Despite their significant impact, comprehensive screenings and detailed analyses of per- and polyfluoroalkyl substance (PFAS) binding strengths at the orthosteric and allosteric sites of NRs are currently lacking. This study addresses this gap by focusing on the binding interaction analysis of both common and uncommon PFAS with the nuclear receptors (NRs) vitamin D receptor (VDR), peroxisome proliferator-activated receptor gamma (PPARγ), pregnane X receptor (PXR), and estrogen receptor alpha (ERα). Advanced docking simulations were used to screen 9507 PFAS chemicals at the orthosteric and allosteric sites of PPARγ, PXR, VDR, and ERα. All receptors exhibited strong binding interactions at the orthosteric and allosteric site with a significant number of PFAS. We verified the accuracy of the docking protocol through multiple docking controls and validations. A mixture modeling analysis indicates that PFAS can bind in various combinations with themselves and endogenous ligands simultaneously, to disrupt the endocrine system and cause carcinogenic responses. These findings reveal that PFAS can interfere with nuclear receptor activity by displacing endogenous or native ligands by binding to the orthosteric and allosteric sites. The purpose of this study is to explore the mechanisms through which PFAS exert their endocrine-disrupting effects, potentially leading to more targeted therapeutic strategies. Importantly, this study is the first to explore the binding of PFAS at allosteric sites and to model PFAS mixtures at nuclear receptors. Given the high concentration and persistence of PFAS in humans, this study further emphasizes the urgent need for further research into the carcinogenic mechanisms of PFAS and the development of therapeutic strategies that target nuclear receptors.

Pregnane X receptor (PXR) has been reported to regulate glycolipid metabolism. The dysfunction of intestinal barrier contributes to metabolic disorders. However, the role of intestinal PXR in metabolic diseases remains largely unknown. Here, we show that activation of PXR by tributyl citrate (TBC), an intestinal-selective PXR agonist, improves high fat diet (HFD)-induced obesity. The metabolic benefit of intestinal PXR activation is associated with upregulation of β-1,3 galactosyltransferase 5 (B3galt5). Our results reveal that B3galt5 mainly expresses in the intestine and is a direct PXR transcriptional target. B3galt5 knockout exacerbates HFD-induced obesity, insulin resistance and inflammation. Mechanistically, B3galt5 is essential to maintain the integrity of intestinal mucus barrier. B3galt5 ablation impairs the O-glycosylation of mucin2, destabilizes the mucus layer, and increases intestinal permeability. Furthermore, B3galt5 deficiency abolishes the beneficial effect of intestinal PXR activation on metabolic disorders. Our results suggest the intestinal-selective PXR activation regulates B3galt5 expression and maintains metabolic homeostasis, making it a potential therapeutic strategy in obesity.

UNASSIGNED: Cannabidiol (CBD), a non-psychoactive phytocannabinoid of cannabis, is therapeutically used as an analgesic, anti-convulsant, anti-inflammatory, and anti-psychotic drug. There is a growing concern about the adverse side effects posed by CBD usage. Pregnane X receptor (PXR) is a nuclear receptor activated by a variety of dietary steroids, pharmaceutical agents, and environmental chemicals. In addition to the role in xenobiotic metabolism, the atherogenic and dyslipidemic effects of PXR have been revealed in animal models. CBD has a low affinity for cannabinoid receptors, thus it is important to elucidate the molecular mechanisms by which CBD activates cellular signaling and to assess the possible adverse impacts of CBD on pro-atherosclerotic events in cardiovascular system, such as dyslipidemia.
UNASSIGNED: Our study aims to explore the cellular and molecular mechanisms by which exposure to CBD activates human PXR and increases the risk of dyslipidemia.
UNASSIGNED: Both human hepatic and intestinal cells were used to test if CBD was a PXR agonist via cell-based transfection assay. The key residues within PXR\'s ligand-binding pocket that CBD interacted with were investigated using computational docking study together with site-directed mutagenesis assay. The C57BL/6 wildtype mice were orally fed CBD in the presence of PXR antagonist resveratrol (RES) to determine how CBD exposure could change the plasma lipid profiles in a PXR-dependent manner. Human intestinal cells were treated with CBD and/or RES to estimate the functions of CBD in cholesterol uptake.
UNASSIGNED: CBD was a selective agonist of PXR with higher activities on human PXR than rodents PXRs and promoted the dissociation of human PXR from nuclear co-repressors. The key amino acid residues Met246, Ser247, Phe251, Phe288, Trp299, and Tyr306 within PXR\'s ligand binding pocket were identified to be necessary for the agonistic effects of CBD. Exposure to CBD increased the circulating total cholesterol levels in mice which was partially caused by the induced expression levels of the key intestinal PXR-regulated lipogenic genes. Mechanistically, CBD induced the gene expression of key intestinal cholesterol transporters, which led to the increased cholesterol uptake by intestinal cells.
UNASSIGNED: CBD was identified as a selective PXR agonist. Exposure to CBD activated PXR signaling and increased the atherogenic cholesterol levels in plasma, which partially resulted from the ascended cholesterol uptake by intestinal cells. Our study provides potential evidence for the future risk assessment of CBD on cardiovascular disease, such as dyslipidemia.

The pregnane X receptor (PXR) is a nuclear hormone receptor that plays a pivotal role in regulating gene expression in response to various ligands, particularly xenobiotics. In this context, the aim of this study was to shed light on the ligand affinity and functions of four NR1J1 paralogs identified in the marine mussel Mytilus galloprovincialis, employing a dual-luciferase reporter assay. To achieve this, the activation patterns of these paralogs in response to various toxins, including freshwater cyanotoxins (Anatoxin-a, Cylindrospermopsin, and Microcystin-LR, -RR, and -YR) and marine algal toxins (Nodularin, Saxitoxin, and Tetrodotoxin), alongside natural compounds (Saint John\'s Wort, Ursolic Acid, and 8-Methoxypsoralene) and microalgal extracts (Tetraselmis, Isochrysis, LEGE 95046, and LEGE 91351 extracts), were studied. The investigation revealed nuanced differences in paralog response patterns, highlighting the remarkable sensitivity of MgaNR1J1γ and MgaNR1J1δ paralogs to several toxins. In conclusion, this study sheds light on the intricate mechanisms of xenobiotic metabolism and detoxification, particularly focusing on the role of marine mussel NR1J1 in responding to a diverse array of compounds. Furthermore, comparative analysis with human PXR revealed potential species-specific adaptations in detoxification mechanisms, suggesting evolutionary implications. These findings deepen our understanding of PXR-mediated metabolism mechanisms, offering insights into environmental monitoring and evolutionary biology research.

BACKGROUND: Our recent studies showed that prolonged administration of novel atypical antipsychotics affected the expression and activity of cytochrome P450 (CYP), as demonstrated in vitro on human hepatocytes and in vivo on the rat liver. The aim of the present work was to study the effect of repeated treatment with asenapine, iloperidone, and lurasidone on the expression of transcription factors regulating CYP drug-metabolizing enzymes in rat liver.
METHODS: The hepatic mRNA (qRT-PCR) and protein levels (Western blotting) of aryl hydrocarbon receptor (AhR), pregnane X receptor (PXR), constitutive androstane receptor (CAR) and peroxisome proliferator-activated receptor (PPARγ) were measured in male Wistar rats after 2 week-treatment with asenapine, iloperidone or lurasidone.
RESULTS: The 2-week treatment with asenapine significantly diminished the AhR and PXR expression (mRNA, protein level), and CAR mRNA level in rat liver. Iloperidone lowered the AhR and CAR expression and PXR protein level. Lurasidone did not affect the expression of AhR and CAR, but increased PXR expression. The antipsychotics did not affect PPARγ.
CONCLUSIONS: Prolonged treatment with asenapine, iloperidone, or lurasidone affects the expression of transcription factors regulating the CYP drug-metabolizing enzymes. The changes in the expression of AhR, CAR, and PXR mostly correlate with alterations in the expression and activity of respective CYP enzymes found in our previous studies. Since these transcription factors are also engaged in the expression of phase II drug metabolism and drug transporters, changes in their expression may affect the metabolism of endogenous substrates and pharmacokinetics of concomitantly used drugs.

Nuclear receptors such as constitutive androstane receptor (CAR), pregnane X receptor (PXR), and peroxisome proliferator-activated receptor-alpha (PPARα), and transcription factors with nuclear receptor type activity such as aryl hydrocarbon receptor (AhR) function as xenobiotic sensors. Hepatocyte nuclear factor 4alpha (HNF4α) is a highly conserved orphan nuclear receptor essential for liver function. We tested the hypothesis that HNF4α is essential for the function of these 4 major xenosensors. Wild-type (WT) and hepatocyte-specific Hnf4a null (HNF4α-KO) mice were treated with the mouse-specific activators of AhR (TCDD, 30 µg/kg), CAR (TCPOBOP, 2.5 µg/g), PXR, (PCN, 100 µg/g), and PPARα (WY-14643, 1 mg/kg). Blood and liver tissue samples were collected to study receptor activation. TCDD (AhR agonist) treatment did not affect the liver-to-body weight ratio (LW/BW) in either WT or HNF4α-KO mice. Further, TCDD activated AhR in both WT and HNF4α-KO mice, confirmed by increase in expression of AhR target genes. TCPOBOP (CAR agonist) significantly increased the LW/BW ratio and CAR target gene expression in WT mice, but not in HNF4α-KO mice. PCN (a mouse PXR agonist) significantly increased LW/BW ratio in both WT and HNF4α-KO mice however, failed to induce PXR target genes in HNF4α-KO mice. The treatment of WY-14643 (PPARα agonist) increased LW/BW ratio and PPARα target gene expression in WT mice but not in HNF4α-KO mice. Together, these data indicate that the function of CAR, PXR, and PPARα but not of AhR was disrupted in HNF4α-KO mice. These results demonstrate that HNF4α function is critical for the activation of hepatic xenosensors, which are critical for toxicological responses.

Nuclear receptors are ligand-activated transcription factors that can often be useful drug targets. Unfortunately, ligand promiscuity leads to two-thirds of receptors remaining clinically untargeted. PXR is a nuclear receptor that can be activated by diverse compounds to elevate metabolism, negatively impacting drug efficacy and safety. This presents a barrier to drug development because compounds designed to target other proteins must avoid PXR activation while retaining potency for the desired target. This problem could be avoided by using PXR antagonists, but these compounds are rare, and their molecular mechanisms remain unknown. Here, we report structurally related PXR-selective agonists and antagonists and their corresponding co-crystal structures to describe mechanisms of antagonism and selectivity. Structural and computational approaches show that antagonists induce PXR conformational changes incompatible with transcriptional coactivator recruitment. These results guide the design of compounds with predictable agonist/antagonist activities and bolster efforts to generate antagonists to prevent PXR activation interfering with other drugs.

Ultrasound therapy is a method of applying ultrasonic energy to the stimulation produced by human body to change the function and tissue state of the body in order to achieve the purpose of treating diseases. Chronic venous ulcer is a common chronic skin ulcer. GSE222503 for ultrasound therapy of chronic venous ulcers was downloaded from gene expression omnibus database, which were used to identify differentially expressed genes. Weighted gene co-expression network analysis, functional enrichment analysis, gene set enrichment analysis, immune infiltration analysis and construction and analysis of protein-protein interaction network were performed. Draw gene expression heatmaps. Comparative toxicogenomics database analysis was performed. Two hundred thirty-five differentially expressed genes were obtained. According to gene ontology analysis, in biological process analysis, they were mainly enriched in positive regulation of cellular biosynthetic process, reproductive cell development, vasculogenesis, vascular morphogenesis, and inflammatory response. In cellular component analysis, they were mainly enriched in leading edge of growing cell, extracellular matrix binding organelle, F-actin capping protein complex. In molecular function analysis, they were mainly concentrated in receptor ligand activity, cytokine receptor binding. In Kyoto encyclopedia of genes and genomes analysis, they were mainly enriched in cytokine-cytokine receptor interaction, PI3K-Akt signaling pathway, HIF-1 signaling pathway, heme biosynthesis. In weighted gene co-expression network analysis, the soft threshold power was set to 9. Thirty modules were generated. PF4, NR1I2, TTC16, H3C12, KLRB1, CYP21A2 identified by 4 algorithms (MCC, EPC, closeness, stress). Heatmap of core gene expression showed that H3C12, KLRB1, PF4, NR1I2 were all underexpressed in samples of ultrasound-treated chronic venous ulcers and overexpressed in samples of untreated chronic venous ulcers. Comparative toxicogenomics database analysis showed that H3C12, KLRB1, PF4, NR1I2 are associated with thrombophlebitis, phlebitis, vascular malformations, metabolic syndrome, ulcers, and inflammation. In samples of chronic venous ulcer tissue treated with ultrasound, NR1I2 shows low expression, while in samples of chronic venous ulcer tissue without ultrasound treatment, it shows high expression. This finding suggests a potential role of NR1I2 in the process of ultrasound therapy for chronic venous ulcers, which may be related to the therapeutic effect of ultrasound therapy on chronic venous ulcers.

This review explores the likely clinical impact of Pregnane X Receptor (PXR) activation by vitamin K on human health. PXR, initially recognized as a master regulator of xenobiotic metabolism in liver, emerges as a key regulator influencing intestinal homeostasis, inflammation, oxidative stress, and autophagy. The activation of PXR by vitamin K highlights its role as a potent endogenous and local agonist with diverse clinical implications. Recent research suggests that the vitamin K-mediated activation of PXR highlights this vitamin\'s potential in addressing pathophysiological conditions by promoting hepatic detoxification, fortifying gut barrier integrity, and controlling pro-inflammatory and apoptotic pathways. PXR activation by vitamin K provides an intricate association with cancer cell survival, particularly in colorectal and liver cancers, to provide new insights into potential novel therapeutic strategies. Understanding the clinical implications of PXR activation by vitamin K bridges molecular mechanisms with health outcomes, further offering personalized therapeutic approaches for complex diseases.

Deoxynivalenol (DON) is a prevalent toxin causing severe liver damage through hepatocellular oxidative stress. However, the underlying mechanisms and effective therapeutic approaches remain unknown. Here, the unique role of the xenobiotic metabolism factor pregnane X receptor (PXR) in mediating DON-induced hepatocellular oxidative stress is investigated. Treatment with the PXR agonist 3-indole-propionic acid (IPA) alleviates DON-induced oxidative stress and liver injury both in vitro and in vivo. Mechanistically, it is discovered for the first time that PXR agonist IPA directly transactivates the m6A demethylase FTO expression, leading to site-specific demethylation and decreased abundance of YTHDC1-bound Malat1 lncRNA at single-nucleotide resolution. The diminished m6A modification of Malat1 lncRNA reduces its stability and augments antioxidant pathways governed by NRF2, consequently mitigating DON-induced liver injury. Furthermore, Malat1 knockout mice exhibit decreased DON-induced liver injury, emphasizing the role of Malat1 lncRNA in oxidative stress. Collectively, the findings establish that PXR-mediated m6A-dependent Malat1 lncRNA expression determines hepatocyte oxidative stress via m6A demethylase FTO, providing valuable insights into the potential mechanisms underlying DON-induced liver injury and offers potential therapeutic strategies for its treatment.