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Objective@#To explore the impact of arsenic on cholesterol efflux and the expression of ATP-binding cassette, sub-family A, member 1 ( ABCA1 ), ATP-binding cassette transporter G1 ( ABCG1 ), and scavenger receptor class B member I ( SRBI ) in macrophages, so as to provide the evidence for the mechanism of arsenic induced atherosclerosis.@*Methods@#The human myeloid leukemia mononuclear cells ( THP-1 ), induced by phorbol myristate acetate, and mouse primary macrophages were treated with 0, 0.625, 1.25, 2.5 and 5 μmol/L NaAsO2 for 48 hours. Then the cells treated with 2.5 μmol/L NaAsO2 were changed to arsenic free mediums for 48 hours and collected every 12 hours to analyze the time effect of arsenic. The expression levels of ABCA1, ABCG1 and SRBI were determined by quantitative polymerase chain reaction and western blotting. Cholesterol efflux rates were measured by 3H isotope tracer. @*Results@#Arsenic significantly down-regulated the expression levels of ABCA1 and ABCG1, and cholesterol efflux in a dose-dependent manner. The levels of ABCA1 mRNA decreased by 69% and 72%, the levels of ABCG1 mRNA decreased by 42% and 34%, and the rate of cholesterol efflux decreased by 55% and 59% in THP-1 and mouse primary macrophages cells treated with 5 μmol/L NaAsO2 ( all P<0.05 ). Arsenic had no significant effect on SRBI expression ( all P>0.05 ). Arsenic inhibited ABCA1 expression and cholesterol efflux in THP-1 in a time-dependent manner. Compared with cells before the exposure of arsenic, the level of ABCA1 mRNA and the rate of cholesterol efflux in THP-1 bottomed at 48 hours by 43% and 42%, and gradually recovered when arsenic was removed. @*Conclusions@#Arsenic inhibits cholesterol efflux by down-regulating the expression of ABCA1 and ABCG1 in macrophages.
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AIM:To study whether homocysteine (Hcy) inhibits the expression of ATP-binding cassette transporter A1 (ABCA1) and ATP-binding cassette transporter G1 (ABCG1) by microRNA-33 (miRNA-33) signaling, and reduces the efficiency of reverse cholesterol transport (RCT).METHODS:RAW264.7 macrophages were induced by oxidized low-density lipoprotein (ox-LDL) to establish foam cell model.Oil red O staining was used to determine whether the model was established successfully.miRNA-33 mimics and miRNA-33 inhibitor were transfected into the cells by Lipofectamine 2000, and the cells were exposed to Hcy at concentration of 5 mmol/L for 24 h.The intracellular lipid droplets were observed by Oil red O staining.The expression of ABCA1 and ABCG1 at mRNA and protein levels was determined by real-time PCR and Western blot.The cellular cholesterol content was analyzed by HPLC, and effluent rate of cholesterol was detected by the method of liquid scintillation counting.RESULTS:Compared with blank control group, the lipid content in miRNA-33 mimics group was increased, and the expression of ABCA1 and ABCG1 at mRNA and protein levels was decreased (P<0.05).The intracellular cholesterol content was increased gradually (P<0.05) , and the cellular cholesterol efflux rate was gradually decreased (P<0.05) in miRNA-33 mimics group.Compared with blank control group, the testing results in miRNA-33 inhibitor group were the opposition of those in miRNA-33 mimics group (P<0.05).No difference of the above indexes among blank control group, miRNA-33 mimics-NC group and miRNA-33 inhibitor-NC group was observed.CONCLUSION:Hcy inhibits the mRNA and protein expression of ABCA1 and ABCG1 through miRNA-33 signaling, and reduces the efficiency of RCT in RAW264.7 macrophage-derived foam cells.
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Objective To investigate the effects of the polymorphisms in the promoter of ATP binding cassette transporter (ABCG1) on the transcription activity,and the relationship of the polymorphisms with the susceptibility to coronary artery disease (CAD).Methods A case-control study was conducted,217 CADpatients and 142 controls were enrolled in this study.Thesingle nucleotide polymorphisms (SNPs) in the promoter of ABCG1 were identified by sequencing.The promoter haplotypes of ABCG1 were determined with allele specific primer sequencing or Gene cloning sequencing.The transcription activity of the promoter haplotypes were evaluated with dual luciferase reporter system.The frequency of SNPs and haplotypes were analyzed between CAD group and the control group,premature CAD and non-premature CAD group,as well as multivessel lesion and single vessel lesion group.The frequency distribution was compared between two groups with x2 test or Fisher exact test.The difference of the luciferase activity was compared between groups by t-test or one-way analysis of variance.Results Only 3 SNPs were found in ABCG1 promoter sequence of about 1 000 bp upstream of the transcription start site,which are-384 (A/G),-204 (A/C) and-134 (T/G),respectively.The 3 SNPs are in strong linkage disequilibrium,Tajima's D =2.655 (P ＜ 0.01),which constituted 3 haplotypes.There was no significant difference in SNPs and haplotype frequency between the CAD group and the normal control group,and the severity of vascular disease and the early onset of coronary heart disease were not associated with the polymorphisms in ABCG1 promoter.There was no significant difference in the transcriptional activity of the three constitutive promoter haplotypes,but the transcriptional activity was notably elevated as the GAT haplotype was mutated into GAG (P ＜ 0.05).Conclusions The 3 SNPs identified in ABCG1 promoter region A did not alter the promoter activity.There was no significant correlation between the frequency distribution of SNPs and promoter haplotypes and the susceptibility to CAD.
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The adenosine triphosphate (ATP)-binding cassette transporter G1 (ABCG1),a member of the superfamily of ATP-binding cassette transporters,is involved in the efflux of cholesterol and phospholipids from cells,and it maintains the intracellular hpid homeostasis.ABCG1 deficiency results in foam cell formation,endothelial dysfunction,and inflammatory reaction,and it further leads to the development and progression of atherosclerosis.However,the role of ABCG1 in atherosclerosis in animal experiments and human studies is still a debatable matter.In this paper,the recent findings on the role of ABCG1 in atherosclerotic disease are reviewed.
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This study was designed to identify inducers of ATP-binding cassette transporter A1(ABCA1) and CD36 and lysosomal integral membrane protein-II analogous-1(CLA-1) and to evaluate the in vitro effect of the active compound on lipid metabolism. Among 20000 compounds screened, E23869 was found as a positive hit using cell-based high throughput screening models. The up-regulating activities of E23869 in ABCA1p-LUC and CLA-1p-LUC HepG2 cells were 196% and 198%, respectively. The EC50 values of E23869 in ABCA1p-LUC and CLA-1p-LUC HepG2 cells were 0.25 μmol·L-1 and 0.66 μmol·L-1, respectively. E23869 significantly upregulated the protein levels of ABCA1, scavenger receptor class B type I (SR-BI)/CLA-1 and ATP-binding cassette transporter G1(ABCG1) in both macrophages RAW264.7 and L02 cells by Western blotting analysis. Foam cell assay showed that E23869 inhibited lipids accumulations in macrophages RAW264.7. Cholesterol efflux assay showed that E23869 induced HDL-mediated cholesterol efflux in macrophages RAW264.7. Moreover, E23869 up-regulated ABCA1, SR-BI/CLA-1 and ABCG1 expressions through activation of PPARα and PPARγ. In addition, E23869 weakly promoted in vitro differentiation of mouse preadipocytes 3T3-L1. In conclusion, E23869 up-regulated ABCA1, SR-BI/CLA-1 and ABCG1 expressions to promote cholesterol efflux, which is a good leading compound for regulation of lipid metabolism.
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Liver X receptor (LXR) plays an important role in reverse cholesterol transport (RCT), and activation of LXR could reduce atherosclerosis. In the present study we used a cell-based screening method to identify new potential LXRβ agonists. A novel benzofuran-2-carboxylate derivative was identified with LXRβ agonist activity: E17110 showed a significant activation effect on LXRβ with an EC50 value of 0.72 μmol/L. E17110 also increased the expression of ATP-binding cassette transporter A1 (ABCA1) and G1 (ABCG1) in RAW264.7 macrophages. Moreover, E17110 significantly reduced cellular lipid accumulation and promoted cholesterol efflux in RAW264.7 macrophages. Interestingly, we found that the key amino acids in the LXRβ ligand-binding domain had distinct interactions with E17110 as compared to TO901317. These results suggest that E17110 was identified as a novel compound with LXRβ agonist activity in vitro via screening, and could be developed as a potential anti-atherosclerotic lead compound.
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AIM: To investigate the signal transduction mechanism of Chlamydia pneumoniae (Cpn) in down-regulating the expression of ATP binding cassette A1 (ABCA1) and ATP binding cassette G1 (ABCG1),the key molecules in cholesterol efflux and atherogenesis,from THP-1-derived macrophages. METHODS: Cpn was propagated in Hep-2 cells. THP-1 monocytes were induced into macrophages by 160 nmol/L phorbol myristate acetate (PMA) for 48 h,and were randomly allocated into 4 groups to incubate continually: control group,50 mg/L low density lipoprotein (LDL); Cpn infection group,Cpn (1×10~6 IFU) and 50 mg/L LDL; Cpn and SP600125 (a special JNK inhibiter) group,THP-1 macrophages were previously treated with different concentrations (1-20 μmol/L) of SP600125 for 1 h,and then infected with Cpn (1×10~6 IFU) and 50 mg/L LDL; SP600125 group,SP600125(20 μmol/L)and 50 mg/L LDL. The expressions of ABCA1/ABCG1 and peroxisome proliferator-activated receptor γ (PPARγ) from each group were detected then. The cholesterol efflux was detected by enzyme-fluorescence. The expressions of ABCA1/ABCG1 and PPARγ mRNA and protein were determined by RT-PCR and Western blotting,respectively. RESULTS: Cpn not only down-regulated the ABCA1/ABCG1 expression,but also down-regulated the expression of PPARγ,which regulated the ABCA1/ABCG1 genes transcriptions. However,the mentioned effects of Cpn infection were restrained by the special JNK inhibitor SP600125 in a dose-dependent manner. CONCLUSION: Chlamydia pneumoniae may down-regulate ABCA1/ABCG1 expression from THP-1-derived macrophages via JNK-PPARγ signal transduction pathway.