High plasma thiocyanate levels in smokers are a key determinant of thiol oxidation induced by myeloperoxidase

TY - JOUR

T1 - High plasma thiocyanate levels in smokers are a key determinant of thiol oxidation induced by myeloperoxidase

AU - Morgan, Philip E

AU - Pattison, David I

AU - Talib, Jihan

AU - Summers, Fiona A

AU - Harmer, Jason A

AU - Celermajer, David S

AU - Hawkins, Clare Louise

AU - Davies, Michael Jonathan

N1 - Copyright © 2011 Elsevier Inc. All rights reserved.

PY - 2011/11/1

Y1 - 2011/11/1

N2 - Smokers have an elevated risk of atherosclerosis but the origins of this elevated risk are incompletely defined, though evidence supports an accumulation of the oxidant-generating enzyme myeloperoxidase (MPO) in the inflamed artery wall. We hypothesized that smokers would have a high level of thiocyanate (SCN -), a preferred substrate for MPO, which in turn would predispose to thiol oxidation, an established independent risk factor for atherosclerosis. In this study it is shown that on exposure to MPO/H 2O 2, thiols on plasma proteins from nonsmokers were increasingly oxidized with increasing added SCN - concentrations. Plasma from smokers contained significantly higher endogenous levels of SCN - than that from nonsmokers (131 ± 31 vs 40 ± 24 μM, P < 0.0001). When plasma from smokers and nonsmokers was exposed to MPO/H 2O 2-stimulated oxidation, a strong positive correlation (r = 0.8139, P < 0.0001) between the extent of thiol oxidation and the plasma SCN - concentrations was observed. Computational calculations indicate a changeover from HOCl to HOSCN as the major MPO-generated oxidant in plasma, with increasing SCN - levels. These data indicate that plasma SCN - levels are a key determinant of the extent of thiol oxidation on plasma proteins induced by MPO, and implicate HOSCN as an important mediator of inflammation-induced oxidative damage to proteins in smokers.

AB - Smokers have an elevated risk of atherosclerosis but the origins of this elevated risk are incompletely defined, though evidence supports an accumulation of the oxidant-generating enzyme myeloperoxidase (MPO) in the inflamed artery wall. We hypothesized that smokers would have a high level of thiocyanate (SCN -), a preferred substrate for MPO, which in turn would predispose to thiol oxidation, an established independent risk factor for atherosclerosis. In this study it is shown that on exposure to MPO/H 2O 2, thiols on plasma proteins from nonsmokers were increasingly oxidized with increasing added SCN - concentrations. Plasma from smokers contained significantly higher endogenous levels of SCN - than that from nonsmokers (131 ± 31 vs 40 ± 24 μM, P < 0.0001). When plasma from smokers and nonsmokers was exposed to MPO/H 2O 2-stimulated oxidation, a strong positive correlation (r = 0.8139, P < 0.0001) between the extent of thiol oxidation and the plasma SCN - concentrations was observed. Computational calculations indicate a changeover from HOCl to HOSCN as the major MPO-generated oxidant in plasma, with increasing SCN - levels. These data indicate that plasma SCN - levels are a key determinant of the extent of thiol oxidation on plasma proteins induced by MPO, and implicate HOSCN as an important mediator of inflammation-induced oxidative damage to proteins in smokers.

KW - Adult

KW - Female

KW - Humans

KW - Male

KW - Oxidation-Reduction

KW - Peroxidase

KW - Smoking

KW - Sulfhydryl Compounds

KW - Thiocyanates

U2 - 10.1016/j.freeradbiomed.2011.08.008

DO - 10.1016/j.freeradbiomed.2011.08.008

M3 - Journal article

C2 - 21884783

SN - 0891-5849

VL - 51

SP - 1815

EP - 1822

JO - Free Radical Biology & Medicine

JF - Free Radical Biology & Medicine

IS - 9

ER -