Growing evidence demonstrates that prolonged exposure to general anesthetics induces widespread neuronal cell death followed by long-term memory and learning disability in animal models, raising serious concerns about the safety of obstetric and pediatric anesthesia. Although the underlying mechanisms of increased anesthetic-induced neurotoxicity are complex and just beginning to be understood, our exciting preliminary data point to the role of microRNAs in neurotoxicity. MicroRNAs are endogenous, small, non- coding RNAs that are powerful regulators in normal development and physiology, and diseases through inhibition of target gene expression. Specifically, miR-21 has been shown to decrease apoptosis in varying cell types. Based on our preliminary data and previous reports by others, we hypothesized that the increased mitochondrial fission conferred by downregulated miR-21 contributes to the anesthetic (propofol) neurotoxicity. Propofol is most widely used for sedation and anesthesia in pediatric and obstetric medicine. We propose to utilize gain- and loss-of-function approaches to examine the role of miR-21 in propofol neurotoxicity in mice, translate the findings to humans using stem cell-derived neurons, and investigate the following molecular mechanisms underlying the roles of miR-21 effect: miR-21 targets and suppresses programmed cell death 4 (PDCD4), which can: 1) activate protein kinase B (Akt), 2) decrease mitochondrial fission, delay opening of mitochondrial permeability transition pore (mPTP), and 3) reduce cell death. Downregulated miR-21, upregulated PDCD4, attenuated activation of Akt, and increased mitochondrial fission are likely to contribute to the neurotoxicity conferred by propofol. Our initial exciting data indicate that propofol causes downregulation of miR-21 in stem cell-derived human neurons. In addition, miR-21 knockout increases the vulnerability of mouse developmental neurons and human neurons to propofol exposure. Overexpression of miR-21 attenuated propofol-induced apoptosis in cultured human neurons. Moreover, the reduction of miR-21 is accompanied with a decrease of Akt activation, an increase of mitochondrial fission, and an increase in mPTP opening in human neurons, strongly supporting our hypothesis. We propose the following Specific Aims for the next five years to test our hypotheses: 1) to examine the role of miR-21 in propofol neurotoxicity in mouse brains; 2) to determine the role of miR-21 in propofol neurotoxicity in human neurons; and 3) to determine the role of miR-21/PDCD4/mitochondrial fission pathway in propofol neurotoxicity in human neurons and mouse brains. This is a highly clinically relevant study that is innovative and at the forefront in this field. Based on the findings from this proposed study, we can develop more rational neuroprotection strategies, leading to major advances toward assuring the safety of anesthesia in pediatric populations.
Growing evidence demonstrates that prolonged anesthesia with general anesthetics induces widespread neuronal cell death followed by long-term memory and learning disabilities in animal models; seriously questioning the safety of obstetric and pediatric anesthesia. The underlying mechanisms of increased neurotoxicity are complex and just beginning to be understood, and so far, there is no information about microRNA effect in anesthetic neurotoxicity. We propose to utilize gain- and loss-of-function approaches to examine the role of miR-21 in anesthetic neurotoxicity in mice, translate the findings to humans using stem cell-derived neurons, and investigate the novel molecular mechanisms underlying the roles of miR-21 effect. This project is highly clinically relevant and the results will be directly pertinent to a better understanding of the neurotoxic effect of anesthetics. Importantly, the proposed research has the potential of translational application: Identification of the microRNA signaling pathways of anesthetic-induced neurotoxicity will allow targeting molecules that can prevent this effect.
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