Pregnane X receptor (PXR) is key transcription factors which mainly regulate the expression of CYP3A genes. At the molecular level, PXR has been revealed the protection mechanism of the body against xenochemicals and a major mode of the drug-drug interactions. Besides playing an important role in drug metabolism and interactions, PXR and its target genes also play an important role in maintaining normal physiological function and homeostasis. Therefore, it is necessary to study the regulation of PXR and its related pharmacological effects of TCM and natural products, and to provide new clues for the new pharmacological pathway.
Animals ; Drug Evaluation, Preclinical ; Drugs, Chinese Herbal ; pharmacology ; Gene Expression ; drug effects ; Humans ; Receptors, Steroid ; antagonists & inhibitors ; genetics ; metabolism

OBJECTIVETo screen a group of traditional Chinese medicines with effect on pregnane X receptor (PXR)-mediated transcription regulation of P450 3A4 (CYP3A4); and to study whether they can induce the expression of CYP3A4 with a dose, time-dependent manner.

METHODTransient cotransfection reporter gene assays were performed with pCI-hPXR-neo, pGL3-CYP3A4-Luc and beta-galactosidase expression plasmid in HepG2 cells.

RESULTRhizoma Curcumae, Atractylodes lancea, A. macrocaphala and Poria cocos could induce transcriptional expression of CYP3A4. In the dose-effect study, 24 h after induction, 500 mg x L(-1) Rhizoma Curcumae, A. lancea, A. macrocaphala and Poria cocos, respectively, could induce the CYP3A4 gene expression with (6.82 +/- 0.09), (6.76 +/- 0.20), (5.49 +/- 0.13) and (4.97 +/- 0.07) folds, as compared with 0.1% DMSO treated cells. In the time-effect study, 500 mg x L(-1) Rhizoma curcumae, A. lancea, A. macrocaphala and Poria cocos for 48 h could induce the CYP3A4 gene expression with (7.74 +/- 0.54), (7.34 +/- 0.10), (5.54 +/- 0.11) and (5.32 +/- 0.18) folds, compared with 0.1% DMSO treated cells.

CONCLUSIONRhizoma Curcumae, A. lancea, A. macrocaphala and Poria cocos could induce the expression of CYP3A4 gene transcription through activating PXR.

Cell Line, Tumor ; Cytochrome P-450 CYP3A ; genetics ; Drugs, Chinese Herbal ; pharmacology ; Humans ; Receptors, Steroid ; metabolism ; Transcription, Genetic ; drug effects

Animals ; Disease Models, Animal ; Endometriosis ; metabolism ; pathology ; Female ; Matrix Metalloproteinase 9 ; genetics ; Mice ; Mice, Nude ; Microscopy, Electron ; RNA, Messenger ; analysis ; Receptors, Steroid ; analysis ; Vascular Endothelial Growth Factor A ; genetics

In order to study effects of ginseng on the metabolism of drug belong to CYP3A4 substrate, screening of pregnane X receptor activation from ginsenosides was performed by reporter assay. Based on PXR-CYP3A stable translation cell lines, 13 ginsenosides were screened for pregnane X receptor activation by reporter assays, and RIF as the positive control. The effect of ginsenosides Rg1 onCYP3A4 mRNA expression was also investigated by RT-PCR. The PXR-CYP3A stable translation cell lines had good response to RIF, and the EC50 is 2.51 micro mol x L(-1). When the condition of final concentration was 10 micromol x L(-1), ginsenoside F2 and protopanaxatriol had moderate inductive effects on PXR. Panaxotriol, Rg2, pseudoginsenoside F11, Rg1, ginsenoside and Rb3 had inhibitory effects on PXR. Ginsenoside Rf1, Rg3, Rh2 and protopanaxdiol had no obvious effects on PXR. Rg1 down-regulated CYP3A4 mRNA expression in a concentration-dependent manner. Activation of pregnane X receptor by ginsenosides may influence the metabolism of drug belong to CYP3A4 substrate, and cause ginseng-drug interactions.
Cytochrome P-450 CYP3A ; genetics ; metabolism ; Drug Interactions ; Ginsenosides ; pharmacology ; Hep G2 Cells ; Humans ; RNA, Messenger ; metabolism ; Receptors, Steroid ; agonists ; antagonists & inhibitors ; genetics ; Sapogenins ; pharmacology ; Transfection

The aim of this study was to obtain the soluble protein of human pregnane X receptor ligand binding domain (PXRLBD) through the coexpression of PXRLBD and 88 amino acids of steroid receptor coactivator-1 (SRC88) and apply the protein to constructing a new model of screening PXR ligands. Expression plasmid of pETDuet-1-SRC88-PXRLBD was constructed and transformed into Escherichia coli Rosetta (DE3) to coexpress PXRLBD and SRC88 via induction by IPTG at low temperature. Then an equilibrium dialysis model was constructed to study the interaction between PXRLBD and drugs including clotrimazole and dexamethasone, using HPLC as the analysis method. The results showed that the soluble protein of PXRLBD was obtained and the HPLC data indicated that clotrimazole bound to PXRLBD, while dexamethasone did not bind to PXRLBD, which indicated the successful establishment of a new method for studying the interaction between PXR and drugs. The new method may be useful in the screening of PXR ligands in vitro.
Clotrimazole ; metabolism ; Dexamethasone ; metabolism ; Dialysis ; methods ; Drug Interactions ; Escherichia coli ; genetics ; metabolism ; Histone Acetyltransferases ; genetics ; metabolism ; Humans ; Ligands ; Nuclear Receptor Coactivator 1 ; Plasmids ; Protein Binding ; Receptors, Steroid ; genetics ; metabolism ; Transcription Factors ; genetics ; metabolism ; Transformation, Genetic

Animals ; Autophagy/genetics* ; Cholesterol/metabolism* ; Gene Expression Regulation ; Integrases/metabolism* ; Leydig Cells/metabolism* ; Male ; Mice, Knockout ; Multienzyme Complexes/metabolism* ; Phosphoproteins/metabolism* ; Primary Cell Culture ; Progesterone Reductase/metabolism* ; RNA Splicing Factors/metabolism* ; Scavenger Receptors, Class B/metabolism* ; Sequestosome-1 Protein/metabolism* ; Signal Transduction ; Sirtuin 1/genetics* ; Sodium-Hydrogen Exchangers/metabolism* ; Steroid 17-alpha-Hydroxylase/metabolism* ; Steroid Isomerases/metabolism* ; Testosterone/genetics*

OBJECTIVETo clone and identify the proteins involved in regulating the transcription of hTERT and study the role of genes in both hTERT transcription and telomerase activity.

METHODSThe full cDNA of COUP-TFII was cloned from HeLa cDNA library by hTERT promoter-based yeast one-hybrid assay and then in-frame inserted into His-tag fusion expression vector pEK318. The His-tag COUP-TFII fusion proteins were purified by Ni-NTA chromatography. The interaction of COUP-TFII with hTERT promoter in vitro was identified by electrophoretic mobility shift assay and Footprint. The role of COUP-TFII in both hTERT transcription and telomerase activity were probed through Luciferase reporter assay, Northern blot, and TRAP-PCR ELISA.

RESULTSCOUP-TFII could firmly bind to the downstream E-box and the other two binding sites in hTERT promoter. Luciferase reporter assay indicated COUP-TFII could suppress hTERT promoter activity and stable introduction of COUP-TFII into HeLa cells also decreased both endogenous hTERT transcription and telomerase activity.

CONCLUSIONThe human COUP-TFII can firmly bind to hTERT promoter, and inhibit telomerase activity through decreasing hTERT transcription. It will greatly facilitate understanding of telomerase regulation in normal and cancer cells.

COUP Transcription Factor II ; COUP Transcription Factors ; Cloning, Molecular ; DNA, Complementary ; genetics ; DNA-Binding Proteins ; genetics ; pharmacology ; E-Box Elements ; genetics ; HeLa Cells ; Humans ; Promoter Regions, Genetic ; RNA, Messenger ; biosynthesis ; genetics ; Receptors, Steroid ; genetics ; Telomerase ; biosynthesis ; genetics ; metabolism ; Transcription Factors ; genetics ; pharmacology ; Transcription, Genetic ; Yeasts ; genetics

This paper is to report the development of a high-throughput in vitro system to screen hPXR/CAR mediated CYP2B6 drug inducers, and the application of it into the quick determination of induction activity toward CYP2B6 by various commonly used traditional Chinese medicines (TCMs) extract. Dual reporter gene assays were performed. The hPXR/CAR expression vectors and the reporter vector pGL3-CYP2B6-Luc involved in the distal and proximal promoters of CYP2B6 were co-transfected into HepG2 cells. Relative luciferase activities in cell lysate were analyzed after 48 h treatment of blank vehicle or drugs to determine the induction activity toward CYP2B6 by various commonly used TCMs extract. The positive hPXR/hCAR activators rifampicin and CITCO were applied to make sure that the reporter gene model was successfully established. Then 5 kinds of commonly used TCM extracts and 1 herbal compound were successfully investigated, some were found to activate hPXR or hCAR and therefore have the potential to induce CYP2B6 enzyme. This is the first domestic article to report the hCAR3-mediated CYP2B6 induction model and the establishment of a reporter gene system for hPXR/CAR-mediated CYP2B6 induction can be an effective and systemic in vitro method to investigate the drug inducers of CYP2B6 and to explain the mechanism involved.
Aryl Hydrocarbon Hydroxylases ; genetics ; metabolism ; Cytochrome P-450 CYP2B6 ; Drugs, Chinese Herbal ; isolation & purification ; pharmacology ; Genes, Reporter ; Genetic Vectors ; Hep G2 Cells ; High-Throughput Screening Assays ; Humans ; Luciferases ; genetics ; metabolism ; Oximes ; pharmacology ; Plants, Medicinal ; chemistry ; Plasmids ; Receptors, Cytoplasmic and Nuclear ; genetics ; metabolism ; Receptors, Steroid ; genetics ; metabolism ; Rifampin ; pharmacology ; Thiazoles ; pharmacology ; Transfection

Animals ; Bridged Bicyclo Compounds ; metabolism ; Cytochrome P-450 CYP3A ; biosynthesis ; genetics ; Drug Design ; Drug Interactions ; Enzyme Induction ; Humans ; Lithocholic Acid ; metabolism ; Phloroglucinol ; analogs & derivatives ; metabolism ; Receptors, Cytoplasmic and Nuclear ; genetics ; metabolism ; physiology ; Receptors, Steroid ; genetics ; physiology ; Signal Transduction ; Terpenes ; metabolism ; Transcription Factors ; genetics ; metabolism

OBJECTIVETo investigate whether kaempferol stimulates pregnane X receptor (PXR)-mediated transcription of CYP3A4.

METHODSTransient cotransfection reporter gene assay was performed with PXR expression plasmid and a reporter plasmid containing the XREs in the CYP3A4 gene promoter in HepG(2)cells.

RESULTSKaempferol activated PXR-mediated transcription of CYP3A4 in a dose, time-dependent manner. In the dose-response study, kaempferol exposure at concentrations of 1.0 x 10(-3), 1.0 x 10(-2), 0.1, 1.0 and 10.0 mol/L for 24 h increased CYP3A4 transcription by (1.31+/-0.27), (1.45+/-0.36), (1.96+/-0.50), (2.90+/-1.07) and (7.93+/-0.75) fold, respectively compared with 0.1% DMSO (P<0.05). The results from time-course study showed that after 48 h exposure 1.0 and 10.0 mol/L of kaempferol enhanced the transcription of CYP3A4 by (3.73+/-1.21) fold and (8.42+/-1.47) fold, respectively.

CONCLUSIONKaempferol may be a human CYP3A4 gene inducer through PXR, and may affect the metabolism of a large number of substrates of CYP3A4 simultaneously taken.

Carcinoma, Hepatocellular ; pathology ; Cytochrome P-450 CYP3A ; Cytochrome P-450 Enzyme System ; biosynthesis ; genetics ; Dose-Response Relationship, Drug ; Genes, Reporter ; Humans ; Kaempferols ; pharmacology ; Liver Neoplasms ; pathology ; Receptors, Steroid ; metabolism ; Transcription, Genetic ; Transfection ; Tumor Cells, Cultured