The determination of phototoxicity in the 3T3 NRU-PT according to OECD Test Guideline 432 is ofte... more The determination of phototoxicity in the 3T3 NRU-PT according to OECD Test Guideline 432 is often the first step in the sequential phototoxicity testing strategy. If the chemical provides a negative result in the 3T3NRU-PT, in most instances no further testing is required. However, if the result is positive, the chemical may be still applied topically at safe concentrations, depending on the absorption and accumulation of the chemical in the skin.Thus, in addition to the information on inherent phototoxicity potential assessed by the 3T3NRU-PT, additional testing may be required to obtain combined information on the phototoxicity and bioavailability of the chemical in the skin.Ideally, confirmatory tests should be performed in vivo on human volunteers, but for ethical reasons, this is not acceptable, if the 3T3NRU-PT has provided a positive result. Thus, to avoid confirmatory testing in vivo in animals, reconstituted human 3-D skin models are offering an attractive in vitro alternative for testing, since such models are characterised by both skin barrier function and viable primary skin cells.In the current study, several substances (mostly cosmetic ingredients) which are known to be safely used in humans, and which provided positive results in the 3T3 NRU PT were evaluated on the reconstructed human skin model EpiDerm and, if the result was negative, tested in a limited group of human volunteers. First results we obtained show, that the human skin model phototoxicity test represents a useful step in the sequential strategy for phototoxicity testing.
The goal of photo-safety testing is to detect the adverse effects of substances and products inth... more The goal of photo-safety testing is to detect the adverse effects of substances and products inthe presence of light. This type of testing is relevant for products that enter the skin via dermalpenetration or systemic circulation. Photo-toxicity testing is required only for substancesthat sufficiently absorb UV-light in the wavelength range 290]700nm and where local and/orsystemic exposure is foreseen. Studies on the extent of photo-stability, structure]activity relationships(SARs), and the generation of reactive oxygen species (ROS) after irradiation by UVand visible light, can provide additional indicators that substance or formulation may triggerphoto-toxicity. However, the biological effect and bioavailability also need to be examined. Forphoto-toxicity testing, a thoroughly validated in vitro method, the 3T3 Neutral Red uptakephoto-toxicity assay (3T3 NRU PT assay), is validated and accepted internationally. Thisassay provides indication that a substance might cause photo-toxicity/photo-allergy or otherphoto-induced effect. While highly sensitive, this assay does not provide information on thebioavailability/accumulation of the substance in the skin or eyes. Therefore, more-advanced invitro 3D tissue constructs are suggested as second tier tests, to exclude possible false positivesfrom 3T3 NRU PT assays. Protocols have been developed for both systemic and dermal exposures.These advanced 3D models can be also used for the assessment of photo-potency andnon-phototoxic doses of a phototoxin, whereby a product (e.g. a pharmaceutical) can be stillused in human therapy after careful considerations of other possible side effects. The use ofthe testing strategy described above may significantly minimise risk of photo-toxicity effects,while still permitting the use of substances that would be excluded from further use by a singletest. This testing strategy is applicable to pharmaceuticals, as well as consumer products/cosmetics, and helps to distinguish the possible hazards from the real risks.
In 2002 the National Co-ordinators of OECD Test Guideline Programme (WNT) endorsed a New Draft Te... more In 2002 the National Co-ordinators of OECD Test Guideline Programme (WNT) endorsed a New Draft Test Guideline TG 431 (Human Skin Model) for In Vitro Skin Corrosion Testing which was finally adopted in April 2004. This guideline specifies general functional and performance criteria that have to be met, if a new skin or epidermal model is intended to be used for the skin corrosion testing of chemicals in vitro.In 2003 ZEBET tested several chemicals with known corrosive potential on the SkinEthic reconstituted human epidermal (RHE) model using the validated EpiDerm test protocol and prediction model. After minor technical adaptations, classifications obtained were comparable to those obtained previously with the validated human skin models EPISKIN and EpiDerm.From December 2003 to February 2004 ZEBET, SafePharm and BASF conducted an inter-laboratory trial with 12 coded reference chemicals proposed by the OECD TG 431 in order to confirm the performance of the SkinEthic skin corrosion assay.In each laboratory, for each of the test chemicals, three independent tests were performed. Results obtained with the SkinEthic epidermal model were reproducible, both within and between laboratories, and over time. Concordance between the in vitro predictions of skin corrosivity potential obtained with the SkinEthic epidermal model and the predictions obtained with the accepted skin models was very good. The new test was able to correctly distinguish between corrosive and non-corrosive reference chemicals and can be regarded as valid method for the use in context with OECD TG 431.
Assessment of the phototoxicity hazard and phototoxic potency (i.e. phototoxic risk) of topically... more Assessment of the phototoxicity hazard and phototoxic potency (i.e. phototoxic risk) of topically or systemically applied compounds and mixtures is a crucial step in the safety assessment of cosmetic, pesticide and pharmaceutical products absorbing UV and visible light. The validated and regulatory accepted in vitro assay, the 3T3 NRU PT (OED TG 432), provides high level of sensitivity and thus also protection for the end-users, however, it has been reported that it also generates high rate of false positive results due to the lack of barrier properties naturally appearing in the human skin or other targeted tissues.
The determination of phototoxicity in the 3T3 NRU-PT according to OECD Test Guideline 432 is ofte... more The determination of phototoxicity in the 3T3 NRU-PT according to OECD Test Guideline 432 is often the first step in the sequential phototoxicity testing strategy. If the chemical provides a negative result in the 3T3NRU-PT, in most instances no further testing is required. However, if the result is positive, the chemical may be still applied topically at safe concentrations, depending on the absorption and accumulation of the chemical in the skin.Thus, in addition to the information on inherent phototoxicity potential assessed by the 3T3NRU-PT, additional testing may be required to obtain combined information on the phototoxicity and bioavailability of the chemical in the skin.Ideally, confirmatory tests should be performed in vivo on human volunteers, but for ethical reasons, this is not acceptable, if the 3T3NRU-PT has provided a positive result. Thus, to avoid confirmatory testing in vivo in animals, reconstituted human 3-D skin models are offering an attractive in vitro alternative for testing, since such models are characterised by both skin barrier function and viable primary skin cells.In the current study, several substances (mostly cosmetic ingredients) which are known to be safely used in humans, and which provided positive results in the 3T3 NRU PT were evaluated on the reconstructed human skin model EpiDerm and, if the result was negative, tested in a limited group of human volunteers. First results we obtained show, that the human skin model phototoxicity test represents a useful step in the sequential strategy for phototoxicity testing.
The goal of photo-safety testing is to detect the adverse effects of substances and products inth... more The goal of photo-safety testing is to detect the adverse effects of substances and products inthe presence of light. This type of testing is relevant for products that enter the skin via dermalpenetration or systemic circulation. Photo-toxicity testing is required only for substancesthat sufficiently absorb UV-light in the wavelength range 290]700nm and where local and/orsystemic exposure is foreseen. Studies on the extent of photo-stability, structure]activity relationships(SARs), and the generation of reactive oxygen species (ROS) after irradiation by UVand visible light, can provide additional indicators that substance or formulation may triggerphoto-toxicity. However, the biological effect and bioavailability also need to be examined. Forphoto-toxicity testing, a thoroughly validated in vitro method, the 3T3 Neutral Red uptakephoto-toxicity assay (3T3 NRU PT assay), is validated and accepted internationally. Thisassay provides indication that a substance might cause photo-toxicity/photo-allergy or otherphoto-induced effect. While highly sensitive, this assay does not provide information on thebioavailability/accumulation of the substance in the skin or eyes. Therefore, more-advanced invitro 3D tissue constructs are suggested as second tier tests, to exclude possible false positivesfrom 3T3 NRU PT assays. Protocols have been developed for both systemic and dermal exposures.These advanced 3D models can be also used for the assessment of photo-potency andnon-phototoxic doses of a phototoxin, whereby a product (e.g. a pharmaceutical) can be stillused in human therapy after careful considerations of other possible side effects. The use ofthe testing strategy described above may significantly minimise risk of photo-toxicity effects,while still permitting the use of substances that would be excluded from further use by a singletest. This testing strategy is applicable to pharmaceuticals, as well as consumer products/cosmetics, and helps to distinguish the possible hazards from the real risks.
In 2002 the National Co-ordinators of OECD Test Guideline Programme (WNT) endorsed a New Draft Te... more In 2002 the National Co-ordinators of OECD Test Guideline Programme (WNT) endorsed a New Draft Test Guideline TG 431 (Human Skin Model) for In Vitro Skin Corrosion Testing which was finally adopted in April 2004. This guideline specifies general functional and performance criteria that have to be met, if a new skin or epidermal model is intended to be used for the skin corrosion testing of chemicals in vitro.In 2003 ZEBET tested several chemicals with known corrosive potential on the SkinEthic reconstituted human epidermal (RHE) model using the validated EpiDerm test protocol and prediction model. After minor technical adaptations, classifications obtained were comparable to those obtained previously with the validated human skin models EPISKIN and EpiDerm.From December 2003 to February 2004 ZEBET, SafePharm and BASF conducted an inter-laboratory trial with 12 coded reference chemicals proposed by the OECD TG 431 in order to confirm the performance of the SkinEthic skin corrosion assay.In each laboratory, for each of the test chemicals, three independent tests were performed. Results obtained with the SkinEthic epidermal model were reproducible, both within and between laboratories, and over time. Concordance between the in vitro predictions of skin corrosivity potential obtained with the SkinEthic epidermal model and the predictions obtained with the accepted skin models was very good. The new test was able to correctly distinguish between corrosive and non-corrosive reference chemicals and can be regarded as valid method for the use in context with OECD TG 431.
Assessment of the phototoxicity hazard and phototoxic potency (i.e. phototoxic risk) of topically... more Assessment of the phototoxicity hazard and phototoxic potency (i.e. phototoxic risk) of topically or systemically applied compounds and mixtures is a crucial step in the safety assessment of cosmetic, pesticide and pharmaceutical products absorbing UV and visible light. The validated and regulatory accepted in vitro assay, the 3T3 NRU PT (OED TG 432), provides high level of sensitivity and thus also protection for the end-users, however, it has been reported that it also generates high rate of false positive results due to the lack of barrier properties naturally appearing in the human skin or other targeted tissues.
Uploads
Papers