Pathophysiological role of neutrophils in acute myocardial infarction

Role of Neutrophils in Cardiac Injury and Repair Following Myocardial Infarction

Neutrophils are first-line responders of the innate immune system. Following myocardial infarction (MI), neutrophils are quickly recruited to the ischemic region, where they initiate the inflammatory response, aiming at cleaning up dead cell debris. However, excessive accumulation and/or delayed removal of neutrophils are deleterious. Neutrophils can promote myocardial injury by releasing reactive oxygen species, granular components, and pro-inflammatory mediators. More recent studies have revealed that neutrophils are able to form extracellular traps (NETs) and produce extracellular vesicles (EVs) to aggravate inflammation and cardiac injury. On the contrary, there is growing evidence showing that neutrophils also exert anti-inflammatory, pro-angiogenic, and pro-reparative effects, thus facilitating inflammation resolution and cardiac repair. In this review, we summarize the current knowledge on neutrophils’ detrimental roles, highlighting the role of recently recognized NETs and EVs, followed by a discussion of their beneficial effects and molecular mechanisms in post-MI cardiac remodeling. In addition, emerging concepts about neutrophil diversity and their modulation of adaptive immunity are discussed.

Biocompatibility Evolves: Phenomenology to Toxicology to Regeneration

The word "biocompatibility," is inconsistent with the observations of healing for so-called biocompatible biomaterials. The vast majority of the millions of medical implants in humans today, presumably "biocompatible," are walled off by a dense, avascular, crosslinked collagen capsule, hardly suggestive of life or compatibility. In contrast, one is now seeing examples of implant biomaterials that lead to a vascularized reconstruction of localized tissue, a biological reaction different from traditional biocompatible materials that generate a foreign body capsule. Both the encapsulated biomaterials and the reconstructive biomaterials qualify as "biocompatible" by present day measurements of biocompatibility. Yet, this new generation of materials would seem to heal "compatibly" with the living organism, where older biomaterials are isolated from the living organism by the dense capsule. This review/perspective article will explore this biocompatibility etymological conundrum by reviewing the history of the concepts around biocompatibility, today's standard methods for assessing biocompatibility, a contemporary view of the foreign body reaction and finally, a compendium of new biomaterials that heal without the foreign body capsule. A new definition of biocompatibility is offered here to address advances in biomaterials design leading to biomaterials that heal into the body in a facile manner.

Current Understanding of the Immunomodulatory Activities of High-Density Lipoproteins

Lipoproteins interact with immune cells, macrophages and endothelial cells - key players of the innate and adaptive immune system. High-density lipoprotein (HDL) particles seem to have evolved as part of the innate immune system since certain HDL subspecies contain combinations of apolipoproteins with immune regulatory functions. HDL is enriched in anti-inflammatory lipids, such as sphingosine-1-phosphate and certain saturated lysophospholipids. HDL reduces inflammation and protects against infection by modulating immune cell function, vasodilation and endothelial barrier function. HDL suppresses immune cell activation at least in part by modulating the cholesterol content in cholesterol/sphingolipid-rich membrane domains (lipid rafts), which play a critical role in the compartmentalization of signaling pathways. Acute infections, inflammation or autoimmune diseases lower HDL cholesterol levels and significantly alter HDL metabolism, composition and function. Such alterations could have a major impact on disease progression and may affect the risk for infections and cardiovascular disease. This review article aims to provide a comprehensive overview of the immune cell modulatory activities of HDL. We focus on newly discovered activities of HDL-associated apolipoproteins, enzymes, lipids, and HDL mimetic peptides.

Mesenchymal Stem Cell Transplantation for Ischemic Diseases: Mechanisms and Challenges

Ischemic diseases are conditions associated with the restriction or blockage of blood supply to specific tissues. These conditions can cause moderate to severe complications in patients, and can lead to permanent disabilities. Since they are blood vessel-related diseases, ischemic diseases are usually treated with endothelial cells or endothelial progenitor cells that can regenerate new blood vessels. However, in recent years, mesenchymal stem cells (MSCs) have shown potent bioeffects on angiogenesis, thus playing a role in blood regeneration. Indeed, MSCs can trigger angiogenesis at ischemic sites by several mechanisms related to their trans-differentiation potential. These mechanisms include inhibition of apoptosis, stimulation of angiogenesis via angiogenic growth factors, and regulation of immune responses, as well as regulation of scarring to suppress blood vessel regeneration when needed. However, preclinical and clinical trials of MSC transplantation in ischemic diseases have shown some limitations in terms of treatment efficacy. Such studies have emphasized the current challenges of MSC-based therapies. Treatment efficacy could be enhanced if the limitations were better understood and potentially resolved. This review will summarize some of the strategies by which MSCs have been utilized for ischemic disease treatment, and will highlight some challenges of those applications as well as suggesting some strategies to improve treatment efficacy.

A double-edged sword of immuno-microenvironment in cardiac homeostasis and injury repair

The response of immune cells in cardiac injury is divided into three continuous phases: inflammation, proliferation and maturation. The kinetics of the inflammatory and proliferation phases directly influence the tissue repair. In cardiac homeostasis, cardiac tissue resident macrophages (cTMs) phagocytose bacteria and apoptotic cells. Meanwhile, NK cells prevent the maturation and transport of inflammatory cells. After cardiac injury, cTMs phagocytose the dead cardiomyocytes (CMs), regulate the proliferation and angiogenesis of cardiac progenitor cells. NK cells prevent the cardiac fibrosis, and promote vascularization and angiogenesis. Type 1 macrophages trigger the cardioprotective responses and promote tissue fibrosis in the early stage. Reversely, type 2 macrophages promote cardiac remodeling and angiogenesis in the late stage. Circulating macrophages and neutrophils firstly lead to chronic inflammation by secreting proinflammatory cytokines, and then release anti-inflammatory cytokines and growth factors, which regulate cardiac remodeling. In this process, dendritic cells (DCs) mediate the regulation of monocyte and macrophage recruitment. Recruited eosinophils and Mast cells (MCs) release some mediators which contribute to coronary vasoconstriction, leukocyte recruitment, formation of new blood vessels, scar formation. In adaptive immunity, effector T cells, especially Th17 cells, lead to the pathogenesis of cardiac fibrosis, including the distal fibrosis and scar formation. CMs protectors, Treg cells, inhibit reduce the inflammatory response, then directly trigger the regeneration of local progenitor cell via IL-10. B cells reduce myocardial injury by preserving cardiac function during the resolution of inflammation.

Tissue Treg Secretomes and Transcription Factors Shared With Stem Cells Contribute to a Treg Niche to Maintain Treg-Ness With 80% Innate Immune Pathways, and Functions of Immunosuppression and Tissue Repair

We used functional -omics angles and examined transcriptomic heterogeneity in CD4⁺Foxp3⁺ regulatory T cells (Treg) from spleen (s-Treg), lymph nodes (LN-Treg), intestine (int-Treg), and visceral adipose tissue (VAT-Treg), and made significant findings: 1) Five new shared Treg genes including NIBAN, TNFRSF1b, DUSP4,VAV2, and KLRG1, and 68 new signatures are identified. Among 27 signaling pathways shared in four tissue Treg, 22 pathways are innate immune pathways (81.5%); 2) s-Treg, LN-Treg, int-Treg, and VAT-Treg have zero, 49, 45, and 116 upregulated pathways, respectively; 3) 12, 7, and 15 out of 373 CD markers are identified as specific for LN-Treg, int-Treg, and VAT-Treg, respectively, which may initiate innate immune signaling; 4) 7, 49, 44, and 79 increased cytokines out of 1176 cytokines are identified for four Treg, respectively, suggesting that Treg have much more secretory proteins/cytokines than IL-10, TGF-β, and IL-35; 5) LN-Treg, int-Treg, and VAT-Treg have 13 additional secretory functions more than s-Treg, found by analyzing 1,706 secretomic genes; 6) 2, 20, 25, and 43 increased transcription factors (TFs) out of 1,496 TFs are identified four Treg, respectively; 7) LN-Treg and int-Treg have increased pyroptosis regulators but VAT-Treg have increased apoptosis regulators; 8) 1, 15, 19, and 31 increased kinases out of 661 kinome are identified for s-Treg, LN-Treg, int-Treg, and VAT-Treg, respectively; 9) comparing with that of s-Treg, LN-Treg, int-Treg, and VAT-Treg increase activated cluster (clusters 1–3) markers; and decrease resting cluster (clusters 4–6) markers; and 10) Treg promote tissue repair by sharing secretomes and TFs AHR, ETV5, EGR1, and KLF4 with stem cells, which partially promote upregulation of all the groups of Treg genes. These results suggest that stem cell-shared master genes make tissue Treg as the first T cell type using a Treg niche to maintain their Treg-ness with 80% innate immune pathways, and triple functions of immunosuppression, tissue repair, and homeostasis maintenance. Our results have provided novel insights on the roles of innate immune pathways on Treg heterogeneity and new therapeutic targets for immunosuppression, tissue repair, cardiovascular diseases, chronic kidney disease, autoimmune diseases, transplantation, and cancers.

Interleukin-6 mediates neutrophil mobilization from bone marrow in pulmonary hypertension

Myeloid cells, such as neutrophils, are produced in the bone marrow in high quantities and are important in the pathogenesis of vascular diseases such as pulmonary hypertension (PH). Although neutrophil recruitment into sites of inflammation has been well studied, the mechanisms of neutrophil egress from the bone marrow are not well understood. Using computational flow cytometry, we observed increased neutrophils in the lungs of patients and mice with PH. Moreover, we found elevated levels of IL-6 in the blood and lungs of patients and mice with PH. We observed that transgenic mice overexpressing Il-6 in the lungs displayed elevated neutrophil egress from the bone marrow and exaggerated neutrophil recruitment to the lungs, resulting in exacerbated pulmonary vascular remodeling, and dysfunctional hemodynamics. Mechanistically, we found that IL-6-induced neutrophil egress from the bone marrow was dependent on interferon regulatory factor 4 (IRF-4)-mediated CX₃CR1 expression in neutrophils. Consequently, Cx₃cr1 genetic deficiency in hematopoietic cells in Il-6-transgenic mice significantly reduced neutrophil egress from bone marrow and decreased neutrophil counts in the lungs, thus ameliorating pulmonary remodeling and hemodynamics. In summary, these findings define a novel mechanism of IL-6-induced neutrophil egress from the bone marrow and reveal a new therapeutic target to curtail neutrophil-mediated inflammation in pulmonary vascular disease.

Colchicine Inhibits Neutrophil Extracellular Trap Formation in Patients With Acute Coronary Syndrome After Percutaneous Coronary Intervention

Background

Release of neutrophil extracellular traps (NETs) after percutaneous coronary intervention (PCI) in acute coronary syndrome (ACS) is associated with periprocedural myocardial infarction, as a result of microvascular obstruction via pro‐inflammatory and prothrombotic pathways. Colchicine is a well‐established anti‐inflammatory agent with growing evidence to support use in patients with coronary disease. However, its effects on post‐PCI NET formation in ACS have not been explored.

Methods and Results

Sixty patients (40 ACS; 20 stable angina pectoris) were prospectively recruited and allocated to colchicine or no treatment. Within 24 hours of treatment, serial coronary sinus blood samples were collected during PCI. Isolated neutrophils from 10 patients with ACS post‐PCI and 4 healthy controls were treated in vitro with colchicine (25 nmol/L) and stimulated with either ionomycin (5 μmol/L) or phorbol 12‐myristate 13‐acetate (50 nmol/L). Extracellular DNA was quantified using Sytox Green and fixed cells were stained with Hoechst 3342 and anti‐alpha tubulin. Baseline characteristics were similar across both treatment and control arms. Patients with ACS had higher NET release versus patients with stable angina pectoris (P<0.001), which was reduced with colchicine treatment (area under the curve: 0.58 versus 4.29; P<0.001). In vitro, colchicine suppressed unstimulated (P<0.001), phorbol 12‐myristate 13‐acetate–induced (P=0.009) and ionomycin‐induced (P=0.002) NET formation in neutrophils isolated from patients with ACS post‐PCI, but not healthy controls. Tubulin organization was impaired in neutrophils from patients with ACS but was restored by colchicine treatment.

Conclusions

Colchicine suppresses NET formation in patients with ACS post‐PCI by restoring cytoskeletal dynamics. These findings warrant further investigation in randomized trials powered for clinical end points.

Registration

URL: https://anzctr.org.au; Unique identifier: ACTRN12619001231134.

Cerebrovascular risk factors associated with ischemic stroke in a young non-diabetic and non-hypertensive population: a retrospective case-control study

Background

Globally, rates of ischemic stroke (IS) have been rising among young adults. This study was designed to identify risk factors associated with IS incidence in young adults unaffected by hypertension or diabetes.

Methods

This was a retrospective case-control study of early-onset IS patients without diabetes and hypertension. Control patients were matched with healthy individuals based upon sex, age (±2 years), and BMI (±3 kg/m²) at a 1:3 ratio. Sociodemographic, clinical, and risk factor-related data pertaining to these patients was collected. The association between these risk factors and IS incidence was then assessed using conditional logistic regression models.

Results

We recruited 60 IS patients and 180 controls with mean ages of 44.37 ± 4.68 and 44.31 ± 4.71 years, respectively, for this study. Relative to controls, IS patients had significantly higher total cholesterol (TG), homocysteine (HCY), white blood cell (WBC), absolute neutrophil count (ANC), systolic blood pressure (SBP), and diastolic blood pressure (DBP) levels, and significantly lower high-density lipoprotein cholesterol (HDL-C) and triglyceride cholesterol (TC), free triiodothyronine (FT3), and free thyroxine (FT4) levels (all P < 0.05). After controlling for potential confounding factors, HCY and ANC were found to be significantly positively associated with IS incidence (OR 1.518, 95%CI 1.165–1.977, P = 0.002 and OR 2.418, 95%CI 1.061–5.511, P = 0.036, respectively), whereas HDL-C and FT3 levels were negatively correlated with IS incidence (OR 0.001, 95%CI 0.000–0.083, P = 0.003 and OR 0.053, 95%CI 0.008–0.326, P = 0.002, respectively).

Conclusions

In young non-diabetic and non-hypertensive patients, lower HDL-C and FT3 levels and higher HCY and ANC levels may be associated with an elevated risk of IS. Additional prospective studies of large patient cohorts will be essential to validate these findings.

Similar Clinical Course and Significance of Circulating Innate and Adaptive Immune Cell Counts in STEMI and COVID-19

This study aimed to assess the time course of circulating neutrophil and lymphocyte counts and their ratio (NLR) in ST-segment elevation myocardial infarction (STEMI) and coronavirus disease (COVID)-19 and explore their associations with clinical events and structural damage. Circulating neutrophil, lymphocyte and NLR were sequentially measured in 659 patients admitted for STEMI and in 103 COVID-19 patients. The dynamics detected in STEMI (within a few hours) were replicated in COVID-19 (within a few days). In both entities patients with events and with severe structural damage displayed higher neutrophil and lower lymphocyte counts. In both scenarios, higher maximum neutrophil and lower minimum lymphocyte counts were associated with more events and more severe organ damage. NLR was higher in STEMI and COVID-19 patients with the worst clinical and structural outcomes. A canonical deregulation of the immune response occurs in STEMI and COVID-19 patients. Boosted circulating innate (neutrophilia) and depressed circulating adaptive immunity (lymphopenia) is associated with more events and severe organ damage. A greater understanding of these critical illnesses is pivotal to explore novel alternative therapies.

Predicting Diagnostic Gene Biomarkers Associated With Immune Infiltration in Patients With Acute Myocardial Infarction

Objective: The present study was designed to identify potential diagnostic markers for acute myocardial infarction (AMI) and determine the significance of immune cell infiltration in this pathology.

Methods: Two publicly available gene expression profiles (GSE66360 and GSE48060 datasets) from human AMI and control samples were downloaded from the GEO database. Differentially expressed genes (DEGs) were screened between 80 AMI and 71 control samples. The LASSO regression model and support vector machine recursive feature elimination (SVM-RFE) analysis were performed to identify candidate biomarkers. The area under the receiver operating characteristic curve (AUC) value was obtained and used to evaluate discriminatory ability. The expression level and diagnostic value of the biomarkers in AMI were further validated in the GSE60993 dataset (17 AMI patients and 7 controls). The compositional patterns of the 22 types of immune cell fraction in AMI were estimated based on the merged cohorts using CIBERSORT.

Results: A total of 27 genes were identified. The identified DEGs were mainly involved in carbohydrate binding, Kawasaki disease, atherosclerosis, and arteriosclerotic cardiovascular disease. Gene sets related to atherosclerosis signaling, primary immunodeficiency, IL-17, and TNF signaling pathways were differentially activated in AMI compared with the control. IL1R2, IRAK3, and THBD were identified as diagnostic markers of AMI (AUC = 0.877) and validated in the GSE60993 dataset (AUC = 0.941). Immune cell infiltration analysis revealed that IL1R2, IRAK3, and THBD were correlated with M2 macrophages, neutrophils, monocytes, CD4⁺ resting memory T cells, activated natural killer (NK) cells, and gamma delta T cells.

Conclusion: IL1R2, IRAK3, and THBD can be used as diagnostic markers of AMI, and can provide new insights for future studies on the occurrence and the molecular mechanisms of AMI.

Neutrophil Extracellular Traps: Signaling Properties and Disease Relevance

Neutrophil extracellular traps (NETs) are characterized as extracellular DNA fibers comprised of histone and cytoplasmic granule proteins. NETs were first described as a form of innate response against pathogen invasion, which can capture pathogens, degrade bacterial toxic factors, and kill bacteria. Additionally, NETs also provide a scaffold for protein and cell binding. Protein binding to NETs further activate the coagulation system which participates in thrombosis. In addition, NETs also can damage the tissues due to the proteins they carry. Many studies have suggested that the excessive formation of NETs may contribute to a range of diseases, including thrombosis, atherosclerosis, autoimmune diseases, and sepsis. In this review, we describe the structure and components of NETs, models of NET formation, and detection methods. We also discuss the molecular mechanism of NET formation and their disease relevance. Modulation of NET formation may provide a new route for the prevention and treatment of releated human diseases.

S100A9 Links Inflammation and Repair in Myocardial Infarction

RATIONALE

The alarmin S100A9 has been identified as a potential therapeutic target in myocardial infarction. Short-term S100A9 blockade during the inflammatory phase post-myocardial infarction inhibits systemic and cardiac inflammation and improves cardiac function long term.

OBJECTIVE

To evaluate the impact of S100A9 blockade on postischemic cardiac repair.

METHODS AND RESULTS

We assessed cardiac function, hematopoietic response, and myeloid phagocyte dynamics in WT (wild type) C57BL/6 mice with permanent coronary artery ligation, treated with the specific S100A9 blocker ABR-238901 for 7 or 21 days. In contrast to the beneficial effects of short-term therapy, extended S100A9 blockade led to progressive deterioration of cardiac function and left ventricle dilation. The treatment reduced the proliferation of Lin^-Sca-1⁺c-Kit⁺ hematopoietic stem and progenitor cells in the bone marrow and the production of proreparatory CD150⁺CD48^-CCR2⁺ hematopoietic stem cells. Monocyte trafficking from the spleen to the myocardium and subsequent phenotype switching to reparatory Ly6C^loMerTK^hi macrophages was also impaired, leading to inefficient efferocytosis, accumulation of apoptotic cardiomyocytes, and a larger myocardial scar. The transcription factor Nur77 (Nr4a1 [nuclear receptor subfamily 4 group A member 1]) mediates the transition from inflammatory Ly6C^hi monocytes to reparatory Ly6C^lo macrophages. S100A9 upregulated the levels and activity of Nur77 in monocytes and macrophages in vitro and in Ly6C^hi/int monocytes in vivo, and S100A9 blockade antagonized these effects. Finally, the presence of reparatory macrophages in the myocardium was also impaired in S100A9^-/- mice with permanent myocardial ischemia, leading to depressed cardiac function long term.

CONCLUSIONS

We show that S100A9 plays an important role in both the inflammatory and the reparatory immune responses to myocardial infarction. Long-term S100A9 blockade negatively impacts cardiac recovery and counterbalances the beneficial effects of short-term therapy. These results define a therapeutic window targeting the inflammatory phase for optimal effects of S100A9 blockade as potential immunomodulatory treatment in acute myocardial infarction.

Macrophage Activities in Myocardial Infarction and Heart Failure

Heart diseases remain the major cause of death worldwide. Advances in pharmacological and biomedical management have resulted in an increasing proportion of patients surviving acute heart failure (HF). However, many survivors of HF in the early stages end up increasing the disease to chronic HF (CHF). HF is an established frequent complication of myocardial infarction (MI), and numerous influences including persistent myocardial ischemia, shocked myocardium, ventricular remodeling, infarct size, and mechanical impairments, as well as hibernating myocardium trigger the development of left ventricular systolic dysfunction following MI. Macrophage population is active in inflammatory process, yet the clear understanding of the causative roles for these macrophage cells in HF development and progression is actually incomplete. Long ago, it was thought that macrophages are of importance in the heart after MI. Also, though inflammation is as a result of adverse HF in patients, but despite the fact that broad immunosuppression therapeutic target has been used in various clinical trials, no positive results have showed up, but rather, the focus on proinflammatory cytokines has proved more benefits in patients with HF. Therefore, in this review, we discuss the recent findings and new development about macrophage activations in HF, its role in the healthy heart, and some therapeutic targets for myocardial repair. We have a strong believe that there is a need to give maximum attention to cardiac resident macrophages due to the fact that they perform various tasks in wound healing, self-renewal of the heart, and tissue remodeling. Currently, it has been discovered that the study of macrophages goes far beyond its phagocytotic roles. If researchers in future confirm that macrophages play a vital role in the heart, they can be therapeutically targeted for cardiac healing.

Traitor or warrior-Treg cells sneaking into the lesions of psoriatic arthritis

Regulatory T (Treg) cells have been recognized to maintain immune tolerance, which contributes to prevention of autoimmune diseases. However, recent evidence has demonstrated different characteristics of these cells between those that are in circulation compared to those in various local tissues. In addition, the ability of Treg cells to have plasticity in certain disease settings and in inflammatory lesions has been increasingly recognized. Herein we summarize updated knowledge of Treg biology and discuss the current understanding of tissue-resident Treg cells in psoriatic arthritis (PsA), attempting to provide new insights into precise role of Treg cells in the immune response and as a possible therapeutic intervention in patients with PsA.

Neutrophil activation and neutrophil derived neutrophil extracellular trap formation in patients with coronary artery ectasia

BACKGROUND

This study investigated neutrophil activation and neutrophil-derived extracellular traps formation in coronary artery ectasia.

METHODS

We enrolled 90 patients who underwent coronary angiography, and included 30 patients with coronary artery ectasia (CAE), 30 patients with obstructive coronary artery disease (CAD) and 30 patients with normal coronary arteries (CON). Intra-neutrophil mean myeloperoxidase index (MPXI) was determined using an automated blood cell counter (ADVIA2120 Hematology System). Serum concentrations of plasma adhesion molecules, cytokines, and neutrophil-derived extracellular traps were quantified.

RESULTS

The intra-neutrophil mean myeloperoxidase index was reduced in CAE patients compared to CAD and CON patients (1.02 ± 3.01, 3.22 ± 3.03, 3.52 ± 4.25, respectively; CAE vs CAD, p = 0.016 and CAE vs CON, p = 0.007). Multiple logistic regression analysis showed that MPXI and dsDNA were independent factors that predicted the presence of CAE. CAE patients had higher levels of plasma adhesion molecules (P-selectin glycoprotein ligand-1, E-selectin, L-selectin) and interleukin 1 beta levels. Neutrophil extracellular trap concentrations were significantly higher in the CAE group compared to CAD and CON patients (284.31(258.33-449.91) ng/mL, 225.12(203.34-257.13) ng/mL, and 247.37(231.04-273.01) ng/mL, respectively; CAE vs CAD, p = 0.000 and CAE vs CON, p = 0.001).

CONCLUSIONS

Peripheral neutrophils from CAE patients were activated and neutrophil extracellular traps were elevated in the plasma. IL-1β and soluble adhesion molecules may be the causal factors for neutrophil activation.

Therapeutic targeting of neutrophil exocytosis

Dysregulation of neutrophil activation causes disease in humans. Neither global inhibition of neutrophil functions nor neutrophil depletion provides safe and/or effective therapeutic approaches. The role of neutrophil granule exocytosis in multiple steps leading to recruitment and cell injury led each of our laboratories to develop molecular inhibitors that interfere with specific molecular regulators of secretion. This review summarizes neutrophil granule formation and contents, the role granule cargo plays in neutrophil functional responses and neutrophil-mediated diseases, and the mechanisms of granule release that provide the rationale for development of our exocytosis inhibitors. We present evidence for the inhibition of granule exocytosis in vitro and in vivo by those inhibitors and summarize animal data indicating that inhibition of neutrophil exocytosis is a viable therapeutic strategy.

Neutrophil-Related Oxidants Drive Heart and Brain Remodeling After Ischemia/Reperfusion Injury

The inflammatory response associated with myocardial and brain ischemia/reperfusion injury (IRI) is a critical determinant of tissue necrosis, functional organ recovery, and long-term clinical outcomes. In the post-ischemic period, reactive oxygen species (ROS) are involved in tissue repair through the clearance of dead cells and cellular debris. Neutrophils play a critical role in redox signaling due to their early recruitment and the large variety of released ROS. Noteworthy, ROS generated during IRI have a relevant role in both myocardial healing and activation of neuroprotective pathways. Anatomical and functional differences contribute to the responses in the myocardial and brain tissue despite a significant gene overlap. The exaggerated activation of this signaling system can result in adverse consequences, such as cell apoptosis and extracellular matrix degradation. In light of that, blocking the ROS cascade might have a therapeutic implication for cardiomyocyte and neuronal loss after acute ischemic events. The translation of these findings from preclinical models to clinical trials has so far failed because of differences between humans and animals, difficulty of agents to penetrate into specific cellular organs, and specifically unravel oxidant and antioxidant pathways. Here, we update knowledge on ROS cascade in IRI, focusing on the role of neutrophils. We discuss evidence of ROS blockade as a therapeutic approach for myocardial infarction and ischemic stroke.

Calcium-Sensing Receptor on Neutrophil Promotes Myocardial Apoptosis and Fibrosis After Acute Myocardial Infarction via NLRP3 Inflammasome Activation

BACKGROUND

The infiltration of neutrophils aggravates inflammatory response in acute myocardial infarction (AMI), and the role of calcium-sensing receptor (CaSR) in neutrophil-associated inflammation is largely unknown. The aim of this study was to evaluate the regulatory effects of CaSR on nucleotide-binding oligomerization domain-like receptor pyrin domain-containing 3 (NLRP3) inflammasome in neutrophils and to explore its role in AMI-related ventricular remodelling.

METHODS

The expression of CaSR, NLRP3 inflammasome, and interleukin 1β (IL-1β) in peripheral blood and infiltrating neutrophils in patients and rats with AMI was detected by western blotting and immunofluorescence. Cardiomyocyte apoptosis was detected by western blotting and transmission electron microscopy. The degree of fibrosis was evaluated by Masson staining and western blotting.

RESULTS

We found upregulation of CaSR, NLRP3 inflammasome, Caspase-1, and IL-1β in peripheral neutrophils from patients with AMI compared with matched healthy controls, peaking on day 1 and decreasing gradually till 7 days. Peripheral and infiltrating neutrophils from rats with AMI showed the same trend. Calindol enhanced NLRP3 inflammasome activation and IL-1β release in neutrophils from healthy volunteers, which was blocked by inhibitors of the PLC-IP₃ pathway and ER-Ca²⁺ release. Calhex-231 decreased NLRP3 inflammasome activation and IL-1β release in neutrophils from patients with AMI. The calindol-stimulated neutrophils from healthy rats promoted cardiomyocyte apoptosis and fibrosis of cardiac fibroblasts from healthy rats, which were inhibited by calhex-231.

CONCLUSION

The results suggest that CaSR activates NLRP3 inflammasome in neutrophils, contributing to ventricular remodelling after AMI. CaSR inhibition may be a potential therapeutic target for heart failure in AMI.

Innovative Therapeutic Potential of Cannabinoid Receptors as Targets in Alzheimer’s Disease and Less Well-Known Diseases

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The discovery of cannabinoid receptors at the beginning of the 1990s, CB1 cloned in 1990 and CB2 cloned in 1993, and the availability of selective and potent cannabimimetics could only be justified by the existence of endogenous ligands that are capable of binding to them. Thus, the characterisation and cloning of the first cannabinoid receptor (CB1) led to the isolation and characterisation of the first endocannabinoid, arachidonoylethanolamide (AEA), two years later and the subsequent identification of a family of lipid transmitters known as the fatty acid ester 2-arachidonoylglycerol (2-AG).

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The endogenous cannabinoid system is a complex signalling system that comprises transmembrane endocannabinoid receptors, their endogenous ligands (the endocannabinoids), the specific uptake mechanisms and the enzymatic systems related to their biosynthesis and degradation.

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The endocannabinoid system has been implicated in a wide diversity of biological processes, in both the central and peripheral nervous systems, including memory, learning, neuronal development, stress and emotions, food intake, energy regulation, peripheral metabolism, and the regulation of hormonal balance through the endocrine system.

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In this context, this article will review the current knowledge of the therapeutic potential of cannabinoid receptor as a target in Alzheimer’s disease and other less well-known diseases that include, among others, multiple sclerosis, bone metabolism, and Fragile X syndrome.

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The therapeutic applications will be addressed through the study of cannabinoid agonists acting as single drugs and multi-target drugs highlighting the CB2 receptor agonist.

α-Tocopherol preserves cardiac function by reducing oxidative stress and inflammation in ischemia/reperfusion injury

OBJECTIVE

Myocardial infarction (MI) is a leading cause of mortality and morbidity worldwide and new treatment strategies are highly sought-after. Paradoxically, reperfusion of the ischemic myocardium, as achieved with early percutaneous intervention, results in substantial damage to the heart (ischemia/reperfusion injury) caused by cell death due to aggravated inflammatory and oxidative stress responses. Chronic therapy with vitamin E is not effective in reducing the cardiovascular event rate, presumably through failing to reduce atherosclerotic plaque instability. Notably, acute treatment with vitamin E in patients suffering a MI has not been systematically investigated.

METHODS AND RESULTS

We applied alpha-tocopherol (α-TOH), the strongest anti-oxidant form of vitamin E, in murine cardiac ischemia/reperfusion injury induced by ligation of the left anterior descending coronary artery for 60 min. α-TOH significantly reduced infarct size, restored cardiac function as measured by ejection fraction, fractional shortening, cardiac output, and stroke volume, and prevented pathological changes as assessed by state-of-the-art strain and strain-rate analysis. Cardioprotective mechanisms identified, include a decreased infiltration of neutrophils into cardiac tissue and a systemic anti-inflammatory shift from Ly6Chigh to Ly6Clow monocytes. Furthermore, we found a reduction in myeloperoxidase expression and activity, as well as a decrease in reactive oxygen species and the lipid peroxidation markers phosphatidylcholine (PC) (16:0)-9-hydroxyoctadecadienoic acid (HODE) and PC(16:0)-13-HODE) within the infarcted tissue.

CONCLUSION

Overall, α-TOH inhibits ischemia/reperfusion injury-induced oxidative and inflammatory responses, and ultimately preserves cardiac function. Therefore, our study provides a strong incentive to test vitamin E as an acute therapy in patients suffering a MI.

Inflammation in myocardial injury: mesenchymal stem cells as potential immunomodulators

Ischemic heart disease is a growing worldwide epidemic. Improvements in medical and surgical therapies have reduced early mortality after acute myocardial infarction and increased the number of patients living with chronic heart failure. The irreversible loss of functional cardiomyocytes puts these patients at significant risk of ongoing morbidity and mortality after their index event. Recent evidence suggests that inflammation is a key mediator of postinfarction adverse remodeling in the heart. In this review, we discuss the cardioprotective and deleterious effects of inflammation and its mediators during acute myocardial infarction. We also explore the role of mesenchymal stem cell therapy to limit secondary injury and promote myocardial healing after myocardial infarction.

Novel findings in neutrophil biology and their impact on cardiovascular disease

Neutrophils are the most abundant circulating leucocytes in healthy humans. These cells are central players during acute inflammatory responses, although a growing body of evidence supports a crucial role in chronic inflammation and chemokines and cytokines related to it as well. Thus, both humoral and cellular components are involved in the development of plaque formation and atherosclerosis. Accordingly, CANTOS trial using an interleukin-1 beta antibody confirmed that inflammatory cytokines contribute to the occurrence of myocardial infarction and cardiac death independent of changes in lipids. Recent data revealed that neutrophils are a heterogeneous population with different subsets and functional characteristics (i.e. CD177+ cells, OLFM4+ neutrophils, proangiogenic neutrophils, neutrophils undergoing reverse migration, and aged neutrophils). Importantly, neutrophils are able to synthesize de novo proteins. Neutrophil extracellular trap generation and NETosis have been considered as very important weapons in sterile inflammation. Neutrophil-derived microvesicles represent another mechanism by which neutrophils amplify inflammatory processes, being found at high levels both at the site of injury and in the bloodstream. Finally, neutrophil aging can influence their functions also in relation with host age. These recent acquisitions in the field of neutrophil biology might pave the way for new therapeutic targets to prevent or even treat patients experiencing cardiovascular (CV) diseases. Here, we discuss novel findings in neutrophil biology, their impact on CV and cerebrovascular diseases, and the potential implementation of these notions into daily clinical practice.

Effect of long-term remote ischemic conditioning on inflammation and cardiac remodeling

Background. Remote ischemic conditioning (RIC) protects against acute ischemia-reperfusion injury and may have beneficial effects in patients with stable cardiovascular disease. We investigated the effect of long-term RIC treatment in patients with chronic ischemic heart failure (CIHF). Methods. Prespecified post-hoc analysis of a prospective, exploratory and outcome-assessor blinded study. Twenty-one patients with compensated CIHF and 21 matched controls without heart failure or ischemic heart disease were treated with RIC once daily for 28 ± 4 days. RIC was conducted as 4 cycles of 5 minutes upper arm ischemia followed by 5 minutes of reperfusion. We evaluated circulating markers of inflammation and cardiac remodeling at baseline and following long-term RIC. Results. RIC reduced C-reactive protein from 1.5 (0.6-2.5) to 1.3 (0.6-2.1) mg/l following long-term RIC treatment (p = .02) and calprotectin from 477 (95% CI 380 to 600) to 434 (95% CI 354 to 533) ng/ml (p = .03) in patients with CIHF, but not in matched controls. Overall, RIC did not affect circulating markers related to adaptive or innate immunology or cardiac remodeling in patients with CIHF. Among patients with CIHF and N-terminal pro-brain natriuretic peptide (NT-proBNP) plasma levels above the geometric mean of 372 ng/l, long-term RIC treatment reduced soluble ST2 (n = 9) from 22.0 ± 3.7 to 20.3 ± 3.9 ng/ml following long-term RIC treatment (p = .01). Conclusion. Our findings suggest that long-term RIC treatment has mild anti-inflammatory effects in patients with compensated CIHF and anti-remodeling effects in those with increased NT-proBNP levels. This should be further investigated in a randomized sham-controlled trial.

Sodium tanshinone IIA sulfonate prevents the adverse left ventricular remodelling: Focus on polymorphonuclear neutrophil-derived granule components

AIMS

The aims of this study were to evaluate the effects of sodium tanshinone IIA sulfonate (STS) on left ventricular (LV) remodelling after for ST-elevated myocardial infarction (STEMI).

METHODS AND RESULTS

In this prospective, randomized clinical trial, 101 patients with the ST-elevated MI (STEMI) and a successful reperfusion were immediately randomized to receive STS (80 mg qd for 7 days) or saline control, along with standard therapy. The primary effectiveness endpoint is the % change in LV end diastolic volumes index (%∆ LVEDVi) as measured by echocardiography from baseline to 6 months. Secondary effectiveness endpoints include 6-month period for major adverse cardiac events (MACE), including the occurrence of recurrent myocardial infarction, death, hospitalization for heart failure and malignant arrhythmia. The 6-month changes in %∆ LVEDVi were significantly smaller in the STS group than in the control group [-5.05% vs 3.32%; P < 0.001]. With respect to MACE, there was a significant difference between those who received STS (8.16%) and those patients on control (26.00%) (P = 0.019). Meaningfully, results of parallel tests aimed at mechanistic explanation of the reported clinical effects, revealed a significantly reduced levels of neutrophils-derived granule components in the blood of STS treated patients.

CONCLUSION

We found that short-term treatment with STS reduced progressive left ventricular remodelling and subsequent better clinical outcome that could be mechanistically linked to the inhibition of the ultimate damage of infarcted myocardium by infiltrating neutrophils.

Neutrophil trafficking to lymphoid tissues: physiological and pathological implications

Recent advances have provided evidence for the involvement of neutrophils in both innate and adaptive immunity, robustly challenging the old dogma that neutrophils are short-lived prototypical innate immune cells solely involved in acute responses to microbes and exerting collateral tissue damage. There is now ample evidence showing that neutrophils can migrate into different compartments of the lymphoid system where they contribute to the orchestration of the activation and/or suppression of lymphocyte effector functions in homeostasis and during chronic inflammation, such as autoimmune disorders and cancer. In support of this notion, neutrophils can generate a wide range of cytokines and other mediators capable of regulating the survival, proliferation and functions of both T and B cells. In addition, neutrophils can directly engage with lymphocytes and promote antigen presentation. Furthermore, there is emerging evidence of the existence of distinct and diverse neutrophil phenotypes with immunomodulatory functions that characterise different pathological conditions, including chronic and autoimmune inflammatory conditions. The aim of this review is to discuss the mechanisms implicated in neutrophil trafficking into the lymphoid system and to provide an overview of the immuno-regulatory functions of neutrophils in health and disease in the context of adaptive immunity. Copyright © 2018 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of Pathological Society of Great Britain and Ireland.

Neutrophils in Post-myocardial Infarction Inflammation: Damage vs. Resolution?

Inflammation not only plays a crucial role in acute ischemic cardiac injury, but also contributes to post-infarction repair and remodeling. Traditionally, neutrophils have been merely considered as detrimental in the setting of an acute myocardial infarction. However, recently published studies demonstrated that neutrophils might also play an important role in cardiac repair by regulating reparative processes. An emerging concept is that different neutrophil subsets exist, which might exhibit separate functional properties. In support of the existence of distinct neutrophil subsets in the ischemic heart, transcriptional changes in cardiac neutrophils have been reported within the first few days after myocardial infarction. In addition, there is an increasing awareness of sex-specific differences in many physiological and pathophysiological responses, including cardiovascular parameters and inflammation. Of particular interest in this context are recent experimental data dissecting sex-specific differences in neutrophil signaling after myocardial infarction. Unraveling the distinct and possibly stage-dependent properties of neutrophils in cardiac repair may provide new therapeutic strategies in order to improve the clinical outcome for myocardial infarction patients. This review will briefly discuss recent advances in our understanding of the neutrophil functional repertoire and emerging insights of sex-specific differences in post-myocardial infarction inflammatory responses.

Cardiac phenotype in mouse models of systemic autoimmunity

Patients suffering from systemic autoimmune diseases are at significant risk of cardiovascular complications. This can be due to systemically increased levels of inflammation leading to accelerated atherosclerosis, or due to direct damage to the tissues and cells of the heart. Cardiac complications include an increased risk of myocardial infarction, myocarditis and dilated cardiomyopathy, valve disease, endothelial dysfunction, excessive fibrosis, and bona fide autoimmune-mediated tissue damage by autoantibodies or auto-reactive cells. There is, however, still a considerable need to better understand how to diagnose and treat cardiac complications in autoimmune patients. A range of inducible and spontaneous mouse models of systemic autoimmune diseases is available for mechanistic and therapeutic studies. For this Review, we systematically collated information on the cardiac phenotype in the most common inducible, spontaneous and engineered mouse models of systemic lupus erythematosus, rheumatoid arthritis and systemic sclerosis. We also highlight selected lesser-known models of interest to provide researchers with a decision framework to choose the most suitable model for their study of heart involvement in systemic autoimmunity.

The neutrophil-to-lymphocyte ratio is associated with mortality in the general population: The Rotterdam Study

Inflammation is a risk factor for morbidity and mortality in the elderly. The neutrophil-to-lymphocyte ratio (NLR) is a marker of systemic inflammation that integrates the information of the leukocyte differentials into one variable. We aimed to assess whether the NLR is a risk indicator for overall and cause-specific mortality in the general population. We analyzed data (2002–2014) from the Rotterdam Study, a long-standing, population-based, prospective cohort study in a community-dwelling ageing population. The association between the NLR and time to all-cause mortality was assessed with Cox proportional hazard models. We additionally assessed cardiovascular, cancer and other mortality. The multivariable analyses were adjusted for age, gender, socio-economic status (SES), smoking status, body mass index, type 2 diabetes, and history of cancer and cardiovascular disease (CVD). Data of 8715 individuals were included. The mean age was 65.9 years (SD 10.5) and the majority were women (57.1%). The NLR was higher in men, higher age categories, smokers and among individuals with lower SES, prevalent diabetes, or a history of cancer or CVD. During the 11.7 years follow-up period, 1641 individuals died. Survival among individuals in the 3rd, 4th, and 5th quintile of the NLR was significantly poorer than that of those in the 1st quintile (P < 0.001). In the multivariable analysis, NLR levels were independently and significantly associated with an increased risk of all-cause mortality (HR 1.64; 95% CI 1.44–1.86), cardiovascular mortality (HR 1.92; 95% CI 1.49–2.48), and other mortality (HR 1.86; 95% CI 1.54–2.24). No significant association was found for cancer mortality (HR 1.20; 95% CI 0.95–1.51). The NLR is a strong and independent risk indicator for mortality in the elderly population. Its clinical value needs to be established in further studies.

Post-cardiac injury syndrome in acute myocardial infarction patients undergoing PCI: a case report and literature review

Background

In the era of primary percutaneous coronary intervention (PPCI), the incidence of post-cardiac injury syndrome (PCIS) in patients with acute myocardial infarction (AMI) following PPCI has become less common. However, the intrinsic pathogenesis of this medical condition remains largely uncertain. Unlike the prior reports, the present paper provides new mechanistic clues concerning the pathogenesis of PCI-related PCIS.

Case presentation

A 45-year-old male with AMI had developed an early onset of PCIS at 3 h after PPCI. A significantly slower TIMI flow (grade ≤ 2) for the culprit arteries was observed through follow-up coronary angiography (CAG); no stent thrombosis or any significant evidence of iatrogenic trauma due the intervention procedures was found. Nevertheless, the the serum level of HsCRP showed similar variation trend as the neutrophil count and troponin T in continuous blood monitoring, which suggested a potential association between PPCI-related coronary microvascular dysfunction (CMD) and pathogenesis of PCIS.

Conclusions

The reported case had excessive inflammatory reaction and CMD resulting from cardiac ischemia-reperfusion injury in an AMI patient with risk factors of endothelial dysfunction. There exists a potential reciprocal causation between PCIS and performance of PPCI in the AMI patient who was susceptible to endothelial damage.

Reduction in TIMP-2 serum levels predicts remission of inflammatory bowel diseases

BACKGROUND

Growing evidence indicates tissue inhibitors of matrix metalloproteinases (TIMPs) as potential players in inflammatory bowel disease (IBD), but, no prospective data are available in IBD remission/relapse.

MATERIAL & METHODS

In this prospective pilot study, a cohort of IBD patients (n = 32) was enrolled and treated with monoclonal anti-TNF-α antibodies. Patients were clinically followed up for a median period of 54 weeks. Serum circulating levels of C-reactive protein (CRP), TIMP-1 and -2, matrix metalloproteinase (MMP)-9 and -8, myeloperoxidase (MPO) and neutrophil elastase (NE) were assessed by ELISA at enrolment and at the end of the treatment.

RESULTS

The percentage (%) TIMP-2 reduction from baseline to end of treatment was independently associated with IBD remission at the end of treatment and follow-up as well. ROC curve analysis further confirmed the good prognostic accuracy of % TIMP-2 reduction over the treatment period. Conversely, no other change in inflammatory molecule concentrations was able to predict short- or long-term IBD remission.

CONCLUSIONS

This study indicates TIMP-2 reduction during IBD treatment with monoclonal anti-TNF-α antibodies as a potential prognostic parameter of short and long term remission. To understand if TIMP-2 is an innocent biomarker or an active pathophysiological factor in IBD remains to be clarified.

Azithromycin therapy reduces cardiac inflammation and mitigates adverse cardiac remodeling after myocardial infarction: Potential therapeutic targets in ischemic heart disease

INTRODUCTION

Acute myocardial infarction (MI) is a primary cause of worldwide morbidity and mortality. Macrophages are fundamental components of post-MI inflammation. Pro-inflammatory macrophages can lead to adverse cardiac remodeling and heart failure while anti-inflammatory/reparative macrophages enhance tissue healing. Shifting the balance between pro-inflammatory and reparative macrophages post-MI is a novel therapeutic strategy. Azithromycin (AZM), a commonly used macrolide antibiotic, polarizes macrophages towards the anti-inflammatory phenotype, as shown in animal and human studies. We hypothesized that AZM modulates post-MI inflammation and improves cardiac recovery.

METHODS AND RESULTS

Male WT mice (C57BL/6, 6-8 weeks old) were treated with either oral AZM (160 mg/kg/day) or vehicle (control) starting 3 days prior to MI and continued to day 7 post-MI. We observed a significant reduction in mortality with AZM therapy. AZM-treated mice showed a significant decrease in pro-inflammatory (CD45+/Ly6G-/F4-80+/CD86+) and increase in anti-inflammatory (CD45+/Ly6G-/F4-80+/CD206+) macrophages, decreasing the pro-inflammatory/anti-inflammatory macrophage ratio in the heart and peripheral blood as assessed by flow cytometry and immunohistochemistry. Macrophage changes were associated with a significant decline in pro- and increase in anti-inflammatory cytokines. Mechanistic studies confirmed the ability of AZM to shift macrophage response towards an anti-inflammatory state under hypoxia/reperfusion stress. Additionally, AZM treatment was associated with a distinct decrease in neutrophil count due to apoptosis, a known signal for shifting macrophages towards the anti-inflammatory phenotype. Finally, AZM treatment improved cardiac recovery, scar size, and angiogenesis.

CONCLUSION

Azithromycin plays a cardioprotective role in the early phase post-MI through attenuating inflammation and enhancing cardiac recovery. Post-MI treatment and human translational studies are warranted to examine the therapeutic applications of AZM.

Oxidative cross-linking of proteins to DNA following ischemia-reperfusion injury

Myocardial infarction (MI) is a life-threatening condition that can occur when blood flow to the heart is interrupted due to a blockage in one or more of the coronary vessels. Current treatments of MI rapidly restore blood flow to the affected myocardium using thrombolytic agents or angioplasty. Adverse effects including inflammation, tissue necrosis, and ventricular dysfunction are, however, not uncommon following reperfusion therapy. These conditions are thought to be caused by a sudden influx of reactive oxygen species (ROS) to the affected myocardium. We employed the model of left anterior descending artery ligation/reperfusion surgery in a rat model to show that ischemia/reperfusion injury is associated with the formation of toxic DNA-protein cross-links (DPCs) in cardiomyocytes. Mass spectrometry based experiments have revealed that these conjugates were formed by a free radical mechanism and involved thymidine residues of DNA and tyrosine side chains of proteins (dT-Tyr). Quantitative proteomics experiments have identified nearly 90 proteins participating in hydroxyl radical-induced DPC formation, including ROS scavengers, contractile proteins, and regulators of apoptosis. Global proteome changes were less pronounced and included increased expression of mitochondrial proteins required for aerobic respiration and biomarkers of sarcomere breakdown following ischemia/reperfusion injury. Overall, our results are consistent with a model where sudden return of oxygen to ischemic tissues induces oxidative stress, inflammation, and the formation of DNA-protein cross-links that may contribute to reperfusion injury by desregulating gene expression and inducing cardiomyocyte death.

Region of Interest analysis using mass spectrometry imaging of mitochondrial and sarcomeric proteins in acute cardiac infarction tissue

Matrix-assisted laser desorption ionization image mass spectrometry (MALDI-IMS) has been developed for the identification of peptides in various tissues. The MALDI-IMS signal distribution patterns and quantification of the signal intensities of the regions of interest (ROI) with healthy regions were compared for identification of the disease specific biomarkers. We performed a new ROI analysis using the conventional t-test and data number independent Cohen’s d-value analysis. Using these techniques, we analysed heart tissues after acute myocardial infarction (AMI). As a result, IMS signals of mitochondrial adenosine triphosphate synthase alpha subunit (ATP5A), myosin-6/7(MYH6/7), aortic actin, and the myosin light chain 3 (MYL3) were identified in the infarcted region. In particular, the signals of MYH7 are significantly greater in the infarcted region using ROI analysis. ROI analysis using MALDI-IMS may be a promising technique for the identification of biomarkers for pathological studies that involve the comparison of diseased and control areas.

The impact of myeloperoxidase on HDL function in myocardial infarction

PURPOSE OF REVIEW

The focus in cardiovascular research is shifting from determining mass HDL cholesterol levels toward investigating HDL functionalities as biomarker for cardiovascular disease. Myeloperoxidase (MPO), a main effector enzyme of the innate immune system, is increasingly implicated to negatively impact HDL function by various chemical modifications of HDL-associated proteins. This review summarizes recent insights how MPO affects HDL function in the setting of acute myocardial infarction (MI), mainly focusing on human data.

RECENT FINDINGS

First the mechanisms how MPO renders HDL particles dysfunctional and the usefulness of MPO as prospective biomarker for MI incidence and outcomes are described. Then the evidence for MPO causing specific HDL function impairments in MI and the clinical value of these observations is discussed in the context of the different HDL function assays employed.

SUMMARY

MPO modification of HDL in acute MI generates dysfunctional HDL. Features of HDL dysfunction can be used to stratify MI patients and seem associated with outcomes. More prospective studies are warranted to explore, if MPO-modified HDL is causally linked to severity and outcomes of MI. If this could be established, MPO would represent an attractive target to improve HDL dysfunction in MI and provide clinical benefit for patients.

Regulatory T-Cells: Potential Regulator of Tissue Repair and Regeneration

The identification of stem cells and growth factors as well as the development of biomaterials hold great promise for regenerative medicine applications. However, the therapeutic efficacy of regenerative therapies can be greatly influenced by the host immune system, which plays a pivotal role during tissue repair and regeneration. Therefore, understanding how the immune system modulates tissue healing is critical to design efficient regenerative strategies. While the innate immune system is well known to be involved in the tissue healing process, the adaptive immune system has recently emerged as a key player. T-cells, in particular, regulatory T-cells (Treg), have been shown to promote repair and regeneration of various organ systems. In this review, we discuss the mechanisms by which Treg participate in the repair and regeneration of skeletal and heart muscle, skin, lung, bone, and the central nervous system.

Dunye Guanxinning Improves Acute Myocardial Ischemia-Reperfusion Injury by Inhibiting Neutrophil Infiltration and Caspase-1 Activity

Acute myocardial infarction is the most serious manifestation of cardiovascular disease, and it is a life-threatening condition. Dunye Guanxinning (DG) is a protective traditional Chinese patent herbal medicine with high clinical efficacy and suitable for the treatment of myocardial infarction. However, the mechanism through which it is beneficial is unclear. In this study, we hypothesized that DG improves acute myocardial ischemia-reperfusion injury by inhibiting neutrophil infiltration and caspase-1 activity. We found that DG administration decreased infarct size and cardiomyocyte apoptosis and improved left ventricular ejection fraction, fractional shortening, end-systolic volume index, end-systolic diameter, and carotid arterial blood flow output in rats. DG administration also improved hemorheological parameters, myocardial damage biomarkers, and oxidative stress indexes. The findings showed that DG administration inhibited neutrophil infiltration and reduced the serum interleukin-1 beta (IL-1β) level and myocardial IL-1β maturation. Moreover, DG administration inhibited caspase-1 activity and activated adenosine monophosphate-activated protein kinase (AMPK) phosphorylation in rat hearts. These results suggested that DG administration inhibits inflammasome activity and IL-1β release through the AMPK pathway. Our findings support the clinical efficacy of DG and partially reveal its mechanism, which is beneficial for understanding the therapeutic effects of this protective traditional Chinese patent drug.

Functional Relevance of Macrophage-mediated Inflammation to Cardiac Regeneration

Cardiovascular disease remains the leading cause of death worldwide and regenerative medicine is a promising therapeutic option for this disease. We have developed various techniques to attenuate the cardiac remodeling and to regenerate cardiovascular systems via stem cell application. Besides cell therapy, we are interested in the modulation of pathological inflammation mediated by macrophages in the damaged heart tissue to arouse endogenous reparative responses with biocompatible small molecules. Certainly, current understanding of mechanisms of tissue regeneration will lead to the development of innovative regenerative medicine for cardiovascular disease.

Peri-interventional endothelin-A receptor blockade improves long-term outcome in patients with ST-elevation acute myocardial infarction

Endothelin (ET)-1 is a pro-fibrotic vasoconstrictive peptide causing microvascular dysfunction and cardiac remodelling after acute ST-elevation myocardial infarction (STEMI). It acts via two distinct receptors, ET-A and ET-B, and is involved in inflammation and atherogenesis. Patients with posterior-wall STEMI were randomly assigned to intravenous BQ-123 at 400 nmol/minute (min) or placebo over 60 min, starting immediately prior to primary percutaneous coronary intervention (n=54). Peripheral blood samples were drawn at baseline as well as after 24 hours and 30 days. Myeloperoxidase (MPO), as a marker of neutrophil activation and matrix metalloproteinase 9 (MMP-9), a marker of extracellular matrix degradation were measured in plasma. Clinical follow-up was conducted by an investigator blinded to treatment allocation over three years. During the median follow-up period of 3.6 years (interquartile range [IQR] 3.3–4.1) we observed a longer event-free survival in patients randomised to receive BQ-123 compared with patients randomised to placebo (mean 4.5 years (95% confidence interval: 3.9–5) versus mean 3 years (2.2–3.7), p=0.031). Patients randomised to ET-A receptor blockade demonstrated a greater reduction of MPO levels from baseline to 24 hours compared to placebo-treated patients (-177 ng/ml (IQR 103–274) vs –108 ng/ml (74–147), p=0.006). In addition, a pronounced drop in MMP-9 levels (-568 ng/ml (44–1157) vs –117 ng/ml (57–561), p=0.018) was observed. There was no significant difference in amino-terminal propetide of pro-collagen type III levels. In conclusion, short-term administration of BQ-123 leads to a reduction in MPO, as well as MMP-9 plasma levels and to a longer event-free survival in patients with STEMI.

ClinicalTrials.gov Identifier: NCT00502528

Pro-oxidant HDL predicts poor outcome in patients with ST-elevation acute coronary syndrome

Oxidative stress affects clinical outcome in patients with ST-elevation acute coronary syndrome (STE-ACS). Although high-density lipoprotein (HDL) particles are generally considered protective, deleterious properties of HDL have been observed in patients with acute myocardial infarction. Here, we analysed the association between pro oxidant HDL and all-cause mortality in STE-ACS patients. We determined the antioxidant function of HDL in 247 prospectively enrolled patients undergoing primary percutaneous coronary intervention for STE-ACS. Patients were stratified as by a pro-oxidant serum HDL oxidant index (HOI 1) or with an antioxidant serum HOI (HOL< 1) capacity. Multivariate regression analysis was used to relate HOI to survival. The median follow-up time was 23 months (IQR 14.4–40.0 months). Pro-oxidant HDL was observed in 44.1 % of STE-ACS patients and was independently associated with all-cause mortality with a hazard ratio of 3.30(95 %CI 1.50–7.27, p = 0.003). Mortality rates were higher in patients with baseline pro-oxidant HDL compared to patients with preserved HDL function at 30 days (11.9 % vs 2.2 %, p=0.002), and at 4 years (22.9 % vs 8.7 %, p=0.002). Elevated neutrophil counts were a strong and independent predictor for pro-oxidant HDL with an odds ratio per standard deviation of 1.50 (95 %CI 1.11–2.03, p=0.008), as was history of prior acute myocardial infarction, elevated triglycerides levels and reduced glomerular filtration rate. In conclusion, pro-oxidant HDL represents a strong and independent predictor of long-term as well as short-term all-cause mortality in STE-ACS patients. Elevated neutrophil counts predicted the presence of serum pro-oxidant HDL. The maintenance of HDL functions might be a promising therapeutic target in STE-ACS patients.

Inactivated Lactobacillus promotes protection against myocardial ischemia-reperfusion injury through NF-κB pathway

Although restoration of blood flow to an ischemic organ is essential to prevent irreversible cellular injury, reperfusion may augment tissue injury in excess of that produced by ischemia alone. So this experiment was designed to study the protective effects and mechanism of inactivated Lactobacillus (Lac) on myocardial ischemia–reperfusion (I–R) injury (MIRI). MIRI rat models were established by ligation of left anterior descending coronary artery for ~30 min and then, reperfusion for 120 min and divided into control group, model group, and Lac (10⁶, 10⁷, and 10⁸ cfu/kg) groups. At the end of the test, the creatine kinase (CK) activity, lactate dehydrogenase (LDH) activity, superoxide dismutase (SOD) activity and malondialdehyde (MDA) content were assayed by corresponding kits. The heart was obtained from rats and the myocardial infarction area was determined by TTC staining and myocardial endothelial cell apoptosis rate was determined by Tunel kit. Besides, A20, IκB, nuclear factor (NF)-κB, and nitric oxide (NO) synthase (NOS) were also assayed by Western blot. When compared with model group, Lac obviously reduces MIRI in the rat by reducing myocardial infarction area and the apoptosis rate of endothelial cells; reduce the serum CK, LDH, and MDA content; increase the serum SOD activity; and suppress NF-κB signaling and NOS expression in the myocardial tissues. Lac pretreatment can inhibit lipid peroxidation and effectively improve MIRI caused by oxygen free radical through inhibiting NF-κB signaling.

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.

Expression and Role of the Calcium-Sensing Receptor in Rat Peripheral Blood Polymorphonuclear Neutrophils

The calcium-sensing receptors (CaSRs) play an important role in many tissues and organs that are involved in inflammatory reactions. Peripheral blood polymorphonuclear neutrophils (PMNs) are important inflammatory cells. However, the expression and functions of CaSR in peripheral blood PMNs are still not reported. In this study, we collected rat peripheral blood PMNs to observe the relationship between CaSR and PMNs. From the results, we found first that the CaSR protein was expressed in PMNs, and it increased after PMNs were activated with fMLP. In addition, CaSR activator cincalcet promoted the expression of CaSR and P-p65 (NF-κB signaling pathway protein) and Bcl-xl (antiapoptosis protein), and it increased the secretion of interleukin-6 (IL-6) and myeloperoxidase (MPO); meanwhile, it decreased proapoptosis protein Bax expression and the production of IL-10 and reactive oxygen species (ROS). At the same time, cincalcet also decreased the PMN apoptosis rate analyzed by flow cytometry. However, CaSR inhibitor NPS-2143 and NF-κB signaling pathway inhibitor PDTC reverse the results cited earlier. All of these results indicated that CaSR can regulate PMN functions and status to play a role in inflammation, which is probably through the NF-κB signaling pathway.

Aspirin-Triggered Resolvin D1-modified materials promote the accumulation of pro-regenerative immune cell subsets and enhance vascular remodeling

Many goals in tissue engineering rely on modulating cellular localization and polarization of cell signaling, including the inhibition of inflammatory infiltrate, facilitation of inflammatory cell egress, and clearance of apoptotic cells. Omega-3 polyunsaturated fatty acid-derived resolvins are gaining increasing recognition for their essential roles in inhibition of neutrophil invasion into inflamed tissue and promotion of macrophage phagocytosis of cellular debris as well as their egress to the lymphatics. Biomaterial-based release of lipid mediators is a largely under-explored approach that provides a method to manipulate local lipid signaling gradients in vivo and direct the recruitment and/or polarization of anti-inflammatory cell subsets to suppress inflammatory signaling and enhance angiogenesis and tissue regeneration. The goal of this study was to encapsulate Aspirin-Triggered Resolvin D1 (AT-RvD1) into a degradable biomaterial in order to elucidate the effects of sustained, localized delivery in a model of sterile inflammation. Flow cytometric and imaging analysis at both 1 and 3days after injury showed that localized AT-RvD1 delivery was able significantly increase the accumulation of anti-inflammatory monocytes and M2 macrophages while limiting the infiltration of neutrophils. Additionally, cytokine profiling and longitudinal vascular analysis revealed a shift towards a pro-angiogenic profile with increased concentrations of VEGF and SDF-1α, and increased arteriolar diameter and tortuosity. These results demonstrate the ability of locally-delivered AT-RvD1 to increase pro-regenerative immune subpopulations and promote vascular remodeling.

STATEMENT OF SIGNIFICANCE

This work is motivated by our efforts to explore the underlying mechanisms of inflammation resolution after injury and to develop biomaterial-based approaches to amplify endogenous mechanisms of resolution and repair. Though specific lipid mediators have been identified that actively promote the resolution of inflammation, biomaterial-based localized delivery of these mediators has been largely unexplored. We loaded Aspirin-Triggered Resolvin D1 into a PLGA scaffold and examined the effects of sustained, localized delivery on the innate immune response. We found that biomaterial delivery of resolvin was able to enhance the accumulation of pro-regenerative populations of immune cells, including anti-inflammatory monocytes, population that has never before been shown to respond to resolvin treatment, and also enhance vascular remodeling in response to tissue injury.

Interaction of 12/15-lipoxygenase with fatty acids alters the leukocyte kinetics leading to improved postmyocardial infarction healing

The metabolic transformation of fatty acids to form oxylipids using 12/15-lipoxygenase (LOX) can promote either resolving or nonresolving inflammation. However, the mechanism of how 12/15-LOX interacts with polyunsaturated fatty acids (PUFA) in postmyocardial infarction (post-MI) healing is unclear. Here, we reported the role of 12/15-LOX in post-MI cardiac remodeling in a PUFA [10% (wt/wt), 22 kcal]-enriched environment. Wild-type (WT; C57BL/6J) and 12/15-LOX-null (12/15-LOX^-/-) male mice of 8-12 wk of age were fed a PUFA-enriched diet for 1 mo and subjected to permanent coronary artery ligation. Post-MI mice were monitored for day 1 or until day 5 along with standard diet-fed MI controls. No-MI surgery mice served as naïve controls. PUFA-fed WT and 12/15-LOX^-/- mice improved ejection fraction and reduced lung edema greater than WT mice at day 5 post-MI (P < 0.05). Post-MI, neutrophil density was decreased in PUFA-fed WT and 12/15-LOX^-/- mice at day 1 (P < 0.05). Deletion of 12/15-LOX in mice led to increased cytochrome P-450-derived bioactive lipid mediator epoxyeicosatrienoic acids (EETs), i.e., 11,12-EpETrE and 14,15-EpETrE, which were further enhanced by acute PUFA intake post-MI. Macrophage density was decreased in WT + PUFA and 12/15-LOX^-/- mice compared with their respective standard diet-fed WT controls at day 5 post-MI. 12/15-LOX^-/- + PUFA mice displayed an increased expression of chemokine (C-C motif) ligand 2 and reparative macrophages markers (Ym-1, Mrc-1, and Arg-1, all P < 0.05) in the infarcted area. Furthermore, 12/15-LOX^-/- mice, with or without PUFA, showed reduced collagen deposition at day 5 post-MI compared with WT mice. In conclusion, deletion of 12/15-LOX and short-term exposure of PUFA promoted leukocyte clearance, thereby limiting cardiac remodeling and promoting an effective resolution of inflammation.NEW & NOTEWORTHY This study determined that 1) deletion of 12/15-lipoxygenase (LOX) promotes the generation of epoxyeicosatrienoic acids, the cytochrome P-450-derived metabolites in postmyocardial infarction (post-MI) healing; 2) acute exposure of fatty acids to 12/15-LOX^-/- mice drives leukocyte (neutrophils and macrophages) clearance post-MI; and 3) metabolic transformation of fats is the significant contributor in leukocyte clearance to drive either resolving or nonresolving inflammation post-MI.