alternariol-monomethyl-ether and Esophageal-Neoplasms

Studies on the genotoxicity of Alternaria mycotoxins focus primarily on the native compounds. Alternariol (AOH) and its methyl ether (AME) have been reported to represent substrates for cytochrome P450 enzymes, generating hydroxylated metabolites. The impact of these phase I metabolites on genotoxicity remains unknown. In the present study, the synthesis and the toxicological effects of the metabolites 4-hydroxy alternariol (4-OH-AOH) and 4-hydroxy alternariol monomethyl ether (4-OH-AME) are presented and compared to the effects of the parent molecules. Although the two phase I metabolites contain a catecholic structure, which is expected to be involved in redox cycling, only 4-OH-AOH increased reactive oxygen species (ROS) in human esophageal cells (KYSE510), 4 times more pronounced than AOH. No ROS induction was observed for 4-OH-AME, although the parent compound showed some minor impact. Under cell-free conditions, both metabolites inhibited topoisomerase II activity comparable to their parent compounds. In KYSE510 cells, both metabolites were found to enhance the level of transient DNA-topoisomerase complexes in the ICE assay. Although the level of ROS was significantly increased by 4-OH-AOH, neither DNA strand breaks nor enhanced levels of formamidopyrimidine-DNA-glycosylase (FPG)-sensitive sites were observed. In contrast, AOH induced significant DNA damage in KYSE510 cells. Less pronounced or even absent effects of hydroxylated metabolites compared to the parent compounds might at least partly be explained by their poor cellular uptake. Glucuronidation as well as sulfation appear to have only a minor influence. Instead, methylation of 4-OH-AOH seems to be the preferred way of metabolism in KYSE510 cells, whereby the toxicological relevance of the methylation product remains to be clarified.

Topics: Antigens, Neoplasm; Cell Line, Tumor; Cell-Free System; DNA Damage; DNA Topoisomerases, Type II; DNA-Binding Proteins; Esophageal Neoplasms; Humans; Hydroxylation; Lactones; Mitochondria; Mutagenicity Tests; NF-E2-Related Factor 2; Oxidative Stress; Reactive Oxygen Species

In this paper, the mutagenicity and carcinogenicity of alternariol monomethyl ether (AME), alternariol (AOH), and their relevance to the etiology of human esophageal cancer were studied. These mycotoxins were produced by Alternaria alternata which was the main contaminating fungi isolated from the grain in Linxian County, an area with high incidence of esophageal cancer. This study demonstrated that: 1. AME and AOH might cause cell mutagenicity and transformation; 2. AME and AOH could combine with the DNA isolated from human fetal esophageal epithelium, activate the oncogens, c-H-ras and c-mys in it, and promote proliferation of human fetal esophageal epithelium in vitro; 3. squamous cell carcinoma of the fetal esophagus could be induced by AOH. According to the results of the studies of AME and AOH mentioned above, we consider that Alternaria alternata plays an important role in the etiology of human esophageal cancer.

Topics: Alternaria; Animals; Carcinoma, Squamous Cell; Cell Transformation, Neoplastic; Cells, Cultured; Esophageal Neoplasms; Humans; Lactones; Mice; Mice, Inbred BALB C; Mutagenicity Tests; Mycotoxins

In order to study the relationship between daily consumption of mouldy food and the incidence of oesophageal cancer, we examined the mutagenicity of Alternaria alternata and Penicillium cyclopium, which seriously contaminate grain in Linxian county, China. We first examined extracts of cultured strains of A. alternata. In the reverse mutation test, positive results were obtained in 85% of strains; positive results were seen in 84% of 19/20 strains in the rec assay. Eight of ten strains induced sister chromatid exchange, and two of eight strains induced chromatid breaks. Six of seven strains induced unscheduled DNA synthesis and DNA synthesis inhibition. One extract induced a higher frequency of sister chromatid exchange in lymphocytes from normal persons than in those from patients with oesophageal cancer, and the spontaneous break-points in patients were related to fragile sites and neoplasia-associated break-points. The toxins alternariol and its monomethyl ether, produced by A. alternata, were examined in the reverse mutation assay and for unscheduled DNA synthesis. The results were similar to those obtained with extracts of the different strains. Alternariol had a four to eight times greater effect than its monomethyl ether. Of 24 strains of P. cyclopium isolated from cereals in Linxian, four were cultured with rice and 19 in Raulin-Thom medium. Cultures in Raulin-Thorn medium, solution and hyphae were then extracted. The strains cultured with rice induced sister chromatid exchange, unscheduled DNA synthesis and DNA synthesis inhibition. The solution extracts of 14 strains were positive in the rec assay, and five strains were positive in the reverse mutation test.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: Alternaria; China; Esophageal Neoplasms; Food Microbiology; Lactones; Mutagens; Penicillium

Although it is uncertain whether fungi can produce the mycotoxins that induce oesophageal cancer, the tumorigenicity of fungi isolated from grain in an area of high incidence of oesophageal cancer has been confirmed. Alternaria alternata is a fungus of importance in this respect. The contamination rate with A. alternata in corn from areas of high morbidity from oesophageal cancer is higher than that in low-morbidity areas. Extracts of A. alternata induced reverse mutation in Escherichia coli, unscheduled DNA synthesis in cultured human amnion FL cells, chromosomal aberrations and sister chromatid exchange in human peripheral blood lymphocytes, mutation in V79 cells and transformation of NIH3T3 cells. Alternariol methyl ether, which is an active compound produced by this fungus, also induced transformation of NIH3T3 cells, and the transformed cells grew in soft agar and were tumorigenic in nude mice. Food mildewed by this fungus induced forestomach tumours in rats. Thus, (i) A. alternata is tumorigenic, (ii) it has been isolated from corn in an area of high incidence of oesophageal cancer, and (iii) contamination with A. alternata in the area of high incidence is higher than that in the area of low incidence. We therefore believe that A. alternata is one of the causes of human oesophageal cancer.

Topics: Alternaria; Animals; DNA; Esophageal Neoplasms; Esophagus; Food Microbiology; Humans; Lactones; Lipid Peroxidation; Mice; Mutagens; Rats