Sevoflurane Promotes Neurodegeneration Through Inflammasome Formation in APP/PS1 Mice

Targeting NLRP3 inflammasome for neurodegenerative disorders

Neuroinflammation is a key pathological feature in neurological diseases, including Alzheimer's disease (AD). The nucleotide-binding domain leucine-rich repeat-containing proteins (NLRs) belong to the pattern recognition receptors (PRRs) family that sense stress signals, which play an important role in inflammation. As a member of NLRs, the NACHT, LRR and PYD domains-containing protein 3 (NLRP3) is predominantly expressed in microglia, the principal innate immune cells in the central nervous system (CNS). Microglia release proinflammatory cytokines to cause pyroptosis through activating NLRP3 inflammasome. The active NLRP3 inflammasome is involved in a variety of neurodegenerative diseases (NDs). Recent studies also indicate the key role of neuronal NLRP3 in the pathogenesis of neurological disorders. In this article, we reviewed the mechanisms of NLRP3 expression and activation and discussed the role of active NLRP3 inflammasome in the pathogenesis of NDs, particularly focusing on AD. The studies suggest that targeting NLRP3 inflammasome could be a novel approach for the disease modification.

Minocycline Attenuates Sevoflurane-Induced Postoperative Cognitive Dysfunction in Aged Mice by Suppressing Hippocampal Apoptosis and the Notch Signaling Pathway-Mediated Neuroinflammation

Postoperative cognitive dysfunction (POCD), an important postoperative neurological complication, is very common and has an elevated incidence in elderly patients. Sevoflurane, an inhaled anesthetic, has been demonstrated to be associated with POCD in both clinical and animal studies. However, how to prevent POCD remains unclear. Minocycline, a commonly used antibiotic can cross the blood-brain barrier and exert an inhibitory effect on inflammation in the central nervous system. The present work aimed to examine the protective effect and mechanism of minocycline on sevoflurane-induced POCD in aged mice. We found that 3% sevoflurane administered 2 h a day for 3 consecutive days led to cognitive impairment in aged animals. Further investigation revealed that sevoflurane impaired synapse plasticity by causing apoptosis and neuroinflammation and thus induced cognitive dysfunction. However, minocycline pretreatment (50 mg/kg, i.p, 1 h prior to sevoflurane exposure) significantly attenuated learning and memory impairments associated with sevoflurane in aged animals by suppressing apoptosis and neuroinflammation. Moreover, a mechanistic analysis showed that minocycline suppressed sevoflurane-triggered neuroinflammation by inhibiting Notch signaling. Similar results were also obtained in vitro. Collectively, these findings suggested minocycline may be an effective drug for the prevention of sevoflurane-induced POCD in elderly patients.

Knockdown of UAF1 alleviates sevoflurane-induced cognitive impairment and neurotoxicity in rats by inhibiting pro-inflammatory signaling and oxidative stress

Evidence has shown that suppression of the activation of NLRP3 inflammasome could ameliorate surgery/sevoflurane (SEV)-induced post-operative cognitive dysfunction (POCD). However, the underlying mechanisms remain unclear. UAF1 acts as a binding partner of USP1, which inhibits the ubiquitination-mediated degradation of NLRP3, indicating that UAF1 may be implicated in POCD through regulating the NLRP3 inflammasome. Here, we studied the role of UAF1/NLRP3 in SEV-induced cognitive impairment and neurotoxicity in rats. Neonatal rats were randomly divided into control, SEV, SEV+AAV-shNC and SEV+AAV-shUAF1 (UAF1-downregulated) groups. Morris water maze (MWM) test was applied to assess cognitive impairment. TUNEL staining, qRT-PCR and ELISA were used to assess the apoptosis and inflammation markers, respectively. The levels of superoxide dismutase (SOD), catalase (CAT) and malondialdehyde (MDA) were quantified to determine oxidative stress. The results showed that SEV treatment led to significant cognitive impairment, increased apoptosis in hippocampal tissues, upregulation of MDA and inflammatory factors (TNF-α, IL-1β, IL-18), as well as a decrease in SOD and CAT levels. All of the above observations were reversed by UAF1 downregulation. Furthermore, depletion of UAF1 neutralized SEV-mediated increase in p-NLRP3, p-IκBα and p-p65 levels. Altogether, the current study demonstrated that knockdown of UAF1 could alleviate SEV-induced cognitive impairment and neurotoxicity in rats by inhibiting pro-inflammatory signaling and oxidative stress.