ABCA1-mediated Cholesterol Efflux Research Articles

Lipoprotein(a) levels and cholesterol efflux capacity: inverse association and impact on atherosclerosis in familial hypercholesterolemia patients on lipid-lowering therapy

Abstract Backgrounds Familial hypercholesterolemia (FH) patients have higher serum lipoprotein(a) (Lp(a)) levels than non-FH patients, and high Lp(a) levels raise atherosclerotic cardiovascular disease (ASCVD) risk 1). We previously reported that decreased cholesterol efflux capacity (CEC) is a risk marker for ASCVD in patients with statin-treated FH 2). Others have reported that Lp(a) interferes with the enhancement of ABCA1-mediated cholesterol efflux by plasminogen and that ABCA1-mediated CEC is lower in patients with Lp(a) >50 mg/dL. However, the association of CEC, not necessarily ABCA1-mediated, with Lp(a) is not clear and has not been studied in patients with FH. It is also unclear whether high Lp(a) and low CEC in patients with FH are associated with the severity of atherosclerosis. Purpose We examined whether Lp(a) levels are negatively associated with ABCA1-independent CEC in patients with FH receiving lipid-lowering therapy. We also examined the impact of the combination of high Lp(a) and low CEC on the presence of corneal arcus, Achilles tendon thickness, carotid intima-media thickness (IMT), and pre-existing ASCVD. Methods This cross-sectional study included 371 patients clinically diagnosed with FH receiving lipid-lowering therapy. CEC was measured in apolipoprotein B-depleted plasma and 3H-cholesterol-labeled J774.1 cells without cAMP-stimulated ABCA1 overexpression. Lp(a) was measured by enzymatic methods (Sekisui Medical, Tokyo, Japan) using an automated analyser. Achilles tendon thickness was measured by X-ray and carotid IMT by ultrasound. Results Mean age was 55±16 years, and 191 (51%) were women. The median serum Lp(a) level was 18.7 mg/dL, higher than the previously reported median level (13 mg/dL) in a Japanese population. One hundred nineteen patients (32%) had serum Lp(a) levels of 30 mg/dL or higher, and they had significantly lower CEC (P=0.0015). This negative association persisted after adjusting for age, sex, BMI, smoking status, serum LDL-cholesterol, serum triglycerides, and eGFR in a multiple linear regression model (beta-coefficient: -0.047, 95% CI: -0.075 - -0.019, P=0.0011). In addition, patients with both Lp(a) > 30 mg/dL and CEC lower than the median had a higher percentage of corneal arcus, thicker Achilles tendons, greater carotid IMT, and a higher prevalence of pre-existing ASCVD compared to patients with either or neither. Conclusions We found an inverse relationship between Lp(a) levels and CEC in FH patients receiving lipid-lowering therapy. Our results suggest that Lp(a) may also inhibit ABCA1-independent CEC, including passive cholesterol diffusion from peripheral cells. Furthermore, the combination of high Lp(a) and low CEC may be a residual risk for patients with FH receiving lipid-lowering therapy. Future studies are needed to determine whether agents that decrease Lp(a) levels will increase CEC and thereby resolve part of the residual ASCVD risk in FH.

Epigenetic programming of host lipid metabolism associated with resistance to TST/IGRA conversion after exposure to Mycobacterium tuberculosis.

Mycobacterium tuberculosis (Mtb) exposure leads to a range of outcomes including clearance, latent TB infection (LTBI), and pulmonary tuberculosis (TB). Some heavily exposed individuals resist tuberculin skin test (TST) and interferon-gamma (IFNγ) release assay (IGRA) conversion (RSTR), which suggests that they employ IFNγ-independent mechanisms of Mtb control. Here, we compare monocyte epigenetic profiles of RSTR and LTBI from a Ugandan household contact cohort. Chromatin accessibility did not differ between uninfected RSTR and LTBI monocytes. By contrast, methylation significantly differed at 174 CpG sites and across 63 genomic regions. Consistent with previous transcriptional findings in this cohort, differential methylation was enriched in lipid- and cholesterol-associated pathways including the genes APOC3, KCNQ1, and PLA2G3. In addition, methylation was enriched in Hippo signaling, which is associated with cholesterol homeostasis and includes CIT and SHANK2. Lipid export and Hippo signaling pathways were also associated with gene expression in response to Mtb in RSTR as well as IFN stimulation in monocyte-derived macrophages (MDMs) from an independent healthy donor cohort. Moreover, serum-derived high-density lipoprotein from RSTR had elevated ABCA1-mediated cholesterol efflux capacity (CEC) compared to LTBI. Our findings suggest that resistance to TST/IGRA conversion is linked to regulation of lipid accumulation in monocytes, which could facilitate early Mtb clearance among RSTR subjects through IFNγ-independent mechanisms.IMPORTANCETuberculosis (TB) remains an enduring global health challenge with millions of deaths and new cases each year. Despite recent advances in TB treatment, we lack an effective vaccine or a durable cure. While heavy exposure to Mycobacterium tuberculosis often results in latent TB latent infection (LTBI), subpopulations exist that are either resistant to infection or contain Mtb with interferon-gamma (IFNγ)-independent mechanisms not indicative of LTBI. These resisters provide an opportunity to investigate the mechanisms of TB disease and discover novel therapeutic targets. Here, we compare monocyte epigenetic profiles of RSTR and LTBI from a Ugandan household contact cohort. We identify methylation signatures in host lipid and cholesterol pathways with potential relevance to early TB clearance before the sustained IFN responses indicative of LTBI. This adds to a growing body of literature linking TB disease outcomes to host lipids.

Contrasting effects of eicosapentaenoic acid (EPA) (C20:5 n-3) on ABCA1-mediated cholesterol efflux from cholesterol-loaded or cholesterol normal-human THP-1 macrophages

Contrasting effects of eicosapentaenoic acid (EPA) (C20:5 n-3) on ABCA1-mediated cholesterol efflux from cholesterol-loaded or cholesterol normal-human THP-1 macrophages

Intersecting Blood Cytokines With Cholesterol Parameters to Profile Patients With Advanced Solid Tumors Receiving Immune Checkpoint Inhibitors.

The study investigated the relationship between serum proinflammatory cytokine levels, cholesterol metabolism, and clinical outcome in cancer patients undergoing immune checkpoint inhibitors (ICIs). Peripheral blood was collected before therapy from ICI-treated advanced cancer patients. We retrospectively assessed plasma total cholesterol (TC), ABCA1- and ABCG1-mediated cholesterol efflux (CE), passive diffusion (PD), cholesterol loading capacity (CLC), and serum IL-6, IL-10, and TNF-α. The association between blood cholesterol parameters and inflammatory cytokines and their effect on overall survival (OS), progression-free survival (PFS), and clinical benefit (CB) from ICIs were statistically assessed. Among 70 consecutively enrolled patients (nonsmall cell lung cancer: 94%; renal cell carcinoma: 6%), TC, CLC, and cholesterol PD resulted significantly higher in IL-6 low and IL-10 low cases ( P <0.05), whereas ABCA1-mediated CE was increased in IL-10 high patients ( P =0.018). Uni- and multivariable analysis revealed meaningfully longer OS and PFS in IL-6 low (HR 2.13 and 2.97, respectively) and IL-10 low (HR 3.17 and 2.62) groups. At univariate analysis all cholesterol-related indices significantly correlated with OS and PFS, whereas at multivariate only high PD was validated as a protection factor (OS, HR 0.75; PFS, HR 0.84). Finally, uni- and multivariable showed a statistically significant inverse association of CB with ABCG1-CE (OR 0.62), as with IL-6 (OR 0.13) and IL-10 (OR 0.10). In-depth characterization of the interplay between blood cholesterol metabolism and immune-inflammatory cytokines might provide novel insights into the complex relationship among cancer, inflammation, lipids profile, and response to immunotherapy.

Abstract 2083: Apolipoprotein A-II Increases Cholesterol Efflux Capacity Of HDL Via The Apolipoprotein A-I C-terminus

The ability of high-density lipoprotein (HDL) to promote cellular cholesterol efflux (CEC) is a more robust predictor of cardiovascular disease protection than its plasma quantity. Previously, we found that fully lipidated HDL containing apolipoprotein A-II (APOA2) promotes cholesterol efflux via the ATP binding cassette transporter (ABCA1). This was surprising given that ABCA1 is thought to primarily interact with lipid-poor apolipoproteins. Having previously focused on isolated lipoproteins, we moved into human plasma with the hypothesis APOA2 can enhance ABCA1-mediated CEC in this more complex environment. Human plasma was incubated with increasing amounts of lipid-free APOA2. The samples were assayed for CEC from macrophages +/- cAMP for ABCA1 stimulation. APOA2 dose dependently increased whole plasma CEC - due mostly to HDL as the effect persisted in apoB-depleted plasma. Next, plasma was incubated with lipid-free APOA1 or APOA2, immediately fractionated by size exclusion chromatography and each fraction assayed for CEC. In unmodified plasma, cholesterol effluxed to peaks corresponding to LDL, HDL and lipid-free apolipoproteins with the latter exclusively increased by ABCA1 expression, as expected. When lipid-free APOA1 was added, efflux to LDL and HDL remained largely unchanged. Strikingly, when APOA2 was added, APOA2 increased ABCA1-mediated cholesterol efflux to the fully lipidated HDL fractions. Proteomic analyses indicated that APOA2 increased in HDL though some APOA1 was retained. To explore the mechanism, we reconstituted HDL particles with APOA1 that either contained or lacked its C-terminal lipid binding helix. APOA2 lost the ability to stimulate ABCA1 efflux to HDL when the C-terminal domain of APOA1 was deleted. Our current hypothesis is that APOA2 displaces the C-terminal helix of APOA1 from the HDL surface which can then interact with ABCA1 - much like it does in lipid-poor APOA1. Reconstituted forms of APOA1 are under development as a therapy to rapidly clear cholesterol from coronary arteries in patients with acute coronary syndrome. Our work suggests APOA2 may be a novel target given its dual benefits for cholesterol efflux.

Novel bioactive lipids enhanced HDL-mediated cholesterol efflux from macrophages through the ABCA1 receptor pathway

High-density lipoprotein (HDL) has traditionally been acknowledged as "good cholesterol" owing to its significant association with a decreased risk of atherosclerosis. This association is primarily attributed to HDL's direct involvement in cholesterol efflux capacity, which plays a pivotal role in reverse cholesterol transport. A novel active compound from Nannochloropsis microalgae termed lyso-DGTS, a lipid that contains EPA fatty acids, was previously isolated and found to increase paraoxonase 1 activity and enhance HDL-mediated cholesterol efflux and HDL-induced endothelial nitric oxide release. Here, the effect of different lyso-DGTS derivatives and analogs on HDL-mediated cholesterol efflux from macrophages was examined, and the mechanism was explored. Structure–activity relationships were established to characterize the essential lipid moieties responsible for HDL-mediated cholesterol efflux from macrophages. Lyso-DGTS, 1-carboxy-N-N-N-trimethyl-3-oleamidopropan-1-aminium, and lyso-platelet-activating factor increased HDL-mediated cholesterol efflux from macrophages dose-dependently, mainly via the ABCA1-mediated cholesterol efflux pathway. The effect of lyso-DGTS derivatives and analogs on the surface polarity of HDL was examined using the Laurdan generalized polarization (GP) assay. A reverse Pearson linear regression was obtained between Laurdan GP values and HDL-mediated cholesterol efflux. Because the incorporation of bioactive lipids into the surface phospholipid layer of HDL leads to a decrease in Laurdan GP, these bioactive lipids may induce lower phospholipid ordering and greater free space on the HDL particle surface, thereby enhancing apolipoprotein A1 binding to the ABCA1 receptor and improving ABCA1 cholesterol-mediated efflux. Our findings suggest a beneficial effect of lyso-DGTS and its bioactive lipid derivatives on increasing HDL-mediated cholesterol efflux activity from macrophages, which may impact atherosclerosis attenuation.

Hepatic steatosis aggravates atherosclerosis via small extracellular vesicle-mediated inhibition of cellular cholesterol efflux

While it is recognized that non-alcoholic fatty liver disease (NAFLD) is associated with cardiovascular disease (CVD), how NAFLD affects the development and progression of CVD remains unclear and debatable. Hence, we aimed to determine the role of steatotic hepatocyte-derived small extracellular vesicles (sEVs) in foam cell formation and atherosclerosis progression. sEVs from steatotic hepatocytes were isolated and characterized. MicroRNA (miRNA) deep sequencing was utilized to identify functional miRNA in sEVs. Lastly, we conducted a cross-sectional study on patients with NAFLD to validate these findings. Treatment of sEVs from steatotic hepatocytes promoted macrophage-derived foam cell formation and atherosclerosis progression via inhibition of ABCA1-mediated cholesterol efflux. Macrophage-specific deletion of Abca1 in ApoE-/- mice abolished the role of steatotic hepatocyte-derived sEVs in atherosclerosis progression. In addition, hepatocyte-specific deletion of Rab27a, which is the key GTPase regulating sEV release, significantly ameliorated high-fat, high-cholesterol diet-induced atherosclerosis progression in ApoE-/- mice. The miRNA deep sequencing results showed that miR-30a-3p was enriched in sEVs from steatotic hepatocytes. miR-30a-3p directly targeted the 3' untranslated region of ABCA1 to inhibit ABCA1 expression and cholesterol efflux. Treatment with antagomiR-30a-3p significantly attenuated atherosclerosis progression in high-fat, high-cholesterol diet-fed ApoE-/- mice. Moreover, serum sEVs from patients with NAFLD and sEV-miR-30a-3p expression were associated with decreased cholesterol efflux levels in foam cells. Steatotic hepatocyte-derived sEVs promote foam cell formation and facilitate atherogenesis via the miR-30a-3p/ABCA1 axis. Reducing sEV secretion by steatotic hepatocytes or targeting miR-30a-3p may be potential therapeutic approaches to slow the progression of NAFLD-driven atherosclerosis. The presence of hepatic steatosis is strongly correlated with the risk of cardiovascular disease and cardiovascular events, yet the molecular mechanisms linking steatosis to progression of atherosclerosis are unclear. Herein, we identified small extracellular vesicles from steatotic hepatocytes as a trigger that accelerated the progression of atherosclerosis. Steatotic hepatocyte-derived small extracellular vesicles promoted foam cell formation via the miR-30a-3p/ABCA1 axis. Our findings not only provide mechanistic insight into non-alcoholic fatty liver disease-driven atherosclerosis but also provide potential therapeutic targets for patients with atherosclerosis.

Specialized Cellular Domains for ABCA1-mediated Cholesterol Efflux Detected by Quantitative Electron Microscopy.

Specialized Cellular Domains for ABCA1-mediated Cholesterol Efflux Detected by Quantitative Electron Microscopy.

Statins influence the relationship between ATP-binding cassette A1 membrane transporter-mediated cholesterol efflux capacity and coronary atherosclerosis in rheumatoid arthritis

ObjectivesCholesterol efflux capacity (CEC) is the main antiatherogenic function of high-density lipoprotein (HDL). ATP-binding-cassette A1 (ABCA1) membrane transporter initiates cholesterol export from arterial macrophages to pre-β HDL particles fostering their maturation; in turn, those accept cholesterol through ABCG1-mediated export. Impaired pre-β HDL maturation may disrupt the collaborative function of the two transporters and adversely affect atherosclerosis. Statins exert atheroprotective functions systemically and locally on plaque. We here evaluated associations between ABCA1-CEC, coronary atherosclerosis and cardiovascular risk and the influence of statins on those relationships in rheumatoid arthritis (RA). MethodsEvaluation with computed tomography angiography was undertaken in 140 patients and repeated in 99 after 6.9 ± 0.3 years. Events comprising cardiovascular death, acute coronary syndromes, stroke, claudication, revascularization and heart failure were recorded. ABCA1-CEC and ABCG1-CEC were evaluated in J774A.1 macrophages and Chinese hamster ovary (CHO) cells respectively and expressed as percentage of effluxed over total intracellular cholesterol. Covariates in all cardiovascular event risk and plaque outcome models included atherosclerotic cardiovascular disease (ASCVD) risk score and high-density lipoprotein cholesterol. ResultsABCA1-CEC negatively correlated with ABCG1-CEC (r = −0.167, p = 0.049). ABCA1-CEC associated with cardiovascular risk (adjusted hazard ratio 2.05 [95%CI 1.20–3.48] per standard deviation [SD] increment). There was an interaction of ABCA1-CEC with time-varying statin use (p = 0.038) such that current statin use inversely associated with risk only in patients with ABCA1-CEC below the upper tertile. ABCA1-CEC had no main effect on plaque or plaque progression; instead, ABCA1-CEC (per SD) associated with fewer baseline total plaques (adjusted rate ratio [aRR] 0.81, [95%CI 0.65–1.00]), noncalcified plaques (aRR 0.78 [95%CI 0.61–0.98]), and vulnerable low-attenuation plaques (aRR 0.41 [95%CI 0.23–0.74]) in statin users, and more low-attenuation plaques (aRR 1.91 [95%CI 1.18–3.08]) in nonusers (p-for-interaction = 0.018, 0.011, 0.025 and < 0.001 respectively). Moreover, ABCA1-CEC (per SD) associated with greater partially/fully-calcified plaque progression (adjusted odds ratio 3.07 [95%CI 1.20–7.86]) only in patients not exposed to statins during follow-up (p-for-interaction = 0.009). ConclusionIn patients with RA, higher ABCA1-CEC may reflect a proatherogenic state, associated with enhanced cardiovascular risk. Statin use may unmask the protective impact of ABCA1-mediated cholesterol efflux on plaque formation, progression and cardiovascular risk.

HECT, UBA and WWE domain containing 1 represses cholesterol efflux during CD4+ T cell activation in Sjögren's syndrome.

Introduction: Sjögren's syndrome (SS) is a chronic autoimmune disorder characterized by exocrine gland dysfunction, leading to loss of salivary function. Histological analysis of salivary glands from SS patients reveals a high infiltration of immune cells, particularly activated CD4+ T cells. Thus, interventions targeting abnormal activation of CD4+ T cells may provide promising therapeutic strategies for SS. Here, we demonstrate that Hect, uba, and wwe domain containing 1 (HUWE1), a member of the eukaryotic Hect E3 ubiquitin ligase family, plays a critical role in CD4+ T-cell activation and SS pathophysiology. Methods: In the context of HUWE1 inhibition, we investigated the impact of the HUWE1 inhibitor BI8626 and sh-Huwe1 on CD4+ T cells in mice, focusing on the assessment of activation levels, proliferation capacity, and cholesterol abundance. Furthermore, we examined the therapeutic potential of BI8626 in NOD/ShiLtj mice and evaluated its efficacy as a treatment strategy. Results: Inhibition of HUWE1 reduces ABCA1 ubiquitination and promotes cholesterol efflux, decreasing intracellular cholesterol and reducing the expression of phosphorylated ZAP-70, CD25, and other activation markers, culminating in the suppressed proliferation of CD4+ T cells. Moreover, pharmacological inhibition of HUWE1 significantly reduces CD4+ T-cell infiltration in the submandibular glands and improves salivary flow rate in NOD/ShiLtj mice. Conclusion: These findings suggest that HUWE1 may regulate CD4+ T-cell activation and SS development by modulating ABCA1-mediated cholesterol efflux and presents a promising target for SS treatment.

Diterpenoids inhibit ox-LDL-induced foam cell formation in RAW264.7 cells by promoting ABCA1 mediated cholesterol efflux.

Introduction: Atherosclerosis is the main cause of many cardiovascular diseases and contributes to morbidity and mortality worldwide. The formation of macrophage-derived foam cells plays a critical role in the early stage of atherosclerosis pathogenesis. Diterpenoids found in the flowers of Callicarpa rubella Lindl., a traditional Chinese medicine, have been reported to have anti-inflammatory activity. However, little is known about the effects of these diterpenoids on macrophage foam cell formation. Methods: A macrophage-derived foam cell formation model was established by treating RAW264.7 cells with oxidized low-density lipoprotein (ox-LDL) for 24 h. Oil red O staining were used to detect the intracellular lipids. The cholesterol efflux capacity was assayed by labeling cells with 22-NBD-cholesterol. Western blots and real-time PCRs were performed to quantify protein and mRNA expressions. Results: Two diterpenoid molecules, 14α-hydroxyisopimaric acid (C069002) and isopimaric acid (C069004), extracted from the flowers of Callicarpa rubella Lindl., significantly attenuated ox-LDL-induced foam cell formation in RAW264.7 macrophages. Further investigation showed that these two diterpenoids could promote cholesterol efflux from RAW264.7 macrophages to apolipoprotein A-I or high-density lipoproteins, which was associated with upregulated expression of ATP-binding cassette A1/G1 (ABCA1/G1), liver X receptor-α (LXRα), and peroxisome proliferator-activated receptor-γ (PPARγ). Unexpectedly, the diterpenoids C069002 and C069004 failed to enhance the mRNA transcription of the ABCG1 gene in macrophage-derived foam cells induced by ox-LDL. To evaluate the effects of diterpenoids on macrophage foam cell formation and determine the underlying mechanism, two drugs (lovastatin and rosiglitazone) were used as positive controls. Although both drugs could reduce macrophage foam cell formation and promote cholesterol efflux, they each had distinctive abilities to modulate the expression of cholesterol efflux-related genes. In contrast to lovastatin, rosiglitazone showed a similar influence on the expression of cholesterol efflux-related genes (including ABCA1, LXRα, and PPARγ) as the diterpenoids regardless of the presence or absence of ox-LDL, implying a similar mechanism by which they may exert atheroprotective effects. Conclusion: Our research indicates that diterpenoids effectively inhibit ox-LDL-induced macrophage foam cell formation by promoting cholesterol efflux from macrophages via the PPARγ-LXRα-ABCA1 pathway. Further investigation of diterpenoids as potential drugs for the treatment of atherosclerosis is warranted.

Human apoA-I[Lys107del] mutation affects lipid surface behavior of apoA-I and its ability to form large nascent HDL

Population studies have found that a natural human apoA-I variant, apoA-I[K107del], is strongly associated with low HDL-C but normal plasma apoA-I levels. We aimed to reveal properties of this variant that contribute to its unusual phenotype associated with atherosclerosis. Our oil-drop tensiometry studies revealed that compared to WT, recombinant apoA-I[K107del] adsorbed to surfaces of POPC-coated triolein drops at faster rates, remodeled the surfaces to a greater extent, and was ejected from the surfaces at higher surface pressures on compression of the lipid drops. These properties may drive increased binding of apoA-I[K107del] to and its better retention on large triglyceride-rich lipoproteins, thereby increasing the variant’s content on these lipoproteins. While K107del did not affect apoA-I capacity to promote ABCA1-mediated cholesterol efflux from J774 cells, it impaired the biogenesis of large nascent HDL particles resulting in the formation of predominantly smaller nascent HDL. Size-exclusion chromatography of spontaneously reconstituted 1,2-dimyristoylphosphatidylcholine-apoA-I complexes showed that apoA-I[K107del] had a hampered ability to form larger complexes but formed efficiently smaller-sized complexes. CD analysis revealed a reduced ability of apoA-I[K107del] to increase α-helical structure on binding to 1,2-dimyristoylphosphatidylcholine or in the presence of trifluoroethanol. This property may hinder the formation of large apoA-I[K107del]-containing discoidal and spherical HDL but not smaller HDL. Both factors, the increased content of apoA-I[K107del] on triglyceride-rich lipoproteins and the impaired ability of the variant to stabilize large HDL particles resulting in reduced lipid:protein ratios in HDL, may contribute to normal plasma apoA-I levels along with low HDL-C and increased risk for CVD.

Multivalent Display of ApoAI Peptides on the Surface of Tobacco Mosaic Virus Nanotubes Improves Cholesterol Efflux.

Atherosclerosis is a progressive cardiovascular disease in which cholesterol-rich plaques build up within arteries, increasing the risk of thrombosis, myocardial infarction, and stroke. One promising therapeutic approach is the use of high-density lipoprotein (HDL) biomimetic formulations based on ApoAI peptides that promote cholesterol efflux from plaques, ultimately leading to cholesterol excretion. Here, we describe the multivalent display of ApoAI peptides on the surface of protein nanotubes derived from the plant virus tobacco mosaic virus (TMV) and protein nanoparticles using virus-like particles from bacteriophage Qβ. Bioconjugation yielded ApoAI conjugates varying in size and morphology. We tested ABCA1-mediated cholesterol efflux using macrophage foam cells, the mitigation of reactive oxygen species in endothelial cells, and wound healing in endothelial cells. We found that the multivalent ApoAI platform, in particular the TMV-based nanotube, significantly improved the efficacy of cholesterol efflux compared to free peptides, Qβ nanoparticle formulations, and traditional HDL therapy. Finally, to better understand the mechanistic basis of enhanced cholesterol efflux, we used confocal microscopy to show that while native TMV was taken up by cells, TMV-ApoAI remained at the exterior of foam cell membranes and efflux was documented using fluorescent cholesterol. Together, these data highlight that high aspect ratio materials with multivalent display of ApoAI peptides offer unique capabilities promoting efficient cholesterol efflux and may find applications in cardiovascular therapy.

Baicalein targets CD36 to prevent foam cell formation by suppressing the excessive uptake of oxLDL and accelerating ABCA1-mediated cholesterol efflux in oxLDL-induced THP-1 macrophages

• Baicalein can prevent oxLDL-induced foam cell formation in THP-1 macrophages. • Baicalein inhibits oxLDL uptake by preventing the binding of CD36 to oxLDL. • The binding of baicalein to CD36 triggers the Src-JNK-ABCA1 signalling pathway. • Baicalein enhances cholesterol efflux to avoid cholesterol accumulation. Oxidized low-density lipoprotein (oxLDL)-induced macrophage foam cell formation plays an important role in atherosclerosis progression. Baicalein is a constituent of Scutellaria baicalensis. Herein, we investigated the effect of baicalein on macrophage foam cell formation and the underlying mechanism. The THP-1 macrophage foam cell was established by oxLDL stimulation and the effects of baicalein on cholesterol uptake and efflux were analysed by molecular docking, ELISA, immunofluorescence, western blot, the inhibitor and siRNA experiment. The results showed that baicalein suppressed oxLDL-induced cholesterol accumulation. Mechanistically, baicalein reduced oxLDL uptake through competitive inhibiting the binding of CD36 to the epitope structure of oxLDL. Moreover, the binding of baicalein to CD36 enhanced the cholesterol efflux via the CD36-Src-JNK-ABCA1 signalling pathway. Meanwhile, Src and JNK inhibitors reversed the baicalein-induced reduction in cholesterol accumulation. In conclusion, these findings suggested that baicalein as a food supplement could inhibit macrophage foam cell formation and play an anti-atherosclerosis effect.

Eicosapentaenoic acid (EPA, c20:5 n-3) increased ABCA1-mediated cholesterol efflux from J774 mouse macrophages or THP-1 human macrophages by modulating secreted eicosanoids

Background and Aims : A diet rich in eicosapentaenoic acid (EPA, C20:5 n-3) is cardioprotective. We studied in vitro the impact of EPA membrane incorporation on the anti-atherogenic ABCA1 efflux pathway in the absence or presence of LPS to create the inflammatory microenvironment observed within atherosclerotic plaques.

Dimerization of cholesterol permits its binding to lipid-free apoA-I

Background and Aims : To model the interaction of lipid-free apoA-I with cholesterol molecules that exist in various self-associated forms in extracellular space. Cholesterol dimerization is exploited to reconcile the existing experimental data on cholesterol binding to apoA-I with extremely low critical micelle concentration of cholesterol.Methods: The interaction of differently self-associated lipid-free apoA-I with cholesterol monomer and tail-to-tail (TT) or face-to-face (FF) cholesterol dimer was modelled with Schrödinger package. Two crystal structures of 1-43 N-truncated apolipoprotein Δ(1-43)A-I tetramer (PDB ID: 1AV1, structure B), 185-243 C-truncated apolipoprotein Δ(185-243)A-I dimer (PDB ID: 3R2P, structure M) were exploited.Results: Cholesterol monomers bind to multiple binding sites in apoA-I monomer, dimer and tetramer with low, moderate and high energy, still insufficient to overcome the thermodynamic restriction by cholesterol micellization (-52.8 kJ/mol). However, apoA-I monomer and dimer existing in structure B, that contain nonoverlapping and non-interacting pairs of binding sites with high affinity for TT and FF cholesterol dimers, can bind in common 14 cholesterol molecules that correspond to existing values. ApoA-I monomer and dimer in structure M can bind in common 6 cholesterol molecules. The values of respective total energy of cholesterol binding for both B and M structures exceed the free energy of cholesterol micellization.Conclusions: Cholesterol dimers may simultaneously interact with extracellular monomer and dimer of lipid-free apoA-I, that accumulate at acid pH in atheroma. The thermodynamically allowed apolipoprotein-cholesterol interaction outside the macrophage may represent a new mechanism of cholesterol transport by apoA-I from atheroma, in addition to ABCA1-mediated cholesterol efflux. Background and Aims : To model the interaction of lipid-free apoA-I with cholesterol molecules that exist in various self-associated forms in extracellular space. Cholesterol dimerization is exploited to reconcile the existing experimental data on cholesterol binding to apoA-I with extremely low critical micelle concentration of cholesterol. Methods: The interaction of differently self-associated lipid-free apoA-I with cholesterol monomer and tail-to-tail (TT) or face-to-face (FF) cholesterol dimer was modelled with Schrödinger package. Two crystal structures of 1-43 N-truncated apolipoprotein Δ(1-43)A-I tetramer (PDB ID: 1AV1, structure B), 185-243 C-truncated apolipoprotein Δ(185-243)A-I dimer (PDB ID: 3R2P, structure M) were exploited. Results: Cholesterol monomers bind to multiple binding sites in apoA-I monomer, dimer and tetramer with low, moderate and high energy, still insufficient to overcome the thermodynamic restriction by cholesterol micellization (-52.8 kJ/mol). However, apoA-I monomer and dimer existing in structure B, that contain nonoverlapping and non-interacting pairs of binding sites with high affinity for TT and FF cholesterol dimers, can bind in common 14 cholesterol molecules that correspond to existing values. ApoA-I monomer and dimer in structure M can bind in common 6 cholesterol molecules. The values of respective total energy of cholesterol binding for both B and M structures exceed the free energy of cholesterol micellization. Conclusions: Cholesterol dimers may simultaneously interact with extracellular monomer and dimer of lipid-free apoA-I, that accumulate at acid pH in atheroma. The thermodynamically allowed apolipoprotein-cholesterol interaction outside the macrophage may represent a new mechanism of cholesterol transport by apoA-I from atheroma, in addition to ABCA1-mediated cholesterol efflux.

PIP2 and cholesterol interplay in inflammation and atherosclerosis

IntroductionCholesterol accumulation in arterial macrophages leads to foam cell formation, Nlrp3 inflammasome activation, and IL‐1b release. Phosphatidylinositol 4, 5‐bisphosphate (PIP2) plays a role in the cholesterol efflux pathway and IL‐1b release. The PIP2 phosphatase TMEM55b modulates cholesterol efflux but the mechanism of this effect is not clear. Miltefosine altered PIP2 localization and blunted Nlrp3 inflammasome in macrophages, but the mechanism of its anti‐atherosclerotic properties is not clear.ObjectivesTo determine the effect of cellular PIP2 levels on ABCA1 mediated cholesterol efflux. To determine the mechanism by which Miltefosine reduces atherosclerosis in mice.Methods and resultsThe correlation between cellular PIP2 levels and ABCA1 mediated cholesterol efflux was determined. PIP2 levels were markedly increased in cholesterol‐loaded cells vs. control macrophages (~ 22 % increase, N=3, mean±SD, *P=0.05). Expression of TMEM55b, a PIP2 phosphatase, in BHK cells resulted in ~ 70 % decrease in ABCA1 mediated cholesterol efflux (N=4, mean ± SD, P&lt;0.0001). Miltefosine treated mice showed blunted in‐vivo Nlrp3 inflammasome assembly and had significantly lowered IL‐1b levels in peritoneal lavage (mean +SD; N=5, **p&lt;0.001). Miltefosine‐fed mice showed significantly higher reverse cholesterol transport to plasma, liver, and feces. The hyperlipidemic apoE‐/‐ KO mice fed with Miltefosine (50 mg/kg/day) gained significantly less weight vs. controls and showed significantly decreased atherosclerotic lesions (≥50% smaller vs. controls; mean + SD, p&lt;0.001 in females with N=10, and p&lt;0.04 in males with N=12). Miltefosine altered gut microbiota in hyperlipidemic apoE‐/‐ KO mice.ConclusionPIP2 regulates ABCA1 mediated cellular cholesterol efflux. Miltefosine can dampen in‐vivo Nlrp3 inflammasome assembly, increase reverse cholesterol transport, reduce high fat diet‐induced weight gain, reduce atherosclerotic lesion area and alter gut microbiota.

Predictive value of HDL function in patients with coronary artery disease: relationship with coronary plaque characteristics and clinical events

Background HDL is endowed with several metabolic, vascular, and immunoinflammatory protective functions. Among them, a key property is to promote reverse cholesterol transport from cells back to the liver. The aim of this study was to estimate the association of scavenger receptor class B type I (SR-BI)- and ATP binding cassette transporter A1 (ABCA1)-mediated cholesterol efflux (the two major routes for cholesterol efflux to HDL) with the presence, extent, and severity of coronary artery disease (CAD), vascular wall remodelling processes, coronary plaque characteristics, and the incidence of myocardial infarction in the different subgroups of patients from the CAPIRE study. Methods Patients (n = 525) from the CAPIRE study were divided into two groups: low-risk factors (RF), with 0–1 RF (n = 263), and multiple-RF, with ≥2 RFs; within each group, subjects were classified as no-CAD or CAD based on the segment involvement score (SIS) evaluated by coronary computed tomography angiography (SIS = 0 and SIS > 5, respectively). SR-BI- and ABCA1-mediated cholesterol efflux were measured using the plasma of all patients. Results SR-BI-mediated cholesterol efflux was significantly reduced in patients with CAD in both the low-RF and multiple-RF groups, whereas ABCA1-mediated cholesterol efflux was similar among all groups. In CAD patients, multivariable analysis showed that SR-BI-mediated cholesterol efflux <25th percentile predicted cardiovascular outcome (odds ratio 4.1; 95% CI: 1.3–13.7; p = .019), whereas ABCA-1-mediated cholesterol efflux and HDL-C levels significantly did not. Despite this finding, reduced SR-BI-mediated cholesterol efflux was not associated with changes in high-risk plaque features or changes in the prevalence of elevated total, non-calcified, and low-attenuation plaque volume. Conclusion SR-BI-mediated cholesterol efflux capacity is lower in patients with diffuse coronary atherosclerosis. In addition, a lower SR-BI-mediated cholesterol efflux capacity is associated with the worst clinical outcomes in patients with CAD, independently of atherosclerotic plaque features. Key Messages Increased cholesterol efflux capacity, an estimate of HDL function, is associated with a reduced CVD risk, regardless of HDL-C levels. HDL-C levels are significantly lower in patients with CAD. Lower SR-BI-mediated cholesterol efflux capacity is observed in patients with diffuse coronary atherosclerosis and is associated with the worst clinical outcomes in patients with CAD, independently of atherosclerotic plaque features.

Rationale for different formulations of omega-3 fatty acids leading to differences in residual cardiovascular risk reduction

Rationale for different formulations of omega-3 fatty acids leading to differences in residual cardiovascular risk reduction

Acid-Sensing Ion Channel 1/Calpain1 Activation Impedes Macrophage ATP-Binding Cassette Protein A1-Mediated Cholesterol Efflux Induced by Extracellular Acidification.

BackgroundExtracellular acidification is a common feature of atherosclerotic lesions, and such an acidic microenvironment impedes ATP-binding cassette transporter A1 (ABCA1)-mediated cholesterol efflux and promotes atherogenesis. However, the underlying mechanism is still unclear. Acid-sensing ion channel 1 (ASIC1) is a critical H+ receptor, which is responsible for the perception and transduction of extracellular acidification signals.AimIn this study, we explored whether or how ASIC1 influences extracellular acidification-induced ABCA1-mediated cholesterol efflux from macrophage-derived foam cells.MethodsRAW 264.7 macrophages were cultured in an acidic medium (pH 6.5) to generate foam cells. Then the intracellular lipid deposition, cholesterol efflux, and ASIC1/calpain1/ABCA1 expressions were evaluated.ResultsWe showed that extracellular acidification enhanced ASIC1 expression and translocation, promoted calpain1 expression and lipid accumulation, and decreased ABCA1 protein expression as well as ABCA1-mediated cholesterol efflux. Of note, inhibiting ASIC1 activation with amiloride or Psalmotoxin 1 (PcTx-1) not only lowered calpain1 protein level and lipid accumulation but also enhanced ABCA1 protein levels and ABCA1-mediated cholesterol efflux of macrophages under extracellular acidification conditions. Furthermore, similar results were observed in macrophages treated with calpain1 inhibitor PD150606.ConclusionExtracellular acidification declines cholesterol efflux via activating ASIC1 to promote calpain1-mediated ABCA1 degradation. Thus, ASIC1 may be a novel therapeutic target for atherosclerosis.