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The nuclear receptors PXR, CAR, and FXR are activated by various ligands and function as transcription factors to control the expression of genes that regulate the synthesis and metabolism of androstenone and skatole. These compounds are produced in entire male pigs and accumulate in the fat to cause the development of a meat quality issue known as boar taint. The extent of this accumulation is influenced by the synthesis and hepatic clearance of androstenone and skatole. For this reason, PXR, CAR, and FXR-mediated signaling pathways have garnered interest as potential targets for specialized treatments designed to reduce the development of boar taint. Recent research has also identified several metabolites produced by gut microbes that act as ligands for these nuclear receptors (e.g., tryptophan metabolites, short-chain fatty acids, bile acids); however, the connection between the gut microbiome and boar taint development is not clear. In this review, we describe the nuclear receptor signaling pathways that regulate the synthesis and metabolism of boar taint compounds and outline the genes involved. We also discuss several microbial-derived metabolites and dietary additives that are known or suspected nuclear receptor ligands and suggest how these compounds could be used to develop novel treatments for boar taint.

Obesity and malnutrition both cause dysbiosis and dampen retinoic acid (RA) signaling pathways, which play pivotal roles in biological processes. The current study evaluates a hypothesis that colitis-associated dysbiosis also has systemic negative impacts on RA signaling. Thus, we studied the effects of inflammation, under a vitamin A-sufficient condition, on RA signaling using mouse colitis models induced by dextran sulfate sodium. That data showed that intestinal inflammation resulted in reduced RA signaling in the liver, brain, gut, and adipose tissues measured by analyzing the expression of genes encoding for the synthesis, oxidation, transport, and receptor of RA. The expression of RA-regulated gut homing molecules including α4β7 integrin, and CCR9, along with MADCAM1 were all reduced in colitis mice revealing compromised immunity due to reduced RA signaling. The data also showed that the development of colitis was accompanied by dysbiosis featured with reduced Lactobacillaceae and Verrucomicrobiaceae but an expansion of Erysipelotrichaceae and others. Colitis resulted in reduced butyrate-producing bacteria and increased methane-generating bacteria. Additionally, dysbiosis was associated with induced Il-1β, Ifn-γ, and Tnf-α mRNA but reduced Il-22, Il-17f, and Rorγt transcripts in the colon. Together, intestinal inflammation inhibits RA signaling in multiple organs. RA is essential in regulating various biological processes, it is critical to detect RA signaling reduction in tissues even when vitamin A deficiency is absent. Moreover, probiotics can potentially prevent dysbiosis and reverse compromised RA signaling, having systemic health benefits.

Peroxisome proliferator-activated receptor β/δ (PPARβ/δ), a ligand-activated nuclear receptor, regulates lipid and glucose metabolism and inflammation. PPARβ/δ can exert an anti-inflammatory effect by suppressing proinflammatory cytokine production. Cyclooxygenase-2 (COX-2)-triggered inflammation plays a crucial role in the development of many inflammatory diseases, including glomerulonephritis. However, the effect of PPARβ/δ on the expression of COX-2 in the kidney has not been fully elucidated. The present study showed that PPARβ/δ was functionally expressed in human mesangial cells (hMCs), where its expression was increased by interleukin-1β (IL-1β) treatment concomitant with enhanced COX-2 expression and prostaglandin E2 (PGE2) biosynthesis. The treatment of hMCs with GW0742, a selective agonist of PPARβ/δ, or the overexpression of PPARβ/δ via an adenovirus-mediated approach significantly increased COX-2 expression and PGE2 production. PPARβ/δ could further augment the IL-1β-induced COX-2 expression and PGE2 production in hMCs. Moreover, both PPARβ/δ activation and overexpression markedly increased sirtuin 1 (SIRT1) expression. The inhibition or knockdown of SIRT1 significantly attenuated the effects of PPARβ/δ on the IL-1β-induced expression of COX-2 and PGE2 biosynthesis. Taken together, PPARβ/δ could augment the IL-1β-induced COX-2 expression and PGE2 production in hMCs via the SIRT1 pathway. Given the critical role of COX-2 in glomerulonephritis, PPARβ/δ may represent a novel target for the treatment of renal inflammatory diseases.

Production of polychlorinated biphenyls (PCBs) was banned a long time ago because of their harmful health effects but humans continue to be exposed to residual PCBs in the environment. In this study, the susceptibility of human nuclear receptors to binding by PCBs was investigated using molecular docking simulation. Findings revealed that PCBs belonging to ortho-substituted, mono-ortho-substituted and non-ortho-substituted congeners could bind to agonistic conformations of androgen (AR), estrogen (ER α and ER β), glucocorticoid (GR) and thyroid hormone (TR α and TR β) receptors as well as antagonistic conformation of androgen receptor (AR an) but only ortho-substituted and mono-ortho-substituted PCBs could bind to estrogen receptors in their antagonistic conformations (ER α an and ER β an). Further molecular docking analyses showed that PCBs mimic the modes of interaction observed for the co-crystallized ligands in the crystal structures of the affected receptors, utilizing 81%, 83%, 78%, 60%, 75%, 60%, 86%, 100% and 75% of the amino acid residues utilized by the co-crystallized ligands for binding in AR, AR an, ER α, ER α an, ER β, ER β an, GR, TR α and TR β respectively. This computational study suggests that PCBs may cause endocrine disruption via formation of non-covalent interactions with androgen, estrogen, glucocorticoid and thyroid hormone receptors.

Multiple sclerosis (MS) is a chronic neurological disease driven by autoimmune, inflammatory and neurodegenerative processes leading to neuronal demyelination and subsequent degeneration. Systemic lipid metabolism is disturbed in people with MS, and lipid metabolic pathways are crucial to the protective process of remyelination. The lipid-activated transcription factors liver X receptors (LXRs) are important integrators of lipid metabolism and immunity. Consequently, there is a strong interest in targeting these receptors in a number of metabolic and inflammatory diseases, including MS. We have reviewed the evidence for involvement of LXR-driven lipid metabolism in the dysfunction of peripheral and brain-resident immune cells in MS, focusing on human studies, both the relapsing remitting and progressive phases of the disease are discussed. Finally, we discuss the therapeutic potential of modulating the activity of these receptors with existing pharmacological agents and highlight important areas of future research.

Cigarette smoke (CS) contains many toxins that collectively harm nearly every organ in the body, and smoking is a key risk factor for many chronic diseases. Aside from its toxic actions, CS may alter expression of the drug- and steroid-binding pregnane X receptor (PXR), which when activated upregulates expression of cytochrome P450 (CYP) enzymes, glutathione transferases (GSTs), and multidrug resistance protein 1 (MDR1), an adaptive metabolic array that mediates clearance of CS component toxins. We sought to identify new PXR agonists that may be useful for restoring PXR activity in conditions wherein it is suppressed, and their mechanisms of PXR binding and activation. PXR has a uniquely larger, hydrophobic, and highly flexible ligand-binding domain (LBD) vs. other nuclear receptors, enabling it to interact with structurally diverse molecules. We tested certain calcium channel blockers (CCBs) as a pharmacological subset of potential PXR ligands, analyzing by molecular docking methods, and identified a putative active site in the PXR LBD, along with the relevant bonds and bonding energies. We analyzed felodipine binding and agonist activity in detail, as it showed the lowest binding energy among CCBs tested. We found felodipine was a potent PXR agonist as measured by luciferase reporter assay, whereas CCBs with higher binding energies were less potent (amlodipine) or nearly inactive (manidipine), and it induced CYP3A4 expression in HepG2 cells, a known target of PXR agonism. Felodipine also both induced PXR mRNA in HepG2 hepatocytes and reduced CS extract-induced diminution of PXR levels, indicating it modulates PXR expression. The results illuminate mechanisms of ligand-induced PXR activation and identify felodipine as a novel PXR agonist. • Analyzed calcium channel blocker (CCB) interactions with pregnane X receptor (PXR). • Identified and characterized selective CCBs as novel PXR agonists. • Cigarette smoke (CS) downregulates PXR mRNA and protein levels. • CCB felodipine reverses such CS-induced downregulation. [ABSTRACT FROM AUTHOR]

Thyroid hormone receptor (THR) belongs to the nuclear receptor (NR) superfamily that is activated by binding of appropriate ligand molecules (thyroid hormones). These receptors directly bind to specific DNA sequences for gene expression, which is essential for metabolism, homeostasis, and the development of organisms, making it an important drug target. Extensive MD-simulation studies of triiodothyronine (T3) docked modeled rnTHRβ1 structures have indicated the presence of twelve conserved water molecules at the DNA-DBD (DNA binding domain) interface. The W1-W5 water centers have been involved in the recognition between the A-chain of DBD to C-chain of DNA, W6 and W7 mediated the interaction between A-chain of DBD and D-chain of DNA, W8 and W9 recognized the B-chain of DBD and C-chain of DNA, and W9-W12 centers conjugated the residues of B-chain of DBD to D-chain of DNA through hydrogen bonds. The conformation flexibility of Phe272 and Met313 residues in the absence of T3 at the LBD (ligand-binding domain) region have been observed and reported. [ABSTRACT FROM AUTHOR]

Introduction: Most Toll-like receptors and IL-1/IL-18 receptors activate a signaling cascade via the adaptor molecule MyD88, resulting in NF-κB activation and inflammatory cytokine and chemokine production. Females are less susceptible than males to inflammatory conditions, presumably due to protection by estrogen. The exact mechanism underlying this protection is unknown. Methods: MCF7 cells expressing wild-type or mutated LXXLL motif were used to determine MyD88/estrogen receptor (ER)-a interaction by immunoprecipitation and cell activation by ELISA and luciferase reporter assay. IL-1b and/or E2 were used to activate MCF7 cells expressing normal or knocked down levels of PRMT1. Finally, in situ proximity ligation assay with anti-MyD88 and anti-methylated ER-a (methER-a) antibodies was used to evaluate MyD88/methylated ER-a interaction in THP1 cells and histological sections. Results: We show that MyD88 interacts with a methylated, cytoplasmic form of estrogen receptor-alpha (methER-α). This interaction is required for NF-κB transcriptional activity and pro-inflammatory cytokine production, and is dissociated by estrogen. Importantly, we show a strong gender segregation in gametogenic reproductive organs, with MyD88/methER-α interactions found in testicular tissues and in ovarian tissues from menopausal women, but not in ovaries from women age 49 and less – suggesting a role for estrogen in disrupting this complex in situ. Discussion: Collectively, our results indicate that the formation of MyD88/methER-α complexes during inflammatory signaling and their disruption by estrogen may represent a mechanism that contributes to gender bias in inflammatory responses. [ABSTRACT FROM AUTHOR]

Multiple sclerosis (MS) is a chronic neurological disease driven by autoimmune, inflammatory and neurodegenerative processes leading to neuronal demyelination and subsequent degeneration. Systemic lipid metabolism is disturbed in people with MS, and lipid metabolic pathways are crucial to the protective process of remyelination. The lipid-activated transcription factors liver X receptors (LXRs) are important integrators of lipid metabolism and immunity. Consequently, there is a strong interest in targeting these receptors in a number of metabolic and inflammatory diseases, including MS. We have reviewed the evidence for involvement of LXR-driven lipid metabolism in the dysfunction of peripheral and brain-resident immune cells in MS, focusing on human studies, both the relapsing remitting and progressive phases of the disease are discussed. Finally, we discuss the therapeutic potential of modulating the activity of these receptors with existing pharmacological agents and highlight important areas of future research. [ABSTRACT FROM AUTHOR]

Knockout of ERß in the mouse leads to nuclear expression of epidermal growth factor receptor (EGFR) in the prostate. To examine whether ERß plays a similar role in the human prostate, we used four cohorts of men: 1) a Swedish cohort of normal prostates and PCa (prostate cancer) of different Gleason grades; 2) men with benign prostatic hyperplasia (BPH) treated with the 5a-reductase inhibitor, finasteride, and finasteride together with the ERß agonists, soy isoflavones; 3) men with PCa above Gleason grade 4 (GG4), treated with ADT (androgen deprivation therapy) and abiraterone (AA), the blocker of androgen synthesis for different durations; and 4) men with GG4 PCa on ADT or ADT with the AR (androgen receptor) blocker, enzalutamide, for 4 mo to 6 mo. In men with BPH, finasteride treatment induced EGFR nuclear expression, but, when finasteride was combined with isoflavones, EGFR remained on the cell membrane. In GG4 patients, blocking of AR for 4 mo to 6 mo resulted in loss of ERß and PTEN expression and increase in patients with nuclear EGFR from 10 to 40%. In the men with GG4 PCa, blocking of adrenal synthesis of testosterone for 2 mo to 7 mo had the beneficial effect of increasing ERß expression, but, on treatment longer than 8 mo, ERß was lost and EGFR moved to the nucleus. Since nuclear EGFR is a predictor of poor outcome in PCa, addition of ERß agonists together with abiraterone should be considered as a treatment that might sustain expression of ERß and offer some benefit to patients. [ABSTRACT FROM AUTHOR]

Pregnane X receptor (PXR) and constitutive androstane receptor (CAR) are nuclear receptors that are highly expressed in the liver and activated by numerous chemicals. While CAR activation by its activators, such as phenobarbital (PB), induces hepatocyte proliferation and liver carcinogenesis in rodents, it remains unclear whether PXR activation drives liver cancer. To investigate the influence of PXR activation on liver carcinogenesis, we treated mice with the PXR activator pregnenolone 16α-carbonitrile (PCN) with or without PB following tumor initiation with diethylnitrosamine (DEN). After 20 weeks of treatment, preneoplastic lesions detected by immunostaining with an anti-KRT8/18 antibody were observed in PB-treated but not PCN-treated mice, and PCN cotreatment augmented the formation of preneoplastic lesions by PB. After 35 weeks of treatment, macroscopic observations indicated that PB-treated and PB/PCN-cotreated mice had increased numbers of liver tumors compared to control and PCN-treated mice. In the pathological analyses of liver sections, all the mice in the PB and PB/PCN groups developed carcinoma and/or eosinophilic adenoma, but in the PB/PCN group, the multiplicity of carcinoma and eosinophilic adenoma was significantly reduced and the size of carcinoma showed a tendency to decrease. No mouse in the control or PCN-treated group developed such tumors. Differentially expressed gene (DEG) and gene set enrichment analyses in combination with RNA sequencing suggested the increased expression of genes related to epithelial–mesenchymal transition (EMT) in mice cotreated with PCN and PB compared to those treated with PB alone. Changes in the hepatic mRNA levels of epithelial marker genes supported the results of the transcriptome analyses. In conclusion, the present results suggest that PXR activation does not promote hepatocarcinogenesis in contrast to CAR and rather attenuates CAR-mediated liver cancer development by suppressing the EMT of liver cancer cells in rodents. [ABSTRACT FROM AUTHOR]

Cholesterol is a major component of the lipid bilayers of cellular membranes. The synthesis of cholesterol is acutely elevated during T‐cell activation to support T‐cell growth and proliferation. There is a limited understanding of cholesterol metabolism reprogramming during T‐cell activation. Retinoic acid receptor‐related orphan receptors (RORs) are ligand‐activated nuclear receptors that regulate the transcription of target genes. In this study, we demonstrated that the activation of RORs by a synthetic agonist (SR1078) impairs the proliferation and survival of postactivated CD8+ T cells. The inhibitory effects of SR1078 on CD8+ T‐cell proliferation and survival were attributed to cholesterol depletion and downregulated expression of cholesterol metabolism‐related genes. The overexpression of RORα or RORγt promoted apoptosis in the postactivated CD8+ T cells in vitro. The expression of RORα (but not that of RORγt) was markedly upregulated in the CD8+ T cells upon stimulation with an antigen in vivo. The functional deficiency of RORα enhanced CD8+ T‐cell expansion during the response to bacterial infection. These results suggest that RORs are involved in the regulation of CD8+ T‐cell‐mediated immune response through the regulation of cholesterol metabolism, which can be modulated by a synthetic ROR agonist. The findings of this study can aid in the development of immunotherapeutic methods that target nuclear receptors. [ABSTRACT FROM AUTHOR]

Objective: The endocannabinoid (eCB) system is increasingly recognized as being crucially important in obesity-related hepatic steatosis. By activating the hepatic cannabinoid-1 receptor (CB1R), eCBs modulate lipogenesis and fatty acid oxidation. However, the underlying molecular mechanisms are largely unknown. Methods: We combined unbiased bioinformatics techniques, mouse genetic manipulations, multiple pharmacological, molecular, and cellular biology approaches, and genomic sequencing to systematically decipher the role of the hepatic CB1R in modulating fat utilization in the liver and explored the downstream molecular mechanisms. Results: Using an unbiased normalized phylogenetic profiling analysis, we found that the CB1R evolutionarily coevolves with peroxisome proliferator-activated receptor-alpha (PPARα), a key regulator of hepatic lipid metabolism. In diet-induced obese (DIO) mice, peripheral CB1R blockade (using AM6545) induced the reversal of hepatic steatosis and improved liver injury in WT, but not in PPARα−/− mice. The antisteatotic effect mediated by AM6545 in WT DIO mice was accompanied by increased hepatic expression and activity of PPARα as well as elevated hepatic levels of the PPARα-activating eCB-like molecules oleoylethanolamide and palmitoylethanolamide. Moreover, AM6545 was unable to rescue hepatic steatosis in DIO mice lacking liver sirtuin 1 (SIRT1), an upstream regulator of PPARα. Both of these signaling molecules were modulated by the CB1R as measured in hepatocytes exposed to lipotoxic conditions or treated with CB1R agonists in the absence/presence of AM6545. Furthermore, using microRNA transcriptomic profiling, we found that the CB1R regulated the hepatic expression, acetylation, and transcriptional activity of p53, resulting in the enhanced expression of miR-22, which was found to specifically target SIRT1 and PPARα. Conclusions: We provide strong evidence for a functional role of the p53/miR-22/SIRT1/PPARα signaling pathway in potentially mediating the antisteatotic effect of peripherally restricted CB1R blockade.

Background: Pathogens or trauma-derived danger signals induced maturation and activation of plasmacytoid dendritic cells (pDCs) is a pivotal step in pDC-dependent host defense. Exposure of pDC to cardiometabolic disease-associated lipids and proteins may well influence critical signaling pathways, thereby compromising immune responses against endogenous, bacterial and viral pathogens. In this study, we have addressed if hyperlipidemia impacts human pDC activation, cytokine response and capacity to prime CD4+ T cells. METHODS AND RESULTS: We show that exposure to pro-atherogenic oxidized low-density lipoproteins (oxLDL) led to pDC lipid accumulation, which in turn ablated a Toll-like receptor (TLR) 7 and 9 dependent up-regulation of pDC maturation markers CD40, CD83, CD86 and HLA-DR. Moreover, oxLDL dampened TLR9 activation induced the production of pro-inflammatory cytokines in a NUR77/IRF7 dependent manner and impaired the capacity of pDCs to prime and polarize CD4+ T helper (Th) cells. CONCLUSION: Our findings reveal profound effects of dyslipidemia on pDC responses to pathogen-derived signals.

Zyxin is an LIM-domain-containing protein that regulates the assembly of F-actin filaments in cell contacts. Additionally, as a result of mechanical stress, Zyxin can enter nuclei and regulate gene expression. Previously, we found that Zyxin could affect mRNA stability of the maternally derived stemness factors of Pou5f3 family in Xenopus laevis embryos through binding to Y-box factor1. In the present work, we demonstrate that Zyxin can also affect mRNA stability of the maternally derived retinoid receptor Rxrγ through the same mechanism. Moreover, we confirmed the functional link between Zyxin and Rxrγ-dependent gene expression. As a result, Zyxin appears to play an essential role in the regulation of the retinoic acid signal pathway during early embryonic development. Besides, our research indicates that the mechanism based on the mRNA destabilization by Zyxin may take part in the control of the expression of a fairly wide range of maternal genes.

Previous studies found that melatonin modulates a combination of green-and-blue-light-induced B-lymphocyte proliferation via its membrane receptors Mel1a and Mel1c. However, in addition to its membrane-bound receptors, melatonin also functions through binding to nuclear receptors RORα/RORβ/RORγ. In this study, we raised 120 chicks under 400–700 nm white (WW), 660 nm red (RR), 560 nm green (GG) and 480 nm blue light (BB) from P0 to P26. From P27 to P42, half of the chickens in green, blue and red were switched to blue (G→B), green (B→G) and red (R→B), respectively. We used immunohistochemistry, Western blotting, qRT-PCR, Elisa and MTT to investigate the influence of various monochromatic light combinations on the bursal B lymphocyte apoptosis and oxidative stress levels as well as estimate whether melatonin and its nuclear receptors were involved in this process. Consistent with the increase in the plasma melatonin concentration and antioxidant enzyme activity, we observed that G→B significantly decreased the RORα, RORγ mRNA level, inhibited Bax, Caspase-3 and p-iκb, p-p65 protein expression, increased the IL-10 level and Nrf2, HO-1 protein expression, down-regulated the MDA and pro-inflammatory IL-6, TNF-α and IFN-γ levels in the bursa compared with WW, RR, GG, BB and R→B, respectively. Our in vitro results showed exogenous melatonin supplementation inhibited B-lymphocyte apoptosis, decreased IL-6, TNF-α, IFN-γ and ROS production, down-regulated RORα, RORγ mRNA level and p-iκb and p-p65 protein expression, whereas it improved the IL-10 level and Nrf2 and the HO-1 protein expression in bursal B lymphocyte. Moreover, these responses were abrogated by RORα agonist SR1078 but were mimicked by RORα antagonist SR3335 or RORγ antagonist GSK2981278. In addition, p65 antagonist BAY reversed RORα/RORγ-mediated G→B-inhibited bursal B lymphocyte apoptosis. Overall, we concluded that melatonin nuclear RORα/RORγ mediates G→B-inhibited bursal B lymphocyte apoptosis via reducing oxidative stress and Nfκb expression.

Retinoid X receptor α (RXRα) is a nuclear receptor (NR) which functions as the primary heterodimeric partner of other NRs including the peroxisome proliferator-activated receptor γ (PPARγ). We previously reported that, in breast cancers (BC), the subcellular localization of these two receptors was strongly associated with patient prognosis. In the present work, we investigated the prognosis value of the combined cytoplasmic expression of RXRα and PPARγ using a retrospective cohort of 250 BC samples. Patients with tumors expressing both NRs in tumor cell cytoplasm exhibited a significant shorter overall (OS) and disease-free survival (DFS). This was also observed for patients with stage 1 tumors. Cox univariate analysis indicated that patients with tumors coexpressing RXRα and PPARγ in the cytoplasm of tumor cells have a decreased 5 y OS rate. Cytoplasmic co-expression of the two NRs significantly correlated with HER2 positivity and with NCAD and CD133, two markers of tumor aggressiveness. Finally, in Cox multivariate analysis, the co-expression of RXRα and PPARγ in the cytoplasm appeared as an independent OS prognosticator. Altogether, this study demonstrates that the cytoplasmic co-expression of RXRα and PPARγ could be of relevance for clinicians by identifying high-risk BC patients, especially amongst those with early and node-negative disease.

DAF-12 is nematode-specific nuclear receptor that has been proposed to govern development of the infectious stage of parasitic species, including Strongyloides stercoralis. Here, we identified a parasite-specific coactivator, called DAF-12 interacting protein-1 (DIP-1), that is required for DAF-12 ligand-dependent transcriptional activity. DIP-1 is found only in Strongyloides spp. and selectively interacts with DAF-12 through an atypical receptor binding motif. Using CRISPR/Cas9-directed mutagenesis, we demonstrate that DAF-12 is required for the requisite developmental arrest and the ligand-dependent reactivation of infectious S. stercoralis infective third-stage larvae, and that these effects require the DIP-1 coactivator. These studies reveal the existence of a distinct nuclear receptor/coactivator signaling pathway that governs parasite development. [ABSTRACT FROM AUTHOR]

Background: Melanoma is the deadliest of skin cancers and has an increasing annual incidence worldwide. It is a multi-factorial disease most likely arising from both genetic predisposition and environmental exposure to ultraviolet light. Genetic variability of the components of the biological circadian clock is recognized to be a risk factor for different type of cancers. Moreover, two variants of a clock gene, RORA, have been associated with melanoma patient's prognosis. Our aim is to test the hypothesis that specific single nucleotide polymorphisms (SNPs) of the circadian clock genes may significantly influence the predisposition to develop cutaneous melanoma or the outcome of melanoma patients.Methods: We genotyped 1239 subjects, 629 cases of melanoma and 610 healthy controls in 14 known SNPs of seven selected clock genes: AANAT, CLOCK, NPAS2, PER1, PER2, RORA, and TIMELESS. Genotyping was conducted by q-PCR. Multivariate logistic regression was employed for susceptibility of melanoma assessment, modeled additively. Subgroup analysis was performed by gender. For the female subgroup, a further discrimination was performed by age. For prognosis of melanoma assessment, multivariate Cox proportional hazard regression was employed. The Benjamini-Hochberg method was utilized as adjustment for multiple comparisons.Results: We identified two RORA SNPs statistically significant with respect to the association with melanoma susceptibility. Considering the putative role of RORA as a nuclear steroid hormone receptor, we conducted a subgroup analysis by gender. Interestingly, the RORA rs339972 C allele was associated with a decreased predisposition to develop melanoma only in the female subgroup (OR 0.67; 95% CI 0.51-0.88; P = 0.003) while RORA rs10519097 T allele was associated with a decreased predisposition to develop melanoma only in the male subgroup (OR 0.62; 95% CI 0.44-0.87; P = 0.005). Moreover, the RORA rs339972 C allele had a decreased susceptibility to develop melanoma only in females aged over 50 years old (OR 0.67; 95% CI 0.54-0.83; P = 0.0002). None of the studied SNPs were significantly associated with the prognosis.Conclusions: Overall, we cannot ascertain that circadian pathway genetic variation is involved in melanoma susceptibility or prognosis. Nevertheless, we identified an interesting relationship between melanoma susceptibility and RORA polymorphisms acting in sex-specific manner and which is worth further future investigation. [ABSTRACT FROM AUTHOR]

G protein-coupled oestrogen receptor 1 (GPER1), predicted to be a novel oestrogen receptor, has been linked to the development and progression of breast cancer. However, the molecular mechanisms underlying its functions remain elusive. Here, we show that the protein levels of GPER1 are negatively associated with those of ERα and that higher expression of GPER1 correlated with a better clinical outcome in oestrogen receptor-positive (ER+) breast cancer patients. Activation of GPER1 decreases ERα protein levels, which subsequently suppresses ERα-mediated transcription and target gene expression but does not affect its mRNA expression in ER + breast cancer cells. A mechanistic study revealed that GPER1 mediates ubiquitin (Ub)-proteasome-dependent degradation of ERα via upregulation of the Cullin3-based E3 ubiquitin ligase adaptor protein speckle-type POZ protein (SPOP), and depletion of SPOP abrogates GPER1-induced ERα ubiquitination and degradation. Functionally, GPER1 activation inhibits 17β-oestradiol (E2)-induced ER + breast cancer cell proliferation, migration, and invasion in vitro and tumour growth in vivo. Our findings reveal a novel mechanism by which GPER1 negatively modulates the ERα signalling pathway via promoting its ubiquitin-proteasome-dependent degradation, which may contribute to its inhibition of breast cancer progression. [ABSTRACT FROM AUTHOR]

Crosstalk between xenobiotic metabolism and energy metabolism in the liver has provided a potential opportunity to target xenobiotic receptors to treat metabolic diseases. Activation of constitutive androstane receptor (CAR), a xenobiotic-sensing nuclear receptor, has been shown to inhibit obesity, suppress hepatic gluconeogenesis, and ameliorate hyperglycemia in rodent models of obesity and type 2 diabetes. However, the underlying molecular mechanism remains to be defined. The growth arrest and DNA damage-inducible gene 45b (Gadd45b), a well-known anti-apoptotic factor, has been shown to be an inducible coactivator of CAR in promoting rapid liver growth. It is unknown whether the effect of CAR on energy metabolism depends on GADD45B. In the present study and by using a high fat diet (HFD)-induced obesity model, we show that reduced body weight gain and improved insulin sensitivity by the CAR agonist 1,4-bis[2-(3,5-dichloropyridyloxy)] benzene (TCPOBOP) were markedly blunted in Gadd45b knockout mice. Mechanistically, the TCPOBOP-responsive inhibition of hepatic lipogenesis, gluconeogenesis, and adipose inflammation observed in wild type mice were largely abolished in Gadd45b knockout mice. We conclude that Gadd45b is required in part for the metabolic benefits of CAR activation. Activation of xenobiotic receptor constitutive androstane receptor (CAR) by its agonist such as TCPOBOP conveys benefits for obesity and diabetes. In this study, it showes that anti-apoptotic factor GADD45B, a coactivator of CAR, is in part required for the anti-obesity effects of CAR activation. Inhibition of hepatic lipogenesis and gluconeogenesis and adipose inflammation by TCPOBOP was largely abolished in mice in the absence of GADD45B. Image 1 [ABSTRACT FROM AUTHOR]

Polychlorinated dibenzo‐p‐dioxins (PCDDs) are hypothesized to exert their toxic effects in wildlife and humans via endocrine disruption. However, very scanty information is available on the underlying molecular interactions that trigger this disruption. In this study, molecular docking simulation was used to predict the susceptibility of 12 nuclear receptors to disruption via PCDD bindings. Findings revealed that androgen (AR and AR an), estrogen (ER α and ER β), glucocorticoid (GR) and thyroid hormone (TR α and TR β) receptors are the most probable protein targets that bind to PCDDs. Further molecular docking analyses showed that PCDD molecules mimic the modes of interaction observed for the co‐crystallized ligands of the affected receptors, resulting in the formation of ligand‐receptor complexes that were stabilized through electrostatic, van der Waals, pi‐effect and hydrophobic interactions with 18, 17, 17, 16, 18, eight and four amino acid residues in the active sites of AR, AR an, ER α, ER β, GR, TR α and TR β respectively. The commonalities of these interacting amino acid residues with those utilized by dihydrotestosterone in AR, bicalutamide in AR an, 17β‐estradiol in ER α, 17β‐estradiol in ER β, cortisol in GR, thyromimetic GC‐1 in TR α and thyromimetic GC‐1 in TR β are 86%, 74%, 94%, 80%, 82%, 50% and 43% respectively. The results obtained in this study provide supporting evidence that PCDD molecules may interfere with the endocrine system via binding interactions with some vital amino acid residues in the binding pockets of AR, ERs, GRs and TRs. Molecular docking simulation was used to predict the susceptibility of 12 nuclear receptors to disruption via PCDD bindings in this paper. Findings revealed that androgen (AR and AR an), estrogen (ER α and ER β), glucocorticoid (GR) and thyroid hormone (TR α and TR β) receptors are the most probable protein targets that bind to PCDDs. The results obtained in this study provide supporting evidence that PCDD molecules may interfere with the endocrine system via binding interactions with some vital amino acid residues in the binding pockets of androgen, estrogen, glucocorticoid and thyroid hormone receptors. [ABSTRACT FROM AUTHOR]

Pregnane X receptor (PXR) is activated by chemicals to transcriptionally regulate drug disposition and possibly decrease drug efficacy and increase resistance, suggesting therapeutic value for PXR antagonists. We previously reported the antagonist SPA70 and its analog SJB7, which unexpectedly is an agonist. Here, we describe another unexpected observation: mutating a single residue (W299A) within the PXR ligand-binding domain converts SPA70 to an agonist. After characterizing wild-type and W299A PXR activity profiles, we used molecular dynamics simulations to reveal that in wild-type PXR, agonists stabilize the activation function 2 (AF-2) helix in an "inward" position, but SPA70 displaces the AF-2. In W299A, however, SPA70 stabilizes the AF-2 "inward", like agonists. We validated our model by predicting the antagonist SJC2 to be a W299A agonist, which was confirmed experimentally. Our work correlates previously unobserved ligand-induced conformational changes to PXR cellular activity and, for the first time, reveals how PXR antagonists work. [ABSTRACT FROM AUTHOR]

This study explores the impact of environmental pollutants on nuclear receptors (CAR, PXR, PPARα, PPARγ, FXR, and LXR) and their heterodimerization partner, the Retinoid X Receptor (RXR). Such interaction may contribute to the onset of non-alcoholic fatty liver disease (NAFLD), which is initially characterized by steatosis and potentially progresses to steatohepatitis and fibrosis. Epidemiological studies have linked NAFLD occurrence to the exposure to environmental contaminants like PFAS. This study aims to assess the simultaneous activation of nuclear receptors via perfluorooctanoic acid (PFOA) and RXR coactivation via Tributyltin (TBT), examining their combined effects on steatogenic mechanisms. Mice were exposed to PFOA (10 mg/kg/day), TBT (5 mg/kg/day) or a combination of them for three days. Mechanisms underlying hepatic steatosis were explored by measuring nuclear receptor target gene and lipid metabolism key gene expressions, by quantifying plasma lipids and hepatic damage markers. This study elucidated the involvement of the Liver X Receptor (LXR) in the combined effect on steatosis and highlighted the permissive nature of the LXR/RXR heterodimer. Antagonistic effects of TBT on the PFOA-induced activation of the Pregnane X Receptor (PXR) and Peroxisome Proliferator-Activated Receptor Gamma (PPARγ) were also observed. Overall, this study revealed complex interactions between PFOA and TBT, shedding light on their combined impact on liver health.

Non-alcoholic fatty liver disease (NAFLD) is one of the most common liver diseases, which can cause serious complications and gradually increase the mortality rate. However, the effects of NAFLD on drug-metabolizing enzymes and transporters remain unclear, which may cause some confusion regarding patient medication. In this study, a NAFLD rat model was constructed by feeding rats with methionine and choline deficiency diets for 6 weeks, and the mRNA and protein levels of drug-metabolizing enzymes and transporter were analyzed by real-time fluorescent quantitative PCR and Western blot, respectively. The activity of drug-metabolizing enzymes was detected by cocktail methods. In the NAFLD rat model, the mRNA expression of phase I enzymes, phase II enzymes, and transporters decreased. At the protein level, only CYP1A1, CYP1B1, CYP2C11, and CYP2J3 presented a decrease. In addition, the activities of CYP1A2, CYP2B1, CYP2C11, CYP2D1, CYP3A2, UGT1A1, UGT1A3, UGT1A6, and UGT1A9 decreased. These changes may be caused by the alteration of FXR, HNF4α, LXRα, LXRβ, PXR, and RXR. In conclusion, NAFLD changes the expression and activity of hepatic drug-metabolizing enzymes and transporters in rats, which may affect drug metabolism and pharmacokinetics. In clinical medication, drug monitoring should be strengthened to avoid potential risks., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

Autophagy during myocardial ischemia/reperfusion (MI/R) exacerbates cardiomyocyte injury. Melatonin (Mel) alleviates myocardial damage by regulating mitochondrial function and mitophagy, but the role of mitophagy in melatonin-induced cardioprotection remains unclear. This study aimed to explore the roles of sirtuin3 (SIRT3) and retinoid-related orphan nuclear receptor-α (RORα) in mitophagy during simulated ischemia reperfusion (SIR) in H9c2 cells. Our data showed that mitophagy was excessively activated after SIR injury, which was consistent with reduced cell survival, enhanced oxidative responses and mitochondrial dysfunction in H9c2 myocytes. Melatonin greatly enhanced cell viability, reduced oxidative stress and improved mitochondrial function. The effects of melatonin protection were involved in excessive mitophagy inhibition, as demonstrated by the reduced levels of mitophagy-linked proteins, including Parkin, Beclin1, NIX and BNIP3, and the LC3 II/LC3 I ratio and elevations in p62. Additionally, the decreases in SIRT3 and RORα in H9c2 myocytes after SIR were reversed by melatonin, and the above effects of melatonin were eliminated by small interfering RNA (siRNA)-mediated knockdown of SIRT3 and RORα. In brief, SIRT3 and RORα are two prospective targets in the cardioprotection of melatonin against mitophagy during SIR in H9c2 myocytes., Competing Interests: The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (© 2024 The Author(s).)

Luciferase is a popular enzyme used for biological analyses, such as reporter assays. In addition to a conventional reporter assay using a pair of firefly and Renilla luciferases, a simple multicolor reporter assay using multiple firefly or beetle luciferases emitting different color luminescence with a single substrate has been reported. Secretory luciferases have also been used for convenient sample preparation in reporter assays; however, reporter assay using secretory luciferase mutants that emit spectrum-shifted luminescence have not yet been reported. In this study, we generated blue- and red-shifted (-16 and 12 nm) luminescence-emitting Cypridina secretory luciferase (CLuc) mutants using multiple cycles of random and site-directed mutagenesis. Even for red-shifted CLuc mutant, which exhibited relatively low activity and stability, its enzymatic activity was sufficiently high for a luciferase assay (3.26 × 10 6 relative light unit/s), light emission was sufficiently prolonged (half-life is 3 min), and stability at 37°C was high. We independently determined the luminescence of these CLuc mutants using a luminometer with an optical filter. Finally, we replaced the commonly used reporters, firefly and Renilla luciferases used in a conventional nuclear receptor-reporter assay with these CLuc mutants and established a secretory luciferase-based single-substrate dual-color nuclear receptor-reporter assay., (© 2023 American Society for Photobiology.)

TR2 and TR4 (NR2C1 and NR2C2, respectively) are evolutionarily conserved nuclear orphan receptors capable of binding direct repeat sequences in a stage-specific manner. Like other nuclear receptors, TR2 and TR4 possess important roles in transcriptional activation or repression with developmental stage and tissue specificity. TR2 and TR4 bind DNA and possess the ability to complex with available cofactors mediating developmental stage-specific actions in primitive and definitive erythrocytes. In erythropoiesis, TR2 and TR4 are required for erythroid development, maturation, and key erythroid transcription factor regulation. TR2 and TR4 recruit and interact with transcriptional corepressors or coactivators to elicit developmental stage-specific gene regulation during hematopoiesis.

Background: In addition to abnormal liver inflammation, the main symptoms of non-alcoholic steatohepatitis (NASH) are often accompanied by gastrointestinal digestive dysfunction, consistent with the concept of spleen deficiency (SD) in traditional Chinese medicine. As an important metabolic sensor, whether peroxisome proliferator-activated receptor alpha (PPARα) participates in regulating the occurrence and development of NASH with SD (NASH-SD) remains to be explored., Methods: Clinical liver samples were collected for RNA-seq analysis. C57BL/6J mice induced by folium sennae (SE) were used as an SD model. qPCR analysis was conducted to evaluate the inflammation and metabolic levels of mice. PPARα knockout mice (PPARα ko ) were subjected to SE and methionine-choline-deficient (MCD) diet to establish the NASH-SD model. The phenotype of NASH and the inflammatory indicators were measured using histopathologic analysis and qPCR as well., Results: The abnormal expression of PPARα signaling, coupled with metabolism and inflammation, was found in the results of RNA-seq analysis from clinical samples. SD mice showed a more severe inflammatory response in the liver evidenced by the increases in macrophage biomarkers, inflammatory factors, and fibrotic indicators in the liver. qPCR results also showed differences in PPARα between SD mice and control mice. In PPARα ko mice, further evidence was found that the lack of PPARα exacerbated the inflammatory response phenotype as well as the lipid metabolism disorder in NASH-SD mice., Conclusion: The abnormal NR signaling accelerated the vicious cycle between lipotoxicity and inflammatory response in NAFLD with SD. Our results provide new evidence for nuclear receptors as potential therapeutic targets for NAFLD with spleen deficiency., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2024 Huang, Li, Peng, Cui, Guo, Duan, Zhou, Huang, Chen, Yi, Qiu, Chen, Wu, Ma, Zhang, Zheng, Tang, Pang, Zhang, Zhong and Gao.)

The transcription factor farnesoid X receptor (FXR) regulates energy metabolism. Specifically, FXR functions to regulate cystic fibrosis transmembrane conductance regulator (CFTR)-mediated Cl - secretion in intestinal epithelial cells. Therefore, this study aimed to investigate the role of FXR in CFTR-mediated Cl - secretion in renal tubular cells and to further elucidate its effects on renal cyst formation and growth. CFTR-mediated Cl - transport was evaluated via short-circuit current ( I SC ) measurements in Madin-Darby canine kidney (MDCK) cell monolayers and primary rat inner medullary collecting duct cells. The role of FXR in renal cyst formation and growth was determined by the MDCK cell-derived cyst model. Incubation with synthesized (GW4064) and endogenous (CDCA) FXR ligands reduced CFTR-mediated Cl - secretion in a concentration- and time-dependent manner. The inhibitory effect of FXR ligands was not due to the result of reduced cell viability and was attenuated by cotreatment with an FXR antagonist. FXR activation significantly decreased CFTR protein but not its mRNA. In addition, FXR activation inhibited CFTR-mediated Cl - secretion in primary renal collecting duct cells. FXR activation decreased ouabain-sensitive I SC without altering Na + -K + -ATPase mRNA and protein levels. Furthermore, FXR activation significantly reduced the number of cysts and renal cyst expansion. These inhibitory effects were correlated with a decrease in the expression of protein synthesis regulators mammalian target of rapamycin/S6 kinase. This study shows that FXR activation inhibits Cl - secretion in renal cells via inhibition of CFTR expression and retards renal cyst formation and growth. The discoveries point to a physiological role of FXR in the regulation of CFTR and a potential therapeutic application in polycystic kidney disease treatment. NEW & NOTEWORTHY The present study reveals that farnesoid X receptor (FXR) activation reduces microcyst formation and enlargement. This inhibitory effect of FXR activation is involved with decreased cell proliferation and cystic fibrosis transmembrane conductance regulator-mediated Cl - secretion in renal collecting duct cells. FXR might represent a novel target for the treatment of autosomal dominant polycystic kidney disease.

Plastics are complex chemical mixtures of polymers and various intentionally and nonintentionally added substances. Despite the well-established links between certain plastic chemicals (bisphenols and phthalates) and adverse health effects, the composition and toxicity of real-world mixtures of plastic chemicals are not well understood. To assess both, we analyzed the chemicals from 36 plastic food contact articles from five countries using nontarget high-resolution mass spectrometry and reporter-gene assays for four nuclear receptors that represent key components of the endocrine and metabolic system. We found that chemicals activating the pregnane X receptor (PXR), peroxisome proliferator receptor γ (PPARγ), estrogen receptor α (ERα), and inhibiting the androgen receptor (AR) are prevalent in plastic packaging. We detected up to 9936 chemical features in a single product and found that each product had a rather unique chemical fingerprint. To tackle this chemical complexity, we used stepwise partial least-squares regressions and prioritized and tentatively identified the chemical features associated with receptor activity. Our findings demonstrate that most plastic food packaging contains endocrine- and metabolism-disrupting chemicals. Since samples with fewer chemical features induce less toxicity, chemical simplification is key to producing safer plastic packaging.

Hiccups can significantly reduce the quality of life of patients and can occur as a drug side effect. Previous reports have revealed sex-specific differences in the incidence of drug-induced hiccups. However, the pathogenesis of drug-induced hiccups remains unknown, and there is limited evidence on its treatment or prevention. This study examined molecular initiating events (MIEs), which are the starting point of adverse events, to investigate the drug-induced pathways of hiccups. We extracted drugs suspected to cause hiccups using the FDA Adverse Event Reporting System, a large database on adverse drug reactions. Information on drugs suspected to be associated with hiccups was extracted from the overall population and sex-specific subgroups were divided. In each data table, the predicted activity values of nuclear receptors and stress response pathways for each drug were calculated using the Toxicity Predictor, a machine-learning model. Transforming growth factor-beta and antioxidant response elements were considered an independent factor for hiccups in the male and female subgroups, respectively. This report first examined one of the mechanisms of drug-induced hiccups and identified MIEs associated with drug-induced hiccups. The use of an adverse event database and the machine-learning model, Toxicity Predictor, may be useful for generating hypotheses for other adverse effects with unknown mechanisms.

Nuclear hormone receptors (NHRs) are a deeply-conserved superfamily of metazoan transcription factors, which fine-tune the expression of their regulatory target genes in response to a plethora of sensory inputs. In nematodes, NHRs underwent an explosive expansion and many species have hundreds of nhr genes, most of which remain functionally uncharacterized. However, recent studies have reported that two sister receptors, Ppa-NHR-1 and Ppa-NHR-40, are crucial regulators of feeding-structure morphogenesis in the diplogastrid model nematode Pristionchus pacificus. In the present study, we functionally characterize Ppa-NHR-10, the sister paralog of Ppa-NHR-1 and Ppa-NHR-40, aiming to reveal whether it too regulates aspects of feeding-structure development. We used CRISPR/CAS9-mediated mutagenesis to create small frameshift mutations of this nuclear receptor gene and applied a combination of geometric morphometrics and unsupervised clustering to characterize potential mutant phenotypes. However, we found that Ppa-nhr-10 mutants do not show aberrant feeding-structure morphologies. Instead, multiple RNA-seq experiments revealed that many of the target genes of this receptor are involved in lipid catabolic processes. We hypothesized that their mis-regulation could affect the survival of mutant worms during starvation, where lipid catabolism is often essential. Indeed, using novel survival assays, we found that mutant worms show drastically decreased starvation resistance, both as young adults and as dauer larvae. We also characterized genome-wide changes to the transcriptional landscape in P. pacificus when exposed to 24 h of acute starvation, and found that Ppa-NHR-10 partially regulates some of these responses. Taken together, these results demonstrate that Ppa-NHR-10 is broadly required for starvation resistance and regulates different biological processes than its closest paralogs Ppa-NHR-1 and Ppa-NHR-40., (© 2024. The Author(s).)

Three peroxisome proliferator-activated receptor subtypes, PPARα, PPAR(ß/)δ, and PPARγ, exert ligand-dependent transcriptional control in concert with retinoid X receptors (RXRs) on various gene sets harboring PPAR response elements (PPREs) in their promoter regions. Ligand-bound PPAR/RXR complexes do not directly regulate transcription; instead, they recruit multiprotein coactivator complexes to specific genomic regulatory loci to cooperatively activate gene transcription. Several coactivators are expressed in a single cell; however, a ligand-bound PPAR can be associated with only one coactivator through a consensus LXXLL motif. Therefore, altered gene transcription induced by PPAR subtypes/agonists may be attributed to the recruitment of various coactivator species. Using a time-resolved fluorescence resonance energy transfer assay, we analyzed the recruitment of four coactivator peptides (PGC1α, CBP, SRC1, and TRAP220) to human PPARα/δ/γ-ligand-binding domains (LBDs) using eight PPAR dual/pan agonists (bezafibrate, fenofibric acid, pemafibrate, pioglitazone, elafibranor, lanifibranor, saroglitazar, and seladelpar) that are/were anticipated to treat nonalcoholic fatty liver disease. These agonists all recruited four coactivators to PPARα/γ-LBD with varying potencies and efficacy. Only five agonists (bezafibrate, pemafibrate, elafibranor, lanifibranor, and seladelpar) recruited all four coactivators to PPARδ-LBD, and their concentration-dependent responses differed from those of PPARα/γ-LBD. These results indicate that altered gene expression through consensus PPREs by different PPAR subtypes/agonists may be caused, in part, by different coactivators, which may be responsible for the unique pharmacological properties of these PPAR agonists.

Aberrant signaling through β-catenin is an important determinant of tumorigenesis in rodents as well as in humans. In mice, xenobiotic activators of the constitutive androstane receptor (CAR), a chemo-sensing nuclear receptor, promote liver tumor growth by means of a non-genotoxic mechanism and, under certain conditions, select for hepatocellular tumors which contain activated β-catenin. In normal hepatocytes, interactions of β-catenin and CAR have been demonstrated with respect to the induction of proliferation and drug metabolism-related gene expression. The molecular details of these interactions are still not well understood. Recently it has been hypothesized that CAR might activate β-catenin signaling, thus providing a possible explanation for some of the observed phenomena. Nonetheless, many aspects of the molecular interplay of the two regulators have still not been elucidated. This review briefly summarizes our current knowledge about the interplay of CAR and β-catenin. By taking into account data and observations obtained with different mouse models and employing different experimental approaches, it is shown that published data also contain substantial evidence that xenobiotic activators of CAR do not activate, or do even inhibit signaling through the β-catenin pathway. The review highlights new aspects of possible ways of interaction between the two signaling cascades and will help to stimulate scientific discussion about the crosstalk of β-catenin signaling and the nuclear receptor CAR. [ABSTRACT FROM AUTHOR]

Prostate cancer (PCa) patients who progress to metastatic castration-resistant PCa (mCRPC) mostly have poor outcomes due to the lack of effective therapies. Our recent study established the orphan nuclear receptor ROR γ as a novel therapeutic target for CRPC. Here, we reveal that elaiophylin (Elai), an antibiotic from Actinomycete streptomyces , is a novel ROR γ antagonist and showed potent antitumor activity against CRPC in vitro and in vivo. We demonstrated that Elai selectively binded to ROR γ protein and potently blocked ROR γ transcriptional regulation activities. Structure–activity relationship studies showed that Elai occupied the binding pocket with several key interactions. Furthermore, Elai markedly reduced the recruitment of ROR γ to its genomic DNA response element (RORE), suppressed the expression of ROR γ target genes AR and AR variants, and significantly inhibited PCa cell growth. Importantly, Elai strongly suppressed tumor growth in both cell line based and patient-derived PCa xenograft models. Taken together, these results suggest that Elai is novel therapeutic ROR γ inhibitor that can be used as a drug candidate for the treatment of human CRPC. Elaiophylin was identified as a novel and potent ROR γ antagonist. It strongly inhibits androgen receptor (AR) expression and cell autophagy via suppressing ROR γ activity, and shows robust antitumor activity against CRPC in vitro and in vivo. Image 1 [ABSTRACT FROM AUTHOR]

Cardiac glycosides are compounds isolated from plants and animals and have been known since ancient times. These compounds inhibit the activity of the sodium potassium pump in eukaryotic cells. Cardiac glycosides were used as drugs in heart ailments to increase myocardial contraction force and, at the same time, to lower frequency of this contraction. An increasing number of studies have indicated that the biological effects of these compounds are not limited to inhibition of sodium-potassium pump activity. Furthermore, an increasing number of data have shown that they are synthesized in tissues of mammals, where they may act as a new class of steroid hormones or other hormones by mimicry to modulate various signaling pathways and influence whole organisms. Thus, we discuss the interactions of cardiac glycosides with the nuclear receptor superfamily of transcription factors activated by low-weight molecular ligands (including hormones) that regulate many functions of cells and organisms. Cardiac glycosides of endogenous and exogenous origin by interacting with nuclear receptors can affect the processes regulated by these transcription factors, including hormonal management, immune system, body defense, and carcinogenesis. They can also be treated as initial structures for combinatorial chemistry to produce new compounds (including drugs) with the desired properties.

An important function of aromatase in the brain is conversion of testosterone secreted from the testis into estradiol. Estradiol produced in the brain is thought to be deeply involved in the formation of sexually dimorphic nuclei and sexual behavior as a neurosteroid. We analyzed the brain-specific promoter to elucidate the control mechanisms of brain aromatase expression that may be highly involved in sexual differentiation of the brain. The 202-bp upstream region of the brain-specific exon 1 has three types of cis-acting elements, aro-AI, AII, and B. We isolated ARP-1 as an aro-AII-binding protein by yeast one-hybrid screening from a cDNA library of mouse fetal brains. ARP-1 is a member of the nuclear receptor superfamily and functions as an orphan-type transcription factor. ARP-1 protein synthesized in vitro showed the same binding property to the aro-AII site as nuclear extract from fetal brains. To determine how the promoter is involved in brain-specific transcription of the aromatase gene, we first detected the in vivo occupancy of the aro-AII site by ARP-1 using chromatin immunoprecipitation assays. Diencephalic regions of fetal brains at embryonic day 16 were analyzed, which revealed ARP-1 recruitment to the aro-AII site. To analyze the effects of ARP-1 on transcriptional regulation of the brain-specific aromatase promoter, a luciferase reporter plasmid driven by the brain-specific promoter was transfected into CV-1 cells together with a plasmid expressing ARP-1 protein. These analyses revealed that ARP-1 induced promoter activity in a dose-dependent manner. Furthermore, to determine whether ARP-1 is required for aromatase expression in neurons, ARP-1 knockdown was conducted in neuronal cell primary culture. Knockdown of ARP-1 significantly suppressed the increase in aromatase mRNA observed in cultured neurons. These results indicate that ARP-1 is involved in the transcriptional regulation of the brain-specific promoter of the aromatase gene.

Non-alcoholic fatty liver disease (NAFLD) has become the most common chronic liver disorder, and yet with no pharmacological treatment approved worldwide. The repositioning of old drugs provides a safe approach for drug development. Vidofludimus, an inhibitor for dihydroorotate dehydrogenase (DHODH) for the treatment of autoimmune disorders, is herein uncovered as a novel modulator for farnesoid X receptor (FXR) by biochemical and crystallographic analysis. We further revealed that vidofludimus exerts in vivo therapeutic effects on dextran sodium sulfate (DSS)-induced colitis in an FXR-dependent manner. Notably, vidofludimus also possesses remarkable beneficial effects in reducing NAFLD by targeting FXR, which may represent a unique approach in developing the treatment for NAFLD. Our findings not only reveal a promising template for the design of novel FXR ligands in treating autoimmune disorders, but also uncover a novel therapeutic effect for vidofludimus on NAFLD based on the newly established relationships among drugs, targets, and diseases.

Summary: Liver X receptors (LXRs) and their ligands are potent regulators of midbrain dopaminergic (mDA) neurogenesis and differentiation. However, the molecular mechanisms by which LXRs control these functions remain to be elucidated. Here, we perform a combined transcriptome and chromatin immunoprecipitation sequencing (ChIP-seq) analysis of midbrain cells after LXR activation, followed by bioinformatic analysis to elucidate the transcriptional networks controlling mDA neurogenesis. Our results identify the basic helix-loop-helix transcription factor sterol regulatory element binding protein 1 (SREBP1) as part of a cluster of proneural transcription factors in radial glia and as a regulator of transcription factors controlling mDA neurogenesis, such as Foxa2. Moreover, loss- and gain-of-function experiments in vitro and in vivo demonstrate that Srebf1 is both required and sufficient for mDA neurogenesis. Our data, thus, identify Srebf1 as a central player in mDA neurogenesis.

NF-E2-related factor 2 (NRF2), an antioxidant transcription factor, is activated in autophagy-deficient mice due to the accumulations of p62/SQSTM1 and its subsequent interaction with Kelch-like-ECH-associated protein 1 (KEAP1), an adaptor component for Cullin3-based E3 ubiquitin ligase complex. Farnesoid x receptor (FXR/NR1H4) is a ligand-dependent transcription factor that belongs to the nuclear receptor superfamily. FXR plays an essential role in bile acid synthesis and enterohepatic circulation, affecting glucose and lipid metabolism. Obeticholic acid as a potent FXR agonist has been approved to treat primary biliary cholangitis and clinical trials for its use in the treatment of other liver diseases are underway. Here we show that NRF2 activation in autophagy defects impedes a transactivation of FXR. Liver-specific Atg7 knockout mice or a treatment of autophagy inhibitor showed decreased inductions of FXR target genes upon its synthetic agonists. Moreover, enforced NRF2 activations with small molecules potently decreased the pharmacological activation of FXR in cultured cells. Finally, we demonstrate that NRF2 activation by the treatment with the food antioxidant butylated hydroxyanisole is necessary and sufficient to inhibit the pharmacological activation of FXR in vivo. These results reveal a novel function of the basal autophagy-NRF2 axis for the regulation of FXR transactivation, and shed light on a potential therapeutic strategy in metabolic disease.

Autophagy is an adaptive self-eating process involved in degradation of various cellular components such as carbohydrates, lipids, proteins, and organelles. Its activity plays an essential role in tissue homeostasis and systemic metabolism in response to diverse challenges, including nutrient depletion, pathogen invasion, and accumulations of toxic materials. Therefore, autophagy dysfunctions are intimately associated with many human diseases such as cancer, neurodegeneration, obesity, diabetes, infection, and aging. Although its acute post-translational regulation is well described, recent studies have also shown that autophagy can be controlled at the transcriptional and post-transcriptional levels. Nuclear receptors (NRs) are in general ligand-dependent transcription factors consisting of 48 members in humans. These receptors extensively control transcription of a variety of genes involved in development, metabolism, and inflammation. In this review, we discuss the roles and mechanisms of NRs in an aspect of transcriptional regulation of hepatic autophagy, and how the NR-driven autophagy pathway can be harnessed to treat various liver diseases.

Farnesoid x receptor (FXR) is a nuclear bile acid receptor that belongs to the nuclear receptor superfamily. It plays an essential role in bile acid biosynthesis, lipid and glucose metabolism, liver regeneration, and vertical sleeve gastrectomy. A loss of the FXR gene or dysregulations of FXR-mediated gene expression are associated with the development of progressive familial intrahepatic cholestasis, tumorigenesis, inflammation, and diabetes mellitus. Magnesium ion (Mg2+) is essential for mammalian physiology. Over 600 enzymes are dependent on Mg2+ for their activity. Here, we show that the Trpm6 gene encoding a Mg2+ channel is a direct FXR target gene in the intestinal epithelial cells of mice. FXR expressed in the intestinal epithelial cells is absolutely required for sustaining a basal expression of intestinal Trpm6 that can be robustly induced by the treatment of GW4064, a synthetic FXR agonist. Analysis of FXR ChIP-seq data revealed that intron regions of Trpm6 contain two prominent FXR binding peaks. Among them, the proximal peak from the transcription start site contains a functional inverted repeat 1 (IR1) response element that directly binds to the FXR-RXRα heterodimer. Based on these results, we proposed that an intestinal FXR-TRPM6 axis may link a bile acid signaling to Mg2+ homeostasis.

1α,25-Dihydroxyvitamin D3 [1α,25(OH)2D3, 1] is an active form of vitamin D3 and regulates various biological phenomena, including calcium and phosphate homeostasis, bone metabolism, and immune response via binding to and activation of vitamin D receptor (VDR). Lithocholic acid (LCA, 2) was identified as a second endogenous agonist of VDR, though its potency is very low. However, the lithocholic acid derivative 3 (Dcha-20) is a more potent agonist than 1α,25(OH)2D3, (1), and its carboxyl group has similar interactions to the 1,3-dihydroxyl groups of 1 with amino acid residues in the VDR ligand-binding pocket. Here, we designed and synthesized amide derivatives of 3 in order to clarify the role of the carboxyl group. The synthesized amide derivatives showed HL-60 cell differentiation-inducing activity with potency that depended upon the substituent on the amide nitrogen atom. Among them, the N-cyanoamide 6 is more active than either 1 or 3.

The ATP-binding cassette transporter ABCB4/MDR3 is critical for biliary phosphatidylcholine (PC) excretion at the canalicular membrane of hepatocytes. Defective ABCB4 gene expression and protein function result in various cholestatic liver and bile duct injuries. Thyroid hormone receptor (THR) is a major regulator of hepatic lipid metabolism; we explored its potential role in ABCB4 regulation. Thyroid hormone T3 stimulation to human hepatocyte models showed direct transcriptional activation of ABCB4 in a dose- and time-dependent manner. To determine whether THRβ1 (the main THR isoform of the liver) is involved in regulation, we tested THRβ1-specific agonists (e.g., GC-1, KB-141); these agonists resulted in greater stimulation than the native hormone. KB-141 activated hepatic ABCB44 expression in mice, which enhanced biliary PC secretion in vivo. We also identified THR response elements 6 kb upstream of the ABCB4 locus that were conserved in humans and mice. Thus, T3-via THRβ1 as a novel transcriptional activator regulates ABCB4 to increase ABCB4 protein levels at the canalicular membrane and promote PC secretion into bile. These findings may have important implications for understanding thyroid hormone function as a potential modifier of bile duct homeostasis and provide pharmacologic opportunities to improve liver function in hepatobiliary diseases caused by low ABCB4 expression.

Abstract The nuclear receptor RXRα (retinoid X receptor-α) is a transcription factor that regulates the expression of multiple genes. Its non-genomic function is largely related to its structure, polymeric forms and modification. Previous research revealed that some non-genomic activity of RXRα occurs via formation of heterodimers with Nur77. RXRα–Nur77 heterodimers translocate from the nucleus to the mitochondria in response to certain apoptotic stimuli and this activity correlates with cell apoptosis. More recent studies revealed a significant role for truncated RXRα (tRXRα), which interacts with the p85α subunit of the PI3K/AKT signaling pathway, leading to enhanced activation of AKT and promoting cell growth in vitro and in animals. We recently reported on a series of NSAID sulindac analogs that can bind to tRXRα through a unique binding mechanism. We also identified one analog, K-80003, which can inhibit cancer cell growth by inducing tRXRα to form a tetramer, thus disrupting p85α–tRXRα interaction. This review analyzes the non-genomic effects of RXRα in normal and tumor cells, and discusses the functional differences based on RXRα protein structure (structure source: the RCSB Protein Data Bank).