ABCA1 Levels Research Articles

PM2.5 induces the abnormal lipid metabolism and leads to atherosclerosis via Notch signaling pathway in rats

PM2.5 can affect the lipid metabolism and cause atherosclerosis. Abnormal lipid metabolism is a sever risk factor of atherosclerosis and the underlying molecular mechanism still remains unclear. In this study, GPL16956 Agilent-045997 Arraystar human lncRNA microarray V3 (Probe Name Version) platform was used to detect the different genes of lipid metabolism between the normal arterial intima and advanced atherosclerotic plaque, which were downloaded from GEO database. A high-fat diet and vitamin D3 were administered to Wistar rats to establish the atherosclerotic model and another normal healthy 56 rats were used as the non-atherosclerotic exposure groups. The atherosclerotic rats and non-atherosclerotic rats were randomly divided into 4 PM2.5 groups (0, 1.5, 7.5, 37.5 mg/kg), respectively. The results of bioinformatics showed changes in the Notch1, Dll1, Hes1, LDLR and ABCG1 levels. PM2.5 exposure could produce damage to the physiological structure of the aorta, and aggravate atherosclerosis in rats from both non-atherosclerotic and atherosclerotic groups. With the increase of the exposure dose, the levels of TC and TG significantly increased. PM2.5 exposure significantly affected the expression levels of PPARγ, ABCA1, LDLR, CD36, SR-BI and SREBP2. PM2.5 exposure could also affect the expression levels of the Notch signaling pathways which was significantly correlated with the levels of TC and TG. The results proved that PM2.5 exposure could induce and aggravate the atherosclerosis in rats by disrupting lipid metabolism in which Notch signaling pathway may play a significant role.

24-Hydroxycholesterol Moderates the Effects of Amyloid-β on Expression of HMG-CoA Reductase and ABCA1 Proteins in Mouse Astrocytes.

Elevated brain cholesterol increases the risk of Alzheimer's disease. Production of 24-hydroxycholesterol (24s-OHC) by neurons prevents cholesterol accumulation in the brain. In this study, we investigated the effect of 24s-OHC on the HMG-COA reductase and ABCA1 which are involved in the brain cholesterol homeostasis with or without β-amyloid in astrocytes. Astrocytes were treated with 24s-OHC with or without Aβ. Western blot and real-time polymerase chain reaction were done to detect protein and gene expression of β-hydroxy-3-methyl-glutaryl-coenzyme A reductase (HMGCR) and ABCA1, respectively. Cholesterol release was determined using a quantitation kit. Protein levels of HMGCR and ABCA1 were significantly increased by Aβ; however, the 24s-OHC was able to restore their levels and diminish the effect of amyloid-β. Aβ did not have a significant effect on HMGCR expression, while 24s-OHC reduced it by 68%. Aβ-induced ABCA1 expression did not increase cholesterol efflux as the lower levels of cholesterol in conditioned medium of Aβ-treated cells were found. Our novel findings show that Aβ affects two key elements in the brain cholesterol homeostasis, HMGCR and ABCA1, which are crucial in cholesterol synthesis and efflux. Since 24s-OHC could suppress the Aβ effects on enhancement of HMGCR and ABCA1, therefore the cytochrome P450 46A1 (Cyp46A1), which is exclusively expressed in the central nervous system and responsible for producing of 24s-OHC, could consider as a therapeutic target in the cholesterol-related neurodegenerative diseases such as Alzheimer's disease.

Administration of an LXR agonist promotes atherosclerotic lesion remodelling in murine inflammatory arthritis.

The leading cause of mortality in patients with rheumatoid arthritis is atherosclerotic cardiovascular disease (CVD). We have shown that murine arthritis impairs atherosclerotic lesion regression, because of cellular cholesterol efflux defects in haematopoietic stem and progenitor cells (HSPCs), causing monocytosis and impaired atherosclerotic regression. Therefore, we hypothesised that improving cholesterol efflux using a Liver X Receptor (LXR) agonist would improve cholesterol efflux and improve atherosclerotic lesion regression in arthritis. Ldlr -/- mice were fed a western-type diet for 14 weeks to initiate atherogenesis, then switched to a chow diet to induce lesion regression and divided into three groups; (1) control, (2) K/BxN serum transfer inflammatory arthritis (K/BxN) or (3) K/BxN arthritis and LXR agonist T0901317 daily for 2 weeks. LXR activation during murine inflammatory arthritis completely restored atherosclerotic lesion regression in arthritic mice, evidenced by reduced lesion size, macrophage abundance and lipid content. Mechanistically, serum from arthritic mice promoted foam cell formation, demonstrated by increased cellular lipid accumulation in macrophages and paralleled by a reduction in mRNA of the cholesterol efflux transporters Abca1, Abcg1 and Apoe. T0901317 reduced lipid loading and increased Abca1 and Abcg1 expression in macrophages exposed to arthritic serum and increased ABCA1 levels in atherosclerotic lesions of arthritic mice. Moreover, arthritic clinical score was also attenuated with T0901317. Taken together, we show that the LXR agonist T0901317 rescues impaired atherosclerotic lesion regression in murine arthritis because of enhanced cholesterol efflux transporter expression and reduced foam cell development in atherosclerotic lesions.

Tetramethylpyrazine and Paeoniflorin Synergistically Attenuate Cholesterol Efflux in Macrophage Cells via Enhancing ABCA1 and ABCG1 Expression.

The formation of foam cells is a characteristic of the occurrence and development of atherosclerosis. ATP-binding cassette subfamily A1 and G1 (ABCA1 and ABCG1) and scavenger receptor B1 (SR-B1) play critical roles in promoting intracellular cholesterol efflux to high-density lipoprotein (HDL) or apolipoprotein A1 (apoA1). We attempted to test the effect of the tetramethylpyrazine-paeoniflorin pair (TP) on cholesterol outflow in foam cells derived from macrophages. In this study, RAW264.7 macrophages were treated with 80 mg/L oxidized low-density lipoprotein (ox-LDL) for 24 h to obtain foam cells. Then they were intervened with TP (tetramethylpyrazine 40 ug/ml plus paeoniflorin 80 ug/ml) for additional 24 h. The distribution of cholesterol in foam cells was evaluated by oil red O staining. The contents of total cholesterol (TC) and free cholesterol (FC) were assessed with commercial kits. Fluorescent imaging was observed with a fluorescent inverted microscope. The capacity of cholesterol efflux was measured with a fluorescent plate reader, and the transcript and protein levels of ABCA1, ABCG1, and SR-B1 were detected by Western blot and quantitative polymerase chain reactions (Q-PCRs). Cytokines in the medium were detected by ELISA and adjusted by total cellular proteins. The results showed that TP decreased ox-LDL-induced cholesterol deposition and foam cell formation by promoting cholesterol efflux to apoA1, which was related to the upregulation of ABCA1 and ABCG1. Moreover, TP decreased the secretion of ox-LDL-induced tumor necrosis factor alpha (TNF-α), interleukin 1 beta (IL-1β), and monocyte chemotactic protein-1 (MCP-1), an important profoam cell cytokine in atherosclerosis.

New insight into the role of lipid metabolism-related proteins in rheumatic heart valve disease

PurposeThe aim of this study was to determine the expression of lipid metabolism-related proteins in rheumatic heart valve disease (RHVD).MethodsThis retrospective study involved a total of 20 cases of moderate or severe rheumatic mitral valve stenosis and 4 cases of mitral regurgitation due to secondary causes from September 2018 to September 2021. The patients enrolled included 12 males and 12 females who underwent surgical excision of the mitral valve at the cardiac surgery department of Hainan General Hospital. The samples of mitral valve were collected during surgery treatment as the study group, and mitral valves collected from patients with ischemic heart disease were allocated into the control group. Hematoxylin–eosin (HE), oil red staining and immunohistochemical (IHC) staining were conducted to compare the expression of lipid metabolism-related proteins (ATP-binding cassette transporter A1 and acyl-coenzyme A: cholesterol acyltransferase-1), and real-time polymerase chain reaction (RT–PCR) was applied to compare the mRNA levels of ABCA1, ACAT1, and the inflammatory cytokines TNF-α, IL-10, and MCP-1.ResultsIn general, the rheumatic mitral valve showed leaflet thickening along with border adhesions and visible yellow fats. Oil red O staining also revealed the abovementioned results as well as fat cells. Both ABCA1 and ACAT1 were expressed in the rheumatic mitral valve via IHC, whereas only ACAT1 showed a faint level of expression in the ischemic mitral valve with no expression of ABCA1. In addition, compared with the ischemic mitral valve, RT-PCT showed increased mRNA expression levels of ABCA1, ACAT1, and the inflammatory cytokines TNF-α, IL-10, and MCP-1 (P < 0.05). After dividing the RMs into two groups for RT–PCR, we found that the higher the expression of ABCA1 and ACAT1 was, the lower the relative expression of inflammatory factors.ConclusionThis study showed that adipose tissue, adipose cells, and lipid transport-related proteins were expressed strongly in the rheumatic mitral valve, suggesting that adipose tissue formation might be one of the important pathways in the pathology of rheumatic heart disease. In addition, adipose tissue and adipocytes were also involved in the inflammatory process. These data provide new insight into pathological mechanisms in rheumatic heart disease.

Insulin Downregulates the Expression of ATP-binding Cassette Transporter A-I in Human Hepatoma Cell Line HepG2 in a FOXO1 and LXR Dependent Manner.

ATP-binding cassette transporter A-I (ABCA1) is an ubiquitously expressed protein whose main function is the transmembrane transport of cholesterol and phospholipids. Synthesis of ABCA1 protein in liver is necessary for high-density lipoprotein (HDL) formation in mammals. Thus, the mechanism of ABCA1 gene expression regulation in hepatocytes are of critical importance. Recently, we have found the insulin-dependent downregulation of other key player in the HDL formation-apolipoprotein A-I gene (J. Cell. Biochem., 2017, 118:382-396). Nothing is known about the role of insulin in the regulation of ABCA1 gene. Here we show for the first time that insulin decreases the mRNA and protein levels of ABCA1 in human hepatoma cell line HepG2. PI3K, p38, MEK1/2, JNK and mTORC1 signaling pathways are involved in the insulin-mediated downregulation of human ABCA1 gene. Transcription factors LXRα, LXRβ, FOXO1 and NF-κB are important contributors to this process, while FOXA2 does not regulate ABCA1 gene expression. Insulin causes the decrease in FOXO1, LXRα and LXRβ binding to ABCA1 promoter, which is likely the cause of the decrease in the gene expression. Interestingly, the murine ABCA1 gene seems to be not regulated by insulin in hepatocytes (in vitro and in vivo). We suggest that the reason for this discrepancy is the difference in the 5'-regulatory regions of human and murine ABCA1 genes.

PCSK9 Affects Astrocyte Cholesterol Metabolism and Reduces Neuron Cholesterol Supplying In Vitro: Potential Implications in Alzheimer's Disease.

The Proprotein Convertase Subtilisin/Kexin Type 9 (PCSK9) involvement in Alzheimer’s disease (AD) is poorly investigated. We evaluated the in vitro PCSK9 modulation of astrocyte cholesterol metabolism and neuronal cholesterol supplying, which is fundamental for neuronal functions. Moreover, we investigated PCSK9 neurotoxic effects. In human astrocytoma cells, PCSK9 reduced cholesterol content (−20%; p < 0.05), with a greater effect in presence of beta amyloid peptide (Aβ) (−37%; p < 0.01). PCSK9 increased cholesterol synthesis and reduced the uptake of apoE-HDL-derived cholesterol (−36%; p < 0.0001), as well as the LDL receptor (LDLR) and the apoE receptor 2 (ApoER2) expression (−66% and −31%, respectively; p < 0.01). PCSK9 did not modulate ABCA1- and ABCG1-cholesterol efflux, ABCA1 levels, or membrane cholesterol. Conversely, ABCA1 expression and activity, as well as membrane cholesterol, were reduced by Aβ (p < 0.05). In human neuronal cells, PCSK9 reduced apoE-HDL-derived cholesterol uptake (−41%; p < 0.001) and LDLR/apoER2 expression (p < 0.05). Reduced cholesterol internalization occurred also in PCSK9-overexpressing neurons exposed to an astrocyte-conditioned medium (−39%; p < 0.001). PCSK9 reduced neuronal cholesterol content overall (−29%; p < 0.05) and increased the Aβ-induced neurotoxicity (p < 0.0001). Our data revealed an interfering effect of PCSK9, in cooperation with Aβ, on brain cholesterol metabolism leading to neuronal cholesterol reduction, a potentially deleterious effect. PCSK9 also exerted a neurotoxic effect, and thus represents a potential pharmacological target in AD.

Inhibition of miR-652-3p Regulates Lipid Metabolism and Inflammatory Cytokine Secretion of Macrophages to Alleviate Atherosclerosis by Improving TP53 Expression.

Purpose The aim was to elucidate the regulatory function of miR-652-3p on lipid metabolism and inflammatory cytokine secretion of macrophages in atherosclerosis. Methods miR-652-3p level in atherosclerosis patients, ox-LDL-treated macrophages, and their controls were monitored by Q-PCR. After ox-LDL treatment and miR-652-3p mimic, si-TP53 and their controls transfection, ELISA, and Q-PCR assays were used to detect IL-1ß, IL-6, and TNF-α levels. oil red O staining was processed to verify cholesterol accumulation. CE/TC and lipid metabolism were also detected. The protein levels of ABCA1, ABCG1, PPARα, CRT1, ADRP, and ALBP were detected by western blot assay. Based on the TargetScan database, the TP53 3′UTR region had complementary bases with miR-652-3p, which was also verified by dual-luciferase reporter gene assay. Finally, the regulation of miR-652-3p and TP53 was confirmed by rescue assay in atherosclerosis. Results miR-652-3p is highly expressed in atherosclerosis, miR-652-3p inhibitor decreased IL-1β, IL-6, and TNF-α expression after ox-LDL treatment. Knockdown of miR-652-3p reduces foam formation in ox-LDL-treated macrophages. miR-652-3p inhibitor ameliorates cholesterol accumulation and lipid metabolism disorder. miR-652-3p negatively regulated TP53 in atherosclerosis. Si-TP53 rescued the effect of miR-652 inhibitor in atherosclerosis. Conclusion miR-652-3p regulates the lipid metabolism of macrophages to alleviate atherosclerosis by inhibiting TP53 expression. It might be a potential target for atherosclerosis treatment.

Metabolic-related gene pairs signature analysis identifies ABCA1 expression levels on tumor-associated macrophages as a prognostic biomarker in primary IDHWT glioblastoma

BackgroundAlthough isocitrate dehydrogenase (IDH) mutation serves as a prognostic signature for routine clinical management of glioma, nearly 90% of glioblastomas (GBM) patients have a wild-type IDH genotype (IDHWT) and lack reliable signatures to identify distinct entities.MethodsTo develop a robust prognostic signature for IDHWT GBM patients, we retrospectively analyzed 4 public datasets of 377 primary frozen tumor tissue transcriptome profiling and clinical follow-up data. Samples were divided into a training dataset (204 samples) and a validation (173 samples) dataset. A prognostic signature consisting of 21 metabolism-related gene pairs (MRGPs) was developed based on the relative ranking of single-sample gene expression levels. GSEA and immune subtype analyses were performed to reveal differences in biological processes between MRGP risk groups. The single-cell RNA-seq dataset was used to examine the expression distribution of each MRG constituting the signature in tumor tissue subsets. Finally, the association of MRGs with tumor progression was biologically validated in orthotopic GBM models.ResultsThe metabolic signature remained an independent prognostic factor (hazard ratio, 5.71 [3.542-9.218], P < 0.001) for stratifying patients into high- and low-risk levels in terms of overall survival across subgroups with MGMTp methylation statuses, expression subtypes, and chemo/ratio therapies. Immune-related biological processes were significantly different between MRGP risk groups. Compared with the low-risk group, the high-risk group was significantly enriched in humoral immune responses and phagocytosis processes, and had more monocyte infiltration and less activated DC, NK, and γδ T cell infiltration. scRNA-seq dataset analysis identified that the expression levels of 5 MRGs (ABCA1, HMOX1, MTHFD2, PIM1, and PTPRE) in TAMs increased with metabolic risk. With tumor progression, the expression level of ABCA1 in TAMs was positively correlated with the population of TAMs in tumor tissue. Downregulation of ABCA1 levels can promote TAM polarization towards an inflammatory phenotype and control tumor growth.ConclusionsThe metabolic signature is expected to be used in the individualized management of primary IDHWT GBM patients.

Application of Micro-Western Array for Identifying Different Serum Protein Expression Profile among Healthy Control, Alzheimer's Disease Patients and Patients' Adult Children.

(1) Background: Alzheimer’s disease (AD) is the most common form of dementia. Increased levels of inflammatory proteins have been observed in brain and plasma samples of AD patients; however, it is not clear if other serum proteins correlate to the development or disease progression of AD. (2) Methods: Micro-Western Array (MWA) is a high-throughput antibody-based proteomics system which allows detection of the expression levels of 24–96 different proteins within 6–30 samples simultaneously. We applied MWA to explore potential serum protein biomarkers correlated to the development and progression of AD by examining the difference in serum protein profile of 31 healthy control (HC), 30 patients with AD and 30 patients’ adult children (ACS). (3) Results: Compared to HC, AD and ACS express similar pattern of serum proteins, including higher protein levels of ABCA1, ABCG1, SREBP1 and LXRβ but lower protein levels of ApoD, ApoE, ApoH, c_Myc, COX2 and Hippo-YAP signaling proteins. AD patients had higher serum levels of ABCG1, ApoD, ApoH, COX2, LXRα and YAP, but lower levels of ABCA1, ApoE, c_Myc, LATS1, MST1, MST2, Nanog, NFκB_p50, PPARγ and SREBP2, as compared to ACS. Pearson’s correlation analysis revealed that the protein expression level of ApoE, c_Myc, LATS1, MST2, NFκB p50, PPARγ and SREBP1 was negatively correlated to age, while that of ApoE, c_Myc, LATS1, MST1, MST2, Nanog, NFκB p50 and PPARγ was positively correlated to age. (4) Conclusions: We identified a group of serum proteins which may correlate to disease progression of AD and can be potential diagnostic serum protein biomarkers.

Expression of ABCA1 Transporter and LXRA/LXRB Receptors in Placenta of Women with Late Onset Preeclampsia.

Background: Appropriate levels of cholesterol are necessary for the mother and developing fetus, but theirexcess may cause preeclampsia. The ABCA1 transporter mediates the secretion of cholesterol and is highly regulated at the transcriptional level via the nuclear liver X receptors (LXRs). Methods: Sixteen preeclamptic and 39 normotensives healthy women with uncomplicated pregnancies were involved in the case-control study. The placental levels of ABCA1, LXRA and LXRB mRNA were quantified by real-time quantitative PCR. The concentrations of ABCA1, LXRA and LXRB proteins from the placenta were determined using an enzyme-linked immunosorbent assay Results: We found in the logistic regression model significantly lower placental expression of LXRB mRNA (crude OR = 0.26, 95% CI: 0.07–0.94, p = 0.040) and LXRA protein level (crude OR = 0.19, 95% CI: 0.05–0.69, p = 0.012) in late-onset preeclamptic women compared to healthy pregnant women. The values remained statistically significant after adjustment for possible confounders. Conclusions: Our results suggest that high placenta LXRA mRNA and LXRA protein expression levels decrease the risk of late-onset preeclampsia. These nuclear receptors could play a role in the development of preeclampsia through disturbances of lipid metabolism.

Amelioration of Cholesterol Rich diet-induced Impaired Cognition in AD Transgenic Mice by an LXR Agonist TO901317 Is Associated with the Activation of the LXR-β-RXR-α-ABCA1 Transmembrane Transport System and Improving the Composition of Lipid Raft

ABSTRACT Background It has been reported that LXR agonist can inhibit Aβ generation and alleviate Aβ-induced various adverse reactions in vivo and in vitro experiments, but the mechanisms have not been clarified. The study aimed to observe the effect of LXR agonist TO901317 on the cognitive function of AD transgenic mice fed with cholesterol-rich diet (CRD), and to explore the possible mechanism. Methods: 32 male 6-month-old double transgenic AD mice were enrolled and randomly divided into 4 groups: control (normal diet) group, CRD treatment group, TO901317 treatment group and GSK2033 treatment group. After 3 month, Morris water maze was for the changes of spatial exploration and memory ability; ELISA was for detecting the production of Aβ42 in the brain; the concentration of total cholesterol (TC), low density lipoprotein (LDL) and high density lipoprotein (HDL) in serum were detected by cholesterol enzyme colorimetry; Finally, the expression of LXR-β, RXR-α, ABCA1, caveolin-1, BACE1 and APP at protein level in the brains was measured by Western blotting. Results Compared with the control group, the learning, memory ability and spatial exploration ability of the mice were more significantly serious in the CRD group (P<0.05); The contents of TC and LDL in the serum and the production of Aβ42 in the brains were significantly increased (P<0.05), but HDL was remarkably decreased (P<0.05); The protein levels of LXR-β, RXR-α and ABCA1 were also significantly decreased (P<0.05); The expression of caveolin-1, APP and BACE1 were evidently increased (P<0.05). However, after treatment with TO901317, the impaired learning and memory and spatial exploration ability of the mice were significantly improved (P<0.05); The contents of TC and LDL in serum and the production of Aβ42 in the brains were significantly decreased (P<0.05), but HLD was increased (P<0.05); The protein levels of LXR-β, RXR-α, ABCA1were all significantly increased (P<0.05), while, the expression of caveolin-1, APP and BACE1 were all significantly decreased (P<0.05). All the changes were reversed by GSK2033 (P<0.05). Conclusions TO901317 attenuated the more serious impairment of spatial exploration, learning and memory in transgenic AD mice induced by CRD, and the mechanism may be that TO901317 could activate the LXR-β/RXR-α/ABCA1 transmembrane transport system, promote the cholesterol efflux, and decreased caveolin-1, APP and BACE1, further reduce Aβ42 in the brains.

Interleukin-1 Induces the Release of Lubricating Phospholipids from Human Osteoarthritic Fibroblast-like Synoviocytes.

(1) Background: Synovial fluid (SF) from knee joints with osteoarthritis (OA) has increased levels of phospholipids (PL). We have reported earlier that TGF-ß and IGF-1 stimulate fibroblast-like synoviocytes (FLS) to synthesize increased amounts of PLs. The current study examined whether IL-1ß induces the release of PLs in FLS and the underlying mechanism. (2) Methods: Cultured human OA FLS were treated with IL-1ß alone and with pathway inhibitors or with synthetic liver X receptor (LXR) agonists. Cholesterol hydroxylases, ABC transporters, apolipoproteins (APO), LXR, sterol regulatory binding proteins (SREBPs), and 3-hydroxy-3-methylglutaryl-coenzyme A reductase (HMGCR) were analyzed by RT-PCR, Western blot, and ELISA. The release of radiolabeled PLs from FLS was determined, and statistical analysis was performed using R (N = 5–9). (3) Results: Like synthetic LXR agonists, IL-1ß induced a 1.4-fold greater release of PLs from FLS. Simultaneously, IL-1ß upregulated the level of the PL transporter ABCA1 and of cholesterol hydroxylases CH25H and CYP7B1. IL-1ß and T0901317 stimulated the expression of SREBP1c, whereas only T0901317 enhanced SREBP2, HMGCR, APOE, LXRα, and ABCG1 additionally. (4) Conclusions: IL-1ß partially controls PL levels in OA-SF by affecting the release of PLs from FLS. Our data show that IL-1ß upregulates cholesterol hydroxylases and thus the formation of oxysterols, which, as natural agonists of LXR, increase the level of active ABCA1, in turn enhancing the release of PLs.

Daeshiho-tang Attenuates Atherosclerosis by Regulating Cholesterol Metabolism and Inducing M2 Macrophage Polarization.

Dyslipidemia, the commonest cause of cardiovascular disease, leads to lipid deposits on the arterial wall, thereby aggravating atherosclerosis. DSHT (Daeshiho-tang) has long been used as an anti-dyslipidemia agent in oriental medicine. However, the anti-atherosclerotic effects of DSHT have not been fully investigated. Therefore, this study was designed to evaluate whether DSHT could exert beneficial anti-atherosclerotic effects. We fed apolipoprotein E-deficient (ApoE-/-) mice on a high-fat diet and treated them with atorvastatin (AT) or DSHT, or the combination of DSHT and AT for 12 weeks. To determine the role of DSHT, atherosclerotic lesions in the aorta, aortic root, and aortic arch; lipids and apolipoprotein levels in serum; and macrophage polarization markers in aorta tissues were examined. We show here that the DSHT decreased the atherosclerotic plaque ratio in the aortic arch, aorta, and aortic root. DSHT also regulated lipid levels by decreasing the ApoB level and increasing the ApoA1 level. Moreover, DSHT effectively regulated cholesterol metabolism by increasing the levels of PPARγ, ABCA1 and ABCG1, and the LDL receptor genes. We further found that DSHT promoted polarization to the M2 phenotype by increasing the levels of M2 macrophage (ARG1, CD163, and PPARγ) markers. Our data suggested that DSHT enhances the anti-atherosclerotic effect by regulating cholesterol metabolism through the activation of the PPARγ signaling pathway and by promoting anti-inflammatory M2 macrophage polarization.

ABCA1 and ABCG1 DNA methylation in epicardial adipose tissue of patients with coronary artery disease

BackgroundRecent studies have focused on the potential role of epicardial adipose tissue (EAT) in the development of coronary artery disease (CAD). ABCA1 and ABCG1 transporters regulate cell cholesterol content and reverse cholesterol transport. We aimed to determine whether DNA methylation and mRNA levels of the ABCA1 and ABCG1 genes in EAT and subcutaneous adipose tissue (SAT) were associated with CAD.MethodsPaired EAT and SAT samples were collected from 82 patients undergoing elective cardiac surgery either for coronary artery bypass grafting (CAD group, N = 66) or valve surgery (NCAD group, N = 16). ABCA1 and ABCG1 mRNA levels in EAT and SAT samples were analyzed using real time polymerase chain reaction, ABCA1 protein levels in EAT samples were assessed by western blotting. ABCA1 and ABCG1 DNA methylation analysis was performed in 24 samples from the CAD group and 9 samples from the NCAD group via pyrosequencing.ResultsDNA methylation levels in the ABCA1 promoter and ABCG1 cg27243685 and cg06500161 CpG sites were higher in EAT samples from patients with CAD compared with NCAD (21.92% vs 10.81%, p = 0.003; 71.51% vs 68.42%, p = 0.024; 46.11% vs 37.79%, p = 0.016, respectively). In patients with CAD, ABCA1 and ABCG1 DNA methylation levels were higher in EAT than in SAT samples (p < 0.05). ABCA1 mRNA levels in EAT samples were reduced in the subgroup of patients with CAD and concomitant carotid artery disease or peripheral artery disease compared with the NCAD group (p = 0.024). ABCA1 protein levels in EAT samples tended to be lower in CAD patients than in the NCAD group (p = 0.053). DNA methylation levels at the ABCG1 cg27243685 site positively correlated with plasma triglyceride concentration (r = 0.510, p = 0.008), body mass index (r = 0.556, p = 0.013) and waist-to-hip ratio (r = 0.504, p = 0.012) in SAT samples.ConclusionCAD is associated with ABCA1 and ABCG1 DNA hypermethylation in EAT. CAD with concomitant carotid artery disease or peripheral artery disease is accompanied by decreased ABCA1 gene expression in EAT. DNA methylation levels at the ABCG1 cg27243685 locus in SAT are associated with hypertriglyceridemia and obesity.

AICAR upregulates ABCA1/ABCG1 expression in the retinal pigment epithelium and reduces Bruch's membrane lipid deposit in ApoE deficient mice

The etiology of age-related macular degeneration (AMD) is diverse; however, recent evidence suggests that the lipid metabolism-cholesterol pathway might be associated with the pathophysiology of AMD. The ATP-binding cassette (ABC) transporters, ABCA1 and ABCG1, are essential for the formation of high-density lipoprotein (HDL) and the regulation of macrophage cholesterol efflux. The failure of retinal or retinal pigment epithelium (RPE) cholesterol efflux to remove excess intracellular lipids causes morphological and functional damage to the retina. In this study, we investigated whether treatment with 5-aminoimidazole-4-carboxamide ribonucleotide (AICAR), an AMP-activated protein kinase (AMPK) activator, improves RPE cholesterol efflux and Bruch's membrane (BM) lipid deposits. The protein and mRNA levels of ABCA1 and ABCG1 in ARPE-19 cells and retinal and RPE/choroid tissue from apolipoprotein E-deficient (ApoE-/-) mice were evaluated after 24 weeks of AICAR treatment. The cholesterol efflux capacity of ARPE-19 cells and the cholesterol-accepting capacity of apoB-depleted serum from mice were measured. The thickness of the BM and the degree of lipid deposition were evaluated using electron microscopy. AICAR treatment increased the phosphorylation of AMPK and the protein and mRNA expression of ABCA1 and ABCG1 in vitro. It promoted cholesterol efflux from ARPE-19 cells and upregulated the protein and mRNA levels of ABCA1 and ABCG1 in the retina and RPE in vivo. ApoB-depleted serum from the AICAR-treated group showed enhanced cholesterol-accepting capacity. Long-term treatment with AICAR reduced BM thickening and lipid deposition in ApoE-/- mice. In conclusion, AICAR treatment increased the expression of lipid transporters in the retina and RPE in vivo, facilitated intracellular cholesterol efflux from the RPE in vitro, and improved the functionality of HDL to accept cholesterol effluxed from the cell, possibly via AMPK activation. Collectively, these effects might contribute to the improvement of early age-related pathologic changes in the BM. Pharmacological improvement of RPE cholesterol efflux via AMPK activation may be a potential treatment strategy for AMD.

High Dietary Intervention of Lauric Triglyceride Might be Harmful to Its Improvement of Cholesterol Metabolism in Obese Rats.

Hypercholesterolemia is often considered to be a major risk factor for atherosclerosis, and medium-chain fatty acids have been found to reduce the total cholesterol (TC) level and maintain low-density lipoprotein cholesterol (LDL-c) stability. However, we unexpectedly found that the levels of TC and LDL-c were increased in obese rats treated with high-dose lauric triglycerides (LT). The study aimed to investigate the effect and mechanism of LT on cholesterol metabolism in obese rats. Our results showed that LT intervention could reduce cholesterol biosynthesis by downregulating the expression of HMG-CoA reductase in obese rats. LT increased the expression levels of PPARγ1, LXRα, ABCA1, and ABCG8 in the liver. These results indicated that LT could improve the lipid transfer and bile acid efflux. However, LT significantly increased the expression of PCSK 9, resulting in accelerated degradation of LDLR, thus reducing the transport of very LDL (VLDL) and LDL to the liver. Together with the increased expression of NPC1L1 protein, LT impaired the uptake of VLDL/LDL by the liver and increased the reabsorption of sterols, leading to an increase in the levels of TC and LDL-c in obese rats.

ABCA1-Labeled Exosomes in Serum Contain Higher MicroRNA-193b Levels in Alzheimer's Disease.

Objective We aimed to establish a method to determine whether microRNA-193b (miR-193b) levels in ABCA1-labeled serum exosomes might serve as a marker for the diagnosis of Alzheimer's disease. Methods We used immunocapture methods to determine the levels of ABCA1-labeled exosomal miR-193b in cultures of white blood cells (WBCs), red blood cells (RBCs), mouse hippocampal neuron HT-22 cells, and primary mouse neuronal cells. ABCA1-labeled exosomal miR-193b levels were also evaluated in the cerebrospinal fluid (CSF) and serum of APP/PS1 double-transgenic mice, as well as control subjects (n = 60) and study participants with subjective cognitive decline (SCD, n = 89), stage and mild cognitive impairment (MCI, n = 92), and dementia of the Alzheimer type (DAT, n = 92). Results ABCA1 levels of exosomes harvested from the medium of HT-22 cells and neurons were significantly higher than those of RBCs and WBCs (P < 0.05). Exosomal ABCA1 from the CSF of APP/PS1 mice were transmitted to the serum of wild-type mice after injection, and high miR-193b levels were observed in both the serum and CSF after injection. The ABCA1-labeled exosomal miR-193b levels were higher in the CSF of MCI and DAT patients compared with the CSF of the control group (P < 0.05). The ABCA1-labeled exosomal miR-193b were also slightly higher (P > 0.05) in the serum of SCD patients and significantly higher in the serum of MCI and DAT patients compared with the serum of the control group (P < 0.05). Conclusion This study provides a method to capture specific exosomes. Detection of serum exosomes labeled with ABCA1 may facilitate the early diagnosis of AD.

Cholesterol loading suppresses the atheroinflammatory gene polarization of human macrophages induced by colony stimulating factors

In atherosclerotic lesions, blood-derived monocytes differentiate into distinct macrophage subpopulations, and further into cholesterol-filled foam cells under a complex milieu of cytokines, which also contains macrophage-colony stimulating factor (M-CSF) and granulocyte–macrophage-colony stimulating factor (GM-CSF). Here we generated human macrophages in the presence of either M-CSF or GM-CSF to obtain M-MØ and GM-MØ, respectively. The macrophages were converted into cholesterol-loaded foam cells by incubating them with acetyl-LDL, and their atheroinflammatory gene expression profiles were then assessed. Compared with GM-MØ, the M-MØ expressed higher levels of CD36, SRA1, and ACAT1, and also exhibited a greater ability to take up acetyl-LDL, esterify cholesterol, and become converted to foam cells. M-MØ foam cells expressed higher levels of ABCA1 and ABCG1, and, correspondingly, exhibited higher rates of cholesterol efflux to apoA-I and HDL2. Cholesterol loading of M-MØ strongly suppressed the high baseline expression of CCL2, whereas in GM-MØ the low baseline expression CCL2 remained unchanged during cholesterol loading. The expression of TNFA, IL1B, and CXCL8 were reduced in LPS-activated macrophage foam cells of either subtype. In summary, cholesterol loading converged the CSF-dependent expression of key genes related to intracellular cholesterol balance and inflammation. These findings suggest that transformation of CSF-polarized macrophages into foam cells may reduce their atheroinflammatory potential in atherogenesis.

CTRP9 Enhances Efferocytosis in Macrophages via MAPK/Drp1-Mediated Mitochondrial Fission and AdipoR1-Induced Immunometabolism.

BackgroundClearance of apoptotic cells (ACs) by phagocytes (efferocytosis) suppresses post-apoptotic necrosis and alleviates inflammation. Defective efferocytosis induces diseases that include atherosclerosis and autoimmune diseases. C1q/TNF-related protein 9 (CTRP9), a novel adipokine, has been reported to protect against various cardiovascular disease; however, the effect of CTRP9 on efferocytosis has not been elucidated.Methods1. The efferocytosis of macrophages incubated with ACs with or without CTRP9 treatment was detected by flow cytometry (FCM) and immunostaining. The unengulfed ACs of CTRP9-KO and wild-type (WT) mice after dexamethasone injection were detected by TUNEL assay. 2. As mitochondrial fission is important for promoting efferocytosis, the effect of CTRP9 on mitochondrial fission was measured by fission/fusion-related proteins (MFN2, DRP1, MFF, and OPA1) and visualized by staining with MitoTracker. 3. On account of metabolism insults in engulfed macrophages, we conducted a two-stage efferocytosis assay, and the protective effects of CTRP9 on metabolism were investigated by Western blot.ResultsCTRP9 significantly facilitated macrophage efferocytosis, and it promoted mitochondrial fission by increasing the expression of p-DRP1 (s616) and the translocation of DRP1 from the cytoplasm to the mitochondria. The p38/Jnk-MAPK pathway was activated after treatment with 1 μg/mL CTRP9. When we blocked the activation of MAPK signaling by SB203580 and SP600125, the mediated effect on p-DRP1 (s616) was reduced. Moreover, CTRP9 increased the levels of ABCA1, PPAR-y, HIF-1a and GLUT1, as well as the release of lactate in basal and engulfed macrophages, which revealed that the metabolism of macrophages was advanced. Apoptotic cell-conditioned media (ACCM) and ACs increased the expression of adiponectin receptor 1 (AdipoR1). Down-regulation of AdipoR1 by siRNA could abrogate the immunometabolism effects of CTRP9.ConclusionCTRP9 promoted efferocytosis in macrophages via MAPK/drp1-mediated mitochondrial fission and AdipoR1-induced immunometabolism.