Open AccessAuthor(s) -
Rupesh Chaturvedi,
Mohammad Asim,
Nuruddeen D. Lewis,
Holly M. Scott Algood,
Timothy L. Cover,
Preston Y. Kim,
Keith T. Wilson
Publication year - 2007
Publication title -
infection and immunity
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.508
H-Index - 220
eISSN - 1070-6313
pISSN - 0019-9567
DOI - 10.1128/iai.00578-07
Subject(s) - nitric oxide synthase , helicobacter pylori , arginase , biology , arginine , nitric oxide , microbiology and biotechnology , omega n methylarginine , immune system , biochemistry , amino acid , immunology , endocrinology , genetics
Helicobacter pylori infection of the stomach causes an active immune response that includes stimulation of inducible nitric oxide (NO) synthase (iNOS) expression. Although NO can killH. pylori , the bacterium persists indefinitely, suggesting that NO production is inadequate. We determined if the NO derived from iNOS in macrophages was dependent on the availability of its substrate,l -arginine (l -Arg). Production of NO byH. pylori -stimulated RAW 264.7 cells was dependent on thel -Arg concentration in the culture medium, and the 50% effective dose forl -Arg was 220 μM, which is above reported plasmal -Arg levels. While iNOS mRNA induction wasl -Arg independent, iNOS protein increased in anl -Arg-dependent manner that did not involve changes in iNOS protein degradation.l -Lysine, an inhibitor ofl -Arg uptake, attenuatedH. pylori -stimulated iNOS protein expression, translation, NO levels, and killing ofH. pylori . Whilel -Arg starvation suppressed global protein translation, at concentrations ofl -Arg at which iNOS protein was only minimally expressed in response toH. pylori , global translation was fully restored and eukaryotic translation initiation factor α was dephosphorylated.H. pylori lacking the generocF , which codes for a bacterial arginase, induced higher levels of NO production by increasing iNOS protein levels. When murine gastric macrophages were activated withH. pylori , supraphysiologic levels ofl -Arg were required to permit iNOS protein expression and NO production. These findings indicate thatl -Arg is rate limiting for iNOS translation and suggest that the levels ofl -Arg that occur in vivo do not permit sufficient NO generation by the host to killH. pylori .