Background/Purpose: Although it has been traditionally assumed that most glycosylation occurs on membrane or secreted proteins and lipids, it is well known that cytoplasmic or even nuclear proteins can be glycosylated, through an O-GlcNAc (O-linked β-N-acetylglucosamine) modification coupled to Ser or Thr residues. Its evaluation in diseases such as cancer or metabolic syndrome has led to the suggestion that they play an active role both in cell metabolism, intracellular signaling and transcription regulation. However, there are still no studies comparing the level of O-GlcNAc between Rheumatoid Arthritis (RA) patients and healthy donors. To compare the levels of O-GlcNAc in the cytoplasm of peripheral blood mononuclear cells (PBMC) of healthy donors and patients with RA, as well as its possible relationship with clinical parameters. 

Methods: Patients were evaluated at the Hospital General de Cuernavaca, SSM. RA disease activity was evaluated through DAS28. The donor blood samples were obtained from the sate blood bank. After isolating the PBMC (Ficoll Hypaque), cytosolic proteins were recovered, in the presence of protease inhibitors. Levels of O-GlcNAc were evaluated using Western blot, employing a specific LR2 antibody. The levels of O-GlcNAc transferase (OGT) and O-GlcNAcase (OGA) expression, responsible for the addition and elimination of the GlcNAc group, were evaluated in parallel. Differences between groups were evaluated using Student’s t and Mann Whitney’s test and their correlation with DAS28 was evaluated using Spearman’s test. 

Results: 21 patients with RA and 20 healthy donors were included. A global comparison showed that patients had significantly less immunoreactivity than donors. The glycosylation pattern was clearly different in patients compared to donors, where the 73 and 112 kDa glycoproteins seem to be exclusive of RA patients. These results were consistent with a greater OGT/OGA balance in donors with respect to patients. On the other hand, levels of O-GlcNAc showed a significant negative correlation with DAS28 (rho=-0.579, p<0.008). 

Conclusion: The results seem to suggest that patients with RA present a reduced ratio of OGT:OGA expression, as well as less O-GlcNAc glycosylation, compared to donors. The relationship between the levels of O-GlcNAc and DAS28 suggests that this glycosylation patterns could reflect a functional state of PBMC in patients with RA. Study financed by CB-2010-2#155392 (CONACyT).

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/intracellular-o-glc-nac-alterations-in-mononuclear-blood-cell-of-rheumatoid-arthritis-patients/