Ruscogenin alleviates cognitive dysfunction by inhibiting the activation of isoflurane-induced NLRP3 inflammasome in aged mice

Ruscogenin exerts an anti-inflammatory effect in the pathogenesis of various human diseases, including pulmonary hypertension, acute lung injury, acute pancreatitis and cerebral ischemia. Its role in isoflurane-induced rats with postoperative cognitive dysfunction (POCD) was investigated in this study. Aged rats were exposed to isoflurane for establishing a model of POCD, and administered with ruscogenin by gavage. Cognitive dysfunction was evaluated by the Morris water maze test. Hematoxylin and Eosin (H&E) staining was designed to assess neuronal damage. Markers of brain damage and neuroinflammation were detected by enzyme-linked-immunosorbent serologic assay. Isoflurane exposure caused impaired cognitive function by increasing escape latency, decreasing the time taken for crossing target and time in target quadrant. However, administration of ruscogenin reversed these cognitive dysfunctions. Abnormal morphological phenomena on neurons and enhanced levels of serum calcium-binding protein β (S-100β) and neuron-specific enolase (NSE) were identified in mice post-isoflurane exposure. Administration of ruscogenin ameliorated the neuronal morphological damages and reduced the levels of S-100β and NSE in the hippocampi of isoflurane-induced aged mice. Ruscogenin also attenuated isoflurane-induced enhancements in the levels of Interleukin (IL)-1β, IL-6 and tumor necrosis factor-alpha in the hippocampi of mice. Isoflurane-induced enhancements in the mRNA expression levels of NLR family pyrin domain containing 3 (NLRP3), ASC, IL-1β and IL-18 proteins were also restored by administration of ruscogenin. Ruscogenin exerted neuroprotective effects against isoflurane-induced cognitive dysfunction and neuroinflammation through blocking of NLRP3 pathway.