Augmentation of cytokine-induced nitric oxide synthesis by hydrogen
peroxide.
Milligan, Shawn A., Michael W. Owens, and Matthew B. Grisham.
Departments of Medicine, and Physiology and Biophysics, VA Medical
Center and Louisiana State University Medical Center, Shreveport, LA.
71101
APStracts 3:0044L, 1996.
The inducible isoform of nitric oxide synthase (iNOS) is induced upon
stimulation of cells with cytokines and lipopolysaccharide (LPS).
Stimulation of rat pleural mesothelial cells with combinations of
interleukin-1[beta] (IL-1), tumor necrosis factor-[alpha] (TNF),
interferon-gamma (IFN-_) and LPS induced the synthesis of nitric
oxide as measured by the oxidation products nitrite (NO2-) and
nitrate (NO3-). Addition of H2O2, 25 - 50 [mu]M, to the cytokines
significantly augmented the synthesis of NO2- and NO3-. Stimulation
with IL-1 and TNF plus H2O2 or IL-1 and LPS plus H2O2 increased the
synthesis of NO2- and NO3- by 3.8- and 3.5-fold, respectively. These
effects were inhibited by NG-nitro-L-arginine methyl ester and
cycloheximide as well as by catalase. Immunoblotting demonstrated
that H2O2 augmented cytokine-induced synthesis of iNOS protein. These
effects were inhibited by certain antioxidants and metal chelators
suggesting that the hydroxyl radical may mediate the oxidant-induced
effect. Northern blotting demonstrated that H2O2 greatly augmented
steady-state levels of iNOS mRNA suggesting that H2O2 acted in part
at the transcriptional level.
Received 28 August 1995; accepted in final form 5 March 1996.
APS Manuscript Number L271-5.
Article publication pending Am. J. Physiol. (Lung Cell. Mol.
Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 27 March 96