Nitric oxide synthase expression in glial cells: suppression by tyrosine kinase inhibitors.
Rat brain glial cells have the capacity to express a calcium-independent form of nitric oxide synthase (iNOS). To test if iNOS induction required tyrosine kinase activity, we made use of genistein, a selective inhibitor of tyrosine kinases. In both primary astrocyte cultures and C6 glioma cells, the presence of genistein prevented both lipopolysaccharide- and cytokine-induced NOS activity in a dose-dependent manner. The presence of tyrphostin-25 (10 microM), which is highly specific for tyrosine kinases, also blocked iNOS induction. Additional characterization showed that genistein blocked iNOS induction in a dose-dependent manner (IC50 of approximately 40 microM), that the continuous presence of genistein was not necessary to observe inhibition, and that preincubation with genistein led to higher levels of inhibition than the simultaneous addition of genistein and inducers. The decrease in iNOS activity due to genistein was accompanied by a decrease in iNOS mRNA level as detected by a specific PCR assay. These results indicate that induction of astroglial iNOS expression requires tyrosine kinase activity.
Feinstein
D L
DL
Division of Neurobiology, Cornell University Medical College, New York, New York 10021.
Galea
E
E
Cermak
J
J
Chugh
P
P
Lyandvert
L
L
Reis
D J
DJ
D000594:Amino Acid Oxidoreductases / Q000037:antagonists & inhibitors* / Q000378:metabolism*; D000818:Animals; D016375:Antisense Elements (Genetics) / Q000235:genetics; D001253:Astrocytes / Q000201:enzymology; D001483:Base Sequence; D004790:Enzyme Induction; D005910:Glioma / Q000201:enzymology / Q000473:pathology; D008969:Molecular Sequence Data; D009457:Neuroglia / Q000201:enzymology*; D019001:Nitric Oxide Synthase; D015345:Oligonucleotide Probes / Q000235:genetics; D016133:Polymerase Chain Reaction; D011505:Protein-Tyrosine Kinases / Q000037:antagonists & inhibitors*; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D014407:Tumor Cells, Cultured
D016375:Antisense Elements (Genetics); D015345:Oligonucleotide Probes; D012333:RNA, Messenger; D019001:Nitric Oxide Synthase; D000594:Amino Acid Oxidoreductases; D011505:Protein-Tyrosine Kinases