The nonessential amino acid cysteine is required to prevent ferroptosis in acute myeloid leukemia.

ABSTRACT: Cysteine is a nonessential amino acid required for protein synthesis, the generation of the antioxidant glutathione, and for synthesizing the nonproteinogenic amino acid taurine. Here, we highlight the broad sensitivity of leukemic stem and progenitor cells to cysteine depletion. By CRISPR/CRISPR-associated protein 9-mediated knockout of cystathionine-γ-lyase, the cystathionine-to-cysteine converting enzyme, and by metabolite supplementation studies upstream of cysteine, we functionally prove that cysteine is not synthesized from methionine in acute myeloid leukemia (AML) cells. Therefore, although perhaps nutritionally nonessential, cysteine must be imported for survival of these specific cell types. Depletion of cyst(e)ine increased reactive oxygen species (ROS) levels, and cell death was induced predominantly as a consequence of glutathione deprivation. nicotinamide adenine dinucleotide phosphate hydrogen oxidase inhibition strongly rescued viability after cysteine depletion, highlighting this as an important source of ROS in AML. ROS-induced cell death was mediated via ferroptosis, and inhibition of glutathione peroxidase 4 (GPX4), which functions in reducing lipid peroxides, was also highly toxic. We therefore propose that GPX4 is likely key in mediating the antioxidant activity of glutathione. In line, inhibition of the ROS scavenger thioredoxin reductase with auranofin also impaired cell viability, whereby we find that oxidative phosphorylation-driven AML subtypes, in particular, are highly dependent on thioredoxin-mediated protection against ferroptosis. Although inhibition of the cystine-glutamine antiporter by sulfasalazine was ineffective as a monotherapy, its combination with L-buthionine-sulfoximine (BSO) further improved AML ferroptosis induction. We propose the combination of either sulfasalazine or antioxidant machinery inhibitors along with ROS inducers such as BSO or chemotherapy for further preclinical testing.

DNA damage and up-regulation of PARP-1 induced by columbin in vitro and in vivo.

Columbin (CLB) is the most abundant (>1.0%) furan-containing diterpenoid lactone in herbal medicine Tinospora sagittate (Oliv.) Gagnep. The furano-terpenoid was found to be hepatotoxic, but the exact mechanisms remain unknown. The present study demonstrated that administration of CLB at 50 mg/kg induced hepatotoxicity, DNA damage and up-regulation of PARP-1 in vivo. Exposure to CLB (10 µM) induced GSH depletion, over-production of ROS, DNA damage, up-regulation of PARP-1 and cell death in cultured mouse primary hepatocytes in vitro. Co-treatment of mouse primary hepatocytes with ketoconazole (10 µM) or glutathione ethyl ester (200 µM) attenuated the GSH depletion, over-production of ROS, DNA damage, up-regulation of PARP-1, and cell death induced by CLB, while co-exposure to L-buthionine sulfoximine (BSO, 1000 µM) intensified such adverse effects resulting from CLB exposure. These results suggest that the metabolic activation of CLB by CYP3A resulted in the depletion of GSH and increase of ROS formation. The resultant over-production of ROS subsequently disrupted the DNA integrity and up-regulated the expression of PARP-1 in response to DNA damage, and ROS-induced DNA damage was involved in the hepatotoxicity of CLB.

Enhanced antitumor effect of L-buthionine sulfoximine or ionizing radiation by copper complexes with 2,2´-biquinoline and sulfonamides on A549 2D and 3D lung cancer cell models.

Two ternary copper(II) complexes with 2,2'-biquinoline (BQ) and with sulfonamides: sulfamethazine (SMT) or sulfaquinoxaline (SDQ) whose formulae are Cu(SMT)(BQ)Cl and Cu(SDQ)(BQ)Cl·CH3OH, in what follows SMTCu and SDQCu, respectively, induced oxidative stress by increasing ROS level from 1.0 µM and the reduction potential of the couple GSSG/GSH2. The co-treatment with L-buthionine sulfoximine (BSO), which inhibits the production of GSH, enhanced the effect of copper complexes on tumor cell viability and on oxidative damage. Both complexes generated DNA strand breaks given by-at least partially-the oxidation of pyrimidine bases, which caused the arrest of the cell cycle in the G2/M phase. These phenomena triggered processes of apoptosis proven by activation of caspase 3 and externalization of phosphatidylserine and loss of cell integrity from 1.0 µM. The combination with BSO induced a marked increase in the apoptotic population. On the other hand, an improved cell proliferation effect was observed when combining SDQCu with a radiation dose of 2 Gy from 1.0 µM or with 6 Gy from 1.5 µM. Finally, studies in multicellular spheroids demonstrated that even though copper(II) complexes did not inhibit cell invasion in collagen gels up to 48 h of treatment at the higher concentrations, multicellular resistance outperformed several drugs currently used in cancer treatment. Overall, our results reveal an antitumor effect of both complexes in monolayer and multicellular spheroids and an improvement with the addition of BSO. However, only SDQCu was the best adjuvant of ionizing radiation treatment.

Melatonin Enhances Anti-tumoral Effects of Menadione on Colon Cancer Cells.

BACKGROUND: Colon cancer is one of the most important causes of death in the entire world. New pharmacological strategies are always needed, especially in resistant variants of this pathology. We have previously reported that drugs such as menadione (MEN), D, L-buthionine-S,R-sulfoximine or calcitriol, used in combination, enhanced cell sensibility of breast and colon tumour models, due to their ability to modify the oxidative status of the cells. Melatonin (MEL), a hormone regulating circadian rhythms, has anti-oxidant and anti-apoptotic properties at low concentrations, while at high doses, it has been shown to inhibit cancer cell growth. OBJECTIVE: The objective of this study is to determine the antitumoral action of the combination MEN and MEL on colon cancer cells. METHODS: Caco-2 cells were employed to evaluate the effects of both compounds, used alone or combined, on cellular growth/morphology, oxidative and nitrosative stress, and cell migration. RESULTS: MEN plus MEL dramatically reduced cell proliferation in a time and dose-dependent manner. The antiproliferative effects began at 48 h. At the same time, the combination modified the content of superoxide anion, induced the formation of reactive nitrogen species and enhanced catalase activity. Cell migration process was delayed. Also, changes in nuclear morphology consistent with cell death were observed. CONCLUSION: The enhanced effect of simultaneous use of MEN and MEL on Caco-2 cells suggests that this combined action may have therapeutic potential as an adjuvant on intestinal cancer acting in different oncogenic pathways.

Glutathione depletion induces oxidative injury and apoptosis via TRPM2 channel activation in renal collecting duct cells.

Oxidative stress (OS)-induced glutathione (GSH) depletion plays an essential role in several kidney diseases such as chronic kidney disease and nephrotoxicity. The OS-dependent activation of TRPM2 cation channel in several neurons and cells were modulated by the concentration of intracellular GSH. However, the effects of GSH alteration on TRPM2 activation, OS, and apoptosis in the cortical collecting duct (mpkCCDc14) cells still remain elusive. We investigated the effects of GSH supplementation on OS-induced TRPM2 activation, mitochondrial oxidative stress, and apoptosis in the human embryonic kidney 293 (HEK293) and mpkCCDc14 cells treated with buthionine-sulfoximine (BSO), a GSH synthase inhibitor. The HEK293 and mpkCCDc14 cells were divided into five groups as control, GSH (10 mM for 2 h), BSO (0.5 mM for 6 h), BSO + GSH, and BSO + TRPM2 channel blockers. Apoptosis, cell death, mitochondrial OS, caspase -3, caspase -9, cytosolic free Zn2+, and Ca2+ concentrations were increased in the BSO group of the TRPM2 expressing mpkCCDc14 cells, although they were diminished by the treatments of GSH, PARP-1 inhibitors (PJ34 and DPQ), and TRPM2 blockers (ACA and 2-APB). The BSO-induced decreases in the levels of cell viability and cytosolic GSH were increased by the treatments of GSH, ACA, and 2-APB. However, the effects of BSO and GSH were not observed in the non-TRPM2 expressing HEK293 cells. Current results show that maintaining GSH homeostasis is not only important for quenching OS in the cortical collecting duct cells but equally critical to modulate TRPM2 activation. Thus, suppressing apoptosis and mitochondrial OS responses elicited by oxidant action of GSH depletion.

Mitochondrial dysfunction underlying sporadic inclusion body myositis is ameliorated by the mitochondrial homing drug MA-5.

Sporadic inclusion body myositis (sIBM) is the most common idiopathic inflammatory myopathy, and several reports have suggested that mitochondrial abnormalities are involved in its etiology. We recruited 9 sIBM patients and found significant histological changes and an elevation of growth differential factor 15 (GDF15), a marker of mitochondrial disease, strongly suggesting the involvement of mitochondrial dysfunction. Bioenergetic analysis of sIBM patient myoblasts revealed impaired mitochondrial function. Decreased ATP production, reduced mitochondrial size and reduced mitochondrial dynamics were also observed in sIBM myoblasts. Cell vulnerability to oxidative stress also suggested the existence of mitochondrial dysfunction. Mitochonic acid-5 (MA-5) increased the cellular ATP level, reduced mitochondrial ROS, and provided protection against sIBM myoblast death. MA-5 also improved the survival of sIBM skin fibroblasts as well as mitochondrial morphology and dynamics in these cells. The reduction in the gene expression levels of Opa1 and Drp1 was also reversed by MA-5, suggesting the modification of the fusion/fission process. These data suggest that MA-5 may provide an alternative therapeutic strategy for treating not only mitochondrial diseases but also sIBM.

Zinc L-Carnosine Protects CCD-18co Cells from L-Buthionine Sulfoximine-Induced Oxidative Stress via the Induction of Metallothionein and Superoxide Dismutase 1 Expression.

Zinc L-carnosine (ZnC) is the chelate form of zinc and L-carnosine and is one of the zinc supplements available in the market. This study aims to determine the protective effects of ZnC against L-buthionine sulfoximine (BSO)-induced oxidative stress in CCD-18co human normal colon fibroblast cell line. CCD-18co cells were pretreated with ZnC (0-100 µM) for 24 h before the induction of oxidative stress by BSO (1 mM) for another 24 h. Results from this present study demonstrated that ZnC up to the concentration of 100 µM was not cytotoxic to CCD-18co cells. Induction with BSO significantly increased the intracellular reactive oxygen species (ROS) levels and reduced the intracellular glutathione (GSH) levels in CCD-18co cells. Pretreatment with ZnC was able to attenuate the increment in intracellular ROS level in CCD-18co cells significantly in a concentration-dependent manner. However, ZnC did not have any effects on intracellular GSH levels and Nrf2 activation. Mechanistically, pretreatment with ZnC was able to upregulate the expression of metallothionein (MT) and superoxide dismutase 1 (SOD1) in CCD-18co cells. Results from dual-luciferase reporter gene assay reported that ZnC was able to increase the MRE-mediated relative luciferase activities in a concentration-dependent manner, suggesting that the induction of MT expression by ZnC was due to the activation of MTF-1 signaling pathway. Taken together, our current findings suggest that ZnC can protect CCD-18co cells from BSO-induced oxidative stress via the induction of MT and SOD1 expression.

Arsenic Disulfide Combined with L-Buthionine-(S, R)-Sulfoximine Induces Synergistic Antitumor Effects in Two-Dimensional and Three-Dimensional Models of MCF-7 Breast Carcinoma Cells.

Three-dimensionally (3D) cultured tumor cells (spheroids) exhibit more resistance to therapeutic agents than the cells cultured in traditional two-dimensional (2D) system (monolayers). We previously demonstrated that arsenic disulfide (As2S2) exerted significant anticancer efficacies in both 2D- and 3D-cultured MCF-7 cells, whereas 3D spheroids were shown to be resistant to the As2S2 treatment. L-buthionine-(S, R)-sulfoximine (BSO), an inhibitor of glutathione (GSH) synthesis, has been regarded to be a potent candidate for combinatorial treatment due to its GSH modulation function. In the present study, we introduced BSO in combination with As2S2 at a low concentration to investigate the possible enhancing anticancer efficacy by the combinatorial treatment on 2D- and 3D-cultured MCF-7 cells. Our results presented for the first time that the combination of As2S2 and BSO exerted potent anticancer synergism in both MCF-7 monolayers and spheroids. The IC50 values of As2S2 in combinatorial treatment were significantly lower than those in treatment of As2S2 alone in both 2D- and 3D-cultured MCF-7 cells (P<0.01, respectively). In addition, augmented induction of apoptosis and enhanced cell cycle arrest along with the regulation of apoptosis- and cell cycle-related proteins, as well as synergistic inhibitions of PI3K/Akt signals, were also observed following co-treatment of As2S2 and BSO. Notably, the combinatorial treatment significantly decreased the cellular GSH levels in both 2D- and 3D-cultured MCF-7 cells in comparison with each agent alone (P<0.05 in each). Our results suggest that the combinatorial treatment with As2S2 and BSO could be a promising novel strategy to reverse arsenic resistance in human breast cancer.

Oxidative stress impairs cGMP-dependent protein kinase activation and vasodilator-stimulated phosphoprotein serine-phosphorylation.

Reactive oxygen species induce vascular dysfunction and hypertension by directly interacting with nitric oxide (NO) which leads to NO inactivation. In addition to a decrease in NO bioavailability, there is evidence that oxidative stress can also modulate NO signaling during hypertension. Here, we investigated the effect of oxidative stress on NO signaling molecules cGMP-dependent protein kinase (PKG) and vasodilator-stimulated phosphoprotein (VASP) which are known to mediate vasodilatory actions of NO. Male Sprague Dawley (SD) rats were provided with tap water (control), 30 mM L-buthionine sulfoximine (BSO, a pro-oxidant), 1 mM tempol (T, an antioxidant) and BSO + T for 3 wks. BSO-treated rats exhibited high blood pressure and oxidative stress. Incubation of mesenteric arterial rings with NO donors caused concentration-dependent relaxation in control rats. However, the response to NO donors was significantly lower in BSO-treated rats with a marked decrease in pD2. In control rats, NO donors activated mesenteric PKG, increased VASP phosphorylation and its interaction with transient receptor potential channels 4 (TRPC4) and inhibited store-operated Ca2+ influx. NO failed to activate these signaling molecules in mesenteric arteries from BSO-treated rats. Supplementation of BSO-treated rats with tempol reduced oxidative stress and blood pressure and normalized the NO signaling. These data suggest that oxidative stress can reduce NO-mediated PKG activation and VASP-TRPC4 interaction which leads to failure of NO to reduce Ca2+ influx in smooth muscle cells. The increase in intracellular Ca2+ contributes to sustained vasoconstriction and subsequent hypertension. Antioxidant supplementation decreases oxidative stress, normalizes NO signaling and reduces blood pressure.

Capsicodendrin from Cinnamosma fragrans Exhibits Antiproliferative and Cytotoxic Activity in Human Leukemia Cells: Modulation by Glutathione.

Capsicodendrin (CPCD, 1), an epimeric mixture of a dimeric drimane-type sesquiterpene, is one of the major compounds present in the three endemic species of Madagascan traditional chemopreventive plants: Cinnamosma species ( C. fragrans, C. macrocarpa, and C. madagascariensis). Despite the popular use of Cinnamosma in Madagascan traditional medicine and the reported antiproliferative properties of CPCD, elucidation of its mechanism(s) of action is still to be accomplished. In the present study, CPCD at low micromolar concentrations was cytotoxic and induced apoptosis in human myeloid leukemia cells in a time- and concentration-dependent manner. The activity of CPCD in HL-60 and K562 cells was modulated by glutathione (GSH), since depletion of this intracellular thiol-based antioxidant with buthionine sulfoximine resulted in significantly ( p < 0.05) greater potency in antiproliferation assays. GSH depletion also significantly potentiated the cytotoxic activity in CPCD-treated human HL-60 cells. Single-cell gel electrophoresis (Comet) assays revealed that GSH depletion in HL-60 cells enhanced the formation of DNA strand breaks in the presence of CPCD. Although CPCD does not contain an obvious Michael acceptor in its structure, 1H NMR analyses indicated that cinnamodial (2), a monomer of CPCD, was formed within a few hours when dissolved in DMSO- d6 and interacts with GSH to form a covalent bond via Michael addition at the C-7 carbon. Together the results strongly suggest that 2 is responsible for the DNA-damaging, pro-apoptotic, and cytotoxic effects of CPCD and that depletion of GSH enhances overall activity by diminishing covalent interaction between GSH and this 2-alkenal decomposition product of CPCD.

D-penicillamine combined with inhibitors of hydroperoxide metabolism enhances lung and breast cancer cell responses to radiation and carboplatin via H2O2-mediated oxidative stress.

D-penicillamine (DPEN), a copper chelator, has been used in the treatment of Wilson's disease, cystinuria, and rheumatoid arthritis. Recent evidence suggests that DPEN in combination with biologically relevant copper (Cu) concentrations generates H2O2 in cancer cell cultures, but the effects of this on cancer cell responses to ionizing radiation and chemotherapy are unknown. Increased steady-state levels of H2O2 were detected in MB231 breast and H1299 lung cancer cells following treatment with DPEN (100µM) and copper sulfate (15µM). Clonogenic survival demonstrated that DPEN-induced cancer cell toxicity was dependent on Cu and was significantly enhanced by depletion of glutathione [using buthionine sulfoximine (BSO)] as well as inhibition of thioredoxin reductase [using Auranofin (Au)] prior to exposure. Treatment with catalase inhibited DPEN toxicity confirming H2O2 as the toxic species. Furthermore, pretreating cancer cells with iron sucrose enhanced DPEN toxicity while treating with deferoxamine, an Fe chelator that inhibits redox cycling, inhibited DPEN toxicity. Importantly, DPEN also demonstrated selective toxicity in human breast and lung cancer cells, relative to normal untransformed human lung or mammary epithelial cells and enhanced cancer cell killing when combined with ionizing radiation or carboplatin. Consistent with the selective cancer cell toxicity, normal untransformed human lung epithelial cells had significantly lower labile iron pools than lung cancer cells. These results support the hypothesis that DPEN mediates selective cancer cell killing as well as radio-chemo-sensitization by a mechanism involving metal ion catalyzed H2O2-mediated oxidative stress and suggest that DPEN could be repurposed as an adjuvant in conventional cancer therapy.

3-bromopyruvate and buthionine sulfoximine effectively kill anoikis-resistant hepatocellular carcinoma cells.

BACKGROUND & AIMS: Acquisition of anoikis resistance is a prerequisite for metastasis in hepatocellular carcinoma (HCC). However, little is known about how energy metabolism and antioxidant systems are altered in anoikis-resistant (AR) HCC cells. We evaluated anti-tumor effects of a combination treatment of 3-bromopyruvate (3-BP) and buthionine sulfoximine (BSO) in AR HCC cells. METHODS: We compared glycolysis, reactive oxygen species (ROS) production, and chemoresistance among Huh-BAT, HepG2 HCC cells, and the corresponding AR cells. Expression of hexokinase II, gamma-glutamylcysteine synthetase (rGCS), and epithelial-mesenchymal transition (EMT) markers in AR cells was assessed. Anti-tumor effects of a combination treatment of 3-BP and BSO were evaluated in AR cells and an HCC xenograft mouse model. RESULTS: AR HCC cells showed significantly higher chemoresistance, glycolysis and lower ROS production than attached cells. Expression of hexokinase II, rGCS, and EMT markers was higher in AR HCC cells than attached cells. A combination treatment of 3-BP/BSO effectively suppressed proliferation of AR HCC cells through apoptosis by blocking glycolysis and enhancing ROS levels. In xenograft mouse models, tumor growth derived from AR HCC cells was significantly suppressed in the group treated with 3-BP/BSO compared to the group treated with 3-BP or sorafenib. CONCLUSIONS: These results demonstrated that a combination treatment of 3-BP/BSO had a synergistic anti-tumor effect in an AR HCC model. This strategy may be an effective adjuvant therapy for patients with sorafenib-resistant HCC.

Metabolic activation of furan moiety makes Diosbulbin B hepatotoxic.

Diosbulbin B (DIOB), a furanoid, is a major constituent of herbal medicine Dioscorea bulbifera L. Exposure to DIOB caused liver injury in humans and experimental animals. The mechanisms of DIOB-induced hepatotoxicities remain unknown. The present study demonstrated that DIOB induced hepatotoxicities in a time- and dose-dependent manner in mice. H&E stained histopathologic image showed the occurrence of necrosis in the liver obtained from the mice treated with DIOB at dose of 200 mg/kg. Pretreatment with KTC protected the animals from hepatotoxicities and hepatic GSH depletion induced by DIOB, increased area under the concentration-time curve of blood DIOB, decreased urinary excretion of GSH conjugates derived from DIOB, and increased urinary excretion of parent drug. Pretreatment with BSO exacerbated DIOB-induced hepatotoxicities. In order to define the role of furan moiety in DIOB-induced liver toxicities, we replaced the furan of DIOB with a tetrahydrofuran group by chemical hydrogenation of the furan ring of DIOB. No liver injury was observed in the animals given the same doses of tetrahydro-DIOB. The furan moiety was essential for DIOB-induced hepatotoxicities. The results implicate the cis-enedial reactive metabolite of DIOB was responsible for the observed toxicities. The observed modest depletion of hepatic GSH in DIOB-treated animals suggests the actions of one or more reactive metabolites, and the hepatic injury observed could be due at least in part to reactions of these metabolites with crucial biomolecules. Cytochrome P450 3A enzymes are implicated in DIOB-induced hepatotoxicities by catalyzing the formation of the reactive metabolite of DIOB.

N-acetylcysteine stimulates protein synthesis in enterocytes independently of glutathione synthesis.

Dietary supplementation with N-acetylcysteine (NAC) has been reported to improve intestinal health and treat gastrointestinal diseases. However, the underlying mechanisms are not fully understood. According to previous reports, NAC was thought to exert its effect through glutathione synthesis. This study tested the hypothesis that NAC enhances enterocyte growth and protein synthesis independently of cellular glutathione synthesis. Intestinal porcine epithelial cells were cultured for 3 days in Dulbecco's modified Eagle medium containing 0 or 100 µM NAC. To determine a possible role for GSH (the reduced form of glutathione) in mediating the effect of NAC on cell growth and protein synthesis, additional experiments were conducted using culture medium containing 100 µM GSH, 100 µM GSH ethyl ester (GSHee), diethylmaleate (a GSH-depletion agent; 10 µM), or a GSH-synthesis inhibitor (buthionine sulfoximine, BSO; 20 µM). NAC increased cell proliferation, GSH concentration, and protein synthesis, while inhibiting proteolysis. GSHee enhanced cell proliferation and GSH concentration without affecting protein synthesis but inhibited proteolysis. Conversely, BSO or diethylmaleate reduced cell proliferation and GSH concentration without affecting protein synthesis, while promoting protein degradation. At the signaling level, NAC augmented the protein abundance of total mTOR, phosphorylated mTOR, and phosphorylated 70S6 kinase as well as mRNA levels for mTOR and p70S6 kinase in IPEC-1 cells. Collectively, these results indicate that NAC upregulates expression of mTOR signaling proteins to stimulate protein synthesis in enterocytes independently of GSH generation. Our findings provide a hitherto unrecognized biochemical mechanism for beneficial effects of NAC in intestinal cells.

Possible role of NAD-dependent glyceraldehyde-3-phosphate dehydrogenase in growth promotion of Arabidopsis seedlings by low levels of selenium.

We explored functional significance of selenium (Se) in Arabidopsis physiology. Se at very low concentrations in cultivation exerted a considerable positive effect on Arabidopsis growth with no indication of oxidative stress, whereas Se at higher concentrations significantly suppressed the growth and brought serious oxidative damage. Respiration, ATP levels, and the activity of NAD-dependent glyceraldehyde-3-phosphate dehydrogenase (NAD-GAPDH) were enhanced in Arabidopsis grown in the medium containing 1.0 µM Se. Addition of an inhibitor of glutathione (GSH) synthesis to the medium abolished both of the Se-dependent growth promotion and NAD-GAPDH up-regulation. Assay of NAD-GAPDH purified from seedlings subjected to Se interventions raised the possibility of a direct connection between the activity of this enzyme and Arabidopsis growth. These results reveal that trace amounts of Se accelerate Arabidopsis growth, and suggest that this pro-growth effect of Se arises enhancing mitochondrial performance in a GSH-dependent manner, in which NAD-GAPDH may serve as a key regulator.

Oxidative DNA damage induced by di-(2-ethylhexyl) phthalate in HEK-293 cell line.

Di-(2-ethylhexyl) phthalate (DEHP) is commonly employed as a plasticizer. We have found that exposure of human embryonic kidney cell line 293 (HEK-293) to DEHP resulted in a crucial dose-dependent increase of DNA strand breaks in a comet assay. To elucidate the role of glutathione (GSH) in the DNA damage, the cells were pretreated with buthionine-(S,R)-sulfoximine (BSO) and pretreated with N-acetylcysteine (NAC), a GSH precursor. Here we show that depletion of GSH in HEK-293 cells with BSO dramatically increased the susceptibility of HEK-293 cells to DEHP-induced DNA damage. Furthermore, when the intracellular GSH content was elevated by NAC, the DNA damage induced by DEHP was almost completely abolished. In addition, DEHP had effect on lysosomal or mitochondrial damage at high dose level. These results indicate that DEHP exerts genotoxic effects in HEK-293 cells, probably through DNA damage induced by oxidative stress; GSH is responsible for cellular defense against DEHP-induced DNA damage; lysosome and mitochondria may be the vital targets in DEHP-induced DNA damage.

GSH protects against oxidative stress and toxicity in VL-17A cells exposed to high glucose.

PURPOSE: The deficiency of glutathione (GSH) has been linked to several diseases. The study investigated the role of GSH as a protective factor against hyperglycemia-mediated injury in VL-17A cells treated with 50 mM glucose. METHODS: The cell viability and different oxidative stress parameters including glyoxalase I activity were measured. RESULTS: GSH supplementation with 2 mM N-acetyl cysteine (NAC) or 0.1 mM ursodeoxycholic acid (UDCA) increased the viability, GSH level and the GSH-dependent glyoxalase I activity in 50 mM glucose-treated VL-17A cells. Further, pretreatment of 50 mM glucose-treated VL-17A cells with NAC or UDCA decreased oxidative stress (levels of reactive oxygen species and protein carbonylation), apoptosis (caspase 3 activity and annexin V-propidium iodide positive cells) and glutathionylated protein formation, a measure of oxidative stress. GSH depletion with 0.4 mM buthionine sulfoximine (BSO) or 1 mM diethyl maleate (DEM) potentiated the decrease in viability, glyoxalase I activity and increase in oxidative stress and apoptosis, with decreased GSH levels in 50 mM glucose-treated VL-17A cells. CONCLUSION: Thus, changes in GSH levels with exogenous agents such as NAC, UDCA, BSO or DEM modulate hyperglycemia-mediated injury in a cell model of VL-17A liver cells.

Effects of fatty acids on benzo[a]pyrene uptake and metabolism in human lung adenocarcinoma A549 cells.

Dietary supplementation with natural chemoprotective agents is receiving considerable attention because of health benefits and lack of toxicity. In recent in vivo and in vitro experimental studies, diets rich in n-3 polyunsaturated fatty acids have been shown to provide significant anti-tumor action. In this investigation, the effects of control fatty acids (oleic acid (OA), linoleic acid (LA)) and n-3 PUFA, e.g., docosahexaenoic acid (DHA) on the uptake and metabolism of the carcinogenic polycyclic aromatic hydrocarbon, benzo[a]pyrene (BaP) was investigated in A549 cells, a human adenocarcinoma alveolar basal epithelial cell line. A549 cells activate BaP through the cytochrome P450 enzyme system to form reactive metabolites, a few of which covalently bind to DNA and proteins. Therefore, multiphoton microscopy spectral analysis combined with linear unmixing was used to identify the parent compound and BaP metabolites formed in cells, in the presence and absence of fatty acids. The relative abundance of select metabolites was associated with altered P450 activity as determined using ethoxyresorufin-O-deethylase activity in cells cultured in the presence of BSA-conjugated fatty acids. In addition, the parent compound within cellular membranes increases significantly in the presence of each of the fatty acids, with the greatest accumulation observed following DHA treatment. DHA treated cells exhibit significantly lower pyrene-like metabolites indicative of lower adducts including DNA adducts compared to control BSA, OA or LA treated cells. Further, DHA reduced the abundance of the proximate carcinogen BaP 7,8-dihydrodiol and the 3-hydroxybenzo[a]pyrene metabolites compared to other treatments. The significant changes in BaP metabolites in DHA treated cells may be mediated by the effects on the physicochemical properties of the membrane known to affect enzyme activity related to phase I and phase II metabolism. In summary, DHA is a highly bioactive chemo-protective agent capable of modulating BaP-induced DNA adducts.

[Effect of D,L-buthionine-S,R-sulfoximine on the ratio of glutathione forms and the growth of tatar buckwheat calli].

We studied the intracellular content of reduced (GSH) and oxidized (GSSG) glutathione, glutathione reductase activity, glutathione-S-transferase, and ascorbate peroxidase in morphogenic and nonmorphogenic Tatar buckwheat calli during the culture cycle as well as under the treatment with D,L-buthionine-S,R-sulfoximine (BSO), an inhibitor of γ-glutamylcysteine synthase, the first enzyme of glutathione biosynthesis. We found that, during passaging, cultures only slightly differed in total glutathione content; however, the content of GSH was higher in the morphogenic culture, whereas the content of GSSG was higher in the nonmorphogenic culture. In the morphogenic callus, the glutathione-S-transferase activity was 10-20 times higher and the glutathione reductase activity, was 2-2.5 times lower than in the nonmorphogenic callus. Under the treatment with BSO, the decrease in the GSH content in the morphogenic callus was temporary (on day 6-8 of passage), whereas that in the nonmorphogenic callus decreased within a day and remained lower than in the control throughout the entire passage. In the morphogenic callus, BSO did not affect the content of GSSG, whereas it caused GSSG accumulation in the nonmorphogenic callus. These differences are probably due to the fact that, in the BSO-containing medium, glutathione reductase is activated in the morphogenic callus and, conversely, inhibited in the nonmorphogenic callus. Although BSO caused a decrease in the total glutathione content only in the nonmorphogenic culture, the cytostatic effect of BSO was more pronounced in the morphogenic callus. In addition, BSO also had a negative effect on the differentiation ofproembryonic cell complexes in the morphogenic callus. The role of the glutathione redox status in maintaining the embryogenic activity of cultured plant cells is discussed.

Glaucocalyxin A and B-induced cell death is related to GSH perturbation in human leukemia HL-60 cells.

Glaucocalyxin (Gla) A-C are major ent-kauranoid diterpenoids isolated from Rabdosia japonica var. glaucocalyx, a plant used in Chinese traditional medicine as an antitumor and anti-inflammatory agent. The present investigation was carried out to observe whether cellular reduced glutathione (GSH) plays important roles in Gla -induced cytotoxicity. Among major ent-kauranoid diterpenoids isolated, Gla A and B dose-dependently decreased the growth of HL-60 cells with an IC50 of approximately 6.15 and 5.86 µM at 24 h, respectively. Both Gla A and B could induce apoptosis, G2/M-phase cycle arrest, DNA damage and the accumulation of reactive oxygen species (ROS) in HL-60 cells. Moreover, Gla A, B caused rapid decrease of the intracellular GSH content, while inhibition of cellular GSH synthesis by buthionine sulfoximine (BSO) augmented the induced cytotoxicity and apoptosis in HL-60 cells. On the other hand, the administration of GSH or GSH precursor N-acetyl-cysteine (NAC) could rescue Gla A, B-depleted cellular GSH, and abrogate the induced cytotoxicity, G2/M-phase cycle arrest, DNA damage and ROS accumulation in HL-60 cells. Furthermore, Gla A, B decreased the activity of the GSH-related enzymes including glutathione reductase (GR) and glutathione peroxidase (GPX). These data suggest that the intracellular GSH redox system plays important roles in regulating the Gla A, B-induced cytotoxicity on HL-60 cells.