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The blood–brain barrier (BBB), a critical guardian of communication between the periphery and the brain, is frequently compromised in neurological diseases such as multiple sclerosis (MS), resulting in the inappropriate passage of molecules and leukocytes into the brain. Here we show that the glucocorticoid anti-inflammatory messenger annexin A1 (ANXA1) is expressed in brain microvascular endothelial cells, where it regulates BBB integrity. In particular, ANXA1 ⁻/⁻ mice exhibit significantly increased BBB permeability as a result of disrupted interendothelial cell tight junctions, essentially related to changes in the actin cytoskeleton, which stabilizes tight and adherens junctions. This situation is reminiscent of early MS pathology, a relationship confirmed by our detection of a selective loss of ANXA1 in the plasma and cerebrovascular endothelium of patients with MS. Importantly, this loss is swiftly restored by i.v. administration of human recombinant ANXA1. Analysis in vitro confirms that treatment of cerebrovascular endothelial cells with recombinant ANXA1 restores cell polarity, cytoskeleton integrity, and paracellular permeability through inhibition of the small G protein RhoA. We thus propose ANXA1 as a critical physiological regulator of BBB integrity and suggest it may have utility in the treatment of MS, correcting BBB function and hence ameliorating disease.

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

Cutaneous leishmaniasis (CL) is an infectious disease characterized by severe local inflammatory response, predominantly mediated by cytokines such as IL-1 β and TNF, and cytotoxicity, contributing to tissue damage and lesion development. Given the high rate of therapeutic failure in Leishmania braziliensis transmission areas, the investigation of molecules that regulate inflammatory response has become a promising adjuvant therapeutical strategy. In this study we investigated the effects of Annexin A1 (ANXA1) on the inflammatory response of CL patients. We initially performed in silico analyses from our previous transcriptome databases and found increased expression of ANXA1, IL1B , and IL10 genes in skin biopsies from CL patients when compared to healthy skin from healthy subjects (HS). Also, increased levels of ANXA1, IL1 β , and IL10 proteins were observed in serum levels and cultures of skin biopsies in CL patients when compared to HS. Treatment of lesion biopsies with recombinant ANXA1 reduced IL-1 β levels without affecting IL-10 secretion, indicating a selective anti-inflammatory effect. Additionally, monocyte-derived macrophages from HS increased ANXA1, IL-1 β , and IL-10 production upon Leishmania infection. Blockade of FPR2 receptor increased ANXA1 levels. Finally, addition of recombinant ANXA1 to macrophages did not affect the ability of these cells to kill Leishmania . Our findings demonstrate that ANXA1 negatively regulates IL-1 β in CL, without impairing anti-inflammatory mechanisms or macrophage microbicidal activity, highlighting its potential use as an adjuvant therapy for controlling inflammation and disease progression.

The tumor microenvironment (TME) is a dynamic system where nontumor and cancer cells intercommunicate through soluble factors and extracellular vesicles (EVs). The TME in pancreatic cancer (PC) is critical for its aggressiveness and the annexin A1 (ANXA1) has been identified as one of the oncogenic elements. Previously, we demonstrated that the autocrine/paracrine activities of extracellular ANXA1 depend on its presence in EVs. Here, we show that the complex ANXA1/EVs modulates the macrophage polarization further contributing to cancer progression. The EVs isolated from wild type (WT) and ANXA1 knock-out MIA PaCa-2 cells have been administrated to THP-1 macrophages finding that ANXA1 is crucial for the acquisition of a protumor M2 phenotype. The M2 macrophages activate endothelial cells and fibroblasts to induce angiogenesis and matrix degradation, respectively. We have also found a significantly increased presence of M2 macrophage in mice tumor and liver metastasis sections previously obtained by orthotopic xenografts with WT cells. Taken together, our data interestingly suggest the relevance of ANXA1 as potential diagnostic/prognostic and/or therapeutic PC marker.

There is currently no therapy available for periprosthetic osteolysis, the most common cause of arthroplasty failure. Here, the role of AnxA1 in periprosthetic osteolysis and potential therapeutics were investigated. Reducing the expression of AnxA1 in calvarial tissue was found to be associated with increased osteolytic lesions and the osteolytic lesions induced by debris implantation were more severe in AnxA1-defecient mice than in wild-type mice. AnxA1 inhibits the differentiation of osteoclasts through suppressing NFκB signaling and promoting the PPAR-γ pathway. Administration of N-terminal-AnxA1 (Ac2-26 peptide) onto calvariae significantly reduced osteolytic lesions triggered by wear debris. These therapeutic effects were abrogated in mice that had received the PPAR-γ antagonist, suggesting that the AnxA1/PPAR-γ axis has an inhibitory role in osteolysis. The administration of Ac2–26 suppressed osteolysis induced by TNF-α and RANKL injections in mice. These findings indicate that AnxA1 is a potential therapeutic agent for the treatment of periprosthetic osteolysis. Periprosthetic osteolysis is a cause of arthroplasty failure without available therapies. Here the authors show that Annexin A1 (AnxA1) is involved in in periprosthetic osteolysis and exerts potential therapeutic effects through suppressing NFκB signaling and promoting the PPAR-γ pathway resulting in inhibition of inflammation and osteoclasts differentiation induced by wear debris.

Background Microglia-induced excessive neuroinflammation plays a crucial role in the pathophysiology of multiple neurological diseases, such as ischaemic stroke. Controlling inflammatory responses is considered a promising therapeutic approach. Sirtuin 5 (SIRT5) mediates lysine desuccinylation, which is involved in various critical biological processes, but its role in ischaemic stroke remains poorly understood. This research systematically explored the function and potential mechanism of SIRT5 in microglia-induced neuroinflammation in ischaemic stroke. Methods Mice subjected to middle cerebral artery occlusion were established as the animal model, and primary cultured microglia treated with oxygen–glucose deprivation and reperfusion were established as the cell model of ischaemic stroke. SIRT5 short hairpin RNA, adenovirus and adeno-associated virus techniques were employed to modulate SIRT5 expression in microglia both in vitro and in vivo. Coimmunoprecipitation, western blot and quantitative real-time PCR assays were performed to reveal the molecular mechanism. Results In the current study, we showed that SIRT5 expression in microglia was increased in the early phase of ischaemic stroke. SIRT5 interacts with and desuccinylates Annexin A1 (ANXA1) at K166, which in turn decreases its SUMOylation level. Notably, the desuccinylation of ANXA1 blocks its membrane recruitment and extracellular secretion, resulting in the hyperactivation of microglia and excessive expression of proinflammatory cytokines and chemokines, ultimately leading to neuronal cell damage after ischaemic stroke. Further investigation showed that microglia-specific forced overexpression of SIRT5 worsened ischaemic brain injury, whereas downregulation of SIRT5 exhibited neuroprotective and cognitive-preserving effects against ischaemic brain injury, as proven by the decreased infarct area, reduced neurological deficit scores, and improved cognitive function. Conclusions Collectively, these data identify SIRT5 as a novel regulator of microglia-induced neuroinflammation and neuronal damage after cerebral ischaemia. Interventions targeting SIRT5 expression may represent a potential therapeutic target for ischaemic stroke.

In this Opinion article, the effector function of annexin A1 in the anti-inflammatory action of glucocorticoids is discussed, and a model to address the opposing effects of glucocorticoids on the expression of annexin A1 by different immune cells is proposed. Glucocorticoids are widely used for the management of inflammatory diseases. Their clinical application stems from our understanding of the inhibitory effect of the corticosteroid hormone cortisol on several components of the immune system. Endogenous and exogenous glucocorticoids mediate their multiple anti-inflammatory effects through many effector molecules. In this Opinion article, we focus on the role of one such effector molecule, annexin A1, and summarize the recent studies that provide insight into its molecular and pharmacological functions in immune responses. In addition, we propose a model in which glucocorticoids regulate the expression and function of annexin A1 in opposing ways in innate and adaptive immune cells to mediate the resolution of inflammation.

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

Epithelial restitution is an essential process that is required to repair barrier function at mucosal surfaces following injury. Prolonged breaches in epithelial barrier function result in inflammation and further damage; therefore, a better understanding of the epithelial restitution process has potential for improving the development of therapeutics. In this work, we demonstrate that endogenous annexin A1 (ANXA1) is released as a component of extracellular vesicles (EVs) derived from intestinal epithelial cells, and these ANXA1-containing EVs activate wound repair circuits. Compared with healthy controls, patients with active inflammatory bowel disease had elevated levels of secreted ANXA1-containing EVs in sera, indicating that ANXA1-containing EVs are systemically distributed in response to the inflammatory process and could potentially serve as a biomarker of intestinal mucosal inflammation. Local intestinal delivery of an exogenous ANXA1 mimetic peptide (Ac2-26) encapsulated within targeted polymeric nanoparticles (Ac2-26 Col IV NPs) accelerated healing of murine colonic wounds after biopsy-induced injury. Moreover, one-time systemic administration of Ac2-26 Col IV NPs accelerated recovery following experimentally induced colitis. Together, our results suggest that local delivery of proresolving peptides encapsulated within nanoparticles may represent a potential therapeutic strategy for clinical situations characterized by chronic mucosal injury, such as is seen in patients with IBD.

Antitumor immunity driven by intratumoral dendritic cells contributes to the efficacy of anthracycline-based chemotherapy in cancer. We identified a loss-of-function allele of the gene coding for formyl peptide receptor 1 (FPR1) that was associated with poor metastasis-free and overall survival in breast and colorectal cancer patients receiving adjuvant chemotherapy. The therapeutic effects of anthracyclines were abrogated in tumor-bearing Fpr1-/- mice due to impaired antitumor immunity. Fpr1-deficient dendritic cells failed to approach dying cancer cells and, as a result, could not elicit antitumor T cell immunity. Experiments performed in a microfluidic device confirmed that FPR1 and its ligand, annexin-1, promoted stable interactions between dying cancer cells and human or murine leukocytes. Altogether, these results highlight the importance of FPR1 in chemotherapy-induced anticancer immune responses.