Inhibition of Glucocorticoid Receptor Binding by Nitric Oxide

• DOI: 10.1124/mol.55.2.317
• Publication Date: 2018-01-08T20:34:17Z
• Authors: Mario D. Galigniana; Graciela Piwien-P...; Jamil Assreuy
• Keywords: Penicillamine; Dithiothreitol

Septic shock is a dangerous condition with high mortality rates. In sepsis, the inducible form of nitric oxide (NO) synthase induced, releasing amounts NO. Glucocorticoids have potent anti-inflammatory properties and are very effective in inhibiting induction this enzyme if administered before onset. It known that glucocorticoid receptor (GR) has critical cysteine residues for steroid binding its hormone-binding DNA-binding domains. also been reported NO reacts —SH groups, forming<i>S</i>-nitrosothiols. Therefore, we examined potential effect on ligand-binding ability GR. donors (<i>S</i>-nitroso-acetyl-dl-penicillamine,<i>S</i>-nitroso-dl-penicillamine, or<i>S</i>-nitroso-glutathione) decreased, time- dose-dependent manner, [³H]triamcinolone to immunoprecipitated GR from mouse L929 fibroblasts. The nonnitrosylated parent molecules,<i>N</i>-acetyl-dl-penicillamine, reduced gluthatione were without effect. Scatchard plots revealed number ligand sites <i>K</i>_d (50%) by donors. Western blot analysis ruled out possibility dissociation GR/heat protein 90 heterocomplex or decrease would account inhibitory Decreased was found when incubated intact Incubation decreased steroid-induced reduction [³H]uridine incorporation into RNA. All these effects inhibited thiol-protecting agent dithiothreitol. Therefore,<i>S</i>-nitrosylation groups consequent decreases affinity may be mechanisms which explain failure glucocorticoids exert their septic shock.