Effects of a novel pharmacologic inhibitor of myeloperoxidase in a mouse atherosclerosis model

A combinatorial approach for achieving CNS-selective RNAi

RNA interference (RNAi) is an endogenous process that can be harnessed using chemically modified small interfering RNAs (siRNAs) to potently modulate gene expression in many tissues. The route of administration and chemical architecture are the primary drivers of oligonucleotide tissue distribution, including siRNAs. Independently of the nature and type, oligonucleotides are eliminated from the body through clearance tissues, where their unintended accumulation may result in undesired gene modulation. Divalent siRNAs (di-siRNAs) administered into the CSF induce robust gene silencing throughout the central nervous system (CNS). Upon clearance from the CSF, they are mainly filtered by the kidneys and liver, with the most functionally significant accumulation occurring in the liver. siRNA- and miRNA-induced silencing can be blocked through substrate inhibition using single-stranded, stabilized oligonucleotides called antagomirs or anti-siRNAs. Using APOE as a model target, we show that undesired di-siRNA-induced silencing in the liver can be mitigated through administration of liver targeting GalNAc-conjugated anti-siRNAs, without impacting CNS activity. Blocking unwanted hepatic APOE silencing achieves fully CNS-selective silencing, essential for potential clinical translation. While we focus on CNS/liver selectivity, coadministration of differentially targeting siRNA and anti-siRNAs can be adapted as a strategy to achieve tissue selectivity in different organ combinations.

Silencing Apoe with divalent-siRNAs improves amyloid burden and activates immune response pathways in Alzheimer's disease

INTRODUCTION

The most significant genetic risk factor for late-onset Alzheimer's disease (AD) is APOE4, with evidence for gain- and loss-of-function mechanisms. A clinical need remains for therapeutically relevant tools that potently modulate APOE expression.

METHODS

We optimized small interfering RNAs (di-siRNA, GalNAc) to potently silence brain or liver Apoe and evaluated the impact of each pool of Apoe on pathology.

RESULTS

In adult 5xFAD mice, siRNAs targeting CNS Apoe efficiently silenced Apoe expression and reduced amyloid burden without affecting systemic cholesterol, confirming that potent silencing of brain Apoe is sufficient to slow disease progression. Mechanistically, silencing Apoe reduced APOE-rich amyloid cores and activated immune system responses.

DISCUSSION

These results establish siRNA-based modulation of Apoe as a viable therapeutic approach, highlight immune activation as a key pathway affected by Apoe modulation, and provide the technology to further evaluate the impact of APOE silencing on neurodegeneration.

Myeloperoxidase creates a permissive microenvironmental niche for the progression of multiple myeloma

Expression of myeloperoxidase (MPO), a key inflammatory enzyme restricted to myeloid cells, is negatively associated with the development of solid tumours. Activated myeloid cell populations are increased in multiple myeloma (MM); however, the functional consequences of myeloid-derived MPO within the myeloma microenvironment are unknown. Here, the role of MPO in MM pathogenesis was investigated, and the capacity for pharmacological inhibition of MPO to impede MM progression was evaluated. In the 5TGM1-KaLwRij mouse model of myeloma, the early stages of tumour development were associated with an increase in CD11b+ myeloid cell populations and an increase in Mpo expression within the bone marrow (BM). Interestingly, MM tumour cell homing was increased towards sites of elevated myeloid cell numbers and MPO activity within the BM. Mechanistically, MPO induced the expression of key MM growth factors, resulting in tumour cell proliferation and suppressed cytotoxic T-cell activity. Notably, tumour growth studies in mice treated with a small-molecule irreversible inhibitor of MPO (4-ABAH) demonstrated a significant reduction in overall MM tumour burden. Taken together, our data demonstrate that MPO contributes to MM tumour growth, and that MPO-specific inhibitors may provide a new therapeutic strategy to limit MM disease progression.

Paraoxonase 1 and atherosclerosis

Paraoxonase 1 (PON1), residing almost exclusively on HDL, was discovered because of its hydrolytic activity towards organophosphates. Subsequently, it was also found to hydrolyse a wide range of substrates, including lactones and lipid hydroperoxides. PON1 is critical for the capacity of HDL to protect LDL and outer cell membranes against harmful oxidative modification, but this activity depends on its location within the hydrophobic lipid domains of HDL. It does not prevent conjugated diene formation, but directs lipid peroxidation products derived from these to become harmless carboxylic acids rather than aldehydes which might adduct to apolipoprotein B. Serum PON1 is inversely related to the incidence of new atherosclerotic cardiovascular disease (ASCVD) events, particularly in diabetes and established ASCVD. Its serum activity is frequently discordant with that of HDL cholesterol. PON1 activity is diminished in dyslipidaemia, diabetes, and inflammatory disease. Polymorphisms, most notably Q192R, can affect activity towards some substrates, but not towards phenyl acetate. Gene ablation or over-expression of human PON1 in rodent models is associated with increased and decreased atherosclerosis susceptibility respectively. PON1 antioxidant activity is enhanced by apolipoprotein AI and lecithin:cholesterol acyl transferase and diminished by apolipoprotein AII, serum amyloid A, and myeloperoxidase. PON1 loses this activity when separated from its lipid environment. Information about its structure has been obtained from water soluble mutants created by directed evolution. Such recombinant PON1 may, however, lose the capacity to hydrolyse non-polar substrates. Whilst nutrition and pre-existing lipid modifying drugs can influence PON1 activity there is a cogent need for more specific PON1-raising medication to be developed.

Neutrophils in aging and aging‐related pathologies

Over the past millennia, life expectancy has drastically increased. While a mere 25 years during Bronze and Iron ages, life expectancy in many European countries and in Japan is currently above 80 years. Such an increase in life expectancy is a result of improved diet, life style, and medical care. Yet, increased life span and aging also represent the most important non-modifiable risk factors for several pathologies including cardiovascular disease, neurodegenerative diseases, and cancer. In recent years, neutrophils have been implicated in all of these pathologies. Hence, this review provides an overview of how aging impacts neutrophil production and function and conversely how neutrophils drive aging-associated pathologies. Finally, we provide a perspective on how processes of neutrophil-driven pathologies in the context of aging can be targeted therapeutically.

Therapeutic enzymes as non-conventional targets in cardiovascular impairments:A Comprehensive Review

Over the last few decades, substantial progress has been made towards the understanding of cardiovascular diseases (CVDs). In-depth mechanistic insights have also provided opportunities to explore novel therapeutic targets and treatment regimens to be discovered. Therapeutic enzymes are an example of such opportunities. The balanced functioning of such enzymes protects against a variety of CVDs while on the other hand, even a small shift in the normal functioning of these enzymes may lead to deleterious outcomes. Owing to the great versatility of these enzymes, inhibition and activation are key regulatory approaches to counter the onset and progression of several cardiovascular impairments. While cardiovascular remedies are already available in excess and of course they are efficacious, a comprehensive description of novel therapeutic enzymes to combat CVDs is the need of the hour. In light of this, the regulation of the functional activity of these enzymes also opens a new avenue for the treatment approaches to be employed. This review describes the importance of non-conventional enzymes as potential candidates in several cardiovascular disorders while highlighting some of the recently targeted therapeutic enzymes in CVDs.

The potential targets in immunotherapy of atherosclerosis

Cardiovascular disease is the most common cause of death, which has the highest mortality rate worldwide. Although a diverse range of inflammatory diseases can affect the cardiovascular system, however, heart failure and stroke occur due to atherosclerosis. Atherosclerosis is a chronic autoinflammatory disease of small to large vessels in which different immune mediators are involved in lipid plaque formation and inflammatory vascular remodeling process. A better understanding of the pathophysiology of atherosclerosis may lead to uncovering immunomodulatory therapies. Despite present diagnostic and therapeutic methods, the lack of immunotherapy in the prevention and treatment of atherosclerosis is perceptible. In this review, we will discuss the promising immunological-based therapeutics and novel preventive approaches for atherosclerosis. This study could provide new insights into a better perception of targeted therapeutic pathways and biological therapies.

Neutrophil extracellular trap-associated molecules: a review on their immunophysiological and inflammatory roles

Neutrophil extracellular traps (NETs) are a defense mechanism against pathogens. They are composed of DNA and various proteins and have the ability to hinder microbial spreading and survival. However, NETs are not only related to infections but also participate in sterile inflammatory events. In addition to DNA, NETs contain histones, serine proteases, cytoskeletal proteins and antimicrobial peptides, all of which have immunomodulatory properties that can augment or decrease the inflammatory response. Extracellular localization of these molecules alerts the immune system of cellular damage, which is triggered by recognition of damage-associated molecular patterns (DAMPs) through specific pattern recognition receptors. However, not all of these molecules are DAMPs and may have other immunophysiological properties in the extracellular space. The release of NETs can lead to production of pro-inflammatory cytokines (due to TLR2/4/9 and inflammasome activation), the destruction of the extracellular matrix, activation of serine proteases and of matrix metallopeptidases (MMPs), modulation of cellular proliferation, induction of cellular migration and adhesion, promotion of thrombogenesis and angiogenesis and disruption of epithelial and endothelial permeability. Understanding the dynamics of NET-associated molecules, either individually or synergically, will help to unravel their role in inflammatory events and open novel perspectives for potential therapeutic targets. We here review molecules contained within NETS and their immunophysiological roles.

NETosis as a Pathogenic Factor for Heart Failure

Heart failure threatens the lives of patients and reduces their quality of life. Heart failure, especially heart failure with preserved ejection fraction, is closely related to systemic and local cardiac persistent chronic low-grade aseptic inflammation, microvascular damage characterized by endothelial dysfunction, oxidative stress, myocardial remodeling, and fibrosis. However, the initiation and development of persistent chronic low-grade aseptic inflammation is unexplored. Oxidative stress-mediated neutrophil extracellular traps (NETs) are the main immune defense mechanism against external bacterial infections. Furthermore, NETs play important roles in noninfectious diseases. After the onset of myocardial infarction, atrial fibrillation, or myocarditis, neutrophils infiltrate the damaged tissue and aggravate inflammation. In tissue injury, damage-related molecular patterns (DAMPs) may induce pattern recognition receptors (PRRs) to cause NETs, but whether NETs are directly involved in the pathogenesis and development of heart failure and the mechanism is still unclear. In this review, we analyzed the markers of heart failure and heart failure-related diseases and comorbidities, such as mitochondrial DNA, high mobility box group box 1, fibronectin extra domain A, and galectin-3, to explore their role in inducing NETs and to investigate the mechanism of PRRs, such as Toll-like receptors, receptor for advanced glycation end products, cGAS-STING, and C-X-C motif chemokine receptor 2, in activating NETosis. Furthermore, we discussed oxidative stress, especially the possibility that imbalance of thiol redox and MPO-derived HOCl promotes the production of 2-chlorofatty acid and induces NETosis, and analyzed the possibility of NETs triggering coronary microvascular thrombosis. In some heart diseases, the deletion or blocking of neutrophil-specific myeloperoxidase and peptidylarginine deiminase 4 has shown effectiveness. According to the results of current pharmacological studies, MPO and PAD4 inhibitors are effective at least for myocardial infarction, atherosclerosis, and certain autoimmune diseases, whose deterioration can lead to heart failure. This is essential for understanding NETosis as a therapeutic factor of heart failure and the related new pathophysiology and therapeutics of heart failure.

Deletion of bone marrow myeloperoxidase attenuates chronic kidney disease accelerated atherosclerosis

Increased myeloperoxidase (MPO) expression and activity are associated with atherosclerotic disease in patients with chronic kidney disease (CKD). However, the causal relationship between MPO and the development and progression of atherosclerosis in patients with CKD is unknown. Eight-week-old male low-density-lipoprotein-receptor-deficient mice were subjected to 5/6 nephrectomy, irradiated, and transplanted with bone marrow from MPO-deficient mice to induce bone marrow MPO deletion (CKD-bMPOKO) or bone marrow from WT mice as a control to maintain preserved bone marrow MPO(CKD-bMPOWT). The mice were maintained on a high-fat/high-cholesterol diet for 16 weeks. As anticipated, both groups of mice exhibited all features of moderate CKD, including elevated plasma creatinine, lower hematocrit, and increased intact parathyroid hormone but did not demonstrate any differences between the groups. Irradiation and bone marrow transplantation did not further affect body weight, blood pressure, creatinine, or hematocrit in either group. The absence of MPO expression in the bone marrow and atherosclerotic lesions of the aorta in the CKD-bMPOKO mice was confirmed by immunoblot and immunohistochemistry, respectively. Decreased MPO activity was substantiated by the absence of 3-chlorotyrosine, a specific by-product of MPO, in aortic atherosclerotic lesions as determined by both immunohistochemistry and highly sensitive LC-MS. Quantification of the aortic lesional area stained with oil red O revealed that CKD-bMPOKO mice had significantly decreased aortic plaque area as compared with CKD-bMPOWT mice. This study demonstrates the reduction of atherosclerosis in CKD mice with the deletion of MPO in bone marrow cells, strongly implicating bone-marrow-derived MPO in the pathogenesis of CKD atherosclerosis.

Inhibition of Myeloperoxidase

Myeloperoxidase participates in innate immune defense mechanism through formation of microbicidal reactive oxidants and diffusible radical species. A unique activity is its ability to use chloride as a cosubstrate with hydrogen peroxide to generate chlorinating oxidants such as hypochlorous acid, a potent antimicrobial agent. However, chronic MPO activation can lead to indiscriminate protein modification causing tissue damage, and has been associated with chronic inflammatory diseases, atherosclerosis, and acute cardiovascular events. This has attracted considerable interest in the development of therapeutically useful MPO inhibitors. Today, based on the profound knowledge of structure and function of MPO and its biochemical and biophysical differences with the other homologous human peroxidases, various rational and high-throughput screening attempts were performed in developing specific irreversible and reversible inhibitors. The most prominent candidates as well as MPO inhibitors already studied in clinical trials are introduced and discussed.

Sesamol: a powerful functional food ingredient from sesame oil for cardioprotection

Phytophenols are important bioactive food based chemical entities, largely present in several natural sources. Among them, sesamol is one of the key natural phenols found in sesame seeds, Piper cubeba etc. Several studies have reported that sesame oil is a potent cardioprotective functional food. Papers on the utility of sesamol in sesame oil (the chemical name of sesamol is methylenedioxyphenol, MDP) have appeared in the literature, though there is no single concise review on the usefulness of sesamol in sesame oil in CVD in the literature. Cardiovascular disease (CVD) is the most challenging health problem encountered by the global population. There has been increasing interest in the growth of effective cardiovascular therapeutics, specifically of natural origin. Among various natural sources of chemicals, phytochemicals are micronutrients and bio-compatible scaffolds having an extraordinary efficacy at multiple disease targets with minimal or no adverse effect. This review offers a perspective on the existing literature on functional ingredients in sesame oil with particular focus on sesamol and its derivatives having nutritional and cardioprotective properties. This is demonstrated to have shown a specifically modulating oxidative enzyme myeloperoxidase (MPO) and other proteins which are detrimental to human well-being. The molecular mechanism of cardioprotection by this food ingredient is primarily attributed to the methylenedioxy group present in the sesamol component.

ROS systems are a new integrated network for sensing homeostasis and alarming stresses in organelle metabolic processes

Reactive oxygen species (ROS) are critical for the progression of cardiovascular diseases, inflammations and tumors. However, the mechanisms of how ROS sense metabolic stress, regulate metabolic pathways and initiate proliferation, inflammation and cell death responses remain poorly characterized. In this analytic review, we concluded that: 1) Based on different features and functions, eleven types of ROS can be classified into seven functional groups: metabolic stress-sensing, chemical connecting, organelle communication, stress branch-out, inflammasome-activating, dual functions and triple functions ROS. 2) Among the ROS generation systems, mitochondria consume the most amount of oxygen; and nine types of ROS are generated; thus, mitochondrial ROS systems serve as the central hub for connecting ROS with inflammasome activation, trained immunity and immunometabolic pathways. 3) Increased nuclear ROS production significantly promotes cell death in comparison to that in other organelles. Nuclear ROS systems serve as a convergent hub and decision-makers to connect unbearable and alarming metabolic stresses to inflammation and cell death. 4) Balanced ROS levels indicate physiological homeostasis of various metabolic processes in subcellular organelles and cytosol, while imbalanced ROS levels present alarms for pathological organelle stresses in metabolic processes. Based on these analyses, we propose a working model that ROS systems are a new integrated network for sensing homeostasis and alarming stress in metabolic processes in various subcellular organelles. Our model provides novel insights on the roles of the ROS systems in bridging metabolic stress to inflammation, cell death and tumorigenesis; and provide novel therapeutic targets for treating those diseases. (Word count: 246).

Myeloperoxidase: a potential therapeutic target for coronary artery disease

INTRODUCTION

Coronary artery disease (CAD) poses significant morbidity and mortality globally. Despite significant advances in treatment interventions, residual cardiovascular risks remain unchecked. Recent clinical trials have shed light on the potential therapeutic benefits of targeting anti-inflammatory pathways. Myeloperoxidase (MPO) plays an important role in atherosclerotic plaque formation and destabilization of the fibrous cap; both increase the risk of atherosclerotic cardiovascular disease and especially CAD.

AREAS COVERED

This article examines the role of MPO in the pathogenesis of atherosclerotic CAD and the mechanistic data from several key therapeutic drug targets. There have been numerous interesting studies on prototype compounds that directly or indirectly attenuate the enzymatic activities of MPO, and subsequently exhibit atheroprotective effects; these include aminobenzoic acid hydrazide, ferulic acid derivative (INV-315), thiouracil derivatives (PF-1355 and PF-06282999), 2-thioxanthines derivative (AZM198), triazolopyrimidines, acetaminophen, N-acetyl lysyltyrosylcysteine (KYC), flavonoids, and alternative substrates such as thiocyanate and nitroxide radical.

EXPERT OPINION

Future investigations must determine if the cardiovascular benefits of direct systemic inhibition of MPO outweigh the risk of immune dysfunction, which may be less likely to arise with alternative substrates or MPO inhibitors that selectively attenuate atherogenic effects of MPO.

Immune-Inflammation in Atherosclerosis: A New Twist in an Old Tale

Background and Objective:

Atherosclerosis, a chronic and progressive inflammatory disease, is triggered by the activation of endothelial cells followed by infiltration of innate and adaptive immune cells including monocytes and T cells in arterial walls. Major populations of T cells found in human atherosclerotic lesions are antigen-specific activated CD4+ effectors and/or memory T cells from Th1, Th17, Th2 and Treg subsets. In this review, we will discuss the significance of T cell orchestrated immune inflammation in the development and progression of atherosclerosis.

Discussion:

Pathogen/oxidative stress/lipid induced primary endothelial wound cannot develop to a full-blown atherosclerotic lesion in the absence of chronically induced inflammation. While the primary inflammatory response might be viewed as a lone innate response, the persistence of such a profound response over time must be (and is) associated with diverse local and systemic T cell responses. The interplay between T cells and innate cells contributes to a phenomenon called immuneinflammation and has an impact on the progression and outcome of the lesion. In recent years immuneinflammation, an old term, has had a comeback in connecting the puzzle pieces of chronic inflammatory diseases.

Conclusion:

Taking one-step back and looking from afar at the players of immune-inflammation may help us provide a broader perspective of these complicated interactions. This may lead to the identification of new drug targets and the development of new therapies as well as preventative measures.

A pre-formulation strategy for the liposome encapsulation of new thioctic acid conjugates for enhanced chemical stability and use as an efficient drug carrier for MPO-mediated atherosclerotic CVD treatment

Lipoyl-apocynin and lipoyl-sesamol are bio-active conjugates of thioctic acid, synthesized using a benign chemical approachviathe combination of thioctic acid and the powerful bio-phytonutrients, apocynin and sesamol, respectively.

Methoxyphenol derivatives as reversible inhibitors of myeloperoxidase as potential antiatherosclerotic agents

Aim: To evaluate new chemical entities, based on ferulic acid scaffolds, as reversible myeloperoxidase inhibitors (MPOI). Methodology & results:In silico docking studies are performed with MPO protein as a target for several ferulic acid analogs followed by multiple in vitro assays to validate this approach. Two lead compounds 2a and 3 are identified with optimum docking and IC50 values: -7.95 kcal/mol, 0.9 μM and -8.35 kcal/mol, 8.5 μM, respectively. These MPOIs are able to inhibit oxidation of high-density lipoprotein and further promoted functionality of high-density lipoprotein. Conclusion: Lead analogs are potent MPOIs that exert specific effects on MPO-mediated oxidation as well as inflammatory pathways. It also acts as promoters of cholesterol efflux that sheds light on pharmacological approach in atherosclerosis treatment.

Inhibition of MPO (Myeloperoxidase) Attenuates Endothelial Dysfunction in Mouse Models of Vascular Inflammation and Atherosclerosis

Objective—

Inflammation-driven endothelial dysfunction initiates and contributes to the progression of atherosclerosis, and MPO (myeloperoxidase) has been implicated as a potential culprit. On release by circulating phagocytes, MPO is thought to contribute to endothelial dysfunction by limiting NO bioavailability via formation of reactive oxidants including hypochlorous acid. However, it remains largely untested whether specific pharmacological inhibition of MPO attenuates endothelial dysfunction. We, therefore, tested the ability of a mechanism-based MPO inhibitor, AZM198, to inhibit endothelial dysfunction in models of vascular inflammation.

Approach and Results—

Three models of inflammation were used: femoral cuff, the tandem stenosis model of plaque rupture in Apoe −/− mice, and C57BL/6J mice fed a high-fat, high-carbohydrate diet as a model of insulin resistance. Endothelial dysfunction was observed in all 3 models, and oral administration of AZM198 significantly improved endothelial function in the femoral cuff and tandem stenosis models only. Improvement in endothelial function was associated with decreased arterial MPO activity, determined by the in vivo conversion of hydroethidine to 2-chloroethidium, without affecting circulating inflammatory cytokines or arterial MPO content. Mechanistic studies in Mpo −/− mice confirmed the contribution of MPO to endothelial dysfunction and revealed oxidation of sGC (soluble guanylyl cyclase) as the underlying cause of the observed limited NO bioavailability.

Conclusions—

Pharmacological inhibition of MPO is a potential strategy to limit endothelial dysfunction in vascular inflammation.

Visual Overview—

An online visual overview is available for this article.

Sodium thiocyanate treatment attenuates atherosclerotic plaque formation and improves endothelial regeneration in mice

Introduction

Atherosclerotic plaque formation is an inflammatory process that involves the recruitment of neutrophil granulocytes and the generation of reactive oxygen species (ROS). ROS formation by myeloperoxidase, a key enzyme in H₂O₂ degradation, can be modulated by addition of sodium thiocyanate (NaSCN). However, the therapeutic use of NaSCN to counteract atherogenesis has been controversial, because MPO oxidizes NaSCN to hypothiocyanous acid, which is a reactive oxygen species itself. Therefore, this study aimed to investigate the effect of NaSCN treatment on atherogenesis in vivo.

Methods

Apolipoprotein E knockout (ApoE^−/−) mice on western-diet were treated with NaSCN for 8 weeks. Blood levels of total cholesterol, IL-10, and IL-6 were measured. Aortic roots from these mice were analyzed histologically to quantify plaque formation, monocyte, and neutrophil granulocyte infiltration. Oxidative damage was evaluated via an L-012 chemiluminescence assay and staining for chlorotyrosine in the aortic walls. Endothelial function was assessed by use of endothelium-dependent vasodilation in isolated aortic rings. Neointima formation was evaluated in wild-type mice following wire injury of the carotid artery.

Results

NaSCN treatment of ApoE^-/- mice lead to a reduction of atherosclerotic plaque size in the aortic roots but had no effect on monocyte or granulocyte infiltration. Serum levels of the pro-inflammatory cytokine IL-6 decreased whereas anti-inflammatory IL-10 increased upon NaSCN treatment. In our experiments, we found oxidative damage to be reduced and the endothelial function to be improved in the NaSCN-treated group. Additionally, NaSCN inhibited neointima formation.

Conclusion

NaSCN has beneficial effects on various stages of atherosclerotic plaque development in mice.

Myeloperoxidase inhibition in mice alters atherosclerotic lesion composition

Myeloperoxidase (MPO) is a highly abundant protein within the neutrophil that is associated with lipoprotein oxidation, and increased plasma MPO levels are correlated with poor prognosis after myocardial infarct. Thus, MPO inhibitors have been developed for the treatment of heart failure and acute coronary syndrome in humans. 2-(6-(5-Chloro-2-methoxyphenyl)-4-oxo-2-thioxo-3,4-dihydropyrimidin-1(2H)-yl)acetamide PF-06282999 is a recently described selective small molecule mechanism-based inactivator of MPO. Here, utilizing PF-06282999, we investigated the role of MPO to regulate atherosclerotic lesion formation and composition in the Ldlr^-/- mouse model of atherosclerosis. Though MPO inhibition did not affect lesion area in Ldlr^-/- mice fed a Western diet, reduced necrotic core area was observed in aortic root sections after MPO inhibitor treatment. MPO inhibition did not alter macrophage content in and leukocyte homing to atherosclerotic plaques. To assess non-invasive monitoring of plaque inflammation, [¹⁸F]-Fluoro-deoxy-glucose (FDG) was administered to Ldlr^-/- mice with established atherosclerosis that had been treated with clinically relevant doses of PF-06282999, and reduced FDG signal was observed in animals treated with a dose of PF-06282999 that corresponded with reduced necrotic core area. These data suggest that MPO inhibition does not alter atherosclerotic plaque area or leukocyte homing, but rather alters the inflammatory tone of atherosclerotic lesions; thus, MPO inhibition could have utility to promote atherosclerotic lesion stabilization and prevent atherosclerotic plaque rupture.

Myeloperoxidase deficiency attenuates systemic and dietary iron-induced adverse effects

Iron deficiency is routinely treated with oral or systemic iron supplements, which are highly reactive and could induce oxidative stress via augmenting the activity of proinflammatory enzyme myeloperoxidase (MPO). To investigate the extent to which MPO is involved in iron-induced toxicity, acute (24 h) iron toxicity was induced by intraperitoneal administration of FeSO₄ (25 mg/kg body weight) to MPO-deficient (MpoKO) mice and their wild-type (WT) littermates. Acute iron toxicity was also assessed in WT mice pretreated with an MPO inhibitor, 4-aminobenzoic acid hydrazide. Systemic iron administration up-regulated circulating MPO and neutrophil elastase and elevated systemic inflammatory and organ damage markers in WT mice. However, genetic deletion of MPO or its inhibition significantly reduced iron-induced organ damage and systemic inflammatory responses. In contrast to the acute model, 8 weeks of 2% carbonyl iron diet feeding to WT mice did not change the levels of circulating MPO and neutrophil elastase but promoted their accumulation in the liver. Even though both MpoKO and WT mice displayed similar levels of diet-induced hyperferremia, MpoKO mice showed significantly reduced inflammatory response and oxidative stress than the WT mice. In addition, WT bone-marrow-derived neutrophils (BMDN) generated more reactive oxygen species than MPO-deficient BMDN upon iron stimulation. Altogether, genetic deficiency or pharmacologic inhibition of MPO substantially attenuated acute and chronic iron-induced toxicity. Our results suggest that targeting MPO during iron supplementation is a promising approach to reduce iron-induced toxicity/side effects in vulnerable population.

Identification and evaluation of anti-inflammatory properties of aqueous components extracted from sesame (Sesamum indicum) oil

We previously reported that sesame oil (SO) has anti-inflammatory, anti-atherosclerotic and lipid lowering properties in vivo. Our recent studies have shown that, an aqueous extract of sesame oil (SOAE) has also anti-inflammatory and anti-atherosclerotic properties but with no lipid lowering effects. The extent of reduction in atherosclerosis led us to identify components of SOAE and evaluate their anti-inflammatory properties in vitro. Liquid chromatography mass spectrometric method was used to detect and identify components of SOAE. Methoxyphenol derivatives, short and long chain carboxylic acids, dicarboxylic acids, hydroxy and oxo- carboxylic acids were detected. To our surprise, sesamol and its derivatives (lignans), were not present in the SOAE. Among the identified, a combination of methoxy phenol compounds were selected and tested their ability to reduce LPS induced inflammatory gene expression. Monocyte derived macrophages/RAW 264.7 macrophages were pre-treated with these compounds for 2 h, followed by LPS stimulation for 24 h and pro-inflammatory gene expressions were analyzed. These methoxyphenol derivatives showed potent anti-inflammatory properties. In conclusion, the anti-inflammatory molecules associated with SO may contribute the anti-inflammatory and anti-atherosclerotic properties. Also, our results shed light for the development of SOAE based non-pharmacological therapeutics, nutritional supplements and health products for various inflammatory diseases in the future.

Oxidative Stress in Aortas of Patients with Advanced Occlusive and Aneurysmal Diseases

BACKGROUND

Aortoiliac occlusive disease (AOD) and abdominal aortic aneurysm (AAA) are very important cardiovascular diseases that present different aspects of pathophysiology; however, oxidative stress and inflammatory response seem be relevant in both of them. Our objective was to evaluate oxidative damage and degree of inflammatory infiltrate in aortas of patients surgically treated for AOD and AAA.

MATERIALS AND METHODS

Levels of reactive oxygen species (ROS), nicotinamide adenine dinucleotide phosphate (NADPH) oxidase activity, and myeloperoxidase (MPO) expression as well as nitrite levels and superoxide dismutase (SOD) and catalase (CAT) activities were evaluated in aortas of patients with AOD (n = 16) or AAA (n = 14), while the control group was formed by cadaveric organ donors (n = 10). We also analyzed the degree of inflammatory infiltrate in these aortas.

RESULTS

There was an increase in ROS levels and NADPH oxidase activity in patients with AOD and AAA when compared with the control group, and the AOD group demonstrated higher ROS production and NADPH oxidase activity and also nitrite levels when compared with the AAA group (P < 0.001). On the other hand, an increase of SOD activity in the AOD group and CAT activity in the AAA group was observed. Inflammatory infiltrate and MPO expression were higher in the AOD group when compared with the control group (P < 0.05).

CONCLUSIONS

Oxidative stress is relevant in both AOD and AAA, though AOD presented higher ROS levels and NADPH activity. Increased activities of antioxidant enzymes may be a compensatory phenomenon which occurs in aortas of patients with AOD and AAA. Perhaps, a relationship between oxidative stress and degree of inflammatory infiltrate may exist in the pathophysiology of AOD and AAA.

High-Density Lipoprotein Reduction Differentially Modulates to Classical and Nonclassical Monocyte Subpopulations in Metabolic Syndrome Patients and in LPS-Stimulated Primary Human Monocytes In Vitro

The effect of metabolic syndrome on human monocyte subpopulations has not yet been studied. Our main goal was to examine monocyte subpopulations in metabolic syndrome patients, while also identifying the risk factors that could directly influence these cells. Eighty-six subjects were divided into metabolic syndrome patients and controls. Monocyte subpopulations were quantified by flow cytometry, and interleukin- (IL-) 1β secretion levels were measured by ELISA. Primary human monocytes were cultured in low or elevated concentrations of high-density lipoprotein (HDL) and stimulated with lipopolysaccharide (LPS). The nonclassical monocyte (NCM) percentage was significantly increased in metabolic syndrome patients as compared to controls, whereas classical monocytes (CM) were reduced. Among all metabolic syndrome risk factors, HDL reduction exhibited the most important correlation with monocyte subpopulations and then was studied in vitro. Low HDL concentration reduced the CM percentage, whereas it increased the NCM percentage and IL-1β secretion in LPS-treated monocytes. The LPS effect was abolished when monocytes were cultured in elevated HDL concentrations. Concurring with in vitro results, IL-1β serum values significantly increased in metabolic syndrome patients with low HDL levels as compared to metabolic syndrome patients without HDL reduction. Our data demonstrate that HDL directly modulates monocyte subpopulations in metabolic syndrome.

Role of neutrophils in atherogenesis: an update

BACKGROUND

The role of neutrophils in the beginning and the progression of the atherosclerotic process did not receive much attention until the last years. On the contrary, recent data, in both the experimental animals and humans, suggest important effects of these cells with possible clinical consequences.

MATERIALS AND METHODS

This narrative review was based on the papers found on PubMed and MEDLINE up to July 2015. The search terms used were 'neutrophil, atherosclerosis' in combination with 'recruitment, chemokine, plaque destabilization and pathophysiology'.

RESULTS

Different models demonstrate the presence and the actions of neutrophils in the early steps of the atherogenesis confirming the fundamental role of these cells in the response of the innate immune system to different pathogens (in this context the modified lipoproteins). However, also the late phases of the atherosclerotic process, in particular the destabilization of a mature plaque, seem to be modulated by the neutrophils, possibly through the interaction with recently discovered biological systems such as the endocannabinoids.

CONCLUSIONS

The understanding of the mechanisms involved in the modulation exerted by neutrophils in atherosclerosis is pivotal in terms of the complete definition of the overall picture. This approach will certainly give us new targets and new pharmacological opportunities for the anti-inflammatory strategy of the cardiovascular prevention.

Methods for measuring myeloperoxidase activity toward assessing inhibitor efficacy in living systems

Myeloperoxidase aids in clearance of microbes by generation of peroxidase-mediated oxidants that kill leukocyte-engulfed pathogens. In this review, we will examine 1) strategies for in vitro evaluation of myeloperoxidase function and its inhibition, 2) ways to monitor generation of certain oxidant species during inflammation, and 3) how these methods can be used to approximate the total polymorphonuclear neutrophil chemotaxis following insult. Several optical imaging probes are designed to target reactive oxygen and nitrogen species during polymorphonuclear neutrophil inflammatory burst following injury. Here, we review the following 1) the broad effect of myeloperoxidase on normal physiology, 2) the difference between myeloperoxidase and other peroxidases, 3) the current optical probes available for use as surrogates for direct measures of myeloperoxidase-derived oxidants, and 4) the range of preclinical options for imaging myeloperoxidase accumulation at sites of inflammation in mice. We also stress the advantages and drawbacks of each of these methods, the pharmacokinetic considerations that may limit probe use to strictly cell cultures for some reactive oxygen and nitrogen species, rather than in vivo utility as indicators of myeloperoxidase function. Taken together, our review should shed light on the fundamental rational behind these techniques for measuring myeloperoxidase activity and polymorphonuclear neutrophil response after injury toward developing safe myeloperoxidase inhibitors as potential therapy for chronic obstructive pulmonary disease and rheumatoid arthritis.

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.

Cytochrome P450 1B1 Contributes to the Development of Atherosclerosis and Hypertension in Apolipoprotein E-Deficient Mice

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Cytochrome P450 (CYP) 1B1 contributes to vascular smooth muscle cell growth and hypertension in male mice. This study was conducted to determine the contribution of CYP1B1 to the development of atherosclerosis and hypertension and associated pathogenesis in 8-week-old male apolipoprotein E–deficient (ApoE^−/−/Cyp1b1^+/+), and ApoE- and CYP1B1-deficient (ApoE^−/−/Cyp1b1^−/−) mice fed a normal or atherogenic diet for 12 weeks. A separate group of ApoE^−/−/Cyp1b1^+/+ mice on an atherogenic diet was injected every third day with the CYP1B1 inhibitor, 2,3′,4,5′-tetramethoxystilbene (300 μg/kg), or its vehicle, dimethyl sulfoxide (30 μL, IP); systolic blood pressure was measured by the tail cuff method. After 12 weeks, mice were euthanized, blood collected for lipid analysis, and aortas harvested for measuring lesions and remodeling, and for infiltration of inflammatory cells by histological and immunohistochemical analysis, respectively, and for reactive oxygen species production. Blood pressure, areas of lipids and collagen deposition, elastin breaks, infiltration of macrophages and T lymphocytes, reactive oxygen species generation in the aorta, and plasma lipid levels were increased in ApoE^−/−/Cyp1b1^+/+ mice on an atherogenic diet; these changes were minimized in mice given 2,3′,4,5′-tetramethoxystilbene, and in ApoE^−/−/Cyp1b1^−/− mice on an atherogenic diet; absorption/production of lipids remained unaltered in these mice. These data suggest that aortic lesions, hypertension, and associated pathogenesis in ApoE^−/−/Cyp1b1^+/+ mice on an atherogenic diet are most likely dependent on CYP1B1-generated oxidative stress and increased plasma lipid levels independent of blood pressure and absorption of lipids. CYP1B1 could serve as a novel target for developing drugs to treat atherosclerosis and hypertension caused by hypercholesterolemia.

Pharmacology and Clinical Drug Candidates in Redox Medicine

SIGNIFICANCE

Oxidative stress is suggested to be a disease mechanism common to a wide range of disorders affecting human health. However, so far, the pharmacotherapeutic exploitation of this, for example, based on chemical scavenging of pro-oxidant molecules, has been unsuccessful.

RECENT ADVANCES

An alternative emerging approach is to target the enzymatic sources of disease-relevant oxidative stress. Several such enzymes and isoforms have been identified and linked to different pathologies. For some targets, the respective pharmacology is quite advanced, that is, up to late-stage clinical development or even on the market; for others, drugs are already in clinical use, although not for indications based on oxidative stress, and repurposing seems to be a viable option.

CRITICAL ISSUES

For all other targets, reliable preclinical validation and drug ability are key factors for any translation into the clinic. In this study, specific pharmacological agents with optimal pharmacokinetic profiles are still lacking. Moreover, these enzymes also serve largely unknown physiological functions and their inhibition may lead to unwanted side effects.

FUTURE DIRECTIONS

The current promising data based on new targets, drugs, and drug repurposing are mainly a result of academic efforts. With the availability of optimized compounds and coordinated efforts from academia and industry scientists, unambiguous validation and translation into proof-of-principle studies seem achievable in the very near future, possibly leading towards a new era of redox medicine.

Permissive and protective roles for neutrophils in leishmaniasis

Leishmania parasites are the causative agents of leishmaniasis, a neglected tropical disease that causes substantial morbidity and considerable mortality in many developing areas of the world. Recent estimates suggest that roughly 10 million people suffer from cutaneous leishmaniasis (CL), and approximately 76,000 are afflicted with visceral leishmaniasis (VL), which is universally fatal without treatment. Efforts to develop therapeutics and vaccines have been greatly hampered by an incomplete understanding of the parasite's biology and a lack of clear protective correlates that must be met in order to achieve immunity. Although parasites grow and divide preferentially in macrophages, a number of other cell types interact with and internalize Leishmania parasites, including monocytes, dendritic cells and neutrophils. Neutrophils appear to be especially important shortly after parasites are introduced into the skin, and may serve a dual protective and permissive role during the establishment of infection. Curiously, neutrophil recruitment to the site of infection appears to continue into the chronic phase of disease, which may persist for many years. The immunological impact of these cells during chronic leishmaniasis is unclear at this time. In this review we discuss the ways in which neutrophils have been observed to prevent and promote the establishment of infection, examine the role of anti-neutrophil antibodies in mouse models of leishmaniasis and consider recent findings that neutrophils may play a previously unrecognized role in influencing chronic parasite persistence.

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Innate immune system cells in atherosclerosis

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Targeting of Rho kinase ameliorates impairment of diabetic endothelial function in intrarenal artery

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N-acetyl lysyltyrosylcysteine amide inhibits myeloperoxidase, a novel tripeptide inhibitor

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