Johannes Sandt - Academia.edu (original) (raw)

Papers by Johannes Sandt

Alternatives to Laboratory Animals

The ECVAM Skin Irritation Task Force was established in November 1996, primarily to prepare a rep... more The ECVAM Skin Irritation Task Force was established in November 1996, primarily to prepare a report on the current status of the development and validation of alternative tests for skin irritation and corrosion and, in particular, to identify any appropriate non-animal tests for predicting human skin irritation which were sufficiently well-developed to warrant ECVAM supporting their prevalidation/validation. The task force based its discussions around the proposed testing strategy for skin irritation/corrosion emanating from an OECD workshop held in January 1996. The following have been reviewed: a) structure-activity and structure-property relationships for skin corrosion and irritation; b) the use of pH and acid/alkaline reserve measurements in predicting skin corrosivity; c) in vitro tests for skin corrosion; d) in vitro tests for skin irritation (keratinocyte cultures, organ cultures, and reconstituted human skin models); and e) human patch tests for skin irritation. It was app...

Alternatives to Laboratory Animals

Various aspects of acute cutaneous toxicity were studied in a skin organ culture model. Chemicals... more Various aspects of acute cutaneous toxicity were studied in a skin organ culture model. Chemicals were applied topically for four hours, after which cytotoxicity was assessed by measuring the conversion of the tetrazolium salt, MTT. The relationship between pKa and cytotoxicity was investigated for a homologous series of benzoic acids. In this series, salicylic acid had the lowest pKa and proved to be the most toxic compound. Furthermore, the pH of the carrier solution was shown to influence the toxicity of chloroacetic acid and acetic acid in a different way. Using skin discs of both human and rabbit origin, we found that human skin was more resistant to toxicity induced by the irritants benzalkonium chloride and formaldehyde. As an additional aspect of dermal toxicology, the percutaneous absorption of testosterone was studied. After topical application to rabbit skin discs, testosterone was absorbed in a dose-dependent manner and concurrent metabolism was demonstrated.

Alternatives to Laboratory Animals

With rapidly increasing knowledge of toxicological processes, the scientific value and relevance ... more With rapidly increasing knowledge of toxicological processes, the scientific value and relevance of toxicity studies for risk assessment must be re-evaluated. In this paper, it is proposed that the rigid risk evaluation currently required should be replaced by a more flexible, case-by-case approach, in order to increase the relevance of each animal test conducted. The development of new types of toxicity studies and their application in risk evaluation are also described.

Alternatives to Laboratory Animals

Since the skin is often exposed, either intentionally or unintentionally, to cosmetic products, i... more Since the skin is often exposed, either intentionally or unintentionally, to cosmetic products, it is clear that the potential for a particular product/ingredient to cause skin irritation, or for a particular ingredient to cause skin corrosion, needs to be carefully evaluated as part of the overall safety assessment process. Dermal irritation is defined as the production of "reversible damage of the skin following the application of a test substance for up to 4 hours" (OECD TG 404; 1). It is generally assessed by the potential of a certain substance to cause erythema/eschar and/or oedema after a single topical application on rabbit skin, based on the Draize score (1). Recently, some general refinement provisions were included in OECD TG 404. This updated version recommends that, prior to undertaking the in vivo animal test for corrosion/irritation of the substance, a sequential testing strategy should be performed. This strategy is based in a stepwise order on a weight of evidence analysis, pH considerations, the use of validated and accepted in vitro tests, and finally, the refinement of the animal testing. The following are some examples of decision-making according to the testing strategy.

Integrated Environmental Assessment and Management

Governments invest in "key enabling technologies," such as nanotechnology, to solve societal chal... more Governments invest in "key enabling technologies," such as nanotechnology, to solve societal challenges and boost the economy. At the same time, governmental agencies demand risk reduction to prohibit any often unknown adverse effects, and industrial parties demand smart approaches to reduce uncertainties. Responsible research and innovation (RRI) is therefore a central theme in policy making. Risk analysis and technology assessment, together referred to as "RATA," can provide a basis to assess human, environmental, and societal risks of new technological developments during the various stages of technological development. This assessment can help both governmental authorities and innovative industry to move forward in a sustainable manner. Here we describe the developed procedures and products and our experiences to bring RATA in practice within a large Dutch nanotechnology consortium. This is an example of how to put responsible innovation in practice as an integrated part of a research program, how to increase awareness of RATA, and how to help technology developers perform and use RATA. Integr Environ Assess Manag 2018;14:9-16.

Regulatory Toxicology and Pharmacology, 2002

The validity of in vitro and in vivo methods for the prediction of percutaneous penetration in hu... more The validity of in vitro and in vivo methods for the prediction of percutaneous penetration in humans was assessed using the fungicide ortho-phenylphenol (OPP) (log Po/w 3.28, MW 170.8, solubility in water 0.7 g/ L). In vivo studies were performed in rats and human volunteers, applying the test compound to the dorsal skin and the volar aspect of the forearm, respectively. In vitro studies were performed using static diffusion cells with viable full-thickness skin membranes (rat and human), nonviable epidermal membranes (rat and human), and a perfused pig ear model. For the purpose of conducting in vitro/in vivo comparisons, standardized experimental conditions were used with respect to dose (120 µg OPP/cm 2), vehicle (60% aqueous ethanol), and exposure duration (4 h). In human volunteers, the potentially absorbed dose (amount applied minus dislogded) was 105 µg/cm 2 , while approximately 27% of the applied dose was excreted with urine within 48 h. In rats these values were 67 µg/cm 2 and 40%, respectively. In vitro methods accurately predicted human in vivo percutaneous absorption of OPP on the basis of the potential absorbed dose. With respect to the other parameters studied (amount systemically available, maximal flux), considerable differences were observed between the various in vitro models. In viable full-thickness skin membranes, the amount systemically available and the potentially absorbed dose correlated reasonably well with the human in vivo situation. In contrast the K p /maximal flux considerably underestimated the human in vivo situation. Although epidermal membranes overestimated human in vivo data, the species differences observed in vivo were reflected correctly in this model. The data generated in the perfused pig ear model were generally intermediate between viable skin membranes and epidermal membranes.

Regulatory Toxicology and Pharmacology, 2011

The present paper aims at identifying strategies to increase the impact and applicability of alte... more The present paper aims at identifying strategies to increase the impact and applicability of alternative testing strategies in risk assessment. To this end, a quantitative and qualitative literature evaluation was performed on (a) current research efforts in the development of in vitro methods aiming for alternatives to animal testing, (b) the possibilities and limitations of in vitro methods for regulatory purposes and (c) the potential of physiologically-based kinetic (PBK) modeling to improve the impact and applicability of in vitro methods in risk assessment practice. Overall, the evaluation showed that the focus of state-of-the-art research activities does not seem to be optimally directed at developing in vitro alternatives for those endpoints that are most animal-demanding, such as reproductive and developmental toxicity, and carcinogenicity. A key limitation in the application of in vitro alternatives to such systemic endpoints is that in vitro methods do not provide so-called points of departure, necessary for regulators to set safe exposure limits. PBK-modeling could contribute to overcoming this limitation by providing a method that allows extrapolation of in vitro concentration-response curves to in vivo dose-response curves. However, more proofs of principle are required.

Alternatives to laboratory animals : ATLA

The European Centre for the Validation of Alternative Methods (ECVAM) Skin Irritation Task Force ... more The European Centre for the Validation of Alternative Methods (ECVAM) Skin Irritation Task Force was established in 1996, to review the status of the development and validation of alternative tests for skin irritation and corrosion, and to identify appropriate non-animal tests for predicting human skin irritation that were sufficiently well-developed to be prevalidated and validated by ECVAM. The EpiDerm method, based on a reconstituted human skin model, was proposed as being sufficiently well advanced to enter a prevalidation (PV) study. Based on a review of test protocols, prediction models (PMs), and data submitted by test developers on ten specified chemicals, with 20% sodium lauryl sulphate as a reference standard, the task force recommended the inclusion of four other tests: EPISKIN and PREDISKIN, based on reconstituted human epidermis or on human skin; the non-perfused pig-ear test, based on pig skin; and the skin integrity function test (SIFT), with ex vivo mouse skin. The p...

Toxicology in Vitro, 1994

In order to reduce animal discomfort and to obtain more quantitative endpoints, there is a need f... more In order to reduce animal discomfort and to obtain more quantitative endpoints, there is a need for reliable, preferably simple and inexpensive in vitro alternatives to skin toxicity testing. An in vitro model was developed in which full-thickness skin from various species can be cultured (rabbit, pig and human). Subsequent to topically applied test compounds, parameters of dermal toxicity were investigated, including cytotoxicity (MTT assay) and the release of inflammatory mediators (HETE's). Moreover, percutaneous absorption and concurrent biotransformation of compounds was studied. MTT conversion was inhibited in a dose-dependent manner following topical application of a wide range of irritants. Repair of initial damage was observed to some extent. The eicosanoid 12-HETE, which is thought to play an important role in chemotaxis, is released. Interestingly, the anti-inflammatory mediator 15-HETE was released only after a prolonged culture time of 48 hr, possibly indicating repair of the induced damage. The metabolic fate of the pesticide propoxur was investigated. Permeation rates were comparable in human and rabbit skin, while pig skin was found to be twice as permeable. Extensive cutaneous metabolism was observed in all three species.

Toxicology in Vitro, 1995

The toxicity of well known irritants was investigated in rabbit and human skin organ cultures. Te... more The toxicity of well known irritants was investigated in rabbit and human skin organ cultures. Test chemicals were selected from various categories of irritants and included both water-soluble and water-insoluble compounds. Using a highly standardized protocol, test chemicals were applied topically at concentrations relevant to the in uiuo situation. Toxicity was assessed by histomorphological examination, inhibition of conversion of the tetrazolium salt MTT, inhibition of epidermal cell proliferation and release of pro-inflammatory hydroxy fatty acids. Chemicals that are known to induce irritation in viuo invariably caused histopathological changes and inhibition of cell proliferation, whereas non-irritating chemicals did not; however, inhibition of MTT conversion and release of hydroxy fatty acids occurred with only a limited number of irritants. The response to the chemical irritants was different in rabbit and human skin cultures. Rabbit skin was slightly more sensitive to sodium dodecyl sulfate and benzalkonium chloride than human skin. Moreover, mineral oil enhanced epidermal cell proliferation in rabbit skin, but not in human skin. This study demonstrates that chemical irritants cause substance-and species-specific effects in skin organ cultures. It is therefore unlikely that irritant potential of chemicals from all irritant categories can be detected in uirro using one single parameter. A multiple endpoint approach and the inclusion of human tissue are recommended for optimal in uilro irritancy testing of chemicals.

Toxicology in Vitro, 2001

A prevalidation study on in vitro tests for acute skin irritation was conducted during 1999 and 2... more A prevalidation study on in vitro tests for acute skin irritation was conducted during 1999 and 2000. The overall objective of validation in this area, of which this prevalidation study is an initial stage, is to identify tests capable of discriminating irritants (I) from non-irritants (NI), as de®ned according to European Union (EU) risk phrases (``R38''; no classi®cation) and the harmonised OECD criteria (``Irritant''; no label). This prevalidation study speci®cally addressed aspects of: protocol re®nement (phase I), protocol transfer (phase II), and protocol performance (phase III), in accordance with the prevalidation scheme de®ned by the European Centre for the Validation of Alternative Methods (ECVAM). The tests evaluated were: EpiDerm TM (phases I, II and III), EPISKIN TM (phases I, II and III), PREDISKIN TM (phases I and II, and additional protocol re®nement), the non-perfused pig ear method (phases I and II, and additional protocol re®nement), and the mouse skin integrity function test (SIFT; phases I and II). Modi®ed, standardised test protocols and well-de®ned prediction models were available for each of the tests at the end of phase I. The results of phase I (intralaboratory reproducibility) were suciently promising for all of the tests to progress to phase II. Protocol transfer between the Lead Laboratory and Laboratory 2 was undertaken for all ®ve tests during phase II, and additional re®nements were made to the test protocols. For EpiDerm, EPISKIN and the SIFT, the intralaboratory and interlaboratory reproducibilities were acceptable; however, better standardisation of certain aspects of the test protocols was needed prior to commencing phase III. Neither PREDISKIN nor the pig ear test performed suciently well in phase II to progress to phase III. The PREDISKIN protocol was overly sensitive, resulting in the prediction of all the NI chemicals as I. The variability in the pig ear test results was too great, indicating that the test would show limited predictive ability. In additional studies (a repeat of phase I), further modi®cation of the PREDISKIN protocol and a change in the prediction model considerably improved the ability of the test to distinguish I from NI chemicals. However, attempts to improve the intralaboratory reproducibility of the pig ear test were unsuccessful. In phase III an initial assessment of the reproducibility and predictive ability, in three independent laboratories per test, was undertaken for the EpiDerm and EPISKIN tests (the SIFT was a late inclusion in the prevalidation study, and is being evaluated in a separate phase III study). A set of 20 coded chemicals (10 I, 10 NI) were tested with the ®nal, re®ned, test protocols.

Journal of Exposure Science and Environmental Epidemiology, 2007

Exposure scenarios form an essential basis for chemical risk assessment reports under the new EU ... more Exposure scenarios form an essential basis for chemical risk assessment reports under the new EU chemicals regulation REACH (Registration, Evaluation, Authorisation and restriction of Chemicals). In case the dermal route of exposure is predominant, information on both exposure and dermal bioavailability is necessary for a proper risk assessment. Various methodologies exist to measure dermal exposure, providing quantitative or semiquantitative information. Although these studies may provide very specific and relevant information, it should be realized that case by case in-depth exposure assessment would be a very expensive process. Dermal bioavailability data are most often obtained from in vitro studies or animal experiments. For the design of studies, which generate data relevant for chemical risk assessment, detailed information on the exposure conditions is crucial (skin surface exposed, exposure duration, dose and physical state of the chemical). Results from non-testing methods for skin absorption, such as (Q)SARs, have been used only to a very limited extent for regulatory purposes. Suggestions are made in order to extend the use these methods to dermal risk assessment of chemical substances, thereby improving the practicability of REACH.

In Vitro Cellular & Developmental Biology - Animal, 1995

Epidermal cell proliferation and differentiation were investigated in vitro after exposure to the... more Epidermal cell proliferation and differentiation were investigated in vitro after exposure to the anionic surfactant sodium dodecyl sulfate (SDS). Human skin organ cultures were exposed topically to various concentrations of SDS for 22 h, after which the irritant was removed. Cell proliferation was measured immunohistochemically by incorporation of bromodeoxyuridine (BrdU) into the DNA of cells during S-phase, while the expression of transglutaminase and involucrin were used as markers of differentiation. Cell proliferation was moderately increased at concentrations of SDS that did not affect the histomorphology (0.1% and 0.2% SDS). A marked increase of cell proliferation was observed 22 to 44 h after removal of SDS at a concentration (0.4%) that induced slight cellular damage. Exposure of human skin organ cultures to a toxic concentration of SDS (1.0%) led to decreased cell proliferation. Transglutaminase and involucrin were expressed in the more basal layers of the epidermis after exposure to 0.4% or 1.0% SDS. Moreover, intra-epidermal sweat gland ducts were positive for transglutaminase at these irritant concentrations. These in vitro data demonstrate that SDS-induced alterations of epidermal cell kinetics, as described in vivo are at least partly due to local mechanisms and do not require the influx of infiltrate cells. However, we were unable to relate the altered cell kinetics to the release of interleukin-la or interleukin-6. Furthermore, supplementation of the culture medium with 12-hydroxyeicosantetraenoic acid did not affect epidermal cell proliferation. Rabbit skin cultures appeared more sensitive to SDS than human skin. At nontoxic doses, the irritant induced an increase of epidermal cell proliferation, similar to that observed in human skin discs.

Human & Experimental Toxicology, 2008

The new regulatory framework REACH (Registration, Evaluation, and Authorisation of Chemicals) for... more The new regulatory framework REACH (Registration, Evaluation, and Authorisation of Chemicals) foresees the use of non-testing approaches, such as read-across, chemical categories, structure–activity relationships (SARs) and quantitative structure–activity relationships (QSARs). Although information on skin absorption data are not a formal requirement under REACH, data on dermal absorption are an integral part of risk assessment of substances/products to which man is predominantly exposed via the dermal route. In this study, we assess the present applicability of publicly available QSARs on skin absorption for risk assessment purposes. We explicitly did not aim to give scientific judgments on individual QSARs. A total of 33 QSARs selected from the public domain were evaluated using the OECD (Organisation for Economic Co-operation and Development) Principles for the Validation of (Q)SAR Models. Additionally, several pragmatic criteria were formulated to select QSARs that are most suit...

Current Drug Metabolism, 2007

In this review, we discuss and compare studies of xenobiotic metabolism in both human skin and 3D... more In this review, we discuss and compare studies of xenobiotic metabolism in both human skin and 3D human skin reconstructs. In comparison to the liver, the skin is a less studied organ in terms of characterising metabolic capability. While the skin forms the major protective barrier to environmental chemical exposure, it is also a potential target organ for adverse health effects. Occupational, accidental or intended-use exposure to toxic chemicals could result in acute or delayed injury to the skin (e.g. inflammation, allergy, cancer). Skin metabolism may play a role in the manifestation or amelioration of adverse effects via the topical route. Today, we have robust testing strategies to assess the potential for local skin toxicity of chemical exposure. Such methods (e.g. the local lymph node assay for assessing skin sensitisation; skin painting carcinogenicity studies) incorporate skin metabolism implicitly in the in vivo model system used. In light of recent European legislation (i.e. 7(th) Amendment to the Cosmetics Directive and Registration Evaluation and Authorisation of existing Chemicals (REACH)), non-animal approaches will be required to reduce and replace animal experiments for chemical risk assessment. It is expected that new models and approaches will need to account for skin metabolism explicitly, as the mechanisms of adverse effects in the skin are deconvoluted. 3D skin models have been proposed as a tool to use in new in vitro alternative approaches. In order to be able to use 3D skin models in this context, we need to understand their metabolic competency in relation to xenobiotic biotransformation and whether functional activity is representative of that seen in human skin.

Alternatives to Laboratory Animals

Integrated Environmental Assessment and Management

Regulatory Toxicology and Pharmacology, 2002

Regulatory Toxicology and Pharmacology, 2011

Alternatives to laboratory animals : ATLA

Toxicology in Vitro, 1994

Toxicology in Vitro, 1995

Toxicology in Vitro, 2001

Journal of Exposure Science and Environmental Epidemiology, 2007

In Vitro Cellular & Developmental Biology - Animal, 1995

Human & Experimental Toxicology, 2008

Current Drug Metabolism, 2007