Human serum paraoxonase (PON 1) is inactivated by oxidized low density lipoprotein and preserved by antioxidants
Human serum paraoxonase (PON 1) is inactivated by oxidized low density lipoprotein and preserved by antioxidants
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DOI：
10.1016/s0891-5849(98)00272-x
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发表时间：
1999-04-01
影响因子：
7.4
通讯作者：
La Du, B
中科院分区：
文献类型：
--
作者：
Aviram, M;Rosenblat, M;La Du, B
人血清对氧磷酶（PON 1）可保护低密度脂蛋白（LDL）免受铜离子或自由基产生剂偶氮双脒基丙烷盐酸盐（AAPH）的氧化。在这两个系统中的LDL氧化过程中，PON芳基酯酶活性的时间依赖性失活观察。氧化低密度脂蛋白（Ox-LDL）与铜离子或AAPH孵育产生的脂蛋白，确实失活PON芳基酯酶活性分别高达47%或58%。三种可能的机制PON失活LDL氧化过程中被认为是和调查：铜离子结合PON，PON的自由基攻击，和/或脂蛋白相关的过氧化物酶的影响。由于残留的铜离子和AAPH都存在于Ox-LDL制剂中，并且可以独立地抑制酶，因此还检查了最低限度氧化（由LDL储存在空气中产生的Ox-LDL）对PON活性的影响。氧化LDL、氧化棕榈酰花生四烯酸磷脂酰胆碱（PAPC）、溶血磷脂酰胆碱（LPC，在LDL氧化过程中通过磷脂酶A2样活性产生）和氧化花生四烯酸胆固醇酯（Ox-CA）都是PON芳基酯酶活性的有效灭活剂（PON活性被抑制35%-61%）。PON治疗Ox-LDL（但不是与天然LDL），或与氧化脂质，抑制其芳基酯酶活性，也降低了酶的能力，以保护LDL氧化。然而，PON芳基酯酶活性不受抑制时，PON的巯基封闭剂，对羟基汞苯甲酸盐（PHMB）的预处理。类似地，在使用重组PON时，其中酶在半胱氨酸-284位置上唯一的游离巯基发生突变，未显示Ox-LDL对酶芳基酯酶活性的失活。这些结果表明，氧化低密度脂蛋白失活的PON涉及氧化脂质的氧化低密度脂蛋白与PON的游离巯基的相互作用。抗氧化剂（例如类黄酮光甘草定或槲皮素）在存在PON的情况下在LDL氧化期间存在时，会减少脂蛋白相关脂质过氧化物的量并保留PON活性，包括其水解Ox-LDL胆固醇亚油酸氢过氧化物的能力。我们的结论是PON的能力，保护LDL氧化是伴随着失活的酶。PON失活由酶游离巯基与氧化脂质如氧化磷脂、氧化胆固醇酯或溶血磷脂酰胆碱之间的相互作用引起，氧化磷脂、氧化胆固醇酯或溶血磷脂酰胆碱在LDL氧化期间形成。抗氧化剂和PON在LDL氧化过程中对LDL的作用对抗动脉粥样硬化特别有益，因为这些试剂通过双重作用减少Ox-LDL的积累：即，防止其形成，并去除LDL氧化过程中产生的Ox-LDL相关氧化脂质。(C)1999 Elsevier Science Inc.
Human serum paraoxonase (PON1) can protect low density lipoprotein (LDL) from oxidation induced by either copper ion or by the free radical generator azo bis amidinopropane hydrochloride (AAPH). During LDL oxidation in both of these systems, a time-dependent inactivation of PON arylesterase activity was observed. Oxidized LDL (Ox-LDL) produced by lipoprotein incubation with either copper ion or with AAPH, indeed inactivated PON arylesterase activity by up to 47% or 58%, respectively. Three possible mechanisms for PON inactivation during LDL oxidation were considered and investigated: copper ion binding to PON, free radical attack on PON, and/or the effect of lipoprotein-associated peroxides on the enzyme. As both residual copper ion and AAPH are present in the Ox-LDL preparations and could independently inactivate the enzyme, the effect of minimally oxidized (Ox-LDL produced by LDL storage in the air) on PON activity was also examined. Oxidized LDL, as well as oxidized palmitoyl arachidonoyl phosphatidylcholine (PAPC), lysophosphatidylcholine (LPC, which is produced during LDL oxidation by phospholipase A2-like activity), and oxidized cholesteryl arachidonate (Ox-CA), were all potent inactivators of PON arylesterase activity (PON activity was inhibited by 35%-61%). PON treatment with Ox-LDL (but not with native LDL), or with oxidized lipids, inhibited its arylesterase activity and also reduced the ability of the enzyme to protect LDL against oxidation. PON Arylesterase activity however was not inhibited when PON was pretreated with the sulfhydryl blocking agent, p-hydroxymercurybenzoate (PHMB). Similarly, on using recombinant PON in which the enzyme's only free sulfhydryl group at the position of cysteine-284 was mutated, no inactivation of the enzyme arylesterase activity by Ox-LDL could be shown. These results suggest that Ox-LDL inactivation of PON involves the interaction of oxidized lipids in Ox-LDL with the PON's free sulfhydryl group. Antioxidants such as the flavonoids glabridin or quercetin, when present during LDL oxidation in the presence of PON, reduced the amount of lipoprotein-associated lipid peroxides and preserved PON activities, including its ability to hydrolyze Ox-LDL cholesteryl linoleate hydroperoxides. We conclude that PON's ability to protect LDL against oxidation is accompanied by inactivation of the enzyme. PON inactivation results from an interaction between the enzyme free sulfhydryl group and oxidized lipids such as oxidized phospholipids, oxidized cholesteryl ester or lysophosphatidylcholine, which are formed during LDL oxidation. The action of antioxidants and PON on LDL during its oxidation can be of special benefit against atherosclerosis since these agents reduce the accumulation of Ox-LDL by a dual effect: i.e, prevention of its formation, and removal of Ox-LDL associated oxidized lipids which are generated during LDL oxidation. (C) 1999 Elsevier Science Inc.