ABSTRACT
High-throughput screening of 3.87 million compounds delivered a novel series of non-steroidal GR antagonists. Subsequent rounds of optimisation allowed progression from a non-selective ligand with a poor ADMET profile to an orally bioavailable, selective, stable, glucocorticoid receptor antagonist.
Subject(s)
Receptors, Glucocorticoid/antagonists & inhibitors , Animals , Drug Evaluation, Preclinical , High-Throughput Screening Assays , Humans , Hydrocortisone/chemistry , Microsomes/metabolism , Rats , Receptors, Glucocorticoid/metabolism , Structure-Activity Relationship , Sulfonamides/chemical synthesis , Sulfonamides/chemistry , Sulfonamides/pharmacokineticsABSTRACT
We investigated the effect of the glucocorticoid receptor (GR) antagonist Org 34850 on fast and delayed inhibition of corticosterone secretion in response to the synthetic glucocorticoid methylprednisolone (MPL). Male rats were implanted with a catheter in the right jugular vein, for blood sampling and MPL administration, and with an s.c. cannula for Org 34850 administration. All experiments were conducted at the diurnal hormonal peak in the late afternoon. Rats were connected to an automated sampling system and blood samples were collected every 5 or 10 min. Org 34850 (10 mg/kg, s.c.) or vehicle (5% mulgofen in saline) was injected at 1630 h; 30 min later, rats received an injection of MPL (500 microg/rat, i.v.) or saline (0.1 ml/rat). We found that an acute administration of MPL rapidly decreased the basal corticosterone secretion and this effect was not prevented by acute pretreatment with Org 34850. However, blockade of GR with Org 34850 prevented delayed inhibition of MPL on corticosterone secretion measured between 4 and 12 h after MPL administration. Our data suggest an involvement of GR in modulating delayed, but not fast, inhibition induced by MPL on basal corticosterone secretion.
Subject(s)
Corticosterone/metabolism , Feedback, Physiological/drug effects , Glucocorticoids/pharmacology , Methylprednisolone/pharmacology , Receptors, Glucocorticoid/antagonists & inhibitors , Steroids/pharmacology , Sulfones/pharmacology , Animals , Circadian Rhythm , Corticosterone/antagonists & inhibitors , Corticosterone/blood , Humans , Male , Rats , Rats, Sprague-Dawley , Receptors, Glucocorticoid/physiology , Time FactorsABSTRACT
Glucocorticoid-induced receptor (GIR) is an orphan G-protein-coupled receptor (GPCR) with predominant expression in brain and thymus. More specifically, high levels of GIR expression have been described in brain regions of mouse, rat and human including limbic forebrain and hypothalamic regions, suggesting a role for GIR in memory, cognition, stress, reward or the control of emotion. Previous in vitro studies performed in murine thymocytes demonstrated an induction of GIR following dexamethasone treatment, suggesting the potential in vivo regulation of GIR by glucocorticoids. Glucocorticoids have been implicated in a number of disorders. In this study we employed in situ hybridisation with semi-quantitative image analysis to assess the level of GIR expression in mouse brain following acute dexamethasone administration. GIR was highly expressed in the nucleus accumbens, striatum, olfactory tubercle and nuclei of the hypothalamus. Three hours following acute dexamethasone treatment (0.05 mg/kg, p.o.), levels of GIR mRNA were found to be significantly decreased in striatum (25%, P<0.05), nucleus accumbens (19%, P<0.05), olfactory tubercle (19%, P<0.05) and CA2 sub-region of the hippocampus (30%, P<0.05) compared with vehicle. Significant decreases in GIR expression were also observed in hypothalamic nuclei including the dorsomedial (48%, P<0.05) and ventrolateral (58%, P<0.05) part of the ventromedial hypothalamic nuclei, dorsomedial hypothalamic nuclei (39%, P<0.01) and arcuate nucleus (54%, P<0.05), compared with vehicle. These data demonstrate the in vivo regulation of GIR in response to glucocorticoids and suggest a potential role for GIR in mediating the response to altered levels of glucocorticoids in disease states.
