Hyperglycemia Aggravates the Cerebral Ischemia Injury via Protein O-GlcNAcylation.

Background: At least one-third of Alzheimer's disease (AD) patients have cerebrovascular abnormalities, micro- and macro-infarctions, and ischemic white matter alterations. Stroke prognosis impacts AD development due to vascular disease. Hyperglycemia can readily produce vascular lesions and atherosclerosis, increasing the risk of cerebral ischemia. Our previous research has demonstrated that protein O-GlcNAcylation, a dynamic and reversible post-translational modification, provides protection against ischemic stroke. However, the role of O-GlcNAcylation in the exacerbation of cerebral ischemia injury due to hyperglycemia remains to be elucidated.

Objective: In this study, we explored the role and underlying mechanism of protein O-GlcNAcylation in the exacerbation of cerebral ischemia injury caused by hyperglycemia.

Methods: High glucose-cultured brain microvascular endothelial (bEnd3) cells were injured by oxygen-glucose deprivation. Cell viability was used as the assay result. Stroke outcomes and hemorrhagic transformation incidence were assessed in mice after middle cerebral artery occlusion under high glucose and streptozotocin-induced hyperglycemic conditions. Western blot estimated that O-GlcNAcylation influenced apoptosis levels in vitro and in vivo.

Results: In in vitro analyses showed that Thiamet-G induces upregulation of protein O-GlcNAcylation, which attenuates oxygen-glucose deprivation/R-induce injury in bEnd3 cells cultured under normal glucose conditions, while aggravated it under high glucose conditions. In in vivo analyses, Thiamet-G exacerbated cerebral ischemic injury and induced hemorrhagic transformation, accompanied by increased apoptosis. While blocking protein O-GlcNAcylation with 6-diazo-5-oxo-L-norleucine alleviated cerebral injury of ischemic stroke in different hyperglycemic mice.

Conclusion: Overall, our study highlights the crucial role of O-GlcNAcylation in exacerbating cerebral ischemia injury under conditions of hyperglycemia. O-GlcNAcylation could potentially serve as a therapeutic target for ischemic stroke associated with AD.