Spontaneous DNA repair increases during hemodialysis

Background: Hemodialysis (HD) patients are subjected to increased oxidative stress. Oxidative stress causes DNA damage, which may be repaired by a DNA repair system. 'Spontaneous DNA repair' expresses DNA repair of in vitro unstimulated cells. The aim of the study was to evaluate the effect of one HD session on spontaneous DNA repair in peripheral blood mononuclear cells (PBMC). Methods: PBMC were separated from blood samples for the determination of spontaneous DNA repair, measured by ³H-thymidine incorporation, before and immediately after one HD session. Percent double-stranded DNA (ds-DNA) was measured by the fluorometric assay of DNA unwinding (FADU). Results: DNA repair increased significantly following HD. To examine if this increase was caused by newly produced DNA damage, we studied the effect of HD on percent ds-DNA in PBMC. HD significantly reduced percent ds-DNA, indicating increased DNA breakage. By repeating FADU in the presence of formamidopyrimidine-DNA glycosylase (Fpg), which nicks DNA at oxidized purine sites, we could show that the increased DNA damage was caused by oxidation. Conclusion: Spontaneous DNA repair increases during HD in response to an increase in DNA damage induced by oxidative stress.