Chronic rapid eye movement sleep deprivation aggravates the pathogenesis of Alzheimer’s disease by decreasing brain O-GlcNAc cycling in mice

This study investigated the role of O-GlcNAc cycling in Alzheimer's disease-related changes in brain pathophysiology induced by chronic REM sleep deprivation (CSD) in mice. CSD increased amyloid beta (Aβ) and p-Tau accumulation and impaired learning and memory (L/M) function. CSD decreased dendritic length and spine density. CSD also increased the intensity of postsynaptic density protein-95 (PSD-95) staining. All of these Alzheimer's disease (AD) pathogenic changes were effectively reversed through glucosamine (GlcN) treatment by enhancing O-GlcNAcylation. Interestingly, the lelvel of O-GlcNAcylated-Tau (O-Tau) exhibited an opposite trend compared to p-Tau, as it was elevated by CSD and suppressed by GlcN treatment. CSD increased neuroinflammation, as indicated by elevated levels of glial fibrillary acidic protein and IBA-1-positive glial cells in the brain, which were suppressed by GlcN treatment. CSD promoted the phosphorylation of GSK3β and led to an upregulation in the expression of endoplasmic reticulum (ER) stress regulatory proteins and genes. These alterations were effectively suppressed by GlcN treatment. Minocycline not only suppressed neuroinflammation induced by CSD, but it also rescued the decrease in O-GlcNAc levels caused by CSD. Minocycline also reduced AD neuropathy without affecting CSD-induced ER stress. Notably, overexpressing O-GlcNAc transferase in the dentate gyrus region of the mouse brain rescued CSD-induced cognitive dysfunction, neuropathy, neuroinflammation, and ER stress responses. Collectively, our findings reveal that dysregulation of O-GlcNAc cycling underlies CSD-induced AD pathology and demonstrate that restoration of OGlcNAcylation protects against CSD-induced neurodegeneration.