7,8-Dihydro-8-oxo-2'-deoxyguanosine; 7,8-Dihydro-8-oxodeoxyguanosine; 8-Hydroxy-2'-deoxyguanosine; 8-Hydroxydeoxyguanosine; 8-Oxo-2'-deoxyguanosine; 8-Oxo-7,8-dihydro-2'-deoxyguanosine; 8-Oxo-7,8-dihydrodeoxyguanosine; 8-Oxo-dG; 8-OH-dG
3D model (JSmol)
|Molar mass||283.24 g/mol|
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
|what is ?)(|
8-Oxo-2'-deoxyguanosine (8-oxo-dG) is an oxidized derivative of deoxyguanosine. 8-Oxo-dG is one of the major products of DNA oxidation. Concentrations of 8-oxo-dG within a cell are a measurement of oxidative stress.
8-oxo-dG in DNA
Steady-state levels of DNA damages represent the balance between formation and repair. Swenberg et al. measured average frequencies of steady state endogenous DNA damages in mammalian cells. The most frequent oxidative DNA damage normally present in DNA is 8-oxo-dG, occurring at an average frequency of 2,400 per cell.
When 8-oxo-dG is induced by a DNA damaging agent it is rapidly repaired. For example, 8-oxo-dG was increased 10-fold in the livers of mice subjected to ionizing radiation, but the excess 8-oxo-dG was rapidly removed with a half-life of 11 minutes.
As reviewed by Valavanidis et al. increased levels of 8-oxo-dG in a tissue can serve as a biomarker of oxidative stress. They also noted that increased levels of 8-oxo-dG are frequently found during carcinogenesis.
In the figure shown in this section, the colonic epithelium from a mouse on a normal diet has a low level of 8-oxo-dG in its colonic crypts (panel A). However, a mouse likely undergoing colonic tumorigenesis (due to deoxycholate added to its diet) has a high level of 8-oxo-dG in its colonic epithelium (panel B). Deoxycholate increases intracellular production of reactive oxygen resulting in increased oxidative stress, and this leads to tumorigenesis and carcinogenesis. Of 22 mice fed the diet supplemented with deoxycholate, 20 (91%) developed colonic tumors after 10 months on the diet, and the tumors in 10 of these mice (45% of mice) included an adenocarcinoma (cancer).
8-oxo-dG in aging
8-oxo-dG increases with age in DNA of mammalian tissues. 8-oxo-dG increases in both mitochonndrial DNA and nuclear DNA with age. Fraga et al. estimated that in rat kidney, for every 54 residues of 8-oxo-dG repaired, one residue remaines unrepaired. (See also DNA damage theory of aging.)
8-oxo-dG in carcinogenesis
Valavanidis et al. pointed out that oxidative DNA damage, such as 8-oxo-dG, likely contributes to carcinogenesis by two mechanisms. The first mechanism involves modulation of gene expression, whereas the second is through the induction of mutations.
Epigenetic alteration, for instance by methylation of CpG islands in a promoter region of a gene, can repress expression of the gene (see DNA methylation). In general, epigenetic alteration can modulate gene expression. As reviewed by Bernstein and Bernstein, the repair of various types of DNA damages can, with low frequency, leave remnants of the different repair processes and thereby cause epigenetic alterations. 8-Oxo-dG is primarily repaired by base excision repair (BER). Li et al. reviewed studies indicating that one or more BER proteins also participate(s) in epigenetic alterations involving DNA methylation, demethylation or reactions coupled to histone modification. Nishida et al. examined 8-oxo-dG levels and also evaluated promoter methylation of 11 tumor suppressor genes (TSGs) in 128 liver biopsy samples. These biopsies were taken from patients with chronic hepatitis C, a condition causing oxidative damages in the liver. Among 5 factors evaluated, only increased levels of 8-oxo-dG was highly correlated with promoter methylation of TSGs (p<0.0001). This promoter methylation could have reduced expression of these tumor suppressor genes and contributed to carcinogenesis.
Yasui et al. examined the fate of 8-oxo-dG when this oxidized derivative of deoxyguanosine was inserted into the thymidine kinase gene in a chromosome within human lymphoblastoid cells in culture. They inserted 8-oxo-dG into about 800 cells, and could detect the products that occurred after the insertion of this altered base, as determined from the clones produced after growth of the cells. 8-Oxo-dG was restored to G in 86% of the clones, probably reflecting accurate base excision repair or translesion synthesis without mutation. G:C to T:A transversions occurred in 5.9% of the clones, single base deletions in 2.1% and G:C to C:G transversions in 1.2%. Together, these more common mutations totaled 9.2% of the 14% of mutations generated at the site of the 8-oxo-dG insertion. Among the other mutations in the 800 clones analyzed, there were also 3 larger deletions, of sizes 6, 33 and 135 base pairs. Thus 8-oxo-dG, if not repaired, can directly cause frequent mutations, some of which may contribute to carcinogenesis.
- Nadja C. de Souza-Pinto; Lars Eide; Barbara A. Hogue; Tanja Thybo; Tinna Stevnsner; Erling Seeberg; Arne Klungland & Vilhelm A. Bohr (July 2001). "Repair of 8-Oxodeoxyguanosine Lesions in Mitochondrial DNA Depends on the Oxoguanine DNA Glycosylase (OGG1) Gene and 8-Oxoguanine Accumulates in the Mitochondrial DNA of OGG1-defective Mice". Cancer Research. 61 (14): 5378–5381. PMID 11454679.
- Prasad AR, Prasad S, Nguyen H, Facista A, Lewis C, Zaitlin B, Bernstein H, Bernstein C (2014). "Novel diet-related mouse model of colon cancer parallels human colon cancer". World J Gastrointest Oncol. 6 (7): 225–43. PMC . PMID 25024814. doi:10.4251/wjgo.v6.i7.225.
- Swenberg JA, Lu K, Moeller BC, Gao L, Upton PB, Nakamura J, Starr TB. (2011) Endogenous versus exogenous DNA adducts: their role in carcinogenesis, epidemiology, and risk assessment. Toxicol Sci. 120(Suppl 1):S130-45. doi:10.1093/toxsci/kfq371 PMID 21163908
- Hamilton ML, Guo Z, Fuller CD, Van Remmen H, Ward WF, Austad SN, Troyer DA, Thompson I, Richardson A (2001). "A reliable assessment of 8-oxo-2-deoxyguanosine levels in nuclear and mitochondrial DNA using the sodium iodide method to isolate DNA". Nucleic Acids Res. 29 (10): 2117–26. PMC . PMID 11353081. doi:10.1093/nar/29.10.2117.
- Valavanidis A, Vlachogianni T, Fiotakis K, Loridas S (2013). "Pulmonary oxidative stress, inflammation and cancer: respirable particulate matter, fibrous dusts and ozone as major causes of lung carcinogenesis through reactive oxygen species mechanisms". Int J Environ Res Public Health. 10 (9): 3886–907. PMC . PMID 23985773. doi:10.3390/ijerph10093886.
- Tsuei J, Chau T, Mills D, Wan YJ. Bile acid dysregulation, gut dysbiosis, and gastrointestinal cancer. Exp Biol Med (Maywood). 2014 Nov;239(11):1489-504. doi: 10.1177/1535370214538743. PMID 24951470
- Ajouz H, Mukherji D, Shamseddine A. Secondary bile acids: an underrecognized cause of colon cancer. World J Surg Oncol. 2014 May 24;12:164. doi: 10.1186/1477-7819-12-164. Review. PMID 24884764
- Nie B, Gan W, Shi F, Hu GX, Chen LG, Hayakawa H, Sekiguchi M, Cai JP (2013). "Age-dependent accumulation of 8-oxoguanine in the DNA and RNA in various rat tissues". Oxid Med Cell Longev. 2013: 303181. PMC . PMID 23738036. doi:10.1155/2013/303181.
- Hamilton ML, Van Remmen H, Drake JA, Yang H, Guo ZM, Kewitt K, Walter CA, Richardson A (2001). "Does oxidative damage to DNA increase with age?". Proc. Natl. Acad. Sci. U.S.A. 98 (18): 10469–74. PMC . PMID 11517304. doi:10.1073/pnas.171202698.
- Fraga CG, Shigenaga MK, Park JW, Degan P, Ames BN (1990). "Oxidative damage to DNA during aging: 8-hydroxy-2'-deoxyguanosine in rat organ DNA and urine". Proc. Natl. Acad. Sci. U.S.A. 87 (12): 4533–7. PMC . PMID 2352934. doi:10.1073/pnas.87.12.4533.
- Bernstein C, Bernstein H (2015). "Epigenetic reduction of DNA repair in progression to gastrointestinal cancer". World J Gastrointest Oncol. 7 (5): 30–46. PMC . PMID 25987950. doi:10.4251/wjgo.v7.i5.30.
- Scott TL, Rangaswamy S, Wicker CA, Izumi T (2014). "Repair of oxidative DNA damage and cancer: recent progress in DNA base excision repair". Antioxid. Redox Signal. 20 (4): 708–26. PMC . PMID 23901781. doi:10.1089/ars.2013.5529.
- Li J, Braganza A, Sobol RW (2013). "Base excision repair facilitates a functional relationship between Guanine oxidation and histone demethylation". Antioxid. Redox Signal. 18 (18): 2429–43. PMC . PMID 23311711. doi:10.1089/ars.2012.5107.
- Nishida N, Arizumi T, Takita M, Kitai S, Yada N, Hagiwara S, Inoue T, Minami Y, Ueshima K, Sakurai T, Kudo M (2013). "Reactive oxygen species induce epigenetic instability through the formation of 8-hydroxydeoxyguanosine in human hepatocarcinogenesis". Dig Dis. 31 (5-6): 459–66. PMID 24281021. doi:10.1159/000355245.
- Yasui M, Kanemaru Y, Kamoshita N, Suzuki T, Arakawa T, Honma M (2014). "Tracing the fates of site-specifically introduced DNA adducts in the human genome". DNA Repair (Amst.). 15: 11–20. PMID 24559511. doi:10.1016/j.dnarep.2014.01.003.