Aviram M, Rosenblat M, Bisgaier C L, Newton R S, Primo-Parmo S L, La Du B N
The Lipid Research Laboratory, Technion Faculty of Medicine, the Rappaport Family Institute for Research in the Medical Sciences and Rambam Medical Center, Haifa, Israel, 31096.
J Clin Invest. 1998 Apr 15;101(8):1581-90. doi: 10.1172/JCI1649.
HDL levels are inversely related to the risk of developing atherosclerosis. In serum, paraoxonase (PON) is associated with HDL, and was shown to inhibit LDL oxidation. Whether PON also protects HDL from oxidation is unknown, and was determined in the present study. In humans, we found serum HDL PON activity and HDL susceptibility to oxidation to be inversely correlated (r2 = 0.77, n = 15). Supplementing human HDL with purified PON inhibited copper-induced HDL oxidation in a concentration-dependent manner. Adding PON to HDL prolonged the oxidation lag phase and reduced HDL peroxide and aldehyde formation by up to 95%. This inhibitory effect was most pronounced when PON was added before oxidation initiation. When purified PON was added to whole serum, essentially all of it became HDL-associated. The PON-enriched HDL was more resistant to copper ion-induced oxidation than was control HDL. Compared with control HDL, HDL from PON-treated serum showed a 66% prolongation in the lag phase of its oxidation, and up to a 40% reduction in peroxide and aldehyde content. In contrast, in the presence of various PON inhibitors, HDL oxidation induced by either copper ions or by a free radical generating system was markedly enhanced. As PON inhibited HDL oxidation, two major functions of HDL were assessed: macrophage cholesterol efflux, and LDL protection from oxidation. Compared with oxidized untreated HDL, oxidized PON-treated HDL caused a 45% increase in cellular cholesterol efflux from J-774 A.1 macrophages. Both HDL-associated PON and purified PON were potent inhibitors of LDL oxidation. Searching for a possible mechanism for PON-induced inhibition of HDL oxidation revealed PON (2 paraoxonase U/ml)-mediated hydrolysis of lipid peroxides (by 19%) and of cholesteryl linoleate hydroperoxides (by 90%) in oxidized HDL. HDL-associated PON, as well as purified PON, were also able to substantially hydrolyze (up to 25%) hydrogen peroxide (H2O2), a major reactive oxygen species produced under oxidative stress during atherogenesis. Finally, we analyzed serum PON activity in the atherosclerotic apolipoprotein E-deficient mice during aging and development of atherosclerotic lesions. With age, serum lipid peroxidation and lesion size increased, whereas serum PON activity decreased. We thus conclude that HDL-associated PON possesses peroxidase-like activity that can contribute to the protective effect of PON against lipoprotein oxidation. The presence of PON in HDL may thus be a major contributor to the antiatherogenicity of this lipoprotein.
高密度脂蛋白（HDL）水平与动脉粥样硬化发生风险呈负相关。在血清中，对氧磷酶（PON）与HDL相关，且已证实其可抑制低密度脂蛋白（LDL）氧化。PON是否也能保护HDL免于氧化尚不清楚，本研究对此进行了测定。在人体中，我们发现血清HDL PON活性与HDL氧化易感性呈负相关（r2 = 0.77，n = 15）。用纯化的PON补充人HDL可浓度依赖性地抑制铜诱导的HDL氧化。向HDL中添加PON可延长氧化延迟期，并使HDL过氧化物和醛的生成减少达95%。当在氧化起始前添加PON时，这种抑制作用最为明显。当将纯化的PON添加到全血清中时，基本上所有的PON都与HDL结合。富含PON的HDL比对照HDL对铜离子诱导的氧化更具抗性。与对照HDL相比，来自PON处理血清的HDL在氧化延迟期延长了66%，过氧化物和醛含量降低了40%。相反，在存在各种PON抑制剂的情况下，由铜离子或自由基产生系统诱导的HDL氧化显著增强。由于PON抑制HDL氧化，因此评估了HDL的两个主要功能：巨噬细胞胆固醇外流以及对LDL氧化的保护作用。与未处理的氧化HDL相比，经PON处理的氧化HDL使J - 774 A.1巨噬细胞的细胞胆固醇外流增加了45%。HDL相关的PON和纯化的PON都是LDL氧化的有效抑制剂。寻找PON诱导HDL氧化抑制的可能机制发现，PON（2对氧磷酶单位/毫升）可介导氧化HDL中脂质过氧化物（19%）和亚油酸胆固醇酯氢过氧化物（90%）的水解。HDL相关的PON以及纯化的PON也能够大量水解（高达25%）过氧化氢（H2O2），H2O2是动脉粥样硬化形成过程中氧化应激下产生的主要活性氧。最后，我们分析了动脉粥样硬化载脂蛋白E缺陷小鼠在衰老和动脉粥样硬化病变发展过程中的血清PON活性。随着年龄增长，血清脂质过氧化和病变大小增加，而血清PON活性降低。因此我们得出结论，HDL相关的PON具有过氧化物酶样活性，这可能有助于PON对脂蛋白氧化的保护作用。因此，HDL中PON的存在可能是这种脂蛋白抗动脉粥样硬化性的主要贡献因素。
