title: Cardiac responses to hypoxia and reoxygenation in Drosophila.
abstract: An adequate supply of oxygen is important for the survival of all tissues, but it is especially critical for tissues with high-energy demands, such as the heart. Insufficient tissue oxygenation occurs under a variety of conditions, including high altitude, embryonic and fetal development, inflammation, and thrombotic diseases, often affecting multiple organ systems. Responses and adaptations of the heart to hypoxia are of particular relevance in human cardiovascular and pulmonary diseases, in which the effects of hypoxic exposure can range in severity from transient to long-lasting. This study uses the genetic model system Drosophila to investigate cardiac responses to acute (30 min), sustained (18 h), and chronic (3 wk) hypoxia with reoxygenation. Whereas hearts from wild-type flies recovered quickly after acute hypoxia, exposure to sustained or chronic hypoxia significantly compromised heart function upon reoxygenation. Hearts from flies with mutations in sima, the Drosophila homolog of the hypoxia-inducible factor alpha subunit (HIF-α), exhibited exaggerated reductions in cardiac output in response to hypoxia. Heart function in hypoxia-selected flies, selected over many generations for survival in a low-oxygen environment, revealed reduced cardiac output in terms of decreased heart rate and fractional shortening compared with their normoxia controls. Hypoxia-selected flies also had smaller hearts, myofibrillar disorganization, and increased extracellular collagen deposition, consistent with the observed reductions in contractility. This study indicates that longer-duration hypoxic insults exert deleterious effects on heart function that are mediated, in part, by sima and advances Drosophila models for the genetic analysis of cardiac-specific responses to hypoxia and reoxygenation.
authors.affiliation: Development, Aging and Regeneration Program, Sanford Burnham Prebys Medical Discovery Institute, La Jolla, California; School of Medicine, University of California-San Diego, La Jolla, California; and.
authors.forename: Rachel
authors.initials: R
authors.lastname: Zarndt
authors.affiliation: Development, Aging and Regeneration Program, Sanford Burnham Prebys Medical Discovery Institute, La Jolla, California;
authors.forename: Sarah
authors.initials: S
authors.lastname: Piloto
authors.affiliation: School of Medicine, University of California-San Diego, La Jolla, California; and.
authors.forename: Frank L
authors.initials: FL
authors.lastname: Powell
authors.affiliation: Department of Pediatrics, University of California-San Diego, La Jolla, California.
authors.forename: Gabriel G
authors.initials: GG
authors.lastname: Haddad
authors.affiliation: Development, Aging and Regeneration Program, Sanford Burnham Prebys Medical Discovery Institute, La Jolla, California;
authors.forename: Rolf
authors.initials: R
authors.lastname: Bodmer
authors.affiliation: Development, Aging and Regeneration Program, Sanford Burnham Prebys Medical Discovery Institute, La Jolla, California; kocorr@sbpdiscovery.org.
authors.forename: Karen
authors.initials: K
authors.lastname: Ocorr
mesh_terms: D000222:Adaptation, Physiological; D000818:Animals; D002302:Cardiac Output; D003094:Collagen / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D029721:Drosophila Proteins / Q000235:genetics / Q000378:metabolism; D004331:Drosophila melanogaster / Q000235:genetics / Q000378:metabolism*; D005260:Female; D005355:Fibrosis; D005838:Genotype; D006339:Heart Rate; D006439:Hemodynamics; D000860:Hypoxia / Q000378:metabolism* / Q000473:pathology / Q000503:physiopathology; D009154:Mutation; D009200:Myocardial Contraction; D009206:Myocardium / Q000378:metabolism* / Q000473:pathology; D010100:Oxygen / Q000378:metabolism*; D010641:Phenotype; D020127:Recovery of Function; D013997:Time Factors
chemical_list: D004268:DNA-Binding Proteins; D029721:Drosophila Proteins; C100429:Sima protein, Drosophila; D003094:Collagen; D010100:Oxygen
keywords: Drosophila; genetic selection; heart; hypoxia; hypoxia-inducible factor; reoxygenation; sima