Midpolarity and Nonpolar Wood Smoke Particulate Matter Fractions Deplete Glutathione in RAW 264.7 Macrophages

Abstract

Wood smoke particulate matter (PM) is a complex mixture of components falling in a spectrum of highly polar to nonpolar species. Wood smoke PM is a likely factor in pulmonary disease and induces oxidative damage. Most toxicity studies focus upon nonpolar species such as polycyclic aromatic hydrocarbons (PAHs). However, the role of more polar PM constituents as toxicants is not clear. In this work, we evaluated the ability of multiple fractions of varying polarity to deplete glutathione (GSH) in RAW 264.7 macrophages and BEAS-2B bronchial epithelial cells. We utilized hot pressurized (subcritical) water to fractionate wood smoke PM into seven fractions of decreasing polarity. In contrast to polar fractions, midpolarity and nonpolar fractions exhibited greater GSH depletion (ED50 at PM concentrations of approximately 50 microg/mL). GSH depletion caused by nonpolar fractions (extracted at 250-300 degrees C) was associated with the presence of PAHs. In midpolarity fractions (extracted at 100-150 degrees C), oxy-PAHs, syringylguaiacyls, disyringyls, and lower molecular weight PAHs were found. Direct comparison of GSH depletion by individual oxy-PAHs and PAHs suggests that oxy-PAHs are contributors to oxidative stress caused by wood smoke PM. However, other unidentified PM constituents contribute to GSH depletion as well. The results indicate the toxicological importance of oxygenated organics found in midpolarity PM fractions.