Dimethyl itaconate inhibits antigen-specific Th17 cell responses and autoimmune inflammation via modulating NRF2/STAT3 signaling

Pathogenic Th17 cells play a crucial role in autoimmune diseases like uveitis and its animal model, experimental autoimmune uveitis (EAU). Dimethyl itaconate (DMI) possesses potent anti-inflammatory effects. However, there is still a lack of knowledge about the role of DMI in regulating pathogenic Th17 cells and EAU. Here, we reported that intraperitoneal administration of DMI significantly inhibited the severity of EAU via selectively suppressing Th17 cell responses. In vitro antigen stimulation studies revealed that DMI dramatically decreased the frequencies and function of antigen-specific Th17, but not Th1, cells. Moreover, DMI hampered the differentiation of naive CD4+ T cells toward pathogenic Th17 cells. DMI-treated DCs produced less IL-1β, IL-6, and IL-23, and displayed an impaired ability to stimulate antigen-specific Th17 activation. Mechanistically, DMI activated the NRF2/HO-1 pathway and suppressed STAT3 signaling, which subsequently restrains p-STAT3 nuclear translocation, leading to decreased pathogenic Th17 cell responses. Thus, we have identified an important role for DMI in regulating pathogenic Th17 cells, supporting DMI as a promising therapy in Th17 cell-driven autoimmune diseases including uveitis.

Combined Therapy of Experimental Autoimmune Uveitis by a Dual-Drug Nanocomposite Formulation with Berberine and Dexamethasone

Purpose

Autoimmune uveitis is a kind of sight-threatening ocular and systemic disorders. Recent treatments on autoimmune uveitis still remain many limitations due to extreme complexity and undetermined pathogenesis. In this study, a novel dual-drug nanocomposite formulation is developed to treat experimental autoimmune uveitis by a combined and sustained therapy method.

Methods

The dual-drug nanocomposite formulation is constructed by integrating berberine (BBR)-loaded mesoporous silica nanoparticles (MSNs) into dexamethasone (DEX)-loaded thermogel (BBR@MSN-DEX@Gel). The BBR@MSN-DEX@Gel is characterized by transmission electron microscopy, dynamic light scattering, Fourier transform infrared spectrometer and rheometer. The in vitro drug release profile, cytotoxicity and anti-inflammation effectiveness of BBR@MSN-DEX@Gel on lipopolysaccharide-stimulated human conjunctival epithelial cells are investigated. After the in vivo drug release profile and biosafety of the dual-drug nanocomposite formulation are confirmed, its treatment effectiveness is fully assessed based on the induced experimental autoimmune uveitis (EAU) Lewis rat's model.

Results

The dual-drug nanocomposite formulation has good injectability and thermosensitivity, suitable for administration by an intravitreal injection. The BBR@MSN-DEX@Gel has been found to sustainably release both drugs for up to 4 weeks. The carrier materials have minimal in vitro cytotoxicity and high in vivo biosafety. BBR@MSN-DEX@Gel presents obviously anti-inflammatory effectiveness in vitro. After administration of BBR@MSN-DEX@Gel into Lewis rat's eye with EAU by an intravitreal injection, the nanocomposite formulation significantly suppresses inflammatory reaction of autoimmune uveitis via a dual-drug combined and sustained therapy method, compared with the equivalent dose of single-component formulations.

Conclusion

BBR@MSN-DEX@Gel serves as a promising dual-drug nanocomposite formulation for future treatment of autoimmune uveitis.

Comprehensive Grading System for Experimental Autoimmune Uveitis in Mice

Experimental autoimmune uveitis (EAU) is the most commonly used animal model to study the progression of chronic uveitis and to test various therapies to treat the disease. However, to accurately evaluate the effectiveness of such treatments, a grading system that combines the latest imaging techniques with definitive quantitative grading thresholds is required. This study aimed to develop a comprehensive grading system that objectively evaluates EAU progression in C57BL/6J mice. EAU was induced following immunisation with interphotoreceptor retinoid-binding protein (IRBP) and pertussis toxin. Weekly fundus and optical coherence tomography (OCT) images were acquired over 12 weeks using a Micron IV imaging system. Each mouse was graded (between 0 to 4) based on changes seen on both the fundus (optic disc, retinal blood vessels and retinal tissue) and OCT (vitreous and retinal layers) images. A total EAU response (with a maximum score of 48) was calculated for each mouse based on the sum of the individual scores each week. Analysis of the clinical scores depicted a gradual increase in inflammatory signs including optic disc and vascular swelling, leukocyte infiltration in the vitreous, lesions in the retina and formation of granulomas and hyper-reflective foci in the retinal layers in EAU mice, with most signs reaching a plateau towards the end of the study period. Development of these signs into sight-threatening complications such as optic disc atrophy, structural damage to the retina and subretinal oedema were noted in 80-90% of mice suggesting consistent disease induction. Overall, a comprehensive and objective grading system encompassing all pathologies occurring in EAU mice was developed to enhance the preclinical evaluation of novel uveitis treatments.

[Pharmacodynamic mechanism of Tibetan medicine Liurui Capsules on experimental autoimmune uveitis in rats based on network pharmacology and animal experiments]

By integrating network pharmacology and animal experiments, we studied the pharmacodynamic mechanism of the Tibetan medicine Liurui Capsules in the treatment of experimental autoimmune uveitis(EAU). The active ingredients and targets of Liurui Capsules were searched against the Encyclopedia of Traditional Chinese Medicine(ETCM), Bioinformatics Analysis Tool for Molecular Mechanism of Traditional Chinese Medicine(BATMAN-TCM), and relevant literatures. The EAU-related targets were obtained from Gene Expression Omnibus(GEO), GeneCards, Online Mendelian Inheritance in Man(OMIM), and Therapeutic Target Database(TTD). The common targets shared by Liurui Capsules and EAU were identified, and the protein-protein interaction(PPI) network was established via STRING. Gene Ontology(GO) annotation and Kyoto Encyclopedia of Genes and Genomes(KEGG) pathway enrichment analysis were conducted via g: Profiler. The rat model of EAU was induced by interphotoreceptor retinoid-binding protein(IRBP) and treated with Liurui Capsules. The inflammatory response of anterior segment and the pathological morphology of retina were observed. The mRNA and protein levels of delta-like ligand 4(DLL4), Notch1, interleukin-17(IL-17), and tumor necrosis factor-alpha(TNF-α) were determined by real-time quantitative PCR(q-PCR) and Western blot, respectively. The network pharmacology analysis predicted 51 common targets of Liurui Capsules and EAU, which were mainly involved in IL-17, TNF, and nuclear factor-kappa B(NF-κB) signaling pathways, as well as liposome receptors and other biological processes. Compared with the control group, the modeling of EAU caused inflammatory changes in the anterior segment and retina and up-regulated mRNA and protein levels of DLL4, Notch1, IL-17, and TNF-α in ocular tissue. Compared with the model group, Liurui Capsules reduced the inflammatory reaction of anterior segment and retina and down-regulated the mRNA and protein levels of DLL4, Notch1, IL-17, and TNF-α. Liurui Capsules can down-regulate the expression of the proteins involved in DLL4/Notch1/IL-17 signaling pathway in ocular tissue and alleviate the ocular inflammation, which may be one of the mechanisms of Liurui Capsules in the treatment of EAU.

Stress Suppresses Systemic Th17/Treg Imbalance in Rats with Experimental Autoimmune Uveitis

PURPOSE

To explore the effect of chronic unpredictable mild stress (CUMS) on the immune response involved in rats with experimental autoimmune uveitis (EAU).

METHODS

Lewis rats were randomly divided into control, EAU, CUMS, and EAU+CUMS groups and received relevant treatments. On days 7, 11, 14, 21 and 28, frequencies of Th17 and Treg cells and the related cytokines were analyzed.

RESULTS

The intraocular inflammation of EAU rats peaked between days 11 and 13, while the severity of inflammation of the rats in EAU+CUMS group fluctuated between 11 and 15 days. Both frequencies of Th17, Treg cells and the related cytokines exhibited a significant difference between the two groups on days 11 and 14.

CONCLUSION

CUMS may protect against the possible harmful effects of immune disorder in rats with EAU through suppressing the immune disorder of T lymphocyte and the related cytokine responses.

Hydroxychloroquine Alleviates EAU by Inhibiting Uveitogenic T Cells and Ameliorating Retinal Vascular Endothelial Cells Dysfunction

Purpose

Inflammation triggers the activation of CD4⁺T cells and the breakdown of blood–retinal barrier, thus contributing to the pathology of experimental autoimmune uveitis (EAU). We explored the anti-inflammatory effect of hydroxychloroquine (HCQ) on EAU and the potential mechanisms active in T cells and retinal vascular endothelial cells (RVECs).

Methods

C57BL/6J mice were immunized with interphotoreceptor retinoid binding protein 1-20 (IRBP_1–20) to induce EAU and then treated with the vehicle or HCQ (100 mg/kg/day). On day 7, 14, 21, 30 and 60 after immunization, clinical scores were evaluated. On day 14, histopathological scores were assessed, and retinas, spleens, and lymph nodes were collected for quantitative polymerase chain reaction or flow cytometry analysis. RVEC dysfunction was induced by tumor necrosis factor α (TNF-α) stimulation. The expression of cytokines, chemokines, adhesion molecules, and lectin-like oxidized LDL receptor-1 (LOX-1)/nuclear factor κB (NF-κB) was measured in RVECs with or without HCQ.

Results

HCQ treatment protected mice from uveitis, evidenced by reduced expression of inflammatory factors, chemokines, and adhesion molecules in the retina. In systemic immune response, HCQ inhibited the activation of naïve CD4⁺T cells and frequencies of T effector cells, and promoted T regulatory cells. HCQ decreased IRBP_1-20–specific T cell responses and proliferation of CD4⁺T cells in vitro. Further studies established that TNF-α induced RVECs to express inflammatory cytokines, chemokines, and adhesion molecules, whereas HCQ alleviated the alterations via the LOX-1/NF-κB pathways.

Conclusions

HCQ alleviates EAU by regulating the Teff/Treg balance and ameliorating RVECs dysfunction via the LOX-1/NF-κB axis. HCQ may be a promising therapeutic candidate for uveitis.

Adhesion Molecule Targeted Therapy for Non-Infectious Uveitis

Non-infectious uveitis (NIU) is an inflammatory eye disease initiated via CD4+ T-cell activation and transmigration, resulting in focal retinal tissue damage and visual acuity disturbance. Cell adhesion molecules (CAMs) are activated during the inflammatory process to facilitate the leukocyte recruitment cascade. Our review focused on CAM-targeted therapies in experimental autoimmune uveitis (EAU) and NIU. We concluded that CAM-based therapies have demonstrated benefits for controlling EAU severity with decreases in immune cell migration, especially via ICAM-1/LFA-1 and VCAM-1/VLA-4 (integrin) pathways. P-selectin and E-selectin are more involved specifically in uveitis related to vasculitis. These therapies have potential clinical applications for the development of a more personalized and specific treatment. Localized therapies are the future direction to avoid serious systemic side effects.

Aging weakens Th17 cell pathogenicity and ameliorates experimental autoimmune uveitis in mice

Aging-induced changes in the immune system are associated with a higher incidence of infection and vaccination failure. Lymph nodes, which filter the lymph to identify and fight infections, play a central role in this process. However, careful characterization of the impact of aging on lymph nodes and associated autoimmune diseases is lacking. We combined single-cell RNA sequencing (scRNA-seq) with flow cytometry to delineate the immune cell atlas of cervical draining lymph nodes (CDLNs) of both young and old mice with or without experimental autoimmune uveitis (EAU). We found extensive and complicated changes in the cellular constituents of CDLNs during aging. When confronted with autoimmune challenges, old mice developed milder EAU compared to young mice. Within this EAU process, we highlighted that the pathogenicity of T helper 17 cells (Th17) was dampened, as shown by reduced GM-CSF secretion in old mice. The mitigated secretion of GM-CSF contributed to alleviation of IL-23 secretion by antigen-presenting cells (APCs) and may, in turn, weaken APCs’ effects on facilitating the pathogenicity of Th17 cells. Meanwhile, our study further unveiled that aging downregulated GM-CSF secretion through reducing both the transcript and protein levels of IL-23R in Th17 cells from CDLNs. Overall, aging altered immune cell responses, especially through toning down Th17 cells, counteracting EAU challenge in old mice.

Overexpressing Kallistatin Aggravates Experimental Autoimmune Uveitis Through Promoting Th17 Differentiation

Kallistatin or kallikrein-binding protein (KBP) has been reported to regulate angiogenesis, inflammation and tumor progression. Autoimmune uveitis is a common, sight-threatening inflammatory intraocular disease. However, the roles of kallistatin in autoimmunity and autoreactive T cells are poorly investigated. Compared to non-uveitis controls, we found that plasma levels of kallistatin were significantly upregulated in patients with Vogt-Koyanagi-Harada (VKH) disease, one of the non-infectious uveitis. Using an experimental autoimmune uveitis (EAU) model induced by human interphotoreceptor retinoid-binding protein peptide 651-670 (hIRBP_651-670), we examined the effects of kallistatin on the pathogenesis of autoimmune diseases. Compared to wild type (WT) mice, kallistatin transgenic (KS) mice developed severe uveitis with dominant Th17 infiltrates in the eye. In addition, the proliferative antigen-specific T cells isolated from KS EAU mice produced increased levels of IL-17A, but not IFN-γ or IL-10 cytokines. Moreover, splenic CD4⁺ T cells from naïve KS mice expressed higher levels of Il17a mRNA compared to WT naïve mice. Under Th17 polarization conditions, KS mice exhibited enhanced differentiation of naïve CD4⁺ T cells into Th17 cells compared to WT controls. Together, our results indicate that kallistatin promotes Th17 differentiation and is a key regulator of aggravating autoinflammation in EAU. Targeting kallistatin might be a potential to treat autoimmune disease.

CD4+ T-Cell Plasticity in Non-Infectious Retinal Inflammatory Disease

Non-infectious uveitis (NIU) is a potentially sight-threatening disease. Effector CD4⁺ T cells, especially interferon-γ-(IFNγ) producing Th1 cells and interleukin-17-(IL-17) producing Th17 cells, are the major immunopathogenic cells, as demonstrated by adoptive transfer of disease in a model of experimental autoimmune uveitis (EAU). CD4⁺FoxP3⁺CD25⁺ regulatory T cells (Tregs) were known to suppress function of effector CD4⁺ T cells and contribute to resolution of disease. It has been recently reported that some CD4⁺ T-cell subsets demonstrate shared phenotypes with another CD4⁺ T-cell subset, offering the potential for dual function. For example, Th17/Th1 (co-expressing IFNγ and IL-17) cells and Th17/Treg (co-expressing IL-17 and FoxP3) cells have been identified in NIU and EAU. In this review, we have investigated the evidence as to whether these ‘plastic CD4⁺ T cells’ are functionally active in uveitis. We conclude that Th17/Th1 cells are generated locally, are resistant to the immunosuppressive effects of steroids, and contribute to early development of EAU. Th17/Treg cells produce IL-17, not IL-10, and act similar to Th17 cells. These cells were considered pathogenic in uveitis. Future studies are needed to better clarify their function, and in the future, these cell subsets may in need to be taken into consideration for designing treatment strategies for disease.

Induction of antigen-specific Treg cells in treating autoimmune uveitis via bystander suppressive pathways without compromising anti-tumor immunity

BACKGROUND

Induction of autoantigen-specific Treg cells that suppress tissue-specific autoimmunity without compromising beneficial immune responses is the holy-grail for immunotherapy to autoimmune diseases.

METHODS

In a model of experimental autoimmune uveitis (EAU) that mimics human uveitis, ocular inflammation was induced by immunization with retinal antigen interphotoreceptor retinoid-binding protein (IRBP). Mice were given intraperitoneal injection of αCD4 antibody (Ab) after the onset of disease, followed by administration of IRBP. EAU was evaluated clinically and functionally. Splenocytes, CD4⁺CD25^- and CD4⁺CD25⁺ T cells were sorted and cultured with IRBP or αCD3 Ab. T cell proliferation and cytokine production were assessed.

FINDINGS

The experimental approach resulted in remission of ocular inflammation and rescue of visual function in mice with established EAU. Mechanistically, the therapeutic effect was mediated by induction of antigen-specific Treg cells that inhibited IRBP-driven Th17 response in TGF-β and IL-10 dependent fashion. Importantly, the Ab-mediated immune tolerance could be achieved in EAU mice by administration of retinal autoantigens, arrestin but not limited to IRBP only, in an antigen-nonspecific bystander manner. Further, these EAU-suppressed tolerized mice did not compromise their anti-tumor T immunity in melanoma model.

INTERPRETATION

We successfully addressed a specific immunotherapy of EAU by in vivo induction of autoantigen-specific Treg cells without compromising host overall T cell immunity, which should have potential implication for patients with autoimmune uveitis.

FUNDING

This study was supported by the Natural Science Foundation of Guangdong Province and the Fundamental Research Fund of the State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center.

MiR-379-5p aggravates experimental autoimmune uveitis in mice via the regulation of SEMA3A

Uveitis is a disease resulting in the inflammation of uveal tracts, but the factors resulting in uveitis is still obscure. Previous studies have shown that miR-379-5p was involved in the pathogenesis of several diseases, however, the role and regulatory mechanism of miR-379-5p in uveitis were unclear. In our study, we established experimental autoimmune uveitis (EAU) mouse models to explore the role of miR-379-5p in uveitis. RT-qPCR identified that miR-379-5p level was increased in serum of EAU mice. In mechanism, SEMA3A 3'UTR was proven to be directly targeted by miR-379-5p and SEMA3A expression was negatively regulated by miR-379-5p in CD4⁺ T cells. Moreover, ELISA analysis revealed that knockdown of miR-379-5p suppressed the production of inflammation cytokines including IL-17, TNF-α and IL-β in vitro. These results were reversed by SEMA3A overexpression. In addition, the reduction of Th17 cells under miR-379-5p inhibitor was neutralised by SEMA3A knockdown in vitro. Furthermore, we demonstrated that knockdown of miR-379-5p significantly reversed the increased clinical scores and inflammatory response resulting from EAU treatment and this effect was further countervailed by SEMA3A silencing. Our study suggested that miR-379-5p aggravated uveitis in EAU mice via the regulation of SEMA3A, which may provide a novel insight for uveitis treatment.

High Ambient Temperature Aggravates Experimental Autoimmune Uveitis Symptoms

Whether ambient temperature influences immune responses leading to uveitis is unknown. We thus tested whether ambient temperature affects the symptoms of experimental autoimmune uveitis (EAU) in mice and investigated possible mechanisms. C57BL/6 mice were kept at a normal (22°C) or high temperature (30°C) housing conditions for 2 weeks and were then immunized with human interphotoreceptor retinoid-binding protein (IRBP651–670) peptide to induce EAU. Histological changes were monitored to evaluate the severity of uveitis. Frequency of Th1 cells and Th17 cells was measured by flow cytometry (FCM). The expression of IFN-γ and IL-17A mRNA was measured by real-time qPCR. The generation of neutrophil extracellular traps (NETs) was quantified by enzyme-linked immunosorbent assay (ELISA). Differential metabolites in the plasma of the mice kept in the aforementioned two ambient temperatures were measured via ultra-high-performance liquid chromatography triple quadrupole mass spectrometry quadrupole time of flight mass spectrometry (UHPLC-QQQ/MS). The differential metabolites identified were used to evaluate their effects on differentiation of Th1 and Th17 cells and generation of NETs in vitro. The results showed that EAU mice kept at high temperature experienced a more severe histopathological manifestation of uveitis than mice kept at a normal temperature. A significantly increased frequency of Th1 and Th17 cells in association with an upregulated expression of IFN-γ and IL-17A mRNA was observed in the splenic lymphocytes and retinas of EAU mice in high temperature. The expression of NETs as evidenced by myeloperoxidase (MPO) and neutrophil elastase (NE), was significantly elevated in serum and supernatants of neutrophils from EAU mice kept at high temperature compared to the normal temperature group. The metabolites in the plasma from EAU mice, fumaric acid and succinic acid, were markedly increased in the high temperature group and could induce the generation of NETs via the NADPH oxidase-dependent pathway, but did not influence the frequency of Th1 and Th17 cells. Our findings suggest that an increased ambient temperature is a risk factor for the development of uveitis. This is associated with the induction of Th1 and Th17 cells as well as the generation of NETs which could be mediated by the NADPH oxidase-dependent pathway.

Melanocortin 5 Receptor Expression and Recovery of Ocular Immune Privilege after Uveitis

Purpose: The therapeutic use of the RPE-neuropeptide α-MSH suppresses experimental autoimmune uveitis (EAU). This suppression is partially through the α-MSH melanocortin 5 receptor (MC5r). Therefore, we examined the possible role of MC5r-expression in the recovery of RPE suppression of phagolysosome-activation in macrophages following α-MSH-treatment of EAUMethods: The conditioned media of cultured in situ RPE-eyecup from α-MSH-treated EAU wild-type and MC5r(-/-) mice were used to treat macrophages to assay for phagolysosome activation.Results: MC5r(-/-) mice treated with α-MSH recovered from EAU, but with greater retinal damage, and the RPE suppressed phagolysosome activation in wild type but not in MC5r(-/-) macrophages. In addition, α-MSH did not suppress phagolysosome activation in MC5r(-/-) macrophages, and resting-MC5r(-/-) macrophages had augmented phagocytic activity.Conclusion: α-MSH treatment of EAU mediates a MC5r-dependent recovery of RPE suppression of phagolysosome activation in macrophages possibly altering antigen processing and presentation. Also, MC5r-expression helps protect the retina from inflammatory damage. In addition, MC5r-expression is important in the homeostatic maintenance of phagosome-maturation within macrophages.

Sirolimus-Loaded Intravitreal Implant for Effective Treatment of Experimental Uveitis

Non-infectious uveitis, an ocular inflammatory condition that affects the iris, ciliary body, choroid, and adjacent tissues (retina, optic nerve, and vitreous), is an important cause of blindness worldwide. Sirolimus (SRL), a potent immunomodulatory drug, has shown promising results in the treatment of inflammatory ocular diseases. Despite this therapeutic potential, its clinical use is a major challenge due to low bioavailability and poor solubility. Poly(lactic-co-glycolic acid) (PLGA) is a biodegradable polymer commonly used for ophthalmic drug delivery due to its suitable characteristics such as biocompatibility, good mechanical properties, and improvement of the pharmacokinetic profile of the drug. In the present study, we investigated the effects of SRL-PLGA implant on experimental autoimmune uveitis in rabbits. Clinical and histopathological examinations were performed, followed by assessment of protein levels and determination of myeloperoxidase (MPO) and N-acetylglucosaminidase (NAG) activity in the aqueous humor/vitreous. As a result, treated eyes had decreased average inflammatory scores, protein significant decreases in treated eyes, assessed after 35 days. Histopathological examination showed less severe intraocular inflammation and decreased tissue damage in treated eyes. According to these results, the SRL-PLGA implant evaluated in this study was apparently safe, reducing inflammation in treated eyes, with an extended effect possibly associated with prolonged release of SRL in the posterior segment of the eye. Therefore, intravitreal SRL-PLGA implant could be a promising alternative for treatment of non-infectious uveitis.

Severity of Experimental Autoimmune Uveitis Is Reduced by Pretreatment with Live Probiotic Escherichia coli Nissle 1917

Non-infectious uveitis is considered an autoimmune disease responsible for a significant burden of blindness in developed countries and recent studies have linked its pathogenesis to dysregulation of the gut microbiota. We tested the immunomodulatory properties of two probiotics, Escherichia coli Nissle 1917 (EcN) and E. coli O83:K24:H31 (EcO), in a model of experimental autoimmune uveitis (EAU). To determine the importance of bacterial viability and treatment timing, mice were orally treated with live or autoclaved bacteria in both preventive and therapeutic schedules. Disease severity was assessed by ophthalmoscopy and histology, immune phenotypes in mesenteric and cervical lymph nodes were analyzed by flow cytometry and the gut immune environment was analyzed by RT-PCR and/or gut tissue culture. EcN, but not EcO, protected against EAU but only as a live organism and only when administered before or at the time of disease induction. Successful prevention of EAU was accompanied by a decrease in IRBP-specific T cell response in the lymph nodes draining the site of immunization as early as 7 days after the immunization and eye-draining cervical lymph nodes when the eye inflammation became apparent. Furthermore, EcN promoted an anti-inflammatory response in Peyer’s patches, increased gut antimicrobial peptide expression and decreased production of inducible nitric oxide synthase in macrophages. In summary, we show here that EcN controls inflammation in EAU and suggest that probiotics may have a role in regulating the gut–eye axis.

CD73+ Dendritic Cells in Cascading Th17 Responses of Experimental Autoimmune Uveitis-Induced Mice

Previous studies have shown that CD73 is pivotal in the conversion of pro-inflammatory adenosine triphosphate into anti-inflammatory adenosine and that immune cells of the same type that express different levels of CD73 are functionally distinct. In this study we show that adenosine enhances the Th17 promoting effect of dendritic cells (DCs), and DCs expressing CD73 critically augment Th17 responses. Bone marrow dendritic cells (BMDCs) do not constantly express CD73; however, a significant portion of the BMDCs expressed CD73 after exposure to Toll-like receptor ligand, leading to stronger Th17 responses by converting adenosine monophosphate to adenosine. We show that the CD73⁺ BMDCs play a critical role in cascading Th17 responses, and CD73⁺ BMDCs are functionally augmented after treatment with Toll-like receptor ligand. Splenic antigen presenting cells (DCs) of CD73^−/− mouse have a poor Th17-stimulating effect, even after exposure to lipopolysaccharide (LPS) or γδ T cells, indicating that induction of CD73⁺ DCs is critically involved in augmented Th17 responses. We conclude that CD73⁺ DCs critically trigger cascading Th17 responses, and the activated Th17 cells that express CD73 further augment Th17 responses, leading to cascading exacerbation. Hence, disabling the CD73 function of DCs should block this cascading response and mitigate Th17 responses.

Apremilast Regulates the Teff/Treg Balance to Ameliorate Uveitis via PI3K/AKT/FoxO1 Signaling Pathway

Autoimmune uveitis (AU), being one of the sight-threatening ocular inflammatory disorders, has been widely regarded by ophthalmologists and immunologists as a great challenge. Apremilast, a phosphodiesterase-4 inhibitor (PDE4i), which was approved by the U.S. Food and Drug Administration (FDA) for the treatment of active psoriatic arthritis in 2014, has been attracting researchers, who are exploring its efficiency and mechanism on uveitis. In this study, we used an experimental autoimmune uveitis (EAU), a representative model for human AU, to investigate the effect of apremilast on regulating anti-inflammatory mediators. Our study demonstrated that apremilast treatment resulted in a decrease in vascular leakage, macular edema, and inflammatory cell infiltration in the retina, corresponding to decreased clinical and pathological scores. Specifically, apremilast decreased the proportion and population of Th17 cells and increased the proportion and population of T regulatory (Treg) cells. Mechanistically, apremilast may regulate Th17 and Treg cells by inhibiting the phosphorylation of the phosphoinositide 3-kinase (PI3K)/protein kinase B(AKT)/Forkhead box O1 (FoxO1) signaling pathway. These findings suggested that apremilast alleviated EAU by regulating Th17 and Treg through the PI3K/AKT/FoxO1 pathway.

Dracocephalum heterophyllum (DH) Exhibits Potent Anti-Proliferative Effects on Autoreactive CD4+ T Cells and Ameliorates the Development of Experimental Autoimmune Uveitis

Experimental autoimmune uveitis (EAU) is a CD4⁺ T cell–mediated organ-specific autoimmune disease and has been considered as a model of human autoimmune uveitis. Dracocephalum heterophyllum (DH) is a Chinese herbal medicine used in treating hepatitis. DH suppressed the production of inflammatory cytokines through the recruitment of myeloid-derived suppressor cells (MDSCs) to the liver. However, it remains elusive whether DH can directly regulate CD4⁺ T cell biology and hence ameliorates the development of CD4⁺ T cell–mediated autoimmune disease. In the current study, we found that DH extract significantly suppressed the production of pro-inflammatory cytokines by CD4⁺ T cells. Further study showed that DH didn’t affect the activation, differentiation, and apoptosis of CD4⁺ T cells. Instead, it significantly suppressed the proliferation of conventional CD4⁺ T cells both in vitro and in vivo. Mechanistic study showed that DH-treated CD4⁺ T cells were partially arrested at the G2/M phase of the cell cycle because of the enhanced inhibitory phosphorylation of Cdc2 (Tyr15). In addition, we demonstrated that treatment with DH significantly ameliorated EAU in mice through suppressing the proliferation of autoreactive antigen specific CD4⁺ T cells. Taken together, the current study indicates that DH-mediated suppression of CD4⁺ T cell proliferation may provide a promising therapeutic strategy for treating CD4⁺ T cell–mediated diseases.

Type I Interferon Therapy Limits CNS Autoimmunity by Inhibiting CXCR3-Mediated Trafficking of Pathogenic Effector T Cells

Type I interferons (IFNs) have therapeutic potential in CNS autoimmune diseases, such as uveitis, but the molecular mechanisms remain unclear. Using a T cell-transfer model of experimental autoimmune uveitis (EAU), we found that IFN-α/β treatment inhibited the migration of IFN-γ-producing pathogenic CD4⁺ T cells to effector sites. IFN-α/β upregulated the expression of the cognate ligands CXCL9, CXCL10, and CXCL11, causing ligand-mediated downregulation of CXCR3 expression and effector T cell retention in the spleen. Accordingly, type I IFN did not alter EAU progression in CXCR3^-/- mice. In uveitis patients, disease exacerbations correlated with reduced serum IFN-α concentrations. IFN-α/β reduced CXCR3 expression and migration by human effector T cells, and these parameters were associated with the therapeutic efficacy of IFN-α in uveitis patients. Our findings provide insight into the molecular basis of type I IFN therapy for CNS autoimmune diseases and identify CXCR3 as a biomarker for effective type I IFN immunotherapy.

Functionally distinct IFN-γ+ IL-17A+ Th cells in experimental autoimmune uveitis: T-cell heterogeneity, migration, and steroid response

Immunopathogenic roles for both Th1 (CD4⁺ IFN-γ⁺ ) and Th17 (CD4⁺ IL-17A⁺ ) cells have been demonstrated in experimental autoimmune uveitis (EAU). However, the role for Th17/Th1 (CD4⁺ T cells co-expressing IFN-γ and IL-17A) cells in EAU is not yet understood. Using interphotoreceptor retinoid-binding protein peptide-induced EAU in mice, we found increased levels of Th17/Th1 cells in EAU retinae (mean 9.6 ± 4.2%) and draining LNs (mean 8.4 ± 3.9%; p = 0.01) relative to controls. Topical dexamethasone treatment effectively reduced EAU severity and decreased retinal Th1 cells (p = 0.01), but had no impact on retinal Th17/Th1 or Th17 cells compared to saline controls. Using in vitro migration assays with mouse CNS endothelium, we demonstrated that Th17/Th1 cells were significantly increased within the migrated population relative to controls (mean 15.6 ± 9.5% vs. 1.9 ± 1.5%; p = 0.01). Chemokine receptor profiles of Th17/Th1 cells (CXCR3 and CCR6) did not change throughout the transendothelial migration process and were unaffected by dexamethasone treatment. These findings support a role for Th17/Th1 cells in EAU and their resistance to steroid inhibition suggests the importance of targeting both Th17 and Th17/Th1 cells for improving therapy.

Cytotoxic effect of specific T cells from mice with experimental autoimmune uveitis on murine photoreceptor cells

AIM

To investigate the cytotoxic effect of specific T cells from mice with experimental autoimmune uveitis (EAU) as well as their secreted interferon (IFN)-γ and interleukin (IL)-17A on murine photoreceptor (661W) cells.

METHODS

An EAU model was established in female mice by injection of interphotoreceptor retinoid binding protein (IRBP) emulsion supplemented with complete Freund's adjuvant (CFA) and Mycobacterium tuberculosis (TB). On day 12 after induction of EAU, specific T cells from spleen and lymph node tissues were isolated and cultured for 4d and the levels of IFN-γ and IL-17A in the supernatants were determined by enzyme-linked immunosorbent assays (ELISAs). T cells and their supernatants were added to 661W cells to observe the alteration of cell morphology; IFN-γ and IL-17A were separately added to 661W cells to observe the effect of IFN-γ and IL-17A on cell proliferation.

RESULTS

The levels of IFN-γ and IL-17A in the T cell supernatants were 1568.64±38.79 pg/mL and 1456.57±46.98 pg/mL, respectively. The supernatants apparently inhibited 661W cell proliferation (P<0.05). T cells could also attach to the surface of 661W cells, and IFN-γ showed a more serious cytotoxic effect on 661W cells than IL-17A, inhibiting cell proliferation (P<0.01).

CONCLUSION

IFN-γ and IL-17A from T cells of EAU mice model can exert cytotoxic effects on murine photoreceptor cell proliferation, and IFN-γ shows more serious cytotoxic effects on murine photoreceptor cells than IL-17A.

The Cytokine IL-17A Limits Th17 Pathogenicity via a Negative Feedback Loop Driven by Autocrine Induction of IL-24

Dysregulated Th17 cell responses underlie multiple inflammatory and autoimmune diseases, including autoimmune uveitis and its animal model, EAU. However, clinical trials targeting IL-17A in uveitis were not successful. Here, we report that Th17 cells were regulated by their own signature cytokine, IL-17A. Loss of IL-17A in autopathogenic Th17 cells did not reduce their pathogenicity and instead elevated their expression of the Th17 cytokines GM-CSF and IL-17F. Mechanistic in vitro studies revealed a Th17 cell-intrinsic autocrine loop triggered by binding of IL-17A to its receptor, leading to activation of the transcription factor NF-κB and induction of IL-24, which repressed the Th17 cytokine program. In vivo, IL-24 treatment ameliorated Th17-induced EAU, whereas silencing of IL-24 in Th17 cells enhanced disease. This regulatory pathway also operated in human Th17 cells. Thus, IL-17A limits pathogenicity of Th17 cells by inducing IL-24. These findings may explain the disappointing therapeutic effect of targeting IL-17A in uveitis.

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IL-17A deficiency does not reduce the pathogenicity of Th17 cells in uveitis

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IL-17A binds to its own receptor on Th17 cells, activating NF-κB

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NF-κB induces IL-24 production, repressing the Th17 cytokine program through SOCS1/3

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Silencing or depleting IL-24 in Th17 cells exacerbates neuroinflammation

Kallistatin Attenuates Experimental Autoimmune Uveitis by Inhibiting Activation of T Cells

Experimental autoimmune uveoretinitis (EAU) is a mouse model of human autoimmune uveitis. EAU spontaneously resolves and is marked by ocular autoantigen-specific regulatory immunity in the spleen. Kallikrein binding protein (KBP) or kallistatin is a serine proteinase inhibitor that inhibits angiogenesis and inflammation, but its role in autoimmune uveitis has not been explored. We report that T cells activation is inhibited and EAU is attenuated in human KBP (HKBP) mice with no significant difference in the Treg population that we previously identified both before and after recovery from EAU. Moreover, following EAU immunization HKBP mice have potent ocular autoantigen specific regulatory immunity that is functionally suppressive.

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.

Probing the Role of Melanocortin Type 1 Receptor Agonists in Diverse Immunological Diseases

Background: The melanocortin α-melanocyte stimulating hormone (α-MSH), an endogenous peptide with high affinity for the melanocortin 1 receptor (MC1r), has demonstrated prevention and reversal of intestinal and ocular inflammation in animal models. Preclinical studies were performed to determine whether two MC1r receptor agonists, PL-8177 and PL-8331, exhibit actions and efficacy similar to α-MSH in preventing and reversing intestinal and ocular inflammation.

Methods: Both PL-8177 and PL-8331 were assessed in a Eurofins LeadProfilingScreen selectivity panel including 72 in vitro assays. PL-8177 and PL-8331 were evaluated in an in vitro assay using human whole blood stimulated by lipopolysaccharide to determine inhibition of tumor necrosis factor alpha (TNF-α); for comparison, adrenocorticotropic hormone (ACTH) and α-MSH were used as positive controls. PL-8177, dosed at 0.5, 1.5, and 5.0 μg, was assessed in a cannulated rat model of dinitrobenzene sulfonic acid (DNBS)-induced bowel inflammation versus vehicle and oral sulfasalazine. PL-8177 was also dosed at 0.3 mg/kg/mouse injected intraperitoneally versus untreated controls and α-MSH treatment in mice with experimental autoimmune uveitis (EAU). PL-8331 at 3 doses, 3 times daily, was evaluated in a murine model of scopolamine-induced dry eye disease (SiccaSystem^TM model), versus twice-daily Restasis^® and Xiidra^®.

Results: Both PL-8177 and PL-8331 demonstrated no significant activity at the 1 μm concentration in any of the 72 in vitro assays. PL-8177 and PL-8331 inhibited lipopolysaccharide-induced TNF-α to a similar degree as ACTH and α-MSH. In the DNBS rat model of bowel inflammation, PL-8177 was significantly superior to untreated controls at all 3 doses (P < 0.05) in reducing bowel inflammation parameters, with effects similar to sulfasalazine. In the murine EAU model, PL-8177 significantly reduced retinal inflammation scores versus untreated controls (P = 0.0001) over 3–5 weeks, and to a similar degree as α-MSH. In the murine scopolamine-induced model of dry eye disease, PL-8331 reduced corneal fluorescein staining scores at all doses, significantly (P = 0.02) for the highest dose (1 × 10^-5 mg⋅mL^-1), and similarly to Restasis^®; Xiidra^® demonstrated no effect.

Conclusion: The MC1r receptor agonists PL-8177 and PL-8331 exhibited actions similar to those of α-MSH in preventing and reversing intestinal and ocular inflammation in preclinical disease models.

Total glucosides of paeony suppresses experimental autoimmune uveitis in association with inhibition of Th1 and Th2 cell function in mice

Total glucosides of paeony (TGP) are active components extracted from the roots of Paeonia lactiflora Pall. In this study, we investigated the role and mechanisms of TGP in experimental autoimmune uveitis (EAU) model of mice. The C57BL/6 mice were randomly divided into three groups: sham group, EAU-control group, and EAU-TGP group. Clinical score of images of the eye fundus were taken on 7, 14, 21, and 28 days after induction of EAU. The concentrations of proinflammatory cytokines in intraocular fluid were measured at 14 days after EAU induction with the use of a multiplex assay system. Flow cytometry was used to analyze the frequency of CD4+, CD8+, interferon-gamma (IFN-γ), and CD4+/CD8+ ratio in spleen and lymph nodes. Western blotting was used to measure expressions of mitogen-activated protein kinase (MAPK) pathway-related proteins in retina. Clinical scores for uveitis were lower in TGP-treated EAU mice than those without TGP treatment. Importantly, the concentrations of cytokines induced by T-helper 1 (Th1) and T-helper 2 (Th2) cells in intraocular fluid were reduced in EAU mice treated with TGP. Furthermore, the frequency of CD4+, IFN-γ, and CD4+/CD8+ ratio was decreased and the frequency of CD8+ was increased in spleen and lymph nodes of mice treated with TGP. The anti-inflammatory effects of TGP were mediated by inhibiting the MAPK signaling pathways. Our results showed that TGP suppressed uveitis in mice via the inhibition of Th1 and Th2 cell function. Thus, TGP may be a promising therapeutic strategy for uveitis, as well as other ocular inflammatory diseases.

Subretinal Transplantation of Human Amniotic Epithelial Cells in the Treatment of Autoimmune Uveitis in Rats

As a featured ocular inflammatory disease, autoimmune uveitis is the major cause of blindness in the clinic. Although current immunosuppressive regimens can alleviate the progression of autoimmune uveitis, they have serious side effects. Therefore, an alternative therapeutic strategy is urgently required. The present study investigated the therapeutic efficacy of human amniotic epithelial cells (hAECs) on autoimmune uveitis in a rat model. Herein, experimental autoimmune uveitis (EAU) was induced in rats via a subcutaneous injection of interphotoreceptor retinoid-binding protein. EAU rats were treated with hAECs or the vehicle solution via a subretinal injection on day 0 and day 6 after immunization, and rats were sacrificed on day 12 and day 18 for further analysis. The pathological development of EAU was evaluated by slit lamp microscopy. Immune cell infiltration and retinal structure damage were examined by histological examination of hematoxylin and eosin (H&E) and immunofluorescence staining. T-cell subsets were detected by flow cytometry, and the levels of inflammatory cytokines were quantified by enzyme-linked immunosorbent assay (ELISA). hAEC treatment ameliorated the pathological progression of EAU and preserved the retinal structure organization and thickness, especially in the preventive group that received a subretinal injection on day 0. Moreover, hAECs inhibited the retinal infiltration of macrophages and T-cells. Mechanistically, hAECs modulated the balance of T-cell subsets by downregulating T helper (Th)17 cells and upregulating T regulatory (Treg) cells, as confirmed by decreased interleukin (IL)-17 and increased IL-10 levels in the spleens and lymph nodes of EAU rats. Furthermore, hAECs improved the local cytokine environment in EAU rats by suppressing the monocyte chemoattractant protein (MCP)-1, IL-17 and interferon (IFN)-γ levels and enhancing the IL-10 in the aqueous humor. Therefore, subretinal transplantation of hAECs in EAU rats ameliorated ocular inflammation, preserved the retinal structure and coordinated the immune balance. The current study provides a novel therapeutic strategy for autoimmune uveitis and related ocular inflammatory diseases in the clinic.

Aryl Hydrocarbon Receptor Regulates Apoptosis and Inflammation in a Murine Model of Experimental Autoimmune Uveitis

Uveitis is characterized as a common cause of blindness worldwide. Aryl hydrocarbon receptor (AhR), a ligand-activated nuclear receptor, has been implicated to play a role in human uveitis, although the exact mechanisms remain poorly understood. The purpose of this study was to enhance our knowledge concerning the role of AhR during intraocular inflammation. We immunized wild-type and AhR-knockout C57BL/6J mice with IRBP_651–670 to induce experimental autoimmune uveitis (EAU). Disease severity was evaluated with both clinical and histopathological grading. Blood–retinal barrier (BRB) integrity was tested by Evans blue and tight junction proteins qualifications. Apoptosis was measured using TdT-mediated dUTP nick end labeling staining. Macrophage/microglia activation and polarization were studied by immunofluorescence and Western blot. Following EAU induction, AhR^−/− mice had more severe clinical and histopathological manifestations of uveitis than AhR^+/+ mice. Increased vascular permeability and apoptotic cells were observed in AhR^−/− EAU mice when compared with AhR^+/+ EAU mice. In addition, AhR^−/− EAU mice showed evidence of a significantly increased macrophage/microglia cells and a stronger polarization from the M2 to the M1 phenotype as compared to AhR^+/+ EAU mice. The levels of pro-inflammatory cytokines including tumor necrosis factor-α (TNF-α), interleukin (IL)-6, and IL-1β were increased in AhR^−/− EAU mice, which was associated with the activation of NF-κB and signal transducers and activators of transcription (STAT) pathways. 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), an agonist of AhR, caused a significant decrease in the clinical and histopathological manifestations, preserved BRB integrity, reduced apoptotic cells, inhibited macrophage/microglia activation, and shifted their polarization from M1 toward M2. Moreover, decreased expression of pro-inflammatory cytokines including TNF-α, IL-6, and IL-1β and inhibition of NF-κB and STAT pathways were found in EAU mice following TCDD treatment. In conclusion, AhR activation with TCDD exhibits an immunomodulatory effect by reducing BRB breakdown, inhibiting retinal cell apoptosis, and reducing pro-inflammatory cytokine expression during EAU. The underlying mechanism may involve the modulation of macrophages/microglia polarization and the downregulation of NF-κB and STAT pathways.

Soluble CD83 Alleviates Experimental Autoimmune Uveitis by Inhibiting Filamentous Actin-Dependent Calcium Release in Dendritic Cells

Soluble CD83 (sCD83) is the extracellular domain of the membrane-bound CD83 molecule, and known for its immunoregulatory functions. Whether and how sCD83 participates in the pathogenesis of uveitis, a serious inflammatory disease of the eye that can cause visual disability and blindness, is unknown. By flow cytometry and imaging studies, we show that sCD83 alleviates experimental autoimmune uveitis (EAU) through a novel mechanism. During onset and recovery of EAU, the level of sCD83 rises in the serum and aqueous humor, and CD83⁺ leukocytes infiltrate the inflamed eye. Systemic or topical application of sCD83 exerts a protective effect by decreasing inflammatory cytokine expression, reducing ocular and splenic leukocyte including CD4⁺ T cells and dendritic cells (DCs). Mechanistically, sCD83 induces tolerogenic DCs by decreasing the synaptic expression of co-stimulatory molecules and hampering the calcium response in DCs. These changes are caused by a disruption of the cytoskeletal rearrangements at the DC–T cell contact zone, leading to altered localization of calcium microdomains and suppressed T-cell activation. Thus, the ability of sCD83 to modulate DC-mediated inflammation in the eye could be harnessed to develop new immunosuppressive therapeutics for autoimmune uveitis.

Clinical Effect of IRT-5 Probiotics on Immune Modulation of Autoimmunity or Alloimmunity in the Eye

Background: Although the relation of the gut microbiota to a development of autoimmune and inflammatory diseases has been investigated in various animal models, there are limited studies that evaluate the effect of probiotics in the autoimmune eye disease. Therefore, we aimed to investigate the effect of IRT-5 probiotics consisting of Lactobacillus casei, Lactobacillus acidophilus, Lactobacillus reuteri, Bifidobacterium bifidum, and Streptococcus thermophilus on the autoimmunity of uveitis and dry eye and alloimmunity of corneal transplantation. Methods: Experimental autoimmune uveitis was induced by subcutaneous immunization with interphotoreceptor-binding protein and intraperitoneal injection of pertussis toxin in C57BL/6 (B6) mice. For an autoimmune dry eye model, 12-weeks-old NOD.B10.H2^b mice were used. Donor cornea of B6 mice was transplanted into BALB/C mice. IRT-5 probiotics or phosphate buffered saline (PBS) were administered for three weeks immediately after induction of uveitis or transplantation. The inflammation score of the retinal tissues, dry eye manifestations (corneal staining and tear secretion), and graft survival were measured in each model. The changes of T cells were evaluated in drainage lymph nodes using fluorescence-activated cell sorting. Results: Retinal histology score in IRT-5 group of uveitis was lower than that in PBS group (p = 0.045). Ocular staining score was lower (p < 0.0001) and tear secretion was higher (p < 0.0001) in the IRT-5 group of NOD.B10.H2^b mice than that in the PBS group. However, the graft survival in the IRT-5 group was not different from those of PBS group. The percentage of regulatory T cells was increased in the IRT-5-treated dry eye models (p = 0.032). The percentage of CD8⁺IL-17^hi (p = 0.027) and CD8⁺ interferon gamma (IFNγ)^hi cells (p = 0.022) were significantly decreased in the IRT-5-treated uveitis models and the percentage of CD8⁺IFNγ^hi cells was markedly reduced (p = 0.036) in IRT-5-treated dry eye model. Conclusion: Our results suggest that administration of IRT-5 probiotics may modulate clinical manifestations of autoimmunity in the eye, but not on alloimmunity of corneal transplantation.

Augmenting Endogenous Levels of Retinal Annexin A1 Suppresses Uveitis in Mice

PURPOSE

The purpose of this study was to examine the expression of the anti-inflammatory protein Annexin A1 (AnxA1) in mice and human retinae during uveitis and to determine whether local administration of human recombinant AnxA1 (hrAnxA1) can suppress uveitis in mice.

METHODS

Retinal sections from mice (healthy normal and uveitis) and postmortem human (no history of eye disease (n = 5) and uveitis (n = 7)) were stained for AnxA1 expression and imaged by immunofluorescence microscopy. AnxA1 cellular expression was determined by colabeling with CD45, glial fibrillary acidic protein (GFAP), and Iba-1 cells, with additional staining of AnxA1 receptors formyl peptide receptor 1 (FPR1) and FPRL1/FPR2. Mice with acute endotoxin-induced uveitis and chronic experimental autoimmune uveitis were treated locally by intravitreal injection with hrAnxA1, and disease was assessed by clinical scoring and quantification of leukocyte infiltrate via flow cytometry.

RESULTS

Constitutive expression of AnxA1 was observed in both healthy mouse and human retinae, and its expression increased during uveitis compared to healthy controls. AnxA1 colocalizes predominantly with CD45⁺ cells, GFAP⁺ macroglia, and to a lesser extent, Iba-1⁺ myeloid cells. We also demonstrate that local treatment with hrAnxA1 attenuates the severity of uveitis in mice.

CONCLUSIONS

These data indicate that locally expressed AnxA1 is elevated in the retina during intraocular inflammation. We demonstrate that local administration of hrAnxA1 to augment levels results in suppression of uveitis in mice.

TRANSLATIONAL RELEVANCE

Our data suggest that elevated expression of retinal AnxA1 in human uveitis may be immunoregulatory and that local supplementation with hrAnxA1 may provide a potential novel treatment for inflammatory eye diseases such as noninfectious uveitis.

Role of PU.1 Expression as an Inflammatory Marker in Experimental Autoimmune Uveoretinitis

PURPOSE

PU.1 is an Ets family transcription factor, which is essential for the development of immune system through generation of myeloid and lymphoid lineages. In this study, we investigated PU.1 expression in the retina of mice with experimental autoimmune uveoretinitis (EAU) and the association between PU.1 expression level and inflammation in EAU.

METHODS

IRBP 1-20 peptide-immunized mice were used. Quantitative PCR, ELISA analysis, cytometric bead array (CBA), assay and immunostaining were conducted using ocular tissues and lymph nodes.

RESULTS

Quantitative PCR showed significant increases in mRNA levels of PU.1 in the retina at the peak of inflammation. Immunostaining of retina flat mounts revealed that most PU.1-positive cells were co-stained with anti-CD11c and anti-F4/80 antibodies. PU.1 knockdown in lymph node cells significantly suppressed IRBP-stimulated IFN-γ production measured by ELISA and IL-2 production measured by CBA.

CONCLUSION

PU.1 may play crucial roles in the development and progression of inflammation in EAU.

Cyclosporine: A Historical Perspective on Its Role in the Treatment of Noninfectious Uveitis

The history of cyclosporine and uveitis is intertwined with the development of experimental autoimmune uveitis (EAU) animal models and the understanding that T lymphocytes play a major role in the pathogenesis of uveitis. The early studies of CsA in uveitis also demonstrated the power of collaborative efforts in translational research. Dr. Robert Nussenblatt and his colleagues were the first to show that CsA can inhibit EAU. Over many years after the initial CsA experiments, Dr. Nussenblatt's group as well as others continued to study CsA under experimental conditions as well as in clinical trials with human patients. The data and observations from these studies significantly advanced our knowledge of uveitis pathophysiology and demonstrated the value of well-designed masked, controlled treatment trials in uveitis. Dr. Nussenblatt and his collaborators delved into the most significant adverse effect of CsA, renal toxicity, and helped elucidate the pathophysiology of renal injury. They explored adjunctive treatments to improve the efficacy and decrease the toxicity of CsA and also studied other members of the cyclosporine family. Among the immunosuppressives used to treat ocular inflammation, CsA was the first, and remains the only medication comprehensively studied under both experimental and clinical conditions.

Notch signalling suppresses regulatory T-cell function in murine experimental autoimmune uveitis

Autoimmune uveitis is an intraocular inflammatory disorder in developed countries. Understanding the mechanisms underlying the development and modulation of immune reaction in uveitic eyes is critical for designing therapeutic interventions. Here we investigated the role of Notch signalling in regulatory T-cell (Treg cell) function during experimental autoimmune uveitis (EAU). Using the Foxp3-GFP reporter mouse strain, the significance of Notch signalling for the function of infiltrating Treg cells was characterized in an EAU model. We found that infiltrating Treg cells substantially expressed Notch-1, Notch-2, JAG1 and DLL1 in uveitic eyes. Activation of Notch signalling, represented by expression of HES1 and HES5, was enhanced in infiltrating Treg cells. Treatment with JAG1 and DLL1 down-regulated Foxp3 expression and immunosuppressive activity of isolated infiltrating Treg cells in vitro, whereas neutralizing antibodies against JAG1 and DLL1 diminished Notch ligand-mediated negative effects on Treg cells. To investigate the significance of Notch signalling for Treg cell function in vivo, lentivirus-derived Notch short hairpin RNAs were transduced into in vitro expanded Treg cells before adoptive transfer of Treg cells into EAU mice. Transfer of Notch-1-deficient Treg cells remarkably reduced pro-inflammatory cytokine production and inflammatory cell infiltration in uveitic eyes. Taken together, Notch signalling negatively modulates the immunosuppressive function of infiltrating Treg cells in mouse EAU.

Mesenchymal stem/stromal cells precondition lung monocytes/macrophages to produce tolerance against allo- and autoimmunity in the eye

Intravenously administered mesenchymal stem/stromal cells (MSCs) engraft only transiently in recipients, but confer long-term therapeutic benefits in patients with immune disorders. This suggests that MSCs induce immune tolerance by long-lasting effects on the recipient immune regulatory system. Here, we demonstrate that i.v. infusion of MSCs preconditioned lung monocytes/macrophages toward an immune regulatory phenotype in a TNF-α-stimulated gene/protein (TSG)-6-dependent manner. As a result, mice were protected against subsequent immune challenge in two models of allo- and autoimmune ocular inflammation: corneal allotransplantation and experimental autoimmune uveitis (EAU). The monocytes/macrophages primed by MSCs expressed high levels of MHC class II, B220, CD11b, and IL-10, and exhibited T-cell-suppressive activities independently of FoxP3(+) regulatory T cells. Adoptive transfer of MSC-induced B220(+)CD11b(+) monocytes/macrophages prevented corneal allograft rejection and EAU. Deletion of monocytes/macrophages abrogated the MSC-induced tolerance. However, MSCs with TSG-6 knockdown did not induce MHC II(+)B220(+)CD11b(+) cells, and failed to attenuate EAU. Therefore, the results demonstrate a mechanism of the MSC-mediated immune modulation through induction of innate immune tolerance that involves monocytes/macrophages.

A2B adenosine receptor activation switches differentiation of bone marrow cells to a CD11c(+)Gr-1(+) dendritic cell subset that promotes the Th17 response

Adenosine is one of the major molecules associated with inflammation. We have previously reported that an adenosine receptor (AR) agonist has an enhancing effect on Th17 autoimmune responses, even though it suppressed Th1 responses. To determine the mechanism involved, we have examined the effect of AR agonists on mouse bone marrow dendritic cell (BMDC) differentiation and function. We show that mouse bone marrow cells (BMCs) differentiated into CD11c(+)Gr-1(+) dentritic cells (DCs) when cultured in granulocyte macrophage colony-stimulating factor (GM-CSF)-containing medium containing an AR agonist. The non-selective AR agonist NECA and an A2BR-specific agonist had a similar effect, and the effect of NECA could be blocked by an A2BR-specific antagonist. Unlike CD11c(+)Gr-1(-) BMDCs, which have a greater stimulatory effect on Th1 T cells than Th17 cells, CD11c(+)Gr-1(+) BMDCs had a greater stimulatory effect on Th17 autoreactive T cells than on Th1 autoreactive T cells and this effect depended on γδ T cell activation.

The critical points in induction of experimental autoimmune uveitis

BACKGROUND

Autoimmune uveitis is a leading cause of visual impairment in developed countries in patients of working age. Animal models of experimental autoimmune uveitis (EAU) have been established to serve as a useful template for novel therapeutic approaches.

METHODS

Experimental autoimmune uveitis is induced in C57BL/6 mice by subcutaneous application of interphotoreceptor retinoid binding protein in complete Freund's adjuvant and pertussis toxin. Clinical and histological grading is used to assess the inflammation intensity of EAU.

RESULTS

The protocol of induction of EAU in mice hides several important aspects, which are crucial for developing the disease. These details have to be addressed to ensure reproducible disease induction. We describe our experience in establishing the model by pointing out the critical steps in EAU protocol which we found important.

CONCLUSION

The mouse model of EAU has practical value for preclinical studies, is robust and well established. However, the induction of inflammation of the eye can be quite challenging when important details of the protocol are not recognized and adhered to.

Influence of Yanyankang Powder on Th1/Th2 in rats with experimental autoimmune uveitis

OBJECTIVE

To study the influence of Yanyankang powder on Th1/Th2 in rats with experimental autoimmune uveitis (EAU).

METHODS

The EAU models were induced in Lewis rats by immunization with interphotoreceptor retinoid binding protein (IRBP) 1177-1191 in complete Freund's adjuvant. The rats were randomly divided into 3 groups: a model control group, a Yanyankang group, and a prednisone group, 9 rats in each group. The model control group was intervened with saline solution by gavage. The Yanyankang group was intervened with Yanyankang powder 4 g/(kg day) by gavage. The prednisone group were intervened with prednisone acetate tablets 5 mg/(kg d) by gavage. All groups were intervened after immunization once every 2 days for 18 days and monitored by slit-lamp biomicroscopy daily until day 18. The levels of gamma interferon (INF-γ) and interleukin-10 (IL-10) in the supernatants of T cells were determined by enzyme-linked immunosorbent assay. Polymerase chain reaction (PCR) technology was used for measuring Th1 and Th2 related cytokine mRNA expressions.

RESULTS

Slighter intraocular inflammation was found in the Yanyankang group and the prednisone group than the control group. The levels of the IFN-γ and IL-10 in the supernatants of the spleen lymph node cells were 382.33±6.30, 155.87±4.46 μg/L in the Yanyankang group and 270.93±7.76, 265.32±11.88 μg/L in the prednisone group. Both had significant differences compared with the control group (941.53±8.59, 20.67±4.65 μg/L; =0.01). The PCR results showed the same tendency.

CONCLUSION

Yanyankang powder showed favorable effects in the rats with EAU by influencing the function of Th1 and Th2 cells.

Pathogenesis of innate immunity and adaptive immunity in the mouse model of experimental autoimmune uveitis

Experimental autoimmune uveitis, a well-established model for human uveitis, is similar to human uveitis in many pathological features. Studies concerning the mechanisms of experimental autoimmune uveitis would cast a light on the pathogenesis of human uveitis as well as the search for more effective therapeutic agents. The cellular components of innate immunity include natural killer cells, gamma delta T lymphocytes, antigen-presenting dendritic cells, phagocytic macrophages, and granulocytes. It is believed that T cells are central in the generation of human uveitis. It has already become clear that CD4(+) effecter cells that predominantly produce interleukin-17 (the so-called Th17 cells) may play an important role in uveitis. In addition, the occurrence and recurrence of uveitis depends on a complex interplay between the elements of innate and adaptive immunity.

Role of dendritic cell subsets in immunity and their contribution to noninfectious uveitis

Dendritic cells (DCs) are a heterogeneous population. Murine DCs consist of conventional DCs (cDCs) and plasmacytoid DCs (pDCs). In humans, the analogous populations are myeloid DCs (mDCs) and pDCs. Though distinct in phenotypes and functions, studies have shown that these DC subsets may interact or "crosstalk" during immune responses. For example, cDCs may facilitate pDC maturation, and pDCs may enhance antigen presentation of cDCs in certain pathogenic conditions or even take on a cDC phenotype themselves. The role of DCs in noninfectious uveitis has been studied primarily in the experimental autoimmune uveitis mouse model and to a more limited extent in patients. Recent evidence shows that the number, phenotype, and function of DC subsets are altered in this disease. We provide an overview of selected recent developments of pDCs and cDCs/mDCs, with special attention to their interaction and the dual roles of DC subsets in noninfectious uveitis.

Anti-inflammatory or proinflammatory effect of an adenosine receptor agonist on the Th17 autoimmune response is inflammatory environment-dependent

Adenosine is a key endogenous signaling molecule that regulates a wide range of physiological functions, including immune system function and inflammation. Studies have shown that adenosine receptor (AR) agonists can be either anti-inflammatory or proinflammatory in immune responses and in inflammation, and the clarification of the mechanisms causing these opposing effects should provide a better guide for therapeutic intervention. Whereas previous studies mostly examined the effects of AR agonists on Th1-type immune responses, in this study, we compared their effect on Th17 and Th1 autoimmune responses in experimental autoimmune uveitis, a mouse model of human uveitis induced by immunization with the human interphotoreceptor retinoid-binding protein peptides 1-20. We showed that injection of mice with a nonselective AR agonist, 5'-N-ethylcarboxamidoadenosine (NECA), at an early stage after immunization had an inhibitory effect on both Th1 and Th17 responses, whereas injection of the same amount of NECA at a late stage inhibited the Th1 response but had an enhancing effect on the Th17 response. We also showed that the effects of NECA on Th1 and Th17 responses were completely dissociated, that the enhancing effect of NECA on Th17 responses was modulated by γδ T cells, and that the response of γδ T cells to NECA was determined by their activation status. We conclude that the inflammatory environment has a strong impact on converting the effect of AR agonist on the Th17 autoimmune response from anti-inflammatory to proinflammatory. Our observation should help in the designing of better AR-targeted therapies.

Therapeutic targeting of STAT pathways in CNS autoimmune diseases

Signal transducers and activators of transcription (STATs) transduce extracellular signals that regulate the initiation, duration and intensity of immune responses. However, unbridled activation of STATs by pro-inflammatory cytokines or growth factors contributes to pathogenic autoimmunity. In this review, we briefly discuss STAT pathways that promote the development and expansion of T cells that mediate two CNS inflammatory diseases, multiple sclerosis (MS) and uveitis. Particular focus is on animal models of MS and uveitis and new approaches to the treatment of CNS autoimmune diseases based on therapeutic targeting of Th17 cells and STAT pathways.

Neuroprotection effect of interleukin (IL)-17 secreted by reactive astrocytes is emerged from a high-level IL-17-containing environment during acute neuroinflammation

An increase in interleukin (IL)-17A-producing cells, particularly at sites of tissue inflammation, is observed frequently, yet the mechanism is not fully understood. This study aims to dissect the role of IL-17 in autoimmunity-mediated neuroinflammation. The cytokine milieu containing elevated IL-17, which often appears in active states of autoimmunity, was mimicked in vitro by a supernatant obtained from rat peripheral blood monocytes stimulated with phorbol mystistate acetate (PMA)/ionomycin. The application of such inflammatory media on only primary cultured cerebellar granule neurones resulted in significant apoptosis, but the presence of astrocytes largely prevented the effect. The supernatants of the stimulated astrocytes, especially those that contained the highest level of IL-17, achieved the best protection, and this effect could be blocked by anti-IL-17 antibodies. Protein IL-17 inhibited intracellular calcium increase and protected the neurones under inflammatory attack from apoptosis. IL-17, but not interferon (IFN)-γ, in the inflammatory media contributed to astrocyte secretion of IL-17, which depended on the Janus kinase/signal transducers and activators of transcription (JAK/STAT) pathway activation. The astrocytes that were treated with IL-17 alone or with prolonged treatment of the inflammatory media failed to produce sufficient levels of IL-17. Moreover, confirmatory data were obtained in vivo in a monophasic experimental autoimmune uveitis (EAU) in Lewis rats; in this preparation, the high-level IL-17-containing the cytokine milieu was demonstrated, along with IL-17 secretion by the resident neural cells. The antagonism of IL-17 at a late stage disturbed the disease resolution and resulted in significant neural apoptosis. Our data show a dynamic role of IL-17 in the maintenance of homeostasis and neuroprotection in active neuroinflammation.

HMGB1 is an early and critical mediator in an animal model of uveitis induced by IRBP-specific T cells

It is largely unknown how invading autoreactive T cells initiate the pathogenic process inside the diseased organ in organ-specific autoimmune disease. In this study, we used a chronic uveitis disease model in mice--EAU--induced by adoptive transfer of uveitogenic IRBP-specific T cells and showed that HMGB1, an important endogenous molecule that serves as a danger signal, was released rapidly from retinal cells into the ECM and intraocular fluid in response to IRBP-specific T cell transfer. HMGB1 release required direct cell-cell contact between retinal cells and IRBP-specific T cells and was an active secretion from intact retinal cells. Administration of HMGB1 antagonists inhibited severity of EAU significantly via mechanisms that include inhibition of IRBP-specific T cell proliferation and their IFN-γ and IL-17 production. The inflammatory effects of HMGB1 may signal the TLR/MyD88 pathway, as MyD88(-/-) mice had a high level of HMGB1 in the eye but did not develop EAU after IRBP-specific T cell transfer. Our study demonstrates that HMGB1 is an early and critical mediator of ocular inflammation initiated by autoreactive T cell invasion.

ITE, a novel endogenous nontoxic aryl hydrocarbon receptor ligand, efficiently suppresses EAU and T-cell-mediated immunity

PURPOSE

Ligands for aryl hydrocarbon receptor (AHR), such as dioxins, are highly toxic. One such ligand, TCDD, was found to exert potent immunosuppressive capacities in mice developing pathogenic autoimmune processes, including EAU, but its toxicity makes it unusable for humans. A recently identified endogenous AHR ligand, ITE, is also immunosuppressive, but is nontoxic and could therefore be useful for therapy in humans. Here, we tested ITE for its capacity to inhibit EAU and related immune responses.

METHODS

EAU was induced in B10.A mice by immunization with interphotoreceptor retinoid-binding protein (IRBP; 40 μg) in CFA. Treatment with ITE was by daily intraperitoneal injection of 0.2 mg. Disease severity was assessed by both fundoscopy and histological examination. Draining lymph node cells were tested for proliferation by thymidine uptake and for cytokine production and release by ELISA. In addition, the intracellular expression of cytokines and Foxp3 was determined by flow cytometry. Serum antibodies were measured by ELISA.

RESULTS

Treatment with ITE efficiently inhibited the development of EAU in mice, as well as the cellular immune responses against IRBP and PPD. ITE treatment inhibited the expansion of both Th1 and Th17 subpopulations, as well as their release of the signature cytokines, IFN-gamma and IL-17. The treatment moderately increased, however, the proportion of Foxp3 expressing T-regulatory cells. Antibody production was not affected by the treatment.

CONCLUSIONS

ITE, an endogenous AHR ligand, efficiently inhibits EAU development and related cellular immune responses. Being nontoxic, ITE may be considered for treatment of pathogenic immunity in humans.

Effective Arrestin-Specific Immunotherapy of Experimental Autoimmune Uveitis with RTL: A Prospect for Treatment of Human Uveitis

PURPOSE

To evaluate the immunotherapeutic efficacy of recombinant T cell receptor ligands (RTLs) specific for arrestin immunity in treatment of experimental autoimmune uveitis (EAU) in humanized leukocyte antigen (HLA-DR3) transgenic (Tg) mice.

METHODS

We generated de novo recombinant human DR3-derived RTLs bearing covalently tethered arrestin peptides 291-310 (RTL351) or 305-324 (RTL352). EAU was induced by immunization of HLA-DR3 mice with arrestin or arrestin peptide and treated with RTLs by subcutaneous delivery. T cell proliferation and cytokine expression was measured in RTL-treated and control mice.

RESULTS

RTL351 prevented the migration of cells outside of the spleen and the recruitment of inflammatory cells into the eye, and provided full protection against inflammation from EAU induced with arrestin or arrestin peptides. RTL351 significantly inhibited T cell proliferation and secretion of inflammatory cytokines interleukin 2 (IL-2), interferon γ (IFN-γ), IL-6, and IL-17 and chemokines (macrophage inflammatory proteins [MIP-1a] and regulated and normal T cell expressed and secreted [RANTES]), which is in agreement with the suppression of intraocular inflammation. RTL350 ("empty," no peptide) and RTL352 were not effective.

CONCLUSIONS

Immunotherapy with a single RTL351 successfully prevented and treated arrestin-induced EAU in HLA-DR3 mice and provided proof of concept for therapy of autoimmune uveitis in human patients. The beneficial effects of RTL351 should be attributed to a significant decrease in Th1/Th17 mediated inflammation.

TRANSLATIONAL RELEVANCE

Successful therapies for autoimmune uveitis must specifically inhibit pathogenic inflammation without inducing generalized immunosuppression. RTLs can offer such an option. The single retina-specific RTLs may have a value as potential immunotherapeutic drug for human autoimmune uveitis because they effectively prevent disease induced by multiple T cell specificities.

Breakdown of immune privilege and spontaneous autoimmunity in mice expressing a transgenic T cell receptor specific for a retinal autoantigen

Despite presence of circulating retina-specific T cells in healthy individuals, ocular immune privilege usually averts development of autoimmune uveitis. To study the breakdown of immune privilege and development of disease, we generated transgenic (Tg) mice that express a T cell receptor (TCR) specific for interphotoreceptor retinoid-binding protein (IRBP), which serves as an autoimmune target in uveitis induced by immunization. Three lines of TCR Tg mice, with different levels of expression of the transgenic R161 TCR and different proportions of IRBP-specific CD4⁺ T cells in their peripheral repertoire, were successfully established. Importantly, two of the lines rapidly developed spontaneous uveitis, reaching 100% incidence by 2 and 3 months of age, respectively, whereas the third appeared "poised" and only developed appreciable disease upon immune perturbation. Susceptibility roughly paralleled expression of the R161 TCR. In all three lines, peripheral CD4⁺ T cells displayed a naïve phenotype, but proliferated in vitro in response to IRBP and elicited uveitis upon adoptive transfer. In contrast, CD4⁺ T cells infiltrating uveitic eyes mostly showed an effector/memory phenotype, and included Th1, Th17 as well as T regulatory cells that appeared to have been peripherally converted from conventional CD4⁺ T cells rather than thymically derived. Thus, R161 mice provide a new and valuable model of spontaneous autoimmune disease that circumvents the limitations of active immunization and adjuvants, and allows to study basic mechanisms involved in maintenance and breakdown of immune homeostasis affecting immunologically privileged sites such as the eye.