Fig. 1. AntiOxLDL mAb DLH3 recognizes OxPC. A: LDL is composed of a number of lipid molecules surrounded by a single molecule of apolipo protein B100 (apoB). When LDL is oxidized, lipid peroxidation products are primarily derived from PUFAcontaini ng phospholipids and triacylglycerol, and some of the peroxidation products bind to apoB, thereby modifying the protein structures. B: One of the lipid oxidation products containing a PC backbone and an aldehyde group, 9CHOPC. This oxidized PC is recognized by the antiOxPC mAb DLH3. It is very likely that th e 1palmitoyl2 linoleoyl PC is the precursor of 9CHOPC. Linoleate moiety in the PC molecule will be attacked at 9 or 13position of the acyl chain. Then 9alkoxy radical could cleave CC bond at910 position to form 9carbon aldehydecontaining PC. section staining allowed the observation that OxPC was often specifically present together with apoB in macrophage-derived foam cells.(8,11,12) The presence of OxLDL in human atheroscle- rotic lesions was further demonstrated by analysis of the lipoprotein fraction extracted from carotid plaques obtained from endarterectomized patients.(12) When either OxLDL or acetylated LDL is incubated with macrophages in culture, the macrophages take up the modified LDL particles and then degrade them in their lysosomes. But the hydrolysis of the modified apoB in the OxLDL was reported to be incomplete compared with acetylated LDL in macrophage lysosomes.(13,14) Interestingly, the OxLDL extracted from the carotid artery lesions was partially degraded.(12) It ranges between 50–150 kDa, while the native apoB-100 is approximately 500 kDa, suggesting that the OxLDL in the lesions is processed by the macrophages. This observation is a good evidence for the presence of OxLDL in vivo (Fig. 2). Circulating OxLDL and Cardiovascular Diseases The anti-OxPC antibody was utilized to establish a sandwich enzyme-linked immunosorbent assay (ELISA) procedure for detecting even small amounts of OxLDL in human plasma.(15) The OxLDL present in human plasma LDL fraction was shown to be detectable even in the LDL from healthy subjects, even though this amount of OxLDL (approximately 0.1 ng/μg LDL protein) was very small. The OxLDL levels of LDL fraction from patients with acute myocardial infarction (AMI), cerebral infarction or chronic renal failure were significantly higher than control subjects.(8,11,15,16) 2 Several research groups have reported methods for the determi- nation of OxLDL in human plasma with mAbs. These methods use similar but different mAbs, as well as different ELISA strategies and standard materials. Thus, the OxLDL values obtained by these methods cannot be directly compared. Despite such formal technical differences in these procedures, the changes in OxLDL levels in patients with severe cardiovascular diseases, including AMI, were detected by all of these methods, which provide strong evidence that the circulating OxLDL level changes under these pathological conditions.(17) Sandwich ELISA using a DLH3 antibody and anti-apoB pAb has been shown to be a powerful tool for studying the changes in the OxLDL levels in human plasma. The plasma OxLDL level is significantly increased in patients with AMI compared with normal subjects.(11) In our procedure, the LDL fraction was separated from each plasma sample using ultracentrifugation， therefore the value obtained by the measurement is indicated as “ng of OxLDL per μg of LDL protein”, which represents the degree of oxidation in the LDL particles. The time course of the change in the plasma OxLDL levels in patients with AMI during the time of treatment in the hospital was studied. It was demonstrated that the plasma OxLDL levels were significantly high in the acute phase after administration in the hospital, but went down to a nearly normal level by the time of discharge.(18) A similar temporal change in plasma OxLDL was observed in the patients with cerebral infarction.(16) These findings suggest that plasma OxLDL is released into the circulation from atherosclerotic lesions upon plaque rapture (Fig. 3).(19) Tsimikas et al.(20) have extensively studied the plasma OxLDL doi: 10.3164/jcbn.1100020R1 ©2012 JCBN