ATP-binding Cassette Proteins Research Articles

Impact of various dietary lipids on amelioration of biomarkers linked to metabolic syndrome in both healthy and diabetic Wistar rats.

The present study was designed to investigate the influence of different dietary lipids (sheep's fat, olive oil, coconut oil, and corn oil) on specific biomarkers associated with metabolic syndrome in both healthy and diabetic rats. The study designed for 45 days, utilized a male diabetic wistar rat (body weight, 180-220g) model induced by streptozotocin (45mg/kg bw). The rats were divided into two sections: five non-diabetic and five diabetic groups, each containing six rats. The first group in each section serving as the control, received a standard diet. Both non-diabetic or diabetic groups, were provided with a standard diet enriched with 15% sheep fat, 15% coconut oil, 15% olive oil, and 15% corn oil, respectively for a duration of 45 days. Post-supplementation, both healthy and diabetic control rats exhibited a higher food intake compared to rats supplemented with lipid diet; notably food intake was higher in diabetic control than healthy control. However, rats fed with coconut oil, olive oil and sheep fat showed weight gain at the end of the experiment, in both healthy and diabetic groups. Coconut oil supplementation significantly (p ≤ 0.05) increased HDL-C and total cholesterol level in diabetic groups compared to healthy group, it was confirmed by an increased PPAR-α and ABCA-1 protein level. Olive oil significantly decreased triglyceride, total cholesterol, and LDL-C levels in diabetic rats when compared to sheep fat or coconut oil. Corn oil significantly decreased fasting glucose, total cholesterol and LDL-C levels compared to all other groups. Corn and olive oil supplemented normal groups, found with significant increase in hepatic glucose-lipid oxidative metabolism associated protein, like FGF-21, MSH, ABCA-1, PPAR-γ and decreased lipogenesis proteins like, SREBP and PPAR-α levels. In contrast, sheep grease and coconut oil increased SREBP and PPAR-α expression in both normal and diabetic groups. Most notably, normal and diabetic groups pretreated with sheep grease resulted in increased inflammatory (MCP-1, IL-1β, TLR-4, TNF-α), and oxidative stress markers (LPO, GSH, GPx, SOD and CAT) linked with metabolic complications. The combination or alternative use of olive oil and corn oil in daily diet may play a significant role in preventing proinflammatory condition associated with insulin resistance and cardiovascular diseases.

Inflammatory corpuscle AIM2 facilitates macrophage foam cell formation by inhibiting cholesterol efflux protein ABCA1

The inflammatory corpuscle recombinant absents in melanoma 2 (AIM2) and cholesterol efflux protein ATP binding cassette transporter A1(ABCA1) have been reported to play opposing roles in atherosclerosis (AS) plaques. However, the relationship between AIM2 and ABCA1 remains unclear. In this study, we explored the potential connection between AIM2 and ABCA1 in the modulation of AS by bioinformatic analysis combined with in vitro experiments. The GEO database was used to obtain AS transcriptional profiling data; screen differentially expressed genes (DEGs) and construct a weighted gene co-expression network analysis (WGCNA) to obtain AS-related modules. Phorbol myristate acetate (PMA) was used to induce macrophage modelling in THP-1 cells, and ox-LDL was used to induce macrophage foam cell formation. The experiment was divided into Negative Control (NC) group, Model Control (MC) group, AIM2 overexpression + ox-LDL (OE AIM2 + ox-LDL) group, and AIM2 short hairpin RNA + ox-LDL (sh AIM2 + ox-LDL) group. The intracellular cholesterol efflux rate was detected by scintillation counting; high-performance liquid chromatography (HPLC) was used to detect intracellular cholesterol levels; apoptosis levels were detected by TUNEL kit; levels of inflammatory markers (IL-1β, IL-18, ROS, and GSH) were detected by ELISA kits; and levels of AIM2 and ABCA1 proteins were detected by Western blot. Bioinformatic analysis revealed that the turquoise module correlated most strongly with AS, and AIM2 and ABCA1 were co-expressed in the turquoise module with a trend towards negative correlation. In vitro experiments demonstrated that AIM2 inhibited macrophage cholesterol efflux, resulting in increased intracellular cholesterol levels and foam cell formation. Moreover, AIM2 had a synergistic effect with ox-LDL, exacerbating macrophage oxidative stress and inflammatory response. Silencing AIM2 ameliorated the above conditions. Furthermore, the protein expression levels of AIM2 and ABCA1 were consistent with the bioinformatic analysis, showing a negative correlation. AIM2 inhibits ABCA1 expression, causing abnormal cholesterol metabolism in macrophages and ultimately leading to foam cell formation. Inhibiting AIM2 may reverse this process. Overall, our study suggests that AIM2 is a reliable anti-inflammatory therapeutic target for AS. Inhibiting AIM2 expression may reduce foam cell formation and, consequently, inhibit the progression of AS plaques.

Discovery of Small Molecule Glycolytic Stimulants for Enhanced ApoE Lipidation in Alzheimer's Disease Cell Model.

Alzheimer's disease (AD) is a progressive neurodegenerative disease characterized by pathophysiological deposits of extracellular amyloid beta (Aβ) peptides and intracellular neurofibrillary tangles of tau. The central role of Aβ in AD pathology is well-established, with its increased deposition attributed mainly to its decreased cerebral clearance. Here, it is noteworthy that apolipoprotein E (ApoE), the most significant risk factor for AD, has been shown to play an isoform-specific role in clearing Aβ deposits (ApoE2 > ApoE3 > ApoE4), owing mainly to its lipidation status. In addition to the pathophysiological Aβ deposits, AD is also characterized by abnormal glucose metabolism, which is a distinct event preceding Aβ deposition. The present study established, for the first time, a possible link between these two major AD etiologies, with glucose metabolism directly influencing ApoE lipidation and its secretion by astrocytes expressing human ApoE4. Specifically, glucose dose-dependently activated liver X receptor (LXR), leading to elevated ABCA1 and ABCG1 protein levels and enhanced ApoE lipidation. Moreover, co-treatment with a glycolytic inhibitor significantly inhibited this LXR activation and subsequent ApoE lipidation, further supporting a central role of glucose metabolism in LXR activation leading to enhanced ApoE lipidation, which may help against AD through potential Aβ clearance. Therefore, we hypothesized that pharmacological agents that can target cellular energy metabolism, specifically aerobic glycolysis, may hold significant therapeutic potential against AD. In this context, the present study also led to the discovery of novel, small-molecule stimulants of astrocytic glucose metabolism, leading to significantly enhanced lipidation status of ApoE4 in astrocytic cells. Three such newly discovered compounds (lonidamine, phenformin, and berberine), owing to their promising cellular effect on the glycolysis-ApoE nexus, warrant further investigation in suitable in vivo models of AD.

Comprehensive pan-cancer analysis: essential role of ABCB family genes in cancer.

The adenosine triphosphate-binding-cassette (ABC) transporter orchestrates the transmembrane transport of diverse substrates with the aid of ATP as an energy source. ABC transporter constitutes a widespread superfamily of transporters prominently present on the cellular membrane of organisms. Advancements in understanding have unveiled additional roles beyond mere intracellular or extracellular transport functions for the ABC protein family, encompassing involvement in DNA repair, protein translation, and gene expression regulation. Yet its role in tumors is still unknown. This study drew support from multiple databases, including Gene Expression Omnibus (GEO), European Genome-phenome Archive (EGA), The Cancer Genome Atlas (TCGA), and employed multidimensional bioinformatics analyses, incorporating online databases and the R-project. Through a comprehensive analysis, we seek to discern transcriptional-level disparities among genes and their consequential impacts on prognosis, tumor microenvironment (TME), stemness score, immune subtypes, clinical characteristics, and drug sensitivity across human cancers. ABC transporter subfamily B (ABCB) family genes exhibited heightened expression across diverse tumors, demonstrating a significant correlation with overall prognosis in pan-cancer contexts. Notably, gene expression levels manifested substantial associations with TME, stemness score, immune subtypes, clinical characteristics, and drug sensitivity in specific cancers, including kidney renal papillary cell carcinoma (KIRP), liver hepatocellular carcinoma (LIHC), and pancreatic adenocarcinoma (PAAD). Within this subset, transporter associated with antigen processing 1 (TAP1), TAP2, and ABCB6 emerged as noteworthy oncogenes. The outcomes of this study contribute to a comprehensive understanding of the implications of ABCB family genes in tumor progression, offering insights into potential therapeutic targets for cancer. Notably, the identification of ABCB6 as a significant oncogene suggests promising avenues for targeted therapies in KIRP, LIHC, and PAAD.

Huayu Qutan Recipe promotes lipophagy and cholesterol efflux through the mTORC1/TFEB/ABCA1-SCARB1 signal axis.

This study aims to investigate the mechanism of the anti-atherosclerosis effect of Huayu Qutan Recipe (HYQT) on the inhibition of foam cell formation. Invivo, the mice were randomly divided into three groups: CTRL group, MOD group and HYQT group. The HYQT group received HYQT oral administration twice a day (20.54 g/kg/d), and the plaque formation in ApoE-/- mice was observed using haematoxylin-eosin (HE) staining and oil red O (ORO) staining. The co-localization of aortic macrophages and lipid droplets (LDs) was examined using fluorescent labelling of CD11b and BODIPY fluorescence probe. Invitro, RAW 264.7 cells were exposed to 50 μg/mL ox-LDL for 48 h and then treated with HYQT for 24 h. The accumulation of LDs was evaluated using ORO and BODIPY. Cell viability was assessed using the CCK-8 assay. The co-localization of LC3b and BODIPY was detected via immunofluorescence and fluorescence probe. LysoTracker Red and BODIPY 493/503 were used as markers for lysosomes and LDs, respectively. Autophagosome formation were observed via transmission electron microscopy. The levels of LC3A/B II/LC3A/B I, p-mTOR/mTOR, p-4EBP1/4EBP1, p-P70S6K/P70S6K and TFEB protein level were examined via western blotting, while SQSTM1/p62, Beclin1, ABCA1, ABCG1 and SCARB1 were examined via qRT-PCR and western blotting. The nuclear translocation of TFEB was detected using immunofluorescence. The components of HYQT medicated serum were determined using Q-Orbitrap high-resolution MS analysis. Molecular docking was employed to identify the components of HYQT medicated serum responsible for the mTOR signalling pathway. The mechanism of taurine was illustrated. HYQT has a remarkable effect on atherosclerotic plaque formation and blood lipid level in ApoE-/- mice. HYQT decreased the co-localization of CD11b and BODIPY. HYQT (10% medicated serum) reduced the LDs accumulation in RAW 264.7 cells. HYQT and RAPA (rapamycin, a mTOR inhibitor) could promote cholesterol efflux, while chloroquine (CQ, an autophagy inhibitor) weakened the effect of HYQT. Moreover, MHY1485 (a mTOR agonist) also mitigated the effects of HYQT by reduced cholesterol efflux. qRT-PCR and WB results suggested that HYQT improved the expression of the proteins ABCA1, ABCG1 and SCARB1.HYQT regulates ABCA1 and SCARB1 protein depending on the mTORC1/TFEB signalling pathway. However, the activation of ABCG1 does not depend on this pathway. Q-Orbitrap high-resolution MS analysis results demonstrated that seven core compounds have good binding ability to the mTOR protein. Taurine may play an important role in the mechanism regulation. HYQT may reduce cardiovascular risk by promoting cholesterol efflux and degrading macrophage-derived foam cell formation. It has been observed that HYQT and ox-LDL regulate lipophagy through the mTOR/TFEB signalling pathway, rather than the mTOR/4EBP1/P70S6K pathway. Additionally, HYQT is found to regulate cholesterol efflux through the mTORC1/TFEB/ABCA1-SCARB1 signal axis, while taurine plays a significant role in lipophagy.

Abstract 174: Cholesterol efflux protein ABCA1 skews macrophages towards an anti-tumor phenotype and consequently impacts breast cancer progression

Abstract With a lifetime risk of approximately 1 in 8, breast cancer maintains in its position as the most prevalent form of cancer and ranks second in terms of cancer-related fatalities in women. The primary cause of mortality is often attributed to the recurrence of metastatic breast cancer. While immune therapy shows some effectiveness, many patients do not exhibit meaningful responses, likely due to immune-suppressive factors present within the tumor microenvironment. These factors include myeloid cells such as Macrophages(MΦ), therefore, there is a strong need to devise strategies to shift (MΦ) from a pro-tumor to an anti-tumor phenotype. Our previous research has uncovered the susceptibility of MΦs to disruptions in cholesterol metabolic balance. Considering these findings, coupled with epidemiological evidence linking elevated plasma cholesterol to unfavorable prognosis, the impact of cholesterol homeostasis in tumor associated MΦs on breast cancer becomes evident. An in-depth computational screen helped us identify ABCA1—a cholesterol efflux protein with elevated mRNA expression associated with increased survival. Beyond cholesterol efflux, ABCA1 also facilitates the movement of cholesterol from the inner membrane layer to the outer layer. Previous work has shown that cholesterol within the inner membrane layer can directly interact with and activate various receptors on the membrane's surface, initiating downstream signaling events. Consequently, the activities of ABCA1 in cholesterol efflux and translocation likely hold substantial regulatory implications. Underscoring the clinical significance of ABCA1 are our findings that heightened ABCA1 expression within breast tumors correlates with augmented levels of cytotoxic T cells, T cell effector enzymes (Prf-1 and Gzmb), and improved survival rates. Crucially, our in vitro investigations indicate that ABCA1 modulates multiple functions of MΦs to adopt an anti-cancer phenotype, encompassing: (1) the ability to infiltrate tumor spheroids, (2) angiogenesis, (3) efferocytosis—an immune-suppressive phagocytic process devoid of antigen presentation, and (4) the expansion, migration, and activity of cytotoxic T cells. ABCA1 transports cholesterol from macrophages to a lipid poor ApoA1 protein and facilitates the formation of nascent HDL via reverse cholesterol transport. We leveraged this mechanism to therapeutically target ABCA1 using ApoA1 mimetics 5A and 4F. Our data so far indicates that these ApoA1 phenocopy ABCA1 overexpression in MΦs. Together, our data provides compelling evidence for the involvement of ABCA1 in the pathophysiology of breast tumors. The anticipated outcomes of this research will establish the basis for the future utilization of ABCA1 and its downstream effects for therapeutic purposes. Citation Format: Shruti V. Bendre, Natalia Krawczynska, Shaunak Bhogale, Erin Weisser, Simon Han, Basel Hajyousif, Avni Singh, Rajendra K C, Yu Wang, Claire P. Schane, Adam T. Nelczyk, Anasuya DasGupta, Hashni E. Gamage, Kevin T. VanBortle, Emad Tajkhorshid, Saurabh Sinha, Wohnwa Cho, Erik R. Nelson. Cholesterol efflux protein ABCA1 skews macrophages towards an anti-tumor phenotype and consequently impacts breast cancer progression [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 174.

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

To validate the adenosine triphosphate (ATP)-binding cassette transporter A1 (ABCA1) expression and distribution in human eyelid tissues and meibomian gland epithelial cells. 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. 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. 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.

Dynamic duo: Kir6 and SUR in KATP channel structure and function

ABSTRACT KATP channels are ligand-gated potassium channels that couple cellular energetics with membrane potential to regulate cell activity. Each channel is an eight subunit complex comprising four central pore-forming Kir6 inward rectifier potassium channel subunits surrounded by four regulatory subunits known as the sulfonylurea receptor, SUR, which confer homeostatic metabolic control of KATP gating. SUR is an ATP binding cassette (ABC) protein family homolog that lacks membrane transport activity but is essential for KATP expression and function. For more than four decades, understanding the structure-function relationship of Kir6 and SUR has remained a central objective of clinical significance. Here, we review progress in correlating the wealth of functional data in the literature with recent KATP cryoEM structures.

Aging and brain free cholesterol concentration on amyloid-β peptide accumulation in guinea pigs.

Alzheimer's disease is a complex multifactorial neurodegenerative disorder wherein age is a major risk factor. The appropriateness of the Hartley guinea pig (GP), which displays high sequence homologies of its amyloid-β (Aβ40 and Aβ42) peptides, Mdr1 and APP(amyloid precursor protein) and similarity in lipid handling to humans, was appraised among 9-40weeks old guinea pigs. Protein expression levels of P-gp (Abcb1) and Cyp46a1 (24(S)-hydroxylase) for Aβ40, and Aβ42 efflux and cholesterol metabolism, respectively, were decreased with age, whereas those for Lrp1 (low-density lipoprotein receptor related protein 1), Rage (receptor for advanced glycation endproducts) for Aβ efflux and influx, respectively, and Abca1 (the ATP binding cassette subfamily A member 1) for cholesterol efflux, were unchanged among the ages examined. There was a strong, negative correlation of the brain Aβ peptide concentrations and Abca1 protein expression levels with free cholesterol. The correlation of Aβ peptide concentrations with Cyp46a1 was, however, not significant, and concentrations of the 24(S)-hydroxycholesterol metabolite revealed a decreasing trend from 20weeks old toward 40weeks old guinea pigs. The composite data suggest a role for free cholesterol on brain Aβ accumulation. The decreases in P-gp and Lrp1 protein levels should further exacerbate the accumulation of Aβ peptides in guinea pig brain.

Inhibition of miR-33a-5p in Macrophage-like Cells In Vitro Promotes apoAI-Mediated Cholesterol Efflux.

Atherosclerosis is caused by cholesterol accumulation within arteries. The intima is where atherosclerotic plaque accumulates and where lipid-laden foam cells reside. Intimal foam cells comprise of both monocyte-derived macrophages and macrophage-like cells (MLC) of vascular smooth muscle cell (VSMC) origin. Foam cells can remove cholesterol via apoAI-mediated cholesterol efflux and this process is regulated by the transporter ABCA1. The microRNA miR-33a-5p is thought to be atherogenic via silencing ABCA1 which promotes cholesterol retention and data has shown inhibiting miR-33a-5p in macrophages may be atheroprotective via enhancing apoAI-mediated cholesterol efflux. However, it is not entirely elucidated whether precisely inhibiting miR-33a-5p in MLC also increases ABCA1-dependent cholesterol efflux. Therefore, the purpose of this work is to test the hypothesis that inhibition of miR-33a-5p in cultured MLC enhances apoAI-mediated cholesterol efflux. In our study, we utilized the VSMC line MOVAS cells in our experiments, and cholesterol-loaded MOVAS cells to convert this cell line into MLC. Inhibition of miR-33a-5p was accomplished by transducing cells with a lentivirus that expresses an antagomiR directed at miR-33a-5p. Expression of miR-33a-5p was analyzed by qRT-PCR, ABCA1 protein expression was assessed via immunoblotting, and apoAI-mediated cholesterol efflux was measured using cholesterol efflux assays. In our results, we demonstrated that lentiviral vector-mediated knockdown of miR-33a-5p resulted in decreasing expression of this microRNA in cultured MLC. Moreover, reduction of miR-33a-5p in cultured MLC resulted in de-repression of ABCA1 expression, which caused ABCA1 protein upregulation in cultured MLC. Additionally, this increase in ABCA1 protein expression resulted in enhancing ABCA1-dependent cholesterol efflux through increasing apoAI-mediated cholesterol efflux in cultured MLC. From these findings, we conclude that inhibiting miR-33a-5p in MLC may protect against atherosclerosis by promoting ABCA1-dependent cholesterol efflux.

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.

Endomembrane-biased dimerization of ABCG16 and ABCG25 transporters determines their substrate selectivity in ABA-regulated plant growth and stress responses

ATP-binding cassette (ABC) transporters are integral membrane proteins that have evolved diverse functions fulfilled via the transport of various substrates. In Arabidopsis, the G subfamily of ABC proteins is particularly abundant and participates in multiple signaling pathways during plant development and stress responses. In this study, we revealed that two Arabidopsis ABCG transporters, ABCG16 and ABCG25, engage in ABA-mediated stress responses and early plant growth through endomembrane-specific dimerization-coupled transport of ABA and ABA-glucosyl ester (ABA-GE), respectively. We first revealed that ABCG16 contributes to osmotic stress tolerance via ABA signaling. More specifically, ABCG16 induces cellular ABA efflux in both yeast and plant cells. Using FRET analysis, we showed that ABCG16 forms obligatory homodimers for ABA export activity and that the plasma membrane-resident ABCG16 homodimers specifically respond to ABA, undergoing notable conformational changes. Furthermore, we demonstrated that ABCG16 heterodimerizes with ABCG25 at the endoplasmic reticulum (ER) membrane and facilitates the ER entry of ABA-GE in both Arabidopsis and tobacco cells. The specific responsiveness of the ABCG16-ABCG25 heterodimer to ABA-GE and the superior growth of their double mutant support an inhibitory role of these two ABCGs in early seedling establishment via regulation of ABA-GE translocation across the ER membrane. Our endomembrane-specific analysis of the FRET signals derived from the homo- or heterodimerized ABCG complexes allowed us to link endomembrane-biased dimerization to the translocation of distinct substrates by ABCG transporters, providing a prototypic framework for understanding the omnipotence of ABCG transporters in plant development and stress responses.

Study of active components and mechanisms mediating the hypolipidemic effect of Inonotus obliquus polysaccharides.

Hyperlipidemia is a multifaceted metabolic disease, which is the major risk factor for atherosclerosis and cardiovascular diseases. Traditional Chinese medicine provides valuable therapeutic strategies in the treatment of hyperlipidemia. Inonotus obliquus has been used in traditional medicine to treat numerous diseases for a long time. To screen and isolate the fractions of I. obliquus polysaccharides (IOP) that can reduce blood lipid in the hyperlipemia animals and cell models, and investigate its mechanisms. The active component IOP-A2 was isolated, purified, and identified. Invivo, rats were randomly divided into blank control group (NG), the high-fat treatment group (MG), lovastatin group (PG), and IOP-A group. Compared with MG, the hyperlipidemic rats treated with IOP-A2 had decreased body weight and organ indexes, with the level of serum total cholesterol (TC), triglyceride (TG), and low-density lipoprotein cholesterol (LDL-C) significantly decreased (p < .05), and level of serum high-density lipoprotein cholesterol (HDL-C) significantly increased (p < .05). Hepatocyte steatosis in hepatic lobules was significantly reduced. Invitro, the accumulation of lipid droplets in the model of fatty degeneration of HepG2 cells was significantly alleviated, and cellular TC and TG content was significantly decreased (p < .01). Moreover, the expression of recombinant cytochrome P450 7A1 (CYP7A1) and Liver X Receptor α (LXRα) were up-regulated (p < .05) both invivo and invitro. The results showed that IOP-A2 may exert its hypolipidemic activity by promoting cholesterol metabolism and regulating the expression of the cholesterol metabolism-related proteins CYP7A1, LXRα, SR-B1, and ABCA1.

Investigating the Effect of Aspirin on apoAI-Induced ATP Binding Cassette Transporter 1 Protein Expression and Cholesterol Efflux in Human Astrocytes.

Neurons need a high amount of cholesterol to maintain the stability of their membrane-rich structures. Astrocytes synthesize and distribute cholesterol to neurons, and ABCA1 is a key mediator of cholesterol efflux to generate HDL for cholesterol transport in the brain. Several studies imply the effect of aspirin on ABCA1 expression in peripheral cells such as macrophages. Here, we compared the effect of aspirin with apoA-I on ABCA1 protein expression and cholesterol efflux in human astrocytes. Human astrocytes were cultured, and the effects of aspirin on the expression and protein levels of ABCA1 were investigated through RT-PCR and Western blot analysis. Additionally, the effect of co-treatment with apoA-I and aspirin on ABCA1 protein level and cholesterol efflux was evaluated. Dose and time-course experiments showed that the maximum effect of aspirin on ABCA1 expression occurred at a concentration of 0.5 mM after 12 h of incubation. RT-PCR and western blot data showed that aspirin upregulates ABCA1 expression by up to 4.7-fold and its protein level by 67%. Additionally, co-treatment with aspirin and apoA-I increased cholesterol release from astrocytes, indicating an additive effect of aspirin on apoAI-mediated cholesterol efflux. The results suggest a potential role of aspirin in increasing ABCA1 expression and cholesterol efflux in astrocytes, similar to the effect of apoA-I. This indicates that aspirin could potentially regulate brain cholesterol balance and can be considered in certain neurological diseases, in particular in some neurological disorders related to cholesterol accumulation such as Alzheimer's disease.

Mass Spectrometry Investigation of Some ATP-Binding Cassette (ABC) Proteins.

Drug resistance remains one of the main causes of poor outcome in cancer therapy. It is also becoming evident that drug resistance to both chemotherapy and to antibiotics is driven by more than one mechanism. So far, there are at least eight recognized mechanisms behind such resistance. In this review, we choose to discuss one of these mechanisms, which is known to be partially driven by a class of transmembrane proteins known as ATP-binding cassette (ABC) transporters. In normal tissues, ABC transporters protect the cells from the toxic effects of xenobiotics, whereas in tumor cells, they reduce the intracellular concentrations of anticancer drugs, which ultimately leads to the emergence of multidrug resistance (MDR). A deeper understanding of the structures and the biology of these proteins is central to current efforts to circumvent resistance to both chemotherapy, targeted therapy, and antibiotics. Understanding the biology and the function of these proteins requires detailed structural and conformational information for this class of membrane proteins. For many years, such structural information has been mainly provided by X-ray crystallography and cryo-electron microscopy. More recently, mass spectrometry-based methods assumed an important role in the area of structural and conformational characterization of this class of proteins. The contribution of this technique to structural biology has been enhanced by its combination with liquid chromatography and ion mobility, as well as more refined labelling protocols and the use of more efficient fragmentation methods, which allow the detection and localization of labile post-translational modifications. In this review, we discuss the contribution of mass spectrometry to efforts to characterize some members of the ATP-binding cassette (ABC) proteins and why such a contribution is relevant to efforts to clarify the link between the overexpression of these proteins and the most widespread mechanism of chemoresistance.

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.

ATP-Binding Cassette Subfamily G Member 2 in Acute Myeloid Leukemia: A New Molecular Target?

Despite the progress in the knowledge of disease pathogenesis and the identification of many molecular markers as potential targets of new therapies, the cure of acute myeloid leukemia remains challenging. Disease recurrence after an initial response and the development of resistance to old and new therapies account for the poor survival rate and still make allogeneic stem cell transplantation the only curative option. Multidrug resistance (MDR) is a multifactorial phenomenon resulting from host-related characteristics and leukemia factors. Among these, the overexpression of membrane drug transporter proteins belonging to the ABC (ATP-Binding Cassette)-protein superfamily, which diverts drugs from their cellular targets, plays an important role. Moreover, a better understanding of leukemia biology has highlighted that, at least in cancer, ABC protein's role goes beyond simple drug transport and affects many other cell functions. In this paper, we summarized the current knowledge of ABCG2 (formerly Breast Cancer Resistance Protein, BCRP) in acute myeloid leukemia and discuss the potential ways to overcome its efflux function and to revert its ability to confer stemness to leukemia cells, favoring the persistence of leukemia progenitors in the bone marrow niche and justifying relapse also after therapy intensification with allogeneic stem cell transplantation.

Genetic and Functional Analyses of Patients with Marked Hypo-High-Density Lipoprotein Cholesterolemia.

This study aimed to analyze two cases of marked hypo-high-density lipoprotein (HDL) cholesterolemia to identify mutations in ATP-binding cassette transporter A1 (ABCA1) and elucidate the molecular mechanism by which these novel pathological mutations contribute to hypo-HDL cholesterolemia in Tangier disease. Wild type and mutant expression plasmids containing a FLAG tag inserted at the C-terminus of the human ABCA1 gene were generated and transfected into HEK293T cells. ABCA1 protein expression and cholesterol efflux were evaluated via Western blotting and efflux assay. The difference in the rate of change in protein expression was evaluated when proteolytic and protein-producing systems were inhibited. In case 1, a 20-year-old woman presented with a chief complaint of gait disturbance. Her HDL-C level was only 6.2 mg/dL. Tangier disease was suspected because of muscle weakness, decreased nerve conduction velocity, and splenomegaly. Whole-exome analysis showed compound heterozygosity for a W484* nonsense mutation and S1343I missense mutation, which confirmed Tangier disease. Cholesterol efflux decreased by a mixture of W484* and S1343I mutations. The S1343I mutation decreased the protein production rate but increased the degradation rate, decreasing the protein levels. This patient also had Krabbe disease. The endogenous ABCA1 protein level of macrophage cell decreased by knocking down its internal galactocerebrosidase.Case 2, a 51-year-old woman who underwent tonsillectomy presented with peripheral neuropathy, corneal opacity, and HDL-C of 3.4 mg/dL. Whole-exome analysis revealed compound heterozygosity for R579* and R1572* nonsense mutations, which confirmed Tangier disease. Case 1 is a new ABCA1 mutation with complex pathogenicity, namely, a W484*/S1343I compound heterozygote with marked hypo-HDL cholesterolemia. Analyses of the compound heterozygous mutations indicated that decreases in ABCA1 protein levels and cholesterol efflux activity caused by the novel S1343I mutation combined with loss of W484* protein activity could lead to marked hypo-HDL cholesterolemia. Galactocerebrosidase dysfunction could also be a potential confounding factor for ABCA1 protein function.

Multifunctional liposomes Co-encapsulating epigallocatechin-3-gallate (EGCG) and miRNA for atherosclerosis lesion elimination.

Atherosclerosis (AS) is a chronic inflammatory disease, characterized by a lipid accumulated plaque. Anti-oxidative and anti-inflammation and lipid metabolism promoting therapeutic strategies have been applied for atherosclerosis treatment. However, the therapeutic effect of a single therapeutic method is limited. It is suggested that a combination of these two strategies could help prevent lipid accumulation caused by inflammation and oxidative stress, and also promote lipid efflux from atherosclerotic plaque, to normalize arteries to the maximum extent. Hence, a strategy involving a multifunctional liposome co-encapsulating an antioxidant and anti-inflammatory drug epigallocatechin-3-gallate (EGCG) and a lipid-efflux-promoting gene miR-223 was established. The system (lip@EGCG/miR-223) could encapsulate miR-223 in core areas of the liposomes to provide a protective effect for gene drugs. Moreover, lip@EGCG/miR-223 was smaller in size (91.28 ± 2.28 nm characterized by DLS), making it easier to target AS lesions, which have smaller vascular endothelial spaces. After being efficiently internalized into the cells, lip@EGCG/miR-223 exhibited excellent antioxidant and anti-inflammatory effects in vitro by eliminating overproduced ROS and decreasing the level of inflammatory cytokines (TNF-α, IL-1β, and MCP-1), which was due to the effect of EGCG. Besides, the lipid-efflux-promoting protein ABCA1 was upregulated when treated with lip@EGCG/miR-223. Through the two therapies mentioned, lip@EGCG/miR-223 could effectively inhibit the formation of foam cells, which are a main component of atherosclerotic plaques. In AS model mice, after intravenous (i.v.) administration, lip@EGCG/miR-223 was effectively accumulated in atherosclerotic plaques, and the distribution of drugs in the heart and aorta compared to that in the kidney was significantly increased when compared with free drugs (the ratio was 6.27% for the free miR-223-treated group, which increased to 66.10% for the lip@EGCG/miR-223-treated group). By decreasing the inflammation level and lipid accumulation, the arterial vessels in AS were normalized, with less macrophages and micro-angiogenesis, when treated with lip@EGCG/miR-223. Overall, this study demonstrated that lip@EGCG/miR-223 could be developed as a potential system for atherosclerosis treatment by a combined treatment of antioxidant, anti-inflammatory, and lipid-efflux-promoting effects, which provides a novel strategy for the safe and efficient management of atherosclerosis.

Decreased expression of ATP-binding cassette protein G1 promotes abnormal adipogenesis of condylar chondrocytes intemporomandibular joint osteoarthritis.

Abnormal lipid metabolism is involved in the development of osteoarthritis (OA). ATP-binding cassette protein G1 (ABCG1) is crucial in mediating the outflow of cholesterol, phosphatidylcholine and sphingomyelin and reducing intracellular lipid accumulation. This study aimed to evaluate whether ABCG1 participates in the abnormal adipogenesis of chondrocytes in osteoarthritic cartilage of temporomandibular joint. Eight-week-old female rats were subjected to unilateral anterior crossbite (UAC) to induce OA in the temporomandibular joint (TMJ). Histochemical staining, immunohistochemical (IHC) staining, and qRT-PCR were performed. Primary condylar chondrocytes of rats were transfected with ABCG1 shRNA or overexpression lentivirus and then stimulated with fluid flow shear stress (FFSS). Cells were collected for oil red O staining, immunofluorescence staining, and qRT-PCR analysis. Abnormal adipogenesis, characterized by increased expression of Adiponectin, CCAAT/enhancer-binding protein α (Cebpα), fatty acid binding protein 4 (Fabp4) and Perilipin1, was enhanced in the degenerative cartilage of TMJ OA in rats with UAC, accompanied by decreased expression of ABCG1. After FFSS stimulation, we observed lipid droplets in the cytoplasm of cultured cells with increased expression of Adiponectin, Cebpα, Fabp4 and Perilipin1 and decreased expression of ABCG1. Knockdown of Abcg1 induced abnormal adipogenesis and differentiation of condylar chondrocytes. Overexpression of ABCG1 alleviated the abnormal adipogenesis and differentiation of condylar chondrocytes induced by FFSS. Abnormal adipogenesis of chondrocytes and decreased ABCG1 expression were observed in degenerative cartilage of TMJ OA. ABCG1 overexpression effectively inhibits the adipogenesis of chondrocytes and thus alleviates TMJ condylar cartilage degeneration.