Peroxynitrite (ONOO-) contributes to coronary microvascular dysfunction in diabetes mellitus (DM). We hypothesized that in DM ONOO- interferes with the function of coronary endothelial caveolae, which plays an important role in nitric-oxide (NO)-dependent vasomotor regulation. Flow-mediated dilation (FMD) of coronary arterioles was investigated in DM (n=41) and nonDM (n=37) patients undergoing heart surgery. NO-mediated coronary FMD was significantly reduced in DM patients, which was restored by ONOO- scavenger, iron-(III)-tetrakis(N-methyl-4'pyridyl)porphyrin-pentachloride or uric-acid, whereas exogenous ONOO- reduced FMD in nonDM subjects. Immuno-electronmicroscopy demonstrated an increased 3-nitrotyrosine formation (ONOO- specific protein nitration) in endothelial plasma membrane in DM, which co-localized with caveolin-1 (Cav-1), the key structural protein of caveolae. The membrane-localized Cav-1 was significantly reduced in DM and also in high glucose-exposed coronary endothelial cells. We also found that DM patients exhibited a decreased number of endothelial caveolae, whereas exogenous ONOO- reduced caveolae number. Correspondingly, pharmacological (methyl-β-cyclodextrin) or genetic disruption of caveolae (Cav-1-knockout mice) abolished coronary FMD, which was rescued by sepiapterin, the stable precursor of NO synthase cofactor, tetrahydrobiopterin. Sepiapterin also restored coronary FMD in DM patients. Thus, we propose that ONOO- selectively targets and disrupts endothelial caveolae, which contributes to NO synthase uncoupling, hence reduced NO-mediated coronary vasodilation in DM patients.
- Received April 10, 2013.
- Accepted December 9, 2013.
- © 2013 by the American Diabetes Association.
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