Probing the biochemistry of toxic metals in the bloodstream

探索血液中有毒金属的生物化学

• 批准号: RGPIN-2014-04156
• 负责人: Gailer, Juergen
• 金额: $ 1.89万
• 依托单位: University of Calgary
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2016
• 资助国家: 加拿大
• 起止时间: 2016-01-01 至 2017-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=610865
• 关键词: Probing; biochemistry; toxic; metals; bloodstream

Human activities, such as fossil fuel consumption and mining, emit quantities of toxic metals (arsenic, cadmium, mercury and manganese) that rival or exceed natural global emissions. These emissions are expected in increase. Coal consumption, for example, is expected to increase by 20% over the next 25 years. In addition, millions of people are exposed to toxic metals at their workplace through the inhalation/ingestion of toxic metal-containing dusts (e.g. sheet metal flame cutting, welding, etc.). Since toxic metals are absorbed from the gastrointestinal tract and/or the lungs, they will eventually enter the bloodstream. Although we accurately know the concentrations of the aforementioned toxic metals in the human bloodstream of the average population (these data are determined in regular intervals by the Centers of Disease Control and Prevention of the United States), we don't know at present what these concentrations mean. This undesirable situation must be largely attributed to our lack of understanding the fundamental chemical processes that unfold once these toxic metals enter the bloodstream, which in turn is associated with the difficulty of analyzing blood. Blood plasma, for example, contains up to 10,000 individual proteins. To gain much needed insight into the interactions of toxic metals in the bloodstream, my group has developed a unique visualization method for the analysis of plasma. Instead of analyzing the latter for the thousands of proteins, our method specifically analyzes plasma for those proteins which contain a bound metal and are therefore referred to as metalloproteins. The latter deliver sufficient amounts of dietary iron, copper and zinc to our organs where they are important building blocks for the assembly of proteins which maintain vital biochemical processes. From a toxicological point of view, the binding of dietary iron, copper and zinc to plasma proteins in the bloodstream is a critical step in their metabolism which can be adversely affected by toxic metals. In addition, a toxic metal may be inadvertently transported to an organ (where it causes toxicity) by binding to certain metalloproteins. Furthermore, the influx of a toxic metal into the bloodstream may change the concentration of certain metalloproteins over time. In order to probe all of these toxicologically highly relevant processes, we will use rabbits as a model organism. We will first conduct experiments with rabbit plasma to which a toxic metal is added. Simultaneous analysis of the plasma for metalloproteins and the added toxic metal will provide insight into the transport of the latter in the bloodstream and will contribute to establish the mechanisms which define the target organ of any given toxic metal. Next we will carry out similar experiments with rabbit whole blood. These investigations are expected to allow us to isolate novel toxic metal containing metabolites, which will be structurally characterized at the Canadian Light Source. This is important to identify metabolites which play a critical role in their toxicity. Since the methodology that we will employ can analyze plasma in 25 minutes, we will complement the aforementioned "test tube" experiments with studies using anesthesized rabbits. After the injection with a toxic metal, the analysis of plasma for the contained metalloproteins over an 8 h period will reveal changes of certain metalloprotein concentrations over time. It is expected that these studies will provide unique insight into the systemic toxicity of toxic metals. Overall, my research program will allow us to obtain fundamentally new insight into the toxicology of metals in the mammalian bloodstream, which will ultimately contribute to better inform Canadian public policy on the regulation of toxic metals.

人类活动，如化石燃料消耗和采矿，排放大量有毒金属（砷、镉、汞和锰），与全球自然排放量相当或超过。预计这些排放量还会增加。例如，未来25年煤炭消费量预计将增长20%。此外，数以百万计的人在工作场所通过吸入/摄入含有有毒金属的粉尘（例如金属板材火焰切割、焊接等）而接触有毒金属。由于有毒金属从胃肠道和/或肺部被吸收，它们最终会进入血液。虽然我们准确地知道上述有毒金属在普通人血液中的浓度（这些数据是由美国疾病控制和预防中心定期确定的），但我们目前还不知道这些浓度意味着什么。这种不受欢迎的情况很大程度上是由于我们对这些有毒金属进入血液后所发生的基本化学过程缺乏了解，而这又与分析血液的困难有关。例如，血浆含有多达10,000种单独的蛋白质。为了深入了解血液中有毒金属的相互作用，我的团队开发了一种独特的可视化方法来分析血浆。我们的方法不是分析血浆中成千上万的蛋白质，而是专门分析血浆中含有结合金属的蛋白质，因此被称为金属蛋白。后者为我们的器官提供足量的膳食铁、铜和锌，它们是维持重要生化过程的蛋白质组装的重要基石。从毒理学的角度来看，饮食中的铁、铜和锌与血液中的血浆蛋白结合是它们代谢的关键步骤，有毒金属会对它们产生不利影响。此外，有毒金属可能通过与某些金属蛋白结合而无意中被运送到器官（在那里引起毒性）。此外，随着时间的推移，有毒金属流入血液可能会改变某些金属蛋白的浓度。为了探索所有这些毒理学上高度相关的过程，我们将使用兔子作为模型生物。我们将首先用添加了有毒金属的兔子血浆进行实验。同时分析血浆中的金属蛋白和添加的有毒金属，将有助于深入了解后者在血液中的运输，并有助于建立确定任何给定有毒金属靶器官的机制。接下来我们将用兔全血进行类似的实验。这些研究有望使我们分离出新的含有毒金属代谢物，这些代谢物将在加拿大光源上进行结构表征。这对于确定在其毒性中起关键作用的代谢物是很重要的。由于我们将采用的方法可以在25分钟内分析血浆，我们将用麻醉兔子的研究来补充上述“试管”实验。注射有毒金属后，在8小时内对血浆中金属蛋白进行分析，可以发现某些金属蛋白浓度随时间的变化。预计这些研究将为有毒金属的全身毒性提供独特的见解。总的来说，我的研究项目将使我们对哺乳动物血液中金属的毒理学有一个全新的认识，这最终将有助于更好地为加拿大有毒金属监管的公共政策提供信息。