The annexin A2 system and vascular homeostasis

Interaction with IGF1 overrides ANXA2-mediated anti-inflammatory functions of IGFBP5 in vivo

Background

IGFBP5 is a differentially expressed gene (DEG) between M1 and M2 macrophages. This study explained why it causes opposite effects in different circumstances.

Methods

Gene expression profiles of various cell subsets were compared by mining a public database. THP-1 cells were treated by siRNAs, recombinant IGFBP5, lipopolysaccharide (LPS), picropodophyllin, IGF1 or the combinations. Clinical implication of IGFBP5 changes was investigated using rheumatoid arthritis (RA) and acute lung injury (ALI) models. IGFBP5-bound and differential proteins were identified by Liquid Chromatography Mass Spectrometry method.

Results

IGFBP5 situated in the center of a network constructed by the DEGs of M0 and M1/2 macrophages. Its expression negatively correlated to inflammation in vitro. When IGFBP5 was silenced, monocytes released more IL-1β and IL-6. NF-κB downstream proteins were overexpressed. IGFBP5 interacted with ANXA2 directly. In ANXA2-silenced cells, it showed no anti-inflammatory effect. Monocytes of adjuvant-induced arthritis rats and RA patients expressed less IGFBP5 than normal controls, but its blood levels increased significantly. Adipocytes secreted large amounts of IGFBP5. This secretion was reinforced by the above sera. IGFBP5 decreased in ALI mice's blood, while its supplement exacerbated inflammation. By binding to IGF1, IGFBP5 prevented its interaction with IGF1R. An IGF1R inhibitor picropodophyllin antagonized functions of IGF1/IGF1R too, but didn't reinforce the effects of IGFBP5.

Conclusion

IGFBP5 eases inflammation by interacting with ANXA2, an activator of NF-κB; as an antagonist of IGF1/IGF1R, IGFBP5 may disrupt immune homeostasis in vivo, due to impairment of the latter's anti-inflammatory functions; excessive IGFBP from adipocytes would be a pathogenic factor in certain diseases.

Annexin A2: the feasibility of being a therapeutic target associated with cancer metastasis and drug resistance in cancer microenvironment

At present, there is still a lack of effective treatment strategies for cancer metastasis and drug resistance, so finding effective biomarkers is particularly important. AnnexinA2 (ANXA2), a vital membrane protein, critically influences cancer progression, tumor invasion, and tumor microenvironment modulation. To assess the possible application of ANXA2 as a therapeutic target against cancer cell metastasis and drug resistance to chemotherapeutic drugs in the tumor microenvironment, we elucidated the functionality of ANXA2 in stromal cells, angiogenic vascular cells, and infiltrated immune cells that mediate metastasis and drug resistance, as well as its potential as a therapeutic target. ANXA2 shows a high expression level in many tissues, and its expression level is even higher in several tumors and their microenvironments. ANXA2 is a crucial regulator of many factors and may serve as a target against drug-resistant cancers.

The intricate role of annexin A2 in kidney: a comprehensive review

Annexin A2 (Anxa2) is a calcium (Ca2+)-regulated phospholipid binding protein composed of a variable N-terminus and a conserved core domain. This protein has been widely found in many tissues and fluids, including tubule cells, glomerular epithelial cells, renal vessels, and urine. In acute kidney injury, the expression level of this protein is markedly elevated in response to acute stress. Moreover, Anxa2 is a novel biomarker and potential therapeutic target with prognostic value in chronic kidney disease. In addition, Anxa2 is associated not only with clear-cell renal cell carcinoma differentiation but also the formation of calcium-related nephrolithiasis. In this review, we discuss the characteristics and functions of Anxa2 and focus on recent reports on the role of Anxa2 in the kidney, which may be useful for future research.

Tale of two systems: the intertwining duality of fibrinolysis and lipoprotein metabolism

Fibrinolysis is an enzymatic process that breaks down fibrin clots, while dyslipidemia refers to abnormal levels of lipids and lipoproteins in the blood. Both fibrinolysis and lipoprotein metabolism are critical mechanisms that regulate a myriad of functions in the body, and the imbalance of these mechanisms is linked to the development of pathologic conditions, such as thrombotic complications in atherosclerotic cardiovascular diseases. Accumulated evidence indicates the close relationship between the 2 seemingly distinct and complicated systems-fibrinolysis and lipoprotein metabolism. Observational studies in humans found that dyslipidemia, characterized by increased blood apoB-lipoprotein and decreased high-density lipoprotein, is associated with lower fibrinolytic potential. Genetic variants of some fibrinolytic regulators are associated with blood lipid levels, supporting a causal relationship between these regulators and lipoprotein metabolism. Mechanistic studies have elucidated many pathways that link the fibrinolytic system and lipoprotein metabolism. Moreover, profibrinolytic therapies improve lipid panels toward an overall cardiometabolic healthier phenotype, while some lipid-lowering treatments increase fibrinolytic potential. The complex relationship between lipoprotein and fibrinolysis warrants further research to improve our understanding of the bidirectional regulation between the mediators of fibrinolysis and lipoprotein metabolism.

Experimental Models of Traumatic Injuries: Do They Capture the Coagulopathy and Underlying Endotheliopathy Induced by Human Trauma?

Trauma-induced coagulopathy (TIC) is a major cause of morbidity and mortality in patients with traumatic injury. It describes the spectrum of coagulation abnormalities that occur because of the trauma itself and the body's response to the trauma. These coagulation abnormalities range from hypocoagulability and hyperfibrinolysis, resulting in potentially fatal bleeding, in the early stages of trauma to hypercoagulability, leading to widespread clot formation, in the later stages. Pathological changes in the vascular endothelium and its regulation of haemostasis, a phenomenon known as the endotheliopathy of trauma (EoT), are thought to underlie TIC. Our understanding of EoT and its contribution to TIC remains in its infancy largely due to the scarcity of experimental research. This review discusses the mechanisms employed by the vascular endothelium to regulate haemostasis and their dysregulation following traumatic injury before providing an overview of the available experimental in vitro and in vivo models of trauma and their applicability for the study of the EoT and its contribution to TIC.

Annexin A2 Loss After Cardiopulmonary Bypass and Development of Acute Postoperative Respiratory Dysfunction in Children

The primary objective of this study was to determine whether expression of the multifunctional and adherens junction-regulating protein, annexin A2 (A2), is altered following cardiopulmonary bypass (CPB). A secondary objective was to determine whether depletion of A2 is associated with post-CPB organ dysfunction in children.

DESIGN

In a prospective, observational study conducted over a 1-year period in children undergoing cardiac surgery requiring CPB, we analyzed A2 expression in peripheral blood mononuclear cells at different time points. We then assessed the relationship of A2 expression with organ function at each time point in the early postoperative period.

SETTING

Twenty-three-bed mixed PICU in a tertiary academic center.

PARTICIPANTS

Patients 1 month to 18 years old undergoing cardiac surgery requiring CPB.

MEAN OUTCOME MEASUREMENTS AND RESULTS

We analyzed A2 expression in 22 enrolled subjects (n = 9, 1-23 mo old; n = 13, 2-18 yr old) and found a proteolysis-mediated decline in intact A2 immediately after bypass (p = 0.0009), reaching a median of 4% of baseline at 6 hours after bypass (p < 0.0001), and recovery by postoperative day 1. The degree of A2 depletion immediately after bypass in 1-23-month-olds correlated strongly with the extent of organ dysfunction, as measured by PICU admission Vasoactive-Ventilation-Renal (p = 0.004) and PEdiatric Logistic Organ Dysfunction-2 (p = 0.039) scores on postoperative day 1. A2 depletion immediately after bypass also correlated with more protracted requirement for both respiratory support (p = 0.007) and invasive ventilation (p = 0.013) in the 1-23-month-olds.

CONCLUSIONS AND RELEVANCE

The degree of depletion of A2 following CPB correlates with more severe organ dysfunction, especially acute respiratory compromise in children under 2 years. These findings suggest that loss of A2 may contribute to pulmonary microvascular leak in young children following CPB.

Shedding Light on the Pathogenesis of Splanchnic Vein Thrombosis

Splanchnic vein thrombosis is a rare but potentially life-threatening manifestation of venous thromboembolism, with challenging implications both at the pathological and therapeutic level. It is frequently associated with liver cirrhosis, but it could also be provoked by myeloproliferative disorders, cancer of various gastroenterological origin, abdominal infections and thrombophilia. A portion of splanchnic vein thrombosis is still classified as idiopathic. Here, we review the mechanisms of splanchnic vein thrombosis, including new insights on the role of clonal hematopoiesis in idiopathic SVT pathogenesis, with important implications from the therapeutic standpoint.

Distinguishing Plasmin-Generating Microvesicles: Tiny Messengers Involved in Fibrinolysis and Proteolysis

A number of stressors and inflammatory mediators (cytokines, proteases, oxidative stress mediators) released during inflammation or ischemia stimulate and activate cells in blood, the vessel wall or tissues. The most well-known functional and phenotypic responses of activated cells are (1) the immediate expression and/or release of stored or newly synthesized bioactive molecules, and (2) membrane blebbing followed by release of microvesicles. An ultimate response, namely the formation of extracellular traps by neutrophils (NETs), is outside the scope of this work. The main objective of this article is to provide an overview on the mechanism of plasminogen reception and activation at the surface of cell-derived microvesicles, new actors in fibrinolysis and proteolysis. The role of microvesicle-bound plasmin in pathological settings involving inflammation, atherosclerosis, angiogenesis, and tumour growth, remains to be investigated. Further studies are necessary to determine if profibrinolytic microvesicles are involved in a finely regulated equilibrium with pro-coagulant microvesicles, which ensures a balanced haemostasis, leading to the maintenance of vascular patency.

Annexin A2 (AnxA2) association with the clinicopathological data in different breast cancer subtypes: A possible role for AnxA2 in tumor heterogeneity and cancer progression

BACKGROUND

Breast cancer is a highly heterogeneous type of neoplasia with molecular and biochemical alterations in the ductal epithelium. AnxA2 has a diverse functions and through intracellular interaction with other molecules promotes carcinogenesis.

AIMS

To study the possible involvement of AnxA2 in breast cancer heterogeneity and cancer progression.

PATIENTS AND METHODS

Tumor tissue and serum were obtained from different breast cancer subtypes. Tumor tissues were processed for histopathological studies. AnxA2 levels were assessed in the tissues by H scoring and in the serum by ELISA. AnxA2 levels were correlated with HER2 and Ki67 and with clinicopathological data. Normal breast tissues and serum from healthy subjects were used as controls.

RESULTS

AnxA2 showed a peculiar distribution in tumor tissues and nearby interstitial tissues. Pattern of expressions varied in different subtypes with the highest expression in triple negative subtype. Tissue and serum AnxA2 showed significant co-upregulations in breast cancer. Moreover, they showed positive correlations with HER2 and Ki67 and associations with clinicopathological data including cancer staging and lymph node metastasis.

CONCLUSION

For the best of our knowledge this is the first study showing correlation between AnxA2, the proposed prognostic marker and the well-established tumor markers; HER2 and Ki67. AnxA2 might contribute to breast cancer heterogeneity and is associated with poor prognosis. AnxA2 might be a prognostic marker and an additional marker for breast cancer grading and clinical staging. Interestingly, tissue and serum AnxA2 showed a strong correlation. Thus, assessing serum AnxA2 can be a noninvasive prognostic tool.

Annexin A2 and Kidney Diseases

Annexin A2 is a Ca²⁺- and phospholipid-binding protein which is widely expressed in various types of cells and tissues. As a multifunctional molecule, annexin A2 is found to be involved in diverse cell functions and processes, such as cell exocytosis, endocytosis, migration and proliferation. As a receptor of plasminogen and tissue plasminogen activator, annexin A2 promotes plasmin generation and regulates the homeostasis of blood coagulation, fibrinolysis and matrix degradation. As an antigen expressed on cell membranes, annexin A2 initiates local inflammation and damage through binding to auto-antibodies. Annexin A2 also mediates multiple signaling pathways induced by various growth factors and oxidative stress. Aberrant expression of annexin A2 has been found in numerous kidney diseases. Annexin A2 has been shown to act as a co-receptor of integrin CD11b mediating NF-kB-dependent kidney inflammation, which is further amplified through annexin A2/NF-kB-triggered macrophage M2 to M1 phenotypic change. It also modulates podocyte cytoskeleton rearrangement through Cdc42 and Rac1/2/3 Rho pathway causing proteinuria. Thus, annexin A2 is implicated in the pathogenesis and progression of various kidney diseases. In this review, we focus on the current understanding of the role of annexin A2 in kidney diseases.

Non-coding RNAs in cancer therapy-induced cardiotoxicity: Mechanisms, biomarkers, and treatments

As a result of ongoing breakthroughs in cancer therapy, cancer patients' survival rates have grown considerably. However, cardiotoxicity has emerged as the most dangerous toxic side effect of cancer treatment, negatively impacting cancer patients' prognosis. In recent years, the link between non-coding RNAs (ncRNAs) and cancer therapy-induced cardiotoxicity has received much attention and investigation. NcRNAs are non-protein-coding RNAs that impact gene expression post-transcriptionally. They include microRNAs (miRNAs), long non-coding RNAs (lncRNAs), and circular RNAs (circRNAs). In several cancer treatments, such as chemotherapy, radiotherapy, and targeted therapy-induced cardiotoxicity, ncRNAs play a significant role in the onset and progression of cardiotoxicity. This review focuses on the mechanisms of ncRNAs in cancer therapy-induced cardiotoxicity, including apoptosis, mitochondrial damage, oxidative stress, DNA damage, inflammation, autophagy, aging, calcium homeostasis, vascular homeostasis, and fibrosis. In addition, this review explores potential ncRNAs-based biomarkers and therapeutic strategies, which may help to convert ncRNAs research into clinical practice in the future for early detection and improvement of cancer therapy-induced cardiotoxicity.

A systematic review of the utility of biomarkers as aids in the early diagnosis and outcome prediction of bovine respiratory disease complex in feedlot cattle

Bovine respiratory disease complex (BRDC) is a common, serious problem in feedlot cattle worldwide. Early diagnosis and outcome prediction are critical for making decisions to prevent economic loss and to limit antimicrobial use. Diagnosing BRDC is commonly based on visual signs and behavioral changes; both assessments are considered to have low diagnostic accuracy. Biomarkers are important for supporting the diagnosis of BRDC, determining the necessity and potential outcomes of treatment, and assisting in research in which differentiating diseased animals is required. There are few reviews summarizing the biomarkers available and utilized. We systematically evaluated the detection and prognostic potential of biomarkers from the literature published between January 1990 and December 2020. We performed a descriptive analysis of 5 biomarker categories: acute-phase proteins, stress-related hormones, other blood biomarkers, omics biomarkers, and non-blood biomarkers. The retrieved articles consisted of studies or trials that assessed the detection value and treatment and/or outcome prediction efficacy of biomarkers for BRDC in feedlot cattle; 23 manuscripts for review and analysis satisfied the selection criteria. Based on our review, we cannot recommend a specific biomarker as the sole method for the early detection or outcome prediction for BRDC, given that the application and efficacy of biomarkers varies in different situations. Our systematic review may serve as a reference for clinical and research investigations of early detection and outcome prediction of BRDC.

Annexin A2: The Diversity of Pathological Effects in Tumorigenesis and Immune Response

Annexin A2 (ANXA2) is widely used as a marker in a variety of tumors. By regulating multiple signal pathways, ANXA2 promotes the epithelial-mesenchymal transition, which can cause tumorigenesis and accelerate thymus degeneration. The elevated ANXA2 heterotetramer facilitates the production of plasmin, which participates in pathophysiologic processes such as tumor cell invasion and metastasis, bleeding diseases, angiogenesis, inducing the expression of inflammatory factors. In addition, the ANXA2 on the cell membrane mediates immune response via its interaction with surface proteins of pathogens, C1q, toll-like receptor 2, anti-dsDNA antibodies and immunoglobulins. Nuclear ANXA2 plays a role as part of a primer recognition protein complex that enhances DNA synthesis and cells proliferation by acting on the G1-S phase of the cell. ANXA2 reduction leads to the inhibition of invasion and metastasis in multiple tumor cells, bleeding complications in acute promyelocytic leukemia, retinal angiogenesis, autoimmunity response and tumor drug resistance. In this review, we provide an update on the pathological effects of ANXA2 in both tumorigenesis and the immune response. We highlight ANXA2 as a critical protein in numerous malignancies and the immune host response.

The Angiostrongylus vasorum Excretory/Secretory and Surface Proteome Contains Putative Modulators of the Host Coagulation

Angiostrongylus vasorum is a cardiopulmonary nematode of canids and is, among others, associated with bleeding disorders in dogs. The pathogenesis of such coagulopathies remains unclear. A deep proteomic characterization of sex specific A. vasorum excretory/secretory proteins (ESP) and of cuticular surface proteins was performed, and the effect of ESP on host coagulation and fibrinolysis was evaluated in vitro. Proteins were quantified by liquid chromatography coupled to mass spectrometry and functionally characterized through gene ontology and pathway enrichment analysis. In total, 1069 ESP (944 from female and 959 from male specimens) and 1195 surface proteins (705 and 1135, respectively) were identified. Among these were putative modulators of host coagulation, e.g., von Willebrand factor type D domain protein orthologues as well as several proteases, including serine type proteases, protease inhibitors and proteasome subunits. The effect of ESP on dog coagulation and fibrinolysis was evaluated on canine endothelial cells and by rotational thromboelastometry (ROTEM). After stimulation with ESP, tissue factor and serpin E1 transcript expression increased. ROTEM revealed minimal interaction of ESP with dog blood and ESP did not influence the onset of fibrinolysis, leading to the conclusion that Angiostrongylus vasorum ESP and surface proteins are not solely responsible for bleeding in dogs and that the interaction with the host's vascular hemostasis is limited. It is likely that coagulopathies in A. vasorum infected dogs are the result of a multifactorial response of the host to this parasitic infection.

5α-Epoxyalantolactone Inhibits Metastasis of Triple-Negative Breast Cancer Cells by Covalently Binding a Conserved Cysteine of Annexin A2

Triple-negative breast cancer (TNBC) has been considered the most aggressive and mortal breast cancer. Thus far, it remains an important challenge to develop TNBC targeted therapy. As revealed from numerous recent studies, ANXA2 may be a potential target to treat TNBC. In the present study, a natural product 5α-epoxyalantolactone (5α-EAL) was discovered as an anti-breast cancer stem cells (BCSCs) lead compound. Furthermore, 5α-EAL was found to be able to notably suppress the function of ANXA2 by covalently targeting cysteine 9 (Cys9) of ANXA2. To the best of our knowledge, 5α-EAL was recognized as the first small molecule functional inhibitor of ANXA2. It could significantly inhibit the formation of the heterotetrameric complex of ANXA2 and S100A10, which is capable of transporting E-cadherin (E-Ca) to the membrane. The above findings may be used as a possible strategy to develop novel anti-TNBC therapies targeting ANXA2.

Annexin A2 in Fibrinolysis, Inflammation and Fibrosis

As a cell surface tissue plasminogen activator (tPA)-plasminogen receptor, the annexin A2 (A2) complex facilitates plasmin generation on the endothelial cell surface, and is an established regulator of hemostasis. Whereas A2 is overexpressed in hemorrhagic disease such as acute promyelocytic leukemia, its underexpression or impairment may result in thrombosis, as in antiphospholipid syndrome, venous thromboembolism, or atherosclerosis. Within immune response cells, A2 orchestrates membrane repair, vesicle fusion, and cytoskeletal organization, thus playing a critical role in inflammatory response and tissue injury. Dysregulation of A2 is evident in multiple human disorders, and may contribute to the pathogenesis of various inflammatory disorders. The fibrinolytic system, moreover, is central to wound healing through its ability to remodel the provisional matrix and promote angiogenesis. A2 dysfunction may also promote tissue fibrogenesis and end-organ fibrosis.

Annexin A2-Mediated Plasminogen Activation in Endothelial Cells Contributes to the Proangiogenic Effect of Adenosine A2A Receptors

Adenosine A_2A receptor mediates the promotion of wound healing and revascularization of injured tissue, in healthy and animals with impaired wound healing, through a mechanism depending upon tissue plasminogen activator (tPA), a component of the fibrinolytic system. In order to evaluate the contribution of plasmin generation in the proangiogenic effect of adenosine A_2A receptor activation, we determined the expression and secretion of t-PA, urokinase plasminogen activator (uPA), plasminogen activator inhibitor-1 (PAI-1) and annexin A2 by human dermal microvascular endothelial cells stimulated by the selective agonist CGS-21680. The plasmin generation was assayed through an enzymatic assay and the proangiogenic effect was studied using an endothelial tube formation assay in Matrigel. Adenosine A_2A receptor activation in endothelial cells diminished the release of PAI-1 and promoted the production of annexin A2, which acts as a cell membrane co-receptor for plasminogen and its activator tPA. Annexin A2 mediated the increased cell membrane-associated plasmin generation in adenosine A_2A receptor agonist treated human dermal microvascular endothelial cells and is required for tube formation in an in vitro model of angiogenesis. These results suggest a novel mechanism by which adenosine A_2A receptor activation promotes angiogenesis: increased endothelial expression of annexin A2, which, in turn, promotes fibrinolysis by binding tPA and plasminogen to the cell surface.

Reduced expression of annexin A2 is associated with impaired cell surface fibrinolysis and venous thromboembolism

Reduced plasma fibrinolysis has been identified as a potential risk factor for venous thromboembolism (VTE), but the role of cell surface fibrinolysis in VTE is unknown. The annexin A2/S100A10 complex serves as a coreceptor for plasminogen and tissue plasminogen activator (tPA), augmenting plasmin generation by 60-fold on the endothelial cell surface. Several studies in both mice and humans support the concept that A2 regulates fibrin homeostasis and intravascular thrombosis in vivo. Here, we examined A2 protein expression and function in 115 adult subjects with VTE and 87 healthy controls. Using peripheral blood mononuclear cells as a surrogate for endothelial cells, we found a 41% mean decrease in cell surface tPA-dependent fibrinolytic activity in subjects who had a positive personal and family history of VTE but tested negative for known inherited thrombophilias (ITs). A2 protein was reduced on average by 70% and messenger RNA levels by 30%, but neither decrease correlated with anticoagulant therapy. Neither cell A2 protein nor cell surface plasmin generation correlated with plasma-based clot lysis times, suggesting that the plasma and cell surface fibrinolytic systems operate independently of one another. These data suggest that reduced expression of annexin A2 protein is associated with cell surface hypofibrinolysis and may represent a novel risk factor for IT.

Coagulation and Fibrinolysis in Obstructive Sleep Apnoea

Obstructive sleep apnoea (OSA) is a common disease which is characterised by repetitive collapse of the upper airways during sleep resulting in chronic intermittent hypoxaemia and frequent microarousals, consequently leading to sympathetic overflow, enhanced oxidative stress, systemic inflammation, and metabolic disturbances. OSA is associated with increased risk for cardiovascular morbidity and mortality, and accelerated coagulation, platelet activation, and impaired fibrinolysis serve the link between OSA and cardiovascular disease. In this article we briefly describe physiological coagulation and fibrinolysis focusing on processes which could be altered in OSA. Then, we discuss how OSA-associated disturbances, such as hypoxaemia, sympathetic system activation, and systemic inflammation, affect these processes. Finally, we critically review the literature on OSA-related changes in markers of coagulation and fibrinolysis, discuss potential reasons for discrepancies, and comment on the clinical implications and future research needs.

Annexins: Involvement in cholesterol homeostasis, inflammatory response and atherosclerosis

The annexin superfamily consists of 12 proteins with a highly structural homology that binds to phospholipids depending on the availability of Ca²⁺-dependent. Different studies of overexpression, inhibition, or using recombinant proteins have linked the main function of these proteins to their dynamic and reversible binding to membranes. Annexins are found in multiple cellular compartments, regulating different functions, such as membrane trafficking, anchoring to the cell cytoskeleton, ion channel regulation, as well as pro- or anti-inflammatory and anticoagulant activities. The use of animals deficient in any of these annexins has established their possible functions in vivo, demonstrating that annexins can participate in relevant functions independent of Ca²⁺ signalling. This review will focus mainly on the role of different annexins in the pathological vascular remodelling that underlies the formation of the atherosclerotic lesion, as well as in the control of cholesterol homeostasis.

Autoantibodies to Annexin A2 and cerebral thrombosis: Insights from a mouse model

Introduction

Antiphospholipid syndrome (APS) is an autoimmune disorder manifested by thromboembolic events, recurrent spontaneous abortions and elevated titers of circulating antiphospholipid antibodies. In addition, the presence of antiphospholipid antibodies seems to confer a fivefold higher risk for stroke or transient ischemic attack. Although the major antigen of APS is β₂ glycoprotein I, it is now well established that antiphospholipid antibodies are heterogeneous and bind to various targets. Recently, antibodies to Annexin A2 (ANXA2) have been reported in APS. This is of special interest since data indicated ANXA2 as a key player in fibrinolysis. Therefore, in the present study we assessed whether anti-ANXA2 antibodies play a pathological role in thrombosis associated disease.

Materials and Methods

Mice were induced to produce anti-ANXA2 antibodies by immunization with ANXA2 (iANXA2) and control mice were immunized with adjuvant only. A middle cerebral artery occlusion stroke model was applied to the mice. The outcome of stroke severity was assessed and compared between the two groups.

Results

Our results indicate that antibodies to ANXA2 lead to a more severe stroke as demonstrated by a significant larger stroke infarct volume (iANXA2 133.9 ± 3.3 mm³ and control 113.7 ± 7.4 mm³; p = 0.017) and a more severe neurological outcome (iANXA2 2.2 ± 0.2, and control 1.5 ± 0.18; p = 0.03).

Conclusions

This study supports the hypothesis that auto-antibodies to ANXA2 are an independent risk factor for cerebral thrombosis. Consequently, we propose screening for anti-ANXA2 antibodies should be more widely used and patients that exhibit the manifestations of APS should be closely monitored by physicians.

The fibrinolytic system in the cornea: A key regulator of corneal wound healing and biological defense

The cornea is a relatively unique tissue in the body in that it possesses specific features such as a lack of blood vessels that contribute to its transparency. The cornea is supplied with soluble blood components such as albumin, globulin, and fibrinogen as well as with nutrients, oxygen, and bioactive substances by diffusion from aqueous humor and limbal vessels as well as a result of its exposure to tear fluid. The healthy cornea is largely devoid of cellular components of blood such as polymorphonuclear leukocytes, monocytes-macrophages, and platelets. The location of the cornea at the ocular surface renders it susceptible to external insults, and its avascular nature necessitates the operation of healing and defense mechanisms in a manner independent of a direct blood supply. The fibrinolytic system, which was first recognized for its role in the degradation of fibrin clots in the vasculature, has also been found to contribute to various biological processes outside of blood vessels. Fibrinolytic factors thus play an important role in biological defense of the cornea. In this review, we address the function of the fibrinolytic system in corneal defense including wound healing and the inflammatory response.

Diagnostic Value of Plasma Annexin A2 in Early-Stage High-Grade Serous Ovarian Cancer

Ovarian cancer (OC) is commonly diagnosed at advanced stage when prognosis is poor. Consequently, there is an urgent clinical need to identify novel biomarkers for early detection to improve survival. We examined the diagnostic value of the calcium phospholipid binding protein annexin A2 (ANXA2), which plays an important role in OC metastasis. Annexin A2 plasma levels in patients with high grade serous OC (n = 105), benign ovarian lesions (n = 55) and healthy controls (n = 143) were measured by ELISA. Annexin A2 levels were found to be significantly increased in patients with stage I (p < 0.0001) and stage IA (p = 0.0027) OC when compared to healthy controls. In the logistic regression models followed by receiver operating characteristics (ROC) curve analyses, plasma annexin A2 showed 46.7% sensitivity at 99.6% specificity in distinguishing stage IA OC patients from healthy controls and 75% sensitivity at 65.5% specificity in the diagnosis of stage IA versus benign ovarian tumors. In the diagnosis of stage IA OC versus normal controls, the combination of plasma annexin A2 and CA125 showed 80% sensitivity at 99.6% specificity (AUC = 0.970) which was significantly higher than for CA125 (53.3% sensitivity at 99.6% specificity; AUC = 0.891) alone. The diagnostic accuracy in distinguishing stage IA OC from benign ovarian disease when combining annexin A2 and CA125 (71.4% accuracy at 100% sensitivity) was almost twice as high compared to CA125 (37.1% accuracy at 100% sensitivity) alone. In conclusion, annexin A2 in combination with CA125 has potential as a biomarker for the early detection of OC and to predict malignancy in patients with ovarian lesions, warranting further investigations.

Gastrodia elata Blume (Tianma): Hope for Brain Aging and Dementia

Since aging-related diseases, including dementia, represent major public health threats to our society, physician-scientists must develop innovative, interdisciplinary strategies to open new avenues for development of alternative therapies. One such novel approach may lie in traditional Chinese medicine (TCM). Gastrodia elata Blume (G. elata, tianma) is a TCM frequently used for treatment of cerebrocardiovascular diseases (CCVDs). Recent studies of G. elata-based treatment modalities, which have investigated its pharmacologically relevant activity, potential efficacy, and safety, have employed G. elata in well-characterized, aging-related disease models, with a focus on models of aging-related dementia, such as Alzheimer's disease (AD). Here, I examine results from previous studies of G. elata, as well as related herbal preparations and pure natural products, as prophylaxis and remedies for aging-related CCVDs and dementia. Concluding, data suggest that tianma treatment may be used as a promising complementary therapy for AD.

Melo E, B. C. T. Coimbra L, Lapa MS, Acencio MMP, Freitas-Filho O, Capelozzi VL, Teixeira LR, Fernandes CJCS, Jatene FB, Laurindo FRM, Terra-Filho M. Shear stress-exposed pulmonary artery endothelial cells fail to upregulate HSP70 in chronic thromboembolic pulmonary hypertension

The pathophysiological mechanisms underlying chronic thromboembolic pulmonary hypertension (CTEPH) are still unclear. Endothelial cell (EC) remodeling is believed to contribute to this pulmonary disease triggered by thrombus and hemodynamic forces disbalance. Recently, we showed that HSP70 levels decrease by proatherogenic shear stress. Molecular chaperones play a major role in proteostasis in neurological, cancer and inflammatory/ infectious diseases. To shed light on microvascular responses in CTEPH, we characterized the expression of molecular chaperones and annexin A2, a component of the fibrinolytic system. There is no animal model that reproduces microvascular changes in CTEPH, and this fact led us to isolated endothelial cells from patients with CTEPH undergoing pulmonary endarterectomy (PEA). We exposed CTEPH-EC and control human pulmonary endothelial cells (HPAEC) to high- (15 dynes/cm2) or low- (5 dynes/cm2) shear stress. After high-magnitude shear stress HPAEC upregulated heat shock protein 70kDa (HSP70) and the HSP ER paralogs 78 and 94kDa glucose-regulated protein (GRP78 and 94), whereas CTEPH-ECs failed to exhibit this response. At static conditions, both HSP70 and HSP90 families in CTEPH-EC are decreased. Importantly, immunohistochemistry analysis showed that HSP70 expression was downregulated in vivo, and annexin A2 was upregulated. Interestingly, wound healing and angiogenesis assays revealed that HSP70 inhibition with VER-155008 further impaired CTEPH-EC migratory responses. These results implicate HSP70 as a novel master regulator of endothelial dysfunction in type 4 PH. Overall, we first show that global failure of HSP upregulation is a hallmark of CTEPH pathogenesis and propose HSP70 as a potential biomarker of this condition.

Co-localization of Interleukin-1α and Annexin A2 at the plasma membrane in response to oxidative stress

Interleukin-1α (IL-1α) and Annexin A2 (AnxA2) are pleiotropic molecules with both intracellular and extracellular roles. They share several characteristics including unconventional secretion aided by S100 proteins, anchoring of the externalized proteins at the outer surface of the plasma membrane and response to oxidative stress. Although IL-1α and AnxA2 have been implicated in a variety of biological processes, including cancer, little is known about the mechanisms of their cellular release. In the present study, employing the non-cancerous breast epithelial MCF10A cells, we demonstrate that IL-1α and AnxA2 establish a close association in response to oxidative stress. Stress conditions lead to translocation of both proteins towards lamellipodia rich in vimentin and association of full-length IL-1α and Tyr23 phosphorylated AnxA2 with the plasma membrane at peripheral sites depleted of F-actin. Notably, membrane-associated IL-1α and AnxA2 preferentially localize to the outer edges of the MCF10A cell islands, suggesting that the two proteins participate in the communication of these epithelial cells with their neighboring cells. Similarly, in U2OS osteosarcoma cell line both endogenous IL-1α and transiently produced IL-1α/EGFP associate with the plasma membrane. While benign MFC10A cells present membrane-associated IL-1α and AnxA2 at the edges of their cell islands, the aggressive cancerous U2OS cells communicate in such manner also with distant cells.

Upregulation of annexin A1 protein expression in the intratumoral vasculature of human non-small-cell lung carcinoma and rodent tumor models

Annexin A1 (anxA1) is an immunomodulatory protein that has been proposed as a tumor vascular target for antitumor biologic agents, yet to date the vascular expression of anxA1 in specific tumor indications has not been systematically assessed. Attempts to evaluate vascular anxA1 expression by immunohistochemistry are complicated by a lack of available antibodies that are both specific for anxA1 and bind the N-terminal–truncated form of anxA1 that has previously been identified in tumor vasculature. To study the vascular expression pattern of anxA1 in non–small-cell lung carcinoma (NSCLC), we isolated an antibody capable of binding N-terminal–truncated anxA1_27-346 and employed it in immunohistochemical studies of human lung specimens. Lung tumor specimens evaluated with this antibody revealed vascular (endothelial) anxA1 expression in five of eight tumor samples studied, but no vascular anxA1 expression was observed in normal lung tissue. Tumor microarray analysis further demonstrated positive vascular staining for anxA1 in 30 of 80 NSCLC samples, and positive staining of neoplastic cells was observed in 54 of 80 samples. No correlation was observed between vascular and parenchymal anxA1 expression. Two rodent tumor models, B16-F10 and Py230, were determined to have upregulated anxA1 expression in the intratumoral vasculature. These data validate anxA1 as a potential vascular anti-tumor target in a subset of human lung tumors and identify rodent models which demonstrate anxA1 expression in tumor vasculature.

[Seronegative antiphospholipid syndrome: Myth or reality?]

The antiphospholipid syndrome (APS) is a systemic autoimmune disease characterized by thrombosis and/or obstetrical manifestations and the persistent presence, at least 12 weeks apart, of antiphospholipid antibodies (aPL) such as lupus anticoagulant (LA) and/or anticardiolipin antibodies (ACL) and/or anti-β2 glycoprotein I antibodies (aβ2GPI). The finding of patients with clinical profile highly suggestive of APS but who are negative for conventional biological criteria has led to the concept of seronegative APS. In the last few years, new antigen targets and methodological approaches have been employed to more clearly identify this syndrome in patients with thrombosis or obstetrical complications without conventional aPL. Although seronegative APS is still controversial, there is increasing recognition of the existence of this subgroup. However, clinical relevance of non conventional aPL need to be confirmed by efforts toward standardizing new biological tools and longitudinal studies involving large cohort of patients.

Homocysteine Modification in Protein Structure/Function and Human Disease

Epidemiological studies established that elevated homocysteine, an important intermediate in folate, vitamin B₁₂, and one carbon metabolism, is associated with poor health, including heart and brain diseases. Earlier studies show that patients with severe hyperhomocysteinemia, first identified in the 1960s, exhibit neurological and cardiovascular abnormalities and premature death due to vascular complications. Although homocysteine is considered to be a nonprotein amino acid, studies over the past 2 decades have led to discoveries of protein-related homocysteine metabolism and mechanisms by which homocysteine can become a component of proteins. Homocysteine-containing proteins lose their biological function and acquire cytotoxic, proinflammatory, proatherothrombotic, and proneuropathic properties, which can account for the various disease phenotypes associated with hyperhomocysteinemia. This review describes mechanisms by which hyperhomocysteinemia affects cellular proteostasis, provides a comprehensive account of the biological chemistry of homocysteine-containing proteins, and discusses pathophysiological consequences and clinical implications of their formation.

Lipoprotein(a) catabolism: a case of multiple receptors

Lipoprotein(a) [Lp(a)] is an apolipoprotein B (apoB)-containing plasma lipoprotein similar in structure to low-density lipoprotein (LDL). Lp(a) is more complex than LDL due to the presence of apolipoprotein(a) [apo(a)], a large glycoprotein sharing extensive homology with plasminogen, which confers some unique properties onto Lp(a) particles. ApoB and apo(a) are essential for the assembly and catabolism of Lp(a); however, other proteins associated with the particle may modify its metabolism. Lp(a) specifically carries a cargo of oxidised phospholipids (OxPL) bound to apo(a) which stimulates many proinflammatory pathways in cells of the arterial wall, a key property underlying its pathogenicity and association with cardiovascular disease (CVD). While the liver and kidney are the major tissues implicated in Lp(a) clearance, the pathways for Lp(a) uptake appear to be complex and are still under investigation. Biochemical studies have revealed an exceptional array of receptors that associate with Lp(a) either via its apoB, apo(a), or OxPL components. These receptors fall into five main categories, namely 'classical' lipoprotein receptors, toll-like and scavenger receptors, lectins, and plasminogen receptors. The roles of these receptors have largely been dissected by genetic manipulation in cells or mice, although their relative physiological importance for removal of Lp(a) from the circulation remains unclear. The LPA gene encoding apo(a) has an overwhelming effect on Lp(a) levels which precludes any clear associations between potential Lp(a) receptor genes and Lp(a) levels in population studies. Targeted approaches and the selection of unique Lp(a) phenotypes within populations has nevertheless allowed for some associations to be made. Few of the proposed Lp(a) receptors can specifically be manipulated with current drugs and, as such, it is not currently clear whether any of these receptors could provide relevant targets for therapeutic manipulation of Lp(a) levels. This review summarises the current status of knowledge about receptor-mediated pathways for Lp(a) catabolism.

Cancer-Associated Thrombosis in Cirrhotic Patients with Hepatocellular Carcinoma

It is common knowledge that cancer patients are more prone to develop venous thromboembolic complications (VTE). It is therefore not surprising that patients with hepatocellular carcinoma (HCC) present with a significant risk of VTE, with the portal vein being the most frequent site (PVT). However, patients with HCC are peculiar as both cancer and liver cirrhosis are conditions that can perturb the hemostatic balance towards a prothrombotic state. Because HCC-related hypercoagulability is not clarified at all, the aim of the present review is to summarize the currently available knowledge on epidemiology and pathogenesis of non-malignant thrombotic complications in patients with liver cirrhosis and HCC. They are at increased risk to develop both PVT and non-splanchnic VTE, indicating that both local and systemic factors can foster the development of site-specific thrombosis. Recent studies have suggested multiple and often interrelated mechanisms through which HCC can tip the hemostatic balance of liver cirrhosis towards hypercoagulability. Described mechanisms include increased fibrinogen concentration/polymerization, thrombocytosis, and release of tissue factor-expressing extracellular vesicles. Currently, there are no specific guidelines on the use of thromboprophylaxis in this unique population. There is the urgent need of prospective studies assessing which patients have the highest prothrombotic profile and would therefore benefit from early thromboprophylaxis.

Regulation of plasminogen activation on cell surfaces and fibrin

The fibrinolytic system dissolves fibrin and maintains vascular patency. Recent advances in imaging analyses allowed visualization of the spatiotemporal regulatory mechanism of fibrinolysis, as well as its regulation by other plasma hemostasis cofactors. Vascular endothelial cells (VECs) retain tissue-type plasminogen activator (tPA) after secretion and maintain high plasminogen (plg) activation potential on their surfaces. As in plasma, the serpin, plasminogen activator inhibitor type 1 (PAI-1), regulates fibrinolytic potential via inhibition of the VEC surface-bound plg activator, tPA. Once fibrin is formed, plg activation by tPA is initiated and effectively amplified on the surface of fibrin, and fibrin is rapidly degraded. The specific binding of plg and tPA to lytic edges of partly degraded fibrin via newly generated C-terminal lysine residues, which amplifies fibrin digestion, is a central aspect of this pathophysiological mechanism. Thrombomodulin (TM) plays a role in the attenuation of plg binding on fibrin and the associated fibrinolysis, which is reversed by a carboxypeptidase B inhibitor. This suggests that the plasma procarboxypeptidase B, thrombin-activatable fibrinolysis inhibitor (TAFI), which is activated by thrombin bound to TM on VECs, is a critical aspect of the regulation of plg activation on VECs and subsequent fibrinolysis. Platelets also contain PAI-1, TAFI, TM, and the fibrin cross-linking enzyme, factor (F) XIIIa, and either secrete or expose these agents upon activation in order to regulate fibrinolysis. In this review, the native machinery of plg activation and fibrinolysis, as well as their spatiotemporal regulatory mechanisms, as revealed by imaging analyses, are discussed.

FNDC3B promotes cell migration and tumor metastasis in hepatocellular carcinoma

Recurrence and metastasis are common in hepatocellular carcinoma (HCC) and correlate with poor prognosis. We investigated the role of fibronectin type III domain containing 3B (FNDC3B) in HCC metastasis. Overexpression of FNDC3B in HCC cell lines enhanced cell migration and invasion. On the other hand, knockdown of FNDC3B using short-hairpin RNA reduced tumor nodule formation in both intra- and extra-hepatic metastasis. High levels of FNDC3B were observed in metastatic HCCs and correlated with poor patient survival and shorter recurrence time. Mutagenesis and LC-MS/MS analyses showed that FNDC3B promotes cell migration by cooperating with annexin A2 (ANXA2). Furthermore, FNDC3B and ANXA2 expression correlated negatively with patient survival. Our results indicate that FNDC3B behaves like an oncogene by promoting cell migration. This suggests FNDC3B could serve as a biomarker and therapeutic target for HCC metastasis.

Molecular Regulation of Sprouting Angiogenesis

The term angiogenesis arose in the 18th century. Several studies over the next 100 years laid the groundwork for initial studies performed by the Folkman laboratory, which were at first met with some opposition. Once overcome, the angiogenesis field has flourished due to studies on tumor angiogenesis and various developmental models that can be genetically manipulated, including mice and zebrafish. In addition, new discoveries have been aided by the ability to isolate primary endothelial cells, which has allowed dissection of various steps within angiogenesis. This review will summarize the molecular events that control angiogenesis downstream of biochemical factors such as growth factors, cytokines, chemokines, hypoxia-inducible factors (HIFs), and lipids. These and other stimuli have been linked to regulation of junctional molecules and cell surface receptors. In addition, the contribution of cytoskeletal elements and regulatory proteins has revealed an intricate role for mobilization of actin, microtubules, and intermediate filaments in response to cues that activate the endothelium. Activating stimuli also affect various focal adhesion proteins, scaffold proteins, intracellular kinases, and second messengers. Finally, metalloproteinases, which facilitate matrix degradation and the formation of new blood vessels, are discussed, along with our knowledge of crosstalk between the various subclasses of these molecules throughout the text. Compr Physiol 8:153-235, 2018.

Protein phosphorylation and its role in the regulation of Annexin A2 function

BACKGROUND

Annexin A2 (AnxA2) is a multifunctional protein involved in endocytosis, exocytosis, membrane domain organisation, actin remodelling, signal transduction, protein assembly, transcription and mRNA transport, as well as DNA replication and repair.

SCOPE OF REVIEW

The current knowledge of the role of phosphorylation in the functional regulation of AnxA2 is reviewed. To provide a more comprehensive treatment of this topic, we also address in depth the phosphorylation process in general and discuss its possible conformational effects. Furthermore, we discuss the apparent limitations of the methods used to investigate phosphoproteins, as exemplified by the study of AnxA2.

MAJOR CONCLUSIONS

AnxA2 is subjected to complex regulation by post-translational modifications affecting its cellular functions, with Ser11, Ser25 and Tyr23 representing important phosphorylation sites. Thus, Ser phosphorylation of AnxA2 is involved in the recruitment and docking of secretory granules, the regulation of its association with S100A10, and sequestration of perinuclear, translationally inactive mRNP complexes. By contrast, Tyr phosphorylation of AnxA2 regulates its role in actin dynamics and increases its association with endosomal compartments. Modification of its three main phosphorylation sites is not sufficient to discriminate between its numerous functions. Thus, fine-tuning of AnxA2 function is mediated by the joint action of several post-translational modifications.

GENERAL SIGNIFICANCE

AnxA2 participates in malignant cell transformation, and its overexpression and/or phosphorylation is associated with cancer progression and metastasis. Thus, tight regulation of AnxA2 function is an integral aspect of cellular homeostasis. The presence of AnxA2 in cancer cell-derived exosomes, as well as the potential regulation of exosomal AnxA2 by phosphorylation or other PTMs, are topics of great interest.

Annexin A2-S100A10 heterotetramer is upregulated by PML/RARα fusion protein and promotes plasminogen-dependent fibrinolysis and matrix invasion in acute promyelocytic leukemia

Aberrant expression of annexin A2-S100A10 heterotetramer (AIIt) associated with PML/RARα fusion protein causes lethal hyperfibrinolysis in acute promyelocytic leukemia (APL), but the mechanism is unclear. To facilitate the investigation of regulatory association between ANXA2 and promyelocytic leukemia/retinoic acid receptor a (PML/RARα) fusion protein, this work was performed to determine the transcription start site of ANXA2 promoter with rapid amplification of 5'-cDNA ends analysis. Zinc-induced U937/PR9 cells expressed PML/RARα fusion protein, and resultant increases in ANXA2 transcripts and translational expressions of both ANXA2 and S100A10, while S100A10 transcripts remained constitutive. The transactivation of ANXA2 promoter by PML/RARα fusion protein was 3.29 ± 0.13 fold higher than that by control pSG5 vector or wild-type RARα. The overexpression of ANXA2 in U937 transfected with full-length ANXA2 cDNA was associated with increased S100A10 subunit, although S100A10 transcripts remained constitutive. The tPA-dependent initial rate of plasmin generation (IRPG) in zinc-treated U937/PR9 increased by 2.13-fold, and cell invasiveness increased by 27.6%. Antibodies against ANXA2, S100A10, or combination of both all remarkably inhibited the IRPG and invasiveness in U937/PR9 and NB4. Treatment of zinc-induced U937/PR9 or circulating APL blasts with all-trans retinoic acid (ATRA) significantly reduced cell surface ANXA2 and S100A10 and associated reductions in IRPG and invasiveness. Thus, PML/RARα fusion protein transactivated the ANXA2 promoter to upregulate ANXA2 and accumulate S100A10. Increased AIIt promoted IRPG and invasiveness, both of which were partly abolished by antibodies against ANXA2 and S100A10 or by ATRA.

Annexin A2 promotes liver fibrosis by mediating von Willebrand factor secretion

BACKGROUND

Liver fibrosis can lead to cirrhosis and hepatocellular carcinoma if not treated in the early stages. The molecular mechanisms of the pathogenesis of hepatic fibrosis remain unclear.

AIM

To identify the molecules involved in the pathogenesis of liver fibrosis and to investigate the potential effect and mechanism of Annexin A2 up-regulation during liver fibrosis progression.

METHODS

Twenty Sprague-Dawley rats were divided into two groups: the carbon tetrachloride (CCl₄)-induced liver fibrosis group and the normal control group. Hematoxylin and eosin staining or Masson Trichrome staining and enzyme-linked immunosorbent assay were applied to assess the degree of liver damage and fibrosis in rats with CCl₄-induced liver fibrosis. Liver tissue protein profiles were analyzed using iTRAQ and mass spectrometry. RT-PCR and western blotting analyses were employed to validate differentially expressed proteins. Small interfering RNA-based silencing was performed to study the function of Annexin A2.

RESULTS

Twelve weeks after CCl₄ injection, significant body weight changes and liver injury and liver fibrosis were observed in rats. In addition, 130 proteins were differentially expressed in the liver fibrosis group. Overexpression of Annexin A2 was confirmed by RT-PCR and Western blotting analysis. Silencing of Annexin A2 expression in HepG2 and LX-2 cells significantly reduced the secretion of von Willebrand factor (vWF).

CONCLUSION

Annexin A2 promotes liver fibrosis by mediating vWF secretion, which can be used to mitigate the progression of liver fibrosis.

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.

The annexin A2 system and angiogenesis

The formation of new blood vessels from pre-existing vasculature, the process known as angiogenesis, is highly regulated by pro- and anti-angiogenic signaling molecules including growth factors and proteases. As an endothelial cell-surface co-receptor for plasminogen and tissue plasminogen activator, the annexin A2 (ANXA2) complex accelerates plasmin generation and facilitates fibrinolysis. Plasmin can subsequently activate a downstream proteolytic cascade involving multiple matrix metalloproteinases. Thus, in addition to maintaining blood vessel patency, the ANXA2 complex can also promote angiogenesis via its pro-fibrinolytic activity. The generation of ANXA2-deficient mice allowed us to first observe the pro-angiogenic role of ANXA2 in vivo. Further investigations have provided additional details regarding the mechanism for ANXA2 regulation of retinal and corneal angiogenesis. Other studies have reported that ANXA2 supports angiogenesis in specific tumor-related settings. Here, we summarize results from in vivo studies that illustrate the pro-angiogenic role of ANXA2, and discuss the critical questions that may lead to an advanced understanding of the molecular mechanisms for ANXA2-mediated angiogenesis. Finally, highlights from studies on ANXA2-interacting agents offer potential therapeutic opportunities for the application of ANXA2-centered pharmaceuticals in angiogenesis-related disorders.

Prostaglandin-endoperoxide synthase-2 deletion affects the natural trafficking of Annexin A2 in monocytes and favours venous thrombosis in mice

Deep-vein thrombosis (DVT) is a common condition that often leads to pulmonary thromboembolism (VTE) and death. The role of prostaglandin-endoperoxide synthase (PTGS)2 in arterial thrombosis has been well established, whereas its impact in venous thrombosis remains unclear. Here, we showed that PTGS2 deletion predisposes to venous thrombosis as suggested by greater clot firmness and clot elasticity, by higher plasma levels of functional fibrinogen, factor VIII and PAI-1 activity, and proved by bigger thrombi detected after inferior vena cava ligation (IVCL) compared to WT mice. PTGS2^-/- thrombi have greater fibrin content, higher number of F4/80⁺, TF⁺ and ANXA2⁺ cells, and lower S100A10⁺ cells. Remarkably, monocyte depletion reduced thrombus size in mutant mice, suggesting an important role of PTGS2^-/- monocytes in this experimental setting. Interestingly, PTGS2 deletion reduced membrane ANXA2, and total S100A10, promoted assembly of ANXA2/p50NF-kB complex and its nuclear accumulation, and induced TF in peritoneal macrophages, whereas ANXA2 silencing decreased dramatically TF. Finally, Carbaprostacyclin treatment prevented venous thrombus formation induced by IVCL in mutant mice, reduced the ANXA2 binding to p50NF-kB subunit and its nuclear trafficking, and decreased TF in PTGS2^-/- macrophages. PTGS2 deletion, changing the natural distribution of ANXA2 in monocytes/macrophages, increases TF expression and activity predisposing to venous thrombosis. Interestingly, Carbaprostacyclin treatment, inhibiting nuclear ANXA2 trafficking, controls monocyte TF activity and prevents DVT occurrence. Our data are of help in elucidating the mechanisms by which PTGS2 inhibition increases DVT risk, and suggest a new role for ANXA2 in venous thrombosis.

Proteomic analysis reveals downregulation of housekeeping proteins in the diabetic vascular proteome

AIMS

Type 2 diabetes (T2D) increases the risk of death associated with cardiovascular complications. However, a complete understanding of protein changes within the diabetic vasculature is still lacking.

METHODS

Herein, we utilized mass spectrometry to perform vascular and urinary proteome analysis using a rat model of high-fat feeding and low-dose streptozotocin to simulate late-stage T2D. The purpose of this study was to identify aortic and urine proteins that are differentially expressed in normal and T2D rats.

RESULTS

High-fat feeding and low-dose streptozotocin resulted in hyperglycemia, hypoinsulinemia and high levels of circulating free fatty acids. Using a shotgun proteomic approach, high-mobility-group protein B1 and spondin-1 were significantly increased in T2D aorta compared to control aorta, suggesting vascular inflammation and smooth muscle proliferation, respectively. However, the majority of differentially expressed aortic proteins were downregulated in T2D, including proteins associated with coagulation, cell differentiation and redox homeostasis. Strikingly, we report a significant downregulation of commonly used cytoskeletal housekeeping proteins in T2D aorta. Urine from T2D rats displayed increased expression of proteins involved in inflammation and oxidative stress and decreased expression of proteins associated with lipid metabolism and cell adhesion. A number of differentially expressed proteins in urine of T2D rats have previously been reported in human T2D, thereby supporting this animal model as a good representation of human T2D.

CONCLUSIONS

Our data offer new information regarding key pathways that could be therapeutically targeted to combat the cardiovascular complications of T2D.

miR-320a mediates doxorubicin-induced cardiotoxicity by targeting VEGF signal pathway

Background

Vascular homeostasis abnormalities may involve in doxorubicin induced cardiotoxicity.

Methods

Enhanced cardiac miR-320a expression, reduced cardiac microvessel density and impaired cardiac function were observed in mice treated by anthracycline doxorubicin. To further explore the role of miR-320a in doxorubicin induced cardiotoxicity, microRNA mimics/inhibitor in vitro and rAAV administration in vivo were employed in mice.

Results

Knockdown of miR-320a not only resulted in enhanced proliferation and inhibited apoptosis in cultured endothelial cells, but also attenuated cardiac abnormalities induced by doxorubicin. On the contrary, overexpression of miR-320a enhanced apoptosis in vitro, and aggravated vessel abnormalities in heart and subsequent cardiac dysfunction in mice. Furthermore, Western blot assays showed that VEGF-A was a potential target of miR-320a, which was verified by anti-Ago2 co-immunoprecipitation. Moreover, as same as miR-320a, siRNA against VEGF-A reinforced doxorubicin induced endothelial cells injury. Finally, the negative effects of miR-320a on vascular homeostasis and cardiac function were alleviated by VEGF-A re-expression in doxorubicin treated mice.

Conclusion

Our observations demonstrate that miR-320a play important roles in doxorubicin induced cardiotoxicity via vessel homeostasis in heart and thus, inhibition of miR-320a may be applied to the treatment of cardiac dysfunction induced by anthracycline.

Role of Annexin A2 in the EGF-induced epithelial-mesenchymal transition in human CaSki cells

The epidermal growth factor receptor (EGF-R) signaling pathway is thought to have an important role in the development and progression of several carcinomas, as it is associated with cell proliferation, differentiation and migration. Activation of EGF-R signaling regulates epithelial-mesenchymal transition (EMT)-associated invasion and migration in normal and malignant epithelial cells. However, the specific mechanisms have not yet been fully elucidated. The present study utilized wound healing assays, western blotting, flow cytometry and MTT assays to demonstrate that Annexin A2 (ANXA2) is a key regulatory factor in EGF-induced EMT in CaSki cervical cancer cells. Moreover, the increased expression levels of ANXA2 promoted cell viability and migration in human CaSki cells. It was also found that silencing ANXA2 partially reverses EGF-induced EMT and inhibits cell viability and migration in CaSki cells. These findings suggest that ANXA2 is a key regulator of EGF-induced EMT in CaSki cervical cancer cells.

TNF-alpha and annexin A2: inflammation in thrombotic primary antiphospholipid syndrome

Antiphospholipid syndrome (APS) is characterized by thromboses and/or pregnancy losses. Laboratory criterion for the diagnosis of APS is the presence of antiphospholipid antibodies (anticardiolipin, anti-beta2-glycoprotein I (aβ2gpI) and lupus anticoagulant). On the one hand, the latest classification criteria for the diagnosis of APS emphasized that thrombotic manifestations of the syndrome should be without any signs of an inflammatory process, while on the other hand, some recent reports have suggested that APS is a "pro-inflammatory state." This article is focused on the importance of TNF-alpha and annexin A2 (anxA2) for patients with vascular (thrombotic) manifestations of the primary APS. The classic antithrombotic and antiplatelet therapy does not protect APS patients from the development of recurrent thrombosis. Therefore, an urgent need for the introduction of new therapeutic approaches in the treatment of APS patients is obvious. This review provides a rationale for the necessity for the use of immunomodulatory medications that could interfere with β2gpI binding to its receptor(s), such as anxA2, and/or inhibit TNF-alpha activity.

Thrombolysis by chemically modified coagulation factor Xa

Essentials Factor Xa (FXa) acquires cleavage-mediated tissue plasminogen activator (tPA) cofactor activity. Recombinant (r) tPA is the predominant thrombolytic drug, but it may cause systemic side effects. Chemically modified, non-enzymatic FXa was produced (Xai-K), which rapidly lysed thrombi in mice. Unlike rtPA, Xai-K had no systemic fibrinolysis activation markers, indicating improved safety.

SUMMARY

Background Enzymatic thrombolysis carries the risk of hemorrhage and re-occlusion must be evaded by co-administration with an anticoagulant. Toward further improving these shortcomings, we report a novel dual-functioning molecule, Xai-K, which is both a non-enzymatic thrombolytic agent and an anticoagulant. Xai-K is based on clotting factor Xa, whose sequential plasmin-mediated fragments, FXaβ and Xa33/13, accelerate the principal thrombolytic agent, tissue plasminogen activator (tPA), but only when localized to anionic phospholipid. Methods The effect of Xai-K on fibrinolysis was measured in vitro by turbidity, thromboelastography and chromogenic assays, and measured in a murine model of occlusive carotid thrombosis by Doppler ultrasound. The anticoagulant properties of Xai-K were evaluated by normal plasma clotting assays, and in murine liver laceration and tail amputation hemostatic models. Results Xa33/13, which participates in fibrinolysis of purified fibrin, was rapidly inhibited in plasma. Cleavage was blocked at FXaβ by modifying residues at the active site. The resultant Xai-K (1 nm) enhanced plasma clot dissolution by ~7-fold in vitro and was dependent on tPA. Xai-K alone (2.0 μg g(-1) body weight) achieved therapeutic patency in mice. The minimum primary dose of the tPA variant, Tenecteplase (TNK; 17 μg g(-1) ), could be reduced by > 30-fold to restore blood flow with adjunctive Xai-K (0.5 μg g(-1) ). TNK-induced systemic markers of fibrinolysis were not detected with Xai-K (2.0 μg g(-1) ). Xai-K had anticoagulant activity that was somewhat attenuated compared with a previously reported analogue. Conclusion These results suggest that Xai-K may ameliorate the safety profile of therapeutic thrombolysis, either as a primary or tPA/TNK-adjunctive agent.

LDL receptor-related protein-1 regulates NFκB and microRNA-155 in macrophages to control the inflammatory response

LDL receptor-related protein-1 (LRP1) is an endocytic and cell-signaling receptor. In mice in which LRP1 is deleted in myeloid cells, the response to lipopolysaccharide (LPS) was greatly exacerbated. LRP1 deletion in macrophages in vitro, under the control of tamoxifen-activated Cre-ER(T) fusion protein, robustly increased expression of proinflammatory cytokines and chemokines. In LRP1-expressing macrophages, proinflammatory mediator expression was regulated by LRP1 ligands in a ligand-specific manner. The LRP1 agonists, α2-macroglobulin and tissue-type plasminogen activator, attenuated expression of inflammatory mediators, even in the presence of LPS. The antagonists, receptor-associated protein (RAP) and lactoferrin (LF), and LRP1-specific antibody had the entirely opposite effect, promoting inflammatory mediator expression and mimicking LRP1 deletion. NFκB was rapidly activated in response to RAP and LF and responsible for the initial increase in expression of proinflammatory mediators. RAP and LF also significantly increased expression of microRNA-155 (miR-155) after a lag phase of about 4 h. miR-155 expression reflected, at least in part, activation of secondary cell-signaling pathways downstream of TNFα. Although miR-155 was not involved in the initial induction of cytokine expression in response to LRP1 antagonists, miR-155 was essential for sustaining the proinflammatory response. We conclude that LRP1, NFκB, and miR-155 function as members of a previously unidentified system that has the potential to inhibit or sustain inflammation, depending on the continuum of LRP1 ligands present in the macrophage microenvironment.

Reactive oxygen species exert opposite effects on Tyr23 phosphorylation of the nuclear and cortical pools of annexin A2

Annexin A2 (AnxA2) is a multi-functional and -compartmental protein whose subcellular localisation and functions are tightly regulated by its post-translational modifications. AnxA2 and its Tyr23-phosphorylated form (pTyr23AnxA2) are involved in malignant cell transformation, metastasis and angiogenesis. Here, we show that H₂O₂ exerts rapid, simultaneous and opposite effects on the Tyr23 phosphorylation status of AnxA2 in two distinct compartments of rat pheochromocytoma (PC12) cells. Reactive oxygen species induce dephosphorylation of pTyr23AnxA2 located in the PML bodies of the nucleus, whereas AnxA2 associated with F-actin at the cell cortex is Tyr23 phosphorylated. The H₂O₂-induced responses in both compartments are transient and the pTyr23AnxA2 accumulating at the cell cortex is subsequently incorporated into vesicles and then released to the extracellular space. Blocking nuclear export by leptomycin B does not affect the nuclear pool of pTyr23AnxA2, but increases the amount of total AnxA2 in this compartment, indicating that the protein might have several functions in the nucleus. These results suggest that Tyr23 phosphorylation can regulate the function of AnxA2 at distinct subcellular sites.

Summary: Reactive oxygen species cause two opposite and transient Tyr23-based modifications of annexin A2; its dephosphorylation in the nucleus and phosphorylation at the cell cortex, resulting in release of the protein in exosomes.

Annexin A2 silencing enhances apoptosis of human umbilical vein endothelial cells in vitro

OBJECTIVE

To study the effects of inhibited Annexin A2 (ANXA2) on human umbilical vein endothelial cells (HUVECs) in vitro.

METHODS

Short hairpin RNA (shRNA) targeting ANXA2 was designed and cloned into double marked lentivirial vector GV248 for RNAi to generate the recombinant expression plasmids, which were stably transfected into HUVECs. The protein and mRNA expression levels of ANXA2 were analyzed by western blotting and real-time polymerase chain reaction, respectively. Cell proliferation (cell counting kit-8 assay), apoptosis (flow cytometry analysis), the expression (western blotting) and the activity of caspases (enzyme-linked immunosorbent assay) were used to assess the effects of silencing ANXA2 on HUVECs in vitro.

RESULTS

The plasmids to express ANXA2-specific shRNA were constructed and were infected into HUVEC resulting in the stably transfected experimental (ANXA2-shRNA), control (control-shRNA) and mock (no plasmid) cell lines, which were verified with western blot and real-time PCR. HUVEC/ANXA2-shRNA showed an inhibition rate 91.89% of ANXA2 expression compared to the mock HUVEC. ANXA2 silencing cell strain obviously presented a lower cell proliferation activity compared to the control and mock HUVECs, with an inhibition rate 82.35% on day 7 in vitro. FACS analysis indicated that the HUVEC/ANXA2-shRNA cells undergoing apoptosis increased by 102.61% compared to the mock HUVECs (P < 0.01). Moreover, the activity levels of caspase-3, caspase-8 and caspase-9 in HUVEC/ANXA2-shRNA cells were increased and the activated cleaved caspase-3, cleaved caspase-8 and cleaved caspase-9 were upregulated evidently compared with that of the control and mock HUVECs by 56.29%, 89.59% and 144.58% (P < 0.01).

CONCLUSIONS

shRNA-mediated silencing of ANXA2 could not only be able to suppress HUVECs proliferation but to upregulate the enzyme activity of caspases, which bring to an increase of cell apoptosis. This work suggested that ANXA2 may represent a useful target of future molecular therapies.