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     

CD40系统与动脉粥样硬化研究的新进展

越来越多的研究证实动脉粥样硬化是一种炎症发应,CD40系统的相互作用是炎症信号的重要传导通路,还参与粥样斑块内重要细胞如血管内皮细胞、血管平滑肌细胞及巨噬细胞等的炎症反应调节。阻断CD40CD40配体之间的相互作用可以抑制动脉粥样斑块的发生发展。最进,动脉粥样硬化(Atherosclerosis,AS)发病机制的研究有了很大进展,以前AS仅仅被认为是脂质堆积造成显著管腔狭窄或闭合。现在许多研究都证实AS是一种多种免疫因素参与的慢性炎症性疾病[1]。炎症发应贯穿于AS的发生、发展、变化的全过程,并在很大程度上决定着动脉粥样斑块的稳定性[2…     

CD40信号与动脉粥样硬化

越来越多的证据表明动脉粥样硬化是一种炎症反应。在炎症免疫调节中,CD40与CD40配体的相互作用是炎症信号传递的重要途径,它参与抗原呈递及淋巴细胞和巨噬细胞激活。近年研究发现,CD40－CD40L相互作用不只局限于炎症细胞之间信号传递,还参与动脉粥样硬化斑块内主要细胞成分如血管内皮细胞、血管平滑肌细胞及巨噬细胞等的炎症反应调节。本文将重点介绍CD40信号与动脉粥样硬化发生发展的关系及其可能的干预途径。     

炎症与动脉粥样硬化关系研究进展

近几十年的研究使人们越来越清楚地认识到炎症在动脉粥样硬化的发生、发展过程中起着重要作用。1动脉粥样硬化炎症学说某些脂类如溶血磷脂、氧固醇、血小板活化因子样磷脂等作为信号分子，与细胞的受体结合后可激活基因表达，生成许多促进炎症的细胞因子，如内皮细胞表达许多粘附分子使血流中的单核细胞，T淋巴细胞粘附于受损内皮区表面，单核细胞趋化蛋白-1（MCP-1）使单核细胞迁移入内皮下，T淋巴细胞也有其相应的趋化诱导因子，单核细胞在巨噬细胞集落刺激因子（M—CSF）作用下分化成巨噬细胞，单核／巨噬细胞及T淋巴细胞是主要的炎症细胞，这个阶段是急性炎症阶段。[第一段]     

动脉粥样硬化中单核细胞招募与泡沫细胞形成

动脉粥样硬化是一种慢性炎症疾病,单核细胞和激活的内皮细胞间的相互作用在动脉粥样硬化病变进程中起着关键性的作用.在动脉粥样硬化的早期阶段,单核细胞在黏附分子和细胞因子的作用下进入内膜并分化为巨噬细胞.在受体和胞饮介导下,分化而来的巨噬细胞对内膜下的脂质进行摄取,脂质负荷的巨噬细胞转化为泡沫细胞,大量泡沫细胞的蓄积将形成动脉粥样硬化的脂质核心.     

动脉粥样硬化的发生与细胞间粘附分子

动脉粥样硬化的发生与单核细胞和血管内皮细胞的粘附密切相关。单核细胞产生自由基等，使低密度脂蛋白氧化，导致动脉粥样硬化，细胞间粘附分子与配体在单核细胞与血管内皮细胞的粘附中起重要作用。ＩＬ－１、ＴＮＦ等细胞因子可能是通过细胞间粘附分子来促使动脉粥样硬化的发生和发展。核因子ｋＢ在转录水平调节细胞站粘附分子的表达、也在动脉粥样硬化的发生发展中起调节作用。     

CXC趋化因子配体16及其受体与动脉粥样硬化的关系

CXC趋化因子配体16(CXCL16)是一种具有黏附分子、趋化因子、清道夫受体功能的趋化因子家族中的一员,可促进活化的T淋巴细胞与内皮细胞间的黏附,平滑肌细胞的增殖及抗原递呈细胞在炎症部位的聚集,增加巨噬细胞对氧化型低密度脂蛋白的摄取,促进泡沫细胞形成,并参与到动脉粥样硬化、血管狭窄、炎症反应的发生发展中。CXCL16及其受体与动脉粥样硬化、冠心病、脑卒中等血液循环系统疾病的发生、严重程度及预后相关,并在临床疾病发生预测中有一定作用。     

过氧化物酶体增殖物激活受体参与动脉粥样硬化炎症反应机制的研究进展

过氧化物酶体增殖物激活受体是配体激活的转录因子,属于核激素受体超家族成员。它调控靶基因的转录,参与体内的许多生理病理过程。过氧化物酶体增殖物激活受体可在多种免疫活性细胞、内皮细胞、血管平滑肌细胞和肾系膜细胞等中表达,可通过改善胰岛素抵抗和改善糖、脂代谢紊乱,发挥抗动脉粥样作用;还可通过对巨噬细胞、平滑肌细胞及血管内皮功能的影响,阻止动脉粥样硬化的形成。本文结合近年来过氧化物酶体增殖物激活受体在抗炎作用方面的研究,探讨其在动脉粥样硬化过程中的抗炎症方面的作用机制。     

可溶性CD40L(sCD40L)可作为预测急性冠脉综合症危险性的一项新指标

CD40L是肿瘤坏死因子超基因家族的一种,它是各种免疫与炎症调节的重要通路,包括调节动脉粥样硬化的演变.已有研究证实在动脉粥样硬化斑块内、血管内皮细胞、血管平滑肌细胞、巨噬细胞,循环中的血小板中可出现CD40L的表达.循环中出现的可溶性CD40L可能主要来源于血小板及T淋巴细胞.CD40L在急性冠脉综合征的作用与其产生的生物学效应有关.有研究发现CD40L可刺激血管内皮细胞、巨噬细胞及血管平滑肌细胞产生与动脉粥样硬化有关的生物活性因子,如E选择素、血管粘附分子、细胞因子等.CD40L还可通过调节粥样斑块的金属蛋白酶表达影响斑块的稳定性.越来越多的研究显示炎症与免疫在动脉粥样硬化的发生、发展中起着重要的作用,并且提示动脉粥样硬化可能是一种慢性炎症性疾病,炎症反应的激活可导致斑块的不稳定,从而引起急性冠脉综合征的发生.     

CD40-CD40L与动脉粥样硬化的研究进展

近年大量研究显示[1]炎症介质CD40-CD40L广泛存在于与动脉粥样硬化(AS)相关的各种细胞,如内皮细胞、巨噬细胞和平滑肌细胞等关键细胞成分上,而在正常动脉组织中没有表达.CD40-CD40L系统在AS各个阶段中均起重要作用,几乎贯穿了AS斑块发生、发展和破裂的全过程,被认为是这一炎症进程的关键环节.研究表明,CD40L与CD40相互作用不仅在体液免疫中起作用,而且在细胞免疫中也发挥重要作用[1].CD40-CD40L信号通路可参与AS斑块内主要细胞成分如血管内皮细胞、血管平滑肌细胞和巨噬细胞等炎症反应的调节[2].目前认为,CD40-CD40L可能是AS发病的始动因素.     

神经导向因子Netrin-1调节单核巨噬细胞迁移与动脉粥样斑块关系的研究进展

动脉粥样硬化是动脉壁的一种慢性炎症性疾病,单核巨噬细胞在其发生发展中起着关键作用。动脉粥样斑块中单核巨噬细胞迁移能力受损,滞留于斑块内,增加了斑块不稳定性,加速动脉粥样硬化病变的进展。目前研究表明动脉粥样斑块中巨噬细胞分泌的神经导向因子Netrin-1通过与巨噬细胞表面相应受体结合,可以抑制巨噬细胞迁出斑块,促进动脉粥样硬化的进展。但在动脉粥样硬化形成初期,血管内皮细胞表达的Netrin-1却被发现对动脉粥样硬化起到保护作用。     

The expression of macrophage migration inhibitory factor 1alpha (MIF 1alpha) in human atherosclerotic plaques is induced by different proatherogenic stimuli and associated with plaque instability

OBJECTIVES: Macrophage migration inhibitory factor 1alpha (MIF), a cytokine with immunoregulatory functions has been suggested to be involved in atherosclerotic plaque development. However, little is known about MIF-inducing conditions in the atherosclerotic process and the association of MIF with plaque instability. METHODS AND RESULTS: Forty-two carotid endatherectomy samples from 36 patients and 4 aortic samples from young accident victims (as healthy controls) were analyzed for MIF staining. MIF expressing tissues in the atherosclerotic plaques are mainly mononuclear cells (MNCs), but also endothelial cells of intimal microvessels (MVECs). The magnitude and the intensity of their MIF expression was associated with the progression of plaques from early lesions (Stary I-III) to complicated plaque stages (Stary IV-VIII). In highly inflammatory and neovascularized regions of the plaques the colocalization of MIF expressing MNCs with CD40-L+ and angiotensin II (Ang II)-producing MNCs could be established. This finding supports the notion that CD40-L fusion protein and Ang II are able to induce MIF production in the monocytic cell line THP-1. Furthermore hypoxia (< or =1% O2) as a further proinflammatory and especially proangiogenetic factor was able to stimulate MIF secretion by THP-1, human monocytes and HUVECs. Hyperglycemia and insulin remained without effect. CONCLUSION: MIF is expressed in advanced atherosclerotic lesions in close correlation with signs of instability, such as mononuclear cell inflammation and neointimal microvessel formation. Furthermore, the colocalization of MIF with Ang II-producing MNCs and CD40-L+ cells in these plaques and the finding that proathero- and -angiogenic mediators such as CD40-L, Ang II and hypoxia are able to stimulate MIF expression in vitro suggest an important role of MIF in the modulation of atherosclerotic plaque stability.     

Low molecular weight hyaluronan increases the Uptaking of oxidized LDL into monocytes

Since accumulation and interaction of immune cells including T cells and monocytes/macrophages are involved in the processes of atherosclerosis, atherosclerosis is currently understood as an inflammatory disorder. Entrapment of extracellular matrices components such as hyaluronan by monocytes and macrophages, as well as uptake of oxidized low-density lipoprotein (ox-LDL) by these cells, plays a central role in foam cell formation and the pathogenesis of atherosclerosis. We investigated the role of CD44, the principal receptor for hyaluronic acid, and ox-LDL in scavenger receptor expression on resting monocytes prepared by counterflow centrifugal elutriation from the endothelium. Our results showed that the low-molecular weight (6.9 kDa) form of hyaluronan increased the expression of CD36 scavenger receptor; the incorporation of (125) I-labeled ox-LDL, and the transendothelial migration of monocytes, which were mediated at least in part via tyrosine kinase and the PKC pathway. Our results imply that low molecular weight hyaluronan produced in large amounts in atherosclerotic lesions induces differentiation of circulating monocytes to macrophages/foam cells and enhances the progression of atherosclerosis via the PKC pathway. Furthermore, low molecular weight hyaluronan also amplifies the migration of monocytes into inflamed atherosclerotic plaques. Thus, we propose that engagement of CD44 with low molecular weight hyaluronan is centrally involved in the inflammatory pathogenesis of athelosclerotic plaques through migration of monocytes and foamed macrophage differentiation.     

Proteolysis of the pericellular matrix: a novel element determining cell survival and death in the pathogenesis of plaque erosion and rupture

The 2 major general concepts about the cell biology of atherogenesis, growth of smooth muscle cells, and lipid accumulation in macrophages, ie, foam cell formation, have not been able to satisfactorily explain the genesis of acute coronary syndromes. Rather, the basic pathology behind the acute atherothrombotic events relates to erosion and rupture of unstable coronary plaques. At the cellular level, we now understand that a switch from cellular growth to cellular death, notably apoptosis, could be involved in turning at least some types of atherosclerotic plaques unstable. Because intimal cells require a proper matrix environment for normal function and survival, the vulnerability of an atherosclerotic plaque may critically depend on the integrity of the pericellular matrix of the plaque cells. In vitro studies have revealed that plaque-infiltrating inflammatory cells, such as macrophages, T-lymphocytes, and mast cells, by secreting a variety of proteases capable of degrading pericellular matrix components, induce death of endothelial cells and smooth muscle cells, and so provide a mechanistic explanation for inflammation-dependent plaque erosion and rupture. Thus, a novel link between inflammation and acute coronary syndromes is emerging. For a more explicit understanding of the role of proteases released by inflammatory cells in the conversion of a clinically silent plaque into a dangerous and potentially killing plaque, animal models of plaque erosion and rupture need to be established.     

Intertwining of thrombosis and inflammation in atherosclerosis

PURPOSE OF REVIEW: The aim of this article is to highlight the importance of thrombotic processes in the development and complications of atherosclerotic vascular disease. RECENT FINDINGS: Thrombin generated at sites of vascular inflammation activates major atheroma-associated cells including endothelial cells, platelets, smooth muscle cells, monocytes, and macrophages. Thrombin-activated cells produce a plethora of inflammatory mediators, such as regulated upon activation normal T cell expressed presumed secreted, macrophage migration inhibitory factor, and CD40 ligand, that promote atherosclerotic lesion formation and atherothrombotic complications of vascular disease. Additionally, thrombin-induced inflammatory mediators stimulate tissue factor procoagulant activity within atheroma to initiate a positive feedback loop where thrombin activation launches inflammatory signals that lead to further thrombin activation. Platelets, the main cellular effectors of the thrombotic system, also play a central role in the biology of atherosclerosis by producing inflammatory mediators and directing leukocyte incorporation into plaques through platelet-mediated leukocyte adhesion. SUMMARY: New research has identified signaling pathways that intertwine thrombotic and inflammatory pathways with the development and progression of atherosclerosis. These signaling pathways contain positive feedback loops that propagate atherogenesis. Targeting molecular regulators at the interface of thrombosis and inflammation simultaneously may reduce thrombosis and inflammation, thus breaking pathological cycles that promote atherosclerosis and associated thrombotic complications.     

Molecular and cellular mechanisms of macrophage survival in atherosclerosis

Macrophages play a key role in the initiation and progression of atherosclerotic plaques. Although a significant number of macrophages undergoes cell death during plaque development as a result of atherogenic stressors, advanced plaques are characterized by a large macrophage content. Macrophage accumulation is mediated by continuous recruitment of monocytes, reduced emigration of macrophages and poor phagocytosis of dead cells which may trigger secondary necrosis and amplification of plaque inflammation. Moreover, an increasing body of evidence indicates that macrophages have developed several strategies to survive and to proliferate in the adverse environment of an advanced atherosclerotic plaque. Macrophages contain organic molecules or enzymes that provide enhanced antioxidant protection. In addition, synthesis of anti-apoptotic proteins is upregulated and several cellular protection mechanisms such as the unfolded protein response and autophagy are activated in macrophages to promote cellular survival. In this review, we discuss these macrophage survival mechanisms that allow growth and destabilization of advanced atherosclerotic plaques.     

Apoptosis in atherosclerosis: beneficial or detrimental?

Several groups have demonstrated apoptotic cell death in atherosclerotic plaques. The significance of apoptosis in atherosclerosis depends on the stage of the plaque, localization and the cell types involved. Both macrophages and smooth muscle cells undergo apoptosis in atherosclerotic plaques. Apoptosis of macrophages is mainly present in regions showing signs of DNA synthesis/repair. Smooth muscle cell apoptosis is mainly present in less cellular regions and is not associated with DNA synthesis/repair. Even in early stages of atherosclerosis smooth muscle cells become susceptible to undergoing apoptosis since they increase different pro-apoptotic factors. Moreover, recent data indicate that smooth muscle cells may be killed by activated macrophages. The loss of the smooth muscle cells can be detrimental for plaque stability since most of the interstitial collagen fibers, which are important for the tensile strength of the fibrous cap, are produced by SMC. Apoptosis of macrophages could be beneficial for plaque stability if apoptotic bodies are removed. Apoptotic cells that are not scavenged in the plaque activate thrombin which could further induce intraplaque thrombosis. It can be concluded that apoptosis in the primary atherosclerosis is detrimental since it could lead to plaque rupture and thrombosis. Recent data of our group indicate that apoptosis decreases after lipid lowering which could be important in our understanding of the cell biology of plaque stabilization.     

EGF mediates monocyte chemotaxis and macrophage proliferation and EGF receptor is expressed in atherosclerotic plaques

The recruitment of peripheral monocytes to the sub-endothelial space, their development into macrophages and subsequent proliferation are critical events during atherosclerosis. Receptors for epidermal growth factor (EGF) have been identified on cells of the myeloid lineage, but a role for them in atherogenesis has yet to be described. We have identified functional EGF receptors (EGFR, ErbB1/HER-1) on peripheral blood monocytes and monocyte-derived macrophages. Uniquely, these receptors were found to mediate both chemotaxis in monocytes and macrophages and proliferation in macrophages. EGFR mRNA was detected in atherosclerotic plaques, but not in morphologically normal aortae and EGFR receptor staining co-localised with macrophage staining in these plaques. The identification of receptors for EGF on peripheral blood monocytes, macrophages and atherosclerotic lesions, together with their transduction of two functionally important cellular events, heightens the potential importance of members of the EGF super-family in atherogenesis and other chronic inflammatory processes.     

Autophagy in atherosclerosis

Autophagy is a catabolic pathway for bulk destruction of long-lived proteins and organelles via lysosomes. Basal autophagy represents a reparative, life-sustaining process, but unrestrained autophagic activity promotes cell death. A growing body of evidence suggests that autophagy occurs in advanced atherosclerotic plaques. Vascular smooth muscle cells, macrophages, or endothelial cells treated in vitro with proatherogenic stimuli reveal certain features typical of autophagy, such as LC3 processing, formation of myelin figures, and extensive vacuolization. However, despite the increasing interest in autophagy, its role in atherosclerosis remains poorly understood. Most likely, autophagy safeguards plaque cells against cellular distress, in particular oxidative injury, by degrading the damaged intracellular material. In this way, autophagy is antiapoptotic and contributes to cellular recovery in an adverse environment. Because atherosclerosis is an inflammatory disorder of the arterial intima, pharmacologic approaches have recently been developed to stabilize vulnerable, rupture-prone lesions through selective induction of macrophage autophagic death.