Nitric oxide-mediated activation of heme oxygenase: an endogenous
mechanism of cytoprotection against the oxidative stress to
endothelium.
Motterlini, Roberto, Roberta Foresti, Marcos Intaglietta, and Robert
M. Winslow.
Department of Bioengineering and Department of Medicine, University
of California San Diego, La Jolla, CA 92093
APStracts 2:0316H, 1995.
We investigated the effect of nitric oxide (NO) on the induction of
the stress protein heme oxygenase and its protective role in vascular
endothelial cells prior exposure to hydrogen peroxide. Treatment of
porcine aortic endothelial cells for 6 h with the NO-releasing
compounds (0.1-1mM) sodium nitroprusside (SNP), S-nitroso-N-acetyl
-penicillamine (SNAP) and 3-Morpholinsydnonimine (SIN-1) resulted in a
concentration-dependent increase in heme oxygenase activity. At 1 mM,
the activity of heme oxygenase augmented 8.5-fold with SNP, 5.8-fold
with SNAP and 5.7-fold with SIN-1 over the control value. In
contrast, endothelial cells exposed to 100 [mu]M 8-bromo-cGMP, a
tissue permeable analogue which mimics the action of cGMP, did not
show any change in heme oxygenase activity. Activation of the
inducible NO synthase by the synergistic action of bacterial
lipopolysaccharide (LPS, 250 ng/ml) and interferon-_ (IFN-_, 100
U/ml) also increased endothelial heme oxygenase activity by 3.2-fold
(p<0.05 vs control). Methylene blue (1 [mu]M), an inhibitor of
both NO synthase and guanylate cyclase activities, completely
abolished this effect. Cells previously exposed to SNAP and SIN-1,
exhibited a significant protection against the cytotoxicity mediated
by hydrogen peroxide (250 [mu]M) (p<0.05). Conversely, SNP did
not show any protective effects, possibly because of catalytic iron
released during its chemical decomposition. In fact, the iron
chelator deferoxamine (5 mM) completely suppressed the SNP-mediated
cytotoxicity and partially attenuated the activity of heme oxygenase
to a level equal to that mediated by SIN-1 and SNAP. These results
indicate that NO is a determinant in the modulation of the activity
of heme oxygenase leading to a major resistance of the endothelium to
oxidative stress.
Received 14 February 1995; accepted in final form 10 July 1995.
APS Manuscript Number H134-5.
Article publication pending Am. J. Physiol. (Heart Circ. Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 30 July 1995.