title: Up-regulation of 8-oxo-dGTPase activity of MTH1 protein in the brain, testes and kidneys of mice exposed to (137)Cs gamma radiation.
abstract: Abstract Mammalian MTH1 protein is an antimutagenic (2'-deoxy)ribonucleoside 5'-triphosphate pyrophosphohydrolase that prevents the incorporation of oxidatively modified nucleotides into nucleic acids. It decomposes most specifically the miscoding products of oxidative damage to purine nucleic acid precursors (e.g. 8-oxo-dGTP, 2-oxo-dATP, 2-oxo-ATP, 8-oxo-GTP) that may cause point mutations or transcription errors when incorporated into DNA and RNA, respectively. The increased expression of MTH1 mRNA and MTH1 protein was previously proposed as a molecular marker of oxidative stress. Therefore, we hypothesized that increased 8-oxo-dGTPase activity of MTH1 protein in mouse organs could serve as a dose-dependent marker of exposure to ionizing radiation, which is known to induce oxidative stress. To test our hypothesis, we measured 8-oxo-dGTPase activity in six organs of male BL6 mice after exposure to 0, 10, 25 and 50 cGy and 1 Gy of (137)Cs gamma radiation given as a single whole-body dose (1 Gy/min). The mice were killed 4, 8 and 24 h after irradiation. A statistically significant induction of 8-oxo-dGTPase was found in brains, testes and kidneys but not in lungs, hearts or livers. Brains, which demonstrated the highest (4.3-fold) increase of 8-oxo-dGTPase activity, were shown to express approximately 50% higher levels of MTH1 protein. However, due to the lack of a simple positive correlation between the dose and the observed 8-oxo-dGTPase activity in brain, testes and kidneys, we conclude that measurements of 8-oxo-dGTPase activity in these organs may serve as a rough indicator rather than a quantifiable marker of radiation-induced oxidative stress.
authors.affiliation: Department of Clinical Biochemistry, Collegium Medicum, Nicolaus Copernicus University, 85-092 Bydgoszcz, Poland. karolb@cm.umk.pl
authors.forename: Karol
authors.initials: K
authors.lastname: Bialkowski
authors.forename: Anna
authors.initials: A
authors.lastname: Szpila
authors.forename: Kazimierz S
authors.initials: KS
authors.lastname: Kasprzak
mesh_terms: D000818:Animals; D001921:Brain / Q000201:enzymology* / Q000528:radiation effects; D002588:Cesium Radioisotopes; D045643:DNA Repair Enzymes / Q000378:metabolism*; D004789:Enzyme Activation / Q000528:radiation effects; D005720:Gamma Rays; D015971:Gene Expression Regulation, Enzymologic / Q000502:physiology / Q000528:radiation effects; D020450:Heavy Ions; D007668:Kidney / Q000201:enzymology* / Q000528:radiation effects; D008297:Male; D008657:Metabolic Clearance Rate / Q000528:radiation effects; D051379:Mice; D008810:Mice, Inbred C57BL; D009928:Organ Specificity / Q000528:radiation effects; D010744:Phosphoric Monoester Hydrolases / Q000378:metabolism*; D013737:Testis / Q000201:enzymology* / Q000528:radiation effects; D014018:Tissue Distribution / Q000187:drug effects; D015854:Up-Regulation / Q000187:drug effects; D014916:Whole-Body Irradiation
chemical_list: D002588:Cesium Radioisotopes; D010744:Phosphoric Monoester Hydrolases; C078207:8-oxodGTPase; C509779:Nudt1 protein, mouse; D045643:DNA Repair Enzymes