Hypoxia inducible factor-1α is involved in the neurodegeneration induced by isoflurane in the brain of neonatal rats

Sevoflurane Postconditioning Protects From an Early Neurological Deficit After Subarachnoid Hemorrhage: Results of a Randomized Laboratory Study in Rats

BACKGROUND

Subarachnoid hemorrhage (SAH) is associated with neurocognitive impairment. Recent data suggest that sevoflurane attenuates edema formation after SAH in rats. However, so far, no information is available about the long-term repair phase, nor if sevoflurane impacts functionality by increasing vascularity. This study tested whether sevoflurane postconditioning would improve long-term neurologic deficit through increased formation of new vessels close to the hemorrhage area.

METHODS

Fifty-three animals were subjected to SAH or sham surgery with or without a 2-hour sevoflurane postconditioning (versus propofol anesthesia). Animal survival, including dropout animals due to death or reaching termination criteria, as well as neurologic deficit, defined by the Garcia score, were assessed 2 hours after recovery until postoperative day 14. On day 14, blood samples and brain tissue were harvested. Vessel density was determined by the number of cluster of differentiation 31 (CD31)-positive vessels, and activated glial cells by glial fibrillary acidic protein (GFAP)-positive astrocytes per field of view.

RESULTS

The survival rate for sham animals was 100%, 69% in the SAH-propofol and 92% in the SAH-sevoflurane groups. According to the log-rank Mantel-Cox test, survival curves were significantly different (P = .024). The short-term neurologic deficit was higher in SAH-propofol versus SAH-sevoflurane animals 2 hours after recovery and on postoperative day 1 (propofol versus sevoflurane: 14. 6 ± 3.4 vs 15. 9 ± 2.7 points, P = .034, and 16. 2 ± 3.5 vs 17. 8 ± 0.9 points, P = .015). Overall complete recovery from neurologic deficit was observed on day 7 in both SAH groups (18. 0 ± 0.0 vs 18. 0 ± 0.0 points, P = 1.000). Cortical vascular density increased to 80. 6 ± 15.0 vessels per field of view in SAH-propofol animals (vs 71. 4 ± 10.1 in SAH-sevoflurane, P < .001). Activation of glial cells, an indicator of neuroinflammation, was assessed by GFAP-positive astrocytes GFAP per field of view. Hippocampal GFAP-positive cells were 201 ± 68 vs 179 ± 84 cells per field of view in SAH-propofol versus SAH-sevoflurane animals (P < .001).

CONCLUSIONS

Sevoflurane postconditioning improves survival by 23% (SAH-sevoflurane versus SAH-propofol). The sevoflurane intervention could attenuate the early neurologic deficit, while the long-term outcome was similar across the groups. A higher vascular density close to the SAH area in the propofol group was not associated with improved outcomes.

Role of hypoxia-inducible factor in postoperative delirium of aged patients: A review

Postoperative delirium is common, especially in older patients. Delirium is associated with prolonged hospitalization, an increased risk of postoperative complications, and significant mortality. The mechanism of postoperative delirium is not yet clear. Cerebral desaturation occurred during the maintenance period of general anesthesia and was one of the independent risk factors for postoperative delirium, especially in the elderly. Hypoxia stimulates the expression of hypoxia-inducible factor-1 (HIF-1), which controls the hypoxic response. HIF-1 may have a protective role in regulating neuron apoptosis in neonatal hypoxia-ischemia brain damage and may promote the repair and rebuilding process in the brain that was damaged by hypoxia and ischemia. HIF-1 has a neuroprotective effect during cerebral hypoxia and controls the hypoxic response by regulating multiple pathways, such as glucose metabolism, angiogenesis, erythropoiesis, and cell survival. On the other hand, anesthetics have been reported to inhibit HIF activity in older patients. So, we speculate that HIF plays an important role in the pathophysiology of postoperative delirium in the elderly. The activity of HIF is reduced by anesthetics, leading to the inhibition of brain protection in a hypoxic state. This review summarizes the possible mechanism of HIF participating in postoperative delirium in elderly patients and provides ideas for finding targets to prevent or treat postoperative delirium in elderly patients.

Tetramethylpyrazine Attenuates Oxygen-glucose Deprivation-induced Neuronal Damage through Inhibition of the HIF-1α/BNIP3 Pathway: From Network Pharmacological Finding to Experimental Validation

AIMS

A network pharmacological analysis combined with experimental validation was used to investigate the neuroprotective mechanism of the natural product Tetramethylpyrazine(TMP).

BACKGROUND

Protecting neurons is critical for acute ischemic stroke treatment. Tetramethylpyrazine is a bioactive component extracted from Chuanxiong. The neuroprotective potential of TMP has been reported, but a systematic analysis of its mechanism has not been performed.

OBJECTIVE

Based on the hints of network pharmacology and bioinformatics analysis, the mechanism by which TMP alleviates oxygen-glucose deprivation-induced neuronal damage through inhibition of the HIF-1α/BNIP3 pathway was verified.

METHOD

In this study, we initially used network pharmacology and bioinformatics analyses to elucidate the mechanisms involved in TMP's predictive targets on a system level. The HIF-1α/BNIP3 pathway mediating the cellular response to hypoxia and apoptosis was considered worthy of focus in the bioinformatic analysis. An oxygen-glucose deprivation (OGD)-induced PC12 cell injury model was established for functional and mechanical validation. Cell viability, lactate dehydrogenase leakage, intracellular reactive oxygen species, percentage of apoptotic cells, and Caspase-3 activity were determined to assess the TMP's protective effects. Transfection with siRNA/HIF-1α or pcDNA/HIF-1α plasmids to silence or overexpress hypoxia-inducible factor 1α(HIF-1α). The role of HIF-1α in OGD-injured cells was observed first. After that, TMP's regulation of the HIF-1α/BNIP3 pathway was investigated. The pcDNA3.1/HIF-1α-positive plasmids were applied in rescue experiments.

RESULT

The results showed that TMP dose-dependently attenuated OGD-induced cell injury. The expression levels of HIF-1α, BNIP3, and the Bax/Bcl-2 increased significantly with increasing OGD duration. Overexpression of HIF-1α decreased cell viability, increased BNIP3 expression, and Bax/Bcl-2 ratio; siRNA-HIF-1α showed the opposite effect. TMP treatment suppressed HIF-1α, BNIP3 expression, and the Bax/Bcl-2 ratio and was reversed by HIF-1α overexpression.

CONCLUSION

Our study shows that TMP protects OGD-damaged PC12 cells by inhibiting the HIF-1α/BNIP3 pathway, which provides new insights into the mechanism of TMP and its neuroprotective potential.

MiR-21-5p but not miR-1-3p expression is modulated by preconditioning in a rat model of myocardial infarction

Isoflurane (Iso) preconditioning (PC) is known to be cardioprotective against ischemia/reperfusion (I/R) injury. It was previously shown that microRNA-21-5p (miR-21-5p) is regulated by Iso-PC. It is unclear, if expression of cardiac enriched miR-1-3p is also affected by Iso-PC, and associated with activation of HIF1α (hypoxia-inducible factor 1-alpha).  Male Wistar rats (n = 6–8) were randomly assigned to treatment with or without 1 MAC Iso for 30 min, followed by 25 min of regional myocardial ischemia, with 120 min reperfusion. At the end of reperfusion, myocardial expression of miR-1-3p, miR-21-5p and mRNAs of two HIF-1α-dependent genes, VEGF (vascular endothelial growth factor) and HO-1 (heme oxygenase-1), were determined by quantitative PCR. Protein expression of a miR-21 target gene, PDCD4 (programmed cell death protein 4), was assessed by western blot analysis. Infarct sizes were analyzed with triphenyltetrazoliumchloride staining. MiR-21-5p expression was increased by Iso, whereas expression of miR-1-3p was not altered. The expression of VEGF but not HO-1 was induced by Iso. Iso-PC reduced infarct sizes compared to untreated controls. No regulation of miRNA and mRNA expression was detected after I/R. PDCD4 protein expression was not affected after Iso exposure. Expression of miR-21-5p, in contrast to miR-1-3p, is altered during this early time point of Iso-PC. HIF1α signaling seems to be involved in miR-21-5p regulation.

Neddylation activity modulates the neurodegeneration associated with fragile X associated tremor/ataxia syndrome (FXTAS) through regulating Sima

Fragile X associated tremor/ataxia syndrome (FXTAS) is a late-onset neurodegenerative disorder caused by expansion of CGG repeats in the 5' UTR of the fragile X mental retardation 1 (FMR1) gene. Using the well-established FXTAS Drosophila model, we performed a high-throughput chemical screen using 3200 small molecules. NSC363998 was identified to suppress the neurodegeneration caused by riboCGG (rCGG) repeats. Three predicted targets of a NSC363998 derivative are isopeptidases in the neddylation pathway and could modulate the neurotoxicity caused by the rCGG repeats. Decreasing levels of neddylation resulted in enhancing neurodegeneration phenotypes, while up-regulation could rescue the phenotypes. Furthermore, known neddylation substrates, Cul3 and Vhl, and their downstream target, Sima, were found to modulate rCGG₉₀-dependent neurotoxicity. Our results suggest that altered neddylation activity can modulate the rCGG repeat-mediated toxicity by regulating Sima protein levels, which could serve as a potential therapeutic target for FXTAS.

Anaesthetic-dependent changes in gene expression following acute and chronic exposure in the rodent brain

Anaesthesia has been predicted to affect gene expression of the memory-related regions of the brain including the primary visual cortex. It is also believed that anaesthesia causes inflammation of neural tissues, increasing elderly patients' chances of developing precursor lesions that lead to Alzheimer's disease and other neurodegeneration related diseases. We have analyzed the expression of over 22,000 genes and 129,800 transcripts using oligonucleotide microarrays to examine the brain expression profiles in Sprague Dawley rats following exposure to acute or chronic doses of the anaesthetics isoflurane, ketamine and propofol. Here we report for the first time molecular and genomic data on the effect on the rodent brain of chronic and acute exposure to isoflurane, ketamine and propofol. Our screen identified multiple genes that responded to all three anaesthetics. Although some of the genes were previously known to be anaesthesia responsive, we have for the most part identified novel genes involved in the acute and chronic rodent brain response to different anaesthesia treatments. The latter may be useful candidate genes in the search to elucidate the molecular pathways mediating anaesthetic effects in the brain and may allow us to identify mechanisms by which anaesthetics could impact on neurodegeneration.

The genetics of isoflurane-induced developmental neurotoxicity

INTRODUCTION

Neurotoxicity induced by early developmental exposure to volatile anesthetics is a characteristic of organisms across a wide range of species, extending from the nematode C. elegans to mammals. Prevention of anesthetic-induced neurotoxicity (AIN) will rely upon an understanding of its underlying mechanisms. However, no forward genetic screens have been undertaken to identify the critical pathways affected in AIN. By characterizing such pathways, we may identify mechanisms to eliminate isoflurane induced AIN in mammals.

METHODS

Chemotaxis in adult C. elegans after larval exposure to isoflurane was used to measure AIN. We initially compared changes in chemotaxis indices between classical mutants known to affect nervous system development adding mutants in response to data. Activation of specific genes was visualized using fluorescent markers. Animals were then treated with rapamycin or preconditioned with isoflurane to test effects on AIN.

RESULTS

Forty-four mutations, as well as pharmacologic manipulations, identified two pathways, highly conserved from invertebrates to humans, that regulate AIN in C. elegans. Activation of one stress-protective pathway (DAF-2 dependent) eliminates AIN, while activation of a second stress-responsive pathway (endoplasmic reticulum (ER) associated stress) causes AIN. Pharmacologic inhibition of the mechanistic Target of Rapamycin (mTOR) blocks ER-stress and AIN. Preconditioning with isoflurane prior to larval exposure also inhibited AIN.

DISCUSSION

Our data are best explained by a model in which isoflurane acutely inhibits mitochondrial function causing activation of responses that ultimately lead to ER-stress. The neurotoxic effect of isoflurane can be completely prevented by manipulations at multiple points in the pathways that control this response. Endogenous signaling pathways can be recruited to protect organisms from the neurotoxic effects of isoflurane.

Quinolinic acid induces cell apoptosis in PC12 cells through HIF-1-dependent RTP801 activation

Neurological disease comprises a series of disorders featuring brain dysfunction and neuronal cell death. Among the factors contributing to neuronal death, excitotoxicity induced by excitatory amino acids, such as glutamate, plays a critical role. However, the mechanisms about how the excitatory amino acids induce neuronal death remain elucidated. In this study, we investigated the role of HIF-1α (hypoxia inducible factor-1α) and RTP801 in cell apoptosis induced by quinolinic acid (QUIN), a glutamatergic agonist, in PC12 cells. We found that QUIN at 5 μM increased the expression of HIF-1α significantly with a peak at 24 h. After the treatment with QUIN (5-20 μM) for 24 h, the cells exhibited decreased viability and cell apoptosis with a concomitant increased expression of apoptosis related proteins. QUIN treatment also induced the generation of intracellular reactive oxygen species and RTP801 up-regulation in a HIF-1α-dependent manner that were inhibited by 2-methoxyestradiol, a HIF-1α inhibitor. Importantly, HIF-1 or RTP801 invalidation by siRNA rescued the cell apoptosis induced by QUIN or cobalt chloride, a chemical inducer of HIF-1. Taken together, these findings support the concept that neurotoxicity induced by QUIN is associated with HIF-1-dependent RTP801 activation and provide insight into the potential of RTP801 inhibitor in treatment of neurological disorders.

Neuronal apoptosis may not contribute to the long-term cognitive dysfunction induced by a brief exposure to 2% sevoflurane in developing rats

BACKGROUND

Sevoflurane is an inhaled anesthetic commonly used in the pediatric. Recent animal studies suggest that early exposure to high concentration of sevoflurane for a long duration can induce neuroapoptosis and later cognitive dysfunction. However, the neurodevelopmental impact induced by lower concentration and shorter exposure duration of sevoflurane is unclear. To investigate whether early exposure to 2% concentration of sevoflurane for a short duration (clinically relevant usage of sevoflurane) can also induce neuroapoptosis and later cognitive dysfunction.

METHODS

Rat pups were subjected to control group, 2% sevoflurane for 3h and 3% sevoflurane for 6h. TUNEL assay and apoptotic enzyme cleaved caspase-3 measured by western blot were used for detection of neuronal apoptosis in frontal cortex and CA1 region of hippocampus 24 after sevoflurane treatment. Long-term cognitive function was evaluated by Morris water maze and passive avoidance test as the rats grew up.

RESULTS

The apoptotic levels in frontal cortex and CA1 region were significantly increased after rats exposed to 3% sevoflurane for 6h (P<0.05), but not 2% sevoflurane for 3h (P>0.05). Exposure to both 2% sevoflurane for 3h and 3% sevoflurane for 6h could cause long-term cognitive dysfunction and animals exposed to 3% sevoflurane for 6h exhibited worse neurodevelopmental outcomes (P<0.05).

CONCLUSION

It was suggested that neuronal apoptosis might not contribute to long-term cognitive dysfunction induced by 2% concentration and short exposure time of sevoflurane. Our findings also suggested that the mechanisms of sevoflurane-induced neurodevelopmental impact might be various, depending on the concentration and exposure duration.

The Role of Cdk5 in Alzheimer's Disease

Alzheimer's disease (AD) is known as the most fatal chronic neurodegenerative disease in adults along with progressive loss of memory and other cognitive function disorders. Cyclin-dependent kinase 5 (Cdk5), a unique member of the cyclin-dependent kinases (Cdks), is reported to intimately associate with the process of the pathogenesis of AD. Cdk5 is of vital importance in the development of CNS and neuron movements such as neuronal migration and differentiation, synaptic functions, and memory consolidation. However, when neurons suffer from pathological stimuli, Cdk5 activity becomes hyperactive and causes aberrant hyperphosphorylation of various substrates of Cdk5 like amyloid precursor protein (APP), tau and neurofilament, resulting in neurodegenerative diseases like AD. Deregulation of Cdk5 contributes to an array of pathological events in AD, ranging from formation of senile plaques and neurofibrillary tangles, synaptic damage, mitochondrial dysfunction to cell cycle reactivation as well as neuronal cell apoptosis. More importantly, an inhibition of Cdk5 activity with inhibitors such as RNA inference (RNAi) could protect from memory decline and neuronal cell loss through suppressing β-amyloid (Aβ)-induced neurotoxicity and tauopathies. This review will briefly describe the above-mentioned possible roles of Cdk5 in the physiological and pathological mechanisms of AD, further discussing recent advances and challenges in Cdk5 as a therapeutic target.

Toxic and protective effects of inhaled anaesthetics on the developing animal brain: systematic review and update of recent experimental work

BACKGROUND

Accumulating preclinical data indicate that neonatal exposure to general anaesthetics is detrimental to the central nervous system. Some studies, however, display potential protective effects of exactly the same anaesthetic agents on the immature brain. The effects of inhaled anaesthetics on the developing brain have received close attention from researchers, clinicians and the public in recent decades.

OBJECTIVES

To summarise the preclinical evidence reported in the last 5 years on both the deleterious effects and the neuroprotective potential in special indications, of inhaled anaesthetics on the developing brain.

DESIGN

A systematic review.

DATA SOURCES

PubMed search performed in June 2013.

ELIGIBILITY CRITERIA

Search terms included brain, development, inhaled anaesthetic, toxicity and protection within the scope of the last 5 years with animals. The reference lists of relevant articles and recent reviews were also hand-searched for additional studies. The type, dose and exposure duration of anaesthetics, species and age of animals, histopathologic indicators, outcomes and affected brain areas, neuro developmental test modules and outcomes, as well as other outcomes and comments were summarised.

RESULTS

Two hundred and nineteen relevant titles were initially revealed. In total, 81 articles were identified, with 68 articles assessing the detrimental effects induced by inhaled anaesthetics in the immature brain along with possible treatments. The remaining 13 articles focused on the protective profile of inhaled anaesthetics on perinatal hypoxic-ischaemic brain injury. Administration of inhaled anaesthetic agents to the immature brain was shown to be deleterious in several preclinical studies. In perinatal hypoxic-ischaemic brain injury models, pre- and postconditioning of inhalational anaesthetics exerted neuroprotective effects.

CONCLUSION

The majority of studies have linked inhaled anaesthetics to toxic effects in the neonatal brain of rodents, piglets and primates. Only a few studies, however, could demonstrate long-lasting cognitive impairment. The results of inhalational anaesthetic-induced neuroprotection in perinatal hypoxic-ischaemic brain injury are a promising basis for more research in this field. In general, prospective clinical trials are needed to further differentiate the effects of inhaled anaesthetics on the immature brain.

Neurodevelopmental implications of the general anesthesia in neonate and infants

Each year, about six million children, including 1.5 million infants, in the United States undergo surgery with general anesthesia, often requiring repeated exposures. However, a crucial question remains of whether neonatal anesthetics are safe for the developing central nervous system (CNS). General anesthesia encompasses the administration of agents that induce analgesic, sedative, and muscle relaxant effects. Although the mechanisms of action of general anesthetics are still not completely understood, recent data have suggested that anesthetics primarily modulate two major neurotransmitter receptor groups, either by inhibiting N-methyl-D-aspartate (NMDA) receptors, or conversely by activating γ-aminobutyric acid (GABA) receptors. Both of these mechanisms result in the same effect of inhibiting excitatory activity of neurons. In developing brains, which are more sensitive to disruptions in activity-dependent plasticity, this transient inhibition may have longterm neurodevelopmental consequences. Accumulating reports from preclinical studies show that anesthetics in neonates cause cellular toxicity including apoptosis and neurodegeneration in the developing brain. Importantly, animal and clinical studies indicate that exposure to general anesthetics may affect CNS development, resulting in long-lasting cognitive and behavioral deficiencies, such as learning and memory deficits, as well as abnormalities in social memory and social activity. While the casual relationship between cellular toxicity and neurological impairments is still not clear, recent reports in animal experiments showed that anesthetics in neonates can affect neurogenesis, which could be a possible mechanism underlying the chronic effect of anesthetics. Understanding the cellular and molecular mechanisms of anesthetic effects will help to define the scope of the problem in humans and may lead to preventive and therapeutic strategies. Therefore, in this review, we summarize the current evidence on neonatal anesthetic effects in the developmental CNS and discuss how factors influencing these processes can be translated into new therapeutic strategies.

Inhibition of aberrant cyclin-dependent kinase 5 activity attenuates isoflurane neurotoxicity in the developing brain

Aberrant CDK5 activity is implicated in a number of neurodegenerative disorders. Isoflurane exposure leads to neuronal apoptosis, and subsequent learning and memory defects in the developing brain. The present study was designed to examine whether and how CDK5 activity plays a role in developmental isoflurane neurotoxicity. Rat pups and hippocampal neuronal cultures were exposed to 1.5% isoflurane for 4 h. The protein and mRNA levels of CDK5, p35 and p25 were detected by western blot and QReal-Time PCR. CDK5 activity was evaluated in vitro using Histone H1 as a substrate. Roscovitine (an inhibitor of CDK5) was applied before isoflurane treatment, cleaved Caspase-3, Bcl-2, Bax, MEF2 and phospho-MEF2A-Ser-408 expressions were determined. Dominant-Negative CDK5 was transfected before isoflurane treatment. Neuronal apoptosis was evaluated by Flow cytometry (FCM) and TUNEL-staining. Cognitive functions were assessed by Morris water maze. We found that isoflurane treatment led to an aberrant CDK5 activation due to its activator p25 that was cleaved from p35 by calpain. Inhibition of CDK5 activity with Roscovitine enhanced Bcl-2, and decreased cleaved Caspase-3 and Bax expressions. In addition, isoflurane exposure resulted in a decrease of MEF2 and increase of phospho-MEF2A-Ser-408, which were rescued by Roscovitine or Dominant-Negative CDK5 transfection. Dominant-Negative CDK5 transfection also decreased the percentage of TUNEL-positive cells in isoflurane neurotoxicity. Moreover, Roscovitine remarkably alleviated the learning and memory deficits induced by postnatal isoflurane exposure. These results indicated that aberrant CDK5 activity-dependent MEF2 phosphorylation mediates developmental isoflurane neurotoxicity. Inhibition of CDK5 overactivation contributes to the relief of isoflurane neurotoxicity in the developing brain.

The volatile anesthetic isoflurane induces ecto-5'-nucleotidase (CD73) to protect against renal ischemia and reperfusion injury

The volatile anesthetic isoflurane protects against renal ischemia and reperfusion injury by releasing renal tubular TGF-β1. Since adenosine is a powerful cytoprotective molecule, we tested whether TGF-β1 generated by isoflurane induces renal tubular ecto-5′-nucleotidase (CD73) and adenosine to protect against renal ischemia and reperfusion injury. Isoflurane induced new CD73 synthesis and increased adenosine generation in cultured kidney proximal tubule cells and in mouse kidney. Moreover, a TGF-β1 neutralizing antibody prevented isoflurane-mediated induction of CD73 activity. Mice anesthetized with isoflurane after renal ischemia and reperfusion had significantly reduced plasma creatinine and decreased renal tubular necrosis, neutrophil infiltration and apoptosis compared to pentobarbital-anesthetized mice. Isoflurane failed to protect against renal ischemia and reperfusion injury in CD73 deficient mice, in mice pretreated with a selective CD73 inhibitor or mice treated with an adenosine receptor antagonist. The TGF-β1 neutralizing antibody or the CD73 inhibitor attenuated isoflurane-mediated protection against HK-2 cell apoptosis. Thus, isoflurane causes TGF-β1-dependent induction of renal tubular CD73 and adenosine generation to protect against renal ischemia and reperfusion injury. Modulation of this pathway may have important therapeutic implications to reduce morbidity and mortality arising from ischemic acute kidney injury.

Neuronal responses to physiological stress

Physiological stress can be defined as any external or internal condition that challenges the homeostasis of a cell or an organism. It can be divided into three different aspects: environmental stress, intrinsic developmental stress, and aging. Throughout life all living organisms are challenged by changes in the environment. Fluctuations in oxygen levels, temperature, and redox state for example, trigger molecular events that enable an organism to adapt, survive, and reproduce. In addition to external stressors, organisms experience stress associated with morphogenesis and changes in inner chemistry during normal development. For example, conditions such as intrinsic hypoxia and oxidative stress, due to an increase in tissue mass, have to be confronted by developing embryos in order to complete their development. Finally, organisms face the challenge of stochastic accumulation of molecular damage during aging that results in decline and eventual death. Studies have shown that the nervous system plays a pivotal role in responding to stress. Neurons not only receive and process information from the environment but also actively respond to various stresses to promote survival. These responses include changes in the expression of molecules such as transcription factors and microRNAs that regulate stress resistance and adaptation. Moreover, both intrinsic and extrinsic stresses have a tremendous impact on neuronal development and maintenance with implications in many diseases. Here, we review the responses of neurons to various physiological stressors at the molecular and cellular level.

Mechanistic insights into neurotoxicity induced by anesthetics in the developing brain

Compelling evidence has shown that exposure to anesthetics used in the clinic can cause neurodegeneration in the mammalian developing brain, but the basis of this is not clear. Neurotoxicity induced by exposure to anesthestics in early life involves neuroapoptosis and impairment of neurodevelopmental processes such as neurogenesis, synaptogenesis and immature glial development. These effects may subsequently contribute to behavior abnormalities in later life. In this paper, we reviewed the possible mechanisms of anesthetic-induced neurotoxicity based on new in vitro and in vivo findings. Also, we discussed ways to protect against anesthetic-induced neurotoxicity and their implications for exploring cellular and molecular mechanisms of neuroprotection. These findings help in improving our understanding of developmental neurotoxicology and in avoiding adverse neurological outcomes in anesthesia practice.

Anesthetic neurotoxicity

Concerns for toxic effects of anesthesia to the brains of the young and the elderly are mounting. While experimental evidence for such effects in the developing brain is strong, the underlying mechanisms are less well understood and debate continues as to whether young humans are at risk for anesthetic neurotoxicity. The phenomenon of postoperative cognitive deterioration in the elderly remains controversial. Time course, severity, and whether or not it persists long term are under debate. For both patient groups, today's evidence is not sufficient to guide change in clinical practice. Well-designed research is therefore imperative to tackle this critical issue.