Myeloperoxidase serum levels predict risk in patients with acute coronary syndromes

Biomarkers in acute myocardial infarction

Myocardial infarction causes significant mortality and morbidity. Timely diagnosis allows clinicians to risk stratify their patients and select appropriate treatment. Biomarkers have been used to assist with timely diagnosis, while an increasing number of novel markers have been identified to predict outcome following an acute myocardial infarction or acute coronary syndrome. This may facilitate tailoring of appropriate therapy to high-risk patients. This review focuses on a variety of promising biomarkers which provide diagnostic and prognostic information. Heart-type Fatty Acid Binding Protein and copeptin in combination with cardiac troponin help diagnose myocardial infarction or acute coronary syndrome in the early hours following symptoms. An elevated N-Terminal Pro-B-type Natriuretic Peptide has been well validated to predict death and heart failure following a myocardial infarction. Similarly other biomarkers such as Mid-regional pro-Atrial Natriuretic Peptide, ST2, C-Terminal pro-endothelin 1, Mid-regional pro-Adrenomedullin and copeptin all provide incremental information in predicting death and heart failure. Growth differentiation factor-15 and high-sensitivity C-reactive protein predict death following an acute coronary syndrome. Pregnancy associated plasma protein A levels following chest pain predicts risk of myocardial infarction and revascularisation. Some biomarkers such as myeloperoxidase and high-sensitivity C-reactive protein in an apparently healthy population predicts risk of coronary disease and allows clinicians to initiate early preventative treatment. In addition to biomarkers, various well-validated scoring systems based on clinical characteristics are available to help clinicians predict mortality risk, such as the Thrombolysis In Myocardial Infarction score and Global Registry of Acute Coronary Events score. A multimarker approach incorporating biomarkers and clinical scores will increase the prognostic accuracy. However, it is important to note that only troponin has been used to direct therapeutic intervention and none of the new prognostic biomarkers have been tested and proven to alter outcome of therapeutic intervention. Novel biomarkers have improved prediction of outcome in acute myocardial infarction, but none have been demonstrated to alter the outcome of a particular therapy or management strategy. Randomised trials are urgently needed to address this translational gap before the use of novel biomarkers becomes common practice to facilitate tailored treatment following an acute coronary event.

Leukocyte counts, myeloperoxidase, and pregnancy-associated plasma protein a as biomarkers for cardiovascular disease: towards a multi-biomarker approach

We evaluated leukocyte counts and levels of CRP, fibrinogen, MPO, and PAPP-A in patients with stable and unstable angina pectoris, acute myocardial infarction, and healthy controls. All biomarkers were analyzed again after 6 months. Leukocyte counts and concentrations of fibrinogen, CRP, MPO, and PAPP-A were significantly increased in patients with acute myocardial infarction. Leukocyte counts and concentrations of MPO were significantly increased in patients with unstable angina pectoris compared with controls. After 6 months, leukocyte counts and MPO concentrations were still increased in patients with acute myocardial infarction when compared to controls. Discriminant analysis showed that leukocyte counts, MPO, and PAPP-A concentrations classified study group designation for acute coronary events correctly in 83% of the cases. In conclusion, combined assessment of leukocyte counts, MPO, and PAPP-A was able to correctly classify acute coronary events, suggesting that this could be a promising panel for a multibiomarker approach to assess cardiovascular risk.

Changes in inflammatory biomarkers in patients treated with ticagrelor or clopidogrel

BACKGROUND

Inflammation is a key factor in the development of atherosclerotic disease and acute coronary syndromes (ACS). The P2Y(12) receptor antagonists ticagrelor (AZD6140) and clopidogrel may have anti-inflammatory effects. The objective of this analysis from the Dose Confirmation Study Assessing Anti-Platelet Effects of AZD6140 vs Clopidogrel in NSTEMI 2 (DISPERSE 2) trial was to compare ticagrelor and clopidogrel for effects on the inflammatory biomarkers C-reactive protein (CRP), interleukin 6 (IL-6), myeloperoxidase (MPO), and soluble CD40 ligand (sCD40L).

HYPOTHESIS

Ticagrelor inhibits the P2Y(12) receptor and inflammation to a greater extent than clopidogrel in nonST-segment elevation ACS (NSTE-ACS) patients.

METHODS

In a double-blind, double-dummy, multicenter trial, 990 patients who had been hospitalized within the previous 48 hours with NSTE-ACS were randomized to receive ticagrelor 90 mg twice daily, ticagrelor 180 mg twice daily, or clopidogrel 300 mg initially and then 75 mg once daily. Within the ticagrelor groups, patients were also randomized to receive or not receive a loading dose of ticagrelor 270 mg initially. All patients received standard treatment for ACS, which included 325 mg aspirin initially and 75 to 100 mg aspirin each day subsequently. Inflammatory biomarkers were measured at baseline, upon hospital discharge, and after 4 weeks.

RESULTS

Inflammatory biomarker measurements were not significantly different among treatment groups at baseline, discharge, and 4 weeks.

CONCLUSIONS

Ticagrelor and clopidogrel appeared not to differ in this study with respect to the inflammatory biomarkers CRP, IL-6, MPO, and sCD40L in patients with NSTE-ACS.

Association between circulating monocytes and coronary plaque progression in patients with acute myocardial infarction

BACKGROUND

Monocytes and macrophages have been shown to play major roles in the progression of atherosclerosis. This study examined whether the circulating monocyte count can be used to predict coronary plaque progression of non-culprit intermediate lesions in acute myocardial infarction (AMI).

METHODS AND RESULTS

Intravascular ultrasound findings of non-culprit intermediate plaque in 90 patients were analyzed in the acute phase and at a 7-month follow up. A higher peak monocyte count after AMI was associated with a greater plaque volume change (r=0.32, P=0.002). Multivariate analysis showed that a peak monocyte count of > or =800 /mm(3) was an independent predictor of plaque progression (odds ratio 5.02, P=0.005). High monocyte (> or =800 /mm(3)) at baseline had a higher monocyte count at 7-month follow up than did those with a lower count (368+/-109 vs 263+/-64 /mm(3), P<0.0001). Moreover, the monocyte count at the 7-month follow up was also associated with plaque volume change (r=0.29, P=0.006).

CONCLUSIONS

The results suggest that circulating monocytes play an important role in the progression of coronary plaque in AMI and that the peak monocyte count during hospitalization might be a predictor of plaque progression.

Soluble lectin-like oxidized low-density lipoprotein receptor-1 predicts prognosis after acute coronary syndrome--a pilot study

BACKGROUND

Lectin-like oxidized low-density lipoprotein receptor-1 (LOX-1) is implicated in atherosclerotic plaque vulnerability. It is shed, in part, by proteases and released as soluble LOX-1 (sLOX-1), which is a specific and sensitive biomarker of acute coronary syndrome (ACS). The present study explored if sLOX-1 can also predict prognosis after ACS.

METHODS AND RESULTS

ACS patients undergoing emergency percutaneous coronary intervention and measurement of circulating sLOX-1 were followed (median: 896 days). Among 94 patients, 13 had ACS recurrence or died (re-ACS/death group). None of age, sex, lipid profile or prevalence of diabetes, smoking or hypertension was significantly different between the re-ACS/death group and the event-free survival group. Circulating sLOX-1 levels, but not those of high-sensitivity C-reactive protein (hs-CRP) or troponin T (TnT), were significantly (P<0.005) higher in the re-ACS/death group than in the event-free survival group. Kaplan-Meier survival curves showed that ACS patients with sLOX-1 values in the highest quartile or tertile had more frequent and earlier ACS recurrence or death. Receiver-operating characteristic curves for prediction of re-ACS or death showed higher sensitivity and specificity for sLOX-1 (area under the curve for sLOX-1, hs-CRP and TnT: 0.764, 0.658 and 0.524, respectively).

CONCLUSIONS

Circulating sLOX-1, a diagnostic biomarker of ACS, also predicts ACS recurrence or death.

Use of myeloperoxidase for risk stratification in acute heart failure

BACKGROUND

Myeloperoxidase (MPO) is a biomarker of inflammation and oxidative stress produced by neutrophils, monocytes, and endothelial cells. Concentrations of MPO predict mortality in patients with chronic heart failure. This study sought to investigate the diagnostic accuracy and prognostic value of MPO in patients with acute heart failure (AHF).

METHODS

We prospectively enrolled 667 patients presenting to the emergency department with dyspnea and observed them for 1 year. MPO and B-type natriuretic peptide (BNP) were measured at presentation. Two independent cardiologists adjudicated final discharge diagnoses.

RESULTS

MPO concentrations were similar in patients with AHF (n = 377, median 139 pmol/L) and patients with noncardiac causes of dyspnea (n = 290, median 150 pmol/L, P = 0.26). The diagnostic accuracy of MPO for AHF was limited [area under the ROC curve (AUC) 0.53] and inferior to that of BNP (AUC 0.95, P < 0.001). In patients with AHF, MPO concentrations above the lowest tertile (MPO >99 pmol/L) were associated with significantly increased 1-year mortality (hazard ratio 1.58, P = 0.02). The combination of MPO (< or = 99 vs >99 pmol/L) and BNP (median of < or = 847 vs >847 ng/L) improved the prediction of 1-year mortality (hazard ratio 2.80 for both variables increased vs both low, P < 0.001). After adjustment for cardiovascular risk factors in multivariable Cox proportional hazard analysis, increases in MPO contributed significantly toward the prediction of 1-year mortality (hazard ratio 1.51, P = 0.045).

CONCLUSIONS

MPO is an independent predictor of 1-year mortality in AHF, is additive to BNP, and could be helpful in identifying patients with a favorable prognosis despite increased BNP concentrations.

Hyperglycemia and oxidative stress strengthen the association between myeloperoxidase and blood pressure

Scavenging of the vasodilator nitric oxide by myeloperoxidase activity in the vasculature may contribute to hypertension. Because hydrogen peroxide is a cosubstrate of myeloperoxidase, hyperglycemia-induced oxidative stress may strengthen the relationship between myeloperoxidase and blood pressure. We investigated this relationship and its modification by hyperglycemia and oxidative stress in a population-based cohort of elderly subjects with normal glucose metabolism (n=267), impaired glucose metabolism (n=189), and type 2 diabetes (n=290). In an age- and sex-adjusted linear regression model, plasma myeloperoxidase was positively associated with systolic blood pressure (2.10 mm Hg per 1 SD increment of myeloperoxidase [95% CI: 0.66 to 3.54]), and this association was stronger at higher levels of fasting glucose (0.61 [-1.70 to 2.93], 1.33 [-1.43 to 4.10], and 3.42 [1.01 to 5.82] for increasing tertiles of glucose) and higher plasma levels of oxidized low-density lipoprotein (0.92 [-1.31 to 3.14], 2.00 [-0.71 to 4.70], and 3.58 [0.98 to 6.19] for increasing tertiles of oxidized low-density lipoprotein). Likewise, the relationship between myeloperoxidase and blood pressure was strongest under conditions associated with oxidative stress, like obesity, low high-density lipoprotein cholesterol, metabolic syndrome, and type 2 diabetes. The strength of these associations was only marginally attenuated by adjustment for other cardiovascular risk factors. Our data demonstrate that myeloperoxidase is positively and independently associated with blood pressure, and this association is strongest in subjects with (hyperglycemia-induced) oxidative stress. These observations, together with emerging evidence that myeloperoxidase-derived oxidants contribute to the initiation and propagation of cardiovascular disease, identify myeloperoxidase as a promising target for drug development.

Myeloperoxidase and C-reactive protein have combined utility for long-term prediction of cardiovascular mortality after coronary angiography

OBJECTIVES

We evaluated the relative and combined value of oxidative stress biomarkers for predicting cardiovascular mortality in patients undergoing selective coronary angiography.

BACKGROUND

Oxidative stress participates in all stages of cardiovascular disease, from lipoprotein modification to plaque rupture, and biomarkers of oxidative stress predict development of coronary artery disease (CAD). Oxidative stress biomarkers merit investigation for the value they may offer for long-term cardiovascular risk prediction.

METHODS

Myeloperoxidase (MPO), nitrotyrosine, oxidized low-density lipoprotein, and antioxidant capacity were measured in a prospective cohort of 885 selective coronary angiography patients followed up for >13 years for cardiovascular mortality.

RESULTS

MPO independently predicted CAD, and top tertile MPO levels predicted a 2.4-fold risk of cardiovascular mortality (95% confidence interval [CI]: 1.47 to 2.98), compared with patients with lowest tertile MPO levels. MPO also improved risk model discrimination and patient risk category classification. Elevations in multiple oxidative stress biomarkers predicted increased mortality risk; however, the strongest risk prediction was achieved by assessing MPO and C-reactive protein (CRP) together. Patients with either MPO or CRP elevated had 5.3-fold higher cardiovascular mortality risk (95% CI: 1.86 to 14.9), and patients with high levels of both MPO and CRP had a 4.3-fold risk compared with patients with only elevated marker (95% CI: 2.26 to 8.31). These results remained significant with adjustment for cardiovascular risk factors and baseline disease burden.

CONCLUSIONS

MPO accurately predicted cardiovascular mortality risk in coronary angiography patients. Considering MPO and CRP together may improve long-term risk assessment and CAD patient outcomes.

The transcription factor ETS-1 mediates proinflammatory responses and neointima formation in carotid artery endoluminal vascular injury

The transcription factor ETS-1 is a critical mediator of vascular inflammation and hypertrophy in hypertension. We tested the hypothesis that ETS-1 is a mediator of proinflammatory responses and neointimal hyperplasia after balloon injury of the carotid artery. For this study, we took advantage of the availability of an ETS-1 dominant-negative (DN) peptide. Sprague-Dawley rats were assigned to treatment with ETS-1 DN, a mutant peptide (ETS-1 MU), or vehicle (Veh) and subjected to balloon injury of the carotid artery. After 2, 24 hours, and 14 days, the rats were euthanized, and both carotid arteries were processed for real-time polymerase chain reaction (2 hours), immunofluorescence and immunohistochemistry (24 hours), and morphometric analysis (14 days). ETS-1 mRNA was up regulated (2.4-fold) in injured carotid arteries. By immunofluorescence, we confirmed increased nuclear expression of ETS-1 24 hours postinjury. The carotid artery mRNA expression of monocyte chemotactic protein-1, cytokine-induced neutrophil chemoattractant-2, P-selectin, E-selectin, vascular cell adhesion molecule, and intercellular adhesion molecule was increased 2 hours after injury. ETS-1 DN but not ETS-1 MU significantly reduced mRNA and protein expression for monocyte chemotactic protein-1, P-selectin, and E-selectin in injured arteries. These changes were accompanied by concomitant reductions in vascular monocyte and leukocyte infiltration. Moreover, treatment with ETS-1 DN but not ETS-1 MU resulted in a 50% reduction in neointima formation at day 14 after balloon injury. This study unveils the role of ETS-1 as a mediator of inflammation and neointima formation in a model of carotid artery balloon injury and may result in the development of novel strategies in the treatment of vascular injury.

Biogenic nanoporous silica-based sensor for enhanced electrochemical detection of cardiovascular biomarkers proteins

The goal of our research is to demonstrate the feasibility of employing biogenic nanoporous silica as a key component in developing a biosensor platform for rapid label-free electrochemical detection of cardiovascular biomarkers from pure and commercial human serum samples with high sensitivity and selectivity. The biosensor platform consists of a silicon chip with an array of gold electrodes forming multiple sensor sites and works on the principle of electrochemical impedance spectroscopy. Each sensor site is overlaid with a biogenic nanoporous silica membrane that forms a high density of nanowells on top of each electrode. When specific protein biomarkers: C-reactive protein (CRP) and myeloperoxidase (MPO) from a test sample bind to antibodies conjugated to the surface of the gold surface at the base of each nanowell, a perturbation of electrical double layer occurs resulting in a change in the impedance. The performance of the biogenic silica membrane biosensor was tested in comparison with nanoporous alumina membrane-based biosensor and plain metallic thin film biosensor. Significant enhancement in the sensitivity and selectivity was achieved with the biogenic silica biosensor, in comparison to the other two, for detecting the two protein biomarkers from both pure and commercial human serum samples. The sensitivity of the biogenic silica biosensor is approximately 1 pg/ml and the linear dose response is observed over a large dynamic range from 1 pg/ml to 1 microg/ml. Based on its performance metrics, the biogenic silica biosensor has excellent potential for development as a point of care handheld electronic biosensor device for detection of protein biomarkers from clinical samples.

Acute infection-inflammation and coronary stent thrombosis: an observational study

Coronary stent thrombosis (CST) is a major concern of interventional cardiology. Several risk factors for CST have been identified, but as a whole they do not explain the pathophysiology of CST. This study was designed to investigate whether acute infection-inflammation could facilitate the occurrence of CST. Forty-one patients, aged 66.6 +/- 11 years, consecutively admitted to our catheterization laboratory for acute, subacute or late CST, were retrospectively analysed. Transient acute infection-inflammation on admission for CST was diagnosed by predefined criteria. Prevalence of known risk factors for CST was also investigated. Twenty-one patients (51%) met predefined criteria for the occurrence of acute infection-inflammation. On admission, in these patients, levels of systemic humoral and cellular inflammatory markers were significantly higher than those of patients without recent or ongoing acute infection-inflammation (p < 0.05 for all). 62% of patients with acute infection-inflammation had less than two known risk factors for CST whereas only 37% patients without infection-inflammation showed less than two risk factors (p = 0.03) and showed more frequent interruption of antiplatelet treatment (17 vs. 2.4%, p = 0.02), mean longer stent length (20.5 +/- 4.8 vs. 16.5 +/- 5.1 mm, p = 0.02) and lower left ventricular ejection fraction before CST (42.9 +/- 14 vs. 47.3 +/- 11%, p = 0.02). In conclusion, acute infection-inflammation could play a role in facilitating the occurrence of CST in a subgroup with low risk profile for known risk factors. Our findings, if confirmed, could suggest new opportunities for prevention and treatment of CST.

The role of hypothiocyanous acid (HOSCN) in biological systems

Hypohalous acids (HOX), produced by peroxidase-catalysed reactions of halide and pseudohalide ions with H(2)O(2), play an important role in the human immune system. However, there is compelling evidence that these oxidants also mediate host tissue damage and contribute to the progression of a number of inflammatory diseases. Although it is well established that significant amounts of hypothiocyanous acid (HOSCN) are formed under physiological conditions, the reactions of this oxidant with host biological systems are relatively poorly characterized. It is generally accepted that HOSCN is a mild oxidant that reacts selectively with thiols. However, it is becoming increasingly recognized that this selectivity can result in the induction of significant cellular damage, which may contribute to disease. This review will outline the formation and reactivity of HOSCN and the role of this oxidant in biological systems.

Elevated plasma free fatty acids increase cardiovascular risk by inducing plasma biomarkers of endothelial activation, myeloperoxidase and PAI-1 in healthy subjects

Background

CVD in obesity and T2DM are associated with endothelial activation, elevated plasma vascular inflammation markers and a prothrombotic state. We examined the contribution of FFA to these abnormalities following a 48-hour physiological increase in plasma FFA to levels of obesity and diabetes in a group of healthy subjects.

Methods

40 non-diabetic subjects (age = 38 ± 3 yr, BMI = 28 ± 1 kg/m², FPG = 95 ± 1 mg/dl, HbA_1c = 5.3 ± 0.1%) were admitted twice and received a 48-hour infusion of normal saline or low-dose lipid. Plasma was drawn for intracellular (ICAM-1) and vascular (VCAM-1) adhesion molecules-1, E-selectin (sE-S), myeloperoxidase (MPO) and total plasminogen inhibitor-1 (tPAI-1). Insulin sensitivity was measured by a hyperglycemic clamp (M/I).

Results

Lipid infusion increased plasma FFA to levels observed in obesity and T2DM and reduced insulin sensitivity by 27% (p = 0.01). Elevated plasma FFA increased plasma markers of endothelial activation ICAM-1 (138 ± 10 vs. 186 ± 25 ng/ml), VCAM-1 (1066 ± 67 vs. 1204 ± 65 ng/ml) and sE-S (20 ± 1 vs. 24 ± 1 ng/ml) between 13-35% and by ≥ 2-fold plasma levels of myeloperoxidase (7.5 ± 0.9 to 15 ± 25 ng/ml), an inflammatory marker of future CVD, and tPAI-1 (9.7 ± 0.6 to 22.5 ± 1.5 ng/ml), an indicator of a prothrombotic state (all p ≤ 0.01). The FFA-induced increase was independent from the degree of adiposity, being of similar magnitude in lean, overweight and obese subjects.

Conclusions

An increase in plasma FFA within the physiological range observed in obesity and T2DM induces markers of endothelial activation, vascular inflammation and thrombosis in healthy subjects. This suggests that even transient (48-hour) and modest increases in plasma FFA may initiate early vascular abnormalities that promote atherosclerosis and CVD.

Current developments in salivary diagnostics

Salivary diagnostics is an emerging field that has progressed through several important developments in the past decade, including the publication of the human salivary proteome and the infusion of federal funds to integrate nanotechnologies and microfluidic engineering concepts into developing compact point-of-care devices for rapid analysis of this secretion. In this article, we discuss some of these developments and their relevance to the prognosis, diagnosis and management of periodontitis, as an oral target, and cardiovascular disease, as a systemic example for the potential of these biodiagnostics. Our findings suggest that several biomarkers are associated with distinct biological stages of these diseases and demonstrate promise as practical biomarkers in identifying and managing periodontal disease, and acute myocardial infarction. The majority of these studies have progressed through biomarker discovery, with the identified molecules requiring more robust clinical studies to enable substantive validation for disease diagnosis. It is predicted that with continued advances in this field the use of a combination of biomarkers in multiplex panels is likely to yield accurate screening tools for these diagnoses in the near future.

Myeloperoxidase levels and mortality in frail community-living elderly individuals

BACKGROUND

Elevated systemic levels of myeloperoxidase (MPO) have been associated with unfavourable clinical outcomes. In the present study, we evaluate the impact of MPO, a pro-oxidant enzyme that catalyzes the initiation of lipid peroxidation and affects nitric oxide levels, on the risk of all-cause mortality in a large population of frail octogenarians and nonagenarians living in community.

METHODS

We analyzed data from the Aging and Longevity Study in the Sirente Geographic Area (ilSIRENTE Study), a prospective cohort study that collected data on all individuals aged 80 years and older living in a mountain community (n = 363). The main outcome measure was the risk of death after 4 years of follow-up. Participants were divided into three groups based on MPO tertiles: lower tertile < or = 61.5 microg/L (n = 120), intermediate tertile 61.6-140.6 microg/L (n = 120), and higher tertile > or = 140.7 microg/L (n = 123).

RESULTS

A total of 150 deaths occurred during 4-years follow-up. The mean MPO level was 170.8 + or - 177.5 microg/L among those who died compared with 135.4 + or - 142.4 microg/L among survivors (p = .03). Individuals in the highest MPO tertile had higher risk of mortality (40% [60/123]) compared with those in the lower tertile (26% [39/120]). After adjusting for potential confounders, compared with participants in the lower tertile, those in the higher tertile had a hazard ratio for mortality of 1.97 (95% confidence interval: 1.02-3.80).

CONCLUSION

Our results obtained from a representative sample of very old and frail elderly individuals expand the knowledge that low levels of MPO are associated with better survival.

Myeloperoxidase, subclinical atherosclerosis, and cardiovascular disease events

OBJECTIVES

We evaluated whether myeloperoxidase (MPO) predicts future cardiovascular disease (CVD) events in asymptomatic adults and whether subclinical atherosclerosis may affect this relation.

BACKGROUND

Myeloperoxidase is a leukocyte-derived enzyme-generating reactive oxidant species that has been shown to predict risk of CVD in selected populations.

METHODS

We studied 1,302 asymptomatic adults (mean age 59 years, 47% women) without known CVD who were followed for 3.8 years. We measured MPO by the use of immunoassay. Coronary artery calcium (CAC), a measure of subclinical atherosclerosis, was measured by computed tomography with the Agatston score categorized as none/minimal (0 to 9), mild (10 to 99), and moderate/significant (> or = 100). Cox regression, adjusted for age, sex, and other risk factors, examined the relation of CAC and/or MPO with incident CVD events.

RESULTS

Persons with MPO levels at or above compared with below the median (257 pM) were more likely (p < 0.05 to p < 0.001) to be women, have a higher body mass index, greater low-density lipoprotein cholesterol, greater systolic and diastolic blood pressure, and lower high-density lipoprotein cholesterol. Mean MPO levels increased according to CAC categories (p trend = 0.02). Incident CVD events were more likely in those at or above versus below the median MPO level (4.6% vs. 2.3%, p = 0.02), even after adjustment for age, sex, CAC, and risk factors (hazard ratio [HR]: 1.9, 95% confidence interval: 1.0 to 3.6, p = 0.04). Combining CAC and MPO categories, CVD incidence ranged from 0.6% in those with a CAC score of 0 to 9 to 7.1% (adjusted HR: 9.2, p < 0.001) in those with CAC scores of > or = 100 and MPO below the median and 14.0% (adjusted HR: 19.5, p < 0.0001) in those with CAC scores of > or = 100 and MPO at or above the median.

CONCLUSIONS

Our study suggests persons with both increased levels of both MPO and CAC are at an increased risk of CVD events. Imaging of subclinical atherosclerosis combined with assessment of biomarkers of plaque vulnerability may help improve CVD risk stratification.

A myeloperoxidase promoter polymorphism is independently associated with mortality in patients with impaired left ventricular function

Circulating levels of myeloperoxidase (MPO), a heme enzyme released upon activation of polymorphonuclear neutrophils, predict adverse outcome in patients with impaired left ventricular (LV) function. The MPO -463 G/A promoter polymorphism (rs 2333227) regulates MPO transcription, with the G allele being linked to increased protein expression. The aim of this study was to assess the prognostic information derived from the -463 G/A MPO polymorphism on outcomes of patients with impaired LV function. The -463 G/A promoter MPO genotype as well as MPO plasma levels were determined in 116 patients with impaired LV function. Patients were prospectively followed for a median of 1050 days. The GG genotype was associated with a decrease in overall survival (chi(2) 5.80; p=0.016). This association remained after multivariate adjustment for plasma levels of NT-proBNP, creatinine, hsCRP, and MPO; leukocyte count; and LV function (hazard ratio 3.16 (95% CI 1.17-8.53), p=0.024) and for classical cardiovascular risk factors (hazard ratio 2.88 (95% CI 1.13-7.33), p=0.026). Interestingly, we observed no association of the MPO polymorphism with total MPO protein concentration or MPO activity in plasma. The -463 G/A MPO polymorphism is linked to adverse clinical outcome of patients with impaired LV function. Further studies are needed to elucidate the value of this polymorphism for risk stratification.

Effects of rosuvastatin on myeloperoxidase levels in patients with chronic heart failure: a randomized placebo-controlled study

BACKGROUND

Studies indicate that myeloperoxidase (MPO) is associated with disease progression and severity in heart failure (HF), while it may provide a mechanistic link between inflammation and adverse cardiac remodeling. The mechanisms that regulate MPO are unclear, while it is unknown whether specific treatments such as HMG-CoA reductase inhibitors and xanthine oxidase inhibitors may modify MPO. Therefore in the present study we examined the effects of rosuvastatin and allopurinol on MPO levels in patients HF.

METHODS

Sixty clinically stable patients with systolic HF were randomized to receive rosuvastatin 10mg/day, allopurinol 300mg/day or placebo and followed up for 1 month. Plasma levels of MPO and serum levels of soluble CD40 ligand, interleukin-6, and oxidized LDL were determined using ELISA. All measurements were made before and after 1-month treatment.

RESULTS

Rosuvastatin significantly reduced plasma levels of MPO (p=0.003), which remained unchanged in the other groups. Furthermore, the change of MPO levels in the rosuvastatin-treated group was significantly different compared with the other groups (p<0.05). Rosuvastatin administration also led to a significant decrease in oxidized LDL (p=0.009), while the other inflammatory markers remained unchanged in all groups. In the total population, a significant correlation was observed between the baseline levels of MPO and hsCRP (r=0.275, p=0.027), fibrinogen (r=0.278, p=0.025), and sCD40L (r=0.288, p=0.021).

CONCLUSIONS

Short-term treatment with rosuvastatin regulates inflammatory process in patients with heart failure by significantly reducing plasma levels of MPO. This finding reveals a novel pleiotropic effect of statins in patients with heart failure, and provides further insights into the pathophysiological mechanisms of MPO in heart failure.

Serial analyses of C-reactive protein and myeloperoxidase in acute coronary syndrome

BACKGROUND

C-reactive protein (CRP) and myeloperoxidase (MPO) are involved in the pathogenesis of atherosclerosis, mainly during periods of instabilization. This study aims to test the hypothesis that patients with acute coronary syndrome (ACS) maintain a persistent inflammatory state, and that this is associated with long-term mortality.

HYPOTHESIS

We hypothesized that serum C-reactive protein and myeloperoxidase collected at the index event and later, could add to the prognostic information in patients with ACS.

METHODS

In a prospective cohort of 115 consecutive patients with ACS, myeloperoxidase and C-reactive protein were measured at admission and 2 y later. Patients were followed-up for the occurrence of cardiac death and other major cardiac events.

RESULTS

Levels of CRP decreased from 26 +/- 34 mg/L in the acute phase to 6 +/- 8 mg/L in the chronic phase (p < 0.001), and MPO levels decreased from 86 +/- 43 pM to 27 +/- 32 pM (p < 0.001). After 29 +/- 12 mo, 27% patients died, 39% had new episode of ACS, and 30% underwent revascularization procedures. Initial CRP levels above 10 mg/L were associated with higher long-term mortality (hazard ratio [HR]: 2.43; 95% confidence interval [CI]: 0.98 to 6.07; p = 0.048). MPO levels were not associated with death or other major events.

CONCLUSIONS

Changes over time or absolute values in the chronic phase of both markers were not associated with clinical outcomes. CRP levels, but not MPO levels, in the index event were predictive of long-term cardiovascular mortality.

Myeloperoxidase: molecular mechanisms of action and their relevance to human health and disease

Myeloperoxidase (MPO) is a heme-containing peroxidase abundantly expressed in neutrophils and to a lesser extent in monocytes. Enzymatically active MPO, together with hydrogen peroxide and chloride, produces the powerful oxidant hypochlorous acid and is a key contributor to the oxygen-dependent microbicidal activity of phagocytes. In addition, excessive generation of MPO-derived oxidants has been linked to tissue damage in many diseases, especially those characterized by acute or chronic inflammation. It has become increasingly clear that MPO exerts effects that are beyond its oxidative properties. These properties of MPO are, in many cases, independent of its catalytic activity and affect various processes involved in cell signaling and cell-cell interactions and are, as such, capable of modulating inflammatory responses. Given these diverse effects, an increased interest has emerged in the role of MPO and its downstream products in a wide range of inflammatory diseases. In this article, our knowledge pertaining to the biologic role of MPO and its downstream effects and mechanisms of action in health and disease is reviewed and discussed.

Association of serum myeloperoxidase with the ankle-brachial index and peripheral arterial disease

Myeloperoxidase (MPO) is an enzymatic mediator of several inflammatory cascades and higher serum levels have been associated with increased risk of adverse cardiovascular events. We investigated the association of serum MPO with the ankle-brachial index (ABI) and peripheral arterial disease (PAD) in a bi-ethnic cohort of African-Americans and non-Hispanic white individuals. Participants included 1324 African-Americans (mean age 64 years, 71% women) and 1237 non-Hispanic white individuals (mean age 59 years, 57% women) belonging to hypertensive sibships. Serum levels of MPO were measured by solid phase sandwich immunoassay. ABI was measured using a standard protocol and PAD was defined as an ABI < 0.90. Multivariable regression analysis using generalized estimating equations were performed to assess whether serum MPO levels were associated with ABI and the presence of PAD. After adjustment for age and sex, higher MPO levels were significantly associated with lower ABI and the presence of PAD in African-Americans (p = 0.004 and p = 0.005, respectively) and in non-Hispanic white individuals (p = 0.001 and p = 0.016, respectively). After additional adjustment for conventional risk factors (diabetes, smoking status, total and high-density lipoprotein cholesterol, waist circumference, hypertension), prior history of myocardial infarction or stroke, and medication use (statins, aspirin, estrogen), higher MPO levels remained significantly associated with lower ABI and the presence of PAD in both African-Americans (p = 0.008 and p = 0.010, respectively) and non-Hispanic white individuals (p = 0.001 and p = 0.018, respectively). We conclude that higher MPO levels are associated with lower ABI and the presence of PAD in African-Americans and non-Hispanic white individuals.

Acute coronary syndromes: diagnosis and management, part I

The term acute coronary syndrome (ACS) refers to any group of clinical symptoms compatible with acute myocardial ischemia and includes unstable angina (UA), non-ST-segment elevation myocardial infarction (NSTEMI), and ST-segment elevation myocardial infarction (STEMI). These high-risk manifestations of coronary atherosclerosis are important causes of the use of emergency medical care and hospitalization in the United States. A quick but thorough assessment of the patient's history and findings on physical examination, electrocardiography, radiologic studies, and cardiac biomarker tests permit accurate diagnosis and aid in early risk stratification, which is essential for guiding treatment. High-risk patients with UA/NSTEMI are often treated with an early invasive strategy involving cardiac catheterization and prompt revascularization of viable myocardium at risk. Clinical outcomes can be optimized by revascularization coupled with aggressive medical therapy that includes anti-ischemic, antiplatelet, anticoagulant, and lipid-lowering drugs. Evidence-based guidelines provide recommendations for the management of ACS; however, therapeutic approaches to the management of ACS continue to evolve at a rapid pace driven by a multitude of large-scale randomized controlled trials. Thus, clinicians are frequently faced with the problem of determining which drug or therapeutic strategy will achieve the best results. This article summarizes the evidence and provides the clinician with the latest information about the pathophysiology, clinical presentation, and risk stratification of ACS and the management of UA/NSTEMI.

Acute coronary syndromes: diagnosis and management, part I

The term acute coronary syndrome (ACS) refers to any group of clinical symptoms compatible with acute myocardial ischemia and includes unstable angina (UA), non-ST-segment elevation myocardial infarction (NSTEMI), and ST-segment elevation myocardial infarction (STEMI). These high-risk manifestations of coronary atherosclerosis are important causes of the use of emergency medical care and hospitalization in the United States. A quick but thorough assessment of the patient's history and findings on physical examination, electrocardiography, radiologic studies, and cardiac biomarker tests permit accurate diagnosis and aid in early risk stratification, which is essential for guiding treatment. High-risk patients with UA/NSTEMI are often treated with an early invasive strategy involving cardiac catheterization and prompt revascularization of viable myocardium at risk. Clinical outcomes can be optimized by revascularization coupled with aggressive medical therapy that includes anti-ischemic, antiplatelet, anticoagulant, and lipid-lowering drugs. Evidence-based guidelines provide recommendations for the management of ACS; however, therapeutic approaches to the management of ACS continue to evolve at a rapid pace driven by a multitude of large-scale randomized controlled trials. Thus, clinicians are frequently faced with the problem of determining which drug or therapeutic strategy will achieve the best results. This article summarizes the evidence and provides the clinician with the latest information about the pathophysiology, clinical presentation, and risk stratification of ACS and the management of UA/NSTEMI.

Myeloperoxidase (MPO) and interleukin-17 (IL-17) plasma levels are increased in patients with acute coronary syndromes

There are several reports of myeloperoxidase (MPO) playing an important role in acute coronary syndromes (ACS). Interleukin-17 (IL-17) is a pro-inflammatory cytokine produced by activated CD4 T cells that has a chemotactic and activating effect on neutrophils. It has also been shown that IL-17 recruits neutrophils via the release of C-X-C chemokines. The roles of MPO and IL-17 in ACS, however, have not been established. This study measured plasma MPO and IL-17 levels in 10 patients with ACS, 11 age- and sex-matched patients with stable angina and 12 healthy control subjects. Plasma MPO and IL-17 levels were significantly elevated in ACS patients compared with the patients with stable angina and the healthy control subjects. In addition, plasma MPO levels correlated with plasma IL-17 levels in all study participants. It is concluded that MPO and IL-17 are powerful indicators of acute coronary inflammation, however the data set was very small, so larger prospective studies are required.

Modification of high density lipoprotein by myeloperoxidase generates a pro-inflammatory particle

High density lipoprotein (HDL) is the major atheroprotective particle in plasma. Recent studies demonstrate that myeloperoxidase (MPO) binds to HDL in vivo, selectively targeting apolipoprotein A1 (apoA1) of HDL for oxidative modification and concurrent loss in cholesterol efflux and lecithin cholesterol acyl transferase activating activities, generating a "dysfunctional HDL" particle. We now show that (patho)physiologically relevant levels of MPO-catalyzed oxidation result in loss of non-cholesterol efflux activities of HDL including anti-apoptotic and anti-inflammatory functions. One mechanism responsible is shown to involve the loss of modified HDL binding to the HDL receptor, scavenger receptor B1, and concurrent acquisition of saturable and specific binding to a novel unknown receptor independent of scavenger receptors CD36 and SR-A1. HDL modification by MPO is further shown to confer pro-inflammatory gain of function activities as monitored by NF-kappaB activation and surface vascular cell adhesion molecule levels on aortic endothelial cells exposed to MPO-oxidized HDL. The loss of non-cholesterol efflux activities and the gain of pro-inflammatory functions requires modification of the entire particle and can be recapitulated by oxidation of reconstituted HDL particles comprised of apoA1 and nonoxidizable phosphatidylcholine species. Multiple site-directed mutagenesis studies of apoA1 suggest that the pro-inflammatory activity of MPO-modified HDL does not involve methionine, tyrosine, or tryptophan, oxidant-sensitive residues previously mapped as sites of apoA1 oxidation within human atheroma. Thus, MPO-catalyzed oxidation of HDL results not only in the loss of classic atheroprotective reverse cholesterol transport activities of the lipoprotein but also both the loss of non-cholesterol efflux related activities and the gain of pro-inflammatory functions.

Coronary stenting is associated with an acute increase in plasma myeloperoxidase in stable angina patients but not in patients with acute myocardial infarction

BACKGROUND

Myeloperoxidase (MPO) has emerged as a critical mediator in the physiopathology of atherosclerosis from plaque formation and growth until destabilization and rupture leading to acute coronary syndrome (ACS). Using coronary stenting as a model of plaque injury, we aimed to determine the evolution of systemic MPO levels following coronary stenting in stable angina patients and in patients with acute myocardial infarction (AMI).

METHODS

Plasma levels of MPO, lactoferrin, interleukin (IL)-6, C-reactive protein and PMN counts were assessed in 13 patients with Non-ST-elevation myocardial infarction (NSTEMI) (Group A) and in 29 patients with stable angina pectoris (Group B), undergoing coronary stenting. Serial blood samples were taken before angioplasty (baseline) and at 1, 6 and 24 h following initial balloon inflation.

RESULTS

Following angioplasty, the overall plasma MPO levels significantly increased at 1 h in group B (120.5+/-79.0 to 166+/-79.5, p=0.003) but not in group A (121+/-63.4 to 124.7+/-76.9, p=0.753). In Group B, the increase in MPO levels at 1 h were significantly higher in the presence of complex lesions compared to patients with simple lesions (p=0.023). Lactoferrin levels showed no change over time except for a significant decrease at 6 h in group B.

CONCLUSIONS

In stable angina patients, coronary stenting is associated with an acute and transient increase in plasma MPO levels, but not in lactoferrin levels, with an enhanced response in the presence of complex lesions. In contrast, we observed no changes in plasma MPO and lactoferrin levels following stenting in patients with AMI. Given its pro-inflammatory properties, the potential implication of MPO release on clinical outcome in stable patients undergoing stenting needs further investigation.

Role of myeloperoxidase as predictor of systemic inflammatory response syndrome in patients with ST-segment elevation myocardial infarction after primary percutaneous coronary intervention

Elevated cytokine levels have been reported after ischemia/reperfusion injury and might cause a systemic inflammatory response syndrome (SIRS) after primary percutaneous coronary intervention (PPCI). High myeloperoxidase (MPO) levels are reported to be a risk factor for early cardiac events in patients with acute coronary syndrome. Its role as a predictor of SIRS in patients with ST-segment elevation myocardial infarction treated with PPCI is unclear. Therefore, the aim of the present study was to investigate the role of MPO as a predictor of SIRS in patients with ST-segment elevation myocardial infarction treated with PPCI. A total of 250 patients with ST-segment elevation myocardial infarction treated with PPCI were admitted to our coronary care unit. The serum MPO levels were measured at admission using a commercially available enzyme-linked immunosorbent assay. Of the 250 patients, 47 developed SIRS within 48 hours after their admission to the coronary care unit; 10 of these patients were excluded from analysis because of the suspicion of sepsis. The remaining 203 patients had no SIRS during their coronary care unit stay. Compared to patients without SIRS, those with SIRS had greater serum MPO values (81.35 +/- 18.07 vs 67.03 +/- 16.98 ng/ml, p <0.0001) after PPCI. After controlling for different baseline clinical, laboratory, and angiographic variables, the baseline serum MPO levels were an independent predictor of SIRS (odds ratio 4.2, 95% confidence interval 1.9 to 8.4, p <0.001). In conclusion, our results have demonstrated that MPO is an independent predictor of SIRS after PPCI, suggesting a new clue for the interpretation of this phenomenon.

Long-term prognosis of patients with Kawasaki disease: at risk for future atherosclerosis?

Kawasaki disease causes coronary artery lesions, such as dilatation, aneurysms, stenosis, and even occlusion in young children, and is one of the most common acquired heart diseases in developed countries. More than 10,000 new cases are reported in Japan every year. In its acute phase, severe coronary arteritis induces morphological changes in coronary arteries. Treatments for Kawasaki disease aim to eliminate coronary artery inflammation as quickly as possible to reduce the chance of causing coronary lesions. Immunoglobulin therapy with aspirin has become the standard therapy of first choice and helps attenuate coronary lesions. In addition to coronary artery disturbances in the acute phase, sclerotic vascular changes were observed in post-Kawasaki disease patients who did not have coronary lesions in the acute phase. Recent studies have revealed peripheral vasculature endothelial dysfunction in post-Kawasaki disease patients with and without coronary lesions. The risk factors for the development of atherosclerosis in adults, such as C-reactive protein, oxidative stress, and inflammatory cytokines, are also increased in the remote phase of Kawasaki disease. This morphological and functional endothelial dysfunction as Kawasaki disease vascular sequelae may suggest the early development of atherosclerosis in patients with Kawasaki disease. However, no direct evidence for this early development has been found so far. Kawasaki disease was first reported slightly more than 40 years ago. The first documented post-Kawasaki disease patients are now becoming old enough to have atherosclerosis. Some case reports suggest myocardial infarction with atherosclerotic changes in young adults who are believed to have a history of Kawasaki disease. This paper reviews Kawasaki disease from the perspective of long-term prognosis.

Hypochlorous acid-induced heme oxygenase-1 gene expression promotes human endothelial cell survival

Hypochlorous acid (HOCl) is a unique oxidant generated by the enzyme myeloperoxidase that contributes to endothelial cell dysfunction and death in atherosclerosis. Since myeloperoxidase localizes with heme oxygenase-1 (HO-1) in and around endothelial cells of atherosclerotic lesions, the present study investigated whether there was an interaction between these two enzymes in vascular endothelium. Treatment of human endothelial cells with the myeloperoxidase product HOCl stimulated a concentration- and time-dependent increase in HO-1 protein that resulted in a significant rise in carbon monoxide (CO) production. The induction of HO-1 protein was preceded by a prominent increase in HO-1 mRNA and total and nuclear factor-erythroid 2-related factor 2 (Nrf2). In addition, HOCl induced a significant rise in HO-1 promoter activity that was blocked by mutating the antioxidant response element (ARE) in the promoter or by overexpressing a dominant-negative mutant of Nrf2. The HOCl-mediated induction of Nrf2 or HO-1 was blocked by the glutathione donor N-acetyl-l-cysteine but was unaffected by ascorbic or uric acid. Finally, treatment of endothelial cells with HOCl stimulated mitochondrial dysfunction, caspase-3 activation, and cell death that was potentiated by the HO inhibitor, tin protoporphyrin-IX, or by the knockdown of HO-1, and reversed by the exogenous administration of biliverdin, bilirubin, or CO. These results demonstrate that HOCl induces HO-1 gene transcription via the activation of the Nrf2/ARE pathway to counteract HOCl-mediated mitochondrial dysfunction and cell death. The ability of HOCl to activate HO-1 gene expression may represent a critical adaptive response to maintain endothelial cell viability at sites of vascular inflammation and atherosclerosis.

Markers for Early Detection of Cardiac Diseases

The existing markers for myocardial necrosis, such as cardiac troponin, creatine kinase-MB, and myoglobin are thought to be released into blood following irreversible myocardial necrosis. Thus results of these tests are usually negative for patients with acute coronary syndromes (ACS) who present to the emergency department (ED) within the first 3 hours after the onset of chest pain. Given the need to make early therapeutic and triage decisions, biomarkers that can be used to diagnose and/or risk stratify ACS patients during their initial ED presentation will be important. Active research in this area has identified several classes of biomarkers that show promise for early detection of disease. These include tests for the presence of acute inflammation and infiltration (e.g., high sensitivity-C-reactive protein, myeloperoxidase), plaque instability (e.g., pregnancy-associated plasma protein-A, placental growth factor), platelet activation (e.g., whole blood choline, platelet density, CD40 ligand), and myocardial ischemia (e.g., ischemia modified albumin, free fatty acids, serum choline, and B-type natriuretic peptide). Each of these tests has demonstrated some utility for early diagnosis. However, as most lack specificity for myocardial disease, routine use may require a multi-marker approach.

Neutrophil activation precedes myocardial injury in patients with acute myocardial infarction

Myeloperoxidase (MPO), a heme protein abundantly expressed and secreted by polymorphonuclear neutrophils (PMN), has emerged as a critical mediator in coronary atherosclerosis. Retrospective analyses have suggested that free plasma levels of MPO predict adverse outcome in patients with low troponin T (TnT) levels who subsequently experience myocardial injury. The aim of this study was to evaluate the time course of MPO plasma levels in the early stages of acute myocardial infarction (AMI). Of 155 consecutive patients hospitalized for acute coronary syndromes, 38 presenting within 2 h of the onset of symptoms and subsequently diagnosed for AMI were included in the study. Serial blood samples taken between 1 and 24 h after the onset of chest pain were analyzed for MPO, TnT, creatine kinase MB, myoglobin, and high sensitive C-reactive protein. Fifty patients with angiographically proven but stable coronary artery disease (CAD) served as controls. In contrast to all other investigated markers, MPO was markedly elevated within 2 h of symptom onset in patients with AMI. Heparin, which is known to increase MPO plasma levels in patients with stable CAD, had no effect on MPO plasma levels in AMI patients. High levels of MPO plasma levels at the time of admission and the rapid peak of free plasma MPO levels after the onset of symptoms suggests that PMN activation is an early event in AMI and potentially precedes myocardial injury.

Airborne particulate matter PM2.5 from Mexico City affects the generation of reactive oxygen species by blood neutrophils from asthmatics: an in vitro approach

Background

The Mexico City Metropolitan Area is densely populated, and toxic air pollutants are generated and concentrated at a higher rate because of its geographic characteristics. It is well known that exposure to particulate matter, especially to fine and ultra-fine particles, enhances the risk of cardio-respiratory diseases, especially in populations susceptible to oxidative stress. The aim of this study was to evaluate the effect of fine particles on the respiratory burst of circulating neutrophils from asthmatic patients living in Mexico City.

Methods

In total, 6 subjects diagnosed with mild asthma and 11 healthy volunteers were asked to participate. Neutrophils were isolated from peripheral venous blood and incubated with fine particles, and the generation of reactive oxygen species was recorded by chemiluminescence. We also measured plasma lipoperoxidation susceptibility and plasma myeloperoxidase and paraoxonase activities by spectrophotometry.

Results

Asthmatic patients showed significantly lower plasma paraoxonase activity, higher susceptibility to plasma lipoperoxidation and an increase in myeloperoxidase activity that differed significantly from the control group. In the presence of fine particles, neutrophils from asthmatic patients showed an increased tendency to generate reactive oxygen species after stimulation with fine particles (PM_2.5).

Conclusion

These findings suggest that asthmatic patients have higher oxidation of plasmatic lipids due to reduced antioxidant defense. Furthermore, fine particles tended to increase the respiratory burst of blood human neutrophils from the asthmatic group.

On the whole, increased myeloperoxidase activity and susceptibility to lipoperoxidation with a concomitant decrease in paraoxonase activity in asthmatic patients could favor lung infection and hence disrupt the control of asthmatic crises.

Myeloperoxidase: a useful biomarker for cardiovascular disease risk stratification?

BACKGROUND

Inflammation and oxidative stress are associated with atherosclerosis. Myeloperoxidase (MPO) is linked to both inflammation and oxidative stress by its location in leukocytes and its role in catalyzing the formation of oxidizing agents. Recent evidence suggests that MPO activity precipitates atherogenesis. Measurement of MPO in plasma may therefore contribute to cardiovascular disease (CVD) risk stratification.

CONTENT

Cross-sectional studies, case-control studies, and prospective-cohort studies investigating the relation between MPO and CVD have been evaluated. Differences in study populations, sample materials, sample handling, and assays were ascertained. Potential causal mechanisms linking MPO to accelerated atherosclerosis are discussed here. A majority of studies indicate that measurement of MPO in plasma was associated with improved CVD risk stratification above and beyond risk stratification results obtained with markers used in routine clinical practice. However, comparison of these epidemiological studies with regard to MPO and outcome is hampered because the reported MPO concentration depends on the assay method, sampling material, and preanalytical and analytical procedures. The link between MPO and CVD can, at least partly, be explained by MPO-dependent oxidation of LDL and HDL, subsequently leading to cholesterol accumulation in the arterial wall. Furthermore, MPO may reduce the bioavailability of nitric oxide, resulting in endothelial dysfunction. Finally, MPO destabilizes atherosclerotic plaques.

SUMMARY

Increasing evidence suggests that MPO is causally linked to atherosclerosis and its measurement may improve CVD risk estimation. Before MPO can be used in routine clinical practice, however, standardization of sampling and laboratory procedures is needed.