MECHANISMS OF 1,3-DINITROBENZENE TESTICULAR TOXICITY

1,3-二硝基苯睾丸毒性机制

• 批准号: 3253986
• 负责人: MARION G MILLER
• 金额: $ 13.41万
• 依托单位: UNIVERSITY OF CALIFORNIA AT DAVIS
• 依托单位国家: 美国
• 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
• 来源: https://reporter.nih.gov/project-details/3253986
• 关键词: biotransformation; chemical binding; cytotoxicity; environmental toxicology; gas chromatography mass spectrometry; gel electrophoresis; hamsters; high performance liquid chromatography; histopathology; human tissue; laboratory rat; liver metabolism; nitrobenzene; oxidation reduction reaction; oxygen consumption; radiotracer; respiratory gas level; testis disorder; tissue /cell culture; toxicant interaction; toxin metabolism

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.

随着人们越来越认识到化学品的不利影响能力 男性生殖，迫切需要增加我们的知识 关于化学品造成生殖损害的机制。 这 需求是显而易见的，因为从实验室推断的能力 动物对人类的毒性测试的改进取决于以下方面的知识 生物系统以及有毒物质如何干扰它。 在提议的 研究中，感兴趣的睾丸毒物类别是 硝基芳烃广泛用作杀虫剂、炸药、 工业合成中的药物和化学中间体。 这 模型睾丸毒物，硝基芳香族化合物是1,3-二硝基苯 (1,3-DNB)。使用实验动物模型，该策略将首先 研究代谢（肝脏和睾丸内）的作用 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 来自动物研究的信息，最终目标是建立 动物模型与人类情况之间的关系 体外研究中的组织。 为了实现这些目标，方法 将在体内测试假设，然后研究特定的细胞 体外事件。第一个具体目标是确定 肝脏参与调节 1,3-DNB 睾丸毒性。 初步研究表明 1,3-DNB 涉及睾丸外事件 睾丸内注射高浓度 1,3-DNB 后的毒性 并没有造成明显的睾丸损伤。 可能有两种情况 设想什么可以解释这个结果。 首先，肝脏可能 将 1,3-DNB 代谢为能够在体内循环的物质 血液并引起睾丸毒性。 亚硝基亚硝基苯将 被调查为循环有毒物质的最有可能的候选者 代谢物。 其次，可以提出一种不太直接的互动，其中 肝脏代谢产生高铁血红蛋白形成代谢物 缺氧的条件。 睾丸内的低氧条件 会促进 1,3-DNB 的还原代谢，或者放大 通过氧化还原增加氧利用率而导致缺氧 循环或增加有毒代谢物的形成，例如 亚硝基亚硝基苯。 缺氧的放大可能导致 破坏支持细胞稳态，从而导致无法 支持生殖细胞群的发育。 对于具体目标二， 体外机制研究将进一步探索体内假设 重点关注1）代谢激活细胞指标的检测 能够进行氧化还原循环的代谢物，以及 2) 的容量 亲电代谢物亚硝基苯与细胞结合 亲核试剂并破坏细胞稳态。 还;亚细胞的 1,3-DNB 涉及的还原酶的定位和鉴定 将研究新陈代谢。 第三个具体目标是比较 人类和动物组织代谢 1,3-DNB 的能力 预测物种之间的相对毒性。