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

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.

Role of High-sensitivity C-reactive Protein in Future Cardiovascular Events in Hemodialysis Patients

BACKGROUND/AIM

The pathogenesis of cardio-vascular disease (CVD) in hemodialysis (HD) patients involves inflammation and oxidative stress. High-sensitivity C-reactive protein (hs-CRP) is an established inflammatory biomarker associated with CVD. Several studies have suggested that the inflammatory biomarker pentraxin-3 (PTX-3) and the oxidative stress-related biomarker soluble lectin-like low-density lipoprotein receptor-1 (sLOX-1) are novel biomarkers for CVD in non-HD populations. This study aimed to clarify the association of these established and novel biomarkers with future cardiovascular (CV) events in HD patients.

PATIENTS AND METHODS

This was a single-center prospective cohort study that included 255 HD patients. The primary outcome was the composite of nonfatal and fatal CV events. The event-free survival rate between the two groups according to the median plasma level of each biomarker at baseline was evaluated using the Kaplan-Meier method. The risk for CV events at elevated levels of each biomarker was estimated using Cox proportional hazard model.

RESULTS

We observed 44 CV events during the median follow-up period of 743 days. The event-free survival rate significantly differed between the two groups in hs-CRP but not in PTX-3 or sLOX-1. The unadjusted hazard ratio (HR) for CV events in patients with hs-CRP levels above the median was 2.63 [95% confidence interval (CI)=1.37-5.02]. The HR remained significant after adjusting for age, sex, history of CVD, and diabetes (HR=2.30; 95%CI=1.20-4.43).

CONCLUSION

In HD patients, hs-CRP may have a predictable role for future CV events, whereas PTX-3 and sLOX-1 do not.

Associations of CKIP-1 and LOX-1 polymorphisms with the risk of type 2 diabetes mellitus with hypertension among Chinese adults

AIMS

Type 2 diabetes mellitus (T2DM) and hypertension are common high-incidence diseases, closely related, and have common pathogenic basis such as oxidative stress. Casein kinase 2 interacting protein-1 (CKIP-1) and low-density lipoprotein receptor (LOX-1) are considered to be important factors affect the level of oxidative stress in the body. The main purpose of this study was to explore the relationship between CKIP-1 (rs6693817 A > T, rs2306235 C > G) and LOX-1 (rs1050283 G > A, rs11053646 C > G) polymorphisms and the risk of hypertension and diabetes, and try to find new candidate genes for diabetes and diabetes with hypertension etiology in Chinese population.

METHODS

574 T2DM patients and 597 controls frequently matched by age and sex were selected for genotyping of CKIP-1 (rs6693817 A > T, rs2306235 C > G) and LOX-1 gene (rs1050283 G > A, rs11053646 C > G). Logistic regression was used to analyze the correlation between different genotypes and the risk of T2DM and T2DM with hypertension, and the results were expressed as odds ratio (OR) and 95% confidence interval (95% CI).

RESULTS

We found that the risk of T2DM in the AA + AT genotype of rs6693817 was higher than that in the TT genotype in Chinese population (OR = 1.318, 95%CI: 1.011-1.717, P = 0.041), and the difference was still significant after adjustment (OR = 1.370, 95%CI: 1.043-1.799, Padjusted = 0.024), the difference of heterozygotes (AT vs TT: OR = 1.374, 95%CI: 1.026-1.840, Padjusted = 0.033) was statistically significant. But after Bonferroni correction, the significance of the above sites disappeared. And rs6693817 was associated with the risk of T2DM combined with hypertension before and after adjustment in dominant model (OR = 1.424, 95% CI: 1.038-1.954, P = 0.028; OR = 1.460, 95% CI: 1.057-2.015, Padjusted = 0.021, respectively) and in heterozygote model (OR = 1.499, 95% CI: 1.069-2.102, P = 0.019; OR = 1.562, 95% CI: 1.106-2.207, Padjusted = 0.011, respectively). However, only the statistical significance of the heterozygous model remained after Bonferroni correction. rs2306235, rs1050283 and rs11053646 were not significantly correlated with T2DM and T2DM combined with hypertension risk (P > 0.05).

CONCLUSIONS

The results suggest that CKIP-1 rs6693817 is related to the susceptibility of Chinese people to T2DM with hypertension, providing a new genetic target for the treatment of diabetes with hypertension with in the future.

LOX-1 variants modulate the severity of cardiovascular disease: state of the art and future directions

Atherosclerosis is one of the major causes of cerebral infarction and many other ischemic cardio-cerebrovascular diseases. Although large randomized clinical trials have highlighted the impressive benefits of lipid-lowering therapies, the 50-70% of patients who have achieved their lipid-lowering goal remain at high cardiovascular disease risk. For this reason, there is a need to investigate other markers of atherosclerosis progression. LOX-1 is a scavenger receptor that accepts oxidized low-density lipoproteins as major ligand and internalizes it by endocytosis favoring its retention in subendothelial layer and triggering a wide variety of proatherogenic events. However, other factors such as cytokines, shear stress, and advanced glycation end-products can upregulate LOX-1. LOX-1 is encoded by the OLR1 gene, located in the p12.3-p13 region of chromosome 12. OLR1 gene has different isoforms induced by splicing, or single-nucleotide polymorphisms (SNPs). According to some authors, the expression of these isoforms induces a different effect on atherosclerosis and cardiovascular disease. In particular, LOXIN, an isoform lacking part of the functional domain, exerts an important role in atherosclerosis protection. In other cases, studies on SNPs showed an association with more severe forms, like in the case of 3'UTR polymorphisms. The knowledge of these variants can give rise to the development of new preventive therapies and can lead to the identification of subjects at greater risk of cardiovascular event. In this review, we reported the state of the art regarding SNPs with known effects on OLR1 splicing and how LOX-1 variants modulate the severity of cardiovascular disease.

Gene Networks of Hyperglycemia, Diabetic Complications, and Human Proteins Targeted by SARS-CoV-2: What Is the Molecular Basis for Comorbidity?

People with diabetes are more likely to have severe COVID-19 compared to the general population. Moreover, diabetes and COVID-19 demonstrate a certain parallelism in the mechanisms and organ damage. In this work, we applied bioinformatics analysis of associative molecular networks to identify key molecules and pathophysiological processes that determine SARS-CoV-2-induced disorders in patients with diabetes. Using text-mining-based approaches and ANDSystem as a bioinformatics tool, we reconstructed and matched networks related to hyperglycemia, diabetic complications, insulin resistance, and beta cell dysfunction with networks of SARS-CoV-2-targeted proteins. The latter included SARS-CoV-2 entry receptors (ACE2 and DPP4), SARS-CoV-2 entry associated proteases (TMPRSS2, CTSB, and CTSL), and 332 human intracellular proteins interacting with SARS-CoV-2. A number of genes/proteins targeted by SARS-CoV-2 (ACE2, BRD2, COMT, CTSB, CTSL, DNMT1, DPP4, ERP44, F2RL1, GDF15, GPX1, HDAC2, HMOX1, HYOU1, IDE, LOX, NUTF2, PCNT, PLAT, RAB10, RHOA, SCARB1, and SELENOS) were found in the networks of vascular diabetic complications and insulin resistance. According to the Gene Ontology enrichment analysis, the defined molecules are involved in the response to hypoxia, reactive oxygen species metabolism, immune and inflammatory response, regulation of angiogenesis, platelet degranulation, and other processes. The results expand the understanding of the molecular basis of diabetes and COVID-19 comorbidity.

sLOX-1: A Molecule for Evaluating the Prognosis of Recurrent Ischemic Stroke

Several clinical parameters and biomarkers have been proposed as prognostic markers for stroke. However, it has not been clarified whether the risk factors affecting the prognosis of patients with recurrent and first-ever stroke are similar. In this study, we aimed to explore the relationship between soluble lectin-like oxidized low-density lipoprotein receptor 1 (sLOX-1) levels and the prediction of the functional outcome in patients with recurrent and first-ever stroke. A total of 266 patients with recurrent and first-ever stroke, who underwent follow-up for 3 months, were included in this study. Plasma samples were collected within 24 h after onset. The results showed that biomarkers for the prognosis of patients with recurrent stroke were different from that of those with first-ever stroke. sLOX-1 levels were correlated with modified Rankin Scale scores of patients with recurrent stroke alone (r = 0.3232, p = 0.001). sLOX-1 levels were also associated with an increased risk of unfavorable outcomes in patients with recurrent stroke with an adjusted odds ratio of 1.489 (95% confidence interval, 1.204–1.842, p < 0.0001). Combining the risk factors showed greater accuracy for prognosis, yielding a sensitivity of 93.2% and a specificity of 75%, with an area under the curve of 0.916, evaluated by the receiver operating characteristic curve. These findings suggest that the diagnosis and prognosis are different between patients with recurrent stroke and those with first-ever stroke, and sLOX-1 level is an independent prognostic marker in patients with recurrent stroke.

LncRNA-MIAT promotes neural cell autophagy and apoptosis in ischemic stroke by up-regulating REDD1

BACKGROUND

Ischemic stroke (IS) accounts for 80% of stroke incidence, which has an impact on the life quality of patients. Long non-coding RNA (LncRNA), a class of non-coding transcripts greater than 200 nucleotidesin length, has been extensively studied in cerebrovascular diseases. Myocardial infarction associated transcript (MIAT) is highly expressed in nervous system. Therefore this study aims to explore the role of LncRNA MIAT in IS and to clarify its underlying mechanism, providing therapeutic value for the treatment of IS.

METHODS

The neurological function of rats was evaluated by neurological deficit score. Triphenyltetrazolium chloride (TTC) staining was used to detect infarct area in brain tissues. Quantitative real-time polymerase chain reaction (qRT-PCR) was performed to examine the expression of MIAT. Western blotting was used to detect the expressions of REDD1, p-mTOR, autophagy-related proteins LC3 and p62, and apoptotic-related proteins Bax, cleaved-caspase3, Bcl-2. Flow cytometry was applied to examine neuronal cell apoptosis. RNA pull-down and RIP assay was used to verify the binding of MIAT and REDD1. The level of REDD1 ubiquitination was detected by ubiquitination and Co-immunoprecipitation (Co-IP) assay.

RESULTS

The expressions of MIAT and REDD1 were increased in IS rats and oxygen-glucose deprivation/reoxygenation (OGD/R)-induced PC12 cell injury. After interference with si-MIAT, the results of flow cytometry showed that the rate of apoptosis was reduced. Western blotting results showed that the expression of LC3II/LC3I, Bax, and cleaved-caspase3 was decreased, while the expression of p-mTOR, p62, and Bcl-2 was increased. RNA pull-down and RIP assay found the binding relationship between MIAT and REDD1, and interference with si-MIAT down-regulated the expression of REDD1. The level of REDD1 ubiquitination was increased and the expression of REDD1 was decreased after interference with si-MIAT in PC12 cells. Co-IP results showed that interference with si-MIAT enhanced the binding ability of CUL4A-DDB1 and REDD1.

CONCLUSION

Altogether, MIAT promotes autophagy and apoptosis of neural cells and aggravates IS by up-regulating the expression of REDD1.

Lipoprotein receptor signalling in atherosclerosis

The founding member of the lipoprotein receptor family, low-density lipoprotein receptor (LDLR) plays a major role in the atherogenesis through the receptor-mediated endocytosis of LDL particles and regulation of cholesterol homeostasis. Since the discovery of the LDLR, many other structurally and functionally related receptors have been identified, which include low-density lipoprotein receptor-related protein (LRP)1, LRP5, LRP6, very low-density lipoprotein receptor, and apolipoprotein E receptor 2. The scavenger receptor family members, on the other hand, constitute a family of pattern recognition proteins that are structurally diverse and recognize a wide array of ligands, including oxidized LDL. Among these are cluster of differentiation 36, scavenger receptor class B type I and lectin-like oxidized low-density lipoprotein receptor-1. In addition to the initially assigned role as a mediator of the uptake of macromolecules into the cell, a large number of studies in cultured cells and in in vivo animal models have revealed that these lipoprotein receptors participate in signal transduction to modulate cellular functions. This review highlights the signalling pathways by which these receptors influence the process of atherosclerosis development, focusing on their roles in the vascular cells, such as macrophages, endothelial cells, smooth muscle cells, and platelets. Human genetics of the receptors is also discussed to further provide the relevance to cardiovascular disease risks in humans. Further knowledge of the vascular biology of the lipoprotein receptors and their ligands will potentially enhance our ability to harness the mechanism to develop novel prophylactic and therapeutic strategies against cardiovascular diseases.

Role of LOX-1 (Lectin-Like Oxidized Low-Density Lipoprotein Receptor 1) as a Cardiovascular Risk Predictor: Mechanistic Insight and Potential Clinical Use

Atherosclerosis, the underlying cause of cardiovascular disease (CVD), is a worldwide cause of morbidity and mortality. Reducing ApoB-containing lipoproteins-chiefly, LDL (low-density lipoprotein)-has been the main strategy for reducing CVD risk. Although supported by large randomized clinical trials, the persistence of residual cardiovascular risk after effective LDL reduction has sparked an intense search for other novel CVD biomarkers and therapeutic targets. Recently, Lox-1 (lectin-type oxidized LDL receptor 1), an innate immune scavenger receptor, has emerged as a promising target for early diagnosis and cardiovascular risk prediction and is also being considered as a treatment target. Lox-1 was first described as a 50 kDa transmembrane protein in endothelial cells responsible for oxLDL (oxidized LDL) recognition, triggering downstream pathways that intensify atherosclerosis via endothelial dysfunction, oxLDL uptake, and apoptosis. Lox-1 is also expressed in platelets, where it enhances platelet activation, adhesion to endothelial cells, and ADP-mediated aggregation, thereby favoring thrombus formation. Lox-1 was also identified in cardiomyocytes, where it was implicated in the development of cardiac fibrosis and myocyte apoptosis, the main determinants of cardiac recovery following an ischemic insult. Together, these findings have revealed that Lox-1 is implicated in all the main steps of atherosclerosis and has encouraged the development of immunoassays for measurement of sLox-1 (serum levels of soluble Lox-1) to be used as a potential CVD biomarker. Finally, the recent development of synthetic Lox-1 inhibitors and neutralizing antibodies with promising results in animal models has made Lox-1 a target for drug development. In this review, we discuss the main findings regarding the role of Lox-1 in the development, diagnosis, and therapeutic strategies for CVD prevention and treatment.

Lipid trafficking in cardiovascular disease

The reduction of plasma apolipoprotein B (apoB) containing lipoproteins has long been pursued as the main modifiable risk factor for the development of cardiovascular disease (CVD). This has led to an intense search for strategies aiming at reducing plasma apoB-lipoproteins, culminating in reduction of overall CV risk. Despite 3 decades of progress, CVD remains the leading cause of morbidity and mortality worldwide and, as such, new therapeutic targets are still warranted. Clinical and preclinical research has moved forward from the original concept, under which some lipids must be accumulated and other removed to achieve the ideal condition in disease prevention, into the concept that mechanisms that orchestrate lipid movement between lipoproteins, cells and organelles is equally involved in CVD. As such, this review scrutinizes potentially atherogenic changes in lipid trafficking and assesses the molecular mechanisms behind it. New developments in risk assessment and new targets for the mitigation of residual CVD risk are also addressed.

LOX-1 and atherosclerotic-related diseases

Lectin-like oxidized low-density lipoprotein receptor-1 (LOX-1), a scavenger receptor of oxidized low-density lipoprotein (ox-LDL) found in various cells, plays a crucial role in the formation and progression of atherosclerotic plaques. Animal studies have suggested that LOX-1 mediates the balance between internalization and degeneration of endothelial cells, thereby contributing to various steps in the atherosclerotic process, from initiation to plaque rupture. Under pathological conditions, the extracellular domain of membrane bound LOX-1 can be largely proteolytically cleaved into a soluble form (sLOX-1), which is proportional and linked to the LOX-1 expression level. Circulating levels of sLOX-1 are regarded as a risk biomarker for plaque rupture and acute coronary syndrome (ACS). Recently, studies have shown that sLOX-1 is also elevated in patients with acute stroke and can be a predictive biomarker for acute stroke. With the discovery of the vital role of LOX-1 in atherosclerosis, there is growing focus on the influence of LOX-1 in atherosclerotic-related diseases, including coronary arterial disease(CAD), stroke, and other cardiovascular events. Genetic polymorphisms of LOX-1 have been investigated and have been found to modulate the risk of these diseases. Most polymorphisms have been found to be risk factors, except for the splicing isoform LOXIN. This review concludes with a discussion of the potential future applications of LOX-1 for atherosclerotic-related diseases.

Association between CTSS gene polymorphism and the risk of acute atherosclerotic cerebral infarction in Chinese population: a case-control study

Objective: To investigate the association between the gene polymorphisms of rs774320676, rs768437857, rs928508030, and rs2275235 loci of Cathepsin S (CTSS) and risk of acute atherosclerotic cerebral infarction. Methods: A total of 315 patients with acute atherosclerotic cerebral infarction (study group) and 220 healthy subjects (control group) were enrolled in the present study. The genetic polymorphism of rs774320676, rs768437857, rs928508030, and rs2275235 loci of CTSS of subjects was analyzed by PCR-Sanger sequencing. Results: The proportion of carriers with mutant T allele at rs774320676 locus and mutant G allele at rs928508030 locus of CTSS in study group was significantly higher than the proportion in control group (P=0.000, adjusted odds ratio (OR) = 1.332, 95% confidence interval (CI) = 1.200-1.460; P<0.001, adjusted OR = 1.185, 95% CI = 1.055-1.314; P=0.002). The T allele at rs774320676 locus and the G allele at rs928508030 locus of CTSS were independent risk factors for acute atherosclerotic cerebral infarction (OR = 2.534, 95% CI = 1.020-4.652, P=0.006; OR = 2.016, 95% CI = 1.031-4.385, P=0.031). Conclusion: The single nucleotide polymorphisms (SNPs) of rs774320676 and rs928508030 of CTSS gene were related with risk for acute atherosclerotic cerebral infarction. The T allele at rs774320676 locus and G allele at rs928508030 locus of CTSS were genetic susceptibility genes of acute atherosclerotic cerebral infarction.

Current advances in circulating inflammatory biomarkers in atherosclerosis and related cardio-cerebrovascular diseases

Atherosclerosis (AS) is a systemic chronic disease affecting both the coronary and cerebral arteries. Inflammation plays a key role in the initiation and progression of AS, and numerous inflammatory factors have been proposed as potential biomarkers. This article reviews recent research in studies on major circulating inflammatory biomarkers to identify surrogates that may reflect processes associated with AS development and the risk of AS-related vascular events, such as Von Willebrand factor, lectin-like oxidized low-density-lipoprotein receptor-1, soluble urokinase plasminogen activator receptor, regulated upon activation, normal T-cell expressed and secreted, and microparticles, which may provide new perspectives for clinical AS evaluation and risk stratification.

Changes of peripheral blood Vδ1 T cells in patients with atherosclerotic cerebral infarction

To observe the ratio of peripheral blood Vδ1 T cells in patients with atherosclerotic cerebral infarction (ACI) and their function changes, and preliminarily explore the mechanism of change in ratio of peripheral blood Vδ1 T cells in ACI patients. 30 ACI patients enrolled in the neurology department in our hospital from January 2016 to December 2016 were selected, and 30 healthy subjects enrolled in the hospital during the same period were selected as healthy controls. Peripheral blood mononuclear cells (PBMC) were obtained by density gradient centrifugation. The ratio of Vδ1 T cells in peripheral blood of ACI patients was detected by flow cytometry, and the correlations between the ratio of Vδ1 T cells and the neurological deficits and infarction size in ACI patients were analyzed. A high proportion of Vδ1 T cells were obtained by in vitro amplification, and high-purity Vδ1 T cells and Naïve CD4 T cells were obtained by flow cytometry and magnetic bead sorting respectively. The effect of Vδ1 T cells on the proliferation of Naïve CD4 T cells and the secretion of IFN-γ were investigated by CFSE staining method; the correlation between the ratio of Vδ1 T cells in peripheral blood and the Ox-LDL level in peripheral blood of ACI patients was analyzed. The Vδ1 T cells in peripheral blood were treated by Ox-LDL, and the effect of Ox-LDL on Vδ1 T cell apoptosis was determined by apoptosis staining method. Compared with the healthy control group, the ratio of Vδ1 T cells in peripheral blood of ACI patients was significantly decreased (P<0.0001). The ratio of Vδ1 T cells in peripheral blood of ACI patients was not significantly correlated with age, sex, hypertension, diabetes and dyslipidemia (P>0.05). However, with the gradual aggravation of neurological deficit and gradual increase of infarct volume, the ratio of Vδ1 T cells in peripheral blood of ACI patients decreased gradually. Besides, the functional studies showed that the immunosuppressive functions of Vδ1 T cells in peripheral blood of ACI patients were also significantly decreased (P<0.0001). The ratio of Vδ1 T cells in peripheral blood of ACI patients was negatively correlated with the Ox-LDL level in peripheral blood (r²=0.1691; P=0.0240); the Ox-LDL treatment of Vδ1 T cells induced apoptosis of Vδ1 T cells, and with the increased Ox-LDL concentration, the ratio of Vδ1 T cell apoptosis gradually increased. The decreased ratio of Vδ1 T cells in peripheral blood and loss of functions in ACI patients lead to the occurrence of immunoinflammatory reactions, which may be one of the possible causes of ACI. In addition, this study also showed that, Ox-LDL could induce Vδ1 T cell apoptosis and lead to decrease in ratio of Vδ1 T cells in peripheral blood, which may be one of the reasons for decreased ratio of Vδ1 T cells in peripheral blood of ACI patients. In summary, this study can further help the understanding of the pathogenesis of ACI.

LOX-1 and Its Splice Variants: A New Challenge for Atherosclerosis and Cancer-Targeted Therapies

Alternative splicing (AS) is a process in which precursor messenger RNA (pre-mRNA) splicing sites are differentially selected to diversify the protein isoform population. Changes in AS patterns have an essential role in normal development, differentiation and response to physiological stimuli. It is documented that AS can generate both “risk” and “protective” splice variants that can contribute to the pathogenesis of several diseases including atherosclerosis. The main endothelial receptor for oxidized low-density lipoprotein (ox-LDLs) is LOX-1 receptor protein encoded by the OLR1 gene. When OLR1 undergoes AS events, it generates three variants: OLR1, OLR1D4 and LOXIN. The latter lacks exon 5 and two-thirds of the functional domain. Literature data demonstrate a protective role of LOXIN in pathologies correlated with LOX-1 overexpression such as atherosclerosis and tumors. In this review, we summarize recent developments in understanding of OLR1 AS while also highlighting data warranting further investigation of this process as a novel therapeutic target.