Recent Trends of Alternative Methods to Phototoxicity Testing in Japan

Several in vitro phototoxicity methods have been developed to assess the phototoxic potential of substances. These can be classified into two groups: the methods for screening purposes and tests focusing on the specific mechanisms of phototoxic reactions. Among these methods the 3T3 Neutral Red uptake phototoxicity test (3T3 NRU PT) was accepted as an established alternative method by ECVAM. In 2000, the EU Commission officially accepted 3T3 NRU PT for classification and labeling of chemicals to assess their acute phototoxic potential. In 2004, 3T3 NRU PT was adopted as an OECD guideline for chemicals (OECD Test Guideline TG432). This paper will describe the peer review of 3T3 NRU PT in Japan and the validation study of a new battery system proposed by Japanese industry. The paper also discusses a few recent studies using 3T3 NRU PT. Key word: in vitro phototoxicity, 3T3NRU phototoxicity test, validation study, Yeast-RBC assay REVIEW Okamoto Y, Recent Trends of Alternative methods to phototoxicty Testing in Japan, AATEX 11(1), 39-48, 2005. 40 PT) assay and the red blood cell photohemolysis (RBC PH) assay to the public advertisement of the scientific research group of the Japanese Ministry of Health, Labor and Welfare. The review of this method was performed by an Assessment Committee of the Japanese Society for Alternatives to Animal Experiments (JSAAE), and the subsequent validation study was consigned to a Validation Committee of JSAAE. The validation study was executed at six facilities. The interim report was presented at the science annual meeting of JSAAE (Mori et al., 2004 b, Yoshimura et al, 2004). In this text, the approach of development of in vitro phototoxicity assays in Japan is described around not only the peer review of 3T3 NRU PT but also the Japanese original validation study to the YeastRBC assay. Current status of development of alternatives to phototoxicity testing Various in vitro phototoxicity assessments are developed based on the mechanism of the phototoxicity. Spielmann (Spielmann, 2001) describes a clear summary about the mechanism of phototoxicity and phototoxicity testing methods. The 3T3 NRU PT is approved as the in vitro phototoxicity alternative test method established by ECVAM in a scientific manner, and has been adopted formally as a screening method of the phototoxicity since 2000. The amendment method from the original of this method was accepted as an in vitro phototoxicity test guideline of the chemical substance in OECD in April 2004. On the other hand, the pre-validation study of the photohemolysis assay using the red blood cells and the hemoglobin photo peroxidation assay was performed as the mechanism evaluation methods in the EU, and the availability of these testing methods was reported (Spielmann et al., 2000). In Japan, Sugiyama et al., are reporting a lot on battery testing systems that combine the mechanism testing method to screening method like the yeast photo growth inhibition and the red blood cell photohemolysis (Sugiyama et al., 1994 a, 1994 b, 2002, Mori et al., 2004 a). Moreover, Tanaka and Wakuri presented on the application of the 3T3 NRU PT to the photoInitial Evaluation of the Physical,Chemical, and Toxicological Properties of the Test Substance • Physico-chemical properties •Chemical structure, structure alerts •UV/vis-absorption •QSAR-photochemistry •General toxicity(including kinetics and metabolism) UV/vis absorption spectra in appropriate solvent(e.g.OECD TG 101) No Absorption Biological Testing not considered necessary