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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 generation of nitric oxide by increasing heat shock protein 90 association and serine phosphorylation



Circulation Research 91(4): 300-306



Chronic hypoxia increases endothelial nitric oxide synthase (eNOS) production of nitric oxide (cntdotNO) 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 cntdotNO, afforded by GA, decreased recovery, GA-treated hearts were perfused with S-nitrosoglutathione (GSNO) as a source of cntdotNO. 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 apprxeq4- 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 Nomega-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 cntdotNO 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.

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Accession: 010321764

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PMID: 12193462

DOI: 10.1161/01.res.0000031799.12850.1e


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