title: Nitric oxide-induced activation of the AMP-activated protein kinase α2 subunit attenuates IκB kinase activity and inflammatory responses in endothelial cells.
abstract: BACKGROUND
  In endothelial cells, activation of the AMP-activated protein kinase (AMPK) has been linked with anti-inflammatory actions but the events downstream of kinase activation are not well understood. Here, we addressed the effects of AMPK activation/deletion on the activation of NFκB and determined whether the AMPK could contribute to the anti-inflammatory actions of nitric oxide (NO).
  
  
  RESULTS
  Overexpression of a dominant negative AMPKα2 mutant in tumor necrosis factor-α-stimulated human endothelial cells resulted in increased NFκB activity, E-selectin expression and monocyte adhesion. In endothelial cells from AMPKα2(-/-) mice the interleukin (IL)-1β induced expression of E-selectin was significantly increased. DETA-NO activated the AMPK and attenuated NFκB activation/E-selectin expression, effects not observed in human endothelial cells in the presence of the dominant negative AMPK, or in endothelial cells from AMPKα2(-/-) mice. Mechanistically, overexpression of constitutively active AMPK decreased the phosphorylation of IκB and p65, indicating a link between AMPK and the IκB kinase (IKK). Indeed, IKK (more specifically residues Ser177 and Ser181) was found to be a direct substrate of AMPKα2 in vitro. The hyper-phosphorylation of the IKK, which is known to result in its inhibition, was also apparent in endothelial cells from AMPKα2(+/+) versus AMPKα2(-/-) mice.
  
  
  CONCLUSIONS
  These results demonstrate that the IKK is a direct substrate of AMPKα2 and that its phosphorylation on Ser177 and Ser181 results in the inhibition of the kinase and decreased NFκB activation. Moreover, as NO potently activates AMPK in endothelial cells, a portion of the anti-inflammatory effects of NO are mediated by AMPK.
authors.affiliation: Centre for Molecular Medicine, Institute for Vascular Signalling, Goethe University, Frankfurt am Main, Germany.
authors.forename: Elke
authors.initials: E
authors.lastname: Bess
authors.forename: Beate
authors.initials: B
authors.lastname: Fisslthaler
authors.forename: Timo
authors.initials: T
authors.lastname: Frömel
authors.forename: Ingrid
authors.initials: I
authors.lastname: Fleming
mesh_terms: D055372:AMP-Activated Protein Kinases / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D019556:COS Cells; D002448:Cell Adhesion / Q000187:drug effects; D002522:Chlorocebus aethiops; D019040:E-Selectin / Q000378:metabolism; D042783:Endothelial Cells / Q000187:drug effects* / Q000201:enzymology* / Q000378:metabolism / Q000473:pathology; D004789:Enzyme Activation / Q000187:drug effects; D017353:Gene Deletion; D005786:Gene Expression Regulation / Q000187:drug effects; D006801:Humans; D051550:I-kappa B Kinase / Q000037:antagonists & inhibitors / Q000378:metabolism*; D007249:Inflammation / Q000201:enzymology / Q000378:metabolism / Q000473:pathology; D051379:Mice; D016328:NF-kappa B / Q000378:metabolism; D009569:Nitric Oxide / Q000494:pharmacology*; D019010:Vascular Cell Adhesion Molecule-1 / Q000378:metabolism
chemical_list: D019040:E-Selectin; D016328:NF-kappa B; D019010:Vascular Cell Adhesion Molecule-1; D009569:Nitric Oxide; D051550:I-kappa B Kinase; D055372:AMP-Activated Protein Kinases