Protective effect of acetyl-l-carnitine on propofol-induced toxicity in embryonic neural stem cells

DPPA2/4 Promote the Pluripotency and Proliferation of Bovine Extended Pluripotent Stem Cells by Upregulating the PI3K/AKT/GSK3β/β-Catenin Signaling Pathway

Developmental pluripotency-associated 2 (DPPA2) and DPPA4 are crucial transcription factors involved in maintaining pluripotency in humans and mice. However, the role of DPPA2/4 in bovine extended pluripotent stem cells (bEPSCs) has not been investigated. In this study, a subset of bEPSC-related differentially expressed genes (DEGs), including DPPA2 and DPPA4, was identified based on multiomics data (ATAC-seq and RNA-seq). Subsequent investigations revealed that double overexpression of DPPA2/4 facilitates the reprogramming of bovine fetal fibroblasts (BFFs) into bEPSCs, whereas knockout of DPPA2/4 in BFFs leads to inefficient reprogramming. DPPA2/4 overexpression and knockdown experiments revealed that the pluripotency and proliferation capability of bEPSCs were maintained by promoting the transition from the G1 phase to the S phase of the cell cycle. By activating the PI3K/AKT/GSK3β/β-catenin pathway in bEPSCs, DPPA2/4 can increase the nuclear accumulation of β-catenin, which further upregulates lymphoid enhancer binding factor 1 (LEF1) transcription factor activity. Moreover, DPPA2/4 can also regulate the expression of LEF1 by directly binding to its promoter region. Overall, our results demonstrate that DPPA2/4 promote the reprogramming of BFFs into bEPSCs while also maintaining the pluripotency and proliferation capability of bEPSCs by regulating the PI3K/AKT/GSK3β/β-catenin pathway and subsequently activating LEF1. These findings expand our understanding of the gene regulatory network involved in bEPSC pluripotency.

Electroacupuncture Pretreatment Attenuates Learning Memory Impairment Induced by Repeated Propofol Exposure and Modulates Hippocampal Synaptic Plasticity in Rats

Background

Recurrent propofol anesthesia in the peak of neurodevelopment may lead to learning-memory decline. This study aimed to examine the efficacy of electroacupuncture pretreatment in ameliorating the aforementioned learning memory deficits and to explore its underlying mechanisms in a rat model of repeated propofol exposure.

Methods

10-day-old Sprague Dawley rats were randomly assigned to five groups: the control, fat emulsion, propofol, electroacupuncture pretreatment and electroacupuncture pretreatment combined with propofol groups. The electroacupuncture pretreatment involved three consecutive daily sessions, while propofol was received intraperitoneally once daily for five days. Following the modeling period, the rats' learning-memory performance was assessed using the New Novel Arm Y-maze, New Object Recognition, and Morris Water Maze. The Nissl staining method was used to observe the development of hippocampal neurons, while Golgi staining was employed to observe hippocampal synaptic development.

Results

The electroacupuncture pretreatment significantly attenuated the learning and memory impairment induced by recurring propofol exposure in rats. Additionally, it facilitated the development of hippocampal neurons and synaptic plasticity in the hippocampus. Immunofluorescence and Western Blot analyses were conducted to detect the expression of proteins related to apoptosis, learning memory, and synaptic plasticity. In the propofol group, the pro-apoptotic factors Caspase-3 and Bax was up-regulated, while the anti-apoptotic factor Bcl-2 was down-regulated, as compared to the blank group. Additionally, the phosphorylated cAMP-response element binding protein (pCREB), brain-derived neurotrophic factor (BDNF), synaptophysin, and growth associated protein-43 (GAP-43) was significantly decreased. In contrast, the electroacupuncture pretreatment combined with propofol group exhibited decreased the Caspase-3 and Bax and increased the Bcl-2, as compared to the propofol group, meanwhile, the pCREB, BDNF, Synaptophysin and GAP-43 was increased.

Conclusion

Our findings indicate that electroacupuncture pretreatment can alleviate the learning and memory impairment induced by recurring propofol exposure in rats. This is achieved by enhancing hippocampal synaptic plasticity, activating the pCREB/BDNF pathway and inhibiting neuronal apoptosis.

The effects of general anesthetics on mitochondrial structure and function in the developing brain

The use of general anesthetics in modern clinical practice is commonly regarded as safe for healthy individuals, but exposures at the extreme ends of the age spectrum have been linked to chronic cognitive impairments and persistent functional and structural alterations to the nervous system. The accumulation of evidence at both the epidemiological and experimental level prompted the addition of a warning label to inhaled anesthetics by the Food and Drug Administration cautioning their use in children under 3  years of age. Though the mechanism by which anesthetics may induce these detrimental changes remains to be fully elucidated, increasing evidence implicates mitochondria as a potential primary target of anesthetic damage, meditating many of the associated neurotoxic effects. Along with their commonly cited role in energy production via oxidative phosphorylation, mitochondria also play a central role in other critical cellular processes including calcium buffering, cell death pathways, and metabolite synthesis. In addition to meeting their immense energy demands, neurons are particularly dependent on the proper function and spatial organization of mitochondria to mediate specialized functions including neurotransmitter trafficking and release. Mitochondrial dependence is further highlighted in the developing brain, requiring spatiotemporally complex and metabolically expensive processes such as neurogenesis, synaptogenesis, and synaptic pruning, making the consequence of functional alterations potentially impactful. To this end, we explore and summarize the current mechanistic understanding of the effects of anesthetic exposure on mitochondria in the developing nervous system. We will specifically focus on the impact of anesthetic agents on mitochondrial dynamics, apoptosis, bioenergetics, stress pathways, and redox homeostasis. In addition, we will highlight critical knowledge gaps, pertinent challenges, and potential therapeutic targets warranting future exploration to guide mechanistic and outcomes research.

Establishment of neural stem cells from fetal monkey brain for neurotoxicity testing

Neurotoxicity assessments are generally performed using laboratory animals. However, as in vitro neurotoxicity models are continuously refined to reach adequate predicative concordance with in vivo responses, they are increasingly used for some endpoints of neurotoxicity. In this study, gestational day 80 fetal rhesus monkey brain tissue was obtained for neural stem cells (NSCs) isolation. Cells from the entire hippocampus were harvested, mechanically dissociated, and cultured for proliferation and differentiation. Immunocytochemical staining and biological assays demonstrated that the harvested hippocampal cells exhibited typical NSC phenotypes in vitro: (1) cells proliferated vigorously and expressed NSC markers nestin and sex-determining region Y-box 2 (SOX2) and (2) cells differentiated into neurons, astrocytes, and oligodendrocytes, as confirmed by positive staining with class III β-tubulin, glial fibrillary acidic protein, and galactocerebroside, respectively. The NSC produced detectable responses following neurotoxicant exposures (e.g. trimethyltin and 3-nitropropionic acid). Our results indicated that non-human primate NSCs may be a practical tool to study the biology of neural cells and to evaluate the neurotoxicity of chemicals in vitro, thereby providing data that are translatable to humans and may also reduce the number of animals needed for developmental neurotoxicological studies.

Propofol-Induced Developmental Neurotoxicity: From Mechanisms to Therapeutic Strategies

Propofol is the most commonly used intravenous general anesthetic in clinical anesthesia, and it is also widely used in general anesthesia for pregnant women and infants. Some clinical and preclinical studies have found that propofol causes damage to the immature nervous system, which may lead to neurodevelopmental disorders and cognitive dysfunction in infants and children. However, its potential molecular mechanism has not been fully elucidated. Recent in vivo and in vitro studies have found that some exogenous drugs and interventions can effectively alleviate propofol-induced neurotoxicity. In this review, we focus on the relevant preclinical studies and summarize the latest findings on the potential mechanisms and therapeutic strategies of propofol-induced developmental neurotoxicity.

Multiple mediation effects on association between prenatal triclosan exposure and birth outcomes

BACKGROUND

Triclosan is a broad-spectrum antimicrobial, and was thought to affect intrauterine development, but the mechanism remains unclear.

OBJECTIVE

To explore the association between prenatal triclosan exposure and birth outcomes.

METHODS

Based on 726 mother-child pairs from the Sheyang Mini Birth Cohort Study (SMBCS), we used the available (published) data of triclosan in maternal urines, the hormones including thyroid-related hormones, gonadal hormones in cord blood, and adipokines, trimethylamine-N-oxide (TMAO) and its precursors in cord blood to explore possible health effects of triclosan on birth outcomes through assessing different hormones and parameters, using Bayesian mediation analysis.

RESULTS

Maternal triclosan exposure was associated with ponderal index (β = 0.317) and head circumference (β = -0.172) in generalized linear models. In Bayesian mediation analysis of PI model, estradiol (β = 0.806) and trimethylamine (TMA, β = 0.164) showed positive mediation effects, while total thyroxine (TT4, β = -0.302), leptin (β = -2.023) and TMAO (β = -0.110) showed negative mediation effects. As for model of head circumference, positive mediation effects were observed in free thyroxine (FT4, β = 0.493), TMA (β = 0.178), and TMAO (β = 0.683), negative mediation effects were observed in TT4 (β = -0.231), testosterone (β = -0.331), estradiol (β = -1.153), leptin (β = -2.361), choline (β = -0.169), betaine (β = -0.104), acetyl-L-carnitine (β = -0.773).

CONCLUSION

The results indicated triclosan can affect intrauterine growth by interfering thyroid-related hormones, gonadal hormones, adipokines, TMAO and its precursors.

Effect of preconditioning on propofol-induced neurotoxicity during the developmental period

At therapeutic concentrations, propofol (PPF), an anesthetic agent, significantly elevates intracellular calcium concentration ([Ca2 +]i) and induces neural death during the developmental period. Preconditioning enables specialized tissues to tolerate major insults better compared with tissues that have already been exposed to sublethal insults. Here, we investigated whether the neurotoxicity induced by clinical concentrations of PPF could be alleviated by prior exposure to sublethal amounts of PPF. Cortical neurons from embryonic day (E) 17 Wistar rat fetuses were cultured in vitro, and on day in vitro (DIV) 2, the cells were preconditioned by exposure to PPF (PPF-PC) at either 100 nM or 1 μM for 24 h. For morphological observations, cells were exposed to clinical concentrations of PPF (10 μM or 100 μM) for 24 h and the survival ratio (SR) was calculated. Calcium imaging revealed significant PPF-induced [Ca2+]i elevation in cells on DIV 4 regardless of PPF-PC. Additionally, PPF-PC did not alleviate neural cell death induced by PPF under any condition. Our findings indicate that PPF-PC does not alleviate PPF-induced neurotoxicity during the developmental period.

Remimazolam induced cognitive dysfunction in mice via glutamate excitotoxicity

Objective

Several lines of evidence demonstrated the role of anesthetic drugs in cognitive functions. Some anesthetic agents have been confirmed to be associated with long-term spatial memory and learning in aged animal models.

Methods

C57BL/6 mice were divided into four different groups based on different concentrations of remimazolam treatments. Behavioral phenotype was observed by open field, rota rod, Morris water maze, and elevated plus maze test. Western blot was performed to see the expression pattern of different proteins. Confocal microscopy images were taken for neuronal and glial cells to see the effect of remimazolam on CNS cells.

Results

We showed that remimazolam, a new anesthetic drug, impaired cognitive behavior. Repetitive doses of remimazolam have been found to induce neuronal loss with a significant change in morphology. Here, we showed that a higher concentration of remimazolam had a significant effect on CNS cell activation. We showed that remimazolam caused memory dysfunction by inducing neuronal apoptosis via glutamate excitotoxicity. It also exhibited amyloid β plaque in the brain via abnormal phosphorylation of tau protein. Remimazolam-mediated regulation of glial cells in mouse cortex was observed and robust activation of astrocytes and microglial cells was found. Finally, we assessed the behavioral phenotype of mice and found that treatment with remimazolam induced significant behavioral changes and memory dysfunction.

Conclusions

This study provides insight into the mechanism of anesthetic drug-induced memory deficits and may help improve the therapeutic effects of anesthesia agents in clinical applications.

Application of Nonhuman Primate Models in the Studies of Pediatric Anesthesia Neurotoxicity

Numerous animal models have been used to study developmental neurotoxicity associated with short-term or prolonged exposure of common general anesthetics at clinically relevant concentrations. Pediatric anesthesia models using the nonhuman primate (NHP) may more accurately reflect the human condition because of their phylogenetic similarity to humans with regard to reproduction, development, neuroanatomy, and cognition. Although they are not as widely used as other animal models, the contribution of NHP models in the study of anesthetic-induced developmental neurotoxicity has been essential. In this review, we discuss how neonatal NHP animals have been used for modeling pediatric anesthetic exposure; how NHPs have addressed key data gaps and application of the NHP model for the studies of general anesthetic-induced developmental neurotoxicity. The appropriate application and evaluation of the NHP model in the study of general anesthetic-induced developmental neurotoxicity have played a key role in enhancing the understanding and awareness of the potential neurotoxicity associated with pediatric general anesthetics.

Dexmedetomidine attenuates propofol-induced apoptosis of neonatal hippocampal astrocytes by inhibiting the Bcl2l1 signalling pathway

Apoptosis shapes brain structure and function during early life. However, aberrant apoptosis, including that associated with the general anaesthetic propofol, is undesirable. Dexmedetomidine (DEX) provides potential neuroprotection against apoptosis, but the underlying mechanism remains unknown. We exposed neonatal rodent hippocampal astrocytes to propofol alone and in combination with DEX and yohimbine (an α₂ -adrenergic receptor antagonist), then evaluated cell viability using the MTT assay. The underlying regulatory mechanism associated with apoptosis-related genes was detected using a combinational strategy including double immunofluorescent staining, real-time reverse transcription polymerase chain reaction (RT-PCR), western blot, and flow cytometry. Propofol reduced matrix metallopeptidase 9 (MMP9) in cultured astrocytes, and activated the rno-miR-665/Bcl2-like 1 (Bcl2l1)/cleaved caspase 9 (CC9)/cleaved caspase 3 (CC3) pathway. Combinations incorporating propofol with A-1155463 (a selective Bcl2l1 inhibitor) or MMP9 antagomir reduced Bcl2l1 and promoted apoptosis. Co-culture of propofol with Bcl2l1 or with MMP9 agomir was sufficient to decrease the pro-apoptotic effects of propofol. Interestingly, DEX alone had no significant effect on apoptosis. When combined with propofol, however, the negative effects of propofol on the MMP9 and apoptosis-related genes (Bcl2l1, CC9, and CC3) were reduced. Furthermore, yohimbine pretreatment blocked the neuroprotective effects of DEX. Rno-miR-665 was also found to reduce MMP9 expression in propofol-treated hippocampal astrocytes. Taken together, the results indicate that DEX pretreatment reduces propofol-associated pro-apoptosis in developing astrocytes via downregulation of anti-apoptotic signalling mediated by Bcl2l1.

The Role of Pink1-Mediated Mitochondrial Pathway in Propofol-Induced Developmental Neurotoxicity

The mechanisms underlying propofol-induced toxicity in developing neurons are still unclear. The aim of present study was to explore the role of Pink1 mediated mitochondria pathway in propofol-induced developmental neurotoxicity. The primary Neural Stem Cells (NSCs) were isolated from the hippocampus of E15.5 mice embryos and then treated with propofol. The effects of propofol on proliferation, differentiation, apoptosis, mitochondria ultrastructure and MMP of NSCs were investigated. In addition, the abundance of Pink1 and a group of mitochondria related proteins in the cytoplasm and/or mitochondria were investigated, which mainly included CDK1, Drp1, Parkin1, DJ-1, Mfn1, Mfn2 and OPA1. Moreover, the relationship between Pink1 and these molecules was explored using gene silencing, or pretreatment with protein inhibitors. Finally, the NSCs were pretreated with mitochondrial specific antioxidant (MitoQ) or Drp1 inhibitor (Mdivi-1), and then the toxic effects of propofol on NSCs were investigated. Our results indicated that propofol treatment inhibited NSCs proliferation and division, and promoted NSCs apoptosis. Propofol induced significant NSCs mitochondria deformation, vacuolization and swelling, and decreased MMP. Additional studies showed that propofol affected a group of mitochondria related proteins via Pink1 inhibition, and CDK1, Drp1, Parkin1 and DJ-1 are the important downstream proteins of Pink1. Finally, the effects of propofol on proliferation, differentiation, apoptosis, mitochondrial ultrastructure and MMP of NSCs were significantly attenuated by MitoQ or Mdivi-1 pretreatment. The present study demonstrated that propofol regulates the proliferation, differentiation and apoptosis of NSCs via Pink1mediated mitochondria pathway.

Propofol Protects against Cerebral Ischemia/Reperfusion Injury by Down-Regulating Long Noncoding RNA SNHG14

Cerebral ischemia-reperfusion (CI/R) injury is a serious central nervous system disease. Propofol (PPF) exerts a neuroprotective effect in CI/R injury; the underlying cause is still unclear. Here, we cultured mouse hippocampal neuron (HT22 cells) in oxygen-glucose deprivation/reoxygenation (OGD/R) conditions to mimic CI/R injury in vitro. PPF treatment promoted cell viability and reduced apoptotic cells in the OGD/R-treated HT22 cells, which was effectively abrogated by SNHG14 overexpression. Moreover, we constructed a CI/R injury mouse model on C57BL/6J mice by middle cerebral artery occlusion/reperfusion (MCAO/R), followed by administration of PPF. PPF reduced neuronal damage and loss, enhanced glial cell hyperplasia, and ameliorated cerebral cortex tissue damage and brain infarct in MCAO/R-induced mice. SNHG14 overexpression aggravated MCAO/R-induced CI/R injury in mice. Furthermore, SNHG14 promoted the expression of Atg5 and Beclin 1 via competitively binding miR-30b-5p, which contributed to activate autophagy and apoptosis in HT22 cells. In addition, the levels of p-p38 and p-SP1 were reduced in the OGD/R-treated HT22 cells in the presence of PPF. SP1 interacted with the promoter of SNHG14 and elevated the expression of SNHG14. PPF treatment inhibited the SP1-mediated up-regulation of SNHG14. In conclusion, this work demonstrates that PPF inhibits SNHG14 expression though the p38 MAPK signaling pathway. SNHG14 promotes Atg5 and Beclin 1 expression by sponging miR-30b-5p and thus activates autophagy and aggravates CI/R injury.

Metabolomics analysis underlay mechanisms in the renal impairment of mice caused by combination of aflatoxin M1 and ochratoxin A

Aflatoxin M1 (AFM1) and ochratoxin A (OTA) are pernicious mycotoxins widely co-existing in the environment. However, nephrotoxicity and underlying mechanism induced by AFM1 coupled with OTA still remain to be explored. In this study, CD-1 mice were treated with 3.5 mg/kg b.w. AFM1, OTA, and AFM1 + OTA for 35 days, and UPLC-MS-based metabolomics method was effectuated to investigate metabolomic profiles of mice kidney. Subsequent experiments on human renal proximal tubular (HK-2) cells were performed to dig out the causal connections between distinguished differential metabolites and nephrotoxicity. Compared with DMSO vehicle group, all three toxin treatments (AFM1 and OTA alone, and in combination) significantly reduced final body weight, and remarkably elevated the concentration of serum creatinine (SCr) and caused abnormal histological phenotypes (shown by histopathological slices). OTA, AFM1 + OTA but not AFM1 reduced the relative weight index of kidney. These phenotypic results indicated that AFM1 and OTA were both toxic to the body, and it seemed that OTA exhibited a notable impairment to kidney while AFM1 had similar but limited effect compared with OTA. Further metabolomics analysis showed that when AFM1 and OTA were combined together, OTA exerted dominant effect on the alteration of metabolic processes. There were few differences in the number of changed metabolites between OTA and AFM1 + OTA group. Among the differentially expressed metabolites affected by OTA, and AFM1 + OTA, lysophosphatidylcholines (LysoPCs) were identified as the main type with significant upregulation, in which LysoPC (16:0) accounted for the most prime proportion. Western blotting results of HK-2 cells showed that single OTA and AFM1 + OTA increased the apoptotic protein expressions of Bax, caspase 3 and PARP, and decreased the expression of Bcl-2; while AFM1 only raised the expression of caspase 3. LysoPC (16:0) but not LysoPC (18:1) lifted the protein level of caspase 3 and PARP in HK-2 cells, and reduced the level of Bcl-2. Taken together, this study is the first effort trying to assess nephrotoxicity of AFM1 with OTA, and we guessed that OTA had a more pronounced toxicity to kidney in contrast to AFM1. No obvious synergism between AFM1 and OTA was found to contribute to the occurrence or development of nephropathy. LysoPC (16:0) might be the pivotal metabolite in response to single OTA and combined AFM1 + OTA engendering renal injury.

Febuxostat Prevents the Cytotoxicity of Propofol in Brain Endothelial Cells

Background and purpose: A high risk of brain injury has been reported with the usage of general anesthetics such as propofol in infants. Experimental data indicated that oxidative stress and inflammation are involved in the neurotoxicity induced by propofol. Febuxostat is a novel anti-gout agent recently reported to exert an anti-inflammatory effect. The present study aims to investigate the protective property of febuxostat against the cytotoxicity of propofol in brain endothelial cells as well as the underlying preliminary mechanism. Methods: The 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay was utilized to screen the optimized incubation concentration of febuxostat. bEnd.3 brain endothelial cells were stimulated with 2% propofol in the presence or absence of febuxostat (10, 20 μM) for 24 h. The lactate dehydrogenase (LDH) release assay was conducted to detect cytotoxicity. The reactive oxygen species (ROS) levels were evaluated using dichloro-dihydro-fluorescein diacetate (DCFH-DA) staining, and the concentration of reduced glutathione (GSH) was determined using a commercial kit. The expressions of TNF-α, IL-6, IL-12, CXCL-1, PDPN, CXCL8, VCAM-1, and E-selectin were determined using a quantitative real-time polymerase chain reaction (qRT-PCR) and an enzyme-linked immunosorbent assay (ELISA). Western blot and qRT-PCR were utilized to determine the expressions of COX-2 and KLF6. The production of PGE₂ was evaluated by ELISA. Results: First, increased LDH release induced by propofol was significantly suppressed by febuxostat. The oxidative stress (elevated ROS levels and decreased GSH level) induced by propofol was alleviated by febuxostat. Second, the upregulated inflammatory factors (TNF-α, IL-6, and IL-12), pro-inflammatory chemokines (CXCL-1, PDPN, and CXCL8), adhesion molecules (VCAM-1 and E-selectin), and inflammatory mediators (COX-2 and PGE₂) induced by propofol were greatly downregulated by febuxostat. Lastly, the expression of KLF6 was significantly suppressed by propofol but greatly elevated by febuxostat. Conclusion: Febuxostat prevented the cytotoxicity of propofol in brain endothelial cells by alleviating oxidative stress and inflammatory response through KLF6.

Protective Effects of Xenon on Propofol-Induced Neurotoxicity in Human Neural Stem Cell-Derived Models

Early life exposure to general anesthetics can have neurotoxic consequences. Evidence indicates that xenon, a rare noble gas with anesthetic properties, may lessen neuronal damage under certain conditions. However, its potential neuroprotective properties, when used alone or in combination with other anesthetics, remain largely unknown. While it is difficult to verify the adverse effects of long duration anesthetic exposure in infants and children, the utilization of relevant non-clinical models (i.e., human-derived neural stem cells) may serve as a "bridging" model for evaluating the vulnerability of the nervous system. Neural stem cells, purchased from PhoenixSongs Biologicals, Inc., were guided to differentiate into neurons, astrocytes, and oligodendrocytes, which were then exposed to propofol (50 μM) for 16 h in the presence or absence of xenon (33%). Differentiation into cells of the neural lineage was confirmed by labelling with cell-specific markers, β-tubulin for neurons, glial fibrillary acidic protein (GFAP) for astrocytes, and galactocerebroside (GALC) for oligodendrocytes after 5 days of differentiation. The presence and severity of neural damage induced by anesthetic exposures were assessed by several methods, including the TUNEL assay, and immuno-histochemical measurements. Our data demonstrate that prolonged exposure to propofol results in a significant increase in the number of TUNEL-positive cells, indicating increased neural apoptosis. No significant changes were detected in the number of GFAP-positive astrocytes or GALC-positive oligodendrocytes. However, the number of β-tubulin-positive neurons was substantially reduced in the propofol-exposed cultures. Co-administration of xenon effectively blocked the propofol-induced neuronal damage/loss. No significant effects were observed when xenon was administered alone. The data indicate that prolonged exposure to propofol during development produces elevated levels of neuronal apoptosis in a human neural stem cell-derived model. However, sub-clinical, non-anesthetic concentrations of xenon, when used in combination with propofol, can prevent or ameliorate the toxic effects associated with prolonged anesthetic exposure. This is important as a more complete understanding of the neurotoxic mechanisms associated with a variety of clinically relevant anesthetic combinations becomes available. Protective approaches are critical for developing sound guidance on best practices for the use of these agents in the pediatric setting.

Neuroprotection of the Developing Brain by Dexmedetomidine Is Mediated by Attenuating Single Propofol-induced Hippocampal Apoptosis and Synaptic Plasticity Deficits

Dexmedetomidine (DEX) has neuroprotective effects and its efficacy was determined in propofol-treated pups. Postnatal day (P) 7 rats were exposed to propofol and DEX to investigate the induced apoptosis-related gene expression. Furthermore, synaptic structural changes at the cellular level were observed by electron microscopy. Induction of hippocampal long-term potentiation (LTP) of P30 rats and long-lasting performance of spatial discrimination at P30 and P60 were evaluated. After a single propofol exposure to P7 rats, DEX pretreatment effectively rescued the profound apoptosis seen in hippocampal neurocytes, and strongly reversed the aberrant expression levels of Bcl2-like 1 (BCL2L1), matrix metallopeptidase 9 (MMP-9) and cleaved caspase 3 (CC3), and sharply enhanced synaptic plasticity. However, there were no significant differences in escape latency or crossing times in a probe test. This was accompanied by no obvious reduction in search strategies among the rat groups. No impairment of long-term learning and memory in P30 or P60 rats was detected when using a single dose propofol treatment during the most vulnerable period of brain development. DEX was shown to ameliorate the rodent developmental neurotoxicity caused by a single neonatal propofol challenge, by altering MMP-9, BCL2L1 and CC3 apoptotic signaling.

Research progress and treatment strategies for anesthetic neurotoxicity

Every year, a large number of infants and young children worldwide are administered general anesthesia. Whether general anesthesia adversely affects the intellectual development and cognitive function of children at a later date remains controversial. Many animal experiments have shown that general anesthetics can cause nerve damage during development, affect synaptic plasticity, and induce apoptosis, and finally affect learning and memory function in adulthood. The neurotoxicity of pediatric anesthetics (PAN) has received extensive attention in the field of anesthesia, which has been listed as a potential problem affecting public health by NFDA of the United States. Previous studies on rodents and non-human primates indicate that inhalation of anesthetics early after birth can induce long-term and sustained impairment of learning and memory function, as well as changes in brain function. Many anti-oxidant drugs, dexmedetomidine, as well as a rich living environment and exercise have been proven to reduce the neurotoxicity of anesthetics. In this paper, we summarize the research progress, molecular mechanisms and current intervention measures of anesthetic neurotoxicity.

Using l-Carnitine as a Pharmacologic Probe of the Interpatient and Metabolic Variability of Sepsis

OBJECTIVE

The objective of this review is to discuss the therapeutic use and differential treatment response to Levo-carnitine (l-carnitine) treatment in septic shock, and to demonstrate common lessons learned that are important to the advancement of precision medicine approaches to sepsis. We propose that significant interpatient variability in the metabolic response to l-carnitine and clinical outcomes can be used to elucidate the mechanistic underpinnings that contribute to sepsis heterogeneity.

METHODS

A narrative review was conducted that focused on explaining interpatient variability in l-carnitine treatment response. Relevant biological and patient-level characteristics considered include genetic, metabolic, and morphomic phenotypes; potential drug interactions; and pharmacokinetics (PKs).

MAIN RESULTS

Despite promising results in a phase I study, a recent phase II clinical trial of l-carnitine treatment in septic shock showed a nonsignificant reduction in mortality. However, l-carnitine treatment induces significant interpatient variability in l-carnitine and acylcarnitine concentrations over time. In particular, administration of l-carnitine induces a broad, dynamic range of serum concentrations and measured peak concentrations are associated with mortality. Applied systems pharmacology may explain variability in drug responsiveness by using patient characteristics to identify pretreatment phenotypes most likely to derive benefit from l-carnitine. Moreover, provocation of sepsis metabolism with l-carnitine offers a unique opportunity to identify metabolic response signatures associated with patient outcomes. These approaches can unmask latent metabolic pathways deranged in the sepsis syndrome and offer insight into the pathophysiology, progression, and heterogeneity of the disease.

CONCLUSIONS

The compiled evidence suggests there are several potential explanations for the variability in carnitine concentrations and clinical response to l-carnitine in septic shock. These serve as important confounders that should be considered in interpretation of l-carnitine clinical studies and broadly holds lessons for future clinical trial design in sepsis. Consideration of these factors is needed if precision medicine in sepsis is to be achieved.

Polymorphism in GSTM1 and GSTT1 genes influence DNA damage in personnel occupationally exposed to volatile anaesthetics (VA), from Peshawar, Pakistan

Objectives

The objective of this study was to assess the influence of antioxidant gene GSTM1 and GSTT1 on DNA damage in personnel occupationally exposed to volatile anaesthetics (VA).

Methods

The study groups were composed of 50 exposed subjects (anaesthesia workers) and 49 controls. Blood samples were collected from both subjects. DNA damage was analysed through the comet assay technique. Biomarker genes GSTM1 and GSTT1 were inspected through PCR technique for polymorphism.

Results

The comet assay technique showed that the Total Comet Score (TCS) in exposed subjects was significantly higher (p=0.0001) than the control. Age and smoking had significant effects on TCS in the study groups (p<0.05). Duration of occupational exposure had significant positive correlation (r=0.755, p<0.001) with DNA damage. The null polymorphism in GSTM1 and GSTT1 gene showed a significant effect (p<0.001 and p<0.000) on the DNA damage.

Conclusions

The polymorphism in GSTM1 and GSTT1 gene significantly damage DNA in personnel occupationally exposed to VA.

Acetyl-l-carnitine does not prevent neurodegeneration in a rodent model of prolonged neonatal anesthesia

Many studies have shown that prolonged or repeated use of general anesthesia early in life can cause an increase in neurodegeneration and lasting changes in behavior. While short periods of general anesthesia appear to be safe, there is a concern about the neurotoxic potential of prolonged or repeated general anesthesia in young children. Unfortunately, the use of general anesthesia in children cannot be avoided. It would be a great benefit to develop a strategy to reduce or reverse anesthesia mitigated neurotoxicity. The mechanisms behind anesthesia related neurotoxicity are unknown, but evidence suggests that mitochondrial dysfunction and abnormal energy utilization are involved. Recent research suggests that a class of compounds known as carnitines may be effective at preventing anesthesia related neurotoxicity by influencing fatty acid metabolism in the mitochondria. However, it is unknown if carnitines can provide protection against changes in behavior associated with early life exposure to anesthesia. Accordingly, we evaluated the neuroprotective potential of acetyl-l-carnitine in 7-day old rats. Rat pups were exposed to 6 h of general anesthesia with sevoflurane or a control condition, with and without acetyl-l-carnitine. The oxygenation level of animals was continuously monitored during sevoflurane exposure, and any animal showing signs of hypoxia was removed from the study. Animals exposed to sevoflurane showed clear signs of neurodegeneration 2 h after sevoflurane exposure. The hippocampus, cortex, thalamus, and caudate putamen all had elevated levels of Fluoro-Jade C staining. Despite the elevated levels of Fluoro-Jade C, few behavioral changes were observed in an independent cohort of animals treated with sevoflurane. Furthermore, acetyl-l-carnitine had little impact on levels of Fluoro-Jade C staining in animals treated with sevoflurane. These data suggest that acetyl-l-carnitine may offer little protection again anesthesia related neurotoxicity in fully oxygenated animals.

Propofol affects mouse embryonic fibroblast survival and proliferation in vitro via ATG5- and calcium-dependent regulation of autophagy

Propofol is a commonly used intravenous anesthetic agent, which has been found to affect cell survival and proliferation especially in early life. Our previous studies show that propofol-induced neurodegeneration and neurogenesis are closely associated with cell autophagy. In the present study we explored the roles of autophagy-related gene 5 (ATG5) in propofol-induced autophagy in mouse embryonic fibroblasts (MEF) in vitro. We showed that ATG5 was functionally related to propofol-induced cell survival and damage: propofol significantly enhanced cell survival and proliferation at a clinically relevant dose (10 µM), but caused cell death at an extremely high concentration (200 µM) in ATG5^−/− MEF, but not in WT cells. The dual effects found in ATG5^−/− MEF could be blocked by intracellular Ca²⁺ channel antagonists. We also found that propofol evoked a moderate (promote cell growth) and extremely high (cause apoptosis) cytosolic Ca²⁺ elevation at the concentrations of 10 µM and 200 µM, respectively, only in ATG5^−/− MEF. In addition, ATG5^−/− MEF themselves released more Ca²⁺ in cytosolic space and endoplasmic reticulum compared with WT cells, suggesting that autophagy deficiency made intracellular calcium signaling more vulnerable to external stimuli (propofol). Altogether, our results reveal that ATG5 plays a crucial role in propofol regulation of cell survival and proliferation by affecting intracellular Ca²⁺ homeostasis.

Effects of Xenon-Based Anesthetic Exposure on the Expression Levels of Polysialic Acid Neural Cell Adhesion Molecule (PSA-NCAM) on Human Neural Stem Cell-Derived Neurons

Numerous studies suggest a long duration of anesthesia during the late gestation period and infancy is associated with an increased risk of neuronal damage and neurocognitive impairment. The noble gas xenon is an anesthetic that is reported to have neuroprotective effects in some circumstances at certain concentrations. Currently, the effects of xenon on the brain and its potential neuroprotective properties, and/or the effects of xenon used in combination with other anesthetics, are not clearly understood and some reported data appear contradictory. In the present study, human neural stem cells were employed as a human-relevant model to evaluate the effects of xenon when it was co-administered with propofol, a frequently used anesthetic in pediatric anesthesia, and to understand the mechanism(s). The expression of polysialic acid (PSA) neural cell adhesion molecule (NCAM) on human neural stem cell-differentiated neurons was investigated as a key target molecule. PSA is a specific marker of developing neurons. It is essential for neuronal viability and plasticity. Human neural stem cells were maintained in neural differentiation medium and directed to differentiate into neuronal and glial lineages, and were exposed to propofol (50 μM) for 16 h in the presence or absence of xenon (33%). The neural stem cell-derived neurons were characterized by labelling cells with PSA-NCAM, after 5 days of differentiation. Propofol- and/or xenon-induced neurotoxicities were determined by measuring PSA immunoreactivity. A time course study showed that neuronal cell surface PSA was clearly cleaved off from NCAM by endoneuraminidase N (Endo-N), and eliminated PSA immunostaining was not re-expressed 4, 8, or 16 h after Endo-N washout. However, in the presence of 33% xenon, intense PSA staining on neuronal cell surface and processes was evident 16 h after Endo-N washout. In addition, prolonged (16 h) propofol exposure significantly decreased the positive rate of PSA-labeled neurons. When combined with xenon, propofol's adverse effects on neurons were attenuated. This work, conducted on the human neural stem cell-derived models, has provided evidence of the beneficiary effects of xenon on neurons and helps develop xenon-based anesthesia regimens in the pediatric population.

Anesthetics: from modes of action to unconsciousness and neurotoxicity

Modern anesthetic compounds and advanced monitoring tools have revolutionized the field of medicine, allowing for complex surgical procedures to occur safely and effectively. Faster induction times and quicker recovery periods of current anesthetic agents have also helped reduce health care costs significantly. Moreover, extensive research has allowed for a better understanding of anesthetic modes of action, thus facilitating the development of more effective and safer compounds. Notwithstanding the realization that anesthetics are a prerequisite to all surgical procedures, evidence is emerging to support the notion that exposure of the developing brain to certain anesthetics may impact future brain development and function. Whereas the data in support of this postulate from human studies is equivocal, the vast majority of animal research strongly suggests that anesthetics are indeed cytotoxic at multiple brain structure and function levels. In this review, we first highlight various modes of anesthetic action and then debate the evidence of harm from both basic science and clinical studies perspectives. We present evidence from animal and human studies vis-à-vis the possible detrimental effects of anesthetic agents on both the young developing and the elderly aging brain while discussing potential ways to mitigate these effects. We hope that this review will, on the one hand, invoke debate vis-à-vis the evidence of anesthetic harm in young children and the elderly, and on the other hand, incentivize the search for better and less toxic anesthetic compounds.

Electron microscopy techniques employed to explore mitochondrial defects in the developing rat brain following ketamine treatment

Ketamine, an FDA-approved N-methyl-D-aspartate (NMDA) receptor antagonist, is commonly used for general pediatric anesthesia. Accumulating evidence has indicated that prolonged exposure to ketamine induces widespread apoptotic cell death in the developing brains of experimental animals. Although mitochondria are known to play a pivotal role in cell death, little is known about the alterations in mitochondrial ultrastructure that occur during ketamine-induced neurotoxicity. The objective of this pilot study was to utilize classic and contemporary methods in electron microscopy to study the impact of ketamine on the structure of mitochondria in the developing rat brain. While transmission electron microscopy (TEM) was employed to comprehensively study mitochondrial inner membrane topology, serial block-face scanning electron microscopy (SBF-SEM) was used as a complementary technique to compare the overall mitochondrial morphology from a representative treated and untreated neuron. In this study, postnatal day 7 (PND-7) Sprague-Dawley rats were treated with ketamine or saline (6 subcutaneous injections × 20 mg/kg or 10 ml/kg, respectively, at 2-h intervals with a 6-h withdrawal period after the last injection, n=6 each group). Samples from the frontal cortex were harvested and analyzed using TEM or SBF-SEM. While classic TEM revealed that repeated ketamine exposure induces significant mitochondrial swelling in neurons, the newer technique of SBF-SEM confirmed the mitochondrial swelling in three dimensions (3D) and showed that ketamine exposure may also induce mitochondrial fission, which was not observable in the two dimensions (2D) of TEM. Furthermore, 3D statistical analysis of these reconstructed mitochondria appeared to show that ketamine-treated mitochondria had significantly larger volumes per unit surface area than mitochondria from the untreated neuron. The ultrastructural mitochondrial alterations demonstrated here by TEM and SBF-SEM support ketamine's proposed mechanism of neurotoxicity in the developing rat brain.

Propofol Regulates Neural Stem Cell Proliferation and Differentiation via Calmodulin-Dependent Protein Kinase II/AMPK/ATF5 Signaling Axis

BACKGROUND

Propofol can cause degeneration of developing brain cells and subsequent long-term learning or memory impairment. However, at the early stage of embryonic development, the molecular mechanism of propofol-induced inhibition in neural stem cells (NSCs) neurogenesis is still unclear. The aim of this study was to determine the role of propofol in NSCs neurogenesis and, more importantly, to explore the underlying mechanism.

METHODS

First, a single intraperitoneal injection of propofol was performed in pregnant mice, and 6 hours after administration of propofol, the hippocampus RNA and the protein of the embryos' brains was extracted to analyze the expression of neuron-specific markers. Second, the primary NSCs were isolated from the hippocampus of mouse embryonic brain and then treated with propofol for cell viability, immunostaining, and transwell assays; more importantly, we performed RNA sequencing (RNA-seq) and q-reverse transcription polymerase chain reaction assays to identify genes regulated by propofol; the Western blot, small interfering RNA (SiRNA), and luciferase reporter assays were used to study the effects of propofol on calmodulin-dependent protein kinase (CaMk) II/5' adenosine monophosphate-activated protein kinase (AMPK)/activating transcription factor 5 (ATF5) signaling pathway.

RESULTS

Our results indicated that propofol treatment could inhibit the proliferation, migration, and differentiation of NSCs. The results of RNA-seq assays showed that propofol treatment resulted in downregulation of a group of Ca-dependent genes. The following mechanism studies showed that propofol regulates the proliferation, differentiation, and migration of NSCs through the CaMkII/phosphorylation of serine at amino acid position 485 (pS485)/AMPK/ATF5 signaling pathway.

CONCLUSIONS

The results from study demonstrated that propofol inhibits the proliferation, differentiation, and migration of NSCs, and these effects are partially mediated by CaMkII/pS485/AMPK/ATF5 signaling pathway.

Intravenous anesthetic-induced calcium dysregulation and neurotoxic shift with age during development in primary cultured neurons

Anesthetic-induced neurotoxicity in the developing brain is a concern. This neurotoxicity is closely related to anesthetic exposure time, dose, and developmental stages. Using calcium imaging and morphological examinations in vitro, we sought to determine whether intravenous anesthetic-induced direct neurotoxicity varies according to different stages of the days in vitro (DIV) of neurons in primary culture. Cortical neurons from E17 Wistar rats were prepared. On DIV 3, 7, and 13, cells were exposed to the intravenous anesthetics thiopental sodium (TPS), midazolam (MDZ), or propofol (PPF), to investigate direct neurotoxicity using morphological experiments. Furthermore, using calcium imaging, the anesthetic-induced intracellular calcium concentration ([Ca²⁺]i) elevation was monitored in cells on DIV 4, 8, and 13. All anesthetics elicited significant [Ca²⁺]i increases on DIV 4. While TPS (100 μM) and MDZ (10 μM) did not alter neuronal death, PPF (10 μM and 100 μM) decreased the survival ratio (SR) significantly. On DIV 8, TPS and MDZ did not elicit [Ca²⁺]i elevation or SR decrease, while PPF still induced [Ca²⁺]i elevation (both at 10 μM and 100 μM) and significant SR decrease at 100 μM (0.76 ± 0.03; P < 0.05), but not at 10 μM (0.91 ± 0.03). Such anesthetic-induced [Ca²⁺]i elevation and SR decrease were not observed on DIV 13-14 for any of the anesthetic drugs. Our study indicates that more caution may be exercised when using PPF compared to TPS or MDZ during development.

Validation and bioinformatic analysis of propofol-induced differentially expressed microRNAs in primary cultured neural stem cells

Propofol, a widely used intravenous anesthetic, was previously considered as a neuroprotective agent. Recently, however, accumulating evidence suggests that it may cause neurotoxicity, especially in the development of neural stem cells (NSCs). The potential mechanisms contributing to propofol-induced neurotoxicity during neurogenesis, such as those involving microRNAs (miRNAs), are still unknown. In this study, a total of 27 differentially expressed miRNAs were identified in our initial screen and 6 miRNAs were validated by qRT-PCR. Three miRNAs were up-regulated (miR-377-5p, miR-194-3p and miR-143-5p), and three were down-regulated (miR-3583-3p, miR-466b-5p and miR-410-5p). Following gene ontology and KEGG pathway enrichment analysis, Gabbr1, Canca1b and Gabbr2, which are enriched in the GABAergic synapse pathway, were selected as genes potentially playing a role in propofol-induced neurotoxicity. Gabbr1 and Cacna1b, which are targeted by miRNAs that are up-regulated following propofol exposure, showed decreased expression at the mRNA and protein levels. Gabbr2, targeted by miRNAs that were down-regulated following treatment with propofol, was up-regulated at both the levels of mRNA and protein expression. The two clusters of miRNAs that show differential expression following propofol exposure may act in a synergistic manner to regulate several genes simultaneously during the development of NSCs. Our results may contribute to clarify the molecular mechanism and provide potential therapeutic targets for propofol induced neurotoxicity.

Lipid profiling as an effective approach for identifying biomarkers/adverse events associated with pediatric anesthesia

Adverse effects related to central nervous system (CNS) function in pediatric populations may, at times, be difficult, if not impossible to evaluate. Prolonged anesthetic exposure affects brain excitability and anesthesia during the most sensitive developmental stages and has been associated with mitochondrial dysfunction, aberrant lipid metabolism and synaptogenesis, subsequent neuronal damage, as well as long-term behavioral deficits. There has been limited research evaluating whether and how anesthetic agents affect cellular lipids, the most abundant components of the brain other than water. Therefore, this review discusses: (1) whether the observed anesthetic-induced changes in lipid profiles seen in preclinical studies represents early signs of neurotoxicity; (2) the potential mechanisms underlying anesthetic-induced brain injury; and (3) whether lipid biomarker(s) identified in preclinical studies can serve as markers for the early clinical detection of anesthetic-induced neurotoxicity.

Effects of Propofol Treatment in Neural Progenitors Derived from Human-Induced Pluripotent Stem Cells

Propofol is an intravenous anesthetic that has been widely used in clinics. Besides its anesthetic effects, propofol has also been reported to influence the regulation of the autonomic system. Controversies exist with regard to whether propofol exposure is safe for pregnant women and young children. In this work, human-induced pluripotent stem cell- (hiPSC-) derived neural progenitor cells (NPCs) were treated with propofol at 20, 50, 100, or 300 μM for 6 h or 24 h, and acute and subacute cell injury, cell proliferation, and apoptosis were evaluated. Comparison of genome-wide gene expression profiles was performed for treated and control iPSC-NPCs. Propofol treatment for 6 h at the clinically relevant concentration (20 or 50 μM) did not affect cell viability, apoptosis, or proliferation, while propofol at higher concentration (100 or 300 μM) decreased NPC viability and induced apoptosis. In addition, 20 μM propofol treatment for 6 h did not alter global gene expression. In summary, propofol treatment at commonly practiced clinical doses for 6 h did not have adverse effects on hiPSC-derived NPCs. In contrast, longer exposure and/or higher concentration could decrease NPC viability and induce apoptosis.

Propofol's Effects on the Fetal Brain for Non-Obstetric Surgery

While the use of Propofol has been increasing in usage for general surgical procedures since its release to market, there has been little work done on its potential link to neurotoxicity in humans. Only recently, following the release of a warning label from the United States Food and Drug Administration (USFDA) regarding a potential link to "neurotoxicity" in the neonate, did the surgical and anesthesiology communities become more aware of its potential for harm. Given the widespread use of this drug in clinical practice, the warning label naturally raised controversy regarding intrapartum Propofol usage. While intended to generate further studies, the lack of a viable anesthetic alternative raises issues regarding its current usage for surgical procedures in pregnant women. To answer the question whether current evidence is supportive of Propofol usage at its current levels in pregnant women, this review summarizes available evidence of fetal Propofol exposure in animal studies.

Recent Insights Into Molecular Mechanisms of Propofol-Induced Developmental Neurotoxicity: Implications for the Protective Strategies

Mounting evidence has demonstrated that general anesthetics could induce developmental neurotoxicity, including acute widespread neuronal cell death, followed by long-term memory and learning abnormalities. Propofol is a commonly used intravenous anesthetic agent for the induction and maintenance of anesthesia and procedural and critical care sedation in children. Compared with other anesthetic drugs, little information is available on its potential contributions to neurotoxicity. Growing evidence from multiple experimental models showed a similar neurotoxic effect of propofol as observed in other anesthetic drugs, raising serious concerns regarding pediatric propofol anesthesia. The aim of this review is to summarize the current findings of propofol-induced developmental neurotoxicity. We first present the evidence of neurotoxicity from animal models, animal cell culture, and human stem cell-derived neuron culture studies. We then discuss the mechanism of propofol-induced developmental neurotoxicity, such as increased cell death in neurons and oligodendrocytes, dysregulation of neurogenesis, abnormal dendritic development, and decreases in neurotrophic factor expression. Recent findings of complex mechanisms of propofol action, including alterations in microRNAs and mitochondrial fission, are discussed as well. An understanding of the toxic effect of propofol and the underlying mechanisms may help to develop effective novel protective or therapeutic strategies for avoiding the neurotoxicity in the developing human brain.

ALCAR promote adult hippocampal neurogenesis by regulating cell-survival and cell death-related signals in rat model of Parkinson's disease like-phenotypes

Parkinson's disease (PD) is characterized by the degeneration of dopaminergic neurons in the nigrostriatal pathway that leading to progressive motor and nonmotor symptoms. The formation of newborn neurons in the adult hippocampus is affected by many factors such as anxiety, depression and impairment in learning and memory that are commonly observed nonmotor symptoms in PD, indicating the role of adult neurogenesis in PD pathophysiology. Acetyl-l-carnitine (ALCAR), regulate mitochondrial metabolism and has been reported to improve cognitive functions in different neurodegenerative disorders through an unknown mechanism. For the first time, we investigated the effect of ALCAR on adult neurogenesis in the 6-hydroxydopamine (6-OHDA) induced rat model of PD-like phenotypes and also explored the possible underlying mechanism of action. A single unilateral administration of 6-OHDA into the medial forebrain bundle reduced neural progenitor cell (NPC) proliferation, long-term survival and neuronal differentiation in the hippocampus. Interestingly, chronic treatment with ALCAR (100 mg/kg/day, i.p) potentially enhanced proliferation, long term survival and neuronal differentiation of NPCs in rat model of PD-like phenotypes. ALCAR treatment stimulates cell survival related signals (AKT and BCL-2) by inhibiting cell death related cues (GSK-3β and BAX) which might be responsible for a neuroprotective effect of ALCAR in rat model of PD-like phenotypes. We conclude that ALCAR exerts neuroprotective effects against 6-OHDA-induced impairment in hippocampal neurogenesis by regulating cell survival and cell death-related signals.

Acetyl-l-carnitine partially prevents benzene-induced hematotoxicity and oxidative stress in C3H/He mice

Benzene is an environmental pollutant and occupational toxicant which induces hematotoxicity. Our previous metabonomics study suggested that acetyl-l-carnitine (ALCAR) decreased in the mouse plasma and bone marrow (BM) cells due to benzene exposure. In the present study, the topic on whether ALCAR influences hematotoxicity caused by benzene exposure was explored. Thirty-two male C3H/He mice were divided into four groups: control group (C: vehicle, oil), benzene group (150mg/kg body weight (b.w.) benzene), benzene+A1 group (150mg/kg b.w. benzene+100mg/kg b.w. ALCAR), and benzene+A2 group (150mg/kg b.w. benzene+200mg/kg b.w. ALCAR). Benzene was injected subcutaneously, and ALCAR was orally administrated via gavage once daily for 4 weeks consecutively. After the experimental period, the blood routine, BM cell number and frequency of hematopoietic stem/progenitor cell (HS/PC) were assessed. The mitochondrial membrane potential and ATP level were determined to evaluate the mitochondrial function. Reactive oxygen species (ROS), hydrogen peroxide (H₂O₂) and malondialdehyde (MDA) levels were also examined, and the comet assay was performed to measure oxidative stress. Results showed that ALCAR intervention can partially reduce the benzene-induced damage on BM and HS/PCs and can simultaneously alleviate the DNA damage by reducing benzene-induced H₂O_2, ROS, and MDA.

Propofol Enhances Hemoglobin-Induced Cytotoxicity in Neurons

BACKGROUND

It has been increasingly suggested that propofol protects against hypoxic-/ischemic-induced neuronal injury. As evidenced by hemorrhage-induced stroke, hemorrhage into the brain may also cause brain damage. Whether propofol protects against hemorrhage-induced brain damage remains unknown. Therefore, in this study, we investigated the effects of propofol on hemoglobin-induced cytotoxicity in cultured mouse cortical neurons.

METHODS

Neurons were prepared from the cortex of embryonic 15-day-old mice. Hemoglobin was used to induce cytotoxicity in the neurons. The neurons were then treated with propofol for 4 hours. Cytotoxicity was determined by lactate dehydrogenase release assay. Caspase-3 activation was examined by Western blot analysis. Finally, the free radical scavenger U83836E was used to examine the potential involvement of oxidative stress in propofol's effects on hemoglobin-induced cytotoxicity.

RESULTS

We found that treatment with hemoglobin induced cytotoxicity in the neurons. Propofol enhanced hemoglobin-induced cytotoxicity. Specifically, there was a significant difference in the amount of lactate dehydrogenase release between hemoglobin plus saline (19.84% ± 5.38%) and hemoglobin plus propofol (35.79% ± 4.41%) in mouse cortical neurons (P = 0.00058, Wilcoxon Mann-Whitney U test, n = 8 in the control group or the treatment group). U83836E did not attenuate the enhancing effects of propofol on hemoglobin-induced cytotoxicity in the neurons, and propofol did not significantly affect caspase-3 activation induced by hemoglobin. These data suggested that caspase-3 activation and oxidative stress might not be the underlying mechanisms by which propofol enhanced hemoglobin-induced cytotoxicity. Moreover, these data suggested that the neuroprotective effects of propofol would be dependent on the condition of the brain injury, which will need to be confirmed in future studies.

CONCLUSIONS

These results from our current proof-of-concept study should promote more research in vitro and in vivo to develop better anesthesia care for patients with hemorrhagic stroke.

Prolonged Treatment with Propofol Transiently Impairs Proliferation but Not Survival of Rat Neural Progenitor Cells In Vitro

Neurocognitive dysfunction is common in survivors of intensive care. Prolonged sedation has been implicated but the mechanisms are unclear. Neurogenesis continues into adulthood and is implicated in learning. The neural progenitor cells (NPC) that drive neurogenesis have receptors for the major classes of sedatives used clinically, suggesting that interruption of neurogenesis may partly contribute to cognitive decline in ICU survivors. Using an in vitro system, we tested the hypothesis that prolonged exposure to propofol concentration- and duration-dependently kills or markedly decreases the proliferation of NPCs. NPCs isolated from embryonic day 14 Sprague-Dawley rat pups were exposed to 0, 2.5, or 5.0 μg/mL of propofol, concentrations consistent with deep clinical anesthesia, for either 4 or 24 hours. Cells were assayed for cell death and proliferation either immediately following propofol exposure or 24 hours later. NPC death and apoptosis were measured by propidium iodine staining and cleaved caspase-3 immunocytochemistry, respectively, while proliferation was measured by EdU incorporation. Staurosporine (1μM for 6h) was used as a positive control for cell death. Cells were analyzed with unbiased high-throughput immunocytochemistry. There was no cell death at either concentration of propofol or duration of exposure. Neither concentration of propofol impaired NPC proliferation when exposure lasted 4 h, but when exposure lasted 24 h, propofol had an anti-proliferative effect at both concentrations (P < 0.0001, propofol vs. control). However, this effect was transient; proliferation returned to baseline 24 h after discontinuation of propofol (P = 0.37, propofol vs. control). The transient but reversible suppression of NPC proliferation, absence of cytotoxicity, and negligible effect on the neural stem cell pool pool suggest that propofol, even in concentrations used for clinical anesthesia, has limited impact on neural progenitor cell biology.

In Vivo Monitoring of Sevoflurane-induced Adverse Effects in Neonatal Nonhuman Primates Using Small-animal Positron Emission Tomography

Background

Animals exposed to sevoflurane during development sustain neuronal cell death in their developing brains. In vivo micro-positron emission tomography (PET)/computed tomography imaging has been utilized as a minimally invasive method to detect anesthetic-induced neuronal adverse effects in animal studies.

Methods

Neonatal rhesus monkeys (postnatal day 5 or 6, 3 to 6 per group) were exposed for 8 h to 2.5% sevoflurane with or without acetyl-l-carnitine (ALC). Control monkeys were exposed to room air with or without ALC. Physiologic status was monitored throughout exposures. Depth of anesthesia was monitored using quantitative electroencephalography. After the exposure, microPET/computed tomography scans using 18F-labeled fluoroethoxybenzyl-N-(4-phenoxypyridin-3-yl) acetamide (FEPPA) were performed repeatedly on day 1, 1 and 3 weeks, and 2 and 6 months after exposure.

Results

Critical physiologic metrics in neonatal monkeys remained within the normal range during anesthetic exposures. The uptake of [18F]-FEPPA in the frontal and temporal lobes was increased significantly 1 day or 1 week after exposure, respectively. Analyses of microPET images recorded 1 day after exposure showed that sevoflurane exposure increased [18F]-FEPPA uptake in the frontal lobe from 0.927 ± 0.04 to 1.146 ± 0.04, and in the temporal lobe from 0.859 ± 0.05 to 1.046 ± 0.04 (mean ± SE, P &lt; 0.05). Coadministration of ALC effectively blocked the increase in FEPPA uptake. Sevoflurane-induced adverse effects were confirmed by histopathologic evidence as well.

Conclusions

Sevoflurane-induced general anesthesia during development increases glial activation, which may serve as a surrogate for neurotoxicity in the nonhuman primate brain. ALC is a potential protective agent against some of the adverse effects associated with such exposures.

Relationship between ketamine-induced developmental neurotoxicity and NMDA receptor-mediated calcium influx in neural stem cell-derived neurons

Ketamine, a noncompetitive NMDA receptor antagonist, is used as a general anesthetic and recent data suggest that general anesthetics can cause neuronal damage when exposure occurs during early brain development. To elucidate the underlying mechanisms associated with ketamine-induced neurotoxicity, stem cell-derived models, such as rodent neural stem cells harvested from rat fetuses and/or neural stem cells derived from human induced pluripotent stem cells (iPSC) can be utilized. Prolonged exposure of rodent neural stem cells to clinically-relevant concentrations of ketamine resulted in elevated NMDA receptor levels as indicated by NR1subunit over-expression in neurons. This was associated with enhanced damage in neurons. In contrast, the viability and proliferation rate of undifferentiated neural stem cells were not significantly affected after ketamine exposure. Calcium imaging data indicated that 50μM NMDA did not cause a significant influx of calcium in typical undifferentiated neural stem cells; however, it did produce an immediate elevation of intracellular free Ca²⁺ [Ca²⁺]_i in differentiated neurons derived from the same neural stem cells. This paper reviews the literature on this subject and previous findings suggest that prolonged exposure of developing neurons to ketamine produces an increase in NMDA receptor expression (compensatory up-regulation) which allows for a higher/toxic influx of calcium into neurons once ketamine is removed from the system, leading to neuronal cell death likely due to elevated reactive oxygen species generation. The absence of functional NMDA receptors in cultured neural stem cells likely explains why clinically-relevant concentrations of ketamine did not affect undifferentiated neural stem cell viability.

Tissue plasminogen activator (tPA) attenuates propofol-induced apoptosis in developing hippocampal neurons

Background

We investigated the effect of propofol on the tissue plasminogen activator (tPA) release in developing hippocampal neurons, and explored the effects of exogenous tPA on the propofol-induced neuron apoptosis.

Methods

Primary hippocampal neurons isolated from neonatal Sprague-Dawley rats were exposed to propofol (20, 50, and 100 μM) for 6 h either one time or three times. Finally, neurons were pretreated with exogenous tPA (5 µg/ml), followed by propofol exposure (100 μM, 6 h). The neuron apoptosis was detected by terminal transferase deoxyuridine triphosphate-biotin nick-end labeling (TUNEL) and the protein expression of cleaved caspase-3 (Cl-Csp3) was analyzed by western blot, the tPA in media was tested by enzyme-linked immunosorbent assay.

Results

Propofol exposure significantly increased the number of TUNEL-positive neurons and Cl-Csp3 expression in developing hippocampal neurons. Propofol decreased tPA level in the media of developing hippocampal neurons. The neuron appotosis induced by propofol was attenuated by pretreatment of tPA.

Conclusion

Propofol exposure decreased tPA release in developing hippocampal neurons. The addition of tPA could partially reverse the apoptotic effect of propofol.

Propofol Suppressed Hypoxia/Reoxygenation-Induced Apoptosis in HBVSMC by Regulation of the Expression of Bcl-2, Bax, Caspase3, Kir6.1, and p-JNK

Recent studies have found that propofol may protect brain from cerebral ischemic-reperfusion injury. However, the underlying mechanism remains unclear. The effects of propofol were evaluated in HBVSMC after hypoxia/reoxygenation (H/R). Cell viability and levels of SOD, LDH, and MDA were measured. Apoptosis was detected by flow cytometry. The levels of Bax, Bcl-2, Caspase3, Sur2b, Kir6.1, JNK, p-JNK, mTOR, and p-mTOR proteins were measured by western blotting. H/R decreased cell viability and SOD activity and increased LDH leakage and MDA content in HBVSMC, all of which were significantly reversed by propofol. Propofol suppressed the levels of H/R-induced apoptosis. The expression of Bcl-2 and p-mTOR was significantly downregulated and the expression levels of Bax, Caspase3, Kir6.1, and p-JNK were upregulated following H/R injury. The ratio of p-JNK/JNK was increased; however, that of p-mTOR/mTOR decreased correspondingly. The effects on the expression of these proteins were reversed by propofol treatment. SP600125 enhanced and Everolimus attenuated the effect of propofol. These findings suggested that the protective effect of propofol against H/R injury in the HBVSMC was through the inhibition of apoptosis by inducing the expression of Bcl-2 and p-mTOR as well as inhibiting the expression levels of Bax, Caspase3, Kir6.1, and p-JNK.

Effects of silver nanoparticles on human and rat embryonic neural stem cells

Silver nano-particles (Ag-NPs) are becoming increasingly prevalent in consumer products as antibacterial agents. The increased use of Ag NP-enhanced products will almost certainly increase environmental silver levels, resulting in increased exposures and the potential for increased adverse reactions including neurotoxic effects. In the present study, embryonic neural stem cells (NSCs) from human and rat fetuses (gestational day-16) were used to determine whether Ag-NPs are capable of causing developmental neurotoxicity. The NSCs were cultured in serum free medium supplemented with appropriate growth factors. On the eighth day in vitro (DIV 8), the cells were exposed to Ag-NPs at concentrations of 1, 5, 10, and 20 μg/ml for 24 h. The cultured cells then were characterized by NSC markers including nestin and SOX2 and a variety of assays were utilized to determine the effects of Ag-NPs on NSC proliferation and viability and the underlying mechanisms associated with these effects. The results indicate that mitochondrial viability (MTT metabolism) was substantially attenuated and LDH release was increased significantly in a dose-dependent manner. Ag-NPs-induced neurotoxicity was further confirmed by up-regulated Bax protein expression, an increased number of TUNEL-positively stained cells, and elevated reactive oxygen species (ROS). NSC proliferation was also significantly decreased by Ag-NPs. Co-administration of acetyl-L-carnitine, an antioxidant agent, effectively blocked the adverse effects associated with Ag-NP exposure.

Positron Emission Tomography with [(18)F]FLT Revealed Sevoflurane-Induced Inhibition of Neural Progenitor Cell Expansion in vivo

Neural progenitor cell expansion is critical for normal brain development and an appropriate response to injury. During the brain growth spurt, exposures to general anesthetics, which either block the N-methyl-d-aspartate receptor or enhance the γ-aminobutyric acid receptor type A can disturb neuronal transduction. This effect can be detrimental to brain development. Until now, the effects of anesthetic exposure on neural progenitor cell expansion in vivo had seldom been reported. Here, minimally invasive micro positron emission tomography (microPET) coupled with 3'-deoxy-3' [(18)F] fluoro-l-thymidine ([(18)F]FLT) was utilized to assess the effects of sevoflurane exposure on neural progenitor cell proliferation. FLT, a thymidine analog, is taken up by proliferating cells and phosphorylated in the cytoplasm, leading to its intracellular trapping. Intracellular retention of [(18)F]FLT, thus, represents an observable in vivo marker of cell proliferation. Here, postnatal day 7 rats (n = 11/group) were exposed to 2.5% sevoflurane or room air for 9 h. For up to 2 weeks following the exposure, standard uptake values (SUVs) for [(18)F]-FLT in the hippocampal formation were significantly attenuated in the sevoflurane-exposed rats (p < 0.0001), suggesting decreased uptake and retention of [(18)F]FLT (decreased proliferation) in these regions. Four weeks following exposure, SUVs for [(18)F]FLT were comparable in the sevoflurane-exposed rats and in controls. Co-administration of 7-nitroindazole (30 mg/kg, n = 5), a selective inhibitor of neuronal nitric oxide synthase, significantly attenuated the SUVs for [(18)F]FLT in both the air-exposed (p = 0.00006) and sevoflurane-exposed rats (p = 0.0427) in the first week following the exposure. These findings suggested that microPET in couple with [(18)F]FLT as cell proliferation marker could be used as a non-invasive modality to monitor the sevoflurane-induced inhibition of neural progenitor cell proliferation in vivo.