The promotion of eosinophil degranulation and adhesion to conjunctival epithelial cells by IgE-activated conjunctival mast cells

PAF-induced inflammatory and immuno-allergic ophthalmic diseases and their mitigation with PAF receptor antagonists: Cell and nuclear effects

Ocular allergies are becoming more prevalent as more airborne pollutants, irritants and microbes pervade our environment. Inflammatory and allergic mediators released by dendritic and mast cells within the conjunctiva cause allergic conjunctivitis (AC), a prevalent ocular surface disorder that affects >40% of the world's human population on a seasonal or perennial basis. Even though histamine is a major culprit, platelet-activating factor (PAF) also contributes to AC, acting either directly or synergistically with histamine and other mediators. PAF receptor-meditated inflammatory reactions, via cell-membrane-bound and nuclear-membrane-bound and nuclear PAF receptors, are also implicated in the etiology of other eye diseases such as uveitis, diabetic retinopathy, corneal and choroidal neovascularization, and age-related macular degeneration which cause serious visual impairment and can lead to blindness. This review highlights the various deleterious elements implicated in the pathological aspects of ocular allergic reactions and inflammation and provides concepts and treatment options to mitigate these eye disorders with a special focus on PAF and PAF receptor antagonists.

An open microfluidic coculture model of fibroblasts and eosinophils to investigate mechanisms of airway inflammation

Interactions between fibroblasts and immune cells play an important role in tissue inflammation. Previous studies have found that eosinophils activated with interleukin-3 (IL-3) degranulate on aggregated immunoglobulin G (IgG) and release mediators that activate fibroblasts in the lung. However, these studies were done with eosinophil-conditioned media that have the capacity to investigate only one-way signaling from eosinophils to fibroblasts. Here, we demonstrate a coculture model of primary normal human lung fibroblasts (HLFs) and human blood eosinophils from patients with allergy and asthma using an open microfluidic coculture device. In our device, the two types of cells can communicate via two-way soluble factor signaling in the shared media while being physically separated by a half wall. Initially, we assessed the level of eosinophil degranulation by their release of eosinophil-derived neurotoxin (EDN). Next, we analyzed the inflammation-associated genes and soluble factors using reverse transcription quantitative polymerase chain reaction (RT-qPCR) and multiplex immunoassays, respectively. Our results suggest an induction of a proinflammatory fibroblast phenotype of HLFs following the coculture with degranulating eosinophils, validating our previous findings. Additionally, we present a new result that indicate potential impacts of activated HLFs back on eosinophils. This open microfluidic coculture platform provides unique opportunities to investigate the intercellular signaling between the two cell types and their roles in airway inflammation and remodeling.

Discovery to Launch of Anti-allergy (Emadine; Patanol/Pataday/Pazeo) and Anti-glaucoma (Travatan; Simbrinza) Ocular Drugs, and Generation of Novel Pharmacological Tools Such as AL-8810

The eye and eyesight are exquistly designed and are precious, and yet we often take them for granted. Good vision is critical for our long-term survival and for humanity's enduring progress. Unfortunately, since ocular diseases do not culminate in life-and-death scenarios, awareness of the plight of millions of people suffering from such eye ailments is not publicized as other diseases. However, losing eyesight or falling victim to visual impairment is a frightening outlook for most people. Glaucoma, a collection of chronic optic neuropathies, of which the most prevalent form, primary open-angle glaucoma (POAG), is the second leading cause of irreversible blindness. POAG currently afflicts >70 million people worldwide and is an insidious, progressive, silent thief of sight that is asymptomatic. On the other hand, allergic conjunctivitis (AC), and the associated rhinitis ("hay-fever"), frequently victimizes a huge number of people worldwide, especially during seasonal changes. While not life-threatening, sufferers of AC soon learn the value of drugs to treat their signs and symptoms of AC as they desire rapid relief to overcome the ocular itching/pain, redness, and tearing AC causes. Herein, I will describe the collective efforts of many researchers whose industrious, diligent, and dedicated team work resulted in the discovery, biochemical/pharmacological characterization, development and eventual launch of drugs to treat AC (e.g., olopatadine [Patanol/Pataday/Pazeo] and emedastine [Emedine]), and for treating ocular hypertension and POAG (e.g., travoprost [Travatan ] and Simbrinza). This represents a personal perspective.

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.

IL-3 and TNFα increase Thymic Stromal Lymphopoietin Receptor (TSLPR) expression on eosinophils and enhance TSLP-stimulated degranulation

BACKGROUND

Thymic stromal lymphopoietin (TSLP) and eosinophils are prominent components of allergic inflammation. Therefore, we sought to determine whether TSLP could activate eosinophils, focusing on measuring the regulation of TSLPR expression on eosinophils and degranulation in response to TSLP, as well as other eosinophil activation responses.

METHODS

Eosinophil mRNA expression of TSLPR and IL-7Rα was examined by real-time quantitative PCR of human eosinophils treated with TNFα and IL-5 family cytokines, and TSLPR surface expression on eosinophils was analyzed by flow cytometry. Eosinophils were stimulated with TSLP (with and without pre-activation with TNFα and IL-3) and evaluated for release of eosinophil derived neurotoxin (EDN), phosphorylation of STAT5, and survival by trypan blue exclusion. A blocking antibody for TSLPR was used to confirm the specificity of TSLP mediated signaling on eosinophil degranulation.

RESULTS

Eosinophil expression of cell surface TSLPR and TSLPR mRNA was upregulated by stimulation with TNFα and IL-3. TSLP stimulation resulted in release of EDN, phosphorylation of STAT5 as well as promotion of viability and survival. TSLP-stimulated eosinophil degranulation was inhibited by a functional blocking antibody to TSLPR. Pre-activation of eosinophils with TNFα and IL-3 promoted eosinophil degranulation at lower concentrations of TSLP stimulation.

CONCLUSIONS

This study demonstrates that eosinophils are activated by TSLP and that eosinophil degranulation in response to TSLP may be enhanced on exposure to cytokines present in allergic inflammation, indicating that the eosinophil has the capacity to participate in TSLP-driven allergic responses.

Cytokines and chemokines in immune-based ocular surface inflammation

Altered levels of several cytokines and chemokines have been found in different types of inflammatory ocular surface diseases, such as allergy or dry-eye syndrome. It has also been demonstrated that epithelial cells play a key role in the persistence and even initiation of chronic mucosal inflammation. The recent development of 'multiplex detection' technologies has facilitated the identification of specific patterns of expression of these molecules in some ocular immune-based inflammatory disorders. Analysis of these molecules in tissues, cells (in vivo and in vitro) and tears has revealed that not only inflammatory cells but also epithelial and fibroblast resident cells are sources of these molecules. The purpose of this review is to summarize recent studies in this field.

Eotaxin selectively binds heparin. An interaction that protects eotaxin from proteolysis and potentiates chemotactic activity in vivo

An important feature of chemokines is their ability to bind to the glycosaminoglycan (GAG) side chains of proteoglycans, predominately heparin and heparan sulfate. To date, all chemokines tested bind to immobilized heparin in vitro, as well as cell surface heparan sulfate in vitro and in vivo. These interactions play an important role in modulating the action of chemokines by facilitating the formation of stable chemokine gradients within the vascular endothelium and directing leukocyte migration, by protecting chemokines from proteolysis, by inducing chemokine oligomerization, and by facilitating transcytosis. Despite the importance of eotaxin in eosinophil differentiation and recruitment being well established, little is known about the interaction between eotaxin and GAGs and the functional consequences of such an interaction. Here we report that eotaxin binds selectively to immobilized heparin with high affinity (K(d) = 1.23 x 10(-8) M), but not to heparan sulfate or a range of other GAGs. The interaction of eotaxin with heparin does not promote eotaxin oligomerization but protects eotaxin from proteolysis directly by plasmin and indirectly by cathepsin G and elastase. In vivo, co-administration of eotaxin and heparin is able to significantly enhance eotaxin-mediated eosinophil recruitment in a mouse air-pouch model. Furthermore, when heparin is co-administered with eotaxin at a concentration that does not normally result in eosinophil infiltration, eosinophil recruitment occurs. In contrast, heparin does not enhance eotaxin-mediated eosinophil chemotaxis in vitro, suggesting protease protection or haptotactic gradient formation as the mechanism by which heparin enhances eotaxin action in vivo. These results suggest a role for mast cell-derived heparin in the recruitment of eosinophils, reinforcing Th2 polarization of inflammatory responses.

Emerging drugs for ocular allergy

Ocular allergy is a common condition that usually affects the conjunctiva of the eye and is, therefore, often referred to as allergic conjunctivitis. The severity of the disease can range from mild itching and redness, as seen in seasonal allergic conjunctivitis, to the more severe, sight-threatening forms such as vernal and atopic keratoconjunctivitis. The central mechanism in the pathogenesis of these diseases is IgE-mediated mast cell degranulation and activation of T lymphocytes, eosinophils and conjunctival structural cells. The pharmacotherapy of allergic conjunctivitis consists of several classes of drugs: antihistamines, mast cell stabilisers, dual-acting agents and corticosteroids. None of the available drugs completely abolishes the development of ocular allergy. For this reason, new topical antiallergic/anti-inflammatory agents are currently and continually under clinical trials. This review provides a background to ocular allergic diseases, the medical need for therapy and current and potential new treatments.

Mast cell stabilization and anti-histamine effects of olopatadine ophthalmic solution: a review of pre-clinical and clinical research

BACKGROUND

Histamine receptor activation and degranulation of mast cells are the mechanisms by which the ocular itching, hyperemia, chemosis, eyelid swelling, and tearing of seasonal allergic conjunctivitis are induced. Some of the topical solutions available as anti-allergy therapies are intended to interfere with these mechanisms, and the body of research regarding the capabilities of these therapeutic molecules continues to expand.

OBJECTIVE

To review the currently available literature regarding one topical ophthalmic anti-allergy agent, olopatadine (Patanol), and its anti-histaminic and mast cell stabilizing actions, both in pre-clinical and clinical settings.

DESIGN AND METHODS

Relevant research of laboratory, animal model, and clinical trial studies performed using olopatadine was reviewed. MEDLINE literature searches were conducted and supplemented by additional reports which furthered relevant discussion or were necessary to verify the information resulting from original searches.

RESULTS

Olopatadine demonstrates unique properties both pre-clinically and clinically which differentiate it from other therapeutic molecules in its class of dual action mast cell stabilizer/anti-histamine. Its non-perturbation of cell membranes, human conjunctival mast cell stabilization in vivo and in vitro, and superior efficacy as compared to other topical anti-allergic medications including mast cell stabilizers, anti-histamines, and dual action agents, all contribute to olopatadine's profile.

CONCLUSIONS

Peer-reviewed literature suggests that olopatadine is clinically superior to the other anti-allergic molecules because of its strong anti-histaminic qualities and its unique ocular mast cell stabilizing properties.

A review of olopatadine for the treatment of ocular allergy

Ocular allergy affects > 20% of the general population and many therapeutic preparations are available to individuals experiencing the most common forms--seasonal and perennial allergic conjunctivitis. 0.1% Olopatadine topical ophthalmic solution is currently approved for the treatment of allergic signs and symptoms in patients > or = 3 years of age. Olopatadine is available in Europe as Opatanol) and in > 30 other countries as Patanol. It inhibits mast cell degranulation and antagonises histamine receptors to manage the itching, redness, chemosis, tearing and lid swelling of the ocular allergic reaction, and its mast cell stabilising ability has been demonstrated both in vitro (using human conjunctival mast cells) and in vivo (human clinical experience). This article reviews both the laboratory and clinical information available on olopatadine, prefaced by a discussion of the current understanding of the ocular allergic reaction and followed by the future implications for this compound. Both laboratory and clinical studies have established the efficacy, safety and comfort of olopatadine in several study design models and comparisons to other antiallergy medications. The application of olopatadine, specifically in the management of lid swelling, an allergic sign recalcitrant to therapy and nasal allergic symptoms has also been established. In the future, a new formulation containing 0.2% olopatadine exhibits a duration of action up to 24 h, supporting once-daily dosing.

Involvement of eotaxin, eosinophils, and pancreatic predisposition in development of type 1 diabetes mellitus in the BioBreeding rat

Allergy and autoimmunity are both examples of deregulated immunity characterized by inflammation and injury of targeted tissues that have until recently been considered disparate disease processes. However, recent findings have implicated mast cells, in coordination with granulocytes and other immune effector cells, in the pathology of these two disorders. The BioBreeding (BB) DRlyp/lyp rat develops an autoimmune insulin-dependent diabetes similar to human type 1 diabetes mellitus (T1DM), whereas the BBDR+/+ rat does not. To better understand immune processes during development of T1DM, gene expression profiling at day (d) 40 (before insulitis) and d65 (before disease onset) was conducted on pancreatic lymph nodes of DRlyp/lyp, DR+/+, and Wistar-Furth (WF) rats. The eosinophil-recruiting chemokine, eotaxin, and the high-affinity IgE receptor (FcepsilonRI) were up-regulated >5-fold in d65 DRlyp/lyp vs d65 DR+/+ pancreatic lymph nodes by microarray (p < 0.05) and quantitative RT-PCR studies (p < 0.05). DR+/+, WF, and d40 DRlyp/lyp animals possessed normal pancreatic histology; however, d65 DRlyp/lyp animals possessed eosinophilic insulitis. Therefore, immunohistochemistry for pancreatic eotaxin expression was conducted, revealing positive staining of d65 DRlyp/lyp islets. Islets of d65 DR+/+ rats also stained positively, consistent with underlying diabetic predisposition in the BB lineage, whereas WF islets did not. Other differentially expressed transcripts included those associated with eosinophils, mast cells, and lymphocytes. These data support an important role for these inflammatory mediators in BB rat T1DM and suggest that the lymphopenia due to the Ian5/(lyp) mutation may result in a deregulation of cells involved in insulitis and beta cell destruction.

Roles of Chemokines in Ocular Allergy and Possible Therapeutic Strategies

The mechanism of ocular surface allergy in the forms of atopic conjunctivitis and vernal keratoconjunctivitis has been highlighted by specific functions of chemokines. In the context of late-phase allergic responses, these molecules have key roles in recruitment and activation of leukocytes. Their interaction with ligands is redundantly regulated; however, results from strategies to block subsets of chemokines have revealed unexpected or highly organized roles of these mediators. Exemplified by analyses of CCL11 function, current concepts of ocular allergy support CCL11 as central mediator. We emphasize the functions as modulator of mast cell activation/differentiation. With the prospect of understanding these functions, new modalities of drugs specifically developed to target CCL11/CCR3 interaction have been discussed.

Participation of chemical mediators in the development of experimental allergic conjunctivitis in rats

In the present study, we investigated the participation of chemical mediators in the development of experimental allergic conjunctivitis in rats. Cetirizine (a histamine H1 receptor antagonist), ramatroban (a thromboxane A2 (TXA2) receptor antagonist) and zafirlukast (a cysteinyl leukotrienes (cys-LTs) receptor antagonist) were orally administered from day 14 to day 42 during repeated topical antigen challenge. An increase in reactivity to antigen- and histamine-induced eye scratching behavior was observed by topical sensitization in sensitized rats. Although increased reactivity to antigen was not influenced by cetirizine, ramatoroban and zafirlukast, increased reactivity to histamine was significantly inhibited by ramatroban. The development of conjunctival edema was also observed for topical sensitization. Cetirizine caused no inhibition of the development of conjunctival edema, but ramatroban and zafirlukast inhibited the development of conjunctival edema. In addition, the number of eosinophils in the conjunctiva was increased by topical sensitization. Cetirizine had no significant effect on the increase in the number of eosinophils. However, ramatroban and zafirlukast were effective in inhibiting an increase in the number of eosinophils induced by topical sensitization. These results indicate that TXA2 is involved in increased histamine reactivity, and TXA2 and cys-LTs are associated with not only the conjunctival edema but also eosinophil infiltration during the development of experimental allergic conjunctivitis in rats.

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.