The complex understanding of Annexin A1 phosphorylation

Cracking the code of Annexin A1-mediated chemoresistance

The annexin superfamily protein, Annexin A1, initially recognized for its glucocorticoid-induced phospholipase A2-inhibitory activities, has emerged as a crucial player in diverse cellular processes, including cancer. This review explores the multifaceted roles of Anx-A1 in cancer chemoresistance, an area largely unexplored. Anx-A1's involvement in anti-inflammatory processes, its complex phosphorylation patterns, and its context-dependent switch from anti-to pro-inflammatory in cancer highlights its intricate regulatory mechanisms. Recent studies highlight Anx-A1's paradoxical roles in different cancers, exhibiting both up- and down-regulation in a tissue-specific manner, impacting different hallmark features of cancer. Mechanistically, Anx-A1 modulates drug efflux transporters, influences cancer stem cell populations, DNA damages and participates in epithelial-mesenchymal transition. This review aims to explore Anx-A1's role in chemoresistance-associated pathways across various cancers, elucidating its impact on survival signaling cascades including PI3K/AKT, MAPK/ERK, PKC/JNK/P-gp pathways and NFκ-B signalling. This review also reveals the clinical implications of Anx-A1 dysregulation in treatment response, its potential as a prognostic biomarker, and therapeutic targeting strategies, including the promising Anx-A1 N-terminal mimetic peptide Ac2-26. Understanding Anx-A1's intricate involvement in chemoresistance offers exciting prospects for refining cancer therapies and improving treatment outcomes.

Anticancer Effects of the Novel Pyrazolyl-Urea GeGe-3

In a screen of over 200 novel pyrazole compounds, ethyl 1-(2-hydroxypentyl)-5-(3-(3-(trifluoromethyl) phenyl)ureido)-1H-pyrazole-4-carboxylate (named GeGe-3) has emerged as a potential anticancer compound. GeGe-3 displays potent anti-angiogenic properties through the presumptive targeting of the protein kinase DMPK1 and the Ca2+-binding protein calreticulin. We further explored the anticancer potential of GeGe-3 on a range of established cancer cell lines, including PC3 (prostate adenocarcinoma), SKMEL-28 (cutaneous melanoma), SKOV-3 (ovarian adenocarcinoma), Hep-G2 (hepatocellular carcinoma), MDA-MB231, SKBR3, MCF7 (breast adenocarcinoma), A549 (lung carcinoma), and HeLa (cervix epithelioid carcinoma). At concentrations in the range of 10 μM, GeGe-3 significantly restricted cell proliferation and metabolism. GeGe-3 also reduced PC3 cell migration in a standard wound closure and trans-well assay. Together, these results confirm the anticancer potential of GeGe-3 and underline the need for more detailed pre-clinical investigations into its molecular targets and mechanisms of action.

The Sirtuin 5 Inhibitor MC3482 Ameliorates Microglia‑induced Neuroinflammation Following Ischaemic Stroke by Upregulating the Succinylation Level of Annexin-A1

In our previous study, we concluded that sirtuin 5 (SIRT5) was highly expressed in microglia following ischaemic stroke, which induced excessive neuroinflammation and neuronal injury. Therefore, SIRT5-targeting interventions should reduce neuroinflammation and protect against ischaemic brain injury. Here, we showed that treatment with a specific SIRT5 inhibitor, MC3482, alleviated microglia-induced neuroinflammation and improved long-term neurological function in a mouse model of stroke. The mice were administrated with either vehicle or 2 mg/kg MC3482 daily for 7 days via lateral ventricular injection following the onset of middle cerebral artery occlusion. The outcome was assessed by a panel of tests, including a neurological outcome score, declarative memory, sensorimotor tests, anxiety-like behavior and a series of inflammatory factors. We observed a significant reduction of infarct size and inflammatory factors, and the improvement of long-term neurological function in the early stages during ischaemic stroke when the mice were treated with MC3482. Mechanistically, the administration of MC3482 suppressed the desuccinylation of annexin-A1, thereby promoting its membrane recruitment and extracellular secretion, which in turn alleviated neuroinflammation during ischaemic stroke. Based on our findings, MC3482 offers promise as an anti-ischaemic stroke treatment that targets directly the disease's underlying factors.

The role of the annexin A protein family at the maternal-fetal interface

Successful pregnancy requires the tolerance of the maternal immune system for the semi-allogeneic embryo, as well as a synchrony between the receptive endometrium and the competent embryo. The annexin family belongs to calcium-regulated phospholipid-binding protein, which functions as a membrane skeleton to stabilize the lipid bilayer and participate in various biological processes in humans. There is an abundance of the annexin family at the maternal-fetal interface, and it exerts a crucial role in embryo implantation and the subsequent development of the placenta. Altered expression of the annexin family and dysfunction of annexin proteins or polymorphisms of the ANXA gene are involved in a range of pregnancy complications. In this review, we summarize the current knowledge of the annexin A protein family at the maternal-fetal interface and its association with female reproductive disorders, suggesting the use of ANXA as the potential therapeutic target in the clinical diagnosis and treatment of pregnancy complications.

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.

The Multifaceted Role of Annexin A1 in Viral Infections

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

Implicative role of epidermal growth factor receptor and its associated signaling partners in the pathogenesis of Alzheimer's disease

Epidermal growth factor receptor (EGFR) plays a pivotal role in early brain development, although its expression pattern declines in accordance with the maturation of the active nervous system. However, recurrence of EGFR expression in brain cells takes place during neural functioning decline and brain atrophy in order to maintain the homeostatic neuronal pool. As a consequence, neurotoxic lesions such as amyloid beta fragment (Aβ_1-42) formed during the alternative splicing of amyloid precursor protein in Alzheimer's disease (AD) elevate the expression of EGFR. This inappropriate peptide deposition on EGFR results in the sustained phosphorylation of the downstream signaling axis, leading to extensive Aβ_1-42 production and tau phosphorylation as subsequent pathogenesis. Recent reports convey that the pathophysiology of AD is correlated with EGFR and its associated membrane receptor complex molecules. One such family of molecules is the annexin superfamily, which has synergistic relationships with EGFR and is known for membrane-bound signaling that contributes to a variety of inflammatory responses. Besides, Galectin-3, tissue-type activated plasminogen activator, and many more, which lineate the secretion of pro-inflammatory cytokines (TNF-α, IL-1β, IL-6, and IL-18) result in severe neuronal loss. Altogether, we emphasized the perspectives of cellular senescence up-regulated by EGFR and its associated membrane receptor molecules in the pathogenesis of AD as a target for a therapeutical alternative to intervene in AD.

Sirtuin 5 aggravates microglia-induced neuroinflammation following ischaemic stroke by modulating the desuccinylation of Annexin-A1

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.

Annexins and cardiovascular diseases: Beyond membrane trafficking and repair

Cardiovascular diseases (CVD) remain the leading cause of mortality worldwide. The main cause underlying CVD is associated with the pathological remodeling of the vascular wall, involving several cell types, including endothelial cells, vascular smooth muscle cells, and leukocytes. Vascular remodeling is often related with the development of atherosclerotic plaques leading to narrowing of the arteries and reduced blood flow. Atherosclerosis is known to be triggered by high blood cholesterol levels, which in the presence of a dysfunctional endothelium, results in the retention of lipoproteins in the artery wall, leading to an immune-inflammatory response. Continued hypercholesterolemia and inflammation aggravate the progression of atherosclerotic plaque over time, which is often complicated by thrombus development, leading to the possibility of CV events such as myocardial infarction or stroke. Annexins are a family of proteins with high structural homology that bind phospholipids in a calcium-dependent manner. These proteins are involved in several biological functions, from cell structural organization to growth regulation and vesicle trafficking. In vitro gain- or loss-of-function experiments have demonstrated the implication of annexins with a wide variety of cellular processes independent of calcium signaling such as immune-inflammatory response, cell proliferation, migration, differentiation, apoptosis, and membrane repair. In the last years, the use of mice deficient for different annexins has provided insight into additional functions of these proteins in vivo, and their involvement in different pathologies. This review will focus in the role of annexins in CVD, highlighting the mechanisms involved and the potential therapeutic effects of these proteins.

Molecular analysis of Annexin expression in cancer

Background

Uptake of apoptotic cells induces a tolerogenic phenotype in phagocytes and promotes peripheral tolerance. The highly conserved Annexin core domain, present in all members of the Annexin family, becomes exposed on the apoptotic cell-surface and triggers tolerogenic signalling in phagocytes via the Dectin-1 receptor. Consequently, Annexins exposed on tumour cells upon cell death are expected to induce tolerance towards tumour antigens, inhibiting tumour rejection.

Methods

Expression analysis for all Annexin family members was conducted in cancer cell lines of diverse origins. Presentation of Annexins on the cell surface during apoptosis of cancer cell lines was investigated using surface washes and immunoblotting. Expression data from the GEO database was analysed to compare Annexin levels between malignant and healthy tissue.

Results

Six Annexins at least were consistently detected on mRNA and protein level for each investigated cell line. AnxA1, AnxA2 and AnxA5 constituted the major part of total Annexin expression. All expressed Annexins translocated to the cell surface upon apoptosis induction in all cell lines. Human expression data indicate a correlation between immune infiltration and overall Annexin expression in malignant compared to healthy tissue.

Conclusions

This study is the first comprehensive analysis of expression, distribution and presentation of Annexins in cancer.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12885-022-10075-8.

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.

FMDV 3A Antagonizes the Effect of ANXA1 to Positively Modulate Viral Replication

The RIG-I-like receptor signaling pathway is crucial for producing type I interferon (IFN-I) against RNA viruses. The present study observed that viral infection increased annexin-A1 (ANXA1) expression, and ANXA1 then promoted RNA virus-induced IFN-I production. Compared to ANXA1 wild-type cells, ANXA1^−/− knockout cells showed IFN-β production decreasing after viral stimulation. RNA virus stimulation induced ANXA1 to regulate IFN-β production through the TBK1-IRF3 axis but not through the NF-κB axis. ANXA1 also interacted with JAK1 and STAT1 to increase signal transduction induced by IFN-β or IFN-γ. We assessed the effect of ANXA1 on the replication of foot-and-mouth disease virus (FMDV) and found that ANXA1 inhibits FMDV replication dependent on IFN-I production. FMDV 3A plays critical roles in viral replication and host range. The results showed that FMDV 3A interacts with ANXA1 to inhibit its ability to promote IFN-β production. We also demonstrated that FMDV 3A inhibits the formation of ANXA1-TBK1 complex. These results indicate that ANXA1 positively regulates RNA virus-stimulated IFN-β production and FMDV 3A antagonizes ANXA1-promoted IFN-β production to modulate viral replication.

IMPORTANCE FMDV is a pathogen that causes one of the world’s most destructive and highly contagious animal diseases. The FMDV 3A protein plays a critical role in viral replication and host range. Although 3A is one of the viral proteins that influences FMDV virulence, its underlying mechanisms remain unclear. ANXA1 is involved in immune activation against pathogens. The present study demonstrated that FMDV increases ANXA1 expression, while ANXA1 inhibits FMDV replication. The results also showed that ANXA1 promotes RNA virus-induced IFN-I production through the IRF3 axis at VISA and TBK1 levels. ANXA1 was also found to interact with JAK1 and STAT1 to strengthen signal transduction induced by IFN-β and IFN-γ. 3A interacted with ANXA1 to inhibit ANXA1-TBK1 complex formation, thereby antagonizing the inhibitory effect of ANXA1 on FMDV replication. This study helps to elucidate the mechanism underlying the effect of the 3A protein on FMDV replication.

Plasma Proteomic Profile of Patients with Tick-Borne Encephalitis and Co-Infections

Despite the increasing number of patients suffering from tick-borne encephalitis (TBE), Lyme disease, and their co-infection, the mechanisms of the development of these diseases and their effects on the human body are still unknown. Therefore, the aim of this study was to evaluate the changes in the proteomic profile of human plasma induced by the development of TBE and to compare it with changes in TBE patients co-infected with other tick-borne pathogens. The results obtained by proteomic analysis using a nanoLC-Q Exactive HF mass spectrometer showed that the most highly elevated groups of proteins in the plasma of TBE patients with co-infection were involved in the pro-inflammatory response and protein degradation, while the antioxidant proteins and factors responsible for protein biosynthesis were mainly downregulated. These results were accompanied by enhanced GSH- and 4-HNE-protein adducts formation, observed in TBE and co-infected patients at a higher level than in the case of patients with only TBE. In conclusion, the differences in the proteomic profiles between patients with TBE and co-infected patients indicate that these diseases are significantly diverse and, consequently, require different treatment, which is particularly important for further research, including the development of novel diagnostics tools.

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.

Arabidopsis annexin 5 is involved in maintenance of pollen membrane integrity and permeability

In Arabidopsis, a dry stigma surface enables a gradual hydration of pollen grains by a controlled release of water. Occasionally the grains may be exposed to extreme precipitations that cause rapid water influx and swelling, eventually leading to pollen membrane rupture. In metazoans, calcium- and phospholipid-binding proteins, referred to as annexins, participate in the repair of plasma membrane damages. It remains unclear, however, how this process is conducted in plants. Here, we examined whether plant annexin 5 (ANN5), the most abundant member of the annexin family in pollen, is involved in the restoration of pollen membrane integrity. We analyzed the cellular dynamics of ANN5 in pollen grains undergoing hydration in favorable or stress conditions. We observed a transient association of ANN5 with the pollen membrane during in vitro hydration that did not occur in the pollen grains being hydrated on the stigma. To simulate a rainfall, we performed spraying of the pollinated stigma with deionized water that induced ANN5 accumulation at the pollen membrane. Interestingly, calcium or magnesium application affected pollen membrane properties differently, causing rupture or shrinkage of pollen membrane, respectively. Both treatments, however, induced ANN5 recruitment to the pollen membrane. Our data suggest a model in which ANN5 is involved in the maintenance of membrane integrity in pollen grains exposed to osmotic or ionic imbalances.

The Pyrazolyl-Urea Gege3 Inhibits the Activity of ANXA1 in the Angiogenesis Induced by the Pancreatic Cancer Derived EVs

The pyrazolyl-urea Gege3 molecule has shown interesting antiangiogenic effects in the tumor contest. Here, we have studied the role of this compound as interfering with endothelial cells activation in response to the paracrine effects of annexin A1 (ANXA1), known to be involved in promoting tumor progression. ANXA1 has been analyzed in the extracellular environment once secreted through microvesicles (EVs) by pancreatic cancer (PC) cells. Particularly, Gege3 has been able to notably prevent the effects of Ac2-26, the ANXA1 mimetic peptide, and of PC-derived EVs on endothelial cells motility, angiogenesis, and calcium release. Furthermore, this compound also inhibited the translocation of ANXA1 to the plasma membrane, otherwise induced by the same ANXA1-dependent extracellular stimuli. Moreover, these effects have been mediated by the indirect inhibition of protein kinase Cα (PKCα), which generally promotes the phosphorylation of ANXA1 on serine 27. Indeed, by the subtraction of intracellular calcium levels, the pathway triggered by PKCα underwent a strong inhibition leading to the following impediment to the ANXA1 localization at the plasma membrane, as revealed by confocal and cytofluorimetry analysis. Thus, Gege3 appeared an attractive molecule able to prevent the paracrine effects of PC cells deriving ANXA1 in the tumor microenvironment.

Acetylation of ANXA1 reduces caspase-3 activation by enhancing the phosphorylation of caspase-9 under OGD/R conditions

SIRT2, a Class III HDACs, aggravates cell damage and activates caspase-3 under oxygen-glucose deprivation/reoxygenation and glucose (OGD/R) conditions. In this paper, we demonstrated the adverse effects of SIRT2 on cells after OGD/R attacks, which were mediated by increased interactions between SIRT2 and ANXA1, and explicated the mechanisms by which acetylated ANXA1 affects the activation and cleavage of caspase-3. We found that the acetylation level of ANXA1 was decreased through the its increased interactions with SIRT2 after the OGD/R insult. The lysine 312 residue (K312) was selected as the target site in ANXA1 because it is associated with SIRT2, and its mimic (K312Q) and silent (K312R) mutants were then established through site mutagenesis. Under OGD/R conditions, the acetylation mimic of K312Q ANXA1 accumulated in the cytoplasm, decreasing the activity levels of caspase-3 and the upstream initiator caspase-9, compared with the levels of WT and K312R ANXA1. Furthermore, K312Q ANXA1 intervened in the interactions of caspase-3 to caspase-9 by increasing the phosphorylation levels of caspase-9 and inhibited its cleavage by downregulating PRKAR2B, a regulatory subunit of protein kinase A (PKA). In this process, K312Q ANXA1 was found to be directly associated with PRKAR2B, diminishing its restriction on the catalytic subunit of PKA. In conclusion, acetylated ANXA1 can promote the phosphorylation of caspase-9 to decrease the activation of caspase-3 by enhancing the expression of a kinase upstream of caspase-9 after the OGD/R stimulation.

Annexin A1 as a Regulator of Immune Response in Cancer

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

ANXA1 with Anti-Inflammatory Properties Might Contribute to Parkinsonism

We here describe the identification of a novel variant in the anti-inflammatory Annexin A1 protein likely to be the cause of disease in two siblings with autosomal recessive parkinsonism. The disease-segregating variant was ascertained through a combination of homozygosity mapping and whole genome sequencing and was shown to impair phagocytosis in zebrafish mutant embryos. The highly conserved variant, absent in healthy individuals and public SNP databases, affected a functional domain of the protein with neuroprotective properties. This study supports the hypothesis that damaged microglia might lead to impairments in the clearance of accumulated and aggregated proteins resulting in parkinsonism. ANN NEUROL 2021;90:319-323.

Insulin-mediated immune dysfunction in the development of preeclampsia

Epidemiological observations implicate insulin resistance as a predisposing factor in the development of preeclampsia (PE). It is also well established that PE manifests in the context of a dysregulated immune response at the maternal-foetal interface, though all the underlying drivers of such immune dysregulation remains to be accounted for. Although it has long been known that various immune cells express insulin receptors following immune activation, it is only recently that insulin signalling has been shown to play a key role in immune cell differentiation, survival and effector function through its canonical activation of the PI3K/Akt/mTOR pathway. Here we argue that hyperinsulinemia, manifesting either from insulin resistance or from intensive insulin therapy, likely plays a direct role in driving immune cell dysfunction which plays a central role in the development of PE. This line of reasoning also explains the superior results of insulin-sparing interventions compared to intensive insulin therapy as monotherapy.

Decreased Annexin A1 expression enhances sensitivity to docetaxel, cisplatin and 5-fluorouracil combination induction chemotherapy in oral squamous cell carcinoma

BACKGROUND

Annexin A1, a member of the Annexin superfamily, has been shown to play a vital role in a broad range of molecular and cellular processes. This study aims to explore the relationship between the Annexin A1 expression and the clinical response to cisplatin, docetaxel and 5-fluorouracil (TPF) as induction chemotherapy in patients with oral squamous cell carcinoma (OSCC).

METHODS

This study recruited two hundred thirty-two patients from a III/IVA OSCC trial. Immunohistochemistry was used to assess the level of Annexin A1 expression. Overexpression and knockdown methods in HB96, HN4 and CAL27 cell lines were used to assess the role of Annexin A1 in the neoplastic cellular response to chemotherapy.

RESULTS

We found that reduced expression of Annexin A1 conferred a prognostic benefit from induction chemotherapy based on the TPF drug combination in patients with moderately/poorly differentiated disease. Using an in vitro model, we found that low Annexin A1 enhanced cellular proliferation by activating the EGFR/AKT signalling pathway and inhibiting p27 expression. Furthermore, low Annexin A1 initiated a significant decrease in cell viability after treatment with TPF agents. In addition, downregulation of Annexin A1 promoted apoptosis induced by docetaxel, cisplatin and 5-fluorouracil, and upregulation of Annexin A1 inhibited apoptosis.

CONCLUSION

Annexin A1 may be of prognostic value in patients with locally advanced OSCC who are managed with TPF chemotherapy, as low Annexin A1 promotes chemosensitivity to TPF chemotherapy in oral cancer cells via enhanced caspase-dependent apoptosis.

Inhibition of SENP6 restrains cerebral ischemia-reperfusion injury by regulating Annexin-A1 nuclear translocation-associated neuronal apoptosis

Rationale: Annexin-A1 (ANXA1) has previously been proposed to play a crucial role in neuronal apoptosis during ischemic stroke injury. Our recent study demonstrated that ANXA1 was modified by SUMOylation, and that this modification was greatly weakened after cerebral ischemia, but its effect on neuronal death and the underlying mechanism have not been fully elucidated. Methods: Mice subjected to middle cerebral artery occlusion were established as the animal model and primary cultured neurons treated with oxygen-glucose deprivation and reperfusion was established as the cell model of ischemic stroke. The Ni²⁺-NTA agarose affinity pull-down assay was carried out to determine the SUMOylation level of ANXA1. Co-immunoprecipitation assays was utilized to explore the protein interaction. Immunoblot analysis, quantitative real-time PCR, Luciferase reporter assay were performed to identify the regulatory mechanism. LDH release and TUNEL staining was performed to investigate the neuronal cytotoxicity and apoptosis, respectively. Results: In this study, we identified the deSUMOylating enzyme sentrin/SUMO-specific protease 6 (SENP6) as a negative regulator of ANXA1 SUMOylation. Notably, we found that SENP6-mediated deSUMOylation of ANXA1 induced its nuclear translocation and triggered neuronal apoptosis during cerebral ischemic injury. A mechanistic study demonstrated that SENP6-mediated deSUMOylation of ANXA1 promoted TRPM7- and PKC-dependent phosphorylation of ANXA1. Furthermore, blocking the deSUMOylation of ANXA1 mediated by SENP6 inhibited the transcriptional activity of p53, decreased Bid expression, suppressed caspase-3 pathway activation and reduced the apoptosis of primary neurons subjected to oxygen-glucose deprivation and reperfusion. More importantly, SENP6 inhibition by overexpression of a SENP6 catalytic mutant in neurons resulted in significant improvement in neurological function in the mouse model of ischemic stroke. Conclusions: Taken together, the results of this study identified a previously unidentified function of SENP6 in neuronal apoptosis and strongly indicated that SENP6 inhibition may provide therapeutic benefits for cerebral ischemia.

Identification of ANXA1 as a potential prognostic biomarker and correlating with immune infiltrates in colorectal cancer

BACKGROUND

ANXA1 is a calcium-dependent phospholipid-binding protein and is frequently associated with inflammation, cell proliferation and apoptosis. However, the relationship between ANXA1 and the prognosis of multiple tumours and tumour infiltrating immune cells remains unclear.

METHODS

Multivariate Cox proportional regression analysis was used for signature genes exploration in the basic of colon adenocarcinoma (COAD) RNA-sequence dataset obtained from TCGA, following the identification of 267 common differentially expressed genes, including ANXA1, among three expression profile datasets (GSE41328, GSE110224, and GSE113513). The differential expression of ANXA1 in different tumours and their corresponding normal tissues were evaluated through the Tumour Immune Estimation Resource (TIMER) and Oncomine database. Subsequently, we investigated the correlation between the expression level of ANXA1 and diverse panel of infiltrating immune cells and their related gene markers in colorectal cancer using correlation analysis in TIMER and GEPIA database.

RESULTS

The high expression of ANXA1 was demonstrated to be closely correlated with poor survival in patients with colorectal cancer. More importantly, we found that changes in ANXA1 expression showed a moderate to strong, and statistically significant, correlation with infiltrating levels of B cells, CD8+ T cells, CD4+ T cells, macrophages, neutrophils and dendritic cells. By contrast, there are only weak correlations between ANXA1 expression and immune cell infiltration in ESCA and STAD. ANXA1 expression was considerably associated with various immune markers involving immune cell recruitment, polarization of tumour-associated macrophages, and T cell exhaustion.

CONCLUSION

ANXA1 is not only an independent risk factor in the prediction of the prognosis of colorectal cancer, but also a crucial regulator in immune cell infiltration. This study may shed light on the clinical value of ANXA1, especially in the areas of early diagnosis of colorectal cancer and therapeutic target discovery.

Phagocytic activity of splenic macrophages is enhanced and accompanied by cytosolic alkalinization in TRPM7 kinase-dead mice

Transient receptor potential melastatin 7 (TRPM7) is a unique protein functioning as a cation channel as well as a serine/threonine kinase and is highly expressed in immune cells such as lymphocytes and macrophages. TRPM7 kinase-dead (KD) mouse model has been used to investigate the role of this protein in immune cells; these animals display moderate splenomegaly and ectopic hemopoiesis. The basal TRPM7 current magnitudes in peritoneal macrophages isolated from KD mice were higher; however, the maximum currents, achieved after cytoplasmic Mg²⁺ washout, were not different. In the present study, we investigated the consequences of TRPM7 kinase inactivation in splenic and peritoneal macrophages. We measured the basal phagocytic activity of splenic macrophages using fluorescent latex beads, pHrodo zymosan bioparticles, and opsonized red blood cells. KD macrophages phagocytized more efficiently and had slightly higher baseline calcium levels compared to WT cells. We found no obvious differences in store-operated Ca²⁺ entry between WT and KD macrophages. By contrast, the resting cytosolic pH in KD macrophages was significantly more alkaline than in WT. Pharmacological blockade of sodium hydrogen exchanger 1 (NHE1) reversed the cytosolic alkalinization and reduced phagocytosis in KD macrophages. Basal TRPM7 channel activity in KD macrophages was also reduced after NHE1 blockade. Cytosolic Mg²⁺ sensitivity of TRPM7 channels measured in peritoneal macrophages was similar in WT and KD mice. The higher basal TRPM7 channel activity in KD macrophages is likely due to alkalinization. Our results identify a novel role for TRPM7 kinase as a suppressor of basal phagocytosis and a regulator of cellular pH.

Annexin-A1 SUMOylation regulates microglial polarization after cerebral ischemia by modulating IKKα stability via selective autophagy

Annexin-A1 (ANXA1) has recently been proposed to play a role in microglial activation after brain ischemia, but the underlying mechanism remains poorly understood. Here, we demonstrated that ANXA1 is modified by SUMOylation, and SUMOylated ANXA1 could promote the beneficial phenotype polarization of microglia. Mechanistically, SUMOylated ANXA1 suppressed nuclear factor κB activation and the production of proinflammatory mediators. Further study revealed that SUMOylated ANXA1 targeted the IκB kinase (IKK) complex and selectively enhanced IKKα degradation. Simultaneously, we detected that SUMOylated ANXA1 facilitated the interaction between IKKα and NBR1 to promote IKKα degradation through selective autophagy. Further work revealed that the overexpression of SUMOylated ANXA1 in microglia/macrophages resulted in marked improvement in neurological function in a mouse model of cerebral ischemia. Collectively, our study demonstrates a previously unidentified mechanism whereby SUMOylated ANXA1 regulates microglial polarization and strongly indicates that up-regulation of ANXA1 SUMOylation in microglia may provide therapeutic benefits for cerebral ischemia.

Evaluation of phytoestrogens in inducing cell death mediated by decreasing Annexin A1 in Annexin A1-knockdown leukemia cells

BACKGROUND

Phytoestrogens are plant compounds that are structurally similar to estrogen and that possess anti-cancer properties. Previous studies have reported that coumestrol, daidzein and genistein could induce cell death by reducing Annexin A1 protein in leukemic cell lines. Annexin A1 (ANXA1) is involved in cell progression, metastasis, and apoptosis in several types of cancer cells. The present study sought to investigate if the effects of phytoestrogens on apoptosis, cell cycle arrest and phagocytosis in ANXA1-knockdown leukemic cells are mediated through ANXA1 or occurred independently.

METHODS

Transfection of ANXA1 siRNA was conducted to downregulate ANXA1 expression in Jurkat, K562 and U937 cells. Apoptosis and cell cycle assays were conducted using flow cytometry. Western blot was performed to evaluate ANXA1, caspases and Bcl-2 proteins expression. Phagocytosis was determined using hematoxylin and eosin staining.

RESULTS

The expression of ANXA1 after the knockdown was significantly downregulated in all cell lines. Genistein significantly induced apoptosis associated with an upregulation of procaspase-3, -9, and - 1 in Jurkat cells. The Bcl-2 expression showed no significant difference in Jurkat, K562 and U937 cells. Treatment with phytoestrogens increased procaspase-1 expression in Jurkat and U937 cells while no changes were detected in K562 cells. Flow cytometry analysis demonstrated that after ANXA1 knockdown, coumestrol and genistein caused cell cycle arrest at G2/M phase in selected type of cells. The percentage of phagocytosis and phagocytosis index increased after the treatment with phytoestrogens in all cell lines.

CONCLUSION

Phytoestrogens induced cell death in ANXA1-knockdown leukemia cells, mediated by Annexin A1 proteins. Graphical abstract.

Comparative expression analysis of phospholipid binding protein annexina1 in nephrogenesis and kidney cancer

Background The expression in the glomerular mesangial cells, papillary, and collecting duct cells demonstrated annexin A1 (AnxA1)'s role in specific renal functions. With varying concentrations of calcium (Ca2+), it is considered to regulate cellular processes such as cell proliferation, apoptosis, and clearance of apoptotic cells by forming ceramides, a key lipid mediator of apoptosis. It also participates in tumorigenesis based on its location. On account of these features, we investigated the expression of this apoptosis-associated protein in fetal kidneys at different gestational periods, mature kidneys and in kidney cancer tissues in order to localize and possibly characterize its role during nephrogenesis and renal tumors. Methods AnxA1 expression was evaluated by an immunohistochemistry technique in "paraffin-embedded" renal tissue sections from autopsied fetuses at different gestational ages, in mature kidneys and renal cancer tissues. Results The current study data demonstrated that AnxA1 is expressed in the mesangial cells and podocytes of maturing glomeruli in the developing renal cortex of fetal kidneys at 14 to 19 weeks of gestation. The expression in the mesangial cells declined in later weeks of gestation and persisted into adulthood. AnxA1 expression increased with the progression of clear cell renal cell carcinoma (CCRCC) and also in other cancer types indicating a potential role of the protein in tumorigenesis. Conclusions We presume that AnxA1 in the podocytes and mesangial cells play important roles in various signaling pathways in the functioning of the glomerulus. These results and concepts provide a framework to further dissect its biological properties and thereby develop diagnostic, prognostic, and therapeutic strategies targeting the molecule in various renal pathologies.

Annexin-1 Mimetic Peptide Ac2-26 Suppresses Inflammatory Mediators in LPS-Induced Astrocytes and Ameliorates Pain Hypersensitivity in a Rat Model of Inflammatory Pain

Ac2-26, a mimetic peptide of Annexin-A1, plays a vital role in the anti-inflammatory response mediated by astrocytes. In this study, we aimed to explore the underlying mechanisms of Ac2-26-mediated anti-inflammatory effect. Specifically, we investigated the inhibitory effects of Ac2-26 on lipopolysaccharide (LPS)-induced astrocyte migration and on pro-inflammatory cytokines and chemokines expressions, as well as one glutathione (GSH) reductase mRNA and total intracellular GSH levels in LPS-induced astrocytes. Additionally, we investigated whether mitogen-activated protein kinases (MAPK) and nuclear factor kappa-B (NF-κB) signaling pathway were involved in this process. Finally, we evaluated the analgesic effect of Ac2-26 in complete Freund's adjuvant (CFA)-induced inflammatory pain model. Our results demonstrated that Ac2-26 inhibited LPS-induced astrocytes migration, reduced the production of pro-inflammatory mediators [tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β), monocyte chemoattractant protein-1 (MCP-1) and macrophage inflammatory protein-1 (MIP-1α)] and upregulated GSH reductase mRNA and GSH levels in LPS-induced astrocytes in vitro. This process was mediated through the p38, JNK-MAPK signaling pathway, but not dependent on the NF-κB pathway. Furthermore, the p38 and JNK inhibitors mimicked the effects of Ac2-26, whereas a p38 and JNK activator anisomycin partially reversed its function. Finally, Ac2-26 treatment reduced CFA-induced activation of astrocytes and production of inflammatory mediators in the spinal cord. These results suggest that Ac2-26 attenuates pain by inhibiting astrocyte activation and the production of inflammatory mediators; thus, this work presents Ac2-26 as a potential drug to treat neuropathic pain.

An Update to Calcium Binding Proteins

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

Annexins in Adipose Tissue: Novel Players in Obesity

Obesity and the associated comorbidities are a growing health threat worldwide. Adipose tissue dysfunction, impaired adipokine activity, and inflammation are central to metabolic diseases related to obesity. In particular, the excess storage of lipids in adipose tissues disturbs cellular homeostasis. Amongst others, organelle function and cell signaling, often related to the altered composition of specialized membrane microdomains (lipid rafts), are affected. Within this context, the conserved family of annexins are well known to associate with membranes in a calcium (Ca²⁺)- and phospholipid-dependent manner in order to regulate membrane-related events, such as trafficking in endo- and exocytosis and membrane microdomain organization. These multiple activities of annexins are facilitated through their diverse interactions with a plethora of lipids and proteins, often in different cellular locations and with consequences for the activity of receptors, transporters, metabolic enzymes, and signaling complexes. While increasing evidence points at the function of annexins in lipid homeostasis and cell metabolism in various cells and organs, their role in adipose tissue, obesity and related metabolic diseases is still not well understood. Annexin A1 (AnxA1) is a potent pro-resolving mediator affecting the regulation of body weight and metabolic health. Relevant for glucose metabolism and fatty acid uptake in adipose tissue, several studies suggest AnxA2 to contribute to coordinate glucose transporter type 4 (GLUT4) translocation and to associate with the fatty acid transporter CD36. On the other hand, AnxA6 has been linked to the control of adipocyte lipolysis and adiponectin release. In addition, several other annexins are expressed in fat tissues, yet their roles in adipocytes are less well examined. The current review article summarizes studies on the expression of annexins in adipocytes and in obesity. Research efforts investigating the potential role of annexins in fat tissue relevant to health and metabolic disease are discussed.

Advancements of Annexin A1 in inflammation and tumorigenesis

Annexin A1 is a Ca²⁺-dependent phospholipid binding protein involved in a variety of pathophysiological processes. Accumulated evidence has indicated that Annexin A1 has important functions in cell proliferation, apoptosis, differentiation, metastasis, and inflammatory response. Moreover, the abnormal expression of Annexin A1 is closely related to the occurrence and development of tumors. In this review article, we focus on the structure and function of Annexin A1 protein, especially the recent evidence of Annexin A1 in the pathophysiological role of inflammatory and cancer. This summary will be very important for further investigation of the pathophysiological role of Annexin A1 and for the development of novel therapeutics of inflammatory and cancer based on targeting Annexin A1 protein.

Annexins in Influenza Virus Replication and Pathogenesis

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

Enhanced antitumor effect of combination of annexin A1 knockdown and bortezomib treatment in multiple myeloma in vitro and in vivo

Bortezomib (BTZ) is one of the most frequently used drugs in treatment of multiple myeloma (MM), but drug-resistance often occurs and limits its clinical efficacy. Annexin A1 (ANXA1) is upregulated in MM, and its knockdown enhances chemosensitivity in MM. However, whether ANXA1 inhibition can increase antitumor activity of BTZ in MM cells remains unknown. In the present study, Cell Counting Kit-8 (CCK-8) and colony formation assays showed that ANXA1 silencing combined with BTZ treatment led to a more significant inhibition of MM cell proliferation than each treatment alone. Cell apoptosis was dramatically promoted in MM cells following silencing of ANXA1 and BTZ administration versus that in ANXA1-silenced alone or BTZ-treated alone cells, as evidenced by decreased expression of phosphorylated signal transducers and activators of transcription 3 and BCL2, and increased expression of BAX. Moreover, we demonstrated that the levels of IL-6 and IL-23 were markedly downregulated in ANXA1-silenced and BTZ-treated MM cells. Furthermore, the combination of ANXA1 knockdown and BTZ treatment distinctly suppressed tumor growth in vivo compared with BTZ treatment alone. Taken together, our results show that downregulation of ANXA1 enhances antitumor activity of BTZ in MM in vitro and in vivo, indicating that ANXA1 may be a promising target for enhancing the chemosensitivity of MM to BTZ.

miR-196a Is Able to Restore the Aggressive Phenotype of Annexin A1 Knock-Out in Pancreatic Cancer Cells by CRISPR/Cas9 Genome Editing

Annexin A1 (ANXA1) is a Ca²⁺-binding protein that is involved in pancreatic cancer (PC) progression. It is able to mediate cytoskeletal organization maintaining a malignant phenotype. Our previous studies showed that ANXA1 Knock-Out (KO) MIA PaCa-2 cells partially lost their migratory and invasive capabilities and also the metastatization process appeared affected in vivo. Here, we investigated the microRNA (miRNA) profile in ANXA1 KO cells finding that the modification in miRNA expression suggests the significant involvement of ANXA1 in PC development. In this study, we focused on miR-196a which appeared down modulated in absence of ANXA1. This miRNA is a well known oncogenic factor in several tumour models and it is able to trigger the agents of the epithelial to mesenchymal transition (EMT), like ANXA1. Our results show that the reintroduction in ANXA1 KO cells of miR-196a through the mimic sequence restored the early aggressive phenotype of MIA PaCa-2. Then, ANXA1 seems to support the expression of miR-196a and its role. On the other hand, this miRNA is able to mediate cytoskeletal dynamics and other protein functions promoting PC cell migration and invasion. This work describes the correlation between ANXA1 and specific miRNA sequences, particularly miR-196a. These results could lead to further information on ANXA1 intracellular role in PC, explaining other aspects that are apart from its tumorigenic behaviour.

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.

Identification of two phosphorylation sites essential for annexin A1 in blood-brain barrier protection after experimental intracerebral hemorrhage in rats

Annexin A1 has been reported to exert a blood-brain barrier protection. This study was designed to examine the role of annexin A1 in intracerebral hemorrhage-induced blood-brain barrier dysfunction. A collagenase intracerebral hemorrhage model was performed in adult male Sprague Dawley rats. First, a possible relationship between annexin A1 and intracerebral hemorrhage pathology was confirmed by a loss of annexin A1 in the cerebrovascular endothelium and serum of intracerebral hemorrhage rats, and the rescue effects of i.v. administration of human recombinant annexin A1 in vivo and annexin A1 overexpression in vitro on the barrier function of brain microvascular endothelial cells exposed to intracerebral hemorrhage stimulus. Second, we found that intracerebral hemorrhage significantly increased the phosphorylation ratio of annexin A1 at the serine/threonine residues. Finally, based on site-specific mutagenesis, we identified two phosphorylation sites (a) annexin A1 phosphorylation at threonine 24 is required for its interaction with actin cytoskeleton, and (b) phosphorylation at serine27 is essential for annexin A1 secretion, both of which were essential for maintaining cytoskeleton integrity and paracellular permeability. In conclusion, annexin A1 prevents intracerebral hemorrhage-induced blood-brain barrier dysfunction in threonine 24 and serine27 phosphorylation-dependent manners. Annexin A1 phosphorylation may be a self-help strategy in brain microvascular endothelial cells after intracerebral hemorrhage; however, that was almost completely abolished by the intracerebral hemorrhage-induced loss of annexin A1.

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.

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

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

Annexin A1 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.

Effect of Annexin A1 gene on the proliferation and invasion of esophageal squamous cell carcinoma cells and its regulatory mechanisms

The aim of this study was to examine the effect of Annexin A1 (ANXA1) on the proliferation, migration and invasion of esophageal squamous cell carcinoma (ESCC) cells and its possible mechanisms of action. After constructing the ANXA1 overexpression plasmid, we transfected this plasmid and/or microRNA (miRNA)‑196a mimic into ESCC cells (Eca109 cell line). Methyl thiazolyl tetrazolium (MTT) assay and Transwell chamber assay were performed to determine cell proliferation, migration and invasion, respectively. Western blot analysis was used to examine the protein expression levels of ANXA1, Snail and E-cadherin. RT-PCR was used to detect the expression of miRNA-196a. Our results revealed that ANXA1 expression was upregulated in the cells transfected with the ANXA1 overexpression plasmid, and cell proliferation, migration and invasion were significantly increased (p=0.004, p<0.001 and p=0.011, respectively). In the cells transfected with the miRNA‑196a mimic, miRNA‑196a expression was significantly upregulated (p<0.001). However, miRNA-196a expression was downregulated in the cells transfected with the ANXA1 overexpression plasmid. In addition, in the cells transfected with the miRNA‑196a mimic, cell proliferation, migration and invasion were significantly decreased (p=0.027, p=0.009 and p=0.021, respectively). In the cells transfected with the ANXA1 overexpression plasmid, the expression of Snail was upregulated and that of E-cadherin was downregulated. However, the opposite was observed in the cells transfected with the miRNA‑196a mimic. Our findings thus demonstrate that ANXA1 promotes the proliferation of Eca109 cells, and increases the expression of Snail, whereas it inhibits that of E-cadherin, thus enhancing the migration and invasion of ESCC cells. miRNA-196a negatively regulates the expression of ANXA1, thereby inhibiting the proliferation, invasion and metastasis of ESCC cells.

Inflammation in Sickle Cell Disease: Differential and Down-Expressed Plasma Levels of Annexin A1 Protein

Sickle cell disease (SCD) is an inherited hemolytic anemia whose pathophysiology is driven by polymerization of the hemoglobin S (Hb S), leading to hemolysis and vaso-occlusive events. Inflammation is a fundamental component in these processes and a continuous inflammatory stimulus can lead to tissue damages. Thus, pro-resolving pathways emerge in order to restore the homeostasis. For example there is the annexin A1 (ANXA1), an endogenous anti-inflammatory protein involved in reducing neutrophil-endothelial interactions, accelerating neutrophil apoptosis and stimulating macrophage efferocytosis. We investigated the expression of ANXA1 in plasma of SCD patients and its relation with anemic, hemolytic and inflammatory parameters of the disease. Three SCD genotypes were considered: the homozygous inheritance for Hb S (Hb SS) and the association between Hb S and the hemoglobin variants D-Punjab (Hb SD) and C (Hb SC). ANXA1 and proinflammatory cytokines were quantified by ELISA in plasma of SCD patients and control individuals without hemoglobinopathies. Hematological and biochemical parameters were analyzed by flow cytometry and spectrophotometer. The plasma levels of ANXA1 were about three-fold lesser in SCD patients compared to the control group, and within the SCD genotypes the most elevated levels were found in Hb SS individuals (approximately three-fold higher). Proinflammatory cytokines were higher in SCD groups than in the control individuals. Anemic and hemolytic markers were higher in Hb SS and Hb SD genotypes compared to Hb SC patients. White blood cells and platelets count were higher in Hb SS genotype and were positively correlated to ANXA1 levels. We found that ANXA1 is down-regulated and differentially expressed within the SCD genotypes. Its expression seems to depend on the inflammatory, hemolytic and vaso-occlusive characteristics of the diseased. These data may lead to new biological targets for therapeutic intervention in SCD.

The restorative role of annexin A1 at the blood-brain barrier

Annexin A1 is a potent anti-inflammatory molecule that has been extensively studied in the peripheral immune system, but has not as yet been exploited as a therapeutic target/agent. In the last decade, we have undertaken the study of this molecule in the central nervous system (CNS), focusing particularly on the primary interface between the peripheral body and CNS: the blood-brain barrier. In this review, we provide an overview of the role of this molecule in the brain, with a particular emphasis on its functions in the endothelium of the blood-brain barrier, and the protective actions the molecule may exert in neuroinflammatory, neurovascular and metabolic disease. We focus on the possible new therapeutic avenues opened up by an increased understanding of the role of annexin A1 in the CNS vasculature, and its potential for repairing blood-brain barrier damage in disease and aging.

Nuclear translocation of annexin 1 following oxygen-glucose deprivation-reperfusion induces apoptosis by regulating Bid expression via p53 binding

Previous data have suggested that the nuclear translocation of annexin 1 (ANXA1) is involved in neuronal apoptosis after ischemic stroke. As the mechanism and function of ANXA1 nuclear migration remain unclear, it is important to clarify how ANXA1 performs its role as an apoptosis 'regulator' in the nucleus. Here we report that importazole (IPZ), an importin β (Impβ)-specific inhibitor, decreased ANXA1 nuclear accumulation and reduced the rate of neuronal death induced by nuclear ANXA1 migration after oxygen-glucose deprivation-reoxygenation (OGD/R). Notably, ANXA1 interacted with the Bid (BH3-interacting-domain death agonist) promoter directly; however; this interaction could be partially blocked by the p53 inhibitor pifithrin-α (PFT-α). Accordingly, ANXA1 was shown to interact with p53 in the nucleus and this interaction was enhanced following OGD/R. A luciferase reporter assay revealed that ANXA1 was involved in the regulation of p53-mediated transcriptional activation after OGD/R. Consistent with this finding, the nuclear translocation of ANXA1 after OGD/R upregulated the expression of Bid, which was impeded by IPZ, ANXA1 shRNA, or PFT-α. Finally, cell-survival testing demonstrated that silencing ANXA1 could improve the rate of cell survival and decrease the expression of both cleaved caspase-3 and cleaved poly(ADP-ribose) polymerase. These data suggested that Impβ-dependent nuclear ANXA1 migration participates in the OGD/R-dependent induction of neuronal apoptosis. ANXA1 interacts with p53 and promotes p53 transcriptional activity, which in turn regulates Bid expression. Silencing ANXA1 decreases the expression of Bid and suppresses caspase-3 pathway activation, thus improving cell survival after OGD/R. This study provides a novel mechanism whereby ANXA1 regulates apoptosis, suggesting the potential for a previously unidentified treatment strategy in minimizing apoptosis after OGD/R.

Annexin A1 Is a Physiological Modulator of Neutrophil Maturation and Recirculation Acting on the CXCR4/CXCL12 Pathway

Neutrophil production and traffic in the body compartments is finely controlled, and the strong evidences support the role of CXCL12/CXCR4 pathway on neutrophil trafficking to and from the bone marrow (BM). We recently showed that the glucocorticoid-regulated protein, Annexin A1 (AnxA1) modulates neutrophil homeostasis and here we address the effects of AnxA1 on steady-state neutrophil maturation and trafficking. For this purpose, AnxA1(-/-) and Balb/C wild-type mice (WT) were donors of BM granulocytes and mesenchymal stem cells and blood neutrophils. In vivo treatments with the pharmacological AnxA1 mimetic peptide (Ac2-26) or the formyl peptide receptor (FPR) antagonist (Boc-2) were used to elucidate the pathway of AnxA1 action, and with the cytosolic glucocorticoid antagonist receptor RU 38486. Accelerated maturation of BM granulocytes was detected in AnxA1(-/-) and Boc2-treated WT mice, and was reversed by treatment with Ac2-26 in AnxA1(-/-) mice. AnxA1 and FPR2 were constitutively expressed in bone marrow granulocytes, and their expressions were reduced by treatment with RU38486. Higher numbers of CXCR4(+) neutrophils were detected in the circulation of AnxA1(-/-) or Boc2-treated WT mice, and values were rescued in Ac2-26-treated AnxA1(-/-) mice. Although circulating neutrophils of AnxA1(-/-) animals were CXCR4(+) , they presented reduced CXCL12-induced chemotaxis. Moreover, levels of CXCL12 were reduced in the bone marrow perfusate and in the mesenchymal stem cell supernatant from AnxA1(-/-) mice, and in vivo and in vitro CXCL12 expression was re-established after Ac2-26 treatment. Collectively, these data highlight AnxA1 as a novel determinant of neutrophil maturation and the mechanisms behind blood neutrophil homing to BM via the CXCL12/CXCR4 pathway. J. Cell. Physiol. 231: 2418-2427, 2016. © 2016 Wiley Periodicals, Inc.

A fragmented form of annexin A1 is secreted from C2C12 myotubes by electric pulse-induced contraction

The main function of annexin A1 (ANXA1), a member of the annexin superfamily, is to bind to cellular membranes in a Ca(2+)-dependent manner. In skeletal muscle, ANXA1 is thought to be involved in the repair of damaged membrane tissue and in the migration of muscle cells. We hypothesized that ANXA1 is one of the myokines secreted during muscle contractions to accelerate the repair of cell damage after contraction. Here we performed cell contractions by electric pulse stimulation; the results revealed that a fragmented form of ANXA1 was cleaved by calpain and selectively secreted from skeletal muscle cells by contraction. We therefore realized that muscle-contraction-induced calpain-dependent ANXA1 fragmentation has a wound-healing effect on damaged cells. This suggested that not the intact form but rather fragmented ANXA1 is a contraction-induced myokine.

Annexin A1 expression in a pooled breast cancer series: association with tumor subtypes and prognosis

BACKGROUND

Annexin A1 (ANXA1) is a protein related with the carcinogenesis process and metastasis formation in many tumors. However, little is known about the prognostic value of ANXA1 in breast cancer. The purpose of this study is to evaluate the association between ANXA1 expression, BRCA1/2 germline carriership, specific tumor subtypes and survival in breast cancer patients.

METHODS

Clinical-pathological information and follow-up data were collected from nine breast cancer studies from the Breast Cancer Association Consortium (BCAC) (n = 5,752) and from one study of familial breast cancer patients with BRCA1/2 mutations (n = 107). ANXA1 expression was scored based on the percentage of immunohistochemical staining in tumor cells. Survival analyses were performed using a multivariable Cox model.

RESULTS

The frequency of ANXA1 positive tumors was higher in familial breast cancer patients with BRCA1/2 mutations than in BCAC patients, with 48.6 % versus 12.4 %, respectively; P <0.0001. ANXA1 was also highly expressed in BCAC tumors that were poorly differentiated, triple negative, EGFR-CK5/6 positive or had developed in patients at a young age. In the first 5 years of follow-up, patients with ANXA1 positive tumors had a worse breast cancer-specific survival (BCSS) than ANXA1 negative (HRadj = 1.35; 95 % CI = 1.05-1.73), but the association weakened after 10 years (HRadj = 1.13; 95 % CI = 0.91-1.40). ANXA1 was a significant independent predictor of survival in HER2+ patients (10-years BCSS: HRadj = 1.70; 95 % CI = 1.17-2.45).

CONCLUSIONS

ANXA1 is overexpressed in familial breast cancer patients with BRCA1/2 mutations and correlated with poor prognosis features: triple negative and poorly differentiated tumors. ANXA1 might be a biomarker candidate for breast cancer survival prediction in high risk groups such as HER2+ cases.