Desferoxamine and ethyl-3,4-dihydroxybenzoate protect myocardium by activating NOS and generating mitochondrial ROS.
Protection from a prolyl hydroxylase domain-containing enzyme (PHD) inhibitor, desferoxamine (DFO), was recently reported to be dependent on production of reactive oxygen species (ROS). Ischemic preconditioning triggers the protected state by stimulating nitric oxide (NO) production to open mitochondrial ATP-sensitive K+ (mitoK(ATP)) channels, generating ROS required for protection. We tested whether DFO and a second PHD inhibitor, ethyl-3,4-dihydroxybenzoate (EDHB), might have similar mechanisms. EDHB and DFO increased ROS generation by 50-75% (P < 0.001) in isolated rabbit cardiomyocytes. This increase after EDHB exposure was blocked by N(omega)-nitro-L-arginine methyl ester (L-NAME), an NO synthase (NOS) inhibitor; ODQ, a guanylyl cyclase antagonist; and Rp-8-bromoguanosine-3',5'-cyclic monophosphorothioate Rp isomer, a PKG blocker, thus implicating the NO pathway in EDHB's signaling. Glibenclamide, a nonselective K(ATP) channel blocker, or 5-hydroxydecanoate, a selective mitoK(ATP) channel antagonist, also prevented EDHB's ROS production, as did blockade of mitochondrial electron transport with myxothiazol. NOS is activated by Akt. However, neither wortmannin, an inhibitor of phosphatidylinositol-3-kinase, nor Akt inhibitor blocked EDHB-induced ROS generation, indicating that EDHB initiates signaling downstream of Akt. DFO also increased ROS production, and this effect was blocked by ODQ, 5-hydroxydecanoate, and N-(2-mercaptopropionyl)glycine, an ROS scavenger. DFO increased cardiomyocyte production of nitrite, a metabolite of NO, and this effect was blocked by an inhibitor of NOS. DFO also spared ischemic myocardium in intact hearts. This infarct-sparing effect was blocked by ODQ, L-NAME, and N-(2-mercaptopropionyl)glycine. Hence, DFO and EDHB stimulate NO-dependent activation of PKG to open mitoK(ATP) channels and produce ROS, which act as second messengers to trigger entrance into the preconditioned state.
Philipp
Sebastian
S
Dept. of Physiology, Univ. of South Alabama College of Medicine, Mobile, AL 36688, USA.
Cui
Lin
L
Ludolph
Barbara
B
Kelm
Malte
M
Schulz
Rainer
R
Cohen
Michael V
MV
Downey
James M
JM
D018528:ATP-Binding Cassette Transporters / Q000037:antagonists & inhibitors; D000730:Androstadienes / Q000494:pharmacology; D000818:Animals; D017869:Cyclic GMP-Dependent Protein Kinases / Q000037:antagonists & inhibitors; D003676:Deferoxamine / Q000494:pharmacology*; D004789:Enzyme Activation; D005260:Female; D005905:Glyburide / Q000494:pharmacology; D006162:Guanylate Cyclase / Q000037:antagonists & inhibitors; D006439:Hemodynamics / Q000187:drug effects; D062385:Hydroxybenzoates / Q000494:pharmacology*; D054086:KATP Channels; D008297:Male; D032383:Myocytes, Cardiac / Q000187:drug effects* / Q000378:metabolism; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D019001:Nitric Oxide Synthase / Q000378:metabolism*; D010069:Oxadiazoles / Q000494:pharmacology; D015221:Potassium Channels / Q000502:physiology; D024661:Potassium Channels, Inwardly Rectifying / Q000037:antagonists & inhibitors; D011393:Procollagen-Proline Dioxygenase / Q000037:antagonists & inhibitors*; D051057:Proto-Oncogene Proteins c-akt / Q000037:antagonists & inhibitors; D011810:Quinoxalines / Q000494:pharmacology; D011817:Rabbits; D017382:Reactive Oxygen Species / Q000378:metabolism*; D000077191:Wortmannin
C095284:1H-(1,2,4)oxadiazolo(4,3-a)quinoxalin-1-one; D018528:ATP-Binding Cassette Transporters; D000730:Androstadienes; D062385:Hydroxybenzoates; D054086:KATP Channels; D010069:Oxadiazoles; D015221:Potassium Channels; D024661:Potassium Channels, Inwardly Rectifying; D011810:Quinoxalines; D017382:Reactive Oxygen Species; C117780:mitochondrial K(ATP) channel; C092520:uK-ATP-1 potassium channel; C018063:ethyl protocatechuate; D011393:Procollagen-Proline Dioxygenase; D019001:Nitric Oxide Synthase; D051057:Proto-Oncogene Proteins c-akt; D017869:Cyclic GMP-Dependent Protein Kinases; D006162:Guanylate Cyclase; D003676:Deferoxamine; D005905:Glyburide; D019331:NG-Nitroarginine Methyl Ester; D000077191:Wortmannin