Cytotoxic effects of 100 reference compounds on Hep G2 and HeLa cells and of 60 compounds on ECC-1 and CHO cells. I Mechanistic assays on ROS, glutathione depletion and calcein uptake

Abstract

In this study fluorometric assays have been used for medium throughput screening on toxicity. Dichlorofluorescein diacetate, monochlorobimane and calcein-AM were fluorophores for the measurement of the formation of reactive oxygen species (ROS), the quantification of glutathione and the membrane stability, respectively. These assays have been carried out in the presence or absence of toxic compounds and with four different cell lines, i.e. human liver (Hep G2), human endometrium (ECC-1), human cervix (HeLa) and Chinese hamster ovary cells (CHO). In these assays the toxic dose of 60 reference compounds was assessed for Hep G2, HeLa, ECC-1 and CHO cells and of 40 pharmaceutical compounds for Hep G2 (ROS, glutathione) or HeLa (calcein) cells, only. These compounds were narcotic analgesics, hypnotics, vasodilators, specific cellular energy blockers, cellular proliferation inhibitors, ion channel blockers, estrogens, antiestrogens, androgens, progestagens and others. The outcome of this study revealed that all four cell lines were responsive to the same set of drugs. Only for some drugs Hep G2 cells appear slightly more sensitive, as compared to the other three cell lines. In general the HeLa cell line was the most sensitive cell line for the calcein uptake, while the Hep G2 cell line shows slightly more sensitivity for dichorofluorescein and monochlorobimane assays than the other three cell lines. Further evaluation at higher toxic dosages with Hep G2 cells for ROS and glutathione depletion and HeLa cells for calcein uptake, demonstrated toxic effects for 56 of the 100 reference compounds in these assays, among which there were estrogens, androgens, progestagens and antiestrogens. In conclusion, almost all tested compounds gave similar dose and toxicity effects on the permanent cell lines used in this study. Only three compounds showed more tissue specific cell responses. This shows that in principle all four cell lines can be used for toxicity screening.