Oxidized LDL but not angiotensin II induces cardiomyocyte hypertrophic responses through the interaction between LOX-1 and AT1 receptors.

It is well known that lectin-like oxidized low-density lipoprotein (ox-LDL) and its receptor LOX-1, angiotensin II (AngII) and its type 1 receptor (AT1-R) play an important role in the development of cardiac hypertrophy. However, the molecular mechanism is not clear. In this study, we found that ox-LDL-induced cardiac hypertrophy was suppressed by inhibition of LOX-1 or AT1-R but not by AngII inhibition. These results suggest that the receptors LOX-1 and AT1-R, rather than AngII, play a key role in the role of ox-LDL. The same results were obtained in mice lacking endogenous AngII and their isolated cardiomyocytes. Ox-LDL but not AngII could induce the binding of LOX-1 and AT1-R; inhibition of LOX-1 or AT1-R but not AngII could abolish the binding of these two receptors. Overexpression of wild type LOX-1 with AT1-R enhanced ox-LDL-induced binding of two receptors and phosphorylation of ERKs, however, transfection of LOX-1 dominant negative mutant (lys266ala / lys267ala) or an AT1-R mutant (glu257ala) not only reduced the binding of two receptors but also inhibited the ERKs phosphorylation. Phosphorylation of ERKs induced by ox-LDL in LOX-1 and AT1-R-overexpression cells was abrogated by an inhibitor of Gq protein rather than Jak2, Rac1 or RhoA. Genetically, an AT1-R mutant lacking Gq protein coupling ability inhibited ox-LDL induced ERKs phosphorylation. Furthermore, through bimolecular fluorescence complementation analysis, we confirmed that ox-LDL rather than AngII stimulation induced the direct binding of LOX-1 and AT1-R. We conclude that direct binding of LOX-1 and AT1-R and the activation of downstream Gq protein are important mechanisms of ox-LDL-induced cardiomyocyte hypertrophy.

Oxidized Low-Density Lipoprotein Receptor in Lymphocytes Prevents Atherosclerosis and Predicts Subclinical Disease.

BACKGROUND: Although the role of Th17 and regulatory T cells in the progression of atherosclerosis has been highlighted in recent years, their molecular mediators remain elusive. We aimed to evaluate the association between the CD69 receptor, a regulator of Th17/regulatory T cell immunity, and atherosclerosis development in animal models and in patients with subclinical disease. METHODS: Low-density lipoprotein receptor-deficient chimeric mice expressing or not expressing CD69 on either myeloid or lymphoid cells were subjected to a high fat diet. In vitro functional assays with human T cells were performed to decipher the mechanism of the observed phenotypes. Expression of CD69 and NR4A nuclear receptors was evaluated by reverse transcription-polymerase chain reaction in 305 male participants of the PESA study (Progression of Early Subclinical Atherosclerosis) with extensive (n=128) or focal (n=55) subclinical atherosclerosis and without disease (n=122). RESULTS: After a high fat diet, mice lacking CD69 on lymphoid cells developed large atheroma plaque along with an increased Th17/regulatory T cell ratio in blood. Oxidized low-density lipoprotein was shown to bind specifically and functionally to CD69 on human T lymphocytes, inhibiting the development of Th17 cells through the activation of NR4A nuclear receptors. Participants of the PESA study with evidence of subclinical atherosclerosis displayed a significant CD69 and NR4A1 mRNA downregulation in peripheral blood leukocytes compared with participants without disease. The expression of CD69 remained associated with the risk of subclinical atherosclerosis in an adjusted multivariable logistic regression model (odds ratio, 0.62; 95% CI, 0.40-0.94; P=0.006) after adjustment for traditional risk factors, the expression of NR4A1, the level of oxidized low-density lipoprotein, and the counts of different leucocyte subsets. CONCLUSIONS: CD69 depletion from the lymphoid compartment promotes a Th17/regulatory T cell imbalance and exacerbates the development of atherosclerosis. CD69 binding to oxidized low-density lipoprotein on T cells induces the expression of anti-inflammatory transcription factors. Data from a cohort of the PESA study with subclinical atherosclerosis indicate that CD69 expression in PBLs inversely correlates with the presence of disease. The expression of CD69 remained an independent predictor of subclinical atherosclerosis after adjustment for traditional risk factors.

The effects of coenzyme Q10 supplementation on gene expression related to insulin, lipid and inflammation in patients with polycystic ovary syndrome.

OBJECTIVE: This research was conducted to assess the effects of coenzyme Q10 (CoQ10) intake on gene expression related to insulin, lipid and inflammation in subjects with polycystic ovary syndrome (PCOS). METHODS: This randomized double-blind, placebo-controlled trial was conducted on 40 subjects diagnosed with PCOS. Subjects were randomly allocated into two groups to intake either 100 mg CoQ10 (n = 20) or placebo (n = 20) per day for 12 weeks. Gene expression related to insulin, lipid and inflammation were quantified in blood samples of PCOS women with RT-PCR method. RESULTS: Results of RT-PCR shown that compared with the placebo, CoQ10 intake downregulated gene expression of oxidized low-density lipoprotein receptor 1 (LDLR) (p < 0.001) and upregulated gene expression of peroxisome proliferator-activated receptor gamma (PPAR-γ) (p = 0.01) in peripheral blood mononuclear cells of subjects with PCOS. In addition, compared to the placebo group, CoQ10 supplementation downregulated gene expression of interleukin-1 (IL-1) (p = 0.03), interleukin-8 (IL-8) (p = 0.001) and tumor necrosis factor alpha (TNF-α) (p < 0.001) in peripheral blood mononuclear cells of subjects with PCOS. CONCLUSIONS: Overall, CoQ10 intake for 12 weeks in PCOS women significantly improved gene expression of LDLR, PPAR-γ, IL-1, IL-8 and TNF-α.

Oxidized LDL (oxLDL) activates the angiotensin II type 1 receptor by binding to the lectin-like oxLDL receptor.

The angiotensin II type 1 receptor (AT1) is a 7-transmembrane domain GPCR that when activated by its ligand angiotensin II, generates signaling events promoting vascular dysfunction and the development of cardiovascular disease. Here, we show that the single-transmembrane oxidized LDL (oxLDL) receptor (LOX-1) resides in proximity to AT1 on cell-surface membranes and that binding of oxLDL to LOX-1 can allosterically activate AT1-dependent signaling events. oxLDL-induced signaling events in human vascular endothelial cells were abolished by knockdown of AT1 and inhibited by AT1 blockade (ARB). oxLDL increased cytosolic G protein by 350% in Chinese hamster ovary (CHO) cells with genetically induced expression of AT1 and LOX-1, whereas little increase was observed in CHO cells expressing only LOX-1. Immunoprecipitation and in situ proximity ligation assay (PLA) assays in CHO cells revealed the presence of cell-surface complexes involving LOX-1 and AT1. Chimeric analysis showed that oxLDL-induced AT1 signaling events are mediated via interactions between the intracellular domain of LOX-1 and AT1 that activate AT1. oxLDL-induced impairment of endothelium-dependent vascular relaxation of vascular ring from mouse thoracic aorta was abolished by ARB or genetic deletion of AT1. These findings reveal a novel pathway for AT1 activation and suggest a new mechanism whereby oxLDL may be promoting risk for cardiovascular disease.

Increased LDL electronegativity in chronic kidney disease disrupts calcium homeostasis resulting in cardiac dysfunction.

Chronic kidney disease (CKD), an independent risk factor for cardiovascular disease, is associated with abnormal lipoprotein metabolism. We examined whether electronegative low-density lipoprotein (LDL) is mechanistically linked to cardiac dysfunction in patients with early CKD. We compared echocardiographic parameters between patients with stage 2 CKD (n = 88) and normal controls (n = 89) and found that impaired relaxation was more common in CKD patients. Reduction in estimated glomerular filtration rate was an independent predictor of left ventricular relaxation dysfunction. We then examined cardiac function in a rat model of early CKD induced by unilateral nephrectomy (UNx) by analyzing pressure-volume loop data. The time constant of isovolumic pressure decay was longer and the maximal velocity of pressure fall was slower in UNx rats than in controls. When we investigated the mechanisms underlying relaxation dysfunction, we found that LDL from CKD patients and UNx rats was more electronegative than LDL from their respective controls and that LDL from UNx rats induced intracellular calcium overload in H9c2 cardiomyocytes in vitro. Furthermore, chronic administration of electronegative LDL, which signals through lectin-like oxidized LDL receptor-1 (LOX-1), induced relaxation dysfunction in wild-type but not LOX-1(-/-) mice. In in vitro and in vivo experiments, impaired cardiac relaxation was associated with increased calcium transient resulting from nitric oxide (NO)-dependent nitrosylation of SERCA2a due to increases in inducible NO synthase expression and endothelial NO synthase uncoupling. In conclusion, LDL becomes more electronegative in early CKD. This change disrupts SERCA2a-regulated calcium homeostasis, which may be the mechanism underlying cardiorenal syndrome.

Diet-induced increase in plasma oxidized LDL promotes early fibrosis in a renal porcine auto-transplantation model.

BACKGROUND: In kidney transplantation, the prevalence of hypercholesterolemia as a co-morbidity factor known to affect graft function, is rising due to the increased number of older donors in response to organ shortage as well as to the hyperlipidemic effects of immunosuppressors in recipient. This study aimed to characterize the effects of hypercholesterolemia on renal graft outcome, investigating the role of oxidized low-density lipoprotein (OxLDL). METHODS: In vivo, we used a porcine preclinical model of renal auto-transplantation modulated by two experimental diets: a normal (n = 6) or a hyperlipidemic diet (n = 5) maintained during the 3 month follow-up after the surgical procedure. Kidney function and OxLDL levels were monitored as well as fibrosis, LOX-1 and TGF beta signaling pathways. In vitro, we used human artery endothelial cells subjected to OxLDL to investigate the TGF beta profibrotic pathway and the role of the scavenger receptor LOX-1. RESULTS: Hyperlipidemic diet-induced increase in plasma OxLDL levels at the time of surgery correlated with an increase in proteinuria 3 months after transplantation, associated with an early graft fibrosis combined with an activation of renal TGF beta signaling. These data suggest a direct involvement of OxLDL in the hyperlipidemic diet-induced activation of the pro-fibrotic TGF beta pathway which seems to be activated by LOX-1 signaling. These results were supported by studies with endothelial cells incubated in culture medium containing OxLDL promoting TGF beta expression inhibited by LOX-1 antibody. CONCLUSIONS: These results implicate OxLDL in the hyperlipidemic diet-promoted fibrosis in transplanted kidneys, suggesting LOX-1 as a potential therapeutic target and reinforce the need to control cholesterol levels in kidney transplant recipients.

Transient receptor potential channel TRPM4 favors oxidized low-density lipoprotein-induced coronary endothelial cell dysfunction via a mechanism involving ferroptosis.

Accelerating the repair of damaged endothelium can effectively inhibit the progression of atherosclerosis (AS). Transient receptor potential channel TRPM4 is a non-selective cation channel activated by internal Ca2+, which is expressed in endothelial cells. This study aimed to reveal the potential role of TRPM4 in AS along with the mechanism. Human coronary artery endothelial cells (HCAECs) induced by ox-LDL was regarded as an in vitro model. The impacts of TRPM4 knockdown on cellular inflammation response, oxidative stress, normal endothelial function and lipid peroxidation were evaluated. Given that ferroptosis promotes AS progression, the effects of TRPM4 on intracellular iron ions and ferroptosis-related proteins was determined. Afterwards, HCAECs were treated with ferroptosis inducer erastin, and the influence of ferroptosis in the cellular model was revealed. TRPM4 was elevated in response to ox-LDL treatment in HCAECs. TRPM4 knockdown reduced the inflammation response, oxidative stress and lipid peroxidation caused by ox-LDL, and maintained the normal function of HCAECs. Erastin treatment destroyed the impacts of TRPM4 knockdown that are beneficial for cells to resist ox-LDL, showing the enhancement of the above adverse factors. Together, this study found that TRPM4 knockdown reduced ox-LDL-induced inflammation, oxidative stress, and dysfunction in HCAECs, possibly via a mechanism involving Fe2+ and ferroptosis-related proteins.

[Relationship of ox-LDL/LOX-1 and vascular endothelial dysfunction of diet-induced obese immature rats and nicotinic acid's intervention outcomes].

OBJECTIVE: To explore the effects of nicotinic acid intervention on vascular endothelial dysfunction mediated by oxidized low density lipoprotein (ox-LDL)/lectin-like oxidized low density lipoprotein receptor-1 (LOX-1) in diet-induced obese immature rats and its possible mechanism through detecting the expression levels of ox-LDL and LOX-1 in abdominal aorta. METHODS: A model of diet-induced obese immature rats was established by high-fat diet. And 30 immature rats were divided randomly and equally into control (n = 10), high-fat (n = 10) and drug control (n = 10) groups. At the end of 12 weeks, the levels of serum total cholesterol (TC), triglyceride (TG), LDL and high-density lipoprotein (HDL) were examined. The levels of ox-LDL, soluble intercellular adhesion molecule-1 (sICAM-1), endothelin and nitric oxide (NO) were detected. The gene and protein expressions of LOX-1 and ICAM-1 in abdominal aorta were detected. And the location protein expressions of LOX-1 and ICAM-1 were examined. RESULTS: High-fat diet induced hyperlipidemia and obesity in immature rats. The serum levels of TG, TC, LDL, ox-LDL and endothelin in high-fat and drug control groups were all higher than control group ((0.98 ± 0.12) and (0.69 ± 0.06) vs (0.49 ± 0.06) mmol/L, (2.11 ± 0.16) and (1.62 ± 0.12) vs (1.30 ± 0.12) mmol/L, (0.71 ± 0.04) and (0.50 ± 0.03) vs (0.30 ± 0.04) mmol/L, (44.2 ± 5.1) and (33.7 ± 2.1) vs (26.6 ± 2.9) µg/L, (187 ± 10) and (157 ± 6) vs (118 ± 7) pg/ml). The indices in high-fat group were higher than those in drug control group (all P < 0.01) . The levels of HDL and NO in high-fat and drug control groups were lower than those in control group (all P < 0.01); the levels of HDL and NO in high-fat group lower than those in drug control group (all P < 0.01). And the levels of LOX-1, ICAM-1 protein and mRNA in high-fat group were higher than those in drug control and control groups (all P < 0.01).ox-LDL was correlated positively with LOX-1, TC, TG, LDL, endothelin and ICAM-1 (r = 0.918, 0.867, 0.857, 0.834, 0.869, 0.644, all P < 0.01) , but negatively with NO and HDL (r = -0.823, -0.872, P < 0.01) . CONCLUSION: Early treatment of nicotinic acid can protect endothelial function through inducing therapeutic effects on hyperlipidemia and antioxidation and down-regulating the expression level of ox-LDL/LOX-1 in vascular endothelium.

LOX-1: a multiligand receptor at the crossroads of response to danger signals.

PURPOSE OF REVIEW: LOX-1 is a multiligand receptor implicated in endothelial dysfunction and atherosclerosis, although it was originally identified as an oxidized LDL receptor. In this review, the roles of various LOX-1 ligands and their interaction with LOX-1 are discussed to understand the pathophysiological significance of LOX-1. RECENT FINDINGS: LOX-1 knockout mice showed resistance of endothelium-dependent vasorelaxation against oxidized LDL and retardation of atherosclerosis progression. LOX-1 ligand reduction in mice also attenuated atherosclerosis progression. In a human cohort study, high concentration of apoB-containing LOX-1 ligands predicted the incidence of cardiovascular disease. Furthermore, modified HDL, which existed in high concentration in the plasma of coronary artery disease patients, was found to induce impairment of endothelial nitric oxide release via LOX-1. In addition to lipoproteins, LOX-1 was found to work as a C-reactive protein receptor providing a scaffold for the activation of the complement system. SUMMARY: LOX-1 is a unique molecule among the sensors of danger signals. LOX-1 is not only sensing danger signals such as modified LDL and heat shock protein, but also scaffolding other danger sensors including C-reactive protein and C1q, and directly commanding responses to danger signals by working as a cell adhesion molecule. Via these functions, LOX-1 might work as a surveillance molecule of vascular homeostasis.

Unsaturated FAs prevent palmitate-induced LOX-1 induction via inhibition of ER stress in macrophages.

Palmitic acid (PA) upregulates oxidized LDL receptor-1 (LOX-1), a scavenger receptor responsible for uptake of oxidized LDL (oxLDL), and enhances oxLDL uptake in macrophages. However, the precise underlying mechanism remains to be elucidated. PA is known to induce endoplasmic reticulum (ER) stress in various cell types. Therefore, we investigated whether ER stress is involved in PA-induced LOX-1 upregulation. PA induced ER stress, as determined by phosphorylation of PERK, eIF2α, and JNK, as well as induction of CHOP in macrophage-like THP-1 cells. Inhibitors [4-phenylbutyric acid (PBA), sodium tauroursodeoxycholate (TUDCA), and salubrinal] and small interfering RNA (siRNA) for the ER stress response decreased PA-induced LOX-1 upregulation. Thapsigargin, an ER stress inducer, upregulated LOX-1, which was decreased by PBA and TUDCA. We next examined whether unsaturated FAs could counteract the effect of PA. Both oleic acid (OA) and linoleic acid (LA) suppressed PA-induced LOX-1. Activation of the ER stress response observed in the PA-treated cells was markedly attenuated when the cells were cotreated with OA or LA. In addition, OA and LA suppressed thapsigargin-induced LOX-1 upregulation with reduced activation of ER stress markers. Our results indicate that activation of ER stress is involved in PA-induced LOX-1 upregulation in macrophages, and that OA and LA inhibit LOX-1 induction through suppression of ER stress.

[Autophagy of human vascular endothelial cells by oxidized low-density lipoprotein: involvement of oxidative stress but no oxidized low density lipoprotein-1].

OBJECTIVE: Our previous studies found that 100 µg/ml oxidized low-density lipoprotein (ox-LDL) could up-regulate the autophagic level in human umbilical vein endothelial cells (HUVEC). The present study was conducted to observe the roles of oxidative stress and lectin-like oxidized low density lipoprotein-1 (LOX-1) in the ox-LDL-induced up-regulation of autophagy. METHODS: Prior to the ox-LDL exposure, LOX-1mAb, vitamin C and vitamin E were used to study the roles of LOX-1 and oxidative stress in the activation of autophagy. The contents of total-superoxide dismutase (T-SOD) and MDA (malondialdehyde) in the culture medium were detected with enzyme linked immunosorbent assay. Western blot was employed to detect the levels of autophagic marker microtubule-associated protein light chain 3 (MAP1-LC3)-II/LC3-I, beclin1 and lysosome associated membrane protein 2a (lamp2a). RESULTS: After the ox-LDL exposure, the down-regulated level of T-SOD [0.5 h (32.73 ± 1.09 vs 40.16 ± 1.28) U/ml, P < 0.01; 6 h (29.32 ± 1.56 vs 40.16 ± 1.28) U/ml, P < 0.01] and the up-regulated level of MDA [0.5 h (1.11 ± 0.04 vs 0.57 ± 0.05) nmol/ml, P < 0.01; 6 h (0.69 ± 0.03 vs 0.57 ± 0.05) nmol/ml, P < 0.05] in culture medium were also significant at 0.5 h and 6 h. The ox-LDL-induced increased ratio of LC3-II/LC3-I was reversed by the pretreatments of vitamin C and vitamin E (0.5 h, vitC: 3.11 ± 0.02 vs 4.31 ± 0.50, P < 0.05; vitE: 3.46 ± 0.19 vs 4.31 ± 0.50, P < 0.05; 6 h, vitC: 1.44 ± 0.05 vs 2.31 ± 0.16, P < 0.05), but not LOX-1mAb. LOX-1mAb decreased the ox-LDL-induced elevated level of lamp2a protein while vitamin C and vitamin E only inhibited the elevation of lamp2a at the timepoint of 6 h, but not 0.5 h. CONCLUSION: Oxidative stress, rather than LOX-1, plays an important role in the ox-LDL-induced up-regulation of autophagy in HUVEC. The formation of autolysosomes is associated with the LOX-1-mediated endocytosis of ox-LDL. Oxidative stress only plays a minor role in the formation of autolysosomes induced by the engulfed ox-LDL.

C-reactive protein uptake by macrophage cell line via class-A scavenger receptor.

BACKGROUND: C-reactive protein (CRP) increases in response to inflammation and is purported to be a risk factor for atherogenesis. We recently demonstrated that a scavenger receptor, lectin-like oxidized LDL receptor (LOX-1), is a receptor for CRP. In light of the overlapping ligand spectrum of scavenger receptors such as modified LDL, bacteria, and advanced glycation end products, we examined whether other scavenger receptors recognize CRP. METHODS: We analyzed the uptake of fluorescently labeled CRP in COS-7 cells expressing a series of scavenger receptors and in a monocytic cell line, THP-1, differentiated into macrophage with phorbol 12-myristate 13-acetate (PMA). We applied small interfering RNA (siRNA) against class-A scavenger receptor (SR-A) to THP-1 cells to suppress the expression of SR-A. We also analyzed the binding of nonlabeled CRP to immobilized recombinant LOX-1 and SR-A in vitro using anti-CRP antibody. RESULTS: COS-7 cells expressing LOX-1 and SR-A internalized fluorescently labeled CRP in a dose-dependent manner, but cells expressing CD36, SR-BI, or CD68 did not. The recombinant LOX-1 and SR-A proteins recognized nonlabeled purified CRP and native CRP in serum in vitro. THP-1 cells differentiated into macrophage-like cells by treatment with PMA-internalized fluorescently labeled CRP. siRNA against SR-A significantly and concomitantly inhibited the expression of SR-A (P < 0.01) and CRP uptake (P < 0.01), whereas control siRNA did not. CONCLUSIONS: CRP is recognized by SR-A as well as LOX-1 and taken up via SR-A in a macrophage-like cell line. This process might be of significance in the pathogenesis of atherosclerotic disease.

Regulation of the migration and survival of monocyte subsets by chemokine receptors and its relevance to atherosclerosis.

Monocytes are central mediators in the advance of atherosclerotic plaque, making them a natural therapeutic target for reducing disease burden. Here, we highlight recent advances in our current understanding of monocyte heterogeneity and its relevance to regulation of monocyte accumulation and function within atherosclerotic plaques. Differences that distinguish monocyte subsets include differential expression of chemokine receptors, especially CCR2 and CX3CR1. Ablation of expression of these 2 receptors (or their ligands) in mice has an additive inhibition on monocyte recruitment to atherosclerotic plaques. Moreover, simultaneously interfering with 3 key pathways--CCR2, CX3CR1, and CCR5--essentially abolishes atherosclerosis in mice. Here, we discuss how these chemokine receptors act at multiple points on at least 1 monocyte subset, regulating their mobilization from bone marrow, survival, or recruitment to plaques. Finally, we discuss how this knowledge may be useful clinically, emphasizing that CX3CR1 may in particular be a viable target for therapeutic manipulation of monocyte-derived cell fate in cardiovascular disease.

Leonurus sibiricus herb extract suppresses oxidative stress and ameliorates hypercholesterolemia in C57BL/6 mice and TNF-alpha induced expression of adhesion molecules and lectin-like oxidized LDL receptor-1 in human umbilical vein endothelial cells.

In Leonurus sibiricus herb extract (LHE)-supplemented animals, plasma cholesterol decreased and high-density lipoprotein-cholesterol increased, resulting in a lowered atherogenic index. The plasma trolox equivalent antioxidant capacity, levels of hepatic thiobarbituric acid-reactive substances, and protein carbonyl values decreased significantly in LHE-supplemented mice (p<0.05), whereas the hepatic antioxidant indicators were all significantly elevated (p<0.05). In human umbilical vein endothelial cells stimulated with tumor necrosis factor alpha, LHE significantly suppressed intracellular reactive oxygen species, LOX-1, and adhesion molecules. LHE supplementation may modulate the lipoprotein composition and attenuate oxidative stress by elevated antioxidant processes, thus suppressing the activation of inflammatory mediators. This is a possible mechanism of the anti-atherogenic effect.

Impact of plasma oxidized low-density lipoprotein removal on atherosclerosis.

BACKGROUND: Several clinical studies of statin therapy have demonstrated that lowering low-density lipoprotein (LDL) cholesterol prevents atherosclerotic progression and decreases cardiovascular mortality. In addition, oxidized LDL (oxLDL) is suggested to play roles in the formation and progression of atherosclerosis. However, whether lowering oxLDL alone, rather than total LDL, affects atherogenesis remains unclear. METHODS AND RESULTS: To clarify the atherogenic impact of oxLDL, lectin-like oxLDL receptor 1 (LOX-1), an oxLDL receptor, was expressed ectopically in the liver with adenovirus administration in apolipoprotein E-deficient mice at 46 weeks of age. Hepatic LOX-1 expression enhanced hepatic oxLDL uptake, indicating functional expression of LOX-1 in the liver. Although plasma total cholesterol, triglyceride, and LDL cholesterol levels were unaffected, plasma oxLDL was markedly and transiently decreased in LOX-1 mice. In controls, atherosclerotic lesions, detected by Oil Red O staining, were markedly increased (by 38%) during the 4-week period after adenoviral administration. In contrast, atherosclerotic progression was almost completely inhibited by hepatic LOX-1 expression. In addition, plasma monocyte chemotactic protein-1 and lipid peroxide levels were decreased, whereas adiponectin was increased, suggesting decreased systemic oxidative stress. Thus, LOX1 expressed in the livers of apolipoprotein E-deficient mice transiently removes oxLDL from circulating blood and possibly decreases systemic oxidative stress, resulting in complete prevention of atherosclerotic progression despite the persistence of severe LDL hypercholesterolemia and hypertriglyceridemia. CONCLUSIONS: OxLDL has a major atherogenic impact, and oxLDL removal is a promising therapeutic strategy against atherosclerosis.

Internal mammary artery smooth muscle cells resist migration and possess high antioxidant capacity.

OBJECTIVE: This study investigated whether differences exist in atherogen-induced migratory behaviors and basal antioxidant enzyme capacity of vascular smooth muscle cells (VSMC) from human coronary (CA) and internal mammary (IMA) arteries. METHODS: Migration experiments were performed using the Dunn chemotaxis chamber. The prooxidant [NAD(P)H oxidase] and antioxidant [NOS, superoxide dismutase, catalase and glutathione peroxidase] enzyme activities were determined by specific assays. RESULTS: Chemotaxis experiments revealed that while both sets of VSMC migrated towards platelet-derived growth factor-BB (1-50 ng/ml) and angiotensin II (1-50 nM), neither oxidized-LDL (ox-LDL, 25-100 microg/ml) nor native LDL (100 microg/ml) affected chemotaxis in IMA VSMC. However, high dose ox-LDL produced significant chemotaxis in CA VSMC that was inhibited by pravastatin (100 nM), mevastatin (10 nM), losartan (10 nM), enalapril (1 microM), and MnTBAP (a free radical scavenger, 50 microM). Microinjection experiments with isoprenoids i.e. geranylgeranylpyrophosphate (GGPP) and farnesylpyrophosphate (FPP) showed distinct involvement of small GTPases in atherogen-induced VSMC migration. Significant increases in antioxidant enzyme activities and nitrite production along with marked decreases in NAD(P)H oxidase activity and O2- levels were determined in IMA versus CA VSMC. CONCLUSIONS: Enhanced intrinsic antioxidant capacity may confer on IMA VSMC resistance to migration against atherogenic agents. Drugs that regulate ox-LDL or angiotensin II levels also exert antimigratory effects.

Cyclic tensile stretch load and oxidized low density lipoprotein synergistically induce lectin-like oxidized ldl receptor-1 in cultured bovine chondrocytes, resulting in decreased cell viability and proteoglycan synthesis.

Mechanical stimulation is known to be an essential factor in the regulation of cartilage metabolism. We tested the hypothesis that expression of lectin-like oxidized low-density lipoprotein receptor-1 (LOX-1) can be modulated by cyclic tensile stretch load in chondrocytes. Cyclic loading of repeated stretch stress at 10 cycles per minute with 10 kPa of stress for 6 h induced expression of LOX-1 to 2.6 times control in cultured bovine articular chondrocytes, equivalent to the addition of 10 microg/mL oxidized low density lipoprotein (ox-LDL) (2.4 times control). Application of the cyclic load to the chondrocytes along with 10 microg/mL ox-LDL resulted in synergistically increased LOX-1 expression to 6.3 times control. Individual application of cyclic loading and 10 microg/mL ox-LDL significantly suppressed chondrocytes viability (84.6% +/- 3.4% and 80.9% +/- 3.2% of control at 24 h, respectively; n = 3; p < 0.05) and proteoglycan synthesis [81.0% +/- 7.1% and 85.7% +/- 5.2% of control at 24 h, respectively; p < 0.05 when compared with 94.6% +/- 4.6% for native-LDL (n = 3)]. Cyclic loading and 10 microg/mL ox-LDL synergistically affected cell viability and proteoglycan synthesis, which were significantly suppressed to 45.6% +/- 4.9% and 48.7% +/- 6.7% of control at 24 h, respectively (n = 3; p < 0.01 when compared with individual application of cyclic loading or 10 microg/mL ox-LDL). In this study, we demonstrated synergistic effects of cyclic tensile stretch load and ox-LDL on cell viability and proteoglycan synthesis in chondrocytes, which may be mediated through enhanced expression of LOX-1 and which has important implications in the progression of cartilage degeneration in osteoarthritis.

Adipocyte: a potential target for the treatment of atherosclerosis.

Obesity is an independent risk factor for coronary heart disease, whereas the underlying mechanisms have not been fully elucidated. Adipocytes may produce various adipokines with favorable and unfavorable cardiovascular effects. The dysregulated secretion of adipokines by adipocytes may contribute to obese associated atherosclerosis. Adipocytes can also function as phagocytes to uptake and degrade oxidized low-density lipoprotein (Ox-LDL), suggesting that adipocytes possibly involve in clearance of Ox-LDL in blood. The dysfunctional adipocytes might be implicated in the atherogenesis. Some cardioprotective drugs mediate their cardiovascular benefits partly through their direct beneficial effects on adipocytes. Therefore, we hypothesized that adipocytes might be potential target for the treatment of atherosclerosis.

[Lox-1--an actor in cardiovascular disease?]. / LOX-1--en aktør ved hjerte- og karsykdommer?

BACKGROUND: Among risk factors such as smoking, hypertension and LDL cholesterol, oxidized LDL (ox-LDL) has emerged as a new and interesting factor. Scavenger receptors are a group of cell-surface receptors located on various cell types within the vessel wall with special affinity for ox-LDL. Of all the scavenger receptors involved in coronary heart disease, the lectin-like oxidized low-density lipoprotein receptor (LOX-1) is probably the most important. MATERIAL AND METHODS: This article provides a general overview of the scavenger receptors, with special emphasis on LOX-1 and its role in hypertension, heart failure, atherosclerotic heart disease and diabetes mellitus, based on the literature and our own published data. RESULTS AND INTERPRETATION: LOX-1 is located in various cell types within atherosclerotic plaque, in humans as well in animals, and it accumulates during the progression of the plaque. The receptor is highly expressed in hypertension, hyperhomocysteinaemia and diabetes mellitus. Data indicate that there is a complex interaction between LOX-1 and a number of different processes, such as inflammation, lipid accumulation and oxidative stress. In addition, LOX-1 seems to have therapeutic potential, and a prospective treatment aiming to reduce the level of LOX-1 may be important in the development of atherosclerotic disease, such as coronary heart disease.

[Effects of LOX-1 on expression of adhesion molecules induced by ox-LDL in HUVECs].

OBJECTIVE: To investigate the effects of oxidized low-density lipoprotein receptor 1 (LOX-1) on secretion of adhesive molecules mediated by ox-LDL in human umbilical endothelial cells (HUVECs). METHODS: HUVECs with different concentration of ox-LDL (0, 10, 20, 50, 100 microg/ml) were incubated for 24 h, or HUVECs were pretreated with 250 microg/ml poly (I) or 250 microg/ml carrageenan for 2 h and then incubated with 50 microg/ml ox-LDL for another 24 h. Expression of LOX-1 was determined by realtime RT-PCR and Western blot. mRNA and protein of ICAM-1, VCAM-1 and E-selectin were examined by RT-PCR and Western blot respectively. RESULTS: Incubation of HUVECs with ox-LDL (10-100 microg/ml) enhanced the expressions of LOX-1, ICAM-1 and E-selectin in a concentration-dependent manner (P < 0.01). On the contrary, ox-LDL did not affect the expression of VCAM-1 by HUVECs. The expression of LOX-1, ICAM-1 and E-selectin induced by ox-LDL were reduced in HUVECs pretreated with 250 microg/ml poly (I) or 250 microg/ml carrageenan for 2 h and then incubated with 50 microg/ml ox-LDL for 24 h. This showed that both poly (I) and carrageenan obviously decreased the expression of LOX-1, ICAM-1 and E-selectin induced by ox-LDL. CONCLUSION: ox-LDL may upregulate the expression of LOX-1, ICAM-1 and E-selectin, and LOX-1 blocker may partly inhibit this upregulation. The results suggest that the expression of inflammatory molecules induced by ox-LDL in HUVECs is mediated by LOX-1.