Identification of multiple MAPK-mediated transcription factors regulated by tobacco smoke in airway epithelial cells

Abstract

May 11, 2007; doi:10.1152/ajplung.00345.2006.-Activation and regulation of transcription factors (TFs) are the major mechanisms regulating changes in gene expression upon environmental exposure. Tobacco smoke (TS) is a complex mixture of chemicals, each of which could act through different signal cascades, leading to the regulation of distinct TFs and alterations in subsequent gene expression. We proposed that TS exposure affects inflammatory gene expression at the transcriptional level by modulating the DNA binding activities of TFs. To investigate transcriptional regulation upon TS exposure, a protein/ DNA array was applied to screen TFs that are affected by TS exposure. This array-based screening allowed us to simultaneously detect 244 different TFs. Our results indicated that multiple TFs were rapidly activated upon TS exposure. DNA-binding activity of differentially expressed TFs was confirmed by EMSA. Our results showed that at least 20 TFs displayed more than twofold expressional changes after smoke treatment. Ten smoke-induced TFs, including NF-B, VDR, ISRE, and RSRFC4, were involved in MAPK signaling pathways. The NF-B family, which is involved in inflammation-induced gene activation, was selected for further study to characterize TS exposure-induced transcriptional activation. Western blot analysis and immunofluorescence microscopy indicated that TS exposure induced phosphorylation of IB and translocation of NF-B p65/p50 heterodimers into the nucleus. This activity was abrogated by the MAPK inhibitors PD98059 and U0126. Our results confirmed that activation of MAPK signaling pathways by TS exposure increased transcriptional activity of NF-B. These data provide a potential mechanism for TS-induced inflammatory gene expression. tobacco smoke; transcription factor; MAPK; NF-B TRANSCRIPTIONAL ACTIVATION in eukaryotes is a highly regulated process that requires the concerted interactions of DNA-binding transcriptional activators, general transcription factors (TFs), and coactivator proteins to stimulate the recruitment and activity of RNA polymerase II to the appropriate gene promoters in response to biological signals. Most of these signals are generated by extracellular signaling molecules that initiate distinct signaling pathways, consequently terminating in the activation of one or more TFs. Abnormalities in signal transduction and TF activation underlie several inflammatory diseases and the majority of cancers (3, 4). Specifically, chronic inflammatory airway diseases and lung cancer are frequently associated with tobacco smoke (TS) exposure, consistent with the high volume of TS to which the lungs are exposed. However, the molecular mechanisms underlying TS-induced pulmonary diseases are not well understood. To better characterize the mechanisms responsible for TS-induced lung diseases, our initial approach was to investigate TS-regulated TF activation in airway epithelial cells and the potential upstream signaling pathways responsible for this upregulation.TS is a chemical mixture that contains mor...

Role of CXCL5 in Leukocyte Recruitment to the Lungs during Secondhand Smoke Exposure

“…These results bring up the speculation that NF-kB is important for early cellular recruitment, and that MAPKs are important for subsequent cellular influx. These findings are consistent with previous reports indicating that the activation of NF-kB and MAPKs in the lungs occurs at different concentrations of mainstream smoke exposure (63,64). However, our findings are the first, to the best of our knowledge, to show the regulation of NF-kB and MAPKs by CXCL5 in the lungs during SHS exposure.…”

Inhibition by Cigarette Smoke of Nuclear Factor-κB–Dependent Response to Bacteria in the Airway

“…Some reports demonstrated induction, whereas others found inhibition or no effect. Low-level NF-kB induction in isolated cells by cigarette smoke was often demonstrated with subconfluent cell testing, low smoke preparation concentrations, or shorter durations of exposure (28,33,39,40). In contrast, the impairment of NF-kB activation or function was often associated with confluent cells or treatment with higher levels of exposure to cigarette smoke, alone or in combination with other stimuli (28,(41)(42)(43).…”

Impact of smoking on inflammation: overview of molecular mechanisms

“…Likewise, Yagi et al [95] demonstrated by immunohistochemistry that airway epithelial cells from ex-smokers with or without COPD also have elevated activation of NF-jB, since increased phosphorylated IjB-a was found. Although most of the studies have demonstrated that increased NF-jB activation is dependent on IKK activation, Zhao et al [96] showed a novel mechanism of NF-jB activation modulated by tobacco smoke. These authors revealed that in A549 cells, a human lung cancer cell line, tobacco smoke exposure significantly induces the microtubule-associated protein kinase (MAPK) signaling pathway via activation of extracellular signal-regulated kinases 1 and 2 (ERK1/ERK2), resulting in direct IjB phosphorylation and NF-jB activation.…”

“…1. Besides NF-jB, Zhao et al [96], using a protein/DNA array approach, identified 19 other transcriptional factors regulated by tobacco smoke. Among these are GATA, PAX5, and Smad 3/4 that were significantly stimulated by tobacco smoke, and ISRE and ICSBP that had their DNA-binding activities significantly decreased after tobacco smoke treatment.…”