Monocytes and neutrophils expressing myeloperoxidase occur in fibrous caps and thrombi in unstable coronary plaques

Neutrophils and neutrophil extracellular traps in oral health and disease

Neutrophils perform essential functions in antimicrobial defense and tissue maintenance at mucosal barriers. However, a dysregulated neutrophil response and, in particular, the excessive release of neutrophil extracellular traps (NETs) are implicated in the pathology of various diseases. In this review, we provide an overview of the basic concepts related to neutrophil functions, including NET formation, and discuss the mechanisms associated with NET activation and function in the context of the prevalent oral disease periodontitis.

Serum myeloperoxidase, paraoxonase, and plasma asprosin concentrations in patients with acute myocardial infarction

Introduction

The objective of this study was to evaluate the usefulness of the serum biomarkers myeloperoxidase (MPO), paraoxonase (PON), and plasma asprosin in acute myocardial infarction (AMI) diagnosis and assess their compatibility with routinely screened cardiac biomarkers.

Methods

This study was conducted using a prospective cross-sectional design and included 90 patients, consisting of 60 patients diagnosed with AMI (30 with ST-segment elevation and 30 with non-ST-segment elevation on ECG) and 30 controls (without a diagnosis of AMI). Changes in the levels of cardiac biomarkers (Hs-cTnI, CK, CK-MB), lipid profile (TC, TG, LDL, HDL), MPO, PON, asprosin, and routine biochemical parameters of patients were evaluated. Furthermore, receiver operating characteristic curve analysis revealed the diagnostic value of Hs-cTnI, MPO, PON, and asprosin in predicting AMI. Binary logistic regression analysis of cardiac marker concentrations was used to predict the presence of AMI. In contrast, multinomial logistic regression analysis was conducted to predict the type of AMI and the control group.

Results

The median levels of MPO and plasma asprosin were found to be higher in the patient group (3.22 [interquartile range {IQR}: 2.4-4.4] ng/ml and 10.84 [IQR: 8.8-17.8] ng/ml, respectively) than in the control group (2.49 [IQR: 1.9-2.9] ng/ml and 4.82 [IQR: 4.6-8.0] ng/ml, respectively) (p = 0.001 and p < 0.001, respectively). The median levels of PON were 8.94 (IQR: 7.6-10.4) ng/ml in the patient group and 10.44 (IQR: 9.1-20.0) ng/ml in the control group (p < 0.001). In the binary logistic regression model, compared with the control group, a 1 ng/ml increase in MPO level increased the odds of having AMI by 3.61 (p = 0.041, 95% CI: 1.055-12.397), whereas a 1 ng/ml increase in asprosin level increased the odds of having AMI by 2.33 (p < 0.001, 95% CI: 1.479-3.683). In the multinominal logistic regression model, compared with the control group, a 1 ng/ml increase in the MPO level increased the odds of having NSTEMI by 4.14 (p = 0.025, 95% CI: 1.195-14.350), whereas a 1 ng/ml increase in asprosin concentrations increased the odds of having NSTEMI by 2.35 (p < 0.001, 95% CI: 1.494-3.721).

Conclusion

Herein, MPO and asprosin concentrations increased with Hs-cTnI, and a decrease in PON concentration indicated that oxidant-antioxidant parameters and adipokines were related to AMI pathogenesis.

Clinical utility of inflammatory and genetic biomarkers for cardiovascular disease prevention, categorization, and treatment

ABSTRACT

The complex interplay of increased atherogenic lipoproteins, inflammation, and immune activation hallmarks the pathogenesis of atherosclerotic cardiovascular disease (ASCVD). Atherosclerotic cardiovascular disease remains a leading cause of death, yet risk estimator tools lack comprehensiveness for genetic/inflammatory biomarkers associated with ASCVD. Unexplained ASCVD risk necessitates a better understanding of primary, secondary, and tertiary prevention variables. This article discusses the clinical utility of genetic and inflammatory biomarkers for ASCVD risk prediction, management, treatment, and recategorization into primary, secondary, and tertiary prevention. Furthermore, nurse practitioners (NPs) should use a ternary prevention classification system instead of the current binary system to mitigate risk in the large group of patients with subclinical ASCVD. High-sensitivity C-reactive protein (hs-CRP)-linearly associated with ASCVD-and lipoprotein-associated phospholipase-A 2 (Lp-PLA 2 ) and myeloperoxidase (MPO), both associated with plaque vulnerability/rupture, are inflammatory biomarkers. Elevated hs-CRP, MPO, and Lp-PLA 2 treatment requires addressing root causes of elevation (e.g., obesity, insulin resistance, tobacco use, gingival disease, and chronic autoimmune/infectious conditions). In addition, haptoglobin (Hp) phenotype determines the antioxidant potential of Hp. Haptoglobin phenotype, a root cause of ASCVD, is a one-time test. Individuals with Hp 2-2 should adopt a gluten-free diet to reduce endothelial and intestinal inflammation. Nurse practitioners should use stricter glycemic goals (hemoglobin A1c ≤6.5%) and add daily vitamin E if this group has type 2 diabetes. Genetic/inflammatory biomarkers should be used to better predict ASCVD risk and tailor primary, secondary, and tertiary prevention treatment. Clinical use of these biomarkers reaches beyond the standard of care to reduce residual ASCVD risk.

Photobiomodulation therapy for osteoarthritis: Mechanisms of action

Photobiomodulation (PBM) is a non-invasive therapeutic modality with demonstrated effects in many fields related to regenerative medicine. In the field of orthopedics, in particular, PBM at various wavelengths has demonstrated the capacity to trigger multiple biological effects associated with protective mechanisms in musculoskeletal tissues. The articles cited in this review show that devices operating close to or within the near infrared range at low intensities can provoke responses which favor the shift in the predominant catabolic microenvironment typically seen in degenerative joint diseases, especially osteoarthritis (OA). These responses include proliferation, differentiation and expression of proteins associated with stable cell cycles. Additionally, PBM can also modulate oxidative stress, inflammation and pain by exerting regulatory effects on immune cells and blocking the transmission of pain through sensory neuron fibers, without adverse events. Collectively, these effects are essential in order to control the progression of OA, which is in part attributed to exacerbated inflammation and degradative enzymatic reactions which gradually contribute to the destruction of joint tissues. PBM may offer medical experts ease of application, financial viability, efficacy and lack of serious adverse events. Therefore, it may prove to be a suitable ally in the management of mild to moderate degrees of OA. This review explores and discusses the principal biological mechanisms of PBM and how the produced effects may contribute to the amelioration of osteoarthritic progression. Literature was reviewed using PubMed and Google Scholar in order to find studies describing the mechanisms of PBM. The investigation included a combination of nomenclature such as: “photobiomodulation”, “phototherapy”, “laser therapy”, “PBM”, “osteoarthritis”, low level light therapy”, “inflammation” and “cartilage”. We considered only articles written in English, with access to the full text.

Neutrophil Extracellular Traps in Atherosclerosis and Thrombosis

Despite effective therapeutic and preventive strategies, atherosclerosis and its complications still represent a substantial health burden. Leukocytes and inflammatory mechanisms are increasingly recognized as drivers of atherosclerosis. Neutrophil granulocytes within the circulation were recently shown to undergo neutrophil extracellular trap (NET) formation, linking innate immunity with acute complications of atherosclerosis. In this chapter, we summarize mechanisms of NET formation, evidence for their involvement in atherosclerosis and thrombosis, and potential therapeutic regimens specifically targeting NET components.

The many roles of myeloperoxidase: From inflammation and immunity to biomarkers, drug metabolism and drug discovery

This review provides a practical guide to myeloperoxidase (MPO) and presents to the reader the diversity of its presence in biology. The review provides a historical background, from peroxidase activity to the discovery of MPO, to its role in disease and drug development. MPO is discussed in terms of its necessity, as specific individuals lack MPO expression. An underlying theme presented throughout brings up the question of the benefit and burden of MPO activity. Enzyme structure is discussed, including accurate masses and glycosylation sites. The catalytic cycle of MPO and its corresponding pathways are presented, with a discussion of the importance of the redox couples of the different states of MPO. Cell lines expressing MPO are discussed and practically summarized for the reader, and locations of MPO (primary and secondary) are provided. Useful methods of MPO detection are discussed, and how these can be used for studying disease processes are implied through the presentation of MPO as a biomarker. The presence of MPO in neutrophil extracellular traps is presented, and the activators of the former are provided. Lastly, the transition from drug metabolism to a target for drug development is where the review concludes.

Mass Spectrometry for the Monitoring of Lipoprotein Oxidations by Myeloperoxidase in Cardiovascular Diseases

Oxidative modifications of HDLs and LDLs by myeloperoxidase (MPO) are regularly mentioned in the context of atherosclerosis. The enzyme adsorbs on protein moieties and locally produces oxidizing agents to modify specific residues on apolipoproteins A-1 and B-100. Oxidation of lipoproteins by MPO (Mox) leads to dysfunctional Mox-HDLs associated with cholesterol-efflux deficiency, and Mox-LDLs that are no more recognized by the LDL receptor and become proinflammatory. Several modification sites on apoA-1 and B-100 that are specific to MPO activity are described in the literature, which seem relevant in patients with cardiovascular risk. The most appropriate analytical method to assess these modifications is based on liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS). It enables the oxidized forms of apoA-1and apoB-100 to be quantified in serum, in parallel to a quantification of these apolipoproteins. Current standard methods to quantify apolipoproteins are based on immunoassays that are well standardized with good analytical performances despite the cost and the heterogeneity of the commercialized kits. Mass spectrometry can provide simultaneous measurements of quantity and quality of apolipoproteins, while being antibody-independent and directly detecting peptides carrying modifications for Mox-HDLs and Mox-LDLs. Therefore, mass spectrometry is a potential and reliable alternative for apolipoprotein quantitation.

The effects of neutrophil-generated hypochlorous acid and other hypohalous acids on host and pathogens

Neutrophils are predominant immune cells that protect the human body against infections by deploying sophisticated antimicrobial strategies including phagocytosis of bacteria and neutrophil extracellular trap (NET) formation. Here, we provide an overview of the mechanisms by which neutrophils kill exogenous pathogens before we focus on one particular weapon in their arsenal: the generation of the oxidizing hypohalous acids HOCl, HOBr and HOSCN during the so-called oxidative burst by the enzyme myeloperoxidase. We look at the effects of these hypohalous acids on biological systems in general and proteins in particular and turn our attention to bacterial strategies to survive HOCl stress. HOCl is a strong inducer of protein aggregation, which bacteria can counteract by chaperone-like holdases that bind unfolding proteins without the need for energy in the form of ATP. These chaperones are activated by HOCl through thiol oxidation (Hsp33) or N-chlorination of basic amino acid side-chains (RidA and CnoX) and contribute to bacterial survival during HOCl stress. However, neutrophil-generated hypohalous acids also affect the host system. Recent studies have shown that plasma proteins act not only as sinks for HOCl, but get actively transformed into modulators of the cellular immune response through N-chlorination. N-chlorinated serum albumin can prevent aggregation of proteins, stimulate immune cells, and act as a pro-survival factor for immune cells in the presence of cytotoxic antigens. Finally, we take a look at the emerging role of HOCl as a potential signaling molecule, particularly its role in neutrophil extracellular trap formation.

Identification of potential oxidative stress biomarkers for spinal cord injury in erythrocytes using mass spectrometry

Oxidative stress is a hallmark of secondary injury associated with spinal cord injury. Identifying stable and specific oxidative biomarkers is of important significance for studying spinal cord injury-associated secondary injury. Mature erythrocytes do not contain nuclei and mitochondria and cannot be transcribed and translated. Therefore, mature erythrocytes are highly sensitive to oxidative stress and may become a valuable biomarker. In the present study, we revealed the proteome dynamics of protein expression in erythrocytes of beagle dogs in the acute and subacute phases of spinal cord injury using mass spectrometry-based approaches. We found 26 proteins that were differentially expressed in the acute (0-3 days) and subacute (7-21 days) phases of spinal cord injury. Bioinformatics analysis revealed that these differentially expressed proteins were involved in glutathione metabolism, lipid metabolism, and pentose phosphate and other oxidative stress pathways. Western blot assays validated the differential expression of glutathione synthetase, transaldolase, and myeloperoxidase. This result was consistent with mass spectrometry results, suggesting that erythrocytes can be used as a novel sample source of biological markers of oxidative stress in spinal cord injury. Glutathione synthetase, transaldolase, and myeloperoxidase sourced from erythrocytes are potential biomarkers of oxidative stress after spinal cord injury. This study was approved by the Experimental Animal Centre of Ningxia Medical University, China (approval No. 2017-073) on February 13, 2017.

Myeloperoxidase: A versatile mediator of endothelial dysfunction and therapeutic target during cardiovascular disease

Myeloperoxidase (MPO) is a prominent mammalian heme peroxidase and a fundamental component of the innate immune response against microbial pathogens. In recent times, MPO has received considerable attention as a key oxidative enzyme capable of impairing the bioactivity of nitric oxide (NO) and promoting endothelial dysfunction; a clinically relevant event that manifests throughout the development of inflammatory cardiovascular disease. Increasing evidence indicates that during cardiovascular disease, MPO is released intravascularly by activated leukocytes resulting in its transport and sequestration within the vascular endothelium. At this site, MPO catalyzes various oxidative reactions that are capable of promoting vascular inflammation and impairing NO bioactivity and endothelial function. In particular, MPO catalyzes the production of the potent oxidant hypochlorous acid (HOCl) and the catalytic consumption of NO via the enzyme's NO oxidase activity. An emerging paradigm is the ability of MPO to also influence endothelial function via non-catalytic, cytokine-like activities. In this review article we discuss the implications of our increasing knowledge of the versatility of MPO's actions as a mediator of cardiovascular disease and endothelial dysfunction for the development of new pharmacological agents capable of effectively combating MPO's pathogenic activities. More specifically, we will (i) discuss the various transport mechanisms by which MPO accumulates into the endothelium of inflamed or diseased arteries, (ii) detail the clinical and basic scientific evidence identifying MPO as a significant cause of endothelial dysfunction and cardiovascular disease, (iii) provide an up-to-date coverage on the different oxidative mechanisms by which MPO can impair endothelial function during cardiovascular disease including an evaluation of the contributions of MPO-catalyzed HOCl production and NO oxidation, and (iv) outline the novel non-enzymatic mechanisms of MPO and their potential contribution to endothelial dysfunction. Finally, we deliver a detailed appraisal of the different pharmacological strategies available for targeting the catalytic and non-catalytic modes-of-action of MPO in order to protect against endothelial dysfunction in cardiovascular disease.

The Metalloproteinase ADAMTS5 Is Expressed by Interstitial Inflammatory Cells in IgA Nephropathy and Is Proteolytically Active on the Kidney Matrix

ADAMTS5 is upregulated in human IgA nephropathy lesions.

ADAMTS5 is related to inflammatory infiltrates in affected kidneys.

ADAMTS5 digests kidney matrix proteins and cleaves complement C3 and fibronectin.

In IgA nephropathy (IgAN), IgA immune complexes are deposited in the mesangium and drive inflammation and extracellular matrix (ECM) remodelling. The functional links between IgA deposition, inflammation, and matrix remodelling are not well characterized. We recently performed urine liquid chromatography–tandem mass spectrometry proteomics and identified multiple ECM glycoproteins whose expression and function in IgAN is unclear. None of the urine glycoproteins was regulated in IgAN transcriptomics, indicating that tissue remodelling rather than increased expression might contribute to their presence in urine. To investigate this, we examined the IgAN expression profile of metalloproteinases, enzymes involved in the remodelling of ECM proteins, and noted that the proteoglycanase ADAMTS5 was upregulated in IgAN kidneys. ADAMTS5 accumulated in areas of inflammation, and ADAMTS5⁺ cells were seen in the tubulointerstitium and glomeruli. The enzyme was expressed by CD64⁺ cells and its expression was increased by IL-1 and LPS. Analysis of myeloid cell transcriptomics revealed that ADAMTS5 is enriched in human classical monocytes. ADAMTS5⁺ cells were present in areas of matrix remodelling and associated with ECM proteins lumican, versican, and collagen-4. Liquid chromatography–tandem mass spectrometry proteomics of kidney explants digested with ADAMTS5, identified multiple kidney proteins affected by ADAMTS5 and revealed specific proteolysis of complement C3 and fibronectin associated with IgA on immune complexes. ADAMTS5 processing of immune complex proteins reduced binding to cultured mesangial cells. ADAMTS5 is associated with interstitial inflammatory cells in IgAN and other kidney lesions and fragments relevant extracellular proteins. The proteolytic enzyme might be a new translational target relevant to inflammation and scarring in kidney disease.

Monocyte recruitment and fate specification after myocardial infarction

Monocytes are critical mediators of the inflammatory response following myocardial infarction (MI) and ischemia-reperfusion injury. They are involved in both initiation and resolution of inflammation and play an integral role in cardiac repair. The antagonistic nature of their function is dependent on their subset heterogeneity and biphasic response following injury. New advancements in single-cell transcriptomics and mass cytometry have allowed us to identify smaller, transcriptionally distinct clusters that may have functional relevance in disease and homeostasis. Additionally, recent insights into the spatiotemporal dynamics of monocytes following ischemic injury and their subsequent interactions with the endothelium and other immune cells reveal a complex interplay between monocytes and the cardiac milieu. In this review, we highlight recent findings on monocyte functional heterogeneity, present new mechanistic insight into monocyte recruitment and fate specification following MI, and discuss promising therapeutic avenues targeting monocytes for the treatment of ischemic heart disease.

Isoniazid and host immune system interactions: A proposal for a novel comprehensive mode of action

The known mode of action of isoniazid (INH) is to inhibit bacterial cell wall synthesis following activation by the bacterial catalase-peroxidase enzyme KatG in Mycobacterium tuberculosis (Mtb). This simplistic model fails to explain (a) how isoniazid penetrates waxy granulomas with its very low lipophilicity, (b) how isoniazid kills latent Mtb lacking a typical cell wall, and (c) why isoniazid treatment time is remarkably long in contrast to most other antibiotics. To address these questions, a novel comprehensive mode of action of isoniazid has been proposed here. Briefly, isoniazid eradicates latent tuberculosis (TB) by prompting slow differentiation of pro-inflammatory monocytes and providing protection against reactive species-induced "self-necrosis" of phagocytes. In the case of active TB, different immune cells form INH-NAD⁺ adducts to inhibit Mtb's cell wall biosynthesis. This additionally suggests that the antibacterial properties of INH do not rely on KatG of Mtb. As such, isoniazid-resistant TB needs to be re-evaluated.

Human protein paucimannosylation: cues from the eukaryotic kingdoms

Paucimannosidic proteins (PMPs) are bioactive glycoproteins carrying truncated α- or β-mannosyl-terminating asparagine (N)-linked glycans widely reported across the eukaryotic domain. Our understanding of human PMPs remains limited, despite findings documenting their existence and association with human disease glycobiology. This review comprehensively surveys the structures, biosynthetic routes and functions of PMPs across the eukaryotic kingdoms with the aim of synthesising an improved understanding on the role of protein paucimannosylation in human health and diseases. Convincing biochemical, glycoanalytical and biological data detail a vast structural heterogeneity and fascinating tissue- and subcellular-specific expression of PMPs within invertebrates and plants, often comprising multi-α1,3/6-fucosylation and β1,2-xylosylation amongst other glycan modifications and non-glycan substitutions e.g. O-methylation. Vertebrates and protists express less-heterogeneous PMPs typically only comprising variable core fucosylation of bi- and trimannosylchitobiose core glycans. In particular, the Manα1,6Manβ1,4GlcNAc(α1,6Fuc)β1,4GlcNAcβAsn glycan (M2F) decorates various human neutrophil proteins reportedly displaying bioactivity and structural integrity demonstrating that they are not degradation products. Less-truncated paucimannosidic glycans (e.g. M3F) are characteristic glycosylation features of proteins expressed by human cancer and stem cells. Concertedly, these observations suggest the involvement of human PMPs in processes related to innate immunity, tumorigenesis and cellular differentiation. The absence of human PMPs in diverse bodily fluids studied under many (patho)physiological conditions suggests extravascular residence and points to localised functions of PMPs in peripheral tissues. Absence of PMPs in Fungi indicates that paucimannosylation is common, but not universally conserved, in eukaryotes. Relative to human PMPs, the expression of PMPs in plants, invertebrates and protists is more tissue-wide and constitutive yet, similar to their human counterparts, PMP expression remains regulated by the physiology of the producing organism and PMPs evidently serve essential functions in development, cell-cell communication and host-pathogen/symbiont interactions. In most PMP-producing organisms, including humans, the N-acetyl-β-hexosaminidase isoenzymes and linkage-specific α-mannosidases are glycoside hydrolases critical for generating PMPs via N-acetylglucosaminyltransferase I (GnT-I)-dependent and GnT-I-independent truncation pathways. However, the identity and structure of many species-specific PMPs in eukaryotes, their biosynthetic routes, strong tissue- and development-specific expression, and diverse functions are still elusive. Deep exploration of these PMP features involving, for example, the characterisation of endogenous PMP-recognising lectins across a variety of healthy and N-acetyl-β-hexosaminidase-deficient human tissue types and identification of microbial adhesins reactive to human PMPs, are amongst the many tasks required for enhanced insight into the glycobiology of human PMPs. In conclusion, the literature supports the notion that PMPs are significant, yet still heavily under-studied biomolecules in human glycobiology that serve essential functions and create structural heterogeneity not dissimilar to other human N-glycoprotein types. Human PMPs should therefore be recognised as bioactive glycoproteins that are distinctly different from the canonical N-glycoprotein classes and which warrant a more dedicated focus in glycobiological research.

Extracellular traps derived from macrophages, mast cells, eosinophils and neutrophils are generated in a time-dependent manner during atherothrombosis

Extracellular traps generated by neutrophils contribute to thrombus progression in coronary atherosclerotic plaques. It is not known whether other inflammatory cell types in coronary atherosclerotic plaque or thrombus also release extracellular traps. We investigated their formation by macrophages, mast cells, and eosinophils in human coronary atherosclerosis, and in relation to the age of thrombus of myocardial infarction patients. Coronary arteries with thrombosed or intact plaques were retrieved from patients who died from myocardial infarction. In addition, thrombectomy specimens from patients with myocardial infarction were classified histologically as fresh, lytic or organised. Neutrophil and macrophage extracellular traps were identified using sequential triple immunostaining of CD68, myeloperoxidase, and citrullinated histone H3. Eosinophil and mast cell extracellular traps were visualised using double immunostaining for eosinophil major basic protein or tryptase, respectively, and citrullinated histone H3. Single‐ and double‐stained immunopositive cells in the plaque, adjacent adventitia, and thrombus were counted. All types of leucocyte‐derived extracellular traps were present in all thrombosed plaques, and in all types of the in vivo‐derived thrombi, but only to a much lower extent in intact plaques. Neutrophil traps, followed by macrophage traps, were the most prominent types in the autopsy series of atherothrombotic plaques, including the adventitia adjacent to thrombosed plaques. In contrast, macrophage traps were more numerous than neutrophil traps in intact plaques (lipid cores) and organised thrombi. Mast cell and eosinophil extracellular traps were also present, but sparse in all instances. In conclusion, not only neutrophils but also macrophages, eosinophils, and mast cells are sources of etosis involved in evolving coronary thrombosis. Neutrophil traps dominate numerically in early thrombosis and macrophage traps in late (organising) thrombosis, implying that together they span all the stages of thrombus progression and maturation. © 2018 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of Pathological Society of Great Britain and Ireland.

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

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

Novel Role of IL (Interleukin)-1β in Neutrophil Extracellular Trap Formation and Abdominal Aortic Aneurysms

OBJECTIVE

Neutrophils promote experimental abdominal aortic aneurysm (AAA) formation via a mechanism that is independent from MMPs (matrix metalloproteinases). Recently, we reported a dominant role of IL (interleukin)-1β in the formation of murine experimental AAAs. Here, the hypothesis that IL-1β-induced neutrophil extracellular trap formation (NETosis) promotes AAA was tested.

APPROACH AND RESULTS

NETs were identified through colocalized staining of neutrophil, Cit-H3 (citrullinated histone H3), and DNA, using immunohistochemistry. NETs were detected in human AAAs and were colocalized with IL-1β. In vitro, IL-1RA attenuated IL-1β-induced NETosis in human neutrophils. Mechanistically, IL-1β treatment of isolated neutrophils induced nuclear localization of ceramide synthase 6 and synthesis of C16-ceramide, which was inhibited by IL-1RA or fumonisin B1, an inhibitor of ceramide synthesis. Furthermore, IL-1RA or fumonisin B1 attenuated IL1-β-induced NETosis. In an experimental model of murine AAA, NETs were detected at a very early stage-day 3 of aneurysm induction. IL-1β-knockout mice demonstrated significantly lower infiltration of neutrophils to aorta and were protected from AAA. Adoptive transfer of wild-type neutrophils promoted AAA formation in IL-1β-knockout mice. Moreover, treatment of wild-type mice with Cl-amidine, an inhibitor NETosis, significantly attenuated AAA formation, whereas, treatment with deoxyribonuclease, a DNA digesting enzyme, had no effect on AAA formation.

CONCLUSIONS

Altogether, the results suggest a dominant role of IL-1β-induced NETosis in AAA formation.

Clinical significance of intracoronary thrombus aspirated during primary percutaneous intervention: An immunohistopathological study

BACKGROUND

Manual thrombus aspiration during primary percutaneous intervention provides us with aspirated thrombus sample, that may contain material from the disrupted plaque. Immunohistopathological analysis of thrombus can yield valuable information about the clinical and cardiovascular outcomes and possible mechanisms of myocardial infarction.

MATERIAL AND METHODS

We studied and analysed the immunohistopathological features of coronary thrombus aspirated from patients undergoing primary percutaneous coronary angioplasty. Immunohistological staining included markers namely CD68, SMA and CD34 for macrophages, smooth muscle actin and endothelium, respectively. Major adverse cardiac events, angiographic outcome and infarct size were also noted.

RESULTS

Fifty-three patients (Mean age - 51.3±13years; males-47) who underwent primary percutaneous coronary intervention with aspiration thrombectomy were enrolled. Thrombus was successfully aspirated in 40 of 53 patients (75.4%). Patients with successful thrombus aspiration had higher ST-segment resolution (≥50%) as compared to patients with failed thrombus aspiration. Presence of RBC-rich thrombus on microscopy was more commonly associated with post-procedure TIMI flow of <2 as compared to patients with fibrin-rich thrombus and a trend towards lower myocardial blush grade<2 (P=0.10), and a significantly higher final infarct size (37.5±5% vs 25±15%; P=0.04 of myocardium) on nuclear scan. Immunohistology revealed presence of plaque material in 72% (26/36) of the samples.

CONCLUSIONS

Immunohistopathological evaluation of intracoronary thrombus may be of prognostic importance. High prevalence of plaque material in the aspirated intracoronary thrombus suggests plaque rupture as a possible etiology for vessel occlusion in these patients.

SHORT SUMMARY

Immunohistopathological evaluation of intracoronary thrombus reveals high prevalence of plaque material in the aspirated intracoronary thrombus suggesting plaque rupture as a possible etiology for vessel occlusion in Indian STEMI patients.

CXCR2 Inhibition - a novel approach to treating CoronAry heart DiseAse (CICADA): study protocol for a randomised controlled trial

Background

There is emerging evidence of the central role of neutrophils in both atherosclerotic plaque formation and rupture. Patients with lower neutrophil counts following acute coronary syndromes tend to have a greater coronary flow reserve, which is a strong predictor of long-term cardiovascular health. But so far, no data are available regarding the impact of neutrophil inhibition on cardiovascular clinical or surrogate endpoints. Therefore, the aim of this study is to investigate the effects of AZD5069, a cysteine-X-cysteine chemokine receptor 2 (CXCR2) inhibitor, on coronary flow reserve and coronary structure and function in patients with coronary artery disease.

Methods/Design

Ninety subjects with coronary artery disease undergoing percutaneous coronary intervention will be included in this investigator-driven, randomised, placebo-controlled, double-blind, phase IIa, single-centre study. Participants will be randomised to receive either AZD5069 (40 mg) administered orally twice daily or placebo for 24 weeks. Change in coronary flow reserve as determined by ¹³N-ammonia positron emission tomography-computed tomography will be the primary outcome. Change in the inflammatory component of coronary plaque structure and the backward expansion wave, an invasive coronary physiological measure of diastolic function, will be assessed as secondary outcomes.

Discussion

Cardiovascular surrogate parameters, such as coronary flow reserve, may provide insights into the potential mechanisms of the cardiovascular effects of CXCR2 inhibitors. Currently, ongoing trials do not specifically focus on neutrophil function as a target of intervention, and we therefore believe that our study will contribute to a better understanding of the role of neutrophil-mediated inflammation in coronary artery disease.

Trial registration

EudraCT, 2016-000775-24. Registered on 22 July 2016.

International Standard Randomised Controlled Trial Number, ISRCTN48328178. Registered on 25 February 2016.

Electronic supplementary material

The online version of this article (doi:10.1186/s13063-017-2210-2) contains supplementary material, which is available to authorized users.

Impact of CD14++CD16+ monocytes on plaque vulnerability in diabetic and non-diabetic patients with asymptomatic coronary artery disease: a cross-sectional study

Background

Previously, we have reported that daily glucose fluctuations could affect coronary plaque vulnerability, but the underlying mechanisms remained unclear. This study sought to investigate the impact of CD14⁺⁺CD16⁺ monocytes on plaque vulnerability, as assessed by virtual histology intravascular ultrasound (VH-IVUS), as well as their relationship to fluctuating glucose levels in patients with asymptomatic coronary artery disease (CAD).

Methods

Fifty-one patients with asymptomatic CAD, who were undergoing lipid-lowering therapy and underwent VH-IVUS evaluation for angiographically mild to moderate lesions, were enrolled in the study. Standard VH-IVUS parameters, including the percentage volume of the necrotic core (%NC) within the plaque and the presence of a virtual histology thin-cap fibroatheroma (VH-TCFA), were then evaluated. Additionally, monocyte subsets were assessed by flow cytometry, and daily glucose fluctuations were analyzed by measuring the mean amplitude of glycemic excursion (MAGE).

Results

Among 82 plaques from 22 diabetes mellitus (DM) patients and 29 non-DM patients, 15 VH-TCFAs were identified. CD14⁺⁺CD16⁺ monocyte counts significantly correlated with both  %NC and the presence of VH-TCFA (%NC: r = 0.339, p = 0.002; VH-TCFA: p = 0.003). Multivariate logistic regression analysis revealed that CD14⁺⁺CD16⁺ monocyte counts were independently associated with VH-TCFA (odds ratio = 1.029, p = 0.004). Furthermore, CD14⁺⁺CD16⁺ monocyte counts were significantly correlated with the MAGE score in the non-DM patients (r = 0.544, p = 0.005).

Conclusions

CD14⁺⁺CD16⁺ monocyte levels are associated with coronary plaque vulnerability and can serve as a biomarker for VH-TCFA in patients with CAD undergoing lipid-lowering therapy. In patients without DM, glucose fluctuations may alter the balance of monocyte subsets.

Trial registration UMIN Registry number: UMIN000021228

Electronic supplementary material

The online version of this article (doi:10.1186/s12933-017-0577-8) contains supplementary material, which is available to authorized users.

Flow Perturbation Mediates Neutrophil Recruitment and Potentiates Endothelial Injury via TLR2 in Mice: Implications for Superficial Erosion

RATIONALE

Superficial erosion currently causes up to a third of acute coronary syndromes; yet, we lack understanding of its mechanisms. Thrombi because of superficial intimal erosion characteristically complicate matrix-rich atheromata in regions of flow perturbation.

OBJECTIVE

This study tested in vivo the involvement of disturbed flow and of neutrophils, hyaluronan, and Toll-like receptor 2 ligation in superficial intimal injury, a process implicated in superficial erosion.

METHODS AND RESULTS

In mouse carotid arteries with established intimal lesions tailored to resemble the substrate of human eroded plaques, acute flow perturbation promoted downstream endothelial cell activation, neutrophil accumulation, endothelial cell death and desquamation, and mural thrombosis. Neutrophil loss-of-function limited these findings. Toll-like receptor 2 agonism activated luminal endothelial cells, and deficiency of this innate immune receptor decreased intimal neutrophil adherence in regions of local flow disturbance, reducing endothelial cell injury and local thrombosis (P<0.05).

CONCLUSIONS

These results implicate flow disturbance, neutrophils, and Toll-like receptor 2 signaling as mechanisms that contribute to superficial erosion, a cause of acute coronary syndrome of likely growing importance in the statin era.

Myeloperoxidase-oxidized high density lipoprotein impairs atherosclerotic plaque stability by inhibiting smooth muscle cell migration

Background

High density lipoprotein (HDL) has been proved to be a protective factor for coronary heart disease. Notably, HDL in atherosclerotic plaques can be nitrated (NO₂-oxHDL) and chlorinated (Cl-oxHDL) by myeloperoxidase (MPO), likely compromising its cardiovascular protective effects.

Method

Here we determined the effects of NO₂-oxHDL and Cl-oxHDL on SMC migration using wound healing and transwell assays, proliferation using MTT and BrdU assays, and apoptosis using Annexin-V assay in vitro, as well as on atherosclerotic plaque stability in vivo using a coratid artery collar implantation mice model.

Results

Our results showed that native HDL promoted SMC proliferation and migration, whereas NO₂-oxHDL and Cl-oxHDL inhibited SMC migration and reduced capacity of stimulating SMC proliferation as well as migration, respectively. OxHDL had no significant influence on SMC apoptosis. In addition, we found that ERK1/2-phosphorylation was significantly lower when SMCs were incubated with NO₂-oxHDL and Cl-oxHDL. Furthermore, transwell experiments showed that differences between native HDL, NO₂-oxHDL and Cl-oxHDL was abolished after PD98059 (MAPK kinase inhibitor) treatment. In aortic SMCs from scavenger receptor BI (SR-BI) deficient mice, differences between migration of native HDL, NO₂-oxHDL and Cl-oxHDL treated SMCs vanished, indicating SR-BI’s possible role in HDL-associated SMC migration. Importantly, NO₂-oxHDL and Cl-oxHDL induced neointima formation and reduced SMC positive staining cells in atherosclerotic plaque, resulting in elevated vulnerable index of atherosclerotic plaque.

Conclusion

These findings implicate MPO-catalyzed oxidization of HDL may contribute to atherosclerotic plaque instability by inhibiting SMC proliferation and migration through MAPK-ERK pathway which was dependent on SR-BI.

Electronic supplementary material

The online version of this article (doi:10.1186/s12944-016-0388-z) contains supplementary material, which is available to authorized users.

Human cells involved in atherosclerosis have a sex

The influence of sex has been largely described in cardiovascular diseases. Atherosclerosis is a complex process that involves many cell types such as vessel cells, immune cells and endothelial progenitor cells; however, many, if not all, studies do not report the sex of the cells. This review focuses on sex differences in human cells involved in the atherosclerotic process, emphasizing the role of sex hormones. Furthermore, we report sex differences and issues related to the processes that determine the fate of the cells such as apoptotic and autophagic mechanisms. The analysis of the data reveals that there are still many gaps in our knowledge regarding sex influences in atherosclerosis, largely for the cell types that have not been well studied, stressing the urgent need for a clear definition of experimental conditions and the inclusion of both sexes in preclinical studies.

Association of Neutrophil/Lymphocyte Ratio with Plaque Morphology in Patients with Asymptomatic Intermediate Carotid Artery Stenosis

Background and Objectives

Non-calcified carotid plaques are more unstable than calcified plaques, and they are associated with a higher risk of rupture, thromboembolism, and consequently, stroke. The purpose of the present study is to compare calcified and non-calcified plaques that cause intermediate carotid artery stenosis with respect to neutrophil/lymphocyte ratio (NLR).

Subjects and Methods

A total number of 139 asymptomatic patients with 50-70% stenosis of the carotid artery were included in this study. Carotid Doppler ultrasound imaging and computed tomography angiography were performed to divide the carotid artery plaques into two groups as calcified and non-calcified. Patients included in the calcified (n=73) and non-calcified (n=66) plaque groups were compared with respect to total neutrophil count, lymphocyte count and NLR.

Results

Total lymphocyte count was statistically significantly lower in the non-calcified plaque group compared to the calcified plaque group (total lymphocyte count in non-calcified/calcified plaque groups [10³/mm³]: 2.1/2.3, respectively) (p=0.002). NLR was statistically significantly higher in the non-calcified plaque group compared to the calcified plaque group (NLR in non-calcified/calcified plaque groups: 2.6/2.1, respectively) (p<0.001). The cut-off value for NLR was found to be >2.54. Multivariate regression analysis showed that NLR was independently associated with non-calcified carotid artery plaques (odds ratio 5.686, 95% CI 2.498-12.944, p<0.001).

Conclusions

NLR is increased in the presence of non-calcified carotid artery plaques that cause asymptomatic intermediate stenosis. Increased NLR can be used as a marker to assess the risk of rupture of non-calcified carotid artery plaques.

Prognostic value of myeloperoxidase concentration in patients with ST-segment elevation myocardial infarction treated with primary percutaneous coronary intervention

Inflammation plays an important role on every stage of atherosclerosis. Myeloperoxidase (MPO), a leukocyte-derived enzyme that participates in the innate immunity, probably is involved in many stages of atherothrombosis. According to the recent studies, MPO is related with unfavorable outcome in patients with chest pain and acute coronary syndromes. Its role in prediction of outcomes after ST-segment elevation myocardial infarction (STEMI) remains unclear. The aim of the study was to assess if elevated MPO level is a predictor of long-term adverse cardiac events in patients with STEMI treated with primary percutaneous coronary intervention (pPCI).

MATERIAL AND METHODS

We evaluated data of 127 patients with STEMI. Plasma levels of MPO collected on admission and the 3rd-4th day of hospitalization were measured by ELISA method. C-reactive protein (CRP) and N-terminal prohormone of B-type natriuretic peptide (NT-proBNP) were also determined. All patients were followed-up prospectively for the occurrence of major adverse cardiovascular events (MACE) defined as unscheduled coronary revascularization procedure, stroke, reinfarction or all-cause death.

RESULTS

After 14months of follow-up 20% of patients developed MACE. Elevated MPO levels collected on the 3rd-4th day of STEMI were the predictor of death, reinfarction, the need for coronary revascularization and all adverse events taken together. In multivariate analysis, MPO and CRP levels assessed on the 3rd-4th day of hospitalization revealed to be significant predictors of MACE. MPO demonstrated to be significantly better predictor of MACE than NT-proBNP level.

CONCLUSIONS

Myeloperoxidase is a prognostic marker in patients with STEMI treated with pPCI.

Inflammatory Biomarkers and Atherosclerosis

Atherosclerosis has been regarded as a form of chronic vascular inflammation. Numerous biomarkers associated with inflammation have been identified as novel targets to monitor atherosclerosis and cardiovascular risk. C-reactive protein (CRP) is one of the most actively studied and established inflammatory biomarkers for cardiovascular events. However, CRP response is triggered by many disorders unrelated to cardiovascular disease, which interferes with the clinical application. This review describes established and traditional inflammatory biomarkers including CRP as well as novel inflammatory biomarkers reflective of local atherosclerotic inflammation. In addition, we focus on the potential usefulness of inflammatory biomarkers in developing anti-atherosclerotic therapeutic approaches.

An in vivo role for Rho kinase activation in the tumour vascular disrupting activity of combretastatin A-4 3-O-phosphate

Background and Purpose

Combretastatin A-4 3-O-phosphate (CA4P) is in clinical trial as a tumour vascular disrupting agent (VDA) but the cause of blood flow disruption is unclear. We tested the hypothesis that activation of Rho/Rho kinase (ROCK) is fundamental to the effects of this drug in vivo.

Experimental Approach

Mouse models of human colorectal carcinoma (SW1222 and LS174T) were used. Effects of the ROCK inhibitor, Y27632, alone or in combination with CA4P, on ROCK activity, vascular function, necrosis and immune cell infiltration in solid tumours were determined. Mean arterial BP (MABP) was measured to monitor systemic interactions and the vasodilator, hydralazine, was used to control for the hypotensive effects of Y27632.

Key Results

Y27632 caused a rapid drop in blood flow in SW1222 tumours, with recovery by around 3 h, which was paralleled by MABP changes. Y27632 pretreatment reduced CA4P-induced ROCK activation and partially blocked CA4P-induced tumour vascular effects, in both tumour types. Y27632 also partially inhibited CA4P-induced tumour necrosis and was associated with reduced immune cell infiltration in SW1222 tumours. Hydralazine caused a similar hypotensive effect as Y27632 but had no protective effect against CA4P treatment.

Conclusions and Implications

These results demonstrate that ROCK activity is critical for full manifestation of the vascular activity of CA4P in vivo, providing the evidence for pharmacological intervention to enhance the anti-tumour efficacy of CA4P and related VDAs.

Expression characteristics of neutrophil and mononuclear-phagocyte related genes mRNA in the stable angina pectoris and acute myocardial infarction stages of coronary artery disease

Objective

To investigate expression differences of neutrophil and mononuclear phagocyte related gene mRNAs among acute myocardial infarction (AMI), stable angina (SA) and control groups, and then discuss their expression characteristics in the stable angina pectoris (SAP) and AMI stages of coronary artery disease (CAD).

Methods

Whole Human Genome Oligo Microarrays were applied to assess the differential expression characteristics of neutrophil and mononuclear phagocyte related mRNAs in patients with AMI (n = 20), SA (n = 20) and controls (n = 20).

Results

(1) Almost all colony-stimulating factors (CSF) and their receptors related mRNAs was up-regulated in AMI and SA groups compared with the control group, and the expression of granulocyte-macrophage colony stimulating factor receptor (GM-CSFR) and granulocyte colony stimulating factor receptor (G-CSFR) mRNAs in the AMI group was significantly up-regulated compared with the other two groups (P < 0.01). (2) The expression of mRNAs related to monocyte chemoattractant protein-1 (MCP-1), CCR2 (MCP-1 receptor) and CXCR2 (IL-8 receptor) was significantly up-regulated (P < 0.01) in AMI group compared with SA and control groups. IL-8 mRNA expression in the AMI group was clearly higher than the controls (P < 0.05). (3) All mRNAs expression related to opsonic receptors (IgG FcR and C3bR/C4bR) was significantly up-regulated in AMI group compared with SA and control group (P < 0.01), and the SA group showed an upward trend compared with controls. (4) Most pattern recognition receptor (PRR)-related mRNAs expression was up-regulated in AMI group compared with SA and control groups. Most toll-like receptor (TLR) mRNAs expression was significantly up-regulated (P < 0.01) than the SA and control groups; macrophage scavenger receptor (MSR) mRNA was significantly up-regulated in AMI group compared with the control group (P < 0.01), and the SA group showed an upward trend compared with the controls.

Conclusions

The expression of most neutrophil and mononuclear-macrophage function related genes mRNAs was significantly up-regulated by stages during the progression of CAD, suggesting that the adhesive, chemotactic and phagocytic functions of neutrophil and mononuclear-macrophage were strengthened in the occurrence and development of coronary atherosclerosis and AMI. This also showed a stepped upward trend as the disease progressed.

Clinical significance of macrophage phenotypes in cardiovascular disease

The emerging understanding of macrophage subsets and their functions in the atherosclerotic plaque has led to the consensus that M1 macrophages are pro-atherogenic while M2 macrophages may promote plaque stability, primarily though their tissue repair and anti-inflammatory properties. As such, modulating macrophage function to promote plaque stability is an exciting therapeutic prospect. This review will outline the involvement of the different macrophage subsets throughout atherosclerosis progression and in models of regression. It is evident that much of our understanding of macrophage function comes from in vitro or small animal models and, while such knowledge is valuable, we have much to learn about the roles of the macrophage subsets in the clinical setting in order to identify the key pathways to target to possibly promote plaque stability.

The development of giant phagocytes in long-term neutrophil cultures

We tested the hypothesis that in long-term culture conditions, some neutrophils remain viable and participate in debris clearance, and autophagy is involved in their prolonged survival. Neutrophils, classified as professional phagocytes, have the shortest half-life among leukocytes and are constitutively committed to apoptosis. Apoptotic neutrophils are actively removed by Mφ/DCs. However, early and acute inflammatory infiltrates primarily consist of neutrophils. Recently, neutrophils were suggested to facilitate debris clearance at inflammatory sites when the Mφ/DC system is insufficient. Here, purified CD15(+)/CD66b(+)/CD63(+) neutrophils were followed up to 7 days in culture using light, time-lapse, and confocal microscopy. After 3 days in culture, Annexin-V(-)/LC3B(+) large vacuolated cells, engulfing cellular residues, were noted among apoptotic neutrophils and cell debris. Thereafter, these cells were vastly enlarged and exhibited a neutrophilic phenotype (CD15(+)/CD63(+)/MPO(+)/CD66b(+)), phagocytosis, and oxidative burst activity. They also expressed CD68 scavenger receptors and internalized oxLDL. But, unlike in fresh neutrophils or cultured monocytes, oxLDL treatment increased their ROS production. Additionally, these phagocytes contained LC3B-coated vacuoles and LC3B aggregates, indicating the activation of autophagy. An intensive LC3B accumulation was also noted during oxLDL internalization. Importantly, the inhibition of autophagy by 3-MA or BafA1 prevented their development. In conclusion, the internalization of neutrophil remnants may induce activation of autophagic mechanisms in some neutrophil subsets or precursors. This may lead to cell adaptation and survival, resulting in their transformation into long-lived Gφ and potentially suggesting their involvement in inflammatory/anti-inflammatory processes.

Combined application of 18F-fluorodeoxyglucose positron emission tomography/computed tomography and magnetic resonance imaging in early diagnosis of vulnerable carotid atherosclerotic plaques

Objective

To assess the correlations between atherosclerotic plaque characteristics and inflammatory activity by combined use of 18F-fluorodeoxyglucose (18F-FDG) positron emission tomography/computed tomography (PET/CT) and magnetic resonance imaging (MRI).

Methods

Patients underwent 18F-FDG PET/CT and MRI. Target/background ratios (TBR) of axial sections were determined from mean standard uptake values (SUV). Correlations between TBR and mean vessel wall thickness, total vessel area, lumen area, vessel wall area and normalized wall index were calculated. Plaque types were defined as calcified, collagen, lipid or haemorrhage. Plaques were also classified as thick, thin, or ruptured fibrous cap.

Results

The study included 31 patients (1178 plaque slices). There was a significant decrease in TBR values across the fibrous cap groups, such that ruptured > thin > thick. Lipid and haemorrhage plaques had significantly higher TBR than calcification and collagen plaques. There were weak positive correlations between TBR and mean vessel wall thickness, vessel wall area and normalized wall index.

Conclusions

Thin or ruptured plaques, lipid-rich plaques and haemorrhagic plaques possess high inflammatory activity. The combination of 18F-FDG PET/CT and MRI could be useful for qualitative and quantitative diagnosis of carotid atherosclerotic plaques.

Myeloperoxidase: a leukocyte-derived protagonist of inflammation and cardiovascular disease

SIGNIFICANCE

The heme-enzyme myeloperoxidase (MPO) is one of the major neutrophil bactericidal proteins and is stored in large amounts inside azurophilic granules of neutrophils. Upon cell activation, MPO is released and extracellular MPO has been detected in a wide range of acute and chronic inflammatory conditions. Recent ADVANCES AND CRITICAL ISSUES: Apart from its role during infection, MPO has emerged as a critical modulator of inflammation throughout the last decade and is currently discussed in the initiation and propagation of cardiovascular diseases. MPO-derived oxidants (e.g., hypochlorous acid) interfere with various cell functions and contribute to tissue injury. Recent data also suggest that MPO itself exerts proinflammatory properties independent of its catalytic activity. Despite advances in unraveling the complex action of MPO and MPO-derived oxidants, further research is warranted to determine the precise nature and biological role of MPO in inflammation.

FUTURE DIRECTIONS

The identification of MPO as a central player in inflammation renders this enzyme an attractive prognostic biomarker and a potential target for therapeutic interventions. A better understanding of the (patho-) physiology of MPO is essential for the development of successful treatment strategies in acute and chronic inflammatory diseases.

Fatty acid binding protein 4 in circulating leucocytes reflects atherosclerotic lesion progression in Apoe(-/-) mice

Discovery of novel biomarkers for atherosclerosis is important to aid in early diagnosis of pre-symptomatic patients at high risk of cardiovascular events. The aim of the present study was therefore to identify potential biomarkers in circulating cells reflecting atherosclerotic lesion progression in the vessel wall. We performed gene arrays on circulating leucocytes from atherosclerosis prone Apoe(-/-) mice with increasing ages, using C57BL/6 mice as healthy controls. We identified fatty acid binding protein 4 (FABP4) mRNA to be augmented in mice with established disease compared with young Apoe(-/-) or controls. Interestingly, the transcript FABP4 correlated significantly with lesion size, further supporting a disease associated increase. In addition, validation of our finding on protein level showed augmented FABP4 in circulating leucocytes whereas, importantly, no change could be observed in plasma. Immunofluorescence analysis demonstrated FABP4 to be present mainly in circulating neutrophils and to some extent in monocytes. Moreover, FABP4-positive neutrophils and macrophages could be identified in the subintimal space in the plaque. Using human circulating leucocytes, we confirmed the presence of FABP4 protein in neutrophils and monocytes. In conclusion, we have showed that cellular levels of FABP4 in circulating leucocytes associate with lesion development in the experimental Apoe(-/-) model. The increased expression is primarily localized to neutrophils, but also in monocytes. We have identified FABP4 in leucocytes as a potential and easy accessible biomarker of atherosclerosis which could be of future clinical relevance.

Effects of soluble epoxide hydrolase inhibitor on the expression of fatty acid synthase in peripheral blood mononuclear cell in patients with acute coronary syndrome

Background

Researches have shown that soluble epoxide hydrolase inhibitors (sEHi) can protect against the development of atherosclerosis. Simultaneously, emerging evidences have implicated the association between fatty acid synthase (FAS) and acute coronary syndrome (ACS). We tested the hypothesis that sEHi could reduce the occurrence of ACS by regulating FAS.

Methods

Hospitalized ACS patients were selected as the ACS group (n = 65) while healthy normal subjects as the control group (n = 65). The blood levels of lipoproteins, fasting glucose, myocardial enzyme and high-sensitivity C-reactive protein (hs-CRP) were measured within 24 hours after admission. The peripheral blood mononuclear cells (PBMCs) were isolated and cultured. Trans-4-[4-(3-Adamantan-1-ylureido)cyclohexyloxy] benzoic acid (t-AUCB), a kind of sEHi, was then added to cells in various concentrations (0, 10, 50, 100 μmol/L). The expression of FAS, interleukin-6 (IL-6) mRNA and protein was detected by real-time PCR or Western blot, respectively.

Results

(1) Compared with the control group, the serum concentration of hs-CRP in the ACS group was increased (P<0.05). The expression of FAS, IL-6 mRNA and protein were significantly increased in PBMCs from the ACS group (all P<0.05). Moreover, the levels of FAS and IL-6 mRNA were positively correlated with the serum concentration of hs-CRP (r = 0.685, P<0.01; r = 0.715, P<0.01) respectively. (2) The expression of FAS, IL-6 mRNA and protein in PBMCs from the ACS group were dose-dependently inhibited by sEHi (all P<0.05).

Conclusions

sEH inhibition regulated FAS and inhibited inflammation in cultured PBMCs from ACS patients, a mechanism that might prevent rupture of atherosclerotic lesions and protect against development of ACS.

Myeloperoxidase may help to differentiate coronary plaque erosion from plaque rupture in patients with acute coronary syndromes

Coronary thrombosis is the most frequent final event leading to an acute coronary syndrome. In approximately two-thirds of cases, the thrombus overlies a ruptured plaque, whereas in one-third of cases it overlies an intact plaque with superficial endothelial erosion, a finding showed initially by histopathological postmortem studies and more recently confirmed by in vivo optical coherence tomography imaging. Interestingly, recent observations suggest that mechanisms leading to plaque rupture or erosion are different. In fact, in a recent study, we showed that myeloperoxidase levels in peripheral blood and expression within thrombi overlying the culprit plaque are much higher in patients with plaque erosion than in those with plaque rupture. These observations suggest that innate immunity activation is likely to play a key role, in particular, in plaque erosion and might become a therapeutic target in this subset of patients.

Do we know enough about the immune pathogenesis of acute coronary syndromes to improve clinical practice?

Morbidities related to atherosclerosis, such as acute coronary syndromes (ACS) including unstable angina and myocardial infarction, remain leading causes of mortality. Unstable plaques are inflamed and infiltrated with macrophages and T lymphocytes. Activated dendritic cells interact with T cells, yielding predominantly Th1 responses involving interferon-gamma (IFN-γ) and tumour necrosis factor-alpha (TNF-α), while the role of interleukin 17 (IL-17) is questionable. The expansion of CD28nullCD4 or CD8 T cells as well as pattern recognition receptors activation (especially Toll-like receptors; TLR2 and TLR4) is characteristic for unstable plaque. Inflammation modifies platelet and fibrin clot characteristics, which are critical for ACS. Understanding of the inflammatory mechanisms of atherothrombosis, bridging inflammation, oxidative stress and immune regulation, will allow for the detection of subjects at risk, through the use of novel biomarkers and imaging techniques including intravascular ultrasound, molecular targeting, magnetic resonance imaging (MRI) and 18F-fluorodeoxyglucose (18F-FDG) positron emission tomography (PET). Moreover, understanding the specific inflammatory pathways of plaque rupture and atherothrombosis may allow for immunomodulation of ACS. Statins and anti-platelet drugs are anti-inflammatory, but importance of immune events in ACS warrants the introduction of novel, specific treatments directed either on cytokines, TLRs or inflammasomes. While the prime time for the introduction of immunologically inspired diagnostic tests and treatments for atherosclerosis have not come yet, we are closer than ever before to finally being able to benefit from this vast body of experimental and clinical evidence. This paper provides a comprehensive review of the role of the immune system and inflammation in ACS.

Connexins in atherosclerosis

Atherosclerosis, a chronic inflammatory disease of the vessel wall, involves multiple cell types of different origins, and complex interactions and signaling pathways between them. Autocrine and paracrine communication pathways provided by cytokines, chemokines, growth factors and lipid mediators are central to atherogenesis. However, it is becoming increasingly recognized that a more direct communication through both hemichannels and gap junction channels formed by connexins also plays an important role in atherosclerosis development. Three main connexins are expressed in cells involved in atherosclerosis: Cx37, Cx40 and Cx43. Cx37 is found in endothelial cells, monocytes/macrophages and platelets, Cx40 is predominantly an endothelial connexin, and Cx43 is found in a large variety of cells such as smooth muscle cells, resident and circulating leukocytes (neutrophils, dendritic cells, lymphocytes, activated macrophages, mast cells) and some endothelial cells. Here, we will systematically review the expression and function of connexins in cells and processes underlying atherosclerosis. This article is part of a Special Issue entitled: The Communicating junctions, roles and dysfunctions.

Aminobenzoic acid hydrazide, a myeloperoxidase inhibitor, alters the adhesive properties of neutrophils isolated from acute myocardial infarction patients

Acute myocardial infarction (AMI) is associated with vascular inflammation, including activation and adherence of neutrophils to vascular endothelial cells via CD11b/CD18 intercellular adhesion molecule interactions. Myeloperoxidase (MPO) induces CD11b surface expression in polymorphonuclear neutrophils (PMNs); however, its role in regulating adhesion in AMI is not well characterized. This study investigates the effects of aminobenzoic acid hydrazide (ABAH), an inhibitor of MPO, antibodies specific for CD11b, on the adhesion of PMNs isolated from AMI patients to endothelial cells. Human neutrophils were isolated from the peripheral blood of 20 patients with AMI or 20 healthy participants as control using Percoll density gradient centrifugation. The major biochemical indicators were detected with different biochemical analyses. The effects of ABAH and anti-CD11b antibodies on neutrophil adhesion to endothelial cell were measured using adhesion assays in vitro. The adhesion rate was significantly higher for neutrophils isolated from AMI patients than healthy individuals (P < 0.001). ABAH significantly inhibited MPO activity in PMNs isolated from AMI patients. Neutrophil adhesion was significantly reduced upon treatment with 10 and 20 μM ABAH in a dose-dependent manner. Treatment with anti-CD11b antibodies also significantly reduced neutrophil adhesion in comparison with the untreated control group (P < 0.001). Thus, both ABAH and anti-CD11b antibodies reduced PMN adhesion. Further studies are necessary to determine whether MPO enhances neutrophil adhesion to endothelial cells in AMI patients through the upregulation of CD11b expression on the surface of neutrophils, which is abrogated by ABAH.

Translational biomarkers: from preclinical to clinical a report of 2009 AAPS/ACCP Biomarker Workshop

There have been some successes in qualifying biomarkers and applying them to drug development and clinical treatment of various diseases. A recent success is illustrated by a collaborative effort among the US Food and Drug Administration, the European Medicines Agency, and the pharmaceutical industry to provide a set of seven preclinical kidney toxicity biomarkers for drug development. Other successes include, but are not limited to, clinical biomarkers for cancer treatment and clinical management of heart transplant patients. The value of fully qualified surrogate endpoints in facilitating successful drug development is undisputed, especially for diseases in which the traditional clinical outcome can only be assessed in large, multi-year trials. Emerging biomarkers, including chemical genomic or imaging biomarkers, and measurement of circulating tumor cells hold great promise for early diagnosis of disease and as prognostic tests for managing treatment of chronic diseases such as osteoarthritis, Alzheimer disease, cardiovascular disease, and cancer. To advance the success of treating and managing these diseases, efforts are needed to establish the temporal relationship between changes in inflammatory or imaging biomarkers with the progression of the chronic disease, and in the case of cancer, between the extent of circulating cancer cells and tumor progression or remission.

The paradox of the neutrophil's role in tissue injury

The neutrophil is an essential component of the innate immune system, and its function is vital to human life. Its production increases in response to virtually all forms of inflammation, and subsequently, it can accumulate in blood and tissue to varying degrees. Although its participation in the inflammatory response is often salutary by nature of its normal interaction with vascular endothelium and its capability to enter tissues and respond to chemotactic gradients and to phagocytize and kill microrganisms, it can contribute to processes that impair vascular integrity and blood flow. The mechanisms that the neutrophil uses to kill microorganisms also have the potential to injure normal tissue under special circumstances. Its paradoxical role in the pathophysiology of disease is particularly, but not exclusively, notable in seven circumstances: 1) diabetic retinopathy, 2) sickle cell disease, 3) TRALI, 4) ARDS, 5) renal microvasculopathy, 6) stroke, and 7) acute coronary artery syndrome. The activated neutrophil's capability to become adhesive to endothelium, to generate highly ROS, and to secrete proteases gives it the potential to induce local vascular and tissue injury. In this review, we summarize the evidence for its role as a mediator of tissue injury in these seven conditions, making it or its products potential therapeutic targets.

Plasma myeloperoxidase predicts incident cardiovascular risks in stable patients undergoing medical management for coronary artery disease

BACKGROUND

Myeloperoxidase (MPO) concentrations predict adverse clinical outcomes in the setting of acute coronary syndromes and heart failure, but the prognostic role of MPO in stable patients with known atherosclerotic burden is unclear.

METHODS

We examined plasma MPO concentrations and their relationship with prevalent significant coronary artery disease (defined as >50% stenosis in any coronary vessel) and incident major adverse cardiovascular events (MACEs), including death, myocardial infarction, and stroke, in a 3-year prospective follow-up study of 1895 patients undergoing elective coronary angiography.

RESULTS

The median plasma MPO concentration was 101 pmol/L (interquartile range 68-187 pmol/L). Patients with plasma MPO concentrations >322 pmol/L (14.6% of population) had increased risk of developing future MACEs [hazard ratio (HR) 1.78, 95% CI 1.33-2.37, P < 0.001], and MPO as a single variable predictor of MACE showed an area under the ROC curve of 0.67. After adjusting for traditional cardiac risk factors, creatinine clearance, B-type natriuretic peptide, and high-sensitivity C-reactive protein (hsCRP), increased MPO concentrations remained significantly associated with incident MACEs over the ensuing 3-year period (HR 1.71; 95% CI 1.27-2.30, P < 0.001). In patients with increased hsCRP, MPO ≤322 pmol/L was associated with lower event rates than observed with MPO >322 pmol/L.

CONCLUSIONS

Plasma MPO concentrations provide independent prognostic value for the prediction of long-term incident MACEs in a stable, medically managed patient population with coronary artery disease. In individuals with increased hsCRP concentrations, we observed lower risk of incident MACEs when concomitant MPO concentrations were low vs when MPO concentrations were high.