An evaluation of a cultured human corneal epithelial tissue model for the determination of the ocular irritation potential of pharmaceutical process materials.

Irritation and other forms of local toxicity following contact with eyes is a potentially serious problem arising from occupational exposure to chemicals. Traditionally, evaluation of the irritant potential of novel chemicals has relied on the use of in vivo studies with rabbits. Concerns about the predictive potential of in vivo methods for human hazard and demand for economical and rapid screening of chemicals has stimulated a great deal of work to investigate in vitro alternatives for evaluating ocular irritation potential. This publication describes a screening study to assess a reconstituted corneal epithelial culture system, as an alternative for testing for ocular irritation with pharmaceutical process materials, extending the chemical domain with which this system has been tested. A total of 21 test chemicals were applied to commercially supplied reconstituted human corneal epithelial (HCE) cultures and effects on tissue viability (MTT reduction assay), tissue histology and IL-alpha expression were assessed. Positive controls (0.5% and 1% SDS) showed dose- and time-related adverse effects on tissues, consistent with known irritant effects. Negative controls showed no histological changes and retained high viability throughout the time-course of the experiment. Concordance was excellent with accuracy at each sampling time point of over 80% when viability (MTT reduction) was compared with existing EU classification of the test articles for ocular irritation (classification based on results of in vivo evaluation). Tissue viability as estimated by MTT reduction appears most useful as the primary means of assessing the irritation potential of the chemicals. Histopathological examination generally agreed with the results of the MTT assay. However, the use of cytokine analysis will need further consideration as results for this parameter showed no relationship with known irritation potential. These results infer that HCE cultures, alone or as a part of a tiered hazard screening programme, have promise for use in reducing reliance on live subject tests and contribute to generation of an appropriate hazard classification and label advice.

Initial in vitro screening approach to investigate the potential health and environmental hazards of Enviroxtrade mark - a nanoparticulate cerium oxide diesel fuel additive.

Nanotechnology is the new industrial revolution of the 21st Century as the various processes lead to radical improvements in medicine, manufacturing, energy production, land remediation, information technology and many other everyday products and applications. With this revolution however, there are undoubted concerns for health, safety and the environment which arise from the unique nature of materials and processes at the nanometre scale.The in vitro assays used in the screening strategy are all validated, internationally accepted protocols and provide a useful indication of potential toxicity of a chemical as a result of effects on various toxicological endpoints such as local site of contact (dermal) irritation, general cytotoxicity and mutagenicity.The initial in vitro screening strategy described in this paper to investigate the potential health implications, if any, which may arise following exposure to one specific application of nanoparticulate cerium oxide used as a diesel fuel borne catalyst, reflects a precautionary approach and the results will inform judgement on how best to proceed to ensure safe use.

Assessment of the human epidermis model SkinEthic RHE for in vitro skin corrosion testing of chemicals according to new OECD TG 431.

Based on two successfully completed ECVAM validation studies for in vitro skin corrosion testing of chemicals, the National Co-ordinators of OECD Test Guideline Programme endorsed in 2002 two new test guidelines: TG 430 'Transcutaneous Electrical Resistance assay' and TG 431 'Human Skin Model Test'. To allow all suitable in vitro human reconstructed (dermal or epidermal) models to be used for skin corrosion testing, the OECD TG 431 defines general and functional conditions that the model must meet before it will be routinely used for skin corrosion testing. In addition, the guideline requires correct prediction of 12 reference chemicals and assessment of intra- and inter-laboratory variability. To show that the OECD TG 431 concept works, in 2003 ZEBET tested several chemicals from the ECVAM validation trials on the SkinEthic reconstituted human epidermal (RHE) model. Based on knowledge that reconstructed human skin models perform similarly in toxicological studies, it was decided to adopt the validated EpiDerm skin corrosion test protocol and prediction model to the SkinEthic model. After minor technical changes, classifications were obtained in concordance with those reported for the validated human skin models EPISKIN and EpiDerm. To allow adequate determination of inter-laboratory reproducibility, a blind trial was conducted in three laboratories -- ZEBET (D), Safepharm (UK) and BASF (D), in which the 12 endorsed reference chemicals were tested. 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 model and the predictions obtained with the accepted tests of OECD TG 430 and TG 431 was very good. The new test was able to distinguish between corrosive and non-corrosive reference chemicals with an accuracy of 93%.