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.86, #12)
Buckyballs (fullerenes): free radical sponges or inflammatory agents?
by C. Cadenas; R. Marchan; J. G. Hengstler (pp. 1807-1808).
Toxicity of pristine versus functionalized fullerenes: mechanisms of cell damage and the role of oxidative stress by Andreja Trpkovic; Biljana Todorovic-Markovic; Vladimir Trajkovic (pp. 1809-1827).
The fullerene C60, due to the physicochemical properties of its spherical cage-like molecule build exclusively from carbon atoms, is able to both scavenge and generate reactive oxygen species. While this unique dual property could be exploited in biomedicine, the low water solubility of C60 hampers the investigation of its behavior in biological systems. The C60 can be brought into water by solvent extraction, by complexation with surfactants/polymers, or by long-term stirring, yielding pristine (unmodified) fullerene suspensions. On the other hand, a modification of the C60 core by the attachment of various functional groups results in the formation of water-soluble fullerene derivatives. Assessment of toxicity associated with C60 preparations is of pivotal importance for their biomedical application as cytoprotective (antioxidant), cytotoxic (anticancer), or drug delivery agents. Moreover, the widespread industrial utilization of fullerenes may also have implications for human health. However, the alterations in physicochemical properties imposed by the utilization of different methods for C60 solubilization profoundly influence toxicological effects of fullerene preparations, thus making the analysis of their potential therapeutic and environmental toxicity difficult. This review provides a comprehensive evaluation of the in vitro and in vivo toxicity of fullerenes, focusing on the comparison between pristine and derivatized C60 preparations and the mechanisms of their toxicity to mammalian cells and tissues.
Keywords: Fullerenes; Cytotoxicity; Genotoxicity; Oxidative stress; In vitro; In vivo
Di-n-butyl phthalate (DnBP) and diisobutyl phthalate (DiBP) metabolism in a human volunteer after single oral doses by H. M. Koch; K. L. Y. Christensen; V. Harth; M. Lorber; T. Brüning (pp. 1829-1839).
An individual (male, 36 years, 87 kg) ingested two separate doses of di-n-butyl phthalate (DnBP) and diisobutyl phthalate (DiBP) at a rate of ~60 μg/kg. Key monoester and oxidized metabolites were identified and quantified in urine continuously collected until 48 h post-dose. For both DnBP and DiBP, the majority of the dose was excreted in the first 24 h (92.2 % of DnBP, 90.3 % of DiBP), while only <1 % of the dose was excreted in urine on day 2. In each case, the simple monoesters were the major metabolites (MnBP, 84 %; MiBP, 71 %). For DnBP, ~8 % was excreted as various side chain oxidized metabolites. For DiBP, approximately 20 % was excreted mainly as the oxidized side chain metabolite 2OH-MiBP, indicating that the extent of oxidative modification is around 2.5 times higher for DiBP than for DnBP. All DnBP and DiBP metabolites reached peak concentrations between 2 and 4 h post-exposure, followed by a monotonic decline. For DnBP metabolites, the elimination halftime of MnBP was 2.6 h; longer elimination halftimes were estimated for the oxidized metabolites (2.9–6.9 h). For DiBP metabolites, MiBP had the shortest halftime (3.9 h), and the oxidized metabolites had somewhat longer halftimes (4.1 and 4.2 h). Together with the simple monoesters, secondary oxidized metabolites are additional and valuable biomarkers of phthalate exposure. This study provides basic human metabolism and toxicokinetic data for two phthalates that have to be considered human reproductive toxicants and that have been shown to be omnipresent in humans.
Keywords: DnBP; DiBP; Phthalate; Metabolism; Human biomonitoring
The effects of sodium diethyldithiocarbamate in fibroblasts V79 cells in relation to cytotoxicity, antioxidative enzymes, glutathione, and apoptosis by I. Rahden-Staroń; E. Grosicka-Maciąg; D. Kurpios-Piec; H. Czeczot; T. Grzela; M. Szumiło (pp. 1841-1850).
Sodium diethyldithiocarbamate (DETC) is the main metabolite of disulfiram. Recently, we reported that mechanism of disulfiram cytotoxicity in V79 cells might be partially connected with thiol redox-state imbalance. Here, we examined the effect of DETC on the level of intracellular glutathione (GSH), protein oxidation (measured as PC—protein carbonyl content), lipid peroxidation (measured as TBARS—thiobarbituric acid reactive substances), antioxidant enzymatic defense, as well as on apoptosis. We used V79 Chinese hamster fibroblasts cells with and without modulated glutathione (GSH) level by N-acetyl-l-cysteine (NAC). We showed that treatment with DETC at concentrations that cause a moderate increase in thiol-state imbalance but not cell death stimulates oxidative stress measured as increased level of PC and TBARS, adaptive response of GSH-related enzymes and apoptosis. Our results show that cellular effects of DETC are partially attributable to the initial redox cellular state, since the increase of GSH level by NAC pre-treatment prevented the observed changes.
Keywords: GSH; TBARS; PC; Antioxidative enzymes; Apoptosis; V79 cells
Fine PM induce airway MUC5AC expression through the autocrine effect of amphiregulin by Stéphanie Val; Esther Belade; Isabelle George; Jorge Boczkowski; Armelle Baeza-Squiban (pp. 1851-1859).
Particulate pollution is suspected to contribute to obstructive lung diseases characterized by chronic inflammation, mucus hypersecretion and bronchial remodeling. Our aim was to study the effect of real-world particulate matter (PM) on the expression of a mucin, MUC5AC, focusing on the role of the epidermal growth factor receptor (EGFR) pathway. MUC5AC induction was studied in vivo in mice trachea and in vitro in human bronchial epithelial cells (HBEC) exposed to urban fine PM. Fine PM were able to induce MUC5AC mRNA in mice trachea after 48 h of exposure (50 μg PM/mouse), and MUC5AC mRNA and protein in HBEC after 24 h of exposure (from 5 μg PM/cm2). It was associated with the increased expression of amphiregulin (AREG), an EGFR ligand. Experiments with conditioned media (media from PM-treated cells) demonstrated the involvement of AREG on MUC5AC induction as MUC5AC induction by media from PM-treated cells was prevented in the presence of either EGFR- or AREG-neutralizing antibodies. The effect of an inhibitor of a metalloprotease involved in the AREG shedding confirmed the autocrine loop made by AREG leading to MUC5AC induction by fine PM. We also demonstrated that IL-8 pro-inflammatory cytokine induction was dependent on the same autocrine mechanisms. We demonstrate for the first time that MUC5AC expression and production is increased by short-term exposure to fine PM through an autocrine effect of AREG. Our study provides mechanistic explanations to the exacerbation of obstructive lung diseases induced by particulate pollution characterized by mucus hypersecretion and chronic inflammation.
Keywords: Atmospheric particle; EGFR pathway; Lung; Mucin; Pro-inflammatory cytokine
Exposure of primary porcine urothelial cells to benzo(a)pyrene: in vitro uptake, intracellular concentration, and biological response by Nisha Verma; Mario Pink; Frank Petrat; Albert W. Rettenmeier; Simone Schmitz-Spanke (pp. 1861-1871).
More than 90 % of all bladder cancers are transitional cell carcinomas arising from the cells lining the inside of the hollow organ (uroepithelium). Cell cultures from primary urinary bladder epithelial cells (PUBEC) of pigs were established to assess the uptake, intracellular concentration, and subcellular distribution of the environmental pollutant benzo(a)pyrene (BaP). During treatment of the cells with 0.5 μM BaP for up to 24 h, intracellular concentration of BaP increased without saturation but with marked differences between various PUBEC pools. Analysis of BaP uptake by laser scanning microscopy indicated that BaP is rapidly partitioned into the cell membrane, while only a slight but significant increase in BaP fluorescence intensity was observed in the cytosol and nucleus. Spectrofluorometric quantification of BaP in PUBEC using ex situ calibration revealed a strong accumulation of BaP, leading to intracellular concentrations ranging from 7.28 to 35.70 μM in cells exposed to 0.5 μM BaP and from 29.9 to 406.64 μM in cells exposed to 10 μM BaP. These results were confirmed by gas chromatographic mass spectrometric analysis. Apoptotic cell nuclei were assessed by TUNEL analysis to see whether BaP exposure at the given concentrations results in a toxic effect. While apoptotic cells were barely detectable in control epithelial cells, there was a marked elevation in apoptosis in the BaP-exposed cells. In conclusion, a comprehensive study on uptake and quantification of BaP in epithelial cells from pig bladder is reported for the first time. The study may be helpful in understanding the pattern of BaP uptake and distribution in bladder and its possible implication in bladder cancer development.
Keywords: Primary urinary bladder epithelial cells (PUBEC); Pig; Polycyclic aromatic hydrocarbon; Benzo(a)pyrene (BaP); Confocal laser microscopy; Quantification; Uptake; Subcellular distribution; Cytosolic medium
Characterization of identity, metabolism and androgenic activity of 17-hydroxyandrosta-3,5-diene by GC–MS and a yeast transactivation system by Anne Bauer; Felicitas Rataj; Oliver Zierau; Patricia Anielski; Joachim Große; Maria-Kristina Parr; Günter Vollmer; Detlef Thieme (pp. 1873-1884).
Anabolic–androgenic steroids are frequently misused compounds in sports, and they belong to the controlled substances according to the requirements of the World Anti-Doping Agency. The classical techniques of steroid detection are mass spectrometry coupled to gas or liquid chromatography. Biological methods that base on the ability of substances to bind the steroid receptor are not applied in routine doping control procedures so far, but they appear to be useful for characterization of steroid androgenic potential. In this study we used the yeast androgen receptor reporter system (YAS), which in the past has already successfully been applied to both various androgenic substances and also urine samples. Giving attention to the androgenic potential of steroidal dietary supplements, we exemplified the analysis using both mass spectrometry techniques and the YAS-based assay on the product “Syntrax Tetrabol” which was a confiscated dietary supplement and marketed as a steroid precursor. Identification, structure and the kinetic behavior of its excreted metabolites were analyzed by NMR, GC–MS and LC–MS/MS. The androgenic potential of the parent compound as well as its metabolites in urine was evaluated with the help of the YAS. The application of urine samples with a previous deconjugation and the inclusion of urine density values were carried out and led to increased responses on the YAS. Further, the possibility of a complementary application of structure-based instrumental analysis and biological detection of androgenicity with the help of the YAS seems to be desirable and is discussed.
Keywords: Doping; Mass spectrometry; Anabolic androgenic steroids; Nutritional supplement; YAS bioassay, metabolites
Evaluation of metabolomic profiling against renal toxicity in Sprague–Dawley rats treated with melamine and cyanuric acid by Tae Hyung Kim; Mee Young Ahn; Hyun Jung Lim; Young Ju Lee; Yu Jin Shin; Umasankar De; Jaewon Lee; Byung Mu Lee; Suhkmann Kim; Hyung Sik Kim (pp. 1885-1897).
Melamine-induced renal toxicity is associated with crystal formation in the kidney following exposure to melamine and cyanuric acid. However, metabolomic profiling of intact kidney tissue after chronic intake of melamine and cyanuric acid (M + CA) mixtures has rarely been studied. The present study investigated the melamine-induced renal toxicity by determining metabolites in the kidney through [1H]nuclear magnetic resonance. Melamine (63 mg/kg) and cyanuric acid (6.3 mg/kg) were co-administered to rats via oral gavage for 30 days. The mixture of M + CA (63/6.3 mg/kg) induced nephrotoxicity, as determined by increased blood urea nitrogen (BUN) and creatinine levels. The kidney weights were significantly increased in the animals treated with M + CA (63/6.3 mg/kg). The histological analysis revealed epithelial degeneration and necrotic cell death in the proximal and distal tubules. Furthermore, various metabolites were altered in both renal medullar and cortical tissues. In the medullar tissues, asparagine, choline, creatinine, cysteine, ethanolamine, glucose, isoleucine, glutamine, and myo-inositol levels were elevated, but glucitol, phenylalanine, tyrosine, and sn-glycero-3-levels were reduced. In the cortex, ethanolamine, hypoxanthine, isoleucine and o-phosphoethanolamine levels were increased, whereas formate, glucose, glutathione, threonine, and myo-inositol levels were decreased, suggesting the M + CA-induced renal cell injury. These data suggest that a mixture of M + CA-induced metabolites may be useful biomarkers for the detection of kidney injury.
Keywords: Melamine; Nephrotoxicity; Metabolomics; [1H]NMR; Biomarkers
The rat prepubertal uterine myometrium and not the luminal epithelium is predominantly affected by a chronic dietary genistein exposure by Frank Josef Möller; Corinna Ledwig; Oliver Zierau; Torsten Hertrampf; Gisela H. Degen; Patrick Diel; Günter Vollmer (pp. 1899-1910).
Current knowledge about dietary soy isoflavone-induced hormonal effects and potential priming effects for the responsiveness of the organism to other estrogens is insufficient. The present study examined the effects of pre- and postnatal soy isoflavone exposure on estrogen responsiveness by estrogen receptor agonists in the uteri of prepubertal Wistar rats. To this end, offspring were generated from dams already maintained on three dietary groups, (1) a phytoestrogen-free diet, (2) a soy isoflavone-rich diet with 232 ppm daidzein and 240 ppm genistein or (3) a custom-made diet supplemented with 700 ppm genistein (GEN). Then, F1 females continuously exposed to isoflavones from GD1 to PND21 and non-exposed controls were subjected to an immature uterotrophic assay to compare physiological parameters and the response to subcutaneous treatment with 17β-estradiol, GEN or an estrogen receptor subtype (ERα and ERβ)–specific agonist. Uterine wet weight (UWW), luminal epithelial height (LEH) and myometrial thickness (MMT) were determined. In addition, isoflavone plasma levels and mRNA expression profiles of relevant steroid receptors and of molecular markers for proliferation and estrogenicity were assessed for all groups. The influence of dietary isoflavones on the sensitivity to various estrogenic stimuli in these prepubertal animals was minor. Yet, the uterus of immature rats with high chronic GEN exposure alone showed already an increase in UWW, LEH and MMT. The myometrial response to GEN was more pronounced than that of the luminal epithelium, which may be due to a non-uniform distribution of steroid receptors, in particular the progesterone receptor. In conclusion, although the impact of a continuous, prenatally initiated exposure to dietary isoflavones on the uterine physiology of juvenile rats is modest, the possible priming effects of this exposure for beneficial or adverse late-onset consequences in adults should not be neglected.
Keywords: Isoflavones; Dietary Exposure; Immature Uterus; Genistein
Characterization of a genotoxic impact compound in Alternaria alternata infested rice as Altertoxin II by Christoph Schwarz; Christine Tiessen; Martin Kreutzer; Timo Stark; Thomas Hofmann; Doris Marko (pp. 1911-1925).
Toxicity-guided fractionation was used to identify DNA strand breaking impact compounds in extracts obtained from rice heavily infested with the Alternaria alternata strains DSM 62006 and DSM 62010. The major genotoxic potential measured in the comet assay using human colon carcinoma cells (HT29) could be attributed to three unknown peaks, whereas the fractions containing alternariol, its monomethylether or tenuazonic acid showed no significant DNA damaging effects. According to 1H and 13C-NMR spectroscopy, one genotoxic impact compound was identified as Altertoxin II (ATXII). ATXII showed potent DNA damaging properties in HT29 cells with substantial induction of formamidopyrimidine DNA glycosylase (FPG)-sensitive sites. However, no effect was observed with respect to the cellular redox status, measured in the DCF assay and as total glutathione. The induction of apoptosis could be excluded as a potential reason for enhanced DNA damage. After 24 h of incubation with 1 μM ATX II, a significant increase of cells in the G0/G1 phase was observed together with an inhibition of cell proliferation in the sulforhodamine B assay. Taken together, ATX II was found to contribute substantially to the genotoxic effects of complex extracts obtained from Alternaria alternata infested rice. The results demonstrate the high genotoxic potency of ATX II in human cells, underlining the necessity for further studies on the occurrence in food and its relevance for food safety.
Keywords: Alternaria alternata ; Altertoxin II; Stemphyltoxin III; Comet assay; Toxicity-guided fractionation
A dual function of the furanocoumarin chalepensin in inhibiting Cyp2a and inducing Cyp2b in mice: the protein stabilization and receptor-mediated activation by Wei-Sheng Lo; Yun-Ping Lim; Chien-Chih Chen; Chih-Chien Hsu; Pavel Souček; Chul-Ho Yun; Wen Xie; Yune-Fang Ueng (pp. 1927-1938).
Chalepensin, a furanocoumarin, is present in several medicinal Rutaceae plants and causes a mechanism-based inhibition of human and mouse cytochrome P450 (P450, CYP) 2A in vitro. To address the in vivo effect, we investigated the effects of chalepensin on multiple hepatic P450 enzymes in C57BL/6JNarl mice. Oral administration of 10 mg/kg chalepensin to mice for 7 days significantly decreased hepatic coumarin 7-hydroxylation (Cyp2a) and increased 7-pentoxyresorufin O-dealkylation (Cyp2b) activities, whereas activities of Cyp1a, Cyp2c, Cyp2e1, and Cyp3a were not affected. Without affecting its mRNA level, the decreased Cyp2a activity was accompanied by an increase in the immunodetected Cyp2a5 protein level. In chalepensin-treated mice, microsomal Cyp2a5 was less susceptible to ATP-fortified cytosolic degradation than that in control mice, resulting in the elevated protein level. The in vitro inactivation through NADPH-fortified pre-incubation with chalepensin also protected microsomal Cyp2a5 against protein degradation. Using cell-based reporter systems, chalepensin at a concentration near unbound plasma concentration activated mouse constitutive androstane receptor (CAR), in agreement with the observed induction of Cyp2b. These findings revealed that suicidal inhibition of Cyp2a5 and the CAR-mediated Cyp2b9/10 induction concurrently occurred in chalepensin-treated mice.
Keywords: Chalepensin; CYP2A; CYP2B; Protein stability; Constitutive androstane receptor; Liver