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AMPK and FoxO1 regulate catalase expression in hypoxic pulmonary arterial smooth muscle
Author(s) -
Awad Hanan,
Nolette Nora,
Hinton Martha,
Dakshinamurti Shyamala
Publication year - 2014
Publication title -
pediatric pulmonology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.866
H-Index - 106
eISSN - 1099-0496
pISSN - 8755-6863
DOI - 10.1002/ppul.22919
Subject(s) - medicine , catalase , ampk , hypoxia (environmental) , foxo1 , cardiology , endocrinology , oxidative stress , enzyme , microbiology and biotechnology , signal transduction , protein kinase a , biochemistry , biology , oxygen , chemistry , protein kinase b , organic chemistry
Summary 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). Design/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. Pediatr Pulmonol. 2014; 49:885–897. © 2013 Wiley Periodicals, Inc.