Differential activation of MAP kinase signaling pathways and nuclear factor-κB in bronchoalveolar cells of smokers and nonsmokers

Abstract

Background: Prolonged exposure of alveolar macrophages (AM) to components of tobacco smoke, including nicotine and aromatic hydrocarbons, may lead to alterations in activation of cellular signaling pathways. In this study, we compared the spontaneous and LPS-stimulated activation of MAP kinases and NF-/κB in bronchoalveolar cells (BAC) from smokers and nonsmokers. Material and Methods: BAC, which were predominantly comprised of AM, were obtained by bronchoalveolar lavage of healthy volunteering adult smokers and non-smokers. Nuclear and cytoplasmic extracts were prepared from cell lysates. Activation of NF-κB was assessed by electrophoretic mobility shift assay. Degradation of the inhibitor of NF-κB (IκB) and total MAP kinases were assessed by Western blot analysis. Activation of MAP kinases, ERK, SAPK/JNK, and p38 were assessed by immunoprecipitation of cell lysates and kinase assays. Results: LPS induced the activation of NF-κB in a dose-dependent manner, but BAC from smokers were approximately 10 times more sensitive, and showed faster kinetics of activation of NF-κB than BAC from nonsmokers. All three classes of MAP kinase - ERK, SAPK, and p38 - were simultaneously activated by LPS in BAC from smokers and nonsmokers. However, the individual MAP kinases exhibited differential kinetics of activation. Activation of p38 was more rapid in BAC from smokers, whereas the activation of ERK and SAPK was similar in both groups. Conclusion: The differences in activation of NF-κB and MAP kinases in BAC from smokers and nonsmokers may relate to the differences in their microenvironment in situ as affected by chronic exposure to cigarette smoke. These differences may contribute to the increased susceptibility of smokers to infections, including infection with HIV-1, and lung disease.