-
Current Eye Research Mar 2023Placental growth factor (PlGF) and Angiopoietin (Ang)-1 are two proteins that are involved in the regulation of endothelial cell (EC) growth and vasculature formation....
PURPOSE
Placental growth factor (PlGF) and Angiopoietin (Ang)-1 are two proteins that are involved in the regulation of endothelial cell (EC) growth and vasculature formation. In the retina and endothelial cells, pericytes are the major source of both molecules. The purpose of this study is to examine the association of PlGF and Ang-1 with human EC/pericyte co-cultures and iPSC-derived vascular organoids.
METHODS
In this study, we used co-cultures of human primary retinal endothelial cells (HREC) and primary human retinal pericytes (HRP), western blotting, immunofluorescent analysis, TUNEL staining, LDH-assays, and RNA seq analysis, as well as human-induced pluripotent stem cells (iPSC), derived organoids (VO) to study the association between PlGF and Ang-1.
RESULTS
Inhibition of PlGF by PlGF neutralizing antibody in HREC-HRP co-cultures resulted in the increased expression of Ang-1 and Tie-2 in a dose-dependent manner. This upregulation was not observed in HREC and HRP monocultures but only in co-cultures suggesting the association of pericytes and endothelial cells. Furthermore, Vascular endothelial growth factor receptor 1 (VEGFR1) inhibition abolished the Ang-1 and Tie-2 upregulation by PlGF inhibition. The pericyte viability in high-glucose conditions was also reduced by VEGFR1 neutralization. Immunofluorescent analysis showed that Ang-1 and Ang-2 were expressed mainly by perivascular cells in the VO. RNA seq analysis of the RNA isolated from VO in high glucose conditions indicated increased PGF and Ang-2 expressions in the VO. PlGF inhibition increased the expression of Ang-1 and Tie-2 in VO, increasing the pericyte coverage of the VO microvascular network.
CONCLUSION
Combined, these results suggest PlGF's role in the regulation of Ang-1 and Tie-2 expression through VEGFR1. These findings provide new insights into the neovascularization process in diabetic retinopathy and new targets for potential therapeutic intervention.
Topics: Humans; Female; Placenta Growth Factor; Pericytes; Angiopoietins; Induced Pluripotent Stem Cells; Vascular Endothelial Growth Factor A; Endothelial Cells; Coculture Techniques; Retina; Glucose
PubMed: 36458540
DOI: 10.1080/02713683.2022.2149808 -
EMBO Molecular Medicine Jul 2021Anti-angiogenic drugs targeting the VEGF pathway are most effective in advanced metastatic disease settings of certain types of cancers, whereas they have been... (Review)
Review
Anti-angiogenic drugs targeting the VEGF pathway are most effective in advanced metastatic disease settings of certain types of cancers, whereas they have been unsuccessful as adjuvant therapies of micrometastatic disease in numerous phase III trials involving early-stage (resectable) cancers. Newer investigational anti-angiogenic drugs have been designed to inhibit the Angiopoietin (Ang)-Tie pathway. Acting through Tie2 receptors, the Ang1 ligand is a gatekeeper of endothelial quiescence. Ang2 is a dynamically expressed pro-angiogenic destabilizer of endothelium, and its upregulation is associated with poor prognosis in cancer. Besides using Ang2 blockers as inhibitors of tumor angiogenesis, little attention has been paid to their use as stabilizers of blood vessels to suppress tumor cell extravasation and metastasis. In clinical trials, Ang2 blockers have shown limited efficacy in advanced metastatic disease settings. This review summarizes preclinical evidence suggesting the potential utility of Ang2 inhibitors or Tie2 activators as neoadjuvant or adjuvant therapies in the prevention or treatment of early-stage micrometastatic disease. We further discuss the rationale and potential of combining these strategies with immunotherapy, including immune checkpoint targeting antibodies.
Topics: Angiogenesis Inhibitors; Angiopoietin-1; Angiopoietin-2; Humans; Immunotherapy; Neoplasms; Neovascularization, Pathologic; Receptor, TIE-2
PubMed: 34125494
DOI: 10.15252/emmm.201708253 -
Endocrinology Nov 2021Pericytes regulate vascular development, stability, and quiescence; their dysfunction contributes to diabetic retinopathy. To explore the role of insulin receptors in...
Pericytes regulate vascular development, stability, and quiescence; their dysfunction contributes to diabetic retinopathy. To explore the role of insulin receptors in pericyte biology, we created pericyte insulin receptor knockout mice (PIRKO) by crossing PDGFRβ-Cre mice with insulin receptor (Insr) floxed mice. Their neonatal retinal vasculature exhibited perivenous hypervascularity with venular dilatation, plus increased angiogenic sprouting in superficial and deep layers. Pericyte coverage of capillaries was unaltered in perivenous and periarterial plexi, and no differences in vascular regression or endothelial proliferation were apparent. Isolated brain pericytes from PIRKO had decreased angiopoietin-1 mRNA, whereas retinal and lung angiopoietin-2 mRNA was increased. Endothelial phospho-Tie2 staining was diminished and FoxO1 was more frequently nuclear localized in the perivenous plexus of PIRKO, in keeping with reduced angiopoietin-Tie2 signaling. Silencing of Insr in human brain pericytes led to reduced insulin-stimulated angiopoietin-1 secretion, and conditioned media from these cells was less able to induce Tie2 phosphorylation in human endothelial cells. Hence, insulin signaling in pericytes promotes angiopoietin-1 secretion and endothelial Tie2 signaling and perturbation of this leads to excessive vascular sprouting and venous plexus abnormalities. This phenotype mimics elements of diabetic retinopathy, and future work should evaluate pericyte insulin signaling in this disease.
Topics: Angiopoietin-2; Angiopoietins; Animals; Cells, Cultured; Endothelial Cells; Insulin; Mice; Mice, Knockout; Pericytes; Receptor, Insulin; Retina; Retinal Vessels; Signal Transduction; Vascular Remodeling
PubMed: 34460911
DOI: 10.1210/endocr/bqab182 -
Postepy Higieny I Medycyny... Jan 2014Obesity is a disease that develops as a result of long-term positive energy balance. In recent years, the influence of gut microflora composition, as a potential factor... (Review)
Review
Obesity is a disease that develops as a result of long-term positive energy balance. In recent years, the influence of gut microflora composition, as a potential factor affecting the energy balance and contributing to fat accumulation, has been studied. It seems that bacteria can affect host energy balance through several mechanisms, such as increased fermentation of undigested polysaccharides and obtaining extra energy from the portion of food, reduced expression of FIAF (fasting-induced adipocyte factor) in the enterocytes with inhibitory activity towards intestinal lipoprotein lipase, and the increased release of peptide YY that slows the intestinal motility. It is also believed that changes in the composition of gut microflora may be one of the factors that induce systemic microinflammation in the obese, an important link in the pathogenesis of obesity related complications, including dyslipidaemia, hypertension and type 2 diabetes. However, the results of previous studies are inconclusive. Many of them have been carried out in an animal model and were not confirmed in studies involving humans. These discrepancies may be due to different composition of the diet, distinct physiological gut microflora and the methodology used in these studies. The present article reviews the current literature on the potential role of gut microflora in the pathogenesis of obesity.
Topics: Angiopoietin-Like Protein 4; Angiopoietins; Animals; Diabetes Mellitus, Type 2; Diet; Disease Models, Animal; Dyslipidemias; Energy Metabolism; Enterocytes; Gastrointestinal Motility; Gastrointestinal Tract; Humans; Hypertension; Intestines; Lipase; Microbiota; Obesity; Peptide YY
PubMed: 24491899
DOI: 10.5604/17322693.1086419 -
Pediatric Research May 2022Sepsis in premature newborns is a risk factor for bronchopulmonary dysplasia (BPD), but underlying mechanisms of lung injury remain unclear. Aberrant expression of...
BACKGROUND
Sepsis in premature newborns is a risk factor for bronchopulmonary dysplasia (BPD), but underlying mechanisms of lung injury remain unclear. Aberrant expression of endothelial cell (EC) angiopoietin 2 (ANGPT2) disrupts angiopoietin 1 (ANGPT1)/TIE2-mediated endothelial quiescence, and is implicated in sepsis-induced acute respiratory distress syndrome in adults. We hypothesized that recombinant ANGPT1 will mitigate sepsis-induced ANGPT2 expression, inflammation, acute lung injury (ALI), and alveolar remodeling in the saccular lung.
METHODS
Effects of recombinant ANGPT1 on lipopolysaccharide (LPS)-induced endothelial inflammation were evaluated in human pulmonary microvascular endothelial cells (HPMEC). ALI and long-term alveolar remodeling were assessed in newborn mice exposed to intraperitoneal LPS and recombinant ANGPT1 pretreatment.
RESULTS
LPS dephosphorylated EC TIE2 in association with increased ANGPT2 in vivo and in vitro. ANGPT1 suppressed LPS and ANGPT2-induced EC inflammation in HPMEC. Neonatal mice treated with LPS had increased lung cytokine expression, neutrophilic influx, and cellular apoptosis. ANGPT1 pre-treatment suppressed LPS-induced lung Toll-like receptor signaling, inflammation, and ALI. LPS-induced acute increases in metalloproteinase 9 expression and elastic fiber breaks, as well as a long-term decrease in radial alveolar counts, were mitigated by ANGPT1.
CONCLUSIONS
In an experimental model of sepsis-induced BPD, ANGPT1 preserved endothelial quiescence, inhibited ALI, and suppressed alveolar simplification.
IMPACT
Key message: Angiopoietin 1 inhibits LPS-induced neonatal lung injury and alveolar remodeling. Additions to existing literature: Demonstrates dysregulation of angiopoietin-TIE2 axis is important for sepsis- induced acute lung injury and alveolar simplification in experimental BPD. Establishes recombinant Angiopoietin 1 as an anti-inflammatory therapy in BPD.
IMPACT
Angiopoietin 1-based interventions may represent novel therapies for mitigating sepsis-induced lung injury and BPD in premature infants.
Topics: Acute Lung Injury; Angiopoietin-1; Angiopoietin-2; Animals; Bronchopulmonary Dysplasia; Endothelial Cells; Endotoxins; Humans; Infant, Newborn; Inflammation; Lipopolysaccharides; Lung; Mice; Sepsis
PubMed: 33980990
DOI: 10.1038/s41390-021-01544-0 -
Proceedings of the National Academy of... Apr 2013Angiogenesis is a complex cellular process involving multiple regulatory growth factors and growth factor receptors. Among them, the ligands for the endothelial-specific...
Angiogenesis is a complex cellular process involving multiple regulatory growth factors and growth factor receptors. Among them, the ligands for the endothelial-specific tunica intima endothelial receptor tyrosine kinase 2 (Tie2) receptor kinase, angiopoietin-1 (Ang1) and Ang2, play essential roles in balancing vessel stability and regression during both developmental and tumor-induced angiogenesis. Despite possessing a high degree of sequence identity, Ang1 and Ang2 have distinct functional roles and cell-signaling characteristics. Here, we present the crystal structures of Ang1 both unbound and in complex with the Tie2 ectodomain. Comparison of the Ang1-containing structures with their Ang2-containing counterparts provide insight into the mechanism of receptor activation and reveal molecular surfaces important for interactions with Tie2 coreceptors and associated signaling proteins. Using structure-based mutagenesis, we identify a loop within the angiopoietin P domain, adjacent to the receptor-binding interface, which confers the specific agonist/antagonist properties of the molecule. We demonstrate using cell-based assays that an Ang2 chimera containing the Ang1 loop sequence behaves functionally similarly to Ang1 as a constitutive Tie2 agonist, able to efficiently dissociate the inhibitory Tie1/Tie2 complex and elicit Tie2 clustering and downstream signaling.
Topics: Angiopoietin-1; Angiopoietin-2; Conserved Sequence; Crystallography, X-Ray; HEK293 Cells; Humans; Models, Molecular; Protein Structure, Tertiary; Receptor, TIE-1; Receptor, TIE-2; Recombinant Proteins; Signal Transduction; Static Electricity; Structure-Activity Relationship
PubMed: 23592718
DOI: 10.1073/pnas.1216890110 -
PloS One 2023The endothelial angiopoietin/Tie2 system is an important regulator of endothelial permeability and targeting Tie2 reduces hemorrhagic shock-induced organ edema in males....
BACKGROUND
The endothelial angiopoietin/Tie2 system is an important regulator of endothelial permeability and targeting Tie2 reduces hemorrhagic shock-induced organ edema in males. However, sexual dimorphism of the endothelium has not been taken into account. This study investigated whether there are sex-related differences in the endothelial angiopoietin/Tie2 system and edema formation.
METHODS
Adult male and female heterozygous Tie2 knockout mice (Tie2+/-) and wild-type controls (Tie2+/+) were included (n = 9 per group). Renal and pulmonary injury were determined by wet/dry weight ratio and H&E staining of tissue sections. Protein levels were studied in plasma by ELISA and pulmonary and renal mRNA expression levels by RT-qPCR.
RESULTS
In Tie2+/+ mice, females had higher circulating angiopoietin-2 (138%, p<0.05) compared to males. Gene expression of angiopoietin-1 (204%, p<0.01), angiopoietin-2 (542%, p<0.001) were higher in females compared to males in kidneys, but not in lungs. Gene expression of Tie2, Tie1 and VE-PTP were similar between males and females in both organs. Renal and pulmonary wet/dry weight ratio did not differ between Tie2+/+ females and males. Tie2+/+ females had lower circulating NGAL (41%, p<0.01) compared to males, whereas renal NGAL and KIM1 gene expression was unaffected. Interestingly, male Tie2+/- mice had 28% higher renal wet/dry weight ratio (p<0.05) compared to Tie2+/+ males, which was not observed in females nor in lungs. Partial deletion of Tie2 did not affect circulating angiopoietin-1 or angiopoietin-2, but soluble Tie2 was 44% and 53% lower in males and females, respectively, compared to Tie2+/+ mice of the same sex. Renal and pulmonary gene expression of angiopoietin-1, angiopoietin-2, estrogen receptors and other endothelial barrier regulators was comparable between Tie2+/- and Tie2+/+ mice in both sexes.
CONCLUSION
Female sex seems to protect against renal, but not pulmonary edema in heterozygous Tie2 knock-out mice. This could not be explained by sex dimorphism in the endothelial angiopoietin/Tie2 system.
Topics: Animals; Female; Male; Mice; Angiopoietin-1; Angiopoietin-2; Angiopoietins; Edema; Endothelium; Kidney; Lipocalin-2; Receptor, TIE-2
PubMed: 37972011
DOI: 10.1371/journal.pone.0293673 -
PloS One 2012The tyrosine kinase Tie-2 and its ligands Angiopoietins (Angs) transduce critical signals for angiogenesis in endothelial cells. This receptor and Ang-1 are coexpressed...
The tyrosine kinase Tie-2 and its ligands Angiopoietins (Angs) transduce critical signals for angiogenesis in endothelial cells. This receptor and Ang-1 are coexpressed in hematopoietic stem cells and in a subset of megakaryocytes, though a possible role of angiopoietins in megakaryocytic differentiation/proliferation remains to be demonstrated. To investigate a possible effect of Ang-1/Ang-2 on megakaryocytic proliferation/differentiation we have used both normal CD34(+) cells induced to megakaryocytic differentiation and the UT7 cells engineered to express the thrombopoietin receptor (TPOR, also known as c-mpl, UT7/mpl). Our results indicate that Ang-1/Ang-2 may have a role in megakaryopoiesis. Particularly, Ang-2 is predominantly produced and released by immature normal megakaryocytic cells and by undifferentiated UT7/mpl cells and slightly stimulated TPO-induced cell proliferation. Ang-1 production is markedly induced during megakaryocytic differentiation/maturation and potentiated TPO-driven megakaryocytic differentiation. Blocking endogenously released angiopoietins partially inhibited megakaryocytic differentiation, particularly for that concerns the process of polyploidization. According to these data it is suggested that an autocrine angiopoietin/Tie-2 loop controls megakaryocytic proliferation and differentiation.
Topics: Angiopoietins; Autocrine Communication; Cell Differentiation; Cell Line; Cell Proliferation; Hematopoietic Stem Cells; Humans; Megakaryocytes; Receptor, TIE-2; Receptors, Thrombopoietin; Ribonuclease, Pancreatic; Signal Transduction; Thrombopoietin
PubMed: 22792187
DOI: 10.1371/journal.pone.0039796 -
Breast Cancer Research and Treatment Feb 2017Angiogenesis is one of the hallmarks of cancer and is essential for cancer progression and metastasis. However, clinical trials with vascular endothelial growth factor...
PURPOSE
Angiogenesis is one of the hallmarks of cancer and is essential for cancer progression and metastasis. However, clinical trials with vascular endothelial growth factor (VEGF) pathway inhibitors have failed to show overall survival benefit in breast cancer. Targeted therapy against the angiopoietin pathway, a downstream angiogenesis cascade, could be effective in breast cancer. This study investigates the association of angiopoietin pathway gene expression with breast cancer survival using a "big data" approach employing RNA sequencing data from The Cancer Genome Atlas (TCGA).
METHODS
A total of 888 patients with adequate gene expression, disease-free survival (DFS), and overall survival (OS) data were selected for analysis. DFS and OS were calculated for patients with high and low expression of angiopoietin and VEGF pathway genes using TCGA data. Gene-specific thresholds to dichotomize patients into high and low expression were determined and survival plots were generated.
RESULTS
The TCGA cohort was representative of national breast cancer patients with respect to stage, pathology, and survival. High Ang2 gene expression was associated with not only decreased DFS (p = 0.05), but also decreased OS (p < 0.05). High co-expression of Ang2 and its receptor Tie2 was associated with both decreased DFS and OS (p < 0.05). There was strong correlation between angiopoietin and VEGF pathway genes. While high expression of VEGFA alone was not associated with survival, high co-expression with Ang2 was associated with decreased OS.
CONCLUSIONS
This study validates TCGA as a representative database providing genomic data and survival outcomes in breast cancer. Our TCGA data support the angiopoietin pathway as a key mediator in the pathologic angiogenic switch in breast cancer.
Topics: Adult; Aged; Angiopoietin-2; Angiopoietins; Breast Neoplasms; Computational Biology; Databases, Genetic; Female; Gene Expression Regulation, Neoplastic; Humans; Kaplan-Meier Estimate; Middle Aged; Neoplasm Staging; Neovascularization, Pathologic; Prognosis; Receptor, TIE-2; SEER Program; Signal Transduction; Vascular Endothelial Growth Factors
PubMed: 28062977
DOI: 10.1007/s10549-017-4102-2 -
Differential expression of Tie-2 receptors and angiopoietins in response to in vivo hypoxia in rats.American Journal of Physiology. Lung... Sep 2001In this study, we assessed the effects of in vivo hypoxia on the expression of Tie-2 receptors and angiopoietins in various organs of conscious rats and correlated these...
In this study, we assessed the effects of in vivo hypoxia on the expression of Tie-2 receptors and angiopoietins in various organs of conscious rats and correlated these effects with the expression of hypoxia-inducible factor-1 (HIF-1). RT-PCR and Southern blotting were used to amplify mRNA expression of angiopoietin-1, -2, and -3, Tie-2, and HIF-1 alpha in tissues of normoxic and hypoxic (fraction of inspired oxygen of 9--10% for either 12 or 48 h) rats. Hypoxia provoked a decline in angiopoietin-1 mRNA and Tie-2 mRNA, protein, and phosphorylation levels in the lung, liver, cerebellum, and heart but not in the kidney and diaphragm. In comparison, hypoxia raised the levels of angiopoietin-2 mRNA in the cerebellum and angiopoietin-3 mRNA in the lung, kidney, and diaphragm. HIF-1 alpha mRNA was abundant in most organs of normoxic rats but was significantly induced in the kidney and diaphragm of hypoxic rats. We conclude that in vivo hypoxia exerts inhibitory effects on the activity of the angiopoietin-1/Tie-2 receptor pathway through reduction of angiopoietin-1 and upregulation of angiopoietin-2 and -3. Induction of angiopoietin-3 in the kidney and diaphragm of hypoxic rats could be mediated through the HIF-1 transcription factor.
Topics: Angiopoietin-1; Angiopoietin-2; Angiopoietin-Like Protein 1; Angiopoietin-like Proteins; Angiopoietins; Animals; Base Sequence; Blotting, Southern; DNA-Binding Proteins; Hypoxia; Hypoxia-Inducible Factor 1; Hypoxia-Inducible Factor 1, alpha Subunit; Intercellular Signaling Peptides and Proteins; Male; Membrane Glycoproteins; Neoplasm Proteins; Nuclear Proteins; Proteins; Proto-Oncogene Proteins; RNA, Messenger; Rats; Rats, Sprague-Dawley; Receptor, TIE-2; Reverse Transcriptase Polymerase Chain Reaction; Transcription Factors
PubMed: 11504684
DOI: 10.1152/ajplung.2001.281.3.L582