In Vitro Assays for Phototoxicity

This paper summarizes a few in vitro methods to assess photodamage in cells irradiated with UV of various wavelengths in the presence of a number of photo-sensitizers. A single in vitro assay for phototoxicity (photoirritation) is not likely to be predictive because of different mechanisms of phototoxicity and diverse cellular targets for injury. A number of methods have to be combined to provide a better prediction of these phenomena. Measurement of mechanistically relevant biomarkers also represents a promising area of in vitro testing for phototoxicity, and it is also briefly reviewed in this paper. Photodynamic sensitizers, representing a large class of phototoxic agents, can now be identified by sensitive measurement of photooxidative damage to cellular RNA and DNA. Currently, US government agencies have not identified a single in vitro assay for phototoxicity which would be acceptable for replacing an in vivo assay for regulatory purposes.