The nuclear receptor superfamily: the second decade

Epigenetic changes associated with increased estrogen receptor alpha mRNA transcript abundance during reproductive maturation in chicken ovaries

Estrogen receptor alpha (ERα) is a ligand-activated transcription factor that regulates cellular responses to estrogens and transcription processes of target genes. In this study, changes in DNA methylation and histone modifications in the promoter region and Exon 1 of the ERα gene were analyzed to ascertain epigenetic changes associated with increased ERα mRNA abundance during reproductive maturation from 90 (egg production not yet initiated) to 160 (after egg production was initiated) d of age (d post-hatching) in chicken ovaries. The results indicate there was no difference in CpG methylation at the promoter and Exon 1 except at the region analyzed with primer pairs F2 and R2, where percentage of methylated CpG of Sites 2 and 8 after reproductive maturation was greater compared with before reproductive maturation. By using the chromatin immunuoprecipitation (ChIP) assay combined with SYBR green quantitative PCR, effects of histone modifications were evaluated, including histone H3K4 di + tri methylation, H3K9 phosphorylation and trimethylation, H3K36 methylation and H3K27 acetylation on chicken ERα mRNA transcript abundance. The results indicated that there was a greater histone H3K27 acetylation and lesser H3K36 trimethylation associated with increased abundance of ERα mRNA transcript in chicken ovaries after reproductive maturation (90 compared with 160 d of age). In consistent with this finding, the relative abundance of transcriptional coactivator p300 mRNA transcript and protein in the ovaries was markedly greater in reproductively mature than immature chickens. Findings provide insights into the epigenetic regulations of the chicken ERα gene expression that is required for chicken ovarian development.

Brain Cleanup as a Potential Target for Poststroke Recovery: The Role of RXR (Retinoic X Receptor) in Phagocytes

Background and Purpose- Phagocytic cells, such as microglia and blood-derived macrophages, are a key biological modality responsible for phagocytosis-mediated clearance of damaged, dead, or displaced cells that are compromised during senescence or pathological processes, including after stroke. This process of clearance is essential to eliminate the source of inflammation and to allow for optimal brain repair and functional recovery. Transcription factor, RXR (retinoic-X-receptor) is strongly implicated in phagocytic functions regulation, and as such could represent a novel target for brain recovery after stroke. Methods- Primary cultured microglia and bone marrow macrophages were used for phagocytic study. Mice with deleted RXR-α in myeloid phagocytes (Mac-RXR-α^-/-) were subjected to transient middle cerebral artery occlusion to mimic ischemic stroke and then treated with RXR agonist bexarotene. RNA-sequencing and long-term recovery were evaluated. Results- Using cultured microglia, we demonstrated that the RXR-α promotes the phagocytic functions of microglia toward apoptotic neurons. Using mice with deleted RXR-α in myeloid phagocytes (Mac-RXR-α^-/-), we have shown that despite behaving similarly to the control at early time points (up to 3 days, damage established histologically and behaviorally), these Mac-RXR-α^-/- mice demonstrated worsened late functional recovery and developed brain atrophy that was larger in size than that seen in control mice. The RXR-α deficiency was associated with reduced expression of genes known to be under control of the prominent transcriptional RXR partner, PPAR (peroxisome proliferator-activated receptor)-γ, as well as genes encoding for scavenger receptors and genes that signify microglia/macrophages polarization to a reparative phenotype. Finally, we demonstrated that the RXR agonist, bexarotene, administered as late as 1 day after middle cerebral artery occlusion, improved neurological recovery, and reduced the atrophy volume as assessed 28 days after stroke. Bexarotene did not improve outcome in Mac-RXR-α^-/- mice. Conclusions- Altogether, these data suggest that phagocytic cells control poststroke recovery and that RXR in these cells represents an attractive target with exceptionally long therapeutic window.

Anti-diabetic drugs recent approaches and advancements

Diabetes is one of the major diseases worldwide and is the third leading cause of death in the United States. Anti-diabetic drugs are used in the treatment of diabetes mellitus to control glucose levels in the blood. Most of the drugs are administered orally, except for a few of them, such as insulin, exenatide, and pramlintide. In this review, we are going to discuss seven major types of anti-diabetic drugs: Peroxisome proliferator-activated receptor (PPAR) agonist, protein tyrosine phosphatase 1B (PTP1B) inhibitors, aldose reductase inhibitors, α-glucosidase inhibitors, dipeptidyl peptidase IV (DPP-4) inhibitors, G protein-coupled receptor (GPCR) agonists and sodium-glucose co-transporter (SGLT) inhibitors. Here, we are also discussing some of the recently reported anti-diabetic agents with its multi-target pharmacological actions. This review summarises recent approaches and advancement in anti-diabetes treatment concerning characteristics, structure-activity relationships, functional mechanisms, expression regulation, and applications in medicine.

Psychosocial Stress, Glucocorticoid Signaling, and Prostate Cancer Health Disparities in African American Men

Recent advances in our understanding of racial disparities in prostate cancer (PCa) incidence and mortality that disproportionately affect African American (AA) men have provided important insights into the psychosocial, socioeconomic, environmental, and molecular contributors. There is, however, limited mechanistic knowledge of how the interplay between these determinants influences prostate tumor aggressiveness in AA men and other men of African ancestry. Growing evidence indicates that chronic psychosocial stress in AA populations leads to sustained glucocorticoid signaling through the glucocorticoid receptor (GR), with negative physiological and pathological consequences. Compelling evidence indicates that treatment of castration-resistant prostate cancer (CRPC) with anti-androgen therapy activates GR signaling. This enhanced GR signaling bypasses androgen receptor (AR) signaling and transcriptionally activates both AR-target genes and GR-target genes, resulting in increased prostate tumor resistance to anti-androgen therapy, chemotherapy, and radiotherapy. Given its enhanced signaling in AA men, GR-together with specific genetic drivers-may promote CRPC progression and exacerbate tumor aggressiveness in this population, potentially contributing to PCa mortality disparities. Ongoing and future CRPC clinical trials that combine standard of care therapies with GR modulators should assess racial differences in therapy response and clinical outcomes in order to improve PCa health disparities that continue to exist for AA men.

The Vitamin D Receptor as Tumor Suppressor in Skin

Cutaneous malignancies including melanomas and keratinocyte carcinomas (KC) are the most common types of cancer, occurring at a rate of over one million per year in the United States. KC, which include both basal cell carcinomas and squamous cell carcinomas, are substantially more common than melanomas and form the subject of this chapter. Ultraviolet radiation (UVR), both UVB and UVA, as occurs with sunlight exposure is generally regarded as causal for these malignancies, but UVB is also required for vitamin D synthesis in the skin. Keratinocytes are the major cell in the epidermis. These cells not only produce vitamin D but contain the enzymatic machinery to metabolize vitamin D to its active metabolite, 1,25(OH)₂D, and express the receptor for this metabolite, the vitamin D receptor (VDR). This allows the cell to respond to the 1,25(OH)₂D that it produces. Based on our own data and that reported in the literature, we conclude that vitamin D signaling in the skin suppresses UVR-induced epidermal tumor formation. In this chapter we focus on four mechanisms by which vitamin D signaling suppresses tumor formation. They are inhibition of proliferation/stimulation of differentiation with discussion of the roles of hedgehog, Wnt/β-catenin, and hyaluronan/CD44 pathways in mediating vitamin D regulation of proliferation/differentiation, regulation of the balance between oncogenic and tumor suppressor long noncoding RNAs, immune regulation, and promotion of DNA damage repair (DDR).

Thyroid hormone activates Xenopus MBD3 gene via an intronic TRE in vivo

Thyroid hormone (T3) is important for adult organ function and vertebrate development. Amphibian metamorphosis is totally dependent on T3 and can be easily manipulated, thus offering a unique opportunity for studying how T3 controls vertebrate development. T3 controls frog metamorphosis through T3 receptor (TR)-mediated regulation of T3 response genes. To identify direct T3 response genes, we previously carried out a ChIP (chromatin immunoprecipitation)-on-chip analysis with a polyclonal anti-TR antibody on the tadpole intestine and identified many putative TR target genes. Among them is the methyl-CpG binding domain protein 3 (MBD3) gene, which has been implicated to play a role in epigenetic regulation of cellular processes as a subunit of the Mi-2/NuRD (Nucleosome Remodeling Deacetylase) complex. We show here that MBD3 is upregulated in the intestine and tail by T3 and its expression peaks at stage 62, the climax of metamorphosis. We further show that a putative TRE within the first intron of the MBD3 gene binds to TR/RXR in vitro and in vivo, and mediates T3 regulation of the MBD3 promoter in vivo.

Differential Roles of Hypothalamic AVPV and Arcuate Kisspeptin Neurons in Estradiol Feedback Regulation of Female Reproduction

Mammalian reproductive function includes puberty onset and completion, reproductive cyclicity, steroidogenesis, gametogenesis, fertilization, pregnancy, and lactation; all are indispensable to perpetuate species. Reproductive cycles are critical for providing the hormonal milieu needed for follicular development and maturation of eggs, but cycles, in and of themselves, do not guarantee ovulation will occur. Here, we review the roles in female reproductive neuroendocrine function of two hypothalamic populations that produce the neuropeptide kisspeptin, demonstrating distinct roles in maintaining cycles and ovulation.

Glucocorticoid receptors function in the pathophysiology of brain hypoxia

Glucocorticoid receptors are ligand-activated transcription factors, which play an important role in the brain, mainly in stress response regulation. There are two types of receptors for glucocorticosteroids: mineralocorticoid receptors (MR) with high-affinity for the ligands and glucocorticoid receptors (GR) with a tenfold lower affinity. Selective activation of the receptors during hypoxia may decide neuronal fate, especially in the hippocampus. Depending on the severity of hypoxia-induced damage, neurons undergo necrosis or apoptosis. In the penumbral region, where neurons die mainly through the process of apoptosis, selective GR activation increases excitotoxicity, interferes with apoptotic signalling pathways and causes energy deficit in the cells, all of which promote cell death. On the other hand, selective MR activation seems to be neuroprotective. It is suggested that the main role of MR in neuroprotection is to regulate the balance between anti- and proapoptotic proteins from bcl-2 family.

Synthesis and vitamin D receptor affinity of 16-oxa vitamin D3 analogues

Two novel 16-oxa-vitamin D₃ analogues were synthesized using a tandem Ti(ii)-mediated enyne cyclization/Cu-catalyzed allylation, Ru-catalyzed ring-closing metathesis reaction, and a low-valent titanium (LVT)-mediated stereoselective radical reduction of 8α,14α-epoxide as the key steps for the synthesis of the 16-oxa-C,D ring unit. The vitamin D receptor-binding affinity of the synthesized analogues, 16-oxa-1α,25-(OH)₂VD₃ and 16-oxa-19-nor-1α,25-(OH)₂VD₃, was evaluated by fluorescence polarization vitamin D receptor competitor assay and time-resolved fluorescence energy transfer vitamin D receptor co-activator assay.

All-Trans Retinoic Acid Enhances Bacterial Flagellin-Stimulated Proinflammatory Responses in Human Monocyte THP-1 Cells by Upregulating CD14

All-trans retinoic acid (ATRA), an active form of vitamin A, exerts immunomodulatory functions. In this study, we examined the immune potentiating effect of ATRA on bacterial flagellin-induced NF-κB activation and proinflammatory cytokine production in human monocytic cell line THP-1. ATRA treatment significantly enhanced the flagellin-induced NF-κB/AP-1 activity in THP-1 via the RAR/RXR pathway. Similarly, ATRA enhanced the expression and production of TNF-α and IL-1β in THP-1 cells upon flagellin challenge. The cell surface expression of toll-like receptor 5 (TLR5), which is the receptor for bacterial flagellin, was significantly reduced by ATRA in a concentration- and time-dependent manner. To determine the mechanisms underlying the ATRA-enhanced immune response against bacterial flagellin despite the reduced cell surface expression of TLR5 in ATRA-treated THP-1, we examined the cell surface expression of CD14, which has been proposed to be a TLR co-receptor that enhances the response to microbial components. The cell surface expression of CD14 was significantly enhanced by ATRA treatment, especially in the presence of flagellin. Anti-CD14 antibody treatment prior to ATRA and flagellin treatments completely abolished ATRA-enhanced TNF-α and IL-1β production. Our results suggest that ATRA enhances flagellin-stimulated proinflammatory responses in human monocyte THP-1 cells by upregulating CD14 in a RAR/RXR-dependent manner.

Regulatory Mechanics of Constitutive Androstane Receptors: Basal and Ligand-Directed Actions

Constitutive androstane receptor (CAR) is a nuclear hormone receptor that primarily functions in sensing and metabolizing xenobiotics. The basal activity of this receptor is relatively high, and CAR is deemed active in the absence of ligand. The (over)activation can promote drug toxicity and tumor growth. Thus, therapeutic treatments seek inverse agonists to inhibit or modulate CAR activities. To advance our understanding of the regulatory mechanisms of CAR, we used computational and experimental approaches to elucidate three aspects of CAR activation and inactivation: (1) ligand-dependent actions, (2) ligand-orthologue specificity, and (3) constitutive activity. For ligand-dependent actions, we examined the ligand-bound simulations and identified two sets of ligand-induced contacts promoting CAR activation via coactivator binding (H11-H12 contact) or inactivation via corepressor binding (H4-H11 contact). For orthologue specificity, we addressed a puzzling fact that murine CAR (mCAR) and human CAR (hCAR) respond differently to the same ligand (CITCO), despite their high sequence homology. We found that the helix H7 of hCAR is responsible for a stronger binding of the ligand CITCO compared to mCAR, hence a stronger CITCO-induced activation. For basal activity, we reported computer-generated unliganded CAR structures and critical mutagenesis (mCAR's V209A and N333D) results of a cell-based transcription assay. Our results reveal that the basal conformation of CAR shares prominent features with the agonist-bound form, and helix HX has an important contribution to the constitutive activity. These findings altogether can be useful for the understanding of constitutively active receptors and the design of drug molecules targeting them.

Bisphenol AF: Halogen bonding effect is a major driving force for the dual ERα-agonist and ERβ-antagonist activities

17β-Estradiol (E2) is a natural steroid ligand for the structurally and physiologically independent estrogen receptors (ERs) ERα and ERβ. We recently observed that CF₃-containing bisphenol AF (BPAF) works as an agonist for ERα but as an antagonist for ERβ. Similar results were also observed for the CCl₃-containing bisphenol designated as HPTE. Both BPAF and HPTE are comprised of a tri-halogenated methyl group in the central alkyl moiety of their bisphenol structures, which strongly suggests that halogens contribute directly to the agonist/antagonist dual biological functions. We conducted this study to investigate the structure-activity relationships by assessing together newly synthesized CF₃- and CBr₃-containing bisphenol E analogs (BPE-X). We first tested bisphenols for their receptor binding ability and then for their transcriptional activities. Halogen-containing bisphenols were found to be fully active for ERα, but almost completely inactive for ERβ. When we examined these bisphenols for their inhibitory activities for E2 in ERβ, we observed that they worked as distinct antagonists. The ascending order of agonist/antagonist dual biological functions was BPE-F < BPE-Cl (HPTE) ≤ BPAF < BPE-Br, demonstrating that the electrostatic halogen bonding effect is a major driving force of the bifunctional ERα agonist and ERβ antagonist activities of BPAF.

Comparative Transcriptome Analysis of Gonads for the Identification of Sex-Related Genes in Giant Freshwater Prawns (Macrobrachium Rosenbergii) Using RNA Sequencing

The giant freshwater prawn (Macrobrachium rosenbergii) exhibits sex dimorphism between the male and female individuals. To date, the molecular mechanism governing gonadal development was unclear, and limited data were available on the gonad transcriptome of M. rosenbergii. Here, we conducted comprehensive gonadal transcriptomic analysis of female (ZW), super female (WW), and male (ZZ) M. rosenbergii for gene discovery. A total of 70.33 gigabases (Gb) of sequences were generated. There were 115,338 unigenes assembled with a mean size of 1196 base pair (bp) and N50 of 2195 bp. Alignment against the National Center for Biotechnology Information (NCBI) non-redundant nucleotide/protein sequence database (NR and NT), the Kyoto Encyclopedia of Genes and Genomes (KEGG) database, SwissProt database, Protein family (Pfam), Gene ontology (GO), and the eukaryotic orthologous group (KOG) database, 36,282 unigenes were annotated at least in one database. Comparative transcriptome analysis observed that 10,641, 16,903, and 3393 genes were significantly differentially expressed in ZW vs. ZZ, WW vs. ZZ, and WW vs. ZW samples, respectively. Enrichment analysis of differentially expressed genes (DEGs) resulted in 268, 153, and 42 significantly enriched GO terms, respectively, and a total of 56 significantly enriched KEGG pathways. Additionally, 23 putative sex-related genes, including Gtsf1, IR, HSP21, MRPINK, Mrr, and other potentially promising candidate genes were identified. Moreover, 56,241 simple sequence repeats (SSRs) were identified. Our findings provide a valuable archive for further functional analyses of sex-related genes and future discoveries of underlying molecular mechanisms of gonadal development and sex determination.

Estrogen receptor coactivator Mediator Subunit 1 (MED1) as a tissue-specific therapeutic target in breast cancer

Breast cancer, one of the most frequent cancer types, is a leading cause of death in women worldwide. Estrogen receptor (ER) α is a nuclear hormone receptor that plays key roles in mammary gland development and breast cancer. About 75% of breast cancer cases are diagnosed as ER-positive; however, nearly half of these cancers are either intrinsically or inherently resistant to the current anti-estrogen therapies. Recent studies have identified an ER coactivator, Mediator Subunit 1 (MED1), as a unique, tissue-specific cofactor that mediates breast cancer metastasis and treatment resistance. MED1 is overexpressed in over 50% of human breast cancer cases and co-amplifies with another important breast cancer gene, receptor tyrosine kinase HER2. Clinically, MED1 expression highly correlates with poor disease-free survival of breast cancer patients, and recent studies have reported an increased frequency of MED1 mutations in the circulating tumor cells of patients after treatment. In this review, we discuss the biochemical characterization of MED1 and its associated MED1/Mediator complex, its crosstalk with HER2 in anti-estrogen resistance, breast cancer stem cell formation, and metastasis both in vitro and in vivo. Furthermore, we elaborate on the current advancements in targeting MED1 using state-of-the-art RNA nanotechnology and discuss the future perspectives as well.

High-throughput custom capture sequencing identifies novel mutations in coloboma-associated genes: Mutation in DNA-binding domain of retinoic acid receptor beta affects nuclear localization causing ocular coloboma

Uveal coloboma is a potentially blinding congenital ocular malformation caused by the failure of optic fissure closure during the fifth week of human gestation. We performed custom capture high‐throughput screening of 38 known coloboma‐associated genes in 66 families. Suspected causative novel variants were identified in TFAP2A and CHD7, as well as two previously reported variants of uncertain significance in RARB and BMP7. The variant in RARB, unlike previously reported disease mutations in the ligand‐binding domain, was a missense change in the highly conserved DNA‐binding domain predicted to affect the protein's DNA‐binding ability. In vitro studies revealed lower steady‐state protein levels, reduced transcriptional activity, and incomplete nuclear localization of the mutant RARB protein compared with wild‐type. Zebrafish studies showed that human RARB messenger RNA partially reduced the ocular phenotype caused by morpholino knockdown of rarga gene, a zebrafish homolog of human RARB. Our study indicates that sequence alterations in known coloboma genes account for a small percentage of coloboma cases and that mutations in the RARB DNA‐binding domain could result in human disease.

Molecular determinants for enzalutamide-induced transcription in prostate cancer

Enzalutamide, a second-generation androgen receptor (AR) antagonist, has demonstrated clinical benefit in men with prostate cancer. However, it only provides a temporary response and modest increase in survival, indicating a rapid evolution of resistance. Previous studies suggest that enzalutamide may function as a partial transcriptional agonist, but the underlying mechanisms for enzalutamide-induced transcription remain poorly understood. Here, we show that enzalutamide stimulates expression of a novel subset of genes distinct from androgen-responsive genes. Treatment of prostate cancer cells with enzalutamide enhances recruitment of pioneer factor GATA2, AR, Mediator subunits MED1 and MED14, and RNA Pol II to regulatory elements of enzalutamide-responsive genes. Mechanistically, GATA2 globally directs enzalutamide-induced transcription by facilitating AR, Mediator and Pol II loading to enzalutamide-responsive gene loci. Importantly, the GATA2 inhibitor K7174 inhibits enzalutamide-induced transcription by decreasing binding of the GATA2/AR/Mediator/Pol II transcriptional complex, contributing to sensitization of prostate cancer cells to enzalutamide treatment. Our findings provide mechanistic insight into the future combination of GATA2 inhibitors and enzalutamide for improved AR-targeted therapy.

The shift in the balance between osteoblastogenesis and adipogenesis of mesenchymal stem cells mediated by glucocorticoid receptor

Mesenchymal stem cells (MSCs) are multipotent cells capable of differentiating into several tissues, such as bone, cartilage, and fat. Glucocorticoids affect a variety of biological processes such as proliferation, differentiation, and apoptosis of various cell types, including osteoblasts, adipocytes, or chondrocytes. Glucocorticoids exert their function by binding to the glucocorticoid receptor (GR). Physiological concentrations of glucocorticoids stimulate osteoblast proliferation and promote osteogenic differentiation of MSCs. However, pharmacological concentrations of glucocorticoids can not only induce apoptosis of osteoblasts and osteocytes but can also reduce proliferation and inhibit the differentiation of osteoprogenitor cells. Several signaling pathways, including the Wnt, TGFβ/BMP superfamily and Notch signaling pathways, transcription factors, post-transcriptional regulators, and other regulators, regulate osteoblastogenesis and adipogenesis of MSCs mediated by GR. These signaling pathways target key transcription factors, such as Runx2 and TAZ for osteogenesis and PPARγ and C/EBPs for adipogenesis. Glucocorticoid-induced osteonecrosis and osteoporosis are caused by various factors including dysfunction of bone marrow MSCs. Transplantation of MSCs is valuable in regenerative medicine for the treatment of osteonecrosis of the femoral head, osteoporosis, osteogenesis imperfecta, and other skeletal disorders. However, the mechanism of inducing MSCs to differentiate toward the osteogenic lineage is the key to an efficient treatment. Thus, a better understanding of the molecular mechanisms behind the imbalance between GR-mediated osteoblastogenesis and adipogenesis of MSCs would not only help us to identify the pathogenic causes of glucocorticoid-induced osteonecrosis and osteoporosis but also promote future clinical applications for stem cell-based tissue engineering and regenerative medicine. Here, we primarily review the signaling mechanisms involved in adipogenesis and osteogenesis mediated by GR and discuss the factors that control the adipo-osteogenic balance.

Indirubin-pregnane X receptor-JNK axis accelerates skin wound healing

Indirubin is a potent anti-inflammatory phytochemical derived from indigo naturalis. It is also endogenously produced in the intestine and detected in the circulation in mammals. Indirubin exerts its biological functions via two xenobiotic receptor systems: aryl hydrocarbon receptor (AHR) and pregnane X receptor (PXR); however, its effects on wound healing remain elusive. To investigate whether indirubin promotes wound healing, we utilized an in vitro scratch injury assay and in vivo full-thickness mouse skin ulcer model and assessed wound closure. Indirubin significantly accelerated wound closure in both the scratch assay and the skin ulcer model. Using inhibitors of cell proliferation or migration, indirubin was found to upregulate the migratory but not the proliferative capacity of keratinocytes. Activation of AHR/PXR by indirubin was confirmed by their nuclear translocation and subsequent upregulation of CYP1A1 (AHR), or UGT1A1 mRNA (PXR) and also by luciferase reporter assay (PXR). Although both AHR and PXR were activated by indirubin, its pro-migratory capacity was canceled by PXR inhibition but not by AHR inhibition and was dependent on the JNK pathway. Moreover, activated PXR was detected in the nuclei of re-epithelialized keratinocytes in human skin ulcers. In conclusion, this study shows that the indirubin-PXR-JNK pathway promotes skin wound healing.

ULK1 Phosphorylates and Regulates Mineralocorticoid Receptor

Mineralocorticoid receptor (MR) signaling regulates both renal Na-Cl reabsorption and K⁺ excretion. We previously demonstrated that phosphorylation of S843 in the MR ligand-binding domain in renal intercalated cells is involved in the balance of these activities by regulating ligand binding and signaling. However, the kinase that phosphorylates MR^S843 is unknown. Using a high-throughput screen assay of 197 kinases, we found that ULK1 is the principal kinase that is responsible for the phosphorylation of MR^S843. The results were confirmed by in vitro kinase assay, mass spectrometry, and siRNA knockdown experiments. Notably, phosphorylation at MR^S843 was markedly reduced in ULK1/2 double knockout mouse embryonic fibroblasts. Upstream, we show that ULK1 activity is inhibited by phosphorylation induced by angiotensin II via mTOR in cell culture and in vivo. These findings implicate mTOR and ULK1 as regulators of MR activity in intercalated cells, a pathway that is critical for maintaining electrolyte homeostasis.

Meglumine acridone acetate, the ionic salt of CMA and N-methylglucamine, induces apoptosis in human PBMCs via the mitochondrial pathway

Meglumine acridone acetate (MA) is used in Russia for the treatment of influenza and other acute respiratory viral infections. It was assumed, until recently, that its antiviral effect was associated with its potential ability to induce type I interferon. Advanced studies, however, have shown the failure of 10-carboxymethyl-9-acridanone (CMA) to activate human STING. As such, MA's antiviral properties are still undergoing clarification. To gain insight into MA's mechanisms of action, we carried out RNA-sequencing analysis of global transcriptomes in MA-treated (MA+) human peripheral blood mononuclear cells (PBMCs). In response to treatment, approximately 1,223 genes were found to be differentially expressed, among which 464 and 759 were identified as either up- or down-regulated, respectively. To clarify the cellular and molecular processes taking place in MA+ cells, we performed a functional analysis of those genes. We have shown that evident MA subcellular localizations are: at the nuclear envelope; inside the nucleus; and diffusely in perinuclear cytoplasm. Postulating that MA may be a nuclear receptor agonist, we carried out docking simulations with PPARα and RORα ligand binding domains including prediction and molecular dynamics-based analysis of potential MA binding poses. Finally, we confirmed that MA treatment enhanced nuclear apoptosis in human PBMCs. The research presented here, in our view, indicates that: (i) MA activity is mediated by nuclear receptors; (ii) MA is a possible PPARα and/or RORα agonist; (iii) MA has an immunosuppressive effect; and (iv) MA induces apoptosis through the mitochondrial signaling pathway.

Association of Vitamin D deficiency and Vitamin D Receptor Gene Polymorphisms with Type 2 diabetes mellitus Saudi patients

Background

Type 2 diabetes mellitus (T2DM) is a global problem. Association of multiple genes in T2DM becomes a hot point recently. This study was aimed to evaluate association of vitamin D receptor gene polymorphisms with susceptibility to T2DM.

Subjects and methods

One hundred T2DM Saudi male patients were included in this study and one hundred healthy Saudi men were used as control. For each individual, fasting blood glucose, cholesterol, HDL-C, LDL-C, HbA1c, insulin and 25-(OH) vitamin D were measured. In addition, Apal, BsmI and TaqI genotypes were performed for each subject. Data was analyzed by SPSS version 16, using Spearman's rho and ANOVA tests.

Results

There was significant inverse correlation between 25-(OH) vitamin D level and T2DM (p<0.01). HbA1c was inversely correlated with 25-(OH) vitamin D level (P<0.05). Genotype study showed that tt of TaqI genotype was higher in T2DM group compared with control group (p<0.05). Moreover, tt genotype has higher HbA1c than both TT and Tt genotypes (p<0.05).

Conclusion

An association was confirmed between TaqI genotypes and T2DM but there is no correlation between BsmI, ApaI and T2DM. In addition, HbA1c is positively correlated with tt genotype of TaqI.

Structure and Function of the Nuclear Receptor Superfamily and Current Targeted Therapies of Prostate Cancer

The nuclear receptor superfamily comprises a large group of proteins with functions essential for cell signaling, survival, and proliferation. There are multiple distinctions between nuclear superfamily classes defined by hallmark differences in function, ligand binding, tissue specificity, and DNA binding. In this review, we utilize the initial classification system, which defines subfamilies based on structure and functional difference. The defining feature of the nuclear receptor superfamily is that these proteins function as transcription factors. The loss of transcriptional regulation or gain of functioning of these receptors is a hallmark in numerous diseases. For example, in prostate cancer, the androgen receptor is a primary target for current prostate cancer therapies. Targeted cancer therapies for nuclear hormone receptors have been more feasible to develop than others due to the ligand availability and cell permeability of hormones. To better target these receptors, it is critical to understand their structural and functional regulation. Given that late-stage cancers often develop hormone insensitivity, we will explore the strengths and pitfalls of targeting other transcription factors outside of the nuclear receptor superfamily such as the signal transducer and activator of transcription (STAT).

Testosterone Induces Relaxation of Human Corpus Cavernosum Tissue of Patients With Erectile Dysfunction

Introduction

Previous research in the field of cardiovascular diseases suggests a relaxing effect of testosterone (T) on smooth muscle cells. Therefore, it was hypothesized that T could play a significant role in erection development.

Aim

To investigate the relaxing effect of T and other molecules of the T signaling pathway on human corpus cavernosum (HCC) tissue.

Methods

Samples of the HCC tissue were obtained from men who underwent penile prosthesis implantation (n = 33) for erectile dysfunction. Samples were used for isometric tension measurement in Ex Vivo experiments. Following standardized precontraction with phenylephrine, increasing doses of T or dihydrotestosterone were administered and blocked by NO/H₂S synthesis inhibitors, a K_ATP blocker, and flutamide (androgen receptor inhibitor).

Main Outcome Measure

The outcome was relaxation of the HCC tissue, normalized to a maximum precontraction achieved by phenylephrine.

Results

A dose-dependent relaxing effect of dihydrotestosterone and T was observed with a relaxation of, respectively, 24.9% ± 23.4% (P < .0001) and 41.7% ± 19.1% (P = .01) compared with 6.8% ± 15.9% for vehicle (dimethylsulfoxide) at 300 μM. The relaxing effect of T was not countered by blocking NO synthesis, H₂S synthesis, K_ATP channels, or the androgen receptor.

Clinical Implications

By understanding the underlying mechanisms of T-induced HCC relaxation, potential new therapeutic targets can be identified.

Strengths & Limitations

The strength of the study is the use of fresh HCC tissues with reproducible results. The limitation is the need for supraphysiological T levels to induce the observed effect.

Conclusion

Rapid androgen-induced relaxation of HCC is likely to occur via nongenomic mechanisms. Previously suggested mechanisms of action by which T modulates HCC relaxation have been excluded.

Van den Broeck T, Soebadi MA, Falter A, et al. Testosterone Induces Relaxation of Human Corpus Cavernosum Tissue of Patients With Erectile Dysfunction. J Sex Med 2019; 8:114–119.

Targeting transcription factors in cancer - from undruggable to reality

Mutated or dysregulated transcription factors represent a unique class of drug targets that mediate aberrant gene expression, including blockade of differentiation and cell death gene expression programmes, hallmark properties of cancers. Transcription factor activity is altered in numerous cancer types via various direct mechanisms including chromosomal translocations, gene amplification or deletion, point mutations and alteration of expression, as well as indirectly through non-coding DNA mutations that affect transcription factor binding. Multiple approaches to target transcription factor activity have been demonstrated, preclinically and, in some cases, clinically, including inhibition of transcription factor-cofactor protein-protein interactions, inhibition of transcription factor-DNA binding and modulation of levels of transcription factor activity by altering levels of ubiquitylation and subsequent proteasome degradation or by inhibition of regulators of transcription factor expression. In addition, several new approaches to targeting transcription factors have recently emerged including modulation of auto-inhibition, proteolysis targeting chimaeras (PROTACs), use of cysteine reactive inhibitors, targeting intrinsically disordered regions of transcription factors and combinations of transcription factor inhibitors with kinase inhibitors to block the development of resistance. These innovations in drug development hold great promise to yield agents with unique properties that are likely to impact future cancer treatment.

Rapid and structure-specific cellular uptake of selected steroids

Steroid hormones and their respective nuclear receptors are essential mediators in numerous physiologic and pathophysiologic processes, ranging from regulation of metabolism, immune function, and reproductive processes to the development of hormone-dependent cancers such as those of the breast and prostate. Because steroids must enter cells before activating nuclear receptors, understanding the mechanisms by which cellular uptake occurs is critical, yet a clear understanding of these mechanisms has been elusive. It is generally assumed that diffusion-driven uptake is similar across various steroids whereas an elevated cellular concentration is thought to reflect active uptake, but these assumptions have not been directly tested. Here we show that intact cells rapidly accumulate free steroids to markedly elevated concentrations. This effect varies widely depending on steroid structure; more lipophilic steroids reach more elevated concentrations. Strong preferences exist for 3β-OH, Δ5-steroids vs. 3-keto, Δ4-structural features and for progestogens vs. androgens. Surprisingly, steroid-structure-specific preferences do not require cell viability, implying a passive mechanism, and occur across cells derived from multiple tissue types. Physiologic relevance is suggested by structure-specific preferences in human prostate tissue compared with serum. On the other hand, the presence of serum proteins in vitro blocks much, but not all, of the passive accumulation, while still permitting a substantial amount of active accumulation for certain steroids. Our findings suggest that both passive and active uptake mechanisms make important contributions to the cellular steroid uptake process. The role of passive, lipophilicity-driven accumulation has previously been largely unappreciated, and its existence provides important context to studies on steroid transport and action both in vitro and in vivo.

Revealing a Mutant-Induced Receptor Allosteric Mechanism for the Thyroid Hormone Resistance

Resistance to thyroid hormone (RTH) is a clinical disorder without specific and effective therapeutic strategy, partly due to the lack of structural mechanisms for the defective ligand binding by mutated thyroid hormone receptors (THRs). We herein uncovered the prescription drug roxadustat as a novel THRβ-selective ligand with therapeutic potentials in treating RTH, thereby providing a small molecule tool enabling the first probe into the structural mechanisms of RTH. Despite a wide distribution of the receptor mutation sites, different THRβ mutants induce allosteric conformational modulation on the same His435 residue, which disrupts a critical hydrogen bond required for the binding of thyroid hormones. Interestingly, roxadustat retains hydrophobic interactions with THRβ via its unique phenyl extension, enabling the rescue of the activity of the THRβ mutants. Our study thus reveals a critical receptor allosterism mechanism for RTH by mutant THRβ, providing a new and viable therapeutic strategy for the treatment of RTH.

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We identified a novel THR ligand that effectively binds to THRβ mutants

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Structures revealed mechanisms for the RTH controlled by a key residue switch

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Roxadustat retains unique hydrophobic interactions with THRβ mutants

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We provide a promising approach to design THR ligands in treating RTH

Nuclear receptors regulate alternative lengthening of telomeres through a novel noncanonical FANCD2 pathway

Alternative lengthening of telomeres (ALT) is known to use homologous recombination (HR) to replicate telomeric DNA in a telomerase-independent manner. However, the detailed process remains largely undefined. It was reported that nuclear receptors COUP-TFII and TR4 are recruited to the enriched GGGTCA variant repeats embedded within ALT telomeres, implicating nuclear receptors in regulating ALT activity. Here, we identified a function of nuclear receptors in ALT telomere maintenance that involves a direct interaction between COUP-TFII/TR4 and FANCD2, the key protein in the Fanconi anemia (FA) DNA repair pathway. The COUP-TFII/TR4-FANCD2 complex actively induces the DNA damage response by recruiting endonuclease MUS81 and promoting the loading of the PCNA-POLD3 replication complex in ALT telomeres. Furthermore, the COUP-TFII/TR4-mediated ALT telomere pathway does not require the FA core complex or the monoubiquitylation of FANCD2, key steps in the canonical FA pathway. Thus, our findings reveal that COUP-TFII/TR4 regulates ALT telomere maintenance through a novel noncanonical FANCD2 pathway.

9-Cis-13,14-dihydroretinoic acid, a new endogenous mammalian ligand of retinoid X receptor and the active ligand of a potential new vitamin A category: vitamin A5

The identity of the endogenous RXR ligand has not been conclusively determined, even though several compounds of natural origin, including retinoids and fatty acids, have been postulated to fulfill this role. Filling this gap, 9-cis-13,14-dihydroretinoic acid (9CDHRA) was identified as an endogenous RXR ligand in mice. This review examines the physiological relevance of various potential endogenous RXR ligands, especially 9CDHRA. The elusive steps in the metabolic synthesis of 9CDHRA, as well as the nutritional/nutrimetabolic origin of 9CDHRA, are also explored, along with the suitability of the ligand to be the representative member of a novel vitamin A class (vitamin A5).

Learning Physiology From Inherited Kidney Disorders

The identification of genes causing inherited kidney diseases yielded crucial insights in the molecular basis of disease and improved our understanding of physiological processes that operate in the kidney. Monogenic kidney disorders are caused by mutations in genes coding for a large variety of proteins including receptors, channels and transporters, enzymes, transcription factors, and structural components, operating in specialized cell types that perform highly regulated homeostatic functions. Common variants in some of these genes are also associated with complex traits, as evidenced by genome-wide association studies in the general population. In this review, we discuss how the molecular genetics of inherited disorders affecting different tubular segments of the nephron improved our understanding of various transport processes and of their involvement in homeostasis, while providing novel therapeutic targets. These include inherited disorders causing a dysfunction of the proximal tubule (renal Fanconi syndrome), with emphasis on epithelial differentiation and receptor-mediated endocytosis, or affecting the reabsorption of glucose, the handling of uric acid, and the reabsorption of sodium, calcium, and magnesium along the kidney tubule.

Estrogen-Receptor Expression and Function in Female Reproductive Disease

Estrogen receptors (ER) include ER alpha, ER beta and new membrane receptor G protein-coupled receptor 30 (GPR30). Estrogen receptors are key receptors to maintain ovarian granulosa cell differentiation, follicle and oocyte growth and development, and ovulation function. The abnormal functions of estrogen, its receptors, and estradiol synthesis-related enzymes are closely related to clinical reproductive endocrine diseases, such as polycystic ovary syndrome (PCOS) and endometriosis (EMS). At present, hormone therapy is the main treatment for ovarian-related diseases, and a stable hormone environment is established by regulating ovarian function. In recent years, some estrogen-related drugs have made great progress, such as clomiphene, which is a nonsteroidal antiestrogen drug in clinical application. This article elaborates on the regulatory role of estrogen and its nuclear receptors and membrane receptors in oocyte development, especially female reproductive diseases related to the abnormal expression of estrogen and its receptors. We also highlighted the latest advances of treatment strategy for these diseases and the application of related targeted small molecule drugs in clinical research and treatment, so as to provide reference for the treatment of female reproductive diseases.

Identification of new octamer transcription factor 1-target genes upregulated in castration-resistant prostate cancer

Octamer transcription factor 1 (OCT1) is an androgen receptor (AR)‐interacting partner and regulates the expression of target genes in prostate cancer cells. However, the function of OCT1 in castration‐resistant prostate cancer (CRPC) is not fully understood. In the present study, we used 22Rv1 cells as AR‐positive CRPC model cells to analyze the role of OCT1 in CRPC. We showed that OCT1 knockdown suppressed cell proliferation and migration of 22Rv1 cells. Using microarray analysis, we identified four AR and OCT1‐target genes, disks large‐associated protein 5 (DLGAP5), kinesin family member 15 (KIF15), non‐SMC condensin I complex subunit G (NCAPG), and NDC80 kinetochore complex component (NUF2) in 22Rv1 cells. We observed that knockdown of DLGAP5 and NUF2 suppresses growth and migration of 22Rv1 cells. Furthermore, immunohistochemical analysis showed that positive expression of DLGAP5 in prostate cancer specimens is related to poor cancer‐specific survival rates of patients. Notably, enhanced expression of DLGAP5 was observed in CRPC tissues of patients. Thus, our findings suggest that these four genes regulated by the AR/OCT1 complex could have an important role in CRPC progression.

Molecular determinants for the polarization of macrophage and osteoclast

Emerging evidence suggest that macrophage and osteoclast are two competing differentiation outcomes from myeloid progenitors. In this review, we summarize recent advances in the understanding of the molecular mechanisms controlling the polarization of macrophage and osteoclast. These include nuclear receptors/transcription factors such as peroxisome proliferator-activated receptor γ (PPARγ) and estrogen-related receptor α (ERRα), their transcription cofactor PPARγ coactivator 1-β (PGC-1β), metabolic factors such as mitochondrial complex I (CI) component NADH:ubiquinone oxidoreductase iron-sulfur protein 4 (Ndufs4), as well as transmembrane receptors such as very-low-density-lipoprotein receptor (VLDLR). These molecular rheostats promote osteoclast differentiation but suppress proinflammatory macrophage activation and inflammation, by acting lineage-intrinsically, systemically or cross generation. These findings provide new insights to the understanding of the interactions between innate immunity and bone remodeling, advancing the field of osteoimmunology.

Therapeutic targeting of nuclear receptors, liver X and retinoid X receptors, for Alzheimer's disease

After 15 years of research into Alzheimer's disease (AD) therapeutics, including billions of US dollars provided by federal agencies, pharmaceutical companies, and private foundations, there are still no meaningful therapies that can delay the onset or slow the progression of AD. An understanding of the proteolytic processing of amyloid precursor protein (APP) and the hypothesis that pathogenic mechanisms in familial and sporadic forms of AD are very similar led to the assumption that pharmacological inhibition of secretases or immunological approaches to clear amyloid depositions in the brain would have been the core to drug discovery strategies and successful therapies. However, there are other understudied approaches including targeting genes, gene networks, and metabolic pathways outside the proteolytic processing of APP. The advancement of newly developed sequencing technologies and mass spectrometry, as well as the availability of animal models expressing human apolipoprotein E isoforms, has been critical in rationalizing additional AD therapeutics. The purpose of this review is to present one of those approaches, based on the role of ligand-activated nuclear liver X and retinoid X receptors in the brain. This therapeutic approach was initially proposed utilizing in vitro models 15 years ago and has since been examined in numerous studies using AD-like mouse models. LINKED ARTICLES: This article is part of a themed section on Therapeutics for Dementia and Alzheimer's Disease: New Directions for Precision Medicine. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v176.18/issuetoc.

Analysis of global and gene-specific acetylation of histones in the liver of American bullfrog (Rana catesbeiana) tadpoles acclimated to low temperature

Severe environmental stressors such as low temperatures can affect gene expression by changing epigenetic states. American bullfrog (Rana catesbeiana) can overwinter as tadpoles, which can be active even in winter. However, the molecular mechanisms of epigenetic controls by which the tadpoles acclimate to low temperature are still unclear. In this study, we aimed to clarify the molecular mechanisms of global and gene-specific epigenetic regulations of low-temperature acclimation. We found that the global acetylation was decreased in the liver of bullfrog tadpoles acclimated to low temperature. The amounts of transcripts for two histone acetyltransferases were higher in the liver of tadpoles acclimated to low temperature than in those acclimated to warm temperature, while we observed no significant differences in the amounts of transcripts for histone deacetylases. We also found that the amounts of transcripts and acetylated histones on the specific temperature-responsive genes scd and cyp7a1 whose transcripts were increased and decreased, respectively, in response to low temperature were positively correlated. Cellular acetyl-CoA levels were higher in the liver of tadpoles acclimated to low temperature than in those acclimated to warm temperature. These results contradicted the states of histone acetylation, suggesting that bullfrog tadpoles have different epigenetic mechanisms to modify the histones when compared with those of other organisms such as reptiles and mammals, even though the relationship between the transcript amount and the states of histone acetylation on temperature-responsive genes was similar to that of mammals.

Nuclear hormone receptors in parasitic Platyhelminths

Nuclear receptors (NRs) belong to a large protein superfamily which includes intracellular receptors for secreted hydrophobic signal molecules, such as steroid hormones and thyroid hormones. They regulate development and reproduction in metazoans by binding to the promoter region of their target gene to activate or repress mRNA synthesis. Isolation and characterization of NRs in the parasitic trematode Schistosoma mansoni identified two homologues of mammalian thyroid receptor (TR). This was the first known protostome exhibiting TR homologues. Three novel NRs each possess a novel set of two DNA binding domains (DBD) in tandem with a ligand binding domain (LBD) (2DBD-NRs) isolated in Schistosoma mansoni revealed a novel NR modular structure: A/B-DBD-DBD-hinge-LBD. Full length cDNA of several NRs have been isolated and studied in the parasitic trematodes S. mansoni, S. japonicum and in the cestode Echinococcus multilocularis. The genome of the blood flukes S. mansoni, S. japonicum and S. haematobium, the liver fluke Clonorchis sinensis and the cestode Echinococcus multilocularis have been sequenced. Study of the NR complement in parasitic Platyhelminths will help us to understand the role of NRs in regulation of their development and understand the evolution of NR in animals.

Engagement of Nuclear Coactivator 7 by 3-Hydroxyanthranilic Acid Enhances Activation of Aryl Hydrocarbon Receptor in Immunoregulatory Dendritic Cells

Indoleamine 2,3-dioxygenase 1 (IDO1) catalyzes the first step in the kynurenine pathway of tryptophan (Trp) degradation that produces several biologically active Trp metabolites. L-kynurenine (Kyn), the first byproduct by IDO1, promotes immunoregulatory effects via activation of the Aryl hydrocarbon Receptor (AhR) in dendritic cells (DCs) and T lymphocytes. We here identified the nuclear coactivator 7 (NCOA7) as a molecular target of 3-hydroxyanthranilic acid (3-HAA), a Trp metabolite produced downstream of Kyn along the kynurenine pathway. In cells overexpressing NCOA7 and AhR, the presence of 3-HAA increased the association of the two molecules and enhanced Kyn-driven, AhR-dependent gene transcription. Physiologically, conventional (cDCs) but not plasmacytoid DCs or other immune cells expressed high levels of NCOA7. In cocultures of CD4⁺ T cells with cDCs, the co-addition of Kyn and 3-HAA significantly increased the induction of Foxp3⁺ regulatory T cells and the production of immunosuppressive transforming growth factor β in an NCOA7-dependent fashion. Thus, the co-presence of NCOA7 and the Trp metabolite 3-HAA can selectively enhance the activation of ubiquitary AhR in cDCs and consequent immunoregulatory effects. Because NCOA7 is often overexpressed and/or mutated in tumor microenvironments, our current data may provide evidence for a new immune check-point mechanism based on Trp metabolism and AhR.

PPAR Receptors Expressed from Vectors Containing CMV Promoter Can Enhance Self-Transcription in the Presence of Fatty Acids from CLA-Enriched Egg Yolks-A Novel Method for Studies of PPAR Ligands

PPAR receptors are ligand-dependent transcription factors activated in response to various small lipophilic ligands controlling the expression of different genes involved in cellular differentiation, development, metabolism, and tumorigenesis. Unexpectedly, our previous studies have shown that single plasmid-based expression of PPARs under the control of CMV promoter/enhancer was significantly elevated in the presence of PPAR agonists. Here we show that the PPAR reporters controlled by the CMV promoter/enhancer, that was shown to contain three internal non-canonical PPRE elements, can be used as a fast screening system for more effective PPAR ligands. This model allowed us to confirm our previous results indicating that fatty acids of CLA-enriched egg yolks (EFA-CLAs) are efficient PPAR ligands that can specifically upregulate the expression of PPARα and PPARγ leading to downregulation of MCF-7 cancer cell proliferation. We also show that synthetic cis9,trans11CLA is more effective in transactivation of PPARγ, while trans10,cis12CLA of PPARα receptor indicating the selectivity of the CLA isomers. This report presents a novel, fast, and reliable strategy for simple testing of PPAR ligands using PPAR expressing plasmids containing the CMV promoter/enhancer that can trigger the positive feedback loop of PPAR self-transcription in the presence of PPAR ligands.

Novel interactions between ERα-36 and STAT3 mediate breast cancer cell migration

Background

Breast cancer is the leading cause of cancer death in women worldwide which is closely related to metastasis. But the exact molecular mechanism of ERα-36 and STAT3 on metastasis is still not fully understood.

Methods

MCF-7 and MDA-MB-231 human breast cancer cell lines and MCF-10A were overexpressioned or knockdown ERα-36 and STAT3 and tested for migration, invasion and proliferation assays. Direct interaction of STAT3 and ERα-36 were analyzed by coimmunoprecipitation assays. The effect of STAT3 and ERα-36 on MMP2/9 expression was analyzed by qPCR and western blotting. STAT3 phospholyation and acetylation by ERα-36 and p300 were observed and quantified by coimmunoprecipitation assays and western blotting.

Results

Cross-talk between ERα-36 and STAT3 was demonstrated to mediate through a direct physical association between the two proteins. Furthermore, the interaction between ERα-36 and STAT3 was demonstrated to give rise to functional changes in their signaling events. Both MMP2 and MMP9 expression require the binding of the newly identified protein complex, ERα-36-STAT3, to its promoter, the second phase, which is more robust, depends on ERα-mediated recruitment of p300 onto the complex and the subsequent acetylation of STAT3. In addition, STAT3 is tyrosine-phosphorylated in a biphasic manner, and the late phase requires ERα-36-mediated p300-dependent acetylation. Furthermore, interference with acetylation of STAT3 by overexpression of acetylation null STAT3 mutant led to the loss of MMP2 and MMP9 expression. ChIP analysis and reporter gene assays revealed that ERα-36-STAT3 complex binding to the MMP2 and MMP9 promoter led to an enhanceosome formation and facilitated MMP2 and MMP9 expression.

Conclusions

Our studies demonstrate for the first time that the function of MMP2 and MMP9 in breast cancer cell migration, which is mediated by interactions between ERα-36 and STAT3.

A Narrative Role of Vitamin D and Its Receptor: With Current Evidence on the Gastric Tissues

Vitamin D is a major steroid hormone that is gaining attention as a therapeutic molecule. Due to the general awareness of its importance for the overall well-being, vitamin D deficiency (VDD) is now recognized as a major health issue. The main reason for VDD is minimal exposure to sunlight. The vitamin D receptor (VDR) is a member of the steroid hormone receptors that induces a cascade of cell signaling to maintain healthy Ca²⁺ levels that serve to regulate several biological functions. However, the roles of vitamin D and its metabolism in maintaining gastric homeostasis have not yet been completely elucidated. Currently, there is a need to increase the vitamin D status in individuals worldwide as it has been shown to improve musculoskeletal health and reduce the risk of chronic illnesses, including some cancers, autoimmune and infectious diseases, type 2 diabetes mellitus, neurocognitive disorders, and general mortality. The role of vitamin D in gastric homeostasis is crucial and unexplored. This review attempts to elucidate the central role of vitamin D in preserving and maintaining the overall health and homeostasis of the stomach tissue.

Androgens sensitise mice to glucocorticoid-induced insulin resistance and fat accumulation

AIMS/HYPOTHESIS

Chronic glucocorticoid therapy causes insulin resistance, dyslipidaemia, abnormal fat accumulation, loss of muscle mass and osteoporosis. Here we describe a hitherto unknown sexual dimorphism in the metabolic response to chronic glucocorticoid exposure in mice. This led us to investigate whether glucocorticoid-induced insulin resistance and obesity were dependent on sex hormones.

METHODS

Male and female CD1 mice were treated for 4 weeks with supraphysiological doses (~250 μg/day) of corticosterone, the main glucocorticoid in rodents, or equivalent volume of vehicle (drinking water without corticosterone). To investigate the effects of sex hormones, a separate group of mice were either orchidectomised or ovariectomised prior to corticosterone treatment, with or without dihydrotestosterone replacement. Body composition was determined before and after corticosterone treatment, and insulin tolerance was assessed after 7 and 28 days of treatment. Adipocyte morphology was assessed in white and brown adipose tissues by immunohistochemistry, and fasting serum concentrations of NEFA, triacylglycerols, total cholesterol and free glycerol were measured using colorimetric assays. Obesity- and diabetes-related hormones were measured using multiplex assays, and RNA and protein expression in adipose tissues were measured by RT-PCR and immunoblotting, respectively.

RESULTS

Chronic corticosterone treatment led to insulin resistance, fasting hyperinsulinaemia, increased adiposity and dyslipidaemia in male, but not female mice. In males, orchidectomy improved baseline insulin sensitivity and attenuated corticosterone-induced insulin resistance, but did not prevent fat accumulation. In androgen-deficient mice (orchidectomised males, and intact and ovariectomised females) treated with dihydrotestosterone, corticosterone treatment led to insulin resistance and dyslipidaemia. In brown adipose tissue, androgens were required for corticosterone-induced intracellular lipid accumulation ('whitening'), and dihydrotestosterone specifically exacerbated corticosterone-induced accumulation of white adipose tissue by increasing adipocyte hypertrophy. Androgens also suppressed circulating adiponectin concentrations, but corticosterone-induced insulin resistance did not involve additional suppression of adiponectin levels. In white adipose tissue, androgens were required for induction of the glucocorticoid target gene Gilz (also known as Tsc22d3) by corticosterone.

CONCLUSIONS/INTERPRETATION

In mice, androgens potentiate the development of insulin resistance, fat accumulation and brown adipose tissue whitening following chronic glucocorticoid treatment.