Expression of ATP-Binding Cassette Transporter A1 (ABCA1) in Eyelid Tissues and Meibomian Gland Epithelial Cells.

Purpose: To validate the adenosine triphosphate (ATP)-binding cassette transporter A1 (ABCA1) expression and distribution in human eyelid tissues and meibomian gland epithelial cells. Methods: Meibomian gland tissues from human eyelids were isolated by collagenase A digestion and cultured in defined keratinocyte serum-free medium (DKSFM). Infrared imaging was used to analyze the general morphology of meibomian glands. Hematoxylin and eosin (H&E) staining and Oil Red O staining were used to observe the morphological structure and lipid secretion in the human meibomian gland tissues. Quantitative real-time polymerase chain reaction, western blotting, and immunostaining were used to detect the mRNA and protein expression and cytolocalization of ABCA1 in the meibomian gland tissues and cultured cells. Results: The degree of loss of human meibomian gland tissue was related to age. Meibomian gland lipid metabolism was also associated with age. Additionally, human meibomian gland tissues express ABCA1 mRNA and protein; glandular epithelial cells express more ABCA1 mRNA and protein than acinar cells, and their expression in acinar cells decreases with differentiation. Furthermore, the expression of ABCA1 was downregulated in abnormal meibomian gland tissues. ABCA1 was mainly localized on the cell membrane in primary human meibomian gland epithelial cells (pHMGECs), whereas it was localized in the cytoplasm of immortalized human meibomian gland epithelial cells (iHMGECs). The mRNA and protein levels of ABCA1 in pHMGECs were higher than those in iHMGECs. Conclusions: Meibomian gland tissues of the human eyelid degenerate with age. ABCA1 expression in acinar cells decreases after differentiation and plays an important role in meibomian gland metabolism.

Antagonism of let-7c reduces atherosclerosis and macrophage lipid accumulation by promoting PGC-1α/LXRα/ABCA1/G1 pathway.

Changes in circulating let-7c were significantly associated with the alter in lipid profile, but its role in intracellular lipid metabolism remains unknown. This work was conducted to explore the effects of let-7c on the lipid accumulation in macrophages and uncover the underlying mechanism. Our results showed that let-7c inhibition relieved atherosclerosis progression in apoE-/- mice. In ox-LDL-treatment macrophages, let-7c knockdown suppressed lipid accumulation but does no affect cholesterol intake. Consistent with this, overexpression of let-7c promoted lipid accumulation by reducing the expression of LXRα and ABCA1/G1. Mechanistically, let-7c targeted PGC-1α to repress the expression of LXRα and ABCA1/G1, thereby regulating cholesterol homeostasis in macrophages. Taken together, these findings suggest that antagonism of let-7c reduces atherosclerosis and macrophage lipid accumulation through the PGC-1α/LXRα/ABCA1/G1 axis.

Cav3.1 T-type calcium channel blocker NNC 55-0396 reduces atherosclerosis by increasing cholesterol efflux.

Calcium channel blockers (CCBs) are commonly used as antihypertensive agents. While certain L-type CCBs exhibit antiatherogenic effects, the impact of Cav3.1 T-type CCBs on antiatherogenesis and lipid metabolism remains unexplored. NNC 55-0396 (NNC) is a highly selective blocker of T-type calcium channels (Cav3.1 channels). We investigated the effects of NNC on relevant molecules and molecular mechanisms in human THP-1 macrophages. Cholesterol efflux, an indicator of reverse cholesterol transport (RCT) efficiency, was assessed using [3H]-labeled cholesterol. In vivo, high cholesterol diet (HCD)-fed LDL receptor knockout (Ldlr-/-) mice, an atherosclerosis-prone model, underwent histochemical staining to analyze plaque burden. Treatment of THP-1 macrophages with NNC facilitated cholesterol efflux and reduced intracellular cholesterol accumulation. Pharmacological and genetic interventions demonstrated that NNC treatment or Cav3.1 knockdown significantly enhanced the protein expression of scavenger receptor B1 (SR-B1), ATP-binding cassette transporter A1 (ABCA1), ATP-binding cassette transporter G1 (ABCG1), and liver X receptor alpha (LXRα) transcription factor. Mechanistic analysis revealed that NNC activates p38 and c-Jun N-terminal kinase (JNK) phosphorylation, leading to increased expression of ABCA1, ABCG1, and LXRα-without involving the microRNA pathway. LXRα isrequired for NNC-induced ABCA1 and ABCG1 expression. Administering NNC diminished atherosclerotic lesion area and lipid deposition in HCD-fed Ldlr-/- mice. NNC's anti-atherosclerotic effects, achieved through enhanced cholesterol efflux and inhibition of lipid accumulation, suggest a promising therapeutic approach for hypertensive patients with atherosclerosis. This research highlights the potential of Cav3.1 T-type CCBs in addressing cardiovascular complications associated with hypertension.

Elder (Sambucus nigra), identified by high-content screening, counteracts foam cell formation without promoting hepatic lipogenesis.

Cholesterol deposition in intimal macrophages leads to foam cell formation and atherosclerosis. Reverse cholesterol transport (RCT), initiated by efflux of excess cholesterol from foam cells, counteracts atherosclerosis. However, targeting RCT by enhancing cholesterol efflux was so far accompanied by adverse hepatic lipogenesis. Here, we aimed to identify novel natural enhancers of macrophage cholesterol efflux suitable for the prevention of atherosclerosis. Plant extracts of an open-access library were screened for their capacity to increase cholesterol efflux in RAW264.7 macrophages trace-labeled with fluorescent BODIPY-cholesterol. Incremental functional validation of hits yielded two final extracts, elder (Sambucus nigra) and bitter orange (Citrus aurantium L.) that induced ATP binding cassette transporter A1 (ABCA1) expression and reduced cholesteryl ester accumulation in aggregated LDL-induced foam cells. Aqueous elder extracts were subsequently prepared in-house and both, flower and leaf extracts increased ABCA1 mRNA and protein expression in human THP-1 macrophages, while lipogenic gene expression in hepatocyte-derived cells was not induced. Chlorogenic acid isomers and the quercetin glycoside rutin were identified as the main polyphenols in elder extracts with putative biological action. In summary, elder flower and leaf extracts increase macrophage ABCA1 expression and reduce foam cell formation without adversely affecting hepatic lipogenesis.

Regulation of lipid metabolism by APOE4 in intrahepatic cholangiocarcinoma via the enhancement of ABCA1 membrane expression.

Intrahepatic cholangiocarcinoma (ICC) is a malignancy with a dismal prognosis, thus the discovery of promising diagnostic markers and treatment targets is still required. In this study, 1,852 differentially expressed genes (DEGs) were identified in the GSE45001 dataset for weighted gene co-expression network analysis (WGCNA), and the turquoise module was confirmed as the key module. Next, the subnetworks of the 1,009 genes in the turquoise module analyzed by MCODE, MCC, and BottleNeck algorithms identified nine overlapping genes (CAT, APOA1, APOC2, HSD17B4, EHHADH, APOA2, APOE4, ACOX1, AGXT), significantly associated with lipid metabolism pathways, such as peroxisome and cholesterol metabolism. Among them, APOE4 exhibited a potential tumor-suppressive role in ICC and high diagnostic value for ICC in both GSE45001 and GSE32879 datasets. In vitro experiments demonstrated Apolipoprotein E4 (APOE4) overexpression suppressed ICC cell proliferation, migration, and invasion, knockdown was the opposite trend. And in ICC modulated lipid metabolism, notably decreasing levels of TG, LDL-C, and HDL-C, while concurrently increasing the expressions of TC. Further, APOE4 also downregulated lipid metabolism-related genes, suggesting a key regulatory role in maintaining cellular homeostasis, and regulating the expression of the membrane protein ATP-binding cassette transporter A1 (ABCA1). These findings highlighted the coordinated regulation of lipid metabolism by APOE4 and ABCA1 in ICC progression, providing new insights into ICC mechanisms and potential therapeutic strategies.

Functional characterization of missense variants affecting the extracellular domains of ABCA1 using a fluorescence-based assay.

Excess cholesterol originating from nonhepatic tissues is transported within HDL particles to the liver for metabolism and excretion. Cholesterol efflux is initiated by lipid-free or lipid-poor apolipoprotein A1 interacting with the transmembrane protein ABCA1, a key player in cholesterol homeostasis. Defective ABCA1 results in reduced serum levels of HDL cholesterol, deposition of cholesterol in arteries, and an increased risk of early onset CVD. Over 300 genetic variants in ABCA1 have been reported, many of which are associated with reduced HDL cholesterol levels. Only a few of these have been functionally characterized. In this study, we have analyzed 51 previously unclassified missense variants affecting the extracellular domains of ABCA1 using a sensitive, easy, and low-cost fluorescence-based assay. Among these, only 12 variants showed a distinct loss-of-function phenotype, asserting their direct association with severe HDL disorders. These findings emphasize the crucial role of functional characterization of genetic variants in pathogenicity assessment and precision medicine. The functional rescue of ABCA1 loss-of-function variants through proteasomal inhibition or by the use of the chemical chaperone 4-phenylbutyric acid was genotype specific. Genotype-specific responses were also observed for the ability of apolipoprotein A1 to stabilize the different ABCA1 variants. In view of personalized medicine, this could potentially form the basis for novel therapeutic strategies.

Flipped C-Terminal Ends of APOA1 Promote ABCA1-Dependent Cholesterol Efflux by Small HDLs.

BACKGROUND: Cholesterol efflux capacity (CEC) predicts cardiovascular disease independently of high-density lipoprotein (HDL) cholesterol levels. Isolated small HDL particles are potent promoters of macrophage CEC by the ABCA1 (ATP-binding cassette transporter A1) pathway, but the underlying mechanisms are unclear. METHODS: We used model system studies of reconstituted HDL and plasma from control and lecithin-cholesterol acyltransferase (LCAT)-deficient subjects to investigate the relationships among the sizes of HDL particles, the structure of APOA1 (apolipoprotein A1) in the different particles, and the CECs of plasma and isolated HDLs. RESULTS: We quantified macrophage and ABCA1 CEC of 4 distinct sizes of reconstituted HDL. CEC increased as particle size decreased. Tandem mass spectrometric analysis of chemically cross-linked peptides and molecular dynamics simulations of APOA1, the major protein of HDL, indicated that the mobility of C-terminus of that protein was markedly higher and flipped off the surface in the smallest particles. To explore the physiological relevance of the model system studies, we isolated HDL from LCAT-deficient subjects, whose small HDLs (like reconstituted HDLs) are discoidal and composed of APOA1, cholesterol, and phospholipid. Despite their very low plasma levels of HDL particles, these subjects had normal CEC. In both the LCAT-deficient subjects and control subjects, the CEC of isolated extra-small HDL (a mixture of extra-small and small HDL by calibrated ion mobility analysis) was 3- to 5-fold greater than that of the larger sizes of isolated HDL. Incubating LCAT-deficient plasma and control plasma with human LCAT converted extra-small and small HDL particles into larger particles, and it markedly inhibited CEC. CONCLUSIONS: We present a mechanism for the enhanced CEC of small HDLs. In smaller particles, the C-termini of the 2 antiparallel molecules of APOA1 are "flipped" off the lipid surface of HDL. This extended conformation allows them to engage with ABCA1. In contrast, the C-termini of larger HDLs are unable to interact productively with ABCA1 because they form a helical bundle that strongly adheres to the lipid on the particle. Enhanced CEC, as seen with the smaller particles, predicts decreased cardiovascular disease risk. Thus, extra-small and small HDLs may be key mediators and indicators of the cardioprotective effects of HDL.

Trimethylamine N-oxide promotes oxidative stress and lipid accumulation in macrophage foam cells via the Nrf2/ABCA1 pathway.

Recently, trimethylamine N-oxide (TMAO) has been considered a risk factor for cardiovascular disease and has a proatherogenic effect. Many studies have found that TMAO is involved in plaque oxidative stress and lipid metabolism, but the specific mechanism is still unclear. In our study, meta-analysis and bioinformatic analysis were firstly conducted in the database, and found that the effect of high plasma TMAO levels on promoting atherosclerotic plaque may be related to the expression of key antioxidant genes nuclear factor erytheroid-derived-2-like 2 (NFE2L2/Nrf2) decreased. Next, we assessed the role of Nrf2-mediated signaling pathway in TMAO-treated foam cells. Our results showed that TMAO can inhibit the expression of Nrf2 and its downstream antioxidant response element such as heme oxygenase-1 (HO-1) and glutathione peroxidase4 (GPX4), resulting in increased production of reactive oxygen species and decreased activity of superoxide dismutase, promoting oxidative stress. And TMAO can also promote lipid accumulation in foam cells by inhibiting cholesterol efflux protein expression. In addition, upregulation of Nrf2 expression partially rescues TMAO-induced oxidative stress and reduces ATP-binding cassette A1 (ABCA1)-mediated lipid accumulation. Therefore, TMAO promotes oxidative stress and lipid accumulation in macrophage foam cells through the Nrf2/ABCA1 pathway, which may provide a potential mechanism for the proatherogenic effect of TMAO.

7-Ketocholesterol plays a key role in cholesterol-induced hepatitis via macrophage and neutrophil infiltration.

This study sought to explore the role of 7-ketocholesterol (7-KC) in liver damage caused by high cholesterol intake and its potential pathological mechanism in mice. Our in vivo findings indicated that mice fed a high-cholesterol diet had elevated serum levels of 7-KC, accompanied by liver injury and inflammation, similar to human nonalcoholic steatohepatitis. Furthermore, the high-cholesterol diet induced neutrophil infiltration, which played a critical role in liver damage through myeloperoxidase (MPO) activity. Upon stimulation with 7-KC, macrophages exhibited increased expression of C-X-C motif chemokine ligand 1 (CXCL1) and CXCL2, as well as ATP-binding cassette transporter A1 (ABCA1) and ABCG1. Hepatocytes, on the other hand, exhibited increased expression of CXCL2 and ABCG1. The infiltration of neutrophils in the liver was primarily caused by CXCL1 and CXCL2, resulting in hepatocyte cell death due to elevated MPO activity. Our data also revealed that the activation of macrophages by 7-KC via ABCA1 or ABCG1 was not associated with lipid accumulation. Collectively, these findings suggest that high cholesterol-induced hepatitis in mice involves, at least partially, the recruitment of neutrophils to the liver by 7-KC-activated macrophages. This is mediated by increased expression of CXCL1 and CXCL2 through ABCA1 or ABCG1, which act as 7-KC efflux transporters. Additionally, hepatocytes contribute to this process by increased expression of CXCL2 through ABCG1. Therefore, our findings suggest that 7-KC may play a role in high cholesterol-induced hepatitis in mice by activating macrophages and hepatocytes, ultimately leading to neutrophil infiltration.

17ß-estradiol regulates adenosine triphosphate-binding cassette transporters A1 expression via estrogen receptor A to increase macrophage cholesterol efflux.

The liver is the focus of research on the effects of estrogen on cholesterol metabolism. Few studies have investigated the effects of estrogen on macrophages despite the significance of cells in atherosclerosis. The purpose of this study is to examine the effect of estrogen on macrophage cholesterol efflux. Macrophage cholesterol efflux, oil red O staining, RT-qPCR, Western blotting analyses were used to determine cholesterol metabolize and the expressions of adenosine triphosphate (ATP)-binding cassette transporter G1 (ABCG1) and ATP-binding cassette transporter A1 (ABCA1) in J774A.1 cells, and the effect of these treatments was compared to without adding 17ß-estradiol (E2). Gain and loss of estrogen receptor alpha (ERα), liver X receptor α (LXRα) were conducted to study interactions between E2, ERα, LXRα and ABCA. Finally, in mice, we validate the relationship between ERα and ABCA1. E2 increases cholesterol efflux from macrophages and decreases the formation of lipid droplets and positively regulates the expression of ABCA1. This suggests that estrogen receptors (ERs) directly regulate ABCA1 translation. We suppressed ERα, which decreased the mRNA and protein expression of ABCA1. At the mRNA level, E2 treatment could partially counteract these phenomena, but not at the protein level. ABCA1 expression decreased after LXRα was inhibited. This suggests that ABCA1 translation is directly regulated by ERα. In the ovariectomized mouse model of ABCA1 protein expression was significantly reduced in the peritoneal macrophages of the ovariectomy (OVX) group. ABCA1 protein expression was greater in the E2+OVX group than in the OVX group. E2 contributes to the positive regulation of ABCA1 expression and promotes cholesterol efflux in macrophages by binding to ERα. The effect is independent of ABCA1 transcription regulation by LXRα.

MP Allosterically Activates AMPK to Enhance ABCA1 Stability by Retarding the Calpain-Mediated Degradation Pathway.

It is widely recognized that macrophage cholesterol efflux mediated by the ATP-binding cassette transporter A1 (ABCA1) constitutes the initial and rate-limiting step of reverse cholesterol transport (RCT), displaying a negative correlation with the development of atherosclerosis. Although the transcriptional regulation of ABCA1 has been extensively studied in previous research, the impact of post-translational regulation on its expression remains to be elucidated. In this study, we report an AMP-activated protein kinase (AMPK) agonist called ((2R,3S,4R,5R)-3,4-dihydroxy-5-(6-((3-hydroxyphenyl) amino)-9H-purin-9-yl) tetrahydrofuran-2-yl) methyl dihydrogen phosphate (MP), which enhances ABCA1 expression through post-translational regulation rather than transcriptional regulation. By integrating the findings of multiple experiments, it is confirmed that MP directly binds to AMPK with a moderate binding affinity, subsequently triggering its allosteric activation. Further investigations conducted on macrophages unveil a novel mechanism through which MP modulates ABCA1 expression. Specifically, MP downregulates the Cav1.2 channel to obstruct the influx of extracellular Ca2+, thereby diminishing intracellular Ca2+ levels, suppressing calcium-activated calpain activity, and reducing the interaction strength between calpain and ABCA1. This cascade of events culminates in the deceleration of calpain-mediated degradation of ABCA1. In conclusion, MP emerges as a potentially promising candidate compound for developing agents aimed at enhancing ABCA1 stability and boosting cellular cholesterol efflux and RCT.

Increased Expression of the ABCA1 and ABCA3 Transporter Genes is Associated with Cisplatin Resistance in Breast Cancer Cells.

OBJECTIVE: Breast cancer (BC) is a highly malignant neoplasm with resistance to therapeutics that are related to genes associated with multidrug resistance. The excessive expression of ATP-binding cassette transporters (ABCs) genes, including ABCA1 and ABCA3, is a primary factor contributing to the increased effluent of cell-toxic drugs and subsequent treatment resistance. Therefore, the current work aimed to explore the role of ABCA1 and ABCA3 in chemoresistance activity against cisplatin in breast cancer cells. METHODS: The current study compared the AMJ13 breast cancer cells derived from a woman Iraqi patient, which are hormone receptor-negative, with MCF-7 breast cancer cells, which are hormone receptor-positive.  Cytotoxic assay (CCK-8 assay) is used to measure the cell's viability and cytotoxic activity after it has been treated with cisplatin. Morphological Study using crystal violet stain to examine cytological changes was conducted. Quantitative RT-PCR is used to measure how much the ABCA1, and 3 genes mRNA are being expressed before and after treatment. RESULTS: The CCK-8 assay found that IC50 values of cisplatin in AMJ13 and MCF-7 cells were 202.2 µg/ml and 90.23 µg/ml, respectively. The IC50 value of AMJ13 is 2-fold higher than in MCF-7 cells. The QPCR study revealed that breast cancer cell lines AMJ13 and MCF-7 subjected to cisplatin showed upregulated levels of ABCA1 and ABCA3 expression. Experiments with cytotoxicity assays demonstrate that higher expression of ABCA1 and ABCA3 in AMJ13 and MCF-7 breast cancer cell lines is linked to their resistance.  Conclusion: The findings of this study suggest that the ABCA1 and ABCA3 transporters play a significant role in the resistance to cisplatin and,.

Evaluation of the participation of ABCA1 transporter in epicardial and mediastinal adipose tissue from patients with coronary artery disease.

Objective: Recent studies have shown a relationship between adipose tissue and coronary artery disease (CAD). The ABCA1 transporter regulates cellular cholesterol content and reverses cholesterol transport. The aim of this study was to determine the relationship between single nucleotide polymorphisms (SNPs) R230C, C-17G, and C-69T and their expression in epicardial and mediastinal adipose tissue in Mexican patients with CAD. Subjects and methods: The study included 71 patients with CAD and a control group consisting of 64 patients who underwent heart valve replacement. SNPs were determined using TaqMan probes. mRNA was extracted using TriPure Isolation from epicardial and mediastinal adipose tissue. Quantification and expression analyses were done using RT-qPCR. Results: R230C showed a higher frequency of the GG genotype in the CAD group (70.4%) than the control group (57.8%) [OR 0.34, 95% CI (0.14-0.82) p = 0.014]. Similarly, C-17G (rs2740483) showed a statistically significant difference in the CC genotype in the CAD group (63.3%) in comparison to the controls (28.1%) [OR 4.42, 95% CI (2.13-9.16), p = 0.001]. mRNA expression in SNP R230C showed statistically significant overexpression in the AA genotype compared to the GG genotype in CAD patients [11.01 (4.31-15.24) vs. 3.86 (2.47-12.50), p = 0.015]. Conclusion: The results suggest that the GG genotype of R230C and CC genotype of C-17G are strongly associated with the development of CAD in Mexican patients. In addition, under-expression of mRNA in the GG genotype in R230C is associated with patients undergoing revascularization.

Expression analysis of ABCA1 in type 2 diabetic Pakistani patients with and without dyslipidemia and correlation with glycemic index and lipid profile.

Diabetes Mellitus type II, earlier considered as an endocrinological disorder is now more regarded as an inflammatory disorder along with lipid aberrations. It demands for regular monitoring, healthy dietary habits and lifestyle modification. This study was focused on gene expression of ATP binding cassette protein 1 (ABCA1) in diabetic dyslipidemia patients in comparison with control groups of only diabetics and healthy individuals. Blood samples and data were collected from recruited 390 patients who were further divided into three groups (130 each). Glycemic index and lipid profile was assessed. Delta Delta Ct method was used that revealed downregulation of the studied gene more in diabetic dyslipidemia patients as compared to only diabetics and healthy controls. The Ct values of ABCA1 were associated with glycemic index and lipid profile using Pearson's correlation. A negative correlation with fasting blood sugar and a positive correlation with HbA1cwas observed in only diabetics group. While in diabetic dyslipidemia and normal healthy controls, a negative correlation was found with both. As far as the lipid profile is concerned a positive correlation was observed among only diabetics with whole lipid profile. In diabetics with dyslipidemia, a negative correlation with all parameters except the TAGs was observed. A positive correlation with all except HDL was observed in healthy controls. The Ct values and fold change were compared among diseased and healthy individuals by applying independent t test. The cycle threshold in only diabetics was p = 0.000018 and in diabetic dyslipdemia individuals was p = 0.00251 while fold change in only diabetics (p = 0.000230) and in diabetics with dyslipidemia (p = 0.001137) was observed to be as statistically significant.

Drug metabolism-related gene ABCA1 augments temozolomide chemoresistance and immune infiltration abundance of M2 macrophages in glioma.

Gliomas are the most prevalent primary tumor in the central nervous system, with an abysmal 5-year survival rate and alarming mortality. The current standard management of glioma is maximum resection of tumors followed by postoperative chemotherapy with temozolomide (TMZ) or radiotherapy. Low chemosensitivity of TMZ in glioma treatment eventuates limited therapeutic efficacy or treatment failure. Hence, overcoming the resistance of glioma to TMZ is a pressing question. Our research centered on identifying the drug metabolism-related genes potentially involved in TMZ-treated resistance of glioma through several bioinformatics datasets and cell experiments. One efflux transporter, ATP-binding cassette transporter subfamily A1 (ABCA1), was discovered with an upregulated expression level and signaled poor clinical outcomes for glioma patients. The transcript level of ABCA1 significantly elevated across the TMZ-resistant glioma cells in contrast with non-resistant cells. Over-expressed ABCA1 restrained the drug activity of TMZ, and ABCA1 knockdown improved the treatment efficacy. Meanwhile, the results of molecular docking between ABCA1 protein and TMZ showed a high binding affinity. Additionally, co-expression and immunological analysis revealed that ABCA1 facilitates the immune infiltration of M2 macrophages in glioma, thereby stimulating tumor growth and aggravating the poor survival of patients. Altogether, we discovered that the ABCA1 transporter was involved in TMZ chemoresistance and the immune infiltration of M2 macrophages in glioma. Treatment with TMZ after ABCA1 knockdown enhances the chemosensitivity, suggesting that inhibition of ABCA1 may be a potential strategy for improving the therapeutic efficacy of gliomas.

[AdipoRon Effect on Expression of Lipid Metabolism Genes in Cultured Human Primary Macrophages].

Atherosclerosis is characterized by excessive uptake of cholesterol-rich low-density lipoprotein (LDL) by vascular wall macrophages. The macrophages are transformed into foam cells, lipids accumulate in the intima of arteries, atherosclerotic plaques arise, and cardiovascular diseases develop. Adiponectin is an adipose tissue adipokine and possess anti-atherogenic and anti-inflammatory activities, which are mediated by adiponectin binding to its receptors AdipoR1 and AdipoR2. To exert its anti-atherogenic effect, adiponectin may regulate the reverse cholesterol transport and prevent foam cells formation. The small-molecule adiponectin receptor agonist AdipoRon was assumed to modulate expression of reverse cholesterol transport and inflammation genes in human macrophages. Several AdipoRon concentrations (0, 5, 10, and 20 µM) were tested for effect on expression of the lipid metabolism genes ABCA1, ABCG1, APOA1, NR1H3 (LXRα), NR1H2 (LXRß), PPARG, and ACAT1 and the inflammation genes IL6, TNFA, and TLR4 in cultured human primary macrophages and the THP-1 macrophage cell line. Cell viability was measured using the MTS assay. ABCA1, ABCG1, APOA1, NR1H3, NR1H2, PPARG, ACAT1, IL6, TNFA, and TLR4 mRNA levels in human primary macrophages were assessed by real-time PCR. The PPARG and ABCA1 relative mRNA levels were found to increase in human primary macrophages treated with 5 or 10 µM AdipoRon for 24 h. A higher AdipoRon concentration (20 µM) was cytotoxic to macrophages, especially THP-1 cells. The effect of AdipoRon on human macrophages and potential adiponectin receptor agonists are of interest to study in view of the need to develop new approaches to atherosclerosis prevention and treatment.

Integration of methylation quantitative trait loci (mQTL) on dietary intake on DNA methylation levels: an example of n-3 PUFA and ABCA1 gene.

BACKGROUND: Epigenetic studies have reported relationships between dietary nutrient intake and methylation levels. However, genetic variants that may affect DNA methylation (DNAm) pattern, called methylation quantitative loci (mQTL), are usually overlooked in these analyses. We investigated whether mQTL change the relationship between dietary nutrient intake and leukocyte DNAm levels with an example of estimated fatty acid intake and ATP-binding cassette transporter A1 (ABCA1). METHODS: A cross-sectional study on 231 participants (108 men, mean age: 62.7 y) without clinical history of cancer and no prescriptions for dyslipidemia. We measured leukocyte DNAm levels of 8 CpG sites within ABCA1 gene by pyrosequencing method and used mean methylation levels for statistical analysis. TaqMan assay was used for genotyping a genetic variant of ABCA1 (rs1800976). Dietary fatty acid intake was estimated with a validated food frequency questionnaire and adjusted for total energy intake by using residual methods. RESULTS: Mean ABCA1 DNAm levels were 5% lower with the number of minor alleles in rs1800976 (CC, 40.6%; CG, 35.9%; GG, 30.6%). Higher dietary n-3 PUFA intake was associated with lower ABCA1 DNAm levels (1st (ref) vs. 4th, ß [95% CI]: -2.52 [-4.77, -0.28]). After controlling for rs180076, the association between dietary n-3 PUFA intake and ABCA1 DNAm levels was attenuated, but still showed an independent association (1st (ref) vs. 4th, ß [95% CI]: -2.00 [-3.84, -0.18]). The interaction of mQTL and dietary n-3 PUFA intake on DNAm levels was not significant. CONCLUSIONS: This result suggested that dietary n-3 PUFA intake would be an independent predictor of DNAm levels in ABCA1 gene after adjusting for individual genetic background. Considering mQTL need to broaden into other genes and nutrients for deeper understanding of DNA methylation, which can contribute to personalized nutritional intervention.

Phospholipid transport by ABCA1: the extracellular translocase or alternating access model?

PURPOSE OF REVIEW: ATP-binding cassette transporter A1 (ABCA1) plays a key role in high-density lipoprotein (HDL) biogenesis and cholesterol export from artery wall cells. Recent evidence challenges the generally accepted model for lipid transport by ABCA1, termed the alternating access mechanism, which proposes that phospholipid moves from the inner leaflet to the outer leaflet of the plasma membrane. RECENT FINDINGS: In contrast to the standard model, our computer simulations of ABCA1 indicate that ABCA1 extracts phospholipid from the plasma membrane's outer leaflet. The lipid then diffuses into the interior of ABCA1 to contact a structure termed the 'gateway'. A conformational change opens the gateway and forces the lipid through a ring-shaped domain, the 'annulus orifice', into the base of an elongated hydrophobic tunnel in the transporter's extracellular domain. Engineered mutations in the gateway and annulus strongly inhibited lipid export by ABCA1 without affecting cell-surface expression levels of the transporter, strongly supporting the proposed model. SUMMARY: Our demonstration that ABCA1 extracts lipid from the outer face of the plasma membrane and forces it into an elongated hydrophobic tunnel contrasts with the alternating access model, which flops phospholipid from the membrane's inner leaflet to its outer leaflet. These results suggest that ABCA1 is a phospholipid translocase that transports lipids by a mechanism distinct from that of other ABC transporters.

Regulation of ABCA1 by miR-33 and miR-34a in the Aging Eye.

Many age-related diseases, including age-related macular degeneration (AMD), go along with local lipid accumulation and dysregulated lipid metabolism. Several genes involved in lipid metabolism, including ATP-binding cassette transporter A1 (ABCA1), were associated with AMD through genome-wide association studies. Recent studies have shown that loss of ABCA1 in the retinal pigment epithelium (RPE) leads to lipid accumulation and RPE atrophy, a hallmark of AMD, and that antagonizing ABCA1-targeting microRNAs (miRNAs) attenuated pathological changes to the RPE or to macrophages. Here, we focus on two lipid metabolism-modulating miRNAs, miR-33 and miR-34a, which show increased expression in aging RPE cells, and on their potential to regulate ABCA1 levels, cholesterol efflux, and lipid accumulation in AMD pathogenesis.

Mechanism of liver X receptor α and ATP binding cassette transporter A1 involved in preeclampsia using an optimized deep learning model.

OBJECTIVE: Preeclampsia (PE) is a complex disease-causing multisystem damage. Many genes, environmental factors, and their interactions are involved in the development and progression of PE. The pathogenesis of PE is not fully understood, limiting the prevention and treatment of PE. The aim of this study was to investigate the effect of 4,4'-diisothiocyanato-stilbene-2,2'-disulfonic acid (DIDS), an ATP-binding cassette transporter A1 (ABCA1) blocker, on apoM mRNA and protein levels. PATIENTS AND METHODS: The role of liver X receptor α (LXRα) and ABCA1 in the pathogenesis of PE was investigated by optimizing the design of DIDS inhibition based on a deep learning model. RESULTS: The proportion of primipara in the research group, EOPE group, LOPE group, and controls was 59.82%, 65.85%, 56.34%, and 21.43%, respectively. The difference between the research group and the controls was statistically significant (p<0.01). In the clinical data, serum-free triiodothyronine (FT3), gestational age at delivery, high-density lipoprotein cholesterol (HDL-C), hemoglobin (HGB), albumin, and platelet (PLT) in the research group were lower than those in the controls (p<0.05). CONCLUSIONS: ABCA1 is considered to affect apoM mRNA expression, G/HDL-C may increase the risk of LOPE, and overweight or obesity, abnormal glycemic regulation, and hypothyroidism are independent risk factors closely related to the pathogenesis of PE and its subgroups.