Annexin A1 and the Resolution of Inflammation: Modulation of Neutrophil Recruitment, Apoptosis, and Clearance

Roles of Annexin A protein family in autophagy regulation and therapy

Annexin A is a kind of calcium-dependent phospholipid-binding proteins, which contributes to the formation of the cell membranes and cytoskeleton and played a part as a membrane skeleton to stabilize lipid bilayer. Autophagy is one of the most important programmed cell death mechanisms. And recently some reports suggest that annexin A family protein is associated with autophagy for annexin A can regulate the formation of vesicular lipid membranes and promote cell exocytosis. In this review, we summarized the roles of annexin A protein family in autophagy regulation and targeted medical treatment for better diagnoses and therapies.

The Resolution Approach to Cystic Fibrosis Inflammation

Despite the high expectations associated with the recent introduction of CFTR modulators, airway inflammation still remains a relevant clinical issue in cystic fibrosis (CF). The classical anti-inflammatory drugs have shown very limited efficacy, when not being harmful, raising the question of whether alternative approaches should be undertaken. Thus, a better knowledge of the mechanisms underlying the aberrant inflammation observed in CF is pivotal to develop more efficacious pharmacology. In this respect, the observation that endogenous proresolving pathways are defective in CF and that proresolving mediators, physiologically generated during an acute inflammatory reaction, do not completely suppress inflammation, but promote resolution, tissue healing and microbial clearance, without compromising immune host defense mechanisms, opens interesting therapeutic scenarios for CF. In this mini-review, we present the current knowledge and perspectives of proresolving pharmacology in CF, focusing on the specialized proresolving lipid mediators and selected peptides.

Profiling tear proteomes of patients with unilateral relapsed Behcet's disease-associated uveitis using data-independent acquisition proteomics

Purpose

To explore whether unilateral relapse of Bechet’s disease-associated uveitis (BDU) causes differences in the tear proteome between the diseased and the contralateral quiescent eye and potential tear biomarkers for uveitis recurrence and disease monitoring.

Method

To minimize interindividual variations, bilateral tear samples were collected from the same patient (n = 15) with unilateral relapse of BDU. A data-independent acquisition (DIA) strategy was used to identify proteins that differed between active and quiescent eyes.

Results

A total of 1,797 confident proteins were identified in the tear samples, of which 381 (21.2%) were also highly expressed in various tissues and organs. Fifty-one (2.8%) proteins differed in terms of expression between tears in active and quiescent eyes, 9 (17.6%) of which were functionally related to immunity or inflammation. Alpha-1-acid glycoprotein 1 (fold change = 3.2, p = 0.007) was increased and Annexin A1 (fold change = −1.7, p < 0.001) was decreased in the tears of the active BDU eye compared to the contralateral quiescent eye.

Conclusions

A substantial amount of confident proteins were detected in the tears of BDU patients, including proteins that were deferentially expressed in the uveitis-relapsed eyes and the contralateral quiescent eyes. Some of these identified tear proteins play important roles in immune and inflammatory processes. Tear proteome might be a good source of biomarkers for uveitis.

Blame the signaling: Role of cAMP for the resolution of inflammation

A complex intracellular signaling governs different cellular responses in inflammation. Extracellular stimuli are sensed, amplified, and transduced through a dynamic cellular network of messengers converting the first signal into a proper response: production of specific mediators, cell activation, survival, or death. Several overlapping pathways are coordinated to ensure specific and timely induction of inflammation to neutralize potential harms to the tissue. Ideally, the inflammatory response must be controlled and self-limited. Resolution of inflammation is an active process that culminates with termination of inflammation and restoration of tissue homeostasis. Comparably to the onset of inflammation, resolution responses are triggered by coordinated intracellular signaling pathways that transduce the message to the nucleus. However, the key messengers and pathways involved in signaling transduction for resolution are still poorly understood in comparison to the inflammatory network. cAMP has long been recognized as an inducer of anti-inflammatory responses and cAMP-dependent pathways have been extensively exploited pharmacologically to treat inflammatory diseases. Recently, cAMP has been pointed out as coordinator of key steps of resolution of inflammation. Here, we summarize the evidence for the role of cAMP at inducing important features of resolution of inflammation.

Neutrophils in Tuberculosis-Associated Inflammation and Lung Pathology

Protective immunity to Mycobacterium tuberculosis (Mtb)—the causative agent of tuberculosis (TB)—is not fully understood but involves immune responses within the pulmonary airways which can lead to exacerbated inflammation and immune pathology. In humans, this inflammation results in lung damage; the extent of which depends on specific host pro-inflammatory processes. Neutrophils, though increasingly linked to the development of inflammatory disorders, have been less well studied in relation to TB-induced lung pathology. Neutrophils mode of action and their specialized functions can be directly linked to TB-specific lung tissue damage observed on patient chest X-rays at diagnosis and contribute to long-term pulmonary sequelae. This review discusses aspects of neutrophil activity associated with active TB, including the resulting inflammation and pulmonary impairment. It highlights the significance of neutrophil function on TB disease outcome and underlines the necessity of monitoring neutrophil function for better assessment of the immune response and severity of lung pathology associated with TB. Finally, we propose that some MMPs, ROS, MPO, S100A8/A9 and Glutathione are neutrophil-related inflammatory mediators with promising potential as targets for developing host-directed therapies for TB.

Annexin A1 Regulates NLRP3 Inflammasome Activation and Modifies Lipid Release Profile in Isolated Peritoneal Macrophages

Annexin A1 (AnxA1) is a potent anti-inflammatory protein that downregulates proinflammatory cytokine release. This study evaluated the role of AnxA1 in the regulation of NLRP3 inflammasome activation and lipid release by starch-elicited murine peritoneal macrophages. C57bl/6 wild-type (WT) and AnxA1-null (AnxA1^-/-) mice received an intraperitoneal injection of 1.5% starch solution for macrophage recruitment. NLRP3 was activated by priming cells with lipopolysaccharide for 3 h, followed by nigericin (1 h) or ATP (30 min) incubation. As expected, nigericin and ATP administration decreased elicited peritoneal macrophage viability and induced IL-1β release, more pronounced in the AnxA1^-/- cells than in the control peritoneal macrophages. In addition, nigericin-activated AnxA1^-/- macrophages showed increased levels of NLRP3, while points of co-localization of the AnxA1 protein and NLRP3 inflammasome were detected in WT cells, as demonstrated by ultrastructural analysis. The lipidomic analysis showed a pronounced release of prostaglandins in nigericin-stimulated WT peritoneal macrophages, while ceramides were detected in AnxA1^-/- cell supernatants. Different eicosanoid profiles were detected for both genotypes, and our results suggest that endogenous AnxA1 regulates the NLRP3-derived IL-1β and lipid mediator release in macrophages.

Targeting ANXA1 abrogates Treg-mediated immune suppression in triple-negative breast cancer

BACKGROUND

Regulatory T (Treg) cells play a negative role in anti-tumor immunity against triple-negative breast cancer, so it is of great significance to find the potential therapeutic target of Treg cells.

METHODS

First, Annexin A1 (ANXA1) expression and survival of patients with breast cancer were analyzed using TCGA data. Then plasma ANXA1 levels in patients with malignant and benign breast tumors were detected by ELISA. Next, the effect of ANXA1 on Treg cells was studied through suppressive assays, and how ANXA1 regulates the function of Treg cells was detected by RNA sequencing. Finally, the in vivo experiment in balb/c mice was conducted to test whether the ANXA1 blocker Boc1 could shrink tumors and affect the function of Treg cells.

RESULTS

Our data suggest that ANXA1 expression is associated with lower survival and a higher risk of breast malignancy. Suppressive assays show that ANXA1 can enhance the inhibition function of Treg cells. RNA-Sequencing results indicate that Boc1 could reduce the expression of granzyme A mRNA in Treg cells. Animal experiments have been done to show that Boc1 can reduce tumor size and down regulate Treg cell function.

CONCLUSIONS

ANXA1 can enhance the function of Treg cells and reduce the survival rate of patients with breast cancer. Targeting ANXA1 can reduce Treg cell function and shrink breast tumors.

Phagocytosis of Apoptotic Cells in Resolution of Inflammation

Efficient inflammation resolution is important not only for the termination of the inflammatory response but also for the restoration of tissue integrity. An integral process to resolution of inflammation is the phagocytosis of dying cells by macrophages, known as efferocytosis. This function is mediated by a complex and well-orchestrated network of interactions amongst specialized phagocytic receptors, bridging molecules, as well as “find-me” and “eat-me” signals. Efferocytosis serves not only as a waste disposal mechanism (clearance of the apoptotic cells) but also promotes a pro-resolving phenotype in efferocytic macrophages and thereby termination of inflammation. Alterations in cellular metabolism are critical for shaping the phenotype and function of efferocytic macrophages, thus, representing an important determinant of macrophage plasticity. Impaired efferocytosis can result in inflammation-associated pathologies or autoimmunity. The present mini review summarizes current knowledge regarding the mechanisms regulating macrophage efferocytosis during clearance of inflammation.

The role of annexin A1 in the modulation of the NLRP3 inflammasome

Annexins are well-known Ca²⁺ phospholipid-binding proteins, which have a wide variety of cellular functions. The role of annexin A1 (AnxA1) in the innate immune system has focused mainly on the anti-inflammatory and proresolving properties through its binding to the formyl-peptide receptor 2 (FPR2)/ALX receptor. However, studies suggesting an intracellular role of AnxA1 are emerging. In this study, we aimed to understand the role of AnxA1 for interleukin (IL)-1β release in response to activators of the nucleotide-binding domain leucine-rich repeat (NLR) and pyrin domain containing receptor 3 (NLRP3) inflammasome. Using AnxA1 knockout mice, we observed that AnxA1 is required for IL-1β release in vivo and in vitro. These effects were due to reduction of transcriptional levels of IL-1β, NLRP3 and caspase-1, a step called NLRP3 priming. Moreover, we demonstrate that AnxA1 co-localize and directly bind to NLRP3, suggesting the role of AnxA1 in inflammasome activation is independent of its anti-inflammatory role via FPR2. Therefore, AnxA1 regulates NLRP3 inflammasome priming and activation in a FPR2-independent manner.

New insights into the novel anti-inflammatory mode of action of glucocorticoids

Inflammation is a physiological intrinsic host response to injury meant for removal of noxious stimuli and maintenance of homeostasis. It is a defensive body mechanism that involves immune cells, blood vessels and molecular mediators of inflammation. Glucocorticoids (GCs) are steroidal hormones responsible for regulation of homeostatic and metabolic functions of body. Synthetic GCs are the most useful anti-inflammatory drugs used for the treatment of chronic inflammatory diseases such as asthma, chronic obstructive pulmonary disease (COPD), allergies, multiple sclerosis, tendinitis, lupus, atopic dermatitis, ulcerative colitis, rheumatoid arthritis and osteoarthritis whereas, the long term use of GCs are associated with many side effects. The anti-inflammatory and immunosuppressive (desired) effects of GCs are usually mediated by transrepression mechanism whereas; the metabolic and toxic (undesired) effects are usually manifested by transactivation mechanism. Though GCs are most potent anti-inflammatory and immunosuppressive drugs, the common problem associated with their use is GC resistance. Several research studies are rising to comprehend these mechanisms, which would be helpful in improving the GC resistance in asthma and COPD patients. This review aims to focus on identification of new drug targets in inflammation which will be helpful in the resolution of inflammation. The ample understanding of GC mechanisms of action helps in the development of novel anti-inflammatory drugs for the treatment of inflammatory and autoimmune disease with reduced side effects and minimal toxicity.

Mechanisms of Mixed Th1/Th2 Responses in Mice Induced by Albizia julibrissin Saponin Active Fraction by in Silico Analysis

The purified active fraction of Albizia julibrissin saponin (AJSAF) is an ideal adjuvant candidate that improves antigen-specific both cellular and humoral immune responses and elicits mixed Th1/Th2 responses, but its mechanisms remain unclear. The key features of action of AJSAF were investigated in mice immunized with Newcastle disease virus-based recombinant influenza vaccine (rL-H5) and AJSAF at the same leg (AJSAF+rL-H5) or different legs (AJSAF/rL-H5). The adjuvant activity of AJSAF on rL-H5 is strictly dependent on their spatial colocalization. Serum H5 antigen (H5Ag)-specific IgG, IgG1, IgG2a, and IgG2b antibody titers in AJSAF+rL-H5 group were significantly higher than those in AJSAF/rL-H5 group. The mechanisms of selectivity of Th1 or Th2 in mice induced by AJSAF was explored by the transcriptomic and proteomic profiles of H5Ag-stimulated splenocytes from the immunized mice using gene microarray and two-dimensional difference gel electrophoresis coupled with matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. Compared to rL-H5 alone, AJSAF/rL-H5 induced more differentially expressed genes (DEGs) than AJSAF+rL-H5, whereas AJSAF+rL-H5 upregulated higher mRNA expression of Th1 (T-bet, IFN-γ, TNF-α, IL-12β, and IL-12Rβ1) and Th2 (IL-10 and AICDA) immune response genes. The neutrophil response and its derived S100A8 and S100A9 might be involved in the AJSAF-mediated Th1 response. Meanwhile, AJSAF might induce the adaptive immune responses by improving a local innate immune microenvironment. These findings expanded the current knowledge on the mechanisms of action of saponin-based adjuvants, and provided new insights into how adjuvants shape adaptive immune responses.

New Advances in Targeting the Resolution of Inflammation: Implications for Specialized Pro-Resolving Mediator GPCR Drug Discovery

Chronic inflammation is a component of numerous diseases including autoimmune, metabolic, neurodegenerative, and cancer. The discovery and characterization of specialized pro-resolving mediators (SPMs) critical to the resolution of inflammation, and their cognate G protein-coupled receptors (GPCRs) has led to a significant increase in the understanding of this physiological process. Approximately 20 ligands, including lipoxins, resolvins, maresins, and protectins, and 6 receptors (FPR2/ALX, GPR32, GPR18, chemerin₁, BLT₁, and GPR37) have been identified highlighting the complex and multilayered nature of resolution. Therapeutic efforts in targeting these receptors have proved challenging, with very few ligands apparently progressing through to preclinical or clinical development. To date, some knowledge gaps remain in the understanding of how the activation of these receptors, and their downstream signaling, results in efficient resolution via apoptosis, phagocytosis, and efferocytosis of polymorphonuclear leukocytes (mainly neutrophils) and macrophages. SPMs bind and activate multiple receptors (ligand poly-pharmacology), while most receptors are activated by multiple ligands (receptor pleiotropy). In addition, allosteric binding sites have been identified signifying the capacity of more than one ligand to bind simultaneously. These fundamental characteristics of SPM receptors enable alternative targeting strategies to be considered, including biased signaling and allosteric modulation. This review describes those ligands and receptors involved in the resolution of inflammation, and highlights the most recent clinical trial results. Furthermore, we describe alternative mechanisms by which these SPM receptors could be targeted, paving the way for the identification of new therapeutics, perhaps with greater efficacy and fidelity.

Cyclic AMP Regulates Key Features of Macrophages via PKA: Recruitment, Reprogramming and Efferocytosis

Macrophages are central to inflammation resolution, an active process aimed at restoring tissue homeostasis following an inflammatory response. Here, the effects of db-cAMP on macrophage phenotype and function were investigated. Injection of db-cAMP into the pleural cavity of mice induced monocytes recruitment in a manner dependent on PKA and CCR2/CCL2 pathways. Furthermore, db-cAMP promoted reprogramming of bone-marrow-derived macrophages to a M2 phenotype as seen by increased Arg-1/CD206/Ym-1 expression and IL-10 levels (M2 markers). Db-cAMP also showed a synergistic effect with IL-4 in inducing STAT-3 phosphorylation and Arg-1 expression. Importantly, db-cAMP prevented IFN-γ/LPS-induced macrophage polarization to M1-like as shown by increased Arg-1 associated to lower levels of M1 cytokines (TNF-α/IL-6) and p-STAT1. In vivo, db-cAMP reduced the number of M1 macrophages induced by LPS injection without changes in M2 and Mres numbers. Moreover, db-cAMP enhanced efferocytosis of apoptotic neutrophils in a PKA-dependent manner and increased the expression of Annexin A1 and CD36, two molecules associated with efferocytosis. Finally, inhibition of endogenous PKA during LPS-induced pleurisy impaired the physiological resolution of inflammation. Taken together, the results suggest that cAMP is involved in the major functions of macrophages, such as nonphlogistic recruitment, reprogramming and efferocytosis, all key processes for inflammation resolution.

Suppression of autoreactive T and B lymphocytes by anti-annexin A1 antibody in a humanized NSG murine model of systemic lupus erythematosus

Systemic lupus erythematosus is a chronic inflammatory disease which involves multiple organs. Self-specific B and T cells play a main role in the pathogenesis of lupus and have been defined as a logical target for selective therapy. The protein annexin A1 (ANX A1) is a modulator of the immune system involving many cell types. An abnormal expression of ANX A1 was found on activated B and T cells during autoimmunity, suggesting its importance as a potential therapeutic target. We hypothesize that it may be possible to down-regulate the activity of autoreactive T and B cells from lupus patients in a humanized immunodeficient mouse model by treating them with an antibody against ANX A1. When cultured in the presence of anti-ANX A1, peripheral blood mononuclear cells (PBMC) from lupus patients showed a decreased number of immunoglobulin (Ig)G anti-dsDNA antibody-secreting plasma cells, decreased T cell proliferation and expression of activation markers and increased B and T cell apoptosis. We employed a humanized model of SLE by transferring PBMCs from lupus patients to immunodeficient non-obese diabetic-severe combined immunodeficient (NOD-SCID) mice. The humanized animals presented autoantibodies, proteinuria and immunoglobulin deposition in the renal glomeruli. Treatment of these NOD-SCID mice with an anti-ANX A1 antibody prevented appearance of anti-DNA antibodies and proteinuria, while the phosphate-buffered saline (PBS)-injected animals had high levels after the transfer. The treatment reduced the levels of autoantibodies to several autoantigens, lupus-associated cytokines and disease symptoms.

Inflammation resolution and specialized pro-resolving lipid mediators in CNS diseases

Introduction: Inflammation resolution induced by specialized pro-resolving lipid mediators (SPMs) is a new concept. The application of SPMs is a promising therapeutic strategy that can potentially supersede anti-inflammatory drugs. Most CNS diseases are associated with hyperreactive inflammatory damage. CNS inflammation causes irreversible neuronal loss and permanent functional impairments. Given the high mortality and morbidity rates, the investigation of therapeutic strategies to ameliorate inflammatory damage is necessary.Areas covered: In this review, we explore inflammation resolution in CNS disorders. We discuss the underlying mechanisms and dynamic changes of SPMs and their precursors in neurological diseases and examine how this can potentially be incorporated into the clinic. References were selected from PubMed; most were published between 2010 and 2019.Expert opinion: Inflammation resolution is a natural process that emerges after acute or chronic inflammation. The evidence that SPMs can effectively ameliorate hyperreactive inflammation, shorten resolution time and accelerate tissue regeneration in CNS disorders. Adjuvants and nanotechnology offer opportunities for SPM drug design; however, more preclinical studies are necessary to investigate basic, critical issues such as safety.

Expression levels and prognostic values of annexins in liver cancer

Annexins are a superfamily of calcium-dependent phospholipid-binding proteins that are implicated in a wide range of biological processes. The annexin superfamily comprises 13 members in humans (ANXAs), the majority of which are frequently dysregulated in cancer. However, the expression patterns and prognostic values of ANXAs in liver cancer are currently largely unknown. The present study aimed to analyze the expression levels of ANXAs and survival data in patients with liver cancer from the Oncomine, GEPIA, Kaplan-Meier plotter and cBioPortal for Cancer Genomics databases. The results demonstrated that ANXA1, A2, A3, A4 and A5 were upregulated, whereas ANXA10 was downregulated in liver cancer compared with normal liver tissues. The expression of ANXA10 was associated with pathological stage. High expression levels of ANXA2 and A5 were significantly associated with poor overall survival (OS) rate whereas ANXA7 and A10 were associated with increased OS. The prognostic values of ANXAs in liver cancer were determined based on sex and clinical stage, which revealed that ANXA2, A5, A7 and A10 were associated with OS in male, but not in female patients. In addition, the potential biological functions of ANXAs were identified by Gene Ontology functional annotation and Kyoto Encyclopedia of Genes Genomes pathway analysis; the results demonstrated that ANXAs may serve a role in liver cancer through the neuroactive ligand-receptor interaction pathway. In conclusion, the results of the present study suggested that ANXA1, A2, A3, A4, A5 and A10 may be potential therapeutic targets for liver cancer treatment, and that ANXA2, A5, A7 and A10 may be potential prognostic biomarkers of liver cancer.

An Update to Calcium Binding Proteins

Ca²⁺ binding proteins (CBP) are of key importance for calcium to play its role as a pivotal second messenger. CBP bind Ca²⁺ in specific domains, contributing to the regulation of its concentration at the cytosol and intracellular stores. They also participate in numerous cellular functions by acting as Ca²⁺ transporters across cell membranes or as Ca²⁺-modulated sensors, i.e. decoding Ca²⁺ signals. Since CBP are integral to normal physiological processes, possible roles for them in a variety of diseases has attracted growing interest in recent years. In addition, research on CBP has been reinforced with advances in the structural characterization of new CBP family members. In this chapter we have updated a previous review on CBP, covering in more depth potential participation in physiopathological processes and candidacy for pharmacological targets in many diseases. We review intracellular CBP that contain the structural EF-hand domain: parvalbumin, calmodulin, S100 proteins, calcineurin and neuronal Ca²⁺ sensor proteins (NCS). We also address intracellular CBP lacking the EF-hand domain: annexins, CBP within intracellular Ca²⁺ stores (paying special attention to calreticulin and calsequestrin), proteins that contain a C2 domain (such as protein kinase C (PKC) or synaptotagmin) and other proteins of interest, such as regucalcin or proprotein convertase subtisilin kexins (PCSK). Finally, we summarise the latest findings on extracellular CBP, classified according to their Ca²⁺ binding structures: (i) EF-hand domains; (ii) EGF-like domains; (iii) ɣ-carboxyl glutamic acid (GLA)-rich domains; (iv) cadherin domains; (v) Ca²⁺-dependent (C)-type lectin-like domains; (vi) Ca²⁺-binding pockets of family C G-protein-coupled receptors.

Mild steel welding is associated with alterations in circulating levels of cancer-related proteins

Welding fumes were recently classified as carcinogenic to humans and worldwide millions work as welders or perform welding operations. The purpose of this study was to identify new biomarkers of welding-induced carcinogenesis. We evaluated a panel of 91 putative cancer-related proteins in serum in a cohort of welders working with mild steel (n = 77) and controls (n = 94) from southern Sweden sampled on two occasions 6-year apart using a longitudinal analysis (linear mixed models). The significant results from the longitudinal analysis were tested for reproducibility in welders (n = 88) and controls (n = 69) sampled once during the same sampling period as timepoint 1 or timepoint 2 (linear regression models), i.e., in a cross-sectional setting. The models were adjusted for age, body-mass index, and use of snus. All study participants were non-smokers at recruitment. Exposure to welding fumes was assessed using questionnaires and respirable dust measurement in the breathing zone that was adjusted for personal respiratory protection equipment. The median respirable dust in welders was 0.7 (0.2-4.2) and 0.5 (0.1-1.9) mg/m³ at the first and second timepoints, respectively. We identified 14 cancer-related proteins that were differentially expressed in welders versus controls in the longitudinal analysis, out of which three were also differentially expressed in the cross-sectional analysis (cross-sectional group). Namely, syndecan 1 (SDC1), folate receptor 1 (FOLR1), and secreted protein acidic and cysteine rich (SPARC) were downregulated, in welders compared with controls. In addition, FOLR1 was negatively associated with years welding. Disease and function analysis indicated that the top proteins are related to lung cancer as well as cell invasion and migration. Our study indicates that moderate exposure to welding fumes is associated with changes in circulating levels of putative cancer-related proteins, out of which FOLR1 showed a clear dose-response relationship. It is, however, unclear to which extent these changes are adaptive or potential early biomarkers of cancer.

Inflammatory and Pro-resolving Mediators in Frontotemporal Dementia and Alzheimer's Disease

Chronic inflammation contributes to neuronal death in Alzheimer's disease (AD) and frontotemporal dementia (FTD). Here we evaluated inflammatory and pro-resolving mediators in AD and behavioural variant of FTD (bvFTD) patients compared with controls, since neuroinflamamtion is a common feature in both diseases. Ninety-eight subjects were included in this study, divided into AD (n = 32), bvFTD (n = 30), and control (n = 36) groups. The levels of hsCRP, IL-1β, IL-6, TNF, and TGF-β1, as well as annexin A1 (AnxA1) and lipoxin A4 (LXA4) were measured in blood and cerebrospinal fluid (CSF). The expression profile of AnxA1 was evaluated in peripheral blood mononuclear cells (PBMCs) as well the distribution of ANXA1 rs2611228 polymorphism. We found reduced peripheral levels of hsCRP and TNF in AD compared with bvFTD patients and controls, and increased levels of TGF-β1 in AD compared to controls. Moreover, reduced plasma levels of AnxA1 were observed in bvFTD compared to AD and controls. There was a significant cleavage of AnxA1 in PBMCs in both dementia groups. The results suggest differential regulation of inflammatory and pro-resolving mediators in bvFTD and AD, while AnxA1 cleavage may impair pro-resolving mechanisms in both groups.

The GR-ANXA1 pathway is a pathological player and a candidate target in epilepsy

Immune changes occur in experimental and clinical epilepsy. Here, we tested the hypothesis that during epileptogenesis and spontaneous recurrent seizures (SRS) an impairment of the endogenous anti-inflammatory pathway glucocorticoid receptor (GR)-annexin A1 (ANXA1) occurs. By administrating exogenous ANXA1, we studied whether pharmacological potentiation of the anti-inflammatory response modifies seizure activity and pathophysiology. We used an in vivo model of temporal lobe epilepsy based on intrahippocampal kainic acid (KA) injection. Video-electroencephalography, molecular biology analyses on brain and peripheral blood samples, and pharmacological investigations were performed in this model. Human epileptic cortices presenting type II focal cortical dysplasia (IIa and b), hippocampi with or without hippocampal sclerosis (HS), and available controls were used to study ANXA1 expression. A decrease of phosphorylated (phospho-) GR and phospho-GR/tot-GR protein expression occurred in the hippocampus during epileptogenesis. Downstream to GR, the anti-inflammatory protein ANXA1 remained at baseline levels while inflammation installed and endured. In peripheral blood, ANXA1 and corticosterone levels showed no significant modifications during disease progression except for an early and transient increase poststatus epilepticus. These results indicate inadequate ANXA1 engagement over time and in these experimental conditions. By analyzing human brain specimens, we found that where significant inflammation exists, the pattern of ANXA1 immunoreactivity was abnormal because the typical perivascular ANXA1 immunoreactivity was reduced. We next asked whether potentiation of the endogenous anti-inflammatory mechanism by ANXA1 administration modifies the disease pathophysiology. Although with varying efficacy, administration of exogenous ANXA1 somewhat reduced the time spent in seizure activity as compared to saline. These results indicate that the anti-inflammatory GR-ANXA1 pathway is defective during experimental seizure progression. The prospect of pharmacologically restoring or potentiating this endogenous anti-inflammatory mechanism as an add-on therapeutic strategy for specific forms of epilepsy is proposed.-Zub, E., Canet, G., Garbelli, R., Blaquiere, M., Rossini, L., Pastori, C., Sheikh, M., Reutelingsperger, C., Klement, W., de Bock, F., Audinat, E., Givalois, L., Solito, E., Marchi, N. The GR-ANXA1 pathway is a pathological player and a candidate target in epilepsy.

Synthesis, characterization, anti-proliferative properties and DNA binding of benzochromene derivatives: Increased Bax/Bcl-2 ratio and caspase-dependent apoptosis in colorectal cancer cell line

3-Amino-1-aryl-1H-benzo[f]chromene-2-carbonitrile derivatives were synthesized from three-component reaction of arylaldehyde, malononitrile and 2-naphthol in the presence of 1, 4-bis(4-ferrocenylbutyl)piperazine as a new catalyst. Cytotoxic potencies of the compounds were tested on HT-29 cells. 3-Amino-1-(4-fluorophenyl)-1H-benzo[f]chromene-2-carbonitrile (4c) was more active among these compounds and was selected for further studies. Apoptosis was investigated by acridine orange/ethidium bromide (AO/EtBr) double staining and flow cytometry. The qRT-PCR was used to analyze the expression of pro- and anti-apoptotic genes. The binding attributes of 4c with calf thymus DNA (ctDNA) was examined using multi-spectroscopic measurements. We found that 4c had potent cytotoxic activity against HT-29 cells with an IC₅₀ value of 60 µM through induction of cell cycle arrest in the sub-G1 phase and apoptosis. RT-PCR analysis demonstrated down-regulation of Bcl-2 expression, while the expression of Bax, caspase-3, -8 and -9 genes was up-regulated in HT-29 cells incubated with 4c compared with control cells. These studies revealed that 4c interacts with DNA through groove binding mode with the intrinsic binding constant (K_b) of 3 × 10² M^-1. Thus, 4c is a valuable candidate for further evaluation as a new series of potent chemotherapeutic family in colon cancer treatment.

Extracellular annexin-A1 promotes myeloid/granulocytic differentiation of hematopoietic stem/progenitor cells via the Ca2+/MAPK signalling transduction pathway

Annexin A1 (AnxA1) modulates neutrophil life span and bone marrow/blood cell trafficking thorough activation of formyl-peptide receptors (FPRs). Here, we investigated the effect of exogenous AnxA1 on haematopoiesis in the mouse. Treatment of C57BL/6 mice with recombinant AnxA1 (rAnxA1) reduced the granulocyte–macrophage progenitor (GMP) population in the bone marrow, enhanced the number of mature granulocytes Gr-1⁺Mac-1⁺ in the bone marrow as well as peripheral granulocytic neutrophils and increased expression of mitotic cyclin B1 on hematopoietic stem cells (HSCs)/progenitor cells (Lin⁻Sca-1⁺c-Kit⁺: LSK). These effects were abolished by simultaneous treatment with Boc-2, an FPR pan-antagonist. In in vitro studies, rAnxA1 reduced both HSC (LSKCD90^lowFLK-2⁻) and GMP populations while enhancing mature cells (Gr1⁺Mac1⁺). Moreover, rAnxA1 induced LSK cell proliferation (Ki67⁺), increasing the percentage of cells in the S/G2/M cell cycle phases and reducing Notch-1 expression. Simultaneous treatment with WRW4, a selective FPR2 antagonist, reversed the in vitro effects elicited by rAnxA1. Treatment of LSK cells with rAnxA1 led to phosphorylation of PCLγ2, PKC, RAS, MEK, and ERK1/2 with increased expression of NFAT2. In long-term bone marrow cultures, rAnxA1 did not alter the percentage of LSK cells but enhanced the Gr-1⁺Mac-1⁺ population; treatment with a PLC (U73122), but not with a PKC (GF109203), inhibitor reduced rAnxA1-induced phosphorylation of ERK1/2 and Elk1. Therefore, we identify here rAnxA1 as an inducer of HSC/progenitor cell differentiation, favouring differentiation of the myeloid/granulocytic lineage, via Ca²⁺/MAPK signalling transduction pathways.

Control of expression and activity of peroxisome proliferated-activated receptor γ by Annexin A1 on microglia during efferocytosis

Annexin A1 (AnxA1) is a protein secreted by phagocytic cells which plays a pivotal role on the resolution of inflammation by enhancing phagocytosis carried out by phagocytes. Which factors and intracellular mechanisms are linked to such actions exerted by AnxA1 are yet to be completely understood. In order to investigate such, BV2 microglial cells were transfected with plasmids aimed at down-modulating AnxA1 expression and also treated with exogenous recombinant rAnxA1; gene and protein expression of proliferated-activated receptor γ (PPARγ) and CD36, STAT6 phosphorylation and phagocytosis of apoptotic neurons were investigated. Down-modulating AnxA1 in BV2 cells impaired gene and protein expression of PPARγ, effects reversed by treatment with recombinant AnxA1 (rAnxA1). Lower levels of CD36 were also verified in AnxA1 down-modulated BV2 cells. AnxA1-mediated phagocytosis of apoptotic cells was abrogated due to blockade of PPARγ activation, and in AnxA1 down-modulated cells exogenous AnxA1 failed to exert any effects on phagocytosis. Lower levels of STAT6/pSTAT6 in AnxA1 down-modulated BV2 cells suggest the involvement of this transcription factor with PPARγ and CD36 synthesis and actions. Data here shown suggest that there is a probable connection between AnxA1, PPARγ, and CD36, which must all act in association in order for efferocytosis to occur properly. AnxA1-mediated phosphorylation of STAT6 is probably involved with intracellular pathways involving PPARγ and CD36 actions. These data evidence that PPARγ/CD36 play a role on AnxA1-mediated efferocytosis in microglial cells. SIGNIFICANCE OF THE STUDY: The findings of this work provide evidence that the glucocorticoid-mediated protein annexin A1 modulates PPARγ expression and that PPARγ is important for annexin A1-mediated efferocytosis. Only recently the interaction between these two factors has begun to be explored, and knowledge on associated cell mechanisms are still scarce. Elucidating how annexin A1 and PPARγ interact with one another provides basis for further research aimed at understanding molecular pathways and cell signaling events involved with these factors, expanding existing knowledge on the anti-inflammatory effects of such factors.

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.

Fighting the Fire: Mechanisms of Inflammatory Gene Regulation by the Glucocorticoid Receptor

For many decades, glucocorticoids have been widely used as the gold standard treatment for inflammatory conditions. Unfortunately, their clinical use is limited by severe adverse effects such as insulin resistance, cardiometabolic diseases, muscle and skin atrophies, osteoporosis, and depression. Glucocorticoids exert their effects by binding to the Glucocorticoid Receptor (GR), a ligand-activated transcription factor which both positively, and negatively regulates gene expression. Extensive research during the past several years has uncovered novel mechanisms by which the GR activates and represses its target genes. Genome-wide studies and mouse models have provided valuable insight into the molecular mechanisms of inflammatory gene regulation by GR. This review focusses on newly identified target genes and GR co-regulators that are important for its anti-inflammatory effects in innate immune cells, as well as mutations within the GR itself that shed light on its transcriptional activity. This research progress will hopefully serve as the basis for the development of safer immune suppressants with reduced side effect profiles.

New therapeutic targets for the prevention of infectious acute exacerbations of COPD: role of epithelial adhesion molecules and inflammatory pathways

Chronic respiratory diseases are among the leading causes of mortality worldwide, with the major contributor, chronic obstructive pulmonary disease (COPD) accounting for approximately 3 million deaths annually. Frequent acute exacerbations (AEs) of COPD (AECOPD) drive clinical and functional decline in COPD and are associated with accelerated loss of lung function, increased mortality, decreased health-related quality of life and significant economic costs. Infections with a small subgroup of pathogens precipitate the majority of AEs and consequently constitute a significant comorbidity in COPD. However, current pharmacological interventions are ineffective in preventing infectious exacerbations and their treatment is compromised by the rapid development of antibiotic resistance. Thus, alternative preventative therapies need to be considered. Pathogen adherence to the pulmonary epithelium through host receptors is the prerequisite step for invasion and subsequent infection of surrounding structures. Thus, disruption of bacterial-host cell interactions with receptor antagonists or modulation of the ensuing inflammatory profile present attractive avenues for therapeutic development. This review explores key mediators of pathogen-host interactions that may offer new therapeutic targets with the potential to prevent viral/bacterial-mediated AECOPD. There are several conceptual and methodological hurdles hampering the development of new therapies that require further research and resolution.

Cdk5 Deletion Enhances the Anti-inflammatory Potential of GC-Mediated GR Activation During Inflammation

The suppression of activated pro-inflammatory macrophages during immune response has a major impact on the outcome of many inflammatory diseases including sepsis and rheumatoid arthritis. The pro- and anti-inflammatory functions of macrophages have been widely studied, whereas their regulation under immunosuppressive treatments such as glucocorticoid (GC) therapy is less well-understood. GC-mediated glucocorticoid receptor (GR) activation is crucial to mediate anti-inflammatory effects. In addition, the anti-cancer drug roscovitine, that is currently being tested in clinical trials, was recently described to regulate inflammatory processes by inhibiting different Cdks such as cyclin-dependent kinase 5 (Cdk5). Cdk5 was identified as a modulator of inflammatory processes in different immune cells and furthermore described to influence GR gene expression in the brain. Whether roscovitine can enhance the immunosuppressive effects of GCs and if the inhibition of Cdk5 affects GR gene regulatory function in innate immune cells, such as macrophages, has not yet been investigated. Here, we report that roscovitine enhances the immunosuppressive Dexamethasone (Dex) effect on the inducible nitric oxide synthase (iNos) expression, which is essential for immune regulation. Cdk5 deletion in macrophages prevented iNos protein and nitric oxide (NO) generation after a combinatory treatment with inflammatory stimuli and Dex. Cdk5 deletion in macrophages attenuated the GR phosphorylation on serine 211 after Dex treatment alone and in combination with inflammatory stimuli, but interestingly increased the GR-dependent anti-inflammatory target gene dual-specificity phosphatase 1 (Dusp1, Mkp1). Mkp1 phosphatase activity decreases the activation of its direct target p38Mapk, reduced iNos expression and NO production upon inflammatory stimuli and Dex treatment in the absence of Cdk5. Taken together, we identified Cdk5 as a potential novel regulator of NO generation in inflammatory macrophages under GC treatment. Our data suggest that GC treatment in combination with specific Cdk5 inhibtior(s) provides a stronger suppression of inflammation and could thus replace high-dose GC therapy which has severe side effects in the treatment of inflammatory diseases.

Functional secretome analysis reveals Annexin-A1 as important paracrine factor derived from fetal mesenchymal stem cells in hepatic regeneration

BACKGROUND

Human mesenchymal stem/stromal cells (MSCs) and their secreted molecules exert beneficial effects in injured tissues by promoting tissue regeneration and angiogenesis and by inhibiting inflammation and fibrosis. We have previously demonstrated that the therapeutic activity of fetal MSCs derived from amniotic fluid (AF-MSCs) and their hepatic progenitor-like cells (HPL) is mediated by paracrine effects in a mouse model of acute hepatic failure (AHF).

METHODS

Herein, we have combined proteomic profiling of the AF-MSCs and HPL cell secretome with ex vivo and in vivo functional studies to identify specific soluble factors, which underpin tissue regeneration in AHF.

FINDINGS

The anti-inflammatory molecule Annexin-A1 (ANXA1) was detected at high levels in both AF-MSC and HPL cell secretome. Further functional analyses revealed that the shRNA-mediated knock-down of ANXA1 in MSCs (shANXA1-MSCs) decreased their proliferative, clonogenic and migratory potential, as well as their ability to differentiate into HPL cells. Liver progenitors (oval cells) from AHF mice displayed reduced proliferation when cultured ex vivo in the presence of conditioned media from shANXA1-MSCs compared to control MSCs secretome. Intra-hepatic delivery of conditioned media from control MSCs but not shANXA1-MSCs reduced liver damage and circulating levels of pro-inflammatory cytokines in AHF.

INTERPRETATION

Collectively, our study uncovers secreted Annexin-A1 as a novel effector of MSCs in liver regeneration and further underscores the potential of cell-free therapeutic strategies for liver diseases. FUND: Fondation Santé, GILEAD Asklipeios Grant, Fellowships of Excellence - Siemens, IKY, Reinforcement of Postdoctoral Researchers, IKY.

Plasminogen and the Plasminogen Receptor, Plg-RKT, Regulate Macrophage Phenotypic, and Functional Changes

Inflammation resolution is an active process that functions to restore tissue homeostasis. Clearance of apoptotic leukocytes by efferocytosis at inflammatory sites plays an important role in inflammation resolution and induces remarkable macrophage phenotypic and functional changes. Here, we investigated the effects of deletion of either plasminogen (Plg) or the Plg receptor, Plg-R_KT, on the resolution of inflammation. In a murine model of pleurisy, the numbers of total mononuclear cells recruited to the pleural cavity were significantly decreased in both Plg^−/− and Plg-R_KT^−/− mice, a response associated with decreased levels of the chemokine CCL2 in pleural exudates. Increased percentages of M1-like macrophages were determined in pleural lavages of Plg^−/− and Plg-R_KT^−/− mice without significant changes in M2-like macrophage percentages. In vitro, Plg and plasmin (Pla) increased CD206/Arginase-1 expression and the levels of IL-10/TGF-β (M2 markers) while decreasing IFN/LPS-induced M1 markers in murine bone-marrow-derived macrophages (BMDMs) and human macrophages. Furthermore, IL4-induced M2-like polarization was defective in BMDMs from both Plg^−/− and Plg-R_KT^−/− mice. Mechanistically, Plg and Pla induced transient STAT3 phosphorylation, which was decreased in Plg^−/− and Plg-R_KT^−/− BMDMs after IL-4 or IL-10 stimulation. The extents of expression of CD206 and Annexin A1 (important for clearance of apoptotic cells) were reduced in Plg^−/− and Plg-R_KT^−/− macrophage populations, which exhibited decreased phagocytosis of apoptotic neutrophils (efferocytosis) in vivo and in vitro. Taken together, these results suggest that Plg and its receptor, Plg-R_KT, regulate macrophage polarization and efferocytosis, as key contributors to the resolution of inflammation.

Purinergic Signaling and Cochlear Injury-Targeting the Immune System?

Hearing impairment is the most common sensory deficit, affecting more than 400 million people worldwide. Sensorineural hearing losses currently lack any specific or efficient pharmacotherapy largely due to the insufficient knowledge of the pathomechanism. Purinergic signaling plays a substantial role in cochlear (patho)physiology. P2 (ionotropic P2X and the metabotropic P2Y) as well as adenosine receptors expressed on cochlear sensory and non-sensory cells are involved mostly in protective mechanisms of the cochlea. They are implicated in the sensitivity adjustment of the receptor cells by a K⁺ shunt and can attenuate the cochlear amplification by modifying cochlear micromechanics. Cochlear blood flow is also regulated by purines. Here, we propose to comprehend this field with the purine-immune interactions in the cochlea. The role of harmful immune mechanisms in sensorineural hearing losses has been emerging in the horizon of cochlear pathologies. In addition to decreasing hearing sensitivity and increasing cochlear blood supply, influencing the immune system can be the additional avenue for pharmacological targeting of purinergic signaling in the cochlea. Elucidating this complexity of purinergic effects on cochlear functions is necessary and it can result in development of new therapeutic approaches in hearing disabilities, especially in the noise-induced ones.

Neutrophil Extracellular Traps protein composition is specific for patients with Lupus nephritis and includes methyl-oxidized αenolase (methionine sulfoxide 93)

NETs constitute a network of DNA and proteins released by neutrophils in response to infectious and immunologic triggers. NET proteins are recognized as autoantigens in ANCA vasculitis; limited knowledge is available in other autoimmune pathologies. The composition of NETs produced ex vivo by resting and Phorbol-myristate acetate (PMA) stimulated neutrophils was analyzed by high-throughput Fusion Orbitrap technology in 16 patients with Systemic Lupus Erythematosus/Lupus nephritis (9 SLE/7 LN) and in 11 controls. Seven-hundred proteins were characterized and specific fingerprints discriminated LN from SLE. We focused on methyl-oxidized αenolase (methionine sulfoxide 93) that was markedly increased in NETs from LN and was localized in NET filaments in tight connection and outlying DNA. The isotype of anti-αenolase antibodies was IgG2 in LN and IgG4 in other autoimmune glomerulonephritis (Membranous Nephropathy, MN); serum anti-αenolase IgG2 were higher in LN than in SLE and absent in MN. The same IgG2 antibodies recognized 5 epitopes of the protein one containing methionine sulphoxide 93. In conclusion, specific NET protein fingerprints characterize different subsets of SLE; methyl-oxidized αenolase is over-expressed in LN. Circulating anti-αenolase IgG2 recognize the oxidized epitope and are high in serum of LN patients. Post-translational modified NET proteins contribute to autoimmunity in patients with LN.

Up-regulation of ANXA1 suppresses polymorphonuclear neutrophil infiltration and myeloperoxidase activity by activating STAT3 signaling pathway in rat models of myocardial ischemia-reperfusion injury

Myocardial ischemia-reperfusion injury (MIRI) is recognized as a major cause of morbidity and mortality which is commonly associated with coronary artery disease. In recent studies, annexin A1 gene (ANXA1) has been discovered to be involved in the treatment for MIRI. In this study, the primary focus was on the molecular mechanism of ANXA1 in polymorphonuclear neutrophil (PMN) infiltration and myeloperoxidase (MPO) activity in rats with MIRI. Initially, microarray analysis was carried out in order to identify differentially expressed genes. Moreover, a rat model of MIRI was established for evaluating the expression of ANXA1, signal transducer and activator of transcription 3 (STAT3) and vascular endothelial growth factor (VEGF) in myocardial tissues. Following this, the ANXA1 vector, siRNA-ANXA1, and Stattic (inhibitor of STAT3 signaling pathway) were utilized for analyzing the regulatory role of ANXA1 in physiological indexes, hemodynamic parameters, inflammatory factors, myocardial infarct size, MPO activity, PMN infiltration, and apoptosis of PMNs. Furthermore, the relationship between ANXA1 and STAT3 signaling pathway was analyzed. Initially, a reduction in the expression of ANXA1, STAT3 and VEGF in myocardial tissues of MIRI rats was found. To elaborate, overexpressed ANXA1 inhibited levels of inflammatory factors, the activation of PMN infiltration, reduced the degree of PMN infiltration, and decreased the apoptosis of PMNs. More importantly, down-regulated ANXA1 inhibited the activation of STAT3 signaling pathway, which thereby suppressed VEGF expression. With this all taken into account, the present study presents that up-regulated ANXA1 inhibits PMN infiltration and MPO activity by activation of STAT3 signaling pathway in rats with MIRI.

Annexin A1-mediated inhibition of inflammatory cytokines may facilitate the resolution of inflammation in acute radiation-induced lung injury

The present study evaluated the role of annexin A1 (ANXA1) in the treatment of acute radiation-induced lung injury (RILI) and investigated the mechanism of its action. The expression of ANXA1, interleukin-6 (IL-6) and myeloperoxidase (MPO) in the plasma of patients with RILI prior to and following hormonotherapy was assessed by enzyme-linked immunosorbent assay. The association of plasma ANXA1 concentration with clinical effect, and the correlation between the expression of ANXA1 and that of IL-6 and MPO were evaluated. ANXA1 was overexpressed or knocked down in a macrophage cell line, and its impact on IL-6 and MPO expression was measured. Following glucocorticoid hormonotherapy, patients with RILI exhibited a higher plasma concentration of ANXA1 compared with that prior to treatment, while IL-6 and MPO levels were lower. The concentration of ANXA1 in plasma was negatively correlated with IL-6 and MPO levels, with a correlation coefficient of -0.492 and -0.437, respectively (P<0.001). The increasing concentration of ANXA1 in plasma following treatment was associated with the clinical effect in patients with RILI (P=0.007). The expression levels of of IL-6 and MPO were inhibited both in the cytoplasm and in the culture solution, when ANXA1 expression was upregulated in a macrophage cell line. In conclusion, ANXA1 inhibited the synthesis and secretion of IL-6 and MPO inflammatory cytokines, indicating that ANXA1 may have therapeutic potential as a treatment target for RILI.

Voices from the dead: The complex vocabulary and intricate grammar of dead cells

Of the roughly one million cells per second dying throughout the body, the vast majority dies by apoptosis, the predominant form of regulated cell death in higher organisms. Long regarded as mere waste, apoptotic cells are now recognized as playing a prominent and active role in homeostatic maintenance, especially resolution of inflammation, and in the sculpting of tissues during development. The activities associated with apoptotic cells are continually expanding, with more recent studies demonstrating their ability to modulate such vital functions as proliferation, survival, differentiation, metabolism, migration, and angiogenesis. In each case, the role of apoptotic cells is active, exerting their effects via new activities acquired during the apoptotic program. Moreover, the capacity to recognize and respond to apoptotic cells is not limited to professional phagocytes. Most, if not all, cells receive and integrate an array of signals from cells dying in their vicinity. These signals comprise a form of biochemical communication. As reviewed in this chapter, this communication is remarkably sophisticated; each of its three critical steps-encoding, transmission, and decoding of the apoptotic cell's "message"-is endowed with exquisite robustness. Together, the abundance and intricacy of the variables at each step comprise the vocabulary and grammar of the language by which dead cells achieve their post-mortem voice. The combinatorial complexity of the resulting communication network permits dying cells, through the signals they emit and the responses those signals elicit, to partake of an expanded role in homeostasis, acting as both sentinels of environmental change and agents of adaptation.

The Resolution of Intestinal Inflammation: The Peace-Keeper's Perspective

The uncontrolled activation of the immune system toward antigens contained in the gut lumen in genetically predisposed subjects is believed to be the leading cause of inflammatory bowel disease (IBD). Two not mutually exclusive hypotheses can explain the pathogenic process leading to IBD. The first and mostly explored hypothesis states that the loss of tolerance toward gut microbiota antigens generates an aberrant inflammatory response that is perpetuated by continuous and unavoidable exposure to the triggering antigens. However, the discovery that the resolution of inflammation is not the mere consequence of clearing inflammatory triggers and diluting pro-inflammatory factors, but rather an active process in which molecular and cellular elements are involved, implies that a defect in the pro-resolving mechanisms might cause chronic inflammation in different immune-mediated diseases, including IBD. Here we review data on pro-resolving and counter-regulatory mechanisms involved in the resolution of inflammation, aiming to identify their possible involvement in the pathogenesis of IBD.

Apoptotic cell-derived extracellular vesicles: structure–function relationships

Apoptosis is an essential process for normal physiology and plays a key role in the resolution of inflammation. Clearance of apoptotic cells (ACs) involves complex signalling between phagocytic cells, ACs, and the extracellular vesicles (EVs) they produce. Here, we discuss apoptotic cell-derived extracellular vesicles (ACdEVs) and how their structure relates to their function in AC clearance and the control of inflammation, focussing on the ACdEV proteome. We review the current knowledge, ongoing work and future directions for research in this field.

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.

miR-196a regulates the proliferation, invasion and migration of esophageal squamous carcinoma cells by targeting ANXA1

MicroRNA (miR)-196a is upregulated in various types of malignancy, including esophageal squamous cell carcinoma (ESCC); however, its role in ESCC is currently unclear. The present study aimed to investigate the biological role and molecular mechanism of miR-196a in ESCC. The expression levels of miR-196a in 25 tumor tissues and adjacent non-tumor tissues from patients with ESCC were measured by reverse transcription-quantitative polymerase chain reaction. In addition, miR-196a expression levels were assessed in the human normal esophageal epithelial cell line Het-1A and the ESCC cell line EC109. The effects of miR-196a on the proliferation, apoptosis, invasion and migration of EC109 cells were determined by MTT, flow cytometry and Transwell assays, respectively. A luciferase reporter assay and western blotting were performed to confirm the target gene of miR-196a, and to explore the molecular mechanism underlying the effects of miR-196a on regulation of ESCC cell phenotypes. The results demonstrated that miR-196a was markedly upregulated in ESCC tissues and EC109 cells. In addition, miR-196a downregulation suppressed EC109 cell proliferation, invasion and migration, but did not affect apoptosis. Annexin A1 (ANXA1) was demonstrated to be a direct target gene of miR-196a. ANXA1 protein knockdown reversed the effects of miR-196a inhibition on EC109 cell proliferation, invasion and migration. Furthermore, alongside the downregulation of miR-196a and the increase in ANXA1 expression, cyclooxygenase 2 (COX2), matrix metalloproteinase (MMP)-2 and Snail were downregulated, and E-cadherin was upregulated in EC109 cells. The results of the present study suggested that miR-196a may act as an oncogene in ESCC, and that miR-196a may regulate the proliferation, invasion and migration of ESCC cells by targeting ANXA1. Subsequently, ANXA1 may further modulate the expression levels of COX2, MMP-2, Snail and E-cadherin. In conclusion, the miR-196a/ANXA1 axis may represent a potential therapeutic target in ESCC.

Triggering the Resolution of Immune Mediated Inflammatory Diseases: Can Targeting Leukocyte Migration Be the Answer?

Leukocyte recruitment is a pivotal process in the regulation and resolution of an inflammatory episode. It is vital for the protective responses to microbial infection and tissue damage, but is the unwanted reaction contributing to pathology in many immune mediated inflammatory diseases (IMIDs). Indeed, it is now recognized that patients with IMIDs have defects in at least one, if not multiple, check-points regulating the entry and exit of leukocytes from the inflamed site. In this review, we will explore our understanding of the imbalance in recruitment that permits the accumulation and persistence of leukocytes in IMIDs. We will highlight old and novel pharmacological tools targeting these processes in an attempt to trigger resolution of the inflammatory response. In this context, we will focus on cytokines, chemokines, known pro-resolving lipid mediators and potential novel lipids (e.g., sphingosine-1-phosphate), along with the actions of glucocorticoids mediated by 11-beta hydroxysteroid dehydrogenase 1 and 2.

Interaction between a 3D collagen matrix used for periodontal soft tissue regeneration and T-lymphocytes: An in vitro pilot study

Previous experimental models showed that activation of the immune system, particularly T cells, is required for optimal healing following wounds or surgery in the oral cavity. Therefore, studies to explore the interactions between the immune system and the collagen matrix are mandated. The specific aim of the present study was to analyze the interactions between T lymphocytes and a resorbable three-dimensional (3D) collagen matrix routinely used for soft tissue regeneration during periodontal surgery. Peripheral venous blood samples were collected from five patients. Following Ficoll-Paque separation, mononuclear cells were grown on fully resorbable 3D collagen matrices for 5 days. Lymphocytes were analyzed by flow cytometry for different surface markers, including CD4, CD8, CD38 and CD69. Cell viability and late apoptosis/necrosis were assessed in each group using an apoptosis assay based on Annexin V/propidium iodide staining. After 5 days in contact with the collagen matrix, the T cells expressed different surface markers. The overall T cell population increased significantly in the collagen matrix group compared to the respective controls (31.9±6.5 vs. 38.7±3.8%). CD8 and CD69 also increased significantly compared to their controls (CD69: 19.7±3.0 vs. 27.1±4.5% for collagen vs. control groups). At the same time, CD4 and CD38 expression was similar in both groups. Viability and apoptosis/necrosis were also identical in the samples and controls. These results show that the interaction between the collagen matrix and the immune cells stimulated activation of T cells and did not impair the healing process.

Extracellular vesicles from Echinococcus granulosus larval stage: Isolation, characterization and uptake by dendritic cells

The secretion of extracellular vesicles (EVs) in helminth parasites is a constitutive mechanism that promotes survival by improving their colonization and adaptation in the host tissue. In the present study, we analyzed the production of EVs from supernatants of cultures of Echinococcus granulosus protoscoleces and metacestodes and their interaction with dendritic cells, which have the ability to efficiently uptake and process microbial antigens, activating T lymphocytes. To experimentally increase the release of EVs, we used loperamide, a calcium channel blocker that increases the cytosolic calcium level in protoscoleces and EV secretion. An exosome-like enriched EV fraction isolated from the parasite culture medium was characterized by dynamic light scattering, transmission electron microscopy, proteomic analysis and immunoblot. This allowed identifying many proteins including: small EV markers such as TSG101, SDCBP, ALIX, tetraspanins and 14-3-3 proteins; proteins involved in vesicle-related transport; orthologs of mammalian proteins involved in the immune response, such as basigin, Bp29 and maspardin; and parasite antigens such as antigen 5, P29 and endophilin-1, which are of special interest due to their role in the parasite-host relationship. Finally, studies on the EVs-host cell interaction demonstrated that E. granulosus exosome-like vesicles were internalized by murine dendritic cells, inducing their maturation with increase of CD86 and with a slight down-regulation in the expression of MHCII molecules. These data suggest that E. granulosus EVs could interfere with the antigen presentation pathway of murine dendritic cells inducing immunoregulation in the host. Further studies are needed to better understand the role of these vesicles in parasite survival and as diagnostic markers and new vaccines.

Human cystic echinococcosis, caused by chronic infection with the larval stage of Echinococcus granulosus, affects over 1 million people worldwide. This helminth parasite secretes numerous excretory/secretory products that are in contact with host tissues where it establishes hydatid cysts. In this study, we comprehensively characterized extracellular vesicles (EVs) from E. granulosus protoscoleces and metacestodes, and demonstrated for the first time that the exosome-like vesicles from helminths can interact with host dendritic cells and carry several immunoregulatory proteins. This study provides valuable data on cestode-host immune communication. Nevertheless, further research on EVs is needed to fully understand their role in the parasite-host interface and obtain new data concerning their function as therapeutic markers and diagnostic tools.

Neutrophil-Initiated Myocardial Inflammation and Its Modulation by B-Type Natriuretic Peptide: A Potential Therapeutic Target

Activation of neutrophils is a critically important component of the innate immune response to bacterial and chemical stimuli, and culminates in the “neutrophil burst”, which facilitates neutrophil phagocytosis via the release of superoxide anion radical (O₂⁻) from NADPH oxidase. Excessive and/or prolonged neutrophil activation results in substantial tissue injury and increases in vascular permeability—resulting in sustained tissue infiltration with neutrophils and monocytes, and persistent vasomotor dysfunction. Cardiovascular examples of such changes include acute and chronic systolic and diastolic heart failure (“heart failure with preserved ejection fraction”), and the catecholamine-induced inflammatory disorder takotsubo syndrome. We have recently demonstrated that B-type natriuretic peptide (BNP), acting via inhibition of activation of neutrophil NADPH oxidase, is an important negative modulator of the “neutrophil burst”, though its effectiveness in limiting tissue injury is partially lost in acute heart failure. The potential therapeutic implications of these findings, regarding the development of new means of treating both acute and chronic cardiac injury states, are discussed.

Transcriptomic and proteomic host response to Aspergillus fumigatus conidia in an air-liquid interface model of human bronchial epithelium

Aspergillus fumigatus (A. fumigatus) is a wide-spread fungus that is a potent allergen in hypersensitive individuals but also an opportunistic pathogen in immunocompromised patients. It reproduces asexually by releasing airborne conidiospores (conidia). Upon inhalation, fungal conidia are capable of reaching the airway epithelial cells (AECs) in bronchial and alveolar tissues. Previous studies have predominantly used submerged monolayer cultures for studying this host-pathogen interaction; however, these cultures do not recapitulate the mucocililary differentiation phenotype of the in vivo epithelium in the respiratory tract. Thus, the aim of this study was to use well-differentiated primary human bronchial epithelial cells (HBECs) grown at the air-liquid interface (ALI) to determine their transcriptomic and proteomic responses following interaction with A. fumigatus conidia. We visualized conidial interaction with HBECs using confocal laser scanning microscopy (CLSM), and applied NanoString nCounter and shotgun proteomics to assess gene expression changes in the human cells upon interaction with A. fumigatus conidia. Western blot analysis was used to assess the expression of top three differentially expressed proteins, CALR, SET and NUCB2. CLSM showed that, unlike submerged monolayer cultures, well-differentiated ALI cultures of primary HBECs were estimated to internalize less than 1% of bound conidia. Nevertheless, transcriptomic and proteomic analyses revealed numerous differentially expressed host genes; these were enriched for pathways including apoptosis/autophagy, translation, unfolded protein response and cell cycle (up-regulated); complement and coagulation pathways, iron homeostasis, nonsense mediated decay and rRNA binding (down-regulated). CALR and SET were confirmed to be up-regulated in ALI cultures of primary HBECs upon exposure to A. fumigatus via western blot analysis. Therefore, using transcriptomics and proteomics approaches, ALI models recapitulating the bronchial epithelial barrier in the conductive zone of the respiratory tract can provide novel insights to the molecular response of bronchial epithelial cells upon exposure to A. fumigatus conidia.

Antiinflammatory peptides: current knowledge and promising prospects

BACKGROUND

Inflammation is part of the regular host reaction to injury or infection caused by toxic factors, pathogens, damaged cells, irritants, and allergens. Antiinflammatory peptides (AIPs) are present in all living organisms, and many peptides from herbal, mammalian, bacterial, and marine origins have been shown to have antimicrobial and/or antiinflammatory properties.

METHODS

In this study, we investigated the effects of antiinflammatory peptides on inflammation, and highlighted the underlying mechanisms responsible for these effects.

RESULTS

In multicellular organisms, including humans, AIPs constitute an essential part of their immune system. In addition, numerous natural and synthetic AIPs are effective immunomodulators and can interfere with signal transduction pathways involved in inflammatory cytokine expression. Among them, some peptides such as antiflammin, N-acetyl-seryl-aspartyl-lysyl-proline (Ac-SDKP), and those derived from velvet antler proteins, bee venom, horse fly salivary gland, and bovine β-casein have received considerable attention over the past few years.

CONCLUSION

This article presents an overview on the major properties and mechanisms of action associated with AIPs as immunomodulatory, chemotactic, antioxidant, and antimicrobial agents. In addition, the results of various studies dealing with effects of AIPs on numerous classical models of inflammation are reviewed and discussed.

Inflammatory cells and their non-coding RNAs as targets for treating myocardial infarction

Myocardial infarction triggers infiltration of several types of immune cells that coordinate both innate and adaptive immune responses. These play a dual role in post-infarction cardiac remodeling by initiating and resolving inflammatory processes, which needs to occur in a timely and well-orchestrated way to ensure a reestablishment of normalized cardiac functions. Thus, therapeutic modulation of immune responses might have benefits for infarct patients. While such strategies have shown great potential in treating cancer, applications in the post-infarction context have been disappointing. One challenge has been the complexity and plasticity of immune cells and their functions in cardiac regulation and healing. The types appear in patterns that are temporally and spatially distinct, while influencing each other and the surrounding tissue. A comprehensive understanding of the immune cell repertoire and their regulatory functions following infarction is sorely needed. Processes of cardiac remodeling trigger additional genetic changes that may also play critical roles in the aftermath of cardiovascular disease. Some of these changes involve non-coding RNAs that play crucial roles in the regulation of immune cells and may, therefore, be of therapeutic interest. This review summarizes what is currently known about the functions of immune cells and non-coding RNAs during post-infarction wound healing. We address some of the challenges that remain and describe novel therapeutic approaches under development that are based on regulating immune responses through non-coding RNAs in the aftermath of the disease.

Annexins in Influenza Virus Replication and Pathogenesis

Influenza A viruses (IAVs) are important human respiratory pathogens which cause seasonal or periodic endemic infections. IAV can result in severe or fatal clinical complications including pneumonia and respiratory distress syndrome. Treatment of IAV infections is complicated because the virus can evade host immunity through antigenic drifts and antigenic shifts, to establish infections making new treatment options desirable. Annexins (ANXs) are a family of calcium and phospholipid binding proteins with immunomodulatory roles in viral infections, lung injury, and inflammation. A current understanding of the role of ANXs in modulating IAV infection and host responses will enable the future development of more effective antiviral therapies. This review presents a comprehensive understanding of the advances made in the field of ANXs, in particular, ANXA1 and IAV research and highlights the importance of ANXs as a suitable target for IAV therapy.