Human Plasma Low Density Lipoproteins Research Articles

Ubiquinol-10 and total peroxyl radical trapping capacity of LDL lipoproteins during aging: The effects of Q-10 supplementation

Evidence is rapidly accumulating that oxidative modification of low density lipoprotein (LDL) may play an important role in the pathogenesis of atherosclerosis. In this study we measured the total peroxyl radical trapping capacity of human plasma LDL phospholipids (TRAP LDL) with a luminescent method. The study was carried out with 70 healthy volunteers, aged 28–77. In males an age-related decrease in TRAP LDL was observed. In the age group under 50 years the mean TRAP LDL was 31.36 ± 1.45 pmol peroxyl radicals/nmol Pi; among those over 50 years it was significantly lower at 26.67 0.94 pmol/nmol Pi. As regards the components of TRAp LDL, the concentration of LDL-ubiquinol did not change and a non-significant decrease in the LDL-tocopherol concentration was detected with age. In females, the mean TRAP LDL, LDL-ubiquinol-10 and tocopherol concentrations did not differ between the age groups. When 17 of the participants were given coenzyme Q 10 (Q 10) supplementation, 100 mg/day, a highly significant increase in LDL-ubiquinol concentration was detected. Our results indicate that LDL antioxidant defenses tend to decrease with age in the Finnish male population. The decline is most significant in males under 50 years; in older age groups the values remain stable at a low level. Q 10 supplementation doubles the number of ubiquinol-10-containing LDL molecules and may therefore have an inhibitory effect on LDL oxidation.

Bilirubin sensitized photooxidation of human plasma low density lipoprotein

Previous investigations have shown that the bile pigment bilirubin can act as peroxyl radicals scavenger and transition metals trap, but also as a prooxidant, to erythrocyte ghost membranes through 102driven photooxidation. In the present study we examined the changes occurring in the lipoprotein particle following bilirubin-sensitized photooxidation of isolated plasma LDL. The oxidative stress resulted in increased TBA reactivity, diene formation, free cholesterol oxidation, apo B fragmentation and enhanced uptake of the modified particle by the mouse macrophage scavenger receptors as well as the decrease binding to the native B, E-receptor on fibroblasts. The marked increase in TBARS production in D20-enriched medium and the inhibition of lipid peroxidation of azide is consistent with singlet oxygen involvement in the oxidation process. The apo B-bound Cu2+ appears to become redox active during photooxidation since the presence of EDTA in the reaction mixture greatly reduced protein fragmentation. It was also found that BHT inhibited almost completely the lipid peroxidation, as determined by the TBA reaction but could not totally abolish the formation of 5 a-hydroxycholesterol, which is the main product formed by the direct attack of 102 on cholesterol. The results of this work strongly suggest that, through photooxidation by light-activated bilirubin, the lipoprotein particle may be modified in the blood stream as well, besides being modified in the well known oxidation site within the arterial wall. Our findings provide the rationale for extending these studies to clinical investigations, which aim at developing strategies for minimizing damage to arterial tissue following phototherapy of hyperbilirubinemic newborns or cancer patients after systemic administration of photosensitizers.

Selective uptake of boronated low-density lipoprotein in melanoma xenografts achieved by diet supplementation.

The lipid core of human plasma low-density lipoprotein (LDL) was extracted using hexane and the LDL reconstituted with the addition of n-octyl-carborane. Biodistribution studies of the boronated LDL were performed in BALB/c mice bearing subcutaneous Harding-Passey melanoma xenografts. When diet supplementation with coconut oil and cholesterol for 21 days and regular dosing with hydrocortisone for 7 days before the studies was used to down-regulate the liver LDL receptors and the adrenal receptors, respectively, the tumour-blood boron concentration ratio of 5:1 was achieved.

Characterization and determinants of an electronegatively charged low-density lipoprotein in human plasma.

There is evidence that oxidative modification of low density lipoprotein (LDL) is an important step in the atherosclerotic process. Electronegatively charged LDL has been found in the atherosclerotic lesions of rabbit and human and it is supposed to represent an early modification of LDL in the oxidative process in vivo. We describe a chromatographic method for determination of an LDL subfraction (LDL-) percentage from plasma LDL and the investigation of the lipid composition of native LDL and LDL- fractions separated by this method. We also studied the main determinants of the change in plasma LDL- level in a population sample of 45 men during a 6-months follow-up period. The LDL- fraction separated by anion-exchange chromatography had significantly higher triglyceride and free cholesterol and significantly lower phospholipid and total cholesterol contents, and lower alpha-tocopherol to triglyceride ratio than native LDL. In a 6-month follow up of 45 subjects, decreases in the ratio of blood glutathione disulphide to reduced glutathione, in serum LDL cholesterol and in serum n-3 polyunsaturated fatty acids, and an increase in plasma beta-carotene concentration had independent associations with a decrease of LDL-. The linear regression model including only these four variables was able to account for 47% of the variation of LDL-. Our findings suggest that the change in the plasma LDL- percentage measured by an anion-exchange liquid chromatography is predicted by changes in the major determinants of lipid peroxidation.

Supplementation with Carotenoids Inhibits Singlet Oxygen-Mediated Oxidation of Human Plasma Low-Density Lipoprotein

To study the role of carotenoids in the antioxidant defense against oxidative modification of low-density lipoprotein (LDL) particles, human LDL rich in β-carotene and lycopene was prepared from a healthy volunteer following long-term supplementation with tomato juice. This carotenoid-supplemented LDL accumulated cholesteryl ester hydroperoxides (CE-OOH) more slowly than the LDL prepared before supplementation when the suspensions containing these LDL were subjected to a singlet oxygen-generating system. However, there was no significant difference in the rate of CE-OOH accumulation between the two suspensions when they were exposed to a water-soluble radical generator. Therefore, it is strongly suggested that supplementation of LDL with carotenoids mainly improves the antioxidant defense against the attack of singlet oxygen. Keywords: Carotenoids; singlet oxygen; low-density lipoprotein; atherosclerosis

The new oral hypoglycemic agent, CS-045, inhibits the lipid peroxidation of human plasma low density lipoprotein in vitro

Several lines of evidence have revealed that the oxidative modification of low-density lipoprotein (LDL) is probably associated with the genesis of the atherosclerotic region. CS-045 is a new (thiazolidine) class of oral hypoglycemic agent which has a hindered phenol in the side chain (an analogue of α-tocopherol). The present results indicate that CS-04S had a relatively high antioxidative potency in inhibiting the lipid peroxidation of human plasma LDL in vitro induced by 2,2′-azobis(2-amidinopropane) dihydrochloride (AAPH) compared with that of α-tocopherol. These findings suggest that CS-045 may be useful in preventing the progression of atherosclerosis in diabetic patients.

Lipid ester-bound aldehydes among copper-catalyzed peroxidation products of human plasma lipoproteins.

We have isolated the core aldehydes (aldehydes still bound to parent molecules) of phosphatidylcholine (PC) and cholesteryl esters (CE) from copper-catalyzed peroxidation of human plasma low (LDL) and high (HDL) density lipoproteins. The aldehydes were isolated by extraction with acidified chloroform-methanol containing 2,4-dinitrophenylhydrazine. The 2,4-dinitrophenylhydrazone (DNPH) derivatives formed were resolved by reversed phase high performance liquid chromatography (HPLC) and identified by on-line quadrupole mass spectrometry (LC/MS). The major PC core aldehydes from oxidized LDL and HDL were identified as 1-palmitoyl-(1-stearoyl) 2-(9-oxononanoyl)-, 1-palmitoyl-(1-stearoyl) 2-(8-oxooctanoyl)-, and 1-palmitoyl-(1-stearoyl) 2-(5-oxovaleroyl)-sn-glycerols after phospholipase C digestion of the DNPH derivatives of the phospholipids. The major aldehydes from peroxidation of cholesteryl esters were the 9-oxononanoyl, 8-oxooctanoyl, and 5-oxovaleroyl esters of cholesterol and 7-ketocholesterol. The core aldehydes were estimated to account for a minimum of 1-2% of the consumed linoleate and arachidonate esters. A relatively smaller yield of the PC core aldehydes from LDL compared to HDL was attributed to the presence of greater amounts of phospholipases in LDL than in HDL. More comparable yields of PC core aldehydes were obtained in the presence of phenylmethylsulfonylfluoride, which inhibits phospholipases. We conclude that peroxidation of LDL and HDL results in formation of detectable amounts of cholesteryl and glycerophospholipid esters containing aldehyde functions. The yield of PC aldehydes varies with the activity of the platelet activating factor (PAF) acetyl hydrolase.

4-Hydroxy-2-nonenal-Trapping ELISA: Direct Evidence for the Release of a Cytotoxic Aldehyde from Oxidized Low Density Lipoproteins

Among the aldehydes that originate from the peroxidation of cellular membrane lipids, 4-hydroxy-2-nonenal (HNE) is thought to be largely responsible for cytopathological effects observed during oxidative stress. Taking advantage of the fact that HNE is very reactive with proteins and forms stable Michael addition-type adducts, a novel immunochemical procedure for quantifying "free" HNE has been developed. The method designated as "HNE-trapping ELISA" is based on the detection of HNE trapped by a protein that has been coated in the immunoplate. The HNE-derived epitopes generated in the coating protein are then detected by the ELISA using a monoclonal antibody (mAbHNEJ-2) specific to the haptenic groups of the HNE-protein conjugates. Using this method, we determined that a considerable amount of HNE was released from human plasma low density lipoproteins (LDL) treated with copper ions or endothelial cells.

Fluorescence properties of oxidised human plasma low-density lipoproteins

Appearance of fluorescence emission between 380–550 nm (λexc 350–400 nm) in freshly prepared low-density lipoprotein from asymptomatic normolipemic human plasma revealed the presence of in vivo oxidative modification of its protein moiety. Low-density lipoprotein elicited seven fluorophores in three dimensional fluorescence spectrogram. Assignment of fluorescent chemical structures originating from oxidative modification of the protein moiety of low-density lipoprotein has been made with the help of second derivative fluorescence spectroscopy.

Structural and functional properties of human and mouse apolipoprotein A-I

Mouse and human plasma apolipoprotein A-I (apo A-I m and apo A-I h, respectively) were investigated to compare their molecular properties in solution, their incorporation into palmitoyloleoylphosphatidylcholine-apo A-I (POPC-apo A-I) discoidal complexes, their structural stability in discoidal complexes and high-density lipoproteins (HDL), and their effect on structural rearrangement of discoidal complexes upon interaction with low-density lipoproteins (LDL). Unlike apo A-I h, only minimal concentration-dependent self-association was observed for apo A-I m. While both apo A-I m and apo A-I h formed discoidal complexes of distinct composition and size that reflected reassembly molar ratios of POPC/apo A-I, apo A-I m demonstrated specific deficiencies in formation of larger-sized complexes. Denaturation of both apo A-I m- or apo A-I h-containing complexes and HDL with guanidine hydrochloride (GuHCl) indicated significantly reduced stabilization of apo A-I m by lipid in these particles. Interaction of apo A-I m- or apo A-I h-containing discoidal complexes with human plasma LDL revealed a more extensive conversion of apo A-I m-complexes to smaller species. Mean hydrophobicities and mean hydrophobic moments of amphipathic helical segments in apo A-I m and apo A-I h were compared; differences potentially contributing to differential lipid-binding properties between apo A-I m and apo A-I h were identified. Our results demonstrate differences between apo A-I m and apo A-I h that may contribute to the major changes in plasma HDL distribution and function observed in apo A-I h transgenic mice.

Combined effects of lipid transfers and lipolysis on gradient gel patterns of human plasma LDL.

The triglyceride content of the plasma very-low-density lipoprotein (VLDL) fraction is the most important factor affecting the size of low-density lipoprotein (LDL) in humans. Because cholesteryl ester transfer protein (CETP) can influence the size distribution of LDL particles in human plasma, the implication of lipid transfers in the formation of small-sized LDL patterns, which have been associated with elevated plasma triglyceride levels, was investigated. The size distribution of LDL particles in 15 plasma samples was determined by electrophoresis of the plasma LDL fraction on 20 to 160 g/L polyacrylamide gradient gels. The apparent diameter of the major LDL subfraction was shown to correlate negatively with triglyceride concentrations (r = -.706, P < .005) and positively with both high-density lipoprotein cholesterol levels (r = .637, P < .02) and the high-density lipoprotein/VLDL + LDL cholesterol ratio (r = .768, P < .001). In addition, LDL size correlated negatively with both the ability of plasma LDL to donate cholesteryl esters (r = -.79, P < .001) and its ability to acquire triglycerides (r = -.72, P < .005). Whereas these observations indicated that CETP-mediated alterations of the triglyceride/cholesteryl ester ratio of the LDL core would contribute to changes in LDL diameter, they suggested that the formation of small-sized gradient gel LDL patterns would require another biochemical event, such as lipolysis, in addition to neutral lipid transfers. To test this hypothesis, total plasma samples with or without added VLDL (added triglyceride concentration, 2.0 g/L) were preincubated for 24 hours at 37 degrees C. Preincubation mainly induced the replacement of cholesteryl esters by triglycerides in the LDL core, and changes in LDL composition were greater when total plasma was supplemented with VLDL. Subsequently, isolated LDL was incubated in the presence of bovine milk lipoprotein lipase as a source of triglyceride hydrolysis activity. Lipolysis tended to reduce the size of the major LDL subpopulation, and the mean change in LDL diameter was significantly greater when plasma was preincubated with VLDL supplementation than when it was not (-0.6 +/- 0.3 versus -0.2 +/- 0.2 nm, respectively; (P < .01). Moreover, sequential effects of lipid transfer and lipolysis activities induced dramatic changes in the general shape of gradient gel LDL patterns. The largest plasma LDL subpopulations tended to disappear, and the formation of new, small LDL particles could be observed. The combined effects of neutral lipid transfers and triglyceride hydrolysis could account for variations of gradient gel LDL profiles in human plasma.(ABSTRACT TRUNCATED AT 400 WORDS)

Long- and medium-chain triacylglycerols in neutral lipid-exchange processes with human plasma low-density lipoproteins.

To explore the effects of various molecular species of triacylglycerols on neutral lipid exchange processes, we compared the in vitro transfer of triacylglycerols and cholesteryl esters between phospholipid-stabilized emulsions of medium-chain triacylglycerols (MCT) or long-chain triacylglycerols (LCT) and human plasma low-density lipoproteins (LDL). Incubations were performed with MCT, LCT, or mixed MCT/LCT (1:1, w/w ratio) emulsions with LDL over varying ratios and/or time periods, in the presence or absence of human cholesteryl ester transfer protein (CETP). Relative triacylglycerol mass content increased up to 5-6-fold in LDL with all emulsions, but LDL cholesteryl ester loss was about 33-50% lower with MCT as compared to LCT emulsion. In the absence of CETP, there was a significant transfer of MCT but not of LCT to LDL, and cholesteryl ester exchange never occurred. Spontaneous transfer of MCT in the absence of CETP accounted for half of the total MCT transfer. In fact, CETP-mediated transfer of MCT was less than that of LCT when normalized to the molar concentrations of MCT and LCT in the incubations. Net triacylglycerol accumulation in LDL was accompanied by LDL cholesteryl ester depletion (i.e., exchange), while the greater MCT accumulation could be related to increased solubility at the LDL phospholipid surface (Deckelbaum et al., 1990). This property may also have contributed to some back transfer of MCT from LDL and decreased LDL cholesteryl ester removal, in the presence of MCT emulsions.(ABSTRACT TRUNCATED AT 250 WORDS)

The ESR characterization of molecular mobility in the lipid surface layer of human serum lipoproteins

Three different nitroxides were used to probe either the head group (Tempil stearate) or acyl chain region (Spin labeled cholestane (ChSl) and methyl ester of 5 doxyl palmitate (MeFASL(10,3))) of human plasma low density lipoproteins (LDL) and very low density lipoproteins (VLDL). The ESR data were compared with the simulated spectra which assume rapid anisotropic motion of nitroxide. The results indicate that in the head group region of both LDL and VLDL only the slowing down of the rotational motion occurred when temperature was lowered and the whole region showed up as a unique compartment. On the other hand, the acyl chain region, probed with MeFASL(10,3), behaved as one compartment at physiological temperatures, while at lower temperatures coexistence of fluid and immobilized components were observed. The ESR spectra of lipoproteins labeled with Cholestane showed even higher sensitivity to the mobility constraints. Here, the LDL spectra revealed a drastic immobilization of ChSl axial rotation already at physiological temperatures. The results of these experiments were discussed in terms of core phase transition and/or lipid-protein interactions.

Consumption of carotenoids in photosensitized oxidation of human plasma and plasma low-density lipoprotein

Human plasma and plasma low-density lipoprotein (LDL) were exposed to photoirradiation in the presence of methylene blue (water-soluble photosensitizer) or 12-(1-pyrene)dodecanoic acid (P-12, lipid-soluble photosensitizer). In methylene-blue-sensitized photooxidation of human plasma and LDL, endegenous carotenoids and tocopherols were consumed with the accumulation of cholesteryl ester hydroperoxides (CE-OOH). Xanthophylls (zeaxanthin and lutein) decreased faster than lycopene and carotenes in the case of human plasma. In P-12-sensitized photooxidation of human plasma and LDL, the decrease rate of xanthophylls was slower than that of lycopene and carotenes. A lower level of β-carotene exerted the effective inhibition of lipid peroxidation and retarded the oxidative loss of α-tocopherol, when the phosphatidy;choline liposomes containing these two lipid-soluble antioxidants were subjected to methylene blue- or P-12-sensitized photooxidation. These results suggest that antioxidant activity of carotenoids in photosensitized oxidation (Type II) of human plasma LDL depends on the site of singlet oxygen ( 1O 2) to be generated and that carotenoids can protect tocopherols from the oxidative loss by 1O 2 in the plasma.

Glycated LDL concentrations in non-diabetic and diabetic subjects measured with monoclonal antibodies reactive with glycated apolipoprotein B epitopes.

The potential importance of the non-enzymatic glycation of low density lipoproteins (LDL) in atherogenesis and in the accelerated atherosclerosis associated with diabetes is well recognized. However, it has been difficult to evaluate LDL glycation in the clinical setting because of the lack of suitable methods. To approach this problem, we produced monoclonal antibodies, designated ES12, that recognize glycated apolipoprotein B epitopes in the LDL complex in human plasma. Here we report the use of these antibodies in a competitive enzyme-linked immunosorbent assay (ELISA) to measure glycated LDL concentrations in plasma from non-diabetic and diabetic subjects. In this assay, glycated LDL in the soluble phase inhibits binding of the ES12 antibody to glycated LDL immobilized to microtitre wells, whereas other glycated proteins and non-glycated LDL do not compete. A linear dose-response relationship for 10-125 ng glycated LDL per well allows the construction of standard curves, from which the concentration of glycated LDL in human plasma can be determined. The mean concentration of glycated LDL in samples from non-diabetic subjects was 21.8 +/- 0.9 mg/l, increasing to 40.8 +/- 2.6 mg/l in samples from patients with type II diabetes, comprising 1.9-4.8% and 3.2-14.8%, respectively, of total apolipoprotein B. Glycated LDL concentrations in samples from diabetic patients correlated positively and significantly with other indices of glycaemic status. The results indicate that circulating glycated LDL, which may have diagnostic and pathophysiologic importance, is increased in diabetes with attendant hyperglycaemia. The results further indicate that the described monoclonal antibody-based competitive ELISA affords a simple and reproducible method for quantitative measurement of glycated LDL.

Glycation and oxidation of human low density lipoproteins reduces heparin binding and modifies charge.

The effects of glycation and oxidation of human low density lipoproteins (LDL) on heparin binding were studied and compared with modifications in the charge of the particles. Glycation of LDL at a molar ratio of 4 mol glucose mol-1 apoB, decreases affinity for heparin, as shown by heparin-agarose affinity chromatography since salt molarity needed for elution decreases from 550 mmol l-1 for control LDL (c-LDL) to 350 mmol l-1 for glycated LDL (glc-LDL). Oxidized LDL (oxi-LDL) shows marked heterogeneity, most of the fractions having decreased affinity. Heparin-agarose affinity chromatography of LDL preparations shows the presence of a small (5-7%), low-affinity fraction in euglycaemic human plasma LDL (c-LDL). Its elution volume coincides with both glc-LDL and a fraction of oxi-LDL, suggesting it may contain glycated and oxidized molecules present in plasma. DEAE-Trisacryl anion exchange chromatography elution profiles of c-LDL preparations shows the presence of a more electronegative fraction accounting for about 10% of total protein. This fraction elutes with 260 mmol l-1 NaCl instead of 130 mmol l-1 for the main fraction, it roughly coincides with elution volumes of main peaks of glc-LDL and oxi-LDL. Results indicate that glycated particles may be present in this fraction. Our data demonstrate then that glycation, and to a lesser degree, oxidation of LDL reduce affinity to heparin. From an analytical approach, modified LDL can be separated from the bulk of native LDL both by DEAE and heparin-agarose chromatographies.(ABSTRACT TRUNCATED AT 250 WORDS)

Cryopreservation with sucrose maintains normal physical and biological properties of human plasma low density lipoproteins.

The ability to preserve low density lipoprotein (LDL) preparations frozen for weeks and months without changes in structure or biological properties is of potential use in long-term comparative studies of LDL. We demonstrate that freeze-thawing of LDL causes marked alterations in its structure and biological behavior, and that such changes can be prevented by the addition of sucrose to the LDL solution prior to freezing. Freezing LDL at -70 degrees C in the absence of sucrose resulted in aggregation and fusion of particles as measured by electron microscopy, spectrophotometric absorption, and column gel filtration. This was associated with increased binding affinity of monoclonal antibodies at epitopes distant from the receptor binding region. Functional changes induced by freezing included 3- to 10-fold increases in binding at 4 degrees C and 37 degrees C, and uptake of LDL in fibroblasts, attributable mainly to increases in nonspecific binding processes. Cryopreservation of LDL in 10% sucrose (w/v) completely prevented the structural and functional changes incurred after short-term freezing, and LDL cryopreserved in sucrose for as long as 18 months displayed cell binding, uptake, and degradation very similar to that of freshly obtained LDL.

Low density lipoprotein-receptors in primary cultures of rat glial cells

Newborn rat glial cells in primary culture contain an active cholesterol side chain cleavage cytochrome P450. Cholesterol can be supplied either by biosynthesis or derive from low density lipoproteins (LDL), which bind apolipoprotein Band E (apoB, E) (LDL)-receptors and undergo receptor-mediated endocytosis. Using antibodies to purified human plasma LDL and antibodies to bovine adreno-cortical LDL-receptor, the presence of LDL-receptors was demonstrated on rat glial cells after 3–4 weeks of primary culture, by ligand blotting, immunoblotting, and indirect immunofluorescence staining. The latter approach indicated that oligodendrocytes express higher levels of LDL-receptors than astrocytes present in the same culture. The immunofluorescence staining was observed not only at the cell surface, but also within the cytoplasm, suggesting that the LDL-receptor complexes had been internalized. Western blotting of LDL-receptors extracted from glial cells indicated a band of ∼130 kDa, the size expected for intact receptors. Their functionality was shown by the conversion of [ 3H]cholesterol linoleate, incorporated into reconstituted LDL and added to the cell cultures, to [ 3H]pregnenolone and/or its 20α-hydroxy-metabolite. This is the first characterization of functional LDL-receptors on isolated, well characterized, normal brain cells.

Heparin binding to human plasma low-density lipoproteins: dependence on heparin sulfation degree and chain length.

Binding between low-density lipoproteins (LDL) and fluorescein-labeled heparin was studied quantitatively with a modified form of a published procedure [Cardin, A. D., Randall, C. I., Hirose, N., & Jackson, R. L. (1987) Biochemistry 26, 5513-5518], using fluorescence anisotropy titrations. Assumption of binding site equivalence satisfactorily interpreted experimental data. Accordingly, the apparent total capacity, n, and the average dissociation constant, Kd, were estimated as n approximately 24 disaccharides per LDL particle and Kd approximately 4 microM in 0.05 M HEPES/0.1 M NaCl, pH 7.4, 22 degrees C. Competition experiments with unlabeled heparins were exploited for the quantitative study of Kd as a function of heparin chain length and sulfation degree (ns = sulfate groups per disaccharide). The former parameter was investigated with a series of bovine lung heparin fractions with Mw ranging from 1,800 to 21,000 and constant sulfation degree (ns = 2.8 +/- 0.1). A series of physically fractionated or chemically modified heparins having 1.2 less than ns less than 3.5 were used to explore the dependence on sulfation degree. LDL affinity was found to increase with increasing both ns and Mw: an empirical Mw-1.6 dependence represented very well the chain length data set; a linear dependence was observed for log Kd as a function of ns, after appropriate allowance was made for chain length differences among samples. This regularity confirmed that LDL-heparin binding is mainly driven by electrostatic forces.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of hypercholesterolemia on the nucleotide content in human blood cells.

In hypercholesterolemia significant changes in the nucleotide pattern of erythrocytes and lymphocytes as determined by high performance liquid chromatography were found. The decrease in ATP of lymphocytes in hypercholesterolemia from 10.4 +/- 0.3 to 7.0 +/- 0.4 nmol mg-1 protein (n = 8) was associated with an increase in ADP from 2.2 +/- 0.2 to 4.0 +/- 0.2 nmol mg-1 protein (P less than 0.005). The pattern of guanosine phosphates likewise was found to be changed in hypercholesterolemia. Akin to lymphocytes, red blood cells displayed marked changes in nucleotide levels. No such changes were observed in platelets. Cultured lymphocytes incubated with human plasma low density lipoproteins (LDL) (140 mg cholesterol dl-1) displayed a reversible fall in ATP and an increase in ADP by about 40% and 160%, respectively, with high density lipoproteins (HDL) or very low density lipoproteins (VLDL) being essentially ineffectual. It is concluded that in hypercholesterolemia a significant change in the nucleotide pattern of blood cells is exerted by the increase in LDL. Possible pathophysiological implications are discussed.