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Alterations in signaling pathways associated with oxidative stress, inflammation and DNA damage are often observed in cells exposed to complex chemical mixtures including cigarette smoke. Our laboratory previously reported that smoke condensate from cigarettes that primarily heat tobacco produce less change in p21, GADD45, COX-2, IL-8, HO-1 and HSP70 mRNA levels in normal human bronchial epithelial (NHBE) cells than smoke condensate from tobacco-burning cigarettes. The NFκB signal transduction pathway is reported to mediate in part the response of bronchial epithelial cells to cigarette smoke through the activation of several genes; including genes coding for COX-2, HO-1, and HSP-70. The objective of this study was to characterize and compare the effect of smoke condensates from tobacco-heating and tobacco-burning cigarettes on NF-κB promoter activation. Cigarette smoke condensate (CSC) was prepared from Kentucky reference 2R4F cigarettes, a tobacco-burning product designed to represent the average low “tar” cigarette in the US market and Eclipse, a cigarette that primarily heats tobacco. A549-NFκB reporter cells stably transfected with a NFκB-luciferase plasmid were exposed to each CSC and NFκB activation was determined by measuring changes in luciferase activity in cell lysates via a standard luciferase assay. Changes in mRNA levels were determined by quantitative RT/PCR. Luciferase analysis of NFκB promoter activation revealed dose- and time-dependent activation following exposure to either condensate. HO-1 and COX-2 mRNA levels were temporally regulated and significantly increased (p<0.05) in cells exposed to K2R4F compared to Eclipse following 6 hours of exposure. K2R4F smoke condensate caused an increase in HSP70 mRNA at low doses and a dose-dependent decrease (p<0.05) at higher doses while Eclipse treatment altered (p<0.05) HSP70 mRNA levels to a lesser degree. The present data suggest that select genes involved in key signal transduction pathways (i.e. NF-κB) following cigarette smoke exposure in an in vitro human bronchial epithelial cell model may serve as biomarkers of effect for assessing some types of potential reduced-risk cigarettes.

98th AACR Annual Meeting-- Apr 14-18, 2007; Los Angeles, CA