VEGFR3 Modulates Vascular Permeability by Controlling VEGF/VEGFR2 Signaling.

Vascular endothelial growth factor (VEGF) is the main driver of angiogenesis and vascular permeability via VEGF receptor 2 (VEGFR2), whereas lymphangiogenesis signals are transduced by VEGFC/D via VEGFR3. VEGFR3 also regulates sprouting angiogenesis and blood vessel growth, but to what extent VEGFR3 signaling controls blood vessel permeability remains unknown. To investigate the role of VEGFR3 in the regulation of VEGF-induced vascular permeability. Long-term global Vegfr3 gene deletion in adult mice resulted in increased fibrinogen deposition in lungs and kidneys, indicating enhanced vascular leakage at the steady state. Short-term deletion of Vegfr3 in blood vascular endothelial cells increased baseline leakage in various tissues, as well as in tumors, and exacerbated vascular permeability in response to VEGF, administered via intradermal adenoviral delivery or through systemic injection of recombinant protein. VEGFR3 gene silencing upregulated VEGFR2 protein levels and phosphorylation in cultured endothelial cells. Consistent with elevated VEGFR2 activity, vascular endothelial cadherin showed reduced localization at endothelial cell-cell junctions in postnatal retinas after Vegfr3 deletion, or after VEGFR3 silencing in cultured endothelial cells. Furthermore, concurrent deletion of Vegfr2 prevented VEGF-induced excessive vascular leakage in mice lacking Vegfr3. VEGFR3 limits VEGFR2 expression and VEGF/VEGFR2 pathway activity in quiescent and angiogenic blood vascular endothelial cells, thereby preventing excessive vascular permeability.

Heinolainen K ，Karaman S ，D'Amico G ，Tammela T ，Sormunen R ，Eklund L ，Alitalo K ，Zarkada G ... -  《-》

Molecular controls of lymphatic VEGFR3 signaling.

Vascular endothelial growth factor receptor 3 (VEGFR3) plays important roles both in lymphangiogenesis and angiogenesis. On stimulation by its ligand VEGF-C, VEGFR3 is able to form both homodimers as well as heterodimers with VEGFR2 and activates several downstream signal pathways, including extracellular signal-regulated kinases (ERK)1/2 and protein kinase B (AKT). Despite certain similarities with VEGFR2, molecular features of VEGFR3 signaling are still largely unknown. Human dermal lymphatic endothelial cells were used to examine VEGF-C-driven activation of signaling. Compared with VEGF-A activation of VEGFR2, VEGF-C-induced VEGFR3 activation led to a more extensive AKT activation, whereas activation of ERK1/2 displayed a distinctly different kinetics. Furthermore, VEGF-C, but not VEGF-A, induced formation of VEGFR3/VEGFR2 complexes. Silencing VEGFR2 or its partner neuropilin 1 specifically abolished VEGF-C-induced AKT but not ERK activation, whereas silencing of neuropilin 2 had little effect on either signaling pathway. Finally, suppression of vascular endothelial phosphotyrosine phosphatase but not other phosphotyrosine phosphatases enhanced VEGF-C-induced activation of both ERK and AKT pathways. Functionally, both ERK and AKT pathways are important for lymphatic endothelial cells migration. VEGF-C activates AKT signaling via formation of VEGFR3/VEGFR2 complex, whereas ERK is activated by VEGFR3 homodimer. Neuropilin 1 and vascular endothelial phosphotyrosine phosphatase are involved in regulation of VEGFR3 signaling.

Deng Y ，Zhang X ，Simons M 《-》

Notch-dependent VEGFR3 upregulation allows angiogenesis without VEGF-VEGFR2 signalling.

Benedito R ，Rocha SF ，Woeste M ，Zamykal M ，Radtke F ，Casanovas O ，Duarte A ，Pytowski B ，Adams RH ... -  《-》

Erythropoietin maintains VE-cadherin expression and barrier function in experimental diabetic retinopathy via inhibiting VEGF/VEGFR2/Src signaling pathway.

To explore the mechanisms of erythropoietin (EPO)'s protection on inner blood-retinal barrier (iBRB) in experimental diabetic retinopathy. Male SD rats were rendered diabetic with streptozotocin, followed by intravitreal injection of EPO. The permeability of iBRB was examined with fluorescein isothiocyanate (FITC)-dextran. Human retinal microvascular endothelial cells (HRMECs) and human umbilical vein endothelial cells (HUVECs) were treated with glyoxal and studied for cell viability and barrier function. The expressions of vascular endothelial (VE)-cadherin, Src kinase, vascular endothelial growth factor (VEGF) and VEGF receptor-2 (VEGFR2) were analyzed with Western blot, ELISA, qPCR, or immunofluorescence. VE-cadherin in rat retinas was down-regulated with diabetes progression. EPO treatment could increase VE-cadherin expression at week 8 and week 16. The expressions of p-Src and p-VE-cadherin were increased at week 2, while decreased at week 8 of diabetes; which were prevented by EPO. The leakage of FITC-dextran in 8-week diabetic rat retinas was ameliorated by EPO. In vitro results showed the expressions of VEGF, p-Src and p-VE-cadherin were increased significantly, accompanied with the decreased barrier function, which were prevented by EPO. Ranibizumab and CGP77675 also inhibited the glyoxal-induced phosphorylation of Src and VE-cadherin. Cellular fractionation showed EPO mitigated the VE-cadherin internalization in glyoxal-treated cells. EPO maintained the expression of VE-cadherin in experimental diabetic retinopathy by inhibiting its phosphorylation and internalization through VEGF/VEGFR2/Src pathway, thus improved the integrity of iBRB.

Liu D ，Xu H ，Zhang C ，Xie H ，Yang Q ，Li W ，Tian H ，Lu L ，Xu JY ，Xu G ，Liu K ，Sun X ，Xu GT ，Zhang J ... -  《-》

VEGFR-3 controls tip to stalk conversion at vessel fusion sites by reinforcing Notch signalling.

Tammela T ，Zarkada G ，Nurmi H ，Jakobsson L ，Heinolainen K ，Tvorogov D ，Zheng W ，Franco CA ，Murtomäki A ，Aranda E ，Miura N ，Ylä-Herttuala S ，Fruttiger M ，Mäkinen T ，Eichmann A ，Pollard JW ，Gerhardt H ，Alitalo K ... -  《-》