Aims:
Protein carbamylation through cyanate is considered as playing a causal role in promoting cardiovascular disease. We recently observed that the phagocyte protein myeloperoxidase (MPO) specifically induces high-density lipoprotein (HDL) carbamylation, rather than chlorination, in human atherosclerotic lesions, raising the possibility that MPO-derived chlorinating species are involved in cyanate formation.
Results:
Here, we show that MPO-derived chlorinating species rapidly decompose the plasma components thiocyanate (SCN) and urea, thereby promoting (lipo)protein carbamylation. Strikingly, the presence of physiologic concentrations of SCN completely prevented MPO-induced 3-chlorotyrosine formation in HDL. SCN scavenged a 2.5-fold molar excess of hypochlorous acid, promoting HDL carbamylation, but not chlorination. Cyanate significantly impaired (i) HDL's ability to activate lecithin-cholesterol acyltransferase; (ii) the activity of paraoxonase, a major HDL-associated anti-inflammatory enzyme; and (iii) the antioxidative activity of HDL.
Innovation:
Here, we report that MPO-derived chlorinating species preferentially induce protein carbamylation—rather than chlorination—in the presence of physiologically relevant SCN concentrations. The carbamylation of HDL results in the loss of its anti-inflammatory and antioxidative activities.
Conclusion:
MPO-mediated decomposition of SCN and/or urea might be a relevant mechanism for generating dysfunctional HDL in human disease. Antioxid. Redox Signal. 00, 000–000.
Supplementary Material
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