Impact of inflammasomes on the ocular surface.

PURPOSE OF REVIEW: The ocular surface is prone to inflammation due to exposure to environmental irritants and pathogens. Inflammasomes are intracellular, multiprotein complexes that communicate potentially dangerous signals to the immune system. The identification of inflammasomes in various inflammatory ocular surface conditions can aid in the development of therapeutics to treat these chronic inflammatory conditions. RECENT FINDINGS: Several inflammasomes have been associated with ocular surface disorders including dry eye disease, keratitis, and allergies. Mechanisms for activation of these inflammasomes with regards to specific disorders have been explored in models to aid in the development of targeted treatments. SUMMARY: Research efforts continue to characterize the types of inflammasomes and activators of these in inflammatory ocular surface conditions. Various therapies targeting specific inflammasome types or pyroptosis are being tested preclinically to assess effects on decreasing the associated chronic inflammation.

Role of CCL7 in Type I Hypersensitivity Reactions in Murine Experimental Allergic Conjunctivitis.

Molecules that are necessary for ocular hypersensitivity reactions include the receptors CCR1 and CCR3; CCL7 is a ligand for these receptors. Therefore, we explored the role of CCL7 in mast cell activity and motility in vitro and investigated the requirement for CCL7 in a murine model of IgE-mediated allergic conjunctivitis. For mast cells treated with IgE and Ag, the presence of CCL7 synergistically enhanced degranulation and calcium influx. CCL7 also induced chemotaxis in mast cells. CCL7-deficient bone marrow-derived mast cells showed decreased degranulation following IgE and Ag treatment compared with wild-type bone marrow-derived mast cells, but there was no difference in degranulation when cells were activated via an IgE-independent pathway. In vivo, CCL7 was upregulated in conjunctival tissue during an OVA-induced allergic response. Notably, the early-phase clinical symptoms in the conjunctiva after OVA challenge were significantly higher in OVA-sensitized wild-type mice than in control challenged wild-type mice; the increase was suppressed in CCL7-deficient mice. In the OVA-induced allergic response, the numbers of conjunctival mast cells were lower in CCL7-deficient mice than in wild-type mice. Our results demonstrate that CCL7 is required for maximal OVA-induced ocular anaphylaxis, mast cell recruitment in vivo, and maximal FcεRI-mediated mast cell activation in vitro. A better understanding of the role of CCL7 in mediating ocular hypersensitivity reactions will provide insights into mast cell function and novel treatments for allergic ocular diseases.

Serum inflammatory markers after rupture retinal laser injury in mice.

BACKGROUND AND OBJECTIVE: To characterize the cellular, immunological, and inflammatory response to retinal photocoagulation of intense rupture laser lesions as a model of retinal degenerative diseases. MATERIALS AND METHODS: Seven C57BL/6 mice were irradiated using a 532-nm laser to induce 10 retinal burns per eye that ruptured Bruch's membrane. Blood was drawn from the saphenous vein before and 2 months after laser treatment. The serum was run on antigen microarrays with 85 molecular markers associated with retinal degenerative diseases. RESULTS: Rupture laser resulted in dramatic changes in the immunoglobulin reactivity of most inflammatory markers 2 months after laser injury. Approximately two-thirds increased expression and one-third decreased expression. Notable markers that were increased included complement C3, CRP, PKM2, and aldolase. CONCLUSION: Rupture laser injury causes a change in the serum inflammatory markers after 2 months similar to macular degeneration, diabetic retinopathy, and cancer-associated retinopathy. This animal model could be used as a biomarker for disease stage and activity in retinal degenerations.

New twists to an old story: novel concepts in the pathogenesis of allergic eye disease.

The prevalence of allergy is rising globally at a very significant rate, which is currently at 20-40% of individuals in westernized nations. In the eye, allergic conditions can take on the acute form such as in seasonal and perennial allergic conjunctivitis, or a more severe and debilitating chronic form such as in vernal and atopic keratoconjunctivitis. Indeed, some key aspects of allergic eye disease pathophysiology are understood, such as the role of mast cells in the acute allergic reaction, and the contribution of eosinophils in late-onset and chronic allergy. However, recent developments in animal models and clinical studies have uncovered new and important roles for previously underappreciated players, including chemokine receptors on ocular surface dendritic cells such as CCR7, the contribution of conjunctival epithelium to immunity, histamine and leukotriene receptors on conjunctival goblet cells and a role for mast cells in late-onset manifestations. Furthermore, recent work in animal models has delineated the contribution of IL-4 in the increased incidence of corneal graft rejection in hosts with allergic conjunctivitis. Recent studies such as these mean that conventional paradigms and concepts should be revisited. The aim of this review is to highlight some of the most recent advances and insights on newly appreciated players in the pathogenesis of allergic eye disease.

The role of TRB3 in mast cells sensitized with monomeric IgE.

Mast cells play a key role in immunoglobulin E (IgE)-associated allergic disorders; however, the cellular effects of sensitization remain poorly understood. Using gene microarrays and the multiplexing ELISA method, we examined the effects of sensitization on RBL-CCR1 cell transcription and chemokine/cytokine secretion. Sensitization most prominently increased transcription of Trb3, the gene for tribbles homolog 3 (TRB3), and also increased the release of most of the cytokines and chemokines tested. Knockdown of TRB3 via RNAi significantly induced the production of tumor necrosis factor-α (TNF-α), interleukin-4 (IL-4), interleukin-6 (IL-6), and the chemokine mast cell protease-1 (MCP-1). TRB3 deficiency also induced IκBα phosphorylation. TRB3 may therefore serve as a negative regulator of pro-inflammatory cytokines and chemokines, controlling the extent of the inflammatory response.

The murine CCR3 receptor regulates both eosinophilia and hyperresponsiveness in IgE-mediated allergic conjunctivitis.

BACKGROUND/AIMS: Allergic conjunctivitis is characterised by early-phase clinical symptoms and late-phase inflammation in the conjunctiva. The role of different chemokine receptors in allergic conjunctivitis, especially during the early-phase reaction, is still unclear. We investigated the importance of CC chemokine receptor (CCR) 3 in a murine model of IgE-mediated allergic conjunctivitis using CCR3-deficient (CCR3(-/-)) mice. METHODS: Allergic conjunctivitis was initiated in wild-type (WT) and CCR3(-/-) mice by passive transfer of ragweed (RW)-specific IgE, followed by topical challenge with RW in eye drops. Early-phase reactions including clinical symptoms and vascular leakage, as well as late-phase eosinophil infiltration of the conjunctiva were evaluated. The expression of mRNAs in the conjunctiva was quantified by real-time PCR analysis. RESULTS: The number of infiltrated eosinophils in the conjunctiva following RW challenge, was significantly higher in RW-IgE-sensitised WT mice compared with those sensitised with phosphate-buffered saline for WT, but this was not observed in similarly treated CCR3(-/-) mice. The early-phase clinical symptoms and vascular leakage were also suppressed in CCR3(-/-) mice. The number of conjunctival mast cells were not different between CCR3(-/-) mice and WT mice, and the mRNAs for FcεRІα and the connective tissue-type mast cell proteases were detected in the conjunctiva of both WT and CCR3(-/-) mice. RW-IgE-sensitised CCR3(-/-) mice displayed significantly reduced expression of CCL2, CCL3, and IL-6 compared with WT mice. CONCLUSIONS: These results demonstrate a direct contribution of CCR3 to both the early-phase reaction and late-phase inflammation during ocular allergy.

Evidence that formation of vimentin mitogen-activated protein kinase (MAPK) complex mediates mast cell activation following FcεRI/CC chemokine receptor 1 cross-talk.

Accumulating evidence points to cross-talk between FcεRI and CC chemokine receptor (CCR)-mediated signaling pathways in mast cells. Here, we propose that vimentin, a protein comprising type III intermediate filament, participates in such cross-talk for CCL2/monocyte chemotactic protein 1 (MCP-1) production in mast cells, which is a mechanism for allergic inflammation. Co-stimulation via FcεRI, using IgE/antigen, and CCR1, using recombinant CCL3/macrophage inflammatory protein-1α (MIP-1α), increased expression of phosphorylated, disassembled, and soluble vimentin in rat basophilic leukemia (RBL)-2H3 cells expressing human CCR1 (RBL-CCR1 cells) and bone marrow-derived murine mast cells, both models of mucosal type mast cells. Furthermore, co-stimulation enhanced production of CCL2 as well as phosphorylation of MAPK. Treating the cells with p38 MAPK inhibitor SB203580, but not with MEK inhibitor PD98058, reduced CCL2 production, suggesting that p38 MAPK, but not ERK1/2, plays a critical role in the chemokine production. Immunoprecipitation analysis showed that vimentin interacts with phosphorylated ERK1/2 and p38 MAPKs in the co-simulated cells. Preventing disassembly of the vimentin by aggregating vimentin filaments using ß,ß'-iminodipropionitrile reduced the interaction of vimentin with phosphorylated MAPKs as well as CCL2 production in the cells. Taken together, disassembled vimentin interacting with phosphorylated p38 MAPK could mediate CCL2 production in mast cells upon FcεRI and CCR1 activation.

Role of periostin and interleukin-4 in recurrence of pterygia.

PURPOSE: To identify the candidate genes for pterygia recurrence from a pterygia transcriptome and to analyze their transcriptional regulation and functional relationships. METHODS: Transcriptional networks for pterygia recurrence were constructed using network analysis that was applied to 184 genes that showed a significant twofold change in the whole genome. Of the identified recurrence-related candidate genes in the major networks, periostin and IL-4 were analyzed for transcriptional relationships using pterygia-derived fibroblasts. Immunohistochemical analysis was used to study pterygia tissue. Effector candidate molecule for recurrence periostin was analyzed for cell adhesive function. RESULTS: The pterygia transcriptome was divided into four major biological networks with high significance scores (P < 10(-17)). The classifier with the highest accuracy using the support vector machine algorithm was periostin, which was successfully linked to the network of cell cycle, connective tissue development and function, and cell morphology. Analyses using pterygia-derived fibroblasts showed that periostin was required for cell adhesion that was mediated by a presumed pterygia-related extracellular matrix protein, fibronectin. Periostin was found to be transcriptionally induced by IL-4. The IL-4-stimulated periostin induction was suppressed by MAP kinase/ERK kinase 1 inhibitor, indicating an involvement of the MAP kinase pathway. Pathologically, IL-4 was transcriptionally elevated in recurrent pterygia tissue and was localized to perivascular tissues and endothelial cells in the stroma of the subconjunctiva of pterygia. CONCLUSIONS: Periostin is induced by IL-4 and is involved in the fibronectin-mediated pterygia fibroblast adhesion. These findings indicate that periostin probably promotes the recurrence of pterygia.

Ablation of type I hypersensitivity in experimental allergic conjunctivitis by eotaxin-1/CCR3 blockade.

The immune response is regulated, in part, by effector cells whose activation requires multiple signals. For example, T cells require signals emanating from the T cell antigen receptor and co-stimulatory molecules for full activation. Here, we present evidence indicating that IgE-mediated hypersensitivity reactions in vivo also require cognate signals to activate mast cells. Immediate hypersensitivity reactions in the conjunctiva are ablated in mice deficient in eotaxin-1, despite normal numbers of tissue mast cells and levels of IgE. To further define the co-stimulatory signals mediated by chemokine receptor 3 (CCR3), an eotaxin-1 receptor, effects of CCR3 blockade were tested with an allergic conjunctivitis model and in ex vivo isolated connective tissue-type mast cells. Our results show that CCR3 blockade significantly suppresses allergen-mediated hypersensitivity reactions as well as IgE-mediated mast cell degranulation. We propose that a co-stimulatory axis by CCR3, mainly stimulated by eotaxin-1, is pivotal in mast cell-mediated hypersensitivity reactions.

Regulatory function of CpG-activated B cells in late-phase experimental allergic conjunctivitis.

PURPOSE: To determine how CpG, an immunostimulatory sequence, affects experimental allergic conjunctivitis and to determine the mechanisms of its action. METHODS: Experimental allergic conjunctivitis was induced in mice to investigate the suppressive mechanism of CpG treatment. Cytokine profiling, fluorescence-activated cell sorting analyses, and adoptive transfer were used to analyze suppressive mechanisms after CpG treatment. RESULTS: Administration of the CpG oligonucleotide induced significant splenomegaly. Adoptive transfer of the splenocytes isolated from CpG-treated mice was able to confer resistance to allergen-induced inflammatory responses in recipient mice. CpG treatment led to a transient upregulation of IL-1ra, IL-18, IL-1alpha, and IL-12 in the spleen, draining lymph nodes, and conjunctiva. In contrast, IL-10 showed a marked and sustained induction in the inductive and effector tissues. Splenomegaly after CpG exposure was reduced in IL-10-deficient mice, indicating that IL-10 is required for immune remodeling of the spleen. Analyses of allergen-sensitized mice deficient in IL-10 exacerbated the late-phase inflammatory responses. Fluorescence-activated cell sorting analysis of the CpG-induced splenocyte subsets showed that the predominant source of IL-10 was B220(+) CD19(+) CD23(+)IgM(+)CD40(+)class II(high) follicular B cells. Adoptive transfer of IL-10-deficient B cells exacerbated eosinophilia. Transfer of an expanded population of cells after CpG treatment, including IL-10-secreting follicular B cells, protected against eosinophilia. CONCLUSIONS: CpG treatment provided B cell-mediated regulation of immune responses and B cell differentiation in CpG-induced immune remodeling with the use of IL-10.

Pathogenesis of herpetic stromal keratitis in CCR5- and/or CXCR3-deficient mice.

PURPOSE: Herpetic stromal keratitis (HSK) is an immunopathological reaction to herpes simplex virus type 1 (HSV-1) corneal infection. It has been reported that CD4+ cells play the most important role in the pathogenesis of this disease. In this study, we have focused on two chemokine receptors, CCR5 and CXCR3, which are expressed on CD4+ Th1 cells in mice HSK model. METHODS: CCR5-deficient (CCR5KO), CXCR3-deficient (CXCR3KO), CCR5/CXCR3 double-deficient (DKO), and wild type (WT) mice (C57/BL6 background) were infected intracorneally with HSV-1 (CHR3 strain). The corneas were examined biomicroscopically, and cryosections of the corneas were examined histologically and immunohistochemically. Real-time RT-PCR and RNase protection assay (RPA) were performed, and the virus titers were measured in excised eyes and trigeminal ganglia (TG). RESULTS: The HSK clinical severity in DKO mice was significantly lower than that in WT mice, and this was reversed by transfer of cells from the spleen of WT mice to DKO mice. Histologically, the numbers of T cells (CD4+ and CD8+ cells) and neutrophils infiltrating the cornea were significantly fewer in CCR5KO, CXCR3KO, and DKO mice. Transcript levels of immune-related cell surface marker in the eye by RPA were reduced in DKO mice. The expression of I-TAC was significantly increased in the cornea of CCR5KO mice, and MIP-1alpha and MIP-1beta were significantly lower in CXCR3KO mice than in WT mice by RT-PCR. There were no significant differences of virus titers in the eye and TG among any groups of mice except the increase in the TG of DKO mice on day 5 PI. CONCLUSIONS: The suppression of chemotaxis and activation of CD4+ Th1 cells by the lacking of CXCR3 and CCR5 causes a decrease of other infiltrating cells, resulting in a lower severity of HSK. These results suggest that targeting chemokine receptors is a promising way to treat HSK.

Conjunctival mast cell as a mediator of eosinophilic response in ocular allergy.

PURPOSE: To determine the contribution of conjunctival mast cells to the allergen-specific inflammatory responses in eyes with allergic conjunctivitis and to test the hypothesis that mast cells act as mediators of the early phase response. METHODS: The participation of mast cells in allergen-induced inflammatory cell recruitment was studied in an experimental murine model of allergic conjunctivitis. Experimental allergic conjunctivitis was induced by a single or multiple sensitizing injections of an allergen. The conjunctiva of allergen-sensitized, mast cell-deficient (Kit(w)/Kit(w-v)) mice were reconstituted with conjunctival mast cells isolated from naïve wild type mice by subconjunctival transfer. Kit(w)/Kit(w-v) mice and conjunctival mast cell reconstituted Kit(w)/Kit(w-v) mice were evaluated for early phase reactions and late phase inflammatory responses. RESULTS: The early phase response was minimal in Kit(w)/Kit(w-v) mice after both a single injection and multiple sensitization injections of the allergen. The early phase responses were fully restored following adoptive transfer of isolated conjunctival mast cells from naïve wild type mice. Eosinophilic inflammatory responses were significantly depressed in Kit(w)/Kit(w-v) mice without the impairment of allergen-specific priming. Reconstitution of the conjunctiva of Kit(w)/Kit(w-v) mice with mast cells from wild type mice fully restored the allergen-specific eosinophilic responses but not the neutrophilic responses. CONCLUSIONS: Our data indicate that conjunctival mast cells are essential for eosinophilic inflammation but not for neutrophilia in allergic conjunctivitis that is mediated by mast cell activation.

Transcriptional analyses before and after suppression of immediate hypersensitivity reactions by CCR3 blockade in eyes with experimental allergic conjunctivitis.

PURPOSE: To characterize the transcriptome of allergic conjunctivitis mediated by eosinophil-related chemokine receptor CCR3 and to identify a candidate for possible therapeutic intervention in eosinophilic inflammation of the eye. METHODS: Mice were sensitized to ragweed pollen, and allergic conjunctivitis was induced by an allergen challenge. The induction of allergic conjunctivitis was used to determine whether an inhibition of CCR3 would suppress eosinophilic inflammation and the allergen-induced immediate hypersensitivity reaction. In addition, sensitized mice were treated with a CCR3 antagonist or an anti-CCR3 antibody before the allergen challenge. Eosinophilic inflammation was evaluated histologically at 24 hours after the allergen challenge. Transcriptional changes with or without a blockade of CCR3 were determined by microarray analyses. RESULTS: Blockade of CCR3 significantly suppressed allergen-induced clinical signs, mast cell degranulation, and eosinophilic inflammation. Clustering analysis of the transcriptome during the early phase identified clusters of genes associated with distinct biological processes. A CCR2 ligand, monocyte chemoattractant protein (MCP)-1, was identified in the cluster of genes related to mast cell activation. MCP-1, an attractant of monocytes but not eosinophils, was in the top 10 transcripts among the genome and was suppressed by CCR3 blockade. Importantly, antibody blockade of MCP-1 suppressed the eosinophilic inflammation significantly. CONCLUSIONS: CCR3 regulates not only the eosinophilic inflammation but also the clinical signs and mast cell degranulation. The CCR3-mediated transcriptome is characterized by many biological processes associated with mast cell activation. Among these CCR3-mediated processes, MCP-1 was found to be significantly involved in eosinophilic inflammation probably by an indirect pathway.

Clinical application of real-time polymerase chain reaction for diagnosis of herpetic diseases of the anterior segment of the eye.

PURPOSE: To assess the value of quantification of herpes simplex virus (HSV) DNA for the differential diagnosis of herpetic diseases of the anterior segment of the eye. METHODS: One hundred forty-four samples from 90 patients with ocular inflammatory diseases were examined for HSV DNA by real-time polymerase chain reaction (PCR) with primers set for the consensus sequence of HSV-1/2 DNA polymerase. The samples included corneal epithelial scrapings, tear fluid (200microl of eye wash), and aqueous humor. RESULTS: In cases of typical herpetic epithelial keratitis, a large number of copies of HSV DNA were detected (mean, 1.0 x 10(7) copies in epithelial scrapings and 3.5 x 10(5) copies in tear fluid). In atypical epithelial keratitis cases, a smaller number of HSV DNA copies were detected. In stromal keratitis cases, the number of copies of HSV DNA in the tear fluid (mean: 4.7 x 10(2) copies) was significantly smaller than in cases of epithelial keratitis. In the aqueous humor, the number of copies was small in endotheliitis cases (mean, 2.9 x 10(2) copies/microl), but the range was great, from (1.2-4.8) x 10(5)/microl in herpetic iridocyclitis. Seventeen percent of cases in which HSV was not suspected to be involved showed a small number of copies of HSV DNA, indicating the unexpected involvement of HSV in these cases. CONCLUSIONS: Real-time PCR is an informative method of diagnosing herpetic eye diseases and evaluating the possible involvement of HSV in other inflammatory ocular diseases.

Prognosis-determinant candidate genes identified by whole genome scanning in eyes with pterygia.

PURPOSE: To identify the genes that can differentiate primary from recurrent pterygia. METHODS: The transcriptional differences of primary and recurrent pterygia were first determined by microarray analyses. Computational analyses were used to extract the biological significance of the genes accurately, and a significant functional classification of the genes was made by unsupervised methodologies. After confirming the functional classification for primary and recurrent pterygia by a clustering algorithm, a support vector machine (SVM) algorithm was applied. Based on a machine learning technique, the minimum number of genes that can accurately classify primary and recurrent pterygia was determined. RESULTS: Clustering analyses classified primary and recurrent pterygia transcriptomes and identified 10 clusters associated with distinct biological processes. When the SVM algorithm was applied to the microarray-analyzed products from three primary and three recurrent cases, periostin, TIMP-2, and L-3-phosphoserine phosphatase homolog (PSPHL) were identified as the minimum set of predictors with 100% accuracy. A differential expression of these genes in primary and recurrent pterygia was confirmed by immunohistochemistry. When the 24 patients with primary disease and the 8 patients with recurrent disease were analyzed with this gene set, an accuracy of classification of 84.38% was achieved. CONCLUSIONS: Periostin, TIMP-2, and PSPHL can be used as predictor genes for the recurrence of pterygia. Their biological activities may explain the events leading to recurrences of pterygia and thus may be genes to target for pharmaceutical interventions.

Role of beta-chemokines in mast cell activation and type I hypersensitivity reactions in the conjunctiva: in vivo and in vitro studies.

Chemokines have a clearly defined role in mobilizing the recruitment of leukocytes to both healthy and inflamed tissues. This review details work from our and other laboratories, indicating that beta-chemokines may play important roles (i) in driving the terminal differentiation of mast cell precursors in mucosal tissues and (ii) in providing priming or costimulatory signals required for mast cell activation, leading to an antigen-driven inflammatory response. These data stem from in vivo, ex vivo, and in vitro studies. Data are also presented that suggest that Fc epsilon RI:chemokine receptor cross talk may involve spatiotemporal dynamics that may control the strength and nature of the complex activating signals controlling mast cell effector function.