Simultaneous activation of several second messengers in hypoxia-induced hyperpermeability of brain derived endothelial cells.
In vivo, ischemia is known to damage the blood-brain barrier (BBB) leading to the development of vasogenic brain edema. Hypoxia-induced vascular endothelial growth factor (VEGF) has been shown to be a key regulator of these permeability changes. However, the signaling pathways that underlie VEGF-induced hyperpermeability are incompletely understood. In this study, we demonstrate that hypoxia- and VEGF-induced permeability changes depend on activation of phospholipase Cgamma (PLCgamma), phosphatidylinositol 3-kinase/Akt (PI3-K/Akt), and protein kinase G (PKG). Inhibition of mitogen-activated protein kinases (MAPK) and of the protein kinase C (PKC) did not affect permeability at all. Paralleling hypoxia- and VEGF-induced permeability changes, localization of the tight junction proteins occludin, zonula occludens-1 (ZO-1), and ZO-2 along the cell membrane changed from a continuous to a more discontinuous expression pattern during hypoxia. In particular, localization of ZO-1 and ZO-2 expression moved from the cell membrane to the cytoplasm and nucleus whereas occludin expression remained at the cell membrane. Inhibition of PLCgamma, PI3-kinase, and PKG abolished these hypoxia-induced changes. These findings demonstrate that hypoxia and VEGF induce permeability through rearrangement of endothelial junctional proteins which involves activation of the PLCgamma and PI3-K/AKT pathway leading to the activation of PKG.
Fischer
Silvia
S
Kerckhoff-Clinic, Department of Anesthesiology and Intensive Care, Bad Nauheim, Germany. s.fischer@kerkhoff.mpg.de
Wiesnet
Marion
M
Marti
Hugo H
HH
Renz
Dieter
D
Schaper
Wolfgang
W
D000818:Animals; D015152:Blotting, Northern; D015153:Blotting, Western; D001921:Brain / Q000098:blood supply* / Q000503:physiopathology; D002199:Capillary Permeability / Q000187:drug effects / Q000502:physiology*; D015687:Cell Hypoxia / Q000502:physiology; D002478:Cells, Cultured; D017869:Cyclic GMP-Dependent Protein Kinases / Q000187:drug effects / Q000378:metabolism; D042783:Endothelial Cells / Q000187:drug effects / Q000378:metabolism* / Q000648:ultrastructure; D004789:Enzyme Activation / Q000187:drug effects / Q000502:physiology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005455:Fluorescent Antibody Technique; D008565:Membrane Proteins / Q000378:metabolism; D062793:Occludin; D019869:Phosphatidylinositol 3-Kinases / Q000187:drug effects / Q000378:metabolism; D051966:Phospholipase C gamma; D010750:Phosphoproteins / Q000378:metabolism; D021381:Protein Transport / Q000502:physiology; D013552:Swine; D019108:Tight Junctions / Q000648:ultrastructure*; D010738:Type C Phospholipases / Q000187:drug effects / Q000378:metabolism; D042461:Vascular Endothelial Growth Factor A / Q000378:metabolism / Q000494:pharmacology; D062826:Zonula Occludens-1 Protein; D062827:Zonula Occludens-2 Protein
D004791:Enzyme Inhibitors; D008565:Membrane Proteins; D062793:Occludin; D010750:Phosphoproteins; D042461:Vascular Endothelial Growth Factor A; D062826:Zonula Occludens-1 Protein; D062827:Zonula Occludens-2 Protein; D019869:Phosphatidylinositol 3-Kinases; D017869:Cyclic GMP-Dependent Protein Kinases; D010738:Type C Phospholipases; D051966:Phospholipase C gamma