AJP - Lung Cellular and Molecular Physiology, Vol 268, Issue 3 501-L508, Copyright © 1995 by American Physiological Society
Pulmonary alveolar epithelial inducible NO synthase gene expression: regulation by inflammatory mediators
H. H. Gutierrez, B. R. Pitt, M. Schwarz, S. C. Watkins, C. Lowenstein, I. Caniggia, P. Chumley and B. A. Freeman
Department of Pediatrics, University of Alabama at Birmingham 35233.
Nitric oxide (.NO) is a short-lived mediator that can be induced by
different cytokines and lipopolysaccharide (LPS) in a variety of cell types
and produces many physiological and metabolic changes in target cells. In
the current study, we show that a combination of cytokines, LPS, and
zymosan-activated serum (ZAS; called for convenience cytomix Z) induces
production of high concentrations of the NO oxidation products nitrite
(NO2-) and nitrate (NO3-) by cultured rat fetal lung epithelial type II
cells in a time-dependent fashion. Interferon-gamma and tumor necrosis
factor-alpha alone did not significantly affect .NO synthesis, whereas ZAS,
LPS, and interleukin-1 beta caused only a modest increase in formation of
.NO oxidation products. Production of NO2- and NO3- was inhibited by
NG-monomethyl-L-arginine and cyclohexmide. After exposure of these cells to
a combination of the above cytokines, Escherichia coli LPS, and ZAS
(cytomix Z), enhanced inducible nitric oxide synthase (iNOS) expression was
indicated by an elevation in steady-state mRNA specific for iNOS (via
Northern blot analysis) and increased immunofluorescence for iNOS after
cell permeabilization, incubation with anti-iNOS antibody, and treatment
with Cy3.18-conjugated rabbit-specific antibody. The extent of inflammatory
mediator-induced.NO production by alveolar epithelium, which exceeds that
of other lung cell types, reveals new insight into mechanisms of pulmonary
host defense and pathways of free radical-mediated lung injury.
