title: Phosphatidylinositol 3-kinase/Akt pathway mediates heme oxygenase-1 regulation by lipopolysaccharide.
abstract: The stress-inducible protein heme oxygenase-1 exerts potent antiinflammatory, antiapoptotic and cytoprotective effects in vitro and in vivo. Another important mediator of cytoprotection, the phosphatidylinositol 3-kinase (PI3K)/Akt signaling pathway activates many proteins involved in the maintenance of cellular homeostasis. Since activation of heme oxygenase-1 and PI3K/Akt both protect the cellular environment, we postulated that PI3K/Akt can regulate the induction of heme oxygenase-1 by proinflammatory stress. The treatment of primary murine macrophage cells (RAW 264.7) with lipopolysaccharide induced heme oxygenase-1 protein and mRNA expression, and increased the phosphorylation of Akt and p38 mitogen activated protein kinase (p38 MAPK). These cellular effects of lipopolysaccharide were markedly diminished by pre-treatment with wortmannin, a specific inhibitor of PI3K. Furthermore, lipopolysaccharide-inducible heme oxygenase expression was blocked by SB203580, a specific inhibitor of p38 MAPK. Both wortmannin and SB203580 decreased lipopolysaccharide-inducible NF-E2-related factor (Nrf2) DNA binding activity. Transfection of macrophages with dominant negative mutants of PI3K, Akt and Nrf2, as well as wortmannin treatment, significantly reduced the transcriptional activity of a minimal heme oxygenase-1 promoter luciferase construct (D33HO-1luc). We demonstrate, to our knowledge for the first time, that upon proinflammatory stimulation heme oxygenase-1 gene expression in macrophages depends on PI3K/Akt and p38 MAPK acting upstream of Nrf2-dependent promoter activation.
authors.affiliation: Division of Pulmonary, Allergy and Critical Care Medicine, University of Pittsburgh School of Medicine, MUH 628NW, Pittsburgh, Pennsylvania 15213, USA.
authors.forename: S E
authors.initials: SE
authors.lastname: Pischke
authors.forename: Z
authors.initials: Z
authors.lastname: Zhou
authors.forename: R
authors.initials: R
authors.lastname: Song
authors.forename: W
authors.initials: W
authors.lastname: Ning
authors.forename: J
authors.initials: J
authors.lastname: Alam
authors.forename: S W
authors.initials: SW
authors.lastname: Ryter
authors.forename: A M K
authors.initials: AM
authors.lastname: Choi
mesh_terms: D000818:Animals; D002460:Cell Line; D005786:Gene Expression Regulation / Q000187:drug effects; D051547:Heme Oxygenase-1 / Q000187:drug effects* / Q000235:genetics / Q000378:metabolism; D007249:Inflammation / Q000378:metabolism; D008070:Lipopolysaccharides / Q000494:pharmacology*; D008264:Macrophages; D051379:Mice; D051267:NF-E2-Related Factor 2 / Q000235:genetics; D019869:Phosphatidylinositol 3-Kinases / Q000235:genetics / Q000378:metabolism*; D011401:Promoter Regions, Genetic; D051057:Proto-Oncogene Proteins c-akt / Q000235:genetics / Q000378:metabolism*; D014162:Transfection; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism
chemical_list: D008070:Lipopolysaccharides; D051267:NF-E2-Related Factor 2; D051547:Heme Oxygenase-1; D019869:Phosphatidylinositol 3-Kinases; D051057:Proto-Oncogene Proteins c-akt; D048051:p38 Mitogen-Activated Protein Kinases