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An integrated framework for probabilistic cumulative risk assessment of chemicals in food
S100
Abstracts / Toxicology Letters 172S (2007) S1–S240
Q02 Ethanol induced vascular smooth muscle contraction independent of nitric oxide synthase activity in concentration dependent manner ˇ Jernej Berden, Blaˇz Groˇselj, Lovro Ziberna, Gorazd Drevenˇsek Institute of Pharmacology and Experimental Toxicology, Faculty of Medicine, University of Ljubljana, Ljubljana, Slovenia Purpose: The aim of our study was to evaluate possible enhancement of KCl, endothelin (ET-1) and norepinephrine thoracic rat aorta rings reactivity induced by acute ethanol application. Materials and methods: Endothelial integrity of aortic rings (basal tension 2.0 g) was assessed by the degree of relaxation caused by acetylcholine (0.1 mM) in the presence of contractile tone induced by norepinephrine (0.1 M). The rings pre-contraction by 60 mM KCl, 10 nM ET-1 and 0.1 M norepinephrine was followed by application of different ethanol concentrations (v/v%): 0.3%, 0.5%, 1.0%, 1.5%, 2.0%, 2.5%, 3.0%, 3.5%. Results: Either case showed ethanol concentrationdependent contraction. Maximal contraction (6.4 ± 0.8%) in KCl pre-contracted rings was reached at 2.5% ethanol concentration. In ET-1 pre-contracted rings maximal contraction (21.4 ± 4.8%) was observed by application of 3.0% ethanol concentration. In norepinephrine pre-contracted rings maximal contraction (12.5 ± 2.9%) was reached at 2.5% ethanol concentration. In higher ethanol concentrations (2.5–3.5%) the amount of contraction was decreasing from 11.0% to 5.0%. In addition, significant contraction of aortic rings at basal tension was observed only by application of ethanol concentration over 2.0%. Pre-incubation of aortic rings with 0.36 mM N(G)-nitro-l-arginine methylester (NOS inhibitor) and 9.8 M indomethacin (COX inhibitor) was followed by identical precontraction method resulting in higher plateau values. In this case the ethanol-induced contraction was also observed although minor responses were reached. Conclusions: The results showed that the ethanol application induces vascular smooth muscle contraction in concentration dependent manner. The mechanism for this action is independent of nitric oxide synthase activity. doi:10.1016/j.toxlet.2007.05.273
Q03 Proposal for a semi-quantitative model for risk prioritization: Health impact appreciation Peter Bos 1 , Polly Boon 2 , Hilko van der Voet 3 , Beat Br¨uschweiler 4 , Elsa Nielsen 5 1 RIVM-National
Institute for Public Health and the Environment, Bilthoven, Netherlands; 2 RIKILT-Institute of Food Safety, Wageningen, Netherlands; 3 Biometris, Wageningen University and Research Centre, Wageningen, Netherlands; 4 Swiss Federal Office of Public Health, Z¨urich, Switzerland; 5 Technical University of Denmark, Soborg, Denmark The EU sixth framework project SAFE FOODS aims at the development of a new integrated Risk Analysis Approach for foods integrating scientific principles, societal aspects and effective public participation. Within this project Work Package 3 entitled “Quantitative Risk Assessment of Combined Exposure to Food Contaminants and Natural Toxins” focuses on the development of a probabilistic risk assessment model. The outcome of this model is a quantitative risk estimate of the intake of chemicals (e.g. pesticides, mycotoxins, natural toxins) via food. There is an increasing need for quantitative risk assessment tools for the purpose of risk–benefit and risk–risk analyses. These tools will also facilitate choices in risk prioritization when the cost-effectiveness of risk reduction measures has to be carefully weighed. Three parameters are important: the fraction of the population at risk, the type of effect and the size (severity) of the effect itself. Further, the information should be provided to risk managers and policy makers in a manner that is easy-to-read. To meet these preconditions a concept is developed based on determination of Health Impact Criteria for toxicity endpoints leading to a Health Impact Appreciation for given exposure situations. The outcome is clearly presented by means of an easy readable Health Impact Chart. This Chart describes the results of a quantitative risk assessment in a graphical form showing the fraction of the population that is expected to be at no, low, medium or high risk for a given exposure situation. The basic concept will be presented and discussed with illustrative examples. doi:10.1016/j.toxlet.2007.05.274 Q04 An integrated framework for probabilistic cumulative risk assessment of chemicals in food
Abstracts / Toxicology Letters 172S (2007) S1–S240
Sieto Bosgra 1 , Hilko van der Voet 2 , Polly Boon 3 , Anne Kirstine M¨uller 4 , Peter Bos 5 , Wout Slob 5 1 Institute
for Risk Assessment Sciences, Utrecht University, Utrecht, Netherlands; 2 Biometris, Wageningen University and Research Centre, Wageningen, Netherlands; 3 RIKILT, Wageningen University and Research Centre, Wageningen, Netherlands; 4 National Food Institute, Technical University of Denmark, Søborg, Denmark; 5 National Institute of Public Health and the Environment, Bilthoven, Netherlands Within Work Package 3 of the EU sixth framework project Safe Foods, a framework has been developed that integrates the most relevant aspects of risk assessment: the relationship between exposure to a chemical and its effects, valuation of the health impact of those effects, variability between individuals in the population and uncertainties in the assessment (Van der Voet and Slob, 2007, in publication). Here, we extend this framework to address the cumulative risk of “common mechanism” chemicals. The classic toxic equivalency factor (TEF) approach is undesirable, since it can only be used if dose–response curves are parallel. This may often not be the case. Instead, we assume that isoboles – lines connecting all isoeffective combinations in the dose–dose space of two chemicals – are straight lines. With this assumption and the fitted dose–response functions for the individual chemicals, the “response surface” for any combination of the two chemicals is defined. Similarly, the effect from the combination of more than two chemicals can be predicted. By Monte Carlo sampling from food consumption data and concentration data, we can evaluate the dietary exposure to mixtures in the human population, and by using the isobole assumption, we can take potential cumulative effects into account. Uncertainty in the dose–responses – and hence in the predicted effect – is accounted for by (parametric) bootstrapping based on the fitted dose–response models for each individual chemical. This approach allows for a full probabilistic risk assessment of any class of chemicals for which the isobole assumption holds.
S101
Walter Brand 1 , Petronella A.I. van der Wel 1 , Gary Williamson 2 , Peter J. van Bladeren 2 , Ivonne M.C.M. Rietjens 1 1 Division
of Toxicology, Wageningen University, Wageningen, Netherlands; 2 Nestl´e Research Center, Nestec Ltd., Vers-chez-les-Blanc, Switzerland Biotransformation and transport from intestinal cells back into the intestinal lumen by ATP binding cassette (ABC) transporters located in the apical membrane of intestinal cells, limit the bioavailability of many biofunctional ingredients, including hesperetin, a citrus flavonoid which is of interest because of its proposed beneficial health effects. We studied the metabolism and transport of hesperetin in vitro using a two-compartment transwell system with Caco-2 cell monolayers, grown on a microporous membrane dividing an apical and basolateral compartment, simulating the lumen and blood/plasma side of the intestinal transport barrier. We exposed the Caco-2 monolayers apically to hesperetin and investigated the formation and transport of hesperetin conjugates. Our results show that un-conjugated hesperetin appears at the basolateral side of the Caco-2 monolayers but is also metabolised extensively into two major metabolites, the dominant one being hesperetin7-O-glucuronide, which was identified by UPLC-MS in combination with 1 H NMR. Both metabolites were transported predominantly to the apical compartment. By co-administrating a range of compounds known to inhibit different classes of ABC transporters, we studied the role of specific ABC transporters present in the apical epithelial membrane of the Caco-2 cells, including P-glycoprotein, MRP2 and Breast Cancer Resistance Protein (BCRP), in the transport of hesperetin and its metabolites. Our results demonstrate that of all ABC transporters BCRP is mainly responsible for the efflux of hesperetin metabolites to the apical side of the Caco2 monolayers. Moreover, upon inhibition of BCRP the transport of hesperetin metabolites to the basolateral side was significantly increased. doi:10.1016/j.toxlet.2007.05.276
doi:10.1016/j.toxlet.2007.05.275
Q06
Q05 Modulating hesperetin bioavailability at the level of its intestinal metabolism and ABC transporter mediated efflux studied in Caco-2 monolayers
See W5, abstract 29. doi:10.1016/j.toxlet.2007.05.055
Abstracts / Toxicology Letters 172S (2007) S1–S240
Q02 Ethanol induced vascular smooth muscle contraction independent of nitric oxide synthase activity in concentration dependent manner ˇ Jernej Berden, Blaˇz Groˇselj, Lovro Ziberna, Gorazd Drevenˇsek Institute of Pharmacology and Experimental Toxicology, Faculty of Medicine, University of Ljubljana, Ljubljana, Slovenia Purpose: The aim of our study was to evaluate possible enhancement of KCl, endothelin (ET-1) and norepinephrine thoracic rat aorta rings reactivity induced by acute ethanol application. Materials and methods: Endothelial integrity of aortic rings (basal tension 2.0 g) was assessed by the degree of relaxation caused by acetylcholine (0.1 mM) in the presence of contractile tone induced by norepinephrine (0.1 M). The rings pre-contraction by 60 mM KCl, 10 nM ET-1 and 0.1 M norepinephrine was followed by application of different ethanol concentrations (v/v%): 0.3%, 0.5%, 1.0%, 1.5%, 2.0%, 2.5%, 3.0%, 3.5%. Results: Either case showed ethanol concentrationdependent contraction. Maximal contraction (6.4 ± 0.8%) in KCl pre-contracted rings was reached at 2.5% ethanol concentration. In ET-1 pre-contracted rings maximal contraction (21.4 ± 4.8%) was observed by application of 3.0% ethanol concentration. In norepinephrine pre-contracted rings maximal contraction (12.5 ± 2.9%) was reached at 2.5% ethanol concentration. In higher ethanol concentrations (2.5–3.5%) the amount of contraction was decreasing from 11.0% to 5.0%. In addition, significant contraction of aortic rings at basal tension was observed only by application of ethanol concentration over 2.0%. Pre-incubation of aortic rings with 0.36 mM N(G)-nitro-l-arginine methylester (NOS inhibitor) and 9.8 M indomethacin (COX inhibitor) was followed by identical precontraction method resulting in higher plateau values. In this case the ethanol-induced contraction was also observed although minor responses were reached. Conclusions: The results showed that the ethanol application induces vascular smooth muscle contraction in concentration dependent manner. The mechanism for this action is independent of nitric oxide synthase activity. doi:10.1016/j.toxlet.2007.05.273
Q03 Proposal for a semi-quantitative model for risk prioritization: Health impact appreciation Peter Bos 1 , Polly Boon 2 , Hilko van der Voet 3 , Beat Br¨uschweiler 4 , Elsa Nielsen 5 1 RIVM-National
Institute for Public Health and the Environment, Bilthoven, Netherlands; 2 RIKILT-Institute of Food Safety, Wageningen, Netherlands; 3 Biometris, Wageningen University and Research Centre, Wageningen, Netherlands; 4 Swiss Federal Office of Public Health, Z¨urich, Switzerland; 5 Technical University of Denmark, Soborg, Denmark The EU sixth framework project SAFE FOODS aims at the development of a new integrated Risk Analysis Approach for foods integrating scientific principles, societal aspects and effective public participation. Within this project Work Package 3 entitled “Quantitative Risk Assessment of Combined Exposure to Food Contaminants and Natural Toxins” focuses on the development of a probabilistic risk assessment model. The outcome of this model is a quantitative risk estimate of the intake of chemicals (e.g. pesticides, mycotoxins, natural toxins) via food. There is an increasing need for quantitative risk assessment tools for the purpose of risk–benefit and risk–risk analyses. These tools will also facilitate choices in risk prioritization when the cost-effectiveness of risk reduction measures has to be carefully weighed. Three parameters are important: the fraction of the population at risk, the type of effect and the size (severity) of the effect itself. Further, the information should be provided to risk managers and policy makers in a manner that is easy-to-read. To meet these preconditions a concept is developed based on determination of Health Impact Criteria for toxicity endpoints leading to a Health Impact Appreciation for given exposure situations. The outcome is clearly presented by means of an easy readable Health Impact Chart. This Chart describes the results of a quantitative risk assessment in a graphical form showing the fraction of the population that is expected to be at no, low, medium or high risk for a given exposure situation. The basic concept will be presented and discussed with illustrative examples. doi:10.1016/j.toxlet.2007.05.274 Q04 An integrated framework for probabilistic cumulative risk assessment of chemicals in food
Abstracts / Toxicology Letters 172S (2007) S1–S240
Sieto Bosgra 1 , Hilko van der Voet 2 , Polly Boon 3 , Anne Kirstine M¨uller 4 , Peter Bos 5 , Wout Slob 5 1 Institute
for Risk Assessment Sciences, Utrecht University, Utrecht, Netherlands; 2 Biometris, Wageningen University and Research Centre, Wageningen, Netherlands; 3 RIKILT, Wageningen University and Research Centre, Wageningen, Netherlands; 4 National Food Institute, Technical University of Denmark, Søborg, Denmark; 5 National Institute of Public Health and the Environment, Bilthoven, Netherlands Within Work Package 3 of the EU sixth framework project Safe Foods, a framework has been developed that integrates the most relevant aspects of risk assessment: the relationship between exposure to a chemical and its effects, valuation of the health impact of those effects, variability between individuals in the population and uncertainties in the assessment (Van der Voet and Slob, 2007, in publication). Here, we extend this framework to address the cumulative risk of “common mechanism” chemicals. The classic toxic equivalency factor (TEF) approach is undesirable, since it can only be used if dose–response curves are parallel. This may often not be the case. Instead, we assume that isoboles – lines connecting all isoeffective combinations in the dose–dose space of two chemicals – are straight lines. With this assumption and the fitted dose–response functions for the individual chemicals, the “response surface” for any combination of the two chemicals is defined. Similarly, the effect from the combination of more than two chemicals can be predicted. By Monte Carlo sampling from food consumption data and concentration data, we can evaluate the dietary exposure to mixtures in the human population, and by using the isobole assumption, we can take potential cumulative effects into account. Uncertainty in the dose–responses – and hence in the predicted effect – is accounted for by (parametric) bootstrapping based on the fitted dose–response models for each individual chemical. This approach allows for a full probabilistic risk assessment of any class of chemicals for which the isobole assumption holds.
S101
Walter Brand 1 , Petronella A.I. van der Wel 1 , Gary Williamson 2 , Peter J. van Bladeren 2 , Ivonne M.C.M. Rietjens 1 1 Division
of Toxicology, Wageningen University, Wageningen, Netherlands; 2 Nestl´e Research Center, Nestec Ltd., Vers-chez-les-Blanc, Switzerland Biotransformation and transport from intestinal cells back into the intestinal lumen by ATP binding cassette (ABC) transporters located in the apical membrane of intestinal cells, limit the bioavailability of many biofunctional ingredients, including hesperetin, a citrus flavonoid which is of interest because of its proposed beneficial health effects. We studied the metabolism and transport of hesperetin in vitro using a two-compartment transwell system with Caco-2 cell monolayers, grown on a microporous membrane dividing an apical and basolateral compartment, simulating the lumen and blood/plasma side of the intestinal transport barrier. We exposed the Caco-2 monolayers apically to hesperetin and investigated the formation and transport of hesperetin conjugates. Our results show that un-conjugated hesperetin appears at the basolateral side of the Caco-2 monolayers but is also metabolised extensively into two major metabolites, the dominant one being hesperetin7-O-glucuronide, which was identified by UPLC-MS in combination with 1 H NMR. Both metabolites were transported predominantly to the apical compartment. By co-administrating a range of compounds known to inhibit different classes of ABC transporters, we studied the role of specific ABC transporters present in the apical epithelial membrane of the Caco-2 cells, including P-glycoprotein, MRP2 and Breast Cancer Resistance Protein (BCRP), in the transport of hesperetin and its metabolites. Our results demonstrate that of all ABC transporters BCRP is mainly responsible for the efflux of hesperetin metabolites to the apical side of the Caco2 monolayers. Moreover, upon inhibition of BCRP the transport of hesperetin metabolites to the basolateral side was significantly increased. doi:10.1016/j.toxlet.2007.05.276
doi:10.1016/j.toxlet.2007.05.275
Q06
Q05 Modulating hesperetin bioavailability at the level of its intestinal metabolism and ABC transporter mediated efflux studied in Caco-2 monolayers
See W5, abstract 29. doi:10.1016/j.toxlet.2007.05.055