The glucocorticoid receptor agonistic modulators CpdX and CpdX-D3 do not generate the debilitating effects of synthetic glucocorticoids.

Seventy years after the discovery of their anti-inflammatory properties, glucocorticoids (GCs) remain the mainstay treatment for major allergic and inflammatory disorders, such as atopic dermatitis, asthma, rheumatoid arthritis, colitis, and conjunctivitis, among others. However, their long-term therapeutical administration is limited by major debilitating side effects, e.g., skin atrophy, osteoporosis, Addison-like adrenal insufficiency, fatty liver, and type 2 diabetes syndrome, as well as growth inhibition in children. These undesirable side effects are mostly related to GC-induced activation of both the direct transactivation and the direct transrepression functions of the GC receptor (GR), whereas the activation of its GC-induced indirect tethered transrepression function results in beneficial anti-inflammatory effects. We have reported in the accompanying paper that the nonsteroidal compound CpdX as well as its deuterated form CpdX-D3 selectively activate the GR indirect transrepression function and are as effective as synthetic GCs at repressing inflammations generated in several mouse models of major pathologies. We now demonstrate that these CpdX compounds are bona fide selective GC receptor agonistic modulators (SEGRAMs) as none of the known GC-induced debilitating side effects were observed in the mouse upon 3-mo CpdX treatments. We notably report that, unlike that of GCs, the administration of CpdX to ovariectomized (OVX) mice does not induce a fatty liver nor type 2 diabetes, which indicates that CpdX could be used in postmenopausal women as an efficient "harmless" GC substitute.

GR SUMOylation and formation of an SUMO-SMRT/NCoR1-HDAC3 repressing complex is mandatory for GC-induced IR nGRE-mediated transrepression.

Unique among the nuclear receptor superfamily, the glucocorticoid (GC) receptor (GR) can exert three distinct transcriptional regulatory functions on binding of a single natural (cortisol in human and corticosterone in mice) and synthetic [e.g., dexamethasone (Dex)] hormone. The molecular mechanisms underlying GC-induced positive GC response element [(+)GRE]-mediated activation of transcription are partially understood. In contrast, these mechanisms remain elusive for GC-induced evolutionary conserved inverted repeated negative GC response element (IR nGRE)-mediated direct transrepression and for tethered indirect transrepression that is mediated by DNA-bound NF-κB/activator protein 1 (AP1)/STAT3 activators and instrumental in GC-induced anti-inflammatory activity. We demonstrate here that SUMOylation of lysine K293 (mouse K310) located within an evolutionary conserved sequence in the human GR N-terminal domain allows the formation of a GR-small ubiquitin-related modifiers (SUMOs)-NCoR1/SMRT-HDAC3 repressing complex mandatory for GC-induced IR nGRE-mediated direct repression in vitro, but does not affect transactivation. Importantly, these results were validated in vivo: in K310R mutant mice and in mice ablated selectively for nuclear receptor corepressor 1 (NCoR1)/silencing mediator for retinoid or thyroid-hormone receptors (SMRT) corepressors in skin keratinocytes, Dex-induced direct repression and the formation of repressing complexes on IR nGREs were impaired, whereas transactivation was unaffected. In mice selectively ablated for histone deacetylase 3 (HDAC3) in skin keratinocytes, GC-induced direct repression, but not bindings of GR and of corepressors NCoR1/SMRT, was abolished, indicating that HDAC3 is instrumental in IR nGRE-mediated repression. Moreover, we demonstrate that the binding of HDAC3 to IR nGREs in vivo is mediated through interaction with SMRT/NCoR1. We also show that the GR ligand binding domain (LBD) is not required for SMRT-mediated repression, which can be mediated by a LBD-truncated GR, whereas it is mandatory for NCoR1-mediated repression through an interaction with K579 in the LBD.