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Editors Selection IGR 16-4

Clinical Forms of Glaucoma: Antioxidant status in exfoliation syndrome

Comment by Robert Ritch & Sandra Fernando on:

24153 Antioxidant status in the aqueous humour of patients with glaucoma associated with exfoliation syndrome, Ferreira SM; Lerner SF; Brunzini R et al., Eye, 2009; 23: 1691-1697

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There are significant differences in the aqueous humor composition of patients with exfoliation syndrome (XFS) compared to controls. Ascorbate and glutathione concentrations are decreased^1,2 while those of 8-isoprostaglandin F_2a and reactive oxygen species (ROS) are increased,^1,3 suggesting a role for free radical induced oxidative damage in the pathobiology of XFS. Ferreira et al. (1163) compared the antioxidant status of the aqueous humor in exfoliative glaucoma (XFG) that of age-matched POAG patients and cataract patients. They found lower total reactive antioxidant potential and ascorbate and greater levels of glutathione peroxidase (GPx) in XFG than in POAG and both of these groups differed significantly from patients with cataract alone. There is increasing evidence that ROS play a key role in the pathogenesis of POAG.^4,5 The results of the current study suggest that greater alterations of the antioxidant defense system are present in the aqueous humor of patients with XFG than in POAG and cataract patients. Ascorbate, which scavenges superoxide anion, hydroxyl radicals, and singlet oxygen, is present at high concentrations in aqueous. GPx removes cytotoxic oxygenderived free radicals utilizing glutathione as a cofactor; therefore an increased GPx activity leads to a decreased glutathione concentration. Glutathione is involved in ascorbic acid metabolism, and its depletion produces ascorbyl radicals that cannot be regenerated to ascorbic acid. Ascorbate also modulates the synthesis of various extracellular molecules such as collagen, elastin, laminin, and glycosaminoglycans. Exfoliation syndrome is a disorder of elastic tissue and the extracellular matrix. Thus, alterations in ascorbate concentrations may influence the exfoliative process itself in addition to a role in glaucomatous damage.

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