ICAM-1/CD54 expression on conjunctival epithelium during pollen season

Les tests de provocation conjonctivaux

The conjunctival provocation test (CPT) is a human model of ocular allergy that has been used to study the ocular response to allergenic stimuli and to evaluate antiallergic therapy. Considerable useful information has been gained on the ocular allergic response and drug efficacy using the conjunctival provocation test and naturally occurring seasonal allergic conjunctivitis. The safety and the efficacy of these CPTs has resulted in many authors using this tool in the etiologic diagnosis of allergic conjunctivitis. This article summarizes the possibilities of these CPTs as a tool for the study, evaluation, diagnosis, and therapeutic follow-up of allergic conjunctivitis.

Reduced structural proteins in the conjunctival epithelium in allergic eye disease

AIMS

Allergic eye disease affects up to 20% of the population with varying severity. The conjunctival epithelium plays a key role in allergic eye disease. The purpose of this study was to determine whether the conjunctival epithelium is abnormal in allergic eye disease.

METHODS

Conjunctival biopsy samples were taken from patients with seasonal allergic conjunctivitis (SAC) 'in' and 'out of season' and nonatopic control subjects. Specimens were fixed in glycol methacrylate, 2 microm serial sections cut and Image-J used to assess the sites and areas of immuno-staining.

RESULTS

E-cadherin, CD44, keratins K5/6, K8, K13, K14, K18 and pan-keratin immuno-staining were all significantly lower in patients 'out of season' compared with normal controls. No structural differences in the epithelium were observed between the two groups. The epithelium of patients 'in season' was thicker and immuno-staining of the above markers similar to controls.

CONCLUSIONS

The expression of a wide spectrum of epithelial cell adhesion proteins and cytoskeletal elements is downregulated in the conjunctiva of SAC patients 'out of season' compared with normal controls. We suggest that this could have an important impact on the ability of the epithelium to protect itself against allergen penetration, potentially influencing the development and course of allergic eye disease and offering a novel area for therapeutic control.

Drug therapy for ocular allergy

The spectrum of ocular allergy ranges from mild, non-sight threatening disease, such as hay fever, to disorders such as atopic keratoconjunctivitis (AKC) which cause permanent ocular surface changes and reduced vision. The ideal treatment is with topical preparations. Launched topical preparations include anti-histamines and mast cell (MC) stabilisers, which are safe, but only moderately potent, steroids, which are very potent, but carry very serious side-effects, and cyclosporin A, which is not widely available and difficult to tolerate. There are a number of anti-histamines, MC stabilisers (and combinations thereof) and steroids in development which are of potential interest. Other possibilities for therapeutic intervention include inhibition of tryptase, cyclooxygenase (COX), leukotrienes (LTs), bradykinins (BKs), platelet activating factor (PAF) and immunoglobulin E (IgE). Therapies based on cytokine antagonism and agonism, T-cell inhibition and adhesion molecule antagonism might be expected to provide safe, but potent new modes of treatment. The increasing interest in research into the pathogenesis of ocular allergic inflammation may lead to more relevant approaches, such as eosinophil inhibition. Success will be highly dependent on the ability to produce suitable topical ophthalmic preparations.

Rapid anti-inflammatory action of azelastine eyedrops for ongoing allergic reactions

BACKGROUND

Some second-generation antihistamines have anti-inflammatory activities, but the clinical relevance of this property is still unclear.

OBJECTIVE

The aim of our study was to investigate the effects of azelastine when administered during the early-phase reaction.

METHODS

This investigation was designed as a randomized, placebo-controlled, double-blind, parallel-group study. Clinical and inflammatory events were evaluated after a single dose of azelastine eyedrops or placebo was administered 30 minutes after an allergen-specific conjunctival challenge. Twenty outpatients with allergic rhinoconjunctivitis attributable to Parietaria judaica were enrolled in the study outside the pollen season. Patients were evaluated at baseline, after allergen challenge (at 30 minutes), and after administration of azelastine (at 30 minutes and at 6 hours). The following variables were evaluated: hyperemia, lacrimation, itching, eyelid swelling, number of inflammatory cells (neutrophils, eosinophils, monocytes, and lymphocytes), and intercellular adhesion molecule-1 expression on conjunctival epithelial cells.

RESULTS

Azelastine, in comparison to placebo, significantly reduced symptom scores, number of inflammatory cells, and intercellular adhesion molecule-1 expression during the early- and late-phase reaction.

CONCLUSIONS

The ability of azelastine to reduce symptoms and inflammation during an ongoing allergic reaction can be considered concrete and convincing proof of a clinically relevant anti-inflammatory activity.

Quantitative flow cytometric analysis of the effects of cetirizine on the expression of ICAM-1/CD54 on primary cultured nasal cells

An in vitro flow cytometric model has been developed to evaluate the effects of antiallergic drugs such as cetirizine (CTZ) on the expression of surface molecules on primary cultured normal cells. Quantitative analysis demonstrated that HLA class I and ICAM-1/CD54 molecules are present on both epithelial and stromal cells, and that their expression is strongly enhanced by treatment with interferon-gamma (IFN-gamma). Nevertheless, the IFN-gamma-mediated upregulation of ICAM-1/CD54 was inhibited by treatment with CTZ, demonstrating a direct effect on both cell types. This finding is particularly interesting because ICAM-1/CD54 is the main rhinovirus receptor, and rhinoviruses are the principal cause of asthma exacerbation in children. Thus, according to data derived from this in vitro model, CTZ should have an important role in the reduction of infectious exacerbation of asthma in atopic patients.

Expression of ICAM-1 and HLA-DR by human conjunctival epithelial cultured cells and modulation by nedocromil sodium

It is unclear whether conjunctival epithelial cells participate in the development of immune-mediated events. Using a previously reported in vitro system of human conjunctival epithelium, we determined whether conjunctival epithelial cells express two relevant markers in the antigenic presentation process. Moreover, the potential capability of nedocromil sodium, an antiallergic and antiinflammatory drug, to modulate such expression was investigated. Primary cultures of human conjunctival epithelium and Chang conjunctival cells, incubated with or without 100 U/ml IL-1beta and/or IFNgamma for 1, 3 or 6 h, were simultaneously exposed to 10(-5) M nedocromil sodium. The expression of the intercellular adhesion molecule-1 (ICAM-1) and the human leukocyte antigen-DR (HLA-DR) was determined immunocytochemically. Constitutive expression of ICAM-1 and HLA-DR was observed in primary cultures and Chang cells and was minimally affected by incubation with IL-1beta and/or IFNgamma. The addition of nedocromil sodium resulted in complete abolition of HLA-DR expression and a notable reduction in ICAM-1 expression in primary cultures and Chang cells. These results suggest that epithelial cells from human conjunctiva constitutively express ICAM-1 and HLA-DR in vitro and that such expression is downregulated by nedocromil sodium. This may indicate that conjunctival epithelial cells may be another target for this drug.

In situ hybridization analysis of ICAM-1 (CD54) mRNA on conjunctival epithelium during allergic inflammation

BACKGROUND

The intercellular adhesion molecule ICAM-1 has been detected by immunohistochemical methods on epithelial cells of the conjunctiva and nose during allergic inflammation.

OBJECTIVE

The aim of the present study was to evaluate whether ICAM-1 expression on conjunctival epithelium derives from endogenous synthesis or is merely due to passive uptake of soluble ICAM-1 released from inflammatory cells.

METHODS

In situ hybridization was performed using a 3' end dygoxygenin-labelled specific DNA oligonucleotide probe on fixed conjunctival smears from allergic subjects challenged with, or naturally exposed to the allergen, and from healthy subjects. Immunocytochemistry for ICAM-1 was performed by alkaline phosphatase antialkaline phosphatase.

RESULTS

In allergic patients, both naturally exposed to the allergen and after specific challenge, a clear hybridization pattern on epithelial cells was apparent. Out of allergen exposure, some symptomfree pollinosic subjects, as well as a few healthy volunteers showed mild ICAM-1 mRNA cytoplasmic staining in the absence of immunohistochemically detectable ICAM-1. This finding may explain the very early appearance of ICAM-1 on conjunctival epithelium following specific challenge in allergic individuals.

CONCLUSIONS

These results indicate that the presence of ICAM-1 on conjunctival epithelium during allergic inflammation derives from endogenous synthesis and not from uptake of soluble ICAM-1.