Lectin-like Oxidized Low-Density Lipoprotein (LDL) Receptor (LOX-1): A Chameleon Receptor for Oxidized LDL

LOX-1 in Cardiovascular Disease: A Comprehensive Molecular and Clinical Review

LOX-1, ORL-1, or lectin-like oxidized low-density lipoprotein receptor 1 is a transmembrane glycoprotein that binds and internalizes ox-LDL in foam cells. LOX-1 is the main receptor for oxidized low-density lipoproteins (ox-LDL). The LDL comes from food intake and circulates through the bloodstream. LOX-1 belongs to scavenger receptors (SR), which are associated with various cardiovascular diseases. The most important and severe of these is the formation of atherosclerotic plaques in the intimal layer of the endothelium. These plaques can evolve into complicated thrombi with the participation of fibroblasts, activated platelets, apoptotic muscle cells, and macrophages transformed into foam cells. This process causes changes in vascular endothelial homeostasis, leading to partial or total obstruction in the lumen of blood vessels. This obstruction can result in oxygen deprivation to the heart. Recently, LOX-1 has been involved in other pathologies, such as obesity and diabetes mellitus. However, the development of atherosclerosis has been the most relevant due to its relationship with cerebrovascular accidents and heart attacks. In this review, we will summarize findings related to the physiologic and pathophysiological processes of LOX-1 to support the detection, diagnosis, and prevention of those diseases.

Reactive Carbonyl Species and Protein Lipoxidation in Atherogenesis

Atherosclerosis is a multifactorial disease of medium and large arteries, characterized by the presence of lipid-rich plaques lining the intima over time. It is the main cause of cardiovascular diseases and death worldwide. Redox imbalance and lipid peroxidation could play key roles in atherosclerosis by promoting a bundle of responses, including endothelial activation, inflammation, and foam cell formation. The oxidation of polyunsaturated fatty acids generates various lipid oxidation products such as reactive carbonyl species (RCS), including 4-hydroxy alkenals, malondialdehyde, and acrolein. RCS covalently bind to nucleophilic groups of nucleic acids, phospholipids, and proteins, modifying their structure and activity and leading to their progressive dysfunction. Protein lipoxidation is the non-enzymatic post-translational modification of proteins by RCS. Low-density lipoprotein (LDL) oxidation and apolipoprotein B (apoB) modification by RCS play a major role in foam cell formation. Moreover, oxidized LDLs are a source of RCS, which form adducts on a huge number of proteins, depending on oxidative stress intensity, the nature of targets, and the availability of detoxifying systems. Many systems are affected by lipoxidation, including extracellular matrix components, membranes, cytoplasmic and cytoskeletal proteins, transcription factors, and other components. The mechanisms involved in lipoxidation-induced vascular dysfunction are not fully elucidated. In this review, we focus on protein lipoxidation during atherogenesis.

LOX-1 Regulation in Anti-atherosclerosis of Active Compounds of Herbal Medicine: Current Knowledge and the New Insight

Lectin-like oxidized low-density lipoprotein receptor-1 (LOX-1) have recently been identified to be closely related to the occurrence and development of atherosclerosis (AS). A growing body of evidence has suggested Chinese medicine takes unique advantages in preventing and treating AS. In this review, the related research progress of AS and LOX-1 has been summarized. And the anti-AS effects of 10 active components of herbal medicine through LOX-1 regulation have been further reviewed. As a potential biomarker and target for intervention in AS, LOX-1 targeted therapy might provide a promising and novel approach to atherosclerotic prevention and treatment.

Genetic variations in OLR1 gene associated with PCOS and atherosclerotic risk factors

Polycystic ovary syndrome (PCOS) is the most common endocrinopathy in women of reproductive age. The aim of this study was to investigate the association of oxidized low-density lipoprotein receptor 1 (OLR1) gene variations with the susceptibility of PCOS and to examine the relationship between the frequencies of OLR1 gene variations and atherosclerotic risk factors. Genomic DNA was extracted from blood samples collected from 49 patients with PCOS and 43 healthy controls. The variants in the OLR1 gene were identified using next-generation sequencing (NGS). Heterozygous rs11053646 (K167N), rs11611438, rs11611453, and rs35688880 genotype frequencies were significantly higher in the PCOS group than that of control group. Single nucleotide polymorphism (SNP) rs34163097 minor A allele increased the PCOS risk by ∼10-fold (p = 0.03). SNPs rs11053646, rs11611438, rs11611453, rs34163097, and rs35688880 were positively correlated with body mass index (BMI). The logistic regression model (area under the curve: 0.770, p = 0.000) further revealed a combination of 2-h plasma glucose (PG-2 h), dehydroepiandrosterone sulfate (DHEAS), and rs11053646 as predictors of PCOS phenotype. This is the first study reporting the NGS data of OLR1 gene variants which might be associated with the pathogenesis of PCOS and several atherosclerotic risk factors, particularly higher BMI and DHEAS. To fully understand the genetic basis of PCOS and the contribution of OLR1 gene variants to PCOS pathogenesis, additional large-scale studies are warranted.

High Plasma Levels of Soluble Lectin-like Oxidized Low-Density Lipoprotein Receptor-1 Are Associated With Inflammation and Cardiometabolic Risk Profiles in Pediatric Overweight and Obesity

Background Lectin-like oxidized low-density lipoprotein (ox-LDL) receptor-1 is a scavenger receptor for oxidized low-density lipoprotein. In adults, higher soluble lectin-like ox-LDL receptor-1 (sLOX-1) levels are associated with cardiovascular disease, type 2 diabetes, and obesity, but a similar link in pediatric overweight/obesity remains uncertain. Methods and Results Analyses were based on the cross-sectional HOLBAEK Study, including 4- to 19-year-olds from an obesity clinic group with body mass index >90th percentile (n=1815) and from a population-based group (n=2039). Fasting plasma levels of sLOX-1 and inflammatory markers were quantified, cardiometabolic risk profiles were assessed, and linear and logistic regression analyses were performed. Pubertal/postpubertal children and adolescents from the obesity clinic group exhibited higher sLOX-1 levels compared with the population (P<0.001). sLOX-1 positively associated with proinflammatory cytokines, matrix metalloproteinases, body mass index SD score, waist SD score, body fat %, plasma alanine aminotransferase, serum high-sensitivity C-reactive protein, plasma low-density lipoprotein cholesterol, triglycerides, systolic and diastolic blood pressure SD score, and inversely associated with plasma high-density lipoprotein cholesterol (all P<0.05). sLOX-1 positively associated with high alanine aminotransferase (odds ratio [OR], 1.16, P=4.1 E-04), insulin resistance (OR, 1.16, P=8.6 E-04), dyslipidemia (OR, 1.25, P=1.8 E-07), and hypertension (OR, 1.12, P=0.02). Conclusions sLOX-1 levels were elevated during and after puberty in children and adolescents with overweight/obesity compared with population-based peers and associated with inflammatory markers and worsened cardiometabolic risk profiles. sLOX-1 may serve as an early marker of cardiometabolic risk and inflammation in pediatric overweight/obesity. Registration The HOLBAEK Study, formerly known as The Danish Childhood Obesity Biobank, ClinicalTrials.gov identifier number NCT00928473, https://clinicaltrials.gov/ct2/show/NCT00928473 (registered June 2009).

Roles of pattern recognition receptors in response to fungal keratitis

Fungal keratitis is one of the leading causes of blindness worldwide, which has become an increasingly serious threat to public ocular health, but no effective treatment strategies are available now. Pattern recognition receptors (PRRs) of the innate immune system are the first line of host defense against fungal infections. They could recognize pathogen-associated molecular patterns (PAMPs) or damage-associated molecular patterns (DAMPs) and trigger an array of inflammatory responses. Over the last decades, research has resulted in significant progress regarding the roles of PRRs in fungal keratitis. This review will highlight the importance of several pattern recognition receptors (C-type lectin-like receptors, Toll-like receptors, and NOD-like receptors) in regulating the innate immunity under fungal keratitis and describe the crosstalk and collaboration in PRRs contributing to disease pathology. Meanwhile, some potential therapy-based PRRs against corneal fungal infections are discussed.

Relationship between Brain Metabolic Disorders and Cognitive Impairment: LDL Receptor Defect

The low-density-lipoprotein receptor (LDLr) removes low-density lipoprotein (LDL), an endovascular transporter that carries cholesterol from the bloodstream to peripheral tissues. The maintenance of cholesterol content in the brain, which is important to protect brain function, is affected by LDLr. LDLr co-localizes with the insulin receptor and complements the internalization of LDL. In LDLr deficiency, LDL blood levels and insulin resistance increase, leading to abnormal cholesterol control and cognitive deficits in atherosclerosis. Defects in brain cholesterol metabolism lead to neuroinflammation and blood–brain-barrier (BBB) degradation. Moreover, interactions between endoplasmic reticulum stress (ER stress) and mitochondria are induced by ox-LDL accumulation, apolipoprotein E (ApoE) regulates the levels of amyloid beta (Aβ) in the brain, and hypoxia is induced by apoptosis induced by the LDLr defect. This review summarizes the association between neurodegenerative brain disease and typical cognitive deficits.

Association of OLR1 gene polymorphism with live body weight and body morphometric traits in Awassi ewes: short communication

BACKGROUND

Oxidized low-density lipoprotein receptor 1 (OLR1) is an endothelial receptor that binds and degrades oxidized low-density lipoproteins (Ox-LDL), thus having a physiological role in metabolism. Polymorphisms in the OLR1 gene are associated with animals with different production traits. Due to this, the study aimed to determine if OLR1 polymorphisms in Awassi ewes associate with live body weight and body measurement.

METHODS AND RESULTS

In this study, 200 ewes between the ages of 2.5 and 5 years, not pregnant or lactating, were selected. Phenotypic measurements including live body weight and body measurements were collected. A sheep's blood was collected to extract genomic DNA, genotyped, and sequenced to confirm the presence of the variants that arose from the amplified fragments. One novel C246A single nucleotide polymorphism (SNP) was identified in the OLR1 gene (exon 3) that assigned two genotypes CC and CA. The study indicated significant differences (P ≤ 0.05) in live body weight and body measurements of the genotype CC compared with the genotype CA. The genotype CC correlated positively with live body weight, height at shoulder, height at hip, chest girth, and chest width (r = 0.67, P = 0.02), (r = 0.54, P = 0.03), (r = 0.61, P = 0.02), (r = 0.53, P = 0.01) and (r = 0.66, P = 0.04) respectively.

CONCLUSIONS

Sheep with the CC genotype had a higher live body weight and larger body measurement, making them better for productivity. These genotypic data and associations can be used to better select sheep for future marker-assisted selection programs.

Expression of Serum sLOX-1 in Patients with Non-Small-Cell Lung Cancer and Its Correlation with Lipid Metabolism

Objective

The aim of this study was to investigate the expression level of soluble LOX-1 (sLOX-1) in the serum of non-small-cell lung cancer (NSCLC) patients and its correlation with lipid metabolism.

Methods

99 inpatients with NSCLC and 81 healthy controls were enrolled in this study. The levels of serum sLOX-1 were compared between the two groups, and the correlation of sLOX-1 with clinicopathological characteristics, blood lipid indices, and carcinoembryonic antigen was analyzed.

Results

Compared with the healthy controls, sLOX-1, low-density lipoprotein, triglyceride, and carcinoembryonic antigen in the patients with NSCLC were significantly higher (p < 0.05), while the expression level of high-density lipoprotein was lower (p < 0.05). The expression level of sLOX-1 in the serum of patients with healthy controls was positively correlated with low-density lipoprotein (r = 0.72, p < 0.05). The levels of sLOX-1 and low-density lipoprotein in the serum of patients with NSCLC were closely related to the lymph node metastasis, distant metastasis, and TNM stage (p < 0.05). Compared with a single index, when the sLOX-1 was combined with the CEA, its specificity increased significantly to 97.5% (AUC = 0.995, p < 0.01, 95% CI: 0.989–1.000).

Conclusion

sLOX-1 and low-density lipoprotein were overexpressed in the serum of patients with NSCLC, positively correlated, and closely related to the TNM stage and metastasis. This result suggested that lipid metabolic disorders may promote the progression of NSCLC through sLOX-1, which could be a potential serological marker with diagnostic value for NSCLC.

Effects of Apigenin on the Expression of LOX-1, Bcl-2, and Bax in Hyperlipidemia Rats

We aimed to investigate the impact of apigenin on LOX-1, Bcl-2, and Bax expression in hyperlipidemia rats and explore the possible molecular pathological mechanism of apigenin in improving hyperlipidemia and preventing atherosclerosis. In hyperlipidemia models, the levels of total cholesterol (TC), triglyceride (TG), low-density lipoprotein cholesterol (LDL-c) and the LOX-1 protein expression were apparently increased (P<0.01), while the high-density lipoprotein cholesterol (HDL-c) levels and the ratio of Bcl-2/Bax were reduced significantly (P<0.01) in comparison with the standard control group. After the treatment of apigenin, the levels of TC, TG, LDL-c, and the LOX-1 protein expression were noticeably decreased (P<0.01), while the levels of HDL-c and the Bcl-2/Bax ratio were increased (P<0.01). The intima was thickened and had protrusions in the hyperlipidemia model group compared to the normal control group. In comparison with the atherosclerosis model group, the degree of aortic lesions in the low-dose, middle-dose, high-dose groups was alleviated. Apigenin can reduce the level of blood lipid, improve hyperlipidemia, and prevent atherosclerosis in hyperlipidemia rats. The molecular mechanism may be related to inhibiting LOX-1 gene expression and increasing the Bcl-2/Bax ratio.

Polycystic ovary syndrome and endothelial dysfunction: A potential role for soluble lectin-like oxidized low density lipoprotein receptor-1

The aims of this study were to investigate whether serum soluble lectin-like oxidized low-density lipoprotein receptor-1 (sLOX-1), oxidized LDL (oxLDL), paraoxonase-1(PON-1) and hydroperoxide (LOOH) levels are altered in women with polycystic ovary syndrome (PCOS) and also to determine if hyperandrogenism, insulin resistance (IR) and Anti-Müllerian Hormone (AMH) are associated with endothelial dysfunction in PCOS. A total of 46 women with PCOS and 46 non-PCOS healthy controls were recruited. Women with PCOS had significantly higher sLOX-1, oxLDL and LOOH concentrations than non-PCOS women [6.16 (3.92-13.95) vs 1.37 (0.63-4.43) ng/mL, p < 0.001; 6.48 ± 1.03 vs 3.16 ± 1.02 μU/L, p < 0.001; 2.45 (1.45-3.45) vs 1.06 (0.64-1.56) μmol/L, p < 0.001]. The mean PON-1 level of PCOS group was lower than non-PCOS group (69.47 ± 10.75 vs 104.08 ± 21.43 U/mL, p < 0.001). There was no significant difference in terms of the sLOX-1, oxLDL, LOOH and PON-1 levels between normal weight and overweight PCOS women. On univariate logistic regression analysis, Ferriman-Gallwey scale (FGS), HOMA-IR and AMH were an independent predictors of high risk group of endothelial dysfunction markers (HR-EDm). Age and BMI were not associated with HR-EDm. When incorporated into the multivariate model, endotelial dysfunction markers independently correlated with clinical hyperandrogenism (FGS) but not with AMH. In conclusion, our results indicated that an increased concentration of sLOX-1 might be an early predictor of endothelial damage in patients with PCOS. Women with PCOS have elevated sLOX-1, oxLDL, LOOH and decreased PON-1 levels, independent of BMI. Endothelial dysfunction in women with PCOS is associated with hyperandrogenism. Further studies are required to confirm our findings.

Oleacein and Foam Cell Formation in Human Monocyte-Derived Macrophages: A Potential Strategy Against Early and Advanced Atherosclerotic Lesions

Background: Oleacein is a secoiridoid group polyphenol found mostly in Olea europea L. and Ligustrum vulgare L. (Oleaceae). The aim of the present study was to investigate a potential role of oleacein in prevention of the foam cell formation. Materials and Methods: Oleacein was isolated from Ligustrum vulgare leaves. Human monocyte-derived macrophages were obtained from monocytes cultured with Granulocyte-macrophage colony-stimulating factor (GM-CSF). Then, cells were incubated with 20 μM or 50 μM of oleacein and with oxidized low-density lipoprotein (oxLDL) (50 μg/mL). Visualization of lipid deposition within macrophages was carried out using Oil-Red-O. Expression of CD36, Scavenger receptor A1 (SRA1) and Lectin-like oxidized low-density lipoprotein receptor 1 (LOX-1) was determined by Reverse transcription polymerase chain reaction (RT-PCR) and by flow cytometry. Apoptosis was determined by flow cytometry using Annexin V assay. STAT3 and Acyl-coenzyme A: cholesterol acyltransferase type 1 (ACAT1) levels were determined by ELISA. P-STAT3, P-JAK1, P-JAK2 expressions were determined by Western blot (WB). Results: Oleacein in dose-dependent manner significantly reduced lipid deposits in macrophages as well as their expression of selected scavenger receptors. The highest decrease of expression was found for CD36 and SRA1 receptors, from above 20% to more than 75% compared to oxLDL and the lowest for LOX-1 receptor, from approx. 8% to approx. 25% compared to oxLDL-stimulated macrophages. Oleacein significantly reduced (2.5-fold) early apoptosis of oxLDL-stimulated macrophages. Moreover, oleacein significantly increased the protein expression of JAK/STAT3 pathway and had no effect on ACAT1 level. Conclusions: Our study demonstrates, for the first time, that oleacein inhibits foam cell formation in human monocyte-derived macrophages and thus can be a valuable tool in the prevention of early and advanced atherosclerotic lesions.

LOX-1: Its cytotopographical variance and disease stress

Lectin-like oxidized low-density lipoprotein receptor-1 (LOX-1) is a canonical receptor for oxidized LDL (oxLDL) among the known modified LDL particles. Topographical variance on LOX-1 expression in different cell types and its influence on the atherogenic potential of the particular cell type is the main focus of this review. Characteristic features of LOX-1 on the atherogenic potential of aortic endothelial cells, macrophages, platelets, and vascular smooth muscle cells have been discussed. Nonspecificity of ligands, besides oxLDL, is also the highlight of this review to show the chameleon characteristics in the functional activity of the receptor protein. Induction of LOX-1 has been reported in diseases like atherosclerosis, diabetes, and hypertension, as well as in the inflammatory response of immune reactions. The expression of LOX-1 is upregulated by the vicious cycle of stimulatory response from proatherogenic molecules.

Absence of Interferon Regulatory Factor 1 Protects Against Atherosclerosis in Apolipoprotein E-Deficient Mice

Deciphering the molecular and cellular processes involved in foam cell formation is critical to understanding the pathogenesis of atherosclerosis. Interferon regulatory factor 1 (IRF1) was first identified as a transcriptional regulator of type-I interferons (IFNs) and IFN inducible genes. Our study aims to explore the role of IRF1 in atherosclerotic foam cell formation and understand the functional diversity of IRF1 in various cell types contributing to atherosclerosis.

Methods: We induced experimental atherosclerosis in ApoE^-/-IRF1^-/- mice and evaluated the effect of IRF1 on disease progression and foam cell formation.

Results: IRF1 expression was increased in human and mouse atherosclerotic lesions. IRF1 deficiency inhibited modified lipoprotein uptake and promoted cholesterol efflux, along with altered expression of genes implicated in lipid metabolism. Gene expression analysis identified scavenger receptor (SR)-AI as a regulated target of IRF1, and SR-AI silencing completely abrogated the increased uptake of modified lipoprotein induced by IRF1. Our data also explain a mechanism underlying endotoxemia-complicated atherogenesis as follows: two likely pro-inflammatory agents, oxidized low-density lipoprotein (ox-LDL) and bacterial lipopolysaccharide (LPS), exert cooperative effects on foam cell formation, which is partly attributable to a shift of IRF1-Ubc9 complex to IRF1- myeloid differentiation primary response protein 88 (Myd88) complex and subsequent IRF1 nuclear translocation. Additionally, it seems that improved function of vascular smooth muscle cells (VSMCs) also accounts for the diminished and more stable atherosclerotic plaques observed in ApoE^-/-IRF1^-/- mice.

Conclusions: Our findings demonstrate an unanticipated role of IRF1 in the regulation of gene expression implicated in foam cell formation and identify IRF1 activation as a new risk factor in the development, progression and instability of atherosclerotic lesions.

Overexpression of scavenger receptor and infiltration of macrophage in epicardial adipose tissue of patients with ischemic heart disease and diabetes

Background

Oxidized low-density lipoproteins and scavenger receptors (SRs) play an important role in the formation and development of atherosclerotic plaques. However, little is known about their presence in epicardial adipose tissue (EAT). The objective of the study was to evaluate the mRNA expression of different SRs in EAT of patients with ischemic heart disease (IHD), stratifying by diabetes status and its association with clinical and biochemical variables.

Methods

We analyzed the mRNA expression of SRs (LOX-1, MSR1, CXCL16, CD36 and CL-P1) and macrophage markers (CD68, CD11c and CD206) in EAT from 45 patients with IHD (23 with type 2 diabetes mellitus (T2DM) and 22 without T2DM) and 23 controls without IHD or T2DM.

Results

LOX-1, CL-P1, CD68 and CD11c mRNA expression were significantly higher in diabetic patients with IHD when compared with those without T2DM and control patients. MSR1, CXCL16, CD36 and CD206 showed no significant differences. In IHD patients, LOX-1 (OR 2.9; 95% CI 1.6–6.7; P = 0.019) and CD68 mRNA expression (OR 1.7; 95% CI 0.98–4.5; P = 0.049) were identified as independent risk factors associated with T2DM. Glucose and glycated hemoglobin were also shown to be risk factors.

Conclusions

SRs mRNA expression is found in EAT. LOX-1 and CD68 and were higher in IHD patients with T2DM and were identified as a cardiovascular risk factor of T2DM. This study suggests the importance of EAT in coronary atherosclerosis among patients with T2DM.

The CH25H-CYP7B1-RORα axis of cholesterol metabolism regulates osteoarthritis

Osteoarthritis-the most common form of age-related degenerative whole-joint disease¹-is primarily characterized by cartilage destruction, as well as by synovial inflammation, osteophyte formation and subchondral bone remodelling^2,3. However, the molecular mechanisms that underlie the pathogenesis of osteoarthritis are largely unknown. Although osteoarthritis is currently considered to be associated with metabolic disorders, direct evidence for this is lacking, and the role of cholesterol metabolism in the pathogenesis of osteoarthritis has not been fully investigated^4-6. Various types of cholesterol hydroxylases contribute to cholesterol metabolism in extrahepatic tissues by converting cellular cholesterol to circulating oxysterols, which regulate diverse biological processes^7,8. Here we show that the CH25H-CYP7B1-RORα axis of cholesterol metabolism in chondrocytes is a crucial catabolic regulator of the pathogenesis of osteoarthritis. Osteoarthritic chondrocytes had increased levels of cholesterol because of enhanced uptake, upregulation of cholesterol hydroxylases (CH25H and CYP7B1) and increased production of oxysterol metabolites. Adenoviral overexpression of CH25H or CYP7B1 in mouse joint tissues caused experimental osteoarthritis, whereas knockout or knockdown of these hydroxylases abrogated the pathogenesis of osteoarthritis. Moreover, retinoic acid-related orphan receptor alpha (RORα) was found to mediate the induction of osteoarthritis by alterations in cholesterol metabolism. These results indicate that osteoarthritis is a disease associated with metabolic disorders and suggest that targeting the CH25H-CYP7B1-RORα axis of cholesterol metabolism may provide a therapeutic avenue for treating osteoarthritis.

Albiflorin inhibits the formation of THP-1-derived foam cells through the LOX-1/NF-κB pathway

BACKGROUND

Foam cells are characteristic pathologic cells of atherosclerosis (AS), they are lipid-loaded macrophages present on atherosclerotic lesions. A large number of studies has shown that the pathogenesis of AS is the result of interactions between the lipid metabolism disorders and chronic inflammatory responses in the body. Albiflorin can inhibit the inflammatory response and it has shown a therapeutic effect on certain inflammatory diseases.

METHODS

In this study, a human acute monocytic leukemia cell line (THP-1)-derived foam cell model was established via oxidized low-density lipoprotein (ox-LDL) to observe the effects of albiflorin on the AS-characteristic foam cells.

RESULTS

Our results showed that, after the treatment with ox-LDL, macrophages induced by propylene glycol methyl ether acetate (PMA), presented large amounts of lipid deposition in their cytoplasm, indicating that the THP-1-derived foam cell model was successfully established. On the other hand, the same cells pretreated with albiflorin presented significantly reduced amounts of lipid deposition, and their contents of total cholesterol and triglyceride were also clearly lower. Besides, the expression levels of low-density lipoprotein receptor-1 (LOX-1) and nuclear factor-κB (NF-κB) were significantly decreased, and the expression levels of downstream factors interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α) were also obviously decreased in the cells treated with albiflorin but not in the negative control cells. Moreover, after treatment of macrophages with different concentrations of ox-LDL, the expression levels of LOX-1 and NF-κB were up-regulated in an ox-LDL concentration-dependent manner, and so were the expression levels of IL-6 and TNF-α. And, it was found after treatment with LOX-1 neutralizing antibody or NF-κB inhibitor (during the foam cell formation induction via ox-LDL) that the lipid deposition in the cytoplasm of the cells was reduced, as in the cells treated with albiflorin.

CONCLUSIONS

Taken together, our findings suggest that albiflorin decreases lipid deposition in the cytoplasm and blocks the foaming process by regulating the LOX-1/NF-κB signaling pathway.

Regulation of lipoxygenase-1 and Dectin-1 on interleukin-10 in mouse Aspergillus fumigatus keratitis

AIM

To investigate the regulation of lipoxygenase (LOX)-1 and Dectin-1 on interleukin-10 (IL-10) production in mice with Aspergillus fumigatus (A. fumigatus) keratitis.

METHODS

The corneas of C57BL/6 mice were pretreated with LOX-1 inhibitor Poly(I) or Dectin-1 siRNA separately before the infection of A. fumigatus. Polymerase chain reaction (PCR) and Western blot were used to detect the expression of IL-10.

RESULTS

The mRNA and protein expressions of IL-10 were significantly increased in mice with A. fumigatus keratitis. Compared with the group pretreated with sterile water before infection, Poly(I) pretreatment suppressed IL-10 expression significantly. Compared with the group pretreated with scrambled siRNA before infection, Dectin-1 siRNA pretreatment significantly reduced IL-10 expression in response to A. fumigatus infection.

CONCLUSION

LOX-1 and Dectin-1 regulate IL-10 production in mouse A. fumigatus keratitis.

Cinnamaldehyde protects VSMCs against ox-LDL-induced proliferation and migration through S arrest and inhibition of p38, JNK/MAPKs and NF-κB

Cinnamaldehyde (Cin), as a traditional flavor constituent isolated from the bark of Cinnamonum cassia Presl, has been commonly used for - digestive, cardiovascular and immune system diseases. The pathology of vascular smooth muscle cells (VSMCs) accelerated the progression of atherosclerosis. In our study, we found that cinnamaldehyde significantly suppressed ox-LDL-induced VSMCs proliferation, migration and inflammatory cytokine overproduction, as well as foam cell formation in VSMCs and macrophages. Moreover, cinnamaldehyde inhibited the phosphorylation of p38, JNK and p65 NF-κB and increased heme oxygenase-1 (HO-1) activity. In addition, cinnamaldehyde reduced monocyte chemotactic protein-1 (MCP-1), matrix metalloproteinase-2 (MMP-2) and lectin-like oxidized low density lipoprotein receptor-1 (LOX-1) expression. Furthermore, cinnamaldehyde arrested cell cycle in S phase. Thus, results indicated that cinnamaldehyde antagonized the ox-LDL-induced VSMCs proliferation, migration, inflammation and foam cell formation through regulation of HO-1, MMP-2, LOX-1 and blockage of cell cycle, and - suppression of p38, JNK/MAPK and NF-κB signaling pathways.

LOX-1 receptor: A potential link in atherosclerosis and cancer

Altered production of reactive oxygen species (ROS), causing lipid peroxidation and DNA damage, contributes to the progression of atherosclerosis and cancer. Lectin-like oxidized low-density lipoprotein receptor-1 (LOX-1) is a lectin-like receptor for oxidized low-density lipoproteins (ox-LDL) primarily expressed in endothelial cells and vasculature-rich organs. LOX-1 receptors is a marker for atherosclerosis, and once activated by ox-LDL or other ligands, stimulates the expression of adhesion molecules, pro-inflammatory signaling pathways and proangiogenic proteins, including NF-kB and VEGF, in vascular endothelial cells and macrophages. Several different types of cancer reported LOX-1 gene upregulation, and numerous interplays exist concerning LOX-1 in atherosclerosis, metabolic diseases and cancer. One of them involves NF-kB, an oncogenic protein that regulates the transcription of several inflammatory genes response. In a model of cellular transformation, the MCF10A ER-Src, inhibition of LOX-1 gene reduces NF-kB activation and the inflammatory and hypoxia pathways, suggesting a mechanistic connection between cellular transformation and atherosclerosis. The remodeling proteins MMP-2 and MMP-9 have been found increased in angiogenesis in atherosclerotic plaque and also in human prostate cancer cells. In this review, we outlined the role of LOX-1 in atherogenesis and tumorigenesis as a potential link in these diseases, suggesting that LOX-1 inhibition could represent a promising strategy in the treatment of atherosclerosis and tumors.

Siglec-5 is a novel marker of critical limb ischemia in patients with diabetes

Critical Limb Ischemia (CLI) is common but uncommonly diagnosed. Improved recognition and early diagnostic markers for CLI are needed. Therefore, the aim of our study was to identify plasma biomarkers of CLI in patients with type 2 diabetes mellitus (T2DM). In this study, antibody-coated glass slide arrays were used to determine the plasma levels of 274 human cytokines in four matched cases of diabetes with and without CLI. Potential biomarkers were confirmed in an independent cohort by ELISA. After adjusting for confounding risk factors, only plasma level of Siglec-5 remained significantly associated with an increased odds ratio (OR) for diabetes with CLI by binary logistic regression analysis. Receiver operating characteristic (ROC) curve analysis revealed the optimal cut-off points for Siglec-5 was 153.1 ng/ml. After entering Siglec-5, the AUC was 0.99, which was higher than that of confounding risk factors only (AUC = 0.97, P < 0.05). Siglec-5 was expressed in plaques, but not in healthy artery wall in T2DM patients. Elevated plasma Siglec-5 was independently associated with CLI in T2DM. Plasma Siglec-5 levels are implicated as an early diagnostic marker of CLI in T2DM patients and it may become a target for the prevention or treatment of CLI in diabetes.

OLR1 and Loxin Expression in PBMCs of Women with a History of Unexplained Recurrent Miscarriage: A Pilot Study

AIMS

The aim of this study was to evaluate the expression of OLR1 and its alternative splicing isoform Loxin in unexplained recurrent miscarriage (uRM).

METHODS

Sixty-three women of reproductive age were recruited and were divided into four groups: 18 pregnant and 23 non-pregnant women with uRM, and 12 pregnant and 10 non-pregnant women with physiological pregnancies. Complementary DNA derived from peripheral blood mononuclear cells (PBMCs) was analyzed by quantitative real-time PCR to evaluate the expression of OLR1 and Loxin. Oxidized low-density lipoproteins (ox-LDLs) were assayed from serum by a commercially available kit.

RESULTS

Pregnant uRM women presented with a higher, though not significant, OLR1/Loxin ratio and a higher ox-LDLs serum level (p ≤ 0.05) compared with pregnant control women. OLR1 and Loxin levels were significantly decreased in non-pregnant uRM women compared with the control (OLR1: 0.00018 vs. 0.00043, p ≤ 0.005; Loxin: 0.00018 vs. 0.00060, p ≤ 0.005, respectively). Loxin expression decreased by about two-thirds (p ≤ 0.005) in pregnant women compared with non-pregnant control women. A higher expression of OLR1 in pregnant women compared with non-pregnant women with uRM (p ≤ 0.05) was observed, but no variation in Loxin expression was observed.

CONCLUSIONS

The results of this study show an association of peripheral OLR1 and Loxin expression levels in uRM women, and they suggest the possible existence of an uncontrolled oxidative stress in these women in the first trimester of pregnancy.