TY - JOUR
T1 - Nucleotide excision repair of oxidised genomic DNA is not a source of urinary 8-oxo-7,8-dihydro-2′-deoxyguanosine
AU - Evans, Mark D.
AU - Mistry, Vilas
AU - Singh, Rajinder
AU - Gackowski, Daniel
AU - Różalski, Rafał
AU - Siomek-Gorecka, Agnieszka
AU - Phillips, David H.
AU - Zuo, Jie
AU - Mullenders, Leon
AU - Pines, Alex
AU - Nakabeppu, Yusaku
AU - Sakumi, Kunihiko
AU - Sekiguchi, Mutsuo
AU - Tsuzuki, Teruhisa
AU - Bignami, Margherita
AU - Oliński, Ryszard
AU - Cooke, Marcus S.
N1 - Funding Information:
This project was supported, in part, by ECNIS (Environmental Cancer Risk, Nutrition and Individual Susceptibility), a network of excellence operating within the European Union 6th Framework Program, Priority 5: “Food Quality and Safety” (Contract no. 513943 ). The following authors were members of ECNIS: MDE, MSC, VM, RS, DG, RR, AS, DHP, PBF, RO.
Publisher Copyright:
© 2016 Elsevier Inc.
PY - 2016/10/1
Y1 - 2016/10/1
N2 - Urinary 8-oxo-7,8-dihydro-2′-deoxyguanosine (8-oxodGuo) is a widely measured biomarker of oxidative stress. It has been commonly assumed to be a product of DNA repair, and therefore reflective of DNA oxidation. However, the source of urinary 8-oxodGuo is not understood, although potential confounding contributions from cell turnover and diet have been ruled out. Clearly it is critical to understand the precise biological origins of this important biomarker, so that the target molecule that is oxidised can be identified, and the significance of its excretion can be interpreted fully. In the present study we aimed to assess the contributions of nucleotide excision repair (NER), by both the global genome NER (GG-NER) and transcription-coupled NER (TC-NER) pathways, and sanitisation of the dGTP pool (e.g. via the activity of the MTH1 protein), on the production of 8-oxodGuo, using selected genetically-modified mice. In xeroderma pigmentosum A (XPA) mice, in which GG-NER and TC-NER are both defective, the urinary 8-oxodGuo data were unequivocal in ruling out a contribution from NER. In line with the XPA data, the production of urinary 8-oxodGuo was not affected in the xeroderma pigmentosum C mice, specifically excluding a role of the GG-NER pathway. The bulk of the literature supports the mechanism that the NER proteins are responsible for removing damage to the transcribed strand of DNA via TC-NER, and on this basis we also examined Cockayne Syndrome mice, which have a functional loss of TC-NER. These mice showed no difference in urinary 8-oxodGuo excretion, compared to wild type, demonstrating that TC-NER does not contribute to urinary 8-oxodGuo levels. These findings call into question whether genomic DNA is the primary source of urinary 8-oxodGuo, which would largely exclude it as a biomarker of DNA oxidation. The urinary 8-oxodGuo levels from the MTH1 mice (both knock-out and hMTH1-Tg) were not significantly different to the wild-type mice. We suggest that these findings are due to redundancy in the process, and that other enzymes substitute for the lack of MTH1, however the present study cannot determine whether or not the 2′-deoxyribonucleotide pool is the source of urinary 8-oxodGuo. On the basis of the above, urinary 8-oxodGuo is most accurately defined as a non-invasive biomarker of oxidative stress, derived from oxidatively generated damage to 2′-deoxyguanosine.
AB - Urinary 8-oxo-7,8-dihydro-2′-deoxyguanosine (8-oxodGuo) is a widely measured biomarker of oxidative stress. It has been commonly assumed to be a product of DNA repair, and therefore reflective of DNA oxidation. However, the source of urinary 8-oxodGuo is not understood, although potential confounding contributions from cell turnover and diet have been ruled out. Clearly it is critical to understand the precise biological origins of this important biomarker, so that the target molecule that is oxidised can be identified, and the significance of its excretion can be interpreted fully. In the present study we aimed to assess the contributions of nucleotide excision repair (NER), by both the global genome NER (GG-NER) and transcription-coupled NER (TC-NER) pathways, and sanitisation of the dGTP pool (e.g. via the activity of the MTH1 protein), on the production of 8-oxodGuo, using selected genetically-modified mice. In xeroderma pigmentosum A (XPA) mice, in which GG-NER and TC-NER are both defective, the urinary 8-oxodGuo data were unequivocal in ruling out a contribution from NER. In line with the XPA data, the production of urinary 8-oxodGuo was not affected in the xeroderma pigmentosum C mice, specifically excluding a role of the GG-NER pathway. The bulk of the literature supports the mechanism that the NER proteins are responsible for removing damage to the transcribed strand of DNA via TC-NER, and on this basis we also examined Cockayne Syndrome mice, which have a functional loss of TC-NER. These mice showed no difference in urinary 8-oxodGuo excretion, compared to wild type, demonstrating that TC-NER does not contribute to urinary 8-oxodGuo levels. These findings call into question whether genomic DNA is the primary source of urinary 8-oxodGuo, which would largely exclude it as a biomarker of DNA oxidation. The urinary 8-oxodGuo levels from the MTH1 mice (both knock-out and hMTH1-Tg) were not significantly different to the wild-type mice. We suggest that these findings are due to redundancy in the process, and that other enzymes substitute for the lack of MTH1, however the present study cannot determine whether or not the 2′-deoxyribonucleotide pool is the source of urinary 8-oxodGuo. On the basis of the above, urinary 8-oxodGuo is most accurately defined as a non-invasive biomarker of oxidative stress, derived from oxidatively generated damage to 2′-deoxyguanosine.
UR - http://www.scopus.com/inward/record.url?scp=84985993956&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=84985993956&partnerID=8YFLogxK
U2 - 10.1016/j.freeradbiomed.2016.08.018
DO - 10.1016/j.freeradbiomed.2016.08.018
M3 - Article
C2 - 27585947
AN - SCOPUS:84985993956
VL - 99
SP - 385
EP - 391
JO - Free Radical Biology and Medicine
JF - Free Radical Biology and Medicine
SN - 0891-5849
ER -