8-Hydroxy-2′-Deoxyguanosine of leukocyte DNA as a marker of oxidative stress in chronic hemodialysis patients

Abstract

In contrast to proteins and lipids, oxidative damage to DNA has not been well studied in patients undergoing hemodialysis (HD). We hypothesized that phagocytes are activated after blood-membrane contact during HD, and oxidants from metabolic activation can damage leukocyte DNA. To test this hypothesis, the 8-hydroxy-2′-deoxyguanosine (8-OHdG) content of leukocyte DNA was measured by high-performance liquid chromatography electrochemical detection method in 35 age- and sex-matched healthy subjects, 22 undialyzed patients with advanced renal failure, and 109 HD patients to assess the relation between oxidative DNA damage and complement-activating membranes, blood antioxidants, and iron status. Dialysis membranes were classified into complement-activating (cellulose; n = 55) and non–complement-activating (polymethylmethacrylate [PMMA]; n = 35; polysulfone [PS]; n = 19) membranes. We found increased oxidative stress in undialyzed and HD patients based on a decrease in plasma levels of ascorbate and α-tocopherol adjusted for blood lipid (α-tocopherol/lipid), serum albumin, and reduced glutathione levels in whole blood and an increase in oxidized glutathione levels in whole blood compared with controls (P < 0.001). The greatest 8-OHdG level in leukocyte DNA was in HD patients, followed by undialyzed patients and healthy controls (P < 0.001), and was significantly greater in HD patients using cellulose membranes than those using PMMA or PS membranes (P < 0.001). 8-OHdG levels correlated with plasma α-tocopherol/lipid (r = –0.314; P < 0.005), serum iron (r = 0.446; P < 0.001), and transferrin saturation values (r = 0.202; P < 0.05) in the analysis of all HD patients. In a 6-week crossover study, 8-OHdG levels significantly decreased after the switch from cellulose to synthetic membranes for 2 weeks and increased after the shift from synthetic to cellulose membranes (P < 0.05). Iron metabolism indices and plasma α-tocopherol/lipid values did not change significantly in the study period. We conclude that 8-OHdG content in leukocyte DNA is a biomarker of oxidant-induced DNA damage in HD patients. Oxidative DNA damage is a consequence of uremia, further augmented by complement-activating membranes.