Limited repair of 8-hydroxy-7,8-dihydroguanine residues in human testicular cells.
Oxidative damage in testicular DNA is associated with poor semen quality, reduced fertility and increased risk of stillbirths and birth defects. These DNA lesions are predominantly removed by base excision repair. Cellular extracts from human and rat testicular cells and three enriched populations of rat male germ cells (primary spermatocytes, round spermatids and elongating/elongated spermatids) all showed proficient excision/incision of 5-hydroxycytosine, thymine glycol and 2,6-diamino-4-hydroxy-5-formamidopyrimidine. DNA containing 8-oxo-7,8-dihydroguanine was excised poorly by human testicular cell extracts, although 8-oxoguanine-DNA glycosylase-1 (hOGG1) was present in human testicular cells, at levels that varied markedly between 13 individuals. This excision was as low as with human mononuclear blood cell extracts. The level of endonuclease III homologue-1 (NTH1), which excises oxidised pyrimidines, was higher in testicular than in somatic cells of both species. Cellular repair studies of lesions recognised by formamidopyrimidine-DNA glycosylase (Fpg) or endonuclease III (Nth) were assayed with alkaline elution and the Comet assay. Consistent with the enzymatic activities, human testicular cells showed poor removal of Fpg-sensitive lesions but efficient repair of Nth-sensitive lesions. Rat testicular cells efficiently repaired both Fpg- and Nth-sensitive lesions. In conclusion, human testicular cells have limited capacity to repair important oxidative DNA lesions, which could lead to impaired reproduction and de novo mutations.
Olsen
Ann-Karin
AK
Department of Chemical Toxicology, Division of Environmental Medicine, Norwegian Institute of Public Health, PO Box 4404 Nydalen, N-0403 Oslo, Norway.
Duale
Nur
N
Bjørås
Magnar
M
Larsen
Cathrine T
CT
Wiger
Richard
R
Holme
Jørn A
JA
Seeberg
Erling C
EC
Brunborg
Gunnar
G
D000293:Adolescent; D000328:Adult; D000368:Aged; D000818:Animals; D002457:Cell Extracts / Q000737:chemistry / Q000494:pharmacology; D003596:Cytosine / Q000031:analogs & derivatives* / Q000378:metabolism; D004260:DNA Repair; D043382:DNA-Formamidopyrimidine Glycosylase; D043224:Deoxyribonuclease (Pyrimidine Dimer); D004706:Endodeoxyribonucleases / Q000378:metabolism; D029968:Escherichia coli Proteins; D006151:Guanosine / Q000031:analogs & derivatives* / Q000378:metabolism*; D006801:Humans; D007963:Leukocytes, Mononuclear / Q000187:drug effects / Q000378:metabolism / Q000528:radiation effects; D008297:Male; D008875:Middle Aged; D009699:N-Glycosyl Hydrolases / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D013737:Testis / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*
D002457:Cell Extracts; D029968:Escherichia coli Proteins; D006151:Guanosine; C046215:8-hydroxyguanosine; C017400:5-hydroxycytosine; D003596:Cytosine; D004706:Endodeoxyribonucleases; D043224:Deoxyribonuclease (Pyrimidine Dimer); C106403:NTH protein, E coli; C468347:NTHL1 protein, human; D009699:N-Glycosyl Hydrolases; D043382:DNA-Formamidopyrimidine Glycosylase