Lymphocyte development and function in the absence of retinoic acid-related orphan receptor alpha

Regulation of RORα Stability through PRMT5-Dependent Symmetric Dimethylation

Retinoic acid receptor-related orphan receptor alpha (RORα), a candidate tumor suppressor, is prevalently downregulated or lost in malignant breast cancer cells. However, the mechanisms of how RORα expression is regulated in breast epithelial cells remain incompletely understood. Protein arginine N-methyltransferase 5 (PRMT5), a type II methyltransferase catalyzing the symmetric methylation of the amino acid arginine in target proteins, was reported to regulate protein stability. To study whether and how PRMT5 regulates RORα, we examined the direct interaction between RORα and PRMT5 by immunoprecipitation and GST pull-down assays. The results showed that PRMT5 directly bound to RORα, and PRMT5 mainly symmetrically dimethylated the DNA-binding domain (DBD) but not the ligand-binding domain (LBD) of RORα. To investigate whether RORα protein stability is regulated by PRMT5, we transfected HEK293FT cells with RORα and PRMT5-expressing or PRMT5-silencing (shPRMT5) vectors and then examined RORα protein stability by a cycloheximide chase assay. The results showed that PRMT5 increased RORα protein stability, while silencing PRMT5 accelerated RORα protein degradation. In PRMT5-silenced mammary epithelial cells, RORα protein expression was decreased, accompanied by an enhanced epithelial-mesenchymal transition morphology and cell invasion and migration abilities. In PRMT5-overexpressed mammary epithelial cells, RORα protein was accumulated, and cell invasion was suppressed. These findings revealed a novel mechanism by which PRMT5 regulates RORα protein stability.

Agonists, inverse agonists, and antagonists as therapeutic approaches to manipulate retinoic acid-related orphan receptors

Retinoic acid-related orphan receptors (RORs) serve as transcription factors that play a pivotal role in a myriad of physiological processes within the body. Their involvement extends to critical biological processes that confer protective effects in the heart, immune system, and nervous system, as well as contributing to the mitigation of several aggressive cancer types. These protective functions are attributed to ROR's regulation of key proteins and the management of various cellular processes, including autophagy, mitophagy, inflammation, oxidative stress, and glucose metabolism, highlighting the emerging need for pharmacological approaches to modulate ROR expression. Thus, the modulation of RORs is a rapidly growing area of research aimed not only at comprehending these receptors, but also at manipulating them to attain the desired physiological response. Despite the presence of natural ROR ligands, the development of synthetic agonists with high selectivity for these receptors holds substantial therapeutic potential. The exploration and advancement of such compounds can effectively target diseases associated with ROR dysregulation, thereby providing avenues for therapeutic interventions. Herein, we provide a comprehensive examination of the multifaceted role of ROR in diverse physiological and pathophysiological conditions, accompanied by an in-depth exploration of a spectrum of ROR agonists, inverse agonists, and antagonists.

Targeting RORα in macrophages to boost diabetic bone regeneration

Diabetes mellitus (DM) has become a serious threat to human health. Bone regeneration deficiency and nonunion caused by DM is perceived as a worldwide epidemic, with a very high socioeconomic impact on public health. Here, we find that targeted activation of retinoic acid-related orphan receptor α (RORα) by SR1078 in the early stage of bone defect repair can significantly promote in situ bone regeneration of DM rats. Bone regeneration relies on the activation of macrophage RORα in the early bone repair, but RORα of DM rats fails to upregulation as hyperglycemic inflammatory microenvironment induced IGF1-AMPK signalling deficiency. Mechanistic investigations suggest that RORα is vital for macrophage-induced migration and proliferation of bone mesenchymal stem cells (BMSCs) via a CCL3/IL-6 depending manner. In summary, our study identifies RORα expressed in macrophages during the early stage of bone defect repair is crucial for in situ bone regeneration, and offers a novel strategy for bone regeneration therapy and fracture repair in DM patients.

The Role of the Circadian Rhythm in Dyslipidaemia and Vascular Inflammation Leading to Atherosclerosis

Cardiovascular diseases (CVD) are among the leading causes of death worldwide. Many lines of evidence suggest that the disturbances in circadian rhythm are responsible for the development of CVDs; however, circadian misalignment is not yet a treatable trait in clinical practice. The circadian rhythm is controlled by the central clock located in the suprachiasmatic nucleus and clock genes (molecular clock) located in all cells. Dyslipidaemia and vascular inflammation are two hallmarks of atherosclerosis and numerous experimental studies conclude that they are under direct influence by both central and molecular clocks. This review will summarise the results of experimental studies on lipid metabolism, vascular inflammation and circadian rhythm, and translate them into the pathophysiology of atherosclerosis and cardiovascular disease. We discuss the effect of time-respected administration of medications in cardiovascular medicine. We review the evidence on the effect of bright light and melatonin on cardiovascular health, lipid metabolism and vascular inflammation. Finally, we suggest an agenda for future research and recommend on clinical practice.

Influence of Different Light Spectra on Melatonin Synthesis by the Pineal Gland and Influence on the Immune System in Chickens

It is well known that the pineal gland in birds influences behavioural and physiological functions, including those of the immune system. The purpose of this research is to examine the endocrine-immune correlations between melatonin and immune system activity. Through a description of the immune-pineal axis, we formulated the objective to determine and describe: the development of the pineal gland; how light influences secretory activity; and how melatonin influences the activity of primary and secondary lymphoid organs. The pineal gland has the ability to turn light information into an endocrine signal suitable for the immune system via the membrane receptors Mel1a, Mel1b, and Mel1c, as well as the nuclear receptors RORα, RORβ, and RORγ. We can state the following findings: green monochromatic light (560 nm) increased serum melatonin levels and promoted a stronger humoral and cellular immune response by proliferating B and T lymphocytes; the combination of green and blue monochromatic light (560-480 nm) ameliorated the inflammatory response and protected lymphoid organs from oxidative stress; and red monochromatic light (660 nm) maintained the inflammatory response and promoted the growth of pathogenic bacteria. Melatonin can be considered a potent antioxidant and immunomodulator and is a critical element in the coordination between external light stimulation and the body's internal response.

Epidermal Loss of RORα Enhances Skin Inflammation in a MC903-Induced Mouse Model of Atopic Dermatitis

Atopic dermatitis (AD) is a chronic inflammatory skin disease featuring skin barrier dysfunction and immune dysregulation. Previously, we reported that the retinoid-related orphan nuclear receptor RORα was highly expressed in the epidermis of normal skin. We also found that it positively regulated the expression of differentiation markers and skin barrier-related genes in human keratinocytes. In contrast, epidermal RORα expression was downregulated in the skin lesions of several inflammatory skin diseases, including AD. In this study, we generated mouse strains with epidermis-specific Rora ablation to understand the roles of epidermal RORα in regulating AD pathogenesis. Although Rora deficiency did not cause overt macroscopic skin abnormalities at the steady state, it greatly amplified MC903-elicited AD-like symptoms by intensifying skin scaliness, increasing epidermal hyperproliferation and barrier impairment, and elevating dermal immune infiltrates, proinflammatory cytokines, and chemokines. Despite the normal appearance at the steady state, Rora-deficient skin showed microscopic abnormalities, including mild epidermal hyperplasia, increased TEWL, and elevated mRNA expression of Krt16, Sprr2a, and Tslp genes, indicating subclinical impairment of epidermal barrier functions. Our results substantiate the importance of epidermal RORα in partially suppressing AD development by maintaining normal keratinocyte differentiation and skin barrier function.

Maresin-1 and Its Receptors RORα/LGR6 as Potential Therapeutic Target for Respiratory Diseases

Maresin-1 is one of the representative specialized pro-resolving mediators that has shown beneficial effects in inflammatory disease models. Recently, two distinct types of receptor molecules were discovered as the targets of maresin-1, further revealing the pro-resolution mechanism of maresin-1. One is retinoic acid-related orphan receptor α (RORα) and the another one is leucine-rich repeat domain-containing G protein-coupled receptor 6 (LGR6). In this review, we summarized the detailed role of maresin-1 and its two different receptors in respiratory diseases. RORα and LGR6 are potential targets for the treatment of respiratory diseases. Future basic research and clinical trials on MaR1 and its receptors should provide useful information for the treatment of respiratory diseases.

Retinoid orphan nuclear receptor alpha (RORα) suppresses the epithelial-mesenchymal transition (EMT) by directly repressing Snail transcription

Retinoid orphan nuclear receptor alpha (RORα) is a member of the orphan nuclear factor family and regulates gene expression by binding to ROR response elements (ROREs). RORα has been identified as a potential tumor suppressor; however, how downregulation of RORα promotes cancer progression is not fully understood. Here, we showed that protein levels of RORα were downregulated during the Snail-, Twist-, or transforming growth factor-β–induced epithelial–mesenchymal transition (EMT). We found that silencing of RORα induced expression of mesenchymal markers in MCF10A cells, accompanied by enhanced cell invasion, migration, and mammosphere formation. Furthermore, ectopic expression of RORα suppressed transforming growth factor-β–induced EMT processes in MCF10A and HMLE cells. These results indicate that downregulation of RORα is crucial for the induction of EMT in mammary epithelial cells. By analyzing gene expression profiles in control and RORα-expressing cells, we also identified Snail, a key regulator of EMT, as a potential target of RORα. We show that RORα expression significantly inhibits Snail transcription in breast cancer cells. Chromatin immunoprecipitation analysis demonstrated that RORα bound to the ROREs in promoter region of SNAI1 gene, and using the luciferase reporter assay, we showed that binding to the ROREs was critical for RORα to repress Snail transcription. Finally, rescue experiments substantiated that Snail mediates RORα function in suppressing EMT and mammosphere formation. These results reveal a novel function of RORα in suppressing EMT and identify Snail as a direct target of RORα in mammary epithelial cells.

Rora Regulates Neutrophil Migration and Activation in Zebrafish

Neutrophil migration and activation are essential for defense against pathogens. However, this process may also lead to collateral tissue injury. We used microRNA overexpression as a platform and discovered protein-coding genes that regulate neutrophil migration. Here we show that miR-99 decreased the chemotaxis of zebrafish neutrophils and human neutrophil-like cells. In zebrafish neutrophils, miR-99 directly targets the transcriptional factor RAR-related orphan receptor alpha (roraa). Inhibiting RORα, but not the closely related RORγ, reduced chemotaxis of zebrafish and primary human neutrophils without causing cell death, and increased susceptibility of zebrafish to bacterial infection. Expressing a dominant-negative form of Rorα or disrupting the roraa locus specifically in zebrafish neutrophils reduced cell migration. At the transcriptional level, RORα regulates transmembrane signaling receptor activity and protein phosphorylation pathways. Our results, therefore, reveal previously unknown functions of miR-99 and RORα in regulating neutrophil migration and anti-microbial defense.

A molecular atlas of innate immunity to adjuvanted and live attenuated vaccines, in mice

Adjuvants hold great potential in enhancing vaccine efficacy, making the understanding and improving of adjuvants critical goals in vaccinology. The TLR7/8 agonist, 3M-052, induces long-lived humoral immunity in non-human primates and is currently being evaluated in human clinical trials. However, the innate mechanisms of 3M-052 have not been fully characterized. Here, we perform flow cytometry, single cell RNA-seq and ATAC-seq to profile the kinetics, transcriptomics and epigenomics of innate immune cells in murine draining lymph nodes following 3M-052-Alum/Ovalbumin immunization. We find that 3M-052-Alum/OVA induces a robust antiviral and interferon gene program, similar to the yellow fever vaccine, which is known to confer long-lasting protection. Activation of myeloid cells in dLNs persists through day 28 and single cell analysis reveals putative TF-gene regulatory programs in distinct myeloid cells and heterogeneity of monocytes. This study provides a comprehensive characterization of the transcriptomics and epigenomics of innate populations in the dLNs after vaccination.

Adjuvants provide additional impetus for the immune response to vaccination regimens, however their modes of activity and impact on particular compartments of the immune response are currently not well understood. Here the authors perform high resolution assessment of the immune response to a well-established vaccination model and show innate immune transcriptomic and epigenomic alterations of innate cells in the lymph nodes following vaccination.

Identification of the RORα Transcriptional Network Contributes to the Search for Therapeutic Targets in Atherosclerosis

The retinoic acid receptor-related orphan receptor α (RORα) is involved in the regulation of several physiological processes, including development, metabolism, and circadian rhythm. RORα-deficient mice display profound atherosclerosis, in which hypoalphalipoproteinemia is reportedly associated with decreased plasma levels of high-density lipoprotein, increased levels of inflammatory cytokines, and ischemia/reperfusion-induced damage. The recent characterization of endogenous ligands (including cholesterol, oxysterols, provitamin D₃, and their derivatives), mediators, and initiation complexes associated with the transcriptional regulation of these orphan nuclear receptors has facilitated the development of synthetic ligands. These findings have also highlighted the potential of application of RORα as a therapeutic target for several diseases, including diabetes, dyslipidemia, and atherosclerosis. In this review, the current literature related to the structure and function of RORα, its genetic inter-individual differences, and its potential as a therapeutic target in atherosclerosis is discussed.

Blockade of T helper 17 cell function ameliorates recurrent Clostridioides difficile infection in mice

Clostridioides difficile infection (CDI) is a common infection of the gastrointestinal tract. Typically, 20%-30% of CDI patients experience recurrent C.difficile infection (RCDI). Although the role of Th17 in infectious and inflammatory diseases including CDI has gained attention, reports on the correlation between Th17 and RCDI are scarce. In this study, CDI and RCDI mice models were challenged with C. difficile. Serum lactic acid dehydrogenase, inflammatory factor levels, reverse transcriptase-polymerase chain reaction, western blot analysis, hematoxylin and eosin staining, immunohistochemistry, flow cytometry analysis, and enzyme-linked immunosorbent assay were performed on the CDI, RCDI, and control group mice. The results showed more serious clinical manifestations in the RCDI group compared with those in the CDI group. More severe gut barrier disruption and higher degree of microbiota translocation were observed in the RCDI group compared with those in the CDI group. Moreover, extremely severe apoptosis was observed in HCT-116 cells incubated with the serum from RCDI mice model. In addition, higher levels of Th17 and IL-17 were detected in the blood or serum from the RCDI mouse model. Treatment with RORγt small molecule inhibitor SR1001 increased the expression of occludin, decreased the apoptotic rate of HCT-116 cells, and decreased the concentrations of Th17 and IL-17. Concisely, Th17 and IL-17 are potential indicators of RCDI and may serve as therapeutic targets for RCDI treatment. This study lays the foundation for future research on RCDI diagnosis and treatment.

Functions for Retinoic Acid-Related Orphan Receptor Alpha (RORα) in the Activation of Macrophages During Lipopolysaccharide-Induced Septic Shock

The transcription factor Related Orphan Receptor Alpha (RORα) plays an important role in regulating circadian rhythm, inflammation, metabolism and cellular development. Herein we show that in the absence of functional RORα in mice there is reduced susceptibility to LPS-induced endotoxic shock, with selective decreases in release of pro-inflammatory cytokines. Treatment of mice with a RORα selective synthetic inhibitor also reduced the severity of LPS-induced endotoxemia. The reduction in responses in Rora deficient mice was associated with an alterations in metabolic and pro-inflammatory functions of macrophages, both in vivo peritoneal macrophages and in vitro generated bone marrow derived macrophages. Using LysM^CreRora^fl/sg mice the reduced susceptibility to LPS was shown to be specific to Rora expression in the macrophages. This study identifies that Rora-mediated regulation of macrophages impacts on the pro-inflammatory responses elicited by LPS.

Modeling the circadian regulation of the immune system: Sexually dimorphic effects of shift work

The circadian clock exerts significance influence on the immune system and disruption of circadian rhythms has been linked to inflammatory pathologies. Shift workers often experience circadian misalignment as their irregular work schedules disrupt the natural light-dark cycle, which in turn can cause serious health problems associated with alterations in genetic expressions of clock genes. In particular, shift work is associated with impairment in immune function, and those alterations are sex-specific. The goal of this study is to better understand the mechanisms that explain the weakened immune system in shift workers. To achieve that goal, we have constructed a mathematical model of the mammalian pulmonary circadian clock coupled to an acute inflammation model in the male and female rats. Shift work was simulated by an 8h-phase advance of the circadian system with sex-specific modulation of clock genes. The model reproduces the clock gene expression in the lung and the immune response to various doses of lipopolysaccharide (LPS). Under normal conditions, our model predicts that a host is more sensitive to LPS at circadian time (CT) CT12 versus CT0 due to a dynamic change of Interleukin 10 (IL-10), an anti-inflammatory cytokine. We identify REV-ERB as a key modulator of IL-10 activity throughout the circadian day. The model also predicts a reversal of the times of lowest and highest sensitivity to LPS, with males and females exhibiting an exaggerated response to LPS at CT0, which is countered by a blunted immune response at CT12. Overall, females produce fewer pro-inflammatory cytokines than males, but the extent of sequelae experienced by males and females varies across the circadian day. This model can serve as an essential component in an integrative model that will yield mechanistic understanding of how shift work-mediated circadian disruptions affect the inflammatory and other physiological responses.

RORα Regulates Odontoblastic Differentiation and Mediates the Pro-Odontogenic Effect of Melatonin on Dental Papilla Cells

Dental papilla cells (DPCs), precursors of odontoblasts, are considered promising seed cells for tissue engineering. Emerging evidence suggests that melatonin promotes odontoblastic differentiation of DPCs and affects tooth development, although the precise mechanisms remain unknown. Retinoid acid receptor-related orphan receptor α (RORα) is a nuclear receptor for melatonin that plays a critical role in cell differentiation and embryonic development. This study aimed to explore the role of RORα in odontoblastic differentiation and determine whether melatonin exerts its pro-odontogenic effect via RORα. Herein, we observed that RORα was expressed in DPCs and was significantly increased during odontoblastic differentiation in vitro and in vivo. The overexpression of RORα upregulated the expression of odontogenic markers, alkaline phosphatase (ALP) activity and mineralized nodules formation (p < 0.05). In contrast, odontoblastic differentiation of DPCs was suppressed by RORα knockdown. Moreover, we found that melatonin elevated the expression of odontogenic markers, which was accompanied by the upregulation of RORα (p < 0.001). Utilising small interfering RNA, we further demonstrated that RORα inhibition attenuated melatonin-induced odontogenic gene expression, ALP activity and matrix mineralisation (p < 0.01). Collectively, these results provide the first evidence that RORα can promote odontoblastic differentiation of DPCs and mediate the pro-odontogenic effect of melatonin.

Peroxisome Proliferator-Activated Receptors as Molecular Links between Caloric Restriction and Circadian Rhythm

The circadian rhythm plays a chief role in the adaptation of all bodily processes to internal and environmental changes on the daily basis. Next to light/dark phases, feeding patterns constitute the most essential element entraining daily oscillations, and therefore, timely and appropriate restrictive diets have a great capacity to restore the circadian rhythm. One of the restrictive nutritional approaches, caloric restriction (CR) achieves stunning results in extending health span and life span via coordinated changes in multiple biological functions from the molecular, cellular, to the whole-body levels. The main molecular pathways affected by CR include mTOR, insulin signaling, AMPK, and sirtuins. Members of the family of nuclear receptors, the three peroxisome proliferator-activated receptors (PPARs), PPARα, PPARβ/δ, and PPARγ take part in the modulation of these pathways. In this non-systematic review, we describe the molecular interconnection between circadian rhythm, CR-associated pathways, and PPARs. Further, we identify a link between circadian rhythm and the outcomes of CR on the whole-body level including oxidative stress, inflammation, and aging. Since PPARs contribute to many changes triggered by CR, we discuss the potential involvement of PPARs in bridging CR and circadian rhythm.

Exosomal miRNA-19a and miRNA-614 Induced by Air Pollutants Promote Proinflammatory M1 Macrophage Polarization via Regulation of RORα Expression in Human Respiratory Mucosal Microenvironment

Air pollution exposure leads to various inflammatory diseases in the human respiratory system. Chronic rhinosinusitis is an inflammatory disease caused by viruses, bacteria, or air pollutants. However, the underlying molecular mechanisms through which air particulate matter (PM) causes inflammation and disease remain unclear. In this article, we report that the induction of exosomal microRNAs (miRNAs) from human nasal epithelial cells upon airborne PM exposure promotes proinflammatory M1 macrophage polarization via downregulated RORα expression. Exposure of human nasal epithelial cells to PM results in inflammation-related miRNA expression, and more miRNA is secreted through exosomes delivered to macrophages. Among these, miRNA-19a and miRNA-614 directly bind to the 3'-untranslated region of RORα mRNA and downregulate RORα expression, which leads to inflammation due to inflammatory cytokine upregulation and induces macrophages to a proinflammatory M1-like state. Finally, we showed enhanced expression of miRNA-19a and miRNA-614 but reduced RORα expression in a chronic rhinosinusitis patient tissue compared with the normal. Altogether, our results suggest that PM-induced exosomal miRNAs might play a crucial role in the proinflammatory mucosal microenvironment and macrophage polarization through the regulation of RORα expression.

Molecular Interactions Between Components of the Circadian Clock and the Immune System

The immune system is under control of the circadian clock. Many of the circadian rhythms observed in the immune system originate in direct interactions between components of the circadian clock and components of the immune system. The main means of circadian control over the immune system is by direct control of circadian clock proteins acting as transcription factors driving the expression or repression of immune genes. A second circadian control of immunity lies in the acetylation or methylation of histones to regulate gene transcription or inflammatory proteins. Furthermore, circadian clock proteins can engage in direct physical interactions with components of key inflammatory pathways such as members of the NFκB protein family. This regulation is transcription independent and allows the immune system to also reciprocally exert control over circadian clock function. Thus, the molecular interactions between the circadian clock and the immune system are manifold. We highlight and discuss here the recent findings with respect to the molecular mechanisms that control time-of-day-dependent immunity. This review provides a structured overview focusing on the key circadian clock proteins and discusses their reciprocal interactions with the immune system.

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The immune system is under control of the circadian clock.

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Circadian clock proteins act as transcription factors controlling genes of the immune system.

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Circadian clock proteins engage in direct physical interactions with inflammatory proteins.

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Immune factors also reciprocally exert control over circadian clock function.

Distinct PLZF+CD8αα+ Unconventional T Cells Enriched in Liver Use a Cytotoxic Mechanism to Limit Autoimmunity

Hepatic immune system is uniquely challenged to mount a controlled effector response to pathogens while maintaining tolerance to diet and microbial Ags. We have identified a novel population of innate-like, unconventional CD8αα+TCRαβ+ T cells in naive mice and in human peripheral blood, called CD8αα Tunc, capable of controlling effector T cell responses. They are NK1.1+ (CD161+ in human), express NK-inhibitory receptors, and express the promyelocytic leukemia zinc finger (PLZF) transcription factor that distinguishes them from conventional CD8+ T cells. These cells display a cytotoxic phenotype and use a perforin-dependent mechanism to control Ag-induced or T cell-mediated autoimmune diseases. CD8αα Tunc are dependent upon IL-15/IL-2Rβ signaling and PLZF for their development and/or survival. They are Foxp3-negative and their regulatory activity is associated with a functionally distinct Qa-1b-dependent population coexpressing CD11c and CD244. A polyclonal TCR repertoire, an activated/memory phenotype, and the presence of CD8αα Tunc in NKT- and in MAIT-deficient as well as in germ-free mice indicates that these cells recognize diverse self-protein Ags. Our studies reveal a distinct population of unconventional CD8+ T cells within the natural immune repertoire capable of controlling autoimmunity and also providing a new target for therapeutic intervention.

ROR alpha protects against LPS-induced inflammation by down-regulating SIRT1/NF-kappa B pathway

Systemic inflammatory response syndrome (SIRS) is associated with excessive inflammatory response, however, the pathophysiology of inflammation is poorly understood. The retinoid-related orphan receptor α (RORα) is a key inflammatory regulator, but the mechanisms underlying its role remain unclear. The aim of this study was to investigate how RORα was involved in the regulation of inflammatory response. Here we put forward a hypothesis that RORα might negatively regulate inflammatory response by controlling silent information regulator Sirtuin 1 (SIRT1) expression. Stimulation of macrophages in vitro with LPS and LPS administration in vivo were used to explore the function of RORα and the relationship between RORα and SIRT1. We found that the level of RORα was suppressed in macrophages stimulated with LPS and overexpression or knockdown of RORα by transfection with lentivirus or siRNAs significantly decreased or increased, respectively, the pro-inflammatory cytokines IL-1β, TNF, IL-6 and MCP-1. Importantly, overexpression of RORα suppressed inflammation and alleviated LPS-induced organ injury in vivo. Further study showed that RORα could regulate SIRT1 expression and, consequently, affect deacetyation and nuclear translocation of nuclear factor-kappa B (NF-κB) subunit p65. Moreover, the activation of SIRT1 by its specific agonist, SR1720, could reduce the expression of proinflammatory cytokines in RORα knockdown macrophages stimulated with LPS. In conclusion, we demonstrated that RORα could alleviate LPS-induced inflammation and organ injury both in vivo and in vitro by blocking NF-κB p65 nuclear translocation and restricting acetylation of NF-κB p65 at lysine 310 via the regulation of SIRT1 expression. Targeting RORα might be a promising therapeutic strategy to regulate inflammatory disorders.

RORα controls inflammatory state of human macrophages

ROR family of nuclear receptor transcription factors forms nodes connecting metabolic and inflammatory signaling pathways. The RORα members of the family have intrinsic transcriptional activity and they are involved in both activation and repression of a wide range of genes. The role of RORα in control of inflammation has been extensively studied using animal models but its function in human cells is not as well understood. To address this shortcoming, we analyzed how RORα is shaping the inflammatory state of human macrophages. Using CRISPR-Cas9 system, we deleted RORA in THP-1 human monocytic cell line. In mutant cells we observed a dramatic increase in basal expression of a subset of NF-κB regulated genes, including TNF, IL-1β and IL-6, at both transcriptional and translational levels. Furthermore, RORA-deletion cells produced notable amounts of pro-IL-1β even in the absence of LPS stimulation. Subsequent LPS stimulation induced cleavage of pro-IL-1β to mature form. Our RNAseq analysis further confirmed the key role of RORA in setting the inflammatory state of macrophages and defined the set of differentially regulated genes. Overall, our data provides evidence supporting the anti-inflammatory function of RORα in human macrophages.

Depot-Specific Response of Adipose Tissue to Diet-Induced Inflammation: The Retinoid-Related Orphan Receptor α (RORα) Involved?

OBJECTIVE

Epididymal adipose tissue (EAT), a visceral fat depot, is more closely associated with metabolic dysfunction than inguinal adipose tissue (IAT), a subcutaneous depot. This study evaluated whether the nuclear receptor RORα, which controls inflammatory processes, could be implicated.

METHODS

EAT and IAT were compared in a RORα loss-of-function mouse (sg/sg) and in wild-type (WT) littermates, fed a standard diet (SD) or a Western diet (WD), to evaluate the impact of RORα expression on inflammatory status and on insulin sensitivity (IS) of each fat depot according to the diet.

RESULTS

Sg/sg mice fed the SD exhibited a decreased inflammatory status and a higher IS in their fat depots than WT mice. WD-induced obesity had distinct effects on the two fat depots. In WT mice, EAT exhibited increased inflammation and insulin resistance while IAT showed reduced inflammation and improved IS, together with a depot-specific increase of RORα, and its target gene IκBα, in the stroma vascular fraction (SVF). Conversely, in sg/sg mice, WD increased inflammation and lowered IS of IAT but not of EAT.

CONCLUSIONS

These findings suggest an anti-inflammatory role for RORα in response to WD, which occurs at the level of SVF of IAT, thus possibly contributing to the "healthy" expansion of IAT.

RORγt and RORα signature genes in human Th17 cells

RORγt and RORα are transcription factors of the RAR-related orphan nuclear receptor (ROR) family. They are expressed in Th17 cells and have been suggested to play a role in Th17 differentiation. Although RORγt signature genes have been characterized in mouse Th17 cells, detailed information on its transcriptional control in human Th17 cells is limited and even less is known about RORα signature genes which have not been reported in either human or mouse T cells. In this study, global gene expression of human CD4 T cells activated under Th17 skewing conditions was profiled by RNA sequencing. RORγt and RORα signature genes were identified in these Th17 cells treated with specific siRNAs to knock down RORγt or RORα expression. We have generated selective small molecule RORγt modulators and they were also utilized as pharmacological tools in RORγt signature gene identification. Our results showed that RORγt controlled the expression of a very selective number of genes in Th17 cells and most of them were regulated by RORα as well albeit a weaker influence. Key Th17 genes including IL-17A, IL-17F, IL-23R, CCL20 and CCR6 were shown to be regulated by both RORγt and RORα. Our results demonstrated an overlapping role of RORγt and RORα in human Th17 cell differentiation through regulation of a defined common set of Th17 genes. RORγt as a drug target for treatment of Th17 mediated autoimmune diseases such as psoriasis has been demonstrated recently in clinical trials. Our results suggest that RORα could be involved in same disease mechanisms and gene signatures identified in this report could be valuable biomarkers for tracking the pharmacodynamic effects of compounds that modulate RORγt or RORα activities in patients.

Retinoid acid receptor-related orphan receptor alpha (RORα) regulates macrophage M2 polarization via activation of AMPKα

Macrophages are able to polarize to pro-inflammatory M1 or anti-inflammatory M2 states with distinct phenotypes and physiological functions. RORα is a member of the nuclear receptor super family and plays important roles in lipid, glucose metabolism, as well as the inflammatory response. In this study, we examined the potential function of RORα in the regulation of macrophage polarization. Treatment of RAW264.7 macrophages with RORα agonist cholesterol sulfate (CH-S) and overexpression of RORα increased M2 macrophage markers expressions (Arg1, Ym1 and Fizz1) both on mRNA and protein levels. Conversely, selective antagonism (SR1001) abrogated the induction of M2 macrophage markers which induced by CH-S. In addition, CH-S induced phosphorylation of Adenosine monophosphate (AMP)-activated protein kinase α (AMPKα), which was accompanied by the activation of acetyl-CoA carboxylase 1 (ACC). However, SR1001 abolished the activation of AMPKα and ACC induced by CH-S. Meanwhile, inactivation of AMPKα by its inhibitor Compound C (CompC) abrogated the mRNA and protein levels of CH-S-induced M2 macrophage markers expressions. Together these findings reveal that RORα regulates macrophage M2 polarization via activation of AMPKα, which may provide a novel beneficial effect of RORα against inflammation.

Emerging roles of orphan nuclear receptors in regulation of innate immunity

Innate immunity constitutes the first line of defense against pathogenic and dangerous insults. However, it is a double-edged sword, as it functions in both clearance of infection and inflammatory damage. It is therefore important that innate immune responses are tightly controlled to prevent harmful excessive inflammation. Nuclear receptors (NRs) are a family of transcription factors that play critical roles in various physiological responses. Orphan NRs are a subset of NRs for which the ligands and functions are unclear. Accumulating evidence has revealed that orphan NRs play essential roles in innate immune responses to prevent pathogenic inflammatory responses and to enhance antimicrobial host defenses. In this review, we describe current knowledge on the roles and mechanisms of orphan NRs in the regulation of innate immune responses. Discovery of new functions of orphan NRs would facilitate development of novel preventive and therapeutic strategies against human inflammatory diseases.

RAR-related orphan receptor A (RORA): A new susceptibility gene for multiple sclerosis

Retinoic acid receptor-related orphan receptor alpha (RORA) is proposed to promote Th17 cells differentiation that play a crucial role in many inflammatory diseases, including multiple sclerosis (MS). The gene is also involved in regulation of inflammatory responses and neuronal cell development. The aim of the present study is to determine if any relation exists between RORA rs11639084 and rs4774388 gene polymorphisms on the individual susceptibility of multiple sclerosis. 410 patients with clinically definite MS and 500 ethnically-matched healthy controls participated in this study. Genotyping was performed using tetra primer-amplification refractory mutation system-PCR (4P-ARMS-PCR) method for the mentioned polymorphisms in the RORA gene. Both variants showed significant differences in allele and genotype distributions between the studied groups. Genotypes were risk associated in additive (P-value of 0.0003 and odds ratio equal to 1.7 (95% CI: 1.27-2.26)), dominant (P-value of <0.0001 and odds ratio equal to 0.55 (95% CI: 0.41-0.73)) and recessive (P-value of 0.04 and odds ratio equal to 0.33 (95% CI: (0.12-0.96)) models for rs11639084. However, the rs4774388 genotypes were risk associated in recessive model with a P-value of 0.036 and an odds ratio of 0.62 (95% CI: (0.4-0.97)). To the best of our knowledge this is the first report concerning the association between RORΑ gene polymorphisms and MS. The further study of RORΑ related pathways and gene networks might result in the better understanding of the pathophysiology of MS and related symptoms.

Lymphocytic, cytokine and transcriptomic profiles in peripheral blood of dogs with atopic dermatitis

Background

Canine atopic dermatitis (cAD) is a common chronic and pruritic skin disease in dogs. The development of cAD involves complex interactions between environmental antigens, genetic predisposition and a number of disparate cell types. The aim of the present study was to perform comprehensive analyses of peripheral blood of AD dogs in relation to healthy subjects in order to determine the changes which would be characteristic for cAD.

Results

The number of cells in specific subpopulations of lymphocytes was analyzed by flow cytometry, concentration of chosen pro- and anti-inflammatory cytokines (IL-4, IL-10, IL-13, TNF-α, TGF-β1) was determined by ELISA; and microarray analysis was performed on RNA samples isolated from peripheral blood nuclear cells of AD and healthy dogs. The number of Th cells (CD3⁺CD4⁺) in AD and healthy dogs was similar, whereas the percentage of Tc (CD3⁺CD8⁺) and Treg (CD4⁺CD25⁺ Foxp3⁺) cells increased significantly in AD dogs. Increased concentrations of IL-13 and TNF-α, and decreased levels of IL-10 and TGF-β1 was observed in AD dogs. The level of IL-4 was similar in both groups of animals. Results of the microarray experiment revealed differentially expressed genes involved in transcriptional regulation (e.g., transcription factors: SMAD2, RORA) or signal transduction pathways (e.g., VEGF, SHB21, PROC) taking part in T lymphocytes lineages differentiation and cytokines synthesis.

Conclusions

Results obtained indicate that CD8⁺ T cells, beside CD4⁺ T lymphocytes, contribute to the development of the allergic response. Increased IL-13 concentration in AD dogs suggests that this cytokine may play more important role than IL-4 in mediating changes induced by allergic inflammation. Furthermore, observed increase in Treg cells in parallel with high concentrations of TNF-α and low levels of IL-10 and TGF-β1 in the peripheral blood of AD dogs point at the functional insufficiency of Treg cells in patients with AD.

Electronic supplementary material

The online version of this article (doi:10.1186/s12917-016-0805-6) contains supplementary material, which is available to authorized users.

A matter of time: study of circadian clocks and their role in inflammation

Circadian rhythms regulate changes in physiology, allowing organisms to respond to predictable environmental demands varying over a 24 h period. A growing body of evidence supports a key role for the circadian clock in the regulation of immune functions and inflammatory responses, which influence the understanding of infections and inflammatory diseases and their treatment. A variety of experimental methods have been used to assess the complex bidirectional crosstalk between the circadian clock and inflammation. In this review, we summarize the organization of the molecular clock, experimental methods used to study circadian rhythms, and both the inflammatory and immune consequences of circadian disturbance.

ROR inverse agonist suppresses insulitis and prevents hyperglycemia in a mouse model of type 1 diabetes

Hyperglycemia associated with type 1 diabetes is a consequence of immune-mediated destruction of insulin producing pancreatic β-cells. Although it is apparent that both CD8(+) T cells and TH1 cells are key contributors to type 1 diabetes, the function of TH17 cells in disease onset and progression remains unclear. The nuclear receptors retinoic acid receptor-related orphan receptors-α and γt (RORα and RORγt) play critical roles in the development of TH17 cells and ROR-specific synthetic ligands have proven efficacy in several mouse models of autoimmunity. To investigate the roles and therapeutic potential for targeting the RORs in type 1 diabetes, we administered SR1001, a selective RORα/γ inverse agonist, to nonobese diabetic mice. SR1001 significantly reduced diabetes incidence and insulitis in the treated mice. Furthermore, SR1001 reduced proinflammatory cytokine expression, particularly TH17-mediated cytokines, reduced autoantibody production, and increased the frequency of CD4(+)Foxp3(+) T regulatory cells. These data suggest that TH17 cells may have a pathological role in the development of type 1 diabetes, and use of ROR-specific synthetic ligands targeting this cell type may prove utility as a novel treatment for type 1 diabetes.

Genetic deletion of calcium/calmodulin-dependent protein kinase kinase β (CaMKK β) or CaMK IV exacerbates stroke outcomes in ovariectomized (OVXed) female mice

BACKGROUND

Stroke is the primary cause of long-term disability in the United States. Interestingly, mounting evidence has suggested potential sex differences in the response to stroke treatment in patients as, at least in part, distinct cell death programs may be triggered in females and males following stroke. The NIH has recognized that females are strikingly under-represented in pre-clinical trials. Calcium/calmodulin-dependent protein kinase kinase (CaMKK) is a major kinase that is activated by elevated intracellular calcium. It has recently been suggested that CaMKK and CaMK IV, a downstream target molecule, are neuroprotective in stroke in males. In this study, we examined stroke outcomes in ovariectomized CaMKK β and CaMK IV deficient females. Cell death/survival signaling and inflammatory responses were assessed.

RESULTS

Our results demonstrated that CaMKK β or CaMK IV KO exacerbated both ischemic injury and behavioral deficits in female mice. Genetic deletion of CaMKK β or CaMK IV increased hemorrhagic transformation after stroke, and this was associated with both increased MMP9 activity and loss of the blood brain barrier (BBB) protein collagen IV. Transcriptional inactivation was observed in mice lacking either CaMKK β or CaMK IV, as indicated by reduced levels of phosphorylated cAMP response element-binding protein (p-CREB) and B-cell lymphoma 2 (BCL-2) proteins. Finally, inhibiting this pathway exacerbated the inflammatory response to stroke as CaMKK β or CaMK IV KO mice had increased levels of the pro-inflammatory serum cytokines tumor necrosis factor alpha (TNFα) and interleukin 6 (IL-6) after stroke. This suggests that the CaMKK pathway is involved in the immune response to brain injury.

CONCLUSIONS

Inhibition of CaMKK signaling exacerbated stroke outcome and increased BBB impairment, transcriptional inactivation and inflammatory responses in females after stroke. Therefore, CaMKK signaling may be a potential target for stroke treatment in both males and females.

RORα binds to E2F1 to inhibit cell proliferation and regulate mammary gland branching morphogenesis

Retinoic acid receptor-related orphan nuclear receptor alpha (RORα) is a potent tumor suppressor that reduces cell proliferation and inhibits tumor growth. However, the molecular mechanism by which it inhibits cell proliferation remains unknown. We demonstrate a noncanonical nuclear receptor pathway in which RORα binds to E2F1 to inhibit cell cycle progression. We showed that RORα bound to the heptad repeat and marked box region of E2F1 and suppressed E2F1-regulated transcription in epithelial cells. Binding of RORα inhibited E2F1 acetylation and its DNA-binding activity by recruiting histone deacetylase 1 (HDAC1) to the protein complexes. Knockdown of HDAC1 or inhibition of HDAC activity at least partially rescued transcription factor activity of E2F1 that was repressed by RORα. Importantly, RORα levels were increased in mammary ducts compared to terminal end buds and inversely correlated with expression of E2F1 target genes and cell proliferation. Silencing RORα in mammary epithelial cells significantly enhanced cell proliferation in the ductal epithelial cells and promoted side branching of the mammary ducts. These results reveal a novel link between RORα and E2F1 in regulating cell cycle progression and mammary tissue morphogenesis.

Regulation of TH17 markers early in life through maternal farm exposure

BACKGROUND

Previous studies suggested that maternal farm exposure during pregnancy modulates early immune development toward an allergy-protective status potentially mediated by TH1 or regulatory T (Treg) cells. However, the underlying mechanisms might involve immune modulation of additional T-cell populations, such as TH17 cells, influenced by genetic predisposition.

OBJECTIVE

We examined the role of maternal farm exposure and genetic predisposition on TH17 cell responses to innate and adaptive immune stimulation in cord blood.

METHODS

Eighty-four pregnant mothers were recruited before delivery. Detailed questionnaires (60 nonfarming mother, 22 farming mothers, and 2 exclusions) assessed farming exposures. Cord blood was stimulated with lipid A, peptidoglycan (Ppg), or PHA. TH17 lineage (retinoic acid receptor-related orphan receptor C [RORC], retinoic acid receptor-related orphan receptor α [RORA], IL-23 receptor [IL23R], IL17, IL17F, and IL22) and Treg cell markers (forkhead box protein 3 [FOXP3], lymphocyte activation gene 3 [LAG3], and glucocorticoid-induced TNF receptor [GITR]) were assessed at the mRNA level. TH17/Treg/TH1/TH2 cytokines and 7 single nucleotide polymorphisms within the TH17 lineage (RORC, IL23R, and IL17) were examined.

RESULTS

TH17 lineage mRNA markers were expressed at birth at low concentrations independent of maternal farm exposure. A positive correlation between TH17 lineage markers and FOXP3 (mRNA) was observed on stimulation (nonfarming mothers: lipid A, Ppg, and PHA; farming mothers: Ppg and PHA), influenced by maternal farming. Specific single nucleotide polymorphisms within the TH17 lineage genes influenced gene expression of TH17 and Treg cell markers and cytokine secretion.

CONCLUSIONS

Gene expression of TH17 lineage markers in cord blood was not influenced by maternal farming. Yet TH17 and Treg cell markers were positively correlated and influenced by maternal farm exposure. Our data suggest that prenatal exposures and genetic predisposition play a role during early TH17 immune maturation, potentially regulating the development of immune-mediated diseases, such as childhood asthma.

The orphan nuclear receptor Ear-2 (Nr2f6) is a novel negative regulator of T cell development

We describe a novel role for the orphan nuclear receptor Ear-2 in regulating T cell development. Retrovirus-mediated overexpression of Ear-2 (EAR-2++) in a bone marrow (BM) transplantation assay resulted in limited T cell development and a greater than tenfold decrease in thymus size and cellularity relative to controls. Ear-2-transduced murine BM hematopoietic stem cells (HSCs) in OP9-DL1 cultures showed a proliferation deficit during days 1-5 after induction of differentiation, which corresponded to increased expression of the cell cycle regulators p21 (cdkn1a) and p27 (cdkn1b), as well as increased expression of Hes1, Notch3, Egr1, and Scl (Tal1) and decreased expression of Gli1, Gfi-1, HoxA9, PU.1, Nrarp, and Tcf1. In addition, there was a block in differentiation at the DN4 to double-positive (DP) transition accompanied by an increase in apoptosis, similar to the deficit seen in the RORγt null mouse. Gene expression profiling revealed that, like the RORγt-deficient mouse, EAR-2++ DP cells had decreased expression of BclXL and increased expression of the proapoptosis gene Bad. In addition, EAR-2++ DP cells had decreased expression of Bcl11b, PU.1, and HoxA9, and increased expression of Id2. Based on these findings, we conclude that EAR-2++ cells were able to migrate to, but not fully repopulate, the thymus because of a cell-intrinsic defect in the proliferation of DN1 cells followed by a block in differentiation from the DN4 to DP stage of T cell development. We conclude that Ear-2 is a novel negative regulator of T-cell development and that downregulation of Ear-2 is indispensable for the proliferation of DN1 cells and the survival of DN4-DP cells.

Disruption of Rorα1 and cholesterol 25-hydroxylase expression attenuates phagocytosis in male Rorαsg/sg mice

We and others have previously demonstrated that congenital deficiency of the nuclear hormone receptor, Rorα1, in staggerer (sg/sg) mice results in resistance to diet-induced obesity and increased insulin sensitivity. Paradoxically, the sg/sg mice are susceptible to atherosclerosis and display impaired innate immunity, underscoring the regulatory links between metabolic disease, inflammation, and susceptibility to infection. Here, we present novel evidence that Rorα1 regulates innate immune function by demonstrating impaired phagocytosis in sg/sg mice. The early stages of Fc-γ receptor-mediated phagocytosis in lipopolysaccharide-activated sg/sg bone marrow-derived macrophages (BMMs) were significantly impaired compared with wild-type cells. Moreover, in sg/sg BMMs, the phagocytic cup membranes had reduced levels of cholesterol. Expression profiling revealed dysregulated expression of genes involved in inflammation and lipid metabolism in sg/sg BMMs. Notably, we identified decreased expression of the mRNA encoding cholesterol 25-hydroxylase (Ch25h), an enzyme that converts cholesterol to 25-hydroxycholesterol (25HC), an oxysterol with emerging roles in immunity. Treatment of sg/sg BMMs with 25HC rescued phagocytosis in a dose-dependent manner, whereas small interfering RNA knockdown of Ch25h mRNA expression in wild-type cells attenuated phagocytosis. Hence, we propose that 25HC is essential for optimizing membrane internalization during phagocytosis and that aberrant Ch25h expression in Rorα1-deficient sg/sg macrophages disrupts phagocytosis. Our studies reveal new roles for Rorα1, Ch25h, and 25HC in phagocytosis. Aberrant 25HC underpins the paradoxical association between insulin sensitivity and impaired innate immunity in Rorα1-deficient mice, heralding a wider and essential role for this oxysterol at the nexus of metabolism and immunity.

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.

Molecular evidence for the involvement of RORα and RORγ in immune response in teleost

In mammals, retinoid-related orphan receptors (ROR) consist of three members as RORα, RORβ and RORγ. It is well known that RORα plays a critical role in cerebellum development while RORγt directs T helper 17 (Th17) cell differentiation. So far, the knowledge on fish ROR family is limited as only zebrafish ROR family members have been characterized, showing that they play roles in embryonic and cerebellar development. In this study, we have cloned two paralogues for RORα (RORα1 and RORα2) and RORγ (RORγ1 and RORγ2) from grass carp (Ctenopharyngodon idellus). Phylogenetic analysis showed that grass carp RORα and RORγ were grouped in the clade of zebrafish RORα and RORγ, respectively. Real-time RT-PCR assay revealed that these four ROR transcripts exhibited similar expression patterns, in particular the high levels in pituitary, brain and some immune-related tissues, suggesting that all of them may play a role in endocrine and immune system of teleost. To explore the immune roles of grass carp RORα and RORγ, their expression was detected in periphery blood lymphocytes (PBLs) challenged by immune stimuli. Results showed that both RORα and RORγ mRNA levels were up-regulated by PHA but not LPS in PBLs, suggesting that their expression may be subject to different immune processes. In the same cell model, poly I:C stimulation induced RORγ1/2 but not RORα1/2 expression, pointing to the different roles of grass carp RORα and RORγ in immune response. Consistently, bacterial challenge significantly up-regulated the expression of these four ROR genes in spleen, headkidney and thymus. These results not only contribute to elucidate the roles of ROR in fish immunity but also facilitate to further clarify the existence of Th17-like cells in fish.

The interplay between retinoic acid receptor-related orphan receptors and human diseases

The retinoic acid receptor-related orphan receptors (RORs) are an important subfamily of transcriptional regulators of the nuclear receptors superfamily. Their discovery over a decade ago by gene cloning strategy have revealed three major isoforms of these orphan receptors in animals. Generation and analyses of isoform-specific ROR null mice have provided revealed-vital roles for the RORs in animals. The RORs undoubtedly participate in a host of biological functions such a metabolism, immunity, development and differentiation, angiogenesis, circadian clock, xenobiotic/drug metabolism and other tissue physiologies for optimal animal survival. Moreover, intense work in the last one decade also revealed a host of human diseases being modulated by the RORs. A number of diseases, such as cancer, autoimmune diseases, inflammation, osteoporosis, metabolic syndrome etc., strongly support the involvement of RORs in their onset and progression. By involving in such diseases, the RORs are indeed a critical factor for optimal cell function and are being intensely investigated as novel targets for drug interventions in the treatment of various diseases. This review focuses on the current knowledge and status about RORs in a number of human disease conditions.

Divergent transcriptional programming of class-specific B cell memory by T-bet and RORα

Antibody class defines function in B cell immunity, but how class is propagated into B cell memory remains poorly understood. Here, we demonstrate that memory B cell subsets unexpectedly diverge across antibody class through the differential impact of major transcriptional regulators. Conditional genetic deletion of Tbx21 selectively blocks the formation and antigen-specific response of IgG2a memory B cells in vivo. Cell intrinsic T-bet expression regulates STAT1 expression, steady-state cell survival and IgG2a BCR transcription. In contrast, RORα was differentially expressed in IgA memory B cells with siRNA knockdown and chemical inhibition supporting its selective control in cell survival and IgA BCR transcription. Thus, divergent transcriptional regulators dynamically maintain subset integrity to promote specialized immune function within class-specific memory B cells.

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.

RORα suppresses breast tumor invasion by inducing SEMA3F expression

Inactivation of tumor suppressors and inhibitory microenvironmental factors is necessary for breast cancer invasion; therefore, identifying those suppressors and factors is crucial not only to advancing our knowledge of breast cancer, but also to discovering potential therapeutic targets. By analyzing gene expression profiles of polarized and disorganized human mammary epithelial cells in a physiologically relevant three-dimensional (3D) culture system, we identified retinoid orphan nuclear receptor alpha (RORα) as a transcription regulator of semaphorin 3F (SEMA3F), a suppressive microenvironmental factor. We showed that expression of RORα was downregulated in human breast cancer tissue and cell lines, and that reduced mRNA levels of RORα and SEMA3F correlated with poor prognosis. Restoring RORα expression reprogrammed breast cancer cells to form noninvasiveness structures in 3D culture and inhibited tumor growth in nude mice, accompanied by enhanced SEMA3F expression. Inactivation of RORα in nonmalignant human mammary epithelial cells inhibited SEMA3F transcription and impaired polarized acinar morphogenesis. Using chromatin immunoprecipitation and luciferase reporter assays, we showed that transcription of SEMA3F is directly regulated by RORα. Knockdown of SEMA3F in RORα-expressing cancer cells rescued the aggressive 3D phenotypes and tumor invasion. These findings indicate that RORα is a potential tumor suppressor and inhibits tumor invasion by inducing suppressive cell microenvironment.

Transcription factor RORα is critical for nuocyte development

Nuocytes are essential in innate type-2 immunity and contribute to the exacerbation of asthma responses. Here we show that nuocytes arise in the bone marrow and differentiate from common lymphoid progenitors, which makes them distinct new members of the lymphoid lineage. Nuocytes required interleukin 7 (IL-7), IL-33 and Notch signalling for development in vitro. Double negative 1 (DN1) and DN2 pro-T-cell progenitors maintained nuocyte potential in vitro, although the thymus was not essential for nuocyte development. Notably, the transcription factor Rorα was critical for nuocyte development and their role in parasitic worm expulsion.

Melatonin synthesized by T lymphocytes as a ligand of the retinoic acid-related orphan receptor

Melatonin modulates a wide array of physiological events with pleiotropic effects on the immune system. While the relevance of specific melatonin membrane receptors has been well established for several biological functions, retinoic acid-related orphan receptor alpha (RORα) has been suggested as a mediator of nuclear melatonin signalling by results obtained from pharmacological approaches. However, a melatonin-mediated downstream effect cannot be ruled out, and further evidence is needed to support a direct interaction between melatonin and RORα. Here, we show that RORα is mainly located in human Jurkat T-cell nucleus, and it is co-immunoprecipitated with melatonin. Moreover, immunocytochemistry studies confirmed the co-localization of melatonin and RORα. Melatonin promoted a time-dependent decrease in nuclear RORα levels, suggesting a role in the RORα transcriptional activity. Interestingly, RORα acts as a molecular switch implicated in the mutually exclusive generation of Th17 and Treg cells, both involved in the harm/protection balance of immune conditions such as autoimmunity or acute transplant rejection. Therefore, the identification of melatonin as a natural modulator of RORα gives it a tremendous therapeutic potential for a variety of clinical disorders.

Protein kinase A activates and phosphorylates RORα4 in vitro and takes part in RORα activation by CaMK-IV

The retinoic acid related orphan receptor RORα positively regulates the transcription of genes important for cerebellar development, immune function, lipid metabolism, and circadian rhythm. In the present study, we identified protein kinase A (PKA) as RORα4 phosphorylating kinase in vitro. The primary sequence of RORα4 contains a PKA recognition motif (R-D-S99) within the c-terminal extension of the DNA-binding domain, and mutation of Ser-99 to Ala prevents RORα4 phosphorylation by PKA. Activation of PKA by dBcAMP results in a marked induction of RORα4 activity. Inhibition of PKA with the selective kinase inhibitor H89 inhibits dBcAMP mediated as well as CaMK-IV triggered increase in RORα4 transcriptional activity. The regulation of RORα activity by PKA as well as CaMK-IV provides a new link in the signalling network that regulates metabolic processes such as glycogen and lipid metabolism.

Screening large numbers of expression patterns of transcription factors in late stages of the mouse thymus

Transcription factor families are well known to be involved in the intrinsic pathways that regulate the organogenesis, early development, and microenvironment of the thymus. However, identification of the transcription factors (TFs) involved in the late development of the thymus, particularly later than embryonic day 15.5 (E15.5), is progressing slowly. In this study, we used in situ hybridization to screen numerous expression patterns of the TFs involved in the development of the mouse thymus. More than 400 members, including unique TFs and some transcription co-factors, were tested. Among the screened TFs, 160 were found to be expressed in the thymus after E15.5, and 74 of these were expressed in restricted areas.

Regulation of metabolism by nuclear hormone receptors

The worldwide epidemic of metabolic disease indicates that a better understanding of the pathways contributing to the pathogenesis of this constellation of diseases need to be determined. Nuclear hormone receptors comprise a superfamily of ligand-activated transcription factors that control development, differentiation, and metabolism. Over the last 15 years a growing number of nuclear receptors have been identified that coordinate genetic networks regulating lipid metabolism and energy utilization. Several of these receptors directly sample the levels of metabolic intermediates and use this information to regulate the synthesis, transport, and breakdown of the metabolite of interest. In contrast, other family members sense metabolic activity via the presence or absence of interacting proteins. The ability of these nuclear receptors to impact metabolism and inflammation will be discussed and the potential of each receptor subfamily to serve as drug targets for metabolic disease will be highlighted.