Mechanisms of methyl dithiocarbamate immunotoxicity

描述（由申请人提供）：甲基二硫代氨基甲酸钠（SMD，也称为元钠）是美国第三大使用最广泛的常规农业农药。它会自发分解形成甲基异硫氰酸酯（MTC），被加州环保局列为有毒空气污染物，并与SMD具有一些免疫调节作用。SMD和MITC均改变小鼠腹膜巨噬细胞中的toll样受体信号，并引起细菌脂多糖（IPS）处理小鼠IL-10浓度的显著升高和IL-12（以及其他促炎细胞因子和趋化因子）浓度的显著降低。SMD还显著降低小鼠对大肠杆菌腹膜炎的先天抵抗力。许多其他化学物质和药物导致IL-10的表达增加，IL-12的表达减少。由于这些变化往往会降低先天免疫，因此了解SMD和MITC影响这些参数的机制对人类健康具有广泛的意义，甚至对未暴露于SMD或MITC的人也是如此。该项目将测试以下假设：SMD通过TLR4改变信号传导，通过改变细胞氧化还原平衡、改变铜的可用性和诱导应激介质来减少IL-12的产生，增加IL-10的产生。这些作用在降低大肠杆菌感染的先天抗性中起关键作用。具体目标1-确定SMD和MITC在腹腔巨噬细胞中增加lps诱导的IL-10产生和减少lps诱导的IL-12产生的机制。特异性目的2-确定SMD改变参与IL-10和IL-12表达的上游激酶激活的机制，并确定IL-10表达增加在SMD和mitc诱导的IL-12表达减少中的作用。特异性目标3-确定目标1和目标2中评估的每种机制在SMD或MITC治疗小鼠对大肠杆菌腹膜炎抵抗力下降中的作用。在每个Aim中，要研究的机制都是假设中提到的（改变氧化还原平衡，改变铜的可用性和诱导应激介质）。在Aim 3中，将开发数学模型来预测或描述信号，基因表达和宿主抗性变化之间的关系。这些结果将代表一种新的（系统生物学）免疫毒理学方法。这些结果将首次允许对SMD和MITC进行基于机制的风险评估。还期望对三种重要作用机制的详细研究可以推广到改变这些参数的其他情况或毒物。

DESCRIPTION (provided by applicant): Sodium methyldithiocarbamate (SMD, also called metam sodium) is the third most abundantly used conventional agricultural pesticide in the U.S. It spontaneously breaks down to form methylisothiocyanate MTC), which has been classified a toxic air contaminant by the California EPA and which shares some immunomodulatory actions, with SMD. Both SMD and MITC alter toll-like receptor signaling in mouse peritoneal macrophages and cause substantial increases in the concentration of IL-10 and substantial decreases in IL-12 (and other pro-inflammatory cytokines and chemokines) in mice treated with bacterial lipopolysaccharide (IPS). SMD also substantially reduces innate resistance to Escherichia coli peritonitis in mice. A number of other chemicals and drugs cause increased expression of IL-10 and decreased expression of IL-12. Because these changes would tend to decrease innate immunity, understanding the mechanisms by which SMD and MITC affect these parameters has broad implications for human health, even for persons not exposed to SMD or MITC. This project will test the following hypothesis: SMD alters signaling through TLR4 to decrease the production of IL-12 and to increase IL-10 production by altering cellular redox balance, altering copper availability, and inducing stress mediators. These effects play key roles in decreasing innate resistance to infection with E. coli. Three aims will be used to test the hypothesis of this project: Specific Aim 1- Determine the mechanism(s) by which SMD and MITC increase LPS-induced IL-10 production and decrease LPS-induced IL-12 production by peritoneal macrophages. Specific Aim 2- Determine the mechanism(s) by which SMD alters activation of upstream kinases involved in IL-10 and IL-12 expression and determine the role of increased IL-10 expression in the SMD and MITC-induced decreases in IL-12 expression. Specific Aim 3- Determine the role of each of the mechanisms evaluated in Aims 1 and 2 in the decreased resistance to E. coli peritonitis in SMD or MITC treated mice. In each Aim the mechanisms to be investigated are those noted in the hypothesis (altered redox balance, altered copper availability, and induction of stress mediators). In Aim 3, mathematical models will be developed to predict or describe the relationships between changes in signaling, gene expression, and host resistance. These results will represent a new (systems biology) approach to immunotoxicology. These results will allow mechanism based risk assessment for SMD and MITC for the first time. It is also expected that the detailed study of three important mechanisms of action, which will be examined in each aim, can be generalized to other situations or toxicants that alter these parameters.