CYTOTOXICITY OF NEPHROTOXIC FUNGAL TOXINS TO KIDNEY-DERIVED LLC-PK1 AND OK CELL-LINES

The nephrotoxic fungal toxins ochratoxin A (OA), ochratoxin B (OB) and citrinin (CIT) are natural contaminants of foods and feeds. While cyt otoxicity assays have proven useful for establishing relative toxicity and structure-function relationships within groups of fungal toxins, a drawback of in vitro bioassays is their susceptibility to variation depending on endpoint, target cell, and dosing strategy. These variabl es were explored for OA, OB, CIT using two continuous kidney cell line s (LLC-PK1 and OK) and four cytotoxicity assay endpoints. The nephroto xic antibiotic gentamicin was used as a positive control for cytotoxic ity throughout. in general, fungal toxin-induced cytotoxicity was more pronounced in LLC-PK1 cultures using mitochondrial dehydrogenase inhi bition (MTT assay) as the endpoint. Altered dosing strategy, but not s eeding density, consistently influenced cytotoxicity: CIT was more tox ic to cells when added at the time of seeding, whereas OA was more tox ic when added 24 h after cultures were seeded. Toxicity rankings for t he fungal toxins were consistent with in vitro studies and were, in or der of most to least toxic, OA>OB>CIT. The data indicate that LLC-PK1 and OK cells compare favorably to existing models in terms of sensitiv ity to nephrotoxic fungal toxins, but also that relatively minor chang es in assay protocols can affect the cytotoxicity of individual toxins and comparative toxicity within a group of toxins.