Inhibition of glucocorticoid receptor binding by nitric oxide in endotoxemic rats.
OBJECTIVE
Nitric oxide is an important participant in septic shock. For example, it causes profound vasodilation and hypotension. Despite their potent antiinflammatory properties, glucocorticoids are not routinely used in septic shock. Some studies show that antiinflammatory doses of glucocorticoids can be beneficial, but other studies do not indicate their use in this situation. We have previously shown the inhibitory effect of nitric oxide on glucocorticoid receptor binding in vitro. Nitric oxide donors decreased the binding of immunoprecipitated glucocorticoid receptor obtained from mouse L929 fibroblasts. These in vitro findings prompted us to study whether in vivo manipulations of the nitric oxide system would interfere with the glucocorticoid receptor binding.


METHODS
Prospective, experimental study.


METHODS
Research laboratory at a university.


METHODS
Female Wistar rats.


METHODS
Injection of bacterial lipopolysaccharide, anesthesia, cardiovascular perfusion, and organ removal for biochemical assays.


RESULTS
Following lipopolysaccharide injection, plasma nitrate + nitrite increased and inducible nitric oxide synthase activity was stimulated in several organs, the highest rates being in the lung and spleen. If dexamethasone was injected before lipopolysaccharide, it completely blocked inducible nitric oxide synthase induction and the increase in plasma nitrate + nitrite. On the other hand, if dexamethasone was injected after lipopolysaccharide, it failed to affect both inducible nitric oxide synthase induction and increased plasma nitrate + nitrite levels. Lipopolysaccharide also caused an inhibition of glucocorticoid receptor binding in lung and spleen. Previous administration of a nitric oxide synthase inhibitor prevented both lipopolysaccharide-induced decrease in glucocorticoid receptor binding and the increase in plasma nitrate + nitrite. Injection of a nitric oxide donor into naive animals significantly decreased glucocorticoid receptor binding activity and prevented dexamethasone-induced increase in liver tyrosine aminotransferase activity.


CONCLUSIONS
The results indicate that the failure of glucocorticoids to exhibit their antiinflammatory effects when administered to endotoxemic rats may be explained, at least in part, by the nitric oxide-induced inhibition of glucocorticoid receptor binding ability, thus precluding the expression of the antiinflammatory effects of both exogenous and endogenous corticosteroids.
Duma
Danielle
D
Universidade Federal de Santa Catarina, Department of Pharmacology, University Campus, Trindade, Florianopolis, Brazil.
Silva-Santos
José Eduardo
JE
Assreuy
Jamil
J
D000818:Animals; D000893:Anti-Inflammatory Agents / Q000276:immunology / Q000494:pharmacology / Q000627:therapeutic use*; D001665:Binding Sites; D003907:Dexamethasone / Q000276:immunology / Q000494:pharmacology / Q000627:therapeutic use*; D004195:Disease Models, Animal; D004305:Dose-Response Relationship, Drug; D004353:Drug Evaluation, Preclinical; D019446:Endotoxemia / Q000188:drug therapy* / Q000276:immunology / Q000378:metabolism / Q000382:microbiology; D004927:Escherichia coli Infections / Q000150:complications; D005260:Female; D008070:Lipopolysaccharides / Q000009:adverse effects; D008099:Liver / Q000737:chemistry / Q000378:metabolism; D008168:Lung / Q000737:chemistry / Q000378:metabolism; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D020030:Nitric Oxide Donors / Q000494:pharmacology; D019001:Nitric Oxide Synthase / Q000032:analysis / Q000037:antagonists & inhibitors / Q000187:drug effects / Q000502:physiology*; D052247:Nitric Oxide Synthase Type II; D051381:Rats; D017208:Rats, Wistar; D011965:Receptors, Glucocorticoid / Q000187:drug effects / Q000378:metabolism / Q000502:physiology; D026423:S-Nitroso-N-Acetylpenicillamine / Q000494:pharmacology; D012772:Shock, Septic / Q000188:drug therapy* / Q000276:immunology / Q000378:metabolism / Q000382:microbiology; D013154:Spleen / Q000737:chemistry / Q000378:metabolism; D014444:Tyrosine Transaminase / Q000032:analysis / Q000378:metabolism
D000893:Anti-Inflammatory Agents; D008070:Lipopolysaccharides; D020030:Nitric Oxide Donors; D011965:Receptors, Glucocorticoid; D026423:S-Nitroso-N-Acetylpenicillamine; D003907:Dexamethasone; D019001:Nitric Oxide Synthase; D052247:Nitric Oxide Synthase Type II; C496318:Nos2 protein, rat; D014444:Tyrosine Transaminase; D019331:NG-Nitroarginine Methyl Ester