In vitro combinatory effects of the Alternaria mycotoxins alternariol and altertoxin II and potentially involved miRNAs.

Alternariol (AOH) and altertoxin II (ATX II) are mycotoxins formed by Alternaria spp. Since they are expected to co-occur in Alternaria-infested food and feed, we addressed the question of combinatory effects. In addition, potentially involved regulatory microRNAs were surveyed in an exploratory approach. Cytotoxicity measurements in constant ratio combinations of 1:10 or 1:1 (ATX II: AOH) mainly revealed additive effects in HepG2, HT29 and HCEC-1CT cells. Yet, in specific high doses antagonism was found. Microarray analysis of miRNA expression profiles in HepG2 cells indicated different patterns of miRNA regulation by AOH and ATX II, including several miRNA species for which no distinct functions are currently known. Among others, miR-4654, miR-4715_3p and miR-6720_3p were up-regulated by AOH and miR-5583_5p was down-regulated by ATX II. Additionally, miR-1323, involved in hindering DNA repair mechanisms, was decreased by ATX II. Digital droplet PCR (ddPCR) analysis of selected miRNAs indicated regulation of miR-29a by AOH, which might play a role in AOH-induced apoptosis. miR-192 and miR-224 regulation was associated with antagonistic cytotoxic effects of AOH and ATX II combinations. Our study represents the first evaluation on combinatory effects of AOH and ATX II.