TL1A promotes the postoperative cognitive dysfunction in mice through NLRP3-mediated A1 differentiation of astrocytes

Actions of dexmedetomidine in regulating NLRP3 in postoperative cognitive dysfunction in aged mice via the autophagy-lysosome pathway

BACKGROUND AND PURPOSE

Autophagy-lysosomal pathway dysfunction leads to postoperative cognitive dysfunction (POCD). Dexmedetomidine (Dex) improves POCD, and we probed the effects of Dex on autophagy-lysosomal pathway dysfunction in a POCD model.

EXPERIMENTAL APPROACH

A POCD mouse model was established and intraperitoneally injected with Dex. Cognitive function was evaluated by Morris water maze/open field test/novel object recognition assay. Levels of neurotransmitters/inflammatory cytokines in hippocampus, and NLRP3/ASC/Cleaved Caspase-1 proteins were determined by ELISA/Western blot. NLRP3 inflammasome-mediated microglial activation/astrocyte A1 differentiation in the hippocampal CA1 region were assessed by immunofluorescence assay. BV-2 cells were treated with lipopolysaccharide (LPS) and Dex and/or the NLRP3 inflammasome activator Nigericin, and transfected with si-TFEB for co-culture with primary reactive astrocytes (RAs) to verify the function of Dex in vitro.

KEY RESULTS

Dex alleviated cognitive dysfunction in POCD mice and repressed NLRP3 inflammasome-mediated microglial activation and astrocyte A1 differentiation. NLRP3 inflammasome activation partially reversed the protective effect of Dex on the POCD condition. In vitro experiments verified the inhibitory properties of Dex on microglial activation and astrocyte A1 differentiation. Dex induces TFEB nuclear translocation, microglial autophagy and lysosomal biogenesis. By activating the autophagy-lysosome pathway, Dex regulated NLRP3 inflammasome-mediated microglial activation, inhibited astrocyte A1 differentiation and alleviated POCD in vivo.

CONCLUSION AND IMPLICATIONS

Dex regulates NLRP3 inflammasome-mediated hippocampal microglial activation by promoting TFEB nuclear translocation and activating the autophagy-lysosome pathway and inhibits astrocyte A1 differentiation, thereby alleviating POCD.

Inhibition of STAT3 phosphorylation attenuates perioperative neurocognitive disorders in mice with D-galactose-induced aging by regulating pro-inflammatory reactive astrocytes

BACKGROUND

Perioperative Neurocognitive Disorders (PND) are associated withanesthesia and surgery, especially in the elderly. Astrocyte activation in old mice correlates with PND development. These cells can switch to a pro-inflammatory or an anti-inflammatory phenotype, regulated by the STAT3 pathway. It remains unclear whether STAT3 can alleviate PND symptoms in elderly mice by modulating the transitions between these astrocyte phenotypes.

METHODS

Senescence was induced in eight-week-old male C57BL/6J mice with D-galactose, followed by tibial fracture surgery under anesthesia to model PND. On the third postoperative day, cognitive function was assessed using fear conditioning, synaptic plasticity using Golgi/ electrophysiology, and astrocyte phenotype /STAT3/pSTAT3(phosphorylated STAT3) using Western blot/immunofluorescence. The content of neurotrophic factors, including brain-derived neurotrophic factor (BDNF) and glial cell line-derived neurotrophic factor (GDNF), was also measured. Primary astrocytes were stimulated with the conditioned medium referred to as ACM to induce pro-inflammatory reactive astrocytes. Stattic, an inhibitor of STAT3 phosphorylation, was used to investigate its effects on astrocyte phenotypic transformation and hippocampus-dependent learning and memory in aging mice, both in vitro and in vivo.

RESULTS

On the third postoperative day, pSTAT3 levels and pro-inflammatory astrocytes increased in the hippocampal CA1 region, with no change in total STAT3 or anti-inflammatory astrocytes, accompanied by a decrease in GDNF and BDNF.ACM treatment of primary astrocytes promoted pro-inflammatory phenotype conversion, which was inhibited by stattic without affecting anti-inflammatory phenotype. Intraperitoneal injection of stattic in mice reduced the accumulation of pro-inflammatory astrocytes, increased the levels of BDNF and GDNF, enhanced synaptic plasticity, and improved hippocampus-dependent learning and memory functions in anesthesia-induced senescent mice, without altering anti-inflammatory astrocytes.

CONCLUSIONS

Inhibiting STAT3 phosphorylation may improve synaptic plasticity in the CA1 region of the hippocampus by modulating pro-inflammatory astrocytes, thereby alleviating perioperative neurocognitive dysfunction in D-galactose-induced aging mice.

Impaired hippocampal neurogenesis associated with regulatory ceRNA network in a mouse model of postoperative cognitive dysfunction

BACKGROUND

Postoperative cognitive dysfunction (POCD) represents a post-surgical complication that features progressive cognitive impairment and memory loss, often occurring in elderly patients. This study aimed to investigate the potential biological mechanisms underlying POCD.

METHODS

Male C57BL/6 mice (2 and 17 months old) were randomly assigned to surgery or control groups. The surgery group underwent laparotomy under 1.5% isoflurane anesthesia, while controls received no intervention. Cognitive function was assessed 7-10 days post-surgery using open field, Y-maze, and novel object recognition tests. Hippocampal mRNA expression was analyzed using Encyclopedia of Genes and Genomes (KEGG) and Gene Ontology (GO) enrichment. A competing endogenous RNA (ceRNA) network was constructed using microRNA (miRNA) target prediction databases (miRanda, miRTarbase, miRcode) and sequencing results. Key findings were validated by RT-qPCR and immunofluorescence. The Connectivity Map (CMap) database was queried to predict potential POCD treatments.

RESULTS

Aging significantly affected mice's spontaneous activity in the open field test (F1, 28 = 8.933, P < 0.01) and the proportion of time spent in the center area (F1, 28 = 5.387, P < 0.05). Surgery significantly reduced the rate of spontaneous alternations in the Y-maze (F1, 28 = 16.94, P < 0.001) and the recognition index in novel object recognition test (F1, 28 = 6.839, P < 0.05) in aging mice, but had no effect on young mice. Transcriptome analysis revealed that aging and surgery downregulated multiple neurogenesis-related genes in the hippocampus. Doublecortin (DCX) immunofluorescence staining confirmed reduced hippocampal neurogenesis in aging mice, which was further decreased after surgery. We identified several key lncRNAs and miRNAs implicated in neurogenesis regulation. Additionally, drugs were predicted as potential therapeutic candidates for POCD treatment.

CONCLUSION

Both aging and surgery have complex effects on the hippocampal transcriptome in mice. The significant decrease in neurogenesis may be a potential reason for the increased susceptibility of aging mice to POCD. The identified key regulatory lncRNAs, miRNAs, and drugs provide potential therapeutic targets for POCD prevention and treatment.

C3/C3aR Bridges Spinal Astrocyte-Microglia Crosstalk and Accelerates Neuroinflammation in Morphine-Tolerant Rats

AIMS

Communication within glial cells acts as a pivotal intermediary factor in modulating neuroimmune pathology. Meanwhile, an increasing awareness has emerged regarding the detrimental role of glial cells and neuroinflammation in morphine tolerance (MT). This study investigated the influence of crosstalk between astrocyte and microglia on the evolution of morphine tolerance.

METHODS

Sprague-Dawley rats were intrathecally treated with morphine twice daily for 9 days to establish morphine-tolerant rat model. Tail-flick latency test was performed to identify the analgesic effect of morphine. The role of microglia, astrocyte and C3-C3aR axis in morphine tolerance were elucidated by real-time quantitative polymerase chain reaction, Western blot, and immunofluorescence.

RESULTS

Chronic morphine treatment notably promoted the activation of microglia, upregulated the production of proinflammatory mediators (interleukin-1 alpha (IL-1α), tumor necrosis factor alpha (TNFα), and complement component 1q (C1q)). Simultaneously, it programed astrocytes to a pro-inflammatory phenotype (A1), which mainly expresses complement 3 (C3) and serping1. PLX3397 (a colony-stimulating factor 1 receptor (CSF1R) inhibitor), Compstain (a C3 inhibitor) and SB290157(a C3aR antagonist) could reverse the above pathological process and alleviate morphine tolerance to different extents.

CONCLUSION

Our findings identify C3-C3aR axis as an amplifier of microglia-astrocyte crosstalk, neuroinflammation and a node for therapeutic intervention in morphine tolerance.

Curcumin activates the Wnt/β-catenin signaling pathway to alleviate hippocampal neurogenesis abnormalities caused by intermittent hypoxia: A study based on network pharmacology and experimental verification

The purpose of this work was to investigate how curcumin (Cur) might enhance cognitive function and to gain a better understanding of the molecular mechanisms behind Cur's impacts on neurogenesis deficits brought on by intermittent hypoxia (IH). Using network pharmacology, we explored possible targets for Cur's obstructive sleep apnea (OSA) therapy. We established an IH model using C57BL/6 mice and c17.2 cells, and we assessed the influence of Cur on treatment outcomes as well as the effect of IH on cognitive function. Hippocampal damage and neurogenesis, as well as expression of core targets, were then examined. Network pharmacology analysis revealed that Cur has the potential for multi-target, multi-pathway therapy, with CTNNB1 and MYC as core target genes. The Morris water maze test showed that Cur (100 mg/kg, intragastrically) significantly improved cognitive dysfunction induced by IH. The hematoxylin and eosin (H&E) and Nissl staining indicated that Cur could alleviate damage to the hippocampus caused by IH. Immunohistochemistry, immunofluorescence, and western blotting results showed that Cur might promote neurogenesis and upregulate the expression of β-catenin and c-myc. In vitro, Cur (0.5 μM) has a protective effect on IH-induced neural stem cells (NSCs) injury and apoptosis and can restore the Wnt/β-catenin. Cur significantly increased the neurogenesis via the Wnt/β-catenin pathway, providing the scientific groundwork for the development of new treatment strategies for neurological damage linked to OSA.

Mitochondrial modulation treating postoperative cognitive dysfunction neuroprotection via DRP1 inhibition by Mdivi1

This study investigated the role of mitochondrial dynamics in postoperative cognitive dysfunction (POCD) and assessed the therapeutic potential of mitochondrial modulation, particularly through the inhibition of dynamin-related protein 1 (DRP1) with Mdivi-1. Our findings indicated that DRP1 inhibition substantially mitigated neuroinflammation mediated by microglial cells, contributing to improved cognitive function in POCD models. The administration of Mdivi-1 led to a notable decrease in mitochondrial fission, reduced reactive oxygen species (ROS) production, and stabilization of mitochondrial membrane potential, all of which correlate with diminished neuroinflammation, as evidenced by lower NOD-like receptor family pyrin domain containing 3 (NLRP3)/ interleukin-1β (IL-1β) expression in microglial cells. Importantly, Mdivi-1 treatment was also found to enhance synaptic plasticity, increasing synaptic spine density in the hippocampal region of POCD mice. This improvement in mitochondrial health and synaptic integrity was paralleled by enhanced cognitive performance, as demonstrated in Y-maze tests. These results underscored the critical role of mitochondrial dynamics in the pathophysiology of POCD and suggested that targeting mitochondrial dysfunction, specifically through DRP1 inhibition, could be an effective approach for POCD treatment.

Inhibiting endoplasmic reticulum stress alleviates perioperative neurocognitive disorders by reducing neuroinflammation mediated by NLRP3 inflammasome activation

AIM

The aim of this study is to explore the key mechanisms of perioperative neurocognitive dysfunction (PND) after anesthesia/surgery (A/S) by screening hub genes.

METHODS

Transcriptome sequencing was conducted on hippocampal samples obtained from 18-month-old C57BL/6 mice assigned to control (Ctrl) and A/S groups. The functionality of differentially expressed genes (DEGs) was investigated using Metascape. Hub genes associated with changes between the two groups were screened by combining weighted gene coexpression network analysis within CytoHubba. Reverse transcription PCR and western blotting were used to validate changes in mRNA and protein expression, respectively. NLRP3 inflammasome activation was detected by western blotting and ELISA. Tauroursodeoxycholic acid (TUDCA), an inhibitor of endoplasmic reticulum (ER) stress, was administrated preoperatively to explore its effects on the occurrence of PND. Immunofluorescence analysis was performed to evaluate the activation of astrocytes and microglia in the hippocampus, and hippocampus-dependent learning and memory were assessed using behavioral experiments.

RESULTS

In total, 521 DEGs were detected between the control and A/S groups. These DEGs were significantly enriched in biological processes related to metabolic processes and their regulation. Four hub genes (Hspa5, Igf1r, Sfpq, and Xbp1) were identified. Animal experiments have shown that mice in the A/S group exhibited cognitive impairments accompanied by increased Hspa5 and Xbp1 expression, ER stress, and activation of NLRP3 inflammasome.

CONCLUSIONS

Inhibiting ER stress alleviated cognitive impairment in A/S mice; particularly, ER stress induced by A/S results in NLRP3 inflammasome activation and neuroinflammation. Moreover, the preoperative administration of TUDCA inhibited ER stress, NLRP3 inflammasome activation, and neuroinflammation.

Post-operative cognitive dysfunction is exacerbated by high-fat diet via TLR4 and prevented by dietary DHA supplementation

Post-operative cognitive dysfunction (POCD) is an abrupt decline in neurocognitive function arising shortly after surgery and persisting for weeks to months, increasing the risk of dementia diagnosis. Advanced age, obesity, and comorbidities linked to high-fat diet (HFD) consumption such as diabetes and hypertension have been identified as risk factors for POCD, although underlying mechanisms remain unclear. We have previously shown that surgery alone, or 3-days of HFD can each evoke sufficient neuroinflammation to cause memory deficits in aged, but not young rats. The aim of the present study was to determine if HFD consumption before surgery would potentiate and prolong the subsequent neuroinflammatory response and memory deficits, and if so, to determine the extent to which these effects depend on activation of the innate immune receptor TLR4, which both insults are known to stimulate. Young-adult (3mo) & aged (24mo) male F344xBN F1 rats were fed standard chow or HFD for 3-days immediately before sham surgery or laparotomy. In aged rats, the combination of HFD and surgery caused persistent deficits in contextual memory and cued-fear memory, though it was determined that HFD alone was sufficient to cause the long-lasting cued-fear memory deficits. In young adult rats, HFD + surgery caused only cued-fear memory deficits. Elevated proinflammatory gene expression in the hippocampus of both young and aged rats that received HFD + surgery persisted for at least 3-weeks after surgery. In a separate experiment, rats were administered the TLR4-specific antagonist, LPS-RS, immediately before HFD onset, which ameliorated the HFD + surgery-associated neuroinflammation and memory deficits. Similarly, dietary DHA supplementation for 4 weeks prior to HFD onset blunted the neuroinflammatory response to surgery and prevented development of persistent memory deficits. These results suggest that HFD 1) increases risk of persistent POCD-associated memory impairments following surgery in male rats in 2) a TLR4-dependent manner, which 3) can be targeted by DHA supplementation to mitigate development of persistent POCD.