Glucose-modified low density lipoprotein enhances human monocyte chemotaxis

In response to stimulation with immobilized anti-CD3 antibody, splenocytes from C57BL/6 and BALB/c mice principally produced INF-gamma and IL-4, respectively. However, both splenocytes equally proliferated in response to ConA. We compared the changes after inoculation with BCG (1 mg/mouse) in their capacity to produce IL-4 or IFN-gamma in response to anti-CD3 antibody and to proliferate in response to ConA. Splenocytes from C57BL/6 and BALB/c mice, that had been inoculated with BCG 4 weeks before, produced IFN-gamma with diminished IL-4 production in response to anti-CD3 antibody. Furthermore these splenocytes became anergic to ConA stimulation and died due to cell apoptosis in stead of proliferation. However, we observed the strain difference at 12 weeks after BCG-infection. BCG-primed C57BL/6 splenocytes, that continuously produced IFN-gamma in response to anti-CD3 antibody, failed to proliferate in response to ConA. In contrast, BCG-primed BALB/c splenocytes, that increased IL-4 production but decreased IFN-gamma production when stimulated with anti-CD3 antibody, could proliferate well in response to ConA. Since the splenocytes of BALB/c mice became ConA responsive along with their shifting from Th1 dominant immune response at 4 weeks to Th2 dominant immune response at 12 weeks after BCG-inoculation, IL-4 was assumed to play a crucial role in activation of anergic T cells. Therefore, we stimulated splenocytes from both strains of mice infected with BCG 4 weeks before with ConA in the presence or absence of IL-4. Splenocytes from BCG-infected BALB/c mice showed marked proliferation, while those from BCG-infected C57BL/6 mice failed. We found that IL-4 protected against ConA-induced cell apoptosis in BALB/c splenocytes but not C57BL/6 splenocytes.     

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.     

Tomato lycopene and low density lipoprotein oxidation: a human dietary intervention study

Increase in low density lipoprotein (LDL) oxidation is hypothesized to be causally associated with increasing risk of atherosclerosis and coronary heart disease. In recent epidemiological studies, tissue and serum levels of lycopene, a carotenoid available from tomatoes, have been found to be inversely related to risk of coronary heart disease. A study was undertaken to investigate the effect of dietary supplementation of lycopene on LDL oxidation in 19 healthy human subjects. Dietary lycopene was provided using tomato juice, spaghetti sauce, and tomato oleoresin for a period of 1 wk each. Blood samples were collected at the end of each treatment. Serum lycopene was extracted and measured by high-performance liquid chromatography using an absorbance detector. Serum LDL was isolated by precipitation with buffered heparin, and thiobarbituric acid-reactive substances (TBARS) and conjugated dienes (CD) were measured to estimate LDL oxidation. Both methods, to measure LDL oxidation LDL-TBARS and LDL-CD, were in good agreement with each other. Dietary supplementation of lycopene significantly increased serum lycopene levels by at least twofold. Although there was no change in serum cholesterol levels (total, LDL, or high-density lipoprotein), serum lipid peroxidation and LDL oxidation were significantly decreased. These results may have relevance for decreasing the risk for coronary heart disease.     

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.     

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.     

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.     

First direct evidence for lipid/protein conjugation in oxidized human low density lipoprotein

It has been postulated that lipids incorporated in atherosclerotic plaques are derived from the uptake of oxidized low density lipoprotein (LDL) by a macrophage-bound receptor. In vitro studies of LDL oxidation have established that reactive lipids are formed and that the exposure of native LDL to these products leads to modified protein with physical properties similar to oxidized LDL. Here we describe the application of highly specific tandem mass spectrometric techniques to the first characterization of lipid-modified LDL by demonstrating the addition of 4-hydroxy-2-nonenal to histidine residues of apolipoprotein B-100, following oxidation of LDL. The modified residues have been assigned to specific locations that have been previously shown to reside on the surface of the LDL particle.     

NADPH oxidase is not essential for low density lipoprotein oxidation by human monocyte-derived macrophages

NADPH oxidase has been reported to be involved in low density lipoprotein (LDL) oxidation by monocytes. We have investigated the ability of monocyte-derived macrophages from four chronic granulomatous disease patients, which lack NADPH oxidase, to oxidise LDL. All the cells oxidised LDL to significantly increase its uptake by mouse macrophages. We conclude therefore that NADPH oxidase is not essential for LDL oxidation by macrophages.     

The effect of probucol on low density lipoprotein oxidation and femoral atherosclerosis

Our knowledge of the traits possessed by extraintestinal isolates of Escherichia coli, necessary for growth and survival in urine, is limited. To identify such determinants, transposon (TnphoA'1,4) mutant libraries of a clinical isolate (CP9) were generated and screened for derivatives exhibiting decreased growth in urine in vitro, and for mutants with active lacZ fusions that were induced in urine relative to laboratory medium. Using this approach we identified two genes, guaA (CPA24) and argC (CPI-1), which were previously unrecognized as being important for growth in human urine. Unexpectedly, not only does CPA24 (guaA) not grow in human urine in vitro, but it is sensitive to its effects, undergoing a 2-3 log loss of viability over 6 h. By contrast, CPA24 neither grows nor is killed in M9 minimal medium and artificial urine. Therefore, we postulate that lack of guanine or its derivatives in urine, and the inability of CPA24 to synthesize these compounds de novo, prevents CPA24 from synthesizing other guanine (or derivatives)-dependent products that are critical for growth and survival in urine. Although it seems logical that decreased growth in urine in vitro should correlate with diminished urovirulence, this concept was tested by challenging mice with CPA24 in vivo in a mouse model of urinary tract infection (UTI). Indeed, CPA24 was found to be significantly less virulent compared with its wild-type parent CP9. CPI-1(argC) was identified because of the significant induction of its argC::lacZ fusion in urine. Subsequent testing in urine demonstrated that its growth was significantly diminished in all urine samples tested (four females, three males). Polyamine synthesis is dependent upon, in part, the arginine biosynthetic pathway. Therefore, we tested whether the induction of argC in urine and/or the decreased growth of CPI-1 was a result of low levels of polyamines or arginine in urine. The results suggest that low levels of arginine, but not polyamines, in human urine are responsible. When tested in vivo in the mouse model of UTI, CPI-1 was also found to be significantly less virulent than CP9. In summary, we have established that guaA and argC are the first genes, which we are aware of, that have been shown to contribute to the growth of E. coli in urine in vitro and both have diminished urovirulence in vivo. These results support the concept that urine can be used in vitro as a screening tool to identify urovirulence traits.     

Effect of soybean phytoestrogen intake on low density lipoprotein oxidation resistance

The oxidation of low density lipoproteins (LDLs) is thought to take place in the arterial intima when the particles have become isolated from circulating water-soluble antioxidants. We hypothesized that isoflavonoid antioxidants derived from soy could be incorporated into lipoproteins and possibly could protect them against oxidation, which is regarded as atherogenic. Six healthy volunteers received 3 soy bars [containing the isoflavonoid antioxidants genistein (12 mg) and daidzein (7 mg)] daily for 2 weeks. LDLs were isolated from blood drawn at the the end of a 2-week dietary baseline period, after 2 weeks on soy, and after discontinuation of soy. Large increases in plasma isoflavonoid levels occurred during soy feeding, but only minute amounts were stably associated with lipoproteins (less than 1% of plasma isoflavonoids in the LDL fraction). The LDLs were subjected to copper-mediated oxidation in vitro. Compared with off soy values, lag phases of LDL oxidation curves were prolonged by a mean of 20 min (P < 0.02) during soy intake, indicating a reduced susceptibility to oxidation. The results suggest that intake of soy-derived antioxidants, such as genistein and daidzein, may provide protection against oxidative modification of LDL. As only very small amounts of these substances were detected in purified LDL, modified LDL particles may have been produced in vivo by circulating isoflavonoids promoting resistance to oxidation ex vivo.     

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.     

Involvement of phospholipids in apolipoprotein B modification during low density lipoprotein oxidation

Metastatic tumors to the choroid plexus are rare. We report a case of renal cell carcinoma metastasizing to the choroid plexus of the lateral ventricular atrium. This tumor was shown by magnetic resonance imaging, followed by craniotomy and histologic confirmation. Computed tomography of the abdomen showed the primary tumor. We also reviewed 40 years of the literature and found 14 cases of metastasis to the choroid plexus. We discuss the clinical features of this intraventricular metastasis.     

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.     

Isradipine lowers human arterial low density lipoprotein retention in vivo

An 84-year-old woman was admitted to our hospital because of left heart failure of acute onset. Transthoracic echocardiography showed diffuse hypertrophy of the normal sized hyperkinetic left ventricle and chordae-like fluttering echoes attached to the mitral valve with severe mitral regurgitation signals. Mosaic flow signals were seen at the left ventricular outflow tract, but the velocity could not be measured. Emergent transesophageal echocardiography detected no obvious mitral valve prolapse. Cardiac catheterization showed greater than 100 mmHg pressure gradient between the left ventricle and femoral artery. Pressures in the femoral artery and pulmonary capillary wedge changed reciprocally in the intensive care unit; a bisferient narrow pulse pressure of the femoral artery was associated with increased v wave of the pulmonary capillary wedge pressure, and a wide pulse pressure of the femoral artery with absent v wave of the pulmonary capillary wedge pressure. Pressure monitoring in the intensive care unit, catheterization laboratory and transesophageal echocardiography were useful to understand the pathophysiology of the patient.     

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.     

Does acute exercise affect the susceptibility of low density lipoprotein to oxidation?

This study describes the effect of an acute exercise bout on the susceptibility of isolated low density lipoprotein (LDL) to in vitro oxidation. LDL was isolated from 23 subjects (exercisers, n = 11; sedentary, n = 12) immediately before and after a single bout of exercise (30 min of treadmill work at 55% & 70% peak oxygen consumption (VO2 peak) for exercisers and sedentary, respectively). A statistically significant decrease in lag time for LDL oxidation was observed following exercise compared to baseline (96.1+/-23.5 min vs. 92.1+/-23.3 minutes; n = 23, p < or = .03) using a 5 microM copper system. There was a statistically significant increase in plasma myeloperoxidase (MPO) levels following exercise compared to baseline values ( 1.58+/-.91 ng/dl versus 2.08+/-1.2 ng/dl; n = 12, p < or = .03). These results suggest that the 30 min exercise bout at a moderate intensity and duration was a sufficient oxidative stress to increase the susceptibility of LDL to in vitro oxidation. Additionally, the exercise bout appeared to activate neutrophils, subsequently releasing MPO protein.     

Troglitazone increases the resistance of low density lipoprotein to oxidation in healthy volunteers

The oxidative modification of low density lipoprotein is of importance in atherogenesis. Antioxidant supplementation has been shown, in published work, to increase low density lipoprotein resistance to oxidation in both healthy subjects and diabetic subjects; in animal studies a contemporary reduction in atherogenesis has been demonstrated. Troglitazone is a novel oral antidiabetic drug which has similarities in structure with vitamin E. The present study assessed the effect of troglitazone 400 mg twice daily for 2 weeks on the resistance of low density lipoprotein to oxidation in healthy male subjects. Ten subjects received troglitazone and ten received placebo in a randomised, placebo-controlled, parallel-group design. The lag phase (a measure of the resistance of low density lipoprotein to oxidation) was determined by measurement of fluorescence development during copper-catalysed oxidative modification of low density lipoprotein. The lag phase was increased by 27 % (p < 0.001) at week 1 and by 24% (p < 0.001) at week 2 in the troglitazone treated group compared with the placebo group. A number of variables known to influence the resistance of low density lipoprotein to oxidation were measured. They included macronutrient consumption, plasma and lipoprotein lipid profile, alpha-tocopherol, beta-carotene levels in low density lipoprotein, low density lipoprotein particle size, mono and polyunsaturated fatty acid content of low density lipoprotein and pre-formed low density lipoprotein hydroperoxide levels in low density lipoprotein. Troglitazone was associated with a significant reduction in the amount of pre-formed low density lipoprotein lipid hydroperoxides. At weeks 1 and 2, the low density lipoprotein hydroperoxide content was 17% (p < 0.05) and 18% (p < 0.05) lower in the troglitazone group compared to placebo, respectively. In summary the increase in lag phase duration in the troglitazone group appeared to be due to the compound's activity as an antioxidant and to its ability to reduce the amount of preformed low density lipoprotein lipid hydroperoxides. This antioxidant activity could provide considerable benefit to diabetic patients where atherosclerosis accounts for the majority of total mortality.     

Effect of estradiol metabolites on the susceptibility of low density lipoprotein to oxidation

The presence of a benign osteoblastoma in the ethmoid sinus is rare and only a few cases have been reported. This is a case of a benign osteoblastoma arising from the perpendicular plate of the ethmoid bone with extension to the nasal cavity. The diagnosis and management of this unusual lesion, as well as the histopathology and the imaging characteristics are reviewed. We also review the previously reported cases of benign osteoblastomas of different origin, with nasal cavity involvement.     

Role of apolipoprotein B-derived radical and alpha-tocopheroxyl radical in peroxidase-dependent oxidation of low density lipoprotein

The peroxidation of low density lipoprotein (LDL) may play an important role in the modification of the lipoprotein to an atherogenic form. The oxidation of LDL by peroxidases has recently been suggested as a model for in vivo transition metal ion-independent oxidation of LDL (Wieland, E., S. Parthasarathy, and D. Steinberg. 1993. Proc. Natl. Acad. Sci. USA. 90: 5929-5933). It is possible that in vivo the peroxidase activities of proteins, such as prostaglandin synthase and myeloperoxidase, promote LDL oxidation. We have used horseradish peroxidase (HRP) and H2O2 as a model of peroxidase-dependent oxidation of LDL and we observed the following during HRP/H2O2-initiated LDL oxidation. i) The oxidation of alpha-tocopherol occurred with the concomitant formation of alpha-tocopheroxyl radical. This was followed by the production of an apolipoprotein B (apoB)-derived radical. The apoB radical and the alpha-tocopheroxyl radical were formed under both aerobic and anaerobic conditions. ii) Inclusion of N-t-butyl-alpha-phenylnitrone (PBN) did not inhibit alpha-tocopheroxyl radical formation. The ESR spectrum of a PBN/LDL-lipid derived adduct was observed after prolonged incubation. iii) There was formation of conjugated dienes, lipid hydroperoxides and thiobarbituric acid reactive substances. Our data indicate that HRP/H2O2 oxidizes both alpha-tocopherol and apoB to the corresponding radicals and concomitantly initiates lipid peroxidation.