Isoflurane anesthesia promotes cognitive impairment by inducing expression of β-amyloid protein-related factors in the hippocampus of aged rats

A high fat diet potentiates neonatal iron overload-induced memory impairments in rats

PURPOSE

The present study aimed at evaluating possible synergistic effects between two risk factors for cognitive decline and neurodegenerative disorders, i.e. iron overload and exposure to a hypercaloric/hyperlipidic diet, on cognition, insulin resistance, and hippocampal GLUT1, GLUT3, Insr mRNA expression, and AKT phosporylation.

METHODS

Male Wistar rats were treated with iron (30 mg/kg carbonyl iron) or vehicle (5% sorbitol in water) from 12 to 14th post-natal days. Iron-treated rats received a standard laboratory diet or a high fat diet from weaning to adulthood (9 months of age). Recognition and emotional memory, peripheral blood glucose and insulin levels were evaluated. Glucose transporters (GLUT 1 and GLUT3) and insulin signaling were analyzed in the hippocampus of rats.

RESULTS

Both iron overload and exposure to a high fat diet induced memory deficits. Remarkably, the association of iron with the high fat diet induced more severe cognitive deficits. Iron overload in the neonatal period induced higher insulin levels associated with significantly higher HOMA-IR, an index of insulin resistance. Long-term exposure to a high fat diet resulted in higher fasting glucose levels. Iron treatment induced changes in Insr and GLUT1 expression in the hippocampus. At the level of intracellular signaling, both iron treatment and the high fat diet decreased AKT phosphorylation.

CONCLUSION

The combination of iron overload with exposure to a high fat diet only led to synergistic deleterious effect on emotional memory, while the effects induced by iron and by the high fat diet on AKT phosphorylation were comparable. These findings indicate that there is, at least to some extent, an additive effect of iron combined with the diet. Further studies investigating the mechanisms associated to deleterious effects on cognition and susceptibility for the development of age-associated neurodegenerative disorders are warranted.

Effects of Exercise Training and L-Arginine Loaded Chitosan Nanoparticles on Hippocampus Histopathology, β-Secretase Enzyme Function, APP, Tau, Iba1and APOE-4 mRNA in Aging Rats

The objective of this study was to evaluate the combined and independent effects of exercise training and L-Arginine loaded chitosan nanoparticles (LA CNPs) supplementation on hippocampal Tau, App, Iba1, and ApoE gene expression, oxidative stress, β-secretase enzyme activity, and hippocampus histopathology in aging rats. Thirty-five male Wistar rats were randomly assigned to five groups (n = 7 in each): Young (8 weeks old), Old (20 months old), old + L-arginine supplementation (Old Sup), old + exercise (Old Exe) and old + L-arginine supplementation + exercise (Old Sup + Exe). LA CNPs were administered to the supplement groups through gavage at a dosage of 500 mg/kg/day for 6-weeks. Exercise groups were subjected to a swimming exercise program five days/week for the same duration. Upon the completion of their interventions, the animals underwent behavioral and open-field task tests and were subsequently sacrificed for hippocampus genetic and histopathological evaluation. For histopathological analysis of brain, Cresyl violet staining was used. Congo Red staining was employed to confirm amyloid plaques in the hippocampus. Expressions of Tau, App, Iba1, and ApoE genes were determined by real-time PCR. In contrast to the Old group, Old Exe and Old Sup + Exe groups spent more time in the central space in the open field task (p < 0.05) and have more live cells in the hippocampus. Old rats (Old, Old Sup and Old Exe groups) exhibited a significant Aβ peptide accumulation and increases in APP, Tau, Iba1, APOE-4 mRNA and MDA, along with decreases in SOD compared to the young group (p < 0.05). However, LA CNPs supplementation, exercise, and their combination (Old Sup, Old Exe and Old Sup + Exe) significantly reduced MDA, Aβ plaque as well as APP, Tau, Iba1, and APOE-4 mRNA compared to the Old group (p < 0.05). Consequently, the administration of LA CNPs supplements and exercise might regulate the risk factors of hippocampus cell and tissue.

Nicotinamide mononucleotide pretreatment improves long-term isoflurane anesthesia-induced cognitive impairment in mice

Postoperative cognitive dysfunction (POCD) is characterized by impaired cognitive function following general anesthesia and surgery. Oxidative stress is a significant pathophysiological manifestation underlying POCD. Previous studies have reported that the decline of nicotinamide adenine dinucleotide (NAD+) -dependent sirtuin 1 (SIRT1) contributes to the activation of oxidative stress. In this study, we investigated whether pretreatment of nicotinamide mononucleotide (NMN), an NAD+ intermediate, improves oxidative stress and cognitive function in POCD. The animal model of POCD was established in C57BL/6 J mice through 6 h isoflurane anesthesia-induced cognitive impairment. Mice were intraperitoneally injected with NMN for 7 days prior to anesthesia, after which oxidative stress and cognitive function were assessed. The level of oxidative stress was determined using flow cytometry analysis and assey kits. The fear condition test and the Y-maze test were utilized to evaluate contextual and spatial memory. Our results showed that cognitive impairment and increased oxidative stress were observed in POCD mice, as well as downregulation of NAD+ levels and related protein expressions of SIRT1 and nicotinamide phosphoribosyltransferase (NAMPT) in the hippocampus. And NMN supplementation could effectively prevent the decline of NAD+ and related proteins, and reduce oxidative stress and cognitive disorders after POCD. Mechanistically, the findings suggested that protection on cognitive function mediated by NMN pretreatment in POCD mice may be regulated by NAD+-SIRT1 signaling pathway. This study indicated that NMN preconditioning reduced oxidative stress damage and alleviated cognitive impairment in POCD mice.

Beta-Site Amyloid Precursor Protein-Cleaving Enzyme Inhibition Partly Restores Sevoflurane-Induced Deficits on Synaptic Plasticity and Spine Loss

Evidence indicates that inhalative anesthetics enhance the β-site amyloid precursor protein (APP)-cleaving enzyme (BACE) activity, increase amyloid beta 1-42 (Aβ_1–42) aggregation, and modulate dendritic spine dynamics. However, the mechanisms of inhalative anesthetics on hippocampal dendritic spine plasticity and BACE-dependent APP processing remain unclear. In this study, hippocampal slices were incubated with equipotent isoflurane (iso), sevoflurane (sevo), or xenon (Xe) with/without pretreatment of the BACE inhibitor LY2886721 (LY). Thereafter, CA1 dendritic spine density, APP processing-related molecule expressions, nectin-3 levels, and long-term potentiation (LTP) were tested. The nectin-3 downregulation on LTP and dendritic spines were evaluated. Sevo treatment increased hippocampal mouse Aβ_1–42 (mAβ_1–42), abolished CA1-LTP, and decreased spine density and nectin-3 expressions in the CA1 region. Furthermore, CA1-nectin-3 knockdown blocked LTP and reduced spine density. Iso treatment decreased spine density and attenuated LTP. Although Xe blocked LTP, it did not affect spine density, mAβ_1–42, or nectin-3. Finally, antagonizing BACE activity partly restored sevo-induced deficits. Taken together, our study suggests that sevo partly elevates BACE activity and interferes with synaptic remodeling, whereas iso mildly modulates synaptic changes in the CA1 region of the hippocampus. On the other hand, Xe does not alternate dendritic spine remodeling.

Effects of Minocycline on Cognitive Impairment, Hippocampal Inflammatory Response, and Hippocampal Alzheimer’s Related Proteins in Aged Rats after Propofol Anesthesia

The aim of this study was to evaluate the effect of minocycline preadministration on cognitive dysfunction, hippocampal inflammatory response, and hippocampal senile dementia-related proteins induced by propofol anesthesia in aged rats. Sixty male SD rats, aged 20 months and weighing 340-410 g, were randomly divided into three groups: normal saline (NC) group, propofol group (prop), and minocycline (M) group. Prop group rats were injected intraperitoneally with 100 mg/kg propofol. The rats in group M were injected intraperitoneally with 50 mg/kg minocycline 30 minutes before injection of 100 mg/kg propofol, and the rest were the same as prop group. The rats in NC group were received intraperitoneal injection of the same amount of normal saline. The results indicated that compared with group C, the expressions of GSK-3β, acetyl-NF-κB (Lys310), Tau, and Amlyoid-beta were upregulated, the levels of TNF-α, IL-1β, and IL-6 were increased, the escape incubation period was prolonged, and the exploration time was shortened in prop group, while the expression of GSK-3β, acetyl-NF-κB (Lys310), Tau, and Amlyoid-beta in minocycline group was downregulated, the levels of TNF-α, IL-1β, and IL-6 were decreased, the escape incubation period was shortened, and the exploration time was shortened. In conclusion, preadministration of minocycline can improve cognitive impairment induced by propofol anesthesia in aged rats, and its mechanism of action may be related to minocycline inhibiting hippocampal inflammatory reaction and downregulating the expression of GSK-3β, acetyl-NF-κB (Lys310), Tau, and Amlyoid-beta proteins in hippocampus.

Inhalational Anesthetics Do Not Deteriorate Amyloid-β-Derived Pathophysiology in Alzheimer's Disease: Investigations on the Molecular, Neuronal, and Behavioral Level

BACKGROUND

Studies suggest that general anesthetics like isoflurane and sevoflurane may aggravate Alzheimer's disease (AD) neuropathogenesis, e.g., increased amyloid-β (Aβ) protein aggregation resulting in synaptotoxicity and cognitive dysfunction. Other studies showed neuroprotective effects, e.g., with xenon.

OBJECTIVE

In the present study, we want to detail the interactions of inhalational anesthetics with Aβ-derived pathology. We hypothesize xenon-mediated beneficial mechanisms regarding Aβ oligomerization and Aβ-mediated neurotoxicity on processes related to cognition.

METHODS

Oligomerization of Aβ 1-42 in the presence of anesthetics has been analyzed by means of TR-FRET and silver staining. For monitoring changes in neuronal plasticity due to anesthetics and Aβ 1-42, Aβ 1-40, pyroglutamate-modified amyloid-(AβpE3), and nitrated Aβ (3NTyrAβ), we quantified long-term potentiation (LTP) and spine density. We analyzed network activity in the hippocampus via voltage-sensitive dye imaging (VSDI) and cognitive performance and Aβ plaque burden in transgenic AD mice (ArcAβ) after anesthesia.

RESULTS

Whereas isoflurane and sevoflurane did not affect Aβ 1-42 aggregation, xenon alleviated the propensity for aggregation and partially reversed AβpE3 induced synaptotoxic effects on LTP. Xenon and sevoflurane reversed Aβ 1-42-induced spine density attenuation. In the presence of Aβ 1-40 and AβpE3, anesthetic-induced depression of VSDI-monitored signaling recovered after xenon, but not isoflurane and sevoflurane removal. In slices pretreated with Aβ 1-42 or 3NTyrAβ, activity did not recover after washout. Cognitive performance and plaque burden were unaffected after anesthetizing WT and ArcAβ mice.

CONCLUSION

None of the anesthetics aggravated Aβ-derived AD pathology in vivo. However, Aβ and anesthetics affected neuronal activity in vitro, whereby xenon showed beneficial effects on Aβ 1-42 aggregation, LTP, and spine density.

Long-term molecular differences between resilient and susceptible mice after a single traumatic exposure

BACKGROUND AND PURPOSE

PTSD is a heterogeneous disorder induced by trauma, resulting in severe long-term impairments of an individual's mental health. Interestingly, PTSD does not develop in every individual; thus, some individuals are more resilient than others. However, the underlying molecular mechanisms are poorly understood. Here, we aimed at shedding light on these processes.

EXPERIMENTAL APPROACH

We used a single-trauma PTSD model in mice to induce long-term maladaptive behaviours and profiled the mice four weeks post-trauma into resilient or susceptible individuals. The phenotype's classification was based on their individual responses in different behavioural experiments. We analysed microbiome, circulating endocannabinoids, and long-term changes in brain phospholipid and transcript levels.

KEY RESULTS

We found a plethora of molecular differences between resilient and susceptible individuals across multiple molecular domains, including lipidome, transcriptome, and gut microbiome. Some of these differences were stable even several weeks after the trauma, indicating the long-term impact of traumatic stimuli on the organism's physiology. Furthermore, the integration of these multi-layered molecular data revealed that resilient and susceptible individuals have very distinct molecular signatures across various physiological systems.

CONCLUSIONS AND IMPLICATIONS

We showed that trauma induces individual-specific behavioural responses that, in combination with a longitudinal characterization of mice, can be used to identify distinct sub-phenotypes within the trauma-exposed group. These groups differ significantly not only in their behaviour but also in specific molecular aspects across a variety of tissues and brain regions. This approach may reveal new targets and predictive biomarkers for the pharmacological treatment and prognosis of stress-related disorders.

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.

Apoptosis inhibition is involved in improvement of sevoflurane-induced cognitive impairment following normobaric hyperoxia preconditioning in aged rats

Sevoflurane, a commonly used anesthetic agent has been confirmed to induce cognitive impairment in aged rats. Normobaric hyperoxia preconditioning has been demonstrated to induce neuroprotection in rats. The present study aimed to determine whether normobaric hyperoxia preconditioning could ameliorate cognitive deficit induced by sevoflurane and the possible mechanism by which it may exert its effect. A total of 66, 20-month-old male Sprague-Dawley rats were randomly divided into 3 groups (n=22 each): Rats in the control (C) and sevoflurane anesthesia (S) groups received no normobaric hyperoxia preconditioning before sevoflurane exposure, rats in the normobaric hyperoxia pretreatment (HO) group received normobaric hyperoxia preconditioning before sevoflurane exposure (95% oxygen for 4 continuous h daily for 6 consecutive days). The anesthesia rats (S and HO groups), were exposed to 2.5% sevoflurane for 5 h, while the sham anesthesia rats (C group) were exposed to no sevoflurane. The neurobehavioral assessment was performed using a Morris water maze test, the expressions of the apoptosis proteins were determined using western blot analysis, and the apoptosis rate and cytosolic calcium concentration were measured by flow cytometry. Normobaric hyperoxia preconditioning improved prolonged escape latency and raised the number of platform crossings induced by sevoflurane in the Morris water maze test, increased the level of bcl-2 protein, and decreased the level of bax and active caspase-3 protein, the apoptosis rate and cytosolic calcium concentration in the hippocampus 24 h after sevoflurane exposure. The findings of the present study may imply that normobaric hyperoxia preconditioning attenuates sevoflurane-induced spatial learning and memory impairment, and this effect may be partly related to apoptosis inhibition in the hippocampus. In conclusion, normobaric hyperoxia preconditioning may be a promising strategy against sevoflurane-induced cognitive impairment by inhibiting the hippocampal neuron apoptosis.

Neurotoxicity of different amyloid beta subspecies in mice and their interaction with isoflurane anaesthesia

Background

The aim of this study was to assess different amyloid beta subspecies’ effects on behaviour and cognition in mice and their interaction with isoflurane anaesthesia.

Methods

After governmental approval, cannulas were implanted in the lateral cerebral ventricle. After 14 days the mice were randomly intracerebroventricularly injected with Aβ 1–40 (Aβ40), Aβ 1–42 (Aβ42), 3NTyr10-Aβ (Aβ nitro), AβpE3-42 (Aβ pyro), or phosphate buffered saline. Four days after the injection, 30 mice (6 animals per subgroup) underwent general anaesthesia with isoflurane. A “sham” anaesthetic procedure was performed in another 30 mice (6 animals per subgroup, 10 subgroups in total). During the next eight consecutive days a blinded assessor evaluated behavioural and cognitive performance using the modified hole-board test. Following the testing we investigated 2 brains per subgroup for insoluble amyloid deposits using methoxy staining. We used western blotting in 4 brains per subgroup for analysis of tumour-necrosis factor alpha, caspase 3, glutamate receptors NR2B, and mGlu5. Data were analysed using general linear modelling and analysis of variance.

Results

Aβ pyro improved overall cognitive performance (p = 0.038). This cognitive improvement was reversed by isoflurane anaesthesia (p = 0.007), presumably mediated by decreased exploratory behaviour (p = 0.022 and p = 0.037). Injection of Aβ42 was associated with increased anxiety (p = 0.079). Explorative analysis on a limited number of brains did not reveal insoluble amyloid deposits or differences in the expression of tumour-necrosis factor alpha, NR2B, mGlu5, or caspase 3.

Conclusions

Testing cognitive performance after intracerebroventricular injection of different amyloid beta subspecies revealed that Aβ pyro might be less harmful, which was reversed by isoflurane anaesthesia. There is minor evidence for Aβ42-mediated neurotoxicity. Preliminary molecular analysis of biomarkers did not clarify pathophysiological mechanisms.

Scrophularia buergeriana Extract Improves Memory Impairment via Inhibition of the Apoptosis Pathway in the Mouse Hippocampus

Scrophularia buergeriana (SB) Miq. (Scrophulariaceae) has been used to help cure swelling and fever and has reported antioxidant and neuro-protective effects. However, few mechanism–based studies have evaluated the memory-improving effects in a beta-amyloid induced memory loss model. As a result of Scrophularia buergeriana extract (SBE) administration (30 and 100 mg/kg) for 28 days significantly recovered beta-amyloid-induced amnesia in the passive avoidance test and improved the impairment of spatial memory in the Morris Water Maze (MWM) task. Furthermore, SBE up-regulated superoxide dismutase-1 (SOD)-1, SOD-2, glutathione peroxidase-1, and B-cell lymphoma (Bcl)-2 protein expression levels. Additionally, SBE downregulated Bcl-2-associated X protein, cleaved caspase-9, cleaved poly (adenosine diphosphate-ribose) polymerase, and Aβ protein expression levels and inhibited the phosphorylation of the tau protein of Aβ-treated mice hippocampus. These results demonstrate that SBE improved memory impairment by reducing beta-amyloid induced neurotoxicity and regulated oxidative stress, anti-apoptotic pathways.

Epigenetic modulation of the MAPK pathway prevents isoflurane-induced neuronal apoptosis and cognitive decline in aged rats

Isoflurane is a broadly used inhalation anesthetic that causes cognitive impairment in rodent models as well as humans. Although previous studies suggested an association between isoflurane exposure and neuro-inflammation, apoptosis and mitochondrial dysfunction, the pathogenesis of isoflurane-induced cognitive decline remains elusive. In the present study, 22-month-old male Sprague-Dawley male rats (n=96) were divided into three groups: Control (Cont), isoflurane (ISO) and MS-275 pre-treated groups. The rats were sacrificed following exposure to isoflurane and a cognitive test. The hippocampus of each animal was harvested for quantitative PCR, TUNEL staining and western blot analysis. Histone deacetylases (HDAC)-1, -2 and -3 exhibited a significant increase at the gene and protein expression levels, whereas negligible mRNA expressions were observed for genes HDAC 4-11 (P>0.05; compared with Cont). Pre-treatment with the HDAC inhibitor MS-275 significantly inhibited the increase in TUNEL-positive cells induced by isoflurane exposure (70.72% decrease; P<0.001; compared with ISO). Furthermore, MS-275 significantly decreased caspase-3 and Bax expression levels while increasing Bcl-2 protein expression. The isoflurane-induced changes in the MAPK pathway signaling proteins ERK1/2, JNK and p38 were also reversed with MS-275 pre-treatment. Finally, in a Morris water maze test, the time to find a hidden platform was reduced in MS-275 pre-treated rats, compared with the ISO group. Therefore, the present study provided insight into the effect of isoflurane exposure on neuronal apoptosis pathways, as well as cognitive decline via epigenetic programming of MAPK signaling in aged rats.

L-Theanine Attenuates Isoflurane-Induced Injury in Neural Stem Cells and Cognitive Impairment in Neonatal Mice

The neurodevelopmental toxicity of isoflurane has been proved by many studies, which makes it essential to explore the underline mechanisms and search for protective agents to attenuate its neurotoxcity. Accumulating evidence showed that L-theanine had neuroprotective effects on injured neurons and the developing brain. The present study was designed to investigate whether L-theanine could attenuate isoflurane-induced damage in neural stem cells and cognitive impairment in young mice, and to discuss the role of protein kinase B (Akt)-glycogen synthase kinase 3β (GSK-3β) signaling pathway in this process. Multipotential neural stem cells (NSCs) and C57BL/6J mice were treated with either gas mixture, isoflurane, or L-theanine 30 min prior to isoflurane exposure, respectively. NSC viability was detected by CCK-8 assay. NSC proliferation and apoptosis were assessed by immunofluorescence and terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick-end labeling (TUNEL) assay, respectively. The levels of cleaved caspase-3 and phosphorylated (p)-Akt and p-GSK-3β in NSCs were tested by Western blotting. Cognitive function of mice was tested by Morris Water Maze at postnatal day (P) 30-35. The results indicated that isoflurane exposure inhibited NSC viability and proliferation, promoted NSC apoptosis as well as increased caspase-3 activation and down-regulated the expressions of p-Akt and p-GSK-3β in NSCs, and that isoflurane exposure on neonatal mice would induce late cognitive impairment. Pretreatment with L-theanine could attenuate isoflurane-caused damage in NSCs and cognitive deficits in young mice. Addinonally, the protective effects of L-theanine on isoflurane-injured NSCs could be reversed by Akt inhibitor Triciribine. Our data showed that pretreatment with L-theanine eliminated the NSC damage and cognitive impairment induced by isoflurane exposure, and that the neuroprotective effect of L-theanine was associated with the Akt-GSK-3β signaling pathway.

Exposure to surgery with general anaesthesia during adult life is not associated with increased brain amyloid deposition in older adults

BACKGROUND

Exposure to surgery with general anaesthesia (surgery/GA) is associated with cortical atrophy, but the aetiology remains unknown. Amyloid-β (Aβ) deposition is one of the hallmark pathological characteristics of Alzheimer's disease (AD). We examined brain Aβ burden in study participants exposed to surgery/GA.

METHODS

We performed a cross-sectional analysis of residents of Olmsted County, MN, USA, in the Mayo Clinic Study of Aging who were aged 70-97 yr and underwent measurement of (i) brain Aβ with Pittsburgh compound B positron emission tomography (PiB PET), (ii) brain glucose metabolism with 18-fluorodeoxyglucose (FDG) PET, and (iii) temporal cortical thickness with MRI. Separate analyses were performed with exposure to surgery/GA, defined as occurring after age 40 yr, and with exposure to surgery/GA, defined as occurring within 20 yr before neuroimaging. Imaging measurements were compared between participants who were exposed to surgery/GA vs not exposed.

RESULTS

Of the 2563 participants, 585 had PET scans. Regardless of the definition used to quantify exposure, no significant associations were detected between exposure and either global PiB PET or FDG PET. In contrast, exposure to surgery/GA was associated with an increased likelihood of abnormal cortical thinning: odds ratio (OR)=1.98 (95% confidence interval [CI]: 1.19-3.31); P=0.010 in those exposed after age 40 yr, and OR=1.64 (95% CI: 1.05-2.55); P=0.029 in those exposed in the prior 20 yr.

CONCLUSIONS

Exposure to surgery/GA is not associated with increases in cortical amyloid deposition. This finding suggests that the modest cortical thinning associated with surgery/GA is not related to AD pathology, but rather is caused by other processes.

Sophoricoside attenuates neuronal injury and altered cognitive function by regulating the LTR-4/NF-κB/PI3K signalling pathway in anaesthetic-exposed neonatal rats

Introduction

This study examined the protective effects of sophoricoside on neuronal injury and cognitive dysfunction in anaesthetic-exposed neonatal rats.

Material and methods

Neuronal injury was induced in rat pups by exposure to isoflurane (0.75%) with 30% oxygen for 6 h on P7. The protective effects of sophoricoside were evaluated by assessing cognitive function using the neurological score and Morris water maze. Neuronal apoptosis was assessed in hippocampus tissue using a TUNEL assay. The cytokine and macrophage inflammatory protein levels were assessed by ELISA. Western blot assays and RT-PCR were performed to assess the expression of NF-κB, TLR-4, Akt, and PI3K proteins in neuronal tissues. Immunohistochemical and histopathological changes were observed in the brain tissues of isoflurane-induced neuronal injury rats.

Results

The sophoricoside treatment improved cognitive and neuronal function in rats exposed to isoflurane. Cytokine and MIP levels in the brain tissues of isoflurane-exposed rats decreased. However, sophoricoside treatment attenuated the expression of TLR-4, PI3K, and Akt protein in the brain tissues of isoflurane-exposed rats. The histopathology improved in the sophoricoside-treated isoflurane-exposed rats.

Conclusions

Sophoricoside treatment protects against neuronal injury and reduced cognitive function in isoflurane-induced neuronal injury rats by regulating TLR-4 signalling.

Application of Acupuncture to Attenuate Immune Responses and Oxidative Stress in Postoperative Cognitive Dysfunction: What Do We Know So Far?

Postoperative cognitive dysfunction (POCD) is a common sequela following surgery and hospitalization. The prevention and management of POCD are important during clinical practice. POCD more commonly affects elderly patients who have undergone major surgery and can result in major decline in quality of life for both patients and their families. Acupuncture has been suggested as an effective intervention for many neurological disorders. In recent years, there are increasing interest in the use of acupuncture to prevent and treat POCD. In this review, we summarized the clinical and preclinical evidence of acupuncture on POCD using a narrative approach and discussed the potential mechanisms involved. The experimental details and findings of studies were summarized in tables and analyzed. Most of the clinical studies suggested that acupuncture before surgery could reduce the incidence of POCD and reduce the levels of systematic inflammatory markers. However, their reliability is limited by methodological flaws. Animal studies showed that acupuncture reduced cognitive impairment and the associated pathology after various types of surgery. It is possible that acupuncture modulates inflammation, oxidative stress, synaptic changes, and other cellular events to mitigate POCD. In conclusion, acupuncture is a potential intervention for POCD. More clinical studies with good research design are required to confirm its effectiveness. At the same time, findings from animal studies will help reveal the protective mechanisms, in which systematic inflammation is likely to play a major role.

Eleutheroside E attenuates isoflurane-induced cognitive dysfunction by regulating the α7-nAChR-NMDAR pathway

There is growing evidence that cognitive dysfunction induced by anesthetics is adversely affecting a large number of elderly surgical patients. Eleutheroside E (EE), a principal component of Eleutherococcus senticosus, exerts obvious protective effects on cognition. The aim of this study was to investigate the neuroprotective effect of EE on isoflurane (ISO)-induced cognitive dysfunction and explore the possible mechanisms. Learning and memory are assessed in novel object recognition and Morris water maze. We found that with ISO exposure, aged rats had a lower preference for the new object and spent less time in the target quarter. However, the amnesia can be alleviated by EE (50 mg/kg, intraperitoneally). Further research focused on the possible protective molecules associated with learning and memory, such as acetylcholine (ACh) and choline acetyltransferase (ChAT), nicotinic acetylcholine receptors (α7-nAChR), and NR2B, is required. The ACh in the hippocampus and serum was decreased after ISO exposure; meanwhile, the expression of ChAT, α7-nAChRs, and NR2B was downregulated. This abnormal state can be reversed by the administration of EE. Here, our results suggested that EE may be a potential therapeutic agent against ISO-induced cognitive dysfunction. The possible mechanism can be attributed to its neuroprotection through enhancing ChAT, which promotes the synthesis of ACh, further influencing the expression of the α7-nAChR-NR2B complex.

Anesthetics influence concussive head injury induced blood-brain barrier breakdown, brain edema formation, cerebral blood flow, serotonin levels, brain pathology and functional outcome

Several lines of evidences show that anesthetics influence neurotoxicity and neuroprotection. The possibility that different anesthetic agents potentially influence the pathophysiological and functional outcome following neurotrauma was examined in a rat model of concussive head injury (CHI). The CHI was produced by an impact of 0.224N on the right parietal bone by dropping a weight of 114.6g from a 20cm height under different anesthetic agents, e.g., inhaled ether anesthesia or intraperitoneally administered ketamine, pentobarbital, equithesin or urethane anesthesia. Five hour CHI resulted in profound volume swelling and brain edema formation in both hemispheres showing disruption of the blood-brain barrier (BBB) to Evans blue and radioiodine. A marked decrease in the cortical CBF and a profound increase in plasma or brain serotonin levels were seen at this time. Neuronal damages were present in several parts of the brain. These pathological changes were most marked in CHI under ether anesthesia followed by ketamine (35mg/kg, i.p.), pentobarbital (50mg/kg, i.p.), equithesin (3mL/kg, i.p.) and urethane (1g/kg, i.p.). The functional outcome on Rota Rod performances or grid walking tests was also most adversely affected after CHI under ether anesthesia followed by pentobarbital, equithesin and ketamine. Interestingly, the plasma and brain serotonin levels strongly correlated with the development of brain edema in head injured animals in relation to different anesthetic agents used. These observations suggest that anesthetic agents are detrimental to functional and pathological outcomes in CHI probably through influencing the circulating plasma and brain serotonin levels, not reported earlier. Whether anesthetics could also affect the efficacy of different neuroprotective agents in CNS injuries is a new subject that is currently being examined in our laboratory.

Effects of intrastriatal dopamine D1 or D2 antagonists on methamphetamine-induced egocentric and allocentric learning and memory deficits in Sprague-Dawley rats

RATIONALE

Methamphetamine (MA) is an abused psychostimulant that causes cognitive deficits after chronic use. Neostriatal dopamine receptors play a role in MA monoamine neurotoxicity. Blocking dopamine receptors prior to MA exposure in adult rats attenuates monoamine reductions and reactive gliosis.

OBJECTIVES

We tested whether blocking dopamine receptors protects against cognitive deficits.

METHODS

First, we determined the effects of MA alone versus MA in combination with the dopamine receptor D1 antagonist SCH-23390 or the dopamine receptor D2 antagonist sulpiride on cFos expression and monoamines at the age when rats in the cognitive experiment were to begin testing and monoamines in rats after cognitive testing.

RESULTS

SCH-23390 infused into the neostriatum prior to systemic administration of MA attenuated MA-induced cFos activation while sulpiride induced cFos activation. Two weeks after MA, rats had dopamine and serotonin reductions that were attenuated by each antagonist. Other rats treated the same way, were tested for egocentric learning and memory in the Cincinnati water maze, for navigational strategy in a star water maze, and spatial learning and memory in a Morris water maze. Pre-treatment with SCH-23390 or sulpiride attenuated the effects of MA on egocentric and spatial learning and memory. MA-treated rats showed a shift from an egocentric to a disorganized strategy in the star maze that was less disorganized in groups receiving MA and an antagonist. Post-behavior monoamine reductions remained but were attenuated by the antagonists but not identically to what was seen in rats not behaviorally tested.

CONCLUSIONS

The results show for the first time that dopamine receptors are mediators of MA-induced cognitive deficits.

TFEB Probably Involved in Midazolam-Disturbed Lysosomal Homeostasis and Its Induced β-Amyloid Accumulation

Alzheimer's disease (AD) is one of the most common neurodegenerative diseases, and β-amyloid (Aβ) plays a leading role in the pathogenesis of AD. The transcription factor EB (TFEB), a main regulating factor of autophagy and lysosome biosynthesis, is involved in the pathogenesis of AD by regulating autophagy-lysosomal pathways. To date, the choice of anesthetics during surgery in patients with neurodegenerative diseases and evaluation of the effects and underlying mechanisms in these patients have rarely been reported. In this study, the HEK293-APP cells overexpressing APP and Hela cells were used. The cells were treated with midazolam at different concentrations and at different times, then lysosomes were stained by lysotracker and their morphology was observed under a fluorescence microscope. The number and size of lysosomes were analyzed using the ImageJ software. The levels of TFEB in the nucleus and APP-cleaved intracellular proteins were detected by nuclear separation and Western Blot. Finally, ELISA was used to detect the levels of Aβ40 and Aβ42 in the cells after drug treatment. We found that 30 μM midazolam decreased the number of lysosomes and increased its size in HEK293 and HeLa cells. However, 15 μM midazolam transiently disturbed lysosomal homeostasis at 24 h and recovered it at 36 h. Notably, there was no significant difference in the extent to which lysosomal homeostasis was disturbed between treatments of different concentrations of midazolam at 24 h. In addition, 30 μM midazolam prevents the transport of TFEB to the nucleus in either normal or starved cells. Finally, the intracellular C-terminal fragment β (CTFβ), CTFα, Aβ40 and Aβ42 levels were all significantly elevated in 30 μM midazolam-treated HKE293-APP cells. Collectively, the inhibition of TFEB transport to the nucleus may be involved in midazolam-disturbed lysosomal homeostasis and its induced Aβ accumulation in vitro. The results indicated the risk of accelerating the pathogenesis of AD by midazolam and suggested that TFEB might be a candidate target for reduction of midazolam-dependent neurotoxicity.

The Effects of Transcranial Direct Current Stimulation on the Cognitive and Behavioral Changes After Electrode Implantation Surgery in Rats

Postoperative delirium can lead to increased morbidity and mortality, and may even be a potentially life-threatening clinical syndrome. However, the neural mechanism underlying this condition has not been fully understood and there is little knowledge regarding potential preventive strategies. To date, investigation of transcranial direct current stimulation (tDCS) for the relief of symptoms caused by neuropsychiatric disorders and the enhancement of cognitive performance has led to promising results. In this study, we demonstrated that tDCS has a possible effect on the fast recovery from delirium in rats after microelectrode implant surgery, as demonstrated by postoperative behavior and neurophysiology compared with sham stimulation. This is the first study to describe the possible effects of tDCS for the fast recovery from delirium based on the study of both electroencephalography and behavioral changes. Postoperative rats showed decreased attention, which is the core symptom of delirium. However, anodal tDCS over the right frontal area immediately after surgery exhibited positive effects on acute attentional deficit. It was found that relative power of theta was lower in the tDCS group than in the sham group after surgery, suggesting that the decrease might be the underlying reason for the positive effects of tDCS. Connectivity analysis revealed that tDCS could modulate effective connectivity and synchronization of brain activity among different brain areas, including the frontal cortex, parietal cortex, and thalamus. It was concluded that anodal tDCS on the right frontal regions may have the potential to help patients recover quickly from delirium.

Dexmedetomidine attenuates the toxicity of β‑amyloid on neurons and astrocytes by increasing BDNF production under the regulation of HDAC2 and HDAC5

Cytotoxicity of β-Amyloid (Aβ) is a major contributor to the pathogenesis of Alzheimer's disease. Dexmedetomidine (Dex) has been revealed to have multiple neuroprotective actions as a clinical anesthetic agent. The aim of the present study was to investigate the protection of Dex against Aβ in neurons and astrocytes, and the possible protective mechanisms. Primary neurons and astrocytes were isolated respectively from the hippocampus and cerebral cortex of neonatal Sprague Dawley rats. The neurons and astrocytes were incubated with Aβ in the presence or absence of Dex, which was followed by evaluation of the cell viability and apoptosis. Reverse transcription‑quantitative polymerase chain reaction, western blotting and ELISA assays were performed to assess the levels of specific genes or proteins. The results revealed that Aβ decreased the viabilities of neurons and astrocytes in a dose‑dependent manner, and elevated the rate of apoptosis. However, Dex attenuated the detrimental effects of Aβ. Aβ caused deacetylation of histone H3 by promoting the accumulation of histone deacetylase (HDAC)‑2 and HDAC5 in the cell nucleus, resulting in the reduced production of brain‑derived neurotrophic factor (BDNF). However, Dex reversed the Aβ‑induced deacetylation of histone H3 and thus, increased BDNF production. Using a HDAC inhibitor or recombinant BDNF protein also protected the neurons and astrocytes against Aβ cytotoxicity. These results suggested that the protective effect of Dex against Aβ is particularly relevant to BDNF. Thus, the present study provides a foundation for the further study of Dex protection against Aβ in animal models and pre‑clinical researches.

Perioperative neurocognition in elderly patients

PURPOSE OF REVIEW

The extrinsic risk factors for postoperative cognitive disturbance have been a source of concern during the perioperative period, and these risk factors remain the subject of controversy. This review of recent studies focuses on the effect of these factors on postoperative cognitive disturbance during the perioperative period.

RECENT FINDINGS

Impairment of cerebral autoregulation may predispose patients to intraoperative cerebral malperfusion, which may subsequently induce postoperative cognitive disturbance. The neurotoxicity of several volatile anesthetics may contribute to cognitive functional decline, and the impact of intravenous anesthesia on cognitive function requires further exploration. Multimodal analgesia may not outperform traditional postoperative analgesia in preventing postoperative delirium. Furthermore, acute pain and chronic pain may exacerbate the cognitive functional decline of patients with preexisting cognitive impairment. The nuclear factor-kappa beta pathway is an important node in the neuroinflammatory network.

SUMMARY

Several intraoperative factors are associated with postoperative cognitive disturbance. However, if these factors are optimized in perioperative management, postoperative cognitive disturbance will improve.

Clinical characteristics and diagnosis of a rare case of systemic AL amyloidosis: a descriptive study

Systemic amyloidosis is a rare disease involving multiple organs. It is difficult to establish diagnosis as the symptoms is diverse and non-specific. And without specific therapy the prognosis is very poor. We analyzed detailed clinical and laboratorial data of a 53-year-old male patient. The characteristic features included refractory pleural effusion, extraordinary hepatomegaly and cardiac failure. The illness lasted 9 months and therapy period spanned 4 months. Fine needle biopsy of liver, lung, heart, pancreas and kidney was performed. Immunohistochemistry, immunofluorescence, Congo staining and hematoxylin and eosin staining were performed. All specimens were stained pink with haematoxylin and eosin staining. Amorphous deposits of eosinophilic material were visible within the Congo red dye stained liver tissue whereas under cross-polarized light pathognomonic apple-green birefringence of amyloid deposits was visible. At last systemic AL amyloidosis diagnosis was confirmed. The report showed an unusual AL amyloidosis case in detail which would be helpful for physician in clinical work.

Dexmedetomidine inhibits inflammation in microglia cells under stimulation of LPS and ATP by c-Fos/NLRP3/caspase-1 cascades

NOD-like receptor 3 (NLRP3) plays critical roles in the initiation of inflammasome-mediated inflammation in microglia, thus becomes an important therapeutic target of Alzheimer's disease (AD). Dexmedetomidine (Dex), a new type of clinical anesthetic agent, shows anti-inflammatory properties and inhibits postoperative cognitive dysfunction in AD patients. The present study was aimed to investigate effect of Dex on NLRP3 activity in activated microglia and reveal the underlying mechanisms. The human microglia clone 3 (HMC3) cells were exposed to 100 ng/ml LPS and 5 mM ATP, in the presence and absence of doses of Dex. Data from ELISA and Western blot assays showed that Dex abrogated the promoting effects of LPS/ATP on the release of pro-inflammatory cytokines including IL-1β and IL-18 in the cell medium and the expression of NLRP3 and its downstream target caspase-1 in HMC3 cells. Furthermore, the present study found that exposure of HMC3 cells to LPS/ATP increased nuclear protein levels of transcription factor c-Fos, but treatment with Dex reversed the increase in c-Fos, as indicated by Western blot and immunofluorescence measures. Luciferase reported assay revealed that c-Fos can bind to the promoter region of NLRP3 gene and positively regulate the expression. These results suggest that Dex inhibiting c-Fos nuclear protein levels promoted by LPS/ATP blocks the up-regulation of NLRP3. This suggestion is supported by co-immunoprecipitation and PCR studies, in which Dex decreased the amount of c-Fos that binds to NLRP3 under the stimulation of LPS/ATP. The present study revealed that Dex inhibits inflammation in microglia cells under stimulation of LPS and ATP by c-Fos/NLRP3/caspase-1 cascades, which adds new understanding of the anti-inflammatory mechanism of Dex.

MicroRNA-188-3p is involved in sevoflurane anesthesia-induced neuroapoptosis by targeting MDM2

Sevoflurane is a commonly used inhalation anesthetic. Sevoflurane-induced neuroapoptosis and cognitive impairments in animals are widely reported, however, the underlying molecular mechanisms remain largely unknown. The results of the present study demonstrated that sevoflurane anesthesia induced spatial memory impairments in rats, as determined by the Morris water maze test. Mechanistically, the current study demonstrated that sevoflurane administration significantly enhanced the expression of microRNA (miR)-188-3p. Furthermore, inhibition of miR-188-3p using lentiviral miR-188-3p inhibitors attenuated sevoflurane-induced cognitive impairments in rats. The present study also demonstrated that miR-188-3p targeted MDM2 proto-oncogene (MDM2) and negatively regulated the expression of MDM2, as determined by luciferase assays, reverse transcription-quantitative polymerase chain reaction and western blot analysis. Furthermore, decreased abundance of MDM2 following transfection with miR-188-3p mimics was associated with increased stability of p53 protein. Suppression of p53 activity using the specific p53 inhibitor pifithrin-α alleviated sevoflurane-induced neuroapoptosis. These results indicate that the miR-188-3p-MDM2-p53 axis may have a critical role in sevoflurane-induced cognitive dysfunction. Therefore, miR-188-3p may be a potential target for the treatment of sevoflurane-induced cognitive impairment.