3-Hydroxyflavone and structural analogues differentially activate pregnane X receptor: Implication for inflammatory...

Area of Science:

• Biochemistry
• Pharmacology
• Molecular Biology

Background:

• Pregnane X receptor (PXR) is a nuclear receptor regulating drug metabolism and transport.
• Flavonols are plant-derived compounds with potential biological activities.
• Understanding PXR modulation by flavonols is crucial for drug development and disease treatment.

Purpose of the Study:

• To investigate the effects of 3-hydroxyflavone and related analogues on PXR activity.
• To determine the species-specific activation of PXR by these compounds.
• To elucidate the structure-activity relationships governing flavonol-PXR interactions.

Main Methods:

• Cell-based reporter gene assays to assess PXR activation.
• Time-resolved fluorescence resonance energy transfer (TR-FRET) for ligand-binding assays.
• Coactivator recruitment assays using steroid receptor coactivators (SRCs).
• mRNA expression analysis of PXR target genes (CYP3A4, CYP3A5, ABCB1) in human colon cells.

Main Results:

• 3-Hydroxyflavone, galangin, kaempferol, quercetin, isorhamnetin, and tamarixetin activated mouse PXR.
• 3-Hydroxyflavone activated rat PXR; 3-hydroxyflavone, galangin, quercetin, isorhamnetin, and tamarixetin activated human PXR (hPXR).
• Specific flavonols bound to hPXR and recruited coactivators, leading to altered expression of drug-metabolizing enzymes and transporters.
• No tested flavonols acted as hPXR antagonists.

Conclusions:

• Flavonols exhibit analogue-specific and species-dependent activation of PXR.
• Structural modifications, particularly at the C2' or C5' positions, abolish hPXR activation.
• Findings provide insights into flavonol-PXR interactions, potentially guiding nutraceutical development for PXR-associated intestinal diseases like inflammatory bowel disease.