(1) The vasculature of the blood-brain barrier allows only comparatively few leukocytes to enter ... more (1) The vasculature of the blood-brain barrier allows only comparatively few leukocytes to enter and survey the healthy central nervous system (CNS). However, during pathological CNS inflammation, the number of leukocytes adhering to and penetrating the CNS vasculature increases strongly. (2) Endothelial adhesion molecules do not only mediate firm adhesion of leukocyte to vascular beds but also trigger signaling cascades within the endothelial cell, which play a crucial role in modulating subsequent leukocyte diapedesis. (3) Signaling through endothelial intercellular adhesion molecule-1 (ICAM-1, CD54) has been shown to induce changes of the endothelial cytoskeleton, transcription, and interendothelial junctions, all of which may be important in modulating endothelial disposition to infiltrating leukocytes. Furthermore, a number of recent reports document that drugs interfering with endothelial ICAM-1 signaling, efficiently reduce leukocyte migration both in vitro and in animal models of CNS inflammation. (4) These approaches are novel in as much as they target vascular beds rather than the penetrating leukocytes. Since endothelial ICAM-1 signaling appears to differ between different vascular beds we propose that such compounds could potentially be used as exquisite drugs in the treatment of neuroinflammatory diseases.
Vascular permeability is important at many sites, but particularly so in diabetic retinopathy whe... more Vascular permeability is important at many sites, but particularly so in diabetic retinopathy where macular oedema is the major cause of blindness. Angiopoietin-2 (Ang-2) and vascular endothelial growth factor (VEGF) are important factors involved in neovascularization and vascular leakage, but there is little data on their interaction to promote increased vascular permeability. Porcine retinal endothelial cells (PREC) were seeded into permeable inserts and cultured in 24-well plates that permit measurement of permeability using fluorescent dextrans. Cell purity was assessed immunohistochemically. At confluency, PREC were treated with increasing concentrations of VEGF (20-100ng/ml) and Ang-2 (15-75ng/ml). The effect on tight junctions was assessed by visualization with an anti-ZO-1 antibody. Immunohistochemistry showed high purity of isolated PREC. Permeability of untreated PREC monolayers was low. The increase in permeability in Ang-2 treated cells (25-30% compared with non-treated cells) was less than that for cells treated with VEGF only (20-100% compared with untreated cells). Highest permeability was seen with a combination of Ang-2 and VEGF (100-400% compared with untreated cells). Permeability increased with time after growth factor application. Preliminary ZO-1 immunohistochemistry appeared to demonstrate the presence of tight junctions between untreated PREC, and loss of tight junctions after treatment with VEGF and Ang-2. VEGF alone is twice as potent in interrupting tight junctions in an endothelial cell monolayer as Ang-2. However, both growth factors acting together increase permeability three times as much as VEGF alone. Treatments designed to reduce vascular permeability in diabetic macular oedema should consider that crosstalk between growth factors including VEGF and the Ang-2/Tie-2 system can multiply their effects.
(1) The vasculature of the blood-brain barrier allows only comparatively few leukocytes to enter ... more (1) The vasculature of the blood-brain barrier allows only comparatively few leukocytes to enter and survey the healthy central nervous system (CNS). However, during pathological CNS inflammation, the number of leukocytes adhering to and penetrating the CNS vasculature increases strongly. (2) Endothelial adhesion molecules do not only mediate firm adhesion of leukocyte to vascular beds but also trigger signaling cascades within the endothelial cell, which play a crucial role in modulating subsequent leukocyte diapedesis. (3) Signaling through endothelial intercellular adhesion molecule-1 (ICAM-1, CD54) has been shown to induce changes of the endothelial cytoskeleton, transcription, and interendothelial junctions, all of which may be important in modulating endothelial disposition to infiltrating leukocytes. Furthermore, a number of recent reports document that drugs interfering with endothelial ICAM-1 signaling, efficiently reduce leukocyte migration both in vitro and in animal models of CNS inflammation. (4) These approaches are novel in as much as they target vascular beds rather than the penetrating leukocytes. Since endothelial ICAM-1 signaling appears to differ between different vascular beds we propose that such compounds could potentially be used as exquisite drugs in the treatment of neuroinflammatory diseases.
The vascular endothelium operates in a highly polarized environment, but to date there has been l... more The vascular endothelium operates in a highly polarized environment, but to date there has been little exploration of apicobasal polarization of its signaling. We show that VEGF-A, histamine, IGFBP3, and LPA trigger unequal endothelial responses when acting from the circulation or the parenchymal side at blood-neural barriers. For VEGF-A, highly polarized receptor distribution contributed to distinct signaling patterns: VEGFR2, which was found to be predominantly abluminal, mediated increased permeability via p38; in contrast, luminal VEGFR1 led to Akt activation and facilitated cytoprotection. Importantly, such differential apicobasal signaling and VEGFR distribution were found in the microvasculature of brain and retina but not lung, indicating that endothelial cells at blood-neural barriers possess specialized signaling compartments that assign different functions depending on whether an agonist is tissue or blood borne.
(1) The vasculature of the blood-brain barrier allows only comparatively few leukocytes to enter ... more (1) The vasculature of the blood-brain barrier allows only comparatively few leukocytes to enter and survey the healthy central nervous system (CNS). However, during pathological CNS inflammation, the number of leukocytes adhering to and penetrating the CNS vasculature increases strongly. (2) Endothelial adhesion molecules do not only mediate firm adhesion of leukocyte to vascular beds but also trigger signaling cascades within the endothelial cell, which play a crucial role in modulating subsequent leukocyte diapedesis. (3) Signaling through endothelial intercellular adhesion molecule-1 (ICAM-1, CD54) has been shown to induce changes of the endothelial cytoskeleton, transcription, and interendothelial junctions, all of which may be important in modulating endothelial disposition to infiltrating leukocytes. Furthermore, a number of recent reports document that drugs interfering with endothelial ICAM-1 signaling, efficiently reduce leukocyte migration both in vitro and in animal models of CNS inflammation. (4) These approaches are novel in as much as they target vascular beds rather than the penetrating leukocytes. Since endothelial ICAM-1 signaling appears to differ between different vascular beds we propose that such compounds could potentially be used as exquisite drugs in the treatment of neuroinflammatory diseases.
Vascular permeability is important at many sites, but particularly so in diabetic retinopathy whe... more Vascular permeability is important at many sites, but particularly so in diabetic retinopathy where macular oedema is the major cause of blindness. Angiopoietin-2 (Ang-2) and vascular endothelial growth factor (VEGF) are important factors involved in neovascularization and vascular leakage, but there is little data on their interaction to promote increased vascular permeability. Porcine retinal endothelial cells (PREC) were seeded into permeable inserts and cultured in 24-well plates that permit measurement of permeability using fluorescent dextrans. Cell purity was assessed immunohistochemically. At confluency, PREC were treated with increasing concentrations of VEGF (20-100ng/ml) and Ang-2 (15-75ng/ml). The effect on tight junctions was assessed by visualization with an anti-ZO-1 antibody. Immunohistochemistry showed high purity of isolated PREC. Permeability of untreated PREC monolayers was low. The increase in permeability in Ang-2 treated cells (25-30% compared with non-treated cells) was less than that for cells treated with VEGF only (20-100% compared with untreated cells). Highest permeability was seen with a combination of Ang-2 and VEGF (100-400% compared with untreated cells). Permeability increased with time after growth factor application. Preliminary ZO-1 immunohistochemistry appeared to demonstrate the presence of tight junctions between untreated PREC, and loss of tight junctions after treatment with VEGF and Ang-2. VEGF alone is twice as potent in interrupting tight junctions in an endothelial cell monolayer as Ang-2. However, both growth factors acting together increase permeability three times as much as VEGF alone. Treatments designed to reduce vascular permeability in diabetic macular oedema should consider that crosstalk between growth factors including VEGF and the Ang-2/Tie-2 system can multiply their effects.
(1) The vasculature of the blood-brain barrier allows only comparatively few leukocytes to enter ... more (1) The vasculature of the blood-brain barrier allows only comparatively few leukocytes to enter and survey the healthy central nervous system (CNS). However, during pathological CNS inflammation, the number of leukocytes adhering to and penetrating the CNS vasculature increases strongly. (2) Endothelial adhesion molecules do not only mediate firm adhesion of leukocyte to vascular beds but also trigger signaling cascades within the endothelial cell, which play a crucial role in modulating subsequent leukocyte diapedesis. (3) Signaling through endothelial intercellular adhesion molecule-1 (ICAM-1, CD54) has been shown to induce changes of the endothelial cytoskeleton, transcription, and interendothelial junctions, all of which may be important in modulating endothelial disposition to infiltrating leukocytes. Furthermore, a number of recent reports document that drugs interfering with endothelial ICAM-1 signaling, efficiently reduce leukocyte migration both in vitro and in animal models of CNS inflammation. (4) These approaches are novel in as much as they target vascular beds rather than the penetrating leukocytes. Since endothelial ICAM-1 signaling appears to differ between different vascular beds we propose that such compounds could potentially be used as exquisite drugs in the treatment of neuroinflammatory diseases.
The vascular endothelium operates in a highly polarized environment, but to date there has been l... more The vascular endothelium operates in a highly polarized environment, but to date there has been little exploration of apicobasal polarization of its signaling. We show that VEGF-A, histamine, IGFBP3, and LPA trigger unequal endothelial responses when acting from the circulation or the parenchymal side at blood-neural barriers. For VEGF-A, highly polarized receptor distribution contributed to distinct signaling patterns: VEGFR2, which was found to be predominantly abluminal, mediated increased permeability via p38; in contrast, luminal VEGFR1 led to Akt activation and facilitated cytoprotection. Importantly, such differential apicobasal signaling and VEGFR distribution were found in the microvasculature of brain and retina but not lung, indicating that endothelial cells at blood-neural barriers possess specialized signaling compartments that assign different functions depending on whether an agonist is tissue or blood borne.
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