Signaling by nuclear receptors

Retinoid X Receptor α Regulates DHA-Dependent Spinogenesis and Functional Synapse Formation In Vivo

Coordinated intracellular and extracellular signaling is critical to synapse development and functional neural circuit wiring. Here, we report that unesterified docosahexaenoic acid (DHA) regulates functional synapse formation in vivo via retinoid X receptor α (Rxra) signaling. Using Rxra conditional knockout (cKO) mice and virus-mediated transient gene expression, we show that endogenous Rxra plays important roles in regulating spinogenesis and excitatory synaptic transmission in cortical pyramidal neurons. We further show that the effects of RXRA are mediated through its DNA-binding domain in a cell-autonomous and reversible manner. Moreover, unesterified DHA increases spine formation and excitatory synaptic transmission in vivo in an Rxra-dependent fashion. Rxra cKO mice generally behave normally but show deficits in behavior tasks associated with social memory. Together, these results demonstrate that unesterified DHA signals through RXRA to regulate spinogenesis and functional synapse formation, providing insight into the mechanism through which DHA promotes brain development and cognitive function.

Endocrine-Disrupting Compounds: An Overview on Their Occurrence in the Aquatic Environment and Human Exposure

Endocrine-disrupting compounds (EDCs) as emerging contaminants have accumulated in the aquatic environment at concentration levels that have been determined to be significant to humans and animals. Several compounds belong to this family, from natural substances (hormones such as estrone, 17-estradiol, and estriol) to synthetic chemicals, especially pesticides, pharmaceuticals, and plastic-derived compounds (phthalates, bisphenol A). In this review, we discuss recent works regarding EDC occurrence in the aquatic compartment, strengths and limitations of current analytical methods used for their detection, treatment technologies for their removal from water, and the health issues that they can trigger in humans. Nowadays, many EDCs have been identified in significant amounts in different water matrices including drinking water, thus increasing the possibility of entering the food chain. Several studies correlate human exposure to high concentrations of EDCs with serious effects such as infertility, thyroid dysfunction, early puberty, endometriosis, diabetes, and obesity. Although our intention is not to explain all disorders related to EDCs exposure, this review aims to guide future research towards a deeper knowledge of EDCs’ contamination and accumulation in water, highlighting their toxicity and exposure risks to humans.

Glyphosate and the key characteristics of an endocrine disruptor: A review

Glyphosate is a large-spectrum herbicide that was introduced on the market in 1974. Due to its important impact on the crop industry, it has been significantly diversified and expanded being considered the most successful herbicide in history. Currently, its massive use has led to a wide environmental diffusion and its human consumption through food products has made possible to detect it in urine, serum, and breast milk samples. Nevertheless, recent studies have questioned its safety and international agencies have conflicting opinions about its effects on human health, mainly as an endocrine-disrupting chemical (EDC) and its carcinogenic capacity. Here, we conduct a comprehensive review where we describe the most important findings of the glyphosate effects in the endocrine system and asses the mechanistic evidence to classify it as an EDC. We use as guideline the ten key characteristics (KCs) of EDC proposed in the expert consensus statement published in 2020 (La Merrill et al., 2020) and discuss the scopes of some epidemiological studies for the evaluation of glyphosate as possible EDC. We conclude that glyphosate satisfies at least 8 KCs of an EDC, however, prospective cohort studies are still needed to elucidate the real effects in the human endocrine system.

Genome-Wide Identification, Comparison, and Expression Analysis of Transcription Factors in Ascidian Styela clava

Tunicates include diverse species, as they are model animals for evolutionary developmental biology study. The embryonic development of tunicates is known to be extensively regulated by transcription factors (TFs). Styela clava, the globally distributed invasive tunicate, exhibits a strong capacity for environmental adaptation. However, the TFs were not systematically identified and analyzed. In this study, we reported 553 TFs categorized into 60 families from S. clava, based on the whole genome data. Comparison of TFs analysis among the tunicate species revealed that the gene number in the zinc finger superfamily displayed the most significant discrepancy, indicating this family was under the highly evolutionary selection and might be related to species differentiation and environmental adaptation. The greatest number of TFs was discovered in the Cys2His2-type zinc finger protein (zf-C2H2) family in S. clava. From the point of temporal view, more than half the TFs were expressed at the early embryonic stage. The expression correlation analysis revealed the existence of a transition for TFs expression from early embryogenesis to the later larval development in S. clava. Eight Hox genes were identified to be located on one chromosome, exhibiting different arrangement and expression patterns, compared to Ciona robusta (C. intestinalis type A). In addition, a total of 23 forkhead box (fox) genes were identified in S. clava, and their expression profiles referred to their potential roles in neurodevelopment and sensory organ development. Our data, thus, provides crucial clues to the potential functions of TFs in development and environmental adaptation in the leathery sea squirt.

Emerging functions of the nuclear receptor LRH-1 in liver physiology and pathology

Nuclear receptors play pleiotropic roles in cell differentiation, development, proliferation, and metabolic processes to govern liver physiology and pathology. The nuclear receptor, liver receptor homolog-1 (LRH-1, NR5A2), originally identified in the liver as a regulator of bile acid and cholesterol homeostasis, was recently recognized to coordinate a multitude of other hepatic metabolic processes, including glucose and lipid processing, methyl group sensing, and cellular stress responses. In this review, we summarize the physiological and pathophysiological functions of LRH-1 in the liver, as well as the molecular mechanisms underlying these processes. This review also focuses on the recent advances highlighting LRH-1 as an attractive target for liver-associated diseases, such as non-alcoholic fatty liver disease (NAFLD) and hepatocellular carcinoma (HCC).

From Oncogenic Signaling Pathways to Single-Cell Sequencing of Immune Cells: Changing the Landscape of Cancer Immunotherapy

Over the past decade, there have been remarkable advances in understanding the signaling pathways involved in cancer development. It is well-established that cancer is caused by the dysregulation of cellular pathways involved in proliferation, cell cycle, apoptosis, cell metabolism, migration, cell polarity, and differentiation. Besides, growing evidence indicates that extracellular matrix signaling, cell surface proteoglycans, and angiogenesis can contribute to cancer development. Given the genetic instability and vast intra-tumoral heterogeneity revealed by the single-cell sequencing of tumoral cells, the current approaches cannot eliminate the mutating cancer cells. Besides, the polyclonal expansion of tumor-infiltrated lymphocytes in response to tumoral neoantigens cannot elicit anti-tumoral immune responses due to the immunosuppressive tumor microenvironment. Nevertheless, the data from the single-cell sequencing of immune cells can provide valuable insights regarding the expression of inhibitory immune checkpoints/related signaling factors in immune cells, which can be used to select immune checkpoint inhibitors and adjust their dosage. Indeed, the integration of the data obtained from the single-cell sequencing of immune cells with immune checkpoint inhibitors can increase the response rate of immune checkpoint inhibitors, decrease the immune-related adverse events, and facilitate tumoral cell elimination. This study aims to review key pathways involved in tumor development and shed light on single-cell sequencing. It also intends to address the shortcomings of immune checkpoint inhibitors, i.e., their varied response rates among cancer patients and increased risk of autoimmunity development, via applying the data from the single-cell sequencing of immune cells.

Molecular modeling and molecular dynamics simulation studies on thyroid hormone receptor from Rattus norvegicus: role of conserved water molecules

Thyroid hormone receptor (THR) belongs to the nuclear receptor (NR) superfamily that is activated by binding of appropriate ligand molecules (thyroid hormones). These receptors directly bind to specific DNA sequences for gene expression, which is essential for metabolism, homeostasis, and the development of organisms, making it an important drug target. Extensive MD-simulation studies of triiodothyronine (T3) docked modeled rnTHRβ1 structures have indicated the presence of twelve conserved water molecules at the DNA-DBD (DNA binding domain) interface. The W1-W5 water centers have been involved in the recognition between the A-chain of DBD to C-chain of DNA, W6 and W7 mediated the interaction between A-chain of DBD and D-chain of DNA, W8 and W9 recognized the B-chain of DBD and C-chain of DNA, and W9-W12 centers conjugated the residues of B-chain of DBD to D-chain of DNA through hydrogen bonds. The conformation flexibility of Phe272 and Met313 residues in the absence of T3 at the LBD (ligand-binding domain) region have been observed and reported.

Cell-specific epigenetic drivers of pathogenesis in rheumatoid arthritis

Rheumatoid arthritis is a complex, inflammatory autoimmune disease, which is characterized by pain, swelling and joint damage driven by the altered behavior of a number of different cell types such as synovial fibroblasts macrophages and lymphocytes. The mechanism underlying pathogenesis is unclear but increasing evidence points to altered epigenetic regulation within these cell types which promotes the activated destructive behavior that underlies disease pathogenesis. This review summarizes the key epigenetic modifications in the most important cells types in rheumatoid arthritis, which are associated with disease activity. We also discuss emerging avenues of research focusing on readers of epigenetic markers which may serve to be potential therapeutic targets.

Heterogeneity in Signaling Pathway Activity within Primary and between Primary and Metastatic Breast Cancer

Targeted therapy aims to block tumor-driving signaling pathways and is generally based on analysis of one primary tumor (PT) biopsy. Tumor heterogeneity within PT and between PT and metastatic breast lesions may, however, impact the effect of a chosen therapy. Whereas studies are available that investigate genetic heterogeneity, we present results on phenotypic heterogeneity by analyzing the variation in the functional activity of signal transduction pathways, using an earlier developed platform to measure such activity from mRNA measurements of pathways' direct target genes. Statistical analysis comparing macro-scale variation in pathway activity on up to five spatially distributed PT tissue blocks (n = 35), to micro-scale variation in activity on four adjacent samples of a single PT tissue block (n = 17), showed that macro-scale variation was not larger than micro-scale variation, except possibly for the PI3K pathway. Simulations using a "checkerboard clone-size" model showed that multiple small clones could explain the higher micro-scale variation in activity found for the TGFβ and Hedgehog pathways, and that intermediate/large clones could explain the possibly higher macro-scale variation of the PI3K pathway. While within PT, pathway activities presented a highly positive correlation, correlations weakened between PT and lymph node metastases (n = 9), becoming even worse for PT and distant metastases (n = 9), including a negative correlation for the ER pathway. While analysis of multiple sub-samples of a single biopsy may be sufficient to predict PT response to targeted therapies, metastatic breast cancer treatment prediction requires analysis of metastatic biopsies. Our findings on phenotypic intra-tumor heterogeneity are compatible with emerging ideas on a Big Bang type of cancer evolution in which macro-scale heterogeneity appears not dominant.

Potential therapeutic uses of rexinoids

The discovery of nuclear receptors, particularly retinoid X receptors (RXR), and their involvement in numerous pathways related to development sparked interest in their immunomodulatory properties. Genetic models using deletion or overexpression of RXR and the subsequent development of several small molecules that are agonists or antagonists of this receptor support a promising therapeutic role for these receptors in immunology. Bexarotene was approved in 1999 for the treatment of cutaneous T cell lymphoma. Several other small molecule RXR agonists have since been synthesized with limited preclinical development, but none have yet achieved FDA approval. Cancer treatment has recently been revolutionized with the introduction of immune checkpoint inhibitors, but their success has been restricted to a minority of patients. This review showcases the emerging immunomodulatory effects of RXR and the potential of small molecules that target this receptor as therapies for cancer and other diseases. Here we describe the essential roles that RXR and partner receptors play in T cells, dendritic cells, macrophages and epithelial cells, especially within the tumor microenvironment. Most of these effects are site and cancer type dependent but skew immune cells toward an anti-inflammatory and anti-tumor effect. This beneficial effect on immune cells supports the promise of combining rexinoids with approved checkpoint blockade therapies in order to enhance efficacy of the latter and to delay or potentially eliminate drug resistance. The data compiled in this review strongly suggest that targeting RXR nuclear receptors is a promising new avenue in immunomodulation for cancer and other chronic inflammatory diseases.

What do Transcription Factors Interact With?

Although we have made significant progress, we still possess a limited understanding of how genomic and epigenomic information directs gene expression programs through sequence-specific transcription factors (TFs). Extensive research has settled on three general classes of TF targets in metazoans: promoter accessibility via chromatin regulation (e.g., SAGA), assembly of the general transcription factors on promoter DNA (e.g., TFIID), and recruitment of RNA polymerase (Pol) II (e.g., Mediator) to establish a transcription pre-initiation complex (PIC). Here we discuss TFs and their targets. We also place this in the context of our current work with Saccharomyces (yeast), where we find that promoters typically lack an architecture that supports TF function. Moreover, yeast promoters that support TF binding also display interactions with cofactors like SAGA and Mediator, but not TFIID. It is unknown to what extent all genes in metazoans require TFs and their cofactors.

Emerging roles of steroid receptor coactivators in stromal cell responses

Tissue parenchyma is the functional unit of an organ and all of the remaining cells within that organ collectively make up the tissue stroma. The stroma includes fibroblasts, endothelial cells, immune cells, and nerves. Interactions between stromal and epithelial cells are essential for tissue development and healing after injury. These interactions are governed by growth factors, inflammatory cytokines and hormone signaling cascades. The steroid receptor coactivator (SRC) family of proteins includes three transcriptional coactivators that facilitate the assembly of multi-protein complexes to induce gene expression in response to activation of many cellular transcription factor signaling cascades. They are ubiquitously expressed and are especially critical for the developmental function of steroid hormone responsive tissues. The SRCs are overexpressed in multiple cancers including breast, ovarian, prostate and endometrial cancers. In this review, we focus on the role of the SRCs in regulating the functions of stromal cell components responsible for angiogenesis, inflammation and cell differentiation.

Androgen Receptor Is Dispensable for X-Zone Regression in the Female Adrenal but Regulates Post-Partum Corticosterone Levels and Protects Cortex Integrity

Adrenal androgens are fundamental mediators of ovarian folliculogenesis, embryonic implantation, and breast development. Although adrenal androgen function in target tissues are well characterized, there is little research covering the role of androgen-signaling within the adrenal itself. Adrenal glands express AR which is essential for the regression of the X-zone in male mice. Female mice also undergo X-zone regression during their first pregnancy, however whether this is also controlled by AR signaling is unknown. To understand the role of the androgen receptor (AR) in the female adrenal, we utilized a Cyp11a1-Cre to specifically ablate AR from the mouse adrenal cortex. Results show that AR-signaling is dispensable for adrenal gland development in females, and for X-zone regression during pregnancy, but is required to suppress elevation of corticosterone levels post-partum. Additionally, following disruption to adrenal AR, aberrant spindle cell development is observed in young adult females. These results demonstrate sexually dimorphic regulation of the adrenal X-zone by AR and point to dysfunctional adrenal androgen signaling as a possible mechanism in the early development of adrenal spindle cell hyperplasia.

Sexual Dimorphism in Innate Immunity: The Role of Sex Hormones and Epigenetics

Sexual dimorphism refers to differences between biological sexes that extend beyond sexual characteristics. In humans, sexual dimorphism in the immune response has been well demonstrated, with females exhibiting lower infection rates than males for a variety of bacterial, viral, and parasitic pathogens. There is also a substantially increased incidence of autoimmune disease in females compared to males. Together, these trends indicate that females have a heightened immune reactogenicity to both self and non-self-molecular patterns. However, the molecular mechanisms driving the sexually dimorphic immune response are not fully understood. The female sex hormones estrogen and progesterone, as well as the male androgens, such as testosterone, elicit direct effects on the function and inflammatory capacity of immune cells. Several studies have identified a sex-specific transcriptome and methylome, independent of the well-described phenomenon of X-chromosome inactivation, suggesting that sexual dimorphism also occurs at the epigenetic level. Moreover, distinct alterations to the transcriptome and epigenetic landscape occur in synchrony with periods of hormonal change, such as puberty, pregnancy, menopause, and exogenous hormone therapy. These changes are also mirrored by changes in immune cell function. This review will outline the evidence for sex hormones and pregnancy-associated hormones as drivers of epigenetic change, and how this may contribute to the sexual dimorphism. Determining the effects of sex hormones on innate immune function is important for understanding sexually dimorphic autoimmune diseases, sex-specific responses to pathogens and vaccines, and how innate immunity is altered during periods of hormonal change (endogenous or exogenous).

(3α,5α)3-hydroxypregnan-20-one (3α,5α-THP) regulation of hypothalamic and extrahypothalamic corticotropin releasing factor (CRF): Sexual dimorphism and brain region specificity in Sprague Dawley rats

CRF is the main activator of the hypothalamic-pituitary-adrenal (HPA) axis in response to stress. CRF neurons are found mainly in the hypothalamus, but CRF positive cells and CRF1 receptors are also found in extrahypothalamic structures, including amygdala (CeA), hippocampus, NAc and VTA. CRF release in the hypothalamus is regulated by inhibitory GABAergic interneurons and extrahypothalamic glutamatergic inputs, and disruption of this balance is found in stress-related disorders and addiction. (3α,5α)3-hydroxypregnan-20-one (3α,5α-THP), the most potent positive modulator of GABA_A receptors, attenuates the stress response reducing hypothalamic CRF mRNA expression and ACTH and corticosterone serum levels. In this study, we explored 3α,5α-THP regulation of hypothalamic and extrahypothalamic CRF mRNA and peptide expression, in male and female Sprague Dawley rats, following vehicle or 3α,5α-THP administration (15 mg/kg). In the hypothalamus, we found sex differences in CRF mRNA expression (females +74%, p < 0.01) and CRF peptide levels (females -71%, p < 0.001). 3α,5α-THP administration reduced hypothalamic CRF mRNA expression only in males (-50%, p < 0.05) and did not alter CRF peptide expression in either sex. In hippocampus and CeA, 3α,5α-THP administration reduced CRF peptide concentrations only in the male (hippocampus -29%, p < 0.05; CeA -62%, p < 0.01). In contrast, 3α,5α-THP injection increased CRF peptide concentration in the VTA of both males (+32%, p < 0.01) and females (+26%, p < 0.01). The results show sex and region-specific regulation of CRF signals and the response to 3α,5α-THP administration. This data may be key to successful development of therapeutic approaches for stress-related disorders and addiction.

Type II nuclear receptors with potential role in Alzheimer disease

Nuclear receptors are ligand-activated transcription factors that can modulated cellular processes involved in the development, homeostasis, cell proliferation, metabolism, and reproduction through the control of the specific genetic and molecular program. In the central nervous system, they are key regulators of neural stem cell fate decisions and can modulate the physiology of different brain cells. Over the past decades, a large body of evidence has supported that nuclear receptors are potential therapeutic targets for the treatment of neurodegenerative disorders such as Alzheimer's disease, the most common dementia worldwide, and the main cause of disability in later life. This disease is characterized by the progressive accumulation of amyloid-beta peptides and hyperphosphorylated tau protein that can explain alterations in synaptic transmission and plasticity; loss of dendritic spines; increased in reactive microglia and inflammation; reduction of neuronal stem cells number; myelin and vascular alterations that finally leads to increased neuronal death. Here, we present a review of type II no steroidal nuclear receptors that form obligatory heterodimers with the Retinoid X Receptor (RXR) and its potential in the therapeutic of AD. Activation of type II nuclear receptor by synthetic agonist leads to transcriptional regulation of specific genes that acts counteracting against the detrimental effects of amyloid-beta peptides and hyperphosphorylated tau in neuronal cells recovering the functionality of the synapses. But also, activation of type II nuclear receptor leads to modifications in APP metabolism, repression of inflammatory cascade and inductors of the generation of neuronal stem cells and progenitor cells supporting its potential therapeutics role for Alzheimer's disease.

Comprehensive mapping of the human cytokine gene regulatory network

Proper cytokine gene expression is essential in development, homeostasis and immune responses. Studies on the transcriptional control of cytokine genes have mostly focused on highly researched transcription factors (TFs) and cytokines, resulting in an incomplete portrait of cytokine gene regulation. Here, we used enhanced yeast one-hybrid (eY1H) assays to derive a comprehensive network comprising 1380 interactions between 265 TFs and 108 cytokine gene promoters. Our eY1H-derived network greatly expands the known repertoire of TF–cytokine gene interactions and the set of TFs known to regulate cytokine genes. We found an enrichment of nuclear receptors and confirmed their role in cytokine regulation in primary macrophages. Additionally, we used the eY1H-derived network as a framework to identify pairs of TFs that can be targeted with commercially-available drugs to synergistically modulate cytokine production. Finally, we integrated the eY1H data with single cell RNA-seq and phenotypic datasets to identify novel TF–cytokine regulatory axes in immune diseases and immune cell lineage development. Overall, the eY1H data provides a rich resource to study cytokine regulation in a variety of physiological and disease contexts.

Nuclear receptors: Lipid and hormone sensors with essential roles in the control of cancer development

Nuclear receptors (NRs) are a superfamily of ligand-activated transcription factors that act as biological sensors and use a combination of mechanisms to modulate positively and negatively gene expression in a spatial and temporal manner. The highly orchestrated biological actions of several NRs influence the proliferation, differentiation, and apoptosis of many different cell types. Synthetic ligands for several NRs have been the focus of extensive drug discovery efforts for cancer intervention. This review summarizes the roles in tumour growth and metastasis of several relevant NR family members, namely androgen receptor (AR), estrogen receptor (ER), glucocorticoid receptor (GR), thyroid hormone receptor (TR), retinoic acid receptors (RARs), retinoid X receptors (RXRs), peroxisome proliferator-activated receptors (PPARs), and liver X receptors (LXRs). These studies are key to develop improved therapeutic agents based on novel modes of action with reduced side effects and overcoming resistance.

Photoswitchable Lipids

Photoswitchable lipids are emerging tools for the precise manipulation and study of lipid function. They can modulate many aspects of membrane biophysics, including permeability, fluidity, lipid mobility and domain formation. They are also very useful in lipid physiology and enable optical control of a wide array of lipid receptors, such as ion channels, G protein-coupled receptors, nuclear hormone receptors, and enzymes that translocate to membranes. Enzymes involved in lipid metabolism often process them in a light-dependent fashion. Photoswitchable lipids complement other functionalized lipids widely used in lipid chemical biology, including isotope-labeled lipids (lipidomics), fluorescent lipids (imaging), bifunctional lipids (lipid-protein crosslinking), photocaged lipids (photopharmacology), and other labeled variants.

RNA-activated protein kinase differentially modulates innate immune response mediated by supraphysiological concentrations of thyroid hormone

Nuclear hormone receptor ligands are known to modulate innate immunity by dampening the immune response induced by pathogens. Here, we report that unlike other ligands, 3,3',5-triiodo-l-thyronine (T3) induced the type 1 IFN response and expression of IFN-stimulated genes (ISGs). T3 action was found to be significantly amplified at supraphysiological concentrations (SPC) and in combination with double-stranded RNA mimic polyinosinic-polycytidylic acid. Induction by T3 was due to non-genomic mechanisms involving integrin binding, calcium mobilization, and phosphatidyl-inositol 3-kinase-AKT pathways, but was independent of TLR3, RIG-I, and IFN-β1 pathways. Whereas siRNA-induced knockdown of RNA-activated protein kinase (PKR) was found to abrogate the T3-induced expression of select ISGs, expression of other T3-induced ISGs was strongly induced by PKR knockdown, indicating the differential role of PKR in modulating T3 action. Together, we describe a novel role of T3 in modulating the innate immune response and identify the importance of PKR in regulating T3-induced immune activation. These findings have important implications in the basic understanding of the mechanisms of T3 function at SPCs and crosstalk involved in the thyroid hormone function and the innate immune response.

Bisphenol A and its analogues: A comprehensive review to identify and prioritize effect biomarkers for human biomonitoring

Human biomonitoring (HBM) studies have demonstrated widespread and daily exposure to bisphenol A (BPA). Moreover, BPA structural analogues (e.g. BPS, BPF, BPAF), used as BPA replacements, are being increasingly detected in human biological matrices. BPA and some of its analogues are classified as endocrine disruptors suspected of contributing to adverse health outcomes such as altered reproduction and neurodevelopment, obesity, and metabolic disorders among other developmental and chronic impairments. One of the aims of the H2020 European Human Biomonitoring Initiative (HBM4EU) is the implementation of effect biomarkers at large scales in future HBM studies in a systematic and standardized way, in order to complement exposure data with mechanistically-based biomarkers of early adverse effects. This review aimed to identify and prioritize existing biomarkers of effect for BPA, as well as to provide relevant mechanistic and adverse outcome pathway (AOP) information in order to cover knowledge gaps and better interpret effect biomarker data. A comprehensive literature search was performed in PubMed to identify all the epidemiologic studies published in the last 10 years addressing the potential relationship between bisphenols exposure and alterations in biological parameters. A total of 5716 references were screened, out of which, 119 full-text articles were analyzed and tabulated in detail. This work provides first an overview of all epigenetics, gene transcription, oxidative stress, reproductive, glucocorticoid and thyroid hormones, metabolic and allergy/immune biomarkers previously studied. Then, promising effect biomarkers related to altered neurodevelopmental and reproductive outcomes including brain-derived neurotrophic factor (BDNF), kisspeptin (KiSS), and gene expression of nuclear receptors are prioritized, providing mechanistic insights based on in vitro, animal studies and AOP information. Finally, the potential of omics technologies for biomarker discovery and its implications for risk assessment are discussed. To the best of our knowledge, this is the first effort to comprehensively identify bisphenol-related biomarkers of effect for HBM purposes.

Signaling pathways have an inherent need for noise to acquire information

BACKGROUND

All living systems acquire information about their environment. At the cellular level, they do so through signaling pathways. Such pathways rely on reversible binding interactions between molecules that detect and transmit the presence of an extracellular cue or signal to the cell's interior. These interactions are inherently stochastic and thus noisy. On the one hand, noise can cause a signaling pathway to produce the same response for different stimuli, which reduces the amount of information a pathway acquires. On the other hand, in processes such as stochastic resonance, noise can improve the detection of weak stimuli and thus the acquisition of information. It is not clear whether the kinetic parameters that determine a pathway's operation cause noise to reduce or increase the acquisition of information.

RESULTS

We analyze how the kinetic properties of the reversible binding interactions used by signaling pathways affect the relationship between noise, the response to a signal, and information acquisition. Our results show that, under a wide range of biologically sensible parameter values, a noisy dynamic of reversible binding interactions is necessary to produce distinct responses to different stimuli. As a consequence, noise is indispensable for the acquisition of information in signaling pathways.

CONCLUSIONS

Our observations go beyond previous work by showing that noise plays a positive role in signaling pathways, demonstrating that noise is essential when such pathways acquire information.

Brassinosteroids Regulate Circadian Oscillation via the BES1/TPL-CCA1/LHY Module in Arabidopsisthaliana

Brassinosteroids (BRs) regulate a variety of physiological processes in plants via extensive crosstalk with diverse biological signaling networks. Although BRs are known to reciprocally regulate circadian oscillation, the molecular mechanism underlying BR-mediated regulation of circadian clock remains unknown. Here, we demonstrate that the BR-activated transcription factor bri1-EMS-SUPPRESSOR 1 (BES1) integrates BR signaling into the circadian network in Arabidopsis. BES1 repressed expression of CIRCADIAN CLOCK-ASSOCIATED 1 (CCA1) and LATE ELONGATED HYPOCOTYL (LHY) at night by binding to their promoters, together with TOPLESS (TPL). The repression of CCA1 and LHY by BR treatment, which occurred during the night, was compromised in bes1-ko and tpl-8 mutants. Consistently, long-term treatment with BR shortened the circadian period, and BR-induced rhythmic shortening was impaired in bes1-ko and tpl-8 single mutants and in the cca1-1lhy-21 double mutant. Overall, BR signaling is conveyed to the circadian oscillator via the BES1/TPL-CCA1/LHY module, contributing to gating diurnal BR responses in plants.

Effects and Mechanisms of Phthalates' Action on Reproductive Processes and Reproductive Health: A Literature Review

The production of plastic products, which requires phthalate plasticizers, has resulted in the problems for human health, especially that of reproductive health. Phthalate exposure can induce reproductive disorders at various regulatory levels. The aim of this review was to compile the evidence concerning the association between phthalates and reproductive diseases, phthalates-induced reproductive disorders, and their possible endocrine and intracellular mechanisms. Phthalates may induce alterations in puberty, the development of testicular dysgenesis syndrome, cancer, and fertility disorders in both males and females. At the hormonal level, phthalates can modify the release of hypothalamic, pituitary, and peripheral hormones. At the intracellular level, phthalates can interfere with nuclear receptors, membrane receptors, intracellular signaling pathways, and modulate gene expression associated with reproduction. To understand and to treat the adverse effects of phthalates on human health, it is essential to expand the current knowledge concerning their mechanism of action in the organism.

The transcriptional repressor REV-ERB as a novel target for disease

REV-ERB is a member of the nuclear receptor superfamily of transcription factors involved in the regulation of many physiological processes, from circadian rhythm, to immune function and metabolism. Accordingly, REV-ERB has been considered as a promising, but difficult drug target for the treatment of numerous diseases. Here, we concisely review current understanding of the function of REV-ERB, modulation by endogenous factors and synthetic ligands, and the involvement of REV-ERB in select human diseases. Particular focus is placed on the medicinal chemistry of synthetic REV-ERB ligands, which demonstrates the need for higher quality ligands to aid in robust validation of this exciting target.

Nuclear Receptors as Autophagy-Based Antimicrobial Therapeutics

Autophagy is an intracellular process that targets intracellular pathogens for lysosomal degradation. Autophagy is tightly controlled at transcriptional and post-translational levels. Nuclear receptors (NRs) are a family of transcriptional factors that regulate the expression of gene sets involved in, for example, metabolic and immune homeostasis. Several NRs show promise as host-directed anti-infectives through the modulation of autophagy activities by their natural ligands or small molecules (agonists/antagonists). Here, we review the roles and mechanisms of NRs (vitamin D receptors, estrogen receptors, estrogen-related receptors, and peroxisome proliferator-activated receptors) in linking immunity and autophagy during infection. We also discuss the potential of emerging NRs (REV-ERBs, retinoic acid receptors, retinoic acid-related orphan receptors, liver X receptors, farnesoid X receptors, and thyroid hormone receptors) as candidate antimicrobials. The identification of novel roles and mechanisms for NRs will enable the development of autophagy-adjunctive therapeutics for emerging and re-emerging infectious diseases.

Redox-dependent PPARγ/Tnpo1 complex formation enhances PPARγ nuclear localization and signaling

The nuclear receptor peroxisome proliferator-activated receptor (PPAR)γ has been implicated in the pathogenesis of various human diseases including fatty liver. Although nuclear translocation of PPARγ plays an important role in PPARγ signaling, details of the translocation mechanisms have not been elucidated. Here we demonstrate that PPARγ2 translocates to the nucleus and activates signal transduction through H₂O₂-dependent formation of a PPARγ2 and transportin (Tnpo)1 complex via redox-sensitive disulfide bonds between cysteine (Cys)176 and Cys180 of the former and Cys512 of the latter. Using hepatocyte cultures and mouse models, we show that cytosolic H₂O₂/Tnpo1-dependent nuclear translocation enhances the amount of DNA-bound PPARγ and downstream signaling, leading to triglyceride accumulation in hepatocytes and liver. These findings expand our understanding of the mechanism underlying the nuclear translocation of PPARγ, and suggest that the PPARγ and Tnpo1 complex and surrounding redox environment are potential therapeutic targets in the treatment of PPARγ-related diseases.

Nuclear Receptors as Potential Therapeutic Targets for Myeloid Leukemia

The nuclear receptor (NR) superfamily has been studied extensively in many solid tumors and some receptors have been targeted to develop therapies. However, their roles in leukemia are less clear and vary considerably among different types of leukemia. Some NRs participate in mediating the differentiation of myeloid cells, making them attractive therapeutic targets for myeloid leukemia. To date, the success of all-trans retinoic acid (ATRA) in treating acute promyelocytic leukemia (APL) remains a classical and unsurpassable example of cancer differentiation therapy. ATRA targets retinoic acid receptor (RAR) and forces differentiation and/or apoptosis of leukemic cells. In addition, ligands/agonists of vitamin D receptor (VDR) and peroxisome proliferator-activated receptor (PPAR) have also been shown to inhibit proliferation, induce differentiation, and promote apoptosis of leukemic cells. Encouragingly, combining different NR agonists or the addition of NR agonists to chemotherapies have shown some synergistic anti-leukemic effects. This review will summarize recent research findings and discuss the therapeutic potential of selected NRs in acute and chronic myeloid leukemia, focusing on RAR, VDR, PPAR, and retinoid X receptor (RXR). We believe that more mechanistic studies in this field will not only shed new lights on the roles of NRs in leukemia, but also further expand the clinical applications of existing therapeutic agents targeting NRs.

Not So Slim Anymore-Evidence for the Role of SUMO in the Regulation of Lipid Metabolism

One of the basic building blocks of all life forms are lipids—biomolecules that dissolve in nonpolar organic solvents but not in water. Lipids have numerous structural, metabolic, and regulative functions in health and disease; thus, complex networks of enzymes coordinate the different compositions and functions of lipids with the physiology of the organism. One type of control on the activity of those enzymes is the conjugation of the Small Ubiquitin-like Modifier (SUMO) that in recent years has been identified as a critical regulator of many biological processes. In this review, I summarize the current knowledge about the role of SUMO in the regulation of lipid metabolism. In particular, I discuss (i) the role of SUMO in lipid metabolism of fungi and invertebrates; (ii) the function of SUMO as a regulator of lipid metabolism in mammals with emphasis on the two most well-characterized cases of SUMO regulation of lipid homeostasis. These include the effect of SUMO on the activity of two groups of master regulators of lipid metabolism—the Sterol Regulatory Element Binding Protein (SERBP) proteins and the family of nuclear receptors—and (iii) the role of SUMO as a regulator of lipid metabolism in arteriosclerosis, nonalcoholic fatty liver, cholestasis, and other lipid-related human diseases.

Drug efflux transporters and metabolic enzymes in human circulating and testicular T-cell subsets: relevance to HIV pharmacotherapy

OBJECTIVES

ATP-binding cassette (ABC) drug efflux transporters and drug metabolic enzymes could reduce antiretroviral concentrations in HIV target cells. The testis has been demonstrated to be a sanctuary site, displaying suboptimal antiretroviral concentrations and persistent HIV infection. Therefore, we compared the expression and function of ABC transporters and metabolic enzymes in CD4 and CD8 T cells isolated from human testis and peripheral blood mononuclear cells (PBMCs), and assessed their expression in circulating naive and memory CD4 T-cell phenotypes.

DESIGN

Testicular tissue and blood were collected from 15 uninfected donors undergoing gender affirmation surgery. Testicular interstitial cells were isolated by enzymatic digestion, whereas PBMCs were isolated from blood by density gradient centrifugation. The expression and/or function of ABC transporters and metabolic enzymes were examined in blood and testicular T-cell subsets by flow cytometry.

RESULTS

ABC transporters (P-gp, BCRP, MRP1) and metabolic enzymes (CYP3A4, UGT1A1) were expressed in testicular and circulating CD4 and CD8 T cells, as well as in circulating naive, central, transitional, and effector memory T-cell phenotypes. MRP1 demonstrated lower frequencies in T cells from testis compared with PBMCs, as well as in circulating naive T cells compared with the memory T-cell phenotypes. Functional activity of P-gp and BCRP was detected in T-cell subsets from testis and PBMCs.

CONCLUSION

Our findings demonstrate for the first time that antiretroviral drug efflux transporters and metabolic enzymes are functionally expressed in T-cell subsets infiltrating the human testis. These transporters and enzymes can reduce antiretroviral intracellular concentrations, potentially contributing to residual HIV replication in the testis, and negatively impact HIV cure strategies.

Piggybacking on Classical Import and Other Non-Classical Mechanisms of Nuclear Import Appear Highly Prevalent within the Human Proteome

One of the most conserved cellular pathways among eukaryotes is the extensively studied classical protein nuclear import pathway mediated by importin-α. Classical nuclear localization signals (cNLSs) are recognized by importin-α and are highly predictable due to their abundance of basic amino acids. However, various studies in model organisms have repeatedly demonstrated that only a fraction of nuclear proteins contain identifiable cNLSs, including those that directly interact with importin-α. Using data from the Human Protein Atlas and the Human Reference Interactome, and proteomic data from BioID/protein-proximity labeling studies using multiple human importin-α proteins, we determine that nearly 50% of the human nuclear proteome does not have a predictable cNLS. Surprisingly, between 25% and 50% of previously identified human importin-α cargoes do not have predictable cNLS. Analysis of importin-α cargo without a cNLS identified an alternative basic rich motif that does not resemble a cNLS. Furthermore, several previously suspected piggybacking proteins were identified, such as those belonging to the RNA polymerase II and transcription factor II D complexes. Additionally, many components of the mediator complex interact with at least one importin-α, yet do not have a predictable cNLS, suggesting that many of the subunits may enter the nucleus through an importin-α-dependent piggybacking mechanism.

Intrinsic transcriptomic sex differences in human endothelial cells at birth and in adults are associated with coronary artery disease targets

Sex differences in endothelial cell (EC) biology may reflect intrinsic differences driven by chromosomes or sex steroid exposure and gender differences accumulated over life. We analysed EC gene expression data from boy-girl twins at birth and in non-twin adults to detect sex differences at different stages of life, and show that 14-25% of the EC transcriptome is sex-biased. By combining data from both stages of life, we identified sex differences that are present at birth and maintained throughout life, and those that are acquired over life. Promisingly, we found that genes that present with an acquired sex difference in ECs are more likely to be targets of sex steroids. Annotating both gene sets with data from multiple genome-wide association studies (GWAS) revealed that genes with an intrinsic sex difference in ECs are enriched for coronary artery disease GWAS hits. This study underscores the need for treating sex as a biological variable.

LXRα Phosphorylation in Cardiometabolic Disease: Insight From Mouse Models

Posttranslational modifications, such as phosphorylation, are a powerful means by which the activity and function of nuclear receptors such as LXRα can be altered. However, despite the established importance of nuclear receptors in maintaining metabolic homeostasis, our understanding of how phosphorylation affects metabolic diseases is limited. The physiological consequences of LXRα phosphorylation have, until recently, been studied only in vitro or nonspecifically in animal models by pharmacologically or genetically altering the enzymes enhancing or inhibiting these modifications. Here we review recent reports on the physiological consequences of modifying LXRα phosphorylation at serine 196 (S196) in cardiometabolic disease, including nonalcoholic fatty liver disease, atherosclerosis, and obesity. A unifying theme from these studies is that LXRα S196 phosphorylation rewires the LXR-modulated transcriptome, which in turn alters physiological response to environmental signals, and that this is largely distinct from the LXR-ligand-dependent action.

Identification of glucocorticoid receptor in Drosophila melanogaster

BACKGROUND

Vertebrate glucocorticoid receptor (GR) is an evolutionary-conserved cortisol-regulated nuclear receptor that controls key metabolic and developmental pathways. Upon binding to cortisol, GR acts as an immunosuppressive transcription factor. Drosophila melanogaster, a model organism to study innate immunity, can also be immunosuppressed by glucocorticoids. However, while the genome of fruit fly harbors 18 nuclear receptor genes, the functional homolog of vertebrate GR has not been identified.

RESULTS

In this study, we demonstrated that while D. melanogaster is susceptible to Saccharomyces cerevisiae oral infection, the oral exposure to cortisol analogs, cortisone acetate or estrogen, increases fly sensitivity to yeast challenge. To understand the mechanism of this steroid-induced immunosuppression, we identified the closest genetic GR homolog as D. melanogaster Estrogen Related Receptor (ERR) gene. We discovered that Drosophila ERR is necessary for cortisone acetate- and estrogen-mediated increase in sensitivity to fungal infection: while ERR mutant flies are as sensitive to the fungal challenge as the wildtype flies, the yeast-sensitivity of ERR mutants is not increased by these steroids. Interestingly, the fungal cortisone analog, ergosterol, did not increase the susceptibility of Drosophila to yeast infection. The immunosuppressive effect of steroids on the sensitivity of flies to fungi is evolutionary conserved in insects, as we show that estrogen significantly increases the yeast-sensitivity of Culex quinquefasciatus mosquitoes, whose genome contains a close ortholog of the fly ERR gene.

CONCLUSIONS

This study identifies a D. melanogaster gene that structurally resembles vertebrate GR and is functionally necessary for the steroid-mediated immunosuppression to fungal infections.

Pseudozyma Priming Influences Expression of Genes Involved in Metabolic Pathways and Immunity in Zebrafish Larvae

Fungi, particularly yeasts, are known essential components of the host microbiota but their functional relevance in development of immunity and physiological processes of fish remains to be elucidated. In this study, we used a transcriptomic approach and a germ-free (GF) fish model to determine the response of newly hatched zebrafish larvae after 24 h exposure to Pseudozyma sp. when compared to conventionally-raised (CR) larvae. We observed 59 differentially expressed genes in Pseudozyma-exposed GF zebrafish larvae compared to their naïve control siblings. Surprisingly, in CR larvae, there was not a clear transcriptome difference between Pseudozyma-exposed and control larvae. Differentially expressed genes in GF larvae were involved in host metabolic pathways, mainly peroxisome proliferator-activated receptors, steroid hormone biosynthesis, drug metabolism and bile acid biosynthesis. We also observed a significant change in the transcript levels of immune-related genes, namely complement component 3a, galectin 2b, ubiquitin specific peptidase 21, and aquaporins. Nevertheless, we did not observe any significant response at the cellular level, since there were no differences between neutrophil migration or proliferation between control and yeast-exposed GF larvae. Our findings reveal that exposure to Pseudozyma sp. may affect metabolic pathways and immune-related processes in germ-free zebrafish, suggesting that commensal yeast likely play a significant part in the early development of fish larvae.

The constitutive androstane receptor and pregnane X receptor in the brain

Since their discovery, the orphan nuclear receptors constitutive androstane receptor (CAR;NR1I3) and pregnane X receptor (PXR;NR1I2) have been regarded as master regulators of drug disposition and detoxification mechanisms. They regulate the metabolism and transport of endogenous mediators and xenobiotics in organs including the liver, intestine and brain. However, with proposals of new physiological functions for NR1I3 and NR1I2, there is increasing interest in the role of these receptors in influencing brain function. This review will summarise key findings regarding the expression and function of NR1I3 and NR1I2 in the brain, hereby highlighting the need for further research in this field.

Estrogen receptor-positive (ER+) breast cancer treatment: Are multi-target compounds the next promising approach?

Endocrine therapy is currently the main therapeutic approach for estrogen receptor-positive (ER⁺) breast cancer, the most frequent subtype of breast cancer in women worldwide. For this subtype of tumors, the current clinical treatment includes aromatase inhibitors (AIs) and anti-estrogenic compounds, such as Tamoxifen and Fulvestrant, being AIs the first-line treatment option for post-menopausal women. Moreover, the recent guidelines also suggest the use of these compounds by pre-menopausal women after suppressing ovaries function. However, besides its therapeutic efficacy, the prolonged use of this type of therapies may lead to the development of several adverse effects, as well as, endocrine resistance, limiting the effectiveness of such treatments. In order to surpass this issues and clinical concerns, during the last years, several studies have been suggesting alternative therapeutic approaches, considering the function of aromatase, ERα and ERβ. Here, we review the structural and functional features of these three targets and their importance in ER⁺ breast cancer treatment, as well as, the current treatment strategies used in clinic, emphasizing the importance of the development of multi-target compounds able to simultaneously modulate these key targets, as a novel and promising therapeutic strategy for this type of cancer.

Hormone-epigenome interactions in behavioural regulation

Interactions between hormones and epigenetic factors are key regulators of behaviour, but the mechanisms that underlie their effects are complex. Epigenetic factors can modify sensitivity to hormones by altering hormone receptor expression, and hormones can regulate epigenetic factors by recruiting epigenetic regulators to DNA. The bidirectional nature of this relationship is becoming increasingly evident and suggests that the ability of hormones to regulate certain forms of behaviour may depend on their ability to induce changes in the epigenome. Moreover, sex differences have been reported for several epigenetic modifications, and epigenetic factors are thought to regulate sexual differentiation of behaviour, although specific mechanisms remain to be understood. Indeed, hormone-epigenome interactions are highly complex and involve both canonical and non-canonical regulatory pathways that may permit for highly specific gene regulation to promote variable forms of behavioural adaptation.

Chronic psychosocial stress during pregnancy affects maternal behavior and neuroendocrine function and modulates hypothalamic CRH and nuclear steroid receptor expression

Postpartum depression (PPD) affects up to 20% of mothers and has negative consequences for both mother and child. Although exposure to psychosocial stress during pregnancy and abnormalities in the hypothalamic pituitary adrenal (HPA) axis have been linked to PPD, molecular changes in the brain that contribute to this disease remain unknown. This study utilized a novel chronic psychosocial stress paradigm during pregnancy (CGS) to investigate the effects of psychosocial stress on maternal behavior, neuroendocrine function, and gene expression changes in molecular regulators of the HPA axis in the early postpartum period. Postpartum female mice exposed to CGS display abnormalities in maternal behavior, including fragmented and erratic maternal care patterns, and the emergence of depression and anxiety-like phenotypes. Dysregulation in postpartum HPA axis function, evidenced by blunted circadian peak and elevation of stress-induced corticosterone levels, was accompanied by increased CRH mRNA expression and a reduction in CRH receptor 1 in the paraventricular nucleus of the hypothalamus (PVN). We further observed decreased PVN expression of nuclear steroid hormone receptors associated with CRH transcription, suggesting these molecular changes could underlie abnormalities in postpartum HPA axis and behavior observed. Overall, our study demonstrates that psychosocial stress during pregnancy induces changes in neuroendocrine function and maternal behavior in the early postpartum period and introduces our CGS paradigm as a viable model that can be used to further dissect the molecular defects that lead to PPD.

Is Alzheimer's Disease a Liver Disease of the Brain?

Clinical specialization is not only a force for progress, but it has also led to the fragmentation of medical knowledge. The focus of research in the field of Alzheimer's disease (AD) is neurobiology, while hepatologists focus on liver diseases and lipid specialists on atherosclerosis. This article on AD focuses on the role of the liver and lipid homeostasis in the development of AD. Amyloid-β (Aβ) deposits accumulate as plaques in the brain of an AD patient long before cognitive decline is evident. Aβ generation is a normal physiological process; the steady-state level of Aβ in the brain is determined by balance between Aβ production and its clearance. We present evidence suggesting that the liver is the origin of brain Aβ deposits and that it is involved in peripheral clearance of circulating Aβ in the blood. Hence the liver could be targeted to decrease Aβ production or increase peripheral clearance.

The Dichotomous Nature of AZ5104 (an EGFR Inhibitor) Towards RORγ and RORγT

The RORC (RAR related orphan receptor C) gene produces two isoforms by alternative promoter usage: RORγ (nuclear receptor ROR-gamma isoform 1) and RORγT (nuclear receptor ROR-gamma isoform 1). Both proteins have distinct tissue distributions and are involved in several physiological processes, including glucose/lipid metabolism and the development of Th17 lymphocytes. Previously, we developed a stably transfected reporter cell line and used it to screen a library of kinase inhibitors. We found that AZ5104 acts as an RORγ agonist at low micromolar concentrations. Molecular docking analysis showed that this compound occupies the ligand binding domain of the receptor with a significant docking score. However, analysis of the biological activity of this compound in Th17 cells revealed that it downregulates RORγT expression and Th17-related cytokine production via inhibition of SRC-ERK-STAT3 (SRC proto-oncogene - extracellular regulated MAP kinase - signal transducer and activator of transcription 3). We thus identified a compound acting as an agonist of RORγ that, due to the inhibition of downstream elements of EGFR (epidermal growth factor receptor) signaling, exerts different biological activity towards a Th17-specific isoform. Additionally, our results may be relevant in the future for the design of treatments targeting signaling pathways that inhibit Th17-related inflammation in certain autoimmune disorders.

C. elegans protein interaction network analysis probes RNAi validated pro-longevity effect of nhr-6, a human homolog of tumor suppressor Nr4a1

Protein-protein interaction (PPI) studies are gaining momentum these days due to the plethora of various high-throughput experimental methods available for detecting PPIs. Proteins create complexes and networks by functioning in harmony with other proteins and here in silico network biology hold the promise to reveal new functionality of genes as it is very difficult and laborious to carry out experimental high-throughput genetic screens in living organisms. We demonstrate this approach by computationally screening C. elegans conserved homologs of already reported human tumor suppressor and aging associated genes. We select by this nhr-6, vab-3 and gst-23 as predicted longevity genes for RNAi screen. The RNAi results demonstrated the pro-longevity effect of these genes. Nuclear hormone receptor nhr-6 RNAi inhibition resulted in a C. elegans phenotype of 23.46% lifespan reduction. Moreover, we show that nhr-6 regulates oxidative stress resistance in worms and does not affect the feeding behavior of worms. These findings imply the potential of nhr-6 as a common therapeutic target for aging and cancer ailments, stressing the power of in silico PPI network analysis coupled with RNAi screens to describe gene function.

Regulation of calcific vascular and valvular disease by nuclear receptors

PURPOSE OF REVIEW

This review addresses recent developments in studies of lipid regulation of calcific disease of arteries and cardiac valves, including the role of nuclear receptors. The role of lipid-soluble signals and their receptors is timely given the recent evidence and concerns that lipid-lowering treatment may increase the rate of progression of coronary artery calcification, which has been long associated with increased cardiovascular risk. Understanding the mechanisms will be important for interpreting such clinical information.

RECENT FINDINGS

New findings support regulation of calcific vascular and valvular disease by nuclear receptors, including the vitamin D receptor, glucocorticoid receptor, nutrient-sensing nuclear receptors (liver X receptor, farnesoid X receptor, and peroxisome proliferator-activated receptors), and sex hormone (estrogen and androgen) receptors. There were two major unexpected findings: first, vitamin D supplementation, which was previously believed to prevent or reduce vascular calcification, showed no cardiovascular benefit in large randomized, controlled trials. Second, both epidemiological studies and coronary intravascular ultrasound studies suggest that treatment with HMG-CoA reductase inhibitors increases progression of coronary artery calcification, raising a question of whether there are mechanically stable and unstable forms of coronary calcification.

SUMMARY

For clinical practice and research, these new findings offer new fundamental mechanisms for vascular calcification and provide new cautionary insights for therapeutic avenues.

Structural Dynamics of Agonist and Antagonist Binding to the Androgen Receptor

Androgen receptor (AR) is a steroid hormone nuclear receptor which upon binding its endogenous androgenic ligands (agonists), testosterone and dihydrotestosterone (DHT), alters gene transcription, producing a diverse range of biological effects. Antiandrogens, such as the pharmaceuticals bicalutamide and hydroxyflutamide, act as agonists in the absence of androgens and as antagonists in their presence or in high concentration. The atomic level mechanism of action by agonists and antagonists of AR is less well characterized. Therefore, in this study, multiple 1 μs molecular dynamics (MD), docking simulations, and perturbation-response analyses were performed to more fully explore the nature of interaction between agonist or antagonist and AR and the conformational changes induced in the AR upon interaction with different ligands. We characterized the mechanism of the ligand entry/exit and found that helix-12 and nearby structural motifs respond dynamically in that process. Modeling showed that the agonist and antagonist/agonist form a hydrogen bond with Thr877/Asn705 and that this interaction is absent for antagonists. Agonist binding to AR increases the mobility of residues at allosteric sites and coactivator binding sites, while antagonist binding decreases mobility at these important sites. A new site was also identified as a potential surface for allosteric binding. These results shed light on the effect of agonists and antagonists on the structure and dynamics of AR.

Proteomics contribution to the elucidation of the steroid hormone receptors functions

Steroid hormones have far-ranging biological impacts and more are continuously being uncovered. Over the last decades, proteomics approaches have become key to better understand biological processes. Due to multiple technical breakthroughs allowing for the concurrent identification and/or quantification of thousands of analytes using mass spectrometers, researchers employing proteomics tools today can now obtain truly holistic views of multiple facets of the human proteome. Here, we review how the field of proteomics has contributed to discoveries about steroid hormones, their receptors and their impact on human pathologies. In particular, the involvement of steroid receptors in cancer initiation, development, metastasis and treatment will be highlighted. Techniques at the forefront of the proteomics field will also be discussed to present how they can contribute to a better understanding of steroid hormone receptors.

A tale of two tracts: history, current advances, and future directions of research on sexual differentiation of reproductive tracts†

Alfred Jost's work in the 1940s laid the foundation of the current paradigm of sexual differentiation of reproductive tracts, which contends that testicular hormones drive the male patterning of reproductive tract system whereas the female phenotype arises by default. Once established, the sex-specific reproductive tracts undergo morphogenesis, giving rise to anatomically and functionally distinct tubular organs along the rostral-caudal axis. Impairment of sexual differentiation of reproductive tracts by genetic alteration and environmental exposure are the main causes of disorders of sex development, and infertility at adulthood. This review covers past and present work on sexual differentiation and morphogenesis of reproductive tracts, associated human disorders, and emerging technologies that have made impacts or could radically expand our knowledge in this field.

Regulation of cellular senescence by retinoid X receptors and their partners

Cellular senescence is a response characterized by a stable cell proliferation arrest and a senescence-associated secretory phenotype (SASP) which can be induced by many stresses, including telomere shortening and oncogene activation. Senescence is crucially involved in a variety of physiopathological contexts, such as cancer and aging. Given the fundamental role of this process, senescence needs to be tightly regulated. In the last decade, the key implication of nuclear receptors in cellular senescence has emerged. Here we will review the mechanisms involved in the control of cellular senescence by retinoid X receptors (RXRs) and their partners. We will also present our current knowledge on the regulation of these receptors during senescence and on their potential role in senescence-associated physiopathological conditions.