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En Face Detection of Nitric Oxide and Superoxide in Endothelial Layer of Intact Arteries
Published on: February 25, 2016
Role of nitric oxide, tetrahydrobiopterin and peroxynitrite in glucose toxicity-associated contractile dysfunction in
1Division of Pharmaceutical Sciences, University of Wyoming College of Health Sciences, Laramie, WY 82071-3375, USA.
Aims/Hypothesis:
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.
Conclusion/Interpretation:
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.
Insights
High glucose impairs heart cell function by increasing nitric oxide and peroxynitrite. Scavengers for these molecules and the NOS cofactor tetrahydrobiopterin (BH(4)) protected against diabetic cardiomyopathy.
Area of Science:
- Cardiovascular Physiology
- Diabetic Complications
- Molecular Medicine
Background:
- Diabetes mellitus is associated with increased nitric oxide (NO) production.
- NO can react with superoxide (O(2)(-)) to form peroxynitrite (ONOO(-)).
- These reactive species are implicated in the development of diabetic cardiomyopathy.
Purpose of the Study:
- To investigate the role of NO, O(2)(-), ONOO(-), and the NOS cofactor tetrahydrobiopterin (BH(4)) in high glucose-induced cardiac contractile dysfunction.
- To evaluate the therapeutic potential of scavengers for these molecules in mitigating diabetic cardiomyopathy.
Main Methods:
- Cultured ventricular myocytes were exposed to normal or high glucose conditions.
- Various scavengers and inhibitors were used, including L-NMMA (NOS inhibitor), SOD (superoxide dismutase), urate and MnTBAP (ONOO(-) scavengers), and BH(4).
- Myocyte mechanics, NOS activity, and protein expression were assessed.
Main Results:
- High glucose significantly impaired myocyte shortening, velocity, and relaxation, associated with reduced cytosolic Ca(2+) rise.
- Cardiac dysfunction induced by high glucose was ameliorated by urate, MnTBAP, L-NMMA, BH(4), and SOD.
- High glucose increased NOS activity and eNOS expression, which were attenuated by L-NMMA and BH(4), respectively.
Conclusions:
- Nitric oxide, peroxynitrite, and the NOS cofactor BH(4) contribute to glucose-induced cardiomyocyte contractile dysfunction.
- These findings suggest a significant role for NO and ONOO(-) in the pathogenesis of diabetic cardiomyopathy.
- Targeting these pathways may offer therapeutic strategies for diabetic heart disease.
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