Highly upregulated expression of CD36 and MSR1 in circulating monocytes of patients with acute coronary syndromes

The effects of a 20-week exercise program on blood-circulating biomarkers related to brain health in overweight or obese children: The ActiveBrains project

BACKGROUND

Emerging research supports the idea that exercise positively affects neurodevelopment. However, the mechanisms linking exercise with brain health are largely unknown. We aimed to investigate the effect of exercise on (a) blood biomarkers selected based on previous evidence (brain-derived neurotrophic factor, β-hydroxybutyrate (BHB), cathepsin B (CTSB), kynurenine, fibroblast growth factor 21 (FGF21), soluble vascular cell adhesion molecule-1 (sVCAM-1)); and (b) a panel of 92 neurology-related proteins (discovery analysis). We also investigated whether changes in these biomarkers mediate the effects of exercise on brain health (hippocampal structure and function, cognitive performance, and mental health).

METHODS

We randomized 81 overweight/obese children (10.1 ± 1.1 years, 41% girls) into 2 groups: either 20 weeks of aerobic plus resistance exercise or control. Candidate biomarkers were assessed using enzyme-linked immunosorbent assay (ELISA) for kynurenine, FGF21, and CTSB; colorimetry for β-hydroxybutyrate; and XMap for brain-derived neurotrophic factor and soluble vascular cell adhesion molecule-1. The 92 neurology-related proteins were analyzed by an antibody-based proteomic analysis.

RESULTS

Our intervention had no significant effect on candidate biomarkers (all p > 0.05). In the discovery analysis, a reduction in circulating macrophage scavenger receptor type-I was observed (standardized differences between groups = -0.3, p = 0.001). This effect was validated using ELISA methods (standardized difference = -0.3, p = 0.01). None of the biomarkers mediated the effects of exercise on brain health.

CONCLUSIONS

Our study does not support a chronic effect of exercise on candidate biomarkers. We observed that while chronic exercise reduced the levels of macrophage scavenger receptor type-I, it did not mediate the effects of exercise on brain health. Future studies should explore the implications of this novel biomarker for overall health.

Genetic variants, gene expression, and soluble CD36 analysis in acute coronary syndrome: Differential protein concentration between ST-segment elevation myocardial infarction and unstable angina

Background

Atherosclerosis plays an important role in the pathophysiology of acute coronary syndrome (ACS). CD36 is a scavenger receptor involved in lipid metabolism. Some single‐nucleotide variants in the non‐coding region could indirectly alter the expression and the function of the protein.

Objective

The aim of this study was to investigate the gene and protein expression associated with CD36 variants (rs1194182;C > G; rs1049654;C > A, rs1334512;G > T, and rs3211892;G > A) in ACS patients from the western Mexican population.

Methods

We recruited 310 ACS patients and 308 subjects in the control group (CG). Genotyping was determined by TaqMan SNP genotyping assays. CD36 expression at the mRNA level was quantified by TaqMan gene expression assays. Soluble CD36 (sCD36) was measured by enzyme‐linked immunosorbent assay.

Results

We show that rs1194182G > C variant provides a protective effect with a 1.7‐fold lower susceptibility to develop ACS (p  = 0.03); however, this association was masked by diabetes and dyslipidemia. We observed a higher sCD36 concentration in patient with ST‐segment elevation myocardial infarction (STEMI) compared with patients with unstable angina (UA) (p  = 0.038). Likewise, in diabetic patients versus non‐diabetic (p < 0.001). We observed in patients an increase in CD36 mRNA expression (1.91 times higher) than in the CG (p  = 0.02).

Conclusion

The rs1194182 seems to be associated with diabetes in a risky manner, in ACS patients and protective for dyslipidemia in both groups. The concentration of sCD36 seems to be associated with the clinical spectrum of the ACS patients and the presence of diabetes, since patients with STEMI present significantly elevated level compared with UA.

Expression of Macrophage Scavenger Receptor (MSR1) in Peripheral Blood Cells from Patients with Different Respiratory Diseases: Beyond Monocytes

Background: Macrophage scavenger receptor 1 (MSR1) has mostly been described in macrophages, but we previously found a significant gene expression increase in peripheral blood mononuclear cells (PBMCs) of asthmatic patients. Objective: To confirm those results and to define its cellular origin in PBMCs. Methods: Four groups of subjects were studied: healthy controls (C), nonallergic asthmatic (NA), allergic asthmatic (AA), and chronic obstructive pulmonary disease (COPD) patients. RNA was extracted from PBMCs. MSR1 gene expression was analyzed by RT-qPCR. The presence of MSR1 on the cellular surface of PBMC cellular subtypes was analyzed by confocal microscopy and flow cytometry. Results: MSR1 gene expression was significantly increased in the three clinical conditions compared to the healthy control group, with substantial variations according to disease type and severity. MSR1 expression on T cells (CD4⁺ and CD8⁺), B cells, and monocytes was confirmed by confocal microscopy and flow cytometry. In all clinical groups, the four immune cell subtypes studied expressed MSR1, with a greater expression on B lymphocytes and monocytes, exhibiting differences according to disease and severity. Conclusions: This is the first description of MSR1’s presence on lymphocytes’ surfaces and reinforces the potential role of MSR1 as a player in asthma and COPD.

Eukaryotic elongation factor 2 kinase regulates foam cell formation via translation of CD36

Eukaryotic elongation factor 2 kinase (eEF2K) is an atypical protein kinase that controls protein synthesis in cells under stress. Although well studied in cancer, less is known about its roles in chronic inflammatory diseases. Here, we examined its regulation of macrophage cholesterol handling in the context of atherosclerosis. eEF2K mRNA expression and protein activity were upregulated in murine bone marrow-derived macrophages (BMDMs) exposed to oxidized low-density lipoprotein cholesterol (oxLDL). When incubated with oxLDL, BMDMs from eEF2K knockout (Eef2k^-/- ) mice formed fewer Oil Red O⁺ foam cells than Eef2k^+/+ BMDMs (12.5% ± 2.3% vs. 32.3% ± 2.0%, p < .01). Treatment with a selective eEF2K inhibitor, JAN-384, also decreased foam cell formation for C57BL/6J BMDMs and human monocyte-derived macrophages. Disabling eEF2K selectively decreased protein expression of the CD36 cholesterol uptake receptor, mediated by a reduction in the proportion of translationally active Cd36 mRNA. Eef2k^-/- mice bred onto the Ldlr^-/- background developed aortic sinus atherosclerotic plaques that were 30% smaller than Eef2k^+/+ -Ldlr^-/- mice after 16 weeks of high cholesterol diet (p < .05). Although accompanied by a reduction in plaque CD36⁺ staining (p < .05) and lower CD36 expression in circulating monocytes (p < .01), this was not associated with reduced lipid content in plaques as measured by oil red O staining. Finally, EEF2K and CD36 mRNA levels were higher in blood mononuclear cells from patients with coronary artery disease and recent myocardial infarction compared to healthy controls without coronary artery disease. These results reveal a new role for eEF2K in translationally regulating CD36 expression and foam cell formation in macrophages. Further studies are required to explore therapeutic targeting of eEF2K in atherosclerosis.

Identification of candidate biomarkers and therapeutic agents for heart failure by bioinformatics analysis

INTRODUCTION

Heart failure (HF) is a heterogeneous clinical syndrome and affects millions of people all over the world. HF occurs when the cardiac overload and injury, which is a worldwide complaint. The aim of this study was to screen and verify hub genes involved in developmental HF as well as to explore active drug molecules.

METHODS

The expression profiling by high throughput sequencing of GSE141910 dataset was downloaded from the Gene Expression Omnibus (GEO) database, which contained 366 samples, including 200 heart failure samples and 166 non heart failure samples. The raw data was integrated to find differentially expressed genes (DEGs) and were further analyzed with bioinformatics analysis. Gene ontology (GO) and REACTOME enrichment analyses were performed via ToppGene; protein-protein interaction (PPI) networks of the DEGs was constructed based on data from the HiPPIE interactome database; modules analysis was performed; target gene-miRNA regulatory network and target gene-TF regulatory network were constructed and analyzed; hub genes were validated; molecular docking studies was performed.

RESULTS

A total of 881 DEGs, including 442 up regulated genes and 439 down regulated genes were observed. Most of the DEGs were significantly enriched in biological adhesion, extracellular matrix, signaling receptor binding, secretion, intrinsic component of plasma membrane, signaling receptor activity, extracellular matrix organization and neutrophil degranulation. The top hub genes ESR1, PYHIN1, PPP2R2B, LCK, TP63, PCLAF, CFTR, TK1, ECT2 and FKBP5 were identified from the PPI network. Module analysis revealed that HF was associated with adaptive immune system and neutrophil degranulation. The target genes, miRNAs and TFs were identified from the target gene-miRNA regulatory network and target gene-TF regulatory network. Furthermore, receiver operating characteristic (ROC) curve analysis and RT-PCR analysis revealed that ESR1, PYHIN1, PPP2R2B, LCK, TP63, PCLAF, CFTR, TK1, ECT2 and FKBP5 might serve as prognostic, diagnostic biomarkers and therapeutic target for HF. The predicted targets of these active molecules were then confirmed.

CONCLUSION

The current investigation identified a series of key genes and pathways that might be involved in the progression of HF, providing a new understanding of the underlying molecular mechanisms of HF.

Intraperitoneal Oil Application Causes Local Inflammation with Depletion of Resident Peritoneal Macrophages

Oil is frequently used as a solvent to inject lipophilic substances into the peritoneum of laboratory animals. Although mineral oil causes chronic peritoneal inflammation, little is known whether other oils are better suited. We show that olive, peanut, corn, or mineral oil causes xanthogranulomatous inflammation with depletion of resident peritoneal macrophages. However, there were striking differences in the severity of the inflammatory response. Peanut and mineral oil caused severe chronic inflammation with persistent neutrophil and monocyte recruitment, expansion of the vasculature, and fibrosis. Corn and olive oil provoked no or only mild signs of chronic inflammation. Mechanistically, the vegetal oils were taken up by macrophages leading to foam cell formation and induction of cell death. Olive oil triggered caspase-3 cleavage and apoptosis, which facilitate the resolution of inflammation. Peanut oil and, to a lesser degree, corn oil, triggered caspase-1 activation and macrophage pyroptosis, which impair the resolution of inflammation. As such, intraperitoneal oil administration can interfere with the outcome of subsequent experiments. As a proof of principle, intraperitoneal peanut oil injection was compared with its oral delivery in a thioglycolate-induced peritonitis model. The chronic peritoneal inflammation due to peanut oil injection impeded the proper recruitment of macrophages and the resolution of inflammation in this peritonitis model. In summary, the data indicate that it is advisable to deliver lipophilic substances, like tamoxifen, by oral gavage instead of intraperitoneal injection. IMPLICATIONS: This work contributes to the reproducibility of animal research by helping to understand some of the undesired effects observed in animal experiments.

CD36 in Atherosclerosis: Pathophysiological Mechanisms and Therapeutic Implications

PURPOSE OF REVIEW

Atherosclerosis is a chronic disease characterized by lipid retention and inflammation in the artery wall. The retention and oxidation of low-density lipoprotein (LDL) in sub-endothelial space play a critical role in atherosclerotic plaque formation and destabilization. Oxidized LDL (ox-LDL) and other modified LDL particles are avidly taken up by endothelial cells, smooth muscle cells, and macrophages mainly through several scavenger receptors, including CD36 which is a class B scavenger receptor and membrane glycoprotein.

RECENT FINDINGS

Animal studies performed on CD36-deficient mice suggest that deficiency of CD36 prevents the development of atherosclerosis, though with some debate. CD36 serves as a signaling hub protein at the crossroad of inflammation, lipid metabolism, and fatty acid metabolism. In addition, the level of soluble CD36 (unattached to cells) in the circulating blood was elevated in patients with atherosclerosis and other metabolic disorders. We performed a state-of-the-art review on the structure, ligands, functions, and regulation of CD36 in the context of atherosclerosis by focusing on the pathological role of CD36 in the dysfunction of endothelial cells, smooth muscle cells, monocytes/macrophages, and platelets. Finally, we highlight therapeutic possibilities to target CD36 expression/activity in atherosclerosis.

Cross-sectional study of blood biomarkers of patients with moderate to severe alopecia areata reveals systemic immune and cardiovascular biomarker dysregulation

BACKGROUND

Although there is increased understanding of the alopecia areata (AA) pathogenesis based on studies in scalp tissues, little is known about its systemic profile.

OBJECTIVE

To evaluate the blood proteomic signature of AA and determine biomarkers associated with increased disease severity.

METHODS

In a cross-sectional study, we assessed 350 inflammatory and cardiovascular proteins using OLINK high-throughput proteomics in patients with moderate to severe AA (n = 35), as compared with healthy individuals (n = 36), patients with moderate to severe psoriasis (n = 19), and those with atopic dermatitis (n = 49).

RESULTS

Seventy-four proteins were significantly differentially expressed between AA and control individuals (false discovery rate, <.05) including innate immunity (interleukin [IL] 6/IL-8), T helper (Th) type 1 (interferon [IFN] γ/CXCL9/CXCL10/CXCL11), Th2 (CCL13/CCL17/CCL7), Th17 (CCL20/PI3/S100A12), and cardiovascular-risk proteins (OLR1/OSM/MPO/PRTN3). Eighty-six biomarkers correlated with AA clinical severity (P < .05), including Th1/Th2, and cardiovascular/atherosclerosis-related proteins, including SELP/PGLYRP1/MPO/IL-18/OSM (P < .05). Patients with AA totalis/universalis showed the highest systemic inflammatory tone, including cardiovascular risk biomarkers, compared to control individuals and even to patients with atopic dermatitis and those with psoriasis. The AA profile showed some Th1/Th2 differences in the setting of concomitant atopy.

LIMITATIONS

Our analysis was limited to 350 proteins.

CONCLUSION

This study defined the abnormalities of moderate to severe AA and associated circulatory biomarkers. It shows that AA has systemic immune, cardiovascular, and atherosclerosis biomarker dysregulation, suggesting the need for systemic treatment approaches.

Myeloid-specific deficiency of pregnane X receptor decreases atherosclerosis in LDL receptor-deficient mice

The pregnane X receptor (PXR) is a nuclear receptor that can be activated by numerous drugs and xenobiotic chemicals. PXR thereby functions as a xenobiotic sensor to coordinately regulate host responses to xenobiotics by transcriptionally regulating many genes involved in xenobiotic metabolism. We have previously reported that PXR has pro-atherogenic effects in animal models, but how PXR contributes to atherosclerosis development in different tissues or cell types remains elusive. In this study, we generated an LDL receptor-deficient mouse model with myeloid-specific PXR deficiency (PXR^ΔMyeLDLR^-/-) to elucidate the role of macrophage PXR signaling in atherogenesis. The myeloid PXR deficiency did not affect metabolic phenotypes and plasma lipid profiles, but PXR^ΔMyeLDLR^-/- mice had significantly decreased atherosclerosis at both aortic root and brachiocephalic arteries compared with control littermates. Interestingly, the PXR deletion did not affect macrophage adhesion and migration properties, but reduced lipid accumulation and foam cell formation in the macrophages. PXR deficiency also led to decreased expression of the scavenger receptor CD36 and impaired lipid uptake in macrophages of the PXR^ΔMyeLDLR^-/- mice. Further, RNA-Seq analysis indicated that treatment with a prototypical PXR ligand affects the expression of many atherosclerosis-related genes in macrophages in vitro. These findings reveal a pivotal role of myeloid PXR signaling in atherosclerosis development and suggest that PXR may be a potential therapeutic target in atherosclerosis management.

CD36 expression in peripheral blood mononuclear cells reflects the onset of atherosclerosis

Together with complex genetic and environmental factors, increased serum cholesterol and ox-LDL levels are considered as major triggering factors of atherosclerosis. Mononuclear cell infiltration to the arterial wall and uptake of ox-LDL, which is facilitated by CD36 receptor through an uncontrolled manner, play a key role in foam cell formation followed by atherogenesis development. The aim of this study was to analyze if CD36 expression in peripheral blood mononuclear cells reflect its aortic tissue level in hypercholesterolemia. In this study, CD36 protein expression was evaluated in aortic specimens of cholesterol or cholesterol plus Vitamin E treated animals in relation to the immunohistochemical analyses for the HNE-protein adducts, as well as for smooth muscle actin and vimentin. The CD36 mRNA expression was determined by RT-PCR in PBMC of hypercholesterolemic rabbits and hypercholesterolemic versus normocholesterolemic individuals. Immunohistochemistry findings revealed that smooth muscle actin, smooth muscle vimentin, HNE-protein conjugates, and CD36 protein expressions were significantly increased in aorta of hypercholesterolemic group where foam cells were present. High cholesterol diet significantly induced CD36 mRNA expression in both rabbit aorta and PBMCs, while positive correlation between aortic and PBMC CD36 expression has been found. In addition, consistent with the rabbit model, CD36 mRNA expression levels in human PBMCs were significantly higher in hypercholesterolemic patients than in normocholesterolemic individuals. Taken together, these results demonstrate that the CD36 mRNA levels of PBMCs could reflect the CD36 mRNA levels in aorta and could be used as a biomarker for diagnosis of atherosclerotic burden. © 2018 BioFactors, 44(6):588-596, 2018.

Association between plasma CD36 levels and incident risk of coronary heart disease among Danish men and women

BACKGROUND AND AIMS

CD36 is a cholesterol receptor involved in the uptake of oxidized low-density lipoprotein cholesterol and development of atherosclerotic plaques. Cross-sectional studies have shown correlations between plasma CD36 and atherosclerosis but no prospective study has examined the association yet. We prospectively examined the association between plasma CD36 levels and risk of incident coronary heart disease (CHD) in a Danish population.

METHODS

Plasma CD36 levels were measured in a case-cohort study nested within the Danish population-based cohort, the Diet, Cancer and Health Study. A total of 1963 incident CHD events occurred between baseline (1993-1997) and 2008, and a sub-cohort of 1759 participants were randomly selected as reference. Cox proportional hazard regression models were used to compute the hazard ratio (HR) and corresponding 95% confidence interval (CI).

RESULTS

After adjusting for CHD risk factors, including history of hypercholesterolemia and diabetes, elevated plasma CD36 levels were not associated with higher CHD risk in the total population, and the HR comparing the highest versus lowest tertile of CD36 levels was 1.02 (95% CI: 0.84-1.23). High CD36 levels were only found to be associated with risk of CHD in combination with prevalent diabetes (HR = 2.83, 95% CI: 1.08-7.45) vs. the joint reference group of lowest CD36 tertile and no diabetes.

CONCLUSIONS

Plasma CD36 levels were not predictive of CHD risk in the general population.

Myeloid receptor CD36 is required for early phagocytosis of myocardial infarcts and induction of Nr4a1-dependent mechanisms of cardiac repair

Phagocytosis after myocardial infarction (MI) is a prerequisite to cardiac repair. Recruited monocytes clear necrotic cardiomyocytes and differentiate into cardiac macrophages. Some studies have linked apoptotic cell receptors on cardiac macrophages to tissue repair; however, the contribution of precursor monocyte phagocytic receptors, which are the first to interact with the cardiac parenchyma, is unclear. The scavenger receptor cluster of differentiation (CD)36 protein was detected on cardiac Ly6cHI monocytes, and bone marrow-derived Cd36 was essential for both early phagocytosis of dying cardiomyocytes and for smaller infarct sizes in female and male mice after permanent coronary ligation. Cd36 deficiency led to reduced expression of phagocytosis receptor Mertk and nuclear receptor Nr4a1 in cardiac macrophages, the latter previously shown to be required for phagocyte survival. Nr4a1 was required for phagocytosis-induced Mertk expression, and Nr4a1 protein directly bound to Mertk gene regulatory elements. To test the overall contribution of the Cd36-Mertk axis, MI was induced in Cd36^-/- Mertk^-/- double-knockout mice and led to increases in myocardial rupture. These data implicate monocyte CD36 in the mitigation of early infarct size and transition to Mertk-dependent macrophage function. Increased myocardial rupture in the absence of both Cd36 and Mertk underscore the physiologic significance of phagocytosis during tissue injury.-Dehn, S., Thorp, E. B. Myeloid receptor CD36 is required for early phagocytosis of myocardial infarcts and induction of Nr4a1-dependent mechanisms of cardiac repair.

Biomarkers associated with disease severity in allergic and nonallergic asthma

Asthma is a complex, chronic respiratory disease with a wide clinical spectrum. Use of high-throughput technologies has generated a great deal of data that require validation. In this work the objective was to validate molecular biomarkers related to asthmatic disease types in peripheral blood samples and define their relationship with disease severity. With this purpose, ninety-four previously described genes were analyzed by qRT-PCR in 30 healthy control (HC) subjects, 30 patients with nonallergic asthma (NA), 30 with allergic asthma (AA), and 14 patients with allergy (rhinitis) but without asthma (AR). RNA was extracted from peripheral blood mononuclear cells (PBMCs) using the TRIzol method. After data normalization, principal component analysis (PCA) was performed, and multiple approaches were used to test for differential gene expression. Relevance was defined by RQ (relative quantification) and corrected P value (<0.05). Protein levels of IL-8 and MSR1 were determined by ELISA and Western blot, respectively. PCA showed 4 gene expression clusters that correlated with the 4 clinical phenotypes. Analysis of differential gene expression between clinical groups and HCs revealed 26 statistically relevant genes in NA and 69 in AA. Protein interaction analysis revealed IL-8 to be a central protein. Average levels of IL-8 were higher in the asthma patients' sera (NA: 452.28±357.72, AA: 327.46±377pg/ml) than in HCs (286.09±179.10), but without reaching statistical significance. Nine genes, especially MSR1, were strongly associated with severe NA. In conclusion, several molecular biomarkers of asthma have been defined, some of which could be useful for the diagnosis or prognosis of disease severity.

Isoflavone supplementation in postmenopausal women does not affect leukocyte LDL receptor and scavenger receptor CD36 expression: A double-blind, randomized, placebo-controlled trial

SCOPE

Isoflavones are discussed to improve serum lipoproteins and body composition and to reduce cardiovascular disease risk in postmenopausal women (PMW). LDL receptors (LDLR) and scavenger receptor CD36 (CD36) play a pivotal role in the regulation of plasma LDL-cholesterol concentrations (LDL-chol). We investigated the impact of isoflavones on the receptor expression of both receptors in leukocytes of PMW.

METHODS AND RESULTS

A randomized, double-blind, placebo-controlled trial in parallel design was conducted to assess the effects of an isoflavone-enriched soy extract (117.4 mg/day isoflavone aglycone equivalents) for 12 weeks on serum LDL-chol, LDLR, and CD36 expression on leukocytes in 170 healthy PMW. Baseline and after 12 weeks, blood lipid concentrations, anthropometric data and body composition were determined. Receptor expression on leukocytes was measured by means of flow cytometry. After the intervention, no significant differences were found for LDLR and CD36 expression on leukocytes. A significant increase of serum LDL-chol was shown for the isoflavone group (p = 0.03) after 12 weeks. Body fat content and VAT were not affected.

CONCLUSION

Isoflavone supplementation for 12 weeks did not change LDLR and CD36 expression on leukocytes of PMW and did not affect body fat content and visceral adipose tissue (VAT), but slightly increased serum LDL-chol.

Low CD36 and LOX-1 Levels and CD36 Gene Subexpression Are Associated with Metabolic Dysregulation in Older Individuals with Abdominal Obesity

Background. Obesity study in the context of scavenger receptors has been linked to atherosclerosis. CD36 and LOX-1 are important, since they have been associated with atherogenic and metabolic disease but not fat redistribution. The aim of our study was to determinate the association between CD36 and LOX-1 in presence of age and abdominal obesity. Methods. This is a cross-sectional study that included 151 healthy individuals, clinically and anthropometrically classified into two groups by age (<30 and ≥30 years old) and abdominal obesity (according to World Health Organization guidelines). We excluded individuals with any chronic and metabolic illness, use of medication, or smoking. Fasting blood samples were taken to perform determination of CD36 mRNA expression by real-time PCR, lipid profile and metabolic and low grade inflammation markers by routine methods, and soluble scavenger receptors (CD36 and LOX-1) by ELISA. Results. Individuals ≥30 years old with abdominal obesity presented high atherogenic index, lower soluble scavenger receptor levels, and subexpression of CD36 mRNA (54% less). On the other hand, individuals <30 years old with abdominal adiposity presented higher levels in the same parameters, except LOX-1 soluble levels. Conclusion. In this study, individuals over 30 years of age presented low soluble scavenger receptors levels pattern and CD36 gene subexpression, which suggest the chronic metabolic dysregulation in abdominal obesity.

Association between rs1761667 polymorphism of CD36 gene and risk of coronary atherosclerosis in Egyptian population

BACKGROUND

Recent studies have demonstrated that CD36 is involved in the progression of atherosclerosis. Associations between rs1761667 polymorphisms of the CD36 gene and susceptibility to coronary artery disease (CAD) are not obvious.

METHODS

We studied the relationship between single nucleotide polymorphisms (SNPs), rs1761667 of CD36 gene and the risk of coronary atherosclerosis in a case-control study composed of 71 CAD patients and 76 healthy controls by assessment of allele frequencies and genotype distributions using real-time polymerase chain reaction (PCR) and the allele discrimination technique. Additionally, we detected CD36 expression by flow cytometry.

RESULTS

The distribution of rs1761667 genotypes between the two groups was significantly different (P<0.001), with the frequency of the AG genotype being significantly higher in the CAD group than in the control group (P<0.001). The expression level of CD36 in the CAD group was significantly higher than that in the control group (P<0.001), with significant differences in the CAD patients with an AG genotype compared with those with an AA and GG genotype (P<0.001). The plasma levels (mg/dL) of low-density lipoprotein (LDL) in the CAD group were much higher than that in the control group (P<0.001). On the other hand, the plasma LDL levels in CAD patients with the AG genotype were remarkably higher than those with the GG and AA genotypes (P=0.046) and AG genotype was significantly more prevalent among type 2 diabetes mellitus (T2DM) and metabolic syndrome (MetS) patients (P<0.05). After adjusted logistic regression analysis, the AG genotype of rs1761667 was associated with an increased risk of CAD (OR=17.97, 95% CI, 3.19-87.85, P=0.001).

CONCLUSIONS

The AG genotype of the rs1761667 polymorphism in the CD36 gene may be involved in CAD pathogenesis as well as increased body mass index (BMI), T2DM and MetS in the Sohag population of Egypt.

Macrophage-mediated cholesterol handling in atherosclerosis

Formation of foam cells is a hallmark at the initial stages of atherosclerosis. Monocytes attracted by pro-inflammatory stimuli attach to the inflamed vascular endothelium and penetrate to the arterial intima where they differentiate to macrophages. Intimal macrophages phagocytize oxidized low-density lipoproteins (oxLDL). Several scavenger receptors (SR), including CD36, SR-A1 and lectin-like oxLDL receptor-1 (LOX-1), mediate oxLDL uptake. In late endosomes/lysosomes of macrophages, oxLDL are catabolysed. Lysosomal acid lipase (LAL) hydrolyses cholesterol esters that are enriched in LDL to free cholesterol and free fatty acids. In the endoplasmic reticulum (ER), acyl coenzyme A: cholesterol acyltransferase-1 (ACAT1) in turn catalyses esterification of cholesterol to store cholesterol esters as lipid droplets in the ER of macrophages. Neutral cholesteryl ester hydrolases nCEH and NCEH1 are involved in a secondary hydrolysis of cholesterol esters to liberate free cholesterol that could be then out-flowed from macrophages by cholesterol ATP-binding cassette (ABC) transporters ABCA1 and ABCG1 and SR-BI. In atherosclerosis, disruption of lipid homoeostasis in macrophages leads to cholesterol accumulation and formation of foam cells.

Splenic metabolic activity predicts risk of future cardiovascular events: demonstration of a cardiosplenic axis in humans

OBJECTIVES

This study sought to determine whether splenic activation after acute coronary syndrome (ACS) is linked to leukocyte proinflammatory remodeling and whether splenic activity independently predicts the risk of cardiovascular disease (CVD) events.

BACKGROUND

Pre-clinical data suggest the existence of a cardiosplenic axis, wherein activation of hematopoietic tissues (notably in the spleen) results in liberation of proinflammatory leukocytes and accelerated atherosclerotic inflammation. However, it is presently unknown whether a cardiosplenic axis exists in humans and whether splenic activation relates to CVD risk.

METHODS

(18)F-fluorodeoxyglucose ((18)FDG)-positron emission tomography (PET) imaging was performed in 508 individuals across 2 studies. In the first study, we performed FDG-PET imaging in 22 patients with recent ACS and 22 control subjects. FDG uptake was measured in spleen and arterial wall, whereas proinflammatory gene expression of circulating leukocytes was assessed by quantitative real-time polymerase chain reaction. In a second study, we examined the relationship between splenic tissue FDG uptake with subsequent CVD events during follow-up (median 4 years) in 464 patients who previously had undergone FDG-PET imaging.

RESULTS

Splenic activity increased after ACS and was significantly associated with multiple indices of inflammation: 1) up-regulated gene expression of proinflammatory leukocytes; 2) increased C-reactive protein; and 3) increased arterial wall inflammation (FDG uptake). Moreover, in the second study, splenic activity (greater than or equal to the median) was associated with an increased risk of CVD events (hazard ratio [HR]: 3.3; 95% confidence interval [CI]: 1.5 to 7.3; p = 0.003), which remained significant after adjustment for CVD risk factors (HR: 2.26; 95% CI: 1.01 to 5.06; p = 0.04) and for arterial FDG uptake (HR: 2.68; 95% CI: 1.5 to 7.4; p = 0.02).

CONCLUSIONS

Our findings demonstrate increased splenic metabolic activity after ACS and its association with proinflammatory remodeling of circulating leukocytes. Moreover, we observed that metabolic activity of the spleen independently predicted risk of subsequent CVD events. Collectively, these findings provide evidence of a cardiosplenic axis in humans similar to that shown in pre-clinical studies.

Osteogenic monocytes within the coronary circulation and their association with plaque vulnerability in patients with early atherosclerosis

OBJECTIVES

This study tests the hypothesis that circulating mononuclear cells expressing osteocalcin (OCN) and bone alkaline phosphatase (BAP) are associated with distinct plaque tissue components in patients with early coronary atherosclerosis.

BACKGROUND

Plaque characteristics implying vulnerability develop at the earliest stage of coronary atherosclerosis. Increasing evidence indicates that cells from the myeloid lineage might serve as important mediators of destabilization. Plaque burden and its components were assessed regarding their relationship to monocytes carrying both pro-inflammatory (CD14) and osteogenic surface markers OCN and BAP.

METHODS

Twenty-three patients with angiographically non-obstructive coronary artery disease underwent coronary endothelial function assessment and virtual histology-intravascular ultrasound of the left coronary artery. Plaque composition was characterized in the total segment (TS) and in the target lesion (TL) containing the highest amount of plaque burden. Blood samples were collected simultaneously from the aorta and the coronary sinus. Circulating cell counts were then identified from each sample and a gradient across the coronary circulation was determined.

RESULTS

Circulating CD14+/BAP+/OCN+ monocytes correlate with the extent of necrotic core and calcification (r=0.53, p=0.010; r=0.55, p=0.006, respectively). Importantly, coronary retention of CD14+/OCN+ cells also correlates with the amount of necrotic core and calcification (r=0.61, p=0.003; r=0.61, p=0.003) respectively.

CONCLUSIONS

Our study links CD14+/BAP+/OCN+ monocytes to the pathologic remodeling of the coronary circulation and therefore associates these cells with plaque destabilization in patients with early coronary atherosclerosis.

A vascular biology network model focused on inflammatory processes to investigate atherogenesis and plaque instability

Background

Numerous inflammation-related pathways have been shown to play important roles in atherogenesis. Rapid and efficient assessment of the relative influence of each of those pathways is a challenge in the era of “omics” data generation. The aim of the present work was to develop a network model of inflammation-related molecular pathways underlying vascular disease to assess the degree of translatability of preclinical molecular data to the human clinical setting.

Methods

We constructed and evaluated the Vascular Inflammatory Processes Network (V-IPN), a model representing a collection of vascular processes modulated by inflammatory stimuli that lead to the development of atherosclerosis.

Results

Utilizing the V-IPN as a platform for biological discovery, we have identified key vascular processes and mechanisms captured by gene expression profiling data from four independent datasets from human endothelial cells (ECs) and human and murine intact vessels. Primary ECs in culture from multiple donors revealed a richer mapping of mechanisms identified by the V-IPN compared to an immortalized EC line. Furthermore, an evaluation of gene expression datasets from aortas of old ApoE^-/- mice (78 weeks) and human coronary arteries with advanced atherosclerotic lesions identified significant commonalities in the two species, as well as several mechanisms specific to human arteries that are consistent with the development of unstable atherosclerotic plaques.

Conclusions

We have generated a new biological network model of atherogenic processes that demonstrates the power of network analysis to advance integrative, systems biology-based knowledge of cross-species translatability, plaque development and potential mechanisms leading to plaque instability.

TNFa alter cholesterol metabolism in human macrophages via PKC-θ-dependent pathway

BACKGROUND

Studies have shown that inflammation promoted atherosclerotic progression; however, it remains unclear whether inflammation promoted atherosclerotic progression properties by altering cholesterol metabolism in human macrophages. In the present study, we evaluated a potential mechanism of inflammation on atherogenic effects. We evaluated the ability of TNFa to affect Reverse cholesterol transport (RCT) and cholesterol uptake and its mechanism(s) of action in human macrophages.

RESULTS

We initially determined the potential effects of TNFa on cholesterol efflux in the human macrophages. We also determined alterations in mRNA and protein levels of ABCA1, ABCG1, LXRa, CD-36, SR-A in human macrophages using quantitative real-time polymerase chain reaction (PCR) and Western immunoblot analyses. The cholesterol efflux rate and protein expression of ABCA1, ABCG1, LXRa, CD-36, SR-A were quantified in human macrophages under PKC-θ inhibition using PKC-θ siRNA. Our results showed that TNFa inhibited the rate of cholesterol efflux and down-regulation the expression levels of ABCA1, ABCG1 and LXRa and up-regulation the expression levels of CD-36, SR-A in human macrophages; PKC-θ inhibition by PKC-θ siRNA attenuated the effect of TNFa on ABCA1, ABCG1, LXRa, SR-A, CD-36 expression.

CONCLUSIONS

Our results suggest TNFa alter cholesterol metabolism in human macrophages through the inhibition of Reverse cholesterol transport and enhancing cholesterol uptake via PKC-θ-dependent pathway, implicating a potential mechanism of inflammation on atherogenic effects.

Monocyte gene expression and coronary artery disease

PURPOSE OF REVIEW

Despite current therapy, coronary artery disease (CAD) remains the major cause of morbidity and mortality worldwide. CAD is the consequence of a complex array of deranged metabolic processes including the immune system. In this context, monocytes and macrophages are indisputable players. Thus, monocyte gene expression analysis could be a powerful tool to provide new insights in the pathophysiology of CAD and improve identification of individuals at risk. We discuss current literature assessing monocyte gene expression and its association with CAD.

RECENT FINDINGS

Monocyte surface markers CD14 ⁺⁺and CD16⁺ have been established as biomarkers for increased cardiovascular disease risk in a large number of studies. More in-depth gene expression analysis identified several interesting genes, such as ABCA1, CD36 and MSR1 with an increased expression in circulating monocytes from patients with CAD. The results for CD36 were replicated in one other study. For ABCA1 and MSR1 conflicting data are published.

SUMMARY

Recent findings indicate that genetic differences exist in circulating monocytes of patients suffering from CAD, giving us more insights into the underlying mechanisms. However, larger studies are required to prove that monocytes' expression signature could serve as a marker for diagnostic purposes in the future.