Targeting the interaction of pleiotrophin and VEGFA165 with protein tyrosine phosphatase receptor zeta 1 inhibits endothelial cell activation and angiogenesis.

Protein tyrosine phosphatase receptor zeta 1 (PTPRZ1) is a transmembrane tyrosine phosphatase (TP) that serves as a receptor for pleiotrophin (PTN) and vascular endothelial growth factor A 165 (VEGFA165) to regulate endothelial cell migration. In the present work, we identify a PTN peptide fragment (PTN97-110) that inhibits the interaction of PTN and VEGFA165 with PTPRZ1 but not VEGF receptor 2. This peptide abolishes the stimulatory effect of PTN and VEGFA165 on endothelial cell migration, tube formation on Matrigel, and Akt activation in vitro. It also partially inhibits VEGFA165-induced VEGF receptor 2 activation but does not affect ERK1/2 activation and cell proliferation. In vivo, PTN97-110 inhibits or dysregulates angiogenesis in the chick embryo chorioallantoic membrane and the zebrafish assays, respectively. In glioblastoma cells in vitro, PTN97-110 abolishes the stimulatory effect of VEGFA165 on cell migration and inhibits their anchorage-independent growth, suggesting that this peptide might also be exploited in glioblastoma therapy. Finally, in silico and experimental evidence indicates that PTN and VEGFA165 bind to the extracellular fibronectin type-III (FNIII) domain to stimulate cell migration. Collectively, our data highlight novel aspects of the interaction of PTN and VEGFA165 with PTPRZ1, strengthen the notion that PTPRZ1 is required for VEGFA165-induced signaling, and identify a peptide that targets this interaction and can be exploited for the design of novel anti-angiogenic and anti-glioblastoma therapeutic approaches.

Genetic deletion or tyrosine phosphatase inhibition of PTPRZ1 activates c-Met to up-regulate angiogenesis and lung adenocarcinoma growth.

Protein tyrosine phosphatase receptor zeta 1 (PTPRZ1) is a transmembrane tyrosine phosphatase (TP) expressed in endothelial cells and required for stimulation of cell migration by vascular endothelial growth factor A165 (VEGFA165 ) and pleiotrophin (PTN). It is also over or under-expressed in various tumor types. In this study, we used genetically engineered Ptprz1-/- and Ptprz1+/+ mice to study mechanistic aspects of PTPRZ1 involvement in angiogenesis and investigate its role in lung adenocarcinoma (LUAD) growth. Ptprz1-/- lung microvascular endothelial cells (LMVEC) have increased angiogenic features compared with Ptprz1+/+ LMVEC, in line with the increased lung angiogenesis and the enhanced chemically induced LUAD growth in Ptprz1-/- compared with Ptprz1+/+ mice. In LUAD cells isolated from the lungs of urethane-treated mice, PTPRZ1 TP inhibition also enhanced proliferation and migration. Expression of beta 3 (ß3 ) integrin is decreased in Ptprz1-/- LMVEC, linked to enhanced VEGF receptor 2 (VEGFR2), c-Met tyrosine kinase (TK) and Akt kinase activities. However, only c-Met and Akt seem responsible for the enhanced endothelial cell activation in vitro and LUAD growth and angiogenesis in vivo in Ptprz1-/- mice. A selective PTPRZ1 TP inhibitor, VEGFA165 and PTN also activate c-Met and Akt in a PTPRZ1-dependent manner in endothelial cells, and their stimulatory effects are abolished by the c-Met TK inhibitor (TKI) crizotinib. Altogether, our data suggest that low PTPRZ1 expression is linked to worse LUAD prognosis and response to c-Met TKIs and uncover for the first time the role of PTPRZ1 in mediating c-Met activation by VEGFA and PTN.

The Coadministration of Levosimendan and Exenatide Offers a Significant Cardioprotective Effect to Isolated Rat Hearts against Ischemia/Reperfusion Injury.

(1) Background: The present study aims to investigate the effect of administration of Levosimendan and Exenatide in various concentrations, as well as of the coadministration of those agents in an ischemia-reperfusion injury isolated heart model. (2) Methods: After 30 min of perfusion, the hearts underwent a 30 min period of regional ischemia followed by a 120 min period of reperfusion. All animals were randomly divided into 12 experimental groups of nine animals in each group: (1) Control, (2) Sham, (3) Digox (Negative control, Digoxin 1.67 µg/min), (4) Levo 1 (Levosimendan 0.01 µg/min), (5) Levo 2 (Levosimendan 0.03 µg/mL), (6) Levo 3 (Levosimendan 0.1 µg/min), (7) Levo 4 (Levosimendan 0.3 µg/min), (8) Levo 5 (Levosimendan 1 µg/min), (9) Exen 1 (Exenatide 0.001 µg/min), (10) Exen 2 (Exenatide 0.01 µg/min), (11) Exen 3 (Exenatide 0.1 µg/min) and (12) Combi (Levosimendan 0.1 µg/mL + Exenatide 0.001 µg/min). The hemodynamic parameters were recorded throughout the experiment. Arrhythmias and coronary flow were also evaluated. After every experiment the heart was suitably prepared and infarct size was measured. Markers of myocardial injury were also measured. Finally, oxidative stress was evaluated measuring reactive oxygen species. (3) Results: A dose-dependent improvement of the haemodynamic response was observed after the administration of both Levosimendan and Exenatide. The coadministration of both agents presented an even greater effect, improving the haemodynamic parameters further than the two agents separately. Levosimendan offered an increase of the coronary flow and both agents offered a reduction of arrhythmias. A dose-dependent reduction of the size of myocardial infarction and myocardial injury was observed after administration of Levosimendan and Exenatide. The coadministration of both agents offered a further improving the above parameters. Levosimendan also offered a significant reduction of oxidative stress. (4) Conclusions: The administration of Levosimendan and Exenatide offers a significant benefit by improving the haemodynamic response, increasing the coronary flow and reducing the occurrence of arrhythmias, the size of myocardial injury and myocardial oxidative stress in isolated rat hearts.

Pleiotrophin selectively binds to vascular endothelial growth factor receptor 2 and inhibits or stimulates cell migration depending on ανß3 integrin expression.

Pleiotrophin (PTN) has a moderate stimulatory effect on endothelial cell migration through ανß3 integrin, while it decreases the stimulatory effect of vascular endothelial growth factor A (VEGFA) and inhibits cell migration in the absence of ανß3 through unknown mechanism(s). In the present work, by using a multitude of experimental approaches, we show that PTN binds to VEGF receptor type 2 (VEGFR2) with a KD of 11.6 nM. Molecular dynamics approach suggests that PTN binds to the same VEGFR2 region with VEGFA through its N-terminal domain. PTN inhibits phosphorylation of VEGFR2 at Tyr1175 and still stimulates endothelial cell migration in the presence of a selective VEGFR2 tyrosine kinase inhibitor. VEGFR2 downregulation by siRNA or an anti-VEGFR2 antibody that binds to the ligand-binding VEGFR2 domain also induce endothelial cell migration, which is abolished by a function-blocking antibody against ανß3 or the peptide PTN112-136 that binds ανß3 and inhibits PTN binding. In cells that do not express ανß3, PTN decreases both VEGFR2 Tyr1175 phosphorylation and cell migration in a VEGFR2-dependent manner. Collectively, our data identify VEGFR2 as a novel PTN receptor involved in the regulation of cell migration by PTN and contribute to the elucidation of the mechanism of activation of endothelial cell migration through the interplay between VEGFR2 and ανß3.

Insight into the role of chondroitin sulfate E in angiogenesis.

Chondroitin sulfate E (CS-E) is a glycosaminoglycan containing type-E disaccharide units (sulfated at C-4 and C-6 of N-acetylgalactosamine). CS-E is covalently linked to a core protein to form chondroitin sulfate proteoglycans (PGs) that are secreted or associated with the plasma membrane of several types of cells. CS-E-containing PGs selectively interact with growth factors and chemokines and control various cellular and/or tissue processes. Angiogenesis is a process that is highly regulated in physiological conditions but deregulated in pathologies, leading to excess or deficient blood vessel formation. Angiogenesis regulation is orchestrated by numerous growth factors, such as vascular endothelial growth factor A, fibroblast growth factors and pleiotrophin, whose functions can be affected by CS-containing PGs. In the present review, we focus on the emerging area of CS-mediated angiogenesis and particularly on the critical assessment of data related to a potential role of CS-E in controlling endothelial cell functions, focusing on angiogenesis regulation and vascular homeostasis in health and disease.