Influence of Antiglaucoma Treatment in Corneal and Conjunctival Adrenergic Receptors and Its Relation With Conjunctival Inflammation

Abstract

Purpose: : The beneficial effects of topical brimonidine include a reduction in intraocular pressure and neuroprotection, but its relation with conjunctival inflammation remains unknown. This study investigates the effect of the topical application of an α-2 agonist adrenergic receptors (AR) anti glaucoma drug (brimonidine) and a ß blocker (timolol) in the ocular surface in vitro.

Methods: : A conjunctival (IOBA-NHC) and a corneal (HCE) cell line were cultured under three different conditions: 1) supplemented DMEM/F-12 culture medium, 2) supplemented DMEM/F-12 culture medium and brimonidine (Alphagan®), 3) supplemented DMEM/F-12 culture medium and brimonidine + timolol (Combigam®) for 24 and 48 hours. RNA was isolated from untreated and treated cells and the cDNA was synthesized. Real time PCR was performed using Taqman Probes to evaluate expression of 2αa, 2αb, and 2αc AR. Amplification of one housekeeping gene (GAPDH) was performed to normalize the amount of expression levels. The results were obtained applying the comparative Ct method, and the untreated cells were used as calibrator.

Results: : The AR expression at basal levels in the HCE cell line were 2A > 2B > 2C and in the IOBA-NHC cell line 2A < 2B < 2C. In both cell lines the AR expression was higher after 24 and 48 hours of the treatment with Alphagan® than the untreated cells. Surprisingly, the expression of all the receptors was the highest after 24 and 48 hours of the treatment with Combigam® except for the 2αc after 48 hours in the HCE cell line, that is lesser than the cells treated with Alphagan® but higher that untreated cells.

Conclusions: : The ß blocker timolol does not reduce the gene expression of α-2 receptors that is induced with the use of an α-2 agonist adrenergic receptor.

Keywords: conjunctiva • cornea: epithelium • conjunctivitis