Characterization of a genotoxic impact compound in Alternaria alternata infested rice as Altertoxin II

Abstract

Toxicity-guided fractionation was used to identify DNA strand breaking impact compounds in extracts obtained from rice heavily infested with the Alternaria alternata strains DSM 62006 and DSM 62010. The major genotoxic potential measured in the comet assay using human colon carcinoma cells (HT29) could be attributed to three unknown peaks, whereas the fractions containing alternariol, its monomethylether or tenuazonic acid showed no significant DNA damaging effects. According to (1)H and (13)C-NMR spectroscopy, one genotoxic impact compound was identified as Altertoxin II (ATXII). ATXII showed potent DNA damaging properties in HT29 cells with substantial induction of formamidopyrimidine DNA glycosylase (FPG)-sensitive sites. However, no effect was observed with respect to the cellular redox status, measured in the DCF assay and as total glutathione. The induction of apoptosis could be excluded as a potential reason for enhanced DNA damage. After 24 h of incubation with 1 μM ATX II, a significant increase of cells in the G(0)/G(1) phase was observed together with an inhibition of cell proliferation in the sulforhodamine B assay. Taken together, ATX II was found to contribute substantially to the genotoxic effects of complex extracts obtained from Alternaria alternata infested rice. The results demonstrate the high genotoxic potency of ATX II in human cells, underlining the necessity for further studies on the occurrence in food and its relevance for food safety.

Tracking emerging mycotoxins in food: development of an LC-MS/MS method for free and modified Alternaria toxins

“…AOH and AME showed genotoxic and mutagenic effects in vitro [7] and AOH was further demonstrated to poison topoisomerases I and II [8]. ATX-II proved to be an even more potent mutagen causing DNA strand breaks [9, 10]. The mechanisms behind its mode of action could not be clarified so far.…”

Characterization of Alternaria strains from Argentinean blueberry, tomato, walnut and wheat

“…Altertoxins (ALXs) have been reported to be more potent mutagens and acute toxic to mice than AOH and AME (Scott, 2004) and recently, high genotoxic potency of ALX-II in mammalian and human cells was demonstrated (Fleck et al, 2012;Schwarz et al, 2012). Other Alternaria A C C E P T E D M A N U S C R I P T…”

“…These metabolites were tested in MRC-5 cells and found to be non-cytotoxic (Ivanova et al, 2010), whereas altertoxins tested in HT29 cells were found to be genotoxic (Schwarz et al, 2012). This suggests that A. infectoria sp.-grp.…”

Activation of the Nrf2-ARE pathway by the Alternaria alternata mycotoxins altertoxin I and II

“…1). These two compounds seem to have high potential to pose a major threat for human health due to their mutagenic and genotoxic properties (Schrader et al 2001; Schwarz et al 2012b; Stack and Prival 1986). Structurally, the two molecules differ only by means of the functional group in positions 7 and 8, where ATX I carries a hydroxyl group and ATX II an epoxide moiety.…”