Understanding the mechanisms underlying alcohol metabolism and its regulation, including the effect of polymorphisms in alcohol-metabolizing enzymes, is crucial for research on Fetal Alcohol Spectrum Disorders. The aim of this study was to identify specific single nucleotide polymorphisms in key alcohol-metabolizing enzymes in a cohort of 71 children, including children with fetal alcohol syndrome, children prenatally exposed to ethanol but without fetal alcohol spectrum disorder, and controls. We hypothesized that certain genetic variants related to alcohol metabolism may be fixed in these populations, giving them a particular alcohol metabolism profile. In addition, the difference in certain isoforms of these enzymes determines their affinity for alcohol, which also affects the metabolism of retinoic acid, which is key to the proper development of the central nervous system. Our results showed that children prenatally exposed to ethanol without fetal alcohol spectrum disorder traits had a higher frequency of the ADH1B*3 and ADH1C*1 alleles, which are associated with increased alcohol metabolism and therefore a protective factor against circulating alcohol in the fetus after maternal drinking, compared to FAS children who had an allele with a lower affinity for alcohol. This study also revealed the presence of an ADH4 variant in the FAS population that binds weakly to the teratogen, allowing increased circulation of the toxic agent and direct induction of developmental abnormalities in the fetus. However, both groups showed dysregulation in the expression of genes related to the retinoic acid pathway, such as retinoic acid receptor and retinoid X receptor, which are involved in the development, regeneration, and maintenance of the nervous system. These findings highlight the importance of understanding the interplay between alcohol metabolism, the retinoic acid pathway and genetic factors in the development of fetal alcohol syndrome.

Fascioliasis is a parasitic infection in animals and humans caused by the parasitic flatworm genus Fasciola, which has two major species, F. hepatica and F. gigantica. A major concern regarding this disease is drug resistance, which is increasingly reported worldwide. Hence, the discovery of a novel drug as well as drug targets is crucially required. Therefore, this study aims to characterize the novel drug target in the adult F. gigantica. In the beginning, we hypothesized that the parasite might interact with some host molecules when it lives inside the liver parenchyma or bile ducts, specifically hormones and hormone-like molecules, through the specific receptors, primarily nuclear receptors (NRs), which are recognized as a major drug target in various diseases. The retinoid X receptor (RXR) is a member of subfamily 2 NRs that plays multitudinous roles in organisms by forming homodimers or heterodimers with other NRs. We obtained the full-length amino acid sequences of F. gigantica retinoid X receptor-alpha (FgRXRα-A) from the transcriptome of F. gigantica that existed in the NCBI database. The FgRXRα-A were computationally predicted for the basic properties, multiple aligned, phylogeny analyzed, and generated of 2D and 3D models. Moreover, FgRXRα-A was molecular cloned and expressed as a recombinant protein (rFgRXRα-A), then used for immunization for specific polyclonal antibodies. The native FgRXRα-A was detected in the parasite extracts and tissues, and the function was investigated by in vitro binding assay. The results demonstrated the conservation of FgRXRα-A to the other RXRs, especially RXRs from the trematodes. Interestingly, the native FgRXRα-A could be detected in the testes of the parasite, where the sex hormones are accumulated. Moreover, the binding assay revealed the interaction of 9-cis retinoic acid and FgRXRα-A, suggesting the function of FgRXRα-A. Our findings suggested that FgRXRα-A will be involved with the sexual reproduction of the parasite by forming heterodimers with other NRs, and it could be the potential target for further drug development of fascioliasis.

BACKGROUND: Human skin is the natural source, place of metabolism, and target for vitamin D3. The classical active form of vitamin D3, 1,25(OH)2D3, expresses pluripotent properties and is intensively studied in cancer prevention and therapy. To define the specific role of vitamin D3 receptor (VDR) and its co-receptor retinoid X receptor alpha (RXRA) in genomic regulation, VDR or RXRA genes were silenced in the squamous cell carcinoma cell line A431 and treated with 1,25(OH)2D3 at long incubation time points 24 h/72 h. Extending the incubation time of A431 WT (wild-type) cells with 1,25(OH)2D3 resulted in a two-fold increase in DEGs (differentially expressed genes) and a change in the amount of downregulated from 37% to 53%. VDR knockout led to a complete loss of 1,25(OH)2D3-induced genome-wide gene regulation at 24 h time point, but after 72 h, 20 DEGs were found, of which 75% were downregulated, and most of them belonged to the gene ontology group \"immune response\". This may indicate the existence of an alternative, secondary response to 1,25(OH)2D3. In contrast, treatment of A431 ΔRXRA cells with 1,25(OH)2D3 for 24 h only partially affected DEGs, suggesting RXRA-independent regulation. Interestingly, overexpression of classic 1,25(OH)2D3 targets, like CYP24A1 (family 24 of subfamily A of cytochrome P450 member 1) or CAMP (cathelicidin antimicrobial peptide) was found to be RXRA-independent. Also, immunofluorescence staining of A431 WT cells revealed partial VDR/RXRA colocalization after 24 h and 72 h 1,25(OH)2D3 treatment. Comparison of transcriptome changes induced by 1,25(OH)2D3 in normal keratinocytes vs. cancer cells showed high cell type specific expression pattern with only a few genes commonly regulated by 1,25(OH)2D3. Activation of the genomic pathway at least partially reversed the expression of cancer-related genes, forming a basis for anti-cancer activates of 1,25(OH)2D3. In summary, VDR or RXRA independent genomic activities of 1,25(OH)2D3 suggest the involvement of alternative factors, opening new challenges in this field.

Upon heterodimerizing with other nuclear receptors, retinoid X receptors (RXR) act as ligand-dependent transcription factors, regulating transcription of critical signaling pathways that impact numerous hallmarks of cancer. By controlling both inflammation and immune responses, ligands that activate RXR can modulate the tumor microenvironment. Several small molecule agonists of these essential receptors have been synthesized. Historically, RXR agonists were tested for inhibition of growth in cancer cells, but more recent drug discovery programs screen new molecules for inhibition of inflammation or activation of immune cells. Bexarotene is the first successful example of an effective therapeutic that molecularly targets RXR; this drug was approved to treat cutaneous T cell lymphoma and is still used as a standard of care treatment for this disease. No additional RXR agonists have yet achieved FDA approval, but several promising novel compounds are being developed. In this review, we provide an overview of the multiple mechanisms by which RXR signaling regulates inflammation and tumor immunity. We also discuss the potential of RXR-dependent immune cell modulation for the treatment or prevention of cancer and concomitant challenges and opportunities.

Molting is a pivotal biological process regulated by the ecdysteroid signaling pathway that requires molecular coordination of two transcription factors, Ecdysone receptor (EcR) and ultraspiracle (USP) in arthropods. However, the molecular interplay of EcR and Retinoid X receptor (RXR), the crustacean homolog of USP in the ecdysteroid signaling pathway, is not well understood.
In this study, we conducted temporal and spatial expression, co-immunoprecipitation (CO-IP), and luciferase reporter assay experiments to investigate the molecular function and interplay of EcR and RXR during the molting process of the Chinese mitten crab, Eriocheir sinensis.
The results showed that the expression level of RXR was more stable and significantly higher than EcR during the entire molting process. However, the expression level of EcR fluctuated dynamically and increased sharply at the premolt stage. The CO-IP and luciferase reporter assay results confirmed the molecular interplay of EcR and RXR. The heterodimer complex formed by the two transcription factors significantly induced the transcription of E75, an essential gene in the ecdysteroid signaling pathway.
Our study unveiled the diverse molecular function and molecular interplay of EcR and RXR; RXR is possibly a \"constitutive-type\" gene, and EcR is possibly a vital speed-limiting gene while both EcR and RXR are required to initiate the ecdysteroid signaling cascade, which may be indispensable for molting regulation in E. sinensis. The results provide a theoretical basis for the endocrine control of molting in E. sinensis and novel insights into the molecular mechanism of molting mediated by the ecdysteroid signaling pathway in crustaceans.

The goal of this study was to pinpoint potential molecular pathways that may have contributed to the onset of pseudoexfoliation syndrome (PEX), a systemic illness associated with aging that has no known cause and is brought on by the deposition of fibrillary white flaky debris in ocular tissues.
Protein pools representing each group were created using two-dimensional gel electrophoresis (2DE) in conjunction with a matrix-assisted laser desorption ionization-time of flight/time of flight (MALDI-TOF/TOF) mass spectrometer. Aqueous humor (AH) from patients with PEX and cataracts was also collected for a comprehensive study of the data; ingenuity pathway analysis (IPA) was used for the discovered proteins.
In comparison to controls, 2DE showed that 10 sites in PEX patients had differently altered gene expression. Two of these proteins, transthyretin (TTR) and apolipoprotein A4 (ApoA4) were significantly overexpressed in PEX patients, but the remaining proteins were only mildly altered. The liver X receptor (LXR) and the retinoid X receptors (RXR) may play a crucial role in the pathophysiology of PEX according to IPA employing these 10 proteins.
The altered proteins, particularly ApoA4 and TTR, may be important in revealing the molecular process behind PEX, as anticipated by IPA.
Toprak M, Yuksel N, Akpinar G, et al. Comparative Proteomic Analysis of the Aqueous Humor from Patients with Pseudoexfoliation Syndrome. J Curr Glaucoma Pract 2023;17(3):118-125.

Previously, the RXR agonist UAB126 demonstrated therapeutic potential to treat obese mice by controlling blood glucose levels (BGL) and altering the expression of genes associated with lipid metabolism and inflammatory response. The purpose of the study was to assess the effects of UAB126 on the progression of diabetic retinopathy (DR) in rodent models of type 1 diabetes (T1D), streptozotocin-induced, and type 2 diabetes (T2D), in db/db mice. UAB126 treatment was delivered either by oral gavage for 6 weeks or by topical application of eye drops for 2 weeks. At the end of the treatment, the retinal function of diabetic mice was assessed by electroretinography (ERG), and their retinal tissue was harvested for protein and gene expression analyses. Bone-marrow cells were isolated and differentiated into bone marrow-derived macrophages (BMDMs). The glycolysis stress test and the 2-DG glucose uptake analysis were performed. Our results demonstrated that in the UAB126-treated diabetic BMDMs, the ECAR rate and the 2-DG uptake were improved as compared to untreated diabetic BMDMs. In UAB126-treated diabetic mice, hyperglycemia was reduced and associated with the preservation of ERG amplitudes and enhanced AMPK activity. Retinas from diabetic mice treated with topical UAB126 demonstrated an increase in Rxr and Ppar and the expression of genes associated with lipid metabolism. Altogether, our data indicate that RXR activation is beneficial to preclinical models of DR.

Type 2 diabetes (T2D) is often accompanied with an induction of retinaldehyde dehydrogenase 1 (RALDH1 or ALDH1A1) expression and a consequent decrease in hepatic retinaldehyde (Rald) levels. However, the role of hepatic Rald deficiency in T2D progression remains unclear. In this study, we demonstrated that reversing T2D-mediated hepatic Rald deficiency by Rald or citral treatments, or liver-specific Raldh1 silencing substantially lowered fasting glycemia levels, inhibited hepatic glucogenesis, and downregulated phosphoenolpyruvate carboxykinase 1 (PCK1) and glucose-6-phosphatase (G6PC) expression in diabetic db/db mice. Fasting glycemia and Pck1/G6pc mRNA expression levels were strongly negatively correlated with hepatic Rald levels, indicating the involvement of hepatic Rald depletion in T2D deterioration. A similar result that liver-specific Raldh1 silencing improved glucose metabolism was also observed in high-fat diet-fed mice. In primary human hepatocytes and oleic acid-treated HepG2 cells, Rald or Rald + RALDH1 silencing resulted in decreased glucose production and downregulated PCK1/G6PC mRNA and protein expression. Mechanistically, Rald downregulated direct repeat 1-mediated PCK1 and G6PC expression by antagonizing retinoid X receptor α, as confirmed by luciferase reporter assays and molecular docking. These results highlight the link between hepatic Rald deficiency, glucose dyshomeostasis, and the progression of T2D, whilst also suggesting RALDH1 as a potential therapeutic target for T2D.

Non-alcoholic steatohepatitis (NASH) is an aggressive form of fatty liver disease with hepatic inflammation and fibrosis for which there is currently no drug treatment. This study determined whether an indoline derivative, AN1284, which significantly reduced damage in a model of acute liver disease, can reverse steatosis and fibrosis in mice with pre-existing NASH and explore its mechanism of action. The mouse model of dietary-induced NASH reproduces most of the liver pathology seen in human subjects. This was confirmed by RNA-sequencing analysis. The Western diet, given for 4 months, caused steatosis, inflammation, and liver fibrosis. AN1284 (1 mg or 5 mg/kg/day) was administered for the last 2 months of the diet by micro-osmotic-pumps (mps). Both doses significantly decreased hepatic damage, liver weight, hepatic fat content, triglyceride, serum alanine transaminase, and fibrosis. AN1284 (1 mg/kg/day) given by mps or in the drinking fluid significantly reduced fibrosis produced by carbon tetrachloride injections. In human HUH7 hepatoma cells incubated with palmitic acid, AN1284 (2.1 and 6.3 ng/ml), concentrations compatible with those in the liver of mice treated with AN1284, decreased lipid formation by causing nuclear translocation of the aryl hydrocarbon receptor (AhR). AN1284 downregulated fatty acid synthase (FASN) and sterol regulatory element-binding protein 1c (SREBP-1c) and upregulated Acyl-CoA Oxidase 1 and Cytochrome P450-a1, genes involved in lipid metabolism. In conclusion, chronic treatment with AN1284 (1mg/kg/day) reduced pre-existing steatosis and fibrosis through AhR, which affects several contributors to the development of fatty liver disease. Additional pathways are also influenced by AN1284 treatment.

The neurovascular unit (NVU) is composed of vascular cells, glia, and neurons that form the basic component of the blood brain barrier. This intricate structure rapidly adjusts cerebral blood flow to match the metabolic needs of brain activity. However, the NVU is exquisitely sensitive to damage and displays limited repair after a stroke. To effectively treat stroke, it is therefore considered crucial to both protect and repair the NVU. Mitochondrial calcium (Ca2+) uptake supports NVU function by buffering Ca2+ and stimulating energy production. However, excessive mitochondrial Ca2+ uptake causes toxic mitochondrial Ca2+ overloading that triggers numerous cell death pathways which destroy the NVU. Mitochondrial damage is one of the earliest pathological events in stroke. Drugs that preserve mitochondrial integrity and function should therefore confer profound NVU protection by blocking the initiation of numerous injury events. We have shown that mitochondrial Ca2+ uptake and efflux in the brain are mediated by the mitochondrial Ca2+ uniporter complex (MCUcx) and sodium/Ca2+/lithium exchanger (NCLX), respectively. Moreover, our recent pharmacological studies have demonstrated that MCUcx inhibition and NCLX activation suppress ischemic and excitotoxic neuronal cell death by blocking mitochondrial Ca2+ overloading. These findings suggest that combining MCUcx inhibition with NCLX activation should markedly protect the NVU. In terms of promoting NVU repair, nuclear hormone receptor activation is a promising approach. Retinoid X receptor (RXR) and thyroid hormone receptor (TR) agonists activate complementary transcriptional programs that stimulate mitochondrial biogenesis, suppress inflammation, and enhance the production of new vascular cells, glia, and neurons. RXR and TR agonism should thus further improve the clinical benefits of MCUcx inhibition and NCLX activation by increasing NVU repair. However, drugs that either inhibit the MCUcx, or stimulate the NCLX, or activate the RXR or TR, suffer from adverse effects caused by undesired actions on healthy tissues. To overcome this problem, we describe the use of nanoparticle drug formulations that preferentially target metabolically compromised and damaged NVUs after an ischemic or hemorrhagic stroke. These nanoparticle-based approaches have the potential to improve clinical safety and efficacy by maximizing drug delivery to diseased NVUs and minimizing drug exposure in healthy brain and peripheral tissues.