Purchase this article with an account.
C. Bucolo, A. Spartà, M. Baiula, A. Qasem, K. W. Ward, S. Spampinato; Levocabastine Interferes With Conjunctival Eosinophil Infiltration by Acting as an Antagonist of the Integrin VLA-4. Invest. Ophthalmol. Vis. Sci. 2007;48(13):2307.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
Levocabastine is an ophthalmic antiallergic agent acting as histamine H1-receptor antagonist. It has been proposed that, in allergic conjunctivitis (AC), levocabastine may also interfere with upregulation of the adhesion molecule ICAM-1 expressed on epithelial conjunctival cells whereas little is know on its effects on eosinophils. Eosinophils are important effector cells in AC. The adhesion molecule very late antigen (VLA)-4 (named also α4ß1 integrin) and its ligand, vascular cell adhesion molecule (VCAM)-1, are expressed in eosinophils and are known to play important roles in their infiltration and activation. In this study we investigated if levocabstine may act as VLA-4 antagonist and may affect conjuctival expression of VLA-4 in a model of AC.
A scintillation proximity assay (SPA) has been developed to measure levocabastine binding to VLA-4. This assay utilizes an anti-α4 integrin monoclonal antibody to simultaneously capture α4ß1 receptor from a cellular lysate and couple the integrin to anti-rabbit IgG antibody-coated SPA beads for binding detection of 125I-fibronectin to VLA-4. HEK 293 cells that stably overexpress human VLA-4 were used as a source of this integrin. This SPA assay allowed measurement of specific 125I-fibronectin binding as defined by displacement by the fibronectin CS-1 fragment (1978-1985). A human cell line, EoL-1, was used as suitable in vitro eosinophilic model. Dunkin-Hartley guinea pigs were used to induce an allergic conjunctivitis. All the animals were treated according to the ARVO Statement for the Use of Animals in Ophthalmic and Vision Research.
IC50 value for displacement of 125I-fibronectin binding by levocabastine was 585 µM. In EoL-1 cells we showed that levocabastine was effective to block the adhesion of cells to VCAM-1 (IC50 = 772 µM). In guinea pigs, sensitized by intraperitoneal injection of ovalbumin, 3 mg/eye of ovalbumin were dropped into the eye for the antigen challenge inducing AC and a significant increase of conjunctival VLA-4 (detected by western blotting). Levocabastine eye drops (500 µg/eye), applied 60 and 30 min before the antigen challenge, produced a noteworthy protection from AC and prevented the conjuctival elevation of VLA-4 as well as conjunctival eosinophil infiltration (evaluated through an eosinophil peroxidase assay).
Our findings indicate that levocabastine, acting as a VLA-4 antagonist, interferes with conjunctival eosinophil infiltration in AC.
This PDF is available to Subscribers Only