Alternariol

The mycelium of Alternaria dauci.

Estrogenic and clastogenic potential of the mycotoxin alternariol in cultured mammalian cells.[Pubmed:16194592]

Food Chem Toxicol. 2006 Mar;44(3):398-408.

The mycotoxin Alternariol (AOH) is found in food and beverages infected by Alternaria alternata. Because consumption of foodstuffs contaminated with A. alternata has been implicated in an elevated incidence of esophageal carcinogenesis, we have investigated the estrogenic potential, the effect on cell proliferation, and the genotoxic effect of AOH in cultured mammalian cells. AOH replaced E2 from isolated human estrogen receptors alpha and beta and increased the level of alkaline phosphatase (ALP) mRNA and the enzymatic activity of ALP in a human endometrial adenocarcinoma cell line (Ishikawa cells). The estrogenicity of AOH was about 0.01% of that of E2. The effects in Ishikawa cells were reversed by the ER antagonist ICI 182,780. Analysis of cell proliferation by flow cytometry and microscopy of Ishikawa and Chinese hamster V79 cells revealed that AOH inhibited cell proliferation by interference with the cell cycle. The genotoxic potential was assessed by the micronucleus (MN) assay and immunochemical differentiation between MN containing whole chromosomes (kinetochore-positive) and DNA fragments (kinetochore-negative) in Ishikawa and V79 cells. AOH induced kinetochore-negative MN in both cell lines. This is the first report on the estrogenic potential, inhibition of cell proliferation and clastogenicity of AOH in Ishikawa and V79 cells in vitro.

Alternariol acts as a topoisomerase poison, preferentially affecting the IIalpha isoform.[Pubmed:18727009]

Mol Nutr Food Res. 2009 Apr;53(4):441-51.

Alternariol (AOH), a mycotoxin formed by Alternaria alternata, has been reported to possess genotoxic properties. However, the underlying mechanism of action is unclear. Here, we tested the hypothesis that interactions with DNA-topoisomerases play a role in the DNA-damaging properties of AOH. First we compared DNA-damaging properties of AOH with other Alternaria mycotoxins such as AOH monomethyl ether (AME), altenuene and isoaltenuene. AOH and AME significantly increased the rate of DNA strand breaks in human carcinoma cells (HT29, A431) at micromolar concentrations, whereas altenuene and isoaltenuene did not affect DNA integrity up to 100 microM. Next, we selected AOH as the most DNA-damaging Alternaria metabolite for further studies of interactions with DNA topoisomerases. In cell-free assays, AOH potently inhibited DNA relaxation and stimulated DNA cleavage activities of topoisomerase I, IIalpha and IIbeta. Stabilisation of covalent topoisomerase II-DNA intermediates by AOH was also detectable in cell culture, and here, the IIalpha isoform was preferentially targeted. AOH is thus characterised as a poison of topoisomerase I and II with a certain selectivity for the IIalpha isoform. Since topoisomerase poisoning and DNA strand breakage occurred within the same concentration range, poisoning of topoisomerase I and II might at least contribute to the genotoxic properties of AOH.

Alternariol, a dibenzopyrone mycotoxin of Alternaria spp., is a new photosensitizing and DNA cross-linking agent.[Pubmed:3899714]

Experientia. 1985 Sep 15;41(9):1188-90.

The mycotoxin Alternariol (3,4',5-trihydroxy-6'-methyldibenzo [a] pyrone) but not Alternariol monomethyl ether (3,4'-dihydroxy-5-methoxy-6'-methyldibenzo [a] pyrone) is phototoxic to Escherichia coli in the presence of near UV light (320-400 nm). The phototoxicity bioassays with a DNA repair-deficient mutant of E. coli suggested that DNA may be the molecular target for photo-induced toxicity of Alternariol. Interactions between Alternariol and double-stranded, supercoiled DNA suggest that Alternariol interacts with DNA by intercalation. No DNA breakage was detected in this system; however, Alternariol forms a complex and cross-links double-stranded DNA in near UV light. These results suggest that Alternariol is a new phototoxic, DNA-intercalating agent and is a DNA cross-linking mycotoxin in near UV light.

Alternariol induces abnormal nuclear morphology and cell cycle arrest in murine RAW 264.7 macrophages.[Pubmed:23454835]

Toxicol Lett. 2013 May 10;219(1):8-17.

The mycotoxin Alternariol (AOH), a frequent contaminant in fruit and cereal products, is known to induce DNA damage with subsequent cell cycle arrest. Here we elucidated the effects of AOH on stages of cell cycle progression using the RAW 264.7 macrophage model. AOH resulted in an accumulation of cells in the G2/M-phase (4N). Most cells exhibited a large G2 nucleus whereas numbers of true mitotic cells were reduced relative to control. Both cyclin B1 and p-cdc2 levels increased, while cyclin B1 remained in the cytoplasm; suggesting arrest in the G2/M transition point. Remarkably, after exposure to AOH for 24h, most of the cells exhibited abnormally shaped nuclei, as evidenced by partly divided nuclei, nuclear blebs, polyploidy and micronuclei (MN). AOH treatment also induced abnormal Aurora B bridges, suggesting that cytokinesis was interfered within cells undergoing karyokinesis. A minor part of the resultant G1 tetraploid (4N) cells re-entered the S-phase and progressed to 8N cells.

Alternariol is a mycotoxin produced by Alternaria species. AOH inhibits the catalytic activity of topoisomerase I and topoisomerase II enzymes. Alternariol exhibits a variety of therapeutic and biological properties such as phytotoxicity, cytotoxicity, anti-HIV, anti-cancer, and anti-microbial properties.

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