Endogenous annexin A1 counter-regulates bleomycin-induced lung fibrosis

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.

Role of histamine H4 receptor in the anti-inflammatory pathway of glucocorticoid-induced leucin zipper (GILZ) in a model of lung fibrosis

INTRODUCTION

This study investigates the interactions between histaminergic system and glucocorticoid-induced leucin zipper (GILZ) in the inflammatory process and glucocorticoid modulation in lung fibrosis.

METHODS

Wild-type (WT) and GILZ Knock-Out (KO) mice were treated with bleomycin (0.05 IU) or saline, delivered by intra-tracheal injection. After surgery, mice received a continuous infusion of JNJ7777120 (JNJ, 2 mg/kg b.wt.) or vehicle for 21 days. Lung function was studied by measuring airway resistance to air insufflation through the analysis of pressure at airway opening (PAO). Lung samples were collected to evaluate the expression of histamine H4R, Anx-A1, and p65-NF-kB, the activity of myeloperoxidase (MPO), and the production of pro-inflammatory cytokines.

RESULTS

Airway fibrosis and remodeling were assessed by measuring TGF-β production and α-SMA deposition. JNJ reduces PAO in WT but not in GILZ KO mice (from 22 ± 1 mm to 15 ± 0.5 and from 24 ± 1.5 to 19 ± 0.5 respectively), MPO activity (from 204 ± 3.13 pmol/mg to 73.88 ± 2.63 in WT and from 221 ± 4.46 pmol/mg to 107 ± 5.54 in GILZ KO), the inflammatory response, TGF-β production, and α-SMA deposition in comparison to WT and GILZ KO vehicle groups.

CONCLUSION

In conclusion, the role of H4R and GILZ in relation to glucocorticoids could pave the way for innovative therapies to counteract pulmonary fibrosis.

New insights into the natural history of bronchopulmonary dysplasia from proteomics and multiplexed immunohistochemistry

Bronchopulmonary dysplasia (BPD) is a disease of prematurity related to the arrest of normal lung development. The objective of this study was to better understand how proteome modulation and cell-type shifts are noted in BPD pathology. Pediatric human donors aged 1-3 yr were classified based on history of prematurity and histopathology consistent with "healed" BPD (hBPD, n = 3) and "established" BPD (eBPD, n = 3) compared with respective full-term born (n = 6) age-matched term controls. Proteins were quantified by tandem mass spectroscopy with selected Western blot validations. Multiplexed immunofluorescence (MxIF) microscopy was performed on lung sections to enumerate cell types. Protein abundances and MxIF cell frequencies were compared among groups using ANOVA. Cell type and ontology enrichment were performed using an in-house tool and/or EnrichR. Proteomics detected 5,746 unique proteins, 186 upregulated and 534 downregulated, in eBPD versus control with fewer proteins differentially abundant in hBPD as compared with age-matched term controls. Cell-type enrichment suggested a loss of alveolar type I, alveolar type II, endothelial/capillary, and lymphatics, and an increase in smooth muscle and fibroblasts consistent with MxIF. Histochemistry and Western analysis also supported predictions of upregulated ferroptosis in eBPD versus control. Finally, several extracellular matrix components mapping to angiogenesis signaling pathways were altered in eBPD. Despite clear parsing by protein abundance, comparative MxIF analysis confirms phenotypic variability in BPD. This work provides the first demonstration of tandem mass spectrometry and multiplexed molecular analysis of human lung tissue for critical elucidation of BPD trajectory-defining factors into early childhood.NEW & NOTEWORTHY We provide new insights into the natural history of bronchopulmonary dysplasia in donor human lungs after the neonatal intensive care unit hospitalization. This study provides new insights into how the proteome and histopathology of BPD changes in early childhood, uncovering novel pathways for future study.

Annexin A12-26 hydrogel improves healing properties in an experimental skin lesion after induction of type 1 diabetes

Diabetes mellitus (DM) is characterized by metabolic alterations that involve defects in the secretion and/or action of insulin, being responsible for several complications, such as impaired healing. Studies from our research group have shown that annexin A1 protein (AnxA1) is involved in the regulation of inflammation and cell proliferation. In light of these findings, we have developed a new technology and evaluated its effect on a wound healing in vivo model using type 1 diabetes (T1DM)-induced mice. We formulated a hydrogel containing AnxA12-26 using defined parameters such as organoleptic characteristics, pH, UV-vis spectroscopy and cytotoxicity assay. UV-vis spectroscopy confirmed the presence of the associated AnxA12-26 peptide in the three-dimensional hydrogel matrix, while the in vitro cytotoxicity assay showed excellent biocompatibility. Mice showed increased blood glucose levels, confirming the efficacy of streptozotocin (STZ) to induce T1DM. Treatment with AnxA12-26 hydrogel showed to improve diabetic wound healing, defined as complete re-epithelialization and tissue remodeling, with reduction of inflammatory infiltrate in diabetic animals. We envisage that the AnxA12-26 hydrogel, with its innovative composition and formulation be efficient on improving diabetic healing and contributing on the expansion of the therapeutic arsenal to treat diabetic wounds, at a viable cost.

Gene knockout inference with variational graph autoencoder learning single-cell gene regulatory networks

In this paper, we introduce Gene Knockout Inference (GenKI), a virtual knockout (KO) tool for gene function prediction using single-cell RNA sequencing (scRNA-seq) data in the absence of KO samples when only wild-type (WT) samples are available. Without using any information from real KO samples, GenKI is designed to capture shifting patterns in gene regulation caused by the KO perturbation in an unsupervised manner and provide a robust and scalable framework for gene function studies. To achieve this goal, GenKI adapts a variational graph autoencoder (VGAE) model to learn latent representations of genes and interactions between genes from the input WT scRNA-seq data and a derived single-cell gene regulatory network (scGRN). The virtual KO data is then generated by computationally removing all edges of the KO gene-the gene to be knocked out for functional study-from the scGRN. The differences between WT and virtual KO data are discerned by using their corresponding latent parameters derived from the trained VGAE model. Our simulations show that GenKI accurately approximates the perturbation profiles upon gene KO and outperforms the state-of-the-art under a series of evaluation conditions. Using publicly available scRNA-seq data sets, we demonstrate that GenKI recapitulates discoveries of real-animal KO experiments and accurately predicts cell type-specific functions of KO genes. Thus, GenKI provides an in-silico alternative to KO experiments that may partially replace the need for genetically modified animals or other genetically perturbed systems.

Annexin A1 Is Associated with Adverse Clinical Outcomes in Patients with COVID-19

Severe coronavirus disease 2019 (COVID-19) is characterized by hyperinflammation, vascular damage, and hypercoagulability. Insufficient responses of Annexin A1 (AnxA1), a pro-resolving inhibitor of neutrophil infiltration and activation, might contribute to a severe course of the disease. We longitudinally evaluated AnxA1's role in terms of inflammation, vascular damage, and clinical outcomes in a large prospective cohort of patients with COVID-19. AnxA1 was measured at presentation and during follow-up in the sera of 220 consecutive patients who presented at our hospital during the first wave. AnxA1 was significantly higher in the moderate and severe cases of COVID-19 compared to the healthy controls. Elevated AnxA1 was associated with markers of inflammation and endothelial damage. AnxA1 was significantly higher in patients with thrombotic events and ICU admission. Multivariable logistic regression indicated baseline AnxA1 (per ten units) as a predictor of thrombotic events. Linear mixed models predicted that AnxA1 tended to increase more steeply over time in patients without adverse events, with a statistically significant rise in patients without thrombotic events. These findings might reflect an insufficient increase in AnxA1 as a response to the excessive hyperinflammation in COVID-19. Future studies should evaluate whether hyperinflammation could be reduced through the administration of human recombinant AnxA1 or Ac2-26 peptide.

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.

The UIP/IPF fibroblastic focus is a collagen biosynthesis factory embedded in a distinct extracellular matrix

Usual interstitial pneumonia (UIP) is a histological pattern characteristic of idiopathic pulmonary fibrosis (IPF). The UIP pattern is patchy with histologically normal lung adjacent to dense fibrotic tissue. At this interface, fibroblastic foci (FF) are present and are sites where myofibroblasts and extracellular matrix (ECM) accumulate. Utilizing laser capture microdissection-coupled mass spectrometry, we interrogated the FF, adjacent mature scar, and adjacent alveoli in 6 fibrotic (UIP/IPF) specimens plus 6 nonfibrotic alveolar specimens as controls. The data were subjected to qualitative and quantitative analysis and histologically validated. We found that the fibrotic alveoli protein signature is defined by immune deregulation as the strongest category. The fibrotic mature scar classified as end-stage fibrosis whereas the FF contained an overabundance of a distinctive ECM compared with the nonfibrotic control. Furthermore, FF were positive for both TGFB1 and TGFB3, whereas the aberrant basaloid cell lining of FF was predominantly positive for TGFB2. In conclusion, spatial proteomics demonstrated distinct protein compositions in the histologically defined regions of UIP/IPF tissue. These data revealed that FF are the main site of collagen biosynthesis and that the adjacent alveoli are abnormal. This essential information will inform future mechanistic studies on fibrosis progression.

Therapeutic potential for targeting Annexin A1 in fibrotic diseases

Annexin A1, a well-known endogenous anti-inflammatory mediator, plays a critical role in a variety of pathological processes. Fibrosis is described by a failure of tissue regeneration and contributes to the development of many diseases. Accumulating evidence supports that Annexin A1 participates in the progression of tissue fibrosis. However, the fundamental mechanisms by which Annexin A1 regulates fibrosis remain elusive, and even the functions of Annexin A1 in fibrotic diseases are still paradoxical. This review focuses on the roles of Annexin A1 in the development of fibrosis of lung, liver, heart, and other tissues, with emphasis on the therapy potential of Annexin A1 in fibrosis, and presents future research interests and directions in fibrotic diseases.

Annexin A1 treatment prevents the evolution to fibrosis of experimental nonalcoholic steatohepatitis (NASH)

Annexin A1 (AnxA1) is an important effector in the resolution of inflammation which is involved in modulating hepatic inflammation in nonalcoholic steatohepatitis (NASH). In this study we have investigated the possible effects of treatment with AnxA1 for counteracting the progression of experimental NASH. NASH was induced in C57BL/6 mice by feeding methionine-choline deficient (MCD) or Western diets and the animals were treated for 4-6 weeks with human recombinant AnxA1 (hrAnxA1; 1µg, daily IP) or saline once NASH was established. In both experimental models, treatment with hrAnxA1 improved parenchymal injury and lobular inflammation without interfering with the extension of steatosis. Furthermore, administration of hrAnxA1 significantly attenuated the hepatic expression of α1-procollagen and TGF-ß1 and reduced collagen deposition, as evaluated by collagen Sirius Red staining. Flow cytometry and immunohistochemistry showed that hrAnxA1 did not affect the liver recruitment of macrophages, but strongly interfered with the formation of crown-like macrophage aggregates and reduced their capacity of producing pro-fibrogenic mediators like osteopontin (OPN) and galectin-3 (Gal-3). This effect was related to an interference with the acquisition of a specific macrophage phenotype characterized by the expression of the Triggering Receptor Expressed on Myeloid cells 2 (TREM-2), CD9 and CD206, previously associated with NASH evolution to cirrhosis. Collectively, these results indicate that, beside ameliorating hepatic inflammation, AnxA1 is specifically effective in preventing NASH-associated fibrosis by interfering with macrophage pro-fibrogenic features. Such a novel function of AnxA1 gives the rational for the development of AnxA1 analogues for the therapeutic control of NASH evolution.

Single-Cell RNA Sequencing Reveals the Interaction of Injected ADSCs with Lung-Originated Cells in Mouse Pulmonary Fibrosis

Pulmonary fibrosis (PF) is a severe chronic lung disease with little effective treatment options other than lung transplantation. Adipose-derived mesenchymal stem cells (ADSCs) have been shown to exert therapeutic effects on PF, but the underlying mechanisms remain to be further elucidated. Here, we show the interaction of ADSCs and lung-originated cells at the single-cell level, using bleomycin- (BLM-) induced mice PF model and green fluorescent protein– (GFP–) labeled mouse ADSCs. The intratracheally injected ADSCs were successfully recollected with flow cytometry and, together with lung-originated cells, were subjected to single-cell RNA sequencing (scRNA-seq). The ADSC treatment drastically changed the transcriptomic profile and composition of lung cells, especially macrophages. We explored the signal pathway interactions between ADSCs and lung-originated cells, showing potentially regulative pathways including NGR, ANNEXIN, HGF, and PERIOSTIN. Our data indicate that the injected ADSCs increased the number of Trem2⁺ antiinflammatory lung macrophages and lowered further inflammation and fibrosis in the lung. Our work realized the direct analysis of injected ADSCs to explore its in vivo interaction with the lung environment under PF and may provide critical information for future engineering of ADSCs to achieve better therapeutic effects in PF.

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.

Innovative Anti-Inflammatory and Pro-resolving Strategies for Pulmonary Hypertension: High Blood Pressure Research Council of Australia Award 2019

Pulmonary hypertension is a rare, ostensibly incurable, and etiologically diverse disease with an unacceptably high 5-year mortality rate (≈50%), worse than many cancers. Irrespective of pathogenic origin, dysregulated immune processes underlie pulmonary hypertension pathobiology, particularly pertaining to pulmonary vascular remodeling. As such, a variety of proinflammatory pathways have been mooted as novel therapeutic targets. One such pathway involves the family of innate immune regulators known as inflammasomes. In addition, a new and emerging concept is differentiating between anti-inflammatory approaches versus those that promote pro-resolving pathways. This review will briefly introduce inflammasomes and examine recent literature concerning their role in pulmonary hypertension. Moreover, it will explore the difference between inflammation-suppressing and pro-resolution approaches and how this links to inflammasomes. Finally, we will investigate new avenues for targeting inflammation in pulmonary hypertension via more targeted anti-inflammatory or inflammation resolving strategies.

Annexin Animal Models-From Fundamental Principles to Translational Research

Routine manipulation of the mouse genome has become a landmark in biomedical research. Traits that are only associated with advanced developmental stages can now be investigated within a living organism, and the in vivo analysis of corresponding phenotypes and functions advances the translation into the clinical setting. The annexins, a family of closely related calcium (Ca²⁺)- and lipid-binding proteins, are found at various intra- and extracellular locations, and interact with a broad range of membrane lipids and proteins. Their impacts on cellular functions has been extensively assessed in vitro, yet annexin-deficient mouse models generally develop normally and do not display obvious phenotypes. Only in recent years, studies examining genetically modified annexin mouse models which were exposed to stress conditions mimicking human disease often revealed striking phenotypes. This review is the first comprehensive overview of annexin-related research using animal models and their exciting future use for relevant issues in biology and experimental medicine.

Identifying Signatures of Selection Related to Comb Development

The aim of this study was to identify genes involved in comb development to provide insights into the molecular mechanism of chickens' comb formation. Fixation index (FST) and average number of base differences (π) of males with large and small combs were calculated based on whole-genome resequencing data. Chromosome regions with larger FST values and smaller π were considered candidate selection regions. Through further annotation of gene functions and pathways, we sought to screen possible selected genes associated with comb development. By screening whole genome resequencing data, FST and π were calculated using a 40 Kb sliding window strategy and eight regions were identified. Quantitative trait loci (QTL; FOX1 gene) related to comb length were found on chromosome 1. QTL (GLP1R, BTBD9, MIR6633, and MDGA1 genes) related to comb weight were found on chromosome 3. QTL (ALDH1A1, TMC1, and ANXA1 genes) associated with comb area were found on the Z chromosome. Nineteen genes, Wnt signaling pathway and neuroactive ligand-receptor interaction signaling pathway directly or indirectly related to comb growth and development were found through functional annotation and GO analysis. Among the selected genes LYN, GLP1R, FOX1, TBK1, STRAP, ST6GALNAC, and Wnt signaling pathways were related to immunity. MDGA1, BTBD9, MTSS1, SrGAPs, and neuroactive ligand receptor interaction signaling pathways related to neural function were screened. ALDH1A1, ANXAl, THBS, HIF-1α, and ACTN1 genes were related to heat dissipation. Among the selected genes FOX1, MDGAl, and ANXAl associated with immunity, neurological function, and heat dissipation function coincided with genes affecting the length, weight, and area of the comb. Comprehensive analysis suggested that comb development was due to multiple genes and signaling pathways.

Rationale for the Use of Radiation-Activated Mesenchymal Stromal/Stem Cells in Acute Respiratory Distress Syndrome

We have previously shown that the combination of radiotherapy with human umbilical-cord-derived mesenchymal stromal/stem cells (MSCs) cell therapy significantly reduces the size of the xenotumors in mice, both in the directly irradiated tumor and in the distant nonirradiated tumor or its metastasis. We have also shown that exosomes secreted from MSCs preirradiated with 2 Gy are quantitatively, functionally and qualitatively different from the exosomes secreted from nonirradiated mesenchymal cells, and also that proteins, exosomes and microvesicles secreted by MSCs suffer a significant change when the cells are activated or nonactivated, with the amount of protein present in the exosomes of the preirradiated cells being 1.5 times greater compared to those from nonirradiated cells. This finding correlates with a dramatic increase in the antitumor activity of the radiotherapy when is combined with MSCs or with preirradiated mesenchymal stromal/stem cells (MSCs*). After the proteomic analysis of the load of the exosomes released from both irradiated and nonirradiated cells, we conclude that annexin A1 is the most important and significant difference between the exosomes released by the cells in either status. Knowing the role of annexin A1 in the control of hypoxia and inflammation that is characteristic of acute respiratory-distress syndrome (ARDS), we designed a hypothetical therapeutic strategy, based on the transplantation of mesenchymal stromal/stem cells stimulated with radiation, to alleviate the symptoms of patients who, due to pneumonia caused by SARS-CoV-2, require to be admitted to an intensive care unit for patients with life-threatening conditions. With this hypothesis, we seek to improve the patients' respiratory capacity and increase the expectations of their cure.

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.

Harnessing inflammation resolving-based therapeutic agents to treat pulmonary viral infections: What can the future offer to COVID-19?

Inflammation is generally accepted as a component of the host defence system and a protective response in the context of infectious diseases. However, altered inflammatory responses can contribute to disease in infected individuals. Many endogenous mediators that drive the resolution of inflammation are now known. Overall, mediators of resolution tend to decrease inflammatory responses and provide normal or greater ability of the host to deal with infection. In the lung, it seems that pro‐resolution molecules, or strategies that promote their increase, tend to suppress inflammation and lung injury and facilitate control of bacterial or viral burden. Here, we argue that the demonstrated anti‐inflammatory, pro‐resolving, anti‐thrombogenic and anti‐microbial effects of such endogenous mediators of resolution may be useful in the treatment of the late stages of the disease in patients with COVID‐19.

The involvement of annexin A1 in human placental response to maternal Zika virus infection

The association of Zika virus infection (ZIKV) with congenital malformation and neurological sequelae brought a significant global concern. Recent studies have shown that maternal viral infection leads to inflammation in the placental tissue. In this context, the antiinflammatory protein annexin 1 (ANXA1) has a major determination of the resolution of inflammation and it has been positively associated with antiparasitic activity in infected placental explants. Although these effects have been explored to some degree, ANXA1 expression and potential properties have not yet been fully elucidated in placentas infected with ZIKV. This study was conducted to evaluate the histopathology, inflammatory process and elucidate if ANXA1 were differently expressed in placentas of ZIKV-infected mothers. Three classification groups were used in this study: Neg/Neg (mother and placenta negative for the virus), Pos/Neg (infected mother, but no virus detected in placenta) and Pos/Pos (mother and placenta infected with ZIKV). ANXA1 was expressed in syncytiotrophoblast cells of all studied groups, and its expression was decreased in Pos/Neg group, which displayed also an increase of the inflammatory response, as evinced from the recruitment of inflammatory cells, increased levels of placenta cytokines, and evidence of impaired tissue repair. The presence of ZIKV in placentas of Pos/Pos group shows structural alterations, including detachment and disorganization of the trophoblastic epithelium. In summary, our results suggest that maternal infection with ZIKV, even without direct tissue infection, leads to a placental inflammatory response probably related to the modulation of ANXA1. After placental infection, structural changes - including inflammatory cells influx - are observed leading to placental dysfunction and reduced fetal weight. Our study sheds additional light on the outcomes of ZIKV infection in trophoblast and reveals a potential involvement of ANXA1 in the placental biology.

Effect of piperlongumine during exposure to cigarette smoke reduces inflammation and lung injury

Chronic obstructive pulmonary disease (COPD) is related to smoking and anti-inflammatory therapy is indicated. Among the mediators with anti-inflammatory properties, we highlight piperlongumine (PL), an alkaloid/amide of Piper longum. Here we evaluated the PL administration on an experimental model of respiratory inflammation resulting from exposure to cigarette smoke. Male Balb/c mice were exposed to burning of 10 commercial cigarettes, 2x/day, for five weeks on specific equipment. PL efficacy was evaluated in control, exposed to smoke without treatment and PL treated (2.0 mg/kg, 3x/week) groups. Animals were weighed and plethysmographic analyses performed at the end of the exposure protocol. Inflammatory cells were evaluated in the bronchoalveolar lavage (BAL) and hemoglobin and glucose in the blood. Lung fragments were processed for histopathological studies and AnxA1, COX-2, NF-kB and neutrophil elastase expressions. Plethysmography revealed that PL maintained pulmonary frequency, volume and ventilation parameters similar to controls, with respiratory volume reduction compared to untreated animals. Final weight was reduced in both exposed groups. PL decreased hemoglobin concentration, attenuated the reduction of glucose levels and reduced influx of lymphocytes, neutrophils and macrophages in BAL. Histopathologically occured infiltration of inflammatory cells, increase of the interalveolar septa and intra-alveolar spaces in untreated animals. But, PL administration recovered lung tissues and, immunohistochemically, promoted increased expression of AnxA1 and reduction of COX-2, NF-kB and neutrophil elastase. Together the results indicate that PL attenuates systemic and pulmonary inflammatory changes, partially by modulating the expression the endogenous AnxA1, and may represent a promising therapy in preventing the inflammation induced by cigarette smoke.

Annexin A1 involved in the regulation of inflammation and cell signaling pathways

With the deepening of research, proteomics has developed into a science covering the study of all the structural and functional characteristics of proteins and the dynamic change rules. The essence of various biological activities is revealed from the perspectives of the biological structure, functional activity and corresponding regulatory mechanism of proteins by proteomics. Among them, phospholipid-binding protein is one of the hotspots of proteomics, especially annexin A1, which is widely present in various tissues and cells of the body. It has the capability of binding to phospholipid membranes reversibly in a calcium ion dependent manner. In order to provide possible research ideas for researchers, who are interested in this protein, the biological effects of annexin A1, such as inflammatory regulation, cell signal transduction, cell proliferation, differentiation and apoptosis are described in this paper.

Annexin A1 accounts for an anti-inflammatory binding target of sesamin metabolites

Sesamin [(7α,7'α,8α,8'α)-3,4:3',4'-bis(methylenedioxy)-7,9':7',9-diepoxylignane] is a major lignan in sesame seeds. Sesamin is converted to the catechol metabolite, SC1 [(7α,7'α,8α,8'α)-3',4'-methylenedioxy-7,9':7',9-diepoxylignane-3,4-diol] with anti-inflammatory effects after oral administration. However, its molecular target remains unknown. Analysis using high-performance affinity nanobeads led to the identification of annexin A1 (ANX A1) as an SC1-binding protein. SC1 was found to bind to the annexin repeat 3 region of ANX A1 with a high-affinity constant (Kd = 2.77 μmol L^-1). In U937 cells, SC1 exhibited an anti-inflammatory effect dependent on ANX A1. Furthermore, administration of sesamin or SC1 attenuated carbon tetrachloride-induced liver damage in mice and concurrently suppressed inflammatory responses dependent on ANX A1. The mechanism involved SC1-induced ANX A1 phosphorylation at serine 27 that facilitates extracellular ANX A1 release. Consequently, the ANX A1 released into the extracellular space suppressed the production of tumor necrosis factor α. This study demonstrates that ANX A1 acts as a pivotal target of sesamin metabolites to attenuate inflammatory responses.

Annexin-A1 deficiency exacerbates pathological remodelling of the mesenteric vasculature in insulin-resistant, but not insulin-deficient, mice

BACKGROUND AND PURPOSE

Arterial stiffness, a characteristic feature of diabetes, increases the risk of cardiovascular complications. Potential mechanisms that promote arterial stiffness in diabetes include oxidative stress, glycation and inflammation. The anti-inflammatory protein annexin-A1 has cardioprotective properties, particularly in the context of ischaemia. However, the role of endogenous annexin-A1 in the vasculature in both normal physiology and pathophysiology remains largely unknown. Hence, this study investigated the role of endogenous annexin-A1 in diabetes-induced remodelling of mouse mesenteric vasculature.

EXPERIMENTAL APPROACH

Insulin-resistance was induced in male mice (AnxA1^+/+ and AnxA1^-/- ) with the combination of streptozotocin (55mg/kg i.p. x 3 days) with high fat diet (42% energy from fat) or citrate vehicle with normal chow diet (20-weeks). Insulin-deficiency was induced in a separate cohort of mice using a higher total streptozocin dose (55mg/kg i.p. x 5 days) on chow diet (16-weeks). At study endpoint, mesenteric artery passive mechanics were assessed by pressure myography.

KEY RESULTS

Insulin-resistance induced significant outward remodelling but had no impact on passive stiffness. Interestingly, vascular stiffness was significantly increased in AnxA1^-/- mice when subjected to insulin-resistance. In contrast, insulin-deficiency induced outward remodelling and increased volume compliance in mesenteric arteries, regardless of genotype. In addition, the annexin-A1 / formyl peptide receptor axis is upregulated in both insulin-resistant and insulin-deficient mice.

CONCLUSION AND IMPLICATIONS

Our study provided the first evidence that endogenous AnxA1 may play an important vasoprotective role in the context of insulin-resistance. AnxA1-based therapies may provide additional benefits over traditional anti-inflammatory strategies for reducing vascular injury in diabetes.

Cell-surface translocation of annexin A2 contributes to bleomycin-induced pulmonary fibrosis by mediating inflammatory response in mice

Bleomycin, a widely used anti-cancer drug, may give rise to pulmonary fibrosis, a serious side effect which is associated with significant morbidity and mortality. Despite the intensive efforts, the precise pathogenic mechanisms of pulmonary fibrosis still remain to be clarified. Our previous study showed that bleomycin bound directly to annexin A2 (ANXA2, or p36), leading to development of pulmonary fibrosis by impeding transcription factor EB (TFEB)-induced autophagic flux. Here, we demonstrated that ANXA2 also played a critical role in bleomycin-induced inflammation, which represents another major cause of bleomycin-induced pulmonary fibrosis. We found that bleomycin could induce the cell surface translocation of ANXA2 in lung epithelial cells through exosomal secretion, associated with enhanced interaction between ANXA2 and p11. Knockdown of ANXA2 or blocking membrane ANXA2 mitigated bleomycin-induced activation of nuclear factor (NF)-κB pathway and production of pro-inflammatory cytokine IL-6 in lung epithelial cells. ANXA2-deficient (ANXA2-/-) mice treated with bleomycin exhibit reduced pulmonary fibrosis along with decreased cytokine production compared with bleomycin-challenged wild-type mice. Further, the surface ANXA2 inhibitor TM601 could ameliorate fibrotic and inflammatory response in bleomycin-treated mice. Taken together, our results indicated that, in addition to disturbing autophagic flux, ANXA2 can contribute to bleomycin-induced pulmonary fibrosis by mediating inflammatory response.

The annexin A1/FPR2 signaling axis expands alveolar macrophages, limits viral replication, and attenuates pathogenesis in the murine influenza A virus infection model

Pattern recognition receptors (PRRs) are key elements in the innate immune response. Formyl peptide receptor (FPR) 2 is a PRR that, in addition to proinflammatory, pathogen-derived compounds, also recognizes the anti-inflammatory endogenous ligand annexin A1 (AnxA1). Because the contribution of this signaling axis in viral infections is undefined, we investigated AnxA1-mediated FPR2 activation on influenza A virus (IAV) infection in the murine model. AnxA1-treated mice displayed significantly attenuated pathology upon a subsequent IAV infection with significantly improved survival, impaired viral replication in the respiratory tract, and less severe lung damage. The AnxA1-mediated protection against IAV infection was not caused by priming of the type I IFN response but was associated with an increase in the number of alveolar macrophages (AMs) and enhanced pulmonary expression of the AM-regulating cytokine granulocyte-M-CSF (GM-CSF). Both AnxA1-mediated increase in AM levels and GM-CSF production were abrogated when mouse (m)FPR2 signaling was antagonized but remained up-regulated in mice genetically deleted for mFPR1, an mFPR2 isoform also serving as AnxA1 receptor. Our results indicate a novel protective function of the AnxA1-FPR2 signaling axis in IAV pathology via GM-CSF–associated maintenance of AMs, expanding knowledge on the potential use of proresolving mediators in host defense against pathogens.—Schloer, S., Hübel, N., Masemann, D., Pajonczyk, D., Brunotte, L., Ehrhardt, C., Brandenburg, L.-O., Ludwig, S., Gerke, V., Rescher, U. The annexin A1/FPR2 signaling axis expands alveolar macrophages, limits viral replication, and attenuates pathogenesis in the murine influenza A virus infection model.

Modulation of the endogenous Annexin A1 in a cigarette smoke cessation model: Potential therapeutic target in reversing the damage caused by smoking?

BACKGROUND

Smoking cessation may help in the reversal of inflammation and damage caused by smoking. The endogenous annexin A1 (AnxA1) protein has anti-inflammatory effects which instigates the understanding of its role in the attenuation of inflammatory processes caused by smoking.

MATERIAL AND METHODS

Wistar rats were exposed to cigarette smoke for 8 weeks. After the exposure period, one of the groups remained other 8 weeks in the absence of smoke. Animals not exposed to smoke were used as control. Blood, trachea and lungs were obtained for histopathological, immunohistochemical and biochemical analyses.

RESULTS

Loss of cilia of the tracheal lining epithelium was found by smoke exposure, but smoking cessation led to recovery of the tracheal epithelium. Similarly, chronically exposed-to-smoke animals showed increased lymphocytes and macrophages in bronchoalveolar lavage and higher levels of glucose and gamma-GT in their blood. Reduction of lymphocytes, glucose and gamma-GT occurred after smoking cessation. In addition, IL-1β, IL-6, IL-10, TNF-α and MCP-1 levels were elevated by smoke exposure. Smoking cessation significantly reduced the levels of IL-1β, IL-6 and MCP-1 but increased the IL-10 concentration. Numerous mast cells and macrophages were observed in the lung of chronically exposed-to-smoke animals with reduction by smoking cigarette abstinence. AnxA1 increased expression and concomitant NF-κB reduction were found in the smoking cessation group.

CONCLUSION

Our results showed that cigarette abstinence promoted partial recovery of the inflammatory process. The attenuation of the inflammatory profile may be associated with the overexpression of AnxA1 protein.

Annexin A1 mimetic peptide Ac2-26 attenuates mechanical injury induced corneal scarring and inflammation

Annexin A1 (AnxA1) has been shown to exert potent anti-inflammatory and anti-fibrotic activities in a range of systemic inflammatory disorders. Corneal scarring is characterized by myofibroblast differentiation and disorganized extracellular matrix deposition. This study was aim to explore the potential therapeutic properties of Ac2-26, a mimetic peptide of AnnexinA1 (AnxA1), on TGF-β induced human corneal myofibroblast differentiation and mechanical injury-induced mouse corneal haze. The results found that Ac2-26 treatment dose dependently reduced α-SMA level and other fibrogenic gene expressions in HTK cells stimulated by exogenous TGF-β1. While this anti-fibrotic effect was abolished by an FPR2/ALX inhibitor WRW4. In mice, topical Ac2-26 application suppressed the development of corneal scarring, inhibited myofibroblast differentiation, while promoted the corneal epithelial wound healing. Moreover, Ac2-26 treatment inhibited Ly6G + neutrophil infiltration and reduced corneal inflammatory response. The results provided in vivo and in vitro supports the anti-fibrotic and anti-inflammatory effects of AnxA1 derived peptide Ac2-26, and suggest that AnxA1 mimetic agents might be a promising strategy for the treatment of corneal scarring.

Annexin A1 is elevated in patients with COPD and affects lung fibroblast function

Purpose

Fibrosis in peripheral airways is responsible for airflow limitation in chronic obstructive pulmonary disease (COPD). Annexin A1 modulates several key biological events during inflammation. However, little is known about its role in airway fibrosis in COPD. We investigated whether levels of Annexin A1 were upregulated in patients with COPD, and whether it promoted airway fibrosis.

Methods

We quantified serum Annexin A1 levels in never-smokers (n=12), smokers without COPD (n=11), and smokers with COPD (n=22). Correlations between Annexin A1 expression and clinical indicators (eg, lung function) were assessed. In vitro, human bronchial epithelial (HBE) cells were exposed to cigarette smoke extract (CSE) and Annexin A1 expression was assessed. Primary human lung fibroblasts were isolated from patients with COPD and effects of Annexin A1 on fibrotic deposition of lung fibroblasts were evaluated.

Results

Serum Annexin A1 was significantly higher in patients with Global Initiative for Chronic Obstructive Lung Disease (GOLD) guidelines stage III or IV than in those with GOLD stages I or II (12.8±0.8 ng/mL versus 9.8±0.7 ng/mL; p=0.016). Annexin A1 expression was negatively associated with airflow obstruction (forced expiratory volume in one second % predicted; r=−0.72, p<0.001). In vitro, Annexin A1 was significantly increased in CSE-exposed HBE cells in a time- and concentration-dependent manner. Annexin A1 promoted lung fibroblasts proliferation, migration, differentiation, and collagen deposition via the ERK1/2 and p38 mitogen-activated protein kinase pathways.

Conclusion

Annexin A1 expression is upregulated in patients with COPD and affects lung fibroblast function. However, more studies are needed to clarify the role of Annexin A1 in airway fibrosis of COPD.

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

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

Annexins - insights from knockout mice

Annexins are a highly conserved protein family that bind to phospholipids in a calcium (Ca2+) - dependent manner. Studies with purified annexins, as well as overexpression and knockdown approaches identified multiple functions predominantly linked to their dynamic and reversible membrane binding behavior. However, most annexins are found at multiple locations and interact with numerous proteins. Furthermore, similar membrane binding characteristics, overlapping localizations and shared interaction partners have complicated identification of their precise functions. To gain insight into annexin function in vivo, mouse models deficient of annexin A1 (AnxA1), A2, A4, A5, A6 and A7 have been generated. Interestingly, with the exception of one study, all mice strains lacking one or even two annexins are viable and develop normally. This suggested redundancy within annexins, but examining these knockout (KO) strains under stress conditions revealed striking phenotypes, identifying underlying mechanisms specific for individual annexins, often supporting Ca2+ homeostasis and membrane transport as central for annexin biology. Conversely, mice lacking AnxA1 or A2 show extracellular functions relevant in health and disease that appear independent of membrane trafficking or Ca2+ signaling. This review will summarize the mechanistic insights gained from studies utilizing mouse models lacking members of the annexin family.

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

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

Annexin A1: shifting the balance towards resolution and repair

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

Phagocytosis imprints heterogeneity in tissue-resident macrophages

Macrophages are important for tissue function, and adapt phenotypically to each tissue by factors produced locally. A-Gonzalez et al. now show that phagocytosis of unwanted cells additionally contributes to imprinting macrophage heterogeneity, thus promoting tissue homeostasis.

Tissue-resident macrophages display varying phenotypic and functional properties that are largely specified by their local environment. One of these functions, phagocytosis, mediates the natural disposal of billions of cells, but its mechanisms and consequences within living tissues are poorly defined. Using a parabiosis-based strategy, we identified and isolated macrophages from multiple tissues as they phagocytosed blood-borne cellular material. Phagocytosis was circadianally regulated and mediated by distinct repertoires of receptors, opsonins, and transcription factors in macrophages from each tissue. Although the tissue of residence defined the core signature of macrophages, phagocytosis imprinted a distinct antiinflammatory profile. Phagocytic macrophages expressed CD206, displayed blunted expression of Il1b, and supported tissue homeostasis. Thus, phagocytosis is a source of macrophage heterogeneity that acts together with tissue-derived factors to preserve homeostasis.

Heterogeneity of mast cells and expression of Annexin A1 protein in a second degree burn model with silver sulfadiazine treatment

Mast cells (MCs) participate in all stages of skin healing and one of their mediators is the Annexin A1 protein (AnxA1), linked to inflammation, proliferation, migration and apoptosis processes, but not studied in thermal burns yet. Therefore, our objectives were to evaluate the behavior of MCs and AnxA1 in a second degree burn model, treated or not with silver sulfadiazine 1% (SDP 1%) and associated to macrophages quantification and cytokines dosages. MCs counts showed few cells in the early stages of repair but increased MCs in the final phases in the untreated group. The normal skin presented numerous tryptase-positive MCs that were reduced after burning in all analyzed periods. Differently, few chymase-positive MCs were observed in the early stages of healing, however, increased chymase-positive MCs were found at the final phase in the untreated group. MCs also showed high immunoreactivity for AnxA1 on day 3 in both groups. In the tissue there was a strong protein expression in the early stages of healing, but in the final phases only in the SDP treated animals. TNF-α, IL-1β, IL-6, IL-10 and MCP-1 levels and macrophages quantification were increased in inflammation and reepithelialization phases. Reduced IL-1β, IL-6 and IL-10 levels and numerous macrophages occurred in the treated animals during tissue repair. Our results indicate modulation in the profile of MCs and AnxA1expression during healing by the treatment with SDP 1%, pointing them as targets for therapeutic interventions on skin burns.

Lung fibrosis: drug screening and disease biomarker identification with a lung slice culture model and subtracted cDNA Library

Pulmonary fibrosis is a progressive and irreversible disorder with no appropriate cure. A practical and effective experimental model that recapitulates the disease will greatly benefit the research community and, ultimately, patients. In this study, we tested the lung slice culture (LSC) system for its potential use in drug screening and disease biomarker identification. Fibrosis was induced by treating rat lung slices with 1ng/ml TGF-β1 and 2.5μM CdCl2, quantified by measuring the content of hydroxyproline, and confirmed by detecting the expression of collagen type III alpha 1 (Col3α1) and connective tissue growth factor (CTGF) genes. The anti-fibrotic effects of pirfenidone, spironolactone and eplerenone were assessed by their capability to reduce hydroxyproline content. A subtractive hybridisation technique was used to create two cDNA libraries (subtracted and unsubtracted) from lung slices. The housekeeping gene glyceraldehyde-3-phosphate dehydrogenase (GAPDH) was employed to assess the subtraction efficiency of the subtracted cDNA library. Clones from the two libraries were sequenced and the genes were identified by performing a BLAST search on the NCBI GenBank database. Furthermore, the relevance of the genes to fibrosis formation was verified. The results presented here show that fibrosis was effectively induced in cultured lung slices, which exhibited significantly elevated levels of hydroxyproline and Col3α1/CTGF gene expression. Several inhibitors have demonstrated their anti-fibrotic effects by significantly reducing hydroxyproline content. The subtracted cDNA library, which was enriched for differentially expressed genes, was used to successfully identify genes associated with fibrosis. Collectively, the results indicate that our LSC system is an effective model for the screening of drug candidates and for disease biomarker identification.

The Interactome of the Glucocorticoid Receptor and Its Influence on the Actions of Glucocorticoids in Combatting Inflammatory and Infectious Diseases

Glucocorticoids (GCs) have been widely used for decades as a first-line treatment for inflammatory and autoimmune diseases. However, their use is often hampered by the onset of adverse effects or resistance. GCs mediate their effects via binding to glucocorticoid receptor (GR), a transcription factor belonging to the family of nuclear receptors. An important aspect of GR's actions, including its anti-inflammatory capacity, involves its interactions with various proteins, such as transcription factors, cofactors, and modifying enzymes, which codetermine receptor functionality. In this review, we provide a state-of-the-art overview of the protein-protein interactions (PPIs) of GR that positively or negatively affect its anti-inflammatory properties, along with mechanistic insights, if known. Emphasis is placed on the interactions that affect its anti-inflammatory effects in the presence of inflammatory and microbial diseases.

Activation of annexin A1 signalling in renal fibroblasts exerts antifibrotic effects

AIM

The anti-inflammatory protein annexin A1 (AnxA1) and its formyl peptide receptor 2 (FPR2) have protective effects in organ fibrosis. Their role in chronic kidney disease (CKD) has not yet been elucidated. Our aim was to characterize the AnxA1/FPR2 system in models of renal fibrosis.

METHODS

Rats were treated with angiotensin receptor antagonist during the nephrogenic period (ARAnp) to induce late-onset hypertensive nephropathy and fibrosis. Localization and regulation of AnxA1 and FPR2 were studied by quantitative real-time PCR and double labelling immunofluorescence. Biological effects of AnxA1 were studied in cultured renal fibroblasts from AnxA1(-/-) and wild-type mice.

RESULTS

Angiotensin receptor antagonist during the nephrogenic period kidneys displayed matrix foci containing CD73(+) fibroblasts, alpha-smooth muscle actin (a-SMA)(+) myofibroblasts and CD68(+) macrophages. TGF-β and AnxA1 mRNAs were ~threefold higher than in controls. AnxA1 was localized to macrophages and fibroblasts; myofibroblasts were negative. FPR2 was localized to fibroblasts, myofibroblasts, macrophages and endothelial cells. AnxA1 and FPR2 immunoreactive signals were increased in the foci, with fibroblasts and macrophages expressing both proteins. AnxA1(-/-) fibroblasts revealed higher α-SMA (sevenfold) and collagen 1A1 (Col1A1; 144-fold) mRNA levels than controls. Treatment of murine WT fibroblasts with TGF-β (22.5 ng mL 24 h(-1)) increased mRNA levels of α-SMA (9.3-fold) and Col1A1 (fourfold). These increases were greatly attenuated upon overexpression of AnxA1 (1.5- and 1.7-fold, respectively; P < 0.05). Human fibroblasts reacted similarly when receiving the FPR2 inhibitor WRW4.

CONCLUSION

Our results demonstrate that AnxA1 and FPR2 are abundantly expressed in the renal interstitium and modulate fibroblast phenotype and extracellular matrix synthesis activity.

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

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

Cardioprotective potential of annexin-A1 mimetics in myocardial infarction

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

Endogenous annexin A1 is a novel protective determinant in nonalcoholic steatohepatitis in mice

Annexin A1 (AnxA1) is an effector of the resolution of inflammation and is highly effective in terminating acute inflammatory responses. However, its role in chronic settings is less investigated. Because changes in AnxA1 expression within adipose tissue characterize obesity in mice and humans, we queried a possible role for AnxA1 in the pathogenesis of nonalcoholic steatohepatitis (NASH), a disease commonly associated with obesity. NASH was induced in wild-type (WT) and AnxA1 knockout (AnxA1 KO) C57BL/6 mice by feeding a methionine-choline deficient (MCD) diet up to 8 weeks. In MCD-fed WT mice, hepatic AnxA1 increased in parallel with progression of liver injury. This mediator was also detected in liver biopsies from patients with NASH and its degree of expression inversely correlated with the extent of fibrosis. In both humans and rodents, AnxA1 production was selectively localized in liver macrophages. NASH in AnxA1 KO mice was characterized by enhanced lobular inflammation resulting from increased macrophage recruitment and exacerbation of the M1 phenotype. Consistently, in vitro addition of recombinant AnxA1 to macrophages isolated from NASH livers down-modulated M1 polarization through stimulation of interleukin-10 production. Furthermore, the degree of hepatic fibrosis was enhanced in MCD-fed AnxA1 KO mice, an effect associated with augmented liver production of the profibrotic lectin, galectin-3. Accordingly, AnxA1 addition to isolated hepatic macrophages reduced galectin-3 expression.

CONCLUSIONS

Macrophage-derived AnxA1 plays a functional role in modulating hepatic inflammation and fibrogenesis during NASH progression, suggesting the possible use of AnxA1 analogs for therapeutic control of this disease.

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.

New insights into the anti-inflammatory mechanisms of glucocorticoids: an emerging role for glucocorticoid-receptor-mediated transactivation

Glucocorticoids are anti-inflammatory drugs that are widely used for the treatment of numerous (autoimmune) inflammatory diseases. They exert their actions by binding to the glucocorticoid receptor (GR), a member of the nuclear receptor family of transcription factors. Upon ligand binding, the GR translocates to the nucleus, where it acts either as a homodimeric transcription factor that binds glucocorticoid response elements (GREs) in promoter regions of glucocorticoid (GC)-inducible genes, or as a monomeric protein that cooperates with other transcription factors to affect transcription. For decades, it has generally been believed that the undesirable side effects of GC therapy are induced by dimer-mediated transactivation, whereas its beneficial anti-inflammatory effects are mainly due to the monomer-mediated transrepressive actions of GR. Therefore, current research is focused on the development of dissociated compounds that exert only the GR monomer-dependent actions. However, many recent reports undermine this dogma by clearly showing that GR dimer-dependent transactivation is essential in the anti-inflammatory activities of GR. Many of these studies used GR(dim/dim) mutant mice, which show reduced GR dimerization and hence cannot control inflammation in several disease models. Here, we review the importance of GR dimers in the anti-inflammatory actions of GCs/GR, and hence we question the central dogma. We summarize the contribution of various GR dimer-inducible anti-inflammatory genes and question the use of selective GR agonists as therapeutic agents.

Regulation of lung fibroblast activation by annexin A1

Annexin-A1 (AnxA1) is a glucocorticoid-induced protein with multiple actions in the regulation of inflammatory cell activation. The contribution of AnxA1 to human cell biology is not well understood. We investigated the contribution of AnxA1 and its receptor, formyl-peptide receptor 2 (FPR2), to the regulation of inflammatory responses in human normal lung fibroblasts (NLF). Silencing constitutive AnxA1 expression in NLF using small interfering RNA (siRNA) was associated with moderate but significant increases in tumor necrosis factor (TNF)-induced proliferation and interleukin (IL)-6 production, accompanied by reduction of ERK and NF-κB activity. AnxA1 regulation of ERK and NF-κB activation was associated with effects on proliferation. Blocking FPR2 using the specific antagonist WRW4 mimicked the effects of AnxA1 silencing on TNF-induced proliferation, IL-6, ERK, and NF-κB activation. AnxA1 silencing also impaired inhibitory effects of glucocorticoid on IL-6 production and on the expression of glucocorticoid-induced leucine zipper (GILZ), but blocking FPR2 failed to mimic these effects of AnxA1 silencing. These data suggest that AnxA1 regulates TNF-induced proliferation and inflammatory responses in lung fibroblasts, via effects on the ERK and NF-κB pathways, which depend on FPR2. AnxA1 also mediates effects of glucocorticoids and GILZ expression, but these effects appear independent of FPR2. These findings suggest that mimicking AnxA1 actions might have therapeutic potential in chronic inflammatory lung diseases.