The regulation of UDP-glucuronosyltransferase genes by tissue-specific and ligand-activated transcription factors

Hepatic Gene Expression and Metabolite Profiles of Androstenone and Skatole Relative to Plasma Estrone Sulfate Levels in Boars

Testicular steroids can alter the activity and expression of enzymes within the liver and may influence the metabolism of skatole and androstenone, which are responsible for boar taint. Plasma levels of estrone sulfate (E1S) are indicative of the steroidogenic capacity of the boar and are variable between animals of similar live weights at slaughter. This study aimed to characterize the relationship between steroidogenic capacity and the metabolism of boar taint compounds by relating plasma E1S levels at slaughter weight to the expression levels of genes regulating the metabolism of androstenone and skatole, along with their respective metabolite profiles. RT-qPCR was used to evaluate gene expression in the liver. Hepatocytes were also isolated and treated with androstenone or skatole, with metabolite levels in the incubation media quantified by high-performance liquid chromatography. Plasma E1S levels ranged from 2.2-108.5 ng/mL and were positively correlated with overall skatole metabolism (p = 0.038), the production of metabolites 3-methyloxindole (p = 0.026) and 3-hydroxy-3-methyloxindole (p = 0.036), and expression levels of key genes involved in skatole metabolism, specifically CYP2C33 (p = 0.0042), CYP2C49 (p = 0.022), and CYB5R1 (p = 0.017). There was no association between androstenone metabolism and plasma E1S concentrations; however, there was evidence of possible co-regulation amongst genes involved in the metabolism of androstenone, skatole, and estrogens. These findings indicate that steroidogenic capacity is related to the rate of skatole, but not androstenone metabolism, in slaughter-weight boars.

Comparison of in vitro thyroxine (T4) metabolism between Wistar rat and human hepatocyte cultures

In vitro assays remain relatively new in exploring human relevance of liver, in particular nuclear receptor-mediated perturbations of the hypothalamus-pituitary-thyroid axis seen in rodents, mainly in the rat. Consistent with in vivo data, we confirm that thyroid hormone thyroxine metabolism was 9 times higher in primary rat hepatocytes (PRH) than in primary human hepatocytes (PHH) cultured in a 2D sandwich (2Dsw) configuration. In addition, thyroxine glucuronide (T4-G) was by far the major metabolite formed in both species (99.1% in PRH and 69.7% in PHH) followed by thyroxine sulfate (T4-S, 0.7% in PRH and 18.1% in PHH) and triiodothyronine/reverse triiodothyronine (T3/rT3, 0.2% in PRH and 12.2% in PHH). After a 7-day daily exposure to orphan receptor-mediated liver inducers, T4 metabolism was strongly increased in PRH, almost exclusively through increased T4-G formation. These results were consistent with the inductions of glucuronosyltransferase Ugt2b1 and canalicular transporter Mrp2. PHH also responded to activation of the three nuclear receptors, with mainly induction of glucuronosyltransferase UGT1A1 and canalicular transporter MRP2. Despite this, T4 disappearance rate and secreted T4 metabolites were only slightly increased in PHH. Overall, our data highlight that cryopreserved hepatocytes in 2Dsw culture allowing long-term exposure and species comparison are of major interest in improving liver-mediated human safety assessment.

Recent Advances in Hepatic Metabolic Regulation by the Nuclear Factor Rev-erbɑ

Rev-erbɑ (NR1D1) is a nuclear receptor superfamily member that plays a vital role in mammalian molecular clocks and metabolism. Rev-erbɑ can regulate the metabolism of drugs and the body's glucose metabolism, lipid metabolism, and adipogenesis. It is even one of the important regulatory factors regulating the occurrence of metabolic diseases (e.g., diabetes, fatty liver). Metabolic enzymes mediate most drug metabolic reactions in the body. Rev-erbɑ has been recognized to regulate drug metabolic enzymes (such as Cyp2b10 and Ugt1a9). Therefore, this paper mainly reviewed that Rev-erbɑ regulates I and II metabolic enzymes in the liver to affect drug pharmacokinetics. The expression of these drug metabolic enzymes (up-regulated or down-regulated) is related to drug exposure and effects/ toxicity. In addition, our discussion extends to Rev-erbɑ regulating some transporters (such as P-gp, Mrp2, and Bcrp), as they also play an essential role in drug metabolism. Finally, we briefly describe the role and mechanism of nuclear receptor Rev-erbɑ in lipid and glucose homeostasis, obesity, and metabolic disorders syndrome. In conclusion, this paper aims to understand better the role and mechanism of Rev-erbɑ in regulating drug metabolism, lipid, glucose homeostasis, obesity, and metabolic disorders syndrome, which explores how to target Rev-erbɑ to guide the design and development of new drugs and provide scientific reference for the molecular mechanism of new drug development, rational drug use, and drug interaction.

Exposure to environmentally relevant concentrations of TnBP results in tissue-specific bio-accumulation and inhibits growth of silver carp (Hypophthalmichthys molitrix)

Tri-n-butyl phosphate (TnBP) is commonly used as flame retardant and rubber plasticizer, and has been widely detected in aquatic organisms and natural waters. However, the potential toxicity of TnBP in fish remains unclear. In the present study, silver carp (Hypophthalmichthys molitrix) larvae were treated with environmentally relevant concentrations (100 or 1000 ng/L) of TnBP for 60 d and then they were depurated in clean water for 15 d, and the accumulation and depuration of the chemical in six tissues of silver carp were measured. Furthermore, effects on growth were evaluated and potential molecular mechanisms were explored. Results indicated that TnBP could be rapidly accumulated and depurated in silver carp tissues. In addition, the bio-accumulation of TnBP displayed tissue-specificity, where intestine contained the greatest and vertebra had the smallest level of TnBP. Furthermore, exposure to environmentally relevant concentrations of TnBP led to time- and concentration-dependent growth inhibition of silver carp, even though TnBP was completely depurated in tissues. Mechanistic studies suggested that exposure to TnBP up- and down-regulated the expression of ghr and igf1 in liver, respectively, and increased GH contents in plasma of silver carp. TnBP exposure also up-regulated the expression of ugt1ab and dio2 in liver, as well as decreased T4 contents in plasma of silver carp. Our findings provide direct evidence of health hazards of TnBP to fish in natural waters, calling for more attention of environmental risks of TnBP in aquatic environment.

Role of Plant-Derived Compounds in the Molecular Pathways Related to Inflammation

Inflammation is the primary response to infection and injury. Its beneficial effect is an immediate resolution of the pathophysiological event. However, sustained production of inflammatory mediators such as reactive oxygen species and cytokines may cause alterations in DNA integrity and lead to malignant cell transformation and cancer. More attention has recently been paid to pyroptosis, which is an inflammatory necrosis that activates inflammasomes and the secretion of cytokines. Taking into consideration that phenolic compounds are widely available in diet and medicinal plants, their role in the prevention and support of the treatment of chronic diseases is apparent. Recently, much attention has been paid to explaining the significance of isolated compounds in the molecular pathways related to inflammation. Therefore, this review aimed to screen reports concerning the molecular mode of action assigned to phenolic compounds. The most representative compounds from the classes of flavonoids, tannins, phenolic acids, and phenolic glycosides were selected for this review. Our attention was focused mainly on nuclear factor-κB (NF-κB), nuclear factor erythroid 2-related factor 2 (Nrf2), and mitogen-activated protein kinase (MAPK) signaling pathways. Literature searching was performed using Scopus, PubMed, and Medline databases. In conclusion, based on the available literature, phenolic compounds regulate NF-κB, Nrf2, and MAPK signaling, which supports their potential role in chronic inflammatory disorders, including osteoarthritis, neurodegenerative diseases, cardiovascular, and pulmonary disorders.

Dysregulated hepatic UDP-glucuronosyltransferases and flavonoids glucuronidation in experimental colitis

Glucuronidation catalyzed by UDP-glucuronosyltransferases (UGTs) is one of the most important phase II mechanisms, facilitating drug clearance via conjugation of glucuronic acid with polar groups of xenobiotics. Accumulating evidence suggests that IBDs impact drug disposition, but whether and how IBDs regulate UGTs and drug glucuronidation remains undefined. In this study, we aim to investigate the expression of UGTs and drug glucuronidation in experimental colitis. Given that glucuronidation occurs primarily in the liver, we analyzed the mRNA changes in hepatic UGTs with a DSS-induced mouse colitis model. Twelve UGTs were downregulated in the liver of colitis mice including UGT1A1 and UGT1A9 (two representative UGTs). Colitis in mice downregulated UGT1A1 and UGT1A9 in the liver but not in small intestine, colon, and kidney. We also established that the downregulation of UGTs was attributed to the disease itself rather than the DSS compound. Moreover, colitis-reduced UGT1A1 and UGT1A9 lead to dampened baicalein and puerarin glucuronidation. PXR was the only UGT regulator significantly downregulated in colitis mice, suggesting dysregulation of PXR is associated with the downregulation of UGT1A1 and UGT1A9, thereby potentially resulting in dysfunction of baicalein and puerarin glucuronidation. Collectively, we establish that UGTs and glucuronidation are dysregulated in colitis, and this effect may cause variation in drug responsiveness in IBDs.

A transcriptional regulatory network of HNF4α and HNF1α involved in human diseases and drug metabolism

HNF4α and HNF1α are core transcription factors involved in the development and progression of a variety of human diseases and drug metabolism. They play critical roles in maintaining the normal growth and function of multiple organs, mainly the liver, and in the metabolism of endogenous and exogenous substances. The twelve isoforms of HNF4α may exhibit different physiological functions, and HNF4α and HNF1α show varying or even opposing effects in different types of diseases, particularly cancer. Additionally, the regulation of CYP450, phase II drug-metabolizing enzymes, and drug transporters is affected by several factors. This article aims to review the role of HNF4α and HNF1α in human diseases and drug metabolism, including their structures and physiological functions, affected diseases, regulated drug metabolism genes, influencing factors, and related mechanisms. We also propose a transcriptional regulatory network of HNF4α and HNF1α that regulates the expression of target genes related to disease and drug metabolism.

Drug metabolism and drug transport of the 100 most prescribed oral drugs

Safe and effective use of drugs requires an understanding of metabolism and transport. We identified the 100 most prescribed drugs in six countries and conducted a literature search on in vitro data to assess contribution of Phase I and II enzymes and drug transporters to metabolism and transport. Eighty-nine of the 100 drugs undergo drug metabolism or are known substrates for drug transporters. Phase I enzymes are involved in metabolism of 67 drugs, while Phase II enzymes mediate metabolism of 18 drugs. CYP3A4/5 is the most important Phase I enzyme involved in metabolism of 43 drugs followed by CYP2D6 (23 drugs), CYP2C9 (23 drugs), CYP2C19 (22 drugs), CYP1A2 (14 drugs) and CYP2C8 (11 drugs). More than half of the drugs (54 drugs) are known substrates for drug transporters. P-glycoprotein (P-gp) is known to be involved in transport of 30 drugs, while breast cancer resistance protein (BCRP) facilitates transport of 11 drugs. A considerable proportion of drugs are subject to a combination of Phase I metabolism, Phase II metabolism and/or drug transport. We conclude that the majority of the most frequently prescribed drugs depend on drug metabolism or drug transport. Thus, understanding variability of drug metabolism and transport remains a priority.

The inhibition of tamoxifen on UGT2B gene expression and enzyme activity in rat liver contribute to the estrogen homeostasis dysregulation

Background

Tamoxifen treatment may induce dysregulation of estrogen homeostasis, leading to the occurrence of related adverse reactions. However, the potential mechanisms are still unclear. The purpose of the present study was to uncover whether tamoxifen treatment would act on estrogen metabolism-related biological enzymes and the regulatory effect on estrogen homeostasis to clarify the key factors and potential mechanisms of adverse reactions caused by long-term use of tamoxifen.

Method

Female SD rats were administrated with tamoxifen CMC-Na solution (p.o.) once daily for four weeks and then housed at room temperature. Serum, breast, liver, uterus, and ovarian tissues were obtained, and the effects of tamoxifen administration on estrogen homeostasis, the expression, and activity of estrogen metabolic enzyme were evaluated.

Results

Compared with the control group, the estrogen homeostasis was disturbed and the expression and activity of UGT2B1 (homology with human UGT2B7) were significantly reduced in the rats administrated with tamoxifen. The inhibitory effect of tamoxifen on UGT2B7 was dominated by hydrophobic and π-π stacking interactions, resulting in a concentration-dependent inhibition of UGT2B7 activity by tamoxifen and the imbalance of ligand-activated transcription factors, leading to abnormal regulation of UGT2B and disturbance of estrogen homeostasis, which in turn led to adverse reactions of tamoxifen.

Conclusion

We established links between estrogen metabolism and tamoxifen administration and we proposed that the UGT2B inhibition was involved in the disturbance of estrogen homeostasis and the occurrence of tamoxifen-related adverse reactions.

Supplementary Information

The online version contains supplementary material available at 10.1186/s40360-022-00574-6.

Comparison of Sweated and Non-Sweated Ethanol Extracts of Salvia miltiorrhiza Bge. (Danshen) Effects on Human and rat Hepatic UDP-Glucuronosyltransferase and Preclinic Herb-Drug Interaction Potential Evaluation

BACKGROUND

The ethanol of Danshen (DEE) preparation has been widely used to treat cardiac-cerebral disease and cancer. Sweating is one of the primary processing methods of Danshen, which greatly influenced its quality and pharmacological properties. Sweated and non-sweated DEE preparation combining with various synthetic drugs, adding up the possibility of herbal-drug interactions.

OBJECTIVE

This study explored the effects of sweated and non-sweated DEE on human and rat hepatic UGT enzymes expression and activity and proposed a potential mechanism.

METHODS

The expression of two processed DEE on rat UGT1A, UGT2B and nuclear receptors including pregnane X receptor (PXR), constitutive androstane receptor (CAR), and peroxisome proliferator-activated receptor α (PPARα) were investigated after intragastric administration in rats by Western blot. Enzyme activity of DEE and its active ingredients (Tanshinone I, Cryptotanshinone, and Tanshinone I) on UGT isoenzymes was evaluated by quantifying probe substrate metabolism and metabolite formation in vitro using Ultra Performance Liquid Chromatography.

RESULTS

The two processed DEE (5.40 g/kg) improved UGT1A (P<0.01) and UGT2B (P<0.05) protein expression, and the non-sweated DEE (2.70 g/kg) upregulated UGT2B expression protein (P<0.05), compared with the CMCNa group. On day 28, UGT1A protein expression was increased (P<0.05) both in two processed DEE groups, meanwhile the non-sweated DEE significantly enhanced UGT2B protein expression (P<0.05) on day 21, compared with the CMCNa group. The process underlying this mechanism involved with the activation of nuclear receptors CAR, PXR, and PPARα; In vitro, sweated DEE (0-80 μg/mL) significantly inhibited the activity of human UGT1A7 (P<0.05) and rat UGT1A1, 1A8, and 1A9 (P<0.05). Non-sweated DEE (0-80 μg/mL) dramatically suppressed the activity of human UGT1A1, 1A3, 1A6, 1A7, 2B4, and 2B15, and rat UGT1A1, 1A3, 1A7, and 1A9 (P<0.05); Tanshinone I (0-1 μM) inhibited the activity of human UGT1A3, 1A6, and 1A7 (P<0.01) and rat UGT1A3, 1A6, 1A7, and 1A8 (P<0.05). Cryptotanshinone (0-1 μM) remarkably inhibited the activity of human UGT1A3 and 1A7 (P<0.05) and rat UGT1A7, 1A8, and 1A9 (P<0.05). Nonetheless, Tanshinone IIA (0-2 μM) is not a potent UGT inhibitor both in humans and rats; Additionally, there existed significant differences between two processed DEE in expression of PXR, and the activity of human UGT1A1, 1A3, 1A6, and 2B15 and rat UGT1A3 and 2B15 (P<0.05).

CONCLUSION

The effects of two processed DEE on hepatic UGT enzyme expression and activity were different. Accordingly, the combined usage of related UGTs substrates with DEE and its monomer components preparations may call for caution, depending on the drug's exposure-response relationship and dose adjustment. Besides, it is vital to pay attention to the distinction between sweated and non-sweated Danshen in clinic, which exerted an important influence on its pharmacological activity.

Regulation of human UDP-glycosyltransferase (UGT) genes by miRNAs

The human UGT gene superfamily is divided into four subfamilies (UGT1, UGT2, UGT3 and UGT8) that encodes 22 functional enzymes. UGTs are critical for the metabolism and clearance of numerous endogenous and exogenous compounds, including steroid hormones, bile acids, bilirubin, fatty acids, carcinogens, and therapeutic drugs. Therefore, the expression and activities of UGTs are tightly regulated by multiple processes at the transcriptional, post-transcriptional and post-translational levels. During recent years, nearly twenty studies have investigated the post-transcriptional regulation of UGT genes by miRNAs using human cancer cell lines (predominantly liver cancer). Overall, 14 of the 22 UGT mRNAs (1A1, 1A3, 1A4, 1A6, 1A8, 1A9, 1A10, 2A1, 2B4, 2B7, 2B10, 2B15, 2B17, UGT8) have been shown to be regulated by various miRNAs through binding to their respective 3' untranslated regions (3'UTRs). Three 3'UTRs (UGT1A, UGT2B7 and UGT2B15) contain the largest number of functional miRNA target sites; in particular, the UGT1A 3'UTR contains binding sites for 12 miRNAs (548d-5p, 183-5p, 214-5p, 486-3p, 200a-3p, 491-3p, 141-3p, 298, 103b, 376b-3p, 21-3p, 1286). Although all nine UGT1A family members have the same 3'UTR, these miRNA target sites appear to be functional in an isoform-specific and cellular context-dependent manner. Collectively, these observations demonstrate that miRNAs represent important post-transcriptional regulators of the UGT gene superfamily. In this article, we present a comprehensive review of reported UGT/miRNA regulation studies, describe polymorphisms within functional miRNA target sites that may affect their functionalities, and discuss potential cooperative and competitive regulation of UGT mRNAs by miRNAs through adjacently located miRNA target sites.

Evaluation of human relevance of Nicofluprole-induced rat thyroid disruption

Nicofluprole is a novel insecticide of the phenylpyrazole class conferring selective antagonistic activity on insect GABA receptors. After repeated daily dietary administration to Wistar rats for 28/90 days, Nicofluprole induced increases in thyroid (and liver) weight, associated with histopathology changes. Nicofluprole did not inhibit thyroid peroxydase nor sodium/iodide symporter, two key players in the biosynthesis of thyroid hormones, indicating the absence of a direct thyroid effect. The results seen in rats suggested a mode of action of Nicofluprole driven by the molecular initiating event of CAR/PXR nuclear receptor activation in livers, with key events of increases in liver weight and hypertrophy, decreasing circulatory thyroid hormones, a compensatory increase in TSH release and follicular cell hypertrophy. To explore the relevance of these changes to humans, well established in vitro rat and human sandwich-cultured hepatocytes were exposed to Nicofluprole up to 7 days. A concentration-dependent CYP3A induction (PXR-activation), an increase in T4-glucuronoconjugation accompanied by UGT1A/2B inductions was observed in rat but not in human hepatocytes. The inductions seen with Nicofluprole in rat (in vivo and in vitro in hepatocytes) that were absent in human hepatocytes represent another example of species-selectivity of nuclear CAR/PXR receptor activators. Importantly, the different pattern observed in rat and human models demonstrate that Nicofluprole-related thyroid effects observed in the rat are with no human relevance.

Transcriptional responses of Daphnis nerii larval midgut to oral infection by Daphnis nerii cypovirus-23

BACKGROUND

Daphnis nerii cypovirus-23 (DnCPV-23) is a new type of cypovirus and has a lethal effect on the oleander hawk moth, Daphnis nerii which feeds on leave of Oleander and Catharanthus et al. After DnCPV-23 infection, the change of Daphnis nerii responses has not been reported.

METHODS

To better understand the pathogenic mechanism of DnCPV-23 infection, 3rd-instar Daphnis nerii larvae were orally infected with DnCPV-23 occlusion bodies and the transcriptional responses of the Daphnis nerii midgut were analyzed 72 h post-infection using RNA-seq.

RESULTS

The results showed that 1979 differentially expressed Daphnis nerii transcripts in the infected midgut had been identified. KEGG analysis showed that protein digestion and absorption, Toll and Imd signaling pathway were down-regulated. Based on the result, we speculated that food digestion and absorption in insect midgut might be impaired after virus infection. In addition, the down-regulation of the immune response may make D. nerii more susceptible to bacterial infections. Glycerophospholipid metabolism and xenobiotics metabolism were up-regulated. These two types of pathways may affect the viral replication and xenobiotic detoxification of insect, respectively.

CONCLUSION

These results may facilitate a better understanding of the changes in Daphnis nerii metabolism during cypovirus infection and serve as a basis for future research on the molecular mechanism of DnCPV-23 invasion.

UDP-glucuronosyltransferases mediate coffee-associated reduction of liver fibrosis in bile duct ligated humanized transgenic UGT1A mice

BACKGROUND

Coffee consumption has been shown to reduce the risk of liver fibrosis and is capable of inducing human UDP-glucuronosyltransferase (UGT) 1A genes. UGT1A enzymes act as indirect antioxidants catalyzing the elimination of reactive metabolites, which in turn are potent initiators of profibrotic mechanisms. The aim of this study was to analyze the role of UGT1A genes as effectors of the protective properties of coffee in bile duct ligation (BDL) induced liver fibrosis.

METHODS

Fourteen days BDL with and without coffee pre- and co-treatment was performed in htgUGT1A-WT and htgUGT1A-SNP mice. Hepatic UGT1A mRNA expression levels, serum bilirubin and aminotransferase activities were determined. Liver fibrosis was assessed by collagen deposition, computational analysis of Sirius red tissue staining and expression of profibrotic marker genes. Oxidative stress was measured by hepatic peroxidase concentrations and immunofluorescence staining.

RESULTS

UGT1A transcription was differentially activated in the livers of htgUGT1A-WT mice after BDL, in contrast to a reduced or absent induction in the presence of SNPs. Co-treated (coffee + BDL) htgUGT1A-WT-mice showed significantly increased UGT1A expression and protein levels and a considerably higher induction compared to water drinking WT mice (BDL), whereas in co-treated htgUGT1A-SNP mice absolute expression levels remained below those observed in htgUGT1A-WT mice. Collagen deposition, oxidative stress and the expression of profibrotic markers inversely correlated with UGT1A expression levels in htgUGT1A-WT and SNP mice after BDL and coffee + BDL co-treatment.

CONCLUSIONS

Coffee exerts hepatoprotective and antioxidative effects via activation of UGT1A enzymes. Attenuated hepatic fibrosis as a result of coffee-mediated UGT1A induction during cholestasis was detected, while the protective action of coffee was lower in a common low-function UGT1A SNP haplotype present in 10% of the Caucasian population. This study suggests that coffee consumption might constitute a potential strategy to support the conventional treatment of cholestasis-related liver diseases.

The Functionality of UDP-Glucuronosyltransferase Genetic Variants and their Association with Drug Responses and Human Diseases

UDP-glucuronosyltransferases (UGTs) are phase II drug-metabolizing enzymes that metabolize endogenous fatty acids such as arachidonic acid metabolites, as well as many prescription drugs, such as opioids, antiepileptics, and antiviral drugs. The UGT1A and 2B genes are highly polymorphic, and their genetic variants may affect the pharmacokinetics and hence the responses of many drugs and fatty acids. This study collected data and updated the current view of the molecular functionality of genetic variants on UGT genes that impact drug responses and the susceptibility to human diseases. The functional information of UGT genetic variants with clinical associations are essential to understand the inter-individual variation in drug responses and susceptibility to toxicity.

Regional distributions of UDP-glucuronosyltransferase activities toward estradiol and serotonin in the liver and small intestine of cynomolgus macaques

The cynomolgus macaque is a nonhuman primate species that is often used in drug metabolism studies during drug development. However, the localization of UDP-glucuronosyltransferases (UGTs), essential drug-metabolizing enzymes, has not been fully investigated in the liver and small intestine of cynomolgus macaques. In this study, UGT activities were analyzed in liver (five lobes) and small intestine (the duodenum and six sections from the proximal jejunum to the distal ileum) using typical probe substrates of human UGTs: 7-hydroxycoumarin, estradiol, serotonin, propofol, and zidovudine. In liver, UGT activities with respect to all substrates were detected, and the activity levels were similar in all liver lobes of the cynomolgus macaques tested. In contrast, in the small intestine, UGT activities toward all substrates were detected, but their levels generally decreased from jejunum to ileum in cynomolgus macaques. The localization of estradiol 3-O-glucuronosyltransferases and serotonin O-glucuronosyltransferases (which are mainly UGT1A enzymes) appear to be different in liver and small intestine. These results collectively suggest that, in cynomolgus macaques, UGT1As are differentially localized in the small intestine but are relatively homogeneously distributed in the liver.

Metabolomics Profiles of Smokers from Two Ethnic Groups with Differing Lung Cancer Risk

African American (AA) smokers are at a higher risk of developing lung cancer compared to whites. The variations in the metabolism of nicotine and tobacco-derived carcinogens in these groups were reported previously with the levels of nicotine metabolites and carcinogen-derived metabolites measured using targeted approaches. While useful, these targeted strategies are not able to detect global metabolic changes for use in predicting the detrimental effects of tobacco use and ultimately lung cancer susceptibility among smokers. To address this limitation, we have performed global untargeted metabolomics profiling in urine of AA and white smokers to characterize the pattern of metabolites, identify differentially regulated pathways, and correlate these profiles with the observed variations in lung cancer risk between these two populations. Urine samples from AA (n = 30) and white (n = 30) smokers were used for metabolomics analysis acquired in both positive and negative electrospray ionization modes. LC-MS data were uploaded onto the cloud-based XCMS online (http://xcmsonline.scripps.edu) platform for retention time correction, alignment, feature detection, annotation, statistical analysis, data visualization, and automated systems biology pathway analysis. The latter identified global differences in the metabolic pathways in the two groups including the metabolism of carbohydrates, amino acids, nucleotides, fatty acids, and nicotine. Significant differences in the nicotine degradation pathway (cotinine glucuronidation) in the two groups were observed and confirmed using a targeted LC-MS/MS approach. These results are consistent with previous studies demonstrating AA smokers with lower glucuronidation capacity compared to whites. Furthermore, the d-glucuronate degradation pathway was found to be significantly different between the two populations, with lower amounts of the putative metabolites detected in AA compared to whites. We hypothesize that the differential regulation of the d-glucuronate degradation pathway is a consequence of the variations in the glucuronidation capacity observed in the two groups. Other pathways including the metabolism of amino acids, nucleic acids, and fatty acids were also identified, however, the biological relevance and implications of these differences across ethnic groups need further investigation. Overall, the applied metabolomics approach revealed global differences in the metabolic networks and endogenous metabolites in AA and whites, which could be used and validated as a new potential panel of biomarkers that could be used to predict lung cancer susceptibility among smokers in population-based studies.

Unveiling the Impact of Morphine on Tamoxifen Metabolism in Mice in vivo

Background: Tamoxifen is used to treat breast cancer and cancer recurrences. After administration, tamoxifen is converted into two more potent antitumor compounds, 4OH-tamoxifen and endoxifen by the CYP3A4/5 and 2D6 enzymes in human. These active compounds are inactivated by the same UDP-glucuronosyltransferase isoforms as those involved in the metabolism of morphine. Importantly, cancer-associated pain can be treated with morphine, and the common metabolic pathway of morphine and tamoxifen suggests potential clinically relevant interactions.

Methods: Mouse liver microsomes were used to determine the impact of morphine on 4OH-tamoxifen metabolism in vitro. For in vivo experiments, female mice were first injected with tamoxifen alone and then with tamoxifen and morphine. Blood was collected, and LC-MS/MS was used to quantify tamoxifen, 4OH-tamoxifen, N-desmethyltamoxifen, endoxifen, 4OH-tamoxifen-glucuronide, and endoxifen-glucuronide.

Results:In vitro, we found increased K_m values for the production of 4OH-tamoxifen-glucuronide in the presence of morphine, suggesting an inhibitory effect on 4OH-tamoxifen glucuronidation. Conversely, in vivo morphine treatment decreased 4OH-tamoxifen levels in the blood while dramatically increasing the formation of inactive metabolites 4OH-tamoxifen-glucuronide and endoxifen-glucuronide.

Conclusions: Our findings emphasize the need for caution when extrapolating results from in vitro metabolic assays to in vivo drug metabolism interactions. Importantly, morphine strongly impacts tamoxifen metabolism in mice. It suggests that tamoxifen efficiency could be reduced when both drugs are co-administered in a clinical setting, e.g., to relieve pain in breast cancer patients. Further studies are needed to assess the potential for tamoxifen-morphine metabolic interactions in humans.

Molecular characterization of functional UDP-glucuronosyltransferases 1A and 2B in common marmosets

UDP-glucuronosyltransferases (UGTs) are essential drug-conjugation enzymes that metabolize a variety of endobiotic and xenobiotic substrates. The molecular characteristics of UGTs have been extensively investigated in humans, but remain to be investigated in common marmosets, a nonhuman primate species widely used in drug metabolism studies. In this study, 11 UGT cDNAs (UGT1A1, 1A3, 1A4, 1A6, 1A7, and 1A9; and UGT2B49, 2B50, 2B51, 2B52, and 2B53) were isolated and characterized in marmosets. Marmoset UGT1As had high sequence identities (89-93%) with human UGT1As, but the sequence identities of marmoset UGT2Bs were lower (82-86%). Marmoset UGTs were found to be phylogenetically close to human UGTs. Just as human UGT1As do, marmoset UGT1A genes shared exons 2-5 and contained a variable exon 1 unique to each gene; in contrast, marmoset UGT2B genes contained six unique exons. Moreover, marmoset and human UGT1A and UGT2B gene clusters were located in corresponding regions in their respective genomes. Among the five tissue types tested, marmoset UGT mRNAs were most abundantly expressed in liver, jejunum, and/or kidney, i.e., in tissues important for drug metabolism, just as human UGTs are. Among the 11 marmoset UGT mRNAs investigated, marmoset UGT1A9, 1A4, and 1A6 mRNAs were the most abundantly expressed in liver, small intestine, and kidney, respectively. Marmoset liver microsomes and recombinant UGT1A proteins catalyzed the glucuronidation of the same substrates that human UGT1As catalyze, including estradiol, trifluoperazine, 4-methylumbelliferone, serotonin, 4-nitrophenol, and propofol. Trifluoperazine was glucuronidated by marmoset liver microsomes, but not by any of the UGT1A isoforms examined under the present conditions. These results collectively suggest that functional marmoset UGTs have generally similar molecular characteristics to human UGTs.

The UDP-Glycosyltransferase (UGT) Superfamily: New Members, New Functions, and Novel Paradigms

UDP-glycosyltransferases (UGTs) catalyze the covalent addition of sugars to a broad range of lipophilic molecules. This biotransformation plays a critical role in elimination of a broad range of exogenous chemicals and by-products of endogenous metabolism, and also controls the levels and distribution of many endogenous signaling molecules. In mammals, the superfamily comprises four families: UGT1, UGT2, UGT3, and UGT8. UGT1 and UGT2 enzymes have important roles in pharmacology and toxicology including contributing to interindividual differences in drug disposition as well as to cancer risk. These UGTs are highly expressed in organs of detoxification (e.g., liver, kidney, intestine) and can be induced by pathways that sense demand for detoxification and for modulation of endobiotic signaling molecules. The functions of the UGT3 and UGT8 family enzymes have only been characterized relatively recently; these enzymes show different UDP-sugar preferences to that of UGT1 and UGT2 enzymes, and to date, their contributions to drug metabolism appear to be relatively minor. This review summarizes and provides critical analysis of the current state of research into all four families of UGT enzymes. Key areas discussed include the roles of UGTs in drug metabolism, cancer risk, and regulation of signaling, as well as the transcriptional and posttranscriptional control of UGT expression and function. The latter part of this review provides an in-depth analysis of the known and predicted functions of UGT3 and UGT8 enzymes, focused on their likely roles in modulation of levels of endogenous signaling pathways.

The nuclear receptor Rev-erbα participates in circadian regulation of Ugt2b enzymes in mice

Circadian clock is known to modulate phase I metabolism, however whether and how the phase II enzymes UDP-glucuronosyltransferases (UGTs) are regulated by circadian clock are largely unknown. In this study, we aimed to investigate a potential role of the clock gene Rev-erbα in regulation of Ugt2b enzymes. Ugt2b mRNA and protein expression in mouse livers were determined at a 4-h interval around the clock. Ugt2b activity was probed using morphine as a specific substrate. Regulation of Ugt2b by Rev-erbα was investigated using mouse hepatoma Hepa-1c1c7 cells and Rev-erbα knock-out (Rev-erbα^-/-) mice. Luciferase reporter, mobility shift and chromatin immunoprecipitation (ChIP) assays were performed to identify the Rev-erbα binding site in Ugt2b36 promoter. Circadian variations in hepatic mRNA expression were observed for six Ugt2b genes (Ugt2b1, Ugt2b5, Ugt2b35, Ugt2b36, Ugt2b37, and Ugt2b38) in mice. Likewise, the total Ugt2b protein showed a circadian fluctuation. Glucuronidation of morphine (an Ugt2b substrate) both in vitro and in vivo was dosing-time dependent. Morphine glucuronidation was more extensive at the dosing time of ZT2 than at ZT14 consistent with the Ugt2b protein levels. Furthermore, Rev-erbα knockdown significantly increased Ugt2b mRNA and protein in Hepa-1c1c7 cells, whereas Rev-erbα overexpression or activation down-regulated Ugt2b expression. Moreover, Rev-erbα ablation in mice up-regulated the mRNA and protein expression of Ugt2b and blunted Ugt2b rhythmicity in the liver. In addition, Rev-erbα repressed the transcription of Ugt2b36 through specific binding to the -30 to -18 bp of promoter region based on a combination of luciferase reporter, mobility shift and ChIP assays. In summary, the clock gene Rev-erbα negatively regulates the expressions of Ugt2b genes, contributing to their circadian variations.

Human relevance of follicular thyroid tumors in rodents caused by non-genotoxic substances

Chronic stimulation of the thyroid gland of rodents by TSH leads to thyroid follicular hyperplasia and subsequently to thyroid follicular adenomas and carcinomas. However, the interpretations of rodent thyroid tumors are contradictory. The U.S. Food and Drug Administration (FDA) concluded that findings with drugs that lead to increased levels of thyroid-stimulating hormone (TSH) in rats are not relevant to humans, whereas the U.S. Environmental Protection Agency (US EPA) concluded that chemicals that produce rodent thyroid tumors may pose a carcinogenic hazard for humans although the thyroid of rodents appears to be more sensitive to a carcinogenic stimulus than that of humans. Meanwhile, based on the CLP Criteria of the European Chemicals Agency (ECHA), rodent thyroid tumors caused by the induction of uridine-diphosphate-glucuronosyl transferases (UDGT) were assessed as not relevant to humans. To clarify these discrepant positions, the function and regulation of the thyroid gland are described and the types of thyroid tumors and the causes of their development in humans and animals are examined. Based on these data and the evidence that so far, except radiation, no chemical is known to increase the incidence of thyroid tumors in humans, it is concluded that rodent thyroid tumors resulting from continuous stimulation of the thyroid gland by increased TSH levels are not relevant to humans. Consequently, compounds that induce such tumors do not warrant classification as carcinogenic.

The clinical significance of CDX2 in leukemia: A new perspective for leukemia research

CDX2 gene encodes a transcription factor involved in primary embryogenesis and hematopoietic development; however, the expression of CDX2 in adults is restricted to intestine and is not observed in blood tissues. The ectopic expression of CDX2 has been frequently observed in acute myeloid and lymphoid leukemia which in most cases is concomitant with poor prognosis. Induction of CDX2 in mice leads to hematologic complications, showing the leukemogenic origin of this gene. CDX2 plays significant role in the most critical pathways as the regulator of important transcription factors targeting cell proliferation, multi-drug resistance and survival. On the whole, the results indicate that CDX2 has the potential to be suggested as the diagnostic marker in hematologic malignancies. This review discusses the role of aberrant expression of CDX2 in the prognosis and the response to treatment in patients with different leukemia in clinical reports in the recent decades. The improvement in this regard could be of high importance in diagnosis and treatment methods.

Contributions of Nrf2 to Puerarin Prevention of Cardiac Hypertrophy and its Metabolic Enzymes Expression in Rats

Previous evidence has suggested that puerarin may attenuate cardiac hypertrophy; however, the potential mechanisms have not been determined. Moreover, the use of puerarin is limited by severe adverse events, including intravascular hemolysis. This study used a rat model of abdominal aortic constriction (AAC)-induced cardiac hypertrophy to evaluate the potential mechanisms underlying the attenuating efficacy of puerarin on cardiac hypertrophy, as well as the metabolic mechanisms of puerarin involved. We confirmed that puerarin (50 mg/kg per day) significantly attenuated cardiac hypertrophy, upregulated Nrf2, and decreased Keap1 in the myocardium. Moreover, puerarin significantly promoted Nrf2 nuclear accumulation in parallel with the upregulated downstream proteins, including heme oxygenase 1, glutathione transferase P1, and NAD(P)H:quinone oxidoreductase 1. Similar results were obtained in neonatal rat cardiomyocytes (NRCMs) treated with angiotensin II (Ang II; 1 μM) and puerarin (100 μM), whereas the silencing of Nrf2 abolished the antihypertrophic effects of puerarin. The mRNA and protein levels of UGT1A1 and UGT1A9, enzymes for puerarin metabolism, were significantly increased in the liver and heart tissues of AAC rats and Ang II-treated NRCMs. Interestingly, the silencing of Nrf2 attenuated the puerarin-induced upregulation of UGT1A1 and UGT1A9. The results of chromatin immunoprecipitation-quantitative polymerase chain reaction indicated that the binding of Nrf2 to the promoter region of Ugt1a1 or Ugt1a9 was significantly enhanced in puerarin-treated cardiomyocytes. These results suggest that Nrf2 is the key regulator of antihypertrophic effects and upregulation of the metabolic enzymes UGT1A1 and UGT1A9 of puerarin. The autoregulatory circuits between puerarin and Nrf2-induced UGT1A1/1A9 are beneficial to attenuate adverse effects and maintain the pharmacologic effects of puerarin.

Modulation of bilirubin neurotoxicity by the Abcb1 transporter in the Ugt1-/- lethal mouse model of neonatal hyperbilirubinemia

Moderate neonatal jaundice is the most common clinical condition during newborn life. However, a combination of factors may result in acute hyperbilirubinemia, placing infants at risk of developing bilirubin encephalopathy and death by kernicterus. While most risk factors are known, the mechanisms acting to reduce susceptibility to bilirubin neurotoxicity remain unclear. The presence of modifier genes modulating the risk of developing bilirubin-induced brain damage is increasingly being recognised. The Abcb1 and Abcc1 members of the ABC family of transporters have been suggested to have an active role in exporting unconjugated bilirubin from the central nervous system into plasma. However, their role in reducing the risk of developing neurological damage and death during neonatal development is still unknown.To this end, we mated Abcb1a/b-/- and Abcc1-/- strains with Ugt1-/- mice, which develop severe neonatal hyperbilirubinemia. While about 60% of Ugt1-/- mice survived after temporary phototherapy, all Abcb1a/b-/-/Ugt1-/- mice died before postnatal day 21, showing higher cerebellar levels of unconjugated bilirubin. Interestingly, Abcc1 role appeared to be less important.In the cerebellum of Ugt1-/- mice, hyperbilirubinemia induced the expression of Car and Pxr nuclear receptors, known regulators of genes involved in the genotoxic response.We demonstrated a critical role of Abcb1 in protecting the cerebellum from bilirubin toxicity during neonatal development, the most clinically relevant phase for human babies, providing further understanding of the mechanisms regulating bilirubin neurotoxicity in vivo. Pharmacological treatments aimed to increase Abcb1 and Abcc1 expression, could represent a therapeutic option to reduce the risk of bilirubin neurotoxicity.

Relation of Transcriptional Factors to the Expression and Activity of Cytochrome P450 and UDP-Glucuronosyltransferases 1A in Human Liver: Co-Expression Network Analysis

Cytochrome P450 (CYPs) and UDP-glucuronosyltransferases (UGTs) play important roles in the metabolism of exogenous and endogenous compounds. The gene transcription of CYPs and UGTs can be enhanced or reduced by transcription factors (TFs). This study aims to explore novel TFs involved in the regulatory network of human hepatic UGTs/CYPs. Correlations between the transcription levels of 683 key TFs and CYPs/UGTs in three different human liver expression profiles (n = 640) were calculated first. Supervised weighted correlation network analysis (sWGCNA) was employed to define hub genes among the selected TFs. The relationship among 17 defined TFs, CYPs/UGTs expression, and activity were evaluated in 30 liver samples from Chinese patients. The positive controls (e.g., PPARA, NR1I2, NR1I3) and hub TFs (NFIA, NR3C2, and AR) in the Grey_sWGCNA Module were significantly and positively associated with CYPs/UGTs expression. And the cancer- or inflammation-related TFs (TEAD4, NFKB2, and NFKB1) were negatively associated with mRNA expression of CYP2C9/CYP2E1/UGT1A9. Furthermore, the effect of NR1I2, NR1I3, AR, TEAD4, and NFKB2 on CYP450/UGT1A gene transcription translated into moderate influences on enzyme activities. To our knowledge, this is the first study to integrate Gene Expression Omnibus (GEO) datasets and supervised weighted correlation network analysis (sWGCNA) for defining TFs potentially related to CYPs/UGTs. We detected several novel TFs involved in the regulatory network of hepatic CYPs and UGTs in humans. Further validation and investigation may reveal their exact mechanism of CYPs/UGTs regulation.

Regulation of UGT2B Expression and Activity by miR-216b-5p in Liver Cancer Cell Lines

The UDP-glucuronosyltransferase (UGT) 2B enzymes are important in the detoxification of a variety of endogenous and exogenous compounds, including many hormones, drugs, and carcinogens. Identifying novel mechanisms governing their expression is important in understanding patient-specific response to drugs and cancer risk factors. In silico prediction algorithm programs were used to screen for microRNAs (miRNAs) as potential regulators of UGT2B enzymes, with miR-216b-5p identified as a potential candidate. Luciferase data suggested the presence of a functional miR-216b-5p binding motif within the 3' untranslated regions of UGTs 2B7, 2B4, and 2B10. Overexpression of miR-216b-5p mimics significantly repressed UGT2B7 (P < 0.001) and UGT2B10 (P = 0.0018) mRNA levels in HuH-7 cells and UGT2B4 (P < 0.001) and UGT2B10 (P = 0.018) mRNA in Hep3B cells. UGT2B7 protein levels were repressed in both HuH-7 and Hep3B cells in the presence of increasing miR-216b-5p concentrations, corresponding with significant (P < 0.001 and P = 0.011, respectively) decreases in glucuronidation activity against the UGT2B7-specific substrate epirubicin. Inhibition of endogenous miR-216b-5p levels significantly increased UGT2B7 mRNA levels in HuH-7 (P = 0.021) and Hep3B (P = 0.0068) cells, and increased epirubicin glucuronidation by 85% (P = 0.057) and 50% (P = 0.012) for HuH-7 and Hep3B cells, respectively. UGT2B4 activity against codeine and UGT2B10 activity against nicotine were significantly decreased in both HuH-7 and Hep3B cells (P < 0.001 and P = 0.0048, and P = 0.017 and P = 0.043, respectively) after overexpression of miR-216b-5p mimic. This is the first evidence that miRNAs regulate UGT 2B7, 2B4, and 2B10 expression, and that miR-216b-5p regulation of UGT2B proteins may be important in regulating the metabolism of UGT2B substrates.

Complexity of vitamin E metabolism

Bioavailability of vitamin E is influenced by several factors, most are highlighted in this review. While gender, age and genetic constitution influence vitamin E bioavailability but cannot be modified, life-style and intake of vitamin E can be. Numerous factors must be taken into account however, i.e., when vitamin E is orally administrated, the food matrix may contain competing nutrients. The complex metabolic processes comprise intestinal absorption, vascular transport, hepatic sorting by intracellular binding proteins, such as the significant α-tocopherol-transfer protein, and hepatic metabolism. The coordinated changes involved in the hepatic metabolism of vitamin E provide an effective physiological pathway to protect tissues against the excessive accumulation of, in particular, non-α-tocopherol forms. Metabolism of vitamin E begins with one cycle of CYP4F2/CYP3A4-dependent ω-hydroxylation followed by five cycles of subsequent β-oxidation, and forms the water-soluble end-product carboxyethylhydroxychroman. All known hepatic metabolites can be conjugated and are excreted, depending on the length of their side-chain, either via urine or feces. The physiological handling of vitamin E underlies kinetics which vary between the different vitamin E forms. Here, saturation of the side-chain and also substitution of the chromanol ring system are important. Most of the metabolic reactions and processes that are involved with vitamin E are also shared by other fat soluble vitamins. Influencing interactions with other nutrients such as vitamin K or pharmaceuticals are also covered by this review. All these processes modulate the formation of vitamin E metabolites and their concentrations in tissues and body fluids. Differences in metabolism might be responsible for the discrepancies that have been observed in studies performed in vivo and in vitro using vitamin E as a supplement or nutrient. To evaluate individual vitamin E status, the analytical procedures used for detecting and quantifying vitamin E and its metabolites are crucial. The latest methods in analytics are presented.

MicroRNA regulation of the major drug-metabolizing enzymes and related transcription factors

Identifying novel mechanisms contributing to patient variability of drug response is a major goal of personalized medicine. Epigenetic regulation of gene expression by microRNA (miRNA) impacts a broad range of cellular processes, but knowledge of its regulation of drug-metabolizing enzymes (DMEs) is more limited. This review provides an introduction to miRNA and their functionality and summarizes known miRNA regulation of DME families, including the cytochrome P450s, UDP-glucuronoslytransferases, glutathione-S-transferases, sulfotransferases and aldo-keto reductases, and the transcription factors known to be involved in DME regulation.

DNA-PKcs-Mediated Transcriptional Regulation Drives Prostate Cancer Progression and Metastasis

Emerging evidence demonstrates that the DNA repair kinase DNA-PKcs exerts divergent roles in transcriptional regulation of unsolved consequence. Here, in vitro and in vivo interrogation demonstrate that DNA-PKcs functions as a selective modulator of transcriptional networks that induce cell migration, invasion, and metastasis. Accordingly, suppression of DNA-PKcs inhibits tumor metastases. Clinical assessment revealed that DNA-PKcs is significantly elevated in advanced disease and independently predicts for metastases, recurrence, and reduced overall survival. Further investigation demonstrated that DNA-PKcs in advanced tumors is highly activated, independent of DNA damage indicators. Combined, these findings reveal unexpected DNA-PKcs functions, identify DNA-PKcs as a potent driver of tumor progression and metastases, and nominate DNA-PKcs as a therapeutic target for advanced malignancies.

Posttranscriptional regulation of uridine diphosphate glucuronosyltransferases

INTRODUCTION

The uridine diphosphate (UDP)-glucuronosyltransferase (UGT) superfamily of enzymes (EC 2.4.1.17) conjugates glucuronic acid to an aglycone substrate to make them more polar and readily excreted. In general, this reaction terminates the activities of chemicals, drugs and toxins, although occasionally a more active or toxic species is produced.

AREAS COVERED

In addition to their well-known transcriptional responsiveness, UGTs are also regulated by posttranscriptional mechanisms. Here, the authors review these mechanisms, including latency, modulation of co-substrate accessibility and binding, dimerization and oligomerization, protein-protein interactions, allosteric inhibition and activation, posttranslational structural and functional modifications and developmental switching for UGTs.

EXPERT OPINION

Posttranscriptional regulation of UGTs has traditionally received less attention than nuclear regulation, in part because mechanisms involving ribosomes and endoplasmic reticula are challenging to investigate. Most promising of the posttranscriptional mechanisms reviewed are likely to be effects on co-substrate (UDP-glucuronic acid) transport and availability and structure-function changes to UGT proteins through, for example, glycosylation and phosphorylation. Although classical biochemistry continues to illuminate many aspects of UGT function, advances in proteomics and structural biology are beginning to assist in the determination of posttranscriptional regulation mechanisms for UGTs.

Transcriptional regulation of human UDP-glucuronosyltransferase genes

Glucuronidation is an important metabolic pathway for many small endogenous and exogenous lipophilic compounds, including bilirubin, steroid hormones, bile acids, carcinogens and therapeutic drugs. Glucuronidation is primarily catalyzed by the UDP-glucuronosyltransferase (UGT) 1A and two subfamilies, including nine functional UGT1A enzymes (1A1, 1A3-1A10) and 10 functional UGT2 enzymes (2A1, 2A2, 2A3, 2B4, 2B7, 2B10, 2B11, 2B15, 2B17 and 2B28). Most UGTs are expressed in the liver and this expression relates to the major role of hepatic glucuronidation in systemic clearance of toxic lipophilic compounds. Hepatic glucuronidation activity protects the body from chemical insults and governs the therapeutic efficacy of drugs that are inactivated by UGTs. UGT mRNAs have also been detected in over 20 extrahepatic tissues with a unique complement of UGT mRNAs seen in almost every tissue. This extrahepatic glucuronidation activity helps to maintain homeostasis and hence regulates biological activity of endogenous molecules that are primarily inactivated by UGTs. Deciphering the molecular mechanisms underlying tissue-specific UGT expression has been the subject of a large number of studies over the last two decades. These studies have shown that the constitutive and inducible expression of UGTs is primarily regulated by tissue-specific and ligand-activated transcription factors (TFs) via their binding to cis-regulatory elements (CREs) in UGT promoters and enhancers. This review first briefly summarizes published UGT gene transcriptional studies and the experimental models and tools utilized in these studies, and then describes in detail the TFs and their respective CREs that have been identified in the promoters and/or enhancers of individual UGT genes.

Complexities of androgen receptor signalling in breast cancer

While the clinical benefit of androgen-based therapeutics in breast cancer has been known since the 1940s, we have only recently begun to fully understand the mechanisms of androgen action in breast cancer. Androgen signalling pathways can have either beneficial or deleterious effects in breast cancer depending on the breast cancer subtype and intracellular context. This review discusses our current knowledge of androgen signalling in breast cancer, including the relationship between serum androgens and breast cancer risk, the prognostic significance of androgen receptor (AR) expression in different breast cancer subtypes and the downstream molecular pathways mediating androgen action in breast cancer cells. Intracrine androgen metabolism has also been discussed and proposed as a potential mechanism that may explain some of the reported differences regarding dichotomous androgen actions in breast cancers. A better understanding of AR signalling in this disease is critical given the current resurgence in interest in utilising contemporary AR-directed therapies for breast cancer and the need for biomarkers that will accurately predict clinical response.

Human hepatic UGT2B15 developmental expression

Human hepatic UGT2B15 developmental expression changes may alter the metabolism of important drugs and toxicants such as bisphenol A (BPA). Previously, UGT2B15 ontogeny knowledge consisted of transcript data, a dubious surrogate for protein expression. Herein, UGT2B15 protein content was determined in human hepatic microsomes (n = 236, 8 weeks gestation to 18 years). The impact of a common, functional single nucleotide polymorphism (g.253G>T), present in UGT2B15*2 and *5 alleles, was also tested. UGT2B15 expression began during late fetal life, at about 18% of mature values (medians = 48, 267 pmoles/mg of microsomal protein, respectively; p < 0.001). UGT2B15 neonatal (n = 39) and late fetal (≥28 weeks, n = 10) content was similar, but lower than that of infants between 3 and 15 weeks age (n = 46; medians = 38, 48, 404 pmoles/mg microsomal protein, respectively; p < 0.001). Values for the latter group were higher compared with the remaining age group (15 weeks to 18 years; n = 82, p < 0.001). UGT2B15 expression varied 31-fold across the entire sample, and within groups, ranged from 4- to 27-fold. Among postnatal samples, age group, the presence of g.253T and male gender were each significantly associated with greater UGT2B15 expression (p < 0.001, <0.01, and <0.05, respectively; stepwise linear regression). In summary, hepatic UGT2B15 protein onset begins in late gestation; however, the greatest rate of change occurs during the first few weeks after birth. We speculate that the fetus and neonate may have lower clearance of some UGT2B15 substrates, such as BPA, compared with older individuals.

Regulation of UDP-glucuronosyltransferase 1A1 expression and activity by microRNA 491-3p

The UDP-glucuronosyltransferase (UGT) 1A enzymes are involved in the phase II metabolism of many important endogenous and exogenous compounds. The nine UGT1A isoforms exhibit high interindividual differences in expression, but their epigenetic regulation is not well understood. The purpose of the present study was to examine microRNA (miRNA) regulation of hepatic UGT1A enzymes and determine whether or not that regulation impacts enzymatic activity. In silico analysis identified miRNA 491-3p (miR-491-3p) as a potential regulator of the UGT1A gene family via binding to the shared UGT1A 3'-untranslated region common to all UGT1A enzymes. Transfection of miR-491-3p mimic into HuH-7 cells significantly repressed UGT1A1 (P < 0.001), UGT1A3 (P < 0.05), and UGT1A6 (P < 0.05) mRNA levels. For UGT1A1, this repression correlated with significantly reduced metabolism of raloxifene into raloxifene-6-glucuronide (ral-6-gluc; P < 0.01) and raloxifene-4'-glucuronide (ral-4'-gluc; P < 0.01). In HuH-7 cells with repressed miR-491-3p expression, there was a significant increase (~80%; P < 0.01) in UGT1A1 mRNA and a corresponding increase in glucuronidation of raloxifene into ral-6-gluc (50%; P < 0.05) and ral-4'-gluc (22%; P < 0.01). Knockdown of endogenous miR-491-3p in HepG2 cells did not significantly alter UGT1A1 mRNA levels but did increase the formation of ral-6-gluc (50%; P < 0.05) and ral-4'-gluc (34%; P < 0.001). A significant inverse correlation between miR-491-3p expression and both UGT1A3 (P < 0.05) and UGT1A6 (P < 0.01) mRNA levels was observed in a panel of normal human liver specimens, with a significant (P < 0.05) increase in UGT1A3 and UGT1A6 mRNA levels observed in miR-491-3p nonexpressing versus expressing liver specimens. These results suggest that miR-491-3p is an important factor in regulating the expression of UGT1A enzymes in vivo.

Dysregulations of UDP-glucuronosyltransferases in rats with valproic acid and high fat diet induced fatty liver

Both high fat diet (HFD) and valproic acid (VPA) interfere with mitochondrial β-oxidation of fatty acids, which subsequently triggers microvesicular fatty liver and hepatic dysfunction. UDP-glucuronosyltransferases, the major phase II drug metabolism enzymes, play a pivotal role in detoxifying various exogenous and endogenous compounds. This study aimed to investigate the dysregulation patterns of major UDP-glucuronosyltransferases (UGTs) induced by VPA and/or HFD. Biochemical and histopathological results showed that chronic treatments of VPA and HFD induced fatty liver and liver dysfunction in a synergistic manner. VPA upregulated the mRNA levels of UGT1A1, 1A6, 1A7, and UGT2B1. Notably, the protein expression and enzymatic activity of UGT1A6 were significantly increased in rats treated with HFD or VPA alone, and were further enhanced by HFD and VPA co-treatment. This dysregulation pattern was largely recapitulated in the in vitro HepG2 cells assay by using VPA and oleic acid treatment. Moreover, the induction of UGTs was accompanied by the increased expression of constitutive androstane receptor (CAR) and peroxisome proliferator-activated receptor α (PPARα). In line with the up-regulation of UGT1A1 and UGT1A6, urine recovery of VPA glucuronide (VPA-G) was sharply increased by VPA treatment, and the co-treatment of HFD further aggravated this change. Since VPA is necessarily prescribed for long-term and the prevalence of HFD life style nowadays, the combined effect of HFD and VPA on disturbing UGTs should take concerns in the clinics.

Phase two steroid metabolism and its roles in breast and prostate cancer patients

Breast and prostate cancer are diseases in which steroids and steroid metabolism could markedly influence clinical outcomes for patients. In both malignancies the modification of ketone and hydroxyl groups attached to the steroid backbone (phase one metabolism) has been examined in detail but the conjugation reactions (phase two metabolism) have not been extensively studied. Therefore, in this review we aim to summarize phase two metabolism in breast and prostate cancers from a number of perspectives, including the impact of variation in serum levels of conjugated steroids, tissue, and pathology specific expression of phase two enzymes, and consequences of genetic variations of these conjugation enzymes. In addition to this biological perspective, we will also address current pharmacological efforts to manipulate phase two metabolism as a potential therapy for hormone dependent cancers, including clinical trials of STS inhibitors and preclinical STS inhibitor development. While this review is not intended to cover any one particular area in great technical depth, it is intended as an introduction to and/or update on the importance of variance in phase two metabolic pathways in breast and prostate cancers.

Enantiomer selective glucuronidation of the non-steroidal pure anti-androgen bicalutamide by human liver and kidney: role of the human UDP-glucuronosyltransferase (UGT)1A9 enzyme

Bicalutamide (Casodex(®) ) is a non-steroidal pure anti-androgen used in the treatment of localized prostate cancer. It is a racemate drug, and its activity resides in the (R)-enantiomer, with little in the (S)-enantiomer. A major metabolic pathway for bicalutamide is glucuronidation catalysed by UDP-glucuronosyltransferase (UGT) enzymes. While (S)bicalutamide is directly glucuronidated, (R)bicalutamide requires hydroxylation prior to glucuronidation. The contribution of human tissues and UGT isoforms in the metabolism of these enantiomers has not been extensively investigated. In this study, both (R) and/or (S)bicalutamide were converted into glucuronide (-G) derivatives after incubation of pure and racemic solutions with microsomal extracts from human liver and kidney. Intestinal microsomes exhibited only low reactivity with these substrates. Km values of liver and kidney samples for (S)bicalutamide glucuronidation were similar, and lower than values obtained with the (R)-enantiomer. Among the 16 human UGTs tested, UGT1A8 and UGT1A9 were able to form both (S) and (R)bicalutamide-G from pure or racemic substrates. UGT2B7 was also able to form (R)bicalutamide-G. Kinetic parameters of the recombinant UGT2B7, UGT1A8 and UGT1A9 enzymes support a predominant role of the UGT1A9 isoform in bicalutamide metabolism. Accordingly, (S)bicalutamide inhibited the ability of human liver and kidney microsomes to glucuronidate the UGT1A9 probe substrate, propofol. In conclusion, the present study provides the first comprehensive analysis of in vitro bicalutamide glucuronidation by human tissues and UGTs and identifies UGT1A9 as a major contributor for (R) and (S) glucuronidation in the human liver and kidney.

Pregnane X receptor dependent up-regulation of CYP2C9 and CYP3A4 in tumor cells by antitumor acridine agents, C-1748 and C-1305, selectively diminished under hypoxia

Induction of proteins involved in drug metabolism and in drug delivery has a significant impact on drug-drug interactions and on the final therapeutic effects. Two antitumor acridine derivatives selected for present studies, C-1748 (9-(2'-hydroxyethylamino)-4-methyl-1-nitroacridine) and C-1305 (5-dimethylaminopropylamino-8-hydroxy-triazoloacridinone), expressed high and low susceptibility to metabolic transformations with liver microsomes, respectively. In the current study, we examined the influence of these compounds on cytochrome P450 3A4 (CYP3A4) and 2C9 (CYP2C9) enzymatic activity and gene expression in HepG2 tumor cells. Luminescence and HPLC examination, real-time RT-PCR and western blot analyses along with transfection of pregnane X receptor (PXR) siRNA and CYP3A4 reporter gene assays were applied. We found that both compounds strongly induced CYP3A4 and CYP2C9 activity and expression as well as expression of UGT1A1 and MDR1 in a concentration- and time-dependent manner. C-1748-mediated CYP3A4 and CYP2C9 mRNA induction equal to rifampicin occurred at extremely low concentrations (0.001 and 0.01μM), whereas 10μM C-1305 induced three-times higher CYP3A4 and CYP2C9 mRNA levels than rifampicin did. CYP3A4 and CYP2C9 expressions were shown to be PXR-dependent; however, neither compound influenced PXR expression. Thus, the observed drug-mediated induction of isoenzymes occurs on a PXR-mediated regulatory level. Furthermore, C-1748 and C-1305 were demonstrated to be selective PXR agonists. These effects are hypoxia-inhibited only in the case of C-1748, which is sensitive to P450 metabolism. In summary, PXR was found to be a new target of the studied compounds. Thus, possible combinations of these compounds with other therapeutics might lead to the PXR-dependent enzyme-mediated drug-drug interactions.