Department of Chemistry, Hong Kong University of Science & Technology, Clear Water Bay, Kowloon, Hong Kong, China.
Department of Chemistry, Hong Kong University of Science & Technology, Clear Water Bay, Kowloon, Hong Kong, China; Division of Environment, Hong Kong University of Science & Technology, Clear Water Bay, Kowloon, Hong Kong, China.
Sci Total Environ. 2019 Dec 20;697:134012. doi: 10.1016/j.scitotenv.2019.134012. Epub 2019 Aug 27.
Excessive generation of reactive oxygen species (ROS) and the corresponding oxidative stress has been recognized as one important cause for the adverse health effects associated with exposure to ambient particulate matter (PM). Transition metals and humic-like substances (HULIS) in PM have been separately demonstrated to contribute to the oxidative potential (OP) of PM, however, only few studies investigated the impact of their interactions on the measured OP and the effect is little understood. HULIS is an abundant fraction of water-soluble organic material in PM and serves to represent real-world PM organics. In this study, we applied a cell-free dithiothreitol (DTT) assay to quantify the OP, termed as OP, by two representative transition metals (i.e., copper (Cu) and manganese (Mn)), HULIS, and mixtures of HULIS and metals in concentration levels relevant to those in human lung fluid resulting from PM inhalation. The organic-metal mixture effect was found to be metal-specific and concentration-specific, covering the possibility spectrum from being synergistic, additive to antagonistic. HULIS was observed to suppress OP up to 10-20% by Cu at a concentration of 0.08 μM while had no discernable effect at 0.5 μM Cu. On the contrary, obvious enhancement of OP was recorded in the mixtures of HULIS and Mn (e.g. up to ~2 times at 2.5 μM of Mn) while no mixture effects could be discerned at 0.5 μM Mn. Our work demonstrates the need for considering the metal-organic interactions and the complexity when evaluating the total OP of their mixtures, such as ambient PM samples. Further work in metal-PM organics interactions should be conducted using methods capable of measuring specific oxidants, in addition to the ability to deplete the reducing agent (i.e., DTT), in order to acquire a deeper mechanistic insight into the interactions.
过量的活性氧（ROS）的产生和相应的氧化应激已被认为是与环境颗粒物（PM）暴露相关的不良健康影响的一个重要原因。PM 中的过渡金属和类腐殖质物质（HULIS）已分别被证明有助于 PM 的氧化潜能（OP），然而，只有少数研究调查了它们相互作用对测量的 OP 的影响，并且对其影响的理解还很少。HULIS 是 PM 中水溶性有机物质的丰富部分，代表了实际 PM 中的有机物。在这项研究中，我们应用无细胞二硫苏糖醇（DTT）测定法来量化 OP，称之为 OP，通过两种代表性的过渡金属（即铜（Cu）和锰（Mn））、HULIS 以及在与 PM 吸入导致的人体肺液中金属浓度水平相关的金属混合物来进行定量。发现有机金属混合物的作用是金属特异性和浓度特异性的，涵盖了从协同作用、加性到拮抗作用的可能性范围。在 0.08 μM 的 Cu 浓度下，HULIS 被观察到抑制 OP 高达 10-20%，而在 0.5 μM 的 Cu 时则没有明显的效果。相反，在 HULIS 和 Mn 的混合物中记录到明显的 OP 增强（例如，在 2.5 μM 的 Mn 下高达约 2 倍），而在 0.5 μM 的 Mn 下则没有混合物效应。我们的工作表明，在评估其混合物的总 OP 时，需要考虑金属-有机相互作用和复杂性，例如环境 PM 样本。在金属-PM 有机物相互作用方面，应采用能够测量特定氧化剂的方法，并结合消耗还原剂（即 DTT）的能力，以更深入地了解相互作用的机制。
