A kinetic microassay for glutathione in cells plated on 96-well microtiter plates

A Mechanism of Action of Metformin in the Brain: Prevention of Methylglyoxal-Induced Glutamatergic Impairment in Acute Hippocampal Slices

Metformin, a biguanide compound (N-1,1-dimethylbiguanide), is widely prescribed for diabetes mellitus type 2 (T2D) treatment. It also presents a plethora of properties, such as anti-oxidant, anti-inflammatory, anti-apoptosis, anti-tumorigenic, and anti-AGE formation activity. However, the precise mechanism of action of metformin in the central nervous system (CNS) needs to be clarified. Herein, we investigated the neuroprotective role of metformin in acute hippocampal slices exposed to methylglyoxal (MG), a highly reactive dicarbonyl compound and a key molecule in T2D developmental pathophysiology. Metformin protected acute hippocampal slices from MG-induced glutamatergic neurotoxicity and neuroinflammation by reducing IL-1β synthesis and secretion and RAGE protein expression. The drug also improved astrocyte function, particularly with regard to the glutamatergic system, increasing glutamate uptake. Moreover, we observed a direct effect of metformin on glutamate transporters, where the compound prevented glycation, by facilitating enzymatic phosphorylation close to Lys residues, suggesting a new neuroprotective role of metformin via PKC ζ in preventing dysfunction in glutamatergic system induced by MG.

Astroglial Alterations in the Hippocampus of Rats Submitted to a Single Trans-Cranial Direct Current Stimulation Trial

Evidence indicates that transcranial direct current stimulation (tDCS) provides therapeutic benefits in different situations, such as epilepsy, depression, inflammatory and neuropathic pain. Despite the increasing use of tDCS, its cellular and molecular basis remains unknown. Astrocytes display a close functional and structural relationship with neurons and have been identified as mediators of neuroprotection in tDCS. Considering the importance of hippocampal glutamatergic neurotransmission in nociceptive pathways, we decided to investigate short-term changes in the hippocampal astrocytes of rats subjected to tDCS, evaluating specific cellular markers (GFAP and S100B), as well as markers of astroglial activity; glutamate uptake, glutamine synthesis by glutamine synthetase (GS) and glutathione content. Data clearly show that a single session of tDCS increases the pain threshold elicited by mechanical and thermal stimuli, as evaluated by von Frey and hot plate tests, respectively. These changes involve inflammatory and astroglial neurochemical changes in the hippocampus, based on specific changes in cell markers, such as S100B and GS. Alterations in S100B were also observed in the cerebrospinal fluid of tDCS animals and, most importantly, specific functional changes (increased glutamate uptake and increased GS activity) were detected in hippocampal astrocytes. These findings contribute to a better understanding of tDCS as a therapeutic strategy for nervous disorders and reinforce the importance of astrocytes as therapeutic targets.

Arundic acid (ONO-2506) downregulates neuroinflammation and astrocyte dysfunction after status epilepticus in young rats induced by Li-pilocarpine

Astrocytes, the most abundant glial cells, have several metabolic functions, including ionic, neurotransmitter and energetic homeostasis for neuronal activity. Reactive astrocytes and their dysfunction have been associated with several brain disorders, including the epileptogenic process. Glial Fibrillary Acidic Protein (GFAP) and S100 calcium-binding protein B (S100B) are astrocyte biomarkers associated with brain injury. We hypothesize that arundic acid (ONO-2506), which is known as an inhibitor of S100B synthesis and secretion, protects the hippocampal tissue from neuroinflammation and astrocyte dysfunction after status epileptics (SE) induction by Li-pilocarpine in young rats. Herein, we investigated the effects of arundic acid treatment, at time points of 6 or 24 h after the induction of SE by Li-pilocarpine, in young rats. In SE animals, arundic acid was able to prevent the damage induced by Li-pilocarpine in the hippocampus, decreasing neuroinflammatory signaling (reducing IL-1β, COX2, TLR4 and RAGE contents), astrogliosis (decreasing GFAP and S100B) and astrocytic dysfunction (recovering levels of GSH, glutamine synthetase and connexin-43). Furthermore, arundic acid improved glucose metabolism and reduced the glutamate excitotoxicity found in epilepsy. Our data reinforce the role of astrocytes in epileptogenesis development and the neuroprotective role of arundic acid, which modulates astrocyte function and neuroinflammation in SE animals.

Early effects of LPS-induced neuroinflammation on the rat hippocampal glycolytic pathway

Neuroinflammation is a common feature during the development of neurological disorders and neurodegenerative diseases, where glial cells, such as microglia and astrocytes, play key roles in the activation and maintenance of inflammatory responses in the central nervous system. Neuroinflammation is now known to involve a neurometabolic shift, in addition to an increase in energy consumption. We used two approaches (in vivo and ex vivo) to evaluate the effects of lipopolysaccharide (LPS)-induced neuroinflammation on neurometabolic reprogramming, and on the modulation of the glycolytic pathway during the neuroinflammatory response. For this, we investigated inflammatory cytokines and receptors in the rat hippocampus, as well as markers of glial reactivity. Mitochondrial respirometry and the glycolytic pathway were evaluated by multiple parameters, including enzymatic activity, gene expression and regulation by protein kinases. Metabolic (e.g., metformin, 3PO, oxamic acid, fluorocitrate) and inflammatory (e.g., minocycline, MCC950, arundic acid) inhibitors were used in ex vivo hippocampal slices. The induction of early inflammatory changes by LPS (both in vivo and ex vivo) enhanced glycolytic parameters, such as glucose uptake, PFK1 activity and lactate release. This increased glucose consumption was independent of the energy expenditure for glutamate uptake, which was in fact diverted for the maintenance of the immune response. Accordingly, inhibitors of the glycolytic pathway and Krebs cycle reverted neuroinflammation (reducing IL-1β and S100B) and the changes in glycolytic parameters induced by LPS in acute hippocampal slices. Moreover, the inhibition of S100B, a protein predominantly synthesized and secreted by astrocytes, inhibition of microglia activation and abrogation of NLRP3 inflammasome assembly confirmed the role of neuroinflammation in the upregulation of glycolysis in the hippocampus. Our data indicate a neurometabolic glycolytic shift, induced by inflammatory activation, as well as a central and integrative role of astrocytes, and suggest that interference in the control of neurometabolism may be a promising strategy for downregulating neuroinflammation and consequently for diminishing negative neurological outcomes.

In vitro effects of European and Latin-American medicinal plants in CYP3A4 gene expression, glutathione levels, and P-glycoprotein activity

Many medicinal plants species from European -such as Artemisia absinthium, Equisetum arvense, Lamium album, Malva sylvestris, Morus nigra, Passiflora incarnata, Frangula purshiana, and Salix alba- as well as Latin American traditions -such as Libidibia ferrea, Bidens pilosa, Casearia sylvestris, Costus spicatus, Monteverdia ilicifolia, Persea americana, Schinus terebinthifolia, Solidago chilensis, Syzygium cumini, Handroanthus impetiginosus, and Vernonanthura phosphorica- are shortlisted by the Brazilian National Health System for future clinical use. However, they lack many data on their action upon some key ADME targets. In this study, we assess non-toxic concentrations (up to100 μg/ml) of their infusions for in vitro ability to modulate CYP3A4 mRNA gene expression and intracellular glutathione levels in HepG2 cells, as well as P-glycoprotein (P-gp) activity in vincristine-resistant Caco-2 cells (Caco-2 VCR). We further investigated the activation of human pregnane X receptor (hPXR) in transiently co-transfected HeLa cells and the inhibition of Gamma-glutamyl transferase (GGT) in HepG2 cells. Our results demonstrate L. ferrea, C. sylvestris, M. ilicifolia, P. americana, S. terebinthifolia, S. cumini, V. phosphorica, E. arvense, P. incarnata, F. purshiana, and S. alba can significantly increase CYP3A4 mRNA gene expression in HepG2 cells. Only F. purshiana shown to do so likely via hPXR activation. P-gp activity was affected by L. ferrea, F. purshiana, S. terebinthifolia, and S. cumini. Total intracellular glutathione levels were significantly depleted by exposure to all extracts except S. alba and S. cumini This was accompanied by a lower GGT activity in the case of C. spicatus, P. americana, S. alba, and S. terebinthifolia, whilst L. ferrea, P. incarnata and F. purshiana increased it. Surprisingly, S. cumini aqueous extract drastically decreased GGT activity (−48%, p < 0.01). In conclusion, this preclinical study shows that the administration of some of these herbal medicines causes in vitro disturbances to key drug metabolism mechanisms. We recommend active pharmacovigilance for Libidibia ferrea (Mart.) L. P. Queiroz, Frangula purshiana Cooper, Schinus terebinthifolia Raddi, and Salix alba L. which were able to alter all targets in our preclinical study.

Arundic Acid (ONO-2506), an Inhibitor of S100B Protein Synthesis, Prevents Neurological Deficits and Brain Tissue Damage Following Intracerebral Hemorrhage in Male Wistar Rats

Stroke is one of the leading causes of mortality and neurological morbidity. Intracerebral hemorrhage (ICH) has the poorest prognosis among all stroke subtypes and no treatment has been effective in improving outcomes. Following ICH, the observed high levels of S100B protein have been associated with worsening of injury and neurological deficits. Arundic acid (AA) exerts neuroprotective effects through inhibition of astrocytic synthesis of S100B in some models of experimental brain injury; however, it has not been studied in ICH. The aim of this study was to evaluate the effects of intracerebroventricular (ICV) administration of AA in male Wistar rats submitted to ICH model assessing the following variables: reactive astrogliosis, S100B levels, antioxidant defenses, cell death, lesion extension and neurological function. Firstly, AA was injected at different doses (0.02, 0.2, 2 and 20 μg/μl) in the left lateral ventricle in order to observe which dose would decrease GFAP and S100B striatal levels in non-injured rats. Following determination of the effective dose, ICH damage was induced by IV-S collagenase intrastrial injection and 2 μg/μl AA was injected through ICV route immediately before injury. AA treatment prevented ICH-induced neurological deficits and tissue damage, inhibited excessive astrocytic activation and cellular apoptosis, reduced peripheral and central S100B levels (in striatum, serum and cerebrospinal fluid), improved neuronal survival and enhanced the antioxidant defences after injury. Altogether, these results suggest that S100B is a viable target for treating ICH and highlight AA as an interesting strategy for improving neurological outcome after experimental brain hemorrhage.

In vitro protective effects of plants frequently used traditionally in cancer prevention in Thai traditional medicine: An ethnopharmacological study

ETHNOPHARMACOLOGICAL RELEVANCE

Thai traditional medicine (TTM) has been used widely in cancer management in Thailand. Although several Thai medicinal plants were screened for pharmacological activities related to cancer treatment, such evidence still suffers from the lack of linking with TTM knowledge.

AIM OF THE STUDY

To document knowledge and species used in cancer prevention in TTM and to preliminary investigate pharmacological activities related to the documented knowledge of twenty-six herbal drugs used in cancer/mareng prevention.

METHODS

Fieldwork gathering data on TTM concept and herbal medicines used in cancer prevention was performed with TTM practitioners across Thailand. Later, water and ethanol extracts from twenty-six herbal drugs mentioned as being used in cancer prevention were screened for their protective effect against tert-butyl hydroperoxide-induced cell death in HepG2 cells. Then active extracts were investigated for their effects on NQO1 activity, glutathione level, and safety in normal rat hepatocytes.

RESULTS

The fieldwork helped in the development of TTM cancer prevention strategy and possible experimental models to test the pharmacological activities of selected medicinal plants. Fifteen plant extracts showed significant protective effect by restoring the cell viability to 40-59.3%, which were comparable or better than the positive control EGCG. Among them, ethanol extracts from S. rugata and T. laurifolia showed the most promising chemopreventive properties by significantly increased NQO1 activity, restored GSH level from oxidative damage, as well as showed non-toxic effect in normal rat hepatocytes.

CONCLUSION

TTM knowledge in cancer prevention was documented and used in the planning of pharmacological experiment to study herbal medicines, especially in cancer, inflammation, and other chronic diseases. The proposed strategy should be applied to in vivo and clinical studies in order to further confirm the validity of such a strategy. Other traditional medical systems that use integrated approaches could also apply our strategy to develop evidence that supports a more rational uses in traditional medicine.

Assessment of hematological, hepato-renal, antioxidant, and hormonal responses of Clarias gariepinus exposed to sub-lethal concentrations of oxyfluorfen

Little is known about the effects of oxyfluorfen, a diphenyl ether herbicide, exposure on the African catfish (Clarias gariepinus) health. Consequently, the existing investigation was designed to highlight the impacts of oxyfluorfen exposure on C. gariepinus hematological indices, liver and kidney functions, reproductive hormones, and oxidative status. Furthermore, a consequent 10-day depuration period was adopted to evaluate the recovery of the disturbed indicators to normal values. In the first experiment, the 96-h lethal concentration 50 (LC₅₀) of oxyfluorfen for C. gariepinus was determined using probit analysis. Next, in a second experiment, 180 healthy fish (average initial body weight: 164.23 ± 0.24) were randomly assigned to 4 experimental groups exposed to 0, 1/10, 1/8, or 1/5 96-h LC₅₀ of oxyfluorfen. The hematological profile, hepatic enzymes, kidney damage byproducts, reproductive hormones, oxidative stress, and lipid peroxidation indicators together with acetylcholinesterase (AChE) content were assessed. A histopathological examination of the hepatic, renal, brain, and testicular tissues was accomplished. Moreover, the expression of the oxidative stress-related gene was carried out. The results showed that 96-h LC₅₀ of oxyfluorfen for C. gariepinus was 11.698 mg/L. Exposure to sublethal levels of oxyfluorfen induced macrocytic hypochromic anemia, leukopenia, lymphopenia, monocytopenia, and eosinopenia. Also, a concentration-dependent increase in alanine transaminase, alkaline phosphatase, aspartate transaminase, urea, creatinine, catalase, and malondialdehyde was detected following oxyfluorfen exposure together with upregulation of catalase gene. But, significant concentration-dependent reductions in AChE, glutathione transferase, reduced to oxidized glutathione ratio, estradiol, and testosterone activities were recorded. These biochemical alterations were accompanied by pathological perturbations in hepatic, renal, brain, and testicular tissues. Following 10 days of recovery, only the hematological impairments were abolished. Conclusively, the herbicides oxyfluorfen could induce multiple negative impacts on C. gariepinus with oxidative stress as a probable underlying mechanism. Additionally, a recovery period of 10 days was not enough to restore these impairments.

Acute toxic effects caused by the co-exposure of nanoparticles of ZnO and Cu in rainbow trout

The toxic effects produced by the co-exposure to low- and non-toxic concentrations of zinc oxide (ZnONPs) and copper nanoparticles (CuNPs) was assessed in rainbow trout following the OECD Test Guideline 203. Four groups of trouts were exposed for 96 h to a range of concentrations (0.0425-0.34 mg/L) of CuNPs (50 nm) in combination with a fixed non-toxic concentration (1.25 mg/L) of ZnONPs (25 nm) determined from an independent concentration-response study. One additional group was exposed to the highest concentration of CuNPs alone. Behaviour and mortality were observed during the experiment. After 96 h exposure, accumulated levels of Cu and Zn in the fish were measured by ICP-MS and ICP-OES, respectively. The induction of oxidative stress in liver and gills was evaluated by the glutathione-S-transferase (GST) activity and the reduced glutathione (GSH) / oxidized glutathione (GSSG) ratio. The ethoxyresorufin-O-deethylase (EROD) activity was also assessed. The results showed that CuNPs at the highest tested concentration do not cause acute toxicity, whereas exposure to all mixtures caused mortality, which was inversely proportional to the concentration of CuNPs (from 28% to 86% survival). Accumulated levels of Cu and Zn in the fish increased with the increasing concentrations of CuNPs, suggesting that the presence of CuNPs favours the entry of Zn. In general, the GST activity increased significantly in the gills of co-exposed groups, whereas the GSH/GSSG ratio was altered in the liver. The EROD activity was not modified. In conclusion, the co-exposure to these NPs potentiates their toxicity, observing an alteration of the GST activity and GSH/GSSG ratio in gill and liver, which was more pronounced at the lowest concentration of CuNPs. The lower toxic effect observed with the highest concentrations of CuNPs coincides with a greater internalization of Zn.

Effects of dexamethasone on the Li-pilocarpine model of epilepsy: protection against hippocampal inflammation and astrogliosis

Background

Temporal lobe epilepsy (TLE) is the most common form of partial epilepsy and is accompanied, in one third of cases, by resistance to antiepileptic drugs (AED). Most AED target neuronal activity modulated by ionic channels, and the steroid sensitivity of these channels has supported the use of corticosteroids as adjunctives to AED. Assuming the importance of astrocytes in neuronal activity, we investigated inflammatory and astroglial markers in the hippocampus, a key structure affected in TLE and in the Li-pilocarpine model of epilepsy.

Methods

Initially, hippocampal slices were obtained from sham rats and rats subjected to the Li-pilocarpine model of epilepsy, at 1, 14, and 56 days after status epilepticus (SE), which correspond to the acute, silent, and chronic phases. Dexamethasone was added to the incubation medium to evaluate the secretion of S100B, an astrocyte-derived protein widely used as a marker of brain injury. In the second set of experiments, we evaluated the in vivo effect of dexamethasone, administrated at 2 days after SE, on hippocampal inflammatory (COX-1/2, PGE2, and cytokines) and astroglial parameters: GFAP, S100B, glutamine synthetase (GS) and water (AQP-4), and K⁺ (Kir 4.1) channels.

Results

Basal S100B secretion and S100B secretion in high-K⁺ medium did not differ at 1, 14, and 56 days for the hippocampal slices from epileptic rats, in contrast to sham animal slices, where high-K⁺ medium decreased S100B secretion. Dexamethasone addition to the incubation medium per se induced a decrease in S100B secretion in sham and epileptic rats (1 and 56 days after SE induction). Following in vivo dexamethasone administration, inflammatory improvements were observed, astrogliosis was prevented (based on GFAP and S100B content), and astroglial dysfunction was partially abrogated (based on Kir 4.1 protein and GSH content). The GS decrease was not prevented by dexamethasone, and AQP-4 was not altered in this epileptic model.

Conclusions

Changes in astroglial parameters emphasize the importance of these cells for understanding alterations and mechanisms of epileptic disorders in this model. In vivo dexamethasone administration prevented most of the parameters analyzed, reinforcing the importance of anti-inflammatory steroid therapy in the Li-pilocarpine model and possibly in other epileptic conditions in which neuroinflammation is present.

Electronic supplementary material

The online version of this article (10.1186/s12974-018-1109-5) contains supplementary material, which is available to authorized users.

Non-protein thiol imaging and quantification in live cells with a novel benzofurazan sulfide triphenylphosphonium fluorogenic compound

Thiols (-SH) play various roles in biological systems. They are divided into protein thiols (PSH) and non-protein thiols (NPSH). Due to the significant roles thiols play in various physiological/pathological functions, numerous analytical methods have been developed for thiol assays. Most of these methods are developed for glutathione, the major form of NPSH. Majority of these methods require tissue/cell homogenization before analysis. Due to a lack of effective thiol-specific fluorescent/fluorogenic reagents, methods for imaging and quantifying thiols in live cells are limited. Determination of an analyte in live cells can reveal information that cannot be revealed by analysis of cell homogenates. Previously, we reported a thiol-specific thiol-sulfide exchange reaction. Based on this reaction, a benzofurazan sulfide thiol-specific fluorogenic reagent was developed. The reagent was able to effectively image and quantify total thiols (PSH+NPSH) in live cells through fluorescence microscopy. The reagent was later named as GUALY's reagent. Here we would like to report an extension of the work by synthesizing a novel benzofurazan sulfide triphenylphosphonium derivative [(((7,7'-thiobis(benzo[c][1,2,5]oxadiazole-4,4'-sulfonyl))bis(methylazanediyl))bis(butane-4,1-diyl))bis(triphenylphosphonium) (TBOP)]. Like GUALY's reagent, TBOP is a thiol-specific fluorogenic agent that is non-fluorescent but forms fluorescent thiol adducts in a thiol-specific fashion. Different than GUALY's reagent, TBOP reacts only with NPSH but not with PSH. TBOP was effectively used to image and quantify NPSH in live cells using fluorescence microscopy. TBOP is a complementary reagent to GUALY's reagent in determining the roles of PSH, NPSH, and total thiols in thiol-related physiological/pathological functions in live cells through fluorescence microscopy. Graphical Abstract Live cell imaging and quantification of non-protein thiols by TBOP.

Comparison of enzymatic properties and small molecule inhibition of γ-glutamyltranspeptidases from pathogenic and commensal bacteria

Helicobacter pylori infects the stomach of 50% of the population worldwide, thus causing chronic gastritis. Although this infection can be cured by antibiotic treatment, therapeutic options are increasingly limited due to the development of resistances. The γ-glutamyl-transpeptidase (gGT) of H. pylori (HpgGT) is a virulence factor important for colonization and contributes to bacterial immune evasion. Therefore, this enzyme is a potential target for developing new anti-infectives. As species specificity of such compounds is required in order to avoid off-target or adverse effects, comparative analysis of the gGTs from different organisms is a prerequisite for drug development. To allow detailed biochemical and enzymatic characterization, recombinant gGTs from five different bacteria as well as Homo sapiens were characterized and compared. Investigation of the enzymatic activity, the binding modes of known inhibitors to the catalytic center, and a high resolution X-ray structure of the HpgGT provided a starting point for the identification of new inhibitory substances targeting HpgGT. Inhibitors with Ki values in the nm to mm range were identified and their binding modes were analyzed by mass spectrometry. The results of this study provide a basis for the development of species-specific lead compounds with anti-infective potential by effectively inhibiting HpgGT.

In vitro Effects of Four Native Brazilian Medicinal Plants in CYP3A4 mRNA Gene Expression, Glutathione Levels, and P-Glycoprotein Activity

Erythrina mulungu Benth. (Fabaceae), Cordia verbenacea A. DC. (Boraginaceae), Solanum paniculatum L. (Solanaceae) and Lippia sidoides Cham. (Verbenaceae) are medicinal plant species native to Brazil shortlisted by the Brazilian National Health System for future clinical use. However, nothing is known about their effects in metabolic and transporter proteins, which could potentially lead to herb-drug interactions (HDI). In this work, we assess non-toxic concentrations (100 μg/mL) of the plant infusions for their in vitro ability to modulate CYP3A4 mRNA gene expression and intracellular glutathione levels in HepG2 cells, as well as P-glycoprotein (P-gp) activity in vincristine-resistant Caco-2 cells (Caco-2 VCR). Their mechanisms of action were further studied by measuring the activation of human pregnane X receptor (hPXR) in transiently co-transfected HeLa cells and the inhibition of γ-glutamyl transferase (GGT) in HepG2 cells. Our results show that P-gp activity was not affected in any case and that only Solanum paniculatum was able to significantly change CYP3A4 mRNA gene expression (twofold decrease, p < 0.05), this being correlated with an antagonist effect upon hPXR (EC50 = 0.38 mg/mL). Total intracellular glutathione levels were significantly depleted by exposure to Solanum paniculatum (-44%, p < 0.001), Lippia sidoides (-12%, p < 0.05) and Cordia verbenacea (-47%, p < 0.001). The latter plant extract was able to decrease GGT activity (-48%, p < 0.01). In conclusion, this preclinical study shows that the administration of some of these herbal medicines may be able to cause disturbances to metabolic mechanisms in vitro. Although Erythrina mulungu appears safe in our tests, active pharmacovigilance is recommended for the other three species, especially in the case of Solanum paniculatum.

Tissue distribution of zinc and subtle oxidative stress effects after dietary administration of ZnO nanoparticles to rainbow trout

The increasing use of ZnO nanoparticles (ZnO NPs) in different fields has raised concerns about the possible environmental risks associated with these NPs entering aquatic systems. In this study, using a dietary exposure route, we have analysed the tissue distribution and depuration pattern of Zn as well as any associated redox balance disturbances in rainbow trout (Oncorhynchus mykiss) following exposure to ZnO NPs (20-30nm). Fish were fed a diet spiked with ZnO NPs prepared from a dispersion in sunflower oil at doses of 300 or 1000mg ZnO NPs/kg feed for 10days. This uptake phase was followed by a 28days depuration phase in which fish from all groups received untreated feed. While no overt signs of toxicity were observed and no important effects in fish growth (weight and length) or in the hepatosomatic index among groups were recorded, we observed high levels of Zn bioaccumulation in the gills and intestine of exposed fish following exposure to both dose levels. Zn levels were not eliminated during the depuration phase and we have evidenced oxidative stress responses in gills associated with such long term ZnO NPs bioaccumulation and lack of elimination. Furthermore, exposures to higher doses of ZnO NPs (1000mg/kg feed) resulted in Zn distribution to the liver of fish following 10days of exposure. Fish from this exposure group experienced biochemical disturbances associated with oxidative stress in the liver and ethoxy-resorufin-O-deethylase (EROD) activity which may point to the ability of ZnO NPs or its ions to interfere with cytochrome P450 metabolic processes.

Complex coordinated extracellular metabolism: Acid phosphatases activate diluted human leukocyte proteins to generate energy flow as NADPH from purine nucleotide ribose

Complex metabolism is thought to occur exclusively in the crowded intracellular environment. Here we report that diluted enzymes from lysed human leukocytes produce extracellular energy. Our findings involve two pathways: the purine nucleotide catabolic pathway and the pentose phosphate pathway, which function together to generate energy as NADPH. Glucose6P fuel for NADPH production is generated from structural ribose of purine ribonucleoside monophosphates, ADP, and ADP-ribose. NADPH drives glutathione reductase to reduce an oxidized glutathione disulfide-glutathione redox couple. Acid phosphatases initiate ribose5P salvage from purine ribonucleoside monophosphates, and transaldolase controls the direction of carbon chain flow through the nonoxidative branch of the pentose phosphate pathway. These metabolic control points are regulated by pH. Biologically, this energy conserving metabolism could function in perturbed extracellular spaces.

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Extracellular metabolism occurs in dilute human leukocyte cytosolic protein solution.

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Extracellular metabolism is activated by acid phosphatases.

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Ribose5P salvage from purine nucleotides and its metabolism produces NADPH.

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Extracellular NADPH generating metabolism influences the redox environment.

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Extracellular metabolism could be a component of inflammation and wound healing.

Recovery of redox homeostasis altered by CuNPs in H4IIE liver cells does not reduce the cytotoxic effects of these NPs: an investigation using aryl hydrocarbon receptor (AhR) dependent antioxidant activity

The generation of reactive oxygen species (ROS) and consequent oxidative stress is regarded as a relevant mechanism for nanoparticle toxicity. In cells, the activation of the aryl hydrocarbon receptor (AhR) triggers a cascade of defence responses against oxidative stress. By increasing AhR dependent cellular anti-oxidant activity, we tested the extent to which the cytotoxic effect of copper nanoparticles (CuNPs) is governed by oxidative stress. H4IIE rat hepatoma cells were challenged with high ROS levels after exposure to CuNPs, while the AhR-induced cellular anti-oxidant defence was simultaneously activated by the AhR ligand beta-Naphthoflavone (ßNF). Activation of phase II detoxification enzymes (as glutathione-S-transferases, GSTs) and anti-oxidants (glutathione, GSH) led to a complete abrogation of CuNP-induced ROS production. However, a concurrent reduction in cytotoxicity was not detected, thereby indicating that CuNPs exert non-oxidative stress mediated cytotoxic effects. Transmission electron microscopy analysis pointed to a direct physical perturbation of cellular structures by CuNPs, thus contributing to their cytotoxicity. Our observations highlight that distinct mechanisms underlie the toxicity of ions and NPs and indicate that while ROS elicitation is CuNP-specific, the cytotoxic action of these particles may not be directly related to their pro-oxidative activity. These findings have important implications with respect to the oxidative stress paradigm used to explain NP toxicity.

γ-Glutamyl cysteine and γ-glutamyl valine inhibit TNF-α signaling in intestinal epithelial cells and reduce inflammation in a mouse model of colitis via allosteric activation of the calcium-sensing receptor

BACKGROUND

The extracellular calcium-sensing receptor (CaSR) is distributed throughout the gastrointestinal tract, and its activation has been shown to promote intestinal homeostasis, suggesting that CaSR may be a promising target for novel therapies to prevent chronic intestinal inflammation such as inflammatory bowel disease (IBD). The γ-glutamyl dipeptides γ-glutamyl cysteine (γ-EC) and γ-glutamyl valine (γ-EV) are dietary flavor enhancing compounds, and have been shown to activate CaSR via allosteric ligand binding. The aim of this study was to examine the anti-inflammatory effects of γ-EC and γ-EV in vitro in intestinal epithelial cells and in a mouse model of intestinal inflammation.

RESULTS

In vitro, treatment of Caco-2 cells with γ-EC and γ-EV resulted in the CaSR-mediated reduction of TNF-α-stimulated pro-inflammatory cytokines and chemokines including IL-8, IL-6, and IL-1β, and inhibited phosphorylation of JNK and IκBα, while increasing expression of IL-10. In vivo, using a mouse model of dextran sodium sulfate (DSS)-induced colitis, γ-EC and γ-EV treatment ameliorated DSS-induced clinical signs, weight loss, colon shortening and histological damage. Moreover, γ-EC and γ-EV reduced the expression of TNF-α, IL-6, INF-γ, IL-1β, and IL-17, and increased the expression of IL-10 in the colon, in a CaSR-dependent manner. The CaSR-mediated anti-inflammatory effects of γ-EC were abrogated in β-arrestin2 knock-down Caco-2 cells, and involvement of β-arrestin2 was found to inhibit TNF-α-dependent signaling via cross-talk with the TNF-α receptor (TNFR).

CONCLUSIONS

Thus CaSR activation by γ-EC and γ-EV can aid in maintaining intestinal homeostasis and reducing inflammation in chronic inflammatory conditions such as IBD.

Rapid and thiol-specific high-throughput assay for simultaneous relative quantification of total thiols, protein thiols, and nonprotein thiols in cells

Thiol groups in biological molecules play a significant role in various physiological functions and pathological conditions. Thiols are divided into two major groups: protein thiols and nonprotein thiols. Numerous methods have been reported for thiol assays. Most of these methods have been developed for glutathione, the principal nonprotein thiol, despite the fact that cellular protein thiols are more abundant than glutathione. Further, these methods usually involve a process of biological sample preparation followed by a separation method, and they are time-consuming. We reported previously a series of thiol-specific fluorogenic benzofurazan sulfides. These nonfluorescent benzofurazan sulfides react rapidly and specifically with a thiol to form a strong fluorescent thiol adduct. The rapid reaction, thiol-specific and fluorogenic nature of the sulfides successfully yielded an application of one of the sulfides for relative quantitation of total thiols in live cells through fluorescence microscopy. In this work, we employed the same compound to develop the first high-throughput method for simultaneous monitoring of protein thiols, nonprotein thiols, and total thiols in cells in a 96-well plate on a fluorescence microplate reader at λ_ex = 430 nm and λ_em = 520 nm, respectively. The method is rapid and sensitive, and has been validated by an HPLC thiol assay method. The method can detect thiols with cell concentrations as low as 500 cells/well. We also demonstrated that the method can readily monitor changes in cellular thiol levels. Although the method cannot provide an absolute quantification for thiols because fluorescence intensity of different thiol adducts varies, it provides an accurate measurement of relative quantification, relative to the control. The method will be a valuable tool in thiol-related biomedical/pharmaceutical research.

Evaluation of zinc oxide nanoparticle toxicity in sludge products applied to agricultural soil using multispecies soil systems

To study the environmental impact of nanoparticles, the sludges of wastewater (WWTS) and water treatment (WTS) plants enriched with ZnO nanoparticles were added to agricultural soil, and the toxic effects of the nanoparticles were studied using a microcosm system based on the soil. The WWTS treated soils were characterised by statistically significant decreases (p<0.05) in Vicia sativa germination at the lowest (76.2%) and medium (95.2%) application rates, decreases in the fresh biomass for Triticum aestivum (19.5%), Raphanus sativus (64.1%), V. sativa (37.4%) and Eisenia fetida (33.6%) at the highest application rate and a dose-related significant increase (p<0.05) in earthworm mortality. In WTS amended soils, significant reductions (p<0.05) of the fresh biomass (17.2%) and the chlorophyll index (24.4%) for T. aestivum and the fresh biomass for R. sativus (31.4%) were only recorded at the highest application doses. In addition, the soil phosphatase enzymatic activity decreased significantly (p<0.05) in both WWTS (dose related) and WTS treatments. For water organisms, a slight inhibition of the growth of Chlorella vulgaris was observed (WWTS treated soils), along with statistically significant dose-related inhibition responses on total glutathione cell content, and statistically significant dose-related induction responses on the glutathione S-transferase enzyme activity and the reactive oxygen species generation on the RTG-2 fish cell line.

Chloride secretion induced by rotavirus is oxidative stress-dependent and inhibited by Saccharomyces boulardii in human enterocytes

Rotavirus (RV) infection causes watery diarrhea via multiple mechanisms, primarily chloride secretion in intestinal epithelial cell. The chloride secretion largely depends on non-structural protein 4 (NSP4) enterotoxic activity in human enterocytes through mechanisms that have not been defined. Redox imbalance is a common event in cells infected by viruses, but the role of oxidative stress in RV infection is unknown. RV SA11 induced chloride secretion in association with an increase in reactive oxygen species (ROS) in Caco-2 cells. The ratio between reduced (GSH) and oxidized (GSSG) glutathione was decreased by RV. The same effects were observed when purified NSP4 was added to Caco-2 cells. N-acetylcysteine (NAC), a potent antioxidant, strongly inhibited the increase in ROS and GSH imbalance. These results suggest a link between oxidative stress and RV-induced diarrhea. Because Saccharomyces boulardii (Sb) has been effectively used to treat RV diarrhea, we tested its effects on RV-infected cells. Sb supernatant prevented RV-induced oxidative stress and strongly inhibited chloride secretion in Caco-2 cells. These results were confirmed in an organ culture model using human intestinal biopsies, demonstrating that chloride secretion induced by RV-NSP4 is oxidative stress-dependent and is inhibited by Sb, which produces soluble metabolites that prevent oxidative stress. The results of this study provide novel insights into RV-induced diarrhea and the efficacy of probiotics.

Peptide-biphenyl hybrid-capped AuNPs: stability and biocompatibility under cell culture conditions

In this study, we explored the biocompatibility of Au nanoparticles (NPs) capped with peptide-biphenyl hybrid (PBH) ligands containing glycine (Gly), cysteine (Cys), tyrosine (Tyr), tryptophan (Trp) and methionine (Met) amino acids in the human hepatocellular carcinoma cell line Hep G2. Five AuNPs, Au[(Gly-Tyr-Met)2B], Au[(Gly-Trp-Met)2B], Au[(Met)2B], Au[(Gly-Tyr-TrCys)2B] and Au[(TrCys)2B], were synthesised. Physico-chemical and cytotoxic properties were thoroughly studied. Transmission electron micrographs showed isolated near-spherical nanoparticles with diameters of 1.5, 1.6, 2.3, 1.8 and 2.3 nm, respectively. Dynamic light scattering evidenced the high stability of suspensions in Milli-Q water and culture medium, particularly when supplemented with serum, showing in all cases a tendency to form agglomerates with diameters approximately 200 nm. In the cytotoxicity studies, interference caused by AuNPs with some typical cytotoxicity assays was demonstrated; thus, only data obtained from the resazurin based assay were used. After 48-h incubation, only concentrations ≥50 μg/ml exhibited cytotoxicity. Such doses were also responsible for an increase in reactive oxygen species (ROS). Some differences were observed among the studied NPs. Of particular importance is the AuNPs capped with the PBH ligand (Gly-Tyr-TrCys)2B showing remarkable stability in culture medium, even in the absence of serum. Moreover, these AuNPs have unique biological effects on Hep G2 cells while showing low toxicity. The production of ROS along with supporting optical microscopy images suggests cellular interaction/uptake of these particular AuNPs. Future research efforts should further test this hypothesis, as such interaction/uptake is highly relevant in drug delivery systems.

In vitro evaluation of cellular responses induced by ZnO nanoparticles, zinc ions and bulk ZnO in fish cells

Zinc oxide nanoparticles (ZnO-NPs) are inevitably released into the environment and are potentially dangerous for aquatic life. However, the potential mechanisms of cytotoxicity of zinc nanoparticles remain unclear. Studying the toxicity of ZnO-NPs with In vitro systems will help to determine their interactions with cellular biomolecules. The aim of this study was to evaluate the cytotoxic potentials of ZnO-NPs in established fish cell lines (RTG-2, RTH-149 and RTL-W1) and compare them with those of bulk ZnO and Zn(2+) ions. Membrane function (CFDA-AM assay), mitochondrial function (MTT assay), cell growth (KBP assay), cellular stress (β-galactosidase assay), reductase enzyme activity (AB assay), reactive oxygen species (ROS), total glutathione cellular content (tGSH assay) and glutathione S-transferase (GST) activities were assessed for all cell lines. ZnO-NPs cytotoxicity was greater than those of bulk ZnO and Zn(2+). ZnO-NPs induced oxidative stress is dependent on their dose. Low cost tests, such as CFDA-AM, ROS, GST activity and tGSH cell content test that use fish cell lines, may be used to detect oxidative stress and redox status changes. Particle dissolution of the ZnO-NPs did not appear to play an important role in the observed toxicity in this study.

Enhanced glutathione content allows the in vivo synthesis of fluorescent CdTe nanoparticles by Escherichia coli

The vast application of fluorescent semiconductor nanoparticles (NPs) or quantum dots (QDs) has prompted the development of new, cheap and safer methods that allow generating QDs with improved biocompatibility. In this context, green or biological QDs production represents a still unexplored area. This work reports the intracellular CdTe QDs biosynthesis in bacteria. Escherichia coli overexpressing the gshA gene, involved in glutathione (GSH) biosynthesis, was used to produce CdTe QDs. Cells exhibited higher reduced thiols, GSH and Cd/Te contents that allow generating fluorescent intracellular NP-like structures when exposed to CdCl(2) and K(2)TeO(3). Fluorescence microscopy revealed that QDs-producing cells accumulate defined structures of various colors, suggesting the production of differently-sized NPs. Purified fluorescent NPs exhibited structural and spectroscopic properties characteristic of CdTe QDs, as size and absorption/emission spectra. Elemental analysis confirmed that biosynthesized QDs were formed by Cd and Te with Cd/Te ratios expected for CdTe QDs. Finally, fluorescent properties of QDs-producing cells, such as color and intensity, were improved by temperature control and the use of reducing buffers.

The HIV-1 transactivator factor (Tat) induces enterocyte apoptosis through a redox-mediated mechanism

The intestinal mucosa is an important target of human immunodeficiency virus (HIV) infection. HIV virus induces CD4+ T cell loss and epithelial damage which results in increased intestinal permeability. The mechanisms involved in nutrient malabsorption and alterations of intestinal mucosal architecture are unknown. We previously demonstrated that HIV-1 transactivator factor (Tat) induces an enterotoxic effect on intestinal epithelial cells that could be responsible for HIV-associated diarrhea. Since oxidative stress is implicated in the pathogenesis and morbidity of HIV infection, we evaluated whether Tat induces apoptosis of human enterocytes through oxidative stress, and whether the antioxidant N-acetylcysteine (NAC) could prevent it. Caco-2 and HT29 cells or human intestinal mucosa specimens were exposed to Tat alone or combined with NAC. In an in-vitro cell model, Tat increased the generation of reactive oxygen species and decreased antioxidant defenses as judged by a reduction in catalase activity and a reduced (GSH)/oxidized (GSSG) glutathione ratio. Tat also induced cytochrome c release from mitochondria to cytosol, and caspase-3 activation. Rectal dialysis samples from HIV-infected patients were positive for the oxidative stress marker 8-hydroxy-2'-deoxyguanosine. GSH/GSSG imbalance and apoptosis occurred in jejunal specimens from HIV-positive patients at baseline and from HIV-negative specimens exposed to Tat. Experiments with neutralizing anti-Tat antibodies showed that these effects were direct and specific. Pre-treatment with NAC prevented Tat-induced apoptosis and restored the glutathione balance in both the in-vitro and the ex-vivo model. These findings indicate that oxidative stress is one of the mechanism involved in HIV-intestinal disease.

Comparison of manganese oxide nanoparticles and manganese sulfate with regard to oxidative stress, uptake and apoptosis in alveolar epithelial cells

Due to their physicochemical characteristics, metal oxide nanoparticles (NPs) interact differently with cells compared to larger particles or soluble metals. Oxidative stress and cellular metal uptake were quantified in rat type II alveolar epithelial cells in culture exposed to three different NPs: manganese(II,III) oxide nanoparticles (Mn(3)O(4)-NPs), the soluble manganese sulfate (Mn-salt) at corresponding equivalent doses, titanium dioxide (TiO(2)-NPs) and cerium dioxide nanoparticles (CeO(2)-NPs). In the presence of reactive oxygen species an increased apoptosis rate was hypothesized. Oxidative stress was assessed by detection of fluorescently labeled reactive oxygen species and by measuring intracellular oxidized glutathione. Catalytic activity was determined by measuring catalyst-dependent oxidation of thiols (DTT-assay) in a cell free environment. Inductively coupled plasma mass spectrometry was used to quantify cellular metal uptake. Apoptosis rate was determined assessing the activity of caspase-3 and by fluorescence microscopic quantification of apoptotic nuclei. Reactive oxygen species were mainly generated in cells treated with Mn(3)O(4)-NPs. Only Mn(3)O(4)-NPs oxidized intracellular glutathione. Catalytic activity could be exclusively shown for Mn(3)O(4)-NPs. Cellular metal uptake was similar for all particles, whereas Mn-salt could hardly be detected within the cell. Apoptosis was induced by both, Mn(3)O(4)-NPs and Mn-salt. The combination of catalytic activity and capability of passing the cell membrane contributes to the toxicity of Mn(3)O(4)-NPs. Apoptosis of samples treated with Mn-salt is triggered by different, potentially extracellular mechanisms.

Egg yolk peptides up-regulate glutathione synthesis and antioxidant enzyme activities in a porcine model of intestinal oxidative stress

Long-term oxidative stress in the gastrointestinal tract can lead to the development of chronic intestinal disorders. Many food-derived antioxidants are effective in vitro, but the variable reports of in vivo efficacy and the pro-oxidant nature of some antioxidants necessitate alternative strategies for the reduction of in vivo oxidative stress. Compounds that up-regulate the production of endogenous antioxidants such as glutathione (GSH) and antioxidant enzymes provide novel approaches for the restoration of redox homeostatis. Egg yolk peptides (EYP) prepared from Alcalase and protease N digestion of delipidated egg yolk proteins were found to exhibit antioxidative stress properties. The effect of EYP supplementation was examined in a hydrogen peroxide-induced human colon cell line and in an animal model of intestinal oxidative stress. EYP significantly reduced the pro-inflammatory cytokine, IL-8, in Caco-2 cells. In piglets given intraperitoneal infusions of hydrogen peroxide, EYP treatment increased GSH and gamma-glutamylcysteine synthetase mRNA expression and activity, significantly increased antioxidant enzyme activities, in particular catalase and glutathione S-transferase activities, and reduced protein and lipid oxidation in the duodenum, jejunum, ileum, and colon. Furthermore, EYP boosted the systemic antioxidant status in blood by increasing the GSH concentration in red blood cells. These results suggest that EYP supplementation is a novel strategy for the reduction of intestinal oxidative stress.

Cysteine biosynthesis, oxidative stress and antibiotic resistance in Salmonella typhimurium

The efficacy of antibiotics varies under different growth conditions due to the induction of specific or more general defense pathways, but the mechanisms are not completely understood. Actively swarming Salmonella show elevated resistance to many types of antibiotics. Previously, we had shown that cysteine biosynthesis was important for the induced antibiotic resistance phenotype of swarm cells. Here we examine the connection of cysteine to oxidative stress and demonstrate that the antioxidant properties of cysteine or cysteine-derived metabolites contribute to the antibiotic resistance in both vegetative and swarm cell populations. We observed that cys auxotrophs were oxidatively stressed, and in wild-type cells expression of the cys regulon was induced during periods of oxidative stress. In swarm cells, we found a 6-fold increase in reduced glutathione compared to swim cells and a corresponding increased resistance to oxidants. Wild-type and cys auxotrophs exhibited the same sensitivities to gentamicin, polymyxin and ciprofloxacin when grown anaerobically, suggesting that induced oxidative stress defense was contributing to elevated antibiotic resistance in swarm cells aerobically. Induction of the CysB regulon by addition of exogenous inducer resulted in elevated antibiotic resistance independently of swarming.

Inhibitory effects of glutathione on dengue virus production

Reduced glutathione (GSH) is the most powerful intracellular antioxidant and also involved in viral infections. The pathogenesis of dengue virus (DV) infection has not been completely clarified. This study investigated the relationship between DV serotype 2 (DV2) infections and host intracellular GSH content. Results showed infection with DV2 resulted in a decrease in intracellular GSH, which caused NF-kappaB activation and increased DV2 production. Supplemental GSH significantly inhibited activation of NF-kappaB, resulting in a decreased production of DV2 in HepG2 cells. Furthermore, high activity of NF-kappaB and increased production of DV2 was observed in HepG2 cells treated with buthionine sulfoximine (BSO), an inhibitor of GSH synthesis. In conclusion, DV2 infection could reduce host intracellular GSH concentration and benefited from this process. Supplemental GSH could inhibit viral production, indicating GSH might be valuable in the prevention and treatment of DV2 infection.

Lindane-induced generation of reactive oxygen species and depletion of glutathione do not result in necrosis in renal distal tubule cells

Lindane is a chlorinated hydrocarbon pesticide, currently used in prescription shampoos and lotions to treat scabies and lice infestations. Lindane is known to be nephrotoxic; however, the mechanism of action is not well understood. In other organ systems, lindane produces cellular damage by generation of free radicals and oxidative stress. Morphological changes were observed in lindane-treated Madin-Darby canine kidney (MDCK) cells indicative of apoptosis. Lindane treatment induced time-dependent reactive oxygen species (ROS) generation. Onset of ROS generation correlated with an initial increase in total glutathione (GSH) levels above control values, with a subsequent decline in a time-dependent manner. This decline may be attributed to quenching of free radicals by GSH, thereby decreasing the cellular stores of this antioxidant. Necrotic injury was assessed by measuring lactate dehydrogenase (LDH) leakage from the cell after lindane exposure. No significant LDH leakage was noted for all concentrations tested over time. Generation of ROS and alterations in cellular protective mechanisms did not result in necrotic injury in MDCK cells, which corresponds with our morphological findings of lindane-induced apoptotic changes as opposed to necrosis in MDCK cells. Thus, lindane exposure results in oxidative damage and alterations in antioxidant response in renal distal tubule cells, followed by cell death not attributed to necrotic injury.

Resveratrol increases glutamate uptake, glutathione content, and S100B secretion in cortical astrocyte cultures

Resveratrol (3,5,4'-trihydroxy-trans-stilbene) is a polyphenol present in grapes and red wine, which has antioxidant properties and a wide range of other biological effects. In this study, we investigated the effect of resveratrol, in a concentration range of 10-250 microM, on primary cortical astrocytes; evaluating cell morphology, parameters of glutamate metabolism such as glutamate uptake, glutamine synthetase activity and glutathione total content, and S100B secretion. Astrocyte cultures were prepared of cerebral cortex from neonate Wistar rats. Morphology was evaluated by phase-contrast microscopy and immunocytochemistry for glial fibrillary acidic protein (GFAP). Glutamate uptake was measured using L-[2,3-3H]glutamate. Glutamine synthetase and content of glutathione were measured by enzymatic colorimetric assays. S100B content was determined by ELISA. Typical polygonal morphology becomes stellated when astrocyte cultures were exposed to 250 microM resveratrol for 24 h. At concentration of 25 microM, resveratrol was able to increase glutamate uptake and glutathione content. Conversely, at 250 microM, resveratrol decreased glutamate uptake. Unexpectedly, resveratrol at this high concentration increased glutamine synthetase activity. Extracellular S100B increased from 50 microM upwards. Our findings reinforce the protective role of this compound in some brain disorders, particularly those involving glutamate toxicity. However, the underlying mechanisms of these changes are not clear at the moment and it is necessary caution with its administration because elevated levels of this compound could contribute to aggravate these conditions.

Antioxidative activity of amino acids on tissue oxidative stress in human intestinal epithelial cell model

The protective effects of amino acids against H 2O 2-induced oxidative stress were investigated in an in vitro assay using human intestinal epithelial cells. Caco-2 cells were pretreated with amino acids (1, 2, and 5 mM) for 2 h and then stimulated with 1 mM H 2O 2 for 6 h. The secretion of IL-8, a proinflammatory mediator, was determined by ELISA as an indicator of tissue oxidative stress. The inhibition of H 2O 2-induced IL-8 secretion from Caco-2 cells was observed by pretreatment with Cys, Val, Ile, Leu, Trp, His, Lys, and Ala. Cys enhanced glutathione (GSH) biosynthesis enzyme activity and increased cellular GSH levels. Branched-chain amino acids such as Val, Ile, and Leu elevated activities of GSH S-transferase (GST) and catalase. Trp, His, and Lys caused increases in GST activity. Ala enhanced GSH reductase activity. These data suggest that specific amino acids exert protective effects against tissue oxidative stress in intestinal epithelial cells based on the structure.

Indomethacin induces apoptosis via a MRP1-dependent mechanism in doxorubicin-resistant small-cell lung cancer cells overexpressing MRP1

Small-cell lung cancers (SCLCs) initially respond to chemotherapy, but are often resistant at recurrence. The non-steroidal anti-inflammatory drug indomethacin is an inhibitor of multidrug resistance protein 1 (MRP1) function. The doxorubicin-resistant MRP1-overexpressing human SCLC cell line GLC(4)-Adr was highly sensitive for indomethacin compared with the parental doxorubicin-sensitive line GLC(4). The purpose of this study was to analyse the relationship between hypersensitivity to indomethacin and MRP1 overexpression. The experimental design involved analysis of the effect of MRP1 downregulation on indomethacin-induced cell survival and apoptosis in GLC(4)-Adr and GLC(4), using siRNA. In addition the effect of indomethacin on glutathione levels and mitochondrial membrane potential was investigated. Small interfering RNAs directed against MRP1 reduced MRP1 mRNA levels twofold and reduced efflux pump function of MRP1, which was reflected by a 1.8-fold higher accumulation of MRP1 substrate carboxyfluorescein, in si-MRP1 versus si-Luciferase-transfected GLC(4)-Adr cells. Multidrug resistance protein 1 downregulation decreased initial high apoptosis levels 2-fold in GLC(4)-Adr after indomethacin treatment for 24 h, and increased cell survival (IC(50)) from 22.8+/-2.6 to 30.4+/-5.1 microM following continuous indomethacin exposure. Multidrug resistance protein 1 downregulation had no effect on apoptosis in GLC(4) or on glutathione levels in both lines. Although indomethacin (20 microM) for 2 h decreased glutathione levels by 31.5% in GLC(4)-Adr, complete depletion of cellular glutathione by L-buthionine (S,R)-sulphoximine only resulted in a small increase in indomethacin-induced apoptosis in GLC(4)-Adr, demonstrating that a reduced cellular glutathione level is not the primary cause of indomethacin-induced apoptosis. Indomethacin exposure decreased mitochondrial membrane potential in GLC(4)-Adr cells, suggesting activation of the mitochondrial apoptosis pathway. Indomethacin induces apoptosis in a doxorubicin-resistant SCLC cell line through an MRP1-dependent mechanism. This may have implications for the treatment of patients with MRP1-overexpressing tumours.

Sympatric Drosophila simulans flies with distinct mtDNA show age related differences in mitochondrial metabolism

The primary causes of age-related changes in mitochondrial metabolism are not known. The goal of this study is to document the influence of naturally occurring mtDNA variation on age dependent changes in mitochondrial respiration, hydrogen peroxide (H(2)O(2)) generation and antioxidant defenses in the fly Drosophila simulans. Possible changes include an increase in rates of reactive oxygen species production with age and/or an age dependent decrease in antioxidant response. For this study we have used flies harboring distinct siII and siIII mtDNA types. Previously we have shown that males harboring siII mtDNA had higher rates of mitochondrial H(2)O(2) production from complex III at 11d compared to males with the siIII mtDNA type. Here, we corroborate those results and show that Drosophila harboring the siII and siIII mtDNA types exhibit significantly different patterns of pro-oxidant and antioxidant activities as they age. Flies harboring siII mtDNA had higher rates of mitochondrial H(2)O(2) production and manganese superoxide dismutase activity at 11 and 18d of age than siIII mtDNA harboring flies. Copper-zinc superoxide dismutase activity increased from 11 to 25d in siII flies while the accumulation of oxidized glutathione did not change between 11 and 25d. In contrast, siIII harboring flies showed an age dependent increase in H(2)O(2) production, reaching higher production rates on day 25 than that observed in siII flies. Copper-zinc superoxide dismutase activities did not change between 11 and 25d while the oxidized glutathione accumulation increased with age. The results show antioxidant levels correlate with pro-oxidant levels in siII but not siIII flies. These results demonstrate our ability to correlate mtDNA variation with differences in whole mitochondrial physiology and individual complex biochemistry.

Protective effects of resveratrol on hydrogen peroxide induced toxicity in primary cortical astrocyte cultures

It is well established that the brain is particularly susceptible to oxidative damage due to its high consumption of oxygen and that astrocytes are involved in a variety of important activities for the nervous system, including a protective role against damage induced by reactive oxygen species (ROS). The use of antioxidant compounds, such as polyphenol resveratrol found in red wine, to improve endogenous antioxidant defenses has been proposed for neural protection. The aim of this study is to evaluate the putative protective effect of resveratrol against acute H2O2-induced oxidative stress in astrocyte cultures, evaluating ROS production, glutamate uptake activity, glutathione content and S100B secretion. Our results confirm the ability of resveratrol to counteract oxidative damage caused by H2O2, not only by its antioxidant properties, but also through the modulation of important glial functions, particularly improving glutamate uptake activity, increasing glutathione content and stimulating S100B secretion, which all contribute to the functional recovery after brain injury.

S100B content and secretion decrease in astrocytes cultured in high-glucose medium

S100B is an astrocyte calcium-binding protein that plays a regulatory role in the cytoskeleton and cell cycle. Moreover, extracellular S100B, a marker of glial activation in several conditions of brain injury, has a trophic or apoptotic effect on neurons, depending on its concentration. Hyperglycemic rats show changes in glial parameters, including S100B expression. Here, we investigated cell density, morphological and biochemical alterations in primary cortical astrocytes from rats and C6 glioma cells cultured in high-glucose medium. Astrocytes and C6 glioma cells have a reduced content of S100B and glial fibrillary acidic protein when cultured in a high-glucose environment, as well as a reduced content of glutathione and cell proliferation rate. Although these cells have been used indistinctly to study S100B secretion, we observed a contrasting profile of S100B secretion in a high-glucose medium: a decrease in primary astrocytes and an increase in C6 glioma cells. Based on the in vitro neurotrophic effects of the S100B protein, our data suggest that chronic elevated glucose levels affect astrocyte activity, reducing extracellular secretion of S100B and that this, in turn, could affect neuronal activity and survival. Such astrocyte alterations could contribute to cognitive deficit and other impairments observed in diabetic patients.

Exogenous hydrogen sulfide induces functional inhibition and cell death of cytotoxic lymphocytes subsets

The toxic effects of exogenous hydrogen sulfide on peripheral blood lymphocytes have been investigated in detail. Hydrogen sulfide is now considered as a gasotransmitter with specific functional roles in different cell types, like neurons and vascular smooth muscle. Here we show that exogenous hydrogen sulfide induces a caspase-independent cell death of peripheral blood lymphocytes that depends on their intracellular glutathione levels, with a physiologically relevant subset specificity for CD8+ T cells and NK cells. Although lymphocyte activation does not modify their sensitivity to HS-, after 24 h exposure to hydrogen sulfide surviving lymphocyte subsets show a dramatically decreased proliferation in response to mitogens and a reduced IL-2 production. Overall, our data demonstrate that HS- reduces the cellular cytotoxic response of peripheral blood lymphocytes as well as their production of IL-2, therefore de-activating the major players of local inflammatory responses, adding new basic knowledge to the clinically well known anti-inflammatory effects of sulfur compounds.

Brain glutathione content and glutamate uptake are reduced in rats exposed to pre- and postnatal protein malnutrition

The brain is particularly susceptible to oxidative insults and its antioxidant defense is dependent on its glutathione content. Protein malnutrition (PMN) is an important and very common insult during development and compromises antioxidant defenses in the body, particularly glutathione levels. We investigated whether brain glutathione content and related metabolic pathways, predominantly regulated by astrocytes (particularly glutamate uptake and glutamine synthesis), are altered by pre- and postnatal PMN in rats. Thus, we measured the glutathione content, glutamine synthetase (GS) activity, and glutamate uptake activity in the cerebral cortex (Cx) and hippocampus of rats subjected to pre- and postnatal PMN and in nourished controls. Although malnourished rats exhibited an ontogenetic profile of glutathione levels in both brain regions similar to that of controls, they had lower levels on postnatal d 2 (P2); in Cx this decrease persisted until postnatal d 15. In addition, we found other changes, such as reduced total antioxidant reactivity and glutathione peroxidase activity on P2, and these were not accompanied by alterations in free radical levels or lipoperoxidation in either brain region. Moreover, malnourished rats had elevated GS and reduced glutamate uptake. Taken together, these alterations indicate specific changes in astrocyte metabolism, possibly responsible for the higher vulnerability to excitotoxic/oxidative damage in malnourished rats. The lower antioxidant defense appears to be the main alteration that causes oxidative imbalance, rather than an increase in reactive oxygen species. Moreover, a recovery of altered metabolic variables may occur during adulthood, despite persistent PMN.

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

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

Association of a bovine CXCR2 gene polymorphism with neutrophil survival and killing ability

Recent research in our lab has demonstrated a significant association between the incidence of subclinical mastitis and specific polymorphisms of the CXCR2 gene in Holstein dairy cows. This gene encodes a receptor for interleukin-8 (IL-8), a key regulator of neutrophil migration, killing and survival. Because of the importance of this gene in neutrophil function, we hypothesized that differences in neutrophil killing and survival may exist among the CXCR2 genotypes and potentially contribute to the observed variation in intramammary infections. To test this hypothesis, neutrophils were isolated from cows representing each CXCR2 +777 genotype (GG, GC or CC) and tested for suppression of apoptosis, reactive oxygen species (ROS) generation, glutathione levels, and bactericidal activity. A significant increase in survival was observed in neutrophils from cows with a CC genotype when compared to those with a GG genotype in response to IL-8, but not dexamethasone. In contrast, a significant reduction in neutrophil ROS generation in response to phorbol-13-myristate-12 acetate (PMA) was observed in cows with a CC genotype when compared to those with a GG genotype. However, no differences in bactericidal activity or glutathione levels were observed among genotypes. The functional activity of neutrophils from cows heterozygous for this polymorphism was intermediate between those with homozygous genotypes for those assays where differences were observed among homozygous genotypes. In summary, our results suggest that neutrophils from Holstein cows with different CXCR2 genotypes vary in their ability to suppress apoptosis and produce ROS. These differences have the potential to influence overall neutrophil function and may partially explain the variation observed with respect to mastitis in vivo. These results provide a foundation for future research aimed at better understanding the basic differences between dairy cows genetically more or less susceptible to mastitis and has the potential to provide novel preventive and therapeutic measures against inflammatory diseases such as mastitis.

Changes in the Tibial Growth Plates of Chickens with Thiram-induced Dyschondroplasia

Tibial dyschondroplasia (TD) is a metabolic cartilage disease of young poultry in which endochondral bone formation is disrupted leading to the retention of a non-calcified, avascular plug of cartilage in the tibial growth plate. Chicks aged 7 days were fed either a control diet or one containing thiram 100 ppm for 48 h to induce TD. Cell multiplication in the growth plate was determined thereafter with bromodeoxyuridine (BrdU) labelling, and metabolic changes by measuring alkaline phosphatase (ALP), tartrate-resistant acid phosphatase (TRAP), and glutathione (GSH) activities. The effect on chondrocyte maturation was examined by reverse transcriptase-polymerase chain reaction (RT-PCR) analysis of gene expression. Terminal deoxynucleotidyl transferase-mediated dUTP nick end labelling (TUNEL) and DNA fragmentation were used to determine the effects of thiram on cell survival. The results showed that thiram-induced TD was not due to the multiplication of cells in the post-proliferative zones. Thiram did not affect ALP activity, which would have indicated a loss of calcification potential, but it reduced both TRAP and the glutathione concentrations, suggesting that the growth plate metabolism and remodelling functions were adversely affected. Thiram appeared to have no effect on the expression of type X collagen, transglutaminase, RUNX2, or matrix metalloproteinase-2 (MMP) genes suggesting that it did not alter the maturation potential of chondrocytes. On the contrary, the expressions of MMP-13 and vascular endothelial growth factor (VEGF) genes were "up-regulated," suggesting that thiram has pro-angiogenic activity. However, TUNEL assay showed that thiram induced endothelial cell apoptosis in the capillary vessels of the growth plates, as early as 10 days of age, when TD was not visually evident. The vascular death increased on subsequent days accompanied by massive death of chondrocytes in the transition zone of the growth plate. The induction of apoptosis in the growth plate was also demonstrated by DNA fragmentation. It was concluded that thiram induced TD not through an increase in the multiplication of chondrocytes in the transition zone and not by altering the expression of genes causing the arrest of chondrocytes in a prehypertrophic state, but by creating a metabolic dysfunction which led to the destruction of blood capillaries in the transition zone chondrocytes.

Organochlorine insecticides: impacts on human HepG2 cytochrome P4501A, 2B activities and glutathione levels

This study examined the effects of the organochlorine (OC) insecticides chlordane, o,p'-DDT, dieldrin, endosulfan, kepone, methoxychlor, and toxaphene on human HepG2 cytochrome P450 (1A-EROD and 2B-PROD) activities and glutathione (GSH) levels. Cells were exposed for 24 h at high concentrations (1, 5 or 10 mM) and for 48 h at lower concentrations ranging from 0.01 to 1 mM to evaluate dose responses. Our results show that after 48 h all but dieldrin significantly induced both P4501A and 2B. P4502B responses were greater at all exposure concentrations and times. Mixed responses in GSH levels were observed. All OCs except dieldrin and MXC significantly depleted GSH after 24 h. At 48 h, chlordane, endosulfan and toxaphene significantly increased GSH at low levels and decreased GSH at high levels, while kepone and methoxychlor produced significant declines in GSH at all concentrations. These results support findings of OC insecticides inducing CYP1A, 2B in rats, with CYP2B responses more important. GSH levels declined when P4502B activity was significantly elevated and were significantly increased in the absence of significant P450 activity, suggesting that GSH levels influence the catalytic activity of the cytochrome P450s and the cytochrome P450s influence the cell's ability to regulate GSH.

Differential expression of copper-associated and oxidative stress related proteins in a new variant of copper toxicosis in Doberman pinschers

BACKGROUND: The role of copper accumulation in the onset of hepatitis is still unclear. Therefore, we investigated a spontaneous disease model of primary copper-toxicosis in Doberman pinschers so to gain insights into the pathophysiology of copper toxicosis, namely on genes involved in copper metabolism and reactive oxygen species (ROS) defences. RESULTS: We used quantitative real-time PCR to determine differentially expressed genes within a target panel, investigating different groups ranging from copper-associated subclinical hepatitis (CASH) to a clinical chronic hepatitis with high hepatic copper concentrations (Doberman hepatitis, DH). Furthermore, a non-copper associated subclinical hepatitis group (N-CASH) with normal hepatic copper concentrations was added as a control. Most mRNA levels of proteins involved in copper binding, transport, and excretion were around control values in the N-CASH and CASH group. In contrast, many of these (including ATP7A, ATP7B, ceruloplasmin, and metallothionein) were significantly reduced in the DH group. Measurements on defences against oxidative stress showed a decrease in gene-expression of superoxide dismutase 1 and catalase in both groups with high copper. Moreover, the anti-oxidative glutathione molecule was clearly reduced in the DH group. CONCLUSION: In the DH group the expression of gene products involved in copper efflux was significantly reduced, which might explain the high hepatic copper levels in this disease. ROS defences were most likely impaired in the CASH and DH group. Overall, this study describes a new variant of primary copper toxicosis and could provide a molecular basis for equating future treatments in dog and in man.