Intestinal epithelial transcriptional machinery regulating P-glycoprotein expression

The intestinal epithelial transcriptional machinery regulating P-glycoprotein (P-gp) expression is a complex network of nuclear receptors and transcription factors that control the synthesis of the ABCB1 (MDR1) gene product (Geick et al., 2001, J. Biol. Chem.). P-gp is a critical efflux transporter located on the apical membrane of enterocytes, where it limits the absorption of various xenobiotics and drugs (Thiebaut et al., 1987, PNAS). Key components of this machinery include the Pregnane X Receptor (PXR), Constitutive Androstane Receptor (CAR), and Vitamin D Receptor (VDR), which sense foreign chemicals and trigger P-gp up-regulation to enhance intestinal clearance (Synold et al., 2001, Nature Medicine; Burk et al., 2005, Drug Metab. Dispos.). Dysregulation of this machinery is implicated in multidrug resistance in cancer and altered drug pharmacokinetics in inflammatory bowel diseases, where pro-inflammatory cytokines like TNF-alpha can suppress P-gp expression via NF-kappaB signaling (Mizuarai et al., 2004, Drug Metab. Pharmacokinet.). Pharmacological modulation of these regulators, such as the induction of PXR by rifampicin or St. John's Wort (hyperforin), can lead to significant drug-drug interactions by reducing the systemic exposure of P-gp substrates like digoxin or indinavir (Fromm, 2004, Trends Pharmacol. Sci.). Understanding this transcriptional network is essential for predicting drug bioavailability and managing therapeutic outcomes in patients receiving complex polypharmacy.

Other names

ABCB1 transcriptional regulationMDR1 gene regulatory networkP-glycoprotein induction pathwayXenobiotic-sensing nuclear receptor signaling

Activation of nuclear receptors such as PXR, CAR, and VDR leads to their binding to specific response elements (e.g., DR4, ER6) in the ABCB1 promoter and enhancer regions, recruiting co-activators to induce the transcription and subsequent protein expression of P-glycoprotein.