Hydrogen sulfide ameliorates cognitive dysfunction in diabetic encephalopathy by activating PI3K/AKT/GSK-3β signaling...

Diabetic encephalopathy (DE) is a serious complication of diabetes mellitus characterized by progressive cognitive dysfunction, but its underlying mechanisms remain incompletely understood. Tau hyperphosphorylation and necroptosis are key pathological events in neurodegenerative diseases, but their roles in DE and the capacity of hydrogen sulfide (H₂S) to regulate these processes have not been investigated. We tested whether H₂S attenuates Tau hyperphosphorylation and necroptosis through the PI3K/AKT/GSK-3β signaling pathway to improve cognitive impairment in DE. In vitro, HT22 hippocampal neurons were exposed to high glucose (85 mM), and in vivo, a streptozotocin-induced diabetic mouse model was established. NaHS served as an exogenous H₂S donor, and LY294002 was employed as a PI3K-specific inhibitor. Phosphoproteomic analysis revealed that high glucose suppressed PI3K/AKT/GSK-3β signaling and concurrently elevated Tau phosphorylation (p-Tau) and necroptosis markers (p-RIPK1, p-MLKL). NaHS treatment activated PI3K/AKT/GSK-3β signaling, reduced p-Tau, p-RIPK1, and p-MLKL levels, and normalized necroptotic morphology observed by transmission electron microscopy. Flow cytometry and lactate dehydrogenase release assays confirmed that NaHS attenuated high glucose-induced cell death. In diabetic mice, NaHS improved spatial learning and memory in the Morris water maze and novel object recognition tests, restored hippocampal CA1 neuron survival, and upregulated synaptic proteins (PSD95, SYP). Co-immunofluorescence demonstrated colocalization of p-Tau and p-MLKL in the hippocampal CA1 region, which was reduced by NaHS. All protective effects of NaHS were partially reversed by LY294002, establishing a PI3K-dependent mechanism. Network pharmacology identified 76 H₂S-DE overlapping targets; machine learning ranked AKT family genes as top predictors. These findings demonstrate that H₂S improves DE by activating PI3K/AKT/GSK-3β signaling, attenuating Tau hyperphosphorylation and necroptosis.