The effect of nitric oxide on heme metabolism in pulmonary artery
endothelial cells.
Yee, Emily L., Bruce R. Pitt, Timothy R. Billiar, and Young-Myeong
Kim.
Departments of Pharmacology, Medicine, and Surgery, University of
Pittsburgh School of Medicine, Pittsburgh, PA 15261
APStracts 3:0086L, 1996.
Primary intracellular targets for NO include nonheme iron-containing
enzymes and protein-bound iron. Since NO is an important effector
molecule in lung inflammation and endothelial cell associated iron is
critical to numerous forms of oxidant mediated lung injury, we
studied the effects of the NO donor S-nitrosoacetylpenicillamine
(SNAP) on heme and iron metabolism in cultured sheep pulmonary artery
endothelial cells (SPAEC). SNAP (300 [mu]M) caused a transient
increase in heme oxygenase-1 (HO-1) mRNA associated with a 5 fold
increase in HO activity that was completely blocked by the
competitive HO inhibitor, tin protoporphyrin IX (SnPP). SNAP-induced
activation of HO caused SnPP-sensitive reduction of activity of the
hemoprotein, catalase, and decrease in heme iron. SNAP caused
increases in iron responsive gene products, ferritin and
mitochondrial aconitase, secondary to the release of iron from heme
stores via HO induction since these changes were also sensitive to
SnPP. The NO-induced increase in non-heme iron was apparent via EPR
where an enhanced SNAP-induced (300 [mu]M; 4h) g=2.04 signal (e.g.
dinitrosyl-iron-sulfur complex) was noted after exposure to a dose of
SNAP (200 [mu]M; 14h) that in itself did not produce a detectable
signal. These data show that exposure of pulmonary endothelial cells
to NO results in profound changes in intracellular heme- and nonheme
-iron homeostasis and that heme oxygenase plays a central role in
affecting this balance.
Received 28 December 1995; accepted in final form 15 May 1996.
APS Manuscript Number L380-5.
Article publication pending Am. J. Physiol. (Lung Cell. Mol.
Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 17 June 96