| 1. |
- Jarvis, Ian W. H., et al.
(författare)
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Persistent activation of DNA damage signaling in response to complex mixtures of PAHs in air particulate matter
- 2013
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Ingår i: Toxicology and Applied Pharmacology. - Stockholm : Elsevier BV. - 0041-008X .- 1096-0333. ; 266:3, s. 408-418
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Tidskriftsartikel (refereegranskat)abstract
- Complex mixtures of polycyclic aromatic hydrocarbons (PAHs) are present in air particulate matter (PM) and have been associated with many adverse human health effects including cancer and respiratory disease. However, due to their complexity, the risk of exposure to mixtures is difficult to estimate. In the present study the effects of binary mixtures of benzo[a]pyrene (BP) and dibenzo[a,l]pyrene (DBP) and complex mixtures of PAHs in urban air PM extracts on DNA damage signaling was investigated. Applying a statistical model to the data we observed a more than additive response for binary mixtures of BP and DBP on activation of DNA damage signaling. Persistent activation of checkpoint kinase 1 (Chk1) was observed at significantly lower BP equivalent concentrations in air PM extracts than BP alone. Activation of DNA damage signaling was also more persistent in air PM fractions containing PAHs with more than four aromatic rings suggesting larger PAHs contribute a greater risk to human health. Altogether our data suggests that human health risk assessment based on additivity such as toxicity equivalency factor scales may significantly underestimate the risk of exposure to complex mixtures of PAHs. The data confirms our previous findings with PAH-contaminated soil (Niziolek-Kierecka et al., 2012) and suggests a possible role for Chk1 Ser317 phosphorylation as a biological marker for future analyses of complex mixtures of PAHs.
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| 2. |
- Abu-Bakar, A'edah, et al.
(författare)
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Inducible bilirubin oxidase : A novel function for the mouse cytochrome P450 2A5
- 2011
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Ingår i: Toxicology and Applied Pharmacology. - : Elsevier BV. - 0041-008X .- 1096-0333. ; 257:1, s. 14-22
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Tidskriftsartikel (refereegranskat)abstract
- We have previously shown that bilirubin (BR), a breakdown product of haem, is a strong inhibitor and a high affinity substrate of the mouse cytochrome P450 2A5 (CYP2A5). The antioxidant BR, which is cytotoxic at high concentrations, is potentially useful in cellular protection against oxygen radicals if its intracellular levels can be strictly controlled. The mechanisms that regulate cellular BR levels are still obscure. In this paper we provide preliminary evidence for a novel function of CYP2A5 as hepatic "BR oxidase''. A high-performance liquid chromatography/electrospray ionisation mass spectrometry screening showed that recombinant yeast microsomes expressing the CYP2A5 oxidise BR to biliverdin, as the main metabolite, and to three other smaller products with m/z values of 301,315 and 333. The metabolic profile is significantly different from that of chemical oxidation of BR. In chemical oxidation the smaller products were the main metabolites. This suggests that the enzymatic reaction is selective, towards biliverdin production. Bilirubin treatment of primary hepatocytes increased the CYP2A5 protein and activity levels with no effect on the corresponding mRNA. Co-treatment with cycloheximide (CHX), a protein synthesis inhibitor, resulted in increased half-life of the CYP2A5 compared to cells treated only with CHX. Collectively, the observations suggest that the CYP2A5 is potentially an inducible "BR oxidase" where BR may accelerate its own metabolism through stabilization of the CYP2A5 protein. It is possible that this metabolic pathway is potentially part of the machinery controlling intracellular BR levels in transient oxidative stress situations, in which high amounts of BR are produced.
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| 3. |
- Abu-Bakar, A'edah, et al.
(författare)
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Metabolism of bilirubin by human cytochrome P450 2A6
- 2012
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Ingår i: Toxicology and Applied Pharmacology. - : Elsevier BV. - 0041-008X .- 1096-0333. ; 261:1, s. 50-58
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Tidskriftsartikel (refereegranskat)abstract
- The mouse cytochrome P450 (CYP) 2A5 has recently been shown to function as hepatic "Bilirubin Oxidase" (Abu-Bakar, A., et al., 2011. Toxicol. Appl. Pharmacol. 257, 14-22). To date, no information is available on human CYP isoforms involvement in bilirubin metabolism. In this paper we provide novel evidence for human CYP2A6 metabolising the tetrapyrrole bilirubin. Incubation of bilirubin with recombinant yeast microsomes expressing the CYP2A6 showed that bilirubin inhibited CYP2A6-dependent coumarin 7-hydroxylase activity to almost 100% with an estimated K-i of 2.231 mu M. Metabolite screening by a high-performance liquid chromatography/electrospray ionisation mass spectrometry indicated that CYP2A6 oxidised bilirubin to biliverdin and to three other smaller products with m/z values of 301,315 and 333. Molecular docking analyses indicated that bilirubin and its positively charged intermediate interacted with key amino acid residues at the enzyme's active site. They were stabilised at the site in a conformation favouring biliverdin formation. By contrast, the end product, biliverdin was less fitting to the active site with the critical central methylene bridge distanced from the CYP2A6 haem iron facilitating its release. Furthermore, bilirubin treatment of HepG2 cells increased the CYP2A6 protein and activity levels with no effect on the corresponding mRNA. Co-treatment with cycloheximide (CHX), a protein synthesis inhibitor, resulted in increased half-life of the CYP2A6 compared to cells treated only with CHX. Collectively, the observations indicate that the CYP2A6 may function as human "Bilirubin Oxidase" where bilirubin is potentially a substrate and a regulator of the enzyme.
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| 4. |
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| 5. |
- Ameer, Syeda Shegufta, et al.
(författare)
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Arsenic exposure from drinking water is associated with decreased gene expression and increased DNA methylation in peripheral blood
- 2017
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Ingår i: Toxicology and Applied Pharmacology. - : Elsevier BV. - 0041-008X .- 1096-0333. ; 321, s. 57-66
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Tidskriftsartikel (refereegranskat)abstract
- Background Exposure to inorganic arsenic increases the risk of cancer and non-malignant diseases. Inefficient arsenic metabolism is a marker for susceptibility to arsenic toxicity. Arsenic may alter gene expression, possibly by altering DNA methylation. Objectives To elucidate the associations between arsenic exposure, gene expression, and DNA methylation in peripheral blood, and the modifying effects of arsenic metabolism. Methods The study participants, women from the Andes, Argentina, were exposed to arsenic via drinking water. Arsenic exposure was assessed as the sum of arsenic metabolites in urine (U-As), using high performance liquid-chromatography hydride-generation inductively-coupled-plasma-mass-spectrometry, and arsenic metabolism efficiency was assessed by the urinary fractions (%) of the individual metabolites. Genome-wide gene expression (N = 80 women) and DNA methylation (N = 93; 80 overlapping with gene expression) in peripheral blood were measured using Illumina DirectHyb HumanHT-12 v4.0 and Infinium Human-Methylation 450K BeadChip, respectively. Results U-As concentrations, ranging 10–1251 μg/L, was associated with decreased gene expression: 64% of the top 1000 differentially expressed genes were down-regulated with increasing U-As. U-As was also associated with hypermethylation: 87% of the top 1000 CpGs were hypermethylated with increasing U-As. The expression of six genes and six individual CpG sites were significantly associated with increased U-As concentration. Pathway analyses revealed enrichment of genes related to cell death and cancer. The pathways differed somewhat depending on arsenic metabolism efficiency. We found no overlap between arsenic-related gene expression and DNA methylation for individual genes. Conclusions Increased arsenic exposure was associated with lower gene expression and hypermethylation in peripheral blood, but with no evident overlap.
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| 6. |
- Amirhosseini, Mehdi, et al.
(författare)
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Autoantibodies in outbred Swiss Webster mice following exposure to gold and mercury
- 2021
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Ingår i: Toxicology and Applied Pharmacology. - : ACADEMIC PRESS INC ELSEVIER SCIENCE. - 0041-008X .- 1096-0333. ; 412
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Tidskriftsartikel (refereegranskat)abstract
- Exposure to heavy metals may have toxic effects on several human organs causing morbidity and mortality. Metals may trigger or exacerbate autoimmunity in humans. Inbred mouse strains with certain H-2 haplotypes are susceptible to xenobiotic-induced autoimmunity; and their immune response to metals such as mercury, gold, and silver have been explored. Serum antinuclear antibodies (ANA), polyclonal B-cell activation, hypergammaglobulinemia and tissue immune complex deposition are the main features of metal-induced autoimmunity in inbred mice. However, inbred mouse strains do not represent the genetic heterogeneity in humans. In this study, outbred Swiss Webster (SW) mice exposed to gold or mercury salts showed immune and autoimmune responses. Intramuscular injection of 22.5 mg/kg.bw aurothiomalate (AuTM) induced IgG ANA in SW mice starting after 5 weeks that persisted until week 15 although with a lower intensity. This was accompanied by elevated serum levels of total IgG antibodies against chromatin and total histones. Exposure to gold led to development of serum IgG autoantibodies corresponding to H1 and H2A histones, and dsDNA. Both gold and mercury induced polyclonal B-cell activation. Eight mg/L mercuric chloride (HgCl2) in drinking water, caused IgG antinucleolar antibodies (ANoA) after 5 weeks in SW mice accompanied by immune complex deposition in kidneys and spleen. Serum IgG antibodies corresponding to anti-fibrillarin, and anti-PM/Scl-100 antibodies, were observed in mercury-exposed SW mice. Gold and mercury trigger systemic autoimmune response in genetically heterogeneous outbred SW mice and suggest them as an appropriate model to study xenobiotic-induced autoimmunity.
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| 7. |
- Andersson, Marie, 1974-, et al.
(författare)
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Potential transfer of neurotoxic amino acid beta-N-methylamino-L-alanine (BMAA) from mother to infant during breast-feeding : Predictions from human cell lines
- 2017
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Ingår i: Toxicology and Applied Pharmacology. - : Elsevier. - 0041-008X .- 1096-0333. ; 320, s. 40-50
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Tidskriftsartikel (refereegranskat)abstract
- β-N-methylamino-alanine (BMAA) is a non-protein amino acid produced by cyanobacteria, diatoms and dinoflagellates. BMAA has potential to biomagnify in a terrestrial food chain, and to bioaccumulate in fish and shellfish. We have reported that administration of [14C]l-BMAA to lactating mice and rats results in a mother to off-spring transfer via the milk. A preferential enantiomer-specific uptake of [14C]l-BMAA has also been demonstrated in differentiated murine mammary epithelium HC11 cells. These findings, together with neurotoxic effects of BMAA demonstrated both in vitro and in vivo, highlight the need to determine whether such transfer could also occur in humans. Here, we used four cell lines of human origin to examine and compare the transport of the two BMAA enantiomers in vitro. The uptake patterns of [14C]l- and [14C]d-BMAA in the human mammary MCF7 cell line were in agreement with the results in murine HC11 cells, suggesting a potential secretion of BMAA into human breast milk. The permeability coefficients for both [14C]l- and [14C]d-BMAA over monolayers of human intestinal Caco2 cells supported an efficient absorption from the human intestine. As a final step, transport experiments confirmed that [14C]l-and [14C]d-BMAA can be taken up by human SHSY5Y neuroblastoma cells and even more efficiently by human U343 glioblastoma cells. In competition experiments with various amino acids, the ASCT2 specific inhibitor benzylserine was the most effective inhibitor of [14C]l-BMAA uptake tested here. Altogether, our results suggest that BMAA can be transferred from an exposed mother, via the milk, to the brain of the nursed infant.
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| 8. |
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| 9. |
- Annas, Anita, et al.
(författare)
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Differential response of cultured human umbilical vein and artery endothelial cells to Ah receptor agonist treatment : CYP-dependent activation of food and environmental mutagens
- 2000
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Ingår i: Toxicology and Applied Pharmacology. - : Elsevier BV. - 0041-008X .- 1096-0333. ; 169:1, s. 94-101
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Tidskriftsartikel (refereegranskat)abstract
- In the present study, 7-ethoxyresorufin O-deethylase (EROD), 7,12-dimethylbenz[a]anthracene (DMBA)-hydroxylase, and covalent binding of H-3-labeled 3-amino-1,4-dimethyl-5H-pyrido[4,3-b]indole (H-3-Trp-P-1) and H-3-DMBA were examined in human umbilical vein endothelial cells (HUVEC) and human umbilical artery endothelial cells (HUAEC) exposed to the aryl hydrocarbon (Ah) receptor agonist beta -naphthoflavone (BNF) or vehicle only. The results revealed a marked induction of enzymatic activity in BNF-treated HUVEC compared with vehicle-treated cells, whereas no similar response was observed in BNF-treated HUAEC. EROD, DMBA hydroxylase, and covalent binding of H-3-Trp-P-1 and H-3-DMBA in BNF-treated HUVEC were reduced in the presence of the CYP1A inhibitor ellipticine. Addition of other CYP1A inhibitors ru-naphthoflavone, miconazole, 1-ethynylpyrene, 1-(1-propynyl)pyrene, or the CYP1A substrate ethoyresorufin to the incubation buffer of BNF-treated HUVEC reduced covalent binding of H-3-Trp-P-1 by 93-98%. Western blot analysis confirmed an induction of CYP1A1 in BNF-treated HUVEC, but not in BNF-treated HUAEC. CYP1A1 was, however, detected in both vehicle- and BNF-treated HUAEC. The results showed that BNF exposure induced CYP1A1 and metabolic activation of xenobiotics in HUVEC, whereas the catalytic activity remained low in BNF-treated HUAEC. Our results suggest that endothelial lining of human veins may be a target for adverse effects of xenobiotics activated into reactive metabolites by Ah receptor-regulated enzymes. Several studies have detected CYP1A1 in endothelial linings, whereas expression of CYP1A2 and CYP1B1 seems to be negligible at this site. This suggests that the metabolic activation and covalent binding of H-3-Trp-P-1 and H-3-DMBA in HUVEC are most likely mediated by CYP1A1.
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| 10. |
- Arpiainen, Satu, et al.
(författare)
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Coactivator PGC-1 alpha regulates the fasting inducible xenobiotic-metabolizing enzyme CYP2A5 in mouse primary hepatocytes
- 2008
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Ingår i: Toxicology and Applied Pharmacology. - : Elsevier BV. - 0041-008X .- 1096-0333. ; 232:1, s. 135-141
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Tidskriftsartikel (refereegranskat)abstract
- The nutritional state of organisms and energy balance related diseases such as diabetes regulate the metabolism of xenobiotics such as drugs, toxins and carcinogens. However, the mechanisms behind this regulation are mostly unknown. The xenobiotic-metabolizing cytochrome P450 (CYP) 2A5 enzyme has been shown to be induced by fasting and by glucagon and cyclic AMP (cAMP), which mediate numerous fasting responses. Peroxisome proliferator-activated receptor gamma coactivator (PGC)-1 alpha triggers many of the important hepatic fasting effects in response to elevated cAMP levels. In the present study, we were able to show that cAMP causes a coordinated induction of PGC-1 alpha expression level by adenovirus mediated gene transfer increased CYP2A5 transcription, Co-transfection of Cyp2a5' promoter constructs with PGC-1 alpha expression vector demonstrated that PGC-1 alpha is able to activate Cyp2a5 transcription through the hepatocyte nuclear factor (HNF)-4 alpha response element in the proximal promoter of the Cyp2a5 gene. Chromartin immunoprecipitation assays showed that PGC-1 alpha binds, together with HNF-4 alpha, to the same region at the Cyp2a5 proximal promoter. In conclusion, PGC-1 alpha mediates the expression of Cyp2A5 induced by cAMP in mouise hepatocytes throuch coactivation of transcription factor HNF-4 alpha. This strongly suggests that PGC-1 alpha is the major factor mediating the fasting response of CYP2A5.
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| 11. |
- Asp, Vendela, et al.
(författare)
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Biphasic hormonal responses to the adrenocorticolytic DDT metabolite 3-methylsulfonyl-DDE in human cells
- 2010
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Ingår i: Toxicology and Applied Pharmacology. - : Elsevier BV. - 0041-008X .- 1096-0333. ; 242:3, s. 281-289
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Tidskriftsartikel (refereegranskat)abstract
- The DDT metabolite 3-methylsulfonyl-DDE (3-MeSO(2)-DDE) has been proposed as a lead compound for an improved adrenocortical carcinoma (ACC) treatment. ACC is a rare malignant disorder with poor prognosis, and the current pharmacological therapy o,p'-DDD (mitotane) has limited efficacy and causes severe adverse effects. 3-MeSO(2)-DDE is bioactivated by cytochrome P450 (CYP) 11B1 in mice and causes formation of irreversibly bound protein adducts, reduced glucocorticoid secretion, and cell death in the adrenal cortex of several animal species. The present study was carried out to assess similarities and differences between mice and humans concerning the adrenocorticolytic effects of 3-MeSO(2)-DDE. The results support previous indications that humans are sensitive to the adrenocorticolytic actions of 3-MeSO(2)-DDE by demonstrating protein adduct formation and cytotoxicity in the human adrenocortical cell line H295R. However, neither the irreversible binding nor the cytotoxicity of 3-MeSO(2)-DDE in H295R cells was inhibited by the CYP11B1 inhibitor etomidate. We also report biphasic responses to 3-MeSO(2)-DDE in cortisol and aldosterone secretion as well as in mRNA levels of the steroidogenic genes StAR, CYP11B1 and CYP11B2. Hormone levels and mRNA levels were increased at lower concentrations of 3-MeSO(2)-DDE, while higher concentrations decreased hormone levels. These biphasic responses were not observed with o,p'-DDD or with the precursor DDT metabolite p,p'-DDE. Based on these results, 3-MeSO(2)-DDE remains a viable lead compound for drug design, although the adrenocorticolytic effects of 3-MeSO(2)-DDE in human cells seem more complex than in murine cells.
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| 12. |
- Bahrami, Fariba, et al.
(författare)
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Persistent Olfactory Mucosal Metaplasia and Increased Olfactory Bulb Glial Fibrillary Acidic Protein Levels Following a Single Dose of Methylsulfonyl-dichlorobenzene in Mice: Comparison of the 2,5- and 2,6-Dichlorinated Isomers
- 2000
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Ingår i: Toxicology and Applied Pharmacology. - : Elsevier BV. - 0041-008X .- 1096-0333. ; 162:1, s. 49-59
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Tidskriftsartikel (refereegranskat)abstract
- Histopathology was used to characterize long-term toxic effects in the olfactory system following a single ip dose (4–65 mg/kg) of methylsulfonyl-2,6-dichlorobenzene, (2,6-(diCl-MeSO2-B)), in female NMRI mice. The effects of 2,6-(diCl-MeSO2-B) and its 2,5-chlorinated isomer, (2,5-(diCl-MeSO2-B)), on the levels of glial fibrillary acidic protein (GFAP; a biomarker for neurotoxicity) in different brain regions were examined by an enzyme-linked immunosorbent assay (ELISA). The histopathologic effects of 2,6-(diCl-MeSO2-B) were dose-, time-, and tissue-dependent. At the highest doses (16–65 mg/kg), the initial effect of 2,6-(diCl-MeSO2-B) was necrosis of the Bowman's glands, followed by a sequence of secondary events including degeneration of the olfactory neuroepithelium, repopulation of the basement membrane by a ciliated respiratorylike epithelium, fibrosis and ossification in the lamina propria, formation of bilateral polyps, angiogenesis, and disappearance of nerve bundles. Remodeling was most pronounced in the dorsal meatus of the olfactory mucosa and persisted for the duration of the experiment (46 weeks). A dose-dependent induction of GFAP in the olfactory bulb of mice treated with 2,6-(diCl-MeSO2-B) was observed at all doses examined (16–65 mg/kg). GFAP levels were highest 2 weeks after treatment (eightfold induction at 65 mg/kg) and then gradually decreased to normal within 26 weeks. The 2,5-substituted isomer (65 mg/kg) did not induce GFAP in the olfactory bulb and or toxicity in the olfactory mucosa. In conclusion, a single dose of 2,6-(diCl-MeSO2-B) results in persistent metaplasia and remodeling of the olfactory mucosa, and a long-lasting but transient induction of GFAP in the olfactory bulb. It is proposed that methylsulfonyl-2,6-dichlorobenzene may serve as an experimental tool with a unique ability to produce persistent primary and/or secondary lesions in the olfactory system of mice.
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| 13. |
- Beausoleil, Claire, et al.
(författare)
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Weight of evidence evaluation of the metabolism disrupting effects of triphenyl phosphate using an expert knowledge elicitation approach
- 2024
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Ingår i: Toxicology and Applied Pharmacology. - : Elsevier. - 0041-008X .- 1096-0333. ; 489
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Tidskriftsartikel (refereegranskat)abstract
- Identification of Endocrine-Disrupting Chemicals (EDCs) in a regulatory context requires a high level of evidence. However, lines of evidence (e.g. human, in vivo, in vitro or in silico) are heterogeneous and incomplete for quantifying evidence of the adverse effects and mechanisms involved. To date, for the regulatory appraisal of metabolism-disrupting chemicals (MDCs), no harmonised guidance to assess the weight of evidence has been developed at the EU or international level. To explore how to develop this, we applied a formal Expert Knowledge Elicitation (EKE) approach within the European GOLIATH project. EKE captures expert judgment in a quantitative manner and provides an estimate of uncertainty of the final opinion. As a proof of principle, we selected one suspected MDC -triphenyl phosphate (TPP) - based on its related adverse endpoints (obesity/adipogenicity) relevant to metabolic disruption and a putative Molecular Initiating Event (MIE): activation of peroxisome proliferator activated receptor gamma (PPARγ). We conducted a systematic literature review and assessed the quality of the lines of evidence with two independent groups of experts within GOLIATH, with the objective of categorising the metabolic disruption properties of TPP, by applying an EKE approach. Having followed the entire process separately, both groups arrived at the same conclusion, designating TPP as a “suspected MDC” with an overall quantitative agreement exceeding 85%, indicating robust reproducibility. The EKE method provides to be an important way to bring together scientists with diverse expertise and is recommended for future work in this area.
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| 14. |
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| 15. |
- Broström, Julia M., et al.
(författare)
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Toluene diisocyanate exposure and autotaxin–lysophosphatidic acid signalling
- 2018
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Ingår i: Toxicology and Applied Pharmacology. - : Elsevier BV. - 0041-008X .- 1096-0333. ; 355, s. 43-51
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Tidskriftsartikel (refereegranskat)abstract
- Toluene diisocyanate (TDI) is a reactive chemical used in manufacturing plastics. TDI exposure adversely affects workers' health, causing occupational asthma, but individuals differ in susceptibility. We recently suggested a role for signalling mediated by the enzyme autotaxin (ATX) and its product, lysophosphatidic acid (LPA), in TDI toxicity. Here we genotyped 118 TDI-exposed workers for six single-nucleotide polymorphisms (SNPs) in genes encoding proteins implicated in ATX–LPA signalling: purinergic receptor P2X7 (P2RX7), C–C motif chemokine ligand 2 (CCL2), interleukin 1β (IL1B), and caveolin 1 (CAV1). Two P2RX7 SNPs (rs208294 and rs2230911) significantly modified the associations between a biomarker of TDI exposure (urinary 2,4-toluene diamine) and plasma LPA; two IL1B SNPs (rs16944 and rs1143634) did not. CAV1 rs3807989 modified the associations, but the effect was not statistically significant (p = 0.05–0.09). In vitro, TDI-exposed bronchial epithelial cells (16HBE14o-) rapidly released ATX and IL-1β. P2X7 inhibitors attenuated both responses, but confocal microscopy showed non-overlapping localizations of ATX and IL-1β, and down-regulation of CAV1 inhibited the ATX response but not the IL-1β response. This study indicates that P2X7 is pivotal for TDI-induced ATX–LPA signalling, which was modified by genetic variation in P2RX7. Furthermore, our data suggest that the TDI-induced ATX and IL-1β responses occur independently.
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| 16. |
- Broström, Julia, et al.
(författare)
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Toluene diisocyanate: Induction of the autotaxin-lysophosphatidic acid axis and its association with airways symptoms.
- 2015
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Ingår i: Toxicology and Applied Pharmacology. - : Elsevier BV. - 1096-0333 .- 0041-008X. ; 287:3, s. 222-231
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Tidskriftsartikel (refereegranskat)abstract
- Diisocyanates are industrial chemicals which have a wide range of applications in developed and developing countries. They are notorious lung toxicants and respiratory sensitizers. However, the mechanisms behind their adverse effects are not adequately characterized. Autotaxin (ATX) is an enzyme producing lysophosphatidic acid (LPA), and the ATX-LPA axis has been implicated in lung related inflammatory conditions and diseases, including allergic asthma, but not to toxicity of environmental low-molecular-weight chemicals. We investigated effects of toluene diisocyanate (TDI) on ATX induction in human lung epithelial cell models, and we correlated LPA-levels in plasma to biomarkers of TDI exposure in urine collected from workers exposed to <5ppb (parts per billion). Information on workers' symptoms was collected through interviews. One nanomolar TDI robustly induced ATX release within 10min in vitro. A P2X7- and P2X4-dependent microvesicle formation was implicated in a rapid ATX release and a subsequent protein synthesis. Co-localization between purinergic receptors and ATX was documented by immunofluorescence and confocal microscopy. The release was modulated by monocyte chemoattractant protein-1 (MCP-1) and by extracellular ATP. In workers, we found a dose-response relationship between TDI exposure biomarkers in urine and LPA levels in plasma. Among symptomatic workers reporting "sneezing", the LPA levels were higher than among non-symptomatic workers. This is the first report indicating induction of the ATX-LPA axis by an environmental low-molecular-weight chemical, and our data suggest a role for the ATX-LPA axis in TDI toxicity.
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| 17. |
- Castellanos, Cesilie Granum, et al.
(författare)
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Differential effects of the persistent DDT metabolite methylsulfonyl-DDE in nonstimulated and LH-stimulated neonatal porcine Leydig cells
- 2013
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Ingår i: Toxicology and Applied Pharmacology. - : Elsevier BV. - 0041-008X .- 1096-0333. ; 267:3, s. 247-255
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Tidskriftsartikel (refereegranskat)abstract
- 3-Methylsulfonyl-DDE (MeSO2-DDE) is a potent adrenal toxicant formed from the persistent insecticide DDT. MeSO2-DDE is widely present in human plasma, milk and fat, and in tissues of marine mammals. In the present study, we investigated endocrine-disrupting properties of MeSO2-DDE in primary neonatal porcine Leydig cells. Unstimulated and LH-stimulated cells were exposed to MeSO2-DDE at concentrations ranging from 0.6 to 20 mu M for 48 h. Cell viability, hormone secretion and expression of steroidogenesis related genes were recorded. Secretion of testosterone and estradiol was increased in a concentration-dependent fashion in unstimulated Leydig cells, while in LH-stimulated cells, secretion of testosterone, estradiol and progesterone was decreased. The expression of important steroidogenic genes was down-regulated both in unstimulated and LH-stimulated cells. Notably, no significant impairment of cell viability occurred at any exposure except the highest concentration (20 mu M) in LH-stimulated cells. This indicated that the effects on hormone secretion and gene expression were not caused by cytotoxicity. We conclude that the adrenal toxicant MeSO2-DDE disrupts hormone secretion in a complex fashion in neonatal porcine Leydig cells. The different endocrine responses in unstimulated and LH-stimulated cells imply that the endocrine disruptive activity of MeSO2-DDE is determined by the physiological status of the Leydig cells.
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| 18. |
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| 19. |
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| 20. |
- De Luca, Chiara, et al.
(författare)
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Biological definition of multiple chemical sensitivity from redox state and cytokine profiling and not from polymorphisms of xenobiotic-metabolizing enzymes
- 2010
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Ingår i: Toxicology and Applied Pharmacology. - : Elsevier BV. - 0041-008X .- 1096-0333. ; 248:3, s. 285-292
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Tidskriftsartikel (refereegranskat)abstract
- Background: Multiple chemical sensitivity (MCS) is a poorly clinically and biologically defined environment-associated syndrome. Although dysfunctions of phase I/phase II metabolizing enzymes and redox imbalance have been hypothesized, corresponding genetic and metabolic parameters in MCS have not been systematically examined. Objectives: We sought for genetic, immunological, and metabolic markers in MCS. Methods: We genotyped patients with diagnosis of MCS. suspected MCS and Italian healthy controls for allelic variants of cytochrome P450 isoforms (CYP2C9, CYP2C19, CYP2D6, and CYP3A5), UDP-glucuronosyl transferase (UGT1A1), and glutathione S-transferases (GSTP1. GSTM1, and GSTT1). Erythrocyte membrane fatty acids, antioxidant (catalase, superoxide dismutase (SOD)) and glutathione metabolizing (GST, glutathione peroxidase (Gpx)) enzymes, whole blood chemiluminescence, total antioxidant capacity, levels of nitrites/nitrates, glutathione, HNE-protein adducts, and a wide spectrum of cytokines in the plasma were determined. Results: Allele and genotype frequencies of CYPs, UGT, GSTM, GSTT, and GSTP were similar in the Italian MCS patients and in the control populations. The activities of erythrocyte catalase and GST were lower, whereas Gpx was higher than normal. Both reduced and oxidised glutathione were decreased, whereas nitrites/nitrates were increased in the MCS groups. The MCS fatty acid profile was shifted to saturated compartment and IFNgamma, IL-8, IL-10, MCP-1. PDGFbb, and VEGF were increased. Conclusions: Altered redox and cytokine patterns suggest inhibition of expression/activity of metabolizing and antioxidant enzymes in MCS. Metabolic parameters indicating accelerated lipid oxidation, increased nitric oxide production and glutathione depletion in combination with increased plasma inflammatory cytokines should be considered in biological definition and diagnosis of MCS. (C) 2010 Elsevier Inc. All rights reserved.
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| 21. |
- DeJongh, J, et al.
(författare)
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Estimation of systemic toxicity of acrylamide by integration of in vitro toxicity data with kinetic simulations.
- 1999
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Ingår i: Toxicology and Applied Pharmacology. - : Elsevier BV. - 0041-008X .- 1096-0333. ; 158:3, s. 261-268
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Tidskriftsartikel (refereegranskat)abstract
- Neurodegenerative properties of acrylamide were studied in vitro by exposure of differentiated SH-SY5Y human neuroblastoma cells for 72 h. The number of neurites per cell and the total cellular protein content were determined every 24 h throughout the exposure and the subsequent 96-h recovery period. Using kinetic data on the metabolism of acrylamide in rat, a biokinetic model was constructed in which the in vitro toxicity data were integrated. Using this model, we estimated the acute and subchronic toxicity of acrylamide for the rat in vivo. These estimations were compared to experimentally derived lowest observed effect doses (LOEDs) for daily intraperitoneal exposure (1, 10, 30, and 90 days) to acrylamide. The estimated LOEDs differed maximally twofold from the experimental LOEDs, and the nonlinear response to acrylamide exposure over time was simulated correctly. It is concluded that the integration of the present in vitro toxicity data with kinetic data gives adequate estimates of acute and subchronic neurotoxicity resulting from acrylamide exposure.
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| 22. |
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| 23. |
- Dubbelboer, Ilse R., et al.
(författare)
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Systematic review of physiologically based kinetic lactation models for transfer of xenobiotic compounds to milk
- 2023
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Ingår i: Toxicology and Applied Pharmacology. - : Elsevier. - 0041-008X .- 1096-0333. ; 467
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Forskningsöversikt (refereegranskat)abstract
- Lactational elimination has been described mathematically for nearly 50 years. Over 40 published articles, containing >50 physiologically based kinetic (PBK) lactation models were included in the systematic review. These PBK models described the lactational elimination of xenobiotic compounds in humans, rats, mice, and dairy cows and goats. A total of 78 compounds have been modelled, ranging from industrial chemicals, pesticides, to pain medication, antibiotics, and caffeine. Few models included several species or compounds, and models were thus generally not translational or generic. Three dairy cow models mechanistically described the intramammary disposition of pharmaceuticals after intramammary administration, including volume changes caused by milking, while empirically describing the remaining pharmacokinetics. The remaining models were semi- or whole body PBK models, describing long-term exposure of environmental pollutants, or short-term exposure of pharmaceuticals. The absolute majority described the disposition to the mammary gland or milk with perfusion limited compartments, but permeability limited models were available as well. With long-term exposure, models often included changes in milk volume and/or consumption by the offspring, and changes in body weight of offspring. Periodic emptying of the mammary gland, as with feeding or milking, was sparsely applied. Rodent models used similar physiological parameters, while values of physiological parameters applied in human models could range widely. When milk composition was included in the models, it most often included the fat content. The review gives an extensive overview of the applied functions and modelling strategies of PBK lactation models.
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| 24. |
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| 25. |
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| 26. |
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| 27. |
- Gaehrs, Maike, et al.
(författare)
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Role of the nuclear xenobiotic receptors CAR and PXR in induction of cytochromes P450 by non-dioxinlike polychlorinated biphenyls in cultured rat hepatocytes
- 2013
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Ingår i: Toxicology and Applied Pharmacology. - : Academic Press. - 0041-008X .- 1096-0333. ; 272:1, s. 77-85
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Tidskriftsartikel (refereegranskat)abstract
- Polychlorinated biphenyls (PCBs) are among the most ubiquitously detectable 'persistent organic pollutants'. In contrast to 'dioxinlike' (DL) PCBs, less is known about the molecular mode of action of the larger group of the 'non-dioxinlike' (NDL) PCBs. Owing to the life-long exposure of the human population, a carcinogenic, i.e., tumor-promoting potency of NDL-PCBs has to be considered in human risk assessment. A major problem in risk assessment of NDL-PCBs is dioxin-like impurities that can occur in commercially available NDL-PCB standards. In the present study, we analyzed the induction of CYP2B1 and CYP3A1 in primary rat hepatocytes using a number of highly purified NDL-PCBs with various degrees of chlorination and substitution patterns. Induction of these enzymes is mediated by the nuclear xenobiotic receptors CAR (Constitutive androstane receptor) and PXR (Pregnane X receptor). For CYP2B1 induction, concentration-response analysis revealed a very narrow window of EC50 estimates, being in the range of 1-4 mu M for PCBs 28 and 52, and between 0.4 and 1 mu M for PCBs 101, 138, 153 and 180. CYP3A1 induction was less sensitive to NDL-PCBs, the most pronounced induction being achieved at 100 mu M with the higher chlorinated congeners. Using okadaic acid and small interfering RNAs targeting CAR and PXR, we could demonstrate that CAR plays a major role and PXR a minor role in NDL-PCB-driven induction of CYPs, both effects showing no stringent structure-activity relationship. As the only obvious relevant determinant, the degree of chlorination was found to be positively correlated with the inducing potency of the congeners. (C) 2013 Elsevier Inc. All rights reserved.
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| 28. |
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| 29. |
- Ganapathy, Suthakar, et al.
(författare)
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Low doses of arsenic, via perturbing p53, promotes tumorigenesis.
- 2016
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Ingår i: Toxicology and applied pharmacology. - : Elsevier BV. - 1096-0333 .- 0041-008X. ; 306, s. 98-104
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Tidskriftsartikel (refereegranskat)abstract
- In drinking water and in workplace or living environments, low doses of arsenic can exist and operate as a potent carcinogen. Due to insufficient understanding and information on the pervasiveness of environmental exposures to arsenic, there is an urgent need to elucidate the underlying molecular mechanisms of arsenic regarding its carcinogenic effect on human health. In this study, we demonstrate that low doses of arsenic exposure mitigate or mask p53 function and further perturb intracellular redox state, which triggers persistent endoplasmic reticulum (ER) stress and activates UPR (unfolded protein response), leading to transformation or tumorigenesis. Thus, the results suggest that low doses of arsenic exposure, through attenuating p53-regulated tumor suppressive function, change the state of intracellular redox and create a microenvironment for tumorigenesis. Our study also provides the information for designing more effective strategies to prevent or treat human cancers initiated by arsenic exposure.
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| 30. |
- Gustafsson, Helena, et al.
(författare)
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Neurofunctional endpoints assessed in human neuroblastoma SH-SY5Y cells for estimation of acute systemic toxicity
- 2010
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Ingår i: Toxicology and Applied Pharmacology. - : Elsevier BV. - 0041-008X .- 1096-0333. ; 245:2, s. 191-202
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Tidskriftsartikel (refereegranskat)abstract
- The objective of the EU-funded integrated project ACuteTox is to develop a strategy in which general cytotoxicity, together with organ-specific toxicity and biokinetic features, are used for the estimation of human acute systemic toxicity. Our role in the project is to characterise the effect of reference chemicals with regard to neurotoxicity. We studied cell membrane potential (CMP), noradrenalin (NA) uptake, acetylcholine esterase (AChE) activity, acetylcholine receptor (AChR) signalling and voltage-operated calcium channel (VOCC) function in human neuroblastoma SH-SY5Y cells after exposure to 23 pharmaceuticals, pesticides or industrial chemicals. Neurotoxic alert chemicals were identified by comparing the obtained data with cytotoxicity data from the neutral red uptake assay in 3T3 mouse fibroblasts. Furthermore, neurotoxic concentrations were correlated with estimated human lethal blood concentrations (LC50). The CMP assay was the most sensitive assay, identifying eight chemicals as neurotoxic alerts and improving the LC50 correlation for nicotine, lindane, atropine and methadone. The NA uptake assay identified five neurotoxic alert chemicals and improved the LC50 correlation for atropine, diazepam, verapamil and methadone. The AChE, AChR and VOCC assays showed limited potential for detection of acute toxicity. The CMP assay was further evaluated by testing 36 additional reference chemicals. Five neurotoxic alert chemicals were generated and orphendrine and amitriptyline showed improved LC50 correlation. Due to the high sensitivity and the simplicity of the test protocol, the CMP assay constitutes a good candidate assay to be included in an in vitro test strategy for prediction of acute systemic toxicity.
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| 31. |
- Gustafsson, Åsa, et al.
(författare)
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Differential cellular responses in healthy mice and in mice with established airway inflammation when exposed to hematite nanoparticles
- 2015
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Ingår i: Toxicology and Applied Pharmacology. - : Elsevier BV. - 0041-008X .- 1096-0333. ; 288:1, s. 1-11
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Tidskriftsartikel (refereegranskat)abstract
- The aim of this study was to investigate the inflammatory and immunological responses in airways and lung-draining lymph nodes (LDLNs), following lung exposure to iron oxide (hematite) nanoparticles (NPs). The responses to the hematite NPs were evaluated in both healthy non-sensitized mice, and in sensitized mice with an established allergic airway disease. The mice were exposed intratracheally to either hematite NPs or to vehicle (PBS) and the cellular responses were evaluated on days 1, 2, and 7, post-exposure. Exposure to hematite NPs increased the numbers of neutrophils, eosinophils, and lymphocytes in the airways of non-sensitized mice on days 1 and 2 post-exposure; at these time points the number of lymphocytes was also elevated in the LDLNs. In contrast, exposing sensitized mice to hematite NPs induced a rapid and unspecific cellular reduction in the alveolar space on day 1 post-exposure; a similar decrease of lymphocytes was also observed in the LDLN. The results indicate that cells in the airways and in the LDLN of individuals with established airway inflammation undergo cell death when exposed to hematite NPs. A possible explanation for this toxic response is the extensive generation of reactive oxygen species (ROS) in the pro-oxidative environment of inflamed airways. This study demonstrates how sensitized and non-sensitized mice respond differently to hematite NP exposure, and it highlights the importance of including individuals with respiratory disorders when evaluating health effects of inhaled nanomaterials.
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| 32. |
- Hagvall, Lina, 1978, et al.
(författare)
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Cytochrome P450-mediated activation of the fragrance compound geraniol forms potent contact allergens.
- 2008
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Ingår i: Toxicology and applied pharmacology. - : Elsevier BV. - 1096-0333 .- 0041-008X. ; 233:2, s. 308-13
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Tidskriftsartikel (refereegranskat)abstract
- Contact sensitization is caused by low molecular weight compounds which penetrate the skin and bind to protein. In many cases, these compounds are activated to reactive species, either by autoxidation on exposure to air or by metabolic activation in the skin. Geraniol, a widely used fragrance chemical, is considered to be a weak allergen, although its chemical structure does not indicate it to be a contact sensitizer. We have shown that geraniol autoxidizes and forms allergenic oxidation products. In the literature, it is suggested but not shown that geraniol could be metabolically activated to geranial. Previously, a skin-like CYP cocktail consisting of cutaneous CYP isoenzymes, was developed as a model system to study cutaneous metabolism. In the present study, we used this system to investigate CYP-mediated activation of geraniol. In incubations with the skin-like CYP cocktail, geranial, neral, 2,3-epoxygeraniol, 6,7-epoxygeraniol and 6,7-epoxygeranial were identified. Geranial was the main metabolite formed followed by 6,7-epoxygeraniol. The allergenic activities of the identified metabolites were determined in the murine local lymph node assay (LLNA). Geranial, neral and 6,7-epoxygeraniol were shown to be moderate sensitizers, and 6,7-epoxygeranial a strong sensitizer. Of the isoenzymes studied, CYP2B6, CYP1A1 and CYP3A5 showed high activities. It is likely that CYP1A1 and CYP3A5 are mainly responsible for the metabolic activation of geraniol in the skin, as they are expressed constitutively at significantly higher levels than CYP2B6. Thus, geraniol is activated through both autoxidation and metabolism. The allergens geranial and neral are formed via both oxidation mechanisms, thereby playing a large role in the sensitization to geraniol.
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| 33. |
- Hallén, I P, et al.
(författare)
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Toxicokinetics of lead in lactating and nonlactating mice.
- 1996
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Ingår i: Toxicology and Applied Pharmacology. - : Elsevier BV. - 0041-008X .- 1096-0333. ; 136:2, s. 342-7
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Tidskriftsartikel (refereegranskat)abstract
- Toxicokinetics of lead in lactating and nonlactating mice were studied after a single intravenous injection of 0.05 mg of lead (2.5 mCi 203Pb)/kg. Lead concentrations in blood, plasma, and milk were measured for 10 days following dosing. The volume of distribution based on plasma lead was more than two times larger in lactating than in nonlactating mice, 133 and 58 liter/kg, respectively. Plasma lead clearance in lactating mice was 4.25 liter/hr/kg compared with 1.07 liter/hr/kg in nonlactating mice. However, no such pronounced difference in blood lead clearance was found between the two groups, indicating that this parameter does not reveal the kinetic characteristics during lactation. Milk was found to be an additional route of excretion for lead. About 1/3 of the administered dose of lead was excreted in milk. Accordingly, milk clearance contributed to 1/3 of the total plasma clearance in the mice. The relationships of lead in plasma to lead in whole blood as well as lead in milk to lead in whole blood were nonlinear, with a relatively higher increase in plasma and in milk lead levels at higher blood lead levels. This nonlinearity may be explained by a reduced uptake of lead in erythrocytes as the lead binding sites of these cells become saturated. In lactating mice, the maximum binding capacity of lead in red blood cells was even lower than in nonlactating mice. Similar nonlinear relationship have have also been found in human studies although at much higher levels of lead in blood. The milk:plasma concentration ratio for lead was found to be between 50 and 100 after 24 hr, demonstrating a much more efficient excretion of lead into milk than what is known from human studies. Differences in the milk composition may be one explanation for the species differences in milk excretion of lead. The present study shows that physiological changes during lactation alter the pharmacokinetics of lead in mice.
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| 34. |
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| 35. |
- Havarinasab, Said, 1964-, et al.
(författare)
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Mercury species in lymphoid and non-lymphoid tissues after exposure to methyl mercury: Correlation with autoimmune parameters during and after treatment in susceptible mice
- 2007
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Ingår i: Toxicology and Applied Pharmacology. - : Elsevier BV. - 0041-008X .- 1096-0333. ; 221:1, s. 21-8
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Tidskriftsartikel (refereegranskat)abstract
- Methylmercury (MeHg) is present in the environment as a result of the global cycling of mercury, although anthropogenic sources may dramatically increase the availability in confined geographical areas. Accumulation of MeHg in the aquatic food chain is the dominating way of exposure in mammals, which accumulate MeHg in all organs, including the brain. Demethylation has been described in the organs, especially in phagocytic cells, but mainly in the flora of the intestinal tract. While most of the inorganic mercury (Hg2+) formed in the intestine is excreted, a fraction is reabsorbed which together with the local demethylation increases the organ Hg2+ concentration. MeHg is a well-known immunosuppressive agent, while Hg2+ is associated with immunostimulation and autoimmunity especially in genetically susceptible rodents, creating a syndrome, i.e. mercury-induced autoimmunity (HgIA). This study aimed at exploring the effect of MeHg with regard to HgIA, and especially the immunological events after stopping treatment, correlated with the presence of MeHg and Hg2+ in the organs.Treatment of A.SW mice for 30 days with 4.2 mg MeHg/L drinking water (corresponding to approximately 420 μg Hg/kg body weight/day) caused all the HgIA features observed after primary treatment with inorganic Hg, except systemic immune complex deposits. The total Hg concentration was 5-fold higher in the kidneys as compared with lymph nodes, but the fraction of Hg2+ was similar (17–20%). After stopping treatment, the renal and lymph node MeHg concentration declined according to first order kinetics during the initial 4–6 weeks, but then slower. A similar decline in the organ Hg2+ concentration occurred during the initial 2 weeks after stopping treatment but then ceased, causing the Hg2+ concentration to exceed that of MeHg in the lymph nodes and kidneys after 3 and 8 weeks, respectively. The selective increase in lymph node Hg2+ fraction is likely to be due to demethylation of MeHg in the macrophage-rich lymphoid tissue. The major autoantibody in HgIA, anti-fibrillarin antibodies, tended to increase during the initial 6 weeks after stopping treatment, while all other HgIA features including antichromatin antibodies declined to control levels after 2–4 weeks. This indicates differences in either dose requirement or induction mechanisms for the different HgIA parameters.The selective accumulation of Hg2+ in lymph nodes following MeHg treatment should be taken into account when the effect of MeHg on the immune system is evaluated.
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| 36. |
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| 37. |
- Honda, Hiroshi, et al.
(författare)
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Characterization of glycidol-hemoglobin adducts as biomarkers of exposure and in vivo dose
- 2014
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Ingår i: Toxicology and Applied Pharmacology. - : Elsevier BV. - 0041-008X .- 1096-0333. ; 275:3, s. 213-220
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Tidskriftsartikel (refereegranskat)abstract
- Hemoglobin adducts have been used as biomarkers of exposure to reactive chemicals. Glycidol, an animal carcinogen, has been reported to form N-(2,3-dihydroxy-propyl)valine adducts to hemoglobin (diHOPrVal). To support the use of these adducts as markers of glycidol exposure, we investigated the kinetics of diHOPrVal formation and its elimination in vitro and in vivo. Five groups of rats were orally administered a single dose of glycidol ranging from 0 to 75 mg/kg bw, and diHOPrVal levels were measured 24 h after administration. A dose-dependent increase in diHOPrVal levels was observed with high linearity (R-2 = 0.943). Blood sampling at different time points (1, 10, 20, or 40 days) from four groups administered glycidol at 12 mg/kg bw suggested a linear decrease in diHOPrVal levels compatible with the normal turnover of rat erythrocytes (life span, 61 days), with the calculated first-order elimination rate constant (k(el)) indicating that the diHOPrVal adduct was chemically stable. Then, we measured the second-order rate constant (k(val)) for the reaction of glycidol with N-terminal valine in rat and human hemoglobin in in vitro experiments with whole blood. The k(val) was 6.7 (+/-) 1.1 and 5.6 +/- 1.3 (pmol/g globin per mu Mh) in rat and human blood, respectively, indicating no species differences. In vivo doses estimated from k(val) and diHOPrVal levels were in agreement with the area under the (concentration-time) curve values determined in our earlier toxicokinetic study in rats. Our results indicate that diHOPrVal is a useful biomarker for quantification of glycidol exposure and for risk assessment.
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| 38. |
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| 39. |
- Högberg, Helena T., 1975-, et al.
(författare)
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Gene expression as a sensitive endpoint to evaluate cell differentiation andmaturation of the developing central nervous system in primary cultures of ratcerebellar granule cells (CGCs) exposed to pesticides
- 2009
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Ingår i: Toxicology and Applied Pharmacology. - : Elsevier BV. - 0041-008X .- 1096-0333. ; 235, s. 268-286
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Tidskriftsartikel (refereegranskat)abstract
- The major advantage of primary neuronal cultures for developmental neurotoxicity (DNT) testing is their ability to replicate the crucial stages of neurodevelopment. In our studies using primary culture of cerebellar granule cells (CGCs) we have evaluated whether the gene expression relevant to the most critical developmental processes such as neuronal differentiation (NF-68 and NF-200) and functional maturation (NMDA and GABA presence of neural precursor cells (nestin and Sox10) could be used as an endpoint for in vitro DNT. The expression of these genes was assessed after exposure to various pesticides (paraquat parathion, dichlorvos, pentachlorophenol and cycloheximide) that could induce developmental neurotoxicity through different mechanisms. All studied pesticides signi different stages of neuronal and/or glial cell development and maturation. The most signi observed after exposure to paraquat and parathion (i.e. down-regulation of mRNA expression of NF-68 and NF-200, NMDA and GABA expression of NF-68 and GABA as signi astrocyte marker (S100 multiple pathways of neurodevelopment can be identi in different stages of cell development and maturation, and that gene expression could be used as a sensitive endpoint for initial screening to identify the compounds with the potential to cause developmental neurotoxicity. A receptors), proliferation and differentiation of astrocytes (GFAP and S100β) as well as theficantly modified the expression of selected genes, related to theficant changes wereA receptors). Similarly, dichlorvos affected mainly neurons (decreased mRNAA receptors) whereas cycloheximide had an effect on neurons and astrocytes,ficant decreases in the mRNA expression of both neurofilaments (NF-68 and NF-200) and theβ) were observed. Our results suggest that toxicity induced by pesticides that targetfied by studying expression of genes that are involved
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| 40. |
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| 43. |
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| 44. |
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| 45. |
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| 46. |
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| 47. |
- Jönsson, Maria E., et al.
(författare)
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Ahr2-dependence of PCB126 effects on the swim bladder in relation to expression of CYP1 and cox-2 genes in developing zebrafish.
- 2012
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Ingår i: Toxicology and Applied Pharmacology. - : Elsevier BV. - 0041-008X .- 1096-0333. ; 265:2, s. 166-174
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Tidskriftsartikel (refereegranskat)abstract
- The teleost swim bladder is assumed a homolog of the tetrapod lung. Both swim bladder and lung are developmental targets of persistent aryl hydrocarbon receptor (AHR(2)) agonists; in zebrafish (Danio rerio) the swim bladder fails to inflate with exposure to 3,3',4,4',5-pentachlorobiphenyl (PCB126). The mechanism for this effect is unknown, but studies have suggested roles of cytochrome P450 1 (CYP1) and cyclooxygenase 2 (Cox-2) in some Ahr-mediated developmental effects in zebrafish. We determined relationships between swim bladder inflation and CYP1 and Cox-2 mRNA expression in PCB126-exposed zebrafish embryos. We also examined effects on β-catenin dependent transcription, histological effects, and Ahr2 dependence of the effect of PCB126 on swim bladder using morpholinos targeting ahr2. One-day-old embryos were exposed to waterborne PCB126 or carrier (DMSO) for 24h and then held in clean water until day 4, a normal time for swim bladder inflation. The effects of PCB126 were concentration-dependent with EC(50) values of 1.4 to 2.0nM for induction of the CYP1s, 3.7 and 5.1nM (or higher) for cox-2a and cox-2b induction, and 2.5nM for inhibition of swim bladder inflation. Histological defects included a compaction of the developing bladder. Ahr2-morpholino treatment rescued the effect of PCB126 (5nM) on swim bladder inflation and blocked induction of CYP1A, cox-2a, and cox-2b. With 2nM PCB126 approximately 30% of eleutheroembryos(3) failed to inflate the swim bladder, but there was no difference in CYP1 or cox-2 mRNA expression between those embryos and embryos showing inflated swim bladder. Our results indicate that PCB126 blocks swim bladder inflation via an Ahr2-mediated mechanism. This mechanism seems independent of CYP1 or cox-2 mRNA induction but may involve abnormal development of swim bladder cells.
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| 48. |
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| 49. |
- Jönsson, Maria E., et al.
(författare)
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Basal and 3,3',4,4',5-pentachlorobiphenyl-induced expression of cytochrome P450 1A, 1B and 1C genes in zebrafish
- 2007
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Ingår i: Toxicology and Applied Pharmacology. - : Elsevier BV. - 0041-008X .- 1096-0333. ; 221:1, s. 29-41
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Tidskriftsartikel (refereegranskat)abstract
- The cytochrome P4501C (CYP1C) gene subfamily was recently discovered in fish, and zebrafish (Danio rerio) CYP1C1 transcript has been cloned. Here we cloned the paralogous CYP1C2, showing that the amino acid sequence is 78% identical to CYP1C1, and examined gene structure and expression of CYP1A, CYP1B1, CYP1C1, and CYP1C2. Xenobiotic response elements were observed upstream of the coding regions in all four genes. Zebrafish adults and embryos were exposed (24 h) to 100 nM 3,3′,4,4′,5-polychlorinated biphenyl (PCB126) or 20 ppm acetone and subsequently held in clean water for 24 h (adults) or 48 h (embryos). All adult organs examined (eye, gill, heart, liver, kidney, brain, gut, and gonads) and embryos showed basal expression of the four genes. CYP1A was most strongly expressed in liver, whereas CYP1B1, CYP1C1, and CYP1C2 were most strongly expressed in heart and eye. CYP1B1 and the CYP1C genes showed an expression pattern similar to one another and to mammalian CYP1B1. In embryos CYP1C1 and CYP1C2 tended to have a higher basal expression than CYP1A and CYP1B1. PCB126 induced CYP1A in all organs, and CYP1B1 and CYP1C1 in all organs except gonads, or gonads and brain, respectively. CYP1C2 induction was significant only in the liver. However, in embryos all four genes were induced strongly by PCB126. The results are consistent with CYP1C1 and CYP1C2, as well as CYP1A and CYP1B1, being regulated by the aryl hydrocarbon receptor. While CYP1A may have a protective role against AHR agonists in liver and gut, CYP1B1, CYP1C1, and CYP1C2 may also play endogenous roles in eye and heart and possibly other organs, as well as during development.
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| 50. |
- Jönsson, Maria E., et al.
(författare)
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New CYP1 genes in the frog Xenopus (Silurana) tropicalis : Induction patterns and effects of AHR agonists during development
- 2011
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Ingår i: Toxicology and Applied Pharmacology. - : Elsevier BV. - 0041-008X .- 1096-0333. ; 250:2, s. 170-183
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Tidskriftsartikel (refereegranskat)abstract
- The Xenopus tropicalis genome shows a single gene in each of the four cytochrome P450 1 (CYP1) subfamilies that occur in vertebrates, designated as CYP1A, CYP1B1, CYP1C1, and CYP1D1. We cloned the cDNAs of these genes and examined their expression in untreated tadpoles and in tadpoles exposed to waterborne aryl hydrocarbon receptor agonists, 3,3',4,4',5-pentachlorobiphenyl (PCB126), β-naphthoflavone (βNF), or indigo. We also examined the effects of PCB126 on expression of genes involved in stress response, cell proliferation, thyroid homeostasis, and prostaglandin synthesis. PCB126 induced CYP1A, CYP1B1, and CYP1C1 but had little effect on CYP1D1 (77-, 1.7-, 4.6- and 1.4-fold induction versus the control, respectively). βNF induced CYP1A and CYP1C1 (26- and 2.5-fold), while, under conditions used, indigo tended to induce only CYP1A (1.9-fold). The extent of CYP1 induction by PCB126 and βNF was positively correlated to the number of putative dioxin response elements 0-20kb upstream of the start codons. No morphological effect was observed in tadpoles exposed to 1nM-10μM PCB126 at two days post-fertilization (dpf) and screened 20days later. However, in 14-dpf tadpoles a slight up-regulation of the genes for PCNA, transthyretin, HSC70, Cu-Zn SOD, and Cox-2 was observed two days after exposure to 1μM PCB126. This study of the full suite of CYP1 genes in an amphibian species reveals gene- and AHR agonist-specific differences in response, as well as a much lower sensitivity to CYP1 induction and short-term toxicity by PCB126 compared with in fish larvae. The single genes in each CYP1 subfamily may make X. tropicalis a useful model for mechanistic studies of CYP1 functions.
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