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J Bacteriol Virol. 2009 Mar;39(1):1-10. English. Original Article.
Lee HM , Shin DM , Jo EK .
Department of Microbiology and Infection Signaling Network Research Center, College of Medicine, Chungnam National University, Daejeon, Korea.

Upon contact with airway epithelial cells, mycobacteria activate several signal transduction events that are required for induction of inflammatory cytokines/chemokines. In this study, we found that Mycobacterium tuberculosis (Mtb)induced reactive oxygen species (ROS) production is essential for the expression of tumor necrosis factor (TNF)-alpha, interleukin (IL)-6, and CXC-chemokine ligand (CXCL) 8 through the activation of mitogen-activated protein kinases [MAPKs; extracellular signal-regulated kinase (ERK) 1/2 and p38 MAPK] in A549 cells representing alveolar epithelial cells. We observed that Mtb rapidly enhanced ROS production after stimulation in a toll-like receptor (TLR) 2-dependent manner. In addition, Mtb triggered ERK1/2 and p38 MAPK signaling pathways which were dependent on ROS generation in A549 cells. Moreover, Mtb stimulation significantly increased the secretion of TNF-alpha, IL-6, and CXCL8 over that in untreated controls. Pretreatment of A549 cells with the antioxidant, N-acetylcysteine and the nicotinamide adenine dinucleotide phosphate (NADPH) oxidase inhibitor, diphenylene iodonium, substantially inhibited Mtb-induced production of TNF-alpha, IL-6, and CXCL8. Studies using inhibitors selective for ERK1/2 and p38 MAPK pathways showed that both pathways play an essential role in the induction of TNF-alpha, IL-6, and CXCL8 at transcriptional levels in A549 cells. Collectively, our findings indicate the critical role of TLR2-dependent ROS in the Mtb-induced inflammatory cytokine/chemokine production in alveolar epithelial cells through MAPK-dependent signaling pathways.

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