title: Production of matrix metalloproteinase-9 by activated human monocytes involves a phosphatidylinositol-3 kinase/Akt/IKKalpha/NF-kappaB pathway.
abstract: Matrix metalloproteinase-9 (MMP-9) is considered to be an important component in the progression of inflammation. Monocytes/macrophages are prominent at inflammation sites, and activation of these cells by stimulants, such as lipopolysaccharide (LPS) or tumor necrosis factor alpha and granulocyte macrophage-colony stimulating factor, leads to the production of significant amounts of MMP-9. Here, we show that LPS stimulation of monocytes results in MMP-9 production through a phosphatidylinositol-3 kinase (PI-3K)/Akt/inhibitor of kappaB (IkappaB) kinase-alpha (IKKalpha)/nuclear factor (NF)-kappaB pathway. This new role for Akt in signaling leading to MMP-9 production was demonstrated by inhibitor and immunoprecipitation studies. LY294002 or wortmannin, inhibitors of PI-3K, suppressed LPS-induced Akt activity and MMP-9 production. Evidence for the participation of Akt in monocyte MMP-9 synthesis was demonstrated by the inhibition of MMP-9 by SH-5, a specific inhibitor of Akt. The mechanism by which Akt regulates MMP-9 is through the activation of NF-kappaB, as shown by coimmunoprecipitation of the phosphorylated form of IKKalpha and Akt as well as the SH-5 suppression of the dissociation of IkappaB from NF-kappaB and the activation of NF-kappaB p65. The role of NF-kappaB in regulation of MMP-9 was demonstrated further by the inhibition of MMP-9 production by proteasome inhibitors, lactacystin and MG-132, which prevented the ubiquitination and dissociation of IkappaB from NF-kappaB. This is the first demonstration that Akt is involved in the signaling pathway leading to the production of monocyte MMP-9 and provides an additional approach in the regulation of this enzyme in human primary monocytes.
authors.affiliation: Immunopathology Sction, National Institute of Dental and Craniofacial Research, National Institute of Health, Bethesda, MD 20892-4352, USA.
authors.forename: Yunbiao
authors.initials: Y
authors.lastname: Lu
authors.forename: Larry M
authors.initials: LM
authors.lastname: Wahl
mesh_terms: D002478:Cells, Cultured; D006801:Humans; D051550:I-kappa B Kinase; D008070:Lipopolysaccharides / Q000494:pharmacology; D020780:Matrix Metalloproteinase 9 / Q000378:metabolism*; D009000:Monocytes / Q000166:cytology / Q000187:drug effects / Q000201:enzymology*; D016328:NF-kappa B / Q000378:metabolism; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism*; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D011518:Proto-Oncogene Proteins / Q000378:metabolism*; D051057:Proto-Oncogene Proteins c-akt; D015398:Signal Transduction / Q000187:drug effects / Q000276:immunology; D051996:Transcription Factor RelA
chemical_list: D051550:I-kappa B Kinase; D008070:Lipopolysaccharides; D020780:Matrix Metalloproteinase 9; D016328:NF-kappa B; D019869:Phosphatidylinositol 3-Kinases; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins; D051057:Proto-Oncogene Proteins c-akt; D051996:Transcription Factor RelA; C494918:AKT1 protein, human; C496559:CHUK protein, human; C496560:IKBKB protein, human; C496565:IKBKE protein, human