Negative Regulation of Human Pregnane X Receptor by MicroRNA-18a-5p: Evidence for Suppression of MicroRNA-18a-5p Expression by Rifampin and Rilpivirine

Abstract

Small noncoding microRNAs act as post-transcriptional regulators of gene expression involved in diverse biologic functions. Pregnane X receptor (PXR, NR1I2), a member of the superfamily of nuclear receptors, is a transcription factor governing the transport and biotransformation of various drugs and other chemicals. In the present study, we identified a specific microRNA (miR) involved in regulating the expression and functionality of human PXR (hPXR). According to bioinformatics analysis employing three commonly used algorithms (TargetScan, miRanda, and DIANA-microT-CDS), miR-18a-5p was predicted to be the top candidate microRNA regulator of hPXR. Consequently, this microRNA was selected for detailed experimental investigation. As shown in cell-based dual-luciferase reporter gene assays, functional interaction occurred between miR-18a-5p and the microRNA recognition element of miR-18a-5p in the 3'-untranslated region of hPXR mRNA. Transfection of LS180 human colorectal adenocarcinoma cells with an miR-18a-5p mimic decreased hPXR mRNA and protein expression, whereas transfection of LS180 cells with an miR-18a-5p inhibitor increased hPXR mRNA and protein expression. The decrease in hPXR expression by the miR-18a-5p mimic was associated with a reduction in the extent of hPXR target gene () induction by rifampin and rilpivirine. Treatment of untransfected LS180 cells with either of these hPXR agonists decreased endogenous expression of miR-18a-5p, and this preceded the onset of induction. In conclusion, miR-18a-5p is a negative regulator of hPXR expression and the hPXR agonists rifampin and rilpivirine are chemical suppressors of miR-18a-5p expression.

MicroRNA-140-3p enhances the sensitivity of hepatocellular carcinoma cells to sorafenib by targeting pregnenolone X receptor

“… 65 , 66 Following on from the paper by Sharma et al that concluded that miR-18a-5p is a negative regulator and research by Vachirayonstien et al that stated that miR-30c-1-3p could be a suppressor of PXR, our results extend the knowledge of miRs on the PXR signaling pathway. 67 , 68 …”

Regulation of CAR and PXR Expression in Health and Disease

“…In human and mouse liver cells, Smutny et al observed a significant upregulation of miRNA-18a-5p expression following 6h of incubation with the PXR ligands rifampicin and PCN, suggesting a negative feedback regulation in hepatic cells [131]. In contrast, Sharma et al reported that miRNA-18a-5p is inhibited in LS180 colon adenocarcinoma cells incubated with rifampicin for 6h [166]. These results highlight the tissue-specific regulation and the importance of temporal profiling.…”

Pregnane X Receptor (PXR) Polymorphisms and Cancer Treatment

“…miR-30c-1-3p is identified as a PXR silencer, thus decreases the mRNA levels of PXR and alters CYP3A4 expression [33]. Other post-translational PXR regulators are miR-18a-5p, miR-148a, miR-34a, miR-150, miR-27a and miR-140-3p, which negatively regulate PXR expression, resulting in decreased CYP3A4 expression [34][35][36][37][38]. miR-449a is described to inhibit PXR through HNF4-a in human hepatocytes [39].…”