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Biomarkers for DNA damage in human biomonitoring
Stockholm University, Faculty of Science, Department of Genetics, Microbiology and Toxicology. (genetisk toxikologi)
2010 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Genomic DNA in humans is constantly exposed to different kinds of damage. Therefore, it is desirable to implement methods for detecting and measuring of inflicted body burden. Human biomonitoring (HBM) can here be a useful tool as a link between environmental exposure and disease outcome. The present thesis aims to monitor DNA damage in humans by studies on: 1) urinary thymidine dimer (T=T) as a novel biomarker (BM) of human exposure to UV-light; 2) enumeration of variants in HPRT gene in human peripheral blood lymphocytes by developing a sensitive flow cytometric (FCM) analysis; 3) the impact of dietary habits on genomic stability in vegetarians and omnivores in terms of micronuclei (MN) induction detected by FCM. Urinary T=T was quantified by a 32P-postlabeling technique, the kinetics of T=T excretion was studied and the method was validated by delivering controlled UV-doses. The major conclusion was that the amount of urinary T=T was determined by the UV dose, and hence T=T can be used as a BM of UV exposure. Moreover, a new approach for rapid and sensitive enumeration of HPRT-variants by FCM was developed. The obtained HPRT-frequencies were comparable to those previously published by others. Finally, the FCM assay for MN enumeration was applied to study effects of dietary habits in vegetarians and omnivores. The main finding was that vegetarians had significantly lower MN frequencies compared to omnivores. In summary, the applied BMs and respective methods have high sensitivity and/or throughput possibility which are important factors considered in HBM.

 

Place, publisher, year, edition, pages
Stockholm: Department of Genetics, Microbiology and Toxicology, Stockholm University , 2010. , 55 p.
Keyword [en]
biomonitoring, biomarkers, DNA damage, cancer, diet, UV-light
Research subject
Molecular Genetics
Identifiers
URN: urn:nbn:se:su:diva-45910ISBN: 978-91-7447-183-0 (print)OAI: oai:DiVA.org:su-45910DiVA: diva2:370314
Public defence
2010-12-17, sal E306, Arrheniuslaboratorierna, Svante Arrhenius väg 20C, Stockholm, 14:00 (English)
Opponent
Supervisors
Note
At the time of the doctoral defense, the following paper was unpublished and had a status as follows: Paper 3: Manscript.Available from: 2010-11-25 Created: 2010-11-16 Last updated: 2010-11-16Bibliographically approved
List of papers
1. Flow cytometric determination of HPRT-variantsin human peripheral blood lymphocytes
Open this publication in new window or tab >>Flow cytometric determination of HPRT-variantsin human peripheral blood lymphocytes
2002 (English)In: Mutation research, ISSN 0027-5107, E-ISSN 1873-135X, Vol. 499, no 1, 63-71 p.Article in journal (Refereed) Published
Abstract [en]

Hypoxanthine guanine phosphoribosyl transferase (HPRT) deficient human peripheral blood lymphocytes are usually enumerated either by the cloning assay or by the autoradiographic short-term assay. The short-term approach presented here is based on flow cytometric (FCM) scoring of 6-thioguanine (6-TG) resistant lymphocytes. HPRT-variants are enumerated on the basis of both DNA synthesis (by use of immunofluorescent detection of incorporated 5-bromo-2-deoxyuridine, BrdU) and total DNA content (by propidium iodide (PI) incorporation) of proliferating cells, i.e. the cells must both be labelled with BrdU and reside in late-S or G(2) phase in order to be scored as a HPRT-variant. This approach is combined with a stringent discrimination of false-positive events, minimising occurrence of phenocopies or other non-specifically labelled cells that might falsely be scored as true HPRT-variants. The HPRT-variant frequency (V-f) found by the presented method varied between 0.8 x 10(-5) and 5.8 x 10(-5) for healthy male and female donors aged between 20 and 74 years. There was no significant gender difference in V-f. A strong linear correlation was found between HPRT-variant frequency and age, showing an increase of 0.56 x 10(-6) per year of age (r(2) = 0.62, P < 0.001). The frequencies of false-positive events found showed a mean of 0.22 x 10(-5) in comparison with a pooled mean V-f of 2.87 x 10(-5). There was no significant age effect on the frequency of false events (r(2) = = 0.15, P < 0.095). The method presented here may provide a rapid and sensitive alternative to the autoradiographic technique for the short-term enumeration of HPRT-variants.

Keyword
HPRT; human lymphocyte; 5-bromo-2-deoxyuridine; flow cytometry; biomonitoring
National Category
Microbiology
Identifiers
urn:nbn:se:su:diva-45905 (URN)
Available from: 2010-11-16 Created: 2010-11-16 Last updated: 2017-12-12Bibliographically approved
2. Urinary Thymidine Dimer as a Marker of Total BodyBurden of UV-Inflicted DNA Damage in Humans
Open this publication in new window or tab >>Urinary Thymidine Dimer as a Marker of Total BodyBurden of UV-Inflicted DNA Damage in Humans
2005 (English)In: Cancer Epidemiology, Biomarkers and Prevention, ISSN 1055-9965, E-ISSN 1538-7755, Vol. 14, no 12, 2868-2872 p.Article in journal (Refereed) Published
Abstract [en]

High levels of DNA damage are induced in human skin following exposure to UV radiation. Cyclobutane thymidine dimer (T = T) is the most common of these lesions, which are enzymatically removed as oligonucleotides from DNA and further degraded before excretion in urine. Analysis of such repair products in the urine could serve as a biomarker of total body burden of UV exposure. The aim of this study was to examine the kinetics of T = T excretion following a single tanning session in a commercial solarium and to validate the method by delivering different doses. Ten individuals used the solarium for a total of 35 sessions of body tanning. Urine was collected before UV exposure and daily thereafter (up to 5 or 11 days) and T = T was analyzed using a very sensitive and quantitative P-32-postlabeling technique combined with high-performance liquid chromatography. Following exposure, T = T levels increased dramatically and reached a peak 3 days later; afterwards, the T = T levels gradually decreased. The total amount of T = T excreted differed about 5-fold among subjects given an equal dose. A 50% excretion time was calculated using the excretion data for the first 5 days and it was found to be between 55 and 76 hours for different individuals. There was a good correlation between the amount of T = T excreted during days 1 to 5 and the delivered UV dose. Reducing exposure time to 50% lowered the amount of T = T to 47%; if half of the lamps were covered, T = T decreased to 44%. Our data show that urinary T = T could be a suitable noninvasive biomarker for UV exposure; a finding which could also be applicable to studies in children.

Keyword
CYCLOBUTANE PYRIMIDINE DIMERS; THYMINE DIMERS; SKIN-CANCER; REPAIR; 8-OXO-2'-DEOXYGUANOSINE; SUNLIGHT; SUN
National Category
Natural Sciences
Identifiers
urn:nbn:se:su:diva-45906 (URN)10.1158/1055-9965.EPI-05-0164 (DOI)
Available from: 2010-11-16 Created: 2010-11-16 Last updated: 2017-12-12Bibliographically approved
3. Vegetarians exhibit a low level of genomic instability
Open this publication in new window or tab >>Vegetarians exhibit a low level of genomic instability
Show others...
(English)Manuscript (preprint) (Other academic)
Identifiers
urn:nbn:se:su:diva-45907 (URN)
Available from: 2010-11-16 Created: 2010-11-16 Last updated: 2010-11-16Bibliographically approved

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