Selective Cytotoxicity of Ochratoxin A: Pro-Apoptotic Effects on Healthy Immune Cells Compared to Leukemia Cells

Ochratoxin A (OTA) is a widespread mycotoxin with documented nephrotoxic, hepatotoxic, immunotoxic, and carcinogenic effects, while its role in hematological malignancies and immune cells remains insufficiently defined. This study examined the cytotoxic and pro-apoptotic OTA activity in three human leukemia cell lines (CCRF-CEM, K-562, HL-60) and in peripheral blood mononuclear cells (PBMCs) from healthy donors. Cell viability was determined using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) and trypan blue assays, mitochondrial membrane potential (ΔΨM) was assessed with JC-1 dye, caspase-3/7 activity was measured by flow cytometry, and the expression of apoptosis-related genes was analyzed by RT-qPCR. OTA did not significantly affect viability, mitochondrial function, or caspase activity in leukemia cell lines, suggesting relative resistance to OTA-induced apoptosis. In contrast, PBMCs exhibited clear dose- and time-dependent sensitivity, manifested by reduced viability, ΔΨM, caspase-3/7 activation, and transcriptional changes consistent with intrinsic apoptosis, including decreased BCL-2 (anti-apoptotic) and increased BAX (pro-apoptotic), APAF1 (apoptosome component), CASP3, and CASP9 (executioner and initiator caspases) expression. These findings demonstrate that OTA selectively targets healthy immune cells rather than leukemia cells, highlighting its pronounced immunotoxic risk and the importance of caution when considering its effect in a hematological context. Although limited to in vitro models, this study underscores the necessity of further research to clarify the molecular basis of differential OTA sensitivity and its contribution to immunosuppression and hematological disease.