Involvement of reactive oxygen intermediate in the enhanced expression of virulence-associated genes of Listeria monocytogenes inside activated macrophages.
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-gamma 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 H2O2 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.
Makino
Masato
M
Department of Bacteriology, University School of Medicine, Niigata, Japan.
Kawai
Mariko
M
Kawamura
Ikuo
I
Fujita
Masashi
M
Gejo
Fumitake
F
Mitsuyama
Masao
M
D000818:Animals; D001427:Bacterial Toxins; D002460:Cell Line; D006360:Heat-Shock Proteins; D006460:Hemolysin Proteins; D007371:Interferon-gamma / Q000494:pharmacology; D008070:Lipopolysaccharides / Q000276:immunology / Q000494:pharmacology; D008089:Listeria monocytogenes / Q000187:drug effects / Q000378:metabolism*; D008262:Macrophage Activation / Q000502:physiology*; D008264:Macrophages / Q000382:microbiology*; D051379:Mice; D017382:Reactive Oxygen Species / Q000378:metabolism*; D015854:Up-Regulation; D037521:Virulence Factors / Q000235:genetics*
D001427:Bacterial Toxins; D006360:Heat-Shock Proteins; D006460:Hemolysin Proteins; D008070:Lipopolysaccharides; D017382:Reactive Oxygen Species; D037521:Virulence Factors; D007371:Interferon-gamma; C038705:hlyA protein, Listeria monocytogenes