The role of adhesion molecules in human eosinophil and basophil recruitment

Cetirizine reduces inflammatory cell recruitment and ICAM-1 (or CD54) expression on conjunctival epithelium in both early- and late-phase reactions after allergen-specific challenge

BACKGROUND

Allergen-specific conjunctival challenge (ASCC) is a safe and reproducible experimental model of allergic conjunctivitis and a useful tool in the evaluation of effectiveness and possible mechanisms of action of drugs commonly used in the treatment of allergic diseases.

OBJECTIVE

The protective effect of cetirizine on inflammatory changes after ASCC was assessed in 12 patients with rhinoconjunctivitis caused by Parietaria judaica in a double-blind study.

METHODS

After a screening ASCC was performed, patients were randomized into two treatment groups; each patient was given cetirizine (oral tablets) 10 mg twice daily, or matching placebo for 3 1/2 days in off-pollen season. Clinical evaluation (itching, hyperemia, lacrimation, and swelling of eyelids) and cytologic assessment (number of inflammatory cells in conjunctival scraping and evaluation of intercellular adhesion molecule-1 (ICAM-1)/CD54 expression on epithelial cells) were performed at baseline, 30 minutes (i.e., early-phase reaction [EPR]), 6 hours, and 24 hours (i.e., late-phase reaction [LPR]) after ASCC, before and after treatment.

RESULTS

The EPR clinical events and the EPR total number of inflammatory cells were significantly reduced by cetirizine compared with placebo. The LPR clinical events and inflammatory cell recruitment were reduced by cetirizine in a similar manner. Both eosinophil and neutrophil numbers were decreased by active drug in EPR and LPR. Furthermore, ICAM-1/CD54 expression was significantly reduced by cetirizine in both the EPR and LPR compared with placebo.

CONCLUSIONS

This study shows that cetirizine has a protective effect on clinical and cellular EPR and LPR events (including ICAM-1/CD54 expression on epithelium) induced by ASCC.

The effects of glucocorticoids on human eosinophils

It is readily apparent that eosinophils are important targets of steroid effects. Disruption of the cytokine network by glucocorticoids can indirectly diminish eosinophil generation, survival, and function. In addition, glucocorticoids appear to have direct effects on the survival, and perhaps on the function, of these cells. Rapid advances in our knowledge of the biochemistry of signal transduction, as well as the interaction between cell surface receptors and RNA transcription machinery, will allow detailed analysis of the mechanisms by which the function and life cycle of eosinophils are influenced by glucocorticoids.