GW4064, an agonist of farnesoid X receptor (FXR), represses CYP3A4 expression in human hepatocytes by inducing small heterodimer partner (SHP) expression

DMD # 62836

17β-Estradiol up-regulates UDP-glucuronosyltransferase 1A9 expression via estrogen receptor α

AbstractUDP-glucuronosyltransferase 1A9 (UGT1A9) is a major phase II enzyme responsible for elimination of drugs and endogenous molecules. Clinical data have shown increased elimination of UGT1A9 substrates in pregnant women or oral contraceptive users, but the role of estrogen in the regulation of UGT1A9 expression remains unknown. In this study, we investigated the effect of 17β-estradiol (E2) on UGT1A9 expression and the role of ERα in the transcriptional regulation of UGT1A9. E2 significantly increased UGT1A9 promoter activity in HepG2 cells in the presence of ERα. UGT1A9 induction by E2 was abrogated by antiestrogen ICI182,780 in HepG2 cells that constitutively express ERα. Results from transient transfection of ERα mutants into HepG2 cells demonstrated that mutation at DNA-binding domain of ERα abrogates increased UGT1A9 promoter activity by E2. Deletion and mutation assays of UGT1A9 promoter revealed a putative ERE located within −2262/−1987 region. Examination of healthy human liver tissues revealed significantly higher UGT1A9 expression in women as compared to men. Together, these findings provide a mechanistic basis for the previous clinical reports and may shed a light on identifying sources for inter-individual variability in UGT1A9-mediated drug metabolism

High Fat Diet Feeding Alters Expression of Hepatic Drug-metabolizing Enzymes in Mice

Abbreviations CAR, constitutive androstane receptor; CYP, cytochrome P450; DMEs, drug-metabolizing enzymes; FGF, fibroblast growth factor; FXR, farnesoid X receptor; Hes6, hes family bHLH transcription factor 6; HFD, high-fat diet; HNF4α, hepatocyte nuclear factor 4α; PXR, pregnane X receptor; qRT-PCR, quantitative real time-PCR; Pck1, phosphoenolpyruvate carboxykinase 1; Oatp1a1, organic anion-transporting polypeptides 1a1; SHP, small heterodimer partner; Tg-CYP2D6, CYP2D6-humanized transgenic mouse. DMD #75655 3 ABSTRACT Medical conditions accompanying obesity often require drug therapy, but whether and how obesity alters the expression of drug-metabolizing enzymes and thus drug pharmacokinetics is poorly defined. Previous studies have shown that high fat diet (HFD) feeding and subsequent obesity in mice lead to altered expression of transcriptional regulators for cytochrome P450 (CYP) 2D6, including hepatocyte nuclear factor 4α (HNF4α, a transcriptional activator of CYP2D6) and small heterodimer partner (SHP, a transcriptional repressor of CYP2D6). The objective of this study is to examine whether diet-induced obesity alters CYP2D6 expression by modulating HNF4α and SHP expression. Male CYP2D6-humanized transgenic (Tg-CYP2D6) mice were fed with HFD or matching control diet for 18 weeks. Hepatic mRNA expression of CYP2D6 decreased to a small extent in HFD group (by 31%), but the differences in CYP2D6 protein and activity levels in hepatic S9 fractions were found insignificant between the groups. While hepatic SHP expression did not differ between the groups, HNF4α mRNA and protein levels decreased by ~30% in HFD group. Among major mouse endogenous Cyp genes, Cyp1a2 and Cyp2c37 showed significant decreases in HFD group while Cyp2e1 expression did not differ between groups. Cyp2b10 and Cyp3a11 expression was higher in HFD group, with corresponding 2.9-fold increases in hepatic CYP3A activities in HFD-fed mice. Together, these results suggest that obesity has minimal effects on CYP2D6-mediated drug metabolism while it modulates the expression of mouse endogenous CYPs in a gene-specific manner

Role of p-glycoprotein in oral bioavailability of its substrates: Tacrolimus as a model compound.

Role of p-glycoprotein in oral bioavailability of its substrates: Tacrolimus as a model compound

Altered Cytochrome P450 Expression in Mice during Pregnancy

Abstract Human pregnancy is known to influence hepatic drug metabolism in a CYP-specific manner. However, the underlying mechanisms remain unknown in part due to a lack of experimental models to study altered drug metabolism during pregnancy. In this study, we examined how pregnancy influences expression of major Cyp isoforms in mice. Liver tissues were isolated from female FVB/N mice at different gestational time points: pre-pregnancy, 7, 14 and 21 days of pregnancy, and 7 days post partum. mRNA expression levels of major Cyp isoforms (Cyp1a2, Cyp2a5, Cyp2b10, Cyp2c37, Cyp2d22, Cyp2e1, Cyp3a11, and Cyp3a41) in the liver tissues were determined by quantitative real-time PCR. While Cyp2a5 expression was unchanged, Cyp3a41 expression was significantly increased during pregnancy. In contrast, expression of Cyp1a2, Cyp2c37, Cyp2d22, Cyp2e1, and Cyp3a11 was all decreased. Expression of Cyp2d22 and Cyp2e1 isoforms correlated with that of PPARα in the mouse livers, suggesting potential involvement of PPARα in downregulation of the Cyp expression during pregnancy. Effects of pregnancy on expression of other Cyp mouse isoforms as well as on in vivo drug disposition remain to be characterized. These results provide a guide for future studies on CYP regulation during pregnancy

GW4064, an Agonist of Farnesoid X Receptor, Represses CYP3A4 Expression in Human Hepatocytes by Inducing Small Heterodimer Partner Expression s

ABSTRACT Farnesoid X receptor (FXR) functions as a regulator of bile acid and lipid homeostasis and is recognized as a promising therapeutic target for metabolic diseases. The biologic function of FXR is mediated in part by a small heterodimer partner (SHP); ligandactivated FXR enhances SHP expression, and SHP in turn represses the activity of multiple transcription factors. This study aimed to investigate the effect of FXR activation on expression of the major drug-metabolizing enzyme CYP3A4. The effects of 3-(2,6-dichlorophenyl)-4-(39-carboxy-2-chlorostilben-4-yl)oxymethyl-5-isopropylisoxazole (GW4064), a synthetic agonist of FXR, on the expression and activity of CYP3A4 were examined in primary human hepatocytes by using quantitative real-time polymerase chain reaction and S9 phenotyping. In human hepatocytes, treatment of GW4064 (1 mM) for 48 hours resulted in a 75% decrease in CYP3A4 mRNA expression and a 25% decrease in CYP3A4 activity, accompanied by ∼3-fold increase in SHP mRNA expression. In HepG2 cells, SHP repressed transactivation of CYP3A4 promoter by pregnane X receptor (PXR), constitutive androstane receptor (CAR), and glucocorticoid receptor. Interestingly, GW4064 did not repress expression of CYP2B6, another target gene of PXR and CAR; GW4064 enhanced CYP2B6 promoter activity. In conclusion, GW4064 represses CYP3A4 expression in human hepatocytes, potentially through upregulation of SHP expression and subsequent repression of CYP3A4 promoter activity. Clinically significant drugdrug interaction involving FXR agonists and CYP3A4 substrates may occur

Clostridium aestuarii sp. nov., from tidal flat sediment

A strictly anaerobic, halophilic, motile, endospore-forming, rod-shaped bacterium, designated strain HY-45-18(T), was isolated from a sediment sample of a tidal flat in Korea. The isolate produced butyric acid, propionic acid, glycerol and H-2 as fermentation end products from glucose. Strain HY-45-18(T) T is halophilic as it was unable to grow in the absence of sea salts. A 16S rRNA gene sequence analysis clearly indicated that the tidal flat isolate is a member of cluster I of the order Clostridiales, which contains the type species of Clostridium, Clostridium butyricum. The closest phylogenetic neighbour of strain HY-45-18(T) was Clostridium ganghwense KCTC 5146(T) (96.5 % 16S rRNA gene sequence similarity). Several phenotypic characteristics can be readily used to differentiate the isolate from phylogenetically related clostridia. Therefore, strain HY-45-18(T) represents a novel species of the genus Clostridium, for which the name Clostridium aestuarii sp. nov. is proposed. The type strain is HY-45-18(T) (= IMSNU 40129(T) = KCTC 5147(T)= JCM 13194(T)).

Clostridium ganghwense sp. nov., isolated from tidal flat sediment

A Gram-negative, strictly anaerobic, halophilic, motile, sporulating and rod-shaped bacterium, T designated strain HY-42-06(T), was isolated from tidal flat sediment from Ganghwa Island in South Korea. The isolate produced glycerol, ethanol and CO2 as fermentation end-products from glucose. Strain HY-42-06(T) grew optimally at 35 degrees C, pH 7(.)5 and 3% (w/v) artificial sea salts. No growth was observed in the absence of sea salts. In phylogenetic analyses based on 16S rRNA gene sequence, strain HY-42-06(T) showed a distinct phyletic line within the members of cluster I of the order Clostridiales. The closest phylogenetic neighbour to strain HY-42-06(T) was Clostridium novyi ATCC 17861(T) (94(.)91% 16S rRNA gene sequence similarity). Several phenotypic characters readily differentiate the tidal flat isolate from phylogenetically related clostridia. On the basis of polyphasic evidence, strain HY-42-06(T) should be classified as a representative of a novel species, for which the name Clostridium ganghwense sp. nov. is proposed. The type strain is HY-42-06(T) (=IMSNU 40127(T) = KCTC 5146(T)=jCM 13193(T)).