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Exposure To An Organic PM Component Induces Inflammatory And Adaptive Gene Expression Through Mitochondrial Oxidative Stress
Citation:
Cheng, W., J. Currier, P. A. Bromberg, R. A. SILBAJORIS, AND J. M. SAMET. Exposure To An Organic PM Component Induces Inflammatory And Adaptive Gene Expression Through Mitochondrial Oxidative Stress. Presented at American Thoracic Society (ATS) Annual Meeting, San Francisco, CA, May 18 - 23, 2012.
Impact/Purpose:
These findings demonstrate the utility of integrating live-cell imaging approaches to mechanistic studies investigating the toxicity of environmental air pollutants in human lung cells.
Description:
RATIONALE. Exposure to ambient particulate matter (PM) has been associated with adverse health effects including inflammatory responses in the lung. Diesel exhaust particles (DEP) are a ubiquitous contributor to the fine and ultrafine PM burden in ambient air. Toxicological studies have correlated inflammatory effects of DEP with its organic constituents, including the organic electrophile 1,2-Napthoquinone {l,2-NQ). To elucidate the mechanisms involved in 1,2-NQ-induced inflammatory responses, we examined the role of oxidant stress in 1,2-NQ-induced expression of inflammatory and adaptive genes in a human airway epithelial cell line. METHODS. Expression of interleukin-8 (IL-8), cyclooxygenase-2 (COX-2), and heme oxygenase-l (HO-l) was measured by RT-PCR in BEAS-2B exposed to 1-100 uM 1,2-NQ for 14 hr . Cytosolic redox status and intracellular concentrations of H202 were measured in real time in living cells using the genetically-encoded GFP-based fluorescent indicators roGFP and HyPer, respectively. RESULTS. Real time imaging analysis of BEAS cells expressing roGFP and HyPer showed rapid elevations in cytoplasmic redox potential and H202 with exposure to 1,2-NQ. Overexpression of catalase diminished the H202 dependent signal but not the 1,2-NQ induced loss of reducing potential. Levels of IL-8, COX-2, and HO-l were markedly induced by exposure to 1,2-NQ in a dose and time-dependent manner. Catalase overexpression inhibited 1,2-NQ-induced IL-8 and COX-2 expression, but had no effect on HO-l mRNA levels. The mitochondrial inhibitor, carbonyl cyanide 3-chlorophenylhydrazone (CCCP) effectively blocked H202 production in 1,2NQ- treated cells and had a lesser effect on 1,2-NQ-induced redox change. CONCLUSIONS. These data establish a mechanistic link between early oxidative effects and subsequent inflammatory and adaptive gene expression resulting from human airway epithelial cell exposure to the organic PM component 1,2-NQ. These findings suggest that the ROS-dependent effect of 1,2-NQ leads to increased inflammatory gene expression, while the ROS-independent events mediate the adaptive response involving HO-1 transcription. These findings demonstrate the utility of integrating live-cell imaging approaches to mechanistic studies investigating the toxicity of environmental air pollutants in human lung cells. THIS ABSTRACT OF A PROPOSED PRESENTAnON DOES NOT NECESSARILY REFLECT EPA POLICY.