Intravenous Iron Exacerbates Oxidative DNA Damage in Peripheral Blood Lymphocytes among Chronic Hemodialysis Patients

• Main Authors: Ko-Lin Kuo, 郭克林
• Other Authors: Der-Cherng Tarng
• Format: Others
• Language: en_US
• Published: 2008
• Online Access: http://ndltd.ncl.edu.tw/handle/72474767334790049070

碩士 === 國立陽明大學 === 臨床醫學研究所 === 96 === Several lines of evidences indicate that oxidative stress frequently occurs in patients undergoing maintenance hemodialysis (HD) due to a decrease of antioxidant defenses and an overproduction of reactive oxygen species (ROS), such as superoxide anion, hydrogen peroxide, hydroxyl radical and hypochlorous acid. Direct measurement of ROS is difficult because of its lower plasma levels and shorter half-life. However, measurement of oxidative byproducts combined with the assessment of antioxidant levels become more feasible. Oxidative damage to cellular constituents, such as membrane lipids, protein and DNA, are fingerprints of oxidative byproducts. Recently, investigators disclosed that 8-hydroxy 2'-deoxyguanosine (8-OHdG) is one of the most abundant oxidative DNA products and a sensitive marker of DNA damage since it can be detected by a high performance liquid chromatography electrochemical detection (HPLC-ECD) method in the femtomole range. Our previous studies have identified peripheral blood leukocytes to be valuable for monitoring 8-OHdG level of cellular DNA in both HD and peritoneal dialysis patients. Accordingly, measurement of 8-OHdG in leukocyte DNA is a useful tool to assess the oxidative DNA damage in chronic dialysis patients. Intravenous (IV) iron therapy is a key component in enhancing the efficacy of erythropoiesis-stimulating agents (ESA) in patients receiving regular dialysis has received increasing attention in recent years. The important reason for IV iron therapy is that it helps to reduce ESA requirements, allows dialysis patients to achieve increased hemoglobin levels, and derives more cost-effectiveness from ESA treatment. However, acute IV administration of high iron doses may provoke the generation of bioactive iron, subsequently enhance oxidative stress with an increase in lipid peroxidation and acute impairment of forearm flow mediated dilatation in healthy individuals. Investigators had disclosed an interrelation among the common carotid artery intima-media thickness, advanced oxidation products of proteins (AOPP) and the annual IV iron dose administered in patients receiving regular HD. It is speculated that chronic repeated IV administration of iron might exaggerate oxidative stress and potentially do much harm to human body. Thereafter, it deserves further appraisal of the potential hazards of enhanced oxidative stress in chronic HD patients receiving maintenance IV iron therapy. Increased concentration of malondialdehyde (MDA), one of the byproducts of the peroxidation of polyunsaturated fatty acids, has been reported in HD patients receiving IV iron therapy. Other investigators further reported increased plasma levels of protein carbonyls and AOPP in chronic HD patients with IV iron supplementation. In contrast to lipid, sugars and proteins, the reactions of DNA with oxidants associated with IV iron therapy have not been well studied in HD patients. Our study focuses on the extent of oxidative DNA damage aggravated by intravenous (IV) iron sucrose in peripheral blood lymphocytes of patients undergoing chronic hemodialysis (HD). 8-Hydroxy-2'-deoxyguanosine (8-OHdG) content in lymphocyte DNA was detected by a high performance liquid chromatography electrochemical detection method. Firstly, 110 HD patients were randomly allocated to 5 groups. Patients in each group were treated with a single dose of 20, 50, 100, 200 and 500 mg iron sucrose, respectively. We found a time- and dose-dependent rise in lymphocyte 8-OHdG levels with a significant increase at 2 h following IV iron of �d200 mg (P ��0.05). Four weeks after the single dose test, a randomized controlled study was carried out for 12 weeks to investigate the cumulative dose effect of IV iron on lymphocyte 8-OHdG levels in HD patients. Iron sucrose (100 mg elemental iron) or 250 mL of normal saline was administered intravenously for 60 min postdialysis once weekly for 12 weeks. At the end of study, a total of 89 patients (IV iron group, n=45, and control group, n=44) completed the study. Mean lymphocyte 8-OHdG contents significantly increased in patients receiving IV iron as compared to controls (P ��0.05), especially in those with ferritin of > 500 �慊/L (P ��0.01). Flow cytometric analysis of intracellular production of reactive oxygen species (ROS) in lymphocytes showed spontaneous and phorbol-12-myristate-13- acetate induced ROS production significantly increased in IV iron group compared with control group. IV iron further resulted in a decrease in plasma ascorbate and ��-tocopherol adjusted for cholesterol and an increased in GSSG/GSH ratio (P ��0.05). These findings were also observed in IV iron group with ferritin of > 500 �慊/L (P ��0.05), but not in controls. Our study indicated that IV iron sucrose exhibits an in vivo pro-oxidant effect to provoke oxidative damage to peripheral blood lymphocyte DNA in HD patients, especially in those with high body iron status, i.e. serum ferritin of > 500 �慊/L