Analysis of the interaction between IFN-gamma and IFN-gammaR in the effector phase of experimental murine allergic conjunctivitis

Antioxidant status and immune activity of glycyrrhizin in allergic rhinitis mice

Oxidative stress is considered as a major risk factor that contributes to increased lipid peroxidation and declined antioxidants in some degenerative diseases. Glycyrrhizin is widely used to cure allergic diseases due to its medicinal properties. In the present study, we evaluated the role of glycyrrhizin on lipid peroxidation and antioxidant status in the blood and nasal mucosa of allergic rhinitis (AR) mice. Mice were divided into six groups: normal control mice, model control (MC) mice, three glycyrrhizin-treated mice groups and lycopene-treated mice. Sensitization-associated increase in lipid peroxidation was observed in the blood and nasal mucosa of MC mice. Activities of antioxidant enzymes like superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GSH-Px), total antioxidant capacity (TAOC) and levels of glutathione (GSH) were found to be significantly decreased in the blood and nasal mucosa in MC mice when compared to normal control mice. However, normalized lipid peroxidation and antioxidant defenses were reported in the glycyrrhizin-treated and lycopene-treated mice. Moreover, glycyrrhizin treatment still enhanced IFN-γ and reduced IL-4 levels in glycyrrhizin-treated mice. These findings demonstrated that glycyrrhizin treatment enhanced the antioxidant status and decreased the incidence of free radical-induced lipid peroxidation and improved immunity activities in the blood and nasal mucosa of AR mice.

Mouse models of allergic diseases

The increasing prevalence of allergic diseases worldwide is posing significant socio-economic challenges. The pathogenesis of these diseases reflects a complex interaction of genetic and environmental factors. The heterogeneity of disease phenotypes challenges the concept of single mechanisms of disease. As human experimentation is limited, animal models have been developed to provide insights into pathogenesis and potential for discovery of novel therapeutics. Mice have served in models of many of the allergic diseases including asthma, allergic rhinitis, food allergy, atopic dermatitis (AD), and allergic conjunctivitis. Although much has been learned from these investigations, there are limitations when these models are translated to the human diseases.

Allergy and the eye

The eye represents an ideal and frequent site for the allergic reactions. The term 'allergic conjunctivitis' refers to a collection of disorders that affect the lid, conjunctiva and/or cornea. Even though the diagnosis is essentially clinical, local tests such as cytology, conjunctival provocation and tear mediator analysis can be performed. The immunoglobulin E (IgE)-mediated mechanism does not explain completely the severity and the clinical course of chronic allergic ocular diseases such as vernal (VKC) and atopic keratoconjunctivitis (AKC), which are probably also related to T cell-mediated responses, massive eosinophil attraction and activation and non-specific hypersensitivity. An altered balance between T helper type 1 (Th1) and Th2 cells and between Th1- and Th2-types of cytokines is thought to be responsible of the development of ocular allergic disorders. New findings suggest that a wide range of cytokines, chemokines, proteases and growth factors are involved by complex interwoven interactions rather than distinct and parallel pathways. In addition, several non-specific enzymatic systems may be activated during acute and chronic allergic inflammation, thus contributing to the complex pathogenesis of the disease. Current drug treatment for ocular allergy targets the key mechanisms involved in the development of clinical disease: mast cells with mast cell stabilizers, histamine with histamine receptor antagonists and inflammation with corticosteroids, severe inflammation with immunomodulators. None of these agents lacks side effects and none abolishes signs and symptoms completely. New therapeutic strategies are still needed to respond to the complex pathogenesis of severe forms of ocular allergy such as VKC and AKC.

Immunopathogenesis of ocular allergy: a schematic approach to different clinical entities

PURPOSE OF REVIEW

The immunopathogenesis of ocular allergic disorders is generally related to the specific immunoglobulin E-mediated mast cell activation and the following cascade of inflammatory mediators. Seasonal and perennial allergic conjunctivitis, however, are the only ocular diseases to involve solely type I hypersensitivity. The other main forms, vernal and atopic keratoconjunctivitis, have a more complex immunological basis and a chronic inflammatory component. Involvement of inflammatory cells, particularly eosinophils and T cells, cytokines and proteases can lead to more serious corneal damage with vision-threatening potential.

RECENT FINDINGS

Experimental allergic conjunctival models and clinical research studies have shown that T helper type 2-related mechanisms are definitely involved in the sensitization phase of ocular allergy, however, both T helper type 1 and type 2 cytokines are overexpressed in the active disease, contributing to the development of ocular inflammation.

SUMMARY

A review of the recent literature allows us to better understand the mechanisms involved in the development of ocular allergy and to guide us toward a more schematic approach, which could possibly be useful in forming a new classification, standardizing clinical phases and individuating new treatment targets.