A novel isoform of the orphan receptor RORγt suppresses IL-17 production in human T cells

Elevated levels of peripheral Th17 cells and Th17-related cytokines in patients with periampullary adenocarcinoma

AIM

Periampullary adenocarcinoma (PAC) is a malignant tumor originating at the ampulla of Vater, distal common bile duct, head of the pancreas, ampulla and duodenum. The levels of circulating Th17 cells and Th17-related cytokines in patients with PAC remain unreported. Therefore, the aim of this study was to determine the levels of circulating Th17 cells and Th17-related cytokines in patients with PAC.

MATERIALS AND METHODS

Flow cytometry was used to measure Th17 cell proportions in PBMCs from 60 PAC patients and 30 healthy controls. Enzyme-linked immunosorbent assay (ELISA) was used to quantify IL-17A and IL-23 levels in serum samples, while quantitative reverse transcription polymerase chain reaction (qRT-PCR) assessed IL-17A mRNA expression and Th17-related transcription factors (RORγt and STAT3) in tissue samples.

RESULTS

The findings showed a substantial increase in Th17 cell percentages, elevated concentrations of IL-17A and IL-23, and higher mRNA expression levels of IL-17A, RORγt, and STAT3 in patients with PAC when compared to healthy controls (HCs).

CONCLUSION

Th17 cells play an important role in the pathogenesis of PAC and may represent potential therapeutic targets.

SIRT3 Activator Honokiol Inhibits Th17 Cell Differentiation and Alleviates Colitis

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Increased circulating Th17 cell populations in patients with pancreatic ductal adenocarcinoma

T-helper 17 (Th17) cells are a subset of CD4+ helper T cells that produce interleukin 17 (IL-17) and play a crucial role in the pathogenesis of inflammatory and autoimmune diseases. Few studies have been conducted to determine the role of Th17 cells in the tumorigenesis and development of pancreatic ductal adenocarcinoma (PDAC); however, its role is still unclear. In this study, the percentage of circulating Th17 cells and serum levels of IL-17A and IL-23 were analyzed using flow cytometry and ELISA, respectively, in 40 PDAC patients, 30 chronic pancreatitis (CP) patients and 30 healthy controls (HC). In addition, the mRNA expression levels of IL-17A, STAT3 and RORγt in tissue samples were quantified by qRT-PCR. The results showed that the percentage of circulating Th17 cells and the concentrations of serum IL-17A and IL-23 were significantly increased in PDAC patients as compared to CP and HC (P < 0.001). In addition, the higher level of IL-17A was significantly correlated with the poor overall survival of the PDAC patients. Furthermore, the frequencies of Th17 cells and IL-17A were significantly higher in stage III+IV PDAC patients versus stage I+II. A significant increase in IL-17A, STAT3 and RORγT mRNA was observed in patients with PDAC. Taken together, these findings suggest that the increased circulating Th17 cells and serum IL-17A may be involved in the development and metastasis of PDAC, and thus represent potential targets for the treatment of PDAC.

Ageing and Low-Level Chronic Inflammation: The Role of the Biological Clock

Ageing is a multifactorial physiological manifestation that occurs inexorably and gradually in all forms of life. This process is linked to the decay of homeostasis due to the progressive decrease in the reparative and regenerative capacity of tissues and organs, with reduced physiological reserve in response to stress. Ageing is closely related to oxidative damage and involves immunosenescence and tissue impairment or metabolic imbalances that trigger inflammation and inflammasome formation. One of the main ageing-related alterations is the dysregulation of the immune response, which results in chronic low-level, systemic inflammation, termed "inflammaging". Genetic and epigenetic changes, as well as environmental factors, promote and/or modulate the mechanisms of ageing at the molecular, cellular, organ, and system levels. Most of these mechanisms are characterized by time-dependent patterns of variation driven by the biological clock. In this review, we describe the involvement of ageing-related processes with inflammation in relation to the functioning of the biological clock and the mechanisms operating this intricate interaction.

Time-course RNA-Seq profiling reveals isoform-level gene expression dynamics of the cGAS-STING pathway

The cGAS-STING pathway, orchestrating complicated transcriptome-wide immune responses, is essential for host antiviral defense but can also drive immunopathology in severe COVID-19. Here, we performed time-course RNA-Seq experiments to dissect the transcriptome expression dynamics at the gene-isoform level after cGAS-STING pathway activation. The in-depth time-course transcriptome after cGAS-STING pathway activation within 12 h enabled quantification of 48,685 gene isoforms. By employing regression models, we obtained 13,232 gene isoforms with expression patterns significantly associated with the process of cGAS-STING pathway activation, which were named activation-associated isoforms. The combination of hierarchical and k-means clustering algorithms revealed four major expression patterns of activation-associated isoforms, including two clusters with increased expression patterns enriched in cell cycle, autophagy, antiviral innate-immune functions, and COVID-19 coronavirus disease pathway, and two clusters showing decreased expression pattern that mainly involved in ncRNA metabolism, translation process, and mRNA processing. Importantly, by merging four clusters of activation-associated isoforms, we identified three types of genes that underwent isoform usage alteration during the cGAS-STING pathway activation. We further found that genes exhibiting protein-coding and non-protein-coding gene isoform usage alteration were strongly enriched for the factors involved in innate immunity and RNA splicing. Notably, overexpression of an enriched splicing factor, EFTUD2, shifted transcriptome towards the cGAS-STING pathway activated status and promoted protein-coding isoform abundance of several key regulators of the cGAS-STING pathway. Taken together, our results revealed the isoform-level gene expression dynamics of the cGAS-STING pathway and uncovered novel roles of splicing factors in regulating cGAS-STING pathway mediated immune responses.

RORγt protein modifications and IL-17-mediated inflammation

RORγt, the master transcription factor for cytokine interleukin (IL)-17, is expressed explicitly in Th17 cells, γδT cells, and type 3 innate lymphoid cells in mice and humans. Since dysregulated IL-17 expression is strongly linked to several human inflammatory diseases, the RORγt-IL-17 axis has been the focus of intense research. Recently, several studies have shown that RORγt is modified by multiple post-translational mechanisms, including ubiquitination, acetylation, SUMOylation, and phosphorylation. This review discusses how post-translational modifications modulate RORγt function and its turnover to regulate IL-17-driven inflammation. Broad knowledge of these pathways is crucial for a clear understanding of the pathogenic role of RORγt+IL-17+ cells and for the development of putative therapeutic strategies to target IL-17-driven diseases such as multiple sclerosis, psoriasis, rheumatoid arthritis, systemic lupus erythematosus, and inflammatory bowel disease.

Discovery and Characterization of Benzimidazole Derivative XY123 as a Potent, Selective, and Orally Available RORγ Inverse Agonist

Receptor-related orphan receptor γ (RORγ) has emerged as an attractive therapeutic target for the treatment of cancer and inflammatory diseases. Herein, we report our effort on the discovery, optimization, and evaluation of benzothiazole and benzimidazole derivatives as novel inverse agonists of RORγ. The representative compound 27h (designated as XY123) potently inhibited the RORγ transcription activity with a half-maximal inhibitory concentration (IC50) value of 64 nM and showed excellent selectivity against other nuclear receptors. 27h also potently suppressed cell proliferation, colony formation, and the expression of androgen receptor (AR)-regulated genes in AR-positive prostate cancer cell lines. In addition, 27h demonstrated good metabolic stability and a pharmacokinetic property with reasonable oral bioavailability (32.41%) and moderate half-life (t1/2 = 4.98 h). Significantly, oral administration of compound 27h achieved complete and long-lasting tumor regression in the 22Rv1 xenograft tumor model in mice. Compound 27h may serve as a new valuable lead compound for further development of drugs for the treatment of prostate cancer.

Systemic Lupus Erythematosus in Children and Young People

PURPOSE OF REVIEW

Juvenile-onset systemic lupus erythematosus ((j)SLE) is an autoimmune/inflammatory disease that results in significant damage and disability. When compared to patients with disease onset in adulthood, jSLE patients exhibit increased disease activity, damage and require more aggressive treatments. This manuscript summarises age-specific pathogenic mechanisms and underscores the need for age group-specific research, classification and treatment.

RECENT FINDINGS

Genetic factors play a significant role in the pathophysiology of jSLE, as > 7% of patients develop disease as a result of single gene mutations. Remaining patients carry genetic variants that are necessary for disease development, but require additional factors. Increased 'genetic impact' likely contributes to earlier disease onset and more severe phenotypes. Epigenetic events have only recently started to be addressed in jSLE, and add to the list of pathogenic mechanisms that may serve as biomarkers and/or treatment targets. To allow meaningful and patient-oriented paediatric research, age-specific classification criteria and treatment targets require to be defined as currently available tools established for adult-onset SLE have limitations in the paediatric cohort. Significant progress has been made in understanding the pathophysiology of jSLE. Meaningful laboratory and clinical research can only be performed using age group-specific tools, classification criteria and treatment targets.

Oxysterols: Old Tale, New Twists

Oxysterols have long been known for their important role in cholesterol homeostasis, where they are involved in both transcriptional and posttranscriptional mechanisms for controlling cholesterol levels. However, they are increasingly associated with a wide variety of other, sometimes surprising cell functions. They are activators of the Hedgehog pathway (important in embryogenesis), and they act as ligands for a growing list of receptors, including some that are of importance to the immune system. Oxysterols have also been implicated in several diseases such as neurodegenerative diseases and atherosclerosis. Here, we explore the latest research into the roles oxy-sterols play in different areas, and we evaluate the current evidence for these roles. In addition, we outline critical concepts to consider when investigating the roles of oxysterols in various situations, which includes ensuring that the concentration and form of the oxysterol are relevant in that context--a caveat with which many studies have struggled.

Variations in T cell transcription factor gene structure and expression associated with the two disease forms of sheep paratuberculosis

Two different forms of clinical paratuberculosis in sheep are recognised, related to the level of bacterial colonization. Paucibacillary lesions are largely composed of lymphocytes with few bacteria, and multibacillary pathology is characterized by heavily-infected macrophages. Analysis of cytokine transcripts has shown that inflammatory Th1/Th17 T cells are associated with development of paucibacillary pathology and Th2 cytokines are correlated with multibacillary disease. The master regulator T cell transcription factors TBX21, GATA3, RORC2 and RORA are critical for the development of these T cell subsets. Sequence variations of the transcription factors have also been implicated in the distinct disease forms of human mycobacterial and gastrointestinal inflammatory diseases. Relative RT-qPCR was used to compare expression levels of each transcript variant of the master regulators in the ileo-caecal lymph nodes of uninfected controls and sheep with defined paucibacillary and multibacillary pathology. Low levels of GATA3 in multibacillary sheep failed to confirm that multibacillary paratuberculosis is caused simply by a Th2 immune response. However, high levels of TBX21, RORC2 and RORC2v1 highlights the role of Th1 and Th17 activation in paucibacillary disease. Increased RORAv1 levels in paucibacillary tissue suggests a role for RORα in Th17 development in sheep; while elevated levels of RORAv4 hints that this variant might inhibit RORα function and depress Th17 development in multibacillary sheep.

Variations in T Cell Transcription Factor Sequence and Expression Associated with Resistance to the Sheep Nematode Teladorsagia circumcincta

This study used selected lambs that varied in their resistance to the gastrointestinal parasite Teladorsagia circumcincta. Infection over 12 weeks identified susceptible (high adult worm count, AWC; high fecal egg count, FEC; low body weight, BW; low IgA) and resistant sheep (no/low AWC and FEC, high BW and high IgA). Resistance is mediated largely by a Th2 response and IgA and IgE antibodies, and is a heritable characteristic. The polarization of T cells and the development of appropriate immune responses is controlled by the master regulators, T-bet (TBX21), GATA-3 (GATA3), RORγt (RORC2) and RORα (RORA); and several inflammatory diseases of humans and mice are associated with allelic or transcript variants of these transcription factors. This study tested the hypothesis that resistance of sheep to T. circumcincta is associated with variations in the structure, sequence or expression levels of individual master regulator transcripts. We have identified and sequenced one variant of sheep TBX21, two variants of GATA3 and RORC2 and five variants of RORA from lymph node mRNA. Relative RT-qPCR analysis showed that TBX21, GATA3 and RORC2 were not significantly differentially-expressed between the nine most resistant (AWC, 0; FEC, 0) and the nine most susceptible sheep (AWC, mean 6078; FEC, mean 350). Absolute RT-qPCR on all 45 animals identified RORVv5 as being significantly differentially-expressed (p = 0.038) between resistant, intermediate and susceptible groups; RORCv2 was not differentially-expressed (p = 0.77). Spearman’s rank analysis showed that RORAv5 transcript copy number was significantly negatively correlated with parameters of susceptibility, AWC and FEC; and was positively correlated with BW. RORCv2 was not correlated with AWC, FEC or BW but was significantly negatively correlated with IgA antibody levels. This study identifies the full length RORA variant (RORAv5) as important in controlling the protective immune response to T. circumcincta infection in sheep.

Ocotillol, a Majonoside R2 Metabolite, Ameliorates 2,4,6-Trinitrobenzenesulfonic Acid-Induced Colitis in Mice by Restoring the Balance of Th17/Treg Cells

In a preliminary experiment, majonoside R2 (MR2), isolated from Vietnamese ginseng (Panax vietnamensis Ha et Grushv.), inhibited differentiation to Th17 cells and was metabolized to ocotillol via pseudoginsenoside RT4 (PRT4) by gut microbiota. Therefore, we examined the inhibitory effects of MR2 and its metabolites PRT4 and ocotillol against Th17 cell differentiation. These ginsenosides significantly suppressed interleukin (IL)-6/tumor growth factor beta-induced differentiation of splenic CD4(+) T cells into Th17 cells and expression of IL-17 in vitro. Among these ginsenosides, ocotillol showed the highest inhibitory effect. We also examined the anti-inflammatory effect of ocotillol in mice with 2,4,6-trinitrobenzenesulfonic acid (TNBS)-induced colitis. Oral administration of ocotillol significantly suppressed TNBS-induced colon shortening, macroscopic score, myeloperoxidase activity, and production of nitric oxide and prostaglandin E2. Ocotillol treatment increased TNBS-suppressed expression of tight junction proteins ZO-1, occludin, and claudin-1 in the colon. Treatment with ocotillol inhibited TNBS-induced expression of tumor necrosis factor (TNF)-α and IL-1β, as well as activation of NF-κB and MAPKs. Moreover, treatment with ocotillol inhibited TNBS- induced differentiation to Th17 cells in the lamina propria of colon, as well as expression of T-bet, RORγt, IL-17, and IL-23. Ocotillol treatment also increased Treg cell differentiation and Foxp3 and IL-10 expression. These findings suggest that orally administered MR2 may be metabolized to ocotillol in the intestine by gut microbiota and the transformed ocotillol may ameliorate inflammatory diseases such as colitis by restoring the balance of Th17/Treg cells.

IMMUNODEFICIENCIES. Impairment of immunity to Candida and Mycobacterium in humans with bi-allelic RORC mutations

Human inborn errors of immunity mediated by the cytokines interleukin-17A and interleukin-17F (IL-17A/F) underlie mucocutaneous candidiasis, whereas inborn errors of interferon-γ (IFN-γ) immunity underlie mycobacterial disease. We report the discovery of bi-allelic RORC loss-of-function mutations in seven individuals from three kindreds of different ethnic origins with both candidiasis and mycobacteriosis. The lack of functional RORγ and RORγT isoforms resulted in the absence of IL-17A/F-producing T cells in these individuals, probably accounting for their chronic candidiasis. Unexpectedly, leukocytes from RORγ- and RORγT-deficient individuals also displayed an impaired IFN-γ response to Mycobacterium. This principally reflected profoundly defective IFN-γ production by circulating γδ T cells and CD4(+)CCR6(+)CXCR3(+) αβ T cells. In humans, both mucocutaneous immunity to Candida and systemic immunity to Mycobacterium require RORγ, RORγT, or both.

CD3-T cell receptor co-stimulation through SLAMF3 and SLAMF6 receptors enhances RORγt recruitment to the IL17A promoter in human T lymphocytes

Th17 lymphocytes play a key role during immune responses against bacteria and fungi and are involved in the pathophysiology of multiple autoimmune disorders. The co-stimulatory molecules SLAMF3 and SLAMF6 have been implicated in the formation of Th17 phenotypes and IL-17A expression. Increased surface expression of SLAMF3 and SLAMF6 has been linked with disease activity in systemic lupus erythematosus. Here we demonstrate that in human total T lymphocytes the canonical CD28 and the non-canonical SLAMF3/SLAMF6 co-stimulatory pathways cooperate in the recruitment of the transcription factor NFAT1 to the IL17A promoter. Furthermore, the dominance of the SLAMF3/SLAMF6 pathway in inducing IL-17A production can be attributed to an increased nuclear abundance and recruitment of RORγt to the IL17A promoter. Thus, we have identified an additional mechanism that may be central for the specific control of IL17A gene regulation in systemic lupus erythematosus T lymphocytes.