Induction of Th17 differentiation by corneal epithelial-derived cytokines

Deletion of TNF in Winnie-APCMin/+ Mice Reveals Its Dual Role in the Onset and Progression of Colitis-Associated Colorectal Cancer

Colorectal cancer (CRC) is among the best examples for depicting the relationship between inflammation and cancer. The introduction of new therapeutics targeting inflammatory mediators showed a marked decrease in the overall risk of CRC, although their chemopreventive potential is still debated. Specifically, a monoclonal antibody that blocks tumor necrosis factor (TNF), infliximab, increases CRC risk in inflammatory bowel disease patients. To address the axis between TNF and CRC development and progression, we depleted the Tnf from our previously established murine model of colitis-associated cancer (CAC), the Winnie-Apc^Min/+ line. We characterized the new Winnie-APC^Min/+-TNF-KO line through macroscopical and microscopical analyses. Surprisingly, the latter demonstrated that the deletion of Tnf in Winnie-Apc^Min/+ mice resulted in an initial reduction in dysplastic lesion incidence in 5-week-old mice followed by a faster disease progression at 8 weeks. Histological data were confirmed by the molecular profiling obtained from both the real-time PCR analysis of the whole tissue and the RNA sequencing of the macrodissected tumoral lesions from Winnie-APC^Min/+-TNF-KO distal colon at 8 weeks. Our results highlight that TNF could exert a dual role in CAC, supporting the promotion of neoplastic lesions onset in the early stage of the disease while inducing their reduction during disease progression.

Hispidulin alleviates imiquimod-induced psoriasis-like skin inflammation by inhibiting splenic Th1/Th17 cell population and keratinocyte activation

Psoriasis is a chronic inflammatory skin disease characterized by hyperproliferation and abnormal differentiation of epidermal keratinocytes accompanied by increased infiltration of immune cells. Previous studies have demonstrated that hispidulin (4',5,7-trihydroxy-6-methoxyflavone, HPD) has various pharmacological benefits such as anti-fungal, anti-inflammation, and anti-allergic effects. This study investigated the effectiveness of HPD to treat psoriasis using an imiquimod (IMQ)-induced mouse model and activated keratinocytes. IMQ was topically applied to the back skin of mice for six consecutive days, and the mice were orally administered HPD. Based on the histological observation and immunological analysis, oral administration of HPD suppressed psoriatic characteristics including skin thickness, psoriasis area severity index, transepidermal water loss, and neutrophil infiltration. HPD alleviated pathologically increased levels of immunoglobulin G2a, myeloperoxidase, and tumor necrosis factor-α. Splenic Th1 and Th17 cell populations were also reduced by HPD in the murine model. In addition, in activated keratinocytes, HPD inhibited gene expression of Th1- and Th17-associated cytokines and chemokines, and phosphorylation of mitogen-activated protein kinases and nuclear factor-κB. In summary, HPD alleviates psoriasis skin inflammation in vivo and in vitro. Therefore, we suggest that HPD would be a potent therapeutic candidate for the treatment of psoriasis.

The role of Th17 immunity in chronic ocular surface disorders

Th17 cells have been implicated in the pathogenesis of numerous inflammatory and autoimmune conditions. At the ocular surface, Th17 cells have been identified as key effector cells in chronic ocular surface disease. Evidence from murine studies indicates that following differentiation and expansion, Th17 cells migrate from the lymphoid tissues to the eye, where they release inflammatory cytokines including, but not limited to, their hallmark cytokine IL-17A. As the acute phase subsides, a population of long-lived memory Th17 cells persist, which predispose hosts both to chronic inflammation and severe exacerbations of disease; of great interest is the small subset of Th17/1 cells that secrete both IL-17A and IFN-γ in acute-on-chronic disease exacerbation. Over the past decade, substantial progress has been made in deciphering how Th17 cells interact with the immune and neuroimmune pathways that mediate chronic ocular surface disease. Here, we review (i) the evidence for Th17 immunity in chronic ocular surface disease, (ii) regulatory mechanisms that constrain the Th17 immune response, and (iii) novel therapeutic strategies targeting Th17 cells.

IL-27 signaling deficiency develops Th17-enhanced Th2-dominant inflammation in murine allergic conjunctivitis model

BACKGROUND

While most studies focus on pro-allergic cytokines, the protective role of immunosuppressive cytokines in allergic inflammation is not well elucidated. This study was to explore a novel anti-inflammatory role and cellular/molecular mechanism of IL-27 in allergic inflammation.

METHODS

A murine model of experimental allergic conjunctivitis (EAC) was induced in BALB/c, C57BL/6 or IL-27Rα-deficient (WSX-1^-/- ) mice by short ragweed pollen, with untreated or PBS-treated mice as controls. The serum, eyeballs, conjunctiva, cervical lymph nodes (CLNs) were used for study. Gene expression was determined by RT-qPCR, and protein production and activation were evaluated by immunostaining, ELISA and Western blotting.

RESULTS

Typical allergic manifestations and stimulated thymic stromal lymphopoietin (TSLP) signaling and Th2 responses were observed in ocular surface of EAC models in BALB/c and C57BL/6 mice. The decrease of IL-27 at mRNA (IL-27/EBI3) and protein levels were detected in serum, conjunctiva and CLN, as evaluated by RT-qPCR, immunofluorescent staining, ELISA and Western blotting. EAC induced in WSX-1^-/- mice showed aggravated allergic signs with higher TSLP-driven Th2-dominant inflammation, accompanied by stimulated Th17 responses, including IL-17A, IL-17F, and transcription factor RORγt. In contrast, Th1 cytokine IFNγ and Treg marker IL-10, with their respective transcription factors T-bet and foxp3, were largely suppressed. Interestingly, imbalanced activation between reduced phosphor (P)-STAT1 and stimulated P-STAT6 were revealed in EAC, especially WSX-1^-/- -EAC mice.

CONCLUSION

These findings demonstrated a natural protective mechanism by IL-27, of which signaling deficiency develops a Th17-type hyperresponse that further aggravates Th2-dominant allergic inflammation.

Protective role of commensal bacteria in Sjögren Syndrome

CD25 knock-out (CD25KO) mice spontaneously develop Sjögren Syndrome (SS)-like inflammation. We investigated the role of commensal bacteria by comparing CD25KO mice housed in conventional or germ-free conditions. Germ-free CD25KO mice have greater corneal barrier dysfunction, lower goblet cell density, increased total lymphocytic infiltration score, increased expression of IFN-γ, IL-12 and higher a frequency of CD4⁺IFN-γ⁺ cells than conventional mice. CD4⁺ T cells isolated from female germ-free CD25KO mice adoptively transferred to naive immunodeficient RAG1KO recipients caused more severe Sjögren-like disease than CD4⁺ T cells transferred from conventional CD25KO mice. Fecal transplant in germ-free CD25KO mice reversed the spontaneous dry eye phenotype and decreased the generation of pathogenic CD4⁺IFN-γ⁺ cells. Our studies indicate that lack of commensal bacteria accelerates the onset and severity of dacryoadenitis and generates autoreactive CD4⁺T cells with greater pathogenicity in the CD25KO model, suggesting that the commensal bacteria or their metabolites products have immunoregulatory properties that protect exocrine glands in the CD25KO SS model.

The Pathophysiology of Dry Eye Disease: What We Know and Future Directions for Research

Clinical and laboratory studies performed over the past few decades have discovered that dry eye is a chronic inflammatory disease that can be initiated by numerous extrinsic or intrinsic factors that promote an unstable and hyperosmolar tear film. These changes in tear composition, in some cases combined with systemic factors, lead to an inflammatory cycle that causes ocular surface epithelial disease and neural stimulation. Acute desiccation activates stress signaling pathways in the ocular surface epithelium and resident immune cells. This triggers production of innate inflammatory mediators that stimulate the production of matrix metalloprotease, inflammatory cell recruitment, and dendritic cell maturation. These mediators, combined with exposure of autoantigens, can lead to an adaptive T cell-mediated response. Cornea barrier disruption develops by protease-mediated lysis of epithelial tight junctions, leading to accelerated cell death; desquamation; an irregular, poorly lubricated cornea surface; and exposure and sensitization of epithelial nociceptors. Conjunctival goblet cell dysfunction and death are promoted by the T helper 1 cytokine interferon gamma. These epithelial changes further destabilize the tear film, amplify inflammation, and create a vicious cycle. Cyclosporine and lifitegrast, the 2 US Food and Drug Administration-approved therapies, inhibit T-cell activation and cytokine production. Although these therapies represent a major advance in dry eye therapy, they are not effective in improving discomfort and corneal epithelial disease in all patients. Preclinical studies have identified other potential therapeutic targets, biomarkers, and strategies to bolster endogenous immunoregulatory pathways. These discoveries will, it is hoped, lead to further advances in diagnostic classification and treatment.

Peripheral Ulcerative Keratitis Associated with Autoimmune Disease: Pathogenesis and Treatment

Peripheral ulcerative keratitis (PUK) is type of crescent-shaped inflammatory damage that occurs in the limbal region of the cornea. PUK is always combined with an epithelial defect and the destruction of the peripheral corneal stroma. PUK may have a connection to systemic conditions, such as long-standing rheumatoid arthritis (RA), systemic lupus erythematosus (SLE), Wegener granulomatosis (WG), relapsing polychondritis, classic polyarteritis nodosa and its variants, microscopic polyangiitis, and Churg-Strauss syndrome. However, the most common connection is with RA, which is also the focus of this review. The pathogenesis of PUK is still unclear. It is thought that circulating immune complexes and cytokines exert an important influence on the progression of this syndrome. Treatment is applied to inhibit certain aspects of PUK pathogenesis.

Inflammatory Response to Lipopolysaccharide on the Ocular Surface in a Murine Dry Eye Model

Purpose

Toll-like receptor 4 (TLR4) alerts cells to the presence of bacteria by initiating an inflammatory response. We hypothesize that disruption of the ocular surface barrier in dry eye enhances TLR4 signaling. This study determined whether dry eye enhances expression of inflammatory mediators in response to topically applied TLR4 ligand.

Methods

A single dose of lipopolysaccharide (LPS) or vehicle (endotoxin-free water) was applied to the cornea of nonstressed (NS) mice or mice subjected to 5 days of desiccating stress (DS). After 4 hours, corneal epithelium and conjunctiva were extracted to analyze expression of inflammatory mediators via PCR. Protein expression was confirmed by immunobead assay and immunostaining.

Results

Topically applied LPS increased expression of inflammatory mediators IL-1β, CXCL10, IL-12a, and IFN-γ in the conjunctiva, and IL-1β and CXCL10 in the cornea of NS mice compared to that in untreated controls. LPS in DS mice produced 3-fold increased expression of IL-1β in cornea and 2-fold increased expression in IL-12a in conjunctiva compared to that in LPS-treated control mice.

Conclusions

LPS increased expression of inflammatory cytokines on the ocular surface. This expression was further increased in dry eye, which suggests that epithelial barrier disruption enhances exposure of LPS to TLR4⁺ cells and that the inflammatory response to endotoxin-producing commensal or pathogenic bacteria may be more severe in dry eye disease.

Interleukin-6 participation in pathology of ocular diseases

Interleukin-6 (IL-6) is a multifunctional cytokine that affects a variety of cells in the body such as osteoclasts, hepatocytes, endothelial cells, epithelial cells, white and red blood cells and etc. Elevated levels of IL-6 have been detected in many ocular diseases. Studies show that IL-6 has a major role in the pathology of glaucoma, CRVO, macular edema, ocular neovascularization, posterior capsule opacity formation, keratitis, dry eye disease, allergic eye disease, ocular autoimmune disease, corneal chemical burn, ocular inflammation and so on. IL-6 does its effects through the classic or trans-signal pathways in cells. Blocking of IL-6 signal pathways via Tocilizumab or other chemicals and therapeutics will help to overcome complications related to ocular diseases.

Prioritizing biological pathways by recognizing context in time-series gene expression data

Background

The primary goal of pathway analysis using transcriptome data is to find significantly perturbed pathways. However, pathway analysis is not always successful in identifying pathways that are truly relevant to the context under study. A major reason for this difficulty is that a single gene is involved in multiple pathways. In the KEGG pathway database, there are 146 genes, each of which is involved in more than 20 pathways. Thus activation of even a single gene will result in activation of many pathways. This complex relationship often makes the pathway analysis very difficult. While we need much more powerful pathway analysis methods, a readily available alternative way is to incorporate the literature information.

Results

In this study, we propose a novel approach for prioritizing pathways by combining results from both pathway analysis tools and literature information. The basic idea is as follows. Whenever there are enough articles that provide evidence on which pathways are relevant to the context, we can be assured that the pathways are indeed related to the context, which is termed as relevance in this paper. However, if there are few or no articles reported, then we should rely on the results from the pathway analysis tools, which is termed as significance in this paper. We realized this concept as an algorithm by introducing Context Score and Impact Score and then combining the two into a single score. Our method ranked truly relevant pathways significantly higher than existing pathway analysis tools in experiments with two data sets.

Conclusions

Our novel framework was implemented as ContextTRAP by utilizing two existing tools, TRAP and BEST. ContextTRAP will be a useful tool for the pathway based analysis of gene expression data since the user can specify the context of the biological experiment in a set of keywords. The web version of ContextTRAP is available at http://biohealth.snu.ac.kr/software/contextTRAP.

Electronic supplementary material

The online version of this article (doi:10.1186/s12859-016-1335-8) contains supplementary material, which is available to authorized users.

Pollen/TLR4 Innate Immunity Signaling Initiates IL-33/ST2/Th2 Pathways in Allergic Inflammation

Innate immunity has been extended to respond environmental pathogen other than microbial components. Here we explore a novel pollen/TLR4 innate immunity in allergic inflammation. In experimental allergic conjunctivitis induced by short ragweed (SRW) pollen, typical allergic signs, stimulated IL-33/ST2 signaling and overproduced Th2 cytokine were observed in ocular surface, cervical lymph nodes and isolated CD4⁺ T cells of BALB/c mice. These clinical, cellular and molecular changes were significantly reduced/eliminated in TLR4 deficient (Tlr4-d) or MyD88 knockout (MyD88^−/−) mice. Aqueous SRW extract (SRWe) directly stimulated IL-33 mRNA and protein expression by corneal epithelium and conjunctiva in wild type, but not in Tlr4-d or MyD88^−/− mice with topical challenge. Furthermore, SRWe-stimulated IL-33 production was blocked by TLR4 antibody and NF-kB inhibitor in mouse and human corneal epithelial cells. These findings for the first time uncovered a novel mechanism by which SRW pollen initiates TLR4-dependent IL-33/ST2 signaling that triggers Th2-dominant allergic inflammation.

Changes of Ocular Surface and the Inflammatory Response in a Rabbit Model of Short-Term Exposure Keratopathy

Purpose

To evaluate the ocular surface change and the inflammatory response in a rabbit model of short-term exposure keratopathy.

Methods

Short term exposure keratopathy by continuous eyelid opening was induced in New Zealand white rabbits for up to 4 hours. Ultrasound pachymetry was used to detect central total corneal thickness. In vivo confocal microscopy and impression cytology were performed to evaluate the morphology of ocular surface epithelium and the infiltration of inflammatory cells. Immunohistochemistry for macrophage,neutrophil, CD4(+) T cells, and CD8(+) T cells were performed to classify the inflammatory cells. Scanning electron microscopy(SEM) was performed to detect ocular surface change.The concentrations of IL-8, IL-17, Line and TNF-αwere analyzed by multiplex immunobead assay. TUNEL staining was performed to detect cellular apoptosis.

Results

Significant decrease ofcentral total cornealthickness were found within the first 5 minutes and remained stable thereafter, while there were no changes of corneal epithelial thickness.No significant change of corneal, limbal and conjunctival epithelial morphology was found by in vivo confocal microscopy except the time dependent increase of superficial cellular defects in the central cornea. Impression cytology also demonstrated time dependent increase of sloughing superficial cells of the central cornea. Aggregations ofinflammatory cells were found at 1 hour in the limbal epithelium, 2 hours in the perilimbal conjunctival epithelium, and 3 hours in the peripheral corneal epithelium.In eyes receiving exposure for 4 hours, the infiltration of the inflammatory cells can still be detected at 8 hours after closing eyes.Immunohistochemical study demonstrated the cells to be macrophages, neutrophils, CD4-T cells and CD-8 T cells.SEM demonstrated time-depending increase of intercellular border and sloughing of superficial epithelial cells in corneal surface. Time dependent increase of IL-8, IL-17 and TNF-α in tear was found.TUNEL staining revealed some apoptotic cells in the corneal epithelium and superficial stroma at 3 hours after exposure.

Conclusions

Short term exposure keratopathy can cause significant changes to the ocular surface and inflammatory response. Decrease of central total corneal thickness, aggregation of inflammatory cells, and cornea epithelial cell and superficial keratocyte apoptosis were found no less than 4 hours following the insult.

The core mechanism of dry eye disease is inflammation

PURPOSE

The purpose of this article is to review the evidence for the hypothesis that the core mechanism of dry eye disease (DED) is inflammation, including evidence from recent basic, clinical, and translational research involving human patients, animal models, and cell cultures.

METHODS

Using the key words "dry eye + inflammation," the authors conducted a comprehensive search of the PubMed and Web of Science databases for scientific articles published in English between January 1, 1900 and August 30, 2013 on the role of inflammation in DED in cell cultures, animal models, and humans. The resulting articles were then categorized and reviewed.

RESULTS

The literature search revealed a total of 458 publications, almost all published after 1992. The percentages of original studies and review articles are 77.29% (354) and 22.71% (104), respectively. Among the original studies, the number of reports on human DED is 200 (43.7%), on animal models is 115 (25.1%), and cell cultures is 39 (8.5%). A yearly distributing plot revealed that 76% were published from 2003 to 2011, 53% from 2008 to 2012, and 11% during the first 9 months of 2013. This distribution signifies a rapidly growing awareness of the importance of inflammation in DED pathogenesis.

CONCLUSIONS

Inflammation plays a key role in the pathogenesis of DED as evidenced by research using tissue culture, animal models, and subjects with DED. Developing biomarkers for inflammation of the ocular surface will provide improved understanding of the mechanisms leading to DED, classification of the severity of DED, and objective metrics for outcome measures of treatment. The chronicity of the disease suggests that dysregulation of immune mechanisms leads to a cycle of continued inflammation, accompanied by alterations in both innate and adaptive immune responses. Given the underlying mechanism for DED, developing effective and safe anti-inflammatory treatments is likely to be beneficial for patients with DED.

Reactive oxygen species activated NLRP3 inflammasomes prime environment-induced murine dry eye

Tear film hyperosmolarity along with exposure to oxidant stress are factors that can induce chronic ocular surface inflammation and pain. However, there is limited information on how increases in reactive oxygen species (ROS) generated by oxidant exposure can induce inflammation. There is emerging evidence in other tissues that innate immune responses to a variety of environmental stresses stem from ROS-induced cytosolic NLRP3 inflammasome activation. Once this occurs, pro-caspase-1 is converted into its catalytic active form, which in turn cleaves pro-IL-1β thereby generating its bioactive form. We determined the role of ROS generation in mediating increases in IL-1β secretion through caspase-1 activation caused by NLRP3 inflammasome activation in an environment-induced murine dry eye (DE) model. An intelligently controlled environmental system (ICES) induced evaporative DE in female 4-6 week old C57BL/6J mice. Increases in ROS production preceded rises in corneal and conjunctival gene expression of NLRP3 inflammasome components and IL-1β that were identified using real-time PCR. Confocal microscopy evaluated concomitant increases in NLPR3, caspase-1 and IL-1β immunostaining. Increases in caspase-1 activity were used as an indicator of inflammasome activation. Rises in ROS generation occurred after 1 week of ICES exposure, which preceded increases in gene expression of three NLRP3 inflammasome components (i.e. NLRP3, ASC and caspase-1) leading to rises in bioactive IL-1β release. Increases in caspase-1 activity occurred after 2 weeks of ICES exposure. Eyedrops containing 0.3% N-acetyl-l-cysteine (NAC) were applied to quench ROS generation by mice kept in the ICES for 2 weeks. This scavenger reduced corneal fluorescein staining and decreased ROS production. NAC also down-regulated both increases in NLRP3, ASC, caspase-1 and IL-1β mRNA levels, along with their immunostaining. It robustly attenuated rises in inflammasome mediated increases in caspase-1 catalytic activity. We show in a dessicating DE disease murine model that rises in ROS generation trigger NLRP3 inflammasome complexation and activation leading to increases in bioactive IL-1β secretion. These results prompt us to suggest that the ROS-NLRP3-IL-1β signaling pathway might play a priming role in environment-induced DE progression. Finally, our findings provide a basis for developing novel strategies that may improve the management of patients requiring treatment for environment-induced dry eye disease.

T helper cytokines in dry eye disease

Dry eye is an inflammatory disease that results from activation of innate inflammatory pathways in resident ocular surface cells, as well as cytokines produced by recruited T helper (Th) cells. Cytokines produced by the infiltrating Th cells alter the normal cytokine balance on the ocular surface and cause ocular surface epithelial pathology. Changes in levels of Th cytokines on the ocular surface have been measured in dry eye and the biological effects of these cytokines have been documented in experimental culture and mouse model systems. The Th2 cytokine IL-13 has a homeostatic role in promoting goblet cell differentiation. In contrast, The Th1 cytokine IFN-γ antagonizes IL-13 and promotes apoptosis and squamous metaplasia of the ocular surface epithelia. The Th17 cytokine, IL-17 promotes corneal epithelial barrier disruption. The ocular surface epithelium expresses receptors to all of these Th cytokines. Therapies that maintain normal IL-13 signaling, or suppress IFN-γ and IL-17 have potential for treating the ocular surface disease of dry eye.

Chemokine receptors CCR6 and CXCR3 are necessary for CD4(+) T cell mediated ocular surface disease in experimental dry eye disease

CD4(+) T cells are essential to pathogenesis of ocular surface disease in dry eye. Two subtypes of CD4(+) T cells, Th1 and Th17 cells, function concurrently in dry eye to mediate disease. This occurs in spite of the cross-regulation of IFN-γ and IL-17A, the prototypical cytokines Th1 and Th17 cells, respectively. Essential to an effective immune response are chemokines that direct and summon lymphocytes to specific tissues. T cell trafficking has been extensively studied in other models, but this is the first study to examine the role of chemokine receptors in ocular immune responses. Here, we demonstrate that the chemokine receptors, CCR6 and CXCR3, which are expressed on Th17 and Th1 cells, respectively, are required for the pathogenesis of dry eye disease, as CCR6KO and CXCR3KO mice do not develop disease under desiccating stress. CD4(+) T cells from CCR6KO and CXCR3KO mice exposed to desiccating stress (DS) do not migrate to the ocular surface, but remain in the superficial cervical lymph nodes. In agreement with this, CD4(+) T cells from CCR6 and CXCR3 deficient donors exposed to DS, when adoptively transferred to T cell deficient recipients manifest minimal signs of dry eye disease, including significantly less T cell infiltration, goblet cell loss, and expression of inflammatory cytokine and matrix metalloproteinase expression compared to wild-type donors. These findings highlight the important interaction of chemokine receptors on T cells and chemokine ligand expression on epithelial cells of the cornea and conjunctiva in dry eye pathogenesis and reveal potential new therapeutic targets for dry eye disease.

Analysis of tear cytokines and clinical correlations in Sjögren syndrome dry eye patients and non-Sjögren syndrome dry eye patients

PURPOSE

To compare concentrations of tear cytokines in 3 groups composed of Sjögren syndrome (SS) dry eye, non-Sjögren syndrome (non-SS) dry eye, and normal subjects. Correlations between ocular surface parameters and tear cytokines were also investigated.

DESIGN

Prospective cross-sectional study.

METHODS

SS dry eye patients (n = 24; 40 eyes) were diagnosed with primary SS according to the criteria set by the American-European Consensus Group. Non-SS dry eye patients (n = 25; 40 eyes) and normal subjects (n = 21; 35 eyes) were also enrolled. Tear concentrations of interleukin (IL)-17, IL-6, IL-10, IL-4, IL-2, interferon γ (IFN-γ), and tumor necrosis factor α (TNF-α) were measured by a multiplex immunobead assay. Ocular Surface Disease Index (OSDI), tear film breakup time (TBUT), Schirmer I test, and fluorescein staining scores were obtained from dry eye patients.

RESULTS

All cytokine levels except for IL-2 were highest in the SS group, followed by non-SS dry eye group and control subjects. Concentrations of IL-17, TNF-α, and IL-6 were significantly different among the 3 groups (IL-17: SS > control P < .001, non-SS > control P = .042, SS > non-SS P < .001; TNF-α: SS > control P = .006, non-SS > control P = .034, SS > non-SS P = .029; IL-6: SS > control P = .002, non-SS > control P = .032, SS > non-SS P = .002). IL-17 was significantly correlated with TBUT (R = -0.22, P = .012) and Schirmer I test (R = -0.36, P = .027) scores in the SS group. IL-6 was significantly correlated only with TBUT (R = -0.38, P = .02) in the non-SS group.

CONCLUSIONS

Differences in tear cytokine levels and correlation patterns between SS dry eye and non-SS dry eye patients suggest the involvement of different inflammatory processes as causes of dry eye syndrome.

Pivotal roles of T-helper 17-related cytokines, IL-17, IL-22, and IL-23, in inflammatory diseases

T-helper 17 (Th17) cells are characterized by producing interleukin-17 (IL-17, also called IL-17A), IL-17F, IL-21, and IL-22 and potentially TNF- α and IL-6 upon certain stimulation. IL-23, which promotes Th17 cell development, as well as IL-17 and IL-22 produced by the Th17 cells plays essential roles in various inflammatory diseases, such as experimental autoimmune encephalomyelitis, rheumatoid arthritis, colitis, and Concanavalin A-induced hepatitis. In this review, we summarize the characteristics of the functional role of Th17 cells, with particular focus on the Th17 cell-related cytokines such as IL-17, IL-22, and IL-23, in mouse models and human inflammatory diseases.

Dry eye as a mucosal autoimmune disease

Dry eye is a common ocular surface inflammatory disease that significantly affects quality of life. Dysfunction of the lacrimal function unit (LFU) alters tear composition and breaks ocular surface homeostasis, facilitating chronic inflammation and tissue damage. Accordingly, the most effective treatments to date are geared towards reducing inflammation and restoring normal tear film. The pathogenic role of CD4+ T cells is well known, and the field is rapidly realizing the complexity of other innate and adaptive immune factors involved in the development and progression of disease. The data support the hypothesis that dry eye is a localized autoimmune disease originating from an imbalance in the protective immunoregulatory and proinflammatory pathways of the ocular surface.

Galectin-1-mediated suppression of Pseudomonas aeruginosa-induced corneal immunopathology

Corneal infection with Pseudomonas aeruginosa leads to a severe immunoinflammatory lesion, often causing vision impairment and blindness. Although past studies have indicated a critical role for CD4(+) T cells, particularly Th1 cells, in corneal immunopathology, the relative contribution of recently discovered Th17 and regulatory T cells is undefined. In this study, we demonstrate that after corneal P. aeruginosa infection, both Th1 and Th17 cells infiltrate the cornea with increased representation of Th17 cells. In addition to Th1 and Th17 cells, regulatory T cells also migrate into the cornea during early as well as late stages of corneal pathology. Moreover, using galectin-1 (Gal-1), an immunomodulatory carbohydrate-binding molecule, we investigated whether shifting the balance among various CD4(+) T cell subsets can modulate P. aeruginosa-induced corneal immunopathology. We demonstrate in this study that local recombinant Gal-1 (rGal-1) treatment by subconjunctival injections significantly diminishes P. aeruginosa-mediated corneal inflammation through multiple mechanisms. Specifically, in our study, rGal-1 treatment significantly diminished corneal infiltration of total CD45(+) T cells, neutrophils, and CD4(+) T cells. Furthermore, rGal-1 treatment significantly reduced proinflammatory Th17 cell response in the cornea as well as local draining lymph nodes. Also, rGal-1 therapy promoted anti-inflammatory Th2 and IL-10 response in secondary lymphoid organs. Collectively, our results indicate that corneal P. aeruginosa infection induces a strong Th17-mediated corneal pathology, and treatment with endogenously derived protein such as Gal-1 may be of therapeutic value for the management of bacterial keratitis, a prevalent cause of vision loss and blindness in humans worldwide.

Association of a NOD2 gene polymorphism and T-helper 17 cells with presumed ocular toxoplasmosis

Retinochoroiditis manifests in patients infected with Toxoplasma gondii. Here, we assessed 30 sibships and 89 parent/case trios of presumed ocular toxoplasmosis (POT) to evaluate associations with polymorphisms in the NOD2 gene. Three haplotype-tagging single-nucleotide polymorphisms (tag-SNPs) within the NOD2 gene were genotyped. The family-based association test showed that the tag-SNP rs3135499 is associated with retinochoroiditis (P = .039). We then characterized the cellular immune response of 59 cases of POT and 4 cases of active ocular toxoplasmosis (AOT). We found no differences in levels of interferon γ (IFN-γ) and interleukin 2 produced by T-helper 1 cells when comparing patients with AOT or POT to asymptomatic individuals. Unexpectedly, we found an increased interleukin 17A (IL-17A) production in patients with POT or OAT. In patients with POT or AOT, the main cellular source of IL-17A was CD4(+)CD45RO(+)T-bet(-)IFN-γ(-) T-helper 17 cells. Altogether, our results suggest that NOD2 influences the production of IL-17A by CD4(+) T lymphocytes and might contribute to the development of ocular toxoplasmosis.

Evaluation of dry eye

Dry eye is a common yet complex condition. Intrinsic and extrinsic factors can cause dysfunction of the lids, lacrimal glands, meibomian glands, ocular surface cells, or neural network. These problems would ultimately be expressed at the tear film-ocular surface interface. The manifestations of these problems are experienced as symptoms such as grittiness, discomfort, burning sensation, hyperemia, and secondary epiphora in some cases. Accurate investigation of dry eye is crucial to correct management of the condition. Techniques can be classed according to their investigation of tear production, tear stability, and surface damage (including histological tests). The application, validity, reliability, compatibility, protocols, and indications for these are important. The use of a diagnostic algorithm may lead to more accurate diagnosis and management. The lack of correlation between signs and symptoms seems to favor tear film osmolarity, an objective biomarker, as the best current clue to correct diagnosis.

Strain-dependent production of interleukin-17/interferon-γ and matrix remodeling-associated genes in experimental Candida albicans keratitis

PURPOSE

The aim of this study was to investigate the role of genetic background in determining the development or prognosis of experimental fungal keratitis by comparing the disease courses and related molecules of experimental Candida albicans in two common mouse strains.

METHODS

After intrastromal inoculation of 1 × 10(5)C. albicans blastospores into corneas of Balb/c and C57BL/6 mice, all mice developed typical keratitis. The disease was monitored using a slit lamp microscope and scored for comparison of symptoms. At desired time points, blood was collected and corneal homogenates were prepared for enzyme-linked immunosorbent assay measurement of interferon (IFN)γ or interleukin (IL)17. Other corneas were processed for histological evaluation, pathogen load measurement, or total RNA extraction, the last of which was subjected to reverse transcription in conjunction with real-time PCR to measure genes of interest in terms of collagens, matrix metalloproteinases (MMPs), and the tissue inhibitors of MMPs (TIMPs).

RESULTS

The infected corneas from the two strains presented different manifestations. Corneal transparency was less affected in Balb/c mice than in C57BL/6 mice, and Balb/c corneas contained fewer pathogens than C57BL/6 corneas during the measured period (10 days). In both strains, keratitis started to resolve around days 7-10, but C57BL/6 mice healed slower than Balb/c mice as indicated by disease presentation, histology, and pathogen burden assay. By day 7 post infection, pseudohyphae were rare but cellular infiltration remained intensive in both strains. The surface of the Balb/c corneas remained relatively intact and smooth, and C57BL/6 corneal lesions produced open erosion areas. Perforation was never seen in the current study setting. In both sera and corneas, IL17 expression increased earlier than IFNγ, and C57BL/6 mice produced higher IL17 levels and lower IFNγ levels than Balb/c mice. Compared with C57BL/6 mice, Balb/c corneas produced more MMP-2, Col3a1, and Col4a1, and less or equivalent TIMP-2 at all detected time points. They also produced more MMP-13, less MMP-8, MMP-9, and TIMP-1 at day 3 post infection, but less MMP-13, basically equivalent MMP-8, and more MMP-9 at later time points.

CONCLUSIONS

The disease course of experimental C. albicans keratitis depends on the genetic background of the host animals. The balance between IL17 and IFNγ, as well as among the common injury- and wound healing-related proteins, may contribute to the pathogenesis of C. albicans keratitis. This study suggests that great variance of disease presentation should be expected for human subjects with Candida keratitis.

Autoantibodies contribute to the immunopathogenesis of experimental dry eye disease

PURPOSE

The purpose of this study was to determine if autoantibodies play a role in the immunopathogenesis of experimental dry eye disease.

METHODS

Dry eye was induced by exposing female C57BL/6 wild-type mice or hen egg lysozyme B-cell receptor transgenic mice to desiccating stress (subcutaneous scopolamine [0.5 mg/0.2 mL] 3 times a day, humidity < 40%, and sustained airflow) for 3 weeks, allowing sufficient time for a humoral immune response. Serum or purified IgG isolated from dry-eye mice or untreated controls was passively transferred to nude recipient mice, which were evaluated for ocular surface inflammation 3 days after transfer. To determine if complement activation contributed to serum-induced dry eye disease, cobra venom factor was used to deplete complement activity.

RESULTS

Autoantibodies against kallikrein 13 were identified in serum from dry-eye mice, but were undetectable in untreated controls. Autoantibody-containing serum or purified IgG from dry-eye mice was sufficient to mediate complement-dependent ocular surface inflammation. Serum or purified IgG caused marked inflammatory burden and tissue damage within the ocular surface tissues, including elevated Gr1+ neutrophil infiltration and proinflammatory cytokines/chemokines associated with goblet cell loss. Moreover, complement C3b deposition was found within the ocular surface tissues of mice receiving dry-eye serum, but not in recipients of control serum. Functionally, complement depletion attenuated the ability to transfer dry-eye-specific serum or IgG-mediated disease.

CONCLUSIONS

These data demonstrate for the first time a complement-dependent pathogenic role of dry-eye-specific autoantibodies, and suggest autoantibody deposition within the ocular surface tissues contributes to the predominantly T-cell-mediated immunopathogenesis of dry eye disease.

Phage display against corneal epithelial cells produced bioactive peptides that inhibit Aspergillus adhesion to the corneas

Dissection of host-pathogen interactions is important for both understanding the pathogenesis of infectious diseases and developing therapeutics for the infectious diseases like various infectious keratitis. To enhance the knowledge about pathogenesis infectious keratitis, a random 12-mer peptide phage display library was screened against cultured human corneal epithelial cells (HCEC). Fourteen sequences were obtained and BLASTp analysis showed that most of their homologue counterparts in GenBank were for defined or putative proteins in various pathogens. Based on known or predicted functions of the homologue proteins, ten synthetic peptides (Pc-A to Pc-J) were measured for their affinity to bind cells and their potential efficacy to interfere with pathogen adhesion to the cells. Besides binding to HCEC, most of them also bound to human corneal stromal cells and umbilical endothelial cells to different extents. When added to HCEC culture, the peptides induced expression of MyD88 and IL-17 in HCEC, and the stimulated cell culture medium showed fungicidal potency to various extents. While peptides Pc-C and Pc-E inhibited Aspergillus fumigatus (A.f) adhesion to HCEC in a dose-dependent manner, the similar inhibition ability of peptides Pc-A and Pc-B required presence of their homologue ligand Alb1p on A.f. When utilized in an eyeball organ culture model and an in vivo A.f keratitis model established in mouse, Pc-C and Pc-E inhibited fungal adhesion to corneas, hence decreased corneal disruption caused by inflammatory infiltration. Affinity pull-down of HCEC membrane proteins with peptide Pc-C revealed several molecules as potential receptors for this peptide. In conclusion, besides proving that phage display-selected peptides could be utilized to interfere with adhesion of pathogens to host cells, hence could be exploited for managing infectious diseases including infectious keratitis, we also proposed that the phage display technique and the resultant peptides could be used to explore host-pathogen interactions at molecular levels.

MUC1/A and MUC1/B splice variants differentially regulate inflammatory cytokine expression

The frequency of a splice variant of mucin 1 (MUC1), MUC1/A was lower in dry eye disease patients compared to normal controls, suggesting a link between the absence of MUC1/A and the development of dry eye disease which is characterized by chronic inflammation. The objectives of the present study were to clone and characterize the phenotype of cells expressing solely MUC1/A versus MUC1/B or a variant lacking the extracellular domain (ΔEX) and to determine whether MUC1/A and MUC1/B differentially modulate inflammatory responses in transfected cells. The additional 27 bp and SNP present in the N-terminus of MUC1/A were cloned into a FLAG-MUC1/B expression vector. Transient transfection of MUC1/A and MUC1/B plasmids into MUC1-null COS-7 cells resulted in similar protein expression and plasma membrane localization. MUC1/B and MUC1/A differed in their ability to modulate tumor necrosis α (TNFα)-induced transcription of IL-1β and IL-8. MUC1/B and MUC1/A inhibited IL-8 induction by TNFα at 4 h. However with 24 h TNFα, MUC1/A increased IL-1β and IL-8 whereas MUC1/B had no effect on cytokine expression. MUC1/B inhibited TNFα-induced luciferase activity from an NF-κB reporter whereas MUC1/A either inhibited or increased this luciferase activity depending on the time of TNFα treatment. MUC1/A, but not MUC1/B, increased the basal TGFβ expression. Both MUC1/B and MUC1/A blocked TNFα-induced miR-21 expression. These data demonstrate that MUC1/A and MUC1/B have different inflammatory activities and support the hypothesis that MUC1 genotypic differences may affect susceptibility to ocular surface damage in dry eye disease.

sPLA2-IIa amplifies ocular surface inflammation in the experimental dry eye (DE) BALB/c mouse model

PURPOSE

sPLA2-IIa is a biomarker for many inflammatory diseases in humans and is found at high levels in human tears. However, its role in ocular surface inflammation remains unclear. An experimentally induced BALB/c mouse dry eye (DE) model was used to elucidate the role of sPLA2-IIa in ocular surface inflammation.

METHODS

BALB/c mice were subcutaneously injected with scopolamine and placed in a daytime air-drying device for 5 to 10 days. Control mice received no treatment. DE status was evaluated with tear production with a phenol-red thread method. Tear inflammatory cytokines were quantified by multiplex immunoassays. Ocular surface inflammation and sPLA2-IIa expression were examined by immune-staining and quantitative (q)RT(2)-PCR. Conjunctiva (CNJ) of the mice was cultured for prostaglandin E2 production induced by sPLA2-IIa with various amount of sPLA2-IIa inhibitor, S-3319.

RESULTS

Treated mice produced fewer tears and heavier corneal (CN) fluorescein staining than the untreated controls (P < 0.001). They also revealed lower goblet cell density (P < 0.001) with greater inflammatory cell infiltration within the conjunctiva, and higher concentration of tear inflammatory cytokines than the controls. Moreover, treated mice showed heavier sPLA2-IIa immune staining than the controls in the CNJ epithelium, but not in the CN epithelium or the lacrimal gland. Treated mice exhibited upregulated sPLA2-IIa and cytokine gene transcription. Furthermore, CNJ cultures treated with sPLA2-IIa inhibitor showed significantly reduced sPLA2-IIa-induced inflammation.

CONCLUSIONS

This is the first report regarding sPLA2-IIa in the regulation of ocular surface inflammation. The findings may therefore lead to new therapeutic strategies for ocular surface inflammation, such as DE disease.

Interleukin-17 in various ocular surface inflammatory diseases

Recently, the association of Th-17 cells or IL-17 with ocular inflammatory diseases such as uveitis, scleritis and dry eye syndrome was discovered. We assessed whether interleukin (IL)-17 was present in the tears of various ocular surface inflammatory diseases and the tear IL-17 concentrations were clinically correlated with various ocular surface inflammatory diseases. We measured concentrations of IL-17 in tears of normal subjects (n = 28) and patients (n = 141) with meibomian gland dysfunction (MGD), dry eye syndrome (DES), Sjögren syndrome (SS), Stevens-Johnson syndrome (SJS), graft-versus-host disease (GVHD), filamentary keratitis, and autoimmune keratitis associated with rheumatoid arthritis or systemic lupus erythematosus. Clinical epitheliopathy scores were based on the surface area of corneal and conjunctival fluorescein staining. The mean concentrations of IL-17 in tears of patients with filamentary keratitis, GVHD, autoimmune keratitis, SS, DES, MGD, SJS were significantly higher in order than that in normal subjects. Tear IL-17 concentration was significantly correlated with clinical epitheilopathy scores in the patients with systemic inflammatory disease, while tear IL-17 was not correlated with clinical severity of the cornea and conjunctiva in the dry eye patients without any systemic inflammatory disease. Tear IL-17 is likely to correlate clinically with corneal disease severity only in the patients with systemic inflammatory disease.

An immunoprotective privilege of corneal epithelial stem cells against Th17 inflammatory stress by producing glial cell-derived neurotrophic factor

Adult stem cells are well known for their self-renewal and regenerative capacity. The mechanisms protecting these cells from inflammatory damage have not been well elucidated. This study investigated the immunoprotective properties of corneal epithelial stem cells from inflammation by producing glial cell-derived neurotrophic factor (GDNF). Primary human limbal epithelial cells (HLECs) cultured from limbal explants were treated with interleukin (IL)-17A, tumor necrosis factor (TNF)-α, or hyperosmotic media, with or without GDNF or nuclear factor kappa B (NF-κB) inhibitor (NF-κB-I) for 4-48 hours. Inflammatory mediators and Th17-inducing cytokines were determined by real-time polymerase chain reaction, enzyme-linked immunosorbent assay, and immunobead assays. NF-κB activation was detected by p65 phosphorylation, immunostaining and Western blotting. GDNF and its receptor, GDNF family receptor α-1, were exclusively immunolocalized in the basal layer of limbal epithelium, whereas IL-17 receptor was negative in these cells. Exogenous IL-17A stimulated the expression and production of inflammatory cytokines (TNF-α, IL-6, and IL-1β) and chemokine IL-8 by HLECs. Th17-inducing cytokines, transforming growth factor (TGF)-β1, IL-6, IL-23, and IL-1β, were significantly increased at mRNA and protein levels by HLECs exposed to TNF-α or hyperosmotic media. IL-17 activated NF-κB by p65 phosphorylation at serine 536 and nuclear translocation. GDNF or NF-κB-I blocked IL-17-induced NF-κB p65 activation and production of inflammatory mediators. Furthermore, GDNF suppressed the production of Th17-inducing cytokines through inhibiting NF-κB activation. These findings demonstrate that limbal progenitor cell-produced neurotrophic factor GDNF suppresses IL-17-mediated inflammation via NF-κB signaling pathway. This may represent a unique immunoprotective property of limbal stem cells against inflammatory challenges on the ocular surface.

Autoimmunity at the ocular surface: pathogenesis and regulation

A healthy ocular surface environment is essential to preserve visual function, and as such the eye has evolved a complex network of mechanisms to maintain homeostasis. Fundamental to the health of the ocular surface is the immune system, designed to respond rapidly to environmental and microbial insults, whereas maintaining tolerance to self-antigens and commensal microbes. To this end, activation of the innate and adaptive immune response is tightly regulated to limit bystander tissue damage. However, aberrant activation of the immune system can result in autoimmunity to self-antigens localized to the ocular surface and associated tissues. Environmental, microbial and endogenous stress, antigen localization, and genetic factors provide the triggers underlying the immunological events that shape the outcome of the diverse spectrum of autoimmune-based ocular surface disorders.