Abstract 237: The Apolipoprotein A-I Mimetic Peptide D-4F Acts As A Scavenger For Myeloperoxidase-Derived Hypochlorous Acid
Abstract only Background: Myeloperoxidase (MPO) and its product hypochlorous acid (HOCl) are proatherogenic molecules that functionally modify lipoproteins and impair endothelial cell function. MPO- and HOCl-induced changes in HDL function are thought to occur via modifications at the level of apoli...
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Published in | Circulation (New York, N.Y.) Vol. 116; no. suppl_16 |
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Main Authors | , , , , , , , |
Format | Journal Article |
Language | English |
Published |
16.10.2007
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Online Access | Get full text |
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Summary: | Abstract only
Background:
Myeloperoxidase (MPO) and its product hypochlorous acid (HOCl) are proatherogenic molecules that functionally modify lipoproteins and impair endothelial cell function. MPO- and HOCl-induced changes in HDL function are thought to occur via modifications at the level of apolipoprotein (apo) A-I.
Objective
: We tested the hypothesis that the apo A-I mimetic peptide D-4F, which possesses HDL-like properties, prevents endothelial dysfunction by acting as a reactive substrate for HOCl.
Methods and Results:
Rat aortic ring segments were isolated and suspended in an isolated tissue bath and exposed to HOCl (10μM, 30min, n=7). Acetylcholine (Ach)-induced relaxation was inhibited by 51% compared to saline-treated controls (n=8). Concurrent exposure to HOCl and D-4F (10μM, n=9) significantly improved the response to Ach (15% inhibition vs control). Incubation of tissues with D-4F alone (n=9) did not impair endothelial function. Since increased superoxide formation has been implicated in HOCl-induced endothelial dysfunction, we tested whether D-4F influences formation of this oxidant. Electroparamagnetic resonance spectroscopy, in conjunction with BMPO (25mM) spin trapping, was used to determine whether D-4F reduces superoxide generated by xanthine (1mM)/xanthine oxidase (15mU). There was no difference in BMPO resonance spectra in the presence and absence of D-4F at concentrations up to 300 μM. In subsequent studies, effects of HOCl on structural properties of D-4F were assessed. Fluorescence spectroscopy revealed a significant reduction in tryptophan fluorescence of D-4F (20μM) in the presence of HOCl (10μM). Time of flight mass spectrometry was used to characterize reaction products formed by HOCl and D-4F. MS analysis of D-4F (20μM) alone yielded a product with the expected m/z ratio of 2,310. Addition of 10μM HOCl to D-4F yielded a new product with a net gain of 16 mass units. MS/MS analysis confirmed the addition of this mass to the tryptophan residue, reflecting oxidation of this residue.
Conclusion:
While D-4F was previously shown to inhibit lesion formation and inflammation in experimental models of atherosclerosis, results of the current studies suggest that D-4F may also serve as a scavenger of MPO-derived HOCl. |
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ISSN: | 0009-7322 1524-4539 |
DOI: | 10.1161/circ.116.suppl_16.II_27 |