MECHANISMS OF 1,3-DINITROBENZENE TESTICULAR TOXICITY

1,3-二硝基苯睾丸毒性机制

基本信息

批准号：
2154508
负责人：
MARION G MILLER
金额：
$ 10.81万
依托单位：
UNIVERSITY OF CALIFORNIA AT DAVIS
依托单位国家：
美国
项目类别：
财政年份：
1993
资助国家：
美国
起止时间：
1993-05-01 至 1996-04-30
项目状态：
已结题

项目摘要

With growing awareness of the capacity of chemicals to adversely affect male reproduction, there is a pressing need to increase our knowledge about the mechanisms by which chemicals cause reproductive damage. The need is apparent since the ability both to extrapolate from laboratory animals to man and to improve toxicity testing depends on knowledge of the biological system and how toxicants perturb it. In the proposed studies, the class of testicular toxicants of interest are the nitroaromatics which are widely used as pesticides, explosives, pharmaceuticals and chemical intermediates in industrial syntheses. The model testicular toxicant and nitroaromatic is 1,3-dinitrobenzene (1,3-DNB). Using laboratory animal models, the strategy will be first to investigate the role of metabolism (both hepatic and intratesticular) in the testicular toxicity of 1,3-DNB. Which metabolite is responsible for toxicity and the nature of its interactions with cellular constituents will represent the second stage of the research. Taking into account the information derived from the animal studies, a final goal is to establish relationship between the animal model and the human situation using human tissue in in vitro studies. To accomplish these objectives, the approach will be to test hypotheses in vivo then investigate specific cellular events in vitro. The first specific aim is to establish what role the liver plays in the modulation of 1,3-DNB testicular toxicity. Preliminary studies have implicated extratesticular events in 1,3-DNB toxicity since intratesticular administration of high levels of 1,3-DNB did not result in significant testicular damage. Two scenarios could be envisioned which could account for this result. Firstly, the liver may metabolize 1,3-DNB to a species which is capable of circulating in the blood and eliciting toxicity in the testes. Nitronitrosobenzene will be investigated as the most likely candidate for a circulating toxic metabolite. Second, a less direct interaction can be proposed where liver metabolism generates methemoglobin-forming metabolite(s) setting up conditions of oxygen deficiency. Low oxygen conditions within the testes would promote reductive metabolism of 1,3-DNB either magnifying the oxygen deficit through an increase in oxygen utilization via redox cycling or increasing the formation of a toxic metabolite such as nitronitrosobenzene. Magnification of the oxygen deficiency could lead to disruption of Sertoli cell homeostasis with a consequent inability to support the developing germ cell population. For specific aim two, in vitro mechanistic studies will explore further the in vivo hypotheses focussing on 1) detection of cellular indicators of metabolic activation to metabolite(s) capable of redox cycling, and 2) the capacity of the electrophilic metabolite nitronitrosobenzene to bind to cellular nucleophiles and disrupt cellular homeostasis. Also; the subcellular localization and identity of the reductases involved in 1,3-DNB metabolism will be investigated. The third specific aim is to compare the capacity of human and animal tissue to metabolize 1,3-DNB and to predict relative toxicity between species.

随着对化学物质能力不利影响能力的认识男性繁殖，迫切需要增加我们的知识关于化学物质会导致生殖损害的机制。这需求是显而易见的，因为两者都可以从实验室推断动物到人并改善毒性测试取决于生物系统以及如何有毒物质扰动它。在提议中研究，感兴趣的睾丸毒物类是硝化植物药被广泛用作农药，炸药，工业合成中的药品和化学中间体。这模型睾丸毒物和氮气为1,3-二硝基苯（1,3-DNB）。使用实验室动物模型，该策略将首先研究代谢（包括肝和肠内）在 1,3-DNB的睾丸毒性。哪种代谢物负责毒性及其与细胞成分相互作用的性质将代表研究的第二阶段。考虑到从动物研究中得出的信息，最终的目标是建立动物模型与人类状况之间的关系在体外研究中组织。为了实现这些目标，方法将在体内检验假设，然后研究特定的细胞体外事件。第一个具体目的是确定角色肝脏在调节1,3-DNB睾丸毒性中发挥作用。初步研究暗示了1,3-DNB中的杀菌性事件毒性以来是静脉内给药高水平的1,3-DNB 没有导致重大睾丸损伤。两种情况可能是设想哪个可以解释此结果。首先，肝脏可能将1,3-DNB代谢为能够循环的物种睾丸中的血液和引起的毒性。硝基苯将是被调查为循环有毒的最有可能的候选人代谢物。其次，可以提出不太直接的互动肝新陈代谢产生高产球蛋白形成代谢物（S）设置氧缺乏的条件。睾丸内的低氧条件将促进1,3-DNB的还原代谢要么放大通过增加氧化还原的氧气利用来增加氧气不足循环或增加有毒代谢物的形成，例如硝基苯苯。氧气不足的放大可能会导致破坏Sertoli细胞稳态，因此无法支持发展中的生殖细胞种群。对于特定目标两个，体外机械研究将进一步探索体内假设专注于1）检测代谢激活的细胞指标能够氧化还原循环的代谢产物和2）亲电代谢产物硝基苯苯与细胞结合亲核和破坏细胞稳态。还;亚细胞涉及1,3-DNB的还原酶的定位和身份将研究代谢。第三个具体目的是比较人类和动物组织代谢1,3-DNB的能力和预测物种之间的毒性。