Understanding PM2.5‐Induced Oxidative Stress In Alveolar Macrophages

Abstract

In situations of oxidative stress, the antioxidant processes of any eukaryotic organism can eventually become overwhelmed. Exposure to ambient particulate matter 2.5 (PM2.5), composed of transition metals and organic compounds 2.5μm or less in diameter, has been shown to cause oxidative stress in alveolar macrophages (AMs). This can lead to various adverse health effects, including cardiovascular and pulmonary diseases. In this study, we examine the capacity of ambient PM2.5 samples collected during periods of peak air pollution in Fresno and Claremont, CA to trigger ROS production in AM cells. These PM2.5 samples were characterized for their chemical content using chromatography and mass spectrometry. A DCF‐fluorescence based microplate assay was used to estimate the potential of the PM2.5 samples to trigger ROS production in NR8383, rat AM cells. Two types of quinones (1,2‐Naphtaquinone and 1,4‐Naphtaquinone) and two transition metals (Cu2+ and Fe2+) were associated with samples that had a high capacity to induce ROS generation in NR8383. While establishing a cytotoxic link between PM2.5 constituents and ROS, we also seek to understand the underlying biological mechanisms through which PM2.5 interacts with AM cells to produce excessive ROS. Previous observations suggest that the upregulation of NADPH Oxidase (NOX1), an enzyme that enhances ROS production, may contribute to cellular oxidative stress in macrophages. In this study, NOX1’s potential role in a PM2.5‐ induced oxidative stress pathway is investigated in NR8383 cells incubated with concentrations of iron and copper relevant with those found in the collected PM2.5 samples. The change in NOX1 expression was quantified using fluorescence‐based western blotting, with zymosan, a well‐known inducer of oxidative stress in macrophages, used as positive control. Our preliminary results indicate that 4‐hour treatments with increasing relevant iron concentrations triggered both an increase of ROS and NOX1 protein levels in NR8383. Our current experiments consist of testing the potential of relevant concentrations of other chemical constituents of PM2.5 suspected of triggering increased ROS production and NOX1 expression (these include naphtaquinones, phenanthraquinones, and copper). Understanding which chemical components of PM2.5 are able to induce significant amounts of ROS will allow us to understand how pollution is pernicious and advocate for the global reduction of PM2.5 emission.Support or Funding InformationThis work is supported by Fresno State ASI, the Division of Research and Graduate Studies, and Fresno State’s CSU‐LSAMP program funded by NSF under grant #HRD‐1826490.