10th International Aerosol Conference September 2 - September 7, 2018 America's Center Convention Complex St. Louis, Missouri, USA
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Oxidative Potential of Quinones in Simulated Epithelial Lining Fluid Alone and in Combination with Redox-Active Metals
KARSTEN BAUMANN, Marco Wietzoreck, Jake Wilson, Pourya Shahpoury, Steven Lelieveld, Haijie Tong, Ulrich Pöschl, Gerhard Lammel, Max Planck Institute for Chemistry
Abstract Number: 744 Working Group: Aerosols and Health - Connecting the Dots
Abstract The human health risk posed by reactive oxygen species (ROS) produced from fine particulate matter (PM2.5) components in epithelial lining fluid (ELF) of the deep lung is a matter of intense scientific interest (Lakey et al. 2016). In aerobic metabolism, oxidative stress can be exerted by excessive ROS comprised of free radicals such as O2-, OH, ROO, RO, and non-radical species such as H2O2 and O3. Upon inhalation, many oxygenated and nitrated polycyclic aromatic hydrocarbons (NOPAHs) in airborne PM2.5 may contribute to ROS formation, most effectively quinones, which form O2- by reactions involving the semiquinone radical. NOPAHs are found regularly in the ultra-fine fraction of PM2.5, and can be emitted by incomplete combustion processes (e.g. from diesel engines and biomass burning) or formed in atmospheric photochemical processes. Quinones are known to trigger and maintain catalytic reaction cycles causing oxidative stress at the cellular level (Bolton et al. 2000). In assays addressing the so-called oxidative potential (OP), which is assumed indicative of ROS formation, different redox-active components of ambient PM2.5, such as quinones or transition metals, esp. Cu, Mn, Fe, can cause synergistic or antagonistic effects (Xiong et al. 2017, Yu et al. 2018). However, this chemistry is not well understood yet.
In order to investigate each redox active species’ OP individually and in combination, we developed an experimental setup representing extracellular conditions in the deep lung that allows reproducible loading of a simulated ELF, containing antioxidants, electrolytes, surfactants and proteins (Boisa et al. 2014). This SELF was refined by sterile filtration, in order to decrease bacterial impurity. Hydrophobic polystyrene latex (PSL) spheres with nominal 60 nm diameter are used to mimic transport of NOPAHs to the alveolar region. The PSL also enhance atomization of select NOPAH compounds dissolved in a mixture of organic solvent (ACN or DMSO) and ultrapure water. The generated particles are collected by continuously refluxed SELF in a mist chamber, and simultaneously on a quartz filter. Delivery and uptake kinetics of two nitro-PAHs and three oxy-PAHs, have been investigated. The OP and ROS yield of the differently loaded SELF is determined by means of three acellular assays, in particular H2O2 formation (Sigma-Aldrich 2014), DTT depletion (Charrier & Anastasio 2012), and antioxidant depletion (glutathione and ascorbic acid). We present and interpret the results in light of possible synergistic or antagonistic effects. Ongoing modeling (Lakey et al. 2016) may benefit from insights gained.
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