Mechanisms of anesthesia mediaited neurotoxicity

描述(申请人提供)：越来越多的证据表明，常用的吸入麻醉剂，特别是异氟醚，会导致发育中的大脑中的神经细胞凋亡，这与记忆丧失和学习障碍有关。这项研究的长期目标是了解麻醉介导的神经毒性的机制，期望这一知识最终将导致更有效和更安全的吸入麻醉药的使用。本研究的直接目的是验证我们的中心假设，即吸入麻醉药通过过度激活内质网(ER)膜上的钙通道(IP3受体)而导致内质网(ER)过度释放钙，从而以剂量和时间依赖的方式通过诱导细胞死亡来诱导细胞死亡。该项目的另一个目标是研究和更好地了解异氟醚在细胞培养和动物模型中的神经毒性和神经保护作用的双重特征。我们将通过以下具体目标来检验这些假设：(1)。目的1通过IP3受体的过度激活，检测异氟醚是否通过导致内质网钙释放过多和内质网钙离子耗竭而诱导细胞凋亡。我们将研究这些效应是否会通过凋亡导致神经元死亡，特别是在IP3受体活性升高的神经元中，例如带有阿尔茨海默氏症早老素-1突变的细胞或亨廷顿病Q111突变的细胞。(2)。目的检测长期暴露于异氟醚是否通过IP3受体的过度激活而诱导发育中大鼠脑内神经细胞的凋亡、随后的记忆和学习障碍。我们还将测试IP3受体拮抗剂xestospongin C(3)是否能抑制这些作用。目的3将研究在细胞培养和动物模型中短期暴露异氟醚是否通过激活IP3受体使神经元从内质网适度释放钙来提供神经保护。AIM 3将进一步研究这些诱导的内源性神经保护机制是通过某些内质网应激蛋白(如GRP78、HSP70)的过度表达还是通过凋亡调节蛋白(如Bcl2/Bax)的变化而发生的。我们的初步研究表明，在相同的浓度下，七氟醚和地氟醚比异氟醚诱导细胞凋亡以及内质网异常钙释放的效力要小得多。我们将进一步比较异氟醚、七氟醚和地氟醚在细胞培养和动物模型中的神经毒性作用。 公共卫生相关性：我们的初步研究表明，常用的吸入麻醉剂，特别是异氟醚，通过过度激活ER膜上的钙通道(IP3受体)，导致内质网过度释放钙，从而导致神经细胞凋亡。因此，我们打算研究吸入麻醉剂通过破坏细胞内钙稳态而诱导神经细胞凋亡的机制。最终，我们希望制定一项战略，以防止这些有害影响。这项研究将增加我们对全身麻醉介导的神经毒性的了解，并使外科患者更安全地使用吸入麻醉药。

DESCRIPTION (provided by applicant): Increasing evidence suggests that commonly used inhaled anesthetics, especially isoflurane, cause neuronal apoptosis in the developing brain, which is associated with memory loss and learning disabilities. The long term goal of this research is to understand the mechanisms of anesthesia-mediated neurotoxicity, with an expectation that this knowledge will eventually lead to more efficacious and safer use of inhaled anesthetics. The immediate goal of the study is to test our central hypothesis that inhaled anesthetics induce cell death by apoptosis in a dose- and time-dependent manner by causing excessive calcium release from the endoplasmic reticulum (ER) via over activation of a calcium channel (IP3 receptor) on the ER membrane. An additional goal of this project is to study and better understand the double features of isoflurane's neurotoxic and neuroprotective effects in both cell culture and animal models. We will test these hypotheses via the following specific aims: (1). Aim 1 will test whether prolonged exposure of isoflurane induces apoptosis by causing excessive calcium release from the ER and depletion of ER calcium via over activation of IP3 receptor. We will examine whether these effects lead to neuronal death by apoptosis, especially in neurons with elevated IP3 receptor activity such as cells with Alzheimer's presenilin-1 mutation or Huntington's Q111 mutation. (2). Aim 2 will test whether prolonged exposure of Isoflurane induces neuronal apoptosis, subsequent memory and learning disabilities in developing rat brains by over activation of IP3 receptors. We will also test whether these effects can be inhibited by the IP3 receptor antagonist xestospongin C. (3). Aim 3 will examine whether a short exposure of isoflurane in cell culture and animal models provides neuroprotection by preconditioning neurons with a moderate calcium release from the ER via activation of IP3 receptors. Aim 3 will further examine whether these induced endogenous neuroprotective mechanisms occur by over expression of some ER stress proteins (e.g. GRP78, HSP70) or changes of apoptotic regulatory proteins (e.g. Bcl-2/Bax). Our preliminary studies have suggested that sevoflurane and desflurane, at equipotent concentrations, have much less potency than isoflurane to cause apoptosis, as well as abnormal calcium release from the ER. We will further compare the neurotoxic effects of isoflurane, sevoflurane and desflurane in both cell culture and animal models. PUBLIC HEALTH RELEVANCE: Our preliminary studies suggest that commonly used inhaled anesthetics, especially isoflurane, induce apoptotic neuronal death by causing excessive calcium release from the endoplasmic reticulum via over activation of a calcium channel (IP3 receptor) on the ER membrane. We therefore intend to study the mechanisms through which inhaled anesthetics induce neuronal apoptosis via disruption of intracellular calcium homeostasis. Ultimately we hope to develop a strategy to prevent these harmful effects. This research will increase our understanding of general anesthesia-mediated neurotoxicity and make a safer use of inhaled anesthetics to surgical patients.