Macrophages play a fundamental role during the clearance of environmental agents from the lung. During this process macrophages are activated to release inflammatory mediators and undergo apoptosis. PLs and their metabolites are involved in inflammation and cell death. However, no comprehensive studies, using contemporary research tools such as mass spectrometry (MS), addressing the oxidation or hydrolysis of PLs (phosphatidylcholine, PC, phosphatidylethanolamine, PE, phosphatidylserine, PS, phosphatidylinositol, PI, and cardiolipin, CL) in macrophages are available at this time. Therefore, we conducted a quantitative characterization, using ESI-MS and fluorescence HPLC/Amplex Red assays, of the oxidative and phospholipase A hydrolysis of individual molecular species of major classes of PLs on silica, zymozan, or single wall carbon nanotube (SWCNT) exposed macrophages (Raw 264.7, IC-21, or primary from C57BL/6 mice). We report that following exposure to silica, SWCNT, or zymozan macrophages experience a rapid, and selective peroxidation of anionic PLs in a manner that is independent of their cell abundance (CL>>PS>>PI). Oxidation of CL in response to silica is followed by the accumulation of the hydrolyzed moiety of CL, monolyso-CL, and oxidized free fatty acids shortly after the release of cyt C, and the externalization of PS in the cell membrane. Subsequently, oxidation of the same species of anionic PLs was identified in lungs of C57BL/6 mice exposed to SWCNT. We concluded that anionic PLs- are important mediators of the macrophage response to environmental agents and that they undergo a highly regulated metabolism during macrophage apoptosis.
Biological-effects; Cell-biology; Cell-damage; Cellular-reactions; Chemical-reactions; Environmental-exposure; Exposure-assessment; Exposure-levels; Exposure-methods; Health-hazards; Inhalation-studies; Laboratory-animals; Laboratory-techniques; Laboratory-testing; Lung-cells; Lung-function; Molecular-biology; Molecular-structure; Particulates; Quantitative-analysis; Respiratory-irritants; Risk-analysis; Statistical-analysis; Toxic-effects
The Toxicologist. Society of Toxicology 49th Annual Meeting and ToxExpo, March 7-11, 2010, Salt Lake City, Utah