Fumonisin B 2 Induces Mitochondrial Stress and Mitophagy in Human Embryonic Kidney (Hek293) Cells-A Preliminary Study.

Ubiquitous soil fungi parasitise agricultural commodities and produce mycotoxins. Fumonisin B 2 (FB 2 ), the structural analogue of the commonly studied Fumonisin B 1 (FB 1 ), is a neglected mycotoxin produced by several Fusarium species. Mycotoxins are known for inducing toxicity via mitochondrial stress alluding to mitochondrial degradation (mitophagy). These processes involve inter-related pathways that are regulated by proteins related to SIRT3 and Nrf2. This study aimed to investigate mitochondrial stress responses in human kidney (Hek293) cells exposed to FB 2 for 24 h. Cell viability was assessed via the methylthiazol tetrazolium (MTT) assay, and the half-maximal inhibitory concentration (IC 50 = 317.4 µmol/L) was estimated using statistical software. Reactive oxygen species (ROS; H 2 DCFDA), mitochondrial membrane depolarisation (JC1-mitoscreen) and adenosine triphosphate (ATP; luminometry) levels were evaluated to assess mitochondrial integrity. The relative expression of mitochondrial stress response proteins (SIRT3, pNrf2, LONP1, PINK1, p62 and HSP60) was determined by Western blot. Transcript levels of SIRT3 , PINK1 and miR-27b were assessed using quantitative PCR (qPCR). FB 2 reduced ATP production ( p = 0.0040), increased mitochondrial stress marker HSP60 ( p  = 0.0140) and suppressed upregulation of mitochondrial stress response proteins SIRT3 ( p  = 0.0026) and LONP1 ( p  = 0.5934). FB 2 promoted mitophagy via upregulation of pNrf2 ( p = 0.0008), PINK1 ( p = 0.0014) and p62 ( p < 0.0001) protein expression. FB 2 also suppressed miR-27b expression ( p < 0.0001), further promoting the occurrence of mitophagy. Overall, the findings suggest that FB 2 increases mitochondrial stress and promotes mitophagy in Hek293 cells.