Promote Macrophage Cholesterol Efflux Research Articles

Imbalance of APOB Lipoproteins and Large HDL in Type 1 Diabetes Drives Atherosclerosis.

Individuals with type 1 diabetes (T1D) generally have normal or even higher HDL (high-density lipoprotein)-cholesterol levels than people without diabetes yet are at increased risk for atherosclerotic cardiovascular disease (CVD). Human HDL is a complex mixture of particles that can vary in cholesterol content by >2-fold. To investigate if specific HDL subspecies contribute to the increased atherosclerosis associated with T1D, we created mouse models of T1D that exhibit human-like HDL subspecies. We also measured HDL subspecies and their association with incident CVD in a cohort of people with T1D. We generated LDL receptor-deficient (Ldlr-/-) mouse models of T1D expressing human APOA1 (apolipoprotein A1). Ldlr-/-APOA1Tg mice exhibited the main human HDL subspecies. We also generated Ldlr-/-APOA1Tg T1D mice expressing CETP (cholesteryl ester transfer protein), which had lower concentrations of large HDL subspecies versus mice not expressing CETP. HDL particle concentrations and sizes and proteins involved in lipoprotein metabolism were measured by calibrated differential ion mobility analysis and targeted mass spectrometry in the mouse models of T1D and in a cohort of individuals with T1D. Endothelial transcytosis was analyzed by total internal reflection fluorescence microscopy. Diabetic Ldlr-/-APOA1Tg mice were severely hyperglycemic and hyperlipidemic and had markedly elevated plasma APOB levels versus nondiabetic littermates but were protected from the proatherogenic effects of diabetes. Diabetic Ldlr-/-APOA1Tg mice expressing CETP lost the atheroprotective effect and had increased lesion necrotic core areas and APOB accumulation, despite having lower plasma APOB levels. The detrimental effects of low concentrations of larger HDL particles in diabetic mice expressing CETP were not explained by reduced cholesterol efflux. Instead, large HDL was more effective than small HDL in preventing endothelial transcytosis of LDL mediated by scavenger receptor class B type 1. Finally, in humans with T1D, increased concentrations of larger HDLs relative to APOB100 negatively predicted incident CVD independently of HDL-cholesterol levels. Our results suggest that the balance between APOB lipoproteins and the larger HDL subspecies contributes to atherosclerosis progression and incident CVD in the setting of T1D and that larger HDLs exert atheroprotective effects on endothelial cells rather than by promoting macrophage cholesterol efflux.

Combination of mangiferin and T0901317 targeting autophagy promotes cholesterol efflux from macrophage foam cell in atherosclerosis

BackgroundThe synthetic liver X receptor ligand (LXR) T0901317 (T0) has been reported to attenuate atherosclerosis (AS) without hyperglyceridemia due to innovative drug combination or nano-sized drug delivery. Given the key roles of mangiferin (MGF) in lipid metabolism and atherogenesis, it is critical to investigate progression of atherosclerotic lesion after combined treatment of MGF and T0.MethodsAtherosclerotic plaque formation and hepatic lipid accumulation were compared in Apoe−/− mice among T0 and/or MGF treatment. The in vitro functions of MGF and T0 were analyzed by Oil-red O staining, cholesterol efflux assay, transmission electron microscopy and western blot analyses with or without acetylated low density lipoprotein.ResultsThe combination therapy are effective regulators for atherosclerotic plaque formation in Apoe−/− mice, due to upregulation of ABCA1 and ABCG1 induced by LXR activation. Subsequently, we identified autophagy promoted by MGF and T0 treatment establishes a positive feedback loop that increases cholesterol efflux, resulted from LXRα activation. Under atherogenic conditions, the autophagy inhibitor CQ abolished the enhancement effect on cholesterol outflow of MGF and T0. Mechanically, MGF and T0 promotes LXRα and mTOR/AMPK signaling cascade in macrophage, and promotes AMPK signaling cascade in hepatocyte, leading to lipid metabolic homeostasis.ConclusionsAltogether, our findings reveal that MGF and T0 engages in AS therapy without side effects by activating AMPK-dependent autophagy to promote macrophage cholesterol efflux, and MGF might serve as a natural compound to assist T0 in AS via targeting autophagy.

IDF2022-0723 Interleukin-4 Improves Metabolic Homeostasis by Inhibiting Lipid Deposits and Promoting Macrophage Cholesterol Efflux

IDF2022-0723 Interleukin-4 Improves Metabolic Homeostasis by Inhibiting Lipid Deposits and Promoting Macrophage Cholesterol Efflux

Pomegranate punicalagin inhibits the foam cells formation in Raw264.7 macrophages

In order to reveal the inhibitory effect of pomegranate punicalagin on macrophage foam cell formation and its possible mechanism, Raw264.7 macrophages were as the experimental carrier to detect the effect of punicalagin on macrophage cholesterol accumulation and outflow, and evaluate the regulation of punicalagin on cholesterol accumulation related genes CD36, PPARγ and outflow related genes ABCA1/G1, LXRα by Western-Blot method. The results showed that punicalagin can inhibit the cholesterol accumulation in raw264.7 macrophages due to restraining the PPARγ-CD36 expression, and meanwhile it could also promote macrophage cholesterol efflux by regulating LXRα-ABCA1/G1 pathway.

CTRP15 promotes macrophage cholesterol efflux and attenuates atherosclerosis by increasing the expression of ABCA1.

C1q tumor necrosis factor-related protein 15 (CTRP15), a newly identified myokine, is closely implicated in cardiovascular disease. However, the role of CTRP15 in atherosclerosis is still unclear. This study aims to determine the role of CTRP15 in atherosclerosis and explore the underlying mechanisms. Our findings revealed that lentivirus-mediated CTRP15 overexpression significantly decreased atherosclerotic plaque lesions and increased reverse cholesterol transport (RCT) efficiency and circulating HDL-C levels in apolipoprotein E-deficient (apoE-/-) mice. Consistently, in vitro, overexpression of CTRP15 also inhibited intracellular lipid accumulation and promoted cholesterol efflux from macrophages. Mechanistically, CTRP15 decreased the expression of miR-101-3p by upregulating T-cadherin, thereby facilitating ABCA1 expression and cholesterol efflux. In summary, these data indicate that CTRP15 inhibits the development of atherosclerosis by enhancing RCT efficiency and increasing plasma HDL-C levels via the T-cadherin/miR-101-3p/ABCA1 pathway. Targeting CTRP15 may serve as a novel and promising therapeutic strategy for atherosclerotic cardiovascular diseases.

New Strategies to Promote Macrophage Cholesterol Efflux.

The capacity of macrophages to dispose of cholesterol deposited in the atherosclerotic plaque depends on their ability to activate cholesterol efflux pathways. To develop athero-protective therapies aimed at promoting macrophage cholesterol efflux, cholesterol metabolism in THP-1 monocyte-derived macrophages has been extensively studied, but the intrinsic sensitivity of monocytes and the lack of a standardized procedure to differentiate THP-1 monocytes into macrophages have made it difficult to utilize THP-1 macrophages in the same or similar degree of differentiation across studies. The variability has resulted in lack of understanding of how the differentiation affects cholesterol metabolism, and here we review and investigate the effects of THP-1 differentiation on cholesterol efflux. The degree of THP-1 differentiation was inversely associated with ATP binding cassette A1 (ABCA1) transporter-mediated cholesterol efflux. The differentiation-associated decrease in ABCA1-mediated cholesterol efflux occurred despite an increase in ABCA1 expression. In contrast, DSC1 expression decreased during the differentiation. DSC1 is a negative regulator of the ABCA1-mediated efflux pathway and a DSC1-targeting agent, docetaxel showed high potency and efficacy in promoting ABCA1-mediated cholesterol efflux in THP-1 macrophages. These data suggest that pharmacological targeting of DSC1 may be more effective than increasing ABCA1 expression in promoting macrophage cholesterol efflux. In summary, the comparison of THP-1 macrophage subtypes in varying degrees of differentiation provided new insights into cholesterol metabolism in macrophages and allowed us to identify a viable target DSC1 for the promotion of cholesterol efflux in differentiated macrophages. Docetaxel and other pharmacological strategies targeting DSC1 may hold significant potential for reducing atherogenic cholesterol deposition.

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.

Editorial expression of concern: “Apolipoprotein A-1 binding protein promotes macrophage cholesterol efflux by facilitating apolipoprotein A-1 binding to ABCA1 and preventing ABCA1 degradation” [Atherosclerosis volume 248, May 2016, pages 149–159

Editorial expression of concern: “Apolipoprotein A-1 binding protein promotes macrophage cholesterol efflux by facilitating apolipoprotein A-1 binding to ABCA1 and preventing ABCA1 degradation” [Atherosclerosis volume 248, May 2016, pages 149–159

SAT-LB92 Sex Hormones Therapy Differentially Modulates HDL Function in Transgender Individuals

Background/aim: The main proposed atheroprotective function of high-density lipoproteins (HDL) lays on their role to promote macrophage cholesterol efflux. An insightful way to learn more about the effects of sex hormones on HDL function is to study changes during hormone therapy. The present study was aimed at evaluating the effects of exogenous sex hormones administration on HDL cholesterol efflux capacity (CEC) within transgender individuals. CEC estimates the ability of HDL to remove cholesterol from cells, i.e. the initial step in reverse cholesterol transport. Subjects/Methods: Transmen were treated with testosterone gel, a mix of testosterone esters once every three weeks) or testosterone undecanoate once every twelve weeks, whereas transwomen were treated with either oral estradiol valerate or a transdermal application of estradiol (patches). Cyproterone acetate was prescribed as a testosterone-blocking agent to all transwomen. HDL function was evaluated by a radioisotopic technique. Hormone levels, lipids and HDL function were evaluated after one year of follow-up. Results: In transmen (n= 15), testosterone markedly increased (+ 97%; p < 0.0001), whereas luteinizing hormone (LH) decreased significantly (- 64%; p = 0.049). Total cholesterol and low-density lipoprotein cholesterol (LDL-C) were not affected by testosterone treatment, whilst triglycerides (TG) were raised (+ 11.76%; p = 0.0078) and HDL-C reduced (- 19.6%, p=0.0103). Concerning HDL CEC, only the aqueous diffusion process was lowered (- 9.8%; p = 0.0032), an effect directly correlated with HDL-C changes (r = 0.6242, p = 0.0002). Total-, ATP-binding cassette transporter (ABCA1)-, and ABCG1-mediated CEC were not affected by testosterone treatment. In transwomen (n= 15), estradiol levels were raised (+200%, p=0.013) whereas LH and testosterone significantly reduced, i.e. - 97% for both. Relative to lipids, estradiol supplementation reduced total cholesterol (- 10.7%, p=0.0017), HDL-C (- 14.3%, p = 0.0024) and LDL-C (- 10.9%, p = 0.0058). Total HDL CEC decreased (- 11%, p=0.0001) with a specific decrement in CEC mediated by the ATP-binding cassette transporter (ABCA1) (-24%, p = 0.0003) and aqueous diffusion (-4.7%, p = 0.0014). This last was associated to a reduction in HDL-C (r = 0.4084, p = 0.0251). Conversely, the drop in ABCA1 and total CEC did not associate to reductions in HDL-C levels. Conclusions: In transmen, testosterone supplementation was associated with a reduction in aqueous diffusion-mediated CEC, an effect potentially dependent to HDL-C changes. In transwomen, estrogen significantly decreased HDL function (CEC), independent of HDL-C levels changes.

Mangiferin promotes macrophage cholesterol efflux and protects against atherosclerosis by augmenting the expression of ABCA1 and ABCG1.

Mangiferin has been identified as a potent cardioprotective factor that enhances high-density lipoprotein cholesterol levels in plasma. The aim of this study was to investigate the impact of mangiferin on macrophage cholesterol efflux and the development of atherosclerosis. The results showed that mangiferin injection significantly decreased atherosclerotic plaque size, and reduced plasma levels of low-density lipoprotein cholesterol, triglyceride, and total cholesterol in apoE knockout mice, whereas reverse cholesterol transport efficiency and high-density lipoprotein cholesterol levels were enhanced. In vitro study showed that mangiferin prevented lipid accumulation and promoted [3H]-cholesterol efflux from acetylated LDL-loaded RAW264.7 macrophages with an increase in the expression of ATP binding cassette A1/G1 (ABCA1/G1), liver X receptor-α (LXRα) and peroxisome proliferator-activated receptor-γ (PPARγ). Moreover, transfection of PPARγ siRNA or LXRα siRNA markedly abolished the positive effects of mangiferin on ABCA1/G1 expression and cholesterol efflux. The opposite effects were observed after treatment with PPARγ agonist rosiglitazone or LXRα agonist T0901317. In conclusion, mangiferin may attenuate atherogenesis by promoting cholesterol efflux from macrophages via the PPARγ-LXRα-ABCA1/G1 pathway.

Cellular Uptake and Clearance of Oxidatively-modified Apolipoprotein E3 by Cerebral Cortex Endothelial Cells.

Apolipoprotein E3 (apoE3) plays a critical role in the metabolism of lipoproteins and lowers plasma lipid levels by serving as a ligand for the low-density lipoprotein receptor (LDLr) family of proteins and by promoting macrophage cholesterol efflux. The current study examines the effect of acrolein (an endogenously generated metabolite and an environmental pollutant) modification on the structure and function of apoE3. Acrolein modification was confirmed in Western blots by reactivity with acrolein–lysine-specific antibody and by the presence of oligomeric species due to cross-linking. LC-MS/MS analysis revealed modification of 10 out of 12 lysines in apoE3, with Nε-(3-methylpyridinium)-lysine being the predominant form of modification, and Lys75 being a ‘hot spot’ in terms of susceptibility to oxidation. Circular dichroism spectroscopy showed no major change in overall secondary structure compared to unmodified apoE3. Reconstituted high density lipoprotein (HDL) bearing acrolein modified apoE3 showed loss of binding to soluble LDLr; however, incubation with mouse endothelioma bEnd.3 cells showed that it was internalized. Incubation with excess LDL did not abolish cellular uptake of acrolein modified apoE3, suggesting alternative mechanism(s) not involving LDLr. Incubation with anti-CD36 antibody did not show a decrease in internalization while incubation with anti- lectin-like oxidized LDL receptor 1 (LOX1) showed partial internalization. However, incubation with anti-scavenger receptor class B type I (SRB1) antibody abolished internalization of acrolein modified apoE3. Taken together, our studies suggest that acrolein modification of apoE3 at lysine residues leads to increase in net negative charge, and as a consequence, results in clearance by LOX1 and SRB1 on endothelial cells. Overall, oxidative modification of apoE3 likely impairs its role in regulating plasma cholesterol homeostasis, eventually leading to lipid disorders.

Impaired HDL (High-Density Lipoprotein)-Mediated Macrophage Cholesterol Efflux in Patients With Abdominal Aortic Aneurysm-Brief Report.

Objective- The ability of HDL (high-density lipoprotein) to promote macrophage cholesterol efflux is considered the main HDL cardioprotective function. Abdominal aortic aneurysm (AAA) is usually characterized by cholesterol accumulation and macrophage infiltration in the aortic wall. Here, we aim to evaluate the composition of circulating HDL particles and their potential for promoting macrophage cholesterol efflux in AAA subjects. Approach and Results- First, we randomly selected AAA and control subjects from Spain. The AAA patients in the Spanish cohort showed lower plasma apoA-I levels concomitantly associated with low levels of plasma HDL cholesterol and the amount of preβ-HDL particles. We determined macrophage cholesterol efflux to apoB-depleted plasma, which contains mature HDL, preβ-HDL particles and HDL regulatory proteins. ApoB-depleted plasma from AAA patients displayed an impaired ability to promote macrophage cholesterol efflux. Next, we replicated the experiments with AAA and control subjects derived from Danish cohort. Danish AAA patients also showed lower apoA-I levels and a defective HDL-mediated macrophage cholesterol efflux. Conclusions- AAA patients show impaired HDL-facilitated cholesterol removal from macrophages, which could be mechanistically linked to AAA.

Global inactivation of carboxylesterase 1 (Ces1/Ces1g) protects against atherosclerosis in Ldlr\u2212/\u2212 mice

Atherosclerotic cardiovascular disease is a leading cause of death in the western world. Increased plasma triglyceride and cholesterol levels are major risk factors for this disease. Carboxylesterase 1 (Ces1/Ces1g) has been shown to play a role in metabolic control. So far, the role of mouse Ces1/Ces1g deficiency in atherosclerosis is not elucidated. We generated Ces1/Ces1g−/− mice. Compared to wild-type mice, Ces1/Ces1g−/− mice had reduced plasma cholesterol levels. We then generated Ces1g−/−Ldlr−/− double knockout (DKO) mice, which were fed a Western diet for 16 weeks. Compared to Ldlr−/− mice, DKO mice displayed decreased plasma cholesterol and TG levels and reduced atherosclerotic lesions. Interestingly, knockdown of hepatic Ces1/Ces1g in Apoe−/− mice resulted in hyperlipidemia and exacerbated Western diet-induced atherogenesis. Mechanistically, global inactivation of Ces1/Ces1g inhibited intestinal cholesterol and fat absorption and Niemann-Pick C1 like 1 expression, and increased macrophage cholesterol efflux by inducing ATP-binding cassette subfamily A member 1 (ABCA1) and ABCG1. Ces1/Ces1g ablation also promoted M2 macrophage polarization and induced hepatic cholesterol 7α-hydroxylase and sterol 12α-hydroxylase expression. In conclusion, global loss of Ces1/Ces1g protects against the development of atherosclerosis by inhibiting intestinal cholesterol and triglyceride absorption and promoting macrophage cholesterol efflux.

Apolipoprotein A-1 binding protein promotes macrophage cholesterol efflux by facilitating apolipoprotein A-1 binding to ABCA1 and preventing ABCA1 degradation

RationalePrevious studies have shown that apolipoprotein-1 (apoA-1) binding protein (AIBP) is highly associated with the regulation of apoA-1 metabolism, suggesting its role in the treatment of atherosclerosis. However, how AIBP regulates foam cell formation remains largely unexplored. ObjectiveTo investigate the mechanisms underlying AIBP inhibition of foam cell formation from macrophages. Methods and resultsTHP-1-derived macrophages were incubated without or with apoA-1 and AIBP, followed by assessing the formation of foam cells and the potential mechanisms. Our results showed that AIBP and apoA-1 enhanced cholesterol efflux, altered the levels of cellular free cholesterol and cholesterol ester and prevented lipid accumulation so as to reduce the formation of foam cells. Meanwhile, lack of AIBP 115–123 amino acids resulted in the loss of AIBP binding to apoA-1. Moreover, our chemiluminescent analysis showed that AIBP promoted biotin-labeled apoA-1 binding to macrophages. Besides with AIBP, more apoA-1 bound to ABCA1, a key transporter responsible for cholesterol efflux to apoA-1, as indicated by our co-immunoprecipitation assay. Our results also showed that AIBP did not regulate ABCA1 mRNA expression, but stabilized its protein from CSN2-mediated degradation. ConclusionsAIBP promotes apoA-1 binding to ABCA1 on the cell membrane of macrophages and prevents ABCA1 protein from CSN2-mediated degradation so as to prevent foam cell formation. AIBP 115–123 amino acids is at least partially responsible for its binding to apoA-1.

The novel selective PPARα modulator (SPPARMα) pemafibrate improves dyslipidemia, enhances reverse cholesterol transport and decreases inflammation and atherosclerosis

BackgroundAtherosclerosis is characterized by lipid accumulation and chronic inflammation in the arterial wall. Elevated levels of apolipoprotein (apo) B-containing lipoproteins are a risk factor for cardiovascular disease (CVD). By contrast, plasma levels of functional high-density lipoprotein (HDL) and apoA-I are protective against CVD by enhancing reverse cholesterol transport (RCT). Activation of peroxisome proliferator-activated receptor-α (PPARα), a ligand-activated transcription factor, controls lipid metabolism, cellular cholesterol trafficking in macrophages and influences inflammation. ObjectiveTo study whether pharmacological activation of PPARα with a novel highly potent and selective PPARα modulator, pemafibrate, improves lipid metabolism, macrophage cholesterol efflux, inflammation and consequently atherosclerosis development in vitro and in vivo using human apolipoprotein E2 Knock-In (apoE2KI) and human apoA-I transgenic (hapoA-I tg) mice. Approach and resultsPemafibrate treatment decreases apoB secretion in chylomicrons by polarized Caco-2/TC7 intestinal epithelium cells and reduces triglyceride levels in apoE2KI mice. Pemafibrate treatment of hapoA-I tg mice increases plasma HDL cholesterol, apoA-I and stimulates RCT to feces. In primary human macrophages, pemafibrate promotes macrophage cholesterol efflux to HDL and exerts anti-inflammatory activities. Pemafibrate also reduces markers of inflammation and macrophages in the aortic crosses as well as aortic atherosclerotic lesion burden in western diet-fed apoE2KI mice. ConclusionsThese results demonstrate that the novel selective PPARα modulator pemafibrate exerts beneficial effects on lipid metabolism, RCT and inflammation resulting in anti-atherogenic properties.

Macrophage Mitochondrial Energy Status Regulates Cholesterol Efflux and Is Enhanced by Anti-miR33 in Atherosclerosis

Therapeutically targeting macrophage reverse cholesterol transport is a promising approach to treat atherosclerosis. Macrophage energy metabolism can significantly influence macrophage phenotype, but how this is controlled in foam cells is not known. Bioinformatic pathway analysis predicts that miR-33 represses a cluster of genes controlling cellular energy metabolism that may be important in macrophage cholesterol efflux. We hypothesized that cellular energy status can influence cholesterol efflux from macrophages, and that miR-33 reduces cholesterol efflux via repression of mitochondrial energy metabolism pathways. In this study, we demonstrated that macrophage cholesterol efflux is regulated by mitochondrial ATP production, and that miR-33 controls a network of genes that synchronize mitochondrial function. Inhibition of mitochondrial ATP synthase markedly reduces macrophage cholesterol efflux capacity, and anti-miR33 required fully functional mitochondria to enhance ABCA1-mediated cholesterol efflux. Specifically, anti-miR33 derepressed the novel target genes PGC-1α, PDK4, and SLC25A25 and boosted mitochondrial respiration and production of ATP. Treatment of atherosclerotic Apoe(-/-) mice with anti-miR33 oligonucleotides reduced aortic sinus lesion area compared with controls, despite no changes in high-density lipoprotein cholesterol or other circulating lipids. Expression of miR-33a/b was markedly increased in human carotid atherosclerotic plaques compared with normal arteries, and there was a concomitant decrease in mitochondrial regulatory genes PGC-1α, SLC25A25, NRF1, and TFAM, suggesting these genes are associated with advanced atherosclerosis in humans. This study demonstrates that anti-miR33 therapy derepresses genes that enhance mitochondrial respiration and ATP production, which in conjunction with increased ABCA1 expression, works to promote macrophage cholesterol efflux and reduce atherosclerosis.

Macrophage mitochondrial energy status regulates cholesterol efflux and is enhanced by anti‐miR33 in atherosclerosis

Therapeutically targeting macrophage reverse cholesterol transport is a promising approach to treat atherosclerosis and miR‐33 has emerged as novel regulator of cholesterol homeostasis. Cellular energy status can significantly influence macrophage function, and bioinformatic analysis predicts that miR‐33 represses a cluster of genes controlling energy metabolism that may contribute to macrophage cholesterol efflux. We hypothesize that miR‐33 represses mitochondria metabolic pathways to reduce cholesterol efflux. Here, we show that macrophage cholesterol efflux is regulated by mitochondrial ATP production and that miR‐33 controls a network of genes that synchronize mitochondrial function. Macrophage cholesterol efflux capacity was markedly reduced by ATP synthase inhibition, confirming the importance of mitochondria in the efflux of excess cholesterol. Specifically, anti‐miR33 derepressed the novel target genes PGC‐1α, PDK4 and SLC25A25 and boosted mitochondrial respiration and ATP production, and mitochondrial respiration was key to the pro‐efflux effects of anti‐miR33. Anti‐miR33 therapy in atherosclerotic Apoe‐/‐ mice reduced aortic sinus lesion area, despite no changes in HDL‐C. Also, this therapy increased expression of mitochondrial target genes in vivo, suggesting that the regulation of mitochondrial genetic networks occur in atherosclerotic lesions.ConclusionWe showed that anti‐miR33 therapy de‐represses genes that enhance mitochondrial respiration and ATP production, which in conjunction with increased ABCA1 expression, promotes macrophage cholesterol efflux and reduces atherosclerosis.

Abstract 262: Anti-miR33 Therapy Promotes PGC1α Expression, Mitochondrial Function and Immunometabolic Pathways in Macrophages in Atherosclerosis

Macrophage foam cells are central to atherosclerotic plaque formation and therapies that increase macrophage cholesterol efflux remain an attractive yet elusive target. Therapeutically inhibiting microRNA-33, a critical regulator of lipid metabolism, increases circulating HDL and reduces atherosclerosis. However, the precise molecular mechanisms that regulate these beneficial effects are unknown. Thus, we sought to uncover novel gene networks regulated by miR33 that may contribute to atherosclerosis. Results: Microarray analysis of macrophages from anti-miR33 treated Ldlr-/- mice revealed several novel miR33 target genes that were de-repressed. Among these genes was PPARγ coactivator 1α (PGC1α), a crucial gene that controls cellular energy homeostasis and mitochondrial metabolism. 3’UTR luciferase assays verified that PGC1α is a specific and direct target of miR33. Macrophages transfected with miR33 mimics or anti-miR33 had decreased or increased PGC1α mRNA and protein respectively. Bioinformatic pathway analysis predicted that in addition to PGC1α, miR33 also regulates multiple mitochondrial proteins, such as pyruvate dehydrogenase kinase 4 (PDK4), solute carrier 25 A25 (SLC25A25) and Acyl-CoA Dehydrogenase (ACADSB). Anti-miR33 treatment of macrophages increases PDK4, SLC25A25 and ACADSB mRNA expression, validating these genes as miR33 targets. Seahorse XF Flux Analyzer studies show that macrophages treated with anti-miR33 have increased basal and maximal oxygen consumption rates, confirming that anti-miR33 therapy impacts positively on mitochondrial respiration and function. miR33 inhibition increased macrophage cholesterol efflux, which was abolished by oligomycin- a mitochondrial respiration inhibitor. This suggests that miR33 regulates cholesterol efflux at least in part by regulating mitochondrial function. Lastly, western-diet-fed apoE-/- mice treated with anti-miR33 injections (10mg/kg) for 8 weeks had a marked reduction in aortic sinus lesion area relative to control (p≤0.05), despite no change in HDL levels. Conclusion: Anti-miR33 therapy can positively impact on mitochondrial function, promoting macrophage cholesterol efflux and may contribute to HDL-independent anti-atherosclerotic effects.

Coenzyme Q10 Promotes Macrophage Cholesterol Efflux by Regulation of the Activator Protein-1/miR-378/ATP-Binding Cassette Transporter G1–Signaling Pathway

Recent studies have shown the role of miRNAs in macrophage reverse cholesterol transport and atherogenesis. We hypothesized that coenzyme Q10 (CoQ10) may increase macrophage reverse cholesterol transport by regulating miRNA expression that contributes to the prevention of atherosclerosis. CoQ10 treatment suppressed oxidized low-density lipoprotein-induced macrophage foam cell formation by ameliorating the binding of activator protein-1 to the putative promoter region of miR-378 primary transcript, thus decreasing the miR-378 level and enhancing the ATP-binding cassette transporter G1-mediated macrophage cholesterol efflux to high-density lipoprotein. Subsequently, the axis of activator protein-1/miR-378/ATP-binding cassette transporter G1 cholesterol efflux was confirmed in peritoneal macrophages isolated from CoQ10-treated apolipoprotein E-deficient mice. Finally, CoQ10 consumption promoted macrophage reverse cholesterol transport and inhibited the progression of atherosclerosis in apolipoprotein E-deficient mice. This study identified activator protein-1/miR-378/ATP-binding cassette transporter G1 as a novel cascade for CoQ10 in facilitating macrophage cholesterol efflux in vitro and in vivo. Our data thus imply that both CoQ10 and miR-378 are promising candidates for atherosclerosis prevention and treatment.

Acrolein Modification Impairs Key Functional Features of Rat Apolipoprotein E: Identification of Modified Sites by Mass Spectrometry

Apolipoprotein E (apoE), an antiatherogenic apolipoprotein, plays a significant role in the metabolism of lipoproteins. It lowers plasma lipid levels by acting as a ligand for the low-density lipoprotein receptor (LDLr) family of proteins, in addition to playing a role in promoting macrophage cholesterol efflux in atherosclerotic lesions. The objective of this study is to examine the effect of acrolein modification on the structure and function of rat apoE and to determine the sites and nature of modification by mass spectrometry. Acrolein is a highly reactive aldehyde, which is generated endogenously as one of the products of lipid peroxidation and is present in the environment in pollutants such as tobacco smoke and heated oils. In initial studies, acrolein-modified apoE was identified by immunoprecipitation using an acrolein-lysine specific antibody in the plasma of 10-week old male rats that were exposed to filtered air (FA) or low doses of environmental tobacco smoke (ETS). While both groups displayed acrolein-modified apoE in the lipoprotein fraction, the ETS group had higher levels in the lipid-free fraction compared with the FA group. This observation provided the rationale to further investigate the effect of acrolein modification on rat apoE at a molecular level. Treatment of recombinant rat apoE with a 10-fold molar excess of acrolein resulted in (i) a significant decrease in lipid-binding and cholesterol efflux abilities, (ii) impairment in the LDLr- and heparin-binding capabilities, and (iii) significant alterations in the overall stability of the protein. The disruption in the functional abilities is attributed directly or indirectly to acrolein modification yielding an aldimine adduct at K149 and K155 (+38); a propanal adduct at K135 and K138 (+56); an N(ε)-(3-methylpyridinium)lysine (MP-lysine) at K64, K67, and K254 (+76), and an N(ε)-(3-formyl-3,4-dehydropiperidino)lysine (FDP-lysine) derivative at position K68 (+94), as determined by matrix-assisted laser desorption/ionization-time of flight/time of flight mass spectrometry (MALDI-TOF/TOF MS). The loss of function may also be attributed to alterations in the overall fold of the protein as noted by changes in the guanidine HCl-induced unfolding pattern and to protein cross-linking. Overall, disruption of the structural and functional integrity of apoE by oxidative modification of essential lysine residues by acrolein is expected to affect its role in maintaining plasma cholesterol homeostasis and lead to dysregulation in lipid metabolism.