Higher Expression of NOD1 and NOD2 is Associated with Vogt-Koyanagi-Harada (VKH) Syndrome But Not Behcet's Disease (BD)

Association of NLRPs with pathogenesis of dry age-related macular degeneration

BACKGROUND

Age-related macular degeneration (AMD) is the leading cause of blindness in the elderly population, and Dry AMD is the most common clinical subtype. However, effective measures for the early diagnosis and treatment of dry AMD have not been proposed. In recent years, NOD-like receptors (NLRs) have received attention in the study of AMD as an important class of pattern recognition receptors. We attempted to elucidate the pathogenesis of NLRs in dry AMD from the perspective of chronic inflammation.

METHODS

This study involved 13 patients with dry AMD, 10 age- and sex-matched normal population without any history of disease and 8 patients with wet AMD as controls. Using RT-qPCR, the mRNA expression levels of NLRs in peripheral blood peripheral blood mononuclear cells (PBMCs) were compared to analyze the statistical differences in the expression contents among the three populations.

RESULTS

The relative RNA expression of nucleotide-binding oligomerization-like receptor protein 12 (NLRP12) with negative regulation of inflammation was significantly lower in dry AMD patients than in normal people and wet AMD patients. And NLRX1, which also has an anti-inflammatory effect, was lower in dry AMD patients than in wet AMD patients. However, NLRP3 with proinflammatory effect was significantly expressed in wet AMD.

CONCLUSION

The significant decrease in NLRP12 in dry AMD may become a breakthrough in the study of dry AMD and systemic chronic inflammatory response. However, NLRP3 may have a more important role in wet AMD.

Gut microbial signatures and their functions in Behcet's uveitis and Vogt-Koyanagi-Harada disease

BACKGROUND

A number of public metagenomic studies reveal an association between the gut microbiome and various immune-mediated diseases including Behcet's uveitis (BU) and Vogt-Koyanagi-Harada disease (VKH). Integrated-analysis and subsequent validation of these results could be a potentially powerful way to understand the microbial signatures and their functions in these two uveitis entities.

METHODS

We integrated the sequencing data of our previous metagenomic studies on two major uveitis entities, BU and VKH as well as four other publicly available immune-mediated diseases datasets, including Ankylosing Spondylitis (AS), Rheumatoid Arthritis (RA), Crohn's disease (CD) and Ulcerative Colitis (UC). Alpha-diversity and beta-diversity analysis were used to compare the gut microbiome signatures between both uveitis entities and other immune-mediated diseases and healthy controls. Amino acid homology between microbial proteins and a uveitogenic peptide of the interphotoreceptor retinoid-binding protein (IRBP)161-180 was investigated using a similarity search in the NCBI protein BLAST program (BLASTP). Enzyme-linked Immunosorbent Assay (ELISA) was performed to evaluate the cross-reactive responses of experimental autoimmune uveitis (EAU)-derived lymphocytes and BU patients-derived peripheral blood mononuclear cells (PBMCs) against homologous peptides. The area under the curve (AUC) analysis was used to test the sensitivity and specificity of gut microbial biomarkers.

RESULTS

Depleted Dorea, Blautia, Coprococcus, Erysipelotrichaceae and Lachnospiraceae as well as enriched Bilophila and Stenotrophomonas were identified in BU patients. An enriched Alistipes along with a lower level of Dorea were observed in VKH patients. A peptide antigen (SteTDR) encoded by BU specifically enriched Stenotrophomonas was identified to share homology with IRBP161-180. In vitro experiments showed that lymphocytes from EAU or PBMCs from BU patients reacted to this peptide antigen as shown by the production of IFN-γ and IL-17. Addition of the SteTDR peptide to the classical IRBP immunization protocol exacerbated EAU severity. Gut microbial marker profiles consisted of 24 species and 32 species respectively differentiated BU and VKH from each other as well as from the other four immune-mediated diseases and healthy controls. Protein annotation identified 148 and 119 specific microbial proteins associated with BU and VKH, respectively. For metabolic function analysis, 108 and 178 metabolic pathways were shown to be associated with BU and VKH, respectively.

CONCLUSIONS

Our study revealed specific gut microbial signatures and their potentially functional roles in BU and VKH pathogenesis that differ significantly from other immune-mediated diseases as well as healthy controls.

Insights gained from single-cell analysis of immune cells in tofacitinib treatment of Vogt-Koyanagi-Harada disease

Vogt-Koyanagi-Harada disease (VKH) is an important refractory uveitis mediated by pathological T cells (TCs). Tofacitinib (TOFA) is a JAK- targeted therapy for several autoimmune diseases. However, the specific pathogenesis and targeted therapeutics for VKH remain largely unknown. Based on single-cell RNA sequencing and mass cytometry, we present what we believe is the first multimodal, high-dimensional analysis to generate a comprehensive human immune atlas regarding subset composition, gene signatures, enriched pathways, and intercellular interactions of VKH patients undergoing TOFA therapy. Patients with VKH are characterized by TCs' polarization from naive to effector and memory subsets, together with accrued monocytes and upregulated cytokines and JAK/STAT signaling pathways. In vitro, TOFA reversed Th17/Treg imbalance and inhibited IL-2-induced STAT1/3 phosphorylation. TOFA alleviated VKH symptoms by restoring pathological TCs' polarization and functional marker expression and downregulating cytokine signaling and lymphocyte function. Remarkably, inflammation-related responses and intercellular interactions decreased after TOFA treatment, particularly in monocytes. Notably, we identified 2 inflammation- and JAK-associated monocyte subpopulations that were strongly implicated in VKH pathogenesis and mechanisms involved in TOFA treatment. Here, we provide a potentially novel JAK-targeted therapy for VKH and elaborate on the possible therapeutic mechanisms of TOFA, expanding our knowledge of VKH pathological patterns.

Identification of differently expressed mRNAs by peripheral blood mononuclear cells in Vogt-Koyanagi-Harada disease

Vogt-Koyanagi-Harada disease (VKH) is a rare autoimmune disease characterized by diffuse and bilateral uveitis, alopecia, tinnitus, hearing loss, vitiligo and headache. The transcriptional expression pattern of peripheral blood mononuclear cells (PBMC) in VKH remains largely unknown. In this study, mRNA sequencing was conducted in PBMC from VKH patients with active uveitis before treatment (n = 7), the same patients after prednisone combined with cyclosporine treatment (n = 7) and healthy control subjects strictly matched with gender and age (n = 7). We found 118 differentially expressed genes (DEGs) between VKH patients and healthy control subjects, and 21 DEGs between VKH patients before and after treatment. TRIB1 was selected as a potential biomarker to monitor the development of VKH according to the mRNA sequencing. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis were performed to predict the possible biological functions and signaling pathways of DEGs. Neutrophil degranulation, peptidase regulator activity, secretory granule membrane, cellular response to peptide, growth factor binding and cell projection membrane were enriched as GO annotations of DEGs. Arachidonic acid metabolism and mitogen-activated protein kinase (MAPK) signaling pathway were potential signaling pathways involved in pathogenesis and drug response of VKH. A protein–protein interaction (PPI) network was constructed by STRING, and colony stimulating factor 1 receptor (CSF1R) was identified as the hubgene of all DEGs by Cytoscape. The cell type presumed to contribute to the aberrant expression of DEGs was analyzed with the use of publicly available single-cell sequencing data of PBMC from a healthy donor and single-cell sequencing dataset of monocytes from VKH patients. Our findings may help to decipher the underlying cellular and molecular pathogenesis of VKH and may lead novel therapeutic applications.

Immunopathogenesis of Behçet's disease and treatment modalities

INTRODUCTION

Behçet's disease (BD) is an auto-inflammatory disease, primarily characterized by recurrent painful mucocutaneous ulcerations.

METHODS

A literature search was performed to write a narrative review into the pathogenesis and current treatment options of BD.

RESULTS

The pathogenesis of BD remains to be elucidated, but is considered a genetically primed disease in which an external trigger causes immune activation resulting in inflammatory symptoms. GWAS data show an association between multiple genetic polymorphisms (HLA-B51, ERAP1, IL10 and IL23R-IL12RB2) and increased susceptibility to BD. Bacteria as streptococci, an unbalanced microbiome or molecular mimicry trigger the inflammation in BD. Increased production or responsiveness of pro-inflammatory components of the innate immune response (TLR, neutrophils, NK-cells or γδ T-cells) to these triggers may be a crucial step in the pathogenesis of BD. Additionally to an increased autoinflammatory response there is evidence of a dysregulated adaptive immune system, with a disturbed Th1/Th2 balance, expansion of Th17 cells and possibly a decrease in regulatory T cells, resulting in a surplus in pro-inflammatory cytokines. The inflammation causes a typical clinical phenotype including orogenital ulcerations, uveitis and skin lesions. Treatment is aimed at the aberrations found in the innate (neutrophils and γδ-T cells) and adaptive immune system (TNF-α, INF-γ, IL-1), directed at organ involvement and individualized based on patient characteristics.

CONCLUSION

We presented an extensive review into the pathogenesis and treatment options of BD.

Comparison of the clinical features between posterior scleritis with exudative retinal detachment and Vogt-Koyanagi-Harada disease

PURPOSE

This study aims to analyse the differences in clinical characteristics between VKH disease and PS with exudative retinal detachment (ERD).

METHODS

The medical records of 18 eyes of 12 patients with PS accompanied by ERD and 32 eyes of 16 patients with VKH disease were retrospectively reviewed.

RESULTS

Single ERD was more common in PS, while hyperreflective dots, multiple ERD, retinal pigment epithelium folds were more common in VKH disease on OCT. Both posterior coat thickness and choroid thickness were higher in VKH eyes. "T" sign was observed in 6 of 18 eyes (33.3%) in the PS group, whereas in none of the eyes of VKH disease. No significant differences were shown in FA imaging between PS and VKH cases. Relapse occurred in 12 eyes (66.7%) in PS group, mainly in the posterior segment, while 6 eyes (18.8%) experienced recurrence in the anterior segment in VKH group.

CONCLUSION

There are characteristic differences in multimodal imaging parameters and clinical course between VKH and PS with ERD.

Role of pattern recognition receptors and the microbiota in neurological disorders

In recent years, the gut microbiota has been increasingly implicated in the development of many extraintestinal disorders, including neurodevelopmental and neurodegenerative disorders. Despite this growing connection, our understanding of the precise mechanisms behind these effects is currently lacking. Pattern recognition receptors (PRRs) are important innate immune proteins expressed on the surface and within the cytoplasm of a multitude of cells, both immune and otherwise, including epithelial, endothelial and neuronal. PRRs comprise four major subfamilies: the Toll-like receptors (TLRs), the nucleotide-binding oligomerization domain leucine rich repeats-containing receptors (NLRs), the retinoic acid inducible gene 1-like receptors and the C-type lectin receptors. Recognition of commensal bacteria by PRRs is critical for maintaining host-microbe interactions and homeostasis, including behaviour. The expression of PRRs on multiple cell types makes them a highly interesting and novel target for regulation of host-microbe signalling, which may lead to gut-brain signalling. Emerging evidence indicates that two of the four known families of PRRs (the NLRs and the TLRs) are involved in the pathogenesis of neurodevelopmental and neurodegenerative disorders via the gut-brain axis. Taken together, increasing evidence supports a role for these PRRs in the development of neurological disorders, including Alzheimer's disease, Parkinson's disease and multiple sclerosis, via the microbiota-gut-brain axis.

Activation of the interleukin-23/interleukin-17 signalling pathway in autoinflammatory and autoimmune uveitis

Uveitis is a group of diseases characterized by intraocular inflammation, of which some are driven by autoinflammatory or autoimmune responses, such as Vogt-Koyanagi-Harada disease, Behçet's disease, uveitis associated with spondyloarthritis, ocular sarcoidosis, sympathetic ophthalmia and birdshot chorioretinopathy. These entities have various clinical forms, but genetic and biomarker data suggest that they share a common molecular basis, activation of the Interleukin (IL)-23/IL-17 pathway. Multiple factors including genetic predisposition, various cytokine imbalances, infectious agents and gut alterations are found to trigger an aberrant response of this pathway. The enhanced activity of the IL-23/IL-17 pathway is committed to the expansion and pathogenicity of Th17 cells. Evidence from animal models demonstrates that the development of pathogenic Th17 cells is responsible for the induction of experimental autoimmune uveitis. Further findings indicate that retinal pigment epithelium (RPE) cells may be a target of IL-17. IL-17 triggers downstream inflammatory cascades and causes dysfunction of RPE cells, which may affect retinal barrier function and thereby promote intraocular inflammation. Currently, several emerging drugs blocking the IL-23/IL-17 pathway have been assessed for the treatment of uveitis in pilot studies. The purpose of this is to summarize updated biological knowledge and preliminary clinical data, providing the rationale for further development and evaluation of novel drugs targeting the IL-23/IL-17 pathway in autoinflammatory and autoimmune uveitis. Future studies may focus on translational medicine targeting the IL-23/IL-17 pathway for the improvement of diagnosis and treatment of uveitis. In conclusion, activation of the IL-23/IL-17 pathway is a critical biological event and can be an important target for the treatment of autoinflammatory and autoimmune uveitis.

NOD2 and inflammation: current insights

The nucleotide-binding oligomerization domain (NOD) protein, NOD2, belonging to the intracellular NOD-like receptor family, detects conserved motifs in bacterial peptidoglycan and promotes their clearance through activation of a proinflammatory transcriptional program and other innate immune pathways, including autophagy and endoplasmic reticulum stress. An inactive form due to mutations or a constitutive high expression of NOD2 is associated with several inflammatory diseases, suggesting that balanced NOD2 signaling is critical for the maintenance of immune homeostasis. In this review, we discuss recent developments about the pathway and mechanisms of regulation of NOD2 and illustrate the principal functions of the gene, with particular emphasis on its central role in maintaining the equilibrium between intestinal microbiota and host immune responses to control inflammation. Furthermore, we survey recent studies illustrating the role of NOD2 in several inflammatory diseases, in particular, inflammatory bowel disease, of which it is the main susceptibility gene.

Determination of Genes Related to Uveitis by Utilization of the Random Walk with Restart Algorithm on a Protein-Protein Interaction Network

Uveitis, defined as inflammation of the uveal tract, may cause blindness in both young and middle-aged people. Approximately 10–15% of blindness in the West is caused by uveitis. Therefore, a comprehensive investigation to determine the disease pathogenesis is urgent, as it will thus be possible to design effective treatments. Identification of the disease genes that cause uveitis is an important requirement to achieve this goal. To begin to answer this question, in this study, a computational method was proposed to identify novel uveitis-related genes. This method was executed on a large protein–protein interaction network and employed a popular ranking algorithm, the Random Walk with Restart (RWR) algorithm. To improve the utility of the method, a permutation test and a procedure for selecting core genes were added, which helped to exclude false discoveries and select the most important candidate genes. The five-fold cross-validation was adopted to evaluate the method, yielding the average F1-measure of 0.189. In addition, we compared our method with a classic GBA-based method to further indicate its utility. Based on our method, 56 putative genes were chosen for further assessment. We have determined that several of these genes (e.g., CCL4, Jun, and MMP9) are likely to be important for the pathogenesis of uveitis.