LOX-1: A Critical Player in the Genesis and Progression of Myocardial Ischemia

Myocardial ischemia is the most common cause of mortality and morbidity in the developed countries and rapidly becoming a common malady in the developing countries. Lectin-like oxidized low-density lipoprotein receptor-1 (LOX-1), encoded by the OLR1 gene, is a scavenger receptor that plays a fundamental role in the genesis and progression of atherosclerosis and its complications. LOX-1 has been identified as a major receptor for oxidized low-density lipoprotein (ox-LDL) in endothelial cells, cardiomyocytes and fibroblast. In vitro and in vivo studies show that LOX-1 is upregulated during acute myocardial ischemia, and continues to be upregulated during chronic ischemia. Further, LOX-1 inhibition reduces ischemic myocardial injury and limits cardiac remodeling. LOX-1 inhibition decreases oxidative stress and inflammatory response to injury resulting in limitation of ischemic injury. Molecular studies show that LOX-1 inhibition reduces release of pro-inflammatory cytokines and expression of angiotensin II type 1 receptor via inhibition of redox-sensitive pathways. These alterations limit cardiomyocyte hypertrophy and collagen accumulation in the ischemic regions. These alterations in molecular signaling and physical alterations can result in improved cardiac function and better survival after ischemic myocardial injury.     

血凝素样氧化低密度脂蛋白受体1——新的药物作用靶点

血凝素样氧化低密度脂蛋白受体1(LOX-1)为最近发现的氧化修饰低密度脂蛋白(ox-LDL)受体,介导内皮细胞摄取代谢ox-LDL,以及ox-LDL对内皮细胞的损伤效应,引起内皮功能失调,导致动脉粥样硬化及相关心血管疾病的发生。适当阻断LOX-1与ox-LDL的结合,将会从源头上阻止ox-LDL对内皮细胞的损伤,从而保护血管功能,防止疾病的发生。所以,LOX-1可能是一个新的药物作用靶点。     

Lectin-like oxidized low-density lipoprotein receptor 1 mediates leukocyte infiltration and articular cartilage destruction in rat zymosan-induced arthritis

OBJECTIVE: The relationship between rheumatoid arthritis and atherosclerosis has been recognized for >20 years. This study aimed to elucidate the roles of oxidized low-density lipoprotein (ox-LDL; one of the main pathogenic factors of atherosclerosis) and its endothelial receptor, lectin-like ox-LDL receptor 1 (LOX-1), in arthritic joints using a rat zymosan-induced arthritis (ZIA) model. METHODS: LOX-1 expression and ox-LDL accumulation in arthritic joints were detected by immunohistochemistry using specific mouse anti-LOX-1 and anti-ox-LDL monoclonal antibodies, respectively. To elucidate the effects of the expressed LOX-1 on arthritis, ZIA rats were treated with anti-LOX-1 antibody or normal mouse IgG. The severity of arthritis was analyzed by joint swelling. Cell infiltration, synovial hyperplasia, and proteoglycan losses were also determined by histologic scoring. Proinflammatory cytokine and nitrite levels in serum and joint fluid were also measured. RESULTS: Immunohistochemical study of ZIA demonstrated LOX-1 expression on synovial endothelium and postcapillary venules at 6 hours after the induction of inflammation, with maximum expression detected at 24 hours. LOX-1 was also expressed weakly on both joint cartilage and synovium. Ox-LDL, a ligand of LOX-1, was also detected in articular chondrocytes. Administration of anti-LOX-1 antibody, which blocks LOX-1 activity, suppressed joint swelling (by 33.5%), leukocyte infiltration, and joint nitrite accumulation at 24 hours, as well as cartilage destruction at 7 days, compared with control rats. CONCLUSION: LOX-1 induction in arthritic joints might play a role in promoting joint inflammation and cartilage destruction by mediating leukocyte infiltration into the arthritic joints of ZIA rats.     

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.     

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.     

Aspirin inhibits ox-LDL-mediated LOX-1 expression and metalloproteinase-1 in human coronary endothelial cells

BACKGROUND: Aspirin is thought to exert salutary effects in vascular disease states by inhibiting platelet aggregation. Endothelial activation, accumulation of oxidized low-density lipoprotein (ox-LDL) and intense inflammation also characterize atherosclerotic plaque in acute myocardial ischemia. Ox-LDL induces expression of lectin-like receptors (LOX-1) on endothelial cells and leads to the expression of matrix metalloproteinases (MMPs), which destabilize the atherosclerotic plaque. We hypothesized that aspirin may interfere with LOX-1 expression and subsequent MMP activation. METHODS AND RESULTS: Cultured human coronary artery endothelial cells (HCAECs) were incubated with aspirin (1-5 mM), sodium salicylate (5 mM) or the cyclo-oxygenase inhibitor indomethacin (0.25 mM) before treatment with ox-LDL. Aspirin, in a dose- and time-dependent fashion, reduced ox-LDL-mediated LOX-1 expression (P<0.01). Ox-LDL also increased MMP-1 expression and activity, and treatment of HCAECs with aspirin decreased this effect (P<0.01). Ox-LDL also enhanced the activity of p38MAPK in HCAECs, and aspirin blocked this effect of ox-LDL (P<0.01). Treatment of HCAECs with salicylate, but not indomethacin, resulted in a suppression of LOX-1 expression, an effect similar to that of aspirin. Importantly, both aspirin and salicylate, but not indomethacin, decreased superoxide anion generation in ox-LDL-treated HCAECs (P<0.05). CONCLUSION: These observations suggest that aspirin inhibits ox-LDL-mediated LOX-1 expression and interferes with the effects of ox-LDL in intracellular signaling (p38MAPK activation) and subsequent MMP-1 activity. These novel effects of aspirin may complement its platelet inhibitory effect in acute myocardial ischemia.     

“氧化型低密度脂蛋白—凝集素样氧化型低密度脂蛋白受体1—活性氧”信号通路参与泡沫细胞的形成

动脉粥样硬化是多因素引起的,以动脉壁内脂质的沉积甚至粥样斑块的形成为特征的慢性血管炎症性疾病.巨噬细胞内胆固醇的堆积和泡沫细胞的形成是早期动脉粥样硬化形成的标志.然而,泡沫细胞形成的确切机制尚未完全阐明.于此,我们推测氧化型低密度脂蛋白(oxidized low density lipoprotein,ox-LDL),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)和活性氧(reactive oxygen species,ROS)组成了一个促进泡沫细胞形成的"信号通路",在泡沫细胞的形成乃至诱导动脉粥样硬化发生中起始动作用.在这一通路中,氧化型低密度脂蛋白,这种经过氧化修饰的低密度脂蛋白,是"激活子";凝集素样氧化型低密度脂蛋白受体1,作为内皮细胞上的氧化型低密度脂蛋白的主要受体是信号"转导子";活性氧,这氧化型低密度脂蛋白与凝集素样氧化型低密度脂蛋白受体1结合后的直接产物是"催化子"和"诱导剂".     

Novel Concepts in the Genesis of Hypertension: Role of LOX-1

Hypertension is a common disease and a potent risk factor for cardiovascular disease. Tremendous strides have been made in understanding its genesis in the last 2 decades. Hypertension is often clustered with other cardiovascular risk factors, such as dyslipidemia and diabetes. The state of hypertension is often associated with increased vascular oxidative stress. Oxidative stress promotes proliferation and hypertrophy of vascular smooth muscle cell and collagen deposition, leading to thickening of the vascular media and narrowing of the vascular lumen. Oxidative stress also injures endothelium, impairs endothelium-dependent vascular relaxation and increases vascular contractile activity. Further, oxidative stress also oxidizes LDL-cholesterol. It has been shown that oxidized low-density lipoprotein (ox-LDL) activates renin-angiotensin system (RAS) and angiotensin II via its type 1 receptor activates ox-LDL receptor LOX-1. This mutually facilitative cross-talk between ox-LDL and RAS may be an important component in the development of hypertension. Lectin-like oxidized low-density lipoprotein receptor-1 (LOX-1) is a receptor for ox-LDL. This review summarizes the role of LOX-1 in the pathogenesis of hypertension.     

睾酮对动脉粥样硬化雄兔血凝素样氧化型低密度脂蛋白受体1表达的影响

目的探讨睾酮对动脉粥样硬化雄兔血凝素样氧化型低密度脂蛋白受体1表达的影响。方法选取雄性新西兰白兔18只,随机分为假手术组、去势-安慰剂组和去势-睾酮组,并建立动脉粥样硬化模型。化学发光法测定各组血清总睾酮。胸主动脉HE染色,图像分析测定内膜和中膜厚度。夹心双抗酶联免疫法检测血清氧化型低密度脂蛋白水平。半定量RT-PCR、免疫组织化学分析法测定血凝素样氧化型低密度脂蛋白受体1的mRNA和蛋白表达。结果雄兔去势-安慰剂组血清总睾酮水平显著下降,而去势-睾酮组血清总睾酮水平未见降低,较假手术组差异无显著性。去势-安慰剂组雄兔胸主动脉内膜和内膜/中膜厚度较假手术组显著增加。各组雄兔血清氧化型低密度脂蛋白水平差异无显著性。去势-安慰剂组雄兔胸主动脉血凝素样氧化型低密度脂蛋白受体1的mR-NA和蛋白表达较假手术组显著升高,而去势-睾酮组胸主动脉均无明显改变。结论睾酮对动脉粥样硬化雄兔血清氧化型低密度脂蛋白没有显著影响,但是可影响血凝素样氧化型低密度脂蛋白受体1基因的转录和翻译,睾酮可能通过调节血凝素样氧化型低密度脂蛋白受体1而非氧化型低密度脂蛋白,进而影响动脉粥样硬化的进程。     

吡格列酮对人脐静脉内皮细胞血凝素样氧化低密度脂蛋白受体1表达的影响

目的探讨氧化型低密度脂蛋白(ox-LDL)作用下,吡格列酮对人脐静脉内皮细胞(HUVECs)血凝素样氧化低密度脂蛋白受体1(LOX-1)表达的影响。方法将培养的第4代HUVECs分5组:空白组(无干预);ox-LDL组(80 mg/L ox-LDL);低浓度组(1μmol/L吡格列酮+80 mg/L ox-LDL);高浓度组(10μmol/L吡格列酮+80 mg/Lox-LDL);对照组(10μmol/L吡格列酮),各组培养24 h后,采用流式细胞仪检测LOX-1的表达,采用RT-PCR检测LOX-1 mRNA的表达。结果与空白组比较,对照组LOX-1及LOX-1 mRNA表达均无明显改变(P0.05),ox-LDL组、低浓度组和高浓度组LOX-1及LOX-1 mRNA表达明显增多(P0.01);与ox-LDL组比较,低浓度组和高浓度组LOX-1及LOX-1 mRNA表达明显降低(P0.01);高浓度组较低浓度组降低更明显(P0.05)。结论吡格列酮能降低ox-LDL刺激下的HUVECs LOX-1及LOX-1 mRNA的表达,提示吡格列酮可能通过干预ox-LDL的病理生理过程起到抗动脉硬化的作用。     

氧化低密度脂蛋白通过血凝素样氧化低密度脂蛋白受体1诱导血管内皮细胞粘附分子的表达

目的探讨血凝素样氧化低密度脂蛋白受体1（LOX-1）在氧化低密度脂蛋白（ox—LDL）诱导血管内皮细胞粘附分子表达中的作用。方法用不同浓度ox-LDL培养人脐静脉内皮细胞（HUVECs）,用RrealtimeRT—PCR测定LOX-1 mRNA的表达;RT—PCR测定细胞间粘附分子1（ICAM-1）、血管细胞粘附分子1（VCAM-1）以及E选择素的mRNA表达;用Westernblot测定LOX-1、ICAM-1、VCAM-1以及E选择素蛋白的表达,观察ox-LDL对血管内皮细胞粘附分子表达的影响。HUVECs预先用聚肌苷酸[poly（I）]和爱兰苔胶处理,再用ox—LDL培养,再分别测定上述粘附分子的表达水平,比较加入LOX-1阻断剂前后粘附分子表达的变化。结果ox-LDL各剂量组皆可上调LOX-1、ICAM-1、E选择素的mRNA和蛋白表达（P〈0．01）,在10～50μm/ml剂量范围内呈现明显的剂量一效应关系（P〈0．01）,但ox—LDL对VCAM-1的表达没影响。HUVECs预先与250μg／ml的poly（Ⅰ）或爱兰苔胶作用2h,然后加入50μg/ml的ox—LDL作用24h。poly（Ⅰ）和爱兰苔胶都能抑制ox—LDL诱导的LOX-1、ICAM-1和E选择素的mRNA和蛋白表达水平,与未阻断组相比,差异皆有统计学意义（P〈0．01）。结论ox—LDL可以上调血管内皮细胞粘附分子的表达,LOX-1受体阻断剂可以部分阻断ox—LDL的上调作用,ox-LDL诱导血管内皮细胞粘附分子的表过是通过LOX-1介导的。     

大鼠心肌缺血-再灌注模型的心电图变化

目的 研究大鼠心肌缺血再灌注模型的心电图变化.方法 将23只雄性大鼠按电脑随机数字表法分为假手术组及缺血再灌注损伤组.缺血再灌注损伤组结扎左前降支35 min,再灌注120 min;而假手术组仅给予左前降支过线不结扎血管.采用氯化三苯基四氮唑(tetrazolium chloride,TTC)染色法检测大鼠缺血再灌注心...     

苯扎贝特对脐静脉内皮细胞基质金属蛋白酶-9表达的影响及机制

目的观察苯扎贝特对氧化型低密度脂蛋白所诱导的人脐静脉内皮细胞基质金属蛋白酶-9（MMP-9）表达的影响及是否与血凝素样氧化型低密度脂蛋白受体1表达相关。方法体外培养人脐静脉内皮细胞,逆转录聚合酶链反应检测MMP-9和血凝素样氧化型低密度脂蛋白受体1 mRNA的表达。结果与对照组（0．151±0．004、0．562±0．021）比较,氧化型低密度脂蛋白组LOX-1 mRNA（0．943±0．003）、MMP-9 mRNA（1．020±0．039）表达均明显增加（P〈0．05）;与氧化型低密度脂蛋白组比较,苯扎贝特组和多聚肌甘酸（血凝素氧化型低密度脂蛋白受体1阻滞剂）组血凝素样氧化型低密度脂蛋白受体1 mRNA（0．258±0．002、0．463±0．007）、MMP-9 mRNA（0．894±0．041、0．872±0．046）表达均减少（P〈0．05）;与苯扎贝特组比较,苯扎贝特组加多聚肌甘酸组血凝素样氧化型低密度脂蛋白受体1 mRNA（0．144±0．003）、MMP-9 mRNA（0．541±0．030）表达均明显减少（P〈0．05）。结论血凝素样氧化型低密度脂蛋白受体1可能参与苯扎贝特下调内皮细胞MMP-9基因的表达。     

Lectin-like, oxidized low-density lipoprotein receptor-1 (LOX-1): a critical player in the development of atherosclerosis and related disorders

LOX-1, a lectin-like 52-kD receptor for oxidized low-density lipoproteins (ox-LDL), is present primarily on endothelial cells. This receptor is upregulated by ox-LDL itself and by angiotensin II, endothelin, cytokines, and shear stress, all participants in atherosclerosis. This receptor is upregulated in the arteries of hypertensive, dyslipidemic, and diabetic animals. Upregulation of LOX-1 has been identified in atherosclerotic arteries of several animal species and humans, not only on the endothelial lining, but also in the neovasculature of the atherosclerotic plaque, and this receptor is often co-localized with apoptotic cells. Recent studies show upregulation of LOX-1 in the ischemic-reperfused myocardium. LOX-1 inhibition is associated with attenuation of atherosclerosis and associated ischemic injury. LOX-1 may be a novel, exciting target for drug therapy.     

氧化型低密度脂蛋白对人血管平滑肌细胞透明质酸表达的影响及机制

目的观察氧化型低密度脂蛋白(ox-LDL)对人主动脉血管平滑肌细胞透明质酸(HA)合成的影响,并初步探究其分子机制。方法体外培养人主动脉血管平滑肌细胞T/G HAVSMC,使用不同浓度(10、25、50、75、100 mg/L)ox-LDL对T/G HAVSMC细胞进行干预,使用CCK-8法检测细胞存活率,并进行分组分析。采用浓度为25和50 mg/L的ox-LDL干预T/G HAVSMC细胞48 h,并设置天然LDL(native-LDL,N-LDL)组(50 mg/L的N-LDL)和对照组,使用HPLC法测定HA含量,使用实时定量PCR检测透明质酸合成酶2(HAS2)和透明质酸合成酶3(HAS3)的mRNA表达,使用Western blot法检测凝集素样氧化型低密度脂蛋白受体1(LOX-1)、低密度脂蛋白受体相关蛋白1(LRP-1)、氧化脂蛋白的清道夫受体(SR-PSOX)以及脂肪酸转位酶(CD36)的表达。结果低于100 mg/L的ox-LDL对T/G HAVSMC细胞无明显细胞毒性。25 mg/L和50 mg/L ox-LDL组HA含量、HAS2和HAS3的mRNA表达量明显高于N-LDL组和对照组(P0.05),N-LDL组与对照组组间差异无显著性(P0.05)。25 mg/L和50 mg/L ox-LDL组LOX-1表达明显高于N-LDL组和对照组(P0.05),而LRP-1、SR-PSOX和CD36表达无明显变化(P0.05)。结论 ox-LDL能够诱导人主动脉平滑肌细胞中HA的合成,其机制可能与结合LOX-1有关。     

Nebivolol and its 4-keto derivative increase nitric oxide in endothelial cells by reducing its oxidative inactivation

OBJECTIVES: The objective of the present study was to elucidate the vasodilator mechanisms of nebivolol, a high selective beta(1)-receptor antagonist with antioxidant properties. BACKGROUND: Oxidative inactivation of nitric oxide (NO) is regarded as an important cause of its decreased biological activity. METHODS: Oxidative stress was induced through the binding of oxidized (ox)-low-density lipoprotein (LDL) to its specific endothelial receptor, called "lectin-like oxidized LDL receptor-1" (LOX-1), in bovine and human endothelial cells and in Chinese hamster ovary cells stably expressing bovine LOX-1 (BLOX-1-CHO cells). Reactive oxygen species (ROS), superoxide (O(2)(*-)), and NO were measured in cells by flow cytometry. RESULTS: Nebivolol and its 4-keto derivative prevented in a dose-dependent manner the increase of ROS (p < 0.001) and O(2)(*-) (p < 0.001) in bovine aortic endothelial cells (BAECs), human umbilical vein endothelial cells (HUVECs), and BLOX-1-CHO cells stimulated with ox-LDL. Atenolol had no effect. The incubation of HUVECs and BAECs with ox-LDL reduced basal and bradykinin-induced NO and nitrite concentration (p from <0.001 to <0.01). Nebivolol and its 4-keto derivative prevented the reduction of basal and stimulated NO and nitrite concentration (p from <0.001 to <0.01) while atenolol had no effect. The preincubation of BAECs with blocking anti-LOX-1 monoclonal antibody (LOX-1 mAb) significantly counteracted the effect of ox-LDL on stimulated generation of NO (p < 0.001), but the effect was significantly lower than that of nebivolol and its 4-keto derivative alone (p < 0.01). CONCLUSIONS: In conclusion, the findings of the present study indicate that nebivolol increases NO also by decreasing its oxidative inactivation.     

LOX-1 deletion alters signals of myocardial remodeling immediately after ischemia-reperfusion

OBJECTIVE: Chronic ischemia is associated with alterations in genes that result in myocardial remodeling. An important biochemical basis of cardiac remodeling is generation of reactive oxygen species (ROS). A few studies have suggested that acute ischemia triggers signals for remodeling. We examined the hypothesis that targeted deletion of lectin-like oxidized-LDL receptor (LOX-1) may inhibit signals related to cardiac remodeling. METHODS AND RESULTS: We generated LOX-1 knockout (KO) mice on C57BL/6 (wild-type mice) background, and subjected wild-type and KO mice to ischemia-reperfusion (I-R). The wild-type mice developed a marked reduction in left ventricular systolic pressure and +/-dp/dt(max) and an increase in left ventricular end-diastolic pressure following I-R, and this change was much less in the LOX-1 KO mice, indicating preservation of left ventricular function with LOX-1 deletion. There was evidence for marked oxidative stress (NADPH oxidase expression, malondialdehyde and 8-isoprostane) following I-R in the wild-type mice, much less so in the LOX-1 KO mice (P<0.01). In concert, collagen deposition (Masson's trichrome and Picro-sirius red staining) increased dramatically in the wild-type mice, but only half as much in the LOX-1 KO mice (P<0.01). Collagen staining data was corroborated with procollagen-I expression. Further, fibronectin and osteopontin expression increased in the wild-type mice, but to a much smaller extent in the LOX-1 KO mice (P<0.01). CONCLUSIONS: These findings provide compelling evidence that LOX-1 is a key modulator of cardiac remodeling which starts immediately following I-R.     

Ox-LDL induces endothelial cell apoptosis via the LOX-1-dependent endoplasmic reticulum stress pathway

Objective

To investigate the effect of lectin-like ox-LDL receptor-1 (LOX-1) on oxidized low-density lipoprotein (ox-LDL)-induced apoptosis and the involvement of the endoplasmic reticulum (ER) stress response pathway.

Methods and results

Human umbilical vein endothelial cells were treated with 50, 100, or 200 μg/ml ox-LDL and cultured for 12, 24, or 48 h for concentration- and time-dependent studies. Cells were transfected with LOX-1 or Nox-4 shRNAs, and target proteins were inhibited with the corresponding antibodies for mechanistic studies. Active proteins and mRNAs were analyzed by Western blotting and RT-PCR, respectively. Cell apoptosis was analyzed by Annexin and Hoechst staining assays. Ox-LDL induced both apoptosis and protein expression of LOX-1 and Nox-4 through activation of ER stress sensors IRE1 and PERK, and nuclear translocation of ATF6 and their subsequent pathways were indicated by JNK, eukaryotic initiation factor 2 phosphorylation, XBP-1, and chaperone GRP78 expression; up-regulation of proapoptotic proteins CHOP and Bcl-2; and caspase-12 activity. LOX-1 gene silencing and treatment with an anti-LOX-1 antibody attenuated the effects of ox-LDL. Pretreatment with irestatin 9389, salubrinal, or AEBSF also blocked ox-LDL-induced expression of CHOP and Bcl-2 and activation of caspase-12 activity, leading to an attenuation of endothelial cell apoptosis. Furthermore, Nox-4 siRNA attenuated the up-regulated expression of GRP78, PERK, IRE1, and XBP-1 to reduce ox-LDL-induced endothelial cell apoptosis.

Conclusions

LOX-1 plays a critical role in ox-LDL-induced endothelial cell apoptosis via the ER stress pathway.     

Betaxolol stimulates eNOS production associated with LOX-1 and VEGF in Dahl salt-sensitive rats

OBJECTIVE: Lectin-like oxidized low-density lipoprotein receptor-1 (LOX-1) and vascular endothelial growth factor (VEGF) may play key roles in atherosclerosis, and have been shown to regulate nitric oxide (NO) production. However, the molecular mechanisms by which betaxolol, a specific beta 1-antagonist, stimulates endothelial NO synthase (eNOS) expression associated with LOX-1 and VEGF are unclear. We hypothesized that in the left ventricle of Dahl salt-sensitive (DS) rats, betaxolol reduces production of LOX-1 by suppressing NAD(P)H oxidase p47phox expression; betaxolol stimulates eNOS production associated with expression of VEGF and LOX-1; and betaxolol inhibits adhesion molecule and signal transduction, which may be involved in cardiovascular remodeling. METHODS: After 5 weeks of feeding an 8% NaCl diet to 6-week-old DS rats (i.e. at 11 weeks of age), a distinct stage of concentric left ventricular hypertrophy was noted. Betaxolol (0.9 mg/kg per day) was administered to 6-week-old DS rats for 5 weeks until the onset of left ventricular hypertrophy stage. RESULTS: Decreased expression of eNOS and VEGF in DS rats was increased by betaxolol. Upregulated LOX-1, NAD(P)H oxidase p47phox, intercellular and vascular cell adhesion molecule-1 expression and phosphorylations of p38 mitogen-activated protein kinase and p65 nuclear factor-kappa B activity were inhibited by betaxolol. Betaxolol administration resulted in significant improvement of cardiovascular remodeling and suppression of transforming growth factor-beta 1 and type I collagen expression. CONCLUSIONS: These results suggest that cardioprotective effects of betaxolol may stimulate eNOS production associated with VEGF and LOX-1, and inhibit adhesion molecule and signal transduction in DS rats.