| 1. |
- Jarvis, Ian W H, et al.
(författare)
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Interactions between polycyclic aromatic hydrocarbons in complex mixtures and implications for cancer risk assessment
- 2014
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Ingår i: Toxicology. - Stockholm : Karolinska Institutet, Institute of Environmental Medicine. - 0300-483X .- 1879-3185.
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Tidskriftsartikel (refereegranskat)abstract
- In this review we discuss the effects of exposure to complex PAH mixtures in vitro and in vivo on mechanisms related to carcinogenesis. Of particular concern regarding exposure to complex PAH mixtures is how interactions between different constituents can affect the carcinogenic response and how these might be included in risk assessment. Overall the findings suggest that the responses resulting from exposure to complex PAH mixtures is varied and complicated. More- and less-than additive effects on bioactivation and DNA damage formation have been observed depending on the various mixtures studied, and equally dependent on the different test systems that are used. Furthermore, the findings show that the commonly used biological end-point of DNA damage formation is insufficient for studying mixture effects. At present the assessment of the risk of exposure to complex PAH mixtures involves comparison to individual compounds using either a surrogate or a component-based potency approach. We discuss how future risk assessment strategies for complex PAH mixtures should be based around whole mixture assessment in order to account for interaction effects. Inherent to this is the need to incorporate different experimental approaches using robust and sensitive biological endpoints. Furthermore, the emphasis on future research should be placed on studying real life mixtures that better represent the complex PAH mixtures that humans are exposed to.
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| 2. |
- Gunnarsson, David, et al.
(författare)
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Cadmium-induced decrement of the LH receptor expression and cAMP levels in the testis of rats
- 2003
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Ingår i: Toxicology. - 0300-483X .- 1879-3185. ; 183:(1-3), s. 57-63
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Tidskriftsartikel (refereegranskat)abstract
- Cadmium (Cd) is a widespread environmental pollutant, characterized by its ability to affect various organs. Adverse effect of Cd on the testis including decreased testosterone production are well-known phenomena, but the cellular events explaining these effects have not yet been established. In the present study the initial steps of gonadotropin mediated testosterone biosynthesis were examined in vivo in rats, in relation to Cd dose and time after injection. In the dose–response experiment Male Sprague–Dawley rats received a single subcutaneous (sc) injection of CdCl2 (1, 5 or 10 μmol/kg body weight) and were sacrificed 48 h after injection. A statistically significant decrease in luteinizing hormone (LH) receptor mRNA level in the testicular tissue was demonstrated at the highest dose (10 μmol/kg). In the temporal–response experiment rats were given 10 μmol/kg of CdCl2 sc and sacrificed 0.48, 4.8, 48 or 144 h after injection. LH receptor mRNA levels as well as cyclic adenosine monophosphate (cAMP) levels were found to be significantly lowered at 48 and 144 h. These observations of the mechanisms whereby Cd exerts its effect on the initial steps of testosterone biosynthesis are the first from in vivo experiments.
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| 3. |
- Lind, Monica, et al.
(författare)
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Change of bone tissue composition and impaired bone strength in rats exposed to 3,3',4,4',5-pentachlorobiphenyl (PCB126)
- 2000
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Ingår i: Toxicology. - 0300-483X .- 1879-3185. ; 150:1-3, s. 41-51
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Tidskriftsartikel (refereegranskat)abstract
- In previous studies we have described structural and functional changes in rat bone tissue caused by 3,3′,4,4′,5-pentachlorobiphenyl (PCB126). Some of the effects caused by PCB126 resemble those found in vitamin C-deficient rats, as well as those found in rats with a high dietary intake of vitamin A. The present investigation was designed to determine if these PCB126-induced changes could be inhibited by addition of vitamin C to the drinking water and if they could be evoked by vitamin A administration. Five groups of female rats were used in this study, which lasted for 12 weeks. Three of the groups were exposed to PCB126 (total dose 320 μg/kg, bw), either alone or in combination with vitamin C added to the drinking water (1 and 10 g/l, respectively). One group was given feed with increased level of vitamin A (600 000 U/kg pellet) and the fifth group served as controls. Using peripheral quantitative computed tomography (pQCT), it was found that PCB126 increased trabecular density and cortical thickness, but reduced the trabecular area. Furthermore, maximum torque and stiffness of the humerus during torsional testing and serum osteocalcin levels were reduced by PCB126. Of the PCB126 induced effects observed, addition of vitamin C only inhibited the reduction of serum osteocalcin. Like PCB126 vitamin A supplementation increased the inorganic content and the bone density and also reduced the trabecular area and polar moment of inertia but did not increase the cortical thickness or reduce maximum torque, stiffness or serum osteocalcin level. Apparently, the effects induced by PCB126 are not mediated either via decreased vitamin C level or increased vitamin A level.
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| 4. |
- Rudén, Christina
(författare)
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Interpretations of primary carcinogenicity data in 29 trichloroethylene risk assessments
- 2001
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Ingår i: Toxicology. - 0300-483X .- 1879-3185. ; 169:3, s. 209-225
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Tidskriftsartikel (refereegranskat)abstract
- This paper explores to what extent interpretations of individual primary carcinogenicity data differ between different risk assessors, and discusses possible reasons for such differences as well as their impact on the overall risk assessment conclusions. For this purpose 29 different TCE carcinogenicity risk assessments are used as examples. It is concluded that the TCE risk assessors surprisingly often interpret and evaluate primary data differently. Two particular reasons for differences in data interpretation are discussed: different assessments of statistics, and different assessments of whether the results obtained in bioassays have toxicological relevance. Differences in the interpretation and evaluation of epidemiological data are also explored and discussed.
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| 5. |
- Ahmed, Fozia, et al.
(författare)
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The effects of bisphenol A and bisphenol S on adipokine expression and glucose metabolism in human adipose tissue
- 2020
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Ingår i: Toxicology. - : Elsevier BV. - 0300-483X .- 1879-3185. ; 445
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Tidskriftsartikel (refereegranskat)abstract
- PurposeThe environmental endocrine disruptors, bisphenol A (BPA) and bisphenol S (BPS) are associated with the development of type 2 diabetes. We aim to study the effects of BPA or BPS exposure on adipokine expression in human adipose tissue and on adipocyte glucose uptake.MethodsHuman subcutaneous adipose tissue was treated for 24 or 72 h with environmentally-relevant and supraphysiological concentrations of BPA or BPS (1–104 nM). Following exposure, gene expression of proinflammatory cytokines, adipokines, and estrogen receptors was measured in adipose tissue. Glucose uptake and the insulin signalling pathway were analyzed in isolated adipocytes following adipose tissue culture with BPA for 24 h.ResultsAdipose tissue treated with BPA for 24 h had reduced expression of the proinflammatory genes (IL6, IL1B, TNFA) and adipokines (ADIPOQ, FABP4). BPA and BPS had no effect on the expression of other proinflammatory genes (IL33), adipokines (LEP), or receptors (ESR1, ESR2) after 72-h exposure. Adipose tissue treated with environmentally-relevant concentrations of BPA for 24 h had reduced insulin-stimulated glucose uptake, without altered gene and protein levels of key insulin signalling pathway markers.ConclusionsWe found that human adipose tissue treated with environmentally-relevant concentrations of BPA for 24 h, but not BPS, reduced expression of proinflammatory genes and adipokines. Furthermore, BPA reduced glucose uptake in adipocytes independently of insulin signalling. Such mechanisms can contribute to the development of insulin resistance associated with BPA exposure.
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| 6. |
- Andersson, Helen, et al.
(författare)
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Effects of PCB126 and 17 beta-oestradiol on endothelium-derived vasoactive factors in human endothelial cells
- 2011
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Ingår i: Toxicology. - : Elsevier BV. - 0300-483X .- 1879-3185. ; 285:1-2, s. 46-56
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Tidskriftsartikel (refereegranskat)abstract
- Epidemiological and experimental studies suggest an association between elevated serum levels of co-planar PCBs and hypertension, and one study indicate that this effect is dependent on the level of oestrogen. This study investigated the effects of 3,3',4,4',5-pentachlorobiphenyl (PCB126) and 17 beta-oestradiol (E-2) on vasoactive factors in human umbilical vein endothelial cells (HUVEC). The results reveal that PCB126 stimulated the vasoconstriction factors COX-2 and PGF(2 alpha), in HUVEC. An up-regulation of COX-2 expression was demonstrated using qRT-PCR, western blot and immunofluorescence and increased production of PGF(2 alpha), was demonstrated using LC/MS2 and enzyme immunoassay. Also. PCB126 slightly increased ROS production and decreased NO production in HUVEC. The addition of E2 enhanced PCB126-induced transcription of CYP1A1, CYP1B1 and COX-2 in HUVEC whereas an increased transcription of eNOS only occurred following combined treatment with E-2 and PCB126. Immunofluorescence demonstrated that HUVEC expressed AHR and ER beta but lacked ER alpha and the involvement of AHR and ER beta on the effects of PCB126 was examined by the addition of AHR and ER antagonists. The binding of PCB126 to AHR was critical for the effects of PCB126 whereas the role of ER beta was equivocal. In conclusion, these studies suggest that PCB126 induced changes in human endothelial cells that are characteristic for endothelial dysfunction in human hypertension and that PCB126-induced transcription of genes important for vascular function in human endothelial cells can be elevated by increased oestrogen levels. These findings may help understanding the mechanism for the association between PCB126 exposure and hypertension reported in human subjects and experimental animals.
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| 7. |
- Andersson, Helén, 1982-, et al.
(författare)
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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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Ingår i: Toxicology. - : Elsevier BV. - 0300-483X .- 1879-3185. ; 262:1, s. 57-64
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Tidskriftsartikel (refereegranskat)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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| 8. |
- Aspenström-Fagerlund, Bitte, et al.
(författare)
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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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Ingår i: Toxicology. - : Elsevier BV. - 0300-483X .- 1879-3185. ; 237:1-3, s. 12-23
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Tidskriftsartikel (refereegranskat)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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| 9. |
- Beronius, Anna, et al.
(författare)
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The influence of study design and sex-differences on results from developmental neurotoxicity studies of bisphenol A, implications for toxicity testing
- 2013
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Ingår i: Toxicology. - : Elsevier BV. - 0300-483X .- 1879-3185. ; 311:1-2, s. 13-26
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Tidskriftsartikel (refereegranskat)abstract
- Developmental neurotoxicity (DNT) of bisphenol A (BPA) has been investigated in a large number of studies. However, there are discrepancies in the results reported between the studies. The aim of this study was to identify and analyze factors that may contribute to these differences and to assess whether there are sex-differences in the sensitivity of certain endpoints or tests used in DNT-studies. Forty-four DNT studies of BPA were identified from the open literature. Details about study design and results from each study, as well as the criteria for DNT testing according to the standardized OECD test guideline (TG) 426, were collected in a database. This enabled systematic and detailed comparisons between studies as well as to the criteria and recommendations stated in TG 426. Multivariate analyses were also used to investigate how different factors of the study design contributed to differences in study results. The analyses showed behavioral effects were often observed for endpoints that are not required according to OECD TG 426, such as anxiety-related, social and sexual behaviors, especially at very low doses and in female offspring. On the other hand relatively few studies observed any effects on motor activity, which is commonly used in screening for neurotoxic effects in regulatory testing. However, varied and to some extent seemingly contradictory results have been reported in these studies, especially for endpoints related to motor activity and anxiety and exploration. Many studies were also poorly reported, limiting these analyses. No strong conclusions could be drawn from the multivariate analyses. A few factors of study design, such as the size of the dose and number of dose levels used and the use of litter or individual pup as statistical unit seemed to have some influence on study results. In conclusion, this analysis suggests that DNT-studies conducted according to the standardized OECD TG 426 may overlook sensitive effects of BPA, and possibly other potential endocrine disruptors, especially in female offspring.
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| 10. |
- Bogdanska, Jasna, et al.
(författare)
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Tissue distribution of (35)S-labelled perfluorooctane sulfonate in adult mice after oral exposure to a low environmentally relevant dose or a high experimental dose
- 2011
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Ingår i: Toxicology. - : Elsevier BV. - 0300-483X .- 1879-3185. ; 284:1-3, s. 54-62
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Tidskriftsartikel (refereegranskat)abstract
- The widespread environmental pollutant perfluorooctane sulfonate (PFOS), detected in most animal species including the general human population, exerts several effects on experimental animals, e.g., hepatotoxicity, immunotoxicity and developmental toxicity. However, detailed information on the tissue distribution of PFOS in mammals is scarce and, in particular, the lack of available information regarding environmentally relevant exposure levels limits our understanding of how mammals (including humans) may be affected. Accordingly, we characterized the tissue distribution of this compound in mice, an important experimental animal for studying PFOS toxicity. Following dietary exposure of adult male C57/BL6 mice for 1-5 days to an environmentally relevant (0.031 mg/kg/day) or a 750-fold higher experimentally relevant dose (23 mg/kg/day) of (35)S-PFOS, most of the radioactivity administered was recovered in liver, bone (bone marrow), blood, skin and muscle, with the highest levels detected in liver, lung, blood, kidney and bone (bone marrow). Following high daily dose exposure, PFOS exhibited a different distribution profile than with low daily dose exposure, which indicated a shift in distribution from the blood to the tissues with increasing dose. Both scintillation counting (with correction for the blood present in the tissues) and whole-body autoradiography revealed the presence of PFOS in all 19 tissues examined, with identification of thymus as a novel site for localization for PFOS and bone (bone marrow), skin and muscle as significant body compartments for PFOS. These findings demonstrate that PFOS leaves the bloodstream and enters most tissues in a dose-dependent manner.
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