Premium
Role of Hypoxia‐Inducible‐Factor‐2α in Transcriptional Regulation of Heme Oxygenase‐1 in Hypoxic Cardiomyocytes
Author(s) -
Eadie Ashley L.,
Allwood Melissa A.,
Platt Mathew J.,
Huber Jason,
Trivedi Purvi C.,
Madhu Malav N.,
Pulinilkunnil Thomas C.,
Simpson Jeremy A.,
Brunt Keith R.
Publication year - 2017
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.31.1_supplement.1069.8
Subject(s) - heme oxygenase , hmox1 , heme , hypoxia (environmental) , hypoxia inducible factors , hemin , chemistry , pharmacology , microbiology and biotechnology , biology , biochemistry , enzyme , oxygen , gene , organic chemistry
The heme metabolism pathway is a novel therapeutic target in the management of heart failure, with cytoprotection mediated through induction of heme oxygenase‐1 (HMOX1). However, translation of HMOX1‐targeted therapeutics to the clinic has not occurred. Understanding of heme bioavailability regulation in cardiomyocytes, particularly during hypoxia or heart failure, is incomplete. The molecular response to hypoxia is largely regulated by hypoxia inducible transcription factors (HIFs). HIF1α transcriptionally regulates HMOX1 in acute, severe hypoxia but the role of HIF2α in heme metabolism is unknown. A detailed understanding of the differences in molecular regulation between acute or chronic and severe or moderate hypoxia in cardiomyocytes is required. HYPOTHESIS Hypoxia‐inducible factor 2α (HIF2α) contains heme‐regulatory motifs that are sensitized by heme bioavailability at various degrees of hypoxia in cardiomyocytes to regulate the acute expression of HMOX1 in vitro and in experimental models of heart failure in vivo . METHODS Acute myocardial infarction (AMI)‐induced heart failure was modeled through permanent surgical ligation of the left anterior descending coronary artery in mice. Hypertensive heart failure was modeled through transverse aortic constriction (TAC). Expression of heme regulatory enzymes and hypoxia inducible factors were measured via Western Blot, qPCR and heme content assay. In vitro , hypoxia was established by incubating H9C2 and neonatal rat cardiomyocytes in an adjustable‐oxygen chamber. HIF1α and HIF2α were knocked down or overexpressed through adenoviral vectors. To investigate the role of heme bioavailability in HIF2α sensitization, cells were incubated with the heme surrogate, hemin. RESULTS In vivo , heme levels were increased in both AMI and TAC‐induced heart failure progressively, however not due to increased heme synthesis enzymes. In vitro , HMOX1 was increased by HIF2α more than by HIF1α overexpression. This response was synergistically increased in heme‐replete hypoxia with HIF2α, but not HIF1α, overexpression. CONCLUSIONS We have shown for the first time that HIF2α is a novel regulator of HMOX1. Further understanding of heme homeostasis in the heart is necessary to optimize therapeutic targeting of the heme metabolic pathway in heart failure. Further, we show that HIF2α has a distinct role from HIF1α as it is sensitive to heme bioavailability and not an exclusive oxygen sensor. Support or Funding Information Natural Sciences and Engineering Research Council of Canada