Oxidized-LDL through LOX-1 increases the expression of angiotensin converting enzyme in human coronary artery endothelial cells

BACKGROUND AND OBJECTIVES: Our previous studies have shown that oxidized low-density lipoprotein (ox-LDL) and angiotensin II (Ang II) influence each other's action in endothelial cells. This study was designed to examine the regulation by ox-LDL of the expression of angiotensin converting enzyme (ACE) gene in human coronary artery endothelial cells (HCAECs). In addition, we studied the effect of the HMG CoA reductase inhibitor simvastatin on this interaction. METHODS AND RESULTS: Cultured HCAECs were incubated with ox-LDL (10-80 microg/ml) for 1-24 h. Ox-LDL increased the expression of ACE in a concentration- and time-dependent fashion. The upregulation of ACE expression in response to ox-LDL was mediated by its endothelial receptor LOX-1, since pretreatment of HCAECs with a blocking antibody to LOX-1 prevented the expression of ACE (P<0.01). Native-LDL had no significant effect on ACE expression. In this process, ox-LDL-induced activation of mitogen-activated protein kinase (MAPK p42/44) played an important role, since pretreatment of HCAECs with the MAPK p42/44 inhibitor (PD98059, 10 microM) inhibited MAPK activation and subsequently attenuated the expression of ACE (P<0.01 vs. ox-LDL alone). In other experiments, we pretreated HCAECs with simvastatin (10 microM) and then exposed the cells to ox-LDL. Simvastatin markedly attenuated ox-LDL-induced MAPK activation, and concurrently reduced ACE expression (P<0.01 vs. ox-LDL alone). CONCLUSIONS: Our observations provide direct evidence that ox-LDL via LOX-1 activation induces ACE gene expression in HCAECs, and MAPK activation plays a signal transduction role in this process. Simvastatin, which inhibits MAPK activation, also blocks ox-LDL-mediated upregulation of ACE.     

Upregulation of endothelial receptor for oxidized LDL (LOX-1) by oxidized LDL and implications in apoptosis of human coronary artery endothelial cells: evidence from use of antisense LOX-1 mRNA and chemical inhibitors

A specific lectin-like endothelial receptor for oxidized low density lipoprotein (LOX-1), distinct from the scavenger receptor in monocytes/macrophages, has been identified and cloned. In this study, we examined the regulation of LOX-1 by oxidized low density lipoprotein (ox-LDL) and determined the role of LOX-1 in ox-LDL-induced apoptosis of cultured human coronary artery endothelial cells (HCAECs). Incubation of HCAECs with ox-LDL (40 microg/mL), but not native LDL, for 24 hours markedly increased LOX-1 expression (mRNA and protein). After 48 hours of preincubation of HCAECs with a specific antisense to LOX-1 mRNA (antisense LOX-1), ox-LDL-mediated upregulation of LOX-1 was suppressed (P<0.01). In contrast, treatment of HCAECs with sense LOX-1 had no effect. Ox-LDL also induced apoptosis (determined by terminal deoxynucleotidyl transferase-mediated dUTP nick end-labeling and DNA laddering) of HCAECs in a concentration- and time-dependent fashion. LOX-1 played an important role in ox-LDL-mediated apoptosis of HCAECs because antisense LOX-1 inhibited this effect of ox-LDL. Polyinosinic acid and carrageenan, 2 different chemical inhibitors of LOX-1, also decreased ox-LDL-mediated apoptosis of HCAECs. Nuclear factor (NF)-kappaB was markedly activated in ox-LDL-treated HCAECs. The critical role of NF-kappaB activation became evident in experiments with antisense LOX-1, which abolished ox-LDL-mediated NF-kappaB activation. In this process, an NF-kappaB inhibitor, caffeic acid phenethyl ester, also inhibited ox-LDL-mediated apoptosis of HCAECs. These findings indicate that ox-LDL upregulates its own endothelial receptor. Ox-LDL-induced apoptosis is mediated by the action of LOX-1. In this process, NF-kappaB activation may play an important role as a signal transduction mechanism.     

Adhesion molecule expression in fibroblasts: alteration in fibroblast biology after transfection with LOX-1 plasmids

The endothelial lectinlike, oxidatively (ox-) modified LDL receptor LOX-1 is a critical player in the pathogenesis of atherosclerosis and myocardial ischemia. Ox-LDL binding of LOX-1 results in the expression of various adhesion molecules, which attract monocytes to endothelial cells, an initial step in atherogenesis. We wished to examine the role of the ox-LDL/LOX-1 signaling pathway in fibroblasts, which naturally express low levels of LOX-1. Rat cardiac fibroblasts were transfected with either cytomegalovirus (CMV)-LOX-1wt (amino acids [aa] 1 to 273) or CMV-LOX-1(1-261) (an ox-LDL-binding negative mutant, aa 1 to 261) plasmid. Western blots showed that LOX-1 protein expression was increased significantly in cells transfected with CMV-LOX-1wt or CMV-LOX-1(1-261) plasmid (P<0.01 vs control). Fibroblasts transfected with CMV-LOX-1wt showed ox-LDL binding, whereas fibroblasts without transfection and those transfected with CMV-LOX-1(1-261) did not bind ox-LDL. Compared with untransfected cells, ox-LDL treatment (50 microg/mL, 24 hours) markedly induced the expression of the leukocyte adhesion molecules intercellular adhesion molecule-1 (ICAM-1), and vascular cell adhesion molecule-1 (VCAM)-1 as well as matrix metalloproteinase (MMP)-1 in cells transfected with CMV-LOX-1wt (P<0.05) but not in cells transfected with CMV-LOX-1(1-261). Concurrently, ox-LDL treatment enhanced the phosphorylation of p38 mitogen-activated protein kinase (MAPK) (P<0.05 vs control) in CMV-LOX-1wt-transfected cells. These data suggest that in cardiac fibroblasts, ox-LDL binds to LOX-1 and activates p38 MAPK, followed by the expression of ICAM-1, VCAM-1, and MMP-1. Thus, fibroblasts transform into an endothelial phenotype on transfection with CMV-LOX-1wt and subsequent exposure to ox-LDL. This study provides a useful model system (plasmid-transfected fibroblasts) to study the molecular biology of LOX-1.     

Role of caspases in Ox-LDL-induced apoptotic cascade in human coronary artery endothelial cells

Oxidized low-density lipoprotein (ox-LDL) induces apoptosis in endothelial cells. However, steps leading to ox-LDL-induced apoptosis remain unclear. We examined the role of ox-LDL and its newly described receptor LOX-1 in the expression of intracellular pro- and antiapoptotic proteins and caspase pathways in human coronary artery endothelial cells (HCAECs). Cells were cultured and treated with different concentrations (10 to 80 microg/mL) of ox-LDL for different times (2 to 24 hours). Ox-LDL induced apoptosis in HCAECs in a concentration- and time-dependent manner. Ox-LDL also activated caspase-9 and caspase-3, but not caspase-8. After ox-LDL treatment, there was a significant release of activators of caspase-9, including cytochrome c and Smac from mitochondria to cytoplasmic compartment, and their release was not affected by treatment of cells with inhibitors of either caspase-8 or caspase-9. Ox-LDL also decreased expression of antiapoptotic proteins Bcl-2 and c-IAP (inhibitory apoptotic protein)-1, which are involved in the release of cytochrome c and Smac and activation of caspase-9, in a concentration- and time-dependent manner. On the other hand, ox-LDL did not change the expression of Fas-associated death domain-like interleukin-1beta-converting enzyme-inhibitory protein (FLIP) and proapoptotic protein Fas, which are required for the activation of caspase-8. Further, ox-LDL did not cause the truncation of Bid, which implies the activation of caspase-8. In other experiments, pretreatment of HCAECs with the caspase-9 inhibitor z-LEHD-fmk, but not the caspase-8 inhibitor z-IETD-fmk, blocked ox-LDL-induced activation of caspase-3 and apoptosis. As expected, pretreatment with the caspase-3 inhibitor DEVD-CHO inhibited ox-LDL-induced activation of caspase-3 and resultant apoptosis. The proapoptotic effects of ox-LDL were mediated by its receptor LOX-1, because pretreatment of HCAECs with antisense-LOX-1, but not sense-LOX-1, blocked these effects of ox-LDL. These findings suggest that ox-LDL through its receptor LOX-1 decreases the expression of antiapoptotic proteins Bcl-2 and c-IAP-1. This is followed by activation of apoptotic signaling pathway, involving release of cytochrome c and Smac and activation of caspase-9 and then caspase-3.     

Lectin-like oxidized LDL receptor-1 (LOX-1) expression is associated with atherosclerotic plaque instability--analysis in hypercholesterolemic rabbits

Lectin-like oxidized LDL receptor-1 (LOX-1), a cell-surface receptor for oxidized LDL (Ox-LDL), has been implicated in vascular cell dysfunction related to atherosclerotic plaque instability, according to cell culture experiments. In the present study, we investigated the relationship between LOX-1 expression and plaque instability in hypercholesterolemic rabbits by immunohistological analyses in vivo. We prepared thirty series of cross sections of the thoracic aorta from six myocardial infarction-prone Watanabe heritable hyperlipidemic (WHHLMI) rabbits (12-24 months), in which seventy atherosclerotic plaques were observed. LOX-1, matrix metalloproteinase-9 (MMP-9), monocyte chemoattractant protein-1 (MCP-1) expression, apoptotic events, plaque instability index (an index of the morphological destabilization of atherosclerotic plaques) and fibromuscular cap thickness in each atherosclerotic plaque were determined by immunohistochemical staining, TUNEL staining and Azan-Mallory staining. LOX-1 expression was positively correlated with the plaque instability index and MMP-9 expression. LOX-1 expression was more prominent in atherosclerotic plaques with thinner fibromuscular cap (<100 microm). Furthermore, LOX-1 expression was shown in the macrophage-rich lipid core area where MCP-1 expression and apoptotic events were prominent. These results indicate that enhanced LOX-1 expression was associated with histologically unstable atherosclerotic plaques in hypercholesterolemic rabbits, suggesting the involvement of LOX-1 in the destabilization of atherosclerotic plaques in vivo.     

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.     

Oxidized LDL,LOX-1 and Atherosclerosis

An elevated level of low density lipoprotein (LDL) cholesterol constitutes a major risk factor for genesis of atherosclerosis. Ox-LDL plays a more important role in the genesis and progression of atherosclerosis than the native LDL. Ox-LDL leads to endothelial dysfunction leading to expression of adhesion molecules and recruitment of monocyte in subendothelial space. Ox-LDL is taken up by macrophages via scavenger receptors, such as SR-A1, SR-A2 and LOX-1. Lately, LOX-1, a type II membrane protein receptor of ox-LDL, has gained much importance in relation to effects of ox-LDL on endothelial biology. Endothelial cells primarily express LOX-1 as receptor for ox-LDL and ox-LDL has been shown to upregulate expression of LOX-1. In addition, ox-LDL promotes the growth and migration of smooth muscle cells, monocytes/macrophages and fibroblasts. In this review we discuss the role of ox-LDL and LOX-1 in genesis and progression of atherosclerosis.     

Oxidized LDL modulates Bax/Bcl-2 through the lectinlike Ox-LDL receptor-1 in vascular smooth muscle cells

Oxidized low density lipoprotein (Ox-LDL) induces apoptosis in vascular smooth muscle cells (VSMCs), which may increase atherosclerotic plaque instability. In this study, we examined the molecular mechanisms causing the Ox-LDL-induced apoptosis in VSMCs, especially focusing on the involvement of Bax/Bcl-2 and the lectinlike Ox-LDL receptor-1 (LOX-1). In cultured bovine aortic smooth muscle cells (BASMCs), Ox-LDL at high concentrations (>60 microg/mL) induced cell death as demonstrated by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. DNA fragmentation was increased in BASMCs treated with high concentrations of Ox-LDL, indicating that the Ox-LDL-induced cell death in VSMCs was apoptosis. Ox-LDL upregulated LOX-1 expression through phosphorylation of extracellular signal-regulated kinase in BASMCs, and a neutralizing anti-LOX-1 monoclonal antibody, which can block LOX-1-mediated cellular uptake of Ox-LDL, prevented the Ox-LDL-induced apoptosis in BASMCs. This antibody also suppressed the increase in the Bax to Bcl-2 ratio induced by Ox-LDL in BASMCs. Furthermore, LOX-1 expression was well colocalized with Bax expression in the rupture-prone shoulder areas of human atherosclerotic plaques in vivo. LOX-1 may play an important role in Ox-LDL-induced apoptosis in VSMCs by modulating the Bax to Bcl-2 ratio. These molecular mechanisms may be involved in destabilization and rupture of atherosclerotic plaques.     

Heparin-binding EGF-like growth factor induces expression of lectin-like oxidized LDL receptor-1 in vascular smooth muscle cells

Receptor-mediated endocytosis of oxidized LDL (Ox-LDL) has been implicated in lipid accumulation and vascular cell dysfunction. Lectin-like Ox-LDL receptor-1 (LOX-1) is highly inducible by proinflammatory cytokines, as well as angiotensin II and Ox-LDL in vitro. LOX-1 is expressed in macrophages and smooth muscle cells accumulated in the intima of advanced atherosclerotic plaques in vivo. Here we show that heparin-binding epidermal growth factor-like growth factor (HB-EGF), a potent mitogen for vascular smooth muscle cells, induces LOX-1 expression in cultured bovine aortic smooth muscle cells. HB-EGF (1-100 ng/ml) induced LOX-1 expression, which was peaked between 8 and 16 h after HB-EGF stimulation. HB-EGF-induced expression of LOX-1 was suppressed by ZD1839, an inhibitor of EGF receptor phosphorylation. Both MEK and p38 mitogen-activated protein kinase (MAPK) inhibitors significantly blocked LOX-1 upregulation induced by HB-EGF. Phosphatidylinositol 3-kinase (PI3K) inhibitors also blocked HB-EGF-induced LOX-1 expression. HB-EGF induced phosphorylation of ERK, p38 MAPK and Akt, which were suppressed by ZD1839. Upregulated expression of LOX-1 was associated with enhanced uptake of DiI-labeled Ox-LDL in smooth muscle cells. Taken together, HB-EGF can also act as an inducer of LOX-1 expression and play an integral role in foam cell transformation, cellular dysfunction, and proliferation of smooth muscle cells in atherogenesis.     

The mode of action of aspirin-like drugs: effect on inducible nitric oxide synthase.

Nitric oxide synthesized by inducible nitric oxide synthase (iNOS) has been implicated as a mediator of inflammation in rheumatic and autoimmune diseases. We report that exposure of lipopolysaccharide-stimulated murine macrophages to therapeutic concentrations of aspirin (IC50 = 3 mM) and hydrocortisone (IC50 = 5 microM) inhibited the expression of iNOS and production of nitrite. In contrast, sodium salicylate (1-3 mM), indomethacin (5-20 microM), and acetaminophen (60-120 microM) had no significant effect on the production of nitrite at pharmacological concentrations. At suprapharmacological concentrations, sodium salicylate (IC50 = 20 mM) significantly inhibited nitrite production. Immunoblot analysis of iNOS expression in the presence of aspirin showed inhibition of iNOS expression (IC50 = 3 mM). Sodium salicylate variably inhibited iNOS expression (0-35%), whereas indomethacin had no effect. Furthermore, there was no significant effect of these nonsteroidal anti-inflammatory drugs on iNOS mRNA expression at pharmacological concentrations. The effect of aspirin was not due to inhibition of cyclooxygenase 2 because both aspirin and indomethacin inhibited prostaglandin E2 synthesis by > 75%. Aspirin and N-acetylimidazole (an effective acetylating agent), but not sodium salicylate or indomethacin, also directly interfered with the catalytic activity of iNOS in cell-free extracts. These studies indicate that the inhibition of iNOS expression and function represents another mechanism of action for aspirin, if not for all aspirin-like drugs. The effects are exerted at the level of translational/posttranslational modification and directly on the catalytic activity of iNOS.     

Lectin-like oxidized low density lipoprotein receptor 1 (LOX-1) expression in human articular chondrocytes

OBJECTIVE: To investigate the involvement of oxidized low density lipoprotein (ox-LDL) and the expression of its receptor lectin-like oxidized low density lipoprotein receptor 1 (LOX-1) in osteoarthritis, by determining the ox-LDL in synovial fluid and the expression of LOX-1 mRNA and protein in osteoarthritic as well as normal cartilage. In addition, the effect of ox-LDL on chondrocyte viability and the effect of ascorbic acid (a well-known anti-oxidant) on LOX-1 expression were studied. METHODS: Fifteen patients were included in the study. Osteoarthritic articular cartilage was obtained from two distinct locations in the knee (n = 10) and hip (n = 5), specifically from weight-bearing and non-weight-bearing areas of the same joints. Five individuals were used as controls. mRNA and protein expression were studied by RT-PCR and immunofluorescence, respectively. Ox-LDL was measured in the synovial fluid and in paired serum samples from the patients using the ELISA method. RESULTS: Ox-LDL was detected in the synovial fluid and its receptor LOX-1 was detected in cartilage from both weight-bearing and non-weight-bearing areas, whereas no LOX-1 expression was found in normal cartilage. Ox-LDL reduced chondrocyte viability in cell cultures, while the addition of ascorbic acid to osteoarthritic chondrocytes resulted in a decrease in LOX-1 mRNA expression. CONCLUSION: The detection of LOX-1 mRNA and protein expression in osteoarthritic cartilage drawn from both weight-bearing and non-weight-bearing regions of the same patients suggest that LOX-1 may be involved in the progression and pathogenesis of osteoarthritis.     

EPA and DHA attenuate ox-LDL-induced expression of adhesion molecules in human coronary artery endothelial cells via protein kinase B pathway

Uptake of oxidized low-density lipoprotein (ox-LDL) by endothelial cells is a critical step for the initiation and development of atherosclerosis. Adhesion molecules are inflammatory makers, which are upregulated by ox-LDL and play a pivotal role in atherogenesis. A number of studies suggest that fish and its constituents can reduce inflammation and decrease atherosclerosis. We hypothesized that fish oil constituents namely docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) may reduce expression of adhesion molecules induced by ox-LDL. Cultured human coronary artery endothelial cells (HCAECs) were incubated with ox-LDL for 24 h. Parallel groups of cells were pretreated with DHA or EPA (10 or 50 microM) overnight before incubation with ox-LDL. Ox-LDL markedly increased the expression of P-selectin and intracellular adhesion molecule-1 (ICAM-1) (both protein and mRNA) in HCAECs, and enhanced the adhesion of monocytes to the cultured HCAECs. Both EPA and DHA decreased ox-LDL-induced upregulation of expression of P-selectin and ICAM-1, and the enhanced adhesion of monocytes to HCAECs. To determine the role of protein kinase B (PKB) as an intracellular-signaling pathway, HCAECs were treated with the PKB upstream inhibitor wortmannin (100 nM) or transfected with plasmids encoding dominant-negative mutants of PKB (PKB-DN) before treatment with DHA. Ox-LDL alone downregulated the activity of PKB; DHA attenuated this effect of ox-LDL, and both wortmannin and PKB-DN blocked the effect of DHA. The present study in human coronary endothelial cells suggests that both EPA and DHA attenuate ox-LDL-induced expression of adhesion molecules, and the adhesion of monocytes to HCAECs by modulation of PKB activation. These effects may be important mechanisms of anti-atherosclerotic effects of fish and fish oils.     

血凝素样氧化型低密度脂蛋白受体1介导氧化型低密度脂蛋白促进血管平滑肌细胞表达白细胞介素6

观察氧化型低密度脂蛋白对血管平滑肌细胞白细胞介素 6表达的影响及血凝素样氧化型低密度脂蛋白受体 1在其中的作用。人脐带动脉平滑肌细胞体外原代培养 ,传至 4～ 5代。氧化型低密度脂蛋白干预 ,观察不同时间点白细胞介素 6mRNA表达 ,及不同浓度氧化型低密度脂蛋白对白细胞介素 6和血凝素样氧化型低密度脂蛋白受体 1mRNA表达的影响。并观察血凝素样氧化型低密度脂蛋白受体 1抑制剂多聚肌酐酸对白细胞介素 6mRNA表达的影响。结果发现 ,(1)氧化型低密度脂蛋白作用后 ,白细胞介素 6mRNA表达显著升高 ,作用 6h出现峰值。随着氧化型低密度脂蛋白浓度升高 ,白细胞介素 6mRNA和血凝素样氧化型低密度脂蛋白受体 1mRNA表达均明显升高 ,后两者呈正相关 (r=0 .94 3,P <0 .0 1)。 (2 )多聚肌酐酸抑制血凝素样氧化型低密度脂蛋白受体 1后 ,白细胞介素 6mRNA表达明显下降。以上表明氧化型低密度脂蛋白明显促进血管平滑肌细胞白细胞介素 6的表达 ,血凝素样氧化型低密度脂蛋白受体 1在此过程中起重要介导作用。     

Cross-talk between dyslipidemia and renin-angiotensin system and the role of LOX-1 and MAPK in atherogenesis studies with the combined use of rosuvastatin and candesartan

There is increasing evidence of cross-talk between dyslipidemia and renin-angiotensin system (RAS) in atherogenesis. Both dyslipidemia and RAS activation enhance the expression of a newly described receptor for oxidized-low density lipoprotein (ox-LDL), lectin-like ox-LDL receptor-1 (LOX-1). We postulated that the blockade of dyslipidemia with rosuvastatin, a 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitor and RAS with candesartan, an angiotensin II type 1 receptor blocker, would have a synergistic inhibitory effect on LOX-1 expression and atherogenesis. Apo-E knockout mice were fed a high-cholesterol diet (1% cholesterol, HC-diet) alone, or HC-diet with rosuvastatin (1mg/(kgd)), candesartan (1mg/(kgd)) or with both. Twelve weeks later the extent of atherosclerosis was determined by Sudan IV staining. Apo-E knockout mice on HC-diet had extensive atherosclerosis. Both rosuvastatin and candesartan decreased the extent of atherosclerosis (by 23 and 26%, respectively), despite the HC-diet; however, the combination of rosuvastatin and candesartan reduced atherosclerosis further (by 67%). Rosuvastatin decreased plasma levels of total cholesterol by over 50%, whereas candesartan had no effect. LOX-1 protein expression was found to be markedly up-regulated in HC-diet-fed apo-E knockout mice. While rosuvastatin and candesartan each had a small inhibitory effect on the expression of LOX-1 in the atherosclerotic tissues, the combination totally blocked the up-regulation of LOX-1. P38 mitogen-activated protein kinase (MAPK) expression and phosphorylation were increased in apo-E knockout mice, attenuated by rosuvastatin or candesartan alone, and completely blocked by the combination of the two agents. P44/42 MAPK expression and phosphorylation were not affected by the HC-diet, rosuvastatin, candesartan, or their combination. This study demonstrates the potent effect of rosuvastatin and candesartan on atherogenesis, as well as on the expression of LOX-1 and on the activation of p38 MAPK, but not p44/42 MAPK.     

New oxidized LDL receptors and their functions in atherogenesis

Oxidized low density lipoprotein (Ox-LDL) appears to play key roles in atherosclerotic progression and plaque rupture. Biological effects of Ox-LDL on vascular cells may, at least in part, be mediated by cell surface receptors for Ox-LDL. Lectin-like oxidized LDL receptor (LOX)-1 and scavenger receptor for phosphatidylserine and oxidized lipoprotein (SR-PSOX) are type II and I membrane glycoprtoeins, respectively, both of which can act as cell-surface endocytosis receptors for atherogenic oxidized LDL (Ox-LDL). LOX-1 expression can dynamically be induced by proinflammatory stimuli, and is detectable in cultured macrophages and activated vascular smooth muscle cells (VSMC), in addition to endothelial cells. LOX-1-dependent uptake of Ox-LDL induced apoptosis of cultured VSMC. In vivo, endothelial cells that cover early atherosclerotic lesions, and intimal macrophages and VSMC in advanced atherosclerotic plaques dominantly express LOX-1. LOX-1 expressed on the cellsurface can be cleaved, in part, and released as soluble molecules, suggesting the diagnostic significance of plasma soluble LOX-1 levels. SR-PSOX appeared to be identical to CXCL16, a novel membrane-anchored chemokine directed to CXCR6-positive lymphocytes, suggesting another role of SR-PSOX as T-cell chemoattractant. In contrast to LOX-1 expressed by a variety of cell types. SR-PSOX expression appeared relatively confined to macrophages in atherogenesis. Taken together, LOX-1 and SR-PSOX may play important roles in atherogenesis and athrosclerotic plaque rupture.     

阿司匹林和氯吡格雷抑制兔粥样硬化主动脉基质金属蛋白酶1的表达

目的研究抗血小板药物阿司匹林、氯吡格雷及两药合用对兔粥样硬化主动脉基质金属蛋白酶1表达和斑块稳定性的影响。方法49只雄性日本大耳白兔随机分为正常对照组、模型组、阿司匹林组、氯吡格雷组及合用组。后四组建立高胆固醇饲料和免疫损伤诱发的主动脉粥样硬化模型。免疫组织化学法测定斑块部位的巨噬细胞和平滑肌细胞阳性百分率并确定基质金属蛋白酶1在动脉壁的分布,Western印迹法测定主动脉基质金属蛋白酶1的表达水平。结果阿司匹林和氯吡格雷均明显减少巨噬细胞阳性百分率、增加平滑肌细胞阳性百分率(P<0.01),斑块中巨噬细胞部位与基质金属蛋白酶1阳性区域存在定位上的对应关系。模型组、阿司匹林组、氯吡格雷组、合用组主动脉基质金属蛋白酶1的表达分别是正常对照组的562%、217%、211%和178%,与模型组相比,阿司匹林组、氯吡格雷组及合用组基质金属蛋白酶1蛋白表达均显著降低(P<0.05)。结论氯吡格雷和阿司匹林能抑制动脉粥样硬化斑块内巨噬细胞表达基质金属蛋白酶1,并通过改变斑块组成对稳定斑块起作用。     

Roles of oxidized low-density lipoprotein and its receptors in the pathogenesis of atherosclerotic diseases

In elderly populations, atherosclerotic diseases, including ischemic heart disease and stroke, frequently impair quality of life and affect mortality. Hypercholesterolemia, especially increased plasma low-density lipoprotein (LDL), is one of the strongest risk factors for atheroscletorotic diseases. Oxidative modification of LDL appears to convert LDL particles to more atherogenic forms. Scavenger receptor class A (SR-A) and CD36 have been identified and well-characerized as receptors for Ox-LDL in macrophages. In addition to these molecules, lectin-like oxidized LDL receptor (LOX)-1 and scavenger receptor for phosphatidylserine and oxidized lipoprotein (SR-PSOX) are type II and I membrane glycoproteins, respectively, both of which can act as cell-surface endocytosis receptors for atherogenic oxidized LDL (Ox-LDL). LOX-1 expression can dynamically be induced by pro-inflammatory stimuli, and is detectable in cultured macrophages and activated vascular smooth muscle cells (VSMC), in addition to endothelial cells. LOX-1-dependent uptake of Ox-LDL induces apoptosis of cultured VSMC. In vivo , endothelial cells that cover early atherosclerotic lesions, and intimal macrophages and VSMC in advanced atherosclerotic plaques dominantly express LOX-1. LOX-1 expressed on the cell-surface can be cleaved in part and released as soluble molecules, suggesting the diagnostic value of soluble LOX-1. SR-PSOX is a newly identified receptor for Ox-LDL, which appears to be identical to CXCL16, a novel membrane-anchored chemokine directed to CXCR6-positive lymphocytes. In contrast to LOX-1, which is expressed by a variety of cell types, SR-PSOX expression appeared relatively confined to macrophages in atherogenesis. Taken together, oxidized LDL receptors, including LOX-1 and SR-PSOX, may play important roles in atherogenesis and atherosclerotic plaque rupture.     

LOX-1在动脉粥样硬化中的作用研究新进展

动脉粥样硬化(AS)是一种血管慢性炎症性病变,其中内皮细胞功能异常、单核细胞的黏附和迁移、平滑肌细胞的凋亡、泡沫细胞的形成和血小板的活化是AS形成的关键环节,最终结果是形成大、中动脉内膜下的粥样硬化斑块,造成管腔狭窄,远端组织器官供血不足甚至栓塞。低密度脂蛋白（LDL） 氧化形成的氧化型LDL（ox-LDL）在AS发生、发展过程中起着重要作用。目前在与AS发生、发展相关的细胞（如血管内皮细胞、血管平滑肌细胞、单核细胞、巨噬细胞以及泡沫细胞）上已经发现和鉴定了多种oxLDL受体,其中瘦素样氧化型低密度脂蛋白受体(LOX)-1表达于血管内皮细胞、巨噬细胞、血小板上,是ox-LDL的主要受体［1］,在AS的发生、发展中起着重要作用,本文将着重阐述近年来LOX-1影响AS发生发展相关效应与机制的新进展。