Anesthetic preconditioning inhibits isoflurane-mediated apoptosis in the developing rat brain

Suberoylanilide hydroxamic acid attenuates cognitive impairment in offspring caused by maternal surgery during mid-pregnancy

Some pregnant women have to experience non-obstetric surgery during pregnancy under general anesthesia. Our previous studies showed that maternal exposure to sevoflurane, isoflurane, propofol, and ketamine causes cognitive deficits in offspring. Histone acetylation has been implicated in synaptic plasticity. Propofol is commonly used in non-obstetric procedures on pregnant women. Previous studies in our laboratory showed that maternal propofol exposure in pregnancy impairs learning and memory in offspring by disturbing histone acetylation. The present study aims to investigate whether HDAC inhibitor suberoylanilide hydroxamic acid (SAHA) could attenuate learning and memory deficits in offspring caused by maternal surgery under propofol anesthesia during mid-pregnancy. Maternal rats were exposed to propofol or underwent abdominal surgery under propofol anesthesia during middle pregnancy. The learning and memory abilities of the offspring rats were assessed using the Morris water maze (MWM) test. The protein levels of histone deacetylase 2 (HDAC2), phosphorylated cAMP response-element binding (p-CREB), brain-derived neurotrophic factor (BDNF), and phosphorylated tyrosine kinase B (p-TrkB) in the hippocampus of the offspring rats were evaluated by immunofluorescence staining and western blot. Hippocampal neuroapoptosis was detected by TUNEL staining. Our results showed that maternal propofol exposure during middle pregnancy impaired the water-maze learning and memory of the offspring rats, increased the protein level of HDAC2 and reduced the protein levels of p-CREB, BDNF and p-TrkB in the hippocampus of the offspring, and such effects were exacerbated by surgery. SAHA alleviated the cognitive dysfunction and rescued the changes in the protein levels of p-CREB, BDNF and p-TrkB induced by maternal propofol exposure alone or maternal propofol exposure plus surgery. Therefore, SAHA could be a potential and promising agent for treating the learning and memory deficits in offspring caused by maternal nonobstetric surgery under propofol anesthesia.

Stress Pathways Induced by Volatile Anesthetics and Failure of Preconditioning in a Mitochondrial Complex I Mutant

BACKGROUND

Carriers of mutations in the mitochondrial electron transport chain are at increased risk of anesthetic-induced neurotoxicity. To investigate the neurotoxicity mechanism and to test preconditioning as a protective strategy, this study used a Drosophila melanogaster model of Leigh syndrome. Model flies carried a mutation in ND23 (ND2360114) that encodes a mitochondrial electron transport chain complex I subunit. This study investigated why ND2360114 mutants become susceptible to lethal, oxygen-modulated neurotoxicity within 24 h of exposure to isoflurane but not sevoflurane.

METHODS

This study used transcriptomics and quantitative real-time reverse transcription polymerase chain reaction to identify genes that are differentially expressed in ND2360114 but not wild-type fly heads at 30 min after exposure to high- versus low-toxicity conditions. This study also subjected ND2360114 flies to diverse stressors before isoflurane exposure to test whether isoflurane toxicity could be diminished by preconditioning.

RESULTS

The ND2360114 mutation had a greater effect on isoflurane- than sevoflurane-mediated changes in gene expression. Isoflurane and sevoflurane did not affect expression of heat shock protein (Hsp) genes (Hsp22, Hsp27, and Hsp68) in wild-type flies, but isoflurane substantially increased expression of these genes in ND2360114 mutant flies. Furthermore, isoflurane and sevoflurane induced expression of oxidative (GstD1 and GstD2) and xenobiotic (Cyp6a8 and Cyp6a14) stress genes to a similar extent in wild-type flies, but the effect of isoflurane was largely reduced in ND2360114 flies. In addition, activating stress response pathways by pre-exposure to anesthetics, heat shock, hyperoxia, hypoxia, or oxidative stress did not suppress isoflurane-induced toxicity in ND2360114 mutant flies.

CONCLUSIONS

Mutation of a mitochondrial electron transport chain complex I subunit generates differential effects of isoflurane and sevoflurane on gene expression that may underlie their differential effects on neurotoxicity. Additionally, the mutation produces resistance to preconditioning by stresses that protect the brain in other contexts. Therefore, complex I activity modifies molecular and physiologic effects of anesthetics in an anesthetic-specific manner.

EDITOR’S PERSPECTIVE

Promotion of ROS-mediated apoptosis, G2/M arrest, and autophagy by naringenin in non-small cell lung cancer

Background: As lung cancer is the leading cause of cancer death worldwide, the development of new medicines is a crucial endeavor. Naringenin, a flavanone derivative, possesses anti-cancer and anti-inflammatory properties and has been reported to have cytotoxic effects on various cancer cells. The current study investigated the underlying molecular mechanism by which naringenin induces cell death in lung cancer. Methods: The expression of apoptosis, cell cycle arrest, and autophagy markers in H1299 and A459 lung cancer cells was evaluated using a terminal deoxynucleotidyl transferase dUTP nick end labeling assay (TUNEL), Western blot, Annexin V/PI stain, PI stain, acridine orange staining, and transmission electron microscopy (TEM). Using fluorescence microscopy, DALGreen was used to observe the degradation of p62, a GFP-LC3 plasmid was used to evaluate puncta formation, and a pcDNA3-GFP-LC3-RFP-LC3ΔG plasmid was used to evaluate autophagy flux. Furthermore, the anti-cancer effect of naringenin was evaluated in a subcutaneous H1299 cell xenograft model. Results: Naringenin treatment of lung cancer cells (H1299 and A459) reduced cell viability and induced cell cycle arrest. Pretreatment of cells with ROS scavengers (N-acetylcysteine or catalase) suppressed the naringenin-induced cleavage of apoptotic protein and restored cyclin-dependent kinase activity. Naringenin also triggered autophagy by mediating ROS generation, thereby activating AMP-activated protein kinase (AMPK) signaling. ROS inhibition not only inhibited naringenin-induced autophagic puncta formation but also decreased the ratio of microtubule-associated proteins 1A/1B light chain 3 II (LC3II)/LC3I and activity of the AMPK signaling pathway. Furthermore, naringenin suppressed tumor growth and promoted apoptosis in the xenograft mouse model. Conclusion: This study demonstrated the potent anti-cancer effects of naringenin on lung cancer cells, thereby providing valuable insights for developing small-molecule drugs that can induce cell cycle arrest, apoptosis, and autophagic cell death.

Acutely increased aquaporin-4 exhibits more potent protective effects in the cortex against single and repeated isoflurane-induced neurotoxicity in the developing rat brain

Damage to hippocampus, cerebellum, and cortex associated with cognitive functions due to anesthetic-induced toxicity early in life may cause cognitive decline later. Aquaporin 4 (AQP4), a key protein in waste clearance pathway of brain, is involved in synaptic plasticity and neurocognition. We investigated the effects of single and repeated isoflurane (Iso) anesthesia on AQP4 levels and brain damage. Postnatal-day (P)7 Wistar albino rats were randomly assigned to Iso or Control (C) groups. For single-exposure, pups were exposed to 1.5% Iso in 30% oxygenated-air for 3-h at P7 (Iso₁). For repeated-exposure, pups were exposed to Iso for 3 days, 3-h each day, at 1-day intervals (P7 + 9+11) starting at P7 (Iso₃). C₁ and C₃ groups received only 30% oxygenated-air. Based on HE-staining and immunoblotting (Bax/Bcl-2, cleaved-caspase3 and PARP1) analyses, Iso exposures caused a higher degree of apoptosis in hippocampus. Anesthesia increased 4HNE, oxidative stress marker; the highest ROS accumulation was determined in cerebellum. Increased inflammation (TNF-α, NF-κB) was detected. Multiple Iso-exposures caused more significant damage than single exposure. Moreover, 4HNE and TNF-α contributed synergistically to Iso-induced neurotoxicity. After anesthesia, higher expression of AQP4 was detected in cortex than hippocampus and cerebellum. There was an inverse correlation between increased AQP4 levels and apoptosis/ROS/inflammation. Correlation analysis indicated that AQP4 had a more substantial protective profile against oxidative stress than apoptosis. Remarkably, acutely increased AQP4 against Iso exhibited a more potent neuroprotective effect in cortex, especially frontal cortex. These findings promote further research to understand better the mechanisms underlying anesthesia-induced toxicity in the developing brain.

The Protective Effect of Picroside II on Isoflurane-Induced Neuronal Injury in Rats via Downregulating miR-195

INTRODUCTION

Numerous pieces of evidence demonstrated that isoflurane induces hippocampal cell injury and cognitive impairments. Picroside II has been investigated for its anti-apoptosis and antioxidant neuroprotective effects. We aimed to explore the protective effects of picroside II and the role of microRNA-195 (miR-195) on isoflurane-induced neuronal injury in rats.

METHODS

The Morris water maze test was used to evaluate the effects of isoflurane on rats regarding escape latency and time in quadrant parameters. Real-time quantitative PCR was used to detect the expression levels of miR-195 and pro-inflammatory cytokines, including inter-leukin-1β (IL-1β), interleukin-6 (IL-6), and tumor necrosis factor-α (TNF-α) mRNA, in the hippocampal tissues and neuronal cells.

RESULTS

The picroside II significantly improves isoflurane-induced higher escape latency and lower time spent in the quadrant compared with the control rats. Picroside II also promotes cell viability and suppresses cell apoptosis of isoflurane-induced neuronal cells. Besides, picroside II suppresses the expression of pro-inflammatory cytokines (IL-1β, IL-6, and TNF-α) and miR-195 in vivo and in vitro. Furthermore, overexpression of miR-195 abrogates the effects of picroside II on the expression of pro-inflammatory cytokines. The appropriate dose of picroside II is 20 mg/kg.

CONCLUSION

Picroside II could protect the nervous system possibly through inhibiting the inflammatory response in the isoflurane-induced neuronal injury of rats. The protective effect of picroside II may be achieved by downregulating the expression of miR-195 and then inhibiting the inflammatory response.

Fraxetin suppresses reactive oxygen species-dependent autophagy by the PI3K/Akt pathway to inhibit isoflurane-induced neurotoxicity in hippocampal neuronal cells

Isoflurane, a common volatile anesthetic, has been widely used to provide general anesthesia in operations. However, exposure to isoflurane may cause widespread neurotoxicity in the developing animal brain. Fraxetin, a natural coumarin derivative extracted from the bark of Fraxinus rhynchophylla, possesses versatile pharmacological properties including anti-oxidative, anti-inflammatory, and neuroprotective effects. However, the effect and action mechanism of fraxetin on neurotoxicity induced by isoflurane are unknown. Reactive oxygen species (ROS) generation, cell viability, lactate dehydrogenase (LDH) release, and apoptosis were estimated by 2',7'-dichlorofluorescin-diacetate (DCFH-DA) staining, MTT, LDH release, and terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick end-labeling (TUNEL) staining assays, respectively. The protein levels of light chain 3 (LC3)-I, LC3-II, p62, protein kinase B (Akt), and phosphorylated Akt (p-Akt) were detected by western blot analysis. Isoflurane induced ROS, LDH release, apoptosis, and autophagy, but inhibited the viability in HT22 cells, which were overturned by fraxetin or ROS scavenger N-acetyl-L-cysteine. Fraxetin suppressed isoflurane-induced PI3K/Akt inactivation in HT22 cells. PI3K/Akt inactivation by LY294002 resisted the effects of fraxetin on isoflurane-induced autophagy and autophagy-modulated neurotoxicity in HT22 cells. In conclusion, fraxetin suppressed ROS-dependent autophagy by activating the PI3K/Akt pathway to inhibit isoflurane-induced neurotoxicity in hippocampal neuronal cells.

miR-124-3p Ameliorates Isoflurane-Induced Learning and Memory Impairment via Targeting STAT3 and Inhibiting Neuroinflammation

INTRODUCTION

Substantial evidence has indicated that isoflurane leads to learning and memory impairment. This study was designed to investigate the potential role of microRNA-124-3p (miR-124-3p) in isoflurane-induced learning and memory impairment in rats.

METHODS

Spatial learning and memory of rats were estimated by the Morris water maze (MWM) test after the construction of isoflurane-treated models. qRT-PCR was performed to assess the expression levels of miR-124-3p. The levels of interleukin-1β, interleukin-6, and tumor necrosis factor-α in the hippocampal tissues were determined by enzyme-linked immunosorbent assay. The luciferase activity was determined by using a dual-luciferase reporter assay system.

RESULTS

The higher escape latency and lower time spent in the original quadrant were shown in isoflurane-treated rats compared with the control rats. Moreover, treatment with isoflurane could induce neuroinflammation, and miR-124-3p was poorly expressed in the hippocampal tissue of isoflurane-treated rats. Furthermore, STAT3 is a functional target of miR-124-3p, and inflammatory cytokine level was downregulated by miR-124-3p.

DISCUSSION/CONCLUSION

Combining the results of the current study demonstrates that miR-124-3p may have pivotal roles in improving isoflurane-induced learning and memory impairment via targeting STAT3 and inhibiting neuroinflammation.

Propofol inhibits the expression of Abelson nonreceptor tyrosine kinase without affecting learning or memory function in neonatal rats

OBJECTIVE

Propofol is one of the most commonly used intravenous drugs to induce and maintain general anesthesia. In vivo and in vitro studies have shown that propofol can affect neuronal growth, leading to apoptosis and impairing cognitive function. The Abelson nonreceptor tyrosine kinase (c-Abl) is associated with both neuritic plaques and neurofibrillary tangles in the brains of patients with Alzheimer's disease and other neurodegenerative diseases. This study aimed to explore the effect of propofol on apoptosis and neurocognition through its regulation of c-Abl expression in vivo and in vitro.

MATERIALS AND METHODS

In this study, primary hippocampal neurons were cultured and exposed to propofol at different concentrations. Protein expression was measured by Western blotting and coimmunoprecipitation. The c-Abl transcription level was verified by fluorescence quantitative PCR. Reactive oxygen species (ROS) levels were detected by flow cytometry. In addition, an animal experiment was conducted to assess neuronal apoptosis by immunofluorescence staining for caspase-3 and to evaluate behavioral changes by the Morris water maze (MWM) test.

RESULTS

The in vitro experiment showed that propofol significantly decreased c-Abl expression and ROS levels. In addition, propofol has no cytotoxic effect and does not affect cell activity. Moreover, in the animal experiment, intraperitoneal injection of 50 mg/kg propofol for 5 days obviously decreased the expression of c-Abl in the neonatal rat brain (p < .05) but did not significantly increase the number of caspase-3-positive cells. Propofol treatment did not significantly reduce the number of platform crossings (p > .05) or prolong the escape latency of neonatal rats (p > .05) in the MWM test.

CONCLUSIONS

The present data suggest that reduced expression of this nonreceptor tyrosine kinase through consecutive daily administration of propofol did not impair learning or memory function in neonatal rats.

Desoxyrhapontigenin attenuates neuronal apoptosis in an isoflurane-induced neuronal injury model by modulating the TLR-4/cyclin B1/Sirt-1 pathway

This study investigated the protective effect of desoxyrhapontigenin (DOP) against isoflurane (ISF)-induced neuronal injury in rats. Neuronal injury was induced in pups by exposing them to 0.75% ISF on postnatal day 7 with 30% oxygen for 6 h. The pups were treated with DOP 10 mg/kg, i.p., for 21 days after ISF exposure. The protective effect of DOP was estimated by assessing cognitive function using the neurological score and the Morris water maze. Neuronal apoptosis was assessed in the hippocampus using the TUNEL assay, and protein expression of caspase-3, Bax, and Bcl-2 was measured by Western blotting. The levels of cytokines and oxidative stress parameters were assessed by ELISA. Western blotting and RT-PCR were performed to measure the expression of NF-kB, TLR-4, Sirt-1, and cyclin B1 protein in the brain. The cognitive function and neurological function scores were improved in the DOP group compared with the ISF group. Moreover, DOP treatment reduced the number of TUNEL-positive cells and the expression of caspase-3, Bax, and Bcl-2 protein in the brains of rats with neuronal injury. The levels of mediators of inflammation and oxidative stress were reduced in the brain tissue of the DOP group. Treatment with DOP attenuated the protein expression of TLR-4, NF-kB, cyclin B1, and Sirt-1 in the brain tissue of rats with neuronal injury. In conclusion, DOP ameliorates neuronal apoptosis and improves cognitive function in rats with ISF-induced neuronal injury. Moreover, DOP treatment can prevent neuronal injury by regulating the TLR-4/cyclin B1/Sirt-1 pathway.

Sevoflurane modulates breast cancer cell survival via modulation of intracellular calcium homeostasis

Background

Some retrospective and in vitro studies suggest that general anesthetics influence breast cancer recurrence and metastasis. We compared the effects of general anesthetics sevoflurane versus propofol on breast cancer cell survival, proliferation and invasion in vitro. The investigation focused on effects in intracellular Ca²⁺ homeostasis as a mechanism for general anesthetic-mediated effects on breast cancer cell survival and metastasis.

Methods

Estrogen receptor-positive (MCF7) and estrogen receptor-negative (MDA-MB-436) human breast cancer cell lines along with normal breast tissue (MCF10A) were used. Cells were exposed to sevoflurane or propofol at clinically relevant and extreme doses and durations for dose- and time-dependence studies. Cell survival, proliferation and migration following anesthetic exposure were assessed. Intracellular and extracellular Ca²⁺ concentrations were modulated using Ca²⁺ chelation and a TRPV1 Ca²⁺ channel antagonist to examine the role of Ca²⁺ in mediating anesthetic effects.

Results

Sevoflurane affected breast cancer cell survival in dose-, time- and cell type-dependent manners. Sevoflurane, but not propofol, at equipotent and clinically relevant doses (2% vs. 2 μM) for 6 h significantly promoted breast cell survival in all three types of cells. Paradoxically, extreme exposure to sevoflurane (4%, 24 h) decreased survival in all three cell lines. Chelation of cytosolic Ca²⁺ dramatically decreased cell survival in both breast cancer lines but not control cells. Inhibition of TRPV1 receptors significantly reduced cell survival in all cell types, an effect that was partially reversed by equipotent sevoflurane but not propofol. Six-hour exposure to sevoflurane or propofol did not affect cell proliferation, metastasis or TRPV1 protein expression in any type of cell.

Conclusion

Sevoflurane, but not propofol, at clinically relevant concentrations and durations, increased survival of breast cancer cells in vitro but had no effect on cell proliferation, migration or TRPV1 expression. Breast cancer cells require higher cytoplasmic Ca²⁺ levels for survival than normal breast tissue. Sevoflurane affects breast cancer cell survival via modulation of intracellular Ca²⁺ homeostasis.

Isoflurane mediated neuropathological and cognitive impairments in the triple transgenic Alzheimer's mouse model are associated with hippocampal synaptic deficits in an age-dependent manner

Many in vivo studies suggest that inhalational anesthetics can accelerate or prevent the progression of neuropathology and cognitive impairments in Alzheimer Disease (AD), but the synaptic mechanisms mediating these ambiguous effects are unclear. Here, we show that repeated exposures of neonatal and old triple transgenic AD (3xTg) and non-transgenic (NonTg) mice to isoflurane (Iso) distinctly increased neurodegeneration as measured by S100β levels, intracellular Aβ, Tau oligomerization, and apoptotic markers. Spatial cognition measured by reference and working memory testing in the Morris Water Maze (MWM) were altered in young NonTg and 3xTg. Field recordings in the cornu ammonis 1 (CA1) hippocampus showed that neonatal control 3xTg mice exhibited hypo-excitable synaptic transmission, reduced paired-pulse facilitation (PPF), and normal long-term potentiation (LTP) compared to NonTg controls. By contrast, the old control 3xTg mice exhibited hyper-excitable synaptic transmission, enhanced PPF, and unstable LTP compared to NonTg controls. Repeated Iso exposures reduced synaptic transmission and PPF in neonatal NonTg and old 3xTg mice. LTP was normalized in old 3xTg mice, but reduced in neonates. By contrast, LTP was reduced in old but not neonatal NonTg mice. Our results indicate that Iso-mediated neuropathologic and cognitive defects in AD mice are associated with synaptic pathologies in an age-dependent manner. Based on these findings, the extent of this association with age and, possibly, treatment paradigms warrant further study.

microRNA-124 attenuates isoflurane-induced neurological deficits in neonatal rats via binding to EGR1

Isoflurane anesthesia induces neuroapoptosis in the development of the brain. In this study, neonatal rats and hippocampal neurons were subjected to isoflurane exposure, in which the effect of miR-124 on the neurological deficits induced by isoflurane was evaluated. Isoflurane anesthesia models were induced in neonatal SD rats aged 7 days and then treated with miR-124 agomir, miR-124 antagomir, or LV-CMV-early growth response 1 (EGR1) plasmids. Then, the spatial learning and memory ability of rats were evaluated by Morris water maze. Furthermore, primary hippocampal neurons cultured 7 days were also exposed to isoflurane and transfected with miR-124 agomir, miR-124 antagomir, or LV-CMV-EGR1 plasmids. The targeting relationship of miR-124 and EGR1 was verified by the dual-luciferase reporter gene assay. To identify the effect of miR-124 on neuron activities, the viability and apoptosis of hippocampal neurons were assessed. In response to isoflurane exposure, miR-124 expression was reduced and EGR1 expression was increased in the hippocampal tissues and neurons. The isoflurane anesthesia damaged rats' spatial learning and memory ability, and reduced viability, and promoted apoptosis of hippocampal neurons. EGR1 was targeted and negatively regulated by miR-124. The treatment of miR-124 agomir improved rats' spatial learning and memory ability and notably increased hippocampal neuron viability and resistance to apoptosis, corresponding to an increased brain-derived neurotrophic factor (BDNF) expression, inhibited expression of proapoptotic factors (cleaved-Caspase-3 and Bax), and enhanced the expression of antiapoptotic factor (Bcl-2). Upregulated miR-124 inhibited the expression of EGR1, by which mechanism miR-124 reduced the neurological deficits induced by isoflurane in neonatal rats through inhibiting apoptosis of hippocampal neurons.

Neuroprotective effects of dexmedetomidine against isoflurane-induced neuronal injury via glutamate regulation in neonatal rats

Background

Considerable evidences support the finding that the anesthesia reagent isoflurane increases neuronal cell death in young rats. Recent studies have shown that dexmedetomidine can reduce isoflurane-induced neuronal injury, but the mechanism remains unclear. We investigated whether isoflurane cause neurotoxicity to the central nervous system by regulating the N-methyl-D-aspartate receptor (NMDAR) and excitatory amino acid transporter1 (EAAT1) in young rats. Furthermore, we examined if dexmedetomidine could decrease isoflurane-induced neurotoxicity.

Methods

Neonatal rats (postnatal day 7, n=144) were randomly divided into four groups of 36 animals each: control (saline injection without isoflurane); isoflurane (2% for 4 h); isoflurane + single dose of dexmedetomidine (75 µg/kg, 20 min before the start of 2% isoflurane for 4 h); and isoflurane + dual doses of dexmedetomidine (25 µg/kg, 20 min before and 2 h after start of isoflurane at 2% for 4 h). Six neonates from each group were euthanatized at 2 h, 12 h, 24 h, 3 days, 7 days and 28 days post-anesthesia. Hippocampi were collected and processed for protein extraction. Expression levels of the NMDAR subunits NR2A and NR2B, EAAT1 and caspase-3 were measured by western blot analysis.

Results

Protein levels of NR2A, EAAT1 and caspase-3 were significantly increased in hippocampus of the isoflurane group from 2 h to 3 days, while NR2B levels were decreased. However, the -induced increase in NR2A, EAAT1 and caspase-3 and the decrease in NR2B in isoflurane-exposed rats were ameliorated in the rats treated with single or dual doses of dexmedetomidine. Isoflurane-induced neuronal damage in neonatal rats is due in part to the increase in NR2A and EAAT1 and the decrease in NR2B in the hippocampus.

Conclusion

Dexmedetomidine protects the brain against the use of isoflurane through the regulation of NR2A, NR2B and EAAT1. However, using the same amount of dexmedetomidine, the trend of protection is basically the same.

HIF-α/PKM2 and PI3K-AKT pathways involved in the protection by dexmedetomidine against isoflurane or bupivacaine-induced apoptosis in hippocampal neuronal HT22 cells

The present study investigated the mechanism underlying the protective effect of dexmedetomidine (Dex) on hippocampal neuronal HT22 cell apoptosis induced by the anesthetics isoflurane and bupivacaine. The cellular morphology was observed using a phase contrast microscope. The effects of anesthetics on cell proliferation were assayed using a Cell Counting Kit-8 (CCK-8). The levels of apoptosis were examined by flow cytometry utilizing Annexin V-fluorescein isothiocyanate/propidium iodide double staining, and the protein expression levels of cleaved caspase-3, phosphorylated phosphoinositide 3′-kinase (p-PI3K), p-protein kinase B (p-AKT), hypoxia inducible factor (HIF-α), pyruvate kinase M2 (PKM2), B-cell lymphoma (Bcl-2)-associated X protein (Bax), Bcl-2 and cytochrome c were detected by western blot analysis. In vitro treatment with anesthetics was identified to decrease cell proliferation (P<0.01), the effect of which was then markedly inhibited by treatment with Dex (P<0.01) or a PI3K/AKT agonist. Exposure to anesthetics induced apoptosis in HT22 cells (75.4%), which was significantly attenuated by co-treatment with Dex (26.2%) or the PI3K/AKT agonist (28.1%). Analysis of the protein expression levels revealed that exposure to anesthetics resulted in the activation of cleaved caspase-3, Bax, cytochrome c, HIF-α and PKM2 and decreased the expression levels of Bcl-2, p-PI3K and p-AKT. However, these changes were inhibited by treatment with Dex or the PI3K/AKT agonist. Dex protected hippocampal neuronal HT22 cells from anesthetic-induced apoptosis through the promotion of the PI3K/AKT pathway and inhibition of the HIF-α/PKM2 axis.

Absence of Neuropathology With Prolonged Isoflurane Sedation in Healthy Adult Rats

BACKGROUND

The use of isoflurane sedation for prolonged periods in the critical care environment is increasing. However, isoflurane-mediated neurotoxicity has been widely reported. The goal of the present study was to determine whether long-term exposure to low-dose isoflurane in mechanically ventilated rodents is associated with evidence of neurodegeneration or neuroinflammation.

METHODS

Adult female Sprague-Dawley rats were used in this study. Experimental animals (n=11) were induced with 1.5% isoflurane, intubated, and given a neuromuscular blockade with α-cobratoxin. EEG electrodes were surgically implanted, subcutaneous precordial EKG Ag wire electrodes, and bladder, femoral artery, and femoral vein cannulas permanently placed. After these procedures, the isoflurane concentration was reduced to 0.5% and, in conjunction with the neuromuscular blockade, continued for 7 days. Arterial blood gases and chemistry were measured at 3 time points and core body temperature servoregulated and maintenance IV fluids were given during the 7 days. Experimental animals and untreated controls (n=9) were euthanized on day 7.

RESULTS

Immunohistochemical and cytochemical assays did not detect evidence of microgliosis, astrocytosis, neuronal apoptosis or necrosis, amyloidosis, or phosphorylated-tau accumulation. Blood glucose levels were significantly reduced on days 3/4 and 6/7 and partial pressure of oxygen was significantly reduced, but still within the normal range, on day 6/7. All other blood measurements were unchanged.

CONCLUSIONS

No neuropathologic changes consistent with neurotoxicity were detected in the brain after 1 week of continuous exposure to 0.5% isoflurane in healthy rats. These data suggest that even long exposures to low concentrations of isoflurane have no overt consequences on neuropathology.

S100β in newborns after C-section with general vs. epidural anesthesia: a prospective observational study

BACKGROUND

Preclinical evidence suggests that general anesthetics can dose dependently induce neurodegeneration in the developing brains of animals which can be reliably determined by measurement of blood S100β, but this correlation remains unclear in humans. We hypothesized that S100β would not be increased in cord arterial blood of fetuses exposed briefly to general anesthetics during a C-section, compared with epidural anesthesia.

METHODS

A prospective observational clinical study comparatively measured changes of brain damage biomarker S100β ratio of umbilical artery over vein (changes after fetus circulation) immediately after delivery under C-section with either epidural or general anesthesia. Newborn blood gas measurements, APGAR scores, and maternal well-being were also compared.

RESULTS

Compared with epidural anesthesia, general anesthesia resulted in the lower S100β ratio of umbilical artery over the vein (medium 2.64 [quartiles 1.39, 3.45] vs. medium 1.59 [quartiles 0.88, 2.01], P = 0.031), without changing the S100β level in the vein of the mother. There was no significant difference between general and epidural anesthesia when comparing other maternal and newborn parameters.

CONCLUSION

S100β levels in newborn after C-section is lower with general anesthesia than epidural anesthesia, with unclear mechanisms.

General Anesthetics Regulate Autophagy via Modulating the Inositol 1,4,5-Trisphosphate Receptor: Implications for Dual Effects of Cytoprotection and Cytotoxicity

General anesthetics are both neuroprotective and neurotoxic with unclear mechanisms. General anesthetics may control cell survival via their effects on autophagy by activation of type 1 inositol triphosphate receptor (InsP₃R-1). DT40 or SH-SY5Y cells with only or over 99% expression of InsP₃R-1 were treated with isoflurane or propofol. Cell viability was determined by MTT reduction or LDH release assays. Apoptosis was determined by measuring Caspase-3 or by TUNEL assay. Autophagy activity was determined by measuring LC3 II and P62. We evaluated mitochondrial integrity using MitoTracker Green and cytosolic ATP levels. Fura2-AM was used to measure the concentrations of cytosolic calcium ([Ca²⁺]_c). Propofol significantly increased peak and integrated calcium response (P < 0.001) in cells with InsP₃R-1 but not in cells with triple knockout of InsP₃R. Both propofol and isoflurane increased autophagy induction (P < 0.05) in an mTOR- and InsP₃R- activity dependent manner. Short exposure to propofol adequately activated InsP₃-1 to provide sufficient autophagy for cytoprotection, while prolonged exposure to propofol induced cell apoptosis via impairment of autophagy flux through over activation of InsP₃-1. Propofol damaged mitochondria and decreased cytosolic ATP. The effects of general anesthetics on apoptosis and autophagy are closely integrated; both are caused by differential activation of the type 1 InsP₃R.

Hydrogen sulfide attenuates isoflurane-induced neuroapoptosis and cognitive impairment in the developing rat brain

Background

Isoflurane-induced neuroapoptosis and cognitive impairment has been previously reported. Hydrogen sulfide (H₂S) has been shown to be a neuromodulator that is thought to have anti-apoptotic, anti-inflammatory, and anti-oxidative benefits. However, it is not known if H₂S is protective against anesthesia-induced apoptosis and cognitive defects.

Methods

In this study, postnatal day 7 (P7) Sprague-Dawley rats were randomly divided into four groups: control group (normal saline), H₂S group (NaHS 28 μM/kg), isoflurane group (normal saline +0.75% isoflurane) and H₂S preconditioning group (NaHS 28 μM/kg + 0.75% isoflurane). After exposure to isoflurane for 6 h, half the numbers of rats in each group were euthanized, and the hippocampus and cerebral cortex were dissected and examined for apoptosis by the terminal deoxynucleotidyl transferase-mediated dUTP nick end-labeling (TUNEL) technique and western blot. After 6 weeks, the remaining rats were subjected to a Morris water maze (MWM) test for behavioral assessment.

Results

The TUNEL assay and western blot showed that when rats were preconditioned with NaHS, neuroapoptosis decreased significantly both in hippocampus and cerebral cortex compering with the isofulrane group. The MWM showed that P7 rats administration of NaHS improved cognitive impairments induced by isoflurane.

Conclusions

The current study demonstrates that H₂S attenuates isoflurane-induced neuroapoptosis and improves cognitive impairments in the developing rat brain.

Propofol Affects Neurodegeneration and Neurogenesis by Regulation of Autophagy via Effects on Intracellular Calcium Homeostasis

BACKGROUND

In human cortical neural progenitor cells, we investigated the effects of propofol on calcium homeostasis in both the ryanodine and inositol 1,4,5-trisphosphate calcium release channels. We also studied propofol-mediated effects on autophagy, cell survival, and neuro- and gliogenesis.

METHODS

The dose-response relationship between propofol concentration and duration was studied in neural progenitor cells. Cell viability was measured by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide and lactate dehydrogenase release assays. The effects of propofol on cytosolic calcium concentration were evaluated using Fura-2, and autophagy activity was determined by LC3II expression levels with Western blot. Proliferation and differentiation were evaluated by bromodeoxyuridine incorporation and immunostaining with neuronal and glial markers.

RESULTS

Propofol dose- and time-dependently induced cell damage and elevated LC3II expression, most robustly at 200 µM for 24 h (67 ± 11% of control, n = 12 to 19) and 6 h (2.4 ± 0.5 compared with 0.6 ± 0.1 of control, n = 7), respectively. Treatment with 200 μM propofol also increased cytosolic calcium concentration (346 ± 71% of control, n = 22 to 34). Propofol at 10 µM stimulated neural progenitor cell proliferation and promoted neuronal cell fate, whereas propofol at 200 µM impaired neuronal proliferation and promoted glial cell fate (n = 12 to 20). Cotreatment with ryanodine and inositol 1,4,5-trisphosphate receptor antagonists and inhibitors, cytosolic Ca chelators, or autophagy inhibitors mostly mitigated the propofol-mediated effects on survival, proliferation, and differentiation.

CONCLUSIONS

These results suggest that propofol-mediated cell survival or neurogenesis is closely associated with propofol's effects on autophagy by activation of ryanodine and inositol 1,4,5-trisphosphate receptors.

Bone-marrow mesenchymal stem-cell administration significantly improves outcome after retinal ischemia in rats

PURPOSE

Ischemia-associated retinal degeneration is one of the leading causes of vision loss, and to date, there are no effective treatment options. We hypothesized that delayed injection of bone-marrow stem cells (BMSCs) 24 h after the onset of ischemia could effectively rescue ischemic retina from its consequences, including apoptosis, inflammation, and increased vascular permeability, thereby preventing retinal cell loss.

METHODS

Retinal ischemia was induced in adult Wistar rats by increasing intraocular pressure (IOP) to 130-135 mmHg for 55 min. BMSCs harvested from rat femur were injected into the vitreous 24 h post-ischemia. Functional recovery was assessed 7 days later using electroretinography (ERG) measurements of the a-wave, b-wave, P2, scotopic threshold response (STR), and oscillatory potentials (OP). The retinal injury and anti-ischemic effects of BMSCs were quantitated by measuring apoptosis, autophagy, inflammatory markers, and retinal-blood barrier permeability. The distribution and fate of BMSC were qualitatively examined using real-time fundus imaging, and retinal flat mounts.

RESULTS

Intravitreal delivery of BMSCs significantly improved recovery of the ERG a- and b-waves, OP, negative STR, and P2, and attenuated apoptosis as evidenced by decreased TUNEL and caspase-3 protein levels. BMSCs significantly increased autophagy, decreased inflammatory mediators (TNF-α, IL-1β, IL-6), and diminished retinal vascular permeability. BMSCs persisted in the vitreous and were also found within ischemic retina.

CONCLUSIONS

Taken together, our results indicate that intravitreal injection of BMSCs rescued the retina from ischemic damage in a rat model. The mechanisms include suppression of apoptosis, attenuation of inflammation and vascular permeability, and preservation of autophagy.

Anesthetic neurotoxicity: Apoptosis and autophagic cell death mediated by calcium dysregulation

A number of findings suggested that general anesthetics induced neural cell death by apoptosis in various animal models. Although clinical evidence regarding the correlation between anesthetic exposures at young age and subsequent cognitive impairments remains unclear, repeated or consistent exposures to general anesthetics may be a potential harmful risk in developing human brains. The mechanisms underlying the anesthetic neurotoxicity have received extensive attention recently. We will attempt a brief review to summarize current understanding on the role of both apoptosis and autophagic cell death mediated by calcium dysregulation in anesthetic neurotoxicity.

Do anesthetics harm the developing human brain? An integrative analysis of animal and human studies

Anesthetics that permit surgical procedures and stressful interventions have been found to cause structural brain abnormalities and functional impairment in immature animals, generating extensive concerns among clinicians, parents, and government regulators regarding the safe use of these drugs in young children. Critically important questions remain, such as the exact age at which the developing brain is most vulnerable to the effects of anesthetic exposure, whether a particular age exists beyond which anesthetics are devoid of long-term effects on the brain, and whether any specific exposure duration exists that does not lead to deleterious effects. Accordingly, the present analysis attempts to put the growing body of animal studies, which we identified to include >440 laboratory studies to date, into a translational context, by integrating the preclinical data on brain structure and function with clinical results attained from human neurocognitive studies, which currently exceed 30 studies. Our analysis demonstrated no clear exposure duration threshold below which no structural injury or subsequent cognitive abnormalities occurred. Animal data did not clearly identify a specific age beyond which anesthetic exposure did not cause any structural or functional abnormalities. Several potential mitigating strategies were found, however, no general anesthetic was identified that consistently lacked neurodegenerative properties and could be recommended over other anesthetics. It therefore is imperative, to expand efforts to devise safer anesthetic techniques and mitigating strategies, even before long-term alterations in brain development are unequivocally confirmed to occur in millions of young children undergoing anesthesia every year.

Sevoflurane-Induced Endoplasmic Reticulum Stress Contributes to Neuroapoptosis and BACE-1 Expression in the Developing Brain: The Role of eIF2α

Neonatal exposure to volatile anesthetics causes apoptotic neurodegeneration in the developing brain, possibly leading to neurocognitive deficits in adulthood. Endoplasmic reticulum (ER) stress might be associated with sevoflurane (sevo)-induced neuroapoptosis. However, the signaling pathway regulating sevo-induced neuroapoptosis is not understood. We investigated the effects of neonatal sevo exposure on ER signaling pathway activation. Seven-day-old mouse pups were divided into control (C) and sevo (S; 3 % sevo exposure, 6 h) groups. ER stress marker [protein kinase RNA-like ER kinase (PERK), eukaryotic translation initiation factor 2α (eIF2α), activating transcription factor 4 (ATF4), CHOP, and caspase-12] levels were determined by western blotting. To understand the role of eIF2α in sevo-induced ER stress and caspase-3 activation, pups were pretreated with an eIF2α dephosphorylation inhibitor, salubrinal, and a potent and selective inhibitor of PERK, GSK2656157, before sevo exposure, and the effects on ER stress signaling and neuroapoptosis were examined. We investigated whether neonatal exposure to sevo increased β-site APP-cleaving enzyme 1 (BACE-1) expression. Neonatal sevo exposure elevated caspase-3 activation. ER stress signaling was activated, along with increased PERK and eIF2α phosphorylation, and upregulation of proapoptotic proteins (ATF4 and CHOP) in the cerebral cortex of the developing brain. Pretreatment with salubrinal augmented sevo-induced eIF2α phosphorylation, which inhibited ER stress-mediated ATF4 and caspase-3 activation. Inhibition of PERK phosphorylation due to GSK2656157 pretreatment reduced the sevo-induced increase in eIF2α phosphorylation. Sevo increased BACE-1 expression, which was attenuated by GSK2656157 and salubrinal pretreatment. Our data suggested that neonatal sevo exposure-induced neuroapoptosis is mediated via the PERK-eIF2α-ATF4-CHOP axis of the ER stress signaling pathway. Modulation of eIF2α phosphorylation may play a key role in sevo-induced neurotoxicity in the developing brain.

From the Cover: Volatile Anesthetics Transiently Disrupt Neuronal Development in Neonatal Rats

Volatile anesthetics can cause neuronal and glial toxicity in the developing mammalian brain, as well as long-term defects in learning and memory. The goals of this study were to compare anesthetics using a clinically relevant exposure paradigm, and to assess the anesthetic effects on hippocampal development and behavior. Our hypothesis was that volatile anesthetics disrupt hippocampal development, causing neurobehavioral defects later in life. Bromodeoxyuridine (BrdU) was administered to rats on postnatal day (P)1, and the rats were exposed to volatile anesthetics (isoflurane, sevoflurane, or desflurane) for 2 h on P2. On days P7 and P14, the BrdU-labeled cells were quantified in the hippocampal dentate gyrus using immunohistochemical assays and fluorescent microscopy. Caspase-3 positive cells were quantified on P2 to evaluate apoptosis. The remaining animals underwent behavioral testing at ages 6 weeks and 6 months, using the Morris Water Maze. Significantly fewer BrdU-positive cells were detected in the hippocampal dentate gyrus in both isoflurane and desflurane-treated animals compared with controls at P7, but there were no changes in cell numbers after sevoflurane exposure. Cell counts for all three anesthetics compared with controls were equivalent at P14. Isoflurane or desflurane exposure yielded slight differences in the behavioral tests at 6 weeks, but no differences at 6 months post-exposure. We conclude that a single 2-h exposure at P2 to either isoflurane or desflurane causes a transient disruption of hippocampal neuronal development with no significant detectable long-term effects on learning and memory, whereas the same exposure to sevoflurane has no effects.

Pharmacologic preconditioning with berberine attenuating ischemia-induced apoptosis and promoting autophagy in neuron

Pharmacologic preconditioning is an intriguing and emerging approach adopted to prevent injury of ischemia/reperfusion. Neuroprotection is the cardinal effect of these pleiotropic actions of berberine. Here we investigated that whether berberine could acts as a preconditioning stimuli contributing to attenuate hypoxia-induced neurons death as well. Male Sprague-Dawley rats of middle cerebral artery occlusion (MCAO) and rat primary cortical neurons undergoing oxygen and glucose deprivation (OGD) were preconditioned with berberine (40 mg/kg, for 24 h in vivo, and 10(-6) mol/L, for 2 h in vitro, respectively). The neurological deficits and cerebral water contents of MCAO rats were evaluated. The autophagy and apoptosis were further determined in primary neurons in vitro. Berberine preconditioning (BP) was then shown to ameliorate the neurological deficits, decrease cerebral water content and promote neurogenesis of MCAO rats. Decreased LDH release from OGD-treated neurons was observed via BP, which was blocked by LY294002 (20 µmol/L), GSK690693 (10 µmol/L), or YC-1 (25 µmol/L). Furthermore, BP stimulated autophagy and inhibited apoptosis via modulated the autophagy-associated proteins LC 3, Beclin-1 and p62, and apoptosis-modulating proteins caspase 3, caspase 8, caspase 9, PARP and BCL-2/Bax. In conclusion, berberine acts as a stimulus of preconditioning that exhibits neuroprotection via promoting autophagy and decreasing anoxia-induced apoptosis.