title: Decreased tetrahydrobiopterin and disrupted association of Hsp90 with eNOS by hyperglycemia impair myocardial ischemic preconditioning.
abstract: Cardioprotection by ischemic preconditioning (IPC) is impaired during hyperglycemia, but the mechanisms underlying this phenomenon are poorly understood. This study investigated the role of hyperglycemia to adversely modulate tetrahydrobiopterin (BH(4)) and heat shock protein 90 (Hsp90) during cardioprotection by IPC. Rabbits or mice underwent 30 min of coronary occlusion followed by reperfusion with or without IPC in the presence or absence of hyperglycemia. IPC significantly (P < 0.05) decreased myocardial infarct size (46 ± 1 to 19 ± 2% of the area at risk in control and IPC rabbits, respectively) and increased BH(4) concentrations (HPLC; 7.6 ± 0.2 to 10.2 ± 0.3 pmol/mg protein, respectively), Hsp90-endothelial nitric oxide synthase (eNOS) association (coimmunoprecipitation and Western blotting in mice; 4.0 ± 0.3 to 5.4 ± 0.1, respectively), and the ratio of phosphorylated eNOS/total eNOS. These beneficial actions of IPC on infarct size, BH(4), Hsp90/eNOS, and phosphorylated eNOS were eliminated by hyperglycemia. Pretreatment of animals with the Hsp90 inhibitor geldanamycin (0.6 mg/kg) or the BH(4) synthesis inhibitor diamino-6-hydroxypyrimidine (1.0 g/kg) also eliminated cardioprotection produced by IPC. In contrast, the BH(4) precursor sepiapterin (2 mg/kg iv) restored the beneficial effects of IPC on myocardial BH(4) concentrations, eNOS dimerization, and infarct size during hyperglycemia. A-23871 increased Hsp90-eNOS association (0.33 ± 0.06 to 0.59 ± 0.3) and nitric oxide production (184 ± 17%) in human coronary artery endothelial cells cultured in normal (5.5 mM) but not high (20 mM) glucose media. These data indicate that hyperglycemia eliminates protection by IPC via decreases in myocardial BH(4) concentration and disruption of the association of Hsp90 with eNOS. The results suggest that eNOS dysregulation may be a central mechanism of impaired cardioprotection during hyperglycemia.
authors: Department of Anesthesiology, Medical College of Wisconsin, Milwaukee, WI 53226, USA.
authors: Nikolina
authors: N
authors: Vladic
authors: Zhi-Dong
authors: ZD
authors: Ge
authors: Thorsten
authors: T
authors: Leucker
authors: Anna K
authors: AK
authors: Brzezinska
authors: Jian-Hai
authors: JH
authors: Du
authors: Yang
authors: Y
authors: Shi
authors: David C
authors: DC
authors: Warltier
authors: Phillip F
authors: PF
authors: Pratt
authors: Judy R
authors: JR
authors: Kersten
mesh_terms: D000818:Animals; D016227:Benzoquinones / Q000494:pharmacology; D001708:Biopterins / Q000031:analogs & derivatives* / Q000378:metabolism; D001786:Blood Glucose / Q000378:metabolism; D015153:Blotting, Western; D002478:Cells, Cultured; D054059:Coronary Occlusion / Q000150:complications* / Q000201:enzymology; D004195:Disease Models, Animal; D042783:Endothelial Cells / Q000378:metabolism; D018841:HSP90 Heat-Shock Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism*; D006943:Hyperglycemia / Q000150:complications* / Q000201:enzymology; D047468:Immunoprecipitation; D019157:Ischemic Preconditioning, Myocardial; D047029:Lactams, Macrocyclic / Q000494:pharmacology; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D009203:Myocardial Infarction / Q000201:enzymology / Q000209:etiology / Q000473:pathology / Q000517:prevention & control*; D015428:Myocardial Reperfusion Injury / Q000201:enzymology / Q000209:etiology / Q000473:pathology / Q000517:prevention & control*; D009206:Myocardium / Q000201:enzymology* / Q000473:pathology; D009569:Nitric Oxide / Q000378:metabolism; D052250:Nitric Oxide Synthase Type III / Q000378:metabolism*; D010766:Phosphorylation; D055503:Protein Multimerization; D011622:Pterins / Q000494:pharmacology; D011817:Rabbits; D013997:Time Factors
chemical_list: D016227:Benzoquinones; D001786:Blood Glucose; D018841:HSP90 Heat-Shock Proteins; D047029:Lactams, Macrocyclic; D011622:Pterins; D001708:Biopterins; D009569:Nitric Oxide; C016727:sepiapterin; D052250:Nitric Oxide Synthase Type III; C496315:Nos3 protein, mouse; C003402:sapropterin; C001277:geldanamycin