Surgical incision-induced nociception causes cognitive impairment and reduction in synaptic NMDA receptor 2B in mice

Anesthesia/surgery activate MMP9 leading to blood-brain barrier disruption, triggering neuroinflammation and POD-like behavior in aged mice

Anesthesia and surgery activate matrix metalloproteinase 9 (MMP9), leading to blood-brain barrier (BBB) disruption and postoperative delirium (POD)-like behavior, especially in the elderly. Aged mice received intraperitoneal injections of either the MMP9 inhibitor SB-3CT, melatonin, or solvent, and underwent laparotomy under 3 % sevoflurane anesthesia(anesthesia/surgery). Behavioral tests were performed 24 h pre- and post-operatively. Serum and cortical tissue levels of interleukin (IL)-1β, IL-6, and tumor necrosis factor-α (TNF-α) were measured using ELISA. Levels of PDGFRβ, MMP9, tight junction, Mfsd2a, caveolin-1, synaptophysin, and postsynaptic densin (PSD)-95 proteins in the prefrontal cortex were assayed using Western blotting. BBB permeability was assessed by detecting IgG in the prefrontal cortex and serum S100β levels. Anesthesia/surgery-induced peripheral inflammation activated MMP9, which in turn injured pericytes and tight junctions and increased transcytosis, thereby disrupting the BBB. Impaired BBB allowed the migration of peripheral inflammation into the central nervous system (CNS), thereby inducing neuroinflammation, synaptic dysfunction, and POD-like behaviors. However, MMP9 inhibition reduced pericyte and tight junction injury and transcytosis, thereby preserving BBB function and preventing the migration of peripheral inflammation into the CNS, thus attenuating synaptic dysfunction and POD-like behavior. In addition, to further validate the above findings, we showed that melatonin exerted similar effects through inhibition of MMP9. The present study shows that after anesthesia/surgery, inflammatory cytokines upregulation is involved in regulating BBB permeability in aged mice through activation of MMP9, suggesting that MMP9 may be a potential target for the prevention of POD.

Single exposure to anesthesia/surgery in neonatal mice induces cognitive impairment in young adult mice

BACKGROUND

The effects of a solitary neonatal exposure to anesthesia plus surgery (anesthesia/surgery) on cognitive function and the underlying mechanism in developing brains remains largely undetermined. We, therefore, set out to investigate the impact of single exposure to anesthesia/surgery in neonatal mice.

METHODS

Six-day-old male and female mice received abdominal surgery under 3% sevoflurane plus 50% oxygen for 2 h. The new object recognition (NOR) and Morris water maze (MWM) were used to evaluate cognitive function in young adult mice. Western blot, ELISA and RT-PCR were used to measure levels of NR2B and IL-6 in medial prefrontal cortex and IL-6 in blood of the mice. We employed NR2B siRNA and IL-6 antibody in the interaction studies.

RESULTS

The anesthesia/surgery decreased the ratio of novel time to novel plus familiar time in NOR and the number of platform crossings, but not escape latency, in MWM compared to sham condition. The mice in anesthesia/surgery group had increased NR2B expression in medial prefrontal cortex, and IL-6 amounts in blood and medial prefrontal cortex. Local injection of NR2B siRNA in medial prefrontal cortex alleviated the anesthesia/surgery-induced cognitive impairment. IL-6 antibody mitigated the anesthesia/surgery-induced upregulation of NR2B and cognitive impairment in young adult mice.

CONCLUSIONS

These results suggest that a single neonatal exposure to anesthesia/surgery causes impairment of memory, but not learning, in young adult mice through IL-6-regulated increases in NR2B concentrations in medial prefrontal cortex, highlighting the need for further research on the underlying mechanisms of anesthesia/surgery's impact on cognitive function in developing brains.

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.

Effect of transverse thoracic muscle plane block on postoperative cognitive dysfunction after open cardiac surgery: A randomized clinical trial

The transversus thoracis muscle plane (TTMP) block provides effective analgesia in cardiac surgery patients. The aim of this study was to assess whether bilateral TTMP blocks can reduce the incidence of postoperative cognitive dysfunction (POCD) in patients undergoing cardiac valve replacement. A group of 103 patients were randomly divided into the TTM group (n = 52) and the PLA (placebo) group (n = 51). The primary endpoint was the incidence of POCD at 1 week after surgery. Secondary outcome measures included a reduction of intraoperative mean arterial pressure (MAP) >20% from baseline, intraoperative and postoperative sufentanil consumption, length of stay in the ICU, incidence of postoperative nausea and vomiting (PONV), time to first faeces, postoperative pain at 24 h after surgery, time to extubation and the length of hospital stay. Interleukin (IL)-6, TNF-α, S-100β, insulin, glucose and insulin resistance were measured at before induction of anaesthesia, 1, 3and 7 days after surgery. The MoCA scores were significantly lower and the incidence of POCD decreased significantly in TTM group compared with PLA group at 7 days after surgery. Perioperative sufentanil consumption, the incidence of PONV and intraoperative MAP reduction >20% from baseline, length of stay in the ICU, postoperative pain at 24 h after surgery, time to extubation and the length of hospital stay were significantly decreased in the TTM group. Postoperatively, IL-6, TNF-α, S-100β, HOMA-IR, insulin, glucose levels increased and the TTM group had a lower degree than the PLA group at 1, 3 and 7 days after surgery. In summary, bilateral TTMP blocks could improve postoperative cognitive function in patients undergoing cardiac valve replacement.

A decrease in NR2B expression mediated by DNA hypermethylation induces perioperative neurocognitive disorder in aged mice

AIMS

This study was designed to investigate the role of NR2B and the contribution of DNA methylation to NR2B expression in the pathogenesis of PND.

METHODS

Eighteen-month-old C57BL/6J mice were subjected to experimental laparotomy under 1.4% isoflurane anesthesia. Hippocampus-dependent learning and memory were evaluated by using the Barnes maze and contextual fear conditioning tests. The protein and mRNA expression levels of NR2B were evaluated by western blotting and qRT-PCR respectively, and the methylation of the NR2B gene was examined by using targeted bisulfite sequencing. Long-term synaptic plasticity (LTP) was measured by electrophysiology.

RESULTS

Mice that underwent laparotomy exhibited hippocampus-dependent cognitive deficits accompanied by decreased NR2B expressions and LTP deficiency. The overexpression of NR2B in the dorsal hippocampus could improve learning and memory in mice subjected to laparotomy. In particular, the decreased NR2B expressions induced by laparotomy was attributed to the NR2B gene hypermethylation. Preoperative administration of S-adenosylmethionine (SAM) could hypomethylate the NR2B gene, upregulate NR2B expression and improve LTP, exerting a dose-dependent therapeutic effect against PND. Moreover, inhibiting NR2B abrogated the benefits of SAM pretreatment.

CONCLUSIONS

Laparotomy cause hippocampus-dependent cognitive decline by hypermethylating the NR2B gene, allowing us to understand the pathogenesis of PND in an epigenetic landscape.

Multimodal Analgesia for Accelerated Rehabilitation after Total Knee Arthroplasty: A Randomized, Double-Blind, Controlled Trial on the Effect of the Co-Application of Local Infiltration Analgesia and Femoral Nerve Block Combined with Dexmedetomidine

Background: Multimodal postoperative pain regimens are widely used following total knee arthroplasty (TKA). However, there are few studies on the rehabilitation of the co-application of local infiltration analgesia (LIA) and femoral nerve block (FNB) combined with dexmedetomidine (DEX) for patients undergoing TKA. This study aimed to investigate the effect of LIA plus FNB and co-application of perioperative DEX on TKA outcomes. Methods: 95 patients were randomized into two groups. Patients in group B (n = 48) received a single preoperative FNB and LIA. Patients in group A (n = 47) received FNB and LIA, as well as continuous intravenous injection of DEX starting from the induction of anesthesia to postoperative day 2. All patients were allowed patient-controlled analgesia postoperatively. Visual analog scale (VAS) scores, knee range of motion (ROM) degrees, narcotic consumption, length of hospital stay (LOS), complications, Hospital for Special Surgery (HSS) scores and Montreal Cognitive Assessment-Basic (MoCA-B) Scores were recorded. Results: In group A, the mean VAS scores at rest and during movement were lower, the amount of rescue analgesia was decreased, first time of ambulation was reduced, ROM was improved, MoCA-B Scores were increased, LOS was shorter, HSS scores were higher postoperatively compared with group B (all p < 0.05). Conclusion: Our study indicated multimodal analgesia involving a single FNB and LIA combined with DEX accelerates rehabilitation for patients undergoing TKA.

Reactive oxygen species contribute to delirium-like behavior by activating CypA/MMP9 signaling and inducing blood-brain barrier impairment in aged mice following anesthesia and surgery

Postoperative delirium (POD) is common in the elderly and is associated with poor clinical outcomes. Reactive oxygen species (ROS) and blood-brain barrier (BBB) damage have been implicated in the development of POD, but the association between these two factors and the potential mechanism is not clear. Cyclophilin A (CypA) is a specifically chemotactic leukocyte factor that can be secreted in response to ROS, which activates matrix metalloproteinase 9 (MMP9) and mediates BBB breakdown. We, therefore, hypothesized that ROS may contribute to anesthesia/surgery-induced BBB damage and delirium-like behavior via the CypA/MMP9 pathway. To test these hypotheses, 16-month-old mice were subjected to laparotomy under 3% sevoflurane anesthesia (anesthesia/surgery) for 3 h. ROS scavenger (N-acetyl-cysteine) and CypA inhibitor (Cyclosporin A) were used 0.5 h before anesthesia/surgery. A battery of behavior tests (buried food test, open field test, and Y maze test) was employed to evaluate behavioral changes at 24 h before and after surgery in the mice. Levels of tight junction proteins, CypA, MMP9, postsynaptic density protein (PSD)-95, and synaptophysin in the prefrontal cortex were assessed by western blotting. The amounts of ROS and IgG in the cortex of mice were observed by fluorescent staining. The concentration of S100β in the serum was detected by ELISA. ROS scavenger prevented the reduction in TJ proteins and restored the permeability of BBB as well as reduced the levels of CypA/MMP9, and further alleviated delirium-like behavior induced by anesthesia/surgery. Furthermore, the CypA inhibitor abolished the increased levels of CypA/MMP, which reversed BBB damage and ameliorated delirium-like behavior caused by ROS accumulation. Our findings demonstrated that ROS may participate in regulating BBB permeability in aged mice with POD via the CypA/MMP9 pathway, suggesting that CypA may be a potential molecular target for preventing POD.

The effect of opioid-sparing anesthesia regimen on short-term cognitive function after thoracoscopic surgery: a prospective cohort study

Background

As type of surgery and opioids are suggested risk factors for the development of cognitive decline after surgery, we evaluated the effect of an opioid-sparing anesthesia regimen involving preoperative erector spinae block and continuous infusion of flurbiprofen on the incidence of cognitive decline after video-assisted thoracoscopic surgery.

Methods

In this observational study, patients over 18 years old presenting for elective video-assisted thoracoscopic surgery were divided into two groups, the erector spinae plane block group (ESPB group, who received preoperative single shot of bi-level ESPB at T4 and T6 levels) and the control group who received intercostal nerve blocks through T5 to T7 intercostal spaces along mid-axillary line after surgery. Continuous infusion of flurbiprofen (8 mg/h) and intravenous oxycodone rescue (1 mg/bolus, lockout time 10 minutes) were provided as postoperative analgesics. Cognitive function was measured one day before and 48 h after surgery with brief Cogstate computerized battery (CCB).

Results

There were 60 patients included with 30 in each group. Perioperative sufentanil dose was significantly reduced in ESPB group. Nine (30%) and 15 (50%) patients had delayed neurocognitive recovery in the ESPB group and the control group respectively. Psychomotor speed and visual attention tests were the two tests that patients showed cognitive decline. The results of multivariate regression revealed that patients who were more than 53.5 years of age (OR 9.213, 95% CI 1.789, 47.437, P = 0.008) and low levels of education (less than 9 years of complimentary education) (OR 6.829, 95% CI 1.068, 43.677, P = 0.042) were independent risk factors for postoperative delayed neurocognitive recovery. For subgroup analysis, ESPB could reduce the occurrence of delayed neurocognitive recovery in patients with both risk factors (6/10 (60%) vs. 11/11 (100%), P = 0.004) compared to the control group.

Conclusions

Middle-aged people and low levels of education are independent risk factors for delayed neurocognitive recovery after thoracoscopic surgery. ESPB has the potential to prevent cognitive decline in high-risk patients.

Trial registration

ChiCTR1800014508 (www.chictr.org.cn, January 17, 2018; Hong Zhao, M.D.). URL: http://www.chictr.org.cn/showproj.aspx?proj=24778. The date of the enrolment of the first participant to the trial was January 22, 2018.

Cerebral Glutamate Regulation and Receptor Changes in Perioperative Neuroinflammation and Cognitive Dysfunction

Glutamate is the major excitatory neurotransmitter in the central nervous system and is intricately linked to learning and memory. Its activity depends on the expression of AMPA and NMDA receptors and excitatory amino transporters on neurons and glial cells. Glutamate transporters prevent the excess accumulation of glutamate in synapses, which can lead to aberrant synaptic signaling, excitotoxicity, or cell death. Neuroinflammation can occur acutely after surgical trauma and contributes to the development of perioperative neurocognitive disorders, which are characterized by impairment in multiple cognitive domains. In this review, we aim to examine how glutamate handling and glutamatergic function are affected by neuroinflammation and their contribution to cognitive impairment. We will first summarize the current data regarding glutamate in neurotransmission, its receptors, and their regulation and trafficking. We will then examine the impact of inflammation on glutamate handling and neurotransmission, focusing on changes in glial cells and the effect of cytokines. Finally, we will discuss these changes in the context of perioperative neuroinflammation and the implications they have for perioperative neurocognitive disorders.

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.

Deficiency of cGAS signaling protects against sepsis-associated encephalopathy

Sepsis is a life-threatening inflammatory syndrome secondary to infection. Thanks to the advances of antibiotics and life-supporting techniques, the mortality of sepsis has been decreasing in recent decades. Nevertheless, sepsis-associated encephalopathy (SAE) is still common in septic patients, which promotes the mortality of septic patients and results in cognitive dysfunction in survivors. Full understanding and effective medicine in the treatment of SAE is currently scant. Here, we revealed a novel role of cGAS signaling in the pathogenesis of SAE. Deficiency of cGas significantly restored cognitive impairment in sepsis mice model. The restoration may attribute to the recovery of neo-neuron decline that associated with the decrease of activated microglia and astrocytes in the hippocampus of cGas-deficient mice. In addition, type I interferon (IFN) signaling, a downstream of cGAS pathway, was boosted in the hippocampus of septic mice, which was dramatically attenuated by deleting cGas. Moreover, administration of recombinant IFNβ markedly reversed the protection of ablation of cGas in the cognitive impairment in sepsis. Collectively, cGAS promotes the pathogenesis of SAE by up-regulating type I IFN signaling. Blocking cGAS may be a promising strategy for preventing encephalopathy in sepsis.

Effect of quadratus lumborum block on postoperative cognitive function in elderly patients undergoing laparoscopic radical gastrectomy: a randomized controlled trial

Background

Quadratus lumborum block (QLB) is a novel and effective postoperative analgesia method for abdominal surgeries. However, whether QLB can affect early postoperative cognitive function by inhibiting surgical traumatic stress and the inflammatory response remains unclear. This study aimed to explore the effect of QLB on postoperative cognitive function in elderly patients undergoing laparoscopic radical gastrectomy.

Methods

Sixty-four elderly patients who underwent laparoscopic radical gastrectomy were randomly divided into the QLB group (Q group, n = 32) and control group (C group, n = 32). The Mini-Mental State Examination (MMSE) and Montreal Cognitive Assessment (MoCA) were used to measure cognitive function 1 day before and 7 days after surgery. Postoperative cognitive dysfunction (POCD) was defined as a decline of ≥ 1 SD in both tests. The visual analog scale (VAS) scores 6 h (T1), 24 h (T2), and 48 h (T3) after surgery were measured. The serum levels of high mobility group box protein 1 (HMGB1), interleukin-6 (IL-6), and tumor necrosis factor-α (TNF-α) were evaluated 1 day before surgery (baseline), and 1 day (day 1) and 3 days after surgery (day 3). The intraoperative remifentanil dosage, sufentanil consumption 24 h after surgery, recovery time from anesthesia, and adverse effects were also compared.

Results

POCD was present in two patients in the QLB group and eight patients in the C group 7 days after surgery (6.7 % vs. 27.6 %, P = 0.032). The MMSE and MoCA scores were similar in both groups preoperatively, and the two scores were higher in the QLB group than in the C group 7 days after surgery (P < 0.05). The VAS scores were significantly lower in the Q group at all times after surgery (P < 0.05). Compared with the C group, the levels of HMGB1, TNF-α, and IL-6 were significantly decreased 1 and 3 days after surgery in the QLB group (P < 0.05). The remifentanil consumption intraoperatively and sufentanil 24 h postoperatively were significantly lower in the QLB group (P < 0.05). The recovery time from anesthesia was shorter in the QLB group (P < 0.05). No severe adverse effects occurred in either group.

Conclusions

QLB could improve postoperative cognitive function in elderly patients undergoing laparoscopic radical gastrectomy. This may be related to the suppression of the inflammatory response after surgery.

Trial registration

Chictr.org.cn identifier ChiCTR1900027574 (Date of registry: 19/11/2019, prospectively registered).

Tourniquet use in total knee replacement surgery: a feasibility study and pilot randomised controlled trial (SAFE-TKR study)

INTRODUCTION

Tourniquets are routinely used during total knee replacement (TKR) surgery. They could increase the risk of thromboembolic events including cerebral emboli, cognitive decline, pain and other adverse events (AEs). A randomised controlled trial to assess whether tourniquet use might safely be avoided is therefore warranted but it is unclear whether such a trial would be feasible.

METHODS

In a single-site feasibility study and pilot randomised controlled trial, adults having a TKR were randomised to surgery with an inflated tourniquet versus a non-inflated tourniquet. Participants underwent brain MRI preoperatively and within 2 days postoperatively. We assessed cognition using the Mini-Mental State Examination (MMSE), Montreal Cognitive Assessment (MoCA) and Oxford Cognitive Screen (OCS) and thigh pain using a Visual Analogue Scale at baseline and days 1 and 2, and 1 week postsurgery. AEs related to surgery were recorded up to 12 months.

RESULTS

We randomised 53 participants (27 tourniquet inflated and 26 tourniquet not inflated). Fifty-one participants received care per-protocol (96%) and 48 (91%) were followed up at 12 months. One new ischaemic brain lesion was detected. Of the cognitive tests, MoCA was easy to summarise, sensitive to change with lower ceiling effects compared with OCS and MMSE. There was a trend towards more thigh pain (mean 49.6 SD 30.4 vs 36.2 SD 28 at day 1) and more AEs related to surgery (21 vs 9) in participants with an inflated tourniquet compared with those with a tourniquet not inflated.

CONCLUSION

A full trial is feasible, but using MRI as a primary outcome is unlikely to be appropriate or feasible. Suitable primary outcomes would be cognition measured using MoCA, pain and AEs, all of which warrant investigation in a large multicentre trial.

TRIAL REGISTRATION NUMBER

ISRCTN20873088.

Silencing IFNγ inhibits A1 astrocytes and attenuates neurogenesis decline and cognitive impairment in endotoxemia

Cognitive impairment, acute or long-term, is a common complication in patients with severe bacterial infection. However, the underlying mechanisms are not fully verified and effective medicine is not available in clinics. Interferon gamma (IFNγ) is a pivotal cytokine against infection and is believed to be a tune in homeostasis of cognitive function. Here, we collected blood and cerebrospinal fluid (CF) from human subjects and mice, and found that plasma and CF levels of IFNγ were significantly increased in septic patients and endotoxin-challenged mice when compared with healthy controls. IFNγ signaling was boosted in the hippocampus of mice after a challenge of lipopolysaccharide (LPS), which was accompanied with cognitive impairment and decline of neurogenesis. Deficiency of IFNγ or its receptor (IFNγR) dramatically attenuated microglia-induced A1 astrocytes and consequently restored neurogenesis and cognitive function in endotoxemia mice model. Using primary microglia, astrocytes and neurons, we found that IFNγ remarkably increased LPS-mediated release of TNFα and IL-1α in microglia and consequently induced the transformation of astrocyte to A1 subtype, which ultimately resulted in neuron damage. Thus, IFNγ promotes cognitive impairment in endotoxemia by enhancing microglia-induced A1 astrocytes. Targeting IFNγ would be a novel strategy for preventing or treating cognitive dysfunction in patients with Gram-negative infection.

Hydrogen sulfide attenuates postoperative cognitive dysfunction through promoting the pathway of Warburg effect-synaptic plasticity in hippocampus

Postoperative cognitive dysfunction (POCD) is deemed to a severe surgical complication without effective treatment. Previous work has confirmed the important modulatory role of hydrogen sulfide (H₂S) in cognitive function. This study was proposed to explore whether H₂S relieves POCD and the possible mechanisms. We demonstrated that NaHS (a donor of H₂S) reversed the inhibited endogenous H₂S generation in the hippocampus of postoperative rats. NaHS attenuated the cognitive impairment of postoperative rats in the Y-maze, Novel object recognition, and Morris water maze tests. NaHS enhanced the expressions of synaptic plasticity-related proteins, synapsin-1 and PSD-95, increased the synaptic density, and decreased the destruction of synaptic structures in the hippocampus of postoperative rats. Moreover, NaHS promoted Warburg effect in the hippocampus of postoperative rats, as reflected by increases in the expressions of hexokinase 2, pyruvate kinase M2, lactate dehydrogenase A, and pyruvate dehydrogenase kinase 1, an enhancement in the content of lactate, and a reduction in the expression of pyruvate dehydrogenase. The inhibitor of Warburg effect, 2-Deoxy-D-glucose (2-DG), not only reversed NaHS-enhanced Warburg effect in the hippocampus of postoperative rats, but also significantly abolished NaHS-exerted protective effect on cognitive function. Furthermore, 2-DG reversed NaHS-exerted enhancement in the expressions of synapsin-1 and PSD-95, increase in the synaptic density, and decrease in the destruction of synaptic structures in the hippocampus of postoperative rats. Collectively, these results indicate that H₂S alleviates POCD through enhancing hippocampal Warburg effect, which subsequently improves synaptic plasticity in the hippocampus.

Differential expression of Cdk5-phosphorylated CRMP2 following a spared nerve injury

Effective treatment of high-impact pain patients is one of the major stated goals of the National Pain Strategy in the United States. Identification of new targets and mechanisms underlying neuropathic pain will be critical in developing new target-specific medications for better neuropathic pain management. We recently discovered that peripheral nerve injury-induced upregulation of an axonal guidance phosphoprotein collapsin response mediator protein 2 (CRMP2) and the N-type voltage-gated calcium (CaV2.2) as well as the NaV1.7 voltage-gated sodium channel, correlates with the development of neuropathic pain. In our previous studies, we found that interfering with the phosphorylation status of CRMP2 is sufficient to confer protection from chronic pain. Here we examined the expression of CRMP2 and CRMP2 phosphorylated by cyclin-dependent kinase 5 (Cdk5, on serine residue 522 (S522)) in sciatic nerve, nerve terminals of the glabrous skin, and in select subpopulations of DRG neurons in the SNI model of neuropathic pain. By enhancing our understanding of the phosphoregulatory status of CRMP2 within DRG subpopulations, we may be in a better position to design novel pharmacological interventions for chronic pain.

Ethyl pyruvate protects against sepsis-associated encephalopathy through inhibiting the NLRP3 inflammasome

BACKGROUND

With the advance of antibiotics and life support therapy, the mortality of sepsis has been decreasing in recent years. However, the incidence of sepsis-associated encephalopathy (SAE), a common complication of sepsis, is still high. There are few effective therapies to treat clinical SAE. We previously found that ethyl pyruvate (EP), a metabolite derivative, is able to effectively inhibit the NLRP3 inflammasome activation. Administration of ethyl pyruvate protects mice against polymicrobial sepsis in cecal ligation and puncture (CLP) model. The aim of present study is to investigate if ethyl pyruvate is able to attenuate SAE.

METHODS

After CLP, C57BL/6 mice were intraperitoneally or intrathecally injected with saline or ethyl pyruvate using the sham-operated mice as control. New Object Recognition (NOR) and Morris Water Maze (MWM) were conducted to determine the cognitive function. Brain pathology was assessed via immunohistochemistry. To investigate the mechanisms by which ethyl pyruvate prevent SAE, the activation of NLRP3 in the hippocampus and the microglia were determined using western blotting, and cognitive function, microglia activation, and neurogenesis were assessed using WT, Nlrp3-/- and Asc-/- mice in the sublethal CLP model. In addition, Nlrp3-/- and Asc-/- mice treated with saline or ethyl pyruvate were subjected to CLP.

RESULTS

Ethyl pyruvate treatment significantly attenuated CLP-induced cognitive decline, microglia activation, and impaired neurogenesis. In addition, EP significantly decreased the NLRP3 level in the hippocampus of the CLP mice, and inhibited the cleavage of IL-1β induced by NLRP3 inflammsome in microglia. NLRP3 and ASC deficiency demonstrated similar protective effects against SAE. Nlrp3-/- and Asc-/- mice significantly improved cognitive function and brain pathology when compared with WT mice in the CLP models. Moreover, ethyl pyruvate did not have additional effects against SAE in Nlrp3-/- and Asc-/- mice.

CONCLUSION

The results demonstrated that ethyl pyruvate confers protection against SAE through inhibiting the NLRP3 inflammasome.

Intranasal Insulin Prevents Anesthesia-induced Cognitive Impairments in Aged Mice

BACKGROUND

Preclinical and clinical evidence suggests that elderly individuals are at increased risk of cognitive decline after general anesthesia. General anesthesia is also believed to be a risk factor for Postoperative Cognitive Dysfunction (POCD) and Alzheimer's Disease (AD). Intranasal administration of insulin, which delivers the drug directly into the brain, improves memory and cognition in both animal studies and small clinical trials. However, how insulin treatment improves cognitive function is poorly understood.

METHODS

Aged mice were pretreated with intranasal insulin or saline before anesthesia. Propofol was added intraperitoneally to the mice from 7th day of insulin/saline treatment, and general anesthesia was induced and maintained for 2 hours/day for 5 consecutive days. Mice were evaluated at 26th day when the mice were continued on insulin or saline administration for another 15 days.

RESULTS

We found that intranasal insulin treatment prevented anesthesia-induced cognitive impairments, as measured by novel object recognition test and contextual-dependent fear conditioning test. Insulin treatment also increased the expression level of Post-synaptic Density Protein 95 (PSD95), as well as upregulated Microtubule-associated Protein-2 (MAP-2) in the dentate gyrus of the hippocampus. Furthermore, we found that insulin treatment restored insulin signaling disturbed by anesthesia via activating PI3K/PDK1/AKT pathway, and attenuated anesthesia-induced hyperphosphorylation of tau at multiple AD-associated sites. We found the attenuation of tau hyperphosphorylation occurred by increasing the level of GSK3β phosphorylated at Ser9, which leads to inactivation of GSK-3β.

CONCLUSION

Intranasal insulin administration might be a promising therapy to prevent anesthesiainduced cognitive deficit in elderly individuals.

Resveratrol Mitigates Sevoflurane-Induced Neurotoxicity by the SIRT1-Dependent Regulation of BDNF Expression in Developing Mice

Various lines of evidence suggest that neonatal exposure to general anesthetics, especially repeatedly, results in neuropathological brain changes and long-term cognitive impairment. Although progress has been made in experimental models, the exact mechanism of GA-induced neurotoxicity in the developing brain remains to be clarified. Sirtuin 1 (SIRT1) plays an important role in synaptic plasticity and cognitive performance, and its abnormal reduction is associated with cognitive dysfunction in neurodegenerative diseases. However, the role of SIRT1 in GA-induced neurotoxicity is unclear to date. In this study, we found that the protein level of SIRT1 was inhibited in the hippocampi of developing mice exposed to sevoflurane. Furthermore, the SIRT1 inhibition in hippocampi was associated with brain-derived neurotrophic factor (BDNF) downregulation modulated by methyl-cytosine-phosphate-guanine-binding protein 2 (MeCP2) and cAMP response element-binding protein (CREB). Pretreatment of neonatal mice with resveratrol nearly reversed the reduction in hippocampal SIRT1 expression, which increased the expression of BDNF in developing mice exposed to sevoflurane. Moreover, changes in the levels of CREB and MeCP2, which were considered to interact with BDNF promoter IV, were also rescued by resveratrol. Furthermore, resveratrol improved the cognitive performance in the Morris water maze test of the adult mice with exposure to sevoflurane in the neonatal stage, without changing motor function in the open field test. Taken together, our findings suggested that SIRT1 deficiency regulated BDNF signaling via regulation of the epigenetic activity of MeCP2 and CREB, and resveratrol might be a promising agent for mitigating sevoflurane-induced neurotoxicity in developing mice.

Influence of postoperative analgesia on systemic inflammatory response and postoperative cognitive dysfunction after femoral fractures surgery: a randomized controlled trial

BACKGROUND AND OBJECTIVES

To investigate the possible effect of postoperatively applied analgesics-epidurally applied levobupivacaine or intravenously applied morphine-on systemic inflammatory response and plasma concentration of interleukin (IL)-6 and to determine whether the intensity of inflammatory response is related to postoperative cognitive dysfunction (POCD).

METHODS

This is a randomized, prospective, controlled study in an academic hospital. Patients were 65 years and older scheduled for femoral fracture fixation from July 2016 to September 2017. Inflammatory response was assessed by leukocytes, neutrophils, C reactive protein (CRP) and fibrinogen levels in four blood samples (before anesthesia, 24 hours, 72 hours and 120 hours postoperatively) and IL-6 concentration from three blood samples (before anesthesia, 24 hours and 72 hours postoperatively). Cognitive function was assessed using the Mini-Mental State Examination preoperatively, from the first to the fifth postoperative day and on the day of discharge.

RESULTS

The study population included 70 patients, 35 in each group. The incidence of POCD was significantly lower in the levobupivacaine group (9%) than in the morphine group (31%) (p=0.03). CRP was significantly lower in the levobupivacaine group 72 hours (p=0.03) and 120 hours (p=0.04) after surgery. IL-6 values were significantly lower in the levobupivacaine group 72 hours after surgery (p=0.02). The only predictor of POCD in all patients was the level of IL-6 72 hours after surgery (p=0.03).

CONCLUSIONS

There is a statistically significant association between use of epidural levobupivacaine and a reduction in some inflammatory markers. Postoperative patient-controlled epidural analgesia reduces the incidence of POCD compared with intravenous morphine analgesia in the studied population.

TRIAL REGISTRATION NUMBER

NCT02848599.

[Research progress of the role of postoperative pain in the development of postoperative cognitive dysfunction in geriatric patients]

Previous studies have shown that postoperative cognitive dysfunction (POCD) is related to multiple factors including age, postoperative trauma, inflammation, postoperative pain, and anesthesia, among which postoperative pain is thought to play an important role in the development of POCD. This review summarizes the recent findings in the study of the role of postoperative pain in the pathogenesis of POCD in light of nerve injuries, neural remodeling and stress, and the progress in the prevention and treatment of POCD in elderly patients. It is of vital important to assess the postoperative pain and formulate adequate analgesic regimens for effective prevention and management of POCD to protect the brain functions of elderly patients.

Intestinal dysbacteriosis mediates the reference memory deficit induced by anaesthesia/surgery in aged mice

BACKGROUND

Postoperative cognitive dysfunction (POCD) is associated with increased morbidity and mortality and has become a major concern for patients and caregivers. POCD is most common in older patients. Previous studies demonstrated that the gut microbiome affects cognitive function and behaviour, and perioperative factors, including the operation itself, antibiotics, opioids or acid-inducing drugs, affect the gut microbiome. Thus, we hypothesised that intestinal dysbacteriosis caused by anaesthesia/surgery induces POCD.

METHODS

Tibial fracture internal fixation was performed in 18-month-old C57BL/6 mice under isoflurane anaesthesia to establish the POCD model. The Morris water maze was used to measure reference memory after anaesthesia/surgery. High-throughput sequencing of 16S rRNA from faecal samples was used to investigate changes in the abundance of intestinal bacteria after anaesthesia/surgery. To confirm the role of the gut microbiome in POCD, we pretreated mice with compound antibiotics or mixed probiotics (VSL#3). Anaesthesia/surgery impaired reference memory and induced intestinal dysbacteriosis in aged mice.

RESULTS

The 16S rRNA sequencing data revealed 37 genera (18 families) of bacteria that changed in abundance after anaesthesia/surgery. Pretreating mice with compound antibiotics or mixed probiotics (VSL#3) prevented the learning and memory deficits induced by anaesthesia/surgery. We further conducted quantitative real-time polymerase chain reaction (qRT-PCR) of 22 common types of bacteria among the 37 total types to verify the results of bacterial flora changes after anaesthesia/surgery. Numbers of 8 types of bacteria changed after anaesthesia/surgery but returned to normal after treatment with a mix of probiotics.

CONCLUSIONS

Our data suggest that deficits in reference memory induced by anaesthesia/surgery are mediated by intestinal dysbacteriosis.

Core Outcome Measures in Preclinical Assessment of Candidate Analgesics

All preclinical procedures for analgesic drug discovery involve two components: 1) a "pain stimulus" (the principal independent variable), which is delivered to an experimental subject with the intention of producing a pain state; and 2) a "pain behavior" (the principal dependent variable), which is measured as evidence of that pain state. Candidate analgesics are then evaluated for their effectiveness to reduce the pain behavior, and results are used to prioritize drugs for advancement to clinical testing. This review describes a taxonomy of preclinical procedures organized into an "antinociception matrix" by reference to their types of pain stimulus (noxious, inflammatory, neuropathic, disease related) and pain behavior (unconditioned, classically conditioned, operant conditioned). Particular emphasis is devoted to pain behaviors and the behavioral principals that govern their expression, pharmacological modulation, and preclinical-to-clinical translation. Strengths and weaknesses are compared and contrasted for procedures using each type of behavioral outcome measure, and the following four recommendations are offered to promote strategic use of these procedures for preclinical-to-clinical analgesic drug testing. First, attend to the degree of homology between preclinical and clinical outcome measures, and use preclinical procedures with behavioral outcome measures homologous to clinically relevant outcomes in humans. Second, use combinations of preclinical procedures with complementary strengths and weaknesses to optimize both sensitivity and selectivity of preclinical testing. Third, take advantage of failed clinical translation to identify drugs that can be back-translated preclinically as active negative controls. Finally, increase precision of procedure labels by indicating both the pain stimulus and the pain behavior in naming preclinical procedures.

COX-2 contributed to the remifentanil-induced hyperalgesia related to ephrinB/EphB signaling

Background and Objectives： Studying the underlying mechanisms of opiate-induced hyperalgesia is fundamental to understanding and treating pain. Our previous study has proved that ephrinB/EphB signaling contributes to opiate-induced hyperagesia, but the manner in which ephrinB/EphB signaling acts on spinal nociceptive information networks to produce hyperalgesia remains unclear. Other studies have suggested that ephrinB/EphB signaling, NMDA receptor and COX-2 act together to participate in the modulation of nociceptive information processes at the spinal level. The objective of this research was to investigate the role of COX-2 in remifentanil-induced hyperalgesia and its relationship with ephrinB/EphB signaling. Methods： We characterized the remifentanil-induced pain behaviours by evaluating thermal hyperalgesia and mechanical allodynia in a mouse hind paw incisional model. Protein expression of COX-2 in spinal cord was assayed by western blotting and mRNA level of COX-2 was assayed by Real-time PCR (RT-PCR). Results： Continuing infusion of remifentanil produced thermal hyperalgesia and mechanical allodynia, which was accompanied by increased expression of spinal COX-2 protein and mRNA. This response was inhibited by pre-treatment with EphB2-Fc, an antagonist of ephrinB/EphB. SC58125 and NS398, inhibitors of COX-2, suppressed pain behaviours induced by remifentanil infusion and reversed the increased pain behaviours induced by intrathecal injection of ephrinB2-Fc, an agonist of ephrinB/EphB. Conclusions: Our findings confirmed that COX-2 is involved in remifentanil-induced hyperalgesia related to ephrinB/EphB signaling. EphrinB/EphB signaling might be the upstream of COX-2.

Surgery Under General Anesthesia Alleviated the Hyperactivity but Had No Effect on the Susceptibility to PND in ADHD Rats

Background: Attention-deficit hyperactivity disorder (ADHD) is a typical neuropsychiatric disorder characterized by inattention, impulsivity, and hyperactivity, particularly in children. Recent studies demonstrated a close relationship between the development of ADHD and surgery under general anesthesia. However, few studies illustrated if ADHD symptoms changed after surgery. Meanwhile, whether these individuals with natural neural impairment were sensitive to postoperative neurocognitive disorder (PND) still remain unclear. Methods: Spontaneously hypertensive rats (SHR) were utilized as spontaneous ADHD animal model and Wistar-Kyoto (WKY) rats as non-ADHD animal model. We evaluated the variation of neurocognitive function and locomotor activity of the rats undergoing experimental laparotomy with general anesthesia by isoflurane. Neurocognitive function was assessed by fear conditioning test for contextual memory and Morris water maze (MWM) for spatial memory. Depressive-like behavior after surgery was detected by forced swim test, and open-field test and elevated plus maze test were utilized to evaluate locomotor activities and anxiety. Furthermore, we compared electroencephalogram (EEG) signal in ADHD and WKY rats under free-moving conditions. Afterward, c-Fos staining was also utilized to detect the excitatory activity of neurons in these rats to explore the neural mechanism. Results: Locomotor activity of SHR assessed by average speed and number of line crossings in the open-field test decreased 1 week after surgery under general anesthesia, but there was no difference concerning anxiety levels between SHR and WKY rats after surgery. This phenomenon was also paralleled with the change in EEG signal (delta band 0∼3 Hz). Surgery under general anesthesia had no effect on spatial and contextual memory, while it improved spontaneous depression in SHR. The expression of c-Fos was downregulated for at least 1 week in the nucleus accumbens (NAc) area of ADHD rats' brain after surgery. Conclusion: ADHD rats were not sensitive to PND. Surgery with general anesthesia could partly improve the hyperactivity symptom of ADHD rats. This mechanism was related to the suppression of neural activity in the cerebral NAc of ADHD rats induced by general anesthetics.

Inhibiting RIPK1 Limits Neuroinflammation and Alleviates Postoperative Cognitive Impairments in D-Galactose-Induced Aged Mice

Neuroinflammation plays a critical role in the pathogenesis of postoperative cognitive dysfunction (POCD) of the elderly patients. Receptor-interacting protein kinase1 (RIPK1) is a key molecular switch modulating inflammation, apoptosis and necroptosis. Here, we investigated whether inhibiting RIPK1 by necrostatin-1 (Nec-1) could limit neuroinflammation and attenuate POCD in D-Galactose (D-Gal)-induced aged mice. The mice were subjected to anesthesia and partial hepatectomy, and necrostatin-1 was administered intraperitoneally 1 h prior to anesthesia and surgery. Cognitive function and movement were tested 24 h after surgery by open field, Barnes maze and puzzle box. The hippocampal tissues were collected to detect the following: neuroinflammation (Iba-1, IL-1α, IL-1β, TNF-α), Necroptosis (Propidium Iodide (PI) labeling, RIPK1, nuclear transcription factor kappa B (NF-κB) and neuroplasticity (doublecortin (DCX), NR2B, GluA1, GluA2). We found that anesthesia and surgery induced a significant deficit in spatial memory acquisition and impairment of executive function and memory to simple task in D-Galactose-induced aged mice. Inhibiting RIPK1 by necrostatin-1 strikingly mitigated cognitive impairment and alleviated postoperative amplified neuroinflammation, necroptosis and GluA1 loss in hippocampus. These suggest that targeting RIPK1 by necrostatin-1 may serve as a promising therapeutics for prevention of POCD in elderly patients.

Role of the Prefrontal Cortex in Pain Processing

The prefrontal cortex (PFC) is not only important in executive functions, but also pain processing. The latter is dependent on its connections to other areas of the cerebral neocortex, hippocampus, periaqueductal gray (PAG), thalamus, amygdala, and basal nuclei. Changes in neurotransmitters, gene expression, glial cells, and neuroinflammation occur in the PFC during acute and chronic pain, that result in alterations to its structure, activity, and connectivity. The medial PFC (mPFC) could serve dual, opposing roles in pain: (1) it mediates antinociceptive effects, due to its connections with other cortical areas, and as the main source of cortical afferents to the PAG for modulation of pain. This is a ‘loop’ where, on one side, a sensory stimulus is transformed into a perceptual signal through high brain processing activity, and perceptual activity is then utilized to control the flow of afferent sensory stimuli at their entrance (dorsal horn) to the CNS. (2) It could induce pain chronification via its corticostriatal projection, possibly depending on the level of dopamine receptor activation (or lack of) in the ventral tegmental area-nucleus accumbens reward pathway. The PFC is involved in biopsychosocial pain management. This includes repetitive transcranial magnetic stimulation, transcranial direct current stimulation, antidepressants, acupuncture, cognitive behavioral therapy, mindfulness, music, exercise, partner support, empathy, meditation, and prayer. Studies demonstrate the role of the PFC during placebo analgesia, and in establishing links between pain and depression, anxiety, and loss of cognition. In particular, losses in PFC grey matter are often reversible after successful treatment of chronic pain.

Central cholinergic system mediates working memory deficit induced by anesthesia/surgery in adult mice

BACKGROUND

Postoperative cognitive dysfunction (POCD) is consistently associated with increased morbidity and mortality, which has become a major concern of patients and caregivers. Although POCD occurs mainly in aged patients, it happens at any age. Previous studies demonstrated that anesthesia/surgery had no effects on reference memory of adult mice. However, whether it impairs working memory remains unclear. Working memory deficit would result in many deficits of executive function. We hypothesized that anesthesia/surgery impaired the working memory of adult mice and the central cholinergic system was involved.

METHOD

Tibial fracture internal fixation under the anesthesia of isoflurane was performed in two-month-old C57BL/6 mice. Two days later, the spatial reference memory and working memory were measured by a Morris Water Maze (MWM). Donepezil, an inhibitor of acetylcholinesterase (AChE), was administered in another cohort mice for 4 weeks. Then, the working memory was measured by MWM 2 days after anesthesia/surgery. Western blot was used to detect the protein levels of acetylcholine transferase (ChAT), AChE, vesicular acetylcholine transporter (VAChT), and choline transporter (ChT) in the prefrontal cortex (PFC).

RESULTS

We found that anesthesia/surgery had no effects on the reference memory, but it impaired the working memory in adult mice. Meanwhile, we also found that the protein level of ChAT in PFC decreased significantly compared with that in control group. Donepezil pretreatment prevented working memory impairment and the decrease of the protein levels of ChAT induced by anesthesia/surgery.

CONCLUSION

These results suggest that anesthesia/surgery leads to working memory deficits in adult mice and central cholinergic system impairment is involved.

A Mouse Model of Orthopedic Surgery to Study Postoperative Cognitive Dysfunction and Tissue Regeneration

Surgery is commonly used to improve and maintain quality of life. Unfortunately, in vulnerable patients such as the elderly, complications may occur and significantly diminish the outcome. Indeed, after routine orthopedic surgery to repair a fracture, as many as 50% of elderly patients suffer from neurologic complications like delirium. Also, the capacity to heal and regenerate tissue after surgery decreases with age, and can impact the quality of fracture repair and even osseous integration of implants. Thus, a better understanding of mechanisms that drive these age-dependent changes could provide strategic targets to minimize risk for such complications and optimize outcomes. Here, we introduce a clinically relevant mouse model of tibial fracture. The postoperative changes in these mice mimic some of the cognitive impairments commonly observed after routine orthopedic surgery in humans. Briefly, an incision is performed in the right hind limb under strictly aseptic conditions. Muscles are disassociated, and a 0.38-mm stainless steel pin is inserted into the upper crest of the tibia, inside the intramedullary canal. Osteotomy is then performed, and the wound is stapled. We have used this model to investigate the effects of surgical trauma on postoperative neuroinflammation and behavioral changes. By applying this fracture model in combination with parabiosis, a surgical model in which 2 mice are anastomosed, we have studied cells and secreted factors that systemically rejuvenate organ function and tissue regeneration after injury. By following our step-by-step protocol, these models can be reproduced with high fidelity, and can be adapted to interrogate many biologic pathways that are altered by surgical trauma.

POCD in patients receiving total knee replacement under deep vs light anesthesia: A randomized controlled trial

Objectives

Clinical observation, as well as randomized controlled trials, indicated an increasing rate of postoperative cognitive dysfunction (POCD) with increasing depth of general anesthesia. However, the findings are subject to bias due to varying degree of analgesia. In this trial, we compared the rate of POCD between patients receiving light versus high anesthesia while holding analgesia comparable using nerve block.

Methods

Elderly patients (≧60 years) receiving elective total knee replacement were randomized to receive the surgery under general anesthesia at BIS 40-50 (LOBIS group) or BIS 55-65 (HIBIS group). The femoral nerve and the sciatic nerve were blocked under ultrasonic guidance in all patients before induction. Cognitive performance was assessed with Montreal cognitive assessment (MoCA) at the baseline and 1d, 3d, and 7d after the surgery. POCD was defined by Z score of >1.96 using cross-reference. The extubation time and recovery time were also compared.

Results

A total of 66 patients were randomized; 60 (n = 30 per group) completed trial as the protocol specified. POCD occurred in six patients (20%) in the LOBIS group vs. in one patient (3.3%) in the HIBIS group (Figure 3, p = .04). In all seven cases, the diagnosis of POCD was based on MoCA assessment on 1d after the surgery. Assessment in 3d and 7d after surgery did not reveal POCD in any case. Extubation time was longer in the LOBIS group (12.16 ± 2.58 vs. 5.77 ± 3.01 min in the HIBIS group (p < .001)). The time of comeback of directional ability was 13.47 ± 3.14 and 6.17 ± 3.23 min in the LOBIS and HIBIS groups, respectively (p < .001).

Conclusions

In elderly patients receiving a total knee replacement, lighter anesthesia could reduce the rate of POCD with complete analgesia during surgery.

Surgical incision induces learning impairment in mice partially through inhibition of the brain-derived neurotrophic factor signaling pathway in the hippocampus and amygdala

Surgical incision-induced nociception contributes to the occurrence of postoperative cognitive dysfunction. However, the exact mechanisms involved remain unclear. Brain-derived neurotrophic factor (BDNF) has been demonstrated to improve fear learning ability. In addition, BDNF expression is influenced by the peripheral nociceptive stimulation. Therefore, we hypothesized that surgical incision-induced nociception may cause learning impairment by inhibiting the BDNF/tropomyosin-related kinase B (TrkB) signaling pathway. The fear conditioning test, enzyme-linked immunosorbent assay, and Western blot analyses were used to confirm our hypothesis and determine the effect of a plantar incision on the fear learning and the BDNF/TrkB signaling pathway in the hippocampus and amygdala. The freezing times in the context test and the tone test were decreased after the plantar incision. A eutectic mixture of local anesthetics attenuated plantar incision-induced postoperative pain and fear learning impairment. ANA-12, a selective TrkB antagonist, abolished the improvement in fear learning and the activation of the BDNF signaling pathway induced by eutectic mixture of local anesthetics. Based on these results, surgical incision-induced postoperative pain, which was attenuated by postoperative analgesia, caused learning impairment in mice partially by inhibiting the BDNF signaling pathway. These findings provide insights into the mechanism underlying surgical incision-induced postoperative cognitive function impairment.

Pre-existing weakness is critical for the occurrence of postoperative cognitive dysfunction in mice of the same age

Occurrence of postoperative cognitive dysfunction (POCD) is age-dependent and heterogenous. Factors deciding the occurrence of POCD in patients of the same age undergone same surgeries remain unclear. Here we investigated the effects of pre-existing weakness on the occurrence of POCD in mice of the same age. Pre-existing weakness of mice was induced by intraperitoneal injection of lipopolysaccharide (8mg/kg) and was evaluated by physical frailty index (by open field test), neuroinflammation level (by Iba1 immunostaining and inflammatory factors TNF-α and IL-1β), and neuronal activity (by p-CREB immunostaining). POCD was induced by partial hepatolobectomy and was evaluated by puzzle box test and Morris water maze test. The brains were collected to detect the levels of neuroinflammation, synaptophysin and NMDA receptor subunits NR2A, NR2B and NR1 (by western blot), and oxidative stress (by Dihydroethidium). Compared to the normal adult mice of the same age, LPS pretreated mice had increased physical frailty index, higher levels of neuroinflammation, and lower neuronal activity. Partial hepatolobectomy induced obvious impairments in executive function, learning and memory in LPS pretreated mice after surgery, but not in normal mice of the same age. Partial hepatolobectomy also induced heightened neuroinflammation, obvious loss of NMDA receptor subunits, strong oxidative stress in LPS pretreated mice on the 1^st and 3^rd postoperative day. However, the POCD-associated pathological changes didn’t occur in normal mice of the same age after surgery. These results suggest that pre-existing weakness is critical for the occurrence of POCD in mice of the same age.

Activation of cannabinoid receptor type 2 attenuates surgery-induced cognitive impairment in mice through anti-inflammatory activity

Background

Neuroinflammation plays a major role in postoperative cognitive dysfunction (POCD). Accumulated evidence indicates that cannabinoid receptor type 2 (CB2R) can mediate anti-inflammatory and immunomodulatory effects in part by controlling microglial activity. However, the impact of CB2R on postoperative cognition has not been investigated. We hypothesized that CB2R is involved in surgery-induced cognitive impairment in adult mice.

Methods

Adult C57BL/6 mice were subjected to intramedullary fixation surgery for tibial fracture under isoflurane anesthesia and CB2R agonist (JWH133) or CB2R antagonist (AM630) treatment. The mice were trained 24 h prior to surgery using a fear conditioning protocol and assessed in a novel context on postoperative days 1, 3, and 7 to evaluate cognitive function. Open-field testing was performed to evaluate the locomotor activity of the mice. The expression levels of IL-1β, TNF-α, MCP-1, and CB2R in the hippocampus and prefrontal cortex were assessed by Western blotting; the expression of microglial marker CD11b in the CA1 area of the hippocampus and medial prefrontal cortex was assessed by immunostaining.

Results

The mice displayed no changes in locomotor activity after surgery and drug treatments. The mice exhibited impaired hippocampal-dependent memory accompanied by an increased expression of proinflammatory factors in the hippocampus and prefrontal cortex 1, 3, and 7 days after surgery, while hippocampal-independent memory remained unaffected at the same time points. JWH133 treatment attenuated surgery-induced memory loss, while AM630 treatment aggravated surgery-induced memory loss, paralleled by a decreased or increased expression of proinflammatory factors in the hippocampus and prefrontal cortex. The expression of CB2R in the hippocampus and prefrontal cortex was upregulated following surgery; however, it was downregulated by postoperative treatment with JWH133. Similarly, the expression of CD11b in the CA1 area of the hippocampus and medial prefrontal cortex was upregulated following surgery and downregulated by postoperative treatment with JWH133.

Conclusions

These findings indicate that CB2R may modulate the neuroinflammatory and cognitive impairment in a mouse model of orthopedic surgery, and the activation of CB2R may effectively ameliorate the hippocampal-dependent memory loss of mice in the early postoperative stage.

Electronic supplementary material

The online version of this article (doi:10.1186/s12974-017-0913-7) contains supplementary material, which is available to authorized users.

Tanshinone IIA Attenuates Sevoflurane Neurotoxicity in Neonatal Mice

BACKGROUND

Sevoflurane is the most widely used inhalational anesthetic in pediatric medicine. Despite this, sevoflurane has been reported to exert potentially neurotoxic effects on the developing brain. Clinical interventions and treatments for these effects are limited. Tanshinone IIA (Tan IIA), extracted from Salvia miltiorrhiza (Danshen), has been documented to alleviate cognitive decline in traditional applications. Therefore, we hypothesized that preadministration of Tan IIA may attenuate sevoflurane-induced neurotoxicity, suggesting that Tan IIA is a new and promising drug capable of counteracting the effects of cognitive dysfunction produced by general anesthetics.

METHODS

To test this hypothesis, neonatal C57 mice (P6) were exposed to 3% sevoflurane for 2 hours with or without Tan IIA pretreatment at a dose of 10 mg/kg or 20 mg/kg for 3 consecutive days. Cognitive behavior tests such as open field tests and fear conditioning were performed to evaluate locomotor and cognitive function at P31 and P32. At P8, other separate tests, including TdT mediated dUTP Nick End Labeling (TUNEL) assay, immunohistochemistry, Western blotting, enzyme-linked immunosorbent assay, and electron microscopy, were performed. The mean differences among groups were compared using 1-way analysis of variance followed by Bonferroni post hoc multiple comparison tests.

RESULTS

Repeated exposure to sevoflurane leads to significant cognitive impairment in mice, which may be explained by increased apoptosis, overexpression of neuroinflammatory markers, and changes in synaptic ultrastructure. Interestingly, preadministration of Tan IIA ameliorated these neurocognitive deficits, as shown by increased freezing percentages on the fear conditioning test (sevoflurane+Tan IIA [20 mg/kg] versus sevoflurane, mean difference, 19, 99% confidence interval for difference, 6.4-31, P < .0001, n = 6). The treatment also reduced the percentage of TUNEL-positive nuclei (sevoflurane versus sevoflurane+Tan IIA [20 mg/kg], 2.6, 0.73-4.5, P = .0004, n = 6) and the normalized expression of cleaved caspase-3 (sevoflurane versus sevoflurane+Tan IIA [20 mg/kg], 0.27, 0.02-0.51, P = .0046, n = 5). Moreover, it attenuated the production of the neuroinflammatory mediators interleukin (IL)-1β and IL-6 (normalized sevoflurane versus sevoflurane+Tan IIA [20 mg/kg]: IL-1β: 0.75, 0.47-1.0; P < .0001; IL-6: 0.66, 0.35-0.97; P < .0001; n = 10 per group). Finally, based on measurements of postsynaptic density, the treatment preserved synaptic ultrastructure (sevoflurane+Tan IIA [20 mg/kg] versus sevoflurane, 42, 20-66; P < .0001; n = 12 per group).

CONCLUSIONS

These results indicate that Tan IIA can alleviate sevoflurane-induced neurobehavioral abnormalities and may decrease neuroapoptosis and neuroinflammation.

Anesthesia, brain changes, and behavior: Insights from neural systems biology

Long-term consequences of anesthetic exposure in humans are not well understood. It is possible that alterations in brain function occur beyond the initial anesthetic administration. Research in children and adults has reported cognitive and/or behavioral changes after surgery and general anesthesia that may be short lived in some patients, while in others, such changes may persist. The changes observed in humans are corroborated by a large body of evidence from animal studies that support a role for alterations in neuronal survival (neuroapoptosis) or structure (altered dendritic and glial morphology) and later behavioral deficits at older age after exposure to various anesthetic agents during fetal or early life. The potential of anesthetics to induce long-term alterations in brain function, particularly in vulnerable populations, warrants investigation. In this review, we critically evaluate the available preclinical and clinical data on the developing and aging brain, and in known vulnerable populations to provide insights into potential changes that may affect the general population of patients in a more, subtle manner. In addition this review summarizes underlying processes of how general anesthetics produce changes in the brain at the cellular and systems level and the current understanding underlying mechanisms of anesthetics agents on brain systems. Finally, we present how neuroimaging techniques currently emerge as promising approaches to evaluate and define changes in brain function resulting from anesthesia, both in the short and the long-term.

Lasting impact of general anaesthesia on the brain: mechanisms and relevance

General anaesthesia is usually considered to safely induce a reversible brain state allowing the performance of surgery under optimal conditions. An increasing number of clinical and experimental observations, however, suggest that anaesthetic drugs, especially when they are administered at the extremes of age, can trigger long-term morphological and functional alterations in the brain. Here, we review available mechanistic data linking general-anaesthesia exposure to impaired cognitive performance in both young and mature nervous systems. We also provide a critical appraisal of the translational value of animal models and highlight the important challenges that need to be addressed to strengthen the link between laboratory work and clinical investigations in the field of anaesthesia-neurotoxicity research.

Memantine improves outcomes after repetitive traumatic brain injury

Repetitive mild traumatic brain injury (rmTBI; e.g., sports concussions) is common and results in significant cognitive impairment. Targeted therapies for rmTBI are lacking, though evidence from other injury models indicates that targeting N-methyl-d-aspartate (NMDA) receptor (NMDAR)-mediated glutamatergic toxicity might mitigate rmTBI-induced neurologic deficits. However, there is a paucity of preclinical or clinical data regarding NMDAR antagonist efficacy in the rmTBI setting. To test whether NMDAR antagonist therapy improves outcomes after rmTBI, mice were subjected to rmTBI injury (4 injuries in 4days) and randomized to treatment with the NMDA antagonist memantine or with vehicle. Functional outcomes were assessed by motor, anxiety/impulsivity and mnemonic behavioral tests. At the synaptic level, NMDAR-dependent long-term potentiation (LTP) was assessed in isolated neocortical slices. At the molecular level, the magnitude of gliosis and tau hyper-phosphorylation was tested by Western blot and immunostaining, and NMDAR subunit expression was evaluated by Western blot and polymerase chain reaction (PCR). Compared to vehicle-treated mice, memantine-treated mice had reduced tau phosphorylation at acute time points after injury, and less glial activation and LTP deficit 1 month after injury. Treatment with memantine also corresponded to normal NMDAR expression after rmTBI. No corresponding protection in behavior outcomes was observed. Here we found NMDAR antagonist therapy may improve histopathological and functional outcomes after rmTBI, though without consistent corresponding improvement in behavioral outcomes. These data raise prospects for therapeutic post-concussive NMDAR antagonism, particularly in athletes and warriors, who suffer functional impairment and neurodegenerative sequelae after multiple concussions.

A Role for Photobiomodulation in the Prevention of Myocardial Ischemic Reperfusion Injury: A Systematic Review and Potential Molecular Mechanisms

Myocardial ischemia reperfusion injury is a negative pathophysiological event that may result in cardiac cell apoptosis and is a result of coronary revascularization and cardiac intervention procedures. The resulting loss of cardiomyocyte cells and the formation of scar tissue, leads to impaired heart function, a major prognostic determinant of long-term cardiac outcomes. Photobiomodulation is a novel cardiac intervention that has displayed therapeutic effects in reducing myocardial ischemia reperfusion related myocardial injury in animal models. A growing body of evidence supporting the use of photobiomodulation in myocardial infarct models has implicated multiple molecular interactions. A systematic review was conducted to identify the strength of the evidence for the therapeutic effect of photobiomodulation and to summarise the current evidence as to its mechanisms. Photobiomodulation in animal models showed consistently positive effects over a range of wavelengths and application parameters, with reductions in total infarct size (up to 76%), decreases in inflammation and scarring, and increases in tissue repair. Multiple molecular pathways were identified, including modulation of inflammatory cytokines, signalling molecules, transcription factors, enzymes and antioxidants. Current evidence regarding the use of photobiomodulation in acute and planned cardiac intervention is at an early stage but is sufficient to inform on clinical trials.

Anesthesia/Surgery Induces Cognitive Impairment in Female Alzheimer's Disease Transgenic Mice

Anesthesia and/or surgery may promote Alzheimer's disease (AD) by accelerating its neuropathogenesis. Other studies showed different findings. However, the potential sex difference among these studies has not been well considered, and it is unknown whether male or female AD patients are more vulnerable to develop postoperative cognitive dysfunction. We therefore set out to perform a proof of concept study to determine whether anesthesia and surgery can have different effects in male and female AD transgenic (Tg) mice, and in female AD Tg plus Cyclophilin D knockout (CypD KO) mice. The mice received an abdominal surgery under sevoflurane anesthesia (anesthesia/surgery). Fear Conditioning System (FCS) was used to assess the cognitive function. Hippocampal levels of synaptic marker postsynaptic density 95 (PSD-95) and synaptophysin (SVP) were measured using western blot analysis. Here we showed that the anesthesia/surgery decreased the freezing time in context test of FCS at 7 days after the anesthesia/surgery in female, but not male, mice. The anesthesia/surgery reduced hippocampus levels of synaptic marker PSD-95 and SVP in female, but not male, mice. The anesthesia/surgery induced neither reduction in freezing time in FCS nor decreased hippocampus levels of PSD-95 and SVP in the AD Tg plus CypD KO mice. These data suggest that the anesthesia/surgery induced a sex-dependent cognitive impairment and reduction in hippocampus levels of synaptic markers in AD Tg mice, potentially via a mitochondria-associated mechanism. These findings could promote clinical investigations to determine whether female AD patients are more vulnerable to the development of postoperative cognitive dysfunction.

Effects of intra-hippocampal microinjection of vitamin B12 on the orofacial pain and memory impairments induced by scopolamine and orofacial pain in rats

In the present study, we investigated the effects of microinjection of vitamin B₁₂ into the hippocampus on the orofacial pain and memory impairments induced by scopolamine and orofacial pain. In ketamine-xylazine anesthetized rats, the right and left sides of the dorsal hippocampus (CA1) were implanted with two guide cannulas. Orofacial pain was induced by subcutaneous injection of formalin (1.5%, 50μl) into the right vibrissa pad, and the durations of face rubbing were recorded at 3-min blocks for 45min. Morris water maze (MWM) was used for evaluation of learning and memory. Finally, locomotor activity was assessed using an open-field test. Vitamin B₁₂ attenuated both phases of formalin-induced orofacial pain. Prior administration of naloxone and naloxonazine, but not naltrindole and nor-binaltorphimine, prevented this effect. Vitamin B₁₂ and physostigmine decreased latency time as well as traveled distance in Morris water maze. In addition, these chemicals improved scopolamine-induced memory impairment. The memory impairment induced by orofacial pain was improved by vitamin B₁₂ and physostigmine used alone. Naloxone prevented, whereas physostigmine enhanced the memory improving effect of vitamin B₁₂ in the pain-induced memory impairment. All the above-mentioned chemicals did not alter locomotor activity. The results of the present study showed that at the level of the dorsal hippocampus, vitamin B₁₂ modulated orofacial pain through a mu-opioid receptor mechanism. In addition, vitamin B₁₂ contributed to hippocampal cholinergic system in processing of memory. Moreover, cholinergic and opioid systems may be involved in improving effect of vitamin B₁₂ on pain-induced memory impairment.

Deferoxamine pre-treatment protects against postoperative cognitive dysfunction of aged rats by depressing microglial activation via ameliorating iron accumulation in hippocampus

Postoperative cognitive dysfunction (POCD) is a common complication of elderly patients after surgery. The mechanisms of POCD have not been clarified. Iron accumulation is a feature of neurodegeneration. Recent reports showed that iron content was increased with impaired cognition induced by surgery. We sought to investigate whether iron chelation would attenuate POCD. In this study, male aged (18 months) Sprague-Dawley rats received 100 mg/kg deferoxamine or saline solution (0.9%) for 6 days before exploratory laparotomy. Cognition was evaluated by Morris water maze before and after surgery. Additional rats received deferoxamine or saline were used to determine hippocampal iron content, iron transport-related proteins (transferrin receptor, divalent metal transporter 1, ferroportin 1 and hepcidin), oxidative stress, microglial activation and brain cell apoptosis. It was found that deferoxamine improved postoperative spatial memory in aged rats. Deferoxamine significantly reduced hippocampal iron concentration and ferritin. Surgery increased divalent metal transporter 1 and hepcidin, decreased transferrin receptor and ferroportin 1, and enhanced ferroportin 1 mRNA. However, deferoxamine reversed the changes of these proteins. Furthermore, deferoxamine sharply reduced the hippocampal reactive oxygen species, malondialdehyde concentration and OX-42 that is a marker of microglia, which might reduce postoperative brain cell apoptosis. This study showed that deferoxamine may improve postoperative cognition of aged rats by ameliorating oxidative stress induced by hippocampal iron accumulation, microglial activation and brain cell apoptosis. This study suggests a potential therapeutic method for reducing POCD.

Adolescent Mice Demonstrate a Distinct Pattern of Injury after Repetitive Mild Traumatic Brain Injury

Recently, there has been increasing interest in outcomes after repetitive mild traumatic brain injury (rmTBI) (e.g., sports concussions). Although most of the scientific attention has focused on elite athlete populations, the sequelae of rmTBI in children and young adults have not been well studied. Prior TBI studies have suggested that developmental differences in response to injury, including differences in excitotoxicity and inflammation, could result in differences in functional and histopathological outcomes after injury. The purpose of this study is to compare outcomes in adolescent (5-week-old) versus adult (4-month-old) mice in a clinically relevant model of rmTBI. We hypothesized that functional and histopathological outcomes after rmTBI would differ in developing adolescent brains compared with mature adult brains. Male adolescent and adult (C57Bl/6) mice were subjected to a weight drop model of rmTBI (n = 10-16/group). Loss of consciousness (LOC) after each injury was measured. Functional outcomes were assessed including tests of balance (rotorod), spatial memory (Morris water maze), and impulsivity (elevated plus maze). After behavioral testing, brains were assessed for histopathological outcomes including microglial immunolabeling and N-methyl-d-aspartate (NMDA) receptor subunit expression. Injured adolescent mice had longer LOC than injured adult mice compared with their respective sham controls. Compared with sham mice, adolescent and adult mice subjected to rmTBI had impaired balance, increased impulsivity, and worse spatial memory that persisted up to 3 months after injury, and the effect of injury was worse in adolescent than in adult mice in terms of spatial memory. Three months after injury, adolescent and adult mice demonstrated increased ionized calcium binding adaptor 1 (IbA1) immunolabeling compared with sham controls. Compared with sham controls, NMDA receptor subtype 2B (NR2B) expression in the hippocampus was reduced by ∼20% in both adolescent and adult injured mice. The data suggest that injured adolescent mice may show a distinct pattern of functional deficits after injury that warrants further mechanistic studies.

Battery of behavioral tests in mice to study postoperative delirium

Postoperative delirium is associated with increased morbidity, mortality and cost. However, its neuropathogenesis remains largely unknown, partially owing to lack of animal model(s). We therefore set out to employ a battery of behavior tests, including natural and learned behavior, in mice to determine the effects of laparotomy under isoflurane anesthesia (Anesthesia/Surgery) on these behaviors. The mice were tested at 24 hours before and at 6, 9 and 24 hours after the Anesthesia/Surgery. Composite Z scores were calculated. Cyclosporine A, an inhibitor of mitochondria permeability transient pore, was used to determine potential mitochondria-associated mechanisms of these behavioral changes. Anesthesia/Surgery selectively impaired behaviors, including latency to eat food in buried food test, freezing time and time spent in the center in open field test, and entries and duration in the novel arm of Y maze test, with acute onset and various timecourse. The composite Z scores quantitatively demonstrated the Anesthesia/Surgery-induced behavior impairment in mice. Cyclosporine A selectively ameliorated the Anesthesia/Surgery-induced reduction in ATP levels, the increases in latency to eat food, and the decreases in entries in the novel arm. These findings suggest that we could use a battery of behavior tests to establish a mouse model to study postoperative delirium.

Parecoxib prevents early postoperative cognitive dysfunction in elderly patients undergoing total knee arthroplasty: A double-blind, randomized clinical consort study

BACKGROUND

Trial design neuroinflammation and postoperative pain after surgery are increasingly reported in association with postoperative cognitive dysfunction (POCD). Parecoxib, a selective cyclooxygenase (COX)-2 inhibitor, is used for postoperative analgesia for its potent anti-inflammatory and analgesic effects. This study aimed to evaluate parecoxib's effects on POCD in elderly patients undergoing total knee arthroplasty.

METHODS

Around 134 elderly patients undergoing total knee arthroplasty were randomly divided into parecoxib (group P) and control (group C) groups, and treated with parecoxib sodium and saline, respectively, shortly after induction of general anesthesia and 12-h postsurgery, respectively. Perioperative plasma IL-1β, IL-6, TNF-α, and C-reactive protein (CRP) 1evels were measured. Postoperative pain was assessed following surgery. Neuropsychological tests were performed before surgery, and 1 week and 3 months postoperation.

RESULTS

POCD incidence in group P was significantly lower compared with that of group C at 1 week after surgery (16.7% vs 33.9%; P < 0.05); no significant difference was found between groups C and P at 3-month follow-up (9.7% vs 6.7%). Compared with group C values, visual analog pain scale (VAS) scores at 3, 6, and 12 hours after surgery were significantly lower in group P(P < 0.05). Plasma IL-1β, IL-6, and TNF-α levels were lower in group P than in group C after the operation (P < 0.05). No significant difference in the plasma CRP level was found between groups P and C.

CONCLUSIONS

Parecoxib sodium decreases POCD incidence after total knee arthroplasty in elderly patients and may explain how this drug suppresses inflammation and acute postoperative pain caused by surgical trauma.

Increased extrasynaptic GluN2B expression is involved in cognitive impairment after isoflurane anesthesia

There is increasing concern regarding the postoperative cognitive dysfunction (POCD) in the aging population, and general anesthetics are believed to be involved. Isoflurane exposure induced increased N-methyl-D-aspartic acid receptor (NMDAR) GluN2B subunit expression following anesthesia, which was accompanied by alteration of the cognitive function. However, whether isoflurane affects this expression in different subcellular compartments, and is involved in the development of POCD remains to be elucidated. The aims of the study were to investigate the effects of isoflurane on the expression of the synaptic and extrasynaptic NMDAR subunits, GluN2A and GluN2B, as well as the associated alteration of cognitive function in aged rats. The GluN2B antagonist, Ro25–6981, was given to rats exposed to isoflurane to determine the role of GluN2B in the isoflurane-induced alteration of cognitive function. The results showed that spatial learning and memory tested in the Morris water maze (MWM) was impaired at least 7 days after isoflurane exposure, and was returned to control levels 30 days thereafter. Ro25-6981 treatment can alleviate this impairment. Extrasynaptic GluN2B protein expression, but not synaptic GluN2B or GluN2A, increased significantly after isoflurane exposure compared to non-isoflurane exposure, and returned to control levels approximately 30 days thereafter. The results of the present study indicated that isoflurane induced the prolonged upregulation of extrasynaptic GluN2B expression after anesthesia and is involved in reversible cognitive impairment.

Protective Effects of Edaravone in Adult Rats with Surgery and Lipopolysaccharide Administration-Induced Cognitive Function Impairment

Postoperative cognitive dysfunction (POCD) is a clinical syndrome characterized by cognitive declines in patients after surgery. Previous studies have suggested that surgery contributed to such impairment. It has been proven that neuroinflammation may exacerbate surgery-induced cognitive impairment in aged rats. The free radical scavenger edaravone has high blood brain barrier permeability, and was demonstrated to effectively remove free radicals from the brain and alleviate the development of POCD in patients undergoing carotid endarterectomy, suggesting its potential role in preventing POCD. For this reason, this study was designed to determine whether edaravone is protective against POCD through its inhibitory effects on inflammatory cytokines and oxidative stress. First, Sprague Dawley adult male rats were administered 3 mg/kg edaravone intraperitoneally after undergoing a unilateral nephrectomy combined with lipopolysaccharide injection. Second, behavioral parameters related to cognitive function were recorded by fear conditioning and Morris Water Maze tests. Last, superoxide dismutase activities and malondialdehyde levels were measured in the hippocampi and prefrontal cortex on postoperative days 3 and 7, and microglial (Iba1) activation, p-Akt and p-mTOR protein expression, and synaptic function (synapsin 1) were also examined 3 and 7 days after surgery. Rats that underwent surgery plus lipopolysaccharide administration showed significant impairments in spatial and working memory, accompanied by significant reductions in hippocampal-dependent and independent fear responses. All impairments were attenuated by treatment with edaravone. Moreover, an abnormal decrease in superoxide dismutase activation, abnormal increase in malondialdehyde levels, significant increase in microglial reactivity, downregulation of p-Akt and p-mTOR protein expression, and a statistically significant decrease in synapsin-1 were observed in the hippocampi and prefrontal cortices of rats at different time points after surgery. All mentioned abnormal changes were totally or partially reversed by edaravone. To our knowledge, few reports have shown greater protective effects of edaravone on POCD induced by surgery plus lipopolysaccharide administration from its anti-oxidative stress and anti-inflammatory effects, as well as maintenance of Akt/mTOR signal pathway activation; these might be closely related to the therapeutic effects of edaravone. Our research demonstrates the potential use of edaravone in the treatment of POCD.

Neuroprotective Effects Against POCD by Photobiomodulation: Evidence from Assembly/Disassembly of the Cytoskeleton

Postoperative cognitive dysfunction (POCD) is a decline in memory following anaesthesia and surgery in elderly patients. While often reversible, it consumes medical resources, compromises patient well-being, and possibly accelerates progression into Alzheimer's disease. Anesthetics have been implicated in POCD, as has neuroinflammation, as indicated by cytokine inflammatory markers. Photobiomodulation (PBM) is an effective treatment for a number of conditions, including inflammation. PBM also has a direct effect on microtubule disassembly in neurons with the formation of small, reversible varicosities, which cause neural blockade and alleviation of pain symptoms. This mimics endogenously formed varicosities that are neuroprotective against damage, toxins, and the formation of larger, destructive varicosities and focal swellings. It is proposed that PBM may be effective as a preconditioning treatment against POCD; similar to the PBM treatment, protective and abscopal effects that have been demonstrated in experimental models of macular degeneration, neurological, and cardiac conditions.