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

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.

RAR-related orphan receptor alpha and the staggerer mice: a fine molecular story

The retinoic acid-related orphan receptor alpha (RORα) protein first came into the limelight due to a set of staggerer mice, discovered at the Jackson Laboratories in the United States of America by Sidman, Lane, and Dickie (1962) and genetically deciphered by Hamilton et al. in 1996. These staggerer mice exhibited cerebellar defects, an ataxic gait, a stagger along with several other developmental abnormalities, compensatory mechanisms, and, most importantly, a deletion of 160 kilobases (kb), encompassing the RORα ligand binding domain (LBD). The discovery of the staggerer mice and the subsequent discovery of a loss of the LBD within the RORα gene of these mice at the genetic level clearly indicated that RORα's LBD played a crucial role in patterning during embryogenesis. Moreover, a chance study by Roffler-Tarlov and Sidman (1978) noted reduced concentrations of glutamic acid levels in the staggerer mice, indicating a possible role for the essence of a nutritionally balanced diet. The sequential organisation of the building blocks of intact genes, requires the nucleotide bases of deoxyribonucleic acid (DNA): purines and pyrimidines, both of which are synthesized, upon a constant supply of glutamine, an amino acid fortified in a balanced diet and a byproduct of the carbohydrate and lipid metabolic pathways. A nutritionally balanced diet, along with a metabolic "enzymatic machinery" devoid of mutations/aberrations, was essential in the uninterrupted transcription of RORα during embryogenesis. In addition to the above, following translation, a ligand-responsive RORα acts as a "molecular circadian regulator" during embryogenesis and not only is expressed selectively and differentially, but also promotes differential activity depending on the anatomical and pathological site of its expression. RORα is highly expressed in the central nervous system (CNS) and the endocrine organs. Additionally, RORα and the clock genes are core components of the circadian rhythmicity, with the expression of RORα fluctuating in a night-day-night sigmoidal pattern and undoubtedly serves as an endocrine-like, albeit "molecular-circadian regulator". Melatonin, a circadian hormone, along with tri-iodothyronine and some steroid hormones are known to regulate RORα-mediated molecular activity, with each of these hormones themselves being regulated rhythmically by the hypothalamic-pituitary axis (HPA). The HPA regulates the circadian rhythm and cyclical release of hormones, in a self-regulatory feedback loop. Irregular sleep-wake patterns affect circadian rhythmicity and the ability of the immune system to withstand infections. The staggerer mice with their thinner bones, an altered skeletal musculature, an aberrant metabolic profile, the ataxic gait and an underdeveloped cerebellar cortex; exhibited compensatory mechanisms, that not only allowed the survival of the staggerer mice, but also enhanced protection from microbial invasions and resistance to high-fat-diet induced obesity. This review has been compiled in its present form, more than 14 years later after a chromatin immunoprecipitation (ChIP) cloning and sequencing methodology helped me identify signal transducer and activator of transcription 5 (STAT5) target sequences, one of which was mapped to the first intron of the RORα gene. The 599-base-long sequence containing one consensus TTCNNNGAA (TTCN3GAA) gamma-activated sequence (GAS) and five other non-consensus TTN5AA sequences had been identified from the clones isolated from the STAT5 target sites (fragments) in human phytohemagglutinin-activated CD8+ T lymphocytes, during my doctoral studies between 2006 and 2009. Most importantly, preliminary studies noted a unique RORα expression profile, during a time-course study on the ribonucleic acid (RNA), extracted from human phytohemagglutinin (PHA) activated CD8+ T lymphocytes stimulated with interleukin-2 (IL-2). This review mainly focuses on the "staggerer mice" with one of its first roles materialising during embryogenesis, a molecular-endocrine mediated circadian-like regulatory process.

House dust mite and Th2 cytokine-mediated epithelial barrier dysfunction attenuation by KL001 in 16-HBE cells

House dust mite (HDM) is a common aeroallergen that can disrupt the airway epithelial barrier leading to dysregulated immune response, resulting in allergic lung diseases such as asthma. Cryptochrome (CRY), a circadian clock gene, plays an important role in the regulation of metabolism, and immune response. It remains unclear whether stabilizing CRY using KL001 can attenuate HDM/Th2 cytokine-induced epithelial barrier dysfunction in 16-HBE cells. We evaluate the effect of KL001 (20 µM) pre-treatment (4 hrs) in HDM/Th2 cytokine (IL-4 or IL-13)-mediated change in epithelial barrier function. HDM and Th2 cytokine-induced changes in transepithelial electrical resistance (TEER) were determined by an xCELLigence real-time cell analyzer and delocalization of adherens junction complex (AJC: E-cadherin and β-catenin) and tight junction proteins (TJP: Occludin and Zonula occludens-1) by immunostaining and confocal microscopy. Finally, quantitative real-time PCR (qRT-PCR) and Western blotting were used to measure altered gene expression and protein abundance of the epithelial barrier function and core clock genes, respectively. HDM and Th2 cytokine treatment significantly decreased TEER associated with altered gene expression and protein abundance of the selected epithelial barrier function and circadian clock genes. However, pre-treatment with KL001 attenuated HDM and Th2 cytokine-induced epithelial barrier dysfunction as early as 12-24 hrs. KL001 pre-treatment showed attenuation of HDM and Th2 cytokine-induced alteration in the localization and gene expression of AJP and TJP (Cdh1, Ocln, and Zo1) and core clock genes (Clock, Arntl/Bmal1, Cry1/2, Per1/2, Nr1d1/Rev-erbα, and Nfil3). We demonstrate, for the first time, the protective role of KL001 in HDM and Th2 cytokine-mediated epithelial barrier dysfunction.

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.

Andrographolide Inhibition of Th17-Regulated Cytokines and JAK1/STAT3 Signaling in OVA-Stimulated Asthma in Mice

Asthma has long been considered a disease of airway inflammation. The excessive or prolonged production of inflammatory mediators can result in airway remodeling and severe clinical syndromes such as dyspnea or even apnea. Therefore, pharmaceutical intervention is required to restrain the excessive release of such inflammatory mediators in control of asthma. Novel therapeutics and mechanistic insight are sought for the management of this chronic inflammatory disease. Andrographolide (AG) is a type of diterpenoid ester compound and is reported to demonstrate multiple properties such as antioxidation and anti-inflammation. However, the anti-inflammatory capacity of AG by regulating immunologic function in airway of asthma has not been fully studied to date. Therefore, this study investigates whether AG is capable of suppressing the inflammatory response of asthma in OVA-stimulated mice and the mechanism by which this is achieved. Animals were randomly divided into 4 groups: control group, OVA model group, OVA + AG (0.1 mg/ml) group, and OVA + dimethylsulfoxide (DMSO) group. The serum, BALF, and lung tissue of the mice were collected separately for the administration of ELISA, rt-PCR, western blot and pathological section and staining. We found that AG attenuated the OVA-induced production of IL-6, IL-17A, IL-17F, and RORγt; inhibited the OVA-mediated phosphorylation of JAK 1 and STAT3; and alleviated airway remodeling and the neutrophil infiltration of lung tissue. We conclude that AG inhibits the inflammatory response of asthma in OVA-stimulated mice by blocking the activation of Th17-regulated cytokines and the JAK1/STAT3 signaling pathway.

Innate lymphoid cell development

Innate lymphoid cells (ILCs) mainly reside at barrier surfaces and regulate tissue homeostasis and immunity. ILCs are divided into 3 groups, group 1 ILCs, group 2 ILCs, and group 3 ILC3, on the basis of their similar effector programs to T cells. The development of ILCs from lymphoid progenitors in adult mouse bone marrow has been studied in detail, and multiple ILC progenitors have been characterized. ILCs are mostly tissue-resident cells that develop in the perinatal period. More recently, ILC progenitors have also been identified in peripheral tissues. In this review, we discuss the stepwise transcription factor-directed differentiation of mouse ILC progenitors into mature ILCs, the critical time windows in ILC development, and the contribution of bone marrow versus tissue ILC progenitors to the pool of mature ILCs in tissues.

Nuclear Receptors in Asthma: Empowering Classical Molecules Against a Contemporary Ailment

The escalation in living standards and adoption of 'Western lifestyle' has an allied effect on the increased allergy and asthma burden in both developed and developing countries. Current scientific reports bespeak an association between allergic diseases and metabolic dysfunction; hinting toward the critical requirement of organized lifestyle and dietary habits. The ubiquitous nuclear receptors (NRs) translate metabolic stimuli into gene regulatory signals, integrating diet inflences to overall developmental and physiological processes. As a consequence of such promising attributes, nuclear receptors have historically been at the cutting edge of pharmacy world. This review discusses the recent findings that feature the cardinal importance of nuclear receptors and how they can be instrumental in modulating current asthma pharmacology. Further, it highlights a possible future employment of therapy involving dietary supplements and synthetic ligands that would engage NRs and aid in eliminating both asthma and linked comorbidities. Therefore, uncovering new and evolving roles through analysis of genomic changes would represent a feasible approach in both prevention and alleviation of asthma.

Long non-coding RNA TUG1 participates in LPS-induced periodontitis by regulating miR-498/RORA pathway

AIM

This study was aimed to investigate the role of TUG1 in LPS-stimulated hPDLCs and to evaluate the potential functions of TUG1 in the pathogenesis of periodontitis.

METHODS

LPS-stimulated hPDLCs were established as the cell model. CCK-8 assay was performed to assess cell proliferation ability. Flow cytometry was performed to detect cell cycle distribution, and quantitative RT-PCR and Western blotting were conducted to measure gene expressions. ELISA kits were used to evaluate the production of inflammatory cytokines. The putative binding site between TUG1 and miR-498 was verified using luciferase reporter and RNA immunoprecipitation assays.

RESULTS

TUG1 was downregulated upon LPS stimulation in hPDLCs. TUG1 overexpression promoted cell proliferation through regulating the cell cycle distribution, along with the decreased expression of p21 and increased expression of CDK2 and cyclin D1. Besides, TUG1 overexpression decreased the production of inflammatory cytokines. The effects were opposite upon TUG1 knockdown. TUG1 negatively regulated its target miR-498, and influenced the expression of RORA, the direct target of miR-498. Simultaneous TUG1 overexpression and miR-498 reversed the effect of TUG1 overexpression alone on alleviating LPS-induced cell injury and inhibition of Wnt/β-catenin signaling, which was further changeover after co-overexpression with RORA.

CONCLUSION

Therefore, TUG1 could protect against periodontitis via regulating miR-498/RORA mediated Wnt/β-catenin signaling.

Role for Retinoic Acid-Related Orphan Receptor Alpha (RORα) Expressing Macrophages in Diet-Induced Obesity

The transcription factor RORα plays an important role in regulating circadian rhythm, inflammation, metabolism, and cellular development. Herein we show a role for RORα-expressing macrophages in the adipose tissue in altering the metabolic state of mice on a high-fat diet. The expression of Rora and RORA is elevated in white adipose tissue from obese mice and humans when compared to lean counterparts. When fed a high-fat diet Rora reporter mice revealed increased expression of Rora-YFP in macrophages in white adipose tissue deposits. To further define the potential role for Rora-expressing macrophages in the generation of an aberrant metabolic state Rora^fl/flLysM^Cre/+ mice, which do not express Rora in myeloid cells, were maintained on a high-fat diet, and metabolic parameters assessed. These mice had significantly impaired weight gain and improved metabolic parameters in comparison to Rora^fl/fl control mice. Further analysis of the immune cell populations within white adipose tissue deposits demonstrates a decrease in inflammatory adipose tissue macrophages (ATM). In obese reporter mouse there was increased in Rora-YFP expressing ATM in adipose tissue. Analysis of peritoneal macrophage populations demonstrates that within the peritoneal cavity Rora-expression is limited to myeloid-derived macrophages, suggesting a novel role for RORα in macrophage development and activation, which can impact on metabolism, and inflammation.

Association analysis between chronic obstructive pulmonary disease and polymorphisms in circadian genes

Background

Circadian genes have been suggested to play an important role in lung pathology. However, it remains unknown whether polymorphisms of these genes are associated with chronic obstructive pulmonary disease (COPD). Here, we aimed to investigate the association of circadian genes polymorphisms with COPD in a case-control study of 477 COPD patient and 323 control Han Chinese persons.

Methods

Genotyping assays were carried out for nine single nucleotide polymorphisms (SNPs) from five circadian genes (PER3, CLOCK, RORB, BMAL1 and CRY2) that were previously identified in lung pathology. Age, sex, BMI and smoking status and comorbidities were recorded for all subjects.

Results

No significant association was found in all SNP sites in overall subjects and no significant difference was found in age, sex, smoking status stratification analysis.

Discussion

The findings of this investigation indicated the effect of circadian genes polymorphisms on COPD susceptibility may only be small and possibly dependent on the subject factors, such as age and sex.

Treg regulation of the epithelial stem cell lineage

Tissue repair and maintenance in adult organisms is dependent on the interactions between stem cells (SCs) and constituent cells of their microenvironment, or niche. Accumulating evidence suggests that immune cells, specifically Foxp3⁺ CD4⁺ Regulatory T cells (Tregs), play an important role as a regulator of the SC niche. Undisputedly, Tregs are the major immunosuppressive lineage of the CD4⁺ T cell compartment, and reside within numerous secondary lymphoid organs, where they exert their functions. These cells are also specialised in facilitating protective functions specific to their tissue of residence. In this review, we discuss the emerging concepts supporting the SC-regulatory functions of tissue-resident Tregs, during both the steady-state and SC-mediated regeneration. We highlight the skin, intestines, and lung as model organs which are subject to recurrent microinjury,exposure to microbiota, and constantly replenished by resident stem cell populations. An in-depth understanding of the biology of the Treg-SC axis will inform ongoing immunotherapeutic endeavours to target specific subpopulations of tissue-resident Tregs.

Retinoid-related orphan nuclear receptor alpha (RORα)-deficient mice display morphological testicular defects

The role of retinoid-related orphan receptor, one of the transcription factors reported in testis, in testicular function is unclear, so this study was performed to evaluate the qualitative and quantitative changes in the testicular structure of RORα-deficient mice using light-, electron-microscopy, and immunohistochemistry. Among the most striking alterations observed in the testis of the mutant mice were hypospermatogenesis, marked reduction in volume proportions of interstitial tissues and number of Leydig cells, significant decrease in the diameter of seminiferous tubules and height of their epithelium, vacuolation in the epithelium of the seminiferous tubules with occurrence of mast cells, appearance of delay spermiation signs, and changes in sperm morphology. Moreover, the testis of mutant mice showed symplasts, in addition to appearance of multinucleated giant bromophenol-positive cells. ATPase activity was limited to spermatogonia and some primary spermatocytes, with higher alkaline phosphatase expression. Stronger vimentin reaction was immunolocalized to spermatogonia, spermatids, Leydig cells, and Sertoli cells. The expression of CD117 (C-kit, stem cell growth factor receptor) was limited to spermatogonia, primary spermatocytes, and Leydig cells. Seminiferous tubules showed overexpression of vascular endothelial growth factor (VEGF). Transmission electron microscopy examination of the mutant mice revealed abnormal Sertoli cells, hypertrophied spermatogonia, spermatocytes with degenerated mitochondria, and incompletely developed sperms. In conclusion, RORα is one of the essential proteins that regulate testicular structure.

RORα is crucial for attenuated inflammatory response to maintain intestinal homeostasis

Retinoic acid-related orphan receptor α (RORα) functions as a transcription factor for various biological processes, including circadian rhythm, cancer, and metabolism. Here, we generate intestinal epithelial cell (IEC)-specific RORα-deficient (RORα^ΔIEC) mice and find that RORα is crucial for maintaining intestinal homeostasis by attenuating nuclear factor κB (NF-κB) transcriptional activity. RORα^ΔIEC mice exhibit excessive intestinal inflammation and highly activated inflammatory responses in the dextran sulfate sodium (DSS) mouse colitis model. Transcriptome analysis reveals that deletion of RORα leads to up-regulation of NF-κB target genes in IECs. Chromatin immunoprecipitation analysis reveals corecruitment of RORα and histone deacetylase 3 (HDAC3) on NF-κB target promoters and subsequent dismissal of CREB binding protein (CBP) and bromodomain-containing protein 4 (BRD4) for transcriptional repression. Together, we demonstrate that RORα/HDAC3-mediated attenuation of NF-κB signaling controls the balance of inflammatory responses, and therapeutic strategies targeting this epigenetic regulation could be beneficial to the treatment of chronic inflammatory diseases, including inflammatory bowel disease (IBD).

RORA Overexpression Alleviates Nasal Mucosal Injury and Enhances Red Blood Cell Immune Adhesion Function in a Mouse Model of Allergic Rhinitis via Inactivation of the Wnt/β-Catenin Signaling Pathway

BACKGROUND

In this study, we examined whether RORA (retinoic acid receptor-related orphan receptor alpha) was capable of alleviating the progression of allergic rhinitis (AR).

METHODS

In order to elucidate the possible effects of RORA and the regulatory mechanism between RORA and the Wnt/β-catenin signaling pathway, mouse AR models were established and treated with RORA vector, siRNA against RORA, or the Wnt/β-catenin pathway inhibitor WIF-1. Subsequently, the serum levels of inflammatory cytokines (IgE, INF-γ, IL-1β, IL-4, and IL-17), red blood cell (RBC) immune adhesion function, the levels of RORA, β-catenin, and GSK3β, as well as the extent of β-catenin and GSK-3β phosphorylation were evaluated and measured.

RESULTS

The OVA-induced AR mouse model exhibited obvious nasal mucosal injury and inflammatory cell infiltration. RORA overexpression or the inactivation of the Wnt/β-catenin signaling pathway was uncovered as a way to ameliorate nasal mucosal injury and eosinophil infiltration of the OVA-induced AR mouse model. On the other hand, it reduced the number of eosinophils and mast cells, which also resulted in downregulated expression of IgE, INF-γ, IL-1β, IL-4, IL-17, β-catenin, and GSK-3β. Moreover, this led to a decreased extent of β-catenin and GSK-3β phosphorylation, while the rates of C3b receptor rosette and Ic rosette were elevated.

CONCLUSION

Taken together, the key findings provided evidence suggesting that the elevated RORA could potentially alleviate nasal mucosal injury and simultaneously enhance RBC immune adhesion function through the inhibition of the Wnt/β-catenin signaling pathway activation in an OVA-induced AR mouse model. This emphasizes a novel therapeutic target for the treatment of AR.

Genetic variants in RORA are associated with asthma and allergy markers in an admixed population

Asthma and allergy affect hundreds of millions of people from childhood to old age. In most of them, the inflammatory process of respiratory allergies involves the participation of type 2 cytokines, derived from T helper-2 (Th2)-cell, and Group 2 Innate Lymphoid (ILC2) Cells. An efficient memory Th2 cell response is dependent on IL-13 produced by ILC2s, causing allergic lung inflammation and elevated serum levels of immunoglobulin E. ILC2 cells are derived from common lymphoid progenitors and their growing depends on the transcription factor RORA. The aim of this work was to identify genetic variants in RORA associated with asthma phenotypes and allergy markers. Genomic DNA samples of 1246 individuals participating from Social Changes Asthma and Allergy in Latin America Program (SCAALA) have been genotyped using Illumina Human 2.5 Omni Beadchip. Logistics regressions have been performed to analyze the association among RORA variants and asthma, skin prick tests (SPT), specific IgE and type 2 cytokine production. Twelve single nucleotide variants (SNVs) were significantly associated with atopy (P < 0.01), in which four of them, rs10162630, rs17191519, rs17270243, and rs55796775 and their haplotypes were strongly and positively associated (P < 0.001). Furthermore, these variants increased the RORA gene expression in silico analysis. Other SNVs in RORA were associated with allergy markers, atopic and non-atopic asthma. Therefore, it is believed that variants in RORA gene may influence immunologic features of asthma and allergies and could be possible targets for future treatment of allergic diseases.

Insulin-Like Growth Factor-1 Signaling in Lung Development and Inflammatory Lung Diseases

Insulin-like growth factor-1 (IGF-1) was firstly identified as a hormone that mediates the biological effects of growth hormone. Accumulating data have indicated the role of IGF-1 signaling pathway in lung development and diseases such as congenital disorders, cancers, inflammation, and fibrosis. IGF-1 signaling modulates the development and differentiation of many types of lung cells, including airway basal cells, club cells, alveolar epithelial cells, and fibroblasts. IGF-1 signaling deficiency results in alveolar hyperplasia in humans and disrupted lung architecture in animal models. The components of IGF-1 signaling pathways are potentiated as biomarkers as they are dysregulated locally or systemically in lung diseases, whereas data may be inconsistent or even paradoxical among different studies. The usage of IGF-1-based therapeutic agents urges for more researches in developmental disorders and inflammatory lung diseases, as the majority of current data are collected from limited number of animal experiments and are generally less exuberant than those in lung cancer. Elucidation of these questions by further bench-to-bedside researches may provide us with rational clinical diagnostic approaches and agents concerning IGF-1 signaling in lung diseases.

The association of RAR-related orphan receptor A (RORA) gene polymorphisms with the risk of asthma

Asthma is a common, heterogeneous chronic respiratory disease characterized by chronic inflammation of the airway, airway hyperreactivity, and airway remodeling. The RAR-related orphan receptor A (RORA) gene has been identified for the pathogenesis of asthma. The purpose of this research was to investigate the relationship between RORA gene polymorphisms and asthma susceptibility in the Chinese Zhuang population. This was a case-control study including 231 children with asthma and 343 healthy controls. The RORA gene polymorphisms were measured by the polymerase chain reaction-ligase detection reaction genotyping assays and confirmed by sequencing. The distribution of the genotype frequencies of the RORA rs11071559 C>T was significantly different in the group of cases and the healthy children (P < 0.05). By haplotype analyses, the haplotype TT (rs7164773/rs11071559) was statistically significant between asthmatics and nonasthmatics, but the association was not significant after correction for multiple comparisons. Our results provided evidence that the RORA rs11071559C>T polymorphism was associated with an elevated susceptibility to pediatric asthma in the Chinese Zhuang population.

National Institute of Environmental Health Sciences: 50 Years of Advancing Science and Improving Lung Health

The American Thoracic Society celebrates the 50th anniversary of the National Institute of Environmental Health Sciences (NIEHS). The NIEHS has had enormous impact through its focus on research, training, and translational science on lung health. It has been an advocate for clean air both in the United States and across the world. The cutting-edge science funded by the NIEHS has led to major discoveries that have broadened our understanding of the pathogenesis and treatment for lung disease. Importantly, the NIEHS has developed and fostered mechanisms that require cross-cutting science across the spectrum of areas of inquiry, bringing together environmental and social scientists with clinicians to bring their expertise on specific areas of investigation. The intramural program of the NIEHS nurtures cutting-edge science, and the extramural program encourages investigator-initiated research while at the same time providing broader direction through important initiatives. Under the umbrella of the NIEHS and guided by Dr. Linda Birnbaum, the director of the NIEHS, important collaborative programs, such as the Superfund Program and the National Toxicology Program, work to discover mechanisms to protect from environmental toxins. The American Thoracic Society has overlapping goals with the NIEHS, and the strategic plans of both august bodies converge to synergize on population lung health. These bonds must be tightened and highlighted as we work toward our common goals.

Retinoic acid receptor-related orphan receptor α stimulates adipose tissue inflammation by modulating endoplasmic reticulum stress

Adipose tissue inflammation has been linked to metabolic diseases such as obesity and type 2 diabetes. However, the molecules that mediate inflammation in adipose tissue have not been addressed. Although retinoic acid receptor-related orphan receptor α (RORα) is known to be involved in the regulation of inflammatory response in some tissues, its role is largely unknown in adipose tissue. Conversely, it is known that endoplasmic reticulum (ER) stress and unfolding protein response (UPR) signaling affect the inflammatory response in obese adipose tissue, but whether RORα regulates these processes remains unknown. In this study, we investigate the link between RORα and adipose tissue inflammation. We showed that the inflammatory response in macrophages or 3T3-L1 adipocytes stimulated by lipopolysaccharide, as well as adipose tissue in obese mice, markedly increased the expression of RORα. Adenovirus-mediated overexpression of RORα or treatment with the RORα-specific agonist SR1078 enhanced the expression of inflammatory cytokines and increased the number of infiltrated macrophages into adipose tissue. Furthermore, SR1078 up-regulated the mRNA expression of ER stress response genes and enhanced phosphorylations of two of the three mediators of major UPR signaling pathways, PERK and IRE1α. Finally, we found that alleviation of ER stress using a chemical chaperone followed by the suppression of RORα induced inflammation in adipose tissue. Our data suggest that RORα-induced ER stress response potentially contributes to the adipose tissue inflammation that can be mitigated by treatment with chemical chaperones. The relationships established here between RORα expression, inflammation, and UPR signaling may have implications for therapeutic targeting of obesity-related metabolic diseases.

Circadian Rhythms in Adipose Tissue Physiology

The different types of adipose tissues fulfill a wide range of biological functions-from energy storage to hormone secretion and thermogenesis-many of which show pronounced variations over the course of the day. Such 24-h rhythms in physiology and behavior are coordinated by endogenous circadian clocks found in all tissues and cells, including adipocytes. At the molecular level, these clocks are based on interlocked transcriptional-translational feedback loops comprised of a set of clock genes/proteins. Tissue-specific clock-controlled transcriptional programs translate time-of-day information into physiologically relevant signals. In adipose tissues, clock gene control has been documented for adipocyte proliferation and differentiation, lipid metabolism as well as endocrine function and other adipose oscillations are under control of systemic signals tied to endocrine, neuronal, or behavioral rhythms. Circadian rhythm disruption, for example, by night shift work or through genetic alterations, is associated with changes in adipocyte metabolism and hormone secretion. At the same time, adipose metabolic state feeds back to central and peripheral clocks, adjusting behavioral and physiological rhythms. In this overview article, we summarize our current knowledge about the crosstalk between circadian clocks and energy metabolism with a focus on adipose physiology. © 2017 American Physiological Society. Compr Physiol 7:383-427, 2017.

Retinoic Acid-Related Orphan Receptors (RORs): Regulatory Functions in Immunity, Development, Circadian Rhythm, and Metabolism

In this overview, we provide an update on recent progress made in understanding the mechanisms of action, physiological functions, and roles in disease of retinoic acid related orphan receptors (RORs). We are particularly focusing on their roles in the regulation of adaptive and innate immunity, brain function, retinal development, cancer, glucose and lipid metabolism, circadian rhythm, metabolic and inflammatory diseases and neuropsychiatric disorders. We also summarize the current status of ROR agonists and inverse agonists, including their regulation of ROR activity and their therapeutic potential for management of various diseases in which RORs have been implicated.

Circadian molecular clock in lung pathophysiology

Disrupted daily or circadian rhythms of lung function and inflammatory responses are common features of chronic airway diseases. At the molecular level these circadian rhythms depend on the activity of an autoregulatory feedback loop oscillator of clock gene transcription factors, including the BMAL1:CLOCK activator complex and the repressors PERIOD and CRYPTOCHROME. The key nuclear receptors and transcription factors REV-ERBα and RORα regulate Bmal1 expression and provide stability to the oscillator. Circadian clock dysfunction is implicated in both immune and inflammatory responses to environmental, inflammatory, and infectious agents. Molecular clock function is altered by exposomes, tobacco smoke, lipopolysaccharide, hyperoxia, allergens, bleomycin, as well as bacterial and viral infections. The deacetylase Sirtuin 1 (SIRT1) regulates the timing of the clock through acetylation of BMAL1 and PER2 and controls the clock-dependent functions, which can also be affected by environmental stressors. Environmental agents and redox modulation may alter the levels of REV-ERBα and RORα in lung tissue in association with a heightened DNA damage response, cellular senescence, and inflammation. A reciprocal relationship exists between the molecular clock and immune/inflammatory responses in the lungs. Molecular clock function in lung cells may be used as a biomarker of disease severity and exacerbations or for assessing the efficacy of chronotherapy for disease management. Here, we provide a comprehensive overview of clock-controlled cellular and molecular functions in the lungs and highlight the repercussions of clock disruption on the pathophysiology of chronic airway diseases and their exacerbations. Furthermore, we highlight the potential for the molecular clock as a novel chronopharmacological target for the management of lung pathophysiology.

Retinoic Acid-Related Orphan Receptors (RORs): Regulatory Functions in Immunity, Development, Circadian Rhythm, and Metabolism

In this overview, we provide an update on recent progress made in understanding the mechanisms of action, physiological functions, and roles in disease of retinoic acid related orphan receptors (RORs). We are particularly focusing on their roles in the regulation of adaptive and innate immunity, brain function, retinal development, cancer, glucose and lipid metabolism, circadian rhythm, metabolic and inflammatory diseases and neuropsychiatric disorders. We also summarize the current status of ROR agonists and inverse agonists, including their regulation of ROR activity and their therapeutic potential for management of various diseases in which RORs have been implicated.

Genetic variations in RORα are associated with chronic obstructive pulmonary disease

Retinoic acid receptor-related orphan receptor-α (RORα) plays a key role in the regulation of lipid and cholesterol metabolism that has been implicated in the development of chronic obstructive pulmonary disease (COPD). The aim of this study was to determine the frequencies of single-nucleotide polymorphisms (SNPs) in RORα gene in a Chinese population and their possible association with COPD susceptibility. Nine tagging SNPs, including rs17270181, rs1898413, rs17270216, rs8033552, rs8036966, rs7169364, rs340002, rs340023 and rs11630262, were screened in 279 COPD patients and 367 controls by the SNaPshot method. Association analysis of genotypes and haplotypes constructed from these loci with COPD was conducted under different genetic models. Alleles or genotypes of rs8033552 distributed significantly differently in COPD patients and controls (allele: P=0.0001, false discovery rate (FDR) Q=0.004, odds ratios (OR): 1.62 and 95% confidence interval (CI): 1.27-2.07; genotype: P=0.0005, FDR Q=0.008). The allele A at rs8033552 was potentially associated with an increased risk of COPD in additive model, displaying ORs of 1.62 (95% CI: 1.17-2.26, P=0.004, FDR Q=0.019) in subjects with genotypes AG vs GG and 2.69 (95% CI: 1.47-4.93, P=0.001, FDR Q=0.011) in subjects with genotypes AA vs GG, respectively. In haplotype analysis, we observed haplotypes GGAGATGTG and GGAGCTGTG had protective effects, whereas haplotypes GGAGATACA and GGAGATACG were significantly associated with the increased risk of COPD. These data suggest that RORα may be a potential risk gene for COPD.

Development and function of group 2 innate lymphoid cells

The innate lymphoid cell (ILC) family has recently expanded with the discovery of type-2 innate lymphoid cells (ILC2). These cells arise from lymphoid progenitors in the bone marrow and, under the control of the transcriptional regulators RORα and Gata3, they mature to give rise to IL-5, IL-9 and IL-13 producing ILC2. These cells are critical components of the innate immune response to parasitic worm infections and have also been implicated in the pathogenesis of asthma and allergy. Recent advances in our understanding of the molecular regulation of ILC2 development and function now present the opportunity to develop new genetic models to assess ILC2 immune function and to investigate possible therapeutic interventions.

Interaction between retinoid acid receptor-related orphan receptor alpha (RORA) and neuropeptide S receptor 1 (NPSR1) in asthma

Retinoid acid receptor-related Orphan Receptor Alpha (RORA) was recently identified as a susceptibility gene for asthma in a genome-wide association study. To investigate the impact of RORA on asthma susceptibility, we performed a genetic association study between RORA single nucleotide polymorphisms (SNPs) in the vicinity of the asthma-associated SNP (rs11071559) and asthma-related traits. Because the regulatory region of a previously implicated asthma susceptibility gene, Neuropeptide S receptor 1 (NPSR1), has predicted elements for RORA binding, we hypothesized that RORA may interact biologically and genetically with NPSR1. 37 RORA SNPs and eight NPSR1 SNPs were genotyped in the Swedish birth cohort BAMSE (2033 children) and the European cross-sectional PARSIFAL study (1120 children). Seven RORA SNPs confined into a 49 kb region were significantly associated with physician-diagnosed childhood asthma. The most significant association with rs7164773 (T/C) was driven by the CC genotype in asthma cases (OR = 2.0, 95%CI 1.36-2.93, p = 0.0003 in BAMSE; and 1.61, 1.18-2.19, p = 0.002 in the combined BAMSE-PARSIFAL datasets, respectively), and strikingly, the risk effect was dependent on the Gln344Arg mutation in NPSR1. In cell models, stimulation of NPSR1 activated a pathway including RORA and other circadian clock genes. Over-expression of RORA decreased NPSR1 promoter activity further suggesting a regulatory loop between these genes. In addition, Rora mRNA expression was lower in the lung tissue of Npsr1 deficient mice compared to wildtype littermates during the early hours of the light period. We conclude that RORA SNPs are associated with childhood asthma and show epistasis with NPSR1, and the interaction between RORA and NPSR1 may be of biological relevance. Combinations of common susceptibility alleles and less common functional polymorphisms may modify the joint risk effects on asthma susceptibility.

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.

Increased peripheral RORα and RORγt mRNA expression is associated with acute-on-chronic hepatitis B liver failure

T helper cells17 (Th17) have accurate but inconclusive roles in the pathogenesis of acute-on-chronic hepatitis B liver failure (ACHBLF). Retinoic acid-related orphan receptor γ t(RORγt) and RORα are two lineage-specific nuclear receptors directly mediating Th17 differentiation. This study was aimed to evaluate the gene expression of RORα and RORγt and their potential role in ACHBLF. Forty patients with liver failure, 30 with chronic hepatitis B (CHB) and 20 healthy controls were studied. The mRNA levels of RORα and RORγt in peripheral mononuclear cells were determined by quantitative real-time polymerase chain reaction. The frequency of peripheral Th17 cells was determined using flow cytometry. The serum levels of interleukin-6(IL-6), transforming growth factor -β (TGF-β), interleukin-17(IL-17), interleukin-23(IL-23) and interferon-γ (IFN-γ) were measured by enzyme-linked immunosorbent assay. The frequency of peripheral Th17 cells in patients with liver failure was significantly increased compared to patients with CHB and controls. The peripheral mRNA levels of RORα and RORγt in hepatitis B-associated acute-on-chronic liver failure were significantly higher than in patients with CHB and controls as were the serum levels of IL-6 and TGF-β. The serum level of IFN-γ in patients with acute-on-chronic liver failure from HBV was significantly higher than patients with CHB but lower than controls. In patients with acute-on-chronic liver failure associated with HBV, RORγt, IL-6 and IL-23 were positively correlated with the frequency of Th17 cells, while RORα, TGF-β and IFN-γ had no correlation with the latter. The mRNA level of RORγt was positively correlated with model of end-stage liver disease (MELD) score, but there was no correlation of RORα and MELD score. RORγt plays an important role in the pathogenesis of acute-on-chronic HBV-associated liver failure and might be considered to be a candidate factor consistent with the severity of disease.

RAGE: a new frontier in chronic airways disease

Asthma and chronic obstructive pulmonary disease (COPD) are heterogeneous inflammatory disorders of the respiratory tract characterized by airflow obstruction. It is now clear that the environmental factors that drive airway pathology in asthma and COPD, including allergens, viruses, ozone and cigarette smoke, activate innate immune receptors known as pattern-recognition receptors, either directly or indirectly by causing the release of endogenous ligands. Thus, there is now intense research activity focused around understanding the mechanisms by which pattern-recognition receptors sustain the airway inflammatory response, and how these mechanisms might be targeted therapeutically. One pattern-recognition receptor that has recently come to attention in chronic airways disease is the receptor for advanced glycation end products (RAGE). RAGE is a member of the immunoglobulin superfamily of cell surface receptors that recognizes pathogen- and host-derived endogenous ligands to initiate the immune response to tissue injury, infection and inflammation. Although the role of RAGE in lung physiology and pathophysiology is not well understood, recent genome-wide association studies have linked RAGE gene polymorphisms with airflow obstruction. In addition, accumulating data from animal and clinical investigations reveal increased expression of RAGE and its ligands, together with reduced expression of soluble RAGE, an endogenous inhibitor of RAGE signalling, in chronic airways disease. In this review, we discuss recent studies of the ligand-RAGE axis in asthma and COPD, highlight important areas for future research and discuss how this axis might potentially be harnessed for therapeutic benefit in these conditions.

Genome-wide association studies of asthma in population-based cohorts confirm known and suggested loci and identify an additional association near HLA

RATIONALE

Asthma has substantial morbidity and mortality and a strong genetic component, but identification of genetic risk factors is limited by availability of suitable studies.

OBJECTIVES

To test if population-based cohorts with self-reported physician-diagnosed asthma and genome-wide association (GWA) data could be used to validate known associations with asthma and identify novel associations.

METHODS

The APCAT (Analysis in Population-based Cohorts of Asthma Traits) consortium consists of 1,716 individuals with asthma and 16,888 healthy controls from six European-descent population-based cohorts. We examined associations in APCAT of thirteen variants previously reported as genome-wide significant (P<5 x 10(-8)) and three variants reported as suggestive (P<5× 10(-7)). We also searched for novel associations in APCAT (Stage 1) and followed-up the most promising variants in 4,035 asthmatics and 11,251 healthy controls (Stage 2). Finally, we conducted the first genome-wide screen for interactions with smoking or hay fever.

MAIN RESULTS

We observed association in the same direction for all thirteen previously reported variants and nominally replicated ten of them. One variant that was previously suggestive, rs11071559 in RORA, now reaches genome-wide significance when combined with our data (P = 2.4 × 10(-9)). We also identified two genome-wide significant associations: rs13408661 near IL1RL1/IL18R1 (P(Stage1+Stage2) = 1.1x10(-9)), which is correlated with a variant recently shown to be associated with asthma (rs3771180), and rs9268516 in the HLA region (P(Stage1+Stage2) = 1.1x10(-8)), which appears to be independent of previously reported associations in this locus. Finally, we found no strong evidence for gene-environment interactions with smoking or hay fever status.

CONCLUSIONS

Population-based cohorts with simple asthma phenotypes represent a valuable and largely untapped resource for genetic studies of asthma.

Retinoic-acid-receptor-related orphan nuclear receptor alpha is required for natural helper cell development and allergic inflammation

Natural helper (NH) cells are innate lymphoid cells (ILCs) that produce T helper-2 (Th2)-cell-type cytokines in the lung- and gut-associated lymphoid tissues. Currently, the lineage relationship between NH cells in different tissues and between NH cells and interleukin-22 (IL-22)-producing retinoic-acid-receptor-related orphan receptor (ROR)γt-positive ILCs is unclear. Here, we report that NH cells express RORα, but not RORγt. RORα-deficient, but not RORγt-deficient, mice lacked NH cells in all tissues, whereas all other lymphocytes, including RORγt(+) ILCs, were unaffected. NH-cell-deficient mice generated by RORα-deficient bone-marrow transplantation had normal Th2 cell responses but failed to develop acute lung inflammation in response to protease allergen, thus confirming the essential role of NH cells in allergic lung inflammation. We have also identified RORα-dependent NH cell progenitors in the bone marrow. Thus, all NH cells belong to a unique RORα-dependent cell lineage separate from other lymphoid cell lineages.

RORγ directly regulates the circadian expression of clock genes and downstream targets in vivo

In this study, we demonstrate that the lack of retinoic acid-related orphan receptor (ROR) γ or α expression in mice significantly reduced the peak expression level of Cry1, Bmal1, E4bp4, Rev-Erbα and Per2 in an ROR isotype- and tissue-selective manner without affecting the phase of their rhythmic expression. Analysis of RORγ/RORα double knockout mice indicated that in certain tissues RORγ and RORα exhibited a certain degree of redundancy in regulating clock gene expression. Reporter gene analysis showed that RORγ was able to induce reporter gene activity through the RORE-containing regulatory regions of Cry1, Bmal1, Rev-Erbα and E4bp4. Co-expression of Rev-Erbα or addition of a novel ROR antagonist repressed this activation. ChIP-Seq and ChIP-Quantitative real-time polymerase chain reaction (QPCR) analysis demonstrated that in vivo RORγ regulate these genes directly and in a Zeitgeber time (ZT)-dependent manner through these ROREs. This transcriptional activation by RORs was associated with changes in histone acetylation and chromatin accessibility. The rhythmic expression of RORγ1 by clock proteins may lead to the rhythmic expression of RORγ1 target genes. The presence of RORγ binding sites and its down-regulation in RORγ-/- liver suggest that the rhythmic expression of Avpr1a depends on RORγ consistent with the concept that RORγ1 provides a link between the clock machinery and its regulation of metabolic genes.

Retinoid-related orphan receptor alpha and the regulation of lipid homeostasis

Many nuclear hormone receptors (NRs) control lipid, glucose and energy homeostasis in an organ specific manner. Concordantly, dysfunctional NR signalling results in metabolic disease. The Retinoic acid receptor-related orphan receptor alpha (RORα), a member of the NR1F subgroup, is expressed in metabolic tissues. Previous studies identified the role of this NR in dyslipidemia, apo-lipoprotein metabolism and atherosclerosis. Recent data is underscoring the significant role of this orphan NR in the regulation of phase I/II metabolism (bile acids, xenobiotics, steroids etc.), adiposity, insulin signalling, and glucose tolerance. Moreover, oxygenated sterols, have been demonstrated to function as native ligands and inverse agonists. This review focuses on the rapidly emerging and evolving role of RORα in the control of lipid and glucose homeostasis in major mass metabolic tissues. Article from the special issue orphan receptors.

Retinoic acid-related orphan receptor-α is induced in the setting of DNA damage and promotes pulmonary emphysema

RATIONALE

The discovery that retinoic acid-related orphan receptor (Rora)-α is highly expressed in lungs of patients with COPD led us to hypothesize that Rora may contribute to the pathogenesis of emphysema.

OBJECTIVES

To determine the role of Rora in smoke-induced emphysema.

METHODS

Cigarette smoke extract in vitro and elastase or cigarette smoke exposure in vivo were used to model smoke-related cell stress and airspace enlargement. Lung tissue from patients undergoing lung transplantation was examined for markers of DNA damage and Rora expression.

MEASUREMENTS AND MAIN RESULTS

Rora expression was induced by cigarette smoke in mice and in cell culture. Gene expression profiling of Rora-null mice exposed to cigarette smoke demonstrated enrichment for genes involved in DNA repair. Rora expression increased and Rora translocated to the nucleus after DNA damage. Inhibition of ataxia telangiectasia mutated decreased the induction of Rora. Gene silencing of Rora attenuated apoptotic cell death in response to cigarette smoke extract, whereas overexpression of Rora enhanced apoptosis. Rora-deficient mice were protected from elastase and cigarette smoke induced airspace enlargement. Finally, lungs of patients with COPD showed evidence of increased DNA damage even in the absence of active smoking.

CONCLUSIONS

Taken together, these findings suggest that DNA damage may contribute to the pathogenesis of emphysema, and that Rora has a previously unrecognized role in cellular responses to genotoxicity. These findings provide a potential link between emphysema and features of premature ageing, including enhanced susceptibility to lung cancer.

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.

Innate lymphoid cells in the airways

The airways, similar to other mucosal surfaces, are continuously exposed to the outside environment and a barrage of antigens, allergens, and microorganisms. Of critical importance therefore is the ability to mount rapid and effective immune responses to control commensal and pathogenic microbes, while simultaneously limiting the extent of these responses to prevent immune pathology and chronic inflammation. The function of the adaptive immune response in controlling these processes at mucosal surfaces has been well documented but the important role of the innate immune system, particularly the recently identified family of innate lymphoid cells, has only lately become apparent. In this review, we give an overview of the innate lymphoid cells that exist in the airways and examine the evidence pertaining to their emerging roles in airways immunity, inflammation, and homeostasis.

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.

Increased expression of IRF4 and ETS1 in CD4+ cells from patients with intermittent allergic rhinitis

BACKGROUND

  The transcription factor (TF) IRF4 is involved in the regulation of Th1, Th2, Th9, and Th17 cells, and animal studies have indicated an important role in allergy. However, IRF4 and its target genes have not been examined in human allergy.

METHODS

  IRF4 and its target genes were examined in allergen-challenged CD4(+) cells from patients with IAR, using combined gene expression microarrays and chromatin immunoprecipitation chips (ChIP-chips), computational target prediction, and RNAi knockdowns.

RESULTS

  IRF4 increased in allergen-challenged CD4(+) cells from patients with IAR, and functional studies supported its role in Th2 cell activation. IRF4 ChIP-chip showed that IRF4 regulated a large number of genes relevant to Th cell differentiation. However, neither Th1 nor Th2 cytokines were the direct targets of IRF4. To examine whether IRF4 induced Th2 cytokines via one or more downstream TFs, we combined gene expression microarrays, ChIP-chips, and computational target prediction and found a putative intermediary TF, namely ETS1 in allergen-challenged CD4(+) cells from allergic patients. ETS1 increased significantly in allergen-challenged CD4(+) cells from patients compared to controls. Gene expression microarrays before and after ETS1 RNAi knockdown showed that ETS1 induced Th2 cytokines as well as disease-related pathways.

CONCLUSIONS

  Increased expression of IRF4 in allergen-challenged CD4(+) cells from patients with intermittent allergic rhinitis leads to activation of a complex transcriptional program, including Th2 cytokines.

Age-related Purkinje cell death is steroid dependent: RORα haplo-insufficiency impairs plasma and cerebellar steroids and Purkinje cell survival

A major problem of ageing is progressive impairment of neuronal function and ultimately cell death. Since sex steroids are neuroprotective, their decrease with age may underlie age-related neuronal degeneration. To test this, we examined Purkinje cell numbers, plasma sex steroids and cerebellar neurosteroid concentrations during normal ageing (wild-type mice, WT), in our model of precocious ageing (Rora(+/sg), heterozygous staggerer mice in which expression of the neuroprotective factor RORα is disrupted) and after long-term hormone insufficiency (WT post-gonadectomy). During normal ageing (WT), circulating sex steroids declined prior to or in parallel with Purkinje cell loss, which began at 18 months of age. Although Purkinje cell death was advanced in WT long-term steroid deficiency, this premature neuronal loss did not begin until 9 months, indicating that vulnerability to sex steroid deficiency is a phenomenon of ageing Purkinje neurons. In precocious ageing (Rora(+/sg)), circulating sex steroids decreased prematurely, in conjunction with marked Purkinje cell death from 9 months. Although Rora(+/sg) Purkinje cells are vulnerable through their RORα haplo-insufficiency, it is only as they age (after 9 months) that sex steroid failure becomes critical. Finally, cerebellar neurosteroids did not decrease with age in either genotype or gender; but were profoundly reduced by 3 months in male Rora(+/sg) cerebella, which may contribute to the fragility of their Purkinje neurons. These data suggest that ageing Purkinje cells are maintained by circulating sex steroids, rather than local neurosteroids, and that in Rora(+/sg) their age-related death is advanced by premature sex steroid loss induced by RORα haplo-insufficiency.

Identification of an IFN-γ/mast cell axis in a mouse model of chronic asthma

Asthma is considered a Th2 cell–associated disorder. Despite this, both the Th1 cell–associated cytokine IFN-γ and airway neutrophilia have been implicated in severe asthma. To investigate the relative contributions of different immune system components to the pathogenesis of asthma, we previously developed a model that exhibits several features of severe asthma in humans, including airway neutrophilia and increased lung IFN-γ. In the present studies, we tested the hypothesis that IFN-γ regulates mast cell function in our model of chronic asthma. Engraftment of mast cell–deficient KitW(-sh/W-sh) mice, which develop markedly attenuated features of disease, with wild-type mast cells restored disease pathology in this model of chronic asthma. However, disease pathology was not fully restored by engraftment with either IFN-γ receptor 1–null (Ifngr1–/–) or Fcε receptor 1γ–null (Fcer1g–/–) mast cells. Additional analysis, including gene array studies, showed that mast cell expression of IFN-γR contributed to the development of many FcεRIγ-dependent and some FcεRIγ-independent features of disease in our model, including airway hyperresponsiveness, neutrophilic and eosinophilic inflammation, airway remodeling, and lung expression of several cytokines, chemokines, and markers of an alternatively activated macrophage response. These findings identify a previously unsuspected IFN-γ/mast cell axis in the pathology of chronic allergic inflammation of the airways in mice.

The Fox and the Rabbits-Environmental Variables and Population Genetics (1) Replication Problems in Association Studies and the Untapped Power of GWAS (2) Vitamin A Deficiency, Herpes Simplex Reactivation and Other Causes of Alzheimer's Disease

Classical population genetics shows that varying permutations of genes and risk factors permit or disallow the effects of causative agents, depending on circumstance. For example, genes and environment determine whether a fox kills black or white rabbits on snow or black ash covered islands. Risk promoting effects are different on each island, but obscured by meta-analysis or GWAS data from both islands, unless partitioned by different contributory factors. In Alzheimer's disease, the foxes appear to be herpes, borrelia or chlamydial infection, hypercholesterolemia, hyperhomocysteinaemia, diabetes, cerebral hypoperfusion, oestrogen depletion, or vitamin A deficiency, all of which promote beta-amyloid deposition in animal models—without the aid of gene variants. All relate to risk factors and subsets of susceptibility genes, which condition their effects. All are less prevalent in convents, where nuns appear less susceptible to the ravages of ageing. Antagonism of the antimicrobial properties of beta-amyloid by Abeta autoantibodies in the ageing population, likely generated by antibodies raised to beta-amyloid/pathogen protein homologues, may play a role in this scenario. These agents are treatable by diet and drugs, vitamin supplementation, pathogen detection and elimination, and autoantibody removal, although again, the beneficial effects of individual treatments may be tempered by genes and environment.

Expression analysis of asthma candidate genes during human and murine lung development

BACKGROUND

Little is known about the role of most asthma susceptibility genes during human lung development. Genetic determinants for normal lung development are not only important early in life, but also for later lung function.

OBJECTIVE

To investigate the role of expression patterns of well-defined asthma susceptibility genes during human and murine lung development. We hypothesized that genes influencing normal airways development would be over-represented by genes associated with asthma.

METHODS

Asthma genes were first identified via comprehensive search of the current literature. Next, we analyzed their expression patterns in the developing human lung during the pseudoglandular (gestational age, 7-16 weeks) and canalicular (17-26 weeks) stages of development, and in the complete developing lung time series of 3 mouse strains: A/J, SW, C57BL6.

RESULTS

In total, 96 genes with association to asthma in at least two human populations were identified in the literature. Overall, there was no significant over-representation of the asthma genes among genes differentially expressed during lung development, although trends were seen in the human (Odds ratio, OR 1.22, confidence interval, CI 0.90-1.62) and C57BL6 mouse (OR 1.41, CI 0.92-2.11) data. However, differential expression of some asthma genes was consistent in both developing human and murine lung, e.g. NOD1, EDN1, CCL5, RORA and HLA-G. Among the asthma genes identified in genome wide association studies, ROBO1, RORA, HLA-DQB1, IL2RB and PDE10A were differentially expressed during human lung development.

CONCLUSIONS

Our data provide insight about the role of asthma susceptibility genes during lung development and suggest common mechanisms underlying lung morphogenesis and pathogenesis of respiratory diseases.

Transcriptional profiling reveals a role for RORalpha in regulating gene expression in obesity-associated inflammation and hepatic steatosis

Retinoid-related orphan receptor (ROR)α4 is the major RORα isoform expressed in adipose tissues and liver. In this study we demonstrate that RORα-deficient staggerer mice (RORα(sg/sg)) fed with a high-fat diet (HFD) exhibited reduced adiposity and hepatic triglyceride levels compared with wild-type (WT) littermates and were resistant to the development of hepatic steatosis, adipose-associated inflammation, and insulin resistance. Gene expression profiling showed that many genes involved in triglyceride synthesis and storage, including Cidec, Cidea, and Mogat1, were expressed at much lower levels in liver of RORα(sg/sg) mice. In contrast, overexpression of RORα in mouse hepatoma Hepa1-6 cells significantly increased the expression of genes that were repressed in RORα(sg/sg) liver, including Sult1b1, Adfp, Cidea, and ApoA4. ChIP and promoter analysis suggested that several of these genes were regulated directly by RORα. In addition to reduced lipid accumulation, inflammation was greatly diminished in white adipose tissue (WAT) of RORα(sg/sg) mice fed with an HFD. The infiltration of macrophages and the expression of many immune response and proinflammatory genes, including those encoding various chemo/cytokines, Toll-like receptors, and TNF signaling proteins, were significantly reduced in RORα(sg/sg) WAT. Moreover, RORα(sg/sg) mice fed with an HFD were protected from the development of insulin resistance. RORα(sg/sg) mice consumed more oxygen and produced more carbon dioxide, suggesting increased energy expenditure in this genotype. Our study indicates that RORα plays a critical role in the regulation of several aspects of metabolic syndrome. Therefore, RORα may provide a novel therapeutic target in the management of obesity and associated metabolic diseases.

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.

Retinoic acid-related orphan receptor γ directly regulates neuronal PAS domain protein 2 transcription in vivo

Retinoic acid-related orphan receptors (RORs) and the basic helix–loop–helix-PAS transcription factor Npas2 have been implicated in the control of circadian rhythm. In this study, we demonstrate that RORγ directly regulates Npas2 expression in vivo. Although the rhythmicity of Npas2 mRNA expression was maintained in RORγ^−/− mice, the peak level of expression was significantly reduced in several tissues, while loss of RORα had little effect. Inversely, overexpression of RORγ in hepatoma Hepa1-6 cells greatly induced the expression of Npas2. RORγ-activated Npas2 transcription directly by binding two ROREs in its proximal promoter. ChIP analysis demonstrated that RORγ was recruited to this promoter in the liver of wild-type mice, but not RORγ-deficient mice. Activation of Npas2 correlated positively with chromatin accessibility and level of H3K9 acetylation. The activation of Npas2 by RORγ was repressed by co-expression with Rev-Erbα or addition of the ROR inverse agonist T0901317. Npas2 expression was also significantly enhanced during brown adipose differentiation and that this induction was greatly suppressed in adipose cells lacking RORγ. Our results indicate that RORγ and Rev-Erbα are part of a feed-back loop that regulates the circadian expression of Npas2 suggesting a regulatory role for these receptors in Npas2-dependent physiological processes.