Coinduction of nitric-oxide synthase and arginase I in cultured rat peritoneal macrophages and rat tissues in vivo by lipopolysaccharide.
Nitric oxide is synthesized by nitric-oxide synthase from arginine, a common substrate of arginase. Rat peritoneal macrophages were cultured in the presence of bacterial lipopolysaccharide (LPS), and expression of the inducible isoform of nitric-oxide synthase (iNOS) and liver-type arginase (arginase I) was analyzed. mRNAs for iNOS and arginase I were induced by LPS in a dose-dependent manner. iNOS mRNA appeared 2 h after LPS treatment and increased to a near maximum at 8-12 h. On the other hand, arginase I mRNA that was undetectable prior to the treatment began to increase after 4 h with a lag time and reached a maximum at 12 h. Immunoblot analysis showed that iNOS and arginase I proteins were also induced. mRNA for arginase II, an arginase isozyme, was not detected in the LPS-activated peritoneal cells. mRNA for CCAAT/enhancer-binding protein beta (C/EBPbeta), a transactivator of the arginase I gene, was also induced, and the induction was more rapid than that of arginase I mRNA. Changes in iNOS and arginase I mRNAs were also examined in LPS-injected rats in vivo. iNOS mRNA increased rapidly in the lung and spleen, reached a maximum 2-6 h after the LPS treatment, and decreased thereafter. Arginase I mRNA was induced markedly and more slowly in both tissues, reaching a maximum in 12 h. Thus, arginase I appears to have an important role in down-regulating nitric oxide synthesis in murine macrophages by decreasing the availability of arginine, and the induction of arginase I is mediated by C/EBPbeta.
Sonoki
T
T
Department of Molecular Genetics, Kumamoto University School of Medicine, Kuhonji 4-24-1, Kumamoto 862, Japan.
Nagasaki
A
A
Gotoh
T
T
Takiguchi
M
M
Takeya
M
M
Matsuzaki
H
H
Mori
M
M
D000818:Animals; D001119:Arginase / Q000378:metabolism*; D022762:CCAAT-Enhancer-Binding Proteins; D002478:Cells, Cultured; D004268:DNA-Binding Proteins / Q000378:metabolism; D004790:Enzyme Induction; D008070:Lipopolysaccharides / Q000494:pharmacology; D008168:Lung / Q000187:drug effects / Q000201:enzymology; D008264:Macrophages / Q000201:enzymology*; D019001:Nitric Oxide Synthase / Q000096:biosynthesis*; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats
D022762:CCAAT-Enhancer-Binding Proteins; D004268:DNA-Binding Proteins; D008070:Lipopolysaccharides; D012333:RNA, Messenger; D019001:Nitric Oxide Synthase; D001119:Arginase