The cytotoxicity of aflatoxin B₁ in human lymphocytes

Objectives: Aflatoxin B₁ (AFB₁) 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 AFB₁ 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 AFB₁ is toxic to human lymphocytes and that its cytotoxicity is mediated by apoptosis and necrosis.