Himmelfarb J, McMenamin M E, Loseto G, Heinecke J W
Division of Nephrology, Maine Medical Center, Portland, ME 04102, USA.
Free Radic Biol Med. 2001 Nov 15;31(10):1163-9. doi: 10.1016/s0891-5849(01)00697-9.
Oxidative stress has been implicated in the cardiovascular complications that affect chronic renal failure patients on hemodialysis, though the physiologically relevant pathways mediating oxidative damage are poorly understood. It is known, however, that hemodialysis activates neutrophils, a well-characterized source of hydrogen peroxide and myeloperoxidase. The phagocyte-derived myeloperoxidase-hydrogen peroxide-chloride system generates hypochlorous acid, which reacts with tyrosine residues of proteins to form 3-chlorotyrosine. To explore the role of activated phagocytes in oxidative stress in chronic renal failure, we used 3-chlorotyrosine as a specific marker of myeloperoxidase activity. Utilizing isotope dilution gas chromatography-mass spectrometry, we compared 3-chlorotyrosine levels in plasma proteins of five patients on chronic hemodialysis therapy with those of age- and sex-matched healthy controls. The oxidized amino acid was present in the plasma proteins of 4 of the hemodialysis patients (3.5 +/- 0.8 micromol per mol tyrosine) but was undetectable in the healthy subjects. Therefore, one pathway for oxidative stress in hemodialysis patients appears to involve hypochlorous acid generated by the myeloperoxidase system of activated phagocytes. We also examined intradialytic 3-chlorotyrosine levels using membranes that activate white blood cells and the alternative pathway of complement. Hemodialysis increased plasma myeloperoxidase and the expression of CD11b/CD18 by circulating phagocytes, but failed to demonstrably increase 3-chlorotyrosine levels. 3-chlorotyrosine was detectable in 12 of 19 samples in total, with significant intrasubject variability. Our observations suggest that oxidants generated by myeloperoxidase contribute to the increased oxidative stress observed in renal-failure patients but do not damage plasma proteins during the hemodialysis procedure itself.
氧化应激与影响接受血液透析的慢性肾衰竭患者的心血管并发症有关，尽管介导氧化损伤的生理相关途径仍知之甚少。然而，已知血液透析会激活中性粒细胞，中性粒细胞是过氧化氢和髓过氧化物酶的一个特征明确的来源。吞噬细胞衍生的髓过氧化物酶-过氧化氢-氯离子系统会产生次氯酸，次氯酸与蛋白质的酪氨酸残基反应形成3-氯酪氨酸。为了探究活化的吞噬细胞在慢性肾衰竭氧化应激中的作用，我们使用3-氯酪氨酸作为髓过氧化物酶活性的特异性标志物。利用同位素稀释气相色谱-质谱联用技术，我们比较了5名接受慢性血液透析治疗的患者与年龄和性别匹配的健康对照者血浆蛋白中的3-氯酪氨酸水平。4名血液透析患者的血浆蛋白中存在这种氧化氨基酸（每摩尔酪氨酸3.5±0.8微摩尔），而在健康受试者中未检测到。因此，血液透析患者氧化应激的一条途径似乎涉及活化吞噬细胞的髓过氧化物酶系统产生的次氯酸。我们还使用能激活白细胞和补体替代途径的膜片检测了透析过程中的3-氯酪氨酸水平。血液透析增加了血浆髓过氧化物酶水平以及循环吞噬细胞CD11b/CD18的表达，但未能显著提高3-氯酪氨酸水平。在总共19个样本中的12个样本中可检测到3-氯酪氨酸，个体内差异显著。我们的观察结果表明，髓过氧化物酶产生的氧化剂导致肾衰竭患者氧化应激增加，但在血液透析过程本身并不会损伤血浆蛋白。
