title: AMPK and FoxO1 regulate catalase expression in hypoxic pulmonary arterial smooth muscle.
abstract: BACKGROUND
  Hypoxia and reactive oxygen species (ROS) including H(2)O(2) play major roles in triggering and progression of pulmonary vascular remodeling in persistent pulmonary hypertension. Catalase (CAT), the major endogenous enzyme scavenging H(2)O(2), is regulated in a tissue- and context-specific manner.
  
  
  OBJECTIVE
  To investigate mechanisms by which hypoxia and H(2)O(2) regulate catalase expression, and the role of AMPK-FoxO pathway, in neonatal porcine pulmonary artery smooth muscle (PASMC).
  
  
  METHODS
  PASMC were grown in hypoxia (10% O(2)) or normoxia (21% O(2)) for 72 hr. We measured catalase activity and lipid peroxidation; CAT, FoxO1, and FoxO3a expression by qPCR; protein contents of CAT, FoxOs, p-AMPK, p-AKT, p-JNK, p-ERK1/2 in whole lysates, and FoxOs in nuclear extracts, by immunoblot; and FoxO-1 nuclear localization by immunocytochemistry, quantified by laser scanning cytometry.
  
  
  RESULTS
  Hypoxia upregulated CAT transcription, content and activity, by increasing CAT transcription factors FoxO1 and FoxO3a mRNA, and promoting nuclear translocation of FoxO1. However, lipid peroxidation increased in hypoxic PASMC. Among candidate FoxO regulatory kinases, hypoxia activated AMPK, and decreased p-Akt and ERK1/2. AMPK activation increased FoxO1 (total and nuclear) and CAT, while AMPK inhibition inhibited FoxO1 and CAT, but not FoxO3a. Exogenous H(2)O(2) decreased p-AMPK and increased p-AKT in hypoxic PASMC. This decreased active FoxO1, and reduced mRNA and protein content of CAT. Hypoxic induction of CAT, AKT inhibition (LY294002), or addition of PEG-catalase partly ameliorated the H(2)O(2) -mediated loss of nuclear FoxO1.
  
  
  CONCLUSIONS
  Hypoxia induces catalase expression, though this adaptation is insufficient to protect PASMC from hypoxia-induced lipid peroxidation. This occurs via hypoxic activation of AMPK, which promotes nuclear FoxO1 and thus catalase expression. Exogenous ROS may downregulate cellular antioxidant defenses; H(2)O(2) activates survival factor Akt, decreasing nuclear FoxO1 and thus catalase.
authors.affiliation: Biology of Breathing Group, Manitoba Institute of Child Health, Winnipeg, Canada.
authors.forename: Hanan
authors.initials: H
authors.lastname: Awad
authors.forename: Nora
authors.initials: N
authors.lastname: Nolette
authors.forename: Martha
authors.initials: M
authors.lastname: Hinton
authors.forename: Shyamala
authors.initials: S
authors.lastname: Dakshinamurti
mesh_terms: D055372:AMP-Activated Protein Kinases / Q000378:metabolism*; D000818:Animals; D002374:Catalase / Q000235:genetics / Q000378:metabolism; D051858:Forkhead Transcription Factors / Q000378:metabolism*; D000860:Hypoxia / Q000378:metabolism*; D015227:Lipid Peroxidation; D009130:Muscle, Smooth / Q000378:metabolism*; D011651:Pulmonary Artery / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism; D017382:Reactive Oxygen Species / Q000378:metabolism; D013552:Swine; D015854:Up-Regulation
chemical_list: D051858:Forkhead Transcription Factors; D012333:RNA, Messenger; D017382:Reactive Oxygen Species; D002374:Catalase; D055372:AMP-Activated Protein Kinases
keywords: AMP kinase; Akt; PPHN; catalase; hydrogen peroxide