed antioxidant roles of sleep. The existing experimental evidence is often contradicting, with studies pointing both toward and against the presence of oxidative stress after sleep deprivation. The main goals of this review were to analyze the existing experimental data regarding the relationship between sleep deprivation and oxidative stress, to attempt to further clarify multiple aspects surrounding this relationship and to identify current knowledge gaps. Systematic searches were conducted in three major online databases for experimental studies performed on rat models with oxidative stress measurements, published between 2015 and 2022. A total of 54 studies were included in the review. Most results seem to point to changes in oxidative stress parameters after sleep deprivation, further suggesting an antioxidant role of sleep. Alterations in these parameters were observed in both paradoxical and total sleep deprivation protocols and in multiple rat strains. Furthermore, the effects of sleep deprivation seem to extend beyond the central nervous system, affecting multiple other body sites in the periphery. Sleep recovery seems to be characterized by an increased variability, with the presence of both normalizations in some parameters and long-lasting changes after sleep deprivation. Surprisingly, most studies revealed the presence of a stress response following sleep deprivation. However, the origin and the impact of the stress response during sleep deprivation remain somewhat unclear. While a definitive exclusion of the influence of the sleep deprivation protocol on the stress response is not possible, the available data seem to suggest that the observed stress response may be determined by sleep deprivation itself as opposed to the experimental conditions. Due to this fact, the observed oxidative changes could be attributed directly to sleep deprivation.

SAR of L-ABBA analogs for GGT1 inhibitory activity and L-ABBA's effect on plasma cysteine and GSH species

Gamma-glutamyl transferase 1 (GGT1) is a critical enzyme involved in the hydrolysis and/or transfer of gamma-glutamyl groups of glutathione, which helps maintain cysteine levels in plasma. In this study, we synthesized L-ABBA analogs to investigate their inhibitory effect on GGT1 hydrolysis and transpeptidase activity, with the goal of defining the pharmacophore of L-ABBA. Our structure-activity relationship (SAR) study revealed that an α-COO^- and α-NH₃⁺ group, as well as a two-CH₂ unit distance between α-C and boronic acid, are essential for the activity. The addition of an R (alkyl) group at the α-C reduced the activity of GGT1 inhibition, with L-ABBA being the most potent inhibitor among the analogs. Next, we investigated the impact of L-ABBA on plasma levels of cysteine and GSH species, with the expectation of observing reduced cysteine levels and enhanced GSH levels due to its GGT1 inhibition. We administered L-ABBA intraperitoneally and determined the plasma levels of cysteine, cystine, GSH, and GSSG using LCMS. Our results showed time- and L-ABBA dose-dependent changes in total plasma cysteine and GSH levels. This study is the first to demonstrate the regulation of plasma thiol species upon GGT1 inhibition, with plasma cystine levels reduced by up to ∼75% with L-ABBA (0.3 mg/dose). Cancer cells are highly dependent on the uptake of cysteine from plasma for maintaining high levels of intracellular glutathione. Thus, our findings suggest that GGT1 inhibitors, such as L-ABBA, have a potential to be used for GSH reduction thereby inducing oxidative stress in cancer cells and reducing their resistance to many chemotherapeutic agents.

SARS-CoV-2 Infection-Of Music and Mechanics of Its Spikes! A Perspective

The COVID-19 pandemic has been inflicted upon humanity by the SARS-CoV-2 virus, the latest insidious incarnation of the coronaviruses group. While in its wake intense scientific research has produced breakthrough vaccines and cures, there still exists an immediate need to further understand the origin, mechanobiology and biochemistry, and destiny of this virus so that future pandemics arising from similar coronaviruses may be contained more effectively. In this Perspective, we discuss the various evidential findings of virus propagation and connect them to respective underpinning cellular biomechanical states leading to corresponding manifestations of the viral activity. We further propose avenues to tackle the virus, including from a "musical" vantage point, and contain its relentless strides that are currently afflicting the global populace.

Elemental Sulfur Inhibits Yeast Growth via Producing Toxic Sulfide and Causing Disulfide Stress

Elemental sulfur is a common fungicide, but its inhibition mechanism is unclear. Here, we investigated the effects of elemental sulfur on the single-celled fungus Saccharomyces cerevisiae and showed that the inhibition was due to its function as a strong oxidant. It rapidly entered S. cerevisiae. Inside the cytoplasm, it reacted with glutathione to generate glutathione persulfide that then reacted with another glutathione to produce H₂S and glutathione disulfide. H₂S reversibly inhibited the oxygen consumption by the mitochondrial electron transport chain, and the accumulation of glutathione disulfide caused disulfide stress and increased reactive oxygen species in S. cerevisiae. Elemental sulfur inhibited the growth of S. cerevisiae; however, it did not kill the yeast for up to 2 h exposure. The combined action of elemental sulfur and hosts’ immune responses may lead to the demise of fungal pathogens.

Protocols to Measure Oxidative Stress and DNA Damage in Asthma

Asthma is associated with oxidative stress and oxidative damage of biomolecules, including DNA. Here, we describe the protocols to quantify reactive oxygen species (ROS) and oxidative stress markers in a mouse model of allergic airway inflammation. We also provide detailed methods to measure DNA damage by long-run real-time PCR for DNA-damage quantification (LORD-Q) assay and gene-specific DNA damage analyses by long amplicon (LA)-qPCR. Additionally, we describe methods to quantify oxidized DNA base lesions in lung genomic DNA by mass spectrometry, and to measure enzymatic activity of 8-oxoguanine DNA glycosylase (OGG1). Using these methods, the levels of oxidative stress and DNA damage in allergic inflammation and asthma can be elucidated.

The Role of the GSTF11 Gene in Resistance to Powdery Mildew Infection and Cold Stress

Oilseed rape (Brassica napus) is an economically important crop. In a temperate climate, powdery mildew Erysiphe crucifertaum can drastically reduce its yield. Nevertheless, cultivars resistant to this fungal disease have not yet been selected. Glutathione S-transferase GSTF11 is involved in glucosinolate (GSL) biosynthesis and response to stress, including fungal deceases. However, the impact of exogenous GSTF11 gene expression on resistance to powdery mildew has not yet been confirmed and requires further investigation. Transgenic B. napus was generated for this purpose. It demonstrated increased GST activity and a higher GSH:GSSG ratio under normal conditions. Powdery mildew Erysiphe crucifertaum caused 50% mortality in wild type (WT) plants. In most of transgenic plants, mycelium growth was inhibited. The infection contributed to higher GSTF11 expression and increased levels of glutathione (GSH) and oxidized glutathione (GSSG) in both transgenic and WT plants. In contrast, GSTF11 mRNA content, GST activity and GSSG level were lower only in WT plants. In transgenic plants, increased resistance to powdery mildew correlated with a lower GSH:GSSG ratio, indicating a higher content of neutralized toxic molecules. GSTF11 expression was also affected by cold stress, but not drought. At -1 °C, the expression level increased only in transgenic plants. Therefore, GSTF11 appears to be nonspecific and is able to protect plants under several types of stress. This gene could be used as a target in the production of stress tolerant cultivars.

Pre-exercise Carbohydrate Drink Adding Protein Improves Post-exercise Fatigue Recovery

Purpose: This study aimed to assess the requirement of protein in pre-exercise carbohydrate drinks for optimal endurance performance at high intensity and post-exercise fatigue recovery.

Methods: Endurance performance at 85% V.⁢O2_peak of young men (age 20 ± 0.9 years, V.⁢_2peak 49.3 ± 0.3 L/min) was measured for two consecutive days using cycling time to exhaustion and total work exerted 2 h after three isocaloric supplementations: RICE (50 g, protein: 1.8 g), n = 7; SOY + RICE (50 g, protein: 4.8 g), n = 7; and WHEY + RICE (50 g, protein: 9.2 g), n = 7.

Results: Endurance performance was similar for the three supplemented conditions. Nevertheless, maximal cycling time and total exerted work from Day 1 to Day 2 were improved in the WHEY + RICE (+21%, p = 0.05) and SOY-RICE (+16%, p = 0.10) supplemented conditions, not the RICE supplemented condition. Increases in plasma interleukin-6 (IL-6) were observed 1 h after exercise regardless of supplemented conditions. Plasma creatine kinase remained unchanged after exercise for all three supplemented conditions. Increases in ferric reducing antioxidant power (FRAP) after exercise were small and similar for the three supplemented conditions.

Conclusion: Adding protein into carbohydrate drinks provides no immediate benefit in endurance performance and antioxidant capacity yet enhances fatigue recovery for the next day. Soy-containing carbohydrate drink, despite 50% less protein content, shows similar fatigue recovery efficacy to the whey protein-containing carbohydrate drink. These results suggest the importance of dietary nitrogen sources in fatigue recovery after exercise.

The Effectiveness of Glutathione Redox Status as a Possible Tumor Marker in Colorectal Cancer

The role of oxidative stress (OS) in cancer is a matter of great interest due to the implication of reactive oxygen species (ROS) and their oxidation products in the initiation of tumorigenesis, its progression, and metastatic dissemination. Great efforts have been made to identify the mechanisms of ROS-induced carcinogenesis; however, the validation of OS byproducts as potential tumor markers (TMs) remains to be established. This interventional study included a total of 80 colorectal cancer (CRC) patients and 60 controls. By measuring reduced glutathione (GSH), its oxidized form (GSSG), and the glutathione redox state in terms of the GSSG/GSH ratio in the serum of CRC patients, we identified significant changes as compared to healthy subjects. These findings are compatible with the effectiveness of glutathione as a TM. The thiol redox state showed a significant increase towards oxidation in the CRC group and correlated significantly with both the tumor state and the clinical evolution. The sensitivity and specificity of serum glutathione levels are far above those of the classical TMs CEA and CA19.9. We conclude that the GSSG/GSH ratio is a simple assay which could be validated as a novel clinical TM for the diagnosis and monitoring of CRC.

Decreased Expression of the Host Long-Noncoding RNA-GM Facilitates Viral Escape by Inhibiting the Kinase activity TBK1 via S-glutathionylation

Viruses have evolved multiple strategies to evade elimination by the immune system. Here we examined the contribution of host long noncoding RNAs (lncRNAs) in viral immune evasion. By functional screening of lncRNAs whose expression decreased upon viral infection of macrophages, we identified a lncRNA (lncRNA-GM, Gene Symbol: AK189470.1) that promoted type I interferon (IFN-I) production and inhibited viral replication. Deficiency of lncRNA-GM in mice increased susceptibility to viral infection and impaired IFN-I production. Mechanistically, lncRNA-GM bound to glutathione S-transferase M1 (GSTM1) and blocked GSTM1 interaction with the kinase TBK1, reducing GSTM1-mediated S-glutathionylation of TBK1. Decreased S-glutathionylation enhanced TBK1 activity and downstream production of antiviral mediators. Viral infection reprogrammed intracellular glutathione metabolism and furthermore, an oxidized glutathione mimetic could inhibit TBK1 activity and promote viral replication. Our findings reveal regulation of TBK1 by S-glutathionylation and provide insight into the viral mediated metabolic changes that impact innate immunity and viral evasion.

Biochemical changes and antioxidant capacity of naringin and naringenin against malathion toxicity in Saccharomyces cerevisiae

Flavonoids are rich in seeds, citrus fruits, olive oil, tea and red wine. Citrus flavonoids constitute an important type of flavonoids. Naringin and naringenin belong to flavonoids with known antioxidant and were found to display antioxidant activities. Malathion is an organophosphorus pesticide that has been broadly used throughout the world to control weeds and pests. It has also been used in public health for mosquito control and fruit fly eradication programs. Malathion, naringin, and naringenin were added to be in 40, 80, and 160 mg doses in Saccharomyces cerevisiae cultures mainly used to determine the antioxidant capacity, it is known that they have shown similar results to man. At the end of the experiment, total protein, malondialdehyde (MDA), reduced glutathione (GSH), oxidized glutathione (GSSG), vitamin K, vitamin E, vitamin D, ergosterol, stigmasterol, β-Sitosterol, and fatty acids were analyzed by HPLC (high performance liquid chromatography) and GC (gas chromatography) devices in the tested S. cerevisiae samples. The contents of the yeast cell of octanoic acid (C8:0), lauric acid (C12:0), myristic acid (C14:0), palmitic acid (C16:0), palmitoleic acid (C16:1n-7), heptadecanoic acid (C17:0), stearic acid (C18:0), oleic acid (C18:1n-9), and linoleic acid (C18:2n-6) were identified. There were statistically significant changes in total protein, MDA, GSH, GSSG, vitamin K, vitamin E, vitamin D, phytosterol and fatty acid levels. It was determined that naringin and naringenin showed statistically significant decreases against malathion toxicity on these parameters. From this study it is found that, the mitigating effect of naringin against DPPH stable free radical was higher than that of naringenin. Citrus flavonoid, naringin showed promising antioxidant activity which can be used as effective protecting agents against oxidative stress.

Oxidized glutathione promotes association between eukaryotic translation elongation factor 1Bγ and Ure2p glutathione transferase from Phanerochaete chrysosporium

The eukaryotic translation elongation factor 1Bγ (eEF1Bγ) is an atypical member of the glutathione transferase (GST) superfamily. Contrary to more classical GSTs having a role in toxic compound detoxification, eEF1Bγ is suggested to act as a scaffold protein, anchoring the elongation factor complex EF1B to the endoplasmic reticulum. In this study, we show that eEF1Bγ from the basidiomycete Phanerochaete chrysosporium is fully active as a glutathione transferase in vitro and undergoes conformational changes upon binding of oxidized glutathione. Using real-time analyses of biomolecular interactions, we show that GSSG allows eEF1Bγ to physically interact with other GSTs from the Ure2p class, opening new perspectives for a better understanding of the role of eEF1Bγ in cellular oxidative stress response.

Measurement of Glutathione as a Tool for Oxidative Stress Studies by High Performance Liquid Chromatography

Background: Maintenance of the ratio of glutathione in the reduced (GSH) and oxidised (GSSG) state in cells is important in redox control, signal transduction and gene regulation, factors that are altered in many diseases. The accurate and reliable determination of GSH and GSSG simultaneously is a useful tool for oxidative stress determination. Measurement is limited primarily to the underestimation of GSH and overestimation GSSG as a result of auto-oxidation of GSH. The aim of this study was to overcome this limitation and develop, optimise and validate a reverse-phase high performance liquid chromatographic (HPLC) assay of GSH and GSSG for the determination of oxidant status in cardiac and chronic kidney diseases. Methods: Fluorescence detection of the derivative, glutathione-O-pthaldialdehyde (OPA) adduct was used. The assay was validated by measuring the stability of glutathione and glutathione-OPA adduct under conditions that could affect the reproducibility including reaction time and temperature. Linearity, concentration range, limit of detection (LOD), limit of quantification (LOQ), recovery and extraction efficiency and selectivity of the method were assessed. Results: There was excellent linearity for GSH (r² = 0.998) and GSSG (r² = 0.996) over concentration ranges of 0.1 µM–4 mM and 0.2 µM–0.4 mM respectively. The extraction of GSH from tissues was consistent and precise. The limit of detection for GSH and GSSG were 0.34 µM and 0.26 µM respectively whilst their limits of quantification were 1.14 µM and 0.88 µM respectively. Conclusion: These data validate a method for the simultaneous measurement of GSH and GSSG in samples extracted from biological tissues and offer a simple determination of redox status in clinical samples.

β-Lapachone Induces Acute Oxidative Stress in Rat Primary Astrocyte Cultures that is Terminated by the NQO1-Inhibitor Dicoumarol

β-lapachone (β-lap) is reduced in tumor cells by the enzyme NAD(P)H: quinone acceptor oxidoreductase 1 (NQO1) to a labile hydroquinone which spontaneously reoxidises to β-lap, thereby generating reactive oxygen species (ROS) and oxidative stress. To test for the consequences of an acute exposure of brain cells to β-lap, cultured primary rat astrocytes were incubated with β-lap for up to 4 h. The presence of β-lap in concentrations of up to 10 µM had no detectable adverse consequences, while higher concentrations of β-lap compromised the cell viability and the metabolism of astrocytes in a concentration- and time-dependent manner with half-maximal effects observed for around 15 µM β-lap after a 4 h incubation. Exposure of astrocytes to β-lap caused already within 5 min a severe increase in the cellular production of ROS as well as a rapid oxidation of glutathione (GSH) to glutathione disulfide (GSSG). The transient cellular accumulation of GSSG was followed by GSSG export. The β-lap-induced ROS production and GSSG accumulation were completely prevented in the presence of the NQO1 inhibitor dicoumarol. In addition, application of dicoumarol to β-lap-exposed astrocytes caused rapid regeneration of the normal high cellular GSH to GSSG ratio. These results demonstrate that application of β-lap to cultured astrocytes causes acute oxidative stress that depends on the activity of NQO1. The sequential application of β-lap and dicoumarol to rapidly induce and terminate oxidative stress, respectively, is a suitable experimental paradigm to study consequences of a defined period of acute oxidative stress in NQO1-expressing cells.

Validation of a simplified procedure for convenient and rapid quantification of reduced and oxidized glutathione in human plasma by liquid chromatography tandem mass spectrometry analysis

Endogenous glutathione (GSH) and glutathione disulfide (GSSG) status is highly sensitive to oxidative conditions and have broad application as a surrogate indicator of redox status in vivo. Established methods for GSH and GSSG quantification in whole blood display limited utility in human plasma, where GSH and GSSG levels are ~3-4 orders of magnitude below those observed in whole blood. This study presents simplified sample processing and analytical LC-MS/MS approaches exhibiting the sensitivity and accuracy required to measure GSH and GSSG concentrations in human plasma samples, which after 5-fold dilution to suppress matrix interferences range from 200 to 500 nm (GSH) and 5-30 nm (GSSG). The utility of the methods reported herein is demonstrated by assay performance and validation parameters which indicate good sensitivity [lower limits of quantitation of 4.99 nm (GSH) and 3.65 nm (GSSG), and high assay precision (intra-assay CVs 3.6 and 1.9%, and inter-assay CVs of 7.0 and 2.8% for GSH and GSSG, respectively). These methods also exhibited exceptional recovery of analyte-spiked plasma samples (98.0 ± 7.64% for GSH and 98.5 ± 12.7% for GSSG). Good sample stability at -80°C was evident for GSH for up to 55 weeks and GSSG for up to 46 weeks, with average CVs <15 and <10%, respectively.

Diastolic dysfunction in men with severe obstructive sleep apnea syndrome but without cardiovascular or oxidative stress-related comorbidities

Background:

We aimed to evaluate whether the severity of obstructive sleep apnea syndrome (OSAS) per se affects the prevalence of left ventricular (LV) diastolic dysfunction in patients without comorbidities.

Methods:

A total of 42 patients with first-diagnosed severe OSAS [apnea–hypopnea index (AHI) > 30] and 25 controls (AHI < 5), having been referred for snoring to the Sleep Laboratory Department of our tertiary Hospital, were enrolled in the study. Inclusion criteria were absence of any cardiovascular or oxidative stress-related comorbidities, and age between 20 and 70 years. Clinical, laboratory, echocardiographic, and polysomnographic data were recorded prospectively. Diastolic dysfunction diagnosis and grading was based on 2016 ASE/EACVI recommendations.

Results:

Severe OSAS was associated with significantly increased prevalence and degree of diastolic dysfunction (26/42; 61.9%) compared with controls (7/25; 28%) (p = 0.007). AHI ⩾ 55 (dichotomous value of severe OSAS subset) was also characterized by greater prevalence and degree of diastolic dysfunction compared with 30 < AHI < 55 patients (p = 0.015). In the severe OSAS subset, age >45 years-old, height <1.745 m, body-mass index (BMI) >27.76 kg m⁻², OSAS severity (AHI > 57.35), oxidative stress (overnight reduction of reduced to oxidized glutathione ratio < 18.44%), and BMI/height ratio > 16.155 kg m⁻³ (an index describing ‘dense’, short-heavy patients) presented significant diagnostic utility in identifying diastolic dysfunction in ROC-curve analysis (0.697 ⩾ AUC ⩾ 0.855, 0.001 ⩽ p ⩽ 0.018). In binary logistic regression model, advanced age (OR 1.23, 95% CI 1.025–1.477; p = 0.026) and AHI (OR 1.123, 95% CI 1.007–1.253; p = 0.036) showed independent association with diastolic dysfunction in severe OSAS.

Conclusions:

The present prospective study may suggest that severe OSAS is significantly associated with LV diastolic dysfunction; OSAS clinical severity exerts a positive influence on (and possibly constitutes an independent risk factor of) LV diastolic dysfunction.

The reviews of this paper are available via the supplementary material section.

Addressing Glutathione Redox Status in Clinical Samples by Two-Step Alkylation with N-ethylmaleimide Isotopologues

Determination of the ratio of reduced to oxidized glutathione is of profound clinical interest in assessing the oxidative status of tissues and body fluids. However, this ratio is not yet a routine clinical parameter due to the analytically challenging interconversion of reduced (free) glutathione to oxidized (bound) glutathione. We aimed to facilitate this ratio determination in order to aid its incorporation as a routine clinical parameter. To this end, we developed a simple derivatization route that yields different isotopologues of N-ethylmaleimide alkylated glutathione from reduced and oxidized glutathione (after its chemical reduction) for mass spectrometric analysis. A third isotopologue can be used as isotopic standard for simultaneous absolute quantification. As all isotopologues have similar chromatographic properties, matrix effects arising from different sample origins can only impact method sensitivity but not quantification accuracy. Robustness, simplified data analysis, cost effectiveness by one common standard, and highly improved mass spectrometric sensitivity by conversion of oxidized glutathione to an alkylated glutathione isotopologue are the main advantages of our approach. We present a method fully optimized for blood, plasma, serum, cell, and tissue samples. In addition, we propose production of N-ethylmaleimide customized blood collection tubes to even further facilitate the analysis in a clinical setting.

The antioxidant system in Olea europaea to enhanced UV-B radiation also depends on flavonoids and secoiridoids

The Mediterranean crop Olea europaea is often exposed to high UV-B irradiation conditions. To understand how this species modulates its enzymatic and non-enzymatic antioxidant system under high UV-B radiation, young O. europaea plants (cultivar "Galega Vulgar") were exposed, for five days, to UV-B radiation (6.5 kJ m^-2 d^-1 and 12.4 kJ m^-2 d^-1). Our data indicate that UV-doses slightly differ in the modulation of the antioxidant protective mechanisms. Particularly, superoxide dismutase (SOD), guaiacol peroxidase (GPox) and catalase (CAT) activities increased contributing to H₂O₂ homeostasis, being more solicited by higher UV-B doses. Also, glutathione reductase (Gr) activity, ascorbate (AsA) and reduced glutathione (GSH) pools increased particularly under the highest dose, suggesting a higher mobilization of the antioxidant system in this dose. The leaf metabolites' profile of this cultivar was analysed by UHPLC-MS. Interestingly, high levels of verbascoside were found, followed by oleuropein and luteolin-7-O-glucoside. Both UV-B treatments affected mostly less abundant flavonoids (decreasing 4'-methoxy luteolin and 4' or 3'-methoxy luteolin glucoside) and hydroxycinnamic acid derivatives (HCAds, increasing β-hydroxyverbascoside). These changes show not only different mobilization with the UV-intensity, but also reinforce for the first time the protective roles of these minor compounds against UV-B, as reactive oxygen species (ROS) scavengers and UV-B shields, in complement with other antioxidant systems (e.g. AsA/GSH cycle), particularly for high UV-B doses. Secoiridoids also standout in the response to both UV-B doses, with decreases of oleuropein and increases 2''-methoxyoleuropein. Being oleuropein an abundant compound, data suggest that secoiridoids play a more important role than flavonoids and HCAds, in O. europaea protection against UV-B, possibly by acting as signalling molecules and ROS scavengers. This is the first report on the influence of UV-B radiation on the secoiridoid oleuropein, and provides a novel insight to the role of this compound in the O. europaea antioxidant defence mechanisms.

Chronic exposure to xenobiotic pollution leads to significantly higher total glutathione and lower reduced to oxidized glutathione ratio in red blood cells of children with autism

Analyses of reduced glutathione (GSH), oxidized glutathione (GSSG), and total glutathione (tGSH) in red blood cell samples from 30 children diagnosed with autism and 30 age, gender, and socioeconomic status matched controls were undertaken. The children's ages ranged from 2 to 9. Samples were obtained from subjects residing in Western Pennsylvania, an area of the United States greatly affected by high levels of mercury deposition and airborne PM 2.5 particulates. Liquid chromatography - mass spectrometry was utilized by following EPA Method 6800 for sample analyses. The children with autism had a significantly lower mean red blood cell (RBC) reduced to oxidized glutathione ratio (GSH/GSSG) compared to the control children (p = 0.025). In addition, compared to the controls, the children with autism had significantly higher RBC tGSH values (p = 0.0076) and GSH values (p = 0.022). These results suggest that exposure to toxic elements may prompt compensatory increases in production of GSH in children with autism in environments higher in toxins. The compensation did not fully correct the anti-oxidant properties of exposure to xenobiotics as demonstrated by the significantly lower GSH/GSSG in children with autism compared to controls. Out of a set of glutathione biomarkers, GSH/GSSG may best determine the degree of compensation for oxidative stress in children with autism.

Exposure of Cultured Astrocytes to Menadione Triggers Rapid Radical Formation, Glutathione Oxidation and Mrp1-Mediated Export of Glutathione Disulfide

Menadione (2-methyl-1,4-naphthoquinone) is a synthetic derivative of vitamin K that allows rapid redox cycling in cells and thereby generates reactive oxygen species (ROS). To test for the consequences of a treatment of brain astrocytes with menadione, we incubated primary astrocyte cultures with this compound. Incubation with menadione in concentrations of up to 30 µM did not affect cell viability. In contrast, exposure of astrocytes to 100 µM menadione caused a time-dependent impairment of cellular metabolism and cell functions as demonstrated by impaired glycolytic lactate production and strong increases in the activity of extracellular lactate dehydrogenase and in the number of propidium iodide-positive cells within 4 h of incubation. In addition, already 5 min after exposure of astrocytes to menadione a concentration-dependent increase in the number of ROS-positive cells as well as a concentration-dependent and transient accumulation of cellular glutathione disulfide (GSSG) were observed. The rapid intracellular GSSG accumulation was followed by an export of GSSG that was prevented in the presence of MK571, an inhibitor of the multidrug resistance protein 1 (Mrp1). Menadione-induced glutathione (GSH) oxidation and ROS formation were found accelerated after glucose-deprivation, while the presence of dicoumarol, an inhibitor of the menadione-reducing enzyme NQO1, did not affect the menadione-dependent GSSG accumulation. Our study demonstrates that menadione rapidly depletes cultured astrocytes of GSH via ROS-induced oxidation to GSSG that is subsequently exported via Mrp1.

Analysis of Coenzymes and Antioxidants in Tissue and Blood Using 1D (1)H NMR Spectroscopy

Cellular coenzymes including coenzyme A (CoA), acetyl coenzyme A (acetyl-CoA), coenzymes of redox reactions and of energy, and antioxidants mediate biochemical reactions fundamental to the functioning of all living cells. The redox coenzymes include NAD⁺ (oxidized nicotinamide adenine dinucleotide), NADH (reduced nicotinamide adenine dinucleotide), NADP⁺ (oxidized nicotinamide adenine dinucleotide phosphate), and NADPH (reduced nicotinamide adenine dinucleotide phosphate); the energy coenzymes include ATP (adenosine triphosphate), ADP (adenosine diphosphate), and AMP (adenosine monophosphate); and the antioxidants include GSSG (oxidized glutathione) and GSH (reduced glutathione). Their measurement is important to better understand cellular metabolism. Recent advances have pushed the limit of metabolite quantitation using NMR methods to an unprecedented level, which offer a new avenue for analysis of the coenzymes and antioxidants. Unlike the conventional enzyme assays, which need separate protocols for analysis, a simple 1D ¹H NMR experiment enables analysis of all these molecular species in one step. In this chapter, we describe protocols for their identification and quantitation in tissue and whole blood using NMR spectroscopy.

Dicoumarol Inhibits Multidrug Resistance Protein 1-Mediated Export Processes in Cultured Primary Rat Astrocytes

Dicoumarol is frequently used as inhibitor of the detoxifying enzyme NAD(P)H:quinone acceptor oxidoreductase 1 (NQO1). In order to test whether dicoumarol may also affect the cellular glutathione (GSH) metabolism, we have exposed cultured primary astrocytes to dicoumarol and investigated potential effects of this compound on the cell viability as well as on the cellular and extracellular contents of GSH and its metabolites. Incubation of astrocytes with dicoumarol in concentrations of up to 100 µM did not acutely compromise cell viability nor was any GSH consumption or GSH oxidation to glutathione disulfide (GSSG) observed. However, unexpectedly dicoumarol inhibited the cellular multidrug resistance protein (Mrp) 1-dependent export of GSH in a time- and concentration-dependent manner with half-maximal effects observed at low micromolar concentrations of dicoumarol. Inhibition of GSH export by dicoumarol was not additive to that observed for the known Mrp1 inhibitor MK571. In addition, dicoumarol inhibited also the Mrp1-mediated export of GSSG during menadione-induced oxidative stress and the export of the GSH-bimane-conjugate (GS-B) that had been generated in the cells after exposure to monochlorobimane. Half-maximal inhibition of the export of Mrp1 substrates was observed at dicoumarol concentrations of around 4 µM (GSH and GSSG) and 30 µM (GS-B). These data demonstrate that dicoumarol strongly affects the GSH metabolism of viable cultured astrocytes by inhibiting Mrp1-mediated export processes and identifies for the first time Mrp1 as additional cellular target of dicoumarol.

Leukocytic toll-like receptor 2 knockout protects against diabetes-induced cardiac dysfunction

Diabetic cardiomyopathy is characterized by the deterioration of the myocardial function. Emerging evidences have indicated that leukocytic toll-like receptor 2 (TLR2) played an important role in the development of diabetic cardiomyopathy. Our study aimed to investigate whether TLR2 knockout (KO) exerted a cardioprotective effect in vivo. The establishment of diabetes model was set up in mice via intraperitoneal injection of streptozotocin (STZ). Results demonstrated that blocking of TLR2 significantly suppressed the enhanced left ventricular end-diastolic dimension (LVEDD), left ventricular end systolic diameter (LVESD) and the reduced the heart rate in diabetic cardiomyopathy mice. The decreased resting cell length, PS, TPS and + dL/dt while increased TR90 and - dL/dt caused by diabetic cardiomyopathy were remarkably inhibited by TLR2 KO. Besides that, the alleviated ΔFFI (360/380), decreased SERCA2a and p-NFATc3 expressions, extended Ca²⁺ decay time and elevated Calcineurin A induced by diabetic cardiomyopathy were vastly repressed by TLR2 KO in cardiocytes. Moreover, TLR2 gene silence could ameliorate oxidative stress-induced apoptosis, evidences were the up-regulated superoxide generation and Bax/Bcl-2 expression while restrained GSH/GSSG ratio caused by diabetic cardiomyopathy were tremendously repressed in TLR2 KO mice. Furthermore, blocking of TLR2 remarkably attenuated the augmented fibrosis areas of heart tissues in mice with diabetic cardiomyopathy. The result of the enhanced α-SMA and collagenⅠ caused by diabetic cardiomyopathy were suppressed in heart tissues of TLR2 KO mice further validate it. All in all, our study demonstrated that diabetes-induced cardiac dysfunction could be attenuated by TLR2 KO.

Acute and (sub)chronic toxicity of the neonicotinoid imidacloprid on Chironomus riparius

Impacts of neonicotinoids on non-target insects, including aquatic species, may significantly influence ecosystem structure and functioning. The present study investigated the sensitivity of Chironomus riparius to imidacloprid exposures during 24-h, 10- and 28-days by assessing larval survival, growth, emergence and oxidative stress-related parameters. C. riparius exhibited high sensitivity compared to other model aquatic species with acute 24-h LC₅₀ being 31.5 μg/L and 10-days LOEC (growth) 0.625 μg/L. A 28-days partial life cycle test demonstrated imidacloprid effects on the emergence of C. riparius. Exposure to sublethal concentrations during 10-days caused an imbalance in the reduced and oxidized glutathione (GSH and GSSG), and slightly induced lipid peroxidation (increased malondialdehyde, MDA). Our results indicate that oxidative stress may be a relevant mechanism in the neonicotinoid toxicity, reflected in the insect development and life cycle parameters.

Antioxidant effect of glutathione on promoting 2-keto-l-gulonic acid production in vitamin C fermentation system

AIMS

Oxidative stress limited the growth of cells and 2-keto-l-gulonic acid (2-KGA) production in vitamin C (Vc) fermentation system. The study aims to investigate the antioxidant effect of glutathione on promoting 2-KGA in Vc fermentation system using Ketogulonicigenium vulgare 25B-1 and Bacillus endophyticus ST-1 as the co-culturing microbes.

METHODS AND RESULTS

The activities of antioxidant-related enzymes and qPCR were used to study the antioxidant effect of glutathione addition in Vc fermentation system. The addition of GSH and GSH/GSSG increased 2-KGA production and decreased fermentation time, and the highest 2-KGA production increased by 40·63% and the lowest fermentation time shortened to 60 h when the addition of optimal concentration ratio of GSH/GSSG was 50 : 1. Moreover, the increased production of 2-KGA was accompanied by up-regulated the activities of total antioxidant capacity (T-AOC), total superoxide dismutase (T-SOD), catalase (CAT) and over-expressed oxidative stress-related genes sod, gst, gr, zwf, gp, which resulted in scavenging reactive oxygen species to reduce oxidative stress in Vc fermentation system.

CONCLUSIONS

Glutathione showed a significant effect on increasing 2-KGA production and decreasing fermentation time in Vc fermentation system. GSH/GSSG could maintain a dynamic balance with two forms of glutathione and the optimal concentration ratio of GSH/GSSG was 50 : 1.

SIGNIFICANCE AND IMPACT OF THE STUDY

Glutathione is proved to be effective to relieve oxidative stress. The promotion effects of GSSG and GSH on 2-KGA production could help to further explore the optimization of co-culture fermentation process for Vc industrial production.

A Procedure for Precise Determination of Glutathione Produced by Saccharomyces cerevisiae

In bioproduction, yields of products must be calculated precisely for accurate evaluation of various fermentation conditions. To evaluate productivity of microorganisms, product amounts per unit of medium volume (e.g., mg-product/L-broth), and/or product amounts per unit of a microorganism amount (e.g., mg-product/mg-dry cell weight) are often used. Nonetheless, detailed procedures for calculation of these production yields are often omitted in research articles, whereas methods for product quantification are described well. Here, we describe a detailed calculation procedure from our previous studies on glutathione production by Saccharomyces cerevisiae. This procedure can be applied to various other products and microorganisms, and therefore, may prove to be useful in various other bioproduction studies.

Glutathione for skin lightening: a regnant myth or evidence-based verity?

The recent hype surrounding the antimelanogenic properties of glutathione has resulted in physicians frequently administering it as a “wonder” drug for skin lightening and treatment of hyperpigmentation, especially in ethnic populations with darker skin tones. This phenomenon has seen a recent surge owing to aggressive marketing and capitalization of pharma-cosmeceutical companies. However, the unbridled and prodigal use of it, especially as a parenteral formulation, seems unjustified, given the lacunae in our knowledge about its antimelanogenic potential, limited clinical evidence favoring its role in skin lightening, and the statutory ban/advisory issued by certain federal agencies. Even though parenteral glutathione is approved only for severe liver disorders and for prevention of chemotherapy associated neurotoxicity, the lack of statutory laws governing the use of systemic glutathione in most countries has contributed to its unchecked use for skin lightening. The current clinical evidence of intravenous glutathione for skin lightening is limited to a single study with a dubious study design and apparently flawed analysis of results, casting doubt on the drug’s efficacy and reported adverse effects. Two studies evaluating oral/sublingual administration and one trial involving the use of topical glutathione reported good safety profile and appreciable but reversible results on skin tone. In this article, we shall review and discuss the current status of glutathione as a skin lightening agent and address the sundry unanswered queries regarding the dosage, duration of use and longevity of accrued effects based on clinical evidence and recent insights into its antimelanogenic mechanism.

The SNP rs10911021 is associated with oxidative stress in coronary heart disease patients from Pakistan

BACKGROUND

rs10911021 (a single nucleotide polymorphism present upstream of the GLUL gene) affects glutamic acid metabolism, and was shown to be associated with coronary heart disease (CHD) in patients with T2DM but a definite mechanism is unknown. It may affect glutathione cycle, an important effector in the antioxidant defense mechanism, in the cells. We checked the association of this SNP with CHD and oxidative stress biomarkers, malondialdeheyde (MDA), GSH and GSSG in Pakistani patients.

METHODS

A total of 650 subjects (425 CHD cases and 225 controls) were genotyped by TaqMan allelic discrimination technique. The levels of MDA, GSH and GSSG were measured by standard protocols.

RESULTS

The risk allele frequency was higher in cases than controls, but the difference was insignificant (p = 0.55). The SNP was not associated with CHD (p = 0.053) but when the analysis was limited to CHD patients having DM, a significant association (p = 0.03) was observed. The blood levels of MDA and GSSG were higher while that of GSH was significantly lower in the cases than the controls (p < 0.05). Each risk allele increased MDA and GSSG by 0.29 (0.036) mmol/l and 0.4 (0.04) mmol/l, respectively, while decreased GSH by -0.36 (0.03) mmol/l. The SNP was not associated with any of the tested blood lipids.

CONCLUSION

The SNP rs10911021 was associated with CHD only in patients having diabetes, but the SNP was associated with total oxidative stress biomarkers MDA and GSH and GSSG levels. As the SNP rs10911021 showed significant association with oxidative stress parameters and these parameters should an increased oxidative stress in the CHD subjects, it can be concluded that the SNP may have contributed to increase the risk of heart diseases in the diabetic subjects by increasing the oxidative stress.

Cellular glutathione level does not predict ovarian cancer cells' resistance after initial or repeated exposure to cisplatin

OBJECTIVE

Cisplatin resistance development is a major obstacle in ovarian cancer treatment. One of the most important mechanisms underlying cisplatin resistance is drug detoxification by glutathione. In the present study, the importance of initial or repeated exposure to cisplatin in glutathione dependent resistance was investigated. To this purpose, some cisplatin sensitive and resistant variants of human ovarian cancer cell lines providing an appropriate range of cisplatin sensitivity were selected. Clonogenic survival assay was performed to evaluate cisplatin resistance and intracellular contents of reduced (GSH) and oxidized (GSSG) glutathione were analyzed using an HPLC method. Our results indicated that the intracellular GSH and GSSG concentrations were nearly equal in A2780 and A2780CP cells, while the A2780CP cells showed 14 times more resistance than the A2780 cells after initial exposure to cisplatin. A2780-R1 and A2780-R3 cells which have been repeatedly exposed to cisplatin also showed no significant difference in glutathione content, even though A2780-R3 was about two times more resistant than A2780-R1. Moreover, intracellular GSH/GSSG ratio decreased in the resistant cells, reflecting a shift towards a more oxidizing intracellular environment indicative of oxidative stress.

CONCLUSION

As a conclusion, it seems that although the intracellular glutathione concentration increases after repeated exposure to cisplatin, there is no clear correlation between the intracellular GSH content in ovarian cancer cells and their resistance to cisplatin neither after initial nor after repeated exposure to this drug.

Determining Glutathione Levels in Plants

Upon exposure to abiotic stresses, plants tend to accumulate excessive amounts of reactive oxygen species (ROS) that inturn react with cellular lipids, proteins, and DNA. Therefore, decreasing ROS accumulation is indispensible to survive under stress, which is accomplished by inducing enzymatic and nonenzymatic antioxidant defense pathways. Glutathione, particularly reduced glutathione (GSH), represents a principal anitioxidant that could decrease ROS through scavenging them directly or indirectly through ascorbate-glutathione cycle or GSH peroxidases. Glutathione content can be determined using HPLC or spectrophotometric assays. In this chapter, we provided detailed assays to determine total, reduced, and oxidized gluathione using spectrophotometric method.

Characterization and response of antioxidant systems in the tissues of the freshwater pond snail (Lymnaea stagnalis) during acute copper exposure

The response of enzymatic (superoxide dismutase, SOD; catalase, CAT; glutathione peroxidase, GPX and glutathione reductase, GR) and non-enzymatic responses (glutathione, GSH, oxidized glutathione, GSSG and GSH/GSSG) against acute Cu toxicity (2-90μg/mL for 48h) in different tissues of Lymnaea stagnalis were measured. Incubation conditions for enzymatic activity measurements were optimized for L. stagnalis tissues. Three examined tissues, the hepatopancreas, the foot muscle and the mantle, exhibited variable responses in antioxidant parameters as a function of Cu concentrations. The most responsive antioxidant enzymes were GPX and CAT while GR appeared less sensitive. In general antioxidant enzymes at higher Cu concentrations though GSH levels at lower Cu concentrations exhibited the greatest changes in hepatopancreas and foot muscle, respectively. All antioxidant enzymes except GR increased after exposure to the highest Cu concentration in mantle. Total and reduced GSH increased in hepatopancreas but decreased with GSH/GSSG ratios at all Cu concentrations in foot muscle. The present results show that antioxidants respond to acute Cu exposure at concentrations as low as 2μg Cu/L in adult L. stagnalis with variable responses in different tissues. Antioxidants both including enzymatic and non-enzymatic parameters may account, in part, for the high tolerance to acute metal exposure observed in adult L. stagnalis and could form suited biomarkers to evaluate the metal exposure and toxicity in aquatic environment even at relatively low level short term exposure.

A direct comparison of methods used to measure oxidized glutathione in biological samples: 2-vinylpyridine and N-ethylmaleimide

The ratio of glutathione disulfide (GSSG) to reduced glutathione (GSH) in biological samples is a frequently used parameter of oxidative stress. As a result, many methods are developed to measure GSSG. The most popular and convenient of these relies on enzymatic cycling following the chemical masking of GSH in the sample using 2-vinylpyridine (2VP). However, 2VP is a slow reactant and its use may result in artificially high GSSG values due to oxidation of the sample over time. Fast-reacting reagents such as N-ethylmaleimide (NEM) may provide more accurate results. We performed a direct comparison of methods using 2VP and NEM. With 2VP, the percentage of total glutathione (GSH+GSSG) in the oxidized form was significantly higher in all tested tissues (kidney, lung and liver) compared to the same procedure performed using NEM. We conclude that NEM, when coupled with a simple solid-phase extraction procedure, is more accurate for the determination of GSSG. We also tested the effects of various handling and storage conditions on GSSG. A detailed description and a discussion of other methods are also included.

Increased TRPC5 glutathionylation contributes to striatal neuron loss in Huntington's disease

Aberrant glutathione or Ca(2+) homeostasis due to oxidative stress is associated with the pathogenesis of neurodegenerative disorders. The Ca(2+)-permeable transient receptor potential cation (TRPC) channel is predominantly expressed in the brain, which is sensitive to oxidative stress. However, the role of the TRPC channel in neurodegeneration is not known. Here, we report a mechanism of TRPC5 activation by oxidants and the effect of glutathionylated TRPC5 on striatal neurons in Huntington's disease. Intracellular oxidized glutathione leads to TRPC5 activation via TRPC5 S-glutathionylation at Cys176/Cys178 residues. The oxidized glutathione-activated TRPC5-like current results in a sustained increase in cytosolic Ca(2+), activated calmodulin-dependent protein kinase and the calpain-caspase pathway, ultimately inducing striatal neuronal cell death. We observed an abnormal glutathione pool indicative of an oxidized state in the striatum of Huntington's disease transgenic (YAC128) mice. Increased levels of endogenous TRPC5 S-glutathionylation were observed in the striatum in both transgenic mice and patients with Huntington's disease. Both knockdown and inhibition of TRPC5 significantly attenuated oxidation-induced striatal neuronal cell death. Moreover, a TRPC5 blocker improved rearing behaviour in Huntington's disease transgenic mice and motor behavioural symptoms in littermate control mice by increasing striatal neuron survival. Notably, low levels of TRPC1 increased the formation of TRPC5 homotetramer, a highly Ca(2+)-permeable channel, and stimulated Ca(2+)-dependent apoptosis in Huntington's disease cells (STHdh(Q111/111)). Taken together, these novel findings indicate that increased TRPC5 S-glutathionylation by oxidative stress and decreased TRPC1 expression contribute to neuronal damage in the striatum and may underlie neurodegeneration in Huntington's disease.

The yeast oligopeptide transporter Opt2 is localized to peroxisomes and affects glutathione redox homeostasis

Glutathione, the most abundant small-molecule thiol in eukaryotic cells, is synthesized de novo solely in the cytosol and must subsequently be transported to other cellular compartments. The mechanisms of glutathione transport into and out of organelles remain largely unclear. We show that budding yeast Opt2, a close homolog of the plasma membrane glutathione transporter Opt1, localizes to peroxisomes. We demonstrate that deletion of OPT2 leads to major defects in maintaining peroxisomal, mitochondrial, and cytosolic glutathione redox homeostasis. Furthermore, ∆opt2 strains display synthetic lethality with deletions of genes central to iron homeostasis that require mitochondrial glutathione redox homeostasis. Our results shed new light on the importance of peroxisomes in cellular glutathione homeostasis.

Novel insights of dietary polyphenols and obesity. J Nutr Biochem. 2014;25:1-18. [PMID: 24314860 DOI: 10.1016/j.jnutbio.2013.09.001]

The prevalence of obesity has steadily increased over the past three decades both in the United States and worldwide. Recent studies have shown the role of dietary polyphenols in the prevention of obesity and obesity-related chronic diseases. Here, we evaluated the impact of commonly consumed polyphenols, including green tea catechins, especially epigallocatechin gallates, resveratrol and curcumin, on obesity and obesity-related inflammation. Cellular studies demonstrated that these dietary polyphenols reduce viability of adipocytes and proliferation of preadipocytes, suppress adipocyte differentiation and triglyceride accumulation, stimulate lipolysis and fatty acid β-oxidation, and reduce inflammation. Concomitantly, the polyphenols modulate signaling pathways including the adenosine-monophosphate-activated protein kinase, peroxisome proliferator activated receptor γ, CCAAT/enhancer binding protein α, peroxisome proliferator activator receptor gamma activator 1-alpha, sirtuin 1, sterol regulatory element binding protein-1c, uncoupling proteins 1 and 2, and nuclear factor-κB that regulate adipogenesis, antioxidant and anti-inflammatory responses. Animal studies strongly suggest that commonly consumed polyphenols described in this review have a pronounced effect on obesity as shown by lower body weight, fat mass and triglycerides through enhancing energy expenditure and fat utilization, and modulating glucose hemostasis. Limited human studies have been conducted in this area and are inconsistent about the antiobesity impact of dietary polyphenols probably due to the various study designs and lengths, variation among subjects (age, gender, ethnicity), chemical forms of the dietary polyphenols used and confounding factors such as other weight-reducing agents. Future randomized controlled trials are warranted to reconcile the discrepancies between preclinical efficacies and inconclusive clinic outcomes of these polyphenols.

Role of the inhibition of oxidative stress and inflammatory mediators in the neuroprotective effects of hydroxytyrosol in rat brain slices subjected to hypoxia reoxygenation

The aim of this study was to analyze the mechanism of the neuroprotective effect of hydroxytyrosol (HT) in an experimental model of hypoxia-reoxygenation in rat brain slices. After reoxygenation the increase in lactate dehydrogenase efflux was inhibited by HT in a concentration-dependent manner and dose-dependent inhibition after oral administration to rats for 7 days (1, 5 and 10 mg/kg per day). Maximum inhibition was 57.4% in vitro and 38.7% ex vivo. Hydroxytyrosol reduced oxidative stress parameters: it inhibited lipid peroxidation and increased enzymatic activities related with the glutathione system both in vitro and after oral administration to rats. The increase in prostaglandin E2 and interleukin 1β after reoxygenation were inhibited after incubation of brain slices with HT and after oral administration. The accumulation of nitric oxide in brain slices was reduced in a concentration-dependent manner. In conclusion, HT exerts a neuroprotective effect in a model of hypoxia-reoxygenation in rat brain slices, both in vitro and after 7 days of oral administration to rats. HT exerts an antioxidant activity and lowered some inflammatory markers in this model.

GSSG/GSH ratios in cryopreserved rat and human hepatocytes as a biomarker for drug induced oxidative stress

The formation of reactive oxygen species (ROS) could cause cellular damage and eventually lead to apoptosis and necrosis. The ratio between oxidized glutathione and reduced glutathione (GSSG-to-GSH ratio) has been used as an important in vitro and in vivo biomarker of the redox balance in the cell and consequently of cellular oxidative stress. This paper optimizes a LC-MS/MS method for the simultaneous determination of GSH and GSSG. The proposed method is based on the derivatization of reduced GSH using iodoacetic acid (IAA) in order to prevent its rapid oxidation to GSSG during sample preparation. The optimized analytical method was applied to evaluate the effect of different pharmaceutical agents on GSSG-to-GSH ratio in cryopreserved rat and human hepatocytes in culture. Hepatocyte viabilities were also determined at the same time by using the WST-1 assay as a direct measurement of cell mitochondrial respiration. The results obtained demonstrate that cryopreserved rat and human hepatocytes in culture are reliable in vitro models for the evaluation of cellular oxidative stress. In addition, the GSSG-to-GSH ratio measurements could be a biomarker of hepatotoxicity providing similar results to those of cytotoxicity assay.

Short time exposure to hydrogen peroxide induces sustained glutathione export from cultured neurons

Hydrogen peroxide is a normal by-product of cellular metabolism that in higher concentrations can cause oxidative stress. Cultured cerebellar granule neurons efficiently disposed of micromolar concentrations of hydrogen peroxide with half-times in the minute range in a process that predominately involved catalase. Application of up to 100 µM hydrogen peroxide did not affect the cell viability for up to 4h, but caused a time- and concentration-dependent increase in the extracellular glutathione (GSH) content that was accompanied by a matching decrease in the cellular GSH content. Hydrogen peroxide at 100 µM stimulated maximally the GSH export from viable neurons, but did not affect GSH export from cultured astrocytes. The peroxide-induced extracellular GSH accumulation from neurons was lowered by 70% in the presence of MK571, an inhibitor of multidrug resistance protein (Mrp) 1. The extracellular GSH content determined after 4h of incubation was already significantly increased after a 5-min exposure of neurons to hydrogen peroxide and became maximal after 15 min of peroxide application. These data demonstrate that just a short exposure of viable cerebellar granule neurons to micromolar concentrations of hydrogen peroxide stimulates a prolonged Mrp1-mediated export of cellular GSH. This process may compromise the antioxidative potential of neurons and increase their sensitivity toward drugs and toxins.

Melia azedarach plants show tolerance properties to water shortage treatment: an ecophysiological study

Candidate species for reforestation of areas prone to drought must combine water stress (WS) tolerance and economic or medicinal interest. Melia azedarach produces high quality timber and has insecticidal and medicinal properties. However, the impact of WS on M. azedarach has not yet been studied. Two-month old M. azedarach plants were exposed to WS during 20 days. After this period, plant's growth, water potential, photosynthetic performance and antioxidant capacity were evaluated. WS did not affect plants' growth, but induced stomatal closure, reduced net CO₂ assimilation rate (A) and the intercellular CO₂ availability in mesophyll (C(i)). WS also reduced the photosynthetic efficiency of PSII but not the pigment levels. WS up-regulated the antioxidant enzymes and stimulated the production of antioxidant metabolites, preventing lipid peroxidation. Therefore, despite some repression of photosynthetic parameters by WS, they did not compromise plant growth, and plants increased their antioxidant capacity. Our data demonstrate that M. azedarach juvenile plants have the potential to acclimate to water shortage conditions, opening new perspectives to the use of this species in reforestation/afforestation programs of drought prone areas.

Oxidative stress in bisphosphonate-related osteonecrosis of the jaws

OBJECTIVES

To analyze whether oxidative stress (OS) changes are present in patients with bisphosphonate-related osteonecrosis of the jaw (BRONJ) versus controls.

MATERIALS AND METHODS

Oxidative stress was analyzed in serum and unstimulated saliva of three groups: Group 1 consisted of 24 patients who had been treated with intravenous bisphosphonates (ivBPs) and developed BRONJ, group 2 consisted of 20 patients who had received ivBPs and did not develop BRONJ, and group 3 comprised 17 control subjects. Reduced glutathione (GSH), malondialdehyde (MDA), oxidized glutathione (GSSG), and 8-oxo-7,8-dihydro-2-deoxyguanosine (8-oxo-dG) levels, as well as the GSSG/GSH ratio, were measured.

RESULTS

Mean serum and saliva levels of MDA, GSSG, and 8-oxo-dG and the GSSG/GSH ratio were significantly higher in patients with BRONJ than in controls. We found no significant difference in OS according to BRONJ stage, sex, or location in the jaws. Logistic regression analysis revealed that the GSSG/GSH ratio was a significant factor predicting the development of BRONJ (P = 0.01).

CONCLUSIONS

Oxidative stress was detected in patients with BRONJ, and the GSSG/GSH ratio was the most significant OS variable found; it was a significant factor predicting the development of BRONJ.

Reduced mitochondrial and ascorbate-glutathione activity after artificial ageing in soybean seed

The effect of artificial ageing on the relationship between mitochondrial activities and the antioxidant system was studied in soybean seeds (Glycine max L. cv. Zhongdou No. 27). Ageing seeds for 18d and 41d at 40°C reduced germination from 99% to 52% and 0%, respectively. In comparison to the control, malondialdehyde content and leachate conductivity in aged seeds increased and were associated with membrane damage. Transmission electron microscopy and Percoll density gradient centrifugation showed that aged seeds mainly contained poorly developed mitochondria in which respiration and marker enzymes activities were significantly reduced. Heavy mitochondria isolated from the interface of the 21% and 40% Percoll were analyzed. Mitochondrial antioxidant enzymes activities including superoxide dismutase, ascorbate peroxidase, glutathione reductase, monodehydroascorbate reductase, and dehydroascorbate reductase were significantly reduced in aged seeds. A decrease in total ascorbic acid (ASC) and glutathione (GSH) content as well as the reduced/oxidized ratio of ASC and GSH in mitochondria with prolonged ageing showed that artificial ageing reduced ASC-GSH cycle activity. These results suggested an elevated reactive oxygen species (ROS) level in the aged seeds, which was confirmed by measurements of superoxide radical and hydrogen peroxide levels. We conclude that mitochondrial dysfunction in artificially aged seeds is due to retarded mitochondrial and ASC-GSH cycle activity and elevated ROS accumulation.

Hydrogen sulfide delays GA-triggered programmed cell death in wheat aleurone layers by the modulation of glutathione homeostasis and heme oxygenase-1 expression

Hydrogen sulfide (H2S) is considered as a cellular signaling intermediate in higher plants, but corresponding molecular mechanisms and signal transduction pathways in plant biology are still limited. In the present study, a combination of pharmacological and biochemical approaches was used to study the effect of H2S on the alleviation of GA-induced programmed cell death (PCD) in wheat aleurone cells. The results showed that in contrast with the responses of ABA, GA brought about a gradual decrease of l-cysteine desulfhydrase (LCD) activity and H2S production, and thereafter PCD occurred. Exogenous H2S donor sodium hydrosulfide (NaHS) not only effectively blocked the decrease of endogenous H2S release, but also alleviated GA-triggered PCD in wheat aleurone cells. These responses were sensitive to hypotaurine (HT), a H2S scavenger, suggesting that this effect of NaHS was in an H2S-dependent fashion. Further experiment confirmed that H2S, rather than other sodium- or sulphur-containing compounds derived from the decomposing of NaHS, was attributed to the rescuing response. Importantly, the reversing effect was associated with glutathione (GSH) because the NaHS triggered increases of endogenous GSH content and the ratio of GSH/oxidized GSH (GSSG) in GA-treated layers, and the NaHS-mediated alleviation of PCD was markedly eliminated by l-buthionine-sulfoximine (BSO, a selective inhibitor of GSH biosynthesis). The inducible effect of NaHS was also ascribed to the modulation of heme oxygenase-1 (HO-1), because the specific inhibitor of HO-1 zinc protoporphyrin IX (ZnPP) significantly suppressed the NaHS-related responses. By contrast, the above inhibitory effects were reversed partially when carbon monoxide (CO) aqueous solution or bilirubin (BR), two of the by-products of HO-1, was added, respectively. NaHS-triggered HO-1 gene expression in GA-treated layers was also confirmed. Together, the above results clearly suggested that the H2S-delayed PCD in GA-treated wheat aleurone cells was associated with the modulation of GSH homeostasis and HO-1 gene expression.

Reduced mitochondrial and ascorbate-glutathione activity after artificial ageing in soybean seed

The effect of artificial ageing on the relationship between mitochondrial activities and the antioxidant system was studied in soybean seeds (Glycine max L. cv. Zhongdou No. 27). Ageing seeds for 18d and 41d at 40°C reduced germination from 99% to 52% and 0%, respectively. In comparison to the control, malondialdehyde content and leachate conductivity in aged seeds increased and were associated with membrane damage. Transmission electron microscopy and Percoll density gradient centrifugation showed that aged seeds mainly contained poorly developed mitochondria in which respiration and marker enzymes activities were significantly reduced. Heavy mitochondria isolated from the interface of the 21% and 40% Percoll were analyzed. Mitochondrial antioxidant enzymes activities including superoxide dismutase, ascorbate peroxidase, glutathione reductase, monodehydroascorbate reductase, and dehydroascorbate reductase were significantly reduced in aged seeds. A decrease in total ascorbic acid (ASC) and glutathione (GSH) content as well as the reduced/oxidized ratio of ASC and GSH in mitochondria with prolonged ageing showed that artificial ageing reduced ASC-GSH cycle activity. These results suggested an elevated reactive oxygen species (ROS) level in the aged seeds, which was confirmed by measurements of superoxide radical and hydrogen peroxide levels. We conclude that mitochondrial dysfunction in artificially aged seeds is due to retarded mitochondrial and ASC-GSH cycle activity and elevated ROS accumulation.

Antioxidative capacity in the fat body of Bombyx mori is increased following oral administration of 4-methylumbelliferone

Plant sources of umbelliferones have tumor-inhibitory effects at the cellular level. However, their physiological functions in animals are largely unresolved. In this study, we provide evidence to show that 4-methylumbelliferone (4-MU) participates in the regulation of antioxidative capacity in the fat body of Bombyx mori, a tissue similar to mammalian liver in this model invertebrate. Larvae (3rd day of the 5th instar) were orally exposed to 4 mM 4-MU, an umbelliferone, which swiftly induced the generation of a large number of ROS (e.g. H2O2 increased 6 to 8-fold), and 4-MU was detected in the fat body 8 min after administration. In addition, the activities of CAT and GPx were up-regulated 4 to 11-fold and 2 to 16-fold, respectively, and were helpful in defending fat body cells against oxidative injury in combination with NADPH. Furthermore, significant increases in the contents of T-AOC (up to approx. 2-fold), antioxidants of ASAFR (by 2 to 4-fold) and GSH were detected.

Water stress reveals differential antioxidant responses of tolerant and non-tolerant sugarcane genotypes

The biochemical responses of the enzymatic antioxidant system of a drought-tolerant cultivar (IACSP 94-2094) and a commercial cultivar in Brazil (IACSP 95-5000) grown under two levels of soil water restriction (70% and 30% Soil Available Water Content) were investigated. IACSP 94-2094 exhibited one additional active superoxide dismutase (Cu/Zn-SOD VI) isoenzyme in comparison to IACSP 95-5000, possibly contributing to the heightened response of IACSP 94-2094 to the induced stress. The total glutathione reductase (GR) activity increased substantially in IACSP 94-2094 under conditions of severe water stress; however, the appearance of a new GR isoenzyme and the disappearance of another isoenzyme were found not to be related to the stress response because the cultivars from both treatment groups (control and water restrictions) exhibited identical changes. Catalase (CAT) activity seems to have a more direct role in H2O2 detoxification under water stress condition and the shift in isoenzymes in the tolerant cultivar might have contributed to this response, which may be dependent upon the location where the excessive H2O2 is being produced under stress. The improved performance of IACSP 94-2094 under drought stress was associated with a more efficient antioxidant system response, particularly under conditions of mild stress.

Deoxynivalenol induced oxidative stress and genotoxicity in human peripheral blood lymphocytes

Deoxynivalenol (DON) is one of the most common mycotoxins. The aim of this study consists in using diverse cellular and molecular assays to evaluate cytotoxicity, genotoxicity as well as oxidative damage and to investigate their mechanisms in human peripheral blood lymphocytes. The human lymphocytes were cultured in eight different doses of DON (0, 6.25, 12.5, 25, 50, 100, 250 and 500 ng/mL) during 6, 12 and 24 h. DON was able to decrease cell viability and cause damage to the membrane, the chromosomes or the DNA at all times of culture. It was also able to induce lipid peroxidation and raise the levels of 8-OHdG and ROS in 6, 12 and 24 h. The results of the RT-PCR and the Western Blot indicated that DON is able to enhance mRNA or protein expressions of DNA repair genes and HO-1 in 6 h and to inhibit these expressions in 24 h. DON potentially triggers genotoxicity in human lymphocytes. This mechanism is probably related to depletion of antioxidase and oxidative damage to the DNA that reduced expression of HO-1, thereby inhibiting the ability of DNA repair.

ERK1/2 activation modulates pyocyanin-induced toxicity in A549 respiratory epithelial cells

Pyocyanin (PCN), a virulence factor produced by Pseudomonas aeruginosa, has many damaging effects on mammalian cells. Several lines of evidence suggest that this damage is primarily mediated by its ability to generate oxidative stress. However mechanisms underlying PCN-induced oxidative injury remain unclear. Although oxidative stress and subsequent MAPK signaling has been shown to modulate cell death in other models, its role in PCN-induced cytotoxicity remains unknown. Therefore the aim of this study was to investigate the role of redox-sensitive MAPK in PCN-induced toxicity in A549 cells. Here we show that PCN (50μM) rapidly increased ERK1/2 phosphorylation after 5min. Pre-treatment of A549 cells with the MEK1/2 inhibitor U0126 (10μM) decreased PCN-induced ERK1/2 phosphorylation and protected cells against apoptosis and cell injury suggesting a role for ERK signalling. In contrast, JNK and p38 MAPK phosphorylation remained unchanged following exposure to PCN and pretreatment with either the JNK or p38 MAPK inhibitors (10μM SP600125 and 10μM SB203580, respectively) did not afford protection against PCN toxicity. This would suggest that PCN-induced cytotoxicity appears to occur independently of JNK and p38 MAPK signaling pathways. Finally, although we confirm that oxidative stress contributes to PCN-induced toxicity, our data suggest the contribution of oxidative stress is independent of ERK1/2 signaling. These findings may provide insight for novel targeted therapies to reduce PCN-mediated lung injury in patients with chronic P. aeruginosa respiratory infections.

Redox-sensitive YFP sensors for monitoring dynamic compartment-specific glutathione redox state

Intracellular redox homeostasis is crucial for many cellular functions but accurate measurements of cellular compartment-specific redox states remain technically challenging. Genetically encoded biosensors including the glutathione-specific redox-sensitive yellow fluorescent protein (rxYFP) may provide an alternative way to overcome the limitations of conventional glutathione/glutathione disulfide (GSH/GSSG) redox measurements. This study describes the use of rxYFP sensors for investigating compartment-specific steady redox state and their dynamics in response to stress in human cells. RxYFP expressed in the cytosol, nucleus, or mitochondrial matrix of HeLa cells was responsive to the intracellular redox state changes induced by reducing as well as oxidizing agents. Compartment-targeted rxYFP sensors were able to detect different steady-state redox conditions among the cytosol, nucleus, and mitochondrial matrix. These sensors expressed in human epidermal keratinocytes HEK001 responded to stress induced by ultraviolet A radiation in a dose-dependent manner. Furthermore, rxYFP sensors were able to sense dynamic and compartment-specific redox changes caused by 100 μM hydrogen peroxide (H2O2). Mitochondrial matrix-targeted rxYFP displayed a greater dynamics of oxidation in response to a H2O2 challenge than the cytosol- and nucleus-targeted sensors, largely due to a more alkaline local pH environment. These observations support the view that mitochondrial glutathione redox state is maintained and regulated independently from that of the cytosol and nucleus. Taken together, our data show the robustness of the rxYFP sensors to measure compartmental redox changes in human cells. Complementary to existing redox sensors and conventional redox measurements, compartment-targeted rxYFP sensors provide a novel tool for examining mammalian cell redox homeostasis, permitting high-resolution readout of steady glutathione state and dynamics of redox changes.

Zinc ions as effectors of environmental oxidative lung injury

The redox-inert transition metal Zn is a micronutrient that plays essential roles in protein structure, catalysis, and regulation of function. Inhalational exposure to ZnO or to soluble Zn salts in occupational and environmental settings leads to adverse health effects, the severity of which appears dependent on the flux of Zn(2+) presented to the airway and alveolar cells. The cellular toxicity of exogenous Zn(2+) exposure is characterized by cellular responses that include mitochondrial dysfunction, elevated production of reactive oxygen species, and loss of signaling quiescence leading to cell death and increased expression of adaptive and inflammatory genes. Central to the molecular effects of Zn(2+) are its interactions with cysteinyl thiols, which alters their functionality by modulating their reactivity and participation in redox reactions. Ongoing studies aimed at elucidating the molecular toxicology of Zn(2+) in the lung are contributing valuable information about its role in redox biology and cellular homeostasis in normal and pathophysiology.

Mild oxidative stress induces S-glutathionylation of STAT3 and enhances chemosensitivity of tumoural cells to chemotherapeutic drugs

STAT3 is a transcription factor constitutively activated in a variety of cancers that has a critical role in the inhibition of apoptosis and induction of chemoresistance. Inhibition of the STAT3 signaling pathway suppresses cell survival signals and leads to apoptosis in cancer cells, suggesting that direct inhibition of STAT3 function is a viable therapeutic approach. Herein, we identify the naturally occurring sesquiterpene lactone cynaropicrin as a potent inhibitor of both IL-6-inducible and constitutive STAT3 activation (IC50=12 μM). Cynaropicrin, which contains an α-β-unsaturated carbonyl moiety and acts as potent Michael reaction acceptor, induces a rapid drop in intracellular glutathione (GSH) concentration, thereby triggering S-glutathionylation of STAT3. Furthermore, glutathione ethylene ester, the cell permeable form of GSH, reverts the inhibitory action of cynaropicrin on STAT3 tyrosine phosphorylation. These findings suggest that this sesquiterpene lactone is able to induce redox-dependent post-translational modification of cysteine residues of STAT3 protein to regulate its function. STAT3 inhibition led to the suppression of two anti-apoptotic genes, Bcl-2 and survivin, in DU145 cells that constitutively express active STAT3. This event may be responsible for the decline in cell viability after cynaropicrin treatment. As revealed by PI/annexin-V staining, PARP cleavage, and DNA ladder formation, cynaropicrin cytotoxicity is mediated by apoptosis. Finally, cynaropicrin displayed a slight to strong synergism with two well-established chemotherapeutic drugs, cisplatin and docetaxel. Taken together our studies suggest that cynaropicrin suppresses the STAT3 pathway, leading to the down-regulation of STAT3-dependent gene expression and chemosensitization of tumour cells to chemotherapy.