Esculetin ameliorates sevoflurane-induced cognitive dysfunction in aged mice by suppressing neuroinflammation via inhibition of NF-κB/NLRP3 signaling.

Abstract

Introduction: The widely used inhalational anesthetic sevoflurane increases susceptibility to postoperative cognitive dysfunction (POCD), especially among the elderly. Esculetin, a natural coumarin compound derived from Cortex Fraxini, possesses anti-inflammatory and neuroprotective activities. This study aimed to determine whether esculetin mitigates sevoflurane-induced POCD and to clarify its underlying mechanisms.

Material and methods: POCD was induced in aged male C57BL/6J mice by 3% sevoflurane inhalation. Esculetin was administered 1 h before each exposure. Learning, memory, and locomotion were evaluated by Morris water maze and open field tests. Hippocampal apoptosis was detected by TUNEL staining and western blotting (WB) of apoptosis-associated proteins. Neuroinflammation was assessed through Iba-1 immunofluorescence, ELISA, WB, and RT-qPCR. NF-κB and NLRP3 inflammasome pathways were analyzed by WB and immunofluorescence. In vitro, HT22 neurons were treated with sevoflurane and/or esculetin, and microglia-mediated neuroinflammation was examined using a BV2-HT22 co-culture system.

Results: In aged mice, esculetin alleviated sevoflurane-induced spatial learning and memory impairments. Hippocampal neuronal apoptosis was reduced, as indicated by fewer TUNEL-positive cells and restored expression of Bcl-2, Bax, and cleaved caspase-3. Esculetin also inhibited microglial activation, along with the sevoflurane-induced elevation of proinflammatory cytokines (TNF-α, IL-1β, IL-6) and M1 microglial markers (iNOS, CD68). Mechanistically, esculetin inhibited sevoflurane-triggered phosphorylation of IκBα and p65, as well as NLRP3, apoptosis-associated speck-like protein containing a CARD (ASC), and caspase-1 upregulation. In vitro, esculetin dose-dependently protected HT22 cells against sevoflurane-induced apoptosis. In the co-culture system, esculetin attenuated microglia-driven neuroinflammation and NF-κB/NLRP3 inflammasome activation in HT22 cells.

Conclusions: Esculetin ameliorates sevoflurane-induced cognitive deficits in aged mice by inhibiting hippocampal neuroinflammation and neuronal apoptosis through NF-κB/NLRP3 inflammasome inhibition.