Selective killing of cancer cells harboring mutant RAS by concomitant inhibition of NADPH oxidase and glutathione biosynthesis.

Oncogenic RAS is a critical driver for the initiation and progression of several types of cancers. However, effective therapeutic strategies by targeting RAS, in particular RASG12D and RASG12V, and associated downstream pathways have been so far unsuccessful. Treatment of oncogenic RAS-ravaged cancer patients remains a currently unmet clinical need. Consistent with a major role in cancer metabolism, oncogenic RAS activation elevates both reactive oxygen species (ROS)-generating NADPH oxidase (NOX) activity and ROS-scavenging glutathione biosynthesis. At a certain threshold, the heightened oxidative stress and antioxidant capability achieve a higher level of redox balance, on which cancer cells depend to gain a selective advantage on survival and proliferation. However, this prominent metabolic feature may irrevocably render cancer cells vulnerable to concurrent inhibition of both NOX activity and glutathione biosynthesis, which may be exploited as a novel therapeutic strategy. In this report, we test this hypothesis by treating the HRASG12V-transformed ovarian epithelial cells, mutant KRAS-harboring pancreatic and colon cancer cells of mouse and human origins, as well as cancer xenografts, with diphenyleneiodonium (DPI) and buthionine sulfoximine (BSO) combination, which inhibit NOX activity and glutathione biosynthesis, respectively. Our results demonstrate that concomitant targeting of NOX and glutathione biosynthesis induces a highly potent lethality to cancer cells harboring oncogenic RAS. Therefore, our studies provide a novel strategy against RAS-bearing cancers that warrants further mechanistic and translational investigation.

In-Silico Identification of the Best Compound Against Leishmania infantum: High Throughput Screening of All FDA Approved Drugs

Objective: Current in-silico research was designed and administered for the screening of 20000 Food and Drug Administration-approved drug compounds with the goal of finding promising drugs against lipophosphoglycan (LPG) and γ-glutamylcysteine synthetase (γ-GCS) of Leishmania infantum. Methods: After the protein sequence of both targets was taken, the 3D structures of protein of interest were predicted and validated. Molecular docking was done among the two putative targets (LPG and γ-GCS) and approved compounds were selected using AutoDock 4.2 program to predict ligand-receptor interactions. Results: After docking experiment was done on 20000 drug compounds, a total number of seven ligands, two for γ-GCS receptor and five for LPG receptor, were assigned as novel, potent anti-leishmanial drugs based on their binding affinity and energy. Of those, five ligands possessed cytotoxic and anti-cancer characteristics and showed good binding capacity to LPG receptor with ΔGbinding up to 8.5 kcal/mol more negative; while two compounds showed good binding capacity to glutamyl receptor with ΔGbinding up to 7.8 kcal/mol more negative. Conclusion: The latest software-based methods are powerful tools for scanning and predicting new peptide templates specific to biological targets in organisms for new drug discovery. However, the use of in vitro and in vivo techniques is a requirement for better evaluation of the potential of projected ligands with the help of in-silico approaches, identifying molecular mechanism of action of the more active compounds is possible. This can help in defining the most likely molecular target, so that the subsequent optimization using in vitro and in vivo techniques can be undertaken.

Deubiquitinases Maintain Protein Homeostasis and Survival of Cancer Cells upon Glutathione Depletion.

Cells are subjected to oxidative stress during the initiation and progression of tumors, and this imposes selective pressure for cancer cells to adapt mechanisms to tolerate these conditions. Here, we examined the dependency of cancer cells on glutathione (GSH), the most abundant cellular antioxidant. While cancer cell lines displayed a broad range of sensitivities to inhibition of GSH synthesis, the majority were resistant to GSH depletion. To identify cellular pathways required for this resistance, we carried out genetic and pharmacologic screens. Both approaches revealed that inhibition of deubiquitinating enzymes (DUBs) sensitizes cancer cells to GSH depletion. Inhibition of GSH synthesis, in combination with DUB inhibition, led to an accumulation of polyubiquitinated proteins, induction of proteotoxic stress, and cell death. These results indicate that depletion of GSH renders cancer cells dependent on DUB activity to maintain protein homeostasis and cell viability and reveal a potentially exploitable vulnerability for cancer therapy.

Targeting the Vulnerability of Glutathione Metabolism in ARID1A-Deficient Cancers.

ARID1A encodes an SWI/SNF chromatin-remodeling factor and is frequently mutated in various cancers. This study demonstrates that ARID1A-deficient cancer cells are specifically vulnerable to inhibition of the antioxidant glutathione (GSH) and the glutamate-cysteine ligase synthetase catalytic subunit (GCLC), a rate-limiting enzyme for GSH synthesis. Inhibition of GCLC markedly decreased GSH in ARID1A-deficient cancer cells, leading to apoptotic cell death triggered by excessive amounts of reactive oxygen species. The vulnerability of ARID1A-deficient cancer cells results from low basal levels of GSH due to impaired expression of SLC7A11. The SLC7A11-encoded cystine transporter supplies cells with cysteine, a key source of GSH, and its expression is enhanced by ARID1A-mediated chromatin remodeling. Thus, ARID1A-deficient cancers are susceptible to synthetic lethal targeting of GCLC.

Pan-Cancer Metabolic Signature Predicts Co-Dependency on Glutaminase and De Novo Glutathione Synthesis Linked to a High-Mesenchymal Cell State.

The enzyme glutaminase (GLS1) is currently in clinical trials for oncology, yet there are no clear diagnostic criteria to identify responders. The evaluation of 25 basal breast lines expressing GLS1, predominantly through its splice isoform GAC, demonstrated that only GLS1-dependent basal B lines required it for maintaining de novo glutathione synthesis in addition to mitochondrial bioenergetics. Drug sensitivity profiling of 407 tumor lines with GLS1 and gamma-glutamylcysteine synthetase (GCS) inhibitors revealed a high degree of co-dependency on both enzymes across indications, suggesting that redox balance is a key function of GLS1 in tumors. To leverage these findings, we derived a pan-cancer metabolic signature predictive of GLS1/GCS co-dependency and validated it in vivo using four lung patient-derived xenograft models, revealing the additional requirement for expression of GAC above a threshold (log2RPKM + 1 ≥ 4.5, where RPKM is reads per kilobase per million mapped reads). Analysis of the pan-TCGA dataset with our signature identified multiple indications, including mesenchymal tumors, as putative responders to GLS1 inhibitors.

The antioxidant glutathione protects against enteric neuron death in situ, but its depletion is protective during colitis.

Enteric glia play an important neuroprotective role in the enteric nervous system (ENS) by producing neuroprotective compounds such as the antioxidant reduced glutathione (GSH). The specific cellular pathways that regulate glial production of GSH and how these pathways are altered during, or contribute to, neuroinflammation in situ and in vivo are not fully understood. We investigated this issue using immunohistochemistry to localize GSH synthesis enzymes within the myenteric plexus and tested how the inhibition of GSH synthesis with the selective inhibitor l-buthionine sulfoximine impacts neuronal survival and inflammation. Both enteric glia and neurons express the cellular machinery necessary for GSH synthesis. Furthermore, glial GSH synthesis is necessary for neuronal survival in isolated preparations of myenteric plexus. In vivo depletion of GSH does not induce colitis but alters myenteric plexus neuronal phenotype and survival. Importantly, global depletion of glutathione is protective against some macroscopic and microscopic measures of colonic inflammation. Together, our data highlight the heterogeneous roles of GSH in the myenteric plexus of the ENS and during gastrointestinal inflammation. NEW & NOTEWORTHY Our results show that both enteric glia and neurons express the cellular machinery necessary for glutathione (GSH) synthesis and that glial GSH synthesis is necessary for neuronal survival in isolated enteric nervous system (ENS) preparations. In vivo depletion of GSH with the selective inhibitor l-buthionine sulfoximine is not sufficient to induce inflammation but does alter neuronal neurochemical composition and survival. Together, our data highlight novel heterogeneous roles for GSH in the ENS and during gastrointestinal inflammation.

The Role of the Glutathione System in Oxidative Modification of Proteins and Dysregulation of Apoptosis in Jurkat Tumor Cells.

We compared changes in the redox status and intensity of oxidative modification of proteins in intact Jurkat tumor cells and cells cultured with buthionine sulfoximine, an inhibitor of the key enzyme of glutathione synthesis γ-glutamylcysteine synthetase. The glutathione system components play a role in modulation of the content of protein-bound glutathione, protein carbonyl derivatives, bityrosine, and oxidized tryptophan, and in dysregulation of apoptosis in Jurkat tumor cells. Inhibition of de novo synthesis of glutathione in Jurkat tumor cells was followed by accumulation of hydroxyl radical, a reduction in the level of protein-bound glutathione and oxidized tryptophan, and a rise in the concentration of protein carbonyl derivatives. These changes were accompanied by activation of programmed cell death.

Buthionine sulfoximine is a multitarget inhibitor of trypanothione synthesis in Trypanosoma cruzi.

Buthionine sulfoximine (BSO) induces decreased glutathione (GSH) and trypanothione [T(SH)2 ] pools in trypanosomatids, presumably because only gamma-glutamylcysteine synthetase (γECS) is blocked. However, some BSO effects cannot be explained by exclusive γECS inhibition; therefore, its effect on the T(SH)2 metabolism pathway in Trypanosoma cruzi was re-examined. Parasites exposed to BSO did not synthesize T(SH)2 even when supplemented with cysteine or GSH, suggesting trypanothione synthetase (TryS) inhibition by BSO. Indeed, recombinant γECS and TryS, but not GSH synthetase, were inhibited by BSO and kinetics and docking analyses on a TcTryS 3D model suggested BSO binding at the GSH site. Furthermore, parasites overexpressing γECS and TryS showed ~ 50% decreased activities after BSO treatment. These results indicated that BSO is also an inhibitor of TryS.

Mitochondrial "power" drives tamoxifen resistance: NQO1 and GCLC are new therapeutic targets in breast cancer.

Here, we identified two new molecular targets, which are functionally sufficient to metabolically confer the tamoxifen-resistance phenotype in human breast cancer cells. Briefly, ~20 proteins were first selected as potential candidates, based on unbiased proteomics analysis, using tamoxifen-resistant cell lines. Then, the cDNAs of the most promising candidates were systematically transduced into MCF-7 cells. Remarkably, NQO1 and GCLC were both functionally sufficient to autonomously confer a tamoxifen-resistant metabolic phenotype, characterized by i) increased mitochondrial biogenesis, ii) increased ATP production and iii) reduced glutathione levels. Thus, we speculate that pharmacological inhibition of NQO1 and GCLC may be new therapeutic strategies for overcoming tamoxifen-resistance in breast cancer patients. In direct support of this notion, we demonstrate that treatment with a known NQO1 inhibitor (dicoumarol) is indeed sufficient to revert the tamoxifen-resistance phenotype. As such, these findings could have important translational significance for the prevention of tumor recurrence in ER(+) breast cancers, which is due to an endocrine resistance phenotype. Importantly, we also show here that NQO1 has significant prognostic value as a biomarker for the prediction of tumor recurrence. More specifically, higher levels of NQO1 mRNA strongly predict patient relapse in high-risk ER(+) breast cancer patients receiving endocrine therapy (mostly tamoxifen; H.R. > 2.15; p = 0.007).

Novel antioxidants' synthesis and their anti-oxidative activity through activating Nrf2 signaling pathway.

Novel structure compounds (WS) containing 3,4,5-trimethoxyphenyl and acyl pyrazole were designed and synthesized based combination principles. Among them, WS13 was screened out to possess desirable anti-oxidative activity in vitro. Cell survival assay and apoptosis experiment in H2O2 induced PC12 cells injury model all showed that its cytoprotection exhibited a concentration-effect manner. WS13 at 10µM could remove ROS with equal effiency to edaravone. Further, it clearly activated Nrf2 nuclear translocation and upregulated GCLC mRNA transcription and protein expression in dose-dependent manner, and its cytoprotection was reversed by GCLC protein inhibitor. In total, WS13 with further promotion can serve as Nrf2-GCLC activator in anti-oxidative therapy.

MYC-driven inhibition of the glutamate-cysteine ligase promotes glutathione depletion in liver cancer.

How MYC reprograms metabolism in primary tumors remains poorly understood. Using integrated gene expression and metabolite profiling, we identify six pathways that are coordinately deregulated in primary MYC-driven liver tumors: glutathione metabolism; glycine, serine, and threonine metabolism; aminoacyl-tRNA biosynthesis; cysteine and methionine metabolism; ABC transporters; and mineral absorption. We then focus our attention on glutathione (GSH) and glutathione disulfide (GSSG), as they are markedly decreased in MYC-driven tumors. We find that fewer glutamine-derived carbons are incorporated into GSH in tumor tissue relative to non-tumor tissue. Expression of GCLC, the rate-limiting enzyme of GSH synthesis, is attenuated by the MYC-induced microRNA miR-18a. Inhibition of miR-18a in vivo leads to increased GCLC protein expression and GSH abundance in tumor tissue. Finally, MYC-driven liver tumors exhibit increased sensitivity to acute oxidative stress. In summary, MYC-dependent attenuation of GCLC by miR-18a contributes to GSH depletion in vivo, and low GSH corresponds with increased sensitivity to oxidative stress in tumors. Our results identify new metabolic pathways deregulated in primary MYC tumors and implicate a role for MYC in regulating a major antioxidant pathway downstream of glutamine.

Characterization of cadmium chloride-induced BiP accumulation in Xenopus laevis A6 kidney epithelial cells.

Endoplasmic reticulum (ER) stress can result in the accumulation of unfolded/misfolded protein in the ER lumen, which can trigger the unfolded protein response (UPR) resulting in the activation of various genes including immunoglobulin-binding protein (BiP; also known as glucose-regulated protein 78 or HSPA5). BiP, an ER heat shock protein 70 (HSP70) family member, binds to unfolded protein, inhibits their aggregation and re-folds them in an ATP-dependent manner. While cadmium, an environmental contaminant, was shown to induce the accumulation of HSP70 in vertebrate cells, less information is available regarding the effect of this metal on BiP accumulation or function. In this study, cadmium chloride treatment of Xenopus laevis A6 kidney epithelial cells induced a dose- and time-dependent increase in BiP, HSP70 and heme oxygenase-1 (HO-1) accumulation. Exposure of cells to a relatively low cadmium concentration at a mild heat shock temperature of 30°C greatly enhanced BiP and HSP70 accumulation compared to cadmium at 22°C. Treatment of cells with the glutathione synthesis inhibitor, buthionine sulfoximine, enhanced cadmium-induced BiP and HSP70 accumulation. Immunocytochemistry revealed that cadmium-induced BiP accumulation occurred in a punctate pattern in the perinuclear region. In some cells treated with cadmium chloride or the proteasomal inhibitor, MG132, large BiP complexes were observed that co-localized with aggregated protein or aggresome-like structures. These BiP/aggresome-like structures were also observed in cells treated simultaneously with cadmium at 30°C or in the presence of buthionine sulfoximine. In amphibians, the association of BiP with unfolded protein and its possible role in aggresome function may be vital in the maintenance of cellular proteostasis.

Redox-Sensitive Cerium Oxide Nanoparticles Protect Human Keratinocytes from Oxidative Stress Induced by Glutathione Depletion.

Cerium oxide nanoparticles (CeNPs) have gathered much attention in the biomedical field due to its unique antioxidant property. It can protect cells and tissues from oxidative stress induced damage due to its autoregenerative redox cycle. Our study explores the antioxidant and antigenotoxic behavior of PEGylated CeNPs toward oxidative insult produced by buthionine sulfoximine (BSO) in human keratinocytes (HaCaT cells). BSO inhibits the γ-glutamylcysteinesynthetase (γ-GCS) enzyme and thus acts as a glutathione (GSH) depleting agent to modulate the cellular redox potential. GSH is a natural ROS scavenger present in the mammalian cells, and its depletion causes generation of reactive oxygen species (ROS). In this study, we challenged HaCaT cells (keratinocytes) with BSO to alter the redox potential within the cell and monitored toxicity, ROS generation, and nuclear fragmentation. We also followed changes in expressions of related proteins and genes. We found that PEGylated CeNPs can protect HaCaT cells from BSO-induced oxidative damage. BSO-exposed cells, preincubated with PEGylated CeNPs, showed better cell survival and significant decrease in the intracellular levels of ROS. We also observed decrease in lactate dehydrogenase (LDH) release and nuclear fragmentation in CeNP-treated cells that were challenged with BSO as compared to treatment with BSO alone. Exposure of HaCaT cells with BSO leads to altered expression of antioxidant genes and proteins, i.e., thioredoxin reductase (TrxR) and peroxiredoxin 6 (Prx6) whereas, in our study, pretreatment of PEGylated CeNPs reduces the need for induction of genes that produce enzymes involved in the defense against oxidative stress. Since, growing evidence argued the involvement of ROS in mediating death of mammalian cells in several ailments, our finding reinforces the use of PEGylated CeNPs as a potent pharmacological agent under the lower cellular GSH/GSSG ratios for the treatment of diseases mediated by free radicals.

Alterations in glutamate cysteine ligase content in the retina of two retinitis pigmentosa animal models.

Retinitis Pigmentosa (RP) comprises a group of rare genetic retinal disorders in which one of several different mutations induces photoreceptor death. Oxidative stress and glutathione (GSH) alterations may be related to the pathogenesis of RP. GSH has been shown to be present in high concentrations in the retina. In addition, the retina has the capability to synthesize GSH. In this study, we tested whether the two subunits of glutamate cysteine ligase, the rate-limiting enzyme in GSH synthesis, and the concentrations of retinal GSH, oxidized glutathione (GSSG), cysteine (Cys) and glutamate are altered in the retina of two different RP mice models. Retinas from C3H and rd1 mice at different postnatal days (P7, P11, P15, P19, P21 and P28) and from C57BL/6 and rd10 mice at P21 were obtained. Western blot analysis was performed to determine the protein content of catalytic and modulatory subunits from glutamate cysteine ligase (GCLC and GCLM, respectively). In another set of experiments, control and rd1 mice were administered buthinine sulfoximine, a glutathione synthase inhibitor, or paraquat. GSH, GSSG, glutamate and Cys concentrations were determined, by HPLC. A decrease in retinal GCLC content was observed in C3H and rd1 mice with age, nevertheless, there was an increase in retinal GCLC in rd1 mice compared to control retinas at P19. No modifications in GCLM content with age and no difference between GCLM content in rd1 and control retinas were observed. The GSH concentration decreased in the rd1 retinas compared with control ones at P15, it increased at P19, and was again similar at P21 and P28. No changes in GSSG concentration in control retinas with age were observed; the GSSG levels in rd1 retinas were similar from P7 to P19 and then increased significantly at P21 and P28. Glutamate concentration was increased in the rd1 retinas compared to control mice from P7 to P15 and were comparable at P21 and P28. The Cys concentrations was measured in control and rd1 retinas, but no significant changes were observed between them. BSO administration decreases GSH retinal concentration in control and rd1 mice, while paraquat administration induced an increase in GSH retinal concentration in control mice and a decrease in GSH in rd1 mice retina. Retinal GCLC was significantly increased in rd10 mice at P21 as well as GSSG. Our results suggest alterations in retinal GCLC content and GSH and/or its precursors in these two RP animal models. Regulation of the enzymes related to GSH metabolism and the retinal concentration of glutamate may be a possible target to delay especially cone death in RP.

A Phase I New Approaches to Neuroblastoma Therapy Study of Buthionine Sulfoximine and Melphalan With Autologous Stem Cells for Recurrent/Refractory High-Risk Neuroblastoma.

BACKGROUND: Myeloablative therapy for high-risk neuroblastoma commonly includes melphalan. Increased cellular glutathione (GSH) can mediate melphalan resistance. Buthionine sulfoximine (BSO), a GSH synthesis inhibitor, enhances melphalan activity against neuroblastoma cell lines, providing the rationale for a Phase 1 trial of BSO-melphalan. PROCEDURES: Patients with recurrent/resistant high-risk neuroblastoma received BSO (3 gram/m(2) bolus, then 24 grams/m(2) /day infusion days -4 to -2), with escalating doses of intravenous melphalan (20-125 mg/m(2) ) days -3 and -2, and autologous stem cells day 0 using 3 + 3 dose escalation. RESULTS: Among 28 patients evaluable for dose escalation, one dose-limiting toxicity occurred at 20 mg/m(2) melphalan (grade 3 aspartate aminotransferase/alanine aminotransferase) and one at 80 mg/m(2) (streptococcal bacteremia, grade 4 hypotension/pulmonary/hypocalcemia) without sequelae. Among 25 patients evaluable for response, there was one partial response (PR) and two mixed responses (MRs) among eight patients with prior melphalan exposure; one PR and three MRs among 16 patients without prior melphalan; one stable disease with unknown melphalan history. Melphalan pharmacokinetics with BSO were similar to reports for melphalan alone. Melphalan Cmax for most patients was below the 10 µM concentration that showed neuroblastoma preclinical activity with BSO. CONCLUSIONS: BSO (75 gram/m(2) ) with melphalan (125 mg/m(2) ) is tolerable with stem cell support and active in recurrent/refractory neuroblastoma. Further dose escalation is feasible and may increase responses.

Extending prematuration with cAMP modulators enhances the cumulus contribution to oocyte antioxidant defence and oocyte quality via gap junctions.

STUDY QUESTION: Can bovine oocyte antioxidant defence and oocyte quality be improved by extending the duration of pre-in vitro maturation (IVM) with cyclic adenosine mono-phosphate (cAMP) modulators? SUMMARY ANSWER: Lengthening the duration of cAMP-modulated pre-IVM elevates intra-oocyte reduced glutathione (GSH) content and reduces hydrogen peroxide (H2O2) via increased cumulus cell-oocyte gap-junctional communication (GJC), associated with an improvement in subsequent embryo development and quality. WHAT IS KNOWN ALREADY: Oocytes are susceptible to oxidative stress and the oocyte's most important antioxidant glutathione is supplied, at least in part, by cumulus cells. A temporary inhibition of spontaneous meiotic resumption in oocytes can be achieved by preventing a fall in cAMP, and cyclic AMP-modulated pre-IVM maintains cumulus-oocyte GJC and improves subsequent embryo development. STUDY DESIGN, SIZE, DURATION: This study consisted of a series of 10 experiments using bovine oocytes in vitro, each with multiple replicates. A range of pre-IVM durations were examined as the key study treatments which were compared with a control. The study was designed to examine if one of the oocyte's major antioxidant defences can be enhanced by pre-IVM with cAMP modulators, and to examine the contribution of cumulus-oocyte GJC on these processes. PARTICIPANTS/MATERIALS, SETTING, METHODS: Immature bovine cumulus-oocyte complexes were treated in vitro without (control) or with the cAMP modulators; 100 µM forskolin (FSK) and 500 µM 3-isobutyl-1-methyxanthine (IBMX), for 0, 2, 4 or 6 h (pre-IVM phase) prior to IVM. Oocyte developmental competence was assessed by embryo development and quality post-IVM/IVF. Cumulus-oocyte GJC, intra-oocyte GSH and H2O2 were quantified at various time points during pre-IVM and IVM, in the presence and the absence of functional inhibitors: carbenoxolone (CBX) to block GJC and buthionine sulfoximide (BSO) to inhibit glutathione synthesis. MAIN RESULTS AND THE ROLE OF CHANCE: Pre-IVM with FSK + IBMX increased subsequent blastocyst formation rate and quality compared with standard IVM (P < 0.05), regardless of pre-IVM duration. The final blastocyst yields (proportion of blastocysts/immature oocyte) were 26.3% for the control, compared with 39.2, 35.2 and 34.2%, for the 2, 4 and 6 h pre-IVM FSK + IBMX treatments, respectively. In contrast to standard IVM (control), pre-IVM with cAMP modulators maintained open gap junctions between cumulus cells and oocytes for the duration (6 h) of pre-IVM examined, and persisted for a further 8 h in the IVM phase. Cyclic AMP-modulated pre-IVM increased intra-oocyte GSH levels at the completion of both pre-IVM and IVM, in a pre-IVM duration-dependent manner (P < 0.05), which was ablated when GJC was blocked using CBX (P < 0.05). By 4 h of pre-IVM treatment with cAMP modulators, oocyte H2O2 levels were reduced compared the control (P < 0.05), although this beneficial effect was lost when oocytes were co-treated with BSO. Inhibiting glutathione synthesis with BSO during pre-IVM ablated any positive benefits of cAMP-mediated pre-IVM on oocyte developmental competence (P < 0.01). LIMITATIONS, REASONS FOR CAUTION: It is unclear if the improvement in oocyte antioxidant defence and developmental competence reported here is due to direct transfer of total and/or reduced glutathione from cumulus cells to the oocyte via gap junctions, or whether a GSH synthesis signal and/or amino acid substrates are supplied to the oocyte via gap junctions. Embryo transfer experiments are required to determine if the cAMP-mediated improvement in blastocyst rates leads to improved live birth rates. WIDER IMPLICATIONS OF THE FINDINGS: IVM offers significant benefits to infertile and cancer patients and has the potential to significantly alter ART practice, if IVM efficiency in embryo production could be improved closer to that of conventional IVF (using ovarian hyperstimulation). Pre-IVM with cAMP modulators is a simple and reliable means to improve IVM outcomes. STUDY FUNDING/COMPETING INTERESTS: This work was supported by grants and fellowships from the National Health and Medical Research Council of Australia (1007551, 627007, 1008137, 1023210) and by scholarships from the Chinese Scholarship Council (CSC) awarded to H.J.L. and the Japanese Society for the Promotion of Science Postdoctoral Fellowship for Research Abroad awarded to S.S. The Fluoview FV10i confocal microscope was purchased as part of the Sensing Technologies for Advanced Reproductive Research (STARR) facility, funded by the South Australian Premier's Science and Research Fund. We acknowledge partial support from the Australian Research Council Centre of Excellence for Nanoscale BioPhotonics (CE140100003). We declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research reported.

Upregulation of cellular glutathione levels in human ABCB5- and murine Abcb5-transfected cells.

BACKGROUND: Previously, we have demonstrated that human ABCB5 is a full-sized ATP-binding cassette transporter that shares strong homology with ABCB1/P-glycoprotein. ABCB5-transfected cells showed resistance to taxanes and anthracyclines. Herein, we further screened ABCB5 substrates, and explored the mechanism of resistance. METHODS: Sensitivity of the cells to test compounds was evaluated using cell growth inhibition assay. Cellular levels of buthionine sulfoximine (BSO), glutathione and amino acids were measured using HPLC and an enzyme-based assay. Cellular and vesicular transport of glutathione was evaluated by a radiolabeled substrate. Expression levels of glutathione-metabolizing enzymes were assessed by RT-PCR. RESULTS: Human ABCB5-transfected 293/B5-11 cells and murine Abcb5-transfected 293/mb5-8 cells showed 6.5- and 14-fold higher resistance to BSO than the mock-transfected 293/mock cells, respectively. BSO is an inhibitor of gamma-glutamylcysteine ligase (GCL), which is a key enzyme of glutathione synthesis. 293/B5-11 and 293/mb5-8 cells also showed resistance to methionine sulfoximine, another GCL inhibitor. A cellular uptake experiment revealed that BSO accumulation in 293/B5-11 and 293/mb5-8 cells was similar to that in 293/mock cells, suggesting that BSO is not an ABCB5 substrate. The cellular glutathione content in 293/B5-11 and 293/mb5-8 cells was significantly higher than that in 293/mock cells. Evaluation of the BSO effect on the cellular glutathione content showed that compared with 293/mock cells the BSO concentration required for a 50 % reduction in glutathione content in 293/B5-11 and 293/mb5-8 cells was approximately 2- to 3-fold higher. This result suggests that the BSO resistance of the ABCB5- and Abcb5-transfected cells can be attributed to the reduced effect of BSO on the transfectants. Cellular and vesicular transport assays showed that the transport of radiolabeled glutathione in 293/B5-11 cells was similar to that in 293/mock cells. The mRNA expression of genes encoding glutathione-metabolizing enzymes in 293/B5-11 cells was similar to that in 293/mock cells. The cellular content of Glu, a precursor of glutathione, in 293/B5-11 and 293/mb5-8 cells was higher than that in 293/mock cells. CONCLUSIONS: ABCB5/Abcb5-transfected cells showed resistance to BSO, which is not a substrate of ABCB5. Our results suggest that ABCB5/Abcb5 upregulates cellular glutathione levels to protect cells from various poisons.

Glutathione plays an essential role in nitric oxide-mediated iron-deficiency signaling and iron-deficiency tolerance in Arabidopsis.

Iron (Fe) deficiency is a common agricultural problem that affects both the productivity and nutritional quality of plants. Thus, identifying the key factors involved in the tolerance of Fe deficiency is important. In the present study, the zir1 mutant, which is glutathione deficient, was found to be more sensitive to Fe deficiency than the wild type, and grew poorly in alkaline soil. Other glutathione-deficient mutants also showed various degrees of sensitivity to Fe-limited conditions. Interestingly, we found that the glutathione level was increased under Fe deficiency in the wild type. By contrast, blocking glutathione biosynthesis led to increased physiological sensitivity to Fe deficiency. On the other hand, overexpressing glutathione enhanced the tolerance to Fe deficiency. Under Fe-limited conditions, glutathione-deficient mutants, zir1, pad2 and cad2 accumulated lower levels of Fe than the wild type. The key genes involved in Fe uptake, including IRT1, FRO2 and FIT, are expressed at low levels in zir1; however, a split-root experiment suggested that the systemic signals that govern the expression of Fe uptake-related genes are still active in zir1. Furthermore, we found that zir1 had a lower accumulation of nitric oxide (NO) and NO reservoir S-nitrosoglutathione (GSNO). Although NO is a signaling molecule involved in the induction of Fe uptake-related genes during Fe deficiency, the NO-mediated induction of Fe-uptake genes is dependent on glutathione supply in the zir1 mutant. These results provide direct evidence that glutathione plays an essential role in Fe-deficiency tolerance and NO-mediated Fe-deficiency signaling in Arabidopsis.

Differential in vivo genotoxicity of arsenic trioxide in glutathione depleted mouse bone marrow cells: expressions of Nrf2/Keap1/P62.

Generation of reactive oxygen species is one of the major contributors in arsenic-induced genotoxicity where reduced glutathione (GSH) could be an important determining factor. To understand the role of endogenous GSH, arsenic trioxide (As2O3) was administered in buthionine sulfoximine (BSO)- and N-acetyl-L-cysteine (NAC)-treated mice. As2O3-induced significant chromosome aberrations (CAs) in all treatment groups compared with the control. BSO-treated mouse bone marrow cells showed significant CAs at a dose of 2 mg As2O3 kg(-1) b.w. Similar induction was not evident at 4 mg As2O3 kg(-1) b.w. and exhibited antagonistic effect at 8 mg As2O3 kg(-1) b.w. To understand this differential effect, expression pattern of Nrf2 was observed. Nrf2 expression increased following As2O3 treatment in a dose-dependent manner up to 4 mg As2O3 kg(-1) b.w after which no further increase was noticed. NAC pre-treatment significantly reduced the extent of As2O3-induced CAs suggesting the protective role of endogenous GSH against arsenic-induced genotoxicity.

Acute glutathione depletion leads to enhancement of airway reactivity and inflammation via p38MAPK-iNOS pathway in allergic mice.

Glutathione (GSH) plays a major role in allergic airway responses through a variety of mechanism which include direct scavenging of oxidative species, being a reducing equivalent and regulation of cellular signaling through redox sensitive mechanisms. Therefore, the aim of the present study was to evaluate the role of acute GSH depletion on airway reactivity, inflammation and NO signaling in a mouse model of allergic asthma. Buthionine sulfoximine (BSO), an inhibitor of gamma-glutamylcysteine synthetase was used for depletion of GSH levels. Acute depletion of GSH with BSO worsened allergen induced airway reactivity and inflammation through increase in nitrosative stress as reflected by increased inducible NO synthase (iNOS) expression, total nitrates and nitrites (NOx), nitrotyrosine, protein carbonyls, and decreased total antioxidant capacity. Treatment with p38 mitogen-activated protein kinase (MAPK) and iNOS inhibitors attenuated the effects of GSH depletion on airway reactivity and inflammation through attenuation of nitrosative stress as evidenced by a decrease in NOx, nitrotyrosine, protein carbonyls and increase in total antioxidant capacity (TAC). In conclusion, these data suggest that acute depletion of glutathione is associated with alteration of airway responses through an increase in nitrosative stress in allergic airways of mice.