CD36在动脉粥样硬化中的研究进展

CD36是巨噬细胞表面的一种清道夫受体,是巨噬细胞吸收氧化低密度脂蛋白(OX-LDL)的主要受体.OX-LDL是导致动脉粥样硬化(AS)发生的重要物质.AS斑块中,80%的成分来源于摄取脂质的巨噬细胞和由其转化形成的泡沫细胞.巨噬细胞通过CD36摄取大量的OX-LDL形成泡沫细胞.抑制CD36的表达可能与抗AS有关.本文就CD36的生物学特性、CD36在AS中作用和CD36的表达调节作一综述.     

硫化氢对THP-1源性巨噬细胞脂质摄取的影响

目的探索硫化氢对THP-1源性巨噬细胞脂质摄取的影响及可能机制。方法采用荧光显微镜测DiI标记的氧化型低密度脂蛋白(DiI-ox-LDL)摄取、RT-PCR和免疫印迹法测定CD36 mRNA和蛋白表达。结果巨噬细胞与DiI-ox-LDL孵育后大量摄取氧化型低密度脂蛋白(ox-LDL),外源性硫化氢供体硫氢化钠显著抑制巨噬细胞摄取氧化型低密度脂蛋白,而炔丙基甘氨酸(一个硫化氢产生酶胱硫醚-γ-裂解酶抑制剂)加剧巨噬细胞摄取氧化型低密度脂蛋白。进而,硫氢化钠呈浓度依赖性抑制巨噬细胞CD36 mRNA和蛋白表达,而炔丙基甘氨酸促进巨噬细胞CD36 mRNA和蛋白表达。结论硫化氢抑制巨噬细胞摄取脂质及清道夫受体CD36表达。     

普罗布考抑制氧化低密度脂蛋白上调巨噬细胞清道夫受体CD36的表达

背景 普罗布考是一降脂药,同时具有抗氧化特性,近年来的研究表明其可以通过多种机制抑制动脉粥样硬化的形成,降低经皮冠状动脉成形术后再狭窄的发生.目的 探讨普罗布考对氧化低密度脂蛋白(Ox-LDL)刺激巨噬细胞后清道夫受体CD36表达的抑制效应.方法 用不同浓度的Ox-LDL刺激人单核细胞系THP-1源性巨噬细胞及用不同浓度普罗布考和核因子κBp65(NF-κBp65)特异性抑制剂(PDTC)预处理细胞后再用氧化低密度脂蛋白刺激,半定量RT-PCR方法检测CD36和NF-κBp65的mRNA的表达,Western-blot检测CD36和细胞核NF-κBp65蛋白表达水平.结果 THP-1单核细胞分化成巨噬细胞后,CD36和NF-κBp65 mRNA和蛋白的表达上调;不同浓度的Ox-LDL刺激后,CD36 mRNA和蛋白的表达呈浓度依赖性增加,同时伴NF-κBp65 mRNA和蛋白的表达增加;PDTC和普罗布考干预后,NF-κBp65和CD36的mRNA和蛋白表达下调.结论 Ox-LDL可以通过NF-κBp65途径上调巨噬细胞CD36的表达;而普罗布考则可以抑制CD36的表达,这种作用与抑制NF-κBp65有关.     

清道夫受体与糖尿病

清道夫受体 (SR)是主要存在于巨噬细胞膜表面的一种糖蛋白 ,能特异性结合并摄取氧化低密度脂蛋白等多种配体从而介导脂类代谢。本文主要介绍与糖尿病相关的SRA、SRB Ⅰ和CD36的结构、分布和功能 ,以及细胞因子等对其调节作用。在 2型糖尿病中CD36表达的水平增加 ,CD36和SRA Ⅰ在糖尿病动脉粥样硬化的形成中介导胆固醇的摄取 ,SRA Ⅱ作为糖基化终末产物的受体在糖尿病肾病中有促进肾小球硬化的作用。     

清道夫受体CD36在动脉粥样硬化中的研究进展

<正>CD36是一种表达于单核细胞、巨噬细胞、微血管内皮细胞、平滑肌细胞、血小板等多种细胞表面的跨膜蛋白模式受体,可与多种配体相结合,介导先天性免疫、血栓形成、炎症和动脉粥样硬化等不同的生物过程[1]。巨噬细胞表面的CD36结合并吞噬氧化型低密度脂蛋白(oxLDL)形成泡沫细胞,并触发炎症级联反应,在动脉粥样硬化整个病理过程的不同阶段发挥重要作用。基因敲除CD36或阻断CD36介导的信号转导途径能够减少斑块的形成。探究CD36的功能     

清道夫受体与糖尿病

清道夫受体(SR)是主要存在于巨噬细胞膜表面的一种糖蛋白，能特异性结合并摄取氧化低密度脂蛋白等多种配体从而介导脂类代谢。本文主要介绍与糖尿病相关的SRA、SRB-Ⅰ和CD36的结构、分布和功能，以及细胞因子等对其调节作用。在2型糖尿病中CD36表达的水平增加，CD36和SRA-Ⅰ在糖尿病动脉粥样硬化的形成中介导胆固醇的摄取，SRA-Ⅱ作为糖基化终末产物的受体在糖尿病肾病中有促进肾小球硬化的作用。     

过氧化体增殖物激活型受体γ对巨噬细胞脂质蓄积及CD36表达的影响

目的观察过氧化体增殖物激活型受体γ激动剂和拮抗剂对THP-1巨噬细胞胆固醇蓄积及CD36表达的影响。方法实验分对照组、氧化型低密度脂蛋白组、Ciglitazone处理组和GW9662处理组,后两组用50 mg/L氧化型低密度脂蛋白分别与过氧化体增殖物激活型受体γ激动剂Ciglitazone(10μmol/L)及拮抗剂GW9662(10μmol/L)共同孵育24 h,高效液相色谱分析法检测细胞总胆固醇蓄积情况,RT-PCR和Western blot分别检测THP-1巨噬细胞CD36 mRNA和蛋白的表达。结果与对照组(76.28±10.36 mg/g)相比,氧化型低密度脂蛋白(121.63±13.32 mg/g)能使细胞总胆固醇含量显著增加,而Ciglitazone能使氧化型低密度脂蛋白处理的细胞总胆固醇含量进一步增加(136.23±14.78 mg/g),GW9662能使氧化型低密度脂蛋白处理的细胞总胆固醇含量减少(98.52±11.45 mg/g)。过氧化体增殖物激活型受体γ拮抗剂GW9662使巨噬细胞CD36 mRNA和蛋白的表达下调及胆固醇蓄积减少,过氧化体增殖物激活型受体γ激动剂Ciglitazone使巨噬细胞CD36 mRNA和蛋白的表达上调及胆固醇蓄积增多。结论过氧化体增殖物激活型受体γ拮抗剂使THP-1巨噬细胞胆固醇蓄积减少及氧化型低密度脂蛋白诱导的CD36表达下调。     

高糖对THP-1巨噬细胞CD36表达及脂质蓄积的影响

目的 观察高糖对THP-1巨噬细胞清道夫受体CD36表达和脂质蓄积的影响。方法 用不同浓度的D-葡萄糖（分别为5.6、11、20、30及35 mmol/L）、50 mg/L氧化型低密度脂蛋白（ox-LDL）、50 mg/L ox-LDL＋20 mmol/L D-葡萄糖孵育THP-1巨噬细胞24 h,油红O染色观察细胞内脂质蓄积情况,高效液相色谱分析法检测细胞内总胆固醇水平,定量PCR与免疫印迹分析法分别检测THP-1巨噬细胞CD36 mRNA和蛋白的表达。结果 随着D-葡萄糖处理THP-1巨噬细胞浓度的增加,CD36 mRNA和蛋白的表达逐渐增加（P<0.05）;高糖可协同ox-LDL诱导THP-1巨噬细胞CD36 mRNA和蛋白的表达上调（P<0.05）,并增加细胞内总胆固醇水平（P<0.05）。结论 高糖可诱导THP-1巨噬细胞CD36的表达上调,并促进细胞内脂质蓄积。     

普罗布考抑制氧化低密度脂蛋白上调巨噬细胞清道夫受体CD36的表达

背景普罗布考是一降脂药，同时具有抗氧化特性，近年来的研究表明其可以通过多种机制抑制动脉粥样硬化的形成，降低经皮冠状动脉成形术后再狭窄的发生。目的探讨普罗布考对氧化低密度脂蛋白（Ox-LDL）刺激巨噬细胞后清道夫受体CD36表达的抑制效应。方法用不同浓度的Ox-LDL刺激人单核细胞系THP-1源性巨噬细胞及用不同浓度普罗布考和核因子κBp65（NF-κBp65）特异性抑制剂（PDTC）预处理细胞后再用氧化低密度脂蛋白刺激，半定量RT—PCR方法检测CD36和NF-κBp65的mRNA的表达，Western-blot检测CD36和细胞核NF-κBp65蛋白表达水平。结果THP-1单核细胞分化成巨噬细胞后，CD36和NF-κBp65 mRNA和蛋白的表达上调；不同浓度的Ox-LDL刺激后，CD36mRNA和蛋白的表达呈浓度依赖性增加，同时伴NF-κBp65 mRNA和蛋白的表达增加；PDTC和普罗布考干预后，NF-κBp65和CD36的mRNA和蛋白表达下调。结论Ox-LDL可以通过NF-κBp65途径上调巨噬细胞CD36的表达；而普罗布考则可以抑制CD36的表达，这种作用与抑制NF-κBp65有关。     

瑞舒伐他汀对TPH-1巨噬细胞清道夫受体CD_（36）、SR-AⅠ表达的影响

目的观察瑞舒伐他汀对氧化型低密度脂蛋白（ox-LDL）诱导的TPH-1巨噬细胞清道夫受体CD36和SR-AⅠ表达的影响。方法体外培养TPH-1巨噬细胞,分三组置6孔培养板中。对照组为正常生长的TPH-1巨噬细胞;ox-LDL组加入100 mg/L的ox-LDL培养24 h,诱导巨噬细胞泡沫化;瑞舒伐他汀组加入100 mg/L的ox-LDL培养24 h,诱导巨噬细胞泡沫化,然后加入瑞舒伐他汀10μmol/L培养2 h。检测各组细胞内清道夫受体CD36、SR-AⅠ蛋白及其mRNA。结果与对照组相比,ox-LDL组CD36、SR-AⅠ蛋白及其mRNA表达增加（P均〈0.05）;与ox-LDL组相比,瑞舒伐他汀组CD36、SR-AⅠ蛋白及mRNA表达明显降低（P均〈0.05）。结论瑞舒伐他汀可降低ox-LDL诱导的TPH-1巨噬细胞中清道夫受体CD36、SR-AⅠ的表达。     

Expression of CD36 in macrophages and atherosclerosis: the role of lipid regulation of PPARgamma signaling

Several macrophage scavenger receptors have been identified that bind and internalize modified low-density lipoprotein particles. Although the pathophysiologic roles played by these receptors in human disease are still unproven, data from murine models of atherosclerosis have demonstrated a significant role in atherosclerotic foam cell development and vascular lesion development for two receptors: the type A scavenger receptor (SR-A) and the type B scavenger receptor, CD36. This review addresses the regulation and potential role of CD36 in macrophage foam cell formation and atherosclerosis, with particular emphasis on the mechanisms by which CD36 expression is altered in response to lipid modulation of peroxisome proliferator-activated receptor gamma signaling.     

C-terminal fragment of alpha1-antitrypsin activates human monocytes to a pro-inflammatory state through interactions with the CD36 scavenger receptor and LDL receptor

Monocyte scavenger receptor, CD36 has been implicated in the pathogenesis of atherosclerosis as a major oxidised LDL receptor mediating lipid accumulation and foam cell formation. Previously, we found that treatment of monocyte cultures with the carboxyl terminal fragment of alpha1-antitrypsin (C-36) increases lipid binding and uptake, induces LDL receptor mRNA and CD36 receptor protein expression, and also significantly increases production of pro-inflammatory molecules. To assess the role of the CD36 receptor in proatherogenic monocyte activation by the C-36 fragment, we tested whether specific anti-CD36 receptor antibodies would block the effects of C-36 on monocyte activation. We find that pre-incubation of cells with anti-LDL and anti-CD36 receptor antibodies (10 microg/ml) blocks binding of 125I-C-36 by about 50%. Similarly, cells pre-incubated with oxidised LDL or native LDL at concentrations from 2.5 to 10 microg/ml showed a loss of 125I-C-36 binding (up to 49 and 57%) and uptake (up to 47 and 59.8%), respectively. In parallel experiments, monocytes were first incubated for 1 or 6 h with anti-CD36 antibodies (10 microg/ml) prior to adding C-36 peptide. Anti-CD36 antibodies suppressed C-36-induced production of gelatinase B, monocyte chemoattractant protein-1, interleukin-6 and cellular oxygen consumption to control levels, whereas levels of TNFalpha were unaffected. In contrast, saturation of LDL receptors with excess of anti-LDL (20 microg/ml) significantly inhibited C-36 induced TNFalpha levels. Results indicate that the C-36 peptide binds to both LDL and CD36 scavenger receptors which involves selective upregulation of pro-inflammatory molecules and activation of the respiratory burst in human monocytes. This also supports important roles for CD36 and LDL receptors in atherogenesis and suggests that blockade of CD36 receptor can be protective in pro-inflammatory activation of human monocytes.     

Scavenger receptors that recognize advanced glycation end products

Scavenger receptors recognize modified low-density lipoproteins (LDLs) such as acetylated LDL and oxidized LDL. Advanced glycation end products (AGE), which are generated through long-term exposure of proteins to glucose, also behave as active ligands for some scavenger receptors, including class A scavenger receptor (SR-A) and class B scavenger receptors such as CD36 and scavenger receptor, class B, type I (SR-BI). SR-BI, the first identified high-density lipoprotein (HDL) receptor, plays key roles in reverse cholesterol transport by promoting selective uptake of cholesteryl esters (CE) in HDL by hepatocytes, and cholesterol efflux of unesterified cholesterol from peripheral cells to HDL. Using Chinese hamster ovary cells overexpressing SR-BI (CHO-SR-BI cells), it was demonstrated that AGE-bovine serum albumin binds to SR-BI and inhibits selective uptake of HDL-CE by CHO-SR-BI cells as well as cholesterol efflux from CHO-SR-BI cells to HDL, suggesting potential roles of AGE in diabetic dyslipidemia and accelerated atherosclerosis in diabetes.     

CD36, serves as a receptor for advanced glycation endproducts (AGE)

Interaction of advanced glycation endproducts (AGE) with AGE receptors induces several cellular phenomena relating potentially to diabetic complications. Five AGE receptors identified so far are receptor for AGE (RAGE), 80 K-H, OST-48, galectin-3, and macrophage scavenger receptor, types I and II (SR-A) [Eur. J. Biochem. 230 (1995) 408; Nature 386 (1997) 292.]. Since SR-A is known to belong to the class A scavenger receptor family and the scavenger receptor collectively represents a family of multiligand lipoprotein receptors, it is possible that CD36 belonging to class B scavenger receptor family (SR-B) can recognize AGE proteins as a ligand. This was tested in the present study at the cellular level by using Chinese hamster ovary (CHO) cells overexpressing human CD36 (CHO-CD36 cells). 125I-AGE-bovine serum albumin (BSA) was endocytosed in a dose-dependent fashion and underwent lysosomal degradation by CHO-CD36, but not wild-type CHO cells. Endocytic uptake of 125I-AGE-BSA by these cells was inhibited 50% by oxidized low-density lipoprotein (Ox-LDL) and 60% by FA6-152, an anti-CD36 antibody inhibiting cellular binding of Ox-LDL. Our results indicate that CD36 expressed by these cells mediates endocytic uptake and subsequent intracellular degradation of AGE proteins. Since CD36 is one of the major Ox-LDL receptors and is up-regulated in macrophage- and smooth muscle cell-derived foam cells in human atherosclerotic lesions, the present results suggest that, like Ox-LDL, AGE proteins generated in situ are recognized by CD36, which might contribute to the pathogenesis of diabetic macrovascular complications.     

Absence of CD36 protects against atherosclerosis in ApoE knock-out mice with no additional protection provided by absence of scavenger receptor A I/II

AIMS: The role of scavenger receptors in atherogenesis is controversial as a result of conflicting reports and a recent hypothesis suggesting that scavenger receptor absence would enhance the pro-inflammatory, pro-atherogenic milieu. This study addresses the effect of combined absence of scavenger receptors CD36 and SRA I/II on atherosclerosis lesion development in the apolipoprotein E knock-out (apoE degrees ) model. METHODS: We created background-related strains of apoE degrees , scavenger receptor A I/II knock-out (SRA degrees )/apoE degrees , CD36 knock-out (CD36 degrees )/apoE degrees , and CD36 degrees /SRA degrees /apoE degrees mice that were >99% C57Bl/6. Four-week-old mice were fed a Western diet for 12 weeks and were assessed for lesion burden/morphology, risk factors for atherosclerosis, inflammatory mediators, and macrophage function. RESULTS: There was a 61 and 74% decrease in total aortic lesion area in CD36 degrees /apoE degrees males and females, respectively, compared with apoE degrees controls. The absence of SRA was protective (32% decrease in lesion) in female mice. The combined absence of CD36 and SRA provided no further protection in either gender. Macrophages from mice lacking CD36 had decreased pro-inflammatory characteristics and less migration to a pro-inflammatory stimulus. Plasma levels of cytokines/chemokines showed that CD36 degrees /apoE degrees and CD36 degrees /SRA degrees /apoE degrees mice had a less pro-inflammatory phenotype compared with apoE degrees and SRA degrees /apoE degrees mice. Oblivious mice in the apoE degrees background ruled out potential 'passenger gene' effects in the case of CD36. CONCLUSION: These results provide new insights into the pro-atherogenic mechanisms of CD36 by implicating processes other than modified lipoprotein uptake.     

Enzymatically degraded LDL preferentially binds to CD14(high) CD16(+) monocytes and induces foam cell formation mediated only in part by the class B scavenger-receptor CD36

Heterogeneity of peripheral blood monocytes is characterized by specific patterns in the membrane expression of Fc gamma-receptor III (FcgammaRIII/CD16) and the lipopolysaccharide receptor (LPS receptor CD14), allowing discrimination of distinct subpopulations. The aim was to analyze the correlation of these phenotypic differences to the early interaction of freshly isolated monocytes with modified lipoproteins by the use of either enzymatically degraded low density lipoprotein (E-LDL), acetylated low density lipoprotein (ac-LDL), oxidized low density lipoprotein (ox-LDL), or native low density lipoprotein. Highest E-LDL binding was observed on CD14(high) CD16(+) monocytes as determined by flow cytometry, suggesting a selective interaction of E-LDL with distinct subpopulations of monocytes. E-LDL induced rapid foam cell formation both in predifferentiated monocyte-derived macrophages and, in contrast to ac-LDL or ox-LDL, also in freshly isolated peripheral blood monocytes. This was accompanied by upregulation of the 2 class B scavenger receptors CLA-1/SR-BI (CD36 and LIMPII Analogous-1/scavenger receptor type B class I) and CD36. Cellular binding and uptake of E-LDL was neither competed by ac-LDL nor the class A scavenger-receptor inhibitor polyinosinic acid but was partially inhibited by an excess of ox-LDL. In predifferentiated monocyte-derived macrophages, an anti-CD36 antibody inhibited cellular binding and uptake of E-LDL by approximately 20%, suggesting that recognition of these hydrolase-modified low density lipoprotein particles is mediated only in part by the class B scavenger receptor CD36.     

CD36, a novel receptor for oxidized low-density lipoproteins, is highly expressed on lipid-laden macrophages in human atherosclerotic aorta.

CD36 has been reported to be a receptor for oxidized LDL (Ox-LDL). In our previous study, the uptake of Ox-LDL in CD36-deficient macrophages was reduced by approximately 50% compared with that in control macrophages, suggesting an important role of CD36 as a receptor for Ox-LDL in humans. In the current study, we examined the immunohistochemical localization of CD36 in human aorta in comparison with that of scavenger receptor class A type I and type II (SRA). Cryostat sections were made from aortic tissues. For immunohistochemical staining, the following antibodies were used: (1) FA6-152, anti-CD36 antibody, and (2) SRI-2, which recognizes both type I and type II SRAs. Immunohistochemical staining for CD36 and SRA was performed using labeled streptavidin method. In macrophages scattered in aortic walls without atherosclerotic lesions, the expression of CD36 was hardly observed, whereas that of SRA was detected weakly but consistently. In contrast, in atherosclerotic lesions, macrophages around the core region showed a weak immunoreactivity to CD36 and a strong immunoreactivity to SRA. Furthermore, lipid-laden macrophages, which mainly existed in the core region, had a strongly positive immunoreactivity to CD36, but a low or moderate level of immunoreactivity to SRA. The distributions of CD36 and SRA were different from each other, and especially foamed, large-sized macrophages in atherosclerotic plaques tended to more abundantly express CD36 protein. These data demonstrate, for the first time, that the expression of both CD36 and SRA might be differentially regulated in aortic walls, and might play different roles in the formation of foam cells in atherosclerotic lesions.     

TGF-beta reduced binding of high-density lipoproteins in murine macrophages and macrophage-derived foam cells

The expression of macrophage scavenger receptors is regulated by intracellular cholesterol levels, as well as by cytokines affecting macrophage effector functions. CD36, a member of the type B scavenger receptor family, will bind a variety of nonlipoprotein and lipoprotein ligands including high-density lipoprotein (HDL). Transforming growth factor-beta (TGF-beta) has been demonstrated to modulate macrophage effector functions and is present within atherosclerotic lesions. In the present study, the effect of TGF-beta on HDL binding by both macrophages and macrophage-derived foam cells was evaluated. TGF-beta, in a dose-dependent manner, reduced the binding of flurochrome-labeled HDL to both macrophages and foam cells. These effects were observed in macrophages derived from nonatherosclerotic (BALB/c) as well as from macrophages obtained from both apolipoprotein E and low-density lipoprotein receptor knockout mice. The decrease in HDL binding was consistent with a significant reduction in CD36 message levels. The effect of TGF-beta on type B scavenger receptor expression was not limited to CD36 as SR-BI message was also downregulated, although the effect was more modest. A similar reduction in HDL binding and CD36 message was also observed with the immunosuppressive glucocorticoid dexamethasone. These results suggest that within the microenvironment of an atherosclerotic lesion, TGF-beta and other agents that inhibit macrophage inflammatory responses may impact lesion progression through mechanisms that include the modulation of HDL-foam cell interactions.     

Uptake of oxidized low-density lipoprotein in a THP-1 cell line lacking scavenger receptor A

We previously isolated THP-1 subtype cells (sTHP-1), a cell line that expresses scanty amounts of scavenger receptor A (ScR-A) and does not undergo foam cell formation when incubated with acetylated low-density lipoprotein (Ac-LDL). In this study, we investigated the accumulation of esterified cholesterol in sTHP-1 cells incubated with oxidized LDL (Ox-LDL), a physiologically modified lipoprotein in human. While sTHP-1 cells incubated with Ac-LDL accumulated only small amounts of esterified cholesterol, those incubated with Ox-LDL accumulated amounts similar to those accumulated by parent THP-1 (pTHP-1) cells. sTHP-1 cells expressed CD36 in amounts similar to the amounts expressed by pTHP-1 cells, and Ox-LDL was internalized through this CD36. The amount of accumulated esterified cholesterol was 73-81% of that accumulated in pTHP-1 cells expressing ScR-A. The levels of 125I-Ox-LDL binding, association, and degradation in sTHP-1 cells were 64-70% of the corresponding levels in pTHP-1 cells. In our experiments utilizing ScR-A-deficient sTHP-1 cells and a specific antibody against human CD36, most of the Ox-LDL interacted with the CD36 receptor. In addition, a substantial amount of Ox-LDL (28-42%) was bound and degraded by sTHP-1 macrophages when both of the two major scavenger receptors, ScR-A and CD36, were deficient or blocked. These results indicate that CD36 in macrophages plays an important role in foam cell formation by Ox-LDL, while additional scavenger receptor(s) may take part in significant pathways of Ox-LDL uptake in macrophages.     

Regulation of platelet function by class B scavenger receptors in hyperlipidemia

Platelets constitutively express class B scavenger receptors CD36 and SR-BI, 2 closely related pattern recognition receptors best known for their roles in lipoprotein and lipid metabolism. The biological role of scavenger receptors in platelets is poorly understood. However, in vitro and in vivo data suggest that class B scavenger receptors modulate platelet function and contribute significantly to thrombosis by sensing pathological or physiological ligands, inducing prothrombotic signaling, and increasing platelet reactivity. Platelet CD36 recognizes a novel family of endogenous oxidized choline phospholipids that accumulate in plasma of hyperlipidemic mice and in plasma of subjects with low high-density lipoprotein levels. This interaction leads to the activation of specific signaling pathways and promotes platelet activation and thrombosis. Platelet SR-BI, on the other hand, plays a critical role in the induction of platelet hyperreactivity and accelerated thrombosis under conditions associated with increased platelet cholesterol content. Intriguingly, oxidized high-density lipoprotein, an SR-BI ligand, can suppress platelet function. These recent findings demonstrate that platelet class B scavenger receptors play roles in thrombosis in dyslipidemia and may contribute to acute cardiovascular events in vivo in hypercholesterolemia.