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Chemical Research in Toxicology

Joseph Tillotson, Christopher J Zerio, Bryan Harder, Andrew Ambrose, Kevin S Jung, MinJin Kang, Donna D Zhang, Eli Chapman
Exposure to arsenic is a worldwide problem that affects more than 200 million people. The underlying mechanisms of arsenic toxicity have been difficult to ascertain due to arsenic's pleotropic effects. A number of recent investigations have shown arsenic can compromise protein quality control through the ubiquitin proteasome system (UPS) or the endoplasmic reticulum associated protein degradation (ERAD) pathway. In this report, a link between arsenic and protein quality control is reported. Biochemical and cellular data demonstrate a misregulation of the ATPase cycle of the ATPase associated with various cellular activities (AAA+) chaperone, p97...
June 21, 2017: Chemical Research in Toxicology
Elana R Elkin, Marie S O'Neill
For decades, many studies have linked maternal smoking to an increased risk of preterm birth. As a result, the scientific community has long hypothesized that exposure to environmental tobacco smoke (ETS), commonly referred to as second-hand smoke, is also associated with an increased risk of preterm birth. Multiple studies have examined this proposed association through different strategies and approaches. Recently, a small number of epidemiology studies have examined preterm birth trends before and after the implementation of antismoking legislation in various jurisdictions...
June 20, 2017: Chemical Research in Toxicology
Jiaojiao Li, Charles Packianathan, Toby G Rossman, Barry P Rosen
Arsenic methylation, the primary biotransformation in the human body, is catalyzed by the enzyme As(III) S-adenosylmethionine (SAM) methyltransferases (hAS3MT). This process is thought to be protective from acute high-level arsenic exposure. However, with long-term low-level exposure, hAS3MT produces intracellular methylarsenite (MAs(III)) and dimethylarsenite (DMAs(III)), which are considerably more toxic than inorganic As(III) and may contribute to arsenic-related diseases. Several single nucleotide polymorphisms (SNPs) in putative regulatory elements of the hAS3MT gene have been shown to be protective...
June 19, 2017: Chemical Research in Toxicology
Pan Wang, Laura H Mills, Ji-Hoon Song, Jina Yu, Bao-Ting Zhu
In animal models, estrogens are complete carcinogens in certain target sites. 4-Hydroxyestradiol (4-OH-E2), an endogenous metabolite of 17β-estradiol (E2), is known to have prominent estrogenic activity plus potential genotoxicity and mutagenicity. We report here our finding that 4-OH-E2 does not induce pituitary tumors in ACI female rats, whereas E2 produces 100% pituitary tumor incidence. To probe the mechanism, we conducted a short-term animal experiment to compare the proliferative effect of 4-OH-E2 in several organs...
June 15, 2017: Chemical Research in Toxicology
Da Yang, Min Zhang, Barry Gold
Wnt signaling is compromised early in the development of human colorectal cancer (CRC) due to truncating nonsense mutations in adenomatous polyposis coli (APC). CRC induced by chemical carcinogens, such as heterocyclic aromatic amines and azoxymethane, in mice also involves dysregulation of Wnt signaling but via activating missense mutations in the β-catenin oncogene despite the fact that genetically modified mice harboring an inactive APC allele efficiently develop CRC. In contrast, activating mutations in β-catenin are rarely observed in human CRC...
June 15, 2017: Chemical Research in Toxicology
Patricia D Koman, Peter Mancuso
From 1999-2014, obesity prevalence increased among adults and youth. Obese individuals may be uniquely susceptible to the proinflammatory effects of ozone because obese humans and animals have been shown to experience a greater decline in lung function than normal-weight subjects. Obesity is independently associated with limitations in lung mechanics with increased ozone dose. However, few epidemiologic studies have examined the interaction between excess weight and ozone exposure among adults. Using PubMed keyword searches and reference lists, we reviewed epidemiologic evidence to identify potential response-modifying factors and determine if obese or overweight adults are at increased risk of ozone-related health effects...
June 15, 2017: Chemical Research in Toxicology
Patrick Tarnow, Steffi Bross, Lisa Wollenberg, Yoshihiro Nakajima, Yoshihiro Ohmiya, Tewes Tralau, Andreas Luch
Consumers are exposed to a plethora of anthropogenic and natural substances that can act as agonists or antagonists for various transcription factors. Depending on the exposure and potency such interactions can potentially lead to adverse health effects, particularly for substances with multiple molecular targets. The early detection of such interactions is thus of high toxicological interest. Here we report on the development of a new cellular dual-colour reporter assay which allows the time-resolved and quantitative recording of estrogen receptor (ER) and aryl hydrocarbon receptor (AHR) activation in living cells...
June 14, 2017: Chemical Research in Toxicology
Gary Williams, Tetyana Kobets, Jian Dong Duan, Michael J Iatropoulos
Exposure to acrylonitrile induces formation of tumors at multiple sites in rats, with females being more sensitive. The present study assessed possible mechanisms of acrylonitrile tumorigenicity, covalent DNA binding, DNA breakage and oxidative DNA damage, in two target tissues, the brain and Zymbal's glands, of sensitive female Fischer (F344) and Sprague-Dawley (SD) rats. One group received acrylonitrile in drinking water at 100 ppm for 28 days. Two other groups were administered either acrylonitrile in drinking water at 100 ppm or drinking water alone for 27 days, followed by a single oral gavage dose of 11 mg/kg bw 14C-acrylonitrile on day 28...
June 14, 2017: Chemical Research in Toxicology
Maria Flynn, Kali Amelia Heale, Laleh Alisaraie
Tamoxifen is an estrogen modulator that acts to competitively inhibit the binding of endogenous estrogens. It is widely used for treatment of breast cancer; however, analogous with many antineoplastic agents, tamoxifen is associated with numerous adverse effects, most prominently nausea. We have identified several off-target receptors of tamoxifen and 22 of its metabolites that include histamine H1 and H3, and muscarinic M1, M4, and M5 subtypes, and dopamine D2 receptor. We have shown how they are associated with tamoxifen and its metabolites' toxicity through a comprehensive computational analysis of their interaction modes, which were also compared to that of the related endogenous substrates of each receptor...
June 14, 2017: Chemical Research in Toxicology
Vincent L M Yip, Xiaoli Meng, James L Maggs, Rosalind E Jenkins, Philippe T Marlot, Anthony G Marson, B Kevin Park, Munir Pirmohamed
Carbamazepine (CBZ) is an effective antiepileptic drug that has been associated with hypersensitivity reactions. The pathogenesis of those reactions is incompletely understood but is postulated to involve a complex interplay between the drug's metabolism, genetic variation in human leukocyte antigens, and adverse activation of the immune system. Multiple T-cell activation mechanisms have been hypothesized including activation by drug-peptide conjugates derived from proteins haptenated by reactive metabolites...
June 12, 2017: Chemical Research in Toxicology
Peng Wang, Maria Voronkova, Sudjit Luanpitpong, Xiaoqing He, Heimo Riedel, Cerasela Zoica Dinu, Liying Wang, Yon Rojanasakul
Carbon nanotubes (CNTs) represent a major class of engineered nanomaterials that are being used in diverse fields. However, their use has increasingly become a concern because of their carcinogenic potential. Accumulating evidence has demonstrated that certain types of CNTs are carcinogenic or tumor-promoting in animal models. However, the underlying molecular and cellular mechanisms are unclear. Here we report that chronic exposure to single-walled (SW) CNTs results in the induction of Slug, a key transcription factor to induce epithelial-mesenchymal transition (EMT), in human lung epithelial cells...
June 9, 2017: Chemical Research in Toxicology
Christopher O Miles
Microcystins are potent cyclic heptapeptide toxins found in some cyanobacteria, and usually contain an α,β-unsaturated carbonyl group that is readily conjugated to thiol-containing amino acids, peptides and proteins in vivo and in vitro. Methods for deconjugating these types of adducts have recently been reported, but the reactions are slow or result in derivatized microcystins. Mercaptoethanol derivatives of a range of microcystins were therefore used as model compounds to develop deconjugation procedures in which the dialkyl sulfide linkage was oxidized to a sulfoxide or sulfone that, when treated with base, rapidly eliminated the adducted thiol as its sulfenate or sulfinate via β-elimination to afford free microcystins with the α,β-unsaturated carbonyl group intact...
June 8, 2017: Chemical Research in Toxicology
Shaojun Yang, Yi-Hua Jan, Vladimir Mishin, Diane E Heck, Debra L Laskin, Jeffrey D Laskin
Reactive carbonyls such as diacetyl (2,3-butanedione) and 2,3-pentanedione in tobacco and many food and consumer products are known to cause severe respiratory diseases. Many of these chemicals are detoxified by carbonyl reductases in the lung, in particular, dicarbonyl/L-xylulose reductase (DCXR), a multifunctional enzyme important in glucose metabolism. DCXR is a member of the short-chain dehydrogenase/reductase (SDR) superfamily. Using recombinant human enzyme, we discovered that DCXR mediates redox cycling of a variety of quinones generating superoxide anion, hydrogen peroxide and, in the presence of transition metals, hydroxyl radicals...
June 8, 2017: Chemical Research in Toxicology
Ryuji Kato, Jack Uetrecht
There is increasing evidence that most idiosyncratic drug-induced liver injury (IDILI) is immune mediated, and in most cases, reactive metabolites appear to be responsible for the induction of this immune response. Reactive metabolites can cause cell damage with the release of damage-associated molecular patterns (DAMPs), which is thought to be involved in immune activation. Presumably, the reason that the liver is a common target of idiosyncratic drug reactions is because it is the major site of drug metabolism and reactive metabolite formation...
June 2, 2017: Chemical Research in Toxicology
Tingting Cai, Medjda Bellamri, Xun Ming, Woon-Puay Koh, Mimi C Yu, Robert J Turesky
Aromatic amines covalently bound to hemoglobin (Hb) as sulfinamide adducts at the cysteine 93 residue of the Hb β chain have served as biomarkers to assess exposure to this class of human carcinogens for the past 30 years. In this study, we report that 2-amino-9H-pyrido[2,3-b]indole (AαC), an abundant carcinogenic heterocyclic aromatic amine formed in tobacco smoke and charred cooked meats, also reacts with Hb to form a sulfinamide adduct. A novel nanoflow liquid chromatography/ion trap multistage mass spectrometry (nanoLC-IT/MS(3)) method was established to assess exposure to AαC and the tobacco-associated bladder carcinogen 4-aminobiphenyl (4-ABP) through their Hb sulfinamide adducts...
May 25, 2017: Chemical Research in Toxicology
Blake R Rushing, Mustafa I Selim
Aflatoxin B2a has been shown to bind to proteins through a dialdehyde intermediate under physiological conditions. The proposed structure of this adduct has been published showing a Schiff base interaction, but adequate verification using structural elucidation instrumental techniques has not been performed. In this work, we synthesized the aflatoxin B2a amino acid adduct under alkaline conditions, and the formation of a new product was determined using high performance liquid chromatography-time-of-flight mass spectrometry...
May 24, 2017: Chemical Research in Toxicology
David W Roberts, Terry W Schultz, Anne Marie Api
The general chemistry principles underlying skin sensitization for Schiff base (SB) electrophiles may be used to develop a quantitative mechanistic model (QMM), based on reactivity supplemented with a hydrophobicity parameter for some but not all structures within the SB reaction domain. For aliphatic Schiff base electrophiles, the log of the no observed effect level (NOEL) values (pNOEL) from the human repeated insult patch test (HRIPT) can be calculated by the reactivity parameter summation of sigma star values (Σσ*) and a hydrophobicity parameter (logP)...
May 24, 2017: Chemical Research in Toxicology
Yanli Zhang, Hui Huang, Biao Gong, Leizhen Duan, Long Sun, Tongkun He, Xuemin Cheng, Zhiyuan Li, Liuxin Cui, Yue Ba
Although increasing evidence suggests that estrogen receptor α (ESRα) genetic variation could modify bone damage caused by environmental fluoride exposure, little is known about epigenetic mechanisms in relation to bone changes. A case-control study was conducted among farmers aged 18-55 years in Henan Province, China. X-ray was used to detect bone changes. Methylation status was determined by methylation-specific PCR. Genotypes were identified by Taqman probe and real-time PCR. In this study, we found that methylation status in the promoter region of the ESRα gene was lower in bone change cases than that in controls, which was only observed in male farmers after stratification by gender...
May 23, 2017: Chemical Research in Toxicology
Hongbin Yang, Jie Li, Zengrui Wu, Weihua Li, Guixia Liu, Yun Tang
Identification of structural alerts for toxicity is useful in drug discovery and other fields such as environmental protection. With structural alerts, researchers can quickly identify potential toxic compounds and learn how to modify them. Hence, it is important to determine structural alerts from a large number of compounds quickly and accurately. There are already many methods reported for identification of structural alerts. However, how to evaluate those methods is a problem. In this paper, we tried to evaluate four of the methods for monosubstructure identification with three indices including accuracy rate, coverage rate, and information gain to compare their advantages and disadvantages...
May 23, 2017: Chemical Research in Toxicology
Mandeep Singh Bakshi
Nanotoxicity of nanomaterials is an important issue in view of their potential applications in systemic circulation and wound healing dressing. This account specifically deals with several characteristic features of different nanomaterials which induce hemolysis and how to make them hemocompatible. The shape, size, and surface functionalities of naked metallic as well as nonmetallic nanoparticles surfaces are responsible for the hemolysis. An appropriate coating of biocompatible molecules dramatically reduces hemolysis and promotes their ability as safe drug delivery vehicles...
May 23, 2017: Chemical Research in Toxicology
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