INVESTIGADORES
GALIGNIANA Mario Daniel
artículos
Título:
Inhibition of glucocorticoid receptor binding by nitric oxide
Autor/es:
GALIGNIANA MD, PIWIEN-PILIPUK G, ASSREUY J
Revista:
MOLECULAR PHARMACOLOGY
Editorial:
AMER SOC PHARMACOLOGY EXPERIMENTAL THERAPEUTICS
Referencias:
Año: 1999 vol. 55 p. 317 - 323
ISSN:
0026-895X
Resumen:
Septic shock is a dangerous condition with high mortality rates. In
sepsis, the inducible form of nitric oxide (NO) synthase is induced,
releasing high amounts of NO. Glucocorticoids have potent
anti-inflammatory properties and are very effective in inhibiting the
induction of this enzyme if administered before the shock onset. It is
known that glucocorticoid receptor (GR) has critical cysteine residues
for steroid binding in its hormone-binding and DNA-binding domains. It
has also been reported that NO reacts with ---SH groups, forming
S-nitrosothiols. Therefore, we examined the potential effect of NO on
the ligand-binding ability of GR. NO donors
(S-nitroso-acetyl-DL-penicillamine, S-nitroso-DL-penicillamine, or
S-nitroso-glutathione) decreased, in a time- and dose-dependent manner,
the binding of [3H]triamcinolone to immunoprecipitated GR from mouse
L929 fibroblasts. The nonnitrosylated parent molecules,
N-acetyl-DL-penicillamine, and reduced gluthatione were without effect.
Scatchard plots revealed that the number of ligand binding sites and Kd
were reduced (50%) by NO donors. Western blot analysis ruled out the
possibility that dissociation of GR/heat shock protein 90 heterocomplex
or decrease in GR protein would account for the inhibitory effect of NO.
Decreased ligand binding to GR was found when NO donors were incubated
with intact fibroblasts. Incubation with NO donors also decreased the
steroid-induced reduction in [3H]uridine incorporation into RNA. All of
these NO effects were inhibited by the thiol-protecting agent
dithiothreitol. Therefore, S-nitrosylation of critical ---SH groups in
GR by NO with consequent decreases in binding and affinity may be the
mechanisms which explain the failure of glucocorticoids to exert their
anti-inflammatory effects in septic shock.