title: LDL attenuates VEGF-induced angiogenesis via mechanisms involving VEGFR2 internalization and degradation following endosome-trans-Golgi network trafficking.
abstract: Considerable efforts have been made to amplify angiogenesis under conditions of hypoxia and ischemia by vascular endothelial growth factor (VEGF) delivery, so far with limited success. Ischemic vascular diseases are often associated with hypercholesterolemia. To elucidate whether the exposure to blood lipids influences VEGF responses of microvessels, we characterized effects of low density lipoprotein (LDL) exposure on the proliferation, migration and tube formation of human umbilical vein endothelial cells. By examining the expression, phosphorylation and downstream signals of VEGF's receptor VEGFR2, we characterized mechanisms controlling angiogenic responses following LDL exposure. LDL attenuated endothelial proliferation, migration and tube formation in a dose-dependent way. Reduced abundance of VEGFR2 and VEGFR1 were noticed in LDL-exposed endothelial cells. In subcellular localization studies that we combined with pharmacological experiments, we showed that the loss of VEGFR2 resulted from its internalization and degradation, the latter of which required syntaxin-16-dependent endosome-trans-Golgi network trafficking. As a consequence, VEGFR2 phosphorylation and downstream signals -specifically Akt and ERK1/2 phosphorylation- were attenuated in response to VEGF treatment. VEGF only partly reversed the effects of LDL on angiogenesis under conditions of normoxia and hypoxia. Our results suggest that angiogenic responses to VEGF are compromised in hypercholesterolemia as a consequence of endosomal VEGFR2 degradation.
authors: Department of Neurology, University Hospital Essen, Hufelandstrasse 55, 45122 Essen, Germany.
authors: Fengyan
authors: F
authors: Jin
authors: Nina
authors: N
authors: Hagemann
authors: Ulf
authors: U
authors: Brockmeier
authors: Simon T
authors: ST
authors: Schäfer
authors: Anil
authors: A
authors: Zechariah
authors: Dirk M
authors: DM
authors: Hermann
mesh_terms: D000704:Analysis of Variance; D015153:Blotting, Western; D002465:Cell Movement / Q000187:drug effects / Q000502:physiology; D049109:Cell Proliferation / Q000187:drug effects; D017931:DNA Primers / Q000235:genetics; D004305:Dose-Response Relationship, Drug; D011992:Endosomes / Q000378:metabolism; D005455:Fluorescent Antibody Technique; D005822:Genetic Vectors; D061307:Human Umbilical Vein Endothelial Cells; D006801:Humans; D006937:Hypercholesterolemia / Q000503:physiopathology*; D000860:Hypoxia / Q000503:physiopathology*; D047468:Immunoprecipitation; D016086:Lentivirus; D008077:Lipoproteins, LDL / Q000494:pharmacology*; D018919:Neovascularization, Physiologic / Q000187:drug effects / Q000502:physiology*; D034622:RNA Interference; D034741:RNA, Small Interfering / Q000235:genetics; D060888:Real-Time Polymerase Chain Reaction; D042461:Vascular Endothelial Growth Factor A / Q000494:pharmacology*; D040301:Vascular Endothelial Growth Factor Receptor-2 / Q000378:metabolism*; D021601:trans-Golgi Network / Q000378:metabolism
chemical_list: D017931:DNA Primers; D008077:Lipoproteins, LDL; D034741:RNA, Small Interfering; D042461:Vascular Endothelial Growth Factor A; D040301:Vascular Endothelial Growth Factor Receptor-2