Prostaglandin D2 induces chemotaxis in eosinophils via its receptor CRTH2 and eosinophils may cause severe ocular inflammation in patients with allergic conjunctivitis.

PURPOSE: Eosinophils are known to have important roles in the pathogenesis of allergic conjunctivitis. Prostaglandin (PG) D2, which has been implicated as a factor in allergic diseases, is known to have chemotactic activity for eosinophils. Its receptor, chemoattractant receptor homologous molecule expressed on TH2 (CRTH2), serves as a receptor for PGD2 and has been reported to mediate PGD2-dependent migration of eosinophils. In the present study, both eosinophil toxic activity for corneal epithelial cells and chemotaxis induced by PGD2 in normal volunteers were investigated. Expression of CRTH2 in normal subjects was also measured.
METHODS: Primary cultured corneal epithelial cells and eosinophils in serum from normal volunteers were used and a human corneal epithelial cell line was established. Studies were performed with/without amniotic membrane. CRTH2 expression on eosinophils was assessed by flow cytometry. Chemotaxis experiments were performed using a modified Boyden chamber technique.
RESULTS: Corneal epithelial cells cultured with eosinophils showed higher floating epithelial cells and epithelial defect than those cultured in the absence of eosinophils. Flow cytometry analysis revealed that eosinophils expressed CRTH2. PGD2 induced chemotaxis of eosinophils.
CONCLUSIONS: Corneal epithelial damage might be caused by eosinophils, which are recruited by PGD2 secretion via CRTH2 expressed on eosinophils.