High plasma thiocyanate levels are associated with enhanced myeloperoxidase-induced thiol oxidation and long-term survival in subjects following a first myocardial infarction

AbstractElevated levels of myeloperoxidase (MPO) are associated with poor cardiovascular outcomes. MPO uses H2O2 to generate oxidants including HOCl and HOSCN, from chloride and thiocyanate (SCN−) ions, respectively. SCN− is the preferred substrate. Elevation of this anion decreases HOCl generation and increases HOSCN formation, a thiol-specific oxidant. Such changes are of potential relevance to people with elevated SCN− levels, such as smokers. In this retrospective study, we examined whether elevated plasma MPO and SCN− levels increased thiol oxidation as a result of increased HOSCN formation, and impacted on long-term survival in 176 subjects (74 non-smokers, 46 smokers, and 56 previous smokers) hospitalized after a first myocardial infarction. Plasma thiols were not significantly altered in smokers compared to non-smokers or past smokers. However, significant positive correlations were detected between SCN− levels and MPO-induced thiol loss in the total population (r = 0.19, P = 0.020) and smokers al...