Kinetics of gene expression profiling in Swiss 3T3 cells exposed to aqueous extracts of cigarette smoke.

Previous studies from different laboratories have demonstrated that cigarette smoke (CS) harbours a strong oxidative stress potential, which broadly impacts exposed cells. Many of these studies have been devoted to identifying differentially expressed genes in exposed cells. Emerging DNA microarray techniques provide a sophisticated tool to characterize gene expression on a more comprehensive basis. Here, we report on kinetic studies performed to characterize gene expression profiles in Swiss 3T3 cells exposed to aqueous extracts of CS ('smoke-bubbled phosphate-buffered saline') up to 24 h through glass chips containing 513 different cDNA probes. The results obtained display a distinct expression pattern of up regulated and repressed genes, which was most evident after 4-8 h of exposure. The CS-related stress response involves mainly antioxidant response genes coding for, e.g. haem oxygenase-1 (HO-1), metallothionein 1/2 (MT1/2) and heat shock proteins (HSPs); genes coding for transcription factors, e.g. JunB and CAAT/enhancer binding protein (C/EBP); cell cycle-related genes, e.g. gadd34 and gadd45; and notably, genes described as mediators of an inflammatory/immune-regulatory response, e.g. st2, kc and id3. From a kinetic perspective, the stress response is characterized by the synchronized up regulation of antioxidant pathways, e.g. as reflected by the co-ordinated expression of ho-1 and ferritin. This expression pattern is obviously orchestrated by stress-responsive transcription factors, as exemplified by the early and strong expression of junB and c/ebp. Interestingly, among the 10 most up regulated genes are five which are known to counteract stress brought about by peroxynitrite. Altogether, these results demonstrate that CS induces a distinct signature of differential gene expression in exposed cells.