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| The Role of Canonical Wnt Signaling Pathway in the Lung Epithelial Cells against Mycobacteria Infection |
| SHI Juan1, YANG Jia-li1, MA Ling-jie1, BAO Shao-wen1, MA Yan1, CHENG Long1, MA Chun-yan1, LI Yong1,2, LIU Xiao-ming1,2 |
1. Key Laboratory of the Ministry of Education for the Conservation and Utilization of Special Biological Resources of Western China, Yinchuan 750021, China;
2. College of Life Science, Ningxia University, Yinchuan 750021, China |
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Abstract Purpose: An increasing number of studies has demonstrated that the epithelial cells of lung play a crucial role in the immunity against infections. In addition to the regulatory roles in the organogenesis and the maintenance of cell homeostasis, the canonical Wnt signaling pathway has recently been revealed to be involved in the regulation of immune responses. The aim is to investigate the potential roles of canonical Wnt signaling in the regulation of lung epithelial cells against Mycobacterium tuberculosis infection, using lung epithelial A549 cells. Methods: The A549 cells was transfected with a Wnt signaling reporter plasmid BAT flash, followed by the infection of Mycobacterium bovis vaccine strain Bacillus Calmette-Guerin (BCG). The alteration of Wnt signaling was then ascertained by measuring luciferase activity using a dual-luciferase assay, and the changes of the protein profiles of main Wnt signaling molecules and pro-inflammatory factors of the cells were determined by an immunoblotting assay or an Enzyme-linked immunosorbent assay (ELISA). Results: An inhibition of Wnt signaling luciferase activity was observed following the BCG stimulation, suggesting a negative regulation of Wnt signaling in the epithelial cells against BCG infection. Such finding was further supported by the results of immunoblotting assay and ELISA, in which an up-regulation of inhibitory proteins of Wnt signaling GSK3β(Glycogen Synthase Kinase 3 beta) and Axin2 (Axis inhibition protein) with an increased concentration of phosphorylated β-catenin, was found in the cytosol fraction of cells; and a down-regulation of Wnt signaling effector, active β-catenin and its down-stream transcription factors TCF4 (T cell factor-4) and Lef-1 (lymphoid enhancer-binding factor-1) was determined in the nuclear proteins. More importantly, overexpression of β-catenin showed a down-regulated expression of pro-inflammatory factors of interleukin-6 (IL-6), nuclear factor-kappa B (NF-κB), and the adaptor of Toll-like receptor (TLR) signaling pathway, myeloid differentiation primary response gene 88 (MyD88) and its downstream signaling TNF-receptor associated factor 6 (TRAF6), but no effect on the expression of Tumor necrosis factor-alpha (TNF-α). These data indicated that the Wnt signaling might repress the immune responses through a TLR signaling pathway in lung epithelial cells in response to BCG. Conclusion: The lung epithelial cells may able to alleviate an immune response against Mycobacteria infection through a mechanism of down-regulation of canonical Wnt signaling pathway, subsequently repress the MyD88/TRAF6/NF-κB pathway and protect the host cells from immune injury.
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Received: 07 August 2013
Published: 25 December 2013
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Cite this article:
SHI Juan, YANG Jia-li, MA Ling-jie, BAO Shao-wen, MA Yan, CHENG Long, MA Chun-yan, LI Yong, LIU Xiao-ming. The Role of Canonical Wnt Signaling Pathway in the Lung Epithelial Cells against Mycobacteria Infection. China Biotechnology, 2013, 33(12): 9-14.
URL:
https://manu60.magtech.com.cn/biotech/ OR https://manu60.magtech.com.cn/biotech/Y2013/V33/I12/9
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