Activation of ERß hijacks the splicing machinery to trigger R-loop formation in triple-negative breast cancer.

Triple-negative breast cancer (TNBC) is a subtype of breast cancer with aggressive behavior and poor prognosis. Current therapeutic options available for TNBC patients are primarily chemotherapy. With our evolving understanding of this disease, novel targeted therapies, including poly ADP-ribose polymerase (PARP) inhibitors, antibody-drug conjugates, and immune-checkpoint inhibitors, have been developed for clinical use. Previous reports have demonstrated the essential role of estrogen receptor ß (ERß) in TNBC, but the detailed molecular mechanisms downstream ERß activation in TNBC are still far from elucidated. In this study, we demonstrated that a specific ERß agonist, LY500307, potently induces R-loop formation and DNA damage in TNBC cells. Subsequent interactome experiments indicated that the residues 151 to 165 of U2 small nuclear RNA auxiliary factor 1 (U2AF1) and the Trp439 and Lys443 of ERß were critical for the binding between U2AF1 and ERß. Combined RNA sequencing and ribosome sequencing analysis demonstrated that U2AF1-regulated downstream RNA splicing of 5-oxoprolinase (OPLAH) could affect its enzymatic activity and is essential for ERß-induced R-loop formation and DNA damage. In clinical samples including 115 patients from The Cancer Genome Atlas (TCGA) and 32 patients from an in-house cohort, we found a close correlation in the expression of ESR2 and U2AF1 in TNBC patients. Collectively, our study has unraveled the molecular mechanisms that explain the therapeutic effects of ERß activation in TNBC, which provides rationale for ERß activation-based single or combined therapy for patients with TNBC.

A structural perspective of liver X receptors.

Liver X receptors α and ß are members of the nuclear receptor family, which comprise a flexible N-terminal domain, a DNA binding domain, a hinge linker, and a ligand binding domain. Liver X receptors are important regulators of cholesterol and lipid homeostasis by controlling the transcription of numerous genes. Key to their transcriptional role is synergetic interaction among the domains. DNA binding domain binds on DNA; ligand binding domain is a crucial switch to control the transcription activity through conformational change caused by ligand binding. The Liver X receptors form heterodimers with retinoid X receptor and then the liganded heterodimer may recruit other necessary transcription components to form an active transcription complex.

Loss of ERß in Aging LXRαß Knockout Mice Leads to Colitis.

Liver X receptors (LXRα and LXRß) are oxysterol-activated nuclear receptors that play key roles in cholesterol homeostasis, the central nervous system, and the immune system. We have previously reported that LXRαß-deficient mice are more susceptible to dextran sodium sulfate (DSS)-induced colitis than their WT littermates, and that an LXR agonist protects against colitis in mice mainly via the regulation of the immune system in the gut. We now report that both LXRα and LXRß are expressed in the colonic epithelium and that in aging LXRαß-/- mice there is a reduction in the intensity of goblet cells, mucin (MUC2), TFF3, and estrogen receptor ß (ERß) levels. The cytoplasmic compartment of the surface epithelial cells was markedly reduced and there was a massive invasion of macrophages in the lamina propria. The expression and localization of ß-catenin, α-catenin, and E-cadherin were not changed, but the shrinkage of the cytoplasm led to an appearance of an increase in staining. In the colonic epithelium there was a reduction in the expression of plectin, a hemidesmosome protein whose loss in mice leads to spontaneous colitis, ELOVL1, a fatty acid elongase protein coding gene whose overexpression is found in colorectal cancer, and non-neuronal choline acetyltransferase (ChAT) involved in the regulation of epithelial cell adhesion. We conclude that in aging LXRαß-/- mice, the phenotype in the colon is due to loss of ERß expression.

Liver X receptors and estrogen receptor ß, two players in a rare subtype of NSCLC.

Liver X receptors (LXRαß) play essential roles in the maintenance of the normal functions of macrophages, in modulation of immune system responses and cholesterol homeostasis. We have reported that LXRαß-/- mice develop squamous cell lung cancer. We now report that those LXRαß-/- mice, which live to 18-months of age, spontaneously develop a second type of lung cancer resembling a rare subtype of NSCLC (TTF-1 and P63-positive). The lesions are characterized as follows: a high proliferation rate; a marked accumulation of abnormal macrophages; an increase in the number of regulatory T cells; a remarkably low level of CD8+ cytotoxic T lymphocytes; enhanced TGFß signaling; an increased expression of matrix metalloproteinases accompanied by degradation of lung collagen; and a loss of estrogen receptor ß (ERß). Because NSCLC is associated with cigarette smoking, we investigated the possible links between loss of LXRαß and CS. A Kaplan-Meier Plotter database revealed reduced expression of LXRαß and ERß was correlated with low overall survival (OS). Thus, reduction of LXRαß expression by cigarette smoking may be one mechanism through which CS causes lung cancer. The possibility that maintenance of LXRαß and ERß signaling could be used in the treatment of NSCLC needs further investigation.

Estrogen receptor ß attenuates renal fibrosis by suppressing the transcriptional activity of Smad3.

Renal fibrosis (RF) is a common pathway leading to chronic kidney disease (CKD), which lacks effective treatment. While estrogen receptor beta (ERß) is known to be present in the kidney, its role in RF remains unclear. The present study aimed to investigate the role and underlying mechanism of ERß during RF progression in patients and animal models with CKD. We found that ERß was highly expressed in the proximal tubular epithelial cells (PTECs) in healthy kidneys but its expression was largely lost in patients with immunoglobin A nephropathy (IgAN) and in mice with unilateral ureter obstruction (UUO) and subtotal nephrectomy (5/6Nx). ERß deficiency markedly exacerbated, whereas ERß activation by WAY200070 and DPN attenuated RF in both UUO and 5/6Nx mouse models, suggesting a protective role of ERß in RF. In addition, ERß activation inhibited TGF-ß1/Smad3 signaling, while loss of renal ERß was associated with overactivation of the TGF-ß1/Smad3 pathway. Furthermore, deletion or pharmacological inhibition of Smad3 prevented the loss of ERß and RF. Mechanistically, activation of ERß competitively inhibited the association of Smad3 with the Smad-binding element, thereby downregulating the transcription of the fibrosis-related genes without altering Smad3 phosphorylation in vivo and in vitro. In conclusion, ERß exerts a renoprotective role in CKD by blocking the Smad3 signaling pathway. Thus, ERß may represent as a promising therapeutic agent for RF.

Estrogen Receptor ß4 Regulates Chemotherapy Resistance and Induces Cancer Stem Cells in Triple Negative Breast Cancer.

Triple Negative Breast Cancer (TNBC) has the worst prognosis among all breast cancers, and survival in patients with recurrence is rarely beyond 12 months due to acquired resistance to chemotherapy, which is the standard of care for these patients. Our hypothesis is that Estrogen Receptor ß1 (ERß1) increases response to chemotherapy but is opposed by ERß4, which it preferentially dimerizes with. The role of ERß1 and ERß4 in influencing chemotherapy sensitivity has never been studied before. CRISPR/CAS9 was used to truncate ERß1 Ligand Binding Domain (LBD) and knock down the exon unique to ERß4. We show that the truncated ERß1 LBD in a variety of mutant p53 TNBC cell lines, where ERß1 ligand dependent function was inactivated, had increased resistance to Paclitaxel, whereas the ERß4 knockdown cell line was sensitized to Paclitaxel. We further show that ERß1 LBD truncation, as well as treatment with ERß1 antagonist 2-phenyl-3-(4-hydroxyphenyl)-5,7-bis(trifluoromethyl)-pyrazolo[1,5-a] pyrimidine (PHTPP), leads to increase in the drug efflux transporters. Hypoxia Inducible Factors (HIFs) activate factors involved in pluripotency and regulate the stem cell phenotype, both in normal and cancer cells. Here we show that the ERß1 and ERß4 regulate these stem cell markers like SOX2, OCT4, and Nanog in an opposing manner; and we further show that this regulation is mediated by HIFs. We show the increase of cancer cell stemness due to ERß1 LBD truncation is attenuated when HIF1/2α is knocked down by siRNA. Finally, we show an increase in the breast cancer stem cell population due to ERß1 antagonist using both ALDEFLUORTM and SOX2/OCT4 response element (SORE6) reporters in SUM159 and MDA-MB-231 cell lines. Since most TNBC cancers are ERß4 positive, while only a small proportion of TNBC patients are ERß1 positive, we believe that simultaneous activation of ERß1 with agonists and inactivation of ERß4, in combination with paclitaxel, can be more efficacious and yield better outcome for chemotherapy resistant TNBC patients.

Triazole fungicides induce adipogenesis and repress osteoblastogenesis in zebrafish.

Triazoles are a major group of azole fungicides commonly used in agriculture, and veterinary and human medicine. Maternal exposure to certain triazole antifungal medication causes congenital malformations, including skeletal malformations. We hypothesized that triazoles used as pesticides in agriculture also pose a risk of causing skeletal malformations in developing embryos. In this study, teratogenic effects of three commonly used triazoles, cyproconazole, paclobutrazol, and triadimenol, were investigated in zebrafish, Danio rerio. Exposure to the triazole fungicides caused bone and cartilage malformations in developing zebrafish larvae. Data from whole-embryo transcriptomics with cyproconazole suggested that exposure to this compound induces adipogenesis while repressing skeletal development. Confirming this finding, the expression of selected bone and cartilage marker genes were significantly downregulated with triazoles exposure as determined by quantitative PCR. The expression of selected adipogenic genes was upregulated by the triazoles. Furthermore, exposure to each of the three triazoles induced adipogenesis and lipid droplet formation in vitro in 3T3-L1 pre-adipocyte cells. In vivo in zebrafish larvae, cyproconazole exposure caused lipid accumulation. These results suggest that exposure to triazoles promotes adipogenesis at the expense of skeletal development, and thus they expand the chemical group of bona fide bone to fat switchers.

Valproic acid exposure decreases neurogenic potential of outer radial glia in human brain organoids.

Valproic acid (VPA) exposure during pregnancy leads to a higher risk of autism spectrum disorder (ASD) susceptibility in offspring. Human dorsal forebrain organoids were used to recapitulate course of cortical neurogenesis in the developing human brain. Combining morphological characterization with massive parallel RNA sequencing (RNA-seq) on organoids to analyze the pathogenic effects caused by VPA exposure and critical signaling pathway. We found that VPA exposure in organoids caused a reduction in the size and impairment in the proliferation and expansion of neural progenitor cells (NPCs) in a dose-dependent manner. VPA exposure typically decreased the production of outer radial glia-like cells (oRGs), a subtype of NPCs contributing to mammalian neocortical expansion and delayed their fate toward upper-layer neurons. Transcriptomics analysis revealed that VPA exposure influenced ASD risk gene expression in organoids, which markedly overlapped with irregulated genes in brains or organoids originating from ASD patients. We also identified that VPA-mediated Wnt/ß-catenin signaling pathway activation is essential for sustaining cortical neurogenesis and oRGs output. Taken together, our study establishes the use of dorsal forebrain organoids as an effective platform for modeling VPA-induced teratogenic pathways involved in the cortical neurogenesis and oRGs output, which might contribute to ASD pathogenesis in the developing brain.

Bisphenol A analogues induce a feed-forward estrogenic response in zebrafish.

Because exposure to bisphenol A (BPA) has been linked to health problems in humans and wildlife, BPA analogues have been synthesized to be considered as replacement molecules. We here have examined estrogenic activity of BPA and five of its analogues, BPAF, BPE, BPC, BPC-Cl, and BPS by a combination of zebrafish-based in vivo and in vitro assays. We used transgenic estrogen reporter (5xERE:GFP) fish to study agonistic effects of bisphenols. Exposures to BPA, BPAF, BPE, and BPC, induced GFP expression in estrogen reporter fish at low exposure concentrations in the heart valves and at higher concentrations in the liver, whereas BPC-Cl activated GFP expression mainly in the liver, and BPS faintly in the heart only. The in vivo response was compared to in vitro estrogenicity of bisphenol exposure using reporter cells that express the zebrafish estrogen receptors driving expression of an estrogen response element (ERE)-luciferase reporter. In these cells, BPA, BPAF, BPC, BPE and BPS preferentially activated Esr1, whereas BPC-Cl preferentially activated Esr2a. By quantitative PCR we found that exposure to BPAF induced expression of the classical estrogen target genes vtg1, esr1, and cyp19a1b in a concentration response manner, but the most responsive target gene was f13a1a. Exposure to BPC-Cl resulted in a different expression pattern of vtg1 and f13a1a with an activation at low concentrations, followed by a declining expression at higher concentrations. Because expression of f13a1a was strongly activated by all compounds tested, we suggest including this mRNA as a biomarker for estrogenicity in larval fish. We further showed that exposure to BPAF and BPC-Cl increased E2 levels in zebrafish larvae, indicating that bisphenol exposures result in a feed-forward response that can further augment the estrogenic activity of these compounds.

Liver X Receptor Regulation of Glial Cell Functions in the CNS.

In this review, we discuss the role of liver X receptors (LXRs) in glial cells (microglia, oligodendrocytes and astrocytes) in the central nervous system (CNS). LXRs are oxysterol-activated nuclear receptors that, in adults, regulate genes involved in cholesterol homeostasis, the modulation of inflammatory responses and glutamate homeostasis. The study of LXR knockout mice has revealed that LXRß plays a key role in maintaining the health of dopaminergic neurons in the substantia nigra, large motor neurons in the spinal cord and retinal ganglion cells in the eye. In the peripheral nervous system (PNS), LXRß is responsible for the health of the spiral ganglion neurons (SGNs) in the cochlea. In addition, LXRs are essential for the homeostasis of the cerebrospinal fluid (CSF), and in LXRαß-/- mice, the lateral ventricles are empty and lined with lipid-laden cells. As LXRαß-/- mice age, lipid vacuoles accumulate in astrocytes surrounding blood vessels. By seven months of age, motor coordination becomes impaired, and there is a loss of motor neurons in the spinal cord of LXRß-/- mice. During development, migration of neurons in the cortex and cerebellum is retarded in LXRß-/- mice. Since LXRs are not expressed in dopaminergic or motor neurons in adult mice, the neuroprotective effects of LXRs appear to come from LXRs in glial cells where they are expressed. However, despite the numerous neurological deficits in LXR-/- rodents, multiple sclerosis has the clear distinction of being the only human neurodegenerative disease in which defective LXR signaling has been identified. In this review, we summarize the regulation and functions of LXRs in glial cells and analyze how targeting LXRs in glial cells might, in the future, be used to treat neurodegenerative diseases and, perhaps, disorders caused by aberrant neuronal migration during development.

Estrogen receptor ß deficiency impairs gut microbiota: a possible mechanism of IBD-induced anxiety-like behavior.

BACKGROUND: Although the lack of estrogen receptor ß (ERß) is a risk factor for the development of inflammatory bowel disease (IBD) and psychiatric disorders, the underlying cellular and molecular mechanisms are not fully understood. Herein, we revealed the role of gut microbiota in the development of IBD and related anxiety-like behavior in ERß-deficient mice. RESULTS: In response to dextran sodium sulfate (DSS) insult, the ERß knockout mice displayed significant shift in α and ß diversity in the fecal microbiota composition and demonstrated worsening of colitis and anxiety-like behaviors. In addition, DSS-induced colitis also induced hypothalamic-pituitary-adrenal (HPA) axis hyperactivity in ERß-deficient mice, which was associated with colitis and anxiety-like behaviors. In addition, RNA sequencing data suggested that ErbB4 might be the target of ERß that is involved in regulating the HPA axis hyperactivity caused by DSS insult. Gut microbiota remodeling by co-housing showed that both the colitis and anxiety-like behaviors were aggravated in co-housed wild-type mice compared to single-housed wild-type mice. These findings suggest that gut microbiota play a critical role in mediating colitis disease activity and anxiety-like behaviors via aberrant neural processing within the gut-brain axis. CONCLUSIONS: ERß has the potential to inhibit colitis development and anxiety-like behaviors via remodeling of the gut microbiota, which suggests that ERß is a promising therapeutic target for the treatment of IBD and related anxiety-like behaviors. Video Abstract.

ERα Signaling in a Subset of CXCL12-Abundant Reticular Cells Regulates Trabecular Bone in Mice.

Estrogen has pronounced effects on the immune system, which also influences bone homeostasis. In recent years, stromal cells in lymphoid organs have gained increasing attention as they not only support the regulation of immune responses but also affect bone remodeling. A conditional knockout mouse model where estrogen receptor alpha (ERα) is deleted in CCL19-expressing stromal cells (Ccl19-Cre ERα fl/fl mice) was generated and bone densitometry was performed to analyze the importance of stromal cell-specific ERα signaling on the skeleton. Results showed that female Ccl19-Cre ERα fl/fl mice display reduced total bone mineral density and detailed X-ray analyses revealed that ERα expression in CCL19-expressing stromal cells is important for trabecular but not cortical bone homeostasis. Further analysis showed that the trabecular bone loss is caused by increased osteoclastogenesis. Additionally, the bone formation rate was reduced; however, the expression of osteoprogenitor genes was not altered. Analysis of the bone marrow stromal cell compartment revealed a deletion of ERα in a subgroup of CXCL12-abundant reticular (CAR) cells resulting in increased secretion of the pro-osteoclastogenic chemokine CXCL12. In conclusion, this study reveals the importance of ERα signaling in CAR cells for bone health. © 2022 The Authors. JBMR Plus published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research.

Ahi1 regulates serotonin production by the GR/ERß/TPH2 pathway involving sexual differences in depressive behaviors.

BACKGROUND: Depression is one of the most common psychiatric diseases. The monoamine transmitter theory suggests that neurotransmitters are involved in the mechanism of depression; however, the regulation on serotonin production is still unclear. We previously showed that Ahi1 knockout (KO) mice exhibited depression-like behavior accompanied by a significant decrease in brain serotonin. METHODS: In the present study, western blot, gene knockdown, immunofluorescence, dual-luciferase reporter assay, and rescue assay were used to detect changes in the Ahi1/GR/ERß/TPH2 pathway in the brains of male stressed mice and male Ahi1 KO mice to explain the pathogenesis of depression-like behaviors. In addition, E2 levels in the blood and brain of male and female mice were measured to investigate the effect on the ERß/TPH2 pathway and to reveal the mechanisms for the phenomenon of gender differences in depression-like behaviors. RESULTS: We found that the serotonin-producing pathway-the ERß/TPH2 pathway was inhibited in male stressed mice and male Ahi1 KO mice. We further demonstrated that glucocorticoid receptor (GR) as a transcription factor bound to the promoter of ERß that contains glucocorticoid response elements and inhibited the transcription of ERß. Our recent study had indicated that Ahi1 regulates the nuclear translocation of GR upon stress, thus proposing the Ahi1/GR/ERß/TPH2 pathway for serotonin production. Interestingly, female Ahi1 KO mice did not exhibit depressive behaviors, indicating sexual differences in depressive behaviors compared with male mice. Furthermore, we found that serum 17ß-estradiol (E2) level was not changed in male and female mice; however, brain E2 level significantly decreased in male but not female Ahi1 KO mice. Further, ERß agonist LY-500307 increased TPH2 expression and 5-HT production. Therefore, both Ahi1 and E2 regulate the ERß/TPH2 pathway and involve sexual differences in brain serotonin production and depressive behaviors. CONCLUSIONS: In conclusion, although it is unclear how Ahi1 controls E2 secretion in the brain, our findings demonstrate that Ahi1 regulates serotonin production by the GR/ERß/TPH2 pathway in the brain and possibly involves the regulation on sex differences in depressive behaviors. Video Abstract.

Ablation of Liver X receptor ß in mice leads to overactive macrophages and death of spiral ganglion neurons.

Age-related hearing loss is the most common type of hearing impairment, and is typically characterized by the loss of spiral ganglion neurons (SGNs). The two Liver X receptors (LXRs) are oxysterol-activated nuclear receptors which in adults, regulate genes involved in cholesterol homeostasis and modulation of macrophage activity. LXRß plays a key role in maintenance of health of dopaminergic neurons in the substantia nigra, large motor neurons in the spinal cord, and retinal ganglion cells in adult mice. We now report that LXRß is expressed in the SGNs of the cochlea and that loss of LXRß leads to age-related cochlea degeneration. We found that in the cochlea of LXRß-/- mice, there is loss of SGNs, activation of macrophages, demyelination in the spiral ganglion, decrease in glutamine synthetase (GS) expression and increase in glutamate accumulation in the cochlea. Part of the cause of damage to the SGNs might be glutamate toxicity which is known to be very toxic to these cells. Our study provides a so far unreported role of LXRß in maintenance of SGNs whose loss is a very common cause of hearing impairment.

Inactivation of AR or ERα in Extrahypothalamic Neurons Does not Affect Osteogenic Response to Loading in Male Mice.

Failure of bone mass maintenance in spite of functional loading is an important contributor to osteoporosis and related fractures. While the link between sex steroids and the osteogenic response to loading is well established, the underlying mechanisms are unknown, hampering clinical relevance. Androgens inhibit mechanoresponsiveness in male mice, but the cell type mediating this effect remains unidentified. To evaluate the role of neuronal sex steroid receptor signaling in the male bone's adaptive capacity, we subjected adult male mice with an extrahypothalamic neuron-specific knockout of the androgen receptor (N-ARKO) or the estrogen receptor alpha (N-ERαKO) to in vivo mechanical stimulation of the tibia. Loading increased cortical thickness in the control animals mainly through periosteal expansion, as total cross-sectional tissue area and cortical bone area but not medullary area were higher in the loaded than the unloaded tibia. Trabecular bone volume fraction also increased upon loading in the control group, mostly due to trabecular thickening. N-ARKO and N-ERαKO males displayed a loading response at both the cortical and trabecular bone compartments that was not different from their control littermates. In conclusion, we show that the presence of androgen receptor or estrogen receptor alpha in extrahypothalamic neurons is dispensable for the osteogenic response to mechanical loading in male mice.

G protein-coupled estrogen receptor activation by bisphenol-A disrupts the protection from apoptosis conferred by the estrogen receptors ERα and ERß in pancreatic beta cells.

17ß-estradiol protects pancreatic ß-cells from apoptosis via the estrogen receptors ERα, ERß and GPER. Conversely, the endocrine disruptor bisphenol-A (BPA), which exerts multiple effects in this cell type via the same estrogen receptors, increased basal apoptosis. The molecular-initiated events that trigger these opposite actions have yet to be identified. We demonstrated that combined genetic downregulation and pharmacological blockade of each estrogen receptor increased apoptosis to a different extent. The increase in apoptosis induced by BPA was diminished by the pharmacological blockade or the genetic silencing of GPER, and it was partially reproduced by the GPER agonist G1. BPA and G1-induced apoptosis were abolished upon pharmacological inhibition, silencing of ERα and ERß, or in dispersed islet cells from ERß knockout (BERKO) mice. However, the ERα and ERß agonists PPT and DPN, respectively, had no effect on beta cell viability. To exert their biological actions, ERα and ERß form homodimers and heterodimers. Molecular dynamics simulations together with proximity ligand assays and coimmunoprecipitation experiments indicated that the interaction of BPA with ERα and ERß as well as GPER activation by G1 decreased ERαß heterodimers. We propose that ERαß heterodimers play an antiapoptotic role in beta cells and that BPA- and G1-induced decreases in ERαß heterodimers lead to beta cell apoptosis. Unveiling how different estrogenic chemicals affect the crosstalk among estrogen receptors should help to identify diabetogenic endocrine disruptors.

Myeloid LXR (Liver X Receptor) Deficiency Induces Inflammatory Gene Expression in Foamy Macrophages and Accelerates Atherosclerosis.

BACKGROUND: Cholesterol loaded macrophage foam cells are a prominent feature of atherosclerotic plaques. Single-cell RNA sequencing has identified foam cells as TREM2 (triggering receptor expressed on myeloid cells 2) positive populations with low expression of inflammatory genes, resembling the TREM2 positive microglia of neurodegenerative diseases. Cholesterol loading of macrophages in vitro results in activation of LXR (liver X receptor) transcription factors and suppression of inflammatory genes. METHODS: To test the hypothesis that LXRs mediate anti-inflammatory effects in Trem2 expressing atherosclerotic plaque foam cells, we performed RNA profiling on plaque cells from hypercholesterolemic mice with myeloid LXR deficiency. RESULTS: Myeloid LXR deficiency led to a dramatic increase in atherosclerosis with increased monocyte entry, foam cell formation, and plaque inflammation. Bulk cell-RNA profiling of plaque myeloid cells showed prominent upregulation of inflammatory mediators including oxidative, chemokine, and chemotactic genes. Single-cell RNA sequencing revealed increased numbers of foamy TREM2-expressing macrophages; however, these cells had reduced expression of the Trem2 gene expression module, including phagocytic and cholesterol efflux genes, and had switched to a proinflammatory and proliferative phenotype. Expression of Trem2 was suppressed by inflammatory signals but not directly affected by LXR activation in bone marrow-derived macrophages. CONCLUSIONS: Our current studies reveal the key role of macrophage LXRs in promoting the Trem2 gene expression program and in suppressing inflammation in foam cells of atherosclerotic plaques.

Expression of Sex Hormone Receptor and Immune Response Genes in Peripheral Blood Mononuclear Cells During the Menstrual Cycle.

Sex hormones are known to interact with the immune system on multiple levels but information on the types of sex hormone receptors (SHR) and their expression levels in immune cells is scarce. Estrogen, testosterone and progesterone are all considered to interact with the immune system through their respective cell receptors (ERα and ERß including the splice variant ERß2, AR and PGR). In this study expression levels of SHR genes in peripheral blood mononuclear cells (PBMCs) and cell subsets (CD4+ and CD8+ T-cells, CD56+ NK-cells, CD14+ monocytes and CD19+ B-cells) were analyzed using standard manual qPCR or a qPCR array (TLDA). Nine healthy individuals including men (n = 2), premenopausal (Pre-MP, n = 5) and postmenopausal (post-MP, n = 2) women were sampled for PBMCs which were separated to cell subsets using FACS. Ten Pre-MP women were longitudinally sampled for total PBMCs at different phases of the menstrual cycle. We found that ERα was most abundant and, unexpectedly, that ERß2 was the dominant ERß variant in several FACS sorted cell subsets. In total PBMCs, SHR (ERα, ERß1, ERß2, and AR) expression did not fluctuate according to the phase of the menstrual cycle and PGR was not expressed. However, several immune response genes (GATA3, IFNG, IL1B, LTA, NFKB1, PDCD1, STAT3, STAT5A, TBX21, TGFB1, TNFA) were more expressed during the ovulatory and mid-luteal phases. Sex hormone levels did not correlate significantly with gene expression of SHR or immune response genes, but sex hormone-binding globulin (SHBG), a steroid hormone transporting protein, was positively correlated to expression of ERß1 gene. This study provides new insights in the distribution of ERs in immune cells. Furthermore, expression patterns of several immune response genes differ significantly between phases of the menstrual cycle, supporting a role for sex hormones in the immune response.

Liver X receptor beta deficiency attenuates autoimmune-associated neuroinflammation in a T cell-dependent manner.

The initiation and progression of autoimmune disorders such as multiple sclerosis (MS) is linked to aberrant cholesterol metabolism and overt inflammation. Liver X receptors (LXR) are nuclear receptors that function at the crossroads of cholesterol metabolism and immunity, and their activation is considered a promising therapeutic strategy to attenuate autoimmunity. However, despite clear functional heterogeneity and cell-specific expression profiles, the impact of the individual LXR isoforms on autoimmunity remains poorly understood. Here, we show that LXRα and LXRß have an opposite impact on immune cell function and disease severity in the experimental autoimmune encephalomyelitis model, an experimental MS model. While Lxrα deficiency aggravated disease pathology and severity, absence of Lxrß was protective. Guided by flow cytometry and by using cell-specific knockout models, reduced disease severity in Lxrß-deficient mice was primarily attributed to changes in peripheral T cell physiology and occurred independent from alterations in microglia function. Collectively, our findings indicate that LXR isoforms play functionally non-redundant roles in autoimmunity, potentially having broad implications for the development of LXR-based therapeutic strategies aimed at dampening autoimmunity and neuroinflammation.

25 years of ERß: a personal journey.

Summary: After the discovery of ERß, a novel role for dihydrotestosterone (DHT) in estrogen signaling was revealed. Instead of just being a better androgen, DHT was found to be a precursor of the ERß agonist 5α-androstane-3ß, 17ß-diol (3ßAdiol), an estrogen which does not require aromatase for its synthesis. ERß was found to oppose androgen signaling and thus is a potential target for treatment of prostate cancer. ERß was also found to have effects that were independent of androgen signaling, particularly in the CNS. Although in rodent models of neurodegenerative diseases (Parkinson's disease, multiple sclerosis, and Alzheimer's disease), ERß agonists are very effective in relieving symptoms and improving pathologies, this has not proven to be the case in humans. In this review we will focus on the main differences in ERß signaling between rodents and humans and will make the point that a very important difference between the two species is in the splice variants which are expressed in humans and not rodents. The main conclusion at this point is that before we think of using ERß agonists clinically, much more work on ERß signaling in the human or in primates needs to be done.