MECHANISMS OF 1,3-DINITROBENZENE TESTICULAR TOXICITY

随着人们日益认识到化学品对环境的不利影响， 男性生殖，迫切需要增加我们的知识 化学物质导致生殖损伤的机制。 的 需要是显而易见的，因为从实验室推断 动物对人类的影响以及改进毒性测试取决于对以下方面的了解： 生物系统以及有毒物质如何干扰它。在拟议的 研究，感兴趣的睾丸毒物的类别是 硝基芳族化合物广泛用作杀虫剂，炸药， 工业合成中的药物和化学中间体。 的 模型睾丸毒物和硝基芳烃为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（肝脏和睾丸内）在 1，3-DNB的睾丸毒性。 哪种代谢产物 毒性及其与细胞成分相互作用的性质 将是研究的第二阶段。 考虑到 从动物研究中获得的信息，最终目标是建立 动物模型与人体状况之间的关系 体外研究中的组织。 为了实现这些目标， 将在体内测试假设，然后研究特定的细胞 vitro事件第一个具体目标是确定 肝脏在1，3-DNB睾丸毒性的调节中起作用。 初步研究表明1，3-DNB中存在睾丸外事件 睾丸内给予高水平1，3-DNB后的毒性 并没有造成睾丸严重损伤 两种情况可能是 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， 血液和引发睾丸毒性。 硝基亚硝基苯将是 作为最有可能的候选人进行调查， 代谢物。 其次，可以提出一种不太直接的相互作用， 肝脏代谢产生高铁血红蛋白形成代谢物， 缺氧的条件。 睾丸内的低氧环境 会促进1，3-DNB的还原代谢， 通过氧化还原增加氧利用而导致氧不足 循环或增加有毒代谢物的形成， 硝基亚硝基苯 缺氧的扩大可能导致 支持细胞稳态的破坏， 支持生殖细胞群体的发育。 具体目标二， 体外机制研究将进一步探索体内假说 集中于1）检测代谢活化的细胞指标 能够进行氧化还原循环的代谢物，和2） 亲电代谢产物硝基亚硝基苯结合细胞 亲核试剂并破坏细胞内稳态。 此外，亚细胞 1，3-DNB中还原酶的定位和鉴定 将研究代谢。 第三个具体目标是比较 人体和动物组织代谢1，3-DNB和 预测物种间的相对毒性。

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.