Med25 is required for estrogen receptor alpha (ERα)-mediated regulation of human CYP2C9 expression

The impact of pregnancy and associated hormones on the pharmacokinetics of Δ9-tetrahydrocannabinol

INTRODUCTION

(-)-Δ9-tetrahydrocannabinol (THC) is the main psychoactive component of cannabis. Cannabis is the most widely used drug of abuse by pregnant individuals, but its maternal-fetal safety is still unclear. The changes in THC disposition during pregnancy may affect THC safety and pharmacology.

AREAS COVERED

This review summarizes the current literature on THC metabolism and pharmacokinetics in humans. It provides an analysis of how hormonal changes during pregnancy may alter the expression of cannabinoid metabolizing enzymes and THC and its metabolite pharmacokinetics. THC is predominately (>70%) cleared by hepatic metabolism to its psychoactive active metabolite, 11-OH-THC by cytochrome P450 (CYP) 2C9 and to other metabolites (<30%) by CYP3A4. Other physiological processes that change during pregnancy and may alter cannabinoid disposition are also reviewed.

EXPERT OPINION

THC and its metabolites disposition likely change during pregnancy. Hepatic CYP2C9 and CYP3A4 are induced in pregnant individuals and in vitro by pregnancy hormones. This induction of CYP2C9 and CYP3A4 is predicted to lead to altered THC and 11-OH-THC disposition and pharmacodynamic effects. More in vitro studies of THC metabolism and induction of the enzymes metabolizing cannabinoids are necessary to improve the prediction of THC pharmacokinetics in pregnant individuals.

Identification of hepatotoxicity and renal dysfunction of pyrene in adult male rats

Polycyclic aromatic hydrocarbons (PAHs) are a group of persistent organic pollutants primarily formed from the incomplete combustion of carbonaceous materials, and have adverse effects on human health. In this study, we investigated whether pyrene, a PAH consisting of 4 fused benzene rings, has adverse effects on rat. Adult male Sprague-Dawly rats were treated daily by oral gavage with vehicle (corn oil) or pyrene at doses of 375, 750, 1500, or 2200 mg/kg/day for 4 days. The results showed that pyrene caused hepatotoxicity in rats. When compared with the control group, relative liver weights, plasma alanine aminotransferase, and direct bilirubin levels significantly increased after pyrene exposure. Hepatocyte swelling and degeneration and decreased hepatic total glutathione (GSH) levels were also found in pyrene-exposed rats. We further observed that mRNA levels of several hepatic metabolizing enzymes regulated by constitutive androstane receptor (CAR) such as CYP2B1 and CYP2B2 significantly increased in pyrene-exposed rats. These results suggest that decreased GSH levels, elevated hepatic metabolizing enzyme gene expression, and CAR activation are important contributors for pyrene-induced hepatotoxicity in rats. Additionally, we found pyrene significantly induced plasma inflammatory indices including white blood cell and lymphocyte counts. We also observed that pyrene exposure increased relative weight of kidneys and disrupted kidney function with elevated urea and creatinine levels in rats.

Nuclear receptor gene polymorphisms and warfarin dose requirements in the Quebec Warfarin Cohort

Warfarin is primarily metabolized by cytochrome 2C9, encoded by gene CYP2C9. Here, we investigated whether variants in nuclear receptor genes which regulate the expression of CYP2C9 are associated with warfarin response. We used data from 906 warfarin users from the Quebec Warfarin Cohort (QWC) and tested the association of warfarin dose requirement at 3 months following the initiation of therapy in nine nuclear receptor genes: NR1I3, NR1I2, NR3C1, ESR1, GATA4, RXRA, VDR, CEBPA, and HNF4A. Three correlated SNPs in the VDR gene (rs4760658, rs11168292, and rs11168293) were associated with dose requirements of warfarin (P = 2.68 × 10^-5, P = 5.81 × 10^-4, and P = 5.94 × 10^-4, respectively). Required doses of warfarin were the highest for homozygotes of the minor allele at the VDR variants (P < 0.0026). Variants in the VDR gene were associated with the variability in response to warfarin, emphasizing the possible clinical relevance of nuclear receptor gene variants on the inter-individual variability in drug metabolism.

Upregulation of human CYP2C9 expression by Bisphenol A via estrogen receptor alpha (ERα) and Med25

Bisphenol A (BPA) is an important industrial chemical, mainly used in the manufacture of polycarbonate plastic and epoxy resins. Due to its widespread use, humans have a high risk of exposure to BPA. BPA has been found to have adverse health effects such as interfering with hormone-related pathways and is well-known to act as an endocrine disruptor. The present study is the first to show the induction effect of BPA on gene expression and enzyme activity of CYP2C9, an important hepatic drug metabolizing enzyme in human. We further identify the mechanism of BPA upregulation of CYP2C9 expression. We show that BPA is able to transcriptionally activate CYP2C9 promoter through ERα and ERE site within the CYP2C9 promoter region in HepG2 cells, and can induce CYP2C9 gene expression and enzyme activity in human primary hepatocytes. Moreover, we demonstrate that Med25, a variable member of the Mediator complex, is a coactivator of ligand-activated ERα that interacts with ERα through its C-terminal LXXLL motif after BPA exposure, and is functionally involved in BPA-induced transcriptional regulation of CYP2C9 expression and enzyme activity. Our findings suggest that BPA exposure has a potential risk for adverse health effects in human liver metabolism by upregulation of CYP2C9 expression. © 2016 Wiley Periodicals, Inc. Environ Toxicol 32: 970-978, 2017.

Pyrene is a Novel Constitutive Androstane Receptor (CAR) Activator and Causes Hepatotoxicity by CAR

Polycyclic aromatic hydrocarbons (PAHs) are a class of ubiquitous persistent environmental pollutants which are primarily formed from the incomplete combustion of organic materials. Many potential sources of human exposure to PAHs exist, including daily exposures from the ambient environment or occupational settings. PAHs have been found to cause harmful effects on human health. Here, we evaluated the adverse effects of pyrene, a common PAH, on the liver. The present study demonstrates that pyrene is able to activate mouse constitutive androstane receptor (CAR). CAR protein, as measured by Western blot analysis, was observed to translocate into the nucleus from the cytoplasm in mouse liver after exposure to pyrene. Utilizing CAR null mice, we identified that CAR mediates pyrene-induced hepatotoxicity. Increased relative liver weight, hepatocellular hypertrophy, and elevated serum alanine aminotransferase levels were found in wild-type but not CAR null mice after orally administered pyrene. We further show that pyrene induced the expression of mouse liver metabolism enzymes including CYP2B10, CYP3A11, GSTm1, GSTm3, and SULT1A1, and caused hepatic glutathione depletion in wild-type but not CAR null mice. Moreover, by luciferase reporter assay and quantitative real-time PCR analysis, pyrene was found to be a potential inducer of CYP2B6 expression via activation of human CAR in HepG2 cells and human primary hepatocytes. Our observations suggest that pyrene is a novel CAR activator and that CAR is essential for mediating pyrene-induced liver injury.

Homozygous missense mutation in MED25 segregates with syndromic intellectual disability in a large consanguineous family

BACKGROUND

Intellectual disability (ID) is a highly heterogeneous condition affecting 2% of the population worldwide. In a field study conducted in a highly inbred area of Northeastern Brazil, we investigated a consanguineous family in which seven adults presented syndromic ID.

METHODS

Genome-Wide Human SNP Array 6.0 (Affymetrix) microarray was used to determine regions of homozygosity-by-descent and whole exome sequencing (WES) was performed in one affected individual using Extended Nextera Rapid-Capture Exome and Illumina HiSeq2500.

RESULTS

We found two regions with an logarithm of the odds (LOD) score of 3.234: a region spanning 4.0 Mb in 19q13.32-q13.33 and a pericentromeric 20 Mb area in chromosome 2 (2p12-q11.2). WES disclosed in the critical region of chromosome 19 a homozygous variant (c.418C>T, p.Arg140Trp) in Mediator complex subunit 25 (MED25), predicted as deleterious by PolyPhen-2, Provean, Mutation Taster and Sorting Intolerant From Tolerant (SIFT). MED25 is a component of the Mediator complex, involved in regulation of transcription of nearly all RNA polymerase II-dependent genes. Deleterious mutations in MED12, MED17 and MED23 have already been associated with ID.

CONCLUSIONS

These findings demonstrate that the combination of field investigation of families in highly inbred regions with modern technologies is an effective way for identifying new genes associated with ID.