Astragalus Polysaccharide Enhances O‐ <scp>GlcNAcylation</scp> Through <scp>OGT</scp> to Improve Intervertebral Disc Degeneration in Rats

Astragalus polysaccharides (APS) are a crucial bioactive component known for their various pharmacological properties. Abnormal O-linked β-N-acetylglucosamine modification (O-GlcNAcylation) is noted in cases of intervertebral disc degeneration (IVDD). Nonetheless, it remains uncertain whether APS regulates the process of O-GlcNAcylation associated with IVDD. We employed molecular docking, cycloheximide chase assay, immunohistochemistry, and immunoprecipitation to investigate APS-mediated OGT/O-GlcNAcylation regulation of Nrf2. The effects of APS and its role in promoting the O-GlcNAcylation of Nrf2 in IVDD through both in vivo and in vitro studies are discussed. In vitro investigations demonstrated an increase in the levels of OGT and O-GlcNAcylation in nucleus pulposus cells (NPCs) following exposure to tert-butyl hydroperoxide (TBHP). APS further facilitated improvements in OGT expression and O-GlcNAcylation processes, restoring the viability of NPCs inhibited by TBHP and promoting the synthesis of collagen II and aggrecan, while reducing apoptosis. Mechanistically, APS promotes the expression of OGT by targeting it. Furthermore, O-GlcNAcylation mediated by OGT stabilizes the expression of Nrf2 via the ubiquitin-proteasome pathway. Rescue experiments indicated that the disruption of either OGT or Nrf2 expression negated the protective role of APS on NPCs. Ultimately, both in vitro and in vivo studies indicated that APS significantly enhanced OGT expression and O-GlcNAcylation, which subsequently improved Nrf2 expression and contributed to the alleviation of IVDD in rats. APS promotes O-GlcNAcylation through OGT, thereby stabilizing the expression of Nrf2, which in turn contributes to the improvement of IVDD.