trans-Activation and Repression Properties of the Novel Nonsteroid Glucocorticoid Receptor Ligand 2,5-Dihydro-9-hydroxy-10-methoxy-2,2,4-trimethyl-5-(1-methylcyclohexen-3-y1)-1H-[1]benzopyrano[3,4-f]quinoline (A276575) and Its Four Stereoisomers

Abstract

Glucocorticoids are potent anti-inflammatory and immunosuppressant agents. However, they also produce serious side effects that limit their usage. It has been proposed that anti-inflammatory properties of glucocorticoids are caused mostly by repression of activator protein 1- and nuclear factor κβ-stimulated synthesis of inflammatory mediators, whereas most of their adverse effects are associated withtrans-activation of genes involved with metabolic processes. Our laboratories have sought to discover novel glucocorticoid receptor (GR) ligands that have high repression but lowtrans-activation activities. We describe here cellular properties of 2,5-dihydro-9-hydroxy-10-methoxy-2,2,4-trimethyl-5-(1-methylcyclohexen-3-y1)-1H-[1]benzopyrano[3,4-f]quinoline (A276575) and its four enantiomers. Similar to dexamethasone, A276575 exhibited high affinity for GR and potently repressed interleukin (IL) 1β-stimulated IL-6 production in human skin fibroblasts, prostaglandin (PG) E₂ production in A549 human lung epithelial cells, and concanavalin A-induced monocyte proliferation. In contrast to dexamethasone, A276575 caused smaller induction of aromatase activity in human skin fibroblasts and antagonized dexamethasone-induced activation of an mouse mammary tumor virus–glucocorticoid-response element (GRE) reporter gene construct. Among the four enantiomers of A276575, the two (−)-enantiomers showed 10- to 30-fold higher affinities for GR than their respective (+)-enantiomers. Both (−)-Syn and (−)-Anti enantiomers of A276575 were potent inhibitors of IL-1β–stimulated PGE2 production in A549 lung epithelial cells; unexpectedly, however, only the (−)-Anti enantiomer inhibited regulated on T-cell activation, normal T-cell expressed and secreted (RANTES) production in A549 cells. In summary, A276575 is a novel, nonsteroidal GR ligand that possesses high repression activities against inflammatory mediator production but has lower GRE trans-activation activities than traditional steroids. Differential repression of RANTES and PGE2 production in a cell by the two (−)-enantiomers of A276575 illustrates the complexity of repression by GR.