MYELOPEROXIDASE RESEARCH

Current role of myeloperoxidase in routine clinical practice

2011-05-09T15:41:00.001-05:00

Abstract:

Recognition of inflammation as a critical contributor to atherothrombosis has led to the pursuit of new approaches for the diagnosis and treatment of patients with coronary heart disease. As the intricate relationships between cellular and noncellular participants in the inflammatory aspects of atherogenesis, plaque destabilization and thrombosis have been defined, specific constituents have emerged as potential noninvasive indicators of these processes. Myeloperoxidase is a protein released during degranulation of neutrophils and monocytes. The available experimental and epidemiologic data provide compelling evidence to sustain strong interest in myeloperoxidase as a candidate for clinical application. Nevertheless, additional investigation will be important to fully evaluate myeloperoxidase as a sensitive predictor for myocardial infarction in patients with chest pain.
Expert Review of Cardiovascular Therapy, Volume 9, Number 2, February 2011 , pp. 223-230(8)

Myeloperoxidase, inflammation, and dysfunctional high-density lipoprotein

2010-10-26T09:30:00.001-05:00

Abstract
High-density lipoprotein (HDL) has many protective activities against atherosclerosis, including its role in reverse cholesterol transport, and its antioxidant, anti-inflammatory, and endothelial cell maintenance functions. However, all HDL is not functionally equivalent. The authors of recent studies have shown that infection, inflammation, diabetes, and coronary artery disease are associated with dysfunctional HDL. HDL can lose its protective activities through a variety of mechanisms, including, but not limited to, altered protein composition, oxidative protein modification mediated by the enzyme myeloperoxidase, and lipid modification. Studies in which the authors used bacterial endotoxin in humans and mice have directly demonstrated changes in HDL composition, loss of HDL’s cholesterol acceptor activity, and decreased hepatic processing and secretion of cholesterol. Although a routine clinical assay for dysfunctional HDL is not currently available, the development of such an assay would be beneficial for a better understanding of the role that dysfunctional HDL plays as a risk factor for coronary artery disease and for the determination of how various drug therapies effect HDL functionality.

Journal of Lipidology: Volume 4, Issue 5, Pages 382-388 (September 2010)

Myeloperoxidase, inflammation, and dysfunctional high-density lipoprotein

2010-10-26T09:30:00.000-05:00

Plasma myeloperoxidase, NT-proBNP, and troponin-I in patients on CAPD compared with those on regular hemodialysis

2010-09-15T14:12:00.001-05:00

Myeloperoxidase (MPO) is a hemoprotein that is released during inflammation and may lead to irreversible protein and lipid modification, increasing levels of oxidized low density lipoprotein, and promoting athrogenesis. Recently, it has been considered as a risk factor for cardiovascular diseases. Similarly, the measurement of carotid intima-media thickness gives an indication about the degree of atherosclerosis and prediction of clinical cardiovascular events.

Elevated white blood cells counts may indicate a state of acute inflammation and follow its progression. Dialysis patients are at a high risk of developing cardiovascular disease compared with healthy subjects. The role of N-terminal pro-brain natriuretic peptide and increased cardiac troponin in identification and prognostication of cardiovascular diseases in end-stage renal disease patients has been investigated. The current study aimed to evaluate plasma MPO and its possible relationship with carotid intima-media thickness, troponin I, N-terminal pro-brain natriuretic peptide (NT-proBNP), and insulin resistance as measured by homeostatic model assessment (HOMA index) in a cohort of Saudi patients who are undergoing hemodialysis (HD) vs. continuous ambulatory peritoneal dialysis for end-stage renal disease.

Plasma MPO was significantly higher in patients on continuous ambulatory peritoneal dialysis (CAPD) than in those on HD and in normal subjects (P<0.001). Conversely, NT-proBNP plasma levels were significantly higher in patients on HD (both predialysis and postdialysis) than in those on CAPD (P<0.01) and than normal subjects. Similarly, plasma troponin-I levels were significantly higher in patients on HD compared with those of CAPD and than normal subjects (P<0.001). Plasma troponin-I and NT-proBNP levels were positively correlated in the 3 groups namely those on CAPD, Pre-HD, and post-HD (r: 0.464 and P=0.047; r: 0.330 and P=0.013; and r: 0.452 and P=0.024), respectively. There was no correlation between the MPO level and carotid intima-media thickness (P>0.05). However, plasma MPO level correlated positively with the white blood cell count in patients on CAPD and in those on HD (P <0.05).

Our findings suggest an increased oxidative stress in CAPD patients compared with HD patients, while the reported difference in plasma NT-proBNP and troponin-I may be related to the rapid decline of residual renal function in HD and type of membrane used in the HD dialysis procedure itself.

Hemodialysis International
Volume 14, Issue 3, pages 308–315, July 2010
Abdulla AL-HWEISH1, Sherif S. SULTAN2, Khaled MOGAZI3, Mohamed Y. ELSAMMAK4

Myeloperoxidase Breaks Down Potentially Toxic Nanomaterials Identified

2010-05-06T11:38:00.002-05:00

ScienceDaily (Apr. 8, 2010) — An international study based at the University of Pittsburgh provides the first identification of a human enzyme that can biodegrade carbon nanotubes-the superstrong materials found in products from electronics to plastics-and in laboratory tests offset the potentially damaging health effects of being exposed to the tiny components, according to findings published online in Nature Nanotechnology.

The results could open the door to the use of carbon nanotubes as a safe drug-delivery tool and also could lead to the development of a natural treatment for people exposed to nanotubes, either in the environment or the workplace, the team reported. The researchers found that carbon nanotubes degraded with the human enzyme myeloperoxidase (hMPO) did not produce the lung inflammation that intact nanotubes have been shown to cause. Furthermore, neutrophils, the white blood cells that contain and emit hMPO to kill invading microorganisms, can be directed to attack carbon nanotubes specifically.

"The successful medical application of carbon nanotubes rely on their effective breakdown in the body, but carbon nanotubes also are notoriously durable," said lead researcher Valerian Kagan, a professor and vice chair in the Department of Environmental and Occupational Health in Pitt's Graduate School of Public Health."The ability of hMPO to biodegrade carbon nanotubes reveals that this breakdown is part of a natural inflammatory response. The next step is to develop methods for stimulating that inflammatory response and reproducing the biodegradation process inside a living organism."

Kagan and his research group led the team of more than 20 researchers from four universities along with the laboratory groups of Alexander Star, an assistant professor of chemistry in Pitt's School of Arts and Sciences, and Judith Klein-Seethharaman, an assistant professor of structural biology in Pitt's School of Medicine. Additional Pitt researchers included Yulia Tyurina, a Pitt assistant professor of environmental and occupational health in the Graduate School of Public Health, and Donna Stolz, an associate professor of cell biology and physiology in Pitt's medical school; other researchers are from Sweden's Karolinska Institute, Trinity College in Ireland, the National Institute for Occupational Safety and Health, and West Virginia University.

Carbon nanotubes are one-atom thick rolls of graphite 100,000 times smaller than a human hair yet stronger than steel. They are used to reinforce plastics, ceramics, or concrete; are excellent conductors of electricity and heat; and are sensitive chemical sensors. However, a nanotube's surface also contains thousands of atoms that could react with the human body in unknown ways. Tests on mice have shown that nanotube inhalation results in severe lung inflammation coupled with an early onset of fibrosis. The tubes' durability raises additional concern about proper disposal and cleanup. In 2008, Star and Kagan reported in "Nano Letters" that carbon nanotubes deteriorate when exposed to the plant enzyme horseradish peroxidase, but their research focused on cleanup after accidental spills during manufacturing or in the environment.

For the current study, the researchers focused on human myeloperoxidase because it works via the release of strong acids and oxidants-similar to the chemicals used to break down carbon nanotubes. They first incubated short, single-walled nanotubes in an hMPO and hydrogen peroxide solution-the hydrogen peroxide sparks and sustains hMPO activity-for 24 hours, after which the structure and bulk of the tube had completely degenerated. The nanotubes degenerated even faster when sodium chloride was added to the solution to produce hypochlorite, a strong oxidizing compound known to break down nanotubes.

After establishing the effectiveness of myeloperoxidase in degrading carbon nanotubes, the team developed a technique to prompt neutrophils to attack nanotubes by capturing them and exposing them to the enzyme. They implanted a sample of nanotubes with antibodies known as immunoglobulin G (IgG), which made them specific neutrophil targets. After 12 hours, 100 percent of IgG nanotubes were degraded versus 30 percent of those without IgG. The researchers also tested the ability of macrophages, another white blood cell, to break down nanotubes, but after two days, only 50 percent of the tubes had degenerated.

In subsequent laboratory tests, lung tissue exposed to the degraded nanotubes for seven days exhibited negligible change when compared to unexposed tissue. On the other hand, tissue exposed to untreated nanotubes developed severe inflammation

Oxidation of apolipoprotein A-I by myeloperoxidase impairs the initial interactions with ABCA1 required for signaling and cholesterol export

2010-03-21T10:26:00.004-05:00

A key cardioprotective effect of high-density lipoprotein (HDL) involves the interaction of its major protein, apolipoprotein A-I (apoA-I), with ATP-binding cassette transporter A1 (ABCA1), a macrophage cholesterol exporter. ApoA I is thought to remove cholesterol from macrophages by a cascade of events. First it binds directly to ABCA1, activating signaling pathways, and then it binds to and solubilizes lipid domains generated by ABCA1.

HDL isolated from human atherosclerotic lesions and blood of subjects with established coronary artery disease contains elevated levels of 3-chlorotyrosine and 3-nitrotyrosine, two characteristic products of myeloperoxidase (MPO), a heme protein secreted by macrophages. Here we show that chlorination--but not nitration--of apoA-I by the MPO pathway impairs its ability to interact directly with ABCA1, to activate the Janus kinase 2 signaling pathway, and to promote efflux of cellular cholesterol. In contrast, oxidation of apoA-I has little effect on its ability to stabilize ABCA1 protein or to solubilize phospholipids.

Our results indicate that chlorination of apoA-I by the MPO pathway selectively inhibits two critical early events in cholesterol efflux: the binding of apoA-I to ABCA1 and activation of a key signaling pathway. Therefore, oxidation of apoA-I in the artery wall by MPO-generated chlorinating intermediates may contribute to atherogenesis by impairing cholesterol efflux from macrophages

Baohai Shao1, Chongren Tang1, Jay W. Heinecke1 and John F. Oram2,*

1 University of Washington, United States;
2 University of Washington Medical Center, United States

Vascular Endothelial Function Is Related to White Blood Cell Count and Myeloperoxidase Among Healthy Middle-Aged and Older Adults

2010-01-28T13:00:00.000-06:00

Abstract—Endothelium-dependent dilation (EDD) is impaired with aging, but there is significant variability among healthy middle-aged and older adults. We tested the hypothesis that EDD is related to white blood cell (WBC) count in healthy men and women aged 55 to 75 years (n=48) who have a WBC count within the clinically normal range. The peak forearm blood flow response to intrabrachial artery infusion of acetylcholine was inversely related to WBC count (r=-0.38; P=0.004) and was 34% smaller in subjects with higher versus lower WBC count (more versus less than the median of 5.0x109 cells per liter; P=0.001).

Vascular smooth muscle responsiveness to NO (peak forearm blood flow response to sodium nitroprusside) was inversely related to WBC count (r=-0.30; P=0.02) but did not fully explain the associations with EDD. Inhibition of NO with NG-monomethyl-L-arginine reduced EDD in subjects with lower (-56%; P=0.01) but not higher WBC count. Tetrahydrobiopterin selectively improved EDD in subjects with higher WBC count (+35%; P=0.01) by increasing NO bioavailability. EDD was related (P<0.05) to neutrophil, eosinophil, and monocyte but not lymphocyte or basophil counts.

Myeloperoxidase, which is secreted by neutrophils and monocytes, consumes NO and produces molecules that oxidize tetrahydrobiopterin, was inversely related to EDD (r=-0.35; P=0.02), and was 42% higher in subjects with a higher WBC count (P=0.02). No other factors contributed to the relation between EDD and WBC count. Among healthy middle-aged and older adults, impaired EDD is related to higher neutrophil, eosinophil, and monocyte-based WBC count mediated by reduced responsiveness to NO and increased myeloperoxidase-associated reductions in tetrahydrobiopterin and NO bioavailability.

Ashley E. Walker; Sara Marian Seibert; Anthony J. Donato; Gary L. Pierce; and Douglas R. Seals*
From the Department of Integrative Physiology, University of Colorado, Boulder, Colo

Usefulness of Myeloperoxidase Levels in Healthy Elderly Subjects to Predict Risk of Developing Heart Failure

2009-11-24T12:06:00.000-06:00

Increased systemic myeloperoxidase (MPO) has been associated with both the presence and severity of heart failure (HF). This study tested the hypothesis that increased systemic MPO in apparently healthy elderly subjects may predict increased risk of developing HF. Systemic MPO was measured in all available samples from the 1992 to 1993 visit of the Cardiovascular Health Study (CHS). After excluding subjects without available blood samples or with a history of prevalent HF, myocardial infarction (MI), or stroke, 3,733 subjects were included. A total of 569 subjects developed incident HF during 7.2 ± 2.3 years of follow-up. Patients in the highest MPO quartile (>432 pmol/L) showed higher risk of developing incident HF after adjusting for MI, age, gender, systolic blood pressure, smoking, low-density lipoprotein cholesterol, diabetes mellitus, and any subclinical cardiovascular disease (hazard ratio 1.34, 95% confidence interval 1.06 to 1.72, p = 0.013). However, the relation was more apparent after censoring subjects with incident MI before incident HF, even when adjusted for C-reactive protein and cystatin C (hazard ratio 1.46, 95% confidence interval 1.08 to 1.97, p = 0.02). Interestingly, stratified analyses showed that the relation between increased MPO and HF risk was stronger in subjects without traditional cardiovascular risk factors (≤75 years old, systolic blood pressure ≤136 mm Hg, no subclinical cardiovascular disease, and no diabetes mellitus). In conclusion, an independent association between increased MPO and the development of HF in apparently healthy elderly subjects was observed, particularly beyond MI and traditional cardiac risk factors.

Myeloperoxidase (MPO) is a leukocyte-derived enzyme that catalyzes the formation of a number of reactive oxidant species and impacts on nitric oxide through complex mechanisms, including direct catalytic consumption resulting in endothelial dysfunction.1,2 Myeloperoxidase has been shown to provide prognostic value in the setting of chest pain and acute coronary syndromes.3–5 Recent studies of the community-based European Prospective Investigation of Cancer (EPIC)/Nolfork population also reported that systemic MPO independently predicted risk of the development of incident cardiovascular disease and death in apparently healthy middle-aged subjects.6 A potential pathogenic role of MPO in the development of left ventricular dysfunction and heart failure (HF) was also emerging.7–9 In animal models, MPO knockout mice showed an important role of MPO in facilitating HF disease progression.10 In humans, systemic MPO was increased in patients with established chronic systolic HF and correlated with diastolic dysfunction independent of age and plasma B-type natriuretic peptide.8 Recent studies also showed that systemic MPO in subjects with myocardial infarction (MI)7 or chronic systolic HF9 may predict long-term adverse clinical events. Here, we hypothesized that MPO may be associated with the long-term risk of developing HF in apparently healthy elderly subjects.

Am J Cardiol. 2009 May 1; 103(9): 1269–1274.

C-Reactive Protein Stimulates Myeloperoxidase Release from Polymorphonuclear Cells and Monocytes: Implications for Acute Coronary Syndromes

2009-11-24T12:04:00.000-06:00

Abstract

Background: C-reactive protein (CRP), the prototypic marker of inflammation, is present in atherosclerotic plaques and appears to promote atherogenesis. Also, CRP has been localized to monocytes and tissue macrophages, which are present in the necrotic core of lesions prone to plaque rupture. Leukocyte-derived myeloperoxidase (MPO), primarily hosted in human polymorphonuclear cells (PMNs), has also been shown to be present in human atherosclerotic lesions. Because MPO and CRP concentrations are increased in acute coronary syndrome (ACS) patients and predict poor outcomes, we tested the effect of CRP on MPO release from PMNs and monocytes.

Methods: We treated human PMNs and monocytes with CRP (25 and 50 mg/L for 6 h) and measured MPO release as total mass and activity in culture supernatants. We also measured nitro-tyrosinylation (NO2-Tyr) of LDL as an indicator of biological activity of CRP-mediated MPO release. Furthermore, we explored the effect of human CRP on MPO release in the rat sterile pouch model.

Results: CRP treatment significantly increased release of MPO (both mass and activity) from human PMNs as well as monocytes (P < 0.05) and caused NO2-Tyr of LDL. Human CRP injection in rats resulted in increased concentrations of MPO in pouch exudates (P < 0.05), thus confirming our in vitro data.

Conclusions: CRP stimulates MPO release both in vitro and in vivo, providing further cogent data for the proinflammatory effect of CRP. These results might further support the role of CRP in ACS.

Uma Singha, Sridevi Devaraj and Ishwarlal Jialal

Department of Medical Pathology and Laboratory Medicine, UC Davis Medical Center, Sacramento, CA

2009-08-20T11:00:00.002-05:00

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 Myeloperoxidase 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 Myeloperoxidase 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

Ali Z, Sarcia P, Mosley TH, Kondragunta V, Kullo IJ.
Division of Cardiovascular Diseases, Mayo Clinic

Neutrophil activation precedes myocardial injury in patients with acute myocardial infarction

2009-05-25T11:04:00.002-05:00

Department of Cardiology and Cardiovascular Research Center, University Heart Center, D-20246 Hamburg, Germany.

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 Myeloperoxidase 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 Myeloperoxidase 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 Myeloperoxidase, 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, Myeloperoxidase 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 Myeloperoxidase MPO plasma levels at the time of admission and the rapid peak of free plasma Myeloperoxidase levels after the onset of symptoms suggests that PMN activation is an early event in AMI and potentially precedes myocardial injury.

Myeloperoxidase, modified lipoproteins, and atherogenesis.

2009-05-20T15:42:00.001-05:00

Departments of Cell Biology and Cardiovascular Medicine, Center for Cardiovascular Diagnostics and Prevention, Cleveland Clinic, Cleveland, OH.

Numerous lines of evidence implicate a role for Myeloperoxidase (MPO) in the pathogenesis of atherosclerosis. Enriched within vulnerable plaque, Myeloperoxidase MPO serves as an enzymatic source of eicosanoids and bioactive lipids and generates atherogenic forms of both low- and high-density lipoproteins. These factors likely contribute to clinical studies demonstrating that increased systemic levels of Myeloperoxidase MPO and its oxidation products predict increased cardiovascular risk. As a result, interest has focused on the potential to target MPO for the development of new risk markers, imaging, and therapies to prevent cardiovascular events.

Association of Major Depressive Disorder with Serum Myeloperoxidase and Other Markers of Inflammation: A Twin Study

2009-01-02T14:38:00.004-06:00

Background
Major depressive disorder (MDD) has been linked to inflammation, but this association may be due to common precursors to both depression and inflammation. Myeloperoxidase (MPO) is an inflammatory enzyme produced by activated leukocytes that predicts risk of coronary heart disease. We sought to examine whether MPO and other markers of inflammation are associated with MDD and whether the association is confounded by genetic or other shared familial factors.

Methods
We examined 178 monozygotic and dizygotic middle-aged male twin pairs. We assessed MDD with the Structured Clinical Interview for DSM-IV. Blood markers of inflammation included MPO , interleukin-6, white blood cell count, C-reactive protein , tumor necrosis factor (TNF)-α, the TNF-α soluble receptor II, and fibrinogen. Analyses were conducted in the overall sample and among 67 twin pairs discordant for MDD using mixed effects regression.

Results
Twins with a history of MDD had 32% higher levels of MPO (p < .0001); this difference persisted after adjusting for other risk factors. Among dizygotic MDD-discordant twin pairs, twins with MDD had 77% higher MPO than their brothers without MDD, after adjusting for other factors (p < .0001). In contrast, no significant association was found in monozygotic twins (p = .13). Similar, but weaker, associations were found between MDD and other inflammatory biomarkers.

Conclusions
Myeloperoxidase is a useful biomarker of immune activation in MDD. However, the association between inflammation and MDD is largely due to common genetic liability. Our results are consistent with the hypothesis that genes promoting inflammation are involved in the pathogenesis of MDD.

Biological Psychiatry , Volume 64 , Issue 6 , Pages 476 - 483
V . Vaccarino , M . Brennan , A . Miller , J . Bremner , J . Ritchie , F . Lindau , E . Veledar , S . Su , N . Murrah , L . Jones

Chitin oligosaccharides inhibit oxidative stress in live cells

2008-08-08T10:32:00.001-05:00

The aim of this research is to identify the cellular antioxidant effects of chitin oligosaccharides (NA-COS; Mw 229.21–593.12 Da) produced by acidic hydrolysis of crab chitin. The inhibitory effect of NA-COS on myeloperoxidase (MPO) activity in human myeloid cells (HL-60) and oxidation of DNA and protein in mouse macrophages (Raw 264.7) were identified. Furthermore, their direct radical scavenging effect by 2′,7′-dichlorofluorescein (DCF) intensity and intracellular glutathione (GSH) level were significantly increased in a time dependent manner, respectively. These results suggest that NA-COS act as a potent antioxidant in live cells.

ARTICLE

Accumulation of Myeloperoxidase-Positive Neutrophils in Atherosclerotic Lesions in LDLR–/– Mice

2008-07-22T15:03:00.002-05:00

Objective—
Atherosclerosis is a chronic inflammatory disease in which the immune system plays an important role. Neutrophils have not been thoroughly studied in the context of atherogenesis. Here, we investigated neutrophils in the development of murine atherosclerotic lesions.

Methods and Results—
LDLR–/– mice were given a high-fat diet for different time periods and subsequently atherosclerotic lesions were studied by immunohistochemistry. Staining with anti–Ly-6G monoclonal antibody, a specific marker for neutrophils, revealed a marked accumulation of neutrophils during atherosclerosis development. Neutrophils were observed in the lesion, attached to the cap, and in the arterial adventitia. In addition, at some sites, neutrophil accumulation colocalized with endothelial E-selectin expression. Immunofluorescence double staining with anti-myeloperoxidase and anti–Ly-6G antibodies demonstrated the presence of myeloperoxidase in atherosclerotic lesions and its colocalization with neutrophils. After introducing the high-fat diet, levels of circulating myeloperoxidase in plasma strongly increased, with a peak at 6 weeks and a subsequent decrease to almost normal levels after 16 weeks of diet.

Conclusions—
We here demonstrate for the first time the presence of neutrophils and myeloperoxidase in murine atherosclerotic lesions. As a major cell type in inflammatory responses the neutrophil may also be an important mediator in the development of atherosclerosis.

We identified myeloperoxidase-positive neutrophils in mouse atherosclerotic lesions. Although neutrophils were not detected in early lesions, they were abundantly present in more advanced stages. In addition, circulating myeloperoxidase levels were strongly increased by high-fat feeding of the mice. Therefore, neutrophils should be considered as a potential important cellular mediator in atherogenesis.

Chitin oligosaccharides inhibit oxidative stress in live cells

2008-07-17T11:27:00.001-05:00

The aim of this research is to identify the cellular antioxidant effects of Chitin oligosaccharides inhibit oxidative stress in live cells

(NA-COS; Mw 229.21–593.12 Da) produced by acidic hydrolysis of crab chitin. The inhibitory effect of NA-COS on myeloperoxidase (MPO) activity in human myeloid cells (HL-60) and oxidation of DNA and protein in mouse macrophages (Raw 264.7) were identified. Furthermore, their direct radical scavenging effect by 2′,7′-dichlorofluorescein (DCF) intensity and intracellular glutathione (GSH) level were significantly increased in a time dependent manner, respectively. These results suggest that NA-COS act as a potent antioxidant in live cells.

ARTICLE

Myeloperoxidase levels are not associated with carotid atherosclerosis progression in patients with familial hypercholesterolemia

2008-07-15T11:25:00.003-05:00

Introduction
myeloperoxidase (MPO), an antimicrobial enzyme of the innate immune system, has been proposed to exert a wide array of pro-atherogenic effects throughout all stages of the atherosclerotic process. In view of the potent anti-inflammatory effects of statins in vitro, we evaluated the impact of statin therapy on plasma MPO levels in patients with heterozygous familial hypercholesterolemia (FH), treated with either intensive or conventional lipid-lowering therapy. Furthermore, we evaluated the relation between myeloperoxidase (MPO)levels and atherosclerosis progression, as determined by intima media thickness (IMT).

Methods
We measured plasma MPO levels, lipoprotein profiles, high sensitivity-C-reactive protein (hs-CRP) as well as IMT of carotid artery segments in 122 FH patients at baseline and after 2-year treatment with atorvastatin 80mg or simvastatin 40mg QD.

Results
Baseline median myeloperoxidase (MPO)values were 147pM (interquartile range (IQR) 122–217) and 144pM (IQR 118–216) and these increased significantly to 221pM (IQR 144–290) and 255pM (IQR 152–324) during 2-year follow-up in both the atorvastatin 80mg and simvastatin 40mg group, respectively. There was no correlation between MPO levels and IMT progression, change in lipoproteins or hs-CRP.

Conclusion
In FH patients, statins do not prevent an increase in MPO levels during follow-up. Moreover, MPO levels are not associated with atherosclerosis progression in these patients.

Evaluation of the ameliorative effects of immunosuppressants on crescentic glomerulonephritis in SCG/Kj mice

2008-07-02T14:20:00.005-05:00

The therapeutic efficacy of immunosuppressants for treating rapidly progressive glomerulonephritis (RPGN) with crescent formation remains controversial. SCG/Kj mice spontaneously develop RPGN-like symptoms, characteristic of crescentic glomerulonephritis and systemic small vessel vasculitis, associated with the presence of anti-neutrophil cytoplasmic antibodies (ANCA). We evaluated the “ameliorative”, not prophylactic, effects of immunosuppressive agents, deoxyspergualin (DSG), cyclophosphamide (CYC) and prednisolone (PDN), on RPGN in these mice. DSG at intraperitoneal doses of 3 and 6 mg/kg, CYC at an oral dose of 12 mg/kg, or PDN at an intraperitoneal dose of 120 mg/kg was administered once a day for 21 days to female mice “at the onset of hematuria”. A set of control SCG/Kj mice received only saline injections. DSG and CYC significantly prolonged survival, improved the proteinuria, hematuria and hyperuremia, and decreased the serum level of myeloperoxidase-ANCA. Moreover, DSG significantly suppressed the formation of crescents in glomeruli. PDN failed to affect any of the parameters. DSG might be useful for inducing remission in crescentic glomerulonephritis involved in RPGN.

ARTICLE

Kinetic evidence for rapid oxidation of (–)-epicatechin by human myeloperoxidase

2008-07-02T13:26:00.002-05:00

Apocynin has been reported to require dimerization by myeloperoxidase (MPO) to inhibit leukocyte NADPH oxidase. (–)-Epicatechin, a dietary flavan-3-ol, has been identified as a ‘prodrug’ of apocynin-like metabolites that inhibit endothelial NADPH oxidase activity and elevate the cellular level of nitric oxide. Since (–)-epicatechin has tentatively been identified as substrate of myeloperoxidase (MPO), we studied the one-electron oxidation of (–)-epicatechin by MPO. By using multi-mixing stopped-flow technique, we demonstrate that (–)-epicatechin is one of the most efficient electron donors for heme peroxidases investigated so far. Second order rate constants for the (–)-epicatechin-mediated conversion of MPO-compound I to compound II and compound II to resting enzyme were estimated to be 1.9 × 107 and 4.5 × 106 M−1 s−1, respectively (pH 7, 25 °C). The data indicate that (–)-epicatechin is capable of undergoing fast MPO-mediated one-electron oxidation.

ARTICLE

Association of Major Depressive Disorder with Serum Myeloperoxidase and Other Markers of Inflammation: A Twin Study

2008-06-26T16:09:00.005-05:00

Background
Major depressive disorder (MDD) has been linked to inflammation, but this association may be due to common precursors to both depression and inflammation. Myeloperoxidase (MPO) is an inflammatory enzyme produced by activated leukocytes that predicts risk of coronary heart disease. We sought to examine whether MPO and other markers of inflammation are associated with MDD and whether the association is confounded by genetic or other shared familial factors.

Methods
We examined 178 monozygotic and dizygotic middle-aged male twin pairs. We assessed MDD with the Structured Clinical Interview for DSM-IV. Blood markers of inflammation included MPO, interleukin-6, white blood cell count, C-reactive protein, necrosis factor (TNF)-α, the TNF-α soluble receptor II, and fibrinogen. Analyses were conducted in the overall sample and among 67 twin pairs discordant for MDD using mixed effects regression.

Results
Twins with a history of MDD had 32% higher levels of MPO (p < .0001); this difference persisted after adjusting for other risk factors. Among dizygotic MDD-discordant twin pairs, twins with MDD had 77% higher MPO than their brothers without MDD, after adjusting for other factors (p < .0001). In contrast, no significant association was found in monozygotic twins (p = .13). Similar, but weaker, associations were found between MDD and other inflammatory biomarkers.

Conclusions
Myeloperoxidase is a useful biomarker of immune activation in MDD. However, the association between inflammation and MDD is largely due to common genetic liability. Our results are consistent with the hypothesis that genes promoting inflammation are involved in the pathogenesis of MDD.

Plasma levels of myeloperoxidase are not elevated in patients with stable coronary artery disease

2008-06-26T16:05:00.003-05:00

Background
Plasma and serum levels of myeloperoxidase (MPO), a redox-active hemoprotein released by polymorphonuclear neutrophils (PMN) upon activation, is now recognized as a powerful prognostic determinant of myocardial infarction in patients suffering acute coronary syndromes. However, there is limited information on whether systemic MPO levels are also elevated and of discriminating value in patients with stable coronary artery disease (CAD) representing different ethnic groups.

Methods
Plasma levels of MPO and traditional CAD risk factors were quantified in African American and Caucasian patients (n = 557) undergoing elective coronary angiography.

Results
MPO levels did not differ significantly between patients with or without CAD [421 pM (321, 533) vs. 412 pM (326, 500), p > 0.05]. MPO levels were similar across ethnicity and gender, and correlated positively with CRP and fibrinogen levels (r = 0.132, p = 0.002 and r = 0.106, p = 0.011, respectively).

Conclusion
In conclusion, plasma MPO levels were not elevated in patients with stable CAD, suggesting that systemic release of MPO is not a characteristic feature of asymptomatic CAD.

Lukas Kubalaa, d , Guijing Lub, Stephan Balduse, Lars Berglundb, f and Jason P. Eiserich

ARTICLE

MPO-ANCA Induces IL-17 Production by Activated Neutrophils in Vitro Via its Fc Region- and Complement-Dependent Manner

2008-05-23T16:29:00.005-05:00

The elevation of serum anti-neutrophil cytoplasmic autoantibodies (ANCA) is significantly associated with the progression of some patients with systemic vasculitis. Especially, myeloperoxidase-specific ANCA (MPO-ANCA) play a pivotal role in the progression of systemic vasculitis including crescentic glomerulonephritis. Here we demonstrated that MPO-ANCA-activated neutrophils allow the local environment to differentiate Th17 cells through IL-6, IL-17A, and IL-23 production. We found a variety of elevated serum cytokines, especially IL-17A, in ANCA-mediated systemic vasculitis mice. Furthermore, activated peritoneal neutrophils in vitro also produced IL-17A and IL-23 in response to MPO-ANCA. Co-stimulation of fungal mannoprotein and complements significantly enhanced the MPO-ANCA-mediated IL-17A expression, but F(ab)′2 fragments of MPO-ANCA diminished the cytokine response. These results suggest that the activated neutrophils produce IL-17A and IL-23 in response to MPO-ANCA via their Fc-region and classical complement pathway, which initiate the first steps of chronic autoimmune inflammation by allowing the local environment to develop Th17-mediated autoimmunity.

Akiyoshi Hoshinoa, b, c, Tomokazu Nagaoc, d, Noriko Nagi-Miurae, Naohito Ohnoe, Masato Yasuharab, Kenji Yamamotoa, b, Toshinori Nakayamad and Kazuo Suzuki

A novel assay system for myeloperoxidase activity in whole saliva.

2008-02-05T12:04:00.002-06:00

OBJECTIVES: The application of a novel assay system for the direct measurement of MPO (myeloperoxidase) activity in whole saliva .

DESIGN AND METHODS: The assay system employs a novel sensitive substrate from 3,3'-diaminobenzidine (DAB) and guaiacol in the presence of dapsone (4,4'-diaminodiphenylsulfone) to determine MPO activity in whole saliva using an original "sandwich" test-disk (DEAE-cellulose paper and cellulose chromatography paper). The saliva (0.1 mL) was directly applied to the sandwich test-disk, and then 0.1 mL of the substrate solution containing 1 mM dapsone in 0.3 M Tris-HCl buffer (pH 7.5) was added. After incubation for 30 min at room temperature, absorbance on the test-disk was measured at 460 nm with an optical analyzer.

RESULTS: The assay system was shown to distinguish MPO from salivary peroxidase in whole mixed saliva and was sensitive, easy and cheap. The assays revealed that MPO activity in whole saliva from subjects with periodontal disease was significantly higher than in saliva from healthy subjects. There was also a significant positive correlation between MPO activity and the probing depth of subgingival pockets (r=0.736, p<0.001).

CONCLUSIONS: These results indicate that this novel assay system for measurement of MPO is a useful technique for predicting the progression of periodontal disease.

Sakamoto W, Fujii Y, Kanehira T, Asano K, Izumi H.
Institute of Well Being, Fuji Women's University , 061-3204 Ishikari, Hokkaido, Japan; Serotec Laboratory, 069-0822 Ebetsu, Hokkaido, Japan. Clin Biochem. 2008 Jan 15

Prognostic value of plasma myeloperoxidase concentration in patients with stable coronary artery disease

2008-01-29T14:01:00.002-06:00

BACKGROUND: There are no studies yet on the usefulness of myeloperoxidase (MPO) as a prognostic tool in patients with stable coronary artery disease (CAD).

METHODS: The study included 382 patients with clinical and angiographic confirmation of stable CAD. Blood samples for MPO measurement were taken before angiography. Myeloperoxidase was determined using an enzyme immunoassay. The primary end point of the study was all-cause mortality.

RESULTS: Patients were categorized into 2 groups: the high-MPO group included patients in the third tertile of MPO levels (>75.0 microg/L; 127 patients), and the low-MPO group included patients in the first (<52.6 microg/L) and second tertiles (52.6-75.0 microg/L) of MPO levels (255 patients). The median follow-up was 3.5 [3.3-4.8] years. There were 35 deaths (9.2%) during the follow-up. The MPO concentration was 60.1 [47.0; 83.8] microg/L in survivors and 72.7 [54.8; 105.1] microg/L in nonsurvivors (P = .06). There were 17 deaths in the high-MPO level and 18 deaths in the low-MPO group: Kaplan-Meier estimates of mortality were 18.3% and 10.5% with an odds ratio of 1.96 (95% confidence interval [1.02-3.76], P = .04). The Cox proportional hazards model adjusting for correlates of mortality showed that plasma MPO was not an independent correlate of mortality (hazard ratio 1.06, 95% confidence interval [0.71-1.59], P = .77 for 1 SD increase in the log variable).

CONCLUSION: Although elevated plasma MPO concentration is associated with a more advanced cardiovascular risk profile, plasma MPO does not predict mortality independent of other cardiovascular risk factors in patients with stable CAD.

Am Heart J. 2008 Feb;155(2):356-60. Epub 2007 Dec 19,Faculty of Medicine, McGill University, Montreal, Quebec, Canada

Myeloperoxidase, but not C-reactive protein, predicts cardiovascular risk in peripheral arterial disease

2007-12-26T16:28:00.002-06:00

Aims: The prognostic role of inflammation in peripheral arterial disease (PAD) remains to be conclusively established. Accordingly, in these patients we investigated the impact of myeloperoxidase (MPOx) and C-reactive protein on the incidence of myocardial infarction and stroke.

Methods and results Of 156 PAD patients, 10 had a myocardial infarction and seven a stroke, during follow-up. We used the receiver operating characteristic curve analysis and the bootstrap approach to identify the myeloperoxidase , C-reactive protein , and ankle brachial index (ABI) threshold levels that provided the best cut-off to predict the outcome. For MPO a cut-off >/=183.7 pM was independently associated with a poor outcome (HR = 6.80, 95% CI 1.20-38.69, P = 0.031).

The result remained unmodified when MPOx was used as a continuous variable (HR = 1.03, 95% CI 1.01-1.05, P = 0.031). Conversely, C-reactive protein was not a prognostic determinant in our series (HR = 0.88, 95% CI 0.60-1.29, P = 0.514). Kaplan-Meier curves for the four groups of patients delineated according to ABI and MPOx values identified using the bootstrap approach showed that the addition of MPOx measurement to ABI improved the ability to identify patients at risk for myocardial infarction and stroke.

Conclusion In PAD, Myeloperoxidase MPO , but not C-reactive protein , predicts an increased risk of major cardiovascular events, and adds to the prognostic value of ABI, currently the most powerful prognostic indicator in these patients.

Brevetti G, Schiano V, Laurenzano E, Giugliano G, Petretta M, Scopacasa F, Chiariello M. Department of Clinical Medicine and Cardiovascular and Immunological Sciences, University of Naples,Eur Heart J. 2007 Dec 21

Usefulness of Baseline Plasma Myeloperoxidase Levels as an Independent Predictor of Myocardial Infarction at Two Years in Patients Presenting With Acu

2007-11-23T13:37:00.002-06:00

Baseline plasma myeloperoxidase (MPO) levels have been shown to independently predict the early risk of myocardial infarction (MI) in patients presenting with chest pain. In addition, baseline MPO levels have been demonstrated to predict the development of adverse cardiac events up to 6 months after an acute coronary syndrome (ACS). However, in contrast to other biomarkers, there are no data about the long-term independent predictive value of baseline MPO values in patients with ACS.

The present study investigated the long-term prognostic significance of baseline Myeloperoxidase MPO levels in a well-characterized cohort of 193 men with ACS who were referred for coronary angiography at a Veterans Administration Medical Center. All patients were followed prospectively for the development of death and MI , and follow-up data were available for all patients at 24 months. After controlling for different baseline clinical, laboratory, and angiographic variables, baseline plasma MPO values were a strong and independent predictor of MI at 24 months by multivariate analysis.

Using the median MPO value of the entire cohort of patients (i.e., 20.34 ng/ml) as a prespecified cutoff, the MI-free survival at 24 months for the group whose baseline MPO values were ≤20.34 ng/ml was 88% compared with 74% in those whose values were >20.34 ng/ml (p = 0.0249 by log-rank test).

In conclusion, these data demonstrate that baseline MPO levels independently predict MI at 2 years in patients with ACS.

The American Journal of Cardiology
Volume 99, Issue 10, 15 May 2007, Pages 1364-1368
cDivision of Cardiovascular Medicine, Department of Medicine, University of Michigan , Ann Arbor, Michigan.
doi:10.1016/j.amjcard.2006.12.060

Prognostic Value of Myeloperoxidase in Patients with Chest Pain

2007-10-19T15:08:00.002-05:00

Myeloperoxidase Research Background: Inflammation is linked to adverse outcomes in acute coronary syndromes. Myeloperoxidase , an abundant leukocyte enzyme , is elevated in culprit lesions that have fissured or ruptured in patients with sudden death from cardiac causes. Numerous lines of evidence suggest mechanistic links between myeloperoxidase and both inflammation and cardiovascular disease.

Conclusions A single initial measurement of plasma myeloperoxidase independently predicts the early risk of myocardial infarction , as well as the risk of major adverse cardiac events in the ensuing 30-day and 6-month periods. Myeloperoxidase levels, in contrast to troponin T , creatine kinase MB isoform , and C-reactive protein levels, identified patients at risk for cardiac events in the absence of myocardial necrosis, highlighting its potential usefulness for risk stratification among patients who present with chest pain. Source: Dr. Hazen at the Center for Cardiovascular Diagnostics and Prevention, Cleveland Clinic Foundation , 9500 Euclid Ave., NC10, Cleveland, OH 44195, published by The New England Journal of Medicine

Human Myeloperoxidase - Our Story

2007-09-25T11:25:00.001-05:00

Since early 2000 Lee Biosolutions, Inc has been producing Leukocytes in bulk 40 liter lots at a time for clients making urine controls. My R and D department headed by Dr. Drewe knowing I wanted new proteins isolated every 4-6 months indicated to me that there was a number of analytes that he could be isolate from the leukocyte extract we had on hand. So we embarked on a journey of purifying as many proteins that I felt we could market to researchers. Over time we had successfully isolated neutrophil proteins such as Cathepsin G , Lysozyme , Proteinase 3 , Lactoferrin and a green protein that was identified as Myeloperoxidase .

It wasn't until I read a study performed by the prestigous Cleveland Clinic Lerner Institute and published by The New England Journal of Medicine Prognostic Value of Myeloperoxidase in Patients with Chest Pain that I knew we potentially had a product that would have one of the greatest impacts on emergency room treatments, at least that was my opinion.

I read all that I could on Myeloperoxidase and current research being peformed. Have you ever had a gut feeling and just went with it? I had all the confidence in the world with my R and D Department. We developed specifications and began selling our first lot of Myeloperoxidase in 2003. Honestly our first lot of MPO bombed with Abbott labs with having a low RZ value in the low 5's, if you could believe it, of all companies. But that didn't deter me, it just proved to me that we were on the right track.

We now produce in bulk and have the capabilities of producing in gram quantities of MPO if required. We sell high quality Myeloperoxidase worldwide and soon you will find companies gaining FDA approval.

We also have isolated Myeloperoxidase Isoform C that is used Protein Crystallization Research. We have been able to separte out Eosinophil Peroxidase and Eosinophil Cationic Protein . These two products definitely are not easy to isolate but the number of requests we have had ensures us that they will be very busy isolating other analytes that we will be putting on the market later on this year.

Burton Lee
President
www.leebio.com

ps. I guess I should indicate that any reference to any organization does not constitute an endorsment of our products. It's that kind of world you guys.