Oxidized VLDL induces less triglyceride accumulation in J774 macrophages than native VLDL due to an impaired extracellular lipolysis

The vitamin E long-chain metabolite α-13'-COOH affects macrophage foam cell formation via modulation of the lipoprotein lipase system

The α-tocopherol-derived long-chain metabolite (α-LCM) α-13'-carboxychromanol (α-13'-COOH) is formed via enzymatic degradation of α-tocopherol (α-TOH) in the liver. In the last decade, α-13'-COOH has emerged as a new regulatory metabolite revealing more potent or even different effects compared with its vitamin precursor α-TOH. The detection of α-13'-COOH in human serum has further strengthened the concept of its physiological relevance as a potential regulatory molecule. Here, we present a new facet on the interaction of α-13'-COOH with macrophage foam cell formation. We found that α-13'-COOH (5 μM) increases angiopoietin-like 4 (ANGPTL4) mRNA expression in human THP-1 macrophages in a time- and dose-dependent manner, while α-TOH (100 μM) showed no effects. Interestingly, the mRNA level of lipoprotein lipase (LPL) was not influenced by α-13'-COOH, but α-TOH treatment led to a reduction of LPL mRNA expression. Both compounds also revealed different effects on protein level: while α-13'-COOH reduced the secreted amount of LPL protein via induction of ANGPTL4 cleavage, i.e. activation, the secreted amount of LPL in the α-TOH-treated samples was diminished due to the inhibition of mRNA expression. In line with this, both compounds reduced the catalytic activity of LPL. However, α-13'-COOH but not α-TOH attenuated VLDL-induced lipid accumulation by 35%. In conclusion, only α-13'-COOH revealed possible antiatherogenic effects due to the reduction of VLDL-induced foam cell formation in THP-1 macrophages. Our results provide further evidence for the role of α-13'-COOH as a functional metabolite of its vitamin E precursor.

Lipoprotein markers associated with disability from multiple sclerosis

Altered lipid metabolism is a feature of chronic inflammatory disorders. Increased plasma lipids and lipoproteins have been associated with multiple sclerosis (MS) disease activity. Our objective was to characterise the specific lipids and associated plasma lipoproteins increased in MS and to test for an association with disability. Plasma samples were collected from 27 RRMS patients (median EDSS, 1.5, range 1–7) and 31 healthy controls. Concentrations of lipids within lipoprotein sub-classes were determined from NMR spectra. Plasma cytokines were measured using the MesoScale Discovery V-PLEX kit. Associations were tested using multivariate linear regression. Differences between the patient and volunteer groups were found for lipids within VLDL and HDL lipoprotein sub-fractions (p < 0.05). Multivariate regression demonstrated a high correlation between lipids within VLDL sub-classes and the Expanded Disability Status Scale (EDSS) (p < 0.05). An optimal model for EDSS included free cholesterol carried by VLDL-2, gender and age (R² = 0.38, p < 0.05). Free cholesterol carried by VLDL-2 was highly correlated with plasma cytokines CCL-17 and IL-7 (R² = 0.78, p < 0.0001). These results highlight relationships between disability, inflammatory responses and systemic lipid metabolism in RRMS. Altered lipid metabolism with systemic inflammation may contribute to immune activation.

VLDL Induced Modulation of Nitric Oxide Signalling and Cell Redox Homeostasis in HUVEC

High levels of circulating lipoprotein constitute a risk factor for cardiovascular diseases, and in this context, the specific role of the very-low-density lipoproteins (VLDL) is poorly understood. The response of human umbilical vein endothelial cells (HUVEC) to VLDL exposure was studied, especially focusing on the pathways involved in alteration of redox homeostasis and nitric oxide (NO) bioavailability. The results obtained by the analysis of the expression level of genes implicated in the NO metabolism and oxidative stress response indicated a strong activation of inducible NO synthase (iNOS) upon 24 h exposure to VLDL, particularly if these have been preventively oxidised. Simultaneously, both mRNA and protein expression of endothelial NO synthase (eNOS) were decreased and its phosphorylation pattern, at the key residues Tyr495 and Ser1177, strongly suggested the occurrence of the eNOS uncoupling. The results are consistent with the observed increased production of nitrites and nitrates (NOx), reactive oxygen species (ROS), 3-nitrotyrosine (3-NT), and, at mitochondrial level, a deficit in mitochondrial O₂ consumption. Altogether, these data suggest that the VLDL, particularly if oxidised, when allowed to persist in contact with endothelial cells, strongly alter NO bioavailability, affecting redox homeostasis and mitochondrial function.

Double Filtration Plasma Apheresis Shortens Hospital Admission Duration of Patients With Severe Hypertriglyceridemia-Associated Acute Pancreatitis

OBJECTIVES

The treatment effectiveness of double filtration plasma apheresis (DFPP) on severe hypertriglyceridemia-associated acute pancreatitis (STAP) has been questioned because the currently defined serum triglyceride level--1000 mg/dL--is too low for STAP. Given this, we aimed to investigate DFPP effectiveness when we elevated STAP definition to 5000 mg/dL serum triglyceride.

METHODS

We performed nested case-control studies for STAP patients and divided them into groups "with" or "without" DFPP. We further recruited outpatient asymptomatic hypertriglyceridemia patients with STAP history, then divided them into groups "with" or "without" prophylactic DFPP once every 3 to 6 months for 2 years. We observed hospitalization duration and STAP recurrence between patients with and patients without DFPP.

RESULTS

Twelve STAP patients receiving DFPP had a median hospitalization of 5 days, whereas 24 patients without DFPP had 10 days (P = 0.009). Six outpatient referrals with STAP history receiving prophylactic DFPP showed no STAP recurrences whereas 6 without DFPP showed 3 recurrences (P = 0.046). For the 25 patients whose serum triglyceride exceeded 5000 mg/dL, 11 receiving DFPP had median hospitalization of 5 days while 14 without DFPP had 11 days (P = 0.012).

CONCLUSIONS

When applied to serum triglyceride in excess of 5000 mg/dL, DFPP removes oxidized and inflammatory lipoproteins, shortens hospitalization duration, and minimizes STAP recurrence.

Effects of long-term antidepressant treatment on oxidative status in major depressive disorder: a 24-week follow-up study

PURPOSE

Major depressive disorder (MDD) is a devastating disease that afflicts large populations and has also been accepted to be an independent risk factor for cardiovascular disease (CVD). Oxidative stress seems to play an essential role in the relationship of MDD and CVD. We aimed to determine the level of oxidative stress in patients with MDD and to investigate the effects of long-term antidepressant (AD) treatment on the oxidative-antioxidative system parameters and CVD risk factors.

METHOD

Fifty patients who fully met the fourth Diagnostic and Statistical Manual of Mental Disorders criteria for MDD and 44 healthy control subjects were included in the study. Control visits of the patients were repeated 6weeks, 12weeks and 24weeks after beginning of the AD treatment. Lipid profiles, oxidation and oxidizability of apolipoprotein B-containing lipoproteins (expressed as apo B-b-MDA and apo B-Δ-MDA, respectively), levels of plasma malondialdehyde (p-MDA), total antioxidative capacity (TAOC), antioxidant molecules and antioxidant enzyme activities including paraoxonase/arylesterase, red blood cell superoxide dismutase (RBC-SOD) and glutathione peroxidase were determined during 24-week of follow-up period.

RESULTS

According to the results of the study, p-MDA, apo B-b-MDA and RBC-SOD activity were increased and arylesterase activity was decreased in MDD patients. Body mass index (BMI), vitamin A and total cholesterol levels in MDD patients increased after 24-weeks of AD treatment. RBC-SOD activity, TAOC, p-MDA and apo B-b-MDA levels were decreased; paraoxonase/arylesterase activities and apo B-Δ-MDA were increased at the end of 24th week.

CONCLUSION

Oxidative stress, demonstrated in MDD patients, was partly improved during 24weeks of AD treatment. Increase in paraoxonase/arylesterase activities and decrease in p-MDA and apo B-b-MDA levels after 24weeks seem to be beneficial for reduction of CVD risk in MDD patients. However increased BMI and apo B-Δ-MDA levels are negative cardiovascular effects of long-term AD treatment.

Lactobacillus gasseri [corrected] CHO-220 and inulin reduced plasma total cholesterol and low-density lipoprotein cholesterol via alteration of lipid transporters

This randomized, double-blind, placebo-controlled, and parallel-designed study was conducted to investigate the effect of a synbiotic product containing Lactobacillus gasseri [corrected] CHO-220 and inulin on lipid profiles of hypercholesterolemic men and women. Thirty-two hypercholesterolemic men and women with initial mean plasma cholesterol levels of 5.7±0.32 mmol/L were recruited for the 12-wk study. The subjects were randomly allocated to 2 groups; namely the treatment group (synbiotic product) and the control group (placebo), and each received 4 capsules of synbiotic or placebo daily. Our results showed that the mean body weight, energy, and nutrient intake of the subjects did not differ between the 2 groups over the study period. The supplementation of synbiotic reduced plasma total cholesterol and low-density lipoprotein (LDL)-cholesterol by 7.84 and 9.27%, respectively, compared with the control over 12 wk. Lipoproteins were subsequently subfractionated and characterized. The synbiotic supplementation resulted in a lower concentration of triglycerides in the very low, intermediate, low, and high-density lipoprotein particles compared with the control over 12 wk. The concentration of triglycerides in lipoproteins is positively correlated with an increased risk of atherosclerosis. Our results showed that the synbiotic might exhibit an atheropreventive characteristic. Cholesteryl ester (CE) in the high-density lipoprotein particles of the synbiotic group was also higher compared with the control, indicating greater transport of cholesterol in the form of CE to the liver for hydrolysis. This may have led to the reduced plasma total cholesterol level of the synbiotic group. The supplementation of synbiotic also reduced the concentration of CE in the LDL particles compared with the control, leading to the formation of smaller and denser particles that are more easily removed from blood. This supported the reduced LDL-cholesterol level of the synbiotic group compared with the control. Our present study showed that the synbiotic product improved plasma total- and LDL-cholesterol levels by modifying the interconnected pathways of lipid transporters. In addition, although Lactobacillus gasseri [corrected] CHO-220 could deconjugate bile, our results showed a statistically insignificant difference in the levels of conjugated, deconjugated, primary, and secondary bile acids between the synbiotic and control groups over 12 wk, indicating safety from bile-related toxicity.

Macrophage adipose triglyceride lipase deficiency attenuates atherosclerotic lesion development in low-density lipoprotein receptor knockout mice

OBJECTIVE

The consequences of macrophage triglyceride (TG) accumulation on atherosclerosis have not been studied in detail so far. Adipose triglyceride lipase (ATGL) is the rate-limiting enzyme for the initial step in TG hydrolysis. Because ATGL knockout (KO) mice exhibit massive TG accumulation in macrophages, we used ATGL KO mice to study the effects of macrophage TG accumulation on atherogenesis.

METHODS AND RESULTS

Low-density lipoprotein receptor (LDLr) KO mice were transplanted with bone marrow from ATGL KO (ATGL KO→LDLr KO) or wild-type (WT→LDLr KO) mice and challenged with a Western-type diet for 9 weeks. Despite TG accumulation in ATGL KO macrophages, atherosclerosis in ATGL KO→LDLr KO mice was 43% reduced associated with decreased plasma monocyte chemoattractant protein-1 (MCP-1) and macrophage interleukin-6 concentrations. This coincided with a reduced amount of macrophages, possibly because of a 39% increase in intraplaque apoptosis and a decreased migratory capacity of ATGL KO macrophages. The reduced number of white blood cells might be due to a 36% decreased Lin(-)Sca-1(+)cKit(+) hematopoietic stem cell population.

CONCLUSIONS

We conclude that the attenuation of atherogenesis in ATGL KO→LDLr KO mice is due to decreased infiltration of less inflammatory macrophages into the arterial wall and increased macrophage apoptosis.

Efficient phagocytosis requires triacylglycerol hydrolysis by adipose triglyceride lipase

Macrophage phagocytosis is an essential biological process in host defense and requires large amounts of energy. To date, glucose is believed to represent the prime substrate for ATP production in macrophages. To investigate the relative contribution of free fatty acids (FFAs) in this process, we determined the phagocytosis rates in normal mouse macrophages and macrophages of adipose triglyceride lipase (ATGL)-deficient mice. ATGL was shown to be the rate-limiting enzyme for the hydrolysis of lipid droplet-associated triacylglycerol (TG) in many tissues. Here, we demonstrate that Atgl(-/-) macrophages fail to efficiently hydrolyze cellular TG stores leading to decreased cellular FFA concentrations and concomitant accumulation of lipid droplets, even in the absence of exogenous lipid loading. The reduced availability of FFAs results in decreased cellular ATP concentrations and impaired phagocytosis suggesting that fatty acids must first go through a cycle of esterification and re-hydrolysis before they are available as energy substrate. Exogenously added glucose cannot fully compensate for the phagocytotic defect in Atgl(-/-) macrophages. Hence, phagocytosis was also decreased in vivo when Atgl(-/-) mice were challenged with bacterial particles. These findings imply that phagocytosis in macrophages depends on the availability of FFAs and that ATGL is required for their hydrolytic release from cellular TG stores. This novel mechanism links ATGL-mediated lipolysis to macrophage function in host defense and opens the way to explore possible roles of ATGL in immune response, inflammation, and atherosclerosis.

The regulated in development and DNA damage response 2 (REDD2) gene mediates human monocyte cell death through a reduction in thioredoxin-1 expression

In a previous study, we identified the regulated in development and DNA damage response 2 (REDD2) gene as a highly expressed gene in human atherosclerotic lesions in comparison to normal artery, as well as in cultured human macrophages, and showed its implication in oxidized low-density lipoprotein (LDL)-induced macrophage death sensitivity. In this article, we attempt to identify the mechanism by which REDD2 induces such a phenomenon. Transient transfection of U-937 monocytic cells with a pCI.CMV.REDD2 expression vector increased by approximately twofold the mRNA levels of REDD2 in comparison to control cells transfected with pCI.CMV.GFP. Reactive oxygen species (ROS) production was significantly induced in REDD2-transfected cells compared with control cells (157+/-48 and 100+/-8 arbitrary units/mg cell protein, respectively; p<0.05). Moreover, a significant increase in parameters known to reflect the oxidative modifications of LDL was observed. Among enzymes involved in ROS production or degradation, we found a specific reduction in thioredoxin-1 (Trx-1) mRNA ( approximately 52+/-7% decrease, p<0.01 vs control cells) and protein ( approximately 60+/-4% decrease, p<0.001 vs control cells) levels in cells overexpressing REDD2 in comparison to control cells. In contrast, transfection of U-937 cells with siRNA against REDD2 decreased the mRNA levels of REDD2 by approximately 60% and increased Trx-1 mRNA and protein levels. Moreover, we observed no or a moderate increase in Bax (proapoptotic) and a significant decrease in Bcl2 (antiapoptotic) gene expression in cells that overexpress REDD2 compared to control cells. In addition, we showed that Trx-1 mRNA and protein levels were increased at low H(2)O(2) doses and decreased at higher doses. Interestingly, macrophages isolated from human atherosclerotic lesions differentially express REDD2 and Trx-1. Indeed, in certain patients, levels of REDD2 mRNA were low and those of Trx-1 mRNA were high. In contrast, in other patients, levels of REDD2 were high and levels of Trx-1 mRNA were low.

Ability to grow on lipids accounts for the fully virulent phenotype in neutropenic mice of Aspergillus fumigatus null mutants in the key glyoxylate cycle enzymes

Incidence and mortality rates of invasive aspergillosis clearly indicate the need of novel antifungals to treat patients suffering from this disease. Fungal proteins playing a crucial role in pathogenesis and with no orthologue in human cells are considered as primary therapeutic targets for the development of new antifungals with a high therapeutic index, one of the major drawbacks of the standard antifungal therapy, so far. In this work, we have analyzed the role in pathogenesis of the key enzymes of the Aspergillus fumigatus glyxoxylate cycle, isocitrate lyase and malate synthase, two possible candidates to primary therapeutic targets in this fungus. Deletion strains lacking isocitrate lyase (DeltaacuD strains) or malate synthase (DeltaacuE mutants) were constructed in this work. The Neurospora crassa pyr-4 gene was used as the replacing marker in gene deletion experiments. The pathogenicities of DeltaacuD and DeltaacuE mutants were tested in neutropenic mice and compared with those of two reference wild-type isolates A. fumigatus 237 and A. fumigatus 293. Interestingly, virulence and cytological studies clearly indicated the dispensability of the A. fumigatus glyoxylate cycle for pathogenicity. In addition, these results suggested the suitability of the pyr-4 gene as a valuable replacing marker for virulence studies in this fungus, a fact that was further confirmed by gene expression analyses. Finally, growth tests were performed to investigate the germination and growth of the DeltaacuD and DeltaacuE strains in nutrient deprivation environments, resembling the conditions that A. fumigatus conidia face after phagocytosis. Results obtained in this work strongly suggest that the ability to grow on lipids (triglycerides) of A. fumigatus isocitrate lyase and malate synthase deletion strains accounts for their fully virulent phenotype.

Oxidation of apolipoprotein B-containing lipoproteins and serum paraoxonase/arylesterase activities in major depressive disorder

Major depressive disorder (MDD) is blaimed to play a role in the onset of coronary artery disease (CAD). The aim of the present study was to investigate serum paraoxonase/arylesterase activities and oxidation of apolipoprotein B-containing lipoproteins in patients with MDD. Oxidation of lipoproteins plays an important role in atherogenesis and the enzyme paraoxonase, has been shown to prevent lipoprotein oxidation. Furthermore, low paraoxonase activity was suggested to predict CAD. Eighty-six patients who fully met the fourth Diagnostic and Statistical Manual of Mental Disorders criteria for MDD and 36 healthy control subjects were included in the study. Serum paraoxonase and arylesterase activities were determined spectrophotometrically. Malondialdehyde (MDA) levels of apolipoprotein B-containing lipoproteins were determined before (basal) and after incubation with copper-sulphate, that yielded basal- and Delta-MDA values, respectively. Serum paraoxonase/arylesterase activities were significantly reduced in the post-treatment group compared with the pre-treatment group. Basal-MDA (MDA) level was significantly higher in the MDD group compared with the control group. Delta-MDA level of the severe MDD group was significantly higher than that of the control group. There was a positive correlation between the oxidizability of apolipoprotein B-containing lipoproteins and the severity of the disease. Total cholesterol, HDL-cholesterol, LDL-cholesterol, apolipoprotein B levels were significantly higher and apolipoprotein AI levels were significantly lower in the MDD group compared with those of the control group. The findings of the present study suggest that: 1) antidepressant treatment might reduce serum paraoxonase activity/mass; 2) oxidation and oxidizability of apolipoprotein B-containing lipoproteins seem to be increased in MDD.

The role of lipolysis in mediating the proinflammatory effects of very low density lipoproteins in mouse peritoneal macrophages

Hypertriglyceridemia is an important risk factor for atherosclerosis, especially in obesity. Macrophages are one of the primary cell types involved in atherogenesis and are thought to contribute to lesion formation through both lipid accumulation and proinflammatory gene expression. In this study, we sought to determine the direct impact of triglyceride (TG)-rich VLDL-induced lipid accumulation on macrophage proinflammatory processes. Incubation of mouse peritoneal macrophages with 100 microg/ml VLDL for 6 h led to 2.8- and 3.7-fold increases in intracellular TGs and FFAs, respectively (P < 0.05). The inflammatory proteins tumor necrosis factor-alpha, interleukin-1beta, monocyte chemoattractant protein-1, intercellular adhesion molecule-1, matrix metalloproteinase 3 (MMP3), and macrophage inflammatory protein-1alpha (MIP-1alpha) were all upregulated by at least 2-fold (P < 0.05) in a dose-dependent manner in VLDL-treated macrophages. The increase in inflammatory gene expression coincided with the phosphorylation of the mitogen-activated protein kinase (MAPK) pathway members extracellular signal-regulated kinase (ERK) 1/2, stress-activated protein kinase/c-Jun NH2-terminal kinase, and p38 MAPK and was ameliorated by U0126, an inhibitor of ERK1/2. Inhibition of extracellular TG hydrolysis with tetrahydrolipstatin (Orlistat) resulted in the absence of intracellular TG and FFA accumulation and was accompanied by the amelioration of ERK1/2 phosphorylation and MIP-1alpha gene expression. These data indicate that VLDL hydrolysis, and the subsequent accumulation of intracellular FFAs and TGs, plays a substantive role in mediating the proinflammatory effects of VLDL. These data have important implications for the direct proatherogenic effects of VLDL on macrophage-driven atherosclerosis.

Oxidizability of apolipoprotein B-containing lipoproteins and serum paraoxonase/arylesterase activities in preeclampsia

OBJECTIVES

Lipoprotein oxidation has been implicated in the pathogenesis of preeclampsia and paraoxonase, an antioxidant enzyme shown to protect lipoproteins from being oxidized. The aim of the present study was to evaluate oxidizability of apolipoprotein B-containing lipoproteins and serum paraoxonase/arylesterase activities in preeclampsia.

DESIGN AND METHODS

Twenty-one women with mild preeclampsia, 21 women with severe preeclampsia, and 20 women with normal uncomplicated pregnancy were included in this study. Serum malondialdehyde (MDA) level, an indicator of lipid peroxidation, was measured by high-performance liquid chromatography (HPLC). The oxidizability of apolipoprotein B-containing lipoproteins was evaluated by copper-induced in vitro peroxidation of the isolated fraction of apolipoprotein B-containing lipoproteins coupled with the thiobarbituric acid-reactive substances assay and expressed as the difference between copper-treated MDA and basal MDA (DeltaMDA). The serum paraoxonase and arylesterase activities were determined spectrophotometrically.

RESULTS

Serum MDA and DeltaMDA levels of apolipoprotein B-containing lipoproteins were significantly higher in both mild and severe preeclampsia groups than in the normal pregnant group. Serum paraoxonase and arylesterase activities were not significantly different among the study groups.

CONCLUSIONS

Enhancement in oxidizability of apolipoprotein B-containing lipoproteins accompanying with dyslipidemia and increased serum MDA levels suggests that those lipoproteins play a role in the pathogenesis of preeclampsia. Further studies are needed to investigate serum paraoxonase activity in women with normal pregnancies and preeclampsia.

Thioredoxin reductase 1 is upregulated in atherosclerotic plaques: specific induction of the promoter in human macrophages by oxidized low-density lipoproteins

Uptake of modified low-density lipoproteins (LDLs) by macrophages in the arterial wall is an important event in atherogenesis. Indeed, oxidatively modified LDLs (oxLDLs) are known to affect various cellular processes by modulating oxidation-sensitive signaling pathways. Here we found that the ubiquitous 55 kDa selenoprotein thioredoxin reductase 1 (TrxR1), which is a key enzyme for cellular redox control and antioxidant defense, was upregulated in human atherosclerotic plaques and expressed in foam cells. Using reverse transcription polymerase chain reaction analysis, we also found that oxLDLs, but not native LDLs (nLDLs), dose-dependently increased TrxR1 mRNA in human monocyte-derived macrophages (HMDMs). This stimulating effect was specific for oxLDLs, as pro-inflammatory factors, such as lipopolysaccharides (LPSs), interleukin-1beta (IL-1beta), interleukin-6 (Il-6), and tumor necrosis factor alpha (TNFalpha), under the same conditions, failed to induce TrxR1 mRNA levels to the same extent. Moreover, phorbol ester-differentiated THP-1 cells or HMDMs transiently transfected with TrxR1 promoter fragments linked to a luciferase reporter gene allowed identification of a defined promoter region as specifically responding to the phospholipid component of oxLDLs (p <.05 vs. phospholipid component of nLDLs). Gel mobility shift analyses identified a short 40-nucleotide stretch of the promoter carrying AP-1 and HoxA5 consensus motifs that responded with an altered shift pattern in THP-1 cells treated with oxLDLs, however, without evident involvement of either the Fos, Jun, Nrf2 or HoxA5 transcription factors.

Effects of red wine consumption on serum paraoxonase/arylesterase activities and on lipoprotein oxidizability in healthy-men

Although there is a general consensus concerning the lower risk for cardiovascular disease in moderate drinkers, the mechanisms responsible for the cardioprotective effect of red wine remain unknown. It has been proposed that increased serum paraoxonase activity may be a mechanism of action underlying reduced cardiovascular disease risk in moderate drinkers, since paraoxonase inhibits lipoprotein oxidation. The aim of this study was to investigate the effects of red wine consumption on serum paraoxonase/arylesterase activities and on lipoprotein oxidizability in healthy-men. Fourteen healthy-men were included in the study. The subjects consumed 0.375 g alcohol / kg body weight for 3 weeks. Paraoxonase and arylesterase activities were studied spectrophotometrically. Oxidizability of apolipoprotein B-containing lipoproteins were determined, after separating them with precipitation method, by incubating with copper-sulfate. Paraoxonase activity did not change, however arylesterase activity significantly decreased after red wine consumption (P < 0.01). There was a reduced susceptibility of apolipoprotein B-containing lipoproteins to copper-sulfate induced oxidation after red wine consumption (P < 0.01). Our results support that red wine protects lipoproteins against oxidation, however there was not any significant change in serum paraoxonase activity after red wine consumption.

Role of monocytes in atherogenesis

This review focuses on the role of monocytes in the early phase of atherogenesis, before foam cell formation. An emerging consensus underscores the importance of the cellular inflammatory system in atherogenesis. Initiation of the process apparently hinges on accumulating low-density lipoproteins (LDL) undergoing oxidation and glycation, providing stimuli for the release of monocyte attracting chemokines and for the upregulation of endothelial adhesive molecules. These conditions favor monocyte transmigration to the intima, where chemically modified, aggregated, or proteoglycan- or antibody-complexed LDL may be endocytotically internalized via scavenger receptors present on the emergent macrophage surface. The differentiating monocytes in concert with T lymphocytes exert a modulating effect on lipoproteins. These events propagate a series of reactions entailing generation of lipid peroxides and expression of chemokines, adhesion molecules, cytokines, and growth factors, thereby sustaining an ongoing inflammatory process leading ultimately to lesion formation. New data emerging from studies using transgenic animals, notably mice, have provided novel insights into many of the cellular interactions and signaling mechanisms involving monocytes/macrophages in the atherogenic processes. A number of these studies, focusing on mechanisms for monocyte activation and the roles of adhesive molecules, chemokines, cytokines and growth factors, are addressed in this review.

VLDL-induced triglyceride accumulation in human macrophages is mediated by modulation of LPL lipolytic activity in the absence of change in LPL mass

Mixed dyslipidemia of phenotype IIB is characterized by elevated levels of very low density lipoprotein (VLDL)-1 and VLDL-2 subfractions and of low density lipoprotein (LDL), which are associated with premature formation of atherosclerotic plaques, characterized by the presence of lipid-rich macrophage foam cells. Lipoprotein lipase (LPL) is a key factor in mediating macrophage lipid accumulation and foam-cell formation from native VLDL particles. The action of macrophage-derived LPL in the induction of intracellular lipid accumulation from triglyceride-rich lipoprotein (TRL) subfractions (VLDL-1, VLDL-2) is, however, indeterminate, as is the potential role of VLDL-1 and VLDL-2 in modulating macrophage LPL expression. We evaluated the role of LPL in the interaction of type IIB VLDL-1 and VLDL-2 with human macrophages. Both VLDL-1 and VLDL-2 subfractions induced significant accumulation of triglyceride (9.8-fold, P<0.0001, and 4.8-fold, P<0.0001, respectively) and of free cholesterol content (1.4-fold, P<0.001, and 1.2-fold, P=0.02, respectively). Specific inhibition (90%) of the lipolytic activity of endogenous LPL by tetrahydrolipstatin (THL) in the presence of VLDL-1 or VLDL-2 resulted in marked reduction in cellular loading of both triglycerides (-89%, P=0.008, and -89%, P=0.015, respectively) and free cholesterol (-76%, P=0.02, and -55%, P=0.06 respectively). Furthermore, VLDL-1 and VLDL-2 induced marked increase in macrophage-derived LPL enzyme activity (+81%, P=0.002, and +45%, P=0.02), but did not modulate macrophage-derived LPL mRNA and protein expression; consequently, LPL specific activity was significantly increased from 1.6 mU/microg at baseline to 4.1 mU/microg (P=0.01) and 3.1 mU/microg (P=0.05), in the presence of VLDL-1 and VLDL-2, respectively. We conclude that type IIB VLDL-1 and VLDL-2 induce triglyceride accumulation in human monocyte-macrophages primarily via the lipolytic action of LPL, which may involve stabilization and activation of the macrophage-secreted enzyme, rather than via modulation of enzyme production.

Effect of human Apo AIV against lipid peroxidation of very low density lipoproteins

Recent studies have demonstrated that Apo AIV exerts a protective effect against atherosclerosis. Moreover, Qin et al. (Am. J. Physiol. 274 (1998) H1836) have demonstrated that Apo AIV, isolated from rat plasma, exerts an inhibitory effect against Cu(2+)-induced lipid peroxidation of intestinal lymph and LDL. The aim of the study was to investigate whether human Apo AIV exerts a protective effect against Cu(2+)-induced lipid peroxidation. Our results demonstrated that human Apo AIV exerted an inhibitory effect against Cu(2+) and AAPH induced lipid peroxidation of VLDL, as shown by the lower increase in the levels of TBARS and conjugated dienes in lipoproteins preincubated with Apo AIV. In addition, the tryptophan (Trp) and probe 2-(dimethylamino)-6-lauroylnaphthalene (Laurdan) fluorescence studies demonstrated that the modifications of spectral properties in both lipoproteins preincubated with Apo AIV were lower with respect to ox-lipoproteins, suggesting that Apo AIV prevents the modification of physico-chemical properties due to peroxidation.

Effect of gemfibrozil on the composition and oxidation properties of very-low-density lipoprotein and high-density lipoprotein in patients with hypertriglyceridemia

Recent studies suggest that both oxidized very-low-density lipoprotein (VLDL) and oxidized high-density lipoprotein (HDL) may play a role in the pathogenesis of atherosclerosis. Gemfibrozil is widely used and is reported to decrease VLDL levels and increase HDL levels. The aim of this study was to investigate the effect of gemfibrozil on the chemical composition and oxidative susceptibility of VLDL and HDL and their relationship with atherosclerosis. Twenty patients with hypertriglyceridemia were treated with 300 mg gemfibrozil, 3 times daily, for 12 weeks. Venous blood samples were collected before treatment, at the end of treatment, and 4 weeks after the end of treatment. Gemfibrozil effectively lowered concentrations of plasma lipid, apolipoprotein (apo) B, and apo E. The lipid and protein content of VLDL were also decreased, but not by the same extent. The surface-to-core ratio and apo E/apo B ratio of VLDL particles were increased after gemfibrozil treatment. HDL(2) cholesteryl ester and HDL(3) apo A-II content were also increased. Gemfibrozil treatment lowered levels of lipid peroxides in both VLDL and HDL particles. The susceptibility of VLDL to oxidation was unchanged, whereas maximal peroxide production was decreased. The oxidative susceptibility of both HDL(2) and HDL(3) decreased with gemfibrozil treatment. These results indicate that after gemfibrozil treatment, VLDL and HDL particles in patients with hypertriglyceridemia are less atherogenic, which may explain why gemfibrozil treatment is beneficial in terms of coronary heart disease in hypertriglyceridemia.

Metabolism of oxidized LDL by macrophages

Oxidation products of lipids and proteins are found in atherosclerotic plaque and in macrophage foam cells. Macrophages avidly endocytose in-vitro oxidized LDL and accumulate sterols. What is the evidence that such a process is involved in in-vivo foam cell formation? The present review surveys current knowledge on the metabolism of oxidized LDL by macrophages, and the types, amounts and location of oxidation products that accumulate in these cells. Comparable studies of lesion lipoproteins and foam cells indicate that limited extracellular lipoprotein oxidation, perhaps followed by more extensive intracellular oxidation subsequent to uptake by macrophages, is a more likely scenario in vivo.