Signaling by nuclear receptors

Toxicity overview of endocrine disrupting chemicals interacting in vitro with the oestrogen receptor

The oestrogen receptor (ER) from the nuclear receptor family is involved in different physiological processes, which can be affected by multiple xenobiotics. Some of these compounds, such as bisphenols, pesticides, and phthalates, are widespread as consequence of human activities and are commonly present also in human organism. Xenobiotics able to interact with ER and trigger a hormone-like response, are known as endocrine disruptors. In this review, we aim to summarize the available knowledge on products derived from human industrial activity and other xenobiotics reported to interact with ER. ER-disrupting chemicals behave differently towards oestrogen-dependent cell lines than endogenous oestradiol. In low concentrations, they stimulate proliferation, whereas at higher concentrations, are toxic to cells. In addition, most of the knowledge on the topic is based on individual compound testing, and only a few studies assess xenobiotic combinations, which better resemble real circumstances. Confirmation from in vivo models is lacking also.

A high-resolution transcriptomic and spatial atlas of cell types in the whole mouse brain

The mammalian brain is composed of millions to billions of cells that are organized into numerous cell types with specific spatial distribution patterns and structural and functional properties. An essential step towards understanding brain function is to obtain a parts list, i.e., a catalog of cell types, of the brain. Here, we report a comprehensive and high-resolution transcriptomic and spatial cell type atlas for the whole adult mouse brain. The cell type atlas was created based on the combination of two single-cell-level, whole-brain-scale datasets: a single-cell RNA-sequencing (scRNA-seq) dataset of ~7 million cells profiled, and a spatially resolved transcriptomic dataset of ~4.3 million cells using MERFISH. The atlas is hierarchically organized into five nested levels of classification: 7 divisions, 32 classes, 306 subclasses, 1,045 supertypes and 5,200 clusters. We systematically analyzed the neuronal, non-neuronal, and immature neuronal cell types across the brain and identified a high degree of correspondence between transcriptomic identity and spatial specificity for each cell type. The results reveal unique features of cell type organization in different brain regions, in particular, a dichotomy between the dorsal and ventral parts of the brain: the dorsal part contains relatively fewer yet highly divergent neuronal types, whereas the ventral part contains more numerous neuronal types that are more closely related to each other. We also systematically characterized cell-type specific expression of neurotransmitters, neuropeptides, and transcription factors. The study uncovered extraordinary diversity and heterogeneity in neurotransmitter and neuropeptide expression and co-expression patterns in different cell types across the brain, suggesting they mediate a myriad of modes of intercellular communications. Finally, we found that transcription factors are major determinants of cell type classification in the adult mouse brain and identified a combinatorial transcription factor code that defines cell types across all parts of the brain. The whole-mouse-brain transcriptomic and spatial cell type atlas establishes a benchmark reference atlas and a foundational resource for deep and integrative investigations of cell type and circuit function, development, and evolution of the mammalian brain.

Sex steroid hormones and DNA repair regulation: Implications on cancer treatment responses

The role of sex steroid hormones (SSHs) has been shown to modulate cancer cytotoxic treatment sensitivity. Dysregulation of DNA repair associated with genomic instability, abnormal cell survival and not only promotes cancer progression but also resistance to cancer treatment. The three major SSHs, androgen, estrogen, and progesterone, have been shown to interact with several essential DNA repair components. The presence of androgens directly regulates key molecules in DNA double-strand break (DSB) repair. Estrogen can promote cell proliferation and DNA repair, allowing cancer cells to tolerate chemotherapy and radiotherapy. Information on the role of progesterone in DNA repair is limited: progesterone interaction with some DNA repair components has been identified, but the biological significance is still unknown. Here, we review the roles of how each SSH affects DNA repair regulation and modulates response to genotoxic therapies and discuss future research that can be beneficial when combining SSHs with cancer therapy. We also provide preliminary analysis from publicly available databases defining the link between progesterone/PR and DDRs & DNA repair regulation that plausibly contribute to chemotherapy response and breast cancer patient survival.

The Duck RXRA Gene Promotes Adipogenesis and Correlates with Feed Efficiency

BACKGROUND

The accumulation of fat in ducks is the main cause of low feed efficiency and metabolic diseases in ducks. Retinoic acid X receptor alpha (RXRA) is a member of the nuclear receptor superfamily involved in lipid, glucose, energy, and hormone metabolism. The effect of the RXRA gene on lipid metabolism in duck preadipocytes (DPACs) and the relationship between SNPs and the feed efficiency traits of ducks are unclear.

METHODS

qRT-PCR and Western blotting analyses were used to detect changes in mRNA and protein in cells. Intracellular triglycerides (TGs) were detected using an ELISA kit. A general linear model analysis was used to determine the association between RXRA SNPs and feed efficiency.

RESULTS

The duck RXRA gene was highly expressed on the fourth day of DPAC differentiation. The RXRA gene increased the content of fat and TG in DPACs and promoted the expression of cell differentiation genes; g.5,952,667 correlated with average daily feed intake (ADFI), residual feed intake (RFI), and feed conversion ratio (FCR).

CONCLUSIONS

Duck RXRA can accelerate fat accumulation, and the polymorphism of the RXRA gene is closely related to feed efficiency, which provides basic data for breeding high feed efficiency ducks.

The Emerging Role of Epigenetics in Metabolism and Endocrinology

Each cell in a multicellular organism has its own phenotype despite sharing the same genome. Epigenetics is a somatic, heritable pattern of gene expression or cellular phenotype mediated by structural changes in chromatin that occur without altering the DNA sequence. Epigenetic modification is an important factor in determining the level and timing of gene expression in response to endogenous and exogenous stimuli. There is also growing evidence concerning the interaction between epigenetics and metabolism. Accordingly, several enzymes that consume vital metabolites as substrates or cofactors are used during the catalysis of epigenetic modification. Therefore, altered metabolism might lead to diseases and pathogenesis, including endocrine disorders and cancer. In addition, it has been demonstrated that epigenetic modification influences the endocrine system and immune response-related pathways. In this regard, epigenetic modification may impact the levels of hormones that are important in regulating growth, development, reproduction, energy balance, and metabolism. Altering the function of the endocrine system has negative health consequences. Furthermore, endocrine disruptors (EDC) have a significant impact on the endocrine system, causing the abnormal functioning of hormones and their receptors, resulting in various diseases and disorders. Overall, this review focuses on the impact of epigenetics on the endocrine system and its interaction with metabolism.

Emerging Role of SMILE in Liver Metabolism

Small heterodimer partner-interacting leucine zipper (SMILE) is a member of the CREB/ATF family of basic leucine zipper (bZIP) transcription factors. SMILE has two isoforms, a small and long isoform, resulting from alternative usage of the initiation codon. Interestingly, although SMILE can homodimerize similar to other bZIP proteins, it cannot bind to DNA. As a result, SMILE acts as a co-repressor in nuclear receptor signaling and other transcription factors through its DNA binding inhibition, coactivator competition, and direct repression, thereby regulating the expression of target genes. Therefore, the knockdown of SMILE increases the transactivation of transcription factors. Recent findings suggest that SMILE is an important regulator of metabolic signals and pathways by causing changes in glucose, lipid, and iron metabolism in the liver. The regulation of SMILE plays an important role in pathological conditions such as hepatitis, diabetes, fatty liver disease, and controlling the energy metabolism in the liver. This review focuses on the role of SMILE and its repressive actions on the transcriptional activity of nuclear receptors and bZIP transcription factors and its effects on liver metabolism. Understanding the importance of SMILE in liver metabolism and signaling pathways paves the way to utilize SMILE as a target in treating liver diseases.

Emerging Role of SMILE in Liver Metabolism

Small heterodimer partner-interacting leucine zipper (SMILE) is a member of the CREB/ATF family of basic leucine zipper (bZIP) transcription factors. SMILE has two isoforms, a small and long isoform, resulting from alternative usage of the initiation codon. Interestingly, although SMILE can homodimerize similar to other bZIP proteins, it cannot bind to DNA. As a result, SMILE acts as a co-repressor in nuclear receptor signaling and other transcription factors through its DNA binding inhibition, coactivator competition, and direct repression, thereby regulating the expression of target genes. Therefore, the knockdown of SMILE increases the transactivation of transcription factors. Recent findings suggest that SMILE is an important regulator of metabolic signals and pathways by causing changes in glucose, lipid, and iron metabolism in the liver. The regulation of SMILE plays an important role in pathological conditions such as hepatitis, diabetes, fatty liver disease, and controlling the energy metabolism in the liver. This review focuses on the role of SMILE and its repressive actions on the transcriptional activity of nuclear receptors and bZIP transcription factors and its effects on liver metabolism. Understanding the importance of SMILE in liver metabolism and signaling pathways paves the way to utilize SMILE as a target in treating liver diseases.

PIMT regulates hepatic gluconeogenesis in mice

The physiological and metabolic functions of PIMT/TGS1, a third-generation transcriptional apparatus protein, in glucose homeostasis sustenance are unclear. Here, we observed that the expression of PIMT was upregulated in the livers of short-term fasted and obese mice. Lentiviruses expressing Tgs1-specific shRNA or cDNA were injected into wild-type mice. Gene expression, hepatic glucose output, glucose tolerance, and insulin sensitivity were evaluated in mice and primary hepatocytes. Genetic modulation of PIMT exerted a direct positive impact on the gluconeogenic gene expression program and hepatic glucose output. Molecular studies utilizing cultured cells, in vivo models, genetic manipulation, and PKA pharmacological inhibition establish that PKA regulates PIMT at post-transcriptional/translational and post-translational levels. PKA enhanced 3'UTR-mediated translation of TGS1 mRNA and phosphorylated PIMT at Ser656, increasing Ep300-mediated gluconeogenic transcriptional activity. The PKA-PIMT-Ep300 signaling module and associated PIMT regulation may serve as a key driver of gluconeogenesis, positioning PIMT as a critical hepatic glucose sensor.

HSP70 mediates a crosstalk between the estrogen and the heat shock response pathways

Cells respond to multiple signals from the environment simultaneously, which often creates crosstalk between pathways affecting the capacity to adapt to the changing environment. Chaperones are an important component in the cellular integration of multiple responses to environmental signals, often implicated in negative feedback and inactivation mechanisms. These mechanisms include the stabilization of steroid hormone nuclear receptors in the cytoplasm in the absence of their ligand. Here, we show using immunofluorescence, chromatin immunoprecipitation, and nascent transcripts production that the heat shock protein 70 (HSP70) chaperone plays a central role in a new crosstalk mechanism between the steroid and heat shock response pathways. HSP70-dependent feedback mechanisms are required to inactivate the heat shock factor 1 (HSF1) after activation. Interestingly, a steroid stimulation leads to faster accumulation of HSF1 in inactive foci following heat shock. Our results further show that in the presence of estrogen, HSP70 accumulates at HSF1-regulated noncoding regions, leading to deactivation of HSF1 and the abrogation of the heat shock transcriptional response. Using an HSP70 inhibitor, we demonstrate that the crosstalk between both pathways is dependent on the chaperone activity. These results suggest that HSP70 availability is a key determinant in the transcriptional integration of multiple external signals. Overall, these results offer a better understanding of the crosstalk between the heat shock and steroid responses, which are salient in neurodegenerative disorders and cancers.

OAT, OATP, and MRP Drug Transporters and the Remote Sensing and Signaling Theory

The coordinated movement of organic anions (e.g., drugs, metabolites, signaling molecules, nutrients, antioxidants, gut microbiome products) between tissues and body fluids depends, in large part, on organic anion transporters (OATs) [solute carrier 22 (SLC22)], organic anion transporting polypeptides (OATPs) [solute carrier organic (SLCO)], and multidrug resistance proteins (MRPs) [ATP-binding cassette, subfamily C (ABCC)]. Depending on the range of substrates, transporters in these families can be considered multispecific, oligospecific, or (relatively) monospecific. Systems biology analyses of these transporters in the context of expression patterns reveal they are hubs in networks involved in interorgan and interorganismal communication. The remote sensing and signaling theory explains how the coordinated functions of drug transporters, drug-metabolizing enzymes, and regulatory proteins play a role in optimizing systemic and local levels of important endogenous small molecules. We focus on the role of OATs, OATPs, and MRPs in endogenous metabolism and how their substrates (e.g., bile acids, short chain fatty acids, urate, uremic toxins) mediate interorgan and interorganismal communication and help maintain and restore homeostasis in healthy and disease states.

To block or not to block-hormonal signaling in the treatment of cancers

The breast and prostate glands are the two major organs that are highly dependent on the gonadal steroid hormones for their development and homeostasis. The cancers of these organs also show a large dependence on steroid hormones and have formed the basis of endocrine therapy. Estrogen deprivation by oophorectomy has been in active practice since the 1970s, and androgen deprivation therapy for prostate cancer was a major breakthrough in medicine in 1941. Since then, several improvisations have happened in these modes of therapy. However, the development of resistance to this deprivation and the emergence of hormone independence are major problems in both cancers. The lessons learned from rodent models have made it clear that the male hormone has a role in females and vice versa. Also, the metabolic products of these hormones may have unintentional effects including proliferative conditions in both sexes. Hence, administering estrogen as a method of chemical castration in males and administering DHT in females may not be the ideal scenario. It would be important to consider the status of the opposite sex hormone signaling and its effects and come up with a combinatorial regime to strike a balance between androgen and estrogen signaling. This review summarizes the current understanding and developments in this field in the context of prostate cancer.

Epigenetic Modifications by Estrogen and Androgen in Alzheimer's Disease

For the development and maintenance of neuron networks in the brain, epigenetic mechanisms are necessary, as indicated by recent findings. This includes some of the high-order brain processes, such as behavior and cognitive functions. Epigenetic mechanisms could influence the pathophysiology or etiology of some neuronal diseases, altering disease susceptibility and therapy responses. Recent studies support epigenetic dysfunctions in neurodegenerative and psychiatric conditions, such as Alzheimer's disease (AD). These dysfunctions in epigenetic mechanisms also play crucial roles in the transgenerational effects of the environment on the brain and subsequently in the inheritance of pathologies. The possible role of gonadal steroids in the etiology and progression of neurodegenerative diseases, including Alzheimer's disease, has become the subject of a growing body of research over the last 20 years. Recent scientific findings suggest that epigenetic changes, driven by estrogen and androgens, play a vital role in brain functioning. Therefore, exploring the role of estrogen and androgen-based epigenetic changes in the brain is critical for the deeper understanding of AD. This review highlights the epigenetic modifications caused by these two gonadal steroids and the possible therapeutic strategies for AD.

A Genomic Study of the Japanese Population Focusing on the Glucocorticoid Receptor Interactome Highlights Distinct Genetic Characteristics Associated with Stress Response

All living organisms have been programmed to maintain a complex inner equilibrium called homeostasis, despite numerous adversities during their lifespan. Any threatening or perceived as such stimuli for homeostasis is termed a stressor, and a highly conserved response system called the stress response system has been developed to cope with these stimuli and maintain or reinstate homeostasis. The glucocorticoid receptor, a transcription factor belonging to the nuclear receptors protein superfamily, has a major role in the stress response system, and research on its interactome may provide novel information regarding the mechanisms underlying homeostasis maintenance. A list of 149 autosomal genes that have an essential role in GR function or are prime examples of GRE-containing genes was composed in order to gain a comprehensive view of the GR interactome. A search for SNPs on those particular genes was conducted on a dataset of 3554 Japanese individuals, with mentioned polymorphisms being annotated with relevant information from the ClinVar, LitVar, and dbSNP databases. Forty-two SNPs of interest and their genomic locations were identified. These SNPs have been associated with drug metabolism and neuropsychiatric, metabolic, and immune system disorders, while most of them were located in intronic regions. The frequencies of those SNPs were later compared with a dataset consisting of 1465 Korean individuals in order to find population-specific characteristics based on some of the identified SNPs of interest. The results highlighted.that rs1043618 frequencies were different in the two populations, with mentioned polymorphism having a potential role in chronic obstructive pulmonary disease in response to environmental stressors. This SNP is located in the HSPA1A gene, which codes for an essential GR co-chaperone, and such information showcases that similar gene may be novel genomic targets for managing or combatting stress-related pathologies.

Using epigenomics to understand cellular responses to environmental influences in diseases

It is a generally accepted model that environmental influences can exert their effects, at least in part, by changing the molecular regulators of transcription that are described as epigenetic. As there is biochemical evidence that some epigenetic regulators of transcription can maintain their states long term and through cell division, an epigenetic model encompasses the idea of maintenance of the effect of an exposure long after it is no longer present. The evidence supporting this model is mostly from the observation of alterations of molecular regulators of transcription following exposures. With the understanding that the interpretation of these associations is more complex than originally recognised, this model may be oversimplistic; therefore, adopting novel perspectives and experimental approaches when examining how environmental exposures are linked to phenotypes may prove worthwhile. In this review, we have chosen to use the example of nonalcoholic fatty liver disease (NAFLD), a common, complex human disease with strong environmental and genetic influences. We describe how epigenomic approaches combined with emerging functional genetic and single-cell genomic techniques are poised to generate new insights into the pathogenesis of environmentally influenced human disease phenotypes exemplified by NAFLD.

A secreted effector with a dual role as a toxin and as a transcriptional factor

Bacteria have evolved multiple secretion systems for delivering effector proteins into the cytosol of neighboring cells, but the roles of many of these effectors remain unknown. Here, we show that Yersinia pseudotuberculosis secretes an effector, CccR, that can act both as a toxin and as a transcriptional factor. The effector is secreted by a type VI secretion system (T6SS) and can enter nearby cells of the same species and other species (such as Escherichia coli) via cell-cell contact and in a contact-independent manner. CccR contains an N-terminal FIC domain and a C-terminal DNA-binding domain. In Y. pseudotuberculosis cells, CccR inhibits its own expression by binding through its DNA-binding domain to the cccR promoter, and affects the expression of other genes through unclear mechanisms. In E. coli cells, the FIC domain of CccR AMPylates the cell division protein FtsZ, inducing cell filamentation and growth arrest. Thus, our results indicate that CccR has a dual role, modulating gene expression in neighboring cells of the same species, and inhibiting the growth of competitors.

Interactions governing transcriptional activity of nuclear receptors

The key players in transcriptional regulation are transcription factors (TFs), proteins that bind specific DNA sequences. Several mechanisms exist to turn TFs ‘on’ and ‘off’, including ligand binding which induces conformational changes within TFs, subsequently influencing multiple inter- and intramolecular interactions to drive transcriptional responses. Nuclear receptors are a specific family of ligand-regulated TFs whose activity relies on interactions with DNA, coregulator proteins and other receptors. These multidomain proteins also undergo interdomain interactions on multiple levels, further modulating transcriptional outputs. Cooperation between these distinct interactions is critical for appropriate transcription and remains an intense area of investigation. In this review, we report and summarize recent findings that continue to advance our mechanistic understanding of how interactions between nuclear receptors and diverse partners influence transcription.

Molecular Cloning and Characterization of a Fasciola gigantica Nuclear Receptor Subfamily 1 (FgNR1)

Fasciola gigantica, a giant liver fluke, causes tremendous loss to the livestock economy in several regions throughout the world. The situation of drug resistance has been emerging increasingly; therefore, novel drugs and drug targets need to be discovered. The adult F. gigantica inhabits the major bile ducts where bile salts accumulate—these are steroid-like molecules that mediate several physiological processes in organisms through interacting with their specific nuclear receptors. However, the molecular mechanism of the interaction in the parasitic organisms have not been clearly understood. In this study, putative nuclear receptor subfamily 1 of F. gigantica (FgNR1) was identified. Nucleotide and amino acid sequences of the FgNR1 homolog were obtained from the transcriptome of F. gigantica and predicted for properties and functions using bioinformatics. The full-length cDNA was cloned and expressed in the bacterial expression system and then used for immunization. Western analysis and immunolocalization suggested that FgNR1 could be detected in the crude worm antigens and was highly expressed in the caeca and testes of the adult parasite. Moreover, the bile could significantly activate the expression of FgNR1 in cultured parasites. Our results indicated that FgNR1 has high potential for the development of a novel anthelminthic drug in the future.

Targeting HSP47 and HSP70: promising therapeutic approaches in liver fibrosis management

Liver fibrosis is a liver disease in which there is an excessive buildup of extracellular matrix proteins, including collagen. By regulating cytokine production and the inflammatory response, heat shock proteins (HSPs) contribute significantly to a wider spectrum of fibrotic illnesses, such as lung, liver, and idiopathic pulmonary fibrosis by aiding in the folding and assembly of freshly synthesized proteins, HSPs serve as chaperones. HSP70 is one of the key HSPs in avoiding protein aggregation which induces its action by sending unfolded and/or misfolded proteins to the ubiquitin–proteasome degradation pathway and antagonizing influence on epithelial-mesenchymal transition. HSP47, on the other hand, is crucial for boosting collagen synthesis, and deposition, and fostering the emergence of fibrotic disorders. The current review aims to provide light on how HSP70 and HSP47 affect hepatic fibrogenesis. Additionally, our review looks into new therapeutic approaches that target HSP70 and HSP47 and could potentially be used as drug candidates to treat liver fibrosis, especially in cases of comorbidities.

Regulation of P-Glycoprotein in the Brain

Maintenance of the tightly regulated homeostatic environment of the brain is facilitated by the blood-brain barrier (BBB). P-glycoprotein (P-gp), an ATP-binding cassette transporter, is expressed on the luminal surface of the endothelial cells in the BBB, and actively exports a wide variety of substrates to limit exposure of the vulnerable brain environment to waste buildup and neurotoxic compounds. Downregulation of P-gp expression and activity at the BBB have been reported with ageing and in neurodegenerative diseases. Upregulation of P-gp at the BBB contributes to poor therapeutic outcomes due to altered pharmacokinetics of CNS-acting drugs. The regulation of P-gp is highly complex, but unravelling the mechanisms involved may help the development of novel and nuanced strategies to modulate P-gp expression for therapeutic benefit. This review summarises the current understanding of P-gp regulation in the brain, encompassing the transcriptional, post-transcriptional and post-translational mechanisms that have been identified to affect P-gp expression and transport activity.

Gut Microsex/Genderome, Immunity and the Stress Response in the Sexes: An Updated Review

Sex has been universally acknowledged as a confounding factor in every type of biological study, while there are strong sex differences in morbidity along the lifespan. Humans have almost identical genomes (99.2%), yet minor variance in their DNA produces remarkable phenotypic diversity across the human population. On the other hand, metagenomic analysis of the human microbiome is more variable, depending on the sex, lifestyle, geography, and age of individuals under study. Immune responses in humans also exhibit variations, with an especially striking sexual dimorphism, which is at play in several other physiologic processes. Sex steroids have noticeable effects on the composition of the human microbiome along the lifespan, accompanied by parallel changes in immunity and the stress response. Gut microsex/genderome, a recently coined term, defines the sexually dimorphic gut microbiome. Apart from the sex steroids, the stress hormones are also at play in the proliferation of microbes. This review summarizes the concept of gut microsex/genderome under the prism of recent studies on the interrelations of the sexually dimorphic microbiome with immunity and stress.

Glucocorticoid Receptor Function and Cognitive Performance in Women With HIV

OBJECTIVE

Alterations in glucocorticoid receptor (GCR) function may be a risk factor for cognitive complications among older people with human immunodeficiency virus (HIV). We evaluated whether HIV serostatus and age modify the GCR function-cognition association among women.

METHODS

Eighty women with HIV ( n = 40, <40 years of age [younger]; n = 40, >50 years of age [older]) and 80 HIV-uninfected women ( n = 40 older, n = 40 younger) enrolled in the Women's Interagency HIV Study completed a comprehensive neuropsychological test battery. Peripheral blood mononuclear cells collected concurrent with neuropsychological testing were assessed for GCR function. Multivariable linear regression analyses were conducted to examine whether a) HIV serostatus and age were associated with GCR function, and b) GCR function-cognition associations are moderated by HIV serostatus and age adjusting for relevant covariates.

RESULTS

Among older women, higher baseline FKBP5 expression level was associated with lower attention/working memory performance among women with HIV ( B = 6.4, standard error = 1.7, p = .0003) but not in women without HIV infection ( B = -1.7, standard error = 1.9, p = .37). There were no significant HIV serostatus by age interactions on dexamethasone (DEX)-stimulated expression of the genes regulated by the GCR or lipopolysaccharide-stimulated tumor necrosis factor α levels (with or without DEX stimulation; p values > .13). HIV serostatus was associated with GC target genes PER1 ( p = .006) and DUSP1 ( p = .02), but not TSC22D3 ( p = .32), after DEX stimulation.

CONCLUSIONS

Collectively, these data suggest that HIV serostatus and age may modify the influence of the GCR, such that the receptor is likely engaged to a similar extent, but the downstream influence of the receptor is altered, potentially through epigenetic modification of target genes.

Sex-specific Effects of Endocrine-disrupting Chemicals on Brain Monoamines and Cognitive Behavior

The period of brain sexual differentiation is characterized by the development of hormone-sensitive neural circuits that govern the subsequent presentation of sexually dimorphic behavior in adulthood. Perturbations of hormones by endocrine-disrupting chemicals (EDCs) during this developmental period interfere with an organism's endocrine function and can disrupt the normative organization of male- or female-typical neural circuitry. This is well characterized for reproductive and social behaviors and their underlying circuitry in the hypothalamus and other limbic regions of the brain; however, cognitive behaviors are also sexually dimorphic, with their underlying neural circuitry potentially vulnerable to EDC exposure during critical periods of brain development. This review provides recent evidence for sex-specific changes to the brain's monoaminergic systems (dopamine, serotonin, norepinephrine) after developmental EDC exposure and relates these outcomes to sex differences in cognition such as affective, attentional, and learning/memory behaviors.

Detection of endocrine and metabolism disrupting xenobiotics in milk-derived fat samples by fluorescent protein-tagged nuclear receptors and live cell imaging

Nuclear receptors (NRs) are ligand-modulated transcription factors that regulate multiple physiological functions in our body. Many NRs in their unliganded state are localized in cytoplasm. The ligand-inducible nuclear translocation of NRs provides a valuable tool for studying the NR-ligand interactions and their downstream effects. The translocation response of NRs can be studied irrespective of the nature of the interacting ligand (agonist, antagonist, or a small molecule modulator). These nuclear translocation studies offer an advantage over promoter-reporter-based transcription assays where transcription response is observed only with the activating hormones or agonistic ligands. Globally, milk serves as a major dietary source. However, suspected presence of endocrine/metabolism disrupting chemicals like bisphenols, parabens, organochlorine pesticides, carbamates, non-steroidal anti-inflammatory drugs, chloramphenicol, brominated flame retardants, etc. has been reported. Considering that these chemicals may impart serious developmental and metabolism-related health concerns, it is essential to develop assays suitable for the detection of xenobiotics present at differing levels in milk. Since milk samples cannot be used directly on cultured cells or for microscopy, a combination of screening strategies has been developed herein based on the revelation that i) lipophilic NR ligands can be successfully retrieved in milk-fat; ii) milk-fat treatment of cells is compatible with live-cell imaging studies; and finally, iii) treatment of cells with xenobiotics-spiked and normal milk derived fat provides a visual and quantifiable response of NR translocation in living cells. Utilizing a milk-fat extraction method and Green Fluorescent Protein (GFP) tagged NRs expressed in cultured mammalian cells, followed by an assessment of NR response proved to be an effective approach for screening xenobiotics present in milk samples.HighlightsDiverse endocrine and metabolism disrupting chemicals are suspected to contaminate milk.Nuclear receptors serve as 'xenosensors' for assessing the presence of xenobiotics in milk.Nuclear import of steroid receptors with (ant)agonist can be examined in live cells.Lipophilic xenobiotics are extracted and observed enriched in milk-fat fraction.A comprehensive cell-based protocol aids in the detection of xenobiotics in milk.

Nutrient-Mediated Perception and Signalling in Human Metabolism: A Perspective of Nutrigenomics

The interaction between selective nutrients and linked genes involving a specific organ reveals the genetic make-up of an individual in response to a particular nutrient. The interaction of genes with food opens opportunities for the addition of bioactive compounds for specific populations comprising identical genotypes. The slight difference in the genetic blueprints of humans is advantageous in determining the effect of nutrients and their metabolism in the body. The basic knowledge of emerging nutrigenomics and nutrigenetics can be applied to optimize health, prevention, and treatment of diseases. In addition, nutrient-mediated pathways detecting the cellular concentration of nutrients such as sugars, amino acids, lipids, and metabolites are integrated and coordinated at the organismal level via hormone signals. This review deals with the interaction of nutrients with various aspects of nutrigenetics and nutrigenomics along with pathways involved in nutrient sensing and regulation, which can provide a detailed understanding of this new leading edge in nutrition research and its potential application to dietetic practice.

Nuclear Receptor Pathways Mediating the Development of Boar Taint

The nuclear receptors PXR, CAR, and FXR are activated by various ligands and function as transcription factors to control the expression of genes that regulate the synthesis and metabolism of androstenone and skatole. These compounds are produced in entire male pigs and accumulate in the fat to cause the development of a meat quality issue known as boar taint. The extent of this accumulation is influenced by the synthesis and hepatic clearance of androstenone and skatole. For this reason, PXR, CAR, and FXR-mediated signaling pathways have garnered interest as potential targets for specialized treatments designed to reduce the development of boar taint. Recent research has also identified several metabolites produced by gut microbes that act as ligands for these nuclear receptors (e.g., tryptophan metabolites, short-chain fatty acids, bile acids); however, the connection between the gut microbiome and boar taint development is not clear. In this review, we describe the nuclear receptor signaling pathways that regulate the synthesis and metabolism of boar taint compounds and outline the genes involved. We also discuss several microbial-derived metabolites and dietary additives that are known or suspected nuclear receptor ligands and suggest how these compounds could be used to develop novel treatments for boar taint.

Mechanism-driven modeling of chemical hepatotoxicity using structural alerts and an in vitro screening assay

Traditional experimental approaches to evaluate hepatotoxicity are expensive and time-consuming. As an advanced framework of risk assessment, adverse outcome pathways (AOPs) describe the sequence of molecular and cellular events underlying chemical toxicities. We aimed to develop an AOP that can be used to predict hepatotoxicity by leveraging computational modeling and in vitro assays. We curated 869 compounds with known hepatotoxicity classifications as a modeling set and extracted assay data from PubChem. The antioxidant response element (ARE) assay, which quantifies transcriptional responses to oxidative stress, showed a high correlation to hepatotoxicity (PPV=0.82). Next, we developed quantitative structure-activity relationship (QSAR) models to predict ARE activation for compounds lacking testing results. Potential toxicity alerts were identified and used to construct a mechanistic hepatotoxicity model. For experimental validation, 16 compounds in the modeling set and 12 new compounds were selected and tested using an in-house ARE-luciferase assay in HepG2-C8 cells. The mechanistic model showed good hepatotoxicity predictivity (accuracy = 0.82) for these compounds. Potential false positive hepatotoxicity predictions by only using ARE results can be corrected by incorporating structural alerts and vice versa. This mechanistic model illustrates a potential toxicity pathway for hepatotoxicity, and this strategy can be expanded to develop predictive models for other complex toxicities.

Exploring Ligand Binding Domain Dynamics in the NRs Superfamily

Nuclear receptors (NRs) are transcription factors that play an important role in multiple diseases, such as cancer, inflammation, and metabolic disorders. They share a common structural organization composed of five domains, of which the ligand-binding domain (LBD) can adopt different conformations in response to substrate, agonist, and antagonist binding, leading to distinct transcription effects. A key feature of NRs is, indeed, their intrinsic dynamics that make them a challenging target in drug discovery. This work aims to provide a meaningful investigation of NR structural variability to outline a dynamic profile for each of them. To do that, we propose a methodology based on the computation and comparison of protein cavities among the crystallographic structures of NR LBDs. First, pockets were detected with the FLAPsite algorithm and then an "all against all" approach was applied by comparing each pair of pockets within the same sub-family on the basis of their similarity score. The analysis concerned all the detectable cavities in NRs, with particular attention paid to the active site pockets. This approach can guide the investigation of NR intrinsic dynamics, the selection of reference structures to be used in drug design and the easy identification of alternative binding sites.

Chemotherapy and Physical Therapeutics Modulate Antigens on Cancer Cells

Cancer cells possess specific properties, such as multidrug resistance or unlimited proliferation potential, due to the presence of specific proteins on their cell membranes. The release of proliferation-related proteins from the membrane can evoke a loss of adaptive ability in cancer cells and thus enhance the effects of anticancer therapy. The upregulation of cancer-specific membrane antigens results in a better outcome of immunotherapy. Moreover, cytotoxic T-cells may also become more effective when stimulated ex-vivo toward the anticancer response. Therefore, the modulation of membrane proteins may serve as an interesting attempt in anticancer therapy. The presence of membrane antigens relies on various physical factors such as temperature, exposure to radiation, or drugs. Therefore, changing the tumor microenvironment conditions may lead to cancer cells becoming sensitized to subsequent therapy. This paper focuses on the therapeutic approaches modulating membrane antigens and enzymes in anticancer therapy. It aims to analyze the possible methods for modulating the antigens, such as pharmacological treatment, electric field treatment, photodynamic reaction, treatment with magnetic field or X-ray radiation. Besides, an overview of the effects of chemotherapy and immunotherapy on the immunophenotype of cancer cells is presented. Finally, the authors review the clinical trials that involved the modulation of cell immunophenotype in anticancer therapy.

Nuclear hormone receptors in demyelinating diseases

Demyelination results from the pathological loss of myelin and is a hallmark of many neurodegenerative diseases. Despite the prevalence of demyelinating diseases, there are no disease modifying therapies that prevent the loss of myelin or promote remyelination. This review aims to summarize studies in the field that highlight the importance of nuclear hormone receptors in the promotion and maintenance of myelination and the relevance of nuclear hormone receptors as potential therapeutic targets for demyelinating diseases. These nuclear hormone receptors include the estrogen receptor, progesterone receptor, androgen receptor, vitamin D receptor, thyroid hormone receptor, peroxisome proliferator-activated receptor, liver X receptor, and retinoid X receptor. Pre-clinical studies in well-established animal models of demyelination have shown a prominent role of these nuclear hormone receptors in myelination through their promotion of oligodendrocyte maturation and development. The activation of the nuclear hormone receptors by their ligands also promotes the synthesis of myelin proteins and lipids in mouse models of demyelination. There are limited clinical studies that focus on how the activation of these nuclear hormone receptors could alleviate demyelination in patients with diseases such as multiple sclerosis (MS). However, the completed clinical trials have reported improved clinical outcome in MS patients treated with the ligands of some of these nuclear hormone receptors. Together, the positive results from both clinical and pre-clinical studies point to nuclear hormone receptors as promising therapeutic targets to counter demyelination.

In vitro profiling of toxic effects of environmental polycyclic aromatic hydrocarbons on nuclear receptor signaling, disruption of endogenous metabolism and induction of cellular stress

Polycyclic aromatic hydrocarbons (PAHs) may interact with multiple intracellular receptors and related signaling pathways. We comprehensively evaluated the toxicity profiles of six environmentally relevant PAHs differing in structure, genotoxicity and their ability to activate the aryl hydrocarbon receptor (AhR). We focused particularly on their impact on intracellular hormone-, xenobiotic- and lipid-sensing receptors, as well as on cellular stress markers, combining a battery of human reporter gene assays and qRT-PCR evaluation of endogenous gene expression in human hepatocyte-like HepaRG cells, with LC/MS-MS analysis of cellular sphingolipids. The effects of PAHs included: activation of estrogen receptor α (in case of fluoranthene (Fla), pyrene (Pyr), benz[a]anthracene (BaA), benzo[a]pyrene (BaP)), suppression of androgen receptor activity (Fla, BaA, BaP and benzo[k]fluoranthene (BkF)), enhancement of dexamethasone-induced glucocorticoid receptor activity (chrysene (Chry), BaA, and BaP), and potentiation of triiodothyronine-induced thyroid receptor α activity (all tested PAHs). PAHs also induced transcription of endogenous gene targets of constitutive androstane receptor (Fla, Pyr), or repression of target genes of pregnane X receptor and peroxisome proliferator-activated receptor α (in case of the AhR-activating PAHs - Chry, BaA, BaP, and BkF) in HepaRG cells. In the same cell model, the AhR agonists reduced the expression of glucose metabolism genes (PCK1, G6PC and PDK4), and they up-regulated levels of glucosylceramides, together with a concomitant induction of expression of UGCG, glucosylceramide synthesis enzyme. Finally, both BaP and BkF were found to induce expression of early stress and genotoxicity markers: ATF3, EGR1, GDF15, CDKN1A/p21, and GADD45A mRNAs, while BaP alone increased levels of IL-6 mRNA. Overall, whereas low-molecular-weight PAHs exerted significant effects on nuclear receptors (with CYP2B6 induction observed already at nanomolar concentrations), the AhR activation by 4-ring and 5-ring PAHs appeared to be a key mechanism underlying their impact on nuclear receptor signaling, endogenous metabolism and induction of early stress and genotoxicity markers.

Transcriptomic and physiological analysis of endocrine disrupting chemicals Impacts on 3D Zebrafish liver cell culture system

In recent decades, extensive efforts have focused on developing in vitro platforms mimicking fish livers to better understand the acute or chronic effects of toxicants on lower aquatic vertebrates. Fish liver cell lines have emerged as a promising culture system for these in vitro platforms because they complement the currently limited in vitro tools that mostly consist of mammalian cell lines and adhere to the 3Rs: replacement, reduction, and refinement of living animal tests. However, monolayer cell lines have lower transcriptional and physiological responses upon exposure to toxic chemicals than freshly isolated primary cells. To overcome this challenge, we utilized a three-dimensional (3D) spheroid-based in vitro platform, in which hepatocyte cells had self-organized into spheroid forms via E-cadherin bonds. This platform exhibited augmented transcriptomic and phenotypic regulation of liver cells in comparison to monolayer cells. We examined the organoid platform using the zebrafish liver (ZFL) cell line as a model system. ZFL cells spontaneously clustered into 3D spheroids with long-term viability by optimizing cell seeding density on a non-adherent substrate. Interestingly, 3D ZFL spheroids treated with estrogenic chemicals were activated to synthesize a higher level of vitellogenin (Vtg) than monolayer cells. Whole-transcriptome sequencing analysis confirmed that 3D ZFL spheroids had greater transcriptional regulation of genes related to reproductive toxicological response and liver functions, such as the urea cycle, estrogen receptors, and vitellogenin, compared to monolayer cells. These results may contribute to the engineering of novel 3D in vitro platforms for screening harmful chemicals and improving understanding of the underlying liver toxicity mechanisms at the molecular and cellular levels.

The power of the (imperfect) palindrome: Sequence-specific roles of palindromic motifs in gene regulation

In human languages, a palindrome reads the same forward as backward (e.g., 'madam'). In regulatory DNA, a palindrome is an inverted sequence repeat that allows a transcription factor to bind as a homodimer or as a heterodimer with another type of transcription factor. Regulatory palindromes are typically imperfect, that is, the repeated sequences differ in at least one base pair, but the functional significance of this asymmetry remains poorly understood. Here, we review the use of imperfect palindromes in Drosophila photoreceptor differentiation and mammalian steroid receptor signaling. Moreover, we discuss mechanistic explanations for the predominance of imperfect palindromes over perfect palindromes in these two gene regulatory contexts. Lastly, we propose to elucidate whether specific imperfectly palindromic variants have specific regulatory functions in steroid receptor signaling and whether such variants can help predict transcriptional outcomes as well as the response of individual patients to drug treatments.

Hsp27, a potential EcR target, protects nonylphenol-induced cellular and organismal toxicity in Drosophila melanogaster

Deciphering the potential mechanism of chemical-induced toxicity enables us to alleviate the cellular and organismal dysfunction. The environmental presence of nonylphenol (endocrine disruptor) has a major health concern due to its widespread usage in our day-to-day life. The current study establishes a novel functional link among nonylphenol-induced oxidative stress, Heat shock protein 27 (Hsp27, member of stress protein family), and Ecdysone receptor (EcR, a nuclear receptor), which eventually coordinates the nonylphenol-induced sub-cellular and organismal level toxicity in a genetically tractable model Drosophila melanogaster. Drosophila larvae exposed to nonylphenol (0.05, 0.5 and 5.0 μg/mL) showed a significant decrease in Hsp27 and EcR mRNA levels in the midgut. In concurrence, reactive oxygen species (ROS) levels were increased with a corresponding decline in glutathione (GSH) level and Thioredoxin reductase (TrxR) activity. Increased lipid peroxidation (LPO), protein carbonyl (PC) contents, and cell death were also observed in a correlation with the nonylphenol concentrations. Sub-cellular toxicity poses a negative organismal response, which was evident by delayed larval development and reduced Drosophila emergence. Subsequently, a positive genetic correlation (p < 0.001) between EcR and Hsp27 revealed that nonylphenol-dependent EcR reduction is a possible link for the downregulation of Hsp27. Further, Hsp27 overexpression in midgut cells showed a reduction in nonylphenol-induced intracellular ROS, LPO, PC content, and cell death through the TrxR mediated regenerative pathway and reduced GSH level improving the organismal response to the nonylphenol exposure. Altogether, the study elucidates the potential EcR-Hsp27 molecular interactions in mitigating the nonylphenol-induced cellular and organismal toxicity.

Retinoid X Receptor: Cellular and Biochemical Roles of Nuclear Receptor with a Focus on Neuropathological Involvement

Retinoid X receptors (RXRs) present a subgroup of the nuclear receptor superfamily with particularly high evolutionary conservation of ligand binding domain. The receptor exists in α, β, and γ isotypes that form homo-/heterodimeric complexes with other permissive and non-permissive receptors. While research has identified the biochemical roles of several nuclear receptor family members, the roles of RXRs in various neurological disorders remain relatively under-investigated. RXR acts as ligand-regulated transcription factor, modulating the expression of genes that plays a critical role in mediating several developmental, metabolic, and biochemical processes. Cumulative evidence indicates that abnormal RXR signalling affects neuronal stress and neuroinflammatory networks in several neuropathological conditions. Protective effects of targeting RXRs through pharmacological ligands have been established in various cell and animal models of neuronal injury including Alzheimer disease, Parkinson disease, glaucoma, multiple sclerosis, and stroke. This review summarises the existing knowledge about the roles of RXR, its interacting partners, and ligands in CNS disorders. Future research will determine the importance of structural and functional heterogeneity amongst various RXR isotypes as well as elucidate functional links between RXR homo- or heterodimers and specific physiological conditions to increase drug targeting efficiency in pathological conditions.

Comprehensive Interactome Mapping of Nuclear Receptors Using Proximity Biotinylation

Nuclear receptors, including hormone receptors, perform their cellular activities by modulating their protein-protein interactions. They engage with specific ligands and translocate to the nucleus, where they bind the DNA and activate extensive transcriptional programs. Therefore, gaining a comprehensive overview of the protein-protein interactions they establish requires methods that function effectively throughout the cell with fast dynamics and high reproducibility. Focusing on estrogen receptor alpha (ESR1), the founding member of the nuclear receptor family, this chapter describes a new lentiviral system that allows the expression of TurboID-hemagglutinin (HA)-2 × Strep tagged proteins in mammalian cells to perform fast proximity biotinylation assays. Key validation steps for these reagents and their use in interactome mapping experiments in two distinct breast cancer cell lines are described. Our protocol enabled the quantification of ESR1 interactome generated by cellular contexts that were hormone-sensitive or not.

T cell transgressions: Tales of T cell form and function in diverse disease states

Insights into T cell form, function, and dysfunction are rapidly evolving. T cells have remarkably varied effector functions including protecting the host from infection, activating cells of the innate immune system, releasing cytokines and chemokines, and heavily contributing to immunological memory. Under healthy conditions, T cells orchestrate a finely tuned attack on invading pathogens while minimizing damage to the host. The dark side of T cells is that they also exhibit autoreactivity and inflict harm to host cells, creating autoimmunity. The mechanisms of T cell autoreactivity are complex and dynamic. Emerging research is elucidating the mechanisms leading T cells to become autoreactive and how such responses cause or contribute to diverse disease states, both peripherally and within the central nervous system. This review provides foundational information on T cell development, differentiation, and functions. Key T cell subtypes, cytokines that create their effector roles, and sex differences are highlighted. Pathological T cell contributions to diverse peripheral and central disease states, arising from errors in reactivity, are highlighted, with a focus on multiple sclerosis, rheumatoid arthritis, osteoarthritis, neuropathic pain, and type 1 diabetes.

Evolution of non-genomic nuclear receptor function

Nuclear receptors (NRs) are responsible for the regulation of diverse developmental and physiological systems in metazoans. NR actions can be the result of genomic and non-genomic mechanisms depending on whether they act inside or outside of the nucleus respectively. While the actions of both mechanisms have been shown to be crucial to NR functions, non-genomic actions are considered less frequently than genomic actions. Furthermore, hypotheses on the origin and evolution of non-genomic NR signaling pathways are rarely discussed in the literature. Here we summarize non-genomic NR signaling mechanisms in the context of NR protein family evolution and animal phyla. We find that NRs across groups and phyla act via calcium flux as well as protein phosphorylation cascades (MAPK/PI3K/PKC). We hypothesize and discuss a possible synapomorphy of NRs in the NR1 and NR3 families, including the thyroid hormone receptor, vitamin D receptor, ecdysone receptor, retinoic acid receptor, steroid receptors, and others. In conclusion, we propose that the advent of non-genomic NR signaling may have been a driving force behind the expansion of NR diversity in Cnidarians, Placozoans, and Bilaterians.

Photosensitized Oxidation of Intracellular Targets: Understanding the Mechanisms to Improve the Efficiency of Photodynamic Therapy

The development of improved photosensitizers is a key aspect in the establishment of photodynamic therapy (PDT) as a reliable treatment modality. In this chapter, we discuss how molecular design can lead to photosensitizers with higher selectivity and better efficiency, with focus on the importance of specific intracellular targeting in determining the cell death mechanism and, consequently, the PDT outcome.

Nuclear receptors modulate inflammasomes in the pathophysiology and treatment of major depressive disorder

Major depressive disorder (MDD) is highly prevalent and is a significant cause of mortality and morbidity worldwide. Currently, conventional pharmacological treatments for MDD produce temporary remission in < 50% of patients; therefore, there is an urgent need for a wider spectrum of novel antidepressants to target newly discovered underlying disease mechanisms. Accumulated evidence has shown that immune inflammation, particularly inflammasome activity, plays an important role in the pathophysiology of MDD. In this review, we summarize the evidence on nuclear receptors (NRs), such as glucocorticoid receptor, mineralocorticoid receptor, estrogen receptor, aryl hydrocarbon receptor, and peroxisome proliferator-activated receptor, in modulating the inflammasome activity and depression-associated behaviors. This review provides evidence from an endocrine perspective to understand the role of activated NRs in the pathophysiology of MDD, and to provide insight for the discovery of antidepressants with novel mechanisms for this devastating disorder.

Old and New Players of Inflammation and Their Relationship With Cancer Development

Pathogens or genotoxic agents continuously affect the human body. Acute inflammatory reaction induced by a non-sterile or sterile environment is triggered for the efficient elimination of insults that caused the damage. According to the insult, pathogen-associated molecular patterns, damage-associated molecular patterns, and homeostasis-altering molecular processes are released to facilitate the arrival of tissue resident and circulating cells to the injured zone to promote harmful agent elimination and tissue regeneration. However, when inflammation is maintained, a chronic phenomenon is induced, in which phagocytic cells release toxic molecules damaging the harmful agent and the surrounding healthy tissues, thereby inducing DNA lesions. In this regard, chronic inflammation has been recognized as a risk factor of cancer development by increasing the genomic instability of transformed cells and by creating an environment containing proliferation signals. Based on the cancer immunoediting concept, a rigorous and regulated inflammation process triggers participation of innate and adaptive immune responses for efficient elimination of transformed cells. When immune response does not eliminate all transformed cells, an equilibrium phase is induced. Therefore, excessive inflammation amplifies local damage caused by the continuous arrival of inflammatory/immune cells. To regulate the overstimulation of inflammatory/immune cells, a network of mechanisms that inhibit or block the cell overactivity must be activated. Transformed cells may take advantage of this process to proliferate and gradually grow until they become preponderant over the immune cells, preserving, increasing, or creating a microenvironment to evade the host immune response. In this microenvironment, tumor cells resist the attack of the effector immune cells or instruct them to sustain tumor growth and development until its clinical consequences. With tumor development, evolving, complex, and overlapping microenvironments are arising. Therefore, a deeper knowledge of cytokine, immune, and tumor cell interactions and their role in the intricated process will impact the combination of current or forthcoming therapies.

Synergistic gene regulation by thyroid hormone and glucocorticoid in the hippocampus

The hippocampus is considered the center for learning and memory in the brain, and its development and function is greatly affected by the thyroid and stress axes. Thyroid hormone (TH) and glucocorticoids (GC) are known to have a synergistic effect on developmental programs across several vertebrate species, and their effects on hippocampal structure and function are well-documented. However, there are few studies that focus on the processes and genes that are cooperatively regulated by the two hormone axes. Cross-regulation of the thyroid and stress axes in the hippocampus occurs on multiple levels such that TH can regulate the expression of the GC receptor (GR) while GC can modulate tissue sensitivity to TH by controlling the expression of TH receptor (TR) and enzymes involved in TH biosynthesis. Thyroid hormone and GC are also known to synergistically regulate the transcription of genes associated with neuronal function and development. Synergistic gene regulation by TH and GC may occur through the direct, cooperative action of TR and GR on common target genes, or by indirect mechanisms involving gene regulatory cascades activated by TR and GR. In this chapter, we describe the known physiological effects and underlying molecular mechanisms of TH and GC synergistic gene regulation in the hippocampus.

Role of Peroxisome Proliferator-Activated Receptors (PPARs) in Energy Homeostasis of Dairy Animals: Exploiting Their Modulation through Nutrigenomic Interventions

Peroxisome proliferator-activated receptors (PPARs) are the nuclear receptors that could mediate the nutrient-dependent transcriptional activation and regulate metabolic networks through energy homeostasis. However, these receptors cannot work properly under metabolic stress. PPARs and their subtypes can be modulated by nutrigenomic interventions, particularly under stress conditions to restore cellular homeostasis. Many nutrients such as polyunsaturated fatty acids, vitamins, dietary amino acids and phytochemicals have shown their ability for potential activation or inhibition of PPARs. Thus, through different mechanisms, all these nutrients can modulate PPARs and are ultimately helpful to prevent various metabolic disorders, particularly in transition dairy cows. This review aims to provide insights into the crucial role of PPARs in energy metabolism and their potential modulation through nutrigenomic interventions to improve energy homeostasis in dairy animals.

Nuclear Receptor-Mediated Metabolic Reprogramming and the Impact on HR+ Breast Cancer

Simple Summary

Breast cancer is the most commonly diagnosed and second leading cause of cancer-related deaths in women in the United States, with hormone receptor positive (HR+) tumors representing more than two-thirds of new cases. Recent evidence has indicated that dysregulation of multiple metabolic programs, which can be driven through nuclear receptor activity, is essential for tumor genesis, progression, therapeutic resistance and metastasis. This study will review the current advances in our understanding of the impact and implication of altered metabolic processes driven by nuclear receptors, including hormone-dependent signaling, on HR+ breast cancer.

Abstract

Metabolic reprogramming enables cancer cells to adapt to the changing microenvironment in order to maintain metabolic energy and to provide the necessary biological macromolecules required for cell growth and tumor progression. While changes in tumor metabolism have been long recognized as a hallmark of cancer, recent advances have begun to delineate the mechanisms that modulate metabolic pathways and the consequence of altered signaling on tumorigenesis. This is particularly evident in hormone receptor positive (HR+) breast cancers which account for approximately 70% of breast cancer cases. Emerging evidence indicates that HR+ breast tumors are dependent on multiple metabolic processes for tumor progression, metastasis, and therapeutic resistance and that changes in metabolic programs are driven, in part, by a number of key nuclear receptors including hormone-dependent signaling. In this review, we discuss the mechanisms and impact of hormone receptor mediated metabolic reprogramming on HR+ breast cancer genesis and progression as well as the therapeutic implications of these metabolic processes in this disease.

A C terminus-dependent conformational change is required for HDAC3 activation by nuclear receptor corepressors

Histone deacetylase 3 (HDAC3) plays an important role in signal-dependent transcription and is dysregulated in diseases such as cancer. Previous studies have shown that the function of HDAC3 requires an activation step, which is mediated by the interactions of HDAC3 with the deacetylase-activation domain (DAD) of nuclear receptor corepressors and inositol tetraphosphate (IP4). However, the role of the unique HDAC3 C-terminal region in HDAC3 activation is elusive. Here multiple biochemical, structural, and functional studies show that HDAC3 activation requires a priming step mediated by the C terminus to remodel HDAC3 conformation. We show that multiple C-terminal mutations prevent HDAC3 activation by preventing this C terminus–dependent conformational change. Mechanistically, we demonstrate that the C terminus–mediated function in altering HDAC3 conformation is required for proper complex formation of HDAC3 with DAD and IP4 by allowing HDAC3 to undergo IP4-dependent interaction with DAD. Remarkably, we found that this C terminus function is conformation dependent, being necessary for HDAC3 activation prior to but not after the conformational change. Together, our study defines two functional states of free HDAC3, reveals the complete HDAC3 activation pathway, and links the C terminus function to the specific interaction between HDAC3 and DAD. These results also have implications in how signaling pathways may converge on the C terminus to regulate HDAC3 and suggest that the C terminus–mediated conformational change could represent a new target for inhibiting HDAC3 in diseases such as cancer.

The transcription factors CREBH, PPARa, and FOXO1 as critical hepatic mediators of diet-induced metabolic dysregulation

The liver is a critical mediator of lipid and/or glucose homeostasis and is a primary organ involved in dynamic changes during feeding and fasting. Additionally, hepatic-centric pathways are prone to dysregulation during pathophysiological states including metabolic syndrome (MetS) and non-alcoholic fatty liver disease. Omics platforms and GWAS have elucidated genes related to increased risk of developing MetS and related disorders, but mutations in these metabolism-related genes are rare and cannot fully explain the increasing prevalence of MetS-related pathologies worldwide. Complex interactions between diet, lifestyle, environmental factors, and genetic predisposition jointly determine inter-individual variability of disease risk. Given the complexity of these interactions, researchers have focused on master regulators of metabolic responses incorporating and mediating the impact of multiple environmental cues. Transcription factors are DNA binding, terminal executors of signaling pathways that modulate the cellular responses to complex metabolic stimuli and are related to the control of hepatic lipid and glucose homeostasis. Among numerous hepatic transcription factors involved in regulating metabolism, three emerge as key players in transducing nutrient sensing, which are dysregulated in MetS-related perturbations in both clinical and preclinical studies: cAMP Responsive Element Binding Protein 3 Like 3 (CREB3L3), Peroxisome Proliferator Activated Receptor Alpha (PPAR), and Forkhead Box O1 (FOXO1). Additionally, these three transcription factors appear to be amenable to dietary and/or nutrient-based therapies, being potential targets of nutritional therapy. In this review we aim to describe the activation, regulation, and impact of these transcription factors in the context of metabolic homeostasis. We also summarize their perspectives in MetS and nutritional therapies.

Identification of Androgen Receptor Metabolic Correlome Reveals the Repression of Ceramide Kinase by Androgens

Prostate cancer (PCa) is one of the most prevalent cancers in men. Androgen receptor signaling plays a major role in this disease, and androgen deprivation therapy is a common therapeutic strategy in recurrent disease. Sphingolipid metabolism plays a central role in cell death, survival, and therapy resistance in cancer. Ceramide kinase (CERK) catalyzes the phosphorylation of ceramide to ceramide 1-phosphate, which regulates various cellular functions including cell growth and migration. Here we show that activated androgen receptor (AR) is a repressor of CERK expression. We undertook a bioinformatics strategy using PCa transcriptomics datasets to ascertain the metabolic alterations associated with AR activity. CERK was among the most prominent negatively correlated genes in our analysis. Interestingly, we demonstrated through various experimental approaches that activated AR reduces the mRNA expression of CERK: (i) expression of CERK is predominant in cell lines with low or negative AR activity; (ii) AR agonist and antagonist repress and induce CERK mRNA expression, respectively; (iii) orchiectomy in wildtype mice or mice with PCa (harboring prostate-specific Pten deletion) results in elevated Cerk mRNA levels in prostate tissue. Mechanistically, we found that AR represses CERK through interaction with its regulatory elements and that the transcriptional repressor EZH2 contributes to this process. In summary, we identify a repressive mode of AR that influences the expression of CERK in PCa.

Nuclear Receptors in Liver Fibrosis

Nuclear receptors are ligand-activated transcription factors that regulate gene expression of a variety of key molecular signals involved in liver fibrosis. The primary cellular driver of liver fibrogenesis are activated hepatic stellate cells. Different NRs regulate the hepatic expression of pro-inflammatory and pro-fibrogenic cytokines that promote the transformation of hepatic stellate cells into fibrogenic myofibroblasts. Importantly, nuclear receptors regulate gene expression circuits that promote hepatic fibrogenesis and/or allow liver fibrosis regression. In this review, we highlight the direct and indirect influence of nuclear receptors on liver fibrosis, with a focus on hepatic stellate cells, and discuss potential therapeutic effects of nuclear receptor modulation in regard to anti-fibrotic and anti-inflammatory effects. Further research on nuclear receptors-related signaling may lead to the clinical development of effective anti-fibrotic therapies for patients with liver disease.

Transcription factors: Bridge between cell signaling and gene regulation

Transcription factors (TFs) are key regulators of intrinsic cellular processes, such as differentiation and development, and of the cellular response to external perturbation through signaling pathways. In this review we focus on the role of TFs as a link between signaling pathways and gene regulation. Cell signaling tends to result in the modulation of a set of TFs that then lead to changes in the cell's transcriptional program. We highlight the molecular layers at which TF activity can be measured and the associated technical and conceptual challenges. These layers include post-translational modifications (PTMs) of the TF, regulation of TF binding to DNA through chromatin accessibility and epigenetics, and expression of target genes. We highlight that a large number of TFs are understudied in both signaling and gene regulation studies, and that our knowledge about known TF targets has a strong literature bias. We argue that TFs serve as a perfect bridge between the fields of gene regulation and signaling, and that separating these fields hinders our understanding of cell functions. Multi-omics approaches that measure multiple dimensions of TF activity are ideally suited to study the interplay of cell signaling and gene regulation using TFs as the anchor to link the two fields.