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Miroslav Styblo - One of the best experts on this subject based on the ideXlab platform.
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exposure to inorganic arsenic and its methylated metabolites alters metabolomics profiles in ins 1 832 13 insulinoma cells and isolated pancreatic islets
Archives of Toxicology, 2020Co-Authors: Christelle Douillet, Madelyn C Huang, Rowan Beck, Susan Sumner, Miroslav StybloAbstract:Inorganic arsenic (iAs) is an environmental diabetogen, but mechanisms underlying its diabetogenic effects are poorly understood. Exposures to arsenite (iAsIII) and its methylated metabolites, methylarsonite (MAsIII) and dimethylarsinite (DMAsIII), have been shown to inhibit glucose-stimulated insulin secretion (GSIS) in pancreatic β-cells and isolated pancreatic islets. GSIS is regulated by complex mechanisms. Increase in ATP production through metabolism of glucose and other substrates is the ultimate trigger for GSIS in β-cells. In the present study, we used metabolomics to identify metabolites and pathways perturbed in cultured INS-1 832/13 rat insulinoma cells and isolated murine pancreatic islets by exposures to iAsIII, MAsIII and DMAsIII. We found that the exposures perturbed multiple metabolites, which were enriched primarily in the pathways of amino acid, carbohydrate, phospholipid and carnitine metabolism. However, the effects of Arsenicals in INS-1 832/13 cells differed from those in the islets and were exposure specific with very few overlaps between the three Arsenicals. In INS-1 832/13 cells, all three Arsenicals decreased succinate, a metabolite of Krebs cycle, which provides substrates for ATP synthesis in mitochondria. Acetylcarnitine was decreased consistently by exposures to Arsenicals in both the cells and the islets. Acetylcarnitine is usually found in equilibrium with acetyl-CoA, which is the central metabolite in the catabolism of macronutrients and the key substrate for Krebs cycle. It is also thought to play an antioxidant function in mitochondria. Thus, while each of the three trivalent Arsenicals perturbed specific metabolic pathways, which may or may not be associated with GSIS, all three Arsenicals appeared to impair mechanisms that support ATP production or antioxidant defense in mitochondria. These results suggest that impaired ATP production and/or mitochondrial dysfunction caused by oxidative stress may be the mechanisms underlying the inhibition of GSIS in β-cells exposed to trivalent Arsenicals.
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comparative oxidation state specific analysis of arsenic species by high performance liquid chromatography inductively coupled plasma mass spectrometry and hydride generation cryotrapping atomic absorption spectrometry
Journal of Analytical Atomic Spectrometry, 2013Co-Authors: Jenna M Currier, Tomáš Matoušek, John T Creed, Jesse R Saunders, Lan Ding, Wanda Bodnar, Peter Hans Cable, Miroslav StybloAbstract:The formation of methylarsonous acid (MAsIII) and dimethylarsinous acid (DMAsIII) in the course of inorganic arsenic (iAs) metabolism plays an important role in the adverse effects of chronic exposure to iAs. High-performance liquid chromatography-inductively coupled plasma-mass spectrometry (HPLC-ICP-MS) and hydride generation-cryotrapping-atomic absorption spectrometry (HG-CT-AAS) have been frequently used for the analysis of MAsIII and DMAsIII in biological samples. While HG-CT-AAS has consistently detected MAsIII and DMAsIII, HPLC-ICP-MS analyses have provided inconsistent and contradictory results. This study compares the capacities of both methods to detect and quantify MAsIII and DMAsIII in an in vitro methylation system consisting of recombinant human arsenic (+3 oxidation state) methyltransferase (AS3MT), S-adenosylmethionine as a methyl donor, a non-thiol reductant tris(2-carboxyethyl)phosphine, and arsenite (iAsIII) or MAsIII as substrate. The results show that reversed-phase HPLC-ICP-MS can identify and quantify MAsIII and DMAsIII in aqueous mixtures of biologically relevant Arsenical standards. However, HPLC separation of the in vitro methylation mixture resulted in significant losses of MAsIII, and particularly DMAsIII with total arsenic recoveries ≤25%. Further analyses showed that MAsIII and DMAsIII bind to AS3MT or interact with other components of the methylation mixture, forming complexes that do not elute from the column. Oxidation of the mixture with H2O2 which converted trivalent Arsenicals to their pentavalent analogs prior to HPLC separation increased total arsenic recoveries to ∼95%. In contrast, HG-CT-AAS analysis found large quantities of methylated trivalent Arsenicals in mixtures incubated with either iAsIII or MAsIII and provided high (≥72%) arsenic recoveries. These data suggest that an HPLC-based analysis of biological samples can underestimate MAsIII and DMAsIII concentrations and that controlling for arsenic species recovery is essential to avoid artifacts.
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metabolism and toxicity of arsenic in human urothelial cells expressing rat arsenic 3 oxidation state methyltransferase
Toxicology and Applied Pharmacology, 2005Co-Authors: Zuzana Drobna, David J. Thomas, Stephen B. Waters, Vicenta Devesa, Anne W. Harmon, Miroslav StybloAbstract:The enzymatic methylation of inorganic As (iAs) is catalyzed by As(+3 oxidation state)-methyltransferase (AS3MT). AS3MT is expressed in rat liver and in human hepatocytes. However, AS3MT is not expressed in UROtsa, human urothelial cells that do not methylate iAs. Thus, UROtsa cells are an ideal null background in which the role of iAs methylation in modulation of toxic and cancer-promoting effects of this metalloid can be examined. A retroviral gene delivery system was used in this study to create a clonal UROtsa cell line (UROtsa/F35) that expresses rat AS3MT. Here, we characterize the metabolism and cytotoxicity of arsenite (iAsIII) and methylated trivalent Arsenicals in parental cells and clonal cells expressing AS3MT. In contrast to parental cells, UROtsa/F35 cells effectively methylated iAsIII, yielding methylarsenic (MAs) and dimethylarsenic (DMAs) containing either AsIII or AsV. When exposed to MAsIII, UROtsa/F35 cells produced DMAsIII and DMAsV. MAsIII and DMAsIII were more cytotoxic than iAsIII in UROtsa and UROtsa/F35 cells. The greater cytotoxicity of MAsIII or DMAsIII than of iAsIII was associated with greater cellular uptake and retention of each methylated trivalent Arsenical. Notably, UROtsa/F35 cells were more sensitive than parental cells to the cytotoxic effects of iAsIII but were more resistant to cytotoxicity of MAsIII. The increased sensitivity of UROtsa/F35 cells to iAsIII was associated with inhibition of DMAs production and intracellular accumulation of MAs. The resistance of UROtsa/F35 cells to moderate concentrations of MAsIII was linked to its rapid conversion to DMAs and efflux of DMAs. However, concentrations of MAsIII that inhibited DMAs production by UROtsa/F35 cells were equally toxic for parental and clonal cell lines. Thus, the production and accumulation of MAsIII is a key factor contributing to the toxicity of acute iAs exposures in methylating cells.
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a novel s adenosyl l methionine arsenic iii methyltransferase from rat liver cytosol
Journal of Biological Chemistry, 2002Co-Authors: Miroslav Styblo, Melinda A Beck, Karen Herbindavis, Larry L Hall, Josef B Simeonsson, David J. ThomasAbstract:S-Adenosyl-l-methionine (AdoMet):arsenic(III) methyltransferase, purified from liver cytosol of adult male Fischer 344 rats, catalyzes transfer of a methyl group from AdoMet to trivalent Arsenicals producing methylated and dimethylated Arsenicals. The kinetics of production of methylated Arsenicals in reaction mixtures containing enzyme, AdoMet, dithiothreitol, glutathione (GSH), and arsenite are consistent with a scheme in which monomethylated Arsenical produced from arsenite is the substrate for a second methylation reaction that yields dimethylated Arsenical. The mRNA for this protein predicts a 369-amino acid residue protein (molecular mass 41056) that contains common methyltransferase sequence motifs. Its sequence is similar to Cyt19, a putative methyltransferase, expressed in human and mouse tissues. Reverse transcription-polymerase chain reaction detects S-adenosyl-l-methionine:arsenic(III) methyltransferase mRNA in rat tissues and in HepG2 cells, a human cell line that methylates arsenite and methylarsonous acid. S-Adenosyl-l-methionine:arsenic(III) methyltransferase mRNA is not detected in UROtsa cells, an immortalized human urothelial cell line that does not methylate arsenite. Because methylation of arsenic is a critical feature of its metabolism, characterization of this enzyme will improve our understanding of this metalloid's metabolism and its actions as a toxin and a carcinogen.
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methylated trivalent arsenic species are genotoxic
Chemical Research in Toxicology, 2001Co-Authors: Marc J Mass, Miroslav Styblo, David J. Thomas, Alan H Tennant, Barbara C Roop, William R Cullen, Andrew D KligermanAbstract:The reactivities of methyloxoarsine (MAs(III)) and iododimethylarsine (DMAs(III)), two methylated trivalent Arsenicals, toward supercoiled phiX174 RFI DNA were assessed using a DNA nicking assay. The induction of DNA damage by these compounds in vitro in human peripheral lymphocytes was assessed using a single-cell gel (SCG, "comet") assay. Both methylated trivalent Arsenicals were able to nick and/or completely degrade phiX174 DNA in vitro in 2 h incubations at 37 degrees C (pH 7.4) depending on concentration. MAs(III) was effective at nicking phiX174 DNA at 30 mM; however, at 150 microM DMAs(III), nicking could be observed. Exposure of phiX174 DNA to sodium arsenite (iAs(III); from 1 nM up to 300 mM), sodium arsenate (from 1 microM to 1 M), and the pentavalent Arsenicals, monomethylarsonic acid (from 1 microM to 3 M) and dimethylarsinic acid (from 0.1 to 300 mM), did not nick or degrade phiX174 DNA under these conditions. In the SCG assay in human lymphocytes, methylated trivalent Arsenicals were much more potent than any other Arsenicals that were tested. On the basis of the slopes of the concentration-response curve for the tail moment in the SCG assay, MAs(III) and DMAs(III) were 77 and 386 times more potent than iAs(III), respectively. Because methylated trivalent Arsenicals were the only arsenic compounds that were observed to damage naked DNA and required no exogenously added enzymatic or chemical activation systems, they are considered here to be direct-acting forms of arsenic that are genotoxic, though they are not, necessarily, the only genotoxic species of arsenic that could exist.
David J. Thomas - One of the best experts on this subject based on the ideXlab platform.
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mouse arsenic 3 oxidation state methyltransferase genotype affects metabolism and tissue dosimetry of Arsenicals after arsenite administration in drinking water
Toxicological Sciences, 2011Co-Authors: Baowei Chen, Lora L Arnold, Samuel M Cohen, David J. ThomasAbstract:Arsenic (+3 oxidation state) methyltransferase (As3mt) catalyzes methylation of inorganic arsenic (iAs) producing a number of methylated arsenic metabolites. Although methylation has been commonly considered a pathway for detoxification of arsenic, some highly reactive methylated Arsenicals may contribute to toxicity associated with exposure to inorganic arsenic. Here, adult female wild-type (WT) C57BL/6 mice and female As3mt knockout (KO) mice received drinking water that contained 1, 10, or 25 ppm (mg/l) of arsenite for 33 days and blood, liver, kidney, and lung were taken for arsenic speciation. Genotype markedly affected concentrations of Arsenicals in tissues. Summed concentrations of Arsenicals in plasma were higher in WT than in KO mice; in red blood cells, summed concentrations of Arsenicals were higher in KO than in WT mice. In liver, kidney, and lung, summed concentrations of Arsenicals were greater in KO than in WT mice. Although capacity for arsenic methylation is much reduced in KO mice, some mono-, di-, and tri-methylated Arsenicals were found in tissues of KO mice, likely reflecting the activity of other tissue methyltransferases or preabsorptive metabolism by the microbiota of the gastrointestinal tract. These results show that the genotype for arsenic methylation determines the phenotypes of arsenic retention and distribution and affects the dose- and organ-dependent toxicity associated with exposure to inorganic arsenic.
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arsenic 3 oxidation state methyltransferase and the methylation of Arsenicals in the invertebrate chordate ciona intestinalis
Toxicological Sciences, 2010Co-Authors: David J. Thomas, Gerardo M Nava, Shiying Cai, James L Boyer, Araceli Hernandezzavala, Rex H GaskinsAbstract:Biotransformation of inorganic arsenic (iAs) involves methylation catalyzed by arsenic (+ 3 oxidation state) methyltransferase (As3mt) yielding mono-, di-, and trimethylated Arsenicals. To investigate the evolution of molecular mechanisms that mediate arsenic biotransformation, a comparative genomic approach focusing on the invertebrate chordate Ciona intestinalis was used. Bioinformatic analyses identified an As3mt gene in the C. intestinalis genome. Constitutive As3mt RNA expression was observed in heart, branchial sac, and gastrointestinal tract. Adult animals were exposed to 0 or 1 ppm of iAs for 1 or 5 days. Steady-state As3mt RNA expression in the gastrointestinal tract was not modulated significantly by 5 days of exposure to iAs. Tissue levels of iAs and its methylated metabolites were determined by hydride generation-cryotrapping-gas chromatography-atomic absorption spectrometry. At either time point, exposure to iAs significantly increased concentrations of iAs and its methylated metabolites in tissues. After 5 days of exposure, total speciated arsenic concentrations were highest in branchial sac (3705 ng/g), followed by heart (1019 ng/g) and gastrointestinal tract (835 ng/g). At this time point, the sum of the speciated Arsenical concentrations in gastrointestinal tract and heart equaled or exceeded that of iAs; in branchial sac, iAs was the predominant species present. Ciona intestinalis metabolizes iAs to its methylated metabolites, which are retained in tissues. This metabolic pattern is consistent with the presence of an As3mt ortholog in its genome and constitutive expression of the gene in prominent organs, making this basal chordate a useful model to examine the evolution of arsenic detoxification.
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exploring the in vitro formation of trimethylarsine sulfide from dimethylthioarsinic acid in anaerobic microflora of mouse cecum using hplc icp ms and hplc esi ms
Toxicology and Applied Pharmacology, 2009Co-Authors: Kevin M Kubachka, John T Creed, Karen Herbindavis, Michael C Kohan, David J. ThomasAbstract:Although metabolism of Arsenicals to form methylated oxoArsenical species has been extensively studied, less is known about the formation of thiolated Arsenical species that have recently been detected as urinary metabolites. Indeed, their presence suggests that the metabolism of ingested arsenic is more complex than previously thought. Recent reports have shown that thiolated Arsenicals can be produced by the anaerobic microflora of the mouse cecum, suggesting that metabolism prior to systemic absorption may be a significant determinant of the pattern and extent of exposure to various arsenic-containing species. Here, we examined the metabolism of 34S labeled dimethylthioarsinic acid (34S-DMTA(V)) by the anaerobic microflora of the mouse cecum using HPLC-ICP-MS and HPLC-ESI-MS/MS to monitor for the presence of various oxo- and thioArsenicals. The use of isotopically enriched 34S-DMTA(V) made it possible to differentiate among potential metabolic pathways for production of the trimethylarsine sulfide (TMAS(V)). Upon in vitro incubation in an assay containing anaerobic microflora of mouse cecum, 34S-DMTA(V) underwent several transformations. Labile 34S was exchanged with more abundant 32S to produce 32S-DMTA(V), a thiol group was added to yield DMDTA(V), and a methyl group was added to yield 34S-TMAS(V). Because incubation of 34S-DMTA(V) resulted in the formation of 34S-TMAS(V), the pathway for its formation must preserve the arsenic-sulfur bond. The alternative metabolic pathway postulated for formation of TMAS(V) from dimethylarsinic acid (DMA(V)) would proceed via a dimethylarsinous acid (DMA(III)) intermediate and would necessitate the loss of 34S label. Structural confirmation of the metabolic product was achieved using HPLC-ESI-MS/MS. The data presented support the direct methylation of DMTA(V) to TMAS(V). Additionally, the detection of isotopically pure 34S-TMAS(V) raises questions about the sulfur exchange properties of TMAS(V) in the cecum material. Therefore, 34S-TMAS(V) was incubated and the exchange was monitored with respect to time. The data suggest that the As-S bond associated with TMAS(V) is less labile than the As-S bond associated with DMTA(V).
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metabolism and toxicity of arsenic in human urothelial cells expressing rat arsenic 3 oxidation state methyltransferase
Toxicology and Applied Pharmacology, 2005Co-Authors: Zuzana Drobna, David J. Thomas, Stephen B. Waters, Vicenta Devesa, Anne W. Harmon, Miroslav StybloAbstract:The enzymatic methylation of inorganic As (iAs) is catalyzed by As(+3 oxidation state)-methyltransferase (AS3MT). AS3MT is expressed in rat liver and in human hepatocytes. However, AS3MT is not expressed in UROtsa, human urothelial cells that do not methylate iAs. Thus, UROtsa cells are an ideal null background in which the role of iAs methylation in modulation of toxic and cancer-promoting effects of this metalloid can be examined. A retroviral gene delivery system was used in this study to create a clonal UROtsa cell line (UROtsa/F35) that expresses rat AS3MT. Here, we characterize the metabolism and cytotoxicity of arsenite (iAsIII) and methylated trivalent Arsenicals in parental cells and clonal cells expressing AS3MT. In contrast to parental cells, UROtsa/F35 cells effectively methylated iAsIII, yielding methylarsenic (MAs) and dimethylarsenic (DMAs) containing either AsIII or AsV. When exposed to MAsIII, UROtsa/F35 cells produced DMAsIII and DMAsV. MAsIII and DMAsIII were more cytotoxic than iAsIII in UROtsa and UROtsa/F35 cells. The greater cytotoxicity of MAsIII or DMAsIII than of iAsIII was associated with greater cellular uptake and retention of each methylated trivalent Arsenical. Notably, UROtsa/F35 cells were more sensitive than parental cells to the cytotoxic effects of iAsIII but were more resistant to cytotoxicity of MAsIII. The increased sensitivity of UROtsa/F35 cells to iAsIII was associated with inhibition of DMAs production and intracellular accumulation of MAs. The resistance of UROtsa/F35 cells to moderate concentrations of MAsIII was linked to its rapid conversion to DMAs and efflux of DMAs. However, concentrations of MAsIII that inhibited DMAs production by UROtsa/F35 cells were equally toxic for parental and clonal cell lines. Thus, the production and accumulation of MAsIII is a key factor contributing to the toxicity of acute iAs exposures in methylating cells.
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a novel s adenosyl l methionine arsenic iii methyltransferase from rat liver cytosol
Journal of Biological Chemistry, 2002Co-Authors: Miroslav Styblo, Melinda A Beck, Karen Herbindavis, Larry L Hall, Josef B Simeonsson, David J. ThomasAbstract:S-Adenosyl-l-methionine (AdoMet):arsenic(III) methyltransferase, purified from liver cytosol of adult male Fischer 344 rats, catalyzes transfer of a methyl group from AdoMet to trivalent Arsenicals producing methylated and dimethylated Arsenicals. The kinetics of production of methylated Arsenicals in reaction mixtures containing enzyme, AdoMet, dithiothreitol, glutathione (GSH), and arsenite are consistent with a scheme in which monomethylated Arsenical produced from arsenite is the substrate for a second methylation reaction that yields dimethylated Arsenical. The mRNA for this protein predicts a 369-amino acid residue protein (molecular mass 41056) that contains common methyltransferase sequence motifs. Its sequence is similar to Cyt19, a putative methyltransferase, expressed in human and mouse tissues. Reverse transcription-polymerase chain reaction detects S-adenosyl-l-methionine:arsenic(III) methyltransferase mRNA in rat tissues and in HepG2 cells, a human cell line that methylates arsenite and methylarsonous acid. S-Adenosyl-l-methionine:arsenic(III) methyltransferase mRNA is not detected in UROtsa cells, an immortalized human urothelial cell line that does not methylate arsenite. Because methylation of arsenic is a critical feature of its metabolism, characterization of this enzyme will improve our understanding of this metalloid's metabolism and its actions as a toxin and a carcinogen.
Samuel Monroe Cohen - One of the best experts on this subject based on the ideXlab platform.
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dietary administration of sodium arsenite to rats relations between dose and urinary concentrations of methylated and thio metabolites and effects on the rat urinary bladder epithelium
Toxicology and Applied Pharmacology, 2010Co-Authors: Shugo Suzuki, Lora L Arnold, Karen L Pennington, Baowei Chen, Hua Naranmandura, Chris X Le, Samuel Monroe CohenAbstract:Abstract Based on epidemiological data, chronic exposure to high levels of inorganic arsenic in drinking water is carcinogenic to humans, inducing skin, urinary bladder and lung tumors. In vivo , inorganic arsenic is metabolized to organic methylated Arsenicals including the highly toxic dimethylarsinous acid (DMA III ) and monomethylarsonous acid (MMA III ). Short-term treatment of rats with 100 μg/g trivalent arsenic (As III ) as sodium arsenite in the diet or in drinking water induced cytotoxicity and necrosis of the urothelial superficial layer, with increased cell proliferation and hyperplasia. The objectives of this study were to determine if these arsenic-induced urothelial effects are dose responsive, the dose of arsenic at which urothelial effects are not detected, and the urinary concentrations of the Arsenical metabolites. We treated female F344 rats for 5 weeks with sodium arsenite at dietary doses of 0, 1, 10, 25, 50, and 100 ppm. Cytotoxicity, cell proliferation and hyperplasia of urothelial superficial cells were increased in a dose-responsive manner, with maximum effects found at 50 ppm As III . There were no effects at 1 ppm As III . The main urinary Arsenical in As III -treated rats was the organic Arsenical dimethylarsinic acid (DMA V ). The thio-metabolites dimethylmonothioarsinic acid (DMMTA V ) and monomethylmonothioarsinic acid (MMMTA V ) were also found in the urine of As III -treated rats. The LC 50 concentrations of DMMTA V for rat and human urothelial cells in vitro were similar to trivalent oxygen-containing Arsenicals. These data suggest that dietary As III -induced urothelial cytotoxicity and proliferation are dose responsive, and the urothelial effects have a threshold corresponding to the urinary excretion of measurable reactive metabolites.
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effects of co administration of dietary sodium arsenite and an nadph oxidase inhibitor on the rat bladder epithelium
Toxicology, 2009Co-Authors: Shugo Suzuki, Lora L Arnold, Karen L Pennington, Satoko Kakiuchikiyota, Samuel Monroe CohenAbstract:Abstract Arsenite (As III ), an inorganic Arsenical, is a known human carcinogen, inducing tumors of the skin, urinary bladder and lung. It is metabolized to organic methylated Arsenicals. Oxidative stress has been suggested as a mechanism for arsenic-induced carcinogenesis. Reactive oxygen species (ROS) can be important factors for carcinogenesis and tumor progression. Nicotinamide adenine dinucleotide phosphate (NADPH) oxidase is known to produce intracellular ROS, therefore, we investigated the ability of apocynin (acetovanillone), an NADPH oxidase inhibitor, to inhibit the cytotoxicity and regenerative cell proliferation of arsenic in vitro and in vivo . Apocynin had similar effects in reducing the cytotoxicity of As III and dimethylarsinous acid (DMA III ) in rat urothelial cells in vitro . When tested at the same concentrations as apocynin, other antioxidants, such as l -ascorbate and N-acetylcysteine, did not inhibit As III -induced cytotoxicity but they were more effective at inhibiting DMA III -induced cytotoxicity compared with apocynin. In vivo , female rats were treated for 3 weeks with 100 ppm As III . Immunohistochemical staining for 8-hydroxy-2′-deoxyguanosine (8-OHdG) showed that apocynin reduced oxidative stress partially induced by As III treatment on rat urothelium, and significantly reduced the cytotoxicity of superficial cells detected by scanning electron microscopy (SEM). However, based on the incidence of simple hyperplasia and the bromodeoxyuridine (BrdU) labeling index, apocynin did not inhibit As III -induced urothelial cell proliferation. These data suggest that the NADPH oxidase inhibitor, apocynin, may have the ability to partially inhibit arsenic-induced oxidative stress and cytotoxicity of the rat bladder epithelium in vitro and in vivo . However, apocynin did not inhibit the regenerative cell proliferation induced by arsenite in a short-term study.
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effects of an epidermal growth factor receptor inhibitor on arsenic associated toxicity in the rat bladder epithelium
Toxicology Letters, 2009Co-Authors: Shugo Suzuki, Lora L Arnold, Karen L Pennington, Baowei Chen, Chris X Le, Samuel Monroe CohenAbstract:Abstract Arsenite (AsIII), an inorganic Arsenical, is a known human carcinogen, inducing tumors of the skin, urinary bladder and lung. It is known to be metabolized to organic methylated Arsenicals in vivo. AsIII has been reported to have the ability to up-regulate the epidermal growth factor receptor (EGFR)-associated pathway in epithelial cells, including human urothelial cells in vitro. EGFR is a cell-surface receptor belonging to the ErbB family of receptor tyrosine kinases, and the EGFR-associated signaling pathway has been reported to play an important role in carcinogenesis and cancer progression, including in bladder cancer. In this study, we investigated the growth effects of AsIII and an organic trivalent Arsenical, dimethylarsinous acid (DMAIII), and the effects of co-exposure of gefitinib, an EGFR inhibitor, with AsIII to a rat urothelial cell line (MYP3). We also investigated the effects of co-administration of dietary AsIII and gefitinib in vivo. In vitro, concentrations of 1.0 μM AsIII or 0.5 μM DMAIII induced cytotoxicity. However, lower concentrations of AsIII treatment had a slight mitogenic growth effect whereas lower concentrations of DMAIII did not. Gefitinib blocked AsIII-induced cell growth in vitro. In vivo, a high dose of gefitinib alone induced slight urothelial cytotoxicity, and did not reduce cytotoxicity and regenerative cell proliferation when co-administered with AsIII. The majority of arsenic metabolites present in the urine of AsIII-treated rats were organic Arsenicals, mainly dimethylarsinic acid (DMAV). AsIII was also present, and its concentration was higher than the concentration required to produce cytotoxicity in vitro. These data suggest that an EGFR inhibitor has the ability to block AsIII-induced cell proliferation in vitro but not in vivo in a short-term study.
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effects of co administration of antioxidants and Arsenicals on the rat urinary bladder epithelium
Toxicological Sciences, 2004Co-Authors: Lora L Arnold, Martin Cano, Samuel Monroe CohenAbstract:Oxidative stress has been increasingly recognized as a possible mechanisminthetoxicityandcarcinogenicityofvariouschemicals, including arsenic. Therefore, treatment with antioxidants may afford a protective effect against arsenic-induced cytotoxicity and carcinogenesis. Dimethylarsinic acid (DMA V ) has been shown to be a bladder carcinogen in rats when administered at high doses (100 ppm) in the diet or in the drinking water. The main purpose of the present study was to evaluate the effects of co-administration of antioxidantswithArsenicalsontheraturinarybladderepitheliumin vitroandinvivo.Inapreviousexperiment,treatmentwith1000ppm melatoninfortwoweeksdidnotinhibitcellproliferationinducedin the rat urothelium by 100 ppm DMA V . In the current study, we examined the effects of five antioxidants that act via different mechanisms, on the in vitro cytotoxicity of various Arsenicals, for the purpose of determining which antioxidants might have protective effects against arsenic-induced cytotoxicity. The antioxidants that inhibited cytotoxicity in vitro were then studied also in vivo. Melatonin showed slight inhibition of the cytotoxicity of arsenite, but had no effect on the other Arsenicals. N-acetylcysteine (NAC) inhibited the cytotoxicity of monomethylarsonous acid (MMA III ), DMA V , dimethylarsinous acid (DMA III ), and trimethylarsine oxide (TMAO). Vitamin C inhibited cytotoxicity induced by arsenate, arsenite, MMA III , and DMA III . Tiron and Trolox had no effect on the cytotoxicity of any Arsenical. The in vitro inhibitory effects of NACandvitamin ConDMA V andonDMA III ,suggestedthat these antioxidants might afford preventive effects on DMA V -induced bladder cytotoxicity and carcinogenesis in rats. To test this hypothesis, a 10-week rat bioassay was conducted. Melatonin was also included to clarify the results of the previous two-week experiment. The sodium salt of vitamin C (Na-Asc), but not melatonin or NAC, inhibited the proliferative effects of DMA V on the bladder epithelium in rats. These results suggest that oxidative stress is at least in part involved in DMA V -induced rat bladder toxicity and prolifera
Lora L Arnold - One of the best experts on this subject based on the ideXlab platform.
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mouse arsenic 3 oxidation state methyltransferase genotype affects metabolism and tissue dosimetry of Arsenicals after arsenite administration in drinking water
Toxicological Sciences, 2011Co-Authors: Baowei Chen, Lora L Arnold, Samuel M Cohen, David J. ThomasAbstract:Arsenic (+3 oxidation state) methyltransferase (As3mt) catalyzes methylation of inorganic arsenic (iAs) producing a number of methylated arsenic metabolites. Although methylation has been commonly considered a pathway for detoxification of arsenic, some highly reactive methylated Arsenicals may contribute to toxicity associated with exposure to inorganic arsenic. Here, adult female wild-type (WT) C57BL/6 mice and female As3mt knockout (KO) mice received drinking water that contained 1, 10, or 25 ppm (mg/l) of arsenite for 33 days and blood, liver, kidney, and lung were taken for arsenic speciation. Genotype markedly affected concentrations of Arsenicals in tissues. Summed concentrations of Arsenicals in plasma were higher in WT than in KO mice; in red blood cells, summed concentrations of Arsenicals were higher in KO than in WT mice. In liver, kidney, and lung, summed concentrations of Arsenicals were greater in KO than in WT mice. Although capacity for arsenic methylation is much reduced in KO mice, some mono-, di-, and tri-methylated Arsenicals were found in tissues of KO mice, likely reflecting the activity of other tissue methyltransferases or preabsorptive metabolism by the microbiota of the gastrointestinal tract. These results show that the genotype for arsenic methylation determines the phenotypes of arsenic retention and distribution and affects the dose- and organ-dependent toxicity associated with exposure to inorganic arsenic.
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dietary administration of sodium arsenite to rats relations between dose and urinary concentrations of methylated and thio metabolites and effects on the rat urinary bladder epithelium
Toxicology and Applied Pharmacology, 2010Co-Authors: Shugo Suzuki, Lora L Arnold, Karen L Pennington, Baowei Chen, Hua Naranmandura, Chris X Le, Samuel Monroe CohenAbstract:Abstract Based on epidemiological data, chronic exposure to high levels of inorganic arsenic in drinking water is carcinogenic to humans, inducing skin, urinary bladder and lung tumors. In vivo , inorganic arsenic is metabolized to organic methylated Arsenicals including the highly toxic dimethylarsinous acid (DMA III ) and monomethylarsonous acid (MMA III ). Short-term treatment of rats with 100 μg/g trivalent arsenic (As III ) as sodium arsenite in the diet or in drinking water induced cytotoxicity and necrosis of the urothelial superficial layer, with increased cell proliferation and hyperplasia. The objectives of this study were to determine if these arsenic-induced urothelial effects are dose responsive, the dose of arsenic at which urothelial effects are not detected, and the urinary concentrations of the Arsenical metabolites. We treated female F344 rats for 5 weeks with sodium arsenite at dietary doses of 0, 1, 10, 25, 50, and 100 ppm. Cytotoxicity, cell proliferation and hyperplasia of urothelial superficial cells were increased in a dose-responsive manner, with maximum effects found at 50 ppm As III . There were no effects at 1 ppm As III . The main urinary Arsenical in As III -treated rats was the organic Arsenical dimethylarsinic acid (DMA V ). The thio-metabolites dimethylmonothioarsinic acid (DMMTA V ) and monomethylmonothioarsinic acid (MMMTA V ) were also found in the urine of As III -treated rats. The LC 50 concentrations of DMMTA V for rat and human urothelial cells in vitro were similar to trivalent oxygen-containing Arsenicals. These data suggest that dietary As III -induced urothelial cytotoxicity and proliferation are dose responsive, and the urothelial effects have a threshold corresponding to the urinary excretion of measurable reactive metabolites.
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effects of co administration of dietary sodium arsenite and an nadph oxidase inhibitor on the rat bladder epithelium
Toxicology, 2009Co-Authors: Shugo Suzuki, Lora L Arnold, Karen L Pennington, Satoko Kakiuchikiyota, Samuel Monroe CohenAbstract:Abstract Arsenite (As III ), an inorganic Arsenical, is a known human carcinogen, inducing tumors of the skin, urinary bladder and lung. It is metabolized to organic methylated Arsenicals. Oxidative stress has been suggested as a mechanism for arsenic-induced carcinogenesis. Reactive oxygen species (ROS) can be important factors for carcinogenesis and tumor progression. Nicotinamide adenine dinucleotide phosphate (NADPH) oxidase is known to produce intracellular ROS, therefore, we investigated the ability of apocynin (acetovanillone), an NADPH oxidase inhibitor, to inhibit the cytotoxicity and regenerative cell proliferation of arsenic in vitro and in vivo . Apocynin had similar effects in reducing the cytotoxicity of As III and dimethylarsinous acid (DMA III ) in rat urothelial cells in vitro . When tested at the same concentrations as apocynin, other antioxidants, such as l -ascorbate and N-acetylcysteine, did not inhibit As III -induced cytotoxicity but they were more effective at inhibiting DMA III -induced cytotoxicity compared with apocynin. In vivo , female rats were treated for 3 weeks with 100 ppm As III . Immunohistochemical staining for 8-hydroxy-2′-deoxyguanosine (8-OHdG) showed that apocynin reduced oxidative stress partially induced by As III treatment on rat urothelium, and significantly reduced the cytotoxicity of superficial cells detected by scanning electron microscopy (SEM). However, based on the incidence of simple hyperplasia and the bromodeoxyuridine (BrdU) labeling index, apocynin did not inhibit As III -induced urothelial cell proliferation. These data suggest that the NADPH oxidase inhibitor, apocynin, may have the ability to partially inhibit arsenic-induced oxidative stress and cytotoxicity of the rat bladder epithelium in vitro and in vivo . However, apocynin did not inhibit the regenerative cell proliferation induced by arsenite in a short-term study.
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effects of an epidermal growth factor receptor inhibitor on arsenic associated toxicity in the rat bladder epithelium
Toxicology Letters, 2009Co-Authors: Shugo Suzuki, Lora L Arnold, Karen L Pennington, Baowei Chen, Chris X Le, Samuel Monroe CohenAbstract:Abstract Arsenite (AsIII), an inorganic Arsenical, is a known human carcinogen, inducing tumors of the skin, urinary bladder and lung. It is known to be metabolized to organic methylated Arsenicals in vivo. AsIII has been reported to have the ability to up-regulate the epidermal growth factor receptor (EGFR)-associated pathway in epithelial cells, including human urothelial cells in vitro. EGFR is a cell-surface receptor belonging to the ErbB family of receptor tyrosine kinases, and the EGFR-associated signaling pathway has been reported to play an important role in carcinogenesis and cancer progression, including in bladder cancer. In this study, we investigated the growth effects of AsIII and an organic trivalent Arsenical, dimethylarsinous acid (DMAIII), and the effects of co-exposure of gefitinib, an EGFR inhibitor, with AsIII to a rat urothelial cell line (MYP3). We also investigated the effects of co-administration of dietary AsIII and gefitinib in vivo. In vitro, concentrations of 1.0 μM AsIII or 0.5 μM DMAIII induced cytotoxicity. However, lower concentrations of AsIII treatment had a slight mitogenic growth effect whereas lower concentrations of DMAIII did not. Gefitinib blocked AsIII-induced cell growth in vitro. In vivo, a high dose of gefitinib alone induced slight urothelial cytotoxicity, and did not reduce cytotoxicity and regenerative cell proliferation when co-administered with AsIII. The majority of arsenic metabolites present in the urine of AsIII-treated rats were organic Arsenicals, mainly dimethylarsinic acid (DMAV). AsIII was also present, and its concentration was higher than the concentration required to produce cytotoxicity in vitro. These data suggest that an EGFR inhibitor has the ability to block AsIII-induced cell proliferation in vitro but not in vivo in a short-term study.
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effects of co administration of antioxidants and Arsenicals on the rat urinary bladder epithelium
Toxicological Sciences, 2004Co-Authors: Lora L Arnold, Martin Cano, Samuel Monroe CohenAbstract:Oxidative stress has been increasingly recognized as a possible mechanisminthetoxicityandcarcinogenicityofvariouschemicals, including arsenic. Therefore, treatment with antioxidants may afford a protective effect against arsenic-induced cytotoxicity and carcinogenesis. Dimethylarsinic acid (DMA V ) has been shown to be a bladder carcinogen in rats when administered at high doses (100 ppm) in the diet or in the drinking water. The main purpose of the present study was to evaluate the effects of co-administration of antioxidantswithArsenicalsontheraturinarybladderepitheliumin vitroandinvivo.Inapreviousexperiment,treatmentwith1000ppm melatoninfortwoweeksdidnotinhibitcellproliferationinducedin the rat urothelium by 100 ppm DMA V . In the current study, we examined the effects of five antioxidants that act via different mechanisms, on the in vitro cytotoxicity of various Arsenicals, for the purpose of determining which antioxidants might have protective effects against arsenic-induced cytotoxicity. The antioxidants that inhibited cytotoxicity in vitro were then studied also in vivo. Melatonin showed slight inhibition of the cytotoxicity of arsenite, but had no effect on the other Arsenicals. N-acetylcysteine (NAC) inhibited the cytotoxicity of monomethylarsonous acid (MMA III ), DMA V , dimethylarsinous acid (DMA III ), and trimethylarsine oxide (TMAO). Vitamin C inhibited cytotoxicity induced by arsenate, arsenite, MMA III , and DMA III . Tiron and Trolox had no effect on the cytotoxicity of any Arsenical. The in vitro inhibitory effects of NACandvitamin ConDMA V andonDMA III ,suggestedthat these antioxidants might afford preventive effects on DMA V -induced bladder cytotoxicity and carcinogenesis in rats. To test this hypothesis, a 10-week rat bioassay was conducted. Melatonin was also included to clarify the results of the previous two-week experiment. The sodium salt of vitamin C (Na-Asc), but not melatonin or NAC, inhibited the proliferative effects of DMA V on the bladder epithelium in rats. These results suggest that oxidative stress is at least in part involved in DMA V -induced rat bladder toxicity and prolifera
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dietary administration of sodium arsenite to rats relations between dose and urinary concentrations of methylated and thio metabolites and effects on the rat urinary bladder epithelium
Toxicology and Applied Pharmacology, 2010Co-Authors: Shugo Suzuki, Lora L Arnold, Karen L Pennington, Baowei Chen, Hua Naranmandura, Chris X Le, Samuel Monroe CohenAbstract:Abstract Based on epidemiological data, chronic exposure to high levels of inorganic arsenic in drinking water is carcinogenic to humans, inducing skin, urinary bladder and lung tumors. In vivo , inorganic arsenic is metabolized to organic methylated Arsenicals including the highly toxic dimethylarsinous acid (DMA III ) and monomethylarsonous acid (MMA III ). Short-term treatment of rats with 100 μg/g trivalent arsenic (As III ) as sodium arsenite in the diet or in drinking water induced cytotoxicity and necrosis of the urothelial superficial layer, with increased cell proliferation and hyperplasia. The objectives of this study were to determine if these arsenic-induced urothelial effects are dose responsive, the dose of arsenic at which urothelial effects are not detected, and the urinary concentrations of the Arsenical metabolites. We treated female F344 rats for 5 weeks with sodium arsenite at dietary doses of 0, 1, 10, 25, 50, and 100 ppm. Cytotoxicity, cell proliferation and hyperplasia of urothelial superficial cells were increased in a dose-responsive manner, with maximum effects found at 50 ppm As III . There were no effects at 1 ppm As III . The main urinary Arsenical in As III -treated rats was the organic Arsenical dimethylarsinic acid (DMA V ). The thio-metabolites dimethylmonothioarsinic acid (DMMTA V ) and monomethylmonothioarsinic acid (MMMTA V ) were also found in the urine of As III -treated rats. The LC 50 concentrations of DMMTA V for rat and human urothelial cells in vitro were similar to trivalent oxygen-containing Arsenicals. These data suggest that dietary As III -induced urothelial cytotoxicity and proliferation are dose responsive, and the urothelial effects have a threshold corresponding to the urinary excretion of measurable reactive metabolites.
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effects of co administration of dietary sodium arsenite and an nadph oxidase inhibitor on the rat bladder epithelium
Toxicology, 2009Co-Authors: Shugo Suzuki, Lora L Arnold, Karen L Pennington, Satoko Kakiuchikiyota, Samuel Monroe CohenAbstract:Abstract Arsenite (As III ), an inorganic Arsenical, is a known human carcinogen, inducing tumors of the skin, urinary bladder and lung. It is metabolized to organic methylated Arsenicals. Oxidative stress has been suggested as a mechanism for arsenic-induced carcinogenesis. Reactive oxygen species (ROS) can be important factors for carcinogenesis and tumor progression. Nicotinamide adenine dinucleotide phosphate (NADPH) oxidase is known to produce intracellular ROS, therefore, we investigated the ability of apocynin (acetovanillone), an NADPH oxidase inhibitor, to inhibit the cytotoxicity and regenerative cell proliferation of arsenic in vitro and in vivo . Apocynin had similar effects in reducing the cytotoxicity of As III and dimethylarsinous acid (DMA III ) in rat urothelial cells in vitro . When tested at the same concentrations as apocynin, other antioxidants, such as l -ascorbate and N-acetylcysteine, did not inhibit As III -induced cytotoxicity but they were more effective at inhibiting DMA III -induced cytotoxicity compared with apocynin. In vivo , female rats were treated for 3 weeks with 100 ppm As III . Immunohistochemical staining for 8-hydroxy-2′-deoxyguanosine (8-OHdG) showed that apocynin reduced oxidative stress partially induced by As III treatment on rat urothelium, and significantly reduced the cytotoxicity of superficial cells detected by scanning electron microscopy (SEM). However, based on the incidence of simple hyperplasia and the bromodeoxyuridine (BrdU) labeling index, apocynin did not inhibit As III -induced urothelial cell proliferation. These data suggest that the NADPH oxidase inhibitor, apocynin, may have the ability to partially inhibit arsenic-induced oxidative stress and cytotoxicity of the rat bladder epithelium in vitro and in vivo . However, apocynin did not inhibit the regenerative cell proliferation induced by arsenite in a short-term study.
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effects of an epidermal growth factor receptor inhibitor on arsenic associated toxicity in the rat bladder epithelium
Toxicology Letters, 2009Co-Authors: Shugo Suzuki, Lora L Arnold, Karen L Pennington, Baowei Chen, Chris X Le, Samuel Monroe CohenAbstract:Abstract Arsenite (AsIII), an inorganic Arsenical, is a known human carcinogen, inducing tumors of the skin, urinary bladder and lung. It is known to be metabolized to organic methylated Arsenicals in vivo. AsIII has been reported to have the ability to up-regulate the epidermal growth factor receptor (EGFR)-associated pathway in epithelial cells, including human urothelial cells in vitro. EGFR is a cell-surface receptor belonging to the ErbB family of receptor tyrosine kinases, and the EGFR-associated signaling pathway has been reported to play an important role in carcinogenesis and cancer progression, including in bladder cancer. In this study, we investigated the growth effects of AsIII and an organic trivalent Arsenical, dimethylarsinous acid (DMAIII), and the effects of co-exposure of gefitinib, an EGFR inhibitor, with AsIII to a rat urothelial cell line (MYP3). We also investigated the effects of co-administration of dietary AsIII and gefitinib in vivo. In vitro, concentrations of 1.0 μM AsIII or 0.5 μM DMAIII induced cytotoxicity. However, lower concentrations of AsIII treatment had a slight mitogenic growth effect whereas lower concentrations of DMAIII did not. Gefitinib blocked AsIII-induced cell growth in vitro. In vivo, a high dose of gefitinib alone induced slight urothelial cytotoxicity, and did not reduce cytotoxicity and regenerative cell proliferation when co-administered with AsIII. The majority of arsenic metabolites present in the urine of AsIII-treated rats were organic Arsenicals, mainly dimethylarsinic acid (DMAV). AsIII was also present, and its concentration was higher than the concentration required to produce cytotoxicity in vitro. These data suggest that an EGFR inhibitor has the ability to block AsIII-induced cell proliferation in vitro but not in vivo in a short-term study.