Papel da O-Glicosilação com N-acetil-glucosamina (O-GlcNAc) na celularidade e na expressão de correceptores de timócitos : envolvimento da caspase-3 via atividade de AMPK

Abstract

The thymus is a primary lymphoid organ, responsible for T cell lymphopoiesis. The activation of these cells induces important metabolic changes to meet their increasing cellular energy demand through aerobic glycolysis and increased pentose phosphate pathway flux. All these metabolic pathways produce substrates for the synthesis of uridine diphosphate-N-acetyl-glucosamine (UDP-GlcNAc), which promotes the elevation of O-GlcNAc levels, a post-translational modification of proteins considered as a nutritional sensor, but little is known about its influence in the thymus. Therefore, this study aims to verify the influence of O-GlcNAc on thymic cellularity, expression of thymocyte correlators, and thymus morphology, through important nutritional and apoptotic markers such as adenosine monophosphateactivated protein kinase (AMPK) and caspase-3. Male wistar rats treated with glucosamine 300mg/kg or saline, via intraperitoneal route for 21 days were used. The thymus was collected for analysis of thymic cellularity, quantification of the following proteins by western blotting: O-GlcNAc, OGT, CD3, CD4, CD8, p-AMPK, caspase-3 and morphometry. Glucosamine treatment was able to increase the global levels of O-GlcNAc in thymic tissue [1.00 vs 2.14±0.19 (Arbitrary Unit-AU)], OGT [1.00 vs 1.31±0.10 AU]. Elevation of O-Glycosylation in the thymus caused an increase in thymic index (0.10±0.00 vs 0.12±0.00 kg/mouse) and cellularity (446.90±55.12 vs 891.10±142.30 cells/ml). We observed that O-GlcNAc interfered with T-cell correlceptor expression, increasing the expression of CD3 (1.00 vs 1.13±0.03 UA) and reducing CD4 (1.00 vs 0.68±0.08 UA) and CD8 (1.00 vs 0.66±0.10 UA). We also saw that high level of O-GlcNAc was able to increase AMPK expression (1.00 vs 1.48±0.09 UA) and decrease caspase-3 expression (1.0 vs 0.44±0.07 UA). Thus OGlcNAc appears to influence cellularity and thymocyte correlceptor expression, and these effects may be associated with the ability of OGlucosylation to decrease caspase-3 activity via AMPK activation.