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Kolosova IA, Mirzapoiazova T, Adyshev D, Usatyuk P, Romer LH,
Jacobson JR, Natarajan V, Pearse DB, Garcia JG, Verin AD. Signaling
pathways involved in adenosine triphosphate-induced endothelial cell
barrier enhancement. Circ Res. 2005;Jul
22;97(2):115-124.
Department of Medicine, Johns Hopkins University School of Medicine,
Baltimore, MD, USA.
Endothelial barrier dysfunction caused by inflammatory agonists is a
frequent underlying cause of vascular leak and edema. Novel strategies
to preserve barrier integrity could have profound clinical impact. Adenosine
triphosphate (ATP) released from endothelial cells by shear stress and
injury has been shown to protect the endothelial barrier in some settings.
We have demonstrated that ATP and its nonhydrolyzed analogues enhanced
barrier properties of cultured endothelial cell monolayers and caused
remodeling of cell-cell junctions. Increases in cytosolic Ca2+ and Erk
activation caused by ATP were irrelevant to barrier enhancement. Experiments
using biochemical inhibitors or siRNA indicated that G proteins (specifically
Galphaq and Galphai2), protein kinase A (PKA), and the PKA substrate
vasodilator-stimulated phosphoprotein were involved in ATP-induced barrier
enhancement. ATP treatment decreased phosphorylation of myosin light
chain and specifically activated myosin-associated phosphatase. Depletion
of Galphaq with siRNA prevented ATP-induced activation of myosin phosphatase.
We conclude that the mechanisms of ATP-induced barrier enhancement are
independent of intracellular Ca2+, but involve activation of myosin phosphatase
via a novel G-protein-coupled mechanism and PKA.
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Abstracts