Apoptosis evaluation in epithelial cells exposed to different chemicals: relevance of floating cells

The recent increase in understanding of cell death has promoted new approac hes in toxicological studies, mainly those dealing with in vitro systems wh ere the evaluation of cell death has been the most widely adopted end-point in measuring the effects of chemical toxicants. The aim of this study was to investigate the possibility of improving the traditional cytotoxicity te st protocols in order to produce more specific information on the type of c ell death induced by exposure to toxicants. In particular, we characterized the mode of cell death in an established epithelial cell line, HEp-2 cells , which is frequently used in cytotoxicity testing owing to its easy handli ng and standardization of culture conditions. Reference chemicals for apopt osis and necrosis were selected as controls, together with other molecules that have been shown, in preliminary studies, to induce various morphologic al and structural modifications in relation to cell death. The results obta ined show that: (a) the floating fraction of treated cells gives the cleare st picture of the necrotic/apoptotic distribution; (b) morphological analys is is crucial for characterization of apoptosis; (c) more than one cytotoxi c end-point is necessary to clearly identify the type of cell death.