The role of electron transfer reactions in the cytotoxicity mechanism of xenobiotics

在环境中发现的外来化学物质是工业副产品，污染，并可能通过职业接触接触。芳胺是一组重要的外来化学物质，可以与生物系统相互作用，如器官和组织的细胞；这通常会导致它们的转换。另一个词是新陈代谢，可以理解的是，新陈代谢产生代谢物。这些代谢物通常具有使它们能够从细胞中移除的特性。然而，在某些情况下，代谢物可能是有害的，并以这种方式与细胞发生反应，导致细胞受损。这些有害的代谢物被称为反应性代谢物，因为它们通常倾向于与细胞的重要分子（如蛋白质或DNA）发生反应。本提案旨在研究一种特定类型的活性代谢物，称为自由基代谢物。芳胺可以与特定的蛋白质（酶）相互作用，这些蛋白质（酶）可以将芳胺代谢成芳胺自由基代谢物。这项提议涉及的酶被称为髓过氧化物酶，它存在于白血病细胞和白细胞中，也与植物、动物和微生物中发现的类似酶相似。在特定条件下，当芳胺与髓过氧化物酶接触时，可触发代谢，产生反应性芳胺自由基代谢物。这些代谢物如果与重要分子发生反应（如上所述），对细胞是有害的。通常，细胞具有通过抗氧化剂清除这些有害代谢物的机制，如维生素C、维生素E或谷胱甘肽。芳胺自由基代谢物与抗氧化剂之间的反应是减少前者可能造成的损害的有效方法。然而，本研究旨在研究芳胺自由基代谢物可以与之相互作用的其他小分子，从而调节它们造成的损害。它们被称为电子转移中间体（ETIs），因为它们能够将电子传递给芳胺自由基代谢物，从而使其不再具有破坏性。初步研究表明，某些ETI具有有效清除芳胺自由基代谢物的特性，但同时导致在ETI上形成新的自由基代谢物。目前尚不清楚，与产生它们的芳胺自由基代谢物相比，ETI自由基的毒性有多大，也不知道ETI自由基是否会对重要分子造成或多或少的损害（如上所述）。重要的是，某些eti是在细胞内发现的，所以如果它们的水平波动，它们与芳胺自由基代谢物的反应可能会发生变化。这项研究的目的是在细胞水平上了解自由基对重要分子和整个细胞更有害的后果。具体目标将集中在：1)通过使用表征自由基的技术来表征芳胺自由基代谢物与ETI相互作用时发生的情况，测量芳胺自由基代谢物与ETI之间的相互作用，并建立方程来确定预测这些相互作用的化学特征；2)比较在存在/不存在eti的情况下芳胺自由基代谢物引起的蛋白质和DNA损伤，以及3)了解当这些反应发生时发生的细胞死亡机制。参与这些专业研究的学员将成为生命系统中自由基的专家，这将与加拿大的工业，学术界或政府相关。

Foreign chemical are found in the environment as industrial byproducts, pollution, and may be encountered through occupational exposure. Arylamines are a significant group of foreign chemical that can interact with biological systems, like the cells of organs and tissues; this usually results in their transformation. Another word for this is metabolism, which, understandably, produces metabolites. These metabolites usually have properties that enable them to be removed from the cell. However, in certain instances, the metabolites can be harmful and react with the cells in such a way that results in their damage. These harmful metabolites are referred to as reactive metabolites as they usually tend to react with vital molecules of cells, such as proteins or DNA. This proposal aims to study a specific type of reactive metabolite known as free radical metabolites. Arylamines can interact with specific proteins (enzymes) that can metabolize the arylamines into arylamine free radical metabolites. The enzyme that this proposal deals with is called myeloperoxidase, which is found in leukemia cells, and white blood cells, and also bears resemblance to similar enzymes found in plants, animals, and microbes. Under specific conditions, when an arylamine comes into contact with myeloperoxidase, it can trigger metabolism that will produce reactive arylamine free radical metabolites. These metabolites are harmful to the cells if they react with vital molecules (discussed above). Usually, cells have mechanisms to remove these types of harmful metabolites through antioxidants, such as Vitamin C, Vitamin E, or glutathione. Reactions between arylamine free radical metabolites and antioxidants are an effective way of minimizing the damage that the former can cause. However, this proposal seeks to study other small molecules that the arylamine free radical metabolites can interact with which can lead to modulating the damage that they cause. These are termed electron transfer intermediates (ETIs) because they are able to give their electrons to the arylamine free radical metabolite so that it is no longer damaging. Preliminary findings have shown that certain ETIs have characteristics that enable them to effectively scavenge arylamine free radical metabolites, but at the same time results in the production of new free radical metabolites formed on the ETI. It is currently unknown how much more toxic are the ETI free radicals compared to the arylamine free radical metabolites which produced them, nor is it known if the ETI free radicals can cause more or less damage to the vital molecules (discussed above). Importantly, certain ETIs are found inside cells, so if their levels fluctuate there could be a variation in their reactions with arylamine free radical metabolites. The objective of this study is to understand the consequences, at the cellular level, of which free radicals are more harmful to vital molecules and the cell as a whole. Specific objectives will focus on: 1) characterization what happens when the arylamine free radical metabolites and ETI interact by using techniques that can characterize free radicals, measure the interaction between arylamine free radical metabolites and ETIs, and develop equations to identify the chemical characteristics that predict these interactions; 2) compare protein and DNA damage caused by arylamine free radical metabolites in the presence/absence of ETIs, and 3) understanding the mechanism of cell death that is occurring when these reactions are taking place. Trainees that are involved in these specialized studies will become experts in free radicals in living systems, which will be relevant for Canadian industry, academia, or government.