Title: Ammonia increases paracellular permeability of rat brain endothelial cells by a mechanism encompassing oxidative/nitrosative stress and activation of matrix metalloproteinases.
Authors: Skowrońska, Marta; Zielińska, Magdalena; Wójcik-Stanaszek, Luiza; Ruszkiewicz, Joanna; Milatovic, Dejan; Aschner, Michael; Albrecht, Jan
Published In J Neurochem, (2012 Apr)
Abstract: Ammonia is responsible for cerebral edema associated with acute liver failure, but the role of the vasogenic mechanism has been a matter of dispute. Here, we tested the hypothesis that ammonia induces changes in blood-brain barrier (BBB) permeability by a mechanism coupled to oxidative/nitrosative stress (ONS) evoked in the BBB-forming cerebral capillary endothelial cells. Treatment of a rat brain endothelial cell line with ammonia (5 mmol/L, 24 h) caused accumulation of ONS markers: reactive oxygen species, nitric oxide and peroxidation products of phospholipid-bound arachidonic acid, F2-isoprostanes. Concurrently, ammonia increased the activity of extracellular matrix metalloproteinases (MMP-2/MMP-9), increased cell permeability to fluorescein isothiocyanate-dextran (40 kDa), and increased the expression of y+LAT2, a transporter that mediates the uptake to the cells of the nitric oxide precursor, arginine. The increase of cell permeability was ameliorated upon co-treatment with a MMP inhibitor, SB-3CT and with an antioxidant, glutathione diethyl ester, which also reduced F2-isoprostanes. Ammonia-induced ONS was attenuated by cytoprotective agents l-ornithine, phenylbutyrate, and their conjugate l-ornithine phenylbutyrate, an ammonia-trapping drug used to treat hyperammonemia. The results support the concept that ONS and ONS-related activation of MMPs in cerebral capillary endothelial cells contribute to the alterations in BBB permeability and to the vasogenic component of cerebral edema associated with acute liver failure.
PubMed ID: 22260250
MeSH Terms: Ammonia/pharmacology*; Animals; Blood-Brain Barrier/drug effects; Blood-Brain Barrier/metabolism; Brain/blood supply*; Brain/drug effects; Brain/enzymology; Cell Membrane Permeability/drug effects; Cell Membrane Permeability/physiology*; Cells, Cultured; Endothelial Cells/drug effects; Endothelial Cells/enzymology; Endothelial Cells/metabolism*; Enzyme Activation/drug effects; Enzyme Activation/physiology; Matrix Metalloproteinases/metabolism*; Nitric Oxide/physiology*; Oxidative Stress/drug effects; Oxidative Stress/physiology*; Rats; Reactive Oxygen Species/metabolism