葡萄糖对巨噬细胞不同脂蛋白受体表达的影响

目的研究不同浓度葡萄糖对巨噬细胞高密度脂蛋白受体(SR-BI)及凝集素样氧化型低密度脂蛋白受体(LOX-1)表达的影响。方法2003年5月至2005年1月在中国医科大学附属第一医院将5.6mmol/L、11.1mmol/L、16.7mmol/L和33.3mmol/L葡萄糖与诱导分化48h后的U937细胞共同孵育24h及16.7mmol/L葡萄糖与诱导分化48h后的U937细胞作用0,12,24,48,72h后,用Western印迹法检测SR-BI及LOX-1蛋白的表达。结果葡萄糖对巨噬细胞SR-BI蛋白表达量无显著影响(P>0.05)。葡萄糖浓度升高及作用时间延长可使LOX-1蛋白表达增加。结论葡萄糖诱导LOX-1蛋白表达增加并呈浓度和时间依赖性。     

氧化型低密度脂蛋白诱导U937细胞LOX-1的表达及卡托普利的干预

目的:探讨应用氧化型低密度脂蛋白(Ox-LDL)培养的单核巨噬系细胞株U937细胞表面氧化型低密度脂蛋白受体-1(LOX-1)表达的情况,并进一步探讨卡托普利对其表达的影响。方法:应用酶联免疫吸附法(ELISA)和蛋白免疫印迹法(Western blot)检测细胞表面LOX-1的表达。结果:细胞在Ox-LDL培养后LOX-1的表达明显增加(P<0.05),并且随着作用时间的延长和浓度的增加,其表达呈先递增后递减变化,在浓度为100μg/ml,时间为24h时达高峰(0.965±0.413),应用LOX-1阻断剂PIA、角叉菜胶和卡托普利干预后其表达明显减少(P<0.05),结果分别为(0.083±0.024),(0.075±0.019),(0.084±0.025)。结论:Ox-LDL可诱导U937细胞表面LOX-1蛋白质的表达,卡托普利可通过抑制LOX-1的表达,从而抑制Ox-LDL对U937细胞的损伤,起到抗动脉粥样硬化的作用。     

ox-LDL促进树突状细胞LOX-1表达及炎症因子分泌

目的应用小鼠高脂模型及树突状细胞株研究血凝素样氧化型低密度脂蛋白受体1(LOX-1)高表达树突状细胞(DC)在动脉粥样硬化中的作用。方法氧化型低密度脂蛋白(ox-LDL)诱导原代培养的C57小鼠骨髓来源的树突状细胞(BMDC),采用Western blot检测BMDC LOX-1蛋白水平;采用流式细胞术检测高表达LOX-1和低表达LOX-1细胞亚群的比例;MACS磁珠分选LOX-1表达水平不同的两种细胞亚群,观察ox-LDL对两种细胞亚群的影响及释放炎症因子的影响;采用C57小鼠高脂模型,在高脂喂养的不同时间(4周、6周、8周)检测小鼠总胆固醇水平和主动脉中DC数量;用不同浓度的Dil标记的ox-LDL(Dil-ox-LDL)刺激DC2.4细胞,荧光显微镜观察各组细胞吞噬作用的差异,Western blot检测LOX-1的表达。结果 DC可分为高表达和低表达LOX-1两种细胞亚群,且ox-LDL能增加LOX-1~(high)DC的比例;分选后的阳性细胞被ox-LDL刺激后,TNF-α和IL-1βmRNA的表达明显上调(P0.01),且阳性细胞的上升比例高于阴性细胞。在C57小鼠高脂模型中,高脂喂养组总胆固醇水平明显升高,且随着总胆固醇水平的升高,小鼠主动脉中DC增多,且LOX-1~(high)DC比例明显增加。用不同浓度的Dil-ox-LDL刺激DC2.4细胞,随着Dil-ox-LDL浓度的升高,DC2.4细胞对ox-LDL的吞噬也增加,并且ox-LDL可以诱导DC2.4细胞表面LOX-1表达,20 mg/L和40 mg/L的ox-LDL对LOX-1表达的诱导作用明显。结论 ox-LDL能够上调DC表面受体LOX-1,增加LOX-1~(high)DC比例,促进炎症因子表达。     

凝集素样氧化型低密度脂蛋白受体-1与动脉粥样硬化关系的研究进展

凝集素样氧化型低密度脂蛋白受体-1（lectin-like oxidized low-density lipoprotein receptor-1,LOX-1）是内皮细胞上氧化型低密度脂蛋白特异性受体,可介导内皮细胞活化、损伤和凋亡,平滑肌细胞和巨噬细胞内脂质聚集,活化血小板促进血栓形成,并增加斑块不稳定性,促进动脉粥样硬化（atherosclerosis,AS）的发生发展。而抑制LOX-1表达可减弱AS病变,提示LOX-1可能成为防治AS的分子靶点。本文就LOX-1与AS的关系作一综述。     

血凝素样氧化低密度脂蛋白受体-1

血凝素样氧化低密度脂蛋白受体-1（LOX-1）是内皮细胞摄取氧化低密度脂蛋白（ox-LDL）的特异性受体。高脂血症、氧化应激等多种因素可以促进LOX-1的表达。LOX-1表达通过诱导各种黏附分子和炎症因子的表达、激活蛋白激酶、诱导细胞凋亡等途径促进平滑肌细胞和巨噬细胞吞噬脂质,并转化为泡沫细胞,促进动脉粥样硬化斑块的形成。     

血凝素样氧化低密度脂蛋白受体-1

血凝素样氧化低密度脂蛋白受体-1(LOX-1)是内皮细胞摄取氧化低密度脂蛋白(ox-LDL)的特异性受体.高脂血症、氧化应激等多种因素可以促进LOX-1的表达.LOX-1表达通过诱导各种黏附分子和炎症因子的表达、激活蛋白激酶、诱导细胞凋亡等途径促进平滑肌细胞和巨噬细胞吞噬脂质,并转化为泡沫细胞,促进动脉粥样硬化斑块的形成.     

糖基化终产物对凝集素样氧化型低密度脂蛋白受体1表达的影响

目的 研究长期高血糖所致糖基化终产物对巨噬细胞凝集素样氧化型低密度脂蛋白受体1表达的影响.方法 U937细胞经佛波酯诱导分化,并将不同浓度或同一浓度糖基化终产物与诱导分化48 h后的U937细胞共同孵育,用Western Blotting法检测凝集素样氧化型低密度脂蛋白受体1蛋白的表达.同时应用ELISA法测定24例2型糖尿病患者及22例正常对照者血清可溶性氧化型低密度脂蛋白受体1的含量.结果 100、200和400 mg/L 糖基化终产物刺激后细胞表面凝集素样氧化型低密度脂蛋白受体1蛋白表达量分别是对照组的1.85、3.22和4.65倍(P<0.05);400 mg/L的糖基化终产物作用12、24、48 h后,U937巨噬细胞该受体蛋白表达量分别为0 h的2.85、3.89和4.3倍(P<0.05).糖尿病患者血清氧化型低密度脂蛋白受体1及糖基化终产物含量较正常对照者显著升高(P<0.01),两者呈正相关(P<0.001). 结论糖基化终产物可增加U937巨噬细胞凝集素样氧化型低密度脂蛋白受体1蛋白表达且呈浓度和时间依赖性.这可能与糖尿病患者加速泡沫细胞形成而易致动脉粥样硬化有关.     

凝集素样氧化低密度脂蛋白受体-1介导氧化低密度脂蛋白促进血管平滑肌细胞血管紧张素转化酶的表达

目的:观察氧化低密度脂蛋白(ox-LDL)对血管平滑肌细胞(VSMC)血管紧张素转化酶(ACE)表达的影响及凝集素样氧化低密度脂蛋白受体-1(LOX-1)在其中的作用。方法:人脐带动脉平滑肌细胞体外原代培养,传至4~5代用于实验。ox-LDL干预,RT-PCR测定VSMC ACE mRNA和LOX-1mRNA表达。并观察予以LOX-1的抑制剂多聚肌苷酸作用后,VSMC ACE mRNA表达的变化。结果:①较高浓度ox-LDL(20mg/L,100mg/L)作用后,VSMC ACE mRNA表达升高,作用1h出现峰值。低浓度ox-LDL(10mg/L)此种作用不明显。②ox-LDL作用后,VSMCLOX-1 mRNA表达升高,且随着ox-LDL浓度的升高而表达增强。③多聚肌苷酸抑制LOX-1后,ACE mRNA表达明显下降。结论:ox-LDL明显促进VSMC ACE表达,LOX-1在此过程中起重要介导作用。     

LOX-1在ox-LDL诱导血管平滑肌细胞表达Fractalkine中的作用及罗布麻的干预

目的:研究血凝素样氧化低密度脂蛋白受体-1(LOX-1)在氧化型低密度脂蛋白(ox-LDL)诱导血管平滑肌细胞(VSMC)表达不规则趋化因子(FKN)中的角色及罗布麻的干预作用.方法:用组织贴块培养法培养大鼠VSMC,应用ELISA法检测LOX-1蛋白表达、RT-PCR法检测FKN mRNA的表达.结果:ox-LDL可诱导大鼠VSMS高表达FKN,分别应用LOX-1的阻断剂角叉菜胶和罗布麻后,FKN的表达均明显下降(P<0.05).结论:在VSMC的炎症反应中,ox-LDL通过LOX-1途径激活了FKN的表达,高浓度罗布麻(0.8 g/L)可抑制FKN的表达,推测罗布麻可能起到抗炎、抗动脉粥样硬化的作用.     

ox-LDL经由LOX-1受体对PPARγ-LXRα-ABCA1通路激活的作用研究

目的探讨氧化型低密度脂蛋白(ox-LDL)经由血凝素样氧化型低密度脂蛋白受体1(LOX-1)受体对PPARγ-LXRα-ABCA1通路激活的作用。方法浓度梯度ox-LDL(0~40 mg/L,12 h)刺激J774A.1巨噬细胞,检测LXRα、ABCA1的表达。构建293T细胞LOX-1过表达的PPARγ双荧光素酶报告基因系统,激光共聚焦及Western blot检测LOX-1的分布与表达,双荧光素酶报告基因系统检测PPARγ的转录活化情况。对J774A.1巨噬细胞分别进行LOX-1 siRNA和PPARγsiRNA沉默,ox-LDL(30 mg/L,12 h)孵育后检测LXRα、ABCA1蛋白的表达。结果ox-LDL可显著上调J774A.1细胞LXRα和ABCA1的表达(P0.01,n=3)。LOX-1过表达的PPARγ双荧光素酶报告基因系统检测显示ox-LDL能够通过LOX-1增加PPARγ的转录活性;对J774A.1巨噬细胞分别进行LOX-1siRNA、PPARγsiRNA沉默后发现,LXRα和ABCA1的表达均显著降低(P0.01,n=3)。结论 ox-LDL可通过LOX-1受体激活PPARγ转录活性,从而上调LXRα、ABCA1蛋白表达,完成PPARγ-LXRα-ABCA1信号通路的激活。     

RNA干扰人血凝素样氧化型低密度脂蛋白受体表达对内皮细胞骨架损伤的影响

目的构建针对人血凝素样氧化型低密度脂蛋白受体1(LOX-1)基因的RNA干扰慢病毒载体,并转染人脐静脉内皮细胞后,采取氧化型低密度脂蛋白(ox-LDL)诱导观察对内皮细胞骨架损伤的影响。方法体外培养人脐静脉内皮细胞分为对照组、ox-LDL组(ox-LDL处理)、阴性转染组(ox-LDL处理+阴性慢病毒转染)和慢病毒转染组(ox-LDL处理+最佳干扰序列慢病毒转染)。荧光显微镜观察转染效率,Western blot检测磷酸化肌球蛋白轻链(p-MLC)、Rho激酶(ROCK)、LOX-1蛋白的表达;免疫荧光法观察细胞骨架肌动蛋白(F-actin)的变化。结果与对照组比较,ox-LDL组和阴性转染组p-MLC、ROCK、LOX-1蛋白表达增高;细胞F-actin发生损伤并伴含量减少(P<0.05)。与阴性转染组比较,慢病毒转染组抑制p-MLC、ROCK、LOX-1蛋白表达,减轻F-actin损伤及伴含量增加(P<0.05)。结论干扰LOX-1表达对ox-LDL诱导引起的内皮细胞ROCK、p-MLC表达增加及细胞骨架损伤均有抑制作用。     

Thrombin- and factor Xa-induced DNA synthesis is mediated by transactivation of fibroblast growth factor receptor-1 in human vascular smooth muscle cells

Thrombin and factor Xa (FXa) are agonists for G protein-coupled receptors (GPRCs) and may contribute to vascular lesion formation by stimulating proliferation of vascular smooth muscle cells (SMCs). Mitogenic signaling of GPCRs requires transactivation of receptor tyrosine kinases (RTKs). In rat SMCs, thrombin transactivates the epidermal growth factor receptor (EGFR) via a pathway that involves heparin-binding EGF-like growth factor (HB-EGF) as ligand for EGFR. The purpose of this study was to investigate in human SMCs the role of receptor transactivation in the mitogenic response to thrombin and FXa. Thrombin (10 nmol/L) and FXa (100 nmol/L) cause a 3.3- and 2.6-fold increase in DNA synthesis, respectively. In human SMCs, neither thrombin nor FXa causes EGFR phosphorylation, and blockade of EGFR kinase does not inhibit DNA synthesis. However, DNA synthesis and phosphorylation of fibroblast growth factor receptor-1 (FGFR-1) induced by thrombin or FXa are inhibited by antibodies neutralizing basic fibroblast growth factor (bFGF) or by heparin. Hirudin inhibits thrombin-, but not FXa-induced mitogenesis, indicating that FXa acts independently of thrombin. We further demonstrate by ELISA that upon thrombin and FXa stimulation, bFGF is released and binds to the extracellular matrix. Our data suggest that in human vascular SMCs, both thrombin and FXa rapidly release bFGF into the pericellular matrix. This is followed by transactivation of the FGFR-1 and increased proliferation. Heparin may inhibit the mitogenic effects of thrombin and FXa in human SMCs by preventing bFGF binding to FGFR-1.     

Inhibition of thromboxane A2 synthesis in human platelets by coagulation factor Xa.

Factor Xa binds to platelets provided that factor Va is present on the platelet surface, an interaction that results in a striking acceleration of the conversion of prothrombin to thrombin. Thrombin then initiates fibrin formation, induces platelet aggregation, and stimulates the intraplatelet synthesis of thromboxane A2 (TXA2). Addition of thrombin (2.4-14.4 nM) to platelet-rich plasma increased the basal level of TXA2, measured as thromboxane B2, from less than 0.5 pmol per 10(8) platelets to (mean +/- SEM) 100 +/- 22 and 250 +/- 10 pmol per 10(8) platelets, respectively. Treatment of platelet-rich plasma with increasing concentrations of factor Xa (1-12 nM) prior to the addition of thrombin progressively inhibited the production of TXA2. Thrombin (9.6 nM), which produced 93% of the maximal formation of TXA2, was inhibited 70% by factor Xa (10 nM). To identify which of these steps in thromboxane synthesis was inhibited by factor Xa, platelets labeled with [14C]arachidonic acid were exposed to thrombin and products of prostaglandin synthesis were separated by thin-layer chromatography. In contrast to the inhibition of TXA2 synthesis, prostaglandin E2 and prostaglandin F2 alpha synthesis were not inhibited suggesting that neither phospholipase(s) nor cycloxygenase was involved. The inhibition of TXA2 formation by factor Xa could be reversed by increasing the molar ratio of thrombin to factor Xa to 5.5. Incubation of platelets with an IgG fraction of a human monoclonal antifactor V antibody, previously shown to inhibit factor Xa binding, was found to block factor Xa inhibition of TXA2 synthesis. The inhibition of TXA2 synthesis requires the presence of the active site serine of factor Xa and is not specific for TXA2 formation induced by thrombin because it is also demonstrable when the agonist is ADP. Further, factor Xa does not require additional plasma components for its action because its inhibitory effects are detected in gel-filtered platelets. The effect of factor Xa was evident at physiological (1.3 mM) calcium concentrations. These results indicate that factor Xa binding to platelets through factor Va not only stimulates thrombin formation but also has a countervailing effect by inhibiting TXA2 formation.     

Role of thrombin in angiogenesis and tumor progression

Clinical, laboratory, histopathological, and pharmacological evidence support the notion that the coagulation system, which is activated in most cancer patients, plays an important role in tumor biology. Our laboratory has provided evidence that thrombin activates angiogenesis, a process which is essential in tumor growth and metastasis. This event is independent of fibrin formation. At the cellular level many actions of thrombin can contribute to activation of angiogenesis: (1). Thrombin decreases the ability of endothelial cells to attach to basement membrane proteins. (2). Thrombin greatly potentiates vascular endothelial growth factor- (VEGF-) induced endothelial cell proliferation. This potentiation is accompanied by up-regulation of the expression of VEGF receptors (kinase insert domain-containing receptor [KDR] and fms-like tyrosine kinase [Flt-1]). (3). Thrombin increases the mRNA and protein levels of alpha (v)beta (3) integrin and serves as a ligand to this receptor. Furthermore, thrombin increases the secretion of VEGF and enhances the expression and protein synthesis of matrix metalloprotease-9 and alpha (v)beta (3) integrin in human prostate cancer PC-3 cells. These results could explain the angiogenic and tumor-promoting effect of thrombin and provide the basis for development of thrombin receptor mimetics or antagonists for therapeutic application.     

Thrombin stimulates cell proliferation in human fibroblast-like synoviocytes in nuclear factor-kappaB activation and protein kinase C mediated pathway

OBJECTIVE: To examine the effect of thrombin on nuclear factor (NF)-kappaB activation and cell proliferation in synovial cells from patients with rheumatoid arthritis (RA). METHODS: Using cultured human synovial cells from patients with RA, electrophoretic mobility shift assay, [3H]thymidine incorporation assay, and MTT assay were performed. We tested the upregulatory effects of thrombin on NF-kappaB activation and cell proliferation. The effect of thrombin on degradation of IkappaB was analyzed by Western blot. RESULTS: Thrombin transiently induced DNA-binding activity of NF-kappaB, followed by degradation of IkappaBalpha, but not IkappaBbeta1. Moreover, synovial cell proliferation was stimulated by thrombin in a dose dependent manner. The kinetics of synovial cell proliferation induced by thrombin were almost parallel to those of NF-kappaB activation. Supershift analysis revealed that thrombin induced DNA-binding complexes were made up principally of the p65 and p50 Rel family members. Further, protein kinase C inhibitor calphostin C repressed thrombin induced NF-kappaB activation and cell proliferation in synovial cells. CONCLUSION: Thrombin stimulates synovial cell proliferation involved in NF-kappaB activation, at least in part, through a protein kinase C mediated pathway, possibly indicating that thrombin plays an important role in synovial hyperplasia in RA.     

异常血流动力对TLR4/NF-κB信号传导通路及其下游炎症因子的影响

目的研究异常血流应力或压力单独作用对人脐静脉内皮细胞(Human umbilical vein endothelial cells,HUVECs)Toll样受体4(Toll-like receptor 4,TLR4)/NF-κB信号传导通路及下游炎症因子:血凝素样氧化低密度脂蛋白受体-1(lectin-like oxidized low-density lipoprotein receptor-1,LOX-1)、肿瘤坏死因子-α(TNF-α)、细胞间粘附分子-1(ICAM-1)及血管细胞粘附分子-1(VCAM-1)等的影响,探讨异常血流动力导致动脉粥样硬化的机制。方法将生长良好的HUVECs以1×105个/ml密度接种于细胞综合应力刺激实验系统(型号BIO-CCS13)中进行干预。将HUVECs按所受的应力不同分成应力组、压力组和正常组。在各组应力作用下培养一天后收集细胞备用,用q PCR方法测定TLR4、髓样分化因子88(myeloid differentiation factor 88,My D88)、肿瘤坏死因子受体相关因子-6(tumor necrosis factor receptor-associated factor-6,TRAF-6)、血凝素样氧化低密度酯蛋白受体-1(LOX-1)、核因子-κB(NF-κB)、TNF-α、ICAM-1及VCAM-1因子的基因表达,用蛋白质印迹方法测定TLR4、NF-κB、LOX-1、TNF-α、ICAM-1及VCAM-1因子的蛋白表达。结果与正常组比较,应力组和压力组TLR4、My D88、TRAF-6、LOX-1、NF-κB、TNF-α、ICAM-1及VCAM-1m RNA表达水平显著升高(P0.01),TLR4、LOX-1、NF-κB、TNF-α、ICAM-1及VCAM-1蛋白表达显著升高,差异有统计学意义(P0.01)。结论异常血流动力导致动脉粥样硬化的机制可能与激活TLR4/NF-κB信号传导通路和增强下游炎症因子:LOX-1、TNF-α、ICAM-1及VCAM-1等的表达有关。     

Glucose enhances human macrophage LOX-1 expression: role for LOX-1 in glucose-induced macrophage foam cell formation

Lectin-like oxidized LDL receptor-1 (LOX-1) is a newly identified receptor for oxidized LDL that is expressed by vascular cells. LOX-1 is upregulated in aortas of diabetic rats and thus may contribute to the pathogenesis of human diabetic atherosclerosis. In this study, we examined the regulation of human monocyte-derived macrophage (MDM) LOX-1 expression by high glucose and the role of LOX-1 in glucose-induced foam cell formation. Incubation of human MDMs with glucose (5.6 to 30 mmol/L) enhanced, in a dose- and time-dependent manner, LOX-1 gene and protein expression. Induction of LOX-1 gene expression by high glucose was abolished by antioxidants, protein kinase C (PKC), mitogen-activated protein kinases (MAPKs), nuclear factor-kappaB (NF-kappaB), and activated protein-1 (AP-1) inhibitors. In human MDMs cultured with high glucose, increased expression of PKCbeta2 and enhanced phosphorylation of extracellular signal-regulated protein kinase 1/2 was observed. Activation of these kinases was inhibited by the antioxidant N-acetyl-L-cysteine (NAC) and by the PKCbeta inhibitor LY379196. High glucose also enhanced the binding of nuclear proteins extracted from human MDMs to the NF-kappaB and AP-1 regulatory elements of the LOX-1 gene promoter. This effect was abrogated by NAC and PKC/MAPK inhibitors. Finally, high glucose induced human macrophage-derived foam cell formation through a LOX-1-dependent pathway. Overall, these results demonstrate that high glucose concentrations enhance LOX-1 expression in human MDMs and that this effect is associated with foam cell formation. Pilot data showing that MDMs of patients with type 2 diabetes overexpress LOX-1 support the relevance of this work to human diabetic atherosclerosis.     

Rho and Rho kinase mediate thrombin-stimulated vascular smooth muscle cell DNA synthesis and migration.

Aberrant regulation of smooth muscle cell proliferation and migration is associated with the pathophysiology of vascular disorders such as hypertension, atherosclerosis, restenosis, and graft rejection. To elucidate molecular mechanisms that regulate proliferation and migration of vascular smooth muscle cells, we determined whether signaling through the small G protein Rho is involved in thrombin- and phenylephrine-stimulated proliferation and migration of rat aortic smooth muscle cells (RASMCs). Thrombin and the thrombin peptide SFLLRNP stimulated DNA synthesis of RASMCs as measured by [3H]thymidine incorporation. Both ligands also increased cell migration as measured by the Boyden chamber method. L-Phenylephrine failed to induce either of these responses but increased inositol phosphate accumulation and mitogen-activated protein kinase activation in these cells, which indicated that the cells were responsive to alpha1-adrenergic stimulation. The C3 exoenzyme, which ADP-ribosylates and inactivates Rho, fully inhibited both thrombin-stimulated proliferation and migration but had no effect on inositol phosphate accumulation. In addition, Y-27632, an inhibitor of the Rho effector p160ROCK/Rho kinase, decreased thrombin-stimulated DNA synthesis and migration. To directly examine Rho activation, Rho-[35S]GTPgammaS binding was measured. The addition of the thrombin peptide SFLLRNP, but not phenylephrine, to RASMC lysates resulted in a significant increase in Rho-[35S]GTPgammaS binding. Thrombin and SFLLRNP, but not phenylephrine, also increased membrane-associated Rho in intact RASMCs, consistent with selective activation of Rho by thrombin. These results indicate that thrombin activates Rho in RASMCs and establish Rho as a critical mediator of thrombin receptor effects on DNA synthesis and cell migration in these cells.     

Lectin-like oxidized low-density lipoprotein receptor 1 mediates matrix metalloproteinase 3 synthesis enhanced by oxidized low-density lipoprotein in rheumatoid arthritis cartilage

OBJECTIVE: To investigate for the presence of oxidized low-density lipoprotein (ox-LDL) and lectin-like oxidized LDL receptor 1 (LOX-1) in cartilage specimens from rheumatoid arthritis (RA) joints and to determine whether the interaction of ox-LDL with LOX-1 can induce matrix metalloproteinase 3 (MMP-3) in articular cartilage explant culture. METHODS: Human articular cartilage specimens obtained from patients with RA, osteoarthritis (OA), and femoral neck fractures were examined for LOX-1 and ox-LDL by confocal fluorescence microscopy. The association between ox-LDL and LOX-1 was evaluated by immunofluorescence analysis. Articular cartilage specimens from patients with femoral neck fractures were incubated with ox-LDL, with or without preincubation with neutralizing anti-LOX-1 antibody. MMP-3 synthesis by chondrocytes in explant cartilage was evaluated by immunofluorescence, and protein secretion into conditioned medium was monitored by immunoblotting and enzyme-linked immunosorbent assay. RESULTS: The majority of the RA chondrocytes stained positively with both anti-LOX-1 and anti-ox-LDL antibodies; however, no positive cells were found in OA and normal cartilage specimens. Anti-LOX-1 antibody suppressed the binding of DiI-labeled ox-LDL to chondrocytes in explant culture, suggesting that the interaction was mediated by LOX-1. In contrast to native LDL, ox-LDL induced MMP-3 synthesis by articular chondrocytes in association with the induction of LOX-1, which resulted in enhanced secretion of MMP-3 into the culture medium. Anti-LOX-1 antibody reversed ox-LDL-stimulated MMP-3 synthesis to control levels. CONCLUSION: Ox-LDL, principally mediated by LOX-1, enhanced MMP-3 production in articular chondrocytes. Increased accumulation of ox-LDL with elevated expression of LOX-1 in RA cartilage indicates a specific role of the receptor-ligand interaction in cartilage pathology in RA.