SIRT1 activation attenuates microglia-mediated synaptic engulfment in postoperative cognitive dysfunction

The NF-κB Pathway: Key Players in neurocognitive functions and related disorders

Perioperative neurocognitive disorder (PND) is a common complication of surgical anesthesia, yet its precise etiology remains unclear. Neuroinflammation is a key feature of PND, influenced by both patient -related and surgical variables. The nuclear factor-κB (NF-κB) transcription factor family plays a critical role in regulating the body's immunological proinflammatory response, which is pivotal in the development of PND. Surgery and anesthesia trigger the activation of the NF-κB signaling pathway, leading to the initiation of inflammatory cascades, disruption of the blood-brain barrier, and neuronal injury. Immune cells and glial cells are central to these pathological processes in PND. Furthermore, this study explores the interactions between NF-κB and various signaling molecules, including Tlr4, P2X, α7-nAChR, ROS, HIF-1α, PI3K/Ak, MicroRNA, Circular RNA, and histone deacetylases, within the context of PND. Targeting NF-κB as a therapeutic approach for PND shows promise as a potential treatment strategy.

Propofol ameliorates cognitive deficits following splenectomy in aged rats by inhibiting ferroptosis via the SIRT1/Nrf2/GPX4 pathway

The aim of this study was to investigate the mechanism by which propofol reduces postoperative cognitive dysfunction after splenectomy in aged rats. The rats in the model group and propofol group were subjected to splenectomy, and anesthetized with isoflurane and propofol, respectively. Utilizing the western blotting to assess the expression of sirtuin-1 (SIRT1) in the hippocampus. Molecular docking technology was used to predict the binding ability of propofol and SIRT1. Behavioral tests were performed using the Morris water maze, and the hippocampus was isolated for mechanistic investigations. Molecular docking showed that propofol and SIRT1 had a strong binding affinity. The expression of SIRT1 and its related proteins Nrf2, HO-1, NQO1, and GPX4 in the model rats was decreased compared with the sham group. Moreover, the model group exhibited cognitive decline, such as extended escape latency and decreased number of platform crossings. Pathological analysis showed that the number of apoptotic neurons, the levels of oxidative stress and neuroinflammation, the iron deposition, and the expressions of ACSL4 and TFR1 were increased, while the expressions of SLC7A11 and FTH1 were decreased in the hippocampal CA1 region within the model group. These pathological changes in the propofol group were, however, less than those in the model group. Nevertheless, the SIRT1 inhibitor increased these pathological changes compared with the propofol group. Compared with isoflurane, propofol inhibits ferroptosis in the hippocampus of splenectomized rats by causing less downregulation of the SIRT1/Nrf2/GPX4 pathway, thereby reducing the negative impact on cognitive function.

Dexmedetomidine enhances Mitophagy via PINK1 to alleviate hippocampal neuronal Pyroptosis and improve postoperative cognitive dysfunction in elderly rat

Postoperative cognitive dysfunction (POCD) is a common complication in elderly surgical patients, significantly affecting their quality of life. Dexmedetomidine (Dex), an anesthetic, has shown promise in alleviating POCD, but its underlying mechanism remains unclear. This study aims to explore how Dex improves POCD in aged rats by targeting the PINK1-mediated mitochondrial autophagy pathway, reducing caspase-1/11-GSDMD-induced hippocampal neuronal pyroptosis. Transcriptome sequencing identified 300 differentially expressed genes enriched in the mitochondrial autophagy pathway in Dex-treated POCD rat hippocampal tissue, with Pink1 as a key candidate. In a POCD rat model, Dex treatment upregulated hippocampal PINK1 expression. In vitro experiments using H19-7 rat hippocampal neurons revealed that Dex enhanced mitochondrial autophagy and suppressed neuronal pyroptosis by upregulating PINK1. Further mechanistic validation demonstrated that Dex activated PINK1-mediated mitochondrial autophagy, inhibiting caspase-1/11-GSDMD-induced neuronal pyroptosis. In vivo experiments confirmed Dex's ability to reduce caspase-1/11-GSDMD-dependent hippocampal neuronal pyroptosis and improve postoperative cognitive function in aged rats. Dexmedetomidine improves postoperative cognitive dysfunction in elderly rats by enhancing mitochondrial autophagy via PINK1 upregulation, mitigating caspase-1/11-GSDMD-induced neuronal pyroptosis.

Interleukin-33 ameliorates perioperative neurocognitive disorders by modulating microglial state

Perioperative neurocognitive disorders (PND) are cognitive dysfunctions that usually occur in elderly patients after anesthesia and surgery. Microglial overactivation is a key underlying mechanism. Interleukin-33 (IL-33) is a member of the IL-1 family that orchestrates microglial function. In the present study, we explored how IL-33, which regulates microglia, contributes to cognitive improvement in a male mouse model of PND. An exploratory laparotomy was performed to establish a PND model. The expression levels of IL-33 and its receptor ST2 were evaluated using Western blot. IL-33/ST2 secretion, microglial density, morphology, phagocytosis of synapse, and proliferation, and dystrophic microglia were assessed using immunofluorescence. Synaptic plasticity was measured using Golgi staining and long-term potentiation. The Morris water maze and open field test were used to evaluate cognitive function and anxiety. Hippocampal expression of IL-33 and ST2 were elevated on postoperative day 3. We confirmed that IL-33 was secreted by astrocytes and neurons, whereas ST2 mainly colocalized with microglia. IL-33 treatment induced microgliosis after anesthesia and surgery. These microglia had larger soma sizes and shorter and fragmented branches. Compared to the Surgery group, IL-33 treatment reduced the synaptic phagocytosis of microglia and increased microglial proliferation and dystrophic microglia. IL-33 treatment also reversed the impaired synaptic plasticity and cognitive function caused by anesthesia and surgery. In conclusion, these results indicate that IL-33 plays a key role in regulating microglial state and synaptic phagocytosis in a PND mouse model. IL-33 treatment has a therapeutic potential for improving cognitive dysfunction in PND.

Peripheral inflammation as a potential mechanism and preventive strategy for perioperative neurocognitive disorder under general anesthesia and surgery

General anesthesia, as a commonly used medical intervention, has been widely applied during surgical procedures to ensure rapid loss of consciousness and pain relief for patients. However, recent research suggests that general anesthesia may be associated with the occurrence of perioperative neurocognitive disorder (PND). PND is characterized by a decline in cognitive function after surgery, including impairments in attention, memory, learning, and executive functions. With the increasing trend of population aging, the burden of PND on patients and society's health and economy is becoming more evident. Currently, the clinical consensus tends to believe that peripheral inflammation is involved in the pathogenesis of PND, providing strong support for further investigating the mechanisms and prevention of PND.

Syringaresinol attenuates Tau phosphorylation and ameliorates cognitive dysfunction induced by sevoflurane in aged rats

Cognitive dysfunction following anesthesia with agents such as sevoflurane is a significant clinical problem, particularly in elderly patients. This study aimed to explore the protective effects of the phytochemical syringaresinol (SYR) against sevoflurane-induced cognitive deficits in aged Sprague-Dawley rats and to determine the underlying mechanisms involved. We assessed the impact of SYR on sevoflurane-induced cognitive impairment, glial activation, and neuronal apoptosis through behavioral tests (Morris water maze), immunofluorescence, Western blotting for key proteins involved in apoptosis and inflammation, and enzyme-linked immunosorbent assays for interleukin-1β, tumor necrosis factor-α, and interleukin-6. SYR treatment mitigated sevoflurane-induced cognitive decline, reduced microglial and astrocyte activation (decreased Iba-1 and GFAP expression), and countered neuronal apoptosis (reduced Bax, cleaved-caspase3, and cleaved-PARP expression). SYR also enhanced Sirtuin-1 (SIRT1) expression and reduced p-Tau phosphorylation; these effects were reversed by the SIRT1 inhibitor EX527. SYR exerts neuroprotective effects on sevoflurane-induced cognitive dysfunction by modulating glial activity, apoptotic signaling, and Tau phosphorylation through the SIRT1 pathway. These findings could inform clinical strategies to safeguard cognitive function in patients undergoing anesthesia.

Impaired synaptic plasticity and decreased glutamatergic neuron excitability induced by SIRT1/BDNF downregulation in the hippocampal CA1 region are involved in postoperative cognitive dysfunction

BACKGROUND

Postoperative cognitive dysfunction (POCD) is a common complication after anesthesia/surgery, especially among elderly patients, and poses a significant threat to their postoperative quality of life and overall well-being. While it is widely accepted that elderly patients may experience POCD following anesthesia/surgery, the exact mechanism behind this phenomenon remains unclear. Several studies have indicated that the interaction between silent mating type information regulation 2 homologue 1 (SIRT1) and brain-derived neurotrophic factor (BDNF) is crucial in controlling cognitive function and is strongly linked to neurodegenerative disorders. Hence, this research aims to explore how SIRT1/BDNF impacts cognitive decline caused by anesthesia/surgery in aged mice.

METHODS

Open field test (OFT) was used to determine whether anesthesia/surgery affected the motor ability of mice, while the postoperative cognitive function of 18 months old mice was evaluated with Novel object recognition test (NORT), Object location test (OLT) and Fear condition test (FC). The expressions of SIRT1 and other molecules were analyzed by western blot and immunofluorescence staining. The hippocampal synaptic plasticity was detected by Golgi staining and Long-term potentiation (LTP). The effects of SIRT1 and BDNF overexpression as well as chemogenetic activation of glutamatergic neurons in hippocampal CA1 region of 18 months old vesicular glutamate transporter 1 (VGLUT1) mice on POCD were further investigated.

RESULTS

The research results revealed that older mice exhibited cognitive impairment following intramedullary fixation of tibial fracture. Additionally, a notable decrease in the expression of SIRT1/BDNF and neuronal excitability in hippocampal CA1 glutamatergic neurons was observed. By increasing levels of SIRT1/BDNF or enhancing glutamatergic neuron excitability in the CA1 region, it was possible to effectively mitigate synaptic plasticity impairment and ameliorate postoperative cognitive dysfunction.

CONCLUSIONS

The decline in SIRT1/BDNF levels leading to changes in synaptic plasticity and neuronal excitability in older mice could be a significant factor contributing to cognitive impairment after anesthesia/surgery.

Liraglutide improves sevoflurane-induced postoperative cognitive dysfunction via activating autophagy and inhibiting apoptosis

BACKGROUND

Postoperative cognitive dysfunction (POCD) is a common postoperative complication in elderly patients. Liraglutide (LRG) has high homology (97%) with natural glucagon like peptide-1, and it has been proved to be effective in some nervous system diseases. Whether LRG could regulate POCD has not been reported.

METHODS

Sevoflurane (Sev) was used to simulate postoperative cognitive dysfunction (POCD) model. Morris water maze test was performed to evaluate the memory ability and neurological function of rats. Escape latency, swim distance, crossing platform times, average velocity, and targeting quadrant time were analyzed. The cell apoptosis, mRNA and protein expression were measured through flow cytometry, PCR, and western blotting, respectively.

RESULTS

LRG significantly improved the memory ability and neurological function of Sev-treated rats, but 3-MA reversed the effects of LRG. LRG remarkably inhibited apoptosis but up-regulated autophagy related proteins both in vivo and in vitro levels. However, knocking down AMPK could markedly reverse the influence of LRG on apoptosis, autophagy, and cell apoptosis.

CONCLUSIONS

LRG induced autophagy activation can maintain cell homeostasis and promote cell survival by blocking the apoptotic pathway. LRG could improve Sev-induced POCD via activating autophagy, inhibiting apoptosis, and regulating AMPK/mTOR signaling pathway. This study provides a novel therapeutic strategy for the prevention and treatment of POCD.

Transforming Growth Factor β1 Ameliorates Microglial Activation in Perioperative Neurocognitive Disorders

Perioperative neurocognitive disorder (PND) is a common complication of surgery and anesthesia, especially among older patients. Microglial activation plays a crucial role in the occurrence and development of PND and transforming growth factor beta 1 (TGF-β1) can regulate microglial homeostasis. In the present study, abdominal surgery was performed on 12-14 months-old C57BL/6 mice to establish a PND model. The expression of TGF-β1, TGF-β receptor 1, TGF-β receptor 2, and phosphor-smad2/smad3 (psmad2/smad3) was assessed after anesthesia and surgery. Additionally, we examined changes in microglial activation, morphology, and polarization, as well as neuroinflammation and dendritic spine density in the hippocampus. Behavioral tests, including the Morris water maze and open field tests, were used to examine cognitive function, exploratory locomotion, and emotions. We observed decreased TGF-β1 expression after surgery and anesthesia. Intranasally administered exogenous TGF-β1 increased psmad2/smad3 colocalization with microglia positive for ionized calcium-binding adaptor molecule 1. TGF-β1 treatment attenuated microglial activation, reduced microglial phagocytosis, and reduced surgery- and anesthesia-induced changes in microglial morphology. Compared with the surgery group, TGF-β1 treatment decreased M1 microglial polarization and increased M2 microglial polarization. Additionally, surgery- and anesthesia-induced increase in interleukin 1 beta and tumor necrosis factor-alpha levels was ameliorated by TGF-β1 treatment at postoperative day 3. TGF-β1 also ameliorated cognitive function after surgery and anesthesia as well as rescue dendritic spine loss. In conclusion, surgery and anesthesia induced decrease in TGF-β1 levels in older mice, which may contribute to PND development; however, TGF-β1 ameliorated microglial activation and cognitive dysfunction in PND mice.

Electroacupuncture pretreatment protects against anesthesia/surgery-induced cognitive decline by activating CREB via the ERK/MAPK pathway in the hippocampal CA1 region in aged rats

Effective preventive measures against postoperative cognitive dysfunction in older adults are urgently needed. In this study, we investigated the effect of electroacupuncture (EA) on anesthesia and surgery-induced cognitive decline in aged rats by RNA-seq analysis, behavioral testing, Golgi-Cox staining, dendritic spine analysis, immunofluorescence assay and western blot analysis. EA ameliorated anesthesia and surgery induced-cognitive decline. RNA-seq analysis identified numerous differentially-expressed genes, including 353 upregulated genes and 563 downregulated genes, after pretreatment with EA in aged rats with postoperative cognitive dysfunction. To examine the role of CREB in EA, we injected adeno-associated virus (AAV) into the CA1 region of the hippocampus bilaterally into the aged rats to downregulate the transcription factor. EA improved synaptic plasticity, structurally and functionally, by activating the MAPK/ERK/CREB signaling pathway in aged rats. Together, our findings suggest that EA protects against anesthesia and surgery-induced cognitive decline in aged rats by activating the MAPK/ERK/CREB signaling pathway and enhancing hippocampal synaptic plasticity.

Research progress of postoperative cognitive dysfunction in cardiac surgery under cardiopulmonary bypass

Cardiopulmonary bypass (CPB) is often used in cardiothoracic surgery because its nonphysiological state causes pathophysiological changes in the body, causing multiorgan and multitissue damage to varying degrees. Postoperative cognitive dysfunction (POCD) is a common central nervous system complication after cardiac surgery. The etiology and mechanism of POCD are not clear. Neuroinflammation, brain mitochondrial dysfunction, cerebral embolism, ischemia, hypoxia, and other factors are related to the pathogenesis of POCD. There is a close relationship between CPB and POCD, as CPB can cause inflammation, hypoxia and reperfusion injury, and microemboli formation, all of which can trigger POCD. POCD increases medical costs, seriously affects patients' quality of life, and increases mortality. Currently, there is a lack of effective treatment methods for POCD. Commonly used methods include preoperative health management, reducing inflammation response during surgery, preventing microemboli formation, and implementing individualized rehabilitation programs after surgery. Strengthening preventive measures can minimize the occurrence of POCD and its adverse effects.

Neuroprotective effects of different doses of Maresin1 pretreatment in aged rats after anesthesia/surgery

OBJECTIVE

The study is to investigate the neuroprotective effect of different doses of Maresin1 pretreatment in aged rats after anesthesia/surgery and the related mechanisms.

METHODS

Aged male rats were randomly divided into a control group, an anesthesia/surgery group, and low, medium, and high-dose Maresin1 pretreatment groups, and the hippocampus was taken for study. The Morris water maze was performed to detect the cognitive ability of rats. Western blot and immunofluorescence were used to detect the expression of glial fibrillary acidic protein (GFAP) and central nervous system-specific protein (S100β). The ultrastructure of astrocytes was observed by a transmission electron microscope. Quantitative real-time PCR was used to detect the relative expression of IL-1β, IL-6, and TNF-α mRNA.

RESULTS

Compared with the control group, the cognition of rats in the anesthesia/surgery group was significantly reduced. The expression of astrocyte markers (GFAP and S100β) in the hippocampus of rats in the anesthesia/surgery group was increased. The levels of hippocampal inflammatory cytokines (TNF-α, IL-1β, and IL-6) were also higher in the anesthesia/surgery group than in the control group. After pretreatment with different doses of Maresin1, the cognitive impairment of rats was alleviated to varying degrees. Maresin1 pretreatment decreased the expression of astrocyte markers and inflammatory factors in the hippocampus of rats after anesthesia/surgery, and improve the microstructures of activated astrocytes, especially in the medium-dose group.

CONCLUSION

Pretreatment with Maresin1 (especially at medium-dose) showed neuroprotective effects in aged rats after anesthesia/surgery, which may be related to the inhibition of astrocyte activation.