A functional variant of the myeloperoxidase gene is associated with cardiovascular disease in end-stage renal disease patients

Thiocyanate Reduces Motor Impairment in the hMPO-A53T PD Mouse Model While Reducing MPO-Oxidation of Alpha Synuclein in Enlarged LYVE1/AQP4 Positive Periventricular Glymphatic Vessels

Parkinson's disease (PD) is due to the oxidation of alpha synuclein (αSyn) contributing to motor impairment. We developed a transgenic mouse model of PD that overexpresses the mutated human αSyn gene (A53T) crossed to a mouse expressing the human MPO gene. This model exhibits increased oxidation and chlorination of αSyn leading to greater motor impairment. In the current study, the hMPO-A53T mice were treated with thiocyanate (SCN^-) which is a favored substrate of MPO as compared to chlorine. We show that hMPO-A53T mice treated with SCN^- have less chlorination in the brain and show an improvement in motor skills compared to the nontreated hMPO-A53T mice. Interestingly, in the hMPO-A53T mice we found a possible link between MPO-related disease and the glymphatic system which clears waste including αSyn from the brain. The untreated hMPO-A53T mice exhibited an increase in the size of periventricular glymphatic vessels expressing the glymphatic marker LYVE1 and aquaporin 4 (AQP4). These vessels also exhibited an increase in MPO and HOCl-modified epitopes in the glymphatic vessels correlating with loss of ependymal cells lining the ventricles. These findings suggest that MPO may significantly promote the impairment of the glymphatic waste removal system thus contributing to neurodegeneration in PD. Moreover, the inhibition of MPO chlorination/oxidation by SCN^- may provide a potential therapeutic approach to this disease.

Framing Cause-Effect Relationship of Acute Coronary Syndrome in Patients with Chronic Kidney Disease

The main causes of death in patients with chronic kidney disease (CKD) are of cardiovascular nature. The interaction between traditional cardiovascular risk factors (CVRF) and non-traditional risk factors (RF) triggers various complex pathophysiological mechanisms that will lead to accelerated atherosclerosis in the context of decreased renal function. In terms of mortality, CKD should be considered equivalent to ischemic coronary artery disease (CAD) and properly monitored. Vascular calcification, endothelial dysfunction, oxidative stress, anemia, and inflammatory syndrome represents the main uremic RF triggered by accumulation of the uremic toxins in CKD subjects. Proteinuria that appears due to kidney function decline may initiate an inflammatory status and alteration of the coagulation-fibrinolysis systems, favorizing acute coronary syndromes (ACS) occurrence. All these factors represent potential targets for future therapy that may improve CKD patient's survival and prevention of CV events. Once installed, the CAD in CKD population is associated with negative outcome and increased mortality rate, that is the reason why discovering the complex pathophysiological connections between the two conditions and a proper control of the uremic RF are crucial and may represent the solutions for influencing the prognostic. Exclusion of CKD subjects from the important trials dealing with ACS and improper use of the therapeutical options because of the declined kidney functioned are issues that need to be surpassed. New ongoing trials with CKD subjects and platelets reactivity studies offers new perspectives for a better clinical approach and the expected results will clarify many aspects.

Status of Catalase, Glutathione Peroxidase, Glutathione S-Transferase, and Myeloperoxidase Gene Polymorphisms in Beta-Thalassemia Major Patients to Assess Oxidative Injury and Its Association with Enzyme Activities

Beta-thalassemic patients require regular blood transfusion to sustain their life which leads to iron overload and causes oxidative stress. The aim of this study was to investigate the status of variants in genes including GSTM1, GSTT1 (null/present), CT-262 (C > T) and CT-89 (A > T), glutathione peroxidase (GPx), and myeloperoxidase (MPO). The genotype studies were conducted with 200 thalassemia major (TM) patients and 200 healthy controls. Genotyping of GST gene was performed by multiplex polymerase chain reaction (PCR), whereas for CT, GPx and MPO genesvariants PCR- restriction fragment length polymorphism technique used. However, the enzyme activities were measured only in the patients group to assess the association with the genotypes. All enzyme estimations were performed by ELISA. We observed higher frequency of GSTT1 null, CT-89 (A > T), GPx1 198 (C > T) and MPO-463 (G > A) polymorphisms in TM patient than healthy controls. However, CT-262 (C > T) polymorphism was not found to be statistically significantly different between patients and controls. Our results suggest that frequency of null allele of glutathione-S-transferase is significantly high among TM patients. The other alleles CT-89 (A > T), GPx1 198 (C > T), and MPO-463 (G > A) are linked to decreased CT, GPX, and MPO enzyme activities.

Plasma myeloperoxidase levels in acute brain ischaemia and high grade carotid stenosis

BACKGROUND AND PURPOSE

Myeloperoxidase (MPO) is an important oxidative enzyme participating in different stages of cardiovascular disease and predicts prognosis. Little is known about its role in acute cerebrovascular events and carotid plaque vulnerability. In this study, the aim was to assess plasma MPO levels in acute stroke patients and their correlation to stroke severity and stroke outcome.

METHODS

Plasma MPO levels were assessed in patients presenting with acute brain ischaemia within 36 h of symptom onset (n = 144, mean age 64.7 ± 11.6 years, 67% men) and in patients with moderate-to-severe carotid stenosis undergoing carotid artery stenting (n = 51, mean age 66.3 ± 8.4 years, 75% men). Patients presenting with acute brain ischaemia were assessed serially for stroke severity and disability.

RESULTS

Plasma MPO concentrations (ng/ml) were associated with interleukin-6 (r = 0.38, P < 0.0001) and gender (median interquartile range) of 68.6 (49.8-107.0) vs. 59.7 (42.7-85.5) in women vs. men (P = 0.02). In acute brain ischaemia, MPO concentrations were associated with non-lacunar subtype (bottom, middle and top tertiles 37.5%, 71.7% and 71.7% respectively; P = 0.001), with stroke severity (baseline National Institutes of Health Stroke Scale score > 10, bottom, middle and top tertiles 6.3%, vs. 41.7% and 31.3%, respectively; P < 0.006) as well as with stroke severity at days 1-2, days 4-5 and at discharge (P < 0.05 for all), but less with disability at discharge (modified Rankin Scale score ≥ 2, 41.7% vs. 60.4% and 58.7% for the bottom, middle and top tertiles, respectively; P = 0.096).

CONCLUSIONS

Amongst patients with acute brain ischaemia, plasma MPO concentrations were associated with stroke severity and non-lacunar subtype, but not with long-term functional disability.

Human myeloperoxidase (hMPO) is expressed in neurons in the substantia nigra in Parkinson's disease and in the hMPO-α-synuclein-A53T mouse model, correlating with increased nitration and aggregation of α-synuclein and exacerbation of motor impairment

α-Synuclein (αSyn) is central to the neuropathology of Parkinson's disease (PD) due to its propensity for misfolding and aggregation into neurotoxic oligomers. Nitration/oxidation of αSyn leads to dityrosine crosslinking and aggregation. Myeloperoxidase (MPO) is an oxidant-generating enzyme implicated in neurodegenerative diseases. In the present work we have examined the impact of MPO in PD through analysis of postmortem PD brain and in a novel animal model in which we crossed a transgenic mouse expressing the human MPO (hMPO) gene to a mouse expressing human αSyn-A53T mutant (A53T) (hMPO-A53T). Surprisingly, our results show that in PD substantia nigra, the hMPO gene is expressed in neurons containing aggregates of nitrated αSyn as well as MPO-generated HOCl-modified epitopes. In our hMPO-A53T mouse model, we also saw hMPO expression in neurons but not mouse MPO. In the mouse model, hMPO was expressed in neurons colocalizing with nitrated αSyn, carbamylated lysine, nitrotyrosine, as well as HOCl-modified epitopes/proteins. RNAscope in situ hybridization confirmed hMPO mRNA expression in neurons. Interestingly, the hMPO protein expressed in hMPO-A53T brain is primarily the precursor proMPO, which enters the secretory pathway potentially resulting in interneuronal transmission of MPO and oxidative species. Importantly, the hMPO-A53T mouse model, when compared to the A53T model, exhibited significant exacerbation of motor impairment on rotating rods, balance beams, and wire hang tests. Further, hMPO expression in the A53T model resulted in earlier onset of end stage paralysis. Interestingly, there was a high concentration of αSyn aggregates in the stratum lacunosum moleculare of hippocampal CA2 region, which has been associated in humans with accumulation of αSyn pathology and neural atrophy in dementia with Lewy bodies. This accumulation of αSyn aggregates in CA2 was associated with markers of endoplasmic reticulum (ER) stress and the unfolded protein response with expression of activating transcription factor 4 (ATF4), C/EBP homologous protein (CHOP), MPO, and cleaved caspase-3. Together these findings suggest that MPO plays an important role in nitrative and oxidative damage that contributes to αSyn pathology in synucleinopathies.

Oxidative stress in chronic kidney disease

Oxidative stress (OS), defined as disturbances in the pro-/antioxidant balance, is harmful to cells due to the excessive generation of highly reactive oxygen (ROS) and nitrogen (RNS) species. When the balance is not disturbed, OS has a role in physiological adaptations and signal transduction. However, an excessive amount of ROS and RNS results in the oxidation of biological molecules such as lipids, proteins, and DNA. Oxidative stress has been reported in kidney disease, due to both antioxidant depletions as well as increased ROS production. The kidney is a highly metabolic organ, rich in oxidation reactions in mitochondria, which makes it vulnerable to damage caused by OS, and several studies have shown that OS can accelerate kidney disease progression. Also, in patients at advanced stages of chronic kidney disease (CKD), increased OS is associated with complications such as hypertension, atherosclerosis, inflammation, and anemia. In this review, we aim to describe OS and its influence on CKD progression and its complications. We also discuss the potential role of various antioxidants and pharmacological agents, which may represent potential therapeutic targets to reduce OS in both pediatric and adult CKD patients.

Association of monocyte myeloperoxidase with incident cardiovascular disease: The Atherosclerosis Risk in Communities Study

Myeloperoxidase (MPO) is a heme-containing peroxidase found in azurophilic granules of neutrophils and monocytes. Epidemiological studies have reported greater plasma MPO concentration to be associated with increased incidence of several cardiovascular diseases (CVD), but the association of intracellular monocyte MPO (mMPO) with CVD is unclear. The prospective population-based Atherosclerosis Risk in Communities (ARIC) cohort study measured mMPO using flow cytometry in 1,465 participants. The association of mMPO with incident cardiovascular disease (CVD, comprising incident coronary heart disease (CHD), heart failure, stroke, peripheral artery disease, and cardiovascular mortality) was examined over a median 9.6 years of follow-up (n = 290 CVD events). There was no statistically significant association between mMPO and all incident CVD events in either age, sex, and race-adjusted proportional hazards models (HR (95% CI) across tertiles of mMPO: 1, 1.09 (0.76, 1.57), and 0.78 (0.52, 1.15), P-trend = 0.21) or adjusted for other major CVD risk factors (HR (95% CI): 1, 1.17 (0.81, 1.69), and 0.87 (0.58, 1.29), P-trend = 0.50). There also was no association between mMPO tertiles and incident CHD, heart failure, or all-cause mortality, examined separately. In conclusion, intracellular monocyte myeloperoxidase was not associated with incident cardiovascular disease in this prospective population-based study.

Association between MPO-463G > A polymorphism and chronic kidney disease: a meta-analysis

BACKGROUND/OBJECTIVE

Previous studies have shown that MPO -463G > A (rs2333227) might be associated with chronic kidney disease (CKD) susceptibility, but sample sizes of those studies are relatively small. Hence, we decided to perform a meta-analysis to evaluate the association. Methods/main results: Two investigators search databases systematically and independently. Odds ratios and 95% confidence intervals were used to pool the effect size. Four articles with 618 cases and 932 controls in total were included in our meta-analysis.

CONCLUSIONS

MPO -463G > A was not associated with CKD susceptibility in recessive model and homozygote comparison. MPO -463G > A was associated with increased risk of CKD in allelic comparison, heterozygote comparison and dominant model, however, the results lacked stability. Owing to insufficient data, the association between MPO -463G > A and CKD cannot be fully confirmed.

Myeloperoxidase-derived oxidants damage artery wall proteins in an animal model of chronic kidney disease-accelerated atherosclerosis

Increased myeloperoxidase (MPO) levels and activity are associated with increased cardiovascular risk among individuals with chronic kidney disease (CKD). However, a lack of good animal models for examining the presence and catalytic activity of MPO in vascular lesions has impeded mechanistic studies into CKD-associated cardiovascular diseases. Here, we show for the first time that exaggerated atherosclerosis in a pathophysiologically relevant CKD mouse model is associated with increased macrophage-derived MPO activity. Male 7-week-old LDL receptor-deficient mice underwent sham (control mice) or 5/6 nephrectomy and were fed either a low-fat or high-fat, high-cholesterol diet for 24 weeks, and the extents of atherosclerosis and vascular reactivity were assessed. MPO expression and oxidation products-protein-bound oxidized tyrosine moieties 3-chlorotyrosine, 3-nitrotyrosine, and o,o'-dityrosine-were examined with immunoassays and confirmed with mass spectrometry (MS). As anticipated, the CKD mice had significantly higher plasma creatinine, urea nitrogen, and intact parathyroid hormone along with lower hematocrit and body weight. On both the diet regimens, CKD mice did not have hypertension but had lower cholesterol and triglyceride levels than the control mice. Despite the lower cholesterol levels, CKD mice had increased aortic plaque areas, fibrosis, and luminal narrowing. They also exhibited increased MPO expression and activity (i.e. increased oxidized tyrosines) that co-localized with infiltrating lesional macrophages and diminished vascular reactivity. In summary, unlike non-CKD mouse models of atherosclerosis, CKD mice exhibit increased MPO expression and catalytic activity in atherosclerotic lesions, which co-localize with lesional macrophages. These results implicate macrophage-derived MPO in CKD-accelerated atherosclerosis.

Effects of MPO-463G/A and -129G/A polymorphisms on coronary artery disease risk and patient survival in a Turkish population

Myeloperoxidase (MPO) is an oxidative hemoprotein compound expressed in polymorphonuclear leukocytes that contributes to inflammatory responses. Coronary artery disease (CAD), as the most prevalent form of heart disease, is considered to originate from an interaction between genetic and environmental factors. In the present study, the potential associations between MPO-463G/A and -129G/A polymorphisms with CAD were investigated in a Turkish population using a polymerase chain reaction-based restriction fragment length polymorphism (RFLP) assay technique. To the best of our knowledge, the study was the first to examine the association of MPO-463G/A and -129G/A with patient survival rate in a Turkish population. The study population consisted of 201 patients with CAD and 201 healthy controls. The results indicated that there was a significant association of the GA genotype of MPO-463G/A with the case population (P=0.048). Meanwhile, in the patients with CAD, the frequency distributions of the MPO-129A allele (P=0.006) and GA genotype (P=0.001) were significantly increased compared with the G allele and GG genotype, respectively, in CAD patients. Additionally, compared with the GG genotype, the frequency distribution of MPO-129A was significantly increased in the patient group regarding smoking status (P=0.001) and the presence of hypercholesterolemia (P=0.028). However, survival analysis did not detect an effect of either polymorphism on the survival rate of the CAD patients (P>0.05). Therefore, the MPO-129GA genotype may be a significant risk factor for the development of CAD.

Oxidative Stress in Hemodialysis Patients: A Review of the Literature

Hemodialysis (HD) patients are at high risk for all-cause mortality and cardiovascular events. In addition to traditional risk factors, excessive oxidative stress (OS) and chronic inflammation emerge as novel and major contributors to accelerated atherosclerosis and elevated mortality. OS is defined as the imbalance between antioxidant defense mechanisms and oxidant products, the latter overwhelming the former. OS appears in early stages of chronic kidney disease (CKD), advances along with worsening of renal failure, and is further exacerbated by the HD process per se. HD patients manifest excessive OS status due to retention of a plethora of toxins, subsidized under uremia, nutrition lacking antioxidants and turn-over of antioxidants, loss of antioxidants during renal replacement therapy, and leukocyte activation that leads to accumulation of oxidative products. Duration of dialysis therapy, iron infusion, anemia, presence of central venous catheter, and bioincompatible dialyzers are several factors triggering the development of OS. Antioxidant supplementation may take an overall protective role, even at early stages of CKD, to halt the deterioration of kidney function and antagonize systemic inflammation. Unfortunately, clinical studies have not yielded unequivocal positive outcomes when antioxidants have been administered to hemodialysis patients, likely due to their heterogeneous clinical conditions and underlying risk profile.

Role of Myeloperoxidase in Patients with Chronic Kidney Disease

Chronic kidney disease (CKD) is a worldwide public health problem. Patients with CKD have a number of disorders in the organism, and the presence of oxidative stress and systemic inflammation in these patients is the subject of numerous studies. Chronic inflammation joined with oxidative stress contributes to the development of numerous complications: accelerated atherosclerosis process and cardiovascular disease, emergence of Type 2 diabetes mellitus, development of malnutrition, anaemia, hyperparathyroidism, and so forth, affecting the prognosis and quality of life of patients with CKD. In this review we presented the potential role of the myeloperoxidase enzyme in the production of reactive/chlorinating intermediates and their role in oxidative damage to biomolecules in the body of patients with chronic kidney disease and end-stage renal disease. In addition, we discussed the role of modified lipoprotein particles under the influence of prooxidant MPO intermediates in the development of endothelial changes and cardiovascular complications in renal failure.

Myeloperoxidase genetic polymorphisms and susceptibility to Kawasaki disease in Taiwanese children

BACKGROUND/PURPOSE

The aim of this study was to investigate the myeloperoxidase (MPO) -463G>A polymorphism in Kawasaki disease (KD) patients, and the relationship between gene polymorphism and MPO levels.

METHODS

A total of 334 KD children and 492 sex-matched controls were assayed for polymorphism analysis. TaqMan assays were used for genotyping. MPO was measured in 37 KD patients and 42 febrile controls.

RESULTS

A significant linear trend of KD risk was found to be related to the G/G genotype (p_{linear trend} = 0.032). The combined genotypes (G/A and A/A) of MPO -463G>A were associated with a significantly decreased KD risk compared to the G/G genotype [adjusted odds ratios (AOR) = 0.71, 95% confidence interval (CI): 0.52-0.99, p = 0.040]. In addition, KD patients with A allele were associated with a significantly decreased KD risk as compared to those with G allele (AOR = 0.73, 95% CI: 0.54-0.98, p = 0.033). MPO levels were significantly elevated in KD patients in preintravenous immunoglobulin (pre-IVIG) stage compared to febrile controls (p = 0.002). KD patients in pre-IVIG stage had significantly higher MPO levels than febrile controls in terms of G/G genotype (p = 0.003) and G allele (p < 0.001). KD patients with A allele had significantly lower MPO levels than those with G allele in post-IVIG acute stage (p = 0.042). However, there was no significant difference of individual MPO change for KD patients from pre- to post-IVIG stage in terms of genotypes (p = 0.837) or alleles (p = 0.631).

CONCLUSION

Our results suggest that G allele of MPO -463G>A polymorphism is a potential genetic marker for KD risk in Taiwanese children.

Wishful Thinking: The Surprisingly Sparse Evidence for a Relationship between Oxidative Stress and Cardiovascular Disease in Hemodialysis Patients

The increased frequency of cardiovascular disease observed in hemodialysis patients is secondary to the combination of many traditional (age, male sex, hypertension, smoking, diabetes mellitus, and dyslipidemia) and novel and uremia-related (inflammation, uremic toxins, adipokine imbalance, coagulation disorders, protein-energy wasting, volume overload, endothelial dysfunction, hyperparathyroidism, and subclinical hypothyroidism) risk factors. Usually, in the latter group, oxidative stress is included. However, after decades of research, it remains essentially unknown if oxidative stress has a causative role in the development of cardiovascular disease in long-term hemodialysis patients because adequate longitudinal studies are lacking. Data deriving from cross-sectional studies suggest that biomarkers of oxidative stress are associated with cardiovascular disease prevalence. Conversely, conflicting and inconclusive results have been obtained on the association between oxidative stress and coronary artery calcification, atherosclerosis, and all-cause and cardiovascular disease-related outcome. It is desirable that further studies are conducted on this topic in the near future.

Niacin decreases leukocyte myeloperoxidase: mechanistic role of redox agents and Src/p38MAP kinase

OBJECTIVES

Leukocyte myeloperoxidase (MPO) is a major player in the pathogenesis of various chronic diseases including atherosclerosis. This study proposes the novel concept that niacin, through reactive oxygen species (ROS)-mediated signaling, decreases neutrophil MPO release and its activity, protects apolipoprotein-AI (apo-AI) modification and improves HDL function.

METHODS

Human blood leukocytes and leukocytic cell line HL-60 cells were treated with niacin, and stimulated with phorbol myristate acetate (PMA). Cellular and released MPO activity in the medium was measured by assessing chlorination of MPO-specific substrate. MPO protein release in the medium and apo-AI degradation was measured by Western blot analysis. Monocyte adhesion to human aortic primary endothelial cells was measured to assess biological function of HDL/apo-AI.

RESULTS

PMA significantly increased leukocyte MPO activity in both intracellular extract and medium. Niacin (0.25-0.5 mM) decreased PMA-induced MPO activity (cellular and released in the media). Niacin also decreased MPO protein mass in the medium without affecting its mRNA expression. Increased NADPH oxidase and ROS production by PMA were also significantly inhibited by niacin. Studies with specific inhibitors suggest that ROS-dependent Src and p38MAP kinase mediate decreased MPO activity by niacin. Niacin blocked apo-AI degradation, and apo-AI from niacin treated cells decreased monocyte adhesion to aortic endothelial cells.

CONCLUSIONS

These findings identify niacin as a potent inhibitor of leukocyte MPO release and MPO-mediated formation of dysfunctional HDL. Niacin and niacin-related chemical entities may form important therapeutic agents for MPO-mediated inflammatory diseases.

Association of myeloperoxidase with total and cardiovascular mortality in individuals undergoing coronary angiography--the LURIC study

Background

The phagocytic enzyme myeloperoxidase (MPO) acts as a front-line defender against microorganisms. However, increased MPO levels have been found to be associated with complex and calcified atherosclerotic lesions and incident cardiovascular disease. Therefore, this study aimed to investigate a predictive role of MPO, a biomarker of inflammation and oxidative stress, for total and cardiovascular mortality in patients referred to coronary angiography.

Methods and results

MPO plasma concentrations along with eight MPO polymorphisms were determined in 3036 participants of the Ludwigshafen Risk and Cardiovascular Health study (median follow-up 7.75 years). MPO concentrations were positively associated with age, diabetes, smoking, markers of systemic inflammation (interleukin-6, fibrinogen, C-reactive protein, serum amyloid A) and vascular damage (vascular cellular adhesion molecule-1 and intercellular adhesion molecule-1) but negatively associated with HDL-cholesterol and apolipoprotein A-I. After adjustment for cardiovascular risk factors MPO concentrations in the highest versus the lowest quartile were associated with a 1.34-fold risk (95% CI: 1.09–1.67) for total mortality. In the adjusted model the hazard ratio for cardiovascular mortality in the highest MPO quartile was 1.42 (95% CI: 1.07–1.88). Five MPO polymorphisms were positively associated with MPO concentrations but not with mortality. Using Mendelian randomization, we did not obtain evidence for a causal association of MPO with either total or cardiovascular mortality.

Conclusions

MPO concentrations but not genetic variants at the MPO locus are independently associated with risk for total and cardiovascular mortality in coronary artery disease patients.

Molecular imaging of macrophage enzyme activity in cardiac inflammation

Molecular imaging is highly advantageous as various insidious inflammatory events can be imaged in a serial and quantitative fashion. Combined with the conventional imaging modalities like computed tomography (CT), magnetic resonance (MR) and nuclear imaging, it helps us resolve the extent of ongoing pathology, quantify inflammation and predict outcome. Macrophages are increasingly gaining importance as an imaging biomarker in inflammatory cardiovascular diseases. Macrophages, recruited to the site of injury, internalize necrotic or foreign material. Along with phagocytosis, activated macrophages release proteolytic enzymes like matrix metalloproteinases (MMPs) and cathepsins into the extracellular environment. Pro-inflammatory monocytes and macrophages also induce tissue oxidative damage through the inflammatory enzyme myeloperoxidase (MPO). In this review we will highlight recent advances in molecular macrophage imaging. Particular stress will be given to macrophage functional and enzymatic activity imaging which targets phagocytosis, proteolysis and myeloperoxidase activity imaging.

Myeloperoxidase activity and its corresponding mRNA expression as well as gene polymorphism in the population living in the coal-burning endemic fluorosis area in Guizhou of China

The myeloperoxidase (MPO) activity and its corresponding mRNA expression as well as gene polymorphism were investigated in the population who live in the endemic fluorosis area. In the study, 150 people were selected from the coal-burning endemic fluorosis area and 150 normal persons from the non-fluorosis area in Guizhou province of China. The blood samples were collected from these people. The activity of MPO in the plasma was determined by spectrophotometer; the expression of MPO mRNA was measured by employing real-time polymerase chain reaction; DNAs were extracted from the leucocytes in blood and five SNP genotypes of MPO promoter gene detected by a multiplex genotyping method, adapter-ligation-mediated allele-specific amplification. The results showed that the MPO activity and its corresponding mRNA in blood were significantly increased in the population living in the area of fluorosis. The different genotype frequencies of MPO, including -1228G/A, -585T/C, -463G/A, and -163C/T, and the three haplotypes with higher frequencies, including -163C-463G-585T-1228G-1276T, -163C-463G-585T-1228G-1276C, and -163C-463G-585T-1228A-1276T, were significantly associated with fluorosis. The results indicated that the elevated activity of MPO induced by endemic fluorosis may be connected in mechanism to the stimulated expression of MPO mRNA and the changed gene polymorphism.

Polymorphisms in the myeloperoxidase gene locus are associated with acute kidney injury-related outcomes

Myeloperoxidase (MPO) is a lysosomal enzyme that may be involved in oxidative stress-mediated kidney injury. Using a 2-step approach, we measured the association of 4 polymorphisms across the length of the MPO gene with systemic markers of oxidative stress; plasma MPO and urinary 15-F_2t-isoprostane levels. Adverse outcomes were measured in a primary cohort of 262 adults hospitalized with acute kidney injury, and a secondary cohort of 277 adults undergoing cardiac surgery with cardiopulmonary bypass and at-risk for postoperative acute kidney injury. Dominant and haplotype multivariable logistic regression analyses found a genotype-phenotype association in the primary cohort between rs2243828, rs7208693, rs2071409, and rs2759 MPO polymorphisms and both markers of oxidative stress. In adjusted analyses, all 4 polymorphic allele groups had 2-3-fold higher odds for composite outcomes of dialysis or in-hospital death or a composite of dialysis, assisted mechanical ventilation or inhospital death. The MPO T-G-A-T haplotype copy-number was associated with lower plasma MPO levels and lower adjusted odds for the composite outcomes. Significant but less consistent associations were found in the secondary cohort. In summary, our 2-step genetic association study identified several polymorphisms spanning the entire MPO gene locus and a common haplotype marker for patients at-risk for acute kidney injury.

Oxidative balance and colon and rectal cancer: interaction of lifestyle factors and genes

Pro-oxidant and anti-oxidant genetic and lifestyle factors can contribute to an individual's level of oxidative stress. We hypothesize that diet, lifestyle and genetic factors work together to influence colon and rectal cancer through an oxidative balance mechanism. We evaluated nine markers for eosinophil peroxidase (EPX), two for myeloperoxidase (MPO), four for hypoxia-inducible factor-1A (HIFIA), and 16 for inducible nitric oxide synthase (NOS2A) in conjunction with dietary antioxidants, aspirin/NSAID use, and cigarette smoking. We used data from population-based case-control studies (colon cancer n=1555 cases, 1956 controls; rectal cancer n=754 cases, 959 controls). Only NOS2A rs2297518 was associated with colon cancer (OR 0.86 95% CI 0.74, 0.99) and EPX rs2302313 and MPO rs2243828 were associated with rectal cancer (OR 0.75 95% CI 0.59, 0.96; OR 0.81 95% CI 0.67, 0.99 respectively) for main effects. However, after adjustment for multiple comparisons we observed the following significant interactions for colon cancer: NOS2A and lutein, EPX and aspirin/NSAID use, and NOS2A (4 SNPs) and cigarette smoking. For rectal cancer we observed the following interactions after adjustment for multiple comparisons: HIF1A and vitamin E, NOS2A (3SNPs) with calcium; MPO with lutein; HIF1A with lycopene; NOS2A with selenium; EPX and NOS2A with aspirin/NSAID use; HIF1A, MPO, and NOS2A (3 SNPs) with cigarette smoking. We observed significant interaction between a composite oxidative balance score and a polygenic model for both colon (p interaction 0.0008) and rectal cancer (p=0.0018). These results suggest the need to comprehensively evaluate interactions to assess the contribution of risk from both environmental and genetic factors.

Risk prediction with serial myeloperoxidase monitoring in patients with acute chest pain

BACKGROUND

Although myeloperoxidase (MPO) monitoring is predictive for cardiovascular outcomes in suspected acute coronary syndromes, the value of serial testing is unknown.

METHODS

We investigated the relationship between serial MPO concentrations in 490 individuals with acute chest pain and incident major adverse cardiac events (MACE) during 6 months of follow-up. We measured MPO with the CardioMPO assay, and cardiac troponin I (cTnI), with the Abbott Architect assay.

RESULTS

Plasma MPO concentrations during the first 16 h were higher in individuals who experienced MACE. Higher MPO quartiles predicted a greater likelihood of 6-month MACE at baseline [OR (95% CI), 2.4 (1.4-4.1), P = 0.001 for highest vs lowest quartile] and all subsequent time points, with strongest predictive ability found in 16-h postbaseline samples [9.9 (4.7-20.9), P < 0.001 for highest vs lowest quartile]. MPO was predictive for MACE among individuals whose cTnI remained within reference intervals (<0.028 μg/L). The lowest rate of missed cases was found when MPO was <640 pmol/L at baseline and all other time points. Serial MPO monitoring predicted MACE risk better than baseline MPO measurements alone (c statistic 0.813 vs 0.602; P = 0.002), including in individuals whose cTnI remained within reference intervals (c statistic 0.903; P = 0.009). Combined serial cTnI and MPO testing improved accuracy for predicting 6-month MACE, reduced the number of missed MACE events from cTnI testing alone, and improved risk classification in 26.1% of patients.

CONCLUSIONS

MPO concentrations are predictive of outcome up to 16 h after presentation with chest pain and predict events missed by cTnI testing, supporting a potential role in rapid patient triage.

Myeloperoxidase modulation by LDL apheresis in familial hypercholesterolemia

BACKGROUND

Myeloperoxidase (MPO) is a marker of plaque vulnerability and a mechanistic bridge between inflammation and cardiovascular disease, and thus is a suitable target for therapeutic strategy against cardiovascular disease.

METHODS

Since hypercholesterolemia is associated with atherosclerosis and inflammation, we tested whether MPO serum levels were up-regulated in Familial Hypercholesterolemia (FH) and whether acute reduction of total cholesterol (TC) would also reduce MPO concentration. FH subjects undergoing LDL-apheresis (LDL-A) treatment are a paradigmatic clinical model where TC rapidly plunges from extremely high to extremely low levels after selective LDL removal, and then spontaneously rebounds to baseline conditions. This clinical setting allows multiple intra-patient observations at different plasma TC concentrations. We measured MPO levels in serum by ELISA tests, and in peripheral leukocytes by immunofluorescence, to learn whether they were affected by the changes in TC levels. Serum MPO was measured before and serially up to the 14th day following LDL-A.

RESULTS

In both serum and peripheral leukocytes, MPO concentrations were i) higher than in sex- and age-matched healthy controls (p < 0.01); ii) decreased with TC reduction; iii) parallel with TC time course; iv) correlated with plasma TC. At regression analysis, plasma TC was the only variable considered that influenced MPO serum levels (β 0.022 ± 0.010, p < 0.0001).

CONCLUSIONS

In FH the MPO serum levels were modulated through changes in the TC concentrations carried out by LDL-A. Further study is needed to determine whether reduced MPO levels obtained by LDL-A could have any therapeutic impact.

Atherosclerosis in chronic kidney disease: the role of macrophages

Patients with chronic kidney disease (CKD) are at increased risk of atherosclerotic cardiovascular disease and loss of renal parenchyma accelerates atherosclerosis in animal models. Macrophages are central to atherogenesis because they regulate cholesterol traffic and inflammation in the arterial wall. CKD influences macrophage behavior at multiple levels, rendering them proatherogenic. Even at normal creatinine levels, macrophages from uninephrectomized Apoe(-/-) mice are enriched in cholesterol owing to downregulation of cholesterol transporter ATP-binding cassette subfamily A member 1 levels and activation of nuclear factor κB, which leads to impaired cholesterol efflux. Interestingly, treatment with an angiotensin-II-receptor blocker (ARB) improves these effects. Moreover, atherosclerotic aortas from Apoe(-/-) mice transplanted into renal-ablated normocholesterolemic recipients show plaque progression and increased macrophage content instead of the substantial regression seen in recipient mice with intact kidneys. ARBs reduce atherosclerosis development in mice with partial renal ablation. These results, combined with the clinical benefits of angiotensin-converting-enzyme (ACE) inhibitors and ARBs in patients with CKD, suggest an important role for the angiotensin system in the enhanced susceptibility to atherosclerosis seen across the spectrum of CKD. The role of macrophages could explain why these therapies may be effective in end-stage renal disease, one of the few conditions in which statins show no clinical benefit.

Effect of blood sample type on the measurement of advanced oxidation protein products as a biomarker of inflammation and oxidative stress in hemodialysis patients

Advanced oxidation protein products (AOPP) is widely used as a uremic biomarker, especially for cardiovascular disease. However, it has not been determined whether it is better to measure AOPP in plasma or serum. In this cross-sectional study, which included 102 patients undergoing maintenance hemodialysis, fibrinogen-free serum and defibrinated plasma samples were prepared. AOPP levels from fibrinogen-free samples displayed a stronger correlation with myeloperoxidase activity and levels of C-reactive protein, interleukin-6 and tumor necrosis factor-alpha, as well as prevalent cardiovascular disease, than AOPP levels obtained from plasma samples. These results demonstrated that fibrinogen interferes with the measurement of AOPP.

Lipid oxidation by hypochlorous acid: chlorinated lipids in atherosclerosis and myocardial ischemia

Leukocytes, containing myeloperoxidase (MPO), produce the reactive chlorinating species, HOCl, and they have important roles in the pathophysiology of cardiovascular disease. Leukocyte-derived HOCl can target primary amines, alkenes and vinyl ethers of lipids, resulting in chlorinated products. Plasmalogens are vinyl ether-containing phospholipids that are abundant in tissues of the cardiovascular system. The HOCl oxidation products derived from plasmalogens are α-chlorofatty aldehyde and unsaturated molecular species of lysophosphatidylcholine. α-chlorofatty aldehyde is the precursor of both α-chlorofatty alcohol and α-chlorofatty acid. Both α-chlorofatty aldehyde and α-chlorofatty acid accumulate in activated neutrophils and have disparate chemotactic properties. In addition, α-chlorofatty aldehyde increases in activated monocytes, human atherosclerotic lesions and rat infarcted myocardium. This article addresses the pathways for the synthesis of these lipids and their biological targets.

Inflammation as a cause of malnutrition, atherosclerotic cardiovascular disease, and poor outcome in hemodialysis patients

Cardiovascular disease (CVD) remains the major cause of morbidity and mortality in end-stage renal disease (ESRD) patients treated by hemodialysis (HD). Although traditional risk factors are common in dialysis patients, they may not alone be sufficient to account for the unacceptable high prevalence of CVD in this patient group. Recent evidence demonstrates that chronic inflammation, a nontraditional risk factor that is commonly observed in HD patients, may cause malnutrition and progressive atherosclerotic CVD by several pathogenetic mechanisms. The cause(s) of inflammation in HD patients is multifactorial and includes both dialysis-related (such as graft and fistula infections, bioincompatibility, impure dialysate, and back-filtration) and dialysis-unrelated factors. Although inflammation may reflect underlying CVD, an acute-phase reaction may also be a direct cause of vascular injury. Available data suggest that proinflammatory cytokines play a central role in the genesis of both malnutrition and CVD in ESRD. Thus, it could be speculated that suppression of the vicious cycle of malnutrition, inflammation, and atherosclerosis (MIA syndrome) would improve survival in dialysis patients. As there is not yet any recognized, or even proposed, targeted treatment for ESRD patients with chronic inflammation; it would be of considerable interest to study the long-term effect of various anti-inflammatory treatment strategies on nutritional and cardiovascular status as well as outcome in these patients.

Relation of myeloperoxidase promoter polymorphism and long‐term hormone replacement therapy to oxidized low‐density lipoprotein autoantibodies in postmenopausal women

OBJECTIVE

The myeloperoxidase enzyme (MPO) is a potent precursor of low-density lipoprotein (LDL) oxidation in atherosclerotic lesions. The MPO gene has a promoter polymorphism, 463G/A, which leads to high (GG) and low-expression (AG, AA) genotypes. Hormone replacement therapy (HRT) is known to affect MPO activity and LDL oxidation. The purpose of this study was to test whether the effect of HRT on the levels of oxLDL-ab varies according to MPO genotype.

MATERIAL AND METHODS

Eighty-seven postmenopausal women aged 45-71 years were divided into three groups based on the use of HRT. The HRT-EVP group (n = 25) used sequential estradiol valerate (EV) plus progestin, the HRT-EV group (n = 32) used EV alone, and the control group (n = 30) no HRT. MPO genotypes were determined by polymerase chain reaction (PCR) and oxLDL-ab by ELISA.

RESULTS

We found a significant HRT group by MPO genotype interaction (p = 0.021) in plasma oxLDL-ab levels. In subjects with the GG genotype, the oxLDL-ab titer increased in the order of 2.13 in controls, 2.53 in the EV group and 3.21 in the EVP group (ANOVA for trend p = 0.006).

CONCLUSIONS

The effects of HRT on LDL oxidation can vary according to MPO genotype and the concurrent progestin therapy with EV may counteract the more neutral effect of EV on LDL oxidation in subjects with the MPO high-expression genotype.

Partial characterization of feline myeloperoxidase and investigation of its potential role as an autoantigen in hyperthyroid cats

OBJECTIVE

To partially characterize the cDNA, amino acid sequence, and tertiary structure of feline myeloperoxidase, describe its cellular location in mature granulocytes, and determine whether hyperthyroid cats have anti-myeloperoxidase antibody.

SAMPLE POPULATION

Bone marrow RNA and whole blood from cats of various sources and feline serum samples submitted for measurement of total thyroxine concentration from September 2006 to July 2007.

PROCEDURES

Feline myeloperoxidase cDNA was amplified from bone marrow RNA; presumptive splice sites were determined by comparison with human sequences. Intracellular localization of myeloperoxidase in granulocytes was determined by use of immunofluorescence and electron microscopy, and molecular weight and partial tertiary structure were determined by use of immunoblotting of granulocyte lysates. Anti-human myeloperoxidase (hMPO) antibody was detected via ELISA.

RESULTS

A 2,493-bp sequence encompassing the 2,160-bp cDNA with presumably the same number and size of exons as hMPO was generated. Translation predicted 85% homology with hMPO. Feline myeloperoxidase was localized to neutrophil primary granules, and immunoblotting revealed heavy and light bands with molecular weights similar to those of hMPO. The prevalence of anti-hMPO antibody did not differ between nonhyperthyroid and hyperthyroid cats or among hyperthyroid cats subclassified by treatment modality.

CONCLUSIONS AND CLINICAL RELEVANCE

Moderate homology existed between feline myeloperoxidase and hMPO cDNA and protein. Although findings suggested a similar tertiary structure and function for the 2 proteins, they also suggested that inability to detect a high prevalence of anti-hMPO antibody in hyperthyroid cats may be attributable to antigenic differences between the human and feline proteins rather than a lack of autoantibody.

Understanding the role of genetic polymorphisms in chronic kidney disease

Although no valid studies clearly indicate increasing or decreasing numbers of incident paediatric patients, the prevalence of chronic kidney disease (CKD) and end-stage renal disease (ESRD) is growing worldwide. This is mainly due to improved access to renal replacement therapy (RRT), increased survival after dialysis and kidney transplantation and an increase in diagnosis and referral of these patients. Although the increase in CKD prevalence is mainly caused by environmental factors, genetic factors may also influence the incidence and/or the progression of CKD and its complications. As CKD patients might be more sensitive to genetic effects due to the exposure to a uraemic milieu, this makes studies of genetic factors especially interesting in this population. The goal of identifying genetic factors that contribute to the outcome of CKD is to gain further understanding of the disease pathogenesis and underlying causes and, possibly, to use this knowledge to predict disease or its complications and to identify a risk population. Therefore, genetic screening of paediatric CKD patients may enhance the impact of preventive measures that could have a positive effect on outcome. Furthermore, by identifying patients' genetic backgrounds, it is possible that a more individualised therapy could be designed.

Association of major depressive disorder with serum myeloperoxidase and other markers of inflammation: a twin study

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)-alpha, the TNF-alpha 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.

Primed polymorphonuclear leukocytes constitute a possible link between inflammation and oxidative stress in hyperlipidemic patients

BACKGROUND

Oxidative stress (OS) and chronic inflammation are involved and contribute to the development of atherosclerosis. Primed polymorphonuclear leukocytes (PMNLs) are a possible source for superoxide radicals and inflammatory mediators, hence can promote OS and inflammation. The involvement of primed PMNLs in clinical states associated with high risk for developing cardiovascular disease and atherosclerosis, such as hypertension, renal failure and diabetes has been described, however, little is known about PMNLs characteristics in hyperlipidemic patients.

METHODS

Hyperlipidemic patients and healthy control (HC) subjects were enrolled in this cross-sectional study. PMNL priming was estimated by measuring the rate of superoxide release and by levels of membrane CD11b. PMNL priming and myeloperoxidase (MPO) levels served as OS indices. Inflammation was linked to peripheral white blood cells and PMNL counts and to apoptosis. Systemic inflammation was estimated by blood levels of fibrinogen, C-reactive protein (CRP), transferrin and albumin. PMNL priming and inflammation parameters were related to the severity of hyperlipidemia.

RESULTS

PMNLs from hyperlipidemic patients are primed compared to HC. A decrease in PMNL-MPO levels with increased levels of serum MPO were found in hyperlipidemic patients. Leukocyte counts tended to be higher in hyperlipidemic patients with increased PMNL apoptosis. PMNL priming and fibrinogen levels correlated positively with the severity of hyperlipidemia (r=0.32, P=0.02 for CD11b vs. cholesterol and r=0.38, P=0.009 for CD11b vs. LDL-c; r=0.35, P=0.01 for fibrinogen vs. cholesterol and r=0.3, P=0.03 for superoxide release vs. LDL-c).

CONCLUSION

PMNLs are primed in hyperlipidemic patients contributing to OS and inflammation in these patients. This study highlights primed PMNLs as an additional risk factor for promoting atherosclerosis in hyperlipidemic patients.

-463 G/A myeloperoxidase promoter polymorphism in giant cell arteritis

OBJECTIVE

To investigate potential associations between-463 G/A myeloperoxidase (MPO) promoter polymorphism and susceptibility to, and clinical features of giant cell arteritis (GCA).

METHODS

A total of 156 patients with biopsy-proven GCA who were residents of Reggio Emilia, Italy, and 235 population-based controls from the same geographic area were genotyped for-463 G/A promoter polymorphism of the MPO gene by molecular methods. The patients were subgrouped according to the presence or absence of polymyalgia rheumatica and severe ischaemic complications (visual loss and/or cerebrovascular accidents).

RESULTS

The distribution of the MPO-G/A genotype differed significantly between patients with GCA and the controls (p(corr) = 0.003). Allele G was significantly more frequent in patients with GCA than in the controls (p(corr) = 0.0002, OR 2.0, 95% CI 1.4 to 2.9). Homozygosity for the G allele was significantly more frequent in patients with GCA than in controls (p(corr) = 0.0002, OR 2.2, 95% CI 1.4 to 3.4). No significant associations were found when patients with GCA with and without polymyalgia rheumatica or with and without severe ischaemic complications were compared.

CONCLUSIONS

Our findings show that the-463 G/A promoter polymorphism of the MPO gene is associated with GCA susceptibility and support a role for MPO in the pathophysiology of GCA.

Applying Translational Research in Understanding Complications and Defining Targets for Intervention: Inflammation in PD as a Model

The bench-to-bedside approach to translational research is becoming increasingly important to efficiently advance understanding of the mechanisms underlying disease and to improve the quality of patient care. Although this investigation model has been practiced since the early days of the therapy, robust research platforms built to practice translational research have only recently been structured in the field of peritoneal dialysis. Experience with a translational research environment that generated most of the information cited in this overview is the core of this manuscript. The central investigation theme described is how to approach the cardiovascular complications of peritoneal dialysis. The research question was, could the continuous activation of inflammatory pathways be central in this process and represent a relevant target for interventions?

The association of myeloperoxidase promoter polymorphism with carotid atherosclerosis is abolished in patients with type 2 diabetes

OBJECTIVES

Type 2 diabetes mellitus (DM) enhances the development of atherosclerosis and reduces the activity of the oxidative myeloperoxidase (MPO) enzyme. MPO gene has a functional promoter polymorphism -463G/A which leads to high- (GG) and low-expression (AG, AA) genotypes.

DESIGN AND METHODS

We studied the association of MPO polymorphism with carotid artery intima-media thickness (IMT) in 198 randomly selected Finnish men of Caucasian origin, 161 non-diabetics and 37 with type 2 DM. Their carotid IMT was measured by high-resolution ultrasonography, and the overall mean IMT value was calculated. MPO genotypes were determined by the PCR-RFLP method.

RESULTS

We found significant MPO genotype-by-study-group (control/DM) interactions with the overall mean IMT and internal carotid IMT (p=0.05 and p=0.04, respectively). Among non-diabetic subjects, the overall carotid IMT was 7.3% higher in subjects with the low-activity genotype when compared to the high-activity (G/G) group. The results remained significant after adjustment for total cholesterol and smoking (p=0.015). No similar genotypic association was found for the subjects with type 2 DM.

CONCLUSIONS

This data suggests that in subjects with normal glucose metabolism, MPO gene variation may modify the carotid artery IMT.

Genetics and reverse epidemiology among patients on chronic hemodialysis

A reversal in the association between traditional and nontraditional risk factors and clinical outcomes is often encountered in patients with chronic illness, including among those with advanced chronic kidney disease (CKD) on maintenance hemodialysis (MHD). The effects of the malnutrition-inflammation complex syndrome (MICS) may play a significant role in the reversal of this risk factor-outcomes association. the MICS, this syndrome complex is not universal in its prevalence among MHD patients. The significant inter- and intra-individual differences in the prevalence of inflammation, oxidative stress, and malnutrition, indicates the influence of genetic factors in this variability. In recent years, enormous advancement in the field of molecular genetics, genomics and bioinformatics, have revolutionized studies of the genetic epidemiology of several diseases. However, genetic association studies are at a preliminary stage in the population with advanced CKD (Table 1). Preliminary studies of the impact of polyphisms in inflammation and oxidative stress-related genes and genes affecting body composition and metabolism suggest that genetic variation may indeed affect the phenotype of the MHD population. Further, some of these gene polymorphisms may also contribute to a reversal of the association between traditional risk factors, such as BMI, blood pressure, and cholesterol and clinical outcomes in this vulnerable patient population. Genetic studies in patients with advanced CKD pose enormous challenges, including recruitment of sufficient numbers of patients to achieve adequate statistical power, resolution of immense genotypic and phenotypic heterogeneity, and gene-environment and gene-gene interactions. However, well-designed adequately powered studies with carefully defined phenotypes may potentially allow definition of risk profiles characterized by combinations of relevant Single nucleotide polymorphisms in the setting of given environmental factors. Accurate risk stratification that takes into account genetic information would allow more informed targeting of pharmacologic intervention and better refined clinical trial methodologies.

Myeloperoxidase level in patients with stable coronary artery disease and acute coronary syndromes

BACKGROUND

No studies have measured plasma myeloperoxidase (MPO) across the entire spectrum of patients with coronary artery disease (CAD). The aim of the study was to compare MPO level across the entire spectrum of CAD, to assess the accuracy of MPO in predicting acute coronary syndromes and to define independent correlates of MPO level.

DESIGN

This case-control study included 874 patients with angiographically proven CAD. Cases included 680 patients with CAD (382 patients with stable CAD, 107 patients with non-ST-segment elevation acute coronary syndromes and 191 patients with ST-segment elevation acute myocardial infarction). Controls included 194 subjects with normal coronary angiograms. MPO was measured using an enzyme immunoassay before angiography and heparin administration.

RESULTS

MPO level [median (25th-75th percentiles)] was 74.5 (52.5-135.3) microg L(-1) in cases vs. 61.2 (44.6-80.9), microg L(-1) in controls (P < 0.001). MPO level was 61.2 (47.5-85.8), microg L(-1) in patients with stable CAD, 99.2 (62.2-154.9), microg L(-1) in patients with non-ST-segment elevation acute coronary syndromes and 129.5 (72.2-216.0) microg L(-1) in patients with acute myocardial infarction (P < 0.001). Elevated MPO level was associated with acute coronary syndromes with an area under receiver operating characteristic (ROC) curve of 0.731 (95% confidence interval 0.692-0.770; P < 0.001). Independent correlates of MPO level were acute coronary syndrome (P < 0.001), high-sensitivity C-reactive protein (P = 0.007), creatinine (P = 0.026), left ventricular ejection fraction (P = 0.027, negative association) and smoking (P = 0.028).

CONCLUSIONS

MPO level is elevated in patients with CAD and higher levels of MPO were found with progression of CAD from stable CAD to non-ST-segment elevation acute coronary syndromes and to acute myocardial infarction.

Place of genotyping and phenotyping in understanding and potentially modifying outcomes in peritoneal dialysis patients

With the landmark publication of the human genome sequence and its subsequent division into haplotype blocks, the characterization of genetic variations is becoming a feasible approach to study both the pathophysiology and risk factors of complex traits. A number of strategies are available today for identifying candidate genes or polymorphisms associated with pertinent phenotypes. For Mendelian diseases with high penetrance owing to mutations in a single gene, such as polycystic kidney disease, linkage studies have been very successful in mapping the disease loci owing to the availability of families with multiple affected members. In contrast to monogenic conditions, complex diseases such as end-stage renal disease (ESRD) and complex traits such as individual variations in membrane transport and complications during the course of peritoneal dialysis (PD) therapy have a number of competing determinants and inhibitors, both genetic and environmental. Current results reflect this complexity, with few studies showing a large effect of any single risk factor on survival or outcome on PD. However, these studies have so far been small (less than 500 patients) and have not utilized bioinformatics or novel technologies (e.g., multiplex genotyping equipment). In the following review, we outline current approaches for using genetic data in clinical studies as well as highlight some of the most promising results in ESRD patients, particularly those on PD.

Associations between the CYBA 242C/T and the MPO –463G/A Polymorphisms, Oxidative Stress and Cardiovascular Disease in Chronic Kidney Disease Patients

Genetic variations in the NADPH/MPO system in chronic kidney disease (CKD) patients might lead to altered activity of these enzymes, and thus to altered risk for oxidative stress (OS) and cardiovascular disease (CVD). We evaluated the impact of 242C/T CYBA and -463G/A MPO polymorphisms on OS and CVD mortality in stage 5 CKD patients starting dialysis. Two hundred and fifty-seven patients were genotyped using Pyrosequencing. Plasmalogen [dimethylacetal (DMA) 16/C16:0] was used as OS marker. CVD was assessed from patient history and clinical symptoms. Prevalence of CVD was higher (35%) in GG patients (MPO) compared to AG (26%) and AA (0%) patients (p < 0.01). Patients with CC genotype (CYBA) had lower levels of DMA 16/C16:0 (ratio 0.071 +/- 0.003) compared to TT patients (0.089 +/- 0.006; p < 0.05). These patients also had increased CVD mortality compared to CT and TT patients (chi(2) 2.19; p < 0.05). We conclude that genetic variations in the NADPH/MPO system are associated with OS, presence of CVD and CVD-related mortality in CKD patients.

Myeloperoxidase promoter polymorphism -463G is associated with more severe clinical expression of cystic fibrosis pulmonary disease

The severity of cystic fibrosis (CF) pulmonary disease is not directly related to CFTR genotype but depends upon several parameters, including neutrophil-dominated inflammation. Identification of agents modulating inflammation constitutes a relevant goal. Myeloperoxidase (MPO) is involved in both microbicidal and proinflammatory neutrophil activities. The aim of this study was to evaluate whether the -463GA MPO promoter polymorphism is linked to clinical severity of CF-associated pulmonary inflammation. This polymorphism significantly affects the level of MPO gene expression in leukocytes and the G allele is more expressing than the A allele. We show that MPO genotype significantly influences the severity of pulmonary disease in early stages, prior to the development of chronic lung infections, with GG genotype being associated with more severe CF disease. Our findings indicate that the level of MPO gene expression influences the CF pathogenesis, presumably reflecting cellular damage by MPO-generated oxidants or other activity of MPO in airway inflammation.

Use of Single-Nucleotide Polymorphisms in the Search for Genetic Modifiers of the Uremic Phenotype

As the modern nephrology community continues to be burdened with growing numbers of patients with end-stage renal disease (ESRD) and exceptionally high mortality rates, it is obvious that progress in the development of preventive and therapeutic strategies has not been sufficient. This urges nephrologists to focus on the underlying mechanisms for ESRD morbidity and mortality, and in particular on cardiovascular disease (CVD), which is the major contributor to premature death in this patient group. The high prevalence of inflammation, vascular ossification, and oxidative stress in ESRD predisposes these patients to CVD. Because genetic risk factors may modulate the pathophysiologic response, genotype-phenotype association studies may provide ways of predicting individual disease progression and may shed some light on key regulatory pathways. Indeed, recent genetic association studies show that polymorphisms in candidate genes related to inflammatory signaling, vascular ossification, and oxidative stress response influence the uremic phenotype. DNA polymorphisms may also be used as nonconfounded tools in observational studies conducted to test causality, as stated by the mendelian randomization approach. To date, the collection of genetic data is no longer a limitation because genetic information is easily accessible in public databases and high-throughput genotyping technologies are available. Advanced bioinformatic tools are now warranted to facilitate the integration of accumulating genetic information with clinical and biochemical end points and, finally, to implement genotype-phenotype data in the care of patients with renal failure to better identify patients at high risk and to design novel personalized therapeutic and preventive strategies.

Evidence that C-Reactive Protein or IL-6 Are Not Surrogates for All Inflammatory Cardiovascular Risk Factors in Hemodialysis Patients

BACKGROUND/AIMS

In otherwise healthy adults, high C-reactive protein (CRP) levels are associated with cardiovascular disease and have been linked to an inflammatory state. The presence of vascular disease is also associated with increased expression of adhesion molecules, including soluble intercellular adhesion molecule (sICAM), vascular endothelial growth factor (VEGF) and leukocyte-derived myeloperoxidase (MPO). These associations suggest potential mechanisms whereby inflammation may injure the vascular endothelium, but the recognition of how these mediators act in concert remain poorly characterized. That the prevalence of atherosclerosis and markers of inflammation are increased in renal failure patients suggests that inflammation causes accelerated vascular disease.

METHODS

In hemodialysis patients, we examined the relationships between plasma CRP and sICAM, VEGF and MPO longitudinally. We determined whether episodes of a high CRP value were paralleled by simultaneous increases in mediators of inflammatory injury or molecules associated with endothelial cell adhesion or growth and whether CRP levels correlated with those of VEGF and MPO.

RESULTS

Episodic increases in CRP were accompanied by higher levels of VEGF, sICAM and MPO. However, there was no correlation between serum CRP levels or other acute phase proteins and either MPO or VEGF, nor was there a constant temporal relationship between MPO and CRP. By contrast, MPO and VEGF levels were closely correlated with one another during episodes of inflammation (p = 0.0001), and CRP and interleukin-6 levels were also correlated. Increases in MPO tended to be restricted to patients with grafts or catheters, and not those with AV fistulas.

CONCLUSIONS

These results suggest that high plasma levels of CRP or other acute phase proteins in cross-sectional studies should be interpreted cautiously when defining mechanisms underlying cardiovascular disease in the hemodialysis patient population. One, or more than one inflammatory repertoire may be activated, one involving hepatic acute phase proteins and the other neutrophil activation and each may contribute separately to outcomes. Better prognostic information may be obtained by measurement of more markers than CRP alone, such as MPO and VEGF.

Oxidative biomarkers in the diagnosis and prognosis of cardiovascular disease

Oxidative damage to lipids and proteins is an important component of atherosclerotic cardiovascular disease (CVD). Studies of oxidation-related molecules are helping to define atherosclerotic mechanisms, and measurements of circulating levels of specific oxidant compounds may improve cardiovascular risk assessment. The present article reviews accumulating data of selected oxidative biomarkers that support their role in providing diagnostic and/or prognostic information. For example, plasma levels of the enzyme myeloperoxidase, which generates the strong oxidizing agent hypochlorous acid, have been found to be correlated with risk for myocardial infarction and endothelial dysfunction. Elevated levels of lipoprotein-associated phospholipase A(2) are associated with coronary artery disease (CAD) and stroke. Oxidized phospholipids play an important role in atherosclerosis. Recent studies measuring circulating levels of oxidized phospholipids have suggested a strong association with CAD, plaque disruption, and response to 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitor ("statin") therapy. Isoprostanes correlate strongly with cardiovascular risk factors, but their role in risk prediction is less well defined. Future studies are expected to clarify the role of oxidative biomarkers in the diagnosis and prognosis of CVD and to determine their value in specific clinical populations.