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

描述(申请人提供)：甲基汞(MeHg)是一种有效的神经毒素。我们推测，在甲基汞诱导的氧化应激条件下，Nrf2协调对抗甲基汞氧化损伤的细胞保护基因的上调，而对Nrf2功能产生负面影响的遗传和生化变化增加了甲基汞的神经毒性。这一假设的推论表明：(I)甲基汞诱发的遗传易感性 神经毒性与Nrf2的表达水平和与抗氧化剂活性相关的下游基因的激活有关，并且(Ii)Nrf2上调的程度代表了细胞特异性(星形胶质细胞与神经元)对甲基汞的适应性反应的关键决定因素。验证这些假说的方法包括Nrf2信号在体内和体外(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重组近交系(RI)小鼠。具体目标1将确定甲基汞暴露在培养的小脑星形胶质细胞和神经元中，以及在体内发育过程中是否诱导与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介导的细胞生存通路是否对Nrf2依赖的甲基汞保护至关重要。具体目标3将测试Nrf2遗传性在调节BXD RI小鼠品系对甲基汞敏感性中的作用。这些特定的目标有望描绘出调节甲基汞神经保护的共同启动信号，揭示与接触这种金属相关的神经毒性机制和易感性。

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.