Several new drug targets of anti-atherosclerosis, emerging in the recent years, such as PPAR agonists, cholesteryl ester transfer protein (CETP) inhibitors, infusion of apolipoprotein A-I (apoA-I), liver X receptor (LXR) activators and phospholipid transfer protein (PLTP) inhibitors etc were reviewed.
Apolipoprotein A-I ; therapeutic use ; Atherosclerosis ; drug therapy ; metabolism ; Benzoates ; chemistry ; therapeutic use ; Benzylamines ; chemistry ; therapeutic use ; Cholesterol Ester Transfer Proteins ; antagonists & inhibitors ; metabolism ; DNA-Binding Proteins ; agonists ; metabolism ; Humans ; Liver X Receptors ; Molecular Structure ; Orphan Nuclear Receptors ; Oxazines ; chemistry ; therapeutic use ; Peroxisome Proliferator-Activated Receptors ; agonists ; metabolism ; Phenylpropionates ; chemistry ; therapeutic use ; Quinolines ; chemistry ; therapeutic use ; Receptors, Cytoplasmic and Nuclear ; agonists ; metabolism

AIMTo investigate the liver X receptors agonists T0901317's effect on expression of FAT/CD36 gene mRNA in adult human skeletal muscle cell.

METHODSMyotubes from humans were exposed to different T0901317 concentrations (0, 0.5, and 1.0 micromol/L) for 24 hours before experiments were performed. Then the expression of FAT/CD36 mRNA in skeletal muscle cell of each experimental group was detected by SYBR Green I real-time quantitative polymerase chain reaction. The relative data were compared among groups by 2-delta delta Ct method.

RESULTS(1) The Ct mean of control group, T0901317 (0.5 micromol/L) group, T0901317 (1 micromol/L) group were analyzed and there was significant difference (P < 0.01). (2) The expression of FAT/CD36 mRNA with liver X receptors agonists T0901317 in human skeletal muscle cell in the T0901317 (0.5 micromol/L) group and T0901317 (1 micromol/L) group were 2.91 times and 3.03 times than the control group.

CONCLUSIONThe expression of FAT/CD36 mRNA in human skeletal muscle cell afer the treatment of liver X receptors agonists T0901317 is increased, so we may propose that T0901317 may increase the risk of resistance in adult human skeletal muscle.

Adult ; CD36 Antigens ; genetics ; metabolism ; Cells, Cultured ; Female ; Humans ; Hydrocarbons, Fluorinated ; pharmacology ; Liver X Receptors ; Male ; Muscle, Skeletal ; cytology ; metabolism ; Orphan Nuclear Receptors ; agonists ; RNA, Messenger ; genetics ; metabolism ; Sulfonamides ; pharmacology

OBJECTIVETo investigate the effect of liver X receptor agonist T0901317 on transforming growth factor-β1 (TGF-β1)-induced expression of α-smooth muscle actin (α-SMA) in normal human lung fibroblasts.

METHODSPrimary normal human lung fibroblast isolated from the lung specimens of lung cancer patients by explant culture technique were identified with immunostaining for vimentin and keratin. The cells in passages 4 to 10 were treated with T0901317 and/or TGF-β1, and RT-PCR, Western blotting and immunofluorescence assay were used to detect α-SMA expression in the fibroblasts.

RESULTSLung fibroblast expressed vimentin but not keratin. The results of RT-PCR, Western blotting and immunofluorescence assay all showed that normal human lung fibroblasts constitutively expressed α-SMA under baseline condition, and TGF-β1 at 5 ng/ml induced a significant upregulation of α-SMA both at the mRNA and protein levels. Liver X receptor agonist T0901317 (5 µg/ml) significantly inhibited TGF-β1-induced upregulation of α-SMA expression.

CONCLUSIONLiver X receptor agonist T0901317 can inhibit the upregulation of α-SMA in normal human lung fibroblasts induced by TGF-β1, suggesting the potential value of liver X receptor agonist in the treatment of lung fibrosis.

Actins ; metabolism ; Cells, Cultured ; Female ; Fibroblasts ; drug effects ; metabolism ; Humans ; Hydrocarbons, Fluorinated ; pharmacology ; Liver X Receptors ; Lung ; cytology ; Middle Aged ; Orphan Nuclear Receptors ; agonists ; RNA, Messenger ; genetics ; Sulfonamides ; pharmacology ; Transforming Growth Factor beta1 ; pharmacology

The nuclear receptors, steroid and xenobiotic receptor (SXR) and constitutive androstane receptor (CAR) play important functions in mediating lipid and drug metabolism in the liver. The present study demonstrates modulatory actions of estrogen in transactivations of SXR-mediated liver X receptor response element (LXRE) and CAR-mediated phenobarbital response element (PBRU). When human estrogen receptor (hERalpha) and SXR were exogenously expressed, treatment with either rifampicin or corticosterone promoted significantly the SXR-mediated transactivation of LXRE reporter gene in HepG2. However, combined treatment with estrogen plus either rifampicin or corticosterone resulted in less than 50% of the mean values of the transactivation by rifampicin or corticosterone alone. Thus, it is suggested that estrogen may repress the SXR-mediated transactivation of LXRE via functional cross-talk between ER and SXR. The CAR-mediated transactivation of PBRU was stimulated by hERalpha in the absence of estrogen. However, the potentiation by CAR agonist, TCPOBOP, was significantly repressed by moxestrol in the presence of ER. Thus, ER may play both stimulatory and inhibitory roles in modulating CAR-mediated transactivation of PBRU depending on the presence of their ligands. In summary, this study demonstrates that estrogen modulates transcriptional activity of SXR and CAR in mediating transactivation of LXRE and PBRU, respectively, of the nuclear receptor target genes through functional cross-talk between ER and the corresponding nuclear receptors.
Corticosterone/pharmacology ; Estrogens/*metabolism ; Ethinyl Estradiol/analogs & derivatives/pharmacology ; Hep G2 Cells ; Humans ; Liver/*metabolism ; Orphan Nuclear Receptors/metabolism ; Phenobarbital/metabolism ; Pyridines/pharmacology ; Receptor Cross-Talk ; Receptors, Cytoplasmic and Nuclear/agonists/*metabolism ; Receptors, Steroid/*metabolism ; Response Elements ; Rifampin/pharmacology ; Transcriptional Activation/*drug effects/physiology

Liver X receptor (LXR), a member of the superfamily of nuclear receptors, plays an important role in the activation of transcription factors involved in cholesterol metabolism, glucose homeostasis inflammation and lipogenesis. It is shown that LXR agnoists have the potentiality to be used as drugs for the prevention and treatment of atherosclerosis, which is its best investigated therapeutic indication. There are many compounds being studied in preclinical evaluation and biological assay. This paper will review briefly the LXR agonists in recent years.
ATP-Binding Cassette Transporters ; metabolism ; Amines ; chemical synthesis ; chemistry ; pharmacology ; Animals ; Atherosclerosis ; drug therapy ; metabolism ; Benzimidazoles ; chemical synthesis ; chemistry ; pharmacology ; Cholesterol ; analogs & derivatives ; pharmacology ; Glucose ; analogs & derivatives ; pharmacology ; Humans ; Lipid Metabolism ; Lipogenesis ; Liver X Receptors ; Orphan Nuclear Receptors ; agonists ; physiology ; Quinolines ; chemical synthesis ; chemistry ; pharmacology ; Sterol Regulatory Element Binding Protein 1 ; metabolism

Hepatic steatosis is common in obese individuals with hyperinsulinemia and is an important hepatic manifestation of metabolic syndrome. Sterol regulatory binding protein-1c (SREBP-1c) is a master regulator of lipogenic gene expression in the liver. Hyperinsulinemia induces transcription of SREBP-1c via activation of liver X receptor (LXR) and specificity protein 1 (Sp1). Cilostazol is an antiplatelet agent that prevents atherosclerosis and decreases serum triglyceride levels. However, little is known about the effects of cilostazol on hepatic lipogenesis. Here, we examined the role of cilostazol in the regulation of SREBP-1c transcription in the liver. The effects of cilostazol on the expression of SREBP-1c and its target genes in response to insulin or an LXR agonist (T0901317) were examined using real-time RT-PCR and western blot analysis on cultured hepatocytes. To investigate the effect of cilostazol on SREBP-1c at the transcriptional level, transient transfection reporter assays and electrophoretic mobility shift assays (EMSAs) were performed. Cilostazol inhibited insulin-induced and LXR-agonist-induced expression of SREBP-1c and its downstream targets, acetyl-CoA carboxylase and fatty acid synthase, in cultured hepatocytes. Cilostazol also inhibited activation of the SREBP-1c promoter by insulin, T0901317 and Sp1 in a luciferase reporter assay. EMSA analysis showed that cilostazol inhibits SREBP-1c expression by repressing the binding of LXR and Sp1 to the promoter region. These results indicate that cilostazol inhibits insulin-induced hepatic SREBP-1c expression via the inhibition of LXR and Sp1 activity and that cilostazol is a negative regulator of hepatic lipogenesis.
Animals ; Cells, Cultured ; Hep G2 Cells ; Hepatocytes/drug effects/*metabolism ; Humans ; Hydrocarbons, Fluorinated/pharmacology ; Insulin/pharmacology ; Lipogenesis ; Mice ; Mice, Inbred C57BL ; Orphan Nuclear Receptors/agonists/*metabolism ; Promoter Regions, Genetic ; Protein Binding ; Rats ; Sp1 Transcription Factor/*metabolism ; Sterol Regulatory Element Binding Protein 1/genetics/*metabolism ; Sulfonamides/pharmacology ; Tetrazoles/*pharmacology

BACKGROUNDABCA7 is a member of the ABCA subfamily that shows a high degree of homology to ABCA1 and, like ABCA1, mediates cellular cholesterol and phospholipid release by apolipoproteins when transfected in vitro. However, expression of ABCA7 has been shown to be downregulated by increased cellular cholesterol while ABCA1 was upregulated.

METHODSThe underlying mechanism for this effect was examined in ABCA1 or ABCA7-transfected HEC293. Lipid content in the medium and cells was determined by enzymatic assays. Gene expression was quantitated by real time PCR, and protein content was determined by Western blotting.

RESULTSWhile ABCA7 mRNA was decreased by 25-hydroxycholesterol treatment, ABCA1 was apparently increased. Treatment with the synthetic LXR agonist T0901317 (T09) upregulated ABCA1 expression and apoAI-mediated cellular lipid release in ABCA1-transfected HEC293 cells, but ABCA7 expression and cellular lipid release in ABCA7-transfected HEC293 cells showed no obvious changes.

CONCLUSIONThe ABCA7 gene is regulated by sterol in a direction opposite to that of ABCA1.

ATP Binding Cassette Transporter 1 ; analysis ; genetics ; physiology ; ATP-Binding Cassette Transporters ; analysis ; genetics ; physiology ; Amino Acid Sequence ; Apolipoprotein A-I ; physiology ; Gene Expression Regulation ; HEK293 Cells ; Humans ; Hydrocarbons, Fluorinated ; pharmacology ; Hydroxycholesterols ; pharmacology ; Lipid Metabolism ; Liver X Receptors ; Molecular Sequence Data ; Orphan Nuclear Receptors ; agonists ; Sulfonamides ; pharmacology