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

Discovery and pharmacological characterization of 1,2,3,4-tetrahydroquinoline derivatives as RORγ inverse agonists against prostate cancer

The retinoic acid receptor-related orphan receptor γ (RORγ) is regarded as an attractive therapeutic target for the treatment of prostate cancer. Herein, we report the identification, optimization, and evaluation of 1,2,3,4-tetrahydroquinoline derivatives as novel RORγ inverse agonists, starting from high throughput screening using a thermal stability shift assay (TSA). The representative compounds 13e (designated as XY039) and 14a (designated as XY077) effectively inhibited the RORγ transcriptional activity and exhibited excellent selectivity against other nuclear receptor subtypes. The structural basis for their inhibitory potency was elucidated through the crystallographic study of RORγ LBD complex with 13e. Both 13e and 14a demonstrated reasonable antiproliferative activity, potently inhibited colony formation and the expression of AR, AR regulated genes, and other oncogene in AR positive prostate cancer cell lines. Moreover, 13e and 14a effectively suppressed tumor growth in a 22Rv1 xenograft tumor model in mice. This work provides new and valuable lead compounds for further development of drugs against prostate cancer.

RORγT agonists as immune modulators in anticancer therapy

RORγT is a transcription factor that directs the development of Th17 lymphocytes and other IL-17-expressing cells (e.g., Tc17 and ILC3 cells). These cells are involved in the body's defense against pathogenic bacteria and fungi, but they also participate in maintaining the proinflammatory environment in some autoimmune diseases and play a role in the immune system's response to cancer. Similar to other members of the nuclear receptor superfamily, the activity of RORγT is regulated by low-molecular-weight ligands. Therefore, extensive efforts have been dedicated to identifying inverse agonists that diminish the activity of this receptor and subsequently inhibit the development of autoimmune diseases. Unfortunately, in the pursuit of an ideal inverse agonist, the development of agonists has been overlooked. It is important to remember that these types of compounds, by stimulating lymphocytes expressing RORγT (Th17 and Tc17), can enhance the immune system's response to tumors. In this review, we present recent advancements in the biology of RORγT agonists and their potential application in anticancer therapy.

Ncoa2 Promotes CD8+ T cell-Mediated Antitumor Immunity by Stimulating T-cell Activation via Upregulation of PGC-1α Critical for Mitochondrial Function

Nuclear receptor coactivator 2 (Ncoa2) is a member of the Ncoa family of coactivators, and we previously showed that Ncoa2 regulates the differentiation of induced regulatory T cells. However, it remains unknown if Ncoa2 plays a role in CD8+ T-cell function. Here, we show that Ncoa2 promotes CD8+ T cell-mediated immune responses against tumors by stimulating T-cell activation via upregulating PGC-1α expression to enhance mitochondrial function. Mice deficient in Ncoa2 in T cells (Ncoa2fl/fl/CD4Cre) displayed defective immune responses against implanted MC38 tumors, which associated with significantly reduced tumor-infiltrating CD8+ T cells and decreased IFNγ production. Consistently, CD8+ T cells from Ncoa2fl/fl/CD4Cre mice failed to reject tumors after adoptive transfer into Rag1-/- mice. Further, in response to TCR stimulation, Ncoa2fl/fl/CD4Cre CD8+ T cells failed to increase mitochondrial mass, showed impaired oxidative phosphorylation, and had lower expression of PGC-1α, a master regulator of mitochondrial biogenesis and function. Mechanically, T-cell activation-induced phosphorylation of CREB triggered the recruitment of Ncoa2 to bind to enhancers, thus, stimulating PGC-1α expression. Forced expression of PGC-1α in Ncoa2fl/fl/CD4Cre CD8+ T cells restored mitochondrial function, T-cell activation, IFNγ production, and antitumor immunity. This work informs the development of Ncoa2-based therapies that modulate CD8+ T cell-mediated antitumor immune responses.

Transcriptional regulation on effector T cells in the pathogenesis of psoriasis

Psoriasis is one of the most common inflammatory diseases, characterized by scaly erythematous plaques on the skin. The accumulated evidence on immunopathology of psoriasis suggests that inflammatory reaction is primarily mediated by T helper (Th) cells. The differentiation of Th cells plays important roles in psoriatic progression and it is regulated by transcription factors such as T-bet, GATA3, RORγt, and FOXP3, which can convert naïve CD4+ T cells, respectively, into Th1, Th2, Th17 and Treg subsets. Through the activation of the JAK/STAT and Notch signaling pathways, together with their downstream effector molecules including TNF-α, IFN-γ, IL-17, TGF-β, these subsets of Th cells are then deeply involved in the pathogenesis of psoriasis. As a result, keratinocytes are abnormally proliferated and abundant inflammatory immune cells are infiltrated in psoriatic lesions. We hypothesize that modulation of the expression of transcription factors for each Th subset could be a new therapeutic target for psoriasis. In this review, we will focus on the recent literature concerning the transcriptional regulation of Th cells in psoriasis.

Deregulated phenotype of autoreactive Th17 and Treg clone cells in pemphigus vulgaris after in-vitro treatment with desmoglein antigen (Dsg-3)

The loss of balance between regulatory T (Treg) and T helper 17 (Th17) causes loss of tolerance against desmoglein (Dsg)-3 leading to pemphigus vulgaris (PV), an autoimmune bullous skin disorder associated with autoantibodies against Dsg-3. We aimed to elucidate the complex relationship of Th17 and Treg cells, their molecules, and the underlying mechanism in the development of PV disease. Using cytokine secretion assays, Th17 and Treg cells were sorted by FACS Aria-III within Dsg-3-responsive PBMC population and homogeneous T cell clones were generated in-vitro. Different cell surface molecules like CD25, GITR, CD122, CD152, CD45RO, IL-23R, STAT3, STAT5, CD127, HLA-DR, CCR4, CCR5, CCR6 and CCR7 were studied. The functional response of Th17 and Treg cells were elucidated by measuring the levels of various cytokines released by IL-10 and IL-17 T cells. The mRNA expression of transcription factors (FoxP3 and RORγt) was also analyzed. IL-17 secreting (Th17) cells with phenotype CD4⁺IL-17⁺ were greatly increased and IL-10 secreting (Treg) cells with phenotype CD4⁺IL-10⁺ were reduced in PV cases than healthy controls. The qPCR analysis showing high expression of retinoic acid receptor-related orphan receptor gamma (RORγt) mRNA in comparison to forkhead box P3 (FoxP3) mRNA confirmed the development of pro-inflammatory Th17 response in PV. Further, the cytokine profile of pro-inflammatory and anti-inflammatory cytokines suggested defective suppressive functions in Treg cells with high inflammatory response. Our findings indicate that autoantigen Dsg-3 specifically allows the proliferation of IL-17 secreting T cells though has a negative effect on IL-10 secreting T cells leading to dysregulation of immunity in PV patients. This antagonistic relationship between Dsg-3-specific Th17 and Treg cells may be critical for the onset and persistence of inflammation in PV cases.

Predicting diagnostic gene expression profiles associated with immune infiltration in patients with lupus nephritis

Objective

To identify potential diagnostic markers of lupus nephritis (LN) based on bioinformatics and machine learning and to explore the significance of immune cell infiltration in this pathology.

Methods

Seven LN gene expression datasets were downloaded from the GEO database, and the larger sample size was used as the training group to obtain differential genes (DEGs) between LN and healthy controls, and to perform gene function, disease ontology (DO), and gene set enrichment analyses (GSEA). Two machine learning algorithms, least absolute shrinkage and selection operator (LASSO) and support vector machine-recursive feature elimination (SVM-RFE), were applied to identify candidate biomarkers. The diagnostic value of LN diagnostic gene biomarkers was further evaluated in the area under the ROC curve observed in the validation dataset. CIBERSORT was used to analyze 22 immune cell fractions from LN patients and to analyze their correlation with diagnostic markers.

Results

Thirty and twenty-one DEGs were screened in kidney tissue and peripheral blood, respectively. Both of which covered macrophages and interferons. The disease enrichment analysis of DEGs in kidney tissues showed that they were mainly involved in immune and renal diseases, and in peripheral blood it was mainly enriched in cardiovascular system, bone marrow, and oral cavity. The machine learning algorithm combined with external dataset validation revealed that C1QA(AUC = 0.741), C1QB(AUC = 0.758), MX1(AUC = 0.865), RORC(AUC = 0.911), CD177(AUC = 0.855), DEFA4(AUC= 0.843)and HERC5(AUC = 0.880) had high diagnostic value and could be used as diagnostic biomarkers of LN. Compared to controls, pathways such as cell adhesion molecule cam, and systemic lupus erythematosus were activated in kidney tissues; cell cycle, cytoplasmic DNA sensing pathways, NOD-like receptor signaling pathways, proteasome, and RIG-1-like receptors were activated in peripheral blood. Immune cell infiltration analysis showed that diagnostic markers in kidney tissue were associated with T cells CD8 and Dendritic cells resting, and in blood were associated with T cells CD4 memory resting, suggesting that CD4 T cells, CD8 T cells and dendritic cells are closely related to the development and progression of LN.

Conclusion

C1QA, C1QB, MX1, RORC, CD177, DEFA4 and HERC5 could be used as new candidate molecular markers for LN. It may provide new insights into the diagnosis and molecular treatment of LN in the future.

Decoupling the role of RORγt in the differentiation and effector function of TH17 cells

RORγt is known to instruct the differentiation of T helper 17 (T_H17) cells that mediate the pathogenesis of autoimmune diseases. However, it remains unknown whether RORγt plays a distinct role in the differentiation and effector function of T_H17 cells. Here, we show that mutation of RORγt lysine-256, a ubiquitination site, to arginine (K256R) separates the RORγt role in these two functions. Preventing ubiquitination at K256 via arginine substitution does not affect RORγt-dependent thymocyte development, and T_H17 differentiation in vitro and in vivo, however, greatly impaired the pathogenesis of T_H17 cell-mediated experimental autoimmune encephalomyelitis (EAE). Mechanistically, K256R mutation impairs RORγt to bind to and activate Runx1 expression critical for T_H17-mediated EAE. Thus, RORγt regulates the effector function of T_H17 cells in addition to T_H17 differentiation. This work informs the development of RORγt-based therapies that specifically target the effector function of T_H17 cells responsible for autoimmunity.

Intrahepatic Cholestasis of Pregnancy Increases Inflammatory Susceptibility in Neonatal Offspring by Modulating Gut Microbiota

Intrahepatic cholestasis of pregnancy (ICP) is a liver disease of pregnancy that is characterized by increased bile acid levels in maternal serum. Studies have shown that cholestatic pregnancy can result in long-term metabolic disturbances in the offspring. However, how ICP shapes the offspring’s immunity and predisposition to inflammatory disorders at an early stage is unknown. In this study, we investigated the effect of maternal cholestasis on neonatal offspring metabolism and immune function. We compared 71 neonates with ICP mothers and 63 neonates with healthy mothers and found that the incidence of jaundice and infection was significantly higher in ICP offspring. Maternal serum total bile acid level was associated with blood cell counts in full-term ICP offspring. In animal experiments, a compensatory activation of hepatic and ileal farnesoid X receptor (FXR) and altered gut microbiota in the first week were found in ICP offspring. We also investigated lipopolysaccharide (LPS)-induced inflammatory responses in neonatal rats and found that ICP offspring were more susceptible to inflammation. To understand the correlation between congenital abnormal FXR activation and tissue immunity dysregulation, we assessed the effects of the FXR agonist GW4064 and FXR antagonist E/Z-GS in ICP offspring after LPS exposure. The expression of several pro-inflammatory cytokines significantly decreased after treatment with E/Z-GS but increased after treatment with GW4064. Treatment with the probiotic Lactobacillus rhamnosus LRX01 that inhibits FXR expression in the ileum reduced susceptibility to LPS exposure in ICP offspring. The current study indicated that cholestatic pregnancy may increase the susceptibility of the offspring to inflammation by altering bile acid metabolism and gut microbiota at an early stage. We suggest that supplementation with Lactobacillus rhamnosus LRX01, which inhibits FXR expression in the ileum, may improve intestinal immunity in ICP offspring.

Biological Activities of Extracts from Ageratum fastigiatum: Phytochemical Study and In Silico Target Fishing Approach

In the present study, the ethanolic extract from aerial parts of Ageratum fastigiatum was evaluated in vitro against epimastigote forms of Trypanosoma cruzi (Y strain), promastigote forms of Leishmania amazonensis (PH8 strain), and L. chagasi (BH400 strain). The extract was also evaluated against Staphylococcus aureus (ATCC 25 923), Escherichia coli (ATCC 11 775), Pseudomonas aeruginosa (ATCC 10 145), and Candida albicans (ATCC 36 802). The phytochemical screening was performed by thin-layer chromatography and high-performance liquid chromatography. The extract was fractionated using flash preparative chromatography. The ethanolic extract showed activity against T. cruzi, L. chagasi, and L. amazonensis and antimicrobial activity against S. aureus, E. coli, P. aeruginosa, and C. albicans. The phytochemical screening revealed coumarins, terpenes/sterols, and flavonoids in the ethanolic extract. In addition, the coumarin identified as ayapin was isolated from this extract. We also performed in silico prediction of potential biological activities and targets for compounds previously found in A. fastigiatum. Several predictions were confirmed both retrospectively and prospectively by experimental results described here or elsewhere. Some activities described in the in silico target fishing approach were validated by the ethnopharmacological use and known biological properties. Some new activities and/or targets were predicted and could guide future studies. These results suggest that A. fastigiatum can be an interesting source of substances with antiparasitic and antimicrobial activities.

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

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

Evaluating the Effects of Epigallocatechin-3-Gallate on HIF-1α Protein and RORC Gene Expression in Peripheral Blood Mononuclear Cells in Patients With Multiple Sclerosis

Introduction:

Multiple Sclerosis (MS) is the chronic inflammation of the Central Nervous System (CNS) and autoimmune disease. MS is most widely considered to be mediated by the activation of myelin-specific T CD4⁺ cells as well as TH1 and TH17 cells. TH17 cells are involved in the pathogenesis of MS in various manners. HIF-1α and RORC are required for the natural differentiation of TH17; they are essential transcription factors for the evolution of TH17 cells. Numerous studies indicated that Epigallocatechin Gallate (EGCG) presents immunomodulatory and anti-inflammatory effects. This study investigated the effects of EGCG on normoxic HIF-1α and RORC2 expression in PBMCs among MS patients.

Methods:

Peripheral Blood Mononuclear Cells (PBMCs) were isolated from the whole blood of new cases of MS. The cells were cultured in the presence of a different concentration of EGCG (25, 50,100μM) for 18 and 48 hours. Next, HIF-1α and RORC2 level expressions were measured by Enzyme-Linked Immunosorbent Assay (ELISA) and Real-Time PCR, respectively.

Results:

The results showed that EGCG significantly decreased RORC2 gene expression. EGCG did not affect the level of HIF-1α.

Conclusion:

However, EGCG did not influence the level of HIF-1α. Our present data has led us to conclude that EGCG could be considered as an anti-inflammatory agent may serve as an achievable therapeutic agent for MS.

The role of Th17 cells in psoriasis

T helper 17 (Th17) cells have been involved in the pathogenesis of many autoimmune and inflammatory diseases, like psoriasis, multiple sclerosis (MS), rheumatoid arthritis (RA), and inflammatory bowel disease (IBD). However, the role of Th17 cells in psoriasis has not been clarified completely. Th17-derived proinflammatory cytokines including IL-17A, IL-17F, IL-21, IL-22, and IL-26 have a critical role in the pathogenesis of these disorders. In this review, we introduced the signaling and transcriptional regulation of Th17 cells. And then, we demonstrate the immunopathology role of Th17 cells and functions of the related cytokines in the psoriasis to get a better understanding of the inflammatory mechanisms mediated by Th17 cells in this disease.

Eriodictyol suppresses Th17 differentiation and the pathogenesis of experimental autoimmune encephalomyelitis

T helper 17 (Th17) cells that express interleukin-17 (IL-17) play a key role in various inflammatory diseases, such as multiple sclerosis (MS), and its animal model experimental autoimmune encephalomyelitis (EAE). The retinoic acid receptor-related orphan receptors γt (RORγt) have an indispensable effect on the differentiation of this cell type, and are thus considered a valuable target in the treatment of Th17-related disorders. In this study, we found that eriodictyol (EDT), a natural flavonoid abundant in citrus fruits and peanuts, was located directly in the binding pocket of RORγt, and induced a conformational change that resulted in the effective suppression of the receptor's activity, thus offering insight into the transcriptional inhibition of RORγt-dependent genes. Consistent with this, EDT dose-dependently (5-10 μM) blocked murine Th17 differentiation, and markedly reduced IL-17A secretion in vitro. Furthermore, this compound has been found to have novel properties for directly inhibiting Th1 cell development and promoting Treg cell differentiation at high doses (≥10 μM). EDT administration significantly decreased the clinical severity in the EAE model, with inhibited demyelination and reduced inflammatory responses in the periphery and in the central nervous system (CNS). In the adoptive transfer model, EDT also remarkably suppressed the Th17 cell infiltration and pathogenicity. Collectively, our data demonstrated that EDT, as an agent for the pharmacological inhibition of RORγt, has great potential for immunomodulation, and for use in the treatment of Th17-mediated autoimmune disease.

Cardiac glycosides with target at direct and indirect interactions with nuclear receptors

Cardiac glycosides are compounds isolated from plants and animals and have been known since ancient times. These compounds inhibit the activity of the sodium potassium pump in eukaryotic cells. Cardiac glycosides were used as drugs in heart ailments to increase myocardial contraction force and, at the same time, to lower frequency of this contraction. An increasing number of studies have indicated that the biological effects of these compounds are not limited to inhibition of sodium-potassium pump activity. Furthermore, an increasing number of data have shown that they are synthesized in tissues of mammals, where they may act as a new class of steroid hormones or other hormones by mimicry to modulate various signaling pathways and influence whole organisms. Thus, we discuss the interactions of cardiac glycosides with the nuclear receptor superfamily of transcription factors activated by low-weight molecular ligands (including hormones) that regulate many functions of cells and organisms. Cardiac glycosides of endogenous and exogenous origin by interacting with nuclear receptors can affect the processes regulated by these transcription factors, including hormonal management, immune system, body defense, and carcinogenesis. They can also be treated as initial structures for combinatorial chemistry to produce new compounds (including drugs) with the desired properties.

Thymoquinone promotes mouse mesenchymal stem cells migration in vitro and induces their immunogenicity in vivo

Mesenchymal stem cells (MSCs) have unique potentials, including migration and immunomodulation. Identification of the factors that enhance these activities can improve clinical applications of MSCs. This study aimed to investigate total antioxidant capacity (TAC) and migration potential of mouse MSCs exposed to thymoquinone (TQ) in vitro, and to examine the effect of TQ-treated MSCs on the expression of mouse immune cell markers. The results of total antioxidant capacity and wound healing assays showed that TQ increased the rate of MSCs TAC and migration in a dose- and time-dependent manner. The maximum TAC and migration were detected at 600 and 250 ng/ml of TQ, respectively. Functionally, the real-time PCR data analysis indicated that TQ induced c-Met and Cxcr4 expression and therefore, there may be a correlation between upregulation of these genes and increased MSCs migration. TQ also enhanced the up and down regulating impact of MSCs on Rorγt and Plzf expression and the expression of Tcf4 in mouse immune cells, respectively. Overall, this study declares that TQ increases the TAC of MSCs. It also proposes that TQ may, through activation of c-MET and CXCR4 signalling pathways, promote MSCs migration. TQ may also augment MSCs immunogenicity through its influence on the expression of genes involved in commitment of mouse immune system cells in vivo.

Using Machine Learning to Classify Bioactivity for 3486 Per- and Polyfluoroalkyl Substances (PFASs) from the OECD List

A recent OECD report estimated that more than 4000 per- and polyfluorinated alkyl substances (PFASs) have been produced and used in a broad range of industrial and consumer applications. However, little is known about the potential hazards (e.g., bioactivity, bioaccumulation, and toxicity) of most PFASs. Here, we built machine-learning-based quantitative structure-activity relationship (QSAR) models to predict the bioactivity of those PFASs. By examining a number of available molecular data sets, we constructed the first PFAS-specific database that contains the bioactivity information on 1012 PFASs for 26 bioassays. On the basis of the collected PFAS data set, we trained 5 different machine learning models that cover a variety of conventional models (e.g., random forest and multitask neural network (MNN)) and advanced graph-based models (e.g., graph convolutional network). Those models were evaluated based on the validation data set. Both MNN and graph-based models demonstrated the best performance. The average of the best area-under-the-curve score for each bioassay is 0.916. For predictions on the OECD list, most of the biologically active PFASs have perfluoroalkyl chain lengths less than 12 and are categorized into fluorotelomer-related compounds and perfluoroalkyl acids and their precursors.

SRC3 Is a Cofactor for RORγt in Th17 Differentiation but Not Thymocyte Development

SRC3, a highly conserved member of the steroid receptor coactivator (SRC) family, is recruited by transcription factors to regulate cellular function. Previously, we demonstrated that SRC1, another highly conserved member of the SRC family, interacts with RORγt to regulate Th17 differentiation. However, the relationship between SRC1 and SRC3 in the regulation of Th17 cell function remains unknown. In this study, we demonstrate that mouse SRC3 interacts with RORγt in Th17 cells but not in thymocytes. In addition, Src3^-/- mice exhibited defective Th17 differentiation and induction of experimental autoimmune encephalomyelitis but normal thymocyte development. Furthermore, a K313 to arginine mutation of RORγt (RORγt-K313R), which disrupts the interaction of RORγt with SRC3 but not with SRC1, impairs Th17 differentiation but not thymocyte development. These data suggest that SRC3 works with SRC1 to regulate RORγt-dependent Th17 differentiation but is not essential for RORγt-dependent thymocyte development.

Sumoylation of RORγt regulates TH17 differentiation and thymocyte development

RORγt controls the differentiation of T_H17 cells, which are mediators of autoimmune conditions such as experimental autoimmune encephalomyelitis (EAE). RORγt also regulates thymocyte development and lymph node genesis. Here we show that the function of RORγt is regulated by its sumoylation. Loss of Sumo3, but not Sumo1, dampens T_H17 differentiation and delays the progression of thymic CD8⁺ immature single-positive cells (ISPs). RORγt is SUMO3-modified by E3 ligase PIAS4 at lysine 31 (K31), and the mutation of K31 to arginine in mice prevents RORγt sumoylation, leading to impaired T_H17 differentiation, resistance to T_H17-mediated EAE, accumulation of thymic ISPs, and a lack of Peyer’s patches. Mechanistically, sumoylation of RORγt-K31 recruits histone acetyltransferase KAT2A, which stabilizes the binding of SRC1 to enhance RORγt transcription factor activity. This study thus demonstrates that sumoylation is a critical mechanism for regulating RORγt function, and reveals new drug targets for preventing T_H17-mediated autoimmunity.

The transcription factor RORγt is essential for the differentiation of T_H17 cells, thymocyte development and lymphoid organogenesis. Here the authors show that the function of RORγt is regulated by PIAS4-mediated sumoylation that stabilize the interaction with SRC1 and KAT2A, to enhance the transcriptional activity of RORγt.

Retinoic acid-related Orphan Receptor γ (RORγ): connecting sterol metabolism to regulation of the immune system and autoimmune disease

Cholesterol and its metabolites are bioactive lipids that interact with and regulate the activity of various proteins and signaling pathways that are implicated in the control of a variety of physiological and pathological processes. Recent studies revealed that retinoic acid-related orphan receptors, RORα and γ, members of the ligand-dependent nuclear receptor superfamily, exhibit quite a wide binding specificity for a number of sterols. Several cholesterol intermediates and metabolites function as natural ligands of RORα and RORγ and act as agonists or inverse agonists. Changes in cholesterol homeostasis that alter the level or type of sterol metabolites in cells, can either enhance or inhibit ROR transcriptional activity that subsequently result in changes in the physiological processes regulated by RORs, including various immune responses and metabolic pathways. Consequently, this might negatively or positively impact pathologies, in which RORs are implicated, such as autoimmune disease, inflammation, metabolic syndrome, cancer, and several neurological disorders. Best studied are the links between cholesterol metabolism, RORγt activity, and their regulation of Th17 differentiation and autoimmune disease. The discovery that Th17-dependent inflammation is significantly attenuated in RORγ-deficient mice in several experimental autoimmune disease models, initiated a search for ROR modulators that led to the identification of a number of small molecular weight RORγ inverse agonists. The inverse agonists suppress Th17 differentiation and IL-17 production and protect against autoimmunity. Together, these studies suggest that RORγt may provide an attractive therapeutic target in the management of several (inflammatory) diseases.

A two-amino-acid substitution in the transcription factor RORγt disrupts its function in TH17 differentiation but not in thymocyte development

RORγt regulates T_H17 differentiation, thymic T cell development and lymph node genesis. Although elimination of RORγt prevents T_H17-mediated experimental autoimmune encephalomyelitis (EAE), it also disrupts thymocyte development, which could lead to lethal thymic lymphoma. Here we identified two amino acid mutations in RORγt (RORγt^M) that preferentially disrupted T_H17 differentiation but not thymocyte development. Mice expressing RORγt^M were resistant to EAE associated with defective T_H17 differentiation, but maintained normal thymocyte development and lymph node genesis, except for Peyer’s patches. RORγt^M showed reduced ubiquitination at K69 that is selectively required for T_H17 differentiation but not T cell development. This study will inform the development of treatments that selectively target T_H17-mediated autoimmunity, but do not affect thymocyte development and induce lymphoma.

Regulation of Th17 Differentiation by IKKα-Dependent and -Independent Phosphorylation of RORγt

Transcription factor retinoid acid-related orphan receptor (ROR)γt transcriptionally regulates the genes required for differentiation of Th17 cells that mediate both protective and pathogenic immunity. However, little is known about the function of posttranslational modifications in the regulation of RORγt activity. Mass spectrometric analysis of immunoprecipitated RORγt from Th17 cells identified multiple phosphorylation sites. Systematic mutation analysis of the identified phosphorylation sites found that phosphorylation of S376 enhances whereas phosphorylation of S484 inhibits Th17 differentiation. IκB kinase (IKK)α binds and phosphorylates RORγt at S376 but not S484. Knockdown of IKKα, dominant-negative IKKα, and RORγt mutants incapable of interacting with IKKα all decrease Th17 differentiation. Furthermore, nonphosophorylatable RORγt mutant (S376A) impairs whereas phosphomimetic mutant (S376E) stimulates Th17 differentiation independent of IKKα. Therefore, IKKα-dependent phosphorylation of S376 stimulated whereas IKKα-independent phosphorylation of S484 inhibited RORγt function in Th17 differentiation.

RAR-Related Orphan Receptor Gamma (ROR-γ) Mediates Epithelial-Mesenchymal Transition Of Hepatocytes During Hepatic Fibrosis

The epithelial‐mesenchymal transition (EMT) is involved in many different types of cellular behavior, including liver fibrosis. In this report, we studied a novel function of RAR‐related orphan receptor gamma (ROR‐γ) in hepatocyte EMT during liver fibrosis. To induce EMT in vitro, primary hepatocytes and FL83B cells were treated with TGF‐β1. Expression of ROR‐γ was analyzed by Western blot in the fibrotic mouse livers and human livers with cirrhosis. To verify the role of ROR‐γ in hepatocyte EMT, we silenced ROR‐γ in FL83B cells using a lentiviral short hairpin RNA (shRNA) vector. The therapeutic effect of ROR‐γ silencing was investigated in a mouse model of TAA‐induced fibrosis by hydrodynamic injection of plasmids. ROR‐γ expression was elevated in hepatocyte cells treated with TGF‐β1, and ROR‐γ protein levels were elevated in the fibrotic mouse livers and human livers with cirrhosis. Knockdown of ROR‐γ resulted in the attenuation of TGF‐β1‐induced EMT in hepatocytes. Strikingly, ROR‐γ bound to ROR‐specific DNA response elements (ROREs) in the promoter region of TGF‐β type I receptor (Tgfbr1) and Smad2, resulting in the downregulation of Tgfbr1 and Smad2 after silencing of ROR‐γ. Therapeutic delivery of shRNA against ROR‐γ attenuated hepatocyte EMT and ameliorated liver fibrosis in a mouse model of TAA‐induced liver fibrosis. Overall, our results suggest that ROR‐γ regulates TGF‐β‐induced EMT in hepatocytes during liver fibrosis. We suggest that ROR‐γ may become a potential therapeutic target in treating liver fibrosis. J. Cell. Biochem. 118: 2026–2036, 2017. © 2016 The Authors. Journal of Cellular Biochemistry Published by Wiley Periodicals Inc.

Ubiquitination of RORγt at Lysine 446 Limits Th17 Differentiation by Controlling Coactivator Recruitment

The transcription factor retinoid acid-related orphan receptor γ t (RORγt) directs the differentiation of Th17 cells. Th17 cells mediate pathological immune responses responsible for autoimmune diseases, including psoriasis and multiple sclerosis. Previous studies focused on RORγt target genes and their function in Th17 differentiation. In this study, we assessed posttranscriptional regulation of RORγt and identified a functional ubiquitination site, K446. Mutation of K446 to arginine to prevent ubiquitination greatly enhanced recruitment of steroid receptor coactivator 1 (SRC1), a coactivator critical for RORγt activity. Correspondingly, the K446 to arginine mutation potentiated Th17 differentiation. We also showed that ubiquitin-specific protease (USP)15 interacted with RORγt, removed ubiquitin from K446, and stimulated RORγt activity by enhancing coactivator SRC1 recruitment. Knockdown of USP15 or expression of inactive USP15 impaired Th17 differentiation, suggesting a positive role for USP15-mediated deubiquitination of RORγt in Th17 differentiation. Therefore, ubiquitination of K446 limits RORγt-mediated Th17 differentiation by inhibiting the recruitment of coactivator SRC1. Our study will inform the development of treatments that target RORγt ubiquitination pathways to limit Th17-mediated autoimmunity.

Distinct characteristics of nasal polyps with and without eosinophilia

Introduction

Eosinophilic and noneosinophilic Nasal polyps (NPs) are different subtypes of NPs and require different treatment methods.

Objective

To compare the histologic characteristics, mRNA and protein expression between Nasal Polyps with and without eosinophilia.

Methods

NPs tissues were obtained from eighty-six NPs patients during surgery. Eosinophilic and noneosinophilic NPs were distinguished according to immunochemical results of the specimen. The histological, mRNA and protein expression features were compared between the two groups.

Results

In eosinophilic NPs, we observed a significantly higher GATA-3, IL-5, IL-4, IL-13 mRNA and protein expression. In noneosinophilic NPs, IL-17, IL-23 and RORc mRNA and protein expression were increased. Immunohistochemistry tests showed, more mast cells and less neutrophils in eosinophilic NPs compared with noneosinophilic NPs. Eosinophilic NPs patient presented more severe symptom scores when compared to noneosinophilic NPs.

Conclusion

We demonstrate for the first time that Th2 is the predominant reaction in eosinophilic NPs while Th17 is the predominant reaction in noneosinophilic NPs. Our study may provide new treatment strategy for NPs.

Synthetic RORγt Agonists Enhance Protective Immunity

The T cell specific RORγ isoform RORγt has been shown to be the key lineage-defining transcription factor to initiate the differentiation program of TH17 and TC17 cells, cells that have demonstrated antitumor efficacy. RORγt controls gene networks that enhance immunity including increased IL17 production and decreased immune suppression. Both synthetic and putative endogenous agonists of RORγt have been shown to increase the basal activity of RORγt enhancing TH17 cell proliferation. Here, we show that activation of RORγt using synthetic agonists drives proliferation of TH17 cells while decreasing levels of the immune checkpoint protein PD-1, a mechanism that should enhance antitumor immunity while blunting tumor associated adaptive immune resistance. Interestingly, putative endogenous agonists drive proliferation of TH17 cells but do not repress PD-1. These findings suggest that synthetic agonists of RORγt should activate TC17/TH17 cells (with concomitant reduction in the Tregs population), repress PD-1, and produce IL17 in situ (a factor associated with good prognosis in cancer). Enhanced immunity and blockage of immune checkpoints has transformed cancer treatment; thus such a molecule would provide a unique approach for the treatment of cancer.

Digoxin reduces atherosclerosis in apolipoprotein E-deficient mice

BACKGROUND AND PURPOSE

Numerous in vitro studies have suggested that digoxin suppresses inflammation and alters lipid metabolism. However, the effect of dioxin on atherosclerosis is poorly understood. The present study was conducted to determine whether digoxin affects the development of atherosclerosis in a murine model of atherosclerotic disease.

EXPERIMENTAL APPROACH

Apolipoprotein E-deficient mice maintained on a Western-type diet were administered PBS (control), low-dose digoxin (1 mg · kg(-1) · day(-1)) or high-dose digoxin (2 mg · kg(-1) · day(-1)) via i.p. injection for 12 weeks.

KEY RESULTS

Digoxin dose-dependently reduced atherosclerotic lesion formation and plasma lipid levels (reductions of 41% in total cholesterol, 54% in triglycerides and 20% in low-density lipoprotein cholesterol in the high-dose digoxin-treated group). Moreover, treatment with digoxin markedly attenuated IL-17A expression and IL-17A-related inflammatory responses and increased the abundance of regulatory T cells (Tregs).

CONCLUSIONS AND IMPLICATIONS

Our data demonstrate that digoxin acts as a specific antagonist of retinoid-related orphan receptor-γ to decrease atherosclerosis by suppressing lipid levels and IL-17A-related inflammatory responses.

Identification of an allosteric binding site for RORγt inhibition

RORγt is critical for the differentiation and proliferation of Th17 cells associated with several chronic autoimmune diseases. We report the discovery of a novel allosteric binding site on the nuclear receptor RORγt. Co-crystallization of the ligand binding domain (LBD) of RORγt with a series of small-molecule antagonists demonstrates occupancy of a previously unreported allosteric binding pocket. Binding at this non-canonical site induces an unprecedented conformational reorientation of helix 12 in the RORγt LBD, which blocks cofactor binding. The functional consequence of this allosteric ligand-mediated conformation is inhibition of function as evidenced by both biochemical and cellular studies. RORγt function is thus antagonized in a manner molecularly distinct from that of previously described orthosteric RORγt ligands. This brings forward an approach to target RORγt for the treatment of Th17-mediated autoimmune diseases. The elucidation of an unprecedented modality of pharmacological antagonism establishes a mechanism for modulation of nuclear receptors.

T-cell phenotypes in chronic rhinosinusitis with nasal polyps in Japanese patients

BACKGROUND

Chronic rhinosinusitis with nasal polyps is characterized by local inflammation and is categorized into two subtypes in Japan: eosinophilic chronic rhinosinusitis, and non-eosinophilic chronic rhinosinusitis. The objective of this study was to investigate the expression of key transcription factors for Treg and Th1/Th2/Th17 cells, in relation to the mRNA expression of representative cytokines in these two subtypes of chronic rhinosinusitis with nasal polyps.

METHODS

The expression of forkhead box P3 (FOXP3), T-box transcription factor (T-bet), GATA3, retinoid acid-related orphan receptor C (RORc), the suppressive cytokines TGF-β1 and IL-10, and Th1/Th2/Th17 cytokines (IFN-γ, IL-4, IL-5, IL-13, IL-17) were analyzed by means of RT-PCR in eosinophilic polyps. Eosinophilic polyps were defined as having an eosinophil count of more than 50 per microscopic field (×400 magnification) using five fields located in the subepithelial area of the polyps, while the non-eosinophilic polyps and controls did not fulfill this criteria. The numbers of T cells, CD4+ T cells, CD8+ T cells and Treg were histologically counted using sections that were immunostained for CD3, CD4, CD8, and FOXP3, respectively.

RESULTS

In eosinophilic polyps, we observed significantly fewer CD4+ T cells and CD8+ T cells, and lower GATA3, RORc and IL-10 mRNA expression, but a significantly higher IL-5, and IL-13 mRNA expression compared with controls, whereas FOXP3 and T-bet mRNA expression were not significantly different compared with controls. In non-eosinophilic polyps, FOXP3, IL-10, IL-17A, TGFβ1 and IFNγ mRNA expression was significantly higher compared with controls, whereas IL-4, 5 and 13 expression was not significantly different from controls.

CONCLUSION

We showed a reduction of GATA3 and RORc mRNA, low Treg-related cytokines and elevated Th2 cytokine levels in eosinophilic chronic rhinosinusitis, whereas we demonstrated the upregulation of Treg cells and increases of Th1 and Th17 cytokines in non-eosinophilic chronic rhinosinusitis in the Japanese population. The different mRNA expression profiles of Treg and Th1/Th2/Th17 signature transcription factors and cytokines between eosinophilic chronic rhinosinusitis and non-eosinophilic chronic rhinosinusitis suggests heterogeneity in the pathogenesis of chronic rhinosinusitis with nasal polyps.

Identification of Tetraazacyclic Compounds as Novel Potent Inhibitors Antagonizing RORγt Activity and Suppressing Th17 Cell Differentiation

CD4⁺ T-helper cells that produce interleukin-17 (Th17 cells) are characterized as pathological T-helper cells in autoimmune diseases. Differentiation of human and mouse Th17 cells requires a key transcription regulator, retinoic acid receptor-related orphan receptor γt (RORγt), which is a potential therapeutic target for autoimmune diseases. To develop a therapeutic agent for Th17-mediated autoimmune diseases, we have established a high-throughput screening (HTS) assay for candidate screening, in which the luciferase activity in RORγt-LBD positive and negative Jurkat cells were analyzed to evaluate induction of RORγt activity by compounds. This technique was applied to screen a commercially-available drug-like chemical compound library (Enamine) which contains 20155 compounds. The screening identified 17 compounds that can inhibit RORγt function in the HTS screen system. Of these, three tetraazacyclic compounds can potently inhibit RORγt activity, and suppress Th17 differentiation and IL-17 production. These three candidate compounds could significantly attenuate the expression of the Il17a by 65%- 90%, and inhibit IL-17A secretion by 47%, 63%, and 74%, respectively. These compounds also exhibited a potent anti-RORγt activity, with EC₅₀ values of 0.25 μM, 0.67 μM and 2.6 μM, respectively. Our data demonstrated the feasibility of targeting the RORγt to inhibit Th17 cell differentiation and function with these tetraazacyclic compounds, and the potential to improve the structure of these compounds for autoimmune diseases therapeutics.

Pharmacologic repression of retinoic acid receptor-related orphan nuclear receptor γ is therapeutic in the collagen-induced arthritis experimental model

OBJECTIVE

The nuclear receptor retinoic acid receptor-related orphan nuclear receptor γ (RORγ; T cell-specific isoform RORγt) is a key regulator of Th17 cell differentiation, controlling the production of the inflammatory cytokine interleukin-17 (IL-17). Lipopolysaccharide (LPS) stimulation of monocytes leads to the induction of RORγ. We previously showed that the potent and selective inverse agonist of RORγ, SR2211, was effective at suppressing IL-17 production in EL4 cells. The aim of this study was to examine the effects of SR2211 treatment on proinflammatory cytokine expression in LPS-stimulated RAW 264.7 cells as well as on joint inflammation in vivo in mice with collagen-induced arthritis (CIA).

METHODS

Collagen was injected into the tail of DBA mice, followed by a booster inoculation 21 days later. Three days prior to the booster inoculation, SR2211 was administered twice daily for 15 days. Thymus, spleen, and draining lymph nodes (DLNs) were then harvested, and Th17 cell differentiation and DLN stimulation were performed.

RESULTS

Treatment of Th17 cells with SR2211 suppressed the expression and production of inflammatory cytokines. Likewise, SR2211 reduced inflammatory cytokine production in LPS-stimulated RAW 264.7 cells. Mice with CIA that received SR2211 twice daily for 15 days exhibited a statistically significant reduction in joint inflammation as compared to mice that received only vehicle. Interestingly, systemic Th1 cell activation was detected in SR2211-treated mice with CIA, as indicated by an increase in interferon-γ levels.

CONCLUSION

The findings of this study support the idea of targeting RORγ to therapeutically repress inflammatory T cell function and macrophage activation in humans with rheumatoid arthritis. Compounds such as SR2211 have potential utility for the treatment of inflammatory disease.

Egr3 induces a Th17 response by promoting the development of γδ T cells

The transcription factor Early Growth Response 3 (Egr3) has been shown to play an important role in negatively regulating T cell activation and promoting T cell anergy in Th1 cells. However, its role in regulating other T helper subsets has yet to be described. We sought to determine the role of Egr3 in a Th17 response using transgenic mice that overexpress Egr3 in T cells (Egr3 TG). Splenocytes from Egr3 TG mice demonstrated more robust generation of Th17 cells even under non-Th17 skewing conditions. We found that while Egr3 TG T cells were not intrinsically more likely to become Th17 cells, the environment encountered by these cells was more conducive to Th17 development. Further analysis revealed a considerable increase in the number of γδ T cells in both the peripheral lymphoid organs and mucosal tissues of Egr3 TG mice, a cell type which normally accounts for only a small fraction of peripheral lymphocytes. Consistent with this marked increase in peripheral γδ T cells, thymocytes from Egr3 TG mice also appear biased toward γδ T cell development. Coculture of these Egr3-induced γδ T cells with wildtype CD4+ T cells increases Th17 differentiation, and Egr3 TG mice are more susceptible to bleomycin-induced lung inflammation. Overall our findings strengthen the role for Egr3 in promoting γδ T cell development and show that Egr3-induced γδ T cells are both functional and capable of altering the adaptive immune response in a Th17-biased manner. Our data also demonstrates that the role played by Egr3 in T cell activation and differentiation is more complex than previously thought.

Discovery of Tertiary Amine and Indole Derivatives as Potent RORγt Inverse Agonists

A novel series of tertiary amines as retinoid-related orphan receptor gamma-t (RORγt) inverse agonists was discovered through agonist/inverse agonist conversion. The level of RORγt inhibition can be enhanced by modulating the conformational disruption of H12 in RORγt LBD. Linker exploration and rational design led to the discovery of more potent indole-based RORγt inverse agonists.

Inflammatory T helper 17 cells promote depression-like behavior in mice

BACKGROUND

Recognition of substantial immune-neural interactions is revising dogmas about their insular actions and revealing that immune-neural interactions can substantially impact central nervous system functions. The inflammatory cytokine interleukin-6 promotes susceptibility to depression and drives production of inflammatory T helper 17 (Th17) T cells, raising the hypothesis that in mouse models, Th17 cells promote susceptibility to depression-like behaviors.

METHODS

Behavioral characteristics were measured in male mice administered Th17 cells, CD4(+) cells, or vehicle and in retinoid-related orphan receptor-γT (RORγT)(+/GFP) mice or male mice treated with RORγT inhibitor or anti-interleukin-17A antibodies.

RESULTS

Mouse brain Th17 cells were elevated by learned helplessness and chronic restraint stress, two common depression-like models. Th17 cell administration promoted learned helplessness in 89% of mice in a paradigm where no vehicle-treated mice developed learned helplessness, and impaired novelty suppressed feeding and social interaction behaviors. Mice deficient in the RORγT transcription factor necessary for Th17 cell production exhibited resistance to learned helplessness, identifying modulation of RORγT as a potential intervention. Treatment with the RORγT inhibitor SR1001, or anti-interleukin-17A antibodies to abrogate Th17 cell function, reduced Th17-dependent learned helplessness.

CONCLUSIONS

These findings indicate that Th17 cells are increased in the brain during depression-like states, promote depression-like behaviors in mice, and specifically inhibiting the production or function of Th17 cells reduces vulnerability to depression-like behavior, suggesting antidepressant effects may be attained by targeting Th17 cells.

The therapeutic potential of RORγ modulators in the treatment of human disease

Nuclear receptors (NR) are ligand-regulated transcription factors that bind DNA in proximity to their target genes and exert their effects as a result of binding by small molecule ligands such as sterols, lipids, fatty acids, retinoids, and steroid hormones. The retinoic acid receptor-related orphan receptors or RORs (NR1F1–NR1F3) are nuclear receptors that regulate multiple cellular processes, including metabolism, cellular differentiation, and apoptosis, in a range of tissues and organs. These receptors bind as monomers to ROR response elements commonly called ROREs present in promoter regions of target genes and tether chromatin remodeling enzymes, facilitating recruitment of transcription machinery. Several recent reports have highlighted the potential role for RORs in human disease, and more importantly, studies have demonstrated that these receptors can be modulated by exogenous synthetic ligands, paving the way for development of novel therapeutics. Here we review the current status of synthetic ligand development as well as the structural aspects governing modulation of ROR signaling pathways as they relate to metabolic diseases and autoimmune disorders.

Intervention of PKC-θ as an immunosuppressive regimen

PKC-θ is selectively enriched in T cells and specifically translocates to immunological synapse where it mediates critical T cell receptor signals required for T cell activation, differentiation, and survival. T cells deficient in PKC-θ are defective in their ability to differentiate into inflammatory effector cells that mediate actual immune responses whereas, their differentiation into regulatory T cells (Treg) that inhibits the inflammatory T cells is enhanced. Therefore, the manipulation of PKC-θ activity can shift the ratio between inflammatory effector T cells and inhibitory Tregs, to control T cell-mediated immune responses that are responsible for autoimmunity and allograft rejection. Indeed, PKC-θ-deficient mice are resistant to the development of several Th2 and Th17-dependent autoimmune diseases and are defective in mounting alloimmune responses required for rejection of transplanted allografts and graft-versus-host disease. Selective inhibition of PKC-θ is therefore considered as a potential treatment for prevention of autoimmune diseases and allograft rejection.

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.

Protein kinase C-θ promotes Th17 differentiation via upregulation of Stat3

Although protein kinase C-θ (PKC-θ)-deficient mice are resistant to the induction of Th17-dependent experimental autoimmune encephalomyelitis, the function of PKC-θ in Th17 differentiation remains unknown. In this article, we show that purified, naive CD4 PKC-θ(-/-) T cells were defective in Th17 differentiation, whereas Th1 and Th2 differentiation appeared normal. Activation of PKC-θ with PMA promoted Th17 differentiation in wild type (WT) but not PKC-θ(-/-) T cells. Furthermore, PKC-θ(-/-) T cells had notably lower levels of Stat3, a transcription factor required for Th17 differentiation, and PMA markedly stimulated the expression of Stat3 in WT but not PKC-θ(-/-) T cells. In contrast, activation of Stat4 and Stat6, which are critical for Th1 and Th2 differentiation, was normal in PKC-θ(-/-) T cells. Forced expression of Stat3 significantly increased Th17 differentiation in PKC-θ(-/-) T cells, suggesting that reduced Stat3 levels were responsible for impaired Th17 differentiation, and that Stat3 lies downstream of PKC-θ. Constitutively active PKC-θ, or WT PKC-θ activated by either PMA or TCR cross-linking, stimulated expression of a luciferase reporter gene driven by the Stat3 promoter. PKC-θ-mediated activation of the Stat3 promoter was inhibited by dominant-negative AP-1 and IκB kinase-β, but stimulated by WT AP-1 and IκB kinase-β, suggesting that PKC-θ stimulates Stat3 transcription via the AP-1 and NF-κB pathways. Lastly, conditions favoring Th17 differentiation induced the highest activation level of PKC-θ. Altogether, the data indicate that PKC-θ integrates the signals from TCR signaling and Th17 priming cytokines to upregulate Stat3 via NF-κB and AP-1, resulting in the stimulation of Th17 differentiation.

Protein kinase C-θ inhibits inducible regulatory T cell differentiation via an AKT-Foxo1/3a-dependent pathway

Protein kinase C (PKC)-θ has been shown to be a critical TCR signaling molecule that promotes the activation and differentiation of naive T cells into inflammatory effector T cells. In this study, we demonstrate that PKC-θ-mediated signals inhibit inducible regulatory T cell (iTreg) differentiation via an AKT-Foxo1/3A pathway. TGF-β-induced iTreg differentiation was enhanced in PKC-θ(-/-) T cells or wild-type cells treated with a specific PKC-θ inhibitor, but was inhibited by the PKC-θ activator PMA, or by CD28 crosslinking, which enhances PKC-θ activation. PKC-θ(-/-) T cells had reduced activity of the AKT kinase, and the expression of a constitutively active form of AKT in PKC-θ(-/-) T cells restored the ability to inhibit iTreg differentiation. Furthermore, knockdown or overexpression of the AKT downstream targets Foxo1 and Foxo3a was found to inhibit or promote iTreg differentiation in PKC-θ(-/-) T cells accordingly, indicating that the AKT-Foxo1/3A pathway is responsible for the inhibition of iTreg differentiation of iTregs downstream of PKC-θ. We conclude that PKC-θ is able to control T cell-mediated immune responses by shifting the balance between the differentiation of effector T cells and inhibitory Tregs.

Allergen induced Th17 response in the peripheral blood mononuclear cells (PBMCs) of patients with nasal polyposis

BACKGROUND

Nasal polyposis (NP) is a chronic inflammatory disease of the nasal cavity and sinuses. Th17 cells have been considered to play roles in allergic airway diseases and various chronic inflammatory disorders.

AIM OF THE STUDY

This study aimed to investigate the population and function of peripheral Th17 cells in response to house dust mite extracts (HDM) allergen in NP patients, and evaluate the possible correlation between Th17 cells and atopy, to explore the role of atopy in the pathogenesis of NP.

METHODS

Peripheral blood mononuclear cells (PBMCs) obtained from atopic NP patients, non-atopic NP patients, and controls were stimulated by phytohemagglutinin (PHA) or HDM plus PHA. The resulting frequency of Th17 cells was detected by flow cytometry and the expression of RORc was measured by real-time PCR. Then the concentrations of IL-17A, INF-γ, IL-4 and IL-5 in the supernatants were assayed by specific ELISAs.

RESULTS

The population and function of Th17 cells in allergen stimulated PBMCs were significantly higher in atopic NP patients. In addition, in atopic group, HDM+PHA stimulation induced significant increase of Th17 population and IL-17A production versus those in PHA stimulated ones. However, the frequency of Th17 cells was not correlated with Th1, Th2 cytokine productions.

CONCLUSION

Th17 immunity is involved in the systemic immune responses to allergen in atopic NP and atopy may aggravate NP by stimulating the increase of Th17 population and IL-17A production. The mechanism of Th17 cells response to allergen may be regulated differently from the regulation of Th1 and Th2 immunity in NP.

Critical role of TCF-1 in repression of the IL-17 gene

Overwhelming activation of IL-17, a gene involved in inflammation, leads to exaggerated Th17 responses associated with numerous autoimmune conditions, such as experimental autoimmune encephalomyelitis (EAE). Here we show that TCF-1 is a critical factor to repress IL-17 gene locus by chromatin modifications during T cell development. Deletion of TCF-1 resulted in increased IL-17 gene expression both in thymus and peripheral T cells, which led to enhanced Th17 differentiation. As a result, TCF-1^-/- mice were susceptible to Th17-dependent EAE induction. Rag1^-/- mice reconstituted with TCF-1^-/- T cells were also susceptible to EAE, indicating TCF-1 is intrinsically required to repress IL-17. However, expression of wild-type TCF-1 or dominant negative TCF-1 did not interfere with Th17 differentiation in mature T cells. Furthermore, expression of TCF-1 in TCF-1^-/- T cells could not restore Th17 differentiation to wild-type levels, indicating that TCF-1 cannot affect IL-17 production at the mature T cell stage. This is also supported by the normal up-regulation or activation in mature TCF-1^-/- T cells of factors known to regulate Th17 differentiation, including RORγt and Stat3. We observed hyperacetylation together with trimethylation of Lys-4 at the IL-17 locus in TCF-1^-/- thymocytes, two epigenetic modifications indicating an open active state of the gene. Such epigenetic modifications were preserved even when TCF-1^-/- T cells migrated out of thymus. Therefore, TCF-1 mediates an active process to repress IL-17 gene expression via epigenetic modifications during T cell development. This TCF-1-mediated repression of IL-17 is critical for peripheral T cells to generate balanced immune responses.

Identification of a novel non-retinoid pan inverse agonist of the retinoic acid receptors

Retinoids are potent forms of vitamin A and are involved in a broad range of physiological processes and the pharmacological effects of retinoids are primarily mediated by the retinoic acid receptors (RARs) and the retinoid X receptors (RXRs). Several natural and synthetic RAR modulators have proven to be clinically useful for a number of therapeutic indications including cancer, psoriasis, and diabetes. Unfortunately, these agents lead to a number of significant side effects. Most synthetic retinoid ligands are based on the retinoid scaffold and thus have similarities to the natural ligand with all previously disclosed RAR ligands having a carboxylic acid that makes a critical ionic bridge within the ligand binding domain of the receptors. The potential therapeutic value offered from RAR modulation provides the impetus to identify novel ligands based on unique scaffolds that may offer improved toxicity and pharmacokinetic profiles. Here we describe the identification of an atypical RAR inverse agonist that represents the first non-acid, non-retinoid direct modulator of RAR receptor subfamily. SR-0065 functions as a pan-RAR inverse agonist suppressing the basal activity of RARα, RARβ, and RARγ, as well as inhibiting agonist-induced RAR activity. SR-0065 treatment enhanced receptor interaction with a peptide representative of the corepressor SMRT, and in cells SR-0065 enhances recruitment of SMRT to the promoter of the RARγ dependent gene, Cyp26A1. The acid form of SR-0065, SR-1758, was inactive in all assays. Thus, SR-0065 represents a new class of non-acid, non-retinoid RAR modulator that may be used as a point to initiate development of improved RAR-targeted drugs.

The Th17-defining transcription factor RORγt promotes glomerulonephritis

Although Th17 responses may contribute to the pathogenesis of glomerulonephritis, whether the key transcription factor in Th17 cell development, RORγt, also promotes glomerulonephritis is unknown. Here, we induced crescentic glomerulonephritis in wild-type and RORγt-deficient (RORγt(-/-)) mice. RORγt(-/-) mice were protected from disease, with reduced histologic and functional injury and decreased leukocyte infiltration. Because RORγt(-/-) mice lack lymph nodes, which may influence the development of nephritis, we performed cell-transfer studies. We reconstituted Rag1(-/-) mice, which lack adaptive immunity but otherwise have normal architecture of the lymphatic system, with splenocytes from naïve wild-type or RORγt(-/-) mice. Mice receiving wild-type splenocytes exhibited high mortality from renal failure after induction of nephritis whereas mice receiving RORγt(-/-) cells were protected. To determine the effect of RORγt deficiency specifically in T helper cells, we isolated naïve CD4(+) T cells from wild-type and RORγt(-/-) mice and transferred them into Rag1(-/-) animals. Recipients of wild-type CD4(+) T cells developed severe glomerulonephritis whereas recipients of RORγt(-/-) cells developed less severe disease. To exclude effects of altered regulatory T cell (Treg) development caused by RORγt deficiency, we transferred naïve CD4(+) T cells depleted of Tregs into Rag1(-/-) mice. Recipients of wild-type, Treg-depleted, CD4(+) T cells developed severe glomerulonephritis whereas recipients of RORγt(-/-), Treg-depleted CD4(+) T cells did not. Taken together, this study demonstrates that RORγt promotes the development of crescentic glomerulonephritis by directing nephritogenic Th17 responses.