Fusaric acid induces mitochondrial stress in human hepatocellular carcinoma (HepG2) cells

Fusarium spp are common contaminants of maize and produce many mycotoxins, including the fusariotoxin fusaric acid (FA). FA is a niacin related compound, chelator of divalent cations, and mediates toxicity via oxidative stress and possible mitochondria] dysregulation. Sirtuin 3 (SIRT3) is a stress response deacetylase that maintains proper mitochondria] function. We investigated the effect of FA on SIRT3 and oxidative and mitochondria] stress pathways in the hepatocellular carcinoma (HepG2) cell line. We determined FA toxicity (24 h incubation; IC50 = 104 mu g/ml) on mitochondria] output, cellular and mitochondria] stress responses, mitochondrial biogenesis and markers of cell death using spectrophotometry, luminometry, OCR and western blots. FA caused a dose dependent decrease in metabolic activity along with significant depletion of intracellular ATP. FA induced a significant increase in lipid peroxidation, despite up-regulation of the antioxidant transcription factor, Nrf2. FA significantly decreased expression of SIRT3 mRNA with a concomitant decrease in protein expression. Lon protease was also significantly down-regulated. FA induced aberrant mitochondrial biogenesis as evidenced by significantly decreased protein expressions of: PGC-1 alpha, p-CREB, NRF1 and HSP70. Finally, FA activated apoptosis as noted by the significantly increased activity of caspases 3/7 and also induced cellular necrosis. This study provides insight into the molecular mechanisms of FA (a neglected mycotoxin) induced hepatotoxicity. (C) 2016 Elsevier Ltd. All rights reserved.