Protein tyrosine kinase activity regulates nitric oxide synthase
induction in rat hepatocytes.
Miller, Danette R., John M. Collier, and Ruth E. Billings.
Department of Environmental Health, Colorado State University, Fort
Collins, CO 80523, Office:(970) 491-2369, FAX: (970) 491-0259
APStracts 3:0171G, 1996.
Regulation of induced nitric oxide synthase in isolated rat
hepatocytes is poorly understood. The specific protein tyrosine
kinase inhibitor, genistein, was used to determine if nitric oxide
synthase (NOS) induction is dependent on protein tyrosine kinase
activation. Genistein inhibited tumor necrosis factor [alpha]
(TNF[alpha])-stimulated induction of NOS activity and NOS protein in
a dose dependent manner. Genistein also impaired TNF[alpha]-induced
NOS mRNA accumulation suggesting protein tyrosine kinase regulation
of NOS induction occurred at the level of transcription/translation.
Like TNF[alpha], genistein inhibited induction of NOS protein by a
second proinflammatory cytokine, interleukin-1[beta], suggesting
similar activation mechanisms by proinflammatory cytokines. NOS
induction by other stimuli, including phorbol myristate acetate and
the superoxide generating system, xanthine/xanthine oxidase was also
inhibited by genistein. Finally, cytokine-stimulated protein tyrosine
kinase activity in hepatocytes was demonstrated by increased tyrosine
phosphorylation of 5 high molecular weight protein bands. Genistein
inhibited this cytokine-induced phosphotyrosine increase. The
commonality of genistein inhibition suggests that protein tyrosine
kinase activity is critical for NOS induction by a variety of
stimuli.
Received 11 March 1996; accepted in final form 12 August 1996.
APS Manuscript Number G91-6.
Article publication pending Am. J. Physiol. (Gastrointest. Liver
Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 19 September 1996