| 1. |
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| 2. |
- Dreij, Kristian, et al.
(författare)
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Cancer Risk Assessment of Airborne PAHs Based on in Vitro Mixture Potency Factors
- 2017
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Ingår i: Environmental Science and Technology. - : American Chemical Society (ACS). - 0013-936X .- 1520-5851. ; 51:15, s. 8805-8814
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Tidskriftsartikel (refereegranskat)abstract
- Complex mixtures of polycyclic aromatic hydrocarbons (PAHs) are common environmental pollutants associated with adverse human health effects including cancer. However, the risk of exposure to mixtures is difficult to estimate, and risk assessment by whole mixture potency evaluations has been suggested. To facilitate this, reliable in vitro based testing systems are necessary. Here, we investigated if activation of DNA damage signaling in vitro could be an endpoint for developing whole mixture potency factors (MPFs) for airborne PAHs. Activation of DNA damage signaling was assessed by phosphorylation of Chid and H2AX using Western blotting. To validate the in vitro approach, potency factors were determined for seven individual PAHs which were in very good agreement with established potency factors based on cancer data in vivo. Applying the method using Stockholm air PAH samples indicated MPFs with orders of magnitude higher carcinogenic potency than predicted by established in vivo-based potency factors. Applying the MPFs in cancer risk assessment suggested that 45.4 (6% of all) cancer cases per year in Stockholm are due to airborne PAHs. Applying established models resulted in <1 cancer case per year, which is far from expected levels. We conclude that our in vitro based approach for establishing MPFs could be a novel method to assess whole mixture samples of airborne PAHs to improve health risk assessment.
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| 3. |
- 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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| 4. |
- Lim, Hwanmi, et al.
(författare)
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Benzo[a]pyrene-specific online high-performance liquid chromatography fractionation of air particulate extracts : a tool for evaluating biological interactions
- 2014
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Ingår i: Journal of Chromatography A. - Stockholm : Karolinska Institutet, Institute of Environmental Medicine. - 0021-9673 .- 1873-3778.
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Tidskriftsartikel (refereegranskat)abstract
- Benzo[a]pyrene (B[a]P) is a known human carcinogen and is commonly used as a surrogate for assessing the carcinogenic risk posed by complex mixtures of polycyclic aromatic hydrocarbons (PAHs) present in air particulate matter (PM). However, studies have shown that using B[a]P as a surrogate may underestimate the carcinogenic potential of PAH mixtures, as the risk assessment approach does not consider interaction effects. Thus, toxicological studies using B[a]P to assess its carcinogenic potential in environmentally derived complex mixtures, as opposed to single compound experiments, could improve risk assessment. The intention of the present study was to develop an online HPLC fractionation system for the selective removal of B[a]P from air PM extracts. Two serial pyrenylethyl (PYE) columns enabled selective separation of B[a]P from its isomers and other PAHs as well as a short fractionation cycle of 30min. One run consisted of three collection steps: the first fraction contained PAHs eluting earlier than B[a]P, the second contained B[a]P and the last contained later-eluting PAHs. The selectivity and recovery of the system was investigated using extracts of Stockholm air PM samples. The overall recovery for all PAHs was approximately 80%, and the system proved to be selective, as it removed 94% of B[a]P and less than 3% of benzo[b]fluoranthene from the complex PAH mixture. Exposing human cells to blanks generated by the fractionation system did not induce cytotoxicity or DNA damage signalling. In conclusion, the online HPLC system was selective for B[a]P fractionation whilst minimising run-to-run variation and allowing repeated fractionations for larger samples due to its relatively short run time.
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| 5. |
- Lim, Hwanmi, et al.
(författare)
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Detection of Benz[j]aceanthrylene in Urban Air and Evaluation of Its Genotoxic Potential
- 2015
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Ingår i: Environmental Science and Technology. - Stockholm : American Chemical Society (ACS). - 0013-936X .- 1520-5851. ; 49:5, s. 3101-3109
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Tidskriftsartikel (refereegranskat)abstract
- Benz[j]aceanthrylene (B[j]A) is a cyclopenta-fused polycyclic aromatic hydrocarbon with strong mutagenic and carcinogenic effects. We have identified B[j]A in air particulate matter (PM) in samples collected in Stockholm, Sweden and in Limeira, Brazil using LC-GC/MS analysis. Determined concentrations ranged between 1.57 and 12.7 and 19.6-30.2 pg/m(3) in Stockholm and Limeira, respectively, which was 11-30 times less than benzo[a]pyrene (B[a]P) concentrations. Activation of the DNA damage response was evaluated after exposure to B[j]A in HepG2 cells in comparison to B[a]P. We found that significantly lower concentrations of B[j]A were needed for an effect on cell viability compared to B[a]P, and equimolar exposure resulted in significant more DNA damage with B[j]A. Additionally, levels of gamma H2AX, pChk1, p53, pp53, and p21 proteins were higher in response to B[j]A than B[a]P. On the basis of dose response induction of pChk1 and gamma H2AX, B[j]A potency was 12.5- and 33.3-fold higher than B[a]P, respectively. Although B[j]A levels in air were low, including B[j]A in the estimation of excess lifetime cancer risk increased the risk up to 2-fold depending on which potency factor for B[j]A was applied. Together, our results show that B[j]A could be an important contributor to the cancer risk of air PM.
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| 6. |
- Mattsson, Åse, et al.
(författare)
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Exposure of HepG2 cells to low levels of PAH-containing extracts from contaminated soils results in unpredictable genotoxic stress responses
- 2009
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Ingår i: Environmental and Molecular Mutagenesis. - : John Wiley & Sons. - 0893-6692 .- 1098-2280. ; 50:4, s. 337-348
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Tidskriftsartikel (refereegranskat)abstract
- Contaminated soil is a serious environmental problem, constituting a risk to humans and the environment. Polycyclic aromatic hydrocarbons (PAHs) are often present at contaminated sites. However, risk levels are difficult to estimate because of the complexity of contaminants present. Here, we compare cellular effects of extracts from contaminated soils collected at six industrial settings in Sweden. Chemical analysis showed that all soils contained complex mixtures of PAHs and oxy-PAHs. Western blotting and immunocytochemistry were used to investigate DNA damage signaling in HepG2 cells exposed to extracts from these soils. The effects on phosphorylated Mdm2, p53, Erk, H2AX, 53BP1, and Chk2, cell cycle regulating proteins (cyclin D1 and p21), and cell proliferation were compared. We found that most soil extracts induced phosphorylation of Mdm2 at the 2A10 epitope at low concentrations. This is in line with previous studies suggesting that this endpoint reflects readily repaired DNA-damage. However, we found concentration and time-dependent gamma H2AX and 53BP1 responses that were sustained for 48 hr. These endpoints may reflect the presence of different types of persistent DNA-damage. High concentrations of soil extracts decreased cyclin D1 and increased p21 response, indicating cell cycle arrest. Phosphorylation of Mdm2 at Ser 166, which attenuates the p53 response and is induced by many tumor promoters, was induced in a time-dependent manner and was associated with Erk phosphorylation. Taken together, the PAH extracts elicited unpredictable signaling responses that differed between samples. More polar compounds, i.e., oxy-PAHs, also contributed to the complexity.
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| 7. |
- Mattsson, Åse
(författare)
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Polycyclic aromatic hydrocarbons : DNA damage and cell signaling
- 2008
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Oxidative stress is a threat to our wellbeing. The formation of reactive oxygen species may result in oxidative lesions in DNA and RNA. When challenging A549 cells with 18O-labeled hydrogen peroxide, we found that RNA was between 14-25 times more sensitive to [18O]-8-oxoGuo formation than [18O]-8-oxodGuo formation in DNA. The A549 cells showed slow turnover rates of adducts in RNA and DNA with half-lifes of approximately 12 h for [18O]-8-oxoGuo in RNA, and 21 h for [18O]-8-oxodGuo in DNA, respectively. Polycyclic aromatic hydrocarbons (PAHs) are widespread mutagenic and carcinogenic environmental contaminants. They require metabolic activation into electrophilic diol epoxides (DEs) to be able to bind to DNA and elicit their biological activity. The bay-region DE of benzo[a]pyrene (BPDE) is more easily removed by nucleotide excision repair (NER) than the fjord-region DE of dibenzo[a,l]pyrene (DBPDE). This could reflect the ability of DBPDE to escape recognition and to investigate this, we studied the affect these DEs have on histone H2AX phosphorylation (gammaH2AX). Human A549 cells were exposed to the DEs for various time and concentration. The results showed that BPDE induced a transient gammaH2AX, while DBPDE exposure resulted in a continuously increasing and persistent gammaH2AX and these data correlated with the known effect on nucleotide excision repair (NER). Thus, the extent of gammaH2AX formation and the persistence was related to both the number of adducts and their structural feature. Further, the gammaH2AX, as well as effects on Mdm2 and p53 were studied in A549 cells in response to the bay-region DEs of chrysene (CDE) and dibenz[a,h]anthracene (DBADE), or the fjord-region DEs of benzo[c]chrysene (B[c]CDE), benzo[g]chrysene (B[g]CDE) and benzo[c]phenanthrene (B[c]PhDE). We found that the fjord-region DEs induced a rapid and concentration-dependent response on Mdm2 2A10 phosphorylation, p53 stabilization and phosphorylation, as well as gammaH2AX, where Mdm2 was the most sensitive marker. The bay-region DEs had less effect on Mdm2 2A10 phosphorylation and induced neither p53 stabilization nor phosphorylation. No gammaH2AX was detected with Western blot in response to bay-region DEs, however, immunostaining revealed reversible gammaH2AX. Also here, the variance between bay- and fjord-region DEs most likely reflect their recognition and handling by NER. PAH contamination of soil at industrial setting constitutes a risk to humans, but the risk is often difficult to estimate due to the complexity of present contaminants. We compared the DNA damage signaling effects in HepG2 cells exposed to PAHs extracted from contaminated soils collected at six different industrial settings in Sweden. Most of the soil extracts induced Mdm2 2A10 phosphorylation at low concentration, which may indicate repairable damage. We found concentration- and time-dependent gammaH2AX and 53BP1 responses, sustaining up to 48 h indicating persistent damage. Effects on cyclin D1 and p21 indicated cell cycle arrest, and phosphorylation of Mdm2 at Ser166, known to attenuate p53 response, was found and was associated with Erk phosphorylation. The PAH extracts elicited unpredictable DNA damage signaling that differed between the samples, and where also more polarcompounds, oxy-PAHs, contributed. We found that established approaches to evaluate carcinogenic potentials of PAH mixtures in contaminated soil are insufficient and call for the development of more sophisticated endpoints.
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| 8. |
- Prigge, Justin R., et al.
(författare)
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Hepatocyte Hyperproliferation upon Liver-Specific Co-disruption of Thioredoxin-1, Thioredoxin Reductase-1, and Glutathione Reductase
- 2017
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Ingår i: Cell Reports. - : Cell Press. - 2211-1247. ; 19:13, s. 2771-2781
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Tidskriftsartikel (refereegranskat)abstract
- Energetic nutrients are oxidized to sustain high intracellular NADPH/NADP(+) ratios. NADPH-dependent reduction of thioredoxin-1 (Trx1) disulfide and glutathione disulfide by thioredoxin reductase-1 (TrxR1) and glutathione reductase (Gsr), respectively, fuels antioxidant systems and deoxyribonucleotide synthesis. Mouse livers lacking both TrxR1 and Gsr sustain these essential activities using an NADPH-independent methionine-consuming pathway; however, it remains unclear how this reducing power is distributed. Here, we show that liver-specific co-disruption of the genes encoding Trx1, TrxR1, and Gsr (triplenull) causes dramatic hepatocyte hyperproliferation. Thus, even in the absence of Trx1, methionine-fueled glutathione production supports hepatocyte S phase deoxyribonucleotide production. Also, Trx1 in the absence of TrxR1 provides a survival advantage to cells under hyperglycemic stress, suggesting that glutathione, likely via glutaredoxins, can reduce Trx1 disulfide in vivo. In triple-null livers like in many cancers, deoxyribonucleotide synthesis places a critical yet relatively low-volume demand on these reductase systems, thereby favoring high hepatocyte turnover over sustained hepatocyte integrity.
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| 9. |
- Roos, Åse, et al.
(författare)
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Protocol for Providing Additional Pseudo-Pregnant Recipient Mice for Embryo Transfer and Intra-Uterine Insemination by Plugging in the Middle of the Day
- 2008
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Ingår i: Scandinavian Journal of Laboratory Animal Science. - 0901-3393. ; 35:4, s. 305-310
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Tidskriftsartikel (refereegranskat)abstract
- The fact that 10% of female mice enter oestrus and allow mating in the middle of the day is an old observation that has been more or less forgotten. We here show that this old knowledge can be used to improve the efficacy of both embryo transfer and insemination protocols. The present technical paper shows that rapid re-arrangements of mating cages, to achieve pseudo-pregnant recipients in the middle of the day, can be of great advantage in emergency situations. Such emergency situations occur repeatedly, i.e. when a scientist has forgotten to re-arrange her/his mating cages, and the last important male suddenly has become ill and may die within a few hours. A rapid technique for uterine artificial insemination in mice in such situations is extremely valuable. An artificial intra-uterine insemination requires only a minimum of planning, a minimum of instrumentation and a minimum of surgical training. The artificial insemination must be performed shortly after mating due to rapid constriction of the utero-tubual junction (UTJ). This means that the timing of the insemination is very important. We here show that the success rate for embryo transfers, when using recipients plugged in the middle of the day, was the same as for ordinary overnight mating protocols. In addition, it: should be noted that the success rate (frequency of pregnancies) for uterine inseminations was 55% if using F1 recipients of C57BL/6J (considerable lower if using recipients of inbred C57BL/6J), which is amazingly high, since inseminations in mice is known to be tricky to perform in a reproducible manner.
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