Chemical Research in Toxicology (CHEM RES TOXICOL )

Publisher: American Chemical Society; International Society for the Study of Xenobiotics, American Chemical Society

Description

This timely, international journal is intended to provide a forum for presentation of research relevant to all aspects of the chemical basis of toxicological responses. It publishes papers devoted to identification of novel toxic agents and reactive intermediates, development of specific and sensitive new methods for detection of modification of biological macromolecules by toxic agents, characterization of the alteration of macromolecular structure and function by interaction with chemical agents, experimental and theoretical studies of chemical factors that control reactivity with specific macromolecules, and metabolism of toxic agents as it contributes to their biological effects. Chemical Research in Toxicology publishes Articles, Communications, Invited Reviews, and Perspectives on structural, mechanistic, and technological advances in research related to the toxicological effects of chemical agents. In addition, a feature entitled Forum is published once a year.

  • Impact factor
    3.67
    Show impact factor history
     
    Impact factor
  • 5-year impact
    4.01
  • Cited half-life
    7.10
  • Immediacy index
    0.81
  • Eigenfactor
    0.02
  • Article influence
    1.08
  • Website
    Chemical Research in Toxicology website
  • Other titles
    Chemical research in toxicology, Chemical research in toxicology. Supporting information
  • ISSN
    0893-228X
  • OCLC
    15464975
  • Material type
    Periodical, Internet resource
  • Document type
    Journal / Magazine / Newspaper, Internet Resource

Publisher details

American Chemical Society

  • Pre-print
    • Author cannot archive a pre-print version
  • Restrictions
    • Must obtain written permission from Editor
    • Must not violate ACS ethical Guidelines
  • Post-print
    • Author cannot archive a post-print version
  • Restrictions
    • If mandated by funding agency or employer/ institution
    • Must obtain written permission from Editor confirming posting does not conflict prior publication policies
    • If mandated to deposit before 12 months, must obtain waiver from Institution/ Agency or use AuthorChoice
    • 12 months
  • Conditions
    • On website or repositories
    • Non-Commercial
    • Must be accompanied by set statement (see policy)
    • Must link to publisher version
    • If mandated sooner than 12 months, must obtain waiver from Editors or use AuthorChoice
    • Publisher's version/PDF may be used, but only via AuthorChoice option
  • Classification
    ​ white

Publications in this journal

  • [Show abstract] [Hide abstract]
    ABSTRACT: Bisphenol-A (4,4'-dihydroxy-2,2-diphenylpropane, BPA, or BPA-A) and its derivatives, when exposed to humans, may affect functions of multiple organs by specific binding to the human estrogen-related receptor γ (ERRγ). We carried out atomistic molecular dynamics (MD) simulations of three ligand compounds including BPA-A, 4-α-cumylphenol (BPA-C), and 2,2-diphenylpropane (BPA-D) binding to the ligand binding domain (LBD) of a human ERRγ to study the structures and energies associated with the binding. We used the implicit Molecular Mechanics/Poisson-Boltzmann Surface Area (MM/PBSA) method to estimate the free energies of binding for the phenyl based compound/ERRγ systems. The addition of hydroxyl groups to the aromatic ring had only a minor effect on binding structures and a significant effect on ligand/protein binding energy in an aqueous solution. Free binding energies of BPA-D to the ERRγ were found to be considerably less than those of BPA-A and BPA-C to the ERRγ. These results are well correlated with those from experiments where no binding affinities were determined in the BPA-D/ERRγ complex. No conformational change was observed for the helix 12 (H-12) of ERRγ upon binding of these compounds preserving an active transcriptional conformation state.
    Chemical Research in Toxicology 08/2014;
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    ABSTRACT: Studies were undertaken to determine whether ERK oscillations regulate a unique subset of genes in human keratinocytes and subsequently, whether the p38 stress response inhibits ERK oscillations. A DNA microarray identified many genes that were unique to ERK oscillations, and network reconstruction predicted an important role for the mediator complex subunit 1 (MED1) node in mediating ERK oscillation-dependent gene expression. Increased ERK-dependent phosphorylation of MED1 was observed in oscillating cells compared to non-oscillating counterparts as validation. Treatment of keratinocytes with a p38 inhibitor (SB203580) increased ERK oscillation amplitudes and MED1 and phospho-MED1 protein levels. Bromate is a probable human carcinogen that activates p38. Bromate inhibited ERK oscillations in human keratinocytes and JB6 cells and induced an increase in phospho-p38 and decrease in phospho-MED1 protein levels. Treatment of normal rat kidney cells and primary salivary gland epithelial cells with bromate decreased phospho-MED1 levels in a reversible fashion upon treatment with p38 inhibitors (SB202190; SB203580). Our results indicate that oscillatory behavior in the ERK pathway alters homeostatic gene regulation patterns and that the cellular response to perturbation may manifest differently in oscillating vs non-oscillating cells.
    Chemical Research in Toxicology 07/2014;
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    ABSTRACT: Xenobiotics may activate the estrogen receptor, resulting in alteration of normal endocrine functions in animals and humans. Consequently, this necessitates development of assay end points capable of identifying estrogenic xenobiotics. In the present study, we screened the potential estrogenicity of chemicals via their ability to induce vitellogenin (VTG) expression in cultured primary hepatocytes from male trout. A routine method for VTG detection measures the secretion of the protein by enzyme-linked immunosorbent assay (ELISA) in freshly isolated trout hepatocytes. However, this lengthy (6 days) culturing procedure requires that hepatocyte isolation is performed each time the assay is run. We optimized this methodology by investigating the utility of cryopreserved hepatocytes, shortening the incubation time, performing a quantitative real-time PCR (qPCR) method for VTG quantification, and verifying the model system with reference chemicals 17β-estradiol, estrone, diethylstilbestrol, hexestrol, genistein, and a negative control, corticosterone. To test the performance of both freshly isolated and cryopreserved hepatocytes, mRNA was collected from hepatocytes following 24 h treatment for VTG gene expression analysis, whereas cell culture media was collected for a VTG ELISA 96 h post-treatment. EC50 values were obtained for each reference chemical except for corticosterone, which exhibited no induction of VTG gene or protein level. Our results show linear concordance between ELISA and qPCR detection methods. Although there was approximately 50% reduction in VTG inducibility following cryopreservation, linear concordance of EC50 values was found between freshly isolated and cryopreserved hepatocytes, indicating that cryopreservation does not alter the functional assessment of estrogen receptor activation and therefore VTG expression. These studies demonstrate that qPCR is a sensitive and specific method for detecting VTG gene expression that can be used together with cryopreserved trout hepatocytes for screening estrogenic chemicals, resulting in a reduction of the time required to perform the assay and enabling greater access to the model system through the approach of cryopreservation.
    Chemical Research in Toxicology 07/2014;
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    ABSTRACT: The quinones 1,4-naphthoquinone (NQ), tetramethyl-1,4-benzoquinone (DQ), 2-methyl-1,4-naphthoquinone (MNQ), 2,3-dimethoxy-5-methyl-1,4-benzoquinone (UBQ-0), 2,6-dimethylbenzoquinone (DMBQ), 2,6-dimethoxybenzoquinone (DMOBQ) and 9,10-phenanthraquinone (PHQ) enhance the rate of H2O2 reduction by ascorbate, under anaerobic conditions, as detected from the amount of methane produced after hydroxyl radical reaction with dimethylsulfoxide. The amount of methane produced increases with an increase in the quinone one-electron reduction potential. The most active quinone in this series, PHQ, is only 14 % less active than the classic Fenton reagent cation, Fe2+, at the same concentration. PHQ is a common toxin present in diesel combustion smoke, the possibility of PHQ catalysis of hydroxyl radical formation similar to that of Fe2+ adds another important pathway to the modes in which PHQ could execute its toxicity. Since quinones are known to enhance the antitumor activity of ascorbate, and ascorbate enhances the formation of H2O2 in tissues, the quinone-mediated reduction of H2O2 should be relevant to this type of antitumor activity, especially under hypoxic conditions.
    Chemical Research in Toxicology 07/2014;
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    ABSTRACT: In peritoneal dialysis (PD), glucose degradation products (GDPs), which are formed during heat sterilization of dialysis fluids, lead to structural and functional changes in the peritoneal membrane, which eventually results in the loss of its ultrafiltration capacity. To determine the molecular mechanisms behind these processes, the present study tested the influence of the six major α-dicarbonyl GDPs in PD fluids, namely glyoxal, methylglyoxal, 3-deoxyglucosone (3-DG), 3-deoxygalactosone (3-DGal), 3,4-dideoxyglucosone-3-ene (3,4-DGE), and glucosone in respect of their potential to impair enzymatic activity of RNase A as well as their effects on cell viability. For comprehensive risk assessment, the α-dicarbonyl GDPs were applied separately and in concentrations as present in conventional PD fluids. Thus, it was shown that after five days, glucosone impaired RNase A activity most distinctly (58% remaining activity, p < 0.001 compared to control), followed by 3,4-DGE (62%, p < 0.001), 3-DGal (66%, p < 0.001) and 3-DG (76%, p < 0.01). Methylglyoxal and glyoxal caused weaker inactivation with significant effects only after 10 days of incubation (79%, 81%, p < 0.001). Profiling of the advanced glycation end-products formed during the incubation of RNase A with methylglyoxal revealed predominant formation of the arginine modifications imidazolinone, CEA/ dihydroxyimidazoline and tetrahydropyrimidine at Arg10, Arg33, Arg39, and Arg85. Particularly modification at Arg39 may severely affect the active site of the enzyme. Additionally, structure- and concentration-specific assessment of the cytotoxicity of the α-dicarbonyl GDPs was performed. Although present at very low concentration, the cytotoxic effect of PD fluids after two days of incubation was exclusively caused by 3,4-DGE (14% cell viability, p < 0.001). After four days of incubation, 3-DGal (13% cell viability, p < 0.001), 3-DG (24%, p < 0.001) and, to a lower extent, glyoxal and methylglyoxal (both 57%, p < 0.01) also reduced cell viability significantly. In conclusion, 3,4-DGE, 3-DGal, and glucosone appear to be most relevant parameters for the biocompatibility of PD fluids.
    Chemical Research in Toxicology 07/2014;
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    ABSTRACT: Organically modified rectorite (OREC) miro/nanoparticles can be synthesized by organic modification from calcium rectorite (Ca2+-REC or REC), a common form of rectorite in nature. Although OREC has potential applications in food packing and drug delivery, its cytotoxicity is not clear. In the present study, we investigated and compared the cytotoxicity of REC and OREC micro/nanoparticles in Chang liver cells, the human normal hepatic cells, and human hepatoma HepG2 cells. The interlayer spacing of OREC was enlarged after organic modification. After treatment with REC or OREC for 24h at 1 and 5 μg/ml, they were uptaken by Chang liver cells. REC and OREC induced cytotoxicity in Chang liver and HepG2 cells at almost all doses (1, 2.5, 5, 7.5, 10 μg/ml) after 6, 24 and 48h treatment (P < 0.05 or P < 0.01). Compared with REC, OREC was more cytotoxic. However, there was no difference in cytotoxicity between the two cell lines. After treatment with REC or OREC at 5, 7.5 and 10 μg/ml for 24h, the apoptotic and necrotic percentages of Chang liver cells were increased (P < 0.05 or P < 0.01). The levels of apoptosis-related proteins Bax, Bcl-2 and pro-caspase-3 were all decreased in Chang liver cells after 24h exposure to REC or OREC at 5, 7.5, 10 μg/ml, especially at 10 μg/ml. There was no change in the relative ratio of Bax/Bcl-2 after treatment, indicating that REC or OREC-induced apoptosis was not associated with Bax-related mitochondria-mediated apoptotic pathway. Our results suggested that OREC was more cytotoxic than REC, but the underlying mechanisms need further investigation.
    Chemical Research in Toxicology 07/2014;
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    ABSTRACT: Thiophene is a five membered, sulphur-containing heteroaromatic ring, commonly used as a building block in drugs. It is considered to be structural alert, since its metabolism can lead to the formation of reactive metabolites. Thiophene S-oxides and thiophene epoxides are highly reactive electrophilic thiophene metabolites, whose formation is cytochrome P450 dependent. These reactive thiophene-based metabolites are quite often responsible for drug induced hepatotoxicity. Tienilic acid is an example of a thiophene based drug that was withdrawn from the market after only a few months of use, due to severe cases of immune hepatitis. However, inclusion of the thiophene moiety in drugs does not necessarily result in toxic effects. The presence of other, less toxic metabolic pathways, as well as an effective detoxification system in our body, protects us from the bioactivation potential of the thiophene ring. Thus, the presence of a structural alert itself is not a sufficient reason for the toxicity of a compound. The question therefore arises as to which factors significantly influence the toxicity of thiophene containing drugs. There is no easy way to answer this question. However, the findings presented here are that, for a number of reasons, 'daily dose' and 'alternative metabolic pathways' are important factors when predicting toxicity, and will therefore be discussed, together with examples.
    Chemical Research in Toxicology 07/2014;
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    ABSTRACT: Prodrugs of 1,2-bis(methylsulfonyl)-1-(2-chloroethyl)hydrazine (90CE) are promising anticancer agents. The 90CE moiety is a readily latentiated, short-lived (t1/2 ~ 30 s) chloroethylating agent that can generate high yields of oxophilic electrophiles responsible for the chloroethylation of the O-6 position of guanine in DNA. These guanine O-6 alkylations are believed to be responsible for the therapeutic effects of 90CE and its prodrugs. Thus, 90CE demonstrates high selectivity towards tumors with diminished levels of >O(6)-alkylguanine-DNA alkyltransferase (MGMT), the resistance protein responsible for O(6)-alkylguanine repair. The formation of >O(6)-(2-chloroethyl)guanine lesions ultimately leads to the generation of highly cytotoxic 1-(N(3)-cytosinyl),-2-(N(1)-guaninyl)ethane DNA interstrand cross-links via N(1),O(6)-ethanoguanine intermediates. The anticancer activity arising from this sequence of reactions is thus identical to this component of the anticancer activity of the clinically used chloroethylnitrosoureas. Herein, we evaluate the ability of glutathione (GSH) and other low molecular weight thiols, as well as GSH coupled with various glutathione-S-transferase enzymes (GSTs) to attenuate the final yields of cross-links generated by 90CE when added prior to or immediately following the initial chloroethylation step to determine the major point(s) of interaction. In contrast to studies utilizing BCNU as a chloroethylating agent by others, GSH (or GSH/GST) did not appreciably quench DNA interstrand cross-link precursors. While thiols alone offered little protection at either alkylation step, the GSH/GST couple was able to diminish the initial yields of cross-link precursors. 90CE exhibited a very different GST isoenzyme susceptibility to that reported for BCNU, this could have important implications in the relative resistance of tumor cells to these agents. The protection afforded by GSH/GST was compared to that produced by MGMT.
    Chemical Research in Toxicology 07/2014;
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    ABSTRACT: Ciguatoxins (CTXs) and maitotoxins (MTXs) are polyether ladder shaped toxins derived from the dinoflagellate Gambierdiscus toxicus. Despite MTXs are 3 times larger than CTXs, part of the structure of MTXs resembles that of CTXs. To date, the synthetic ciguatoxin, CTX 3C has been reported to activate voltage gated sodium channels whereas the main effect of MTX is inducing calcium influx into the cell leading to cell death. However there is a lack of information regarding the effects of these toxins in a common cellular model. Here, in order to have an overview of the main effects of these toxins in mice cortical neurons, we examined the effects of MTX and the synthetic ciguatoxin CTX 3C on the main voltage dependent ion channels in neurons, sodium, potassium and calcium channels as well as on membrane potential, cytosolic calcium concentration ([Ca2+]c), intracellular pH (pHi), and neuronal viability. Regarding voltage gated ion channels, neither CTX 3C nor MTX affected voltage gated calcium or potassium channels, but while CTX 3C had a large effect on voltage gated sodium channels (VGSC) by shifting the activation and inactivation curves to more hyperpolarized potentials and decreasing peak sodium channel amplitude, MTX, at 5 nM, had no effect on VGSC activation and inactivation but decreased peak sodium current amplitude. Other major differences between both toxins were the massive calcium influx and intracellular acidification produced by MTX but not by CTX 3C. Indeed, the novel finding that MTX produces acidosis supports a pathway recently described in which MTX produces calcium influx via the sodium hydrogen exchanger (NHX). For the first time, we found that VGSC blockers partially blocked the MTX-induced calcium influx, intracellular acidification and protected against the short term MTX-induced cytotoxicity. The results presented here, provide the first report that shows the comparative effects of two prototypical ciguatera toxins, CTX 3C and MTX, in a neuronal model. We hypothesize that the analogies and differences in the bioactivity of these two toxins, produced by the same microorganism, may be strongly linked to their chemical structure.
    Chemical Research in Toxicology 07/2014;
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    ABSTRACT: Clozapine is effective in the treatment of schizophrenia; however, its use is limited by a relatively high incidence of idiosyncratic agranulocytosis. The mechanism of clozapine-induced idiosyncratic agranulocytosis is unknown. Although most patients treated with clozapine do not develop agranulocytosis, most do have an immune response with an increase in inflammatory cytokines such as IL-6, and a release of immature neutrophils with neutrophilia rather than agranulocytosis. We have previously shown that treatment of rabbits with clozapine also causes an early release of neutrophils. Clozapine is oxidized to a reactive nitrenium ion that covalently binds to neutrophils, and this reactive metabolite may be responsible for the observed effects. Olanzapine has a very similar structure as clozapine, and it is also oxidized to a reactive nitrenium ion; however, if it ever causes agranulocytosis, the incidence is much lower than that of clozapine. One possible basis for the difference in incidence of agranulocytosis between clozapine and olanzapine is that the therapeutic dose of olanzapine is much lower than that of clozapine. In this study we compared the effects of clozapine and olanzapine in Sprague Dawley rats at an equimolar dose and found that only clozapine had a significant effect on neutrophil kinetics. This suggests that the immune response and effects on neutrophil kinetics induced by clozapine are related to its ability to cause agranulocytosis.
    Chemical Research in Toxicology 06/2014;
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    ABSTRACT: Clozapine is an atypical antipsychotic that is limited in its use due to the risk of idiosyncratic agranulocytosis. The bone marrow is suspected to be the site of the reaction, and indirect measurements in patients suggest that neutrophil production and maturation are altered in the marrow by clozapine. Specifically, the majority of patients have elevated neutrophil counts at the start of treatment, often paired with increased serum granulocyte-colony stimulating factor (G-CSF). Employing a rat model of clozapine treatment, we set out to determine if the neutrophilia observed at the start of treatment is characteristic of G-CSF-associated bone marrow stimulation. Female Sprague-Dawley rats were treated with 30 mg/kg/day of clozapine for 10 days, and sustained neutrophilia was evident after 1 week of treatment paired with spikes in G-CSF. Within the bone marrow, clozapine was found to induce proliferation of the granulocyte progenitor colonies as measured by a methylcellulose assay. This led to elevated granulopoiesis observed by H&E and myeloperoxidase staining of bone marrow slices. Increased release of neutrophils from the marrow to the circulation was measured through 5-bromo-2'-deoxyuridine labeling in vivo, and these neutrophils appeared to be less mature based on: a) a decrease in the nuclear lobe count and; b) increased expression of surface CD62L. Furthermore, faster transit of the neutrophils through the marrow was suggested by a shift towards elevated numbers of neutrophils in the bone marrow maturation pool, and increased CD11b and CD18 staining on the less mature neutrophils residing in the marrow. Taken together, these data indicate that clozapine stimulates the bone marrow to produce more neutrophils in a manner that is characteristic of endogenous G-CSF stimulation, and it is consistent with the inflammatory response observed in patients treated with clozapine.
    Chemical Research in Toxicology 06/2014;
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    ABSTRACT: Brevetoxins produced during algal blooms of the dinoflagellate Karenia are metabolized by shellfish into reduction, oxidation, and conjugation products. Brevetoxin metabolites comprised of amino acid- and lipid- conjugates account for a large proportion of the toxicity associated with the consumption of toxic shellfish. However, the disposition of these brevetoxin metabolites has not been established. Using intravenous exposure to C57BL/6 mice, we investigated the disposition in the body of three radiolabeled brevetoxin metabolites. Amino acid brevetoxin conjugates represented by S-desoxy-BTX-B2 (cysteine-BTX-B) and lipid brevetoxin conjugates represented by N-palmitoyl-S-desoxy-BTX-B2 were compared to dihydro-BTX-B. Tissue concentration profiles were unique to each of the brevetoxin metabolites tested, with dihydro-BTX-B being widely distributed to all tissues, S-desoxy-BTX-B2 concentrated in kidney, and N-palmitoyl-S-desoxy-BTX-B2 having the highest concentrations in spleen, liver and lung. Elimination patterns were also unique: dihydro-BTX-B had a greater fecal versus urinary elimination, whereas urine was a more important elimination route for S-desoxy-BTX-B2, and N-palmitoyl-S-desoxy-BTX-B2 persisted in tissues and was eliminated equally in both urine and feces. The structures particular to each brevetoxin metabolite resulting from the reduction, amino acid conjugation, or fatty acid addition of BTX-B were likely responsible for these tissue-specific distributions and unique elimination patterns. These observed differences provide further insight into the contribution each brevetoxin metabolite class has on the observed potencies.
    Chemical Research in Toxicology 06/2014;
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    ABSTRACT: The conformational preference of the O6-benzyl-guanine (BzG) adduct was computationally examined using nucleoside, nucleotide and DNA models, which provided critical information about the potential mutagenic consequences and toxicity of the BzG adduct in our cells. Substantial conformational flexibility of the BzG moiety, including rotation of the bulky group with respect to the base and the internal conformation of the bulk moiety, is seen in the nucleoside and nucleotide models. This large conformational flexibility suggests the conformation adopted by BzG is dependent on the local environment of the BzG adduct. Upon incorporation of the adduct into the DNA helix, the BzG conformational flexibility is maintained. The range of BzG conformations adopted in DNA likely arises due to a combination of the long and flexible (-CH2¬-) linker, the small adduct size and the lack of discrete interactions between the bulky moiety and G. Due to the conformational flexibility of the adduct, many DNA conformations are observed for BzG adducted DNA, including those not previously reported in the literature, and thus a modified nomenclature for adducted DNA conformations is presented. Furthermore, the preferred conformation of BzG adducted DNA is greatly dependent on a number of factors, including the pairing nucleotide, the discrete interactions in the helix and the solvation of the benzyl moiety. These factors in turn lead to a complicated mutagenic and toxic profile that may invoke pairing with natural C, mispairs, or deletion mutations, which is supported by previously reported experimental biochemical studies. Despite this complex mutagenic profile, pairing with C leads to the most stable helical structure, which is the first combined structural and energetic explanation for experimental studies reporting a higher rate of C incorporation than any other nucleobase upon the BzG replication.
    Chemical Research in Toxicology 06/2014;
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    ABSTRACT: In the present study, we attempt to shed light on the underlying molecular mechanism of anticancer activity of pterostilbene (PTS) in HepG2 cells through proteomic approach. PTS found to induce apoptosis by altering the expression of apoptotic genes and G2/M phase of cell cycle arrest. Further, 2-DE map showed the expression of 72 differentially regulated proteins in PTS treated HepG2 cells, of which 8 spots with >2 fold up- or down- regulated level were identified by MALDI-TOF analysis, which has regulatory role in apoptosis. These findings for the first time offer valuable insights into the mechanism of apoptotis by PTS in HepG2 cells.
    Chemical Research in Toxicology 06/2014;
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    ABSTRACT: High-aspect-ratio nanomaterials (HARN) (typically, single-walled carbon nanotubes (SWCNT) or multiwalled carbon nanotubes (MWCNT)) impair airway barrier function and are toxic to macrophages. Here, we assess the biological effects of nanotubes of imogolite (INT), a hydrated alumino-silicate [(OH)3Al2O3SiOH] occurring as single-walled NT, on murine macrophages and human airway epithelial cells. Cell viability was assessed with resazurin. RT-PCR was used to study the expression of Nos2 and Arg1, markers of classical or alternative macrophage activation, respectively, and nitrite concentration in the medium was determined to assess NO production. Epithelial barrier integrity was evaluated from the trans-epithelial electrical resistance (TEER). Potential genotoxicity of INT was assessed with comet and cytokinesis-block micronucleus cytome assays. Compared to MWCNT and SWCNT, INT caused much smaller effects on RAW264.7 and MH-S macrophage viability. The incubation of macrophages with INT at doses as high as 120 μg/cm(2) for 72 h did not alter either Nos2 or Arg1 expression nor did it increase NO production, whereas IL6 was induced in RAW264.7 cells but not in MH-S cells. INT did not show any genotoxic effect in RAW264.7 and A549 cells except for a decrease in DNA integrity observed in epithelial A549 cells after treatment with the highest dose (80 μg/cm(2)). No significant change in permeability was recorded in Calu-3 epithelial cell monolayers exposed to INT, whereas comparable doses of both SWCNT and MWCNT lowered TEER. Thus, in spite of their fibrous nature, INT appear not to be markedly toxic for in vitro models of lung-blood barrier cells.
    Chemical Research in Toxicology 06/2014;
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    ABSTRACT: 8-Oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodGuo) is a commonly formed DNA lesion that is useful as a biomarker for oxidative stress. Although methods for selective quantification of 8-oxodGuo exist, there is room for additional methods that are sensitive and utilize instrumentation that is widely available. We previously took advantage of the reported reactivity of 8-oxodGuo to develop a method for detecting the lesion by selectively covalently tagging it with a molecule equipped with a biotin label that can be used subsequently with a reporting method ( Xue , L. and Greenberg , M. M. ( 2007 ) J. Am. Chem. Soc. 129 , 7010 ). We now report a method that can detect as little as 14 amol of 8-oxodGuo by tagging DNA with a reagent containing a disulfide that reduces background due to nonspecific binding. The reagent also contains biotin that enables capturing target DNA on streptavidin-coated magnetic beads. The captured DNA is quantified using quantitative PCR. The method is validated by comparing the amount of 8-oxodGuo detected as a function of Fe(2+)/H2O2/ascorbate-dose to that reported previously using mass spectrometry.
    Chemical Research in Toxicology 06/2014;
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    ABSTRACT: Z-DNA is the only DNA conformation that has a left-handed helical twist. Although Z-DNA has been implicated in both carcinogenesis and mutagenesis, its specific biological role remains uncertain. We have demonstrated that the formation of C8-arylguanine DNA adducts, derived from arylhydrazines, shifts the B/Z-DNA equilibrium toward the Z-DNA conformation in d(CG)5 sequences. However, our previous work examined the effect of two adducts in the duplex and it is unclear whether the two base modifications were working together to cause the equilibrium shift toward the Z-DNA formation. Here we report the synthesis and characterization of a hairpin oligonucleotide sequence (d(CG)5T4(CG)5) containing only one C8-arylguanine modified base. The unmodified hairpin and the previously studied unmodified double-stranded oligonucleotide were conformationally similar and each required ~3 M NaCl to yield a B/Z-DNA ratio of 1:1. The introduction of a single C8-arylguanine modification significantly reduced the NaCl concentration needed to produce a 1:1 B/Z-DNA ratio in the hairpin. Further, the addition of MgCl2 and spermine to the C8-arylguanine modified hairpin shifts the B/Z-DNA equilibrium such that the Z form predominated under physiological conditions. NMR and molecular modeling indicated the conformational effects produced by the C8-arylguanine modification occurred locally at the site of modification while CD data demonstrated that the C8-arylguanine modified base destabilized the B form. Additionally, our data show that adopting the Z-DNA conformation is preferred over denaturation to the single-stranded form. Finally, the conformational effects of the C8-arylguanine modifications were not additive and the introduction of any such modifications drive Z-DNA formation under physiological conditions, which may provide a novel carcinogenesis mechanism where DNA adducts confer their carcinogenicity through a Z-DNA mediated mechanism.
    Chemical Research in Toxicology 06/2014;

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