Interactions between plant-derived oestrogenic substances and the mycoestrogen zearalenone in a bioassay with MCF-7 cells.

Human and animal diets may contain several non-steroidal oestrogenic compounds which originate either from plants (phytoestrogens) or from fungi that infect plants (mycoestrogens such as zearalenone (ZEN)). Phytoestrogens may compete with ZEN in binding to the oestrogen receptor ß and thereby may counteract the oestrogenic activity of ZEN. Using a modified version of the E-screen assay, plant-derived oestrogenic substances were tested for their proliferative or anti-proliferative effect on oestrogen-dependent MCF-7 cells. The samples were additionally tested for their ability to influence the oestrogenic activity of ZEN (1 µM). Among the individual substances tested, 8-prenylnaringenin had the strongest effect, as cell proliferation was increased by 78% at the lowest concentration (0.23 µM), and by 167% at the highest concentration (29.4 µM). Coumestrol (5.83 µM) increased cell proliferation by 39%, and genistein (370 µM) by 61%, respectively. Xanthohumol and enterolactone did not stimulate cell proliferation significantly. In the co-incubation experiments with ZEN, none of the single substances was able to decrease the oestrogenic activity of ZEN. Only for 8-prenylnaringenin (14.7 and 29.4 µM) was a trend towards an increase in the ZEN-induced cell proliferation up to 72% observed. In conclusion, with the exception of 8-prenylnaringenin, no substantial interaction between phytoestrogens and the mycotoxin ZEN could be detected using a bioassays with MCF-7 cells.

Use of Trichosporon mycotoxinivorans to suppress the effects of ochratoxicosis on the immune system of broiler chicks.

(1) The objective of this study was to determine whether the dietary inclusion of Trichosporon mycotoxinivorans (TRM) could suppress the detrimental effects of ochratoxin A (OTA) on the immune system of broiler chicks. (2) Six experimental treatments were tested in 300 1-d-old broiler chicks. Treatments included addition to a standard broiler ration of neither OTA nor TRM (Diet 1), OTA alone (500 microg/kg), OTA plus TRM at three inclusion rates (10(4) CFU/g of feed, 10(5) CFU/g, 10(6) CFU/g) and TRM alone at 10(5) CFU/g of feed. The ration was fed to chicks for 42 d. (3) Blood samples were collected at d 10, 20, 30 and 40 and macrophages and heterophils were isolated. The following variables were determined in macrophages and heterophils activated by phorbol myristate acetate (65 microM): cell viability, total cell-associated urokinase-plasminogen activator (u-PA), membrane-bound u-PA, free u-PA binding sites and superoxide production. (4) There was a decrease in the viability of macrophages and heterophils from chicks receiving OTA-contaminated feed compared to the viability of cells from control birds at d 40. Dietary TRM completely blocked the effect of OTA on cell viability; all three inclusion rates were equally effective. There was a decrease in total cell-associated and membrane-bound u-PA in macrophages and heterophils of chicks receiving OTA-contaminated feed compared to the corresponding values in control birds for heterophils at d 30 and 40 and for the macrophages at d 40. (5) Similarly, dietary TRM abolished the effect of OTA on total cell-associated and membrane-bound u-PA activity. All three inclusion rates of yeast were equally effective. Heterophils, but not macrophages, isolated from chicks receiving OTA-contaminated diet produced less superoxide anion compared to all other diet groups at d 30 and 40. (6) The immune system is a primary target of OTA toxicity in broilers: several functional properties of macrophages and heterophils were depressed in chicks fed OTA-contaminated feed. There was a delay of 30d before the immunosuppressive effect became apparent. The dietary inclusion of TRM completely blocked the detrimental effects of OTA on several immune properties in broilers.

Toxicity of ochratoxin A in aBrevibacillus brevis - Growth inhibition assay.

Ochratoxin A (OTA) is a nephrotoxic, carcinogenic and immunosuppressive mycotoxin. It can be detoxified by various microorganisms, e.g. different yeast strains, via metabolisation into ochratoxin α (OTα). Within this study a growth inhibition assay was developed to compare the toxicity of OTA and its degradation product OTα. As an indicator organismBrevibacillus brevis was used. The assay was performed in microtiterplates. Growth inhibition was determined by comparing the optical density values ofBrevibacillus brevis cultures grown in medium supplemented with OTA/OTα and OTA/OTα-free medium, respectively.It could be shown thatB. brevis is sensitive to OTA (EC100=0.5 mg/L±0.03 mg/L), which is not the case for its metabolite OTα. Therefore this bioassay is a useful tool to show the detoxification of OTA to OTα by microbial degradation.