Sjögren's syndrome-associated SNPs increase GTF2I expression in salivary gland cells to enhance inflammation development

GGT1 is a SNP eQTL gene involved in STAT3 activation and associated with the development of Post-ERCP pancreatitis

Post-ERCP pancreatitis (PEP) is an acute pancreatitis caused by endoscopic-retrograde-cholangiopancreatography (ERCP). About 10% of patients develop PEP after ERCP. Here we show that gamma-glutamyltransferase 1 (GGT1)-SNP rs5751901 is an eQTL in pancreatic cells associated with PEP and a positive regulator of the IL-6 amplifier. More PEP patients had the GGT1 SNP rs5751901 risk allele (C) than that of non-PEP patients at Hokkaido University Hospital. Additionally, GGT1 expression and IL-6 amplifier activation were increased in PEP pancreas samples with the risk allele. A mechanistic analysis showed that IL-6-mediated STAT3 nuclear translocation and STAT3 phosphorylation were suppressed in GGT1-deficient cells. Furthermore, GGT1 directly associated with gp130, the signal-transducer of IL-6. Importantly, GGT1-deficiency suppressed inflammation development in a STAT3/NF-κB-dependent disease model. Thus, the risk allele of GGT1-SNP rs5751901 is involved in the pathogenesis of PEP via IL-6 amplifier activation. Therefore, the GGT1-STAT3 axis in pancreas may be a prognosis marker and therapeutic target for PEP.

DDX6 is involved in the pathogenesis of inflammatory diseases via NF-κB activation

The IL-6 amplifier was originally discovered as a mechanism for the enhanced activation of NF-κB in non-immune cells. In the IL-6 amplifier, IL-6-STAT3 and NF-κB stimulation is followed by an excessive production of IL-6, chemokines, and growth factors to develop chronic inflammation preceding the development of inflammatory diseases. Previously, using a shRNA-mediated genome-wide screening, we found that DEAD-Box Helicase 6 (DDX6) is a candidate positive regulator of the amplifier. Here, we investigate whether DDX6 is involved in the pathogenesis of inflammatory diseases via the IL-6 amplifier. We found that DDX6-silencing in non-immune cells suppressed the NF-κB pathway and inhibited activation of the IL-6 amplifier, while the forced expression of DDX6 enhanced NF-κB promoter activity independent of the RNA helicase activity of DDX6. The imiquimod-mediated dermatitis model was suppressed by the siRNA-mediated gene downregulation of DDX6. Furthermore, silencing DDX6 significantly reduced the TNF-α-induced phosphorylation of p65/RelA and IκBα, nuclear localization of p65, and the protein levels of IκBα. Mechanistically, DDX6 is strongly associated with p65 and IκBα, but not TRADD, RIP, or TRAF2, suggesting a novel function of DDX6 as an adaptor protein in the NF-κB pathway. Thus, our findings demonstrate a possible role of DDX6 beyond RNA metabolism and suggest DDX6 is a therapeutic target for inflammatory diseases.

The gateway reflex regulates tissue-specific autoimmune diseases

The dynamic interaction and movement of substances and cells between the central nervous system (CNS) and peripheral organs are meticulously controlled by a specialized vascular structure, the blood-brain barrier (BBB). Experimental and clinical research has shown that disruptions in the BBB are characteristic of various neuroinflammatory disorders, including multiple sclerosis. We have been elucidating a mechanism termed the "gateway reflex" that details the entry of immune cells, notably autoreactive T cells, into the CNS at the onset of such diseases. This process is initiated through local neural responses to a range of environmental stimuli, such as gravity, electricity, pain, stress, light, and joint inflammation. These stimuli specifically activate neural pathways to open gateways at targeted blood vessels for blood immune cell entry. The gateway reflex is pivotal in managing tissue-specific inflammatory diseases, and its improper activation is linked to disease progression. In this review, we present a comprehensive examination of the gateway reflex mechanism.

Computer model of IL-6-dependent rheumatoid arthritis in F759 mice

The interleukin-6 (IL-6) amplifier, which describes the simultaneous activation of signal transducer and activator of transcription 3 (STAT3) and NF-κb nuclear factor kappa B (NF-κB), in synovial fibroblasts causes the infiltration of immune cells into the joints of F759 mice. The result is a disease that resembles human rheumatoid arthritis. However, the kinetics and regulatory mechanisms of how augmented transcriptional activation by STAT3 and NF-κB leads to F759 arthritis is unknown. We here show that the STAT3-NF-κB complex is present in the cytoplasm and nucleus and accumulates around NF-κB binding sites of the IL-6 promoter region and established a computer model that shows IL-6 and IL-17 (interleukin 17) signaling promotes the formation of the STAT3-NF-κB complex followed by its binding on promoter regions of NF-κB target genes to accelerate inflammatory responses, including the production of IL-6, epiregulin, and C-C motif chemokine ligand 2 (CCL2), phenotypes consistent with in vitro experiments. The binding also promoted cell growth in the synovium and the recruitment of T helper 17 (Th17) cells and macrophages in the joints. Anti-IL-6 blocking antibody treatment inhibited inflammatory responses even at the late phase, but anti-IL-17 and anti-TNFα antibodies did not. However, anti-IL-17 antibody at the early phase showed inhibitory effects, suggesting that the IL-6 amplifier is dependent on IL-6 and IL-17 stimulation at the early phase, but only on IL-6 at the late phase. These findings demonstrate the molecular mechanism of F759 arthritis can be recapitulated in silico and identify a possible therapeutic strategy for IL-6 amplifier-dependent chronic inflammatory diseases.

An inflammatory bowel disease-associated SNP increases local thyroglobulin expression to develop inflammation in miniature dachshunds

Inflammatory colorectal polyp (ICRP) in miniature dachshunds (MDs) is a chronic inflammatory bowel disease (IBD) characterized by granulomatous inflammation that consists of neutrophil infiltration and goblet cell hyperplasia in the colon. Recently, we identified five MD-associated single-nucleotide polymorphisms (SNPs), namely PLG, TCOF1, TG, COL9A2, and COL4A4, by whole-exome sequencing. Here, we investigated whether TG c.4567C>T (p.R1523W) is associated with the ICRP pathology. We found that the frequency of the T/T SNP risk allele was significantly increased in MDs with ICRP. In vitro experiments showed that TG expression in non-immune cells was increased by inducing the IL-6 amplifier with IL-6 and TNF-α. On the other hand, a deficiency of TG suppressed the IL-6 amplifier. Moreover, recombinant TG treatment enhanced the activation of the IL-6 amplifier, suggesting that TG is both a positive regulator and a target of the IL-6 amplifier. We also found that TG expression together with two NF-κB targets, IL6 and CCL2, was increased in colon samples isolated from MDs with the T/T risk allele compared to those with the C/C non-risk allele, but serum TG was not increased. Cumulatively, these results suggest that the T/T SNP is an expression quantitative trait locus (eQTL) of TG mRNA in the colon, and local TG expression triggered by this SNP increases the risk of ICRP in MDs via the IL-6 amplifier. Therefore, TG c.4567C>T is a diagnostic target for ICRP in MDs, and TG-mediated IL-6 amplifier activation in the colon is a possible therapeutic target for ICRP.

Dupuytren's contracture-associated SNPs increase SFRP4 expression in non-immune cells including fibroblasts to enhance inflammation development

Dupuytren's contracture (DC) is an inflammatory fibrosis characterized by fibroproliferative disorders of the palmar aponeurosis, for which there is no effective treatment. Although several genome-wide association studies have identified risk alleles associated with DC, the functional linkage between these alleles and the pathogenesis remains elusive. We here focused on two single nucleotide polymorphisms (SNPs) associated with DC, rs16879765 and rs17171229, in secreted frizzled related protein 4 (SFRP4). We investigated the association of SRFP4 with the IL-6 amplifier, which amplifies the production of IL-6, growth factors and chemokines in non-immune cells and aggravates inflammatory diseases via NF-κB enhancement. Knockdown of SFRP4 suppressed activation of the IL-6 amplifier in vitro and in vivo, whereas the overexpression of SFRP4 induced the activation of NF-κB-mediated transcription activity. Mechanistically, SFRP4 induced NF-κB activation by directly binding to molecules of the ubiquitination SFC complex, such as IkBα and βTrCP, followed by IkBα degradation. Furthermore, SFRP4 expression was significantly increased in fibroblasts derived from DC patients bearing the risk alleles. Consistently, fibroblasts with the risk alleles enhanced activation of the IL-6 amplifier. These findings indicate that the IL-6 amplifier is involved in the pathogenesis of DC, particularly in patients harboring the SFRP4 risk alleles. Therefore, SFRP4 is a potential therapeutic target for various inflammatory diseases and disorders, including DC.

Gateway reflexes are neural circuits that establish the gateway of immune cells to regulate tissue specific inflammation

INTRODUCTION

Tissue-specific inflammatory diseases are regulated by several mechanisms. The gateway reflex and IL-6 amplifier are two mechanisms involved in diseases that depend on the inflammatory cytokine IL-6. The gateway reflex activates specific neural pathways that cause autoreactive CD4+ T cells to pass through gateways in blood vessels toward specific tissues in tissue-specific inflammatory diseases. These gateways are mediated by the IL-6 amplifier, which describes enhanced NF-κB activation in nonimmune cells including endothelial cells at specific sites. In total, we have reported six gateway reflexes defined by their triggering stimulus: gravity, pain, electric stimulation, stress, light, and joint inflammation.

AREAS COVERED

This review summarizes the gateway reflex and IL-6 amplifier for the development of tissue-specific inflammatory diseases.

EXPERT OPINION

We expect that the IL-6 amplifier and gateway reflex will lead to novel therapeutic and diagnostic methods for inflammatory diseases, particularly tissue-specific ones.

Human thymoma-associated mutation of the GTF2I transcription factor impairs thymic epithelial progenitor differentiation in mice

Few human tumours present with a recurrent pathognomonic mutation in a transcription factor. Thymomas are an exception, with the majority of some subtypes exhibiting a distinct somatically acquired missense mutation in the general transcription factor GTF2I. Co-dominant expression of wild-type and mutated forms of Gtf2i in the mouse thymic epithelium is associated with aberrant thymic architecture and reduced thymopoietic activity. Phenotypic and molecular characterization of the mutant epithelium indicates that medullary differentiation is particularly affected as a result of impaired differentiation of bi-potent epithelial progenitors. The resulting gene expression signature is dominated by that of immature cortex-like thymic epithelial cells. TCR repertoire analysis of the cytopenic T cell compartment indicates efficient intrathymic selection; hence, despite marked homeostatic proliferation of T cell clones, autoimmunity is not observed. Thus, our transgenic mouse model recapitulates some aspects of the pathophysiology of a genetically defined type of human thymoma.

Thymic architecture and T cell repertoire analysis of a mouse model for thymoma and the role of the transcription factor GTF2I shows suitability of this model to recapitulate human thymomas and a severe effect of Gtf2i mutations on the medullary compartment.

Composition and regulation of the immune microenvironment of salivary gland in Sjögren’s syndrome

Primary Sjögren’s syndrome (pSS) is a systemic autoimmune disease characterized by exocrine gland dysfunction and inflammation. Patients often have dry mouth and dry eye symptoms, which seriously affect their lives. Improving dry mouth and eye symptoms has become a common demand from patients. For this reason, researchers have conducted many studies on external secretory glands. In this paper, we summarize recent studies on the salivary glands of pSS patients from the perspective of the immune microenvironment. These studies showed that hypoxia, senescence, and chronic inflammation are the essential characteristics of the salivary gland immune microenvironment. In the SG of pSS, genes related to lymphocyte chemotaxis, antigen presentation, and lymphocyte activation are upregulated. Interferon (IFN)-related genes, DNA methylation, sRNA downregulation, and mitochondrial-related differentially expressed genes are also involved in forming the immune microenvironment of pSS, while multiple signaling pathways are involved in regulation. We further elucidated the regulation of the salivary gland immune microenvironment in pSS and relevant, targeted treatments.

Transcriptomic Mapping of Human Parotid Gland at Single-Cell Resolution

As the largest salivary gland in oral cavity, the parotid gland plays an important role in initial digesting and lubricating food. The abnormal secretory function of the parotid gland can lead to dental caries and oral mucosal inflammation. In recent years, single-cell RNA sequencing (scRNA-seq) has been used to explore the heterogeneity and diversity of cells in various organs and tissues. However, the transcription profile of the human parotid gland at single-cell resolution has not been reported yet. In this study, we constructed the cell atlas of human parotid gland using the 10× Genomics platform. Characteristic gene analysis identified the biological functions of serous acinar cell populations in secreting digestive enzymes and antibacterial proteins. We revealed the specificity and similarity of the parotid gland compared to other digestive glands through comparative analyses of other published scRNA-seq data sets. We also identified the cell-specific expression of hub genes for Sjögren syndrome in the human parotid gland by integrating the results of genome-wide association studies and bulk RNA-seq, which highlighted the importance of immune cell dysfunction in parotid Sjögren syndrome pathogenesis.