Markers for DNA damage are induced in the rat colon by the Alternaria toxin altertoxin-II, but not a complex extract of cultured Alternaria alternata

Abstract

Mycotoxins produced by Alternaria spp. act genotoxic in cell-based studies, but data on their toxicity in vivo is scarce and urgently required for risk assessment. Thus, male Sprague-Dawley rats received single doses of a complex Alternaria toxin extract (CE; 50 mg/kg bw), altertoxin II (ATX-II; 0.21 mg/kg bw) or vehicle by gavage, one of the most genotoxic metabolites in vitro and were sacrificed after 3 or 24 h, respectively. Using SDS-PAGE/Western Blot, a significant increase of histone 2a.X phosphorylation and depletion of the native protein was observed for rats that were exposed to ATX-II for 24 h. Applying RT-PCR array technology we identified genes of interest for qRT-PCR testing, which in turn confirmed an induction of Rnf8 transcription in the colon of rats treated with ATX-II for 3 h and CE for 24 h. A decrease of Cdkn1a transcription was observed in rats exposed to ATX-II for 24 h, possibly indicating tissue repair after chemical injury. In contrast to the observed response in the colon, no markers for genotoxicity were induced in the liver of treated animals. We hereby provide the first report of ATX-II as a genotoxicant in vivo. Deviating results for similar concentrations of ATX-II in a natural Alternaria toxin mixture argue for substantial mixture effects.

Hazard characterization of Alternaria toxins to identify data gaps and improve risk assessment for human health

“…The high potency of ATX-II results likely from the epoxide group in the molecule that can react with DNA without metabolic activation in contrast to AME and AOH (Fleck et al 2012 ; Soukup et al 2020 ). So far, ATX-II was only investigated in one in vivo study in rats with a single bolus application, resulting in enhanced levels of γH2AX in the colon of the animals after 24 h (Aichinger et al 2022b ; Puntscher et al 2019a ).…”

Development and validation of a simultaneous quantitative analytical method for two Alternaria toxins and their metabolites in plasma and urine using ultra‐high‐performance liquid chromatography‐tandem mass spectrometry

“…The cytotoxic effects of 4‐OH‐AOH were found to be the same as those of the parent compounds [4]. Although many animal experiments have shown that Alternaria toxins have no genotoxicity or cytotoxicity in the liver, contaminated food by the toxins may produce hepatotoxic effects, and genotoxic and mutagenic activities in humans [8–10].…”