Regulation Of Cholesterol Efflux Research Articles

HDL and microRNAs.

In previous chapters, we know that high-density lipoproteins (HDLs) could act at multiple cell lines and then trigger intracellular molecular pathway to prevent several metabolic diseases. Besides the classic genes regulating cholesterol efflux and reverse cholesterol transport (RCT), microRNAs (miRNAs) could also affect HDLs biogenesis, metabolism, and functions. This chapter summarizes the miRNAs, which regulate HDLs functions in table. In addition, HDLs are good vectors for miRNAs. They could carry miRNAs in circulation and take them into several cells such as macrophages and endothelial cells. Complete understanding of the miRNAs associated with HDL regulation would give us broader insights to prevent and treat metabolic diseases.

MiR-125b downregulates macrophage scavenger receptor type B1 and reverse cholesterol transport

ObjectiveTo determine whether miR-125b regulates cholesterol efflux in vivo and in vitro through the regulation of scavenger receptor type B1 (SR-B1). Approach and resultsWe demonstrated that miR-125b is up-regulated in the human aortas of patients with CAD and is located in macrophages and vascular smooth muscle cells (VSMCs). We identified SCARB1 as a direct target of miR-125b by repressing the activity of the SCARB1 3′-untranslated region reporter construct. Moreover, the overexpression of miR-125b in both human and mouse macrophages as well as VSMCs was found to downregulated the expression of the SCARB1 and the SR-B1 protein levels, thereby impairing α-HDL-mediated macrophage cholesterol efflux in vitro. The in vivo reverse cholesterol transport (RCT) rate from non-cholesterol-loaded macrophages transfected with miR-125b to feces was also found to be decreased when compared with that of control mimic-transfected macrophages. ConclusionsTogether, these results provide evidence that miR-125b downregulates SCARB1 and SR-B1 in both human and mouse macrophages as well as VSMCs, thereby impairing macrophage cholesterol efflux in vitro and the whole macrophage-specific RCT pathway in vivo.

Risk of gallstones based on ABCG8 rs11887534 single nucleotide polymorphism among Taiwanese men and women

BackgroundGallstones are abnormal masses caused by impaired metabolism of cholesterol, bilirubin, or bile salts in the gallbladder or biliary tract. ATP-binding cassette subfamily G member 8 (ABCG8) is a protein that regulates cholesterol efflux from the liver. Genome-wide association studies (GWAS) and meta-analyses of GWAS revealed the ABCG8 rs11887534 variant as the most common genetic determinant of gallstones in humans. These findings have not been extensively replicated in Taiwanese. Therefore, we appraised the relationship between gallstones and rs11887534 in a relatively large Taiwanese sample.MethodsWe retrieved data collected through questionnaires, physical and biochemical tests from the Taiwan Biobank Bank (TWB). The study participants comprised 7388 men and 13,880 women who voluntarily enrolled in the Taiwan Biobank project between 2008 and 2019. Gallstones were self-reported.ResultsThe overall sample size was 21,268 comprising 938 gallstone patients and 20,330 non-gallstone individuals. Among the participants, 20,640 had the GG and 628 had the GC + CC genotype. At p-value < 0.05, the baseline genotypes and gallstone status between men and women were not significantly different. The risk of gallstones was higher in participants having the GC + CC compared to the GG genotype: odds ratio (OR); 95% confidence interval (CI) = 1.698; 1.240–2.325), but was lower in men compared to women (OR = 0.763; 95% CI = 0.638–0.913). Compared to men with the rs11887534 GG genotype, women with the GG and GC + CC genotypes had a higher risk of gallstone (OR; 95% CI = 1.304; 1.087–1.565 for GG and 2.291; 1.514–3.467 for GC + CC). The positive association between GC + CC and gallstones was retained after we restricted the analysis to the female participants (OR; 95% CI = 1.789 = 1.208–2.648). Hormone use was associated with an elevated risk of gallstones (OR; 95% CI = 1.359; 1.107–1.668). Relative to GG and no hormone use, we found a significantly high risk among hormone users with the GC + CC genotype (OR; 95% CI = 3.596; 1.495–8.650).ConclusionsThe rs11887534 GC + CC genotype was independently associated with a higher risk of gallstones. This risk was much higher among women, especially those who used hormones for various gynecological purposes.

CRISPR/dCas9 Transcriptional Activation of Endogenous Apolipoprotein AI and Paraoxonase 1 in Enterocytes Alleviates Endothelial Cell Dysfunction

Atherosclerosis is the main cause of cardiovascular diseases with high prevalence worldwide. A promising therapeutic strategy to reverse atherosclerotic process is to improve the athero-protective potential of high-density lipoproteins (HDL). Since the small intestine is a source of HDL, we aimed to activate transcription of the endogenous HDL major proteins, apolipoprotein AI (ApoAI) and paraoxonase 1 (PON1), in enterocytes, and to evaluate their potential to correct the pro-inflammatory status of endothelial cells (EC). Caco-2 enterocytes were transfected with CRISPR activation plasmids targeting ApoAI or PON1, and their gene and protein expression were measured in cells and conditioned medium (CM). ATP binding cassette A1 and G8 transporters (ABCA1, ABCG8), scavenger receptor BI (SR-BI), and transcription regulators peroxisome proliferator-activated receptor γ (PPARγ), liver X receptors (LXRs), and sirtuin-1 (SIRT1) were assessed. Anti-inflammatory effects of CM from transfected enterocytes were estimated through its ability to inhibit tumor necrosis factor α (TNFα) activation of EC. Transcriptional activation of ApoAI or PON1 in enterocytes induces: (i) increase of their gene and protein expression, and secretion in CM; (ii) stimulation of ABCA1/G8 and SR-BI; (iii) upregulation of PPARγ, LXRs, and SIRT1. CM from transfected enterocytes attenuated the TNFα-induced inflammatory and oxidative stress in EC, by decreasing TNF receptor 1, monocyte chemoattractant protein-1, and p22phox. In conclusion, transcriptional activation of endogenous ApoAI or PON1 in enterocytes by CRISPR/dCas9 system is a realistic approach to stimulate biogenesis and function of major HDL proteins which can regulate cholesterol efflux transporters and reduce the inflammatory stress in activated EC.

Mechanistic Insight into PPARγ and Tregs in Atherosclerotic Immune Inflammation

Atherosclerosis (AS) is the main pathological cause of acute cardiovascular and cerebrovascular diseases, such as acute myocardial infarction and cerebral apoplexy. As an immune-mediated inflammatory disease, the pathogenesis of AS involves endothelial cell dysfunction, lipid accumulation, foam cell formation, vascular smooth muscle cell (VSMC) migration, and inflammatory factor infiltration. The nuclear receptor peroxisome proliferator-activated receptor gamma (PPARγ) plays an important role in lipid metabolism, inflammation, and apoptosis by antagonizing the Wnt/β-catenin pathway and regulating cholesterol efflux and inflammatory factors. Importantly, PPARγ-dependant fatty acid uptake is critical for metabolic programming. Activated PPARγ can exert an anti-atherosclerotic effect by inhibiting the expression of various inflammatory factors, improving endothelial cell function, and restraining the proliferation and migration of VSMCs. Regulatory T cells (Tregs) are the only subset of T lymphocytes that have a completely negative regulatory effect on the autoimmune response. They play a critical role in suppressing excessive immune responses and inflammatory reactions and widely affect AS-associated foam cell formation, plaque rupture, and other processes. Recent studies have shown that PPARγ activation promotes the recruitment of Tregs to reduce inflammation, thereby exerting its anti-atherosclerotic effect. In this review, we provide an overview of the anti-AS roles of PPARγ and Tregs by discussing their pathological mechanisms from the perspective of AS and immune-mediated inflammation, with a focus on basic research and clinical trials of their efficacies alone or in combination in inhibiting atherosclerotic inflammation. Additionally, we explore new ideas for AS treatment and plaque stabilization and establish a foundation for the development of natural PPARγ agonists with Treg recruitment capability.

MicroRNA-33-5p inhibits cholesterol efflux in vascular endothelial cells by regulating citrate synthase and ATP-binding cassette transporter A1

BackgroundA high level of total cholesterol is associated with several lipid metabolism disorders, including atherosclerosis and cardiovascular diseases. ATP-binding cassette (ABC) transporter A1 (ABCA1) and miR-33-5p play crucial roles in atherosclerosis by controlling cholesterol efflux. While citrate is a precursor metabolite for lipid and cholesterol synthesis, little is known about the association between citrate synthase (CS) and cholesterol efflux. This study investigated the role of the miR-33-5p/ABCA1/CS axis in regulating cholesterol efflux in vascular endothelial cells (VECs).Materials and methodsVECs were treated with oxidized low-density lipoprotein cholesterol (ox-LDL), or pretreated with plasmids overexpressing CS, ABCA1, siRNAs against CS and ABCA1, and an miR-33-5p inhibitor. Cell apoptosis, cellular senescence-associated β-galactosidase activity, inflammation, and cholesterol efflux were detected.ResultsTreatment with ox-LDL decreased ABCA1 and CS levels and increased miR-33-5p expression and apoptosis in dose-dependent manners. In contrast, treatment with the miR-33-5p inhibitor and ABCA1 and CS overexpression plasmids inhibited the above-mentioned ox-LDL-induced changes. In addition, treatment with ox-LDL decreased cholesterol efflux, induced aging, and promoted the production of inflammatory cytokines (i.e., IL-6 and tumor necrosis factor TNF-α), as well as the expression of Bax and Caspase 3 proteins in VECs. All these changes were rescued by miR-33-5p inhibition and ABCA1 and CS overexpression. The inhibition of ABCA1 and CS by siRNAs eliminated the effects mediated by the miR-33-5p inhibitor, and knockdown of CS eliminated the effects of ABCA1 on VECs.ConclusionsThis study demonstrated the crucial roles played by the miR-33-5p/ABCA1/CS axis in regulating cholesterol efflux, inflammation, apoptosis, and aging in VECs, and also suggested the axis as a target for managing lipid metabolism disorders.

Rosmarinic Acid Increases Macrophage Cholesterol Efflux through Regulation of ABCA1 and ABCG1 in Different Mechanisms.

Lipid dysregulation in diabetes mellitus escalates endothelial dysfunction, the initial event in the development and progression of diabetic atherosclerosis. In addition, lipid-laden macrophage accumulation in the arterial wall plays a significant role in the pathology of diabetes-associated atherosclerosis. Therefore, inhibition of endothelial dysfunction and enhancement of macrophage cholesterol efflux is the important antiatherogenic mechanism. Rosmarinic acid (RA) possesses beneficial properties, including its anti-inflammatory, antioxidant, antidiabetic and cardioprotective effects. We previously reported that RA effectively inhibits diabetic endothelial dysfunction by inhibiting inflammasome activation in endothelial cells. However, its effect on cholesterol efflux remains unknown. Therefore, in this study, we aimed to assess the effect of RA on cholesterol efflux and its underlying mechanisms in macrophages. RA effectively reduced oxLDL-induced cholesterol contents under high glucose (HG) conditions in macrophages. RA enhanced ATP-binding cassette transporter A1 (ABCA1) and G1 (ABCG1) expression, promoting macrophage cholesterol efflux. Mechanistically, RA differentially regulated ABCA1 expression through JAK2/STAT3, JNK and PKC-p38 and ABCG1 expression through JAK2/STAT3, JNK and PKC-ERK1/2/p38 in macrophages. Moreover, RA primarily stabilized ABCA1 rather than ABCG1 protein levels by impairing protein degradation. These findings suggest RA as a candidate therapeutic to prevent atherosclerotic cardiovascular disease complications related to diabetes by regulating cholesterol efflux in macrophages.

Loss of Nfat5 promotes lipid accumulation in vascular smooth muscle cells.

The nuclear factor of activated T-cells 5 (NFAT5) is a transcriptional regulator of macrophage activation and T-cell development, which controls stabilizing responses of cells to hypertonic and biomechanical stress. In this study, we detected NFAT5 in the media layer of arteries adjacent to human arteriosclerotic plaques and analyzed its role in vascular smooth muscle cells (VSMCs) known to contribute to arteriosclerosis through the uptake of lipids and transformation into foam cells. Exposure of both human and mouse VSMCs to cholesterol stimulated the nuclear translocation of NFAT5 and increased the expression of the ATP-binding cassette transporter Abca1, required to regulate cholesterol efflux from cells. Loss of Nfat5 promoted cholesterol accumulation in these cells and inhibited the expression of genes involved in the management of oxidative stress or lipid handling, such as Sod1, Plin2, Fabp3, and Ppard. The functional relevance of these observations was subsequently investigated in mice fed a high-fat diet upon induction of a smooth muscle cell-specific genetic ablation of Nfat5 (Nfat5(SMC)-/- ). Under these conditions, Nfat5(SMC)-/- but not Nfat5fl/fl mice developed small, focal lipid-rich lesions in the aorta after 14 and 25weeks, which were formed by intracellular lipid droplets deposited in the sub-intimal VSMCs layer. While known for being activated by external stimuli, NFAT5 was found to mediate the expression of VSMC genes associated with the handling of lipids in response to a cholesterol-rich environment. Failure of this protective function may promote the formation of lipid-laden arterial VSMCs and pro-atherogenic vascular responses.

Substrate Stiffness Regulates Cholesterol Efflux in Smooth Muscle Cells.

The infiltration and deposition of cholesterol in the arterial wall play an important role in the initiation and development of atherosclerosis. Smooth muscle cells (SMCs) are the major cell type in the intima. Upon exposure to cholesterol, SMCs may undergo a phenotype switching into foam cells. Meanwhile, the pathological processes of the blood vessel such as cholesterol deposition and calcification induce the changes in the substrate stiffness around SMCs. However, whether substrate stiffness affects the cholesterol accumulation in SMCs and the formation of foam cells is not well-understood. In this study, SMCs were cultured on the substrates with different stiffnesses ranging from 1 to 100 kPa and treated with cholesterol. We found that cholesterol accumulation in SMCs was higher on 1 and 100 kPa substrates than that on intermediate stiffness at 40 kPa; consistently, total cholesterol (TC) content on 1 and 100 kPa substrates was also higher. As a result, the accumulation of cholesterol increased the expression of macrophage marker CD68 and downregulated SMC contractile marker smooth muscle α-actin (ACTA2). Furthermore, the mRNA and protein expression level of cholesterol efflux gene ATP-binding cassette transporter A1 (ABCA1) was much higher on 40 kPa substrate. With the treatment of a liver X receptor (LXR) agonist GW3965, the expression of ABCA1 increased and cholesterol loading decreased, showing an additive effect with substrate stiffness. In contrast, inhibition of LXR decreased ABCA1 gene expression and increased cholesterol accumulation in SMCs. Consistently, when ABCA1 gene was knockdown, the cholesterol accumulation was increased in SMCs on all substrates with different stiffness. These results revealed that substrate stiffness played an important role on SMCs cholesterol accumulation by regulating the ABCA1 expression. Our findings on the effects of substrate stiffness on cholesterol efflux unravel a new mechanism of biophysical regulation of cholesterol metabolism and SMC phenotype, and provide a rational basis for the development of novel therapies.

Canagliflozin Facilitates Reverse Cholesterol Transport Through Activation of AMPK/ABC Transporter Pathway.

Background and PurposeCholesterol is an essential lipid and its homeostasis is a major factor for many diseases, such as hyperlipidemia, atherosclerosis, diabetes, and obesity. Sodium-glucose cotransporter 2 (SGLT2) inhibitor canagliflozin (Cana) is a new kind of hypoglycemic agent, which decreases urinary glucose reabsorption and reduces hyperglycemia. Cana has been shown to regulate serum lipid, decrease serum triglyceride and increase serum high-density lipoprotein-cholesterol (HDL-C), and improve cardiovascular outcomes. But evidence of how Cana impacted the cholesterol metabolism remains elusive.MethodsWe treated Cana on mice with chow diet or western diet and then detected cholesterol metabolism in the liver and intestine. To explore the mechanism, we also treated hepG2 cells and Caco2 cells with different concentrations of Cana.ResultsIn this study, we showed that Cana facilitated hepatic and intestinal cholesterol efflux. Mechanically, Cana via activating adenosine monophosphate-activated protein kinase (AMPK) increased the expression of ATP-binding cassette (ABC) transporters ABCG5 and ABCG8 in liver and intestine, increased biliary and fecal cholesterol excretion.ConclusionThis research confirms that Cana regulates cholesterol efflux and improves blood and hepatic lipid; this may be a partial reason for improving cardiovascular disease.

CircDENND1B Participates in the Antiatherosclerotic Effect of IL-1β Monoclonal Antibody in Mouse by Promoting Cholesterol Efflux via miR-17-5p/Abca1 Axis.

Inflammation is a crucial mediator of atherosclerosis, and several therapeutic methods that focus on inflammatory cytokines, including interleukin-1β (IL-1β), have proven effective in preventing atherogenesis. Circular RNAs (circRNAs) are a subclass of non-coding RNAs (ncRNAs) that can exert critical functions in the regulation of atherosclerosis. Here, using circRNA sequencing, we revealed that circRNA circDENND1B (mmu_circ_0000081) is a promising novel mediator of atherosclerosis in mouse. The expression of circDENND1B is negatively related to the progression of atherosclerosis and foam cell formation, and the upregulation of circDENND1B significantly alleviates foam cell formation induced by ox-LDL by promoting cholesterol efflux. Moreover, circDENND1B participates in the anti-atherosclerotic effect of IL-1β monoclonal antibody (IL-1β mAb), both in vivo and in vitro. With bioinformatic prediction and RNA pull-down assays, we determined that circDENND1B sponges mmu-miR-17-5p to promote Abca1 expression in cells treated with IL-1β mAb. Our study revealed that circDENND1B, a novel regulator of cholesterol efflux, is a potential therapeutic target in atherosclerosis and provides new insights into the interaction between inflammation and cholesterol transport.

Yin-xing-tong-mai decoction attenuates atherosclerosis via activating PPARγ-LXRα-ABCA1/ABCG1 pathway

Atherosclerosis is now the major cause of mortality and morbidity worldwide. Formation of macrophage-derived foam cells is a hallmark of atherosclerosis, which is regulated by cholesterol uptake, intracellular metabolism, and efflux. PPARγ-LXRα-ABCA1/ABCG1 pathway plays an important part in regulating cholesterol efflux and this pathway could be a promising target for treating atherosclerosis. However, due to undesirable systemic effects, PPARγ agonist therapy for atherosclerosis remains challenging. Many traditional Chinese medicine has been well accepted and applied in atherosclerosis treatment. Yin-xing-tong-mai decoction (YXTMD) has been applied for treating atherosclerosis for decades. However, the mechanism remains to be explored. Here, we showed that YXTMD effectively attenuated atherosclerosis in ApoE-/- mice. YXTMD increased cholesterol efflux of foam cell by upregulation of ABCA1 and ABCG1 in vivo and in vitro. Through bioinformatic analysis and experimental validation, we found that PPARγ was an important downstream effector of YXTMD in macrophages. Reduction of PPARγ significantly decreased LXRα, ABCA1, and ABCG1 expression in macrophages, with reduced cholesterol efflux. In conclusion, these findings confirmed that YXTMD attenuated atherosclerosis by activating the PPARγ-LXRα- ABCA1/ABCG1 pathway to enhance cholesterol efflux.

Site‐Specific MicroRNA‐33 Antagonism by pH‐Responsive Nanotherapies for Treatment of Atherosclerosis via Regulating Cholesterol Efflux and Adaptive Immunity

AbstractAtherosclerosis remains the leading cause of a broad spectrum of deadliest cardiovascular diseases. MicroRNA‐33 is a new therapeutic target for atherosclerosis due to its diverse functions. However, it remains a great challenge in clinical translation of nucleic acid‐based microRNA‐targeting therapeutics. Considering lesional acidosis, herein cyclodextrin‐derived pH‐responsive and integrin‐targeting nanoparticles containing an antisense oligonucleotide against microRNA‐33 (anti‐miR33) are engineered for precision therapy of atherosclerosis. A desirable anti‐miR33 nanotherapy (AAM NP) is initially developed by screening carrier materials. AAM NP is further decorated with a peptide ligand cRGDfK for integrin to afford an active targeting nanotherapy RAAM NP, to achieve more effective delivery of anti‐miR33 to plaques and target cells. Both nanotherapies can be efficiently internalized by different cells relevant to atherosclerosis. After intravenous delivery, AAM NP passively accumulates in atherosclerotic plaques and related cells in apolipoprotein E‐deficient mice. Correspondingly, AAM NP treatment significantly attenuates atherosclerosis in mice and notably reduces vulnerable plaques. Decoration with cRGDfK considerably enhances the targeting capability and therapeutic effects of RAAM NP. Mechanistically, anti‐miR33 nanotherapies significantly promote reverse cholesterol transport and notably regulate adaptive immunity via modulating macrophage polarization and regulatory T cell differentiation. Consequently, the pH‐responsive anti‐miR33 nanotherapies are promising for targeted treatment of atherosclerosis.

Cholesterol metabolism in macrophages

Disturbance of lipid metabolism can lead to the development of pathological processes. Atherosclerosis is a chronic disease characterized by the development of atherosclerotic lesions as a result of the lipid accumulation in the great arterial walls. As a result of cholesterol accumulation by macrophage within the atherosclerotic lesions, they differentiate into foam cells. Macrophage lipid uptake may occur either though the receptor-dependent pathway by low-density lipoprotein receptors and the SR-A, CD36 and LOX-1 scavenger receptors, or the receptor-independent pathway by pinocytosis and phagocytosis. Various enzymes such as ACAT-1 and Abstract NCEH, enzymes of the biosynthesis and fatty acid oxidation pathways, as well as various transcription factors - SREBP, Nrf1 and Nrf2 participate in the intracellular regulation of lipids. High-density lipoproteins and transporters such as ABCA1, ABCG1 and SR-BI play a vital role in the regulation of cholesterol efflux from cells. Players of lipid metabolism are regulated by various kinase signaling pathways that activate many transcription factors - LXR, RXR, PPARy, NF-kB, etc. Regulation disturbance of intracellular metabolism and imbalance in uptake and efflux of cholesterol from macrophages lead to their differentiation into foam cells. The aim of this review is to describe the mechanisms underlaying lipid metabolism in macrophages and resulting in the transformation of these cells into foam cells.

Bifunctional supramolecular nanofiber inhibits atherosclerosis by enhancing plaque stability and anti-inflammation in apoE-/- mice.

Background and Purpose: Atherosclerosis is vascular disease of chronic inflammation and lipid disorder, which is a major cause of coronary heart disease. Foam cell formation is key progress during the atherosclerosis development. Insulin-like growth factor (IGF)-1 is a growth hormone that plays a crucial role in growth, metabolism, and homeostasis. Previous studies have demonstrated that increase in circulating IGF-1 can reduce atherosclerotic burden. However, active IGF-1 is characterized with poor tissue retention and is at a very low level in circulation system. Therefore, supplementation of exogenous IGF-1 to restore the physiological level is a promising approach to inhibit atherosclerosis. In this study, we develop a self-assembling, anti-inflammatory drug-modified peptide derived from IGF-1 to mimic IGF-1 bioactivity and simultaneously with an anti-inflammatory property for the treatment of atherosclerosis.Methods: ApoE-/- mice were subcutaneously (s.c.) injected with the different hydrogels or natural IGF-1 protein solution per week and simultaneously fed a high-fat diet for 16 weeks. Atherosclerotic lesion formation and stability were assessed after treatment. Moreover, peritoneal macrophage and serum samples were collected to determine lipid profile and inflammatory cytokines. Concurrently, we determined the effect of bifunctional supramolecular nanofibers/hydrogel on cholesterol efflux, foam cell formation, phenotypic transformation of VSMC to macrophage-like cells, and macrophage polarization in vitro or in vivo.Results: Bifunctional supramolecular nanofibers/hydrogel for the treatment of atherosclerosis was formed by a short peptide consisting of a tetrapeptide SSSR from C-region of growth factor IGF-1, an anti-inflammatory drug naproxen (Npx), and a powerful self-assembling D-peptide DFDF. The resulting hydrogel of Npx-DFDFGSSSR (Hydrogel 1, H1) possessed both the anti-inflammatory and IGF-1 mimicking properties, and it efficiently promoted the expression of ABCA1 and ABCG1, thereby significantly reducing cholesterol accumulation in macrophages and preventing foam cell formation. Moreover, H1 markedly inhibited the transformation of vascular smooth muscle cells (VSMCs) into macrophage-like cells which also contributed to foam cell formation. In addition, H1 significantly reduced the inflammatory response in vitro and in vivo. Most importantly, the IGF-1 mimetic peptide showed comparable performance to IGF-1 in vivo and inhibited atherosclerosis by markedly reducing lesion area and enhancing plaque stability.Conclusions: Our study provides a novel supramolecular nanomaterial to inhibit pathological progress of atherosclerosis through regulating cholesterol efflux and inflammation, which may contribute to the development of a promising nanomedicine for the treatment of atherosclerosis in the clinic.

ASSOCIATION OF CHOLESTEROL ESTER TRANSFER PROTEIN GENE POLYMORPHISM AND DIET TO CHANGES IN SERUM LIPID PROFILE

The cholesterol ester transfer protein regulates cholesterol efflux from peripheral tissues. The cholesterol ester transfer protein is encoded by CETP gene. The review describes the association of CETP gene variants with metabolic changes in different diets. The association of diet and metabolic changes depends on the sample size, individual and age characteristics of the patients, the duration of the observation, and the analysis of the spectrum of the CETP gene variants.

Mono-(2-Ethylhexyl)phthalate Regulates Cholesterol Efflux via MicroRNAs Regulated m6A RNA Methylation.

Mono-(2-ethylhexyl)phthalate (MEHP) is a major bioactive metabolite which occurs from the widely used industrial plasticizer di(2-ethylhexyl)phthalate, which has been found to be toxic to several human physiological systems, including the cardiometabolic system. Recently, RNA methylation has been shown to be involved in cardio-metabolic regulation. Despite the importance of m6A mRNA methylation in physiological processes, studies of RNA methylation associated with endocrine disrupting chemicals are lacking. Here, we investigated the effects of MEHP in a cholesterol efflux pathway and the roles of m6A methylation using murine macrophage Raw 264.7 cells. MEHP exposure significantly reduced (P < 0.01 for 50 μM) m6A mRNA methylation with decreases in both mRNA (P < 0.01 for 5 and 50 μM) and protein (P < 0.05 for 0.5 μM; P < 0.01 for 5 μM; and P < 0.001 for 50 μM) expression levels of METTL14, a component of the methyltransferase complex. However, m5C RNA methylation remained unchanged. MEHP significantly reduced the expression of Scavenger Receptor B type 1 (SR-B1) (P < 0.01 for 5 μM and P < 0.05 for 50 μM). Additionally, we demonstrated that silencing METTL14 with MEHP decreased SR-B1 gene expression compared to the MEHP treatment (P < 0.01) or silencing METTL14 alone (P < 0.05). Furthermore, MEHP significantly promoted the m6A modification in SR-B1 (P < 0.001) and activated miRNAs which are predicted to regulate METTL14, such as miR16-1-3p (P < 0.05 for 50 μM MEHP), miR101a-3p (P < 0.05 for 5 and 50 μM MEHP), miR362-3-5p (P < 0.05 for 50 μM MEHP), miR501-5p (P < 0.01 for 50 μM MEHP), miR532-3p (P < 0.05 for 50 μM MEHP), and miR542-3p (P < 0.05 for 50 μM MEHP). Together, these results reveal for the first time that MEHP can modulate RNA methylation to regulate SR-B1 in a cholesterol efflux pathway.

Carvedilol Ameliorates Experimental Atherosclerosis by Regulating Cholesterol Efflux and Exosome Functions.

Carvedilol (Cav), a nonselective β-blocker with α1 adrenoceptor blocking effect, has been used as a standard therapy for coronary artery disease. This study investigated the effects of Cav on exosome expression and function, ATP-binding cassette transporter A1 (ABCA1) expression, and cholesterol efflux that are relevant to the process of atherosclerosis. Human monocytic (THP-1) cell line and human hepatic (Huh-7) cells were treated with Cav, and cholesterol efflux was measured. Exosomes from cell culture medium or mice serum were isolated using glycan-coated recognition beads. Low-density lipoprotein receptor knockout (ldlr−/−) mice were fed with high-fat diet and treated with Cav. Cav accentuated cholesterol efflux and enhanced the expressions of ABCA1 protein and mRNA in both THP-1 and Huh-7 cells. In addition, Cav increased expression and function of exosomal ABCA1 in THP-1 macrophage exosomes. The mechanisms were associated with inhibition of nuclear factor-κB (NF-κB) and protein kinase B (Akt). In hypercholesterolemic ldlr−/− mice, Cav enhanced serum exosomal ABCA1 expression and suppressed atherosclerosis by inhibiting lipid deposition and macrophage accumulation. Cav halts atherosclerosis by enhancing cholesterol efflux and increasing ABCA1 expression in macrophages and in exosomes, possibly through NF-κB and Akt signaling, which provides mechanistic insights regarding the beneficial effects of Cav on atherosclerotic cardiovascular disease.

Enhanced cellular cholesterol efflux by naringenin is mediated through inhibiting endoplasmic reticulum stress - ATF6 activity in macrophages

Naringenin improves lipoprotein profile and protects against cardiovascular disease. ATF6 is an endoplasmic reticulum (ER) stress sensor with the same activation processes with sterol regulator SREBPs. Clinical data revealed that ATF6 expression was associated with plasma cholesterol level. Here, we investigated whether naringenin was involved in the regulation of cholesterol efflux and tested the role of ER stress-ATF6 in the naringenin function. Results showed that naringenin increased cholesterol efflux to both apoA-I and HDL and gene expressions in ABCA1, ABCG1 and LXRα in RAW264.7 macrophages. Naringenin inhibited the cleaved ATF6 nuclear translocation and its target GRP78 and XBP-1 expressions. Naringenin-induced cholesterol efflux was modulated by treatment with ER stress inhibitor 4-phenylbutyric acid, inducer tunicamycin and ATF6 overexpression in RAW264.7 and/or THP-1 cells, which suggested the naringenin functions were mediated through inhibiting ER stress-ATF6 pathway. Next, we found high-fat diet (HFD) supplemented with naringenin increased by >1.2-fold in cholesterol efflux capacity in primary peritoneal macrophage in apoE−/− mice compared to only HFD-fed mice. The increase was significantly reduced by tunicamycin treatment. Naringenin decreased GRP78, XBP-1 and nuclear ATF6 levels in peritoneal macrophage and aorta and reduced atherosclerotic lesion at aortic root, but reversed by tunicamycin. These confirmed participation of ER stress-ATF6 in naringenin efficacy. Finally, we found naringenin promoted AKT phosphorylation; PI3K inhibitor LY294002 treatment increased nuclear ATF6 and reduced naringenin-enhanced ABCA1 expression and cholesterol efflux. We concluded naringenin as a regulator for cholesterol efflux, and the regulation was mediated by ATF6 branch of ER stress and PI3K/AKT pathway.

Regulation of lipid rafts, angiogenesis and inflammation by AIBP.

Recent studies demonstrate an important role of the secreted apolipoprotein A-I binding protein (AIBP) in regulation of cholesterol efflux and lipid rafts. The article discusses these findings in the context of angiogenesis and inflammation. Lipid rafts are cholesterol-rich and sphingomyelin-rich membrane domains in which many receptor complexes assemble upon activation. AIBP mediates selective cholesterol efflux, in part via binding to toll-like receptor-4 (TLR4) in activated macrophages and microglia, and thus reverses lipid raft increases in activated cells. Recent articles report AIBP regulation of vascular endothelial growth factor receptor-2, Notch1 and TLR4 function. In zebrafish and mouse animal models, AIBP deficiency results in accelerated angiogenesis, increased inflammation and exacerbated atherosclerosis. Spinal delivery of recombinant AIBP reduces neuraxial inflammation and reverses persistent pain state in a mouse model of chemotherapy-induced polyneuropathy. Inhalation of recombinant AIBP reduces lipopolysaccharide-induced acute lung injury in mice. These findings are discussed in the perspective of AIBP's proposed other function, as an NAD(P)H hydrate epimerase, evolving into a regulator of cholesterol trafficking and lipid rafts. Novel findings of AIBP regulatory circuitry affecting lipid rafts and related cellular processes may provide new therapeutic avenues for angiogenic and inflammatory diseases.