MiR-135b-5p relieves sevoflurane-induced postoperative cognitive dysfunction by inhibiting JAK2–STAT3-mediated hepcidin upregulation

Postoperative cognitive dysfunction (POCD) is a prevalent neurological complication following anesthesia and surgery. Recent evidence has implicated dysregulation of cerebral iron metabolism in the pathogenesis of this condition. Our previous studies have demonstrated that sevoflurane anesthesia disrupts iron homeostasis, ultimately leading to POCD. Hepcidin plays a crucial role in maintaining systemic iron homeostasis. The JAK2–STAT3 signaling pathway is essential for hepcidin transcription. According to earlier research, microRNA-135b-5p (miR-135b-5p) targets JAK2 to suppress the JAK2-STAT3 pathway. However, little is currently known about how miR-135b-5p contributes to the dysregulation of iron metabolism induced by sevoflurane. This study sought to determine whether miR-135b-5p reduces sevoflurane-induced POCD by inhibiting the JAK2-STAT3 pathway, thereby lowering hepcidin production. A mouse model of sevoflurane-induced cognitive impairment was established. Behavioral changes were assessed at various time points following exposure using novel objective recognition (NOR) and fear conditioning (FC) tests. Molecular and structural modifications were examined using Prussian blue staining, local field potential recordings, western blotting, Real- Time Quantitative PCR, and immunofluorescence staining. Besides, the detection of malondialdehyde (MDA), glutathione (GSH), reactive oxygen species (ROS), and lipid peroxidation (LPO) levels was conducted by biochemical methods. Our results demonstrated that sevoflurane exposure resulted in decreased freezing time during the cue period of the FCT, a lower recognition index, and reduced β power in local field potentials. Besides, diminished NeuN intensity was observed in the CA1 region during histological analysis, along with increased Perls’ Prussian blue staining, and upregulation of Ferritin-L/H and TfR1. Molecular analyses revealed elevated levels of ROS, MDA, and LPO, accompanied by decreased GSH and GPX4, consistent with oxidative stress. Further assessments, including Western blotting, Real- Time Quantitative PCR, and immunofluorescence, confirmed enhanced JAK2 and STAT3 phosphorylation, as well as downregulation of FPN1, and increased Hepcidin expression. These changes were attenuated by MiR-135b-5p. However, the protective effects of MiR-135b-5p were abolished by pharmacological activation of JAK2 with Coumermycin A1. Our findings suggest that miR-135b-5p attenuates sevoflurane-induced POCD in mice by suppressing hepcidin expression through inhibition of the JAK2–STAT3 pathway, indicating a potential therapeutic approach for sevoflurane-induced POCD. • This study identifies miR-135b-5p as a novel protective factor against sevoflurane-induced cognitive deficits. • Sevoflurane anesthesia causes cognitive impairment by disrupting iron metabolism and promoting oxidative stress in the hippocampus. • Overexpression of miR-135b-5p alleviates hippocampal iron overload, oxidative damage, and neuronal loss following sevoflurane exposure. • The cognitive benefits of miR-135b-5p include the rescue of memory function and the restoration of hippocampal network activity. • The neuroprotection conferred by miR-135b-5p is effectively reversed by pharmacological activation of JAK2, confirming its crucial upstream role.