A study of zearalenone cytotoxicity on human peripheral blood mononuclear cells

The mycotoxin zearalenone (ZEA) is a common contaminant of all major cereal grains worldwide with estrogenic and anabolic activity. We investigated the in vitro cytopathic effects of ZEA on freshly isolated human peripheral blood mononuclear cells (PBMC) in relation to proliferation and cell death patterns of untreated and mitogen-activated cells. The higher concentration of 30 μg/ml ZEA was found to totally inhibit T and B lymphocyte proliferation from the stimulation with phytohemagglutinin and pokeweed mitogen. The inhibitory effects of ZEA were further related to cell necrosis/apoptosis. Flow cytometry analysis showed a distinct necrotic effect on PBMC, irrespective of mitogen stimulation, whereas apoptotic activity was less evident. Necrosis was observed in both the lymphocyte and monocyte/granulocyte gates. Measurements of ZEA-induced intracellular calcium ion (Ca2+) mobilization showed an increase of both Ca2+ levels and the number of cells with high Ca2+ only in the monocyte/granulocyte gated cells. Using phenylmethyl sulfonyl fluoride (PMSF), a serine protease inhibitor, and ammonium chloride (NH4Cl), a lysosomal inhibitor, both associated with cell necrosis inhibition, we showed that PMSF at 0.05 mM and NH4Cl at 1 and 10 mM reduced the cytopathic effects induced by 30 μg/ml ZEA, whereas apoptosis was less affected. Expose of PBMC to 1 μg/ml ZEA did not alter the viability of the cells. Our results suggest that high ZEA concentrations in the blood may well exert cytotoxic effects that merit further investigation.