Synergistic Immunosuppression by PAHs and Arsenite

描述(申请人提供)：这些研究的目的是评估多环芳烃(PAHs)和亚砷酸钠(As3)联合暴露对小鼠和人类的免疫抑制机制。众所周知，免疫系统的抑制与抗击感染和癌症的能力下降有关。初步数据显示，当小鼠通过食物和饮用水暴露于体内的As3和PAHs时，表现出协同免疫抑制作用。我们还提供了初步数据，表明人类外周血单个核细胞(HPBMC)在饮用水中发现的与环境相关的钠AS 3水平上受到免疫抑制。PAHs还能增加As3诱导的免疫抑制量。因此，重要的是要了解当暴露单独或联合发生时，这些制剂产生免疫抑制的机制(S)。在这一应用中要检验的中心假设是，PAHs和As3通过DNA损伤和修复途径产生协同免疫抑制。重要的是开发动物模型来研究协同免疫抑制，并进行与人类暴露相关的机制研究。这些研究将确定，在小鼠模型中，饮用水中的砷3和饮食中的多环芳烃(存在于我们呼吸的空气和食物中)的共同暴露是否会比之前发现的任何一类制剂单独作用时产生更大的抑制。我们将确定可能导致这些相互作用的生化机制，并确定饮用水中存在的锌是否可以保护小鼠免受As3的影响。最后，由于我们发现，在美国和世界其他地方的许多人群中，人类血液T淋巴细胞对饮用水中存在的低浓度As3极其敏感，因此我们将确定不同人类(不同年龄和种族的男性和女性)对这些暴露的敏感性。我们将从这些人身上获取外周血细胞，以确定他们的免疫反应是否受到体外单独或联合给予As3和PAH的抑制。这些研究的结果将对理解调节人类免疫系统的环境因素做出重要贡献，并可能为干预饮用水接触砷提供一种方法。 公共卫生相关性：这些研究的目的是评估多环芳烃(PAHs)和亚砷酸钠(As3)联合暴露对小鼠和人类的免疫抑制机制。众所周知，免疫系统的抑制与抗击感染和癌症的能力下降有关。初步数据显示，在体内暴露于As3和PAHs时，小鼠表现出协同免疫抑制作用。我们还提供了初步数据，表明人外周血单个核细胞(HPBMC)对与环境相关的钠砷3暴露水平的T细胞免疫抑制非常敏感，多环芳烃也与AS 3显著相互作用。因此，重要的是要了解当暴露单独或联合发生时，这些制剂产生免疫抑制的机制(S)。在这一应用中需要检验的中心假设是，PAHs和As3通过DNA加合物形成和DNA修复抑制所产生的遗传毒性途径产生协同免疫抑制。重要的是开发体内模型来研究协同免疫抑制，并进行与人类暴露相关的机制研究。在SA1中，我们将利用我们建立的小鼠模型来研究多环芳烃对小鼠脾T依赖抗体反应(TDAR)和骨髓(BM)细胞的前B细胞和粒/单核细胞(GM)祖细胞活性的联合影响。我们提供了令人振奋的新的体外数据，证明了锌可以克服暴露于As3所产生的免疫抑制(脾TDAR)，这可能是基于下面讨论的锌指蛋白理论。我们知道，遗传毒性和P53信号是PAHs产生免疫抑制的重要机制，可能对小鼠的As3也是如此。因此，我们将使用P53基因缺失的小鼠来研究P53对脾和骨髓的抑制作用。在SA2中，我们将确定协同作用的机制是否源于对DNA修复的抑制。我们的初步数据显示，As3抑制DNA修复，多环芳烃和As3联合暴露可能导致PAH体积增加和氧化应激加合物增加，从而增加P53信号转导。我们在以前的研究中发现，AS 3与锌指蛋白PARP-1和XPA结合，导致核苷酸切除修复(NER)和碱基切除修复(BER)途径中的DNA修复受到抑制。我们将在小鼠体内验证补充锌可以逆转As3作用的假说。在SA3中，我们将基于我们的初步数据 人T细胞在体外可被低纳摩尔浓度的As3所抑制。我们还将在体外检测锌2逆转HPBMC这种免疫抑制的能力。由于我们发现个体间存在显著差异，我们将对150个不同的个体进行砷3和多环芳烃暴露的初步表征。这些研究的完成将产生与我们的中心假设有关的关键新数据，并将确定人类免疫系统对多环芳烃和砷3二元暴露的潜在敏感性。

DESCRIPTION (provided by applicant): The purpose of these studies is to evaluate the mechanisms of immunosuppression in mice and humans associated with combined exposures to polycyclic aromatic hydrocarbons (PAHs) and sodium arsenite (As+3). Suppression of the immune system is known to be associated with a decreased ability to fight infections and cancer. Preliminary data is presented that mice demonstrate synergistic immunosuppression when exposed to As+3 and PAHs in vivo through their food and drinking water. We also present preliminary data demonstrating that human peripheral blood mononuclear cells (HPBMC) are immunosuppressed at environmentally relevant levels of sodium As+3 found in drinking water. PAHs were found to increase the amount of As+3 induced immune suppression as well. Therefore, it is important to understand the mechanism(s) of immunosuppression produced by these agents when exposures occur alone or in combination. The central hypothesis to be tested in this application is that PAHs and As+3 produce synergistic immunosuppression through DNA- damaging and repair pathways. It is important to develop animal models to study synergistic immunosuppression and to pursue mechanistic studies of relevance to human exposures. These studies will determine whether co-exposures from As+3 in drinking water and PAHs in the diet (which are present in the air we breathe and the food we eat) in mouse models result in greater suppression than has previously been found for either class of agents on their own. We will determine the biochemical mechanisms potentially responsible for these interactions, and we will determine whether Zn+2 present in drinking water can protect mice from As+3 exposures. Finally, because we found that human blood T lymphocytes are extremely sensitive to low concentrations of As+3 that are present in drinking water in many populations in the U.S. and elsewhere in the world, we will determine the sensitivities of various humans (males and females of different ages and ethnicities) to these exposures. We will obtain peripheral blood cells from these individuals to determine whether their immune response are suppressed by As+3 and PAH given in vitro alone or in combination. The results of these studies will make an important contribution to understanding environmental agents that modulate the human immune system and perhaps provide an approach to intervention for As+3 drinking water exposures. PUBLIC HEALTH RELEVANCE: The purpose of these studies is to evaluate the mechanisms of immunosuppression in mice and humans associated with combined exposures to polycyclic aromatic hydrocarbons (PAHs) and sodium arsenite (As+3). Suppression of the immune system is known to be associated with a decreased ability to fight infections and cancer. Preliminary data is presented that mice demonstrate synergistic immunosuppression when exposed to As+3 and PAHs in vivo. We also present preliminary data demonstrating that human peripheral blood mononuclear cells (HPBMC) are extremely sensitive to T cell immunosuppression by environmentally relevant levels of exposure to sodium As+3 and that PAHs interact significantly with As+3 as well. Therefore, it is important to understand the mechanism(s) of immunosuppression produced by these agents when exposures occur alone or in combination. The central hypothesis to be tested in this application is that PAHs and As+3 produce synergistic immunosuppression through genotoxic pathways resulting from DNA adduct formation and inhibition of DNA repair. It is important to develop in vivo models to study synergistic immunosuppression and to pursue mechanistic studies of relevance to human exposures. In SA1 we will utilize our established mouse model for studies of the combined effects of PAHs, on the T-dependent antibody response (TDAR) in murine spleen and pre-B and granulocyte/monocyte (GM) progenitor cell activity of bone marrow (BM) cells. We provide exciting new in vitro data demonstrating that Zn+2 can overcome the immunosuppression (spleen TDAR) produced by exposures to As+3, perhaps based on the zinc finger protein theory discussed below. We know that genotoxicity and p53 signaling are important mechanisms of immunosuppression produced by PAHs, and perhaps for As+3 in mice. Therefore, we will examine the p53- dependence of spleen and BM suppression using p53 null mice. In SA2 we will determine whether the mechanism of synergy is due to inhibition of DNA repair. Our preliminary data show that As+3 inhibits DNA repair and that co-exposures to PAHs and As+3 may lead to an increase in PAH bulky and oxidative stress adducts resulting in increased p53 signaling. In our previous studies we showed that As+3 binds to the zinc finger proteins, PARP-1 and XPA, leading to inhibition of DNA repair in both Nucleotide Excision Repair (NER) and Base Excision Repair (BER) pathways. We will test the hypothesis that Zn+2 supplementation can reverse the effects of As+3 in vivo in mice. In SA3, we will build on our preliminary data that human T cells are inhibited by low nanomolar (nM) concentrations of As+3 exposures in vitro. We will also examine the ability of Zn+2 to reverse this immunosuppression in HPBMC in vitro. Because we have found that there are significant inter-individual differences, we will perform initial characterization of As+3 and PAH exposure in 150 different individuals. Completion of these studies will yield critical new data relating to our central hypothesis and will determine th potential sensitivities of the human immune system to binary exposures of PAHs and As+3.