Vascular endothelial growth factor stimulates differential signaling pathways in in vivo microcirculation

Abstract

Vascular endothelial growth factor (VEGF) induces mild vasodilation and strong increases in microvascular permeability. Using intravital microscopy and digital integrated optical intensity image analysis, we tested, in the hamster cheek pouch microcirculation, the hypothesis that differential signaling pathways in arterioles and venules represent an in vivo regulatory mechanism in the control of vascular diameter and permeability. The experimental design involved blocking specific signaling molecules and simultaneously assessing VEGF-induced changes in arteriolar diameter and microvascular transport of FITC-Dextran 150. Inhibition of Akt [indirectly via phosphatidylinositol 3-kinase with LY-294002 or wortmannin] or PKC (with bisindolylmaleimide) reduced VEGF-induced hyperpermeability. However, phosphatidylinositol 3-kinase/Akt inhibition enhanced the early phase and attenuated the late phase of VEGF-induced vasodilation, whereas blocking PKC had no effect. Inhibition of extracellular signal-regulated kinase (ERK)-1/2 (with PD-98059 or AG-126) also reduced VEGF-induced hyperpermeability but did not block VEGF-induced vasodilation. Blockade of endothelial nitric oxide synthase (with Nω-monomethyl-l-arginine) inhibited VEGF-induced changes in both permeability and diameter. Furthermore, immunofluorescence studies with human umbilical vein endothelial cells revealed that bisindolylmaleimide, PD-98059, and l-NMMA attenuate VEGF-induced reorganization of vascular endothelial cadherin. Our data demonstrate that 1) endothelial nitric oxide synthase is a common convergence pathway for VEGF-induced changes in arteriolar diameter and microvascular permeability; 2) PKC and ERK-1/2 do not play a major role in VEGF-induced vasodilation in the hamster cheek pouch microcirculation; and 3) Akt, PKC, and ERK-1/2 are elements of the signaling cascade that regulates VEGF-stimulated microvascular hyperpermeability. Our data provide evidence for differential signaling as a regulatory step in VEGF-stimulated microvascular dynamics.

eNOS derived nitric oxide regulates endothelial barrier function via VE cadherin and Rho GTPases

“…Several studies have demonstrated that eNOS is essential for VEGF-mediated changes in microvascular permeability (Aramoto et al, 2004;Fukumura et al, 1997;Gratton et al, 2003a;Hatakeyama et al, 2006;Murohara et al, 1998).…”

Autocrine VEGF mediates the antiapoptotic effect of CD154 on CLL cells

“…46 Both VEGFRs and CD40 can generate other signals in addition to NF-kB activation and, moreover, CD40 can generate both proapoptotic and antiapoptotic signals. [47][48][49] Exactly how different signals induced by CD154 and VEGF cooperate to provide rescue of CLL cells was beyond the scope of the current study. However, It is known that CD40 ligation induces the production of antiapoptotic proteins including IAPs.…”

In vivo delivery of fluoresceinated dextrans to the murine growth plate: Imaging of three vascular routes by multiphoton microscopy

“…The Ihh/ PTHrP negative feedback loop acts to put the brakes on at the junction between the end of proliferation and the initiation of hypertrophy, requiring communication between growth plate chondrocytes and the perichondrium (Vortkamp et al, 1996;Long and Linsenmayer, 1998;Pathi et al, 1999;Volk and Leboy, 1999;Pateder et al, 2000;DiNino et al, 2002;Allen et al, 2004). Recent studies provide data that vascular endothelial growth factor (VEGF) alters the permeability characteristics of the vascular endothelium in paracrine regulation of the growth plate involving the perichondrium (Roberts and Palade, 1995;Esser et al, 1998;Zelzer et al, 2002;Ericksson et al, 2003;Aramoto et al, 2004;Cao et al, 2004;Zelzer and Olsen, 2005). VEGF's more established role for paracrine regulation exists at the metaphyseal COJ, where it is produced by hypertrophic chondrocytes, and here VEGF may be responsible for the extreme vascular permeability to the surrounding bone matrix (Vu et al, 1998;Gerber et al, 1999;Gerber and Ferrara, 2000;Aramoto et al, 2004).…”

“…Recent studies provide data that vascular endothelial growth factor (VEGF) alters the permeability characteristics of the vascular endothelium in paracrine regulation of the growth plate involving the perichondrium (Roberts and Palade, 1995;Esser et al, 1998;Zelzer et al, 2002;Ericksson et al, 2003;Aramoto et al, 2004;Cao et al, 2004;Zelzer and Olsen, 2005). VEGF's more established role for paracrine regulation exists at the metaphyseal COJ, where it is produced by hypertrophic chondrocytes, and here VEGF may be responsible for the extreme vascular permeability to the surrounding bone matrix (Vu et al, 1998;Gerber et al, 1999;Gerber and Ferrara, 2000;Aramoto et al, 2004).…”