title: Extracellular signal-regulated kinase mediates expression of arginase II but not inducible nitric-oxide synthase in lipopolysaccharide-stimulated macrophages.
abstract: The mitogen-activated protein kinases (MAPK) have been shown to participate in iNOS induction following lipopolysaccharide (LPS) stimulation, while the role of MAPKs in the regulation of arginase remains unclear. We hypothesized that different MAPK family members are involved in iNOS and arginase expression following LPS stimulation. LPS-stimulated RAW 264.7 cells exhibited increased protein and mRNA levels for iNOS, arginase I, and arginase II; although the induction of arginase II was more robust than that for arginase I. A p38 inhibitor completely prevented iNOS expression while it only attenuated arginase II induction. In contrast, a MEK1/2 inhibitor (ERK pathway) completely abolished arginase II expression while actually enhancing iNOS induction in LPS-stimulated cells. Arginase II promoter activity was increased by ∼4-fold following LPS-stimulation, which was prevented by the ERK pathway inhibitor. Arginase II promoter activity was unaffected by a p38 inhibitor or JNK pathway interference. Transfection with a construct expressing a constitutively active RAS mutant increased LPS-induced arginase II promoter activity, while transfection with a vector expressing a dominant negative ERK2 mutant or a vector expressing MKP-3 inhibited the arginase II promoter activity. LPS-stimulated nitric oxide (NO) production was increased following siRNA-mediated knockdown of arginase II and decreased when arginase II was overexpressed. Our results demonstrate that while both the ERK and p38 pathways regulate arginase II induction in LPS-stimulated macrophages, iNOS induction by LPS is dependent on p38 activation. These results suggest that differential inhibition of the MAPK pathway may be a potential therapeutic strategy to regulate macrophage phenotype.
authors.affiliation: From the Pulmonary Hypertension Group, Center for Perinatal Research, The Research Institute at Nationwide Children's Hospital, Columbus, Ohio 43215.
authors.forename: Yi
authors.initials: Y
authors.lastname: Jin
authors.affiliation: From the Pulmonary Hypertension Group, Center for Perinatal Research, The Research Institute at Nationwide Children's Hospital, Columbus, Ohio 43215.
authors.forename: Yusen
authors.initials: Y
authors.lastname: Liu
authors.affiliation: From the Pulmonary Hypertension Group, Center for Perinatal Research, The Research Institute at Nationwide Children's Hospital, Columbus, Ohio 43215 Leif.Nelin@nationwidechildrens.org.
authors.forename: Leif D
authors.initials: LD
authors.lastname: Nelin
mesh_terms: D000256:Adenoviridae / Q000378:metabolism; D000818:Animals; D001119:Arginase / Q000378:metabolism*; D002460:Cell Line; D000242:Cyclic AMP / Q000378:metabolism; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism*; D015971:Gene Expression Regulation, Enzymologic; D006801:Humans; D008070:Lipopolysaccharides / Q000737:chemistry; D020935:MAP Kinase Signaling System; D008264:Macrophages / Q000166:cytology / Q000201:enzymology*; D051379:Mice; D052247:Nitric Oxide Synthase Type II / Q000378:metabolism*; D010641:Phenotype; D010766:Phosphorylation; D011401:Promoter Regions, Genetic; D034741:RNA, Small Interfering / Q000378:metabolism; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism
chemical_list: D008070:Lipopolysaccharides; D034741:RNA, Small Interfering; D000242:Cyclic AMP; C496319:NOS2 protein, human; D052247:Nitric Oxide Synthase Type II; C496317:Nos2 protein, mouse; D048049:Extracellular Signal-Regulated MAP Kinases; D048051:p38 Mitogen-Activated Protein Kinases; C477631:ARG2 protein, human; C481673:Arg2 protein, mouse; D001119:Arginase
keywords: Macrophage Phenotype; Mitogen-activated Protein Kinase (MAPK); Toll-like Receptor 4 (TLR4); c-Jun N-terminal Kinase (JNK); cyclic AMP (cAMP); p38 MAPK