Impaired T cell activation and increased Th2 lineage commitment in Annexin-1-deficient T cells

Implication of the Annexin 1/FPR axis in leishmanial exosome-mediated Leishmania major skin hyperpathogenesis

Introduction

Exosomes produced by the protozoan parasite Leishmania (LeishEXO) are well-established drivers of virulence, though mechanisms underlying their exacerbation of experimental leishmaniasis remain elusive. Expression of Annexin A1 (ANXA1), a protein implicated in exosome-mediated pathologies and viral internalization, has been shown to correlate with cutaneous leishmaniasis severity. Given ANXA1's regulation of myeloid cells - the canonical hosts for Leishmania - we studied the potential role of ANXA1 and its receptors FPR1/2 in exerting LeishEXO's effects.

Methods

Murine and in vitro ANXA1-/- models were used to study the generation of protective TH1 responses during experimental L. major infection with and without LeishEXO. Recruitment of inflammatory cells was assessed using a peritoneal cell recruitment assay and immunophenotyping, and production of inflammatory mediators was measured using a cytokine and chemokine array. Treatment of experimental models with FPR2 antagonist WRW4 and FPR1/2 agonist WKYMVm was used to delineate the role of the FPR/ANXA1 axis in LeishEXO-mediated hyperpathogenesis.

Results

We established that ANXA1 deficiency prohibits LeishEXO-mediated pathogenesis and myeloid cell infection, with minimal alterations to adaptive and innate immune phenotypes. FPR2 blockade with WRW4 similarly inhibited leishmanial hyperpathogenesis, while direct activation of FPRs with WKYMVm enhanced infection and recapitulated the LeishEXO-mediated phenotype. This research describes LeishEXO's utilization of the ANXA1/FPR axis to facilitate parasitic internalization and pathogenesis, which may be leveraged in the development of therapeutics for leishmaniasis.

Structural characterization of Russula griseocarnosa polysaccharide and its improvement on hematopoietic function

The hematopoietic function of a polysaccharide derived from Russula griseocarnosa was demonstrated in K562 cells, and subsequently purified through chromatography to obtain RGP1. RGP1 is a galactan composed of 1,6-α-D-Galp as the main chain, with partial substitutions. A -CH3 substitution was detected at O-3 of 1,6-α-D-Galp. The possible branches at O-2 of 1,6-α-D-Galp was α-L-Fucp. In mice with cyclophosphamide (CTX)-induced hematopoietic dysfunction, RGP1 alleviated bone marrow damage and multinucleated giant cell infiltration of the spleen, increased the number of long-term hematopoietic stem cells, and regulated the levels of myeloid cells in the peripheral blood. Furthermore, RGP1 promoted the differentiation of activated T cells and CD4+ T cells without affecting natural killer cells and B cells. Proteomic analysis, detection of cytokines, and western blotting revealed that RGP1 could alleviate hematopoietic dysfunction by promoting the activation of CD4+ T cells and the Janus kinase/ signal transducer and activator of transcription 3 pathway. The present study provides experimental evidence to support the application of RGP1 in CTX-induced hematopoietic dysfunction.

Annexin A1 improves immune responses and control of tissue parasitism during Leishmania amazonensis infection in BALB/c mice

Leishmaniases, a group of diseases caused by the species of the protozoan parasite Leishmania, remains a significant public health concern worldwide. Host immune responses play a crucial role in the outcome of Leishmania infections, and several mediators that regulate inflammatory responses are potential targets for therapeutic approaches. Annexin A1 (AnxA1), an endogenous protein endowed with anti-inflammatory and pro-resolving properties, has emerged as a potential player. We have shown that during L. braziliensis infection, deficiency of AnxA1 exacerbates inflammatory responses but does not affect parasite burden. Here, we have investigated the role of AnxA1 in L. amazonensis infection, given the non-healing and progressive lesions characteristic of this infectious model. Infection of AnxA1 KO BALB/c mice resulted in increased lesion size and tissue damage associated with higher parasite burdens and enhanced inflammatory response. Notably, therapeutic application of the AnxA1 peptidomimetic Ac2-26 improves control of parasite replication and increases IL-10 production in vivo and in vitro, in both WT and AnxA1 KO mice. Conversely, administration of WRW4, an inhibitor of FPR2/3, resulted in larger lesions and decreased production of IL-10, suggesting that the effects of AnxA1 during L. amazonensis infection are associated with the engagement of these receptors. Our study illuminates the role of AnxA1 in L. amazonensis infection, demonstrating its impact on the susceptibility phenotype of BALB/c mice. Furthermore, our results indicate that targeting the AnxA1 pathway by using the Ac2-26 peptide could represent a promising alternative for new treatments for leishmaniasis.

ANXA1 is identified as a key gene associated with high risk and T cell infiltration in primary sclerosing cholangitis

BACKGROUND

Primary sclerosing cholangitis (PSC) is a chronic cholestatic liver disease, with unclear pathogenesis. Although immune disorders, especially T cell infiltration, are thought to play a vital role in PSC, the specific pathogenesis mechanisms remain incompletely understood. This study evaluated the potential key gene associated with the PSC pathogenesis and analyzed the associations of the key gene with prognosis and immune cell infiltration by combining bioinformatics analysis and experimental verification.

METHODS

Transcriptome data of PSC and normal human liver tissues (GSE159676) were obtained from the gene expression omnibus database. Differentially expressed genes (DEGs) were identified, and differences in biological states were analyzed. A protein-protein interaction (PPI) network was constructed. Hub genes were identified, and their expression was verified using transcriptome data of mice fed 0.1% 3,5-diethoxycarbonyl-1,4-dihydrocollidine (DDC) and Mdr2-/- mice (GSE179993, GSE80776), as well as by immunohistochemistry staining on clinical samples. The correlations between the key gene and other factors were evaluated by Pearson's correlation coefficient. Immune cell infiltration into human liver (GSE159676) was analyzed by xCell and verified by immunofluorescence staining on PSC liver samples.

RESULTS

Of the 185 DEGs identified, 113 were upregulated and 72 were downregulated genes in PSC. Genes associated with immune cell infiltration and fibrosis were significantly enriched in PSC. PPI network showed close interactions among DEGs. A module strongly associated with immune infiltration was identified, with annexin A1 (ANXA1) being the core gene. High expression of ANXA1 in PSC was confirmed in two public datasets and by immunohistochemistry staining on clinical samples. High ANXA1 expression was strongly associated with high-risk score for PSC. Also, ANXA1 expression was positively associated with chemokines and chemokine receptors and with the infiltration of immune cells, especially T cells, into liver with PSC. Immune infiltration, fibrosis, and cancer-related processes were markedly enriched in PSC with high expression of ANXA1.

CONCLUSION

ANXA1 is a key gene associated with high risk and infiltration of immune cells, especially T cells, in PSC. These findings provide new insight into the key biomarker of PSC and suggest that targeting ANXA1 may be a valuable strategy for the treatment of PSC.

Annexin A1 is a cell-intrinsic metalloregulator of zinc in human ILC2s

Group 2 innate lymphoid cells (ILC2s) produce large amounts of type 2 cytokines including interleukin-5 (IL-5) and IL-13 in response to various stimuli, causing allergic and eosinophilic diseases. However, the cell-intrinsic regulatory mechanisms of human ILC2s remain unclear. Here, we analyze human ILC2s derived from different tissues and pathological conditions and identify ANXA1, encoding annexin A1, as a commonly highly expressed gene in non-activated ILC2s. The expression of ANXA1 decreases when ILC2s activate, but it increases autonomously as the activation subsides. Lentiviral vector-based gene transfer experiments show that ANXA1 suppresses the activation of human ILC2s. Mechanistically, ANXA1 regulates the expression of the metallothionein family genes, including MT2A, which modulate intracellular zinc homeostasis. Furthermore, increased intracellular zinc levels play an essential role in the activation of human ILC2s by promoting the mitogen-activated protein kinase (MAPK) and nuclear factor κB (NF-κB) pathways and GATA3 expression. Thus, the ANXA1/MT2A/zinc pathway is identified as a cell-intrinsic metalloregulatory mechanism for human ILC2s.

From a cell model to a fish trial: Immunomodulatory effects of heat-killed Lactiplantibacillus plantarum as a functional ingredient in aquafeeds for salmonids

Paraprobiotics (dead/inactivated probiotics) are promising candidates in functional feeds to promote growth performance, modulate intestinal microbiota and enhance immune response of fish. During industrial production, fish are exposed to several stressful conditions such as handling, sub-optimal nutrition and diseases that can lead to reduced growth, increased mortalities and large economical losses. Such problems can be mitigated by use of functional feeds, leading to more-sustainable aquaculture and improved animal welfare. Lactiplantibacillus plantarum strain L-137 is a common bacterium found in fermented Southeast Asian dish made from fish and rice. The benefits of its heat-killed form (HK L-137) related to growth performance and immunomodulation have been studied in farmed fish such as Nile Tilapia (Oreochromis niloticus), striped catfish (Pangasianodon hypophthalmus) and bighead catfish (Clarias macrocephalus). To study if such benefits can also be observed in salmonids, we worked both at in vitro level using an intestinal epithelium cell line from rainbow trout (Oncorhynchus mykiss; RTgutGC) stimulated with HK L-137 (Feed LP20™) and at in vivo level with pre-smolt Atlantic salmon (Salmo salar) fed HK L-137 at different inclusion levels (20, 100 and 500 mg of Feed LP20™ kg-1 feed). In RTgutGC, the results showed that the barrier function of the cell monolayer was strengthened along with an increased production of IL-1β and a decreased production of Anxa1, indicating a modulation of the immune response. Interestingly, a similar trend was detected at the in vivo level in distal intestine from fish fed the highest inclusion level of HK L-137. Here, a lower production of Anxa1 was also detected (after a 61-day feeding period) in addition to an increase of total plasma IgM in the same group. Furthermore, the RNA-seq analysis showed that HK L-137 was able to modulate the gene expression of pathways related to molecular function, biological process and cellular component in distal intestine, without compromising fish performance and gut microbiota. Taken together, our study has shown that HK L-137 can modulate physiological response of Atlantic salmon, making fish more robust against stressful conditions during production.

Annexin A1 exerts renoprotective effects in experimental crescentic glomerulonephritis

Non-resolving inflammation plays a critical role during the transition from renal injury towards end-stage renal disease. The glucocorticoid-inducible protein annexin A1 has been shown to function as key regulator in the resolution phase of inflammation, but its role in immune-mediated crescentic glomerulonephritis has not been studied so far.

Methods: Acute crescentic glomerulonephritis was induced in annexin A1-deficient and wildtype mice using a sheep serum against rat glomerular basement membrane constituents. Animals were sacrificed at d5 and d10 after nephritis induction. Renal leukocyte abundance was studied by immunofluorescence and flow cytometry. Alterations in gene expression were determined by RNA-Seq and gene ontology analysis. Renal levels of eicosanoids and related lipid products were measured using lipid mass spectrometry.

Results: Histological analysis revealed an increased number of sclerotic glomeruli and aggravated tubulointerstitial damage in the kidneys of annexin A1-deficient mice compared to the wildtype controls. Flow cytometry analysis confirmed an increased number of CD45⁺ leukocytes and neutrophil granulocytes in the absence of annexin A1. Lipid mass spectrometry showed elevated levels of prostaglandins PGE2 and PGD2 and reduced levels of antiinflammatory epoxydocosapentaenoic acid regioisomers. RNA-Seq with subsequent gene ontology analysis revealed induction of gene products related to leukocyte activation and chemotaxis as well as regulation of cytokine production and secretion.

Conclusion: Intrinsic annexin A1 reduces proinflammatory signals and infiltration of neutrophil granulocytes and thereby protects the kidney during crescentic glomerulonephritis. The annexin A1 signaling cascade may therefore provide novel targets for the treatment of inflammatory kidney disease.

Transcriptome analysis of Homo sapiens and Mus musculus reveals mechanisms of CD8+ T cell exhaustion caused by different factors

T cell exhaustion is a state of T cell dysfunction during chronic infection and cancer. Antibody-targeting immune checkpoint inhibitors to reverse T cell exhaustion is a promising approach for cancer immunotherapy. However, molecular mechanisms of T cell exhaustion remain incompletely understood. Here, we performed a transcriptome analysis by integrating seven exhaustion datasets caused by multiple diseases in both humans and mice. In this study, an overlap of 21 upregulated and 37 downregulated genes was identified in human and mouse exhausted CD8+ T cells. These genes were significantly enriched in exhaustion response-related pathways, such as signal transduction, immune system processes, and regulation of cytokine production. Gene expression network analysis revealed that the well-documented exhaustion genes were defined as hub genes in upregulated genes. In addition, a weighted gene co-expression analysis identified 175 overlapping genes that were significantly correlated with the exhaustion trait in both humans and mice. This study found that overlapping six genes were significantly upregulated and highly related to T cell exhaustion. Finally, we revealed that CD200R1 and ADGRG1, less described previously in exhaustion, contributed to T cell exhaustion. Overall, our findings reveal the mechanisms of T cell exhaustion and provide an important reference to the immunology community.

Annexin-A1-Derived Peptide Ac2-26 Suppresses Allergic Airway Inflammation and Remodelling in Mice

Annexin-A1 (AnxA1) and its N-terminal derived peptide Ac2-26 regulate the inflammatory response in several experimental models of disorders. This study evaluated the effect of endogenous AnxA1 and its N-terminal peptide Acetyl 2-26 (Ac2-26) on allergic asthma triggered by house dust mite (HDM) extract in mice. ANXA1^−/− and wildtype (WT) mice were exposed to intranasal instillation of HDM every other day for 3 weeks, with analyses performed 24 h following the last exposure. Intranasal administration of peptide Ac2-26 was performed 1 h before HDM, beginning 1 week after the initial antigen application. ANXA1^−/− mice stimulated with HDM showed marked exacerbations of airway hyperreactivity (AHR), eosinophil accumulation, subepithelial fibrosis, and mucus hypersecretion, all parameters correlating with overexpression of cytokines (IL-4, IL-13, TNF-α, and TGF-β) and chemokines (CCL11/eotaxin-1 and CCL2/MCP-1). Intranasal treatment with peptide Ac2-26 decreased eosinophil infiltration, peribronchiolar fibrosis, and mucus exacerbation caused by the allergen challenge. Ac2-26 also inhibited AHR and mediator production. Collectively, our findings show that the AnxA1-derived peptide Ac2-26 protects against several pathological changes associated with HDM allergic reaction, suggesting that this peptide or related AnxA1-mimetic Ac2-26 may represent promising therapeutic candidates for the treatment of allergic asthma.

Annexin-A1; the culprit or the solution?

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

Skewed peripheral B- and T-cell compartments in patients with ANCA-associated vasculitis

OBJECTIVES

To characterize lymphocytes dysregulation in patients with granulomatosis with polyangiitis (GPA) and microscopic polyangiitis (MPA).

METHODS

Using flow cytometry, we analysed B- and T-cell subsets in peripheral blood from 37 untreated patients with active disease (29 GPA and 8 MPA) and 22 healthy controls (HCs).

RESULTS

GPA patients had increased Th2 (1.8 vs 1.0%, P = 0.02), Th9 (1.1 vs 0.2%, P = 0.0007) and Th17 (1.4 vs 0.9%, P = 0.03) cells compared with HC. Patients with MPO-ANCAs had significantly more CD21- B cells than HC or PR3-ANCA patients (6.9 vs 3.3% and 4.4%, P = 0.01). CD69 expressing B cells were significantly higher in GPA and MPA (3.0 and 5.9 vs 1.4%, P = 0.02 and P = 0.03, respectively) compared with HC, whereas B-cell activating factor-receptor expression was decreased in GPA and MPA (median fluorescence intensity ratio 11.8 and 13.7 vs 45.1 in HC, P < 0.0001 and P = 0.003, respectively). Finally, IL-6-producing B cells were increased in GPA vs HC (25.8 vs 14.9%, P < 0.0001) and decreased in MPA vs HC (4.6 vs 14.9%, P = 0.005), whereas TNF-α-producing B cells were lower in both GPA and MPA patients compared with controls (15 and 8.4 vs 30%, P = 0.01 and P = 0.006, respectively).

CONCLUSION

Skewed T-cell polarization towards Th2, Th9 and Th17 responses characterizes GPA, whereas B-cell populations are dysregulated in both GPA and MPA with an activated phenotype and a decreased B-cell activating factor-receptor expression. Finally, inflammatory B cells producing IL-6 are dramatically increased in GPA, providing an additional mechanism by which rituximab could be effective.

HDX-MS for Epitope Characterization of a Therapeutic ANTIBODY Candidate on the Calcium-Binding Protein Annexin-A1

Annexin-A1 (ANXA1) belongs to a class of highly homologous Ca2+-dependent phospholipid-binding proteins. Its structure consists of a core region composed of four homologous repeats arranged in a compact, hydrolysis-resistant structure and an N-terminal region with a Ca2+-dependent conformation. ANXA1 is involved in several processes, including cell proliferation, apoptosis, metastasis, and the inflammatory response. Therefore, the development of antibodies blocking selected regions on ANXA1 holds great potential for the development of novel therapeutics treating inflammatory and cancer diseases. Here, we report the interaction site between an ANXA1-specific antibody known to inhibit T cell activation without adverse cytotoxic effects and ANXA1 using amide hydrogen-deuterium exchange mass spectrometry (HDX-MS). For the epitope determination, we applied two bottom-up HDX-MS approaches with pepsin digestion in solution and immobilized on beads. Both strategies revealed the interaction region within domain III of ANXA1 in Ca2+-bound conformation. The antibody-binding region correlates with the hydrophobic binding pocket of the N-terminal domain formed in the absence of calcium. This study demonstrates that even cryptic and flexible binding regions can be studied by HDX-MS, allowing a fast and efficient determination of the binding sites of antibodies which will help to define a mode of action profile for their use in therapy.

Antigen-driven PD-1+ TOX+ BHLHE40+ and PD-1+ TOX+ EOMES+ T lymphocytes regulate juvenile idiopathic arthritis in situ

T lymphocytes accumulate in inflamed tissues of patients with chronic inflammatory diseases (CIDs) and express pro-inflammatory cytokines upon re-stimulation in vitro. Further, a significant genetic linkage to MHC genes suggests that T lymphocytes play an important role in the pathogenesis of CIDs including juvenile idiopathic arthritis (JIA). However, the functions of T lymphocytes in established disease remain elusive. Here we dissect the transcriptional and the clonal heterogeneity of synovial T lymphocytes in JIA patients by single-cell RNA sequencing combined with T cell receptor profiling on the same cells. We identify clonally expanded subpopulations of T lymphocytes expressing genes reflecting recent activation by antigen in situ. A PD-1⁺ TOX⁺ EOMES⁺ population of CD4⁺ T lymphocytes expressed immune regulatory genes and chemoattractant genes for myeloid cells. A PD-1⁺ TOX⁺ BHLHE40⁺ population of CD4⁺ , and a mirror population of CD8⁺ T lymphocytes expressed genes driving inflammation, and genes supporting B lymphocyte activation in situ. This analysis points out that multiple types of T lymphocytes have to be targeted for therapeutic regeneration of tolerance in arthritis.

Immuno-moodulin: A new anxiogenic factor produced by Annexin-A1 transgenic autoimmune-prone T cells

Patients suffering from autoimmune diseases are more susceptible to mental disorders yet, the existence of specific cellular and molecular mechanisms behind the co-morbidity of these pathologies is far from being fully elucidated. By generating transgenic mice overexpressing Annexin-A1 exclusively in T cells to study its impact in models of autoimmune diseases, we made the unpredicted observation of an increased level of anxiety. Gene microarray of Annexin-A1 CD4⁺ T cells identified a novel anxiogenic factor, a small protein of approximately 21 kDa encoded by the gene 2610019F03Rik which we named Immuno-moodulin. Neutralizing antibodies against Immuno-moodulin reverted the behavioral phenotype of Annexin-A1 transgenic mice and lowered the basal levels of anxiety in wild type mice; moreover, we also found that patients suffering from obsessive compulsive disorders show high levels of Imood in their peripheral mononuclear cells. We thus identify this protein as a novel peripheral determinant that modulates anxiety behavior. Therapies targeting Immuno-moodulin may lead to a new type of treatment for mental disorders through regulation of the functions of the immune system, rather than directly acting on the nervous system.

Admixture and natural selection shaped genomes of an Austronesian-speaking population in the Solomon Islands

People in the Solomon Islands today are considered to have derived from Asian- and Papuan-related ancestors. Papuan-related ancestors colonized Near Oceania about 47,000 years ago, and Asian-related ancestors were Austronesian (AN)-speaking population, called Lapita, who migrated from Southeast Asia about 3,500 years ago. These two ancestral populations admixed in Near Oceania before the expansion of Lapita people into Remote Oceania. To understand the impact of the admixture on the adaptation of AN-speaking Melanesians in Near Oceania, we performed the genome-wide single nucleotide polymorphism (SNP) analysis of 21 individuals from Munda, the main town of the New Georgia Islands in the western Solomon Islands. Population samples from Munda were genetically similar to other Solomon Island population samples. The analysis of genetic contribution from the two different ancestries to the Munda genome revealed significantly higher proportions of Asian- and Papuan-related ancestries in the region containing the annexin A1 (ANXA1) gene (Asian component > 82.6%) and in the human leukocyte antigen (HLA) class II region (Papuan component > 85.4%), respectively. These regions were suspected to have undergone natural selection since the time of admixture. Our results suggest that admixture had affected adaptation of AN-speaking Melanesians in the Solomon Islands.

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.

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.

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.

Integrated systems analysis reveals conserved gene networks underlying response to spinal cord injury

Spinal cord injury (SCI) is a devastating neurological condition for which there are currently no effective treatment options to restore function. A major obstacle to the development of new therapies is our fragmentary understanding of the coordinated pathophysiological processes triggered by damage to the human spinal cord. Here, we describe a systems biology approach to integrate decades of small-scale experiments with unbiased, genome-wide gene expression from the human spinal cord, revealing a gene regulatory network signature of the pathophysiological response to SCI. Our integrative analyses converge on an evolutionarily conserved gene subnetwork enriched for genes associated with the response to SCI by small-scale experiments, and whose expression is upregulated in a severity-dependent manner following injury and downregulated in functional recovery. We validate the severity-dependent upregulation of this subnetwork in rodents in primary transcriptomic and proteomic studies. Our analysis provides systems-level view of the coordinated molecular processes activated in response to SCI.

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.

Phosphoproteomics reveals network rewiring to a pro-adhesion state in annexin-1-deficient mammary epithelial cells

Background

Annexin-1 (ANXA1) plays pivotal roles in regulating various physiological processes including inflammation, proliferation and apoptosis, and deregulation of ANXA1 functions has been associated with tumorigenesis and metastasis events in several types of cancer. Though ANXA1 levels correlate with breast cancer disease status and outcome, its distinct functional involvement in breast cancer initiation and progression remains unclear. We hypothesized that ANXA1-responsive kinase signaling alteration and associated phosphorylation signaling underlie early events in breast cancer initiation events and hence profiled ANXA1-dependent phosphorylation changes in mammary gland epithelial cells.

Methods

Quantitative phosphoproteomics analysis of mammary gland epithelial cells derived from ANXA1-heterozygous and ANXA1-deficient mice was carried out using stable isotope labeling with amino acids in cell culture (SILAC)-based mass spectrometry. Kinase and signaling changes underlying ANXA1 perturbations were derived by upstream kinase prediction and integrated network analysis of altered proteins and phosphoproteins.

Results

We identified a total of 8110 unique phosphorylation sites, of which 582 phosphorylation sites on 372 proteins had ANXA1-responsive changes. A majority of these phosphorylation changes occurred on proteins associated with cytoskeletal reorganization spanning the focal adhesion, stress fibers, and also the microtubule network proposing new roles for ANXA1 in regulating microtubule dynamics. Comparative analysis of regulated global proteome and phosphoproteome highlighted key differences in translational and post-translational effects of ANXA1, and suggested closely coordinated rewiring of the cell adhesion network. Kinase prediction analysis suggested activity modulation of calmodulin-dependent protein kinase II (CAMK2), P21-activated kinase (PAK), extracellular signal-regulated kinase (ERK), and IκB kinase (IKK) upon loss of ANXA1. Integrative analysis revealed regulation of the WNT and Hippo signaling pathways in ANXA1-deficient mammary epithelial cells, wherein there is downregulation of transcriptional effects of TEA domain family (TEAD) suggestive of ANXA1-responsive transcriptional rewiring.

Conclusions

The phosphoproteome landscape uncovered several novel perspectives for ANXA1 in mammary gland biology and highlighted its involvement in key signaling pathways modulating cell adhesion and migration that could contribute to breast cancer initiation.

Electronic supplementary material

The online version of this article (doi:10.1186/s13058-017-0924-4) contains supplementary material, which is available to authorized users.

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

INTRODUCTION

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

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 influences in breast cancer: Controversies on contributions to tumour, host and immunoediting processes

Annexin A1 is a multifunctional protein characterised by its actions in modulating the innate and adaptive immune response. Accumulating evidence of altered annexin A1 expression in many human tumours raises interest in its functional role in cancer biology. In breast cancer, altered annexin A1 expression levels suggest a potential influence on tumorigenic and metastatic processes. However, reports of conflicting results reveal a relationship that is much more complex than first conceptualised. In this review, we explore the diverse actions of annexin A1 on breast tumour cells and various host cell types, including stromal immune and structural cells, particularly in the context of cancer immunoediting.

Interaction between ANXA1 and GATA-3 in Immunosuppression of CD4+ T Cells

Decreased Th1/Th2 ratio is one of the major characteristics of immunosuppression in sepsis. Both membrane adhesive protein Annexin-A1 (ANXA1) and transcription factor GATA-3 have been reported to play important roles in T cell differentiation. However, the relationship between ANXA1 and GATA-3 in Th1/Th2 shift is unknown. Our study investigated the interaction effects of ANXA1 and GATA-3 to influence T cell differentiation in CD4+ T cells. We found that GATA-3 and ANXA1 were coexpressed on Th0/Th1/Th2 cytoplasm and nuclear. Overexpressed ANXA1 significantly increased the expression of IFNγ and reduced IL-4 expression in T cells, while ANXA1-silenced T cells exhibited decreased production of IFNγ and increased production of IL-4. Knockdown of ANXA1 promoted higher expression level of GATA-3 and low level of T-box transcription factor (T-bet/Tbx21). Further study demonstrated that ANXA1 regulated GATA-3 expression through the formyl peptide receptor like-1 (FPRL-1) downstream signaling pathways ERK and PKB/Akt. These results suggested that ANXA1 modulates GATA-3/T-bet expression induced Th0/Th1 differentiation. Moreover, we found that GATA-3 inhibited ANXA1 expression by binding to its promoter for the first time. It is proposed that the interactions between ANXA1 and GATA-3 may provide clues to understand the immunosuppression and have potential as new therapeutic targets in immunotherapy after sepsis.

Impact of Enriched Environment on Murine T Cell Differentiation and Gene Expression Profile

T cells are known to be plastic and to change their phenotype according to the cellular and biochemical milieu they are embedded in. In this study, we transposed this concept at a macroscopic level assessing whether changes in the environmental housing conditions of C57/BL6 mice would influence the phenotype and function of T cells. Our study shows that exposure to 2 weeks in an enriched environment (EE) does not impact the T cell repertoire in vivo and causes no changes in the early TCR-driven activation events of these cells. Surprisingly, however, T cells from enriched mice showed a unique T helper effector cell phenotype upon differentiation in vitro. This was featured by a significant reduction in their ability to produce IFN-γ and by an increased release of IL-10 and IL-17. Microarray analysis of these cells also revealed a unique gene fingerprint with key signaling pathways involved in autoimmunity being modulated. Together, our results provide first evidence for a specific effect of EE on T cell differentiation and its associated changes in gene expression profile. In addition, our study sheds new light on the possible mechanisms by which changes in environmental factors can significantly influence the immune response of the host and favor the resolution of the inflammatory response.

Divergent Annexin A1 expression in periphery and gut is associated with systemic immune activation and impaired gut immune response during SIV infection

HIV-1 disease progression is paradoxically characterized by systemic chronic immune activation and gut mucosal immune dysfunction, which is not fully defined. Annexin A1 (ANXA1), an inflammation modulator, is a potential link between systemic inflammation and gut immune dysfunction during the simian immunodeficiency virus (SIV) infection. Gene expression of ANXA1 and cytokines were assessed in therapy-naïve rhesus macaques during early and chronic stages of SIV infection and compared with SIV-negative controls. ANXA1 expression was suppressed in the gut but systemically increased during early infection. Conversely, ANXA1 expression increased in both compartments during chronic infection. ANXA1 expression in peripheral blood was positively correlated with HLA-DR+CD4+ and CD8+ T-cell frequencies, and negatively associated with the expression of pro-inflammatory cytokines and CCR5. In contrast, the gut mucosa presented an anergic cytokine profile in relation to ANXA1 expression. In vitro stimulations with ANXA1 peptide resulted in decreased inflammatory response in PBMC but increased activation of gut lymphocytes. Our findings suggest that ANXA1 signaling is dysfunctional in SIV infection, and may contribute to chronic inflammation in periphery and with immune dysfunction in the gut mucosa. Thus, ANXA1 signaling may be a novel therapeutic target for the resolution of immune dysfunction in HIV infection.

Expression of annexin A1 in Leishmania-infected skin and its correlation with histopathological features

INTRODUCTION

The aim of this study was quantify annexin A1 expression in macrophages and cluster of differentiation 4 (CD4) + and cluster of differentiation 8 (CD8)+ T cells from the skin of patients with cutaneous leishmaniasis (n=55) and correlate with histopathological aspects.

METHODS

Infecting species were identified by polymerase chain reaction-restriction fragment length polymorphism, and expression of annexin A1 was analyzed by immunofluorescence.

RESULTS

All patients (n = 55) were infected with Leishmania braziliensis . Annexin A1 was expressed more abundantly in CD163 + macrophages in infected skin (p < 0.0001) than in uninfected skin. In addition, macrophages in necrotic exudative reaction lesions expressed annexin A1 at higher levels than those observed in granulomatous (p < 0.01) and cellular lesions p < 0.05). This difference might be due to the need to clear both parasites and necrotic tissue from necrotic lesions. CD4 + cells in cellular lesions expressed annexin A1 more abundantly than did those in necrotic (p < 0.05) and granulomatous lesions (p < 0.01). Expression in CD8 + T cells followed the same trend. These differences might be due to the pervasiveness of lymphohistiocytic and plasmacytic infiltrate in cellular lesions.

CONCLUSIONS

Annexin A1 is differentially expressed in CD163 + macrophages and T cells depending on the histopathological features of Leishmania -infected skin, which might affect cell activation.

Annexin1 regulates DC efferocytosis and cross-presentation during Mycobacterium tuberculosis infection

The phagocytosis of apoptotic cells and associated vesicles (efferocytosis) by DCs is an important mechanism for both self tolerance and host defense. Although some of the engulfment ligands involved in efferocytosis have been identified and studied in vitro, the contributions of these ligands in vivo remain ill defined. Here, we determined that during Mycobacterium tuberculosis (Mtb) infection, the engulfment ligand annexin1 is an important mediator in DC cross-presentation that increases efferocytosis in DCs and intrinsically enhances the capacity of the DC antigen-presenting machinery. Annexin1-deficient mice were highly susceptible to Mtb infection and showed an impaired Mtb antigen-specific CD8+ T cell response. Importantly, annexin1 expression was greatly downregulated in Mtb-infected human blood monocyte-derived DCs, indicating that reduction of annexin1 is a critical mechanism for immune evasion by Mtb. Collectively, these data indicate that annexin1 is essential in immunity to Mtb infection and mediates the power of DC efferocytosis and cross-presentation.

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.

Cardioprotective potential of annexin-A1 mimetics in myocardial infarction

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

Mass spectrometry based quantitative proteomics and integrative network analysis accentuates modulating roles of annexin-1 in mammary tumorigenesis

Annexin-1 (ANXA1) is known to be involved in important cellular processes and implicated in cancer. Our previous study showed its roles in cell migration and DNA-damage response processes in breast cancer initiation. In order to understand its roles in tumorigenesis, we extended our studies to analyze tumors derived from polyomavirus middle T-antigen ANXA1 heterozygous (ANXA1(+/-) ) and ANXA1 null (ANXA1(-/-) ) mice. We performed quantitative comparison of ANXA1(+/-) and ANXA1(-/-) tumors employing reductive dimethyl labeling quantitative proteomics. We observed 253 differentially expressed proteins (DEPs) with high statistical significance among over 5000 quantified proteins. Combinatorial use of pathway and network-based computational analyses of the DEPs revealed that ANXA1 primarily modulates processes related to cytoskeletal remodeling and immune responses in these mammary tumors. Of particular note, ANXA1(-/-) tumor showed reduced expression of a known epithelial-to-mesenchymal transition (EMT) marker vimentin, as well as myosin light-chain kinase, which has been reported to induce Rho-kinase mediated assembly of stress fibers known to be implicated in EMT. Integrative network analysis of established interactome of ANXA1 alongside with DEPs further highlights the involvement of ANXA1 in EMT. Functional role of ANXA1 in tumorigenesis was established in invasion assay where knocking down ANXA1 in murine mammary tumor cell line 168FARN showed lower invasive capability. Altogether, this study emphasizes that ANXA1 plays modulating roles contributing to invasion-metastasis in mammary tumorigenesis, distinctive to its roles in cancer initiation.

Quantitative proteome profiling of CNS-infiltrating autoreactive CD4+ cells reveals selective changes during experimental autoimmune encephalomyelitis

Experimental autoimmune encephalomyelitis (EAE) is a murine model of multiple sclerosis, a chronic neurodegenerative and inflammatory autoimmune condition of the central nervous system (CNS). Pathology is driven by the infiltration of autoreactive CD4(+) lymphocytes into the CNS, where they attack neuronal sheaths causing ascending paralysis. We used an isotope-coded protein labeling approach to investigate the proteome of CD4(+) cells isolated from the spinal cord and brain of mice at various stages of EAE progression in two EAE disease models: PLP139-151-induced relapsing-remitting EAE and MOG35-55-induced chronic EAE, which emulate the two forms of human multiple sclerosis. A total of 1120 proteins were quantified across disease onset, peak-disease, and remission phases of disease, and of these 13 up-regulated proteins of interest were identified with functions relating to the regulation of inflammation, leukocyte adhesion and migration, tissue repair, and the regulation of transcription/translation. Proteins implicated in processes such as inflammation (S100A4 and S100A9) and tissue repair (annexin A1), which represent key events during EAE progression, were validated by quantitative PCR. This is the first targeted analysis of autoreactive cells purified from the CNS during EAE, highlighting fundamental CD4(+) cell-driven processes that occur during the initiation of relapse and remission stages of disease.

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.

Annexin A1: potential for glucocorticoid sparing in RA

Glucocorticoids have broad-ranging and powerful anti-inflammatory and immunomodulatory effects. Unsurprisingly, therefore, glucocorticoids are widely and persistently used to treat a large number of inflammatory diseases, including rheumatoid arthritis (RA), despite the well-described adverse effects of these drugs. Annexin A1 is a glucocorticoid-induced molecule that is known to replicate many of the described anti-inflammatory effects of glucocorticoids. In addition to the well-documented roles of this protein in neutrophil function, emerging evidence suggests that annexin A1 is involved in the modulation of T-cell function and the adaptive immune responses relevant to RA. Interest in annexin A1 was renewed after the delineation of the receptors for this protein. This breakthrough also led to advances in our understanding of anti-inflammatory annexin A1 mimetic peptides and agonistic compounds targeting these receptors, particularly those specific for the receptor N-formyl peptide receptor 2 (FPR2). Herein, we review the current knowledge of the biological activities of annexin A1 and their relevance to RA pathogenesis. We also discuss the potential of annexin A1 mimics and strategies aimed at potentiating annexin A1 signalling to become viable approaches to minimizing glucocorticoid use in RA and other inflammatory disorders.

Pro-inflammatory and pathogenic properties of Annexin-A1: the whole is greater than the sum of its parts

According to Aristotle, "The whole is greater than the sum of its parts" and yet, although a long time has passed still, we seem to struggle to accept this universal concept. Searching in the literature for the biological function of Annexin-A1, one would find a wealth of information on its homeostatic and protective anti-inflammatory effects. However, very little has been said on its emerging role in a wide variety of pathological conditions ranging from cancer to autoimmunity. In this commentary, we will focus our attention on this novel pro-inflammatory and pathogenic "dark side" of Annexin-A1. We will summarize our current understanding of the signaling pathways regulated by this protein and link it to clinical and experimental evidences. Finally we will discuss assets and limitations of Annexin-A1 therapeutic strategies. Most importantly, we hope that this commentary will provide scientific support to "controversial" findings one might encounter while studying this fascinating protein.

Deficiency of annexin A1 in CD4+ T cells exacerbates T cell-dependent inflammation

Annexin A1 (AnxA1) is recognized as an endogenous anti-inflammatory molecule. However, its effects on the adaptive immune response and, in particular, on T cells remain unclear. In this study, we investigated the actions of AnxA1 in three distinct models of T cell-mediated inflammation. In contact hypersensitivity, collagen-induced arthritis, and inflammation induced by OT-II TCR transgenic T cells responding to OVA, AnxA1 deficiency significantly increased Ag-induced T cell proliferation and the resultant level of inflammation. In the contact hypersensitivity model, this was associated with increased adhesion of CD4(+) T cells, CD8(+) T cells, and neutrophils in the dermal microvasculature, as well as increased T cell expression of RORγt and IL-17A. In collagen-induced arthritis, deficiency of endogenous AnxA1 increased susceptibility to arthritis and Ag-specific T cell activation. Deficiency of AnxA1 also increased OVA-induced cutaneous delayed-type hypersensitivity and IFN-γ and IL-17 release. Transfer experiments using CD4(+) T cells from AnxA1(-/-) mice demonstrated that the absence of AnxA1 solely in T cells resulted in increased inflammatory responses in wild-type recipients. Similarly, experiments using AnxA1(-/-) OT-II CD4(+) T cells demonstrated that the absence of AnxA1 in T cells was sufficient to induce increased Ag-specific CD4(+) T cell proliferation in vivo, augment T cell production of IFN-γ, IL-17, TNF, and IL-6, and increase Akt, ERK, and p38 activation. Together, these findings indicate that T cell-expressed AnxA1 functions to attenuate T cell-driven inflammatory responses via T cell-intrinsic effects on intracellular signaling, proliferation, and Th1/Th17 cytokine release.

Annexin A1 and the regulation of innate and adaptive immunity

Inflammation is the body’s way of defending itself against noxious stimuli and pathogens. Under normal circumstances, the body is able to eliminate the insult and subsequently promote the resolution of inflammation and the repair of damaged tissues. The concept of homeostasis is one that not only requires a fine balance between both pro-inflammatory mediators and pro-resolving/anti-inflammatory mediators, but also that this balance occurs in a time and space-specific manner. This review examines annexin A1, an anti-inflammatory protein that, when used as an exogenous therapeutic, has been shown to be very effective in limiting inflammation in a diverse range of experimental models, including myocardial ischemia/reperfusion injury, arthritis, stroke, multiple sclerosis, and sepsis. Notably, this glucocorticoid-inducible protein, along with another anti-inflammatory mediator, lipoxin A₄, is starting to help explain and shape our understanding of the resolution phase of inflammation. In so doing, these molecules are carving the way for innovative drug discovery, based on the stimulation of endogenous pro-resolving pathways.

Systems analysis of a mouse xenograft model reveals annexin A1 as a regulator of gene expression in tumor stroma

Annexin A1 is a multi functional molecule which is involved in inflammation, innate and adaptive immune systems, tumor progression and metastasis. We have previously showed the impaired tumor growth, metastasis, angiogenesis and wound healing in annexin A1 knockout mice. While tumor is a piece of heterogeneous mass including not only malignant tumor cells but also the stroma, the importance of the tumor stroma for tumor progression and metastasis is becoming increasingly clear. The tumor stroma is comprised by various components including extracellular matrix and non-malignant cells in the tumor, such as endothelial cells, fibroblasts, immune cells, inflammatory cells. Based on our previous finding of pro-angiogenic functions for annexin A1 in vascular endothelial cell sprouting, wound healing, tumor growth and metastasis, and the previously known properties for annexin A1 in immune cells and inflammation, this study hypothesized that annexin A1 is a key functional player in tumor development, linking the various components in tumor stroma by its actions in endothelial cells and immune cells. Using systems analysis programs commercially available, this paper further compared the gene expression between tumors from annexin A1 wild type mice and annexin A1 knockout mice and found a list of genes that significantly changed in the tumor stroma that lacked annexin A1. This revealed annexin A1 to be an effective regulator in tumor stroma and suggested a mechanism that annexin A1 affects tumor development and metastasis through interaction with the various components in the microenvironment surrounding the tumor cells.

Clinical significance of annexin A1 expression in breast cancer

PURPOSE

The expression of Annexin A1 (ANXA1) is known to be reduced in human breast cancer; however, the role of ANXA1 expression in the development of breast cancer remains unclear. In this study, we determined the relationship between the expression features of ANXA1 and the prognostic factors of breast cancer.

METHODS

Human breast tissues were obtained from patients specimens who had undergone breast surgery or core needle biopsies. The patterns of ANXA1 expression were analyzed by immunohistochemical staining in relation to histopathological diagnosis, clinical characteristics and outcomes.

RESULTS

One hundred eighty-two cases were included and the mean age of the patients was 46.34 ± 11.5 years. A significant loss of ANXA1 expression was noted in both ductal carcinoma in situ (DCIS) and invasive carcinomas compared to normal breast tissues (p<0.001) and benign breast diseases (p<0.001). There was a significant alteration in ANXA1 expression according to hormone receptor status (p<0.001), cancer intrinsic type (p<0.001), and nuclear grade (p=0.004) in invasive cancer. In a univariate analysis, ANXA1 positivity tended to be related with poor breast cancer-related survival (p=0.062); however, the same results was not realized in multivariate results (p=0.406). HER2 overexpression and TNM staging were significantly associated with relapse-free survivals (RFS) in the multivariate analysis (p=0.037, p=0.048, respectively). In particular, in node-positive patients (p=0.048), HER2 overexpressed patients (p=0.013), and non-triple negative breast cancer patients (p=0.002), ANXA1 overexpression was correlated with poor RFS.

CONCLUSION

Although significant loss of ANXA1 expression was noted in breast cancer including DCIS and invasive carcinoma, in cases of invasive cancer, overexpression of ANXA1 was related to unfavorable prognostic factors. And these results imply that ANXA1 plays dualistic roles and is involved in variable mechanisms related to cancer development and progression.

Annexin-1-deficient mice exhibit spontaneous airway hyperresponsiveness and exacerbated allergen-specific antibody responses in a mouse model of asthma

BACKGROUND

Glucocorticoids are the mainstream drugs used in the treatment and control of inflammatory diseases such as asthma. Annexin-1 (ANXA1) is an anti-inflammatory protein which has been described as an endogenous protein responsible for some anti-inflammatory glucocorticoid effects. Previous studies have identified its importance in other immune diseases such as rheumatoid arthritis and cystic fibrosis. ANXA1-deficient ((-/-)) mice are Th2 biased, and ANXA1 N-terminus peptide exhibits anti-inflammatory activity in a rat model of pulmonary inflammation.

OBJECTIVE

ANXA1 protein is found in bronchoalveolar lavage fluid from asthmatics. However, the function of ANXA1 in the pathological development of allergy or asthma is unclear. Thus, in this study we intended to examine the effect of ANXA1 deficiency on allergen-specific antibody responses and airway responses to methacholine (Mch).

METHODS

ANXA1(-/-) mice were sensitized with ovalbumin (OVA) and challenged with aerosolized OVA. Airway resistance, lung compliance and enhanced pause (PenH) were measured in naïve, sensitized and saline or allergen-challenged wild-type (WT) and ANXA1(-/-) mice. Total and allergen-specific antibodies were measured in the serum.

RESULTS

We show that allergen-specific and total IgE, IgG2a and IgG2b levels were significantly higher in ANXA1(-/-) mice. Furthermore, naïve ANXA1(-/-) mice displayed higher airway hypersensitivity to inhaled Mch, and significant differences were also observed in allergen-sensitized and allergen-challenged ANXA1(-/-) mice compared with WT mice.

CONCLUSIONS

In conclusion, ANXA1(-/-) mice possess multiple features characteristic to allergic asthma, such as airway hyperresponsiveness and enhanced antibody responses, suggesting that ANXA1 plays a critical regulatory role in the development of asthma.

CLINICAL RELEVANCE

We postulate that ANXA1 is an important regulatory factor in the development of allergic disease and dysregulation of its expression can lead to pathological changes which may affect disease progression.

The anti-inflammatory and immunosuppressive effects of glucocorticoids, recent developments and mechanistic insights

Since the discovery of glucocorticoids in the 1940s and the recognition of their anti-inflammatory effects, they have been amongst the most widely used and effective treatments to control inflammatory and autoimmune diseases. However, their clinical efficacy is compromised by the metabolic effects of long-term treatment, which include osteoporosis, hypertension, dyslipidaemia and insulin resistance/type 2 diabetes mellitus. In recent years, a great deal of effort has been invested in identifying compounds that separate the beneficial anti-inflammatory effects from the adverse metabolic effects of glucocorticoids, with limited effect. It is clear that for these efforts to be effective, a greater understanding is required of the mechanisms by which glucocorticoids exert their anti-inflammatory and immunosuppressive actions. Recent research is shedding new light on some of these mechanisms and has produced some surprising new findings. Some of these recent developments are reviewed here.

Comparative analysis of Annexin A1-formyl peptide receptor 2/ALX expression in human leukocyte subsets

Recent studies have associated the dysregulated expression of Annexin-A1/Formyl peptide receptor 2 (FPR2/ALX) system with the development of autoimmune diseases. In this study we systematically scanned human leukocyte subsets for the presence of this pathway aiming to provide a roadmap that will help investigators to explore possible links between the development of immune related disorders and the expression of this system. Our results show that neutrophils, monocytes and NK cells express higher levels of both AnxA1 and FPR2/ALX compared to T or B cells. Further analysis of specific T cell subsets revealed higher levels in activated CD25(+) and memory CD45RO CD4 T cells compared to resting CD25(-) or naïve CD45RA CD4 T cells. Together the results expand our knowledge of the AnxA1-FPR2/ALX system in immune cells and provide new avenues for investigation into the functions of this signalling pathway in systems other than that classically described for neutrophils.

Therapeutic anti-inflammatory potential of formyl-peptide receptor agonists

The need for novel anti-inflammatory drugs justifies the search for innovative targets that could satisfy this goal. For quite some time now, we have proposed the study of endogenous anti-inflammation as a distinctive approach to the discovery of new drugs. This approach requires development of new compounds that activate specific receptor targets to downregulate the cellular and tissue pathways operative in the host during inflammation. Here we dwell on a family of G-protein coupled receptors (GPCR) termed FPRs, acronym for formyl-peptide receptors. With three and seven members in man and mouse, respectively, these receptors harness many biological functions, spanning odour perception and hair growth, to the control of multiple facets (pain; cell migration; oxidative burst; xenobiotic engulfment) of the inflammatory reaction. We focus on FPR biology with particular attention to molecules able to produce pharmacological effects by interacting with these GPCRs, describing endogenous agonists of FPRs and, more relevantly, the current development of synthetic agonists. Besides being potential leads for the development of the anti-inflammatory therapeutics of the future, these compounds could also help clarify the properties and roles that each FPR might play in the complex network of pathways that is inflammation. We conclude that FPR2 agonists could be valid warhorses for defining a novel philosophy for anti-inflammatory drug discovery programmes: mimicking - with new compounds - the way our body disposes of inflammation could be a viable approach to regulate aberrant inflammatory responses as in the case of several chronic rheumatic and cardiovascular pathologies.