Retinal cells suppress intraocular inflammation (uveitis) through production of interleukin-27 and interleukin-10

Microglial mediators in autoimmune Uveitis: Bridging neuroprotection and neurotoxicity

Autoimmune uveitis, a severe inflammatory condition of the eye, poses significant challenges due to its complex pathophysiology and the critical balance between protective and detrimental immune responses. Central to this balance are microglia, the resident immune cells of the central nervous system, whose roles in autoimmune uveitis are multifaceted and dynamic. This review article delves into the dual nature of microglial functions, oscillating between neuroprotective and neurotoxic outcomes in the context of autoimmune uveitis. Initially, we explore the fundamental aspects of microglia, including their activation states and basic functions, setting the stage for a deeper understanding of their involvement in autoimmune uveitis. The review then navigates through the intricate mechanisms by which microglia contribute to disease onset and progression, highlighting both their protective actions in immune regulation and tissue repair, and their shift towards a pro-inflammatory, neurotoxic profile. Special emphasis is placed on the detailed pathways and cellular interactions underpinning these dual roles. Additionally, the review examines the potential of microglial markers as diagnostic and prognostic indicators, offering insights into their clinical relevance. The article culminates in discussing future research directions, and the ongoing challenges in translating these findings into effective clinical applications. By providing a comprehensive overview of microglial mechanisms in autoimmune uveitis, this review underscores the critical balance of microglial activities and its implications for disease management and therapy development.

Vision loss associated with silicone oil endotamponade in vitreoretinal surgery - a review

PURPOSE

To clarify the definition, prevalence and classification of different types of unexplained vision loss associated with silicone oil (SO) endotamponades (SO in situ (SOIS) or after removal of SO (ROSO)) in vitreoretinal surgery and identifying the most specific clinical findings and suggesting possible causes.

METHODS

Review of the literature regarding randomized clinical trials (RCTs), retrospective case-control, cohort studies and case series evaluating the risk of using SO, published in English between 1994 and 2023, conducting a computer-based search of the following databases: PubMed, Web of Science, Scopus and Embase. The search was supplemented using the Medline option 'Related Articles' and consulting review articles on the topic.

RESULTS

Findings from reported clinical examinations in SOIS and ROSO are analyzed and finally different theories regarding the underlying pathophysiology are described. From the clinical point of view, findings have been found in OCT, OCTA, microperimetry and electrophysiological studies. Other clearly identifiable causes of vision loss related to the use of SO are listed and commented as differential diagnosis. Finally, the different physiopathological theories of the two types of causes of unexplained vision have been analyzed.

CONCLUSION

Unexpected vision loss under or after SO tamponade (SOIS and ROSO) is a significant concern which is probably underestimated because it is not a clearly defined and known entity. The most frequently described changes were in the ganglion cell complex but this unexpected vision loss remains a serious and unexplained concern for vitreoretinal surgeons and should be identified by clinicians, addressed by manufacturers and reported to Health Authorities as a serious incident according to the new regulation.

Impaired Immunomodulatory Properties of the Retina from the Inflammatory Environment of the Damaged Eye

The retina represents a highly specialized structure with the primary function to capture a light signal and to convert it into electrical impulses. Any damage or disease of the retina can cause visual impairment. Since retinal degenerative diseases are generally associated with immune cell infiltration, a local inflammatory reaction, and cytokine burn, there is a need for mechanisms to prevent the retina from damage by a deleterious immune reaction. In this study, we show that mouse retinal explants co-cultivated with stimulated spleen cells, inhibit in a dose-dependent manner the activation of T cells, and suppress the production of cytokines interleukin-2, interleukin-10, and interferon-[Formula: see text]. The immunoregulatory properties of the retina were mainly mediated by a paracrine effect since retinal explants, separated by a semipermeable membrane, or supernatants obtained after the cultivation of retinal explants, inhibited the reactivity of immune cells. A model of retinal damage was established by the application of sodium iodate which selectively destroys photoreceptors, as it was demonstrated by a decrease in the number of rhodopsin-positive cells. This process was accompanied by increased infiltration of the retina with cells of the immune system and by a local inflammatory reaction. The pharmacologically damaged retina had significantly decreased the ability to inhibit T cell activation and production of cytokines by immune cells. Overall, the results showed that the retina possesses immunoregulatory properties and inhibits the activation and functions of T cells. However, the immunomodulatory properties of the retina are decreased if the retina is damaged.

Advances in pathogenesis and treatment of ocular involvement in Behcet's disease

Behcet's disease (BD) is a chronic multi-systemic disease characterized by relapsing-remitting oral ulcers, genital ulcers, ocular inflammatory involvements, and numerous other systemic features. Ocular involvements are quite common in BD and may cause severe tissue damage and potentially blindness. Even though the pathogenesis of BD remains ambiguous, growing evidences have shown that genetic factors, environmental triggers and immunological abnormalities play significant roles in its development and progression. Novel biotherapies targeting IFN-γ, TNF-α and interleukins have been used in recent years. In this review, we mainly pay attention to the ocular involvement of BD, and discuss the current understanding of mechanisms and advances in therapeutic approaches, especially novel biologics. Finally, we discuss the management in patients with pregnancy.

IL-27-containing exosomes secreted by innate B-1a cells suppress and ameliorate uveitis

Introduction

IL-27 is a heterodimeric cytokine composed of Ebi3 and IL-27p28 and can exert proinflammatory or immune suppressive effects depending on the physiological context. Ebi3 does not contain membrane-anchoring motifs, suggesting that it is a secreted protein while IL-27p28 is poorly secreted. How IL-27p28 and Ebi3 dimerize in-vivo to form biologically active IL-27 is unknown. Major impediment to clinical use of IL-27 derives from difficulty of determining exact amount of bioavailable heterodimeric IL-27 needed for therapy.

Methods

To understand how IL-27 mediates immune suppression, we characterized an innate IL-27-producing B-1a regulatory B cell population (i27-Breg) and mechanisms i27-Bregs utilize to suppress neuroinflammation in mouse model of uveitis. We also investigated biosynthesis of IL-27 and i27-Breg immunobiology by FACS, immunohistochemical and confocal microscopy.

Results

Contrary to prevailing view that IL-27 is a soluble cytokine, we show that i27-Bregs express membrane-bound IL-27. Immunohistochemical and confocal analyses co-localized expression of IL-27p28 at the plasma membrane in association with CD81 tetraspanin, a BCR-coreceptor protein and revealed that IL-27p28 is a transmembrane protein in B cells. Most surprising, we found that i27-Bregs secrete IL-27-containing exosomes (i27-exosomes) and adoptive transfer of i27-exosomes suppressed uveitis by antagonizing Th1/Th17 cells, up-regulating inhibitory-receptors associated with T-cell exhaustion while inducing Treg expansion.

Discussion

Use of i27-exosomes thus obviates the IL-27 dosing problem, making it possible to determine bioavailable heterodimeric IL-27 needed for therapy. Moreover, as exosomes readily cross the blood-retina-barrier and no adverse effects were observed in mice treated with i27-exosome, results of this study suggest that i27-exosomes might be a promising therapeutic approach for CNS autoimmune diseases.

Single-cell transcriptomics-based multidisease analysis revealing the molecular dynamics of retinal neurovascular units under inflammatory and hypoxic conditions

The retinal neurovascular unit (NVU) is paramount to maintaining the homeostasis of the retina and determines the progression of various diseases, including diabetic retinopathy (DR), glaucoma, and retinopathy of prematurity (ROP). Although some studies have investigated these diseases, a combined analysis of disease-wide etiology in the NUV at the single-cell level is lacking. Herein, we constructed an atlas of the NVU under inflammatory and hypoxic conditions by integrating single-cell transcriptome data from retinas from wild-type, AireKO, and NdpKO mice. Based on the heterogeneity of the NVU structure and transcriptome diversity under normal and pathological conditions, we discovered two subpopulations of Müller cells: Aqp4^hi and Aqp4^lo cells. Specifically, Aqp4^lo cells expresses phototransduction genes and represent a special type of Müller cell distinct from Aqp4^hi cells, classical Müller cells. AireKO mice exhibit experimental autoimmune uveitis (EAU) with severe damage to the NVU structure, mainly degeneration of Aqp4^hi cells. NdpKO mice exhibited familial exudative vitreoretinopathy (FEVR), with damage to the endothelial barrier, endothelial cell tight junction destruction and basement membrane thickening, accompanied by the reactive secretion of proangiogenic factors by Aqp4^hi cells. In both EAU and FEVR, Aqp4^hi cells are a key factor leading to NVU damage, and the mechanism by which they are generated is regulated by different transcription factors. By studying the pattern of immune cell infiltration in AireKO mice, we constructed a regulatory loop of "inflammatory cells/NVU - monocytes - APCs - Ifng⁺ T cells", providing a new target for blocking the inflammatory cascade. Our elucidation of the cell-specific molecular changes, cell-cell interactions and transcriptional mechanisms of the retinal NVU provides new insights to support the development of multipurpose drugs to block or even reverse NVU damage.

Vitreous inflammatory and angiogenic factors on patients with proliferative diabetic retinopathy or diabetic macular edema: the role of Lipocalin2

PURPOSE

Quantitative analysis of vitreous inflammatory and angiogenic factors from patients with proliferative diabetic retinopathy (PDR) or diabetic macular edema (DME).

MATERIALS AND METHODS

Collection of undiluted vitreous samples from 20 diabetic patients: 13 with proliferative diabetic retinopathy (PDR) and 7 with diabetic macular edema (DME). DME patients had suboptimal response to anti-VEGF treatment. Samples from 11 control patients, with vitreomacular interface pathology such as idiopathic epiretinal membrane (iERM) (n = 4), vitreomacular traction syndrome (VMT) (n = 3) and full thickness macular hole (FTMH) (n = 3), were also collected. The levels of IL1b, IL6, IL8, IL27, TNFα, ICAM-1, VCAM, MCP-1, VEGFA and LCN2 were measured using cytometry flow analysis. Median values were compared with Mann-Whitney test since the distributions were skewed. Statistical analysis was performed with the Statistical Package for Social Sciences software (IBM Corp. Released 2012. IBM SPSS Statistics for Windows, Version 21.0. Armonk, NY: IBM Corp.).

RESULTS

The median concentration of LCN2, IL6, IL8, IL1b, IL27, ICAM, VCAM-1, MCP-1, TNFa and VEGFA was higher in PDR patients than in controls. Similarly, the median concentration of LCN2, IL6, IL8, IL27, ICAM, VCAM-1, TNFa and VEGFA was higher in DME patients than in controls. In particular, median LCN2 concentration in diabetic patients was 5,711 pg/ml (interquartile range [IR] = 2,534), while in controls was 2,586 pg/ml (IR = 2,345). Moreover, median LCN2 was 6,534 pg/ml in the DME group (IR = 6,850) and 4,785 pg/ml in the PDR group (IR = 2,608), (p = 0.025).

CONCLUSION

Various inflammatory and angiogenic factors are involved in the pathophysiology of PDR and DME. Elevated vitreous levels of LCN2 in PDR and especially in DME patients reveal a potential pathogenic association. More extended studies could verify LCN2 as an alternative therapeutic target.

Exploring the role of interleukin-27 as a regulator of neuronal survival in central nervous system diseases

Interleukin-27 is a pleiotropic cytokine that is involved in tissue responses to infection, cell stress, neuronal disease, and tumors. Recent studies in various tissues indicate that interleukin-27 has complex activating and inhibitory properties in innate and acquired immunity. The availability of recombinant interleukin-27 protein and mice with genetic deletions of interleukin-27, its receptors and signaling mediators have helped define the role of interleukin-27 in neurodegenerative diseases. Interleukin-27 has been well-characterized as an important regulator of T cell activation and differentiation that enhances or suppresses T cell responses in autoimmune conditions in the central nervous system. Evidence is also accumulating that interleukin-27 has neuroprotective activities in the retina and brain. Interleukin-27 is secreted from and binds to infiltrating microglia, macrophage, astrocytes, and even neurons and it promotes neuronal survival by regulating pro- and anti-inflammatory cytokines, neuroinflammatory pathways, oxidative stress, apoptosis, autophagy, and epigenetic modifications. However, interleukin-27 can have the opposite effect and induce inflammation and cell death in certain situations. In this review, we describe the current understanding of regulatory activities of interleukin-27 on cell survival and inflammation and discuss its mechanisms of action in the brain, spinal cord, and retina. We also review evidence for and against the therapeutic potential of interleukin-27 for dampening harmful neuroinflammatory responses in central nervous system diseases.

The cytokine IL-27 reduces inflammation and protects photoreceptors in a mouse model of retinal degeneration

BACKGROUND

Retinal degenerative diseases are a group of conditions characterized by photoreceptor death and vision loss. Excessive inflammation and microglial activation contribute to the pathology of retinal degenerations and a major focus in the field is identifying more effective anti-inflammatory therapeutic strategies that promote photoreceptor survival. A major challenge to developing anti-inflammatory treatments is to selectively suppress detrimental inflammation while maintaining beneficial inflammatory responses. We recently demonstrated that endogenous levels of the IL-27 cytokine were upregulated in association with an experimental treatment that increased photoreceptor survival. IL-27 is a pleiotropic cytokine that regulates tissue reactions to infection, neuronal disease and tumors by inducing anti-apoptotic and anti-inflammatory genes and suppressing pro-inflammatory genes. IL-27 is neuroprotective in the brain, but its function during retinal degeneration has not been investigated. In this study, we investigated the effect of IL-27 in the rd10 mouse model of inherited photoreceptor degeneration.

METHODS

Male and female rd10 mice were randomly divided into experimental (IL-27) and control (saline) groups and intravitreally injected at age post-natal day (P) 18. Retina function was analyzed by electroretinograms (ERGs), visual acuity by optomotor assay, photoreceptor death by TdT-mediated dUTP nick-end labeling (TUNEL) assay, microglia/macrophage were detected by immunodetection of IBA1 and inflammatory mediators by cytoplex and QPCR analysis. The distribution of IL-27 in the retina was determined by immunohistochemistry on retina cross-sections and primary Muller glia cultures.

RESULTS

We demonstrate that recombinant IL-27 decreased photoreceptor death, increased retinal function and reduced inflammation in the rd10 mouse model of retinal degeneration. Furthermore, IL-27 injections led to lower levels of the pro-inflammatory proteins Ccl22, IL-18 and IL-12. IL-27 expression was localized to Muller glia and IL-27 receptors to microglia, which are key cell types that regulate photoreceptor survival.

CONCLUSION

Our results identify for the first time anti-inflammatory and neuroprotective activities of IL-27 in a genetic model of retinal degeneration. These findings provide new insight into the therapeutic potential of anti-inflammatory cytokines as a treatment for degenerative diseases of the retina.

JAK-STAT Signaling Pathway in Non-Infectious Uveitis

Non-infectious uveitis (NIU) refers to various intraocular inflammatory disorders responsible for severe visual loss. Cytokines participate in the regulation of ocular homeostasis and NIU pathological processes. Cytokine receptors transmit signals by activating Janus kinase (JAK) and signal transducer and activator of transcription (STAT) proteins. Increasing evidence from human NIU and experimental models reveals the involvement of the JAK-STAT signaling pathway in NIU pathogenesis. Several small-molecule drugs that potentially inhibit multiple cytokine-dependent pathways are under investigation for treating autoimmune diseases, implicating possible applications for NIU treatment. This review summarizes the current understanding of the diverse roles of the JAK-STAT signaling pathway in ocular homeostasis and NIU pathology, providing a rationale for targeting JAKs and STATs for NIU treatment. Moreover, available evidence for the safety and efficacy of JAK inhibitors for refractory uveitis and potential approaches for treatment optimization are discussed.

Inhibition of Mer exacerbates early brain injury by regulating microglia/macrophage phenotype after subarachnoid hemorrhage in mice

BACKGROUND

Polarization of microglia/macrophages toward the pro-inflammatory phenotype is a crucial contributor to neuroinflammation after subarachnoid hemorrhage (SAH). Mer belongs to the TAM receptor tyrosine kinases family, which is known to play a significant role in the resolution of inflammation. However, the effect and mechanism of Mer after SAH remain unclear. In this study, we explored the effect of Mer on modulating the microglia/macrophage phenotype and neuroinflammation and possible potential mechanism after SAH.

METHOD

Endovascular perforation model of SAH was performed. There are 3 parts in this study. Firstly, the time course of Mer expression was determined within 72 hours after SAH. Secondly, the effect of Mer downregulation on brain water content, neurological function, and microglial polarization was evaluated at 24 h after SAH. Thirdly, the neuroprotective effects of pharmacological Mer agonist were assessed.

RESULT

The expression of Mer increased after SAH, and was prominently localized in microglia/macrophages. Treatment with Mer siRNA increased pro-inflammatory phenotype and decreased anti-inflammatory phenotype of microglia/macrophage, thus resulted in exacerbation of neurological deficits and brain edema after SAH. Mechanistically, the downregulation of Mer inhibited the downstream anti-inflammatory signals, SOCS1/SOCS3, by decreasing phosphorylated STATs.

CONCLUSION

Mer is involved in the microglia/macrophage polarization and inflammation resolution after SAH, and that mechanism, at least in part, may contribute to the involvement of the STATs/SOCSs pathway.

Photoreceptor Cells Constitutively Express IL-35 and Promote Ocular Immune Privilege

Interleukin-27 is constitutively secreted by microglia in the retina or brain, and upregulation of IL-27 during neuroinflammation suppresses encephalomyelitis and autoimmune uveitis. However, while IL-35 is structurally and functionally similar to IL-27, the intrinsic roles of IL-35 in CNS tissues are unknown. Thus, we generated IL-35/YFP-knock-in reporter mice (p35-KI) and demonstrated that photoreceptor neurons constitutively secrete IL-35, which might protect the retina from persistent low-grade inflammation that can impair photoreceptor functions. Furthermore, the p35-KI mouse, which is hemizygous at the il12a locus, develops more severe uveitis because of reduced IL-35 expression. Interestingly, onset and exacerbation of uveitis in p35-KI mice caused by extravasation of proinflammatory Th1/Th17 lymphocytes into the retina were preceded by a dramatic decrease of IL-35, attributable to massive death of photoreceptor cells. Thus, while inflammation-induced death of photoreceptors and loss of protective effects of IL-35 exacerbated uveitis, our data also suggest that constitutive production of IL-35 in the retina might have housekeeping functions that promote sterilization immunity in the neuroretina and maintain ocular immune privilege.

IL-27-producing B-1a cells suppress neuroinflammation and CNS autoimmune diseases

Regulatory B cells (Breg cells) that secrete IL-10 or IL-35 (i35-Breg) play key roles in regulating immunity in tumor microenvironment or during autoimmune and infectious diseases. Thus, loss of Breg function is implicated in development of autoimmune diseases while aberrant elevation of Breg prevents sterilizing immunity, exacerbates infectious diseases, and promotes cancer metastasis. Breg cells identified thus far are largely antigen-specific and derive mainly from B2-lymphocyte lineage. Here, we describe an innate-like IL-27-producing natural regulatory B-1a cell (i27-Breg) in peritoneal cavity and human umbilical cord blood. i27-Bregs accumulate in CNS and lymphoid tissues during neuroinflammation and confers protection against CNS autoimmune disease. i27-Breg immunotherapy ameliorated encephalomyelitis and uveitis through up-regulation of inhibitory receptors (Lag3, PD-1), suppression of Th17/Th1 responses, and propagating inhibitory signals that convert conventional B cells to regulatory lymphocytes that secrete IL-10 and/or IL-35 in eye, brain, or spinal cord. Furthermore, i27-Breg proliferates in vivo and sustains IL-27 secretion in CNS and lymphoid tissues, a therapeutic advantage over administering biologics (IL-10, IL-35) that are rapidly cleared in vivo. Mutant mice lacking irf4 in B cells exhibit exaggerated increase of i27-Bregs with few i35-Bregs, while mice with loss of irf8 in B cells have abundance of i35-Bregs but defective in generating i27-Bregs, identifying IRF8/BATF and IRF4/BATF axis in skewing B cell differentiation toward i27-Breg and i35-Breg developmental programs, respectively. Consistent with its developmental origin, disease suppression by innate i27-Bregs is neither antigen-specific nor disease-specific, suggesting that i27-Breg would be effective immunotherapy for a wide spectrum of autoimmune diseases.

IL-10 as a Th2 Cytokine: Differences Between Mice and Humans

The discovery of IL-10 more than 30 years ago marked the beginning of our understanding of how cytokines regulate immune responses, based on cross-regulation between Th1 and Th2 cytokines. Although multiple cell types were shown to produce IL-10, its identity as a Th2 cytokine remained strong because it was rigidly associated with Th2 clones in mice, whereas both Th1 and Th2 clones could secrete IL-10 in humans. However, as new Th1/Th2 cell functionalities emerged, anti-inflammatory action of IL-10 gained more attention than its inhibitory effect on Th1 cells, which may occur as an indirect consequence of suppression of APCs. This notion is also supported by the discovery of regulatory T cells, whose suppressor functions involve the mediation of IL-10, among other molecules. From this perspective, we discuss the functionalities of IL-10 by highlighting important differences between mice and humans with an emphasis on the Th1 and Th2 paradigm.

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.

Retinoid X receptor activation promotes photoreceptor survival and modulates the inflammatory response in a mouse model of retinitis pigmentosa

Photoreceptor cell (PHR) death is a hallmark of most retinal neurodegenerative diseases, in which inflammation plays a critical role. Activation of retinoid X receptors (RXR) modulates and integrates multiple cell functions, and has beneficial effects in animal models of chronic inflammatory diseases. Nonetheless, the mechanisms involved and their role in retina neuroprotection are poorly understood. In this work we assessed whether RXR activation prevents inflammation and/or PHR death in retinitis pigmentosa, an inherited retina neurodegeneration, using as an ex vivo model, retinas from the rd1 mice, a murine model of this disease. We demonstrated that rd1 retinas had lower levels of RXR alpha isoform than their wt counterparts at early developmental times, whereas its distribution pattern remained similar. In mixed neuro-glial cultures obtained from either rd1 or wt retinas, both PHR and Müller glial cells (MGC) expressed RXRalpha, and RXR activation by its synthetic pan-agonist PA024 selectively increased mRNA levels of RXRgamma isoform. PA024 decreased PHR death in rd1 mixed cultures; it reduced the amount of non-viable neurons, delayed the onset of PHR apoptosis, and decreased Bax mRNA levels. PA024 also reduced MGC reactivity in vitro before and at the onset of degeneration, decreasing GFAP expression, increasing glutamine synthetase mRNA levels, and promoting the transcription of the anti-inflammatory cytokine, Il-10. These results suggest that RXR activation rescues rd1 PHR and decreases MGC reactivity, promoting an anti-inflammatory environment in the rd1 retina, thus supporting the potential of RXR agonists as pharmacological tools for treating retina degenerative diseases.

Uveitis: Molecular Pathogenesis and Emerging Therapies

The profound impact that vision loss has on human activities and quality of life necessitates understanding the etiology of potentially blinding diseases and their clinical management. The unique anatomic features of the eye and its sequestration from peripheral immune system also provides a framework for studying other diseases in immune privileged sites and validating basic immunological principles. Thus, early studies of intraocular inflammatory diseases (uveitis) were at the forefront of research on organ transplantation. These studies laid the groundwork for foundational discoveries on how immune system distinguishes self from non-self and established current concepts of acquired immune tolerance and autoimmunity. Our charge in this review is to examine how advances in molecular cell biology and immunology over the past 3 decades have contributed to the understanding of mechanisms that underlie immunopathogenesis of uveitis. Particular emphasis is on how advances in biotechnology have been leveraged in developing biologics and cell-based immunotherapies for uveitis and other neuroinflammatory diseases.

Oral Ursodeoxycholic Acid Crosses the Blood Retinal Barrier in Patients with Retinal Detachment and Protects Against Retinal Degeneration in an Ex Vivo Model

Rhegmatogenous retinal detachment (RD) is a threatening visual condition and a human disease model for retinal degenerations. Despite successful reattachment surgery, vision does not fully recover, due to subretinal fluid accumulation and subsequent photoreceptor cell death, through mechanisms that recapitulate those of retinal degenerative diseases. Hydrophilic bile acids are neuroprotective in animal models, but whether they can be used orally for retinal diseases is unknown. Ursodeoxycholic acid (UDCA) being approved for clinical use (e.g., in cholestasis), we have evaluated the ocular bioavailability of oral UDCA, administered to patients before RD surgery. The level of UDCA in ocular media correlated with the extent of blood retinal barrier disruption, evaluated by the extent of detachment and the albumin concentration in subretinal fluid. UDCA, at levels measured in ocular media, protected photoreceptors from apoptosis and necrosis in rat retinal explants, an ex vivo model of RD. The subretinal fluid from UDCA-treated patients, collected during surgery, significantly protected rat retinal explants from cell death, when compared to subretinal fluid from control patients. Pan-transcriptomic analysis of the retina showed that UDCA upregulated anti-apoptotic, anti-oxidant, and anti-inflammatory genes. Oral UDCA is a potential neuroprotective adjuvant therapy in RD and other retinal degenerative diseases and should be further evaluated in a clinical trial.

Glial Cells in Glaucoma: Friends, Foes, and Potential Therapeutic Targets

Glaucoma is the second leading cause of blindness worldwide, affecting ~80 million people by 2020 (1, 2). The condition is characterized by a progressive loss of retinal ganglion cells (RGCs) and their axons accompanied by visual field loss. The underlying pathophysiology of glaucoma remains elusive. Glaucoma is recognized as a multifactorial disease, and lowering intraocular pressure (IOP) is the only treatment that has been shown to slow the progression of the condition. However, a significant number of glaucoma patients continue to go blind despite intraocular pressure-lowering treatment (2). Thus, the need for alternative treatment strategies is indisputable. Accumulating evidence suggests that glial cells play a significant role in supporting RGC function and that glial dysfunction may contribute to optic nerve disease. Here, we review recent advances in understanding the role of glial cells in the pathophysiology of glaucoma. A particular focus is on the dynamic and essential interactions between glial cells and RGCs and potential therapeutic approaches to glaucoma by targeting glial cells.

Cytokines that Modulate the Differentiation of Th17 Cells in Autoimmune Uveitis

Increasing evidence has suggested that T helper 17 (Th17) cells play a central role in the pathogenesis of ocular immune disease. The association between pathogenic Th17 cells and the development of uveitis has been confirmed in experimental and clinical studies. Several cytokines affect the initiation and stabilization of the differentiation of Th17 cells. Therefore, understanding the mechanism of related cytokines in the differentiation of Th17 cells is important for exploring the pathogenesis and the potential therapeutic targets of uveitis. This article briefly describes the structures, mechanisms, and targeted drugs of cytokines-including interleukin (IL)-6, transforming growth factor-β1 (TGF-β1), IL-1β, IL-23, IL-27, IL-35, IL-2, IL-4, IL-21, and interferon (IFN)-γ-which have an important influence on the differentiation of Th17 cells and discusses their potential as therapeutic targets for treating autoimmune uveitis.

IL-27 regulation of innate immunity and control of microbial growth

IL-27 is a pleiotropic cytokine capable of influencing both innate and adaptive immune responses. With anti- and pro-inflammatory activity, IL-27 exerts its opposing effects in a cell-dependent and infectious context-specific manner. Upon pathogenic stimuli, IL-27 regulates innate immune cells, such as monocytes, dendritic cells, macrophages and neutrophils. Immune responses involving these innate cells that are negatively regulated by IL-27 signaling include inflammatory cytokine production, phagolysosomal acidification following phagocytosis, oxidative burst and autophagy. IL-27 signaling is crucial in maintaining the subtle balance between Th1 and Th2 immunity, in which protective inflammation is upregulated within the early stages of infection and subsequently downregulated once microbial growth is controlled. The immunomodulatory effects of IL-27 provide promising therapeutic targets for multiple disease types.

A primary role of IL-27 is to communicate between various immune cells to initiate different immune responses. Among these responses are those involved with destroying and eliminating microbial pathogens and then turning off inflammatory responses when the infectious threat has been resolved. IL-27 possesses both anti- and pro-inflammatory activity that varies with context, immune cell and pathogen stimulus. Depending on the precise formula of these details, there are important implications for IL-27 in disease outcomes. As such, harnessing or opposing IL-27 activity may have the potential to treat a variety of infectious diseases.

IL-27 Counteracts Neuropathic Pain Development Through Induction of IL-10

Neuroimmune–glia interactions have been implicated in the development of neuropathic pain. Interleukin-27 (IL-27) is a cytokine that presents regulatory activity in inflammatory conditions of the central nervous system. Thus, we hypothesized that IL-27 would participate in the neuropathic pain process. Here, we found that neuropathic pain caused by peripheral nerve injury (spared nerve injury model; SNI), was enhanced in IL-27-deficient^(−/−) mice, whereas nociceptive pain is similar to that of wild-type mice. SNI induced an increase in the expression of IL-27 and its receptor subunit (Wsx1) in the sensory ganglia and spinal cord. IL-27 receptor was expressed mainly in resident macrophage, microglia, and astrocytes of the sensory ganglia and spinal cord, respectively. Finally, we identify that the antinociceptive effect of IL-27 was not observed in IL-10^−/− mice. These results provided evidence that IL-27 is a cytokine produced after peripheral nerve injury that counteracts neuropathic pain development through induction of the antinociceptive cytokine IL-10. In summary, our study unraveled the role of IL-27 as a regulatory cytokine that counteracts the development of neuropathic pain after peripheral nerve damage. In conclusion, they indicate that immunotherapies based on IL-27 could emerge as possible therapeutic approaches for the prevention of neuropathic pain development after peripheral nerve injury.

Single Eye mRNA-Seq Reveals Normalisation of the Retinal Microglial Transcriptome Following Acute Inflammation

Background: Whether retinal microglia can maintain or restore immune homeostasis during and after inflammation is unclear. We performed single-eye mRNA-sequencing on microglia at different timepoints following a single inflammatory stimulus to characterise their transcriptome during and after resolution of endotoxin-induced uveitis (EIU). Experimental Approach: Cx3cr1 ^CreER :R26-tdTomato (C57BL/6) male heterozygotes were administered tamoxifen via different regimes at 4-5 weeks of age. Four weeks post-tamoxifen, mice were injected intravitreally with 10 ng lipopolysaccharide (endotoxin induced uveitis, EIU). Six-hundred retinal microglia were obtained by FACS from individual naïve retinas and at 4 h, 18 h, and 2 weeks following EIU induction. Samples were sequenced to a depth of up to 16.7 million reads using the SMART-Seq v4 Ultra Low Input RNA kit. The data was analysed using Partek software and Ingenuity Pathway Analysis. Genes were considered differentially-expressed (DEG) if the FDR step-up p-value was ≤0.05 and the fold-change was ≥±2. Results: Flow cytometric analysis indicates that the Cx3cr1 ^CreER :R26-tdTomato strain is both sensitive (>95% tagging) and specific (>95% specificity) for microglia when tamoxifen is administered topically to the eye for 3 days. During "early" activation, 613 DEGs were identified. In contrast, 537 DEGs were observed during peak cellular infiltrate and none at 2 weeks, compared to baseline controls (1,069 total unique DEGs). Key marker changes were validated by qPCR, flow cytometry, and fluorescence microscopy. C5AR1 was identified and validated as a robust marker of differentiating microglial subsets during an LPS response. Conclusion: Using EIU to provide a single defined inflammatory stimulus, mRNA-Seq identified acute transcriptional changes in retinal microglia which returned to their original transcriptome after 2 weeks. Yolk-sac derived microglia are capable of restoring their homeostatic state after acute inflammation.

Resolution of uveitis

Autoimmune uveitis is a sight-threatening, rare disease, potentially leading to blindness. Uveitis is a synonym for intraocular inflammation, presenting as various clinical phenotypes with different underlying immune responses in patients, whereas different animal models usually represent one certain clinical and immunological type of uveitis due to genetic uniformity and the method of disease induction. T cells recognizing intraocular antigens initiate the disease, recruiting inflammatory cells (granulocytes, monocytes/macrophages) to the eyes, which cause the damage of the tissue. The treatment of uveitis so far aims at downregulation of inflammation to protect the ocular tissues from damage, and at immunosuppression to stop fueling T cell reactivity. Uveitis is usually prevented by specific mechanisms of the ocular immune privilege and the blood-eye-barriers, but once the disease is induced, mechanisms of the immune privilege as well as a variety of novel regulatory features including new Treg cell populations and suppressive cytokines are induced to downregulate the ocular inflammation and T cell responses and to avoid relapses and chronicity. Here we describe mechanisms of regulation observed in experimental animal models as well as detected in studies with peripheral lymphocytes from patients.

GnRH impairs diabetic wound healing through enhanced NETosis

It has been reported that neutrophil extracellular traps (NETs) impair wound healing in diabetes and that inhibiting NET generation (NETosis) improves wound healing in diabetic mice. Gonadotropin-releasing hormone (GnRH) agonists are associated with a greater risk of diabetes. However, the role of GnRH in diabetic wound healing is unclear. We determined whether GnRH-promoted NETosis and induced more severe and delayed diabetic wound healing. A mouse model of diabetes was established using five injections with streptozotocin. Mice with blood glucose levels >250 mg/dL were then used in the experiments. GnRH agonist treatment induced delayed wound healing and increased NETosis at the skin wounds of diabetic mice. In contrast, GnRH antagonist treatment inhibited GnRH agonist-induced delayed wound healing. The expression of NETosis markers PAD4 and citrullinated histone H3 were increased in the GnRH-treated diabetic skin wounds in diabetic mice and patients. In vitro experiments also showed that neutrophils expressed a GnRH receptor and that GnRH agonist treatment increased NETosis markers and promoted phorbol myristate acetate (PMA)-induced NETosis in mouse and human neutrophils. Furthermore, GnRH antagonist treatment suppressed the expression of NETosis markers and PMA-induced NETosis, which were increased by GnRH treatment. These results indicated that GnRH-promoted NETosis and that increased NETosis induced delayed wound healing in diabetic skin wounds. Thus, inhibition of GnRH might be a novel treatment of diabetic foot ulcers.

Immunopathogenesis of Behcet's Disease

Behcet's disease (BD) is a chronic systemic inflammatory vasculitis of unknown etiology characterized by recurrent episodes of oral aphthous ulcers, genital ulcers, skin lesions, ocular lesions, and other manifestations. Although the pathogenesis of BD is unclear, some studies have shown that immunological aberrations play an important role in the development and progression of BD. Infection-related trigger factors, including antigens and autoantigens, are believed to mediate the development of BD in patients with a genetic predisposition and subsequently activate the innate and adaptive immune systems, resulting in the production of numerous cytokines and chemokines to combat the infection-related factors. The study of the immunological mechanism of BD paves the way for the development of innovative therapies. Recently, novel biotherapy approaches, including interferon-α (IFN-α), tumor necrosis factor-α (TNF-α) antagonists, and other agents that target interleukins and their receptors, have shown promising results in the treatment of patients with refractory BD and have improved the prognosis of BD. In this review, we provide the current concepts of BD immunopathogenesis.

Controlled release of corticosteroid with biodegradable nanoparticles for treating experimental autoimmune uveitis

Noninfectious uveitis is a potentially blinding ocular condition that often requires treatment with corticosteroids to prevent inflammation-related ocular complications. Severe forms of uveitis such as panuveitis that affects the whole eye often require a combination of topical and either regional or systemic corticosteroid. Regional corticosteroids are currently delivered inside the eye by intravitreal injection (e.g. Ozurdex®, an intravitreal dexamethasone implant). Intravitreal injection is associated with rare but potentially serious side effects, including endophthalmitis, retinal and vitreous hemorrhage, and retinal detachment. Subconjunctival (SCT) injection is a less invasive option that is a common route used for post-surgical drug administration and treatment of infection and severe inflammation. However, it is the water soluble form of dexamethasone, dexamethasone sodium phosphate (DSP), that has been demonstrated to achieve high intraocular penetration with subconjunctival injection. It is difficult to load highly water soluble drugs, such as DSP, and achieve sustained drug release using conventional encapsulation methods. We found that use of carboxyl-terminated poly(lactic-co-glycolic acid) (PLGA) allowed encapsulation of DSP into biodegradable nanoparticles (NP) with relatively high drug content (6% w/w) if divalent zinc ions were used as an ionic "bridge" between the PLGA and DSP. DSP-Zn-NP had an average diameter of 210 nm, narrow particle size distribution (polydispersity index ~0.1), and near neutral surface charge (-9 mV). DSP-Zn-NP administered by SCT injection provided detectable DSP levels in both the anterior chamber and vitreous chamber of the eye for at least 3 weeks. In a rat model of experimental autoimmune uveitis (EAU), inflammation was significantly reduced in both the front and back of the eye in animals that received a single SCT injection of DSP-Zn-NP as compared to animals that received either aqueous DSP solution or phosphate buffered saline (PBS). DSP-Zn-NP efficacy was evidenced by a reduced clinical disease score, decreased expression of various inflammatory cytokines, and preserved retinal structure and function. Furthermore, SCT DSP-Zn-NP significantly reduced microglia cell density in the retina, a hallmark of EAU in rats. DSP-Zn-NP hold promise as a new strategy to treat noninfectious uveitis and potentially other ocular inflammatory disorders.

Non-thermal atmospheric plasma ameliorates imiquimod-induced psoriasis-like skin inflammation in mice through inhibition of immune responses and up-regulation of PD-L1 expression

Plasma medicine is an emerging novel therapeutic field. It has been reported that plasma can kill bacteria, promote wound healing and induce apoptosis of tumor cells. However, the effects of plasma on immune cells and immune related skin diseases have not been well studied. In this study, we demonstrated that non-thermal atmospheric plasma (NTP) treatment could inhibit psoriasis-like skin inflammation in mice. NTP treatment in imiquimod-induced psoriasis-like mouse skin inhibited increases in epithelial cell thickness and expression of pro-inflammatory molecules compared to ones without the NTP treatment. In addition, differentiation of Th17 cells, an important cell type for pathogenesis of psoriasis, was inhibited in the NTP-treated mouse lymph nodes. It was also demonstrated that liquid type plasma (LTP), which is also known as indirect plasma, inhibited Th17 cell differentiation in vitro. Other in vitro experiments showed that LTP inhibited bone marrow-derived dendritic cell activation. Interestingly, LTP enhanced PD-L1 expression in HaCaT cells, suggesting that NTP may inhibit unwanted over-activation of T cells through increased PD-L1 expression. Taken together, these results suggest that NTP may be used in treatment of CD4+ T cell-mediated autoimmune diseases such as psoriasis.

Plasma interleukin-27 levels in patients with coronary artery disease

Interleukin (IL)-27, one of cytokines in the IL-12 family, is considered to have both pro- and anti-inflammatory properties. However, blood IL-27 levels in coronary artery disease (CAD) have not been fully elucidated yet. This cross-sectional study was done to elucidate the association between blood IL-27 levels and CAD.We investigated plasma IL-27 and high-sensitivity C-reactive protein (hsCRP) levels in 274 consecutive patients who underwent elective coronary angiography for suspected CAD. CAD was present in 177 patients [30 acute coronary syndrome (ACS) and 147 stable CAD]. Compared with 97 patients without CAD, 177 patients with CAD had higher IL-27 (median 0.26 vs 0.22 ng/mL, P < .05) and higher hsCRP (0.98 vs 0.41 mg/L, P < .001) levels. However, there was no significant difference in IL-27 levels among 3 groups of ACS, stable CAD, and CAD(-) (0.26, 0.25, and 0.22 ng/mL), whereas hsCRP levels were significantly higher in ACS and stable CAD than in CAD(-) (2.09, 0.91 vs 0.41 mg/L, P < .001) and were highest in ACS. IL-27 levels tended to increase with the number of >50% stenotic coronary vessels: 0.22 in CAD(-), 0.22 in 1-vessel disease, 0.31 in 2-vessel disease, and 0.27 ng/mL in 3-vessel disease (P < .05). A stepwise increase in hsCRP levels was also found: 0.41 in CAD(-), 0.75 in 1-vessel, 1.05 in 2-vessel, and 1.85 mg/L in 3-vessel disease (P < .001). Plasma hsCRP levels significantly (r = 0.35), but IL-27 levels weakly (r = 0.15), correlated with the number of stenotic coronary segments. In multivariate analysis, both IL-27 and hsCRP levels were independent factors associated with CAD. However, hsCRP, but not IL-27, was also a factor for ACS.While plasma IL-27 levels were high in patients with CAD, these levels were an independent factor for only CAD, not ACS, and weakly correlated with the severity of CAD. Our results suggest that IL-27 is unlikely to be a good biomarker reflecting the severity of CAD or the presence of ACS, or to play a major role in the progression of CAD.

IL-12p35 induces expansion of IL-10 and IL-35-expressing regulatory B cells and ameliorates autoimmune disease

Interleukin 35 (IL-35) is a heterodimeric cytokine composed of IL-12p35 and Ebi3 subunits. IL-35 suppresses autoimmune diseases while preventing host defense to infection and promoting tumor growth and metastasis by converting resting B and T cells into IL-10-producing and IL-35-producing regulatory B (Breg) and T (Treg) cells. Despite sharing the IL-12p35 subunit, IL-12 (IL-12p35/IL-12p40) promotes inflammatory responses whereas IL-35 (IL-12p35/Ebi3) induces regulatory responses, suggesting that IL-12p35 may have unknown intrinsic immune-regulatory functions regulated by its heterodimeric partner. Here we show that the IL-12p35 subunit has immunoregulatory functions hitherto attributed to IL-35. IL-12p35 suppresses lymphocyte proliferation, induces expansion of IL-10-expressing and IL-35-expressing B cells and ameliorates autoimmune uveitis in mice by antagonizing pathogenic Th17 responses. Recapitulation of essential immunosuppressive activities of IL-35 indicates that IL-12p35 may be utilized for in vivo expansion of Breg cells and autologous Breg cell immunotherapy. Furthermore, our uveitis data suggest that intrinsic immunoregulatory activities of other single chain IL-12 subunits might be exploited to treat other autoimmune diseases.

IL-12p35 is common to IL-35 and IL-12, which have opposing effects on inflammation. Here the authors show that the IL-12p35 subunit induces regulatory B cells and can be used therapeutically to limit autoimmune uveitis in mice.

Roles of interleukin-17 in uveitis

Th17 cells, a CD4+ T-cell subset, produce interleukin (IL)-17, a pro-inflammatory cytokine that has been shown to be involved in several forms of infectious and noninfectious uveitis. Here, we explore the roles of this IL in uveitic disorders as well as in experimental autoimmune uveitis, the possible pathogenic implications of several cytokines associated with IL-17 and analyze the current outcomes and goals for drugs aiming for the IL-17 pathway.

Serum and aqueous humor concentrations of interleukin-27 in diabetic retinopathy patients

PURPOSE

Interleukin (IL)-27 has been reported to possess anti- and proinflammatory properties in several immune related-disorders, but its role in diabetic retinopathy is still elusive. Here, we aimed to (i) evaluate IL-27 concentrations in serum and aqueous humor of diabetic patients with or without retinopathy and (ii) test whether IL-27 is correlated with some risk factors of diabetic retinopathy.

METHODS

The study comprised 60 diabetic patients with and without retinopathy along with 20 healthy controls. Serum and aqueous humor concentrations of IL-27 were assessed by ELISA.

RESULTS

The mean of IL-27 concentration in aqueous humor in patients with diabetic retinopathy (6.7 ± 2.7 ng/L) was significantly elevated in comparison with either diabetic patients without retinopathy (4.6 ± 0.5 ng/L) or healthy control group (4.1 ± 0.8 ng/L). Besides, IL-27 concentration in aqueous humor was positively correlated with serum glucose, lipid profile and glycated hemoglobin (HbA1c).

CONCLUSIONS

Based on this study, IL-27 is implicated in the pathogenesis of diabetic retinopathy and positively correlates with the disorder progression.

Rapid monocyte infiltration following retinal detachment is dependent on non-canonical IL6 signaling through gp130

BACKGROUND

Retinal detachment (RD) can lead to proliferative vitreoretinopathy (PVR), a leading cause of intractable vision loss. PVR is associated with a cytokine storm involving common proinflammatory molecules like IL6, but little is known about the source and downstream signaling of IL6 and the consequences for the retina. Here, we investigated the early immune response and resultant cytokine signaling following RD in mice.

METHODS

RD was induced in C57BL/6 J and IL6 knockout mice, and the resulting inflammatory response was examined using immunohistochemistry and flow cytometry. Cytokines and signaling proteins of vitreous and retinas were quantified by multiple cytokine arrays and Western blotting. To attempt to block IL6 signaling, a neutralizing antibody of IL6 receptor α (IL6Rα) or IL6 receptor β (gp-130) was injected intravitreally immediately after RD.

RESULTS

Within one day of RD, bone marrow-derived Cd11b + monocytes had extravasated from the vasculature and lined the vitreal surface of the retina, while the microglia, the resident macrophages of the retina, were relatively unperturbed. Cytokine arrays and Western blot analysis revealed that this sterile inflammation did not cause activation of IL6 signaling in the neurosensory retina, but rather only in the vitreous and aqueous humor. Monocyte infiltration was inhibited by blocking gp130, but not by IL6 knockout or IL6Rα blockade.

CONCLUSIONS

Together, our results demonstrate that monocytes are the primary immune cell mediating the cytokine storm following RD, and that any resulting retinal damage is unlikely to be a direct result of retinal IL6 signaling, but rather gp130-mediated signaling in the monocytes themselves. These results suggest that RD should be treated immediately, and that gp130-directed therapies may prevent PVR and promote retinal healing.

Effects of hydrogen-rich saline on endotoxin-induced uveitis

The therapeutic effects of hydrogen-rich saline (HRS) have been reported for a wide range of diseases mainly via selectively reducing the amount of reactive oxygen species. Oxidative stress plays an important role in the pathogenesis of uveitis and endotoxin-induced uveitis (EIU). In this study, we investigated whether HRS can mitigate EIU in rats. Sprague-Dawley rats were randomly divided into Norm group, Model group, HRS group, dexamethasone (DEX) group, and rats in the latter three groups were injected with equal amount of lipopolysaccharide (LPS) to induce EIU of different severities (by 1 mg/kg of LPS, or 1/8 mg/kg of LPS). Rats in HRS group were injected with HRS intraperitoneally at three different modes to purse an ameliorating effect of EIU (10 mL/kg of HRS immediately after injection of 1 mg/kg of LPS, 20 mL/kg of HRS once a day for 1 week before injection of 1 mg/kg of LPS and at 0, 0.5, 1, 2, 6, 8, 12 hours after LPS administration, or 20 mL/kg of HRS once a day for 1 week before injection of 1/8 mg/kg of LPS, and at 0, 0.5, 1, 2, 6, 8, 12, 24 hours and once a day for 3 weeks after LPS administration). Rats of DEX group were injected with 1 mL/kg of DEX solution intraperitoneally immediately after LPS administration. Rats in Norm and Model groups did not receive any treatment. All rats were examined under slit lamp microscope and graded according to the clinical signs of uveitis. Electroretinogram, quantitative analysis of protein in aqueous humor (AqH) and histological examination of iris and ciliary body were also carried out. Our results showed that HRS did not obviously ameliorate the signs of uveitis under slit lamp examination and the inflammatory cells infiltration around iris and cilliary body of EIU induced by 1 mg/kg or 1/8 mg/kg of LPS (P > 0.05), while DEX significantly reduced the inflammation reflected by the above two indicators (P < 0.05). The impaired retinal function of mild EIU induced by 1/8 mg/kg of LPS, showed by delay of peak time of b-wave of Dark adapted 3.0 electroretinogram, was not significantly restored by HRS (P > 0.05), while DEX had an obvious therapeutic effect (P < 0.05). However, HRS exerted an inhibition trend on elevation of protein in AqH of EIU induced by 1 mg/kg of LPS, and significantly reduced the increasing amount of protein in AqH of mild EIU induced by 1/8 mg/kg of LPS (P < 0.05). In conclusion, HRS could not obviously mitigate EIU in rats, while it could inhibit the elevation of AqH protein.

Human umbilical cord blood-derived mesenchymal stem cells ameliorate psoriasis-like skin inflammation in mice

Mesenchymal stem cells (MSCs) inhibit the proliferation or activation of lymphocytes, and their inhibitory effects do not require human leukocyte antigen (HLA)-matching because MSCs express low levels of HLA molecules. Therefore, MSCs may be able to regulate immune responses. In this study, we determined whether MSCs could inhibit psoriasis-like skin inflammation in mice. After induction of psoriasis-like skin inflammation using intradermal injection of IL-23 or topical application of imiquimod with or without treatment with MSC, mouse skins were collected, and H&E staining and real-time PCR were performed. IL-23-induced skin inflammation was inhibited when MSCs were injected on day −1 and day 7. The expression of proinflammatory cytokines such as IL-6, IL-17, and TNF-α was inhibited by MSC injection, and the expression of chemokines such as CCL17, CCL20, and CCL27 was also decreased in mouse skin. We also determined whether MSCs could not only prevent but also treat psoriasis-like skin inflammation in mice. Furthermore, in vitro experiments also showed anti-inflammatory effects of MSCs. Dendritic cells which are co-cultured with MSCs suppressed CD4+ T cell activation and differentiation, which are important for the pathogenesis of psoriasis. These results suggest that MSCs could be useful for treating psoriasis.

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Mesenchymal stem cells inhibit psoriasis-like skin inflammation in mice.

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Mesenchymal stem cells modulate dendritic cell function.

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Dendritic cells that co-cultured with mesenchymal stem cells regulate CD4+ T cell differentiation.

Extracellular superoxide dismutase ameliorates house dust mite-induced atopic dermatitis-like skin inflammation and inhibits mast cell activation in mice

Extracellular superoxide dismutase (EC-SOD) is an enzyme that catalyses the dismutation of superoxide anions. It has multiple functions, such as reactive oxygen species scavenging, anti-angiogenic, anti-inflammatory, antichemotatic and antitumor activities. Recently, we demonstrated that EC-SOD inhibits ovalbumin-induced allergic airway inflammation in mice. However, the anti-allergic effect of EC-SOD on skin tissue and the role of EC-SOD in mast cells, which are important for allergic responses, have not been well studied. In this study, we investigated whether EC-SOD can alleviate atopic dermatitis in mice and inhibit mast cell activation. Treatment with human recombinant EC-SOD ameliorated house dust mite-induced atopic dermatitis in mice. Furthermore, the levels of pro-allergic cytokine gene expression and histamine release increased in EC-SOD KO mast cells and decreased in EC-SOD overexpressing mast cells, suggesting that EC-SOD inhibits mast cell activation. Consistently, a passive cutaneous anaphylaxis experiment showed more blood leakage from EC-SOD KO mouse ear skin, implying that the lack of EC-SOD increases allergic responses. These results suggest that EC-SOD inhibits mast cell activation and atopic dermatitis and that the loss of EC-SOD causes more severe allergic responses, implying that EC-SOD might be a good drug candidate for treatment of allergic disorders, such as atopic dermatitis.

Leger AJ, Yu CR, He C, Mahdi RM, Chan CC, Wang H, Morse HC, Egwuagu CE. Interferon Regulator Factor 8 (IRF8) Limits Ocular Pathology during HSV-1 Infection by Restraining the Activation and Expansion of CD8+ T Cells

Interferon Regulatory Factor-8 (IRF8) is constitutively expressed in monocytes and B cell lineages and plays important roles in immunity to pathogens and cancer. Although IRF8 expression is induced in activated T cells, the functional relevance of IRF8 in T cell-mediated immunity is not well understood. In this study, we used mice with targeted deletion of Irf8 in T-cells (IRF8KO) to investigate the role of IRF8 in T cell-mediated responses during herpes simplex virus 1 (HSV-1) infection of the eye. In contrast to wild type mice, HSV-1-infected IRF8KO mice mounted a more robust anti-HSV-1 immune response, which included marked expansion of HSV-1-specific CD8⁺ T cells, increased infiltration of inflammatory cells into the cornea and trigeminal ganglia (TG) and enhanced elimination of virus within the trigeminal ganglion. However, the consequence of the enhanced immunological response was the development of ocular inflammation, limbitis, and neutrophilic infiltration into the cornea of HSV-1-infected IRF8KO mice. Surprisingly, we observed a marked increase in virus-specific memory precursor effector cells (MPEC) in IRF8KO mice, suggesting that IRF8 might play a role in regulating the differentiation of effector CD8⁺ T cells to the memory phenotype. Together, our data suggest that IRF8 might play a role in restraining excess lymphocyte proliferation. Thus, modulating IRF8 levels in T cells can be exploited therapeutically to prevent immune-mediated ocular pathology during autoimmune and infectious diseases of the eye.

Primate neural retina upregulates IL-6 and IL-10 in response to a herpes simplex vector suggesting the presence of a pro-/anti-inflammatory axis

Injection of herpes simplex virus vectors into the vitreous of primate eyes induces an acute, transient uveitis. The purpose of this study was to characterize innate immune responses of macaque neural retina tissue to the herpes simplex virus type 1-based gene delivery vector hrR3. PCR array analysis demonstrated the induction of the pro-inflammatory cytokine IL-6, as well as the anti-inflammatory cytokine IL-10, following hrR3 exposure. Secretion of IL-6 was detected by ELISA and cone photoreceptors and Muller cells were the predominant IL-6 positive cell types. RNA in situ hybridization confirmed that IL-6 was expressed in photoreceptor and Muller cells. The IL-10 positive cells in the inner nuclear layer were identified as amacrine cells by immunofluorescence staining with calretinin antibody. hrR3 challenge resulted in activation of NFκB (p65) in Muller glial cells, but not in cone photoreceptors, suggesting a novel regulatory mechanism for IL-6 expression in cone cells. hrR3 replication was not required for IL-6 induction or NFκB (p65) activation. These data suggest a pro-inflammatory (IL-6)/anti-inflammatory (IL-10) axis exists in neural retina and the severity of acute posterior uveitis may be determined by this interaction. Further studies are needed to identify the trigger for IL-6 and IL-10 induction and the mechanism of IL-6 induction in cone cells.

Suppressor of cytokine signaling 1 (SOCS1) mitigates anterior uveitis and confers protection against ocular HSV-1 infection

Immunological responses to pathogens are stringently regulated in the eye to prevent excessive inflammation that damage ocular tissues and compromise vision. Suppressors of cytokine signaling (SOCS) regulate intensity/duration of inflammatory responses. We have used SOCS1-deficient mice and retina-specific SOCS1 transgenic rats to investigate roles of SOCS1 in ocular herpes simplex virus (HSV-1) infection and non-infectious uveitis. We also genetically engineered cell-penetrating SOCS proteins (membrane-translocating sequence (MTS)-SOCS1, MTS-SOCS3) and examined whether they can be used to inhibit inflammatory cytokines. Overexpression of SOCS1 in transgenic rat eyes attenuated ocular HSV-1 infection while SOCS1-deficient mice developed severe non-infectious anterior uveitis, suggesting that SOCS1 may contribute to mechanism of ocular immune privilege by regulating trafficking of inflammatory cells into ocular tissues. Furthermore, MTS-SOCS1 inhibited IFN-γ-induced signal transducers and activators of transcription 1 (STAT1) activation by macrophages while MTS-SOCS3 suppressed expansion of pathogenic Th17 cells that mediate uveitis, indicating that MTS-SOCS proteins maybe used to treat ocular inflammatory diseases of infectious or autoimmune etiology.

Production of IL-27 in multiple sclerosis lesions by astrocytes and myeloid cells: Modulation of local immune responses

The mechanisms whereby human glial cells modulate local immune responses are not fully understood. Interleukin-27 (IL-27), a pleiotropic cytokine, has been shown to dampen the severity of experimental autoimmune encephalomyelitis, but it is still unresolved whether IL-27 plays a role in the human disease multiple sclerosis (MS). IL-27 contribution to local modulation of immune responses in the brain of MS patients was investigated. The expression of IL-27 subunits (EBI3 and p28) and its cognate receptor IL-27R (the gp130 and TCCR chains) was elevated within post-mortem MS brain lesions compared with normal control brains. Moreover, astrocytes (GFAP(+) cells) as well as microglia and macrophages (Iba1(+) cells) were important sources of IL-27. Brain-infiltrating CD4 and CD8 T lymphocytes expressed the IL-27R specific chain (TCCR) implying that these cells could respond to local IL-27 sources. In primary cultures of human astrocytes inflammatory cytokines increased IL-27 production, whereas myeloid cell inflammatory M1 polarization and inflammatory cytokines enhanced IL-27 expression in microglia and macrophages. Astrocytes in postmortem tissues and in vitro expressed IL-27R. Moreover, IL-27 triggered the phosphorylation of the transcription regulator STAT1, but not STAT3 in human astrocytes; indeed IL-27 up-regulated MHC class I expression on astrocytes in a STAT1-dependent manner. These findings demonstrated that IL-27 and its receptor were elevated in MS lesions and that local IL-27 can modulate immune properties of astrocytes and infiltrating immune cells. Thus, therapeutic strategies targeting IL-27 may influence not only peripheral but also local inflammatory responses within the brain of MS patients.

IL-27-induced modulation of autoimmunity and its therapeutic potential

Interleukin-27 (IL-27) is a new member of the IL-12 family. It is produced by activated antigen-presenting cells and plays an important role in the regulation of CD4+ T cell differentiation and immune response. IL-27 activates multiple signaling cascades, including the JAK-STAT and p38 MAPK pathways. Several studies have revealed that IL-27 promotes the differentiation of Th1 and Tr1, but inhibits Th2, Th17, and Treg cells. However, a few studies have shown an opposite effect on certain T cell subsets, such as Treg. IL-27 displays both pro- and anti- inflammatory activities in different autoimmune diseases. Here, we have discussed the role of IL-27 in rheumatoid arthritis, multiple sclerosis, colitis, lupus, psoriasis, type 1 diabetes, and uveitis. Most of this information is derived from experimental models of these autoimmune diseases. The mechanistic basis of the dual role of IL-27 in inflammation and autoimmunity is still not fully defined. In general, the pro-/anti-inflammatory activity of IL-27 is influenced by the underlying immune effector pathways, the phase of the disease, the presence or absence of counter-regulatory cytokines/T cell subsets, and the tissue/cell type under study. Despite a spectrum of outcomes in various autoimmune diseases, mostly anti-inflammatory and immunomodulatory effects of IL-27 have been observed in this category of diseases. Accordingly, IL-27 represents a novel, promising target/agent for the treatment of autoimmune diseases.

Genetic of uveitis

Immune-mediated uveitis may be associated with a systemic disease or may be localized to the eye. T-cell-dependent immunological events are increasingly being regarded as extremely important in the pathogenesis of uveitis. Several studies have also shown that macrophages are major effectors of tissue damage in uveitis. Uveitis phenotypes can differ substantially, and most uveitis diseases are considered polygenic with complex inheritance patterns. This review attempts to present the current state of knowledge from in vitro and in vivo research on the role of genetics in the development and clinical course of uveitis. A review of the literature in the PubMed, MEDLINE, and Cochrane databases was conducted to identify clinical trials, comparative studies, case series, and case reports describing host genetic factors as well as immune imbalance which contribute to the development of uveitis. The search was limited to primary reports published in English with human subjects from 1990 to the present, yielding 3590 manuscripts. In addition, referenced articles from the initial searches were hand searched to identify additional relevant reports. After title and abstract selection, duplicate elimination, and manual search, 55 papers were selected for analysis and reviewed by the authors for inclusion in this review. Studies have demonstrated associations between various genetic factors and the development and clinical course of intraocular inflammatory conditions. Genes involved included genes expressing interleukins, chemokines, chemokine receptors, and tumor necrosis factor and genes involved in complement system. When considering the genetics of uveitis, common threads can be identified. Genome-wide scans and other genetic methods are becoming increasingly successful in identifying genetic loci and candidate genes in many inflammatory disorders that have a uveitic component. It will be important to test these findings as uveitis-specific genetic factors. Therefore, the burgeoning understanding of the human genome promises to result in new insight into the pathogenesis of uveitis.

Dual Function of the IRF8 Transcription Factor in Autoimmune Uveitis: Loss of IRF8 in T Cells Exacerbates Uveitis, Whereas Irf8 Deletion in the Retina Confers Protection

IFN regulatory factor 8 (IRF8) is constitutively expressed in monocytes and B cells and plays a critical role in the functional maturation of microglia cells. It is induced in T cells following Ag stimulation, but its functions are less well understood. However, recent studies in mice with T cell-specific Irf8 disruption under direction of the Lck promoter (LCK-IRF8KO) suggest that IRF8 directs a silencing program for Th17 differentiation, and IL-17 production is markedly increased in IRF8-deficient T cells. Paradoxically, loss of IRF8 in T cells has no effect on the development or severity of experimental autoimmune encephalomyelitis (EAE), although exacerbating colitis in a mouse colitis model. In contrast, mice with a macrophage/microglia-specific Irf8 disruption are resistant to EAE, further confounding our understanding of the roles of IRF8 in host immunity and autoimmunity. To clarify the role of IRF8 in autoimmune diseases, we have generated two mouse strains with targeted deletion of Irf8 in retinal cells, including microglial cells and a third mouse strain with targeted Irf8 deletion in T cells under direction of the nonpromiscuous, CD4 promoter (CD4-IRF8KO). In contrast to the report that IRF8 deletion in T cells has no effect on EAE, experimental autoimmune uveitis is exacerbated in CD4-IRF8KO mice and disease enhancement correlates with significant expansion of Th17 cells and a reduction in T regulatory cells. In contrast to CD4-IRF8KO mice, Irf8 deletion in retinal cells confers protection from uveitis, underscoring divergent and tissue-specific roles of IRF8 in host immunity. These results raise a cautionary note in the context of therapeutic targeting of IRF8.

Interleukin 35: Critical regulator of immunity and lymphocyte-mediated diseases

Cytokines coordinate the activities of innate and adaptive immune systems and the Interleukin 12 (IL-12) family of cytokines has emerged as critical regulators of immunity in infectious and autoimmune diseases. While some members (IL-12 and IL-23) are associated with the pathogenesis of chronic inflammatory diseases, others (IL-27 and IL-35) mitigate autoimmune diseases. Unlike IL-12, IL-23 and IL-27 that are produced mainly by antigen presenting cells, IL-35 is predominantly secreted by regulatory B (i35-Bregs) and T (iTR35) cells. The discovery that IL-35 can induce the conversion or expansion of lymphocytes to regulatory B and T cells has considerable implications for therapeutic use of autologous regulatory B and T cells in human diseases. Although our current understanding of the immunobiology of IL-35 or its subunits (p35 and Ebi3) is still rudimentary, our goal in this review is to summarize what we know about this enigmatic cytokine and its potential clinical use, particularly in the treatment of CNS autoimmune diseases.

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.

Capsiate Inhibits DNFB-Induced Atopic Dermatitis in NC/Nga Mice through Mast Cell and CD4+ T-Cell Inactivation

Capsaicin has many biological effects, such as antioxidant, anticancer, and antiangiogenic effects, but it is rarely used because of its high pungency. Capsiate, a nonpungent capsaicin analog, also has multiple biological effects, similar to those of capsaicin, but does not cause irritation. However, the effect of capsiate on allergic responses and immune cells has not been well studied. In this study, we investigated the effect of capsiate on atopic dermatitis, mouse CD4+ T cells, and mast cell activation. Capsiate inhibited DNFB-induced atopic dermatitis in NC/Nga mice. Topical treatment with capsiate suppressed serum IgE levels and cytokine and chemokine expression in the skin of DNFB-treated NC/Nga mice. In addition, it suppressed the activation of CD4+ T cells and mast cells, which are implicated in allergic diseases. Capsiate inhibited the differentiation of naïve CD4+ T cells into T helper type 1 (Th1), Th2, and Th17 cells. Treatment with capsiate inhibited the expression of pro-inflammatory cytokines and degranulation from activated bone marrow-derived mast cells through the inhibition of extracellular signal-regulated kinase signal pathways. Consistent with these results, treatment with capsiate inhibited passive cutaneous anaphylaxis. Taken together, our results suggest that capsiate might be a good candidate molecule for the treatment of allergic diseases such as atopic dermatitis.

Interleukin 12 (IL-12) family cytokines: Role in immune pathogenesis and treatment of CNS autoimmune disease

Cytokines play crucial roles in coordinating the activities of innate and adaptive immune systems. In response to pathogen recognition, innate immune cells secrete cytokines that inform the adaptive immune system about the nature of the pathogen and instruct naïve T cells to differentiate into the appropriate T cell subtypes required to clear the infection. These include Interleukins, Interferons and other immune-regulatory cytokines that exhibit remarkable functional redundancy and pleiotropic effects. The focus of this review, however, is on the enigmatic Interleukin 12 (IL-12) family of cytokines. This family of cytokines plays crucial roles in shaping immune responses during antigen presentation and influence cell-fate decisions of differentiating naïve T cells. They also play essential roles in regulating functions of a variety of effector cells, making IL-12 family cytokines important therapeutic targets or agents in a number of inflammatory diseases, such as the CNS autoimmune diseases, uveitis and multiple sclerosis.

Activated adult microglia influence retinal progenitor cell proliferation and differentiation toward recoverin-expressing neuron-like cells in a co-culture model

PURPOSE

Microglia contribute to immune homeostasis of the retina, and thus act as a potential regulator determining successful repair or retinal stem cell transplantation. We investigated the interaction between human microglia and retinal progenitor cells in cell co-culture to further our exploration on developing a new therapeutic strategy for retinal degeneration.

METHODS

Microglia and retinal progenitor cultures were developed using CD11b(+) and CD133(+), respectively, from adult donor retina. Microglia activation was developed using interferon-gamma and lipopolysaccharide. Retinal progenitor differentiation was analysed in co-culture with or without microglial activation. Retinal progenitor proliferation was analysed in presence of conditioned medium from activated microglia. Phenotype and function of adult human retinal cell cultures were examined using cell morphology, immunohistochemistry and real-time PCR.

RESULTS

By morphology, neuron-like cells generated in co-culture expressed photoreceptor marker recoverin. Neurospheres derived from retinal progenitor cells showed reduced growth in the presence of conditioned medium from activated microglia. Delayed retinal progenitor cell migration and reduced cellular differentiation was observed in co-cultures with activated microglia. In independent experiments, activated microglia showed enhanced mRNA expression of CXCL10, IL-27, IL-6, and TNF-alpha compared to controls.

CONCLUSION

Adult human retina retains retinal progenitors or potential to reprogram cells to then proliferate and differentiate into neuron-like cells in vitro. Human microglia support retinal progenitor differentiation into neuron-like cells, but such capacity is altered following microglial activation. Modulating microglia activity is a potential approach to promote retinal repair and facilitate success of stem-cell transplantation.