Astrocytic Cystine/Glutamate Antiporters Promote Diabetic Encephalopathy via the Induction of Glutamate Excitotoxicity

Background Cystine/glutamate antiporter (xCT) imports extracellular cystine in exchange for intracellular glutamate. Although it plays an essential role in diabetes-associated processes such as impaired wound healing, its contribution to diabetic encephalopathy (DE) remains unclear. Methods Wild-type and xCT-deficient (xCT-/-) mice were subjected to type 2 diabetes mellitus (T2DM) induction using a highfat diet combined with streptozotocin. xCT expression and activity in the brain were evaluated through quantitative polymerase chain reaction, Western blotting, immunofluorescence, chloride-dependent [14C]-L-cystine uptake, and measurements of extracellular glutamate. An adeno-associated virus (AAV)-mediated Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR)/Cas9 approach was employed to generate region-specific, cell type-restricted xCT knockout animals. Neuronal injury and cognitive function were evaluated via in vivo propidium iodide (PI) and neuronal nuclei antigen (NeuN) double staining, the Y-maze spontaneous alternation test, the Morris water maze test, and the object location test. Results xCT deficiency protected mice from T2DM-induced DE. Mechanistically, hyperglycemia upregulated xCT expression via activating transcription factor 4 (ATF4), thereby enhancing xCT function in hippocampal astrocytes. This maladaptive increase promoted excessive extracellular glutamate, neuronal loss, and cognitive impairment. Both astrocyte-specific deletion of xCT and pharmacological inhibition of xCT ameliorated these deficits. Conclusion These findings identify astrocytic xCT as a key driver of diabetes-induced glutamate excitotoxicity and DE progression, underscoring its potential as a therapeutic target.