General anesthetic isoflurane modulates inositol 1,4,5-trisphosphate receptor calcium channel opening

Sevoflurane upregulates neuron death process-related Ddit4 expression by NMDAR in the hippocampus

Postoperative cognitive dysfunction (POCD) is a serious and common complication induced by anesthesia and surgery. Neuronal apoptosis induced by general anesthetic neurotoxicity is a high-risk factor. However, a comprehensive analysis of general anesthesia-regulated gene expression patterns and further research on molecular mechanisms are lacking. Here, we performed bioinformatics analysis of gene expression in the hippocampus of aged rats that received sevoflurane anesthesia in GSE139220 from the GEO database, found a total of 226 differentially expressed genes (DEGs) and investigated hub genes according to the number of biological processes in which the genes were enriched and performed screening by 12 algorithms with cytoHubba in Cytoscape. Among the screened hub genes, Agt, Cdkn1a, Ddit4, and Rhob are related to the neuronal death process. We further confirmed that these genes, especially Ddit4, were upregulated in the hippocampus of aged mice that received sevoflurane anesthesia. NMDAR, the core target receptor of sevoflurane, rather than GABAAR, mediates the sevoflurane regulation of DDIT4 expression. Our study screened sevoflurane-regulated DEGs and focused on the neuronal death process to reveal DDIT4 as a potential target mediated by NMDAR, which may provide a new target for the treatment of sevoflurane neurotoxicity.

Anesthetics and Cell-Cell Communication: Potential Ca2+-Calmodulin Role in Gap Junction Channel Gating by Heptanol, Halothane and Isoflurane

Cell–cell communication via gap junction channels is known to be inhibited by the anesthetics heptanol, halothane and isoflurane; however, despite numerous studies, the mechanism of gap junction channel gating by anesthetics is still poorly understood. In the early nineties, we reported that gating by anesthetics is strongly potentiated by caffeine and theophylline and inhibited by 4-Aminopyridine. Neither Ca²⁺ channel blockers nor 3-isobutyl-1-methylxanthine (IBMX), forskolin, CPT-cAMP, 8Br-cGMP, adenosine, phorbol ester or H7 had significant effects on gating by anesthetics. In our publication, we concluded that neither cytosolic Ca²⁺_i nor pH_i were involved, and suggested a direct effect of anesthetics on gap junction channel proteins. However, while a direct effect cannot be excluded, based on the potentiating effect of caffeine and theophylline added to anesthetics and data published over the past three decades, we are now reconsidering our earlier interpretation and propose an alternative hypothesis that uncoupling by heptanol, halothane and isoflurane may actually result from a rise in cytosolic Ca²⁺ concentration ([Ca²⁺]_i) and consequential activation of calmodulin linked to gap junction proteins.

Nonapoptotic caspases in neural development and in anesthesia-induced neurotoxicity

Apoptosis, classically initiated by caspase pathway activation, plays a prominent role during normal brain development as well as in neurodegeneration. The noncanonical, nonlethal arm of the caspase pathway is evolutionarily conserved and has also been implicated in both processes, yet is relatively understudied. Dysregulated pathway activation during critical periods of neurodevelopment due to environmental neurotoxins or exposure to compounds such as anesthetics can have detrimental consequences for brain maturation and long-term effects on behavior. In this review, we discuss key molecular characteristics and roles of the noncanonical caspase pathway and how its dysregulation may adversely affect brain development. We highlight both genetic and environmental factors that regulate apoptotic and sublethal caspase responses and discuss potential interventions that target the noncanonical caspase pathway for developmental brain injuries.

Calcium Ions Aggravate Alzheimer's Disease Through the Aberrant Activation of Neuronal Networks, Leading to Synaptic and Cognitive Deficits

Alzheimer’s disease (AD) is a neurodegenerative disease that is characterized by the production and deposition of β-amyloid protein (Aβ) and hyperphosphorylated tau, leading to the formation of β-amyloid plaques (APs) and neurofibrillary tangles (NFTs). Although calcium ions (Ca²⁺) promote the formation of APs and NFTs, no systematic review of the mechanisms by which Ca²⁺ affects the development and progression of AD has been published. Therefore, the current review aimed to fill the gaps between elevated Ca²⁺ levels and the pathogenesis of AD. Specifically, we mainly focus on the molecular mechanisms by which Ca²⁺ affects the neuronal networks of neuroinflammation, neuronal injury, neurogenesis, neurotoxicity, neuroprotection, and autophagy. Furthermore, the roles of Ca²⁺ transporters located in the cell membrane, endoplasmic reticulum (ER), mitochondria and lysosome in mediating the effects of Ca²⁺ on activating neuronal networks that ultimately contribute to the development and progression of AD are discussed. Finally, the drug candidates derived from herbs used as food or seasoning in Chinese daily life are summarized to provide a theoretical basis for improving the clinical treatment of AD.

Anesthetic Exposure in Staged Versus Single-Stage Cleft Lip and Palate Repair: Can We Reduce Risk of Anesthesia-Induced Developmental Neurotoxicity?

ABSTRACT

Cleft lip and palate (CLP) repair is typically performed in a staged fashion, which requires multiple instances of anesthetic exposure during a critical period of infant neurodevelopment. One solution to this concern includes the implementation of a single-stage CLP repair performed between 6 and 12 months of age. This study aimed to compare total anesthetic exposure between single-stage and staged CLP repairs. A retrospective review of unilateral CLP repairs between 2013 and 2018 conducted at a single institution was performed. Patients underwent either traditional, staged lip and palate repair, or single-stage complete cleft repair, where palate, lip, alveolus, and nasal repair was performed simultaneously. Primary endpoints included: total surgical time and total anesthetic exposure. Secondary endpoints included: excess anesthesia time, recovery room time, length of stay, and type of anesthetic administered. Two hundred twenty-five (n = 225) unilateral CLP repairs were conducted at the Loma Linda University. Detailed anesthetic data for eighty-six (n = 86) single-stage and twenty-eight (n = 28) staged operations were available. There was a statistically significant decrease in anesthetic exposure in single-stage versus staged repairs (316 minutes versus 345 minutes, P = 0.017), despite similar procedure times (260 minutes versus 246 minutes, P = 0.224). This resulted in near double excess anesthetic exposure time in the staged group (98 minutes versus 56 minutes, P < 0.001), primarily occurring during induction. This analysis suggests that single-stage CLP repair can reduce wasted time under general anesthesia and potentially reduce harmful neuronal toxicity in the developmental period in this at-risk population.

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

Background

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

Methods

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

Results

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

Conclusion

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

Alzheimer's Disease Presenilin-1 Mutation Sensitizes Neurons to Impaired Autophagy Flux and Propofol Neurotoxicity: Role of Calcium Dysregulation

BACKGROUND

Disruption of intracellular Ca2+ homeostasis and associated autophagy dysfunction contribute to neuropathology in Alzheimer's disease (AD).

OBJECTIVE

To study the effects of propofol on cell viability via its effects on intracellular Ca2+ homeostasis, and the impact of autophagy, in a neuronal model of presenilin-mutated familial AD (FAD).

METHODS

We treated PC12 cells, stably transfected with either mutated presenilin-1 (L286V) or wild type (WT) controls, with propofol at different doses and durations, in the presence or absence of extracellular Ca2+, antagonists of inositol trisphosphate receptors (InsP3R, xestospongin C) and/or ryanodine receptors (RYR, dantrolene), or an inhibitor of autophagy flux (Bafilomycin). We determined cell viability, cytosolic Ca2+ concentrations ([Ca2+]c), vATPase protein expression, and lysosomal acidification.

RESULTS

The propofol dose- and time-dependently decreased cell viability significantly more in L286V than WT cells, especially at the pharmacological dose (>50μM), and together with bafilomycin (40 nM). Clinically used concentrations of propofol (<20μM) tended to increase cell viability. Propofol significantly increased [Ca2+]c more in L286V than in WT cells, which was associated with decrease of vATPase expression and localization to the lysosome. Both toxicity and increased Ca2+ levels were ameliorated by inhibiting InsP3R/RYR. However, the combined inhibition of both receptors paradoxically increased [Ca2+]c, by inducing Ca2+ influx from the extracellular space, causing greater cytotoxicity.

CONCLUSION

Impairment in autophagy function acts to deteriorate cell death induced by propofol in FAD neuronal cells. Cell death is ameliorated by either RYR or InsP3R antagonists on their own, but not when both are co-administered.

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.

Chronic Calcineurin Inhibition via Cyclosporine A Impairs Visuospatial Learning After Isoflurane Anesthesia

BACKGROUND

Clinical studies implicate the perioperative period in cognitive complications, and increasing experimental evidence shows that the anesthetic agents can affect neuronal processes that underpin learning and memory. Calcineurin, a Ca-dependent phosphatase critically involved in synaptic plasticity, is activated after isoflurane exposure, but its role in the neurological response to anesthesia is unclear.

METHODS

We investigated the effect of chronic calcineurin inhibition on postanesthetic cognitive function. Mice were treated with 30 minutes of isoflurane anesthesia during a chronic cyclosporine A regimen. Behavioral end points during the perianesthesia period were quantified. Visuospatial learning was assessed with the water radial arm maze. Total and biotinylated surface protein expression of the α5β3γ2 γ-aminobutyric acid (GABA) type A receptors was measured. Expression of the GABA synthesis enzyme glutamate decarboxylase (GAD)-67 was also measured.

RESULTS

Mice treated with cyclosporine A before anesthesia showed significant deficits in visuospatial learning compared to sham and cyclosporine A-treated mice (n = 10 per group, P = .0152, Tukey post hoc test). Induction and emergence were unaltered by cyclosporine A. Analysis of hippocampal protein expression revealed an increased surface expression of the α5 GABA type A receptor subunit after isoflurane treatment (P = .019, Dunnett post hoc testing), as well as a decrease in GAD-67 expression. Cyclosporine A did not rescue either effect.

CONCLUSIONS

Our results confirm the work of others that isoflurane induces changes to inhibitory network function and exclude calcineurin inhibition via cyclosporine A as an intervention. Further, our studies suggest that calcineurin mediates a protective role in the neurological response to anesthesia, and patients receiving cyclosporine A may be an at-risk group for memory problems related to anesthesia.

General Anesthetic-Induced Neurotoxicity in the Immature Brain: Reevaluating the Confounding Factors in the Preclinical Studies

General anesthetic (GA) is used clinically to millions of young children each year to facilitate surgical procedures, relieve perioperative stress, and provide analgesia and amnesia. During recent years, there is a growing concern regarding a causal association between early life GA exposure and subsequently long-term neurocognitive abnormalities. To address the increasing concern, mounting preclinical studies and clinical trials have been undergoing. Until now, nearly all of the preclinical findings show that neonatal exposure to GA causally leads to acute neural cell injury and delayed cognitive impairment. Unexpectedly, several influential clinical findings suggest that early life GA exposure, especially brief and single exposure, does not cause adverse neurodevelopmental outcome, which is not fully in line with the experimental findings and data from several previous cohort trials. As the clinical data have been critically discussed in previous reviews, in the present review, we try to analyze the potential factors of the experimental studies that may overestimate the adverse effect of GA on the developing brain. Meanwhile, we briefly summarized the advance in experimental research. Generally, our purpose is to provide some useful suggestions for forthcoming preclinical studies and strengthen the powerfulness of preclinical data.

A pharmacodynamic model of respiratory rate and end-tidal carbon dioxide values during anesthesia in children

It is essential to monitor the end-tidal carbon dioxide (ETCO₂) during general anesthesia and adjust the tidal volume and respiratory rate (RR). For the purpose of this study, we used a population pharmacodynamic modeling approach to establish the relationship between RR versus ETCO₂ data during general anesthesia in children, and to identify the clinical variables affecting this relationship. A prospective observational study was designed to include 51 patients (aged ≤ 12 years), including users of antiepileptic drugs (levetiracetam, valproic, or phenobarbital (n = 21)) and non-users (n = 30), scheduled to receive general anesthesia during elective surgery. When the ETCO₂ was at 40 mmHg, the RR was adjusted 1 breath per every 2 min until the ETCO₂ was 30 mmHg and recovered to 40 mmHg. Pharmacodynamic analysis using a sigmoid E_max model was performed to assess the RR-ETCO₂ relationship. As RR varied from 3 to 37 breaths per minute, the ETCO₂ changed from 40 to 30 mmHg. Hysteresis between the RR and ETCO₂ was observed and accounted for when the model was developed. The C_e50 (RR to achieve 50% of maximum decrease in ETCO₂; i.e. 35 mmHg) was 20.5 in non-users of antiepileptic drugs and 14.9 in those on antiepileptic drug medication. The values of γ (the steepness of the concentration-response relation curve) and k_eo (the first-order rate constant determining the equilibration between the RR and ETCO₂) were 7.53 and 0.467 min^-1, respectively. The C_e50 and ETCO₂ data fit to a sigmoid E_max model. In conclusion, the RR required to get the target ETCO₂ was much lower in children patients taking antiepileptic drugs than that of non-user children patients during the general anesthesia.

Lasting effects of general anesthetics on the brain in the young and elderly: "mixed picture" of neurotoxicity, neuroprotection and cognitive impairment

General anesthetics are commonly used in major surgery. To achieve the depth of anesthesia for surgery, patients are being subjected to a variety of general anesthetics, alone or in combination. It has been long held an illusory concept that the general anesthesia is entirely reversible and that the central nervous system is returned to its pristine state once the anesthetic agent is eliminated from the active site. However, studies indicate that perturbation of the normal functioning of these targets may result in long-lasting desirable or undesirable effects. This review focuses on the impact of general anesthetic exposure to the brain and summarizes the molecular and cellular mechanisms by which general anesthetics may induce long-lasting undesirable effects when exposed at the developing stage of the brain. The vulnerability of aging brain to general anesthetics, specifically in the context of cognitive disorders and Alzheimer’s disease pathogeneses are also discussed. Moreover, we will review emerging evidence regarding the neuroprotective property of xenon and anesthetic adjuvant dexmedetomidine in the immature and mature brains. In conclusion, “mixed picture” effects of general anesthetics should be well acknowledged and should be implemented into daily clinical practice for better patient outcome.

Protective Effect of Extract of Bletilla Striata on Isoflurane Induced Neuronal Injury By Altering PI3K/Akt Pathway

Background

Present investigation evaluates the neuroprotective effect of Bletilla striata on isoflurane induced neuronal injury rat model.

Methodology

Neuronal injury was induced by exposing the pups (P7) isoflurane (0.75%) in oxygen (30%) for the period of 6 hr and rats were treated with Bletilla striata at a dose of 35, 70 and 140 mg/kg, p.o. for the period of 21 days. At the end of protocol neurological score was estimated and serum concentration of inflammatory cytokines was estimated. Isolated brains tissue was prepared to perform immunohistochemical analysis, TUNEL assay and western blot assay.

Results

Result of the study reveals that treatment with BS significantly (p<0.01) reduces the neurological score compared to negative control group. Level of inflammatory cytokines in the serum and the expression of p-Akt, Bcl-xL and Bad protein were significantly attenuated in BS treated group. Moreover the cleaved caspase-3 and TUNEL positive cell was significantly (p<0.01) reduced in BS treated group compared to negative control group of rats.

Conclusion

Present study concludes that ethanolic extract of Bletilla striata protects the neuronal injury by reducing apoptosis in isoflurane induced neuronal injury rats.

Anesthetic effects of isoflurane and the molecular mechanism underlying isoflurane‑inhibited aggressiveness of hepatic carcinoma

Anesthesia is produced by drugs or other methods, and refers to the attenuation of pain via reversible suppression of neuronal transmission in the central and peripheral nervous systems, during surgery. Clinical investigations have indicated that the anesthetic action of isoflurane is efficient to alleviate pain during tumor resection clinical trials. In addition, it has been reported that isoflurane can induce caspase-3 activation and is associated with apoptosis of tumor cells. The present study investigated the anesthetic effects and molecular mechanisms underlying isoflurane-induced apoptosis in patients with hepatic carcinoma. Furthermore, the pain of patients with hepatic carcinoma was evaluated during the perioperative period according to the pain index. The apoptotic rate of hepatic carcinoma cells was analyzed in tumor tissues using TUNEL assay. The expression levels of apoptosis-associated proteins were detected in liver cancer cells following anesthesia in patients. Phosphoinositide 3-kinase/protein kinase B (PI3K/AKT) and nuclear factor (NF)-κB signaling pathways were also analyzed in liver cancer cells following treatment with isoflurane. The results demonstrated that isoflurane inhibited growth and decreased viability of liver cancer cells in vitro and in vivo. In addition, the apoptotic rate was increased in cells obtained from isoflurane-treated patients. The results also demonstrated that isoflurane upregulated the expression levels of proapoptotic genes and downregulated anti-apoptotic mRNA expression. In addition, a molecular mechanism analysis indicated that isoflurane inhibited PI3K and AKT expression in liver cancer cells. Isoflurane also induced caspase-3 activation in liver cancer cells. Furthermore, isoflurane treatment attenuated NF-κB activity and inhibited migration and invasion of liver cancer cells. In conclusion, these findings indicated that isoflurane treatment efficiently attenuated surgical pain and inhibited tumor aggressiveness via regulation of NF-κB activity and the PI3K/AKT signaling pathway, thus suggesting that isoflurane is an efficient anesthetic drug that induces pain remission and promotes apoptosis of liver cancer cells.

Volatile anaesthetics enhance the metastasis related cellular signalling including CXCR2 of ovarian cancer cells

The majority of ovarian cancer patients relapse after surgical resection. Evidence is accumulating regarding the role of surgery in disseminating cancer cells; in particular anaesthesia may have an impact on cancer re-occurrence. Here, we have investigated the metastatic potential of volatile anaesthetics isoflurane, sevoflurane and desflurane on ovarian cancer cells.

Human ovarian carcinoma cells (SKOV3) were exposed to isoflurane (2%), sevoflurane (3.6%) or desflurane (10.3%) for 2 hours. Metastatic related gene expression profiles were measured using the Tumour Metastasis PCR Array and qRT-PCR. Subsequently vascular endothelial growth factor A (VEGF-A), matrix metalloproteinase 11 (MMP11), transforming growth factor beta-1 (TGF-β1) and chemokine (C-X-C motif) receptor 2 (CXCR2) proteins expression were determined using immunofluorescent staining. The migratory capacities of SK-OV3 cells were assessed with a scratch assay and the potential role of CXCR2 in mediating the effects of volatile anaesthetics on cancer cell biology were further investigated with CXCR2 knockdown by siRNA.

All three volatile anaesthetics altered expression of 70 out of 81 metastasic related genes with significant increases in VEGF-A, MMP-11, CXCR2 and TGF-β genes and protein expression with a magnitude order of desflurane (greatest), sevoflurane and isoflurane. Scratch analysis revealed that exposure to these anesthetics increased migration, which was abolished by CXCR2 knockdown.

Volatile anaesthetics at clinically relevant concentrations have strong effects on cancer cell biology which in turn could enhance ovarian cancer metastatic potential. This work raises the urgency for further in vivo studies and clinical trials before any conclusions can be made in term of the alteration of clinical practice.

Effect of repeated neonatal sevoflurane exposure on the learning, memory and synaptic plasticity at juvenile and adult age

Currently sevoflurane is the volatile anesthetic most wildly used in pediatric surgery. Whether neonatal exposure to sevoflurane brings about a long-lasting adverse impact even at juvenile and adult age, attracts extensive concerns. However, to date the consensus has not been reached and how exposure to sevoflurane in early life affects long-term ability of learning and memory is not fully elucidated. To obtain further insight into this issue, 32 neonatal SD rats were assigned into control group (group C, n=16) and sevoflurane group (group SEV, n=16). At postnatal day 7 (P7), 14 (P14) and 21 (P21) rats pups in group SEV received repeated exposure to 2.6% sevoflurane for 2 h. At juvenile and adult age, Morris water maze (MWM) was used to determine the spatial memory performance. Subsequently long-term and short-term synaptic plasticity in hippocampal CA1 region were investigated by in vivo electrophysiological method. Our behavioral data revealed that repeated exposure to 2.6% sevoflurane in early life did not result in marked behavioral abnormalities. However, in electrophysiological experiment, long-term potentiation (LTP) in hippocampal neurons of animals neonatally exposed to sevoflurane was significantly inhibited as compared to animals in group C at both juvenile and adult age. Pair-pulse facilitation (PPF) ratio in group SEV at juvenile and adult age was augmented to varying extent. These effects were most noticeable at juvenile stage with tendency of alleviation during adulthood. The present study provides an alternative explanation for the mechanism underlying developmental neurotoxicity of sevoflurane, which may ameliorate future preventive and therapeutic strategies.

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

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

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Neurotoxicity of propofol on rat hypoglossal motoneurons in vitro

Although propofol is a widely used intravenous general anaesthetic, many studies report its toxic potential, particularly on the developing central nervous system. We investigated its action on hypoglossal motoneurons (HMs) that control two critical functions in neonates, namely tongue muscle activity and airway patency. Thus, clinically relevant concentrations of propofol (1 and 5μM) were applied (4h) to neonatal rat brainstem slices to evaluate the expression of apoptosis-inducing factor (AIF) as biomarker of toxicity. This anaesthetic strongly increased AIF in the cytoplasm and the nucleus, without early loss of HMs. Electrophysiological recordings from HMs showed that propofol (5μM) enhanced GABA- and glycine-evoked current amplitude and lengthened GABAergic current decay time. Propofol also depressed NMDA receptor-mediated responses without affecting AMPA receptors. Since GABA and glycine depolarize neonatal HMs, we propose that the damaging action by propofol on these motoneurons might arise from the facilitated action of these transmitters with subsequent cytoplasmic Ca²⁺ overload. This phenomenon, in turn, may trigger cell death mechanisms manifested as increased expression of AIF and its translocation into the nucleus. Since propofol is also employed for induction and maintenance of paediatric surgery, caution is needed because its potential neurotoxicity might negatively impact neurodevelopment.

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

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

Dantrolene, a treatment for Alzheimer disease?

Alzheimer disease (AD) is a fatal progressive disease and the most common form of dementia without effective treatments. Previous studies support that the disruption of endoplasmic reticulum Ca through overactivation of ryanodine receptors plays an important role in the pathogenesis of AD. Normalization of intracellular Ca homeostasis could be an effective strategy for AD therapies. Dantrolene, an antagonist of ryanodine receptors and an FDA-approved drug for clinical treatment of malignant hyperthermia and muscle spasms, exhibits neuroprotective effects in multiple models of neurodegenerative disorders. Recent preclinical studies consistently support the therapeutic effects of dantrolene in various types of AD animal models and were summarized in the current review.

Acute and Long-Term Effects of Brief Sevoflurane Anesthesia During the Early Postnatal Period in Rats

The possibility that exposure to general anesthetics during early life results in long-term impairment of neural function attracted considerable interest over the past decade. Extensive laboratory data suggest that administration of these drugs during critical stages of central nervous system development can lead to cell death, impaired neurogenesis, and synaptic growth as well as cognitive deficits. These observations are corroborated by several recent human epidemiological studies arguing that such cognitive impairment might also occur in humans. Despite the potential public health importance of this issue, several important questions remain open. Amongst them, how the duration of anesthesia exposure impact on outcome is as yet not fully elucidated. To gain insight into this question, here we focused on the short- and long-term impact of a 30-min-long exposure to clinically relevant concentrations of sevoflurane in rat pups at 2 functionally distinct stages of the brain growth spurt. We show that this treatment paradigm induced developmental stage-dependent and brain region-specific acute but not lasting changes in dendritic spine densities. Electrophysiological recordings in hippocampal brain slices from adult animals exposed to anesthesia in the early postnatal period revealed larger paired-pulse facilitation but no changes in the long-term potentiation paradigm when compared with nonanesthetized controls. 5-bromo-2-deoxyuridine pulse and pulse-chase experiments demonstrated that neither proliferation nor differentiation and survival of hippocampal progenitors were affected by sevoflurane exposure. In addition, behavioral testing of short- and long-term memory showed no differences between control and sevoflurane-exposed animals. Overall, these results suggest that brief sevoflurane exposure during critical periods of early postnatal development, although it does not seem to exert major long-term effects on brain circuitry development, can induce subtle changes in synaptic plasticity and spine density of which the physiological significance remains to be determined.