Exogenous hydrogen sulphide alleviates diabetes-associated cognitive decline by inhibiting ferroptosis through Nrf2/GPX4 signalling pathway

Aims Neuronal ferroptosis affects the pathogenesis of diabetes-associated cognitive decline (DACD). Exogenous hydrogen sulphide (H 2 S) treatment ameliorates cognitive deficits in diabetic mice. This study aimed to explore whether H 2 S exerts neuroprotective effects by suppressing ferroptosis through activation of Nrf2/GPX4 signalling pathway. Materials and methods STZ-induced diabetic mice received NaHS or NaHS combined with the Nrf2 inhibitor ML385, after which cognitive functions were evaluated using the Morris water maze test. Hippocampal neuronal damage and mitochondrial morphological changes were identified using transmission electron microscopy, haematoxylin and eosin (H&E) staining, Nissl staining, and immunofluorescence staining. The expression levels of reactive oxygen species (ROS), malondialdehyde (MDA), superoxide dismutase (SOD), glutathione (GSH), and iron were determined using assay kits. Western blotting was performed to evaluate the expression of the Nrf2/GPX4 axis, iron transport-related proteins, and GSH synthesis enzymes. Key findings Exogenous H 2 S treatment ameliorated cognitive deficits by mitigating hippocampal neuronal loss and improving synaptic ultrastructural integrity. The levels of ROS, MDA, and iron were reduced, whereas SOD, GSH, and Nrf2/GPX4 expression were increased following NaHS administration. Exogenous H 2 S also ameliorated mitochondrial impairment and suppressed ferroptosis in the hippocampal neurones. However, these neuroprotective effects were abolished by ML385. Diabetic mice cotreated with ML385 and NaHS exhibited prolonged escape latency and reduced time in the target quadrant. Additionally, ML385 co-administration with NaHS exacerbated neuronal damage, oxidative stress, synaptic ultrastructural abnormalities, and iron dysregulation, while downregulating Nrf2/GPX4 expression and inhibiting ferroptosis suppression. Significance Exogenous H 2 S treatment alleviates DACD by suppressing ferroptosis via activation of the Nrf2/GPX4 signalling pathway.