The effect of sevoflurane anesthesia on cognitive function and the expression of Insulin-like Growth Factor-1 in CA1 region of hippocampus in old rats

Sevoflurane anesthesia reduces the expression of inflammatory response genes and β-site amyloid precursor protein-cleaving enzyme in hippocampi of diabetic mice

Diabetes and inhaled anesthesia are associated with an increased likelihood of developing postoperative cognitive dysfunction in humans and animal models, but the mechanisms are unclear. This study aimed to investigate the effect and mechanism of sevoflurane anesthesia on cognitive function in diabetic (DM) mice. Spontaneously diabetic db/db and control db/m mice were subject to sevoflurane anesthesia or allowed to breathe air, respectively. The Morris water maze test as spatial learning and novel object recognition test as recognition memory were performed. The expression of inflammatory cytokines and neurotoxicity-related genes in the hippocampus of four groups was measured using real-time PCR. The expression level of neurotoxicity and neuroprotection-related proteins in DM mice hippocampus were estimated using Western blot assay. It is found that DM mice developed cognitive impairment; however, the cognitive impairment was not exacerbated in sevoflurane-exposed mice. Sevoflurane anesthesia led to a decrease in mRNA levels of inflammatory cytokines in DM mice hippocampi, including interleukin 17 (IL-17), C-C motif chemokine (CCL20), CCL7 as well as high mobility group box 1 and beta-site amyloid-β cleaving enzyme 1; and no effect was observed on the expression of neurotoxicity genes, including amyloid precursor protein, choline O-acetyltransferase, tumor necrosis factor, alpha-induced protein 1, B-cell lymphoma 2 and estrogen receptor 2. In addition, we observed elevated phosphorylation of cAMP response element-binding protein in DM mice exposed to sevoflurane anesthesia. In conclusion, sevoflurane did not exacerbate DM-associated cognitive impairment.

Necrostatin-1 Against Sevoflurane-Induced Cognitive Dysfunction Involves Activation of BDNF/TrkB Pathway and Inhibition of Necroptosis in Aged Rats

Postoperative cognitive dysfunction (POCD) induced by anesthesia or surgery has become a common complication in the aged population. Sevoflurane, a clinical inhalation anesthetic, could stimulate calcium overload and necroptosis to POCD. In addition, necroptosis inhibitor necrostatin-1 (Nec-1) alleviated cognitive impairment caused by multiple causes, including postoperative cognitive impairment. However, whether Nec-1 exerts a neuroprotective effect on POCD via calcium and necroptosis remains unclear. We anesthetized Sprague-Dawley rats with sevoflurane to construct the POCD model and to explore the mechanism underlying neuroprotective effects of Nec-1 in POCD. Rats were treated with Nec-1 (6.25 mg/kg) 1 h prior to anesthesia. Open field test and Morris water maze were employed to detect the cognitive function. In this study, rats exposed to sevoflurane displayed cognitive dysfunction without changes in spontaneous activity; however, the sevoflurane-induced POCD could be relieved by Nec-1 pretreatment. Nec-1 decreased sevoflurane-induced calcium overload and calpain activity in the hippocampus. In addition, Nec-1 alleviated the expression of p-RIPK1, RIPK1, p-RIPK3, RIPK3, p-MLKL and MLKL. Furthermore, Nec-1 remarkably increased BDNF and p-TrkB/TrkB expression in the hippocampus of aged rats. Ultimately, our research manifests evidence that Nec-1 may play a neuroprotective role against sevoflurane-induced cognitive impairment via the increase of BDNF/TrkB and suppression of necroptosis-related pathway.

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.

Sevoflurane-induced inflammation development: involvement of cholinergic anti-inflammatory pathway

Chronic inflammation plays an important role in the mechanisms underpinning the development of anesthesia-induced cognitive dysfunction. However, less is known about how anesthesia causes inflammation. One possibility is that the inflammation is related to alteration of the activity of the alpha 7 nicotinic acetylcholine receptor cholinergic anti-inflammatory pathway. This study analyzed the effect of sevoflurane administration on the cognitive function by using a novel object recognition test and Y-maze test, and on acetylcholinesterase activity and expression in hippocampal tissue by using an acetylcholinesterase assay kit and quantitative real-time PCR. This study also evaluated the effect of alpha 7 nicotinic acetylcholine receptor agonist PNU-282987 and antagonist methyllycaconitine on cognitive function and the level of hippocampal tumor necrosis factor-α in aged rats exposed to sevoflurane anesthesia. We found that 3% sevoflurane significantly impaired cognitive function and increased acetylcholinesterase activity by upregulating its expression in hippocampal tissue. Sevoflurane-induced impairment of cognitive function was significantly rescued by PNU-282987 but aggravated by methyllycaconitine. In addition to impairment of cognitive function, sevoflurane also significantly increased tumor necrosis factor-α level in plasma and hippocampal tissue. Similarly, this sevoflurane-induced change of tumor necrosis factor-α level in rats was antagonized by PNU-282987 but amplified by methyllycaconitine. In conclusion, our data show that the development of inflammation in sevoflurane-induced cognitive decline is associated with the downregulation of alpha 7 nicotinic acetylcholine receptor cholinergic anti-inflammatory pathway in aged rats.

MicroRNA-96 is responsible for sevoflurane-induced cognitive dysfunction in neonatal rats via inhibiting IGF1R

Sevoflurane is an experimental potent yet volatile anesthesia agent characterized by a low blood/gas partition coefficient. However, exposure to sevoflurane in neonatal mice has been speculated to result in learning deficits and abnormal social behavior. The aim of the present study was to investigate the relationship between sevoflurane and miR-96, in an attempt to identify the means by which it mediates IGF1R to influence the cognitive dysfunction (CD) in neonatal rats. Relationship between differentially expressed miRNAs and sevoflurane concentration was identified. The potential underlying regulatory mechanisms involved with sevoflurane were investigated through the administration of varying concentrations of the agent (1%, 2% and 4%), combined with miR-96 mimic or an inhibitor. A target prediction program was utilized, while the luciferase activity was determined in order to verify whether miR-96 targets IGF1R. The mRNA and protein levels of IGF1R, Bcl-2, Bax, and caspase-3 were measured followed by the determination of hippocampal neuron apoptosis. Learning and memory performance was assessed using the Morris water maze (MWM) test and step-down test. The obtained results highlighted a positive correlation between miR-96 and the concentration of sevoflurane, while miR-96 was confirmed to negatively target IGF1R. Our analyses indicated that 4% sevoflurane had a significantly stronger effect on reducing the levels of IGF1R and Bcl-2, while elevating the levels of miR-96, Bax and caspase-3 more so than that of 1% or 2% sevoflurane, which resulted in increased hippocampal neuron apoptosis but diminished the learning and memory performance of the rats. The addition of miR-96 mimic was demonstrated to exacerbate the influence of sevoflurane on hippocampal neurons as well as the cognitive function of the rats. The key findings of our study highlighted the role of miR-96 in the potential mechanism of sevoflurane anesthesia-induced CD in neonatal rats through the downregulation of IGF1R.

Sevoflurane induces liver injury by modulating the expression of insulin-like growth factor 1 via miR-214

This study aimed to detect the effect of sevoflurane anesthesia on liver injury through modulating IGF-1. The expression of IGF-1 and IGF-1R in liver tissues of sevoflurane-exposed rats was examined by qRT-PCR and Western blot. The expression levels of miR-214 in liver cells treated with different concentration of sevoflurane at different time points were detected by qRT-PCR. Enzyme-linked immunosorbent (ELISA) assay was used to analyze serum IGF-1 concentration in cell culture media. After pre-treatment with 100 nM miR-214 inhibitor followed by exposure to sevoflurane, the expression level of miR-214 and IGF-1 protein in liver cells was examined. Hematoxylin-Eosin (HE) staining and TUNEL assay was performed to analyze liver tissue necrosis and apoptosis. The expression levels of apoptosis-related proteins (caspase 3 and Bcl-xL) were examined using Western blot. The mRNA and protein expression level of IGF-1 and IGF-1R in rats was significantly down-regulated after 90 min exposure to sevoflurane. QRT-PCR results suggested that exposure to sevoflurane upregulated the expression level of miR-214 and decreased the concentration of IGF-1 in a dose and time dependent manner. Sevoflurane inhibited the expression of IGF-1 through up-regulating miR-214. IGF-1 inhibited the positive effect of sevoflurane on cell necrosis and apoptosis. Sevoflurane could induce liver injury by modulating IGF-1 expression via miR-214.

The effect of celastrol on learning and memory in diabetic rats after sevoflurane inhalation

INTRODUCTION

The aim was to devise an animal model showing some of the neuropathological changes seen in senile dementia, and to investigate the effect of celastrol on cognition neuropathology in this model.

MATERIAL AND METHODS

Forty male Sprague Dawley rats weighing 300-350 g were randomly divided into 5 groups (n = 8 each): control (Con); inhaled sevoflurane (Sev); diabetes mellitus (DM); diabetes mellitus + inhaled sevoflurane (DM/Sev); diabetes + inhaled sevoflurane + celastrol (Cel). Diabetes was induced by an intraperitoneal injection of streptozotocin (STZ). After 20 days, the Sev, DM/Sev and Cel group rats inhaled 3% sevoflurane for 2 h, while the control and DM groups inhaled air. Cel group rats were given intraperitoneal injections of celastrol (0.7 mg/kg) daily for 4 days, while the control group received intraperitoneal injections of an equal volume of dimethylsulfoxide. The Morris water maze test was performed to test cognition. Animals were killed after the last water maze test and Congo red staining was used to observe deposition of amyloid substance in the hippocampus. The expression of GFAP and IGF-1 in the hippocampus was observed by immunohistochemistry.

RESULTS

Diabetes decreased cognition, increased amyloid substance and GFAP expression, and decreased IGF-1 expression in the hippocampus (all p-values < 0.05). Sevoflurane administration intensified and celastrol decreased these changes (all p-values < 0.05).

CONCLUSIONS

Sev/DM rats showed cognitive and neurochemical changes similar to those seen in senile dementia. Celastrol decreased these changes and should be evaluated further as a possible clinical agent in dementia.

Downregulation of circulating insulin-like growth factor 1 contributes to memory impairment in aged mice after sevoflurane anesthesia

Insulin-like growth factor 1 (IGF-1) is a neuroprotective hormone and a decrease in levels of circulating IGF-1 contributes toward cognitive decline. The aim of this study was to investigate the effect of sevoflurane on the level of circulating IGF-1 and cognitive function in aged mice and the role of circulating IGF-1 in the cognitive dysfunction induced by sevoflurane. Aged mice were exposed to 1 or 2 minimal alveolar concentrations of sevoflurane for 4 or 8 h. Before and after the exposure, blood was collected from the tail vein and serum IGF-1 was measured by an enzyme-linked immunosorbent assay. After exposure, spatial learning and memory were tested in the Morris water maze. An intraperitoneal injection of IGF-1 was used to study the role of IGF-1 in the cognitive impairment induced by sevoflurane. Sevoflurane dose dependently decreased the serum IGF-1 concentration, and resulted in aged mice taking significantly longer and traveling significantly further to find the platform. Sevoflurane significantly decreased the times crossing the platform and %time spent in target quadrant relative to the control group. IGF-1 attenuated this effect, but could not completely reverse it. We conclude that downregulation of circulating IGF-1 contributes toward the cognitive impairment induced by sevoflurane.

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

AIMS

Critically ill old patients sometimes require repeated surgical interventions, and thus it is important to determine the influence of repeated exposure to anesthetics on learning and memory. Sevoflurane, a widely used inhalation anesthetic, has few neurological adverse effects and offers a rapid return to consciousness. But the long-term influence of sevoflurane exposure and the effect of repeated sevoflurane exposure on cognition have rarely been reported, and available studies are contradictory.

MATERIALS AND METHODS

In the present study, the Morris water maze test was employed to investigate the long-term influence of single (4h) or repeated (2h daily for 5 consecutive days) exposure to 1.5% or 2.5% sevoflurane on the learning ability and memory of old (16-18months old) male rats. Testing was performed from 1day to 4weeks after the last exposure. In the hippocampus, brain derived neurotrophic factor (BDNF), NF-κB mRNA, and apoptosis rate were also examined to determine whether cellular biochemical changes related to cognition and memory occurred after single or repeated exposure to sevoflurane.

KEY FINDINGS

Repeated exposure to 2.5% sevoflurane decreased hippocampal levels of BDNF protein, enhanced hippocampal levels of NF-κB mRNA, and increased the apoptosis rate of pyramidal cells. Single exposure to 2.5% sevoflurane, and repeated exposure to either 1.5% or 2.5% sevoflurane significantly compromised learning and memory of old male rats.

SIGNIFICANCE

Repeated exposure to sevoflurane impaired the learning and memory of old male rats, an impairment that was accompanied by cognition-related biochemical changes in the hippocampus.

Sevoflurane exposure in postnatal rats induced long-term cognitive impairment through upregulating caspase-3/cleaved-poly (ADP-ribose) polymerase pathway

The association of anesthetic exposure in infants or young children with the long-term impairment of neurologic functions has been reported previously; however, the underlying mechanisms remain largely unknown. In order to identify dysregulated gene expression underlying long-term cognitive impairment caused by sevoflurane exposure at the postnatal stage, the present study initially performed behavioral tests on adult Wistar rats, which received 3% sevoflurane at postnatal day 7 (P7) for different time course. Subsequently, transcriptome profiling of hippocampal tissues from experimental and control rats was performed. Significant impairment of the working memory was observed in adult rats with sevoflurane exposure for 4-6 h, when compared with the control rats. The results indicated that a total of 264 genes were aberrantly expressed (51 downregulated and 213 upregulated; fold change >2.0; P<0.05; false discovery rate <0.05) in the hippocampus of experimental adult rats compared with those from control rats. Particularly, the expression of caspase-3 gene (CASP3), encoding caspase-3 protein, presented the most significant upregulation, which was further validated by quantitative polymerase chain reaction and immunohistochemical analysis. Further analysis revealed that CASP3 expression level was negatively correlated with the rats' spatial working memory performance, as indicated by the Y-maze test. The level of cleaved-poly (ADP-ribose) polymerase (PARP), a substrate of caspase-3, was also increased in the hippocampus of experimental adult rats. Thus, the present study revealed that upregulation of caspase-3/cleaved-PARP may be involved in long-term cognitive impairment caused by sevoflurane exposure in infants, which may be useful for the clinical prevention of cognitive impairment.

Sevoflurane downregulates IGF‑1 via microRNA‑98

Insulin-like growth factor (IGF)-1 functions as a neuroprotective hormone and may protect against cognitive impairment, which may occur as a result of sevoflurane exposure. The aim of the present study was to assess the effect of sevoflurane on the production of IGF‑1 and investigate the molecular mechanisms underlying this regulation. The BRL rat hepatocyte cell line and adult mice were exposed to 1 or 2 minimal alveolar concentrations sevoflurane for 4 or 8 h. IGF‑1 and microRNA‑98 levels were quantified using an enzyme‑linked immunosorbent assay, western blotting and reverse transcription‑quantitative polymerase chain reaction analyses. The importance of microRNA‑98 in the regulation of IGF‑1 by sevoflurane was investigated using a microRNA‑98 inhibitor. Sevoflurane treatment reduced IGF‑1 levels and simultaneously upregulated microRNA‑98 expression levelsin rat hepatocytes and adult mice. Inhibition of microRNA‑98 attenuated this effect. Therefore, sevoflurane may reduce the synthesis of IGF‑1 by upregulating microRNA‑98 expression.

The role of general anesthetics and the mechanisms of hippocampal and extra-hippocampal dysfunctions in the genesis of postoperative cognitive dysfunction

Postoperative cognitive dysfunction (POCD) is a multifactorial process with a huge number of predisposing, causal, and precipitating factors. In this scenario, the neuroinflammation and the microglial activation play a pivotal role by triggering and amplifying a complex cascade involving the immuno-hormonal activation, the micro circle alterations, the hippocampal oxidative stress activation and, finally, an increased blood-brain barrier's permeability. While the role of anesthetics in the POCD's genesis in humans is debated, a huge number of preclinical studies have been conducted on the topic and many mechanisms have been proposed to explain the potential neurodegenerative effects of general anesthetics. Probably, the problem concerns on what we are searching for and how we are searching and, surprisingly, preclinical studies showed that anesthetics may also manifest neuroprotective properties. The aim of this paper is to offer an overview on the potential impact of general anesthetics on POCD. Mechanisms of hippocampal and extra-hippocampal dysfunction due to neuroinflammation are discussed, whereas further research perspectives are also given.

Neonatal Repeated Exposure to Isoflurane not Sevoflurane in Mice Reversibly Impaired Spatial Cognition at Juvenile-Age

Inhalation anesthetics facilitate surgical procedures in millions of children each year. However, animal studies demonstrate that exposure to the inhalation anesthetic isoflurane may cause neuronal cell death in developing brains. The long-term cytotoxic effects of sevoflurane, the most popular pediatric anesthetic, have not been compared with isoflurane. Thus, this study was designed to compare the effects of equipotent doses of these two anesthetics on neonatal long-term neurotoxicity. Postnatal 7-day-old (P7) C57/BL male mice were exposed to 1.5% isoflurane or 2.2% sevoflurane 2 h a day for 3 days. Non-anesthetized mice served as controls. The effects of anesthesia on learning and memory were assessed using the Morris Water Maze (MWM) at Postnatal days 30 (P30) and P60 respectively. The hippocampal content of N-methyl-D-aspartate receptor subunits (NMDA), brain-derived neurotrophic factor (BDNF), and synaptophysin (Syn) were determined by Western Blot. Neuron structure and apoptosis were assessed via Nissl and TUNEL staining, respectively. The isoflurane group exhibited cognitive impairment at P30. Repeated inhalation of isoflurane or sevoflurane caused different degrees of apoptosis and damaged hippocampal neurons in neonatal mice, particularly isoflurane. In neonatal mice, repeated exposure to isoflurane, but not sevoflurane, caused spatial cognitive impairments in juvenile mice. Our findings suggest that isoflurane induces significantly greater neurodegeneration than an equipotent minimum alveolar concentration of sevoflurane.

Decreased PSD95 expression in medial prefrontal cortex (mPFC) was associated with cognitive impairment induced by sevoflurane anesthesia

OBJECTIVE

Though sevoflurane has been widely used as an anesthetic in surgery, recent studies have shown that exposure to sevoflurane alone could lead to postoperative cognitive dysfunction (POCD), of which the mechanisms still remain largely unknown. The medial prefrontal cortex (mPFC) is known to be implicated in various cognitive impairments, including working memory and attentional processes. In the present study, we tried to identify dysregulated gene expression in mPFC and investigate the underlying mechanisms involved in POCD.

METHODS

Behavioral tests, including elevated plus-maze, O-maze, and Y-maze tests, were performed on Wistar rats exposed to sevoflurane. Whole-genome mRNA profiling of mPFC from Wistar rats after exposure to sevoflurane was carried out. Real-time polymerase chain reaction (PCR) was done to verify the differentially expressed genes.

RESULTS

Significant impairment of working memory of rats after exposure to sevoflurane was observed. A total of 119 of 7319 detected mRNAs showed significantly different expression between rats with and without sevoflurane exposure (fold change (FC)>2.0, P<0.05, and false discovery rate (FDR)<0.05), among which 74 mRNAs were down-regulated and 45 mRNAs were up-regulated. Postsynaptic density-95 (PSD95, also named DLG4) showed the most significantly decreased expression in mPFC and further investigation indicated that PSD95 expression level was correlated with spatial working memory performance.

CONCLUSIONS

Our study revealed that PSD95 might be involved in the mechanism of POCD, which could provide clues for preventing POCD in clinical operations.

Postoperative cognitive dysfunction and neuroinflammation; Cardiac surgery and abdominal surgery are not the same

Postoperative cognitive dysfunction (POCD) is a debilitating surgical complication, with cardiac surgery patients at particular risk. To gain insight in the mechanisms underlying the higher incidence of POCD after cardiac versus non-cardiac surgery, systemic and central inflammatory changes, alterations in intraneuronal pathways, and cognitive performance were studied after cardiac and abdominal surgery in rats. Male Wistar rats were subjected to ischemia reperfusion of the upper mesenteric artery (abdominal surgery) or the left coronary artery (cardiac surgery). Control rats remained naïve, received anesthesia only, or received thoracic sham surgery. Rats were subjected to affective and cognitive behavioral tests in postoperative week 2. Plasma concentrations of inflammatory factors, and markers for neuroinflammation (NGAL and microglial activity) and the BDNF pathway (BDNF, p38MAPK and DCX) were determined. Spatial memory was impaired after both abdominal and cardiac surgery, but only cardiac surgery impaired spatial learning and object recognition. While all surgical procedures elicited a pronounced acute systemic inflammatory response, NGAL and TNFα levels were particularly increased after abdominal surgery. Conversely, NGAL in plasma and the paraventricular nucleus of the hypothalamus and microglial activity in hippocampus and prefrontal cortex on postoperative day 14 were increased after cardiac, but not abdominal surgery. Both surgery types induced hippocampal alterations in BDNF signaling. These results suggest that POCD after cardiac surgery, compared to non-cardiac surgery, affects different cognitive domains and hence may be more extended rather than more severe. Moreover, while abdominal surgery effects seem limited to hippocampal brain regions, cardiac surgery seems associated with more wide spread alterations in the brain.

Sevoflurane anesthesia induces neither contextual fear memory impairment nor alterations in local population connectivity of medial prefrontal cortex local field potentials networks in aged rats

Sevoflurane has been found to increase apoptosis and pathologic markers associated with Alzheimer disease, provoking concern over their potential contribution to postoperative cognitive dysfunction. This study aimed to determine the effects of sevoflurane on contextual fear memory of aged rats and to characterize local population connectivity of local field potentials (LFPs) in medial prefrontal cortex (mPFC) of aged rats during contextual fear memory. Eighteen-month-old male SD rats were implanted with one multichannel electrode array in mPFC. The aged rats were divided into control group, sevoflurane group (1 MAC sevoflurane for 2 h) and surgical group with 1.0 MAC sevoflurane for 2 h. We then assessed the effect of the anesthesia on contextual fear memory, and alterations in the local population connectivity of mPFC LFP networks by partial directed coherence (PDC). Surgery impaired contextual fear memory and reduced local population connectivity of mPFC LFP networks in aged rats at day 1 after the surgery and anesthesia. 1 MAC Sevoflurane anesthesia induced neither contextual fear memory impairment nor alterations in local population connectivity of mPFC LFP networks in aged rats when tested 1, 7, 15 and 30 days after exposure (P > 0.05). PDC values of theta band mPFC LFPs became strongly increased during contextual fear memory at 1, 7, 15, and 30 days after anesthesia. Our results suggest that 1 MAC sevoflurane anesthesia does not induce contextual fear memory impairment in aged rats and suggest that the increased local population connectivity in theta bands LFPs of mPFC plays a role in contextual fear memory.

Insulin-like growth factor-1 and insulin-like growth factor binding protein 3 and risk of postoperative cognitive dysfunction

Insulin-like growth factor (IGF)-1 is implicated in learning and memory. Experimental studies have suggested that the IGF-1 system is beneficial in cognition, especially in Alzheimer’s disease (AD), by opposing Aβ amyloid processing and hyperphosphorylated tau toxicity. Low IGF-I and insulin-like growth factor binding protein (IGFBP)-3 serum levels are significantly associated with AD. To assess the relationship between circulating IGF-I and IGFBP3 levels and change of postoperative cognition. The study was performed in patients scheduled for elective head and neck carcinoma surgery under general anesthesia. On the day before the operation and postoperative days 1, 3 and 7, mini-mental state examination (MMSE) was performed by the same doctor, and blood samples were collected at 08:00 h after overnight fasting. The circulating levels of IGF-1 and IGFBP3 were measured by enzyme-linked immunosorbent assay. One hundred and two patients completed all four MMSE tests and forty-four of them completed all the four blood samples collection. Postoperative circulating IGF-1 level, ratio of IGF-1/IGFBP3 and MMSE score significantly decreased, whereas IGFBP3 level significantly increased compared with preoperative values in total patients. The change trends of circulating IGF-1 level and MMSE score were similar. Preoperative circulating IGF-1 level, ratio and MMSE score were significantly lower in POCD group compared to non-POCD group. There was no significant difference in preoperative level of circulating IGFBP3 between the two groups. Preoperative circulating IGF-1 level was negatively correlated with age and positively with MMSE. Logistic regression analysis revealed that lower preoperative IGF-1 level and elderly patients increased the odds of POCD. Down-regulation of circulating IGF-1 level may be involved in the mechanism of postoperative cognitive dysfunction. Older patients had lower circulating IGF-1 levels and were more susceptible to POCD.

The change of circulating insulin like growth factor binding protein 7 levels may correlate with postoperative cognitive dysfunction

Insulin-like growth factor binding protein (IGFBP) 7 may be a critical regulator of memory consolidation. This study was performed to assess the relationship between circulating IGFBP7 levels and postoperative cognition dysfunction (POCD) in patients scheduled for elective head and neck carcinoma surgery under general anesthesia. Among one hundred and two patients included in this study, forty-four patients completed collection of all four blood samples and thirty-five patients were diagnosed with POCD. The results of Mini-Mental State Examination (MMSE) test and enzyme-linked immunosorbent assay showed that postoperative MMSE score and circulating insulin-like growth factor (IGF)-1 level were lower and circulating IGFBP7 level was higher than preoperative level. Circulating IGF-1 level was significantly lower and D-value of preoperative and postoperative day 1 circulating IGFBP7 levels (ΔIGFBP7(1)) was significantly higher in the POCD group. Age preoperative MMSE, IGF-1 level and ΔIGFBP7(1) significantly correlated with POCD, but preoperative IGFBP7 level not. Logistic regression analysis revealed that older patients, lower preoperative MMSE score, IGF-1 level and higher IGFBP7 level significantly increased the risk of POCD, but ΔIGFBP7(1) not. Hence, circulating IGF-1 and IGFBP7 levels and their changes during operation under general anesthesia may correlate with POCD, but further investigation in larger samples is needed.

Isoflurane reversibly destabilizes hippocampal dendritic spines by an actin-dependent mechanism

General anesthetics produce a reversible coma-like state through modulation of excitatory and inhibitory synaptic transmission. Recent evidence suggests that anesthetic exposure can also lead to sustained cognitive dysfunction. However, the subcellular effects of anesthetics on the structure of established synapses are not known. We investigated effects of the widely used volatile anesthetic isoflurane on the structural stability of hippocampal dendritic spines, a postsynaptic structure critical to excitatory synaptic transmission in learning and memory. Exposure to clinical concentrations of isoflurane induced rapid and non-uniform shrinkage and loss of dendritic spines in mature cultured rat hippocampal neurons. Spine shrinkage was associated with a reduction in spine F-actin concentration. Spine loss was prevented by either jasplakinolide or cytochalasin D, drugs that prevent F-actin disassembly. Isoflurane-induced spine shrinkage and loss were reversible upon isoflurane elimination. Thus, isoflurane destabilizes spine F-actin, resulting in changes to dendritic spine morphology and number. These findings support an actin-based mechanism for isoflurane-induced alterations of synaptic structure in the hippocampus. These reversible alterations in dendritic spine structure have important implications for acute anesthetic effects on excitatory synaptic transmission and synaptic stability in the hippocampus, a locus for anesthetic-induced amnesia, and have important implications for anesthetic effects on synaptic plasticity.

Sevoflurane causes neuronal apoptosis and adaptability changes of neonatal rats

BACKGROUND

Neonatal exposure to sevoflurane can induce neurodegeneration and learning deficits in developing brain. We hypothesised that with the increase in the concentration and duration of sevoflurane, neurodegeneration of neonatal rats aggravates and causes behaviour changes as the rats grow.

METHODS

Twenty-one post-natal day (P)7 Wistar rats were randomly divided into seven groups. Blood analysis was performed after anaesthesia. According to the results, 120 P7 Wistar rats were randomly divided into five groups: Con sham anaesthesia; Sevo 1%-2 h: exposed to 1% sevoflurane for 2 h; Sevo 1%-4 h, Sevo 2%-2 h and Sevo 2%-4 h. Caspase-3 positive cells in brain were detected by immunohistochemistry at 6 h after the end of anaesthesia. The cleaved poly(ADP-ribose) polymerase (c-PARP-1) in cortex and hippocampus was detected by Western blot analysis. Behavioural tests such as Morris water maze and Open-field Test were performed when the rats were 5-week old, 8-week old, and 14-week old.

RESULTS

Three per cent sevoflurane induced carbon dioxide accumulation. The level of c-PARP-1 in hippocampus area was significantly increased in Group 2%-4h. The number of caspase-3 positive cells in Group Sevo 1%-2h, Group Sevo 2%-2h and Group Sevo 2%-4h was greater than that in Group Con. Rats exposed to sevoflurane had longer travel distance and time in open field when they were 5 weeks old. Animals from different groups had similar performance in Morris water maze.

CONCLUSION

Exposure to 2% sevoflurane causes neuronal apoptosis of neonatal rats, and long-time exposure aggravates that. The adaptability in new environment is transiently decreased when the anaesthesia rats are 5 weeks old.

Early life exposure to sevoflurane impairs adulthood spatial memory in the rat

Sevoflurane is a general anesthetic commonly used in the pediatric setting because it is sweet-smelling, nonflammable, fast acting and has a very short recovery time. Although recent clinical data suggest that early anesthesia exposure is associated with subsequent learning and memory problems, it is difficult to determine the exact scope of developmental neurotoxicity associated with exposure to specific anesthetics such as sevoflurane. This is largely due to inconsistencies in the literature. Thus, in the present studies we evaluated the effect of early life exposure to sevoflurane (1%, 2%, 3% or 4%) on adulthood memory impairment in Sprague-Dawley rats. Animals were exposed to different regimens of sevoflurane anesthesia on postnatal days (PNDs) 3, 7, or 14 or at 7 weeks (P7W) of age and spatial memory performance was assessed in adulthood using the Morris Water Maze (MWM). Rats exposed to sevoflurane exhibited significant memory impairment which was concentration and exposure duration dependent. Disruption of MWM performance was more severe in animals exposed on both PNDs 3 and 7 than in animals exposed on both PNDs 3 and 14. The younger the animal's age at the time of exposure, the more significant the effect on later MWM performance. Compared to the neonates, animals exposed at P7W were relatively insensitive to sevoflurane: memory was impaired in this group only after repeated exposures to low doses or single exposures to high doses. Early life exposure to sevoflurane can result in spatial memory impairments in adulthood and the shorter the interval between exposures, the greater the deficit.

Parecoxib mitigates spatial memory impairment induced by sevoflurane anesthesia in aged rats

BACKGROUND

Inflammation in brain plays a critical role in the pathogenesis of cognitive impairment. Anti-inflammatory therapy may thus constitute a novel approach for associated cognitive dysfunction. The present study investigated the effects of parecoxib in the prevention of cognitive impairments induced by sevoflurane in aged rats.

METHODS

Sixty-six aged rats were divided randomly into three groups: control group (n = 22, sham anesthesia), sevoflurane group (n = 22, received 2% sevoflurane for 5 h) and parecoxib group (n = 22, received intraperitoneal injections of 10 mg/kg parecoxib and then exposed to 2% sevoflurane for 5 h). Spatial learning performance was tested by Morris water maze. The expression of cyclooxygenase-2 protein and ultrastructure of synapse in hippocampus were measured.

RESULTS

Sevoflurane anesthesia impaired the spatial learning and memory in aged rats. Compared with sevoflurane group, parecoxib group showed shorter escape latency and more number of crossings over the previous platform area. Furthermore, parecoxib treatment also significantly prevented the synaptic changes induced by sevoflurane.

CONCLUSION

Parecoxib mitigates spatial memory impairment induced by sevoflurane anesthesia in aged rats. The synaptic morphometry change may be one of the mechanisms involved in learning and memory deficit.