Angiotensin II-induced fluid phase endocytosis in human cerebromicrovascular endothelial cells is regulated by the inositol-phosphate signaling pathway.
The involvement of the early signaling messengers, inositol tris-phosphate (IP3), intracellular calcium, [Ca2+]i, and protein kinase C (PKC), in angiotensin II (AII)-induced fluid phase endocytosis was investigated in human brain capillary and microvascular endothelial cells (HCEC). ALL (0.01-10 microM) stimulated the uptake of Lucifer yellow CH, an inert dye used as a marker for fluid phase endocytosis, in HCEC by 50-230%. AII also triggered a fast accumulation of IP3 and a rapid increase in [Ca2+]i in cells loaded with the Ca(2+)-responsive fluorescent dye fura-2. The prompt AII-induced [Ca2+]i spike was not affected by incubating HCEC in Ca(2+)-free medium containing 2 mM EGTA or by pretreating the cultures with the Ca2+ channel blockers, methoxyverapamil (D600; 50 microM), nickel (1 mM), or lanthanum (1 mM), suggesting that the activation of AII receptors on HCEC triggers the release of Ca2+ from intracellular stores. The AII-triggered increases in IP3, [Ca2+]i, and Lucifer yellow uptake were inhibited by the nonselective AII receptor antagonist, Sar1, Val5, Ala8-AII (SVA-AII), and by the phospholipase C (PLC) inhibitors, neomycin and U-73122. By contrast, the protein kinase C (PKC) inhibitors, staurosporine and calphostin C, failed to affect any of these AII-induced events. This study demonstrates that increased fluid phase endocytotosis induced by AII in human brain capillary endothelium, an event thought to be linked to the observed increases in blood-brain barrier permeability in acute hypertension, is likely dependent on PLC-mediated changes in [Ca2+]i and independent of PKC.
Stanimirovic
D
D
Institute for Biological Sciences, National Research Council of Canada, Ottawa, Ontario, Canada.
Morley
P
P
Ball
R
R
Hamel
E
E
Mealing
G
G
Durkin
J P
JP
D000804:Angiotensin II / Q000502:physiology*; D001812:Blood-Brain Barrier; D002118:Calcium / Q000502:physiology*; D002478:Cells, Cultured; D004705:Endocytosis / Q000187:drug effects; D004730:Endothelium, Vascular; D006801:Humans; D007295:Inositol Phosphates / Q000502:physiology*; D008833:Microcirculation; D010716:Phosphatidylinositols / Q000378:metabolism; D011493:Protein Kinase C / Q000502:physiology; D015398:Signal Transduction; D010738:Type C Phospholipases / Q000037:antagonists & inhibitors / Q000502:physiology; D014841:von Willebrand Factor / Q000378:metabolism
D007295:Inositol Phosphates; D010716:Phosphatidylinositols; D014841:von Willebrand Factor; D000804:Angiotensin II; D011493:Protein Kinase C; D010738:Type C Phospholipases; D002118:Calcium