Multifunctional Protein Alpha2-Macroglobulin in Tear Fluid and Blood Serum of Patients with Glaucoma

Alpha2-macroglobulin (α2-MG) is a multifunctional glycoprotein. Due to the variety of its functions there can be several ways of its involvement in the pathogenesis of the glaucomatous optic neuropathy, including neuroinflammation, amyloid deposition, neurotoxicity. It is known that α2-MG level in aqueous humor is increased in glaucoma but there is scant information about its concentration in blood and tear fluid.

Purpose. To determine the α2-MG activity in tear fluid and blood serum of glaucoma patients to broaden of understanding of its role in the pathogenesis of glaucoma and to estimate its informativity for the characterization of the disease clinical course.

Methods. Tear fluid was collected from 21 patients with primary open-angle glaucoma and 17 healthy adults. Activity of α2-MG was measured enzymatically with BAPNA as a substrate.

Results. Activity of α2-MG in tears was 20 times lower than in blood serum. In healthy controls it was 4.66 ± 0.27 nmol / min×ml in tears and 92.35 ± 5.44 nmol / min×ml in blood. Totally in glaucoma patients it was 54 % higher than in controls in tears (р < 0.008), and 35 % higher in blood (р < 0.05). Particularly patients without pseudoexfoliative syndrome showed a significant α2-MG activity increase in tears (2 times) while in serum it was 67 % higher than in controls. In patients with pseudoexfoliative glaucoma α2-MG activity was not increased in tears nor in blood.

Conclusion. Primary open-angle glaucoma without pseudoexfoliative syndrome cause the increase of α2-MG activity in tears and in blood in contrast with pseudoexfoliative glaucoma. This fact indicates that pathogenetic ways of these types of glaucoma are different. The increased α2-MG activity may be the risk factor for the development of glaucoma without pseudoexfoliative syndrome.

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