A human intervention study with foods containing natural Ah-receptor agonists does not significantly show AhR-mediated effects as measured in blood cells and urine |
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Authors: | de Waard Pim W J Peijnenburg Ad A C M Baykus Hakan Aarts Jac M M J G Hoogenboom Ron L A P van Schooten Frederik J de Kok Theo M C M |
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Institution: | a Centre for Biological Medicines and Medical Technology, RIVM, PO Box 1, 3720 BA Bilthoven, The Netherlands b Department of Health Risk Analysis and Toxicology, Maastricht University, PO Box 616, 6200 MD Maastricht, The Netherlands c Toxicology & Effect Monitoring Group, RIKILT Institute of Food Safety, PO Box 230, 6700 EA Wageningen, The Netherlands d Division of Toxicology, Wageningen University, PO Box 8000, 6700 EA Wageningen, The Netherlands |
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Abstract: | Binding and activation of the aryl hydrocarbon receptor (AhR) is thought to be an essential step in the toxicity of the environmental pollutants dioxins and dioxin-like PCBs. However, also a number of natural compounds, referred to as NAhRAs (natural Ah-receptor agonists), which are present in, for example, fruits and vegetables, can bind and activate this receptor. To study their potential effects in humans, we first investigated the effect of the prototypical AhR agonist 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) on gene expression in ex vivo exposed freshly isolated human lymphocytes, and compared the resulting gene expression profile with those caused by the well-known NAhRA indolo3,2-b]carbazole (ICZ), originating from cruciferous vegetables, and by a hexane extract of NAhRA-containing grapefruit juice (GJE). Only ICZ induced a gene expression profile similar to TCDD in the lymphocytes, and both significantly up-regulated CYP1B1 and TIPARP (TCDD-inducible poly (ADP-ribose) polymerase) mRNA.Next, we performed a human intervention study with NAhRA-containing cruciferous vegetables and grapefruit juice. The expression of the prototypical AhR-responsive genes CYP1A1, CYP1B1 and NQO1 in whole blood cells and in freshly isolated lymphocytes was not significantly affected. Also enzyme activities of CYP1A2, CYP2A6, N-acetyltransferase 2 (NAT2) and xanthine oxidase (XO), as judged by caffeine metabolites in urine, were unaffected, except for a small down-regulation of NAT2 activity by grapefruit juice. Examination of blood plasma with DR CALUX® showed a 12% increased AhR agonist activity 3 and 24 h after consumption of cruciferous vegetables, but did not show a significant effect of grapefruit juice consumption. We conclude that intake of NAhRAs from food may result in minor AhR-related effects measurable in human blood and urine. |
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Keywords: | AhR aryl hydrocarbon receptor DMSO dimethyl sulfoxide GJE grapefruit juice extract ICZ indolo[3 2-b]carbazole NAhRA natural AhR agonist TCDD 2 3 7 8-tetrachlorodibenzo-p-dioxin |
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