Conversion of Mycobacterium smegmatis to a pathogenic phenotype via passage of epithelial cells during macrophage infection

Su Young Kim, Hosung Sohn, Go Eun Choi, Sang Nae Cho, Taegwon Oh, Hwa Jung Kim, Jake Whang, Jong Seok Kim, Eui Hong Byun, Woo Sik Kim, Ki Nam Min, Jin Man Kim, Sung Jae Shin

Research output: Contribution to journalArticle

4 Citations (Scopus)

Abstract

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.

Original languageEnglish
Pages (from-to)177-191
Number of pages15
JournalMedical Microbiology and Immunology
Volume200
Issue number3
DOIs
Publication statusPublished - 2011 Aug

All Science Journal Classification (ASJC) codes

  • Immunology and Allergy
  • Immunology
  • Microbiology (medical)

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