TY - JOUR
T1 - The prolyl hydroxylase oxygen-sensing pathway is cytoprotective and allows maintenance of mitochondrial membrane potential during metabolic inhibition
AU - Sridharan, Vijayalakshmi
AU - Guichard, Jason
AU - Bailey, Rachel M.
AU - Kasiganesan, Harinath
AU - Beeson, Craig
AU - Wright, Gary L.
PY - 2007/2
Y1 - 2007/2
N2 - 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-Dglucose (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 (ΔΨmito) collapses in control myocytes during cyanide and 2-DG treatment and it fails to completely recover upon washout. In contrast, ΔΨmito 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 ΔΨmito in PHI-pretreated myocytes. Thus, continued complex I activity was implicated in the maintenance of ΔΨ mito in PHI-treated myocytes, whereas a role for the "reverse mode" operation of the F1F0-ATP synthase was ruled out. Further examination of mitochondrial function revealed that PHI treatment downregulated basal oxygen consumption to only ∼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.
AB - 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-Dglucose (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 (ΔΨmito) collapses in control myocytes during cyanide and 2-DG treatment and it fails to completely recover upon washout. In contrast, ΔΨmito 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 ΔΨmito in PHI-pretreated myocytes. Thus, continued complex I activity was implicated in the maintenance of ΔΨ mito in PHI-treated myocytes, whereas a role for the "reverse mode" operation of the F1F0-ATP synthase was ruled out. Further examination of mitochondrial function revealed that PHI treatment downregulated basal oxygen consumption to only ∼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.
KW - Anaplerotic
KW - Cardioprotection
KW - Fumarate
KW - Hibernation
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UR - http://www.scopus.com/inward/citedby.url?scp=33847028349&partnerID=8YFLogxK
U2 - 10.1152/ajpcell.00100.2006
DO - 10.1152/ajpcell.00100.2006
M3 - Article
C2 - 17050618
AN - SCOPUS:33847028349
SN - 0363-6143
VL - 292
SP - C719-C728
JO - American Journal of Physiology - Cell Physiology
JF - American Journal of Physiology - Cell Physiology
IS - 2
ER -