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Induction of Nitric Oxide Synthase Inhibits Gap Junction Permeability in Cultured Rat Astrocytes
Author(s) -
Bolaños Juan P.,
Medina José M.
Publication year - 1996
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1046/j.1471-4159.1996.66052091.x
Subject(s) - peroxynitrite , chemistry , nitric oxide , nitric oxide synthase , biochemistry , gap junction , superoxide , biophysics , xanthine oxidase , intracellular , biology , enzyme , organic chemistry
Nitric oxide ( • NO) synthase (NOS) was induced in cultured rat astrocytes by incubation with lipopolysaccharide (LPS) for 18 h and gap junction permeability was assessed by the scrape‐loading/Lucifer yellow transfer technique. Induction of NOS was confirmed by determining either the N G ‐methyl‐ l ‐arginine (NMMA)‐inhibitable production of nitrites and nitrates or the conversion of l ‐[ 3 H]arginine to l ‐[ 3 H]citrulline. Incubation with LPS dose‐dependently inhibited gap junction permeability to 63.3% at 0.05 µg/ml LPS and no further inhibition was observed on increasing the LPS concentration up to 0.5 µg/ml. LPS‐mediated gap junction inhibition was irreversible but was prevented by incubation with the NOS inhibitor NMMA and with the superoxide anion (O 2 •− ) scavenger superoxide dismutase. Incubation of the cells with both the • NO donor S ‐nitroso‐ N ‐acetylpenicillamine and the O 2 •− ‐generating system xanthine/xanthine oxidase inhibited gap junction permeability. These results suggest that the in situ reaction between • NO and O 2 •− , to form the peroxynitrite anion (ONOO − ), may be responsible for the inhibition of gap junction permeability. Scavenging the ONOO − derivative hydroxyl radical ( • OH) with either dimethyl sulfoxide or mannitol prevented the LPS‐mediated inhibition of gap junction permeability. Finally, exposure of astrocytes to authentic ONOO − caused a dose‐dependent inhibition of gap junction permeability (65.7% of inhibition at 0.5 m M ONOO − ). The pathophysiological relevance of ONOO − ‐mediated inhibition of gap junctional communication in astrocytes after NOS induction by LPS is discussed, stressing the possible role played by this mechanism in some neurodegenerative diseases.