Annexin 1 peptides protect against experimental myocardial ischemia-reperfusion: analysis of their mechanism of action

Human monocyte subtype expression of neuroinflammation and regeneration-related genes is linked to age and sex

Stroke is a leading cause of disability and the third cause of death. The immune system plays an essential role in post-stroke recovery. After an ischemic stroke, monocytes infiltrate the injured brain tissue and can exacerbate or mitigate the damage. Ischemic stroke is more prevalent in the aged population, and the aging brain exhibits an altered immune response. There are also sex disparities in ischemic stroke incidence, outcomes, and recovery, and these differences may be hormone-driven and determined by genetic and epigenetic factors. Here, we studied whether human peripheral blood monocyte subtype (classical, intermediate, and non-classical) expression of neuronal inflammation- and regeneration-related genes depends on age and sex. A FACS analysis of blood samples from 44 volunteers (male and female, aged 28 to 98) showed that in contrast to other immune cells, the proportion of natural killer cells increased in females. The proportion of B-cells decreased in both sexes with age, and subtypes of monocytes were not linked to age or sex. Gene expression analysis by qPCR identified several genes differentially correlating with age and sex within different monocyte subtypes. Interestingly, ANXA1 and CD36 showed a consistent increase with aging in all monocytes, specifically in intermediate (CD36) and intermediate and non-classical (ANXA1) subtypes. Other genes (IL-1β, S100A8, TNFα, CD64, CD33, TGFβ1, TLR8, CD91) were differentially changed in monocyte subtypes with increased aging. Most age-dependent gene changes were differentially expressed in female monocytes. Our data shed light on the nuanced interplay of age and sex in shaping the expression of inflammation- and regeneration-related genes within distinct monocyte subtypes. Understanding these dynamics could pave the way for targeted interventions and personalized approaches in post-stroke care, particularly for the aging population and individuals of different sexes.

Inflammation Resolution in the Cardiovascular System: Arterial Hypertension, Atherosclerosis, and Ischemic Heart Disease

Significance: Chronic inflammation has emerged as a major underlying cause of many prevalent conditions in the Western world, including cardiovascular diseases. Although targeting inflammation has emerged as a promising avenue by which to treat cardiovascular disease, it is also associated with increased risk of infection. Recent Advances: Though previously assumed to be passive, resolution has now been identified as an active process, mediated by unique immunoresolving mediators and mechanisms designed to terminate acute inflammation and promote tissue repair. Recent work has determined that failures of resolution contribute to chronic inflammation and the progression of human disease. Specifically, failure to produce pro-resolving mediators and the impaired clearance of dead cells from inflamed tissue have been identified as major mechanisms by which resolution fails in disease. Critical Issues: Drawing from a rapidly expanding body of experimental and clinical studies, we review here what is known about the role of inflammation resolution in arterial hypertension, atherosclerosis, myocardial infarction, and ischemic heart disease. For each, we discuss the involvement of specialized pro-resolving mediators and pro-reparative cell types, including T regulatory cells, myeloid-derived suppressor cells, and macrophages. Future Directions: Pro-resolving therapies offer the promise of limiting chronic inflammation without impairing host defense. Therefore, it is imperative to better understand the mechanisms underlying resolution to identify therapeutic targets. Antioxid. Redox Signal. 40, 292-316.

The Annexin-A1 mimetic RTP-026 promotes acute cardioprotection through modulation of immune cell activation

AIMS

The cardio-protective and immuno-regulatory properties of RTP-026, a synthetic peptide that spans the Annexin-A1 (AnxA1) N-terminal region, were tested in rat acute myocardial infarction.

METHODS AND RESULTS

In vitro, selective activation of formyl-peptide receptor type 2 (FPR2) by RTP-026 occurred with apparent EC50 in the 10-30 nM range. With human primary cells, RTP-026 counteracted extension of neutrophil life-span and augmented phagocytosis of fluorescent E.coli by blood myeloid cells. An in vivo model of rat acute infarction was used to quantify tissue injury and phenotype immune cells in myocardium and blood. The rat left anterior descending coronary artery was occluded and then reopened for 2-hour or 24-hour reperfusion. For the 2-hour reperfusion protocol, RTP-026 (25-500 µg/kg; given i.v. at the start of reperfusion) significantly reduced infarct size by ∼50 %, with maximal efficacy at 50 µg/kg. Analyses of cardiac immune cells showed that RTP-026 reduced neutrophil and classical monocyte recruitment to the damaged heart. In the blood, RTP-026 (50 µg/kg) attenuated activation of neutrophils and monocytes monitored through CD62L and CD54 expression. Modulation of vascular inflammation by RTP-026 was demonstrated by reduction in plasma levels of mediators like TNF-α, IL-1β, KC, PGE2 and PGF2α⊡ For the 24-hour reperfusion protocol, RTP-026 (30 µg/kg given i.v. at 0, 3 and 6 h reperfusion) reduced necrotic myocardium by ∼40 %.

CONCLUSIONS

RTP-026 modulate immune cell responses and decreases infarct size of the heart in preclinical settings. Tempering over-exuberant immune cell activation by RTP-026 is a suitable approach to translate the biology of AnxA1 for therapeutic purposes.

Formyl Peptide Receptor Type 2 Deficiency in Myeloid Cells Amplifies Sepsis-Induced Cardiac Dysfunction

Using a global formyl peptide receptor (Fpr) 2 knockout mouse colony, we have reported the modulatory properties of this pro-resolving receptor in polymicrobial sepsis. Herein, we have used a humanized FPR2 (hFPR2) mouse colony, bearing an intact or a selective receptor deficiency in myeloid cells to dwell on the cellular mechanisms. hFPR2 mice and myeloid cell-specific hFPR2 KO (KO) mice were subjected to cecal ligation and puncture (CLP)-induced polymicrobial sepsis. Compared with hFPR2 mice, CLP caused exacerbated cardiac dysfunction (assessed by echocardiography), worsened clinical outcome, and impaired bacterial clearance in KO mice. This pathological scenario was paralleled by increased recruitment of pro-inflammatory monocytes and reduced M2-like macrophages within the KO hearts. In peritoneal exudates of KO mice, we quantified increased neutrophil and MHC II+ macrophage numbers but decreased monocyte/macrophage and MHC II- macrophage recruitment. hFPR2 upregulation was absent in myeloid cells, and local production of lipoxin A4 was reduced in septic KO mice. Administration of the FPR2 agonist annexin A1 (AnxA1) improved cardiac function in hFPR2 septic mice but had limited beneficial effects in KO mice, in which the FPR2 ligand failed to polarize macrophages toward an MHC II- phenotype. In conclusion, FPR2 deficiency in myeloid cells exacerbates cardiac dysfunction and worsens clinical outcome in polymicrobial sepsis. The improvement of cardiac function and the host immune response by AnxA1 is more effective in hFPR2-competent septic mice.

The role of annexin A1 peptide in regulating PI3K/Akt signaling pathway to reduce lung injury after cardiopulmonary bypass in rats

INTRODUCTION

Cardiopulmonary bypass (CPB) -induced lung ischemia-reperfusion (I/R) injury remains a large challenge in cardiac surgery; up to date, no effective treatment has been found. Annexin A1 (AnxA1) has an anti-inflammatory effect, and it has been proven to have a protective effect on CPB-induced lung injury. However, the specific mechanism of AnxA1 in CPB-induced lung injury is not well studied. Therefore, we established a CPB-induced lung injury model to explore the relevant mechanism of AnxA1 and try to find an effective treatment for lung protection.

METHODS

Male rats were randomized into five groups (n = 6, each): sham (S group), I/R exposure (I/R group), I/R + dimethyl sulfoxide (D group), I/R + Ac2-26 (AnxA1 peptide) (A group), and I/R + LY294002 (a PI3K specific inhibitor) (AL group). Arterial blood gas analysis and calculation of the oxygenation index, and respiratory index were performed. The morphological changes in lung tissues were observed under light and electron microscopes. TNF-α and IL-6 and total protein in lung bronchoalveolar lavage fluid were detected via enzyme-linked immunosorbent assay. The expressions of PI3K, Akt, and NF-κB (p65) as well as p-PI3K, p-Akt, p-NF-κB (p65), and AnxA1 were detected via western blotting.

RESULTS

Compared with the I/R group, the A group showed the following: lower lung pathological damage score; decreased expression of IL-6 and total protein in the bronchoalveolar lavage fluid, and TNF-α in the lung; increased lung oxygenation index; and improved lung function. These imply the protective role of Ac2-26, and show that LY294002 inhibited the ameliorative preconditioning effect of Ac2-26.

CONCLUSION

This finding suggested that the AnxA1 peptide Ac2-26 decreased the inflammation reaction and CPB-induced lung injury in rats, the lung protective effects of AnxA1may be correlated with the activation of PI3K/Akt signaling pathway.

Annexins and cardiovascular diseases: Beyond membrane trafficking and repair

Cardiovascular diseases (CVD) remain the leading cause of mortality worldwide. The main cause underlying CVD is associated with the pathological remodeling of the vascular wall, involving several cell types, including endothelial cells, vascular smooth muscle cells, and leukocytes. Vascular remodeling is often related with the development of atherosclerotic plaques leading to narrowing of the arteries and reduced blood flow. Atherosclerosis is known to be triggered by high blood cholesterol levels, which in the presence of a dysfunctional endothelium, results in the retention of lipoproteins in the artery wall, leading to an immune-inflammatory response. Continued hypercholesterolemia and inflammation aggravate the progression of atherosclerotic plaque over time, which is often complicated by thrombus development, leading to the possibility of CV events such as myocardial infarction or stroke. Annexins are a family of proteins with high structural homology that bind phospholipids in a calcium-dependent manner. These proteins are involved in several biological functions, from cell structural organization to growth regulation and vesicle trafficking. In vitro gain- or loss-of-function experiments have demonstrated the implication of annexins with a wide variety of cellular processes independent of calcium signaling such as immune-inflammatory response, cell proliferation, migration, differentiation, apoptosis, and membrane repair. In the last years, the use of mice deficient for different annexins has provided insight into additional functions of these proteins in vivo, and their involvement in different pathologies. This review will focus in the role of annexins in CVD, highlighting the mechanisms involved and the potential therapeutic effects of these proteins.

Evidence of an Annexin A4 mediated plasma membrane repair response to biomechanical strain associated with glaucoma pathogenesis

Glaucoma is a common neurodegenerative blinding disease that is closely associated with chronic biomechanical strain at the optic nerve head (ONH). Yet, the cellular injury and mechanosensing mechanisms underlying the resulting damage have remained critically unclear. We previously identified Annexin A4 (ANXA4) from a proteomic analyses of human ONH astrocytes undergoing pathological biomechanical strain that mimics glaucomatous conditions. Annexins are a family of calcium-dependent phospholipid binding proteins with key functions in plasma membrane repair (PMR); an active mechanism to limit and mend cellular injury that involves membrane and cytoskeletal reorganizations. However, a role for direct membrane damage and PMR has not been well studied in the context of biomechanical strain, such as that associated with glaucoma. Here we report that this moderate strain surprisingly damages cell membranes to increase permeability in a calcium-dependent manner, and induces rapid aggregation of ANXA4 at injury sites. ANXA4 loss-of-function increases permeability, while exogenous ANXA4 reduces it. Furthermore, ANXA4 aggregation is associated with F-actin dynamics in vitro, and remarkably this interaction and aggregation signature is also observed in the glaucomatous ONH in patient samples. Together these studies link moderate biomechanical strain with direct membrane damage and actin dynamics, and identify an active PMR role for ANXA4 in new model of cell injury associated with glaucoma pathogenesis.

Therapeutic Peptides to Treat Myocardial Ischemia-Reperfusion Injury

Cardiovascular diseases (CVD) including acute myocardial infarction (AMI) rank first in worldwide mortality and according to the World Health Organization (WHO), they will stay at this rank until 2030. Prompt revascularization of the occluded artery to reperfuse the myocardium is the only recommended treatment (by angioplasty or thrombolysis) to decrease infarct size (IS). However, despite beneficial effects on ischemic lesions, reperfusion leads to ischemia-reperfusion (IR) injury related mainly to apoptosis. Improvement of revascularization techniques and patient care has decreased myocardial infarction (MI) mortality however heart failure (HF) morbidity is increasing, contributing to the cost-intense worldwide HF epidemic. Currently, there is no treatment for reperfusion injury despite promising results in animal models. There is now an obvious need to develop new cardioprotective strategies to decrease morbidity/mortality of CVD, which is increasing due to the aging of the population and the rising prevalence rates of diabetes and obesity. In this review, we will summarize the different therapeutic peptides developed or used focused on the treatment of myocardial IR injury (MIRI). Therapeutic peptides will be presented depending on their interacting mechanisms (apoptosis, necroptosis, and inflammation) reported as playing an important role in reperfusion injury following myocardial ischemia. The search and development of therapeutic peptides have become very active, with increasing numbers of candidates entering clinical trials. Their optimization and their potential application in the treatment of patients with AMI will be discussed.

Annexin-A1; the culprit or the solution?

Annexin‐A1 has a well‐defined anti‐inflammatory role in the innate immune system, but its function in adaptive immunity remains controversial. This glucocorticoid‐induced protein has been implicated in a range of inflammatory conditions and cancers, as well as being found to be overexpressed on the T cells of patients with autoimmune disease. Moreover, the formyl peptide family of receptors, through which annexin‐A1 primarily signals, has also been implicated in these diseases. In contrast, treatment with recombinant annexin‐A1 peptides resulted in suppression of inflammatory processes in murine models of inflammation. This review will focus on what is currently known about annexin‐A1 in health and disease and discuss the potential of this protein as a biomarker and therapeutic target.

Formyl peptide receptor 2 and heart disease

Formyl peptide receptor type 2 (FPR2) regulates the initiation and resolution phases of the inflammatory response. In the setting of heart injury and disease, dysregulated inflammation can potentiate maladaptive healing and pathological remodeling of the heart leading to cardiac dysfunction and failure. The potential to regulate and resolve adverse inflammation is postulated to improve outcome in the setting of heart disease. This review covers emerging concepts on the role of FPR2 in heart disease and strategies to activate pro-resolution processes to limit disease progression. We summarize key preclinical studies that support use of FPR2 agonists in heart disease. Finally, we briefly discuss the status of FPR2 agonists under evaluation in the clinic.

Therapeutic Potential of Annexin A1 Modulation in Kidney and Cardiovascular Disorders

Renal and cardiovascular disorders are very prevalent and associated with significant morbidity and mortality. Among diverse pathogenic mechanisms, the dysregulation of immune and inflammatory responses plays an essential role in such disorders. Consequently, the discovery of Annexin A1, as a glucocorticoid-inducible anti-inflammatory protein, has fueled investigation of its role in renal and cardiovascular pathologies. Indeed, with respect to the kidney, its role has been examined in diverse renal pathologies, including acute kidney injury, diabetic nephropathy, immune-mediated nephropathy, drug-induced kidney injury, kidney stone formation, and renal cancer. Regarding the cardiovascular system, major areas of investigation include the role of Annexin A1 in vascular abnormalities, atherosclerosis, and myocardial infarction. Thus, this review briefly describes major structural and functional features of Annexin A1 followed by a review of its role in pathologies of the kidney and the cardiovascular system, as well as the therapeutic potential of its modulation for such disorders.

Neutrophil crosstalk during cardiac wound healing after myocardial infarction

Myocardial infarction (MI) initiates an intense inflammatory response that induces neutrophil infiltration into the infarct region. Neutrophils commence the pro-inflammatory response that includes upregulation of cytokines and chemokines (e.g., interleukin-1 beta) and degranulation of pre-formed proteases (e.g., matrix metalloproteinases -8 and -9) that degrade existing extracellular matrix to clear necrotic tissue. An increase or complete depletion of neutrophils both paradoxically impair MI resolution, indicating a complex role of neutrophils in cardiac wound healing. Following pro-inflammation, the neutrophil shifts to a reparative phenotype that promotes inflammation resolution and aids in scar formation. Across the shifts in phenotype, the neutrophil communicates with other cells to coordinate repair and scar formation. This review summarizes our current understanding of neutrophil crosstalk with cardiomyocytes and macrophages during MI wound healing.

Ac2-26 mitigated acute respiratory distress syndrome rats via formyl peptide receptor pathway

BACKGROUND

Acute respiratory distress syndrome (ARDS) is characterized by severe local and systemic inflammation. Ac2-26, an Annexin A1 Peptide, can reduce the lung injury induced by reperfusion via the inhibition of inflammation. The present study aims to evaluate the effect and mechanism of Ac2-26 in ARDS.

METHODS

Thirty-two rats were anaesthetized and randomized into four groups: sham (S), ARDS (A), ARDS/Ac2-26 (AA), and ARDS/Ac2-26/BOC-2 (AAB) groups. Rats in the S group received saline for intratracheal instillation, while rats in the other three groups received endotoxin for intratracheal instillation, in order to prepare the ARDS and inject the saline, Ac2-26, and Ac2-26 combined with BOC-2. After 24 h, the PaO2/FiO2 ratio was calculated. The lung tissue wet-to-dry weight ratio and the protein level in bronchoalveolar lavage fluid (BALF) were tested. Then, the cytokines in BALF and serum, and the inflammatory cells in BALF were investigated. Afterwards, the oxidative stress response and histological injury was evaluated. Subsequently, the epithelium was cultured and analyzed to estimate the effect of Ac2-26 on apoptosis.

RESULTS

Compared to the S group, all indexes worsened in the A, AA, and AAB groups. Furthermore, compared to the S group, Ac2-26 significantly improved the lung injury and alveolar-capillary permeability, and inhibited the oxidative stress response. In addition, Ac2-26 reduced the local and systemic inflammation through the regulation of pro- and anti-inflammatory cytokines, and the decrease in inflammatory cells in BALF. Moreover, Ac2-26 inhibited the epithelium apoptosis induced by LPS through the modulation of apoptosis-regulated proteins. The protective effect of Ac2-26 on ARDS was partially reversed by the FPR inhibitor, BOC-2.

CONCLUSION

Ac2-26 reduced the lung injury induced by LPS, promoted alveolar-capillary permeability, ameliorated the local and systemic inflammation, and inhibited the oxidative stress response and apoptosis. The protection of Ac2-26 on ARDS was mainly dependent on the FPR pathway.

Therapeutic Potential of Annexins in Sepsis and COVID-19

Sepsis is a continuing problem in modern healthcare, with a relatively high prevalence, and a significant mortality rate worldwide. Currently, no specific anti-sepsis treatment exists despite decades of research on developing potential therapies. Annexins are molecules that show efficacy in preclinical models of sepsis but have not been investigated as a potential therapy in patients with sepsis. Human annexins play important roles in cell membrane dynamics, as well as mediation of systemic effects. Most notably, annexins are highly involved in anti-inflammatory processes, adaptive immunity, modulation of coagulation and fibrinolysis, as well as protective shielding of cells from phagocytosis. These discoveries led to the development of analogous peptides which mimic their physiological function, and investigation into the potential of using the annexins and their analogous peptides as therapeutic agents in conditions where inflammation and coagulation play a large role in the pathophysiology. In numerous studies, treatment with recombinant human annexins and annexin analogue peptides have consistently found positive outcomes in animal models of sepsis, myocardial infarction, and ischemia reperfusion injury. Annexins A1 and A5 improve organ function and reduce mortality in animal sepsis models, inhibit inflammatory processes, reduce inflammatory mediator release, and protect against ischemic injury. The mechanisms of action and demonstrated efficacy of annexins in animal models support development of annexins and their analogues for the treatment of sepsis. The effects of annexin A5 on inflammation and platelet activation may be particularly beneficial in disease caused by SARS-CoV-2 infection. Safety and efficacy of recombinant human annexin A5 are currently being studied in clinical trials in sepsis and severe COVID-19 patients.

Annexin A1 attenuates cardiac diastolic dysfunction in mice with inflammatory arthritis

Rheumatoid arthritis (RA) carries a twofold increased incidence of heart failure with preserved ejection fraction, accompanied by diastolic dysfunction, which can lead to death. The causes of diastolic dysfunction are unknown, and there are currently no well-characterized animal models for studying these mechanisms. Current medications for RA do not have marked beneficial cardio-protective effects. K/BxN F1 progeny and KRN control mice were analyzed over time for arthritis development, monitoring left ventricular diastolic and systolic function using echocardiography. Excised hearts were analyzed by flow cytometry, qPCR, and histology. In pharmacological experiments, K/BxN F1 mice were treated with human recombinant AnxA1 (hrAnxA1, 1 μg/mouse) or vehicle daily. K/BxN F1 mice exhibited fully developed arthritis with normal cardiac function at 4 wk; however, by week 8, all mice displayed left ventricular diastolic dysfunction with preserved ejection fraction. This dysfunction was associated with cardiac hypertrophy, myocardial inflammation and fibrosis, and inflammatory markers. Daily treatment of K/BxN F1 mice with hrAnxA1 from weeks 4 to 8 halted progression of the diastolic dysfunction. The treatment reduced cardiac transcripts of proinflammatory cytokines and profibrotic markers. At the cellular level, hrAnxA1 decreased activated T cells and increased MHC II^low macrophage infiltration in K/BxN F1 hearts. Similar effects were obtained when hrAnxA1 was administered from week 8 to week 15. We describe an animal model of inflammatory arthritis that recapitulates the cardiomyopathy of RA. Treatment with hrAnxA1 after disease onset corrected the diastolic dysfunction through modulation of both fibroblast and inflammatory cell phenotype within the heart.

Cardiac Dysfunction in Rheumatoid Arthritis: The Role of Inflammation

Rheumatoid arthritis is a chronic, systemic inflammatory disease that carries an increased risk of mortality due to cardiovascular disease. The link between inflammation and atherosclerotic disease is clear; however, recent evidence suggests that inflammation may also play a role in the development of nonischemic heart disease in rheumatoid arthritis (RA) patients. We consider here the link between inflammation and cardiovascular disease in the RA community with a focus on heart failure with preserved ejection fraction. The effect of current anti-inflammatory therapeutics, used to treat RA patients, on cardiovascular disease are discussed as well as whether targeting resolution of inflammation might offer an alternative strategy for tempering inflammation and subsequent inflammation-driven comorbidities in RA.

Regulation of Inflammation and Oxidative Stress by Formyl Peptide Receptors in Cardiovascular Disease Progression

G protein-coupled receptors (GPCRs) are the most important regulators of cardiac function and are commonly targeted for medical therapeutics. Formyl-Peptide Receptors (FPRs) are members of the GPCR superfamily and play an emerging role in cardiovascular pathologies. FPRs can modulate oxidative stress through nicotinamide adenine dinucleotide phosphate (NADPH) oxidase-dependent reactive oxygen species (ROS) production whose dysregulation has been observed in different cardiovascular diseases. Therefore, many studies are focused on identifying molecular mechanisms of the regulation of ROS production. FPR1, FPR2 and FPR3 belong to the FPRs family and their stimulation triggers phosphorylation of intracellular signaling molecules and nonsignaling proteins that are required for NADPH oxidase activation. Some FPR agonists trigger inflammatory processes, while other ligands activate proresolving or anti-inflammatory pathways, depending on the nature of the ligands. In general, bacterial and mitochondrial formylated peptides activate a proinflammatory cell response through FPR1, while Annexin A1 and Lipoxin A4 are anti-inflammatory FPR2 ligands. FPR2 can also trigger a proinflammatory pathway and the switch between FPR2-mediated pro- and anti-inflammatory cell responses depends on conformational changes of the receptor upon ligand binding. Here we describe the detrimental or beneficial effects of the main FPR agonists and their potential role as new therapeutic and diagnostic targets in the progression of cardiovascular diseases.

Untangling Local Pro-Inflammatory, Reparative, and Regulatory Damage-Associated Molecular-Patterns (DAMPs) Pathways to Improve Transplant Outcomes

Detrimental inflammatory responses after solid organ transplantation are initiated when immune cells sense pathogen-associated molecular patterns (PAMPs) and certain damage-associated molecular patterns (DAMPs) released or exposed during transplant-associated processes, such as ischemia/reperfusion injury (IRI), surgical trauma, and recipient conditioning. These inflammatory responses initiate and propagate anti-alloantigen (AlloAg) responses and targeting DAMPs and PAMPs, or the signaling cascades they activate, reduce alloimmunity, and contribute to improved outcomes after allogeneic solid organ transplantation in experimental studies. However, DAMPs have also been implicated in initiating essential anti-inflammatory and reparative functions of specific immune cells, particularly Treg and macrophages. Interestingly, DAMP signaling is also involved in local and systemic homeostasis. Herein, we describe the emerging literature defining how poor outcomes after transplantation may result, not from just an over-abundance of DAMP-driven inflammation, but instead an inadequate presence of a subset of DAMPs or related molecules needed to repair tissue successfully or re-establish tissue homeostasis. Adverse outcomes may also arise when these homeostatic or reparative signals become dysregulated or hijacked by alloreactive immune cells in transplant niches. A complete understanding of the critical pathways controlling tissue repair and homeostasis, and how alloimmune responses or transplant-related processes disrupt these will lead to new immunotherapeutics that can prevent or reverse the tissue pathology leading to lost grafts due to chronic rejection.

The role and mechanism of the annexin A1 peptide Ac2-26 in rats with cardiopulmonary bypass lung injury

The main causes of lung injury after cardiopulmonary bypass (CPB) are systemic inflammatory response syndrome (SIRS) and pulmonary ischaemia‐reperfusion injury (IR‐I). SIRS and IR‐I are often initiated by a systemic inflammatory response. The present study investigated whether the annexin A1 (ANX‐A1) peptidomimetic Ac2‐26 by binding to formyl peptide receptors (FPRs) inhibit inflammatory cytokines and reduce lung injury after CPB. Male rats were randomized to the following five groups (n = 6, each): sham, exposed to pulmonary ischaemic‐reperfusion (IR‐I), IR‐I plus Ac2‐26, IR‐I plus the FPR antagonist, BoC2 (N‐tert‐butyloxycarbonyl‐Phe‐Leu‐Phe‐Leu‐Phe) and IR‐I plus Ac2‐26 and BoC2. Treatment with Ac2‐26 improved the oxygenation index, an effect blocked by BoC2. Histopathological analysis of the lung tissue revealed that the degree of lung injury was significantly less (P < 0.05) in the Ac2‐26‐treated rats compared to the other experimental groups exposed to IR‐I. Ac2‐26 treatment reduced the levels of the inflammatory cytokines TNF‐α, IL‐1β, ICAM‐1 and NF‐κB‐p65 (P < 0.05) compared to the vehicle‐treated group exposed to IR‐I. In conclusion, the annexin A1 (ANX‐A1) peptidomimetic Ac2‐26 by binding to formyl peptide receptors inhibit inflammatory cytokines and reduce ischaemic‐reperfusion lung injury after cardiopulmonary bypass.

Role of Annexin A1 in NLRP3 Inflammasome Activation in Murine Neutrophils

This study evaluated the role of endogenous and exogenous annexin A1 (AnxA1) in the activation of the NLRP3 inflammasome in isolated peritoneal neutrophils. C57BL/6 wild-type (WT) and AnxA1 knockout mice (AnxA1-/-) received 0.3% carrageenan intraperitoneally and, after 3 h, the peritoneal exudate was collected. WT and AnxA1-/- neutrophils were then stimulated with lipopolysaccharide, followed by the NLRP3 agonists nigericin or ATP. To determine the exogenous effect of AnxA1, the neutrophils were pretreated with the AnxA1-derived peptide Ac2-26 followed by the NLRP3 agonists. Ac2-26 administration reduced NLRP3-derived IL-1β production by WT neutrophils after nigericin and ATP stimulation. However, IL-1β release was impaired in AnxA1-/- neutrophils stimulated by both agonists, and there was no further impairment in IL-1β release with Ac2-26 treatment before stimulation. Despite this, ATP- and nigericin-stimulated AnxA1-/- neutrophils had increased levels of cleaved caspase-1. The lipidomics of supernatants from nigericin-stimulated WT and AnxA1-/- neutrophils showed potential lipid biomarkers of cell stress and activation, including specific sphingolipids and glycerophospholipids. AnxA1 peptidomimetic treatment also increased the concentration of phosphatidylserines and oxidized phosphocholines, which are lipid biomarkers related to the inflammatory resolution pathway. Together, our results indicate that exogenous AnxA1 negatively regulates NLRP3-derived IL-1β production by neutrophils, while endogenous AnxA1 is required for the activation of the NLRP3 machinery.

Annexin A1 is a Potential Novel Biomarker of Congestion in Acute Heart Failure

OBJECTIVES

This study sought to identify the role of annexin A1 (AnxA1) as a congestion marker in acute heart failure (AHF) and to identify its putative role in predicting clinical outcomes.

BACKGROUND

AnxA1 is a protein that inhibits inflammation following ischemia-reperfusion injury in cardiorenal tissues. Because AHF is a state of tissue hypoperfusion, we hypothesized that plasma AnxA1 levels are altered in AHF.

METHODS

In the Renal Optimization Strategies Evaluation (ROSE) trial, patients hospitalized for AHF with kidney injury were randomized to receive dopamine, nesiritide, or placebo for 72 hours in addition to diuresis. In a subanalysis, plasma AnxA1 levels were measured at baseline and at 72 hours in 275 patients. Participants were divided into 3 tertiles based on their baseline AnxA1 levels.

RESULTS

The prevalence of peripheral edema 2+ increased with increasing AnxA1 levels (P < .007). Cystatin C, blood urea nitrogen, and kidney injury molecule-1 plasma levels were higher among participants in tertile 3 vs tertiles 1 or 2 (P< .05). Patients with a congestion score of 4 had a mean baseline AnxA1 level 8.63 units higher than those with a congestion score of 0 (P = .03). Patients in tertiles 2 and 3 were twice as likely to experience creatinine elevation as patients in tertile 1 (P = .03). Patients in tertiles 2 and 3 were at a higher risk of 60-day all-cause mortality or heart failure hospitalization and 180-day all-cause mortality (P < .05).

CONCLUSIONS

Among patients hospitalized for AHF with impaired kidney function, elevated AnxA1 levels are associated with worse congestion, higher risk for further creatinine elevation, and higher rates of 60-day morbidity or all-cause mortality and 180-day all-cause mortality.

CLINICAL TRIAL REGISTRATION

clinicaltrials.gov Identifier: NCT01132846.

Pro-Angiogenic Macrophage Phenotype to Promote Myocardial Repair

BACKGROUND

Heart failure following myocardial infarction (MI) remains one of the major causes of death worldwide, and its treatment is a crucial challenge of cardiovascular medicine. An attractive therapeutic strategy is to stimulate endogenous mechanisms of myocardial regeneration.

OBJECTIVES

This study evaluates the potential therapeutic treatment with annexin A1 (AnxA1) to induce cardiac repair after MI.

METHODS

AnxA1 knockout (AnxA1^-/-) and wild-type mice underwent MI induced by ligation of the left anterior descending coronary artery. Cardiac functionality was assessed by longitudinal echocardiographic measurements. Histological, fluorescence-activated cell sorting, dot blot analysis, and in vitro/ex vivo studies were used to assess the myocardial neovascularization, macrophage content, and activity in response to AnxA1.

RESULTS

AnxA1^-/- mice showed a reduced cardiac functionality and an expansion of proinflammatory macrophages in the ischemic area. Cardiac macrophages from AnxA1^-/- mice exhibited a dramatically reduced ability to release the proangiogenic mediator vascular endothelial growth factor (VEGF)-A. However, AnxA1 treatment enhanced VEGF-A release from cardiac macrophages, and its delivery in vivo markedly improved cardiac performance. The positive effect of AnxA1 treatment on cardiac performance was abolished in wild-type mice transplanted with bone marrow derived from Cx₃cr1cre^ERT2Vegf^flox/flox or in mice depleted of macrophages. Similarly, cardioprotective effects of AnxA1 were obtained in pigs in which full-length AnxA1 was overexpressed by use of a cardiotropic adeno-associated virus.

CONCLUSIONS

AnxA1 has a direct action on cardiac macrophage polarization toward a pro-angiogenic, reparative phenotype. AnxA1 stimulated cardiac macrophages to release high amounts of VEGF-A, thus inducing neovascularization and cardiac repair.

Recombinant annexin A6 promotes membrane repair and protects against muscle injury

Membrane repair is essential to cell survival. In skeletal muscle, injury often associates with plasma membrane disruption. Additionally, muscular dystrophy is linked to mutations in genes that produce fragile membranes or reduce membrane repair. Methods to enhance repair and reduce susceptibility to injury could benefit muscle in both acute and chronic injury settings. Annexins are a family of membrane-associated Ca2+-binding proteins implicated in repair, and annexin A6 was previously identified as a genetic modifier of muscle injury and disease. Annexin A6 forms the repair cap over the site of membrane disruption. To elucidate how annexins facilitate repair, we visualized annexin cap formation during injury. We found that annexin cap size positively correlated with increasing Ca2+ concentrations. We also found that annexin overexpression promoted external blebs enriched in Ca2+ and correlated with a reduction of intracellular Ca2+ at the injury site. Annexin A6 overexpression reduced membrane injury, consistent with enhanced repair. Treatment with recombinant annexin A6 protected against acute muscle injury in vitro and in vivo. Moreover, administration of recombinant annexin A6 in a model of muscular dystrophy reduced serum creatinine kinase, a biomarker of disease. These data identify annexins as mediators of membrane-associated Ca2+ release during membrane repair and annexin A6 as a therapeutic target to enhance membrane repair capacity.

Annexin A1 Bioactive Peptide Promotes Resolution of Neuroinflammation in a Rat Model of Exsanguinating Cardiac Arrest Treated by Emergency Preservation and Resuscitation

Neuroinflammation initiated by damage-associated molecular patterns, including high mobility group box 1 protein (HMGB1), has been implicated in adverse neurological outcomes following lethal hemorrhagic shock and polytrauma. Emergency preservation and resuscitation (EPR) is a novel method of resuscitation for victims of exsanguinating cardiac arrest, shown in preclinical studies to improve survival with acceptable neurological recovery. Sirtuin 3 (SIRT3), the primary mitochondrial deacetylase, has emerged as a key regulator of metabolic and energy stress response pathways in the brain and a pharmacological target to induce a neuronal pro-survival phenotype. This study aims to examine whether systemic administration of an Annexin-A1 bioactive peptide (ANXA1sp) could resolve neuroinflammation and induce sirtuin-3 regulated cytoprotective pathways in a novel rat model of exsanguinating cardiac arrest and EPR. Adult male rats underwent hemorrhagic shock and ventricular fibrillation, induction of profound hypothermia, followed by resuscitation and rewarming using cardiopulmonary bypass (EPR). Animals randomly received ANXA1sp (3 mg/kg, in divided doses) or vehicle. Neuroinflammation (HMGB1, TNFα, IL-6, and IL-10 levels), cerebral cell death (TUNEL, caspase-3, pro and antiapoptotic protein levels), and neurologic scores were assessed to evaluate the inflammation resolving effects of ANXA1sp following EPR. Furthermore, western blot analysis and immunohistochemistry were used to interrogate the mechanisms involved. Compared to vehicle controls, ANXA1sp effectively reduced expression of cerebral HMGB1, IL-6, and TNFα and increased IL-10 expression, which were associated with improved neurological scores. ANXA1sp reversed EPR-induced increases in expression of proapoptotic protein Bax and reduction in antiapoptotic protein Bcl-2, with a corresponding decrease in cerebral levels of cleaved caspase-3. Furthermore, ANXA1sp induced autophagic flux (increased LC3II and reduced p62 expression) in the brain. Mechanistically, these findings were accompanied by upregulation of the mitochondrial protein deacetylase Sirtuin-3, and its downstream targets FOXO3a and MnSOD in ANXA1sp-treated animals. Our data provide new evidence that engaging pro-resolving pharmacological strategies such as Annexin-A1 biomimetic peptides can effectively attenuate neuroinflammation and enhance the neuroprotective effects of EPR after exsanguinating cardiac arrest.

Annexin-A1: Therapeutic Potential in Microvascular Disease

Annexin-A1 (ANXA1) was first discovered in the early 1980's as a protein, which mediates (some of the) anti-inflammatory effects of glucocorticoids. Subsequently, the role of ANXA1 in inflammation has been extensively studied. The biology of ANXA1 is complex and it has many different roles in both health and disease. Its effects as a potent endogenous anti-inflammatory mediator are well-described in both acute and chronic inflammation and its role in activating the pro-resolution phase receptor, FPR2, has been described and is now being exploited for therapeutic benefit. In the present mini review, we will endeavor to give an overview of ANXA1 biology in relation to inflammation and functions that mediate pro-resolution that are independent of glucocorticoid induction. We will focus on the role of ANXA1 in diseases with a large inflammatory component focusing on diabetes and microvascular disease. Finally, we will explore the possibility of exploiting ANXA1 as a novel therapeutic target in diabetes and the treatment of microvascular disease.

Cardioprotective Actions of the Annexin-A1 N-Terminal Peptide, Ac2-26, Against Myocardial Infarction

The anti-inflammatory, pro-resolving annexin-A1 protein acts as an endogenous brake against exaggerated cardiac necrosis, inflammation, and fibrosis following myocardial infarction (MI) in vivo. Little is known, however, regarding the cardioprotective actions of the N-terminal-derived peptide of annexin A1, Ac_2-26, particularly beyond its anti-necrotic actions in the first few hours after an ischemic insult. In this study, we tested the hypothesis that exogenous Ac_2-26 limits cardiac injury in vitro and in vivo. Firstly, we demonstrated that Ac_2-26 limits cardiomyocyte death both in vitro and in mice subjected to ischemia-reperfusion (I-R) injury in vivo (Ac_2-26, 1 mg/kg, i.v. just prior to post-ischemic reperfusion). Further, Ac_2-26 (1 mg/kg i.v.) reduced cardiac inflammation (after 48 h reperfusion), as well as both cardiac fibrosis and apoptosis (after 7-days reperfusion). Lastly, we investigated whether Ac_2-26 preserved cardiac function after MI. Ac_2-26 (1 mg/kg/day s.c., osmotic pump) delayed early cardiac dysfunction 1 week post MI, but elicited no further improvement 4 weeks after MI. Taken together, our data demonstrate the first evidence that Ac_2-26 not only preserves cardiomyocyte survival in vitro, but also offers cardioprotection beyond the first few hours after an ischemic insult in vivo. Annexin-A1 mimetics thus represent a potential new therapy to improve cardiac outcomes after MI.

Transcriptomic Signature of Right Ventricular Failure in Experimental Pulmonary Arterial Hypertension: Deep Sequencing Demonstrates Mitochondrial, Fibrotic, Inflammatory and Angiogenic Abnormalities

Right ventricular failure (RVF) remains the leading cause of death in pulmonary arterial hypertension (PAH). We investigated the transcriptomic signature of RVF in hemodynamically well-phenotyped monocrotaline (MCT)-treated, male, Sprague-Dawley rats with severe PAH and decompensated RVF (increased right ventricular (RV) end diastolic volume (EDV), decreased cardiac output (CO), tricuspid annular plane systolic excursion (TAPSE) and ventricular-arterial decoupling). RNA sequencing revealed 2547 differentially regulated transcripts in MCT-RVF RVs. Multiple enriched gene ontology (GO) terms converged on mitochondria/metabolism, fibrosis, inflammation, and angiogenesis. The mitochondrial transcriptomic pathway is the most affected in RVF, with 413 dysregulated genes. Downregulated genes included TFAM (−0.45-fold), suggesting impaired mitochondrial biogenesis, CYP2E1 (−3.8-fold), a monooxygenase which when downregulated increases oxidative stress, dehydrogenase/reductase 7C (DHRS7C) (−2.8-fold), consistent with excessive autonomic activation, and polypeptide N-acetyl-galactose-aminyl-transferase 13 (GALNT13), a known pulmonary hypertension (PH) biomarker (−2.7-fold). The most up-regulated gene encodes Periostin (POSTN; 4.5-fold), a matricellular protein relevant to fibrosis. Other dysregulated genes relevant to fibrosis include latent-transforming growth factor beta-binding protein 2 (LTBP2), thrombospondin4 (THBS4). We also identified one dysregulated gene relevant to all disordered transcriptomic pathways, ANNEXIN A1. This anti-inflammatory, phospholipid-binding mediator, is a putative target for therapy in RVF-PAH. Comparison of expression profiles in the MCT-RV with published microarray data from the RV of pulmonary artery-banded mice and humans with bone morphogenetic protein receptor type 2 (BMPR2)-mutations PAH reveals substantial conservation of gene dysregulation, which may facilitate clinical translation of preclinical therapeutic and biomarkers studies. Transcriptomics reveals the molecular fingerprint of RVF to be heavily characterized by mitochondrial dysfunction, fibrosis and inflammation.

Annexin A1 in inflammation and breast cancer: a new axis in the tumor microenvironment

Targeting inflammation in cancer has shown promise to improve and complement current therapies. The tumor microenvironment plays an important role in cancer growth and metastasis and -tumor associated macrophages possess pro-tumoral and pro-metastatic properties. Annexin A1 (ANXA1) is an immune-modulating protein with diverse functions in the immune system and in cancer. In breast cancer, high ANXA1 expression leads to poor prognosis and increased metastasis. Here, we will review ANXA1 as a modulator of inflammation, and discuss its importance in breast cancer and highlight its new role in alternative macrophage activation in the tumor microenvironment. This review may provide an updated understanding into the various roles of ANXA1 which may enable future therapeutic developments for the treatment of breast cancer.

Overexpression of Annexin A1 protects against benzo[a]pyrene‑induced bronchial epithelium injury

The incidence of asthma is increasing worldwide. Bronchial epithelium injury is common in asthma. The regulatory role of Annexin A1 (ANXA1) in bronchial epithelium injury is currently not well understood. The aim of the present study was to evaluate the role of ANXA1 on bronchial epithelium injury. The cell viability and levels of apoptosis were respectively tested by Cell Counting Kit-8 and flow cytometry. Reactive oxygen species (ROS) content and the activity of oxidative indicators were assessed by commercial kits. Enzyme linked immunosorbent assay was performed to detect the activity of active caspase-3. Reverse transcription-quantitative polymerase chain reaction and western blot assays were used to determine the expression levels of the target factors. The results demonstrated that ANXA1 improved the viability of benzo[a]pyrene (Bap)-treated bronchial epithelial cells. The Bap-induced oxidative stress was mitigated by the reduction in ROS generation, and the regulation of the activity of superoxide dismutase, glutathione peroxidases, malondialdehyde and lactic dehydrogenase. In addition, apoptosis was decreased by ANXA1 via the reduction of the expression of B-cell lymphoma 2 (Bcl-2), and the increase in the expression of Bcl-2-associated X protein and cyclin D1. Furthermore, the expression of phosphatase and tensin homolog (PTEN) and focal adhesion kinase (FAK) was rescued and the phosphorylation of phosphatidylinositol 3-kinase (PI3K)/protein kinase B (Akt) was depressed by ANXA1, when compared with the Bap group. SF1670 treatment reversed the anti-apoptotic effect of ANXA1. In conclusion, the results highlighted the protective effects of ANXA1 on bronchial epithelium injury, which most likely occurred via the PTEN/FAK/PI3K/Akt signaling pathway. Thus, the present study contributes to a potential therapeutic strategy for asthma patients.

Therapeutic Potential of Annexin A1 in Ischemia Reperfusion Injury

Cardiovascular disease (CVD) continues to be the leading cause of death in the world. Increased inflammation and an enhanced thrombotic milieu represent two major complications of CVD, which can culminate into an ischemic event. Treatment for these life-threatening complications remains reperfusion and restoration of blood flow. However, reperfusion strategies may result in ischemia-reperfusion injury (I/RI) secondary to various cardiovascular pathologies, including myocardial infarction and stroke, by furthering the inflammatory and thrombotic responses and delivering inflammatory mediators to the affected tissue. Annexin A1 (AnxA1) and its mimetic peptides are endogenous anti-inflammatory and pro-resolving mediators, known to have significant effects in resolving inflammation in a variety of disease models. Mounting evidence suggests that AnxA1, which interacts with the formyl peptide receptor (FPR) family, may have a significant role in mitigating I/RI associated complications. In this review article, we focus on how AnxA1 plays a protective role in the I/R based vascular pathologies.

Endogenous Annexin-A1 Regulates Haematopoietic Stem Cell Mobilisation and Inflammatory Response Post Myocardial Infarction in Mice In Vivo

Endogenous anti-inflammatory annexin-A1 (ANX-A1) plays an important role in preserving left ventricular (LV) viability and function after ischaemic insults in vitro, but its long-term cardioprotective actions in vivo are largely unknown. We tested the hypothesis that ANX-A1-deficiency exaggerates inflammation, haematopoietic stem progenitor cell (HSPC) activity and LV remodelling in response to myocardial ischaemia in vivo. Adult ANX-A1^−/− mice subjected to coronary artery occlusion exhibited increased infarct size and LV macrophage content after 24–48 h reperfusion compared with wildtype (WT) counterparts. In addition, ANX-A1^−/− mice exhibited greater expansion of HSPCs and altered pattern of HSPC mobilisation 8 days post-myocardial infarction, with increased circulating neutrophils and platelets, consistent with increased cardiac inflammation as a result of increased myeloid invading injured myocardium in response to MI. Furthermore, ANX-A1^−/− mice exhibited significantly increased expression of LV pro-inflammatory and pro-fibrotic genes and collagen deposition after MI compared to WT counterparts. ANX-A1-deficiency increased cardiac necrosis, inflammation, hypertrophy and fibrosis following MI, accompanied by exaggerated HSPC activity and impaired macrophage phenotype. These findings suggest that endogenous ANX-A1 regulates mobilisation and differentiation of HSPCs. Limiting excessive monocyte/neutrophil production may limit LV damage in vivo. Our findings support further development of novel ANX-A1-based therapies to improve cardiac outcomes after MI.

Annexin A1 and specialized proresolving lipid mediators: promoting resolution as a therapeutic strategy in human inflammatory diseases

INTRODUCTION

The timely resolution of inflammation is essential to restore tissue homeostasis and to avoid chronic inflammatory diseases. Resolution of inflammation is an active process modulated by various proresolving mediators, including annexin A1 (AnxA1) and specialized proresolving lipid mediators (SPMs), which counteract excessive inflammatory responses and stimulate proresolving mechanisms. Areas covered: The protective effects of AnxA1 and SPMs have been extensively explored in pre-clinical animal models. However, studies investigating the function of these molecules in human diseases are just emerging. This review highlights recent advances on the role of proresolving mediators, and pharmacological opportunities of promoting resolution pathways in preclinical models and patients with various human diseases. Expert opinion: Dysregulation or 'failure' in proresolving mechanisms might be involved in the pathogenesis of chronic inflammatory diseases. Altered levels of proresolving mediators were found in a wide range of human diseases. In some cases, AnxA1 and SPMs are up-regulated in human blood and tissues but fail to engage in proresolving signaling and, hence, to regulate excessive inflammation. Thus, the new concept of 'resolution pharmacology' could be applied to compensate deficiency of endogenous proresolving mediators' generation and/or possible failures in the engagement of resolution pathways observed in many chronic inflammatory diseases.

Ac2-26, an Annexin A1 Peptide, Attenuates Ischemia-Reperfusion-Induced Acute Lung Injury

Annexin A1 (AnxA1) is an endogenous protein that modulates anti-inflammatory processes, and its therapeutic potential has been reported in a range of inflammatory diseases. The effect of AnxA1 on ischemia-reperfusion (IR)-induced lung injury has not been examined. In this study, isolated, perfused rat lungs were subjected to IR lung injury induced by ischemia for 40 min, followed by reperfusion for 60 min. The rat lungs were randomly treated with vehicle (phosphate-buffered saline), and Ac2-26 (an active N-terminal peptide of AnxA1) with or without an N-formyl peptide receptor (FPR) antagonist N-Boc-Phe-Leu-Phe-Leu-Phe (Boc2). An in vitro study of the effects of Ac2-26 on human alveolar epithelial cells subjected to hypoxia-reoxygenation was also investigated. Administration of Ac2-26 in IR lung injury produced a significant attenuation of lung edema, pro-inflammatory cytokine production recovered in bronchoalveolar lavage fluid, oxidative stress, apoptosis, neutrophil infiltration, and lung tissue injury. Ac2-26 also decreased AnxA1 protein expression, inhibited the activation of nuclear factor-κB and mitogen-activated protein kinase pathways in the injured lung tissue. Finally, treatment with Boc2 abolished the protective action of Ac2-26. The results indicated that Ac2-26 had a protective effect against acute lung injury induced by IR, which may be via the activation of the FPR.

Annexin A1 and resolution of inflammation: tissue repairing properties and signalling signature

Inflammation is essential to protect the host from exogenous and endogenous dangers that ultimately lead to tissue injury. The consequent tissue repair is intimately associated with the fate of the inflammatory response. Restoration of tissue homeostasis is achieved through a balance between pro-inflammatory and anti-inflammatory/pro-resolving mediators. In chronic inflammatory diseases such balance is compromised, resulting in persistent inflammation and impaired healing. During the last two decades the glucocorticoid-regulated protein Annexin A1 (AnxA1) has emerged as a potent pro-resolving mediator acting on several facets of the innate immune system. Here, we review the therapeutic effects of AnxA1 on tissue healing and repairing together with the molecular targets responsible for these complex biological properties.

Small-molecule-biased formyl peptide receptor agonist compound 17b protects against myocardial ischaemia-reperfusion injury in mice

Effective treatment for managing myocardial infarction (MI) remains an urgent, unmet clinical need. Formyl peptide receptors (FPR) regulate inflammation, a major contributing mechanism to cardiac injury following MI. Here we demonstrate that FPR1/FPR2-biased agonism may represent a novel therapeutic strategy for the treatment of MI. The small-molecule FPR1/FPR2 agonist, Compound 17b (Cmpd17b), exhibits a distinct signalling fingerprint to the conventional FPR1/FPR2 agonist, Compound-43 (Cmpd43). In Chinese hamster ovary (CHO) cells stably transfected with human FPR1 or FPR2, Compd17b is biased away from potentially detrimental FPR1/2-mediated calcium mobilization, but retains the pro-survival signalling, ERK1/2 and Akt phosphorylation, relative to Compd43. The pathological importance of the biased agonism of Cmpd17b is demonstrable as superior cardioprotection in both in vitro (cardiomyocytes and cardiofibroblasts) and MI injury in mice in vivo. These findings reveal new insights for development of small molecule FPR agonists with an improved cardioprotective profile for treating MI.

G Protein-Coupled Receptors (GPCRs) can adopt different conformations, each linked to distinct cellular outcomes. Here the authors show that compound 17b, a novel agonist of the GPCR family member FPR, robustly activates cardioprotective but not detrimental FPR signalling, showing beneficial therapeutic effect in a mouse model of cardiac infarction.

The Potential Therapeutic Application of Peptides and Peptidomimetics in Cardiovascular Disease

Cardiovascular disease (CVD) remains a leading cause of mortality and morbidity worldwide. Numerous therapies are currently under investigation to improve pathological cardiovascular complications, but yet, there have been very few new medications approved for intervention/treatment. Therefore, new approaches to treat CVD are urgently required. Attempts to prevent vascular complications usually involve amelioration of contributing risk factors and underlying processes such as inflammation, obesity, hyperglycaemia, or hypercholesterolemia. Historically, the development of peptides as therapeutic agents has been avoided by the Pharmaceutical industry due to their low stability, size, rate of degradation, and poor delivery. However, more recently, resurgence has taken place in developing peptides and their mimetics for therapeutic intervention. As a result, increased attention has been placed upon using peptides that mimic the function of mediators involved in pathologic processes during vascular damage. This review will provide an overview on novel targets and experimental therapeutic approaches based on peptidomimetics for modulation in CVD. We aim to specifically examine apolipoprotein A-I (apoA-I) and apoE mimetic peptides and their role in cholesterol transport during atherosclerosis, suppressors of cytokine signaling (SOCS)1-derived peptides and annexin-A1 as potent inhibitors of inflammation, incretin mimetics and their function in glucose-insulin tolerance, among others. With improvements in technology and synthesis platforms the future looks promising for the development of novel peptides and mimetics for therapeutic use. However, within the area of CVD much more work is required to identify and improve our understanding of peptide structure, interaction, and function in order to select the best targets to take forward for treatment.

Formyl Peptide Receptor 2 Is Involved in Cardiac Repair After Myocardial Infarction Through Mobilization of Circulating Angiogenic Cells

Increasing evidence suggests that circulating angiogenic cells (CACs) promote repair of ischemic tissues. Activation of formyl peptide receptor 2 (Fpr2) has been reported to stimulate repair of ischemic heart. This study was conducted to investigate the role of Fpr2 on CAC mobilization and cardiac protection in myocardial infarction (MI). WKYMVm, a strong agonist for Fpr2, was administered in a murine model of acute MI, and mobilization of CACs including endothelial progenitor cells (CD34⁺ Flk1⁺ or Sca1⁺ Flk1⁺ cells) in peripheral blood was monitored. CAC mobilization by daily injection of WKYMVm for the first 4 days after MI was as efficient as granulocyte colony-stimulating factor and provided myocardial protection from apoptosis with increased vascular density and preservation of cardiac function. Transplantation of bone marrow (BM) from green fluorescent protein mice showed that BM-derived cells homed to ischemic heart after WKYMVm treatment and contributed to tissue protection. Transplantation of BM from Fpr2 knockout mice showed that Fpr2 in BM cells is critical in mediation of WKYMVm-stimulated myocardial protection and neovascularization after MI. These results suggest that activation of Fpr2 in BM after WKYMVm treatment provides cardiac protection through mobilization of CACs after MI, which may lead to the development of a new clinical protocol for treating patients with ischemic heart conditions. Stem Cells 2017;35:654-665.

The advantageous role of annexin A1 in cardiovascular disease

The inflammatory response protects the human body against infection and injury. However, uncontrolled and unresolved inflammation can lead to tissue damage and chronic inflammatory diseases. Therefore, active resolution of inflammation is essential to restore tissue homeostasis. This review focuses on the pro-resolving molecule annexin A1 (ANXA1) and its derived peptides. Mechanisms instructed by ANXA1 are multidisciplinary and affect leukocytes as well as endothelial cells and tissue resident cells like macrophages and mast cells. ANXA1 has an outstanding role in limiting leukocyte recruitment and different aspects of ANXA1 as modulator of the leukocyte adhesion cascade are discussed here. Additionally, this review details the therapeutic relevance of ANXA1 and its derived peptides in cardiovascular diseases since atherosclerosis stands out as a chronic inflammatory disease with impaired resolution and continuous leukocyte recruitment.

Inflammation in Sickle Cell Disease: Differential and Down-Expressed Plasma Levels of Annexin A1 Protein

Sickle cell disease (SCD) is an inherited hemolytic anemia whose pathophysiology is driven by polymerization of the hemoglobin S (Hb S), leading to hemolysis and vaso-occlusive events. Inflammation is a fundamental component in these processes and a continuous inflammatory stimulus can lead to tissue damages. Thus, pro-resolving pathways emerge in order to restore the homeostasis. For example there is the annexin A1 (ANXA1), an endogenous anti-inflammatory protein involved in reducing neutrophil-endothelial interactions, accelerating neutrophil apoptosis and stimulating macrophage efferocytosis. We investigated the expression of ANXA1 in plasma of SCD patients and its relation with anemic, hemolytic and inflammatory parameters of the disease. Three SCD genotypes were considered: the homozygous inheritance for Hb S (Hb SS) and the association between Hb S and the hemoglobin variants D-Punjab (Hb SD) and C (Hb SC). ANXA1 and proinflammatory cytokines were quantified by ELISA in plasma of SCD patients and control individuals without hemoglobinopathies. Hematological and biochemical parameters were analyzed by flow cytometry and spectrophotometer. The plasma levels of ANXA1 were about three-fold lesser in SCD patients compared to the control group, and within the SCD genotypes the most elevated levels were found in Hb SS individuals (approximately three-fold higher). Proinflammatory cytokines were higher in SCD groups than in the control individuals. Anemic and hemolytic markers were higher in Hb SS and Hb SD genotypes compared to Hb SC patients. White blood cells and platelets count were higher in Hb SS genotype and were positively correlated to ANXA1 levels. We found that ANXA1 is down-regulated and differentially expressed within the SCD genotypes. Its expression seems to depend on the inflammatory, hemolytic and vaso-occlusive characteristics of the diseased. These data may lead to new biological targets for therapeutic intervention in SCD.

Anti-inflammatory and anti-fibrotic effects of annexin1 on erectile function after cavernous nerve injury in rats

The aim of this study was to investigate the effect of the anti-inflammatory and anti-fibrotic actions of ANX1 on erectile function (EF). Forty-eight male Wistar rats were randomly distributed into four equal groups: one group (sham operation-control) and three groups (bilateral cavernous nerve (CN) crush injury). Crush injury groups were treated prior to injury with an intravascular injection of either ANX1 (50 or 100 μg kg^-1) or vehicle. EF was assessed by CN electrical stimulation at 2 and 7 days after CN injury with histomorphometric and immunohistochemical analysis. ANX1 demonstrated functional preservation as the increase in intracavernous pressure (ICP). A dose-response relationship regarding the effect on penile tissue was confirmed, and preservation of the penile dorsal nerves and anti-apoptotic effects in the corpus cavernosum (real P-value vs injured control). ANX1 treatment prevented collagen deposition and smooth muscle loss in the penis. ANX1 normalized the expression of vascular endothelial growth factor and decreased tumor necrosis factor-α in the lumen of the blood vessels of the organ. ANX1 proved effective in preserving EF in a rat model of neurogenic erectile dysfunction. ANX1 treatment before CN injury in rats improved erectile recovery, enhanced vascular regeneration and preserved the micro-architecture of the corpus cavernosum. The clinical availability of this compound merits application in penile rehabilitation studies following radical prostatectomy.

Targeting and therapeutic peptides in nanomedicine for atherosclerosis

Peptides in atherosclerosis nanomedicine provide structural, targeting, and therapeutic functionality and can assist in overcoming delivery barriers of traditional pharmaceuticals. Moreover, their inherent biocompatibility and biodegradability make them especially attractive as materials intended for use in vivo In this review, an overview of nanoparticle-associated targeting and therapeutic peptides for atherosclerosis is provided, including peptides designed for cellular targets such as endothelial cells, monocytes, and macrophages as well as for plaque components such as collagen and fibrin. An emphasis is placed on recent advances in multimodal strategies and a discussion on current challenges and barriers for clinical applicability is presented.

A fragmented form of annexin A1 is secreted from C2C12 myotubes by electric pulse-induced contraction

The main function of annexin A1 (ANXA1), a member of the annexin superfamily, is to bind to cellular membranes in a Ca(2+)-dependent manner. In skeletal muscle, ANXA1 is thought to be involved in the repair of damaged membrane tissue and in the migration of muscle cells. We hypothesized that ANXA1 is one of the myokines secreted during muscle contractions to accelerate the repair of cell damage after contraction. Here we performed cell contractions by electric pulse stimulation; the results revealed that a fragmented form of ANXA1 was cleaved by calpain and selectively secreted from skeletal muscle cells by contraction. We therefore realized that muscle-contraction-induced calpain-dependent ANXA1 fragmentation has a wound-healing effect on damaged cells. This suggested that not the intact form but rather fragmented ANXA1 is a contraction-induced myokine.

Lack of TNFRI signaling enhances annexin A1 biological activity in intestinal inflammation

We evaluated whether the lack of TNF-α signaling increases mucosal levels of annexin A1 (AnxA1); the hypothesis stems from previous findings showing that TNF-α neutralization in Crohn's disease patients up-regulates systemic AnxA1 expression. Biopsies from healthy volunteers and patients under anti-TNF-α therapy with remittent ulcerative colitis (UC) showed higher AnxA1 expression than those with active disease. We also evaluated dextran sulfate sodium (DSS)-acute colitis in TNF-α receptor 1 KO (TNFR1-/-) strain with impaired TNF-α signaling and C57BL/6 (WT) mice. Although both strains developed colitis, TNFR1-/- mice showed early clinical recovery, lower myeloperoxidase (MPO) activity and milder histopathological alterations. Colonic epithelium from control and DSS-treated TNFR1-/- mice showed intense AnxA1 expression and AnxA1+ CD4+ and CD8+ T cells were more frequent in TNFR1-/- animals, suggesting an extra supply of AnxA1. The pan antagonist of AnxA1 receptors exacerbated the colitis outcome in TNFR1-/- mice, supporting the pivotal role of AnxA1 in the early recovery. Our findings demonstrate that the TNF-α signaling reduction favors the expression and biological activity of AnxA1 in inflamed intestinal mucosa.

Cardioprotective potential of annexin-A1 mimetics in myocardial infarction

Myocardial infarction (MI) and its resultant heart failure remains a major cause of death in the world. The current treatments for patients with MI are revascularization with thrombolytic agents or interventional procedures. These treatments have focused on restoring blood flow to the ischemic tissue to prevent tissue necrosis and preserve organ function. The restoration of blood flow after a period of ischemia, however, may elicit further myocardial damage, called reperfusion injury. Pharmacological interventions, such as antioxidant and Ca(2+) channel blockers, have shown premises in experimental settings; however, clinical studies have shown limited success. Thus, there is a need for the development of novel therapies to treat reperfusion injury. The therapeutic potential of glucocorticoid-regulated anti-inflammatory mediator annexin-A1 (ANX-A1) has recently been recognized in a range of systemic inflammatory disorders. ANX-A1 binds to and activates the family of formyl peptide receptors (G protein-coupled receptor family) to inhibit neutrophil activation, migration and infiltration. Until recently, studies on the cardioprotective actions of ANX-A1 and its peptide mimetics (Ac2-26, CGEN-855A) have largely focused on its anti-inflammatory effects as a mechanism of preserving myocardial viability following I-R injury. Our laboratory provided the first evidence of the direct protective action of ANX-A1 on myocardium, independent of inflammatory cells in vitro. We now review the potential for ANX-A1 based therapeutics to be seen as a "triple shield" therapy against myocardial I-R injury, limiting neutrophil infiltration and preserving both cardiomyocyte viability and contractile function. This novel therapy may thus represent a valuable clinical approach to improve outcome after MI.

miR-146a and miR-196a2 polymorphisms in patients with ischemic stroke in the northern Chinese Han population

MicroRNAs are endogenous non-coding RNAs about 22 nucleotides in length that can repress the expression of proteins by binding to the 3'-untranslated regions of target messenger RNAs. We hypothesized that polymorphisms in miR-146a and miR-196a2 are associated with risk of ischemic stroke in the northern Chinese Han population. In a case-control study of 368 ischemic stroke patients and 381 control subjects that were frequency matched by age and gender, we genotyped two single nucleotide polymorphisms (rs11614913 in miR-196a2 and rs2910164 in miR-146a) using polymerase chain reaction-ligation detection reaction. The frequencies of the rs2910164 CC genotype and C allele within miR-146a were not significantly different in patients with ischemic stroke compared with those in the healthy control group. In subgroup meta-analysis, rs2910164 in miR-146a and large-artery atherosclerosis, rather than small-vessel disease, showed the significant association under the dominant model (CC vs CG+GG, OR 1.694; 95 % CI 1.199-2.395 p = 0.003). After adjusting for confounding risk factors of ischemic stroke by logistic regression analysis, this significant correlation remained. In addition, the distributions of the miR-196a2 genotypes and alleles were not statistically different between ischemic stroke and healthy groups. We also did not find any significant association from stroke subtypes. The CC genotype and C allele of rs2910164 within miR-146a are associated with an increased incidence of large-artery atherosclerotic stroke in the northern Chinese Han population. This study indicates that miR-146a (rs2910164) might contribute to ischemic stroke susceptibility in the northern Chinese Han population.

Aspirin-triggered Lipoxin A4 attenuates mechanical allodynia in association with inhibiting spinal JAK2/STAT3 signaling in neuropathic pain in rats

Aspirin-triggered Lipoxin A4 (ATL), as a Lipoxin A4 (LXA4) epimer, is endogenously produced by aspirin-acetylated cycloxygenase-2 (COX-2) and plays a vital role in endogenous anti-inflammation via the LXA4 receptor (ALX). Recent investigations have indicated that spinal neuroinflammation and the activation of the Janus Kinase 2 (JAK2)/Signal Transducers and Transcription Activators 3 (STAT3) signaling pathway are involved in neuropathic pain states. However, the effect of ATL on neuroinflammation and JAK2/STAT3 signaling in chronic constriction injury (CCI)-induced neuropathic pain in rats has not been well-studied. The present study demonstrated the anti-inflammatory and analgesic effect of ATL on neuropathic pain and assessed the role of spinal JAK2/STAT3 signaling on the effect of ATL. Intrathecal administration of ATL significantly attenuated mechanical allodynia via spinal ALX and inhibited the upregulation of pro-inflammatory cytokines (IL-1β, IL-6, and TNF-α) on day 7 of CCI surgery. In addition, ATL markedly suppressed the upregulation of p-STAT3 induced by the neuropathic pain. Blockade of JAK2-STAT3 signaling with intrathecal administration of the JAK2 inhibitor AG490 or the STAT3 inhibitor S3I-201 clearly reduced mechanical allodynia and the upregulation of pro-inflammatory cytokines in CCI rats. Interestingly, inhibition of JAK2/STAT3 signaling via ATL or the specific signaling inhibitor (AG49, S3I-201) further promoted the increased expression of suppressor of cytokine signaling 3 (SOCS3) mRNA in the spinal cord induced by CCI surgery. Taken together, our results suggested that the analgesic effect of ATL was mediated by inhibiting spinal JAK2/STAT3 signaling and hence the spinal neuroinflammation in CCI rats.

Reperfusion-induced myocardial dysfunction is prevented by endogenous annexin-A1 and its N-terminal-derived peptide Ac-ANX-A1(2-26)

BACKGROUND AND PURPOSE

Annexin-A1 (ANX-A1) is an endogenous, glucocorticoid-regulated anti-inflammatory protein. The N-terminal-derived peptide Ac-ANX-A1(2-26) preserves cardiomyocyte viability, but the impact of ANX-A1-peptides on cardiac contractility is unknown. We now test the hypothesis that ANX-A1 preserves post-ischaemic recovery of left ventricular (LV) function.

EXPERIMENTAL APPROACH

Ac-ANX-A1(2-26) was administered on reperfusion, to adult rat cardiomyocytes as well as hearts isolated from rats, wild-type mice and mice deficient in endogenous ANX-A1 (ANX-A1(-/-)). Myocardial viability and recovery of LV function were determined.

KEY RESULTS

Ischaemia-reperfusion markedly impaired both cardiomyocyte viability and recovery of LV function by 60%. Treatment with exogenous Ac-ANX-A1(2-26) at the onset of reperfusion prevented cardiomyocyte injury and significantly improved recovery of LV function, in both intact rat and wild-type mouse hearts. Ac-ANX-A1(2-26) cardioprotection was abolished by either formyl peptide receptor (FPR)-nonselective or FPR1-selective antagonists, Boc2 and cyclosporin H, but was relatively insensitive to the FPR2-selective antagonist QuinC7. ANX-A1-induced cardioprotection was associated with increased phosphorylation of the cell survival kinase Akt. ANX-A1(-/-) exaggerated impairment of post-ischaemic recovery of LV function, in addition to selective LV FPR1 down-regulation.

CONCLUSIONS AND IMPLICATIONS

These data represent the first evidence that ANX-A1 affects myocardial function. Our findings suggest ANX-A1 is an endogenous regulator of post-ischaemic recovery of LV function. Furthermore, the ANX-A1-derived peptide Ac-ANX-A1(2-26) on reperfusion rescues LV function, probably via activation of FPR1. ANX-A1-based therapies may thus represent a novel clinical approach for the prevention and treatment of myocardial reperfusion injury.

Urine annexin A1 as an index for glomerular injury in patients

Background. We recently demonstrated high urine levels of annexin A1 (ANXA1) protein in a mouse Adriamycin-induced glomerulopathy (ADG) model. Objective. To establish ANXA1 as a potential biomarker for glomerular injury in patients. Methods. A time-course study in the mouse ADG model, followed by renal tissues and urine samples from patients with various types of glomerular disorders for ANXA1. Results. Urinary ANXA1 protein was (1) detectable in both the ADG model and in patients except those with minimal change disease (MCD); (2) positively correlated with renal lesions in patients; and (3) early detectable in diabetes patients with normoalbuminuria. Conclusions. ANXA1 is a universal biomarker that is helpful in the early diagnosis, prognostic prediction, and outcome monitoring of glomerular injury. Measurement of urinary ANXA1 protein levels can help in differentiating MCD from other types of glomerular disorders.

The essential role of annexin A1 mimetic peptide in the skin allograft survival

Immunosuppressive drugs have a critical role in inhibiting tissue damage and allograft rejection. Studies have demonstrated the anti-inflammatory effects of the annexin A1 (AnxA1) in the regulation of transmigration and apoptosis of leucocytes. In the present study, an experimental skin allograft model was used to evaluate a potential protective effect of AnxA1 in transplantation survival. Mice were used for the skin allograft model and pharmacological treatments were carried out using either the AnxA1 mimetic peptide Ac2-26, with or without cyclosporine A (CsA), starting 3 days before surgery until rejection. Graft survival, skin histopathology, leucocyte transmigration and expression of AnxA1 and AnxA5 post-transplantation were analysed. Pharmacological treatment with Ac2-26 increased skin allograft survival related with inhibition of neutrophil transmigration and induction of apoptosis, thereby reducing the tissue damage compared with control animals. Moreover, AnxA1 and AnxA5 expression increased after Ac2-26 treatment in neutrophils. Interestingly, the combination of Ac2-26 and cyclosporine A showed similar survival of transplants when compared with the cyclosporine A group, which could be attributed to a synergistic effect of both drugs. Investigations in vitro revealed that cyclosporine A inhibited extracellular-signal-regulated kinase (ERK) phosphorylation induced by Ac2-26 in neutrophils. Overall, the results suggest that AnxA1 has an essential role in augmenting the survival of skin allograft, mainly owing to inhibition of neutrophil transmigration and enhancement of apoptosis. This effect may lead to the development of new therapeutic approaches relevant to transplant rejection.