Postoperative cognitive dysfunction: Involvement of neuroinflammation and neuronal functioning

Advancing minimally invasive surgery for elderly colorectal cancer patients: Bridging evidence to practice

The recent study by Min et al provides evidence supporting laparoscopic radical resection of colorectal cancer (LRRCC) as a superior surgical approach for elderly patients. Their retrospective analysis of 104 patients demonstrated that LRRCC offers higher therapeutic efficacy, reduced postoperative complications, faster recovery, and attenuated systemic inflammatory responses compared to open surgery. While the study underscores the clinical advantages of minimally invasive techniques, it also highlights critical gaps, such as single-center design and limited long-term follow-up. This editorial contextualizes these findings within the broader literature, emphasizing the role of LRRCC in enhancing postoperative quality of life for elderly patients. We further discuss the implications of inflammatory biomarker modulation, advocate for multidisciplinary care models, and call for prospective trials to validate long-term outcomes.

Association between serum chemokines levels and delayed neurocognitive recovery after non-cardiac surgery in elderly patients: a nested case-control study

BACKGROUND

Perioperative neurocognitive disorders encompass delayed neurocognitive recovery (dNCR). Emerging evidence suggests that chemokines play a crucial role in the pathogenesis of various cognitive impairment diseases. However, the association between chemokines and dNCR remains unclear. Therefore, we aimed to investigate the relationship between serum chemokine levels and dNCR in elderly patients undergoing non-cardiac surgery.

METHODS

A total of 144 patients undergoing elective major non-cardiac surgery were accessed in neuropsychological testing 1 day prior to and 1 week following the surgery. Blood samples were collected before the initiation of anesthesia and one hour following the cessation of anesthesia. We employed a retrospective nested case-control study design, utilizing one control per dNCR case. Matching criteria included age (± 5 years), duration of surgery (± 90 min), and baseline MMSE score (± 3). We compared the serum levels of CCL2, CCL5, CCL11, and CXCL8 between the matched dNCR and non-dNCR groups.

RESULTS

dNCR was observed in 31.25% (45 of 144) of the patients seven days post-surgery, resulting in a final matched sample size of 21 pairs. In the preoperative comparison, the serum concentration of CCL11 was significantly higher in the matched dNCR group compared to the matched non-dNCR group (P = 0.039). In the postoperative comparison, the CCL5 concentration was significantly lower in the dNCR than in the non-dNCR group (P = 0.030). When comparing the differences between postoperative and preoperative levels, the absolute change in CCL11 was significantly greater in the dNCR group compared to the non-dNCR group (P = 0.046). Additionally, the postoperative-to-preoperative ratios of CCL5 and CCL11 in the dNCR group were both significantly lower than those in the non-dNCR group (P = 0.046, P = 0.005). There were no significant differences in CCL2 or CXCL8 levels between the two matched groups.

CONCLUSIONS

Serum levels of CCL 5 and CCL 11 significantly decreased in elderly patients with dNCR following non-cardiac surgery, which may contribute to the identification of patients at high risk for dNCR.

TRIAL REGISTRATION

This study was registered on chictr.org.cn (ChiCTR1800014473, 16/01/2018).

Remimazolam vs. propofol for induction and maintenance of general anesthesia: A systematic review and meta-analysis of emergence agitation risk in surgical populations

INTRODUCTION

The association between remimazolam and emergence agitation (EA) remains unclear. This meta-analysis aimed to compare the relative risk of developing EA when using remimazolam vs. propofol in induction and maintenance of general anesthesia.

METHOD

We searched PubMed, clinicaltrials.gov, Web of Science, Cochrane Library, and Embase databases to identify studies meeting the inclusion criteria. The primary outcome was the incidence of EA. Secondary outcomes included the incidence of postoperative delirium (POD) within 7 days after surgery, emergence time, extubation time, length of post-anesthesia care unit (PACU) stay, and adverse events.

RESULTS

A total of 19 randomized controlled trials with 3031 patients were included in the meta-analysis. There was no statistically significant difference in the incidence of EA (RR = 0.82; 95 % confidence interval [CI], 0.41-1.65; p = 0.585) between remimazolam and propofol. Likewise, there were no significant intergroup differences in POD incidence, extubation time, emergence time, or length of PACU stay. Remimazolam exhibited superior hemodynamic stability, with a significantly reduced incidence of postinduction hypotension and intraoperative hypotension compared with propofol, while maintaining comparable safety profiles in terms of postoperative nausea and vomiting (PONV), intraoperative awareness, and hypoxemia. Subgroup analysis revealed that without routine postoperative antagonist administration, remimazolam was associated with prolonged extubation and length of PACU stay relative to propofol. In contrast, following antagonizing with flumazenil, the extubation and emergence times of the remimazolam group were shorter than those of the propofol group, while comparable PACU discharge time was maintained.

CONCLUSION

The use of remimazolam for the induction and maintenance of general anesthesia does not lead to a higher occurrence of EA in adult patients undergoing surgery, relative to propofol. However, in patients with ASA III-IV, remimazolam may be linked to a greater risk of POD than propofol.

Basic research on postoperative cognitive dysfunction in the past decade: a bibliometric analysis

Objective

Postoperative cognitive dysfunction (POCD) is a prevalent complication following anesthesia and surgery that particularly affects elderly patients, and poses significant health risks. In recent years, there has been an increase in basic research on POCD, with a particular focus on its molecular mechanisms, which have become a prominent area of inquiry. However, no bibliometric analysis has been conducted in this field. This study aims to employ bibliometric methods to comprehensively summarize the current status and developmental trends of basic research on POCD, providing new ideas and strategies for future scientific investigations.

Methods

Relevant literature published between January 1, 2014, and October 30, 2024, was retrieved from the Web of Science Core Collection. Eligible articles were exported in plain text format. The annual output of published papers and data on authors, countries/institutions, journals, keywords, co-cited journals, and co-cited literature were analyzed and visualized using Microsoft Excel, VOSviewer, and CiteSpace software.

Results

A total of 479 papers from 13 countries were included, with a noticeable upward trend in publications over the past decade, particularly in the last 3 years. A total of 105 core authors published four or more papers, with Professor Zuozhiyi identified as the leading contributor. "The Journal of Neuroinflammation" emerged as the most prolific publication source, while Chinese scholars accounted for the highest number of contributions and Dutch scholars led in citations per article. The University of Virginia was the leading institution for publications. Analysis of research hotspots revealed "neuroinflammation," "surgery," "impairment," "memory," and "information" as frequently occurring keywords. Notably, "pyroptosis" was identified as a current research hotspot and "synaptic plasticity" as a rapidly emerging term. The top five cited journals were all ranked as Q1 journals, with "Anesthesiology" being the most cited. Within co-cited articles, the "hippocampal CA1 region" represented the largest cluster, and literature on "neuroinflammation" was a key reference in current discussions.

Conclusion

Over the past decade, basic research on POCD has steadily increased, particularly among Chinese scholars. Bibliometric analysis revealed that the molecular mechanisms underlying POCD are likely crucial focuses of current and future research. This field holds significant potential for further development.

Preoperative continuation vs. discontinuation of angiotensin-converting enzyme inhibitors/angiotensin II receptor blockers on early cognitive function in elderly patients undergoing noncardiac surgery: a randomized controlled trial

Objectives

To evaluate the effect of preoperative continuation vs. discontinuation of angiotensin-converting enzyme inhibitors (ACEIs) and angiotensin II receptor blockers (ARBs) on early cognitive function in elderly patients undergoing noncardiac surgery.

Methods

This prospective randomized controlled study was performed at the Affiliated Hospital of Xuzhou Medical University. Elderly patients aged 65 years or older, scheduled for elective noncardiac surgery under general anesthesia, and receiving long-term ACEI/ARBs therapy were randomly assigned to either continue or discontinue ACEI/ARBs therapy on the morning of surgery. The primary outcome was postoperative early cognitive function, assessed via neuropsychological tests including Auditory Verbal Learning Test-Huashan (AVLT-H), Clock Drawing Test (CDT), Number Connection Test (NCT), and Digit Span Test (DST) preoperatively and on postoperative day 1 (POD1). Secondary outcomes included intraoperative hypotension, use of phenylephrine, intraoperative fluid administration, incidence of hypertension, and length of hospital stay.

Results

The NCT scores in the discontinued use of ACEI/ARBs group showed a significant decline on POD1 compared to baseline (p = 0.038). Both groups exhibited an increase in immediate recall scores from preoperative to POD1 (p = 0.003 and p = 0.002, respectively). The continued use of ACEI/ARBs group showed an increase in short-delayed recall (p = 0.007). However, there were no significant differences between the two groups (p > 0.05). The discontinued ACEI/ARB group had fewer episodes of intraoperative hypotension (p = 0.037) and lower requirements for phenylephrine (p = 0.016), despite a higher incidence of preoperative hypertension (p = 0.012). The continued use group received a larger volume of crystalloid fluids during surgery (p = 0.020). No significant differences were observed between the groups in the volume of colloid fluids administered (p > 0.05). There were no significant differences in postoperative hypertension or length of hospital stay between the groups (p > 0.05).

Conclusion

Preoperative continuation or discontinuation of ACEI/ARBs did not significantly affect early postoperative cognitive function in elderly patients.

Vagus nerve stimulation (VNS) preventing postoperative cognitive dysfunction (POCD): two potential mechanisms in cognitive function

Postoperative cognitive dysfunction (POCD) impacts a significant number of patients annually, frequently impairing their cognitive abilities and resulting in unfavorable clinical outcomes. Aimed at addressing cognitive impairment, vagus nerve stimulation (VNS) is a therapeutic approach, which was used in many mental disordered diseases, through the modulation of vagus nerve activity. In POCD model, the enhancement of cognition function provided by VNS was shown, demonstrating VNS effect on cognition in POCD. In the present study, we primarily concentrates on elucidating the role of the VNS improving the cognitive function in POCD, via two potential mechanisms: the inflammatory microenvironment and epigenetics. This study provided a theoretical support for the feasibility that VNS can be a potential method to enhance cognition function in POCD.

Aged hippocampal single-cell atlas screening unveils disrupted neuroglial system in postoperative cognitive impairment

Glia-neuron interaction is a crucial feature in aged hippocampus during the occurrence of postoperative cognitive impairment. However, the regulatory effects of microglia, astrocytes, and oligodendrocytes in this glia-neuron interaction, the potential mechanisms and gene targets are still to be elucidated. Here, single-cell RNA sequencing was performed to detect the perioperative genomic expression characteristics of neuroglial system in the hippocampus of aged mice, and to investigate the potential cross-cellular mechanisms and valuable treatment options for glia-neuron interaction-related cognitive impairment. We found that postoperative neurons and glia cells exhibited protein dysmetabolism and mitochondrial electron misrouting. Impaired autophagy and circadian rhythm worsened microglia activation/neuroinflammation, and exacerbated these metabolic alterations. Reactive microglia also aggravated astrocyte and oligodendrocyte cytotoxicity through the PGD2/DP and complement pathways, altering glutamate level and synaptic function via the "tripartite synapses" model, and affecting neuronal myelination. Ligand-receptor communication also indicated these synaptic and axonal dysfunctions via enhanced MDK and PTN pathways. Additionally, we found that anesthetic dexmedetomidine hold therapeutic potential within the disrupted neuroglial system. It enhanced neuronal metabolic rebalance (Atf3-related) and reduced neuroinflammation from a multicellular perspective, therefore improving postoperative cognitive impairment. Together, our study proposes an aged hippocampal cell atlas and provides insights into the role of disrupted glia-neuron cycle in postoperative cognitive impairment. Our findings also elucidate the therapeutic potential and mechanism of dexmedetomidine intervention.

Tanshinone IIA mitigates postoperative cognitive dysfunction in aged rats by inhibiting hippocampal inflammation and ferroptosis: Role of Nrf2/SLC7A11/GPX4 axis activation

OBJECTIVE

Postoperative cognitive dysfunction (POCD) is a common and debilitating complication in elderly patients following surgery, leading to increased morbidity and reduced quality of life. This study aims to investigate the neuroprotective effects of Tanshinone IIA, a lipophilic compound derived from Salvia miltiorrhiza, in an aged rat model of POCD, and explore its underlying molecular mechanisms.

METHODS

POCD model was established by a modified abdominal exploratory laparotomy. Rats were then intraperitoneally administered with Tanshinone IIA (10 mg/kg, 20 mg/kg, or 40 mg/kg) for 30 days. Cognitive functions were assessed using the morris water maze, novel object recognition test, and Y-maze test. Synaptic structures in the hippocampal CA1 region were examined by electron microscopy. Inflammatory and ferroptosis pathways were evaluated by measuring inflammatory cytokines (TNF-α, IL-6, IL-1β, IL-4), nitric oxide synthase (iNOS) activity, lipid peroxidation products (malondialdehyde [MDA]; 4-hydroxy-2-nonenal [4-HNE]), Fe2 + levels, and antioxidant enzymes (superoxide dismutase [SOD], glutathione [GSH]) using ELISA and commercial kits. mRNA and proteins levels were quantified by real-time quantitative polymerase chain reaction and western blot analysis.

RESULTS

Tanshinone IIA significantly ameliorated cognitive deficits in aged POCD rats according to behavioral tests. It also restored synaptic ultrastructure in the hippocampal CA1 region and upregulated the expressions of synaptic proteins, including synapsin-1 and PSD-95. In addition, Tanshinone IIA effectively suppressed the hippocampal inflammatory pathway, as evidenced by the decreased levels of pro-inflammatory cytokines (TNF-α, IL-6, IL-1β), an increased level of the anti-inflammatory cytokine IL-4, and the upregulation of the iNOS/NO pathway in the hippocampus. Furthermore, Tanshinone IIA mitigated ferroptosis by reducing MDA and 4-HNE contents, lowering Fe2+ level, and enhancing SOD activity and GSH level. Notably, Tanshinone IIA activated the Nrf2/SLC7A11/GPX4 axis in the hippocampus of aged POCD rats.

CONCLUSION

These findings suggest that Tanshinone IIA exerts neuroprotective effects in an aged rat model of POCD by attenuating hippocampal inflammation and ferroptosis, primarily through the activation of the Nrf2/SLC7A11/GPX4 axis.

Role of Microglial Mitophagy in Alleviating Postoperative Cognitive Dysfunction: a Mechanistic Study

Postoperative cognitive dysfunction (POCD), a common complication following anesthesia and surgery, is influenced by hippocampal neuroinflammation and microglial activation. Mitophagy, a process regulating inflammatory responses by limiting the accumulation of damaged mitochondria, plays a significant role. This study aimed to determine whether regulating microglial mitophagy and the cGAS-STING pathway could alleviate cognitive decline after surgery. Exploratory laparotomy was performed to establish a POCD model using mice. Western blotting, immunofluorescence staining, transmission electron microscopy, and mt-Keima assays were used to examine microglial mitophagy and the cGAS-STING pathway. Quantitative polymerase chain reaction (qPCR) was used to detect inflammatory mediators and cytosolic mitochondrial DNA (mtDNA) levels in BV2 cells. Exploratory laparotomy triggered mitophagy and enhanced the cGAS-STING pathway in mice hippocampi. Pharmacological treatment reduced microglial activation, neuroinflammation, and cognitive impairment after surgery. Mitophagy suppressed the cGAS-STING pathway in mice hippocampi. In vitro, microglia-induced inflammation was mediated by mitophagy and the cGAS-STING pathway. Small interfering RNA (siRNA) of PINK1 hindered mitophagy activation and facilitated the cytosolic release of mtDNA, resulting in the initiation of the cGAS-STING pathway and innate immune response. Microglial mitophagy inhibited inflammatory responses via the mtDNA-cGAS-STING pathway inducing microglial mitophagy and inhibiting the mtDNA-cGAS-STING pathway may be an effective therapeutic approach for patients with POCD.

Proposing Bromo-epi-androsterone (BEA) for perioperative neurocognitive disorders with Interleukin-6 as a druggable target

Cognitive impairment following surgery is a significant complication, affecting multiple neurocognitive domains. The term "perioperative neurocognitive disorders" (PND) is recommended to encompass this entity. Individuals who develop PND are typically older and have increases in serum and brain pro-inflammatory cytokines notwithstanding the type of surgery undergone. Surgical trauma induces production of small biomolecules, damage-associated molecular patterns (DAMP), particularly the DAMP known as high molecular group box 1 protein (HMGB1). Mechanistically, peripheral surgical trauma promotes pro-inflammatory cytokines that stimulate central nervous system (CNS) inflammation by disrupting the blood-brain barrier (BBB) causing functional neuronal disruption that leads to PND. PND is strongly linked to elevations in serum and CNS pro-inflammatory cytokines interleukin-1 beta (IL-1β), interleukin-6 (IL-6) and tumor necrosis factor alpha (TNFα); these cytokines cause further release of HMGB1 creating a positive feedback loop that amplifies the inflammatory response. The cytokine IL-6 is necessary and sufficient for PND. Dehydroepiandrosterone (DHEA) is a principal component of the steroid metabolome and is involved in immune homeostasis. DHEA has been shown to suppress expression of several pro-inflammatory cytokines by regulation of the NF-kB pathway. Bromo-epi-androsterone (BEA) is a potent synthetic analog of DHEA; unlike DHEA, it is non-androgenic, non-anabolic and is an effective modulator of immune dysregulation. In a randomized, placebo-controlled clinical trial, BEA effected significant and sustained decreases in IL-1β, TNFα and IL-6. This article presents BEA as a potential candidate for clinical trials targeting PND and further suggests the use of BEA in elective total hip arthroplasty as a well-documented surgical entity relevant to the management of PND.

Bibliometric Analysis of Neuroinflammation and Postoperative Cognitive Dysfunction

BACKGROUND

The occurrence and development of postoperative cognitive dysfunction (POCD) are closely linked to neuroinflammation. This bibliometric analysis aims to provide novel insights into the research trajectory, key research topics, and potential future development trends in the field of neuroinflammation-induced POCD.

METHODS

The Web of Science Core Collection (WoSCC) database was searched to identify publications from 2012 to 2023 on neuroinflammation-induced POCD. Bibliometric analysis, involving both statistical and visual analyses, was conducted using CiteSpace, VOSviewer, and the R software.

RESULTS

Research on neuroinflammation-induced POCD has exhibited an increasing trend over the past 12 years. China had the highest number of publications, Nanjing Medical University had the most collaboration with other institutions, Zhiyi Zuo was the most published author, and the Journal of Neuroinflammation served as the primary publication in the field of neuroinflammation-induced POCD. The most frequent keyword was POCD. Keyword clustering analysis indicated that the predominant cluster is dexmedetomidine. Burst detection revealed that postoperative delirium (POD), perioperative neurocognitive disorders (PND), apoptosis, and epigenetic modifications were the future research trends.

CONCLUSIONS

Our analysis identified the following key research areas associated with neuroinflammation-induced POCD: anesthesia, surgery, dexmedetomidine, NLRP3 inflammasome, and mechanism of neuroinflammation-induced POCD. The potential future research topics comprise POD, PND, apoptosis, and epigenetic modifications.

Foxq1 activates CB2R with oleamide to alleviate POCD

Postoperative cognitive dysfunction (POCD) is a major concern, particularly among older adults. This study used social isolation (ISO) and multiomics analyses in aged mice to investigate potential mechanisms underlying POCD development. Aged mice were divided into two groups: ISO and paired housing (PH). Oleamide and the cannabinoid receptor type 2 (CB2R) antagonist AM630 were administered intraperitoneally, while Foxq1 adeno-associated viral (AAV) vector was injected directly into the hippocampus. Intramedullary tibial surgeries were subsequently performed to establish the POCD models. Behavioral tests comprising the Y-maze, open field test, and novel object recognition were conducted 2 days after surgery. Hippocampal and serum inflammatory cytokines were assessed. Following surgery, ISO mice demonstrated intensified cognitive impairments and escalated inflammatory markers. Integrative transcriptomic and metabolomic analysis revealed elevated oleamide concentrations in the hippocampus and serum of PH mice, with associative investigations indicating a close relationship between the Foxq1 gene and oleamide levels. While oleamide administration and Foxq1 gene overexpression substantially ameliorated postoperative cognitive performance and systemic inflammation in mice, CB2R antagonist AM630 impeded these enhancements. The Foxq1 gene and oleamide may be crucial in alleviating POCD. While potentially acting through CB2R-mediated pathways, these factors may modulate neuroinflammation and attenuate proinflammatory cytokine levels within the hippocampus, substantially improving cognitive performance postsurgery. This study lays the groundwork for future research into therapeutic approaches targeting the Foxq1-oleamide-CB2R axis, with the ultimate goal of preventing or mitigating POCD.

Genetically humanized phenylketonuria mouse model as a testing tool for human genome editing in fertilized eggs

Targeted genome editing has made significant advancements; however, safety and ethical issues have not been fully elucidated, resulting in strict control of the technique. We tested genome editing tools on gametes from a genetically humanized mouse model using a phenylketonuria (PKU) mouse model to gain insights into genome editing in human embryos. The human PKU mouse model PahhR111X mice was generated. The junctional region between exon 3 and intron 3 of Pah was replaced with a 120 bp corresponding human PAH sequence, including the pathogenic common variant c.331C > T in PahhR111X mice. PahhR111X mice successfully recapitulated the PKU phenotype and showed cognitive dysfunction and depressive-like behavior, which are observed in human patients with PKU. Genome editing was applied to fertilized eggs of PahhR111X mice utilizing sgRNA that targets the human sequence. Mice with the corrected allele exhibited normal serum phenylalanine levels. Through genome editing, we validated the utility of sgRNA. The genetically humanized mouse model suggested that germ-line genome editing of the pathogenic variant may be feasible for monogenic disorders by revealing the recovery of the phenotype; however, there are remaining issues with the tool, including its efficiency and accuracy. This genome editing protocol using a genetically humanized mouse model will provide insights for improving current issues and contribute to the establishment of heritable human genome editing protocols.

Effects of Remimazolam on Intraoperative Frontal Alpha Band Power Spectrum Density and Postoperative Cognitive Function in Older Adults Undergoing Lower Extremity Fractures Surgeries: A Randomized Controlled Trial

Purpose

Low density of electroencephalogram alpha band power was reported to be associated with perioperative cognitive dysfunction. Few studies have conducted to explore the effects of remimazolam on intraoperative frontal alpha band power spectrum density in older adults. Here, we aimed to explore the impact of remimazolam on intraoperative frontal brain wave alpha band activity and postoperative cognitive function in older adults undergoing lower extremity fractures surgeries.

Methods

Patients undergoing elective general anesthesia for lower extremity fracture surgery were randomly allocated to remimazolam group (Group R) and midazolam group (Group M). Group R was induced with remimazolam bolus 0.1 mg/kg followed by a maintenance dose of 0.1 mg·kg-1·h-1 for general anesthesia. Group M was induced with midazolam 0.05 mg/kg followed by normal saline maintenance of 0.1 mL·kg-1·h-1. The rest anesthesia protocol was the same for both groups. Electroencephalogram data was recorded before anesthesia induction till the end of surgery. Cognitive function was assessed preoperatively, and at the first, third, fifth, and seventh day postoperatively.

Results

Compared with Group M, Group R had significantly higher intraoperative power spectral density of the frontal alpha band (P < 0.001), and significantly lower incidence of postoperative cognitive dysfunction at T8 and T9 (P = 0.031 and P = 0.017, respectively).

Conclusion

Remimazolam can increase frontal brain wave alpha band power spectrum density and improve postoperative cognitive function in older adults undergoing lower extremity fractures surgeries.

Microglia in the aged brain develop a hypoactive molecular phenotype after surgery

BACKGROUND

Microglia, the resident immune cells of the brain, play a crucial role in maintaining homeostasis in the central nervous system (CNS). However, they can also contribute to neurodegeneration through their pro-inflammatory properties and phagocytic functions. Acute post-operative cognitive deficits have been associated with inflammation, and microglia have been implicated primarily based on morphological changes. We investigated the impact of surgery on the microglial transcriptome to test the hypothesis that surgery produces an age-dependent pro-inflammatory phenotype in these cells.

METHODS

Three-to-five and 20-to-22-month-old C57BL/6 mice were anesthetized with isoflurane for an abdominal laparotomy, followed by sacrifice either 6 or 48 h post-surgery. Age-matched controls were exposed to carrier gas. Cytokine concentrations in plasma and brain tissue were evaluated using enzyme-linked immunosorbent assays (ELISA). Iba1+ cell density and morphology were determined by immunohistochemistry. Microglia from both surgically treated mice and age-matched controls were isolated by a well-established fluorescence-activated cell sorting (FACS) protocol. The microglial transcriptome was then analyzed using quantitative polymerase chain reaction (qPCR) and RNA sequencing (RNAseq).

RESULTS

Surgery induced an elevation in plasma cytokines in both age groups. Notably, increased CCL2 was observed in the brain post-surgery, with a greater change in old compared to young mice. Age, rather than the surgical procedure, increased Iba1 immunoreactivity and the number of Iba1+ cells in the hippocampus. Both qPCR and RNAseq analysis demonstrated suppression of neuroinflammation at 6 h after surgery in microglia isolated from aged mice. A comparative analysis of differentially expressed genes (DEGs) with previously published neurodegenerative microglia phenotype (MGnD), also referred to disease-associated microglia (DAM), revealed that surgery upregulates genes typically downregulated in the context of neurodegenerative diseases. These surgery-induced changes resolved by 48 h post-surgery and only a few DEGs were detected at that time point, indicating that the hypoactive phenotype of microglia is transient.

CONCLUSIONS

While anesthesia and surgery induce pro-inflammatory changes in the plasma and brain of mice, microglia adopt a homeostatic molecular phenotype following surgery. This effect seems to be more pronounced in aged mice and is transient. These results challenge the prevailing assumption that surgery activates microglia in the aged brain.

A derivative of honokiol HM568 has an anti-neuroinflammatory effect in Parkinson's disease

Parkinson's disease (PD) is the fastest growing neurodegenerative disease in the world at present. Neuroinflammation plays an important role in Parkinson's disease. In our study, we initially screened magnolol/honokiol derivatives synthesized by our group for their potential anti-neuroinflammatory properties. This was done using LPS-activated BV-2 microglial cell and MPP + -induced PC-12 cell models. Most of derivatives had increased anti-inflammatory activities and decreased toxicities compared to raw materials. Then, compounds were scored with inflammatory factors IL-1β, TNF-α and IL-6 by molecular docking in silico. Our studies revealed the strongest binding compound HM568 which binds with honokiol and metformin. Furthermore, HM568 showed no acute toxicity in mice through acute toxicity. And it is stable under high temperature, high humidity and strong light irradiation. Combining cell experiments and computer results, HM568 was considered for further in vivo pharmacological validations. Intraperitoneal injection administration of MPTP into C57BL/6 mice was utilized as Parkinson's animal model. Results showed that administration of HM568 for 14 days in MPTP-PD mice led to a significant alleviation in weight loss and movement disorders. Further HM568 could significantly down-regulate the expression levels of inflammatory factors IL-1β, IL-6 and TNF-α in brain tissue of the mouse model, reduce the level of caspase-3 and the ratio of Bcl-2/Bax, and up-regulate the level of transforming factor TGF-β, thus producing anti-apoptosis and anti-neuroinflammatory effects on neuronal cells. In terms of pathological features, HM568 could reduce the infiltration of neuronal cells and alleviate the development of lesions, promote the transformation of microglia from M1 negative phenotype to M2 type, and reverse the reduction of TH-positive immune cells in mouse neurons induced by MPTP. The administration of HM568 could reduce the abnormal accumulation of α-syn, and thus produce neuroprotective effect on MPTP-PD mice. Cell experiments, molecular docking and animal experiments thus depict HM568 as a promising agent to delay neuronal degeneration in PD, and its mechanism is related to anti-neuroinflammation.

The impact of maternal anti-inflammatory drugs on surgical anesthesia-induced neuroinflammation and cognitive impairment in offspring mice

Background

The impact of maternal surgery combined with general anesthesia on neuroinflammation and the development of learning and memory impairment in offspring remains unclear. This study utilized a pathogen-free laparotomy model to investigate these changes during the second trimester, as well as their response to anti-inflammatory therapy.

Methods

C57BL/6 pregnant mice at the 14.5-day embryo stage (E 14.5) were either exposed to sevoflurane anesthesia alone or underwent laparotomy procedure. The neuroinflammatory response was evaluated at 7, 14, 21, and 28 days postnatal (P7, P14, P21, P28). Tau phosphorylation and cognitive ability were assessed at P28 and P30, respectively. The impact of perioperative administration of ibuprofen (60 mg/kg) on these aforementioned changes was subsequently evaluated.

Results

In the laparotomy group, levels of inflammatory factors (IL-4, IL-8, IL-17A, TGF-β, M-CSF, CCL2) in the brains of offspring mice, including the cerebral cortex and hippocampus, remained consistently elevated from P7 to P28. At P14, while the majority of inflammatory cytokine has no statistical difference, there was still a significant reactivation of inflammatory cytokines observed in the frontal cortex and hippocampus at P28. Furthermore, abnormal phosphorylation of tau and deficits in learning and memory were observed at P28 and P30. Administration of perioperative ibuprofen led to improvements in cognitive performance, reduction of systemic inflammation, and inhibiting abnormal phosphorylation of tau in the frontal cortex and hippocampus.

Conclusion

Our findings indicate that cognitive dysfunction is correlated with elevated levels of inflammatory cytokines and tau phosphorylation. Cognitive impairment and tau phosphorylation after laparotomy can persist at least until P28. Anti-inflammatory medications have been shown to enhance cognitive function by rapidly reducing inflammation in the brain, while also impacting neurological changes. This discovery may have implications for the development of treatment strategies aimed at managing cognitive impairment in post-operative patients.

Electroacupuncture and Transcutaneous Electrical Acupoint Stimulation for Perioperative Neurocognitive Disorder in Older Patients Undergoing Cardiac Surgery: Protocol for Systematic Review and Meta-Analysis

BACKGROUND

Perioperative neurocognitive disorder (PND) is a critical concern for older patients undergoing cardiac surgery, impacting cognitive function and quality of life. Electroacupuncture and transcutaneous electrical acupoint stimulation (TEAS) hold promise for mitigating PND. This protocol outlines a systematic review and meta-analysis to thoroughly assess the efficacy of electroacupuncture and TEAS in older patients undergoing cardiac surgery with PND, providing up-to-date evidence for PND prevention and treatment.

OBJECTIVE

This study aimed to thoroughly assess the efficacy of electroacupuncture and TEAS in older patients undergoing cardiac surgery with PND, providing up-to-date evidence for PND prevention and treatment.

METHODS

A comprehensive and systematic approach will be used to identify eligible studies from a diverse range of electronic databases, including 9 major sources such as PubMed (NLM) and Cochrane (Wiley), as well as 2 clinical trial registration websites. These studies will focus on investigating the effects of electroacupuncture and TEAS on PND in older patients undergoing cardiac surgery. The study selection will adhere to the criteria outlined in the patient, intervention, comparison, outcome, and studies (PICOS) format. Data extraction will be carried out by 2 independent researchers (YP and LS), using established tools to evaluate the risk of bias. The primary outcome will be PND incidence, with secondary outcomes including Mini Mental State Examination scores, neuron-specific enolase, S100β, interleukin-1β, interleukin-6, tumor necrosis factor-α, time to first flatus, first defecation, bowel sound recovery, and hospitalization duration to be selectively reported. Adverse events linked to acupuncture, such as bleeding, needle site pain, and local reactions, rather than serious adverse events, will also be considered. Meta-analysis will be performed using appropriate statistical methods to assess the overall effect of electroacupuncture and TEAS on PND prevention, treatment, or other relevant outcomes. The Cochrane Collaboration Risk of Bias tool will be used for assessment, and data synthesis will be executed using the RevMan 5.4 software (Cochrane).

RESULTS

We plan to summarize the eligible studies through the use of a PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) flowchart. The findings will be showcased in the form of a summary table of evidence. Figures and forest plots will be used to illustrate the outcomes of the meta-analysis.

CONCLUSIONS

The impacts of electroacupuncture and TEAS interventions on PND in older patients undergoing cardiac surgery have not yet been established. This protocol addresses a critical gap by thoroughly assessing electroacupuncture and TEAS for PND in older patients undergoing cardiac surgery, enhancing understanding of nonpharmacological interventions, and guiding future research and clinical practices in this field. Its strength lies in rigorous methodology, including comprehensive search strategies, independent review processes, and thorough assessments of the risk of bias.

TRIAL REGISTRATION

PROSPERO CRD42023411927; https://tinyurl.com/39xdz6jb.

INTERNATIONAL REGISTERED REPORT IDENTIFIER (IRRID)

PRR1-10.2196/55996.

miR-206-3p Targets Brain-Derived Neurotrophic Factor and Affects Postoperative Cognitive Function in Aged Mice

Postoperative cognitive dysfunction (POCD) occurs after surgery and severely impairs patients' quality of life. Finding POCD-associated variables can aid in its diagnosis and prognostication. POCD is associated with noncoding RNAs, such as microRNAs (miRNAs), involved in metabolic function, immune response alteration, and cognitive ability impairment; however, the underlying mechanisms remain unclear. The aim of this study was to investigate hub miRNAs (i.e., miRNAs that have an important regulatory role in diseases) regulating postoperative cognitive function and the associated mechanisms. Hub miRNAs were identified by bioinformatics, and their expression in mouse hippocampus tissues was determined using real-time quantitative polymerase chain reaction. Hub miRNAs were overexpressed or knocked down in cell and animal models to test their effects on neuroinflammation and postoperative cognitive function. Six differentially expressed hub miRNAs were identified. miR-206-3p was the only broadly conserved miRNA, and it was used in follow-up studies and animal experiments. Its inhibitors reduced the release of proinflammatory cytokines in BV-2 microglia by regulating its target gene, brain-derived neurotrophic factor (BDNF), and the downstream signaling pathways. miR-206-3p inhibition suppressed microglial activation in the hippocampi of mice and improved learning and cognitive decline. Therefore, miR-206-3p significantly affects POCD, implying its potential as a therapeutic target.

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.

Propionic acid ameliorates cognitive function through immunomodulatory effects on Th17 cells in perioperative neurocognitive disorders

Background

Elderly patients undergoing surgery are prone to cognitive decline known as perioperative neurocognitive disorders (PND). Several studies have shown that the microglial activation and the decrease of short-chain fatty acids (SCFAs) in gut induced by surgery may be related to the pathogenesis of PND. The purpose of this study was to determine whether microglia and short-chain fatty acids were involved in cognitive dysfunction in aged rats.

Methods

Male wild-type Wistar rats aged 11-12 months were randomly divided into control group (Ctrl: Veh group), propionic acid group (Ctrl: PA group), exploratory laparotomy group (LP: Veh group) and propionic acid + exploratory laparotomy group (LP: PA group) according to whether exploratory laparotomy (LP) or PA pretreatment for 21 days was performed. The motor ability of the rats was evaluated by open field test on postoperative day 3 (POD3), and then the cognitive function was evaluated by Y-maze test and fear conditioning test. The expression of IL-1β, IL-6, RORγt and IL-17A mRNA in hippocampus was detected by RT-qPCR, the expression of IL-17A and IL-17RA in hippocampus was detected by Western blot, and the activation of microglia was detected by immunofluorescence.

Results

The PND rat model was successfully established by laparotomy. Compared with Ctrl: Veh group, the body weight of LP: Veh group decreased, the percentage of spontaneous alternations in Y maze decreased (P < 0.001), and the percentage of freezing time in contextual fear test decreased (P < 0.001). Surgery triggers neuroinflammation, manifested as the elevated levels of the inflammatory cytokines IL-1β (P < 0.001) and IL-6 (P < 0.001), the increased expression of the transcription factor RORγt (P = 0.0181, POD1; P = 0.0073, POD5)and major inflammatory cytokines IL-17A (P = 0.0215, POD1; P = 0.0071, POD5), and the increased average fluorescence intensity of Iba1 (P < 0.001, POD1; P < 0.001, POD5). After PA preconditioning, the recovery of rats in LP: PA group was faster than that in LP: Veh group as the body weight lost on POD1 (P = 0.0148) was close to the baseline level on POD5 (P = 0.1846), and they performed better in behavioral tests. The levels of IL-1β (P < 0.001) and IL-6 (P = 0.0035) inflammatory factors in hippocampus decreased on POD1 and the average fluorescence intensity of Iba1 decreased (P = 0.0024, POD1; P < 0.001, POD5), representing the neuroinflammation was significantly improved. Besides, the levels of RORγt mRNA (P = 0.0231, POD1; P = 0.0251, POD5) and IL-17A mRNA (P = 0.0208, POD1; P = 0.0071, POD5) in hippocampus as well as the expression of IL-17A (P = 0.0057, POD1; P < 0.001, POD5) and IL-17RA (P = 0.0388) decreased.

Conclusion

PA pretreatment results in reduced postoperative neuroinflammation and improved cognitive function, potentially attributed to the regulatory effects of PA on Th17-mediated immune responses.

Knowledge mapping and research trends on perioperative neurocognitive disorder from 1990 to 2022: a bibliometric analysis

Introduction

Perioperative neurocognitive disorder (PND) has attracted consistently increasing attention worldwide. However, there are few bibliometric studies that systematically evaluate this field. This study aimed to visualize the knowledge structure and research trends in PND through bibliometrics to help understand the future development of basic and clinical research.

Methods

Literature related to PND in Web of Science and PubMed from 1990 to 2022 were collected through keywords retrospectively. Additionally, the source information, citation information, etc. of these publications were extracted. Finally, bibliometric analysis was performed by visualization software and statistical software.

Results

There were 2837 articles and reviews in total. An exponential rise in PND-related publications was observed. China had the most publication, followed by the US and Germany. The institution with the most output and citations was Harvard University (149 papers, 8966 citations). The most prominent author was Marcantonio Edward R with 66 publications and 5721 citations. The journal with the highest productivity for PND research was Frontiers in Aging Neuroscience followed by Anesthesia and Analgesia. Keywords were identified as six topics, including postoperative delirium, postoperative neurocognitive disorder, cardiac surgery, anaesthesia, orthopedic surgery, and dementia. According to keyword analysis, the most recent popular keywords in PND research were prevention, older patients, emergence delirium, orthopedic surgery, and dexmedetomidine.

Conclusions

Publications on PND are increasing at an alarming rate from 1990 to 2022. Current research and future trends will concentrate on the prevention and treatment of PND, as well as PND associated with orthopedic surgery in older adults.

Effects of electroacupuncture on postoperative cognitive dysfunction and its underlying mechanisms: a literature review of rodent studies

With the aging of the population, the health of the elderly has become increasingly important. Postoperative cognitive dysfunction (POCD) is a common neurological complication in elderly patients following general anesthesia or surgery. It is characterized by cognitive decline that may persist for weeks, months, or even longer. Electroacupuncture (EA), a novel therapy that combines physical nerve stimulation with acupuncture treatment from traditional Chinese medicine, holds potential as a therapeutic intervention for preventing and treating POCD, particularly in elderly patients. Although the beneficial effects of EA on POCD have been explored in preclinical and clinical studies, the reliability of EA is limited by methodological shortcomings, and the underlying mechanisms remain largely unexplored. Therefore, we have synthesized existing evidence and proposed potential biological mechanisms underlying the effects of EA on neuroinflammation, oxidative stress, autophagy, the microbiota-gut-brain axis, and epigenetic modification. This review summarizes recent advances in EA and POCD, provides a theoretical foundation, explores potential molecular mechanisms for the prevention and treatment of POCD, and offers a basis for conducting relevant clinical trials.

Effect of subanesthetic dose of esketamine on postoperative pain in elderly patients undergoing laparoscopic gastrointestinal tumor Surgery:A prospective, double-blind, randomized controlled trial

Purpose

Postoperative pain is prevalent and severe complication in elderly surgical patients. Multiple studies propose that a small dose of esketamine administered intraoperatively can alleviate postoperative pain and curtail opioid usage. We aimed to evaluate the impact of esketamine on postoperative acute pain among elderly patients with gastrointestinal tumors.

Patients and methods

This is a prospective, parallel-group, randomized controlled trial. Ninety patients aged 60 and above, undergoing resection of gastrointestinal tumors, were randomly assigned to two groups: esketamine group (Group S, a single dose of 0.25 mg/kg and 0.1 mg/kg/h infusion) and control group (Group C, saline). Visual Analogue Scale (VAS) pain scores were the primary outcome. Remifentanil consumption, instances of rescue analgesia, delirium, sleep quality, postoperative recovery quality, serum levels of inflammatory cytokines, and adverse events within 72 h post-surgery were secondary outcomes, respectively.

Results

Data of 87 of 99 eligible patients were analyzed. VAS scores at rest in Group S were lower than those in Group C at 6 h [1.2 (0.6, 1.6) vs 1.6 (1.0, 2.0), P = 0.003], 12 h [1.4 (1.0, 2.0) vs 2.0 (1.5, 2.0), P < 0.001], and 24 h [1.8 (1.3, 2.0) vs 2.2 (1.6, 2.6), P < 0.001] postoperatively. At 6 h post-surgery, VAS score during coughing was lower in Group S than Group C [2.0 (2.0, 2.3) vs 2.0 (2.0, 3.0), P = 0.009]. The instances of rescue analgesia were fewer in group S compared to group C (P = 0.007). Furthermore, the esketamine group showed improved sleep quality and QoR-15 score (P < 0.05) postoperatively.

Conclusion

Intravenous administration of esketamine as an adjunct to general anesthesia can decrease the intensity of pain for 24 h without additional adverse effects after laparoscopic gastrointestinal tumor surgery.

Dietary Restriction Improves Perioperative Neurocognitive Disorders by Inhibiting Neuroinflammation and Gut Microbial Dysbiosis

Anesthesia/surgery have been identified as potential factors contributing to perioperative neurocognitive disorders, with a notably heightened risk observed in aging populations. One of the primary drivers of this impairment is believed to be neuroinflammation, specifically inflammation of hippocampal microglia. Dietary restriction has demonstrated a favorable impact on cognitive impairment across various disorders, primarily by quelling neuroinflammation. However, the precise influence of dietary restriction on perioperative neurocognitive disorders remains to be definitively ascertained. This investigation aims to explore the effects of dietary restriction on perioperative neurocognitive disorders and propose innovative therapeutic strategies for their management. The model of perioperative neurocognitive disorder was induced through exploratory laparotomy under isoflurane anesthesia. Cognitive performance was evaluated using the open field test, Barnes maze test, and fear conditioning test. The enzyme-linked immunosorbent assay (ELISA) was employed to quantify concentrations of interleukin-1β (IL-1β), interleukin-6 (IL-6), and tumor necrosis factor-alpha (TNF-α) in both serum and hippocampal samples. The Western blot technique was utilized to assess expression levels of hippocampal PSD 95, Synaptophysin, TLR4, MyD88, and NF-kB p65. Microglial polarization was gauged using a combination of reverse transcription quantitative polymerase chain reaction (RT-qPCR) and immunofluorescence labeling techniques. We conducted 16S rRNA sequencing to investigate the impact of dietary restriction on the intestinal flora of aged mice following anesthesia/surgery. Our findings indicate that dietary restrictions have the potential to ameliorate anesthesia/surgery-induced cognitive dysfunction. This effect is achieved through the modulation of gut microbiota, suppression of inflammatory responses in hippocampal microglia, and facilitation of neuronal repair and regeneration.

The P38MAPK/ATF2 signaling pathway is involved in PND in mice

Accumulating evidence indicates that microglia-mediated neuroinflammation in the hippocampus contributes to the development of perioperative neurocognitive disorder (PND). P38MAPK, a point of convergence for different signaling processes involved in inflammation, can be activated by various stresses. This study aims to investigate the role of the P38MAPK/ATF2 signaling pathway in the development of PND in mice. Aged C57BL/6 mice were subjected to tibial fracture surgery under isoflurane anesthesia to establish a PND animal model. The open field test was used to evaluate the locomotor activity of the mice. Neurocognitive function was assessed with the Morris water maze (MWM) and fear conditioning test (FCT) on postoperative days 1, 3 and 7. The mice exhibited cognitive impairment accompanied by increased expression of proinflammatory factors (IL-1β, TNF-α), proapoptotic molecules (caspase-3, bax) and microglial activation in the hippocampus 1, 3 and 7 days after surgery. Treatment with SB239063 (a P38MAPK inhibitor) decreased the expression of proinflammatory factors, proapoptotic molecules and Iba-1 in the CA1 region of the hippocampus. The number of surviving neurons was significantly increased. Inhibition of the P38MAPK/ATF2 signaling pathway attenuates hippocampal neuroinflammation and neuronal apoptosis in aged mice with PND, thus improving the perioperative cognitive function of the mice.

J147 affects cognition and anxiety after surgery in Zucker rats

Vulnerable patients are at risk for neuroinflammation-mediated post-operative complications, including depression (POD) and cognitive dysfunction (POCD). Zucker rats, expressing multiple risk factors for post-operative complications in humans, may provide a clinically relevant model to study pathophysiology and explore potential interventions. J147, a newly developed anti-dementia drug, was shown to prevent POCD in young healthy rats, and improved early post-surgical recovery in Zucker rats. Aim of the present study was to investigate POCD and the therapeutic potential of J147 in male Zucker rats. Risk factors in the Zucker rat strain were evaluated by comparison with lean littermates. Zucker rats were subjected to major abdominal surgery. Acute J147 treatment was provided by a single iv injection (10 mg/kg) at the start of surgery, while chronic J147 treatment was provided in the food (aimed at 30 mg/kg/day), starting one week before surgery and up to end of protocol. Effects on behavior were assessed, and plasma, urine and brain tissue were collected and processed for immunohistochemistry and molecular analyses. Indeed, Zucker rats displayed increased risk factors for POCD, including obesity, high plasma triglycerides, low grade systemic inflammation, impaired spatial learning and decreased neurogenesis. Surgery in Zucker rats reduced exploration and increased anxiety in the Open Field test, impaired short-term spatial memory, induced a shift in circadian rhythm and increased plasma neutrophil gelatinase-associated lipocalin (NGAL), microglia activity in the CA1 and blood brain barrier leakage. Chronic, but not acute J147 treatment reduced anxiety in the Open Field test and protected against the spatial memory decline. Moreover, chronic J147 increased glucose sensitivity. Acute J147 treatment improved long-term spatial memory and reversed the circadian rhythm shift. No anti-inflammatory effects were seen for J147. Although Zucker rats displayed risk factors, surgery did not induce extensive POCD. However, increased anxiety may indicate POD. Treatment with J147 showed positive effects on behavioral and metabolic parameters, but did not affect (neuro)inflammation. The mixed effect of acute and chronic treatment may suggest a combination for optimal treatment.

Bridging the Gap: Investigating the Link between Inflammasomes and Postoperative Cognitive Dysfunction

Postoperative cognitive dysfunction (POCD) is a cluster of cognitive problems that may arise after surgery. POCD symptoms include memory loss, focus inattention, and communication difficulties. Inflammasomes, intracellular multiprotein complexes that control inflammation, may have a significant role in the development of POCD. It has been postulated that the NLRP3 inflammasome promotes cognitive impairment by triggering the inflammatory response in the brain. Nevertheless, there are many gaps in the current literature to understand the underlying pathophysiological mechanisms and develop future therapy. This review article underlines the limits of our current knowledge about the NLRP3 (NOD-, LRR- and pyrin domain-containing protein 3) inflammasome and POCD. We first discuss inflammasomes and their types, structures, and functions, then summarize recent evidence of the NLRP3 inflammasome's involvement in POCD. Next, we propose a hypothesis that suggests the involvement of inflammasomes in multiple organs, including local surgical sites, blood circulation, and other peripheral organs, leading to systemic inflammation and subsequent neuronal dysfunction in the brain, resulting in POCD. Research directions are then discussed, including analyses of inflammasomes in more clinical POCD animal models and clinical trials, studies of inflammasome types that are involved in POCD, and investigations into whether inflammasomes occur at the surgical site, in circulating blood, and in peripheral organs. Finally, we discuss the potential benefits of using new technologies and approaches to study inflammasomes in POCD. A thorough investigation of inflammasomes in POCD might substantially affect clinical practice.

Neuroinflammation: The central enabler of postoperative cognitive dysfunction

The proportion of advanced age patients undergoing surgical procedures is on the rise owing to advancements in surgical and anesthesia technologies as well as an overall aging population. As a complication of anesthesia and surgery, older patients frequently suffer from postoperative cognitive dysfunction (POCD), which may persist for weeks, months or even longer. POCD is a complex pathological process involving multiple pathogenic factors, and its mechanism is yet unclear. Potential theories include inflammation, deposition of pathogenic proteins, imbalance of neurotransmitters, and chronic stress. The identification, prevention, and treatment of POCD are still in the exploratory stages owing to the absence of standardized diagnostic criteria. Undoubtedly, comprehending the development of POCD remains crucial in overcoming the illness. Neuroinflammation is the leading hypothesis and a crucial component of the pathological network of POCD and may have complex interactions with other mechanisms. In this review, we discuss the possible ways in which surgery and anesthesia cause neuroinflammation and investigate the connection between neuroinflammation and the development of POCD. Understanding these mechanisms may likely ensure that future treatment options of POCD are more effective.

Inhibition of adult hippocampal neurogenesis induced by postoperative CD8 + T-cell infiltration is associated with cognitive decline later following surgery in adult mice

BACKGROUND

Some patients show persistent cognitive decline for weeks, months or even years after surgery, which seriously affects their long-term prognosis and quality of life. However, most previous basic studies have focused mainly on the mechanisms of early postoperative cognitive decline, whereas cognitive decline in the longer term after surgery is less well-understood. The subgranular zone of the dentate gyrus exhibits life-long neurogenesis, supporting hippocampus-dependent learning and memory.

MAIN TEXT

The aim of this study was to investigate whether adult hippocampal neurogenesis (AHN) involves in cognitive decline later following surgery and to further explore the roles of CD8 + T lymphocytes infiltrating the hippocampal parenchyma after surgery in this pathological process. Cognitive function was examined in adult mice that underwent laparotomy combined with partial hepatectomy, and the results showed that cognitive decline persisted in mice who underwent surgery during the first postoperative month, even though there was a trend toward continuous improvement over time. Significantly decreased numbers of DCX + cells, BrdU + cells, and BrdU + /DCX + cells were observed on day 8 after surgery, and a significantly decreased number of NeuN + /BrdU + cells was observed on day 28 after surgery, which indicated inhibition of AHN. After surgery, T lymphocytes, the majority of which were CD8 + T cells, infiltrated the hippocampus and secreted Interferon-γ (IFN-γ). Depletion of CD8 + T cells could inhibit the increase of IFN-γ synthesis, improve hippocampal neurogenesis, and improve postoperative cognitive function. Hippocampal microinjection of IFN-γ neutralizing antibody or adeno-associated virus to knock down IFN-γ receptor 1 (IFNGR1) could also partially attenuate the inhibition of AHN and improve postoperative cognitive function.

CONCLUSIONS

These results demonstrate that postoperative infiltration of CD8 + T cells into the hippocampus and subsequent secretion of IFN-γ contribute to the inhibition of AHN and cognitive decline later following surgery.

Evaluation of the brain cellular damage during liver transplantations

Background

Neuroinflammation in patients undergoing major surgery can lead to neuronal damage, and neuronal damage can be detected through the measurement of biochemical markers of brain damage. S100 beta (S100 β), neuron-specific enolase (NSE), and glial fibrillary acidic protein (GFAP) levels are considered good biomarkers to detect brain damage that emerged with neurotoxicity.

Aim

To evaluate neuronal damage during liver transplantations.

Materials and Methods

After approval of the ethics committee and patient consents, preoperative and postoperative cognitive functions of 33 patients undergoing liver transplantation were measured using the Mini Mental State Examination (MMSE), whereas simultaneous neuronal damage was evaluated through the measurement of S100β, NSE, and GFAP levels.

Results

There was no statistically significant difference between preoperative and postoperative MMSE. There was a statistically significant decrease in postoperative GFAP (P < 0.05) and a statistically significant increase in NSE (P < 0.05) compared to preoperative values. The decrease in S100β (P > 0.05) level was statistically insignificant.

Conclusions

Neuroprotective approaches in anesthesia protocol protect patients from brain damage during liver transplantation and prevent the development of postoperative cognitive dysfunction. Since the significant increase in NSE levels during liver transplantations was deemed to have been associated with causes other than neuronal damage, NSE should not be evaluated as a marker of brain damage in these operations.

Fluoxetine alleviates postoperative cognitive dysfunction by attenuating TLR4/MyD88/NF-κB signaling pathway activation in aged mice

OBJECTIVE AND DESIGN

Postoperative cognitive dysfunction (POCD) is a common complication following surgery among elderly patients. Emerging evidence demonstrates that neuroinflammation plays a pivotal role in the pathogenesis of POCD. This study tested the hypothesis that fluoxetine can protect against POCD by suppressing hippocampal neuroinflammation through attenuating TLR4/MyD88/NF-κB signaling pathway activation.

SUBJECTS

Aged C57BL/6 J male mice (18 months old) were studied.

TREATMENT

Aged mice were intraperitoneally injected with fluoxetine (10 mg/kg) or saline for seven days before splenectomy. In addition, aged mice received an intracerebroventricular injection of a TLR4 agonist or saline seven days before splenectomy in the rescue experiment.

METHODS

On postoperative days 1, 3, and 7, we assessed hippocampus-dependent memory, microglial activation status, proinflammatory cytokine levels, protein levels related to the TLR4/MyD88/NF-κB signaling pathway, and hippocampal neural apoptosis in our aged mouse model.

RESULTS

Splenectomy induced a decline in spatial cognition, paralleled by parameters indicating exacerbation of hippocampal neuroinflammation. Fluoxetine pretreatment partially restored the deteriorated cognitive function, downregulated proinflammatory cytokine levels, restrained microglial activation, alleviated neural apoptosis, and suppressed the increase in TLR4, MyD88, and p-NF-κB p65 in microglia. Intracerebroventricular injection of LPS (1 μg, 0.5 μg/μL) before surgery weakened the effect of fluoxetine.

CONCLUSION

Fluoxetine pretreatment suppressed hippocampal neuroinflammation and mitigated POCD by inhibiting microglial TLR4/MyD88/NF-κB pathway activation in aged mice.

Whole-body vibration as a passive alternative to exercise after myocardial damage in middle-aged female rats: Effects on the heart, the brain, and behavior

Background

Females with cardiovascular disease seem more vulnerable to develop concomitant mental problems, such as depression and cognitive decline. Although exercise is shown beneficial in cardiovascular disease as well as in mental functions, these patients may be incapable or unmotivated to perform exercise. Whole body vibration (WBV) could provide a passive alternative to exercise. Aim of the present study was to compare WBV to exercise after isoproterenol (ISO)-induced myocardial damage in female rats, regarding effects on heart, brain and behavior.

Methods

One week after ISO (70 mg/kg s.c., on 2 consecutive days) or saline injections, 12 months old female rats were assigned to WBV (10 minutes daily), treadmill running (30 minutes daily) or pseudo intervention for 5 weeks. During the last 10 days, behavioral tests were performed regarding depressive-like behavior, cognitive function, and motor performance. Rats were sacrificed, brains and hearts were dissected for (immuno)histochemistry.

Results

Significant ISO-induced cardiac collagen deposition (0.67 ± 0.10 vs 0.18 ± 0.03%) was absent after running (0.45 ± 0.26 vs 0.46 ± 0.08%), but not after WBV (0.83 ± 0.12 vs 0.41 ± 0.05%). However, WBV as well as running significantly reduced hippocampal (CA3) collagen content in ISO-treated rats. Significant regional differences in hippocampal microglia activity and brain derived neurotrophic factor (BDNF) expression were observed. Significant ISO-induced CA1 microglia activation was reduced after WBV as well as running, while opposite effects were observed in the CA3; significant reduction after ISO that was restored by WBV and running. Both WBV and running reversed the ISO-induced increased BDNF expression in the CA1, Dentate gyrus and Hilus, but not in the CA3 area. Whereas running had no significant effect on behavior in the ISO-treated rats, WBV may be associated with short-term spatial memory in the novel location recognition test.

Conclusion

Although the female rats did not show the anticipated depressive-like behavior or cognitive decline after ISO, our data indicated regional effects on neuroinflammation and BDNF expression in the hippocampus, that were merely normalized by both WBV and exercise. Therefore, apart from the potential concern about the lack of cardiac collagen reduction, WBV may provide a relevant alternative for physical exercise.

Lactobacillus paracasei HP7 with Portulaca oleracea Linn. Alleviates Scopolamine-Induced Cognitive Decline via Regulation of Neurotrophic Factor and Inflammation Signals in Mice

People often experience cognitive deterioration of various degrees, from early-stage mild cognitive impairment to severe cognitive decline. Cognitive deterioration is related to many diseases and studied to alleviated inflammation reaction or oxidative stress. In the present study, the levels of various memory-related proteins: brain-derived neurotrophic factor (BDNF), amyloid beta (Aβ) 42, Aβ40, interleukin-6 and tumor necrosis factor-alpha were measured. Among Lactobacillus paracasei HP7 (HP7), Portulaca oleracea Linn. (PO) and HP7 together with PO (HP7A), the HP7A group had the best effect on increasing BDNF expression and suppressing Aβ40 expression. Also, we measured the protective effect on scopolamine-induced cognitive decline in mice. In the acquisition test, the HP7A group most reliably relieved cognitive decline from days 2 to 5 of scopolamine injection. When the probe test was performed on the day 6 of scopolamine injection, the HP7A group had the shortest escape latency. Based on the results of the Morris water maze tasks, we suggest that HP7A is most useful for ameliorating cognitive decline. It is suggested that the HP7A ameliorating scopolamine-induced cognitive decline via the increase of BDNF expression and the suppression of Aβ40 expression.

Whole body vibration, an alternative for exercise to improve recovery from surgery?

Although exercise is usually associated with beneficial effects on physical and mental health, patients recovering from surgery may be hampered to perform active exercise. Whole body vibration (WBV) is suggested a passive alternative for physical training. Aim of the present study was to explore the therapeutic potential of WBV compared to physical exercise during early post-surgery recovery.

Male three months old Wistar rats underwent major abdominal surgery. Starting the day after surgery, rats were subjected to either daily WBV or exercise (treadmill running) for 15 consecutive days. Control rats underwent pseudo treatment. During the first week after surgery, effects of interventions were obtained from continuous recording of hemodynamic parameters, body temperature and activity (via an implanted transducer). Behavioral tests were performed during the second post-surgical week to evaluate anxiety-like behavior, short and long-term memory functions, cognitive flexibility and motor performance. Animals were sacrificed 15 days after surgery and brain tissue was collected for analysis of hippocampal neuroinflammation and neurogenesis.

Surgery significantly impacted all parameters measured during the first post-surgery week, irrespective of the type of surgery. Effect on cognitive performance was limited to cognitive flexibility; both WBV and exercise prevented the surgery-induced decline. Exercise, but not WBV increased anxiety-like behavior and grip strength. WBV as well as exercise prevented the surgery-induced declined neurogenesis, but surgery-associated hippocampal neuroinflammation was not affected.

Our results indicated that active exercise and WBV share similar therapeutic potentials in the prevention of surgery induced decline in cognitive flexibility and hippocampal neurogenesis. In contrast to exercise, WBV did not increase anxiety-like behavior. Since neither intervention affected hippocampal neuroinflammation, other mechanisms and/or brain areas may be involved in the behavioral effects. Taken together, we conclude that WBV may provide a relevant alternative to active exercise during the early stage of post-operative recovery.

•

Both whole body vibration (WBV) and running exercise restored the reduced cognitive flexibility caused by surgery.

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WBV as well as active exercise prevented surgery-induced declined neurogenesis.

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Active exercise, but not WBV, induced anxiety-like behavior after surgery.

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Neither WBV nor active exercise affected surgery-induced neuroinflammation.

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Neither WBV nor active exercise influenced hemodynamic recovery from surgery.

Emotion recognition dysfunction after anesthesia and cardiac surgery

Cognitive dysfunction after anesthesia and surgery has long been recognized. Recently, researchers provided empirical evidence for social cognition dysfunction (SCD) after anesthesia and surgery. In the present study, we concentrated on the deficits in emotion recognition, one of the most important clinical perspectives in SCD, in patients who underwent cardiac surgery. Biological motion (BM) was considered as the stimulus of interest, and patients' abilities of BM emotion perception and action perception before and after anesthesia and surgery were examined. In total, 60 adult patients (40-72 years old) completed the BM recognition task, which required them to label the types of actions and emotions of perceived BM. The results showed that while action perception remained intact after cardiac surgery, 18.3% of patients exhibited deficits in emotion perception, further confirming the existence of SCD after anesthesia and surgery.

Effects of different types of non-cardiac surgical trauma on hippocampus-dependent memory and neuroinflammation

Background

Older individuals have been reported to suffer from cognitive disorders after surgery. Various types of surgical trauma have been used to establish postoperative cognitive dysfunction (POCD) animal models in preclinical studies. However, few comparative analyses of these animal models were conducted.

Methods

Tibial surgery, abdominal surgery, and extended abdominal surgery were performed on aged ICR mice to establish POCD models. Behavioral tests included open field, novel object recognition, fear conditioning, and Morris water maze tests. The Z-score methodology was adopted to obtain a comprehensive and integrated memory performance profile. The changes in hippocampal neuroinflammation were analyzed by ELISA, PCR, and immunofluorescence.

Results

In this study, we found that each type of non-cardiac surgical trauma has a different effects on locomotor activity. Tibial and extended abdominal surgeries led to more significant cognitive impairment than abdominal surgery. Inflammatory cytokines peaked on postoperative day 1 and decreased to control levels on days 3 and 7. Hippocampal neuroinflammation indicators between the three surgery types on postoperative day 1 had no statistical differences.

Conclusion

Overall, the type and intensity of non-cardiac surgical trauma can affect cognitive behavioral outcomes and central inflammation. The shortcomings and emerging issues of POCD animal research methods need to be further studied and solved.

Neuroprotective Effect of Dexmedetomidine against Postoperative Cognitive Decline via NLRP3 Inflammasome Signaling Pathway

Dexmedetomidine (Dex), widely used as a sedative in surgical procedures and intensive care units, induces sympatholytic, anxiolytic, analgesic, and sedative effects. Postoperative cognitive dysfunction (POCD) is routinely observed in postoperative care following surgery and general anesthesia. The NLRP3 inflammasome complex plays a critical role in innate immune response by detecting pathogenic microorganisms and activating pro-inflammatory cytokines. Although there are numerous protective effects of Dex among the neurological diseases, specific mechanisms including NLRP3 inflammasome-mediated neuroinflammation via oxidative stress response in a POCD model are not fully understood. Here, we investigated whether Dex exhibits neurocognitive effects through the NLRP3 inflammasome signaling in a POCD mouse model using a neurobehavioral test and ELISA analysis. We also confirmed the level of oxidative stress-related response in the in vitro system in the POCD model. Furthermore, we evaluated the NLRP3 inflammasome complex by immunoprecipitation analysis. In summary, the results of the present study indicated that Dex showed a neuroprotective effect in the POCD model by reducing oxidative stress response through NLRP3 inflammasome-mediated neuroinflammation.

Sex dimorphism in isoproterenol-induced cardiac damage associated neuroinflammation and behavior in old rats

Acute cardiac damage can be induced by isoproterenol injections in animals. The associated inflammatory response could be reflected in the brain as neuroinflammation, with potential consequences for brain function and behavior. Although cardiac responses are reported age and sex-related, for neuroinflammation and brain function this is virtually unknown. Therefore, cardiac damage and its consequences for neuroinflammation, brain function and behavior were compared in aged male and female rats. Wistar rats of 24 months of age were treated with isoproterenol (ISO, twice s.c.) or saline. Four weeks after injections, exploratory behavior and short-term memory were tested. Then, rats were sacrificed. Hearts were collected to measure cardiac damage. Brain tissue was collected to obtain measures of neuroinflammation and brain function. In male-, but not in female rats, ISO induced significant cardiac damage. Accordingly, mortality was higher in males than in females. Baseline hippocampal microglia activity was lower in females, while ISO induced neuroinflammation in both sexes, Hippocampal brain-derived neurotrophic factor expression appeared lower in females, without effects of ISO. In the open field test, ISO-treated males, but not females, displayed anxiety-like behavior. No effects of ISO were observed on short-term memory in either sex. In conclusion, sex dimorphism in effects of ISO was observed for cardiac damage and open field behavior. However, these effects could not be related to differences in hippocampal neuroinflammation or neuronal function.

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.

Dexmedetomidine attenuates hippocampal neuroinflammation in postoperative neurocognitive disorders by inhibiting microRNA-329-3p and activating the CREB1/IL1RA axis

RATIONALE

Due to its anti-inflammatory effect, dexmedetomidine (DEX) can confer neuroprotection in postoperative neurocognitive disorders (NCD). Here, the mechanism responsible for this effect of DEX is rarely ascertained.

OBJECTIVES

Our research was implemented to figure out mechanism governing the protection of DEX against hippocampal neuroinflammation in postoperative NCD.

METHODS

Exploratory laparotomy was applied for generating a postoperative NCD mouse model before bilateral hippocampal injection with microRNA (miR)-329-3p-agomir and intraperitoneal injection with DEX. Cognitive function of mice was evaluated by water maze test and fear conditioning test. Immunofluorescence was performed to assess microglial activation in hippocampus. After cell transfection and DEX treatment, mouse microglial cells (BV-2) were stimulated by lipopolysaccharide (LPS). IL-1β, IL-6, and TNF-α levels and the number of phagocytes were assessed by ELISA and flow cytometry. Dual-luciferase reporter assay was adopted to assess the relationship between miR-329-3p and CREB1.

RESULTS

miR-329-3p expression was reduced in the postoperative NCD mice after DEX treatment. DEX treatment or miR-329-3p downregulation caused attenuated cognitive dysfunction and microglia activation as well as reduced IL-1β, IL-6, and TNF-α levels in the hippocampus of the postoperative NCD mice. Mechanistically, miR-329-3p inversely targeted CREB1 that activated IL1RA in LPS-induced BV-2 cells. DEX treatment, miR-329-3p inhibition, or CREB1 or IL1RA upregulation curtailed the release of proinflammatory proteins and the number of phagocytes in LPS-induced BV-2 cells.

CONCLUSIONS

Collectively, our data provided the novel insight of the neuroprotective mechanism of DEX in postoperative NCD pertaining to the miR-329-3p/CREB1/IL1RA axis.

sVCAM1 in the Hippocampus Contributes to Postoperative Cognitive Dysfunction in Mice by Inducing Microglial Activation Through the VLA-4 Receptor

Postoperative cognitive dysfunction (POCD) is a severe postsurgical complication, but its underlying mechanisms remain unclear. Neuroinflammation mediated by microglial activation plays a major role in POCD pathophysiology. Upregulation of vascular cell adhesion molecule 1 (VCAM1) on brain endothelial cells is closely correlated with microglial activation in the mouse hippocampus. However, the role of VCAM1 upregulation in microglial activation remains unknown. Soluble VCAM1 (sVCAM1) activates the very late antigen-4 (VLA-4) receptor under inflammatory conditions. Therefore, we hypothesized that sVCAM1 which is shed from VCAM1 contributes to POCD by triggering hippocampal microglial activation through the VLA-4 receptor. We found that VCAM1 and sVCAM1 expression in the mouse hippocampus was upregulated after surgery, and the upregulation was accompanied by hippocampal microglial activation. sVCAM1 levels in mouse and human serum were increased after surgery. Anti-VCAM1 treatment inhibited microglial activation, proinflammatory cytokine production, VLA-4 expression and P38 mitogen-associated protein kinase (MAPK) pathway activation and attenuated hippocampal-dependent cognitive dysfunction. In vitro, recombinant sVCAM1 promoted M1 polarization in BV2 cells, increased VLA-4 expression and activated the P38 MAPK pathway. These effects were reversed by VLA-4 receptor blockade. Anti-VLA-4 treatment ameliorated hippocampal-dependent cognitive dysfunction after surgery by inhibiting microglial activation, proinflammatory cytokine production and P38 pathway activation. In conclusion, increased sVCAM1 in the hippocampus is involved in microglial activation and cognitive dysfunction induced by surgery. Inhibiting the sVCAM1-VLA-4 interaction in microglia may be a therapeutic strategy for POCD.

The effects of exercise training on heart, brain and behavior, in the isoproterenol-induced cardiac infarct model in middle-aged female rats

Women with cardiovascular disease may be more susceptible to concomitant mental health problems, such as depression and cognitive decline. Exercise training has beneficial effects on the cardiovascular system as well as on mental functions. Aim of the present study was to study the effects of exercise training on heart, brain and behavior in the isoproterenol (ISO) model in middle-aged female rats. Twelve months old female Wistar rats were submitted to ISO injections (70 mg/kg s.c., on two consecutive days) or received saline. One week later, rats were assigned to either exercise training (treadmill running) or control handling for five weeks. During the last 7 days, tests were performed regarding depressive-like behavior and cognitive function. Then, rats were sacrificed and heart and brains were dissected for (immuno)histochemistry. ISO-induced cardiac effects were eminent from cardiac fibrosis and declined cardiac function. Exercise training reversed cardiac damage and partly restored ISO-induced cardiac dysfunction. However, ISO treatment could not be associated with neuroinflammation, nor impaired hippocampal neurogenesis or neuronal function. Accordingly, no cognitive impairment or depressive-like behavior were observed. Actually, hippocampal microglia hyper-ramification was observed after ISO. Exercise left neuroinflammation and behavior merely unaltered, and even reduced neuronal function. Our data indicated that the cardiac damage after ISO in middle-aged female rats, and the subsequent beneficial effects of five weeks exercise training on the heart, were not reflected in changes in the brain nor in altered behavior.

Dexmedetomidine attenuates perioperative neurocognitive disorders by suppressing hippocampal neuroinflammation and HMGB1/RAGE/NF-κB signaling pathway

Surgical trauma can induce an inflammatory response in the central nervous system. Neuroinflammation is a crucial pathological mechanism of perioperative neurocognitive disorders (PND). Dexmedetomidine (Dex) is an alpha (α)-2 adrenoceptor agonist that is widely used in the perioperative period. Previous studies have shown that Dex has neuroprotection in various nerve injury models, but its role in PND remains unclear. Our study aimed to observe the neuroprotective effect of Dex pretreatment on postoperative cognitive change and explore the effects of hippocampal neuroinflammation, microglial polarization and HMGB1/RAGE/NF-κB signaling pathway involved in Dex on PND in rats. Rats were pretreated with Dex alone or in combination with yohimbine (α-2 adrenoceptor antagonist) before surgery. Behavioral tests results showed that Dex ameliorated surgery-induced cognitive impairment in rats. Nissl, immunohistochemistry and TUNEL-NeuN staining results indicated that Dex reduced hippocampus damage and neuronal apoptosis caused by surgery. Dex preconditioning reduced the expression of the proinflammatory cytokines IL-1β, TNF-α and IL-6 in hippocampus. Immunohistochemical and immunofluorescence results showed that Dex preconditioning inhibited the activation of glial cells induced by surgery. Western blot analysis showed that Dex preconditioning downregulated the expression of M1 phenotype markers (CD86 and iNOS), HMGB1, RAGE and nuclear NF-κB and upregulated the expression of M2 phenotype markers (Arginase 1 and CD206) and cytoplasmic NF-κB. Yohimbine could inhibit the neuroprotective effect of Dex. These results indicated that Dex pretreatment could improve postoperative short-term cognitive impairment, and the neuroprotective mechanism may involve the suppression of hippocampal neuroinflammation, regulation of M1/M2 polarization, and inhibition of HMGB1/RAGE/NF-κB signal transduction.

Dexmedetomidine Mitigates Microglial Activation Associated with Postoperative Cognitive Dysfunction by Modulating the MicroRNA-103a-3p/VAMP1 Axis

Surgery-induced microglial activation is critical in mediating postoperative cognitive dysfunction (POCD) in elderly patients, where the important protective effect of dexmedetomidine has been indicated. However, the mechanisms of action of dexmedetomidine during the neuroinflammatory response that underlies POCD remain largely unknown. We found that lipopolysaccharide (LPS) induced substantial inflammatory responses in primary and BV2 microglial cells. The screening of differentially expressed miRNAs revealed that miR-103a-3p was downregulated in these cell culture models. Overexpression of miR-103a-3p mimics and inhibitors suppressed and enhanced the release of inflammatory factors, respectively. VAMP1 expression was upregulated in LPS-treated primary and BV-2 microglial cells, and it was validated as a downstream target of miR-103-3p. VAMP1-knockdown significantly inhibited the LPS-induced inflammatory response. Dexmedetomidine treatment markedly inhibited LPS-induced inflammation and the expression of VAMP1, and miR-103a-3p expression reversed this inhibition. Moreover, dexmedetomidine mitigated microglial activation and the associated inflammatory response in a rat model of surgical trauma that mimicked POCD. In this model, dexmedetomidine reversed miR-103a-3p and VAMP1 expression; this effect was abolished by miR-103a-3p overexpression. Taken together, the data show that miR-103a-3p/VAMP1 is critical for surgery-induced microglial activation of POCD.

TREM2 ameliorates anesthesia and surgery-induced cognitive impairment by regulating mitophagy and NLRP3 inflammasome in aged C57/BL6 mice

Postoperative cognitive dysfunction (POCD) is a major postoperative complication. Triggering receptor expressed on myeloid cells 2 (TREM2) exerts a neuroprotective function against neuro-inflammatory responses. The present study investigated the role of TREM2 in anesthesia and surgery-induced cognitive impairment and the potential related mechanism. Our results revealed that TREM2 was downregulated, coupled with activation of the NLRP3 inflammasome and subsequent IL-1β expression on postoperative day 3. A corresponding decline in PSD-95 and BDNF was found at the same time point. The key regulator of mitophagy PINK1 and Parkin protein levels were significantly decreased following surgery and anesthesia. TREM2 overexpression partially reversed postoperative cognitive impairment and enhanced PSD-95 and BDNF expression. TREM2 overexpression also improved mitophagy function and inhibited activation of the NLRP3 inflammasome and associated production of IL-1β. Our findings demonstrate that TREM2 rescues anesthesia and surgery-induced spatial learning and memory impairment and neuro-inflammation in aged C57/BL6 mice, which may be at least partially mediated through the activation of mitophagy and subsequent inhibition of the NLRP3 inflammasome.

Sigesbeckia orientalis L. Derived Active Fraction Ameliorates Perioperative Neurocognitive Disorders Through Alleviating Hippocampal Neuroinflammation

Neuroinflammation is closely related to the pathogenesis of perioperative neurocognitive disorders (PNDs), which is characterized by the activation of microglia, inflammatory pathways and the release of inflammatory mediators. Sigesbeckia orientalis L. (SO) is a traditional Chinese medicine which demonstrates anti-inflammatory activities in different models. In this study, we aim to isolate the active fraction from the extract of SO with higher anti-inflammatory potential and confirm if the selected fraction exerts neuroprotection against the development of PND in an animal model. Moreover, the components in the selected fraction would be determined by UPLC-PDA analysis. Three fractions were prepared by column chromatography packed with three different macroporous resins. Anti-inflammatory activities of prepared fractions were accessed in microglial BV2 cultures by nitric oxide release, gene expression of inflammatory cytokines and activation of inflammatory JNK and NF-kB pathway molecules. Our results demonstrated that the fraction prepared from D101 macroporous resin (D101 fraction) exhibited a more potent anti-neuroinflammatory effect. The neuroprotective effect of D101 fraction was further examined in postoperative mice. Our results showed that surgery-induced cognitive dysfunction was attenuated by the D101 fraction treatment. This fraction also reduced microglial activation, inflammatory cytokines and inhibiting JNK and NF-kB pathway molecules in the hippocampus. In addition, surgery induced dendritic spine loss while D101 fraction ameliorated the spine loss in the hippocampus. For safety concerns, anti-thrombotic effect was examined by tail bleeding assay and no significant change of the bleeding pattern was found. UPLC-PDA analysis indicated that flavonoids (rutin, isochlorogenic acid A, isochlorogenic acid C) and terpenoid (darutoside) were the most important components in the D101 fraction. Our results support a therapeutic, as well as the translational potential for D101 fraction in ameliorating postoperative neuroinflammation and subsequent PND in the clinical setting without increasing bleeding tendencies.

Neuroinflammation as the Underlying Mechanism of Postoperative Cognitive Dysfunction and Therapeutic Strategies

Postoperative cognitive dysfunction (POCD) is a common neurological complication following surgery and general anesthesia, especially in elderly patients. Severe cases delay patient discharge, affect the patient’s quality of life after surgery, and are heavy burdens to society. In addition, as the population ages, surgery is increasingly used for older patients and those with higher prevalences of complications. This trend presents a huge challenge to the current healthcare system. Although studies on POCD are ongoing, the underlying pathogenesis is still unclear due to conflicting results and lack of evidence. According to existing studies, the occurrence and development of POCD are related to multiple factors. Among them, the pathogenesis of neuroinflammation in POCD has become a focus of research in recent years, and many clinical and preclinical studies have confirmed the correlation between neuroinflammation and POCD. In this article, we reviewed how central nervous system inflammation occurred, and how it could lead to POCD with changes in peripheral circulation and the pathological pathways between peripheral circulation and the central nervous system (CNS). Furthermore, we proposed some potential therapeutic targets, diagnosis and treatment strategies at the cellular and molecular levels, and clinical applications. The goal of this article was to provide a better perspective for understanding the occurrence of POCD, its development, and preventive strategies to help manage these vulnerable geriatric patients.