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

FGF19 promotes nasopharyngeal carcinoma progression by inducing angiogenesis via inhibiting TRIM21-mediated ANXA2 ubiquitination

PURPOSE

Nasopharyngeal carcinoma (NPC) has characteristics of high invasion and early metastasis. Most NPC patients present with locoregionally advanced illness when first diagnosed. Therefore, it is urgent to discover NPC biomarkers. Fibroblast growth Factor 19 (FGF19) plays a role in various physiological or pathological processes, including cancer. In this research, we discovered the importance of FGF19 in NPC, and clarified its role in tumour angiogenesis.

METHODS

Western blotting, immunohistochemistry and ELISA were used to investigate FGF19 expression in NPC. Then we took CCK8, colony formation, Transwell and wound healing assays to identify the influence of FGF19 on NPC malignant behaviours. The proliferative and metastatic capacity of FGF19 were evaluated in nude mice and zebrafish. The role of FGF19 in angiogenesis was investigated by tube formation and Matrigel plug angiogenesis assays. We then evaluated the variation in Annexin A2(ANXA2) levels with the treatment of FGF19. Lastly, co-immunoprecipitation and ubiquitination assays were performed to identify the mechanisms involved.

RESULTS

FGF19 levels were elevated in tissues and serum of NPC patients and were associated with poor clinical stages. High expression of FGF19 promoted NPC malignant behaviours. In particular, FGF19 expression was correlated with microvessel density in tissues and NPC-derived FGF19 could accelerate angiogenesis in vitro and in vivo. Mechanistically, FGF19 influenced ANXA2 expression to promote angiogenesis. Moreover, tripartite motif-containing 21(TRIM21) interacted with ANXA2 and was responsible for ANXA2 ubiquitination.

CONCLUSION

FGF19 promoted NPC angiogenesis by inhibiting TRIM21-mediated ANXA2 ubiquitination. It may serve as a noninvasive biomarker for NPC and provides new insights for therapy.

Translational implications of targeting annexin A2: From membrane repair to muscular dystrophy, cardiovascular disease and cancer

Annexin A2 (A2) contributes to several key cellular functions and processes, including membrane repair. Effective repair prevents cell death and degeneration, especially in skeletal or cardiac muscle, epithelia, and endothelial cells. To maintain cell integrity after damage, mammalian cells activate multiple membrane repair mechanisms. One protein family that facilitates membrane repair processes are the Ca2+-regulated phospholipid-binding annexins. Annexin A2 facilitates repair in association with S100A10 and related S100 proteins by forming a plug and linking repair to other physiologic functions. Deficiency of annexin A2 enhances cellular degeneration, exacerbating muscular dystrophy and degeneration. Downstream of repair, annexin A2 links membrane with the cytoskeleton, calcium-dependent endocytosis, exocytosis, cell proliferation, transcription, and apoptosis to extracellular roles, including vascular fibrinolysis, and angiogenesis. These roles regulate cardiovascular disease progression. Finally, annexin A2 protects cancer cells from membrane damage due to immune cells or chemotherapy. Since these functions are regulated by post-translational modifications, they represent a therapeutic target for reducing the negative consequences of annexin A2 expression. Thus, connecting the roles of annexin A2 in repair to its other physiologic functions represents a new translational approach to treating muscular dystrophy and cardiovascular diseases without enhancing its pro-tumorigenic activities.

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.

Annexin A Protein Family in Atherosclerosis

Atherosclerosis, a silent chronic vascular pathology, is the cause of the majority of cardiovascular ischaemic events. Atherosclerosis is characterized by a series of deleterious changes in cellularity, including endothelial dysfunction, transmigration of circulating inflammatory cells into the arterial wall, pro-inflammatory cytokines production, lipid accumulation in the intima, vascular local inflammatory response, atherosclerosis-related cells apoptosis and autophagy. Proteins of Annexin A (AnxA) family, the well-known Ca²⁺ phospholipid-binding protein, have many functions in regulating inflammation-related enzymes and cell signaling transduction, thus influencing cell adhesion, migration, differentiation, proliferation and apoptosis. There is now accumulating evidence that some members of the AnxA family, such as AnxA1, AnxA2, AnxA5 and AnxA7, play major roles in the development of atherosclerosis. This article discusses the major roles of AnxA1, AnxA2, AnxA5 and AnxA7, and the multifaceted mechanisms of the main biological process in which they are involved in atherosclerosis. Considering these evidences, it has been proposed that AnxA are drivers- and not merely participator- on the road to atherosclerosis, thus the progression of atherosclerosis may be prevented by targeting the expression or function of the AnxA family proteins.

Upregulation of microRNA-576-5p protects from steroid-induced avascular necrosis of the femoral head by suppressing ANXA2

Steroid-induced avascular necrosis of the femoral head (SANFH) is a common orthopedic disease. Evidence has shown that microRNAs (miRNAs) played essential roles in the development of SANFH. Nevertheless, the role of miR-576-5p in SANFH remains unknown. The rabbit SANFH models were constructed by injection of horse serum and methylprednisolone. Bone mineral density (BMD) of the proximal femur (including the femoral head), pathological changes, bone cell apoptosis and expressions of OPG/RANK in femoral head bone tissue were assessed upon treatment of up-regulation of miR-576-5p or knockdown of ANXA2. Osteoblasts were extracted from SANFH rabbit femoral head and cultured. Proliferation, apoptosis and mineralization were tested upon treatment of up-regulation of miR-576-5p or knockdown of ANXA2. The targeting relationship between miR-576-5p and ANXA2 was verified. Up-regulated miR-576-5p or down-regulated ANXA2 inhibited the decrease of BMD, improved pathological changes, limited cell apoptosis and increased OPG/RANKL ratio in bone tissues of SANFH rabbits. Up-regulating miR-576-5p or down-regulating ANXA2 promoted proliferation and mineralization and inhibited apoptosis of osteoblasts from SANFH rabbits. In addition, ANXA2 was found to be a target gene of miR-576-5p. Furthermore, overexpression of ANXA2 abolished the protective role of elevated miR-576-5p against femoral head necrosis. Elevated miR-576-5p or reduced ANXA2 repressed the progression of SANFH. This study may provide novel biomarkers for SANFH diagnosis and treatment.

Clinical Limitations of Tissue Annexin A2 Level as a Predictor of Postoperative Overall Survival in Patients with Hepatocellular Carcinoma

Hepatocellular carcinoma (HCC) is the second common cause of cancer-related death in Taiwan. Tumor recurrence is frequently observed in HCC patients receiving surgical resection, resulting in unsatisfactory overall survival (OS). Therefore, it is pivotal to identify effective prognostic makers, so that intensive surveillance or adjuvant treatments can be applied to predictively unfavorable patients. Previous studies indicated that Annexin A2 (ANXA2) was an effective prognostic marker in several cancers, including HCC. However, the prognostic value of ANXA2 in Taiwanese HCC patients remains unclear, where a great proportion of patients had chronic hepatitis B with liver cirrhosis. Here, ANXA2 was highly expressed in HCC tissues compared with para-neoplastic noncancerous tissues. Furthermore, high ANXA2 expression in HCC tissues independently predicted shorter OS. In subgroup analysis, however, ANXA2 expression could not effectively predict OS in the following subgroups: female, age > 65 years old, Child–Pugh classification B, hepatitis B virus surface antigen negative or anti-hepatitis C antibody positive, alcoholism, tumor number >1, presence of micro- or macrovascular invasion, absence of capsule, non-cirrhosis and high alpha-fetoprotein. In conclusion, ANXA2 expression in HCC tissues could predict postoperative OS. However, the predictive value was limited in patients with specific clinical conditions.

Proteins inform survival-based differences in patients with glioblastoma

BACKGROUND

Improving the care of patients with glioblastoma (GB) requires accurate and reliable predictors of patient prognosis. Unfortunately, while protein markers are an effective readout of cellular function, proteomics has been underutilized in GB prognostic marker discovery.

METHODS

For this study, GB patients were prospectively recruited and proteomics discovery using liquid chromatography-mass spectrometry analysis (LC-MS/MS) was performed for 27 patients including 13 short-term survivors (STS) (≤10 months) and 14 long-term survivors (LTS) (≥18 months).

RESULTS

Proteomics discovery identified 11 941 peptides in 2495 unique proteins, with 469 proteins exhibiting significant dysregulation when comparing STS to LTS. We verified the differential abundance of 67 out of these 469 proteins in a small previously published independent dataset. Proteins involved in axon guidance were upregulated in STS compared to LTS, while those involved in p53 signaling were upregulated in LTS. We also assessed the correlation between LS MS/MS data with RNAseq data from the same discovery patients and found a low correlation between protein abundance and mRNA expression. Finally, using LC-MS/MS on a set of 18 samples from 6 patients, we quantified the intratumoral heterogeneity of more than 2256 proteins in the multisample dataset.

CONCLUSIONS

These proteomic datasets and noted protein variations present a beneficial resource for better predicting patient outcome and investigating potential therapeutic targets.

Annexin A2 upregulation protects human retinal endothelial cells from oxygen-glucose deprivation injury by activating autophagy

Retinal neovascularization is a common pathological change in multiple diseases of the eyes and the upregulation of annexin A2 (A2) under a hypoxic and ischemic microenvironment has been demonstrated to be a key factor in the pathological process. However, the underlying mechanism by which A2 regulates retinal neovascularization remains unclear. In the present study, oxygen-glucose deprivation (OGD) was used to mimic the hypoxic and ischemic microenvironment, to observe the role of A2 in retinal neovascularization regulation by focusing on autophagy. The results showed that OGD treatment significantly increased the mRNA and protein levels of A2 in human retinal endothelial cells (HRECs), which was dependent on activation of hypoxia inducible factor (HIF)-1α signaling. The OGD-induced activation of autophagy was attenuated when A2 was silenced, but increased when A2 was overexpressed, suggesting that A2 upregulation contributed to OGD-induced cell autophagy activation. Furthermore, knockdown of A2 decreased cell viability and promoted cell apoptosis under OGD conditions. Overexpression of A2 increased cell viability and reduced cell apoptosis under OGD conditions, and inhibiting autophagy using an inhibitor, reversed these changes, suggesting that upregulation of A2 by OGD serves a cytoprotective role by inducing cell autophagy in HRECs. Taken together, the results of the present study suggested that promoting retinal endothelial cell survival by autophagy activation via the HIF-1α signaling pathway in a hypoxic and ischemic microenvironment may underlie the mechanism by which A2 regulates retinal neovascularization. The present study is the first study to demonstrate the novel role of A2 during retinal neovascularization under pathological conditions, to the best of our knowledge. Therefore, A2 may serve as a potential therapeutic target for treating neovascularization-associated conditions of the eye.

The interaction between ANXA2 and lncRNA Fendrr promotes cell apoptosis in caerulein-induced acute pancreatitis

BACKGROUND

Annexin A2 (ANXA2) plays a crucial role in acute pancreatitis (AP). However, its potential mechanism remains unclear.

METHODS

In the present study, we used caerulein-treated AR42J rat pancreatic acinar cells as cell model of AP to investigate the potential functions of ANXA2 and its predicted long noncoding RNA (lncRNA) FOXF1 adjacent noncoding developmental regulatory RNA (lncRNA Fendrr). Cell apoptosis was evaluated by flow cytometry using annexinV-fluorescein isothiocyanate/propidium iodide staining. The expressions of ANAX2 and lncRNA Fendrr were detected by quantitative real-time polymerase chain reaction (qRT-PCR). Furthermore, Western blot analysis was performed to determine the protein levels of ANXA2, Bcl-2, and Bax. The association between lncRNA Fendrr and ANXA2 was disclosed by RNA pull-down, RNA immunoprecipitation, and electrophoretic mobility shift assays.

RESULTS

ANXA2 was elevated in caerulein-induced AP model and promoted apoptosis of AR42J cells. LncRNA Fendrr was also upregulated in AP cell model and directly bound ANXA2 protein. Further studies indicated that the interaction between ANXA2 and lncRNA Fendrr contributed to the apoptosis of AR42J cells in AP cell model.

CONCLUSION

Our study demonstrated that ANXA2 promoted AP progression via interacting with lncRNA Fendrr in vitro, which will provide a novel insight into the therapeutic target for AP.

Role of the long non‑coding RNA‑Annexin A2 pseudogene 3/Annexin A2 signaling pathway in biliary atresia‑associated hepatic injury

Biliary atresia (BA) is the most common cause of chronic cholestasis in children. The long non‑coding RNA (lncRNA) Annexin A2 pseudogene 3 (ANXA2P3) and Annexin A2 (ANXA2) have been suggested to serve pivotal roles in BA; however, the clinical significance and biological roles of ANXA2P3 and ANXA2 in BA remain to be elucidated. The present study aimed to elucidate the function of ANAX2P3 and ANXA2 in BA‑induced liver injury using a human liver cell line and liver tissues from patients with BA. Reverse transcription‑quantitative polymerase chain reaction, western blotting and immunohistochemistry were conducted to determine the expression levels of ANXA2 and ANXA2P3 in liver tissues from patients with BA. Classification of fibrosis was analyzed by Masson staining. The functional roles of ANXA2 and ANXA2P3 in liver cells were determined by Cell Counting kit‑8 assay, and flow cytometric and cell cycle analyses. Activation of the ANXA2/ANXA2P3 signaling pathway in liver cells was evaluated by western blot analysis. According to the present results, the expression levels of ANXA2 and ANXA2P3 were significantly increased in liver tissues from patients with BA. In addition, knocking down the expression of ANXA2P3 and ANXA2 may result in reduced liver cell proliferation, cell cycle arrest in G1 phase and increased apoptosis of liver cells in vitro. Furthermore, in cells in which ANXA2 and ANXA2P3 were overexpressed, cell apoptosis was reduced and cell cycle arrest in G2 phase. Taken together, these results indicated that ANXA2P3 and ANXA2 may have protective effects against liver injury progression and may be considered biomarkers in patients with BA.

Acetylome in Human Fibroblasts From Parkinson's Disease Patients

Parkinson's disease (PD) is a multifactorial neurodegenerative disorder. The pathogenesis of this disease is associated with gene and environmental factors. Mutations in leucine-rich repeat kinase 2 (LRRK2) are the most frequent genetic cause of familial and sporadic PD. Moreover, posttranslational modifications, including protein acetylation, are involved in the molecular mechanism of PD. Acetylation of lysine proteins is a dynamic process that is modulated in PD. In this descriptive study, we characterized the acetylated proteins and peptides in primary fibroblasts from idiopathic PD (IPD) and genetic PD harboring G2019S or R1441G LRRK2 mutations. Identified acetylated peptides are modulated between individuals' groups. Although acetylated nuclear proteins are the most represented in cells, they are hypoacetylated in IPD. Results display that the level of hyperacetylated and hypoacetylated peptides are, respectively, enhanced in genetic PD and in IPD cells.

Annexin A2 (ANXA2) interacts with nonstructural protein 1 and promotes the replication of highly pathogenic H5N1 avian influenza virus

BACKGROUND

Non-structural protein 1 (NS1) is a multifunctional protein and a crucial regulatory factor in the replication and pathogenesis of avian influenza virus (AIV). Studies have shown that NS1 can interact with a variety of host proteins to modulate the viral life cycle. We previously generated a monoclonal antibody against NS1 protein; In the current research study, using this antibody, we immunoprecipitated host proteins that interact with NS1 to better understand the roles played by NS1 in communications between virus and host.

RESULTS

Co-immunoprecipitation experiments identified annexin A2 (ANXA2) as a target molecule interacting with NS1. Results from confocal laser scanning microscopy indicated that NS1 co-localized with ANXA2 in the cell cytoplasm. Overexpression of ANXA2 significantly increased the titer of H5N1 subtype HPAIV, whereas siRNA-mediated knockdown of ANXA2 markedly inhibited the expression of viral proteins and reduced the progeny virus titer.

CONCLUSIONS

Our results indicate that ANXA2 interacts with NS1 and ANXA2 expression increases HPAIV replication.

P16 INK4a Deletion Ameliorated Renal Tubulointerstitial Injury in a Stress-induced Premature Senescence Model of Bmi-1 Deficiency

To determine whether p16 ^INK4a deletion ameliorated renal tubulointerstitial injury by inhibiting a senescence-associated secretory phenotype (SASP) in Bmi-1-deficient (Bmi-1 ^-/-) mice, renal phenotypes were compared among 5-week-old Bmi-1 and p16 ^INK4a double-knockout, and Bmi-1 ^-/- and wild-type mice. Fifth-passage renal interstitial fibroblasts (RIFs) from the three groups were analyzed for senescence and proliferation. The effect of Bmi-1 deficiency on epithelial-to-mesenchymal transition (EMT) was examined in Bmi-1-knockdown human renal proximal tubular epithelial (HK2) cells, which were treated with concentrated conditioned medium (CM) from the fifth-passage renal interstitial fibroblasts (RIFs) of above three group mice or with exogenous TGF-β1. Our results demonstrated that p16 ^INK4a deletion largely rescued renal aging phenotypes caused by Bmi-1 deficiency, including impaired renal structure and function, decreased proliferation, increased apoptosis, senescence and SASP, DNA damage, NF-κB and TGF-β1/Smad signal activation, inflammatory cell infiltration, and tubulointerstitial fibrosis and tubular atrophy. P16 ^INK4a deletion also promoted proliferation, reduced senescence and SASP of RIFs and subsequently inhibited EMT of Bmi-1-knockdown HK2 cells. TGF-β1 further induced the EMT of Bmi-1-knockdown HK2 cells. Thus, p16 ^INK4a positive senescent cells would be a therapeutic target for preventing renal tubulointerstitial injury.