Repeated exposure to sevoflurane impairs the learning and memory of older male rats

Sevoflurane-induced overexpression of extrasynaptic α5-GABAAR via the RhoA/ROCK2 pathway impairs cognitive function in aged mice

Perioperative neurocognitive disorder (PND) is a serious neurologic complication in aged patients and might be associated with sevoflurane exposure. However, the specific pathogenesis is still unclear. The distribution of α5-GABAAR, a γ-aminobutyric acid type A receptor (GABAAR) subtype, at extrasynaptic sites is influenced by the anchor protein radixin, whose phosphorylation is regulated via the RhoA/ROCK2 signaling pathway and plays a crucial role in cognition. However, whether sevoflurane affects the ability of radixin phosphorylation to alter extrasynaptic receptor expression is unknown. Aged mice were exposed to sevoflurane to induce cognitive impairment. Both total proteins and membrane proteins were extracted for analysis. Cognitive function was evaluated using the Morris water maze and fear conditioning test. Western blotting was used to determine the expression of ROCK2 and the phosphorylation of radixin. Furthermore, the colocalization of p-radixin and α5-GABAAR was observed. To inhibit ROCK2 activity, either an adeno-associated virus (AAV) or fasudil hydrochloride was administered. Aged mice treated with sevoflurane exhibited significant cognitive impairment accompanied by increased membrane expression of α5-GABAAR. Moreover, the colocalization of α5-GABAAR and p-radixin increased after treatment with sevoflurane, and this change was accompanied by an increase in ROCK2 expression and radixin phosphorylation. Notably, inhibiting the RhoA/ROCK2 pathway significantly decreased the distribution of extrasynaptic α5-GABAAR and improved cognitive function. Sevoflurane activates the RhoA/ROCK2 pathway and increases the phosphorylation of radixin. Excess α5-GABAAR is anchored to extrasynaptic sites and impairs cognitive ability in aged mice. Fasudil hydrochloride administration improves cognitive function.

Sevoflurane Alters Serum Metabolites in Elders and Aging Mice and Increases Inflammation in Hippocampus

Purpose

Postoperative cognitive dysfunction (POCD) is a central nervous system complication that occurs after anesthesia, particularly among the elderly. However, the neurological pathogenesis of postoperative cognitive dysfunction remains unclear. The aim of this study was to evaluate the effects of sevoflurane exposure on serum metabolites and hippocampal gene expression in elderly patients and aging mice by metabolomics and transcriptomic analysis and to explore the pathogenesis of sevoflurane induced POCD.

Patients and Methods

Human serum samples from five patients over 60 years old were collected before sevoflurane anesthesia and 1 hour after anesthesia. Besides, mice aged at 12 months (n=6 per group) were anesthetized with sevoflurane for 2 hours or with sham procedure. Subsequently, serum and hippocampal tissues were harvested for analysis. Further investigation into the relationship between isatin and neuroinflammation was conducted using BV2 microglial cells.

Results

Sevoflurane anesthesia led to the activation of inflammatory pathways, an increased presence of hippocampal astrocytes and microglia, and elevated expression of neuroinflammatory cytokines. Comparative analysis identified 12 differential metabolites that exhibited changes in both human and mouse serum post-sevoflurane anesthesia. Notably, isatin levels were significantly decreased after anesthesia. Notably, isatin levels significantly decreased after anesthesia, a factor known to stimulate proliferation and proinflammatory gene expression in microglia-the pivotal cell type in inflammatory responses.

Conclusion

Sevoflurane-induced alterations in serum metabolites in both elderly patients and aging mice, subsequently contributing to increased inflammation in the hippocampus.

Necroptosis involved in sevoflurane-induced cognitive dysfunction in aged mice by activating NMDA receptors increasing intracellular calcium

Perioperative neurocognitive disorders are a common surgical and postanesthesia complication. Necroptosis contributes to the emergence of various neurological disorders. We conjecture that cognitive impairment is associated with necroptosis of hippocampal neurons, which is mediated by NMDA receptors leading to cytoplasmic calcium imbalance. C57BL/6 J male mice ( 18 months) were randomly divided into the C ( control group), S ( sevoflurane group), S+M ( sevoflurane plus the NMDA receptor antagonist memantine group) and S+N ( sevoflurane plus necrostatin-1) group. We exposed the mice to 3% sevoflurane for 2 h a day for three consecutive days in the S, S+M and S+N groups. Memantine ( 20 mg/kg) or Nec-1 ( 10 mg/kg) was injected intraperitoneally 1 h before sevoflurane anesthesia in the S+M or S+N group. We used the animal behavior tests to evaluate the cognitive function. Pathological damage, the rate of necroptosis, [Ca2+]i, and the expression of necroptosis-related proteins were evaluated. The cognitive function tests, pathological damage, the rate of necroptosis, the expression of necroptosis-related proteins, NMDAR2A and NMDAR2B were significantly different in the S group ( P < 0.05). Alleviated pathological damage, decreased the rate of necroptosis and down-regulated the expression of necroptosis-related proteins occurred in the S+M and S+N group ( P < 0.05). The lower elevated [Ca2+]i, expression of NMDAR2A and NMDAR2B were found in the S+M group. Our findings highlighted sevoflurane-induced cognitive dysfunction is associated with an imbalance in cytoplasmic calcium homeostasis by activating NMDA receptors, which causes hippocampus neurons to undergo necroptosis and ultimately affects cognitive performance in aged mice.

Intergenerational Perioperative Neurocognitive Disorder

Accelerated neurocognitive decline after general anesthesia/surgery, also known as perioperative neurocognitive disorder (PND), is a widely recognized public health problem that may affect millions of patients each year. Advanced age, with its increasing prevalence of heightened stress, inflammation, and neurodegenerative alterations, is a consistent contributing factor to the development of PND. Although a strong homeostatic reserve in young adults makes them more resilient to PND, animal data suggest that young adults with pathophysiological conditions characterized by excessive stress and inflammation may be vulnerable to PND, and this altered phenotype may be passed to future offspring (intergenerational PND). The purpose of this narrative review of data in the literature and the authors' own experimental findings in rodents is to draw attention to the possibility of intergenerational PND, a new phenomenon which, if confirmed in humans, may unravel a big new population that may be affected by parental PND. In particular, we discuss the roles of stress, inflammation, and epigenetic alterations in the development of PND. We also discuss experimental findings that demonstrate the effects of surgery, traumatic brain injury, and the general anesthetic sevoflurane that interact to induce persistent dysregulation of the stress response system, inflammation markers, and behavior in young adult male rats and in their future offspring who have neither trauma nor anesthetic exposure (i.e., an animal model of intergenerational PND).

Echinatin mitigates sevoflurane-induced hippocampal neurotoxicity and cognitive deficits through mitigation of iron overload and oxidative stress

CONTEXT

Sevoflurane (Sev) is a commonly used surgical anaesthetic; it has neurotoxic effects on the brain. Echinatin (Ech) is reported to have anti-inflammatory and antioxidant activity.

OBJECTIVE

This research confirms the effect of Ech on Sev-induced neurotoxicity and cognitive deficits.

MATERIALS AND METHODS

Primary rat hippocampal neurons were treated with 4.1% Sev for 6 h in the presence of Ech (5, 10, and 20 μM) or vehicle, followed by a further 42 h of culture. Male Sprague-Dawley aged rats were divided into 6 groups (n = 6): control, Sev, Sev + Ech (20 mg/kg;), Sev + Ech (40 mg/kg), and Sev + Ech (80 mg/kg). Rats were intraperitoneally injected with Ech or vehicle 1 h before Sev exposure (2% Sev for 5 h).

RESULTS

We found that Ech (5, 10, and 20 μM) elevated cell viability (1.29-, 1.51-, 1.68-fold) but mitigated apoptosis (23.87% vs. 16.48%, 12.72%, 9.02%), oxidative stress, and ferroptosis in hippocampal neurons with Sev treatment. Ech activated the Nrf2 expression in Sev-induced in vitro and in vivo models of anaesthetic neurotoxicity. Ech also weakened neurotoxicity in hippocampal neurons with Sev treatment by increasing Nrf2 expression level. Moreover, Ech alleviated hippocampus neurons apoptosis (19.38% vs. 16.05%, 11.71%, 8.88%), oxidative stress, and ferroptosis in rats with Sev treatment. Ech improved Sev-induced cognitive deficits in rats.

CONCLUSIONS

Ech alleviates Sev-induced neurotoxicity and cognitive deficits by mitigation of ferroptosis and oxidative stress. Ech may be developed as a new promising therapeutic drug for treatment of cerebral nerve injury caused by surgical anaesthesia.

miRNA-384-3p alleviates sevoflurane-induced nerve injury by inhibiting Aak1 kinase in neonatal rats

OBJECTIVE

Sevoflurane is a common anesthetic and is widely used in pediatric clinical surgery to induce and maintain anesthesia through inhalation. Increasing studies have revealed that sevoflurane has neurotoxic effects on neurons, apoptosis, and memory impairment. miR-384 is involved in the process of neurological diseases. However, the role of miRNA-384-3p in sevoflurane-induced nerve injury is not clear. This study focused on exploring the roles and mechanisms of miRNA-384-3p in sevoflurane-induced nerve injury.

METHODS

Seven-day-old rats were exposed to 2.3% sevoflurane to induce nerve injury. The morphological changes in neurons in the hippocampal CA1 region were detected by HE staining and Nissl staining. Neuronal apoptosis was detected by TUNEL and Western blot assays. Spatial memory and learning ability were detected by the Morris water maze assay. The target gene of miRNA-384-3p was verified through a luciferase reporter assay. A rescue experiment was used to confirm the miRNA-384-3p pathway in sevoflurane-induced nerve injury.

RESULTS

Sevoflurane reduced miRNA-384-3p expression in the rat hippocampus. miRNA-384-3p alleviated sevoflurane-induced morphological changes in hippocampal neurons and apoptosis of neurons in the hippocampal CA1 region. Meanwhile, miRNA-384-3p attenuated the decline in spatial memory and learning ability induced by sevoflurane. miRNA-384-3p alleviated sevoflurane-induced nerve injury by inhibiting the expression of adaptor-associated kinase 1 (Aak1).

CONCLUSION

Our findings revealed the role and mechanism of miRNA-384-3p in sevoflurane-induced nerve injury, suggesting that miRNA-384-3p could be a novel and promising strategy for reducing sevoflurane-induced neurotoxicity.

Docosahexaenoic acid supplementation alleviates behavioral memory impairment caused via repeated administration of sevoflurane in aged rats

Elderly patients often need repeated surgical intervention, so it is important to determine the impact of repeated exposure to anesthetics on learning and memory. Docosahexaenoic acid (DHA) is considered to be an essential nutrient for maintaining brain health. The aim of the present study was to explore the potential effects of DHA on memory impairment induced by repeated sevoflurane anesthesia in aged rats. A total of 54 Sprague Dawley aged rats (18 months) were randomly divided into the following six groups: i) Control group; ii) sevoflurane group (Sev, 2.5% for 5 min); iii) DHA group (3 g/kg); iv) Sev + DHA (0.3 g/kg) group; v) Sev + DHA (1 g/kg) group; and vi) Sev + DHA (3 g/kg) group. Morris water maze experiment was performed to evaluate the learning and memory ability of the rats following treatment. H&E staining was used to observe any histological changes. Superoxide dismutase, malondialdehyde and glutathione peroxidase levels were detected using ELISA. Immunohistochemistry and western blotting were used to determine nuclear factor erythroid-2-related factor 2 (Nrf2) and heme oxygenase 1 (HO-1) protein expression levels. Following repeated sevoflurane anesthesia, rats exhibited a prolonged escape latency. The number of times rats crossed the platform and the time spent in the target quadrant were also significantly reduced by repeated sevoflurane anesthesia. However, rats treated with Sev + DHA exhibited a reduced escape latency, whilst the number of times they crossed the platform and the time spent in the target quadrant increased compared with Sev treatment alone. Histopathological examination revealed that DHA treatment ameliorated the disordered neuron arrangement, deep staining of the neuronal nucleus pyknosis and cell edema observed in the brain tissue induced by repeated sevoflurane anesthesia. Furthermore, the protein expression levels of Nrf2 and HO-1 were demonstrated to be significantly increased in rats treated with DHA and exposed to repeated sevoflurane anesthesia compared with those in untreated rats that underwent repeated sevoflurane anesthesia. In conclusion, the present study revealed that DHA exerted protective effects against impairments in learning and memory induced by repeated sevoflurane anesthesia in aged rats, which may be associated with the Nrf2/HO-1 signaling pathway.

MicroRNA-367-3p suppresses sevoflurane-induced adult rat astrocyte apoptosis by targeting BCL2L11

The present study aimed to characterize the effect of microRNA (miR)-367-3p on sevoflurane anesthesia and elucidate the underlying mechanism. A total of 36 4-month-old adult Sprague-Dawley rats were divided into six groups. Sevoflurane was inhaled at concentrations of 0, 1, 2, 4, 8 and 16% for a total of 6 h; the hippocampus of the brain was subsequently minced and digested, and astrocytes were isolated. Various methods, including reverse transcription-quantitative (RT-q)PCR, western blotting and TUNEL staining, were used to determine the expression levels of Bax, BCL-2 and BCL-2-like protein 11 (BCL2L11), as well as the level of apoptosis. The rats were treated with 8% sevoflurane and the astrocytes from the rats were transfected with miR-367-3p or anti-miR-367-3p. The present study demonstrated that sevoflurane promoted astrocytes apoptosis. Western blotting revealed that with an increase of sevoflurane concentration, the expression levels of the apoptotic proteins Bax and BCL2L11 were significantly increased, whereas the protein expression levels of BCL-2 were significantly decreased. However, overexpression of miR-367-3p reversed these effects. TUNEL staining revealed that sevoflurane promoted the apoptosis of astrocytes, while apoptosis was reversed by miR-367-3p overexpression. RT-qPCR demonstrated that sevoflurane inhibited the expression of miR-367-3p. Notably, miR-367-3p reduced the expression of BCL2L11, thereby inhibiting the apoptosis of astrocytes originating from the hippocampal area of adult rats induced by sevoflurane. Therefore, miR-367-3p and BCL2L11 may act as effective targets for the study of anesthesia.

The Mechanisms of Sevoflurane-Induced Neuroinflammation

Sevoflurane is one of the most commonly used inhaled anesthetics due to its low blood gas coefficient, fast onset, low airway irritation, and aromatic smell. However, recent studies have reported that sevoflurane exposure may have deleterious effects on cognitive function. Although neuroinflammation was most widely mentioned among the established mechanisms of sevoflurane-induced cognitive dysfunction, its upstream mechanisms have yet to be illustrated. Thus, we reviewed the relevant literature and discussed the most mentioned mechanisms, including the modulation of the microglial function, blood–brain barrier (BBB) breakdown, changes in gut microbiota, and ease of cholinergic neurotransmission to help us understand the properties of sevoflurane, providing us new perspectives for the prevention of sevoflurane-induced cognitive impairment.

Effects of general anesthetics on synaptic transmission and plasticity

General anesthetics depress excitatory and/or enhance inhibitory synaptic transmission principally by modulating the function of glutamatergic or GABAergic synapses, respectively, with relative anesthetic agent-specific mechanisms. Synaptic signaling proteins, including ligand- and voltage-gated ion channels, are targeted by general anesthetics to modulate various synaptic mechanisms, including presynaptic neurotransmitter release, postsynaptic receptor signaling, and dendritic spine dynamics to produce their characteristic acute neurophysiological effects. As synaptic structure and plasticity mediate higher-order functions such as learning and memory, long-term synaptic dysfunction following anesthesia may lead to undesirable neurocognitive consequences depending on the specific anesthetic agent and the vulnerability of the population. Here we review the cellular and molecular mechanisms of transient and persistent general anesthetic alterations of synaptic transmission and plasticity.

Effects of sevoflurane general anesthesia during early pregnancy on AIM2 expression in the hippocampus and parietal cortex of Sprague-Dawley offspring rats

The aim of the present study was to investigate the effect of exposure to sevoflurane general anesthesia during early pregnancy on interferon-inducible protein AIM2 (AIM2) expression in the hippocampus and parietal cortex of the offspring Sprague-Dawley (SD) rats. A total of 18 SD rats at a gestational age of 5-7 days were randomly divided into three groups: i) A control group (control); ii) 2-h sevoflurane general anesthesia, group 1 (S1); and iii) 4-h sevoflurane general anesthesia, group 2 (S2). The six offspring rats in each group were maintained for 30 days and assessed by Morris water maze testing. Brain specimens were collected from offspring rats 30 days after birth. Changes in the structural morphology of neurons in the hippocampus and parietal cortex were observed using hematoxylin and eosin staining. Nissl bodies in the hippocampus and parietal cortex were observed by Nissl staining. The expression of glial fibrillary acidic protein (GFAP), AIM2, CD45 and IL-1β was detected by immunohistochemistry and the protein levels of CD45, IL-1β, pro-caspase-1 and caspase-1 p10 were detected by western blotting. Compared with the control group, offspring rats in the S1 and S2 groups exhibited poor long-term learning and memory ability and experienced different degrees of damage to both the hippocampus and parietal cortex. The expression levels of GFAP, AIM2, CD45, IL-1β, caspase-1 and caspase-1 p10 in the offspring of both the S1 and the S2 groups were significantly increased (P<0.05) compared with offspring of the control group. Moreover, compared with the offspring of the S1 group, hippocampal and parietal cortex injury in the offspring of the S2 group was further aggravated, and the expression of GFAP, AIM2, CD45, IL-1β, pro-caspase-1 and cleaved-caspase-1 was significantly increased (P<0.05). In conclusion, sevoflurane general anesthesia in SD rat early pregnancy promoted the expression of AIM2 and the inflammatory response in the hippocampus and parietal cortex of offspring rats.

Ribbon Synapses and Hearing Impairment in Mice After in utero Sevoflurane Exposure

Introduction

In utero, exposure to sevoflurane (a commonly used inhalation anesthetic) can lead to hearing impairment in offspring mice, but the underlying impairment mechanism is not known.

Materials and Methods

Day-15 pregnant mice were treated with 2.5% sevoflurane for 2 h to investigate sevoflurane ototoxicity. Cochleae from offspring mice were harvested for hair-cell and ribbon-synapse assessments. Hearing in offspring mice was assessed at postnatal day 30 using an auditory brainstem-response (ABR) test. Cochlear-explant cultures from offspring mice were exposed to 2.5% sevoflurane for 6 h. Immediately after treatment, explants were assessed for hair-cell morphology, mitochondrial oxidative stress, and autophagy.

Results

In utero, sevoflurane exposure impaired hearing in the offspring is demonstrated by a decrease in ABR wave I amplitudes, a marker for ribbon-synapse functionality. Sevoflurane exposure caused no obvious damage to hair cells, but cochlear ribbon synapses were reduced in postnatal day 15 offspring, and partially recovered by postnatal day 30. Sevoflurane treatment also increased mitochondrial reactive-oxygen species stress and decreased autophagy in the cochlear explants.

Conclusion

These results suggest that oxidative stress and reduced autophagy may underly ribbon-synapse involvement in sevoflurane-induced hearing loss.

Sevoflurane leads to learning and memory dysfunction via breaking the balance of tPA/PAI-1

Exposure to general anesthesia in early childhood may lead to adverse effects on adolescent neurocognition. This study investigated the effects of multiple inhalations of sevoflurane on long-term learning and memory in developing rats, and explored the mechanistic role of the tissue plasminogen activator (tPA)/plasminogen activator inhibitor-1 (PAI-1) fibrinolysis system and its regulatory relationship with the brain derived neurotrophic factor (BDNF) by activation of tropomysin related kinase B (TrkB). After rats were inhaled with sevoflurane for 2 h/d for three days, the expression levels of tPA, PAI-1, BDNF, its precursor(proBDNF), TrkB and phosphorylation of TrkB (p-TrkB) were detected at different time points. After 28 d, Morris water maze was used to examine learning and memory function; Golgi staining was used to investigate synaptic plasticity and synaptic-related proteins, such as Synapsin I(SYN1), growth associated protein 43(GAP-43), and postsynaptic density protein 95(PSD-95). Rats were given exogenous tPA and an inhibitor of PAI-1, TM5275. The results showed multiple inhalation of sevoflurane led to learning and memory dysfunction, downregulated the expression of the synaptic-related proteins, decreased dendritic spine density in the hippocampus, increased the expression level of proBDNF and PAI-1, and reduced expression of BDNF, tPA, and p-TrkB. Interestingly, tPA or TM5275 partially reversed the learning and memory dysfunction and the reduction of synaptic plasticity induced by sevoflurane exposure. Furthermore, they blocked the upregulation of proBDNF and PAI-1 protein expression and increased the expression of BDNF, tPA, and p-TrkB. The protective effect of tPA or TM5275 on rats following multiple sevoflurane inhalation was blocked by a TrkB inhibitor. Multiple inhalation of sevoflurane in rats inhibited the cleavage of proBDNF by disrupting the balance of the tPA/PAI-1 fibrinolysis system. This blocked the activation of the downstream TrkB signaling pathway and reduced hippocampal synaptic plasticity, leading to long-term learning and memory dysfunction. Therefore, Sevoflurane exposure could lead to learning and memory dysfunction by inhibiting BDNF cleavage via breaking the balance of tPA/PAI-1.

Tetramethylpyrazine Attenuated Sevoflurane-Induced Neurotoxicity by Enhancing Autophagy through GPR50/CREB Pathway in SH-SY5Y Cells

Tetramethylpyrazine has shown neuroprotective and axonal outgrowth-promoting effects and can improve cognitive deficit in a rat model of chronic hypoperfusion. However, the role of tetramethylpyrazine in sevoflurane-induced neurotoxicity is still vague. Therefore, this study was designed to investigate the effects and mechanisms of tetramethylpyrazine on sevoflurane-induced autophagy, apoptosis, and the expression of BACE1 and A[Formula: see text] in SH-SY5Y cells. We measured the expression levels of the apoptosis protein markers Bax and Bcl-2, autophagy protein markers Atg5 and LC3-II, BACE1, and A[Formula: see text] in SH-SY5Y cells after sevoflurane treatment and determined the effects of tetramethylpyrazine on sevoflurane-induced expression of these proteins after silencing GPR50 or Atg5 with siRNA in vitro. We found that exposure to 3.4% sevoflurane for 6 h decreased the expression of autophagy protein markers and increased the expression of the apoptosis protein markers, BACE1, and A[Formula: see text] in SH-SY5Y cells. The number of red puncta (autolysosomes) and yellow puncta (autophagosomes) in each SH-SY5Y cell decreased after transient transfection with the mRFP-GFP-LC3 expression plasmid. Silencing of GPR50 decreased the expression of pCREB, Atg5, and LC3-II, while silencing of Atg5 increased the expression of BACE1 and A[Formula: see text] in SH-SY5Y cells. Our results demonstrate that tetramethylpyrazine attenuated sevoflurane-induced neurotoxicity by enhancing autophagy through the GPR50/CREB pathway in SH-SY5Y cells.

Anesthesiology and cognitive impairment: a narrative review of current clinical literature

Background

The impact of general anesthesia on cognitive impairment is controversial and complex. A large body of evidence supports the association between exposure to surgery under general anesthesia and development of delayed neurocognitive recovery in a subset of patients. Existing literature continues to debate whether these short-term effects on cognition can be attributed to anesthetic agents themselves, or whether other variables are causative of the observed changes in cognition. Furthermore, there is conflicting data on the relationship between anesthesia exposure and the development of long-term neurocognitive disorders, or development of incident dementia in the patient population with normal preoperative cognitive function. Patients with pre-existing cognitive impairment present a unique set of anesthetic considerations, including potential medication interactions, challenges with cooperation during assessment and non-general anesthesia techniques, and the possibility that pre-existing cognitive impairment may impart a susceptibility to further cognitive dysfunction.

Main body

This review highlights landmark and recent studies in the field, and explores potential mechanisms involved in perioperative cognitive disorders (also known as postoperative cognitive dysfunction, POCD). Specifically, we will review clinical and preclinical evidence which implicates alterations to tau protein, inflammation, calcium dysregulation, and mitochondrial dysfunction. As our population ages and the prevalence of Alzheimer’s disease and other forms of dementia continues to increase, we require a greater understanding of potential modifiable factors that impact perioperative cognitive impairment.

Conclusions

Future research should aim to further characterize the associated risk factors and determine whether certain anesthetic approaches or other interventions may lower the potential risk which may be conferred by anesthesia and/or surgery in susceptible individuals.

Characterization of DNA hydroxymethylation in the hypothalamus of elderly mice with post-operative cognitive dysfunction

Post-operative cognitive dysfunction (POCD) is a common syndrome characterized by perioperative cerebral damage in elderly patients, including cognitive impairment and memory loss. Recent studies have revealed that anesthesia is one of the key causes of POCD. Ubiquitin-like with PHD and ring finger domains 2 (Uhrf2) has been reported to play a crucial role in regulating DNA methylation and hydroxymethylation, which are closely connected with memory building and erasure. However, whether narcotic drugs can affect Uhrf2 to impact on DNA methylation and hydroxymethylation in POCD is poorly understood. In this study, a POCD model was established in elderly mice through sevoflurane treatment, and these mice were found to have compromised levels of global DNA 5'-hydroxymethylcytosine (5hmC) and Uhrf2 in the hippocampus and the amygdaloid nucleus, when compared with non-POCD and control mice. The results of immunoprecipitation and quantitative PCR revealed that 5hmC modification of the promoters of genes associated with neural protection and development, such as glial cell-derived neurotrophic factor, brain derived neurotrophic factor, glucocorticoid receptor and acyl-CoA sythetase short chain family member 2, was reduced in the hippocampus of POCD mice when compared with non-POCD and control mice. Taken together, the findings of the present study suggest that loss of 5hmC, in the hippocampus and the amygdaloid nucleus modulated by Uhrf2 suppression, may result in the learning and memory ability impairment seen in mice with POCD.

Plasma amyloid beta level changes in aged mice with cognitive dysfunction following sevoflurane exposure

INTRODUCTION

Previous studies have stated that cognitive impairment induced by anesthetics was associated with amyloid beta (Aβ). However, few researchers have investigated the transport of Aβ inside and outside of the brain.

AIM

We attempted to probe the effects of sevoflurane on cognitive functions, the plasma Aβ, and transporters of Aβ in aged mice. The receptor for advanced glycation end-products (RAGE) is an Aβ influx protein, and Low-density lipoprotein receptor-related protein-1 (LRP-1) is an Aβ efflux protein.

METHODS

Aged mice were divided into the control group and the sevoflurane group. The mice were exposed to 100% oxygen or 2.5% sevoflurane for 2 h. The abilities of spatial learning and memory in mice were tested using the Morris water maze. Aβ concentrations of plasma were measured with enzyme-linked immunosorbent assay kits. The RAGE and LRP-1 gene levels in the brain were assessed with quantitative polymerase chain reaction, and the protein levels were determined by western blot analysis. The locations of RAGE in the brain were confirmed via immunofluorescence.

RESULTS

In the sevoflurane group mice, the escape latency was increased on the 5th day of training, and the time spent in the target quadrant was decreased on the 7th day after anesthesia. Sevoflurane reduced the concentration of plasma Aβ1-40. In addition, sevoflurane increased both gene and protein levels of RAGE in the brain, and increased RAGE proteins co-localized with the hippocampal vascular endothelial cells.

CONCLUSION

RAGE over-expression in the hippocampal vascular endothelial cells possibly resulted in the excessive transport of the plasma Aβ1-40 into the brain after treatment with sevoflurane, which was associated with sevoflurane-induced cognitive dysfunction in aged mice.

Pediatric neuroanesthesia

PURPOSE OF REVIEW

Pediatric neuroanesthesia is a fascinating, yet challenging branch of anesthesia. This review highlights some of the recent insights into pediatric neuroanesthesia from the past 18 months.

RECENT FINDINGS

Although there are incontrovertible evidences in animals suggesting that prolonged exposure to general anesthesia causes long-term neurological impairment, the translational relevance of these findings in humans is debatable. Early surgery for pediatric drug-refractory epilepsy is supported by emerging literature, but poses unique perioperative problems for the treating neuroanesthesiologist. Similarly, minimizing intraoperative blood loss and blood transfusion concerns every anesthesiologist managing small children. The usefulness of tranexamic acid in children is further enhanced by some studies in spine surgeries. Some pertinent issues related to intraoperative neuromonitoring are also discussed in the text.

SUMMARY

There are several logistical and ethical problems of carrying out high-quality prospective studies in children but important findings on prevention of anesthetic neurotoxicity; minimizing intraoperative blood loss, intraoperative neurophysiological monitoring, examining optimal doses and choices of anesthetic agents in epilepsy surgery have been published recently.

miR-34a Inhibitor May Effectively Protect against Sevoflurane-Induced Hippocampal Apoptosis through the Wnt/β-Catenin Pathway by Targeting Wnt1

PURPOSE

Research has shown that sevoflurane-induced toxicity causes neurodegeneration in the developing brain. miR-34a has been found to negatively regulate ketamine-induced hippocampal apoptosis and memory impairment. However, the role of miR-34a in sevoflurane-induced hippocampal neurodegeneration remains largely unclear.

MATERIALS AND METHODS

C57/BL6 mice (7-day-old) inhaled 2.3% sevoflurane for 2 h/day over 3 consecutive days. miR-34a expression was reduced through intracerebroventricular injection with miR-34a interference lentivirus vector (LV-anti-miR-34a) into mouse hippocampus after anesthesia on the first day of exposure. Hippocampal apoptosis was detected by TUNEL assay and flow cytometry analysis. Spatial memory ability was evaluated by the Morris water maze test. The interaction between miR-34a and Wnt1 was confirmed by luciferase reporter assay, RNA immunoprecipitation, Western blot, and immunofluorescence staining. The effects of miR-34a on protein levels of B-cell lymphoma 2 (Bcl-2), bcl-2-like protein 4 (Bax), and Wnt/β-catenin pathway-related proteins were evaluated using Western blot analysis.

RESULTS

Sevoflurane upregulated hippocampal miR-34a, and miR-34a inhibitor attenuated sevoflurane-induced hippocampal apoptosis and memory impairment. miR-34a negatively regulated Wnt1 expression by targeting miR-34a in hippocampal neurons. Moreover, forced expression of Wnt1 markedly undermined miR-34a-mediated enhancement of sevoflurane-induced apoptosis of hippocampal neurons, while Wnt1 silencing greatly restored anti-miR-34a-mediated repression of sevoflurane-induced apoptosis of hippocampal neurons. Increased expression of miR-34a inhibited the Wnt/β-catenin pathway in hippocampal neurons exposed to sevoflurane, while anti-miR-34a exerted the opposite effects.

CONCLUSION

miR-34a inhibitor may effectively protect against sevoflurane-induced hippocampal apoptosis via activation of the Wnt/β-catenin pathway by targeting Wnt1.