Gut microbiota and undigested food constituents modify toxin composition and suppress the genotoxicity of a naturally occurring mixture of Alternaria toxins in vitro

Abstract

Molds of the genus Alternaria produce several mycotoxins, some of which may pose a threat for health due to their genotoxicity. Due to the lack of adequate toxicological and occurrence data, they are currently not regulated. Interactions between mycotoxins, gut microbiota and food constituents might occur after food ingestion, modifying the bioavailability and, therefore, overall toxicity of mycotoxins. The present work aimed to investigate the impact of in vitro short-term fecal incubation on the in vitro DNA-damaging effects exerted by 5 µg/mL of an Alternaria alternata extract, containing, among others, 15 nM alternariol, 12 nM alternariol monomethyl ether, 241 nM altertoxin II and 301 nM stemphyltoxin III, all of which are known as genotoxic. The involvement of microorganisms, undigested food constituents and soluble substances of human fecal samples in modifying the composition and the genotoxicity of the extract was investigated through the application of LC–MS/MS analysis and comet assays in HT-29 cells. Results showed that the potential of the mycotoxins to induce DNA strand breaks was almost completely quenched, even before anaerobic incubation, by contact with the different fractions of the fecal samples, while the potency to induce formamidopyrimidine DNA glycosylase (FPG)-sensitive sites was only slightly reduced. These effects were in line with a reduction of mycotoxin concentrations found in samples analyzed by LC–MS/MS. Although a direct correlation between the metabolic activity of the gut microbiota and modifications in mycotoxin contents was not clearly observed, adsorptive phenomena to bacterial cells and to undigested food constituents might explain the observed modifications.

In vitro interactions of Alternaria mycotoxins, an emerging class of food contaminants, with the gut microbiota: a bidirectional relationship

“…The ability of gut microorganisms from broilers, pigs, and rats to transform the epoxide-carrying compounds DON into de-epoxy-DON was also reported (Worrell et al 1989;He et al 1992;Kollarczik et al 1994;Young et al 2007). Although in the present study, ATX-II was found neither in samples containing bacteria nor in media controls after 24 h incubation, in our previous study, we reported ATX-II to be still present after 3 h incubation (Crudo et al 2020). Thus, it is probable that the transformation of ATX-II into ATX-I mediated by B. eggerthii, P. distasonis, and Bifidobacterium sp.…”

“…This transformation was also reported in eukaryotic cell lines (Fleck et al 2014a , b ). Moreover, in a recent study (Crudo et al 2020 ), we found higher concentrations of ATX-I in samples of fecal slurries of 3 out 4 donors after a 3 h anaerobic incubation with the same Alternaria extract used in the present study. The ability of gut microorganisms from broilers, pigs, and rats to transform the epoxide-carrying compounds DON into de-epoxy-DON was also reported (Worrell et al 1989 ; He et al 1992 ; Kollarczik et al 1994 ; Young et al 2007 ).…”

“…The LC-MS/MS method used in the present study has been already used in our recent work for the quantification of Alternaria mycotoxins in human fecal slurries (Crudo et al 2020). Briefly, a Supelco Ascentis ® Express C18 column (100 × 2.1 mm, 2.7 µm) equipped with a pre-column (SecurityGuard™, C18, 2 mm, Phenomenex, Torrance, CA, USA) was employed for the chromatographic separation.…”

Microfiltration results in the loss of analytes and affects the in vitro genotoxicity of a complex mixture of Alternaria toxins

“…Despite their low occurrence data in food, they are evidently among the predominantly formed secondary metabolites of Alternaria molds grown under laboratory conditions (Puntscher et al 2019c;Zwickel et al 2018). For epoxide-carrying representatives like ATX-II and STTX-III, the chemical reactivity towards co-occurring food constituents and fibers might at least contribute to this mystery (Aichinger et al 2018;Crudo et al 2020). However, for non-reactive metabolites like ATX-I or ALP, our data suggests that filtration might be a major source of compound loss.…”

Biological and chemical characterization of antimicrobial activity in Arthrobacter spp. isolated from disease‐suppressive compost

“…On tomato, the fungus causes Alternaria rot disease (also known as black mold) with fruit symptoms including dark sunken lesions, as well as early blight disease on plants, which exhibit symptoms such as leaf spots, rots, and stem cankers [21,22]. A. alternata is also known to produce a large number of spores [23] and toxic compounds [24], which may affect human and animal health, such as respiratory issues [23] and genotoxic effects [25].…”