Local S100A8 Levels Correlate With Recurrence of Experimental Autoimmune Uveitis and Promote Pathogenic T Cell Activity

S-100 Proteins: Basics and Applications as Biomarkers in Animals with Special Focus on Calgranulins (S100A8, A9, and A12)

S100 proteins are a group of calcium-binding proteins which received this name because of their solubility in a 100% saturated solution of ammonium sulphate. They have a similar molecular mass of 10-12 KDa and share 25-65% similarity in their amino acid sequence. They are expressed in many tissues, and to date 25 different types of S100 proteins have been identified. This review aims to provide updated information about S100 proteins and their use as biomarkers in veterinary science, with special emphasis on the family of calgranulins that includes S100A8 (calgranulin A; myeloid-related protein 8, MRP8), S100A9 (calgranulin B; MRP14), and S100A12 (calgranulin C). The proteins SA100A8 and S100A9 can be linked, forming a heterodimer which is known as calprotectin. Calgranulins are related to the activation of inflammation and the immune system and increase in gastrointestinal diseases, inflammation and sepsis, immunomediated diseases, and obesity and endocrine disorders in different animal species. This review reflects the current knowledge about calgranulins in veterinary science, which should increase in the future to clarify their role in different diseases and potential as biomarkers and therapeutic targets, as well as the practical use of their measurement in non-invasive samples such as saliva or feces.

Pertussis toxin-induced inhibition of Wnt/β-catenin signaling in dendritic cells promotes an autoimmune response in experimental autoimmune uveitis

BACKGROUND

Previous reports have indicated that disrupting the Wnt/β-catenin pathway in dendritic cells (DCs) may affect the progression of autoimmune inflammation; however, the factors and timing that regulate Wnt/β-catenin signaling have not been clearly understood.

METHODS

Experimental autoimmune uveitis (EAU) mice and Vogt-Koyanagi-Harada disease (VKH) patient samples were used to detect the expression of Wnt/β-catenin pathway genes. Western blot, real-time PCR, flow cytometry, and ELISA were performed to examine the expression of components of the Wnt/β-catenin pathway and inflammatory factors. DC-specific β-catenin knockout mice and 6-bromoindirubin-3'-oxime (BIO) administered mice were used to observe the effect of disrupting the Wnt pathway on EAU pathogenesis.

RESULTS

Wnt/β-catenin signaling was inhibited in DCs during the induction phase of EAU. The inhibition was mediated by pertussis toxin (PTX), which promoted DC maturation, in turn promoting pathogenic T cell proliferation and differentiation. In vivo experiments confirmed that deleting β-catenin in DCs enhanced EAU severity, and pre-injection of PTX advanced EAU onset. Administration of a Wnt activator (BIO) limited the effects of PTX, in turn ameliorating EAU.

CONCLUSIONS

Our results demonstrate that PTX plays a key role as a virulence factor in initiating autoimmune inflammation via DCs by inhibiting Wnt/β-catenin signaling in EAU, and highlight the potential mechanism by which infection can trigger apparent autoimmunity.

Single-Cell RNA-Seq of Bone Marrow Cells in Aplastic Anemia

Aplastic anemia (AA) is an autoimmune disease characterized by peripheral blood pancytopenia and bone marrow failure. Recently, a research study verified bone marrow failure of AA patients resulting from hematopoietic stem and progenitor cell (HSPC) attack by active T cells. Nonetheless, whether B cells, as one of the important immune cells, destruct the hematopoiesis is still unclear. Here, a large-scale single-cell transcriptomic sequencing of 20,000 bone marrow cells from AA patients and healthy donors was performed. A total of 17 clusters and differentially expressed genes were identified in each cluster relative to other clusters, which were considered potential marker genes in each cluster. The top differentially expressed genes in HSPCs (S100A8, RETN, and TNFAIP3), monocytes (CXCL8, JUN, and IL1B), and neutrophils and granulocytes (CXCL8, NFKBIA, and MT-CYB) were related to immune and inflammatory injury. Then, the B-cell receptor (BCR) diversities and pairing frequencies of V and J genes were analyzed. The highest pairing frequencies in AA patients were IGHV3-20-IGKJ2, IGHV3-20-IGKJ4, and IGHV3-20-IGHLJ2. Meanwhile, there were 3 V genes, including IGHV3-7, IGHV3-33, and IGLV2-11, with elevated expression in B cells from AA patients. Cell type-specific ligand-receptor was further identified in B-cell interaction with hematopoietic cells in the bone marrow. The changed ligand-receptor pairs involved antigen presentation, inflammation, apoptosis, and proliferation of B cells. These data showed the transcriptomic landscape of hematopoiesis in AA at single-cell resolution, providing new insights into hematopoiesis failure related with aberrance of B cells, and provide available targets of treatment for AA.

Tasquinimod efficacy and S100A9 expression in glucose-treated HREC cells

PURPOSE

Diabetic retinopathy (DR) is one of the leading causes of blindness in working-aged people. Few studies were on the relationship between S100 Calcium Binding Protein A9 (S100A9) protein and DR, and none on endothelial cells induced by tasquinimod in high glucose. Therefore, we assessed the relationship between tasquinimod and S100A9 in DR.

METHODS

DR pathogenesis was simulated using high-glucose-induced human retinal endothelial cells (HRECs) to study the mRNA expression of s100a9, thrombospondin-1 (tsp-1), hypoxia-inducible factor 1-alpha (hif1-α), intercellular adhesion molecule 1 (icam-1), and vascular endothelial growth factor (vegf) after tasquinimod treatment. The protein expression of S100A9, TSP-1, extracellular signal-regulated kinase (ERK), ICAM-1 and VEGF was also analyzed.

RESULT

A total of 28 eyes of 26 patients were included in this experiment. A significantly higher expression of S100A9 as well as enhanced proliferation and mobility was observed in the high-glucose-treated HRECs compared with that in low-glucose-treated cells. However, these were significantly inhibited when treated with high glucose with 50 μM tasquinimod. The mRNA expression of tsp-1 was increased, whereas that of hif1-α, icam-1 and vegf was decreased after tasquinimod treatment. Western blot indicated the increased TSP-1 but decreased ERK, ICAM-1 and VEGF expression after treating with tasquinimod.

CONCLUSION

High glucose promoted the expression of s100a9, S100A9 protein in DR patients and HRECs. Tasquinimod inhibited the proliferation, migration and lumen formation of HRECs under a high glucose environment. Tasquinimod might play a vital role in inhibiting angiogenesis through inducing TSP-1 and inhibiting VEGF, ICAM-1 and ERK.

Vaccination with circulating exosomes in autoimmune uveitis prevents recurrent intraocular inflammation

BACKGROUND

Exosomes participate in intercellular communication and act as important molecular vehicles in the regulation of numerous physiological and pathological processes, including autoimmune development. The role of circulating exosomes in the development of autoimmune uveitis is unknown. In this study, using the rat model of experimental autoimmune uveitis, which has clinical and histological features of pan uveitis in man, we evaluated the immunoregulatory function of circulating exosomes.

METHODS

Experimental autoimmune uveitis was induced in Lewis rats either immunised with interphotoreceptor retinoid-binding protein R16 peptides or injected with activated R16-specific T cells. The disease incidence and severity were examined by indirect fundoscopy and flow cytometry. Circulating exosomes were isolated from peripheral blood of naïve and Day 14 R16 immunised Lewis rats. The effect of exosomes on specific T cells was evaluated by R16-specific T cell proliferation, cytokine production and recurrent uveitis induction.

RESULTS

Circulating exosomes derived from active immunised uveitis rats selectively inhibited immune responses of R16-specific T cells in vitro. Vaccination of naïve rats with these exosomes reduced the incidence of recurrent uveitis in an antigen-specific manner. Antigen-specific uveitogenic T cells reduced IFN-γ production and increased IL-10 after vaccination.

CONCLUSIONS

Circulating exosomes in autoimmune uveitis have the potential to be a novel treatment for recurrent autoimmune uveitis.

Immune Resolution Dilemma: Host Antimicrobial Factor S100A8/A9 Modulates Inflammatory Collateral Tissue Damage During Disseminated Fungal Peritonitis

Intra-abdominal infection (peritonitis) is a leading cause of severe disease in surgical intensive care units, as over 70% of patients diagnosed with peritonitis develop septic shock. A critical role of the immune system is to return to homeostasis after combating infection. S100A8/A9 (calprotectin) is an antimicrobial and pro-inflammatory protein complex used as a biomarker for diagnosis of numerous inflammatory disorders. Here we describe the role of S100A8/A9 in inflammatory collateral tissue damage (ICTD). Using a mouse model of disseminated intra-abdominal candidiasis (IAC) in wild-type and S100A8/A9-deficient mice in the presence or absence of S100A9 inhibitor paquinimod, the role of S100A8/A9 during ICTD and fungal clearance were investigated. S100A8/A9-deficient mice developed less ICTD than wild-type mice. Restoration of S100A8/A9 in knockout mice by injection of recombinant protein resulted in increased ICTD and fungal clearance comparable to wild-type levels. Treatment with paquinimod abolished ICTD and S100A9-deficient mice showed increased survival compared to wild-type littermates. The data indicates that S100A8/A9 controls ICTD levels and antimicrobial activity during IAC and that targeting of S100A8/A9 could serve as promising adjunct therapy against this challenging disease.

The Role of Plasma Calprotectin in Non-infectious Uveitis

PURPOSE

To investigate the role of plasma calprotectin in non-infectious uveitis.

METHODS

This is an observational both cross-sectional and prospective study. Patients with active non-infectious uveitis were recruited as well as nonuveitic controls. Plasma calprotectin was determined and an ophthalmological examination was performed for both patients and controls. Independent variables possibly influencing levels of plasma calprotectin were recorded and analyzed. Categorical variables were compared by chi-square test (applying correction by continuity if necessary). T-test (or Kruskal-Wallis when appropriate) was used to compare averages. Multiple linear regression analysis was used to assess relationship between plasma calprotectin levels and independent variables. Spearman coefficient was calculated in order to establish correlation between plasma calprotectin and anterior chamber cell grading. Changes in plasma calprotectin levels between the flare beginning and its resolution were determined with mixed model for repeated measures. R software (version 3.6.0) was used to perform the statistical analysis.

RESULTS

We included 74 patients and 40 controls in the cross-sectional study. Plasma calprotectin levels were higher in uveitis patients compared to those of controls (p = .003), being higher in younger patients and patients with posterior uveitis. No correlation between calprotectin and anterior chamber inflammation degree was found (p = .198). For the prospective study, we included 36 patients. We found no significant differences in calprotectin levels between active and inactive uveitis (p = .344).

CONCLUSIONS

Plasma calprotectin levels are elevated in uveitis patients and are influenced by age and anatomical location of uveitis. Further investigation is needed to assess the relationship between calprotectin and uveitis activity.

Quantitative proteomic analysis of rat retina with experimental autoimmune uveitis based on tandem mass tag (TMT) peptide labeling coupled with LC-MS/MS

Uveitis is a recurrent, inflammatory eye disease that occurs in the retina, iris, ciliary body and choroid. Currently, the detailed mechanism is still unclear. Proteomics can offer a powerful set of tools for the direct high-throughput study and a key contribution to the understanding of protein functions. This approach can also allow us to compare the protein profiling of the cells in healthy and diseased states that can be used to identify proteins associated with disease development and progression. In the present study, we first established an autoimmune uveitis (EAU) rat model. On day 12 after immunization, we isolated the rat retinas from both normal and EAU animals to collect total proteins. Using tandem mass tag (TMT) peptide labeling coupled with LC-MS/MS quantitative proteomics technique, we identified the differentially expressed proteins in EAU rat retinas, performed bioinformatics analyses, validated the expression of the COX1, NADH1, C3, and C9 proteins, and determined the adenosine triphosphate (ATP) levels. The results indicated that there were 190 upregulated and 103 downregulated proteins in EAU rat retinas. Bioinformatics analysis revealed the differentially expressed proteins were mainly involved in acute inflammatory response, visual perception and eye photoreceptor cell differentiation that were mainly related to complement and coagulation cascades, phagosome, PI3K-Akt signaling, and metabolic pathways. In conclusion, based on the TMT-based quantitative proteomics technique, the differentially expressed proteins in EAU rat retinas were mainly associated with complement and coagulation cascades and metabolic pathways. Our findings will facilitate the understanding of the pathogenesis of uveitis and will be useful for subsequent studies.

Proteomic analysis of intermediate uveitis suggests myeloid cell recruitment and implicates IL-23 as a therapeutic target

Purpose

To profile vitreous protein expression of intermediate uveitis (IU) patients.

Observations

We identified a mean of 363 ± 41 unique proteins (mean ± SD) in IU vitreous and 393 ± 69 unique proteins in control samples using liquid chromatography-tandem mass spectrometry (LC-MS/MS) analysis of liquid vitreous biopsies collected during pars plana vitrectomy. A total of 233 proteins were differentially expressed among control and IU samples, suggesting a protein signature that could distinguish the two groups. Pathway analysis identified 22 inflammatory mediators of the interleukin-12 (IL-12) signaling pathway in IU vitreous. Upstream regulator analysis identified downstream mediators of IL-23 and myeloid differentiation primary response protein (MYD88), both of which are involved in the recruitment and differentiation of myeloid cells. Taken together, our results suggest the recruitment of myeloid cells as an upstream pathway in the pathogenesis of IU.

Conclusions

This study provides insights into proteins that will serve as biomarkers and therapeutic targets for IU. These biomarkers will help design future clinical trials using rational molecular therapeutics.

Uveitis Therapy With Shark Variable Novel Antigen Receptor Domains Targeting Tumor Necrosis Factor Alpha or Inducible T-Cell Costimulatory Ligand

Purpose

We assess the efficacy of two next-generation biologic therapies in treating experimental autoimmune uveitis.

Methods

Variable binding domains from shark immunoglobulin novel antigen receptors (VNARs) were fused with a mouse IgG2a constant domain (Fc) to generate VNAR-Fc molecules with binding specificity to tumor necrosis factor alpha (TNFα) or inducible T-cell costimulatory ligand (ICOSL). Treatment with VNAR-Fc fusion proteins was compared to treatment with dexamethasone or vehicle in the Lewis rat model of experimental autoimmune uveitis (EAU). Inflammation control was determined by comparing OCT clinical and histologic scores, and aqueous humor protein concentration. The concentration of 27 inflammatory cytokines in the aqueous humor was measured using a multiplex enzyme-linked immunosorbent assay platform.

Results

Administration of S17-Fc significantly decreased clinical, histologic, and aqueous protein levels when compared to vehicle treatment. Inflammation scores and aqueous protein levels in A5-Fc–treated animals were decreased compared to vehicle treatment, but not significantly. The concentration of vascular endothelial growth factor (VEGF), regulated on activation, normal T cell expressed and secreted (RANTES), macrophage inflammatory protein 1 alpha (MIP-1α), interleukin (IL)-1β, LPS-induced CXC chemokine (LIX), monocyte chemoattractant protein-1 (MCP-1), and interferon (IFN)-γ were significantly decreased in the eyes of animals treated with dexamethasone. VNAR treatment demonstrated a trend towards decreased cytokine concentrations, but only VEGF and RANTES were significantly decreased by S17-Fc.

Conclusions

Treatment with the anti-TNFα VNAR S17-Fc ameliorates EAU as effectively as treatment with corticosteroids.

Translational Relevance

VNAR-Fc molecules are a next-generation therapeutic biologic that overcome the limitations of classical biologic monoclonal antibodies, such as complex structure, large size, and limited tissue penetration. This is a novel drug modality that could result in the development of new therapy options for patients with noninfectious uveitis.

Innate immune response in retinal homeostasis and inflammatory disorders

Innate immune cells such as neutrophils, monocyte-macrophages and microglial cells are pivotal for the health and disease of the retina. For the maintenance of retinal homeostasis, these cells and immunosuppressive molecules in the eye actively regulate the induction and the expression of inflammation in order to prevent excessive activation and subsequent tissue damage. In the disease context, these regulatory mechanisms are modulated genetically and/or by environmental stimuli such as damage-associated molecular patterns (DAMPs), and a chronic innate immune response regulates or contributes to the formation of diverse retinal disorders such as uveitis, retinitis pigmentosa, retinal vascular diseases and retinal fibrosis. Here we summarize the recent knowledge regarding the innate immune response in both ocular immune regulation and inflammatory retinal diseases, and we describe the potential of the innate immune response as a biomarker and therapeutic target.

Correlation between systemic S100A8 and S100A9 levels and severity of diabetic retinopathy in patients with type 2 diabetes mellitus

AIMS

S100A8 and S100A9 are myeloid-related damage-associated molecular patterns (DAMPs) primarily involved in the modulation of innate immune response to cellular injury. This study evaluated the correlation between circulating concentrations of S100A8 and S100A9 proteins with the severity of diabetic retinopathy (DR) in patients with type 2 diabetes (T2DM).

METHODS

T2DM patients with HbA1c levels >7%, fasting blood glucose >126 mg/dl and history of diabetes were included in this study. DR severity was graded based on ETDRS and Gloucestershire classifications. Plasma samples were evaluated for S100A8 and S100A9 levels using ELISA.

RESULTS

In this comparative study, DR patients (n = 89) had increased plasma S100A8 and S100A9 proteins compared to age-matched T2DM controls (n = 28), which was directly related to the severity of DR. Female DR subjects had increased S100A8 expression compared to their male counterparts. Substantial retention of S100A8 and S100A9 production was seen in DR patients above 50 years of age. Duration of T2DM was not found to affect protein levels, however T2DM onset at >50 years old significantly increased S100A8 and S100A9 concentrations.

CONCLUSIONS

Our findings suggest that systemic circulation levels of S100A8 and S100A9 are correlated with the progression of DR in T2DM patients, indicating their potential role in DR pathogenesis.

S100A8/A9 induces microglia activation and promotes the apoptosis of oligodendrocyte precursor cells by activating the NF-κB signaling pathway

S100A8/A9, a heterodimer complex composed of calcium-binding proteins S100A8 and S100A9, is significantly increased in the serum of multiple sclerosis (MS) patients. Relevant reports have revealed that MS pathology is commonly associated with the activation of microglial cells and the damage of oligodendrocyte precursor cells (OPCs). Moreover, microglia activation following stimulation increases the expression of pro-inflammatory cytokines, such as interleukin-1β (IL-1β) and tumor necrosis factor-α (TNF-α), which further exacerbate the damage to OPCs. In this study, we were the first to confirm that S100A8/A9 treatment induced the activation, proliferation and migration of the murine microglia cell line BV-2; moreover, this treatment caused the cells to switch from an anti-inflammatory activated (M2) phenotype to a pro-inflammatory activated (M1) phenotype. Meanwhile, the level of the phosphorylated nuclear factor-κB (p-NF-κB) P65 protein was remarkably elevated, and the production of pro-inflammatory factors (IL-1β, TNF-α, MMP-9) and chemokines (CCL2, CCL3, CXCL10) was also increased in the S100A8/A9-treated BV-2 microglial cells. Inhibition of NF-κB P65 phosphorylation reversed the effects of S100A8/A9 on the production of pro-inflammatory factors and chemokines. We also explored the effects of S100A8/A9 and S100A8/A9-activated BV-2 microglial cells on the viability of OPCs. The results showed that both the S100A8/A9 complex and the conditioned medium (CM) of the S100A8/A9-activated BV-2 microglial cells resulted in OPC apoptosis, which was more pronounced in the case of the CM treatment. However, OPC apoptosis in the CM group was obviously decreased through the inhibition of NF-κB p65 phosphorylation. This study indicates that S100A8/A9 induces the activation of BV-2 microglial cells and promotes the production of pro-inflammatory factors by activating the NF-κB signaling pathway, which further exacerbates OPC damage.