The influence of Hurricanes Katrina and Rita on the inflammatory cytokine response and protein expression in A549 cells exposed to PM2.5 collected in the Baton Rouge–Port Allen industrial corridor of Southeastern Louisiana in 2005

Abstract

Hurricanes Katrina and Rita hit the coast of Louisiana in 2005 and killed more than 2000 people. The two storms resulted in a significant spike in particulate matter (PM2.5) levels across the state of Louisiana. This report focuses on PM2.5 samples collected in 2005 from two monitoring sites in the neighboring cities of Baton Rouge and Port Allen, Louisiana. Inductively coupled plasma (ICP) revealed the presence of PM2.5-adsorbed representative and Fenton-active transition metals. Gas chromatography/mass spectrometry (GC-MS) analyses revealed the presence of 23 PAH compounds. Endotoxins were also detected. Metals and endotoxins were extracted with water. PAH were extracted with dichloromethane. In order to assess cytotoxicity, aqueous PM2.5 extracts were introduced to A549 Human Epithelial Lung Carcinoma Cells. Results indicated decreased cell viability in a dose-dependent manner, with an LC50 of 235 µg/ml and 250 µg/ml, respectively, for the two sites featured here. Endotoxins alone were not cytotoxic. The concentration of reactive oxygen species (ROS) and released LDH activity increased following exposure of A549 cells to aqueous PM2.5 extracts. Fluorescence microscopy revealed apoptotic and necrotic cell death mechanisms. ELISA revealed increased secretion of primary pro-inflammatory cytokines, IL-6, IL-8, and TNF-α. Global PCR gene expression revealed up-regulation of proteins associated with the cytokine storm; e.g. interleukins, chemokines, and TNF-α. Global antibody microarray was consistent with an inflammatory response, with up-regulation of cytokines involved in the down-field activation of the caspase cascade and kinase pathways. The up-regulation of metal-redox sensitive transcription factors, NF-κβ and AP-1, is consistent with a cell death mechanism initiated by Fenton-active transition metal redox catalysis.