Chronic hypoxia increases endothelial nitric oxide synthase generation of nitric oxide by increasing heat shock protein 90 association and serine phosphorylation.
Chronic hypoxia increases endothelial nitric oxide synthase (eNOS) production of nitric oxide (*NO) and cardioprotection in neonatal rabbit hearts. However, the mechanism by which this occurs remains unclear. Recent studies suggest that heat shock protein 90 (hsp90) alters eNOS function. In the present study, we examined the role of hsp90 in eNOS-dependent cardioprotection in neonatal rabbit hearts. Chronic hypoxia increased recovery of postischemic left ventricular developed pressure (LVDP). Geldanamycin (GA), which inhibits hsp90 and increases oxidative stress, decreased functional recovery in normoxic and hypoxic hearts. To determine if a loss in *NO, afforded by GA, decreased recovery, GA-treated hearts were perfused with S-nitrosoglutathione (GSNO) as a source of *NO. GSNO increased recovery of postischemic LVDP in GA-treated normoxic and hypoxic hearts to baseline levels. Although chronic hypoxia decreased phosphorylated eNOS (S1177) levels by approximately 4- to 5-fold and total Akt and phosphorylated Akt by 4- and 5-fold, it also increased hsp90 association with eNOS by more than 3-fold. Using hydroethidine (HEt), a fluorescent probe for superoxide, we found that hypoxic hearts contained less ethidine (Et) staining than normoxic hearts. Normoxic hearts generated 3 times more superoxide by an N(omega)-nitro-L-arginine methyl ester (L-NAME)-inhibitable mechanism than hypoxic hearts. Taken together, these data indicate that the association of hsp90 with eNOS is important for increasing *NO production and limiting eNOS-dependent superoxide anion generation. Such changes in eNOS function appear to play a critical role in protecting the myocardium against ischemic injury.
Division of Pediatric Surgery, Medical College of Wisconsin, Milwaukee, WI 53226, USA. yangshi@mcw.edu
Yang
Y
Shi
John E
JE
Baker
Chenyang
C
Zhang
James S
JS
Tweddell
Jidong
J
Su
Kirkwood A
KA
Pritchard
D000818:Animals; D000831:Animals, Newborn; D016227:Benzoquinones; D015153:Blotting, Western; D002908:Chronic Disease; D004789:Enzyme Activation / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005456:Fluorescent Dyes; D018841:HSP90 Heat-Shock Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism*; D000860:Hypoxia / Q000150:complications / Q000378:metabolism*; D066298:In Vitro Techniques; D047029:Lactams, Macrocyclic; D017202:Myocardial Ischemia / Q000150:complications / Q000378:metabolism*; D009569:Nitric Oxide / Q000378:metabolism*; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors / Q000378:metabolism*; D052250:Nitric Oxide Synthase Type III; D018384:Oxidative Stress / Q000187:drug effects; D010766:Phosphorylation / Q000187:drug effects; D011485:Protein Binding; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt; D011809:Quinones / Q000494:pharmacology; D011817:Rabbits; D020127:Recovery of Function / Q000187:drug effects; D012694:Serine / Q000378:metabolism; D013481:Superoxides / Q000378:metabolism; D016277:Ventricular Function, Left / Q000187:drug effects
D016227:Benzoquinones; D004791:Enzyme Inhibitors; D005456:Fluorescent Dyes; D018841:HSP90 Heat-Shock Proteins; D047029:Lactams, Macrocyclic; D011518:Proto-Oncogene Proteins; D011809:Quinones; D013481:Superoxides; D009569:Nitric Oxide; D012694:Serine; D019001:Nitric Oxide Synthase; D052250:Nitric Oxide Synthase Type III; D017346:Protein Serine-Threonine Kinases; D051057:Proto-Oncogene Proteins c-akt; C001277:geldanamycin