Glucose enhances endothelial LOX-1 expression: role for LOX-1 in glucose-induced human monocyte adhesion to endothelium

LOX-1 regulation of H-type vascular endothelial cell regeneration in hyperglycemia

AIMS

Diabetic osteoporosis (DOP) is the most common secondary form of osteoporosis. Diabetes mellitus affects bone metabolism; however, the underlying pathophysiological mechanisms remain unclear. Lectin-like oxidized low-density lipoprotein receptor-1 (LOX-1) expression is upregulated in conditions characterized by vascular injury, such as atherosclerosis, hypertension, and diabetes. Additionally, Notch, HIF-1α, and VEGF are involved in angiogenesis and bone formation. Therefore, we aimed to investigate the expression of Notch, HIF-1α, and VEGF in the LOX-1 silencing state.

METHODS

Rat bone H-type vascular endothelial cells (THVECs) were isolated and cultured in vitro. Cell identification was performed using immunofluorescent co-expression of CD31 and Emcn. Lentiviral silencing vector (LV-LOX-1) targeting LOX-1 was constructed using genetic recombination technology and transfected into the cells. The experimental groups included the following: NC group, HG group, LV-LOX-1 group, LV-CON group, HG + LV-LOX-1 group, HG + LV-CON group, HG + LV-LOX-1 + FLI-06 group, HG + LV-CON + FLI-06 group, HG + LV-LOX-1 + LW6 group, and HG + LV-CON + LW6 group. The levels of LOX-1, Notch, Hif-1α, and VEGF were detected using PCR and WB techniques to investigate whether the expression of LOX-1 under high glucose conditions has a regulatory effect on downstream molecules at the gene and protein levels, as well as the specific molecular mechanisms involved.

RESULTS

High glucose (HG) conditions led to a significant increase in LOX-1 expression, leading to inhibition of angiogenesis, whereas silencing LOX-1 can reverse this phenomenon. Further analysis reveals that changes in LOX-1 will promote changes in Notch/HIF-1α and VEGF. Moreover, Notch mediates the activation of HIF-1α and VEGF.

CONCLUSIONS

The activation of LOX-1 and the inhibition of Notch/HIF-1α/VEGF in THVECs are the main causes of DOP. These findings contribute to our understanding of the pathogenesis of DOP and offer a novel approach for preventing and treating osteoporosis.

Remnant cholesterol is independently asssociated with an increased risk of peripheral artery disease in type 2 diabetic patients

BACKGROUND

Remnant cholesterol (RC) has been correlated with a higher risk of atherosclerosis. It has been confirmed that in the general population, an elevated RC level is related to a 5-fold higher risk of peripheral arterial disease (PAD). Diabetes is one of the strongest risk factors for PAD development. However, the association between RC and PAD in the specific population of type 2 diabetes mellitus (T2DM) has not been investigated. Herein, the correlation was investigated between RC and PAD in T2DM patients.

METHODS

In the retrospective study, the hematological parameter data of 246 T2DM patients without PAD (T2DM - WPAD) and 270 T2DM patients with PAD (T2DM - PAD) was collected. Differences in RC levels between the two groups were compared, and the association between RC and PAD severity was examined. Multifactorial regression was used to determine whether RC was a significant contributor to the development of T2DM - PAD. The diagnostic potential of RC was tested using receiver operating characteristic (ROC) curve.

RESULTS

The RC levels in T2DM - PAD individuals were considerably greater than in T2DM - WPAD individuals (P < 0.001). RC had a positive correlation with disease severity. Further, multifactorial logistic regression analyses found that elevated RC levels were a major contributor to T2DM - PAD (P < 0.001). The area under the curve (AUC) of the RC for T2DM - PAD patients was 0.727. The cut-off value of RC was 0.64 mmol/L.

CONCLUSION

The RC levels were higher in T2DM - PAD patients, and were independently linked with its severity. Diabetic patients with RC levels > 0.64 mmol/L had an elevated risk of developing PAD.

Effect of repeated bolus and continuous glucose infusion on a panel of circulating biomarkers in healthy volunteers

HYPOTHESIS

Glycaemic variability (GV) refers to fluctuations in the blood glucose level and may contribute to complications in patients suffering from Diabetes. Several studies show negative effects of GV on the cardiovascular system, however there is still a lack of conclusive evidence. Using an explorative cardiovascular panel, it is possible to simultaneously measure the effects on proteins relevant for cardiovascular processes. The aim of this study was to investigate the effects of rapid glucose excursions on cardiovascular and metabolic parameters in healthy individuals.

METHODS

An explorative single-blinded cross-over study was performed in ten healthy men. Subjects received 3 times 20 grams of glucose i.v. over 5 minutes or 60 grams of glucose continuously over 3 hours. Blood was taken for repeated measurements of the cardiovascular panel over the following 6 hours and again after 24 and 48 hours.

RESULTS

We observed a significant elevation of 7 cardiovascular biomarkers (BMP6, SLAMF7, LOX-1, ADAMTS13, IL-1RA, IL-4RA, PTX3) at t = 360min after rapid glucose infusion compared to a continuous glucose infusion.

CONCLUSIONS

Intraday GV seems to have acute effects on cardiovascular proteins in healthy test persons. Rapid glucose administration compared to continuous administration showed significant changes in BMP6, SLAMF7, ADAMTS13, IL1RA, PTX3, IL-4RA and LOX-1.

CLINICAL TRIAL REGISTRATION

NCT04488848.

LOX-1 attenuates high glucose-induced autophagy via AMPK/HNF4α signaling in HLSECs

Type 2 diabetes mellitus (T2DM) combined with nonalcoholic fatty liver disease (NAFLD) is a common cause of death. Lectin-like oxidized low-density lipoprotein receptor-1 (LOX-1) is involved in the regulation of autophagy and associated with a variety of diseases, such as atherosclerosis, diabetes, and NAFLD. This study aimed to investigate the effect of LOX-1 on autophagy induced by high glucose levels in human liver sinusoidal endothelial cells (HLSECs) and whether it regulates autophagy through the adenosine monophosphate-activated protein kinase/hepatocyte nuclear factor 4α (AMPK/HNF4α) pathway. In this study, HLSECs cultured with high glucose medium showed increased expression of LOX-1, whereas autophagy was inhibited. High glucose levels decreased the AMPK phosphorylation, increased the HNF4α phosphorylation, and retained the HNF4α in the cytoplasm. By contrast, silencing of LOX-1 reversed the phenomenon induced by high glucose levels and restored the HNF4a localization. Taken together, our findings reveal a novel mechanism of high glucose-induced autophagy in HLSECs, namely, the LOX-1-mediated AMPK/HNF4α signaling pathway. Therefore, LOX-1 is an important target molecule for the regulation of autophagy in HLSECs.

Inflammatory gene silencing in activated monocytes by a cholesterol tagged-miRNA/siRNA: a novel approach to ameliorate diabetes induced inflammation

There is a major unmet need for the development of effective therapies for diabetes induced inflammation. Increased adenosine-uridine rich elements (AREs) containing mRNAs of inflammatory molecules are reported in inflamed monocytes. Destabilizing these inflammatory mRNAs by the miR-16 could reduce inflammation. DNA microarrays and in vitro cell studies showed that exogenous miR16 and its mimic treatment, in LPS/PMA induced monocytes, significantly downregulated several ARE containing inflammatory cytokine mRNAs similar to those seen in the normal monocytes. Ingenuity pathway analyses showed exogenous miR-16 or its synthetic mimic treatment alleviates inflammatory responses. To selectively target uptake, especially to inflamed cells, one of the CD36 substrate cholesterol was tagged to miR16/siRNA. Cholesterol tagged miR-16/ARE-siRNA showed enhanced uptake in CD36 expressing inflamed cells. In LPS or PMA, treated monocytes, candidate genes expressions levels such as IL-6, IL-8, IL-12β, IP-10, and TNF-α mRNA were increased, as measured by RT-qPCR as seen in primary monocytes of diabetes patients. Exogenous miR16 or ARE-siRNA transfection reduced mRNAs of pro-inflammatory cytokines levels in monocyte, and its adhesion. Increased uptake of cholesterol tagged miR-16 through the CD36 receptor was observed. This destabilizes numerous inflammatory ARE containing mRNAs and alleviates inflammatory responses. Cholesterol-tagged miR-16 and its mimic are novel anti-inflammatory molecules that can be specifically targeted to, via through CD36 expressing, "inflamed" cells and thus serve as therapeutic candidates to alleviate inflammatory diseases.

Advancements in nanomedicines for the detection and treatment of diabetic kidney disease

In the diabetic kidneys, morbidities such as accelerated ageing, hypertension and hyperglycaemia create a pro-inflammatory microenvironment characterised by extensive fibrogenesis. Radiological techniques are not yet optimised generating inconsistent and non-reproducible data. The gold standard procedure to assess renal fibrosis is kidney biopsy, followed by histopathological assessment. However, this method is risky, invasive, subjective and examines less than 0.01% of kidney tissue resulting in diagnostic errors. As such, less than 10% of patients undergo kidney biopsy, limiting the accuracy of the current diabetic kidney disease (DKD) staging method. Standard treatments suppress the renin-angiotensin system to control hypertension and use of pharmaceuticals aimed at controlling diabetes have shown promise but can cause hypoglycaemia, diuresis and malnutrition as a result of low caloric intake. New approaches to both diagnosis and treatment are required. Nanoparticles (NPs) are an attractive candidate for managing DKD due to their ability to act as theranostic tools that can carry drugs and enhance image contrast. NP-based point-of-care systems can provide physiological information previously considered unattainable and provide control over the rate and location of drug release. Here we discuss the use of nanotechnology in renal disease, its application to both the treatment and diagnosis of DKD. Finally, we propose a new method of NP-based DKD classification that overcomes the current systems limitations.

Native and Oxidized Low-Density Lipoproteins Increase the Expression of the LDL Receptor and the LOX-1 Receptor, Respectively, in Arterial Endothelial Cells

Atherosclerotic artery disease is the major cause of death and an immense burden on healthcare systems worldwide. The formation of atherosclerotic plaques is promoted by high levels of low-density lipoproteins (LDL) in the blood, especially in the oxidized form. Circulating LDL is taken up by conventional and non-classical endothelial cell receptors and deposited in the vessel wall. The exact mechanism of LDL interaction with vascular endothelial cells is not fully understood. Moreover, it appears to depend on the type and location of the vessel affected and the receptor involved. Here, we analyze how native LDL (nLDL) and oxidized LDL (oxLDL) modulate the expression of their receptors-classical LDLR and alternative LOX-1-in endothelial cells derived from human umbilical artery (HUAECs), used as an example of a medium-sized vessel, which is typically affected by atherosclerosis. Exposure of HUAECs to nLDL resulted in moderate nLDL uptake and gradual increase in LDLR, but not LOX-1, expression over 24 h. Conversely, exposure of HUAECs to oxLDL, led to significant accumulation of oxLDL and rapid induction of LOX-1, but not LDLR, within 7 h. These activation processes were associated with phosphorylation of protein kinases ERK1/2 and p38, followed by activation of the transcription factor AP-1 and its binding to the promoters of the respective receptor genes. Both nLDL-induced LDLR mRNA expression and oxLDL-induced LOX-1 mRNA expression were abolished by blocking ERK1/2, p-38 or AP-1. In addition, oxLDL, but not nLDL, was capable of inducing LOX-1 through the NF-κB-controlled pathway. These observations indicate that in arterial endothelial cells nLDL and oxLDL signal mainly via LDLR and LOX-1 receptors, respectively, and engage ERK1/2 and p38 kinases, and AP-1, as well as NF-κB transcription factors to exert feed-forward regulation and increase the expression of these receptors, which may perpetuate endothelial dysfunction in atherosclerosis.

H2O2-responsive prodrug-nanosystem based on auto-fluorescent perylenetetracarboxylic diimide hinders foaming progress in RAW264.7 cells

Oxidative stress can lead to a variety of diseases, and oxalate bond can consume excess reactive oxygen species（ROS）in cells. In this study, the H2O2 responsive prodrug-nanosystem was synthesized by oxalate...

The Reciprocal Relationship between LDL Metabolism and Type 2 Diabetes Mellitus

Type 2 diabetes mellitus and insulin resistance feature substantial modifications of the lipoprotein profile, including a higher proportion of smaller and denser low-density lipoprotein (LDL) particles. In addition, qualitative changes occur in the composition and structure of LDL, including changes in electrophoretic mobility, enrichment of LDL with triglycerides and ceramides, prolonged retention of modified LDL in plasma, increased uptake by macrophages, and the formation of foam cells. These modifications affect LDL functions and favor an increased risk of cardiovascular disease in diabetic individuals. In this review, we discuss the main findings regarding the structural and functional changes in LDL particles in diabetes pathophysiology and therapeutic strategies targeting LDL in patients with diabetes.

Endothelin-1 and LOX-1 as Markers of Endothelial Dysfunction in Obstructive Sleep Apnea Patients

INTRODUCTION

The search of biochemical markers of endothelial dysfunction: lectin-like oxidized low-density lipoprotein receptor-1 (LOX-1)-involved in atherosclerotic plaques formation-and endothelin-1 (ET-1)-potent vasoconstrictor-might help in detecting obstructive sleep apnea (OSA) patients at high risk of cardiovascular diseases.

MATERIAL AND METHODS

In 71 OSA patients (apnoea/hypopnoea index, AHI 28.2 ± 17.9/hour) and in 21 healthy controls the serum levels of LOX-1 and ET-1 were measured.

RESULTS

There were increased levels of ET-1 (1.58 ± 0.65 vs. 1.09 ± 0.38 pg/mL; p < 0.001) but not of LOX-1 in OSA patients as compared with healthy controls. In the patients' group ET-1 levels negatively correlated with serum LDL levels. LOX-1 levels positively correlated with fasting glucose levels and were higher in the patients with than without diabetes. Neither ET-1 nor LOX-1 correlated with OSA severity. In mild OSA patients, there was a negative correlation between LOX-1 and mean arterial oxygen saturation during sleep. In severe OSA patients, there was a positive correlation between LOX-1 levels and uric acid.

CONCLUSION

There is endothelial dysfunction in OSA patients as indicated by increased serum levels of ET-1 and possibly endothelial dysfunction in diabetic OSA patients as indicated by increased serum levels of LOX-1 and its correlation with fasting glucose levels.

Proteolytic Regulation of the Lectin-Like Oxidized Lipoprotein Receptor LOX-1

The lectin-like oxidized-LDL (oxLDL) receptor LOX-1, which is broadly expressed in vascular cells, represents a key mediator of endothelial activation and dysfunction in atherosclerotic plaque development. Being a member of the C-type lectin receptor family, LOX-1 can bind different ligands, with oxLDL being the best characterized. LOX-1 mediates oxLDL uptake into vascular cells and by this means can promote foam cell formation. In addition, LOX-1 triggers multiple signaling pathways, which ultimately induce a pro-atherogenic and pro-fibrotic transcriptional program. However, the molecular mechanisms underlying this signal transduction remain incompletely understood. In this regard, proteolysis has recently emerged as a regulatory mechanism of LOX-1 function. Different proteolytic cleavages within the LOX-1 protein can initiate its turnover and control the cellular levels of this receptor. Thereby, cleavage products with individual biological functions and/or medical significance are produced. Ectodomain shedding leads to the release of a soluble form of the receptor (sLOX1) which has been suggested to have diagnostic potential as a biomarker. Removal of the ectodomain leaves behind a membrane-bound N-terminal fragment (NTF), which despite being devoid of the ligand-binding domain is actively involved in signal transduction. Degradation of this LOX-1 NTF, which represents an athero-protective mechanism, critically depends on the aspartyl intramembrane proteases Signal peptide peptidase-like 2a and b (SPPL2a/b). Here, we present an overview of the biology of LOX-1 focusing on how proteolytic cleavages directly modulate the function of this receptor and, what kind of pathophysiological implications this has in cardiovascular disease.

Transcriptional profiling of mouse cavernous pericytes under high-glucose conditions: Implications for diabetic angiopathy

Purpose

Penile erection requires integrative interactions between vascular endothelial cells, pericytes, smooth muscle cells, and autonomic nerves. Furthermore, the importance of the role played by pericytes in the pathogenesis of angiopathy has only recently been appreciated. However, global gene expression in pericytes in diabetes mellitus-induced erectile dysfunction (DMED) remains unclear. We aimed to identify potential target genes related to DMED in mouse cavernous pericytes (MCPs).

Materials and Methods

Mouse cavernous tissue was allowed to settle under gravity in collagen I-coated dishes, and sprouted cells were subcultivated for experiments. To imitate diabetic conditions, MCPs were treated with normal-glucose (NG, 5 mM) or high-glucose (HG, 30 mM) media for 3 days. Microarray technology was used to evaluate gene expression profiles, and RT-PCR was used to validate sequencing data. Histological examinations and Western blot were used to validate final selected target genes related to DMED.

Results

Decreased tube formation and increased apoptosis were detected in MCPs exposed to the HG condition. As shown by microarray analysis, the gene expression profiles of MCPs exposed to the NG or HG condition differed. A total of 2,523 genes with significantly altered expression were classified into 15 major gene categories. After further screening based on gene expression and RT-PCR and histologic results, we found that Hebp1 gene expression was significantly diminished under the HG condition and in DM mice.

Conclusions

This gene profiling study provides new potential targets responsible for diabetes in MCPs. Validation studies suggest that Hebp1 may be a suitable biomarker for DMED.

Melatonin inhibits high glucose-induced ox-LDL/LDL expression and apoptosis in human umbilical endothelial cells

BACKGROUND

Cardiovascular disease (CVD) is one of the major cause of mortality in diabetic patients. Evidence suggests that hyperglycemia in diabetic patients contributes to increased risk of CVD. This study is to investigate the therapeutic effects of melatonin on glucose-treated human umbilical vein endothelial cells (HUVEC) and provide insights on the underlying mechanisms.

MATERIALS AND METHODS

Cell viability was determined using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. Reactive oxygen species (ROS) and membrane potential was detected using 2',7'-dichlorofluorescein diacetate and 5,5',6,6'-tetrachloro-1,1',3,3'-tetraethylbenzimidazolcarbocyanine iodide (JC-1) dye staining, respectively. While, cell apoptosis was determined by Annexin-V staining and protein expression was measured using Western blot.

RESULTS

Our results suggested that melatonin inhibited glucose-induced ROS elevation, mitochondria dysfunction and apoptosis on HUVEC. Melatonin inhibited glucose-induced HUVEC apoptosis via PI3K/Akt signaling pathway. Activation of Akt further activated BcL-2 pathway through upregulation of Mcl-1 expression and downregulation Bax expression in order to inhibit glucose-induced HUVEC apoptosis. Besides that, melatonin promoted downregulation of oxLDL/LOX-1 in order to inhibit glucose-induced HUVEC apoptosis.

CONCLUSIONS

In conclusion, our results suggested that melatonin exerted vasculoprotective effects against glucose-induced apoptosis in HUVEC through PI3K/Akt, Bcl-2 and oxLDL/LOX-1 signaling pathways.

Effects of Nigella sativa on endothelial dysfunction in diabetes mellitus: A review

ETHNOPHARMACOLOGICAL RELEVANCE

Endothelial dysfunction is involved in lesion generation by the promotion of both early and late mechanism(s) of atherosclerosis such as adhesion molecules up-regulation, increased chemokine secretion and leukocyte adherence, increased cell permeability, enhanced low-density lipoprotein oxidation, cytokine elaboration, platelet activation and vascular smooth muscle cell migration, and proliferation. Nigella sativa is from the Ranunculaceae family which is used in some countries for various medicinal purposes. Nigella sativa seed has been widely used in traditional medicine for the treatment of diabetes.

AIM OF THE REVIEW

This review article summarized the therapeutic effects of Nigella sativa on endothelial dysfunction.

METHODS

Databases such as PubMed, Web of Science, Google Scholar, Scopus, and Iran Medex were considered. The search terms were " Nigella sativa " or "endothelium" and " Diabetes"," endothelial dysfunction ", " Thymoquinone " and " anti-inflammatory effect ".

RESULTS

The current review shows that Nigella sativa and Thymoquinone have a protective effect on endothelial dysfunction induced by diabetes. This is done by several mechanisms such as reduction of inflammatory and apoptotic markers, improving hyperglycemia, hyperlipidemia and antioxidant function, inhibiting platelet aggregation, and regulating eNOS, VCAM-1 and LOX-1 genes expression that involve in the endothelial dysfunction. Thymoquinone also reduces expression and secretion of some cytokines such as MCP-1, interleukin-1β, TNF-α, NF-κB, and Cox-2 that result in anti-inflammation effect.

CONCLUSION

Thymoquinone, the main phenolic terpene found in Nigella sativa, has several important properties such as antidiabetic, anti-inflammatory, and antioxidant activity. Therefore, Nigella sativa can improve endothelial dysfunction.

Could remnant-like particle cholesterol become a risk factor in diabetic menopausal women with coronary artery disease? A cross-sectional study of single academic center in China

Background and aims

It has been confirmed that remnant-like particle cholesterol (RLP-C) mediates the progression of coronary artery disease (CAD). Currently there is limited information on RLP-C in menopausal women. With the special status of diabetes mellitus (DM) combined with the special body changes of the menopausal women, the RLP-C is particularly important when studying the changes that occurred in response to CAD and its associated risk factors. This study discussed whether RLP-C could be an independent risk factor for menopausal women with CAD and DM.

Methods

The cohort consisted of 4753 menopausal women who had undergone coronary angiography. Subjects were separated into CAD and non-CAD groups, and univariate and multivariate logistic regression analysis of CAD risk factors were performed. All patients with a history of DM were divided into DM subgroups. Then, the univariate and multivariate logistic regression analysis of the risk factors of CAD and the comparison among age groups in the DM subgroup were performed. After age stratification of the DM group, the Kruskal-Wallis test was used to analyze the differences of various lipid indexes among age groups.

Results

The multivariate logistic regression showed that RLP-C was an independent risk factor for CAD in menopausal women (OR 1.232, 95%CI 1.070–1.419). In the DM subgroup, it was also found that RLP-C was an independent risk factor for CAD (OR 1.366, 95%CI 1.043–1.791). Kruskal-Wallis test analysis found that RLP-C had no significant difference among three groups (P > 0.05).

Conclusions

RLP-C was proved to be an independent risk factor for menopausal women with CAD and DM.

Targeting Foam Cell Formation in Atherosclerosis: Therapeutic Potential of Natural Products

Foam cell formation and further accumulation in the subendothelial space of the vascular wall is a hallmark of atherosclerotic lesions. Targeting foam cell formation in the atherosclerotic lesions can be a promising approach to treat and prevent atherosclerosis. The formation of foam cells is determined by the balanced effects of three major interrelated biologic processes, including lipid uptake, cholesterol esterification, and cholesterol efflux. Natural products are a promising source for new lead structures. Multiple natural products and pharmaceutical agents can inhibit foam cell formation and thus exhibit antiatherosclerotic capacity by suppressing lipid uptake, cholesterol esterification, and/or promoting cholesterol ester hydrolysis and cholesterol efflux. This review summarizes recent findings on these three biologic processes and natural products with demonstrated potential to target such processes. Discussed also are potential future directions for studying the mechanisms of foam cell formation and the development of foam cell-targeted therapeutic strategies.

Serum Levels of Carbamylated LDL and Soluble Lectin-Like Oxidized Low-Density Lipoprotein Receptor-1 Are Associated with Coronary Artery Disease in Patients with Metabolic Syndrome

Background and objectives: Lectin-like oxidized low density lipoprotein receptor-1 (LOX-1) has been recognized as the primary receptor for carbamylated low-density lipoproteins (cLDL) and is increasingly being viewed as a critical mediator of vascular inflammation and atherosclerosis. The aim of the current study was to evaluate the possible role of circulating cLDL and soluble LOX-1 (sLOX-1) as potential biomarkers of metabolic syndrome (MetS) as well as of coronary artery disease (CAD) among MetS patients. Materials and Methods: The serum levels of cLDL and sLOX-1 were measured by ELISA in 30 MetS patients without CAD, 30 MetS patients with CAD, and 30 healthy controls. Results: Patients with MetS had significantly higher serum levels of both cLDL and sLOX-1 than the healthy controls but lower in comparison to MetS + CAD subjects. Serum sLOX-1 concentration correlated significantly with fasting glucose (r_s = 0.414, p = 0.001) and high-density lipoprotein (HDL)-cholesterol (r_s = −0.273, p = 0.035) in the whole MetS cohort, whereas it correlated with cLDL only in the MetS + CAD subgroup (r_s = 0.396, p = 0.030). The receiver-operating characteristic (ROC) curves of cLDL and sLOX-1 for MetS diagnosis had area under the curve (AUC) values of 0.761 and 0.692, respectively. AUC values of cLDL and sLOX-1 for CAD diagnosis among MetS patients were 0.811 and 0.739. Elevated serum levels of cLDL and sLOX-1 were associated with a higher risk of MetS development [odds ratio (OR) 24.28, 95% confidence interval (CI): 5.86–104.61, p < 0.001 and OR 4.75; 95% CI: 1.58–14.25, p = 0.009] as well as with presence of CAD among MetS subjects (OR 11.23; 95% CI: 3.10–40.71, p < 0.001 and OR 4.03; 95% CI: 1.73–11.84, p = 0.019, respectively). Conclusions: The present study underscores the potential of cLDL and sLOX-1 as promising biomarkers for diagnosis and risk assessment of MetS and CAD among the MetS population.

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.

Requisite roles of LOX-1, JNK, and arginase in diabetes-induced endothelial vasodilator dysfunction of porcine coronary arterioles

Diabetes is associated with cardiac inflammation and impaired endothelium-dependent coronary vasodilation, but molecular mechanisms involved in this dysfunction remain unclear. We examined contributions of inflammatory molecules lectin-like oxidized low-density lipoprotein receptor-1 (LOX-1), stress-activated kinases (c-Jun N-terminal kinase [JNK] and p38), arginase, and reactive oxygen species to coronary arteriolar dysfunction in a porcine model of type 1 diabetes. Coronary arterioles were isolated from streptozocin-induced diabetic pigs and control pigs for vasoreactivity and molecular/biochemical studies. Endothelium-dependent nitric oxide (NO)-mediated vasodilation to serotonin was diminished after 2 weeks of diabetes, without altering endothelium-independent vasodilation to sodium nitroprusside. Superoxide scavenger TEMPOL, NO precursor L-arginine, arginase inhibitor nor-NOHA, anti-LOX-1 antibody or JNK inhibitors SP600125 and BI-78D3 improved dilation of diabetic vessels to serotonin. However, hydrogen peroxide scavenger catalase, anti-IgG antibody or p38 kinase inhibitor SB203580 had no effect. Combined inhibition of arginase and superoxide levels did not further improve vasodilation. Arginase-I mRNA expression, LOX-1 and JNK protein expression, and superoxide levels were elevated in diabetic arterioles. In conclusion, sequential activation of LOX-1, JNK, and L-arginine consuming enzyme arginase-I in diabetes elicits superoxide-dependent oxidative stress and impairs endothelial NO-mediated dilation in coronary arterioles. Therapeutic targeting of these adverse vascular molecules may improve coronary arteriolar function during diabetes.

Bioinformatics analysis of microRNAs related to blood stasis syndrome in diabetes mellitus patients

In traditional Chinese medicine (TCM), blood stasis syndrome (BSS) is mainly manifested by the increase of blood viscosity, platelet adhesion rate and aggregation, and the change of microcirculation, resulting in vascular endothelial injury. It is an important factor in the development of diabetes mellitus (DM). The aim of the present study was to screen out the potential candidate microRNAs (miRNAs) in DM patients with BSS by high-throughput sequencing (HTS) and bioinformatics analysis. Human umbilical vein endothelial cells (HUVECs) were incubated with 10% human serum to establish models of DM with BSS, DM without BSS (NBS), and normal control (NC). Total RNA of each sample was extracted and sequenced by the Hiseq2000 platform. Differentially expressed miRNAs (DE-miRNAs) were screened between samples and compared with known changes in mRNA abundance. Target genes of miRNAs were predicted by softwares. Gene Ontology (GO) and pathway enrichment analysis of the target genes were conducted. According to the significantly enriched GO annotations and pathways (P-value ≤ 0.001), we selected the key miRNAs of DM with BSS. It showed that the number of DE-miRNAs in BSS was 32 compared with non-blood stasis syndrome (NBS) and NC. The potential candidate miRNAs were chosen from GO annotations in which target genes were significantly enriched (-log10 (P-value) > 5), which included miR-140-5p, miR-210, miR-362-5p, miR-590-3p, and miR-671-3p. The present study screened out the potential candidate miRNAs in DM patients with BSS by HTS and bioinformatics analysis. The miRNAs will be helpful to provide valuable suggestions on clinical studies of DM with BSS at the gene level.

Contribution of lectin-like oxidized low-density lipoprotein receptor-1 and LOX-1 modulating compounds to vascular diseases

The lectin-like oxidized low-density lipoprotein receptor-1 (LOX-1) is the major receptor for binding and uptake of oxidized low-density lipoprotein (oxLDL) in endothelial cells. LOX-1 is also expressed in macrophages, smooth muscle cells and platelets. Following internalization of oxLDL, LOX-1 initiates a vicious cycle from activation of pro-inflammatory signaling pathways, thus promoting an increased reactive oxygen species formation and secretion of pro-inflammatory cytokines. LOX-1 plays a pivotal role in the development of endothelial dysfunction, foam cell and advanced lesions formation as well as in myocardial ischemia. Furthermore, it is known that LOX-1 plays a pivotal role in mitochondrial DNA damage, vascular cell apoptosis, and autophagy. A large number of studies provide evidence of a LOX-1's role in endothelial dysfunction, hypertension, diabetes, and obesity. In addition, novel insights into LOX-1 ligands and the activated signaling pathways have been gained. Recent studies have shown an interaction of LOX-1 with microRNA's, thus providing novel tools to regulate LOX-1 function. Because LOX-1 is increased in atherosclerotic plaques and contributes to endothelial dysfunction, several compounds were tested in vivo and in vitro to modulate the LOX-1 expression in therapeutic approaches.

Involvement of epithelial-mesenchymal transition afforded by activation of LOX-1/ TGF-β1/KLF6 signaling pathway in diabetic pulmonary fibrosis

BACKGROUND AND OBJECTIVE

Diabetic pulmonary fibrosis is a severe disease that increases mortality risk of diabetes. However, the molecular mechanisms leading to pulmonary fibrosis in diabetes are poorly understood. This study investigated the roles of epithelial-mesenchymal transition (EMT) and the associated molecular mechanisms in streptozotocin (STZ)-induced rat pulmonary fibrosis.

METHODS

The rat model of diabetic pulmonary fibrosis was established by intraperitoneal injection of a single dose of STZ (35 mg/kg). Typical lesions of diabetic pulmonary fibrosis were observed 8 weeks after STZ injection by hematoxylin-eosin (HE) and Masson staining. Human bronchial epithelial cells (HBECs) and A549 cells were treated by high glucose. Gene or protein expression was measured by real-time PCR, Western blot, immunohistochemistry or immunofluorescence. The knockdown of lectin-like oxidized low density lipoprotein receptor-1 (LOX-1) or transforming growth factor-β1 (TGF-β1) was conducted by siRNA.

RESULTS

Activation of EMT was observed in lung tissues of STZ-induced diabetic rats, exhibiting a loss in the epithelial cell marker E-cadherin and an increase in the mesenchymal marker Vimentin. The protein and mRNA levels of LOX-1, TGF-β1 and krüppel-like factor 6 (KLF6) in the lung tissues were increased. Incubation of HBECs and A549 cells with high glucose activated EMT and induced an increase in LOX-1, TGF-β1 and KLF-6 expression. LOX-1 siRNA inhibited high glucose-induced EMT in HBECs and A549 cells, which correlated with the reduction of TGF-β1. TGF-β1 siRNA decreased the expression of LOX-1 and KLF6.

CONCLUSIONS

EMT was involved in the pathological process of diabetic pulmonary fibrosis, which was activated by LOX-1/TGF-β1/KLF6 signaling pathway.

Establishment of in vitro model of erectile dysfunction for the study of high-glucose-induced angiopathy and neuropathy

Penile erection requires complex interaction between vascular endothelial cells, smooth muscle cells, pericytes, and autonomic nerves. Diabetes mellitus is one of the most common causes of erectile dysfunction (ED) and multiple pathogenic factors, such as cavernous angiopathy and autonomic neuropathy, are associated with diabetic ED. Although a variety of animal models of diabetic ED play an important role in understanding pathophysiologic mechanisms of diabetes-induced ED, these animal models have limitations for addressing the exact cellular or molecular mechanisms involved in ED. Therefore, we established an in vitro model of ED for the study of high-glucose-induced angiopathy and neuropathy. We successfully isolated and cultivated mouse cavernous endothelial cells (MCECs) and mouse cavernous pericytes (MCPs). The cells were exposed to the normal-glucose (5 mmoL) or high-glucose (30 mmoL) condition for 48 h. In vitro matrigel assay revealed impairments in tube formation in primary cultured MCECs or MCPs exposed to high-glucose condition. To study cellular interaction between MCECs and MCPs, co-culture systems including indirect contact, indirect non-contact, and direct mixed co-culture system, were established. We observed impaired tube formation and increased permeability in MCECs-MCPs co-culture exposed to high-glucose condition. To evaluate the effect of high-glucose on neurite sprouting, the mouse major pelvic ganglion (MPG) tissue was harvested and cultivated in matrigel. Neurite outgrowth and nNOS-positive nerve fibers were significantly lower in MPG tissues exposed to the high-glucose condition than in the tissues exposed to the normal-glucose condition. We believe that in vitro model of ED will aid us to understand the role of each cellular component in the pathogenesis of diabetic ED, and also be a useful tool for determining the efficacy of candidate therapeutics targeting vascular or neuronal function. This model would present a new avenue for drug discovery and development of novel therapeutic modalities for erectile dysfunction.

Association of the LOX-1 rs1050283 Polymorphism with Risk for Atherosclerotic Cerebral Infarction and its Effect on sLOX-1 and LOX-1 Expression in a Chinese Population

AIMS

The interaction between lectin-like oxidized low density lipoprotein (LDL) receptor-1 (LOX-1) and oxidized LDL (ox-LDL) has been viewed as an important pathogenic factor for cardiovascular diseases. This study aimed to explore the association of a functional polymorphism rs1050283 in the 3'-untranslated region of the LOX-1 gene with atherosclerotic cerebral infarction (ACI) susceptibility, and we also investigated the effects of the rs1050283 polymorphism on LOX-1 expression and serum levels of sLOX-1 in patients with ACI.

METHODS

A case-controlled study was performed in 526 patients with ACI and 640 healthy controls. Genotyping was performed by DNA sequencing method. Real-time PCR and Western blotting were used to determine the level of LOX-1 expression. Serum levels of sLOX-1 were quantified using ELISA according to the manufacturer's instruction.

RESULTS

The results of the present study showed that the frequency of rs1050283 T allele was significantly higher in patients with ACI than in healthy controls. We also found that the rs1050283 polymorphism T allele was associated with increased LOX-1 expression at mRNA and protein levels in patients with ACI. Furthermore, we also observed that among patients with ACI, those with the rs1050283 T allele showed an increased serum level of sLOX-1.

CONCLUSION

Our research demonstrated that the rs1050283 T allele of LOX-1 is strongly associated with an increased risk for ACI in a Chinese population, which also affects levels of LOX-1 and sLOX-1.

Cryptotanshinone inhibits TNF-α-induced LOX-1 expression by suppressing reactive oxygen species (ROS) formation in endothelial cells

Cryptotanshinone (CPT) is a natural compound isolated from traditional Chinese medicine Salvia miltiorrhiza Bunge. In the present study, the regulatory effect and potential mechanisms of CPT on tumor necrosis factor alpha (TNF-α) induced lectin-like receptor for oxidized low density lipoprotein (LOX-1) were investigated. Human umbilical vein endothelial cells (HUVECs) were cultured and the effect of TNF-α on LOX-1 expression at mRNA and protein levels was determined by Real-time PCR and Western blotting respectively. The formation of intracellular ROS was determined with fluorescence probe CM-DCFH₂-DA. The endothelial ox-LDL uptake was evaluated with DiI-ox-LDL. The effect of CPT on LOX-1 expression was also evaluated with SD rats. TNF-α induced LOX-1 expression in a dose- and time-dependent manner in endothelial cells. TNF-α induced ROS formation, phosphorylation of NF-κB p65 and ERK, and LOX-1 expression, which were suppressed by rotenone, DPI, NAC, and CPT. NF-κB inhibitor BAY11-7082 and ERK inhibitor PD98059 inhibited TNF-α-induced LOX-1 expression. CPT and NAC suppressed TNF-α-induced LOX-1 expression and phosphorylation of NF-κB p65 and ERK in rat aorta. These data suggested that TNF-α induced LOX-1 expression via ROS activated NF-κB/ERK pathway, which could be inhibited by CPT. This study provides new insights for the anti-atherosclerotic effect of CPT.

Puerarin Improves Diabetic Aorta Injury by Inhibiting NADPH Oxidase-Derived Oxidative Stress in STZ-Induced Diabetic Rats

OBJECTIVE

Puerarin is a natural flavonoid isolated from the TCM lobed kudzuvine root. This study investigated the effect and mechanisms of puerarin on diabetic aorta in rats.

METHODS

Streptozotocin- (STZ-) induced diabetic rats were administered with puerarin for 3 weeks. Levels of serum insulin (INS), PGE2, endothelin (ET), glycated hemoglobin (GHb), H2O2, and nitric oxide (NO) in rats were measured by ELISA and colorimetric assay kits. The aortas were stained with H&E. Moreover, the mRNA expression of ICAM-1, LOX-1, NADPH oxidase 2 (NOX2), and NOX4 and the protein expression of ICAM-1, LOX-1, NF-κB p65, E-selectin, NOX2, and NOX4 in aorta tissues were measured by real-time PCR and Western blot, respectively. The localization of ICAM-1, NF-κB p65, NOX2, and NOX4 in the aorta tissues was also determined through immunohistochemistry.

RESULTS

Puerarin treatment exerted no effect on fasting blood glucose levels but significantly reduced the serum levels of INS, GHb, PGE2, ET, H2O2, and NO. In addition, puerarin improved the pathological alterations and inhibited the expression of ICAM-1, LOX-1, NOX2, and NOX4 at both mRNA and protein levels. Puerarin also significantly reduced the number of cells showing positive staining for ICAM-1, NOX2, NOX4, and NF-κB p65.

CONCLUSION

Puerarin demonstrated protective effect on the STZ-induced diabetic rat aorta. The protective mechanisms may include regulation of NF-κB and inhibition of NOX2 and NOX4 followed by inhibition of cell adhesion molecule expression.

Chronic Aerobic Exercise Decreases Lectin-Like Low Density Lipoprotein (LOX-1) Receptor Expression in Heart of Diabetic Rat

BACKGROUND

Overexpression of lectin-like low density lipoprotein (LOX-1) receptor plays an important role in hyperglycemia-induced vascular complications such as atherosclerosis. Based on the beneficial effects of exercise on preventing cardiovascular complications of diabetes, we aimed to examine the protective effects of aerobic exercise on expression of LOX-1 receptor and production of free radicals in the heart of diabetic rats.

METHODS

Four groups of rats were used: (n = 5 per group): sedentary normal, trained normal, sedentary diabetes and trained diabetes. Diabetes was induced by a single intraperitoneal injection of streptozotocin (50 mg/kg). The exercise protocol was consisted of swimming 30 min/day, 5 days/week for eight weeks. Plasma glucose was evaluated at initiation, weeks 4 and 8 of experiment. At the end of experiment, rats were sacrificed and the heart was removed for determination of nitrate, malondialdehyde, and LOX-1 gene expression.

RESULTS

In normal non-diabetic rats, the blood glucose level was <150 mg/dl; however, the induction of diabetes resulted in levels more than >400 mg/dl. Gene expression of LOX-1 was increased in the heart of diabetic rats. Exercise reduced the gene expression of this protein in diabetic states without reducing the blood glucose. Finally, swimming exercise decreased the malondialdehyde and nitrate levels in heart tissue both in control and diabetic rats.

CONCLUSION

Swimming exercise reduces heart expression of the LOX-1 receptor in accompany with reduction of free radicals production. Since these parameters are important in generation of diabetic complications, swimming exercise is a good candidate for reducing these complications.

LOX-1 gene variants and maternal levels of plasma oxidized LDL and malondialdehyde in patients with gestational diabetes mellitus

PURPOSE

The aim of this study was to investigate the relationships between the maternal levels of oxidized LDL (ox-LDL), lipid peroxidation marker malondialdehyde (MDA) and LOX-1 3'UTR188C/T and K167N single nucleotide polymorphisms in pregnant Turkish women with gestational diabetes mellitus (GDM).

METHODS

116 pregnant women with GDM and 120 healthy pregnant women from the same geographic region were included in the study. Polymerase chain reaction-based restriction analysis was used to identify 3'UTR188C/T and K167N polymorphisms of the LOX-1 gene. Plasma ox-LDL and MDA levels were determined by enzyme-linked immunosorbent assay and spectrophotometric method in all study subjects, respectively.

RESULTS

Our results indicated that the distribution of the LOX-1 3'UTR188C/T and K167N genotypes and alleles did not differ significantly among subjects with or without GDM (p > 0.05). TT and NN genotype carriers are associated with some glucose metabolism parameters (p < 0.05). There were no significant differences among plasma ox-LDL and MDA levels with regard to LOX-1 3'UTR188C/T and K167N polymorphisms in GDM group and control subjects (p > 0.05). According to the combined genotype analysis of LOX-1 3'UTR 188 TT and K167N NN polymorphisms, plasma MDA and ox-LDL levels were significantly different between women with GDM and healthy subjects either with or without combined TT/NN genotype carriers (p < 0.001).

CONCLUSIONS

According to our results, ox-LDL and MDA levels were increased in GDM pregnant women and healthy pregnant women either with or without combined TT/NN genotype carriers, for our Turkish sample, these genotype carriers appear to be related with increased oxidative stress in patients with GDM.

Plasma soluble lectin-like oxidized low-density lipoprotein receptor-1 as a novel prognostic biomarker in patients with ST-segment elevation acute myocardial infarction

BACKGROUND

Soluble lectin-like oxidized low-density lipoprotein receptor-1 (sLOX-1) level is a reliable prognostic biomarker in acute coronary syndrome. However, it is unclear whether its plasma level at acute phase is related to the long-term prognosis in patients with ST-segment elevation acute myocardial infarction (STEMI). METHODS AND RESULTS: We prospectively examined the relation between plasma sLOX-1 level on admission and prognosis in 153 consecutive STEMI patients admitted within 24 h of onset. Primary percutaneous coronary intervention was performed in 144 patients. The patients were divided into 2 groups by the median value (71 pg/ml) of plasma sLOX-1 level on admission [sLOX-1 level ≤71 pg/ml (n=77) and >71 pg/ml (n=76)], and were followed for median of 1,156 days. All-cause mortality and the combined endpoints of major adverse cardiovascular events (MACE) defined as cardiovascular mortality and recurrent MI were both significantly higher in patients with sLOX-1 values above median than in those below median (25.0% vs. 3.9%, P<0.001, and 19.4% vs. 6.5%, P=0.019 by log-rank test, respectively). Even after adjustment for confounders, a level of sLOX-1 above median was an independent predictor for all-cause mortality (hazard ratio (HR): 5.893; 95% confidence interval (CI): 1.665-20.854, P=0.006) and MACE (HR: 3.457; 95% CI: 1.164-10.270, P=0.030).

CONCLUSIONS

Elevated plasma sLOX-1 level on admission independently predicts long-term all-cause mortality and MACE after STEMI.

Association of LOXIN, a new functional splicing isoform of the OLR1 gene, with severity and prognostic localization of critical coronary artery stenoses

AIMS

To evaluate the association between LOXIN, a new functional protective splicing isoform of the oxidized LDL receptor 1 (OLR1) gene, and the severity of coronary artery stenoses.

METHODS

We analyzed 100 consecutive patients with coronary artery disease (CAD) and 100 controls, all evaluated by a new molecular biology test using highly specific allele primers able to identify the single nucleotide variation (IVS4-14 A>G) in the OLR1 gene (Loxin Test - Technogenetics). All the patients and the controls underwent coronary angiography and, for quantitative evaluation, we used both vessel and stenosis score, and SYNTAX score to evaluate the severity of CAD. Moreover, we defined the prognostic localization of CAD as a critical stenosis (>50%) of the left main and/or proximal segment of left anterior descending artery (LAD). Finally, we evaluated a correlation with the presence of diabetes mellitus, dyslipidemia, hypertension, smoking and family history of CAD.

RESULTS

In this selected population, even though the 'AA nonrisk haplotype' is more frequent in the controls, we did not find any statistically significant correlation between the severity of CAD or the prognostic localization of critical stenosis and the difference of IVS4-14 A>G OLR1 genotype (P > 0.05). CAD patients showed significantly higher frequencies of dyslipidemia and smoking (P < 0.05) than controls, but no significant association was found between overall risk factors and the OLR1 polymorphism.

CONCLUSION

In this selected population, we did not find any correlation of LOXIN with the severity or prognostic localization of CAD on left main and/or proximal LAD.

Role of microangiopathy in diabetic cardiomyopathy

Although heart disease due to diabetes is mainly associated with complications of the large vessels, microvascular abnormalities are also considered to be involved in altering cardiac structure and function. Three major defects, such as endothelial dysfunction, alteration in the production/release of hormones, and shift in metabolism of smooth muscle cells, have been suggested to produce damage to the small arteries and capillaries (microangiopathy) due to hyperglycemia, and promote the development of diabetic cardiomyopathy. These factors may either act alone or in combination to produce oxidative stress as well as changes in cellular signaling and gene transcription, which in turn cause vasoconstriction and structural remodeling of the coronary vessels. Such alterations in microvasculature produce hypoperfusion of the myocardium and thereby lower the energy status resulting in changes in Ca(2+)-handling, apoptosis, and decreased cardiac contractile force. This article discusses diabetes-induced mechanisms of microvascular damage leading to cardiac dysfunction that is characterized by myocardial dilatation, cardiac hypertrophy as well as early diastolic and late systolic defects. Metabolic defects and changes in neurohumoral system due to diabetes, which promote disturbances in vascular homeostasis, are highlighted. In addition, increase in the vulnerability of the diabetic heart to the development of heart failure and the signaling pathways integrating nuclear factor κB and protein kinase C in diabetic cardiomyopathy are also described for comparison.

Lipopolysaccharide induced LOX-1 expression via TLR4/MyD88/ROS activated p38MAPK-NF-κB pathway

Lectin-like receptor for oxidized low density lipoprotein (LOX-1) plays a key role in endothelial ox-LDL endocytosis, endothelial dysfunction and atherogenesis. In the present study, the effect of lipopolysaccharide (LPS) on LOX-1 expression and the underlying molecular pathways were investigated. Human umbilical vein endothelial cells (HUVECs) were treated with LPS and the protein expressions of LOX-1, TLR4, TLR2, MyD88, Nox4, Nox2, PI3K, p38MAPK, JNK, ERK, Nrf1, Nrf2 and p65 were examined by Western blotting. The intracellular reactive oxygen species (ROS) production was examined by flow cytometry with fluorescence probe DCFH2-DA. The role of TLR4, MyD88 and Nox4 were determined with specific siRNA. The endothelial ox-LDL uptake and the endothelial-monocyte adhesion were evaluated with DiI-ox-LDL and Hoechst 33342 respectively. The effect of LPS on LOX-1 expression in aorta tissue was also studied with male C57/BL6 mice by intraperitoneal injection of LPS. The results showed that LPS induced LOX-1 protein expression in a time- and concentration-dependent manner. The mRNA expression of LOX-1 was also upregulated. The protein expression of LOX-1 and phosphorylated p38MAPK, p65 was significantly enhanced by LPS both in vitro and in vivo. LPS induced LOX-1 expression was blocked by siRNA for TLR4, MyD88, and Nox4 and inhibitors for p38MAPK, NF-κB, cyclooxygenase-2, and NADPH oxidase. Both LPS induced ox-LDL uptake and endothelial-monocyte adhesion were significantly inhibited by anti-LOX-1 antibody. LPS dramatically induced LOX-1 protein expression in aorta tissues. In conclusion, our data suggested that LPS induces LOX-1 expression via TLR4/MyD88/ROS activated p38MAPK/NF-κB pathway in endothelial cells, which provides new regulatory mechanisms for LOX-1 expression.

Role of lectin-like oxidized low density lipoprotein-1 in fetoplacental vascular dysfunction in preeclampsia

The bioavailability of nitric oxide (NO) represents a key marker in vascular health. A decrease in NO induces a pathological condition denominated endothelial dysfunction, syndrome observed in different pathologies, such as obesity, diabetes, kidney disease, cardiovascular disease, and preeclampsia (PE). PE is one of the major risks for maternal death and fetal loss. Recent studies suggest that the placenta of pregnant women with PE express high levels of lectin-like oxidized LDL receptor-1 (LOX-1), which induces endothelial dysfunction by increasing reactive oxygen species (ROS) and decreasing intracellular NO. Besides LOX-1 activation induces changes in migration and apoptosis of syncytiotrophoblast cells. However, the role of this receptor in placental tissue is still unknown. In this review we will describes the physiological roles of LOX-1 in normal placenta development and the potential involvement of this receptor in the pathophysiology of PE.

Insulin regulates monocyte trans-endothelial migration through surface expression of macrophage-1 antigen

During the pathogenesis of atherosclerosis, adhesion of monocytes to vascular endothelium and subsequent migration across the endothelium has been recognized as a key process in the chronic inflammatory response in atherosclerosis. As type 2 diabetes is closely associated with the pathogenesis of atherosclerosis, we investigated whether monocyte adhesion and migration were affected by insulin. We found that insulin activated Akt and induced subsequent migration in THP-1. However, glucose and insulin-like growth factor-1, which is a growth factor that is structurally similar to insulin, were not effective. Insulin-dependent migration of THP-1 was blocked by inhibition of PI3K or Akt and by silencing of Akt1. Insulin-dependent migration of bone marrow-derived monocytic cells (BDMCs) was attenuated by inhibition of PI3K and Akt. In addition, BDMCs from Akt1(-/-) mice showed defects in insulin-dependent migration. Stimulation of THP-1 with insulin caused adhesion with human vein endothelial cells (HUVECs) that was blocked by silencing of Akt1. However, stimulation of HUVECs did not cause adhesion with THP-1. Moreover, BDMCs from Akt1(-/-) mice showed defects in insulin-dependent adhesion with HUVECs. Insulin induced surface expression of Mac-1, and neutralization of Mac-1 blocked insulin-induced adhesion of THP-1 as well as BDMCs. Surface expression of Mac-1 was blocked in THP-1 with silenced Akt1, and in BDMCs isolated from mice lacking Akt1. Finally, trans-endothelial migration of THP-1 and BDMCs was blocked by Mac-1-neutralizing antibody, in THP-1 with silenced Akt1 and in BDMCs from Akt1(-/-) mice. These results suggest that insulin stimulates monocyte trans-endothelial migration through Akt-dependent surface expression of Mac-1, which may be part of the atherogenesis in type 2 diabetes.

Soluble Lectin-Like Oxidized LDL Receptor 1 as a Possible Mediator of Endothelial Dysfunction in Patients With Metabolic Syndrome

BACKGROUND

Metabolic syndrome (MetS) defines a well-known cluster of metabolic disturbances associated with an increased risk of cardiovascular disease and diabetes. The aim of this study was to examine the distribution of soluble lectin-like oxidized low-density lipoprotein (LDL) receptor-1 (sLOX-1) levels in patients with MetS, possible association of sLOX-1 with oxidized LDL (oxLDL), endothelial nitric oxide synthase (eNOS), nitric oxide (NOx), endothelin-1 (ET-1), paraoxonase 1 (PON1), and arylesterase (ARE) activities, and these parameters compared with healthy controls.

METHODS

A total of 55 patients (37 women, 18 men) with MetS and 29 healthy controls (19 women, 10 men) with a body mass index (BMI) less than 25 kg/m(2) were enrolled in the study.

RESULTS

sLOX-1, oxLDL, and ET-1 levels were significantly higher in patients with MetS than in control subjects (P = 0.023 P < 0.001, and P < 0.001, respectively). MetS patients have significantly lower eNOS and NOx levels, and PON1 and ARE activities than control subjects (P = 0.017, P < 0.004, P < 0.001, and P = 0.010, respectively). A positive correlation was observed between the sLOX-1 levels and the oxLDL, ET-1, BMI, glucose levels. ET-1 levels also exhibited significant negative correlation with ARE activity.

CONCLUSION

sLOX-1 levels are associated with cardiovascular risk factors, such as increased oxLDL, obesity, and diabetes, in patients with MetS. An increased concentration of sLOX-1 could be an early predictor of endothelial damage in MetS. In addition, it appears that oxLDL, ET-1, eNOS, NOx, PON1, and ARE activities may accurately reflect the levels of endothelial dysfunction in MetS patients.

Oxidized LDL receptor 1 gene polymorphism in patients with metabolic syndrome

AIMS

The lectin-like oxidized low-density lipoprotein receptor-1 (LOX-1), encoded by the OLR1 gene, has been implicated in the pathogenesis of atherosclerosis. We therefore evaluated the genotyping of OLR1 gene in a sample of 55 patients with Metabolic Syndrome, a clinical condition characterized by a high cardiovascular risk.

METHODS AND PATIENTS

The genotyping of the LOX-1 was performed by polymerase chain reaction (PCR) analysis of the IVS4-14 A>G OLR1 polymorphism embedded within the OLR1 Linkage Disequilibrium block. Patients were assessed for routine serum parameters, microalbuminuria, insulin resistance (HOMA) and oxidative stress (thiobarbituric acid reactive substances, TBARs and thioredoxin).

RESULTS

The allele or genotype distribution of the OLR1 IVS4-14 A>G was not statistically different between MS and controls subjects. A positive association was found between IVS4-14 GG genotype, microalbuminuria and fasting glycaemia as well as a higher frequency of type 2 diabetes, elevated microalbuminuria, fasting serum glucose and HOMA index in the same subjects. Thioredoxin values were higher in patients with MS but did not differ in relation to OLR1 IVS4-14 A>G genotype. The TBARs/Cholesterol ratio was higher in MS both in IVS4-14 GG and in IVS4-14 AG.

CONCLUSION

IVS4-14 GG genotype seems to be related to glucose metabolism disturbance, elevated insulin level and lipid peroxidation in patients with MS.

The association between soluble lectin-like oxidized low-density lipoprotein receptor-1 levels and patients with isolated coronary artery ectasia

Some evidence suggests that chronic inflammation plays a critical role in the development and progression of coronary artery ectasia. Lectin-like oxidized low-density lipoprotein receptor-1 is involved in multiple phases of vascular dysfunction, including endothelial dysfunction, atherogenesis, initiation of plaque rupture, and restenosis. The objectives was to study the purpose of the current study was to determine whether soluble lectin-like oxidized low-density lipoprotein receptor-1 is associated with isolated coronary artery ectasia patients. Forty-six patients with isolated coronary artery ectasia without stenosis and 46 control subjects with angiographically normal coronary arteries were included in this study. Lectin-like oxidized low-density lipoprotein receptor-1 levels were measured in serum by sandwich enzyme-linked immunosorbent assay. Baseline characteristics of the two groups were similar. Plasma levels of lectin-like oxidized low-density lipoprotein receptor-1 were significantly higher in the coronary artery ectasia group than normal coronary artery group (1.7 ± 0.8 ng/ml vs. 1.1 ± 0.3 ng/ml, P < 0.001, respectively). No correlation was found between plasma soluble lectin-like oxidized low-density lipoprotein receptor-1 levels and different types of ectasia in patients with coronary artery ectasia. In this study, we found significantly higher levels of soluble lectin-like oxidized low-density lipoprotein receptor-1 in coronary artery ectasia patients when compared to control subjects with normal coronary arteries, suggesting that soluble lectin-like oxidized low-density lipoprotein receptor-1 may be involved in the pathogenesis of coronary artery ectasia.

LOX-1 in atherosclerosis: biological functions and pharmacological modifiers

Lectin-like oxidized LDL (oxLDL) receptor-1 (LOX-1, also known as OLR-1), is a class E scavenger receptor that mediates the uptake of oxLDL by vascular cells. LOX-1 is involved in endothelial dysfunction, monocyte adhesion, the proliferation, migration, and apoptosis of smooth muscle cells, foam cell formation, platelet activation, as well as plaque instability; all of these events are critical in the pathogenesis of atherosclerosis. These LOX-1-dependent biological processes contribute to plaque instability and the ultimate clinical sequelae of plaque rupture and life-threatening tissue ischemia. Administration of anti-LOX-1 antibodies inhibits atherosclerosis by decreasing these cellular events. Over the past decade, multiple drugs including naturally occurring antioxidants, statins, antiinflammatory agents, antihypertensive and antihyperglycemic drugs have been demonstrated to inhibit vascular LOX-1 expression and activity. Therefore, LOX-1 represents an attractive therapeutic target for the treatment of human atherosclerotic diseases. This review aims to integrate the current understanding of LOX-1 signaling, regulation of LOX-1 by vasculoprotective drugs, and the importance of LOX-1 in the pathogenesis of atherosclerosis.

CIKS (Act1 or TRAF3IP2) mediates high glucose-induced endothelial dysfunction

Hyperglycemia-induced endothelial dysfunction is characterized by enhanced inflammatory cytokine and adhesion molecule expression, and endothelial-monocyte adhesion. The adapter molecule CIKS (connection to IKK and SAPK/JNK; also known as Act1 or TRAF3IP2) is an upstream regulator of NF-κB and AP-1, and plays a role in inflammation and injury. Here we show that high glucose (HG; 25mM vs. 5mM d-glucose)-induced endothelial-monocyte adhesion and inhibition of endothelial cell (EC) migration were both reversed by CIKS knockdown. In EC, HG induced CIKS mRNA and protein expression via DPI-inhibitable Nox4-dependent ROS generation. Further, HG induced CIKS transcription and enhanced CIKS promoter-dependent reporter gene activation via Nox4, ROS, AP-1 and C/EBP. Coimmunoprecipitation and immunoblotting revealed CIKS/IKKβ/JNK physical association under basal conditions that was enhanced by HG treatment. Importantly, CIKS knockdown inhibited HG-induced (i) IKKβ and JNK phosphorylation, (ii) p65 and c-Jun nuclear translocation, and (iii) NF-κB- and AP-1-dependent proinflammatory cytokine, chemokine, and adhesion molecule expression. Similar to HG, the deleterious metabolic products of chronic hyperglycemia, AGE-HSA, AOPPs-HSA and oxLDL, also induced CIKS-dependent endothelial dysfunction. Notably, aortas from streptozotocin-induced and the autoimmune type 1 diabetic NOD and Akita mice showed enhanced DPI-inhibitable ROS generation and CIKS expression. Since CIKS mediates high glucose-induced NF-κB and AP-1-dependent inflammatory signaling and endothelial dysfunction, targeting CIKS may delay progression of vascular diseases during diabetes mellitus and atherosclerosis.

Tanshinone II-A inhibits oxidized LDL-induced LOX-1 expression in macrophages by reducing intracellular superoxide radical generation and NF-κB activation

Lectin-like oxidized LDL (oxLDL) receptor-1 (LOX-1), a novel scavenger receptor highly expressed in human and experimental atherosclerotic lesions, is responsible for the uptake of oxLDL in vascular cells. We demonstrated previously that Tanshinone II-A (Tan), a pharmacologically active compound extracted from the rhizome of the Chinese herb Salvia miltiorrhiza Bunge, inhibits atherogenesis in hypercholesterolemic rats, rabbits, and apolipoprotein-E deficient (ApoE⁻/⁻) mice. However, the precise mechanism by which Tan protects against atherogenesis remains to be elucidated. Therefore, we hypothesized that Tan can suppress the uptake of oxLDL by diminishing the expression of LOX-1 via suppression of NF-κB signaling pathway, thereby contributing to reduced macrophage foam cell formation. In cultured murine macrophages, oxLDL induced LOX-1 expression at the mRNA and protein levels, was abrogated by addition of Tan or pyrrolidinedithiocarbamic acid ammonium salt (PDTC), a widely used inhibitor of NF-κB, suggesting the involvement of NF-κB. Tan also reduced LOX-1 expression in atherosclerotic lesions of ApoE⁻/⁻ mice fed a high cholesterol diet. Mechanistically, Tan suppressed the nuclear translocation of NF-κB P65 subunit and phosphorylation of IκB-α induced by oxLDL. Electrophoretic mobility shift assay (EMSA) demonstrated that Tan inhibited the nuclear protein binding to NF-κB consensus sequence. Functionally, we observed that Tan inhibited DiI-oxLDL uptake by macrophages in a fashion similar to that produced by LOX-1 neutralizing antibody. Our current findings reveal a novel mechanism by which Tan protects against atherogenesis and shed new light on the potential therapeutic application of Tan to the treatment and prevention of atherosclerotic cardiovascular diseases.

The discovery of LOX-1, its ligands and clinical significance

LOX-1 is an endothelial receptor for oxidized low-density lipoprotein (oxLDL), a key molecule in the pathogenesis of atherosclerosis.The basal expression of LOX-1 is low but highly induced under the influence of proinflammatory and prooxidative stimuli in vascular endothelial cells, smooth muscle cells, macrophages, platelets and cardiomyocytes. Multiple lines of in vitro and in vivo studies have provided compelling evidence that LOX-1 promotes endothelial dysfunction and atherogenesis induced by oxLDL. The roles of LOX-1 in the development of atherosclerosis, however, are not simple as it had been considered. Evidence has been accumulating that LOX-1 recognizes not only oxLDL but other atherogenic lipoproteins, platelets, leukocytes and CRP. As results, LOX-1 not only mediates endothelial dysfunction but contributes to atherosclerotic plaque formation, thrombogenesis, leukocyte infiltration and myocardial infarction, which determine mortality and morbidity from atherosclerosis. Moreover, our recent epidemiological study has highlighted the involvement of LOX-1 in human cardiovascular diseases. Further understandings of LOX-1 and its ligands as well as its versatile functions will direct us to ways to find novel diagnostic and therapeutic approaches to cardiovascular disease.

LOX-1, oxidative stress and inflammation: a novel mechanism for diabetic cardiovascular complications

Diabetes mellitus is a common metabolic disease characterized by a state of oxidative stress, inflammation and endothelial dysfunction. This malady can lead to a number of complications such as ischemic heart disease, nephropathy, neuropathy, retinopathy and impaired wound healing. The etiology of diabetic complications is multifactorial, and is closely associated with oxidative stress and inflammation. Lectin-like oxidized low-density lipoprotein receptor-1 (LOX-1), a receptor for oxidized low density lipoprotein (ox-LDL), plays critical roles in multiple signal transduction pathways and is involved in the process of oxidative stress and inflammation. Recent studies provide important insights into the roles of LOX-1 in the development and progression of diabetic vasculopathy which is the underlying mechanism of diabetic complications. In this review, we summarize mechanistic studies, mainly related to LOX-1, on the development and progression of diabetes mellitus and its cardiovascular complications.

LOX-1 transcription

The importance of the lectin-like oxidized LDL receptor (LOX-1) gene in cardiovascular and other diseases is slowly being revealed. LOX-1 gene expression appears to be a "canary in a coal mine" for atherogenesis, being strongly up-regulated early on in a number of cell types when they are activated, and predicting the sites of future disease. From this early time point the LOX-1 protein often participates in the disease process itself. While gene/protein expression can be regulated on a multiplicity of levels, the most basic and important mode of regulation is usually transcriptional. There are very few studies on the transcriptional regulation of the human LOX-1 promoter; fewer still on definitive mapping of the transcription factors involved. It is known that a wide variety of stimuli up-regulate LOX-1, usually/probably on the transcriptional level. Angiotensin II (Ang II) is one important regulator of renin-angiotensin system and stimulator LOX-1. Ang II is known to up-regulate LOX-1 transcription through an NF-kB motif located at nt -2158. Oxidized low density lipoprotein (ox-LDL) is another important cardiovascular regulator, particularly of atherosclerotic disease, and a strong stimulator of LOX-1. Ox-LDL is known to up-regulate LOX-1 transcription through an Oct-1 motif located at nt -1556. The subsequent enhanced LOX-1 receptor numbers and their binding by ox-LDL ligand triggers a positive feedback loop, increasing further LOX-1 expression, with a presently unknown regulatory governor. The Oct-1 gene also has its own Oct-1-driven positive feedback loop, which likely also contributes to LOX-1 up-regulation. There is also data which suggests the involvement of the transcription factor AP-1 during stimulation with Phorbol 12-myristate acetate. While the importance of NF-κB as a transcriptional regulator of cardiovascular-relevant genes is well known, the importance of Oct-1 is not. Data suggests that Oct-1-mediated up-regulation of transcription is an early event in the stimulation of LOX-1 by ox-LDL. Yet Oct-1 also down-regulates cardiovascular-relevant genes by suppressing NF-κB transactivation. Thus, Oct-1 is presently somewhat of an enigma, up-regulating and down-regulating genes seemingly at random without an overall theme (with the exception of cell cycle). Yet the up-regulation of LOX-1 by ox-LDL is a very important event in atherogenesis (both early and late) and Oct-1 is, therefore, an important transcriptional gatekeeper of this important atherogenic trigger.

Oxidative stress and lectin-like ox-LDL-receptor LOX-1 in atherogenesis and tumorigenesis

Lectin-like oxidized low-density lipoprotein receptor-1 (LOX-1) has been identified as a major receptor for oxidized low-density lipoprotein (ox-LDL) in endothelial cells, monocytes, platelets, cardiomyocytes, and vascular smooth muscle cells. Its expression is minimal under physiological conditions but can be induced under pathological conditions. The upregulation of LOX-1 by ox-LDL appears to be important for physiologic processes, such as endothelial cell proliferation, apoptosis, and endothelium remodeling. Pathophysiologic effects of ox-LDL in atherogenesis have also been firmly established, including endothelial cell dysfunction, smooth muscle cell growth and migration, monocyte transformation into macrophages, and finally platelet aggregation-seen in atherogenesis. Recent studies show a positive correlation between increased serum ox-LDL levels and an increased risk of colon, breast, and ovarian cancer. As in atherosclerosis, ox-LDL and its receptor LOX-1 activate the inflammatory pathway through nuclear factor-kappa B, leading to cell transformation. LOX-1 is important for maintaining the transformed state in developmentally diverse cancer cell lines and for tumor growth, suggesting a molecular connection between atherogenesis and tumorigenesis.

LOX-1 and angiotensin receptors, and their interplay

The renin-angiotensin system (RAS) plays an important role in regulating blood pressure, water-salt balance and the pathogenesis of cardiovascular diseases. Angiotensin II (Ang II) is the physiologically active mediator and mediates the main pathophysiological actions in RAS. Ang II exerts the effects by activating its receptors, primarily type 1 (AT1R) and type 2 (AT2R). Most of the known pathophysiological effects of Ang II are mediated by AT1R activation. The precise physiological function of AT2R is still not clear. Generally, AT2R is considered to oppose the effects of AT1R. Lectin-like oxidized low-density lipoprotein scavenger receptor-1 (LOX-1) is one of the major receptors responsible for binding, internalizing and degrading ox-LDL. The activation of LOX-1 has been known to be related to many pathophysiological events, including endothelial dysfunction and injury, fibroblast growth, and vascular smooth muscle cell hypertrophy. Many of these alterations are present in atherosclerosis, hypertension, and myocardial ischemia and remodeling. A growing body of evidence suggests the existence of a cross-talk between LOX-1 and Ang II receptors. Their interplays are embodied in the reciprocal regulation of their expression and activity. Their interplays are involved in a series of signals. Recent studies suggests that reactive oxygen species (ROS), nitric oxide (NO), protein kinase C (PKC) and mitogen activated protein kinases (MAPKs) are important signals responsible for their cross-talk. This paper reviews these aspects of dyslipidemia and RAS activation.

Soluble lectin-like oxidized LDL receptor-1 and high-sensitivity troponin T as diagnostic biomarkers for acute coronary syndrome. Improved values with combination usage in emergency rooms

BACKGROUND

Although highly sensitive assays for troponin T (hs-TnT) have been developed, the sensitivity and specificity of hs-TnT for diagnosing acute coronary syndrome (ACS) remains imperfect. We evaluated the diagnostic value of a new biomarker of plaque vulnerability (soluble lectin-like oxidized low-density lipoprotein receptor-1, sLOX-1) as compared with hs-TnT in the emergency room (ER).

METHODS AND RESULTS

Plasma sLOX-1 and serum hs-TnT levels were measured in 200 consecutive patients presenting with chest symptoms and ECG abnormalities in the ER (116 ST elevation ACS [STEACS], 44 non-ST elevation ACS [NSTEACS], 40 non-ACS). The non-ACS group consisted of patients with cardiovascular diseases such as coronary spastic angina pectoris, pulmonary thromboembolism, perimyocarditis and takotsubo cardiomyopathy. Levels of sLOX-1 and hs-TnT were significantly higher in STEACS and NSTEACS than in non-ACS patients. The receiver-operating characteristic (ROC) curves of sLOX-1 and hs-TnT for detecting ACS, using the non-ACS patients as negative references, showed that the area under the curve (AUC) values of sLOX-1 and hs-TnT were 0.769 and 0.739, respectively. In the lower hs-TnT (<0.0205ng/ml) subgroup, the AUC value of the ROC curve of sLOX-1 for detecting ACS was 0.869.

CONCLUSIONS

The diagnostic value for ACS was comparable between sLOX-1 and hs-TnT, and the accuracy of ACS diagnosis appeared to improve when sLOX-1 and hs-TnT were measured in combination.

Soluble lectin-like oxidized low-density lipoprotein receptor-1 as an early biomarker for ST elevation myocardial infarction: time-dependent comparison with other biomarkers: time-dependent comparison with other biomarkers

BACKGROUND

The diagnostic sensitivity of myocardial necrosis markers, such as creatine kinase-MB (CK-MB), cardiac troponins, myoglobin and heart-type fatty acid-binding protein (H-FABP) for the earliest stage of ST-elevation myocardial infarction (STEMI), remains insufficient. We compared a new biomarker of plaque vulnerability (soluble lectin-like oxidized low-density lipoprotein receptor-1, sLOX-1) with other biomarkers at the earliest stage of STEMI.

METHODS AND RESULTS

Plasma sLOX-1 levels were measured in 125 STEMI, 44 non-STEMI (NSTEMI) and 125 non-acute myocardial infarction (non-AMI) patients and were significantly (P < 0.0001) higher in the STEMI and NSTEMI than in the non-AMI patients (median, 25th and 75th percentiles: 241.0, 132.3 and 472.2 vs. 147.3, 92.9 and 262.4 vs. 64.3, 54.4 and 84.3 pg/ml, respectively). At the optimal cut-off value of 91.0 pg/ml, sLOX-1 discriminated STEMI from non-AMI with 89.6% sensitivity and 82.4% specificity. Time-dependent changes in sLOX-1, H-FABP, myoglobin, troponin T and CK-MB were analyzed in 27 STEMI patients. Elevated plasma sLOX-1 levels persisted for 24h after admission, whereas other markers were not elevated at the time of admission and peaked at ≥ 2h thereafter. The diagnostic sensitivity of sLOX-1, H-FABP, myoglobin, troponin T and CK-MB for STEMI upon admission (89 min after onset) was 93%, 78%, 70%, 56% and 33%, respectively.

CONCLUSIONS

Plasma sLOX-1 diagnosed the early stages of STEMI more accurately than H-FABP, myoglobin, troponin T and CK-MB.