@article{sen_drobna_keung_2021, title={Evaluation of UBE3A antibodies in mice and human cerebral organoids}, volume={11}, ISSN={["2045-2322"]}, DOI={10.1038/s41598-021-85923-x}, abstractNote={Abstract}, number={1}, journal={SCIENTIFIC REPORTS}, author={Sen, Dilara and Drobna, Zuzana and Keung, Albert J.}, year={2021}, month={Mar} }
 @article{drobna_2020, title={Activation of Lrrk2 and alpha-Synuclein in substantia nigra, striatum, and cerebellum after chronic exposure to arsenite}, volume={408}, ISSN={["1096-0333"]}, DOI={10.1016/j.taap.2020.115278}, abstractNote={Arsenic is a neurotoxin and environmental exposure to it correlates with an incidence of neurodegenerative diseases. Considering that arsenic has the potential to inhibit autophagic flux, it was hypothesized that arsenite (NaAsO2) may interplay with LRRK2 and α-Synuclein, affecting their phosphorylation in brain regions prone to neurodegeneration. After 15 weeks of chronic exposure to arsenite, a reduction in grip strength of C57BL/6 male mice was observed. Thirty minutes exposure to arsenite increased phosphorylation of Lrrk2 and α-Synuclein in organotypic brain slice cultures from the cerebellum and striatum, respectively. Chronic exposure of mice to a wide-range of concentrations of arsenite led to a significant induction of Lrrk2 phosphorylation in substantia nigra and cerebellum and α-Synuclein phosphorylation in substantia nigra and striatum. Strong correlations between phosphorylated forms of Lrrk2 and α-Synuclein in substantia nigra, Lrrk2 levels between substantia nigra and striatum, and between Lrrk2 in striatum and α-Synuclein in substantia nigra observed in control animals were completely disrupted by arsenic exposure at 50, 500, and 5000 ppb. A transcriptome analysis identified specific genes and canonical pathways that distinguish striatum, substantia nigra, and cerebellum from each other in control animals and compare individual brain regions to arsenite exposed animals. Chronic arsenite exposure altered transcripts of glutathione redox reactions and serotonin receptor signaling in striatum, axonal guidance signaling, NF-κB and androgen signaling in substantia nigra and mitochondrial dysfunction, oxidative phosphorylation, apoptosis and sirtuin signaling in the cerebellum. These data suggest that arsenite affects processes associated with neurodegenerative diseases in brain region specific manner.}, journal={TOXICOLOGY AND APPLIED PHARMACOLOGY}, author={Drobna, Zuzana}, year={2020}, month={Dec} }
 @article{sen_voulgaropoulos_drobna_keung_2020, title={Human Cerebral Organoids Reveal Early Spatiotemporal Dynamics and Pharmacological Responses of UBE3A}, volume={15}, ISSN={["2213-6711"]}, DOI={10.1016/j.stemcr.2020.08.006}, abstractNote={Angelman syndrome is a complex neurodevelopmental disorder characterized by delayed development, intellectual disability, speech impairment, and ataxia. It results from the loss of UBE3A protein, an E3 ubiquitin ligase, in neurons of the brain. Despite the dynamic spatiotemporal expression of UBE3A observed in rodents and the potential clinical importance of when and where it is expressed, its expression pattern in humans remains unknown. This reflects a common challenge of studying human neurodevelopment: prenatal periods are hard to access experimentally. In this work, human cerebral organoids reveal a change from weak to strong UBE3A in neuronal nuclei within 3 weeks of culture. Angelman syndrome human induced pluripotent stem cell-derived organoids also exhibit early silencing of paternal UBE3A, with topoisomerase inhibitors partially rescuing UBE3A levels and calcium transient phenotypes. This work establishes human cerebral organoids as an important model for studying UBE3A and motivates their broader use in understanding complex neurodevelopmental disorders.}, number={4}, journal={STEM CELL REPORTS}, author={Sen, Dilara and Voulgaropoulos, Alexis and Drobna, Zuzana and Keung, Albert J.}, year={2020}, month={Oct}, pages={845–854} }
 @article{drobna_talarovicova_schrader_fennell_snyder_rissman_2019, title={Bisphenol F has different effects on preadipocytes differentiation and weight gain in adult mice as compared with Bisphenol A and S}, volume={420}, ISSN={["0300-483X"]}, DOI={10.1016/j.tox.2019.03.016}, abstractNote={Bisphenol S (2,2-bisulfone, BPS) and Bisphenol F (2,2-bis [4-hydroxyphenol]methane, BPF) are analogs of Bisphenol A (2,2-bis[4-hydroxyphenyl]propane, BPA), a widely used endocrine disrupting compound present in polycarbonate plastics, thermal receipts and epoxy resins that line food cans. Here we examined effects of BPA, BPS, and BPF in low concentrations on differentiation in murine 3T3-L1 preadipocytes. We also fed adult male mice chow with one of three doses of BPF (0, 0.5, 5, 50 mg/kg chow, or approximately 0.044, 0.44 and 4.4 mg/kg body weight per day) for 12 weeks, collected body weights, food intake, and tested for glucose tolerance. The doses of BPF used produced mean concentrations of 0, 6.2, 43.6, and 561 ng/mL in plasma. In 3T3-L1 cells BPS had the greatest effects, along with BPA, both increased expression of several genes required for preadipocyte differentiation over 12 days in culture. In contrast, BPF decreased expression of several genes late in differentiation. This dichotomy was also reflected in lipid accumulation as BPA and BPS treated cells had elevated lipid concentrations compared to controls or cells treated with BPF. Male mice fed either the highest or lowest concentrations of BPF gained less weight than controls with no effects on glucose levels or glucose tolerance. Plasma levels of BPF reflected doses in food with no overlap between doses. In summary, our results suggest that BPS has a strong potential to be obesogenic while effects of BPF are subtler and potentially in the opposite direction.}, journal={TOXICOLOGY}, author={Drobna, Zuzana and Talarovicova, Alzbeta and Schrader, Hannah E. and Fennell, Timothy R. and Snyder, Rodney W. and Rissman, Emilie F.}, year={2019}, month={May}, pages={66–72} }
 @article{wolstenholme_drobna_henriksen_goldsby_stevenson_irvin_flaws_rissman_2019, title={Transgenerational Bisphenol A Causes Deficits in Social Recognition and Alters Postsynaptic Density Genes in Mice}, volume={160}, ISSN={["1945-7170"]}, DOI={10.1210/en.2019-00196}, abstractNote={Abstract}, number={8}, journal={ENDOCRINOLOGY}, author={Wolstenholme, Jennifer T. and Drobna, Zuzana and Henriksen, Anne D. and Goldsby, Jessica A. and Stevenson, Rachel and Irvin, Joshua W. and Flaws, Jodi A. and Rissman, Emilie F.}, year={2019}, month={Aug}, pages={1854–1867} }
 @article{drobna_henriksen_wolstenholme_montiel_lambeth_shang_harris_zhou_flaws_adli_et al._2018, title={Transgenerational Effects of Bisphenol A on Gene Expression and DNA Methylation of Imprinted Genes in Brain}, volume={159}, ISSN={["1945-7170"]}, DOI={10.1210/en.2017-00730}, abstractNote={Bisphenol A (BPA) is a ubiquitous man-made endocrine disrupting compound (EDC). Developmental exposure to BPA changes behavioral and reproductive phenotypes, and these effects can last for generations. We exposed embryos to BPA, producing two lineages: controls and BPA exposed. In the third filial generation (F3), brain tissues containing the preoptic area, the bed nucleus of the stria terminalis, and the anterior hypothalamus were collected. RNA sequencing (RNA-seq) and subsequent data analyses revealed 50 differentially regulated genes in the brains of F3 juveniles from BPA vs control lineages. BPA exposure can lead to loss of imprinting, and one of the two imprinted genes in our data set, maternally expressed gene 3 (Meg3), has been associated with EDCs and neurobehavioral phenotypes. We used quantitative polymerase chain reaction to examine the two imprinted genes in our data set, Meg3 and microRNA-containing gene Mirg (residing in the same loci). Confirming the RNA-seq, Meg3 messenger RNA was higher in F3 brains from the BPA lineage than in control brains. This was true in brains from mice produced with two different BPA paradigms. Next, we used pyrosequencing to probe differentially methylated regions of Meg3. We found transgenerational effects of BPA on imprinted genes in brain. Given these results, and data on Meg3 methylation in humans, we suggest this gene may be a biomarker indicative of early life environmental perturbation.}, number={1}, journal={ENDOCRINOLOGY}, author={Drobna, Zuzana and Henriksen, Anne D. and Wolstenholme, Jennifer T. and Montiel, Catalina and Lambeth, Philip S. and Shang, Stephen and Harris, Erin P. and Zhou, Changqing and Flaws, Jodi A. and Adli, Mazhar and et al.}, year={2018}, month={Jan}, pages={132–144} }
 @article{huang_douillet_su_zhou_wu_chen_galanko_drobná_saunders_martin_et al._2017, title={Metabolomic profiles of arsenic (+3 oxidation state) methyltransferase knockout mice: effect of sex and arsenic exposure}, volume={91}, ISSN={0340-5761 1432-0738}, url={http://dx.doi.org/10.1007/S00204-016-1676-0}, DOI={10.1007/S00204-016-1676-0}, abstractNote={Arsenic (+3 oxidation state) methyltransferase (As3mt) is the key enzyme in the pathway for methylation of inorganic arsenic (iAs). Altered As3mt expression and AS3MT polymorphism have been linked to changes in iAs metabolism and in susceptibility to iAs toxicity in laboratory models and in humans. As3mt-knockout mice have been used to study the association between iAs metabolism and adverse effects of iAs exposure. However, little is known about systemic changes in metabolism of these mice and how these changes lead to their increased susceptibility to iAs toxicity. Here, we compared plasma and urinary metabolomes of male and female wild-type (WT) and As3mt-KO (KO) C57BL/6 mice and examined metabolomic shifts associated with iAs exposure in drinking water. Surprisingly, exposure to 1 ppm As elicited only small changes in the metabolite profiles of either WT or KO mice. In contrast, comparisons of KO mice with WT mice revealed significant differences in plasma and urinary metabolites associated with lipid (phosphatidylcholines, cytidine, acyl-carnitine), amino acid (hippuric acid, acetylglycine, urea), and carbohydrate (l-sorbose, galactonic acid, gluconic acid) metabolism. Notably, most of these differences were sex specific. Sex-specific differences were also found between WT and KO mice in plasma triglyceride and lipoprotein cholesterol levels. Some of the differentially changed metabolites (phosphatidylcholines, carnosine, and sarcosine) are substrates or products of reactions catalyzed by other methyltransferases. These results suggest that As3mt KO alters major metabolic pathways in a sex-specific manner, independent of iAs treatment, and that As3mt may be involved in other cellular processes beyond iAs methylation.}, number={1}, journal={Archives of Toxicology}, publisher={Springer Science and Business Media LLC}, author={Huang, Madelyn C. and Douillet, Christelle and Su, Mingming and Zhou, Kejun and Wu, Tao and Chen, Wenlian and Galanko, Joseph A. and Drobná, Zuzana and Saunders, R. Jesse and Martin, Elizabeth and et al.}, year={2017}, month={Jan}, pages={189–202} }
 @article{laine_bailey_olshan_smeester_drobna_styblo_douillet_garcia-vargas_rubio-andrade_pathmasiri_et al._2017, title={Neonatal Metabolomic Profiles Related to Prenatal Arsenic Exposure}, volume={51}, ISSN={["1520-5851"]}, DOI={10.1021/acs.est.6b04374}, abstractNote={Prenatal inorganic arsenic (iAs) exposure is associated with health effects evident at birth and later in life. An understanding of the relationship between prenatal iAs exposure and alterations in the neonatal metabolome could reveal critical molecular modifications, potentially underpinning disease etiologies. In this study, nuclear magnetic resonance (NMR) spectroscopy-based metabolomic analysis was used to identify metabolites in neonate cord serum associated with prenatal iAs exposure in participants from the Biomarkers of Exposure to ARsenic (BEAR) pregnancy cohort, in Gómez Palacio, Mexico. Through multivariable linear regression, ten cord serum metabolites were identified as significantly associated with total urinary iAs and/or iAs metabolites, measured as %iAs, %monomethylated arsenicals (MMAs), and %dimethylated arsenicals (DMAs). A total of 17 metabolites were identified as significantly associated with total iAs and/or iAs metabolites in cord serum. These metabolites are indicative of changes in important biochemical pathways such as vitamin metabolism, the citric acid (TCA) cycle, and amino acid metabolism. These data highlight that maternal biotransformation of iAs and neonatal levels of iAs and its metabolites are associated with differences in neonate cord metabolomic profiles. The results demonstrate the potential utility of metabolites as biomarkers/indicators of in utero environmental exposure.}, number={1}, journal={ENVIRONMENTAL SCIENCE & TECHNOLOGY}, author={Laine, Jessica E. and Bailey, Kathryn A. and Olshan, Andrew F. and Smeester, Lisa and Drobna, Zuzana and Styblo, Miroslav and Douillet, Christelle and Garcia-Vargas, Gonzalo and Rubio-Andrade, Marisela and Pathmasiri, Wimal and et al.}, year={2017}, month={Jan}, pages={625–633} }
 @article{grau-perez_kuo_spratlen_thayer_mendez_hamman_dabelea_adgate_knowler_bell_et al._2017, title={The Association of Arsenic Exposure and Metabolism With Type 1 and Type 2 Diabetes in Youth: The SEARCH Case-Control Study}, volume={40}, ISSN={["1935-5548"]}, DOI={10.2337/dc16-0810}, abstractNote={
                  OBJECTIVE
                  Little is known about arsenic and diabetes in youth. We examined the association of arsenic with type 1 and type 2 diabetes in the SEARCH for Diabetes in Youth Case-Control (SEARCH-CC) study. Because one-carbon metabolism can influence arsenic metabolism, we also evaluated the potential interaction of folate and vitamin B12 with arsenic metabolism on the odds of diabetes.
               }, number={1}, journal={DIABETES CARE}, author={Grau-Perez, Maria and Kuo, Chin-Chi and Spratlen, Miranda and Thayer, Kristina A. and Mendez, Michelle A. and Hamman, Richard F. and Dabelea, Dana and Adgate, John L. and Knowler, William C. and Bell, Ronny A. and et al.}, year={2017}, month={Jan}, pages={46–53} }
 @article{drobna_martin_kim_smeester_bommarito_rubio-andrade_garcia-vargas_styblo_zou_fry_2016, title={Analysis of maternal polymorphisms in arsenic (+3 oxidation state)-methyltransferase AS3MT and fetal sex in relation to arsenic metabolism and infant birth outcomes: Implications for risk analysis}, volume={61}, ISSN={["0890-6238"]}, DOI={10.1016/j.reprotox.2016.02.017}, abstractNote={Arsenic (+3 oxidation state) methyltransferase (AS3MT) is the key enzyme in the metabolism of inorganic arsenic (iAs). Polymorphisms of AS3MT influence adverse health effects in adults, but little is known about their role in iAs metabolism in pregnant women and infants. The relationships between seven single nucleotide polymorphisms (SNPs) in AS3MT and urinary concentrations of iAs and its methylated metabolites were assessed in mother-infant pairs of the Biomarkers of Exposure to ARsenic (BEAR) cohort. Maternal alleles for five of the seven SNPs (rs7085104, rs3740400, rs3740393, rs3740390, and rs1046778) were associated with urinary concentrations of iAs metabolites, and alleles for one SNP (rs3740393) were associated with birth outcomes/measures. These associations were strongly dependent upon the male sex of the fetus but independent of fetal genotype for AS3MT. These data highlight a potential sex-dependence of the relationships among maternal genotype, iAs metabolism and infant health outcomes.}, journal={REPRODUCTIVE TOXICOLOGY}, author={Drobna, Zuzana and Martin, Elizabeth and Kim, Kyung Su and Smeester, Lisa and Bommarito, Paige and Rubio-Andrade, Marisela and Garcia-Vargas, Gonzalo G. and Styblo, Miroslav and Zou, Fei and Fry, Rebecca C.}, year={2016}, month={Jun}, pages={28–38} }
 @article{mendez_gonzález-horta_sánchez-ramírez_ballinas-casarrubias_cerón_morales_terrazas_maría_gutiérrez-torres_saunders_et al._2016, title={Arsenic exposure and cardiometabolic risk in Chihuahua, Mexico}, volume={259}, ISSN={0378-4274}, url={http://dx.doi.org/10.1016/J.TOXLET.2016.07.653}, DOI={10.1016/J.TOXLET.2016.07.653}, abstractNote={The Spiking Neural P (SN P) system is defined as a type of parallel computing mechanism bio-inspired by the behavior of the soma. Several authors have been employing these systems in order to create efficient arithmetic divisor circuits exploiting at maximum their intrinsic parallel processing. However, the current neural divisors expend a large amount of neurons with complex spiking rules to synchronize the input information to be processed by the soma. This work proposes a compact neural divisor that uses eight neurons and two type spiking rules per neuron. In addition, the proposed circuit includes the dendrite’s behavior as feedback connections, dendritic delays, reduction in the dendrite length and dendritic pruning into the conventional SN P systems in order to simplify the synchronization of the neural processing carried out by the soma. The results show that the proposed neural divisor can be implemented in embedded neuromorphic circuits. This, potentially allows its use in portable applications such as vision processing systems for mobile robots and cryptographic systems for mobile communication devices.}, journal={Toxicology Letters}, publisher={Elsevier BV}, author={Mendez, M.A. and González-Horta, C. and Sánchez-Ramírez, B. and Ballinas-Casarrubias, L. and Cerón, R. Hernández and Morales, D. Viniegra and Terrazas, F. Baeza and María, C. Ishida and Gutiérrez-Torres, D. and Saunders, R.J. and et al.}, year={2016}, month={Oct}, pages={S32–S33} }
 @article{xu_drobna_voruganti_barron_gonzalez-horta_sanchez-ramirez_ballinas-casarrubias_hernandez ceron_viniegra morales_baeza terrazas_et al._2016, title={Association Between Variants in Arsenic (+3 Oxidation State) Methyltranserase (AS3MT) and Urinary Metabolites of Inorganic Arsenic: Role of Exposure Level}, volume={153}, ISSN={["1096-0929"]}, DOI={10.1093/toxsci/kfw112}, abstractNote={Variants in AS3MT, the gene encoding arsenic (+3 oxidation state) methyltranserase, have been shown to influence patterns of inorganic arsenic (iAs) metabolism. Several studies have suggested that capacity to metabolize iAs may vary depending on levels of iAs exposure. However, it is not known whether the influence of variants in AS3MT on iAs metabolism also vary by level of exposure. We investigated, in a population of Mexican adults exposed to drinking water As, whether associations between 7 candidate variants in AS3MT and urinary iAs metabolites were consistent with prior studies, and whether these associations varied depending on the level of exposure. Overall, associations between urinary iAs metabolites and AS3MT variants were consistent with the literature. Referent genotypes, defined as the genotype previously associated with a higher percentage of urinary dimethylated As (DMAs%), were associated with significant increases in the DMAs% and ratio of DMAs to monomethylated As (MAs), and significant reductions in MAs% and iAs%. For 3 variants, associations between genotypes and iAs metabolism were significantly stronger among subjects exposed to water As >50 versus ≤50 ppb (water As X genotype interaction P < .05). In contrast, for 1 variant (rs17881215), associations were significantly stronger at exposures ≤50 ppb. Results suggest that iAs exposure may influence the extent to which several AS3MT variants affect iAs metabolism. The variants most strongly associated with iAs metabolism-and perhaps with susceptibility to iAs-associated disease-may vary in settings with exposure level.}, number={1}, journal={TOXICOLOGICAL SCIENCES}, author={Xu, Xiaofan and Drobna, Zuzana and Voruganti, V. Saroja and Barron, Keri and Gonzalez-Horta, Carmen and Sanchez-Ramirez, Blanca and Ballinas-Casarrubias, Lourdes and Hernandez Ceron, Roberto and Viniegra Morales, Damian and Baeza Terrazas, Francisco A. and et al.}, year={2016}, month={Sep}, pages={112–123} }
 @article{currier_douillet_drobná_stýblo_2016, title={Oxidation state specific analysis of arsenic species in tissues of wild-type and arsenic (+ 3 oxidation state) methyltransferase-knockout mice}, volume={49}, ISSN={1001-0742}, url={http://dx.doi.org/10.1016/J.JES.2016.06.018}, DOI={10.1016/J.JES.2016.06.018}, abstractNote={Arsenic methyltransferase (As3mt) catalyzes the conversion of inorganic arsenic (iAs) to its methylated metabolites, including toxic methylarsonite (MAsIII) and dimethylarsinite (DMAsIII). Knockout (KO) of As3mt was shown to reduce the capacity to methylate iAs in mice. However, no data are available on the oxidation states of As species in tissues of these mice. Here, we compare the oxidation states of As species in tissues of male C57BL/6 As3mt-KO and wild-type (WT) mice exposed to arsenite (iAsIII) in drinking water. WT mice were exposed to 50 mg/L As and As3mt-KO mice that cannot tolerate 50 mg/L As were exposed to 0, 15, 20, 25 or 30 mg/L As. iAsIII accounted for 53% to 74% of total As in liver, pancreas, adipose, lung, heart, and kidney of As3mt-KO mice; tri- and pentavalent methylated arsenicals did not exceed 10% of total As. Tissues of WT mice retained iAs and methylated arsenicals: iAsIII, MAsIII and DMAsIII represented 55%‐68% of the total As in the liver, pancreas, and brain. High levels of methylated species, particularly MAsIII, were found in the intestine of WT, but not As3mt-KO mice, suggesting that intestinal bacteria are not a major source of methylated As. Blood of WT mice contained significantly higher levels of As than blood of As3mt-KO mice. This study is the first to determine oxidation states of As species in tissues of As3mt-KO mice. Results will help to design studies using WT and As3mt-KO mice to examine the role of iAs methylation in adverse effects of iAs exposure.}, journal={Journal of Environmental Sciences}, publisher={Elsevier BV}, author={Currier, Jenna M. and Douillet, Christelle and Drobná, Zuzana and Stýblo, Miroslav}, year={2016}, month={Nov}, pages={104–112} }
 @article{rager_tilley_tulenko_smeester_ray_yosim_currier_ishida_gonzález-horta_sánchez-ramírez_et al._2015, title={Identification of Novel Gene Targets and Putative Regulators of Arsenic-Associated DNA Methylation in Human Urothelial Cells and Bladder Cancer}, volume={28}, ISSN={0893-228X 1520-5010}, url={http://dx.doi.org/10.1021/TX500393Y}, DOI={10.1021/TX500393Y}, abstractNote={There is strong epidemiologic evidence linking chronic exposure to inorganic arsenic (iAs) to myriad adverse health effects, including cancer of the bladder. We set out to identify DNA methylation patterns associated with arsenic and its metabolites in exfoliated urothelial cells (EUCs) that originate primarily from the urinary bladder, one of the targets of arsenic-induced carcinogenesis. Genome-wide, gene-specific promoter DNA methylation levels were assessed in EUCs from 46 residents of Chihuahua, Mexico, and the relationship was examined between promoter methylation profiles and the intracellular concentrations of total arsenic and arsenic species. A set of 49 differentially methylated genes was identified with increased promoter methylation associated with EUC tAs, iAs, and/or monomethylated As (MMAs) enriched for their roles in metabolic disease and cancer. Notably, no genes had differential methylation associated with EUC dimethylated As (DMAs), suggesting that DMAs may influence DNA methylation-mediated urothelial cell responses to a lesser extent than iAs or MMAs. Further analysis showed that 22 of the 49 arsenic-associated genes (45%) are also differentially methylated in bladder cancer tissue identified using The Cancer Genome Atlas repository. Both the arsenic- and cancer-associated genes are enriched for the binding sites of common transcription factors known to play roles in carcinogenesis, demonstrating a novel potential mechanistic link between iAs exposure and bladder cancer.}, number={6}, journal={Chemical Research in Toxicology}, publisher={American Chemical Society (ACS)}, author={Rager, Julia E. and Tilley, Sloane K. and Tulenko, Samantha E. and Smeester, Lisa and Ray, Paul D. and Yosim, Andrew and Currier, Jenna M. and Ishida, María C. and González-Horta, Maria del Carmen and Sánchez-Ramírez, Blanca and et al.}, year={2015}, month={Jun}, pages={1144–1155} }
 @article{bailey_wu_ward_smeester_rager_garcía-vargas_del razo_drobná_stýblo_fry_2013, title={Arsenic and the Epigenome: Interindividual Differences in Arsenic Metabolism Related to Distinct Patterns of DNA Methylation}, volume={27}, ISSN={1095-6670}, url={http://dx.doi.org/10.1002/jbt.21462}, DOI={10.1002/jbt.21462}, abstractNote={ABSTRACT}, number={2}, journal={Journal of Biochemical and Molecular Toxicology}, publisher={Wiley}, author={Bailey, Kathryn A. and Wu, Michael C. and Ward, William O. and Smeester, Lisa and Rager, Julia E. and García-Vargas, Gonzalo and Del Razo, Luz-Maria and Drobná, Zuzana and Stýblo, Miroslav and Fry, Rebecca C.}, year={2013}, month={Jan}, pages={106–115} }
 @article{rager_bailey_smeester_miller_parker_laine_drobná_currier_douillet_olshan_et al._2013, title={Prenatal arsenic exposure and the epigenome: Altered microRNAs associated with innate and adaptive immune signaling in newborn cord blood}, volume={55}, ISSN={0893-6692}, url={http://dx.doi.org/10.1002/EM.21842}, DOI={10.1002/EM.21842}, abstractNote={The Biomarkers of Exposure to ARsenic (BEAR) pregnancy cohort in Gómez Palacio, Mexico was recently established to better understand the impacts of prenatal exposure to inorganic arsenic (iAs). In this study, we examined a subset (n = 40) of newborn cord blood samples for microRNA (miRNA) expression changes associated with in utero arsenic exposure. Levels of iAs in maternal drinking water (DW‐iAs) and maternal urine were assessed. Levels of DW‐iAs ranged from below detectable values to 236 µg/L (mean = 51.7 µg/L). Total arsenic in maternal urine (U‐tAs) was defined as the sum of iAs and its monomethylated and dimethylated metabolites (MMAs and DMAs, respectively) and ranged from 6.2 to 319.7 µg/L (mean = 64.5 µg/L). Genome‐wide miRNA expression analysis of cord blood revealed 12 miRNAs with increasing expression associated with U‐tAs. Transcriptional targets of the miRNAs were computationally predicted and subsequently assessed using transcriptional profiling. Pathway analysis demonstrated that the U‐tAs‐associated miRNAs are involved in signaling pathways related to known health outcomes of iAs exposure including cancer and diabetes mellitus. Immune response‐related mRNAs were also identified with decreased expression levels associated with U‐tAs, and predicted to be mediated in part by the arsenic‐responsive miRNAs. Results of this study highlight miRNAs as novel responders to prenatal arsenic exposure that may contribute to associated immune response perturbations. Environ. Mol. Mutagen. 55:196–208, 2014. © 2013 The Authors. Environmental and Molecular Mutagenesis Published by Wiley Periodicals, Inc.}, number={3}, journal={Environmental and Molecular Mutagenesis}, publisher={Wiley}, author={Rager, Julia E. and Bailey, Kathryn A. and Smeester, Lisa and Miller, Sloane K. and Parker, Joel S. and Laine, Jessica E. and Drobná, Zuzana and Currier, Jenna and Douillet, Christelle and Olshan, Andrew F. and et al.}, year={2013}, month={Dec}, pages={196–208} }
 @article{drobná_del razo_garcía-vargas_sánchez-peña_barrera-hernández_stýblo_loomis_2012, title={Environmental exposure to arsenic, AS3MT polymorphism and prevalence of diabetes in Mexico}, volume={23}, ISSN={1559-0631 1559-064X}, url={http://dx.doi.org/10.1038/jes.2012.103}, DOI={10.1038/jes.2012.103}, abstractNote={Exposure to arsenic in drinking water is associated with increased prevalence of diabetes. We previously reported an association of diabetes and urinary concentration of dimethylarsinite (DMAs(III)), a toxic product of arsenic methylation by arsenic (+3 oxidation state) methyltransferase (AS3MT). Here we examine associations between AS3MT polymorphism, arsenic metabolism and diabetes. Fasting blood glucose, oral glucose tolerance and self-reported diagnoses were used to identify diabetic individuals. Inorganic arsenic and its metabolites were measured in urine. Genotyping analysis focused on six polymorphic sites of AS3MT. Individuals with M287T and G4965C polymorphisms had higher levels of urinary DMAs(III) and were more frequently diabetic than the respective wild-type carriers, although the excess was not statistically significant. Odds ratios were 11.4 (95% confidence interval (CI) 2.2-58.8) and 8.8 (95% CI 1.6-47.3) for the combined effects of arsenic exposure >75th percentile and 287T and 4965C genotypes, respectively. Carriers of 287T and 4965C may produce more DMAs(III) and be more likely to develop diabetes when exposed to arsenic.}, number={2}, journal={Journal of Exposure Science & Environmental Epidemiology}, publisher={Springer Science and Business Media LLC}, author={Drobná, Zuzana and Del Razo, Luz M and García-Vargas, Gonzalo G and Sánchez-Peña, Luz C and Barrera-Hernández, Angel and Stýblo, Miroslav and Loomis, Dana}, year={2012}, month={Oct}, pages={151–155} }
 @article{ding_saunders_drobná_walton_xun_thomas_stýblo_2012, title={Methylation of arsenic by recombinant human wild-type arsenic (+3 oxidation state) methyltransferase and its methionine 287 threonine (M287T) polymorph: Role of glutathione}, volume={264}, ISSN={0041-008X}, url={http://dx.doi.org/10.1016/j.taap.2012.07.024}, DOI={10.1016/j.taap.2012.07.024}, abstractNote={Arsenic (+3 oxidation state) methyltransferase (AS3MT) is the key enzyme in the pathway for methylation of arsenicals. A common polymorphism in the AS3MT gene that replaces a threonyl residue in position 287 with a methionyl residue (AS3MT/M287T) occurs at a frequency of about 10% among populations worldwide. Here, we compared catalytic properties of recombinant human wild-type (wt) AS3MT and AS3MT/M287T in reaction mixtures containing S-adenosylmethionine, arsenite (iAs(III)) or methylarsonous acid (MAs(III)) as substrates and endogenous or synthetic reductants, including glutathione (GSH), a thioredoxin reductase (TR)/thioredoxin (Trx)/NADPH reducing system, or tris (2-carboxyethyl) phosphine hydrochloride (TCEP). With either TR/Trx/NADPH or TCEP, wtAS3MT or AS3MT/M287T catalyzed conversion of iAs(III) to MAs(III), methylarsonic acid (MAs(V)), dimethylarsinous acid (DMAs(III)), and dimethylarsinic acid (DMAs(V)); MAs(III) was converted to DMAs(III) and DMAs(V). Although neither enzyme required GSH to support methylation of iAs(III) or MAs(III), addition of 1mM GSH decreased K(m) and increased V(max) estimates for either substrate in reaction mixtures containing TR/Trx/NADPH. Without GSH, V(max) and K(m) values were significantly lower for AS3MT/M287T than for wtAS3MT. In the presence of 1mM GSH, significantly more DMAs(III) was produced from iAs(III) in reactions catalyzed by the M287T variant than in wtAS3MT-catalyzed reactions. Thus, 1mM GSH modulates AS3MT activity, increasing both methylation rates and yield of DMAs(III). AS3MT genotype exemplified by differences in regulation of wtAS3MT and AS3MT/M287T-catalyzed reactions by GSH may contribute to differences in the phenotype for arsenic methylation and, ultimately, to differences in the disease susceptibility in individuals chronically exposed to inorganic arsenic.}, number={1}, journal={Toxicology and Applied Pharmacology}, publisher={Elsevier BV}, author={Ding, Lan and Saunders, R. Jesse and Drobná, Zuzana and Walton, Felecia S. and Xun, Pencheng and Thomas, David J. and Stýblo, Miroslav}, year={2012}, month={Oct}, pages={121–130} }
 @article{tsang_fry_niculescu_rager_saunders_paul_zeisel_waalkes_stýblo_drobná_2012, title={The epigenetic effects of a high prenatal folate intake in male mouse fetuses exposed in utero to arsenic}, volume={264}, ISSN={0041-008X}, url={http://dx.doi.org/10.1016/j.taap.2012.08.022}, DOI={10.1016/j.taap.2012.08.022}, abstractNote={Inorganic arsenic (iAs) is a complete transplacental carcinogen in mice. Previous studies have demonstrated that in utero exposure to iAs promotes cancer in adult mouse offspring, possibly acting through epigenetic mechanisms. Humans and rodents enzymatically convert iAs to its methylated metabolites. This reaction requires S-adenosylmethionine (SAM) as methyl group donor. SAM is also required for DNA methylation. Supplementation with folate, a major dietary source of methyl groups for SAM synthesis, has been shown to modify iAs metabolism and the adverse effects of iAs exposure. However, effects of gestational folate supplementation on iAs metabolism and fetal DNA methylation have never been thoroughly examined. In the present study, pregnant CD1 mice were fed control (i.e. normal folate, or 2.2 mg/kg) or high folate diet (11 mg/kg) from gestational day (GD) 5 to 18 and drank water with 0 or 85 ppm of As (as arsenite) from GD8 to 18. The exposure to iAs significantly decreased body weight of GD18 fetuses and increased both SAM and S-adenosylhomocysteine (SAH) concentrations in fetal livers. High folate intake lowered the burden of total arsenic in maternal livers but did not prevent the effects of iAs exposure on fetal weight or hepatic SAM and SAH concentrations. In fact, combined folate-iAs exposure caused further significant body weight reduction. Notably, iAs exposure alone had little effect on DNA methylation in fetal livers. In contrast, the combined folate-iAs exposure changed the CpG island methylation in 2,931 genes, including genes known to be imprinted. Most of these genes were associated with neurodevelopment, cancer, cell cycle, and signaling networks. The canonical Wnt-signaling pathway, which regulates fetal development, was among the most affected biological pathways. Taken together, our results suggest that a combined in utero exposure to iAs and a high folate intake may adversely influence DNA methylation profiles and weight of fetuses, compromising fetal development and possibly increasing the risk for early-onset of disease in offspring.}, number={3}, journal={Toxicology and Applied Pharmacology}, publisher={Elsevier BV}, author={Tsang, Verne and Fry, Rebecca C. and Niculescu, Mihai D. and Rager, Julia E. and Saunders, Jesse and Paul, David S. and Zeisel, Steven H. and Waalkes, Michael P. and Stýblo, Miroslav and Drobná, Zuzana}, year={2012}, month={Nov}, pages={439–450} }
 @article{smeester_rager_bailey_guan_smith_garcía-vargas gonzalo_del razo_drobná zuzana_kelkar_stýblo miroslav_et al._2011, title={Epigenetic Changes in Individuals with Arsenicosis}, volume={24}, ISSN={0893-228X 1520-5010}, url={http://dx.doi.org/10.1021/tx1004419}, DOI={10.1021/tx1004419}, abstractNote={Inorganic arsenic (iAs) is an environmental toxicant currently poisoning millions of people worldwide, and chronically exposed individuals are susceptible to arsenicosis or arsenic poisoning. Using a state-of-the-art technique to map the methylomes of our study subjects, we identified a large interactome of hypermethylated genes that are enriched for their involvement in arsenic-associated diseases, such as cancer, heart disease, and diabetes. Notably, we have uncovered an arsenic-induced tumor suppressorome, a complex of 17 tumor suppressors known to be silenced in human cancers. This finding represents a pivotal clue in unraveling a possible epigenetic mode of arsenic-induced disease.}, number={2}, journal={Chemical Research in Toxicology}, publisher={American Chemical Society (ACS)}, author={Smeester, Lisa and Rager, Julia E. and Bailey, Kathryn A. and Guan, Xiaojun and Smith, Nikia and García-Vargas Gonzalo and Del Razo, Luz-Maria and Drobná Zuzana and Kelkar, Hemant and Stýblo Miroslav and et al.}, year={2011}, month={Feb}, pages={165–167} }
 @article{drobná_del razo_garcia-vargas_sánchez-ramírez_gonzález-horta_ballinas-casarrubias_loomis_stýblo_2011, title={Identification of theGST-T1andGST-M1Null Genotypes Using High Resolution Melting Analysis}, volume={25}, ISSN={0893-228X 1520-5010}, url={http://dx.doi.org/10.1021/tx200457u}, DOI={10.1021/tx200457u}, abstractNote={Glutathione S-transferases, including GST-T1 and GST-M1, are known to be involved in the phase II detoxification pathways for xenobiotics as well as in the metabolism of endogenous compounds. Polymorphisms in these genes have been linked to an increased susceptibility to carcinogenesis and associated with risk factors that predispose to certain inflammatory diseases. In addition, GST-T1 and GST-M1 null genotypes have been shown to be responsible for interindividual variations in the metabolism of arsenic, a known human carcinogen. To assess the specific GST genotypes in the Mexican population chronically exposed to arsenic, we have developed a multiplex High Resolution Melting PCR (HRM-PCR) analysis using a LightCycler480 instrument. This method is based on analysis of the PCR product melting curve that discriminates PCR products according to their lengths and base sequences. Three pairs of primers that specifically recognize GST-T1, GST-M1, and β-globin, an internal control, to produce amplicons of different length were designed and combined with LightCycler480 High Resolution Melting Master Mix containing ResoLight, a completely saturating DNA dye. Data collected from melting curve analysis were evaluated using LightCycler480 software to determine specific melting temperatures of individual melting curves representing target genes. Using this newly developed multiplex HRM-PCR analysis, we evaluated GST-T1 and GST-M1 genotypes in 504 DNA samples isolated from the blood of individuals residing in Zimapan, Lagunera, and Chihuahua regions in Mexico. We found that the Zimapan and Lagunera populations have similar GST-T1 and GST-M1 genotype frequencies which differ from those of the Chihuahua population. In addition, 14 individuals have been identified as carriers of the double null genotype, i.e., null genotypes in both GST-T1 and GST-M1 genes. Although this procedure does not distinguish between biallelic (+/+) and monoallelic (+/-) genotypes, it can be used in an automated workflow as a simple, sensitive, and time and money saving procedure for rapid identification of the GST-T1 and GST-M1 positive or null genotypes.}, number={1}, journal={Chemical Research in Toxicology}, publisher={American Chemical Society (ACS)}, author={Drobná, Zuzana and Del Razo, Luz Maria and Garcia-Vargas, Gonzalo and Sánchez-Ramírez, Blanca and González-Horta, Carmen and Ballinas-Casarrubias, Lourdes and Loomis, Dana and Stýblo, Miroslav}, year={2011}, month={Dec}, pages={216–224} }
 @article{drobná_walton_harmon_thomas_stýblo_2010, title={Interspecies differences in metabolism of arsenic by cultured primary hepatocytes}, volume={245}, ISSN={0041-008X}, url={http://dx.doi.org/10.1016/j.taap.2010.01.015}, DOI={10.1016/j.taap.2010.01.015}, abstractNote={Biomethylation is the major pathway for the metabolism of inorganic arsenic (iAs) in many mammalian species, including the human. However, significant interspecies differences have been reported in the rate of in vivo metabolism of iAs and in yields of iAs metabolites found in urine. Liver is considered the primary site for the methylation of iAs and arsenic (+3 oxidation state) methyltransferase (As3mt) is the key enzyme in this pathway. Thus, the As3mt-catalyzed methylation of iAs in the liver determines in part the rate and the pattern of iAs metabolism in various species. We examined kinetics and concentration–response patterns for iAs methylation by cultured primary hepatocytes derived from human, rat, mice, dog, rabbit, and rhesus monkey. Hepatocytes were exposed to [73As]arsenite (iAsIII; 0.3, 0.9, 3.0, 9.0 or 30 nmol As/mg protein) for 24 h and radiolabeled metabolites were analyzed in cells and culture media. Hepatocytes from all six species methylated iAsIII to methylarsenic (MAs) and dimethylarsenic (DMAs). Notably, dog, rat and monkey hepatocytes were considerably more efficient methylators of iAsIII than mouse, rabbit or human hepatocytes. The low efficiency of mouse, rabbit and human hepatocytes to methylate iAsIII was associated with inhibition of DMAs production by moderate concentrations of iAsIII and with retention of iAs and MAs in cells. No significant correlations were found between the rate of iAs methylation and the thioredoxin reductase activity or glutathione concentration, two factors that modulate the activity of recombinant As3mt. No associations between the rates of iAs methylation and As3mt protein structures were found for the six species examined. Immunoblot analyses indicate that the superior arsenic methylation capacities of dog, rat and monkey hepatocytes examined in this study may be associated with a higher As3mt expression. However, factors other than As3mt expression may also contribute to the interspecies differences in the hepatocyte capacity to methylate iAs.}, number={1}, journal={Toxicology and Applied Pharmacology}, publisher={Elsevier BV}, author={Drobná, Zuzana and Walton, Felecia S. and Harmon, Anne W. and Thomas, David J. and Stýblo, Miroslav}, year={2010}, month={May}, pages={47–56} }
 @article{valenzuela_drobná_hernández-castellanos_sánchez-peña_garcía-vargas_borja-aburto_stýblo_del razo_2009, title={Association of AS3MT polymorphisms and the risk of premalignant arsenic skin lesions}, volume={239}, ISSN={0041-008X}, url={http://dx.doi.org/10.1016/j.taap.2009.06.007}, DOI={10.1016/j.taap.2009.06.007}, abstractNote={Exposure to naturally occurring inorganic arsenic (iAs), primarily from contaminated drinking water, is considered one of the top environmental health threats worldwide. Arsenic (+3 oxidation state) methyltransferase (AS3MT) is the key enzyme in the biotransformation pathway of iAs. AS3MT catalyzes the transfer of a methyl group from S-adenosyl-L-methionine to trivalent arsenicals, resulting in the production of methylated (MAs) and dimethylated arsenicals (DMAs). MAs is a susceptibility factor for iAs-induced toxicity. In this study, we evaluated the association of the polymorphism in AS3MT gene with iAs metabolism and with the presence of arsenic (As) premalignant skin lesions. This is a case-control study of 71 cases with skin lesions and 51 controls without skin lesions recruited from a iAs endemic area in Mexico. We measured urinary As metabolites, differentiating the trivalent and pentavalent arsenical species, using the hydride generation atomic absorption spectrometry. In addition, the study subjects were genotyped to analyze three single nucleotide polymorphisms (SNPs), A-477G, T14458C (nonsynonymus SNP; Met287Thr), and T35587C, in the AS3MT gene. We compared the frequencies of the AS3MT alleles, genotypes, and haplotypes in individuals with and without skin lesions. Marginal differences in the frequencies of the Met287Thr genotype were identified between individuals with and without premalignant skin lesions (p=0.055): individuals carrying the C (TC+CC) allele (Thr) were at risk [odds ratio=4.28; 95% confidence interval (1.0-18.5)]. Also, individuals with C allele of Met287Thr displayed greater percentage of MAs in urine and decrease in the percentage of DMAs. These findings indicate that Met287Thr influences the susceptibility to premalignant As skin lesions and might be at increased risk for other adverse health effects of iAs exposure.}, number={2}, journal={Toxicology and Applied Pharmacology}, publisher={Elsevier BV}, author={Valenzuela, Olga L. and Drobná, Zuzana and Hernández-Castellanos, Erika and Sánchez-Peña, Luz C. and García-Vargas, Gonzalo G. and Borja-Aburto, Víctor H. and Stýblo, Miroslav and Del Razo, Luz M.}, year={2009}, month={Sep}, pages={200–207} }
 @article{drobna_naranmandura_kubachka_edwards_herbin-davis_styblo_le_creed_maeda_hughes_et al._2009, title={Disruption of the Arsenic (+3 Oxidation State) Methyltransferase Gene in the Mouse Alters the Phenotype for Methylation of Arsenic and Affects Distribution and Retention of Orally Administered Arsenate}, volume={22}, ISSN={0893-228X 1520-5010}, url={http://dx.doi.org/10.1021/tx900179r}, DOI={10.1021/tx900179r}, abstractNote={The arsenic (+3 oxidation state) methyltransferase (As3mt) gene encodes a 43 kDa protein that catalyzes methylation of inorganic arsenic. Altered expression of AS3MT in cultured human cells controls arsenic methylation phenotypes, suggesting a critical role in arsenic metabolism. Because methylated arsenicals mediate some toxic or carcinogenic effects linked to inorganic arsenic exposure, studies of the fate and effects of arsenicals in mice which cannot methylate arsenic could be instructive. This study compared retention and distribution of arsenic in As3mt knockout mice and in wild-type C57BL/6 mice in which expression of the As3mt gene is normal. Male and female mice of either genotype received an oral dose of 0.5 mg of arsenic as arsenate per kg containing [(73)As]-arsenate. Mice were radioassayed for up to 96 h after dosing; tissues were collected at 2 and 24 h after dosing. At 2 and 24 h after dosing, livers of As3mt knockouts contained a greater proportion of inorganic and monomethylated arsenic than did livers of C57BL/6 mice. A similar predominance of inorganic and monomethylated arsenic was found in the urine of As3mt knockouts. At 24 h after dosing, As3mt knockouts retained significantly higher percentages of arsenic dose in liver, kidneys, urinary bladder, lungs, heart, and carcass than did C57BL/6 mice. Whole body clearance of [(73)As] in As3mt knockouts was substantially slower than in C57BL/6 mice. At 24 h after dosing, As3mt knockouts retained about 50% and C57BL/6 mice about 6% of the dose. After 96 h, As3mt knockouts retained about 20% and C57BL/6 mice retained less than 2% of the dose. These data confirm a central role for As3mt in the metabolism of inorganic arsenic and indicate that phenotypes for arsenic retention and distribution are markedly affected by the null genotype for arsenic methylation, indicating a close linkage between the metabolism and retention of arsenicals.}, number={10}, journal={Chemical Research in Toxicology}, publisher={American Chemical Society (ACS)}, author={Drobna, Zuzana and Naranmandura, Hua and Kubachka, Kevin M. and Edwards, Brenda C. and Herbin-Davis, Karen and Styblo, Miroslav and Le, X. Chris and Creed, John T. and Maeda, Noboyu and Hughes, Michael F. and et al.}, year={2009}, month={Oct}, pages={1713–1720} }
 @article{drobná_walton_paul_xing_thomas_stýblo_2009, title={Metabolism of arsenic in human liver: the role of membrane transporters}, volume={84}, ISSN={0340-5761 1432-0738}, url={http://dx.doi.org/10.1007/S00204-009-0499-7}, DOI={10.1007/S00204-009-0499-7}, abstractNote={Metabolism of inorganic arsenic (iAs) is one of the key factors determining the character of adverse effects associated with exposure to iAs. Results of previous studies indicate that liver plays a primary role in iAs metabolism. This paper reviews these results and presents new data that link the capacity of human hepatocytes to metabolize iAs to the expression of specific membrane transporters. Here, we examined relationship between the expression of potential arsenic transporters (AQP9, GLUT2, P-gp, MRP1, MRP2, and MRP3) and the production and cellular retention of iAs and its methylated metabolites in primary cultures of human hepatocytes exposed for 24 h to subtoxic concentrations of arsenite. Our results show that the retention of iAs and methylarsenic metabolites (MAs) by hepatocytes exposed to sub-micromolar concentrations of arsenite correlates negatively with MRP2 expression. A positive correlation was found between MRP2 expression and the production of dimethylarsenic metabolites (DMAs), specifically, the concentration of DMAs in culture media. After exposures to high micromolar concentrations of arsenite which almost completely inhibited MAs and DMAs production, a positive correlation was found between the expression of GLUT2 and cellular retention of iAs and MAs. MRP3, AQP9, or P-gp expression had no effect on the production or distribution of iAs, MAs, or DMAs, regardless of the exposure level. Hepatocytes from seven donors used in this study did not contain detectable amounts of MRP1 protein. These data suggest that MRP2 plays an important role in the efflux of DMAs, thus, regulating kinetics of the methylation reactions and accumulation of iAs and MAs by human hepatocytes. The membrane transport of iAs by high-capacity GLUT2 transporters is not a rate-limiting step for the metabolism of arsenite at low exposure level, but may play a key role in accumulation of iAs after acute exposures which inhibit iAs methylation.}, number={1}, journal={Archives of Toxicology}, publisher={Springer Science and Business Media LLC}, author={Drobná, Zuzana and Walton, Felecia S. and Paul, David S. and Xing, Weibing and Thomas, David J. and Stýblo, Miroslav}, year={2009}, month={Dec}, pages={3–16} }
 @article{matoušek_hernández-zavala_svoboda_langrová_adair_drobná_thomas_stýblo_dědina_2008, title={Oxidation state specific generation of arsines from methylated arsenicals based on l-cysteine treatment in buffered media for speciation analysis by hydride generation-automated cryotrapping-gas chromatography-atomic absorption spectrometry with the multiatomizer}, volume={63}, ISSN={0584-8547}, url={http://dx.doi.org/10.1016/j.sab.2007.11.037}, DOI={10.1016/j.sab.2007.11.037}, abstractNote={An automated system for hydride generation - cryotrapping- gas chromatography - atomic absorption spectrometry with the multiatomizer is described. Arsines are preconcentrated and separated in a Chromosorb filled U-tube. An automated cryotrapping unit, employing nitrogen gas formed upon heating in the detection phase for the displacement of the cooling liquid nitrogen, has been developed. The conditions for separation of arsines in a Chromosorb filled U-tube have been optimized. A complete separation of signals from arsine, methylarsine, dimethylarsine, and trimethylarsine has been achieved within a 60 s reading window. The limits of detection for methylated arsenicals tested were 4 ng l(-1). Selective hydride generation is applied for the oxidation state specific speciation analysis of inorganic and methylated arsenicals. The arsines are generated either exclusively from trivalent or from both tri- and pentavalent inorganic and methylated arsenicals depending on the presence of L-cysteine as a prereductant and/or reaction modifier. A TRIS buffer reaction medium is proposed to overcome narrow optimum concentration range observed for the L-cysteine modified reaction in HCl medium. The system provides uniform peak area sensitivity for all As species. Consequently, the calibration with a single form of As is possible. This method permits a high-throughput speciation analysis of metabolites of inorganic arsenic in relatively complex biological matrices such as cell culture systems without sample pretreatment, thus preserving the distribution of tri- and pentavalent species.}, number={3}, journal={Spectrochimica Acta Part B: Atomic Spectroscopy}, publisher={Elsevier BV}, author={Matoušek, Tomáš and Hernández-Zavala, Araceli and Svoboda, Milan and Langrová, Lenka and Adair, Blakely M. and Drobná, Zuzana and Thomas, David J. and Stýblo, Miroslav and Dědina, Jiří}, year={2008}, month={Mar}, pages={396–406} }
 @article{hernández-zavala_matoušek_drobná_paul_walton_adair_dědina_thomas_stýblo_2008, title={Speciation analysis of arsenic in biological matrices by automated hydride generation-cryotrapping-atomic absorption spectrometry with multiple microflame quartz tube atomizer (multiatomizer)}, volume={23}, ISSN={0267-9477 1364-5544}, url={http://dx.doi.org/10.1039/b706144g}, DOI={10.1039/b706144g}, abstractNote={Analyses of arsenic (As) species in tissues and body fluids of individuals chronically exposed to inorganic arsenic (iAs) provide essential information about the exposure level and pattern of iAs metabolism. We have previously described an oxidation state-specific analysis of As species in biological matrices by hydride-generation atomic absorption spectrometry (HG-AAS), using cryotrapping (CT) for preconcentration and separation of arsines. To improve performance and detection limits of the method, HG and CT steps are automated and a conventional flame-in-tube atomizer replaced with a recently developed multiple microflame quartz tube atomizer (multiatomizer). In this system, arsines from As(III)-species are generated in a mixture of Tris-HCl (pH 6) and sodium borohydride. For generation of arsines from both As(III)- and As(V)-species, samples are pretreated with L-cysteine. Under these conditions, dimethylthioarsinic acid, a newly described metabolite of iAs, does not interfere significantly with detection and quantification of methylated trivalent arsenicals. Analytical performance of the automated HG-CT-AAS was characterized by analyses of cultured cells and mouse tissues that contained mono- and dimethylated metabolites of iAs. The capacity to detect methylated As(III)- and As(V)-species was verified, using an in vitro methylation system containing recombinant rat arsenic (+3 oxidation state) methyltransferase and cultured rat hepatocytes treated with iAs. Compared with the previous HG-CT-AAS design, detection limits for iAs and its metabolites have improved significantly with the current system, ranging from 8 to 20 pg. Recoveries of As were between 78 and 117%. The precision of the method was better than 5% for all biological matrices examined. Thus, the automated HG-CT-AAS system provides an effective and sensitive tool for analysis of all major human metabolites of iAs in complex biological matrices.}, number={3}, journal={J. Anal. At. Spectrom.}, publisher={Royal Society of Chemistry (RSC)}, author={Hernández-Zavala, Araceli and Matoušek, Tomáš and Drobná, Zuzana and Paul, David S. and Walton, Felecia and Adair, Blakely M. and Dědina, Jiří and Thomas, David J. and Stýblo, Miroslav}, year={2008}, pages={342–351} }
 @article{drobná_xing_thomas_stýblo_2006, title={shRNA Silencing of AS3MT Expression Minimizes Arsenic Methylation Capacity of HepG2 Cells}, volume={19}, ISSN={0893-228X 1520-5010}, url={http://dx.doi.org/10.1021/tx060076u}, DOI={10.1021/tx060076u}, abstractNote={Several methyltransferases have been shown to catalyze the oxidative methylation of inorganic arsenic (iAs) in mammalian species. However, the relative contributions of these enzymes to the overall capacity of cells to methylate iAs have not been characterized. Arsenic (+3 oxidation state) methyltransferase (AS3MT) that is expressed in rat and human hepatocytes catalyzes the conversion of iAs, yielding methylated metabolites that contain arsenic in +3 or +5 oxidation states. This study used short hairpin RNA (shRNA) to knock down AS3MT expression in human hepatocellular carcinoma (HepG2) cells. In a stable clonal HepG2/A cell line, AS3MT mRNA and protein levels were reduced by 83 and 88%, respectively. In comparison, the capacity to methylate iAs decreased only by 70%. These data suggest that AS3MT is the major enzyme in this pathway, although an AS3MT-independent process may contribute to iAs methylation in human hepatic cells.}, number={7}, journal={Chemical Research in Toxicology}, publisher={American Chemical Society (ACS)}, author={Drobná, Zuzana and Xing, Weibing and Thomas, David J. and Stýblo, Miroslav}, year={2006}, month={Jul}, pages={894–898} }
 @article{li_waters_drobna_devesa_styblo_thomas_2005, title={Arsenic (+3 oxidation state) methyltransferase and the inorganic arsenic methylation phenotype}, volume={204}, ISSN={0041-008X}, url={http://dx.doi.org/10.1016/j.taap.2004.12.002}, DOI={10.1016/j.taap.2004.12.002}, abstractNote={Inorganic arsenic is enzymatically methylated; hence, its ingestion results in exposure to the parent compound and various methylated arsenicals. Both experimental and epidemiological evidences suggest that some of the adverse health effects associated with chronic exposure to inorganic arsenic may be mediated by these methylated metabolites. If iAs methylation is an activation process, then the phenotype for inorganic arsenic methylation may determine risk associated with exposure to this metalloid. We examined inorganic arsenic methylation phenotypes and arsenic (+3 oxidation state) methyltransferase genotypes in four species: three that methylate inorganic arsenic (human (Homo sapiens), rat (Rattus norwegicus), and mouse (Mus musculus)) and one that does not methylate inorganic arsenic (chimpanzee, Pan troglodytes). The predicted protein products from arsenic (+3 oxidation state) methyltransferase are similar in size for rat (369 amino acid residues), mouse (376 residues), and human (375 residues). By comparison, a 275-nucleotide deletion beginning at nucleotide 612 in the chimpanzee gene sequence causes a frameshift that leads to a nonsense mutation for a premature stop codon after amino acid 205. The null phenotype for inorganic arsenic methylation in the chimpanzee is likely due to the deletion in the gene for arsenic (+3 oxidation state) methyltransferase that yields an inactive truncated protein. This lineage-specific loss of function caused by the deletion event must have occurred in the Pan lineage after Homo-Pan divergence about 5 million years ago.}, number={2}, journal={Toxicology and Applied Pharmacology}, publisher={Elsevier BV}, author={Li, Jiaxin and Waters, Stephen B. and Drobna, Zuzana and Devesa, Vicenta and Styblo, Miroslav and Thomas, David J.}, year={2005}, month={Apr}, pages={164–169} }
 @article{adair_waters_devesa_drobna_styblo_thomas_2005, title={Commonalities in Metabolism of Arsenicals}, volume={2}, ISSN={1448-2517}, url={http://dx.doi.org/10.1071/EN05054}, DOI={10.1071/EN05054}, abstractNote={Environmental Context. Health effects associated with inorganic arsenic include various cancers and increased risk of diabetes. Millions of people in Bangladesh and India are at risk through use of contaminated drinking water. When humans ingest inorganic arsenic, it is rapidly converted to methylated metabolites. Although this methylation process is largely understood, the metabolism of other arsenicals (e.g. arsenosugars to dimethylarsenic) is very unclear. Connections among pathways for metabolism of various arsenicals are now being elucidated. Commonalities and differences in these pathways may be important determinants of the risk associated with exposure to these agents. Abstract. Elucidating the pathway of inorganic arsenic metabolism shows that some of methylated arsenicals formed as intermediates and products are reactive and toxic species. Hence, methylated arsenicals likely mediate at least some of the toxic and carcinogenic effects associated with exposure to arsenic. Trimethylarsonium compounds and arsenosugars are two other classes of arsenicals to which humans are routinely exposed and there is evidence that both classes are metabolized to produce methylated arsenicals. Here, we review evidence for production of methylated metabolism and consider the challenges posed in unraveling a complex web for metabolism of arsenicals in humans.}, number={3}, journal={Environmental Chemistry}, publisher={CSIRO Publishing}, author={Adair, Blakely M. and Waters, Stephen B. and Devesa, Vicenta and Drobna, Zuzana and Styblo, Miroslav and Thomas, David J.}, year={2005}, pages={161} }
 @article{drobna_waters_devesa_harmon_thomas_styblo_2005, title={Metabolism and toxicity of arsenic in human urothelial cells expressing rat arsenic (+3 oxidation state)-methyltransferase}, volume={207}, ISSN={0041-008X}, url={http://dx.doi.org/10.1016/j.taap.2004.12.007}, DOI={10.1016/j.taap.2004.12.007}, abstractNote={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 (iAs(III)) and methylated trivalent arsenicals in parental cells and clonal cells expressing AS3MT. In contrast to parental cells, UROtsa/F35 cells effectively methylated iAs(III), yielding methylarsenic (MAs) and dimethylarsenic (DMAs) containing either As(III) or As(V). When exposed to MAs(III), UROtsa/F35 cells produced DMAs(III) and DMAs(V). MAs(III) and DMAs(III) were more cytotoxic than iAs(III) in UROtsa and UROtsa/F35 cells. The greater cytotoxicity of MAs(III) or DMAs(III) than of iAs(III) 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 iAs(III) but were more resistant to cytotoxicity of MAs(III). The increased sensitivity of UROtsa/F35 cells to iAs(III) was associated with inhibition of DMAs production and intracellular accumulation of MAs. The resistance of UROtsa/F35 cells to moderate concentrations of MAs(III) was linked to its rapid conversion to DMAs and efflux of DMAs. However, concentrations of MAs(III) that inhibited DMAs production by UROtsa/F35 cells were equally toxic for parental and clonal cell lines. Thus, the production and accumulation of MAs(III) is a key factor contributing to the toxicity of acute iAs exposures in methylating cells.}, number={2}, journal={Toxicology and Applied Pharmacology}, publisher={Elsevier BV}, author={Drobna, Z and Waters, S and Devesa, V and Harmon, A and Thomas, D and Styblo, M}, year={2005}, month={Sep}, pages={147–159} }
 @article{devesa_maria del razo_adair_drobná_waters_hughes_stýblo_thomas_2004, title={Comprehensive analysis of arsenic metabolites by pH-specific hydride generation atomic absorption spectrometry}, volume={19}, ISSN={0267-9477 1364-5544}, url={http://dx.doi.org/10.1039/b407388f}, DOI={10.1039/b407388f}, abstractNote={In a variety of biological systems, inorganic arsenic (iAs) is metabolized to yield methylated arsenicals that contain arsenic in +5 or +3 oxidation states. Atomic absorption spectrometry (AAS) coupled with a pH-specific generation of arsines has been used for selective analysis of trivalent and pentavalent inorganic, mono-, and dimethylated arsenicals in biological matrices. We have optimized this method to permit simultaneous detection and quantification of all relevant metabolites of iAs, including trimethylarsine oxide (TMAsVO). The optimization includes increasing the density of the chromatographic adsorbent used for cold-trapping of generated arsines and modification of the temperature gradient for release of arsines from the cold trap. These modifications improve the boiling-point separation of arsine, methylarsine, dimethylarsine, and trimethylarsine before the detection by AAS. Arsines from trivalent arsenicals and from TMAsVO are selectively generated at pH 6. At pH 1, arsines are generated from both tri- and pentavalent arsenicals. Thus, the optimized technique permits analysis of arsenite (iAsIII), arsenate (iAsV), monomethylarsonic acid (MAsV), monomethylarsonous acid (MAsIII), dimethylarsinic acid (DMAsV), dimethylarsinous acid (DMAsIII), and TMAsVO. The detection limits range from 0.14 ng As (for TMAsVO) to 0.40 ng As (for iAsV). Calibration curves are linear over the concentration range of 0.5–100 ng As. Recoveries vary between 85 and 124%. The precision of the method in various biological matrices ranges from 1.0 to 14.5%. Using the optimized technique, both trivalent and pentavalent methylated and dimethylated arsenicals, but not TMAsVO, have been detected in cultured primary human hepatocytes exposed to iAsIII. In contrast, TMAsVO was detected as the final product of in vitro methylation of iAsIII by rat AsIII-methyltransferase, cyt19. TMAsVO was also detected in the urine of mice treated with MAsV or DMAsV. Thus, the optimized method improves the efficiency of arsenic speciation analysis in biological matrices, providing a more comprehensive picture of the role of metabolism in the disposition and action of iAs.}, number={11}, journal={J. Anal. At. Spectrom.}, publisher={Royal Society of Chemistry (RSC)}, author={Devesa, Vicenta and Maria Del Razo, Luz and Adair, Blakely and Drobná, Zuzana and Waters, Stephen B. and Hughes, Michael F. and Stýblo, Miroslav and Thomas, David J.}, year={2004}, pages={1460–1467} }
 @article{walton_harmon_paul_drobna_patel_styblo_2004, title={Inhibition of insulin-dependent glucose uptake by trivalent arsenicals: possible mechanism of arsenic-induced diabetes}, volume={198}, ISSN={0041-008X}, url={http://dx.doi.org/10.1016/j.taap.2003.10.026}, DOI={10.1016/j.taap.2003.10.026}, abstractNote={Chronic exposures to inorganic arsenic (iAs) have been associated with increased incidence of noninsulin (type-2)-dependent diabetes mellitus. Although mechanisms by which iAs induces diabetes have not been identified, the clinical symptoms of the disease indicate that iAs or its metabolites interfere with insulin-stimulated signal transduction pathway or with critical steps in glucose metabolism. We have examined effects of iAs and methylated arsenicals that contain trivalent or pentavalent arsenic on glucose uptake by 3T3-L1 adipocytes. Treatment with inorganic and methylated pentavalent arsenicals (up to 1 mM) had little or no effect on either basal or insulin-stimulated glucose uptake. In contrast, trivalent arsenicals, arsenite (iAs(III)), methylarsine oxide (MAs(III)O), and iododimethylarsine (DMAs(III)O) inhibited insulin-stimulated glucose uptake in a concentration-dependent manner. Subtoxic concentrations of iAs(III) (20 microM), MAs(III)O (1 microM), or DMAs(III)I (2 microM) decreased insulin-stimulated glucose uptake by 35-45%. Basal glucose uptake was significantly inhibited only by cytotoxic concentrations of iAs(III) or MAs(III)O. Examination of the components of the insulin-stimulated signal transduction pathway showed that all trivalent arsenicals suppressed expression and possibly phosphorylation of protein kinase B (PKB/Akt). The concentration of an insulin-responsive glucose transporter (GLUT4) was significantly lower in the membrane region of 3T3-L1 adipocytes treated with trivalent arsenicals as compared with untreated cells. These results suggest that trivalent arsenicals inhibit insulin-stimulated glucose uptake by interfering with the PKB/Akt-dependent mobilization of GLUT4 transporters in adipocytes. This mechanism may be, in part, responsible for the development of type-2 diabetes in individuals chronically exposed to iAs.}, number={3}, journal={Toxicology and Applied Pharmacology}, publisher={Elsevier BV}, author={Walton, F and Harmon, A.W. and Paul, D.S. and Drobna, Z. and Patel, Y.M. and Styblo, M.}, year={2004}, month={Aug}, pages={424–433} }
 @article{drobná_waters_walton_lecluyse_thomas_stýblo_2004, title={Interindividual variation in the metabolism of arsenic in cultured primary human hepatocytes}, volume={201}, ISSN={0041-008X}, url={http://dx.doi.org/10.1016/j.taap.2004.05.004}, DOI={10.1016/j.taap.2004.05.004}, abstractNote={Liver is a prime site for conversion of inorganic arsenic (iAs) to methylated metabolites, including methylarsenicals (MAs) and dimethylarsenicals (DMAs). To assess interindividual variation in the capacity of liver to metabolize iAs, we examined the metabolic fate of arsenite (iAsIII) in normal primary human hepatocytes obtained from eight donors and cultured under standard conditions. Methylation rates, yields, and distribution of arsenicals were determined for hepatocytes exposed to 0.3–30 nmol of iAsIII/mg of protein for 24 h. Although the accumulation of arsenic (As) by cells was a linear function of the initial concentration of iAsIII in culture, the concentration of As retained in cells varied several fold among donors. DMAs was the major methylated metabolite found in cultures exposed to low concentrations of iAsIII; at higher concentrations, MAs was always predominant. Maximal rates for methylation of iAsIII were usually attained at 3 or 9 nmol of iAsIII/mg of protein and varied about 7-fold among donors. For most donors, the methylation rate decreased at the highest iAsIII concentrations. MAs was the major methylated metabolite retained in cells regardless of exposure level. DMAs was the major methylated metabolite found in medium. The interindividual differences in rates for iAsIII methylation were not strictly associated with variations in basal mRNA levels for cyt19, an As-methyltransferase. Analysis of the coding sequence of cyt19 identified one heterozygote with Met287Thr mutation in a single allele. Thus, genetic polymorphism of cyt19 along with other cellular factors is likely responsible for interindividual differences in the capacity of primary human hepatocytes to retain and metabolize iAsIII.}, number={2}, journal={Toxicology and Applied Pharmacology}, publisher={Elsevier BV}, author={Drobná, Zuzana and Waters, Stephen B. and Walton, Felecia S. and LeCluyse, Edward L. and Thomas, David J. and Stýblo, Miroslav}, year={2004}, month={Dec}, pages={166–177} }
 @article{kupsáková_rybár_dočolomanský_drobná_stein_walther_barančı́k miroslav_breier_2004, title={Reversal of P-glycoprotein mediated vincristine resistance of L1210/VCR cells by analogues of pentoxifylline}, volume={21}, ISSN={0928-0987}, url={http://dx.doi.org/10.1016/j.ejps.2003.10.019}, DOI={10.1016/j.ejps.2003.10.019}, abstractNote={In our previous papers we described the ability of methylxanthine pentoxifylline (PTX) to depress the P-glycoprotein (P-gp) mediated multidrug resistance (MDR) of the mouse leukemic cell line L1210/VCR. Other methylxanthines like caffeine and theophylline were found to be ineffective in this respect. In the present paper we have analysed the capability of 25 methylxanthines to depress MDR of L1210/VCR cells. These methylxanthines structurally differ in substituents located in positions N1, N3, N7 and C8. The results indicate that for an effective reversal of P-gp mediated MDR of our cells the existence of a longer polar substituent in the position N1 plays a crucial role. The elongation of the substituent in the positions N3 and N7 (from methyl to propyl) increases and in the position C8 (from H to propyl) decreases the efficacy of xanthines to reverse the vincristine resistance of L1210/VCR cells. The multiple linear regression for effectiveness of methylxanthines in reversal of P-gp mediated MDR of L1210/VCR cells (expressed as respective IC(50r) values) has been computed, with molar weight: M(w), molar volume: V(M), molar refractivity: R(M), crystal density: d and partition coefficient n-octanol/water: logP as descriptors. A high intercorrelation of M(W), V(M) and R(M) was found for the tested group of methylxanthines indicating that only one of these parameters is necessary for testing a potential correlation. The best fit in the multiple linear regression was obtained for R(M) applied together with d and logP and resulted in a QSAR model given by the following equation: IC(50r)=-[(32.3+/-7.2)x10(-3)xR(M)]+[(10.1+/-2.3)xd]+[(0.74+/-0.10)xlogP]-[10.5+/-3.2]. Model revealed that: (i) the molar refractivity influences the effectiveness of xanthine positively; (ii) the crystal density and partition coefficient influence the MDR reversal effectiveness of xanthine negatively.}, number={2-3}, journal={European Journal of Pharmaceutical Sciences}, publisher={Elsevier BV}, author={Kupsáková, Ivana and Rybár, Alfons and Dočolomanský, Peter and Drobná, Zuzana and Stein, Ulrike and Walther, Wolfgang and Barančı́k Miroslav and Breier, Albert}, year={2004}, month={Feb}, pages={283–293} }