title: Role of tetrahydrobiopterin in resistance to myocardial ischemia in Brown Norway and Dahl S rats.
abstract: Previously we showed that Brown Norway (BN/Mcw) rats are more resistant to myocardial ischemia-reperfusion (I/R) injury than Dahl S (SS/Mcw) rats due to increased nitric oxide (x NO) generation secondary to increased heat shock protein 90 (HSP90) association with endothelial nitric oxide synthase (NOS3). Here we determined whether increased resistance to I/R injury in BN/Mcw hearts is also related to tetrahydrobiopterin (BH(4)) and GTP cyclohydrolase I (GCH-1), the rate-limiting enzyme for BH(4) synthesis. We observed that BH(4) supplementation via sepiapterin (SP) and inhibition of GCH-1 via 2,4-diamino-6-hydroxypyrimidine (DAHP) differentially modulate cardioprotection and that SP alters the association of HSP90 with NOS3. BH(4) levels were significantly higher and 7,8-dihydrobiopterin (BH(2)) levels were significantly lower in BN/Mcw than in SS/Mcw hearts. The BH(4)-to-BH(2) ratio in BN/Mcw was more than two times that in SS/Mcw hearts. After I/R, BH(4) decreased and BH(2) increased in hearts from both strains compared with their preischemia levels. However, the increase in BH(2) in SS/Mcw hearts was significantly higher than in BN/Mcw hearts. Real-time PCR revealed that BN/Mcw hearts contained more GCH-1 transcripts than SS/Mcw hearts. SP increased recovery of left ventricular developed pressure (rLVDP) following I/R as well as decreased superoxide (O(2)(x-)) and increased x NO in SS/Mcw hearts but not in BN/Mcw hearts. DAHP decreased rLVDP as well as increased O(2)(x-) and decreased x NO in BN/Mcw hearts compared with controls but not in SS/Mcw hearts. SP increased the association of HSP90 with NOS3. These data indicate that BH(4) mediates resistance to I/R by acting as a cofactor and enhancing HSP90-NOS3 association.
authors.affiliation: Department of Pediatric Surgery, Medical College of Wisconsin, Milwaukee, WI 53226, USA.
authors.forename: Jianzhong
authors.initials: J
authors.lastname: An
authors.forename: Jianhai
authors.initials: J
authors.lastname: Du
authors.forename: Na
authors.initials: N
authors.lastname: Wei
authors.forename: Hao
authors.initials: H
authors.lastname: Xu
authors.forename: Kirkwood A
authors.initials: KA
authors.lastname: Pritchard
authors.forename: Yang
authors.initials: Y
authors.lastname: Shi
mesh_terms: D000818:Animals; D001708:Biopterins / Q000031:analogs & derivatives* / Q000378:metabolism; D004195:Disease Models, Animal; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D006136:GTP Cyclohydrolase / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects; D018841:HSP90 Heat-Shock Proteins / Q000378:metabolism; D007042:Hypoxanthines / Q000494:pharmacology*; D017202:Myocardial Ischemia / Q000150:complications / Q000188:drug therapy* / Q000378:metabolism / Q000503:physiopathology; D015428:Myocardial Reperfusion Injury / Q000209:etiology / Q000378:metabolism / Q000503:physiopathology / Q000517:prevention & control*; D032383:Myocytes, Cardiac / Q000187:drug effects* / Q000378:metabolism; D009569:Nitric Oxide / Q000378:metabolism; D052250:Nitric Oxide Synthase Type III / Q000378:metabolism; D011622:Pterins / Q000378:metabolism / Q000494:pharmacology*; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D011914:Rats, Inbred BN; D020303:Rats, Inbred Dahl; D013045:Species Specificity; D013481:Superoxides / Q000378:metabolism; D016277:Ventricular Function, Left / Q000187:drug effects; D017725:Ventricular Pressure / Q000187:drug effects
chemical_list: D004791:Enzyme Inhibitors; D018841:HSP90 Heat-Shock Proteins; D007042:Hypoxanthines; D011622:Pterins; D012333:RNA, Messenger; D013481:Superoxides; D001708:Biopterins; D009569:Nitric Oxide; C017226:7,8-dihydrobiopterin; C016727:sepiapterin; D052250:Nitric Oxide Synthase Type III; C496316:Nos3 protein, rat; D006136:GTP Cyclohydrolase; C017202:2,4-diaminohypoxanthine; C003402:sapropterin