Both GSK-3β/CRMP2 and CDK5/CRMP2 pathways participate in the protection of dexmedetomidine against propofol-induced learning and memory impairment in neonatal rats

Effects of dexmedetomidine on depression-like behaviour in chronic restraint stress mice: Involvement of specific brain regions

It is crucial to develop novel antidepressants. Dexmedetomidine (DEX) can exert antidepressant effects, but its underlying mechanism remains unclear. We used chronic restraint stress (CRS) to induce depression-like behaviour in mice and administered low-dose DEX (2 μg/kg per day) during CRS modelling or one injection of high-dose DEX (20 μg/kg) after CRS. The results of the behavioural tests revealed that both methods ameliorated CRS-induced depression. The brain slices of the mice were subjected to immunohistochemical staining for c-fos and phosphorylated ERK (pERK). Results showed that the continuous low-dose DEX-treated group, but not the single high-dose DEX-treated group expressed less c-fos in the nucleus locus coeruleus (LC) with a mean optical density (MOD) of 0.06. Other brain regions, including the dentate gyrus (DG), pyriform cortex (Pir), anterior part of paraventricular thalamic nucleus (PVA), arcuate nucleus (Arc), and core or shell of accumbens nucleus (Acbc or Acbs), presented differences in c-fos expression. In contrast, the low-dose DEX-treated group exhibited three-fold greater pERK expression in the LC of the CRS mice, with a MOD of 0.15. Pir, cingulate cortex (Cg) and, anterior and posterior part of paraventricular thalamic nucleus (PVA and PVP) exhibited pERK expression differences due to distinct reagent treatments. These changes indicate that the responses of brain regions to different DEX administration methods and doses vary. This study confirmed the ability of DEX to ameliorate CRS-induced depression and identified candidate target brain regions, thus providing new information for the antidepressant mechanism of DEX.

Astrocyte-derived exosomes-transported miRNA-26a-5p ameliorates sevoflurane-induced cognitive dysfunction in aged mice

Prolonged sevoflurane anesthesia is the primary factor contributing to the development of perioperative neurocognitive disorders (PND). Recent studies have highlighted neuronal apoptosis and abnormal dendritic structures as crucial features of PND. Astrocytes-derived exosomes (ADEs) have been identified as carriers of microRNAs (miRNAs), playing a vital role in cell-to-cell communication through transmitting genetic material. Nevertheless, the specific mechanisms by which miRNAs in ADEs contribute to sevoflurane-induced cognitive deficit are currently unknown. Through a series of in vivo and in vitro experiments, we demonstrated that ADEs contributed to improved neurocognitive outcomes by reducing neuronal apoptosis and promoting dendritic development. Our miRNA microarray analysis revealed a significant increase in the expression level of miR-26a-5p within ADEs. Furthermore, we identified NCAM as the downstream target gene of miR-26a-5p. Subsequent gain- and loss-of-function experiments were conducted to validate the role of the miR-26a-5p/NCAM axis. Finally, we found that the AKT/GSK3-β/CRMP2 signaling pathway was involved in regulating neurons through exosomal miR-26a-5p. Taken together, our findings suggest that the treatment with miR-26a-5p in ADEs can improve neurocognitive outcomes induced by long-term sevoflurane anesthesia, suggesting a promising approach for retarding the progress of PND.

Dexmedetomidine attenuates postoperative spatial memory impairment after surgery by reducing cytochrome C

BACKGROUND

Anesthesia and surgery can induce perioperative neurocognitive disorders (PND). Mitochondrial dysfunction has been proposed to be one of the earliest triggering events in surgery-induced neuronal damage. Dexmedetomidine has been demonstrated to attenuate the impairment of cognition in aged rats induced by surgery in our previous study.

METHODS

Male Sprague-Dawley rats underwent hepatic apex resection under anesthesia with propofol to clinically mimic human abdominal surgery. The rats were divided into three groups: Control group, Model group and Dexmedetomidine (Dex) group. Cognitive function was evaluated with the Morris water maze (MWM), Open Field Test (OFT)and Novel object recognition task (NOR). Ultrastructural change in neuronal mitochondria was measured by transmission electron microscopy. Mitochondrial function was measured by mitochondrial membrane potential and activities of mitochondrial complexes. Neuronal morphology was observed with H&E staining and the activation of glial cells was observed by immunohistochemistry in the hippocampus. Protein levels were measured by Western blot (WB) and immunofluorescence at 3 and 7 days after surgery.

RESULTS

Surgery-induced cognitive decline lasts three days, but not seven days after surgery in the model group. Transmission electron microscope showed the mitochondrial structure damage in the model group, similar changes were not induced in the Dex group. Dexmedetomidine may reverse the decrease in mitochondrial membrane potential and mitochondrial complex activity. Compared with the Control group, the expression of cytochrome c was significantly increased in model group by Western blot and immunofluorescence on days 3, but not day 7. Rats from the Model group expressed significantly greater levels of Iba-1 and GFAP compared with the Control group and the Dex group.

CONCLUSION

Dexmedetomidine appears to reverse surgery-induced behavior, mitigate the higher density of Iba-1 and GFAP, reduce the damage of mitochondrial structure and function by alleviating oxidative stress and protect mitochondrial respiratory chain, thus increasing cytochrome c oxidase (COX) expression and downregulate the expression of cytochrome c protein in the hippocampus of rats.

Propofol-Induced Developmental Neurotoxicity: From Mechanisms to Therapeutic Strategies

Propofol is the most commonly used intravenous general anesthetic in clinical anesthesia, and it is also widely used in general anesthesia for pregnant women and infants. Some clinical and preclinical studies have found that propofol causes damage to the immature nervous system, which may lead to neurodevelopmental disorders and cognitive dysfunction in infants and children. However, its potential molecular mechanism has not been fully elucidated. Recent in vivo and in vitro studies have found that some exogenous drugs and interventions can effectively alleviate propofol-induced neurotoxicity. In this review, we focus on the relevant preclinical studies and summarize the latest findings on the potential mechanisms and therapeutic strategies of propofol-induced developmental neurotoxicity.

Dexmedetomidine: An Alternative to Pain Treatment in Neonatology

Infants might be exposed to pain during their admissions in the neonatal intensive care unit [NICU], both from their underlying conditions and several invasive procedures required during their stay. Considering the particularities of this population, recognition and adequate management of pain continues to be a challenge for neonatologists and investigators. Diverse therapies are available for treatment, including non-pharmacological pain management measures and pharmacological agents (sucrose, opioids, midazolam, acetaminophen, topical agents…) and research continues. In recent years one of the most promising drugs for analgesia has been dexmedetomidine, an alpha-2 adrenergic receptor agonist. It has shown a promising efficacy and safety profile as it produces anxiolysis, sedation and analgesia without respiratory depression. Moreover, studies have shown a neuroprotective role in animal models which could be beneficial to neonatal population, especially in preterm newborns. Side effects of this therapy are mainly cardiovascular, but in most studies published, those were not severe and did not require specific therapeutic measures for their resolution. The main objective of this article is to summarize the existing literature on neonatal pain management strategies available and review the efficacy of dexmedetomidine as a new therapy with increasing use in the NICU.

Role of ferroptosis in hypoxic preconditioning to reduce propofol neurotoxicity

Background: An increasing number of studies have reported that neurotoxicity of propofol may cause long-term learning and cognitive dysfunction. Hypoxic preconditioning has been shown to have neuroprotective effects, reducing the neurotoxicity of propofol. Ferroptosis is a new form of death that is different from apoptosis, necrosis, autophagy and pyroptosis. However, it is unclear whether hypoxic preconditioning reduces propofol neurotoxicity associated with ferroptosis. Thus, we aimed to evaluate the effect of propofol on primary hippocampal neurons in vitro to investigate the neuroprotective mechanism of hypoxic preconditioning and the role of ferroptosis in the reduction of propofol neurotoxicity by hypoxic preconditioning. Methods: Primary hippocampal neurons were cultured for 8 days in vitro and pretreated with or without propofol, hypoxic preconditioning, agonists or inhibitors of ferroptosis. Cell counting kit-8, Calcein AM, Reactive oxygen species (ROS), Superoxide dismutase (SOD), Ferrous iron (Fe²⁺), Malondialdehyde (MDA) and Mitochondrial membrane potential assay kit with JC-1 (JC-1) assays were used to measure cell viability, Reactive oxygen species level, Superoxide dismutase content, Fe²⁺ level, MDA content, and mitochondrial membrane potential. Cell apoptosis was evaluated using flow cytometry analyses, and ferroptosis-related proteins were determined by Western blot analysis. Results: Propofol had neurotoxic effects that led to decreased hippocampal neuronal viability, reduced mitochondrial membrane potential, decreased SOD content, increased ROS level, increased Fe²⁺ level, increased MDA content, increased neuronal apoptosis, altered expression of ferroptosis-related proteins and activation of ferroptosis. However, hypoxic preconditioning reversed these effects, inhibited ferroptosis caused by propofol and reduced the neurotoxicity of propofol. Conclusion: The neurotoxicity of propofol in developing rats may be related to ferroptosis. Propofol may induce neurotoxicity by activating ferroptosis, while hypoxic preconditioning may reduce the neurotoxicity of propofol by inhibiting ferroptosis.

Preventive Effect of Hippocampal Sparing on Cognitive Dysfunction of Patients Undergoing Whole-Brain Radiotherapy and Imaging Assessment of Hippocampal Volume Changes

Objective

Preventive effect of hippocampal sparing on cognitive dysfunction of patients undergoing whole-brain radiotherapy and imaging assessment of hippocampal volume changes.

Methods

Forty patients with brain metastases who attended Liaoning Cancer Hospital from January 2018 to December 2019 were identified as research subjects and were randomly divided into a control group and an experimental group, with 20 cases in each group. The control group was treated with whole-brain radiotherapy (WBRT), and the experimental group was treated with hippocampal sparing-WBRT (HS-WBRT). The Montreal Cognitive Assessment (MoCA) score, Eastern Cooperative Oncology Group (ECOG) score, cancer quality-of-life questionnaire (QLQ-C3O) score, hippocampal volume changes, and prognosis of the two groups were compared.

Results

The MoCA scores decreased in both groups at 3, 6, and 12 months after radiotherapy, with significantly higher scores in the experimental group than in the control group (P < 0.05). After radiotherapy, both groups had lower ECOG scores, with those in the experimental group being significantly lower than those in the control group (P < 0.05). After radiotherapy, the QLQ-C30 score was elevated in both groups, and that of the experimental group was significantly higher than that of the control group (P < 0.05). The experimental group outperformed the control group in terms of the prognosis (P < 0.05). The hippocampal volume of the control group was significantly smaller than that of the experimental group (P < 0.05).

Conclusion

The application of hippocampal sparing in patients receiving whole-brain radiotherapy is effective in preventing cognitive dysfunction, improving the quality of life and prognosis of patients, and avoiding shrinkage of hippocampal volume.

Dexmedetomidine reduces propofol-induced hippocampal neuron injury by modulating the miR-377-5p/Arc pathway

BACKGROUND

Propofol and dexmedetomidine (DEX) are widely used in general anesthesia, and exert toxic and protective effects on hippocampal neurons, respectively. The study sought to investigate the molecular mechanisms of DEX-mediated neuroprotection against propofol-induced hippocampal neuron injury in mouse brains.

METHODS

Hippocampal neurons of mice and HT22 cells were treated with propofol, DEX, and propofol+DEX. In addition, transfection of miR-377-5p mimics or inhibitors was performed in HT22 cells. Neuronal apoptosis was evaluated by a means of terminal deoxynucleotidyl transferase (TdT)-mediated dUTP nick end labeling (TUNEL) or Hochest 33,258 staining; Arc positive expression in hippocampus tissues was detected using a microscope in immunohistochemistry assays; miRNA-377-5p expression was quantified by RT-qPCR; the protein levels of Arc, DNMT3A, and DNMT3B were determined using western blot; Cell Counting Kit-8 (CCK-8) assay was used to detect the viability and apoptotic rate of the neurons; methylation analysis in the miR-377-5p promoter was performed through methylated DNA immunoprecipitation (MeDIP) assay; dual luciferase reporter assay was performed to confirm whether Arc was under targeted regulation of miR-377-5p.

RESULTS

In the current study, both in vitro and in vivo, propofol treatment induced hippocampal neuron apoptosis and suppressed cell viability. DNMT3A and DNMT3B expression levels were decreased following propofol treatment, resulting in lowered methylation in the miR-377-5p promoter region and then enhanced expression of miR-377-5p, leading to a decrease in the expression of downstream Arc. Conversely, the expression levels of DNMT3A and DNMT3B were increased following DEX treatment, thus methylation in miR-377-5p promoter region was improved, and miR-377-5p expression was decreased, leading to an increase in the expression of downstream Arc. Eventually, DEX pretreatment protected hippocampal neurons against propofol-induced neurotoxicity by recovering the expression levels of DNMT3A, miR-377-5p, and Arc to the normal levels. Additionally, DNMT3A knockdown improved miR-377-5p expression but reduced Arc expression, and DNMT3A overexpression exerted the opposite effects. Dual luciferase reporter assay revealed a binding target between miR-377-5p and Arc 3'UTR. The neuroprotective effect of DEX against propofol-induced neuronal apoptosis was diminished after Arc knockdown. Silencing Arc independently triggered the apoptosis of HT22 cells, which was alleviated through transfection of miR-377-5p inhibitors.

CONCLUSIONS

DEX reduced propofol-induced hippocampal neuron injury via the miR-377-5p/Arc signaling pathway.

The role of 5-HT7R in the memory impairment of mice induced by long-term isoflurane anesthesia

General anesthesia is widely utilized in the clinic for surgical and diagnostic procedures. However, growing evidence suggests that anesthetic exposure may affect cognitive function negatively. Unfortunately, little is known about the underlying mechanisms and efficient prevention and therapeutic strategies for the anesthesia-induced cognitive dysfunction. 5-HT₇R, a serotonin receptor family member, is functionally associated with learning and memory. It has recently become a potential therapeutic target in various neurological diseases as its ligands have a wide range of neuropharmacological effects. However, it remains unknown the role of 5-HT₇R in the long-term isoflurane anesthesia-induced memory impairment and whether prior activation or blockade of 5-HT₇R before anesthesia has modulating effects on this memory impairment. In this study, 5-HT₇R selective agonist LP-211 and 5-HT₇R selective antagonist SB-269970 were pretreated intraperitoneally to mice before anesthesia; their effects on the cognitive performance of mice were assessed using fear conditioning test and novel object recognition test. Furthermore, the transcriptional level of 5-HT₇R in the hippocampus was detected using qRT-PCR, and proteomics was conducted to probe the underlying mechanisms. As a result, long-term exposure to isoflurane anesthesia caused memory impairment and an increase in hippocampal 5-HT₇R mRNA expression, which could be attenuated by SB-269970 pretreatment but not LP-211pretreatment. According to the proteomics results, the antiamnestic effect of SB-269970 pretreatment was probably attributed to its action on the gene expression of Slc6a11, Itpka, Arf3, Srcin1, and Epb41l2, and synapse organization in the hippocampus. In conclusion, 5-HT₇R is involved in the memory impairment induced by long-term isoflurane anesthesia, and the prior blockade of 5-HT₇R with SB-269970 protects the memory impairment. This finding may help to improve the understanding of the long-term isoflurane anesthesia-induced memory impairment and to construct potential preventive and therapeutic strategies for the adverse effects after long-term isoflurane exposure.

Trillium tschonoskii rhizomes' saponins induces oligodendrogenesis and axonal reorganization for ischemic stroke recovery in rats

ETHNOPHARMACOLOGICAL RELEVANCE

Trillium tschonoskii Maxim. is one of traditional Chinese medical herbs that has been utilized to treat brain damages and cephalalgia. The neuroprotective effect of total saponins from Trillium tschonoskii rhizome (TSTT) has been demonstrated efficacy in rats following ischemia. However, the axonal remodeling effect of TSTT and the detailed mechanisms after ischemic stroke have not been investigated.

AIM OF THE STUDY

We aimed to estimate therapeutic role of TSTT in axonal remodeling using magnetic resonance imaging (MRI) technique, and explored possible mechanisms underlying this process followed by histological assays in ischemic rats.

METHODS

Male Sprague-Dawley (SD) rats underwent permanently focal cerebral ischemia induced by occluding right permanent middle cerebral artery. TSTT was intragastrically administrated 6 h after surgery and once daily for consecutive 15 days. Neurological function was assessed by the motor deficit score and beam walking test. T2 relaxation mapping and diffusion tensor imaging (DTI) were applied for detecting cerebral tissues damages and microstructural integrity of axons. Luxol fast blue (LFB) and transmission electron microscope (TEM) were performed to evaluate histopathology in myelinated axons. Double immunofluorescent staining was conducted to assess oligodendrogenesis. Furthermore, the protein expressions regarding to axonal remodeling related signaling pathways were detected by Western blot assays.

RESULTS

TSTT treatment (65, 33 mg/kg) markedly improved motor function after ischemic stroke. T2 mapping MRI demonstrated that TSTT decreased lesion volumes, and DTI further confirmed that TSTT preserved axonal microstructure of the sensorimotor cortex and internal capsule. Meanwhile, diffusion tensor tractography (DTT) showed that TSTT elevated correspondent density and length of fiber in the internal capsule. These MRI measurements were confirmed by histological examinations. Notably, TSTT significantly increased Ki67/NG2, Ki67/CNPase double-labeled cells along the boundary zone of ischemic cortex and striatum. Meanwhile, TSTT treatment up-regulated the phosphorylation level of Ser 9 in GSK-3β, and down-regulated phosphorylated β-catenin and CRMP-2 expression.

CONCLUSION

Taken together, our findings indicated that TSTT (65, 33 mg/kg) enhanced post-stroke functional recovery, amplified endogenous oligodendrogenesis and promoted axonal regeneration. The beneficial role of TSTT might be correlated with GSK-3/β-catenin/CRMP-2 modulating axonal reorganization after ischemic stroke.

The potential role of dexmedetomidine on neuroprotection and its possible mechanisms: Evidence from in vitro and in vivo studies

Neurological disorders following brain injuries and neurodegeneration are on the rise worldwide and cause disability and suffering in patients. It is crucial to explore novel neuroprotectants. Dexmedetomidine, a selective α2-adrenoceptor agonist, is commonly used for anxiolysis, sedation and analgesia in clinical anaesthesia and critical care. Recent studies have shown that dexmedetomidine exerts protective effects on multiple organs. This review summarized and discussed the current neuroprotective effects of dexmedetomidine, as well as the underlying mechanisms. In preclinical studies, dexmedetomidine reduced neuronal injury and improved functional outcomes in several models, including hypoxia-induced neuronal injury, ischaemic-reperfusion injury, intracerebral haemorrhage, post-traumatic brain injury, anaesthetic-induced neuronal injury, substance-induced neuronal injury, neuroinflammation, epilepsy and neurodegeneration. Several mechanisms are associated with the neuroprotective function of dexmedetomidine, including neurotransmitter regulation, inflammatory response, oxidative stress, apoptotic pathway, autophagy, mitochondrial function and other cell signalling pathways. In summary, dexmedetomidine has the potential to be a novel neuroprotective agent for a wide range of neurological disorders.

Dexmedetomidine alleviates traumatic spinal cord injury in rats via inhibiting apoptosis induced by endoplasmic reticulum stress

OBJECTIVE

To investigate the protective effect of dexmedetomidine (Dex) on traumatic spinal cord injury (TSCI) and to evaluate the involvement of inhibition of endoplasmic reticulum (ER) stress response in the potential mechanism.

METHOD

Sprague-Dawley rats were randomly divided into five groups. The hind limb locomotor function of rats was evaluated at 1, 3 and 7 days after the operation. At 7 days after the operation, spinal cord specimens were obtained for hematoxylin and eosin (H&E), Nissl and TUNEL staining, as well as immunofluorescence and Western blot analyses to detect the level of apoptosis and the levels of proteins related to ER stress.

RESULTS

7 days after the operation, Dex treatment promoted the recovery and also inhibited apoptosis of neurons in the spinal cord. Additionally, Dexinhibited the expression of proteins related to ER stress response after spinal cord injury.

CONCLUSIONS

Dex improves the neurological function of rats with TSCI and reduces apoptosis of spinal cord neurons. The potential mechanism is related to the inhibition of the ER stress response.

Dexmedetomidine Ameliorates Postoperative Cognitive Dysfunction in Aged Mice

Neuroinflammation and oxidative stress coexist and interact in the progression of postoperative cognitive dysfunction (POCD) and other neurodegenerative disease. Mounting studies reveal that Dexmedetomidine (Dex) possesses anti-inflammatory and antioxidant properties. Nevertheless, whether Dex exerts neuroprotective effect on the cognitive sequelae of oxidative stress and inflammatory process remains unclear. A mouse model of abdominal exploratory laparotomy-induced cognitive dysfunction was employed to explore the underlying mechanism of neuroprotective effects exerted by Dex in POCD. Aged mice were treated with Dex (20 µg/kg) 20 min prior to surgery. Open field test (OFT) and Morris water maze (MWM) were employed to examine the cognitive function on postoperative day 3 (POD 3) or POD 7. In the present study, mice underwent surgery exhibited cognitive impairment without altering spontaneous locomotor activity, while the surgery-induced cognitive impairment could be alleviated by Dex pretreatment. Dex inhibited surgery-induced pro-inflammatory cytokines accumulation and microglial activation in the hippocampi of mice. Furthermore, Dex decreased MDA levels, enhanced SOD activity, modulated CDK5 activity and increased BDNF expression in the hippocampus. In addition, Dex remarkably reduced the surgery-induced increased ratio of Bax/Bcl-2 and apoptotic neurons in the hippocampi of aged mice. Collectively, our study provides evidence that Dex may exert neuroprotective effects against surgery-induced cognitive impairment through mechanisms involving its anti-inflammatory and antioxidant properties, as well as the suppression on the mitochondrial permeability transition pore and apoptosis-related pathway.

BDNF Participates in Chronic Constriction Injury-Induced Neuropathic Pain via Transcriptionally Activating P2X7 in Primary Sensory Neurons

Neuropathic pain, resulting from the pathological changes of the somatosensory nervous system, remains a severe public health problem worldwide. The effect of treatment targeting neuropathic pain is very limited, as the underlying mechanism of neuropathic pain is largely unknown. In this study, we demonstrated that the expression level of brain-derived neurotrophic factor (BDNF) was remarkably and time-dependently increased in dorsal root ganglion (DRG) neurons. DRG microinjection of BDNF siRNA in DRG ameliorated chronic constriction injury (CCI) induced mechanical, thermal, and cold nociceptive hypersensitivities. Overexpressing BDNF through microinjection of the AAV5-BDNF in DRG caused enhanced responses to basal mechanical, thermal, and cold stimuli in mice exposed to CCI. Mechanically, the P2X₇ promoter activity was enhanced by CCI-induced increase of DRG BDNF protein and was involved in the CCI-induced upregulation of DRG P2X₇ protein. The overexpression of BDNF also increased P2X₇ expression in DRG neurons, which was validated in in vivo and in vitro experiments. BDNF may exert crucial effect via transcriptionally activating the P2X₇ gene in primary sensory neurons, since P2X₇ acts as a role of endogenous agitator in neuropathic pain and BDNF largely co-expresses with P2X₇ in DRG neurons. Therefore, our data provide evidence that BDNF may be a promising therapeutic target for neuropathic pain.

Galectin-1 ameliorates perioperative neurocognitive disorders in aged mice

Introduction

The incidence of perioperative neurocognitive disorders (PND) is higher in the elderly patients undergoing surgery. Microglia activation‐mediated neuroinflammation is one of the hallmarks of PND. Galectin‐1 has been identified as a pivotal modulator in the central nervous system (CNS), while the role of galectin‐1 in PND induced by microglia‐mediated neuroinflammation is still undetermined.

Methods

An exploratory laparotomy model anesthetized with isoflurane was employed to investigate the role of galectin‐1 on PND in aged mice. Open field test and Morris water maze were used to test the cognitive function 3‐ or 7‐days post‐surgery. The activation of microglia in the hippocampus of aged mice was tested by immunohistochemistry. Western blot, enzyme‐linked immunosorbent assay (ELISA), and quantitative real‐time polymerase chain reaction (qRT‐PCR) were employed to elucidate the underlying mechanisms.

Results

Galectin‐1 attenuated the cognitive dysfunction induced by surgery in aged mice and inhibited microglial activity. Moreover, galectin‐1 decreased the expression level of inflammatory proteins (interleukin‐1β, interleukin‐6, and tumor necrosis factor‐α), and prevented neuronal loss in the hippocampus. Galectin‐1 inhibited the inflammation of BV2 microglial cells induced by lipopolysaccharide via decreasing the translocation of NF‐κB p65 and c‐Jun, while this kind of inhibition was rescued when overexpressing IRAK1.

Conclusion

Our findings provide evidence that galectin‐1 may inhibit IRAK1 expression, thus suppressing inflammatory response, inhibiting neuroinflammation, and improving ensuing cognitive dysfunction. Collectively, these findings unveil that galectin‐1 may elicit protective effects on surgery‐induced neuroinflammation and neurocognitive disorders.

Prophylactic Melatonin Treatment Ameliorated Propofol-Induced Cognitive Dysfunction in Aged Rats

Considering the fact that melatonin acts as protective agent in various cognitive impairment, we decided to explore the precise effect of pretreatment with melatonin on cognitive function, mitochondrial activity, apoptosis and synaptic integrity in aged rats anesthetized by propofol. We first randomly allocated the thirty Sprague Dawley rats into three groups: Control vehicle-treated group (Con), Propofol-treated group (Pro) and Melatonin + Propofol group (Mel + Pro). The Barnes maze, open field and contextual fear conditioning test were employed to evaluate spatial memory, exploratory behavior and general locomotor activity, and hippocampus-dependent learning and memory ability, respectively. Moreover, mitochondrial function (including reactive oxygen species, mitochondrial membrane potential and ATP levels) and apoptosis were detected in the regions of hippocampus (HIP) and prefrontal cortex (PFC). The results of behavioral tests suggested that melatonin improved propofol-induced memory impairment in aged rats. Melatonin mitigated mitochondrial dysfunction and decreased the apoptotic cell counts in the regions of HIP and PFC. Furthermore, prophylactic melatonin treatment also reversed the propofol-induced inactivation of PKA/CREB/BDNF signaling and synaptic dysfunction. On the whole, our results indicated that melatonin ameliorated the propofol-induced cognitive disorders via attenuating mitochondrial dysfunction, apoptosis, inactivation of PKA/CREB/BDNF signaling and synaptic dysfunction.

Edaravone Alleviated Propofol-Induced Neurotoxicity in Developing Hippocampus by mBDNF/TrkB/PI3K Pathway

Background

To investigate the neuroprotective effect of edaravone on excessive-dose propofol-induced neurotoxicity in the hippocampus of newborn rats and HT22 cells.

Methods

Cell proliferation was investigated by assessing ki67 expression in the neural stem of the hippocampus of newborn rats and by cell counting kit-8 (CCK8) assay in HT22 cells. Cell apoptosis was assessed in vivo by caspase 3 detection in Western blots and measurement of apoptosis in neurons and glial cells by terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) assay. Apoptosis was analyzed by flow cytometry in HT22 cells. The Morris water maze was used to evaluate the long-term learning and memory ability of rats. Inflammatory factors were detected by enzyme-linked immunosorbent assay (ELISA). The expression of mBDNF/TrkB/PI3K pathway-related proteins was detected by Western blot and quantitative reverse transcription-polymerase chain reaction (q-RT PCR).

Results

In neonatal rat hippocampus and HT22 cells, edaravone increased cell proliferation and decreased cell apoptosis after excessive propofol-induced neurotoxicity. In addition, the levels of proinflammatory factors interleukin (IL)-6 and tumor necrosis factor (TNF)-α were reduced by edaravone pretreatment. The use of the tropomyosin receptor kinase B (TrkB) antagonist ANA-12 and TrkB agonist 7,8DHF with propofol groups showed that edaravone mitigated excessive propofol-induced neurotoxicity through the mature brain-derived neurotrophic factor (mBDNF)/TrkB/phosphoinositide 3-kinase (PI3K) pathway. However, the current dose of propofol did not significantly affect long-term learning and memory in rats.

Conclusion

Edaravone pretreatment ameliorated propofol-induced proliferation inhibition, neuroapoptosis, and neural inflammation by activating the mBDNF/TrkB/PI3K pathway.

Regulation of CRMP2 by Cdk5 and GSK-3β participates in sevoflurane-induced dendritic development abnormalities and cognitive dysfunction in developing rats

BACKGROUND

General anesthetics such as sevoflurane interfere with dendritic development and synaptogenesis, resulting in cognitive impairment. The collapsin response mediator protein2 (CRMP2) plays important roles in dendritic development and synaptic plasticity and its phosphorylation is regulated by cycline dependent kinase-5 (Cdk5) and glycogen synthase kinase-3β (GSK-3β). Here we investigated whether Cdk5/CRMP2 or GSK-3β/CRMP2 pathway is involved in sevoflurane-induced developmental neurotoxicity.

METHODS

Rats at postnatal day 7 (PND7) were i.p. injected with Cdk5 inhibitor roscovitine, GSK-3β inhibitor SB415286 or saline 20 min. before exposure to 2.8% sevoflurane for 4 h. Western-blotting was applied to measure the expression of Cdk5/CRMP2 and GSK-3β/CRMP2 pathway proteins in the hippocampus 6 h after the sevoflurane exposure. When rats grew to adolescence (from PND25), they were tested for open-field and contextual fear conditioning, and then long term potentiation (LTP) from hippocampal slices was recorded, and morphology of pyramidal neuron was examined by Golgi staining and synaptic plasticity-related proteins expression in hippocampus were measured by western-blotting. In another batch of experiment, siRNA-CRMP2 or vehicle control was injected into hippocampus on PND5.

RESULTS

Sevoflurane activated Cdk5/CRMP2 and GSK-3β/CRMP2 pathways in the hippocampus of neonatal rats, reduced dendritic length, branches and the density of dendritic spine in pyramidal neurons. It also reduced the expressions of PSD-95, drebrin and synaptophysin in hippocampus, impaired memory ability of rats and inhibited LTP in hippocampal slices. All the impairment effects by sevoflurane were attenuated by pretreatment with inhibitor of Cdk5 or GSK-3β. Furthermore, rat transfected with siRNA-CRMP2 eliminated the neuroprotective effects of Cdk5 or GSK-3β blocker in neurobehavioral and LTP tests.

CONCLUSION

Cdk5/CRMP2 and GSK-3β/CRMP2 pathways participate in sevoflurane-induced dendritic development abnormalities and cognitive dysfunction in developing rats.

Activation of PI3K/Akt/HIF-1α Signaling is Involved in Lung Protection of Dexmedetomidine in Patients Undergoing Video-Assisted Thoracoscopic Surgery: A Pilot Study

Background

Lung resection and one lung ventilation (OLV) during video-assisted thoracoscopic surgery (VATS) may lead to acute lung injury. Dexmedetomidine (DEX), a highly selective α₂ adrenergic receptor agonist, improves arterial oxygenation in adult patients undergoing thoracic surgery. The aim of this pilot study was to explore possible mechanism related to lung protection of DEX in patients undergoing VATS.

Patients and Methods

Seventy-four patients scheduled for VATS were enrolled in this study. Three timepoints (before anesthesia induction (T₀), 40 min after OLV (T₁), and 10 min after two-lung ventilation (T₂)) of arterial blood gas were obtained. Meanwhile, lung histopathologic examination, immunohistochemistry analysis (occludin and ZO-1), levels of tumor necrosis factor (TNF)-α and interleukin (IL)-6 in lung tissue and plasma, and activation of phosphoinositide-3-kinase (PI3K)/AKT/hypoxia-inducible factor (HIF)-1α signaling were detected. Postoperative outcomes including duration of withdrawing the pleural drainage tube, length of hospital stay, hospitalization expenses, and postoperative pulmonary complications (PPCs) were also recorded.

Results

Sixty-seven patients were randomly divided into DEX group (group D, n=33) and control group (group N, n=34). DEX improved oxygenation at T₁ and T₂ (group D vs group N; T₁: 191.8 ± 49.8 mmHg vs 159.6 ± 48.1 mmHg, P = 0.009; T₂: 406.0 mmHg [392.2–423.7] vs 374.5 mmHg [340.2–378.2], P = 0.001). DEX alleviated the alveolar capillary epithelial structure damage, increased protein expression of ZO-1 and occludin, inhibited elevation of the expression of TNF-α and IL-6 in lung tissue and plasma, and increased protein expression of p-PI3K, p-AKT and HIF-1α. Dex administered had better postoperative outcomes with less risk of PPCs and hospitalization expenses as well as shorter duration of withdrawing the pleural drainage tube and length of hospital stay.

Conclusion

Activation of PI3K/Akt/HIF-1α signaling might be involved in lung protection of DEX in patients undergoing VATS.