Original articles
Tomas Smutny, Jan Dusek, Lucie Hyrsova, Jana Nekvindova, Alzbeta Horvatova, Stanislav Micuda, Sabine Gerbal-Chaloin, Petr Pavek. The 3'-untranslated region contributes to the pregnane X receptor (PXR) expression down-regulation by PXR ligands and up-regulation by glucocorticoids[J]. Acta Pharmaceutica Sinica B, 2020, 10(1): 136-152

The 3'-untranslated region contributes to the pregnane X receptor (PXR) expression down-regulation by PXR ligands and up-regulation by glucocorticoids
Tomas Smutnya, Jan Duseka, Lucie Hyrsovaa, Jana Nekvindovab, Alzbeta Horvatovaa, Stanislav Micudac, Sabine Gerbal-Chaloind, Petr Paveka
a Department of Pharmacology and Toxicology, Faculty of Pharmacy in Hradec Kralove, Charles University, Hradec Kralove CZ-500 05, Czech Republic;
b Institute of Clinical Biochemistry and Diagnostics, University Hospital Hradec Kralove, Hradec Kralove CZ-500 05, Czech Republic;
c Department of Pharmacology, Faculty of Medicine in Hradec Kralove, Charles University, Hradec Kralove CZ-500 03, Czech Republic;
d IRMB, INSERM, University Montpellier, Montpellier, France
Pregnane X receptor (PXR) is the major regulator of xenobiotic metabolism. PXR itself is controlled by various signaling molecules including glucocorticoids. Moreover, negative feed-back regulation has been proposed at the transcriptional level. We examined the involvement of the 3'-untranslated region (3'-UTR) of NR1I2 mRNA and microRNAs in PXR- and glucocorticoid receptor (GR)-mediated regulation of NR1I2 gene expression. PXR ligands were found to significantly downregulate NR1I2 mRNA expression in a set of 14 human hepatocyte cultures. Similarly, PXR was downregulated by PCN in the C57/BL6 mice liver. In mechanistic studies with the full-length 3'-UTR cloned into luciferase reporter or expression vectors, we showed that the 3'-UTR reduces PXR expression. From the miRNAs tested, miR-18a-5p inhibited both NR1I2 expression and CYP3A4 gene induction. Importantly, we observed significant upregulation of miR-18a-5p expression 6 h after treatment with the PXR ligand rifampicin, which indicates a putative mechanism underlying NR1I2 negative feed-back regulation in hepatic cells. Additionally, glucocorticoids upregulated NR1I2 expression not only through the promoter region but also via 3'-UTR regulation, which likely involves downregulation of miR-18a-5p. We conclude that miR-18a-5p is involved in the down-regulation of NR1I2 expression by its ligands and in the upregulation of NR1I2 mRNA expression by glucocorticoids in hepatic cells.
Key words:    Gene expression    MicroRNA    Glucocorticoid    Regulation    Pregnane X receptor    Cytochrome P450 3A4   
Received: 2019-07-22     Revised: 2019-09-10
DOI: 10.1016/j.apsb.2019.09.010
Funds: This work was supported by grants from the Czech Science Foundation 17-06841S to Petr Pavek and EFSA-CDN (No. CZ.02.1.01/0.0/0.0/16_019/0000841, Czech Republic) co-funded by ERDF to Tomas Smutny.
Corresponding author: Petr Pavek     Email:petr.pavek@faf.cuni.cz
Author description:
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Tomas Smutny
Jan Dusek
Lucie Hyrsova
Jana Nekvindova
Alzbeta Horvatova
Stanislav Micuda
Sabine Gerbal-Chaloin
Petr Pavek

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