Factor VII Activation, Apolipoprotein A-I and Reverse Cholesterol Transport: Possible Relevance for Postprandial Lipaemia

Postprandial lipaemia is associated with activation of factor VII (FVII) and efflux of cholesterol from tissues to nascent plasma high density lipoproteins (HDL) containing apolipoprotein A-I (apo A-I). To determine whether FVII activation and cholesterol efflux occur together in other situations, the responses to intravenous infusion of HDL-like apo A-I/phosphatidylcholine discs were measured in 10 healthy men. Disc infusion (40 mg apo A-I/kg body weight) over 4 h was followed by increases in HDL cholesteryl ester and plasma apo A-I (p <0.0001). Significant activation of FVII was apparent during infusion in fasting subjects (p = 0.03), activated FVII averaging 123% of baseline value by 12 h (p <0.0001). Plasma thrombin-antithrombin (TAT) complex increased to 156% of baseline level by 12 h (p >0.05) but individual responses differed considerably. Peak TAT post-infusion was associated inversely with peak HDL triglyceride concentration (p = 0.004). The coagulation responses to disc-infusion may be due to transfer of phosphatidylserine to cell surfaces during cholesterol efflux.

Very Low Activated Factor VII and Reduced Factor VII Antigen in Familial Abetalipoproteinaemia

Abetalipoproteinaemia is a rare disorder of apolipoprotein B metabolism associated with extremely low plasma concentrations of triglyce-ride. To discover whether the general positive association between factor VII and triglyceride levels extends to this condition, 5 patients were compared with 18 controls. All patients had a triglyceride below 100 μmol/l. Plasma unesterified fatty acid concentration was normal. Although factor IX activity was only slightly reduced (mean 88% standard) and factor IX antigen was normal, mean activated factor VII in patients was strikingly reduced to 34% of that in controls, a level similar to that found in haemophilia B. The patients’ mean factor VII activity and factor VII antigen were also significantly reduced to 54% and 63% of those in controls, respectively. Mean factor XI activity and tissue factor pathway inhibitor activity were reduced in patients to 70% and 75% of control values respectively, while factor XII, factor XI antigen, factor X, prothrombin and protein C were normal.

Isotopic Thermal Diffusion Factors for Helium and Neon at Low Temperatures

With an all-metal “swing separator” having unique features, thermal diffusion factors αT for He3/He4 and Ne20Ne22 have been measured with improved accuracy down to average gas temperatures T̅=136°K. For helium αT is 0.0696 ± 0.0010 at 136°K, dropping gradually to 0.0651 ±0.0010 at 313°K. These data, plus measurements by Van der Valk and de Vries at somewhat higher temperatures, agree best with values predicted by an exp-six intermolecular potential with ε/k=9.16 and α=12.7. We are extending these helium measurements down to T=4°K for the lower temperature, to detect if possible quantum corrections to the intermolecular potential. For neon αT increases from 0.0166 ± 0.0010 at 136°K to 0.0233 ± 0.0020 at 310°K, considerably higher than our previously reported values. These T. D. factors for neon are in good agreement with values calculated from an exp-six potential with ε/k = 46.0 ± 0.6 and α=13.

Regulation of macrophage activation

IFN-gamma rapidly primes the macrophage via JAK1/2-STAT1 pathway so that it can subsequently undergo a slower classical type 1 activation upon exposure to T helper (Th)1 cytokines such as IFNgamma or other activators, including tumor necrosis factor and lipopolysaccharide, e.g. in intracellular killing of phagocytosed Mycobacterium tuberculosis. If instead it is driven by Th2 cytokines interleukin (IL)-4 and IL-13, it undergoes alternate type 2 activation, which enhances endocytotic antigen uptake and presentation, mast cell and eosinophil involvement and type 2 granuloma formation, e.g. in response to parasitic and extracellular pathogens. Particle-induced macrophage activation was shown to differ from classical and alternate activation, showing in DNA microarray experiments (complete linkage/ Euclidean distance metric analysis) upregulation of nonsecreted structural/signaling molecules and lack of secreted proinflammatory cyto- and chemokines. The switch-off (deactivation) of already activated macrophages is an active, controlled process in which IL-10 and corticosteroids play important roles and to which 15dPGJ2, PGA1/2 and vasoactive intestinal peptide often contribute.

Factor VII activation, apolipoprotein A-I and reverse cholesterol transport: possible relevance for postprandial lipaemia

Postprandial lipaemia is associated with activation of factor VII (FVII) and efflux of cholesterol from tissues to nascent plasma high density lipoproteins (HDL) containing apolipoprotein A-I (apo A-I). To determine whether FVII activation and cholesterol efflux occur together in other situations, the responses to intravenous infusion of HDL-like apo A-I/phosphatidylcholine discs were measured in 10 healthy men. Disc infusion (40 mg apo A-I/kg body weight) over 4 h was followed by increases in HDL cholesteryl ester and plasma apo A-I (p <0.0001). Significant activation of FVII was apparent during infusion in fasting subjects (p = 0.03), activated FVII averaging 123% of baseline value by 12 h (p <0.0001). Plasma thrombin-antithrombin (TAT) complex increased to 156% of baseline level by 12 h (p >0.05) but individual responses differed considerably. Peak TAT post-infusion was associated inversely with peak HDL triglyceride concentration (p = 0.004). The coagulation responses to disc-infusion may be due to transfer of phosphatidylserine to cell surfaces during cholesterol efflux.

Genetic and environmental determinants of plasma high density lipoprotein cholesterol and apolipoprotein AI concentrations in healthy middle-aged men

The effects of common variants of cholesteryl ester transfer protein (CETP) (TaqIB), hepatic lipase (HL) (-514C>T), lipoprotein lipase (LPL) (S447X) and lecithin cholesterol acyl transferase (LCAT) (S208T) on the determination of high density lipoprotein cholesterol (HDL-C) and apolipoprotein AI (apoAI) levels were examined in 2773 healthy middle-aged men participating in the second Northwick Park Heart Study. The extent of gene:gene, gene:smoking and gene:alcohol interactions were determined. For HDL-C levels, only CETP genotype was associated with significant effects (p&0.0001), with the B2 allele being associated with higher levels in both smokers and non-smokers. This interaction was significant at the lowest tertile of TG, suggesting that TG levels were rate limiting. As previously reported, CETP, LPL and HL genotypes were all associated with significant effects on apoAI levels (all p&0.01), with carriers of the rare alleles having higher levels and with no evidence of heterogeneity of effects in smokers and non-smokers. LCAT genotype was not associated with significant effects on either trait. There was no significant interaction between any of the genotypes and alcohol consumption on either HDL-C or apoAI levels. All genotypic effects were additive for HDL-C and apoAI. Environmental and TG levels explained more than 20% and 5.5% of the variance in HDL-C and apoAI, respectively. The novel aspect of this finding is that genetic variation at these loci explained in total only 2.5% of the variance in HDL-C and 1.89% of the variance in apoAI levels. Thus despite the key roles played by these enzymes in HDL metabolism, variation at these loci, at least as detected by these common genotypes, contributes minimally to the variance in HDL-C and apoAI levels in healthy men, highlighting the polygenic and multifactorial control of HDL-C.

Intravenous apoA-I/lecithin discs increase pre-beta-HDL concentration in tissue fluid and stimulate reverse cholesterol transport in humans

The extent to which plasma HDL concentration regulates reverse cholesterol transport (RCT) is not known. The principal acceptors of unesterified cholesterol (UC) from cultured cells are small pre-beta-HDL, which we have shown increase in plasma during intravenous infusion of apolipoprotein A-I/phosphatidylcholine (apoA-I/PC) discs in humans. We have now examined the effects on tissue fluid HDL and RCT. ApoA-I/PC or proapoA-I/PC discs were infused into 16 healthy males. Eleven had been given intravenous radiocholesterol to label tissue pools; in 12 prenodal leg lymph was collected throughout; and in 8 all feces were collected. The rise in small pre-beta-HDL in plasma was associated with increases in 1) pre-beta-HDL concentration in lymph (all subjects), 2) the size of other lymph HDL (four of four subjects), 3) the cholesterol content of lymph lipoproteins relative to plasma lipoproteins (P < 0.01, n = 4), 4) cholesterol-specific radioactivity in lymph (five of nine subjects), 5) plasma lathosterol (P < 0.004, n = 4), 6) plasma cholesterol esterification rate (P < 0.001, n = 4), and 7) fecal bile acid excretion (P < 0.001, n = 8). These results support the hypothesis that small pre-beta-HDL generated in plasma readily cross endothelium into tissue fluid, and thereby promote efflux of UC from peripheral cells. After delivery to the liver, peripheral cholesterol appears to be utilized more for bile acid synthesis than for biliary cholesterol secretion in humans.

High density lipoproteins reduce organ injury and organ dysfunction in a rat model of hemorrhagic shock

High density lipoproteins (HDLs) inhibit the cytokine-induced expression of endothelial cell adhesion molecules both in vitro and in vivo. We examined the ability of HDLs to mediate a functional anti-inflammatory effect by measuring their ability to prevent neutrophil adhesion and transmigration in vitro. Treatment of human endothelial cell cultures with physiologic concentrations of HDLs inhibited neutrophil binding by 68 +/- 5.9% (mean and se, n=6, P<0.05) and neutrophil transmigration by 48.7 +/- 6.7% (n=8, P<0.05). We then examined the effect of HDLs on inflammatory infiltration and subsequent multiple organ dysfunction syndrome (MODS), associated with trauma in a rat model of hemorrhagic shock. Rats given human HDLs (80 mg apo A-I/kg, i.v.) 90 min after hemorrhage (which reduced mean arterial pressure to 50 mmHg) and 1 min before resuscitation showed attenuation of the increases in the serum levels of markers of MODS normally observed in this model. Severe disruption of the architecture of tissues and the extensive cellular infiltration into those tissues were also largely inhibited in animals that received HDLs. Human HDLs attenuate the MODS associated with ischemia and reperfusion injury after hemorrhagic shock in rats.

Do total and high density lipoprotein cholesterol and triglycerides act independently in the prediction of ischemic heart disease? Ten-year follow-up of Caerphilly and Speedwell Cohorts

Several studies have suggested that men with raised plasma triglycerides (TGs) in combination with adverse levels of other lipids may be at special risk of subsequent ischemic heart disease (IHD). We examined the independent and combined effects of plasma lipids at 10 years of follow-up. We measured fasting TGs, total cholesterol (TC), and high density lipoprotein cholesterol (HDLC) in 4362 men (aged 45 to 63 years) from 2 study populations and reexamined them at intervals during a 10-year follow-up. Major IHD events (death from IHD, clinical myocardial infarction, or ECG-defined myocardial infarction) were recorded. Five hundred thirty-three major IHD events occurred. All 3 lipids were strongly and independently predictive of IHD after 10 years of follow-up. Subjects were then divided into 27 groups (ie, 3(3)) by the tertiles of TGs, TC, and HDLC. The number of events observed in each group was compared with that predicted by a logistic regression model, which included terms for the 3 lipids (without interactions) and potential confounding variables. The incidence of IHD was 22.6% in the group with the lipid risk factor combination with the highest expected risk (high TGs, high TC, and low HDLC) and 4.7% in the group with the lowest expected risk (P<0.01). A comparison of the predicted number of events in the 27 groups with the number of events observed showed that a logistic regression provided an adequate fit without the need to incorporate interactions between lipids in the model. Conclusions are as follows: (1) Serum TGs, TC, and HDLC are independently predictive of IHD at 10 years of follow-up. (2) Combinations of adverse levels of the 3 major lipid risk factors have no greater impact on IHD than that expected from their individual contributions in a logistic regression model. There was no evidence that men with low HDL/raised TGs were at significantly greater risk than that predicted from the independent effects of the 2 lipids considered individually.

Global modulation of cellular transcription by human cytomegalovirus is initiated by viral glycoprotein B

Human cytomegalovirus (HCMV) infection alters the expression of many cellular genes, including IFN-stimulated genes (ISGs) [Zhu, H., Cong, J.-P., Mamtora, G., Gingeras, T. & Shenk, T. (1998) Proc. Natl. Acad. Sci. USA 95, 14470-14475]. By using high-density cDNA microarrays, we show that the HCMV-regulated gene expression profile in fibroblasts does not differ substantially from the response generated by IFN. Furthermore, we identified the specific viral component triggering this response as the envelope glycoprotein B (gB). Cells treated with gB, but not other herpesviral glycoproteins, exhibited the same transcriptional profile as HCMV-infected cells. Thus, the interaction of gB with its as yet unidentified cellular receptor is the principal mechanism by which HCMV alters cellular gene expression early during infection. These findings highlight a pioneering paradigm for the consequences of virus-receptor interactions.

Composition and ultrastructure of size subclasses of normal human peripheral lymph lipoproteins: quantification of cholesterol uptake by HDL in tissue fluids

Peripheral lymph lipoproteins have been characterized in animals, but there is little information about their composition, and none about their ultrastructure, in normal humans. Therefore, we collected afferent leg lymph from 16 healthy males and quantified lipids and apolipoproteins in fractions separated by high performance-size exclusion chromatography. Apolipoprotein B (apoB) was found almost exclusively in low density lipoproteins. The distribution of apoA-I, particularly in lipoprotein A-I (LpA-I) without A-II particles, was shifted toward larger particles relative to plasma. The fractions containing these particles were also enriched in apoA-II, apoE, total cholesterol, and phospholipids and had greater unesterified cholesterol-to-cholesteryl ester ratios than their counterparts in plasma. Fractions containing smaller apoA-I particles were enriched in phospholipid. Most apoA-IV was lipid poor or lipid free. Most apoC-III coeluted with large apoA-I-containing particles. Electron microscopy showed that lymph contained discoidal particles not seen in plasma. These findings support other evidence that high density lipoproteins (HDL) undergo extensive remodeling in human tissue fluid. Total cholesterol concentration in lymph HDL was 30% greater (P < 0.05) than could be explained by the transendothelial transfer of HDL from plasma, providing direct confirmation that HDL acquire cholesterol in the extravascular compartment. Net transport rates of new HDL cholesterol in the cannulated vessels corresponded to a mean whole body reverse cholesterol transport rate via lymph of 0.89 mmol (344 mg)/day.

Radical SAM, a novel protein superfamily linking unresolved steps in familiar biosynthetic pathways with radical mechanisms: functional characterization using new analysis and information visualization methods

A novel protein superfamily with over 600 members was discovered by iterative profile searches and analyzed with powerful bioinformatics and information visualization methods. Evidence exists that these proteins generate a radical species by reductive cleavage of S:-adenosylmethionine (SAM) through an unusual Fe-S center. The superfamily (named here Radical SAM) provides evidence that radical-based catalysis is important in a number of previously well- studied but unresolved biochemical pathways and reflects an ancient conserved mechanistic approach to difficult chemistries. Radical SAM proteins catalyze diverse reactions, including unusual methylations, isomerization, sulfur insertion, ring formation, anaerobic oxidation and protein radical formation. They function in DNA precursor, vitamin, cofactor, antibiotic and herbicide biosynthesis and in biodegradation pathways. One eukaryotic member is interferon-inducible and is considered a candidate drug target for osteoporosis; another is observed to bind the neuronal Cdk5 activator protein. Five defining members not previously recognized as homologs are lysine 2,3-aminomutase, biotin synthase, lipoic acid synthase and the activating enzymes for pyruvate formate-lyase and anaerobic ribonucleotide reductase. Two functional predictions for unknown proteins are made based on integrating other data types such as motif, domain, operon and biochemical pathway into an organized view of similarity relationships.

Lymph draining from foot joints in rheumatoid arthritis provides insight into local cytokine and chemokine production and transport to lymph nodes

OBJECTIVE

Rheumatoid arthritis (RA) is characterized by inflammatory reactions in joints and adjacent tissues unaccompanied by clinically evident changes in lymphatics and lymph nodes draining the inflamed areas. The explanation for this phenomenon, which contrasts with infectious processes in joints and soft tissues that evoke major changes in the lymphatic system, is unclear. To determine which inflammatory factors produced in the joints of RA patients are transported in lymph to lymph nodes, we measured levels of immunoglobulins, cytokines, and chemokines in prenodal lymph from the foot joints of RA patients and quantified their rate of transport to regional lymph nodes.

METHODS

Lymph was collected from the cannulated lymphatics draining the foot joints, tendons, fascia, and skin of 20 RA patients. Lymph flow rate and concentrations of proteins and immunoglobulins were measured. Cytokine and chemokine levels were quantified by enzyme-linked immunosorbent assays. Results were compared with those obtained in 20 control subjects.

RESULTS

In the cannulated vessel, the mean +/- SEM lymph flow rate in RA patients was almost 2-fold that in control subjects (22.6 +/- 3.2 ml/24 hours versus 13.2 +/- 1.1 ml/24 hours; P < 0.01). Lymph concentrations of total protein, IgG, and IgM were 1.80 +/- 0.14 gm/dl, 384 +/- 45 mg/dl, and 32.0 +/- 1.5 mg/dl, respectively, in RA patients and 1.66 +/- 0.14 gm/dl, 238 +/- 32 mg/dl, and 15.0 +/- 1.3 mg/dl, respectively, in control subjects. The corresponding lymph:serum (L:S) ratios were 0.21 +/- 0.02, 0.22 +/- 0.02, and 0.15 +/- 0.02, respectively, in RA patients and 0.22 +/- 0.02, 0.19 +/- 0.02, and 0.11 +/- 0.02, respectively, in control subjects. The L:S ratios of <1 and the absence of significant differences between groups suggested a lack of local production of immunoglobulins. In RA patients, lymph concentrations (in pg/ml) were as follows: interleukin-1beta (IL-1beta) 14.8 +/- 3.9, IL-6 511 +/- 143, tumor necrosis factor alpha (TNFalpha) 9.9 +/- 1.1, IL-1 receptor antagonist (IL-1Ra) 4,274 +/- 737, IL-10 13.3 +/- 4.4, IL-8 846 +/- 174, IL-15 6.2 +/- 0.9, granulocyte-macrophage colony-stimulating factor (GM-CSF) 2.30 +/- 0.15, vascular endothelial growth factor (VEGF) 80.4 +/- 8.6, and macrophage inflammatory protein 1alpha (MIP-1alpha) 171 +/- 34. In control subjects, these values were as follows: IL-1beta 1.50 +/- 0.25, IL-6 79.0 +/- 14.6, TNFalpha 4.4 +/- 1.1, IL-1Ra 208 +/- 52, IL-10 0.0, IL-8 216 +/- 83, IL-15 5.00 +/- 0.45, GM-CSF 0.40 +/- 0.05, VEGF 42.0 +/- 2.4, and MIP-1alpha 3.4 +/- 1.7 (P < 0.05 versus RA patients for all except IL-15). The L:S ratio was >1 in all RA patient samples for IL-1beta, IL-6, IL-1Ra, IL-8, GM-CSF, IL-10, IL-15, TNFalpha, and MIP-1alpha, indicating local production of cytokines. Great variability in lymph cytokine concentrations, presumably reflecting differences in the intensity of local inflammation, was not reflected in serum cytokine concentrations. Intravenously infused methylprednisolone decreased lymph cytokine levels to normal within 12 hours. In contrast, their concentrations in serum showed little or no change.

CONCLUSION

High lymph concentrations of cyto kines and chemokines, exceeding those in serum, were found in RA patients. The L:S concentration ratios of > 1 indicate the local production of these cytokines and chemokines in the inflamed tissues. High flow rates of lymph containing high cytokine concentrations through the regional lymph nodes are likely to affect node lymphocytes and dendritic cells. Analysis of cytokines in lymph should provide insight into events in inflamed tissues in RA and in regional lymph nodes.

Elevation of plasma high-density lipoprotein concentration reduces interleukin-1-induced expression of E-selectin in an in vivo model of acute inflammation

BACKGROUND

Although there is strong evidence that plasma HDL levels correlate inversely with the incidence of coronary artery disease, the precise mechanism(s) for the protective effect of HDLs remains unclear. We recently showed that HDLs inhibit endothelial cell expression of cytokine-induced leukocyte adhesion molecules in vitro. Our study therefore sought to test the hypothesis that elevating the level of circulating HDLs would inhibit endothelial cell activation in vivo.

METHODS AND RESULTS

We used a porcine model of inflammation previously established in our laboratory, in which the level of vascular endothelial cell expression of E-selectin in interleukin (IL)-1alpha-induced skin lesions was measured by the uptake of a radiolabeled anti-E-selectin antibody (1.2B6). Porcine plasma HDL levels were elevated by use of a bolus injection of reconstituted discoidal HDL (recHDL). These particles resemble nascent HDL particles in shape and contain apolipoprotein A-I as the sole protein and soybean phosphatidylcholine as the sole phospholipid. We found that recHDLs inhibited the expression of IL-1alpha-induced E-selectin by porcine aortic endothelial cells in vitro, confirming that the inhibitory effect is conserved with synthetic HDLs and demonstrating that the phenomenon is not restricted to human endothelial cells. In vivo, elevating the circulating level of HDLs approximately 2-fold led to significant inhibition of basal and IL-1alpha-induced E-selectin expression by porcine microvascular endothelial cells.

CONCLUSIONS

These observations demonstrate the potential anti-inflammatory action of HDLs and provide support for the further investigation of the mechanisms underlying the inhibitory effects of HDLs on endothelial cell activation.

Promethazine as a motion sickness treatment: impact on human performance and mood states

PURPOSE

Intramuscular (i.m.) injections of promethazine in 25 mg or 50 mg dosages are commonly used to treat space motion sickness in astronauts. The present study examined the effects of i.m. injections of promethazine on performance, mood states, and motion sickness in humans.

METHODS

Subjects were 12 men, mean age 36 + 3.1, who participated in 1 training day and 3 treatment conditions: a 25-mg injection of promethazine, a 50-mg injection of promethazine, and a placebo injection of sterile saline. Each condition, scheduled at 7-d intervals, required an 8-10-h day in which subjects were tested on 12 performance tasks, and were given a rotating chair motion sickness test. On the training day subjects were trained on each task to establish stability and proficiency. Treatment conditions were counterbalanced and a double-blind procedure was used to administer the medication or placebo.

RESULTS

Statistically significant decrements in performance were observed for both dosages of promethazine as compared with the placebo. Performance decrements were associated with mean blood alcohol dose equivalency levels of 0.085% for 25 mg and 0.137% for 50 mg doses. Mood scale results showed significant changes in individual subjective experiences with maximum deterioration in the arousal state and fatigue level. Only the 25-mg dosage significantly increased motion sickness tolerance when compared with the placebo.

CONCLUSIONS

These data suggest that effective doses of promethazine currently used to counteract motion sickness in astronauts may significantly impair task components of their operational performance.

Distribution of phospholipid transfer protein in human plasma: presence of two forms of phospholipid transfer protein, one catalytically active and the other inactive

Plasma phospholipid transfer protein (PLTP) plays an important role in the maintenance of plasma high-density lipoprotein (HDL) content and remodeling of HDL in the circulation. In the present study we have used different fractionation methods to investigate the distribution of PLTP in human plasma. A novel enzyme-linked immunosorbent assay developed during the study allowed for simultaneous assessment of both PLTP mass and activity in the fractions obtained. Size-exclusion chromatography and plasma fractionation by nondenaturing polyacrylamide gel electrophoresis (PAGE) yielded similar results demonstrating that PLTP associates in native plasma with two distinct particle populations, while ultracentrifugation with high salt leads to detachment of PLTP from lipoprotein particles and loss of a majority of its phospholipid transfer activity. Interestingly, analysis of the size-exclusion chromatography fractions demonstrated that PLTP exists in the circulation as an active population that elutes in the position of HDL corresponding to an average molecular mass of 160+/-40 kDa and an inactive form with an average mass of 520+/-120 kDa. The inactive fraction containing approximately 70% of the total PLTP protein eluted between HDL and low density lipoprotein (LDL). Thus, the two PLTP pools are associated with different types of lipoprotein particles, suggesting that the PLTP activity in circulation is modulated by the plasma lipoprotein profile and lipid composition.

Expression of human apolipoprotein A-I/C-III/A-IV gene cluster in mice induces hyperlipidemia but reduces atherogenesis

The apolipoprotein (apo)A-I/C-III/A-IV gene cluster is involved in lipid metabolism and atherosclerosis. Overexpression of apoC-III in mice causes hypertriglyceridemia and induces atherogenesis, whereas overexpression of apoA-I or apoA-IV increases cholesterol in plasma high density lipoprotein (HDL) and protects against atherosclerosis. Each gene has been studied alone in transgenic mice but not in combination as the entire cluster. To determine which phenotype is produced by the expression of the entire gene cluster, transgenic mice were generated with a 33-kb human DNA fragment. The results showed that the transgene contained the necessary elements to direct hepatic and intestinal expression of the 3 genes. In the pooled data, plasma concentrations were 257+/-9, 7.1+/-0.5, and 1.0+/-0.2 mg/dL for human apoA-I, apoC-III, and apoA-IV, respectively (mean+/-SEM). Concentrations of these apolipoproteins were higher in males than in females. Human apoA-I and apoC-III concentrations were positively correlated, suggesting that they are coregulated. Transgenic mice exhibited gross hypertriglyceridemia and accumulation of apoB(48)-containing triglyceride-rich lipoproteins. Plasma triglyceride and cholesterol concentrations were correlated positively with human apoC-III concentration, and HDL cholesterol was correlated with apoA-I concentration. In an apoE-deficient background, despite being markedly hypertriglyceridemic, cluster transgenic animals compared with nontransgenic animals showed a 61% reduction in atherosclerosis. This suggests that apoA-I and/or apoA-IV can protect against atherosclerosis even in the presence of severe hyperlipidemia. These mice provide a new model for studies of the regulation of the 3 human genes in combination.

Concentrations of electrophoretic and size subclasses of apolipoprotein A-I-containing particles in human peripheral lymph

When cultured cells are exposed to plasma, the initial acceptors of unesterified cholesterol are small lipid-poor apolipoprotein A-I (apoA-I)-containing high density lipoproteins (HDLs) with pre-beta electrophoretic mobility. These are converted by lecithin:cholesterol acyltransferase into larger spheroidal cholesteryl ester-rich HDLs with alpha mobility. To study the determinants of the concentration of small pre-beta HDLs in tissue fluids, we collected prenodal peripheral lymph from 34 fasted normal men. By crossed immunoelectrophoresis, the concentration of pre-beta HDLs in lymph averaged 20% of that in plasma. On multiple regression analysis, pre-beta apoA-I concentration in lymph was directly related to pre-beta apoA-I concentration in plasma and independently to alpha apoA-I concentration in lymph. Similar results were obtained when the same apoA-I-containing particles were quantified by size exclusion chromatography. Lymph pre-beta apoA-I concentration was low in a subject with familial lecithin:cholesterol acyltransferase deficiency, despite a normal plasma pre-beta apoA-I concentration, but was normal in a subject with familial lipoprotein lipase deficiency. These results suggest that the concentration of small pre-beta HDLs in human tissue fluids is determined only in part by the transfer of pre-beta HDLs across capillary endothelium from plasma. Local production, by remodeling of spheroidal alpha HDLs in tissue fluids, may be equally important. Lipolysis of triglyceride-rich lipoproteins by lipoprotein lipase appears to have little effect.

Normal high density lipoprotein inhibits three steps in the formation of mildly oxidized low density lipoprotein: step 1

Apolipoprotein A-I (apoA-I) and an apoA-I peptide mimetic removed seeding molecules from human low density lipoprotein (LDL) and rendered the LDL resistant to oxidation by human artery wall cells. The apoA-I-associated seeding molecules included hydroperoxyoctadecadienoic acid (HPODE) and hydroperoxyeicosatetraenoic acid (HPETE). LDL from mice genetically susceptible to fatty streak lesion formation was highly susceptible to oxidation by artery wall cells and was rendered resistant to oxidation after incubation with apoA-I in vitro. Injection of apoA-I (but not apoA-II or murine serum albumin) into mice rendered their LDL resistant to oxidation within 3 h. Infusion of apoA-I into humans rendered their LDL resistant to oxidation within 6 h. We conclude that 1) oxidation of LDL by artery wall cells requires seeding molecules that include HPODE and HPETE; 2) LDL from mice genetically susceptible to atherogenesis is more readily oxidized by artery wall cells; and 3) normal HDL and its components can remove or inhibit the activity of lipids in freshly isolated LDL that are required for oxidation by human artery wall cells.

Measurement of human plasma phospholipid transfer protein by sandwich ELISA

BACKGROUND

Plasma phospholipid transfer protein (PLTP) plays a central role in the remodeling of HDLs. Reliable and accurate methods for assaying PLTP concentration are required.

METHODS

A sandwich ELISA for PLTP has been developed, using two monoclonal antibodies against recombinant human PLTP (rhPLTP) expressed in Chinese hamster ovary cells. The ELISA allows for the quantification of PLTP in the range 0.625-15.0 ng/assay (1.2-30.0 mg/L). Intra- and interassay CVs were <3.0% and <4.2% respectively. The assay was used to quantify plasma PLTP concentrations in 132 Japanese subjects (75 males and 57 females).

RESULTS

PLTP concentrations were 12.0 +/- 3. 0 mg/L (mean +/- SD; range, 4.9-20.5 mg/L). No sex difference was observed. Plasma PLTP concentration was positively correlated with HDL-cholesterol (r = 0.72; P: <0.001), apolipoprotein (apo) A-I (r = 0.62; P: <0.001) and HDL(2)-cholesterol (r = 0.72; P: <0.001), and was negatively correlated with triacylglycerol (r = -0.45; P: <0. 001). There was no correlation with plasma apo A-II. These results agree with other evidence that plasma PLTP is associated with large apo A-I-containing lipoproteins. There was no correlation (r = -0. 01) between plasma PLTP and plasma phosphatidylcholine transfer activity (range, 3.5-10.5 micromol. mL(-1). h(-1)), suggesting that PLTP may exist in active and inactive forms.

CONCLUSION

This new ELISA will be of value for further studies of PLTP in health and disease.

Lipid and apolipoprotein concentrations in prenodal leg lymph of fasted humans. Associations with plasma concentrations in normal subjects, lipoprotein lipase deficiency, and LCAT deficiency

The extent to which lipid and apolipoprotein (apo) concentrations in tissue fluids are determined by those in plasma in normal humans is not known, as all studies to date have been performed on small numbers of subjects, often with dyslipidemia or lymphedema. Therefore, we quantified lipids, apolipoproteins, high density lipoprotein (HDL) lipids, and non-HDL lipids in prenodal leg lymph from 37 fasted ambulant healthy men. Lymph contained almost no triglycerides, but had higher concentrations of free glycerol than plasma. Unesterified cholesterol (UC), cholesteryl ester (CE), phosphatidylcholine (PC), and sphingomyelin (SPM) concentrations in whole lymph were not significantly correlated with those in plasma. HDL lipids, but not non-HDL lipids, were directly related to those in plasma. Lymph HDLs were enriched in UC. However, as the HDL cholesterol/non-HDL cholesterol ratio in lymph exceeded that in plasma, whole lymph nevertheless had a lower UC/CE ratio than plasma. Lymph also had a significantly higher SPM/PC ratio. The lymph/plasma (L/P) ratios of apolipoproteins were as follows: A-IV > A-I and A-II > C-III and E > B. Comparison with the L/P ratios of seven nonlipoprotein proteins suggested that apoA-IV was predominantly lipid free. Concentrations of apolipoproteins A-II, A-IV, C-III, and E in lymph, but not of apolipoproteins A-I or B, were positively correlated with those in plasma. The L/P ratios of apolipoproteins B, C-III, and E in two subjects with lipoprotein lipase (LPL) deficiency, and of apolipoproteins A-I and A-IV in a subject with lecithin:cholesterol acyltransferase (LCAT) deficiency, were low relative to those in normal subjects. Thus, the concentrations of lipids, apolipoproteins, and lipoproteins in human tissue fluid are determined only in part by their concentrations in plasma. Other factors, including the actions of LPL and LCAT, are at least as important.

A sandwich enzyme-linked immunosorbent assay for human serum paraoxonase concentration

Serum paraoxonase (PON) is associated with plasma high density lipoproteins, and prevents the oxidative modification of low density lipoproteins. We have developed a sensitive sandwich enzyme-linked immunosorbent assay (ELISA), using two monoclonal antibodies against PON, to measure serum PON concentration. The concentration of PON in healthy Japanese subjects was 59.3 +/- 1.3 microgram/mL (mean +/- SEM; n = 87). Serum PON concentrations in relation to the PON 192 genetic polymorphism were: 69.5 +/- 2.9 microgram/mL in the QQ genotype; 63.0 +/- 1.9 microgram/mL in the QR genotype; and 52.8 +/- 1.7 microgram/mL in the RR genotype. Concentrations were significantly lower in the RR than in the QQ genotype (P < 0.01). Serum paraoxonase specific activity was higher in RR than in QQ subjects (18.6 +/- 0.40 vs. 2. 56 +/- 0.05 nmol/min/microgram, P < 0.01), but arylesterase specific activity was unrelated to genotype. PON concentration was positively associated (P < 0.001) with both serum arylesterase activity and, after adjusting for the effect of the position 192 polymorphism, with serum paraoxonase activity. Subjects with angiographically verified coronary heart disease had significantly lower PON concentrations than the healthy controls (52.0 +/- 2.3 microgram/mL; n = 35, P < 0.01). This association was independent of the position 192 genotype. Our new ELISA should be of value for epidemiologic and clinical studies of serum PON concentration. immunosorbent assay for human serum paraoxonase concentration.

Haemostatic factors in human peripheral afferent lymph

Peripheral afferent lymph was obtained by cannulation of a collecting vessel in 17 healthy men (mean age 26 years). Lymph/plasma ratios of all vitamin K-dependent factors were lower than expected from molecular weight. Factor VII, factor IX and tissue factor pathway inhibitor (TFPI) lymph/plasma activity ratios were higher than antigen ratios. Activated factor VII (FVIIa) and TFPI-Xa complex concentrations were higher in lymph than plasma, and the raised FVIIa did not appear to be due to cannulation. The fibrinogen lymph/plasma activity (Clauss) ratio averaged about 20% of the antigen ratio. The result of an ELISA for D-dimer was higher in lymph than plasma, often more than five-fold. This high level in lymph was not explored but may indicate proteolysis of fibrinogen and fibrin with release of D-like and D-dimer-like fragments in interstitial fluid.

Analysis of apolipoproteins and lipoproteins by capillary electrophoresis

Capillary electrophoresis provides a valuable analytical tool for the analysis of apolipoproteins and lipoproteins. Sodium dodecyl sulfate (SDS) capillary gel electrophoresis can resolve human and animal apolipoprotein (apo) A-I, apo A-II, apo E and apo A-IV in isolated high density lipoproteins (HDLs) and is capable of analysing HDL apo A-I and apo A-II content with a coefficient of variation (CV) of less than 5%. Capillary zone electrophoresis (CZE) using coated capillaries with Tricine-urea buffer can also be used for the analysis of HDL apolipoproteins and is also capable of resolving apo A-I isoforms, pro-apo A-I, mature apo A-I and deamidated apo A-I. Furthermore it can separate human A-I from endogenous rabbit A-I in transgenic rabbits expressing the human apo A-I gene. Capillary isoelectric focusing can also separate apo A-I isoforms. Analysis of charge-modified low density lipoprotein (LDL) (ox-LDL) produced by in vitro lipid peroxidation can be performed by CZE and the technique can be used to monitor simultaneous changes in the electrophoretic mobility and absorption spectra of LDL.

High-density lipoproteins differentially modulate cytokine-induced expression of E-selectin and cyclooxygenase-2

Atherogenesis is a multifactorial chronic inflammatory disease in which low plasma levels of HDLs are a strong predictor of the condition. Although the mechanism of protection by HDLs is not precisely known, HDLs have been shown to influence many of the events involved in the development of atherosclerosis. Previously we have shown that HDLs inhibited the cytokine-induced expression of adhesion molecules (E-selectin, VCAM-1, and ICAM-1) by endothelial cells (ECs). As the complete transcriptional regulation of all 3 genes requires the NF-kappaB family of transcription factors, we examined the effect of HDLs on activation of NF-kappaB. We also investigated the effect of HDLs on 2 other cytokine-induced genes, granulocyte-macrophage colony-stimulating factor (GM-CSF) and cyclooxygenase (Cox-2; prostaglandin H2 synthase, EC 0.1.14.99.1). E-selectin expression in response to tumor necrosis factor-alpha (TNFalpha) was, as expected, inhibited in ECs that had been preincubated with HDLs. However, the level of secretion of GM-CSF in the same cultures was no different from control. In a similar manner, although HDLs had no effect on steady-state mRNA levels of GM-CSF, the levels of E-selectin were significantly inhibited by HDLs. In transient cotransfection experiments we found that HDLs inhibited the cytokine-induced expression of a reporter gene driven by the E-selectin proximal promoter (-383 to 80) but had no effect on the expression of a reporter gene driven under the control of the proximal promoter of GM-CSF (-627 to 28). As would be predicted from this differential response, HDLs did not influence the nuclear translocation or DNA binding of NF-kappaB, or alter the kinetics of degradation and resynthesis of the inhibitory protein IkappaBalpha. We found that HDLs synergized with cytokine to enhance the expression of Cox-2 and induce the synthesis of its main EC product, prostacyclin (PGI2), a potent inhibitor of platelet and leukocyte functions. In conclusion, HDL induces an antiinflammatory phenotype in cytokine-induced ECs, synergizing with cytokine to induce elevation of Cox-2 in addition to inhibiting adhesion molecule expression. Our studies show that these differential effects are mediated in a manner that is likely to be independent of NF-kappaB per se.

Acute effects of intravenous infusion of ApoA1/phosphatidylcholine discs on plasma lipoproteins in humans

To investigate the metabolism of nascent HDLs, apoA1/phosphatidylcholine (apoA1/PC) discs were infused IV over 4 hours into 7 healthy men. Plasma total apoA1 and phospholipid (PL) concentrations increased during the infusions. The rise in plasma apoA1 was greatest in small prebeta-migrating particles not present in the infusate. Total HDL unesterified cholesterol (UC) also increased simultaneously. After stopping the infusion, the concentrations of apoA1, PL, HDL UC, and small prebeta HDLs decreased, whereas those of HDL cholesteryl ester (CE) and large alpha-migrating apoA1 containing HDLs increased. ApoB-containing lipoproteins became enriched in CEs. Addition of apoA1/PC discs to whole blood at 37 degrees C in vitro also generated small prebeta HDLs, but did not augment the transfer of UC from erythrocytes to plasma. We conclude that the disc infusions increased the intravascular production of small prebeta HDLs in vivo, and that this was associated with an increase in the efflux and esterification of UC derived from fixed tissues. The extent to which the increase in tissue cholesterol efflux was dependent on that in prebeta HDL production could not be determined. Infusion of discs also reduced the plasma apoB and apoA2 concentrations, and increased plasma triglycerides and apoC3. Thus, nascent HDL secretion may have a significant impact on prebeta HDL production, reverse cholesterol transport and lipoprotein metabolism in humans.

Plant monoterpenes do not raise plasma high-density-lipoprotein concentrations in humans

BACKGROUND

Low plasma concentrations of HDLs are associated with an increased risk of coronary artery disease. Two uncontrolled studies suggested that plant monoterpenes may have substantial HDL-cholesterol-elevating activity in humans. Each study used a proprietary mixture of 6 monoterpenes in olive oil.

OBJECTIVE

The present study was undertaken to test more rigorously the hypothesis that monoterpenes raise HDL concentrations in men with hypoalphalipoproteinemia.

DESIGN

A double-blind, placebo-controlled crossover design was used. Twenty-four men aged 58-68 y (x: 62.3 y) with plasma HDL cholesterol <1.1 mmol/L, plasma triacylglycerols <3.5 mmol/L, and plasma total cholesterol <5.5 mmol/L at recruitment were randomly assigned to 6 capsules daily of a proprietary mixture of 6 monoterpenes in olive oil or 6 capsules daily of olive oil alone for 24 wk, followed by a washout period of 8 wk, and then the alternative capsules for 24 wk.

RESULTS

Five men dropped out. In the others, compliance was excellent as judged by capsule counts and urinary menthol glucuronide concentrations. No significant effects were observed on plasma HDL-cholesterol or apolipoprotein A-I concentrations, nor on plasma triacylglycerol, LDL-cholesterol, or apolipoprotein B concentrations.

CONCLUSIONS

Plant monoterpenes have no HDL-elevating activity of potential value for coronary artery disease prevention.

Very low activated factor VII and reduced factor VII antigen in familial abetalipoproteinaemia

Abetalipoproteinaemia is a rare disorder of apolipoprotein B metabolism associated with extremely low plasma concentrations of triglyceride. To discover whether the general positive association between factor VII and triglyceride levels extends to this condition, 5 patients were compared with 18 controls. All patients had a triglyceride below 100 micromol/l. Plasma unesterified fatty acid concentration was normal. Although factor IX activity was only slightly reduced (mean 88% standard) and factor IX antigen was normal, mean activated factor VII in patients was strikingly reduced to 34% of that in controls, a level similar to that found in haemophilia B. The patients' mean factor VII activity and factor VII antigen were also significantly reduced to 54% and 63% of those in controls, respectively. Mean factor XI activity and tissue factor pathway inhibitor activity were reduced in patients to 70% and 75% of control values respectively, while factor XII, factor XI antigen, factor X, prothrombin and protein C were normal.

Capillary electrophoresis to monitor the oxidative modification of low density lipoproteins

A procedure has been developed that uses high performance capillary electrophoresis to monitor the changes in the electrophoretic mobility of low density lipoproteins (LDL) resulting from Cu2+-catalyzed lipid peroxidation. Using uncoated fused silica capillaries, methylglucamine-Tricine, pH 9.0, as electrophoresis buffer and a field strength of 350 V/cm, separation of native LDL and oxidized LDL could be achieved in 8-10 min. The electrophoretic mobility of native LDL under these conditions was 1.32 x 10(-4) cm2 x V(-1) x s(-1), and the migration time could be measured with a coefficient of variation of 0.44%. The increase in the electronegativity of LDLs during incubation with 10 microM Cu2+ for 0.25-2.0 h resulted in a progressive increase in migration time. Monitoring the absorbance of the migrating LDL particles at a wavelength of 234 nm showed a progressive increase in peak area, which paralleled that in diene conjugation measured spectrophotometrically. Electronegative LDL particles formed by modification with malondialdehyde could also be separated from native LDL particles under these conditions. This new procedure should be useful in studies of factors influencing low density lipoprotein oxidation in vitro and in vivo.

Analysis of high density lipoprotein apolipoproteins by capillary zone and capillary SDS gel electrophoresis

We describe new methods for analyzing the apolipoproteins (apo) of the high density lipoproteins (HDL) of several species by two modes of capillary electrophoresis: size separation using a molecular sieving buffer, and capillary zone electrophoresis (CZE) using neutral coated capillaries. By either mode HDL apos were resolved within 25 min. Results for apoA-I and apoA-II mass agreed with those by electroimmunoassay; intra-assay coefficients of variation were 1.8-4.2%. The migration times of human, rat, rabbit, and bovine apoA-I during CZE were proportional to their net charge/Mr ratios. This enabled human and rabbit apoA-I to be quantified simultaneously in transgenic rabbit HDLs. CZE also resolved human apoA-I isoforms, deamidated apoA-I, and pro-apoA-I.