Nuclear receptors and pathogenesis of pancreatic cancer

Pancreatic ductal adenocarcinoma (PDAC) is a devastating disease with a median overall survival time of 5 mo and the five years survival less than 5%, a rate essentially unchanged over the course of the years. A well defined progression model of accumulation of genetic alterations ranging from single point mutations to gross chromosomal abnormalities has been introduced to describe the origin of this disease. However, due to the its subtle nature and concurring events PDAC cure remains elusive. Nuclear receptors (NR) are members of a large superfamily of evolutionarily conserved ligand-regulated DNA-binding transcription factors functionally involved in important cellular functions ranging from regulation of metabolism, to growth and development. Given the nature of their ligands, NR are very tempting drug targets and their pharmacological modulation has been widely exploited for the treatment of metabolic and inflammatory diseases. There are now clear evidences that both classical ligand-activated and orphan NR are involved in the pathogenesis of PDAC from its very early stages; nonetheless many aspects of their role are not fully understood. The purpose of this review is to highlight the striking connections that link peroxisome proliferator activated receptors, retinoic acid receptors, retinoid X receptor, androgen receptor, estrogen receptors and the orphan NR Nur, chicken ovalbumin upstream promoter transcription factor II and the liver receptor homologue-1 receptor to PDAC development, connections that could lead to the identification of novel therapies for this disease.

Hepatic drug transporters and nuclear receptors:Regulation by therapeutic agents

The canalicular membrane represents the excretory pole of hepatocytes.Bile is an important route of elimination of potentially toxic endo-and xenobiotics(including drugs and toxins),mediated by the major canalicular transporters:multidrug resistance protein 1(MDR1, ABCB1),also known as P-glycoprotein,multidrug resistance-associated protein 2(MRP2,ABCC2),and the breast cancer resistance protein(BCRP,ABCG2).Their activities depend on regulation of expression and proper localization at the canalicular membrane,as regulated by transcriptional and post-transcriptional events,respectively.At transcriptional level,specific nuclear receptors(NR)s modulated by ligands,co-activators and co-repressors,mediate the physiological requirements of these transporters.This complex system is also responsible for alterations occurring in specific liver pathologies.We briefly describe the major ClassⅡNRs, pregnane X receptor(PXR)and constitutive androstane receptor(CAR),and their role in regulating expression of multidrug resistance proteins.Several therapeutic agents regulate the expression of relevant drug transporters through activation/inactivation of these NRs.We provide some representative examples of the action of therapeutic agents modulating liver drug transporters, which in addition,involve CAR or PXR as mediators.

Expression of P450 and nuclear receptors in normal and end-stage Chinese livers

AIM: To investigate the expression of P450 enzyme genes by using end-stage liver disease samples and trimmed normal Chinese donor livers.

Role of nuclear receptors in breast cancer stem cells

The recapitulation of primary tumour heterogenity and the existence of a minor sub-population of cancer cells,capable of initiating tumour growth in xenografts on serial passages, led to the hypothesis that cancer stem cells(CSCs) exist. CSCs are present in many tumours, among which is breast cancer. Breast CSCs(BCSCs) are likely to sustain the growth of the primary tumour mass, as wellas to be responsible for disease relapse and metastatic spreading. Consequently, BCSCs represent the most significant target for new drugs in breast cancer therapy. Both the hypoxic condition in BCSCs biology and proinflammatory cytokine network has gained increasing importance in the recent past. Breast stromal cells are crucial components of the tumours milieu and are a major source of inflammatory mediators. Recently, the antiinflammatory role of some nuclear receptors ligands has emerged in several diseases, including breast cancer. Therefore, the use of nuclear receptors ligands may be a valid strategy to inhibit BCSCs viability and consequently breast cancer growth and disease relapse.

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

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

Effect of Marine Collagen Peptides on Markers of Metabolic Nuclear Receptors in Type 2 Diabetic Patients with/without Hypertension

Objective To explore Effects of marine collagen peptides （MCPs） on markers of metablic nuclear receptors, i.e peroxisome proliferator-activated receptor （PPARs）, liver X receptor （LXRs） and farnesoid X receptor （FXRs） in type 2 diabetic patients with/without hypertension. Method Study population consisted of 200 type 2 diabetic patients with/without hypertension and 50 healthy subjects, all of whom were randomly assigned to MCPs-treated diabetics （n=50）, placebo-treated diabetics （n=50）, MCPs-treated diabetics with hypertension （n=50）, placebo-treated diabetics with hypertension （n=50）, and healthy controls （n=50）. MCPs or placebo （water-soluble starch） were given daily before breakfast and bedtime over three months. Levels of free fatty acid, cytochrome P450, leptin, resistin, adiponectin, bradykinin, NO, and Prostacyclin were determined before intervention, and 1.5 months, and 3 months after intervention. Hypoglycemia and the endpoint events during the study were recorded and compared among the study groups. Result At the end of the study period, MCPs-treated patients showed marked improvement compared with patients receiving placebo. The protection exerted by MCPs seemed more profound in diabetics than in diabetics with hypertension. In particular, after MCPs intervention, levels of free fatty acid, hs-CRP, resistin, Prostacyclin decreased significantly in diabetics and tended to decrease in diabetic and hypertensive patients whereas levels of cytochrome P450, leptin, NO tended to decrease in diabetics with/without hypertension. Meanwhile, levels of adiponectin and bradykinin rose markedly in diabetics following MCPs administration. Conclusion MCPs could offer protection against diabetes and hypertension by affecting levels of molecules involved in diabetic and hypertensive pathogenesis. Regulation on metabolic nuclear receptors by MCPs may be the possible underlying mechanism for its observed effects in the study. Further study into its action may shed light on development of new drugs based on bioactive peptides from marine sources.

Targeting nuclear receptors for NASH/MASH:From bench to bedside

The onset of metabolic dysfunction-associated steatohepatitis(MASH)or non-alcoholic steatohepatitis(NASH)represents a tipping point leading to liver injury and subsequent hepatic complications in the natural progression of what is now termed metabolic dysfunction-associated steatotic liver diseases(MASLD),formerly known as non-alcoholic fatty liver disease(NAFLD).With no pharmacological treat-ment currently available for MASH/NASH,the race is on to develop drugs targeting multiple facets of hepatic metabolism,inflammation,and pro-fibrotic events,which are major drivers of MASH.Nuclear receptors(NRs)regulate genomic transcription upon binding to lipophilic ligands and govern multiple aspects of liver metabolism and inflammation.Ligands of NRs may include hormones,lipids,bile acids,and synthetic ligands,which upon binding to NRs regulate the transcriptional activities of target genes.NR ligands are presently the most promising drug candidates expected to receive approval from the United States Food and Drug Administration as a pharmacological treatment for MASH.This review aims to cover the current understanding of NRs,including nuclear hormone receptors,non-steroid hormone receptors,circadian NRs,and orphan NRs,which are currently undergoing clinical trials for MASH treatment,along with NRs that have shown promising results in preclinical studies.

Reversal of multidrug resistance in cancer treatment by regulating multidrug resistance gene1: focus on nuclear receptors and epigenetics

Overexpression of P-glycoprotein （P-gp） encoded by the multidrug resistance gene-1 （MDR-1） is the main mechanism responsible for multidrug resistance （MDR） in a majority of cancer cells. However, the mechanism by which cancer cells acquire high levels of P-gp has not been well defined. Accumulating evidence suggests that nuclear receptors （NRs）, especially human pregnane X receptor （PXR）, play a crucial role in multidrug resistance. It has been shown that chemotherapeutic drug activates PXR and then enhances P-gp expression. Genetic knockdown or pharmacologic inhibition of PXR led to attenuation of drug-induced MDR1 over expression, implying that NRs may be an effective target to reverse multidrug resistance. Recent investigations suggested that transcriptional activity of NRs is mediated by methylases, the important enzymes involved in epigenetic regulation. Other epigenetic modifications, such as promoter methylation, histone deacetylases and microRNAs, were also found to be involved in activation of MDR1 promoter, though the underlying mechanisms are not thoroughly known. In this review, we summarized recent researches in the regulation of P-gp expression, with particular focus on NRs and epigenetics, aiming to provide references and options to reverse and/or prevent MDR in cancer treatment.

Editor profile:Guest editor of special issue “Bile Acids and Nuclear Receptors in Digestive System and Therapy”

Associate Prof.Grace Liejun Guo is a tenured faculty in the Department of Pharmacology and Toxicology in the School of Pharmacy at the Rutgers University in New Jersey,USA.Dr.Guo graduated from the West China University of Medical Sciences in 1993.In 1997,Dr.Guo obtained a MS degree

Nuclear receptors and non-alcoholic fatty liver disease:An update

Non-alcoholic fatty liver disease(NAFLD)has become the leading cause of chronic liver disease in adults and children worldwide.The symptoms of NAFLD range from simple steatosis and non-alcoholic stea-tohepatitis(NASH)to hepatic fibrosis or cirrhosis,even ultimately develops to hepatocellular carcinoma.Nuclear receptors(NRs)are a superfamily of ligand-activated transcription factors,most of which are ligand-activated that control cellular homeostasis in the liver and other tissues.A growing number of studies demonstrated the important role of NRs in NAFLD.In this review,the current findings on the role of NRs in NAFLD are summarized and future perspectives to target NRs for NAFLD are discussed.

Understanding the physiological functions of the host xenobiotic-sensing nuclear receptors PXR and CAR on the gut microbiome using genetically modified mice

Pharmacological activation of the xenobiotic-sensing nuclear receptors pregnane X receptor(PXR) and constitutive androstane receptor(CAR) is well-known to increase drug metabolism and reduce inflammation. Little is known regarding their physiological functions on the gut microbiome. In this study, we discovered bivalent hormetic functions of PXR/CAR modulating the richness of the gut microbiome using genetically engineered mice. The absence of PXR or CAR increased microbial richness, and absence of both receptors synergistically increased microbial richness. PXR and CAR deficiency increased the pro-inflammatory bacteria Helicobacteraceae and Helicobacter. Deficiency in both PXR and CAR increased the relative abundance of Lactobacillus, which has bile salt hydrolase activity, corresponding to decreased primary taurine-conjugated bile acids(BAs) in feces, which may lead to higher internal burden of taurine and unconjugated BAs, both of which are linked to inflammation, oxidative stress, and cytotoxicity. The basal effect of PXR/CAR on the gut microbiome was distinct from pharmacological and toxicological activation of these receptors. Common PXR/CAR-targeted bacteria were identified, the majority of which were suppressed by these receptors. h PXR-TG mice had a distinct microbial profile as compared to wild-type mice. This study is the first to unveil the basal functions of PXR and CAR on the gut microbiome.

Endocrine pheromones couple fat rationing to dauer diapause through HNF4αnuclear receptors

Developmental diapause is a widespread strategy for animals to survive seasonal starvation and environmental harshness.Diapaused animals often ration body fat to generate a basal level of energy for enduring survival.How diapause and fat rationing are coupled,however,is poorly understood.The nematode Caenorhabditis elegans excretes pheromones to the environment to induce a diapause form called dauer larva.Through saturated forward genetic screens and CRISPR knockout,we found that dauer pheromones feed back to repress the transcription of ACOX-3,MAOC-1,DHS-28,DAF-22(peroxisomalβ-oxidation enzymes dually involved in pheromone synthesis and fat burning),ALH-4(aldehyde dehydrogenase for pheromone synthesis),PRX-10 and PRX-11(peroxisome assembly and proliferation factors).Dysfunction of these pheromone enzymes and factors relieves the repression.Surprisingly,transcription is repressed not by pheromones excreted but by pheromones endogenous to each animal.The endogenous pheromones regulate the nuclear translocation of HNF4αfamily nuclear receptor NHR-79 and its co-receptor NHR-49,and,repress transcription through the two receptors.The feedback repression maintains pheromone homeostasis,increases fat storage,decreases fat burning,and prolongs dauer lifespan.Thus,the exocrine dauer pheromones possess an unexpected endocrine function to mediate a peroxisome-nucleus crosstalk,coupling dauer diapause to fat rationing.

Screening of agonistic activities against four nuclear receptors in wastewater treatment plants in Japan using a yeast two-hybrid assay

To assess the potential endocrine disruptive effects through multiple nuclear receptors （NRs）, especially non-steroidal NRs, in municipal wastewater, we examined the agonistic activities on four NRs （estrogen receptor α, thyroid hormone receptor α, retinoic acid receptor ct and retinoid X receptor α） of untreated and treated wastewater from municipal wastewater treatment plants （WWTPs） in Japan using a yeast two-hybrid assay. Investigation of the influent and effluent of seven WWTPs revealed that agonistic activities against steroidal and non-steroidal NRs were always detected in the influents and partially remained in the effluents. Further investigation of four WWTPs employing conventional activated sludge, pseudo-anoxic-oxic, anoxic-oxic and anaerobic-anoxic-oxic processes revealed that the ability to reduce the agonistic activity against each of the four NRs varies depending on the treatment process. These results indicated that municipal wastewater in Japan commonly contains endocrine disrupting chemicals that exert agonistic activities on steroidal and non-steroidal NRs, and that some of these chemicals are released into the natural aquatic environment. Although the results obtained in yeast assays suggested that measured levels of non-steroidal NR agonists in the effluent of WWTPs were not likely to cause any biological effect, further study is required to assess their possible risks in detail.

Chromatin remodeling regulated by steroid and nuclearreceptors

Coactivators and corepressors regulate transcriptionby controlling interactions between sequence-specific transcription factors, the basal transcriptional machinery andthe chromatin environment. This review consider the access of nuclear and steroid receptors to chromatin, theiruse of corepressors and coactivators to modify chromatinstructure and the implications for transcriptional control.The assembly of specific nucleoprotein architectures andtargeted histone modification emerge as central controlling elements for gene expression.

Transcriptional Crosstalk between Nuclear Receptors and Cytokine Signal Transduction Pathways in Immunity

The nuclear receptor superfamily and the transcriptional factors associated with cytokines are inherently different families of signaling molecules and activate gene transcription by binding to their respective responsive element.However,it has become increasingly clear from our works and others that nuclear receptors are important regulators of cytokine production and function through complex and varied interactions between these distinct transcriptional factors.This review provides a general overview of the mechanism of action of nuclear receptors and their transcriptional crosstalk with transcriptional factors associated with cytokine transduction pathways.One of the most important mechanistic aspects is protein to protein interaction through a direct or co-regulator-mediated indirect manner.Such crosstalk is crucially involved in physiological and therapeutic roles of nuclear receptors and their iigands in immunity, inflammation and cytokine-related tumors.Cellular & Molecular Immunology.2004;1(6):416-424.

Aryl hydrocarbon receptor nuclear translocator 2 as a prognostic biomarker and immunotherapeutic indicator for clear cell renal cell carcinoma

Background:In many cancer types,aryl hydrocarbon receptor nuclear translocator 2(ARNT2)has been found to be associated with tumor cell proliferation and prognosis.However,the role of ARNT2 in clear cell renal cell carcinoma(ccRCC)has not been completely elucidated.In this study,the potential role of ARNT2 in ccRCC development was characterized.Methods:A pan-cancer dataset(TCGA-TARGET-GTEx)was accessed from UCSC Xena Data Browser.ARNT2 expression in normal and tumor samples was compared.Univariate Cox regression was performed to evaluate the prognostic value of ARNT2.Single sample gene set enrichment analysis(ssGSEA)was used to estimate the enrichment of functional pathways and gene signatures.CIBERSORT and ESTIMATE methods evaluated the immune infiltration.The ARNT2 expression was determined in ccRCC tissue and cell lines using RT-qPCR and Western blot.Results:ARNT2 expression was significantly dysregulated in 23 out of 30 cancer types.Pan-cancer data revealed a strong correlation between ARNT2 expression and immune modulators,immune cell infiltration,and genomic alternations.In ccRCC patients,the low-ARNT2 expression group had higher immune infiltration,CD8 T cells,and programmed cell death ligand 1 expression,as well as higher enrichment score of immunotherapeutic predictors than those in the high-ARNT2 expression group.Low-ARNT2 expression group was more responsive to immunotherapy.Moreover,low ARNT2 expression was observed in ccRCC tissue and cell lines.Conclusions:Dysregulated ARNT2 expression is involved in cancer development and the modulation of the immune microenvironment.ARNT2 can be potentially used as a prognostic indicator and an immunotherapeutic indicator for ccRCC.

Clinical and genetic characteristics of a child with Sotos syndrome and attention-deficit/hyperactivity disorder:A case report

BACKGROUND Sotos syndrome is an autosomal dominant disorder,whereas attention-deficit/hyperactivity disorder(ADHD)is a neurodevelopmental condition.This report aimed to summarize the clinical and genetic features of a pediatric case of Soros syndrome and ADHD in a child exhibiting precocious puberty.CASE SUMMARY The patient presented with accelerated growth and advanced skeletal maturation;however,she lacked any distinct facial characteristics related to specific genetic disorders.Genetic analyses revealed a paternally inherited heterozygous synonymous mutation[c.4605C>T(p.Arg1535Arg)].Functional analyses suggested that this mutation may disrupt splicing,and bioinformatics analyses predicted that this mutation was likely pathogenic.After an initial diagnosis of Sotos syndrome,the patient was diagnosed with ADHD during the follow-up period at the age of 8 years and 7 months.CONCLUSION The potential for comorbid ADHD in Sotos syndrome patients should be considered to avoid the risk of a missed diagnosis.

Jianpi Gushen Huayu decoction ameliorated diabetic nephropathy through modulating metabolites in kidney,and inhibiting TLR4/NF-κB/NLRP3 and JNK/P38 pathways

BACKGROUND Jianpi Gushen Huayu Decoction(JPGS)has been used to clinically treat diabetic nephropathy(DN)for many years.However,the protective mechanism of JPGS in treating DN remains unclear.AIM To evaluate the therapeutic effects and the possible mechanism of JPGS on DN.METHODS We first evaluated the therapeutic potential of JPGS on a DN mouse model.We then investigated the effect of JPGS on the renal metabolite levels of DN mice using non-targeted metabolomics.Furthermore,we examined the effects of JPGS on c-Jun N-terminal kinase(JNK)/P38-mediated apoptosis and the inflammatory responses mediated by toll-like receptor 4(TLR4)/nuclear factor-kappa B(NF-κB)/NOD-like receptor family pyrin domain containing 3(NLRP3).RESULTS The ameliorative effects of JPGS on DN mice included the alleviation of renal injury and the control of inflammation and oxidative stress.Untargeted metabolomic analysis revealed that JPGS altered the metabolites of the kidneys in DN mice.A total of 51 differential metabolites were screened.Pathway analysis results indicated that nine pathways significantly changed between the control and model groups,while six pathways significantly altered between the model and JPGS groups.Pathways related to cysteine and methionine metabolism;alanine,tryptophan metabolism;aspartate and glutamate metabolism;and riboflavin metabolism were identified as the key pathways through which JPGS affects DN.Further experimental validation showed that JPGS treatment reduced the expression of TLR4/NF-κB/NLRP3 pathways and JNK/P38 pathway-mediated apoptosis related factors.CONCLUSION JPGS could markedly treat mice with streptozotocin(STZ)-induced DN,which is possibly related to the regulation of several metabolic pathways found in kidneys.Furthermore,JPGS could improve kidney inflammatory responses and ameliorate kidney injuries in DN mice via the TLR4/NF-κB/NLRP3 pathway and inhibit JNK/P38 pathwaymediated apoptosis in DN mice.

Expression and role of nuclear receptor coregulators in colorectal cancer

Colorectal cancer(CRC) is one of the most common human cancers and the cause of about 700000 deaths per year worldwide. Deregulation of the WNT/β-catenin pathway is a key event in CRC initiation. This pathway interacts with other nuclear signaling pathways, including members of the nuclear receptor superfamily and their transcription coregulators. In this review, we provide an overview of the literature dealing with the main coactivators(NCo A-1 to 3, NCo A-6, PGC1-α, p300, CREBBP and MED1) and corepressors(N-Co R1 and 2, NRIP1 and MTA1) of nuclear receptors and summarize their links with the WNT/β-catenin signaling cascade, their expression in CRC and their role in intestinal physiopathology.

Analysis of ileal sodium/bile acid cotransporter and related nuclear receptor genes in a family with multiple cases of idiopathic bile acid malabsorption

The etiology of most cases of idiopathic bile acid malabsorption （IBAH） is unknown. In this study, a Swedish family with bile acid malabsorption in three consecutive generations was screened for mutations in the ileal apical sodium-bile acid cotransporter gene （ASBT; gene symbol, SLC10A2） and in the genes for several of the nuclear receptors known to be important for ASBT expression： the farnesoid X receptor （FXR） and peroxisome proliferator activated receptor alpha （PPARα）. The patients presented with a clinical history of idiopathic chronic watery diarrhea, which was responsive to cholestyramine treatment and consistent with IBAH. Bile acid absorption was determined using ^75Se-homocholic acid taurine （SeHCAT）; bile acid synthesis was estimated by measuring the plasma levels of 7α-hydroxy-4-cholesten-3-one （C4）. The ASBT, FXR, and PPARα genes in the affected and unaffected family members were analyzed using single stranded conformation polymorphism （SSCP）, denaturing HPLC, and direct sequencing. No ASBT mutations were identified and the ASBT gene did not segregate with the bile acid malabsorption phenotype. Similarly, no mutations or polymorphisms were identified in the FXR or PPARα genes associated with the bile acid malabsorption phenotype. These studies indicate that the intestinal bile acid malabsorption in these patients cannot be attributed to defects in ASBT. In the absence of apparent ileal disease, alternative explanations such as accelerated transit through the small intestine may be responsible for the IBAM.