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 cytotoxicity 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 variables were explored for OA, OB, CIT using two continuous kidney cell lines (LLC-PK1 and OK) and four cytotoxicity assay endpoints. The nephrotoxic antibiotic gentamicin was used as a positive control for cytotoxicity throughout. In general, fungal toxin-induced cytotoxicity was more pronounced in LLC-PK1 cultures using mitochondrial dehydrogenase inhibition (MTT assay) as the endpoint. Altered dosing strategy, but not seeding density, consistently influenced cytotoxicity: CIT was more toxic to cells when added at the time of seeding, whereas OA was more toxic when added 24 h after cultures were seeded. Toxicity rankings for the fungal toxins were consistent with in vivo studies and were, in order 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 sensitivity to nephrotoxic fungal toxins, but also that relatively minor changes in assay protocols can affect the cytotoxicity of individual toxins and comparative toxicity within a group of toxins.