Assessment of human DNA repair (NER) capacity with DNA repair rate (DRR) by comet assay.
OBJECTIVE
Alkaline comet assay was used to evaluate DNA repair (nucleotide excision repair, NER) capacity of human fresh lymphocytes from 12 young healthy non-smokers (6 males and 6 females).


METHODS
Lymphocytes were exposed to UV-C (254 nm) at the dose rate of 1.5 J/m2/sec. Novobiocin (NOV) and aphidicolin (APC), DNA repair inhibitors, were utilized to imitate the deficiency of DNA repair capacity at the incision and ligation steps of NER. Lymphocytes from each donor were divided into three grougs: UVC group, UVC plus NOV group, and UVC plus APC group. DNA single strand breaks were detected in UVC irradiated cells incubated for 0, 30, 60, 90, 120, 180, and 240 min after UVC irradiation. DNA repair rate (DRR) served as an indicator of DNA repair capacity.


RESULTS
The results indicated that the maximum DNA damage (i.e. maximum tail length) in the UVC group mainly appeared at 90 min. The ranges of DRRs in the UVC group were 62.84%-98.71%. Average DRR value was 81.84%. The DRR difference between males and females was not significant (P < 0.05). However, the average DRR value in the UVC plus NOV group and the UVC plus APC group was 52.98% and 39.57% respectively, which were significantly lower than that in the UVC group (P < 0.01).


CONCLUSIONS
The comet assay is a rapid, simple and sensitive screening test to assess individual DNA repair (NER) capacity. It is suggested that the time to detect DNA single strand breaks in comet assay should include 0 (before UV irradiation), 90 and 240 min after exposure to 1.5 J x m(-2) UVC at least. The DRR, as an indicator, can represent the individual DNA repair capacity in comet assay.
Institute of Occupational and Environmental Health, Medical College of Zhejiang University, Hangzhou 310006, Zhejiang, China.
Wei
W
Zheng
Ji-Liang
JL
He
Li-Fen
LF
Jin
Jian-Lin
JL
Lou
Bao-Hong
BH
Wang
D000328:Adult; D016590:Aphidicolin / Q000494:pharmacology; D020552:Comet Assay / Q000379:methods; D004249:DNA Damage / Q000187:drug effects / Q000528:radiation effects*; D004260:DNA Repair / Q000187:drug effects / Q000235:genetics / Q000528:radiation effects*; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D005260:Female; D006801:Humans; D008214:Lymphocytes / Q000187:drug effects / Q000378:metabolism / Q000528:radiation effects*; D008297:Male; D009675:Novobiocin / Q000494:pharmacology; D018570:Risk Assessment; D013997:Time Factors; D014466:Ultraviolet Rays / Q000009:adverse effects*
D004791:Enzyme Inhibitors; D009675:Novobiocin; D016590:Aphidicolin