ATP-binding Cassette Subfamily A Member 1 Research Articles

Mechanisms of reduced Apolipoprotein E4 lipidation in iPSC‐derived astrocytes

AbstractBackgroundCarrying the apolipoprotein E ε4 (APOE4) allele is the highest known genetic risk factor for late‐onset Alzheimer’s disease (LOAD). Although how APOE4 leads to LOAD is not known, dysregulated endo‐lysosomal trafficking and lipid metabolism are key defects associated with APOE4. Cholesterol accumulation in glia instigates intracellular trafficking defects, increases cellular stress, and disrupts secretion. Additionally, enlarged endosomes were observed in the frontal lobes of APOE4‐carrying individuals, decades before the appearance of Aβ fibrilization. Therefore, we asked if cholesterol and endo‐lysosomal trafficking dysregulation in APOE4 carriers were due to differential lipidation of APOE3 and APOE4.MethodLocalization of ATP Binding Cassette Subfamily A Member 1 (ABCA1) in early, late, and recycling endosomal compartments were analyzed in human isogenic induced pluripotent stem cell (iPSC)‐derived neural cells and in cell lines treated with recombinant APOE in microscopic images. Membrane and cytoplasmic ABCA1 were compared using Western blots. Secreted high‐density lipoprotein (HDL) particles containing fluorescently tagged APOE3 or APOE4 were analyzed using ion‐mobility spectrometry. CS‐6253, an ABCA1 agonist peptide, was used to increase APOE lipidation.ResultThe protein levels of ABCA1, which mediates cholesterol and phospholipid efflux to the nascent apolipoprotein particles, were lower in APOE4/4 iPSC‐derived astrocytes compared to astrocytes derived from isogenic APOE3/3 iPSCs. Advanced image analysis revealed lower ABCA1 protein levels in Rab11+ recycling endosomes and less colocalization between ABCA1 and Rab7, a late endosome marker, in APOE4/4 astrocytes than APOE3/3 astrocytes. Consequently, less ABCA1 was detected at the cell membrane. Combined with previous data, these findings suggest APOE4 lipidation was reduced due to reduced ABCA1 activity. Additionally, BHK cells treated with recombinant APOE3 or APOE4 showed differences in ABCA1 localization that were altered by increasing APOE lipidation by activating ABCA1 via CS‐6253. Finally, fluorescently tagged APOE3 and APOE4 were incorporated in HDL particles and were secreted whose sizes were altered after CS‐6253 treatment, suggesting differences in lipidation levels.ConclusionWe demonstrated that diminished APOE4 lipidation is, at least in part, due to dysregulation of endo‐lysosomal trafficking of ABCA1 and that increasing APOE4 lipidation could alleviate cellular defects.

Impact of Ring Finger Protein 20 and Its Downstream Regulation on Renal Tubular Injury in a Unilateral Nephrectomy Mouse Model Fed a High-Fat Diet.

Abnormal lipid metabolism increases the relative risk of kidney disease in patients with a single kidney. Using transcriptome analysis, we investigated whether a high-fat diet leads to abnormalities in lipid metabolism and induces kidney cell-specific damage in unilateral nephrectomy mice. Mice with unilateral nephrectomy fed a high-fat diet for 12 weeks exhibited progressive renal dysfunction in proximal tubules, including lipid accumulation, vacuolization, and cell damage. Ring finger protein 20 (RNF20) is a ligase of nuclear receptor corepressor of peroxisome proliferator-activated receptors (PPARs). The transcriptome analysis revealed the involvement of RNF20-related transcriptome changes in PPAR signaling, lipid metabolism, and water transmembrane transporter under a high-fat diet and unilateral nephrectomy. In vitro treatment of proximal tubular cells with palmitic acid induced lipotoxicity by altering RNF20, PPARα, and ATP-binding cassette subfamily A member 1 (ABCA1) expression. PPARγ and aquaporin 2 (AQP2) expression decreased in collecting duct cells, regulating genetic changes in the water reabsorption process. In conclusion, a high-fat diet induces lipid accumulation under unilateral nephrectomy via altering RNF20-mediated regulation and causing functional damage to cells as a result of abnormal lipid metabolism, thereby leading to structural and functional kidney deterioration.

THU490 Role Of Cholesterol Efflux Pump ABCA1 In Macrophages And Subsequent Modulation Of The Tumor Microenvironment

Abstract Disclosure: S.V. Bendre: None. N. Krawczynska: None. S. Bhogale: None. A. Das Gupta: None. A. Nelczyk: None. H. Vidana Gamage: None. S. Han: None. E. Tajkhorshid: None. S. Sinha: None. W. Cho: None. E.R. Nelson: None. Breast cancer constitutes about 30% of all new female cancers each year. Although there has been an overall decrease in death rates, mortalities associated with recurrent metastatic cancer remain high. Hence, development of targeted therapeutics against metastatic breast cancer is of utmost importance. Although breast cancer is generally considered immunologically “cold”, clinical studies have shown that immunotherapy has potential to improve patient outcomes. One of the challenges of immunotherapy is overcoming the highly immune suppressive tumor microenvironment. Myeloid cells, such as macrophages, which are abundant within the tumor micro-environment, play a key role in cancer cell survival, progression, and metastasis. Several aspects of cholesterol metabolism and regulation have been implicated in breast cancer progression. ABCA1 (ATP Binding Cassette subfamily A member 1) is a membrane bound cholesterol efflux protein, which facilitates cholesterol transport across, as well as between, membrane leaflets. Although implicated in macrophage biology, little is known about how ABCA1 impacts macrophage function in terms of tumor biology. Therefore, the goal of the current work is to determine the effect of altering ABCA1 within macrophages and its subsequent effect on the tumor microenvironment. Intriguingly, our analysis of publicly available transcriptomes indicates that ABCA1 expression within breast tumors is associated with good prognosis, supporting a role for ABCA1 in tumor progression. Important aspects of macrophage function are efferocytosis, antigen presentation, interaction with and activation of T cells, and promotion of angiogenesis. Therefore, we investigated each of these aspects under conditions where ABCA1 expression was manipulated. Our results indicate that knocking down ABCA1 in macrophages decreased the activation and expansion of T cells. Those T cells that were activated, had a decreased anti-cancer cytotoxic response. Over expression of ABCA1 had the opposite effects, supporting our conclusion that ABCA1 in macrophages is critical for normal T cell activation and function. Furthermore, we are finding that ABCA1 is involved in several other aspects of macrophage biology with relevance to tumor progression. Specifically, knockdown of ABCA1 increased the efficiency of efferocytosis, increased angiogenesis, and decreased macrophage infiltration into breast cancer organoids. All these activities suggest that the loss of ABCA1 shifts macrophages into a functional state that is immune-suppressive and pro-tumorigenic. In summary, our results to date indicate that ABCA1 expression within macrophages reduces their pro-tumor functions. Therefore, it will be important to explore this biology in the hopes of developing ABCA1 as a therapeutic target to shape the tumor microenvironment into being less permissive to tumor growth. Presentation: Thursday, June 15, 2023

Role of ATP Binding Cassette Subfamily A Member 1 (ABCA1) in Chemoradiotherapy-induced Renal Injury

Radiation therapy (RT) alone or combined with chemotherapy reduces cholesterol efflux and causes chronic kidney disease (CKD). There is no treatment for CKD except renal replacement strategies such as dialysis or transplantation. We hypothesize that cancer treatment-induced ABCA1 deficiency leads to dysregulation of cholesterol metabolism, making podocytes susceptible and cancerous cells resistant to treatment-induced injuries. To quantify the cell index of LNCaP, 786-0, and Podcytes were grown in an e-plate reader (Roche) for 24 h and then were treated with either enzalutamide (10µM) or sunitinib (1.0 µM) or cyclophosphamide (10µM) with or without RT (4Gy) or ABCA1 inducer (liver-X-receptors agonist (GW3965; Sigma; 10µM). Podocyte cholesterol efflux assay was measured using NBD-cholesterol efflux assay, and expression of ABCA1 and cleaved caspase-3 were measured by western blotting. 10-14-week-old C57BL/6 male and female mice were given bilateral kidney X-irradiation of 4Gy with or without cisplatin (3mg/kg; IV). Functional kidney parameters, histopathological changes, and ultrastructural changes were measured at baseline and 20 weeks after treatment. GFR was measured using a FITC-sinistrin-based transdermal monitor. In vitro studies suggest that after radiation exposure (4Gy and 8Gy), ABCA1 expression decreases in a dose and time-dependent manner in cultured podocytes (p < 0.05), which coincides with reduced cholesterol efflux (p < 0.05) and increased podocyte apoptosis (p < 0.01). In contrast, LXR agonist treatment in vitro prevents reduced ABCA1 expression and cholesterol efflux and prevents podocytes from radiation-induced apoptosis. Our in vitro studies further suggest that Enzalutamide treatment alone reduces the growth of LNCaP and podocytes, and RT (5Gy) plus enzalutamide combination treatment further decreases the growth of LNCaP and podocytes. However, LXR agonist treatment further increased the efficacy of enzalutamide and RT treatment against LNCaP and increased podocyte growth simultaneously. Similarly, Sunitinib with or without RT reduces the growth of renal cancer cells (786-0) and podocytes. LXR agonist treatment further increases the efficacy of the sunitinib and RT against 786-0 cells and simultaneously increases podocyte growth. Cyclophosphamide reduces the growth of the podocytes, and LXR agonist treatment improves the podocyte growth after CP treatment. In vivo studies observed that focal bilateral kidney irradiation with or without cisplatin of C57BL/6 mice induces lipid accumulation in the kidney cortex and increases GBM thickness (p < 0.001), which correlates with decreased Abca1 expression, podocyte number, and GFR. This study shows that LXR agonist treatment protects podocytopathy in vitro and chemotherapy or radiotherapy-induced kidney injury in vivo. ABCA1 may be an important therapeutic target for chemoradiotherapy-induced kidney injuries in cancer patients.

The metabolic adaptation of bile acids and cholesterol after biliary atresia in lamprey via transcriptome-based analysis

Lamprey underwent biliary atresia (BA) at its metamorphosis stage. In contrast to patients with BA who develop progressive disease, lamprey can grow and develop normally, suggesting that lamprey has several adaptations for BA. Here we show that adaptive changes in bile acid and cholesterol metabolism are produced after lamprey BA. Among 1102 differentially expressed genes (DGEs) after BA in lamprey, many are enriched in gene ontology (GO) terms and pathways related to steroid metabolism. We find that among the DGEs related to bile acids and cholesterol metabolism, the expression of cytochrome P450 family 7 subfamily A member 1 (CYP7A1), sodium-dependent taurine cotransport polypeptide (NTCP) are significantly downregulated, whereas nuclear receptor farnesoid X receptor (FXR), multidrug resistance-associated protein 3 (MRP3), 3-hydroxy-3-methylglutaryl-CoA reductase (HMGCR), sterol O-acyltransferase 1 (SOAT1), and ATP binding cassette subfamily A member 1 (ABCA1) are remarkably upregulated. The changes in expression level are also validated by RT-qPCR. Furthermore, the level of high-density lipoprotein-cholesterol (HDL-C) and low-density lipoprotein-cholesterol (LDL-C) in juvenile serum is higher compared to larvae. Taken together, the findings collectively indicate that after BA, lamprey may maintain bile acids and cholesterol homeostasis in liver tissue by inhibiting bile acids synthesis and uptake, promoting its efflux back to circulation, and enhancing cholesterol esterification for storage as lipid droplets and its egress to form nascent HDL (nHDL). Understanding the possible molecular mechanisms of lamprey metabolic adaptation sheds new light on the understanding of the development and treatment of diseases caused by abnormal bile acid and cholesterol metabolism in humans.

Regulation of cholesterol metabolism during high fatty acid–induced lipid deposition in calf hepatocytes

Cholesterol in the circulation is partly driven by changes in feed intake, but aspects of cholesterol metabolism during development of fatty liver are not well known. The objective of this study was to investigate mechanisms of cholesterol metabolism in calf hepatocytes challenged with high concentrations of fatty acids (FA). To address mechanistic insights regarding cholesterol metabolism, liver samples were collected from healthy control dairy cows (n = 6; 7-13 d in milk) and cows with fatty liver (n = 6; 7-11 d in milk). In vitro, hepatocytes isolated from 3 healthy female calves (1 d old) were challenged with or without a mix of 1.2 mM FA to induce metabolic stress. In addition, hepatocytes were processed with 10 µmol/L of the cholesterol synthesis inhibitor simvastatin or 6 µmol/L of the cholesterol intracellular transport inhibitor U18666A with or without the 1.2 mM FA mix. To evaluate the role of cholesterol addition, hepatocytes were treated with 0.147 mg/mL methyl-β-cyclodextrin (MβCD + FA) or 0.147 mg/mL MβCD with or without 10 and 100 µmol/L cholesterol before incubation with FA (CHO10 + FA and CHO100 + FA). In vivo data from liver biopsies were analyzed by 2-tailed unpaired Student's t-test. Data from in vitro calf hepatocytes were analyzed by one-way ANOVA. Compared with healthy cows, blood plasma total cholesterol and plasma low-density lipoprotein cholesterol content in cows with fatty liver was markedly lower, whereas the hepatic total cholesterol content did not differ. In contrast, compared with healthy controls, the triacylglycerol content in the liver and the content of FA, β-hydroxybutyrate, and aspartate aminotransferase in the plasma of cows with fatty liver were greater. The results revealed that both fatty liver in vivo and challenge of calf hepatocytes with 1.2 mM FA in vitro led to greater mRNA and protein abundance of sterol regulatory element binding transcription factor 1 (SREBF1) and fatty acid synthase (FASN). In contrast, mRNA and protein abundance of sterol regulatory element binding transcription factor 2 (SREBF2), acyl coenzyme A-cholesterol acyltransferase, and ATP-binding cassette subfamily A member 1 (ABCA1) were lower. Compared with the FA group, the cholesterol synthesis inhibitor simvastatin led to greater protein abundance of microsomal triglyceride transfer protein and mRNA abundance of SREBF2, 3-hydroxy-3-methylglutaryl-CoA reductase (HMGCR), ACAT2, and lower ABCA1 and FASN protein abundance. In contrast, compared with the FA group, the cholesterol intracellular transport inhibitor U18666A + FA led to greater total cholesterol concentration and greater protein and mRNA abundance of FASN. Compared with the MβCD + FA group, the addition of 10 µmol/L cholesterol led to greater concentration of cholesteryl ester and excretion of apolipoprotein B100, and greater protein and mRNA abundance of ABCA1 and microsomal triglyceride transfer protein, and lower concentration of malondialdehyde. Overall, a reduction in cholesterol synthesis promoted FA metabolism in hepatocytes likely to relieve the oxidative stress caused by the high FA load. The data suggest that maintenance of normal cholesterol synthesis promotes very low-density lipoprotein excretion and can reduce lipid accumulation and oxidative stress in dairy cows that experience fatty liver.

Astaxanthin Alleviates Foam Cell Formation and Promotes Cholesterol Efflux in Ox-LDL-Induced RAW264.7 Cells via CircTPP2/miR-3073b-5p/ABCA1 Pathway

Atherosclerosis (AS) is a common cardiovascular disease and remains the leading cause of death in the world. It is generally believed that the deposition of foam cells in the arterial wall is the main cause of AS. Moreover, promoting cholesterol efflux and enhancing the ability of reverse cholesterol transport (RCT) can effectively inhibit the formation of foam cells, thereby preventing the occurrence and development of AS. Astaxanthin, with a powerful antioxidant ability, has a potential role in the prevention of atherosclerosis, but how it works in preventing atherosclerosis remains unknown. Here, our experimental results suggest that astaxanthin can upregulate the expression of circular RNA tripeptidyl-peptidase II (circTPP2) and eventually promote cholesterol efflux by modulating ATP-binding cassette subfamily A member 1 (ABCA1). The expression of ABCA1 was significantly suppressed after knocking down circTPP2 in macrophage-derived foam cells. In addition, the experimental results showed that circTPP2 could downregulate the expression of microRNA-3073b-5p (miR-3073b-5p), and ABCA1 was identified as the target gene of miR-3073b-5p. In conclusion, the circTPP2/miR-3073b-5p/ABCA1 axis may be the specific mechanism of astaxanthin promoting cholesterol efflux.

Association of pro-inflammatory cytokines, inflammatory proteins with atherosclerosis index in obese male subjects.

Investigation the association of pro-inflammatory markers interleukin (IL)-1β and IL- 10 expression, serum levels of C-reactive protein (CRP), cyclooxygenase-2 (COX2), High-density lipoprotein (HDL), Apolipoprotein A1 (ApoA1), and ATP Binding Cassette Subfamily A Member 1 (ABCA1) inflammatory proteins with atherosclerosis index (homocysteine) in normal-weight and obese male subjects. 59 males including 30 obese (Body mass index (BMI) of≥30kg/m2) and 29 normal-weight (BMI of 18.5-24.9kg/m2) were joined to this study. Plasma levels of IL-1β and IL-10 (pg/mL), CRP (pg/mL), COX-2 (ng/mL), APOA1 (mg/dL), ABCA1 (ng/mL), HDL, Cholesterol, and Triglyceride (TG) (mg/dL), and homocysteine (µmol/L) was measured. Association of these biomarkers with homocysteine was determined. Obese subjects had higher serum levels of IL10, IL1β, CRP, COX-2, TG, and cholesterol concentrations (allp<0.05 except IL-10 and cholesterol) and low levels of HDL, APOA1, and ABCA1 (non-significant differences) in comparison to normal-weight group. Homocysteine levels were high in obese men with no significant differences between the two groups. In obese subjects, homocysteine had a significant inverse correlation with APOA1, ABCA1, and HDL, and a strong and moderate positive correlation was found with CRP and TG levels, respectively. High level of homocysteine and its correlation with inflammation proteins and markers in obese subjects appear to be contributed with atherosclerosis development.

The Functionality of Apigenin as a Novel Cardioprotective Nutraceutical with Emphasize on Regulating Cardiac Micro RNAs:.

Cardiovascular diseases (CVDs) are considered the most common disorder and the leading cause of mortality globally. The etiology of CVDs depends on a variety of genetic and acquired parameters. Nowadays, a dramatic surge appeared in published reports to find the association between microRNAs (miRNAs) and CVDs in order to understand the cause of the disease, rapid diagnosis with the introduction of valid biomarkers, and target as a therapeutic approach. Apigenin is a novel nutraceutical flavonoid that cardioprotective properties are suggested. The current review aimed to evaluate the beneficial features of this phytochemical against CVDs with an emphasis on its ability to regulate the miRNAs. The findings demonstrated that Apigenin could regulate cardiac miRNAs, including miR-103, miR-122-5p, miR-15b, miR-155, and miR-33. Consequently, preventing CVDs is possible through different effects such as the promotion of cholesterol efflux, prevention of hyperlipidemia, alteration in ATP Binding Cassette Subfamily A Member 1 (ABCA1) levels, reducing of cardiocytes apoptosis, and retarding myocytes fibrosis. Also, it can regulate signaling pathways, protect against endothelial dysfunction, maintain oxidative balance, and decrease inflammatory factors and reactive oxygen species. Hence, apigenin regulatory characteristics affecting miRNAs expression could introduce this flavonoid as a novel cardioprotective phytochemical against different CVDs.

A rare case of nephrotic syndrome and Tangier disease.

Rarely, disorders of lipid metabolism cause nephrotic syndrome with progressive kidney disease. Tangier disease is a rare condition belonging to this family of lipid disorders; however, it is not associated with kidney disease. We report a patient presenting with nephrotic syndrome, leading to the unmasking of Tangier disease. A 34-year-old man presented with ankle oedema, nephrotic-range proteinuria and hypoalbuminaemia. Kidney biopsy demonstrated membranous nephropathy with features of immunoperoxidase staining, suggesting a secondary aetiology. Acute serology was negative. Imaging showed lymphadenopathy with splenomegaly suggestive of lymphoproliferative disorder. Bone marrow biopsy revealed foamy macrophages with widespread lipid deposition. Genomic sequencing revealed a pathological homozygous variant for ATP-binding cassette subfamily A member 1 (ABCA1) c.1510-1G > A, consistent with Tangier disease. Review of the ultrastructural kidney biopsy features demonstrated, in addition to membranous subepithelial and intramembranous usual-type electron-dense deposits, intramembranous osmiophilic lipid deposits similar to those in LCAT deficiency. The patient's renal function gradually declined (serum creatinine 133µmol/L); therefore, he was started on rituximab. Metabolic disorders causing nephrotic syndrome are rare and even more so their association with membranous nephropathy. These should be considered in cases with unexplained persistent nephrotic syndrome with progressive kidney disease and lipid deposits on renal biopsy.

Cholesterol efflux regulator ABCA1 exerts protective role against high shear stress-induced injury of HBMECs via regulating PI3K/Akt/eNOS signaling

BackgroundIn brain, microvascular endothelial cells are exposed to various forces, including shear stress (SS). However, little is known about the effects of high shear stress (HSS) on human brain microvascular endothelial cells (HBMECs) and the underlying mechanism. The cholesterol efflux regulator ATP-binding cassette subfamily A member 1 (ABCA1) has been demonstrated to exert protective effect on HBMECs. However, whether ABCA1 is involved in the mechanism underneath the effect of HSS on HBMECs remains obscure. In the present study, a series of experiments were performed to better understand the effect of HSS on cellular processes of HBMECs and the possible involvement of ABCA1 and PI3K/Akt/eNOS in the underlying mechanisms.ResultsHBMECs were subjected to physiological SS (PSS) or high SS (HSS). Cell migration was evaluated using Transwell assay. Apoptotic HBMECs were detected by flow cytometry or caspase3/7 activity. IL-1β, IL-6, MCP-1 and TNF-α levels were measured by ELISA. RT-qPCR and western blotting were used for mRNA and protein expression detection, respectively. ROS and NO levels were detected using specific detection kits. Compared to PSS, HBMECs exhibited decreased cell viability and migration and increased cell apoptosis, increased levels of inflammatory cytokines, and improved ROS and NO productions after HSS treatment. Moreover, HSS downregulated ABCA1 but upregulated the cholesterol efflux-related proteins MMP9, AQP4, and CYP46 and activated PI3K/Akt/eNOS pathway. Overexpression of ABCA1 in HBMECS inhibited PI3K/Akt/eNOS pathway and counteracted the deleterious effects of HSS. Contrary effects were observed by ABCA1 silencing. Inhibiting PI3K/Akt/eNOS pathway mimicked ABCA1 effects, suggesting that ABCA1 protects HBMECs from HSS via PI3K/Akt/eNOS signaling.ConclusionThese results advanced our understanding on the mechanisms of HSS on HBMECs and potentiated ABCA1/PI3K/Akt/eNOS pathway as therapeutic target for cerebrovascular diseases.

Prognostic Model and Immune Infiltration of Ferroptosis Subcluster-Related Modular Genes in Gastric Cancer.

Background Gastric cancer (GC) is one of the gastrointestinal tumors with the highest mortality rate. The number of GC patients is still high. As a way of iron-dependent programmed cell death, ferroptosis activates lipid peroxidation and accumulates large reactive oxygen species. The role of ferroptosis in GC prognosis was underrepresented. The objective was to investigate the role of ferroptosis-related genes (FRGs) in the prognosis and development of GC. Methods Datasets of GC patients were obtained from the Gene Expression Omnibus (GEO) and The Cancer Genome Atlas (TCGA) database that include clinical information and RNA seq data. Through nonnegative matrix factorization (NMF) clustering, we identified and unsupervised cluster analysis of the expression matrix of FRGs. And we constructed the co-expression network between genes and clinical characteristics by consensus weighted gene co-expression network analysis (WGCNA). The prognostic model was constructed by univariate and multivariate regression analysis. The potential mechanisms of development and prognosis in GC were explored by Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis, gene ontology (GO), tumor immune microenvironment (TIME), and tumor mutation burden (TMB). Results Two molecular subclusters with different expression patterns of FRGs were identified, which have significantly different survival states. Ferroptosis subcluster-related modular genes were identified by WGCNA. Based on 8 ferroptosis subcluster-related modular genes (collagen triple helix repeat containing 1 (CTHRC1), podoplanin (PDPN), procollagen-lysine,2-oxoglutarate 5-dioxygenase 2 (PLOD2), glutamine-fructose-6-phosphate transaminase 2 (GFPT2), ATP-binding cassette subfamily A member 1 (ABCA1), G protein-coupled receptor 176 (GPR176), serpin family E member 1 (SERPINE1), dual specificity phosphatase 1 (DUSP1)) and clinicopathological features, a nomogram was constructed and validated for their predictive efficiency on GC prognosis. Through receiver operating characteristic (ROC) analysis, the results showed that the area under the curve (AUC) of 1-, 3-, and 5-year survival were 0.721, 0.747, and 0.803, respectively, indicating that the risk-scoring model we constructed had good prognosis efficacy in GC. The degree of immune infiltration in high-risk group was largely higher than low-risk group. It indicated that the immune cells have a good response in high-risk group of GC. The TMB of high-risk group was higher, which could generate more mutations and was more conducive to the body's resistance to the development of cancer. Conclusion The risk-scoring model based on 8 ferroptosis subcluster-related modular genes has shown outstanding advantages in predicting patient prognosis. The interaction of ferroptosis in GC development may provide new insights into exploring molecular mechanisms and targeted therapies for GC patients.

A Review: Molecular Mechanism of Regulation of ABCA1 Expression.

ATP-binding cassette subfamily A member 1 (ABCA1) protein plays an essential role in a variety of events, such as cholesterol and phospholipid efflux, nascent high-density lipoprotein (HDL) biosynthesis, phospholipid translocation. Thus, there has been much research activity aimed at understanding the molecular mechanisms of regulating ABCA1 expression. In this review, we first discuss ABCA1 structure, tissue distribution, cellular localization, and trafficking, as well as its function. Furthermore, current understanding of the molecular mechanisms involved in the regulation of ABCA1 expression is summarized. ABCA1 transcriptional regulation is mediated by a very complicated system, including nuclear receptor systems, factors binding to other sites in the ABCA1 promoter, cytokines, hormones, growth factors, lipid metabolites, enzymes, and other messengers/factors/pathways. In addition, ABCA1 posttranscriptional regulation is mediated by microRNA, long noncoding RNA, RNA-binding proteins, proteases, fatty acids, PDZ proteins, signaling proteins, and other factors. Compared to the transcriptional regulation of ABCA1, which is well established, the post-transcriptional regulation of ABCA1 expression is poorly understood.

Crocin ameliorates atherosclerosis by promoting the reverse cholesterol transport and inhibiting the foam cell formation via regulating PPARγ/LXR-α

ABSTRACT Crocin (CRO) is feasible in alleviating atherosclerosis (AS), the mechanism of which was therefore explored in the study. High-fat diet (HFD)-induced apolipoprotein E-deficient (ApoE−/−) mice and lysophosphatidic acid (LPA)-treated macrophages received CRO treatment. Treated macrophage viability was determined via MTT assay. In both murine and macrophage, the lipid level and total Cholesterol/Cholesteryl l Ester (TC/CE) levels were quantified by oil-red-O staining and ELISA, respectively. Lipid droplet, aortic plaque formation and collagen deposition were detected via Oil-red-O staining, hematoxylin–eosin staining and Masson staining, respectively. Liver X Receptor-α (LXR-α), Peroxisome Proliferator-Activated Receptor γ (PPARγ), CD68, PCSK9, CD36, ATP Binding Cassette Subfamily A Member 1 (ABCA1), phosphorylated (p)-AKT, and AKT expressions were detected via Western blot, the former three also being detected using Immunohistochemistry and the first being measured by qRT-PCR. CRO decreased HFD-induced weight gain, ameliorated the abnormal serum lipid levels of HFD-treated mice, and inhibited aortic plaque formation and lipid deposition, and increased collagen fibers, with upregulated high-density lipoprotein-cholesterol (HDL-C) and downregulated TC and low-density lipoprotein-cholesterol (LDL-C). CRO alleviated the HFD-induced upregulations of CD68, PCSK9 and CD36 as well as downregulations of PPARγ/LXR-α, ABCA1 and AKT phosphorylation. In LPA-treated macrophages, CRO alone exerted no effect on the viability yet inhibited the lipid droplets formation and downregulated TC/CE levels. Silent LXR-α reversed the effect of CRO on the lipid droplets formation and levels of lipid metabolism-related factors. CRO ameliorated AS by inhibiting foam cells formation and promoting reverse cholesterol transport via PPARγ/LXR-α.

Reverse Cholesterol Transport Pathway and Cholesterol Efflux in Diabetic Retinopathy.

Cholesterol esters, synthesized from cholesterol with long-chain fatty acids, are essential components of plasma lipoproteins and cell membranes that participate in various metabolic processes in the body. Cholesterol can be excreted through the cholesterol reverse transport (RCT) pathway when excessive cholesterol is produced in the extrahepatic cells, which is regulated by the liver X receptor (LXR) and its downstream regulators ATP-binding cassette subfamily A member 1 (ABCA1) and ATP-binding cassette subfamily G member 1 (ABCG1) genes. Abnormal cholesterol metabolism is closely associated with the development of diabetic retinopathy (DR). However, the precise underlying mechanism of the RCT pathway in the pathogenesis of DR is still not fully understood. This review focused on cholesterol metabolism, with a particular emphasis on the RCT pathway and its correlation with the development of DR. Particular attention has been paid to the key regulators of the RCT pathway: LXR, ABCA1, and ABCG1 genes and their potential therapeutic targets in the management of DR.

Amentoflavone prevents ox-LDL-induced lipid accumulation by suppressing the PPARγ/CD36 signal pathway

The formation of fat-laden foam cells plays an important role in the initiation and progression of atherosclerosis (AS). Amentoflavone (AF) is found in various traditional Chinese medicines, such as ginkgo biloba, which are used to treat cardiovascular diseases (CVDs). We aimed to explore the potential effects and mechanisms of AF on lipid accumulation, and its possible application in atherosclerotic cardiovascular disease (ASCVD). Cellular models of lipid accumulation were established by treatment of HUASMCs and THP-1 cells with oxidized low-density lipoprotein (ox-LDL). Cell viability, lipid accumulation, and ox-LDL uptake were assessed. Small interfering RNAs (siRNAs) and overexpression plasmids were used to reveal the hierarchical correlations of regulatory pathways. AF reduced the lipid accumulation and ox-LDL uptake induced by ox-LDL, and reduced the expression levels of cluster of differentiation 36 (CD36) and peroxisome proliferator-activated receptor gamma (PPARγ) proteins, while the expression level of ATP binding cassette subfamily A member 1 (ABCA1) increased. Knockdown of PPARγ or CD36 with siRNAs prevented ox-LDL-induced lipid accumulation. Overexpression of CD36 or PPARγ promoted the lipid accumulation induced by ox-LDL and eliminated the effect of AF on ox-LDL-induced lipid accumulation. Overall, AF prevents ox-LDL-induced lipid accumulation by suppressing the PPARγ/CD36 signaling pathway.

Morroniside Promotes PGC-1α-Mediated Cholesterol Efflux in Sodium Palmitate or High Glucose-Induced Mouse Renal Tubular Epithelial Cells.

Lipid deposition is an etiology of renal damage caused by lipid metabolism disorder in diabetic nephropathy (DN). Thus, reducing lipid deposition is a feasible strategy for the treatment of DN. Morroniside (MOR), an iridoid glycoside isolated from the Chinese herb Cornus officinalis Sieb. et Zucc., is considered to be an effective drug in inhibiting oxidative stress, reducing inflammatory response, and countering apoptosis. To explore the protective mechanism of MOR in attenuating renal lipotoxicity in DN, we investigated the effect of MOR on an in vitro model of lipid metabolism disorder of DN established by stimulating mouse renal tubular epithelial cells (mRTECs) with sodium palmitate (PA) or high glucose (HG). Oil Red O and filipin cholesterol staining assays were used to determine intracellular lipid accumulation status. Results revealed that PA or HG stimulation inhibited the expressions of peroxisome proliferator-activated receptor γ coactivator 1α (PGC-1α), liver X receptors (LXR), ATP-binding cassette subfamily A member 1 (ABCA1), ABCG1, and apolipoprotein E (ApoE) in mRTECs as evidenced by western blot and quantitative real-time PCR, resulting in increased intracellular lipid deposition. Interestingly, MOR upregulated expressions of PGC-1α, LXR, ABCA1, ABCG1, and ApoE, thus reducing cholesterol accumulation in mRTECs, suggesting that MOR might promote cholesterol efflux from mRTECs via the PGC-1α/LXR pathway. Of note, silencing PGC-1α reversed the promotive effect of MOR on PA- or HG-induced cellular cholesterol accumulation. In conclusion, our results suggest that MOR has a protective effect on mRTECs under high lipid or high glucose conditions, which may be related to the promotion of intracellular cholesterol efflux mediated by PGC-1α.

Two putative probiotic strains improve diet‐induced hypercholesterolemia through modulating intestinal cholesterol uptake and hepatic cholesterol efflux

Two putative probiotic strains, Lacticaseibacillus (Lc.) rhamnosus BFE5264 and Lactiplantibacillus (Lp.) plantarum NR74, have been shown to suppress cholesterol uptake and promote cholesterol efflux in Caco-2 cells. However, an in vivo beneficial effect of these strains on plasma cholesterol levels has not been verified yet; neither have the underlying mechanisms of regulating cholesterol metabolism clarified thus far. This study has focused on these two aspects. A murine model has been used, and the animals receiving a high-fat/high-cholesterol diet showed elevated plasma cholesterol levels. However, supplementation of Lc. rhamnosus BFE5264 and Lp. plantarum NR74 resulted in the down regulation of Niemann-Pick C1-like 1 (NPC1L1) in the intestine in addition to counteracting the diet-induced suppression of low-density lipoprotein receptor expression in the liver. ATP Binding Cassette Subfamily A Member 1 (ABCA1) was only significantly increased upon administration of Lc. rhamnosus BFE5264. The present findings demonstrate that supplementation with Lc. rhamnosus BFE5264 and Lp. plantarum NR74may improve diet-induced hypercholesterolemia by suppression of cholesterol absorption in the small intestine and by supporting the regulation of cholesterol metabolism in the liver. This work contributes to understanding the beneficial effects of probiotics on host cholesterol metabolism and underlying mechanisms related to hypercholesterolemia.

Protective role of ABCA1 in ischemic preconditioning is mediated by downregulation of miR-33-5p and miR-135-5p

Ischemic preconditioning (IPC) significantly reduces ischemia–reperfusion injury in the brain by inducing ischemic tolerance. Although emerging evidence suggests that microRNAs (miRNAs) contribute to the pathogenesis of brain ischemia and IPC-induced neuroprotection, the role of miRNAs and their underlying mechanisms are still unclear. IPC was induced in male C57BL/6 mice by brief bilateral common carotid artery occlusion. After 24 h, mice underwent transient middle cerebral artery occlusion followed by 3 h of reperfusion. Expression levels of messenger RNAs (mRNAs) and proteins were examined in the ipsilateral cortex, and mimics and inhibitors of selective miRNAs were transfected into Neuro-2a cells before oxygen–glucose deprivation (OGD). Post-IPC miRNA expression profiling identified neuroprotection-associated changes in miRNA expression in the ipsilateral cortex after ischemic stroke. Among them, miR-33-5p and miR-135b-5p were significantly downregulated by IPC. Inhibition of miR-33-5p and miR-135b-5p expression protected Neuro-2a cells from OGD-induced apoptosis. Inhibition of these two miRNAs significantly increased mRNA and protein levels of ATP-binding cassette subfamily A member 1 (ABCA1), and a binding assay showed that these two miRNAs showed specificity for Abca1 mRNA. Overexpression of ABCA1 decreased the Bax/Bcl2 mRNA ratio and activation of caspase-9 and caspase-3, whereas knockdown of ABCA1 expression increased the Bax/Bcl2 mRNA ratio and the percentage of Neuro-2a cells with a loss of mitochondrial membrane potential after OGD-treatment. In conclusion, ABCA1 expression is regulated by miR-33-5p and miR-135b-5p. Increased ABCA1 expression following IPC exerts a protective influence against cerebral ischemia via suppression of a mitochondria-dependent apoptosis pathway.

Protective effects of phenethyl isothiocyanate on foam cell formation by combined treatment of oxidized low-density lipoprotein and lipopolysaccharide in THP-1 macrophage.

Accumulation of cholesterol‐laden macrophage foam cells characteristic of early stage atherosclerotic lesions. Phenethyl isothiocyanate (PEITC) is a naturally occurring isothiocyanate found in cruciferous vegetables that has reported a variety of activities including antioxidant and anti‐inflammatory properties. However, the protective effect of PEITC on foam cell formation and its precise mechanism is not yet clear. Therefore, we investigated whether PEITC suppresses foam cell formation and regulates the expression of genes related to lipid accumulation, cholesterol efflux, and inflammation in THP‐1 derived‐macrophages. We exposed THP‐1 derived‐macrophages to oxidized low‐density lipoprotein (ox‐LDL) (20 μg/mL) and lipopolysaccharide (LPS) (500 ng/ml) to mimic foam cell formation. Here, PEITC downregulated the expression of lectin‐like oxidized low‐density lipoprotein receptor‐1 (LOX‐1), cluster of differentiation 36 (CD36), scavenger receptor A1 (SR‐A1), and nuclear factor‐κB (NF‐κB), while upregulated ATP binding cassette subfamily A member 1 (ABCA1)/liver‐X‐receptor α (LXR‐α)/peroxisome proliferator‐activated receptor gamma (PPARγ) and sirtuin 1 (SIRT1) expression compared to co‐treated with ox‐LDL and LPS. Taken together, PEITC, at least in part, inhibits foam cell formation and reduces lipid accumulation in foam cells. Therefore, we suggest that PEITC may be a potential candidate for the treatment and prevention of vascular inflammation and atherosclerosis.