The Experts below are selected from a list of 14418 Experts worldwide ranked by ideXlab platform
Frank G Gerberick - One of the best experts on this subject based on the ideXlab platform.
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application of the dermal Sensitization threshold concept to chemicals classified as high potency category for Skin Sensitization assessment of ingredients for consumer products
Regulatory Toxicology and Pharmacology, 2020Co-Authors: Taku Nishijo, Frank G Gerberick, Anne Marie Api, David W. Roberts, Masaaki Miyazawa, Robert J Safford, Hitoshi SakaguchiAbstract:Abstract Skin Sensitization evaluation is a key part of the safety assessment of ingredients in consumer products, which may have Skin sensitizing potential. The dermal Sensitization threshold (DST) concept, which is based on the concept of the thresholds of toxicological concern, has been proposed for the risk assessment of chemicals to which Skin exposure is very low level. There is negligible risk of Skin Sensitization if a Skin exposure level for the substance of interest was below the reactive DST which would protect against 95% of protein-reactive chemicals. For the remaining 5%, the substance with the defined knowledge of chemical structure (i.e., High Potency Category (HPC) rules) needs to be excluded from the application. However, the DST value for HPC chemicals has not yet been proposed. In this study, we calculated the 95th percentile probabilities estimate from distributions of Skin Sensitization potency data and derived a novel DST for HPC chemicals (HPC DST) of 1.5 μg/cm2. This value presents a useful default approach for unidentified substances in ingredients considering, as a worst-case scenario, that the unidentified compound may be a potent Skin sensitizer. Finally, we developed a novel risk assessment workflow incorporating the HPC DST along with the previously published DSTs.
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assessing Skin Sensitization hazard in mice and men using non animal test methods
Regulatory Toxicology and Pharmacology, 2015Co-Authors: Daniel Urbisch, Tzutzuy Ramirez, Petra Kern, Susanne Noreen Kolle, Robert Landsiedel, Annette Mehling, Joanna Jaworska, Naveed Honarvar, Katharina Guth, Frank G GerberickAbstract:Abstract Sensitization, the prerequisite event in the development of allergic contact dermatitis, is a key parameter in both hazard and risk assessments. The pathways involved have recently been formally described in the OECD adverse outcome pathway (AOP) for Skin Sensitization. One single non-animal test method will not be sufficient to fully address this AOP and in many cases the use of a battery of tests will be necessary. A number of methods are now fully developed and validated. In order to facilitate acceptance of these methods by both the regulatory and scientific communities, results of the single test methods (DPRA, KeratinoSens™, LuSens, h-CLAT, (m)MUSST) as well for a the simple ‘2 out of 3’ ITS for 213 substances have been compiled and qualitatively compared to both animal and human data. The dataset was also used to define different mechanistic domains by probable protein-binding mechanisms. In general, the non-animal test methods exhibited good predictivities when compared to local lymph node assay (LLNA) data and even better predictivities when compared to human data. The ‘2 out of 3’ prediction model achieved accuracies of 90% or 79% when compared to human or LLNA data, respectively and thereby even slightly exceeded that of the LLNA.
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bayesian integrated testing strategy to assess Skin Sensitization potency from theory to practice
Journal of Applied Toxicology, 2013Co-Authors: Joanna Jaworska, Petra Kern, Frank G Gerberick, Yuri Dancik, Andreas NatschAbstract:Frameworks to predict in vivo effects by integration of in vitro, in silico and in chemico information using mechanistic insight are needed to meet the challenges of 21st century toxicology. Expert-based approaches that qualitatively integrate multifaceted data are practiced under the term ’weight of evidence’, whereas quantitative approaches remain rare. To address this gap we previously developed a methodology to design an Integrated Testing Strategy (ITS) in the form of a Bayesian Network (BN). This study follows up on our proof of concept work and presents an updated ITS to assess Skin Sensitization potency expressed as local lymph node assay (LLNA) potency classes. Modifications to the ITS structure were introduced to include better mechanistic information. The parameters of the updated ITS were calculated from an extended data set of 124 chemicals. A detailed validation analysis and a case study were carried out to demonstrate the utility of the ITS for practical application. The improved BN ITS predicted correctly 95% and 86% of chemicals in a test set (n = 21) for hazard and LLNA potency classes, respectively. The practical value of using the BN ITS is far more than a prediction framework when all data are available. The BN ITS can develop a hypothesis using subsets of data as small as one data point and can be queried on the value of adding additional tests before testing is commenced. The ITS represents key steps of the Skin Sensitization process and a mechanistically interpretable testing strategy can be developed. These features are illustrated in the manuscript via practical examples. Copyright © 2013 John Wiley & Sons, Ltd.
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a dataset on 145 chemicals tested in alternative assays for Skin Sensitization undergoing prevalidation
Journal of Applied Toxicology, 2013Co-Authors: Andreas Natsch, Leslie M. Foertsch, Frank G Gerberick, Cindy A Ryan, Joanna Jaworska, Roger Emter, Petra KernAbstract:Skin Sensitization is a key endpoint for cosmetic ingredients, with a forthcoming ban for animal testing in Europe. Four alternative tests have so far been submitted to ECVAM prevalidation: (i) MUSST and (ii) h-Clat assess surface markers on dendritic cell lines, (iii) the direct peptide reactivity assay (DPRA) measures reactivity with model peptides and (iv) the KeratinoSens(TM) assay which is based on detection of Nrf2-induced luciferase. It is anticipated that only an integrated testing strategy (ITS) based on a battery of tests might give a full replacement providing also a Sensitization potency assessment, but this concept should be tested with a data-driven analysis. Here we report a database on 145 chemicals reporting the quantitative endpoints measured in a U937- test, the DPRA and KeratinoSens(TM) . It can serve to develop data-driven ITS approaches as we show in a parallel paper and provides a view as to the current ability to predict with in vitro tests as we are entering 2013. It may also serve as reference database when benchmarking new molecules with in vitro based read-across and find use as a reference database when evaluating new tests. The tests and combinations thereof were evaluated for predictivity, and overall a similar predictivity was found as before on three-fold smaller datasets. Analysis of the dose-response parameters of the individual tests indicates a correlation to Sensitization potency. Detailed analysis of chemicals false-negative and false-positive in two tests helped to define limitations in the tests but also in the database derived from animal studies.
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the incorporation of lysine into the peroxidase peptide reactivity assay for Skin Sensitization assessments
Toxicological Sciences, 2011Co-Authors: John A Troutman, Leslie M. Foertsch, Petra Kern, Jean-pierre Lepoittevin, J Lalko, Hong Jian Dai, Mike Quijano, Roy L M Dobson, Frank G GerberickAbstract:To establish further a practical quantitative in chemico reactivity assay for screening contact allergens, lysine peptide was incorporated into a liquid chromatography and tandem mass spectrometry-based assay for reactivity assessments of hapten and pre-/pro-hapten chemical sensitizers. Loss of peptide was determined following 24 h coincubation with test chemical using a concentration-response study design. A total of 70 chemicals were tested in discrete reactions with cysteine or lysine peptide, in the presence and absence of horseradish peroxidase-hydrogen peroxide oxidation system. An empirically derived prediction model for discriminating sensitizers from nonsensitizers resulted in an accuracy of 83% for 26 haptens, 19 pre-/pro-haptens, and 25 nonsensitizers. Four sensitizers were shown to selectively react with lysine including two strong/extreme and two weak sensitizers. In addition, seven sensitizers were identified as having higher reactivity toward lysine compared with cysteine. The majority of sensitizing chemicals (27/45) were reactive toward both cysteine and lysine peptides. An estimate of the relative reactivity potency was determined based on the concentration of test chemical that depletes peptide at or above a threshold positive value. Here, we report the use of EC15 as one example to illustrate the use of the model for screening the Skin Sensitization potential of novel chemicals. Results from this initial assessment highlight the utility of lysine for assessing a chemical's potential to elicit Sensitization reactions or induce hypersensitivity. This approach has the potential to qualitatively and quantitatively evaluate an important mechanism in contact allergy for hazard and quantitative risk assessments without animal testing.
David W. Roberts - One of the best experts on this subject based on the ideXlab platform.
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application of the dermal Sensitization threshold concept to chemicals classified as high potency category for Skin Sensitization assessment of ingredients for consumer products
Regulatory Toxicology and Pharmacology, 2020Co-Authors: Taku Nishijo, Frank G Gerberick, Anne Marie Api, David W. Roberts, Masaaki Miyazawa, Robert J Safford, Hitoshi SakaguchiAbstract:Abstract Skin Sensitization evaluation is a key part of the safety assessment of ingredients in consumer products, which may have Skin sensitizing potential. The dermal Sensitization threshold (DST) concept, which is based on the concept of the thresholds of toxicological concern, has been proposed for the risk assessment of chemicals to which Skin exposure is very low level. There is negligible risk of Skin Sensitization if a Skin exposure level for the substance of interest was below the reactive DST which would protect against 95% of protein-reactive chemicals. For the remaining 5%, the substance with the defined knowledge of chemical structure (i.e., High Potency Category (HPC) rules) needs to be excluded from the application. However, the DST value for HPC chemicals has not yet been proposed. In this study, we calculated the 95th percentile probabilities estimate from distributions of Skin Sensitization potency data and derived a novel DST for HPC chemicals (HPC DST) of 1.5 μg/cm2. This value presents a useful default approach for unidentified substances in ingredients considering, as a worst-case scenario, that the unidentified compound may be a potent Skin sensitizer. Finally, we developed a novel risk assessment workflow incorporating the HPC DST along with the previously published DSTs.
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non animal assessment of Skin Sensitization hazard is an integrated testing strategy needed and if so what should be integrated
Journal of Applied Toxicology, 2018Co-Authors: David W. Roberts, Grace PatlewiczAbstract:There is an expectation that to meet regulatory requirements, and avoid or minimize animal testing, integrated approaches to testing and assessment will be needed that rely on assays representing key events (KEs) in the Skin Sensitization adverse outcome pathway. Three non-animal assays have been formally validated and regulatory adopted: the direct peptide reactivity assay (DPRA), the KeratinoSens™ assay and the human cell line activation test (h-CLAT). There have been many efforts to develop integrated approaches to testing and assessment with the "two out of three" approach attracting much attention. Here a set of 271 chemicals with mouse, human and non-animal Sensitization test data was evaluated to compare the predictive performances of the three individual non-animal assays, their binary combinations and the "two out of three" approach in predicting Skin Sensitization potential. The most predictive approach was to use both the DPRA and h-CLAT as follows: (1) perform DPRA - if positive, classify as sensitizing, and (2) if negative, perform h-CLAT - a positive outcome denotes a sensitizer, a negative, a non-sensitizer. With this approach, 85% (local lymph node assay) and 93% (human) of non-sensitizer predictions were correct, whereas the "two out of three" approach had 69% (local lymph node assay) and 79% (human) of non-sensitizer predictions correct. The findings are consistent with the argument, supported by published quantitative mechanistic models that only the first KE needs to be modeled. All three assays model this KE to an extent. The value of using more than one assay depends on how the different assays compensate for each other's technical limitations. Copyright © 2017 John Wiley & Sons, Ltd.
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is Skin penetration a determining factor in Skin Sensitization potential and potency refuting the notion of a logkow threshold for Skin Sensitization
Journal of Applied Toxicology, 2017Co-Authors: Jeremy M Fitzpatrick, David W. RobertsAbstract:It is widely accepted that substances that cannot penetrate through the Skin will not be sensitizers. LogKow and molecular weight (MW) have been used to set thresholds for Sensitization potential. Highly hydrophilic substances e.g. LogKow ≤ 1 are expected not to penetrate effectively to induce Sensitization. To investigate whether LogKow >1 is a true requirement for Sensitization, a large dataset of substances that had been evaluated for their Skin Sensitization potential under Registration, Evaluation, Authorisation and restriction of CHemicals (REACH), together with available measured LogKow values was compiled using the OECD eChemPortal. The incidence of sensitizers relative to non-sensitizers above and below a LogKow of 1 was explored. Reaction chemistry principles were used to explain the Sensitization observed for the subset of substances with a LogKow ≤0. 1482 substances were identified with Skin Sensitization data and measured LogKow values. 525 substances had a measured LogKow ≤ 1, 100 of those were sensitizers. There was no significant difference in the incidence of sensitizers above and below a LogKow of 1. Reaction chemistry principles that had been established for lower MW and more hydrophobic substances were found to be still valid in rationalizing the Skin sensitizers with a LogKow ≤ 0. The LogKow threshold arises from the widespread misconception that the ability to efficiently penetrate the stratum corneum is a key determinant of Sensitization potential and potency. Copyright © 2016 John Wiley & Sons, Ltd.
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Can currently available non-animal methods detect pre and pro-haptens relevant for Skin Sensitization?
Regulatory Toxicology and Pharmacology, 2016Co-Authors: Silvia Casati, Andrew P. Worth, Jean-pierre Lepoittevin, David W. Roberts, David Asturiol, Karin AschbergerAbstract:Predictive testing to characterize substances for their Skin Sensitization potential has historically been based on animal tests such as the Local Lymph Node Assay (LLNA). In recent years, regulations in the cosmetics and chemicals sectors have provided strong impetus to develop non-animal alternatives. Three test methods have undergone OECD validation: the direct peptide reactivity assay (DPRA), the KeratinoSens™ and the human Cell Line Activation Test (h-CLAT). Whilst these methods perform relatively well in predicting LLNA results, a concern raised is their ability to predict chemicals that need activation to be sensitizing (pre- or pro-haptens). This current study reviewed an EURL ECVAM dataset of 127 substances for which information was available in the LLNA and three non-animal test methods. Twenty eight of the sensitizers needed to be activated, with the majority being pre-haptens. These were correctly identified by 1 or more of the test methods. Six substances were categorized exclusively as pro-haptens, but were correctly identified by at least one of the cell-based assays. The analysis here showed that Skin metabolism was not likely to be a major consideration for assessing Sensitization potential and that sensitizers requiring activation could be identified correctly using one or more of the current non-animal methods.
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towards aop application implementation of an integrated approach to testing and assessment iata into a pipeline tool for Skin Sensitization
Regulatory Toxicology and Pharmacology, 2014Co-Authors: Chanita Kuseva, David W. Roberts, Antonia Kesova, I Popova, Teodor Zhechev, Todor Pavlov, Ovanes MekenyanAbstract:Since the OECD published the Adverse Outcome Pathway (AOP) for Skin Sensitization, many efforts have focused on how to integrate and interpret nonstandard information generated for key events in a manner that can be practically useful for decision making. These types of frameworks are known as Integrated Approaches to Testing and Assessment (IATA). Here we have outlined an IATA for Skin Sensitization which focuses on existing information including non testing approaches such as QSAR and read-across. The IATA was implemented into a pipeline tool using OASIS technology to provide a means of systematically collating and compiling relevant information which could be used in an assessment of Skin Sensitization potential. A test set of 100 substances with available Skin Sensitization information was profiled using the pipeline IATA. In silico and in chemico profiling information alone was able to correctly predict Skin Sensitization potential, with a preliminary accuracy of 73.85%. Information from other relevant endpoints (e.g., Ames mutagenicity) was found to improve the accuracy (to 87.6%) when coupled with a reaction chemistry mechanistic understanding. This pipeline platform could be useful in the assessment of Skin Sensitization potential and marks a step change in how non testing approaches can be practically applied.
Ian Kimber - One of the best experts on this subject based on the ideXlab platform.
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Skin Sensitization tests the llna and the rhe il 18 potency assay
Methods of Molecular Biology, 2021Co-Authors: Emanuela Corsini, Ian Kimber, Susan Gibbs, Erwin Ludo Roggen, David A BasketterAbstract:Contact allergy is of considerable importance to the toxicologist, and regulatory authorities worldwide require testing for Skin Sensitization potential and appropriate hazard labeling to enable management of the risk to human health. Although traditionally the identification of Skin-sensitizing chemicals has been carried out using animal models, in Europe legislative changes have promoted, and now require, the use of non-animal methods (i.e., Cosmetic Directive, REACH). Several in vitro alternatives for hazard identification have now been validated, but do not provide information on the potency of a Skin sensitizer. Here, we describe an animal model, the local lymph node assay (LLNA), and an in vitro model, the RhE IL-18 potency assay, in the context of the identification and potency classification of Skin sensitizers. These two assays have been chosen among the different available tests as representative of an alternative in vivo model (the LLNA) and a promising in vitro method with the potential of both hazard identification and potency classification.
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Immunoregulation of Skin Sensitization and regulatory T cells
Contact Dermatitis, 2012Co-Authors: Ian Kimber, Mark A Travis, Stefan F Martin, Rebecca Jane DearmanAbstract:It is well established that, in common with other adaptive immune responses, the acquisition of Skin Sensitization is carefully orchestrated and finely controlled. This is achieved in a number of ways. However, in recent years, there has been an increasing interest in the roles that regulatory T cells (Tregs) play in allergic contact dermatitis. Here, we review briefly the phenotype and function of Tregs, and consider how they may impact on various aspects of Skin Sensitization, including: inter-individual differences in susceptibility; variations in the potency of chemical allergens; and the prevention of excessive, and potentially damaging, levels of Sensitization.
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Updating the Skin Sensitization in vitro data assessment paradigm in 2009
Journal of Applied Toxicology, 2009Co-Authors: Ian KimberAbstract:Approaches to the interpretation of guinea pig Skin Sensitization data for both hazard identification and potency assessment have been understood for many years. More recently, the local lymph node assay has to a large extent replaced the earlier guinea pig assays, not least because it provides a more clearly defined and transparent means of identifying hazard, and the ability to measure relative Skin Sensitization potency. However, beginning in 2009 there will be considerable pressure replace all in vivo assays for Skin Sensitization with alternative approaches that do not require the use of animals (in vitro and/or in silico methods). As there is a common view that multiple assays will be needed to achieve complete replacement of the in vivo tests, a strategy for the integration of the available data will be required. There has been at least one previous attempt to develop a framework that would provide for integration of relevant information from different sources to reach informed decisions about Skin Sensitization potential and potency. It is timely now, in the light of recent developments and initiatives, to revisit this paradigm with a view to developing recommendations for modification and refinement. In addition to this, the need for performance standards and an agreed 'gold standard' dataset against which to validate both alternatives and new prediction models is discussed.
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dose metrics in the acquisition of Skin Sensitization thresholds and importance of dose per unit area
Regulatory Toxicology and Pharmacology, 2008Co-Authors: Ian Kimber, Rebecca Jane Dearman, Frank G Gerberick, J Lalko, Cindy A Ryan, Pauline Mcnamee, Anne Marie ApiAbstract:Allergic contact dermatitis is a common occupational and environmental health problem and many hundreds of chemicals have been implicated as Skin sensitizers. Sensitization is acquired following topical exposure to a contact allergen and induction of a cutaneous immune response of an appropriate magnitude. For effective assessment and management of human health risks there is a need to appreciate the dose metrics that drive the induction of Skin Sensitization. The available evidence suggests that under most normal conditions of exposure it is the dose per unit area of chemical that has over-riding impact on the effectiveness of Sensitization. The exception to this rule is when the area of the application site drops below a certain critical level. Here we review in detail the evidence which supports dose per unit area as being the critical exposure metric in the induction of Skin Sensitization, and the mechanistic bases for this relationship.
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mechanistic applicability domain classification of a local lymph node assay dataset for Skin Sensitization
Chemical Research in Toxicology, 2007Co-Authors: David W. Roberts, Rebecca Jane Dearman, Petra Kern, Frank G Gerberick, Ian Kimber, Cindy A RyanAbstract:The goal of eliminating animal testing in the predictive identification of chemicals with the intrinsic ability to cause Skin Sensitization is an important target, the attainment of which has recently been brought into even sharper relief by the EU Cosmetics Directive and the requirements of the REACH legislation. Development of alternative methods requires that the chemicals used to evaluate and validate novel approaches comprise not only confirmed Skin sensitizers and non-sensitizers but also substances that span the full chemical mechanistic spectrum associated with Skin Sensitization. To this end, a recently published database of more than 200 chemicals tested in the mouse local lymph node assay (LLNA) has been examined in relation to various chemical reaction mechanistic domains known to be associated with Sensitization. It is demonstrated here that the dataset does cover the main reaction mechanistic domains. In addition, it is shown that assignment to a reaction mechanistic domain is a critical fir...
Petra Kern - One of the best experts on this subject based on the ideXlab platform.
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assessing Skin Sensitization hazard in mice and men using non animal test methods
Regulatory Toxicology and Pharmacology, 2015Co-Authors: Daniel Urbisch, Tzutzuy Ramirez, Petra Kern, Susanne Noreen Kolle, Robert Landsiedel, Annette Mehling, Joanna Jaworska, Naveed Honarvar, Katharina Guth, Frank G GerberickAbstract:Abstract Sensitization, the prerequisite event in the development of allergic contact dermatitis, is a key parameter in both hazard and risk assessments. The pathways involved have recently been formally described in the OECD adverse outcome pathway (AOP) for Skin Sensitization. One single non-animal test method will not be sufficient to fully address this AOP and in many cases the use of a battery of tests will be necessary. A number of methods are now fully developed and validated. In order to facilitate acceptance of these methods by both the regulatory and scientific communities, results of the single test methods (DPRA, KeratinoSens™, LuSens, h-CLAT, (m)MUSST) as well for a the simple ‘2 out of 3’ ITS for 213 substances have been compiled and qualitatively compared to both animal and human data. The dataset was also used to define different mechanistic domains by probable protein-binding mechanisms. In general, the non-animal test methods exhibited good predictivities when compared to local lymph node assay (LLNA) data and even better predictivities when compared to human data. The ‘2 out of 3’ prediction model achieved accuracies of 90% or 79% when compared to human or LLNA data, respectively and thereby even slightly exceeded that of the LLNA.
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bayesian integrated testing strategy to assess Skin Sensitization potency from theory to practice
Journal of Applied Toxicology, 2013Co-Authors: Joanna Jaworska, Petra Kern, Frank G Gerberick, Yuri Dancik, Andreas NatschAbstract:Frameworks to predict in vivo effects by integration of in vitro, in silico and in chemico information using mechanistic insight are needed to meet the challenges of 21st century toxicology. Expert-based approaches that qualitatively integrate multifaceted data are practiced under the term ’weight of evidence’, whereas quantitative approaches remain rare. To address this gap we previously developed a methodology to design an Integrated Testing Strategy (ITS) in the form of a Bayesian Network (BN). This study follows up on our proof of concept work and presents an updated ITS to assess Skin Sensitization potency expressed as local lymph node assay (LLNA) potency classes. Modifications to the ITS structure were introduced to include better mechanistic information. The parameters of the updated ITS were calculated from an extended data set of 124 chemicals. A detailed validation analysis and a case study were carried out to demonstrate the utility of the ITS for practical application. The improved BN ITS predicted correctly 95% and 86% of chemicals in a test set (n = 21) for hazard and LLNA potency classes, respectively. The practical value of using the BN ITS is far more than a prediction framework when all data are available. The BN ITS can develop a hypothesis using subsets of data as small as one data point and can be queried on the value of adding additional tests before testing is commenced. The ITS represents key steps of the Skin Sensitization process and a mechanistically interpretable testing strategy can be developed. These features are illustrated in the manuscript via practical examples. Copyright © 2013 John Wiley & Sons, Ltd.
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a dataset on 145 chemicals tested in alternative assays for Skin Sensitization undergoing prevalidation
Journal of Applied Toxicology, 2013Co-Authors: Andreas Natsch, Leslie M. Foertsch, Frank G Gerberick, Cindy A Ryan, Joanna Jaworska, Roger Emter, Petra KernAbstract:Skin Sensitization is a key endpoint for cosmetic ingredients, with a forthcoming ban for animal testing in Europe. Four alternative tests have so far been submitted to ECVAM prevalidation: (i) MUSST and (ii) h-Clat assess surface markers on dendritic cell lines, (iii) the direct peptide reactivity assay (DPRA) measures reactivity with model peptides and (iv) the KeratinoSens(TM) assay which is based on detection of Nrf2-induced luciferase. It is anticipated that only an integrated testing strategy (ITS) based on a battery of tests might give a full replacement providing also a Sensitization potency assessment, but this concept should be tested with a data-driven analysis. Here we report a database on 145 chemicals reporting the quantitative endpoints measured in a U937- test, the DPRA and KeratinoSens(TM) . It can serve to develop data-driven ITS approaches as we show in a parallel paper and provides a view as to the current ability to predict with in vitro tests as we are entering 2013. It may also serve as reference database when benchmarking new molecules with in vitro based read-across and find use as a reference database when evaluating new tests. The tests and combinations thereof were evaluated for predictivity, and overall a similar predictivity was found as before on three-fold smaller datasets. Analysis of the dose-response parameters of the individual tests indicates a correlation to Sensitization potency. Detailed analysis of chemicals false-negative and false-positive in two tests helped to define limitations in the tests but also in the database derived from animal studies.
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the incorporation of lysine into the peroxidase peptide reactivity assay for Skin Sensitization assessments
Toxicological Sciences, 2011Co-Authors: John A Troutman, Leslie M. Foertsch, Petra Kern, Jean-pierre Lepoittevin, J Lalko, Hong Jian Dai, Mike Quijano, Roy L M Dobson, Frank G GerberickAbstract:To establish further a practical quantitative in chemico reactivity assay for screening contact allergens, lysine peptide was incorporated into a liquid chromatography and tandem mass spectrometry-based assay for reactivity assessments of hapten and pre-/pro-hapten chemical sensitizers. Loss of peptide was determined following 24 h coincubation with test chemical using a concentration-response study design. A total of 70 chemicals were tested in discrete reactions with cysteine or lysine peptide, in the presence and absence of horseradish peroxidase-hydrogen peroxide oxidation system. An empirically derived prediction model for discriminating sensitizers from nonsensitizers resulted in an accuracy of 83% for 26 haptens, 19 pre-/pro-haptens, and 25 nonsensitizers. Four sensitizers were shown to selectively react with lysine including two strong/extreme and two weak sensitizers. In addition, seven sensitizers were identified as having higher reactivity toward lysine compared with cysteine. The majority of sensitizing chemicals (27/45) were reactive toward both cysteine and lysine peptides. An estimate of the relative reactivity potency was determined based on the concentration of test chemical that depletes peptide at or above a threshold positive value. Here, we report the use of EC15 as one example to illustrate the use of the model for screening the Skin Sensitization potential of novel chemicals. Results from this initial assessment highlight the utility of lysine for assessing a chemical's potential to elicit Sensitization reactions or induce hypersensitivity. This approach has the potential to qualitatively and quantitatively evaluate an important mechanism in contact allergy for hazard and quantitative risk assessments without animal testing.
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integrating non animal test information into an adaptive testing strategy Skin Sensitization proof of concept case
ALTEX-Alternatives to Animal Experimentation, 2011Co-Authors: Joanna Jaworska, Petra Kern, Artsiom Harol, G F GerberickAbstract:there is a pressing need for non-animal test methods, driven by the forthcoming ban on animal testing for cosmetic ingredients in Europe, the large number of tests potentially required to fill in data gaps for the ReACH legislation, and animal welfare concerns. Skin Sensitization was identified as the hazard endpoint for which most animal tests would need to be conducted and which required a large number of animals (van der Jagt et al., 2004). the individual steps involved in the Skin Sensitization process are illustrated in File A (Supplementary Data at www.altexedition.org). In short, the chemical must penetrate the Skin to react with endogenous proteins, either directly or after activation through enzymatic or oxidative processes. Next, epidermal langerhans cells (lC) and immature dendritic cells (DC) take up and process haptenated proteins. lC cells mature into antigen presenting cells, which after migration to the lymph nodes present haptenized protein fragments to t-cells. Many research groups are working on the development of alternative tests for Skin Sensitization (Vandebriel and van loveren, 2010; Aeby et al., 2010). As a chemical’s reactivity towards proteins is deemed a key determining factor in its ability to act as a Skin sensitizer, a lot of research has focused on in chemico measurements of reactivity with model nucleophiles. Various nucleophiles are used and experiments are either done by direct peptide reactivity measurements (Gerberick et al., 2008), semi-kinetic (Aptula et al., 2006) or more complex kinetics (Aleksic et al., 2009). In addition, the induction of an antioxidant response element (ARe) dependent gene activity in a recombinant cell line (Natsch et al., 2008) can be used to indirectly characterize reactivity. to further elucidate the Skin Sensitization induction process, various measures of dendritic cell activation are considered. Recent advances in the in vitro generation of immature dendritic cells and the availability of cell line surrogates with various DC-like characteristics has led to the development of in vitro tests based on the measurement of various cell surface markers or secretion of cytokines modulated upon exposure to chemicals (Aeby et al., 2010; Ryan et al., 2005; lambrechts et al., 2010). Numerous attempts were also made to predict in silico the Skin Sensitization potential in vivo (Roberts et al., 2007; Patlewicz et al., 2007, 2008; Patlewicz and Worth, 2008; Karlberg et al., 2008). Many authors share the opinion that a single test method cannot replace the in vivo Skin Sensitization animal testing; however, it remains open which tests are actually needed. to address this point of view, several data integration frameworks have been developed. Jowsey et al. (2006) proposed a conceptual scoring system based on Structure Activity Relationships (SAR), penetration, peptide reactivity, and dendritic and t-cell activation Summary There is an urgent need to develop data integration and testing strategy frameworks allowing interpretation of results from animal alternative test batteries. To this end, we developed a Bayesian Network Integrated Testing Strategy (BN ITS) with the goal to estimate Skin Sensitization hazard as a test case of previously developed concepts (Jaworska et al., 2010). The BN ITS combines in silico, in chemico, and in vitro data related to Skin penetration, peptide reactivity, and dendritic cell activation, and guides testing strategy by Value of Information (VoI). The approach offers novel insights into testing strategies: there is no one best testing strategy, but the optimal sequence of tests depends on information at hand, and is chemical-specific. Thus, a single generic set of tests as a replacement strategy is unlikely to be most effective. BN ITS offers the possibility of evaluating the impact of generating additional data on the target information uncertainty reduction before testing is commenced.
Cindy A Ryan - One of the best experts on this subject based on the ideXlab platform.
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a dataset on 145 chemicals tested in alternative assays for Skin Sensitization undergoing prevalidation
Journal of Applied Toxicology, 2013Co-Authors: Andreas Natsch, Leslie M. Foertsch, Frank G Gerberick, Cindy A Ryan, Joanna Jaworska, Roger Emter, Petra KernAbstract:Skin Sensitization is a key endpoint for cosmetic ingredients, with a forthcoming ban for animal testing in Europe. Four alternative tests have so far been submitted to ECVAM prevalidation: (i) MUSST and (ii) h-Clat assess surface markers on dendritic cell lines, (iii) the direct peptide reactivity assay (DPRA) measures reactivity with model peptides and (iv) the KeratinoSens(TM) assay which is based on detection of Nrf2-induced luciferase. It is anticipated that only an integrated testing strategy (ITS) based on a battery of tests might give a full replacement providing also a Sensitization potency assessment, but this concept should be tested with a data-driven analysis. Here we report a database on 145 chemicals reporting the quantitative endpoints measured in a U937- test, the DPRA and KeratinoSens(TM) . It can serve to develop data-driven ITS approaches as we show in a parallel paper and provides a view as to the current ability to predict with in vitro tests as we are entering 2013. It may also serve as reference database when benchmarking new molecules with in vitro based read-across and find use as a reference database when evaluating new tests. The tests and combinations thereof were evaluated for predictivity, and overall a similar predictivity was found as before on three-fold smaller datasets. Analysis of the dose-response parameters of the individual tests indicates a correlation to Sensitization potency. Detailed analysis of chemicals false-negative and false-positive in two tests helped to define limitations in the tests but also in the database derived from animal studies.
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predicting Skin Sensitization potential and inter laboratory reproducibility of a human cell line activation test h clat in the european cosmetics association colipa ring trials
Toxicology in Vitro, 2010Co-Authors: Hitoshi Sakaguchi, Cindy A Ryan, Jeanmarc Ovigne, Klaus Schroeder, Takao AshikagaAbstract:Regulatory policies in Europe prohibited the testing of cosmetic ingredients in animals for a number of toxicological endpoints. Currently no validated non-animal test methods exist for Skin Sensitization. Evaluation of changes in cell surface marker expression in dendritic cell (DC)-surrogate cell lines represents one non-animal approach. The human Cell Line Activation Test (h-CLAT) examines the level of CD86 and CD54 expression on the surface of THP-1 cells, a human monocytic leukemia cell line, following 24h of chemical exposure. To examine protocol transferability, between-lab reproducibility, and predictive capacity, the h-CLAT has been evaluated by five independent laboratories in several ring trials (RTs) coordinated by the European Cosmetics Association (COLIPA). The results of the first and second RTs demonstrated that the protocol was transferable and basically had good between-lab reproducibility and predictivity, but there were some false negative data. To improve performance, protocol and prediction model were modified. Using the modified prediction model in the first and second RT, accuracy was improved. However, about 15% of the outcomes were not correctly identified, which exposes some of the limitations of the assay. For the chemicals evaluated, the limitation may due to chemical being a weak allergen or having low solubility (ex. alpha-hexylcinnamaldehyde). The third RT evaluated the modified prediction model and satisfactory results were obtained. From the RT data, the feasibility of utilizing cell lines as surrogate DC in development of in vitro Skin Sensitization methods shows promise. The data also support initiating formal pre-validation of the h-CLAT in order to fully understand the capabilities and limitations of the assay.
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dose metrics in the acquisition of Skin Sensitization thresholds and importance of dose per unit area
Regulatory Toxicology and Pharmacology, 2008Co-Authors: Ian Kimber, Rebecca Jane Dearman, Frank G Gerberick, J Lalko, Cindy A Ryan, Pauline Mcnamee, Anne Marie ApiAbstract:Allergic contact dermatitis is a common occupational and environmental health problem and many hundreds of chemicals have been implicated as Skin sensitizers. Sensitization is acquired following topical exposure to a contact allergen and induction of a cutaneous immune response of an appropriate magnitude. For effective assessment and management of human health risks there is a need to appreciate the dose metrics that drive the induction of Skin Sensitization. The available evidence suggests that under most normal conditions of exposure it is the dose per unit area of chemical that has over-riding impact on the effectiveness of Sensitization. The exception to this rule is when the area of the application site drops below a certain critical level. Here we review in detail the evidence which supports dose per unit area as being the critical exposure metric in the induction of Skin Sensitization, and the mechanistic bases for this relationship.
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mechanistic applicability domain classification of a local lymph node assay dataset for Skin Sensitization
Chemical Research in Toxicology, 2007Co-Authors: David W. Roberts, Rebecca Jane Dearman, Petra Kern, Frank G Gerberick, Ian Kimber, Cindy A RyanAbstract:The goal of eliminating animal testing in the predictive identification of chemicals with the intrinsic ability to cause Skin Sensitization is an important target, the attainment of which has recently been brought into even sharper relief by the EU Cosmetics Directive and the requirements of the REACH legislation. Development of alternative methods requires that the chemicals used to evaluate and validate novel approaches comprise not only confirmed Skin sensitizers and non-sensitizers but also substances that span the full chemical mechanistic spectrum associated with Skin Sensitization. To this end, a recently published database of more than 200 chemicals tested in the mouse local lymph node assay (LLNA) has been examined in relation to various chemical reaction mechanistic domains known to be associated with Sensitization. It is demonstrated here that the dataset does cover the main reaction mechanistic domains. In addition, it is shown that assignment to a reaction mechanistic domain is a critical fir...
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mechanistic applicability domain classification of a local lymph node assay dataset for Skin Sensitization
Chemical Research in Toxicology, 2007Co-Authors: David W. Roberts, Rebecca Jane Dearman, Petra Kern, Frank G Gerberick, Cindy A Ryan, Ian Kimber, Grace Patlewicz, Aynur O AptulaAbstract:The goal of eliminating animal testing in the predictive identification of chemicals with the intrinsic ability to cause Skin Sensitization is an important target, the attainment of which has recently been brought into even sharper relief by the EU Cosmetics Directive and the requirements of the REACH legislation. Development of alternative methods requires that the chemicals used to evaluate and validate novel approaches comprise not only confirmed Skin sensitizers and non-sensitizers but also substances that span the full chemical mechanistic spectrum associated with Skin Sensitization. To this end, a recently published database of more than 200 chemicals tested in the mouse local lymph node assay (LLNA) has been examined in relation to various chemical reaction mechanistic domains known to be associated with Sensitization. It is demonstrated here that the dataset does cover the main reaction mechanistic domains. In addition, it is shown that assignment to a reaction mechanistic domain is a critical first step in a strategic approach to understanding, ultimately on a quantitative basis, how chemical properties influence the potency of Skin sensitizing chemicals. This understanding is necessary if reliable non-animal approaches, including (quantitative) structure-activity relationships (Q)SARs, read-across, and experimental chemistry based models, are to be developed.
