The T-lymphocyte chemoattractant Mig is highly expressed in vernal keratoconjunctivitis

Chemokines in allergic conjunctivitis

PURPOSE OF REVIEW

Chemokines are a large group of low molecular weight cytokines that attract and activate leukocytes throughout the body and therefore have a key role in the framework of late-phase allergic responses. The purpose of this article is to provide an overview of the main chemokines involved in allergic conjunctivitis, their primary functions and their physiological roles, and therapies targeted at chemokines and their receptors for ocular allergic diseases.

RECENT FINDINGS

In recent years, there have been considerable advances in the understanding of ocular pathophysiology of ocular surface inflammatory diseases including both allergic eye diseases and dry eye syndrome. Several therapies being developed for dry eye inflammation are recognized as possible therapies for ocular allergic diseases as there are often common chemokines involved in both disease spectra.

SUMMARY

Chemokines represent an integral part of the late-phase cascade of ocular allergic inflammation. A deep understanding of specific chemokines and their interactions will help in targeting therapies to effectively manage ocular clinical findings and symptoms of allergic eye disease.

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.

Expression Analysis of Cytokine and Chemokine Genes during the Natural Course of Murine Experimental Autoimmune Uveoretinitis

C57BL/6 mice were immunized with human interphotoreceptor retinoid-binding protein peptides to induce experimental autoimmune uveoretinitis (EAU). From the day of immunization to 30 days later, RNA was isolated daily from the mouse eyes. Dynamic changes in gene expression during the pathogenesis of EAU were analyzed by TaqMan gene expression assay that contained most chemokines/cytokines and their receptors, and signal transducer and activator of transcription (STAT) family genes, using beta-actin as the endogenous control. Gene clusters based on their expression profiles were analyzed to determine the candidate genes for the pathogenesis of inflammation. Hierarchical cluster analysis showed gene expression during EAU development in seven clustering patterns. Hierarchical cluster analysis also identified four distinct phases in daily expression: entrance, acceleration, deceleration, and remission. Gene expression changes in the EAU active phase showed synergetic upregulation of Th1-type genes (IFN-gamma and CXCL10/IP-10) with elevated Th2-type genes (CCL17/TARC and IL-5). Sequential expression changes of STAT1, STAT6, and STAT3 genes represented the dynamic changes of Th1, Th2, and Th17-type inflammatory genes, respectively. The expression pattern of STAT1 was representative of many gene movements. Our results suggested that coordinated action of Th1, Th2, and Th17 genes and STAT family genes are involved in EAU development and resolution.

Immune mechanisms in allergic eye diseases: what is new?

PURPOSE OF REVIEW

The purpose of this review will be to focus on new findings that expand our understanding of the immune mechanisms occurring in the various forms of allergic eye disease and in experimental models, and some novel therapeutic approaches.

RECENT FINDINGS

The novel data encompass three main areas: effector mechanisms in allergic eye disease; cytokines and chemokines in conjunctival responses; combinations of drugs for improving treatment options for allergic eye disease.

SUMMARY

The term 'allergic eye disease' describes a spectrum of clinical conditions, ranging from the common, milder conditions of seasonal and perennial allergic conjunctivitis (SAC, PAC), to the rare and more severe diseases, vernal keratoconjunctivitis (VKC) and atopic keratoconjunctivitis (AKC). These latter two diseases can involve the cornea, leading to impaired vision. Although there is an underlying allergic mechanism, each of these ocular surface conditions involves different cellular responses and much effort has been made to identify the molecular pathways, which could be used as potential targets for therapeutic intervention. Currently available drugs, in particular for chronic forms of disease, are inadequate and there is an urgent need for safer, more localized and effective treatment.

Corneal and conjunctival fibroblasts are major sources of eosinophil-recruiting chemokines

BACKGROUND

Differential expression of chemokine genes were investigated in various types of ocular surface cells.

METHODS

Primary cultures of human corneal epithelial cells (n = 3), corneal fibroblasts (n = 2), conjunctival epithelial cells (n = 2) and conjunctival fibroblasts (n = 2) were established and incubated with or without interleukin (IL)-4 (30ng/ml) and tumor necrosis factor (TNF)-alpha(30ng/ml) for 24 hours. Gene transcription levels of 33 chemokines and production of 4 chemokines were analyzed.

RESULTS

After stimulation, chemokine expression increased for 18 of 33 coded chemokine gene transcripts. In stimulated conjunctival and corneal cells, CC chemokine genes increased in fibroblasts (expression of 6 out of 8 genes), while CXC chemokine genes increased in both epithelial cells (expression of 4 out of 9 genes in conjunctival epithelial cells and 7 out of 9 genes in corneal epithelial cells) and in fibroblasts (expression of 8 out of 9 genes in conjunctival and corneal fibroblasts). Except for MCP-1, gene transcription levels for most CC chemokines were inducible and, except for IP-10 and I-TAC, most CXC chemokines were constitutively expressed. Corneal epithelial cell and fibroblast production patterns for eotaxin-1, MCP-1 and IP-10 were comparable to the mRNA expression pattern.

CONCLUSIONS

Corneal and conjunctival fibroblasts exhibited marked increases in the expression of chemokines upon stimulation with TNF-alpha and IL-4, suggesting that fibroblasts may be one of the primary sources of chemokines in allergic conjunctival diseases. Therefore, regulation of chemokine production from these cells may be an effective strategy for treating such diseases.

Mast Cell Chymase Decreases the Barrier Function and Inhibits the Migration of Corneal Epithelial Cells

PURPOSE

We investigated the in vitro effects of human mast cell chymase on corneal epithelial cells.

METHODS

Human corneal epithelial cells were incubated with human chymase at activity levels that were likely to exist in the tears of patients with vernal keratoconjunctivitis.

RESULTS

Incubation of chymase resulted in a decrease of barrier function of corneal epithelium. Occludin protein was cleaved by chymase. In the wound assay, incubation with chymase resulted in an inhibition of cell migration.

CONCLUSION

Human chymase causes the proteolysis of occludin and fibronectin, resulting in a decrease of barrier function and inhibition of the migration of corneal epithelial cells.

Vernal keratoconjunctivitis: a major review

Vernal keratoconjunctivitis (VKC) is a chronic, bilateral, at times asymmetrical, seasonally exacerbated, allergic inflammation of the ocular surface, involving tarsal and/or bulbar conjunctiva. Though the allergic nature of this entity has been accepted for a long time, the accumulation of a large amount of immunological data has proved that the pathogenesis of VKC is much more complex than a mere type 1 hypersensitivity reaction. In the past several years, many clinical and experimental studies about the cells and mediators involved in initiating and perpetuating the ocular allergic inflammation have shown that T helper type 2 cells and their cytokines, corneal fibroblasts and epithelium along with various growth factors play an important role in the pathogenesis of VKC. Based on this information about the pathogenesis of VKC newer, more selective drugs like anti-chemokine receptor antibodies and leukotriene receptor antagonists are under evaluation. Cyclosporine has been shown to be effective in the treatment of VKC but further randomized control trials are required to establish the minimum effective concentration.

Multiple cytokines in human tear specimens in seasonal and chronic allergic eye disease and in conjunctival fibroblast cultures

BACKGROUND

Several cytokines are involved in the recruitment and activation of inflammatory cells in ocular allergic diseases. The purpose of the study was to assay multiple cytokines and chemokines in tears, to compare subgroups of allergic conjunctivitis (AC) with controls, and in culture supernatants to determine whether conjunctival fibroblasts produce some of these cytokines.

METHODS

Fifty to one hundred microlitre tears were obtained from patients with active seasonal allergic conjunctivitis (SAC; n=12), vernal keratoconjunctivitis (VKC; n=18), atopic keratoconjunctivitis (AKC; n=6) and non-atopic controls (n=14). Primary conjunctival fibroblasts grown in vitro were stimulated with IL-4, IL-13 or TNF-alpha for 24 h. Cell-free tear and culture supernatants were assayed for IL-1beta, IL-2, IL-4, IL-5, IL-6, IL-8, IL-10, IL-12, IL-13, IFN-gamma, TNF-alpha, eotaxin, MCP-1 and RANTES using multiplex bead analysis. Induction of chemokine gene expression was determined by PCR.

RESULTS

IL-1beta, IL-2, IL-5, IL-6, IL-12, IL-13, MCP-1 were increased in all tears groups compared with controls, with highly significant correlations between many of these molecules. In addition IL-4, IFN-gamma, and IL-10 were elevated in SAC and VKC, while eotaxin and TNF-alpha were only increased in VKC. IL-6, IL-8, MCP-1, RANTES and eotaxin were detected from fibroblasts cultures, and were all up-regulated by TNF-alpha. By PCR, fibroblasts expressed MCP-1 transcripts constitutively, whereas IP-10 and Mig were up-regulated by TNF-alpha.

CONCLUSIONS

Differential cytokine levels support tears as a useful indicator of immune mechanisms occurring during AC. The striking similarities in chemokine profiles between tears and fibroblasts suggest these cells as likely sources of chemokines in tears.

Case series of 406 vernal keratoconjunctivitis patients: a demographic and epidemiological study

PURPOSE

To evaluate the specific allergic sensitization and epidemiological characteristics of vernal keratoconjunctivitis (VKC).

METHODS

This retrospective non-comparative case series included 406 VKC patients. Data included patient and family histories, and results of allergic tests. Annual incidence and prevalence rates were calculated for a cohort of 128 VKC patients from the greater Padua area.

RESULTS

The great majority of VKC patients were male (76%), with a male : female ratio of 3.3 : 1. A skin prick test, specific serum IgE or conjunctival challenge was positive in 43%, 56% and 58% of patients, respectively. In the cohort of patients from the Padua area, the prevalence of the disease was 7.8/100,000, with a higher rate in young males (57/100,000) compared with young females (22/100,000), and lower rates in people over 16 years of age (3.8/100,000 in males, 1/100,000 in females). The incidence of VKC was 1/100,000, with a higher rate in males under 16 years of age (10/100,000) compared with females (4.2/100,000). In people over 16 years of age, the incidence of the disease was 0.06/100,000, with no difference between males and females.

CONCLUSION

An IgE-mediated sensitization was found in only half of the VKC patients. Vernal keratoconjunctivitis is not a rare event in the paediatric population but is an extremely rare new disease in adults.

Th1- and Th2-type cytokines in chronic ocular allergy

BACKGROUND

Previous reports have suggested that Th2-type cytokines are important in the pathogenesis of ocular allergic diseases. The purpose of this study is to measure levels and mRNA expression of Th1- and Th2-type cytokines in patients with active vernal keratoconjunctivitis (VKC) and atopic keratoconjunctivitis (AKC).

METHODS

Tear samples and tear-isolated cells were obtained from 9 healthy participants (CT--controls), 28 VKC, and 6 AKC patients. IL-4, IL-13, and interferon gamma (IFNgamma) tear levels were determined by ELISA, and IL-4 and IFNgamma tear cell mRNA expression by RT-PCR. Effects of these cytokines on IL-6 and IL-8 secretion, and on ICAM-1 expression by conjunctival fibroblasts, were evaluated by ELISA and flow cytometry respectively.

RESULTS

Interleukin-4 tear levels were increased in VKC and AKC compared with CT, but only IFNgamma significantly correlated with corneal involvement. An IL-4/13-dominant profile was found in 50% of VKC and in 17% of AKC patients, while a IFNgamma-dominant profile was found in 18% of VKC and in 17% of AKC patients. IL-4 and IFNgamma transcripts were detected in tear cells from 11 out of 12 VKC patients. IFNgamma upregulated expression of ICAM-1 on conjunctival fibroblasts and the secretion of IL-6 and IL-8.

CONCLUSIONS

Although both IL-4 and IFNgamma are detected in tears, only IFNgamma levels correlated with disease severity and upregulated ICAM-1 on conjunctival fibroblasts, suggesting the role of IFNgamma in the inflammatory phase of chronic allergic eye diseases.

Basic science and pathophysiology of ocular allergy

Ocular allergy includes several clinical subtypes ranging from the mild seasonal allergic conjunctivitis to the potentially sight-threatening atopic keratoconjunctivitis. Current therapies, particularly for the severe forms of disease, need to be more localized and with fewer side effects. For this to be achieved, it requires a better understanding of the basic mechanisms involved. In this chapter, recent findings are discussed that suggest that it is important to take an integrated approach, including both immune and structural elements of the eye. This provides potential new strategies for therapy, addressing the influence of structural cells in disease. These might influence the immune processes that take place and, as the structural cells are precisely localized, topical application is likely to be effective.

Association of a haplotype block spanning SDAD1 gene and CXC chemokine genes with allergic rhinitis

BACKGROUND

Seasonal allergic rhinitis (SAR) is a common allergic disorder characterized by episodes of sneezing, rhinorrhea, and swelling of the nasal mucosa. Although the pathogenesis of SAR remains unclear, there does appear to be a genetic predisposition to development of SAR. We previously identified regions of chromosomes 1p, 4q, and 9q linked to SAR in 48 families (188 members) identified through children with SAR against orchard grass pollens.

OBJECTIVE

The aim of the current study was to identify susceptibility genes for SAR on 4q.

METHODS

We screened for markers associated with SAR on 4q with 17 microsatellite markers and then for mutations in 11 genes. We genotyped 44 single nucleotide polymorphisms (SNPs) in 48 SAR families and performed haplotype-based haplotype relative risk statistics implemented in the UNPHASED program. We also examined expression of genes with human multiple tissue and immune system cDNA panels.

RESULTS

We found that 1 microsatellite marker, D4S3042, was associated with SAR (P = .034). The haplotype-based haplotype relative risk approach revealed that SNPs in SDA1 domain containing 1; chemokine, CXC motif, ligand (CXCL)-9; CXCL10; and CXCL11 were associated with SAR (P = .001-.04). These SNPs made up a haplotype block, and the most common haplotype of this block was transmitted preferentially to affected offspring (P = .002).

CONCLUSION

Our results suggests that genetic variations in a haplotype block spanning the SDA1 domain containing 1 and CXC chemokine genes on 4q21 may contribute to development of SAR in the Japanese population.

Ocular allergic disease

PURPOSE OF REVIEW

This review will focus on recent advances in our understanding of the pathogenesis of allergic eye diseases. Common findings in acute allergic conjunctivitis (seasonal and perennial) and chronic allergic conjunctivitis (vernal keratoconjunctivitis, atopic keratoconjunctivitis, and giant papillary conjunctivitis) include evidence of mast cell activation and eosinophil attraction and activation. Cytokine levels found in tears, conjunctival impression cytology and biopsy specimens, and serum have been evaluated as markers of disease, and as targets of therapeutic intervention.

RECENT FINDINGS

Human conjunctival epithelial cells respond to tumor necrosis factor alpha, interleukin-1 beta, and interferon-gamma individually and in combination. Intracellular adhesion molecule-1 expression is upregulated by interleukin-1 beta and tumor necrosis factor alpha. Conjunctival epithelial cells release interleukin-8 in response to interleukin-1 beta and tumor necrosis factor alpha but not interferon-gamma. Supernatants from activated mast cells cause increased adhesion of eosinophils to conjunctival epithelium. Tear levels of tumor necrosis factor alpha were elevated in vernal keratoconjunctivitis patients compared with normal controls. T cell lines from chronic allergic eye disease patients showed inconsistent production of cytokines in atopic and vernal keratoconjunctivitis and low levels in giant papillary conjunctivitis. Vernal keratoconjunctivitis patients have differing levels of eosinophil cationic protein in their serum if they were serum specific immunoglobulin E positive compared to serum specific immunoglobulin E negative patients.

SUMMARY

Recent findings continue to expand our basic knowledge of mechanisms and differences between seasonal and perennial allergic conjunctivitis and atopic and vernal keratoconjunctivitis. Understanding the complex interactions and cross talk between cells, cytokines and other mediators is relevant for new therapeutic approaches directed at specific disease entities.