| 1. |
- Andersson, Helén, 1982-, et al.
(author)
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Low levels of the air pollutant 1-nitropyrene induce DNA damage, increased levels of reactive oxygen species and endoplasmic reticulum stress in human endothelial cells
- 2009
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In: Toxicology. - : Elsevier BV. - 0300-483X .- 1879-3185. ; 262:1, s. 57-64
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Journal article (peer-reviewed)abstract
- Both epidemiological and experimental studies suggest that exposure to high levels of air pollution is a risk factor associated with cardiovascular disease. Traffic emission is a major source of exposure to persistent air pollutants such as nitrated polycyclic aromatic hydrocarbons (nitro-PAHs). 1-Nitropyrene (1-NP), one of the most abundant nitro-PAHs in diesel exhausts, was selected as a model nitro-PAH for the present study. The aim of the study was to investigate the effects of 1-NP in human umbilical vein endothelial cells (HUVECs) and the metabolic pathways involved. The nitroreductase inhibitor dicoumarol and the coplanar aryl hydrocarbon receptor (AhR) ligand PCB 126 were used to modulate the metabolism of 1-NP. The results revealed that low levels (< or =10microM) of 1-NP induced DNA damage, increased levels of reactive oxygen species (ROS) and increased protein expression of the endoplasmic reticulum (ER) stress chaperone GRP78. A decrease in cell viability was only observed following exposure to a higher level of 1-NP (15microM). Inhibition of nitroreductive metabolism by dicoumarol attenuated the induction of DNA damage, intracellular ROS levels and GRP78 expression. This suggests that the effects of 1-NP on HUVEC were mediated by metabolites mainly formed at nitroreduction. Our findings suggest that the human blood vessel endothelium is a sensitive target tissue for the major nitro-PAH constituent in diesel exhaust.
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| 2. |
- Aspenström-Fagerlund, Bitte, et al.
(author)
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Oleic acid and docosahexaenoic acid cause an increase in the paracellular absorption of hydrophilic compounds in an experimental model of human absorptive enterocytes
- 2007
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In: Toxicology. - : Elsevier BV. - 0300-483X .- 1879-3185. ; 237:1-3, s. 12-23
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Journal article (peer-reviewed)abstract
- Surface active compounds present in food possibly have the ability to enhance the absorption of water soluble toxic agents. Therefore, we investigated whether fatty acids such as oleic acid and docosahexaenoic acid (DHA), both commonly present in food, negatively affect the integrity of tight junctions (TJ) in the intestinal epithelium and thereby increase the absorption of poorly absorbed hydrophilic substances. Caco-2 cells, which are derived from human absorptive enterocytes, were grown on permeable filters for 20-25 days. Differentiated cell monolayers were apically exposed for 90min to mannitol in emulsions of oleic acid (5, 15 or 30mM) or DHA (5, 15 or 30mM) in an experimental medium with or without Ca(2+) and Mg(2+). Absorption of (14)C-mannitol increased and trans-epithelial electrical resistance (TEER) decreased in cell monolayers exposed to oleic acid and DHA, compared to controls. Cytotoxicity, measured as leakage of LDH, was higher in groups exposed to 30mM oleic acid and all concentrations of DHA. Morphology of the cell monolayers was studied by using fluorescence microscopy. Exposure of cell monolayers to 5mM DHA for 90min resulted in a profound alteration of the cell-cell contacts as detected by staining the cells for beta-catenin. Oleic acid (30mM) treatment also induced dissolution of the cell-cell contacts but the effect was not as pronounced as with DHA. Cell monolayers were also exposed for 180min to 250nM cadmium (Cd) in emulsions of oleic acid (5 or 30mM) or DHA (1 or 5mM), in an experimental medium with Ca(2+) and Mg(2+). Retention of Cd in Caco-2 cells was higher after exposure to 5mM oleic acid but lower after exposure to 30mM oleic acid and DHA. Absorption of Cd through the monolayers increased after DHA exposure but not after exposure to oleic acid. Our results indicate that fatty acids may compromise the integrity of the intestinal epithelium and that certain lipids in food may enhance the paracellular absorption of poorly absorbed hydrophilic substances.
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| 3. |
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| 4. |
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| 5. |
- Fischer, Celia, et al.
(author)
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Neonatal co-exposure to low doses of an ortho-PCB (PCB 153) and methyl mercury exacerbate defective developmental neurobehavior in mice
- 2008
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In: Toxicology. - : Elsevier BV. - 0300-483X .- 1879-3185. ; 244:2-3, s. 157-165
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Journal article (peer-reviewed)abstract
- Epidemiological studies have shown a discrepancy between children in the Faeroe Islands and children in the Seychelles with regard to neuropsychological defects during early development. Both populations have a high consumption of MeHg-contaminated fish. The defective neuropsychological differences seen in children from the Faeroe Islands could be attributed to PCBs via the mother's dietary consumption of whale meat and blubber in addition to MeHg. We have previously reported that certain persistent environmental toxicants like PCBs, DDT and PBDEs can induce permanent developmental neurotoxic effects in mice when these agents are present during a critical period of the neonatal brain development. The present study investigates whether PCB 153 (an ortho-substituted PCB) can interact with MeHg to enhance developmental neurotoxic effects on spontaneous behavior and habituation. Neonatal NMRI male mice were exposed at 10 days of age to a single oral dose of one of the following doses: PCB 153 (1.4 μmol/kg body weight), MeHg (0.08, 0.40, or 4.0 mg/kg body weight), PCB 153 plus MeHg, or a vehicle (20% fat emulsion). Spontaneous behavior, habituation, and cognitive function were observed in 2- and 4-month-old mice. The present study demonstrates that an interaction from co-exposure to low doses of PCB 153 and MeHg enhances developmental neurotoxic effects. These effects are manifested as disrupted spontaneous behavior, lack of habituation, and reduced cognitive functions. These effects occur at doses within the same order of magnitude as reported for exposed children.
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| 6. |
- Hansson, Sven Ove, et al.
(author)
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Evaluating the risk decision process
- 2006
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In: Toxicology. - : Elsevier BV. - 0300-483X .- 1879-3185. ; 218:03-feb, s. 100-111
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Journal article (peer-reviewed)abstract
- In order to ensure that risk assessment and risk management serve their purposes efficiently, it is essential to systematically evaluate actual practices. In this overview, it is proposed that such evaluation studies constitute an important field Of Study that should be recognized as a Subdiscipline of regulatory toxicology with its own research issues and its own methodologies. Previous Such evaluation studies are summarized. Methods are described that can be used for comparing different risk assessments of one of the same substance, for checking the consistency of harmonized classifications with the available data, for assessing the actual margin of safety (i.e. size Of Uncertainty factors) in exposure limits, and for comparing different lists of exposure limits. In conclusion, some important problem areas for future evaluation studies are pointed out.
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| 7. |
- Havarinasab, Said, 1964-, et al.
(author)
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Dose and Hg species determine the T-helper cell activation in murine autoimmunity
- 2007
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In: Toxicology. - : Elsevier BV. - 0300-483X .- 1879-3185. ; 229:1-2, s. 23-32
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Journal article (peer-reviewed)abstract
- Inorganic mercury (mercuric chloride-HgCl2) induces in mice an autoimmune syndrome (HgIA) with T cell-dependent polyclonal B cell activation and hypergammaglobulinemia, dose- and H-2-dependent production of autoantibodies targeting the 34 kDa nucleolar protein fibrillarin (AFA), and systemic immune-complex deposits. The organic mercury species methylmercury (MeHg) and ethylmercury (EtHg-in the form of thimerosal) induce AFA, while the other manifestations of HgIA seen after treatment with HgCl2 are present to varying extent. Since these organic Hg species are converted to the autoimmunogen Hg2+ in the body, their primary autoimmunogen potential is uncertain and the subject of this study. A moderate dose of HgCl2 (8 mg/L drinking water - internal dose 148 μg Hg/kg body weight [bw]/day) caused the fastest AFA response, while the induction was delayed after higher (25 mg/L) and lower (1.5 and 3 mg/L) doses. The lowest dose of HgCl2 inducing AFA was 1.5 mg/L drinking water which corresponded to a renal Hg2+ concentration of 0.53 μg/g. Using a dose of 8 mg HgCl2/L this threshold concentration was reached within 24 h, and a consistent AFA response developed after 8-10 days. The time lag for the immunological part of the reaction leading to a consistent AFA response was therefore 7-9 days. A dose of thimerosal close to the threshold dose for induction of AFA (2 mg/L drinking water-internal dose 118 μg Hg/kg bw per day), caused a renal Hg2+ concentration of 1.8 μg/g. The autoimmunogen effect of EtHg might therefore be entirely due to Hg2+ formed from EtHg in the body. The effect of organic and inorganic Hg species on T-helper type 1 and type 2 cells during induction of AFA was assessed as the presence and titre of AFA of the IgG1 and IgG2a isotype, respectively. EtHg induced a persistent Th1-skewed response irrespectively of the dose and time used. A low daily dose of HgCl2 (1.5-3 mg/L) caused a Th1-skewed AFA response, while a moderate dose (8 mg/L) after 2 weeks resulted in a balanced or even Th2-skewed response. Higher daily doses of HgCl2 (25 mg/L) caused a balanced Th2-Th1 response already from onset. In conclusion, while metabolically formed Hg2+ might be the main AFA-inducing factor also after treatment with EtHg, the quality of the Hg-induced AFA response is modified by the species of Hg as well as the dose. © 2006 Elsevier Ireland Ltd. All rights reserved.
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| 8. |
- Hermsen, Sanne A. B., et al.
(author)
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In utero and lactational exposure to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) affects bone tissue in rhesus monkeys
- 2008
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In: Toxicology. - : Elsevier BV. - 0300-483X .- 1879-3185. ; 253:1-3, s. 147-152
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Journal article (peer-reviewed)abstract
- Bone tissue is one of the target tissues for dioxins and dioxin-like compounds. Therefore, the aim of this study was to investigate effects of in utero and lactational exposure to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), oil bone tissue in rhesus monkey, the most human-like experimental model available, Pregnant rhesus monkeys (Macaca mulatta; age 4-10 years) were exposed to TCDD with a total dose of 40.5-42.0 or 405-420 ng/kg bodyweight by repeated subcutaneous injections starting at gestational day 20 and followed by injections every 30 days until 90 clays after delivery. At a mean age of 7 years the offspring were sacrificed and the femur bone dissected. Results from peripheral Quantitative Computed Tomography (pQCT) analyses of the metaphyseal part of the femur bones in female offspring showed significant increases in trabecular bone mineral content (BMC; +84.6%, p < 0.05, F-value (F)=5.9) in the low-dose treatment group compared with the controls. In the same animals, analysis of the mid-diaphyseal part revealed increases in total BMC (+21.3%. p < 0.05, F = 5.2) and cortical cross-sectional area (CSA; +16.4%. p < 0.01, F=7.4) compared with the controls. In males, changes in biomechanical properties indicating more fragile bone were observed. Displacement at failure were significantly increased in the male low-dose group compared to the controls (+38.0%, p, < 0.05, F=11). The high dose of TCDD did not induce any significant changes in bone morphology.
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| 9. |
- Häggqvist, Bo, 1962-, et al.
(author)
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The immunosuppressive effect of methylmercury does not preclude development of autoimmunity in genetically susceptible mice
- 2005
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In: TOXICOLOGY. - : Elsevier BV. - 0300-483X .- 1879-3185. ; 208:1, s. 149-64
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Journal article (peer-reviewed)abstract
- Methylmercury (MeHg) is a common environmental pollutant due to both natural and anthropogenic sources. Although the central nervous system (CNS) is considered the critical organ for the toxic effect of MeHg, it has recently been suggested that the immune system might be at least as sensitive as the CNS.We have examined the effects of MeHg on the immune system in genetically metal-susceptible mice. Subcutaneous (sc) injections of 2 mg MeHg/kg body weight (bw) every third day (internal dose ca. 540 μg Hg/kg bw/day) to A.SW mice of the H-2s haplotype, caused during the first week a 47 and 9% reduction of B- and T-cells, respectively, which indicates immunosuppression. Subsequently, an autoimmune syndrome developed which shared certain features with the syndrome induced by inorganic mercury in H-2s mice, including antibodies targeting the 34 kDa nucleolar protein fibrillarin, increased expression of IL-4 mRNA, increase of Th2-type of immunoglobulins (IgE and IgG1), and increased MHC class II expression on B-cells. However, the response using MeHg was attenuated compared with even lower doses of Hg in the form of inorganic mercury, and specifically lacked the increased expression of IL-2 and IFN-γ mRNA, the polyclonal B-cell activation (PBA), and the systemic immune-complex (IC) deposits which are induced by inorganic mercury. Increasing the dose of MeHg increased the titre of anti-nucleolar antibodies and shortened the induction time, but did not lead to stronger immunostimulation or systemic IC-deposits. The kidney and liver selectively accumulated MeHg, while the blood, spleen and lymph nodes showed lower levels of MeHg. The accumulation of MeHg and Hg2+ increased throughout the 30-day period. The fraction of Hg2+ in the kidney varied between 4 and 22%, and the lymph nodes showed a maximum of 30% Hg2+.We conclude first that MeHg has quantitatively different effect on the immune system compared with inorganic mercury, and secondly that an initial immunosuppression induced by a xenobiotic does not preclude subsequent immunostimulation and autoimmunity.
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| 10. |
- Kilk, Kalle, et al.
(author)
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Analysis of in vitro toxicity of five cell-penetrating peptides by metabolic profiling
- 2009
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In: Toxicology. - : Elsevier BV. - 0300-483X .- 1879-3185. ; 265:3, s. 87-95
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Journal article (peer-reviewed)abstract
- Cell-penetrating peptides (CPPs) are promising candidates for safe and efficient delivery vectors for a wide range of cargoes. However, any compound that is internalized into cells may affect the cell homeostasis. The plethora of possible biological responses makes large scale “omics” studies appealing approaches for hunting any unsuspected side-effects and evaluate the toxicity of drug candidates. Here we have compared the alterations in cytosolic metabolome of CHO cells caused by five representatives of the most common CPPs: transportan (TP), penetratin (pAntp), HIV Tat derived peptide (pTat), nonaarginine (R9) and model amphipathic peptide (MAP). Analysis was done by liquid chromatography–mass spectrometry techniques, principal component analysis and heatmap displays. Results showed that the intracellular metabolome was the most affected by TP followed by pTat and MAP. Only minor changes could be associated with pAntp or R9 treatment. The cells could recover from a treatment with 5 μM TP, but no recovery was observed at higher concentration. Both metabolomic and control experiments showed that TP affected cellular redox potential, depleted energy and the pools of purines and pyrimidines. In conclusion, we have performed a metabolomic analysis comparing the safety of cell-penetrating peptides and demonstrate the toxicity of one of them.
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