Cytotoxic and apoptotic effects of fumonisin B 1, beauvericin and ochratoxin A on porcine kidney PK-15 cells

Abstract

Fumonisin B1 (FB1), beauvericin (BEA) and ochratoxin A (OTA) are widespread mycotoxins, which contaminate food and feed, particularly maize. Their co-occurrence was established in 6% (two toxins) and 2% (three toxins) of maize samples in Croatia with average concentrations 0.62 mg/kg of FB1, 0.39 mg/kg of BEA and 0.02 mg/kg of OTA. Fumonisin B1 and OTA could be implicated in development of various diseases in animals and humans, including nephrotoxicosis and carcinogenesis. Cytotoxic and apoptotic activity of BEA was observed in few cell lines including human B-lymphocytes, rodent colangiocytes and human cell lines of myeloid origin. However, possible nephrotoxic effects of BEA have not been investigated yet. In this study we explored cytotoxic (cell viability) and apoptotic (index of apoptosis and activation of caspase-3) effects of FB1, BEA and OTA in PK-15 cells (porcine kidney epithelial cells). Cells were treated with lower concentrations of mycotoxins (0.05, 0.5 and 5  g/mL) for 24 and 48 hours. Decrease of cell viability shows that FB1, BEA and OTA are cytotoxic to PK-15 cells in dose dependent manner. Cell viability was significantly decreased after 24 hours of exposure to 5  g/mL of FB1 (25%), BEA (30%) and OTA (40%), as compared to untreated control cells (P<0.05). On the other hand, index of apoptosis was increased by 110-140% after 48 hours of exposure to individual mycotoxins (5  g/mL), as compared to control samples (P<0.05). OTA activated caspase-3 after 24 hours of treatment with 0.5  g/mL (84%), while BEA (319%) and FB1 (419%) significantly affected this enzyme after prolonged exposure (P<0.05). Combined treatment with two or three mycotoxins (0.05 and 0.5  g/mL) showed additive effects on cell viability. Beauvericin and OTA (5  g/mL) synergistically increased apoptotic index after 24 hours of treatment. Synergistic effects on caspase-3 activities were observed after 24 hours of exposure to BEA+OTA and FB1+BEA+OTA (0.05 and 0.5  g/mL), as well as to FB1+BEA and BEA+OTA (5  g/mL). From the mycotoxicological risk point of view, frequent maize contamination by fungal species that produce FB1 and BEA (Fusarum spp.), as well as OTA (Aspergillus spp. and Penicillium spp.), is one of the greatest concern. Co-occurrence and accumulation of these mycotoxins in grains and their synergistic action might be an important trigger for development of chronic renal diseases, especially after long-term exposure of consumers.