Macrophage myeloperoxidase regulation by granulocyte macrophage colony-stimulating factor in human atherosclerosis and implications in acute coronary syndromes

Riboflavin along with antibiotics balances reactive oxygen species and inflammatory cytokines and controls Staphylococcus aureus infection by boosting murine macrophage function and regulates inflammation

Background

Macrophages serve as intracellular reservoirs of S. aureus. Recent in vitro studies have confirmed high level resistance by S. aureus to macrophage mediated killing and the intracellular persistence of Staphylococci may play an important role in the pathogenesis. Since this localization protects them from both cell-mediated and humoral immune responses, therefore, a successful anti-staphylococcal therapy should include the elimination of intracellular bacteria, further protecting the host cells from staphylococci-induced cell death. So, only antibiotic therapy may not be helpful, successful therapy needs combination of drugs not only for elimination of pathogen but also for rescuing the host cell for S. aureus induced cell death.

Methods

In keeping with this idea an in vitro study has been done to examine the effect of Riboflavin along with antibiotics on phagocytosis, hydorgen peroxide, superoxide production, antioxidant enzyme levels, and cytokine levels in mouse macrophages for amelioration of the Staphylococcus aureus burden. The immune boosting effects of Riboflavin have been validated through perturbations of redox homeostasis and pro-inflammatory cytokines measurements.

Results

It was observed that the supplementation of Vitamin B-2 (Riboflavin) not only enhances macrophage function as previously reported but also decreases pro-inflammatory responses in Staphylococcus aureus infected macrophages. The observed influence of Riboflavin on enhanced antimicrobial effects such as enhanced phagocytosis of macrophages exposed to S. aureus, hydrogen peroxide or superoxide production when combined with either ciprofloxacin (CIP) or Azithromycin (AZM) and decrease in pro-inflammatory responses of IFN-γ, IL-6, IL-1β. Riboflavin treatment also decreased NO and TNF-α level possibly by inhibiting the NF-κβ pathway. The increased antioxidant enzymes like glutathione reductase, SOD and GSH level helped in maintaining a stable redox state in the cell.

Conclusion

Riboflavin plus antibiotic pretreatment not only enhances macrophage functions but also decreases proinflammatory responses in Staphylococcus aureus infected macrophages indicating better bacterial clearance and regulated inflammation which may be considered as a novel and important therapeutic intervention.

The roles of myeloperoxidase in coronary artery disease and its potential implication in plaque rupture

Atherosclerosis is the main pathophysiological process underlying coronary artery disease (CAD). Acute complications of atherosclerosis, such as myocardial infarction, are caused by the rupture of vulnerable atherosclerotic plaques, which are characterized by thin, highly inflamed, and collagen-poor fibrous caps. Several lines of evidence mechanistically link the heme peroxidase myeloperoxidase (MPO), inflammation as well as acute and chronic manifestations of atherosclerosis. MPO and MPO-derived oxidants have been shown to contribute to the formation of foam cells, endothelial dysfunction and apoptosis, the activation of latent matrix metalloproteinases, and the expression of tissue factor that can promote the development of vulnerable plaque. As such, detection, quantification and imaging of MPO mass and activity have become useful in cardiac risk stratification, both for disease assessment and in the identification of patients at risk of plaque rupture. This review summarizes the current knowledge about the role of MPO in CAD with a focus on its possible roles in plaque rupture and recent advances to quantify and image MPO in plasma and atherosclerotic plaques.

MicroRNA-181b Controls Atherosclerosis and Aneurysms Through Regulation of TIMP-3 and Elastin

Supplemental Digital Content is available in the text.

Rationale:

Atherosclerosis and aneurysms are leading causes of mortality worldwide. MicroRNAs (miRs) are key determinants of gene and protein expression, and atypical miR expression has been associated with many cardiovascular diseases; although their contributory role to atherosclerotic plaque and abdominal aortic aneurysm stability are poorly understood.

Objective:

To investigate whether miR-181b regulates tissue inhibitor of metalloproteinase-3 expression and affects atherosclerosis and aneurysms.

Methods and Results:

Here, we demonstrate that miR-181b was overexpressed in symptomatic human atherosclerotic plaques and abdominal aortic aneurysms and correlated with decreased expression of predicted miR-181b targets, tissue inhibitor of metalloproteinase-3, and elastin. Using the well-characterized mouse atherosclerosis models of Apoe^−/− and Ldlr^−/−, we observed that in vivo administration of locked nucleic acid anti-miR-181b retarded both the development and the progression of atherosclerotic plaques. Systemic delivery of anti-miR-181b in angiotensin II–infused Apoe^−/− and Ldlr^−/− mice attenuated aneurysm formation and progression within the ascending, thoracic, and abdominal aorta. Moreover, miR-181b inhibition greatly increased elastin and collagen expression, promoting a fibrotic response and subsequent stabilization of existing plaques and aneurysms. We determined that miR-181b negatively regulates macrophage tissue inhibitor of metalloproteinase-3 expression and vascular smooth muscle cell elastin production, both important factors in maintaining atherosclerotic plaque and aneurysm stability. Validation studies in Timp3^−/− mice confirmed that the beneficial effects afforded by miR-181b inhibition are largely tissue inhibitor of metalloproteinase-3 dependent, while also revealing an additional protective effect through elevating elastin synthesis.

Conclusions:

Our findings suggest that the management of miR-181b and its target genes provides therapeutic potential for limiting the progression of atherosclerosis and aneurysms and protecting them from rupture.

Levels of inflammation and oxidative stress, and a role for taurine in dystropathology of the Golden Retriever Muscular Dystrophy dog model for Duchenne Muscular Dystrophy

Duchenne Muscular Dystrophy (DMD) is a fatal skeletal muscle wasting disease presenting with excessive myofibre necrosis and increased inflammation and oxidative stress. In the mdx mouse model of DMD, homeostasis of the amino acid taurine is altered, and taurine administration drastically decreases muscle necrosis, dystropathology, inflammation and protein thiol oxidation. Since the severe pathology of the Golden Retriever Muscular Dystrophy (GRMD) dog model more closely resembles the human DMD condition, we aimed to assess the generation of oxidants by inflammatory cells and taurine metabolism in this species. In muscles of 8 month GRMD dogs there was an increase in the content of neutrophils and macrophages, and an associated increase in elevated myeloperoxidase, a protein secreted by neutrophils that catalyses production of the highly reactive hypochlorous acid (HOCl). There was also increased chlorination of tyrosines, a marker of HOCl generation, increased thiol oxidation of many proteins and irreversible oxidative protein damage. Taurine, which functions as an antioxidant by trapping HOCl, was reduced in GRMD plasma; however taurine was increased in GRMD muscle tissue, potentially due to increased muscle taurine transport and synthesis. These data indicate a role for HOCl generated by neutrophils in the severe dystropathology of GRMD dogs, which may be exacerbated by decreased availability of taurine in the blood. These novel data support continued research into the precise roles of oxidative stress and taurine in DMD and emphasise the value of the GRMD dogs as a suitable pre-clinical model for testing taurine as a therapeutic intervention for DMD boys.

Local Matrix Metalloproteinase 9 Level Determines Early Clinical Presentation of ST-Segment-Elevation Myocardial Infarction

OBJECTIVE

Early clinical presentation of ST-segment-elevation myocardial infarction (STEMI) and non-ST-segment-elevation myocardial infarction affects patient management. Although local inflammatory activities are involved in the onset of MI, little is known about their impact on early clinical presentation. This study aimed to investigate whether local inflammatory activities affect early clinical presentation.

APPROACH AND RESULTS

This study comprised 94 and 17 patients with MI (STEMI, 69; non-STEMI, 25) and stable angina pectoris, respectively. We simultaneously investigated the culprit lesion morphologies using optical coherence tomography and inflammatory activities assessed by shedding matrix metalloproteinase 9 (MMP-9) and myeloperoxidase into the coronary circulation before and after stenting. Prevalence of plaque rupture, thin-cap fibroatheroma, and lipid arc or macrophage count was higher in patients with STEMI and non-STEMI than in those with stable angina pectoris. Red thrombus was frequently observed in STEMI compared with others. Local MMP-9 levels were significantly higher than systemic levels (systemic, 42.0 [27.9-73.2] ng/mL versus prestent local, 69.1 [32.2-152.3] ng/mL versus poststent local, 68.0 [35.6-133.3] ng/mL; P<0.01). Poststent local MMP-9 level was significantly elevated in patients with STEMI (STEMI, 109.9 [54.5-197.8] ng/mL versus non-STEMI: 52.9 [33.0-79.5] ng/mL; stable angina pectoris, 28.3 [14.2-40.0] ng/mL; P<0.01), whereas no difference was observed in the myeloperoxidase level. Poststent local MMP-9 and the presence of red thrombus are the independent determinants for STEMI in multivariate analysis.

CONCLUSIONS

Local MMP-9 level could determine the early clinical presentation in patients with MI. Local inflammatory activity for atherosclerosis needs increased attention.

An Ultrasensitive Cyclization-Based Fluorescent Probe for Imaging Native HOBr in Live Cells and Zebrafish

Bromine has been reported recently as being the 28(th) essential element for human health. HOBr, which is generated in vivo from bromide, is a required factor in the formation of sulfilimine crosslinks in collagen IV. However, to date, no method for the specific detection of native HOBr in vivo has been reported. Herein, we develop a simple small molecular probe for imaging HOBr based on a specific cyclization catalyzed by HOBr. The probe can be easily synthesized in high yield through a Suzuki cross-coupling reaction. The probe exhibits ultrahigh sensitivity at the picomole level, in addition to specificity for HOBr and real-time response. Importantly, without Br(-) stimulation, this probe reports native HOBr levels in HepG2 cells. Thus, the probe is a promising new tool for imaging endogenous HOBr and may provide a means for finding new physiological functions of HOBr in living organisms.

Increased intermediate CD14++CD16++ monocyte subset levels associate with restenosis after peripheral percutaneous transluminal angioplasty

BACKGROUND AND AIMS

We aimed at studying the association of three major human monocyte subsets after percutaneous transluminal angioplasty (PTA) in patients with femoropopliteal disease.

METHODS

We prospectively studied 67 sequential patients (40 male, 27 female; mean age 71 ± 11 years) treated with femoropopliteal angioplasty. Multi-color flow cytometry characterized monocyte subsets from venous blood for expression of CD14 and CD16 and intracellular myeloperoxidase (MPO) prior to, and 3, 6 and 12 months post PTA. Analyses tested associations between monocyte subsets and risk for restenosis.

RESULTS

16/67 patients (24%) developed restenosis within 12 months after PTA. Patients with hyperlipidemia had increased risk for restenosis (HR = 1.7, 95% CI 0.7-2.9, p = 0.001). Increased baseline monocytes associated with an increased risk of late restenosis (HR = 4.9, 95% CI: 1.3-18.6, p = 0.047). CD14⁺⁺CD16⁺⁺ 'intermediate' monocytes assessed at baseline, and after 3, 6, and 12 months significantly associated with the risk for subsequent restenosis: HR = 3.9 (95% CI: 2.4-6.5, p = 0.029), HR = 5.7 (95% CI = 0.7-44.7, p = 0.013), HR = 6.5 (95% CI: 2.5-16.9, p = 0.001) and HR = 1.5 (95% CI = 1.4-15.5 p = 0.001), respectively. Moreover, the probability for freedom of restenosis decreased with increased levels of intermediate subsets at 12 months after PTA. Additionally, intracellular MPO expression in CD14⁺⁺CD16⁺⁺ measured at 3, 6 and 12 months associated with an increased restenosis risk (HR = 1.5, 95% CI: 0.8-2.1, p = 0.214, HR = 1.9, 95% CI: 1.0-2.3 p = 0.051 and HR = 1.4, 95% CI: 1.0-1.8, p = 0.052).

CONCLUSIONS

Our results imply altered innate immunity after angioplasty. Elevated CD14⁺⁺CD16⁺⁺ intermediate monocyte frequencies and increased MPO expression may identify individuals at heightened risk for restenosis.

Leukocytes Link Local and Systemic Inflammation in Ischemic Cardiovascular Disease: An Expanded "Cardiovascular Continuum"

Physicians have traditionally viewed ischemic heart disease in a cardiocentric manner: plaques grow in arteries until they block blood flow, causing acute coronary and other ischemic syndromes. Recent research provides new insight into the integrative biology of inflammation as it contributes to ischemic cardiovascular disease. These results have revealed hitherto unsuspected inflammatory signaling networks at work in these disorders that link the brain, autonomic nervous system, bone marrow, and spleen to the atherosclerotic plaque and to the infarcting myocardium. A burgeoning clinical published data indicates that such inflammatory networks-far from a mere laboratory curiosity-operate in our patients and can influence aspects of ischemic cardiovascular disease that determine decisively clinical outcomes. These new findings enlarge the circle of the traditional "cardiovascular continuum" beyond the heart and vessels to include the nervous system, the spleen, and the bone marrow.

Plasma Myeloperoxidase and Total Sialic Acid as Prognostic Indicators in Acute Coronary Syndrome

INTRODUCTION

Acute Coronary Syndrome (ACS) is the leading cause of death worldwide. Oxidative stress and inflammation play important role in the destabilization of plaques leading to ACS. Markers which reflect this pathophysiologic mechanism may have prognostic value. Myeloperoxidase (MPO) and Sialic acid are markers of inflammation and oxidative stress. Both these markers are increased in patients with ACS. Their prognostic value in ACS is not well established.

AIM

To analyse the prognostic value of plasma myeloperoxidase and total sialic acid levels in patients with suspected acute coronary syndrome.

MATERIALS AND METHODS

A prospective study was conducted on 93 consecutively admitted patients with chest pain from July 2011 to September 2011. Plasma MPO and total sialic acid levels on admission were estimated spectrophotometrically. These were compared with extent of disease, development of complications during the hospital stay, left ventricular ejection fraction and mean duration of stay in hospital.

RESULTS

Plasma MPO and total sialic acid levels were significantly higher in patients with myocardial infarction than those with unstable and stable angina (p<0.001 and p<0.007 respectively). The levels of plasma MPO and sialic acid levels were significantly higher in patients who developed complications like heart failure, arrhythmias, renal failure during their stay in hospital (p<0.011 and p<0.006 respectively). Ejection fraction was significantly low in patients with high MPO levels (p<0.011).

CONCLUSION

In patients with ACS, plasma MPO and total sialic acid levels on admission could predict the development of complications during their hospital stay. MPO levels correlated with ejection fraction in patients with ACS.

Pimaradienoic Acid Inhibits Carrageenan-Induced Inflammatory Leukocyte Recruitment and Edema in Mice: Inhibition of Oxidative Stress, Nitric Oxide and Cytokine Production

Pimaradienoic acid (PA; ent-pimara-8(14),15-dien-19-oic acid) is a pimarane diterpene found in plants such as Vigueira arenaria Baker (Asteraceae) in the Brazilian savannas. Although there is evidence on the analgesic and in vitro inhibition of inflammatory signaling pathways, and paw edema by PA, its anti-inflammatory effect deserves further investigation. Thus, the objective of present study was to investigate the anti-inflammatory effect of PA in carrageenan-induced peritoneal and paw inflammation in mice. Firstly, we assessed the effect of PA in carrageenan-induced leukocyte recruitment in the peritoneal cavity and paw edema and myeloperoxidase activity. Next, we investigated the mechanisms involved in the anti-inflammatory effect of PA. The effect of PA on carrageenan-induced oxidative stress in the paw skin and peritoneal cavity was assessed. We also tested the effect of PA on nitric oxide, superoxide anion, and inflammatory cytokine production in the peritoneal cavity. PA inhibited carrageenan-induced recruitment of total leukocytes and neutrophils to the peritoneal cavity in a dose-dependent manner. PA also inhibited carrageenan-induced paw edema and myeloperoxidase activity in the paw skin. The anti-inflammatory mechanism of PA depended on maintaining paw skin antioxidant activity as observed by the levels of reduced glutathione, ability to scavenge the ABTS cation and reduce iron as well as by the inhibition of superoxide anion and nitric oxide production in the peritoneal cavity. Furthermore, PA inhibited carrageenan-induced peritoneal production of inflammatory cytokines TNF-α and IL-1β. PA presents prominent anti-inflammatory effect in carrageenan-induced inflammation by reducing oxidative stress, nitric oxide, and cytokine production. Therefore, it seems to be a promising anti-inflammatory molecule that merits further investigation.

Protective effect of diallyl trisulfide against naphthalene-induced oxidative stress and inflammatory damage in mice

The aim of this study was to investigate the possible protective effects of diallyl trisulfide (DATS) against naphthalene-induced oxidative and inflammatory damage in the livers and lungs of mice. Elevated serum alanine aminotransferase (ALT) and aspartate aminotransferase (AST) levels showed significant hepatic damage after the challenge with 100 mg/kg naphthalene. Hepatic malondialdehyde (MDA) contents and the activity of myeloperoxidase (MPO) increased significantly, accompanying a decrease in the hepatic activity of total superoxide dismutase (SOD) and glutathione (GSH) levels after the naphthalene damage. In addition, the serum levels of nitric oxide (NO), tumor necrosis factor α (TNF-α), and interleukin 8 (IL-8) increased significantly in the groups damaged with naphthalene. The main parameters related to oxidative stress and inflammatory responses in the lungs, including the NO, MPO, and GSH contents, were determined, and the histopathological and immunohistochemical changes in the lung and liver tissues were also observed. In the DATS-treated groups, all of the oxidative and inflammatory damage in the serum, liver, and lung tissues were significantly prevented.

Neutrophil-Mediated Regulation of Innate and Adaptive Immunity: The Role of Myeloperoxidase

Neutrophils are no longer seen as leukocytes with a sole function of being the essential first responders in the removal of pathogens at sites of infection. Being armed with numerous pro- and anti-inflammatory mediators, these phagocytes can also contribute to the development of various autoimmune diseases and can positively or negatively regulate the generation of adaptive immune responses. In this review, we will discuss how myeloperoxidase, the most abundant neutrophil granule protein, plays a key role in the various functions of neutrophils in innate and adaptive immunity.

Neutrophil proteolytic activation cascades: a possible mechanistic link between chronic periodontitis and coronary heart disease

Cardiovascular diseases are chronic inflammatory diseases that affect a large segment of society. Coronary heart disease (CHD), the most common cardiovascular disease, progresses over several years and affects millions of people worldwide. Chronic infections may contribute to the systemic inflammation and enhance the risk for CHD. Periodontitis is one of the most common chronic infections that affects up to 50% of the adult population. Under inflammatory conditions the activation of endogenous degradation pathways mediated by immune responses leads to the release of destructive cellular molecules from both resident and immigrant cells. Matrix metalloproteinases (MMPs) and their regulators can activate each other and play an important role in immune response via degrading extracellular matrix components and modulating cytokines and chemokines. The action of MMPs is required for immigrant cell recruitment at the site of inflammation. Stimulated neutrophils represent the major pathogen-fighting immune cells that upregulate expression of several proteinases and oxidative enzymes, which can degrade extracellular matrix components (e.g. MMP-8, MMP-9 and neutrophil elastase). The activity of MMPs is regulated by endogenous inhibitors and/or candidate MMPs (e.g. MMP-7). The balance between MMPs and their inhibitors is thought to mirror the proteolytic burden. Thus, neutrophil-derived biomarkers, including myeloperoxidase, may activate proteolytic destructive cascades that are involved in subsequent immune-pathological events associated with both periodontitis and CHD. Here, we review the existing studies on the contribution of MMPs and their regulators to the infection-related pathology. Also, we discuss the possible proteolytic involvement and role of neutrophil-derived enzymes as an etiological link between chronic periodontitis and CHD.

Association of myeloperoxidase levels with cardiometabolic factors and renal function in prepubertal children

INTRODUCTION

Myeloperoxidase (MPO), an enzyme linking obesity and cardiovascular (CV) risk in adults, has rarely been studied in young children and no studies assessed its association with renal function. We sought to explore a possible association between serum MPO levels, obesity, CV risk factors and renal function in prepubertal children.

MATERIALS/METHODS

Cross-sectional evaluation of 309 children aged 8-9 years (161 normal weight, 148 overweight/obese), members of the birth cohort Generation I (Portugal). Anthropometrics (body mass index (BMI), waist-to-height ratio (WHtR) and % body fat mass (%BFM) by bioelectrical impedance analysis), 24-h ambulatory blood pressure monitoring and pulse wave velocity (PWV) were measured. Insulin resistance was estimated by the HOMA index (considering serum fasting glucose and insulin determinations). Serum MPO levels were assessed by immunoenzymatic assay.

RESULTS

MPO levels were positively associated with obesity indices (BMI z-score, WHtR and %BFM). Higher MPO levels were associated with higher 24-h and night-time mean arterial pressure, with nondipping and with higher values of insulin resistance. In normal weight children, the endothelial function, as evaluated indirectly by PWV, was an independent predictor of MPO levels. In overweight/obese children, estimated glomerular filtration rate increased significantly across tertiles of MPO (Ptrend = 0·031) and this association held after adjustment for age, sex, neutrophil and monocyte counts and CV risk factors.

CONCLUSIONS

Our results reinforce the role of MPO as a risk marker in obesity and related CV morbidities in young children. MPO levels associate with the dipping pattern and PWV and, among overweight/obese children, an association exists between MPO and renal function.

Traditional and non-traditional risk factors for incident peripheral arterial disease among patients with chronic kidney disease

BACKGROUND

The risk of peripheral arterial disease (PAD) is higher in patients with chronic kidney disease (CKD) compared with those without. However, reasons for this increased risk are not fully understood.

METHODS

We studied risk factors for incident PAD among 3169 participants in the Chronic Renal Insufficiency Cohort (CRIC) Study. Patients with CKD aged 21-74 years were recruited between 2003 and 2008 and followed for a median of 6.3 years. Incident PAD was defined as a new onset ankle-brachial index (ABI) of <0.9 or confirmed clinical PAD.

RESULTS

In a multivariate-adjusted model, older age, female sex, non-Hispanic Black, current smoking, diabetes, higher pulse pressure, lower high-density lipoprotein cholesterol, higher low-density lipoprotein cholesterol, and lower estimated glomerular filtration rate were significantly associated with the increased risk of incident PAD. After adjustment for these traditional risk factors as well as use of medications and CRIC Study clinic sites, the following baseline novel risk factors were significantly associated with risk of incident PAD [hazard ratio and 95% confidence interval (CI) for a one standard deviation (SD) higher level]: log[C-reactive protein (CRP)] (1.16, 1.06-1.25, P < 0.001), white blood cell count (1.09, 1.01-1.18, P = 0.03), fibrinogen (1.15, 1.06-1.26, P = 0.002), log(myeloperoxidase) (1.12, 1.03-1.23, P = 0.01), uric acid (0.88, 0.80-0.97, P = 0.01), glycated hemoglobin (1.16, 1.05-1.27, P = 0.003), log(homeostatic model assessment-insulin resistance) (1.21, 1.10-1.32, P < 0.001) and alkaline phosphatase (1.15, 1.07-1.24, P < 0.001).

CONCLUSIONS

Among patients with CKD, inflammation, prothrombotic state, oxidative stress, glycated hemoglobin, insulin resistance and alkaline phosphatase are associated with an increased risk of PAD, independent of traditional risk factors.

Trypanosoma cruzi P21: a potential novel target for chagasic cardiomyopathy therapy

Chagas disease, which is caused by the parasite Trypanosoma cruzi, is an important cause of cardiomyopathy in Latin America. It is estimated that 10%–30% of all infected individuals will acquire chronic chagasic cardiomyopathy (CCC). The etiology of CCC is multifactorial and involves parasite genotype, host genetic polymorphisms, immune response, signaling pathways and autoimmune progression. Herein we verified the impact of the recombinant form of P21 (rP21), a secreted T. cruzi protein involved in host cell invasion, on progression of inflammatory process in a polyester sponge-induced inflammation model. Results indicated that rP21 can recruit immune cells induce myeloperoxidase and IL-4 production and decrease blood vessels formation compared to controls in vitro and in vivo. In conclusion, T. cruzi P21 may be a potential target for the development of P21 antagonist compounds to treat chagasic cardiomyopathy.

Host antioxidant enzymes and TLR-2 neutralization modulate intracellular survival of Staphylococcus aureus: Evidence of the effect of redox balance on host pathogen relationship during acute staphylococcal infection

Staphylococcus aureus is an important pathogen in bone disease and innate immune recognition receptor, TLR-2 is reported to be crucial for inflammatory bone loss. Role of TLR-2 in bacterial clearance and cytokine response to S. aureus infection in murine bone marrow macrophages has been reported but the role of host derived ROS in host-pathogen relationship still remains an obvious question. In the present study, blocking of SOD and catalase in TLR-2 neutralized fresh bone marrow cells (FBMC) with Diethyldithiocarbamic acid (DDC) and 3-Amino-1,2,4-triazole (ATZ), separately, during acute S. aureus infection, produces moderate level of ROS and limits inflammation as compared with only TLR-2 non-neutralized condition and leads to decreased bacterial count compared with only TLR-2 neutralized condition. In summary, host SOD and catalase modulates ROS generation, cytokine levels and TLR-2 expression in FBMCs during acute S. aureus infection which might be useful in the alleviation of S. aureus infection and bone loss.

Clinical Application of NOX Activity and Other Oxidative Biomarkers in Cardiovascular Disease: A Critical Review

SIGNIFICANCE

The oxidative stress theory of atherosclerosis is based on the assumption that the production of reactive oxidant species (ROS) by blood, as well as resident cells of the artery wall, elicits the formation of oxidized low-density lipoproteins (ox-LDL), which, in turn, promotes a series of inflammatory responses, ultimately leading to atherosclerotic plaque. This theory prompted the development of new laboratory methodologies that aimed at assessing the relationship between oxidative stress and clinical progression of human atherosclerosis.

CRITICAL ISSUES

Markers assessing the oxidation of phospholipid and protein components of LDL were among the first to be developed. Clinical trials included cross-sectional as well as retrospective and prospective studies that, however, provided equivocal results. Thus, clear evidence that oxidative biomarkers add more to the risk stratification by common atherosclerotic risk factors is still lacking.

RECENT ADVANCES

More recently, the analysis of oxidative stress focused on enzymatic pathways generating ROS, such as NADPH oxidase and myeloperoxidase (MPO). Experimental and clinical studies suggest that both enzymes may be implicated in promoting atherosclerotic disease. Novel laboratory methodologies have been, therefore, developed to study NADPH oxidase and MPO in patients with stable atherosclerosis as well as in patients with acute coronary and cerebro-vascular syndromes.

FUTURE DIRECTIONS

This review will analyze the strengths and weaknesses of the current methodology to study these enzymes in human atherosclerosis with particular regard to their clinical application in several settings of cardiovascular disease. Clinical methodology and results of previous studies with regard to markers of LDL oxidation have also been reviewed as a useful background for the future development of clinical trials.

Myeloperoxidase impairs the contractile function in isolated human cardiomyocytes

We set out to characterize the mechanical effects of myeloperoxidase (MPO) in isolated left-ventricular human cardiomyocytes. Oxidative myofilament protein modifications (sulfhydryl (SH)-group oxidation and carbonylation) induced by the peroxidase and chlorinating activities of MPO were additionally identified. The specificity of the MPO-evoked functional alterations was tested with an MPO inhibitor (MPO-I) and the antioxidant amino acid Met. The combined application of MPO and its substrate, hydrogen peroxide (H2O2), largely reduced the active force (Factive), increased the passive force (Fpassive), and decreased the Ca(2+) sensitivity of force production (pCa50) in permeabilized cardiomyocytes. H2O2 alone had significantly smaller effects on Factive and Fpassive and did not alter pCa50. The MPO-I blocked both the peroxidase and the chlorinating activities, whereas Met selectively inhibited the chlorinating activity of MPO. All of the MPO-induced functional effects could be prevented by the MPO-I and Met. Both H2O2 alone and MPO + H2O2 reduced the SH content of actin and increased the carbonylation of actin and myosin-binding protein C to the same extent. Neither the SH oxidation nor the carbonylation of the giant sarcomeric protein titin was affected by these treatments. MPO activation induces a cardiomyocyte dysfunction by affecting Ca(2+)-regulated active and Ca(2+)-independent passive force production and myofilament Ca(2+) sensitivity, independent of protein SH oxidation and carbonylation. The MPO-induced deleterious functional alterations can be prevented by the MPO-I and Met. Inhibition of MPO may be a promising therapeutic target to limit myocardial contractile dysfunction during inflammation.

Myeloperoxidase evokes substantial vasomotor responses in isolated skeletal muscle arterioles of the rat

Aims

Myeloperoxidase (MPO) catalyses the formation of a wide variety of oxidants, including hypochlorous acid (HOCl), and contributes to cardiovascular disease progression. We hypothesized that during its action MPO evokes substantial vasomotor responses.

Methods

Following exposure to MPO (1.92 mU mL⁻¹) in the presence of increasing concentrations of hydrogen peroxide (H₂O₂), changes in arteriolar diameter of isolated gracilis skeletal muscle arterioles (SMAs) and coronary arterioles (CAs) and in the isometric force in basilar arteries (BAs) of the rat were monitored.

Results

Myeloperoxidase increased vascular tone to different degrees in CAs, SMAs and BAs. The mechanism of increased vasoconstriction was studied in detail in SMAs. MPO-evoked vasoconstrictions were prevented by the MPO inhibitor 4-aminobenzhydrazide (50 μm), by endothelium removal in the SMAs. Surprisingly, the HOCl scavenger L-methionine (100 μm), the thromboxane A2 (TXA2) antagonist SQ-29548 (1 μm) or the non-specific cyclooxygenase (COX) antagonist indomethacin (1 μm) converted the MPO-evoked vasoconstrictions to pronounced vasodilations in SMAs, not seen in the presence of H₂O₂. In contrast to noradrenaline-induced vasoconstrictions, the MPO-evoked vasoconstrictions were not accompanied by significant increases in arteriolar [Ca²⁺] levels in SMAs.

Conclusion

These data showed that H₂O₂-derived HOCl to be a potent vasoconstrictor upon MPO application. HOCl activated the COX pathway, causing the synthesis and release of a TXA2-like substance to increase the Ca²⁺ sensitivity of the contractile apparatus in vascular smooth muscle cells and thereby to augment H₂O₂-evoked vasoconstrictions. Nevertheless, inhibition of the HOCl–COX–TXA2 pathway unmasked the effects of additional MPO-derived radicals with a marked vasodilatory potential in SMAs.

The nitroxide radical TEMPOL prevents obesity, hyperlipidaemia, elevation of inflammatory cytokines, and modulates atherosclerotic plaque composition in apoE-/- mice

OBJECTIVE

The nitroxide compound TEMPOL (4-hydroxy-2,2,6,6-tetramethylpiperidine-N-oxyl radical) has been shown to prevent obesity-induced changes in adipokines in cell and animal systems. In this study we investigated whether supplementation with TEMPOL inhibits inflammation and atherosclerosis in apoE-/- mice fed a high fat diet (HFD).

METHODS

ApoE-/- mice were fed for 12 weeks on standard chow diet or a high-fat diet. Half the mice were supplemented with 10 mg/g TEMPOL in their food. Plasma samples were analysed for triglycerides, cholesterol, low- and high-density lipoprotein cholesterol, inflammatory cytokines and markers (interleukin-6, IL-6; monocyte-chemotactic protein, MCP-1; myeloperoxidase, MPO; serum amyloid A, SAA; adiponectin; leptin). Plaques in the aortic sinus were analysed for area, and content of collagen, lipid, macrophages and smooth muscle cells.

RESULTS

High fat feeding resulted in marked increases in body mass and plasma lipid levels. Dietary TEMPOL decreased both parameters. In the high-fat-fed mice significant elevations in plasma lipid levels and the inflammatory markers IL-6, MCP-1, MPO, SAA were detected, along with an increase in leptin and a decrease in adiponectin. TEMPOL supplementation reversed these effects. When compared to HFD-fed mice, TEMPOL supplementation increased plaque collagen content, decreased lipid content and increased macrophage numbers.

CONCLUSIONS

These data indicate that in a well-established model of obesity-associated hyperlipidaemia and atherosclerosis, TEMPOL had a significant impact on body mass, atherosclerosis, hyperlipidaemia and inflammation. TEMPOL may therefore be of value in suppressing obesity, metabolic disorders and increasing atherosclerotic plaque stability.

3-nitrotyrosine modified proteins in atherosclerosis

Cardiovascular disease is the leading cause of premature death worldwide, and atherosclerosis is the main contributor. Lipid-laden macrophages, known as foam cells, accumulate in the subendothelial space of the lesion area and contribute to consolidate a chronic inflammatory environment where oxygen and nitrogen derived oxidants are released. Oxidatively modified lipids and proteins are present both in plasma as well as atherosclerotic lesions. A relevant oxidative posttranslational protein modification is the addition of a nitro group to the hydroxyphenyl ring of tyrosine residues, mediated by nitric oxide derived oxidants. Nitrotyrosine modified proteins were found in the lesion and also in plasma from atherosclerotic patients. Despite the fact of the low yield of nitration, immunogenic, proatherogenic, and prothrombotic properties acquired by 3-nitrotyrosine modified proteins are in agreement with epidemiological studies showing a significant correlation between the level of nitration found in plasma proteins and the prevalence of cardiovascular disease, supporting the usefulness of this biomarker to predict the outcome and to take appropriate therapeutic decisions in atherosclerotic disease.

Myeloperoxidase is associated with insulin resistance and inflammation in overweight subjects with first-degree relatives with type 2 diabetes mellitus

BACKGROUND

Family history of type 2 diabetes mellitus (T2DM) is one of risk factors for that in future a subject can develop diabetes. Insulin resistance (IR) is important in the pathogenesis of T2DM. There is evidence that oxidative stress plays an important role in the etiology and/or progression of diabetes. Myeloperoxidase (MPO) participates in developing of inflammation. The objective was to investigate if MPO is associated with IR and inflammation in individuals with first-degree relatives of T2DM.

METHODS

Cross-sectional study in 84 overweight individuals with family history of T2DM divided in two groups according to IR, group with IR (homeostasis model assessment [HOMA] ≥2.5; n=43) and control group (CG; HOMA <2.5; n=41). Complete clinical history and a venous blood sample were collected for measuring glucose and lipids profile, insulin, interleukin-6 (IL-6), tumor necrosis factor-α (TNF-α), MPO, glutathione reductase (GRd), glutathione peroxidase, and superoxide dismutase.

RESULTS

MPO, TNF-α, and IL-6 were higher in patients with IR than in CG (MPO: 308.35 [190.85 to 445.42] vs. 177.35 [104.50 to 279.85], P=0.0001; TNF-α: 13.46 [10.58 to 18.88] vs. 9.39 [7.53 to 11.25], P=0.0001; IL-6: 32.93 [24.93 to 38.27] vs. 15.60 [12.93 to 26.27]; P=0.0001, respectively). MPO was associated with IR (rho de Spearman=0.362, P=0.001). In the analysis of lineal regression, MPO predicts IR (β, 0.263; t, 2.520; P=0.014). In the univariate analysis, MPO had an odds ratio of 9.880 for risk of IR (95% confidence interval, 2.647 to 36.879).

CONCLUSION

MPO had relation with IR and inflammation parameters in overweight subjects with first-degree relatives of T2DM. We need studies on a casual relationship and molecular mechanisms among the increased serum MPO levels, inflammation markers, and IR.

HDL from apoA1 transgenic mice expressing the 4WF isoform is resistant to oxidative loss of function

HDL functions are impaired by myeloperoxidase (MPO), which selectively targets and oxidizes human apoA1. We previously found that the 4WF isoform of human apoA1, in which the four tryptophan residues are substituted with phenylalanine, is resistant to MPO-mediated loss of function. The purpose of this study was to generate 4WF apoA1 transgenic mice and compare functional properties of the 4WF and wild-type human apoA1 isoforms in vivo. Male mice had significantly higher plasma apoA1 levels than females for both isoforms of human apoA1, attributed to different production rates. With matched plasma apoA1 levels, 4WF transgenics had a trend for slightly less HDL-cholesterol versus human apoA1 transgenics. While 4WF transgenics had 31% less reverse cholesterol transport (RCT) to the plasma compartment, equivalent RCT to the liver and feces was observed. Plasma from both strains had similar ability to accept cholesterol and facilitate ex vivo cholesterol efflux from macrophages. Furthermore, we observed that 4WF transgenic HDL was partially (∼50%) protected from MPO-mediated loss of function while human apoA1 transgenic HDL lost all ABCA1-dependent cholesterol acceptor activity. In conclusion, the structure and function of HDL from 4WF transgenic mice was not different than HDL derived from human apoA1 transgenic mice.

Oximated ruthenium tris-bipyridyl complex: synthesis and luminescent response specifically for ClO− in water containing multiple ions

A novel Ru(bpy)₃²⁺ complex capable of a selective response to ClO⁻ in pH 4–11 water in the presence of other anions and cations is reported.

A two-photon fluorescent probe for detecting endogenous hypochlorite in living cells

A highly selective two-photon fluorescent probe (HQ) for endogenous hypochlorite (ClO⁻) was developed.

A ratiometric fluorescent probe for in situ quantification of basal mitochondrial hypochlorite in cancer cells

The first mitochondria-targeted ratiometric fluorescent probe to image exogenous and endogenous ClO⁻was presented with high selectivity and sensitivity.

Light up ClO−in live cells using an aza-coumarin based fluorescent probe with fast response and high sensitivity

An aza-coumarin based fluorescent and colorimetricAC-ClOfor the ClO⁻determination with fast response and high sensitivity.AC-ClOwas successfully applied for the live-cell imaging of exogenous and endogenous ClO⁻.

Multiple sclerosis: myeloperoxidase immunoradiology improves detection of acute and chronic disease in experimental model

PURPOSE

To test if MPO-Gd, a gadolinium-based magnetic resonance (MR) imaging probe that is sensitive and specific for the proinflammatory and oxidative enzyme myeloperoxidase (MPO), which is secreted by certain inflammatory cells, is more sensitive than diethylenetriaminepentaacetic acid (DTPA)-Gd in revealing early subclinical and chronic disease activity in the brain in experimental autoimmune encephalomyelitis (EAE), a mouse model of multiple sclerosis.

MATERIALS AND METHODS

The protocol for animal experiments was approved by the institutional animal care committee. A total of 61 female SJL mice were induced with EAE. Mice underwent MPO-Gd- or DTPA-Gd-enhanced MR imaging on days 6, 8, and 10 after induction, before clinical disease develops, and during chronic disease at remission and the first relapse. Brains were harvested at these time points for flow cytometric evaluation of immune cell subtypes and immunohistochemistry. Statistical analysis was performed, and P < .05 was considered to indicate a significant difference.

RESULTS

MPO-Gd helps detect earlier (5.2 vs 2.3 days before symptom onset, P = .004) and more (3.1 vs 0.3, P = .008) subclinical inflammatory lesions compared with DTPA-Gd, including in cases in which there was no evidence of overt blood-brain barrier (BBB) breakdown detected with DTPA-Gd enhancement. The number of MPO-Gd-enhancing lesions correlated with early infiltration of MPO-secreting monocytes and neutrophils into the brain (r = 0.91). MPO-Gd also helped detect more lesions during subclinical disease at remission (5.5 vs 1.3, P = .006) and at the first relapse (9.0 vs 2.7, P = .03) than DTPA-Gd, which also correlated well with the presence and accumulation of MPO-secreting inflammatory cells in the brain (r = 0.93).

CONCLUSION

MPO-Gd specifically reveals lesions with inflammatory monocytes and neutrophils, which actively secrete MPO. These results demonstrate the feasibility of detection of subclinical inflammatory disease activity in vivo, which is different from overt BBB breakdown.

The role of macrophages in the innate immune response to Streptococcus pneumoniae and Staphylococcus aureus: mechanisms and contrasts

Macrophages are critical mediators of innate immune responses against bacteria. The Gram-positive bacteria Streptococcus pneumoniae and Staphylococcus aureus express a range of virulence factors, which challenge macrophages' immune competence. We review how macrophages respond to this challenge. Macrophages employ a range of strategies to phagocytose and kill each pathogen. When the macrophages capacity to clear bacteria is overwhelmed macrophages play important roles in orchestrating the inflammatory response through pattern recognition receptor-mediated responses. Macrophages also ensure the inflammatory response is tightly constrained, to avoid tissue damage, and play an important role in downregulating the inflammatory response once initial bacterial replication is controlled.

Benzanthrone induced immunotoxicity via oxidative stress and inflammatory mediators in Balb/c mice

Benzanthrone (BA) is an important dye intermediate which is used in the manufacturing of several polycyclic vat and disperse dyes in textile industries. Several studies have indicated that the general population is also exposed to BA owing to its release from furnace effluents and automobile exhausts in the environment. In several clinical studies, it has been shown that workers exposed to BA developed itching, burning sensation, erythema and hyperpigmentation of the skin, which could be an outcome of the dysregulated immune response. In this study, we have used female Balb/c mice as a model to study the immuno-inflammatory changes after systemic administration of BA (7.5mg/kgb.w. and 15mg/kgb.w.) for one week. BA exposed animals exhibited the signs of intense systemic inflammation as evident by enhanced DTH response, MPO activity, hyperplastic and dysplastic histopathological organization of spleen and lung tissue. Splenic evaluation revealed enhanced oxidative stress, upregulation of prominent inflammatory markers like iNOS and COX-2 and DNA damage. In coherence with the observed immuno-inflammatory alterations, the levels of several inflammatory and regulatory cytokines (IL-17, TNF-α, IFN-γ, IL-1, IL-10, IL-4) were significantly enhanced in serum as well as the spleen. In addition, BA administration significantly induced the activation of ERK1/2, p38, JNK MAPKs and their downstream transcription factors AP-1 (c-fos, c-jun), NF-κB and Nrf2 which comprise important mechanistic pathways involved in inflammatory manifestations. These results suggest the immunotoxic nature of the BA and have implications for the risk assessment and management of occupational workers, and even common masses considering its presence as an environmental contaminant.

Hypochlorous acid as a precursor of free radicals in living systems

Hypochlorous acid (HOCl) is produced in the human body by the family of mammalian heme peroxidases, mainly by myeloperoxidase, which is secreted by neutrophils and monocytes at sites of inflammation. This review discusses the reactions that occur between HOCl and the major classes of biologically important molecules (amino acids, proteins, nucleotides, nucleic acids, carbohydrates, lipids, and inorganic substances) to form free radicals. The generation of such free radical intermediates by HOCl and other reactive halogen species is accompanied by the development of halogenative stress, which causes a number of socially important diseases, such as cardiovascular, neurodegenerative, infectious, and other diseases usually associated with inflammatory response and characterized by the appearance of biomarkers of myeloperoxidase and halogenative stress. Investigations aimed at elucidating the mechanisms regulating the activity of enzyme systems that are responsible for the production of reactive halogen species are a crucial step in opening possibilities for control of the development of the body's inflammatory response.

Effects of G-CSF on serum cholesterol and development of atherosclerotic plaque in apolipoprotein E-deficient mice

Macrophage colony stimulating factor (M-CSF) is known to have profound effects upon vascular pathologies, but potential roles of other colony stimulating factors (CSF) are not well understood. We treated apo E deficient (apo E-/-) mice with granulocyte colony stimulating factor (G-CSF) or vehicle daily for 9 weeks, during which time they were fed a Western-style diet. G-CSF treatment resulted in increased proportions of circulating monocytes (6.9 ± 2.2% vs. 3.8 ± 0.3%; p < 0.05), a trend towards increased neutrophils (33.5 ± 19.1% vs. 22.2 ± 7.8%; p = 0.17), and decreased serum levels of total cholesterol (981 ± 594 vs. 1495 ± 1009 mg/dL; p < 0.005) compared to control mice. There was a trend towards less low density lipoprotein (LDL) in G-CSF treated mice (24.6 ± 2.4% vs. 37.4 ± 12.3%; p = 0.10). A greater proportion of bone marrow cells from G-CSF treated mice expressed membrane type 1 matrix metalloprotease (MT1-MMP) (G-CSF: 14.5 ± 5.5%;

CONTROL

6.2 ± 5.0%; p < 0.05) compared to bone marrow cells from vehicle treated mice. G-CSF treatment was also associated with smaller atheromatous plaque, decreased Oil red O staining, and decreased infiltration of both Monocyte/Macrophage Marker Antibody (MOMA-2) and F4/80 dependent macrophage populations into aortic lesions. However, decreased plaque area appeared to be largely due to lower cholesterol levels in G-CSF-treated mice. Lesions in G-CSF treated mice appeared to be structurally distinct from control mice, containing relatively less lipid and macrophages. Our results suggest important roles for G-CSF in cholesterol metabolism, mobilization of bone marrow stem cells that might alter plaque development, and accumulation of lipids and macrophages into atherosclerotic lesions.

A myeloperoxidase-containing complex regulates neutrophil elastase release and actin dynamics during NETosis

Neutrophils contain granules loaded with antimicrobial proteins and are regarded as impermeable organelles that deliver cargo via membrane fusion. However, during the formation of neutrophil extracellular traps (NETs), neutrophil elastase (NE) translocates from the granules to the nucleus via an unknown mechanism that does not involve membrane fusion and requires reactive oxygen species (ROS). Here, we show that the ROS triggers the dissociation of NE from a membrane-associated complex into the cytosol and activates its proteolytic activity in a myeloperoxidase (MPO)-dependent manner. In the cytosol, NE first binds and degrades F-actin to arrest actin dynamics and subsequently translocates to the nucleus. The complex is an example of an oxidative signaling scaffold that enables ROS and antimicrobial proteins to regulate neutrophil responses. Furthermore, granules contain protein machinery that transports and delivers cargo across membranes independently of membrane fusion.

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A complex of antimicrobials drives neutrophil elastase to the nucleus during NETosis

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The “azurosome” complex mediates protein release across intact membranes

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Myeloperoxidase is required for neutrophil elastase release

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Neutrophil elastase degrades F-actin and arrests actin dynamics

MicroRNA-24 regulates macrophage behavior and retards atherosclerosis

OBJECTIVE

Our recent studies have highlighted membrane type-1 matrix metalloproteinase (MMP)-14 as a selective marker for an invasive subset of macrophages potentially related to atherosclerotic plaque progression. Moreover, colony stimulating factors (CSF) may exert divergent effects on macrophage MMP expression, possibly through microRNAs. We, therefore, aim to identify and test the pathophysiological role of microRNAs, which modulate macrophage MMP-14 expression in atherosclerotic plaque progression.

APPROACH AND RESULTS

Compared with macrophage CSF-differentiated macrophages, granulocyte/macrophage CSF-matured macrophages exhibited reduced MMP-14 mRNA levels but increased protein expression and activity, which resulted in heightened macrophage invasion. MicroRNA-24, identified to target MMP-14, was accordingly increased in macrophage CSF compared with granulocyte/macrophage CSF macrophages. Silencing microRNA-24 in macrophage CSF macrophages significantly increased MMP-14 expression and enhanced their invasive capacity, mimicking granulocyte/macrophage CSF macrophages, and suggesting that granulocyte/macrophage CSF modulates MMP-14 protein expression and subsequent macrophage invasion in a microRNA-24-dependent manner. In human coronary atherosclerotic plaques, increased MMP-14 protein expression in foam cell macrophages was associated with lesions exhibiting histological characteristics associated with an unstable phenotype. Furthermore, microRNA-24 expression in these atherosclerotic plaques was inversely related to MMP-14 protein expression. Moreover, stable plaques contained higher microRNA-24 levels than unstable plaques, and microRNA-24 colocalized with foam cell macrophages that exhibited low MMP-14 protein expression. Finally, in atherosclerotic mice (apolipoprotein E-deficient), microRNA-24 inhibition increased plaque size and macrophage MMP-14 expression.

CONCLUSIONS

Taken together, our data demonstrates that downregulation of microRNA-24 promotes an invasive macrophage subset and plays a novel regulatory role in MMP-14 proteolytic activity and, therefore, plaque stability, highlighting its therapeutic potential.