Enhanced expression of cyclooxygenase-2 in glaucomatous dog eyes

Cyclooxygenase-2 (COX-2)-derived prostaglandins (PGs) are shown to play important pathophysiologic roles in various disease states. Recently, the effectiveness of topical PGs in reducing intraocular pressure (IOP) has stimulated further interest in the physiologic function of COX-2 and PGs in normal and glaucomatous eyes. Therefore, we investigated the cell-type distribution and expression of COX-2 in normal and glaucomatous dog eyes.

Using isoform-specific antibodies, we immunohistochemically evaluated COX-2 expression in formalin-fixed and paraffin-embedded normal (n = 5) and glaucomatous (n = 17) dog eyes.

In the normal eyes, only minimal COX-2 immunoreactivity was observed in the ciliary epithelium. In the glaucomatous eyes, COX-2 expression was further observed in the cornea and corneoscleral limbus. In the cornea, moderate to strong COX-2 expression was observed in all corneal layers (epithelium, stromal cells and endothelium), with the greatest expression present in the epithelial layer. In the corneoscleral limbus area, COX-2 immunoreactivity was noted in the stromal cells of sclera, trabecular meshwork and endothelial cells of the angular aqueous plexus.

Increased expression of COX-2 in dog glaucomatous eyes suggests that COX-2-derived PGs may have a potential role in the pathogenesis of canine glaucoma.