The Cytotoxicity of Aflatoxin B1 in Human Lymphocytes

Objectives:  Aflatoxin B 1  (AFB 1 ) is a naturally occurring carcinogenic and immunosuppressive compound. This study was designed to measure its toxic effects on human peripheral blood mononuclear cells (PBMC).  Methods:  The study recruited 7 healthy volunteers. PBMC were isolated and cellular respiration was monitored using a phosphorescence oxygen analyser. The intracellular caspase activity was measured by the caspase-3 substrate N-acetyl-asp-glu-val-asp-7-amino-4-methylcoumarin. Phosphatidylserine exposure and membrane permeability to propidium iodide (PI) were measured by flow cytometry.  Results:  Cellular oxygen consumption was inhibited by 2.5 μM and 25 μM of AFB1. Intracellular caspase activity was noted after two hours of incubation with 100 μM of AFB1. The number of Annexin V-positive cells increased as a function of AFB 1  concentration and incubation time. At 50 μM, a significant number of cells became necrotic after 24 hours (Annexin V-positive and PI-positive).  Conclusion:  The results show AFB 1  is toxic to human lymphocytes and that its cytotoxicity is mediated by apoptosis and necrosis.