Glycation accelerates the oxidation of low density lipoprotein by copper ions

The American Cancer Society recommends periodic mammography, clinical breast examination and breast self-examination beginning at age 40 years for asymptomatic women at average risk of breast cancer. Although there is substantial evidence from meta-analyses and non-randomized studies to support these recommendations, individual randomized clinical trials of breast cancer screening have not demonstrated mortality reduction in women aged 40-49 years. The opportunity to study this issue further in the United States has been diminished by the high prevalence of screening already being conducted in that population of younger women. The International Union Against Cancer, the American Cancer Society and the National Cancer Institute of the United States have convened a series of workshops and planning meetings to consider the available data and outline plans for future research. Plans are being developed to conduct a randomized trial of mammography in women younger than 50 years in multiple European sites. Successful completion of this trial may provide critical data on efficacy of breast cancer screening in younger women.     

Inhibition of oxidation of low density lipoprotein by troglitazone

The effect of a new oral hypoglycemic agent troglitazone, (+/-)-5-[4-(6-hydroxy-2,5,7,8-tetramethylchroman-2-yl-methoxy)benz yl]-2,4-thiazolidinedione as an antioxidant against the free radical-mediated oxidation of low density lipoprotein (LDL) was studied. The oxidation of LDL gives cholesteryl ester hydroperoxide and phosphatidylcholine hydroperoxide as major primary products. Troglitazone incorporated exogenously into LDL inhibited the oxidations of LDL induced by either aqueous or lipophilic peroxyl radicals and suppressed the formation of lipid hydroperoxides efficiently. Ascorbic acid added into the aqueous phase spared both endogenous alpha-tocopherol and troglitazone in LDL. It was also found by absorption spectroscopic and electron spin resonance (ESR) studies that troglitazone reacted rapidly with a galvinoxyl radical to give a chromanoxyl radical which gives the same ESR spectrum as alpha-tocopherol. This ESR spectrum disappeared rapidly when ascorbic acid was added into the system. These results show that troglitazone acts as a potent antioxidant and protects LDL from oxidative modification.     

Receptors for oxidized low density lipoprotein

An increasing body of evidence indicates that oxidized low density lipoprotein (LDL) is involved in the pathogenesis of atherosclerosis. One of the first biologic actions of oxidized LDL to be identified in vitro was its ability to interact with the 'acetyl LDL receptor' discovered by Goldstein and Brown. Over the past decade, considerable progress has been made in identifying and characterizing cell-surface receptors for oxidized LDL. Most of these receptors are thought to be multifunctional because they interact with several structurally different ligands, and accordingly have been termed 'scavenger receptors'. The objective of this article is to review the most important publications dealing with structure, ligand specificity, regulation, and function of scavenger receptors.     

Charge properties of low density lipoprotein subclasses

Measurements of electrophoretic mobility and particle size of low density lipoproteins (LDL) allowed use of standard electrokinetic theory to quantitate LDL charge characteristics from subjects with predominance of large LDL (pattern A, n = 9) or small LDL (pattern B, n = 8). Pattern A LDL was found to have significantly lower (P < or = 0.001) mobility (-0.22 +/- 0.01 micron s-1 cm V-1), surface potential (-4.2 +/- 0.3 mV) and charge density (-500 +/- 34 esu/cm2) than pattern B LDL (-0.25 +/- 0.01 micron s-1 cm V-1, -4.9 +/- 0.3 mV, and -580 +/- 30 esu/cm2), but no significant difference in particle valence (-22.0 +/- 1.4 for pattern A vs. -21.8 +/- 1.9 for pattern B). Thus, the greater mobility of pattern B LDL is due to similar net charge residing on a smaller particle. Comparison of subfractions in pattern B relative to pattern A LDL revealed greater surface potential in all pattern B subfractions and greater charge density in fractions of d > or = 1.032 g/ml. In a subset of subjects incubation with neuraminidase produced significant reductions in all LDL charge parameters for all subfractions, but did not abolish the differences between pattern A and B. Thus increased surface potential and charge density of unfractionated pattern B LDL is due both to charge properties of particles across the size and density spectrum as well as enrichment of pattern B LDL with smaller, denser particles that have higher surface charge density.     

Effects of low dose oral contraceptives on very low density and low density lipoprotein metabolism

Oral contraceptives (OC) raise plasma triglyceride and VLDL levels, which may be of concern, since some conditions characterized by elevated triglycerides are associated with atherosclerosis. To identify the responsible mechanism, we studied 11 healthy premenopausal women, 5 of whom were taking OC containing 0.035 mg ethinyl estradiol, and 6 of whom were not. Their rates of VLDL and LDL metabolism were measured by endogenously labeling apoB, the protein component of VLDL and LDL, by an intravenous infusion of deuterated leucine. OC use had the greatest effect on the large, triglyceride-rich VLDL subfraction (Sf 60-400), increasing plasma levels threefold and production rates fivefold (P < 0.05). Among OC users, small VLDL (Sf 20-60) levels were 2.2 times higher, and production rates were 3.4-fold higher (P < 0.05). The fractional catabolic rates of large and small VLDL were similar among OC users and nonusers. LDL levels and metabolic rates were not significantly different between the two groups. Thus, contemporary low dose OC substantially raise VLDL levels by increasing the production rate of large, triglyceride-rich VLDL, and not by slowing VLDL catabolism. Since VLDL catabolism is not impaired, we speculate that the hypertriglyceridemia induced by OC may be less atherogenic than that of hypertriglyceridemia resulting from impaired lipolysis. This may explain why long-term OC use does not appear to promote atherosclerosis.     

The isoflavone genistein inhibits copper and peroxyl radical mediated low density lipoprotein oxidation in vitro

OBJECTIVES: Hormone-independent and cytotoxic drug-resistant tumor growth in osteoblastic metastases defines poor survival in patients with advanced prostate cancer. Therefore, we analyzed the ability of human osteoblast-like cells (MG-63 cells) and MG-63 conditioned media (MG-63 CM) to protect PC-3 human prostate cancer cells from adriamycin cytotoxicity in vitro. METHODS: Adriamycin cytotoxicity was assessed in MG-63 osteoblast-like and PC-3 prostate cancer monolayer and three-dimensional collagen coculture systems using the DNA content and trypan blue exclusion assays, analysis of indexes of cell cycle by flow cytometry, determination of DNA fragmentation on simple agarose gel and terminal deoxynucleotidyl transferase-mediated nick end labeling (TUNEL) assay, and immunocytochemistry. RESULTS: Adriamycin (100 nM) arrested both the PC-3 and MG-63 cells at the G2/M phase in the cell cycle but induced apoptosis only in PC-3 cells, as assessed by flow cytometry, trypan blue exclusion, and agarose gel. Optimal doses of MG-63 CM (50 microg/mL), insulin-like growth factor I (50 ng/mL), and transforming growth factor-beta-1 (25 ng/mL), as determined by DNA content assay, partially neutralized the adriamycin cytotoxicity of PC-3 cells detected by flow cytometry and trypan blue exclusion. In addition, MG-63 cells rescued PC-3 cells from adriamycin apoptosis in the three-dimensional type I collagen gel coculture system, as analyzed by TUNEL assay. CONCLUSIONS: These data suggest that osteoblast-like cells and osteoblast-derived growth factors can optimize survival of metastatic prostate cancer cells, thereby helping to develop cytotoxic drug-resistant growth in vitro.     

Lipoxygenase-catalyzed oxidation of chlorpromazine by hydrogen peroxide at acidic pH

The hydroperoxidase activity of soybean lipoxygenase, a non-heme protein, oxidizes chlorpromazine using H2O2 at acidic pHs ranging from 3.0 to 4.0. The enzyme is assayed at pH 3.5, at which the half-life is 2 h (lower pHs cause higher inactivation rates). This oxidation is enzymatical since boiled enzyme or even iron ions both with H2O2 failed to produce any increase in absorbance. In addition, the concentration of CPZ radical cation formed and the concomitant enzyme activity directly depends on the enzyme concentration up to 0.23 microM. The Vmax value is 125 mumol/min per mg protein and the Km for chlorpromazine and H2O2 are 2.1 mM and 0.25 mM, respectively. Similar results were obtained when linoleic acid hydroperoxide was used instead of H2O2 with a Km value of 95 microM. The radical cation obtained in the oxidation of chlorpromazine by lipoxygenase decays by a disproportionation reaction. This permits to consider the overall reaction as a sum of an enzymatic reaction coupled with a chemical second order reaction with substrate regeneration, similar to those produced by peroxidases from different sources.     

Protection of low density lipoprotein oxidation at chemical and cellular level by the antioxidant drug dipyridamole

1. The oxidative modification of low density lipoprotein (LDL) is thought to be an important factor in the initiation and development of atherosclerosis. Natural and synthetic antioxidants have been shown to protect LDL from oxidation and to inhibit atherosclerosis development in animals. Synthetic antioxidants are currently being tested, by they are not necessarily safe for human use. 2. We have previously reported that dipyridamole, currently used in clinical practice, is a potent scavenger of free radicals. Thus, we tested whether dipyridamole could affect LDL oxidation at chemical and cellular level. 3. Chemically induced LDL oxidation was made by Cu(II), Cu(II) plus hydrogen peroxide or peroxyl radicals generated by thermolysis of 2,2'-azo-bis(2-amidino propane). Dipyridamole, (1-10 microM), inhibited LDL oxidation as monitored by diene formation, evolution of hydroperoxides and thiobarbituric acid reactive substances, apoprotein modification and by the fluorescence of cis-parinaric acid. 4. The physiological relevance of the antioxidant activity was validated by experiments at the cellular level where dipyridamole inhibited endothelial cell-mediated LDL oxidation, their degradation by monocytes, and cytotoxicity. 5. In comparison with ascorbic acid, alpha-tocopherol and probucol, dipyridamole was the more efficient antioxidant with the following order of activity: dipyridamole > probucol > ascorbic acid > alpha-tocopherol. The present study shows that dipyridamole inhibits oxidation of LDL at pharmacologically relevant concentrations. The inhibition of LDL oxidation is unequivocally confirmed by use of three different methods of chemical oxidation, by several methods of oxidation monitoring, and the pharmacological relevance is demonstrated by the superiority of dipyridamole over the naturally occurring antioxidants, ascorbic acid and alpha-tocopherol and the synthetic antioxidant probucol.     

Oxidation of free fatty acids in low density lipoprotein by 15-lipoxygenase stimulates nonenzymic, alpha-tocopherol-mediated peroxidation of cholesteryl esters

15-Lipoxygenase has been implicated in the in vivo oxidation of low density lipoprotein (LDL) a process thought to be important in the origin and/or progression of human atherogenesis. We have suggested previously that oxidation of LDL's cholesteryl esters (CE) and phospholipids by soybean (SLO) or human recombinant 15-lipoxygenase (rhLO) can be ascribed largely to alpha-tocopherol (alpha-TOH)-mediated peroxidation (TMP). In this study we demonstrate that addition to LDL of unesterified linoleate (18:2), other free fatty acid (FFA) substrates, or phospholipase A2 (PLA2) significantly enhanced the accumulation of CE hydro(pero)xides (CE-O(O)H) induced by rhLO, whereas the corresponding CE and nonsubstrate FFA were without effect. The enhanced CE-O(O)H accumulation showed a dependence on the concentration of free 18:2 in LDL. In contrast, addition of 18:2 had little effect on LDL oxidation induced by aqueous peroxyl radicals or Cu2+ ions. Analyses of the regio- and stereoisomers of oxidized 18:2 in SLO-treated native LDL demonstrated that the small amounts of 18:2 associated with the lipoprotein were oxidized enzymically and within minutes, whereas cholesteryl linoleate (Ch18:2) was oxidized nonenzymically and continuously over hours. alpha-Tocopheroxyl radical (alpha-TO.) formed in LDL exposed to SLO was enhanced by addition of 18:2 or PLA2. With rhLO and 18:2-supplemented LDL, oxidation of 18:2 was entirely enzymic, whereas that of Ch18:2 was largely, though not completely, nonenzymic. The small extent of enzymic Ch18:2 oxidation increased with increasing enzyme to LDL ratios. Ascorbate and the reduced form of coenzyme Q, ubiquinol-10, which are both capable of reducing alpha-TO. and thereby preventing TMP, inhibited nonenzymic Ch18:2 oxidation induced by rhLO. Trolox and ascorbyl palmitate, which also inhibit TMP, ameliorated both enzymic and nonenzymic oxidation of LDL's lipids, whereas probucol, a radical scavenger not capable of preventing TMP, was ineffective. These results demonstrate that rhLO-induced oxidation of CE is largely nonenzymic and increases with LDL's content of FFA substrates. We propose that conditions which increase LDL's FFA content, such as the presence of lipases, increase 15-LO-induced LDL lipid peroxidation and that this process requires only an initial, transient enzymic activity.     

Oleuropein protects low density lipoprotein from oxidation

The Mediterranean diet, rich in fruit, vegetables, grain, and vegetable oil (mainly olive oil) is correlated with a lower incidence of coronary heart disease (CHD). Natural antioxidants contained in the Mediterranean diet might also play a role in the prevention of cardiovascular diseases, through inhibition of LDL oxidation. We tested this hypothesis "in vitro" by inducing LDL oxidation with copper sulphate and preincubating the samples with oleuropein, the bitter principle of olives, that is one of the major components of the polyphenolic fraction of olive oil. Oleuropein 10(-5) M effectively inhibited CuSO4-induced LDL oxidation, as assessed by various parameters. We demonstrate in this investigation that polyphenolic components of the Mediterranean diet interfere with biochemical events that are implicated in atherogenetic disease, thus proposing a new link between the Mediterranean diet and prevention of CHD.     

Antioxidation of human low density lipoprotein by unconjugated and conjugated bilirubins

We demonstrate here that both unconjugated bilirubin (Bu) and conjugated bilirubin (Bc) can protect human low density lipoprotein(LDL) against oxidation by oxyradicals generated by 2,2'-azo-bis (2 amidinopropane) dihydrochloride at 37 degrees. The oxidation was assessed by agarose gel electrophoresis and was further corroborated by assaying the malondialdehydes and lipid peroxides formed throughout oxidation. On a per mole basis, Bu and less so Bc was more effective than ascorbate in preventing LDL oxidation. Since oxidative modification of human LDL was implicated in plaque formation in blood vessels leading to atherogenesis, the data suggested that either bile pigment may help reduce the risk of atherogenesis.     

Attenuation of plasma low density lipoprotein cholesterol by select 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitors in mice devoid of low density lipoprotein receptors

Low density lipoprotein (LDL) reduction independent of LDL receptor regulation was investigated using HMG-CoA reductase inhibitors in LDL receptor-deficient mice. In males, LDL cholesterol dose-dependently decreased with atorvastatin treatment after 1 week. As untreated mice grew older, their LDL cholesterol progressively rose above basal levels, but was quelled with atorvastatin treatment. In females, atorvastatin treatment time-dependently decreased LDL cholesterol levels and induced hepatic HMG-CoA reductase activity. Unlike males, cholesterol-lowering effects of the drug were sustained in females. Lovastatin, simvastatin, and pravastatin also reduced total and LDL cholesterol; however, additional studies in females demonstrated that atorvastatin caused the greatest dose-dependent and sustained effect after 2 weeks. In females, hepatic HMG-CoA reductase mRNA inversely correlated with LDL cholesterol lowering, with atorvastatin showing the greatest increase in mRNA levels (17.2-fold), followed by lovastatin (10.7-fold), simvastatin (4.1-fold), and pravastatin (2.5-fold). Atorvastatin effects on lipoprotein production were determined after acute (1 day) or chronic (2 week) treatment prior to intraperitoneal injection of Triton WR1339. Acute treatment reduced cholesterol (-29%) and apoB (-16%) secretion, with no change in triglyceride secretion. In contrast, chronic treatment elevated cholesterol (+20%), apoB (+31%), and triglyceride (+57%) secretion. Despite increased cholesterol and apoB secretion, plasma levels were reduced by 51% and 46%, respectively. Overall, under acute or chronic conditions, apoB paralleled cholesterol secretion rates, and triglyceride to cholesterol secretion ratios were elevated by 38% and 32%, respectively. We propose that atorvastatin limits cholesterol for lipoprotein assembly, which is compensated for by triglyceride enrichment. In addition, with either acute or chronic atorvastatin treatment, apoB-100 secretion was blocked, and compensated for by an increased secretion of apoB-48. The apoB-48 particles produced are cleared by LDL receptor-independent mechanisms, with an overall effect of reducing LDL production in these mice. These studies support the idea that HMG-CoA reductase inhibitors modulate lipoprotein levels independent of LDL receptors, and suggest they may have utility in hyperlipidemias caused by LDLreceptor disorders.     

Inhibitory action of silibinin on low density lipoprotein oxidation

The purpose of this study is to demonstrate a method of how to remove epithelium grown beneath the hinge area after laser in situ keratomileusis (LASIK) without affecting the refractive part of the lenticule. In three cases, an incision was made at the base of the hinge by RK diamond knife to free the lenticule from the stroma. The lenticule was lifted from the nasal edge. The epithelium grown along the interface beneath the hinge area was removed with a Bard-Parker No. 15 knife. The lenticular flap was repositioned with interrupted sutures using 10-0 nylon. No further epithelial ingrowth was observed. The central cornea remained clear leaving a peripheral ring-shaped opacity without affecting the preoperative naked visual acuity. In conclusion, epithelial ingrowth along the interface after LASIK can be removed safely without affecting the refractive part by the incision of the hinge area with a RK diamond knife, removal of the epithelium, and suturing of the lenticule to the stromal bed.     

Oxidized low density lipoprotein--an extreme example of lipoprotein heterogeneity

Toilet training is as necessary a developmental step for the child with chronic illness as it is for the healthy child. Helping families and children to achieve this task, despite the demands of the illness, may require modification of usual techniques. Assessment of readiness and impediments to toilet training along with suggested intervention approaches are addressed. Case examples demonstrate individualization to specific children's needs.     

Detection of low density lipoprotein particle fusion by proton nuclear magnetic resonance spectroscopy

Recent evidence suggests that fusion of low density lipoprotein (LDL) particles is a key process in the initial accumulation of lipid in the arterial intima. In order to gain a better understanding of this early event in the development of atherosclerosis, it would thus be necessary to characterize the process of LDL fusion in detail. Such studies, however, pose severe methodological difficulties, such as differentiation of particle fusion from aggregation. In this paper we describe the use of novel methodology, based on 1H NMR spectroscopy, to study lipoprotein particle fusion. To test the methodology, we chose proteolytic fusion of LDL particles, an in vitro model that has been well characterized in our laboratory. The spectroscopic data suggested that proteolysis of LDL with alpha-chymotrypsin induced slow initiation of fusion, which was followed by particle fusion at an increased rate. Moreover, 1H NMR spectroscopic data on different kinds of LDL interactions, for example, when LDL formed aggregates with antibodies against human apolipoprotein B-100, were obtained and compared with the electron microscopic characteristics of these preparations. An important finding was that limited aggregation of LDL particles did not disturb the 1H NMR spectroscopic parameters used for the detection of particle fusion and preserved the physico-chemical information on the particles. The 1H NMR methodology developed is sensitive to and specific for low density lipoprotein (LDL) fusion and may also allow for studies of the fate of LDL particles in other in vitro preparations that mimic the arterial interactions in vivo.     

Both hypothyroidism and hyperthyroidism enhance low density lipoprotein oxidation

Hypothyroidism is frequently associated with hypercholesterolemia and an increased risk for atherosclerosis, whereas hyperthyroidism is known to precipitate angina or myocardial infarction in patients with underlying coronary heart disease. We have shown previously that L-T4 functions as an antioxidant in vitro and inhibits low density lipoprotein (LDL) oxidation in a dose-dependent fashion. The present study was designed to evaluate the changes in LDL oxidation in subjects with hypothyroidism and hyperthyroidism. Fasting blood samples for LDL oxidation analyses, lipoprotein determinations, and thyroid function tests were collected at baseline and after the patients were rendered euthyroid. The lag phase (mean +/- SEM hours) of the Cu+2-catalyzed LDL oxidation in the hypothyroid state and the subsequent euthyroid states were 4 +/- 0.0.65 and 14 +/- 0.68 h, respectively (P < 0.05). The lag phase during the hyperthyroid phase was 6 +/- 0.55 h, and that during the euthyroid phase was 12 +/- 0.66 h (P < 0.05). The total and LDL cholesterol levels were higher in hypothyroidism than in euthyroidism and were lower in hyperthyroidism than in the euthyroid state. We conclude that LDL has more susceptibility to oxidation in both the hypothyroid and hyperthyroid states. Thus, the enhanced LDL oxidation may play a role in the cardiac disease process in both hypothyroidism and hyperthyroidism.     

Effect of homocysteine on copper ion-catalyzed, azo compound-initiated, and mononuclear cell-mediated oxidative modification of low density lipoprotein

Homocysteine is an independent risk factor for cardiovascular diseases. The mechanisms by which elevated plasma concentrations of homocysteine are related to the pathogenesis of atherosclerosis are not fully understood. To examine whether homocysteine is implicated in atherogenesis through the modification of low density lipoprotein (LDL), the effect of homocysteine on the oxidation of LDL was studied by three different oxidation systems. Thus, LDL was subjected to Cu(2+)-catalyzed, azo compound-initiated, and peripheral blood mononuclear cell-mediated oxidative modification. The extent of modification was assessed by measuring the formation of conjugated dienes, lipid peroxides, thiobarbituric acid-reactive substances, and the relative electrophoretic mobility. Homocysteine at a normal plasma concentration (6 microM) showed no effect, whereas a concentration corresponding to moderate hyperhomocysteinemia (25 microM) or to concentrations seen in homocystinuria patients (100, 250, and 500 microM) protected LDL from modification of the lipid as well as of the protein moiety. One exception was observed: when the oxidation was initiated by copper ions, homocysteine at concentrations 6 and 25 microM stimulated the lipid peroxidation of LDL to a small, but statistically significant extent. High concentrations of homocysteine showed antioxidative properties as long as the thiol groups were intact, thereby delaying the onset of the oxidation. The 1,1-diphenyl-2-picrylhydracyl radical test demonstrated that homocysteine at concentrations > or = 50 microM possessed marked free radical scavenging capacity. Finally, LDL isolated from two patients with homozygous homocystinuria showed similar extent of Cu(2+)-catalyzed oxidation as LDL from a group of healthy control subjects. Taken together, our data suggest that low concentrations of homocysteine in the presence of copper ions may enhance the lipid peroxidation of LDL, whereas high concentrations of homocysteine may protect LDL against oxidative modification in the lipid as well as in the protein moiety. Thus, homocysteine-induced atherosclerosis may be explained by mechanisms other than oxidative modification of low density lipoprotein.     

Leishmania mexicana: induction of metacyclogenesis by cultivation of promastigotes at acidic pH

Cultivation of recently transformed Leishmania mexicana promastigotes at pH 5.5 in Schneider's Drosophila medium supplemented with 20% fetal calf serum produced a homogeneous stationary phase population morphologically similar to metacyclic forms. The cultured forms developed functional characteristics consistent with being metacyclic: they were resistant to complement-mediated lysis, possessed a discernable surface membrane coat in transmission electron micrographs, and were highly infective to peritoneal macrophages in vitro. In contrast, growth of promastigotes at pH 7.0 produced morphologically mixed populations of stationary phase promastigotes, but including a subpopulation with metacyclic-like morphology. These results provide a method for culturing pure populations of L. mexicana metacyclics and provide evidence that metacyclics are biochemically preadapted for survival at acidic pH as amastigotes in macrophage phagolysosomes.     

Identification of oxidized low density lipoprotein in human renal biopsies

BACKGROUND: Intraglomerular lipid deposition is frequently observed in routine renal biopsies, and it has been suggested that lipid peroxidation of low density lipoprotein (LDL) may be implicated in the pathogenesis of progressive glomerulosclerosis. We have examined whether oxidized LDL (Ox-LDL) is present in the glomeruli of patients with renal disease and whether intrinsic human glomerular cells express NADPH-oxidase (a superoxide-generating enzyme found in professional phagocytes). METHODS: Immunocytochemical study was performed on 939 renal biopsy specimens, using monoclonal antibodies (mAbs) OL-10, 48 and 449, and polyclonal antibody against human apolipoprotein (apo) B. Mouse mAb OL-10 recognizes malondialdehyde (MDA)-modified peptide epitope, and mAbs 48 and 449 react with alpha and beta subunits of cytochrome b558, an essential component of NADPH-oxidase. RESULTS: Sixty-two (6.6%) of the 939 patients with renal disease exhibited a staining for MDA-altered protein or Ox-LDL in the glomeruli, mainly in the sclerotic segments or mesangial areas. Group 1 patients with heavy Ox-LDL deposition mainly in the sclerotic segments showed a higher frequency of renal insufficiency and heavy proteinuria and a greater degree of glomerulosclerosis, compared to those in group 2 with mesangial Ox-LDL staining. The distribution of MDA protein epitopes, in general, paralleled the deposition of apo B epitopes. Immunoelectron microscopy of ultrathin frozen sections showed the presence of immunogold particles for mAbs 48 and 449 in the cytoplasm of resident glomerular cells of both normal and diseased kidneys. When immunoblotted with mAb OL-10, one band from the IgA nephropathy and focal segmental glomerulosclerosis groups at approximately 260 kD was labeled, whereas immunostaining of normal control samples revealed no staining. CONCLUSIONS: These results indicate that Ox-LDL is present mainly in the lesions of glomerulosclerosis and mesangial areas in human renal biopsies. They also suggest that patients with heavy Ox-LDL accumulation in the sclerotic segments of glomeruli have more advanced renal disease than those with mesangial Ox-LDL and that resident glomerular cells generate cytochrome b558, the potential of which may not suffice to induce peroxidation of LDL in the diseased glomeruli.     

Decreased production of low density lipoprotein by atorvastatin after apheresis in homozygous familial hypercholesterolemia

Apheresis only partially controls raised low density lipoprotein cholesterol levels in patients with homozygous familial hypercholesterolemia, who usually respond poorly to lipid-lowering drugs. The efficacy and mechanism of action of a new 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitor, atorvastatin, was therefore investigated in seven homozygotes undergoing apheresis. One receptor-negative and six receptor-defective homozygotes undergoing plasma exchange or LDL apheresis every 2 weeks were studied during 2 months each on placebo and on atorvastatin 80 mg daily. Changes in plasma lipids and mevalonic acid, an index of cholesterol synthesis, were measured and the kinetics of the rebound of low density lipoprotein cholesterol and apolipoprotein B after apheresis were analyzed. All subjects had significant improvements on atorvastatin. Mean decreases in low density lipoprotein cholesterol were 31% greater both pre- and post-apheresis on atorvastatin compared with placebo, accompanied by a 63% decrease in mevalonic acid. Percentage changes in low density lipoprotein cholesterol and mevalonic acid were closely correlated (r = 0.89, P = 0.007). The mean production rates of low density lipoprotein cholesterol and apolipoprotein B were 21% and 25% lower, respectively, on atorvastatin than on placebo (P < 0.005 and <0.02) but changes in mean fractional clearance rates were not statistically significant. We conclude that atorvastatin enhances the efficacy of plasma exchange and low density lipoprotein apheresis in patients who lack low density lipoprotein receptors. This effect appears to be due to marked inhibition of cholesterol synthesis which results in a decreased rate of production of low density lipoprotein.