Genetic Modulation of MeHg-Induced Oxidative Stress in the Developing Brain

描述（由申请人提供）：甲基汞（MeHg）是一种强效神经毒素。我们假设在甲基汞诱导的氧化应激条件下，Nrf2 协调细胞保护基因的上调，以对抗甲基汞诱导的氧化损伤，并且对 Nrf2 功能产生负面影响的遗传和生化变化会增加甲基汞的神经毒性。这一假设的推论意味着 (i) 对甲基汞诱发的遗传易感性 神经毒性与 Nrf2 表达水平和与抗氧化活性相关的下游基因的激活相关，并且 (ii) Nrf2 上调程度代表细胞特异性（星形胶质细胞与神经元）对 MeHg 适应性反应的关键决定因素。测试这些假设的方法包括体内和体外 Nrf2 信号传导（原代星形胶质细胞和神经元）的生化和分子表征，以及神经生物学表型（生化、形态学和神经行为终点）的遗传相关性，充分利用独特的 BXD 重组近交 (RI) 小鼠。具体目标 1 将确定在培养的小鼠原代小脑星形胶质细胞和神经元中以及在体内发育过程中接触 MeHg 是否会诱导与 Nrf2 转录激活相关的氧化应激。具体目标 2 将评估磷脂酰肌醇 3 激酶 (PI3K)-丝氨酸/苏氨酸蛋白激酶 Akt 介导的细胞存活途径对于 Nrf2 依赖性的 MeHg 保护是否至关重要。具体目标 3 将测试 Nrf2 遗传力在调节 BXD RI 小鼠品系的甲基汞敏感性中的作用。这些具体目标有望描述甲基汞神经保护调节的常见引发信号，揭示与接触这种金属相关的神经毒性机制和敏感性。

DESCRIPTION (provided by applicant): Methylmercury (MeHg) is a potent neurotoxin. We hypothesize that under conditions of MeHg-induced oxidative stress, Nrf2 coordinates the upregulation of cytoprotective genes that combat MeHg- induced oxidative injury, and that genetic and biochemical changes that negatively impact upon Nrf2 function increase MeHg's neurotoxicity. Corollaries of this hypothesis imply (i) that genetic susceptibility to MeHg-induced neurotoxicity correlates with Nrf2 expression levels and activation of downstream genes associated with antioxidant activity, and (ii) the degree of Nrf2 upregulation represents a critica determinant of cell-specific (astrocytes vs. neurons) adaptive responses to MeHg. The approach to testing these hypotheses includes biochemical and molecular characterization of Nrf2 signaling both in vivo and in vitro (primary astrocytes and neurons), and genetic correlates of neurobiological phenotypes (biochemical, morphological and neurobehavioral endpoints), taking full advantage of the unique BXD recombinant inbred (RI) mice. Specific Aim 1 will determine if MeHg exposure in cultured murine primary cerebellar astrocytes and neurons, and during development in vivo induces oxidative stress that correlates with Nrf2 transcriptional activation. Specific Aim 2 will evaluate whether the phosphatidylinositol 3-kinase (PI3K)-serine/threonine protein kinase Akt-mediated cell survival pathway is essential for Nrf2-dependent protection against MeHg. Specific Aim 3 will test the role of Nrf2 heritability in modulating MeHg susceptibility in BXD RI mouse strains. These specific aims hold the promise of delineating common initiator signals for the modulation of MeHg neuroprotection, shedding light on neurotoxic mechanisms and susceptibility associated with exposure to this metal.