金花茶叶醇提物通过调节胆固醇逆向转运关键蛋白的表达抑制动脉粥样硬化

目的：探讨金花茶叶醇提物调节胆固醇逆向转运（RCT）关键蛋白细胞质膜微囊蛋白-1（caveolin-1）、清道夫受体B1（SR-B1）、A1型三磷酸腺苷结合盒转运体（ABCA1）、蛋白激酶A（PKA）的表达而抑制巨噬细胞向泡沫细胞衍变、拮抗动脉粥样硬化（AS）的潜在药理作用机制。方法：乙醇回流提取获得金花茶叶醇提物,制备金花茶叶醇提物含药大鼠血清。体外测试金花茶叶醇提物含药血清对巨噬细胞经典活化、吞噬氧化低密度脂蛋白（ox-LDL）并衍变为泡沫细胞以及caveolin-1、SR-B1、ABCA1、PKA表达的调节作用。高脂饲喂雄性ApoE^-/-小鼠建立AS小鼠模型,体内测试金花茶叶醇提物对小鼠主动脉弓AS斑块形成以及内膜caveolin-1、SR-B1、ABCA1、PKA表达的调节作用。结果：10%金花茶叶醇提物含药血清显著抑制巨噬细胞经典活化,阻止其衍变为泡沫细胞,上调caveolin-1、SR-B1、ABCA1、PKA表达。金花茶叶醇提物显著上调AS小鼠主动脉内膜caveolin-1、SR-B1、ABCA1、PKA表达,抑制AS斑块形成。结论：金花茶叶醇提物可阻止巨噬细胞向泡沫细胞衍变,抑制AS斑块形成,可能与其上调RCT关键蛋白caveolin-1、SR-B1、ABCA1、PKA表达有关。     

化合物E0869体外抗动脉粥样硬化的活性研究

ATP结合盒转运体A1(ATP-binding cassette transporter A1,ABCA1)和清道夫受体B型I(scavenger receptor class B type I,SR-BI/CLA-1)是胆固醇逆转运过程中的重要蛋白。ABCA1和SR-BI/CLA-1的高表达能降低动脉粥样硬化的危险性。因此,本研究利用前期已建立的人ABCA1和CLA-1表达上调剂筛选模型,对20 000个化合物进行筛选,获得能上调ABCA1和CLA-1表达的化合物E0869[4-甲磺酰甲基苯甲酸-1-(3,4-二甲基苯基)-1-丙酮-2-酯],其上调活性分别为160%和175%,EC50值分别为3.79和1.42μmol·L-1;进一步研究发现,活性化合物E0869能上调肝细胞Hep G2以及巨噬细胞RAW264.7中ABCA1、SR-BI/CLA-1以及ABCG1的m RNA和蛋白水平,但不影响FAS、SREBP-1c、CD36的表达;E0869能使泡沫化巨噬细胞RAW264.7胞内脂滴量明显减少,并能增加其胆固醇的流出。因此,化合物E0869能够上调ABCA1和CLA-1活性,并且具有较好的体外抗动脉粥样硬化效果。     

二氢杨梅素对巨噬细胞源性泡沫细胞胆固醇流出的影响

摘要：目的 观察二氢杨梅素 （DMY） 对鼠源巨噬细胞性泡沫细胞胆固醇流出的影响并探讨其可能机制。方法 用 50 mg/L 的氧化低密度脂蛋白 （ox-LDL） 孵育鼠源性巨噬细胞 RAW264.7 经 48 h 诱导细胞泡沫化。将泡沫细胞分为对照组 （只加 RPMI 1640 的培养基培养） 和 DMY1~4 组 （分别用 10、 20、 40 和 80 μmol/L DMY 处理）, 培养 24 h。采用[ 3 H]标记的胆固醇检测细胞胆固醇的流出率, 高效液相色谱测定细胞内游离胆固醇 （FC）、 胆固醇酯 （CE） 和总胆固醇 （TC） 的水平, Western blot 检测细胞中三磷酸腺苷结合盒转运体 A1 （ABCA1） 的表达。结果 与对照组比较, 20、 40 和 80 μmol/L DMY 组细胞的胆固醇流出率均显著增加, 细胞内 FC、 TC 和 CE 水平及 CE/TC 的比值均显著减少, ABCA1 的表达显著上调, 均呈剂量依赖性 （均 P < 0.05）。与对照组比较, DMY （10 μmol/L） 组细胞胆固醇流出率,细胞内 FC、 TC 和 CE 水平,ABCA1 的表达差异均无统计学意义 （均 P > 0.05）。结论 DMY 促进了鼠源巨噬细胞性泡沫细胞胆固醇流出, 其机制可能与上调泡沫细胞中 ABCA1的表达有关。 ,     

ABCA1：动脉粥样硬化治疗的新方向

动脉粥样硬化是导致心血管疾病的主要原因，血浆中的HDL水平与AS呈现高度负相关性。ABCA1是ATP-结合盒转运蛋白超家族中的一员，能介导转运胆固醇至细胞膜与载脂蛋白结合形成HDL，从而从外周细胞转运胆固醇至肝脏，再从胆汁分泌中清除，防止胆固醇在巨噬细胞中沉积，防止AS的发生。有ABCA1基因突变引起的tangier病纯合子发生AS的几率几乎比正常人高6倍。由此可见，ABCA1在胆固醇转运，HDL代谢和防动脉粥样硬化中都起到一定作用。     

辛伐他汀对新诊断2型糖尿病患者单核巨噬细胞胆固醇外流的影响

目的研究新诊断2型糖尿病患者外周血单核巨噬细胞SR-B1、ABCA1表达及胆固醇外流的变化,以及辛伐他汀治疗对上述指标的影响。方法采用Western印迹法及RT-PCR方法检测新诊断糖尿病患者(A1、B1组)、正常对照组(C组)及辛伐他汀治疗后(A2、B2组)外周血单核巨噬细胞SR-B1、ABCA1蛋白及mRNA表达、胆固醇外流率。结果新诊断糖尿病患者单核巨噬细胞SR-B1蛋白及mRNA表达各组间以及治疗前后比较差异无统计学意义(P>0.05)。ABCA1蛋白及mRNA表达明显降低(P<0.05),辛伐他汀治疗后B2组升高明显(P<0.05),但仍显著低于C组(P<0.05)。两个糖尿病组胆固醇外流率明显下降(P<0.05),A1、B1两组间差异无统计学意义(P>0.05)。治疗后的A2组胆固醇外流率轻度升高,但差异无统计学意义(P>0.05),B2组胆固醇外流率显著升高(P<0.05),但未达到C组水平(P<0.05)。巨噬细胞胆固醇外流率与ABCA1蛋白及mRNA表达密切相关(r1=0.752,r2=0.724,P<0.05)。结论新诊断2型糖尿病患者的外周血单核巨噬细胞胆固醇外流率较正常对照组明显下降,这种变化可能与转运体ABCA1表达下降有关。辛伐他汀治疗可能通过部分提高ABCA1表达从而增加胆固醇外流而起到抗动脉粥样硬化作用。     

阿托伐他汀对金黄地鼠糖尿病模型巨噬细胞胆固醇外流的影响

目的：研究不同剂量阿托伐他汀对糖尿病动物模型体内巨噬细胞胆固醇含量的影响，进一步探讨他汀类药物抑制动脉粥样硬化斑块进展的机制。方法：建立糖尿病金黄地鼠动物模型，体外培养腹腔巨噬细胞，在体外与不同剂量阿托伐他汀孵育，利用酶法结合高效液相色谱法测定细胞内胆固醇及胆固醇脂含量。RT—PCR方法检测细胞ABCA1 mRNA表达量的不同。结果：在apoA1存在时，阿托伐他汀可以显著促进巨噬细胞内胆固醇外流，可能与药物增强细胞内胆固醇酯水解酶活性、促进巨噬细胞AB—CA1的表达有关。结论：阿托伐他汀促进ABCA1介导的细胞内胆固醇外流。     

EGCG通过miR-33a上调ABCA1表达减少巨噬细胞脂质蓄积

目的研究EGCG是否通过影响miR-33a的表达,进而调控ABCA1表达,促进巨噬细胞内胆固醇流出。方法先建立THP~(-1)巨噬细胞源性泡沫细胞,然后用EGCG处理,Real time PCR检测细胞miR-33a表达。细胞随机分为3组:空白对照组、50μmol·L~(-1)EGCG处理组、50μmol·L~(-1)EGCG+80 nmol·L~(-1)miR-33a mimic处理组,Real time PCR和Werstern blot检测细胞ABCA1 mRNA和蛋白表达,油红O染色和高效液相色谱法检测细胞内脂质含量,[3H]法检测细胞内胆固醇流出。结果在不影响细胞活性状况下,EGCG呈浓度和时间依赖性下调miRNA33a表达;EGCG能明显上调ABCA1 mRNA和蛋白的表达,但能被转染miRNA33 mimic抑制;EGCG可减少THP~(-1)巨噬细胞源性泡沫细胞中的脂质蓄积,但能被细胞中转染miRNA33 mimic所弱化;EGCG减少细胞内胆固醇蓄积是与其促进细胞内胆固醇流出有关,细胞中转入过量miRNA33a可以抑制胆固醇流出。结论 EGCG可通过减少miRNA33a的生成,进而上调ABCA1表达,促进巨噬细胞中胆固醇流出,这可能是EGCG抗动脉粥样硬化作用的分子机制之一。     

PPARγ激活剂罗格列酮对兔动脉粥样硬化斑块消退的影响

过氧化物酶体增殖激活受体γ(PPARγ)是一个核受体,在血管壁内皮细胞、巨噬细胞/泡沫细胞及血管平滑肌细胞都有较高表达。PPARγ通过对这些细胞的调控作用,还影响着炎性因子的水平,在动脉粥样硬化(AS)疾病中发挥着重要的作用[1]。本实验通过高选择性PPARγ激动剂罗格列酮对高胆     

Rolipram对THP-1巨噬细胞源性泡沫细胞胆固醇流出和ABCA1表达的影响

目的　以THP 1巨噬细胞源性泡沫细胞为研究对象 ,探讨磷酸二酯酶抑制剂rolipram对THP 1巨噬细胞源性泡沫细胞ABCA1表达及细胞内胆固醇流出的影响。方法　用液体闪烁计数器检测细胞内胆固醇流出 ,运用逆转录 -多聚酶链反应和Westernblot印迹分别检测ABCA1mRNA与ABCA1蛋白的表达 ,采用低pH值EIA法测定细胞内cAMP水平。结果　实验显示PDE4抑制剂rolipram能引起THP 1巨噬细胞源性泡沫细胞cAMP水平、ABCA1表达和apoA 1介导的胆固醇流出成平衡增加 ,而细胞内总胆固醇、游离胆固醇与胆固醇酯明显减少。结论　PDE4抑制剂rolipram增加THP 1巨噬细胞源性泡沫细胞ABCA1表达及细胞内胆固醇流出 ,这为防治动脉粥样硬化发生发展提供一个新的策略     

青心酮对载脂蛋白E缺陷小鼠主动脉粥样硬化形成及斑块中主要细胞的TLR4表达的影响

目的观察青心酮对小鼠动脉粥样硬化（AS）斑块中平滑肌细胞、内皮细胞、巨噬细胞Toll样受体4表达（Toll-like receptor 4,TLR4）的影响,及对载脂蛋白E基因敲除小鼠主动脉粥样硬化病变的影响。方法取小鼠胸主动脉,进行平滑肌细胞、内皮细胞的原代培养,RAW264.7（小鼠巨噬细胞）细胞株传代培养。实验分4组：空白对照组,脂多糖（LPS）组,青心酮组,辛伐他汀组。收集各组细胞总mRNA及蛋白,应用RT-PCR及Western-blot方法检测TLR4 mRNA及蛋白。取30只8周龄雄性ApoE（-/-）小鼠,随机分成3组：模型组（n=10）,每天生理盐水灌胃;青心酮治疗组（n=10）经胃管灌注青心酮10mg·kg^-1·d^-1,辛伐他汀治疗组（n=10）经胃管灌注辛伐他汀10mg·kg^-1·d^-1。所有实验小鼠均饲以＂西方类型膳食＂饲料12周。剪取主动脉根部切片及HE染色观察主动脉粥样硬化病变情况。结果1×10^-7mol·L^-1青心酮组血管平滑肌细胞、内皮细胞、巨噬细胞TLR4 mRNA和蛋白含量明显低于未处理组（P〈0.01）;与辛伐他汀组比较无显著性差异;青心酮组AS病灶形成减少。结论青心酮可下调LPS活化的小鼠平滑肌细胞、内皮细胞、巨噬细胞TLR4mRNA和蛋白的表达,在一定程度上能减少AS病灶的形成,可能通过TLR4途径发挥其作用。     

Signal transduction pathways provide opportunities to enhance HDL and apoAI-dependent reverse cholesterol transport

Binding of High Density Lipoprotein (HDL) and its major apolipoprotein A-I (apoA-I) to cell surface receptors is believed to initiate a plethora of signaling cascades that promote atheroprotective cell behavior, including the removal of excess cholesterol from lipid-loaded macrophages. More specifically, HDL and apoA-I binding to scavenger receptor BI (SR-BI) and ATP-binding cassette (ABC) transporter A1 has been shown to activate protein kinase A and C (PKA, PKC), Rac/Rho GTPases, Janus Kinase 2 (JAK2), calmodulin as well as mitogen-activated protein kinases (MAPK). Some of these signaling events upregulate mobilization of cholesterol from cellular pools, while others promote efflux pathways through increased expression, stability, and cell surface localization of SR-BI and ABCA1. This review aims to summarize the current knowledge of HDL- and apoA-I -induced signal transduction pathways that are linked to cholesterol efflux and discusses the underlying mechanisms that could couple ligand binding to SR-BI and ABCA1 with signaling and cholesterol export. Additional focus is given on the potential of pharmacological intervention to modulate the activity of signaling cascades for the inhibition or regression of cholesterol accumulation in atherosclerotic lesions.     

ATP-binding cassette transporters A1 and G1, HDL metabolism, cholesterol efflux, and inflammation: important targets for the treatment of atherosclerosis

Atherosclerosis has been characterized as a chronic inflammatory response to cholesterol deposition in arteries. Plasma high density lipoprotein (HDL) levels bear a strong independent inverse relationship with atherosclerotic cardiovascular disease. One central antiatherogenic role of HDL is believed to be its ability to remove excessive peripheral cholesterol back to the liver for subsequent catabolism and excretion, a physiologic process termed reverse cholesterol transport (RCT). Cholesterol efflux from macrophage foam cells, the initial step of RCT is the most relevant step with respect to atherosclerosis. The ATP-binding cassette (ABC) transporters ABCA1 and ABCG1 play crucial roles in the efflux of cellular cholesterol to HDL and its apolipoproteins. Moreover, ABCA1 and ABCG1 affect cellular inflammatory cytokine secretion by modulating cholesterol content in the plasma membrane and within intracellular compartments. In humans, ABCA1 mutations can cause a severe HDL-deficiency syndrome characterized by cholesterol deposition in tissue macrophages and prevalent atherosclerosis. Disrupting Abca1 or Abcg1 in mice promotes accumulation of excessive cholesterol in macrophages, and physiological manipulation of ABCA1 expression affects atherogenesis. Here we review recent advances in the role of ABCA1 and ABCG1 in HDL metabolism, macrophage cholesterol efflux, inflammation, and atherogenesis. Next, we summarize the structure, expression, and regulation of ABCA1 and ABCG1. Finally, we give an update on the progress and pitfalls of therapeutic approaches that target ABCA1 and ABCG1 to stimulate the flux of lipids through the RCT pathway.     

Modulation of HDL metabolism by the niacin receptor GPR109A in mouse hepatocytes

The niacin receptor GPR109A is a G_i-protein-coupled receptor which mediates the effects of niacin on inhibiting intracellular triglyceride lipolysis in adipocytes. However, the role of GPR109A in mediating the effects of niacin on high density lipoprotein (HDL) metabolism is unclear. We found niacin has no effect on HDL-C in GPR109A knockout mice. Furthermore, niacin lowered intracellular cAMP in primary hepatocytes mediated by GPR109A. We used an adeno-associated viral (AAV) serotype 8 vector encoding GPR109A under the control of the hepatic-specific thyroxine-binding globulin promoter to specifically overexpress GPR109A in mouse liver. Plasma HDL-C, hepatic ABCA1 and the HDL cholesterol production rate were significantly reduced in mice overexpressing GPR109A. Overexpression of GPR109A reduced primary hepatocyte free cholesterol efflux to apoA-I; conversely, GPR109A deficient hepatocytes had increased ABCA1-mediated cholesterol efflux. These data support the concept that the HDL-C lowering effect of niacin in wild-type mice is mediated through stimulation of GPR109A in hepatocytes; such an effect then leads to reduced hepatocyte ABCA1 expression and activity, decreased cholesterol efflux to nascent apoA-I, and reduced HDL-C levels. These results indicate that niacin-mediated activation of GP109A in liver lowers ABCA1 expression leading to reduced hepatic cholesterol efflux to HDL.     

Reverse cholesterol transport and future pharmacological approaches to the treatment of atherosclerosis

The apparent protective effect of high density lipoprotein cholesterol (HDL) with respect to coronary heart disease (CHD) is generally thought to reside in its ability to transport cholesterol from peripheral cells to the liver for excretion from the body. Knozon as reverse cholesterol transport (RCT), this process involves many key steps and lipoprotein interconversions, and there is no consensus as to which step is most suitable for possible drug intervention. The membrane proteins, scavenger receptor class B, type 1 (SR-B1) and the ATP-binding cassette 1 (ABC1), have been strongly implicated as being important in cholesterol efflux; the former as a bona fide receptor for HDL and the latter as a lipid transporter. Lecithin:cholesterol acyltransferase (LCAT) then esterifies the effluxed cholesterol to form cholesteryl esters (Step 2), which are then transferred to apoB-containing lipoproteins by cholesteryl ester transfer protein (CETP, Step 3). Despite the complexities and uncertainties, drugs should be developed which impact all of the above steps, and short-term endpoints need to be defined for a cautious, systematic approach to clinical evaluation.     

Tributyltin chloride induces ABCA1 expression and apolipoprotein A-I-mediated cellular cholesterol efflux by activating LXRalpha/RXR

Organotins, including tri-butyltin chloride (TBTC), are widely used in agricultural and chemical industries and cause persistent and widespread pollution. TBTC has been shown to activate nuclear receptor retinoid X receptor (RXR)/PPARγ signaling by interacting with RXR to modulate adipogenesis. However, whether TBTC affects liver X receptor (LXR)/RXR activity and subsequently the expression of cholesterol mobilizing genes is not known. In this study, we evaluated the ability of TBTC to activate LXR/RXR and ABC transporter A1 (ABCA1) expression. ABCA1 plays a critical role in HDL generation, maintaining cholesterol homeostasis, and cholesterol accumulation-induced diseases, such as atherosclerosis and pancreatic islet dysfunction. In a reporter gene assay, TBTC activated LXRα/RXR but not LXRβ/RXR. In mouse macrophage RAW264 cells, TBTC activated the ABCA1 promoter in an LXR-responsive element dependent manner and increased ABCA1 mRNA expression. TBTC augmented ABCA1 protein levels and apolipoprotein A-I-dependent cellular cholesterol efflux (HDL generation). The LXR-target fatty acid synthase and Spα mRNA levels were also increased by TBTC exposure. We conclude that TBTC has the ability to activate permissive LXRα/RXR signaling and thereby modulate cellular cholesterol efflux.     

Tributyltin chloride induces ABCA1 expression and apolipoprotein A-I-mediated cellular cholesterol efflux by activating LXRα/RXR

Organotins, including tri-butyltin chloride (TBTC), are widely used in agricultural and chemical industries and cause persistent and widespread pollution. TBTC has been shown to activate nuclear receptor retinoid X receptor (RXR)/PPARγ signaling by interacting with RXR to modulate adipogenesis. However, whether TBTC affects liver X receptor (LXR)/RXR activity and subsequently the expression of cholesterol mobilizing genes is not known. In this study, we evaluated the ability of TBTC to activate LXR/RXR and ABC transporter A1 (ABCA1) expression. ABCA1 plays a critical role in HDL generation, maintaining cholesterol homeostasis, and cholesterol accumulation-induced diseases, such as atherosclerosis and pancreatic islet dysfunction. In a reporter gene assay, TBTC activated LXRα/RXR but not LXRβ/RXR. In mouse macrophage RAW264 cells, TBTC activated the ABCA1 promoter in an LXR-responsive element dependent manner and increased ABCA1 mRNA expression. TBTC augmented ABCA1 protein levels and apolipoprotein A-I-dependent cellular cholesterol efflux (HDL generation). The LXR-target fatty acid synthase and Spα mRNA levels were also increased by TBTC exposure. We conclude that TBTC has the ability to activate permissive LXRα/RXR signaling and thereby modulate cellular cholesterol efflux.     

PPARγ activation redirects macrophage cholesterol from fecal excretion to adipose tissue uptake in mice via SR-BI

PPARγ agonists, used in the treatment of Type 2 diabetes, can raise HDL-cholesterol, therefore could potentially stimulate macrophage-to-feces reverse cholesterol transport (RCT). We aimed to test whether PPARγ activation promotes macrophage RCT in vivo. Macrophage RCT was assessed in mice using cholesterol loaded/³H-cholesterol labeled macrophages. PPARγ agonist GW7845 (20 mg/kg/day) did not change ³H-tracer plasma appearance, but surprisingly decreased fecal ³H-free sterol excretion by 43% (P < 0.01) over 48 h. Total free cholesterol efflux from macrophages to serum (collected from control and GW7845 groups) was not different, although ABCA1-mediated efflux was significantly higher with GW7845. To determine the effect of PPARγ activation on HDL cholesterol uptake by different tissues, the metabolic fate of HDL labeled with ³H-cholesteryl ether (CE) was also measured. We observed two-fold increase in HDL derived ³H-CE uptake by adipose tissue (P < 0.005) with concomitant 22% decrease in HDL derived ³H-CE uptake by the liver (P < 0.05) in GW7845 treated wild type mice. This was associated with a significant increase in SR-BI protein expression in adipose tissue, but not liver. The same experiment in SR-BI knockout mice, showed no difference in HDL derived ³H-CE uptake by adipose tissue or liver. In conclusion, PPARγ activation decreases the fecal excretion of macrophage derived cholesterol in mice. This is not due to inhibition of cholesterol efflux from macrophages, but rather involves redirection of effluxed cholesterol from liver towards adipose tissue uptake via SR-BI. This represents a novel mechanism for regulation of RCT and may extend the therapeutic implications of these ligands.     

ATP binding cassette transporter A1 (ABCA1) associated proteins: potential drug targets in the metabolic syndrome and atherosclerotic disease?

The metabolic syndrome is defined as a cluster of disorders including visceral obesity, insulin resistance, hypertension, hypertriglyceridemia and low HDL. Patients have an increased risk to develop atherosclerotic disease characterized by excessive macrophage cholesterol deposition in the vascular wall. HDL removes excess cellular cholesterol which is subsequently transported to the liver for biliary excretion and thereby preserves cholesterol homeostasis. Circulating HDL levels are maintained by hepatic ATP-binding cassette transporter A1 (ABCA1) which also transports peripheral cell cholesterol to extracellular lipid acceptors. Lipid export activity of ABCA1 improves pancreatic -cell function and ameliorates insulin release. ABCA1 affects plasma membrane cholesterol distribution and formation of lipid rafts representing signalling platforms for diverse receptors including toll-like receptor 4 (TLR4). Pharmacological activation of ABCA1 pathways presumably progresses metabolic diseases, and current approaches demonstrate beneficial effects of small peptides mimicking ABCA1 ligands which stabilize ABCA1 and enhance lipid efflux similar to its physiological acceptor apolipoprotein A-I. Research of the last decade has resulted in the identification of several ABCA1 binding proteins influencing ABCA1 signalling, stability and activity. In the current review the proteins suggested to form a complex with ABCA1 are summarized and their up to now characterized features towards ABCA1 functions are described.     

Rate‐limiting factors of cholesterol efflux in reverse cholesterol transport: Acceptors and donors

1. Plasma levels of high‐density lipoprotein (HDL) are believed to be inversely related to coronary artery disease. High‐density lipoprotein plays a key role in the process of reverse cholesterol transport, by which HDL is able to extract excess cholesterol from peripheral tissues and transfer it to the liver for biliary excretion. 2. Efflux of lipids (cholesterol and phospholipids) is the first step in reverse cholesterol transport. Several cellular membrane transporters, including ABCA1 and ABCG1, as well as scavenger receptor (SR)‐BI receptor, are believed to facilitate the active efflux of cholesterol to lipid‐poor apolipoprotein A‐I and mature HDL, respectively. Furthermore, overexpression or deletion of one or more specific genes supports the view that HDL is involved in cholesterol efflux. 3. In conclusion, current evidence supports a critical role for HDL in atheroprotection via an active efflux pathway through reverse cholesterol transport, with the substantial support of appropriate functions of cell donors.