Curcumin promotes venous thrombi resolve process in a mouse deep venous thrombosis model via regulating miR-499

BACKGROUND/AIMS

The morbidity of deep venous thrombosis (DVT) is increasing rapidly and the current therapeutic strategies for DVT are unsatisfactory. Accumulating evidence suggest that venous thrombi resolve (VTR) may provide new insights into DVT therapeutic strategies. The aim of this study was to investigate the role of curcumin in VTR process and try to reveal the potential mechanism.

METHODS

Immunofluorescence and HE staining were performed to investigate the therapeutic angiogenesis effect of curcumin in VTR process. Microarray analysis and RT-PCR were performed to examine the expression level of miR-499 in thrombosis after curcumin administration. Cell proliferation, migration and angiogenesis capacity were tested by CCK8 assay, Transwell assay and Tube formation assay, respectively. Dual-luciferase reporter assay (DLR) was used to confirm the connection between miR-499 and paired phosphate and tension homology deleted on chromosome ten (PTEN).

RESULTS

We found that curcumin could effectively promote VTR process by activating angiogenesis in thrombus in vivo. The expression of miR-499 exhibited notably downregulated after curcumin administration. The proangiogenic effect of curcumin in HUVECs could be blocked by miR-499 overexpression. In addition, we confirmed that miR-499 directly target to the 3'UTR region of PTEN.

CONCLUSION

Curcumin promotes VTR process in DVT through activating therapeutic angiogenesis. Mechanically, curcumin promotes therapeutic angiogenesis by regulating miR-499 mediated PTEN/VEGF/Ang-1 signaling pathway.

Angiopoietin-1 enhanced myocyte mitosis, engraftment, and the reparability of hiPSC-CMs for treatment of myocardial infarction

AIMS

To examine whether transient over-expression of angiopoietin-1 (Ang-1) increases the potency of hiPSC-CMs for treatment of heart failure.

METHODS AND RESULTS

Atrial hiPSC-CMs (hiPSC-aCMs) were differentiated from hiPSCs and purified by lactic acid and were transfected with Ang-1 (Ang-1-hiPSC-aCMs) plasmid using lipoSTEM. Ang-1 gene transfection efficiency was characterized in vitro. Gene transfected CMs (1×106) were seeded into a fibrin/thrombin patch and implanted on the rat-infarcted left ventricular (LV) anterior wall after myocardial infarction (MI). Echo function was determined at 1- and 6 weeks post-MI. Immunohistochemistry study was performed at 6 weeks post-MI. Ang-1 (20 and 40 ng/mL) protected hiPSC-aCMs from hypoxia through up-regulating pERK1/2 and inhibiting Bax protein expressions. Ang-1-hiPSC-aCMs transiently secreted Ang-1 protein up to 14 days, with peak level on day-2 post-transfection (24.39 ± 13.02 ng/mL) in vitro. Animal study showed that transplantation of Ang-1-hiPSC-aCM seeded patch more effectively limited rat heart apoptosis at 1 day post-MI as compared with LipoSTEM-Ang-1 or hiPSC-aCMs transplantation. Ang-1-hiPSC-aCMs transplantation induced host (rat) and donor (human) CM mitosis and arteriole formation, improved cell engraftment rate, more effectively limited LV dilation (EDV = 460.7 ± 96.1 μL and ESV = 219.8 ± 72.9 μL) and improved LV global pump function (EF = 53.1 ± 9%) as compared with the MI (EDV = 570.9 ± 91.8 μL, P = 0.033; ESV = 331.6 ± 71.2 μL, P = 0.011; EF = 42.3 ± 4.1%, P = 0.02) or the LipoSTEM-Ang-1 injected (EDV = 491.4 ± 100.4 μL, P = 0.854; ESV = 280.9 ± 71.5 μL, P = 0.287; EF = 43.2 ± 4.6, P = 0.039) or hiPSC-CM transplanted (EDV = 547.9 ± 55.5 μL, P = 0.095; ESV = 300.2 ± 88.4 μL, P = 0.075; EF = 46 ± 10.9%, P = 0.166) animal groups at 6 weeks post-MI and treatment.

CONCLUSION

Transient over-expression of Ang-1 enhanced hiPSC-aCM mitosis and engraftment and increased the reparability potency of hiPSC-aCMs for treatment of MI.

Heightened activation of embryonic megakaryocytes causes aneurysms in the developing brain of mice lacking podoplanin

During early embryonic development in mammals, including humans and mice, megakaryocytes (Mks) first originate from primitive hematopoiesis in the yolk sac. These embryonic Mks (eMks) circulate in the vasculature with unclear function. Herein, we report that podoplanin (PDPN), the ligand of C-type lectin-like receptor (CLEC-2) on Mks/platelets, is temporarily expressed in neural tissue during midgestation in mice. Loss of PDPN or CLEC-2 resulted in aneurysms and spontaneous hemorrhage, specifically in the lower diencephalon during midgestation. Surprisingly, more eMks/platelets had enhanced granule release and localized to the lower diencephalon in mutant mouse embryos than in wild-type littermates before hemorrhage. We found that PDPN counteracted the collagen-1-induced secretion of angiopoietin-1 from fetal Mks, which coincided with enhanced TIE-2 activation in aneurysm-like sprouts of PDPN-deficient embryos. Blocking platelet activation prevented the PDPN-deficient embryo from developing vascular defects. Our data reveal a new role for PDPN in regulating eMk function during midgestation.

Overexpression of COMP-Angiopoietin-1 in K14-Expressing Cells Impairs Hematopoiesis and Disturbs Erythrocyte Maturation

Numerous studies highlight the potential benefits potentials of supplemental cartilage oligomeric matrix protein-angiopoietin-1 (COMP-Ang1) through improved angiogenic effects. However, our recent findings show that excessive overexpression of COMP-Ang1 induces an impaired bone marrow (BM) microenvironment and senescence of hematopoietic stem cells (HSCs). Here, we investigated the underlying mechanisms of how excessive COMP-Ang1 affects the function of BM-conserved stem cells and hematopoiesis using K14-Cre;inducible-COMP-Ang1-transgenic mice. Excessive COMP-Ang1 induced peripheral egression and senescence of BM HSCs and mesenchymal stem cells (MSCs). Excessive COMP-Ang1 also caused abnormal hematopoiesis along with skewed differentiation of HSCs toward myeloid lineage rather than lymphoid lineage. Especially, excessive COMP-Ang1 disturbed late-stage erythroblast maturation, followed by decreased expression of stromal cell-derived factor 1 (SDF-1) and globin transcription factor 1 (GATA-1) and increased levels of superoxide anion and p-p38 kinase. However, transplantation with the mutant-derived BM cells or treatment with rhCOMP-Ang1 protein did not alter the frequency or GATA-1 expression of erythroblasts in recipient mice or in cultured BM cells. Together, our findings suggest that excessive COMP-Ang1 impairs the functions of BM HSCs and MSCs and hematopoietic processes, eventually leading to abnormal erythropoiesis via imbalanced SDF-1/CXCR4 axis and GATA-1 expression rather than Ang1/Tie2 signaling axis alterations.

Cannabidiol induces osteoblast differentiation via angiopoietin1 and p38 MAPK

In this study, we report the potential of cannabidiol, one of the major cannabis constituents, for enhancing osteoblastic differentiation in U2OS and MG-63 cells. Cannabidiol increased the expression of Angiopoietin1 and the enzyme activity of alkaline phosphatase in U2OS and MG-63. Invasion and migration assay results indicated that the cell mobility was activated by cannabidiol in U2OS and MG-63. Western blotting analysis showed that the expression of tight junction related proteins such as Claudin1, Claudin4, Occuludin1, and ZO1 was increased by cannabidiol in U2OS and MG-63. Alizarin Red S staining analysis showed that calcium deposition and mineralization was enhanced by cannabidiol in U2OS and MG-63. Western blotting analysis indicated that the expression of osteoblast differentiation related proteins such as distal-less homeobox 5, bone sialoprotein, osteocalcin, type I collagen, Runt-related transcription factor 2 (RUNX2), osterix (OSX), and alkaline phosphatase was time dependently upregulated by cannabidiol in U2OS and MG-63. Mechanistically, cannabidiol-regulated osteoblastic differentiation in U2OS and MG-63 by strengthen the protein-protein interaction among RUNX2, OSX, or the phosphorylated p38 mitogen-activated protein kinase (MAPK). In conclusion, cannabidiol increased Angiopoietin1 expression and p38 MAPK activation for osteoblastic differentiation in U2OS and MG-63 suggesting that cannabidiol might provide a novel therapeutic option for the bone regeneration.

Novel Insights on the Corpus Luteum Function: Role of Vaspin on Porcine Luteal Cell Angiogenesis, Proliferation and Apoptosis by Activation of GRP78 Receptor and MAP3/1 Kinase Pathways

Formation and limited lifespan of corpus luteum (CL) are important for proper ovarian periodicity and fertility. Failed vascularization, imbalance between proliferation and apoptosis leads to luteal phase deficiency and infertility. The aim of this study was to examine the effect of vaspin on angiogenesis, apoptosis and proliferation as well as the involvement of 78-kDa glucose-regulated protein receptor (GRP78) and mitogen-activated kinase (MAP3/1) in these processes. Porcine luteal cells were incubated with vaspin (0.1-10 ng/mL) for 24 h to 72 h and then mRNA and protein expression of angiogenesis: vascular endothelial growth factor (VEGFA), fibroblast growth factor 2 (FGF2), angiopoietin 1 (ANGPT1), VEGFA receptors (VEGFR1, VEGFR2), apoptosis: caspase 3, bcl-2-like protein 4 (BAX), B-cell lymphoma (BCL2), and proliferation: proliferating cells nuclear antigen (PCNA), cyclin A factors as well as secretion of VEGFA, FGF2, ANGT1 were measured by real-time polymerase chain reaction (PCR), immunoblotting and enzyme-linked immunosorbent assay (ELISA), respectively. Moreover, apoptosis was assessed by caspase activity using the Caspase-Glo 3/7 assay, while proliferation was by alamarBlue. We found that vaspin enhanced luteal cell angiogenesis, proliferation, and significantly decreased apoptosis. Additionally, using GRP78 siRNA and the pharmacological inhibitor of MAP3/1 (PD98059), we observed that the effect of vaspin was reversed to the control level in all investigated processes. Taken together, our results suggest that vaspin is a new regulator of female fertility by direct regulation of CL formation and maintenance of luteal cell function.

Pro-Angiogenic Actions of CMC-Derived Extracellular Vesicles Rely on Selective Packaging of Angiopoietin 1 and 2, but Not FGF-2 and VEGF

While the fundamental mechanism by which cardiac cell therapy mitigates ventricular dysfunction in the post ischemic heart remains poorly defined, donor cell paracrine signaling is presumed to be a chief contributor to the afforded benefits. Of the many bioactive molecules secreted by transplanted cells, extracellular vesicles (EVs) and their proteinaceous, nucleic acid, and lipid rich contents, comprise a heterogeneous assortment of prospective cardiotrophic factors-whose involvement in the activation of endogenous cardiac repair mechanism(s), including reducing fibrosis and promoting angiogenesis, have yet to be fully explained. In the current study we aimed to interrogate potential mechanisms by which cardiac mesenchymal stromal cell (CMC)-derived EVs contribute to the CMC pro-angiogenic paracrine signaling capacity in vitro. Vesicular transmission and biological activity of human CMC-derived EVs was evaluated in in vitro assays for human umbilical vein endothelial cell (HUVEC) function, including EV uptake, cell survival, migration, tube formation, and intracellular pathway activation. HUVECs incubated with EVs exhibited augmented cell migration, tube formation, and survival under peroxide exposure; findings which paralleled enhanced activation of the archetypal pro-survival/pro-angiogenic pathways, STAT3 and PI3K-AKT. Cytokine array analyses revealed preferential enrichment of a subset of prototypical angiogenic factors, Ang-1 and Ang-2, in CMC EVs. Interestingly, pharmacologic inhibition of Tie2 in HUVECs, the cognate receptors of angiopoietins, efficiently attenuated CMC-EV-induced HUVEC migration. Further, in additional assays a Tie2 kinase inhibitor exhibited specificity to inhibit Ang-1-, but not Ang-2-, induced HUVEC migration. Overall, these findings suggest that the pro-angiogenic activities of CMC EVs are principally mediated by Ang-1-Tie2 signaling.

Suppression of Ocular Vascular Inflammation through Peptide-Mediated Activation of Angiopoietin-Tie2 Signaling

Persistent inflammation is a complication associated with many ocular diseases. Changes in ocular vessels can amplify disease responses and contribute to vision loss by influencing the delivery of leukocytes to the eye, vascular leakage, and perfusion. Here, we report the anti-inflammatory activity for AXT107, a non-RGD, 20-mer αvβ3 and α5β1 integrin-binding peptide that blocks vascular endothelial growth factor (VEGF)-signaling and activates tyrosine kinase with immunoglobulin and EGF-like domains 2 (Tie2) using the normally inhibitory ligand angiopoietin 2 (Ang2). Tumor necrosis factor α (TNFα), a central inflammation mediator, induces Ang2 release from endothelial cells to enhance its stimulation of inflammation and vascular leakage. AXT107 resolves TNFα-induced vascular inflammation in endothelial cells by converting the endogenously released Ang2 into an agonist of Tie2 signaling, thereby disrupting both the synergism between TNFα and Ang2 while also preventing inhibitor of nuclear factor-κB α (IκBα) degradation directly through Tie2 signaling. This recovery of IκBα prevents nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) nuclear localization, thereby blocking NF-κB-induced inflammatory responses, including the production of VCAM-1 and ICAM-1, leukostasis, and vascular leakage in cell and mouse models. AXT107 also decreased the levels of pro-inflammatory TNF receptor 1 (TNFR1) without affecting levels of the more protective TNFR2. These data suggest that AXT107 may provide multiple benefits in the treatment of retinal/choroidal and other vascular diseases by suppressing inflammation and promoting vascular stabilization.

Loss of Endothelial Glycocalyx Hyaluronan Impairs Endothelial Stability and Adaptive Vascular Remodeling After Arterial Ischemia

We recently reported that loss of hyaluronan (HA) from the endothelial glycocalyx leads to loss of vessel stability in specific microcirculatory vascular beds. Here we hypothesized that such derangements in the glycocalyx may also impair the adaptive response to vascular ischemia. Endothelial specific conditional hyaluronan synthase 2-KO (Has2-cKO) mice revealed reduced endothelial HA expression and lower hindlimb perfusion at baseline compared to control mice. After a single ligation of the common femoral artery in these mice, we observed dysregulated angiogenesis in the gastrocnemius muscle which did not restore capillary perfusion. Mechanistically, decreased endothelial binding of the pericyte-derived molecule angiopoietin1 (Ang1) could be observed in the Has2-cKO mouse. In vitro angiogenesis assays with an endothelial cell-pericyte coculture confirmed such disturbed Ang1-TIE2 signaling resulting in excessive angiogenesis upon loss of HA. These data could be of relevance to diabetes patients, where we confirm loss of endothelial HA in the microcirculation of muscle tissue, indicating that this may contribute to the known disturbed adaptation to ischemia in these patients. In summary, loss of endothelial HA results in impaired microvascular perfusion and endothelial stability in ischemic gastrocnemius muscle. Endothelial HA is a potential target to improve angiogenic therapy in diabetic patients with critical limb ischemia.

Amorphous Silicon Oxynitrophosphide-Coated Implants Boost Angiogenic Activity of Endothelial Cells

Lack of osteointegration is a major cause of aseptic loosening and failure of implants used in bone replacement. Implants coated with angiogenic biomaterials can improve osteointegration and potentially reduce these complications. Silicon- and phosphorus-based materials have been shown to upregulate expression of angiogenic factors and improve endothelial cell functions. In the present study, we hypothesize that implants coated with amorphous silica-based coatings in the form of silicon oxynitrophosphide (SiONP) by using plasma-enhanced chemical vapor deposition (PECVD) technique could enhance human umbilical vein endothelial cell angiogenic properties in vitro. The tested groups were: glass coverslip (GCS), tissue culture plate, SiON, SiONP1 (O: 7.3 at %), and SiONP2 (O: 14.2 at %) implants. The SiONP2 composition demonstrated 3.5-fold more fibronectin deposition than the GCS (p < 0.001). The SiONP2 group also presented a significant improvement in the capillary tubule length and thickness compared with the other groups (p < 0.01). At 24 h, we observed at least a twofold upregulation of vascular endothelial growth factor A, hypoxia-inducible factor-1α, angiopoietin-1, and nesprin-2, more evident in the SiONP1 and SiONP2 groups. In conclusion, the studied amorphous silica-coated implants, especially the SiONP2 composition, could enhance the endothelial cell angiogenic properties in vitro and may induce faster osteointegration and healing. Impact Statement In this study, we report for the first time the significant enhancement of human umbilical vein endothelial cell angiogenic properties (in vitro) by the amorphous silica-based coatings in the form of silicon oxynitrophosphide (SiONP). The SiONP2 demonstrated 3.5-fold more fibronectin deposition than the glass coverslip and presented a significant improvement in the capillary tubule length and thickness. At 24 h, SiONP reported twofold upregulation of vascular endothelial growth factor A, hypoxia-inducible factor-1α, angiopoietin-1, and nesprin-2. The studied amorphous silica-coated implants enhance the endothelial cell angiogenic properties in vitro and may induce faster osteointegration and healing.

DHA Attenuates Hypoxia/Reoxygenation Injury by Activating SSeCKS in Human Cerebrovascular Pericytes

Docosahexaenoic acid (DHA) can alleviate cerebral ischemia/reperfusion injury by reducing blood–brain barrier permeability and maintaining its integrity, accompanied by an increased Ang-1/Ang-2 ratio; however, the underlying mechanisms of these effects remain unclear. Src-suppressed C kinase substrates (SSeCKS), a substrate of protein kinase C, plays an important role in maintaining cell junctions and cell morphology and regulating cell permeability. However, whether DHA can increase SSeCKS expression and then mediate the Ang-1/Ang-2 ratio still needs to be studied. Human cerebrovascular pericytes (HBVPs) cultured in vitro were divided into groups, treated with or without DHA along with SSeCKS siRNA to knockdown SSeCKS expression, and then subjected to 24 h of hypoxia followed by 6 h of reoxygenation. Cell viability; lactate dehydrogenase (LDH) release; and Ang-1, Ang-2 and VEGF activity were detected by using ELISA kits. The apoptosis rate was assessed by TUNEL flow cytometry. Expression of the SSeCKS, Ang-1, Ang-2 and VEGF proteins was evaluated by western blotting. Pretreatment with 10 μM or 40 μM DHA efficiently attenuated hypoxia/reoxygenation (H/R) injury by activating SSeCKS to increase the Ang-1/Ang-2 ratio and downregulate VEGF expression in HBVPs, as evidenced by decreased LDH release and apoptotic rates and increased HBVPs viability. Meanwhile, after we used SSeCKS siRNA to knock down SSeCKS protein expression, the protective effect of DHA on HBVPs following H/R injury was reversed. In conclusion, DHA can activate SSeCKS to increase the Ang-1/Ang-2 ratio and downregulate VEGF expression in HBVPs, thus reducing H/R injury.

Overexpression of Circulating Soluble Nogo-B Improves Diabetic Kidney Disease by Protecting the Vasculature

Damage to the vasculature is the primary mechanism driving chronic diabetic microvascular complications such as diabetic nephropathy, which manifests as albuminuria. Therefore, treatments that protect the diabetic vasculature have significant therapeutic potential. Soluble neurite outgrowth inhibitor-B (sNogo-B) is a circulating N-terminus isoform of full-length Nogo-B, which plays a key role in vascular remodeling following injury. However, there is currently no information on the role of sNogo-B in the context of diabetic nephropathy. We demonstrate that overexpression of sNogo-B in the circulation ameliorates diabetic kidney disease by reducing albuminuria, hyperfiltration, and abnormal angiogenesis and protecting glomerular capillary structure. Systemic sNogo-B overexpression in diabetic mice also associates with dampening vascular endothelial growth factor-A signaling and reducing endothelial nitric oxide synthase, AKT, and GSK3β phosphorylation. Furthermore, sNogo-B prevented the impairment of tube formation, which occurred when human endothelial cells were exposed to sera from patients with diabetic kidney disease. Collectively, these studies provide the first evidence that sNogo-B protects the vasculature in diabetes and may represent a novel therapeutic target for diabetic vascular complications.

PDE5 Inhibition Stimulates Tie2-Expressing Monocytes and Angiopoietin-1 Restoring Angiogenic Homeostasis in Diabetes

CONTEXT

Vascular dysfunction is a common feature in end-organ complications of type 2 diabetes mellitus (T2DM). The endothelium-specific receptor tyrosine kinase Tie2 and its ligand, angiopoietin-1 (Ang1), participate in the processes of vessel repair, renewal, and maturation. However, their dysregulation in T2DM has seldom been investigated.

OBJECTIVES

To examine the relationship between angiogenic Tie2-expressing monocytes (TEMs) and Ang1, and their pharmacological modulation by the phosphodiesterase type 5 inhibitor (PDE5i) sildenafil, in T2DM and in db/db mouse model.

DESIGN AND SETTING

Randomized, double-blind, placebo-controlled study.

PATIENTS AND INTERVENTION

db/db male mice were randomly assigned to receive 8 weeks of sildenafil or vehicle. Diabetic men were randomly assigned to receive 4 weeks of sildenafil or placebo.

MAIN OUTCOMES AND MEASURES

Peripheral blood cells were investigated by flow cytometry to quantify inflammatory myeloid CD11b+ Gr1+ cells and proangiogenic TEMs in mice and classical CD14++CD16neg monocytes and proangiogenic TEMs in humans at baseline and after treatment. In vitro human tube formation assay was used to test serum angiogenic potential.

RESULTS

We show that TEMs and Ang1 are defective in mouse and human models of diabetes and are normalized by PDE5i treatment. Serum angiogenic properties are impaired in diabetes because they do not support the in vitro formation of capillary-like structures, but they are reestablished by in vivo PDE5i treatment.

CONCLUSIONS

Restoring a more physiological Tie2-Ang1 axis with sildenafil reestablishes serum angiogenic properties in diabetes, promoting angiogenic homeostasis.

β-Cell-Derived Angiopoietin-1 Regulates Insulin Secretion and Glucose Homeostasis by Stabilizing the Islet Microenvironment

Islets are highly vascularized for prompt insulin secretion. Although angiopoietin-1 (Ang1) is a well-known angiogenic factor, its role in glucose homeostasis remains largely unknown. The objective of this study was to investigate whether and how Ang1 contributes to glucose homeostasis in response to metabolic challenge. We used inducible systemic Ang1 knockout (Ang1^sys-/-) and β-cell-specific Ang1 knockout (Ang1^β-cell-/-) mice fed a high-fat diet for 24 weeks. Although the degree of insulin sensitivity did not differ between Ang1^sys-/- and Ang1^sys+/+ mice, serum insulin levels were lower in Ang1^sys-/- mice, resulting in significant glucose intolerance. Similar results were observed in Ang1^β-cell-/- mice, suggesting a critical role of β-cell-derived Ang1 in glucose homeostasis. There were no differences in β-cell area or vasculature density, but glucose-stimulated insulin secretion was significantly decreased, and PDX-1 expression and GLUT2 localization were altered in Ang1^β-cell-/- compared with Ang1^β-cell+/+ mice. These effects were associated with less pericyte coverage, disorganized endothelial cell ultrastructure, and enhanced infiltration of inflammatory cells and upregulation of adhesion molecules in the islets of Ang1^β-cell-/- mice. In conclusion, β-cell-derived Ang1 regulates insulin secretion and glucose homeostasis by stabilizing the blood vessels in the islet and may be a novel therapeutic target for diabetes treatment in the future.

Gamma-Tocotrienol Induces Apoptosis in Prostate Cancer Cells by Targeting the Ang-1/Tie-2 Signalling Pathway

Emerging evidence suggests that gamma-tocotrienol (γ-T3), a vitamin E isomer, has potent anti-cancer properties against a wide-range of cancers. γ-T3 not only inhibited the growth and survival of cancer cells in vitro, but also suppressed angiogenesis and tumour metastasis under in vivo conditions. Recently, γ-T3 was found to target cancer stem cells (CSCs), leading to suppression of tumour formation and chemosensitisation. Despite its promising anti-cancer potential, the exact mechanisms responsible for the effects of γ-T3 are still largely unknown. Here, we report the identification of Ang-1 (Angiopoietin-1)/Tie-2 as a novel γ-T3 downstream target. In prostate cancer cells, γ-T3 treatment leads to the suppression of Ang-1 at both the mRNA transcript and protein levels. Supplementing the cells with Ang-1 was found to protect them against the anti-CSC effect of γ-T3. Intriguingly, inactivation of Tie-2, a member receptor that mediates the effect of Ang-1, was found to significantly enhance the cytotoxic effect of γ-T3 through activation of AMP-activated protein kinase (AMPK) and subsequent interruption of autophagy. Our results highlighted the therapeutic potential of using γ-T3 in combination with a Tie-2 inhibitor to treat advanced prostate cancer.

Tie2 activation promotes choriocapillary regeneration for alleviating neovascular age-related macular degeneration

Choriocapillary loss is a major cause of neovascular age-related macular degeneration (NV-AMD). Although vascular endothelial growth factor (VEGF) blockade for NV-AMD has shown beneficial outcomes, unmet medical needs for patients refractory or tachyphylactic to anti-VEGF therapy exist. In addition, the treatment could exacerbate choriocapillary rarefaction, necessitating advanced treatment for fundamental recovery from NV-AMD. In this study, Tie2 activation by angiopoietin-2-binding and Tie2-activating antibody (ABTAA) presents a therapeutic strategy for NV-AMD. Conditional Tie2 deletion impeded choriocapillary maintenance, rendering eyes susceptible to NV-AMD development. Moreover, in a NV-AMD mouse model, ABTAA not only suppressed choroidal neovascularization (CNV) and vascular leakage but also regenerated the choriocapillaris and relieved hypoxia. Conversely, VEGF blockade degenerated the choriocapillaris and exacerbated hypoxia, although it suppressed CNV and vascular leakage. Together, we establish that angiopoietin-Tie2 signaling is critical for choriocapillary maintenance and that ABTAA represents an alternative, combinative therapeutic strategy for NV-AMD by alleviating anti-VEGF adverse effects.

Therapeutic Implications of Human Umbilical Cord Mesenchymal Stromal Cells in Attenuating Influenza A(H5N1) Virus-Associated Acute Lung Injury

Background

Highly pathogenic avian influenza viruses can cause severe forms of acute lung injury (ALI) in humans, where pulmonary flooding leads to respiratory failure. The therapeutic benefits of bone marrow mesenchymal stromal cells (MSCs) have been demonstrated in a model of ALI due to influenza A(H5N1) virus. However, clinical translation is impractical and limited by a decline in efficacy as the age of the donor increases. Umbilical cord MSCs (UC-MSCs) are easier to obtain by comparison, and their primitive source may offer more-potent therapeutic effects.

Methods

Here we investigate the therapeutic efficacy of UC-MSCs on the mechanisms of pulmonary edema formation and alveolar fluid clearance and protein permeability of A(H5N1)-infected human alveolar epithelial cells. UC-MSCs were also tested in a mouse model of influenza ALI.

Results

We found that UC-MSCs were effective in restoring impaired alveolar fluid clearance and protein permeability of A(H5N1)-infected human alveolar epithelial cells. UC-MSCs consistently outperformed bone marrow MSCs, partly because of greater growth factor secretion of angiopoietin 1 and hepatocyte growth factor. Conditioned UC-MSC medium and UC-MSC exosomes were also able to recapitulate these effects. However, UC-MSCs only slightly improved survival of A(H5N1)-infected mice.

Conclusions

Our results suggest that UC-MSCs are effective in restoring alveolar fluid clearance and protein permeability in A(H5N1)-associated ALI and confer functional in addition to practical advantages over conventional bone marrow MSCs.

Advanced Glycation End-Products and Hyperglycemia Increase Angiopoietin-2 Production by Impairing Angiopoietin-1-Tie-2 System

The angiopoietin-Tie-2 system plays a crucial role in the maintenance of endothelial integrity. Hyperglycemia and advanced glycation end-products (AGEs) are involved in endothelial cell dysfunction responsible of the pathogenesis of microvascular complications of diabetes. Here, we investigated whether glycated serum (GS) or hyperglycemia (HG) affect the angiopoietin-Tie-2 system in the microvascular endothelial cells HMEC-1. We found that culture for 5 days in the presence of AGEs and HG (alone or in combination) decreased cell proliferation, increased reactive oxygen species (ROS) production, and reduced ratio between the oxidized and the reduced form of glutathione. Since angiopoietin-1 (Ang-1) signaling regulates angiopoietin-2 (Ang-2) expression through inactivation of the forkhead transcription factor FoxO1, we investigated intracellular signaling of Ang-1 and expression of Ang-2. HG and AGEs reduced phosphorylation of Akt and abrogated phosphorylation of FoxO1 induced by Ang-1 without affecting neither Tie-2 expression nor its activation. Furthermore, AGEs and/or HG induced nuclear translocation of FoxO1 and increased Ang-2 production. In conclusion, we demonstrated that both hyperglycemia and AGEs affect the angiopoietin-Tie-2 system by impairing Ang-1/Tie-2 signaling and by increasing Ang-2 expression. These results suggest that therapeutic strategies useful in preventing or delaying the onset of diabetic vascular complications should be aimed to preserve Ang-1 signaling.

Neutrophil elastase inhibition effectively rescued angiopoietin-1 decrease and inhibits glial scar after spinal cord injury

After spinal cord injury (SCI), neutrophil elastase (NE) released at injury site disrupts vascular endothelium integrity and stabilization. Angiopoietins (ANGPTs) are vascular growth factors that play an important role in vascular stabilization. We hypothesized that neutrophil elastase is one of the key determinants of vascular endothelium disruption/destabilization and affects angiopoietins expression after spinal cord injury. To test this, tubule formation and angiopoietins expression were assessed in endothelial cells exposed to different concentrations of recombinant neutropil elastase. Then, the expression of angiopoietin-1, angiopoietin-2, and neutrophil elastase was determined at 3 h and at 1, 3, 5, 7, 14, 21, and 28 days in a clinically relevant model of moderate compression (35 g for 5 min at T10) spinal cord injury. A dichotomy between the levels of angiopoietin-1 and angiopoietin-2 was observed; thus, we utilized a specific neutrophil elastase inhibitor (sivelestat sodium; 30 mg/kg, i.p., b.i.d.) after spinal cord injury. The expression levels of neutropil elastase and angiopoietin-2 increased, and that of angiopoietin-1 decreased after spinal cord injury in rats. The sivelestat regimen, optimized via a pharmacokinetics study, had potent effects on vascular stabilization by upregulating angiopoietin-1 via the AKT pathway and preventing tight junction protein degradation. Moreover, sivelestat attenuated the levels of inflammatory cytokines and chemokines after spinal cord injury and hence subsequently alleviated secondary damage observed as a reduction in glial scar formation and the promotion of blood vessel formation and stabilization. As a result, hindlimb locomotor function significantly recovered in the sivelestat-treated animals as determined by the Basso, Beattie, and Bresnahan scale and footprint analyses. Furthermore, sivelestat treatment attenuated neuropathic pain as assessed by responses to von Frey filaments after spinal cord injury. Thus, our result suggests that inhibiting neutropil elastase by administration of sivelestat is a promising therapeutic strategy to inhibit glial scar and promote functional recovery by upregulating angiopoietin-1 after spinal cord injury.

MicroRNA-711-Induced Downregulation of Angiopoietin-1 Mediates Neuronal Cell Death

Angiopoietin-1 (Ang-1) is a well-known endothelial growth factor, but its effects on neurons have yet to be elucidated. We show that Ang-1 is rapidly downregulated in the injured brain after controlled cortical impact (CCI), a mouse experimental traumatic brain injury (TBI) model and in etoposide-induced neuronal apoptosis in vitro. Ang-1 treatment inhibits etoposide-induced upregulation of proapoptotic B-cell lymphoma 2 (Bcl-2) family members Noxa, p53 upregulated modulator of apoptosis (Puma), Bcl-2 interacting mediator of cell death (Bim), and Bcl-2-associated X protein (Bax); reduces markers of caspase-dependent (cytochrome c release/caspase activation) and caspase-independent (apoptosis-inducing factor release) pathways; and limits neuronal cell death. Ang-1 treatment phosphorylates receptors Tunica interna endothelial cell kinase 2 (Tie2), and β1-integrin and limits the etoposide-induced decrease in protein kinase B (Akt) activity. Blocking Tie2 and β1-integrin signaling reduces Ang-1 neuroprotective effects. After both TBI and etoposide treatment microRNA (miR)-711 are upregulated, consistent with its putative role as a negative regulator of Ang-1. We show that miR-711 directly targets the Ang-1 messenger RNA (mRNA), decreasing Ang-1 expression. Increased levels of miR-711 and Ang-1 mRNA are found in the RNA-induced silencing complex complex site of miR-mediated degradation of target mRNAs after etoposide treatment and the miR-711mimic downregulates Ang-1. Administration of miR-711 inhibitor elevates Ang-1 after TBI whereas Ang-1 administration increases Akt activation; reduces Puma, Noxa, Bim, and Bax levels; and attenuates caspase-dependent and -independent neuronal apoptosis 24 h after TBI. Ang-1 also attenuates neuronal degeneration, increases gene expression of molecules that maintain blood-brain barrier integrity, and reduces post-traumatic lesion volume/edema 24 h after TBI. Although we only observed short-term neuroprotective effects after Ang-1 administration, miR-711-dependent downregulation of Ang-1, followed by Akt pathway inhibition, may play a role in neuronal cell death after neuronal injury in vitro and after experimental TBI.

Pericyte-Derived Dickkopf2 Regenerates Damaged Penile Neurovasculature Through an Angiopoietin-1-Tie2 Pathway

Penile erection requires well-coordinated interactions between vascular and nervous systems. Penile neurovascular dysfunction is a major cause of erectile dysfunction (ED) in patients with diabetes, which causes poor response to oral phosphodiesterase-5 inhibitors. Dickkopf2 (DKK2), a Wnt antagonist, is known to promote angiogenesis. Here, using DKK2-Tg mice or DKK2 protein administration, we demonstrate that the overexpression of DKK2 in diabetic mice enhances penile angiogenesis and neural regeneration and restores erectile function. Transcriptome analysis revealed that angiopoietin-1 and angiopoietin-2 are target genes for DKK2. Using an endothelial cell-pericyte coculture system and ex vivo neurite sprouting assay, we found that DKK2-mediated juxtacrine signaling in pericyte-endothelial cell interactions promotes angiogenesis and neural regeneration through an angiopoietin-1-Tie2 pathway, rescuing erectile function in diabetic mice. The dual angiogenic and neurotrophic effects of DKK2, especially as a therapeutic protein, will open new avenues to treating diabetic ED.

Complementary actions of melatonin on angiogenic factors, the angiopoietin/Tie2 axis and VEGF, in co‑cultures of human endothelial and breast cancer cells

Melatonin exerts oncostatic activity in breast cancer through antiangiogenic actions. There, the aim of the present study was to ascertain whether melatonin modulates, in a coordinated action, angiopoietin-1 (ANG-1), ANG-2, their cognate Tie2 receptor and VEGF in co-cultures of human endothelial cells (HUVECs) and breast cancer (MCF-7) cells. To accomplish this we used co-cultures of human breast cancer cells (MCF-7) or non-malignant human mammary epithelial cells (MCF‑10A) with endothelial cells (HUVECs). The presence of breast cancer cells increased HUVEC proliferation and 1 mM melatonin prevented this effect. ANG-1, ANG-2 and VEGF levels in co-culture media and mRNA expression were upregulated and Tie2 mRNA expression was downregulated in the HUVECs and MCF-7. Melatonin (1 mM) downregulated ANG-1, ANG-2 and VEGF levels in the co-culture media and mRNA expression in both types of cells and upregulated Tie2 mRNA expression in HUVECs. ANG-1, ANG-2, Tie2 and VEGF mRNA expression were not modified during HUVEC/MCF-10A co-culture. Estradiol (10 nM) increased ANG-1, ANG-2 and VEGF mRNA expression in HUVECs and melatonin (1 mM) counteracted this effect. We conclude that melatonin simultaneously coordinates downregulation of angiopoietins with a reduction in VEGF, which could be an effective therapeutic strategy for blocking tumor angiogenesis.

Bicarbonate buffered peritoneal dialysis fluid upregulates angiopoietin-1 and promotes vessel maturation

Background

Ultrafiltration decline is a progressive issue for patients on chronic peritoneal dialysis (PD) and can be caused by peritoneal angiogenesis induced by PD fluids. A recent pediatric trial suggests better preservation of ultrafiltration with bicarbonate versus lactate buffered fluid; underlying molecular mechanisms are unknown.

Methods

Angiogenic cytokine profile, tube formation capacity and Receptor Tyrosine Kinase translocation were assessed in primary human umbilical vein endothelial cells following incubation with bicarbonate (BPDF) and lactate buffered (LPDF), pH neutral PD fluid with low glucose degradation product content and lactate buffered, acidic PD fluid with high glucose degradation product content (CPDF). Peritoneal biopsies from age-, PD-vintage- and dialytic glucose exposure matched, peritonitis-free children on chronic PD underwent automated histomorphometry and immunohistochemistry.

Results

In endothelial cells angiopoietin-1 mRNA and protein abundance increased 200% upon incubation with BPDF, but decreased by 70% with LPDF as compared to medium control; angiopoietin-2 remained unchanged. Angiopoietin-1/Angiopoietin-2 protein ratio was 15 and 3-fold increased with BPDF compared to LPDF and medium. Time-lapse microscopy with automated network analysis demonstrated less endothelial cell tube formation with BPDF compared to LPDF and CPDF incubation. Receptor Tyrosine Kinase translocated to the cell membrane in BPDF but not in LPDF or CPDF incubated endothelial cells. In children dialyzed with BPDF peritoneal vessels were larger and angiopoietin-1 abundance in CD31 positive endothelium higher compared to children treated with LPDF.

Conclusion

Bicarbonate buffered PD fluid promotes vessel maturation via upregulation of angiopoietin-1 in vitro and in children on dialysis. Our findings suggest a molecular mechanism for the observed superior preservation of ultrafiltration capacity with bicarbonate buffered PD fluid with low glucose degradation product content.

Impaired angiopoietin/Tie2 signaling compromises Schlemm's canal integrity and induces glaucoma

Primary open-angle glaucoma (POAG) is often caused by elevated intraocular pressure (IOP), which arises due to increased resistance to aqueous humor outflow (AHO). Aqueous humor flows through Schlemm's canal (SC), a lymphatic-like vessel encircling the cornea, and via intercellular spaces of ciliary muscle cells. However, the mechanisms underlying increased AHO resistance are poorly understood. Here, we demonstrate that signaling between angiopoietin (Angpt) and the Angpt receptor Tie2, which is critical for SC formation, is also indispensable for maintaining SC integrity during adulthood. Deletion of Angpt1/Angpt2 or Tie2 in adult mice severely impaired SC integrity and transcytosis, leading to elevated IOP, retinal neuron damage, and impairment of retinal ganglion cell function, all hallmarks of POAG in humans. We found that SC integrity is maintained by interconnected and coordinated functions of Angpt-Tie2 signaling, AHO, and Prox1 activity. These functions diminish in the SC during aging, leading to impaired integrity and transcytosis. Intriguingly, Tie2 reactivation using a Tie2 agonistic antibody rescued the POAG phenotype in Angpt1/Angpt2-deficient mice and rejuvenated the SC in aged mice. These results indicate that the Angpt-Tie2 system is essential for SC integrity. The impairment of this system underlies POAG-associated pathogenesis, supporting the possibility that Tie2 agonists could be a therapeutic option for glaucoma.