Toxic effects of human pancreatic and snake and bee venom phospholipases A2 on MCF-7 cells in culture.

The toxicity of phospholipase A2 (PLA2) has been suggested to be involved in the pathology of a number of severe diseases including septic shock and acute pancreatitis. However, testing the toxicity of these substances is difficult in vivo. In the present study we compared the toxicity of PLA2s from three snake venoms, bee venom and human pancreas on MCF-7 cells grown in culture. Tetrazolium microculture assays were developed to test the cytostatic and cytotoxic effects of PLA2 on MCF-7 cells. These tests are based on the ability of viable cells to reduce a tetrazolium-based compound MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide] to a blue formazan product. Leakage of lactate dehydrogenase (LD) from the cells into the culture medium was also measured. There were marked differences in the toxicity of the PLA2s tested. Cobra (Naja mosambique mosambique) venom PLA2 was toxic to the cells at a concentration of 4.5 U/ml. Light microscopic changes were seen in the injured cells after 3 hr treatment. Sixty-seven per cent of cells were dead after 24 hr treatment. Treatment for 4 hr caused irreversible changes in the cells. Leakage of LD was noted from 4 hr onwards. Other snake (Crotalus adamanteus and Laticauda semifasciata) venom PLA2s, even after continuous exposure to 4.5 U/ml caused only slight decreases in values obtained in the MTT test. No morphologic changes suggesting a cytotoxic effect were seen. PLA2 from bee (Apis mellifera) venom had no toxic effect, either. Continuous exposure of cells to human pancreatic PLA2 caused a 15% decrease in the MTT-test.(ABSTRACT TRUNCATED AT 250 WORDS)