The Pathophysiological Role of Neutrophil Extracellular Traps in Inflammatory Diseases

Neutrophil pathogen-killing mechanism termed neutrophil extracellular traps (NETs) has been recently identified. NETs consist of chromatin and histones along with serine proteases and myeloperoxidase and are induced by a great variety of infectious and non-infectious stimuli. NETosis is a kind of programmed neutrophil death characterized by chromatin decondensation and release of nuclear granular contents, mainly driven by peptidylarginine deiminase 4 citrullination of histones. Although classically related to the protection against infectious pathogens, nowadays NETs have been described as a player of several pathophysiological processes. Neutrophil dysregulation has been demonstrated in the pathogenesis of most representative vascular diseases, such as acute coronary syndrome, stroke and venous thrombosis. Indeed, NETs have been identified within atherosclerotic lesions and arterial thrombi in both human beings and animal models. Moreover, an imbalance in this mechanism has been proposed as a critical source of modified and/or externalized autoantigens in autoimmune and inflammatory diseases. Finally, an update on the role of NETs in the pathogenesis of cancer has been included. In the present review, based on papers released on PubMed and MEDLINE up to July 2017, we point to update the knowledge on NETs, from their structure to their roles in infectious diseases as well as in cardiovascular diseases, autoimmunity, metabolic disorders and cancer, with a look to future perspectives and therapeutic opportunities.

Serum adiponectin levels predict acute coronary syndrome (ACS) in patients with severe carotid stenosis

As endocrine organ, adipose tissue may modulate inflammatory response by releasing a wide range of mediators, known as adipocytokines. Due to the complex balance between pro- and anti-inflammatory activity their pathophysiological and prognostic role in cardiovascular (CV) diseases still remains debated. Here, we consider the potential associations of circulating adipocytokines adiponectin, leptin and their ratio (LAR), with metabolic and inflammatory profiles in 217 patients with severe carotid stenosis. A prospective analysis investigating their predictive role toward acute coronary syndromes (ACS) was also drawn over a 12-month follow-up period. Serum leptin was positively associated with fasting insulinemia and HOMA-IR, but not with lipid profile and inflammation. Conversely, adiponectin was negatively associated with glucose, insulin, HOMA-IR, triglycerides and both systemic and intraplaque inflammatory markers whereas a positive association with high-density lipoprotein cholesterol (HDL-c) was observed. Accordingly, a significant association with metabolic profile was reported for LAR. According to the cut-off point identified by ROC curve, adiponectin values≤2.56μg/mL were correlated with a higher risk of ACS occurrence at 12months' follow-up (p-value for Log Rank test=0.0003). At Cox regression analysis the predictive ability of low serum adiponectin was confirmed also after adjustment for age, male gender and diabetes. In conclusion, adiponectin may be considered a biomarker of metabolic compensation, inversely associated with chronic low-grade inflammation. Circulating adiponectin is also associated with lower risk of adverse CV events in patients with severe carotid stenosis.

Targeting Inflammation in Primary Cardiovascular Prevention

BACKGROUND

In the last decade, the development of anti-inflammatory strategies emerged as new trend in cardiovascular (CV) pharmacotherapy. Anti-inflammatory properties have been previously identified in different classes of drugs used in primary CV prevention. However, the extent to which the modification of inflammatory profile contributes in determining CV outcome remains controversial.

METHODS

Focusing on potential beneficial effects in primary prevention, this narrative review provides a comprehensive and critical analysis of randomized clinical trials testing anti-inflammatory treatments in CV disease.

RESULTS

As upstream regulator of the hepatic production of C-reactive protein, tumor necrosis factor-α, interleukin (IL)-6 and IL-1 pathways early emerged as potential targets for CV prevention. More recently, additional strategies targeting lipoprotein-associated phospholipase A2, pro-protein convertase subtilisin/kexin type 9, and intracellular pathways (such as p38 MAPK and different isoforms of NADPH oxidase) have been tested.

CONCLUSION

Conflicting results emerged from clinical trials, emphasized the need to characterize the inflammatory profile of the patients, to minimize the heterogeneity of study populations and to clarify the true value of CRP as specific biomarker of atherosclerosis-related inflammation.

Pathophysiological relevance of macrophage subsets in atherogenesis

Macrophages are highly heterogeneous and plastic cells. They were shown to play a critical role in all stages of atherogenesis, from the initiation to the necrotic core formation and plaque rupture. Lesional macrophages primarily derive from blood monocyte, but local macrophage proliferation as well as differentiation from smooth muscle cells have also been described. Within atherosclerotic plaques, macrophages rapidly respond to changes in the microenvironment, shifting between pro- (M1) or anti-inflammatory (M2) functional phenotypes. Furthermore, different stimuli have been associated with differentiation of newly discovered M2 subtypes: IL-4/IL-13 (M2a), immunecomplex (M2b), IL-10/glucocorticoids (M2c), and adenosine receptor agonist (M2d). More recently, additional intraplaque macrophage phenotypes were also recognized in response to CXCL4 (M4), oxidized phospholipids (Mox), haemoglobin/haptoglobin complexes (HAmac/M(Hb)), and heme (Mhem). Such macrophage polarization was described as a progression among multiple phenotypes, which reflect the activity of different transcriptional factors and the cross-talk between intracellular signalling. Finally, the distribution of macrophage subsets within different plaque areas was markedly associated with cardiovascular (CV) vulnerability. The aim of this review is to update the current knowledge on the role of macrophage subsets in atherogenesis. In addition, the molecular mechanisms underlying macrophage phenotypic shift will be summarised and discussed. Finally, the role of intraplaque macrophages as predictors of CV events and the therapeutic potential of these cells will be discussed.

Anti-apoA-1 auto-antibodies increase mouse atherosclerotic plaque vulnerability, myocardial necrosis and mortality triggering TLR2 and TLR4

Auto-antibodies to apolipoprotein A-1 (anti-apoA-1 IgG) were shown to promote inflammation and atherogenesis, possibly through innate immune receptors signalling. Here, we aimed at investigating the role of Toll-like receptors (TLR) 2 and 4 on anti-apoA-1 IgG-induced athero-sclerotic plaque vulnerability, myocardial necrosis and mortality in mice. Adult male apolipoprotein E knockout (ApoE)-/- (n=72), TLR2-/-ApoE-/- (n=36) and TLR4-/-Apo-/- (n=28) mice were intravenously injected with 50 µg/mouse of endotoxin-free polyclonal anti-apoA-1 IgG or control isotype IgG (CTL IgG) every two weeks for 16 weeks. Atherosclerotic plaque size and vulnerability were assessed by histology. Myocardial ischaemia and necrosis, respectively, were determined by electrocardiographic (ECG) changes assessed by telemetry and serum troponin I (cTnI) measurements. Impact on survival was assessed by Kaplan-Meier analyses. In ApoE-/- mice, anti-apoA-1 IgG passive immunisation enhanced histological features of athero-sclerotic plaque vulnerability (increase in neutrophil and MMP-9 and reduction in collagen content), induced a substantial cTnI elevation (p=0.001), and increased mortality rate by 23 % (LogRank, p=0.04) when compared to CTL IgG. On a subgroup of ApoE-/- mice equipped with telemetry (n=4), a significant ST-segment depression was noted in anti-apoA-1 IgG-treated mice when compared to CTL IgG recipients (p< 0.001), and an acute ST-segment elevation myocardial infarction preceding mouse death was observed in one case. The deleterious effects of anti-apoA-1 IgG on atherosclerotic plaque vulnerability, myocardial necrosis and death were partially reversed in TLR2-/-ApoE-/- and TLR4-/-ApoE-/- backgrounds. In conclusion, anti-apoA-1 auto-antibodies seem to be active mediators of atherosclerotic plaque vulnerability, myocardial necrosis, and mortality in mice through TLR2- and TLR4-mediated pathways.

Update on the role of Pentraxin 3 in atherosclerosis and cardiovascular diseases

Pentraxin 3 (PTX3) is an acute-phase protein that was recently demonstrated to play pleiotropic activities in cardiovascular (CV) diseases. Tumor necrosis factor and interleukins up-regulates PTX3 transcription in different cell types (i.e. endothelial cells, phagocytes, smooth muscle cells, fibroblasts and glial cells) involved in atherogenesis. By interacting with numerous ligands, PTX3 acts as a modulatory molecule of complement system, inflammatory response, angiogenesis, and vascular/tissue remodeling. Experimental data point to a beneficial role of PTX3 in atherosclerotic plaque development and vulnerability. Animal studies indicated a protective role of PTX3 signaling in ischemic/reperfusion injury and failing heart. Clinical studies have so far provided contrasting results, highlighting a debated role of PTX3 as an active mediator of endothelial dysfunction, atherosclerotic plaque vulnerability and worse outcome after ischemic events. Therefore, substantial evidence suggests a dual role of PTX3 as modulator or amplifiers of the innate immune response. The final result of PTX3 activation might be determined by a fine tuning of time, space and environmental signals. The aim of this review is to provide an overview of biological properties of PTX3 in CV diseases and to discuss the ability of PTX3 to act as a crossroad between pro- and anti-inflammatory pathways.

Monocyte count at onset predicts poststroke outcomes during a 90-day follow-up

BACKGROUND

Acute ischaemic stroke (AIS) triggers both systemic and neurovascular inflammation, influencing poststroke recovery. In smokers with AIS, inflammation might be further upregulated, increasing ischaemia/reperfusion injury. Here, the predictive value of leucocyte and adhesion molecules levels on poststroke outcomes was investigated.

MATERIALS AND METHODS

A total of 89 patients with AIS (n = 30 smokers and n = 59 nonsmokers) were recruited and evaluated 1, 7 and 90 days after the onset to assess stroke severity by the National Institute of Health Stroke Scale (NIHSS) score as well as clinical recovery at 90 days by the modified Rankin Scale (mRS). Lesion volume was assessed by noncontrast computed tomography. Haematological parameters, blood chemistry and soluble adhesion molecules were measured.

RESULTS

Smokers experienced a more severe stroke and at a younger age with respect to nonsmokers, moreover, they had higher circulating levels of monocytes, neutrophils and soluble adhesion molecules. Baseline monocytes positively correlated with stroke severity and disability across all time points in the overall cohort. No correlation was shown between adhesion molecules and poststroke outcomes. A monocyte count >0·63 × 10⁹ /L predicted worse stroke severity (defined as NIHSS ≥5) at day 90 independently of age, hypertension, thrombolysis and active smoking in the overall cohort. Similarly, a monocyte count >0·64 × 10⁹ /L predicted poor neurological recovery at day 90 (defined as mRS > 2).

CONCLUSIONS

Smoker had more severe AIS and higher leucocytes and adhesion molecule levels. In the overall cohort, monocyte count was an independent predictor of worse poststroke outcome. Although larger trials are needed, monocyte count might be a cheap prognostic parameter in AIS.

4D cardiac imaging at clinical 3.0T provides accurate assessment of murine myocardial function and viability

OBJECTIVES

We validate a 4D strategy tailored for 3T clinical systems to simultaneously quantify function and infarct size in wild type mice after ischemia/reperfusion, with improved spatial and temporal resolution by comparison to previous published protocols using clinical field MRI systems.

METHODS

C57BL/6J mice underwent 60min ischemia/reperfusion (n=14) or were controls without surgery (n=6). Twenty-four hours after surgery mice were imaged with gadolinium injection and sacrificed for post-mortem MRI and histology with serum also taken for Troponin I levels. The double ECG- and respiratory-triggered 3D FLASH (Fast Low Angle Shot) gradient echo (GRE) cine sequence had an acquired isotropic resolution of 344μm, TR/TE of 7.8/2.9ms and acquisition time 25-35min. The conventional 2D FLASH cine sequence had the same in-plane resolution of 344μm, 1mm slice thickness and TR/TE 11/5.4ms for an acquisition time of 20-25min plus 5min for planning. Left ventricle (LV) and right ventricle (RV) volumes were measured and functional parameters compared 2D to 3D, left to right and for inter and intra observer reproducibility. MRI infarct volume was compared to histology.

RESULTS

For the function evaluation, the 3D cine outperformed 2D cine for spatial and temporal resolution. Protocol time for the two methods was equivalent (25-35min). Flow artifacts were reduced (p=0.008) and epi/endo-cardial delineation showed good intra and interobserver reproducibility. Paired t-test comparing ejection volume left to right showed no significant difference for 3D (p=0.37), nor 2D (p=0.30) and correlation slopes of left to right EV were 1.17 (R²=0.75) for 2D and 1.05 (R²=0.50) for 3D. Quantifiable 'late gadolinium enhancement' infarct volume was seen only with the 3D cine and correlated to histology (R²=0.89). Left ejection fraction and MRI-measured infarct volume correlated (R²>0.3).

CONCLUSIONS

The 4D strategy, with contrast injection, was validated in mice for function and infarct quantification from a single scan with minimal slice planning.

Treatment with Proprotein Convertase Subtilisin/Kexin Type 9 (PCSK9) Inhibitors to Reduce Cardiovascular Inflammation and Outcomes

Proprotein Convertase Subtilisin/Kexin type 9 (PCSK9) is a serine protease involved in cholesterol homeostasis. After binding to the complex low-density lipoprotein (LDL)-receptor, PCSK9 induces its intracellular degradation, thus reducing serum LDL clearance. PCSK9 is mainly secreted by the liver, but it is also expressed to a lesser extent in other organs. Apart from the well-known activity concerning hepatic LDL receptor-mediated pathway, PCSK9 has been supposed to potentially interfere with vascular inflammation in atherogenesis. Vascular smooth muscle cells have been demonstrated to produce higher amounts of PCSK9 as compared to endothelial cells especially in an inflammatory microenvironment. Low shear stress regions increase PCSK9 expression within SMCs, while higher shear stress gradually reduced PCSK9 expression. Moreover, a crosstalk between PCSK9 and reactive oxygen species has been also described. Oxidized LDL was shown to up regulate the expression of PCKS9 by influencing dose-dependently the secretion of interleukin (IL)-1α, IL-6, and tumor necrosis factor-α. After the identification of gene loss-of-function mutations and no detectable circulating protein levels, PCSK9 has attracted a great interest as an effective target for cholesterol-lowering therapies. Different strategies have been implemented to block the effects of both intracellular and circulating PCSK9. In particular, monoclonal antibodies represent the most promising approach and two of these, alirocumab and evolocumab, have been approved for clinical use in patients affected by familial hypercholesterolemia with encouraging results. In the next future, the improvement of the knowledge of the "pleiotropic" effects of PCSK9 inhibitors might unveil therapeutic potential on cardiovascular outcome independently on the cholesterol lowering activity.

High baseline C-reactive protein levels predict partial type 2 diabetes mellitus remission after biliopancreatic diversion

BACKGROUND AND AIMS

Several studies demonstrated that surgery can improve inflammation parameters, such as C-reactive protein (CRP). Few biomarkers have been investigated to potentially predict type 2 diabetes mellitus (T2DM) remission. We aimed at determining whether pre-surgery serum CRP levels could predict T2DM remission after 3 years in patients undergoing bariatric surgery, especially biliopancreatic diversion (BPD).

METHODS AND RESULTS

This study was conducted from 2007 to 2009 at the Surgical Department of the University of Genoa, Italy. Forty-four patients with T2DM undergoing BPD (n = 38) or Roux-en-Y gastric bypass (n = 6) were enrolled. The primary endpoint was to evaluate whether pre-surgery CRP levels could predict T2DM partial remission at 3-year follow-up. Secondary endpoints were to assess whether glycaemic, lipid, and inflammatory parameters modified during the follow-up. At baseline, patients with T2DM ranged from overweight to morbid obesity, had mild dyslipidaemia, and a low-grade inflammation. Bariatric surgery improved body weight, lipid and glycaemic profile both at 1- and 3-year follow-up. Pre-surgery CRP levels progressively decreased at 1- and 3-year follow-up. Among inflammatory pre-surgery parameters, only high CRP levels were shown to predict T2DM partial remission after 3 years. Multivariate analysis confirmed the predictive value of pre-surgery CRP levels independently of age, gender, type of surgery, and body mass index.

CONCLUSION

Bariatric surgery, in particular BPD, improved both metabolic and inflammatory biomarkers at 1- and 3-year follow-up. Pre-surgery high CRP levels predicted 3-year T2DM partial remission, indicating a promising target population to be especially treated with BPD.

5-fluorouracil causes endothelial cell senescence: potential protective role of glucagon-like peptide 1

BACKGROUND AND PURPOSE

5-fluorouracil (5FU) and its prodrug, capecitabine, can damage endothelial cells, whilst endothelial integrity is preserved by glucagon-like peptide 1 (GLP-1). Here, we studied the effect of 5FU on endothelial senescence and whether GLP-1 antagonizes it.

EXPERIMENTAL APPROACH

EA.hy926 cells were exposed to 5FU or sera from patients taking capecitabine, with or without pre-incubation with GLP-1. Senescence was identified by expression of senescence-associated β-galactosidase and p16^INK4a and reduced cell proliferation. Soluble vascular cell adhesion molecule-1 (sVCAM-1), soluble intercellular adhesion molecule-1 (sICAM-1) and CD146 (marker of endothelial injury) were measured by ELISA before and at completion of capecitabine chemotherapy. RT-PCR, western blotting, functional experiments with signalling inhibitors and ERK1/2 silencing were performed to characterize 5FU-induced phenotype and elucidate the pathways underlying 5FU and GLP-1 activity.

KEY RESULTS

Both 5FU and sera from capecitabine-treated patients stimulated endothelial cell senescence. 5FU-elicited senescence occurred via activation of p38 and JNK, and was associated with decreased eNOS and SIRT-1 levels. Furthermore, 5FU up-regulated VCAM1 and TYMP (encodes enzyme activating capecitabine and 5FU), and sVCAM-1 and CD146 concentrations were higher after than before capecitabine chemotherapy. A non-significant trend for higher ICAM1 levels was also observed. GLP-1 counteracted 5FU-initiated senescence and reduced eNOS and SIRT-1 expression, this protection being mediated by GLP-1 receptor, ERK1/2 and, possibly, PKA and PI3K.

CONCLUSIONS AND IMPLICATIONS

5FU causes endothelial cell senescence and dysfunction, which may contribute to its cardiovascular side effects. 5FU-triggered senescence was prevented by GLP-1, raising the possibility of using GLP-1 analogues and degradation inhibitors to treat 5FU and capecitabine vascular toxicity.

LINKED ARTICLES

This article is part of a themed section on New Insights into Cardiotoxicity Caused by Chemotherapeutic Agents. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v174.21/issuetoc.

Alamandine abrogates neutrophil degranulation in atherosclerotic mice

BACKGROUND

Neutrophil-mediated inflammation was recently identified as an active contributor to athero-progression. Therapeutic strategies inhibiting neutrophil degranulation or recruitment were hypothesized to positively impact on plaque vulnerability. In this study, we investigated whether treatment with the recently discovered agonist of the Mas-related G-coupled receptor type D (MrgD) alamandine would impact on neutrophil degranulation in vivo and in vitro.

MATERIALS AND METHODS

Fifteen-week-old ApoE^-/- mice were fed with a Western-type diet for an additional 11 weeks. After the first 2 weeks of diet, mice were surgically implanted with a carotid 'cast' device that alters the blood shear stress and induces different carotid plaque phenotypes. During the last 4 weeks before euthanasia, mice were randomly assigned to subcutaneously receive vehicle (NaCl 0·15 M) or alamandine (24 μg/kg/h) by micropump. For in vitro experiments, neutrophils were obtained after thioglycollate intraperitoneal injection in ApoE^-/- mice.

RESULTS

Treatment with alamandine was well-tolerated, but failed to affect lipid, macrophage, neutrophil or collagen content within carotid and aortic root plaques. Also, treatment with alamandine did not affect Th-cell polarization in lymphoid organs. Conversely, alamandine administration was associated with a reduction in serum levels of neutrophil granule enzymes, such as MMP-9 and MPO as well as MMP-9 content within aortic root plaques. In vitro, preincubation with alamandine dose-dependently abrogated PMA-induced neutrophil degranulation of MMP-9 and MPO.

CONCLUSION

These results suggest that treatment with the MrgD agonist alamandine led to a reduced release of neutrophil granule products, potentially interfering with pro-atherosclerotic neutrophil activation.

The Role of Adipocytokines in Coronary Atherosclerosis

PURPOSE OF REVIEW

The aim of this review is to overview the pathophysiological role of adipocytokines in atherogenesis, focusing on their potential role as biomarkers of coronary disease.

RECENT FINDINGS

Several lines of evidence indicated adipose tissue not only as depot but rather as an endocrine organ. In this context, the balance between pro- and anti-inflammatory adipocytokines has been shown to critically regulate vascular homeostasis in both physiological and pathophysiological conditions. Overweight and obesity are characterized by dysfunctional adipose tissue and then the prevalence of pro-inflammatory mediators, with a detrimental effect on vascular health. As opposite to adiponectin, pro-inflammatory adipocytokines, such as leptin and resistin, promote endothelial dysfunction and inflammatory processes involved in atherosclerotic plaque progression and vulnerability. Therefore, many adipocytokines have been investigated as potential biomarkers of cardiovascular (CV) risk, but their role has not yet been clearly established. Furthermore, the perivascular adipose tissue recently emerged as a critical modulator of atherosclerotic processes, due to the close interaction with the underlying vascular tissue. The ongoing discovery of new adipocytokines and the complex pathophysiological role of the different adipose tissue depots strongly contribute to define the complexity of adipocytokines network. Understanding those complex interactions may allow determining new potential biomarkers of CV risk and potential therapeutic targets.

Decreased serum PCSK9 levels after ischaemic stroke predict worse outcomes

BACKGROUND

Soluble mediators have been investigated to predict the prognosis of acute ischaemic stroke (AIS). Among them, proprotein convertase subtilisin/kexin type 9 (PCSK9) might have both clinical and pathophysiological relevance.

MATERIALS AND METHODS

All available serum samples from a cohort of patients with first AIS (n = 72) were tested for PCSK9 and included in this substudy analysis. The primary endpoint investigated the predictive value of early PCSK9 level variations (ΔPCSK9) from AIS onset to day 7 or from day 1 to day 7, towards a 90-day outcome by modified Rankin Scale (mRS). The secondary endpoint explored the association between ΔPCSK9 and the risk of major adverse cardiovascular events (MACEs).

RESULTS

Decreased serum PCSK9 levels at days 1 and 7 were associated with poor clinical outcomes at day 90. At the cut-off point identified by ROC curve analysis (-61·28 ng/mL), ΔPCSK9 day 7-day 1 predicted a poor mRS at day 90 after AIS. ΔPCSK9 day 7-day 1 ≤ -61·28 ng/mL was associated with an increased rate of MACEs.

CONCLUSION

A decrease in PCSK9 levels was a predictor for poor outcome and increased MACEs after AIS. Additional studies targeting post-AIS PCSK9 levels and activity are required to clarify the prognostic and pathophysiological relevance of PCSK9 after AIS.