St. John's Wort alleviates dextran sodium sulfate-induced colitis through pregnane X receptor-dependent NFκB antagonism

Characterization of NR1J1 Paralog Responses of Marine Mussels: Insights from Toxins and Natural Activators

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.

Reverse metabolomics for the discovery of chemical structures from humans

Determining the structure and phenotypic context of molecules detected in untargeted metabolomics experiments remains challenging. Here we present reverse metabolomics as a discovery strategy, whereby tandem mass spectrometry spectra acquired from newly synthesized compounds are searched for in public metabolomics datasets to uncover phenotypic associations. To demonstrate the concept, we broadly synthesized and explored multiple classes of metabolites in humans, including N-acyl amides, fatty acid esters of hydroxy fatty acids, bile acid esters and conjugated bile acids. Using repository-scale analysis1,2, we discovered that some conjugated bile acids are associated with inflammatory bowel disease (IBD). Validation using four distinct human IBD cohorts showed that cholic acids conjugated to Glu, Ile/Leu, Phe, Thr, Trp or Tyr are increased in Crohn's disease. Several of these compounds and related structures affected pathways associated with IBD, such as interferon-γ production in CD4+ T cells3 and agonism of the pregnane X receptor4. Culture of bacteria belonging to the Bifidobacterium, Clostridium and Enterococcus genera produced these bile amidates. Because searching repositories with tandem mass spectrometry spectra has only recently become possible, this reverse metabolomics approach can now be used as a general strategy to discover other molecules from human and animal ecosystems.

LncRNA PSCK6-AS1-HIPK2 promotes Th1 differentiation via STAT1 phosphorylation to regulate colitis-related mucosal barrier damage

This work aimed to investigate the role of long non-coding RNA (lncRNA) PCSK6-AS1 in inflammatory bowel disease (IBD). The levels of PCSK6-AS1 in human samples were detected, and its target protein HIPK2 was explored by protein mass spectrometry and ground select test (GST) method. Meanwhile, the HIPK2-STAT1 interaction relation was verified by pull-down assay. In the mouse model, Dextran Sulfate Sodium（DSS） was used to induce mouse colitis, then the effect of PCSK6-AS1 on mouse mucosal barrier was detected by immunohistochemical (IHC) staining, hematoxylin and eosin (H&E) staining, and the proportion of T-helper cells 1（Th1) cells was measured by flow cytometry (FCM). For in-vitro experiments, Th0 cells were used as the objects, and the effect of PCSK6-AS1 on Th1 differentiation was explored by FCM and enzyme-linked immunosorbent assay (ELISA). According to our results, the expression of PCSK6-AS1 in colitis tissues increased. PCSK6-AS1 interacted with HIPK2 to promote the expression of the latter, while HIPK2 promoted STAT1 phosphorylation to regulate Th1 differentiation. Th1 differentiation accelerated the mucosal barrier injury and aggravated the progression of colitis. In the Th0 model, PCSK6-AS1 promoted Th1 differentiation. In the animal model, PCSK6-AS1 enhanced Th1 differentiation in the tissues, decreased the tight junction (TJ) protein levels, and improved the mucosal barrier permeability. Suppressing PCSK6-AS1 and the HIPK2 inhibitor tBID decreased Th1 differentiation and tissue inflammation. According to our results, PCSK6-AS1 promotes Th1 cell differentiation via the HIPK2-STAT1 signaling, thus aggravating the chronic colitis-related mucosal barrier damage and tissue inflammation. PCSK6-AS1 has an important role in the occurrence and development of IBD.

The Function of Xenobiotic Receptors in Metabolic Diseases

Metabolic diseases are a series of metabolic disorders that include obesity, diabetes, insulin resistance, hypertension, and hyperlipidemia. The increased prevalence of metabolic diseases has resulted in higher mortality and mobility rates over the past decades, and this has led to extensive research focusing on the underlying mechanisms. Xenobiotic receptors (XRs) are a series of xenobiotic-sensing nuclear receptors that regulate their downstream target genes expression, thus defending the body from xenobiotic and endotoxin attacks. XR activation is associated with the development of a number of metabolic diseases such as obesity, nonalcoholic fatty liver disease, type 2 diabetes, and cardiovascular diseases, thus suggesting an important role for XRs in modulating metabolic diseases. However, the regulatory mechanism of XRs in the context of metabolic disorders under different nutrient conditions is complex and remains controversial. This review summarizes the effects of XRs on different metabolic components (cholesterol, lipids, glucose, and bile acids) in different tissues during metabolic diseases. As chronic inflammation plays a critical role in the initiation and progression of metabolic diseases, we also discuss the impact of XRs on inflammation to comprehensively recognize the role of XRs in metabolic diseases. This will provide new ideas for treating metabolic diseases by targeting XRs. SIGNIFICANCE STATEMENT: This review outlines the current understanding of xenobiotic receptors on nutrient metabolism and inflammation during metabolic diseases. This work also highlights the gaps in this field, which can be used to direct the future investigations on metabolic diseases treatment by targeting xenobiotic receptors.

Hyperforin Elicits Cytostatic/Cytotoxic Activity in Human Melanoma Cell Lines, Inhibiting Pro-Survival NF-κB, STAT3, AP1 Transcription Factors and the Expression of Functional Proteins Involved in Mitochondrial and Cytosolic Metabolism

Hyperforin (HPF), the main component responsible for the antidepressant action of Hypericum perforatum, displays additional beneficial properties including anti-inflammatory, antimicrobic, and antitumor activities. Among its antitumor effects, HPF activity on melanoma is poorly documented. Melanoma, especially BRAF-mutated melanoma, is still a high-mortality tumor type and the currently available therapies do not provide solutions. We investigated HPF's antimelanoma effectiveness in A375, FO1 and SK-Mel-28 human BRAF-mutated cell lines. Cell viability assays documented that all melanoma cells were affected by low HPF concentrations (EC50% 2-4 µM) in a time-dependent manner. A Br-deoxy-uridine incorporation assay attested a significant reduction of cell proliferation accompanied by decreased expression of cyclin D1 and A2, CDK4 and of the Rb protein phosphorylation, as assessed by immunoblots. In addition, the expression of P21/waf1 and the activated form of P53 were increased in A375 and SK-Mel-28 cells. Furthermore, HPF exerts cytotoxic effects. Apoptosis is induced 24 h after HPF administration, documented by an increase of cleaved-PARP1 and a decrease of both Bcl2 and Bcl-xL expression levels. Autophagy is induced, attested by an augmented LC3B expression and augmentation of the activated form of AMPK. Moreover, HPF lowers GPX4 enzyme expression, suggesting ferroptosis induction. HPF has been reported to activate the TRPC6 Ca⁺⁺ channel and/or Ca⁺⁺ and Zn⁺⁺ release from mitochondria stores, increasing cytosolic Ca⁺⁺ and Zn⁺⁺ concentrations. Our data highlighted that HPF affects many cell-signaling pathways, including signaling induced by Ca⁺⁺, such as FRA1, pcJun and pCREB, the expression or activity of which are increased shortly after treatment. However, the blockage of the TRPC6 Ca⁺⁺ channel or the use of Ca⁺⁺ and Zn⁺⁺ chelators do not hinder HPF cytostatic/cytotoxic activity, suggesting that damages induced in melanoma cells may pass through other pathways. Remarkably, 24 h after HPF treatment, the expression of activated forms of the transcription factors NF-κB P65 subunit and STAT3 are significantly lowered. Several cytosolic (PGM2, LDHA and pPKM2) and mitochondrial (UQCRC1, COX4 and ATP5B) enzymes are downregulated by HPF treatment, suggesting a generalized reduction of vital functions in melanoma cells. In line with these results is the recognized ability of HPF to affect mitochondrial membrane potential by acting as a protonophore. Finally, HPF can hinder both melanoma cell migration and colony formation in soft agar. In conclusion, we provide evidence of the pleiotropic antitumor effects induced by HPF in melanoma cells.

Schisandrol B protects against cholestatic liver injury by inhibiting pyroptosis through pregnane X receptor

Previously, we demonstrated that Schisandrol B (SolB) protected against lithocholic acid (LCA)-induced cholestatic liver injury (CLI) through pregnane X receptor (PXR). Additionally, growing evidence has revealed that pyroptosis is involved in CLI. Whether the hepatoprotective effect of SolB driven by PXR activation is related to pyroptosis in CLI remains unclear. First, the hepatoprotective effect of SolB was confirmed, as evidenced by the decreased mortality, morphological and histopathological changes, and biochemical parameters. The upregulated serum lactic dehydrogenase (LDH) level, increased number of TUNEL-positive cells, and formation of hepatocyte membrane pores induced by LCA were significantly alleviated after SolB pretreatment, indicating that SolB attenuated LCA-induced hepatocyte damage. Further analysis revealed that both NOD-like receptor protein 3 (NLRP3) inflammasome-induced canonical pyroptosis and apoptosis protease activating factor-1 (Apaf-1) pyroptosome-induced noncanonical pyroptosis were significantly inhibited after SolB pretreatment, as illustrated by the decreased expression levels of NLRP3, ASC, caspase-1, and GSDMD and the levels of Apaf-1, caspase-11 p20, caspase-3 p20, and GSDME. Furthermore, the activation of the NF-κB and FoxO1 signaling pathways was inhibited after SolB pretreatment. In addition, the activation of PXR via SolB was proven by luciferase reporter gene assays and the upregulation of PXR targets. The results illustrated that SolB could significantly inhibit NLRP3 inflammasome-induced canonical pyroptosis through the PXR/NF-κB/NLRP3 axis and inhibit Apaf-1 pyroptosome-induced noncanonical pyroptosis through the PXR/FoxO1/Apaf-1 axis. Collectively, this study revealed that SolB protected against CLI by inhibiting pyroptosis through PXR, providing new insights for understanding the molecular mechanism of SolB as a promising anti-cholestatic agent.

The Interface between Cell Signaling Pathways and Pregnane X Receptor

Highly expressed in the enterohepatic system, pregnane X receptor (PXR, NR1I2) is a well-characterized nuclear receptor (NR) that regulates the expression of genes in the liver and intestines that encode key drug metabolizing enzymes and drug transporter proteins in mammals. The net effect of PXR activation is to increase metabolism and clear drugs and xenobiotics from the body, producing a protective effect and mediating clinically significant drug interaction in patients on combination therapy. The complete understanding of PXR biology is thus important for the development of safe and effective therapeutic strategies. Furthermore, PXR activation is now known to specifically transrepress the inflammatory- and nutrient-signaling pathways of gene expression, thereby providing a mechanism for linking these signaling pathways together with enzymatic drug biotransformation pathways in the liver and intestines. Recent research efforts highlight numerous post-translational modifications (PTMs) which significantly influence the biological function of PXR. However, this thrust of research is still in its infancy. In the context of gene-environment interactions, we present a review of the recent literature that implicates PXR PTMs in regulating its clinically relevant biology. We also provide a discussion of how these PTMs likely interface with each other to respond to extracellular cues to appropriately modify PXR activity.