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Retinitis Pigmentosa is a leading cause of severe vision loss. Retinitis Pigmentosa can present with a broad range of phenotypes impacted by disease age of onset, severity, and progression. This variation is influenced both by different gene mutations as well as unique variants within the same gene. Mutations in the nuclear hormone receptor 2 family e, member 3 are associated with several forms of retinal degeneration, including Retinitis Pigmentosa. In our previous studies we demonstrated that subretinal administration of one Nr2e3 dose attenuated retinal degeneration in rd7 mice for at least 3 months. Here we expand the studies to evaluate the efficacy and longitudinal impact of the NR2E3 therapeutic by examining three different doses administered at early or intermediate stages of retinal degeneration in the rd7 mice. Our study revealed retinal morphology was significantly improved 6 months post for all doses in the early-stage treatment groups and for the low and mid doses in the intermediate stage treatment groups. Similarly, photoreceptor function was significantly improved in the early stage for all doses and intermediate stage low and mid dose groups 6 months post treatment. This study demonstrated efficacy in multiple doses of NR2E3 therapy., (© 2024. The Author(s).)

Mutations in NR2E3, a gene encoding an orphan nuclear transcription factor, cause two retinal dystrophies with a distinct phenotype, but the precise role of NR2E3 in rod and cone transcriptional networks remains unclear. To dissect NR2E3 function, we performed scRNA-seq in the retinas of wildtype and two different Nr2e3 mouse models that show phenotypes similar to patients carrying NR2E3 mutations. Our results reveal that rod and cone populations are not homogeneous and can be separated into different sub-classes. We identify a previously unreported cone pathway that generates hybrid cones co-expressing both cone- and rod-related genes. In mutant retinas, this hybrid cone subpopulation is more abundant and includes a subpopulation of rods transitioning towards a cone cell fate. Hybrid photoreceptors with high misexpression of cone- and rod-related genes are prone to regulated necrosis. Overall, our results shed light on the role of NR2E3 in modulating photoreceptor differentiation towards cone and rod fates and explain how different mutations in NR2E3 lead to distinct visual disorders in humans., Competing Interests: Declarationof competing interest The authors declare no conflict of interest., (Copyright © 2024 The Author(s). Published by Elsevier Inc. All rights reserved.)

While dysfunction and death of light-detecting photoreceptor cells underlie most inherited retinal dystrophies, knowledge of the species-specific details of human rod and cone photoreceptor cell development remains limited. Here, we generated retinal organoids carrying retinal disease-causing variants in NR2E3, as well as isogenic and unrelated controls. Organoids were sampled using single-cell RNA sequencing (scRNA-Seq) across the developmental window encompassing photoreceptor specification, emergence, and maturation. Using scRNA-Seq data, we reconstruct the rod photoreceptor developmental lineage and identify a branch point unique to the disease state. We show that the rod-specific transcription factor NR2E3 is required for the proper expression of genes involved in phototransduction, including rhodopsin, which is absent in divergent rods. NR2E3-null rods additionally misexpress several cone-specific phototransduction genes. Using joint multimodal single-cell sequencing, we further identify putative regulatory sites where rod-specific factors act to steer photoreceptor cell development. Finally, we show that rod-committed photoreceptor cells form and persist throughout life in a patient with NR2E3-associated disease. Importantly, these findings are strikingly different from those observed in Nr2e3 rodent models. Together, these data provide a road map of human photoreceptor development and leverage patient induced pluripotent stem cells to define the specific roles of rod transcription factors in photoreceptor cell emergence and maturation in health and disease.

The unfavorable prognosis of many neurological conditions could be attributed to limited tissue regeneration in central nervous system (CNS) and overwhelming inflammation, while liver X receptor (LXR) may regulate both processes due to its pivotal role in cholesterol metabolism and inflammatory response, and thus receives increasing attentions from neuroscientists and clinicians. Here, we summarize the signal transduction of LXR pathway, discuss the therapeutic potentials of LXR agonists based on preclinical data using different disease models, and analyze the dilemma and possible resolutions for clinical translation to encourage further investigations of LXR related therapies in CNS disorders., (© 2024. The Author(s).)

A strategy integrating in silico molecular docking with LXRα and phenotypic assays was adopted to discover anti-hypercholesterolemia agents in a small library containing 205 marine microorganism-derived natural products, collected by our group in recent years. Two fumitremorgin derivatives, 12 R ,13 S -dihydroxyfumitremorgin C ( 1 ) and tryprostatin A ( 3 ), were identified as potential LXRα agonists, by real-time qPCR and Western blot (WB) analysis, together with a surface plasmon resonance (SPR) assay. The anti-hypercholesterolemic effects of 1 and 3 , together with their mechanisms, were investigated in depth using different cell and mouse models, among which the study of LXRα is of crucial importance. Compound 1 or 3 exhibited the capacity to effectively reverse excessive lipid accumulation in a hepatic steatosis cell model and significantly reduce liver damage and blood cholesterol levels in high cholesterol diet (HCD)-fed wild-type mice, whereas those beneficial effects were completely nullified in HCD-fed LXRα-knockout mice. Furthermore, 1 and 3 outperformed common LXRα agonists by suppressing the expression of sterol regulatory element-binding protein 1 (SREBP1) in HCD-fed mice, mitigating lipotoxicity. Thus, this study highlights the discovery of two marine microorganism-derived anti-hypercholesterolemia agents targeting LXRα.

Nuclear receptor subfamily 2 group F (Nr2f) proteins are essential for brain development in mice, but little is known about their precise roles and their evolutionary diversification. In the present study, the expression patterns of major nr2f genes (nr2f1a, nr2f1b, and nr2f2) during early brain development were investigated in zebrafish. Comparisons of their expression patterns revealed similar but temporally and spatially distinct patterns after early somite stages in the brain. Frameshift mutations in the three nr2f genes, achieved using the CRISPR/Cas9 method, resulted in a smaller telencephalon and smaller eyes in the nr2f1a mutants; milder forms of those defects were present in the nr2f1b and nr2f2 mutants. Acridine orange staining revealed enhanced cell death in the brain and/or eyes in all nr2f homozygous mutants. The expression of regional markers in the brain did not suggest global defects in brain regionalization; however, shha expression in the preoptic area and hypothalamus, as well as fgf8a expression in the anterior telencephalon, was disturbed in nr2f1a and nr2f1b mutants, potentially leading to a defective telencephalon. Specification of the retina and optic stalk was also significantly affected. The overexpression of nr2f1b by injection of mRNA disrupted the anterior brain at a high dose, and the expression of pax6a in the eyes and fgf8a in the telencephalon at a low dose. The results of these loss- and gain-of-function approaches showed that nr2f genes regulate the development of the telencephalon and eyes in zebrafish embryos., (© 2024 The Authors. Development, Growth & Differentiation published by John Wiley & Sons Australia, Ltd on behalf of Japanese Society of Developmental Biologists.)

Background: Tetranucleotide repeat domain protein 39B (TTC39B) was found to combine with ubiquitin ligase E3, and promote the ubiquitination modification of liver X receptor (LXR), which led to the inhibition of reverse cholesterol transport and development of atherosclerosis. QiShenYiQi pill (QSYQ) is a modern Chinese patent drug for treating ischemic cardiovascular diseases, the underlying mechanism is found to promote the expression of LXR-α/ ATP-binding cassette transporter G5 (ABCG5) in the liver of atherosclerotic mice., Purpose: The aim of this study is to investigate the effect of QSYQ on TTC39B-LXR mediated reverse cholesterol transport in atherosclerotic mice., Study Design and Methods: Male apolipoprotein E gene knockout mice (7 weeks old) were fed with high-fat diet and treated with low dose of QSYQ (QSYQ-l, 0.3 g/kg·d), high dose of QSYQ (QSYQ-H, 1.2 g/kg·d) and LXR-α agonist (LXR-A, GW3965 10 mg/kg·d) for 8 weeks. C57BL/6 J mice were fed with normal diet and used as negative control. Oil red O staining, HE staining, ELISA, RNA sequencing, western blot, immunohistochemistry, RT-PCR, cell culture and RNA interference were performed to analyze the effect of QSYQ on atherosclerosis., Results: HE staining showed that QSYQ reduced the atherosclerotic lesion significantly when compared to the control group. ELISA measurement showed that QSYQ decreased serum VLDL and increased serum ApoA1. Oil Red O staining showed that QSYQ reduced the lipid content of liver and protect liver function. Comparative transcriptome RNA-sequence of liver showed that DEGs after QSYQ treatment enriched in high-density lipoprotein particle, ubiquitin ligase complex, bile secretion, etc. Immunohistochemical staining and western blot proved that QSYQ increased the protein expression of hepatic SR-B1, LXR-α, LXR-β, CYP7A1 and ABCG5. Targeted inhibiting Ttc39b gene in vitro further established that QSYQ inhibited the gene expression of Ttc39b, increased the protein expression of SR-B1, LXR-α/β, CYP7A1 and ABCG5 in rat hepatocyte., Conclusion: Our results demonstrated the new anti-atherosclerotic mechanism of QSYQ by targeting TTC39B-LXR mediated reverse cholesterol transport in liver. QSYQ not only promoted reverse cholesterol transport, but also improved fatty liver and protected liver function., 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 © 2023 The Author(s). Published by Elsevier GmbH.. All rights reserved.)

Background: Inflammation-exacerbated secondary brain injury and limited tissue regeneration are barriers to favourable prognosis after intracerebral haemorrhage (ICH). As a regulator of inflammation and lipid metabolism, Liver X receptor (LXR) has the potential to alter microglia/macrophage (M/M) phenotype, and assist tissue repair by promoting cholesterol efflux and recycling from phagocytes. To support potential clinical translation, the benefits of enhanced LXR signalling are examined in experimental ICH., Methods: Collagenase-induced ICH mice were treated with the LXR agonist GW3965 or vehicle. Behavioural tests were conducted at multiple time points. Lesion and haematoma volume, and other brain parameters were assessed using multimodal MRI with T2-weighted, diffusion tensor imaging and dynamic contrast-enhanced MRI sequences. The fixed brain cryosections were stained and confocal microscopy was applied to detect LXR downstream genes, M/M phenotype, lipid/cholesterol-laden phagocytes, oligodendrocyte lineage cells and neural stem cells. Western blot and real-time qPCR were also used. CX3CR1 CreER : Rosa26 iDTR mice were employed for M/M-depletion experiments., Results: GW3965 treatment reduced lesion volume and white matter injury, and promoted haematoma clearance. Treated mice upregulated LXR downstream genes including ABCA1 and Apolipoprotein E, and had reduced density of M/M that apparently shifted from proinflammatory interleukin-1β + to Arginase1 + CD206 + regulatory phenotype. Fewer cholesterol crystal or myelin debris-laden phagocytes were observed in GW3965 mice. LXR activation increased the number of Olig2 + PDGFRα + precursors and Olig2 + CC1 + mature oligodendrocytes in perihaematomal regions, and elevated SOX2 + or nestin + neural stem cells in lesion and subventricular zone. MRI results supported better lesion recovery by GW3965, and this was corroborated by return to pre-ICH values of functional rotarod activity. The therapeutic effects of GW3965 were abrogated by M/M depletion in CX3CR1 CreER : Rosa26 iDTR mice., Conclusions: LXR agonism using GW3965 reduced brain injury, promoted beneficial properties of M/M and facilitated tissue repair correspondent with enhanced cholesterol recycling., Competing Interests: Competing interests: None declared., (© Author(s) (or their employer(s)) 2023. Re-use permitted under CC BY-NC. No commercial re-use. See rights and permissions. Published by BMJ.)

We explored the involvement of orphan nuclear receptor 4 A1 (NR4A1) in myocardial fibrosis mediated by transforming growth factor-beta1 (TGF-β1) and its response to cytosporone B (Csn-B). We developed a diabetic cardiomyopathy mouse model by administering a high-fat diet in conjunction with a low-dose streptozotocin injection. Our analysis involved monitoring alterations in blood glucose and lipid levels, cardiac function and structure, as well as profibrotic factors such as α smooth muscle actin (α-SMA), collagen I, collagen III, TGF-β1, connective tissue growth factor, and fibronectin. These assessments were conducted using biochemical techniques, Doppler ultrasound, histopathology, and real-time quantitative polymerase chain reaction. Cardiac fibroblasts (CFs) were extracted from suckling mice and cultivated in a high-glucose medium to simulate diabetes-induced myocardial fibrosis in vitro. These CFs were then subjected to coculture experiments with TGF-β1 or Csn-B. The proliferation and migration of CFs were assessed using cell counting kit 8 (CCK-8) assays and Transwell assays, respectively. Western blotting and immunofluorescence assays were employed to evaluate the expression levels of NR4A1, p-NR4A1, and α-SMA in CFs treated with TGF-β1 after NR4A1 knockdown or Csn-B administration, respectively. In diabetic heart tissue, the expression of p-NR4A1 was notably elevated. Furthermore, CFs exhibited enhanced proliferative capabilities and increased p-NR4A1 expression following high glucose exposure. Interestingly, NR4A1 knockdown resulted in a significant increase in the expression of fibrosis-related proteins in CFs following treatment with TGF-β1. Moreover, our observations revealed a marked decrease in p-NR4A1 levels and a reduction in the expression of fibrosis-related proteins after Csn-B treatment. In diabetic mice treated with Csn-B, we noted diminished NR4A1 phosphorylation and a mitigation of myocardial fibrosis. We concluded that in the mouse model, Csn-B played a pivotal role in inhibiting diabetes-induced myocardial fibrosis by activating NR4A1.

Objective: Pancreatic ductal adenocarcinoma (PDAC) has an unfavorable outlook due to its aggressive characteristics, delayed diagnosis, and limited effective treatment options for advanced stages of the disease. The significant mortality rate has prompted investigations into additional factors that could aid in managing this type of cancer. Liver X receptors, specifically LXRα and LXRβ, are nuclear receptors that oversee the expression of genes related to cholesterol, glucose, lipid metabolism, and inflammatory responses. LXRs have also emerged as potential targets for addressing PDAC, and recent findings have demonstrated that LXR ligands can impede cell proliferation in various cancer forms, notably pancreatic cancer. This comprehensive computational research study involving oncological in silico mechanism discovery explored inhibitory ligands for Liver X receptors (LXRα and LXRβ), which are believed to have prognostic significance in PDAC., Methods: The study utilized Baicalein, Beta-Sitosterol, Polydatin ligands in molecular docking and dynamics and post-molecular Hydrogen bonding contact analyses dynamics to characterize receptor inhibition., Result: The outcomes suggest that Baicalein exhibits versatile inhibitory effects on both receptors, while Beta-Sitosterol emerges as a highly effective inhibitor of LXRβ., Conclusion: Further in vitro and in vivo investigations will be beneficial and would shed light onto the mechanism to decipher the suppression of PDAC evaluating the potential of Baicalein, Beta-Sitosterol, Polydatin natural ligand compounds.

Liver X receptors (LXRs) are master regulators of various biological processes, including metabolism, inflammation, development, and reproduction. As well-known nuclear oxysterol receptors of the nuclear receptor (NR) family, LXRs have two homologous subtypes, LXRα (NR1H3) and LXRβ (NR1H2). Since the mid-1990s, numerous LXR-targeted drugs have been designed to treat diseases such as atherosclerosis, systemic lupus erythematosus, and cancer. These modulators include agonists and antagonists, and the selectivity of them have been development from diverse aspects, including subtype-specific, cell-specific, tissue-specific types. Meanwhile, advanced delivery systems are also exploreed to facilitate the application of LXR drugs in clinical setting. One of the most promising delivery systems involves the use of nanoparticles and is expected to increase the clinical potential of LXR modulators. This review discusses our current understanding of LXR biology and pharmacology, focusing on the development of modulators for LXRα and/or LXRβ, and the nanoparticle-based delivery systems for promising LXR modulators with potential for use as drugs., Competing Interests: Declaration of competing interest This manuscript has not been published or presented elsewhere in part or in entirety and is not under consideration by another journal. We have read and understood your journal's policies, and we believe that neither the manuscript nor the study violates any of these. There are no conflicts of interest to declare., (Copyright © 2023 The Authors. Published by Elsevier B.V. All rights reserved.)

Liver X receptors (LXRs) are nuclear transcription factors important in the regulation of cholesterol transport, and glucose and fatty acid metabolism. The antiproliferative role of LXRs has been studied in a variety of malignancies and may represent a therapeutic opportunity in cancers lacking targeted therapies, such as triple-negative breast cancer. In this study, we investigated the impact of LXR agonists alone and in combination with carboplatin in preclinical models of breast cancer. In vitro experiments revealed a dose-dependent decrease in tumor cell proliferation in estrogen receptor-positive breast cancer cells, whereas LXR activation in vivo resulted in an increased growth inhibitory effect in a basal-like breast cancer model (in combination with carboplatin). Functional proteomic analysis identified differences in protein expression between responding and nonresponding models related to Akt activity, cell-cycle progression, and DNA repair. Furthermore, pathway analysis suggested that the LXR agonist in combination with carboplatin inhibits the activity of targets of E2F transcription factors and affects cholesterol homeostasis in basal-like breast cancer., (© 2023 The Authors. Molecular Oncology published by John Wiley & Sons Ltd on behalf of Federation of European Biochemical Societies.)

The development of chronic liver disease can be promoted by excessive fat accumulation, dysbiosis, viral infections and persistent inflammatory responses, which can lead to liver inflammation, fibrosis and carcinogenesis. An in-depth understanding of the etiology leading to chronic liver disease and the underlying mechanisms influencing its development can help identify potential therapeutic targets for targeted treatment. Orphan nuclear receptors (ONRs) are receptors that have no corresponding endogenous ligands to bind to them. The study of these ONRs and their biological properties has facilitated the development of synthetic ligands, which are important for investigating the effective targets for the treatment of a wide range of diseases. In recent years, it has been found that ONRs are essential for maintaining normal liver function and their dysfunction can affect a variety of liver diseases. ONRs can influence pathophysiological activities such as liver lipid metabolism, inflammatory response and cancer cell proliferation by regulating hormones/transcription factors and affecting the biological clock, oxidative stress, etc. This review focuses on the regulation of ONRs, mainly including retinoid related orphan nuclear receptors (RORs), pregnane X receptor (PXR), leukocyte cell derived chemotaxin 2 (LECT2), Nur77, and hepatocyte nuclear factor 4α (HNF4α), on the development of different types of chronic liver diseases in different ways, in order to provide useful references for the therapeutic strategies of chronic liver diseases based on the regulation of ONRs.

Introduction: NR2F6 (nuclear receptor subfamily 2 group F member 6, also called Ear-2) is known to be an orphan nuclear receptor that has been characterized as an intracellular immune checkpoint in effector T cells and, therefore, may control tumor development and growth. The prognostic impact of NR2F6 in endometrial cancers is evaluated in this study., Materials and Methods: Expression analysis of NR2F6 in 142 endometrial cancer patients was performed by immunohistochemistry of primary paraffin‑embedded tumor samples. Staining intensity of positive tumor cells was automatically assessed semi-quantitatively, and results were correlated with clinicopathological characteristics and survival., Results: Forty five of 116 evaluable samples (38.8%) showed an overexpression of NR2F6. This leads to an improvement of the overall survival (OS) and progression-free survival (PFS). In NR2F6-positive patients, the estimated mean OS was 156.9 months (95% confidence interval (CI) 143.1-170.7) compared to 106.2 months in NR2F6-negative patients (95% CI 86.2-126.3; p = 0.022). The estimated PFS differed by 63 months (152 months (95% CI 135.7-168.4) vs. 88.3 months (95% CI 68.5-108.0), p = 0.002). Furthermore, we found significant associations between NR2F6 positivity, MMR status, and PD1 status. A multivariate analysis suggests NR2F6 to be an independent factor influencing the OS (p = 0.03)., Conclusion: In this study, we could demonstrate that there is a longer progression-free and overall survival for NR2F6-positive patients with endometrial cancer. We conclude that NR2F6 might play an essential role in endometrial cancers. Further studies are required to validate its prognostic impact., (© 2023. The Author(s).)

Objective: Preeclampsia (PE) is a complex disease-causing multisystem damage. Many genes, environmental factors, and their interactions are involved in the development and progression of PE. The pathogenesis of PE is not fully understood, limiting the prevention and treatment of PE. The aim of this study was to investigate the effect of 4,4'-diisothiocyanato-stilbene-2,2'-disulfonic acid (DIDS), an ATP-binding cassette transporter A1 (ABCA1) blocker, on apoM mRNA and protein levels., Patients and Methods: The role of liver X receptor α (LXRα) and ABCA1 in the pathogenesis of PE was investigated by optimizing the design of DIDS inhibition based on a deep learning model., Results: The proportion of primipara in the research group, EOPE group, LOPE group, and controls was 59.82%, 65.85%, 56.34%, and 21.43%, respectively. The difference between the research group and the controls was statistically significant (p<0.01). In the clinical data, serum-free triiodothyronine (FT3), gestational age at delivery, high-density lipoprotein cholesterol (HDL-C), hemoglobin (HGB), albumin, and platelet (PLT) in the research group were lower than those in the controls (p<0.05)., Conclusions: ABCA1 is considered to affect apoM mRNA expression, G/HDL-C may increase the risk of LOPE, and overweight or obesity, abnormal glycemic regulation, and hypothyroidism are independent risk factors closely related to the pathogenesis of PE and its subgroups.

Introduction: Liver X receptors (LXRs) have emerged as novel targets for tumor treatment. LXRs within the tumor microenvironment show the capacity to impact tumorigenesis and tumor development by regulating the infiltration of immune cells and release of cytokines to moderate inflammation., Areas Covered: In this review, we present a systematic description of recent progress in understanding the impact of LXRs on the tumor microenvironment and tumorigenesis. We also summarize the antitumor effects mediated by LXRs via their regulation of cytokine expression. Additionally, we discuss the limitations of LXR research in tumor studies to date., Expert Opinion: Previous studies have demonstrated abnormal LXR expression in tumor tissues, and activation of LXRs has been shown to inhibit tumorigenesis and promote apoptosis in tumor cells. However, LXRs can also affect tumorigenesis by regulating immune cell functions within the tumor immune microenvironment. By summarizing the impact of LXRs on immune cells, we provide new insights into the multifaceted nature of LXRs as antitumor targets.

NR2E3 is a nuclear hormone receptor gene required for the correct development of the retinal rod photoreceptors. Expression of NR2E3 protein in rod cell precursors suppresses cone-specific gene expression and, in concert with other transcription factors including NRL, activates the expression of rod-specific genes. Pathogenic variants involving NR2E3 cause a spectrum of retinopathies, including enhanced S-cone syndrome, Goldmann-Favre syndrome, retinitis pigmentosa, and clumped pigmentary retinal degeneration, with limited evidence of genotype-phenotype correlations. A common feature of NR2E3 -related disease is an abnormally high number of cone photoreceptors that are sensitive to short wavelength light, the S-cones. This characteristic has been supported by mouse studies, which have also revealed that loss of Nr2e3 function causes photoreceptors to develop as cells that are intermediate between rods and cones. While there is currently no available cure for NR2E3 -related retinopathies, there are a number of emerging therapeutic strategies under investigation, including the use of viral gene therapy and gene editing, that have shown promise for the future treatment of patients with NR2E3 variants and other inherited retinal diseases. This review provides a detailed overview of the current understanding of the role of NR2E3 in normal development and disease, and the associated clinical phenotypes, animal models, and therapeutic studies.

CD8 + T cells undergo rapid expansion followed by contraction and the development of memory cells after their receptors are activated. The development of immunological memory following acute infection is a complex phenomenon that involves several molecular, transcriptional, and metabolic mechanisms. As memory cells confer long-term protection and respond to secondary stimulation with strong effector function, understanding the mechanisms that influence their development is of great importance. Orphan nuclear receptors, NR4As, are immediate early genes that function as transcription factors and bind with the NBRE region of chromatin. Interestingly, the NBRE region of activated CD8 + T cells is highly accessible at the same time the expression of NR4As is induced. This suggests a potential role of NR4As in the early events post T cell activation that determines cell fate decisions. In this review, we will discuss the influence of NR4As on the differentiation of CD8 + T cells during the immune response to acute infection and the development of immunological memory. We will also discuss the signals, transcription factors, and metabolic mechanisms that control cell fate decisions. HIGHLIGHTS: Memory CD8 + T cells are an essential subset that mediates long-term protection after pathogen encounters. Some specific environmental cues, transcriptional factors, and metabolic pathways regulate the differentiation of CD8 + T cells and the development of memory cells. Orphan nuclear receptor NR4As are early genes that act as transcription factors and are highly expressed post-T cell receptor activation. NR4As influence the effector function and differentiation of CD8 + T cells and also control the development of immunological memory following acute infection., (© 2022. The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.)

It was recently reported that the hydroxyflavones quercetin and kaempferol bind the orphan nuclear receptor 4A1 (NR4A1, Nur77) and act as antagonists in cancer cells and tumors, and they inhibit pro-oncogenic NR4A1-regulated genes and pathways. In this study, we investigated the interactions of flavone, six hydroxyflavones, seven dihydroxyflavones, three trihydroxyflavones, two tetrahydroxyflavones, and one pentahydroxyflavone with the ligand-binding domain (LBD) of NR4A1 using direct-binding fluorescence and an isothermal titration calorimetry (ITC) assays. Flavone and the hydroxyflavones bound NR4A1, and their K D values ranged from 0.36 µM for 3,5,7-trihydroxyflavone (galangin) to 45.8 µM for 3'-hydroxyflavone. K D values determined using ITC and K D values for most (15/20) of the hydroxyflavones were decreased compared to those obtained using the fluorescence assay. The results of binding, transactivation and receptor-ligand modeling assays showed that K D values, transactivation data and docking scores for these compounds are highly variable with respect to the number and position of the hydroxyl groups on the flavone backbone structure, suggesting that hydroxyflavones are selective NR4A1 modulators. Nevertheless, the data show that hydroxyflavone-based neutraceuticals are NR4A1 ligands and that some of these compounds can now be repurposed and used to target sub-populations of patients that overexpress NR4A1.

Background: It has been reported that LXR agonist can inhibit Aβ generation and alleviate Aβ-induced various adverse reactions in vivo and in vitro experiments, but the mechanisms have not been clarified. The study aimed to observe the effect of LXR agonist TO901317 on the cognitive function of AD transgenic mice fed with cholesterol-rich diet (CRD), and to explore the possible mechanism. Methods: 32 male 6-month-old double transgenic AD mice were enrolled and randomly divided into 4 groups: control (normal diet) group, CRD treatment group, TO901317 treatment group and GSK2033 treatment group. After 3 month, Morris water maze was for the changes of spatial exploration and memory ability; ELISA was for detecting the production of Aβ42 in the brain; the concentration of total cholesterol (TC), low density lipoprotein (LDL) and high density lipoprotein (HDL) in serum were detected by cholesterol enzyme colorimetry; Finally, the expression of LXR-β, RXR-α, ABCA1, caveolin-1, BACE1 and APP at protein level in the brains was measured by Western blotting., Results: Compared with the control group, the learning, memory ability and spatial exploration ability of the mice were more significantly serious in the CRD group (P<0.05); The contents of TC and LDL in the serum and the production of Aβ42 in the brains were significantly increased (P<0.05), but HDL was remarkably decreased (P<0.05); The protein levels of LXR-β, RXR-α and ABCA1 were also significantly decreased (P<0.05); The expression of caveolin-1, APP and BACE1 were evidently increased (P<0.05). However, after treatment with TO901317, the impaired learning and memory and spatial exploration ability of the mice were significantly improved (P<0.05); The contents of TC and LDL in serum and the production of Aβ42 in the brains were significantly decreased (P<0.05), but HLD was increased (P<0.05); The protein levels of LXR-β, RXR-α, ABCA1were all significantly increased (P<0.05), while, the expression of caveolin-1, APP and BACE1 were all significantly decreased (P<0.05). All the changes were reversed by GSK2033 (P<0.05)., Conclusions: TO901317 attenuated the more serious impairment of spatial exploration, learning and memory in transgenic AD mice induced by CRD, and the mechanism may be that TO901317 could activate the LXR-β/RXR-α/ABCA1 transmembrane transport system, promote the cholesterol efflux, and decreased caveolin-1, APP and BACE1, further reduce Aβ42 in the brains.

Nuclear receptor modulation enables pharmacological control of gene expression thus rendering the 48 human nuclear receptors as attractive targets for drug discovery. Several nuclear receptor ligands like glucocorticoids are approved and highly important drugs illustrating the therapeutic potential of nuclear receptor modulation. However, a significant portion of the nuclear receptor family is still poorly explored for new therapeutic opportunities which is due to a lack of potent, selective and well-characterized ligands. Preliminary evidence supports great therapeutic potential of several orphan nuclear receptors in various pathologies underlining the need for high-quality chemical tools to enable target validation. Here, we evaluate the characteristics of available nuclear receptor modulators and the gaps in coverage of the nuclear receptor family with chemical tools. We review successful approaches to nuclear receptor modulator development and highlight the opportunities and challenges in closing the gaps of missing tools for understudied nuclear receptors to open new therapeutic avenues.

ATP-binding cassette transporter A-I (ABCA1) is an ubiquitously expressed protein whose main function is the transmembrane transport of cholesterol and phospholipids. Synthesis of ABCA1 protein in liver is necessary for high-density lipoprotein (HDL) formation in mammals. Thus, the mechanism of ABCA1 gene expression regulation in hepatocytes are of critical importance. Recently, we have found the insulin-dependent downregulation of other key player in the HDL formation-apolipoprotein A-I gene (J. Cell. Biochem., 2017, 118:382-396). Nothing is known about the role of insulin in the regulation of ABCA1 gene. Here we show for the first time that insulin decreases the mRNA and protein levels of ABCA1 in human hepatoma cell line HepG2. PI3K, p38, MEK1/2, JNK and mTORC1 signaling pathways are involved in the insulin-mediated downregulation of human ABCA1 gene. Transcription factors LXRα, LXRβ, FOXO1 and NF-κB are important contributors to this process, while FOXA2 does not regulate ABCA1 gene expression. Insulin causes the decrease in FOXO1, LXRα and LXRβ binding to ABCA1 promoter, which is likely the cause of the decrease in the gene expression. Interestingly, the murine ABCA1 gene seems to be not regulated by insulin in hepatocytes (in vitro and in vivo). We suggest that the reason for this discrepancy is the difference in the 5'-regulatory regions of human and murine ABCA1 genes., (© 2022. The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.)

Liver X receptors (LXRs) are members of the nuclear receptor family of ligand-dependent transcription factors which regulate the expression of lipid and cholesterol metabolism genes. Moreover, LXRs and their ligands have been shown to inhibit tumor growth in a variety of cancers. We have previously identified the small molecule compound GAC0001E5 (1E5) as an LXR inverse agonist and a potent inhibitor of pancreatic cancer cells. Transcriptomic and metabolomic studies showed that 1E5 disrupts glutamine metabolism, an essential metabolic pathway commonly reprogrammed during malignant transformation, including in breast cancers. To determine the role of LXRs and potential application of 1E5 in breast cancer, we examined LXR expression in publicly available clinical samples, and found that LXR expression is elevated in breast tumors as compared to normal tissues. In luminal A, endocrine therapy-resistant, and triple-negative breast cancer cells, 1E5 exhibited LXR inverse agonist and "degrader" activity and strongly inhibited cell proliferation and colony formation. Treatments with 1E5 downregulated the transcription of key glutaminolysis genes, and, correspondingly, biochemical assays indicated that 1E5 lowered intracellular glutamate and glutathione levels and increased reactive oxygen species. These results indicate that novel LXR ligand 1E5 is an inhibitor of glutamine metabolism and redox homeostasis in breast cancers and suggest that modulating LXR activity and expression in tumor cells is a promising strategy for targeting metabolic reprogramming in breast cancer therapeutics.

Background: Patients with type 2 diabetes mellitus have a high cardiovascular risk due, in part, to abnormalities of high-density lipoprotein mediated cholesterol efflux. The ATP-binding cassette A1 and G1 play a pivotal role in the regulation of cholesterol efflux. However, the regulation of these transporters in type 2 diabetes mellitus remains obscure., Objectives: This study aimed to investigate the expression of ATP-binding cassette A1 and G1 and their regulation by Liver X receptors in monocyte-derived macrophages in type 2 diabetes mellitus, and to determine whether the alteration of these transporters might affect cholesterol efflux from macrophages., Methods: Blood was collected from type 2 diabetic patients and healthy controls. Peripheral monocytes were differentiated into macrophages. Quantitative real-time PCR, western blots, and cholesterol efflux assays were performed. The Liver X receptor and Liver X receptor element complex in the ATP-binding cassette G1 gene promoter were detected by electrophoretic mobility supershift assay., Results: Macrophage ATP-binding cassette G1 expression and high density lipoproteininduced cholesterol efflux were significantly reduced in type 2 diabetic patients. However, the mRNA expression of ATP-binding cassette G1 in type 2 diabetic patients was not inhibited by Liver X receptor siRNA and the Liver X receptor- Liver X receptor element complexes remain unchanged similarly., Conclusion: The study suggested that the expression of ATP-binding cassette G1 and high density lipoprotein-induced cholesterol efflux in macrophages were reduced in type 2 diabetes mellitus. Impairment of cholesterol efflux and ATP-binding cassette G1 gene expression in type 2 diabetes mellitus might be regulated by a Liver X receptorindependent pathway., (Copyright© Bentham Science Publishers; For any queries, please email at epub@benthamscience.net.)

Nuclear receptors are among one of the major transcriptional factors that induces gene regulation in the nucleus. Liver X receptor (LXR) is a transcription factor which regulates essential lipid homeostasis in the body including fatty acid, cholesterol and phospholipid synthesis. Liver X receptor-retinoid X receptor (LXR-RXR) heterodimer is activated by either of the ligand binding on LXR or RXR. The promoter region of the gene which is targeted by LXR is bound to the response element of LXR. The activators bind to the heterodimer once the corepressor is dissociated. The cellular process such as endocytosis aids in intracellular trafficking and endosomal formation in transportation of molecules for essential signaling within the cell. LXR isotypes play a crucial role in maintaining lipid homeostasis by regulating the level of cholesterol. In the liver, the deficiency of LXRα can alter the normal physiological conditions depicting the symptoms of various cardiovascular and liver diseases. LXR can degrade low density lipoprotein receptors (LDLR) by the signaling of LXR-IDOL through endocytic trafficking in lipoprotein uptake. Various gene expressions associated with cholesterol level and lipid synthesis are regulated by LXR transcription factor. With its known diversified ligand binding, LXR is capable of regulating expression of various specific genes responsible for the progression of autoimmune diseases. The agonists and antagonists of LXR stand to be an important factor in transcription of the ABC family, essential for high density lipoprotein (HDL) formation. Endocytosis and signaling mechanism of the LXR family is broad and complex despite their involvement in cellular growth and proliferation. Here in this chapter, we aimed to emphasize the master regulation of LXR activation, regulators, and their implications in various metabolic activities especially in lipid homeostasis. Furthermore, we also briefed the significant role of LXR endocytosis in T cell immune regulation and a variety of human diseases including cardiovascular and neuroadaptive., (Copyright © 2023 Elsevier Inc. All rights reserved.)

Enhanced S-cone Syndrome (ESCS) is an autosomal recessive inherited retinal disease mostly associated with disease-causing variants in the NR2E3 gene. During retinal development in ESCS, rod photoreceptor precursors are misdirected to form photoreceptors similar to short-wavelength cones, or S-cones. Compared to a normal human retina, patients with ESCS have no rods and significantly increased numbers of S-cones. Night blindness is the main visual symptom, and visual acuity and color vision can be normal at early disease stages. Histology of donor eyes and adaptive optics imaging revealed increased S-cone density outside of the fovea compared to normal. Visual function testing reveals absent rod function and abnormally enhanced sensitivity to short-wavelength light. Unlike most retinal degenerative diseases, ESCS results in a gain in S-cone photoreceptor function. Research involving ESCS could improve understanding of this rare retinal condition and also shed light on the role of NR2E3 expression in photoreceptor survival., (© 2023. The Author(s), under exclusive license to Springer Nature Switzerland AG.)

Objectives: Elimination of brain tumour initiating cells (BTICs) is important for the good prognosis of malignant brain tumour treatment. To develop a novel strategy targeting BTICs, we studied NR2E1(TLX) involved self-renewal mechanism of BTICs and explored the intervention means., Materials and Methods: NR2E1 and its interacting protein-LSD1 in BTICs were studied by gene interference combined with cell growth, tumour sphere formation, co-immunoprecipitation and chromatin immunoprecipitation assays. NR2E1 interacting peptide of LSD1 was identified by Amide Hydrogen/Deuterium Exchange and Mass Spectrometry (HDX-MS) and analysed by in vitro functional assays. The in vivo function of the peptide was examined with intracranial mouse model by transplanting patient-derived BTICs., Results: We found NR2E1 recruits LSD1, a lysine demethylase, to demethylate mono- and di-methylated histone 3 Lys4 (H3K4me/me2) at the Pten promoter and repress its expression, thereby promoting BTIC proliferation. Using Amide Hydrogen/Deuterium Exchange and Mass Spectrometry (HDX-MS) method, we identified four LSD1 peptides that may interact with NR2E1. One of the peptides, LSD1-197-211 that locates at the LSD1 SWIRM domain, strongly inhibited BTIC proliferation by promoting Pten expression through interfering NR2E1 and LSD1 function. Furthermore, overexpression of this peptide in human BTICs can inhibit intracranial tumour formation., Conclusion: Peptide LSD1-197-211 can repress BTICs by interfering the synergistic function of NR2E1 and LSD1 and may be a promising lead peptide for brain tumour therapy in future., (© 2022 The Authors. Cell Proliferation published by Beijing Institute for Stem Cell and Regenerative Medicine and John Wiley & Sons Ltd.)

Lipids-lowering is considered as the most effective approach to decrease the risk of Atherosclerotic cardiovascular disease (ASCVD), of which atherosclerosis is the most common cause. Natural products containing a unique type of α-pyrone was reported to suppress atherosclerosis in which α-pyrone might be considered as an important pharmacore. In this study, an efficient one-pot intramolecular C-H activation strategy was applied to the synthesis of potentially bioactive α-pyrone derivatives. As the result, three different scaffolds were quickly and conveniently generated, including thiophenes, pyrrole and indole derivatives. Among of them, eight α-pyrone derivatives showed potential effects to promote the uptake of LDL in HepG2 cells. Active unique α-pyrones compounds exhibiting potent in vitro and in vivo lipids-lowering effects, and a novel mechanism associated with the regulation of LXR-IDOL-LDLR axis, the new pathway targeted pharmacologically to control plasma cholesterol levels, were disclosed firstly in this study., 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 © 2022 Elsevier Masson SAS. All rights reserved.)

Hepatocellular carcinoma (HCC) commonly possesses chronical elevation of IRE1α-ASK1 signaling. Orphan nuclear receptor Nur77, a promising therapeutic target in various cancer types, is frequently silenced in HCC. In this study, we show that cryptomeridiol (Bkh126), a naturally occurring sesquiterpenoid derivative isolated from traditional Chinese medicine Magnolia officinalis , has therapeutic efficacy in HCC by aggravating the pre-activated UPR and activating the silenced Nur77. Mechanistically, Nur77 is induced to sense IRE1α-ASK1-JNK signaling and translocate to the mitochondria, which leads to the loss of mitochondrial membrane potential (Δψm). The Bkh126-induced aggravation of ER stress and mitochondrial dysfunction result in increased cytotoxic product of reactive oxygen species (ROS). The in vivo anti-HCC activity of Bkh126 is superior to that of sorafenib, currently used to treat advanced HCC. Our study shows that Bkh126 induces Nur77 to connect ER stress to mitochondria-mediated cell killing. The identification of Nur77 as a molecular target of Bhk126 provides a basis for improving the leads for the further development of anti-HCC drugs.

We have reported excess B-cell activating factor (BAFF) in the blood of HIV-infected progressors, which was concomitant with increased frequencies of precursor-like marginal zone (MZp) B-cells, early on and despite antiretroviral therapy (ART). In controls, MZp possess a strong B-cell regulatory (Breg) potential. They highly express IL-10, the orphan nuclear receptors (NR)4A1, NR4A2 and NR4A3, as well as the ectonucleotidases CD39 and CD73, all of which are associated with the regulation of inflammation. Furthermore, we have shown MZp regulatory function to involve CD83 signaling. To address the impact of HIV infection and excessive BAFF on MZp Breg capacities, we have performed transcriptomic analyses by RNA-seq of sorted MZp B-cells from the blood of HIV-infected progressors. The Breg profile and function of blood MZp B-cells from HIV-infected progressors were assessed by flow-cytometry and light microscopy high-content screening (HCS) analyses, respectively. We report significant downregulation of NR4A1, NR4A2, NR4A3 and CD83 gene transcripts in blood MZp B-cells from HIV-infected progressors when compared to controls. NR4A1, NR4A3 and CD83 protein expression levels and Breg function were also downregulated in blood MZp B-cells from HIV-infected progressors and not restored by ART. Moreover, we observe decreased expression levels of NR4A1, NR4A3, CD83 and IL-10 by blood and tonsillar MZp B-cells from controls following culture with excess BAFF, which significantly diminished their regulatory function. These findings, made on a limited number of individuals, suggest that excess BAFF contributes to the alteration of the Breg potential of MZp B-cells during HIV infection and possibly in other situations where BAFF is found in excess., 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.

Stricture formation is a common complication of Crohn's disease (CD), driven by enhanced deposition of extracellular matrix (ECM) and expansion of the intestinal smooth muscle layers. Nuclear receptor subfamily 4 group A member 1 (NR4A1) is an orphan nuclear receptor that exhibits anti-proliferative effects in smooth muscle cells (SMCs). We hypothesized that NR4A1 regulates intestinal SMC proliferation and muscle thickening in the context of inflammation. Intestinal SMCs isolated from Nr4a1 +/+ and Nr4a1 -/- littermates were subjected to shotgun proteomic analysis, proliferation, and bioenergetic assays. Proliferation was assessed in the presence and absence of NR4A1 agonists, cytosporone-B (Csn-B) and 6-mercaptopurine (6-MP). In vivo, we compared colonic smooth muscle thickening in Nr4a1 +/+ and Nr4a1 -/- mice using the chronic dextran sulfate sodium (DSS) model of colitis. Second, SAMP1/YitFc mice (a model of spontaneous ileitis) were treated with Csn-B and small intestinal smooth muscle thickening was assessed. SMCs isolated from Nr4a1 -/- mice exhibited increased abundance of proteins related to cell proliferation, metabolism, and ECM production, whereas Nr4a1 +/+ SMCs highly expressed proteins related to the regulation of the actin cytoskeleton and contractile processes. SMCs isolated from Nr4a1 -/- mice exhibited increased proliferation and alterations in cellular metabolism, whereas activation of NR4A1 attenuated proliferation. In vivo, Nr4a1 -/- mice exhibited increased colonic smooth muscle thickness following repeated cycles of DSS. Activating NR4A1 with Csn-B, in the context of established inflammation, reduced ileal smooth muscle thickening in SAMP1/YitFc mice. Targeting NR4A1 may provide a novel approach to regulate intestinal SMC phenotype, limiting excessive proliferation that contributes to stricture development in CD., (© 2022 Federation of American Societies for Experimental Biology.)

Gestational diabetes mellitus (GDM) is a common pregnancy complication with a high incidence in women. Orphan nuclear receptor NUR77 is involved in regulating glucose metabolism. However, its role in GDM has not been fully elucidated yet. In this study, an animal model of GDM was established by feeding mice with a high-fat diet (HFD) before and during pregnancy. NUR77 expression was abnormally upregulated in placenta tissues of GDM mice. We performed gain- and loss-of-function studies of NUR77 in HTR-8/SVneo cells. Cells were incubated with 1 × 10 -6  M insulin for 48 h to induce insulin resistance (IR). The expression of NUR77 was downregulated in HTR-8/SVneo cells following IR induction. Overexpression of NUR77 promoted cell proliferation, migration, and invasion. Notably, NUR77 promoted glucose uptake and enhanced insulin sensitivity in vitro. NUR77 increased the ratio of p-insulin receptor β (IRβ) Tyr1361 /IRβ, p-insulin receptor substrate (IRS)-1 Tyr612 /IRS-1, p-Akt/Akt and decreased p-IRS-1 Ser307 /IRS-1, as well as lowered the expression of glucose transport protein type 1 (GLUT1) and elevated GLUT4. These results suggest the involvement of IRβ/IRS/Akt/GLUT4 signaling activation in the regulatory effects of NUR77 on IR in HTR-8/SVneo cells. Silencing of NUR77 displayed opposite effects. Besides, NUR77 enhanced the expression of autophagy-related protein Beclin 1 and the ratio of LC3II/LC3I. Further study demonstrated that the inhibitory effect of NUR77 on IR was partially attributed to the activation of autophagy. Therefore, we demonstrate that NUR77 enhances insulin sensitivity in HTR-8/SVneo cells likely through activating IRβ/IRS/Akt/GLUT4 pathway and regulating autophagy., (© 2022. The Author(s) under exclusive licence to University of Navarra.)

Chronic oxidative stress, which is caused by aberrant non-receptor tyrosine kinase (c-Abl) signaling, plays a key role in the progression of β-cell loss in diabetes mellitus. Recent studies, however, have linked ferroptotic-like death to the β-cell loss in diabetes mellitus. Here, we report that oxidative stress-driven reduced/oxidized glutathione (GSH/GSSG) loss and proteasomal degradation of glutathione peroxidase 4 (GPX4) promote ferroptotic-like cell damage through increased lipid peroxidation. Mechanistically, treatment with GNF2, a non-ATP competitive c-Abl kinase inhibitor, selectively preserves β-cell function by inducing the orphan nuclear receptor estrogen-related receptor gamma (ERRγ). ERRγ-driven glutaminase 1 (GLS1) expression promotes the elevation of the GSH/GSSG ratio, and this increase leads to the inhibition of lipid peroxidation by GPX4. Strikingly, pharmacological inhibition of ERRγ represses the expression of GLS1 and reverses the GSH/GSSG ratio linked to mitochondrial dysfunction and increased lipid peroxidation mediated by GPX4 degradation. Inhibition of GLS1 suppresses the ERRγ agonist DY131-induced GSH/GSSG ratio linked to ferroptotic-like death owing to the loss of GPX4. Furthermore, immunohistochemical analysis showed enhanced ERRγ and GPX4 expression in the pancreatic islets of GNF2-treated mice compared to that in streptozotocin-treated mice. Altogether, our results provide the first evidence that the orphan nuclear receptor ERRγ-induced GLS1 expression augments the glutathione antioxidant system, and its downstream signaling leads to improved β-cell function and survival under oxidative stress conditions., (Copyright © 2022 Elsevier Inc. All rights reserved.)

GATA4 is a transcription factor known for its crucial role in the development of many tissues, including the liver; however, its role in adult liver metabolism is unknown. Here, using high-throughput sequencing technologies, we identified GATA4 as a transcriptional regulator of metabolism in the liver. GATA4 expression is elevated in response to refeeding, and its occupancy is increased at enhancers of genes linked to fatty acid and lipoprotein metabolism. Knocking out GATA4 in the adult liver (Gata4LKO) decreased transcriptional activity at GATA4 binding sites, especially during feeding. Gata4LKO mice have reduced plasma HDL cholesterol and increased liver triglyceride levels. The expression of a panel of GATA4 binding genes involved in hepatic cholesterol export and triglyceride hydrolysis was down-regulated in Gata4LKO mice. We further demonstrate that GATA4 collaborates with LXR nuclear receptors in the liver. GATA4 and LXRs share a number of binding sites, and GATA4 was required for the full transcriptional response to LXR activation. Collectively, these results show that hepatic GATA4 contributes to the transcriptional control of hepatic and systemic lipid homeostasis., (© 2022 Bideyan et al.; Published by Cold Spring Harbor Laboratory Press.)

Acetaminophen (APAP) is a widely used analgesic and antipyretic drug, but its overdose can cause acute liver failure. The dosage-sensitive sex reversal adrenal hypoplasia congenita critical region on the X chromosome, gene 1 (DAX-1, NR0B1), is an orphan nuclear receptor that acts as a transcriptional co-repressor of various genes. In this study, we identified the role of DAX-1 in APAP-induced liver injury using hepatocyte-specific Dax-1 knockout ( Dax-1 LKO) mice. Mouse primary hepatocytes were used as a comparative in vitro study. APAP overdose led to decreased plasma alanine aminotransferase and aspartate aminotransferase levels in Dax-1 LKO mice compared to C57BL/6J (WT) controls, accompanied by reduced liver necrosis. The expression of the genes encoding the enzymes catalyzing glutathione (GSH) synthesis and metabolism and antioxidant enzymes was increased in the livers of APAP-treated Dax-1 LKO mice. The rapid recovery of GSH levels in the mitochondrial fraction of APAP-treated Dax-1 LKO mice led to reduced reactive oxygen species levels, resulting in the inhibition of the prolonged JNK activation. The hepatocyte-specific DAX-1 deficiency increased the protein expression of nuclear factor erythroid 2-related factor 2 (Nrf2) compared with WT controls after APAP administration. These results indicate that DAX-1 deficiency in hepatocytes protects against APAP-induced liver injury by Nrf2-regulated antioxidant defense.

Regulation of cellular catabolic metabolism in immune cells has recently become a major concept for resolution of inflammation. Nuclear receptors (NRs), including peroxisome proliferator activator receptors, 1,25-dihydroxyvitamin D (3) receptor, liver X receptors, glucocorticoid receptors, oestrogen-related receptor α and nuclear receptor 4A1, have been identified as major modulators of inflammation, affecting innate immune cells, such as macrophages. Evidence emerges on how NRs regulate cellular metabolism in macrophages during inflammatory processes and contribute to the resolution of inflammation. This could have new implications for our understanding of how NRs shape immune responses and inform anti-inflammatory drug design. This review will highlight the recent developments about NRs and their role in cellular metabolism in macrophages., (© 2022 The Authors. FEBS Letters published by John Wiley & Sons Ltd on behalf of Federation of European Biochemical Societies.)

Muscle atrophy is defined as the progressive degeneration or shrinkage of myocytes and is triggered by factors such as aging, cancer, injury, inflammation, and immobilization. Considering the total amount of body iron stores and its crucial role in skeletal muscle, myocytes may have their own iron regulation mechanism. Although the detrimental effects of iron overload or iron deficiency on muscle function have been studied, the molecular mechanism of iron-dependent muscle atrophy has not been elucidated. Using human muscle tissues and in the mouse rotator cuff tear model, we confirmed an association between injury-induced iron depletion in myocytes and muscle atrophy. In differentiated C2C12 myotubes, the effects of iron deficiency on myocytes and the molecular mechanism of muscle atrophy by iron deficiency were evaluated. Our study revealed that the lower iron concentration in injured muscle was associated with the upregulation of ferroportin, an iron exporter that transports iron out of cells. Ferroportin expression was increased by hypoxia-inducible factor 1α (HIF1α), which is activated by muscle injury, and its expression is controlled by HIF1 inhibitor treatment. Iron deprivation caused myocyte loss and a marked depletion of mitochondrial membrane potential leading to muscle atrophy, together with increased levels of myostatin, the upstream regulator of atrogin1 and muscle RING-finger protein-1 (MuRF1). Myostatin expression under iron deficiency was mediated by an orphan nuclear receptor, dosage-sensitive sex reversal-adrenal hypoplasia congenita critical region on the X chromosome (DAX1)., Competing Interests: The authors declare no conflict of interest.

Genetic susceptibility to dyslipidaemia remains incompletely understood. The liver X receptors (LXRs), members of the nuclear receptor superfamily of ligand dependent transcription factors, are homeostatic regulators of lipid metabolism. Multiple single nucleotide polymorphisms (SNPs)have been identified previously in the coding and regulatory regions of the LXRs. The aim of this systematic review and meta-analysis was to summarise associations between SNPs of LXRs (α and β isoforms) with blood lipid and lipoprotein traits. Five databases (PubMed, Ovid Embase, Scopus, Web of Science, and the Cochrane Library) were systematically searched for population-based studies that assessed associations between one or more blood lipid/lipoprotein traits and LXR SNPs. Of seventeen articles included in the qualitative synthesis, ten were eligible for meta-analysis. Nine LXRα SNPs and five LXRβ SNPs were identified, and the three most studied LXRα SNPs were quantitatively summarised. Carriers of the minor allele A of LXRα rs12221497 (-115G>A) had higher triglyceride levels than GG homozygotes (0.13 mmol/L; 95%CI: [0.03, 0.23], P = 0.01). Heterozygote carriers of LXRα rs2279238 (297C/T) had higher total cholesterol levels (0.12 mmol/L; (95%CI: [0.01, 0.23], P = 0.04) than either CC or TT homozygotes. For LXRα rs11039155 (-6G>A), no significant differences in blood levels of either triglyceride (P = 0.39) or HDL-C (P = 0.98) were detected between genotypes in meta-analyses. In addition, there were no strong associations for other SNPs of LXRα and LXRβ. This study provides the evidence of an association between LXRα, but not LXRβ, SNPs and blood-lipid traits. Systematic review registration: PROSPERO No. CRD42021246158., (Copyright © 2022 The Authors. Published by Elsevier Inc. All rights reserved.)

The immune response mediated by Th17 cells is essential in the pathogenesis of periodontitis. Emerging evidence has demonstrated that lipopolysaccharide from Porphyromonas gingivalis (Pg-LPS) could promote Th17-cell differentiation directly, while the downstream signaling remains elusive. This study was aimed to explore the role of JMJD3 (a JmjC family histone demethylase) and signal transducers and activators of transcription 3 (STAT3) in Th17-cell differentiation triggered by Pg-LPS and clarify the interaction between them. We found that the expression of JMJD3 and STAT3 was significantly increased under Th17-polarizing conditions. Pg-LPS could promote Th17-cell differentiation from CD4 + T cells, with an increased expression of JMJD3 and STAT3 compared to the culture without Pg-LPS. The coimmunoprecipitation results showed that the interactions of JMJD3 and STAT3, STAT3 and retinoid-related orphan nuclear receptor γt (RORγt) were enhanced following Pg-LPS stimulation during Th17-cell differentiation. Further blocking assays were performed and the results showed that inhibition of STAT3 or JMJD3 both suppressed the Th17-cell differentiation, JMJD3 inhibitor could reduce the expression of STAT3 and p-STAT3, while JMJD3 expression was not affected when STAT3 was inhibited. Taken together, this study found that JMJD3 could promote Pg-LPS induced Th17-cell differentiation by modulating the STAT3-RORc signaling pathway.

Introduction: Liver X receptors (LXRs) are master regulators of atherogenesis. Their anti-atherogenic potential has been attributed to their role in the inhibition of macrophage-mediated inflammation and promotion of reverse cholesterol transport. Owing to the significance of their anti-atherogenic potential, it is essential to develop and test new-generation LXR agonists, both synthetic and natural, to identify potential LXR-targeted therapeutics for the future., Areas Covered: This review describes the role of LXRs in atherosclerotic development, and provides a summary of LXR agonists and future directions for atherosclerosis research. We searched PubMed, Scopus, and Google Scholar for relevant reports, from last 10 years, using atherosclerosis, liver X receptor, and LXR agonist as keywords., Expert Opinion: LXRα has gained widespread recognition as a regulator of cholesterol homeostasis and expression of inflammatory genes. Further research using models of cell type-specific knockout and specific agonist-targeted LXR isoforms is warranted. Enthusiasm for therapeutic value of LXR agonists has been tempered due to LXRα-mediated induction of hepatic lipogenesis. LXRα agonism and LXRβ targeting, gut-specific inverse LXR agonists, investigations combining LXR agonists with other lipogenesis-mitigating agents, like IDOL antagonists and synthetic HDL, and targeting ABCA1, M2 macrophages, and LXRα phosphorylation remain as promising possibilities.

Dysregulation of cholesterol homeostasis is associated with many diseases such as cardiovascular disease and cancer. Liver X receptors (LXRs) are major upstream regulators of cholesterol homeostasis and are activated by endogenous cholesterol metabolites such as 27-hydroxycholesterol (27HC). LXRs and various LXR ligands such as 27HC have been described to influence several extra-hepatic biological systems. However, disparate reports of LXR function have emerged, especially with respect to immunology and cancer biology. This would suggest that, similar to steroid nuclear receptors, the LXRs can be selectively modulated by different ligands. Here, we use RNA-sequencing of macrophages and single-cell RNA-sequencing of immune cells from metastasis-bearing murine lungs to provide evidence that LXR satisfies the 2 principles of selective nuclear receptor modulation: (1) different LXR ligands result in overlapping but distinct gene expression profiles within the same cell type, and (2) the same LXR ligands differentially regulate gene expression in a highly context-specific manner, depending on the cell or tissue type. The concept that the LXRs can be selectively modulated provides the foundation for developing precision pharmacology LXR ligands that are tailored to promote those activities that are desirable (proimmune), but at the same time minimizing harmful side effects (such as elevated triglyceride levels)., (© The Author(s) 2022. Published by Oxford University Press on behalf of the Endocrine Society. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)

Background: Liver x receptor α (LXRα) is a ligand-activated transcription factor belonging to the nuclear receptor superfamily. Oxysterols (endogenous oxidized cholesterol derivatives) are the most potent endogenous LXRα-agonist. LXRα has a direct impact on several members of drug transporter superfamilies; ATP-binding cassette (ABC) and solute linked carrier (SLC)., Objective: The current study aimed to investigate the effect of LXRα-activation by either endogenous oxysterols or a synthetic LXRα-agonist (LXRa) such as TO901317 on hepatic and cardiac gene expression of ABCC10 and SLC17A5 drug transporters in an experimentally hypercholesterolemic rat model., Methods: 48 male rats were divided randomly into four groups (n = 12); control group rats received vehicle; hypercholesterolemic group (HCH group) rats received diet contain 2.5% cholesterol &deoxycholic acid for 8 weeks; (LXRa group) rats were fed standard pellet chow for 8 weeks, then a single dose of LXRa was administered (IP) at a dose of 10 mg/kg; (HCH + LXRa group) rats received diet contain 2.5% cholesterol &deoxycholic acid for 8 weeks, then a single dose of LXRa was administered (IP) at a dose of 10 mg/kg., Results: Our findings revealed that hypercholesterolemia and LXRa significantly activated LXRα to varying degrees in both hepatic and cardiac tissues with subsequent alteration of LXRα and ABCC10 gene expression. Whereas, SLC17A5 gene expression was primarily affected by elevated serum cholesterol level and unmediated via LXRα-activation., Conclusions: Accordingly, it was concluded that ABCC10 is a specific LXRα-target gene and that LXRα autoregulates its own expression in rats., Competing Interests: Declarations 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 © 2022 Elsevier Inc. All rights reserved.)

Background: The identification of new cellular receptors has been increasing rapidly. A receptor is called "orphan" if an endogenous ligand has not been identified yet., Methods: Here we review receptors that contribute to prostate cancer and are considered orphan or partially orphan. This means that the full spectrum of their endogenous ligands remains unknown., Results: The orphan receptors are divided into two major families. The first group includes G protein-coupled receptors. Most are orphan olfactory receptors. OR51E1 inhibits cell proliferation and induces senescence in prostate cancer. OR51E2 inhibits prostate cancer growth, but promotes invasiveness and metastasis. GPR158, GPR110, and GPCR-X play significant roles in prostate cancer development and progression. However, GPR160 induces cell cycle arrest and apoptosis. The other major subset of orphan receptors are nuclear receptors. Receptor-related orphan receptor α (RORα) inhibits tumor growth, but RORγ stimulates androgen receptor signaling. PXR contributes to metabolic deactivation of androgens and inhibits cell proliferation. TLX has protumorigenic effects in prostate cancer, while its knockdown triggers cellular senescence and growth arrest. Estrogen-related receptor ERRγ can inhibit tumor growth but ERRα is protumorigenic. Dax1 and short heterodimeric partner are also inhibitory in prostate cancer., Conclusion: There is a "zoo" of relatively underappreciated orphan receptors that play key roles in prostate cancer., (© 2022 Wiley Periodicals LLC.)

Background/aim: Liver X receptors (LXRs) are nuclear receptors with various functions, including the regulation of cholesterol metabolism, glucose homeostasis, and inflammation. We previously reported that LXR activation inhibits the growth of oral cancer cells by inducing cellular cholesterol efflux and that LXRβ is expressed mainly in small-cell lung cancer (SCLC) tissues. SCLC is one of the most aggressive cancers, and identifying an effective therapeutic target molecule is desirable. Therefore, we investigated whether LXRβ could be an effective target molecule for SCLC treatment through in vitro experiments., Materials and Methods: We evaluated the influence of treatment with the LXR agonist T0901317 on cell proliferation and apoptosis in SCLC cell lines using cell viability, BrdU-ELISA, FACS, and western blot analyses. Moreover, the mechanism by which T0901317 inhibits SCLC cell proliferation was elucidated using qRT-PCR, western blot, a cholesterol quantification assay, and a genome editing technique., Results: We showed that cultivated SCLC cells expressed LXRβ and that an LXR agonist inhibited the proliferation of SCLC cells without toxicity to normal cells. Furthermore, the antitumoral effect of an LXR agonist on SCLC cells was attributed to the induction of ABCA1 by LXRβ activation, resulting in an increase in cellular cholesterol efflux via ABCA1., Conclusion: The activation of LXRβ up-regulates ABCA1 expression, causing cholesterol depletion in cancer cells. This mechanism could be a novel target strategy for SCLC., (Copyright © 2022 International Institute of Anticancer Research (Dr. George J. Delinasios), All rights reserved.)

Hyperlipidemia and increased circulating cholesterol levels are associated with increased cardiovascular disease risk. The liver X receptors (LXRs) are regulators of de novo lipogenesis and cholesterol transport and have been validated as potential therapeutic targets for the treatment of atherosclerosis. However, efforts to develop LXR agonists to reduce cardiovascular diseases have failed due to poor clinical outcomes-associated increased hepatic lipogenesis and elevated low-density lipoprotein (LDL) cholesterol (C). Here, we report that LXR inverse agonists are effective in lowering plasma LDL cholesterol and triglycerides in several models of hyperlipidemia, including the Ldlr null mouse model of atherosclerosis. Mechanistic studies demonstrate that LXR directly regulates the expression of Soat2 enzyme in the intestine, which is directly responsible for the re-uptake or excretion of circulating lipids. Oral administration of a gut-specific LXR inverse agonist leads to reduction of Soat2 expression in the intestine and effectively lowers circulating LDL cholesterol and triglyceride levels without modulating LXR target genes in the periphery. In summary, our studies highlight the therapeutic potential of the gut-restricted molecules to treat hyperlipidemia and atherosclerosis through the intestinal LXR- Soat2 axis.

Backgroud and Aims: Liver type 1 innate lymphoid cells (ILC1s), also known as liver-resident natural killer (LrNK) cells, comprise a high proportion of total hepatic ILCs. However, factors regulating their maintenance and function remain unclear., Approach and Results: In this study, we found high expression of retinoid-related orphan nuclear receptor alpha (RORα) in LrNK cells/ILC1s. Mice with conditional ablation of retinoid-related orphan nuclear receptor alpha (Rorα) in LrNK cells/ILC1s and conventional natural killer (cNK) cells had decreased LrNK cells/ILC1s but normal numbers of cNK cells. RORα-deficient LrNK cells/ILC1s displayed increased apoptosis and significantly altered transcriptional profile. Using a murine model of colorectal cancer liver metastasis, we found that RORα conditional deficiency resulted in more aggressive liver tumor progression and impaired effector molecule expression in LrNK cells/ILC1s. Consequently, treatment with the RORα agonist efficiently limited liver metastases and promoted effector molecule expression of LrNK cells/ILC1s., Conclusions: This study reveals a role of RORα in LrNK cell/ILC1 maintenance and function, providing insights into the harnessing of LrNK cell/ILC1 activity in the treatment of liver cancer., (© 2021 American Association for the Study of Liver Diseases.)

Although the "lymphoid" function of regulatory T (Treg) cells is crucial for organismal homeostasis, these cells are also known to suppress the antitumor immune response in the tumor microenvironments. Thus, a detailed understanding of Treg cell maintenance and function in both lymphoid organs and tumor environments may help to establish novel methods for the reactivating antitumor immunity, while retaining necessary immune tolerance towards self and non-hazardous antigens. Previous studies have hypothesized that Treg cells behave similarly in lymphoid organs and in tumor environments; however, few studies have been conducted specifically researching Treg cell activity in tumor environments. In addition, several recent studies identified a novel mechanism regulating Treg cell function in tumor environments. Our group has previously described the critical roles of the Nr4a family of nuclear orphan receptors, comprising Nr4a1, Nr4a2, and Nr4a3, in the differentiation and maintenance of Treg cells in lymphoid organs. Subsequently, it was found that Nr4a factors help to maintain Treg cell function in tumor environments, thereby playing a suppressive role against T cell antitumor immunity. Importantly, there were some differences between the activities of these Nr4a factors under these conditions, including the specific function of the COX/PGE2 axis in tumor environments. This review was designed to investigate the role of Nr4a factors in the regulation of Treg cell activities both in the lymphoid organs and tumor environments, highlighting the commonalities and differences in their behaviors between Treg cells in these two different environments., Competing Interests: The author declares 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 © 2022 Sekiya.)

As a master regulator of neurogenesis, the orphan nuclear receptor tailless homologue (TLX, NR2E1) maintains neuronal stem cell homeostasis by acting as a transcriptional repressor of tumor suppressor genes. It is hence considered as an appealing target for the treatment of neurodegenerative diseases, but a lack of potent TLX modulators as tools to probe pharmacological TLX control hinders further validation of its promising potential. Here, we report the development of a potent TLX agonist based on fragment screening, pharmacophore modeling, and fragment fusion. Pharmacophore similarity of a fragment screening hit and the TLX ligand ccrp2 provided a rational basis for fragment linkage, which resulted in several TLX activator scaffolds. Among them, the fused compound 10 evolved as a valuable TLX agonist tool with submicromolar potency and high selectivity over related nuclear receptors, rendering it suitable for functional studies on TLX.

Oxysterols are oxygenated cholesterol derivatives and important regulators of cholesterol metabolism, lipid homeostasis, the immune system, and membrane fluidity regulation. Although the detailed mechanism of action of oxysterols remains unclear, activation of some nuclear receptors, such as liver X receptor α (LXRα) and RAR-related orphan receptors, have been believed to be critical for the regulation of various physiological processes in multiple tissues. 27-Hydroxycholesterol (27-OHC) is an endogenous oxysterol, which has an intermediate function in cholesterol catabolism to bile acid synthesis. According to previous studies, however, there are opposing opinions on whether 27-OHC activates human LXR. Recently, several studies have shown that 27-OHC can activate or inhibit the function of estrogen receptors ERα and ERβ in a tissue-specific manner, indicating that the understanding of 27-OHC-mediated biological output is very complicated. This review summarizes the pathophysiological relevance of 27-OHC in various tissues, with a special discussion on their functions in human diseases., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

The nuclear receptor (NR) superfamily of transcription factors encodes expression of 48 human genes that are important for maintaining cellular homeostasis and in pathophysiology, and this has been observed for all sub-families including orphan receptors for which endogenous ligands have not yet been identified. The orphan NR4A1 (Nur77 and TR3) and other members of this sub-family (NR4A2 and NR4A3) are immediate early genes induced by diverse stressors, and these receptors play an important role in the immune function and are up-regulated in some inflammatory diseases including solid tumors. Although endogenous ligands for NR4A have not been identified, several different classes of compounds have been characterized as NR4A1 ligands that bind the receptor. These compounds include cytosporone B and structurally related analogs, bis-indole derived (CDIM) compounds, the triterpenoid celastrol and a number of other chemicals including polyunsaturated fatty acids. NR4A1 ligands bind different regions/surfaces of NR4A1 and exhibit selective NR4A1 modulator (SNR4AM) activities that are dependent on ligand structure and cell/tissue context. NR4A1 ligands exhibit pharmacologic activities in studies on cancer, endometriosis metabolic and inflammatory diseases and are promising agents with clinical potential for treating multiple diseases., (© 2021 The Author(s). Published by Portland Press Limited on behalf of the Biochemical Society.)