Novel pathways of vitamin D3, lumisterol 3 (L3), and tachysterol 3 (T3) activation have been discovered, initiated by CYP11A1 and/or CYP27A1 in the case of L3 and T3. The resulting hydroxymetabolites enhance protection of skin against DNA damage and oxidative stress; stimulate keratinocyte differentiation; exert anti-inflammatory, antifibrogenic, and anticancer activities; and inhibit cell proliferation in a structure-dependent manner. They act on nuclear receptors, including vitamin D receptor, aryl hydrocarbon receptor, LXRα/β, RAR-related orphan receptor α/γ, and peroxisome proliferator-activated receptor-γ, with selectivity defined by their core structure and distribution of hydroxyl groups. They can activate NRF2 and p53 and inhibit NF-κB, IL-17, Shh, and Wnt/β-catenin signaling. Thus, they protect skin integrity and physiology.

The pregnane X receptor (PXR, NR1I2), a xenobiotic-sensing nuclear receptor signaling potentiates ethanol (EtOH)-induced hepatotoxicity in male mice, however, how PXR signaling modulates EtOH-induced hepatotoxicity in female mice is unknown. Wild type (WT) and Pxr-null mice received 5 % EtOH-containing diets or paired-fed control diets for 8 weeks followed by assessment of liver injury, EtOH elimination rates, histology, and changes in gene and protein expression; microarray and bioinformatic analyses were also employed to identify PXR targets in chronic EtOH-induced hepatotoxicity. In WT females, EtOH ingestion significantly increased serum ethanol and alanine aminotransferase (ALT) levels, hepatic Pxr mRNA, constitutive androstane receptor activation, Cyp2b10 mRNA and protein, oxidative stress, endoplasmic stress (phospho-elF2α) and pro-apoptotic (Bax) protein expression. Unexpectedly, EtOH-fed female Pxr-null mice displayed increased EtOH elimination and elevated levels of hepatic acetaldehyde detoxifying aldehyde dehydrogenase 1a1 (Aldh1a1) mRNA and protein, EtOH-metabolizing alcohol dehydrogenase 1 (ADH1), and lipid suppressing microsomal triglyceride transport protein (MTP) protein, aldo-keto reductase 1b7 (Akr1b7) and Cyp2a5 mRNA, but suppressed CYP2B10 protein levels, with evidence of protection against chronic EtOH-induced oxidative stress and hepatotoxicity. While liver injury was not different between the two WT sexes, female sex may suppress EtOH-induced macrovesicular steatosis in the liver. Several genes and pathways important in retinol and steroid hormone biosynthesis, chemical carcinogenesis, and arachidonic acid metabolism were upregulated by EtOH in a PXR-dependent manner in both sexes. Together, these data establish that female Pxr-null mice are resistant to chronic EtOH-induced hepatotoxicity and unravel the PXR-dependent and -independent mechanisms that contribute to EtOH-induced hepatotoxicity.

Bile acids are the end products of cholesterol catabolism. Hepatic bile acid synthesis accounts for a major fraction of daily cholesterol turnover in humans. Biliary secretion of bile acids generates bile flow and facilitates biliary secretion of lipids, endogenous metabolites and xenobiotics. In intestine, bile acids facilitate the digestion and absorption of dietary lipids and fat-soluble vitamins. Through activation of nuclear receptors and G protein-coupled receptors and interaction with gut microbiome, bile acids critically regulate host metabolism and innate and adaptive immunity, and are involved in the pathogenesis of cholestasis, metabolic dysfunction-associated steatotic liver disease (MASLD), alcohol-associated liver disease (ALD), type-2 diabetes, and inflammatory bowel diseases (IBD). Bile acids and their derivatives have been developed as potential therapeutic agents for treating chronic metabolic and inflammatory liver diseases and gastrointestinal disorders. Significance Statement Bile acids facilitate biliary cholesterol solubilization and dietary lipid absorption, regulate host metabolism and immunity, and modulate gut microbiome. Targeting bile acid metabolism and signaling hold promise for treating metabolic and inflammatory diseases.

The essential Mediator (MED) coactivator complex plays a well-understood role in regulation of basal transcription in all eukaryotes, but the mechanism underlying its role in activator-dependent transcription remains unknown. We investigated modulation of metazoan MED interaction with RNA polymerase II (RNA Pol II) by antagonistic effects of the MED26 subunit and the CDK8 kinase module (CKM). Biochemical analysis of CKM-MED showed that the CKM blocks binding of the RNA Pol II carboxy-terminal domain (CTD), preventing RNA Pol II interaction. This restriction is eliminated by nuclear receptor (NR) binding to CKM-MED, which enables CTD binding in a MED26-dependent manner. Cryoelectron microscopy (cryo-EM) and crosslinking-mass spectrometry (XL-MS) revealed that the structural basis for modulation of CTD interaction with MED relates to a large intrinsically disordered region (IDR) in CKM subunit MED13 that blocks MED26 and CTD interaction with MED but is repositioned upon NR binding. Hence, NRs can control transcription initiation by priming CKM-MED for MED26-dependent RNA Pol II interaction.

Chlorpyrifos (CPF) is a widely used pesticide inducing adverse neurodevelopmental and reproductive effects. However, knowledge of the underlying mechanisms is limited, particularly in the hypothalamus. We investigated the mode of action of CPF at human relevant concentrations (1 nM-100 nM) in immortalized mouse hypothalamic GnRH neurons (GT1-7), an elective model for studying disruption of the hypothalamus-pituitary-gonads (HPG) axis. We firstly examined cell vitality, proliferation, and apoptosis/necrosis. At not-cytotoxic concentrations, we evaluated neuron functionality, gene expression, Transmission Electron Microscopy (TEM) and proteomics profiles, validating results by immunofluorescence and western blotting (WB). CPF decreased cell vitality with a dose-response but did not affect cell proliferation. At 100 nM, CPF inhibited gene expression and secretion of GnRH; in addition, CPF reduced the immunoreactivity of the neuronal marker Map2 in a dose-dependent manner. The gene expression of Estrogen Receptor α and β (Erα, Erβ), Androgen Receptor (Ar), aromatase and oxytocin receptor was induced by CPF with different trends. Functional analysis of differentially expressed proteins identified Autophagy, mTOR signaling and Neutrophil extracellular traps (NETs) formation as significant pathways affected at all concentrations. This finding was phenotypically supported by the TEM analysis, showing marked autophagy and damage of mitochondria, as well as by protein analysis demonstrating a dose-dependent decrease of mTOR and its direct target pUlk1 (Ser 757). The bioinformatics network analysis identified a core module of interacting proteins, including Erα, Ar, mTOR and Sirt1, whose down-regulation was confirmed by WB analysis. Overall, our results demonstrate that CPF is an inhibitor of the mTOR pathway leading to autophagy in GnRH neurons; a possible involvement of the Erα/Ar signaling is also suggested. The evidence for adverse effects of CPF in the hypothalamus in the nanomolar range, as occurs in human exposure, increases concern on potential adverse outcomes induced by this pesticide on the HPG axis.

The emerging concern about chemicals in electronic cigarettes, even those without nicotine, demands the development of advanced criteria for their exposure and risk assessment. This study aims to highlight the sensitivity of lung nuclear receptors (NRs) to electronic cigarette e-liquids, independent of nicotine presence, and the influence of the sex variable on these effects. Adult male and female C57BL/6J mice were exposed to electronic cigarettes with 0%, 3%, and 6% nicotine daily (70 mL, 3.3 s, 1 puff per min/30 min) for 14 days, using the inExpose full body chamber (SCIREQ). Following exposure, lung tissues were harvested, and RNA extracted. The expression of 84 NRs was determined using the RT2 profiler mRNA array (Qiagen). Results exhibit a high sensitivity to e-liquid exposure irrespective of the presence of nicotine, with differential expression of NRs, including one (females) and twenty-four (males) in 0% nicotine groups compared to non-exposed control mice. However, nicotine-dependent results were also significant with seven NRs (females), fifty-three NRs (males) in 3% and twenty-three NRs (female) twenty-nine NRs (male) in 6% nicotine groups, compared to 0% nicotine mice. Sex-specific changes were significant, but sex-related differences were not observed. The study provides a strong rationale for further investigation.

Melanoma, originating through malignant transformation of melanin-producing melanocytes, is a formidable malignancy, characterized by local invasiveness, recurrence, early metastasis, resistance to therapy, and a high mortality rate. This review discusses etiologic and risk factors for melanoma, diagnostic and prognostic tools, including recent advances in molecular biology, omics, and bioinformatics, and provides an overview of its therapy. Since the incidence of melanoma is rising and mortality remains unacceptably high, we discuss its inherent properties, including melanogenesis, that make this disease resilient to treatment and propose to use AI to solve the above complex and multidimensional problems. We provide an overview on vitamin D and its anticancerogenic properties, and report recent advances in this field that can provide solutions for the prevention and/or therapy of melanoma. Experimental papers and clinicopathological studies on the role of vitamin D status and signaling pathways initiated by its active metabolites in melanoma prognosis and therapy are reviewed. We conclude that vitamin D signaling, defined by specific nuclear receptors and selective activation by specific vitamin D hydroxyderivatives, can provide a benefit for new or existing therapeutic approaches. We propose to target vitamin D signaling with the use of computational biology and AI tools to provide a solution to the melanoma problem.

Contamination of aquatic environments has been steadily increasing due to human activities. The Pacific oyster Crassostrea gigas has been used as a key species in studies assessing the impacts of contaminants on human health and the aquatic biome. In this context, cytochrome P450 (CYPs) play a crucial role in xenobiotic metabolism. In vertebrates many of these CYPs are regulated by nuclear receptors (NRs) and little is known about the NRs role in C. gigas. Particularly, the CgNR5A represents a homologue of SF1 and LRH-1 found in vertebrates. Members of this group can regulate genes of CYPs involved in lipid/steroid metabolism, with their activity regulated by other NR, called as DAX-1, generating a NR complex on DNA response elements (REs). As C. gigas does not exhibit steroid biosynthesis pathways, CgNR5A may play other physiological roles. To clarify this issue, we conducted an in silico investigation of the interaction between CgNR5A and DNA to identify potential C. gigas CYP target genes. Using molecular docking and dynamics simulations of the CgNR5A on DNA molecules, we identified a monomeric interaction with extended REs. This RE was found in the promoter region of 30 CYP genes and also the NR CgDAX. When the upstream regulatory region was analyzed, CYP2C39, CYP3A11, CYP4C21, CYP7A1, CYP17A1, and CYP27C1 were mapped as the main genes regulated by CgNR5A. These identified CYPs belong to families known for their involvement in xenobiotic and lipid/steroid metabolism. Furthermore, we reconstructed a trimeric complex, previously proposed for vertebrates, with CgNR5A:CgDAX and subjected it to molecular dynamics simulations analysis. Heterotrimeric complex remained stable during the simulations, suggesting that CgDAX may modulate CgNR5A transcriptional activity. This study provides insights into the potential physiological processes involving these NRs in the regulation of CYPs associated with xenobiotic and steroid/lipid metabolism.

The orphan nuclear receptor NR2E3 (Nuclear receptor subfamily 2 group E, Member 3) is an epigenetic player that modulates chromatin accessibility to activate p53 during liver injury. Nonetheless, a precise tumor suppressive and epigenetic role of NR2E3 in hepatocellular carcinoma (HCC) development remains unclear. HCC patients expressing low NR2E3 exhibit unfavorable clinical outcomes, aligning with heightened activation of the Wnt/β-catenin signaling pathway. The murine HCC models utilizing NR2E3 knockout mice consistently exhibits accelerated liver tumor formation accompanied by enhanced activation of Wnt/β-catenin signaling pathway and inactivation of p53 signaling. At cellular level, the loss of NR2E3 increases the acquisition of aggressive cancer cell phenotype and tumorigenicity and upregulates key genes in the WNT/β-catenin pathway with increased chromatin accessibility. This event is mediated through increased formation of active transcription complex involving Sp1, β-catenin, and p300, a histone acetyltransferase, on the promoters of target genes. These findings demonstrate that the loss of NR2E3 activates Wnt/β-catenin signaling at cellular and organism levels and this dysregulation is associated with aggressive HCC development and poor clinical outcomes. In summary, NR2E3 is a novel tumor suppressor with a significant prognostic value, maintaining epigenetic homeostasis to suppress the Wnt/β-catenin signaling pathway that promotes HCC development.

Calixarenes are displaying great potential for the development of new drug delivery systems, diagnostic imaging, biosensing devices and inhibitors of biological processes. In particular, calixarene derivatives are able to interact with many different enzymes and function as inhibitors. By screening of the potential drug target database (PDTD) with a reverse docking procedure, we identify and discuss a selection of 100 proteins that interact strongly with calix[4]arene. We also discover that leucine (23.5 %), isoleucine (11.3 %), phenylalanines (11.3 %) and valine (9.5 %) are the most frequent binding residues followed by hydrophobic cysteines and methionines and aromatic histidines, tyrosines and tryptophanes. Top binders are peroxisome proliferator-activated receptors that already are targeted by commercial drugs, demonstrating the practical interest in calix[4]arene. Nuclear receptors, potassium channel, several carrier proteins, a variety of cancer-related proteins and viral proteins are prominent in the list. It is concluded that calix[4]arene, which is characterized by facile access, well-defined conformational characteristics, and ease of functionalization at both the lower and higher rims, could be a potential lead compound for the development of enzyme inhibitors and theranostic platforms.