HOMOGENTISIC ACID AUTOXIDATION AND OXYGEN RADICAL GENERATION - IMPLICATIONS FOR THE ETIOLOGY OF ALKAPTONURIC ARTHRITIS
HOMOGENTISIC ACID AUTOXIDATION AND OXYGEN RADICAL GENERATION - IMPLICATIONS FOR THE ETIOLOGY OF ALKAPTONURIC ARTHRITIS
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DOI：
10.1016/s0891-5849(87)80031-x
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发表时间：
1987-01-01
影响因子：
7.4
通讯作者：
BATKOFF, B
中科院分区：
文献类型：
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作者：
MARTIN, JP;BATKOFF, B
代谢性疾病黑酸尿症的特征是血清中2，5-二羟基苯乙酸（尿黑酸）水平升高，软骨和结缔组织色素沉着，最终发展为炎性关节炎。在尿黑酸自氧化过程中产生的氧自由基的特点是在体外评估的可能性，氧自由基作为分子剂的尿黑酸性关节炎在体内。尿黑酸在生理pH及以上条件下自氧化产生超氧阴离子（O2 - 2）和过氧化氢（H2 O2），尿黑酸自氧化速率与氧有关，与尿黑酸浓度成正比，与温度和pH有关。氧化产物苯醌乙酸的形成被还原剂、NADH、还原型谷胱甘肽和抗坏血酸抑制，并被SOD和焦磷酸锰加速。二乙烯三胺五乙酸（DTPA）抑制锰刺激的自氧化。在pH7.45时，高锰酸自氧化刺激抗坏血酸的快速共氧化。过氧化氢是共氧化的产物之一。尿黑酸和Fe ~（3+）-EDTA的组合刺激羟基自由基（OH ′）的形成，通过水杨酸羟基化来估计。Fe ~（3+）-EDTA是一种比游离Fe ~（3+）或Fe ~（3+）-DTPA更好的催化剂。超氧化物歧化酶加速OH 1生产尿黑酸H2 O2一样，和过氧化氢逆转了大部分的SOD，过氧化氢酶单独的刺激，和羟基自由基清除剂，硫脲和甲酸钠，抑制水杨酸羟基化。匀浆酸和Fe ~（3+）-EDTA也促进滑液中主要粘性成分透明质酸的降解。透明质酸解聚是时间依赖性的，并与尿黑酸浓度成正比，直至100 μM。观察到的降解水平与同等浓度抗坏血酸的降解水平相当。羟基自由基是解聚反应的活性中间体。因此，过氧化氢和羟基自由基清除剂，硫脲和二甲基亚砜，几乎完全抑制解聚反应。尿黑酸通过自氧化产生O2−、H2 O2和OH'的能力，以及尿黑酸通过OH'产生介导的透明质酸降解的能力表明，氧自由基在尿黑酸性关节炎的病因学中起着重要作用。
The metabolic disorder, alkaptonuria, is distinguished by elevated serum levels of 2,5-dihydroxyphenylacetic acid (homogentisic acid), pigmentation of cartilage and connective tissue and, ultimately, the development of inflammatory arthritis. Oxygen radical generation during homogentisic acid autoxidation was characterized in vitro to assess the likelihood that oxygen radicals act as molecular agents of alkaptonuric arthritis in vivo. For homogentisic acid autoxidized at physiological pH and above, yielding superoxide (O2−2and hydrogen peroxide (H2O2), the homogentisic acid autoxidation rate was oxygen dependent, proportional to homogentisic acid concentration, temperature dependent and pH dependent. Formation of the oxidized product, benzoquinoneacetic acid was inhibited by the reducing agents, NADH, reduced glutathione, and ascorbic acid and accelerated by SOD and manganese-pyrophosphate. Manganese stimulated autoxidation was suppressed by diethylenetriaminepentaacetic acid (DTPA). Homogentisic acid autoxidation stimulated a rapid cooxidation of ascorbic acid at pH 7.45. Hydrogen peroxide was among the products of cooxidation. The combination of homogentisic acid and Fe3+-EDTA stimulated hydroxyl radical (OH') formation estimated by salicylate hydroxylation. Ferric iron was required for the reaction and Fe3+-EDTA was a better catalyst than either free Fe3+or Fe3+-DTPA. SOD accelerated OH1production by homogentisic acid as did H2O2, and catalane reversed much of the stimulation by SOD, Catalase alone, and the hydroxyl radical scavengers, thiourea and sodium formate, suppressed salicylate hydroxylation. Homogentisic acid and Fe3+-EDTA also stimulated the degradation of hyaluronic acid, the chief viscous element of synovial fluid. Hyaluronic acid depolymerization was time dependent and proportional to the homogentisic acid concentration up to 100 μM. The level of degradation observed was comparable to that obtained with ascorbic acid at equivalent concentrations. The hydroxyl radical was an active intermediate in depolymerization. Thus, catalane and the hydroxyl radical scavengers, thiourea and dimethyl sulfoxide, almost completely suppressed the depolymerization reaction. The ability of homogentisic acid to generate O2−, H2O2and OH' through autoxidation and the degradation of hyaluronic acid by homogentisic acid-mediated by OH' production suggests that oxygen, radicals play a significant role in the etiology of alkaptonuric arthritis.