Pregnane X receptor (NR1I2) deficiency in mice reveals context-dependent regulation of inflammatory homeostasis

Nuclear receptor subfamily 1 group I member 2 (NR1I2; mouse ortholog Nr1i2), also known as the pregnane X receptor (PXR) or steroid and xenobiotic receptor (SXR), is a ligand-activated transcription factor classically known for its role in xenobiotic metabolism and detoxification. Beyond these canonical functions, accumulating evidence identifies NR1I2 as a key regulator of inflammation and intestinal homeostasis, particularly in inflammatory bowel disease (IBD), where dysregulated inflammatory responses are central to disease pathogenesis and NR1I2 expression is often reduced. In this review, we integrate data from whole-body and tissue-specific Nr1i2-deficient mouse models, as well as knockdown and ligand-based approaches, to define the role of Nr1i2 in intestinal inflammation under basal and pathological conditions. These studies collectively show that whole-body Nr1i2 deficiency disrupts intestinal homeostasis, impairs barrier integrity, and enhances innate immune activation, whereas tissue-restricted deletion, especially within the epithelium, frequently fails to reproduce these phenotypes, underscoring the importance of coordinated Nr1i2 activity across multiple cellular compartments. Across experimental models, most often Nr1i2 deficiency commonly exacerbates intestinal injury, particularly in response to microbial toxins or chemical damage, however attenuated inflammatory responses have been reported in selected metabolic or injury contexts. Conversely, pharmacological activation of Nr1i2 confers protective and restorative effects in a ligand-, tissue-, and context-dependent manner. Together, these findings establish NR1I2 not as a simple anti-inflammatory switch, but as an immune-metabolic integrator that coordinates xenobiotic detoxification, microbial-derived signal sensing, and restraint of innate inflammatory pathways. This review provides a conceptual framework for future studies aimed at elucidating the cell- and context-specific functions of NR1I2 and for guiding the development of targeted therapeutic strategies for intestinal inflammatory disorders.