Glycosylation Patterns and Gel Forming Mucins According to Severity of Dry Eye Syndrome

Abstract

Purpose:: To identify gel-forming mucin concentrations and glycosylation patterns of tear proteins of different patient groups according to severity and etiology of dry eye syndrome.

Methods:: Patients were classified in 7 groups of dry eye syndrome according to tear film break-up time (BUT) <7 sec, Schirmer II test (ST) <7 mm and symptoms <12 points in a validated questionnaire by Donate, et al. We obtained a tear sample of both eyes and performed a quantification of protein concentration. ELISA for MUC5AC and MUC2 and lectin modified ELISA with Sambucus nigra agglutinin, SNA (recognizes syalic acid at α2,6 position), Maackia amurensis agglutinin, MAA (recognizes syalic acid at α2,3 position) and Amaranthus caudatus lectin, ACL (recognizes N-acetylgalactosamine 1-3) were performed. Each probe was performed using 1 ∝g of total protein. Descriptive statistics were performed for demographic variables and ANOVA test for identification of differences between groups.

Results:: 65 patients were included, mean age 44 years (18-83), 37% male (n=24) and 63% female (n=41). Secondary Sjögren group showed the greatest concentration of MUC5AC and MUC2 compared with the other groups (p < 0.05), and also the lowest concentration of protein identified with SNA and the highest identified with MAA (p < 0.05). The lowest total protein concentration was obtained in the group with low ST and low BUT compared with the other groups (p < 0.05). The protein concentration identified with ACL did not have significative difference between groups.

Conclusions:: The secondary Sjögren patients showed a high MUC5AC and MUC2 concentration and up-regulation of syalic acid in α2,3 position with down regulation of syalic acid in α2-6 position in total protein. There were no significative differences in the tests performed between the groups of dry eye syndrome according to symptoms, BUT and ST. This suggests that the clinical severity of dry eye did not affect the glycosylation patterns as demonstrated by the different probes. The results suggest that the inflammation observed in Sjögren patients affects the glycosylation and also the regulation of expression of gel forming mucins. Despite the severity of symptoms, low BUT and low ST the groups that are not associated with surface inflammation did not show altered protein glycosylation compared with healthy subjects.

Keywords: protein structure/function • cornea: basic science • detection