T. Sonoki et al., COINDUCTION OF NITRIC-OXIDE SYNTHASE AND ARGINASE-I IN CULTURED RAT PERITONEAL-MACROPHAGES AND RAT-TISSUES IN-VIVO BY LIPOPOLYSACCHARIDE, The Journal of biological chemistry, 272(6), 1997, pp. 3689-3693
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-ty
pe arginase (arginase I) was analyzed, mRNAs for iNOS and arginase I w
ere 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 treatme
nt began to increase after 4 h with a lag time and reached a maximum a
t 12 h. Immunoblot analysis showed that iNOS and arginase I proteins w
ere also induced, mRNA for arginase II, an arginase isozyme, was not d
etected in the LPS-activated peritoneal cells, mRNA for CCAAT/enhancer
-binding protein beta (C/EBP beta), 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 exami
ned in LPS-injected rats in vivo. iNOS mRNA increased rapidly in the l
ung and spleen, reached a maximum 2-6 h after the LPS treatment, and d
ecreased thereafter. Arginase I mRNA was induced markedly and more slo
wly in both tissues, reaching a maximum in 12 h. Thus, arginase I appe
ars to have an important role in down regulating nitric oxide synthesi
s in murine macrophages by decreasing the availability of arginine, an
d the induction of arginase I is mediated by C/EBP beta.