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J Bacteriol Virol. 2009 Mar;39(1):1-10. English. Original Article. https://doi.org/10.4167/jbv.2009.39.1.1
Lee HM , Shin DM , Jo EK .
Department of Microbiology and Infection Signaling Network Research Center, College of Medicine, Chungnam National University, Daejeon, Korea. hayoungj@cnu.ac.kr
Abstract

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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