Emerging actions of the nuclear receptor LRH-1 in the gut

Liver receptor homolog-1 (NR5A2) orchestrates hepatic inflammation and TNF-induced cell death

The nuclear receptor liver receptor homolog-1 (LRH-1) has been shown to promote apoptosis resistance in various tissues and disease contexts; however, its role in liver cell death remains unexplored. Hepatocyte-specific deletion of LRH-1 causes mild steatosis and inflammation but unexpectedly shields female mice from tumor necrosis factor (TNF)-induced hepatocyte apoptosis and associated hepatitis. LRH-1-deficient hepatocytes show markedly attenuated estrogen receptor alpha and elevated nuclear factor κB (NF-κB) activity, while LRH-1 overexpression inhibits NF-κB activity. This inhibition relies on direct physical interaction of LRH-1's ligand-binding domain and the Rel homology domain of NF-κB subunit RelA. Mechanistically, increased transcription of anti-apoptotic NF-κB target genes and the proteasomal degradation of pro-apoptotic BCL-2 interacting mediator of cell death prevent mitochondrial apoptosis and ultimately protect mice from TNF-induced liver damage. Collectively, our study emphasizes LRH-1 as a critical, sex-dependent regulator of cell death and inflammation in the healthy and diseased liver.

International Union of Basic and Clinical Pharmacology CXIII: Nuclear Receptor Superfamily-Update 2023

The NR superfamily comprises 48 transcription factors in humans that control a plethora of gene network programs involved in a wide range of physiologic processes. This review will summarize and discuss recent progress in NR biology and drug development derived from integrating various approaches, including biophysical techniques, structural studies, and translational investigation. We also highlight how defective NR signaling results in various diseases and disorders and how NRs can be targeted for therapeutic intervention via modulation via binding to synthetic lipophilic ligands. Furthermore, we also review recent studies that improved our understanding of NR structure and signaling. SIGNIFICANCE STATEMENT: Nuclear receptors (NRs) are ligand-regulated transcription factors that are critical regulators of myriad physiological processes. NRs serve as receptors for an array of drugs, and in this review, we provide an update on recent research into the roles of these drug targets.

Nuclear receptor 5A2 regulation of Agrp underlies olanzapine-induced hyperphagia

Antipsychotic (AP) drugs are efficacious treatments for various psychiatric disorders, but excessive weight gain and subsequent development of metabolic disease remain serious side effects of their use. Increased food intake leads to AP-induced weight gain, but the underlying molecular mechanisms remain unknown. In previous studies, we identified the neuropeptide Agrp and the transcription factor nuclear receptor subfamily 5 group A member 2 (Nr5a2) as significantly upregulated genes in the hypothalamus following AP-induced hyperphagia. While Agrp is expressed specifically in the arcuate nucleus of the hypothalamus and plays a critical role in appetite stimulation, Nr5a2 is expressed in both the CNS and periphery, but its role in food intake behaviors remains unknown. In this study, we investigated the role of hypothalamic Nr5a2 in AP-induced hyperphagia and weight gain. In hypothalamic cell lines, olanzapine treatment resulted in a dose-dependent increase in gene expression of Nr5a2 and Agrp. In mice, the pharmacological inhibition of NR5A2 decreased olanzapine-induced hyperphagia and weight gain, while the knockdown of Nr5a2 in the arcuate nucleus partially reversed olanzapine-induced hyperphagia. Chromatin-immunoprecipitation studies showed for the first time that NR5A2 directly binds to the Agrp promoter region. Lastly, the analysis of single-cell RNA seq data confirms that Nr5a2 and Agrp are co-expressed in a subset of neurons in the arcuate nucleus. In summary, we identify Nr5a2 as a key mechanistic driver of AP-induced food intake. These findings can inform future clinical development of APs that do not activate hyperphagia and weight gain.

Single-cell analyses define a continuum of cell state and composition changes in the malignant transformation of polyps to colorectal cancer

To chart cell composition and cell state changes that occur during the transformation of healthy colon to precancerous adenomas to colorectal cancer (CRC), we generated single-cell chromatin accessibility profiles and single-cell transcriptomes from 1,000 to 10,000 cells per sample for 48 polyps, 27 normal tissues and 6 CRCs collected from patients with or without germline APC mutations. A large fraction of polyp and CRC cells exhibit a stem-like phenotype, and we define a continuum of epigenetic and transcriptional changes occurring in these stem-like cells as they progress from homeostasis to CRC. Advanced polyps contain increasing numbers of stem-like cells, regulatory T cells and a subtype of pre-cancer-associated fibroblasts. In the cancerous state, we observe T cell exhaustion, RUNX1-regulated cancer-associated fibroblasts and increasing accessibility associated with HNF4A motifs in epithelia. DNA methylation changes in sporadic CRC are strongly anti-correlated with accessibility changes along this continuum, further identifying regulatory markers for molecular staging of polyps.

Regulation of the Intestinal Extra-Adrenal Steroidogenic Pathway Component LRH-1 by Glucocorticoids in Ulcerative Colitis

Ulcerative colitis (UC) is an inflammatory bowel disease (IBD) and can be treated with glucocorticoids (GC), although some patients are unresponsive to this therapy. The transcription factor LRH-1/NR5A2 is critical to intestinal cortisol production (intestinal steroidogenesis), being reduced in UC patients. However, the relationship between LRH-1 expression and distribution with altered corticosteroid responses is unknown. To address this, we categorized UC patients by their steroid response. Here, we found that steroid-dependent and refractory patients presented reduced glucocorticoid receptor (GR)-mediated intestinal steroidogenesis compared to healthy individuals and responder patients, possibly related to increased colonic mucosa GR isoform beta (GRβ) content and cytoplasmic LRH-1 levels in epithelial and lamina propria cells. Interestingly, an intestinal epithelium-specific GR-induced knockout (GR^iKO) dextran sodium sulfate (DSS)-colitis mice model presented decreased epithelial LRH-1 expression, whilst it increased in the lamina propria compared to DSS-treated control mice. Mechanistically, GR directly induced NR5A2 gene expression in CCD841CoN cells and human colonic organoids. Furthermore, GR bound to two glucocorticoid-response elements within the NR5A2 promoter in dexamethasone-stimulated CCD841CoN cells. We conclude that GR contributes to intestinal steroidogenesis by inducing LRH-1 in epithelial cells, suggesting LRH-1 as a potential marker for glucocorticoid-impaired response in UC. However, further studies with a larger patient cohort will be necessary to confirm role of LRH-1 as a therapeutic biomarker.

NR5A2/LRH-1 regulates the PTGS2-PGE2-PTGER1 pathway contributing to pancreatic islet survival and function

LRH-1/NR5A2 is implicated in islet morphogenesis postnatally, and its activation using the agonist BL001 protects islets against apoptosis, reverting hyperglycemia in mouse models of Type 1 Diabetes Mellitus. Islet transcriptome profiling revealed that the expression of PTGS2/COX2 is increased by BL001. Herein, we sought to define the role of LRH-1 in postnatal islet morphogenesis and chart the BL001 mode of action conferring beta cell protection. LRH-1 ablation within developing beta cells impeded beta cell proliferation, correlating with mouse growth retardation, weight loss, and hypoglycemia leading to lethality. LRH-1 deletion in adult beta cells abolished the BL001 antidiabetic action, correlating with beta cell destruction and blunted Ptgs2 induction. Islet PTGS2 inactivation led to reduced PGE₂ levels and loss of BL001 protection against cytokines as evidenced by increased cytochrome c release and cleaved-PARP. The PTGER1 antagonist—ONO-8130—negated BL001-mediated islet survival. Our results define the LRH-1/PTGS2/PGE₂/PTGER1 signaling axis as a key pathway mediating BL001 survival properties.

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LRH-1 ablation during development impedes neonatal beta cell replication

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LRH-1 knockout in adult beta cells negates BL001-mediated antidiabetic properties

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Islets lacking PTGS2 are refractory to BL001-mediated protection against cytokines

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PTGER1 relays the BL001/LRH-1/PTGS2/PGE2 signaling axis to islet survival

A phospholipid mimetic targeting LRH-1 ameliorates colitis

Phospholipids are ligands for nuclear hormone receptors (NRs) that regulate transcriptional programs relevant to normal physiology and disease. Here, we demonstrate that mimicking phospholipid-NR interactions is a robust strategy to improve agonists of liver receptor homolog-1 (LRH-1), a therapeutic target for colitis. Conventional LRH-1 modulators only partially occupy the binding pocket, leaving vacant a region important for phospholipid binding and allostery. Therefore, we constructed a set of molecules with elements of natural phospholipids appended to a synthetic LRH-1 agonist. We show that the phospholipid-mimicking groups interact with the targeted residues in crystal structures and improve binding affinity, LRH-1 transcriptional activity, and conformational changes at a key allosteric site. The best phospholipid mimetic markedly improves colonic histopathology and disease-related weight loss in a murine T cell transfer model of colitis. This evidence of in vivo efficacy for an LRH-1 modulator in colitis represents a leap forward in agonist development.

Regulation of male fertility and accessory gland gene expression by the Drosophila HR39 nuclear receptor

Successful reproduction is dependent on the transfer of male seminal proteins to females upon mating. These proteins arise from secretory tissues in the male reproductive tract, including the prostate and seminal vesicles in mammals and the accessory gland in insects. Although detailed functional studies have provided important insights into the mechanisms by which accessory gland proteins support reproduction, much less is known about the molecular mechanisms that regulate their expression within this tissue. Here we show that the Drosophila HR39 nuclear receptor is required for the proper expression of most genes that encode male accessory gland proteins. Consistent with this role, HR39 mutant males are infertile. In addition, tissue-specific RNAi and genetic rescue experiments indicate that HR39 acts within the accessory glands to regulate gene expression and male fertility. These results provide new directions for characterizing the mammalian orthologs of HR39, the SF-1 and LRH-1 nuclear receptors, both of which are required for glandular secretions and reproduction. In addition, our studies provide a molecular mechanism to explain how the accessory glands can maintain the abundant levels of seminal fluid production required to support fertility.

Nuclear receptor subfamily 5 group A member 2 (NR5A2): role in health and diseases

Nuclear receptors are the regulatory molecules that mediate cellular signals as they interact with specific DNA sequences. NR5A2 is a member of NR5A subfamily having four members (Nr5a1-Nr5a4). NR5A2 shows involvement in diverse biological processes like reverse cholesterol transport, embryonic stem cell pluripotency, steroidogenesis, development and differentiation of embryo, and adult homeostasis. NR5A2 haploinsufficiency has been seen associated with chronic pancreatitis, pancreatic and gastrointestinal cancer. There is a close relationship between the progression of pancreatic cancer from chronic pancreatitis, NR5A2 serving a common link. NR5A2 activity is regulated by intracellular phospholipids, transcriptional coregulators and post-translational modifications. The specific ligand of NR5A2 is unknown hence called an orphan receptor, but specific phospholipids such as dilauroyl phosphatidylcholine and diundecanoyl phosphatidylcholine act as a ligand and they are established drug targets in various diseases. This review will focus on the NR5A2 structure, regulation of its activity, and role in biological processes and diseases. In future, need more emphasis on discovering small molecule agonists and antagonist, which act as a drug target for therapeutic applications.

Triacylglycerol rich in docosahexaenoic acid regulated appetite via the mediation of leptin and intestinal epithelial functions in high-fat, high-sugar diet-fed mice

High-fat, high-sugar diet (HFHS) induced leptin resistance and intestinal epithelial dysfunction is implicated in hyperphagia and metabolic disorders. Numerous studies have demonstrated the efficacy of dietary interventions for reducing appetite. This study aims to investigate whether triacylglycerol rich in DHA (DHA-TG) could regulate appetite in mice fed with a HFHS diet and the mechanism by which it achieves that. DHA-TG could reduce food intake and regulate neuropeptides (POMC, AgRP, and NPY) expression in HFHS diet-fed mice. Hypothalamic transcriptome analysis reveals that these effects might be attributed to the role of DHA-TG in modulating hormone secretion and digestive system process. According to ELISA and RT-qPCR analysis, DHA-TG ameliorated leptin secretion and attenuated central leptin resistance induced by HFHS diet feeding. Besides, DHA-TG prevented the damage of intestinal epithelial barrier in nutritive obese mice by improving leptin sensitivity. Based on jejunal transcriptome analysis, DHA-TG also protected intestinal endocrine function, especially the secretion of another anorectic hormone, cholecystokinin (CCK), in HFHS diet-fed mice. Furthermore, DHA-TG was ineffective in repressing appetite, and improving gut leakage in leptin-deficient mice (ob/ob mice). In conclusion, DHA-TG has a potential to regulate appetite with the action of leptin, and intestinal epithelial functions in HFHS diet-fed mice.

Immunosuppressive glucocorticoids at epithelial barriers in the regulation of anti-viral immune response

The anti-inflammatory action of adrenal-derived glucocorticoids has been recognized since several decades. This knowledge has found broad application in the clinics and today synthetic glucocorticoids are widely used in the treatment of various inflammatory diseases. However, the use of synthetic glucocorticoids in the treatment of diseases associated with viral infections of epithelial surfaces, like the lung or the intestine, is still under debate and seems not as efficient as desired. Basic research on the anti-viral immune responses and on regulatory mechanisms in the prevention of immunopathological disorders, however, has led us back again to focus on endogenous glucocorticoid synthesis. It has become established that this synthesis is not restricted to the adrenal glands alone, but that numerous tissues also produce glucocorticoids in situ. Extra-adrenal derived glucocorticoids have the capacity to locally control and maintain immune homeostasis under steady-state and inflammatory conditions. Here, we discuss the current knowledge of extra-adrenal glucocorticoid synthesis in the lung and the intestine, and its role in the regulation of anti-viral immune responses.

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

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

Another One Bites the Gut: Nuclear Receptor LRH-1 in Intestinal Regeneration and Cancer

The process of self-renewal in normal intestinal epithelium is characterized by a fine balance between proliferation, differentiation, migration, and cell death. When even one of these aspects escapes the normal control, cellular proliferation and differentiation are impaired, with consequent onset of tumorigenesis. In humans, colorectal cancer (CRC) is the main pathological manifestation of this derangement. Nowadays, CRC is the world's fourth most deadly cancer with a limited survival after treatment. Several conditions can predispose to CRC development, including dietary habits and pre-existing inflammatory bowel diseases. Given their extraordinary ability to interact with DNA, it is widely known that nuclear receptors play a key role in the regulation of intestinal epithelium, orchestrating the expression of a series of genes involved in developmental and homeostatic pathways. In particular, the nuclear receptor Liver Receptor Homolog-1 (LRH-1), highly expressed in the stem cells localized in the crypts, promotes intestine cell proliferation and renewal in both direct and indirect DNA-binding manner. Furthermore, LRH-1 is extensively correlated with diverse intestinal inflammatory pathways. These evidence shed a light in the dynamic intestinal microenvironment in which increased regenerative epithelial cell turnover, mutagenic insults, and chronic DNA damages triggered by factors within an inflammatory cell-rich microenvironment act synergistically to favor cancer onset and progression.

Colon cancer cells produce immunoregulatory glucocorticoids

Expression or release of immunosuppressive molecules may protect tumor cells from the recognition and destruction by the immune system. New findings indicate that colorectal tumors produce immunoregulatory glucocorticoids and thereby suppress immune cell activation. The nuclear receptor LRH-1 plays a critical role in the regulation of colorectal tumor proliferation and glucocorticoid synthesis.

Impact of NR5A2 and RYR2 3'UTR polymorphisms on the risk of breast cancer in a Chinese Han population

OBJECTIVES

The NR5A2 and RYR2 genes are important players in steroid metabolism and play an important role in cancer research. In this research, we want to evaluate the effect of NR5A2 and RYR2 polymorphisms on breast cancer (BC).

METHODS

Four single nucleotide polymorphisms on NR5A2 and RYR2 were selected to genotype by Agena MassARRAY in 379 BC patients and 407 healthy controls. Using the PLINK software to calculate the Odds ratio (OR) and 95% confidence intervals (CIs) via the logistic regression analysis to evaluate the risk for BC.

RESULTS

We found that NR5A2 rs2246209 significantly decreased the risk of BC with the AA genotype (OR 0.58, 95%CI 0.34-0.99, p = 0.049), and recessive model (OR 0.59, 95%CI 0.35-0.99, p = 0.046); rs12594 in the RYR2 gene significantly decreased the risk of BC in the GG genotype (OR 0.44, 95%CI 0.22-0.88, p = 0.020), and recessive model (OR 0.43, 95%CI 0.21-0.85, p = 0.016). Further stratification analysis showed that NR5A2 rs2246209 was related to a lower incidence of BC affected by age, lymph nodes metastasis, and tumor stage; RYR2 rs12594 was related to a decreased BC risk restricted by age, estrogen receptor (ER), progesterone receptor (PR), menopausal status, tumor size, and tumor stage. Rs12594 in the RyR2 gene remained significant on the genetic susceptibility of PR-positive BC after Bonferroni correction (p < 0.0125).

CONCLUSIONS

This study provides an evidence that NR5A2 rs2246209 and RYR2 rs12594 decreased the risk of breast cancer.

Extra-adrenal glucocorticoid biosynthesis: implications for autoimmune and inflammatory disorders

Glucocorticoid synthesis is a complex, multistep process that starts with cholesterol being delivered to the inner membrane of mitochondria by StAR and StAR-related proteins. Here its side chain is cleaved by CYP11A1 producing pregnenolone. Pregnenolone is converted to cortisol by the enzymes 3-βHSD, CYP17A1, CYP21A2 and CYP11B1. Glucocorticoids play a critical role in the regulation of the immune system and exert their action through the glucocorticoid receptor (GR). Although corticosteroids are primarily produced in the adrenal gland, they can also be produced in a number of extra-adrenal tissue including the immune system, skin, brain, and intestine. Glucocorticoid production is regulated by ACTH, CRH, and cytokines such as IL-1, IL-6 and TNFα. The bioavailability of cortisol is also dependent on its interconversion to cortisone which is inactive, by 11βHSD1/2. Local and systemic glucocorticoid biosynthesis can be stimulated by ultraviolet B, explaining its immunosuppressive activity. In this review, we want to emphasize that dysregulation of extra-adrenal glucocorticoid production can play a key role in a variety of autoimmune diseases including multiple sclerosis (MS), lupus erythematosus (LE), rheumatoid arthritis (RA), and skin inflammatory disorders such as psoriasis and atopic dermatitis (AD). Further research on local glucocorticoid production and its bioavailability may open doors into new therapies for autoimmune diseases.

Time for a paradigm shift in treating type 1 diabetes mellitus: coupling inflammation to islet regeneration

Type 1 diabetes mellitus (T1DM) is an autoimmune disease that targets the destruction of islet beta-cells resulting in insulin deficiency, hyperglycemia and death if untreated. Despite advances in medical devices and longer-acting insulin, there is still no robust therapy to substitute and protect beta-cells that are lost in T1DM. Attempts to refrain from the autoimmune attack have failed to achieve glycemic control in patients highlighting the necessity for a paradigm shift in T1DM treatment. Paradoxically, beta-cells are present in T1DM patients indicating a disturbed equilibrium between the immune attack and beta-cell regeneration reminiscent of unresolved wound healing that under normal circumstances progression towards an anti-inflammatory milieu promotes regeneration. Thus, the ultimate T1DM therapy should concomitantly restore immune self-tolerance and replenish the beta-cell mass similar to wound healing. Recently the agonistic activation of the nuclear receptor LRH-1/NR5A2 was shown to induce immune self-tolerance, increase beta-cell survival and promote regeneration through a mechanism of alpha-to-beta cell phenotypic switch. This trans-regeneration process appears to be facilitated by a pancreatic anti-inflammatory environment induced by LRH-1/NR5A2 activation. Herein, we review the literature on the role of LRH1/NR5A2 in immunity and islet physiology and propose that a cross-talk between these cellular compartments is mandatory to achieve therapeutic benefits.

Host Transcription Factors in Hepatitis B Virus RNA Synthesis

The hepatitis B virus (HBV) chronically infects over 250 million people worldwide and is one of the leading causes of liver cancer and hepatocellular carcinoma. HBV persistence is due in part to the highly stable HBV minichromosome or HBV covalently closed circular DNA (cccDNA) that resides in the nucleus. As HBV replication requires the help of host transcription factors to replicate, focusing on host protein–HBV genome interactions may reveal insights into new drug targets against cccDNA. The structural details on such complexes, however, remain poorly defined. In this review, the current literature regarding host transcription factors’ interactions with HBV cccDNA is discussed.

Development of the First Low Nanomolar Liver Receptor Homolog-1 Agonist through Structure-guided Design

As a key regulator of metabolism and inflammation, the orphan nuclear hormone receptor, liver receptor homolog-1 (LRH-1), has potential as a therapeutic target for diabetes, nonalcoholic fatty liver disease, and inflammatory bowel diseases (IBD). Discovery of LRH-1 modulators has been difficult, in part due to the tendency for synthetic compounds to bind unpredictably within the lipophilic binding pocket. Using a structure-guided approach, we exploited a newly discovered polar interaction to lock agonists in a consistent orientation. This enabled the discovery of the first low nanomolar LRH-1 agonist, one hundred times more potent than the best previous modulator. We elucidate a novel mechanism of action that relies upon specific polar interactions deep in the LRH-1 binding pocket. In an organoid model of IBD, the new agonist increases expression of LRH-1-controlled steroidogenic genes and promotes anti-inflammatory gene expression changes. These studies constitute major progress in developing LRH-1 modulators with potential clinical utility.

The Role of Protein SUMOylation in the Pathogenesis of Atherosclerosis

Atherosclerosis is a progressive, inflammatory cardiovascular disorder characterized by the development of lipid-filled plaques within arteries. Endothelial cell dysfunction in the walls of blood vessels results in an increase in vascular permeability, alteration of the components of the extracellular matrix, and retention of LDL in the sub-endothelial space, thereby accelerating plaque formation. Epigenetic modification by SUMOylation can influence the surface interactions of target proteins and affect cellular functionality, thereby regulating multiple cellular processes. Small ubiquitin-like modifier (SUMO) can modulate NFκB and other proteins such as p53, KLF, and ERK5, which have critical roles in atherogenesis. Furthermore, SUMO regulates leukocyte recruitment and cytokine release and the expression of adherence molecules. In this review, we discuss the regulation by SUMO and SUMOylation modifications of proteins and pathways involved in atherosclerosis.

Nuclear Receptors Regulate Intestinal Inflammation in the Context of IBD

Gastrointestinal (GI) homeostasis is strongly dependent on nuclear receptor (NR) functions. They play a variety of roles ranging from nutrient uptake, sensing of microbial metabolites, regulation of epithelial intestinal cell integrity to shaping of the intestinal immune cell repertoire. Several NRs are associated with GI pathologies; therefore, systematic analysis of NR biology, the underlying molecular mechanisms, and regulation of target genes can be expected to help greatly in uncovering the course of GI diseases. Recently, an increasing number of NRs has been validated as potential drug targets for therapeutic intervention in patients with inflammatory bowel disease (IBD). Besides the classical glucocorticoids, especially PPARγ, VDR, or PXR-selective ligands are currently being tested with promising results in clinical IBD trials. Also, several pre-clinical animal studies are being performed with NRs. This review focuses on the complex biology of NRs and their context-dependent anti- or pro-inflammatory activities in the regulation of gastrointestinal barrier with special attention to NRs already pharmacologically targeted in clinic and pre-clinical IBD treatment regimens.

Nr5a2 promotes tumor growth and metastasis of gastric cancer AGS cells by Wnt/beta-catenin signaling

Purpose: Nr5a2 (nuclear receptor subfamily 5 group A member 2, also known as LRH-1), which belongs to the NR5A (Ftz-F1) subfamily of nuclear receptors, is a key regulator in stem cell pluripotency and the development of several types of cancer. However, the data are controversial. Since Nr5a2 plays different roles in multiple types of cancer and the function of Nr5a2 in gastric cancer (GC) has not been revealed, we studied the role and molecular mechanism of Nr5a2 in GC. Methods: In this study, we have investigated the effect of Nr5a2 on tumor growth and metastasis by in vivo and in vitro models. Results: The results showed that knockdown of Nr5a2 could inhibit cell proliferation via arresting the cell cycle in the G2/M phase and suppress cell mobility through preventing the epithelial-mesenchymal transition (EMT) process in AGS cells. In addition, knockdown of Nr5a2 could suppress tumorigenesis and metastasis of AGS cells in vivo. We also demonstrated that knockdown of Nr5a2 inhibited cellular proliferation and mobility by suppressing the Wnt/beta-catenin signaling pathway. Conclusion: Nr5a2 may act as an oncogene in GC development. The EMT process and the Wnt/beta-catenin signaling pathway play an important role in the Nr5a2 induced GC development.

Transcriptional Regulation of Ovarian Steroidogenic Genes: Recent Findings Obtained from Stem Cell-Derived Steroidogenic Cells

Ovaries represent one of the primary steroidogenic organs, producing estrogen and progesterone under the regulation of gonadotropins during the estrous cycle. Gonadotropins fluctuate the expression of various steroidogenesis-related genes, such as those encoding steroidogenic enzymes, cholesterol deliverer, and electronic transporter. Steroidogenic factor-1 (SF-1)/adrenal 4-binding protein (Ad4BP)/NR5A1 and liver receptor homolog-1 (LRH-1) play important roles in these phenomena via transcriptional regulation. With the aid of cAMP, SF-1/Ad4BP and LRH-1 can induce the differentiation of stem cells into steroidogenic cells. This model is a useful tool for studying the molecular mechanisms of steroidogenesis. In this article, we will provide insight into the transcriptional regulation of steroidogenesis-related genes in ovaries that are revealed from stem cell-derived steroidogenic cells. Using the cells derived from the model, novel SF-1/Ad4BP- and LRH-1-regulated genes were identified by combined DNA microarray and promoter tiling array analyses. The interaction of SF-1/Ad4BP and LRH-1 with transcriptional regulators in the regulation of ovarian steroidogenesis was also revealed.

Liver receptor homologue 1, a novel prognostic marker in colon cancer patients

Liver receptor homologue 1 (LRH-1) is an orphan nuclear receptor that is highly expressed in a variety of cancer tissues, promotes tumor cell proliferation and metastasis, and is involved in the tumor cell cycle and apoptosis. The aim of the present study was to assess the association between the expression of LRH-1 and the prognosis of patients with colon cancer. Immunohistochemistry was used to detect the expression of LRH1 in 128 cases of colon cancer and adjacent tissues. The 5-year survival rate was obtained from telephone follow-up data, outpatient review and through access to medical records. Positive expression of LRH-1 was found in 108/128 colon cancer samples, compared with 17/128 normal tissues. Statistical analysis showed that positive LRH-1 expression was significantly associated with clinical pathological stage, depth of invasion and lymph node metastasis. The overall survival (OS) rate of patients with positive LRH-1 expression was significantly lower than that of patients with low expression. Multivariate analysis showed that LRH-1 expression could be used as an independent predictor of OS. In conclusion, the present findings suggest that LRH-1 may serve an important role in the development and progression of colon cancer, with potential value as a prognostic molecular marker that could be used to assist in the diagnosis and evaluation of colon cancer. LRH-1 may become a target for novel therapies for patients with colon cancer.

LRH-1 agonism favours an immune-islet dialogue which protects against diabetes mellitus

Type 1 diabetes mellitus (T1DM) is due to the selective destruction of islet beta cells by immune cells. Current therapies focused on repressing the immune attack or stimulating beta cell regeneration still have limited clinical efficacy. Therefore, it is timely to identify innovative targets to dampen the immune process, while promoting beta cell survival and function. Liver receptor homologue-1 (LRH-1) is a nuclear receptor that represses inflammation in digestive organs, and protects pancreatic islets against apoptosis. Here, we show that BL001, a small LRH-1 agonist, impedes hyperglycemia progression and the immune-dependent inflammation of pancreas in murine models of T1DM, and beta cell apoptosis in islets of type 2 diabetic patients, while increasing beta cell mass and insulin secretion. Thus, we suggest that LRH-1 agonism favors a dialogue between immune and islet cells, which could be druggable to protect against diabetes mellitus.

Type 1 diabetes mellitus (T1DM) is characterized by beta cell loss because of an autoimmune attack. Here the authors show that an agonist for LRH-1/NR5A2, a nuclear receptor known to be protective against beta cell apoptosis, inhibits immune-mediated inflammation and hyperglycemia in T1DM mouse models.

Identification of the principal transcriptional regulators for low-fat and high-fat meal responsive genes in small intestine

BACKGROUND

High-fat (HF) diet is a well-known cause of obesity. To identify principle transcriptional regulators that could be therapeutic targets of obesity, we investigated transcriptomic modulation in the duodenal mucosa following low-fat (LF) and HF meal ingestion.

METHODS

Whereas one group of mice was sacrificed after fasting, the others were fed ad libitum with LF or HF meal, and sacrificed 30 min, 1 h and 3 h after the beginning of the meal. A transcriptome analysis of the duodenal mucosa of the 7 groups was conducted using both microarray and serial analysis of gene expression (SAGE) method followed by an Ingenuity Pathways Analysis (IPA).

RESULTS

SAGE and microarray showed that the modulation of a total of 896 transcripts in the duodenal mucosa after LF and/or HF meal, compared to the fasting condition. The IPA identified lipid metabolism, molecular transport, and small molecule biochemistry as top three molecular and cellular functions for the HF-responsive, HF-specific, HF-delay, and LF-HF different genes. Moreover, the top transcriptional regulator for the HF-responsive and HF-specific genes was peroxisome proliferator-activated receptor alpha (PPARα). On the other hand, the LF-responsive and LF-specific genes were related to carbohydrate metabolism, cellular function and maintenance, and cell death/cellular growth and proliferation, and the top transcriptional regulators were forkhead box protein O1 (FOXO1) and cAMP response element binding protein 1 (CREB1), respectively.

CONCLUSIONS

These results will help to understand the molecular mechanisms of intestinal response after LF and HF ingestions, and contribute to identify therapeutic targets for obesity and obesity-related diseases.

LRH-1 expression patterns in breast cancer tissues are associated with tumour aggressiveness

The significance and regulation of liver receptor homologue 1 (LRH-1, NR5A2), a tumour-promoting transcription factor in breast cancer cell lines, is unknown in clinical breast cancers. This study aims to determine LRH-1/NR5A2 expression in breast cancers and relationship with DNA methylation and tumour characteristics. In The Cancer Genome Atlas breast cancer cohort NR5A2 expression was positively associated with intragenic CpG island methylation (1.4-fold expression for fully methylated versus not fully methylated, p=0.01) and inversely associated with promoter CpG island methylation (0.6-fold expression for fully methylated versus not fully methylated, p=0.036). LRH-1 immunohistochemistry of 329 invasive carcinomas and ductal carcinoma in situ (DCIS) was performed. Densely punctate/coarsely granular nuclear reactivity was significantly associated with high tumour grade (p<0.005, p=0.033 in invasive carcinomas and DCIS respectively), negative estrogen receptor status (p=0.008, p=0.038 in overall cohort and invasive carcinomas, respectively), negative progesterone receptor status (p=0.003, p=0.013 in overall cohort and invasive carcinomas, respectively), HER2 amplification (overall cohort p=0.034) and non-luminal intrinsic subtype (p=0.018, p=0.038 in overall cohort and invasive carcinomas, respectively). These significant associations of LRH-1 protein expression with tumour phenotype suggest that LRH-1 is an important indicator of tumour biology in breast cancers and may be useful in risk stratification.

Nuclear Receptors Resolve Endoplasmic Reticulum Stress to Improve Hepatic Insulin Resistance

Chronic endoplasmic reticulum (ER) stress culminating in proteotoxicity contributes to the development of insulin resistance and progression to type 2 diabetes mellitus. Pharmacologic interventions targeting several different nuclear receptors have emerged as potential treatments for insulin resistance. The mechanistic basis for these antidiabetic effects has primarily been attributed to multiple metabolic and inflammatory functions. Here we review recent advances in our understanding of the association of ER stress with insulin resistance and the role of nuclear receptors in promoting ER stress resolution and improving insulin resistance in the liver.

The characterization of an intestine-like genomic signature maintained during Barrett's-associated adenocarcinogenesis reveals an NR5A2-mediated promotion of cancer cell survival

Barrett’s oesophagus (BO), an intestinal-type metaplasia (IM), typically arising in conjunction with gastro-oesophageal reflux disease, is a prominent risk factor for the development of oesophageal adenocarcinoma (OAC). The molecular similarities between IM and normal intestinal tissues are ill-defined. Consequently, the contribution of intestine-enriched factors expressed within BO to oncogenesis is unclear. Herein, using transcriptomics we define the intestine-enriched genes expressed in meta-profiles of BO and OAC. Interestingly, 77% of the genes differentially expressed in a meta-profile of BO were similarly expressed in intestinal tissues. Furthermore, 85% of this intestine-like signature was maintained upon transition to OAC. Gene networking analysis of transcription factors within this signature revealed a network centred upon NR5A2, GATA6 and FOXA2, whose over-expression was determined in a cohort of BO and OAC patients. Simulated acid reflux was observed to induce the expression of both NR5A2 and GATA6. Using siRNA-mediated silencing and an NR5A2 antagonist we demonstrate that NR5A2-mediated cancer cell survival is facilitated through augmentation of GATA6 and anti-apoptotic factor BCL-XL levels. Abrogation of NR5A2-GATA6 expression in conjunction with BCL-XL co-silencing resulted in synergistically increased sensitivity to chemotherapeutics and photo-dynamic therapeutics. These findings characterize the intestine-like signature associated with IM which may have important consequences to adenocarcinogenesis.

Structures and regulation of non-X orphan nuclear receptors: A retinoid hypothesis

Nuclear receptors are defined as a family of ligand regulated transcription factors [1-6]. While this definition reflects that ligand binding is a key property of nuclear receptors, it is still a heated subject of debate if all the nuclear receptors (48 human members) can bind ligands (ligands referred here to both physiological and synthetic ligands). Recent studies in nuclear receptor structure biology and pharmacology have undoubtedly increased our knowledge of nuclear receptor functions and their regulation. As a result, they point to new avenues for the discovery and development of nuclear receptor regulators, including nuclear receptor ligands. Here we review the recent literature on orphan nuclear receptor structural analysis and ligand identification, particularly on the orphan nuclear receptors that do not heterodimerize with retinoid X receptors, which we term as non-X orphan receptors. We also propose a speculative "retinoid hypothesis" for a subset of non-X orphan nuclear receptors, which we hope to help shed light on orphan nuclear receptor biology and drug discovery. This article is part of a Special Issue entitled 'Orphan Nuclear Receptors'.

LRH-1 drives colon cancer cell growth by repressing the expression of the CDKN1A gene in a p53-dependent manner

Liver receptor homologue 1 (LRH-1) is an orphan nuclear receptor that has been implicated in the progression of breast, pancreatic and colorectal cancer (CRC). To determine mechanisms underlying growth promotion by LRH-1 in CRC, we undertook global expression profiling following siRNA-mediated LRH-1 knockdown in HCT116 cells, which require LRH-1 for growth and in HT29 cells, in which LRH-1 does not regulate growth. Interestingly, expression of the cell cycle inhibitor p21 (CDKN1A) was regulated by LRH-1 in HCT116 cells. p21 regulation was not observed in HT29 cells, where p53 is mutated. p53 dependence for the regulation of p21 by LRH-1 was confirmed by p53 knockdown with siRNA, while LRH-1-regulation of p21 was not evident in HCT116 cells where p53 had been deleted. We demonstrate that LRH-1-mediated p21 regulation in HCT116 cells does not involve altered p53 protein or phosphorylation, and we show that LRH-1 inhibits p53 recruitment to the p21 promoter, likely through a mechanism involving chromatin remodelling. Our study suggests an important role for LRH-1 in the growth of CRC cells that retain wild-type p53.

Regulation of Steroidogenesis, Development, and Cell Differentiation by Steroidogenic Factor-1 and Liver Receptor Homolog-1

Steroidogenic factor-1 (SF-1) and liver receptor homolog-1 (LRH-1) belong to the nuclear receptor superfamily and are categorized as orphan receptors. In addition to other nuclear receptors, these play roles in various physiological phenomena by regulating the transcription of target genes. Both factors share very similar structures and exhibit common functions. Of these, the roles of SF-1 and LRH-1 in steroidogenesis are the most important, especially that of SF-1, which was originally discovered and named to reflect such roles. SF-1 and LRH-1 are essential for steroid hormone production in gonads and adrenal glands through the regulation of various steroidogenesis-related genes. As SF-1 is also necessary for the development of gonads and adrenal glands, it is also considered a master regulator of steroidogenesis. Recent studies have clearly demonstrated that LRH-1 also represents another master regulator of steroidogenesis, which similarly to SF-1, can induce differentiation of non-steroidogenic stem cells into steroidogenic cells. Here, we review the functions of both factors in these steroidogenesis-related phenomena.

Unexpected Allosteric Network Contributes to LRH-1 Co-regulator Selectivity

Phospholipids (PLs) are unusual signaling hormones sensed by the nuclear receptor liver receptor homolog-1 (LRH-1), which has evolved a novel allosteric pathway to support appropriate interaction with co-regulators depending on ligand status. LRH-1 plays an important role in controlling lipid and cholesterol homeostasis and is a potential target for the treatment of metabolic and neoplastic diseases. Although the prospect of modulating LRH-1 via small molecules is exciting, the molecular mechanism linking PL structure to transcriptional co-regulator preference is unknown. Previous studies showed that binding to an activating PL ligand, such as dilauroylphosphatidylcholine, favors LRH-1's interaction with transcriptional co-activators to up-regulate gene expression. Both crystallographic and solution-based structural studies showed that dilauroylphosphatidylcholine binding drives unanticipated structural fluctuations outside of the canonical activation surface in an alternate activation function (AF) region, encompassing the β-sheet-H6 region of the protein. However, the mechanism by which dynamics in the alternate AF influences co-regulator selectivity remains elusive. Here, we pair x-ray crystallography with molecular modeling to identify an unexpected allosteric network that traverses the protein ligand binding pocket and links these two elements to dictate selectivity. We show that communication between the alternate AF region and classical AF2 is correlated with the strength of the co-regulator interaction. This work offers the first glimpse into the conformational dynamics that drive this unusual PL-mediated nuclear hormone receptor activation.

Down-regulation of MicroRNA-381 promotes cell proliferation and invasion in colon cancer through up-regulation of LRH-1

The expression and roles of MicroRNA-381 (miR-381) has been explored in several types of human cancers. However, its biological functions in colon cancer remain largely unknown. Quantitative real-time PCR assays were used to detect the expression of miR-381 in human colon cancer tissues and adjacent normal tissues. miR-381 antisense oligos and mimics were introduced into SW480 and HCT116 cells. Bioinformatic prediction analysis was performed to identify the potential targets of miR-381. Protein expression analysis, luciferase assays and rescue assays were used to confirm the substrate of miR-381. We found that miR-381 was significantly down-regulated in human colon cancer tissues, compared with adjacent normal tissues. Introduction of miR-381 antisense oligos into SW480 and HCT116 cells promoted cell proliferation and invasion. Besides, inhibition of miR-381 could also support tumor growth in the nude mice. Additionally, bioinformatic prediction suggested that the nuclear receptor liver receptor homologue 1 (LRH-1) is a target gene of miR-381. Thus, our data suggested that down-regulation of miR-381 plays an important role in the colon cancer progression.

LRH-1 mediates anti-inflammatory and antifungal phenotype of IL-13-activated macrophages through the PPARγ ligand synthesis

Liver receptor homologue-1 (LRH-1) is a nuclear receptor involved in the repression of inflammatory processes in the hepatointestinal tract. Here we report that LRH-1 is expressed in macrophages and induced by the Th2 cytokine IL-13 via a mechanism involving STAT6. We show that loss-of-function of LRH-1 in macrophages impedes IL-13-induced macrophage polarization due to impaired generation of 15-HETE PPARγ ligands. The incapacity to generate 15-HETE metabolites is at least partially caused by the compromised regulation of CYP1A1 and CYP1B1. Mice with LRH-1-deficient macrophages are, furthermore, highly susceptible to gastrointestinal and systemic Candida albicans infection. Altogether, these results identify LRH-1 as a critical component of the anti-inflammatory and fungicidal response of alternatively activated macrophages that acts upstream from the IL-13-induced 15-HETE/PPARγ axis.

Associations of NR5A2 gene polymorphisms with the clinicopathological characteristics and survival of gastric cancer

The orphan nuclear receptor (NR5A2), which belongs to the NR5A subfamily of nuclear receptors, is expressed in developing and adult tissues of endodermal origin, and can contribute to the development of several cancers through regulating cell proliferation. NR5A2 (rs3790843 and rs3790844) single nucleotide polymorphisms (SNPs) genotyping were examined in DNA samples, extracted from paraffin-embedded cancer tissue. Clinicopathologic and follow-up data were collected from 944 patients with gastric cancer (GC). Associations of the 2 SNPs with the progression and prognosis in gastric cancer patients were analyzed using the SPSS version 18.0. We found that NR5A2 rs3790843 polymorphism was significantly associated with the risk of GC which had regional lymph node metastasis (p = 0.044) or distant metastasis (p = 0.020). Our results also indicated that rs3790844 polymorphism was associated with the increased overall survival (OS) of GC patients in the dominant model (GG vs. GA/AA, HR (hazard ratio) = 0.823, 95% CI (confidence interval) = 0.679–0.997), suggesting a potential protective role of the variant A allele. Additionally, in the stratified analysis, both NR5A2 rs3790843 and rs3790844 polymorphism were associated with significantly lower risk of death in the groups of female, tumor size >5 cm in a dominant model. Our results represent the first demonstration that the NR5A2 rs3790844 polymorphism is associated with increased OS of GC patients in the dominant model, and similar results were found among the female group and tumor size >5 cm group for NR5A2 rs3790843 polymorphism. Further validation in other larger studies with different ethnic populations and functional evaluations are needed.

SUMOylation-dependent LRH-1/PROX1 interaction promotes atherosclerosis by decreasing hepatic reverse cholesterol transport

Reverse cholesterol transport (RCT) is an antiatherogenic process in which excessive cholesterol from peripheral tissues is transported to the liver and finally excreted from the body via the bile. The nuclear receptor liver receptor homolog 1 (LRH-1) drives expression of genes regulating RCT, and its activity can be modified by different posttranslational modifications. Here, we show that atherosclerosis-prone mice carrying a mutation that abolishes SUMOylation of LRH-1 on K289R develop less aortic plaques than control littermates when exposed to a high-cholesterol diet. The mechanism underlying this atheroprotection involves an increase in RCT and its associated hepatic genes and is secondary to a compromised interaction of LRH-1 K289R with the corepressor prospero homeobox protein 1 (PROX1). Our study reveals that the SUMOylation status of a single nuclear receptor lysine residue can impact the development of a complex metabolic disease such as atherosclerosis.

The Concise Guide to PHARMACOLOGY 2013/14: nuclear hormone receptors

The Concise Guide to PHARMACOLOGY 2013/14 provides concise overviews of the key properties of over 2000 human drug targets with their pharmacology, plus links to an open access knowledgebase of drug targets and their ligands (www.guidetopharmacology.org), which provides more detailed views of target and ligand properties. The full contents can be found at http://onlinelibrary.wiley.com/doi/10.1111/bph.12444/full.

Nuclear hormone receptors are one of the seven major pharmacological targets into which the Guide is divided, with the others being G protein-coupled receptors, ligand-gated ion channels, ion channels, catalytic receptors, transporters and enzymes. These are presented with nomenclature guidance and summary information on the best available pharmacological tools, alongside key references and suggestions for further reading. A new landscape format has easy to use tables comparing related targets.

It is a condensed version of material contemporary to late 2013, which is presented in greater detail and constantly updated on the website www.guidetopharmacology.org, superseding data presented in previous Guides to Receptors and Channels. It is produced in conjunction with NC-IUPHAR and provides the official IUPHAR classification and nomenclature for human drug targets, where appropriate. It consolidates information previously curated and displayed separately in IUPHAR-DB and the Guide to Receptors and Channels, providing a permanent, citable, point-in-time record that will survive database updates.

Cytochromes p450 and skin cancer: role of local endocrine pathways

Skin is the largest body organ forming a metabolically active barrier between external and internal environments. The metabolic barrier is composed of cytochromes P450 (CYPs) that regulate its homeostasis through activation or inactivation of biologically relevant molecules. In this review we focus our attention on local steroidogenic and secosteroidogenic systems in relation to skin cancer, e.g., prevention, attenuation of tumor progression and therapy. The local steroidogenic system is composed of locally expressed CYPs involved in local production of androgens, estrogens, gluco- and mineralo-corticosteroids from cholesterol (initiated by CYP11A1) or from steroid precursors delivered to the skin, and of their metabolism and/or inactivation. Cutaneous 7-hydroxylases (CYP7A1, CYP7B1 and CYP39) potentially can produce 7-hydroxy/oxy-steroids/sterols with modifying effects on local tumorigenesis. CYP11A1 also transforms 7-dehydrocholesterol (7DHC)→22(OH)7DHC→20,22(OH)2-7DHC→7-dehydropregnenolone, which can be further metabolized to other 5,7- steroidal dienes. These 5,7-dienal intermediates are converted by ultraviolet radiation B (UVB) into secosteroids which show pro-differentiation and anti-cancer properties. Finally, the skin is the site of activation of vitamin D3 through two alternative pathways. The classical one involves sequential hydroxylation at positions 25 and 1 to produce active 1,25(OH)2D3, which is further inactivated through hydroxylation at C24. The novel pathway is initiated by CYP11A1 with predominant production of 20(OH)D3 which is further metabolized to biologically active but non-calcemic D3-hydroxyderivatives. Classical and non-classical (novel) vitamin D analogs show pro-differentiation, anti-proliferative and anticancer properties. In addition, melatonin is metabolized by local CYPs. In conclusion cutaneously expressed CYPs have significant effects on skin physiology and pathology trough regulation of its chemical milieu.

The nuclear hormone receptor family member NR5A2 controls aspects of multipotent progenitor cell formation and acinar differentiation during pancreatic organogenesis

The orphan nuclear receptor NR5A2 is necessary for the stem-like properties of the epiblast of the pre-gastrulation embryo and for cellular and physiological homeostasis of endoderm-derived organs postnatally. Using conditional gene inactivation, we show that Nr5a2 also plays crucial regulatory roles during organogenesis. During the formation of the pancreas, Nr5a2 is necessary for the expansion of the nascent pancreatic epithelium, for the subsequent formation of the multipotent progenitor cell (MPC) population that gives rise to pre-acinar cells and bipotent cells with ductal and islet endocrine potential, and for the formation and differentiation of acinar cells. At birth, the NR5A2-deficient pancreas has defects in all three epithelial tissues: a partial loss of endocrine cells, a disrupted ductal tree and a >90% deficit of acini. The acinar defects are due to a combination of fewer MPCs, deficient allocation of those MPCs to pre-acinar fate, disruption of acinar morphogenesis and incomplete acinar cell differentiation. NR5A2 controls these developmental processes directly as well as through regulatory interactions with other pancreatic transcriptional regulators, including PTF1A, MYC, GATA4, FOXA2, RBPJL and MIST1 (BHLHA15). In particular, Nr5a2 and Ptf1a establish mutually reinforcing regulatory interactions and collaborate to control developmentally regulated pancreatic genes by binding to shared transcriptional regulatory regions. At the final stage of acinar cell development, the absence of NR5A2 affects the expression of Ptf1a and its acinar specific partner Rbpjl, so that the few acinar cells that form do not complete differentiation. Nr5a2 controls several temporally distinct stages of pancreatic development that involve regulatory mechanisms relevant to pancreatic oncogenesis and the maintenance of the exocrine phenotype.

Identification of transcription factors and single nucleotide polymorphisms of Lrh1 and its homologous genes in Lrh1-knockout pancreas of mice

BACKGROUND

To identify transcription factors (TFs) and single nucleotide polymorphisms (SNPs) of Lrh1 (also named Nr5a2) and its homologous genes in Lrh1-knockout pancreas of mice.

METHODS

The RNA-Seq data GSE34030 were downloaded from Gene Expression Omnibus (GEO) database, including 2 Lrh1 pancreas knockout samples and 2 wild type samples. All reads were processed through TopHat and Cufflinks package to calculate gene-expression level. Then, the differentially expressed genes (DEGs) were identified via non-parametric algorithm (NOISeq) methods in R package, of which the homology genes of Lrh1 were identified via BLASTN analysis. Furthermore, the TFs of Lrh1 and its homologous genes were selected based on TRANSFAC database. Additionally, the SNPs were analyzed via SAM tool to record the locations of mutant sites.

RESULTS

Total 15683 DEGs were identified, of which 23 was Lrh1 homology genes (3 up-regulated and 20 down-regulated). Fetoprotein TF (FTF) was the only TF of Lrh1 identified and the promoter-binding factor of FTF was CYP7A. The SNP annotations of Lrh1 homologous genes showed that 92% of the mutation sites were occurred in intron and upstream. Three SNPs of Lrh1 were located in intron, while 1819 SNPs of Phkb were located in intron and 1343 SNPs were located in the upstream region.

CONCLUSION

FTF combined with CYP7A might play an important role in Lrh1 regulated pancreas-specific transcriptional network. Furthermore, the SNPs analysis of Lrh1 and its homology genes provided the candidate mutant sites that might affect the Lrh1-related production and secretion of pancreatic fluid.

Nr5a2 heterozygosity sensitises to, and cooperates with, inflammation in KRas(G12V)-driven pancreatic tumourigenesis

OBJECTIVES

Nr5a2 participates in biliary acid metabolism and is a major regulator of the pancreatic exocrine programme. Single nucleotide polymorphisms in the vicinity of NR5A2 are associated with the risk of pancreatic ductal adenocarcinoma (PDAC).

AIMS

To determine the role of Nr5a2 in pancreatic homeostasis, damage-induced regeneration and mutant KRas-driven pancreatic tumourigenesis.

DESIGN

Nr5a2+/- and KRas(G12V);Ptf1a-Cre;Nr5a2+/- mice were used to investigate whether a full dose of Nr5a2 is required for normal pancreas development, recovery from caerulein-induced pancreatitis, and protection from tumour development.

RESULTS

Adult Nr5a2+/- mice did not display histological abnormalities in the pancreas but showed a more severe acute pancreatitis, increased acino-ductal metaplasia and impaired recovery from damage. This was accompanied by increased myeloid cell infiltration and proinflammatory cytokine gene expression, and hyperactivation of nuclear factor κb and signal transducer and activator of transcription 3 signalling pathways. Induction of multiple episodes of acute pancreatitis was associated with more severe damage and delayed regeneration. Inactivation of one Nr5a2 allele selectively in pancreatic epithelial cells was sufficient to cause impaired recovery from pancreatitis. In comparison with Nr5a2+/+ mice, KRas(G12V);Ptf1a(Cre/+);Nr5a2+/- mice showed a non-statistically significant increase in the area affected by preneoplastic lesions. However, a single episode of acute pancreatitis cooperated with loss of one Nr5a2 allele to accelerate KRas(G12V)-driven development of preneoplastic lesions.

CONCLUSIONS

A full Nr5a2 dose is required to restore pancreatic homeostasis upon damage and to suppress the KRas(G12V)-driven mouse pancreatic intraepithelial neoplasia progression, indicating that Nr5a2 is a novel pancreatic tumour suppressor. Nr5a2 could contribute to PDAC through a role in the recovery from pancreatitis-induced damage.

Key role of CRF in the skin stress response system

The discovery of corticotropin-releasing factor (CRF) or CRH defining the upper regulatory arm of the hypothalamic-pituitary-adrenal (HPA) axis, along with the identification of the corresponding receptors (CRFRs 1 and 2), represents a milestone in our understanding of central mechanisms regulating body and local homeostasis. We focused on the CRF-led signaling systems in the skin and offer a model for regulation of peripheral homeostasis based on the interaction of CRF and the structurally related urocortins with corresponding receptors and the resulting direct or indirect phenotypic effects that include regulation of epidermal barrier function, skin immune, pigmentary, adnexal, and dermal functions necessary to maintain local and systemic homeostasis. The regulatory modes of action include the classical CRF-led cutaneous equivalent of the central HPA axis, the expression and function of CRF and related peptides, and the stimulation of pro-opiomelanocortin peptides or cytokines. The key regulatory role is assigned to the CRFR-1α receptor, with other isoforms having modulatory effects. CRF can be released from sensory nerves and immune cells in response to emotional and environmental stressors. The expression sequence of peptides includes urocortin/CRF→pro-opiomelanocortin→ACTH, MSH, and β-endorphin. Expression of these peptides and of CRFR-1α is environmentally regulated, and their dysfunction can lead to skin and systemic diseases. Environmentally stressed skin can activate both the central and local HPA axis through either sensory nerves or humoral factors to turn on homeostatic responses counteracting cutaneous and systemic environmental damage. CRF and CRFR-1 may constitute novel targets through the use of specific agonists or antagonists, especially for therapy of skin diseases that worsen with stress, such as atopic dermatitis and psoriasis.

The orphan nuclear receptors at their 25-year reunion

The nuclear receptor superfamily includes many receptors, identified based on their similarity to steroid hormone receptors but without a known ligand. The study of how these receptors are diversely regulated to interact with genomic regions to control a plethora of biological processes has provided critical insight into development, physiology, and the molecular pathology of disease. Here we provide a compendium of these so-called orphan receptors and focus on what has been learned about their modes of action, physiological functions, and therapeutic promise.

Co-regulated gene expression by oestrogen receptor α and liver receptor homolog-1 is a feature of the oestrogen response in breast cancer cells

Oestrogen receptor α (ERα) is a nuclear receptor that is the driving transcription factor expressed in the majority of breast cancers. Recent studies have demonstrated that the liver receptor homolog-1 (LRH-1), another nuclear receptor, regulates breast cancer cell proliferation and promotes motility and invasion. To determine the mechanisms of LRH-1 action in breast cancer, we performed gene expression microarray analysis following RNA interference for LRH-1. Interestingly, gene ontology (GO) category enrichment analysis of LRH-1-regulated genes identified oestrogen-responsive genes as the most highly enriched GO categories. Remarkably, chromatin immunoprecipitation coupled to massively parallel sequencing (ChIP-seq) to identify genomic targets of LRH-1 showed LRH-1 binding at many ERα binding sites. Analysis of select binding sites confirmed regulation of ERα-regulated genes by LRH-1 through binding to oestrogen response elements, as exemplified by the TFF1/pS2 gene. Finally, LRH-1 overexpression stimulated ERα recruitment, while LRH-1 knockdown reduced ERα recruitment to ERα binding sites. Taken together, our findings establish a key role for LRH-1 in the regulation of ERα target genes in breast cancer cells and identify a mechanism in which co-operative binding of LRH-1 and ERα at oestrogen response elements controls the expression of oestrogen-responsive genes.

Steroidogenesis in the skin: implications for local immune functions

The skin has developed a hierarchy of systems that encompasses the skin immune and local steroidogenic activities in order to protect the body against the external environment and biological factors and to maintain local homeostasis. Most recently it has been established that skin cells contain the entire biochemical apparatus necessary for production of glucocorticoids, androgens and estrogens either from precursors of systemic origin or, alternatively, through the conversion of cholesterol to pregnenolone and its subsequent transformation to biologically active steroids. Examples of these products are corticosterone, cortisol, testosterone, dihydrotesterone and estradiol. Their local production can be regulated by locally produced corticotropin releasing hormone (CRH), adrenocorticotropic hormone (ACTH) or cytokines. Furthermore the production of glucocorticoids is affected by ultraviolet B radiation. The level of production and nature of the final steroid products are dependent on the cell type or cutaneous compartment, e.g., epidermis, dermis, adnexal structures or adipose tissue. Locally produced glucocorticoids, androgens and estrogens affect functions of the epidermis and adnexal structures as well as local immune activity. Malfunction of these steroidogenic activities can lead to inflammatory disorders or autoimmune diseases. The cutaneous steroidogenic system can also have systemic effects, which are emphasized by significant skin contribution to circulating androgens and/or estrogens. Furthermore, local activity of CYP11A1 can produce novel 7Δ-steroids and secosteroids that are biologically active. Therefore, modulation of local steroidogenic activity may serve as a new therapeutic approach for treatment of inflammatory disorders, autoimmune processes or other skin disorders. In conclusion, the skin can be defined as an independent steroidogenic organ, whose activity can affect its functions and the development of local or systemic inflammatory or autoimmune diseases. This article is part of a Special Issue entitled 'CSR 2013'.