title: The prolyl hydroxylase oxygen-sensing pathway is cytoprotective and allows maintenance of mitochondrial membrane potential during metabolic inhibition.
abstract: The cellular oxygen sensor is a family of oxygen-dependent proline hydroxylase domain (PHD)-containing enzymes, whose reduction of activity initiate a hypoxic signal cascade. In these studies, prolyl hydroxylase inhibitors (PHIs) were used to activate the PHD-signaling pathway in cardiomyocytes. PHI-pretreatment led to the accumulation of glycogen and an increased maintenance of ATP levels in glucose-free medium containing cyanide. The addition of the glycolytic inhibitor 2-deoxy-d-glucose (2-DG) caused a decline of ATP levels that was indistinguishable between control and PHI-treated myocytes. Despite the comparable levels of ATP depletion, PHI-preconditioned myocytes remained significantly protected. As expected, mitochondrial membrane potential (DeltaPsi(mito)) collapses in control myocytes during cyanide and 2-DG treatment and it fails to completely recover upon washout. In contrast, DeltaPsi(mito) is partially maintained during metabolic inhibition and recovers completely on washout in PHI-preconditioned cells. Inclusion of rotenone, but not oligomycin, with cyanide and 2-DG was found to collapse DeltaPsi(mito) in PHI-pretreated myocytes. Thus, continued complex I activity was implicated in the maintenance of DeltaPsi(mito) in PHI-treated myocytes, whereas a role for the "reverse mode" operation of the F(1)F(0)-ATP synthase was ruled out. Further examination of mitochondrial function revealed that PHI treatment downregulated basal oxygen consumption to only approximately 15% that of controls. Oxygen consumption rates, although initially lower in PHI-preconditioned myocytes, recovered completely upon removal of metabolic poisons, while reaching only 22% of preinsult levels in control myocytes. We conclude that PHD oxygen-sensing mechanism directs multiple compensatory changes in the cardiomyocyte, which include a low-respiring mitochondrial phenotype that is remarkably protected against metabolic insult.
authors.affiliation: Dept. of Pharmaceutical Sciences, Medical Univ. of South Carolina, 280 Calhoun St., Charleston, SC 29425, USA.
authors.forename: Vijayalakshmi
authors.initials: V
authors.lastname: Sridharan
authors.forename: Jason
authors.initials: J
authors.lastname: Guichard
authors.forename: Rachel M
authors.initials: RM
authors.lastname: Bailey
authors.forename: Harinath
authors.initials: H
authors.lastname: Kasiganesan
authors.forename: Craig
authors.initials: C
authors.lastname: Beeson
authors.forename: Gary L
authors.initials: GL
authors.lastname: Wright
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D000600:Amino Acids, Dicarboxylic / Q000494:pharmacology; D000818:Animals; D000831:Animals, Newborn; D002470:Cell Survival / Q000187:drug effects; D002478:Cells, Cultured; D003486:Cyanides / Q000494:pharmacology; D019610:Cytoprotection; D003847:Deoxyglucose / Q000494:pharmacology; D006003:Glycogen / Q000378:metabolism; D062385:Hydroxybenzoates / Q000494:pharmacology; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000378:metabolism; D053078:Membrane Potential, Mitochondrial; D051379:Mice; D025261:Mitochondrial Proton-Translocating ATPases / Q000378:metabolism; D032383:Myocytes, Cardiac / Q000187:drug effects / Q000378:metabolism*; D010100:Oxygen / Q000378:metabolism*; D010101:Oxygen Consumption; D011393:Procollagen-Proline Dioxygenase / Q000037:antagonists & inhibitors / Q000378:metabolism*; D015398:Signal Transduction
chemical_list: D000600:Amino Acids, Dicarboxylic; D003486:Cyanides; C497443:Hif1a protein, mouse; D062385:Hydroxybenzoates; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; C018063:ethyl protocatechuate; D000255:Adenosine Triphosphate; D006003:Glycogen; D003847:Deoxyglucose; D011393:Procollagen-Proline Dioxygenase; C474451:F1F0-ATP synthase; D025261:Mitochondrial Proton-Translocating ATPases; D010100:Oxygen; C040947:oxalylglycine