Early Developmental Exposure to General Anesthetic Agents in Primary Neuron Culture Disrupts Synapse Formation via Actions on the mTOR Pathway

Abstract

Human epidemiologic studies and laboratory investigations in animal models suggest that exposure to general anesthetic agents (GAs) have harmful effects on brain development. The mechanism underlying this putative iatrogenic condition is not clear and there are currently no accepted strategies for prophylaxis or treatment. Recent evidence suggests that anesthetics might cause persistent deficits in synaptogenesis by disrupting key events in neurodevelopment. Using an in vitro model consisting of dissociated primary cultured mouse neurons we demonstrate abnormal pre- and post-synaptic marker expression after a clinically relevant isoflurane anesthesia exposure conducted during neuron development. We find that pharmacologic inhibition of the mechanistic target of rapamycin (mTOR) pathway can reverse the observed changes. Isoflurane exposure increases expression of phospho-S6, a marker of mTOR pathway activity, in a concentration-dependent fashion and this effect occurs throughout neuronal development. The mTOR 1 complex (mTORC1) and the mTOR 2 complex (mTORC2) branches of the pathway are both activated by isoflurane exposure and this is reversible with branch-specific inhibitors. Upregulation of mTOR is also seen with sevoflurane and propofol exposure, suggesting that this mechanism of developmental anesthetic neurotoxicity may occur with all the commonly used GAs in pediatric practice. We conclude that GAs disrupt the development of neurons during development by activating a well-defined neurodevelopmental disease pathway and that this phenotype can be reversed by pharmacologic inhibition.

Linoleic acid‐derived metabolites constitute the majority of oxylipins in the rat pup brain and stimulate axonal growth in primary rat cortical neuron‐glia co‐cultures in a sex‐dependent manner

“…Male and female pups were euthanized at birth or on post‐natal day 1 by decapitation using sterile scissors following cold‐induced anesthesia. This method of anesthesia was chosen over CO 2 or chemical sedatives because neonatal pups are resistant to CO 2 ‐induced anesthesia (Duffy et al ), and common chemical sedatives they are known to interfere with neuronal morphogenesis (Xu et al ). Euthanasia was performed between 8 am and 12 noon.…”

Isoflurane Exposure in Juvenile Caenorhabditis elegans Causes Persistent Changes in Neuron Dynamics

“…29 A growing body of literature further describes mTOR-dependent anesthesia-induced effects in neurodevelopmentally immature rodents. Mintz and colleagues 32,33 have demonstrated in mouse models that isoflurane anesthesia is capable of eliciting abnormal dendrite arbor and spine development, pre-and postsynaptic marker expression, and also deficiencies in spatial learning and memory. These effects were all blocked by rapamycin administration.…”

Resveratrol Mitigates Sevoflurane-Induced Neurotoxicity by the SIRT1-Dependent Regulation of BDNF Expression in Developing Mice

“…Amounts of studies implied that resveratrol could influence autophagy, oxidative stress, and inflammation through the mTOR pathway [49,[82][83][84]. Additionally, the mTOR pathway was found to take part in the regulation of dendritic growth, synapse formation, and synaptic protein expression [85][86][87]. It was reported that general anesthetics, including sevoflurane, induced developmental neuronal injury by activating the mTOR pathway [87][88][89][90].…”

“…Additionally, the mTOR pathway was found to take part in the regulation of dendritic growth, synapse formation, and synaptic protein expression [85][86][87]. It was reported that general anesthetics, including sevoflurane, induced developmental neuronal injury by activating the mTOR pathway [87][88][89][90]. In light of the fact that mTOR and BDNF interact in a complicated way in physiological or pathological settings [91,92], we did not explore the crosstalk between BDNF and mTOR signaling in the sevoflurane-induced injury in the present study.…”