Annexin 1-deficient neutrophils exhibit enhanced transmigration in vivo and increased responsiveness in vitro

Ac2-26 Reduced Lung Injury After Cardiopulmonary Bypass via the AKT1/GSK3β/eNOS Pathway

INTRODUCTION

Cardiopulmonary bypass (CPB) leads to severe inflammation and lung injury. Our previous study showed that Ac2-26 (an active n-terminal peptide of Annexin A1) can reduce acute lung injury. The aim of this study was to evaluate the effect of Ac2-26 on lung injury in CPB rats.

METHODS

Forty rats were randomly divided into the sham, CPB, Ac, Ac/serine/threonine kinase 1 (AKT1), and Ac/ glycogen synthase kinase (GSK)-3β groups. The rats in the sham group only received anesthesia, intubation, and cannulation. The rats in the other 4 groups received the standard CPB procedure. The rats in the CPB, Ac, Ac/AKT1, and Ac/GSK3β groups were immediately injected with saline, Ac2-26 (1 mg/kg), Ac2-26 combined with short hairpin RNA (AKT1), or Ac2-26 combined with a GSK3β inhibitor after CPB. At 12 h after the end of CPB, the PaO2/ fraction of inspired oxygen ratio, wet/dry weight ratio and protein content in the bronchoalveolar lavage fluid (BALF) were recorded. The numbers of macrophages and neutrophils in the BALF and blood were determined. Cytokine levels in the blood and BALF were investigated. Lung tissue histology and apoptosis were estimated. The expression of nuclear factor kappa- B, AKT1, GSK3β, endothelial nitric oxide synthase and apoptosis-related proteins was analyzed. The survival of all the rats was recorded.

RESULTS

Compared with the rats in the sham group, all the parameters examined worsened in the rats that received CPB. Compared with those in the CPB group, Ac2-26 significantly improved pulmonary capillary permeability, reduced cytokine levels, and decreased histological scores and apoptosis. The protective effect of Ac2-26 on lung injury was significantly reversed by AKT1 short hairpin RNA or a GSK3β inhibitor.

CONCLUSIONS

Ac2-26 significantly reduced lung injury and inflammation after CPB. The protective effect of Ac2-26 mainly depended on the AKT1/GSK3β/endothelial nitric oxide synthase pathway.

Ac2-26 reduced the liver injury after cardiopulmonary bypass in rats via AKT1/GSK3β/eNOS pathway

OBJECTIVE

About 10% of patients after cardiopulmonary bypass (CPB) would undergo acute liver injury, which aggravated the mortality of patients. Ac2-26 has been demonstrated to ameliorate organic injury by inhibiting inflammation. The present study aims to evaluate the effect and mechanism of Ac2-26 on acute liver injury after CPB.

METHODS

A total of 32 SD rats were randomized into sham, CPB, Ac, and Ac/AKT1 groups. The rats only received anesthesia, and rats in other groups received CPB. The rats in Ac/AKT1 were pre-injected with the shRNA to interfere with the expression of AKT1. The rats in CPB were injected with saline, and rats in Ac and Ac/AKT1 groups were injected with Ac2-26. After 12 h of CPB, all the rats were sacrificed and the peripheral blood and liver samples were collected to analyze. The inflammatory factors in serum and liver were detected. The liver function was tested, and the pathological injury of liver tissue was evaluated.

RESULTS

Compared with the sham group, the inflammatory factors, liver function, and pathological injury were worsened after CPB. Compared with the CPB group, the Ac2-26 significantly decreased the pro-inflammatory factors and increased the anti-inflammatory factor, improved liver function, and ameliorated the pathological injury. All the therapeutic effects of Ac2-26 were notably attenuated by the shRNA of AKT1. The Ac2-26 increased the GSK3β and eNOS, and this promotion was inhibited by the shRNA.

CONCLUSION

The Ac2-26 significantly treated the liver injury, inhibited inflammation, and improved liver function. The effect of Ac2-26 on liver injury induced by CPB was partly associated with the promotion of AKT1/GSK3β/eNOS.

Beyond host defense and tissue injury: the emerging role of neutrophils in tissue repair

Neutrophils, the most abundant immune cells in human blood, play a fundamental role in host defense against invading pathogens and tissue injury. Neutrophils carry potentially lethal weaponry to the affected site. Inadvertent and perpetual neutrophil activation could lead to nonresolving inflammation and tissue damage, a unifying mechanism of many common diseases. The prevailing view emphasizes the dichotomy of their function, host defense versus tissue damage. However, tissue injury may also persist during neutropenia, which is associated with disease severity and poor outcome. Numerous studies highlight neutrophil phenotypic heterogeneity and functional versatility, indicating that neutrophils play more complex roles than previously thought. Emerging evidence indicates that neutrophils actively orchestrate resolution of inflammation and tissue repair and facilitate return to homeostasis. Thus, neutrophils mobilize multiple mechanisms to limit the inflammatory reaction, assure debris removal, matrix remodeling, cytokine scavenging, macrophage reprogramming, and angiogenesis. In this review, we will summarize the homeostatic and tissue-reparative functions and mechanisms of neutrophils across organs. We will also discuss how the healing power of neutrophils might be harnessed to develop novel resolution and repair-promoting therapies while maintaining their defense functions.

Anti-Inflammatory and Pro-Resolving Actions of the N-Terminal Peptides Ac2-26, Ac2-12, and Ac9-25 of Annexin A1 on Conjunctival Goblet Cell Function

Annexin A1 (AnxA1) is the primary mediator of the anti-inflammatory actions of glucocorticoids. AnxA1 functions as a pro-resolving mediator in cultured rat conjunctival goblet cells to ensure tissue homeostasis through stimulation of intracellular [Ca2+] ([Ca2+]i) and mucin secretion. AnxA1 has several N-terminal peptides with anti-inflammatory properties of their own, including Ac2-26, Ac2-12, and Ac9-25. The increase in [Ca2+]i caused by AnxA1 and its N-terminal peptides in goblet cells was measured to determine the formyl peptide receptors used by the compounds and the action of the peptides on histamine stimulation. Changes in [Ca2+]i were determined by using a fluorescent Ca2+ indicator. AnxA1 and its peptides each activated formyl peptide receptors in goblet cells. AnxA1 and Ac2-26 at 10-12 mol/L and Ac2-12 at 10-9 mol/L inhibited the histamine-stimulated increase in [Ca2+]i, as did resolvin D1 and lipoxin A4 at 10-12 mol/L, whereas Ac9-25 did not. AnxA1 and Ac2-26 counter-regulated the H1 receptor through the p42/p44 mitogen-activated protein kinase/extracellular regulated kinase 1/2, β-adrenergic receptor kinase, and protein kinase C pathways, whereas Ac2-12 counter-regulated only through β-adrenergic receptor kinase. In conclusion, current data show that the N-terminal peptides Ac2-26 and Ac2-12, but not Ac9-25, share multiple functions with the full-length AnxA1 in goblet cells, including inhibition of histamine-stimulated increase in [Ca2+]i and counter-regulation of the H1 receptor. These actions suggest a potential pharmaceutical application of the AnxA1 N-terminal peptides Ac2-26 and Ac2-12 in homeostasis and ocular inflammatory diseases.

Mechanisms Limiting Renal Tissue Protection and Repair in Glomerulonephritis

Glomerulonephritis are renal disorders resulting from different pathogenic mechanisms (i.e., autoimmunity, complement, inflammatory activation, etc.). Clarifying details of the pathogenic cascade is basic to limit the progression from starting inflammation to degenerative stages. The balance between tissue injury, activation of protective systems and renal tissue repair determines the final outcome. Induction of an oxidative stress is part of glomerular inflammation and activation of protective antioxidant systems has a crucial role in reducing tissue effects. The generation of highly reactive oxygen species can be evaluated in vivo by tracing the inner-layer content of phosphatidyl ethanolamine and phosphatidyl serine in cell membranes. Albumin is the major antioxidant in serum and the level of oxidized albumin is another indirect sign of oxidative stress. Studies performed in Gn, specifically in FSGS, showed a high degree of oxidation in most contexts. High levels of circulating anti-SOD2 antibodies, limiting the detoxyfing activity of SOD2, have been detected in autoimmune Gn(lupus nephritis and membranous nephropathy) in association with persistence of proteinuria and worsening of renal function. In renal transplant, high levels of circulating anti-Glutathione S-transferase antibodies have been correlated with chronic antibody rejection and progressive loss of renal function. Annexins, mainly ANXA1 and ANXA2, play a general anti-inflammatory effect by inhibiting neutrophil functions. Cytosolic ANXA1 is decreased in apoptotic neutrophils of patients with glomerular polyangitis in association with delayed apoptosis that is considered the mechanism for polyangitis. High circulating levels of anti-ANXA1 and anti-ANXA2 antibodies characterize lupus nephritis implying a reduced anti-inflammatory effect. High circulating levels of antibodies targeting Macrophages (anti-FMNL1) have been detected in Gn in association with proteinuria. They potentially modify the intra-glomerular presence of protective macrophages (M2a, M2c) thus acting on the composition of renal infiltrate and on tissue repair.

The Multifaceted Role of Annexin A1 in Viral Infections

Dysregulated inflammatory responses are often correlated with disease severity during viral infections. Annexin A1 (AnxA1) is an endogenous pro-resolving protein that timely regulates inflammation by activating signaling pathways that culminate with the termination of response, clearance of pathogen and restoration of tissue homeostasis. Harnessing the pro-resolution actions of AnxA1 holds promise as a therapeutic strategy to control the severity of the clinical presentation of viral infections. In contrast, AnxA1 signaling might also be hijacked by viruses to promote pathogen survival and replication. Therefore, the role of AnxA1 during viral infections is complex and dynamic. In this review, we provide an in-depth view of the role of AnxA1 during viral infections, from pre-clinical to clinical studies. In addition, this review discusses the therapeutic potential for AnxA1 and AnxA1 mimetics in treating viral infections.

Identification of 2-Aminoacyl-1,3,4-thiadiazoles as Prostaglandin E2 and Leukotriene Biosynthesis Inhibitors

The application of a multi-step scientific workflow revealed an unprecedented class of PGE₂/leukotriene biosynthesis inhibitors with in vivo activity. Specifically, starting from a combinatorial virtual library of ∼4.2 × 10⁵ molecules, a small set of compounds was identified for the synthesis. Among these, four novel 2-aminoacyl-1,3,4-thiadiazole derivatives (3, 6, 7, and 9) displayed marked anti-inflammatory properties in vitro by strongly inhibiting PGE₂ biosynthesis, with IC₅₀ values in the nanomolar range. The hit compounds also efficiently interfered with leukotriene biosynthesis in cell-based systems and modulated IL-6 and PGE₂ biosynthesis in a lipopolysaccharide-stimulated J774A.1 macrophage cell line. The most promising compound 3 showed prominent in vivo anti-inflammatory activity in a mouse model, with efficacy comparable to that of dexamethasone, attenuating zymosan-induced leukocyte migration in mouse peritoneum with considerable modulation of the levels of typical pro-/anti-inflammatory cytokines.

Annexin A1-FPR2/ALX Signaling Axis Regulates Acute Inflammation during Chikungunya Virus Infection

Chikungunya (CHIKV) is an arthritogenic alphavirus that causes a self-limiting disease usually accompanied by joint pain and/or polyarthralgia with disabling characteristics. Immune responses developed during the acute phase of CHIKV infection determine the rate of disease progression and resolution. Annexin A1 (AnxA1) is involved in both initiating inflammation and preventing over-response, being essential for a balanced end of inflammation. In this study, we investigated the role of the AnxA1-FPR2/ALX pathway during CHIKV infection. Genetic deletion of AnxA1 or its receptor enhanced inflammatory responses driven by CHIKV. These knockout mice showed increased neutrophil accumulation and augmented tissue damage at the site of infection compared with control mice. Conversely, treatment of wild-type animals with the AnxA1 mimetic peptide (Ac_2–26) reduced neutrophil accumulation, decreased local concentration of inflammatory mediators and diminished mechanical hypernociception and paw edema induced by CHIKV-infection. Alterations in viral load were mild both in genetic deletion or with treatment. Combined, our data suggest that the AnxA1-FPR2/ALX pathway is a potential therapeutic strategy to control CHIKV-induced acute inflammation and polyarthralgia.

Inflammation Resolution: Implications for Atherosclerosis

Resolution is an active and highly coordinated process that occurs in response to inflammation to limit tissue damage and promote repair. When the resolution program fails, inflammation persists. It is now understood that failed resolution is a major underlying cause of many chronic inflammatory diseases. Here, we will review the major failures of resolution in atherosclerosis, including the imbalance of proinflammatory to pro-resolving mediator production, impaired clearance of dead cells, and functional changes in immune cells that favor ongoing inflammation. In addition, we will briefly discuss new concepts that are emerging as possible regulators of resolution and highlight the translational significance for the field.

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.

Annexin A1 as a Regulator of Immune Response in Cancer

Annexin A1 is a 37 kDa phospholipid-binding protein that is expressed in many tissues and cell types, including leukocytes, lymphocytes and epithelial cells. Although Annexin A1 has been extensively studied for its anti-inflammatory activity, it has been shown that, in the cancer context, its activity switches from anti-inflammatory to pro-inflammatory. Remarkably, Annexin A1 shows pro-invasive and pro-tumoral properties in several cancers either by eliciting autocrine signaling in cancer cells or by inducing a favorable tumor microenvironment. Indeed, the signaling of the N-terminal peptide of AnxA1 has been described to promote the switching of macrophages to the pro-tumoral M2 phenotype. Moreover, AnxA1 has been described to prevent the induction of antigen-specific cytotoxic T cell response and to play an essential role in the induction of regulatory T lymphocytes. In this way, Annexin A1 inhibits the anti-tumor immunity and supports the formation of an immunosuppressed tumor microenvironment that promotes tumor growth and metastasis. For these reasons, in this review we aim to describe the role of Annexin A1 in the establishment of the tumor microenvironment, focusing on the immunosuppressive and immunomodulatory activities of Annexin A1 and on its interaction with the epidermal growth factor receptor.

Structure-based screening for the discovery of 1,2,4-oxadiazoles as promising hits for the development of new anti-inflammatory agents interfering with eicosanoid biosynthesis pathways

The multiple inhibition of biological targets involved in pro-inflammatory eicosanoid biosynthesis represents an innovative strategy for treating inflammatory disorders in light of higher efficacy and safety. Herein, following a multidisciplinary protocol involving virtual combinatorial screening, chemical synthesis, and in vitro and in vivo validation of the biological activities, we report the identification of 1,2,4-oxadiazole-based eicosanoid biosynthesis multi-target inhibitors. The multidisciplinary scientific approach led to the identification of three 1,2,4-oxadiazole hits (compounds 1, 2 and 5), all endowed with IC₅₀ values in the low micromolar range, acting as 5-lipoxygenase-activating protein (FLAP) antagonists (compounds 1 and 2), and as a multi-target inhibitor (compound 5) of arachidonic acid cascade enzymes, namely cyclooxygenase-1 (COX-1), 5-lipoxygenase (5-LO) and microsomal prostaglandin E₂ synthase-1 (mPGES-1). Moreover, our in vivo results demonstrate that compound 5 is able to attenuate leukocyte migration in a model of zymosan-induced peritonitis and to modulate the production of IL-1β and TNF-α. These results are of interest for further expanding the chemical diversity around the 1,2,4-oxadiazole central core, enabling the identification of novel anti-inflammatory agents characterized by a favorable pharmacological profile and considering that moderate interference with multiple targets might have advantages in re-adjusting homeostasis.

β2 Integrin Regulation of Neutrophil Functional Plasticity and Fate in the Resolution of Inflammation

Neutrophils act as the first line of cellular defense against invading pathogens or tissue injury. Their rapid recruitment into inflamed tissues is critical for the elimination of invading microorganisms and tissue repair, but is also capable of inflicting damage to neighboring tissues. The β₂ integrins and Mac-1 (CD11b/CD18, α_Mβ₂ or complement receptor 3) in particular, are best known for mediating neutrophil adhesion and transmigration across the endothelium and phagocytosis of microbes. However, Mac-1 has a broad ligand recognition property that contributes to the functional versatility of the neutrophil population far beyond their antimicrobial function. Accumulating evidence over the past decade has demonstrated roles for Mac-1 ligands in regulating reverse neutrophil transmigration, lifespan, phagocytosis-induced cell death, release of neutrophil extracellular traps and efferocytosis, hence extending the traditional β₂ integrin repertoire in shaping innate and adaptive immune responses. Understanding the functions of β₂ integrins may partly explain neutrophil heterogeneity and may be instrumental to develop novel therapies specifically targeting Mac-1-mediated pro-resolution actions without compromising immunity. Thus, this review details novel insights on outside-in signaling through β₂ integrins and neutrophil functional heterogeneity pertinent to the resolution of inflammation.

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.

The role of annexin A1 in Candida albicans and Candida auris infections in murine neutrophils

Annexin A1 (AnxA1) is an anti-inflammatory protein expressed in various cell types, especially macrophages and neutrophils. Because neutrophils play important roles in infections and inflammatory processes and the relationship between AnxA1 and Candida spp. infections is not well-understood, our study examined whether AnxA1 can serve as a target protein for the regulation of the immune response during fungal infections. C57BL/6 wild-type (WT) and AnxA1 knockout (AnxA1^-/-) peritoneal neutrophils were coinfected with Candida albicans or Candida auris for 4 h. AnxA1^-/- neutrophils exhibited a marked increase in cyclooxygenase 2 (COX-2), phosphorylated extracellular signal-related kinase (ERK), p-38, and c-Jun N-terminal kinase (JNK) levels after coinfection with both Candida spp. A lipidomics approach showed that AnxA1 deficiency produced marked differences in the supernatant lipid profiles of both control neutrophils and neutrophils coinfected with Candida spp. compared with WT cells, especially the levels of glycerophospholipids and glycerolipids. Our results showed that endogenous AnxA1 regulates the neutrophil response under fungal infection conditions, altering lipid membrane organization and metabolism.

Leucine-rich alpha-2 glycoprotein 1, high mobility group box 1, matrix metalloproteinase 3 and annexin A1 as biomarkers of ulcerative colitis endoscopic and histological activity

OBJECTIVE

The LRG, HMGB1, MMP3 and ANXA1 proteins have been implicated in different inflammatory pathways in ulcerative colitis (UC), but their role as specific biomarkers of both endoscopic and histological activity has yet to be elucidated. In the present study, we aimed to evaluate the LRG1, HMGB1, MMP3 and ANXA1 as potential serum biomarkers for UC endoscopic and histological activity.

METHODS

This cross-sectional study included UC patients under 5-ASA, and healthy controls (HC) undergoing colonoscopy. Blood and biopsy samples were obtained and endoscopic Mayo sub-score (Ms) was recorded for the UC patients. Intramucosal calprotectin as a marker of histologic activity was evaluated in all biopsy samples and serum LRG1, HMGB1, MMP3 and ANXA1 levels were measured in the blood samples.

RESULTS

The HCs ANXA1 level was lower compared to that of the UC group [P = 0.00, area under the curve (AUC) = 0.881] and so was the HCs MMP3 level compared to that of patients (P = 0.00, AUC = 0.835). The HCs ANXA1 levels were also lower compared to these of the independent Ms groups, even to the Ms = 0 (P = 0.00, AUC = 0.913). UC endoscopic activity was associated with MMP3 levels (r = 0.54, P = 0.000) but not with ANXA1, LRG1 and HMGB1 levels CONCLUSION: Serum ANXA1 is a potential diagnostic biomarker of UC and serum MMP3 is a potential biomarker of UC endoscopic and histological activity.

ANXA1 directs Schwann cells proliferation and migration to accelerate nerve regeneration through the FPR2/AMPK pathway

Many factors are involved in the process of nerve regeneration. Understanding the mechanisms regarding how these factors promote an efficient remyelination is crucial to deciphering the molecular and cellular processes required to promote nerve repair. Schwann cells (SCs) play a central role in the process of peripheral nerve repair/regeneration. Using a model of facial nerve crush injury and repair, we identified Annexin A1 (ANXA1) as the extracellular trigger of SC proliferation and migration. ANXA1 activated formyl peptide receptor 2 (FPR2) receptors and the downstream adenosine 5'-monophosphate (AMP)-activated protein kinase (AMPK) signaling cascade, leading to SC proliferation and migration in vitro. SCs lacking FPR2 or AMPK displayed a defect in proliferation and migration. After facial nerve injury (FNI), ANXA1 promoted the proliferation of SCs and nerve regeneration in vivo. Collectively, these data identified the ANXA1/FPR2/AMPK axis as an important pathway in SC proliferation and migration. ANXA1-induced remyelination and SC proliferation promotes FNI regeneration.

Neutrophil heterogeneity and fate in inflamed tissues: implications for the resolution of inflammation

Neutrophils are polymorphonuclear leukocytes that play a central role in host defense against infection and tissue injury. They are rapidly recruited to the inflamed site and execute a variety of functions to clear invading pathogens and damaged cells. However, many of their defense mechanisms are capable of inflicting collateral tissue damage. Neutrophil-driven inflammation is a unifying mechanism underlying many common diseases. Efficient removal of neutrophils from inflammatory loci is critical for timely resolution of inflammation and return to homeostasis. Accumulating evidence challenges the classical view that neutrophils represent a homogeneous population and that halting neutrophil influx is sufficient to explain their rapid decline within inflamed loci during the resolution of protective inflammation. Hence, understanding the mechanisms that govern neutrophil functions and their removal from the inflammatory locus is critical for minimizing damage to the surrounding tissue and for return to homeostasis. In this review, we briefly address recent advances in characterizing neutrophil phenotypic and functional heterogeneity and the molecular mechanisms that determine the fate of neutrophils within inflammatory loci and the outcome of the inflammatory response. We also discuss how these mechanisms may be harnessed as potential therapeutic targets to facilitate resolution of inflammation.

Upregulation of annexin A1 protein expression in the intratumoral vasculature of human non-small-cell lung carcinoma and rodent tumor models

Annexin A1 (anxA1) is an immunomodulatory protein that has been proposed as a tumor vascular target for antitumor biologic agents, yet to date the vascular expression of anxA1 in specific tumor indications has not been systematically assessed. Attempts to evaluate vascular anxA1 expression by immunohistochemistry are complicated by a lack of available antibodies that are both specific for anxA1 and bind the N-terminal–truncated form of anxA1 that has previously been identified in tumor vasculature. To study the vascular expression pattern of anxA1 in non–small-cell lung carcinoma (NSCLC), we isolated an antibody capable of binding N-terminal–truncated anxA1_27-346 and employed it in immunohistochemical studies of human lung specimens. Lung tumor specimens evaluated with this antibody revealed vascular (endothelial) anxA1 expression in five of eight tumor samples studied, but no vascular anxA1 expression was observed in normal lung tissue. Tumor microarray analysis further demonstrated positive vascular staining for anxA1 in 30 of 80 NSCLC samples, and positive staining of neoplastic cells was observed in 54 of 80 samples. No correlation was observed between vascular and parenchymal anxA1 expression. Two rodent tumor models, B16-F10 and Py230, were determined to have upregulated anxA1 expression in the intratumoral vasculature. These data validate anxA1 as a potential vascular anti-tumor target in a subset of human lung tumors and identify rodent models which demonstrate anxA1 expression in tumor vasculature.

Temporin L-derived peptide as a regulator of the acute inflammatory response in zymosan-induced peritonitis

Antimicrobial peptides (AMPs) are an ancient group of defense molecules distributed in nature being found in mammals, birds, amphibians, insects, plants, and microorganisms. They display antimicrobial as well as immunomodulatory properties. The aim of this study was to investigate, for the first time, the anti-inflammatory activities of two synthetic temporin-L analogues (here named peptide 1 and 2) by an in vivo model of inflammation caused by intraperitoneal sub-lethal dose of zymosan. Our results show that peptide 1 and 2 exert anti-inflammatory activity in vivo in response to zymosan-induce peritonitis. Simultaneous administration of 10 mg/kg of both temporins, with a sub-lethal dose of zymosan (500 mg/kg), significantly rescued mice from the classical hallmarks of inflammation, including leukocyte infiltration and synthesis of inflammatory mediators including IL-6, TNF-α and MCP-1. More importantly, flow cytometry analysis highlighted a selective modulation of infiltrating inflammatory monocytes (defined as B220^-/GR1^hi-F480^hi/CD115⁺) after peptide 2 treatment. Our results and presented models offer the possibility to test, in a preclinical setting, the potential of temporin analogues as anti-inflammatory agents.

Reduced Annexin A1 Expression Associates with Disease Severity and Inflammation in Multiple Sclerosis Patients

Chronic neuroinflammation is a key pathological hallmark of multiple sclerosis (MS) that suggests that resolution of inflammation by specialized proresolving molecules is dysregulated in the disease. Annexin A1 (ANXA1) is a protein induced by glucocorticoids that facilitates resolution of inflammation through several mechanisms that include an inhibition of leukocyte recruitment and activation. In this study, we investigated the ability of ANXA1 to influence T cell effector function in relapsing/remitting MS (RRMS), an autoimmune disease sustained by proinflammatory Th1/Th17 cells. Circulating expression levels of ANXA1 in naive-to-treatment RRMS subjects inversely correlated with disease score and progression. At the cellular level, there was an impaired ANXA1 production by CD4⁺CD25^- conventional T and CD4⁺RORγt⁺ T (Th17) cells from RRMS subjects that associated with an increased migratory capacity in an in vitro model of blood brain barrier. Mechanistically, ANXA1 impaired monocyte maturation secondarily to STAT3 hyperactivation and potently reduced T cell activation, proliferation, and glycolysis. Together, these findings identify impaired disease resolution pathways in RRMS caused by dysregulated ANXA1 expression that could represent new potential therapeutic targets in RRMS.

Long-Lasting Anti-Inflammatory and Antinociceptive Effects of Acute Ammonium Glycyrrhizinate Administration: Pharmacological, Biochemical, and Docking Studies

The object of the study was to estimate the long-lasting effects induced by ammonium glycyrrhizinate (AG) after a single administration in mice using animal models of pain and inflammation together with biochemical and docking studies. A single intraperitoneal injection of AG was able to produce anti-inflammatory effects in zymosan-induced paw edema and peritonitis. Moreover, in several animal models of pain, such as the writhing test, the formalin test, and hyperalgesia induced by zymosan, AG administered 24 h before the tests was able to induce a strong antinociceptive effect. Molecular docking studies revealed that AG possesses higher affinity for microsomal prostaglandin E synthase type-2 compared to type-1, whereas it seems to locate better in the binding pocket of cyclooxygenase (COX)-2 compared to COX-1. These results demonstrated that AG induced anti-inflammatory and antinociceptive effects until 24-48 h after a single administration thanks to its ability to bind the COX/mPGEs pathway. Taken together, all these findings highlight the potential use of AG for clinical treatment of pain and/or inflammatory-related diseases.

Ac2-26 ameliorates lung ischemia-reperfusion injury via the eNOS pathway

BACKGROUND

Lung ischemia-reperfusion injury (LIRI) is a major complication after lung transplantation. Annexin A1 (AnxA1) ameliorates inflammation in various injured organs. This study aimed to determine the effects and mechanism of AnxA1 on LIRI after lung transplantation.

METHODS

Thirty-two rats were randomized into sham, saline, Ac2-26 and Ac2-26/L groups. Rats in the saline, Ac2-26 and Ac2-26/L groups underwent left lung transplantation and received saline, Ac2-26, and Ac2-26/L-NIO, respectively. After 24 h of reperfusion, serum and transplanted lung tissues were examined.

RESULTS

The partial pressure of oxygen (PaO₂) was increased in the Ac2-26 group compared to that in the saline group but was decreased by L-NIO treatment. In the Ac2-26 group, the wet-to-dry (W/D) weight ratios, total protein concentrations, proinflammatory factors and inducible nitric oxide synthase levels were notably decreased, but the concentrations of anti-inflammatory factors and endothelial nitric oxide synthase levels were significantly increased. Ac2-26 attenuated histological injury and cell apoptosis, and this improvement was reversed by L-NIO.

CONCLUSIONS

Ac2-26 reduced LIRI and improved alveoli-capillary permeability by inhibiting oxygen stress, inflammation and apoptosis. The protective effect of Ac2-26 on LIRI largely depended on the endothelial nitric oxide synthase pathway.

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.

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.

The role of non-resolving inflammation in atherosclerosis

Non-resolving inflammation drives the development of clinically dangerous atherosclerotic lesions by promoting sustained plaque inflammation, large necrotic cores, thin fibrous caps, and thrombosis. Resolution of inflammation is not merely a passive return to homeostasis, but rather an active process mediated by specific molecules, including fatty acid-derived specialized pro-resolving mediators (SPMs). In advanced atherosclerosis, there is an imbalance between levels of SPMs and proinflammatory lipid mediators, which results in sustained leukocyte influx into lesions, inflammatory macrophage polarization, and impaired efferocytosis. In animal models of advanced atherosclerosis, restoration of SPMs limits plaque progression by suppressing inflammation, enhancing efferocytosis, and promoting an increase in collagen cap thickness. This Review discusses the roles of non-resolving inflammation in atherosclerosis and highlights the unique therapeutic potential of SPMs in blocking the progression of clinically dangerous plaques.

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.

Annexin A1 and Autoimmunity: From Basic Science to Clinical Applications

Annexin A1 is a protein with multifunctional roles in innate and adaptive immunity mainly devoted to the regulation of inflammatory cells and the resolution of inflammation. Most of the data regarding Annexin A1 roles in immunity derive from cell studies and from mice models lacking Annexin A1 for genetic manipulation (Annexin A1^−/−); only a few studies sought to define how Annexin A1 is involved in human diseases. High levels of anti-Annexin A1 autoantibodies have been reported in systemic lupus erythematosus (SLE), suggesting this protein is implicated in auto-immunity. Here, we reviewed the evidence available for an association of anti-Annexin A1 autoantibodies and SLE manifestations, in particular in those cases complicated by lupus nephritis. New studies show that serum levels of Annexin A1 are increased in patients presenting renal complications of SLE, but this increment does not correlate with circulating anti-Annexin A1 autoantibodies. On the other hand, high circulating Annexin A1 levels cannot explain per se the development of autoantibodies since post-translational modifications are necessary to make a protein immunogenic. A hypothesis is presented here and discussed regarding the possibility that Annexin A1 undergoes post-translational modifications as a part of neutrophil extracellular traps (NETs) that are produced in response to viral, bacterial, and/or inflammatory triggers. In particular, focus is on the process of citrullination of Annexin A1, which takes place within NETs and that mimics, to some extent, other autoimmune conditions, such as rheumatoid arthritis, that are characterized by the presence of anti-citrullinated peptides in circulation. The description of pathologic pathways leading to modification of Annexin A1 as a trigger of autoimmunity is a cognitive evolution, but requires more experimental data before becoming a solid concept for explaining autoimmunity in human beings.

Annexin A1: Uncovering the Many Talents of an Old Protein

Annexin A1 (ANXA1) has long been classed as an anti-inflammatory protein due to its control over leukocyte-mediated immune responses. However, it is now recognized that ANXA1 has widespread effects beyond the immune system with implications in maintaining the homeostatic environment within the entire body due to its ability to affect cellular signalling, hormonal secretion, foetal development, the aging process and development of disease. In this review, we aim to provide a global overview of the role of ANXA1 covering aspects of peripheral and central inflammation, immune repair and endocrine control with focus on the prognostic, diagnostic and therapeutic potential of the molecule in cancer, neurodegeneration and inflammatory-based disorders.

Role of negative regulation of immune signaling pathways in neutrophil function

Polymorphonuclear neutrophils (PMNs) play a critical role in host defense against infection and in the resolution of inflammation. However, immune responses mediated by PMN must be tightly regulated to facilitate elimination of invading pathogens without inducing detrimental inflammation and host tissue damage. Specific engagement of cell surface immunoreceptors by a diverse range of extracellular signals regulates PMN effector functions through differential activation of intracellular signaling cascades. Although mechanisms of PMN activation mediated via cell signaling pathways have been well described, less is known about negative regulation of PMN function by immune signaling cascades. Here, we provide an overview of immunoreceptor-mediated negative regulation of key PMN effector functions including maturation, migration, phagocytosis, reactive oxygen species release, degranulation, apoptosis, and NET formation. Increased understanding of mechanisms of suppression of PMN effector functions may point to possible future therapeutic targets for the amelioration of PMN-mediated autoimmune and inflammatory diseases.

More than just innate affairs - on the role of annexins in adaptive immunity

In more than 30 years of research annexins have been demonstrated to regulate immune responses. The prototype member of this family, annexin (Anx) A1, has been widely recognized as an anti-inflammatory mediator affecting migration and cellular responses of various cell types of the innate immune system. Evidently, effects on innate immune cells also impact on the course of adaptive immune responses. Innate immune cells provide a distinct cytokine milieu during initiation of adaptive immunity which regulates the development of T cell responses. Moreover, innate immune cells such as monocytes can differentiate into dendritic cells and take an active part in T cell stimulation. Accumulating evidence shows a direct role for annexins in adaptive immunity. Anx A1, the annexin protein studied in most detail, has been shown to influence antigen presentation as well as T cells directly. Moreover, immune modulatory roles have been described for several other annexins such as Anx A2, Anx A4, Anx A5 and Anx A13. This review will focus on the involvement of Anx A1 and other annexins in central aspects of adaptive immunity, such as recruitment and activation of antigen presenting cells, T cell differentiation and the anti-inflammatory removal of apoptotic cells.

Annexin A1: shifting the balance towards resolution and repair

Epithelial barriers play an important role in regulating mucosal homeostasis. Upon injury, the epithelium and immune cells orchestrate repair mechanisms that re-establish homeostasis. This process is highly regulated by protein and lipid mediators such as Annexin A1 (ANXA1). In this review, we focus on the pro-repair properties of ANXA1.

Mast cells mediate early neutrophil recruitment and exhibit anti-inflammatory properties via the formyl peptide receptor 2/lipoxin A4 receptor

BACKGROUND AND PURPOSE

In recent years, studies have focused on the resolution of inflammation, which can be achieved by endogenous anti-inflammatory agonists such as Annexin A1 (AnxA1). Here, we investigated the effects of mast cells (MCs) on early LPS-induced neutrophil recruitment and the involvement of the AnxA1-formyl peptide receptor 2/ALX (FPR2/ALX or lipoxin A₄ receptor) pathway.

EXPERIMENTAL APPROACH

Intravital microscopy (IVM) was used to visualize and quantify the effects of LPS (10 μg per mouse i.p.) on murine mesenteric cellular interactions. Furthermore, the role that MCs play in these inflammatory responses was determined in vivo and in vitro, and effects of AnxA1 mimetic peptide Ac2-26 were assessed.

KEY RESULTS

LPS increased both neutrophil endothelial cell interactions within the mesenteric microcirculation and MC activation (determined by IVM and ruthenium red dye uptake), which in turn lead to the early stages of neutrophil recruitment. MC recruitment of neutrophils could be blocked by preventing the pro-inflammatory activation (using cromolyn sodium) or enhancing an anti-inflammatory phenotype (using Ac2-26) in MCs. Furthermore, MCs induced neutrophil migration in vitro, and MC stabilization enhanced the release of AnxA1 from neutrophils. Pharmacological approaches (such as the administration of FPR pan-antagonist Boc2, or the FPR2/ALX antagonist WRW4) revealed neutrophil FPR2/ALX to be important in this process.

CONCLUSIONS AND IMPLICATIONS

Data presented here provide evidence for a role of MCs, which are ideally positioned in close proximity to the vasculature, to act as sentinel cells in neutrophil extravasation and resolution of inflammation via the AnxA1-FPR2/ALX pathway.

Role of the glucocorticoid-induced leucine zipper gene in dexamethasone-induced inhibition of mouse neutrophil migration via control of annexin A1 expression

The glucocorticoid-induced leucine zipper (GILZ) gene is a pivotal mediator of the anti-inflammatory effects of glucocorticoids (GCs) that are known to regulate the function of both adaptive and innate immunity cells. Our aim was to investigate the role of GILZ in GC-induced inhibition of neutrophil migration, as this role has not been investigated before. We found that GILZ expression was induced by dexamethasone (DEX), a synthetic GC, in neutrophils, and that it regulated migration of these cells into inflamed tissues under DEX treatment. Of note, inhibition of neutrophil migration was not observed in GILZ-knockout mice with peritonitis that were treated by DEX. This was because DEX was unable to up-regulate annexin A1 (Anxa1) expression in the absence of GILZ. Furthermore, we showed that GILZ mediates Anxa1 induction by GCs by transactivating Anxa1 expression at the promoter level via binding with the transcription factor, PU.1. The present findings shed light on the role of GILZ in the mechanism of induction of Anxa1 by GCs. As Anxa1 is an important protein for the resolution of inflammatory response, GILZ may represent a new pharmacologic target for treatment of inflammatory diseases.-Ricci, E., Ronchetti, S., Pericolini, E., Gabrielli, E., Cari, L., Gentili, M., Roselletti, E., Migliorati, G., Vecchiarelli, A., Riccardi, C. Role of the glucocorticoid-induced leucine zipper gene in dexamethasone-induced inhibition of mouse neutrophil migration via control of annexin A1 expression.

Annexin A1 promotes timely resolution of inflammation in murine gout

Gout is a self-limited inflammatory disease caused by deposition of monosodium urate (MSU) crystals in the joints. Resolution of inflammation is an active process leading to restoration of tissue homeostasis. Here, we studied the role of Annexin A1 (AnxA1), a glucocorticoid-regulated protein that has anti-inflammatory and proresolving actions, in resolution of acute gouty inflammation. Injection of MSU crystals in the knee joint of mice induced inflammation that was associated with expression of AnxA1 during the resolving phase of inflammation. Neutralization of AnxA1 with antiserum or blockade of its receptor with BOC-1 (nonselective) or WRW₄ (selective) prevented the spontaneous resolution of gout. There was greater neutrophil infiltration after challenge with MSU crystals in AnxA1 knockout mice (AnxA1^-/- ) and delayed resolution associated to decreased neutrophil apoptosis and efferocytosis. Pretreatment of mice with AnxA1-active N-terminal peptide (Ac_2-26 ) decreased neutrophil influx, IL-1β, and CXCL1 production in periarticular joint. Posttreatment with Ac_2-26 decreased neutrophil accumulation, IL-1β, and hypernociception, and improved the articular histopathological score. Importantly, the therapeutic effects of Ac_2-26 were associated with increased neutrophils apoptosis and shortened resolution intervals. In conclusion, AnxA1 plays a crucial role in the context of acute gouty inflammation by promoting timely resolution of inflammation.

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.

Annexin-1 Mediates Microglial Activation and Migration via the CK2 Pathway during Oxygen-Glucose Deprivation/Reperfusion

Annexin-1 (ANXA1) has shown neuroprotective effects and microglia play significant roles during central nervous system injury, yet the underlying mechanisms remain unclear. This study sought to determine whether ANXA1 regulates microglial response to oxygen–glucose deprivation/reperfusion (OGD/R) treatment and to clarify the downstream molecular mechanism. In rat hippocampal slices, OGD/R treatment enhanced the ANXA1 expression in neuron, the formyl peptide receptor (FPRs) expression in microglia, and the microglial activation in the CA1 region (cornu ammonis 1). These effects were reversed by the FPRs antagonist Boc1. The cell membrane currents amplitude of BV-2 microglia (the microglial like cell-line) was increased when treated with Ac2-26, the N-terminal peptide of ANXA1. Ac2-26 treatment enhanced BV-2 microglial migration whereas Boc1 treatment inhibited the migration. In BV-2 microglia, both the expression of the CK2 target phosphorylated α-E-catenin and the binding of casein kinase II (CK2) with α-E-catenin were elevated by Ac2-26, these effects were counteracted by the CK2 inhibitor TBB and small interfering (si) RNA directed against transcripts of CK2 and FPRs. Moreover, both TBB and siRNA-mediated inhibition of CK2 blocked Ac2-26-mediated BV-2 microglia migration. Our findings indicate that ANXA1 promotes microglial activation and migration during OGD/R via FPRs, and CK2 target α-E-catenin phosphorylation is involved in this process.

Salivary Cytoprotective Proteins in Inflammation and Resolution during Experimental Gingivitis--A Pilot Study

Objective: The protective mechanisms that maintain periodontal homeostasis in gingivitis and prevent periodontal tissue destruction are poorly understood. The aim of this study was to identify changes in the salivary proteome during experimental gingivitis.

Study design: We used oral neutrophil quantification and whole saliva (WS) proteomics to assess changes that occur in the inflammatory and resolution phases of gingivitis in healthy individuals. Oral neutrophils and WS samples were collected and clinical parameters measured on days 0, 7, 14, 21, 28, and 35.

Results: Increased oral neutrophil recruitment and salivary cytoprotective proteins increased progressively during inflammation and decreased in resolution. Oral neutrophil numbers in gingival inflammation and resolution correlated moderately with salivary β-globin, thioredoxin, and albumin and strongly with collagen alpha-1 and G-protein coupled receptor 98.

Conclusions: Our results indicate that changes in salivary cytoprotective proteins in gingivitis are associated with a similar trend in oral neutrophil recruitment and clinical parameters.

Clinical relevance: We found moderate to strong correlations between oral neutrophil numbers and levels of several salivary cytoprotective proteins both in the development of the inflammation and in the resolution of gingivitis. Our proteomics approach identified and relatively quantified specific cytoprotective proteins in this pilot study of experimental gingivitis; however, future and more comprehensive studies are needed to clearly identify and validate those protein biomarkers when gingivitis is active.

Absence of Annexin A1 impairs host adaptive immunity against Mycobacterium tuberculosis in vivo

The role of Annexin A1 (ANXA1) in counter-regulating the activities of innate immune cells, such as the migration of neutrophils and monocytes, and the generation of pro-inflammatory mediators in various models of inflammatory and autoimmune diseases is well documented. However, while ANXA1 has been proposed as an important mediator of the adaptive immune response, its involvement in this respect has been less studied. Furthermore, while there have been numerous studies on the role of ANXA1 in inflammatory diseases, less has been reported on its influence in immunity against infection. A recent study reported a link between ANXA1 and tuberculosis, and proposed a model in which Mycobacterium tuberculosis exerts its virulence by manipulating the ANXA1-mediated host apoptotic response. This has prompted us to further investigate the role of ANXA1 in the pathogenesis of tuberculosis in vivo. Here, we show that ANXA1(-/-) mice are more susceptible to M. tuberculosis infection, as evidenced by a transient increase in the pulmonary bacterial burden, and exacerbated and disorganized granulomatous inflammation. These pathological manifestations correlated with an impaired ability of ANXA1(-/-) dendritic cells to activate naïve T cells, thereby supporting a role for ANXA1 in shaping the adaptive immunity against M. tuberculosis.

Hyperosmolar stress induces neutrophil extracellular trap formation: implications for dry eye disease

PURPOSE

To determine if hyperosmolar stress can stimulate human neutrophils to form neutrophil extracellular traps (NETs) and to investigate potential strategies to reduce formation of NETs (NETosis) in a hyperosmolar environment.

METHODS

Neutrophils were isolated from peripheral venous blood of healthy subjects and incubated in iso-osmolar (280 mOsM) or hyperosmolar (420 mOsM) media for 4 hours. Neutrophil extracellular traps were quantified using a PicoGreen dye assay to measure extracellular DNA. Two known inhibitors of NETosis, staurosporine and anti-β2 integrin blocking antibody, and two proresolution formyl peptide receptor 2 (FPR2) agonists, annexin/lipocortin-1 mimetic peptide and 15-epi-lipoxin A4, were evaluated as possible strategies to reduce hyperosmolarity-induced NETosis.

RESULTS

The amount of NETs induced by hyperosmolar medium (420 mOsM) increased linearly over time to 3.2 ± 0.3 times that induced by iso-osmolar medium at 4 hours (P < 0.05). NETosis increased exponentially with increasing osmolarity and was independent of the stimulus used to increase osmolarity. Upon neutrophil exposure to hyperosmolar stress, restoration of iso-osmolar conditions decreased NET formation by 52.7% ± 5% (P < 0.05) but did not completely abrogate it. Among the strategies tested to reduce NETosis in a hyperosmolar environment, annexin-1 peptide was the most efficacious.

CONCLUSIONS

Hyperosmolarity induces formation of NETs by neutrophils. This NETosis mechanism may explain the presence of excessive NETs on the ocular surface of patients with dry eye disease. Because they reduce hyperosmolarity-induced NETosis, FPR2 agonists may have therapeutic potential in these patients.

Alterations in the profile of blood neutrophil membrane receptors caused by in vivo adrenocorticotrophic hormone actions

Elevated levels of adrenocorticotrophic hormone (ACTH) mobilize granulocytes from bone marrow into the blood, although these neutrophils are refractory to a full migratory response into inflamed tissues. Here, we investigated the dependence of glucocorticoid receptor activation and glucocorticoid-regulated protein annexin A1 (ANXA1) on ACTH-induced neutrophilia and the phenotype of blood neutrophil after ACTH injection, focusing on adhesion molecule expressions and locomotion properties. ACTH injection (5 μg ip, 4 h) induced neutrophilia in wild-type (WT) mice and did not alter the elevated numbers of neutrophils in RU-38486 (RU)-pretreated or ANXA1(-/-) mice injected with ACTH. Neutrophils from WT ACTH-treated mice presented higher expression of Ly6G⁺ANXA1(high), CD18(high), CD62L(high), CD49(high), CXCR4(high), and formyl-peptide receptor 1 (FPR1(low)) than those observed in RU-pretreated or ANXA1(-/-) mice. The membrane phenotype of neutrophils collected from WT ACTH-treated mice was paralleled by elevated fractions of rolling and adherent leukocytes to the cremaster postcapillary venules together with impaired neutrophil migration into inflamed air pouches in vivo and in vitro reduced formyl-methionyl-leucyl-phenylalanine (fMLP) or stromal-derived factor-1 (SDF-1α)-induced chemotaxis. In an 18-h senescence protocol, neutrophils from WT ACTH-treated mice had a higher proportion of ANXAV(low)/CXCR4(low), and they were less phagocytosed by peritoneal macrophages. We conclude that alterations on HPA axis affect the pattern of membrane receptors in circulating neutrophils, which may lead to different neutrophil phenotypes in the blood. Moreover, ACTH actions render circulating neutrophils to a phenotype with early reactivity, such as in vivo leukocyte-endothelial interactions, but with impaired locomotion and clearance.

Proteome profiling of lipopolysaccharide induced L6 rat skeletal muscle cells response to flavonoids from Scutellaria baicalensis Georgi

Background

Scutellaria baicalensis Georgi is a commonly used medicinal herb in several Asian countries like Korea, China and Japan for thousands of years. It has been reported to have various medicinal properties such as anti-microbial, anti-inflammatory and anti-cancer effects. However, the anti-inflammatory mechanism of S. baicalensis G at proteome level has not yet been reported. Hence, we performed a proteome analysis to study differentially expressed proteins and its anti-inflammatory role in lipopolysaccharide (LPS) stimulated L6 skeletal muscle cells response to flavonoids isolated from S. baicalensis G.

Methods

For that, 150 μg of proteins from the L6 cells of the control (Vehicle only), LPS treated and flavonoid treated groups were separated using 18 cm, pH 4–7 IPG strips in the first dimension and resolved by 12% linear gradient SDS-polyacrylamide gel electrophoresis (SDS-PAGE). The silver stained gels were analyzed by using progenesis SameSpots software and twenty six differentially expressed protein spots (≥2 fold, p < 0.05) were selected for matrix assisted laser desorption ionization- time of flight mass spectroscopy/mass spectrometry (MALDI-TOF/MS) analysis. Also, the expression of COX-2, iNOS and Annexin A2 proteins were analyzed by western blot.

Results

Totally, 12 differentially expressed proteins were successfully identified by MALDI-TOF/MS and database searching, that’s involved in inflammatory responses such vimentin, T-box transcription factor TBX3, annexin A1, annexin A2 and annexin A5. In addition, flavonoids inhibited the expression of COX-2, iNOS and Annexin A2 proteins in LPS-stimulated L6 skeletal muscle cells.

Conclusions

The findings revealed that the flavonoids from S. baicalensis G. directly protect the LPS stimulated inflammation process in L6 cells and, would be helpful to study further the muscle cell inflammatory mechanism. This is the first proteome study provide the anti-inflammatory mechanism of flavonoids from S. baicalensis G. in LPS stimulated L6 skeletal muscle cells.

ICAM-2 regulates vascular permeability and N-cadherin localization through ezrin-radixin-moesin (ERM) proteins and Rac-1 signalling

Background

Endothelial junctions control functions such as permeability, angiogenesis and contact inhibition. VE-Cadherin (VECad) is essential for the maintenance of intercellular contacts. In confluent endothelial monolayers, N-Cadherin (NCad) is mostly expressed on the apical and basal membrane, but in the absence of VECad it localizes at junctions. Both cadherins are required for vascular development. The intercellular adhesion molecule (ICAM)-2, also localized at endothelial junctions, is involved in leukocyte recruitment and angiogenesis.

Results

In human umbilical vein endothelial cells (HUVEC), both VECad and NCad were found at nascent cell contacts of sub-confluent monolayers, but only VECad localized at the mature junctions of confluent monolayers. Inhibition of ICAM-2 expression by siRNA caused the appearance of small gaps at the junctions and a decrease in NCad junctional staining in sub-confluent monolayers. Endothelioma lines derived from WT or ICAM-2-deficient mice (IC2neg) lacked VECad and failed to form junctions, with loss of contact inhibition. Re-expression of full-length ICAM-2 (IC2 FL) in IC2neg cells restored contact inhibition through recruitment of NCad at the junctions. Mutant ICAM-2 lacking the binding site for ERM proteins (IC2 ΔERM) or the cytoplasmic tail (IC2 ΔTAIL) failed to restore junctions. ICAM-2-dependent Rac-1 activation was also decreased in these mutant cell lines. Barrier function, measured in vitro via transendothelial electrical resistance, was decreased in IC2neg cells, both in resting conditions and after thrombin stimulation. This was dependent on ICAM-2 signalling to the small GTPase Rac-1, since transendothelial electrical resistance of IC2neg cells was restored by constitutively active Rac-1. In vivo, thrombin-induced extravasation of FITC-labeled albumin measured by intravital fluorescence microscopy in the mouse cremaster muscle showed that permeability was increased in ICAM-2-deficient mice compared to controls.

Conclusions

These results indicate that ICAM-2 regulates endothelial barrier function and permeability through a pathway involving N-Cadherin, ERMs and Rac-1.

Dysregulation of anti-inflammatory annexin A1 expression in progressive Crohns Disease

Background

Development of inflammatory bowel disease (IBD) involves the interplay of environmental and genetic factors with the host immune system. Mechanisms contributing to immune dysregulation in IBD are not fully defined. Development of novel therapeutic strategies is focused on controlling aberrant immune response in IBD. Current IBD therapy utilizes a combination of immunomodulators and biologics to suppress pro-inflammatory effectors of IBD. However, the role of immunomodulatory factors such as annexin A1 (ANXA1) is not well understood. The goal of this study was to examine the association between ANXA1 and IBD, and the effects of anti-TNF-α, Infliximab (IFX), therapy on ANXA1 expression.

Methods

ANXA1 and TNF-α transcript levels in PBMC were measured by RT PCR. Clinical follow up included the administration of serial ibdQs. ANXA1 expression in the gut mucosa was measured by IHC. Plasma ANXA1 levels were measured by ELISA.

Results

We found that the reduction in ANXA1 protein levels in plasma coincided with a decrease in the ANXA1 mRNA expression in peripheral blood of IBD patients. ANXA1 expression is upregulated during IFX therapy in patients with a successful intervention but not in clinical non-responders. The IFX therapy also modified the cellular immune activation in the peripheral blood of IBD patients. Decreased expression of ANXA1 was detected in the colonic mucosa of IBD patients with incomplete resolution of inflammation during continuous therapy, which correlated with increased levels of TNF-α transcripts. Gut mucosal epithelial barrier disruption was evident by increased plasma bacterial 16S levels.

Conclusion

Loss of ANXA1 expression may support inflammation during IBD and can serve as a biomarker of disease progression. Changes in ANXA1 levels may be predictive of therapeutic efficacy.

Annexin-A1 regulates TLR-mediated IFN-β production through an interaction with TANK-binding kinase 1

TLRs play a pivotal role in the recognition of bacteria and viruses. Members of the family recognize specific pathogen sequences to trigger both MyD88 and TRIF-dependent pathways to stimulate a plethora of cells. Aberrant activation of these pathways is known to play a critical role in the development of autoimmunity and cancer. However, how these pathways are entirely regulated is not fully understood. In these studies, we have identified Annexin-A1 (ANXA1) as a novel regulator of TLR-induced IFN-β and CXCL10 production. We demonstrate that in the absence of ANXA1, mice produce significantly less IFN-β and CXCL10, and macrophages and plasmacytoid dendritic cells have a deficiency in activation following polyinosinic:polycytidylic acid administration in vivo. Furthermore, a deficiency in activation is observed in macrophages after LPS and polyinosinic:polycytidylic acid in vitro. In keeping with these findings, overexpression of ANXA1 resulted in enhanced IFN-β and IFN-stimulated responsive element promoter activity, whereas silencing of ANXA1 impaired TLR3- and TLR4-induced IFN-β and IFN-stimulated responsive element activation. In addition, we show that the C terminus of ANXA1 directly associates with TANK-binding kinase 1 to regulate IFN regulatory factor 3 translocation and phosphorylation. Our findings demonstrate that ANXA1 plays an important role in TLR activation, leading to an augmentation in the type 1 IFN antiviral cytokine response.

Presence of auto-antibody against two placental proteins, annexin A1 and vitamin D binding protein, in sera of women with pre-eclampsia

Pre-eclampsia (PE) is one of the most complex and life-threatening pregnancy disorders. PE is characterized by maternal hypertension and proteinuria. There is much evidence to support an immunological etiology for PE and auto-immunity is considered a predisposing factor for PE. The aim of the present study was the investigation of placental proteins as targets for auto-antibodies in PE patients. 2D-PAGE technique was used for separation of the total human placental proteins. After separation, protein spots were transferred to the PVDF membranes and blotted with sera from 20 PE patients and compared with membranes blotted with 20 sera from normal women. MALDI TOF/TOF mass spectrometry technique was used for identification of differentially blotted spots. Moreover, the results of mass analysis were confirmed using western blot with commercial mAbs and RT-PCR technique. The results indicated that two placental proteins, annexin A1 and vitamin D binding protein (DBP), might be targeted by PE sera. The expression of annexin A1 and DBP was also confirmed at RNA level using the RT-PCR technique. Furthermore, the mass results were confirmed by western blotting with commercial mAbs against two targeted proteins. The data of the present study suggest two new placental proteins, annexin A1 and DBP, as placental immune targets. Considering the relation among vitamin D deficiency, increased risk of PE, and the role of annexin A1 in the resolution of inflammation, production of antibody against annexin A1 and DBP may be considered a new auto-immune hypothesis in pre-eclampsia that calls for further investigation in future work.

Role and interactions of annexin A1 and oestrogens in the manifestation of sexual dimorphisms in cerebral and systemic inflammation

BACKGROUND AND PURPOSE

Gender differences in inflammation are well described, with females often showing more robust, oestrogen-associated responses. Here, we investigated the influence of gender, oestrogen and the anti-inflammatory protein annexin A1 (AnxA1) on lipopolysaccharide (LPS)-induced leukocyte-endothelial cell interactions in murine cerebral and mesenteric microvascular beds.

EXPERIMENTAL APPROACH

Intravital microscopy was used to visualize and quantify the effects of LPS (10 μg·per mouse i.p.) on leukocyte-endothelial interactions in male and female wild-type (WT) mice. The effects of ovariectomy ± oestrogen replacement were examined in WT and AnxA1-null (AnxA1(-/-) ) female mice.

KEY RESULTS

LPS increased leukocyte adherence in the cerebral and mesenteric beds of both male and female WT mice; females showed exacerbated responses in the brain versus males, but not the mesentery. Ovariectomy further enhanced LPS-induced adhesion in the brain but not the mesentery; its effects were reversed by oestrogen treatment. OVX AnxA1(-/-) mice also showed exaggerated adhesive responses to LPS in the brain. However, these were unresponsive to ovariectomy and, paradoxically, responded to oestrogen with a pronounced increase in basal and LPS-induced leukocyte adhesion in the cerebrovasculature.

CONCLUSIONS AND IMPLICATIONS

Our data confirm the fundamental role of AnxA1 in limiting the inflammatory response in the central and peripheral microvasculature. They also (i) show that oestrogen acts via an AnxA1-dependent mechanism to protect the cerebral, but not the mesenteric, vasculature from the damaging effects of LPS and (ii) reveal a paradoxical and potentially toxic effect of the steroid in potentiating the central response to LPS in the absence of AnxA1.