Search Results (115)

Background/Objectives: Neurofibromatosis type 1 (NF1) is a prevalent inherited disorder, with approximately 50% of affected individuals developing plexiform neurofibromas (PNFs), which can progress to highly aggressive malignant peripheral nerve sheath tumors (MPNSTs). While selumetinib is FDA-approved for PNFs, its efficacy in MPNSTs is limited and associated with dose-limiting toxicities. NF1 deficiency drives tumorigenesis and alters immune dynamics via RAS hyperactivation. Given the substantial macrophage infiltration in NF1 lesions and its association with disease progression, we hypothesized that targeting tumor-promoting immune cells with the retinoid X receptor (RXR) agonist MSU-42011 could be an alternative therapeutic strategy, as it has shown promise in KRAS-driven cancers by decreasing pERK levels and reducing tumor-promoting immune cells. Methods: We examined the effects of MSU-42011 and selumetinib, alone and in combination, on NF1-deficient cells and in a syngeneic MPNST model. Results: In vivo, the combination of MSU-42011 and selumetinib significantly reduced tumor growth, pERK levels, and tumor-promoting macrophages and increased activated CD8⁺ T cells in syngeneic MPNST models. In NF1-deficient cells, MSU-42011 or selumetinib reduced pERK levels, with combination treatment achieving greater reductions. Conditioned media (CM) from NF1-deficient cells increased the protein and mRNA levels of several cytokines and chemokines in human THP1 cells and bone marrow-derived macrophages (BMDMs). MSU-42011 and selumetinib, alone or in combination, partially reversed this induction. Conclusions: These findings suggest RXR agonists may have therapeutic potential against NF1, and their combination with MEK inhibitors could represent a promising strategy for NF1-associated tumors. Further studies are needed to validate these results and assess their translational relevance. Full article

This study investigated the therapeutic potential of the nuclear retinoid X receptor (RXR) in mitigating the progression of alpha-synucleinopathies (αSNPs), particularly in Parkinson’s disease (PD). PD-like pathology in mice was successfully induced through the co-delivery of AAV expressing human α-synuclein (αS) and αS preformed fibrils (PFFs) into the substantia nigra pars compacta (SNpc). Significant increases in Lewy body (LB)-like inclusions, loss of tyrosine hydroxylase-positive (TH+) neurons, and reductions in dopamine (DA) levels in the striatum were observed. Additionally, diminished levels of PPARα and NURR1—proteins essential for neuronal survival—along with elevated expression of IBA1 and GFAP, markers of microglial activation and astrocytic gliosis, respectively, are associated with the pathogenesis of Parkinson’s disease. AAV-mediated overexpression of human RXRα demonstrated preservation of TH+ neurons, prevention of DA decline, and attenuation of αS accumulation. Furthermore, RXR-treated PD brains showed a reduced number of GFAP+ and Iba1+ cells, decreased GFAP+ and IBA1+ immunoreactivity, and fewer and less widespread LB-like aggregates. RXR overexpression also enhanced the production of PPARα and NURR1. These findings suggest that RXRα upregulation promotes neuroprotection by mitigating αSNPs and chronic neuroinflammation, a major contributor to PD progression. This research underscores the therapeutic potential of targeting nuclear receptors, such as RXR, in neurodegenerative diseases like PD. Full article

Hepatoblastoma (HB) is the most common pediatric primary liver tumor. About 20% of affected children have pulmonary metastasis at presentation. Survival rates for these children are dismal, not exceeding 25%. To study this subset of patients, we sequenced a metastatic HB cell line, HLM_2, and identified downregulation of the Liver X Receptor (LXR)/Retinoid X Receptor (RXR) pathway. LXR/RXRs function as transcriptional regulators that influence genes implicated in HB development, including the Wnt/β-catenin signaling pathway. We assessed the effects of a novel LXR/RXR agonist, UAB116, on metastatic HB, hypothesizing that this compound would affect genes governing the Wnt/β-catenin pathway, decreasing the metastatic phenotype of HLM_2 metastatic HB cells. We evaluated its effects on viability, proliferation, stemness, clonogenicity, and motility, and performed RNA sequencing to study differential gene regulation. Treatment with UAB116 for 72 h decreased HLM_2 proliferation, stemness, clonogenicity, and invasion. RNA sequencing identified an eight-fold increase in TRIM29, a gene known to inhibit β-catenin, in cells treated with UAB116. Administration of the LXR/RXR agonist, UAB116, reduces proliferation, stemness, and invasiveness of metastatic HB cells, potentially by upregulation of TRIM29, a known modulator of the Wnt/β-catenin pathway, providing support for further exploration of LXR/RXR agonism as a therapeutic strategy for metastatic HB. Full article

Peroxisome proliferator-activated receptors (PPARs), composed of the α/δ/γ subtypes, are ligand-activated nuclear receptors/transcription factors that sense endogenous fatty acids or therapeutic drugs to regulate lipid/glucose metabolism and oxidative stress. PPAR forms a multiprotein complex with a retinoid X receptor and corepressor complex in an unliganded/inactive state, and ligand binding induces the replacement of the corepressor complex with the coactivator complex to initiate the transcription of various genes, including the metabolic and antioxidant ones. We investigated the processes by which the corepressor is replaced with the coactivator or in which two coactivators compete for the PPARα/δ/γ-ligand-binding domains (LBDs) using single- and dual-emission fluorescence resonance energy transfer (FRET) assays. Single-FRET revealed that the respective PPARα/δ/γ-selective agonists (pemafibrate, seladelpar, and pioglitazone) induced the dissociation of the two corepressor peptides, NCoR1 and NCoR2, from the PPARα/δ/γ-LBDs and the recruitment of the two coactivator peptides, CBP and TRAP220. Meanwhile, dual-FRET demonstrated that these processes are simultaneous and that the four coactivator peptides, CBP, TRAP220, PGC1α, and SRC1, were competitively recruited to the PPARα/δ/γ-LBDs with different preferences upon ligand activation. Furthermore, the five newly obtained cocrystal structures using X-ray diffraction, PPARα-LBDs–NCoR2/CBP/TRAP220/PGC1α and PPARγ-LBD–NCoR2, were co-analyzed with those from our previous studies. This illustrates that these coactivators bound to the same PPARα-LBD loci via their consensus LXXLL motifs in the liganded state; that NCoR1/NCoR2 corepressors bound to the same loci via the IXXXL sequences within their consensus LXXXIXXXL motifs in the unliganded state; and that ligand activation induced AF-2 helix 12 formation that interfered with corepressor binding and created a binding space for the coactivator. These PPARα/γ-related biochemical and physicochemical findings highlight the coregulator dynamics on limited PPARα/δ/γ-LBDs loci. Full article

Vitamin A (retinol) and its derivatives (retinoids) assume critical roles in neural development, cellular differentiation, axon elongation, programmed cell apoptosis and various fundamental cellular processes. Retinoids function by binding to specific nuclear receptors, such as retinoic acid receptors (RARs) and retinoid X receptors (RXRs), activating specific signalling pathways in the cells. The disruption of the retinoic acid signalling pathway can result in neuroinflammation, oxidative and ER stress and mitochondrial dysfunction and has been implicated in a wide range of neurodegenerative diseases. The present study explored the potential therapeutic application of our innovative CNS-permeable synthetic retinoid, Ellorarxine, for the treatment of neurodegenerative disorders in vitro. An MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) tetrazolium assay, lactate dehydrogenase (LDH) assay, enzyme-linked immunosorbent assay (ELISA), immunocytochemistry and immunofluorescence staining were performed. Ellorarxine increased Cyp26 and, selectively, RARβ protein expression in neurons, glia and microglia. Ellorarxine significantly reduced cell death (neurons, glia), increased mitochondrial viability (neurons), modulated cytokine release (microglia), and positively regulated cellular autophagy (neurons, glia, microglia). These results suggest that Ellorarxine is a promising drug candidate that should be further investigated in the treatment of neurodegenerative diseases. Full article

Tazarotene, a retinoid derivative, is widely used in treating skin conditions such as psoriasis and acne. Recent studies have demonstrated its potential as a promising therapeutic agent for treating melanoma in situ. Its primary mechanism of action involves the selective activation of retinoic acid receptors (RAR-β and RAR-γ), which play important roles in regulating cell growth, differentiation, and apoptosis. By activating these receptors, tazarotene influences the expression of several downstream inducible genes, such as tazarotene-induced gene-1 (TIG1), TIG2, and TIG3. These genes play crucial roles in regulating melanoma cell proliferation, invasiveness, and immune responses in the tumor microenvironment. This review aims to provide a comprehensive overview of the current status of retinoid derivatives—particularly tazarotene—in melanoma treatment and the latest research regarding their molecular mechanisms. We will explore how tazarotene suppresses melanoma growth through gene regulation mechanisms and discuss its potential role in immune responses within the tumor microenvironment. Additionally, we assess the advantages and challenges of using tazarotene as a topical treatment and explore its future clinical applications. These studies contribute to a wider understanding of tazarotene’s antitumor mechanisms, providing a solid theoretical foundation for its potential as a therapeutic option for melanoma in situ. Full article

PEG400 is widely used as a pharmaceutical excipient in the biomedical field. Increasing evidence suggests that PEG400 is not an inert drug carrier; it can influence the activity of various drug-metabolizing enzymes and transporters, thereby affecting the in vivo process of drugs. It can also alleviate obesity and adipose tissue inflammation induced by a high-fat diet. In this study, we employed proteomics to investigate the impact of PEG400 on hepatic protein expression in rats. We found that over 40 metabolic enzymes were altered, with UDP-glucuronosyltransferase 1a9 (Ugt1a9) showing the most significant upregulation. This observation is consistent with our previous findings. KEGG pathway enrichment analysis revealed that PEG400 influences retinol metabolism, steroid hormone biosynthesis, drug metabolism, bile secretion, fatty acid degradation, peroxisome proliferator-activated receptor (PPAR) signaling pathway, and pentose and glucuronate interconversions. Western blot and molecular docking were used to quantitatively analyze related proteins. The results demonstrated that PEG400 promotes the metabolism of retinol to produce retinoic acid; enhances bile secretion by upregulating bile acid synthesis and transporter proteins; and activates the PPARα signaling pathway to regulate the expression of fat metabolism-related proteins, thereby reducing lipid accumulation. Furthermore, as natural ligands for nuclear receptors, retinoic acid and bile acids may activate nuclear receptors and initiate the regulation of target gene expression. We found upregulation of the nuclear receptors PPARα, retinoid X receptor alpha (RXRα), and pregnane X receptor (PXR). RXRα can form a dimer with PPARα or PXR to regulate the expression of target genes, which may explain the changes in the expression of numerous metabolic enzymes. This study provides a comprehensive understanding of the effects of PEG400 on liver metabolism in rats, reveals its potential biological functions, and offers new insights into the application and development of PEG400. Full article

Retinol is well-known anti-aging material in the cosmetics industry, owing to its proven superior efficacy both in vitro and in vivo. Despite its high efficacy, retinol is associated with limitations, such as skin irritation and its potential photodegradation. Retinol is converted into retinoid acid within cells, which then exerts a cellular response by activating both the retinoic acid receptor (RAR) and retinoid x receptor (RXR). Noting that RAR activity is associated with skin irritation and RXR activation alone can enhance skin-related indicators without inducing inflammation, we developed an alternative approach for skin anti-aging focusing solely on RXR activation. We found that combined treatment of andrographolide and Bidens pilosa extract successfully activated RXR alpha and enhanced RXRA gene expression. Moreover, we investigated their efficacy using dermal fibroblasts and keratinocytes and found that they enhanced the gene expression of extracellular matrix (ECM) proteins with anti-oxidant and anti-inflammation efficacies. Finally, in a human clinical trial, we confirmed that our materials successfully improved wrinkles in various areas, skin elasticity and hydration without causing irritating side effects. These findings highlight the potential of our RXR alpha-activating materials as an anti-wrinkle solution that avoids the typical side effects associated with retinol. Full article

Nuclear receptors (NRs) are ligand-activated transcription factors that regulate a broad array of biological processes, including inflammation, lipid metabolism, cell proliferation, and apoptosis. Among the diverse family of NRs, peroxisome proliferator-activated receptors (PPARs), estrogen receptor (ER), liver X receptor (LXR), farnesoid X receptor (FXR), retinoid X receptor (RXR), and aryl hydrocarbon receptor (AhR) have garnered significant attention for their roles in neurodegenerative diseases, particularly Alzheimer’s disease (AD). NRs influence the pathophysiology of AD through mechanisms such as modulation of amyloid-beta (Aβ) deposition, regulation of inflammatory pathways, and improvement of neuronal function. However, the dual role of NRs in AD progression, where some receptors may exacerbate the disease while others offer therapeutic potential, presents a critical challenge for their application in AD treatment. This review explores the functional diversity of NRs, highlighting their involvement in AD-related processes and discussing the therapeutic prospects of NR-targeting strategies. Furthermore, the key challenges, including the necessity for the precise identification of beneficial NRs, detailed structural analysis through molecular dynamics simulations, and further investigation of NR mechanisms in AD, such as tau pathology and autophagy, are also discussed. Collectively, continued research is essential to clarify the role of NRs in AD, ultimately facilitating their potential use in the diagnosis, prevention, and treatment of AD. Full article

Background: Cutaneous T-cell lymphoma (CTCL) is a type of non-Hodgkin’s lymphoma that primarily affects the skin, rich in hyaluronic acid (HA). HA is a component of the extracellular matrix in the dermis and likely affects the development of CTCL, but the mechanism is poorly understood. Here we show that low-molecular-weight HA (LMWHA) possibly exacerbates CTCL, and bexarotene, already used in CTCL treatment, decreases HA production. Methods: We conducted immunohistochemistry, qRT-PCR, immunoblotting, and HA quantification using both mouse and human specimens to evaluate the impact of HA on CTCL. Additionally, we assessed the effect of bexarotene, which is already used for CTCL treatment, on HA metabolism. Results: HA expression was higher in patients’ serum and skin sections than in healthy controls. HA extracted from the skin of mice inoculated with tumors showed an increase in LMWHA. LMWHA increased lymphoma cell proliferation in vitro and accelerated tumor formation in mice in vivo. LMWHA also created a favorable environment for tumor cells by affecting fibroblasts, vascular endothelial cells, and tumor-associated macrophages. Thus, increased levels of HA, mainly LMWHA, exacerbate CTCL progression by affecting tumor cells and their microenvironment. Bexarotene treatment reduced the amount of total HA in murine tumor-inoculated skin, as well as the supernatant of cultured normal human dermal fibroblasts (NHDFs) and HuT78 cells. Detailed in vitro analyses showed that bexarotene treatment decreased HA synthase (HAS)1 and HAS2 expression in NHDFs and HAS1 and HAS3, and CEMIP expression in HuT78 cells. Chromatin immunoprecipitation assays revealed that bexarotene reduced retinoid X receptor-α binding to the HAS1 and HAS2 promoters in NHDFs. Conclusions: Bexarotene potentially exerts its anti-tumor effect by reducing HA levels through decreased expression of HAS. These findings provide new insights into the process of CTCL development and additional insights regarding bexarotene treatment. Full article

To explore the molecular targets for regulating glucose metabolism in carnivorous fish, the turbot (Scophthalmus maximus) was selected as the research object to study. Farnesoid X receptor (FXR; NR1H4), as a ligand-activated transcription factor, plays an important role in glucose metabolism in mammals. However, the mechanisms controlling glucose metabolism mediated by FXR in fish are not understood. It was first found that the protein levels of FXR and its target gene, small heterodimer partner (SHP), were significantly decreased in the high-glucose group (50 mM, HG) compared with those in the normal glucose group (15 mM, CON) in primary hepatocytes of turbot. By further exploring the function of FXR in turbot, the full length of FXR in turbot was cloned, and its nuclear localization function was characterized by subcellular localization. The results revealed that the FXR had the highest expression in the liver, and its capability to activate SHP expression through heterodimer formation with retinoid X receptor (RXR) was proved, which proved RXR could bind to 15 binding sites of FXR by forming hydrogen bonds. Activation of FXR in both the CON and HG groups significantly increased the expression of glucokinase (gk) and pyruvate kinase (pk), while it decreased the expression of cytosolic phosphoenolpyruvate carboxykinase (cpepck), mitochondrial phosphoenolpyruvate carboxykinase (mpepck), glucose-6-phosphatase 1 (g6pase1) and glucose-6-phosphatase 2 (g6pase2), and caused no significant different in glycogen synthetase (gs). ELISA experiments further demonstrated that under the condition of high glucose with activated FXR, it could significantly decrease the activity of PEPCK and G6PASE in hepatocytes. In a dual-luciferase reporter assay, the FXR could significantly inhibit the activity of G6PASE2 and cPEPCK promoters by binding to the binding site ‘ATGACCT’. Knockdown of SHP after activation of FXR reduced the inhibitory effect on gluconeogenesis. In summary, FXR can bind to the mpepck and g6pase2 promoters to inhibit their expression, thereby directly inhibiting the gluconeogenesis pathway. FXR can also indirectly inhibit the gluconeogenesis pathway by activating shp. These findings suggest the possibility of FXR as a molecular target to regulate glucose homeostasis in turbot. Full article

Antarctic krill oil has been proven to be able to promote the ovarian development of crustaceans, but its optimal application dose and potential regulatory mechanism in Macrobrachium rosenbergii are still unclear. In this study, five isonitrogenous and isolipidic diets with gradient additions of Antarctic krill oil (0%, 1.5%, 3%, 4.5%, and 6%) were served exposed to 8 weeks of feeding. The results show that 3–4.5% Antarctic krill oil supplementation significantly increases the weight gain rate and specific growth rate of M. rosenbergii (p < 0.05). In addition, 3–4.5% Antarctic krill oil supplementation significantly increased the content of hemolymph vitellogenin (VTG) and the levels of reproductive hormones, including methyl farnesoate (MF), estradiol (E₂), and progesterone (P₄) (p < 0.05). The differences in ovarian index, oocyte volume, yolk granule deposition in oocytes, and the transcription levels of VTG genes in hepatopancreas and ovarian tissues demonstrated that the addition of Antarctic krill oil significantly promoted ovarian development and vitellogenesis, especially at the 4.5% addition level. In terms of molecular signaling, this study confirms that the retinol metabolic signaling pathway, MF signaling pathway, steroid hormone signaling pathway, and ecdysone signaling pathway, along with their specific molecules, such as Farnesoic acid-O-methyltransferase (FAMeT), retinoid x receptor (RXR), ecdysone receptor (EcR), and estrogen-related receptor (ERR), are involved in the regulation of the ovarian development of M. rosenbergii by adding Antarctic krill oil at appropriate doses. The findings indicate that the supplementation of 4.5% Antarctic krill oil in the diet is optimal for stimulating the secretion of reproductive hormones in female M. rosenbergii, thereby promoting vitellogenesis and ovarian development. Full article

The active form of vitamin D, 1,25-dihydroxyvitamin D (1,25D), binds to the vitamin D receptor (VDR) with high affinity. The VDR then heterodimerizes with the retinoid X receptor (RXR) and associates with vitamin D response elements (VDREs) to regulate the transcription of target genes. Bexarotene (Bex) is an RXR ligand (rexinoid) developed to treat cutaneous T-cell lymphoma and is a putative therapeutic for other diseases. We postulate that VDR ligands (1,25D) and RXR ligands (Bex/analogs) can “synergize” to “super-activate” the VDR-RXR heterodimer. This “cross-talk” could allow disorders treated with high-dose Bex therapy (leading to significant adverse side effects) to instead be treated using both low-dose Bex and vitamin D. Thus, we designed experiments to examine the effect of both VDR and RXR ligands, alone and in combination, to activate VDR-RXR-mediated transcription. The goal was to determine if selected RXR-specific ligands can synergize with vitamin D to amplify RXR-VDR activity. The results demonstrate a synergistic effect with both Bex and 1,25D which could be further modulated by (1) the protein levels (or polymorphic version) of VDR present in the cell, (2) the concentration of the ligands, (3) the cellular “background” (e.g., brain cells versus kidney cells), (4) the nature of the VDRE platform, or (5) the type of rexinoid (Bex analogs). Our findings suggest that diseases that respond to treatment with either vitamin D, or with rexinoids, may be amenable to enhanced therapeutic potential by employing multi-ligand dosing via combinatorial therapy. Full article

The nuclear hormone family of receptors regulates gene expression. The androgen receptor (AR), upon ligand binding and homodimerization, shuttles from the cytosol into the nucleus to activate gene expression. Thyroid hormone receptors (TRs), retinoic acid receptors (RARs), and the vitamin D receptor (VDR) are present in the nucleus bound to chromatin as a heterodimer with the retinoid X receptors (RXRs) and repress gene expression. Ligand binding leads to transcription activation. The hormonal ligands for these receptors play crucial roles to ensure the proper conduct of very many tissues and exert effects on prostate cancer (PCa) cells. Androgens support PCa proliferation and androgen deprivation alone or with chemotherapy is the standard therapy for PCa. RARγ activation and 3,5,3′-triiodo-L-thyronine (T3) stimulation of TRβ support the growth of PCa cells. Ligand stimulation of VDR drives growth arrest, differentiation, and apoptosis of PCa cells. Often these receptors are explored as separate avenues to find treatments for PCa and other cancers. However, there is accumulating evidence to support receptor interactions and crosstalk of regulatory events whereby a better understanding might lead to new combinatorial treatments. Full article

Benzo[a]pyrene (B[a]P) is known to inhibit neurodifferentiation and induce neurodegeneration. Agarwood or Aquilaria crassna (AC), a plant with health-promoting properties, may counteract the neurotoxic effects of B[a]P by promoting neuronal growth and survival. This study investigated the protective effect of AC leaf ethanolic extract (ACEE) on the B[a]P-induced impairment of neuronal differentiation. A transcriptomic analysis identified the canonical pathway, the biological network, and the differentially expressed genes (DEGs) that are changed in response to neuronal differentiation and neurogenesis. Several genes, including CXCR4, ENPP2, GAP43, GFRA2, NELL2, NFASC, NSG2, NGB, BASP1, and NEUROD1, in B[a]P-treated SH-SY5Y cells were up-regulated after treatment with ACEE. Notably, a Western blot analysis further confirmed that ACEE increased the protein levels of GAP43 and neuroglobin. B[a]P treatment led to decreased phosphorylation of Akt and increased phosphorylation of ERK in SH-SY5Y cells; however, ACEE was able to reverse these effects. Clionasterol and lupenone were identified in ACEE. Molecular docking showed that these two phytochemicals had significant interactions with CXCR4, GDNF family receptor alpha (GFRA), and retinoid X receptors (RXRs). In conclusion, ACEE may be a potential alternative medicine for the prevention of impaired neuronal differentiation and neurodegenerative diseases. Full article