14 results on '"de Kok, T. M. C. M."'
Search Results
2. Inflammatory bowel disease stimulates formation of carcinogenic N-nitroso compounds
- Author
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de Kok, T M C M, Engels, L G J B, Moonen, E J, and Kleinjans, J C S
- Published
- 2005
3. Effects on Cell Proliferation, Activator Protein-1 and Genotoxicity by Fecal Water from Patients with Colorectal Adenomas
- Author
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Nordling, M M., Glinghammar, B, Karlsson, P C., de Kok, T M. C. M., and Rafter, J J.
- Published
- 2003
4. The benefits and risks of beetroot juice consumption: a systematic review.
- Author
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Zamani, H., de Joode, M. E. J. R., Hossein, I. J., Henckens, N. F. T., Guggeis, M. A., Berends, J. E., de Kok, T. M. C. M., and van Breda, S. G. J.
- Subjects
BEETS ,NITRIC oxide ,HUMAN body ,BLOOD pressure ,RISK assessment - Abstract
Beetroot juice (BRJ) has become increasingly popular amongst athletes aiming to improve sport performances. BRJ contains high concentrations of nitrate, which can be converted into nitric oxide (NO) after consumption. NO has various functions in the human body, including a vasodilatory effect, which reduces blood pressure and increases oxygen- and nutrient delivery to various organs. These effects indicate that BRJ may have relevant applications in prevention and treatment of cardiovascular disease. Furthermore, the consumption of BRJ also has an impact on oxygen delivery to skeletal muscles, muscle efficiency, tolerance and endurance and may thus have a positive impact on sports performances. Aside from the beneficial aspects of BRJ consumption, there may also be potential health risks. Drinking BRJ may easily increase nitrate intake above the acceptable daily intake, which is known to stimulate the endogenous formation of N-nitroso compounds (NOC's), a class of compounds that is known to be carcinogenic and that may also induce several other adverse effects. Compared to studies on the beneficial effects, the amount of data and literature on the negative effects of BRJ is rather limited, and should be increased in order to perform a balanced risk assessment. [ABSTRACT FROM AUTHOR]
- Published
- 2021
- Full Text
- View/download PDF
5. The benefits and risks of beetroot juice consumption: a systematic review.
- Author
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Zamani, H, de Joode, M E J R, Hossein, I J, Henckens, N F T, Guggeis, M A, Berends, J E, de Kok, T M C M, and van Breda, S G J
- Subjects
NITRATE analysis ,BEETS ,ANTIOXIDANTS ,DIETARY supplements ,RISK assessment ,IMPACT of Event Scale - Abstract
Beetroot juice (BRJ) has become increasingly popular amongst athletes aiming to improve sport performances. BRJ contains high concentrations of nitrate, which can be converted into nitric oxide (NO) after consumption. NO has various functions in the human body, including a vasodilatory effect, which reduces blood pressure and increases oxygen- and nutrient delivery to various organs. These effects indicate that BRJ may have relevant applications in prevention and treatment of cardiovascular disease. Furthermore, the consumption of BRJ also has an impact on oxygen delivery to skeletal muscles, muscle efficiency, tolerance and endurance and may thus have a positive impact on sports performances. Aside from the beneficial aspects of BRJ consumption, there may also be potential health risks. Drinking BRJ may easily increase nitrate intake above the acceptable daily intake, which is known to stimulate the endogenous formation of N-nitroso compounds (NOC's), a class of compounds that is known to be carcinogenic and that may also induce several other adverse effects. Compared to studies on the beneficial effects, the amount of data and literature on the negative effects of BRJ is rather limited, and should be increased in order to perform a balanced risk assessment. [ABSTRACT FROM AUTHOR]
- Published
- 2020
- Full Text
- View/download PDF
6. Inflammatory bowel disease stimulates formation of carcinogenic N-introso compounds.
- Author
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de Kok, T. M. C. M., Engels, L. G. J. B., Moonen, E. J., and Kleinjans, J. C. S.
- Subjects
- *
LETTERS to the editor , *INFLAMMATORY bowel diseases - Abstract
Presents a letter to the editor on research related to inflammatory bowel disease.
- Published
- 2005
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7. Ah receptor agonist activity in frequently consumed food items.
- Author
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De Waard WJ, Aarts JM, Peijnenburg AC, De Kok TM, Van Schooten FJ, and Hoogenboom LA
- Subjects
- Animals, Biological Assay methods, Environmental Pollutants analysis, Feeding Behavior, Food Analysis methods, Humans, Rats, Tumor Cells, Cultured, Vegetables chemistry, Food Contamination analysis, Polychlorinated Dibenzodioxins analysis, Receptors, Aryl Hydrocarbon agonists
- Abstract
The aryl hydrocarbon receptor (AhR) receives much attention for its role in the toxicity of dioxins and dioxin-like polychlorinated biphenyls. However, many other compounds have also been reported to bind and activate AhR, of which natural food components are of special interest from a human health perspective. Using the dioxin receptor-chemical-activated luciferase gene expression (DR CALUX) bioassay, extracts from many food items frequently consumed in the Netherlands were screened to estimate the intake of natural AhR agonists (NAhRAs). Using the prototypical AhR agonist 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) as standard, it was estimated that the daily intake of NAhRAs might be considerably higher than the reported intake of dioxins and dioxin-like polychlorinated biphenyls. Potatoes, cruciferous vegetables, bread, hamburgers, and grapefruit juice contained most NAhRAs. Food preparation and acid treatment can show a significant effect on AhR activation. The interaction of natural and xenobiotic AhR agonists should be taken into account when performing risk-benefit analysis of both types of compounds.
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- 2008
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8. Gene expression profiling in Caco-2 human colon cells exposed to TCDD, benzo[a]pyrene, and natural Ah receptor agonists from cruciferous vegetables and citrus fruits.
- Author
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de Waard WJ, Aarts JM, Peijnenburg AA, Baykus H, Talsma E, Punt A, de Kok TM, van Schooten FJ, and Hoogenboom LA
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- Caco-2 Cells, Chromatography, High Pressure Liquid, Cytochrome P-450 CYP1A1 metabolism, DNA, Complementary biosynthesis, DNA, Complementary genetics, Gene Expression drug effects, Genes, Reporter, Humans, Luciferases genetics, Oligonucleotide Array Sequence Analysis, Plant Extracts chemistry, RNA biosynthesis, RNA genetics, Reverse Transcriptase Polymerase Chain Reaction, Xenobiotics toxicity, Benzo(a)pyrene toxicity, Citrus chemistry, Environmental Pollutants toxicity, Gene Expression Profiling, Polychlorinated Dibenzodioxins toxicity, Receptors, Aryl Hydrocarbon agonists, Vegetables chemistry
- Abstract
Cruciferous vegetables and citrus fruits are reported to possess health-beneficial properties, but also have been shown to contain natural aryl hydrocarbon receptor (AhR) agonists (NAhRAs). Binding to the AhR is widely assumed to activate the main pathway by which dioxins, like 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) exert their toxicity. To establish whether or not activation of the AhR pathway by NAhRAs and dioxin-like substances results in similar cellular responses, gene expression profiles induced in Caco-2 cells were studied using microarray analysis. Cells were exposed to indolo[3,2-b]carbazole (ICZ), an acid reaction product from cruciferous vegetables, and to extracts of citrus pulp and grapefruit juice. Gene expression profiles induced by these NAhRAs were compared to those of the xenobiotic AhR agonists TCDD and benzo[a]pyrene (B[a]P). Over 20 genes were found more than 1.5 times up- or down-regulated by TCDD, and the expression of most of these genes was modulated in the same direction and to a similar extent by B[a]P and the NAhRAs. Results were confirmed by RT-PCR, and many of these genes may be involved in dioxin-related toxic effects. In conclusion, this in vitro study showed similar effects induced by NAhRAs, TCDD and B[a]P at the transcriptome level in a human intestinal cell line.
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- 2008
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9. [Relationship between the composition of fine dust particles in the air and lung function in school children].
- Author
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van Schayck CP, Hogervorst JG, de Kok TM, Briedé JJ, Wesseling G, and Kleinjans JC
- Abstract
Objective: To determine whether or not there is a relationship between the lung function of school children and the ability of fine dust particles in the air to generate radicals., Design: Descriptive., Method: Six primary schools in locations with different traffic volumes were selected in Maastricht, the Netherlands. Air samples were taken in these schools over a period of 4 days; the concentration of fine dust was measured in the 6 pooled samples. Lung function tests were performed in children in the age of 8-13 and their parents filled out a questionnaire on the state of their children's health., Results: An average of 66% of the children (184 girls and 158 boys, with an average age of 10 years (range: 8-13 years)) participated. The average FEV1 for the children from the 6 schools was not related with the total amount of fine dust particles in the air. However, a lower average FEV1 was associated with a higher radical-generating capacity in the air samples. No direct association was observed between the radical-generating capacity of the dust and the traffic intensity., Conclusion: There was a clear relationship between lung function and the radical-generating capacity of fine dust in the air. On the basis of these findings future guidelines could be based on chemical properties of the fine dust particles and not exclusively on the quantity of fine dust.
- Published
- 2006
10. Radicals in the church.
- Author
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de Kok TM, Hogervorst JG, Kleinjans JC, and Briedé JJ
- Subjects
- Humans, Netherlands, Particle Size, Religion, Air Pollution, Indoor analysis, Fires, Free Radicals analysis
- Published
- 2004
- Full Text
- View/download PDF
11. Effects of polyunsaturated fatty acids on prostaglandin synthesis and cyclooxygenase-mediated DNA adduct formation by heterocyclic aromatic amines in human adenocarcinoma colon cells.
- Author
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Moonen HJ, Dommels YE, van Zwam M, van Herwijnen MH, Kleinjans JC, Alink GM, and de Kok TM
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- Adenocarcinoma enzymology, Cell Survival drug effects, Colonic Neoplasms enzymology, Cytochrome P-450 CYP1A2 metabolism, Cytochrome P-450 CYP1A2 Inhibitors, Enzyme Inhibitors pharmacology, Humans, Linoleic Acid metabolism, Tumor Cells, Cultured, Adenocarcinoma pathology, Amines pharmacology, Colonic Neoplasms pathology, DNA Adducts metabolism, Dinoprostone metabolism, Fatty Acids, Unsaturated pharmacology, Heterocyclic Compounds pharmacology, Prostaglandin-Endoperoxide Synthases metabolism
- Abstract
Dietary heterocyclic aromatic amines (HCA) and polyunsaturated fatty acids (PUFA) are both believed to play a role in colon carcinogenesis, and are both substrate for the enzyme cyclooxygenase (COX). In HCA-7 cells, highly expressing isoform COX-2, we investigated the effects of PUFA on prostaglandin synthesis and DNA adduct formation by the HCA 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) and 2-amino-3-methylimidazo[4,5-f]quinoline (IQ). Furthermore, we studied the role of COX, COX-2 in particular, and cytochrome P4501A2 (CYP1A2) by using the enzyme inhibitors indomethacin (IM), NS-398, and phenethyl isothiocyanate (PEITC), respectively. COX-mediated formation of prostaglandin E2 (PGE2) from linoleic acid (LA) showed that HCA-7 cells can convert LA into arachidonic acid (AA). Alternatively, eicosapentaenoic acid (EPA) was found to compete with AA for COX. Strongly decreased PGE2 levels by addition of IM demonstrated involvement of COX in PUFA metabolism. Both IM and NS-398 inhibited adduct formation by HCA to nearly the same extent, indicating involvement of COX-2 rather than COX-1, while CYP1A2 activity in HCA-7 cells was demonstrated by addition of PEITC. Overall, inhibiting effects were stronger for PhIP than for IQ. HCA-DNA adduct formation was stimulated by addition of PUFA, although high PUFA concentrations partly reduced this stimulating effect. Finally, similar effects for n-3 and n-6 fatty acids suggested that adduct formation may not be the crucial mechanism behind the differential effects of PUFA on colon carcinogenesis that have been described. These results show that COX, and COX-2 in particular, can play a substantial role in HCA activation, especially in extrahepatic tissues like the colon. Furthermore, the obvious interactions between PUFA and HCA in COX-2 expressing cancer cells may be important in modulating colorectal cancer risk., (Copyright 2004 Wiley-Liss, Inc.)
- Published
- 2004
- Full Text
- View/download PDF
12. Analysis of oxidative DNA damage after human dietary supplementation with linoleic acid.
- Author
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de Kok TM, Zwingman I, Moonen EJ, Schilderman PA, Rhijnsburger E, Haenen GR, and Kleinjans JC
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- Adult, Analysis of Variance, Dietary Supplements, Dose-Response Relationship, Drug, Female, Humans, Linoleic Acid blood, Linoleic Acid pharmacokinetics, Linoleic Acid toxicity, Malondialdehyde blood, Oxidation-Reduction, Palmitic Acid administration & dosage, Reactive Oxygen Species, Vitamin A blood, alpha-Tocopherol blood, beta Carotene blood, Antioxidants metabolism, DNA Damage drug effects, Linoleic Acid administration & dosage, Lipid Peroxidation, Lymphocytes metabolism
- Abstract
It has been hypothesized that oxygen radicals generated by peroxidation of dietary linoleic acid may induce genetic damage and thereby increase cancer risk. We examined the effect of dietary supplementation with linoleic acid on the levels of oxidative DNA damage in peripheral lymphocytes and on the blood plasma antioxidant potential. Thirty volunteers received during 6 weeks either a high dose of linoleic acid (15 g/day), an intermediate dose of linoleic acid (7.5 g/day) or an isocaloric supplement without linoleic acid (15 g palmitic acid/day). After the intervention, no significant increase in oxidative DNA damage, measured as relative amounts of 7,8-dihydro-8-oxo-2'-deoxyguanosine (8-oxodG) in DNA from peripheral lymphocytes, was observed in both high and intermediate linoleic acid-supplemented groups (increase of respectively 13 and 21%; P>0.05). Also, the differences between levels of oxidative DNA damage in the high or intermediate linoleic acid-supplemented group and the control group receiving palmitic acid (23% decrease) were not significant. Furthermore, no statistically significant differences were found between the total antioxidant capacities of blood plasma from the different experimental groups. Plasma levels of malondialdehyde, an important end-product of lipid peroxidation, were not increased after supplementation, nor were effects found on the plasma concentrations of retinol, alpha-tocopherol and beta-carotene. Despite the experimental design that excludes several forms of bias introduced in studies based on modulation of dietary composition, our results provide no indication of increased oxidative stress or genetic damage as a result of increased dietary intake of linoleic acid. Therefore, we see no scientific basis to reconsider the public health policy to stimulate the intake of polyunsaturated fatty acids aimed at the reduction of coronary heart diseases.
- Published
- 2003
- Full Text
- View/download PDF
13. Methodologies for bulky DNA adduct analysis and biomonitoring of environmental and occupational exposures.
- Author
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de Kok TM, Moonen HJ, van Delft J, and van Schooten FJ
- Subjects
- Humans, DNA Adducts analysis, Environmental Exposure, Occupational Exposure
- Abstract
It is undisputed that DNA adduct formation is one of the key processes in early carcinogenesis. Therefore, analysis of DNA adduct levels may be one of the best tools available to characterize exposure to complex mixtures of genotoxic chemicals as occurring in different environmental and occupational exposure settings. However, from an analytical point of view the detection and quantification of DNA adducts is a challenging enterprise as extremely high sensitivity and selectivity are required. The entire spectrum of chromatographic techniques, including thin-layer chromatography (TLC), gas and liquid chromatography as well as capillary electrophoresis has been used in combination with different detection systems, all with their own specific characteristics. Among the various combinations of techniques, the TLC-(32)P-postlabeling combination appears to meet best with criteria of sensitivity and requirements of minimal amounts of material. Recent developments in the application of capillary electrophoresis in combination with either immunochemical or mass spectrometric detection techniques may offer new and promising approaches, with higher selectivity as compared to TLC-(32)P postlabeling. The applicability of these new techniques in biomonitoring studies aiming at the exposure and risk assessment of low and chronic exposures remains to be determined. In this paper we compare and discuss the advantages and limitations of different techniques used in DNA adduct analysis, with specific emphasis on those adducts formed by the polycyclic aromatic hydrocarbons and heterocyclic aromatic amines., (Copyright 2002 Elsevier Science B.V.)
- Published
- 2002
- Full Text
- View/download PDF
14. A molecular dosimetry approach to assess human exposure to environmental tobacco smoke in pubs.
- Author
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Besaratinia A, Maas LM, Brouwer EM, Moonen EJ, De Kok TM, Wesseling GJ, Loft S, Kleinjans JC, and Van Schooten FJ
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- Adult, Air Pollutants analysis, Biomarkers blood, Chromatography, Gas, Cotinine blood, Female, Humans, Male, Nicotine blood, Polycyclic Aromatic Hydrocarbons analysis, Sputum cytology, Surveys and Questionnaires, DNA Adducts analysis, DNA Damage drug effects, Environmental Exposure analysis, Environmental Monitoring methods, Lymphocytes drug effects, Tobacco Smoke Pollution adverse effects
- Abstract
Although the involvement of environmental tobacco smoke (ETS) in human lung cancer is no longer a matter of dispute, the magnitude of its impact still is. This is mainly due to the inefficiency of methodology to assess exposure to ETS especially in public places. Setting a real life exposure condition (3 h stay in local pubs) and using a matched-control study design, we quantified smoke-related DNA adducts in induced sputum and peripheral blood lymphocytes (PBL) of healthy non-smokers (n = 15) before and after a single pub visit by means of the (32)P-post-labeling assay. For verification, we also measured a spectrum of polycyclic aromatic hydrocarbons (PAH) in the ambient air of the pubs by personal air monitors, and determined the plasma concentrations of nicotine and cotinine by gas chromatography/mass spectrometry. The ambient air concentrations of all PAH were several orders of magnitude higher than those already reported for other indoor environments. The plasma concentrations of both nicotine and cotinine increased significantly after the pub visit (P = 0.001 and P = 0.0007, respectively). Accordingly, the overall DNA adduct profile in induced sputum, but not in PBL, changed quantitatively and qualitatively after the pub visit. Of most significance was the formation of a distinct DNA adduct in induced sputum of three individuals consequent to ETS exposure. This adduct co-migrated with the standard (+/-)-anti-benzo[a]pyrene diol epoxide-DNA adduct, which is known to form at lung cancer mutational hotspots. We conclude that real life exposure to ETS can give rise to pro-mutagenic lesions in the lower airway, and this can be best investigated in a relevant surrogate matrix such as induced sputum.
- Published
- 2002
- Full Text
- View/download PDF
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