Review OtjJ01RKhcoC980ebyexu.18Bvon3rS20int1Ne-oia1605w,cl-4d0iJ0oe/08aj0ftc96py0biCa2fnzlo0i.n1rRi1eF1c-ra0el0deB0R2ioa0cdRlhi1ceoaml iRswtersyea dnrcdhNeJuaptnraitniosn ity lipoprotein as a biomarker of in vivo oxidative stress: from atherosclerosis to periodontitis Hiroyuki Itabe* Department of Biological Chemistry, Showa University School of Pharmacy, 158 Hatanodai, Shinagawaku, Tokyo 1428555, Japan (Re7ceived 14 November, 2011; Accepted 28 November, 2011; Published online 30 March, 2012) svCOtixrdi2TCeiceda0hotdite1zipsdvt2eyhedireusiglsoaCoehnrwo,itgmodd©ipienmsen2atnorls0iinw1batsy2ucoctlrJiAiekopCsntosiBt,srpaiNrapbrontruitodcteiploiernnerdplisyirLsoktcirdnciitueobecnuwdtst.ineod,nauswinahdniaecnrihmythppmeoertertemdarimniuttmsfoa,ucfpnttorhoere- in the development of atherosclerosis. The introduction of a sensitive procedure for the determination of oxidized lowdensity lipoprotein in human circulating plasma using a monoclonal anti body recognizing oxidized phosphatidylcholines has opened new fields of research based on in vivo oxidized lowdensity lipo protein. The plasma oxidized lowdensity lipoprotein levels are significantly elevated in patients with acute myocardial infarction, cerebral infarction or chronic renal failure accompanied by hemo dialysis. It was found that the plasma oxidized lowdensity lipoprotein level increased prior to aortic atherosclerotic lesion enlargement in apolipoprotein Eknockout mice. Recent studies have pointed out that oxidized lowdensity lipoprotein is trans ferrable between vessel wall tissue and the circulation, so it is a reasonable hypothesis that plasma oxidized lowdensity lipo protein levels reflect the oxidative status at local sites of athero genesis. Oxidized lowdensity lipoprotein measurement has been applied to human gingival crevicular fluids, which can be collected easily and safely, and relatively high levels of oxidized low density lipoprotein were shown to be present. These findings, together with recent clinical followup studies, suggest that oxidized lowdensity lipoprotein is a predictive biomarker of a variety of diseases related to oxidative stress. This review summarizes the current understanding of in vivo oxidized low density lipoprotein and its potential significance as a biomarker of disease. Key Words: oxidized lowdensity lipoprotein, oxidized phophatidylcholine, oxidative stress, atherosclerosis, periodontitis Detection of OxLDL in Atherosclerotic Lesions Oxidative stress is involved in a variety of pathological condi- tions, such as inflammation, atherosclerosis, obesity, and cancer. Aerobic organisms cannot live without oxygen, and oxygen is an active molecule which elicits oxidative modifications of essential compounds of our body. In particular, polyunsaturated fatty acids (PUFA) are molecules very susceptible to oxidation reactions. Low-density lipoprotein (LDL) is a major carrier of cholesterol in the circulation. Since cholesterol is insoluble in water, it resides in a large complex composed of various lipids and proteins, which is called lipoprotein. Triglycerides and cholesteryl esters are packed in the core of the lipoprotein particles, and it is surrounded by a phospholipid monolayer sheet. In each LDL particle, one molecule of apolipoprotein B-100 (apoB) is included (Fig. 1). Nearly 80% of human LDL is composed of lipids, and more than a half of the lipid molecules are PUFA-containing lipids.(1) When LDL is exposed to oxidation, the PUFA moieties in those lipids doi: 10.3164/jcbn.1100020R1 ©2012 JCBN are easily oxidized so as to produce a variety of oxidation products containing oxidized functional groups, such as hydroperoxides, epoxides, endoperoxides, isoprostanes, aldehydes, carboxylic acids and unsaturated ketones. They are chemically active and induce secondary reactions with the side chains of amino acid residues in apolipoproteins. Oxidized low-density lipoprotein (OxLDL) is characterized by the presence of various oxidized lipids and amino acid residues modified with oxidized lipids, and OxLDL is thus a mixture of those heterogeneously modified LDL particles. Foam cells, which accumulate neutral lipids in cytoplasmic lipid droplets, are a typical feature of atherosclerotic lesions. Chemically modified forms of LDL were first reported to induce foam cell formation by macrophages in the 1980s.(2) In particular, the oxidation of LDL was found to occur under various physio- logical and phathological conditions. This suggested that lipid oxidation and its products could be important clues to under- standing the molecular basis of a variety of diseases. Subsequently, macrophage scavenger receptors, which recognize chemically modified LDL, including OxLDL, came to be extensively studied. The first scavenger receptor identified and cloned was SR-A.(3) Since then, a number of scavenger receptors have been identi- fied.(4) These in vitro studies strengthened the OxLDL hypothesis, but further studies are still needed to obtain corroborating in vivo evidence for the variety of activities of OxLDL. We have tried to identify the specific materials which are present in atherosclerotic lesions by raising lesion-related monoclonal antibodies (mAb).(5–7) Among many antibodies against atherosclerotic lesions, a clone that strongly reacts with copper-induced OxLDL was raised.(8) The antibody, DLH3, recognizes oxidized phosphatidylcholines (OxPC), where 1- palmitoyl-2-(9-oxo)nonanoyl-PC (9CHO-PC, also called PONPC) is one of the potent antigenic molecules (Fig. 1).(9) It has been extensively studied that various short-chain con- taining PC molecules are produced during oxidative modifica- tion.(10) Fig. 1B shows a presumed scheme of 9CHO-PC formation. Linoleate moiety in the PC molecule will be attacked at 9- or 13-position of the acyl chain. Then 9-alkoxy radical could cleave C-C bond at 9-10 position to form 9-carbon aldehyde- containing PC. The antibody DLH3 was also shown to be useful immuno- histochemically as a probe for the detection of OxPC in combina- tion with an anti-apoB polyclonal antibody (pAb). In human atherosclerotic lesions, immuno-double staining or adjacent serial *To whom correspondence should be addressed. Email: hitabe@pharm.showau.ac.jp He received “SFRR Japan Award of Scientific Excellent” in 2011 in recognition of his outstanding work. J. Clin. Biochem. Nutr. | July 2012 | vol. 51 | no. 1 | 1–8