Extra-virgin olive oil consumption improves the capacity of HDL to mediate cholesterol efflux and increases ABCA1 and ABCG1 expression in human macrophages.

The present study was aimed to investigate the effect of 12 weeks of extra-virgin olive oil (EVOO) consumption on the capacity of HDL to promote cholesterol efflux (CE) and to determine which CE pathways are modulated by EVOO consumption. Whole HDL and HDL2/HDL3 subclasses were isolated from the plasma of twenty-six healthy volunteers before and after 12 weeks of EVOO consumption (25 ml/d). EVOO consumption increased the capacity of serum and HDL to mediate CE from THP-1, J774 macrophages and Fu5AH cells by 9·8-24·57 %, depending on the cell type. The increase in CE was independent of both HDL concentration and subclass distribution. The three HDL-mediated CE pathways (ATP-binding cassette (ABC) A1, ABCG1 and scavenger receptor class B type I (SR-BI)) were modulated by EVOO consumption. The fluidity of the phospholipidic layer of HDL increased by 13 % (P< 0·001) following EVOO consumption compared with baseline. EVOO consumption also increased the release of excess cholesterol from human monocyte-derived macrophages (HMDM) by 44 % (P< 0·001), and ABCA1 and ABCG1 mRNA transcription by 16·08 % (P< 0·001) and 35·79 % (P< 0·01), respectively. The protein expression of these two cholesterol transporters also increased after EVOO consumption. In contrast, SR-BI mRNA and protein expression in HMDM were significantly lower after 12 weeks of EVOO consumption. Incubating J774 macrophages with EVOO polyphenol extracts induced a concentration-dependent up-regulation of ABCA1 and ABCG1 expression in macrophages. After 12 weeks of EVOO consumption, the capacity of HDL to mediate CE was improved and the ability of HMDM to release excess cholesterol was enhanced by increasing the expression of ABCA1 and ABCG1 transporters.

Extra-virgin olive oil consumption reduces the age-related decrease in HDL and paraoxonase 1 anti-inflammatory activities.

Paraoxonase 1 (PON1) is associated with HDL and modulates the antioxidant and anti-inflammatory role of HDL. The goals of the present study were to investigate the effect of ageing and the role of PON1 on the anti-inflammatory activity of HDL, and to determine whether extra-virgin olive oil (EVOO) consumption could improve the atheroprotective activity of HDL. HDL and PON1 were isolated from the plasma of ten young (Y-HDL and Y-PON1) and ten elderly (E-HDL and E-PON1) healthy volunteers before and after 12 weeks of EVOO consumption. Inflammation was assessed by measuring intracellular adhesion molecule 1 (ICAM-1) expression. THP-1 (human acute monocytic leukaemia cell line) monocyte chemotaxis was measured using a Boyden chamber. Oxidative damage to HDL was assessed by measuring conjugated diene formation and changes in electrophoretic migration. Y-HDL had more anti-inflammatory activity than E-HDL. The conjugated diene content and the electrophoretic mobility of E-HDL were higher than those of Y-HDL. Y-PON1 had significant anti-inflammatory activity, reducing ICAM-1 expression by 32·64 (SD 2·63)%, while E-PON1 had no significant effect. THP-1 chemotaxis measurements confirmed the ICAM-1 expression results. The 12 weeks of EVOO consumption significantly increased the anti-inflammatory activities of both HDL and PON1. The anti-inflammatory activity of HDL was modulated by PON1 and was lower in the elderly volunteers. EVOO consumption increased the anti-inflammatory effect of HDL and reduced the age-related decrease in anti-atherogenic activity.

Purified human paraoxonase-1 interacts with plasma membrane lipid rafts and mediates cholesterol efflux from macrophages.

Paraoxonase-1 (PON1) is a high-density lipoprotein (HDL)-associated serum enzyme thought to make a major contribution to the antioxidant and anti-inflammatory capacities of HDLs. However, the role of PON1 in the modulation of cholesterol efflux is poorly understood. The aim of our study was to investigate the involvement of PON1 in the regulation of cholesterol efflux, especially the mechanism by which it modulates HDL-mediated cholesterol transport. The enrichment of HDL(3) with human PON1 enhanced, in a dose-dependent manner, cholesterol efflux from THP-1 macrophage-like cells and ABCA1-enriched J774 macrophages. Moreover, an additive effect was observed when ABCA1-enriched J774 macrophages were incubated with both PON1 and apo-AI. Interestingly, PON1 alone was able to mediate cholesterol efflux from J774 macrophages and to upregulate ABCA1 expression on J774 macrophages. Immunofluorescence measurement showed an increase in PON1 levels in the cytoplasm of J774 macrophages overexpressing ABCA1. PON1 used an apo-AI-like mechanism to modulate cholesterol efflux from rapid and slow efflux pools derived from the lipid raft and nonraft domains of the plasma membrane, respectively. This was supported by the fact that ABCA1 protein was incrementally expressed by J774 macrophages within the first few hours of incubation with cholesterol-loaded J774 macrophages and that cyclodextrin significantly inhibited the capacity of PON1 to modulate cholesterol efflux from macrophages. This finding suggested that PON1 plays an important role in the antiatherogenic properties of HDLs and may exert its protective function outside the lipoprotein environment.

The anti-inflammatory effect of paraoxonase 1 against oxidized lipids depends on its association with high density lipoproteins.

AIM: The aims of this study were to investigate whether purified PON1 can reduce the pro-inflammatory effect of oxidized phospholipids and whether the effect depended on its association with HDL. MAIN METHODS: Lipid peroxidation was induced by copper ions and was measured using the conjugated diene method. Lysophosphatidylcholine (lyso-PC) formation was measured by HPLC with evaporative light scattering detection (ELSD) and ICAM-1 expression on Ea.hy926 endothelial cells was analyzed by flow cytometry. KEY FINDINGS: Purified PON1 significantly inhibited copper-induced oxidation of LDL and HDL, causing a 60.5% and 77.7% decrease in conjugated diene formation, respectively. Incubating PON1 with oxLDL caused a significant increase in lyso-PC levels, while oxHDL caused a significant decrease. PON1 (12.5 to 50 µg/mL) had a pro-inflammatory effect in the presence of oxLDL, increasing ICAM-1 levels in Ea.hy926 cells by 33.0% and 40.6% (p<0.001) respectively, and had an anti-inflammatory effect in the presence of oxHDL, causing a 3-fold reduction in ICAM-1 levels. PON1 also caused a significant decrease in TNFα and purified lyso-PC-induced ICAM-1 expression. The results obtained with reconstituted HDL as well as LCAT and PAF-AH inhibitors suggested that the anti-inflammatory effect of PON1 against oxidized lipids is dependent on its association with HDL. SIGNIFICANCE: Our results clearly showed that PON1 is involved in the anti-inflammatory effect of HDL and that the effect appears to depend on its association with HDL.

A new insight into resveratrol as an atheroprotective compound: inhibition of lipid peroxidation and enhancement of cholesterol efflux.

Resveratrol, a polyphenolic constituent of red wine, is known for its anti-atherogenic properties and is thought to be beneficial in reducing the incidence of cardiovascular diseases (CVD). However, the mechanism of action by which it exerts its anti-atherogenic effect remains unclear. In this study, we investigated the relationship between the antioxidant effects of resveratrol and its ability to promote cholesterol efflux. We measured the formation of conjugated dienes and the rate of lipid peroxidation, and observed that resveratrol inhibited copper- and irradiation-induced LDL and HDL oxidation as observed by a reduction in oxidation rate and an increase in the lag phase (p<0.05). We used DPPH screening to measure free radical scavenging activity and observed that resveratrol (0-50microM) significantly reduced the content of free radicals (p<0.001). Respect to its effect on cholesterol homeostasis, resveratrol also enhanced apoA-1-mediated cholesterol efflux (r(2)=0.907, p<0.05, linear regression) by up-regulating ABCA-1 receptors, and reduced cholesterol influx or uptake in J774 macrophages (r(2)=0.89, p<0.05, linear regression). Incubation of macrophages (J774, THP-1 and MPM) with Fe/ascorbate ion, attenuated apoA-1 and HDL(3)-mediated cholesterol efflux whereas resveratrol (0-25microM) significantly redressed this attenuation in a dose-dependent manner (p<0.001). Resveratrol thus appears to be a natural antioxidant that enhances cholesterol efflux. These properties make it a potential natural antioxidant that could be used to prevent and treat CVD.