Mediated Cholesterol Efflux Research Articles

Zerumbone, A Natural Cyclic Sesquiterpene, Promotes ABCA1-Dependent Cholesterol Efflux from Human THP-1 Macrophages

This study was conducted to explore the effect of zerumbone, isolated from Zingiberzerumbet Smith, on apolipoprotein A-I (apoA-I)-mediated cholesterol efflux from THP-1 macrophages. THP-1 macrophages were treated with different concentrations (10-100 μmol/l) of zerumbone and cholesterol efflux was measured. The involvement of ATP-binding cassette (ABC) transporters ABCA1 and ABCG1 and ERK1/2 signaling was checked. Notably, zerumbone caused a concentration-dependent induction of ABCA1 but not ABCG1, coupled with enhanced phosphorylation of ERK1/2. Pre-treatment with PD98059 (a potent ERK1/2 inhibitor) significantly blocked the upregulation of ABCA1 by zerumbone. Small interfering RNA-mediated downregulation of ABCA1 but not ABCG1 significantly impaired the promotion of apoA-I-mediated cholesterol efflux by zerumbone. Taken together, zerumbone has the capacity to facilitate apoA-I-mediated cholesterol efflux from macrophages through the activation of ERK1/2 signaling and upregulation of ABCA1.

Newly developed apolipoprotein A-I mimetic peptide promotes macrophage reverse cholesterol transport in vivo

BackgroundWe elucidated the effect of newly developed Fukuoka Apolipoprotein A-I Mimetic Peptide (FAMP) on in vivo macrophage reverse cholesterol transport (RCT) and the underlying mechanisms. Methods and resultsCholesteryl ester transfer protein transgenic mice were divided into FAMP, and placebo control groups, and injected with FAMP or phosphate buffer saline intraperitoneally for 5days. The FAMP group showed a significant decrease in plasma high-density lipoprotein cholesterol (HDL-C), and plasma from the FAMP group had an increased ability to promote ATP-binding cassette transporter A1 (ABCA1)-mediated cholesterol efflux from bone marrow macrophages ex vivo. Furthermore, mice were injected intraperitoneally with 3H-cholesterol-labeled and cholesterol-loaded macrophages and monitored for the appearance of 3H-tracer. The amount of 3H-tracer excreted into feces over 48h in the FAMP group was significantly higher than that in the control group. 3H-cholesterol ester (CE)-HDL was injected intravenously and 3H-cholesterol in blood was counted. In the FAMP group, plasma 3H-CE-HDL decreased rapidly, and treatment with FAMP markedly increased the fractional catabolic rate. ConclusionsThe administration of FAMP promoted ABCA1-dependent efflux ex vivo, HDL turnover in vivo, and macrophage RCT in vivo despite reduced plasma HDL-C levels. FAMP might have atheroprotective potential.

Abstract 473: Development of High-throughput ABCA1, ABCG1 and SR-BI Mediated HDL Efflux Assays

Studies have shown an inverse association between HDL-efflux capacity and cardiovascular disease (CVD). The efflux of cholesterol from cells to HDL can occur by several mechanisms, including unmediated aqueous diffusion and ABCA1, ABCG1 and SR-BI specifically mediated process. We developed a high throughput assay to measure pathway specific HDL efflux capacity using BHK cells expressing inducible ABCA1, ABCG1, or SR-BI in 96-well plate format. We found that ABCA1-mediated cholesterol efflux in BHK cells correlated significantly with that of J774 macrophages when apoA-I, HDL or 2% apoB-depleted serum were used as acceptors (R 2 =0.98 to 0.99, p<0.0001). Compared with J774 macrophages, ABCA1-mediated efflux using BHK cells is more sensitive, consistent and has better reproducibility (Intro-assay CV=3.0%, R 2 =0.99; Inter assay CV=3.2%, R 2 =0.98). The consistence and reproducibility for ABCG1 and SR-BI mediated cholesterol efflux were also excellent as judged by intro-assay and inter-assay CV and R 2 . When pathway specific assay was employed in a high-throughput format to measure HDL efflux capacity among subjects with or without CVD, we found that ABCA1-mediated cholesterol efflux was significantly lower in CVD subjects when compared with that of control (p<0.01), while ABCG1 or SR-BI mediated cholesterol efflux was not significantly different among the two groups. ABCG1-mediated cholesterol efflux was significantly associated with HDL-C (R 2= 0.65, p<0.01), but ABCA1 or SR-BI mediated cholesterol efflux was not correlated with HDL-C. Those studies demonstrate that BHK cells with inducible ABCA1, ABCG1, or SR-BI expression provide a sensitive, reproducible high throughput efflux assay that can be used to screen large number of serums in mechanistic studies or drug discovery program.

Abstract 706: HDL and ApoA-I Inhibit Palmitate-induced Lipid Raft Trafficking of TLR4 and Inflammatory Cytokines Expression in Adipocytes

Background: Adipose tissue inflammation induces inflammatory molecules production leading to insulin resistance and increased cardiovascular disease risk. Recently it has become apparent that innate immune system is activated by saturated fatty acids (SFAs) by a process involved in TLR4 signaling. HDL and apoA-I has anti-inflammatory effects, however the mechanisms are not well understood in adipocytes. Aims: We examined to elucidate the effect of HDL and/or ApoA-I mediated cholesterol efflux on induction of inflammatory gene expression by palmitate in adipocytes via TLR4 dependent immune system. Methods: 3T3-L1 adipocytes are exposure to 250uM palmitate for periods of up to 24 hours with or without HDL or Apo A-I. Antisense directed to ABCG-1 or ABCA-1 is added 24 hours prior to each reagent challenge. Cells were harvested and estimated for expression of Saa 3 gene using real-time PCR or detection of TLR4 in raft or non raft by western blotting. Lipid rafts were purified by ultracentrifugation on discontinuous sucrose gradient, and identified by the presence of caveolin-1. Results: TLR4 was translocated into lipid raft from non raft within 15 minutes and dislocated by 60 minutes after palmitate exposure. Saa 3 gene expression was significantly up-regulated by 24 hours palmitate exposure in adipocytes. TLR4 translocation to raft and Saa 3 gene up- regulation induced by palmitate was significantly inhibited by pretreatment of HDL or Apo A-I for 6 hours. Antisense directed to ABCG-1 or SRB1 abrogated these inhibitory effects by HDL, but not ApoA-I whereas antisense to ABCA-1 did by Apo A-I but not HDL. Conclusions: These findings suggest that TLR4 mediates palmitate-induced Saa 3 gene expression in adipocytes. A reduction in membrane cholesterol mediated by ABCG-1, SRB1 or ABCA-1 can account for the ability of HDL or ApoA-I to disrupt stimulation of inflammatory cytokines by palmitate

Abstract 323: ABCA1 Expression Promotes ApoAI Acidification on the Plasma Membrane via Recruitment of Vacuolar ATPase

Objective: We have shown that ABCA1 mediates unfolding of apoAI N-terminal helical hairpin on the cell surface. Others have shown that apoAI can solubilize liposomes made with egg PC:PS (8:2) only at acidic pH, where apoAI has unfolded to expose more hydrophobic surfaces. We postulated that ABCA1 may mediate the local acidification of the plasma membrane to promote apoAI unfolding and lipidation. Methods and Results: We found that apoAI unfolding in guanidine was facilitated at pH 5.0 vs. pH 7.5 (EC50 = 0.75 M and 0.94 M guanidine, respectively). We confirmed that apoAI solubilization of and binding to POPC:PS liposomes was only effective at pH < 5.5. We then designed a fluorescent ratiometric apoAI pH indicator labeling apoAI with FITC and Alexa647, and validated it in solution assays showing that the FITC/Alexa647 ratio decreased as the pH decreased. Using flow cytometry in both RAW264.7 and BHK cell lines, we found that incubation of the apoAI pH indicator with ABCA1 expressing cells at 37 o C led to a large acidification of apoAI, which may be due to the uptake of apoAI into endosomes/lysosomes. However, incubation of the apoAI pH indicator with ABCA1 expressing cells at 21 o C or with an inhibitor of endocytosis, where the vast majority of apoAI is on the cell surface, still led to mild apoAI acidification. To elucidate the mechanism of ABCA1 effects on local acidification of the plasma membrane, we examined if ABCA1 regulates vacuolar ATPase (V-ATPase) proton pump, which is composed of a peripheral V 1 domain and an embedded V 0 domain. We observed that bafilomycin, the V-ATPase inhibitor, dose dependently inhibited ABCA1 mediated cholesterol efflux to apoAI, and also eliminated the pH shift of apoAI on plasma membrane. We showed V-ATPase was expressed on the cell surface by cell surface biotinylation. Although the total level of V 0 A1 subunit didn’t change in ABCA1 expressing cells, ABCA1 induced the cell surface level of the V 0 A1 subunit. Conclusion: Our results support that ABCA1 induces the levels of V-ATPase on the cell surface leading to local acidification of apoAI, which may promote apoAI unfolding and lipidation.

Decreased cholesterol uptake and increased liver x receptor-mediated cholesterol efflux pathways during prostaglandin F2 alpha-induced and spontaneous luteolysis in sheep.

In nonprimate species, it has been well established that prostaglandin F2 alpha (PGF2alpha) initiates luteolysis. Changes in intracellular cholesterol concentrations caused by modulation of cholesterol uptake and efflux may mediate PGF2alpha-induced luteolysis. These changes in cholesterol efflux and uptake are controlled, in part, by the liver x receptors (LXR) alpha (NR1H3) and beta (NR1H2), nuclear receptors that increase expression of genes necessary for cholesterol efflux or limiting cholesterol uptake. Therefore, we hypothesized that PGF2alpha reduces expression of cholesterol uptake and increases expression of cholesterol efflux genes, mediated in part by enhanced LXR activity. To test this hypothesis, an induced luteolysis model was used whereby ewes were treated during their midluteal phase with saline or PGF2alpha and corpora lutea (CL) collected 12, 24, or 48 h later for determination of mRNA and protein concentrations by quantitative real-time PCR and Western blot analysis, respectively. As a complementary approach, CL undergoing spontaneous luteolysis were compared to midluteal phase CL. The lipoprotein receptors responsible for cholesterol uptake were significantly decreased in both luteolysis models. Expression of the LXR target gene ATP binding cassette subfamily A1 (ABCA1), an important mediator of cholesterol efflux, was significantly increased in both experimental models. Chromatin immunoprecipitation confirmed that PGF2alpha treatment resulted in enhanced NR1H3 and NR1H2 binding to the ABCA1 promoter. Qualitative changes in lipid droplet distribution were also observed following PGF2alpha treatment. These data support the hypothesis that reduced cholesterol uptake and increased efflux mediate luteolysis in sheep, which is partially controlled by PGF2alpha stimulation of LXR activity.

Abstract P224: The Haptoglobin (Hp) Genotype Predicts Coronary Artery Disease (CAD) During 25 Years of Follow-up in Type 1 Diabetes: Potential Pole of Impaired HDL Cholesterol Efflux Capacity

Background: The Hp 2-2 genotype has been associated with increased cardiovascular risk in type 2 diabetes, potentially relating to dysfunctional HDL mediated cholesterol efflux. We have shown that the Hp 2 allele predicts the development of both coronary artery disease (CAD) and kidney dysfunction also in childhood onset type 1 diabetes over 18 years of follow-up in the Epidemiology of Diabetes Complications (EDC) study. We now present results on the Hp-CAD association after an additional 7 year follow-up and Hp’s relation to impaired sterol efflux capacity, a proposed cardioprotective effect of HDL. Methods: Participants free of CAD at baseline and with Hp determined were studied (n=565; mean age, 27 and duration, 19 years; 11.5% Hp 1-1, 42.5% Hp 2-2). CAD was defined as EDC physician diagnosed angina, ischemic ECG changes (MC 1.3, 4.1-4.3, 5.1-5.3, 7.1), confirmed MI (MC 1.1, 1.2 or validated medical records), stenosis >50%, revascularization or CAD death. In a pilot study, serum HDL sterol efflux was assessed in Mifepristone stimulated ABCA1-BHK cells among 20 individuals (6 Hp 1-1; 7 Hp 2-1; 7 Hp 2-2) attending the 25 year exam. Results: During follow-up, 186 (32.9%) developed CAD. Incidence increased with the number of Hp 2 alleles (24.6% in Hp 1-1, 31.1% in Hp 2-1 and 37.1% in Hp 2-2, p-trend=0.04; Fig. 1). Multivariably, Hp 2-2 significantly increased risk by almost 80% (HR=1.79, 1.03-3.09). The risk associated with Hp 2-1 did not reach significance (HR=1.46, 0.85-2.53). In the pilot study, serum HDL sterol efflux was lower in Hp 2 allele carriers: 14.0% in Hp 1-1, 12.5% in Hp 2-1, 12.4% in Hp 2-2, p-trend=0.06, p-value Hp 1-1 vs Hp 2-1/2-2 =0.04. Conclusion: These results extend our previous findings of increased CAD risk associated with the Hp 2 allele in type 1 diabetes and further suggest that this allele associates with impaired sterol efflux capacity. These results support the hypothesis that sterol efflux explains the increased Hp 2 risk for CAD and should be confirmed prospectively. Figure 1. CAD-free survival curves by Hp genotype

Case report: A novel apolipoprotein A-I missense mutation apoA-I (Arg149Ser)Boston associated with decreased lecithin-cholesterol acyltransferase activation and cellular cholesterol efflux

We report a novel heterozygous apolipoprotein A-I (apoA-I) missense mutation (c.517C>A, p.Arg149Ser, designated as apoA-IBoston) in a 67-year-old woman and her 2 sons, who had mean serum high-density lipoprotein (HDL) cholesterol, apoA-I, and apoA-I in very large α-1 HDL that were 10%, 35%, and 16% of normal, respectively (all P < .05). The percentage of HDL cholesterol in the esterified form was also significantly (P < .05) reduced to 52% of control values. Cholesteryl ester tranfer protein (CETP) activity was normal. The mean global, adenosine triphosphate (ATP)-binding cassette transporter A1 and scavenger receptor B type I–mediated cellular cholesterol efflux capacity in apoB-depleted serum from affected family members were 41%, 37%, 47%, 54%, and 48% of control values, respectively (all P < .05). lecithin-cholesterol acyltransferase (LCAT) activity in plasma was 71% of controls, whereas in the cell-based assay, it was 73% of control values (P < .05). The data indicate that this novel apoA-I missense is associated with markedly decreased levels of HDL cholesterol and very large α-1 HDL, as well as decreased serum cellular cholesterol efflux and LCAT activity, but not with premature coronary heart disease, similar to other apoA-I mutations that have been associated with decreased LCAT activity.

The implication of cigarette smoking and cessation on macrophage cholesterol efflux in coronary artery disease patients

We investigated ATP-binding cassette transporters A1/G1 expression and function in mediating cholesterol efflux by examining the macrophages of cigarette-smoking patients with coronary artery disease (CAD) before and after smoking abstinence. Peripheral blood monocyte cells were collected from nonsmokers (n = 17), non-CAD (NCAD) smokers (n = 35), and CAD smokers (n = 32) before and after 3 months of smoking cessation. We found that the ABCA1 expression level was lower in macrophages from NCAD and CAD smokers than from nonsmokers at baseline. The ABCA1 function of mediating cholesterol efflux was reduced in NCAD and CAD smokers as compared with nonsmokers. After 3 months of smoking cessation, ABCA1 expression and function were improved in CAD smokers. However, ABCG1 expression and function did not change after smoking cessation. Furthermore, ABCA1 expression was inhibited by tar in human acute monocytic leukemia cell line THP-1-derived macrophages through the inhibition of liver X receptors. Nicotine and carbon monoxide did not inhibit ABCA1 expression. Our results indicate that chronic cigarette smoking impaired ABCA1-mediated cholesterol efflux in macrophages and that tobacco abstinence reversed the function and expression of ABCA1, especially in CAD patients. It was tobacco tar, rather than nicotine or carbon monoxide, that played a major role in the tobacco-induced disturbance of cellular cholesterol homeostasis.

Plasma cholesterol efflux capacity from human THP-1 macrophages is reduced in HIV-infected patients: impact of HAART

The capacity of HDL to remove cholesterol from macrophages is inversely associated with the severity of angiographic coronary artery disease. The effect of human immunodeficiency virus (HIV) infection or its treatment on the ability of HDL particles to stimulate cholesterol efflux from human macrophages has never been studied. We evaluated the capacity of whole plasma and isolated HDL particles from HIV-infected subjects (n = 231) and uninfected controls (n = 200), as well as in a subset of 41 HIV subjects receiving highly active antiretroviral therapy (HAART) to mediate cholesterol efflux from human macrophages. Plasma cholesterol efflux capacity was reduced (-12%; P = 0.001) in HIV patients as compared with controls. HIV infection reduced by 27% (P < 0.05) the capacity of HDL subfractions to promote cholesterol efflux from macrophages. We observed a reduced ABCA1-dependent efflux capacity of plasma (-27%; P < 0.0001) from HIV-infected subjects as a result of a reduction in the efflux capacity of HDL3 particles. HAART administration restored the capacity of plasma from HIV patients to stimulate cholesterol efflux from human macrophages (9.4%; P = 0.04). During HIV infection, the capacity of whole plasma to remove cholesterol from macrophages is reduced, thus potentially contributing to the increased coronary heart disease in the HIV population. HAART administration restored the removal of cholesterol from macrophages by increasing HDL functionality.

Small, dense HDL subfractions are the most efficient mediators of cholesterol efflux

Small, dense HDL subfractions are the most efficient mediators of cholesterol efflux

Effect of ferulic acid on cholesterol efflux in macrophage foam cell formation and potential mechanism

The formation of macrophage-derived foam cells is a typical feature of atherosclerosis (AS). Reverse cholesterol efflux (RCT) is one of important factors for the formation of macrophage foam cells. In this study, macrophage form cells were induced by oxidized low density lipoprotein (ox-LDL) and then treated with different concentrations of ferulic acid, so as to observe the effect of ferulic acid on the intracellular lipid metabolism in the ox-LDL-induced macrophage foam cell formation, the cholesterol efflux and the mRNA expression and protein levels of ATP binding cassette transporter A1 (ABCA1) and ATP binding cassette transporter G1 (ABCG1) that mediate cholesterol efflux, and discuss the potential mechanism of ferulic acid in resisting AS. According to the findings, compared with the control group, the ox-LDL-treated group showed significant increase in intracellular lipid content, especially for the cholesterol content; whereas the intracellular lipid accumulation markedly decreased, after the treatment with ferulic acid. The data also demonstrated that the mRNA and protein expressions of ABCA1 and ABCG1 significantly increased after macrophage foam cells were treated with different concentrations of ferulic acid. In summary, ferulic acid may show the anti-atherosclerosis effect by increasing the surface ABCA1 and ABCG1 expressions of macrophage form cells and promoting cholesterol efflux.

Akt inhibition promotes ABCA1-mediated cholesterol efflux to ApoA-I through suppressing mTORC1.

ATP-binding cassette transporter A1 (ABCA1) plays an essential role in mediating cholesterol efflux to apolipoprotein A-I (apoA-I), a major housekeeping mechanism for cellular cholesterol homeostasis. After initial engagement with ABCA1, apoA-I directly interacts with the plasma membrane to acquire cholesterol. This apoA-I lipidation process is also known to require cellular signaling processes, presumably to support cholesterol trafficking to the plasma membrane. We report here that one of major signaling pathways in mammalian cells, Akt, is also involved. In several cell models that express ABCA1 including macrophages, pancreatic beta cells and hepatocytes, inhibition of Akt increases cholesterol efflux to apoA-I. Importantly, Akt inhibition has little effect on cells expressing non-functional mutant of ABCA1, implicating a specific role of Akt in ABCA1 function. Furthermore, we provide evidence that mTORC1, a major downstream target of Akt, is also a negative regulator of cholesterol efflux. In cells where mTORC1 is constitutively activated due to tuberous sclerosis complex 2 deletion, cholesterol efflux to apoA-I is no longer sensitive to Akt activity. This suggests that Akt suppresses cholesterol efflux through mTORC1 activation. Indeed, inhibition of mTORC1 by rapamycin or Torin-1 promotes cholesterol efflux. On the other hand, autophagy, one of the major pathways of cholesterol trafficking, is increased upon Akt inhibition. Furthermore, Akt inhibition disrupts lipid rafts, which is known to promote cholesterol efflux to apoA-I. We therefore conclude that Akt, through its downstream targets, mTORC1 and hence autophagy, negatively regulates cholesterol efflux to apoA-I.

Paeonol suppresses lipid accumulation in macrophages via upregulation of the ATP‑binding cassette transporter A1 and downregulation of the cluster of differentiation 36.

Paeonol, a potent antioxidant isolated from cortex moutan, possesses athero‑protective activity, yet the detailed mechanisms are not fully investigated. This study was conducted to explore the role of paeonol and its underlying mechanisms in RAW264.7 macrophages and apolipoprotein E‑deficient (ApoE(‑/‑)) mice. Paeonol treatment significantly attenuated intracellular lipid accumulation in macrophages, which may be the result of decreased oxidized low‑density lipoprotein (ox‑LDL) uptake and increased cholesterol efflux. Additionally, paeonol markedly inhibited the mRNA and protein expression of the cluster of differentiation 36 (CD36) by decreasing nuclear translocation of c‑Jun [a subunit of activator protein‑1 (AP‑1)]. Moreover, paeonol upregulated the protein stability of ATP‑binding cassette transporter A1 (ABCA1) by inhibiting calpain activity, while ABCA1 mRNA expression was not altered. Furthermore, small hairpin RNA (shRNA) targeting haem oxygenase‑1 (HO‑1) inhibited the paeonol‑mediated beneficial effects on the expression of c‑Jun, CD36, ABCA1, calpain activity and lipid accumulation in macrophages. Accordingly, paeonol retarded the progress of atherosclerosis in ApoE(‑/‑) mice and modulated the expression of CD36 and ABCA1 in aortas similarly to that observed in macrophages. These results indicate that paeonol provides protective effects on foam cell formation by a novel HO‑1‑dependent mediation of cholesterol efflux and lipid accumulation in macrophages.

N-acetylcysteine prevents endoplasmic reticulum stress elicited in macrophages by serum albumin drawn from chronic kidney disease rats and selectively affects lipid transporters, ABCA-1 and ABCG-1

In chronic kidney disease (CKD) nontraditional risk factors, such as oxidative stress and advanced glycation end products (AGE) contribute to cardiovascular disease. Particularly, disturbances in reverse cholesterol transport favor the development of atherosclerosis. We analyzed the influence of N-acetylcysteine (NAC) in CKD rats on plasma concentration of lipid peroxides (TBARS) and AGE and on the impact of serum albumin in the development of macrophage endoplasmic reticulum stress (ERS) and cholesterol efflux, namely apo A-I and HDL2-mediated cholesterol removal and ABCA-1 and ABCG-1 protein level. CKD was induced by 5/6 nephrectomy in 2-month old male Wistar rats. Controls (Sham) were false operated. Animals were treated or not with NAC (600 mg/L of water). After 60 days serum albumin was isolated by FPLC and purified by alcoholic extraction. J774 macrophages were incubated with serum albumin (1 mg/mL; 18 h) from all groups, and the expression of ERS markers (protein disulfide isomerase – PDI, Grp78 and Grp94), ABCA-1 and ABCG-1 determined by immunoblot. HDL2 or apo A-I were used for cholesterol efflux assays. Protein and lipid composition of total HDL from Sham and CKD was determined and these particles tested on their abilities to accept cell cholesterol. Comparisons were done by one-way ANOVA and Newman Keuls post test. After 60 days of CKD, body weight was 10% lower in CKD compared to Sham (p < 0.01). This was prevented by NAC. Urea, creatinine, total cholesterol (TC), triglycerides (TG) (mg/dL), proteinuria (mg/24 h) (Sham, n = 31; Sham + NAC, n = 20; CKD, n = 74; CKD + NAC, n = 32), total AGE and pentosidine (n = 8; fluorescence arbitrary unit) and TBARS (n = 7; nmoL/mL) were higher in CKD (122 ± 8; 0.9 ± 0.07; 151 ± 6; 83 ± 4; 46 ± 2.5; 32,620 ± 673; 16,700 ± 1,370; 6.6 ± 0.5, respectively) and in CKD + NAC (91.4 ± 5; 0.6 ± 0.02; 126 ± 7.5; 73 ± 6; 51 ± 3.5; 24,720 ± 1,114; 10,080 ± 748; 4.5 ± 0.5, respectively) in comparison to Sham (41 ± 0.9; 0.4 ± 0.03; 76 ± 2.7; 51.5 ± 3; 14 ± 0.9; 21,750 ± 960; 5,314 ± 129; 2.0 ± 0.2, respectively; p < 0.001) and Sham + NAC (40 ± 0.9; 0.3 ± 0.02; 76 ± 2.6; 68 ± 4; 18.4 ± 1.5; 20,040 ± 700; 5,050 ± 267; 1.8 ± 0.2, respectively; p < 0.001). TC, urea, creatinine, total AGE, pentosidine and TBARS were respectively, 17%, 25%, 33%, 24%, 40% and 28% (p < 0.01) lower in CKD + NAC, than in CKD. Glycemia was higher in Sham + NAC (107 ± 4.6) and CKD + NAC (107 ± 2.6) than in Sham (96 ± 1.8; p < 0.05) and CKD (98 ± 1.6; p < 0.01), respectively. In macrophages (n = 6), CKD albumin increased PDI (3 and 6 times, p < 0.01) and Grp94 (66% and 80%, p < 0.01) in comparison to Sham and CKD + NAC-albumin treated cells, respectively. ABCA-1 expression was lower (87% and 70%, p < 0.001) in macrophage treated with Sham + NAC and CKD albumin respectively in comparison to Sham albumin; ABCG-1 was higher (4 and 7 times, p < 0.001) in macrophages treated with Sham + NAC and CKD + NAC albumin, respectively in comparison to Sham and CKD albumin. Apo A-I mediated cholesterol efflux was lower (59% and 70%, p < 0.0001) in macrophage treated with Sham + NAC and CKD albumin respectively in comparison to Sham albumin, however, the HDL2 mediated cholesterol efflux was higher (54% and 25%, p < 0.0001) in macrophage treated with Sham + NAC albumin, in comparison to Sham and CKD + NAC albumin, respectively. CKD-HDL was enriched in total protein and lipids compared to Sham-HDL but preserved its capacity to remove cholesterol from macrophages. NAC reduces plasma lipid peroxidation and AGE and abrogates ERS induced by CKD-albumin. Despite diminishing ABCA-1, NAC increases ABCG-1 that counteracts the reduction in apo A-I-mediated cholesterol efflux. NAC may contribute to attenuate the deleterious effects of CKD-albumin on lipid accumulation in macrophages helping to prevent atherogenesis in CKD.

Alteration of HDL functionality and PON1 activities in acute coronary syndrome patients

ObjectiveThe functionality of HDL has been suggested as an important factor in the prevention of cardiovascular and coronary artery diseases. The objective of the present study was to investigate the functionality of HDL and the factors that may affect the anti-atherogenic properties of HDL in ACS patients. Methods and resultsOne hundred healthy subjects and 205 ACS patients were recruited. HDL functionality was evaluated by measuring their capacity to mediate cholesterol efflux from J774 macrophages. Oxidative stress status was determined by measuring plasma malondialdehyde (MDA), protein carbonyl, and vitamin E levels by HPLC. The PON1 Q192R polymorphism status and PON1 paraoxonase and arylesterase activities of the healthy subjects and ACS patients were also determined. The HDL of ACS patients displayed a limited capacity to mediate cholesterol efflux, especially via the ABCA1-pathway. MDA (7.06±0.29μM) and protein carbonyl (9.29±0.26μM) levels were significantly higher in ACS patients than in healthy subjects (2.29±0.21μM and 3.07±0.17μM, respectively, p<0.0001), while α- and γ-tocopherol (vitamin E) levels in ACS patients were 8-fold (p<0.001) and 2-fold (p<0.05) lower than in healthy subjects. Paraoxonase, arylesterase and HDL-corrected PON1 activities (PON1 activity/HDL ratio) were significantly lower in ACS patients. Logistic regression analyses showed that high PON1 paraoxonase and arylesterase activities had a significant protective effect (OR=0.413, CI 0.289–0.590, p<0.001; OR=0.232 CI 0.107–0.499, p<0.001, respectively) even when adjusted for HDL level, age, BMI, and PON1 polymorphism. ConclusionThe results of the present study showed that the functionality of HDL is impaired in ACS patients and that the impairment may be due to oxidative stress and an alteration of PON1 activities.

Cellular cholesterol transport proteins in diabetic nephropathy.

BackgroundLipid accumulation has been shown to accelerate renal injury, and the intracellular accumulation of lipids may be caused by alterations in synthesis as well as lipid uptake and efflux. We have investigated the role of cellular cholesterol transport proteins including adenosine triphosphate binding cassette transporter A1 (ABCA1), G1 (ABCG1) and scavenger receptor class B type I (SR-BI) in diabetic nephropathy.MethodsProtein expression and the ability to mediate cholesterol efflux of ABCA1, ABCG1 and SR-BI was determined in human renal mesangial cells and proximal tubular epithelial cells cultured under normal or high glucose conditions. Renal expression of these cholesterol transporters was examined in a murine model of streptozotocin-induced type 1 diabetes.ResultsABCA1, ABCG1 and SR-BI were expressed in both human renal mesangial cells and proximal tubular epithelial cells, and mediated cholesterol efflux to apolipoprotein AI and HDL. In vitro, hyperglycemia reduced the expression and the ability to mediate cholesterol efflux of all three cholesterol transporters (p<0.05). In vivo studies showed that intra-renal accumulation of lipids was increased in diabetic mice, particularly in mice with nephropathy. This was associated with a significant reduction in the expression of ABCA1, ABCG1 and SR-BI in the kidneys. These changes were already seen in diabetic mice without nephropathy and preceded the development of nephropathy. Diabetic mice with nephropathy had the lowest level of these cholesterol transporters.ConclusionInducing diabetes with streptozotocin significantly reduced renal expression of ABCA1, ABCG1 and SR-BI. Defects in cholesterol export pathway in renal cells could therefore promote cholesterol accumulation and might contribute to the development of diabetic nephropathy.

Cholesterol and lipoprotein metabolism: Early Career Committee contribution.

Cholesterol and lipoprotein metabolism: Early Career Committee contribution.

Rosuvastatin activates ATP-binding cassette transporter A1-dependent efflux ex vivo and promotes reverse cholesterol transport in macrophage cells in mice fed a high-fat diet.

It is controversial whether statins improve high-density lipoprotein (HDL) function, which plays an important role in reverse cholesterol transport in vivo. The aim of the present study was to clarify the effects of rosuvastatin and atorvastatin on reverse cholesterol transport in macrophage cells in vivo and their underlying mechanisms. Male C57BL mice were divided into 3 groups (rosuvastatin, atorvastatin, and control groups) and orally administered rosuvastatin, atorvastatin, or placebo for 6 weeks under feeding with a 0.5% cholesterol+10% coconut oil diet. After administration, although there were no changes in plasma HDL cholesterol levels among the groups, plasma from the rosuvastatin group showed an increased ability to promote ATP-binding cassette transporter A1-mediated cholesterol efflux ex vivo. In addition, capillary electrophoresis revealed a shift in HDL toward the pre-β HDL fraction only in the rosuvastatin group. Mice in all 3 groups were intraperitoneally injected with (3)H-cholesterol-labeled and cholesterol-loaded macrophages and then were monitored for the appearance of (3)H-tracer in plasma and feces. The amount of (3)H-tracer excreted into feces during 48 hours in the rosuvastatin group was greater than that in the control group. Finally, (3)H-cholesteryl oleate-HDL was intravenously injected into all groups, blood samples were taken, and the count of (3)H-cholesterol was analyzed. Plasma (3)H-cholesteryl oleate-HDL changed similarly, and no differences in fractional catabolic rates were observed. Rosuvastatin enhanced the ATP-binding cassette transporter A1-dependent HDL efflux function of reverse cholesterol transport, and this finding highlights the potential of rosuvastatin for the regression of atherosclerosis.

Lower Apo A-I and lower HDL-C levels are associated with higher intermediate CD14++CD16+ monocyte counts that predict cardiovascular events in chronic kidney disease.

Patients with chronic kidney disease (CKD) display impaired cholesterol efflux capacity and elevated CD14(++)CD16(+) monocyte counts. In mice, dysfunctional cholesterol efflux causes monocytosis. It is unknown whether cholesterol efflux capacity and monocyte subsets are associated in CKD. In 438 patients with CKD, mediators of cholesterol efflux capacity (high-density lipoprotein cholesterol/apolipoprotein A-I) and monocyte subsets were analyzed as predictors of cardiovascular events. Monocyte subset-specific intracellular lipid content, CD36, CD68, and ABCA1 were measured in a subgroup. Experimentally, we analyzed subset-specific cholesterol efflux capacity and response to oxidized low-density lipoprotein cholesterol stimulation in CKD. Epidemiologically, both low Apo-I and low high-density lipoprotein cholesterol were associated with high CD14(++)CD16(+) monocyte counts in linear regression analyses (apolipoprotein A-I: β=-0.171; P<0.001; high-density lipoprotein cholesterol: β=-0.138; P=0.005), but not with counts of other monocyte subsets. In contrast to apolipoprotein A-I or high-density lipoprotein cholesterol, higher CD14(++)CD16(+) monocyte counts independently predicted cardiovascular events (hazard ratio per increase of 1 cell/μL: 1.011 [1.003-1.020]; P=0.007). Experimentally, CD14(++)CD16(+) monocytes demonstrated preferential lipid accumulation, high CD36, CD68, and low ABCA1 expression and, consequently, displayed low cholesterol efflux capacity, avid oxidized low-density lipoprotein cholesterol uptake, and potent intracellular interleukin-6, interleukin-1β, and tumor necrosis factor-α production. Taken together, mediators of cholesterol efflux are associated with CD14(++)CD16(+) monocyte counts, which independently predict adverse outcome in CKD.