Role of nitric oxide, tetrahydrobiopterin and peroxynitrite in glucose toxicity-associated contractile dysfunction in ventricular myocytes.
OBJECTIVE
Local overproduction of nitric oxide is seen in early stages of diabetes, which can react with superoxide (O(2)(-)) to form peroxynitrite (ONOO(-)). The aim of this study was to examine the effect of scavengers for nitric oxide, O(2)(-), ONOO(-) and NOS cofactor tetrahydrobiopterin (BH(4)) on high glucose-induced cardiac contractile dysfunction.


METHODS
Ventricular myocytes were cultured for 24 h with either normal (N, 5.5 mmol/l) or high (25.5 mmol/l) glucose, with or without the nitric oxide scavengers haemoglobin (100 nmol/l), PTIO (100 micromol/l), the NOS inhibitor L-NMMA (100 micromol/l), superoxide dismutase (SOD, 500 U/ml), the ONOO(-) scavengers urate (100 micromol/l), MnTABP (100 micromol/l), BH(4) (10 micromol/l) and its inactive analogue NH(4) (10 micromol/l), and the GTP cyclohydrolase I inhibitor DAHP (1 mmol/l). Myocyte mechanics, NOS protein expression and activity were evaluated.


RESULTS
High glucose myocytes showed reduced peak shortening, decreased maximal velocity of shortening/relengthening (+/- dL/dt), prolonged relengthening (TR(90)) and normal shortening duration (TPS) associated with reduced cytosolic Ca(2+) rise compared to normal myocytes. The high glucose-induced abnormalities were abrogated or attenuated by urate, MnTBAP, L-NMMA, BH(4), and SOD, whereas unaffected by haemoglobin, PTIO and NH(4). L-NMMA reduced peak shortening while PTIO and DAHP depressed +/- dL/dt and prolonged TPS or TR(90) in normal myocytes. High glucose increased NOS activity, protein expression of eNOS but not iNOS, which were attenuated by L-NMMA and BH(4), respectively.


CONCLUSIONS
These results suggested that NOS cofactor, NO and ONOO(-) play a role in glucose-induced cardiomyocyte contractile dysfunction and in the pathogenesis of diabetic cardiomyopathy.
Esberg
L B
LB
Division of Pharmaceutical Sciences, University of Wyoming College of Health Sciences, Laramie, WY 82071-3375, USA.
Ren
J
J
D000818:Animals; D001708:Biopterins / Q000031:analogs & derivatives* / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism; D002478:Cells, Cultured; D004791:Enzyme Inhibitors / Q000494:pharmacology; D016166:Free Radical Scavengers / Q000494:pharmacology; D005947:Glucose / Q000506:poisoning*; D007425:Intracellular Membranes / Q000378:metabolism; D008297:Male; D009200:Myocardial Contraction / Q000187:drug effects*; D032383:Myocytes, Cardiac / Q000187:drug effects / Q000378:metabolism; D009569:Nitric Oxide / Q000378:metabolism*; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors / Q000378:metabolism; D030421:Peroxynitrous Acid / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D013482:Superoxide Dismutase / Q000494:pharmacology; D018754:Ventricular Dysfunction / Q000378:metabolism / Q000503:physiopathology*; D019323:omega-N-Methylarginine / Q000494:pharmacology
D004791:Enzyme Inhibitors; D016166:Free Radical Scavengers; D030421:Peroxynitrous Acid; D001708:Biopterins; D019323:omega-N-Methylarginine; D009569:Nitric Oxide; D019001:Nitric Oxide Synthase; D013482:Superoxide Dismutase; C003402:sapropterin; D005947:Glucose; D002118:Calcium