Postconditioning with Sevoflurane or Propofol Alleviates Lipopolysaccharide-Induced Neuroinflammation but Exerts Dissimilar Effects on the NR2B Subunit and Cognition

Adiponectin deficiency is a critical factor contributing to cognitive dysfunction in obese mice after sevoflurane exposure

BACKGROUND

The number of major operations performed in obese patients is expected to increase given the growing prevalence of obesity. Obesity is a risk factor for a range of postoperative complications including perioperative neurocognitive disorders. However, the mechanisms underlying this vulnerability are not well defined. We hypothesize that obese subjects are more vulnerable to general anaesthesia induced neurotoxicity due to reduced levels of adiponectin. This hypothesis was tested using a murine surgical model in obese and adiponectin knockout mice exposed to the volatile anaesthetic agent sevoflurane.

METHODS

Obese mice were bred by subjecting C57BL/6 mice to a high fat diet. Cognitive function, neuroinflammatory responses and neuronal degeneration were assessed in both obese and lean mice following exposure to 2 h of sevoflurane to confirm sevoflurane-induced neurotoxicity. Thereafter, to confirm the role of adiponectin deficiency in, adiponectin knockout mice were established and exposed to the sevoflurane. Finally, the neuroprotective effects of adiponectin receptor agonist (AdipoRon) were examined.

RESULTS

Sevoflurane triggered significant cognitive dysfunction, neuroinflammatory responses and neuronal degeneration in the obese mice while no significant impact was observed in the lean mice. Similar cognitive dysfunction and neuronal degeneration were also observed in the adiponectin knockout mice after sevoflurane exposure. Administration of AdipoRon partially prevented the deleterious effects of sevoflurane in both obese and adiponectin knockout mice.

CONCLUSIONS

Our findings demonstrate that obese mice are more susceptible to sevoflurane-induced neurotoxicity and cognitive impairment in which adiponectin deficiency is one of the underlying mechanisms. Treatment with adiponectin receptor agonist ameliorates this vulnerability. These findings may have therapeutic implications in reducing the incidence of anaesthesia related neurotoxicity in obese subjects.

Effect of General Anesthetic Agents on Microglia

The effects of general anesthetic agents (GAAs) on microglia and their potential neurotoxicity have attracted the attention of neuroscientists. Microglia play important roles in the inflammatory process and in neuromodulation of the central nervous system. Microglia-mediated neuroinflammation is a key mechanism of neurocognitive dysfunction during the perioperative period. Microglial activation by GAAs induces anti-inflammatory and pro-inflammatory effects in microglia, suggesting that GAAs play a dual role in the mechanism of postoperative cognitive dysfunction. Understanding of the mechanisms by which GAAs regulate microglia may help to reduce the incidence of postoperative adverse effects. Here, we review the actions of GAAs on microglia and the consequent changes in microglial function. We summarize clinical and animal studies associating microglia with general anesthesia and describe how GAAs interact with neurons via microglia to further explore the mechanisms of action of GAAs in the nervous system.

Dual roles of anesthetics in postoperative cognitive dysfunction: Regulation of microglial activation through inflammatory signaling pathways

Postoperative cognitive dysfunction (POCD) is a prevalent clinical entity following surgery and is characterized by declined neurocognitive function. Neuroinflammation mediated by microglia is the essential mechanism of POCD. Anesthetics are thought to be a major contributor to the development of POCD, as they promote microglial activation and induce neuroinflammation. However, this claim remains controversial. Anesthetics can exert both anti- and pro-inflammatory effects by modulating microglial activation, suggesting that anesthetics may play dual roles in the pathogenesis of POCD. Here, we review the mechanisms by which the commonly used anesthetics regulate microglial activation via inflammatory signaling pathways, showing both anti- and pro-inflammatory properties of anesthetics, and indicating how perioperative administration of anesthetics might either relieve or worsen POCD development. The potential for anesthetics to enhance cognitive performance based on their anti-inflammatory properties is further discussed, emphasizing that the beneficial effects of anesthetics vary depending on dose, exposure time, and patients' characteristics. To minimize the incidence of POCD, we recommend considering these factors to select appropriate anesthetics.

Perioperative considerations in patients with chemotherapy-induced cognitive impairment: a narrative review

Patients with cancer may suffer from a decline in their cognitive function after various cancer therapies, including surgery, radiation, and chemotherapy, and in some cases, this decline in cognitive function persists even years after completion of treatment. Chemobrain or chemotherapy-induced cognitive impairment, a well-established clinical syndrome, has become an increasing concern as the number of successfully treated cancer patients has increased significantly. Chemotherapy-induced cognitive impairment can originate from direct neurotoxicity, neuroinflammation, and oxidative stress, resulting in alterations in grey matter volume, white matter integrity, and brain connectivity. Surgery has been associated with exacerbating the inflammatory response associated with chemotherapy and predisposes patients to develop postoperative cognitive dysfunction. As the proportion of patients living longer after these therapies increases, the magnitude of impact and growing concern of post-treatment cognitive dysfunction in these patients has also come to the fore. We review the clinical presentation, potential mechanisms, predisposing factors, diagnostic methods, neuropsychological testing, and imaging findings of chemotherapy-induced cognitive impairment and its intersection with postoperative cognitive dysfunction.

Egr2 contributes to age-dependent vulnerability to sevoflurane-induced cognitive deficits in mice

Sevoflurane inhalation is prone to initiate cognitive deficits in infants. The early growth response-2 (Egr-2) gene is DNA-binding transcription factor, involving in cognitive function. In this study we explored the molecular mechanisms underlying the vulnerability to cognitive deficits after sevoflurane administration. Six-day-old (young) and 6-week-old (early adult) mice received anesthesia with 3% sevoflurane for 2 h daily for 3 days. We showed that multiple exposures of sevoflurane induced significant learning ability impairment in young but not early adult mice, assessed in Morris water maze test on postnatal days 65. The integrated differential expression analysis revealed distinct transcription responses of Egr family members in the hippocampus of the young and early adult mice after sevoflurane administration. Particularly, Egr2 was significantly upregulated after sevoflurane exposure only in young mice. Microinjection of Egr2 shRNA recombinant adeno-associated virus into the dentate gyrus alleviated sevoflurane-induced cognitive deficits, and abolished sevoflurane-induced dendritic spins loss and BDNF downregulation in young mice. On the contrary, microinjection of the Egr2 overexpression virus in the dentate gyrus aggravated learning ability impairment induced by sevoflurane in young mice but not early adult mice. Furthermore, we revealed that sevoflurane markedly upregulated the nuclear factors of activated T-cells NFATC1 and NFATC2 in young mice, which were involved in Egr2 regulation. In conclusion, Egr2 serves as a critical factor for age-dependent vulnerability to sevoflurane-induced cognitive deficits.

Sevoflurane Post-treatment Mitigates Oxygen-glucose Deprivationinduced Pyroptosis of Hippocampal Neurons by Regulating the Mafb/DUSP14 Axis

BACKGROUND

Ischemic brain injury often results in irreversible pyroptosis of neurons. Sevoflurane (Sevo) post-treatment exerts an alleviative role in neuroinflammation.

OBJECTIVES

This work evaluated the mechanism of Sevo post-treatment in oxygen-glucose deprivation (OGD)-induced pyroptosis of rat hippocampal neurons.

METHODS

Rat hippocampal neuron cell line H19-7 cells were treated with OGD, followed by posttreatment of 2% Sevo. The expression patterns of Mafb ZIP Transcription Factor B (Mafb) and dual- specificity phosphatase 14 (DUSP14) were determined via quantitative real-time polymerase chain reaction (qRT-PCR) and Western blotting methods. H19-7 cell viability and the release of lactate dehydrogenase (LDH) were examined via the cell counting kit-8 and LDH assay kits. Levels of pyroptosis-related proteins and cytokines NOD-like receptor family, pyrin domain containing 3 (NLRP3), N-term cleaved Gasdermin-D (GSDMD-N), cleaved-caspase-1, interleukin (IL)-1β, and IL-18 were also examined. The binding relation between Mafb and the DUSP14 promoter was detected. Besides, the roles of Mafb/DUSP14 in OGD-induced pyroptosis of rat hippocampal neurons were investigated through functional rescue experiments.

RESULTS

Mafb and DUSP14 expression levels were decreased in OGD-induced hippocampal neurons. Sevo post-treatment up-regulated Mafb and DUSP14, facilitated H19-7 cell viability, inhibited LDH release, and reduced levels of NLRP3, GSDMD-N, cleaved-caspase-1, IL-1β, and IL-18. Mafb increased DUSP14 expression via binding to the DUSP14 promoter. Repressing Mafb or DUSP14 exacerbated pyroptosis of hippocampal neurons.

CONCLUSION

Sevo post-treatment increased Mafb and DUSP14 expressions, which repressed OGDinduced pyroptosis of hippocampal neurons.

Transient neuroinflammation following surgery contributes to long-lasting cognitive decline in elderly rats via dysfunction of synaptic NMDA receptor

Background

Perioperative neurocognitive disorders (PNDs) are considered the most common postoperative complication in geriatric patients. However, its pathogenesis is not fully understood. Surgery-triggered neuroinflammation is a major contributor to the development of PNDs. Neuroinflammation can influence N-methyl-D-aspartate receptor (NMDAR) expression or function which is closely associated with cognition. We, therefore, hypothesized that the persistent changes in NMDAR expression or function induced by transient neuroinflammation after surgery were involved in the development of PNDs.

Methods

Eighteen-month-old male Sprague–Dawley rats were subjected to abdominal surgery with sevoflurane anesthesia to establish the PNDs animal model. Then, we determined the transient neuroinflammation by detecting the protein levels of proinflammatory cytokines and microglia activation using ELISA, western blot, immunohistochemistry, and microglial morphological analysis from postoperative days 1–20. Persistent changes in NMDAR expression were determined by detecting the protein levels of NMDAR subunits from postoperative days 1–59. Subsequently, the dysfunction of synaptic NMDAR was evaluated by detecting the structural plasticity of dendritic spine using Golgi staining. Pull-down assay and western blot were used to detect the protein levels of Rac1-GTP, phosphor-cofilin, and Arp3, which contribute to the regulation of the structural plasticity of dendritic spine. Finally, glycyrrhizin, an anti-inflammatory agent, was administered to further explore the role of synaptic NMDAR dysfunction induced by transient neuroinflammation in the neuropathogenesis of PNDs.

Results

We showed that transient neuroinflammation induced by surgery caused sustained downregulation of synaptic NR2A and NR2B subunits in the dorsal hippocampus and led to a selective long-term spatial memory deficit. Meanwhile, the detrimental effect of neuroinflammation on the function of synaptic NMDARs was shown by the impaired structural plasticity of dendritic spines and decreased activity of the Rac1 signaling pathways during learning. Furthermore, anti-inflammatory treatment reversed the downregulation and hypofunction of synaptic NR2A and NR2B and subsequently rescued the long-term spatial memory deficit.

Conclusions

Our results identify sustained synaptic NR2A and NR2B downregulation and hypofunction induced by transient neuroinflammation following surgery as important contributors to the development of PNDs in elderly rats.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12974-022-02528-5.

Sevoflurane Induces Neurotoxicity in the Animal Model with Alzheimer's Disease Neuropathology via Modulating Glutamate Transporter and Neuronal Apoptosis

Perioperative neurocognitive disorders are frequently observed in postoperative patients and previous reports have shown that pre-existing mild cognitive impairment with accumulated neuropathology may be a risk factor. Sevoflurane is a general anesthetic agent which is commonly used in clinical practice. However, the effects of sevoflurane in postoperative subjects are still controversial, as both neurotoxic or neuroprotective effects were reported. The purpose of this study is to investigate the effects of sevoflurane in 3 × Tg mice, a specific animal model with pre-existing Alzheimer’s disease neuropathology. 3 × Tg mice and wild-type mice were exposed to 2 h of sevoflurane respectively. Cognitive function, glutamate transporter expression, MAPK kinase pathways, and neuronal apoptosis were accessed on day 7 post-exposure. Our findings indicate that sevoflurane-induced cognitive deterioration in 3 × Tg mice, which was accompanied with the modulation of glutamate transporter, MAPK signaling, and neuronal apoptosis in the cortical and hippocampal regions. Meanwhile, no significant impact was observed in wild-type mice. Our results demonstrated that prolonged inhaled sevoflurane results in the exacerbation of neuronal and cognitive dysfunction which depends on the neuropathology background.