Recent advances in the mechanisms of action and physiological functions of the retinoid-related orphan receptors (RORs)

SIRT3 Activator Honokiol Inhibits Th17 Cell Differentiation and Alleviates Colitis

BACKGROUND

Honokiol (HKL), a natural extract of the bark of the magnolia tree and an activator of the mitochondrial protein sirtuin-3 (SIRT3), has been proposed to possess anti-inflammatory effects. This study investigated the inhibitory effects of HKL on T helper (Th) 17 cell differentiation in colitis.

METHODS

Serum and biopsies from 20 participants with ulcerative colitis (UC) and 18 healthy volunteers were collected for the test of serum cytokines, flow cytometry analysis (FACS), and relative messenger RNA (mRNA) levels of T cell subsets, as well as the expression of SIRT3 and phosphorylated signal transducer and activator of transcription/retinoic acid-related orphan nuclear receptor γt (p-STAT3/RORγt) signal pathway in colon tissues. In vitro, naïve clusters of differentiation (CD) 4 + T cells isolated from the mouse spleen differentiated to subsets including Th1, Th2, Th17, and regulatory T (Treg) cells. Peripheral blood monocytes (PBMCs) from healthy volunteers were induced to the polarization of Th17 cells. After HKL treatment, changes in T cell subsets, related cytokines, and transcription factors were measured. The dextran sulfate sodium (DSS)-induced colitis and interleukin (IL)-10-deficient mice were intraperitoneally injected with HKL. These experiments were conducted to study the effect of HKL on the development, cytokines, and expression of signaling pathway proteins in colitis.

RESULTS

Patients with UC had higher serum IL-17 and a higher proportion of Th17 differentiation in blood compared with healthy participants; while IL-10 level and the proportion of Treg cells were lower. Higher relative mRNA levels of RORγt and a lower SIRT3 expression in colon tissues were observed. In vitro, HKL had little effect on the differentiation of naïve CD4+ T cells to Th1, Th2, or Treg cells, but it downregulated IL-17 levels and the Th17 cell ratio in CD4+ T cells from the mouse spleen and human PBMCs under Th17 polarization. Even with a STAT3 activator, HKL still significantly inhibited IL-17 levels. In DSS-induced colitis mice and IL-10 deficient mice treated with HKL, the length of the colon, weight loss, disease activity index, and histopathological scores were improved, IL-17 and IL-21 levels, and the proportion of Th17 cells were decreased. Sirtuin-3 expression was increased, whereas STAT3 phosphorylation and RORγt expression were inhibited in the colon tissue of mice after HKL treatment.

CONCLUSIONS

Our study demonstrated that HKL could partially protect against colitis by regulating Th17 differentiation through activating SIRT3, leading to inhibition of the STAT3/RORγt signaling pathway. These results provide new insights into the protective effects of HKL against colitis and may facilitate the research of new drugs for inflammatory bowel disease.

Circadian gene expression in mouse renal proximal tubule

Circadian variability in kidney function is well recognized but is often ignored as a potential confounding variable in physiological experiments. Here, we have created a data resource consisting of expression levels for mRNA transcripts in microdissected proximal tubule segments from mice as a function of the time of day. Small-sample RNA sequencing was applied to microdissected S1 proximal convoluted tubules and S2 proximal straight tubules. After stringent filtering, the data were analyzed using JTK-Cycle to detect periodicity. The data set is provided as a user-friendly webpage at https://esbl.nhlbi.nih.gov/Databases/Circadian-Prox2/. In proximal convoluted tubules, 234 transcripts varied in a circadian manner (4.0% of the total). In proximal straight tubules, 334 transcripts varied in a circadian manner (5.3%). Transcripts previously known to be associated with corticosteroid action and with increased flow were found to be overrepresented among circadian transcripts peaking during the "dark" portion of the day [zeitgeber time (ZT)14-22], corresponding to peak levels of corticosterone and glomerular filtration rate in mice. To ask whether there is a time-of-day dependence of protein abundances in the kidney, we carried out LC-MS/MS-based proteomics in whole mouse kidneys at ZT12 and ZT0. The full data set (n = 6,546 proteins) is available at https://esbl.nhlbi.nih.gov/Databases/Circadian-Proteome/. Overall, 293 proteins were differentially expressed between ZT12 and ZT0 (197 proteins greater at ZT12 and 96 proteins greater at ZT0). Among the regulated proteins, only nine proteins were found to be periodic in the RNA-sequencing analysis, suggesting a high level of posttranscriptional regulation of protein abundances.NEW & NOTEWORTHY Circadian variation in gene expression can be an important determinant in the regulation of kidney function. The authors used RNA-sequencing transcriptomics and LC-MS/MS-based proteomics to identify gene products expressed in a periodic manner. The data were used to construct user-friendly web resources.

Dose-Sparing Intradermal DTaP-sIPV Immunization With a Hollow Microneedle Leads to Superior Immune Responses

Dose-sparing intradermal (ID) vaccination may induce the same immune responses as intramuscular (IM) vaccination, which can increase vaccine supplies and save costs. In this study, rats were immunized with fractional-dose of Sabin-derived IPV combined with diphtheria-tetanus-acellular pertussis vaccine (DTaP-sIPV) intradermally with hollow microneedle devices called MicronJet600 and the vaccine immunogenicity and efficacy were evaluated and compared with those of full-dose intramuscular immunization. We tested levels of antibodies and the subclass distribution achieved via different immunization routes. Furthermore, gene transcription in the lung and spleen, cytokine levels and protection against Bordetella pertussis (B. pertussis) infection were also examined. The humoral immune effect of DTaP-sIPV delivered with MicronJet600 revealed that this approach had a significant dose-sparing effect and induced more effective protection against B. pertussis infection by causing Th1/Th17 responses. In conclusion, ID immunization of DTaP-sIPV with the MicronJet600 is a better choice than IM immunization, and it has the potential to be a new DTaP-sIPV vaccination strategy.

5,6,7,8-Tetrahydrobenzo[4,5]thieno[2,3-d]pyrimidine derivative attenuates lupus nephritis with less effect to thymocyte development

Retinoic‑acid‑receptor‑related orphan nuclear hormone receptor gamma t (RORγt), a critical transcriptional factor of Th17 cells, is a potential therapeutic target for Th17-mediated autoimmune diseases. In addition, RORγt is essential for thymocyte survival and lymph node development, and RORγt inhibition or deficiency causes abnormal thymocyte development, thymus lymphoma, and lymph node defect. Recent study demonstrated that specific regulation of Th17 differentiation related to the hinge region of RORγt. In this research, we investigated the effect of RORγt inhibitor, 5,6,7,8-tetrahydrobenzo[4,5]thieno[2,3-d]pyrimidine derivative (TTP), in the therapy of lupus nephritis and its safety on thymocyte development. We demonstrated that TTP repressed the development of Th17 cells and ameliorated the autoimmune disease manifestation in the pristane-induced lupus nephritis mice model. The treatment of TTP in the mice did not interfere with thymocyte development, including total thymocyte number and proportion of CD4+CD8+ double-positive populations in the thymus, and had no substantial effects on the pathogenesis of thymoma. The TTP had a stronger affinity with full-length RORγt protein compared with the truncated RORγt LBD region via surface plasmon resonance, which indicated TTP binding to RORγt beyond LBD region. Molecular docking computation showed that the best binding pocket of TTP to RORγt is located in the hinge region of RORγt. In summary, as a RORγt inhibitor, TTP had a potential to develop the clinical medicine for treating Th17-mediated autoimmune diseases with low safety risk for thymocyte development.

Time-restricted feeding downregulates cholesterol biosynthesis program via RORγ-mediated chromatin modification in porcine liver organoids

BACKGROUND

Time-restricted feeding (TRF) is a dieting strategy based on nutrients availability and diurnal rhythm, shown to improve lipid metabolism efficiency. We have demonstrated previously that retinoic acid-related (RAR) orphan receptor (ROR) γ is the primary transcription factor controlling cholesterol (CHO) biosynthesis program of animals. However, the functional role of RORγ in liver physiology of pigs in response to TRF has not been determined, largely due to the lack of functional models and molecular tools. In the present study, we established porcine liver organoids and subjected them to restricted nutrients supply for 10-h during the light portion of the day.

RESULTS

Our results showed that TRF regimen did not alter hepatocyte physiology, including unchanged cell viability, caspase 3/7 enzyme activity and the gene signature of cell proliferation in porcine liver organoids, compared to the control group (P > 0.05). Furthermore, we found that TRF downregulated the hepatic CHO biosynthesis program at both mRNA and protein levels, along with the reduced cellular CHO content in porcine liver organoids (P < 0.05). Using unbiased bioinformatic analysis of a previous ChIP-seq data and ChIP-qPCR validation, we revealed RORγ as the predominant transcription factor that responded to TRF, amongst the 12 targeted nuclear receptors (NRs) (P < 0.05). This was likely through RORγ direct binding to the MVK gene (encoding mevalonate kinase). Finally, we showed that RORγ agonists and overexpression enhanced the enrichment of co-factor p300, histone marks H3K27ac and H3K4me1/2, as well as RNA polymerase II (Pol-II) at the locus of MVK, in TRF-porcine liver organoids, compared to TRF-vector control (P < 0.05).

CONCLUSIONS

Our findings demonstrate that TRF triggers the RORγ-mediated chromatin remodeling at the locus of CHO biosynthesis genes in porcine liver organoids and further improves lipid metabolism.

Retinoic Acid Receptor-Related Receptor Alpha Ameliorates Autoimmune Arthritis via Inhibiting of Th17 Cells and Osteoclastogenesis

Rheumatoid arthritis (RA) is a chronic inflammatory polyarthritis characterized by progressive joint destruction. IL-17-producing CD4⁺ T (Th17) cells play pivotal roles in RA development and progression. Retinoic acid receptor-related orphan receptor alpha (RORα) is a negative regulator of inflammatory responses, whereas RORγt, another member of the ROR family, is a Th17 lineage-specific transcription factor. Here, we investigated the immunoregulatory potential of RORα in collagen-induced arthritis (CIA) mice, an experimental model of RA. Cholesterol sulfate (CS) or SR1078, a ligand of RORα, inhibited RORγt expression and Th17 differentiation in vitro. In addition, fortification of RORα in T cells inhibited the expression levels of glycolysis-associated genes. We found that RORα overexpression in CIA mice attenuated the clinical and histological severities of inflammatory arthritis. The anti-arthritic effect of RORα was associated with suppressed Th17 differentiation and attenuated mTOR-STAT3 signaling in T cells. Furthermore, altered RORα activity could directly affect osteoclastogenesis implicated in progressive bone destruction in human RA. Our findings defined a critical role of RORα in the pathogenesis of RA. These data suggest that RORα may have novel therapeutic uses in the treatment of RA.

Discovery and pharmacological evaluation of indole derivatives as potent and selective RORγt inverse agonist for multiple autoimmune conditions

Targeting nuclear receptor RORγ is recognized to be beneficial in multiple autoimmune disorders. We disclosed new indole analogues as potent RORγ inverse agonists. RO-2 as one of the potent and orally bioavailable compounds was evaluated in various models of autoimmune disorder. It showed potent suppression of downstream markers of RORγt activity in murine and human primary cells, ex vivo PD assay and in multiple animal models of autoimmune diseases. The results indicate the potential of these indole analogues as orally bioavailable small molecule inverse agonists of RORγt, efficacious in various Th17 driven models of autoimmune disorders.

Methylation status of the putative Pax6 promoter in olive ridley sea turtle embryos with eye defects: An initial approach

Normal development involves the interplay of genetic and epigenetic regulatory mechanisms. Pax6 is an eye-selector factor responsible for initiating the regulatory cascade for the development of the eyes. For the olive ridley sea turtle (Lepidochelys olivacea), a threatened species, eye malformations have been reported. In order to study the DNA methylation status of the putative promoter of the Pax6 gene in embryos with ocular malformations, an exploratory study was carried out in which DNA was isolated from embryos with anophthalmia, microphthalmia, and cyclopia, as well as from their normal counterparts. The 5'-flanking region from the Pax6 gene was isolated, showing two CpG islands (CGIs). The methylation status of CGIs in malformed embryos was compared with that of normal embryos by bisulfite sequencing. Putative transcription factor binding sites and regulatory features were identified. Methylation patterns were observed in both CpG and non-CpG contexts, and were unique for each malformed embryo; in the CpG context, an embryo with cyclopia showed a methylated cytosine upstream the CGI-1 not present in other embryos, an embryo with left anophthalmia presented two methylated cytosines in the CGI-1, whereas an embryo with left anophthalmia and right microphthalmia showed two methylated cytosines in the CGI-2. Normal embryos did not show methylated cytosines in the CGI-1, but one of them showed one methylcytosine in the CGI-2. Methylated transcription factor-binding sites may affect Pax6 expression associated to the cellular response to environmental compounds and hypoxia, signal transduction, cell cycle, lens physiology and development, as well as the transcription rate. Although preliminary, these results suggest that embryos with ocular malformations present unique DNA methylation patterns in the putative promoter of the Pax6 gene in L. olivacea, and probably those subtle, random changes in the methylation status can cause (at least in part) the aberrant phenotypes observed in these embryos.

Blood-based biomarkers predicting response to antidepressants

Major depressive disorder is a common, serious and in some cases, life-threatening condition and affects approximately 350 million people globally. Although there is effective treatment available for it, more than 50% of the patients fail to respond to the first antidepressant they receive. The selection of a distinct treatment is still exclusively based on clinical judgment without incorporating lab-derived objective measures. However, there is growing evidence of biomarkers that it helps to improve diagnostic processes and treatment algorithms. Here genetic markers and blood-based biomarkers of the monoamine pathways, inflammatory pathways and the hypothalamic-pituitary-adrenal (HPA) axis are reviewed. Promising findings arise from studies investigating inflammatory pathways and immune markers that may identify patients suitable for anti-inflammatory based treatment regimes. Next, an early normalization of a disturbed HPA axis or depleted neurotrophic factors may predict stable treatment response. Genetic markers within the serotonergic system may identify patients who are vulnerable because of stressful life events, but evidence for guiding treatment regimes still is inconsistent. Therefore, there is still a great need for studies investigating and validating biomarkers for the prediction of treatment response to facilitate the treatment selection and shorten the time to remission and thus provide personalized medicine in psychiatry.

Identification of novel quinazolinedione derivatives as RORγt inverse agonist

Novel small molecules were synthesized and evaluated as retinoic acid receptor-related orphan receptor-gamma t (RORγt) inverse agonists for the treatment of inflammatory and autoimmune diseases. A hit compound, 1, was discovered by high-throughput screening of our compound library. The structure-activity relationship (SAR) study of compound 1 showed that the introduction of a chlorine group at the 3-position of 4-cyanophenyl moiety increased the potency and a 3-methylpentane-1,5-diamide linker is favorable for the activity. The carbazole moiety of 1 was also optimized; a quinazolinedione derivative 18i suppressed the increase of IL-17A mRNA level in the lymph node of a rat model of experimental autoimmune encephalomyelitis (EAE) upon oral administration. These results indicate that the novel quinazolinedione derivatives have great potential as orally available small-molecule RORγt inverse agonists for the treatment of Th17-driven autoimmune diseases. A U-shaped bioactive conformation of this chemotype with RORγt protein was also observed.

A high-throughput, computational system to predict if environmental contaminants can bind to human nuclear receptors

Some pollutants can bind to nuclear receptors (NRs) and modulate their activities. Predicting interactions of NRs with chemicals is required by various jurisdictions because these molecular initiating events can result in adverse, apical outcomes, such as survival, growth or reproduction. The goal of this study was to develop a high-throughput, computational method to predict potential agonists of NRs, especially for contaminants in the environment or to which people or wildlife are expected to be exposed, including both persistent and pseudo-persistent chemicals. A 3D-structure database containing 39 human NRs was developed. The database was then combined with AutoDock Vina to develop a System for Predicting Potential Effective Nuclear Receptors (SPEN), based on inverse docking of chemicals. The SPEN was further validated and evaluated by experimental results for a subset of 10 chemicals. Finally, to assess the robustness of SPEN, its ability to predict potentials of 40 chemicals to bind to some of the most studied receptors was evaluated. SPEN is rapid, cost effective and powerful for predicting binding of chemicals to NRs. SPEN was determined to be useful for screening chemicals so that pollutants in the environment can be prioritized for regulators or when considering alternative compounds to replace known or suspected contaminants with poor environmental profiles.

The Functional Stability of FOXP3 and RORγt in Treg and Th17 and Their Therapeutic Applications

The balance of CD4⁺CD25⁺FOXP3⁺ regulatory T cells (Tregs) and effector T cells plays a key role in maintaining immune homeostasis, while the imbalance of them is related to many inflammatory diseases in both human and mice. Here we discuss about the plasticity of Tregs and Th17 cells, and the related human diseases resulted from the imbalance of them. Further, we will focus on the mechanisms regulating the plasticity between Tregs and Th17 cells and the potential therapeutic strategies by targeting regulators of the expression and activity of FOXP3 and RORγt or regulators of Treg/Th17 balance in autoimmune diseases, allergy, infection, and cancer.

T helper 17 cells may drive neuroprogression in major depressive disorder: Proposal of an integrative model

The exact pathophysiology of major depressive disorder (MDD) remains elusive. The monoamine theory, which hypothesizes that MDD emerges as a result of dysfunctional serotonergic, dopaminergic and noradrenergic pathways, has guided the therapy of this illness for several decades. More recently, the involvement of activated immune, oxidative and nitrosative stress pathways and of decreased levels of neurotrophic factors has provided emerging insights regarding the pathophysiology of MDD, leading to integrated theories emphasizing the complex interplay of these mechanisms that could lead to neuroprogression. In this review, we propose an integrative model suggesting that T helper 17 (Th17) cells play a pivotal role in the pathophysiology of MDD through (i) microglial activation, (ii) interactions with oxidative and nitrosative stress, (iii) increases of autoantibody production and the propensity for autoimmunity, (iv) disruption of the blood-brain barrier, and (v) dysregulation of the gut mucosa and microbiota. The clinical and research implications of this model are discussed.

Th17 master transcription factors RORα and RORγ regulate the expression of IL-17C, IL-17D and IL-17F in Cynoglossus semilaevis

The RAR-related orphan receptors (RORs) are members of the nuclear receptor family of intracellular transcription factors. In this study, we examined the regulatory properties of RORα (CsRORα) and RORγ (CsRORγ) in tongue sole (Cynoglossus semilaevis). CsRORα and CsRORγ expression was detected in major lymphoid organs and altered to significant extents after bacterial and viral infection. CsRORα enhanced the activities of CsIL-17C, CsIL-17D, and CsIL-17F promoters, which contain CsRORα and CsRORγ binding sites. CsRORγ also upregulated the promoter activities of CsIL-17D and CsIL-17F but not CsIL-17C. CsRORα and CsRORγ proteins were detected in the nucleus, and overexpression of CsRORα in tongue sole significantly increased the expression of CsIL-17C, CsIL-17D, and CsIL-17F, whereas overexpression of CsRORγ significantly increased the expression of CsIL-17C and CsIL-17F but no CsIL-17D. These results indicate that RORα and RORγ in teleost regulate the expression of IL-17 members in different manners.

Inhibition of RORγt activity and Th17 differentiation by a set of novel compounds

BACKGROUND

Retinoic acid receptor-related orphan receptor gamma t (RORγt) is the master regulator of Th17 cell differentiation, which plays a critical role in the pathology of several autoimmune diseases. By directing Th17 cells function, RORγt could be a potential target for drug development for Th17 related autoimmune disease.

METHODS

A Jurkat cell-based reporter assay system was used for screening RORγt inhibitors from a drug-like chemical library, following with mouse Th17 cells differentiation study to identify the effect of targeted compounds in primary T cells. 293T cell-based reporter assay was conducted to determine the cell specificity, and MTT assay was performed to determine the cell toxicity of those compounds.

RESULTS

In this study, we identified four lead compounds that suppressed RORγt activity, Th17 differentiation and IL-17A secretion. These candidates displayed inhibition ability on RORγt activity in T cell derived Jurkat cell, but not in 293 T cell, which indicated the restricted effects of these compounds to other cells or tissues. Futhermore, our results demonstrated that these candidates exhibited more robust inhibitory on IL-17 F transcription expression than IL-17A, which is different from one reported compound, SR1001, that mainly suppressed IL-17A, rather than IL-17 F production.

CONCLUSIONS

Our study discovered four novel compounds that inhibited RORγt activity and Th17 function, which indicates their potential in therapeutic application of Th17 related autoimmune disorders.

Retinoic acid-related orphan receptor RORβ, circadian rhythm abnormalities and tumorigenesis (Review)

Nuclear receptors are a superfamily of transcription factors including the steroid hormone receptors, non-steroid hormone receptors and the orphan nuclear receptor family. Retinoic acid-related orphan receptor (ROR)β, as a member of the orphan nuclear receptor family, plays an important regulatory role in the maintenance of a variety of physiological and pathological processes. RORβ has been determined to act as an osteogenic repressor in regulating bone formation, and is involved in regulating circadian rhythm. The findings of recent studies concerning the association between tumorigenesis and circadian rhythm have shown that an aberrant circadian rhythm may promote tumorigenesis and tumor progression. The mechanisms discussed in this review demonstrate how aberrant RORβ-induced circadian rhythm may become a new direction for future studies on tumorigenesis and strategy design for cancer prevention.

RNA expression profiling in depressed patients suggests retinoid-related orphan receptor alpha as a biomarker for antidepressant response

Response to antidepressant treatment is highly variable with some patients responding within a few weeks, whereas others have to wait for months until the onset of clinical effects. Gene expression profiling may be a tool to identify markers of antidepressant treatment response and new potential drug targets. In a first step, we selected 12 male, age- and severity-matched pairs of remitters and nonresponders, and analyzed expression profiles in peripheral blood at admission and after 2 and 5 weeks of treatment using Illumina expression arrays. We identified 127 transcripts significantly associated with treatment response with a minimal P-value of 9.41 × 10(-)(4) (false discovery rate-corrected). Analysis of selected transcripts in an independent replication sample of 142 depressed inpatients confirmed that lower expression of retinoid-related orphan receptor alpha (RORa, P=6.23 × 10(-4)), germinal center expressed transcript 2 (GCET2, P=2.08 × 10(-2)) and chitinase 3-like protein 2 (CHI3L2, P=4.45 × 10(-2)) on admission were associated with beneficial treatment response. In addition, leukocyte-specific protein 1 (LSP1) significantly decreased after 5 weeks of treatment in responders (P=2.91 × 10(-2)). Additional genetic, in vivo stress responsitivity data and murine gene expression findings corroborate our finding of RORa as a transcriptional marker of antidepressant response. In summary, using a genome-wide transcriptomics approach and subsequent validation studies, we identified several transcripts including the circadian gene transcript RORa that may serve as biomarkers indicating antidepressant treatment response.

Endometrial gene expression profiling in pregnant Meishan and Yorkshire pigs on day 12 of gestation

Background

Litter size in pigs is a major factor affecting the profitability in the pig industry. The peri-implantation window in pigs is characterized by the coordinated interactions between the maternal uterine endometrium and the rapidly elongating conceptuses and represents a period of time during which a large percentage of the developing conceptuses are lost. However, the gene expression and regulatory networks in the endometrium contributing to the establishment of the maternal: placental interface remain poorly understood.

Results

We characterized the endometrial gene expression profile during the peri-implantation stage of development by comparing two breeds that demonstrate very different reproductive efficiencies. We employed the porcine Affymetrix GeneChip® to assay the transcriptomic profiles of genes expressed in the uterine endometrium obtained from Meishan and Yorkshire gilts (n = 4 for each breed) on day 12 of gestation (M12 and Y12, respectively). Total of 17,076 probesets were identified as "present" in at least two arrays. A mixed model-based statistical analysis predicted a total of 2,656 (q < 0.1) transcripts as differentially expressed between Meishan and Yorkshire pigs. Eighteen differentially expressed transcripts of interest were validated by quantitative real-time PCR. Gene ontology (GO) annotation revealed that the known functions of the differentially expressed genes were involved in a series of important biological processes relevant to early pregnancy establishment in the pig.

Conclusions

The results identified endometrial gene expression profiles of two breeds differing in litter size and identified candidate genes that are related to known physiological pathways related to reproductive prolificacy. These findings provide a deeper understanding of molecular pathways differing between two breeds at the critical peri-implantation stage of pregnancy, which can be utilized to better understand the events contributing to pregnancy establishment in the pig.

Retinoic acid-related orphan receptors α and γ: key regulators of lipid/glucose metabolism, inflammation, and insulin sensitivity

Retinoic acid-related orphan receptors RORα and RORγ play a regulatory role in lipid/glucose homeostasis and various immune functions, and have been implicated in metabolic syndrome and several inflammatory diseases. RORα-deficient mice are protected against age- and diet-induced obesity, hepatosteatosis, and insulin resistance. The resistance to hepatosteatosis in RORα-deficient mice is related to the reduced expression of several genes regulating lipid synthesis, transport, and storage. Adipose tissue-associated inflammation, which plays a critical role in the development of insulin resistance, is considerably diminished in RORα-deficient mice as indicated by the reduced infiltration of M1 macrophages and decreased expression of many proinflammatory genes. Deficiency in RORγ also protects against diet-induced insulin resistance by a mechanism that appears different from that in RORα deficiency. Recent studies indicated that RORs provide an important link between the circadian clock machinery and its regulation of metabolic genes and metabolic syndrome. As ligand-dependent transcription factors, RORs may provide novel therapeutic targets in the management of obesity and associated metabolic diseases, including hepatosteatosis, adipose tissue-associated inflammation, and insulin resistance.

Altered expression of NFY-C and RORA in colorectal adenocarcinomas

NFY-C, a subunit of the transcription factor NFY, binds to the promoters of several eukaryotic genes, including cell cycle-related genes. RORA is a steroid hormone receptor implicated in a range of important cellular processes. We evaluated the expression of NFY-C and RORA in colorectal adenocarcinomas and normal colonic tissue. NFY-C expression was elevated in adenocarcinomas. Moreover, NFY-C mRNA levels correlated with time to disease progression, while NFY-C protein expression was significantly higher in metastatic disease. RORA expression was downregulated in CRC adenocarcinomas compared to normal controls and correlated with time to disease progression. The role of NFY-C and RORA in CRC merits further investigation.

N-methylthioureas as new agonists of retinoic acid receptor-related orphan receptor

Thirty two thiourea derivatives were prepared and their agonistic activities on the retinoic acid receptor-related orphan receptor α (RORα) were evaluated. The replacement of the 3-allyl-2-imino-thiazolidin-4-one moiety of the lead compound CGP52608 (1) with various functional group substituted aromatic rings, improved the agonistic activity of RORα. Among the prepared derivatives, 1-methyl-3-(4-phenoxy-benzyl)-thiourea (32) showed 2.6-fold higher agonistic activity than CGP52608 in the RORα-activation assay.

Melatonin, the circadian multioscillator system and health: the need for detailed analyses of peripheral melatonin signaling

Evidence is accumulating regarding the importance of circadian core oscillators, several associated factors, and melatonin signaling in the maintenance of health. Dysfunction of endogenous clocks, melatonin receptor polymorphisms, age- and disease-associated declines of melatonin likely contribute to numerous diseases including cancer, metabolic syndrome, diabetes type 2, hypertension, and several mood and cognitive disorders. Consequences of gene silencing, overexpression, gene polymorphisms, and deviant expression levels in diseases are summarized. The circadian system is a complex network of central and peripheral oscillators, some of them being relatively independent of the pacemaker, the suprachiasmatic nucleus. Actions of melatonin on peripheral oscillators are poorly understood. Various lines of evidence indicate that these clocks are also influenced or phase-reset by melatonin. This includes phase differences of core oscillator gene expression under impaired melatonin signaling, effects of melatonin and melatonin receptor knockouts on oscillator mRNAs or proteins. Cross-connections between melatonin signaling pathways and oscillator proteins, including associated factors, are discussed in this review. The high complexity of the multioscillator system comprises alternate or parallel oscillators based on orthologs and paralogs of the core components and a high number of associated factors with varying tissue-specific importance, which offers numerous possibilities for interactions with melatonin. It is an aim of this review to stimulate research on melatonin signaling in peripheral tissues. This should not be restricted to primary signal molecules but rather include various secondarily connected pathways and discriminate between direct effects of the pineal indoleamine at the target organ and others mediated by modulation of oscillators.

The distribution of immunomodulatory cells in the lungs of patients with idiopathic pulmonary fibrosis

We have characterized the immune system involvement in the disease processes of idiopathic pulmonary fibrosis in novel ways. To do so, we analyzed lung tissue from 21 cases of idiopathic pulmonary fibrosis and 21 (non-fibrotic, non-cancerous) controls for immune cell and inflammation-related markers. The immunohistochemical analysis of the tissue was grouped by patterns of severity in disease pathology. There were significantly greater numbers of CD68(+) and CD80(+) cells and significantly fewer CD3(+), CD4(+), and CD45RO(+) cells in areas of relatively (histologically) normal lung in biopsy samples from idiopathic pulmonary fibrosis patients compared with controls. In zones of active disease, characterized by epithelial cell regeneration and fibrosis, there were significantly more cells expressing CD4, CD8, CD20, CD68, CD80, chemokine receptor 6 (CCR6), S100, IL-17, tumor necrosis factor-α, and retinoic acid-related orphan receptors compared with histologically normal lung areas from idiopathic pulmonary fibrosis patients. Inflammation was implicated in these active regions by the cells that expressed retinoid orphan receptor-α, -β, and -γ, CCR6, and IL-17. The regenerating epithelial cells predominantly expressed these pro-inflammatory molecules, as evidenced by co-expression analyses with epithelial cytokeratins. Macrophages in pseudo-alveoli and CD3(+) T cells in the fibrotic interstitium also expressed IL-17. Co-expression of IL-17 with retinoid orphan receptors and epithelial cytoskeletal proteins, CD68, and CD3 in epithelial cells, macrophages, and T-cells, respectively, confirmed the production of IL-17 by these cell types. There was little staining for forkhead box p3, CD56, or CD34 in any idiopathic pulmonary fibrosis lung regions. The fibrotic regions had fewer immune cells overall. In summary, our study shows participation of innate and adaptive mononuclear cells in active-disease regions of idiopathic pulmonary fibrosis lung, where the regenerating epithelial cells appear to propagate inflammation. The regenerative mechanisms become skewed to ultimately result in lethal, fibrotic restriction of lung function.

Genetic controls of Th17 cell differentiation and plasticity

CD4+ T lymphocytes play a major role in regulation of adaptive immunity. Upon activation, naïve T cells differentiate into different functional subsets. In addition to the classical Th1 and Th2 cells, several novel effector T cell subsets have been recently identified, including Th17 cells. There has been rapid progress in characterizing the development and function of Th17 cells. Here I summarize and discuss on the genetic controls of their differentiation and emerging evidence on their plasticity. This information may benefit understanding and treating immune diseases.

Prospective study of common variants in the retinoic acid receptor-related orphan receptor α gene and risk of neovascular age-related macular degeneration

OBJECTIVES

The retinoic acid receptor (RAR)-related orphan receptor α gene (RORA) is implicated as a candidate for age-related macular degeneration (AMD) through a previous microarray expression study, linkage data, biological plausibility, and 2 clinic-based cross-sectional studies. We aimed to determine if common variants in RORA predict future risk of neovascular AMD.

METHODS

We measured genotypes for 18 variants in intron 1 of the RORA gene among 164 cases who developed neovascular AMD and 485 age- and sex-matched controls in a prospective, nested, case-control study within the Nurses' Health Study and the Health Professionals Follow-up Study. We determined the incidence rate ratios and 95% confidence intervals (CI) for neovascular AMD for each variant and examined interactions with other AMD-associated variants and modifiable risk factors.

RESULTS

We identified one single-nucleotide polymorphism (rs12900948) that was significantly associated with increased incidence of neovascular AMD. Participants with 1 and 2 copies of the G allele were 1.73 (CI, 1.32-2.27) and 2.99 (CI, 1.74-5.14) times more likely to develop neovascular AMD. Individuals homozygous for both the G allele of rs12900948 and ARMS2 A69S had a 40.8-fold increased risk of neovascular AMD (CI, 10.1-164; P = .017). Cigarette smokers who carried 2 copies of the G allele had a 9.89-fold risk of neovascular AMD but the interaction was not significant (P = .08). We identified a significant AMD-associated haplotype block containing the single-nucleotide polymorphisms rs730754, rs8034864, and rs12900948, with P values for ACA = 1.16 × 10(-9), ACG = 5.85 × 10(-12), and GAA = .0001 when compared with all other haplotypes.

CONCLUSIONS

Common variants and haplotypes within the RORA gene appear to act synergistically with the ARMS2 A69S polymorphism to increase risk of neovascular AMD. These data add further evidence of a high level of complexity linking genetic and modifiable risk factors to AMD development and should help efforts at risk prediction.

Orphan nuclear receptors in breast cancer pathogenesis and therapeutic response

Nuclear receptors comprise a large family of highly conserved transcription factors that regulate many key processes in normal and neoplastic tissues. Most nuclear receptors share a common, highly conserved domain structure that includes a carboxy-terminal ligand-binding domain. However, a subgroup of this gene family is known as the orphan nuclear receptors because to date there are no known natural ligands that regulate their activity. Many of the 25 nuclear receptors classified as orphan play critical roles in embryonic development, metabolism, and the regulation of circadian rhythm. Here, we review the emerging role(s) of orphan nuclear receptors in breast cancer, with a particular focus on two of the estrogen-related receptors (ERRalpha and ERRgamma) and several others implicated in clinical outcome and response or resistance to cytotoxic or endocrine therapies, including the chicken ovalbumin upstream promoter transcription factors, nerve growth factor-induced B, DAX-1, liver receptor homolog-1, and retinoic acid-related orphan receptor alpha. We also propose that a clearer understanding of the function of orphan nuclear receptors in mammary gland development and normal mammary tissues could significantly improve our ability to diagnose, treat, and prevent breast cancer.

Orphan nuclear receptors as targets for drug development

Orphan nuclear receptors regulate diverse biological processes. These important molecules are ligand-activated transcription factors that act as natural sensors for a wide range of steroid hormones and xenobiotic ligands. Because of their importance in regulating various novel signaling pathways, recent research has focused on identifying xenobiotics targeting these receptors for the treatment of multiple human diseases. In this review, we will highlight these receptors in several physiologic and pathophysiologic actions and demonstrate how their functions can be exploited for the successful development of newer drugs.

The Drosophila nuclear receptors DHR3 and betaFTZ-F1 control overlapping developmental responses in late embryos

Studies of the onset of metamorphosis have identified an ecdysone-triggered transcriptional cascade that consists of the sequential expression of the transcription-factor-encoding genes DHR3, betaFTZ-F1, E74A and E75A. Although the regulatory interactions between these genes have been well characterized by genetic and molecular studies over the past 20 years, their developmental functions have remained more poorly understood. In addition, a transcriptional sequence similar to that observed in prepupae is repeated before each developmental transition in the life cycle, including mid-embryogenesis and the larval molts. Whether the regulatory interactions between DHR3, betaFTZ-F1, E74A and E75A at these earlier stages are similar to those defined at the onset of metamorphosis, however, is unknown. In this study, we turn to embryonic development to address these two issues. We show that mid-embryonic expression of DHR3 and betaFTZ-F1 is part of a 20-hydroxyecdysone (20E)-triggered transcriptional cascade similar to that seen in mid-prepupae, directing maximal expression of E74A and E75A during late embryogenesis. In addition, DHR3 and betaFTZ-F1 exert overlapping developmental functions at the end of embryogenesis. Both genes are required for tracheal air filling, whereas DHR3 is required for ventral nerve cord condensation and betaFTZ-F1 is required for proper maturation of the cuticular denticles. Rescue experiments support these observations, indicating that DHR3 has essential functions independent from those of betaFTZ-F1. DHR3 and betaFTZ-F1 also contribute to overlapping transcriptional responses during embryogenesis. Taken together, these studies define the lethal phenotypes of DHR3 and betaFTZ-F1 mutants, and provide evidence for functional bifurcation in the 20E-responsive transcriptional cascade.

The roles of testicular orphan nuclear receptor 4 (TR4) in cerebellar development

Since Testicular Receptor 4 (TR4) was cloned, efforts have been made to elucidate its physiological function. To examine the putative functions of TR4, the conventional TR4 knockout (TR4(-/-)) mouse model was generated. Throughout postnatal and adult stages, TR4(-/-) mice exhibited behavioral deficits in motor coordination, suggesting impaired cerebellar function. Histological examination of the postnatal and adult TR4(-/-) cerebellum revealed gross abnormalities in foliation. Further analyses demonstrated changes in the lamination of the TR4(-/-) cerebellar cortex, including reduction in the thickness of both the molecular layer (ML) and the internal granule layer (IGL). Analyses of the developing TR4(-/-) cerebellum indicate that the lamination irregularities observed may result from disrupted granule cell proliferation within the external granule cell layer (EGL), delayed inward migration of post-mitotic granule cells, and increased apoptosis during cerebellar development. In addition, abnormal development of Purkinje cells was observed in the postnatal TR4(-/-) cerebellum, as indicated by aberrant dendritic arborization. In postnatal, neuronal-specific TR4 knockout mice, architectural changes in the cerebellum were similar to those seen in TR4(-/-) animals, suggesting that TR4 function in neuronal lineages might be important for cerebellar morphogenesis, and that the effect on Purkinje cell development is likely mediated by changes elsewhere, such as in granule cells, or is highly dependent on developmental stage. Together, our findings from various TR4 knockout mouse models suggest that TR4 is required for normal cerebellar development and that failure to establish proper cytoarchitecture results in dysfunction of the cerebellum and leads to abnormal behavior.

Mouse Th17 cells: current understanding of their generation and regulation

IL-17-expressing CD4(+) T cells have been recently recognized as a new subset of Th cells, namely Th17 cells. Considerable progress has been made in understanding the developmental regulation of mouse Th17 cells. Here, I summarize this knowledge and discuss on the relationship of Th17 with regulatory and follicular Th cells.

Retinoid-related orphan receptors (RORs): critical roles in development, immunity, circadian rhythm, and cellular metabolism

The last few years have witnessed a rapid increase in our knowledge of the retinoid-related orphan receptors RORα, -β, and -γ (NR1F1-3), their mechanism of action, physiological functions, and their potential role in several pathologies. The characterization of ROR-deficient mice and gene expression profiling in particular have provided great insights into the critical functions of RORs in the regulation of a variety of physiological processes. These studies revealed that RORα plays a critical role in the development of the cerebellum, that both RORα and RORβ are required for the maturation of photoreceptors in the retina, and that RORγ is essential for the development of several secondary lymphoid tissues, including lymph nodes. RORs have been further implicated in the regulation of various metabolic pathways, energy homeostasis, and thymopoiesis. Recent studies identified a critical role for RORγ in lineage specification of uncommitted CD4⁺ T helper cells into Th17 cells. In addition, RORs regulate the expression of several components of the circadian clock and may play a role in integrating the circadian clock and the rhythmic pattern of expression of downstream (metabolic) genes. Study of ROR target genes has provided insights into the mechanisms by which RORs control these processes. Moreover, several reports have presented evidence for a potential role of RORs in several pathologies, including osteoporosis, several autoimmune diseases, asthma, cancer, and obesity, and raised the possibility that RORs may serve as potential targets for chemotherapeutic intervention. This prospect was strengthened by recent evidence showing that RORs can function as ligand-dependent transcription factors.

A role for nuclear receptors in mammalian hibernation

Hibernation is one of the most dramatic examples of phenotypic plasticity in mammals. During periods of food shortage and/or reduced ambient temperatures hibernating mammals become heterothermic, allowing their body temperature to decrease while entering an energy-conserving torpid state. In order to survive the multi-month hibernation season many species engage in hyperphagy, dramatically increasing adipose stores prior to the onset of hibernation. Nuclear receptors are a superfamily of transcription factors many of which bind lipophilic molecules as ligands. They regulate a variety of processes including energy homeostasis, carbohydrate and lipid metabolism, inflammation and circadian rhythm. Given that lipids are integral in the hibernation phenotype they may play important regulatory roles through their interactions with nuclear receptors. Here we review current knowledge and suggest possible roles in mammalian hibernation for peroxisome proliferator-activated receptors (PPARs), farnesoid X receptors (FXRs), liver X receptors (LXRs), retinoid-related orphan receptors (RORs) and Rev-ERBs.

Regulation and function of proinflammatory TH17 cells

Naïve CD4(+) helper T (TH) cells, upon activation by antigen-presenting cells (APC), differentiate into different types of effector cells that are characterized by their distinct cytokine production profiles and immune regulatory functions. In addition to TH1 and TH2 cells, a third subset of effector TH cells has recently been described and termed TH17. Since their identification, TH17 cells have emerged as crucial players in infectious, inflammatory, and autoimmune diseases, and cancer. In this review, we summarize the latest discoveries on the cytokine-mediated regulation and transcriptional programming of TH17 cells and their roles in different immune responses and diseases.

Transcriptional activation of HIF-1 by RORalpha and its role in hypoxia signaling

OBJECTIVE

Hypoxia-inducible factor 1alpha (HIF-1alpha) is primarily involved in the adapting of cells to changes in oxygen levels, which is essential for normal vascular function. Recently, physiological roles for retinoic acid-related orphan receptor alpha (RORalpha) have been implicated in cardiovascular diseases such as atherosclerosis. In this study, we have investigated the potential roles of RORalpha in the hypoxia signaling pathway in connection with activation of HIF-1alpha.

METHODS AND RESULTS

Under hypoxic conditions, expression of RORalpha was induced. When RORalpha was introduced exogenously, protein level as well as transcriptional activity of HIF-1alpha was enhanced. Putative ligands of RORalpha, such as melatonin and cholesterol sulfate, induced transcriptional activity for HIF-1alpha, which was abolished by RNA interference against RORalpha. RORalpha was physically associated with HIF-1alpha through DNA binding domain, which was required to the RORalpha-induced stabilization and transcriptional activation of HIF-1alpha. Finally, either infection with adenovirus encoding RORalpha or treatment with ROR ligands enhanced the formation of capillary tubes by human umbilical vascular endothelial cells.

CONCLUSIONS

Our results provide a new insight for the function of RORalpha in amplification of hypoxia signaling and suggest a potential application of RORalpha ligands for the therapy of hypoxia-associated vascular diseases.

TH17 cells in development: an updated view of their molecular identity and genetic programming

Following activation, CD4+ T cells differentiate into different lineages of helper T (T(H)) cells that are characterized by distinct developmental regulation and biological functions. T(H)17 cells have recently been identified as a new lineage of effector T(H) cells, and they have been shown to be important in immune responses to infectious agents, as well as in various immune diseases. Over the past two to three years, there has been a rapid progress in our understanding of the differentiation programme of T(H)17 cells. Here, I summarize our current knowledge of the unique gene expression, cytokine-mediated regulation and transcriptional programming of T(H)17 cells, and provide my personal perspectives on the future studies that are required to elucidate this lineage in more detail.

T helper 17 lineage differentiation is programmed by orphan nuclear receptors ROR alpha and ROR gamma

T cell functional differentiation is mediated by lineage-specific transcription factors. T helper 17 (Th17) has been recently identified as a distinct Th lineage mediating tissue inflammation. Retinoic acid receptor-related orphan receptor gamma (ROR gamma) was shown to regulate Th17 differentiation; ROR gamma deficiency, however, did not completely abolish Th17 cytokine expression. Here, we report Th17 cells highly expressed another related nuclear receptor, ROR alpha, induced by transforming growth factor-beta and interleukin-6 (IL-6), which is dependent on signal transducer and activator of transcription 3. Overexpression of ROR alpha promoted Th17 differentiation, possibly through the conserved noncoding sequence 2 in Il17-Il17f locus. ROR alpha deficiency resulted in reduced IL-17 expression in vitro and in vivo. Furthermore, ROR alpha and ROR gamma coexpression synergistically led to greater Th17 differentiation. Double deficiencies in ROR alpha and ROR gamma globally impaired Th17 generation and completely protected mice against experimental autoimmune encephalomyelitis. Therefore, Th17 differentiation is directed by two lineage-specific nuclear receptors, ROR alpha and ROR gamma.

Chronobiology in the endocrine system

Biological signaling occurs in a complex web with participation and interaction of the central nervous system, the autonomous nervous system, the endocrine glands, peripheral endocrine tissues including the intestinal tract and adipose tissue, and the immune system. All of these show an intricate time structure with rhythms and pulsatile variations in multiple frequencies. Circadian (about 24-hour) and circannual (about 1-year) rhythms are kept in step with the cyclic environmental surrounding by the timing and length of the daily light span. Rhythmicity of many endocrine variables is essential for their efficacy and, even in some instances, for the qualitative nature of their effects. Indeed, the continuous administration of certain hormones and their synthetic analogues may show substantially different effects than expected. In the design of drug-delivery systems and treatment schedules involving directly or indirectly the endocrine system, consideration of the human time organization is essential. A large amount of information on the endocrine time structure has accumulated, some of which is discussed in this review.

Gene expression profiling reveals a regulatory role for ROR alpha and ROR gamma in phase I and phase II metabolism

Retinoid-related orphan receptors alpha (ROR alpha) and gamma (ROR gamma) are both expressed in liver; however, their physiological functions in this tissue have not yet been clearly defined. The ROR alpha1 and ROR gamma 1 isoforms, but not ROR alpha 4, show an oscillatory pattern of expression during circadian rhythm. To obtain insight into the physiological functions of ROR receptors in liver, we analyzed the gene expression profiles of livers from WT, ROR alpha-deficient staggerer (sg) mice (ROR alpha(sg/sg)), ROR gamma(-/-), and ROR alpha(sg/sg)ROR gamma(-/-) double knockout (DKO) mice by microarray analysis. DKO mice were generated to study functional redundancy between ROR alpha and ROR gamma. These analyses demonstrated that ROR alpha and ROR gamma affect the expression of a number of genes. ROR alpha and ROR gamma are particularly important in the regulation of genes encoding several phase I and phase II metabolic enzymes, including several 3beta-hydroxysteroid dehydrogenases, cytochrome P450 enzymes, and sulfotransferases. In addition, our results indicate that ROR alpha and ROR gamma each affect the expression of a specific set of genes but also exhibit functional redundancy. Our study shows that ROR alpha and ROR gamma receptors influence the regulation of several metabolic pathways, including those involved in the metabolism of steroids, bile acids, and xenobiotics, suggesting that RORs are important in the control of metabolic homeostasis.

Retinoid-related orphan receptor gamma t is a potential therapeutic target for controlling inflammatory autoimmunity

Retinoid-related orphan receptor gamma t (RORgamma t) is a member of the nuclear receptor family that is specifically expressed in T cell compartments. RORgamma t regulates the development of T cells in the thymus and the differentiation of effector T cells in the periphery. During T cell development, RORgamma t enhances CD4(+)CD8(+) double positive thymocyte survival by upregulating Bcl-x(L). In the periphery, RORgamma t regulates IL-17 production and dictates the differentiation of pro-inflammatory T helper 17 (T(H)17) cells that play a critical role in inflammatory conditions and autoimmunity. RORgamma t-deficient T cells fail to differentiate into T(H)17 cells, whereas forced expression of RORgamma t is sufficient to induce naive T cells to produce IL-17. T(H)17 cells are believed to be the major inflammatory cells in autoimmune diseases. Therefore, inhibition of RORgamma t activity could potentially alleviate the symptoms associated with the T(H)17-dependent inflammatory autoimmune diseases. RORgamma t is thus potentially an excellent therapeutic target for the intervention of inflammatory autoimmunity.

Functional analysis of cholesterol biosynthesis by RNA interference

Inborn errors of cholesterol biosynthesis caused by dysfunctionality of single enzymes are known to cause severe malformation syndromes like X-linked chondrodysplasia punctata (CDPX2), CHILD syndrome or Smith-Lemli-Opitz-syndrome (SLOS). In this study we established the method of RNA interference (RNAi) for analyzing the molecular mechanisms underlying disrupted cholesterol biosynthesis. For different genes involved in the cholesterol biosynthesis pathway-NAD(P) dependent steroid dehydrogenase-like (NSDHL), 17-beta hydroxysteroid dehydrogenase type 7 (HSD17B7) and emopamil binding protein (EBP)-shRNA sequences were designed and tested for their effectiveness. For a better comparability of the experiments and to avoid different transfection efficiencies, examined shRNA sequences which reached a knock down of at least 80% were stably transfected in a HeLa cell line with a tetracycline-regulated expression (HeLa T-REx). These stable transfected cell lines represent novel tools for the analysis of cholesterol biosynthesis.

Retinoid-related orphan receptor gamma controls immunoglobulin production and Th1/Th2 cytokine balance in the adaptive immune response to allergen

The retinoid-related orphan receptors (ROR) comprise a distinct subfamily of nuclear receptors with the capacity to act as both repressors and activators of transcription. RORgamma, the most recently identified member of the ROR family, has been shown to be important for the development of normal lymphocyte compartments as well as organogenesis of some lymphoid organs. In this report, we examine the capacity of RORgamma-deficient mice to develop an adaptive immune response to Ag using OVA-induced inflammation in mice as a model for allergic airway disease. In sham-treated mice lacking RORgamma, low-grade pulmonary inflammation was observed and characterized by the perivascular accumulation of B and T lymphocytes, increased numbers of inflammatory cells in the lung lavage fluid, and polyclonal Ig activation. Following sensitization and challenge, the capacity of these animals to develop the allergic phenotype was severely impaired as evidenced by attenuated eosinophilic pulmonary inflammation, reduced numbers of CD4+ lymphocytes, and lower Th2 cytokines/chemokine protein and mRNA expression in the lungs. IFN-gamma and IL-10 production was markedly greater in splenocytes from RORgamma-deficient mice following in vitro restimulation with OVA compared with wild-type splenocytes, and a shift toward a Th1 immune response was observed in sensitized/challenged RORgamma-deficient animals in vivo. These data reveal a critical role for RORgamma in the regulation of Ig production and Th1/Th2 balance in adaptive immunity.

The zebrafish retinoid-related orphan receptor (ror) gene family

The retinoid-related orphan receptors Rora, b and c are highly conserved transcription factors belonging to the steroid hormone receptor superfamily. Mammalian ROR proteins perform key regulatory roles in a number of processes during embryonic development and in the adult including neurogenesis, bone metabolism and modulation of circadian rhythms. A more recent area of interest has been their roles in the development and function of the immune system. In particular, RORA has been implicated in the regulation of inflammatory cytokine production, and RORC has been shown to be essential in the development of the T lymphocyte repertoire and of secondary lymphoid organs. We cloned the zebrafish orthologs for the Ror gene family. Assignment of orthologies was supported by analysis of the phylogenetic relationships between zebrafish and other vertebrate Ror genes based on sequence similarities, and conserved syntenies with the human Ror gene loci.

Melatonin and type 2 diabetes - a possible link?

The aim of the present study was to determine the existence of melatonin membrane receptors and to examine the mRNA expression of nuclear orphan receptors in human pancreatic tissue, in an effort to explain differences between type 2 diabetic and metabolically healthy patients. Molecular and immunocytochemical investigations established the presence of the melatonin membrane receptors MT1 and MT2 in human pancreatic tissue and, notably, also in the islets of Langerhans. Results of a calculation model to determine mRNA expression ratios, as well as subjective analysis of immunoreactions, showed elevated MT1 receptor expression in comparison with MT2 expression. mRNA transcript levels of melatonin receptors appeared to be significantly higher in type 2 diabetic patients than in a control group. An upregulation of receptor expression in type 2 diabetic patients was also observed in immunocytochemical investigations. In addition, transcripts of the nuclear orphan receptors RORalpha, RZRbeta, RORgamma and RevErbalpha were detected in human pancreatic tissue and islets. In correlation with membrane melatonin receptors, data indicate increased mRNA expression levels of RORalpha, RZRbeta, and RORgamma in type 2 diabetic patients. Thus, our data demonstrate the existence of the melatonin membrane receptors MT1 and MT2 as well as mRNA expression of nuclear orphan receptors in human pancreatic tissue, with upregulated expression levels in type 2 diabetic patients.

International Union of Pharmacology. LXVI. Orphan nuclear receptors

Half of the members of the nuclear receptors superfamily are so-called "orphan" receptors because the identity of their ligand, if any, is unknown. Because of their important biological roles, the study of orphan receptors has attracted much attention recently and has resulted in rapid advances that have helped in the discovery of novel signaling pathways. In this review we present the main features of orphan receptors, discuss the structure of their ligand-binding domains and their biological functions. The paradoxical existence of a pharmacology of orphan receptors, a rapidly growing and innovative field, is highlighted.

The orphan nuclear receptor RORgammat directs the differentiation program of proinflammatory IL-17+ T helper cells

IL-17-producing T lymphocytes have been recently shown to comprise a distinct lineage of proinflammatory T helper cells, termed Th17 cells, that are major contributors to autoimmune disease. We show here that the orphan nuclear receptor RORgammat is the key transcription factor that orchestrates the differentiation of this effector cell lineage. RORgammat induces transcription of the genes encoding IL-17 and the related cytokine IL-17F in naïve CD4(+) T helper cells and is required for their expression in response to IL-6 and TGF-beta, the cytokines known to induce IL-17. Th17 cells are constitutively present throughout the intestinal lamina propria, express RORgammat, and are absent in mice deficient for RORgammat or IL-6. Mice with RORgammat-deficient T cells have attenuated autoimmune disease and lack tissue-infiltrating Th17 cells. Together, these studies suggest that RORgammat is a key regulator of immune homeostasis and highlight its potential as a therapeutic target in inflammatory diseases.

Modulatory role for retinoid-related orphan receptor alpha in allergen-induced lung inflammation

RATIONALE

Nuclear receptors play a critical role in the regulation of inflammation, thus representing attractive targets for the treatment of asthma.

OBJECTIVE

In this study, we assess the potential regulatory function of retinoid-related orphan receptor alpha (RORalpha) in the adaptive immune response using ovalbumin (OVA)-induced airway inflammation as a model.

METHODS

Allergen-induced inflammation was compared between wild-type (WT) and staggerer (RORalpha(sg/sg)) mice, a natural mutant strain that is deficient in RORalpha expression.

MEASUREMENTS AND MAIN RESULTS

Despite robust increases in OVA-specific IgE, RORalpha(sg/sg) mice developed significantly less pulmonary inflammation, mucous cell hyperplasia, and eosinophilia compared with similarly treated WT animals. Induction of Th2 cytokines, including interleukin (IL)-4, IL-5, and IL-13, was also significantly less in RORalpha(sg/sg) mice. Microarray analysis using lung RNA showed increased expression of many genes, previously implicated in inflammation, in OVA-treated WT mice. These include mucin Muc5b, the chloride channel calcium-activated 3 (Clca3), macrophage inflammatory protein (MIP) 1alpha and 1beta, eotaxin-2, serum amyloid A3 (Saa3), and insulin-like growth factor 1 (Igf1). These genes were induced to a greater extent in OVA-treated WT mice relative to RORalpha(sg/sg) mice.

CONCLUSIONS

Our study demonstrates that mice deficient in RORalpha exhibit an attenuated allergic inflammatory response, indicating that RORalpha plays a critical role in the development of Th2-driven allergic lung inflammation in mice, and suggests that this nuclear receptor should be further evaluated as a potential asthma target.