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...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 NR 112 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 NR1I2expression by its ligands and in the upregulation of NR1I2 mRNA expression by glucocorticoids in hepatic cells.展开更多
基金supported by grants from the Czech Science Foundation 17-06841S to Petr PavekEFSA-CDN(No.CZ.02.1.01/0.0/0.0/16_019/0000841,Czech Republic)co-funded by ERDF to Tomas Smutny.
文摘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 NR 112 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 NR1I2expression by its ligands and in the upregulation of NR1I2 mRNA expression by glucocorticoids in hepatic cells.
