Forgot your password?
New user?
New Window Opens on the Secret Life of Microbes: Scientists Develop First Microbial Profiles of Ecosystems
CAS announces the release of SciFinder Scholar for Mac OS X
Press Releases
Press Releases
| Check out our New Publishers' Select for Free Articles |
Archives of Toxicology (v.85, #11)
The field of tension between toxicology and basic and clinical sciences
by H. M. Bolt; J. D. Stewart (pp. 1311-1312).
Toxicology and pharmacology of selenium: emphasis on synthetic organoselenium compounds by Cristina W. Nogueira; João B. T. Rocha (pp. 1313-1359).
The advance in the area of synthesis and reactivity of organoselenium, as well as the discovery that selenium was the cause of severe intoxication episodes of livestock in the 1930s and the subsequent determination that selenium was an essential trace element in the diet for mammals, has motivated intense studies of the biological properties of both organic and inorganic selenium compounds. In this review, we shall cover a wide range of toxicological and pharmacological effects, in which organoselenium compounds are involved but the effects of inorganic compounds were not discussed in detail here. The molecular toxicity of inorganic selenium was described in relation to its interaction with endogenous –SH groups to allow a comparison with that of synthetic organoselenium compounds. Furthermore, in view of the recent points of epidemiological evidence that overexposure to selenium can facilitate the appearance of chronic degenerative diseases, we also briefly revised the history of selenium toxicity and physiology and how environmental selenium can reach inside the mammalian cells. The biological narrative of the element selenium, in the last century, has been marked by a contrast between its toxic and its beneficial effects. Thus, the potential therapeutic use of simple organoselenium compounds has not yet been sufficiently explored and, consequently, we cannot discard this class of compounds as promising pharmaceutical agents. In effect, the future of the organochalcogens as pharmacological agents will depend on more detailed toxicological studies in the oncoming years.
Keywords: Selenium; Diselenides; Toxicology; Pharmacology; Thiol; Organoselenium; Ebselen; Oxidative stress
Developmental toxicity testing in the 21st century: the sword of Damocles shattered by embryonic stem cell assays? by Andrea Seiler; Michael Oelgeschläger; Manfred Liebsch; Ralph Pirow; Christian Riebeling; Tewes Tralau; Andreas Luch (pp. 1361-1372).
Modern society faces an inherent dilemma. In our globalized society, we are spoilt for choice by an ever-increasing number of products, many of which are made of new materials and compound mixtures. At the same time, as consumers we got accustomed to the idea of a life minimized for risk, including our own exposure to chemicals from the environment or to compounds present in and released from everyday products. Chemical safety testing bridges these obviously diverging interests, and the corresponding legislation has hence been tremendously extended (e.g., introduction of the European legislation REACH in 2007). However, the underlying regulatory toxicology still relies mainly on animal testing, which is relatively slow, expensive, and ethically arguable. Meanwhile, recent years have seen a surge in efforts to develop alternative testing systems and strategies. Expectations are particularly high for the applicability of stem cells as test systems especially for developmental toxicity testing in vitro. For the first time in history, test systems can be based on differentiating cells and tissue progenitors in culture, thus bringing the ‘vision of toxicity testing in the 21st century’ a step closer.
Keywords: Developmental toxicity testing; Embryonic stem cells; ‘3R’-concept; Alternatives to animal testing; Cell-based in vitro systems ; Toxicology in the 21st century
Effect of UDP-glucuronosyltransferase 2B15 polymorphism on bisphenol A glucuronidation by Nobumitsu Hanioka; Hiroyuki Oka; Kenjiro Nagaoka; Shinichi Ikushiro; Shizuo Narimatsu (pp. 1373-1381).
Bisphenol A (BPA) is one of a number of potential endocrine-disrupting chemicals, which are metabolized mainly by UDP-glucuronosyltransferase 2B15 (UGT2B15) in humans. Six UGT2B15 allelic variants (UGT2B15*2, UGT2B15*3, UGT2B15*4, UGT2B15*5, UGT2B15*6, and UGT2B15*7; wild-type, UGT2B15*1) with amino acid substitutions have been found in Caucasian, African-American, Hispanic, and Oriental populations to date. In this study, the effects of amino acid substitutions in UGT2B15 on BPA glucuronidation were studied using recombinant UGT2B15 enzymes of wild-type (UGT2B15.1) and all identified variants (UGT2B15.2, UGT2B15.3, UGT2B15.4, UGT2B15.5, UGT2B15.6, and UGT2B15.7) expressed in insect (Sf9) cells. The K m, V max, and CL int values of UGT2B15.1 for BPA glucuronidation were 3.9 μM, 650 pmol/min/mg protein, and 170 μL/min/mg protein, respectively. Although there is no significant difference in the K m value between wild-type and any variant UGT2B15, the V max and CL int values of UGT2B15 variants having D85Y substitution were markedly reduced to 14 and 10% for UGT2B15.2, and 4.3 and 3.9% for UGT2B15.5 compared with those of UGT2B15.1, respectively. However, the K m, V max, and CL int values of UGT2B15.3, UGT2B15.4, UGT2B15.6, and UGT2B15.7 having L86S, T352I, and/or K523T substitution(s) for BPA glucuronidation were comparable to those of UGT2B15.1. These findings suggest that D85Y substitution in UGT2B15 decreases enzymatic function and that the polymorphic alleles of UGT2B15 are closely associated with variations in the metabolism and toxicity of BPA. The information gained in this study should help with in vivo extrapolation to assess the toxicity of endocrine-disrupting chemicals.
Keywords: Bisphenol A; Glucuronidation; UDP-glucuronosyltransferase 2B15 (UGT2B15); Genetic polymorphism
Depletion of CD4+CD25+Foxp3+ regulatory T cells with anti-CD25 antibody may exacerbate the 1,3-β-glucan-induced lung inflammatory response in mice by Fangwei Liu; Dong Weng; Ying Chen; Laiyu Song; Cuiying Li; Lei Dong; Yuan Wang; Shasha Tao; Jie Chen (pp. 1383-1394).
1,3-β-Glucan was a major cell wall component of fungus. The existing studies showed that 1,3-β-glucan exposure could induce lung inflammation that involved both Th1 and Th2 cytokines. Regulatory T cells (Treg cells) played a critical role in regulating immune homeostasis by adjusting the Th1/Th2 balance. The role of Treg cells and regulatory mechanism in 1,3-β-glucan-induced lung inflammation is still unclear. In our study, mice were exposed to 1,3-β-glucan by intratracheal instillation. To investigate the role of Treg cells in response to 1,3-β-glucan, we generated Treg-depleted mice by intraperitoneal administration of anti-CD25 mAb. The Treg-depleted mice showed more inflammatory cells and severer pathological inflammatory change in lung tissue. Depletion of Treg cells led to increased Th1 cytokines and decreased Th2 cytokines. Treg-depleted mice showed a decreased expression of anti-inflammation cytokine and lower-level expression of CTLA-4. In all, our study indicated that Treg cells participated in regulating the 1,3-β-glucan-induced lung inflammation. Depletion of Treg cells aggravated the 1,3-β-glucan-induced lung inflammation, regulated the Th1/Th2 balance by enhancing Th1 response. Treg cells exerted their modulation function depending on both direct and indirect mechanism during the 1,3-β-glucan-induced lung inflammation.
Keywords: 1,3-β-glucan; Regulatory T cells; Lung inflammation; Th1/Th2
Anti-apoptotic, anti-inflammatory, and immunomodulatory activities of 3,3′-diselenodipropionic acid in mice exposed to whole body γ-radiation by A. Kunwar; P. P. Bag; S. Chattopadhyay; V. K. Jain; K. I. Priyadarsini (pp. 1395-1405).
The present study was designed to evaluate the possible protective effects of 3,3′-diselenodipropionic acid (DSePA), a potent radioprotector, against oxidative organ damage induced by whole body γ-irradiation and explore its mechanistic effects. The mice were subjected to whole body γ-irradiation at 5 Gy for the detection of oxidative stress, apoptosis, and proliferation in the intestinal (jejunum) tissue and at 7 Gy for the examination of intestinal inflammation and immune imbalance. Groups of mice received intraperitoneal injections of DSePA (2 mg/kg/day) or vehicle (phosphate-buffered saline) for 5 consecutive days prior to irradiation. The whole body γ-irradiation of mice led to the induction of oxidative stress and apoptosis in the intestinal tissue, and pretreatment with DSePA significantly reduced both these parameters. It was also found to abrogate the radiation-induced intestinal inflammatory response and augment the proliferation of intestinal cells. Additionally, irradiation-induced polarization of Th1/Th2 immune balance toward the Th2-dominant direction and pretreatment with DSePA ameliorated this shift, which may be beneficial for the recovery from radiation injury. In conclusion, pretreatment with DSePA prevented radiation-induced oxidative damage in small intestine and the underlying mechanisms responsible for this could be attributed to inhibition of oxidative stress, apoptosis, and inflammation.
Keywords: Apoptosis; Diselenodipropionic acid; Intestine; Inflammation; Proliferation; γ-Radiation
Sodium fluoride suppress proliferation and induce apoptosis through decreased insulin-like growth factor-I expression and oxidative stress in primary cultured mouse osteoblasts by Zhi Wang; Xiaoyu Yang; Shiyong Yang; Gaixian Ren; Miro Ferreri; Yong Su; Liben Chen; Bo Han (pp. 1407-1417).
It has been reported that sodium fluoride suppressed proliferation and induced apoptosis in osteoblasts. However, the details about the mechanism at work in bone metabolism are limited. In this study, we further investigated the mechanisms of NaF on proliferation and apoptosis in the primary cultured mouse osteoblasts, which were exposed to different concentration of NaF (10−6–5 × 10−4 M). We examined the effect of NaF on proliferation, cell cycle, apoptosis, oxidative stress, and the protein level of insulin-like growth factor-I (IGF-I) in osteoblasts. All the tested NaF inhibited proliferation and arrested cell cycle at S phase in osteoblasts, and further demonstrated to induce apoptosis in osteoblasts. On the other hand, we found that NaF increased oxidative stress and decreased protein expression of IGF-I. Our study herein suggested that NaF caused proliferation suppression, and apoptosis may contribute to decrease IGF-I expression and increased oxidative stress damage by NaF in the primary mouse osteoblasts.
Keywords: Sodium fluoride; Proliferation; Apoptosis; Insulin-like growth factor-I; Oxidative stress
Effects of 5-chloro-2-methyl-4-isothiazolin-3-one and other candidate biodiesel biocides on rat alveolar macrophages and NR8383 cells by R. Poon; M. Rigden; N. Edmonds; N. Charman; S. Lamy (pp. 1419-1427).
Biocides are added to biodiesels to inhibit and remove microbial growth. The effects of 5-chloro-2-methyl-4-isothiazolin-3-one (CMIT), a candidate biodiesel biocide, were studied using freshly isolated rat alveolar macrophages (AM) and NR8383 cell line. CMIT markedly inhibited phagocytic oxidative burst as measured by zymosan-induced chemiluminescence, and cellular cytokine secretion as measured by zymosan-induced TNF-α secretion. The 50% inhibition concentration (LC50) for CMIT was 0.002–0.004 mM for both cellular functions. AM exposed to CMIT for as little as 2 min showed markedly inhibited functions that persisted for at least 5 h. Sodium metabisulfite was able to partially neutralize the inhibitory activity of CMIT. Cysteine and glutathione, when present at a molar ratio of 2–1 or higher against CMIT, were effective neutralizers, while serine, histidine, alanine, and albumin were without effect. When the AM testing system was used to compare the toxicity of CMIT against three other candidate biodiesel biocides, methylene dithiocyanate (MDC) was found to be of comparable toxicity to CMIT, 2-methyl-4-isothiazolin-3-one (MIT) was much less toxic, and dimethyl acetylenedicarboxylate (DMAD) was non-toxic. Because AM is among the first cell-type exposed to inhaled biodiesel aerosols, the result suggested that CMIT present in biodiesel may produce respiratory effects, and further investigations including animal studies are warranted.
Keywords: CMIT; Biocides; Biodiesel; Alveolar macrophages; Toxicity
Cytotoxic effects of hydroxylated fullerenes on isolated rat hepatocytes via mitochondrial dysfunction by Yoshio Nakagawa; Toshinari Suzuki; Hidemi Ishii; Dai Nakae; Akio Ogata (pp. 1429-1440).
The cytotoxic effects of hydroxylated fullerenes, also termed fullerenols or fullerols [C60(OH) n ], which are known nanomaterials and water-soluble fullerene derivatives, were studied in freshly isolated rat hepatocytes. The exposure of hepatocytes to C60(OH)24 caused not only concentration (0–0.25 mM)- and time (0–3 h)-dependent cell death accompanied by the formation of cell blebs, loss of cellular ATP, reduced glutathione (GSH), and protein thiol levels, but also the accumulation of glutathione disulfide and malondialdehyde, indicating lipid peroxidation. Of the other analogues examined, the cytotoxic effects of C60(OH)12 and fullerene C60 at a concentration of 0.125 mM were less than those of C60(OH)24. The loss of mitochondrial membrane potential and generation of oxygen radical species in hepatocytes incubated with C60(OH)24 were greater than those with C60(OH)12 and fullerene C60. In the oxygen consumption of mitochondria isolated from rat liver, the ratios of state-3/state-4 respiration were more markedly decreased by C60(OH)24 and C60(OH)12 compared with C60. In addition, C60(OH)24 and C60(OH)12 resulted in the induction of the mitochondrial permeability transition (MPT), and the effects of C60(OH)12 were less than those of C60(OH)24. Taken collectively, these results indicate that (a) mitochondria are target organelles for fullerenols, which elicit cytotoxicity through mitochondrial failure related to the induction of the MPT, mitochondrial depolarization, and inhibition of ATP synthesis in the early stage and subsequently oxidation of GSH and protein thiols, and lipid peroxidation through oxidative stress at a later stage; and (b) the toxic effects of fullerenols may depend on the number of hydroxyl groups participating in fullerene in rat hepatocytes.
Keywords: Hydroxylated fullerene; Fullerenols; Mitochondrial dysfunction; Oxidative stress; Cytotoxicity; Rat hepatocytes
Fluoride-induced apoptosis and gene expression profiling in mice sperm in vivo by Zilong Sun; Ruiyan Niu; Bin Wang; Zhibin Jiao; Jinming Wang; Jianhai Zhang; Shaolin Wang; Jundong Wang (pp. 1441-1452).
Exposure to fluoride can induce low sperm quality; however, little is known about the molecular mechanisms by which fluoride exerts its toxic effects. This study was conducted to evaluate ultrastructure, oxidative stress, and apoptosis in sperm of mice treated with 150 mg/l NaF for 49 days. Furthermore, microarray analysis was also utilized to characterize the effects of fluoride in gene expression profiling on mice sperm. An increased ROS and a decreased TAC accompanied with distinct morphological changes and significant apoptosis were observed in mice sperm from the fluoride group. Fluoride exposure also significantly elevated the protein expressions of cytochrome c and active caspase-3. In global gene expression profiling, 34 up-regulated and 63 down-regulated genes, which are involved in several sperm biological processes including signal transduction, oxidative stress, apoptosis, electron transport, glycolysis, chemotaxis, spermatogenesis, and sperm capacitation, were significantly differentially expressed. Based on these findings, it was proposed that oxidative stress induced by excessive ROS may trigger sperm apoptosis through mitochondrial impairment, resulting in decreased fertility in mice exposed to fluoride. Microarray analysis also provided several important biological clues for further investigating fluoride-induced damage in sperm morphology and functions.
Keywords: Fluoride; Mice; Sperm; Apoptosis; Gene expression profiling
Bisphenol A-glycidyl methacrylate induces a broad spectrum of DNA damage in human lymphocytes by Kinga Drozdz; Daniel Wysokinski; Renata Krupa; Katarzyna Wozniak (pp. 1453-1461).
Bisphenol A-glycidyl methacrylate (BisGMA) is monomer of dental filling composites, which can be released from these materials and cause adverse biologic effects in human cells. In the present work, we investigated genotoxic effect of BisGMA on human lymphocytes and human acute lymphoblastic leukemia cell line (CCRF-CEM) cells. Our results indicate that BisGMA is genotoxic for human lymphocytes. The compound induced DNA damage evaluated by the alkaline, neutral, and pH 12.1 version of the comet assay. This damage included oxidative modifications of the DNA bases, as checked by DNA repair enzymes EndoIII and Fpg, alkali-labile sites and DNA double-strand breaks. BisGMA induced DNA-strand breaks in the isolated plasmid. Lymphocytes incubated with BisGMA at 1 mM were able to remove about 50% of DNA damage during 120-min repair incubation. The monomer at 1 mM evoked a delay of the cell cycle in the S phase in CCRF-CEM cells. The experiment with spin trap—DMPO demonstrated that BisGMA induced reactive oxygen species, which were able to damage DNA. BisGMA is able to induce a broad spectrum of DNA damage including severe DNA double-strand breaks, which can be responsible for a delay of the cell cycle in the S phase.
Keywords: BisGMA; DNA damage; DNA repair; Reactive oxygen species; Cell cycle
Use of the γH2AX assay for assessing the genotoxicity of bisphenol A and bisphenol F in human cell lines by Marc Audebert; L. Dolo; E. Perdu; J. -P. Cravedi; D. Zalko (pp. 1463-1473).
Bisphenol A (BPA) and bisphenol F (BPF) are widely used to manufacture plastics and epoxy resins. Both compounds have been shown to be present in the environment and are food contaminants, with, as a result, a low but chronic exposure of humans. However, the fate and possible bioactivation of these compounds at the level of human cell lines was not completely elucidated yet. In this study, we investigated the ability of human cells (intestinal cell line: LS174T, hepatoma cell line: HepG2, and renal cell line: ACHN) to biotransform BPA and BPF, and focused on the cytotoxicity and genotoxicity of these two bisphenols, through the use of a novel and efficient genotoxic assay based on the detection of histone H2AX phosphorylation. BPA and BPF were extensively metabolized in HepG2 and LS174T cell lines, with stronger biotransformation capabilities in intestinal cells than observed in liver cells. Both cell lines produced the glucuronide as well as the sulfate conjugates of BPA. Conversely, the ACHN cell line was found to be devoid of any metabolic capabilities for the two examined bisphenols. Cytotoxicity was tested for BPA, BPF, as well as one metabolite of BPF produced in vivo in rat, namely dihydroxybenzophenone (DHB). In the three cell lines used, we observed similar ranges of toxicity, with DHB being weakly cytotoxic, BPF exhibiting an intermediary cytotoxicity, and BPA being the most cytotoxic compound tested. BPA and DHB were not found to be genotoxic, whatever the cell line examined. BPF was clearly genotoxic in HepG2 cells. These results demonstrate that some human cell lines extensively metabolize bisphenols and establish the genotoxic potential of bisphenol F.
Keywords: Bisphenol A; Bisphenol F; Metabolism; Genotoxicity; H2AX; LS174T
Suppressive effect of enzymatically modified isoquercitrin on phenobarbital-induced liver tumor promotion in rats by Reiko Morita; Keisuke Shimamoto; Yuji Ishii; Kazunori Kuwata; Bun-ichiro Ogawa; Masako Imaoka; Shim-mo Hayashi; Kazuhiko Suzuki; Makoto Shibutani; Kunitoshi Mitsumori (pp. 1475-1484).
To investigate the effect of enzymatically modified isoquercitrin (EMIQ) on hepatocellular tumor promotion induced by phenobarbital (PB), male rats were administered a single intraperitoneal injection of 200 mg/kg N-diethylnitrosamine (DEN) and then fed with a diet containing PB (500 ppm) for 8 weeks, with or without EMIQ (2,000 ppm) in the drinking water. One week after PB administration, rats underwent a two-thirds partial hepatectomy. The PB-induced increase in the number and area of glutathione S-transferase placental form-positive foci and the proliferating cell nuclear antigen-positive ratio was significantly suppressed by EMIQ. Real-time reverse transcription–polymerase chain reaction analysis revealed increases in mRNA expression levels of Cyp2b2 and Mrp2 in the DEN-PB and DEN-PB-EMIQ groups compared with the DEN-alone group, while the level of Mrp2 decreased in the DEN-PB-EMIQ group compared with the DEN-PB group. There were no significant changes in microsomal reactive oxygen species (ROS) production and oxidative stress markers between the DEN-PB and DEN-PB-EMIQ groups. Immunohistochemically, the constitutive active/androstane receptor (CAR) in the DEN-PB group was clearly localized in the nuclei, but its immunoreactive intensity was decreased in the DEN-PB-EMIQ group. These results indicate that EMIQ suppressed the liver tumor-promoting activity of PB by inhibiting nuclear translocation of CAR, and not by suppression of oxidative stress.
Keywords: Enzymatically modified isoquercitrin; Phenobarbital; Reactive oxygen species; CYP2B inducer; Liver tumor; Rat