Monoclonal antibodies recognizing lipid-laden cells and extracellular regions with lipid-deposits in atherosclerotic aorta

Oxidized low-density lipoprotein as a biomarker of in vivo oxidative stress: from atherosclerosis to periodontitis

Oxidized low-density lipoprotein is known as an important factor in the development of atherosclerosis. The introduction of a sensitive procedure for the determination of oxidized low-density lipoprotein in human circulating plasma using a monoclonal antibody recognizing oxidized phosphatidylcholines has opened new fields of research based on in vivo oxidized low-density lipoprotein. The plasma oxidized low-density lipoprotein levels are significantly elevated in patients with acute myocardial infarction, cerebral infarction or chronic renal failure accompanied by hemodialysis. It was found that the plasma oxidized low-density lipoprotein level increased prior to aortic atherosclerotic lesion enlargement in apolipoprotein E-knockout mice. Recent studies have pointed out that oxidized low-density lipoprotein is transferrable between vessel wall tissue and the circulation, so it is a reasonable hypothesis that plasma oxidized low-density lipoprotein levels reflect the oxidative status at local sites of atherogenesis. Oxidized low-density 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 follow-up studies, suggest that oxidized low-density 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.

Presence of phospholipid-neutral lipid complex structures in atherosclerotic lesions as detected by a novel monoclonal antibody

A novel monoclonal antibody (ASH1a/256C) that recognizes atherosclerotic lesions in human and Watanabe heritable hyperlipidemic (WHHL) rabbit aortae is described. When (123)I-labeled ASH1a/256C antibody is injected intravenously into WHHL rabbits, it associates specifically with fatty streaks on the aorta. The antigen recognized by the antibody is lipid, based on extraction with chloroform and methanol from WHHL rabbit tissues. The antigen, purified by high performance liquid chromatography, was shown to be phosphatidylcholine (PC), which contains unsaturated fatty acyl groups based on analyses utilizing (1)H and (13)C nuclear magnetic resonance, Fourier transfer-infrared spectrum, and mass spectrometry. The antibody did not react with other classes of phospholipids or neutral lipids when tested using an enzyme-linked immunosorbent assay. When PC was mixed with either cholesterol, cholesteryl ester, or triacylglycerol, however, the reactivity of the antibody to PC increased up to 8-fold. Homogenates of aorta tissue obtained from normal and WHHL rabbits were fractionated using sucrose density gradient ultracentrifugation in which neutral lipid droplets, cellular membranes, and proteins are separated. The phospholipid content in cellular membrane fractions from WHHL rabbits was twice as high as that of normal rabbits, and there was an enormous difference in the antigenic activity in these fractions. The content of cholesterol in the cellular membrane fraction of WHHL rabbits was approximately 50 times higher than that of normal rabbits. Addition of neutral lipids to the cellular membrane fraction of normal rabbit markedly increased the antigenic activity. Atheromatous lesions in thickened WHHL rabbit aortic intima that were rich in lipid droplets were stained positively with ASH1a/256C immunohistochemically. These results strongly suggest that PC-neutral lipid complex domains are formed in atherosclerotic lesions.

Characterization of vitronectins in atherosclerotic lesions

Vitronectin is one of the major extracellular matrix proteins that accumulates in atherosclerotic lesions. A monoclonal antibody (EMR1a/212D) specifically stained the extracellular regions in thickened intima which colocalized well with lipid deposition. The antigenic glycoprotein with a molecular weight of 66KDa was revealed to be rabbit vitronectin. When homogenates of WHHL rabbit atheroma were subjected to immunoblot analysis using EMR1a/212D, four molecules with molecular weight 66, 56, 50 and 47KDa were detected. To confirm whether these smaller immunopositive bands were derived from mature vitronectin, another monoclonal antibody (EMR1b/244H) recognizing the polypeptide region of vitronectin was prepared. All four molecules were detected by EMR1b/244H as well as by EMR1a/212D. Two smaller vitronectins (56KDa and 50KDa) were found in atherosclerotic lesions and increased markedly during the development of atherosclerosis. On the other hand, the vitronectin detected in normal rabbit aorta was mainly of the mature type, while 56KDa and 47KDa forms were not detected. The total amount of the four vitronectins in atherosclerotic lesions was 38.5 +/- 5.0 ng/mg wet weight tissue, a value approximately 9.5 fold higher than that found in normal aorta. In conclusions, we found massive accumulation of these vitronectins concomitant with atherosclerotic development in rabbit aorta.

Inheritability of atherosclerosis and the role of lipoproteins as risk factors in the development of atherosclerosis in WHHL rabbits: risk factors related to coronary atherosclerosis are different from those related to aortic atherosclerosis

Inheritability of atherosclerosis and the influences of serum lipids on atherosclerosis were examined by following its progression in selectively bred WHHL rabbits. Our studies indicate (1) coronary atherosclerosis is clearly inherited from parents by offspring whereas inheritability of aortic atherosclerosis is uncertain; (2) coronary stenosis is positively correlated to serum cholesterol level, although the correlation coefficient is markedly low: in contrast, no relationship between serum lipid levels and aortic atherosclerosis was observed; (3) cholesterol-rich VLDL showed atherogenicity in aorta, but not in coronary arteries; (4) an unknown lipoprotein detected by 3.6% polyacrylamide gel electrophoresis was related to coronary atherosclerosis, although no relationship between the unknown lipoprotein and aortic atherosclerosis was observed. These findings suggest that there are two types of genetic factors involved in atherosclerosis, one of which is unique to coronary atherosclerosis whereas the other is related to only aortic atherosclerosis.

Characterization of liver-specific expression of rat uricase using monoclonal antibodies and cloned cDNAs

Tissue distribution of uricase (urate oxidase, EC 1.7.3.3) was studied by immunoblotting and RNA slot blot analysis. For immunoblotting, highly specific monoclonal antibodies against rat liver uricase were obtained, and for mRNA detection, a cloned uricase cDNA was used. Among seven tissues studied, uricase was immunologically detected only in the liver. The contents of uricase in other tissues, i.e., brain, thymus, heart, spleen, kidney and lactating mammary gland, were estimated to be less than 2% of that in the liver. Uricase mRNA was also detected only in the liver. The steady-state level of the mRNA in the isolated hepatocytes was relatively constant during the 8-day culture period when compared with those of other mRNAs expressed in the liver, suggesting a unique control mechanism of its expression.