Roles of nitric oxide in inducible resistance of Escherichia coli to activated murine macrophages.
Nitric oxide (NO.) is produced as a cytotoxic free radical through enzymatic oxidation of L-arginine in activated macrophages. Pure NO. gas was previously found to induce the Escherichia coli soxRS oxidative stress regulon, which is readily monitored by using a soxS'::lac fusion. The soxRS system includes antioxidant defenses, such as a superoxide dismutase and a DNA repair enzyme for oxidative damage, and protects E. coli from the cytotoxicity of NO.-generating macrophages. Previous experiments involved exposing E. coli to a bolus of NO. rather than the steadily generated gas expected of activated macrophages. We show here detectable induction of soxS transcription by NO. delivered at rates as low as 25 microM/h. Maximal induction was observed at 25 microM NO. per h under anaerobic conditions but at 125 microM/h aerobically. After incubation with murine macrophages, soxS expression was induced in the phagocytosed bacteria up to approximately 30-fold after an 8-h exposure. This in vivo induction was almost completely eliminated by the NO. synthase inhibitor NG-monomethyl-L-arginine. The inhibitor increased the survival of a delta soxRS strain but not that of wild-type E. coli after phagocytosis, which suggests that induction of the soxRS regulon by NO. can counteract most of the cytotoxic effects of NO. production by the macrophages. We show that the soxRS-regulated enzyme glucose-6-phosphate dehydrogenase is an important element of the defense against macrophages.
Nunoshiba
T
T
Department of Molecular and Cellular Toxicology, Harvard School of Public Health, Boston, Massachusetts 02115.
DeRojas-Walker
T
T
Tannenbaum
S R
SR
Demple
B
B
D000818:Animals; D001426:Bacterial Proteins / Q000096:biosynthesis* / Q000235:genetics; D043603:DNA-(Apurinic or Apyrimidinic Site) Lyase; D043223:Deoxyribonuclease IV (Phage T4-Induced); D004706:Endodeoxyribonucleases / Q000096:biosynthesis; D004790:Enzyme Induction; D004926:Escherichia coli / Q000235:genetics* / Q000276:immunology; D029968:Escherichia coli Proteins; D015964:Gene Expression Regulation, Bacterial; D005954:Glucosephosphate Dehydrogenase / Q000096:biosynthesis; D017737:Macrophages, Peritoneal / Q000276:immunology / Q000382:microbiology*; D051379:Mice; D009569:Nitric Oxide / Q000378:metabolism*; D018384:Oxidative Stress / Q000235:genetics; D010587:Phagocytosis; D012333:RNA, Messenger / Q000032:analysis; D018085:Regulon / Q000235:genetics; D015534:Trans-Activators; D014157:Transcription Factors / Q000096:biosynthesis* / Q000235:genetics; D014158:Transcription, Genetic
D001426:Bacterial Proteins; D029968:Escherichia coli Proteins; D012333:RNA, Messenger; D015534:Trans-Activators; D014157:Transcription Factors; C070724:SoxR protein, Bacteria; C070725:SoxS protein, E coli; D009569:Nitric Oxide; D005954:Glucosephosphate Dehydrogenase; D004706:Endodeoxyribonucleases; D043223:Deoxyribonuclease IV (Phage T4-Induced); C468972:endonuclease IV, E coli; D043603:DNA-(Apurinic or Apyrimidinic Site) Lyase