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Involvement of Reactive Oxygen Intermediate in the Enhanced Expression of Virulence‐Associated Genes of Listeria monocytogenes inside Activated Macrophages
Author(s) -
Makino Masato,
Kawai Mariko,
Kawamura Ikuo,
Fujita Masashi,
Gejo Fumitake,
Mitsuyama Masao
Publication year - 2005
Publication title -
microbiology and immunology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.664
H-Index - 70
eISSN - 1348-0421
pISSN - 0385-5600
DOI - 10.1111/j.1348-0421.2005.tb03661.x
Subject(s) - listeria monocytogenes , listeriolysin o , virulence , biology , microbiology and biotechnology , reactive oxygen species , phagosome , virulence factor , phagocytosis , gene expression , catalase , macrophage , downregulation and upregulation , gene , listeria , bacteria , biochemistry , oxidative stress , in vitro , genetics
Listeriolysin O encoded by 1,587 bp hly is the essential virulence factor of Listeria monocytogenes that replicates in the cytosolic space after escaping from phagosome of macrophages. By using murine macrophage‐like J774.1 cells with or without activation by IFN‐γ plus LPS, the expression of both hly and its positive regulator prfA was monitored by means of RT‐PCR. In activated J774.1 cells, the level of hly expression was enhanced although the multiplication of bacteria was significantly suppressed. The elevated expression of hly inside activated macrophage was abolished by addition of SOD and catalase, suggesting that reactive oxygen intermediates contribute to the upregulation of prfA and hly transcriptions. Moreover, we found that exposure of L. monocytogenes to H 2 O 2 dramatically enhanced the expression of both prfA and hly mRNAs. Spontaneous ONOO – generator, SIN‐1, also promoted the transcription to a certain level. These results suggested that oxygen radicals generated in activated macrophages provide a positive signal for up‐regulation of virulence genes in L. monocytogenes .