Abstract
Purpose: :
In a recent study, a carbohydrate–binding protein, E–selectin (ELAM–1), was identified as a specific molecular marker of glaucoma. Selectins are a family of transmembrane, carbohydrate–binding proteins characterized by their affinity for sialated and sulfated Lewisx (Lex) and Lewisa (Lea) oligosaccharides. In our attempt to understand the role of carbohydrate–based recognition systems in the pathogenesis of glaucoma, the goal of the present study was to determine which specific members of the selectin family and/or their counterreceptors are differentially expressed in trabecular meshwork (TM) and aqueous humor of patients with POAG.
Methods: :
TaqMan Q–PCR was used to determine which specific members of the selectin family are differentially expressed in whole glaucomatous and normal TM tissue. Slotblot analysis was performed to determine whether selectins and their counter–receptors, specifically sialyl–Lex , are differentially expressed in the aqueous humor of normal subjects and of patients with POAG.
Results: :
Q–PCR analysis revealed that the expression of E–selectin as well as that of another member of the selectin family, P–selectin, is markedly upregulated in TMs of donors with POAG (Normal:POAG, E–selectin 1:10.3; P–selectin 1:12.7, triplicate samples from three normal and two glaucoma specimens were analyzed). Slot blot analysis revealed that E–selectin as well as its counterreceptor, sialyl–Lex, were also present in significantly higher amounts in aqueous humor of patients with POAG compared to the aqueous humor collected from cataract patients (Sialyl Lex [ng/µl]: Glaucoma, 24.42 ± 4.34, Control: 9.93 ± 3.29; E–selectin: POAG [ng/µl]: 110.85± 21.33, Control, 51.36 ng ± 7.58; triplicate samples from two each of control and POAG samples were analyzed). Analysis of additional aqueous samples as well as P–selectin and sialyl–Lea is currently underway.
Conclusions: :
These data support the hypothesis that one or more selectin–mediated, carbohydrate–based recognition systems have the potential to play a role in the pathogenesis of glaucoma.
Keywords: aqueous • glycoconjugates/glycoproteins • gene/expression