Nitrative and oxidative modifications of enolase are associated with iron in iron-overload rats and in vitro
Nitrative and oxidative modifications of enolase are associated with iron in iron-overload rats and in vitro
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DOI：
10.1007/s00775-010-0747-6
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发表时间：
2011-03
期刊：
影响因子：
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通讯作者：
Naihao Lu;Xueli Li;Jinyang Li;Wenjing Xu;Hailing Li;Zhonghong Gao
中科院分区：
文献类型：
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作者：
Naihao Lu;Xueli Li;Jinyang Li;Wenjing Xu;Hailing Li;Zhonghong Gao
铁超载是最常见的铁相关毒性之一，而肝脏是受损的主要器官。虽然氧化应激在铁超载的病理机制中被广泛接受，但肝脏的硝化修饰和铁的作用相对未知。本研究在铁超载大鼠模型中研究了肝脏的硝化和氧化应激。结果发现，给铁葡聚糖15周后，与大鼠肝脏中铁含量的增加一致，蛋白质酪氨酸硝化和蛋白质氧化均明显升高。免疫沉淀分析发现，铁超载肝脏中烯醇化酶的硝化和氧化状态显著升高，α-烯醇化酶的表达和活性明显降低。在体外进一步研究了不同形式的铁对NaNO2-H2O2 -和过氧亚硝酸盐（ONOO−）依赖性烯醇化酶硝化和氧化的影响，以阐明铁在体内烯醇化酶功能障碍中的可能作用。与EDTA-Fe （III）、柠檬酸铁和铁蛋白相比，血红素（血红素和血红蛋白）在两种模型中都表现出更高的蛋白质硝化催化效率。游离铁（Fe2+和Fe3+）除了催化蛋白质氧化的主要作用外，Fe2+还直接作为竞争性抑制剂，使酶活性显著降低。这些结果表明，多种形式铁的存在是铁超载相关综合征发生发展过程中硝酸盐/氧化修饰升高和α-烯醇化酶活性降低的重要因素。
Iron overload is one of the most common iron-related toxicities, and liver is the major organ that is injured. Although oxidative stress is well accepted in the pathological mechanism of iron overload, nitrative modification in liver and the role of iron are relatively unknown. In this work, the nitrative and oxidative stress in liver was investigated in an iron-overload rat model. It was found that after 15 weeks of iron dextran administration, consistent with the increase of iron content in rat liver, both protein tyrosine nitration and protein oxidation were clearly elevated. By means of immunoprecipitation analysis, it was found that enolase nitration and oxidation status were significantly increased in iron-overload liver, whereas both α-enolase expression and activity were clearly decreased. The effects of different forms of iron on NaNO2–H2O2- and peroxynitrite (ONOO−)-dependent enolase nitration and oxidation were further investigated in vitro to elucidate the possible role of iron in enolase dysfunction in vivo. Compared with EDTA–Fe(III), ferric citrate, and ferritin, heme (hemin and hemoglobin) showed higher efficiency in catalyzing protein nitration in both models. Besides the major contribution of free iron (Fe2+and Fe3+) to catalyze protein oxidation, Fe2+also directly acted as a competitive inhibitor and produced a significant decrease in enzyme activity. These results suggest that the existence of various forms of iron is an important contributing factor to the elevated nitrative/oxidative modifications and diminished activity of α-enolase in the development and progress of iron-overload-associated syndromes.