Conversion of Mycobacterium smegmatis to a pathogenic phenotype via passage of epithelial cells during macrophage infection
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Mycobacteria encounter many different cells during infection within their hosts. Although alveolar epithelial cells play an essential role in host defense as the first cells to be challenged upon contact with mycobacteria, they may contribute to the acquisition of mycobacterial virulence by increasing the expression of virulence or adaptation factors prior to being ingested by macrophages on the side of pathogens. From this aspect, the enhanced virulence of nonpathogenic Mycobacterium smegmatis (MSM) passed through human alveolar A549 epithelial cells (A-MSM) was compared to the direct infection of MSM (D-MSM) in THP-1 macrophages and mouse models. The intracellular growth rate and cytotoxicity of A-MSM were significantly increased in THP-1 macrophages. In addition, compared to D-MSM, A-MSM induced relatively greater interleukin (IL)-1β, IL-6, IL-8, IL-12, TNF-α, MIP-1α, and MCP-1 in THP-1 macrophages. As a next step, a more persistent A-MSM infection was observed in a murine infection model with the development of granulomatous inflammation. Finally, 58 genes induced specifically in A-MSM were partially identified by differential expression using a customized amplification library. These gene expressions were simultaneously maintained in THP-1 infection but no changes were observed in D-MSM. Bioinformatic analysis revealed that these genes are involved mainly in bacterial metabolism including energy production and conversion, carbohydrate, amino acid, and lipid transport, and metabolisms. Conclusively, alveolar epithelial cells promoted the conversion of MSM to the virulent phenotype prior to encountering macrophages by activating the genes required for intracellular survival and presenting its pathogenicity.
KeywordsMycobacterium smegmatis Enhanced virulence Epithelial cell Pathogenicity Induced gene
This research was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government (MEST) (2010-0008728) and Basic Science Research Program through the NRF (R13-2007-020-00000-0).
- 15.Alland D, Kramnik I, Weisbrod TR, Otsubo L, Cerny R, Miller LP, Jacobs WR Jr, Bloom BR (1998) Identification of differentially expressed mRNA in prokaryotic organisms by customized amplification libraries (DECAL): the effect of isoniazid on gene expression in Mycobacterium tuberculosis. Proc Natl Acad Sci USA 95(22):13227–13232PubMedCrossRefGoogle Scholar
- 17.Bermudez LE, Sangari FJ, Kolonoski P, Petrofsky M, Goodman J (2002) The efficiency of the translocation of Mycobacterium tuberculosis across a bilayer of epithelial and endothelial cells as a model of the alveolar wall is a consequence of transport within mononuclear phagocytes and invasion of alveolar epithelial cells. Infect Immun 70(1):140–146PubMedCrossRefGoogle Scholar
- 18.Sangari FJ, Goodman J, Bermudez LE (2000) Mycobacterium avium enters intestinal epithelial cells through the apical membrane, but not by the basolateral surface, activates small GTPase Rho and, once within epithelial cells, expresses an invasive phenotype. Cell Microbiol 2(6):561–568PubMedCrossRefGoogle Scholar
- 24.Crystal RJ (1991) Alveolar macrophages. In: Crystal RJ, West JB (eds) The lung: scientific foundations. Raven Press, New York, pp 527–538Google Scholar
- 25.Schneeberger EE (1991) Alveolar type II cells. In: Crystal RJ, West JB (eds) The lung: scientific foundations. Raven Press, New York, pp 736–758Google Scholar
- 27.Sawai T, Inoue Y, Doi S, Izumikawa K, Ohno H, Yanagihara K, Higashiyama Y, Miyazaki Y, Hirakata Y, Tashiro T, Kohno S (2006) A case of Mycobacterium nonchromogenicum pulmonary infection showing multiple nodular shadows in an immunocompetent patient. Diagn Microbiol Infect Dis 54(4):311–314PubMedCrossRefGoogle Scholar
- 33.Patel D, Danelishvili L, Yamazaki Y, Alonso M, Paustian ML, Bannantine JP, Meunier-Goddik L, Bermudez LE (2006) The ability of Mycobacterium avium subsp. paratuberculosis to enter bovine epithelial cells is influenced by preexposure to a hyperosmolar environment and intracellular passage in bovine mammary epithelial cells. Infect Immun 74(5):2849–2855PubMedCrossRefGoogle Scholar
- 43.Silver RF, Li Q, Ellner JJ (1998) Expression of virulence of Mycobacterium tuberculosis within human monocytes: virulence correlates with intracellular growth and induction of tumor necrosis factor alpha but not with evasion of lymphocyte-dependent monocyte effector functions. Infect Immun 66(3):1190–1199PubMedGoogle Scholar