Background Recent studies in various animal models have suggested that anesthetics such as propofol, when administered early in life, can lead to neurotoxicity. These studies have raised significant safety concerns regarding the use of anesthetics in the pediatric population and highlight the need for a better model by which to study anesthetic-induced neurotoxicity in humans. Human embryonic stem cells (hESCs) are capable of differentiating into any cell type and represent a promising model to study mechanisms governing anesthetic-induced neurotoxicity. Methods Cell death in hESC-derived neurons was assessed using TUNEL staining and microRNA (miR) expression was assessed using quantitative reverse transcription polymerase chain reaction (qRTPCR). miR-21 was overexpressed and knocked down using a miR-21 mimic and antagomir, respectively. Sprouty 2 was knocked down using a small interfering RNA and the expression of the miR-21 targets of interest was assessed by Western blot. Results Propofol dose and exposure time-dependently induced significant cell death (n = 3) in the neurons and downregulated several microRNAs, including miR-21. Overexpression of miR-21 and knockdown of Sprouty 2 attenuated the increase in TUNEL-positive cells following propofol exposure. In addition, miR-21 knockdown increased the number of TUNEL-positive cells by 30% (n = 5). Finally, activated Signal Transducer and Activator of Transcription 3 (STAT3) and protein kinase B (Akt) were downregulated and Sprouty 2 was upregulated following propofol exposure (n = 3). Conclusions These data suggest that: (1) hESC-derived neurons represent a promising in vitro human model for studying anesthetic-induced neurotoxicity, (2) propofol induces cell death in hESC-derived neurons and (3) the propofol-induced cell death may occur via a STAT3/miR-21/Sprouty2-dependent mechanism.

Background Studies in developing animals have shown that when anesthetic agents are administered early in life, it can lead to neuronal cell death and learning disabilities. Development of human embryonic stem cell (hESC)-derived neurons has provided a valuable tool for understanding the effects of anesthetics on developing human neurons. Unbalanced mitochondrial fusion/fission leads to various pathological conditions including neurodegeneration. The aim of this study was to dissect the role of mitochondrial dynamics in propofol-induced neurotoxicity. Methods TUNEL staining was used to assess cell death in hESC-derived neurons. Mitochondrial fission was assessed using TOM20 staining and electron microscopy. Expression of mitochondrial fission-related proteins was assessed by Western blot and confocal microscopy was used to assess opening time of the mitochondrial permeability transition pore (mPTP). Results Exposure to 6 hours of 20 μg/mL propofol increased cell death from 3.18±0.17% in the control-treated group to 9.6±0.95% and led to detrimental increases in mitochondrial fission (n=5 coverslips/group) accompanied by increased expression of activated dynamin-related protein 1 (Drp1) and cyclin-dependent kinase 1 (CDK1), key proteins responsible for mitochondrial fission. Propofol exposure also induced earlier opening of the mPTP from 118.9±3.1 seconds in the control-treated group to 73.3±1.6 seconds. Pretreatment of the cells with mdivi-1, a mitochondrial fission blocker rescued the propofol-induced toxicity, mitochondrial fission and mPTP opening time (n=75 cells/group). Inhibiting CDK1 attenuated the increase in cell death and fission and the increase in expression of activated Drp1. Conclusions These data demonstrate for the first time that propofol-induced neurotoxicity occurs through a mitochondrial fission/mPTP-mediated pathway.

Mounting pre-clinical evidence in rodents and non-human primates has demonstrated that prolonged exposure of developing animals to general anesthetics can induce widespread neuronal cell death followed by long-term memory and learning disabilities. In vitro experimental evidence from cultured neonatal animal neurons confirmed the in vivo findings. However, there is no direct clinical evidence of the detrimental effects of anesthetics in human fetuses, infants, or children. Development of an in vitro neurogenesis system using human stem cells has opened up avenues of research for advancing our understanding of human brain development and the issues relevant to anesthetic-induced developmental toxicity in human neuronal lineages. Recent studies from our group, as well as other groups, showed that isoflurane influences human neural stem cell proliferation and neurogenesis, while ketamine induces neuroapoptosis. Application of this high throughput in vitro stem cell neurogenesis approach is a major stride toward assuring the safety of anesthetic agents in young children. This in vitro human model allows us to (1) screen the toxic effects of various anesthetics under controlled conditions during intense neuronal growth, (2) find the trigger for the anesthetic-induced catastrophic chain of toxic events, and (3) develop prevention strategies to avoid this toxic effect. In this paper, we reviewed the current findings in anesthetic-induced neurotoxicity studies, specifically focusing on the in vitro human stem cell model.

Background Anesthetic cardioprotection reduces myocardial infarct size following ischemia-reperfusion injury. Currently, the role of microRNA in this process remains unknown. MicroRNAs are short, non-coding nucleotide sequences that negatively regulate gene expression through degradation or suppression of messenger RNA. In this study, we uncovered the functional role of microRNA-21 (miR-21) upregulation after anesthetic exposure. Methods MicroRNA and messenger RNA expression changes were analyzed by quantitative real-time polymerase chain reaction in cardiomyocytes after exposure to isoflurane. Lactate dehydrogenase release assay and propidium iodide staining were conducted after inhibition of miR-21. miR-21 target expression was analyzed by Western Blot. The functional role of miR-21 was confirmed in vivo in both wild type and miR-21 knockout mice. Results Isoflurane induces an acute upregulation of miR-21 in both in vivo and in vitro rat models (n = 6, 247.8 ± 27.5% and 258.5 ± 9.0%), which mediates protection to cardiomyocytes through downregulation of programmed cell death protein 4 (PDCD4) messenger RNA (n = 3, 82.0 ± 4.9% of control group). This protective effect was confirmed through knockdown of miR-21 and PDCD4 in vitro. Additionally, the protective effect of isoflurane was abolished in miR-21 knockout mice in vivo, with no significant decrease in infarct size compared to non-exposed controls (n = 8, 62.3 ± 4.6% and 56.2 ± 3.2%). Conclusions We demonstrate for the first time that isoflurane mediates protection of cardiomyocytes against oxidative stress via a miR-21/PDCD4 pathway. These results reveal a novel mechanism by which the damage done by ischemia-reperfusion injury may be decreased.

BACKGROUND Hyperglycemia can blunt the cardioprotective effects of isoflurane in the setting of ischemia-reperfusion injury. Previous studies suggest that reactive oxygen species (ROS) and increased mitochondrial fission play a role in cardiomyocyte death during ischemia-reperfusion injury. To investigate, the role of glucose concentration in ROS production and mitochondrial fission during ischemia-reperfusion (with and without anesthetic protection), we used the novel platform of human-induced pluripotent stem-cell-derived cardiomyocytes (iPSC-CMs). METHODS Cardiomyocyte differentiation from iPSC was characterized by the expression of CM-specific markers using immunohistochemistry and by measuring contractility. iPSC-CMs were exposed to varying glucose conditions (5, 11, 25 mM) for 24 hours. Mitochondrial permeability transition pore (mPTP) opening, cell viability, and ROS generation end-points were used to assess the effects of various treatment conditions. Mitochondrial fission was monitored by the visualization of fragmented mitochondria using confocal microscopy. Expression of activated dynamin-related protein 1 (Drp1), a key protein responsible for mictochodrial fission was assessed by western blot. RESULTS Cardiomyocytes were successfully differentiated from iPSC. Elevated glucose conditions (11 and 25 mM) significantly increased ROS generation, while only the 25 mM high glucose condition induced mitochondrial fission and increased the expression of activated Drp1 in iPSC-CMs. Isoflurane delayed mPTP opening and protected iPSC-CMs from oxidative stress in 5 and 11 mM glucose conditions to a similar level as previously observed in various isolated animal cardiomyocytes. Scavenging ROS with Trolox or inhibiting mitochondrial fission with mdivi-1 restored the anesthetic cardioprotective effects in iPSC-CMs in 25 mM glucose conditions. CONCLUSIONS Human iPSC-CM is a useful, relevant model for studying isoflurane cardioprotection, and can be manipulated to recapitulate complex clinical perturbations. We demonstrate that the cardioprotective effects of isoflurane in elevated glucose conditions can be restored by scavenging ROS or inhibiting mitochondrial fission. These findings may contribute to further understanding and guidance for restoring pharmacological cardioprotection in hyperglycemic patients.